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, 2008
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 @ifset VERSION_PACKAGE
53 @value{VERSION_PACKAGE}
55 Version @value{GDBVN}.
57 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
58 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006@*
59 Free Software Foundation, Inc.
61 Permission is granted to copy, distribute and/or modify this document
62 under the terms of the GNU Free Documentation License, Version 1.1 or
63 any later version published by the Free Software Foundation; with the
64 Invariant Sections being ``Free Software'' and ``Free Software Needs
65 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
66 and with the Back-Cover Texts as in (a) below.
68 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
69 this GNU Manual. Buying copies from GNU Press supports the FSF in
70 developing GNU and promoting software freedom.''
74 @title Debugging with @value{GDBN}
75 @subtitle The @sc{gnu} Source-Level Debugger
77 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
78 @ifset VERSION_PACKAGE
80 @subtitle @value{VERSION_PACKAGE}
82 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
86 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
87 \hfill {\it Debugging with @value{GDBN}}\par
88 \hfill \TeX{}info \texinfoversion\par
92 @vskip 0pt plus 1filll
93 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
94 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
95 Free Software Foundation, Inc.
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
102 Permission is granted to copy, distribute and/or modify this document
103 under the terms of the GNU Free Documentation License, Version 1.1 or
104 any later version published by the Free Software Foundation; with the
105 Invariant Sections being ``Free Software'' and ``Free Software Needs
106 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
107 and with the Back-Cover Texts as in (a) below.
109 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
110 this GNU Manual. Buying copies from GNU Press supports the FSF in
111 developing GNU and promoting software freedom.''
113 This edition of the GDB manual is dedicated to the memory of Fred
114 Fish. Fred was a long-standing contributor to GDB and to Free
115 software in general. We will miss him.
120 @node Top, Summary, (dir), (dir)
122 @top Debugging with @value{GDBN}
124 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
126 This is the @value{EDITION} Edition, for @value{GDBN}
127 @ifset VERSION_PACKAGE
128 @value{VERSION_PACKAGE}
130 Version @value{GDBVN}.
132 Copyright (C) 1988-2006 Free Software Foundation, Inc.
134 This edition of the GDB manual is dedicated to the memory of Fred
135 Fish. Fred was a long-standing contributor to GDB and to Free
136 software in general. We will miss him.
139 * Summary:: Summary of @value{GDBN}
140 * Sample Session:: A sample @value{GDBN} session
142 * Invocation:: Getting in and out of @value{GDBN}
143 * Commands:: @value{GDBN} commands
144 * Running:: Running programs under @value{GDBN}
145 * Stopping:: Stopping and continuing
146 * Stack:: Examining the stack
147 * Source:: Examining source files
148 * Data:: Examining data
149 * Macros:: Preprocessor Macros
150 * Tracepoints:: Debugging remote targets non-intrusively
151 * Overlays:: Debugging programs that use overlays
153 * Languages:: Using @value{GDBN} with different languages
155 * Symbols:: Examining the symbol table
156 * Altering:: Altering execution
157 * GDB Files:: @value{GDBN} files
158 * Targets:: Specifying a debugging target
159 * Remote Debugging:: Debugging remote programs
160 * Configurations:: Configuration-specific information
161 * Controlling GDB:: Controlling @value{GDBN}
162 * Sequences:: Canned sequences of commands
163 * Interpreters:: Command Interpreters
164 * TUI:: @value{GDBN} Text User Interface
165 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
166 * GDB/MI:: @value{GDBN}'s Machine Interface.
167 * Annotations:: @value{GDBN}'s annotation interface.
169 * GDB Bugs:: Reporting bugs in @value{GDBN}
171 * Command Line Editing:: Command Line Editing
172 * Using History Interactively:: Using History Interactively
173 * Formatting Documentation:: How to format and print @value{GDBN} documentation
174 * Installing GDB:: Installing GDB
175 * Maintenance Commands:: Maintenance Commands
176 * Remote Protocol:: GDB Remote Serial Protocol
177 * Agent Expressions:: The GDB Agent Expression Mechanism
178 * Target Descriptions:: How targets can describe themselves to
180 * Copying:: GNU General Public License says
181 how you can copy and share GDB
182 * GNU Free Documentation License:: The license for this documentation
191 @unnumbered Summary of @value{GDBN}
193 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
194 going on ``inside'' another program while it executes---or what another
195 program was doing at the moment it crashed.
197 @value{GDBN} can do four main kinds of things (plus other things in support of
198 these) to help you catch bugs in the act:
202 Start your program, specifying anything that might affect its behavior.
205 Make your program stop on specified conditions.
208 Examine what has happened, when your program has stopped.
211 Change things in your program, so you can experiment with correcting the
212 effects of one bug and go on to learn about another.
215 You can use @value{GDBN} to debug programs written in C and C@t{++}.
216 For more information, see @ref{Supported Languages,,Supported Languages}.
217 For more information, see @ref{C,,C and C++}.
220 Support for Modula-2 is partial. For information on Modula-2, see
221 @ref{Modula-2,,Modula-2}.
224 Debugging Pascal programs which use sets, subranges, file variables, or
225 nested functions does not currently work. @value{GDBN} does not support
226 entering expressions, printing values, or similar features using Pascal
230 @value{GDBN} can be used to debug programs written in Fortran, although
231 it may be necessary to refer to some variables with a trailing
234 @value{GDBN} can be used to debug programs written in Objective-C,
235 using either the Apple/NeXT or the GNU Objective-C runtime.
238 * Free Software:: Freely redistributable software
239 * Contributors:: Contributors to GDB
243 @unnumberedsec Free Software
245 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
246 General Public License
247 (GPL). The GPL gives you the freedom to copy or adapt a licensed
248 program---but every person getting a copy also gets with it the
249 freedom to modify that copy (which means that they must get access to
250 the source code), and the freedom to distribute further copies.
251 Typical software companies use copyrights to limit your freedoms; the
252 Free Software Foundation uses the GPL to preserve these freedoms.
254 Fundamentally, the General Public License is a license which says that
255 you have these freedoms and that you cannot take these freedoms away
258 @unnumberedsec Free Software Needs Free Documentation
260 The biggest deficiency in the free software community today is not in
261 the software---it is the lack of good free documentation that we can
262 include with the free software. Many of our most important
263 programs do not come with free reference manuals and free introductory
264 texts. Documentation is an essential part of any software package;
265 when an important free software package does not come with a free
266 manual and a free tutorial, that is a major gap. We have many such
269 Consider Perl, for instance. The tutorial manuals that people
270 normally use are non-free. How did this come about? Because the
271 authors of those manuals published them with restrictive terms---no
272 copying, no modification, source files not available---which exclude
273 them from the free software world.
275 That wasn't the first time this sort of thing happened, and it was far
276 from the last. Many times we have heard a GNU user eagerly describe a
277 manual that he is writing, his intended contribution to the community,
278 only to learn that he had ruined everything by signing a publication
279 contract to make it non-free.
281 Free documentation, like free software, is a matter of freedom, not
282 price. The problem with the non-free manual is not that publishers
283 charge a price for printed copies---that in itself is fine. (The Free
284 Software Foundation sells printed copies of manuals, too.) The
285 problem is the restrictions on the use of the manual. Free manuals
286 are available in source code form, and give you permission to copy and
287 modify. Non-free manuals do not allow this.
289 The criteria of freedom for a free manual are roughly the same as for
290 free software. Redistribution (including the normal kinds of
291 commercial redistribution) must be permitted, so that the manual can
292 accompany every copy of the program, both on-line and on paper.
294 Permission for modification of the technical content is crucial too.
295 When people modify the software, adding or changing features, if they
296 are conscientious they will change the manual too---so they can
297 provide accurate and clear documentation for the modified program. A
298 manual that leaves you no choice but to write a new manual to document
299 a changed version of the program is not really available to our
302 Some kinds of limits on the way modification is handled are
303 acceptable. For example, requirements to preserve the original
304 author's copyright notice, the distribution terms, or the list of
305 authors, are ok. It is also no problem to require modified versions
306 to include notice that they were modified. Even entire sections that
307 may not be deleted or changed are acceptable, as long as they deal
308 with nontechnical topics (like this one). These kinds of restrictions
309 are acceptable because they don't obstruct the community's normal use
312 However, it must be possible to modify all the @emph{technical}
313 content of the manual, and then distribute the result in all the usual
314 media, through all the usual channels. Otherwise, the restrictions
315 obstruct the use of the manual, it is not free, and we need another
316 manual to replace it.
318 Please spread the word about this issue. Our community continues to
319 lose manuals to proprietary publishing. If we spread the word that
320 free software needs free reference manuals and free tutorials, perhaps
321 the next person who wants to contribute by writing documentation will
322 realize, before it is too late, that only free manuals contribute to
323 the free software community.
325 If you are writing documentation, please insist on publishing it under
326 the GNU Free Documentation License or another free documentation
327 license. Remember that this decision requires your approval---you
328 don't have to let the publisher decide. Some commercial publishers
329 will use a free license if you insist, but they will not propose the
330 option; it is up to you to raise the issue and say firmly that this is
331 what you want. If the publisher you are dealing with refuses, please
332 try other publishers. If you're not sure whether a proposed license
333 is free, write to @email{licensing@@gnu.org}.
335 You can encourage commercial publishers to sell more free, copylefted
336 manuals and tutorials by buying them, and particularly by buying
337 copies from the publishers that paid for their writing or for major
338 improvements. Meanwhile, try to avoid buying non-free documentation
339 at all. Check the distribution terms of a manual before you buy it,
340 and insist that whoever seeks your business must respect your freedom.
341 Check the history of the book, and try to reward the publishers that
342 have paid or pay the authors to work on it.
344 The Free Software Foundation maintains a list of free documentation
345 published by other publishers, at
346 @url{http://www.fsf.org/doc/other-free-books.html}.
349 @unnumberedsec Contributors to @value{GDBN}
351 Richard Stallman was the original author of @value{GDBN}, and of many
352 other @sc{gnu} programs. Many others have contributed to its
353 development. This section attempts to credit major contributors. One
354 of the virtues of free software is that everyone is free to contribute
355 to it; with regret, we cannot actually acknowledge everyone here. The
356 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
357 blow-by-blow account.
359 Changes much prior to version 2.0 are lost in the mists of time.
362 @emph{Plea:} Additions to this section are particularly welcome. If you
363 or your friends (or enemies, to be evenhanded) have been unfairly
364 omitted from this list, we would like to add your names!
367 So that they may not regard their many labors as thankless, we
368 particularly thank those who shepherded @value{GDBN} through major
370 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
371 Jim Blandy (release 4.18);
372 Jason Molenda (release 4.17);
373 Stan Shebs (release 4.14);
374 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
375 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
376 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
377 Jim Kingdon (releases 3.5, 3.4, and 3.3);
378 and Randy Smith (releases 3.2, 3.1, and 3.0).
380 Richard Stallman, assisted at various times by Peter TerMaat, Chris
381 Hanson, and Richard Mlynarik, handled releases through 2.8.
383 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
384 in @value{GDBN}, with significant additional contributions from Per
385 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
386 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
387 much general update work leading to release 3.0).
389 @value{GDBN} uses the BFD subroutine library to examine multiple
390 object-file formats; BFD was a joint project of David V.
391 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
393 David Johnson wrote the original COFF support; Pace Willison did
394 the original support for encapsulated COFF.
396 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
398 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
399 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
401 Jean-Daniel Fekete contributed Sun 386i support.
402 Chris Hanson improved the HP9000 support.
403 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
404 David Johnson contributed Encore Umax support.
405 Jyrki Kuoppala contributed Altos 3068 support.
406 Jeff Law contributed HP PA and SOM support.
407 Keith Packard contributed NS32K support.
408 Doug Rabson contributed Acorn Risc Machine support.
409 Bob Rusk contributed Harris Nighthawk CX-UX support.
410 Chris Smith contributed Convex support (and Fortran debugging).
411 Jonathan Stone contributed Pyramid support.
412 Michael Tiemann contributed SPARC support.
413 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
414 Pace Willison contributed Intel 386 support.
415 Jay Vosburgh contributed Symmetry support.
416 Marko Mlinar contributed OpenRISC 1000 support.
418 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
420 Rich Schaefer and Peter Schauer helped with support of SunOS shared
423 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
424 about several machine instruction sets.
426 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
427 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
428 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
429 and RDI targets, respectively.
431 Brian Fox is the author of the readline libraries providing
432 command-line editing and command history.
434 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
435 Modula-2 support, and contributed the Languages chapter of this manual.
437 Fred Fish wrote most of the support for Unix System Vr4.
438 He also enhanced the command-completion support to cover C@t{++} overloaded
441 Hitachi America (now Renesas America), Ltd. sponsored the support for
442 H8/300, H8/500, and Super-H processors.
444 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
446 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
449 Toshiba sponsored the support for the TX39 Mips processor.
451 Matsushita sponsored the support for the MN10200 and MN10300 processors.
453 Fujitsu sponsored the support for SPARClite and FR30 processors.
455 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
458 Michael Snyder added support for tracepoints.
460 Stu Grossman wrote gdbserver.
462 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
463 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
465 The following people at the Hewlett-Packard Company contributed
466 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
467 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
468 compiler, and the Text User Interface (nee Terminal User Interface):
469 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
470 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
471 provided HP-specific information in this manual.
473 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
474 Robert Hoehne made significant contributions to the DJGPP port.
476 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
477 development since 1991. Cygnus engineers who have worked on @value{GDBN}
478 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
479 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
480 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
481 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
482 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
483 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
484 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
485 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
486 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
487 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
488 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
489 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
490 Zuhn have made contributions both large and small.
492 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
493 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
495 Jim Blandy added support for preprocessor macros, while working for Red
498 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
499 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
500 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
501 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
502 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
503 with the migration of old architectures to this new framework.
505 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
506 unwinder framework, this consisting of a fresh new design featuring
507 frame IDs, independent frame sniffers, and the sentinel frame. Mark
508 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
509 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
510 trad unwinders. The architecture-specific changes, each involving a
511 complete rewrite of the architecture's frame code, were carried out by
512 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
513 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
514 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
515 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
518 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
519 Tensilica, Inc.@: contributed support for Xtensa processors. Others
520 who have worked on the Xtensa port of @value{GDBN} in the past include
521 Steve Tjiang, John Newlin, and Scott Foehner.
524 @chapter A Sample @value{GDBN} Session
526 You can use this manual at your leisure to read all about @value{GDBN}.
527 However, a handful of commands are enough to get started using the
528 debugger. This chapter illustrates those commands.
531 In this sample session, we emphasize user input like this: @b{input},
532 to make it easier to pick out from the surrounding output.
535 @c FIXME: this example may not be appropriate for some configs, where
536 @c FIXME...primary interest is in remote use.
538 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
539 processor) exhibits the following bug: sometimes, when we change its
540 quote strings from the default, the commands used to capture one macro
541 definition within another stop working. In the following short @code{m4}
542 session, we define a macro @code{foo} which expands to @code{0000}; we
543 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
544 same thing. However, when we change the open quote string to
545 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
546 procedure fails to define a new synonym @code{baz}:
555 @b{define(bar,defn(`foo'))}
559 @b{changequote(<QUOTE>,<UNQUOTE>)}
561 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
564 m4: End of input: 0: fatal error: EOF in string
568 Let us use @value{GDBN} to try to see what is going on.
571 $ @b{@value{GDBP} m4}
572 @c FIXME: this falsifies the exact text played out, to permit smallbook
573 @c FIXME... format to come out better.
574 @value{GDBN} is free software and you are welcome to distribute copies
575 of it under certain conditions; type "show copying" to see
577 There is absolutely no warranty for @value{GDBN}; type "show warranty"
580 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
585 @value{GDBN} reads only enough symbol data to know where to find the
586 rest when needed; as a result, the first prompt comes up very quickly.
587 We now tell @value{GDBN} to use a narrower display width than usual, so
588 that examples fit in this manual.
591 (@value{GDBP}) @b{set width 70}
595 We need to see how the @code{m4} built-in @code{changequote} works.
596 Having looked at the source, we know the relevant subroutine is
597 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
598 @code{break} command.
601 (@value{GDBP}) @b{break m4_changequote}
602 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
606 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
607 control; as long as control does not reach the @code{m4_changequote}
608 subroutine, the program runs as usual:
611 (@value{GDBP}) @b{run}
612 Starting program: /work/Editorial/gdb/gnu/m4/m4
620 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
621 suspends execution of @code{m4}, displaying information about the
622 context where it stops.
625 @b{changequote(<QUOTE>,<UNQUOTE>)}
627 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
629 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
633 Now we use the command @code{n} (@code{next}) to advance execution to
634 the next line of the current function.
638 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
643 @code{set_quotes} looks like a promising subroutine. We can go into it
644 by using the command @code{s} (@code{step}) instead of @code{next}.
645 @code{step} goes to the next line to be executed in @emph{any}
646 subroutine, so it steps into @code{set_quotes}.
650 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
652 530 if (lquote != def_lquote)
656 The display that shows the subroutine where @code{m4} is now
657 suspended (and its arguments) is called a stack frame display. It
658 shows a summary of the stack. We can use the @code{backtrace}
659 command (which can also be spelled @code{bt}), to see where we are
660 in the stack as a whole: the @code{backtrace} command displays a
661 stack frame for each active subroutine.
664 (@value{GDBP}) @b{bt}
665 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
667 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
669 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
670 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
672 #4 0x79dc in expand_input () at macro.c:40
673 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
677 We step through a few more lines to see what happens. The first two
678 times, we can use @samp{s}; the next two times we use @code{n} to avoid
679 falling into the @code{xstrdup} subroutine.
683 0x3b5c 532 if (rquote != def_rquote)
685 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
686 def_lquote : xstrdup(lq);
688 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
691 538 len_lquote = strlen(rquote);
695 The last line displayed looks a little odd; we can examine the variables
696 @code{lquote} and @code{rquote} to see if they are in fact the new left
697 and right quotes we specified. We use the command @code{p}
698 (@code{print}) to see their values.
701 (@value{GDBP}) @b{p lquote}
702 $1 = 0x35d40 "<QUOTE>"
703 (@value{GDBP}) @b{p rquote}
704 $2 = 0x35d50 "<UNQUOTE>"
708 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
709 To look at some context, we can display ten lines of source
710 surrounding the current line with the @code{l} (@code{list}) command.
716 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
718 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
721 538 len_lquote = strlen(rquote);
722 539 len_rquote = strlen(lquote);
729 Let us step past the two lines that set @code{len_lquote} and
730 @code{len_rquote}, and then examine the values of those variables.
734 539 len_rquote = strlen(lquote);
737 (@value{GDBP}) @b{p len_lquote}
739 (@value{GDBP}) @b{p len_rquote}
744 That certainly looks wrong, assuming @code{len_lquote} and
745 @code{len_rquote} are meant to be the lengths of @code{lquote} and
746 @code{rquote} respectively. We can set them to better values using
747 the @code{p} command, since it can print the value of
748 any expression---and that expression can include subroutine calls and
752 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
754 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
759 Is that enough to fix the problem of using the new quotes with the
760 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
761 executing with the @code{c} (@code{continue}) command, and then try the
762 example that caused trouble initially:
768 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
775 Success! The new quotes now work just as well as the default ones. The
776 problem seems to have been just the two typos defining the wrong
777 lengths. We allow @code{m4} exit by giving it an EOF as input:
781 Program exited normally.
785 The message @samp{Program exited normally.} is from @value{GDBN}; it
786 indicates @code{m4} has finished executing. We can end our @value{GDBN}
787 session with the @value{GDBN} @code{quit} command.
790 (@value{GDBP}) @b{quit}
794 @chapter Getting In and Out of @value{GDBN}
796 This chapter discusses how to start @value{GDBN}, and how to get out of it.
800 type @samp{@value{GDBP}} to start @value{GDBN}.
802 type @kbd{quit} or @kbd{Ctrl-d} to exit.
806 * Invoking GDB:: How to start @value{GDBN}
807 * Quitting GDB:: How to quit @value{GDBN}
808 * Shell Commands:: How to use shell commands inside @value{GDBN}
809 * Logging Output:: How to log @value{GDBN}'s output to a file
813 @section Invoking @value{GDBN}
815 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
816 @value{GDBN} reads commands from the terminal until you tell it to exit.
818 You can also run @code{@value{GDBP}} with a variety of arguments and options,
819 to specify more of your debugging environment at the outset.
821 The command-line options described here are designed
822 to cover a variety of situations; in some environments, some of these
823 options may effectively be unavailable.
825 The most usual way to start @value{GDBN} is with one argument,
826 specifying an executable program:
829 @value{GDBP} @var{program}
833 You can also start with both an executable program and a core file
837 @value{GDBP} @var{program} @var{core}
840 You can, instead, specify a process ID as a second argument, if you want
841 to debug a running process:
844 @value{GDBP} @var{program} 1234
848 would attach @value{GDBN} to process @code{1234} (unless you also have a file
849 named @file{1234}; @value{GDBN} does check for a core file first).
851 Taking advantage of the second command-line argument requires a fairly
852 complete operating system; when you use @value{GDBN} as a remote
853 debugger attached to a bare board, there may not be any notion of
854 ``process'', and there is often no way to get a core dump. @value{GDBN}
855 will warn you if it is unable to attach or to read core dumps.
857 You can optionally have @code{@value{GDBP}} pass any arguments after the
858 executable file to the inferior using @code{--args}. This option stops
861 @value{GDBP} --args gcc -O2 -c foo.c
863 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
864 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
866 You can run @code{@value{GDBP}} without printing the front material, which describes
867 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
874 You can further control how @value{GDBN} starts up by using command-line
875 options. @value{GDBN} itself can remind you of the options available.
885 to display all available options and briefly describe their use
886 (@samp{@value{GDBP} -h} is a shorter equivalent).
888 All options and command line arguments you give are processed
889 in sequential order. The order makes a difference when the
890 @samp{-x} option is used.
894 * File Options:: Choosing files
895 * Mode Options:: Choosing modes
896 * Startup:: What @value{GDBN} does during startup
900 @subsection Choosing Files
902 When @value{GDBN} starts, it reads any arguments other than options as
903 specifying an executable file and core file (or process ID). This is
904 the same as if the arguments were specified by the @samp{-se} and
905 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
906 first argument that does not have an associated option flag as
907 equivalent to the @samp{-se} option followed by that argument; and the
908 second argument that does not have an associated option flag, if any, as
909 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
910 If the second argument begins with a decimal digit, @value{GDBN} will
911 first attempt to attach to it as a process, and if that fails, attempt
912 to open it as a corefile. If you have a corefile whose name begins with
913 a digit, you can prevent @value{GDBN} from treating it as a pid by
914 prefixing it with @file{./}, e.g.@: @file{./12345}.
916 If @value{GDBN} has not been configured to included core file support,
917 such as for most embedded targets, then it will complain about a second
918 argument and ignore it.
920 Many options have both long and short forms; both are shown in the
921 following list. @value{GDBN} also recognizes the long forms if you truncate
922 them, so long as enough of the option is present to be unambiguous.
923 (If you prefer, you can flag option arguments with @samp{--} rather
924 than @samp{-}, though we illustrate the more usual convention.)
926 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
927 @c way, both those who look for -foo and --foo in the index, will find
931 @item -symbols @var{file}
933 @cindex @code{--symbols}
935 Read symbol table from file @var{file}.
937 @item -exec @var{file}
939 @cindex @code{--exec}
941 Use file @var{file} as the executable file to execute when appropriate,
942 and for examining pure data in conjunction with a core dump.
946 Read symbol table from file @var{file} and use it as the executable
949 @item -core @var{file}
951 @cindex @code{--core}
953 Use file @var{file} as a core dump to examine.
955 @item -pid @var{number}
956 @itemx -p @var{number}
959 Connect to process ID @var{number}, as with the @code{attach} command.
961 @item -command @var{file}
963 @cindex @code{--command}
965 Execute @value{GDBN} commands from file @var{file}. @xref{Command
966 Files,, Command files}.
968 @item -eval-command @var{command}
969 @itemx -ex @var{command}
970 @cindex @code{--eval-command}
972 Execute a single @value{GDBN} command.
974 This option may be used multiple times to call multiple commands. It may
975 also be interleaved with @samp{-command} as required.
978 @value{GDBP} -ex 'target sim' -ex 'load' \
979 -x setbreakpoints -ex 'run' a.out
982 @item -directory @var{directory}
983 @itemx -d @var{directory}
984 @cindex @code{--directory}
986 Add @var{directory} to the path to search for source and script files.
990 @cindex @code{--readnow}
992 Read each symbol file's entire symbol table immediately, rather than
993 the default, which is to read it incrementally as it is needed.
994 This makes startup slower, but makes future operations faster.
999 @subsection Choosing Modes
1001 You can run @value{GDBN} in various alternative modes---for example, in
1002 batch mode or quiet mode.
1009 Do not execute commands found in any initialization files. Normally,
1010 @value{GDBN} executes the commands in these files after all the command
1011 options and arguments have been processed. @xref{Command Files,,Command
1017 @cindex @code{--quiet}
1018 @cindex @code{--silent}
1020 ``Quiet''. Do not print the introductory and copyright messages. These
1021 messages are also suppressed in batch mode.
1024 @cindex @code{--batch}
1025 Run in batch mode. Exit with status @code{0} after processing all the
1026 command files specified with @samp{-x} (and all commands from
1027 initialization files, if not inhibited with @samp{-n}). Exit with
1028 nonzero status if an error occurs in executing the @value{GDBN} commands
1029 in the command files.
1031 Batch mode may be useful for running @value{GDBN} as a filter, for
1032 example to download and run a program on another computer; in order to
1033 make this more useful, the message
1036 Program exited normally.
1040 (which is ordinarily issued whenever a program running under
1041 @value{GDBN} control terminates) is not issued when running in batch
1045 @cindex @code{--batch-silent}
1046 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1047 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1048 unaffected). This is much quieter than @samp{-silent} and would be useless
1049 for an interactive session.
1051 This is particularly useful when using targets that give @samp{Loading section}
1052 messages, for example.
1054 Note that targets that give their output via @value{GDBN}, as opposed to
1055 writing directly to @code{stdout}, will also be made silent.
1057 @item -return-child-result
1058 @cindex @code{--return-child-result}
1059 The return code from @value{GDBN} will be the return code from the child
1060 process (the process being debugged), with the following exceptions:
1064 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1065 internal error. In this case the exit code is the same as it would have been
1066 without @samp{-return-child-result}.
1068 The user quits with an explicit value. E.g., @samp{quit 1}.
1070 The child process never runs, or is not allowed to terminate, in which case
1071 the exit code will be -1.
1074 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1075 when @value{GDBN} is being used as a remote program loader or simulator
1080 @cindex @code{--nowindows}
1082 ``No windows''. If @value{GDBN} comes with a graphical user interface
1083 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1084 interface. If no GUI is available, this option has no effect.
1088 @cindex @code{--windows}
1090 If @value{GDBN} includes a GUI, then this option requires it to be
1093 @item -cd @var{directory}
1095 Run @value{GDBN} using @var{directory} as its working directory,
1096 instead of the current directory.
1100 @cindex @code{--fullname}
1102 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1103 subprocess. It tells @value{GDBN} to output the full file name and line
1104 number in a standard, recognizable fashion each time a stack frame is
1105 displayed (which includes each time your program stops). This
1106 recognizable format looks like two @samp{\032} characters, followed by
1107 the file name, line number and character position separated by colons,
1108 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1109 @samp{\032} characters as a signal to display the source code for the
1113 @cindex @code{--epoch}
1114 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1115 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1116 routines so as to allow Epoch to display values of expressions in a
1119 @item -annotate @var{level}
1120 @cindex @code{--annotate}
1121 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1122 effect is identical to using @samp{set annotate @var{level}}
1123 (@pxref{Annotations}). The annotation @var{level} controls how much
1124 information @value{GDBN} prints together with its prompt, values of
1125 expressions, source lines, and other types of output. Level 0 is the
1126 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1127 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1128 that control @value{GDBN}, and level 2 has been deprecated.
1130 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1134 @cindex @code{--args}
1135 Change interpretation of command line so that arguments following the
1136 executable file are passed as command line arguments to the inferior.
1137 This option stops option processing.
1139 @item -baud @var{bps}
1141 @cindex @code{--baud}
1143 Set the line speed (baud rate or bits per second) of any serial
1144 interface used by @value{GDBN} for remote debugging.
1146 @item -l @var{timeout}
1148 Set the timeout (in seconds) of any communication used by @value{GDBN}
1149 for remote debugging.
1151 @item -tty @var{device}
1152 @itemx -t @var{device}
1153 @cindex @code{--tty}
1155 Run using @var{device} for your program's standard input and output.
1156 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1158 @c resolve the situation of these eventually
1160 @cindex @code{--tui}
1161 Activate the @dfn{Text User Interface} when starting. The Text User
1162 Interface manages several text windows on the terminal, showing
1163 source, assembly, registers and @value{GDBN} command outputs
1164 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1165 Text User Interface can be enabled by invoking the program
1166 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1167 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1170 @c @cindex @code{--xdb}
1171 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1172 @c For information, see the file @file{xdb_trans.html}, which is usually
1173 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1176 @item -interpreter @var{interp}
1177 @cindex @code{--interpreter}
1178 Use the interpreter @var{interp} for interface with the controlling
1179 program or device. This option is meant to be set by programs which
1180 communicate with @value{GDBN} using it as a back end.
1181 @xref{Interpreters, , Command Interpreters}.
1183 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1184 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1185 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1186 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1187 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1188 @sc{gdb/mi} interfaces are no longer supported.
1191 @cindex @code{--write}
1192 Open the executable and core files for both reading and writing. This
1193 is equivalent to the @samp{set write on} command inside @value{GDBN}
1197 @cindex @code{--statistics}
1198 This option causes @value{GDBN} to print statistics about time and
1199 memory usage after it completes each command and returns to the prompt.
1202 @cindex @code{--version}
1203 This option causes @value{GDBN} to print its version number and
1204 no-warranty blurb, and exit.
1209 @subsection What @value{GDBN} Does During Startup
1210 @cindex @value{GDBN} startup
1212 Here's the description of what @value{GDBN} does during session startup:
1216 Sets up the command interpreter as specified by the command line
1217 (@pxref{Mode Options, interpreter}).
1221 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1222 DOS/Windows systems, the home directory is the one pointed to by the
1223 @code{HOME} environment variable.} and executes all the commands in
1227 Processes command line options and operands.
1230 Reads and executes the commands from init file (if any) in the current
1231 working directory. This is only done if the current directory is
1232 different from your home directory. Thus, you can have more than one
1233 init file, one generic in your home directory, and another, specific
1234 to the program you are debugging, in the directory where you invoke
1238 Reads command files specified by the @samp{-x} option. @xref{Command
1239 Files}, for more details about @value{GDBN} command files.
1242 Reads the command history recorded in the @dfn{history file}.
1243 @xref{Command History}, for more details about the command history and the
1244 files where @value{GDBN} records it.
1247 Init files use the same syntax as @dfn{command files} (@pxref{Command
1248 Files}) and are processed by @value{GDBN} in the same way. The init
1249 file in your home directory can set options (such as @samp{set
1250 complaints}) that affect subsequent processing of command line options
1251 and operands. Init files are not executed if you use the @samp{-nx}
1252 option (@pxref{Mode Options, ,Choosing Modes}).
1254 @cindex init file name
1255 @cindex @file{.gdbinit}
1256 @cindex @file{gdb.ini}
1257 The @value{GDBN} init files are normally called @file{.gdbinit}.
1258 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1259 the limitations of file names imposed by DOS filesystems. The Windows
1260 ports of @value{GDBN} use the standard name, but if they find a
1261 @file{gdb.ini} file, they warn you about that and suggest to rename
1262 the file to the standard name.
1266 @section Quitting @value{GDBN}
1267 @cindex exiting @value{GDBN}
1268 @cindex leaving @value{GDBN}
1271 @kindex quit @r{[}@var{expression}@r{]}
1272 @kindex q @r{(@code{quit})}
1273 @item quit @r{[}@var{expression}@r{]}
1275 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1276 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1277 do not supply @var{expression}, @value{GDBN} will terminate normally;
1278 otherwise it will terminate using the result of @var{expression} as the
1283 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1284 terminates the action of any @value{GDBN} command that is in progress and
1285 returns to @value{GDBN} command level. It is safe to type the interrupt
1286 character at any time because @value{GDBN} does not allow it to take effect
1287 until a time when it is safe.
1289 If you have been using @value{GDBN} to control an attached process or
1290 device, you can release it with the @code{detach} command
1291 (@pxref{Attach, ,Debugging an Already-running Process}).
1293 @node Shell Commands
1294 @section Shell Commands
1296 If you need to execute occasional shell commands during your
1297 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1298 just use the @code{shell} command.
1302 @cindex shell escape
1303 @item shell @var{command string}
1304 Invoke a standard shell to execute @var{command string}.
1305 If it exists, the environment variable @code{SHELL} determines which
1306 shell to run. Otherwise @value{GDBN} uses the default shell
1307 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1310 The utility @code{make} is often needed in development environments.
1311 You do not have to use the @code{shell} command for this purpose in
1316 @cindex calling make
1317 @item make @var{make-args}
1318 Execute the @code{make} program with the specified
1319 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1322 @node Logging Output
1323 @section Logging Output
1324 @cindex logging @value{GDBN} output
1325 @cindex save @value{GDBN} output to a file
1327 You may want to save the output of @value{GDBN} commands to a file.
1328 There are several commands to control @value{GDBN}'s logging.
1332 @item set logging on
1334 @item set logging off
1336 @cindex logging file name
1337 @item set logging file @var{file}
1338 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1339 @item set logging overwrite [on|off]
1340 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1341 you want @code{set logging on} to overwrite the logfile instead.
1342 @item set logging redirect [on|off]
1343 By default, @value{GDBN} output will go to both the terminal and the logfile.
1344 Set @code{redirect} if you want output to go only to the log file.
1345 @kindex show logging
1347 Show the current values of the logging settings.
1351 @chapter @value{GDBN} Commands
1353 You can abbreviate a @value{GDBN} command to the first few letters of the command
1354 name, if that abbreviation is unambiguous; and you can repeat certain
1355 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1356 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1357 show you the alternatives available, if there is more than one possibility).
1360 * Command Syntax:: How to give commands to @value{GDBN}
1361 * Completion:: Command completion
1362 * Help:: How to ask @value{GDBN} for help
1365 @node Command Syntax
1366 @section Command Syntax
1368 A @value{GDBN} command is a single line of input. There is no limit on
1369 how long it can be. It starts with a command name, which is followed by
1370 arguments whose meaning depends on the command name. For example, the
1371 command @code{step} accepts an argument which is the number of times to
1372 step, as in @samp{step 5}. You can also use the @code{step} command
1373 with no arguments. Some commands do not allow any arguments.
1375 @cindex abbreviation
1376 @value{GDBN} command names may always be truncated if that abbreviation is
1377 unambiguous. Other possible command abbreviations are listed in the
1378 documentation for individual commands. In some cases, even ambiguous
1379 abbreviations are allowed; for example, @code{s} is specially defined as
1380 equivalent to @code{step} even though there are other commands whose
1381 names start with @code{s}. You can test abbreviations by using them as
1382 arguments to the @code{help} command.
1384 @cindex repeating commands
1385 @kindex RET @r{(repeat last command)}
1386 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1387 repeat the previous command. Certain commands (for example, @code{run})
1388 will not repeat this way; these are commands whose unintentional
1389 repetition might cause trouble and which you are unlikely to want to
1390 repeat. User-defined commands can disable this feature; see
1391 @ref{Define, dont-repeat}.
1393 The @code{list} and @code{x} commands, when you repeat them with
1394 @key{RET}, construct new arguments rather than repeating
1395 exactly as typed. This permits easy scanning of source or memory.
1397 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1398 output, in a way similar to the common utility @code{more}
1399 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1400 @key{RET} too many in this situation, @value{GDBN} disables command
1401 repetition after any command that generates this sort of display.
1403 @kindex # @r{(a comment)}
1405 Any text from a @kbd{#} to the end of the line is a comment; it does
1406 nothing. This is useful mainly in command files (@pxref{Command
1407 Files,,Command Files}).
1409 @cindex repeating command sequences
1410 @kindex Ctrl-o @r{(operate-and-get-next)}
1411 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1412 commands. This command accepts the current line, like @key{RET}, and
1413 then fetches the next line relative to the current line from the history
1417 @section Command Completion
1420 @cindex word completion
1421 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1422 only one possibility; it can also show you what the valid possibilities
1423 are for the next word in a command, at any time. This works for @value{GDBN}
1424 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1426 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1427 of a word. If there is only one possibility, @value{GDBN} fills in the
1428 word, and waits for you to finish the command (or press @key{RET} to
1429 enter it). For example, if you type
1431 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1432 @c complete accuracy in these examples; space introduced for clarity.
1433 @c If texinfo enhancements make it unnecessary, it would be nice to
1434 @c replace " @key" by "@key" in the following...
1436 (@value{GDBP}) info bre @key{TAB}
1440 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1441 the only @code{info} subcommand beginning with @samp{bre}:
1444 (@value{GDBP}) info breakpoints
1448 You can either press @key{RET} at this point, to run the @code{info
1449 breakpoints} command, or backspace and enter something else, if
1450 @samp{breakpoints} does not look like the command you expected. (If you
1451 were sure you wanted @code{info breakpoints} in the first place, you
1452 might as well just type @key{RET} immediately after @samp{info bre},
1453 to exploit command abbreviations rather than command completion).
1455 If there is more than one possibility for the next word when you press
1456 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1457 characters and try again, or just press @key{TAB} a second time;
1458 @value{GDBN} displays all the possible completions for that word. For
1459 example, you might want to set a breakpoint on a subroutine whose name
1460 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1461 just sounds the bell. Typing @key{TAB} again displays all the
1462 function names in your program that begin with those characters, for
1466 (@value{GDBP}) b make_ @key{TAB}
1467 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1468 make_a_section_from_file make_environ
1469 make_abs_section make_function_type
1470 make_blockvector make_pointer_type
1471 make_cleanup make_reference_type
1472 make_command make_symbol_completion_list
1473 (@value{GDBP}) b make_
1477 After displaying the available possibilities, @value{GDBN} copies your
1478 partial input (@samp{b make_} in the example) so you can finish the
1481 If you just want to see the list of alternatives in the first place, you
1482 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1483 means @kbd{@key{META} ?}. You can type this either by holding down a
1484 key designated as the @key{META} shift on your keyboard (if there is
1485 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1487 @cindex quotes in commands
1488 @cindex completion of quoted strings
1489 Sometimes the string you need, while logically a ``word'', may contain
1490 parentheses or other characters that @value{GDBN} normally excludes from
1491 its notion of a word. To permit word completion to work in this
1492 situation, you may enclose words in @code{'} (single quote marks) in
1493 @value{GDBN} commands.
1495 The most likely situation where you might need this is in typing the
1496 name of a C@t{++} function. This is because C@t{++} allows function
1497 overloading (multiple definitions of the same function, distinguished
1498 by argument type). For example, when you want to set a breakpoint you
1499 may need to distinguish whether you mean the version of @code{name}
1500 that takes an @code{int} parameter, @code{name(int)}, or the version
1501 that takes a @code{float} parameter, @code{name(float)}. To use the
1502 word-completion facilities in this situation, type a single quote
1503 @code{'} at the beginning of the function name. This alerts
1504 @value{GDBN} that it may need to consider more information than usual
1505 when you press @key{TAB} or @kbd{M-?} to request word completion:
1508 (@value{GDBP}) b 'bubble( @kbd{M-?}
1509 bubble(double,double) bubble(int,int)
1510 (@value{GDBP}) b 'bubble(
1513 In some cases, @value{GDBN} can tell that completing a name requires using
1514 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1515 completing as much as it can) if you do not type the quote in the first
1519 (@value{GDBP}) b bub @key{TAB}
1520 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1521 (@value{GDBP}) b 'bubble(
1525 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1526 you have not yet started typing the argument list when you ask for
1527 completion on an overloaded symbol.
1529 For more information about overloaded functions, see @ref{C Plus Plus
1530 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1531 overload-resolution off} to disable overload resolution;
1532 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1534 @cindex completion of structure field names
1535 @cindex structure field name completion
1536 @cindex completion of union field names
1537 @cindex union field name completion
1538 When completing in an expression which looks up a field in a
1539 structure, @value{GDBN} also tries@footnote{The completer can be
1540 confused by certain kinds of invalid expressions. Also, it only
1541 examines the static type of the expression, not the dynamic type.} to
1542 limit completions to the field names available in the type of the
1546 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1547 magic to_delete to_fputs to_put to_rewind
1548 to_data to_flush to_isatty to_read to_write
1552 This is because the @code{gdb_stdout} is a variable of the type
1553 @code{struct ui_file} that is defined in @value{GDBN} sources as
1560 ui_file_flush_ftype *to_flush;
1561 ui_file_write_ftype *to_write;
1562 ui_file_fputs_ftype *to_fputs;
1563 ui_file_read_ftype *to_read;
1564 ui_file_delete_ftype *to_delete;
1565 ui_file_isatty_ftype *to_isatty;
1566 ui_file_rewind_ftype *to_rewind;
1567 ui_file_put_ftype *to_put;
1574 @section Getting Help
1575 @cindex online documentation
1578 You can always ask @value{GDBN} itself for information on its commands,
1579 using the command @code{help}.
1582 @kindex h @r{(@code{help})}
1585 You can use @code{help} (abbreviated @code{h}) with no arguments to
1586 display a short list of named classes of commands:
1590 List of classes of commands:
1592 aliases -- Aliases of other commands
1593 breakpoints -- Making program stop at certain points
1594 data -- Examining data
1595 files -- Specifying and examining files
1596 internals -- Maintenance commands
1597 obscure -- Obscure features
1598 running -- Running the program
1599 stack -- Examining the stack
1600 status -- Status inquiries
1601 support -- Support facilities
1602 tracepoints -- Tracing of program execution without
1603 stopping the program
1604 user-defined -- User-defined commands
1606 Type "help" followed by a class name for a list of
1607 commands in that class.
1608 Type "help" followed by command name for full
1610 Command name abbreviations are allowed if unambiguous.
1613 @c the above line break eliminates huge line overfull...
1615 @item help @var{class}
1616 Using one of the general help classes as an argument, you can get a
1617 list of the individual commands in that class. For example, here is the
1618 help display for the class @code{status}:
1621 (@value{GDBP}) help status
1626 @c Line break in "show" line falsifies real output, but needed
1627 @c to fit in smallbook page size.
1628 info -- Generic command for showing things
1629 about the program being debugged
1630 show -- Generic command for showing things
1633 Type "help" followed by command name for full
1635 Command name abbreviations are allowed if unambiguous.
1639 @item help @var{command}
1640 With a command name as @code{help} argument, @value{GDBN} displays a
1641 short paragraph on how to use that command.
1644 @item apropos @var{args}
1645 The @code{apropos} command searches through all of the @value{GDBN}
1646 commands, and their documentation, for the regular expression specified in
1647 @var{args}. It prints out all matches found. For example:
1658 set symbol-reloading -- Set dynamic symbol table reloading
1659 multiple times in one run
1660 show symbol-reloading -- Show dynamic symbol table reloading
1661 multiple times in one run
1666 @item complete @var{args}
1667 The @code{complete @var{args}} command lists all the possible completions
1668 for the beginning of a command. Use @var{args} to specify the beginning of the
1669 command you want completed. For example:
1675 @noindent results in:
1686 @noindent This is intended for use by @sc{gnu} Emacs.
1689 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1690 and @code{show} to inquire about the state of your program, or the state
1691 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1692 manual introduces each of them in the appropriate context. The listings
1693 under @code{info} and under @code{show} in the Index point to
1694 all the sub-commands. @xref{Index}.
1699 @kindex i @r{(@code{info})}
1701 This command (abbreviated @code{i}) is for describing the state of your
1702 program. For example, you can show the arguments passed to a function
1703 with @code{info args}, list the registers currently in use with @code{info
1704 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1705 You can get a complete list of the @code{info} sub-commands with
1706 @w{@code{help info}}.
1710 You can assign the result of an expression to an environment variable with
1711 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1712 @code{set prompt $}.
1716 In contrast to @code{info}, @code{show} is for describing the state of
1717 @value{GDBN} itself.
1718 You can change most of the things you can @code{show}, by using the
1719 related command @code{set}; for example, you can control what number
1720 system is used for displays with @code{set radix}, or simply inquire
1721 which is currently in use with @code{show radix}.
1724 To display all the settable parameters and their current
1725 values, you can use @code{show} with no arguments; you may also use
1726 @code{info set}. Both commands produce the same display.
1727 @c FIXME: "info set" violates the rule that "info" is for state of
1728 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1729 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1733 Here are three miscellaneous @code{show} subcommands, all of which are
1734 exceptional in lacking corresponding @code{set} commands:
1737 @kindex show version
1738 @cindex @value{GDBN} version number
1740 Show what version of @value{GDBN} is running. You should include this
1741 information in @value{GDBN} bug-reports. If multiple versions of
1742 @value{GDBN} are in use at your site, you may need to determine which
1743 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1744 commands are introduced, and old ones may wither away. Also, many
1745 system vendors ship variant versions of @value{GDBN}, and there are
1746 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1747 The version number is the same as the one announced when you start
1750 @kindex show copying
1751 @kindex info copying
1752 @cindex display @value{GDBN} copyright
1755 Display information about permission for copying @value{GDBN}.
1757 @kindex show warranty
1758 @kindex info warranty
1760 @itemx info warranty
1761 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1762 if your version of @value{GDBN} comes with one.
1767 @chapter Running Programs Under @value{GDBN}
1769 When you run a program under @value{GDBN}, you must first generate
1770 debugging information when you compile it.
1772 You may start @value{GDBN} with its arguments, if any, in an environment
1773 of your choice. If you are doing native debugging, you may redirect
1774 your program's input and output, debug an already running process, or
1775 kill a child process.
1778 * Compilation:: Compiling for debugging
1779 * Starting:: Starting your program
1780 * Arguments:: Your program's arguments
1781 * Environment:: Your program's environment
1783 * Working Directory:: Your program's working directory
1784 * Input/Output:: Your program's input and output
1785 * Attach:: Debugging an already-running process
1786 * Kill Process:: Killing the child process
1788 * Threads:: Debugging programs with multiple threads
1789 * Processes:: Debugging programs with multiple processes
1790 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1794 @section Compiling for Debugging
1796 In order to debug a program effectively, you need to generate
1797 debugging information when you compile it. This debugging information
1798 is stored in the object file; it describes the data type of each
1799 variable or function and the correspondence between source line numbers
1800 and addresses in the executable code.
1802 To request debugging information, specify the @samp{-g} option when you run
1805 Programs that are to be shipped to your customers are compiled with
1806 optimizations, using the @samp{-O} compiler option. However, many
1807 compilers are unable to handle the @samp{-g} and @samp{-O} options
1808 together. Using those compilers, you cannot generate optimized
1809 executables containing debugging information.
1811 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1812 without @samp{-O}, making it possible to debug optimized code. We
1813 recommend that you @emph{always} use @samp{-g} whenever you compile a
1814 program. You may think your program is correct, but there is no sense
1815 in pushing your luck.
1817 @cindex optimized code, debugging
1818 @cindex debugging optimized code
1819 When you debug a program compiled with @samp{-g -O}, remember that the
1820 optimizer is rearranging your code; the debugger shows you what is
1821 really there. Do not be too surprised when the execution path does not
1822 exactly match your source file! An extreme example: if you define a
1823 variable, but never use it, @value{GDBN} never sees that
1824 variable---because the compiler optimizes it out of existence.
1826 Some things do not work as well with @samp{-g -O} as with just
1827 @samp{-g}, particularly on machines with instruction scheduling. If in
1828 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1829 please report it to us as a bug (including a test case!).
1830 @xref{Variables}, for more information about debugging optimized code.
1832 Older versions of the @sc{gnu} C compiler permitted a variant option
1833 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1834 format; if your @sc{gnu} C compiler has this option, do not use it.
1836 @value{GDBN} knows about preprocessor macros and can show you their
1837 expansion (@pxref{Macros}). Most compilers do not include information
1838 about preprocessor macros in the debugging information if you specify
1839 the @option{-g} flag alone, because this information is rather large.
1840 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1841 provides macro information if you specify the options
1842 @option{-gdwarf-2} and @option{-g3}; the former option requests
1843 debugging information in the Dwarf 2 format, and the latter requests
1844 ``extra information''. In the future, we hope to find more compact
1845 ways to represent macro information, so that it can be included with
1850 @section Starting your Program
1856 @kindex r @r{(@code{run})}
1859 Use the @code{run} command to start your program under @value{GDBN}.
1860 You must first specify the program name (except on VxWorks) with an
1861 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1862 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1863 (@pxref{Files, ,Commands to Specify Files}).
1867 If you are running your program in an execution environment that
1868 supports processes, @code{run} creates an inferior process and makes
1869 that process run your program. In some environments without processes,
1870 @code{run} jumps to the start of your program. Other targets,
1871 like @samp{remote}, are always running. If you get an error
1872 message like this one:
1875 The "remote" target does not support "run".
1876 Try "help target" or "continue".
1880 then use @code{continue} to run your program. You may need @code{load}
1881 first (@pxref{load}).
1883 The execution of a program is affected by certain information it
1884 receives from its superior. @value{GDBN} provides ways to specify this
1885 information, which you must do @emph{before} starting your program. (You
1886 can change it after starting your program, but such changes only affect
1887 your program the next time you start it.) This information may be
1888 divided into four categories:
1891 @item The @emph{arguments.}
1892 Specify the arguments to give your program as the arguments of the
1893 @code{run} command. If a shell is available on your target, the shell
1894 is used to pass the arguments, so that you may use normal conventions
1895 (such as wildcard expansion or variable substitution) in describing
1897 In Unix systems, you can control which shell is used with the
1898 @code{SHELL} environment variable.
1899 @xref{Arguments, ,Your Program's Arguments}.
1901 @item The @emph{environment.}
1902 Your program normally inherits its environment from @value{GDBN}, but you can
1903 use the @value{GDBN} commands @code{set environment} and @code{unset
1904 environment} to change parts of the environment that affect
1905 your program. @xref{Environment, ,Your Program's Environment}.
1907 @item The @emph{working directory.}
1908 Your program inherits its working directory from @value{GDBN}. You can set
1909 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1910 @xref{Working Directory, ,Your Program's Working Directory}.
1912 @item The @emph{standard input and output.}
1913 Your program normally uses the same device for standard input and
1914 standard output as @value{GDBN} is using. You can redirect input and output
1915 in the @code{run} command line, or you can use the @code{tty} command to
1916 set a different device for your program.
1917 @xref{Input/Output, ,Your Program's Input and Output}.
1920 @emph{Warning:} While input and output redirection work, you cannot use
1921 pipes to pass the output of the program you are debugging to another
1922 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1926 When you issue the @code{run} command, your program begins to execute
1927 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1928 of how to arrange for your program to stop. Once your program has
1929 stopped, you may call functions in your program, using the @code{print}
1930 or @code{call} commands. @xref{Data, ,Examining Data}.
1932 If the modification time of your symbol file has changed since the last
1933 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1934 table, and reads it again. When it does this, @value{GDBN} tries to retain
1935 your current breakpoints.
1940 @cindex run to main procedure
1941 The name of the main procedure can vary from language to language.
1942 With C or C@t{++}, the main procedure name is always @code{main}, but
1943 other languages such as Ada do not require a specific name for their
1944 main procedure. The debugger provides a convenient way to start the
1945 execution of the program and to stop at the beginning of the main
1946 procedure, depending on the language used.
1948 The @samp{start} command does the equivalent of setting a temporary
1949 breakpoint at the beginning of the main procedure and then invoking
1950 the @samp{run} command.
1952 @cindex elaboration phase
1953 Some programs contain an @dfn{elaboration} phase where some startup code is
1954 executed before the main procedure is called. This depends on the
1955 languages used to write your program. In C@t{++}, for instance,
1956 constructors for static and global objects are executed before
1957 @code{main} is called. It is therefore possible that the debugger stops
1958 before reaching the main procedure. However, the temporary breakpoint
1959 will remain to halt execution.
1961 Specify the arguments to give to your program as arguments to the
1962 @samp{start} command. These arguments will be given verbatim to the
1963 underlying @samp{run} command. Note that the same arguments will be
1964 reused if no argument is provided during subsequent calls to
1965 @samp{start} or @samp{run}.
1967 It is sometimes necessary to debug the program during elaboration. In
1968 these cases, using the @code{start} command would stop the execution of
1969 your program too late, as the program would have already completed the
1970 elaboration phase. Under these circumstances, insert breakpoints in your
1971 elaboration code before running your program.
1973 @kindex set exec-wrapper
1974 @item set exec-wrapper @var{wrapper}
1975 @itemx show exec-wrapper
1976 @itemx unset exec-wrapper
1977 When @samp{exec-wrapper} is set, the specified wrapper is used to
1978 launch programs for debugging. @value{GDBN} starts your program
1979 with a shell command of the form @kbd{exec @var{wrapper}
1980 @var{program}}. Quoting is added to @var{program} and its
1981 arguments, but not to @var{wrapper}, so you should add quotes if
1982 appropriate for your shell. The wrapper runs until it executes
1983 your program, and then @value{GDBN} takes control.
1985 You can use any program that eventually calls @code{execve} with
1986 its arguments as a wrapper. Several standard Unix utilities do
1987 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1988 with @code{exec "$@@"} will also work.
1990 For example, you can use @code{env} to pass an environment variable to
1991 the debugged program, without setting the variable in your shell's
1995 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1999 This command is available when debugging locally on most targets, excluding
2000 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2005 @section Your Program's Arguments
2007 @cindex arguments (to your program)
2008 The arguments to your program can be specified by the arguments of the
2010 They are passed to a shell, which expands wildcard characters and
2011 performs redirection of I/O, and thence to your program. Your
2012 @code{SHELL} environment variable (if it exists) specifies what shell
2013 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2014 the default shell (@file{/bin/sh} on Unix).
2016 On non-Unix systems, the program is usually invoked directly by
2017 @value{GDBN}, which emulates I/O redirection via the appropriate system
2018 calls, and the wildcard characters are expanded by the startup code of
2019 the program, not by the shell.
2021 @code{run} with no arguments uses the same arguments used by the previous
2022 @code{run}, or those set by the @code{set args} command.
2027 Specify the arguments to be used the next time your program is run. If
2028 @code{set args} has no arguments, @code{run} executes your program
2029 with no arguments. Once you have run your program with arguments,
2030 using @code{set args} before the next @code{run} is the only way to run
2031 it again without arguments.
2035 Show the arguments to give your program when it is started.
2039 @section Your Program's Environment
2041 @cindex environment (of your program)
2042 The @dfn{environment} consists of a set of environment variables and
2043 their values. Environment variables conventionally record such things as
2044 your user name, your home directory, your terminal type, and your search
2045 path for programs to run. Usually you set up environment variables with
2046 the shell and they are inherited by all the other programs you run. When
2047 debugging, it can be useful to try running your program with a modified
2048 environment without having to start @value{GDBN} over again.
2052 @item path @var{directory}
2053 Add @var{directory} to the front of the @code{PATH} environment variable
2054 (the search path for executables) that will be passed to your program.
2055 The value of @code{PATH} used by @value{GDBN} does not change.
2056 You may specify several directory names, separated by whitespace or by a
2057 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2058 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2059 is moved to the front, so it is searched sooner.
2061 You can use the string @samp{$cwd} to refer to whatever is the current
2062 working directory at the time @value{GDBN} searches the path. If you
2063 use @samp{.} instead, it refers to the directory where you executed the
2064 @code{path} command. @value{GDBN} replaces @samp{.} in the
2065 @var{directory} argument (with the current path) before adding
2066 @var{directory} to the search path.
2067 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2068 @c document that, since repeating it would be a no-op.
2072 Display the list of search paths for executables (the @code{PATH}
2073 environment variable).
2075 @kindex show environment
2076 @item show environment @r{[}@var{varname}@r{]}
2077 Print the value of environment variable @var{varname} to be given to
2078 your program when it starts. If you do not supply @var{varname},
2079 print the names and values of all environment variables to be given to
2080 your program. You can abbreviate @code{environment} as @code{env}.
2082 @kindex set environment
2083 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2084 Set environment variable @var{varname} to @var{value}. The value
2085 changes for your program only, not for @value{GDBN} itself. @var{value} may
2086 be any string; the values of environment variables are just strings, and
2087 any interpretation is supplied by your program itself. The @var{value}
2088 parameter is optional; if it is eliminated, the variable is set to a
2090 @c "any string" here does not include leading, trailing
2091 @c blanks. Gnu asks: does anyone care?
2093 For example, this command:
2100 tells the debugged program, when subsequently run, that its user is named
2101 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2102 are not actually required.)
2104 @kindex unset environment
2105 @item unset environment @var{varname}
2106 Remove variable @var{varname} from the environment to be passed to your
2107 program. This is different from @samp{set env @var{varname} =};
2108 @code{unset environment} removes the variable from the environment,
2109 rather than assigning it an empty value.
2112 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2114 by your @code{SHELL} environment variable if it exists (or
2115 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2116 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2117 @file{.bashrc} for BASH---any variables you set in that file affect
2118 your program. You may wish to move setting of environment variables to
2119 files that are only run when you sign on, such as @file{.login} or
2122 @node Working Directory
2123 @section Your Program's Working Directory
2125 @cindex working directory (of your program)
2126 Each time you start your program with @code{run}, it inherits its
2127 working directory from the current working directory of @value{GDBN}.
2128 The @value{GDBN} working directory is initially whatever it inherited
2129 from its parent process (typically the shell), but you can specify a new
2130 working directory in @value{GDBN} with the @code{cd} command.
2132 The @value{GDBN} working directory also serves as a default for the commands
2133 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2138 @cindex change working directory
2139 @item cd @var{directory}
2140 Set the @value{GDBN} working directory to @var{directory}.
2144 Print the @value{GDBN} working directory.
2147 It is generally impossible to find the current working directory of
2148 the process being debugged (since a program can change its directory
2149 during its run). If you work on a system where @value{GDBN} is
2150 configured with the @file{/proc} support, you can use the @code{info
2151 proc} command (@pxref{SVR4 Process Information}) to find out the
2152 current working directory of the debuggee.
2155 @section Your Program's Input and Output
2160 By default, the program you run under @value{GDBN} does input and output to
2161 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2162 to its own terminal modes to interact with you, but it records the terminal
2163 modes your program was using and switches back to them when you continue
2164 running your program.
2167 @kindex info terminal
2169 Displays information recorded by @value{GDBN} about the terminal modes your
2173 You can redirect your program's input and/or output using shell
2174 redirection with the @code{run} command. For example,
2181 starts your program, diverting its output to the file @file{outfile}.
2184 @cindex controlling terminal
2185 Another way to specify where your program should do input and output is
2186 with the @code{tty} command. This command accepts a file name as
2187 argument, and causes this file to be the default for future @code{run}
2188 commands. It also resets the controlling terminal for the child
2189 process, for future @code{run} commands. For example,
2196 directs that processes started with subsequent @code{run} commands
2197 default to do input and output on the terminal @file{/dev/ttyb} and have
2198 that as their controlling terminal.
2200 An explicit redirection in @code{run} overrides the @code{tty} command's
2201 effect on the input/output device, but not its effect on the controlling
2204 When you use the @code{tty} command or redirect input in the @code{run}
2205 command, only the input @emph{for your program} is affected. The input
2206 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2207 for @code{set inferior-tty}.
2209 @cindex inferior tty
2210 @cindex set inferior controlling terminal
2211 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2212 display the name of the terminal that will be used for future runs of your
2216 @item set inferior-tty /dev/ttyb
2217 @kindex set inferior-tty
2218 Set the tty for the program being debugged to /dev/ttyb.
2220 @item show inferior-tty
2221 @kindex show inferior-tty
2222 Show the current tty for the program being debugged.
2226 @section Debugging an Already-running Process
2231 @item attach @var{process-id}
2232 This command attaches to a running process---one that was started
2233 outside @value{GDBN}. (@code{info files} shows your active
2234 targets.) The command takes as argument a process ID. The usual way to
2235 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2236 or with the @samp{jobs -l} shell command.
2238 @code{attach} does not repeat if you press @key{RET} a second time after
2239 executing the command.
2242 To use @code{attach}, your program must be running in an environment
2243 which supports processes; for example, @code{attach} does not work for
2244 programs on bare-board targets that lack an operating system. You must
2245 also have permission to send the process a signal.
2247 When you use @code{attach}, the debugger finds the program running in
2248 the process first by looking in the current working directory, then (if
2249 the program is not found) by using the source file search path
2250 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2251 the @code{file} command to load the program. @xref{Files, ,Commands to
2254 The first thing @value{GDBN} does after arranging to debug the specified
2255 process is to stop it. You can examine and modify an attached process
2256 with all the @value{GDBN} commands that are ordinarily available when
2257 you start processes with @code{run}. You can insert breakpoints; you
2258 can step and continue; you can modify storage. If you would rather the
2259 process continue running, you may use the @code{continue} command after
2260 attaching @value{GDBN} to the process.
2265 When you have finished debugging the attached process, you can use the
2266 @code{detach} command to release it from @value{GDBN} control. Detaching
2267 the process continues its execution. After the @code{detach} command,
2268 that process and @value{GDBN} become completely independent once more, and you
2269 are ready to @code{attach} another process or start one with @code{run}.
2270 @code{detach} does not repeat if you press @key{RET} again after
2271 executing the command.
2274 If you exit @value{GDBN} while you have an attached process, you detach
2275 that process. If you use the @code{run} command, you kill that process.
2276 By default, @value{GDBN} asks for confirmation if you try to do either of these
2277 things; you can control whether or not you need to confirm by using the
2278 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2282 @section Killing the Child Process
2287 Kill the child process in which your program is running under @value{GDBN}.
2290 This command is useful if you wish to debug a core dump instead of a
2291 running process. @value{GDBN} ignores any core dump file while your program
2294 On some operating systems, a program cannot be executed outside @value{GDBN}
2295 while you have breakpoints set on it inside @value{GDBN}. You can use the
2296 @code{kill} command in this situation to permit running your program
2297 outside the debugger.
2299 The @code{kill} command is also useful if you wish to recompile and
2300 relink your program, since on many systems it is impossible to modify an
2301 executable file while it is running in a process. In this case, when you
2302 next type @code{run}, @value{GDBN} notices that the file has changed, and
2303 reads the symbol table again (while trying to preserve your current
2304 breakpoint settings).
2307 @section Debugging Programs with Multiple Threads
2309 @cindex threads of execution
2310 @cindex multiple threads
2311 @cindex switching threads
2312 In some operating systems, such as HP-UX and Solaris, a single program
2313 may have more than one @dfn{thread} of execution. The precise semantics
2314 of threads differ from one operating system to another, but in general
2315 the threads of a single program are akin to multiple processes---except
2316 that they share one address space (that is, they can all examine and
2317 modify the same variables). On the other hand, each thread has its own
2318 registers and execution stack, and perhaps private memory.
2320 @value{GDBN} provides these facilities for debugging multi-thread
2324 @item automatic notification of new threads
2325 @item @samp{thread @var{threadno}}, a command to switch among threads
2326 @item @samp{info threads}, a command to inquire about existing threads
2327 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2328 a command to apply a command to a list of threads
2329 @item thread-specific breakpoints
2330 @item @samp{set print thread-events}, which controls printing of
2331 messages on thread start and exit.
2335 @emph{Warning:} These facilities are not yet available on every
2336 @value{GDBN} configuration where the operating system supports threads.
2337 If your @value{GDBN} does not support threads, these commands have no
2338 effect. For example, a system without thread support shows no output
2339 from @samp{info threads}, and always rejects the @code{thread} command,
2343 (@value{GDBP}) info threads
2344 (@value{GDBP}) thread 1
2345 Thread ID 1 not known. Use the "info threads" command to
2346 see the IDs of currently known threads.
2348 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2349 @c doesn't support threads"?
2352 @cindex focus of debugging
2353 @cindex current thread
2354 The @value{GDBN} thread debugging facility allows you to observe all
2355 threads while your program runs---but whenever @value{GDBN} takes
2356 control, one thread in particular is always the focus of debugging.
2357 This thread is called the @dfn{current thread}. Debugging commands show
2358 program information from the perspective of the current thread.
2360 @cindex @code{New} @var{systag} message
2361 @cindex thread identifier (system)
2362 @c FIXME-implementors!! It would be more helpful if the [New...] message
2363 @c included GDB's numeric thread handle, so you could just go to that
2364 @c thread without first checking `info threads'.
2365 Whenever @value{GDBN} detects a new thread in your program, it displays
2366 the target system's identification for the thread with a message in the
2367 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2368 whose form varies depending on the particular system. For example, on
2369 @sc{gnu}/Linux, you might see
2372 [New Thread 46912507313328 (LWP 25582)]
2376 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2377 the @var{systag} is simply something like @samp{process 368}, with no
2380 @c FIXME!! (1) Does the [New...] message appear even for the very first
2381 @c thread of a program, or does it only appear for the
2382 @c second---i.e.@: when it becomes obvious we have a multithread
2384 @c (2) *Is* there necessarily a first thread always? Or do some
2385 @c multithread systems permit starting a program with multiple
2386 @c threads ab initio?
2388 @cindex thread number
2389 @cindex thread identifier (GDB)
2390 For debugging purposes, @value{GDBN} associates its own thread
2391 number---always a single integer---with each thread in your program.
2394 @kindex info threads
2396 Display a summary of all threads currently in your
2397 program. @value{GDBN} displays for each thread (in this order):
2401 the thread number assigned by @value{GDBN}
2404 the target system's thread identifier (@var{systag})
2407 the current stack frame summary for that thread
2411 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2412 indicates the current thread.
2416 @c end table here to get a little more width for example
2419 (@value{GDBP}) info threads
2420 3 process 35 thread 27 0x34e5 in sigpause ()
2421 2 process 35 thread 23 0x34e5 in sigpause ()
2422 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2428 @cindex debugging multithreaded programs (on HP-UX)
2429 @cindex thread identifier (GDB), on HP-UX
2430 For debugging purposes, @value{GDBN} associates its own thread
2431 number---a small integer assigned in thread-creation order---with each
2432 thread in your program.
2434 @cindex @code{New} @var{systag} message, on HP-UX
2435 @cindex thread identifier (system), on HP-UX
2436 @c FIXME-implementors!! It would be more helpful if the [New...] message
2437 @c included GDB's numeric thread handle, so you could just go to that
2438 @c thread without first checking `info threads'.
2439 Whenever @value{GDBN} detects a new thread in your program, it displays
2440 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2441 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2442 whose form varies depending on the particular system. For example, on
2446 [New thread 2 (system thread 26594)]
2450 when @value{GDBN} notices a new thread.
2453 @kindex info threads (HP-UX)
2455 Display a summary of all threads currently in your
2456 program. @value{GDBN} displays for each thread (in this order):
2459 @item the thread number assigned by @value{GDBN}
2461 @item the target system's thread identifier (@var{systag})
2463 @item the current stack frame summary for that thread
2467 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2468 indicates the current thread.
2472 @c end table here to get a little more width for example
2475 (@value{GDBP}) info threads
2476 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2478 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2479 from /usr/lib/libc.2
2480 1 system thread 27905 0x7b003498 in _brk () \@*
2481 from /usr/lib/libc.2
2484 On Solaris, you can display more information about user threads with a
2485 Solaris-specific command:
2488 @item maint info sol-threads
2489 @kindex maint info sol-threads
2490 @cindex thread info (Solaris)
2491 Display info on Solaris user threads.
2495 @kindex thread @var{threadno}
2496 @item thread @var{threadno}
2497 Make thread number @var{threadno} the current thread. The command
2498 argument @var{threadno} is the internal @value{GDBN} thread number, as
2499 shown in the first field of the @samp{info threads} display.
2500 @value{GDBN} responds by displaying the system identifier of the thread
2501 you selected, and its current stack frame summary:
2504 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2505 (@value{GDBP}) thread 2
2506 [Switching to process 35 thread 23]
2507 0x34e5 in sigpause ()
2511 As with the @samp{[New @dots{}]} message, the form of the text after
2512 @samp{Switching to} depends on your system's conventions for identifying
2515 @kindex thread apply
2516 @cindex apply command to several threads
2517 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2518 The @code{thread apply} command allows you to apply the named
2519 @var{command} to one or more threads. Specify the numbers of the
2520 threads that you want affected with the command argument
2521 @var{threadno}. It can be a single thread number, one of the numbers
2522 shown in the first field of the @samp{info threads} display; or it
2523 could be a range of thread numbers, as in @code{2-4}. To apply a
2524 command to all threads, type @kbd{thread apply all @var{command}}.
2526 @kindex set print thread-events
2527 @cindex print messages on thread start and exit
2528 @item set print thread-events
2529 @itemx set print thread-events on
2530 @itemx set print thread-events off
2531 The @code{set print thread-events} command allows you to enable or
2532 disable printing of messages when @value{GDBN} notices that new threads have
2533 started or that threads have exited. By default, these messages will
2534 be printed if detection of these events is supported by the target.
2535 Note that these messages cannot be disabled on all targets.
2537 @kindex show print thread-events
2538 @item show print thread-events
2539 Show whether messages will be printed when @value{GDBN} detects that threads
2540 have started and exited.
2543 @cindex automatic thread selection
2544 @cindex switching threads automatically
2545 @cindex threads, automatic switching
2546 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2547 signal, it automatically selects the thread where that breakpoint or
2548 signal happened. @value{GDBN} alerts you to the context switch with a
2549 message of the form @samp{[Switching to @var{systag}]} to identify the
2552 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2553 more information about how @value{GDBN} behaves when you stop and start
2554 programs with multiple threads.
2556 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2557 watchpoints in programs with multiple threads.
2560 @section Debugging Programs with Multiple Processes
2562 @cindex fork, debugging programs which call
2563 @cindex multiple processes
2564 @cindex processes, multiple
2565 On most systems, @value{GDBN} has no special support for debugging
2566 programs which create additional processes using the @code{fork}
2567 function. When a program forks, @value{GDBN} will continue to debug the
2568 parent process and the child process will run unimpeded. If you have
2569 set a breakpoint in any code which the child then executes, the child
2570 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2571 will cause it to terminate.
2573 However, if you want to debug the child process there is a workaround
2574 which isn't too painful. Put a call to @code{sleep} in the code which
2575 the child process executes after the fork. It may be useful to sleep
2576 only if a certain environment variable is set, or a certain file exists,
2577 so that the delay need not occur when you don't want to run @value{GDBN}
2578 on the child. While the child is sleeping, use the @code{ps} program to
2579 get its process ID. Then tell @value{GDBN} (a new invocation of
2580 @value{GDBN} if you are also debugging the parent process) to attach to
2581 the child process (@pxref{Attach}). From that point on you can debug
2582 the child process just like any other process which you attached to.
2584 On some systems, @value{GDBN} provides support for debugging programs that
2585 create additional processes using the @code{fork} or @code{vfork} functions.
2586 Currently, the only platforms with this feature are HP-UX (11.x and later
2587 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2589 By default, when a program forks, @value{GDBN} will continue to debug
2590 the parent process and the child process will run unimpeded.
2592 If you want to follow the child process instead of the parent process,
2593 use the command @w{@code{set follow-fork-mode}}.
2596 @kindex set follow-fork-mode
2597 @item set follow-fork-mode @var{mode}
2598 Set the debugger response to a program call of @code{fork} or
2599 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2600 process. The @var{mode} argument can be:
2604 The original process is debugged after a fork. The child process runs
2605 unimpeded. This is the default.
2608 The new process is debugged after a fork. The parent process runs
2613 @kindex show follow-fork-mode
2614 @item show follow-fork-mode
2615 Display the current debugger response to a @code{fork} or @code{vfork} call.
2618 @cindex debugging multiple processes
2619 On Linux, if you want to debug both the parent and child processes, use the
2620 command @w{@code{set detach-on-fork}}.
2623 @kindex set detach-on-fork
2624 @item set detach-on-fork @var{mode}
2625 Tells gdb whether to detach one of the processes after a fork, or
2626 retain debugger control over them both.
2630 The child process (or parent process, depending on the value of
2631 @code{follow-fork-mode}) will be detached and allowed to run
2632 independently. This is the default.
2635 Both processes will be held under the control of @value{GDBN}.
2636 One process (child or parent, depending on the value of
2637 @code{follow-fork-mode}) is debugged as usual, while the other
2642 @kindex show detach-on-fork
2643 @item show detach-on-fork
2644 Show whether detach-on-fork mode is on/off.
2647 If you choose to set @samp{detach-on-fork} mode off, then
2648 @value{GDBN} will retain control of all forked processes (including
2649 nested forks). You can list the forked processes under the control of
2650 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2651 from one fork to another by using the @w{@code{fork}} command.
2656 Print a list of all forked processes under the control of @value{GDBN}.
2657 The listing will include a fork id, a process id, and the current
2658 position (program counter) of the process.
2660 @kindex fork @var{fork-id}
2661 @item fork @var{fork-id}
2662 Make fork number @var{fork-id} the current process. The argument
2663 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2664 as shown in the first field of the @samp{info forks} display.
2666 @kindex process @var{process-id}
2667 @item process @var{process-id}
2668 Make process number @var{process-id} the current process. The
2669 argument @var{process-id} must be one that is listed in the output of
2674 To quit debugging one of the forked processes, you can either detach
2675 from it by using the @w{@code{detach fork}} command (allowing it to
2676 run independently), or delete (and kill) it using the
2677 @w{@code{delete fork}} command.
2680 @kindex detach fork @var{fork-id}
2681 @item detach fork @var{fork-id}
2682 Detach from the process identified by @value{GDBN} fork number
2683 @var{fork-id}, and remove it from the fork list. The process will be
2684 allowed to run independently.
2686 @kindex delete fork @var{fork-id}
2687 @item delete fork @var{fork-id}
2688 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2689 and remove it from the fork list.
2693 If you ask to debug a child process and a @code{vfork} is followed by an
2694 @code{exec}, @value{GDBN} executes the new target up to the first
2695 breakpoint in the new target. If you have a breakpoint set on
2696 @code{main} in your original program, the breakpoint will also be set on
2697 the child process's @code{main}.
2699 When a child process is spawned by @code{vfork}, you cannot debug the
2700 child or parent until an @code{exec} call completes.
2702 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2703 call executes, the new target restarts. To restart the parent process,
2704 use the @code{file} command with the parent executable name as its
2707 You can use the @code{catch} command to make @value{GDBN} stop whenever
2708 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2709 Catchpoints, ,Setting Catchpoints}.
2711 @node Checkpoint/Restart
2712 @section Setting a @emph{Bookmark} to Return to Later
2717 @cindex snapshot of a process
2718 @cindex rewind program state
2720 On certain operating systems@footnote{Currently, only
2721 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2722 program's state, called a @dfn{checkpoint}, and come back to it
2725 Returning to a checkpoint effectively undoes everything that has
2726 happened in the program since the @code{checkpoint} was saved. This
2727 includes changes in memory, registers, and even (within some limits)
2728 system state. Effectively, it is like going back in time to the
2729 moment when the checkpoint was saved.
2731 Thus, if you're stepping thru a program and you think you're
2732 getting close to the point where things go wrong, you can save
2733 a checkpoint. Then, if you accidentally go too far and miss
2734 the critical statement, instead of having to restart your program
2735 from the beginning, you can just go back to the checkpoint and
2736 start again from there.
2738 This can be especially useful if it takes a lot of time or
2739 steps to reach the point where you think the bug occurs.
2741 To use the @code{checkpoint}/@code{restart} method of debugging:
2746 Save a snapshot of the debugged program's current execution state.
2747 The @code{checkpoint} command takes no arguments, but each checkpoint
2748 is assigned a small integer id, similar to a breakpoint id.
2750 @kindex info checkpoints
2751 @item info checkpoints
2752 List the checkpoints that have been saved in the current debugging
2753 session. For each checkpoint, the following information will be
2760 @item Source line, or label
2763 @kindex restart @var{checkpoint-id}
2764 @item restart @var{checkpoint-id}
2765 Restore the program state that was saved as checkpoint number
2766 @var{checkpoint-id}. All program variables, registers, stack frames
2767 etc.@: will be returned to the values that they had when the checkpoint
2768 was saved. In essence, gdb will ``wind back the clock'' to the point
2769 in time when the checkpoint was saved.
2771 Note that breakpoints, @value{GDBN} variables, command history etc.
2772 are not affected by restoring a checkpoint. In general, a checkpoint
2773 only restores things that reside in the program being debugged, not in
2776 @kindex delete checkpoint @var{checkpoint-id}
2777 @item delete checkpoint @var{checkpoint-id}
2778 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2782 Returning to a previously saved checkpoint will restore the user state
2783 of the program being debugged, plus a significant subset of the system
2784 (OS) state, including file pointers. It won't ``un-write'' data from
2785 a file, but it will rewind the file pointer to the previous location,
2786 so that the previously written data can be overwritten. For files
2787 opened in read mode, the pointer will also be restored so that the
2788 previously read data can be read again.
2790 Of course, characters that have been sent to a printer (or other
2791 external device) cannot be ``snatched back'', and characters received
2792 from eg.@: a serial device can be removed from internal program buffers,
2793 but they cannot be ``pushed back'' into the serial pipeline, ready to
2794 be received again. Similarly, the actual contents of files that have
2795 been changed cannot be restored (at this time).
2797 However, within those constraints, you actually can ``rewind'' your
2798 program to a previously saved point in time, and begin debugging it
2799 again --- and you can change the course of events so as to debug a
2800 different execution path this time.
2802 @cindex checkpoints and process id
2803 Finally, there is one bit of internal program state that will be
2804 different when you return to a checkpoint --- the program's process
2805 id. Each checkpoint will have a unique process id (or @var{pid}),
2806 and each will be different from the program's original @var{pid}.
2807 If your program has saved a local copy of its process id, this could
2808 potentially pose a problem.
2810 @subsection A Non-obvious Benefit of Using Checkpoints
2812 On some systems such as @sc{gnu}/Linux, address space randomization
2813 is performed on new processes for security reasons. This makes it
2814 difficult or impossible to set a breakpoint, or watchpoint, on an
2815 absolute address if you have to restart the program, since the
2816 absolute location of a symbol will change from one execution to the
2819 A checkpoint, however, is an @emph{identical} copy of a process.
2820 Therefore if you create a checkpoint at (eg.@:) the start of main,
2821 and simply return to that checkpoint instead of restarting the
2822 process, you can avoid the effects of address randomization and
2823 your symbols will all stay in the same place.
2826 @chapter Stopping and Continuing
2828 The principal purposes of using a debugger are so that you can stop your
2829 program before it terminates; or so that, if your program runs into
2830 trouble, you can investigate and find out why.
2832 Inside @value{GDBN}, your program may stop for any of several reasons,
2833 such as a signal, a breakpoint, or reaching a new line after a
2834 @value{GDBN} command such as @code{step}. You may then examine and
2835 change variables, set new breakpoints or remove old ones, and then
2836 continue execution. Usually, the messages shown by @value{GDBN} provide
2837 ample explanation of the status of your program---but you can also
2838 explicitly request this information at any time.
2841 @kindex info program
2843 Display information about the status of your program: whether it is
2844 running or not, what process it is, and why it stopped.
2848 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2849 * Continuing and Stepping:: Resuming execution
2851 * Thread Stops:: Stopping and starting multi-thread programs
2855 @section Breakpoints, Watchpoints, and Catchpoints
2858 A @dfn{breakpoint} makes your program stop whenever a certain point in
2859 the program is reached. For each breakpoint, you can add conditions to
2860 control in finer detail whether your program stops. You can set
2861 breakpoints with the @code{break} command and its variants (@pxref{Set
2862 Breaks, ,Setting Breakpoints}), to specify the place where your program
2863 should stop by line number, function name or exact address in the
2866 On some systems, you can set breakpoints in shared libraries before
2867 the executable is run. There is a minor limitation on HP-UX systems:
2868 you must wait until the executable is run in order to set breakpoints
2869 in shared library routines that are not called directly by the program
2870 (for example, routines that are arguments in a @code{pthread_create}
2874 @cindex data breakpoints
2875 @cindex memory tracing
2876 @cindex breakpoint on memory address
2877 @cindex breakpoint on variable modification
2878 A @dfn{watchpoint} is a special breakpoint that stops your program
2879 when the value of an expression changes. The expression may be a value
2880 of a variable, or it could involve values of one or more variables
2881 combined by operators, such as @samp{a + b}. This is sometimes called
2882 @dfn{data breakpoints}. You must use a different command to set
2883 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2884 from that, you can manage a watchpoint like any other breakpoint: you
2885 enable, disable, and delete both breakpoints and watchpoints using the
2888 You can arrange to have values from your program displayed automatically
2889 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2893 @cindex breakpoint on events
2894 A @dfn{catchpoint} is another special breakpoint that stops your program
2895 when a certain kind of event occurs, such as the throwing of a C@t{++}
2896 exception or the loading of a library. As with watchpoints, you use a
2897 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2898 Catchpoints}), but aside from that, you can manage a catchpoint like any
2899 other breakpoint. (To stop when your program receives a signal, use the
2900 @code{handle} command; see @ref{Signals, ,Signals}.)
2902 @cindex breakpoint numbers
2903 @cindex numbers for breakpoints
2904 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2905 catchpoint when you create it; these numbers are successive integers
2906 starting with one. In many of the commands for controlling various
2907 features of breakpoints you use the breakpoint number to say which
2908 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2909 @dfn{disabled}; if disabled, it has no effect on your program until you
2912 @cindex breakpoint ranges
2913 @cindex ranges of breakpoints
2914 Some @value{GDBN} commands accept a range of breakpoints on which to
2915 operate. A breakpoint range is either a single breakpoint number, like
2916 @samp{5}, or two such numbers, in increasing order, separated by a
2917 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2918 all breakpoints in that range are operated on.
2921 * Set Breaks:: Setting breakpoints
2922 * Set Watchpoints:: Setting watchpoints
2923 * Set Catchpoints:: Setting catchpoints
2924 * Delete Breaks:: Deleting breakpoints
2925 * Disabling:: Disabling breakpoints
2926 * Conditions:: Break conditions
2927 * Break Commands:: Breakpoint command lists
2928 * Error in Breakpoints:: ``Cannot insert breakpoints''
2929 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2933 @subsection Setting Breakpoints
2935 @c FIXME LMB what does GDB do if no code on line of breakpt?
2936 @c consider in particular declaration with/without initialization.
2938 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2941 @kindex b @r{(@code{break})}
2942 @vindex $bpnum@r{, convenience variable}
2943 @cindex latest breakpoint
2944 Breakpoints are set with the @code{break} command (abbreviated
2945 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2946 number of the breakpoint you've set most recently; see @ref{Convenience
2947 Vars,, Convenience Variables}, for a discussion of what you can do with
2948 convenience variables.
2951 @item break @var{location}
2952 Set a breakpoint at the given @var{location}, which can specify a
2953 function name, a line number, or an address of an instruction.
2954 (@xref{Specify Location}, for a list of all the possible ways to
2955 specify a @var{location}.) The breakpoint will stop your program just
2956 before it executes any of the code in the specified @var{location}.
2958 When using source languages that permit overloading of symbols, such as
2959 C@t{++}, a function name may refer to more than one possible place to break.
2960 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
2964 When called without any arguments, @code{break} sets a breakpoint at
2965 the next instruction to be executed in the selected stack frame
2966 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2967 innermost, this makes your program stop as soon as control
2968 returns to that frame. This is similar to the effect of a
2969 @code{finish} command in the frame inside the selected frame---except
2970 that @code{finish} does not leave an active breakpoint. If you use
2971 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2972 the next time it reaches the current location; this may be useful
2975 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2976 least one instruction has been executed. If it did not do this, you
2977 would be unable to proceed past a breakpoint without first disabling the
2978 breakpoint. This rule applies whether or not the breakpoint already
2979 existed when your program stopped.
2981 @item break @dots{} if @var{cond}
2982 Set a breakpoint with condition @var{cond}; evaluate the expression
2983 @var{cond} each time the breakpoint is reached, and stop only if the
2984 value is nonzero---that is, if @var{cond} evaluates as true.
2985 @samp{@dots{}} stands for one of the possible arguments described
2986 above (or no argument) specifying where to break. @xref{Conditions,
2987 ,Break Conditions}, for more information on breakpoint conditions.
2990 @item tbreak @var{args}
2991 Set a breakpoint enabled only for one stop. @var{args} are the
2992 same as for the @code{break} command, and the breakpoint is set in the same
2993 way, but the breakpoint is automatically deleted after the first time your
2994 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2997 @cindex hardware breakpoints
2998 @item hbreak @var{args}
2999 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3000 @code{break} command and the breakpoint is set in the same way, but the
3001 breakpoint requires hardware support and some target hardware may not
3002 have this support. The main purpose of this is EPROM/ROM code
3003 debugging, so you can set a breakpoint at an instruction without
3004 changing the instruction. This can be used with the new trap-generation
3005 provided by SPARClite DSU and most x86-based targets. These targets
3006 will generate traps when a program accesses some data or instruction
3007 address that is assigned to the debug registers. However the hardware
3008 breakpoint registers can take a limited number of breakpoints. For
3009 example, on the DSU, only two data breakpoints can be set at a time, and
3010 @value{GDBN} will reject this command if more than two are used. Delete
3011 or disable unused hardware breakpoints before setting new ones
3012 (@pxref{Disabling, ,Disabling Breakpoints}).
3013 @xref{Conditions, ,Break Conditions}.
3014 For remote targets, you can restrict the number of hardware
3015 breakpoints @value{GDBN} will use, see @ref{set remote
3016 hardware-breakpoint-limit}.
3019 @item thbreak @var{args}
3020 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3021 are the same as for the @code{hbreak} command and the breakpoint is set in
3022 the same way. However, like the @code{tbreak} command,
3023 the breakpoint is automatically deleted after the
3024 first time your program stops there. Also, like the @code{hbreak}
3025 command, the breakpoint requires hardware support and some target hardware
3026 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3027 See also @ref{Conditions, ,Break Conditions}.
3030 @cindex regular expression
3031 @cindex breakpoints in functions matching a regexp
3032 @cindex set breakpoints in many functions
3033 @item rbreak @var{regex}
3034 Set breakpoints on all functions matching the regular expression
3035 @var{regex}. This command sets an unconditional breakpoint on all
3036 matches, printing a list of all breakpoints it set. Once these
3037 breakpoints are set, they are treated just like the breakpoints set with
3038 the @code{break} command. You can delete them, disable them, or make
3039 them conditional the same way as any other breakpoint.
3041 The syntax of the regular expression is the standard one used with tools
3042 like @file{grep}. Note that this is different from the syntax used by
3043 shells, so for instance @code{foo*} matches all functions that include
3044 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3045 @code{.*} leading and trailing the regular expression you supply, so to
3046 match only functions that begin with @code{foo}, use @code{^foo}.
3048 @cindex non-member C@t{++} functions, set breakpoint in
3049 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3050 breakpoints on overloaded functions that are not members of any special
3053 @cindex set breakpoints on all functions
3054 The @code{rbreak} command can be used to set breakpoints in
3055 @strong{all} the functions in a program, like this:
3058 (@value{GDBP}) rbreak .
3061 @kindex info breakpoints
3062 @cindex @code{$_} and @code{info breakpoints}
3063 @item info breakpoints @r{[}@var{n}@r{]}
3064 @itemx info break @r{[}@var{n}@r{]}
3065 @itemx info watchpoints @r{[}@var{n}@r{]}
3066 Print a table of all breakpoints, watchpoints, and catchpoints set and
3067 not deleted. Optional argument @var{n} means print information only
3068 about the specified breakpoint (or watchpoint or catchpoint). For
3069 each breakpoint, following columns are printed:
3072 @item Breakpoint Numbers
3074 Breakpoint, watchpoint, or catchpoint.
3076 Whether the breakpoint is marked to be disabled or deleted when hit.
3077 @item Enabled or Disabled
3078 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3079 that are not enabled.
3081 Where the breakpoint is in your program, as a memory address. For a
3082 pending breakpoint whose address is not yet known, this field will
3083 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3084 library that has the symbol or line referred by breakpoint is loaded.
3085 See below for details. A breakpoint with several locations will
3086 have @samp{<MULTIPLE>} in this field---see below for details.
3088 Where the breakpoint is in the source for your program, as a file and
3089 line number. For a pending breakpoint, the original string passed to
3090 the breakpoint command will be listed as it cannot be resolved until
3091 the appropriate shared library is loaded in the future.
3095 If a breakpoint is conditional, @code{info break} shows the condition on
3096 the line following the affected breakpoint; breakpoint commands, if any,
3097 are listed after that. A pending breakpoint is allowed to have a condition
3098 specified for it. The condition is not parsed for validity until a shared
3099 library is loaded that allows the pending breakpoint to resolve to a
3103 @code{info break} with a breakpoint
3104 number @var{n} as argument lists only that breakpoint. The
3105 convenience variable @code{$_} and the default examining-address for
3106 the @code{x} command are set to the address of the last breakpoint
3107 listed (@pxref{Memory, ,Examining Memory}).
3110 @code{info break} displays a count of the number of times the breakpoint
3111 has been hit. This is especially useful in conjunction with the
3112 @code{ignore} command. You can ignore a large number of breakpoint
3113 hits, look at the breakpoint info to see how many times the breakpoint
3114 was hit, and then run again, ignoring one less than that number. This
3115 will get you quickly to the last hit of that breakpoint.
3118 @value{GDBN} allows you to set any number of breakpoints at the same place in
3119 your program. There is nothing silly or meaningless about this. When
3120 the breakpoints are conditional, this is even useful
3121 (@pxref{Conditions, ,Break Conditions}).
3123 @cindex multiple locations, breakpoints
3124 @cindex breakpoints, multiple locations
3125 It is possible that a breakpoint corresponds to several locations
3126 in your program. Examples of this situation are:
3130 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3131 instances of the function body, used in different cases.
3134 For a C@t{++} template function, a given line in the function can
3135 correspond to any number of instantiations.
3138 For an inlined function, a given source line can correspond to
3139 several places where that function is inlined.
3142 In all those cases, @value{GDBN} will insert a breakpoint at all
3143 the relevant locations@footnote{
3144 As of this writing, multiple-location breakpoints work only if there's
3145 line number information for all the locations. This means that they
3146 will generally not work in system libraries, unless you have debug
3147 info with line numbers for them.}.
3149 A breakpoint with multiple locations is displayed in the breakpoint
3150 table using several rows---one header row, followed by one row for
3151 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3152 address column. The rows for individual locations contain the actual
3153 addresses for locations, and show the functions to which those
3154 locations belong. The number column for a location is of the form
3155 @var{breakpoint-number}.@var{location-number}.
3160 Num Type Disp Enb Address What
3161 1 breakpoint keep y <MULTIPLE>
3163 breakpoint already hit 1 time
3164 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3165 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3168 Each location can be individually enabled or disabled by passing
3169 @var{breakpoint-number}.@var{location-number} as argument to the
3170 @code{enable} and @code{disable} commands. Note that you cannot
3171 delete the individual locations from the list, you can only delete the
3172 entire list of locations that belong to their parent breakpoint (with
3173 the @kbd{delete @var{num}} command, where @var{num} is the number of
3174 the parent breakpoint, 1 in the above example). Disabling or enabling
3175 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3176 that belong to that breakpoint.
3178 @cindex pending breakpoints
3179 It's quite common to have a breakpoint inside a shared library.
3180 Shared libraries can be loaded and unloaded explicitly,
3181 and possibly repeatedly, as the program is executed. To support
3182 this use case, @value{GDBN} updates breakpoint locations whenever
3183 any shared library is loaded or unloaded. Typically, you would
3184 set a breakpoint in a shared library at the beginning of your
3185 debugging session, when the library is not loaded, and when the
3186 symbols from the library are not available. When you try to set
3187 breakpoint, @value{GDBN} will ask you if you want to set
3188 a so called @dfn{pending breakpoint}---breakpoint whose address
3189 is not yet resolved.
3191 After the program is run, whenever a new shared library is loaded,
3192 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3193 shared library contains the symbol or line referred to by some
3194 pending breakpoint, that breakpoint is resolved and becomes an
3195 ordinary breakpoint. When a library is unloaded, all breakpoints
3196 that refer to its symbols or source lines become pending again.
3198 This logic works for breakpoints with multiple locations, too. For
3199 example, if you have a breakpoint in a C@t{++} template function, and
3200 a newly loaded shared library has an instantiation of that template,
3201 a new location is added to the list of locations for the breakpoint.
3203 Except for having unresolved address, pending breakpoints do not
3204 differ from regular breakpoints. You can set conditions or commands,
3205 enable and disable them and perform other breakpoint operations.
3207 @value{GDBN} provides some additional commands for controlling what
3208 happens when the @samp{break} command cannot resolve breakpoint
3209 address specification to an address:
3211 @kindex set breakpoint pending
3212 @kindex show breakpoint pending
3214 @item set breakpoint pending auto
3215 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3216 location, it queries you whether a pending breakpoint should be created.
3218 @item set breakpoint pending on
3219 This indicates that an unrecognized breakpoint location should automatically
3220 result in a pending breakpoint being created.
3222 @item set breakpoint pending off
3223 This indicates that pending breakpoints are not to be created. Any
3224 unrecognized breakpoint location results in an error. This setting does
3225 not affect any pending breakpoints previously created.
3227 @item show breakpoint pending
3228 Show the current behavior setting for creating pending breakpoints.
3231 The settings above only affect the @code{break} command and its
3232 variants. Once breakpoint is set, it will be automatically updated
3233 as shared libraries are loaded and unloaded.
3235 @cindex automatic hardware breakpoints
3236 For some targets, @value{GDBN} can automatically decide if hardware or
3237 software breakpoints should be used, depending on whether the
3238 breakpoint address is read-only or read-write. This applies to
3239 breakpoints set with the @code{break} command as well as to internal
3240 breakpoints set by commands like @code{next} and @code{finish}. For
3241 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3244 You can control this automatic behaviour with the following commands::
3246 @kindex set breakpoint auto-hw
3247 @kindex show breakpoint auto-hw
3249 @item set breakpoint auto-hw on
3250 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3251 will try to use the target memory map to decide if software or hardware
3252 breakpoint must be used.
3254 @item set breakpoint auto-hw off
3255 This indicates @value{GDBN} should not automatically select breakpoint
3256 type. If the target provides a memory map, @value{GDBN} will warn when
3257 trying to set software breakpoint at a read-only address.
3260 @value{GDBN} normally implements breakpoints by replacing the program code
3261 at the breakpoint address with a special instruction, which, when
3262 executed, given control to the debugger. By default, the program
3263 code is so modified only when the program is resumed. As soon as
3264 the program stops, @value{GDBN} restores the original instructions. This
3265 behaviour guards against leaving breakpoints inserted in the
3266 target should gdb abrubptly disconnect. However, with slow remote
3267 targets, inserting and removing breakpoint can reduce the performance.
3268 This behavior can be controlled with the following commands::
3270 @kindex set breakpoint always-inserted
3271 @kindex show breakpoint always-inserted
3273 @item set breakpoint always-inserted off
3274 This is the default behaviour. All breakpoints, including newly added
3275 by the user, are inserted in the target only when the target is
3276 resumed. All breakpoints are removed from the target when it stops.
3278 @item set breakpoint always-inserted on
3279 Causes all breakpoints to be inserted in the target at all times. If
3280 the user adds a new breakpoint, or changes an existing breakpoint, the
3281 breakpoints in the target are updated immediately. A breakpoint is
3282 removed from the target only when breakpoint itself is removed.
3285 @cindex negative breakpoint numbers
3286 @cindex internal @value{GDBN} breakpoints
3287 @value{GDBN} itself sometimes sets breakpoints in your program for
3288 special purposes, such as proper handling of @code{longjmp} (in C
3289 programs). These internal breakpoints are assigned negative numbers,
3290 starting with @code{-1}; @samp{info breakpoints} does not display them.
3291 You can see these breakpoints with the @value{GDBN} maintenance command
3292 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3295 @node Set Watchpoints
3296 @subsection Setting Watchpoints
3298 @cindex setting watchpoints
3299 You can use a watchpoint to stop execution whenever the value of an
3300 expression changes, without having to predict a particular place where
3301 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3302 The expression may be as simple as the value of a single variable, or
3303 as complex as many variables combined by operators. Examples include:
3307 A reference to the value of a single variable.
3310 An address cast to an appropriate data type. For example,
3311 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3312 address (assuming an @code{int} occupies 4 bytes).
3315 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3316 expression can use any operators valid in the program's native
3317 language (@pxref{Languages}).
3320 You can set a watchpoint on an expression even if the expression can
3321 not be evaluated yet. For instance, you can set a watchpoint on
3322 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3323 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3324 the expression produces a valid value. If the expression becomes
3325 valid in some other way than changing a variable (e.g.@: if the memory
3326 pointed to by @samp{*global_ptr} becomes readable as the result of a
3327 @code{malloc} call), @value{GDBN} may not stop until the next time
3328 the expression changes.
3330 @cindex software watchpoints
3331 @cindex hardware watchpoints
3332 Depending on your system, watchpoints may be implemented in software or
3333 hardware. @value{GDBN} does software watchpointing by single-stepping your
3334 program and testing the variable's value each time, which is hundreds of
3335 times slower than normal execution. (But this may still be worth it, to
3336 catch errors where you have no clue what part of your program is the
3339 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3340 x86-based targets, @value{GDBN} includes support for hardware
3341 watchpoints, which do not slow down the running of your program.
3345 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3346 Set a watchpoint for an expression. @value{GDBN} will break when the
3347 expression @var{expr} is written into by the program and its value
3348 changes. The simplest (and the most popular) use of this command is
3349 to watch the value of a single variable:
3352 (@value{GDBP}) watch foo
3355 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3356 clause, @value{GDBN} breaks only when the thread identified by
3357 @var{threadnum} changes the value of @var{expr}. If any other threads
3358 change the value of @var{expr}, @value{GDBN} will not break. Note
3359 that watchpoints restricted to a single thread in this way only work
3360 with Hardware Watchpoints.
3363 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3364 Set a watchpoint that will break when the value of @var{expr} is read
3368 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3369 Set a watchpoint that will break when @var{expr} is either read from
3370 or written into by the program.
3372 @kindex info watchpoints @r{[}@var{n}@r{]}
3373 @item info watchpoints
3374 This command prints a list of watchpoints, breakpoints, and catchpoints;
3375 it is the same as @code{info break} (@pxref{Set Breaks}).
3378 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3379 watchpoints execute very quickly, and the debugger reports a change in
3380 value at the exact instruction where the change occurs. If @value{GDBN}
3381 cannot set a hardware watchpoint, it sets a software watchpoint, which
3382 executes more slowly and reports the change in value at the next
3383 @emph{statement}, not the instruction, after the change occurs.
3385 @cindex use only software watchpoints
3386 You can force @value{GDBN} to use only software watchpoints with the
3387 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3388 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3389 the underlying system supports them. (Note that hardware-assisted
3390 watchpoints that were set @emph{before} setting
3391 @code{can-use-hw-watchpoints} to zero will still use the hardware
3392 mechanism of watching expression values.)
3395 @item set can-use-hw-watchpoints
3396 @kindex set can-use-hw-watchpoints
3397 Set whether or not to use hardware watchpoints.
3399 @item show can-use-hw-watchpoints
3400 @kindex show can-use-hw-watchpoints
3401 Show the current mode of using hardware watchpoints.
3404 For remote targets, you can restrict the number of hardware
3405 watchpoints @value{GDBN} will use, see @ref{set remote
3406 hardware-breakpoint-limit}.
3408 When you issue the @code{watch} command, @value{GDBN} reports
3411 Hardware watchpoint @var{num}: @var{expr}
3415 if it was able to set a hardware watchpoint.
3417 Currently, the @code{awatch} and @code{rwatch} commands can only set
3418 hardware watchpoints, because accesses to data that don't change the
3419 value of the watched expression cannot be detected without examining
3420 every instruction as it is being executed, and @value{GDBN} does not do
3421 that currently. If @value{GDBN} finds that it is unable to set a
3422 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3423 will print a message like this:
3426 Expression cannot be implemented with read/access watchpoint.
3429 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3430 data type of the watched expression is wider than what a hardware
3431 watchpoint on the target machine can handle. For example, some systems
3432 can only watch regions that are up to 4 bytes wide; on such systems you
3433 cannot set hardware watchpoints for an expression that yields a
3434 double-precision floating-point number (which is typically 8 bytes
3435 wide). As a work-around, it might be possible to break the large region
3436 into a series of smaller ones and watch them with separate watchpoints.
3438 If you set too many hardware watchpoints, @value{GDBN} might be unable
3439 to insert all of them when you resume the execution of your program.
3440 Since the precise number of active watchpoints is unknown until such
3441 time as the program is about to be resumed, @value{GDBN} might not be
3442 able to warn you about this when you set the watchpoints, and the
3443 warning will be printed only when the program is resumed:
3446 Hardware watchpoint @var{num}: Could not insert watchpoint
3450 If this happens, delete or disable some of the watchpoints.
3452 Watching complex expressions that reference many variables can also
3453 exhaust the resources available for hardware-assisted watchpoints.
3454 That's because @value{GDBN} needs to watch every variable in the
3455 expression with separately allocated resources.
3457 If you call a function interactively using @code{print} or @code{call},
3458 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3459 kind of breakpoint or the call completes.
3461 @value{GDBN} automatically deletes watchpoints that watch local
3462 (automatic) variables, or expressions that involve such variables, when
3463 they go out of scope, that is, when the execution leaves the block in
3464 which these variables were defined. In particular, when the program
3465 being debugged terminates, @emph{all} local variables go out of scope,
3466 and so only watchpoints that watch global variables remain set. If you
3467 rerun the program, you will need to set all such watchpoints again. One
3468 way of doing that would be to set a code breakpoint at the entry to the
3469 @code{main} function and when it breaks, set all the watchpoints.
3471 @cindex watchpoints and threads
3472 @cindex threads and watchpoints
3473 In multi-threaded programs, watchpoints will detect changes to the
3474 watched expression from every thread.
3477 @emph{Warning:} In multi-threaded programs, software watchpoints
3478 have only limited usefulness. If @value{GDBN} creates a software
3479 watchpoint, it can only watch the value of an expression @emph{in a
3480 single thread}. If you are confident that the expression can only
3481 change due to the current thread's activity (and if you are also
3482 confident that no other thread can become current), then you can use
3483 software watchpoints as usual. However, @value{GDBN} may not notice
3484 when a non-current thread's activity changes the expression. (Hardware
3485 watchpoints, in contrast, watch an expression in all threads.)
3488 @xref{set remote hardware-watchpoint-limit}.
3490 @node Set Catchpoints
3491 @subsection Setting Catchpoints
3492 @cindex catchpoints, setting
3493 @cindex exception handlers
3494 @cindex event handling
3496 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3497 kinds of program events, such as C@t{++} exceptions or the loading of a
3498 shared library. Use the @code{catch} command to set a catchpoint.
3502 @item catch @var{event}
3503 Stop when @var{event} occurs. @var{event} can be any of the following:
3506 @cindex stop on C@t{++} exceptions
3507 The throwing of a C@t{++} exception.
3510 The catching of a C@t{++} exception.
3513 @cindex Ada exception catching
3514 @cindex catch Ada exceptions
3515 An Ada exception being raised. If an exception name is specified
3516 at the end of the command (eg @code{catch exception Program_Error}),
3517 the debugger will stop only when this specific exception is raised.
3518 Otherwise, the debugger stops execution when any Ada exception is raised.
3520 @item exception unhandled
3521 An exception that was raised but is not handled by the program.
3524 A failed Ada assertion.
3527 @cindex break on fork/exec
3528 A call to @code{exec}. This is currently only available for HP-UX
3532 A call to @code{fork}. This is currently only available for HP-UX
3536 A call to @code{vfork}. This is currently only available for HP-UX
3540 @itemx load @var{libname}
3541 @cindex break on load/unload of shared library
3542 The dynamic loading of any shared library, or the loading of the library
3543 @var{libname}. This is currently only available for HP-UX.
3546 @itemx unload @var{libname}
3547 The unloading of any dynamically loaded shared library, or the unloading
3548 of the library @var{libname}. This is currently only available for HP-UX.
3551 @item tcatch @var{event}
3552 Set a catchpoint that is enabled only for one stop. The catchpoint is
3553 automatically deleted after the first time the event is caught.
3557 Use the @code{info break} command to list the current catchpoints.
3559 There are currently some limitations to C@t{++} exception handling
3560 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3564 If you call a function interactively, @value{GDBN} normally returns
3565 control to you when the function has finished executing. If the call
3566 raises an exception, however, the call may bypass the mechanism that
3567 returns control to you and cause your program either to abort or to
3568 simply continue running until it hits a breakpoint, catches a signal
3569 that @value{GDBN} is listening for, or exits. This is the case even if
3570 you set a catchpoint for the exception; catchpoints on exceptions are
3571 disabled within interactive calls.
3574 You cannot raise an exception interactively.
3577 You cannot install an exception handler interactively.
3580 @cindex raise exceptions
3581 Sometimes @code{catch} is not the best way to debug exception handling:
3582 if you need to know exactly where an exception is raised, it is better to
3583 stop @emph{before} the exception handler is called, since that way you
3584 can see the stack before any unwinding takes place. If you set a
3585 breakpoint in an exception handler instead, it may not be easy to find
3586 out where the exception was raised.
3588 To stop just before an exception handler is called, you need some
3589 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3590 raised by calling a library function named @code{__raise_exception}
3591 which has the following ANSI C interface:
3594 /* @var{addr} is where the exception identifier is stored.
3595 @var{id} is the exception identifier. */
3596 void __raise_exception (void **addr, void *id);
3600 To make the debugger catch all exceptions before any stack
3601 unwinding takes place, set a breakpoint on @code{__raise_exception}
3602 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3604 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3605 that depends on the value of @var{id}, you can stop your program when
3606 a specific exception is raised. You can use multiple conditional
3607 breakpoints to stop your program when any of a number of exceptions are
3612 @subsection Deleting Breakpoints
3614 @cindex clearing breakpoints, watchpoints, catchpoints
3615 @cindex deleting breakpoints, watchpoints, catchpoints
3616 It is often necessary to eliminate a breakpoint, watchpoint, or
3617 catchpoint once it has done its job and you no longer want your program
3618 to stop there. This is called @dfn{deleting} the breakpoint. A
3619 breakpoint that has been deleted no longer exists; it is forgotten.
3621 With the @code{clear} command you can delete breakpoints according to
3622 where they are in your program. With the @code{delete} command you can
3623 delete individual breakpoints, watchpoints, or catchpoints by specifying
3624 their breakpoint numbers.
3626 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3627 automatically ignores breakpoints on the first instruction to be executed
3628 when you continue execution without changing the execution address.
3633 Delete any breakpoints at the next instruction to be executed in the
3634 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3635 the innermost frame is selected, this is a good way to delete a
3636 breakpoint where your program just stopped.
3638 @item clear @var{location}
3639 Delete any breakpoints set at the specified @var{location}.
3640 @xref{Specify Location}, for the various forms of @var{location}; the
3641 most useful ones are listed below:
3644 @item clear @var{function}
3645 @itemx clear @var{filename}:@var{function}
3646 Delete any breakpoints set at entry to the named @var{function}.
3648 @item clear @var{linenum}
3649 @itemx clear @var{filename}:@var{linenum}
3650 Delete any breakpoints set at or within the code of the specified
3651 @var{linenum} of the specified @var{filename}.
3654 @cindex delete breakpoints
3656 @kindex d @r{(@code{delete})}
3657 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3658 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3659 ranges specified as arguments. If no argument is specified, delete all
3660 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3661 confirm off}). You can abbreviate this command as @code{d}.
3665 @subsection Disabling Breakpoints
3667 @cindex enable/disable a breakpoint
3668 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3669 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3670 it had been deleted, but remembers the information on the breakpoint so
3671 that you can @dfn{enable} it again later.
3673 You disable and enable breakpoints, watchpoints, and catchpoints with
3674 the @code{enable} and @code{disable} commands, optionally specifying one
3675 or more breakpoint numbers as arguments. Use @code{info break} or
3676 @code{info watch} to print a list of breakpoints, watchpoints, and
3677 catchpoints if you do not know which numbers to use.
3679 Disabling and enabling a breakpoint that has multiple locations
3680 affects all of its locations.
3682 A breakpoint, watchpoint, or catchpoint can have any of four different
3683 states of enablement:
3687 Enabled. The breakpoint stops your program. A breakpoint set
3688 with the @code{break} command starts out in this state.
3690 Disabled. The breakpoint has no effect on your program.
3692 Enabled once. The breakpoint stops your program, but then becomes
3695 Enabled for deletion. The breakpoint stops your program, but
3696 immediately after it does so it is deleted permanently. A breakpoint
3697 set with the @code{tbreak} command starts out in this state.
3700 You can use the following commands to enable or disable breakpoints,
3701 watchpoints, and catchpoints:
3705 @kindex dis @r{(@code{disable})}
3706 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3707 Disable the specified breakpoints---or all breakpoints, if none are
3708 listed. A disabled breakpoint has no effect but is not forgotten. All
3709 options such as ignore-counts, conditions and commands are remembered in
3710 case the breakpoint is enabled again later. You may abbreviate
3711 @code{disable} as @code{dis}.
3714 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3715 Enable the specified breakpoints (or all defined breakpoints). They
3716 become effective once again in stopping your program.
3718 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3719 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3720 of these breakpoints immediately after stopping your program.
3722 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3723 Enable the specified breakpoints to work once, then die. @value{GDBN}
3724 deletes any of these breakpoints as soon as your program stops there.
3725 Breakpoints set by the @code{tbreak} command start out in this state.
3728 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3729 @c confusing: tbreak is also initially enabled.
3730 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3731 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3732 subsequently, they become disabled or enabled only when you use one of
3733 the commands above. (The command @code{until} can set and delete a
3734 breakpoint of its own, but it does not change the state of your other
3735 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3739 @subsection Break Conditions
3740 @cindex conditional breakpoints
3741 @cindex breakpoint conditions
3743 @c FIXME what is scope of break condition expr? Context where wanted?
3744 @c in particular for a watchpoint?
3745 The simplest sort of breakpoint breaks every time your program reaches a
3746 specified place. You can also specify a @dfn{condition} for a
3747 breakpoint. A condition is just a Boolean expression in your
3748 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3749 a condition evaluates the expression each time your program reaches it,
3750 and your program stops only if the condition is @emph{true}.
3752 This is the converse of using assertions for program validation; in that
3753 situation, you want to stop when the assertion is violated---that is,
3754 when the condition is false. In C, if you want to test an assertion expressed
3755 by the condition @var{assert}, you should set the condition
3756 @samp{! @var{assert}} on the appropriate breakpoint.
3758 Conditions are also accepted for watchpoints; you may not need them,
3759 since a watchpoint is inspecting the value of an expression anyhow---but
3760 it might be simpler, say, to just set a watchpoint on a variable name,
3761 and specify a condition that tests whether the new value is an interesting
3764 Break conditions can have side effects, and may even call functions in
3765 your program. This can be useful, for example, to activate functions
3766 that log program progress, or to use your own print functions to
3767 format special data structures. The effects are completely predictable
3768 unless there is another enabled breakpoint at the same address. (In
3769 that case, @value{GDBN} might see the other breakpoint first and stop your
3770 program without checking the condition of this one.) Note that
3771 breakpoint commands are usually more convenient and flexible than break
3773 purpose of performing side effects when a breakpoint is reached
3774 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3776 Break conditions can be specified when a breakpoint is set, by using
3777 @samp{if} in the arguments to the @code{break} command. @xref{Set
3778 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3779 with the @code{condition} command.
3781 You can also use the @code{if} keyword with the @code{watch} command.
3782 The @code{catch} command does not recognize the @code{if} keyword;
3783 @code{condition} is the only way to impose a further condition on a
3788 @item condition @var{bnum} @var{expression}
3789 Specify @var{expression} as the break condition for breakpoint,
3790 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3791 breakpoint @var{bnum} stops your program only if the value of
3792 @var{expression} is true (nonzero, in C). When you use
3793 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3794 syntactic correctness, and to determine whether symbols in it have
3795 referents in the context of your breakpoint. If @var{expression} uses
3796 symbols not referenced in the context of the breakpoint, @value{GDBN}
3797 prints an error message:
3800 No symbol "foo" in current context.
3805 not actually evaluate @var{expression} at the time the @code{condition}
3806 command (or a command that sets a breakpoint with a condition, like
3807 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3809 @item condition @var{bnum}
3810 Remove the condition from breakpoint number @var{bnum}. It becomes
3811 an ordinary unconditional breakpoint.
3814 @cindex ignore count (of breakpoint)
3815 A special case of a breakpoint condition is to stop only when the
3816 breakpoint has been reached a certain number of times. This is so
3817 useful that there is a special way to do it, using the @dfn{ignore
3818 count} of the breakpoint. Every breakpoint has an ignore count, which
3819 is an integer. Most of the time, the ignore count is zero, and
3820 therefore has no effect. But if your program reaches a breakpoint whose
3821 ignore count is positive, then instead of stopping, it just decrements
3822 the ignore count by one and continues. As a result, if the ignore count
3823 value is @var{n}, the breakpoint does not stop the next @var{n} times
3824 your program reaches it.
3828 @item ignore @var{bnum} @var{count}
3829 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3830 The next @var{count} times the breakpoint is reached, your program's
3831 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3834 To make the breakpoint stop the next time it is reached, specify
3837 When you use @code{continue} to resume execution of your program from a
3838 breakpoint, you can specify an ignore count directly as an argument to
3839 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3840 Stepping,,Continuing and Stepping}.
3842 If a breakpoint has a positive ignore count and a condition, the
3843 condition is not checked. Once the ignore count reaches zero,
3844 @value{GDBN} resumes checking the condition.
3846 You could achieve the effect of the ignore count with a condition such
3847 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3848 is decremented each time. @xref{Convenience Vars, ,Convenience
3852 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3855 @node Break Commands
3856 @subsection Breakpoint Command Lists
3858 @cindex breakpoint commands
3859 You can give any breakpoint (or watchpoint or catchpoint) a series of
3860 commands to execute when your program stops due to that breakpoint. For
3861 example, you might want to print the values of certain expressions, or
3862 enable other breakpoints.
3866 @kindex end@r{ (breakpoint commands)}
3867 @item commands @r{[}@var{bnum}@r{]}
3868 @itemx @dots{} @var{command-list} @dots{}
3870 Specify a list of commands for breakpoint number @var{bnum}. The commands
3871 themselves appear on the following lines. Type a line containing just
3872 @code{end} to terminate the commands.
3874 To remove all commands from a breakpoint, type @code{commands} and
3875 follow it immediately with @code{end}; that is, give no commands.
3877 With no @var{bnum} argument, @code{commands} refers to the last
3878 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3879 recently encountered).
3882 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3883 disabled within a @var{command-list}.
3885 You can use breakpoint commands to start your program up again. Simply
3886 use the @code{continue} command, or @code{step}, or any other command
3887 that resumes execution.
3889 Any other commands in the command list, after a command that resumes
3890 execution, are ignored. This is because any time you resume execution
3891 (even with a simple @code{next} or @code{step}), you may encounter
3892 another breakpoint---which could have its own command list, leading to
3893 ambiguities about which list to execute.
3896 If the first command you specify in a command list is @code{silent}, the
3897 usual message about stopping at a breakpoint is not printed. This may
3898 be desirable for breakpoints that are to print a specific message and
3899 then continue. If none of the remaining commands print anything, you
3900 see no sign that the breakpoint was reached. @code{silent} is
3901 meaningful only at the beginning of a breakpoint command list.
3903 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3904 print precisely controlled output, and are often useful in silent
3905 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3907 For example, here is how you could use breakpoint commands to print the
3908 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3914 printf "x is %d\n",x
3919 One application for breakpoint commands is to compensate for one bug so
3920 you can test for another. Put a breakpoint just after the erroneous line
3921 of code, give it a condition to detect the case in which something
3922 erroneous has been done, and give it commands to assign correct values
3923 to any variables that need them. End with the @code{continue} command
3924 so that your program does not stop, and start with the @code{silent}
3925 command so that no output is produced. Here is an example:
3936 @c @ifclear BARETARGET
3937 @node Error in Breakpoints
3938 @subsection ``Cannot insert breakpoints''
3940 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3942 Under some operating systems, breakpoints cannot be used in a program if
3943 any other process is running that program. In this situation,
3944 attempting to run or continue a program with a breakpoint causes
3945 @value{GDBN} to print an error message:
3948 Cannot insert breakpoints.
3949 The same program may be running in another process.
3952 When this happens, you have three ways to proceed:
3956 Remove or disable the breakpoints, then continue.
3959 Suspend @value{GDBN}, and copy the file containing your program to a new
3960 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3961 that @value{GDBN} should run your program under that name.
3962 Then start your program again.
3965 Relink your program so that the text segment is nonsharable, using the
3966 linker option @samp{-N}. The operating system limitation may not apply
3967 to nonsharable executables.
3971 A similar message can be printed if you request too many active
3972 hardware-assisted breakpoints and watchpoints:
3974 @c FIXME: the precise wording of this message may change; the relevant
3975 @c source change is not committed yet (Sep 3, 1999).
3977 Stopped; cannot insert breakpoints.
3978 You may have requested too many hardware breakpoints and watchpoints.
3982 This message is printed when you attempt to resume the program, since
3983 only then @value{GDBN} knows exactly how many hardware breakpoints and
3984 watchpoints it needs to insert.
3986 When this message is printed, you need to disable or remove some of the
3987 hardware-assisted breakpoints and watchpoints, and then continue.
3989 @node Breakpoint-related Warnings
3990 @subsection ``Breakpoint address adjusted...''
3991 @cindex breakpoint address adjusted
3993 Some processor architectures place constraints on the addresses at
3994 which breakpoints may be placed. For architectures thus constrained,
3995 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3996 with the constraints dictated by the architecture.
3998 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3999 a VLIW architecture in which a number of RISC-like instructions may be
4000 bundled together for parallel execution. The FR-V architecture
4001 constrains the location of a breakpoint instruction within such a
4002 bundle to the instruction with the lowest address. @value{GDBN}
4003 honors this constraint by adjusting a breakpoint's address to the
4004 first in the bundle.
4006 It is not uncommon for optimized code to have bundles which contain
4007 instructions from different source statements, thus it may happen that
4008 a breakpoint's address will be adjusted from one source statement to
4009 another. Since this adjustment may significantly alter @value{GDBN}'s
4010 breakpoint related behavior from what the user expects, a warning is
4011 printed when the breakpoint is first set and also when the breakpoint
4014 A warning like the one below is printed when setting a breakpoint
4015 that's been subject to address adjustment:
4018 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4021 Such warnings are printed both for user settable and @value{GDBN}'s
4022 internal breakpoints. If you see one of these warnings, you should
4023 verify that a breakpoint set at the adjusted address will have the
4024 desired affect. If not, the breakpoint in question may be removed and
4025 other breakpoints may be set which will have the desired behavior.
4026 E.g., it may be sufficient to place the breakpoint at a later
4027 instruction. A conditional breakpoint may also be useful in some
4028 cases to prevent the breakpoint from triggering too often.
4030 @value{GDBN} will also issue a warning when stopping at one of these
4031 adjusted breakpoints:
4034 warning: Breakpoint 1 address previously adjusted from 0x00010414
4038 When this warning is encountered, it may be too late to take remedial
4039 action except in cases where the breakpoint is hit earlier or more
4040 frequently than expected.
4042 @node Continuing and Stepping
4043 @section Continuing and Stepping
4047 @cindex resuming execution
4048 @dfn{Continuing} means resuming program execution until your program
4049 completes normally. In contrast, @dfn{stepping} means executing just
4050 one more ``step'' of your program, where ``step'' may mean either one
4051 line of source code, or one machine instruction (depending on what
4052 particular command you use). Either when continuing or when stepping,
4053 your program may stop even sooner, due to a breakpoint or a signal. (If
4054 it stops due to a signal, you may want to use @code{handle}, or use
4055 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4059 @kindex c @r{(@code{continue})}
4060 @kindex fg @r{(resume foreground execution)}
4061 @item continue @r{[}@var{ignore-count}@r{]}
4062 @itemx c @r{[}@var{ignore-count}@r{]}
4063 @itemx fg @r{[}@var{ignore-count}@r{]}
4064 Resume program execution, at the address where your program last stopped;
4065 any breakpoints set at that address are bypassed. The optional argument
4066 @var{ignore-count} allows you to specify a further number of times to
4067 ignore a breakpoint at this location; its effect is like that of
4068 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4070 The argument @var{ignore-count} is meaningful only when your program
4071 stopped due to a breakpoint. At other times, the argument to
4072 @code{continue} is ignored.
4074 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4075 debugged program is deemed to be the foreground program) are provided
4076 purely for convenience, and have exactly the same behavior as
4080 To resume execution at a different place, you can use @code{return}
4081 (@pxref{Returning, ,Returning from a Function}) to go back to the
4082 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4083 Different Address}) to go to an arbitrary location in your program.
4085 A typical technique for using stepping is to set a breakpoint
4086 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4087 beginning of the function or the section of your program where a problem
4088 is believed to lie, run your program until it stops at that breakpoint,
4089 and then step through the suspect area, examining the variables that are
4090 interesting, until you see the problem happen.
4094 @kindex s @r{(@code{step})}
4096 Continue running your program until control reaches a different source
4097 line, then stop it and return control to @value{GDBN}. This command is
4098 abbreviated @code{s}.
4101 @c "without debugging information" is imprecise; actually "without line
4102 @c numbers in the debugging information". (gcc -g1 has debugging info but
4103 @c not line numbers). But it seems complex to try to make that
4104 @c distinction here.
4105 @emph{Warning:} If you use the @code{step} command while control is
4106 within a function that was compiled without debugging information,
4107 execution proceeds until control reaches a function that does have
4108 debugging information. Likewise, it will not step into a function which
4109 is compiled without debugging information. To step through functions
4110 without debugging information, use the @code{stepi} command, described
4114 The @code{step} command only stops at the first instruction of a source
4115 line. This prevents the multiple stops that could otherwise occur in
4116 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4117 to stop if a function that has debugging information is called within
4118 the line. In other words, @code{step} @emph{steps inside} any functions
4119 called within the line.
4121 Also, the @code{step} command only enters a function if there is line
4122 number information for the function. Otherwise it acts like the
4123 @code{next} command. This avoids problems when using @code{cc -gl}
4124 on MIPS machines. Previously, @code{step} entered subroutines if there
4125 was any debugging information about the routine.
4127 @item step @var{count}
4128 Continue running as in @code{step}, but do so @var{count} times. If a
4129 breakpoint is reached, or a signal not related to stepping occurs before
4130 @var{count} steps, stepping stops right away.
4133 @kindex n @r{(@code{next})}
4134 @item next @r{[}@var{count}@r{]}
4135 Continue to the next source line in the current (innermost) stack frame.
4136 This is similar to @code{step}, but function calls that appear within
4137 the line of code are executed without stopping. Execution stops when
4138 control reaches a different line of code at the original stack level
4139 that was executing when you gave the @code{next} command. This command
4140 is abbreviated @code{n}.
4142 An argument @var{count} is a repeat count, as for @code{step}.
4145 @c FIX ME!! Do we delete this, or is there a way it fits in with
4146 @c the following paragraph? --- Vctoria
4148 @c @code{next} within a function that lacks debugging information acts like
4149 @c @code{step}, but any function calls appearing within the code of the
4150 @c function are executed without stopping.
4152 The @code{next} command only stops at the first instruction of a
4153 source line. This prevents multiple stops that could otherwise occur in
4154 @code{switch} statements, @code{for} loops, etc.
4156 @kindex set step-mode
4158 @cindex functions without line info, and stepping
4159 @cindex stepping into functions with no line info
4160 @itemx set step-mode on
4161 The @code{set step-mode on} command causes the @code{step} command to
4162 stop at the first instruction of a function which contains no debug line
4163 information rather than stepping over it.
4165 This is useful in cases where you may be interested in inspecting the
4166 machine instructions of a function which has no symbolic info and do not
4167 want @value{GDBN} to automatically skip over this function.
4169 @item set step-mode off
4170 Causes the @code{step} command to step over any functions which contains no
4171 debug information. This is the default.
4173 @item show step-mode
4174 Show whether @value{GDBN} will stop in or step over functions without
4175 source line debug information.
4178 @kindex fin @r{(@code{finish})}
4180 Continue running until just after function in the selected stack frame
4181 returns. Print the returned value (if any). This command can be
4182 abbreviated as @code{fin}.
4184 Contrast this with the @code{return} command (@pxref{Returning,
4185 ,Returning from a Function}).
4188 @kindex u @r{(@code{until})}
4189 @cindex run until specified location
4192 Continue running until a source line past the current line, in the
4193 current stack frame, is reached. This command is used to avoid single
4194 stepping through a loop more than once. It is like the @code{next}
4195 command, except that when @code{until} encounters a jump, it
4196 automatically continues execution until the program counter is greater
4197 than the address of the jump.
4199 This means that when you reach the end of a loop after single stepping
4200 though it, @code{until} makes your program continue execution until it
4201 exits the loop. In contrast, a @code{next} command at the end of a loop
4202 simply steps back to the beginning of the loop, which forces you to step
4203 through the next iteration.
4205 @code{until} always stops your program if it attempts to exit the current
4208 @code{until} may produce somewhat counterintuitive results if the order
4209 of machine code does not match the order of the source lines. For
4210 example, in the following excerpt from a debugging session, the @code{f}
4211 (@code{frame}) command shows that execution is stopped at line
4212 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4216 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4218 (@value{GDBP}) until
4219 195 for ( ; argc > 0; NEXTARG) @{
4222 This happened because, for execution efficiency, the compiler had
4223 generated code for the loop closure test at the end, rather than the
4224 start, of the loop---even though the test in a C @code{for}-loop is
4225 written before the body of the loop. The @code{until} command appeared
4226 to step back to the beginning of the loop when it advanced to this
4227 expression; however, it has not really gone to an earlier
4228 statement---not in terms of the actual machine code.
4230 @code{until} with no argument works by means of single
4231 instruction stepping, and hence is slower than @code{until} with an
4234 @item until @var{location}
4235 @itemx u @var{location}
4236 Continue running your program until either the specified location is
4237 reached, or the current stack frame returns. @var{location} is any of
4238 the forms described in @ref{Specify Location}.
4239 This form of the command uses temporary breakpoints, and
4240 hence is quicker than @code{until} without an argument. The specified
4241 location is actually reached only if it is in the current frame. This
4242 implies that @code{until} can be used to skip over recursive function
4243 invocations. For instance in the code below, if the current location is
4244 line @code{96}, issuing @code{until 99} will execute the program up to
4245 line @code{99} in the same invocation of factorial, i.e., after the inner
4246 invocations have returned.
4249 94 int factorial (int value)
4251 96 if (value > 1) @{
4252 97 value *= factorial (value - 1);
4259 @kindex advance @var{location}
4260 @itemx advance @var{location}
4261 Continue running the program up to the given @var{location}. An argument is
4262 required, which should be of one of the forms described in
4263 @ref{Specify Location}.
4264 Execution will also stop upon exit from the current stack
4265 frame. This command is similar to @code{until}, but @code{advance} will
4266 not skip over recursive function calls, and the target location doesn't
4267 have to be in the same frame as the current one.
4271 @kindex si @r{(@code{stepi})}
4273 @itemx stepi @var{arg}
4275 Execute one machine instruction, then stop and return to the debugger.
4277 It is often useful to do @samp{display/i $pc} when stepping by machine
4278 instructions. This makes @value{GDBN} automatically display the next
4279 instruction to be executed, each time your program stops. @xref{Auto
4280 Display,, Automatic Display}.
4282 An argument is a repeat count, as in @code{step}.
4286 @kindex ni @r{(@code{nexti})}
4288 @itemx nexti @var{arg}
4290 Execute one machine instruction, but if it is a function call,
4291 proceed until the function returns.
4293 An argument is a repeat count, as in @code{next}.
4300 A signal is an asynchronous event that can happen in a program. The
4301 operating system defines the possible kinds of signals, and gives each
4302 kind a name and a number. For example, in Unix @code{SIGINT} is the
4303 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4304 @code{SIGSEGV} is the signal a program gets from referencing a place in
4305 memory far away from all the areas in use; @code{SIGALRM} occurs when
4306 the alarm clock timer goes off (which happens only if your program has
4307 requested an alarm).
4309 @cindex fatal signals
4310 Some signals, including @code{SIGALRM}, are a normal part of the
4311 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4312 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4313 program has not specified in advance some other way to handle the signal.
4314 @code{SIGINT} does not indicate an error in your program, but it is normally
4315 fatal so it can carry out the purpose of the interrupt: to kill the program.
4317 @value{GDBN} has the ability to detect any occurrence of a signal in your
4318 program. You can tell @value{GDBN} in advance what to do for each kind of
4321 @cindex handling signals
4322 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4323 @code{SIGALRM} be silently passed to your program
4324 (so as not to interfere with their role in the program's functioning)
4325 but to stop your program immediately whenever an error signal happens.
4326 You can change these settings with the @code{handle} command.
4329 @kindex info signals
4333 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4334 handle each one. You can use this to see the signal numbers of all
4335 the defined types of signals.
4337 @item info signals @var{sig}
4338 Similar, but print information only about the specified signal number.
4340 @code{info handle} is an alias for @code{info signals}.
4343 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4344 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4345 can be the number of a signal or its name (with or without the
4346 @samp{SIG} at the beginning); a list of signal numbers of the form
4347 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4348 known signals. Optional arguments @var{keywords}, described below,
4349 say what change to make.
4353 The keywords allowed by the @code{handle} command can be abbreviated.
4354 Their full names are:
4358 @value{GDBN} should not stop your program when this signal happens. It may
4359 still print a message telling you that the signal has come in.
4362 @value{GDBN} should stop your program when this signal happens. This implies
4363 the @code{print} keyword as well.
4366 @value{GDBN} should print a message when this signal happens.
4369 @value{GDBN} should not mention the occurrence of the signal at all. This
4370 implies the @code{nostop} keyword as well.
4374 @value{GDBN} should allow your program to see this signal; your program
4375 can handle the signal, or else it may terminate if the signal is fatal
4376 and not handled. @code{pass} and @code{noignore} are synonyms.
4380 @value{GDBN} should not allow your program to see this signal.
4381 @code{nopass} and @code{ignore} are synonyms.
4385 When a signal stops your program, the signal is not visible to the
4387 continue. Your program sees the signal then, if @code{pass} is in
4388 effect for the signal in question @emph{at that time}. In other words,
4389 after @value{GDBN} reports a signal, you can use the @code{handle}
4390 command with @code{pass} or @code{nopass} to control whether your
4391 program sees that signal when you continue.
4393 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4394 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4395 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4398 You can also use the @code{signal} command to prevent your program from
4399 seeing a signal, or cause it to see a signal it normally would not see,
4400 or to give it any signal at any time. For example, if your program stopped
4401 due to some sort of memory reference error, you might store correct
4402 values into the erroneous variables and continue, hoping to see more
4403 execution; but your program would probably terminate immediately as
4404 a result of the fatal signal once it saw the signal. To prevent this,
4405 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4409 @section Stopping and Starting Multi-thread Programs
4411 When your program has multiple threads (@pxref{Threads,, Debugging
4412 Programs with Multiple Threads}), you can choose whether to set
4413 breakpoints on all threads, or on a particular thread.
4416 @cindex breakpoints and threads
4417 @cindex thread breakpoints
4418 @kindex break @dots{} thread @var{threadno}
4419 @item break @var{linespec} thread @var{threadno}
4420 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4421 @var{linespec} specifies source lines; there are several ways of
4422 writing them (@pxref{Specify Location}), but the effect is always to
4423 specify some source line.
4425 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4426 to specify that you only want @value{GDBN} to stop the program when a
4427 particular thread reaches this breakpoint. @var{threadno} is one of the
4428 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4429 column of the @samp{info threads} display.
4431 If you do not specify @samp{thread @var{threadno}} when you set a
4432 breakpoint, the breakpoint applies to @emph{all} threads of your
4435 You can use the @code{thread} qualifier on conditional breakpoints as
4436 well; in this case, place @samp{thread @var{threadno}} before the
4437 breakpoint condition, like this:
4440 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4445 @cindex stopped threads
4446 @cindex threads, stopped
4447 Whenever your program stops under @value{GDBN} for any reason,
4448 @emph{all} threads of execution stop, not just the current thread. This
4449 allows you to examine the overall state of the program, including
4450 switching between threads, without worrying that things may change
4453 @cindex thread breakpoints and system calls
4454 @cindex system calls and thread breakpoints
4455 @cindex premature return from system calls
4456 There is an unfortunate side effect. If one thread stops for a
4457 breakpoint, or for some other reason, and another thread is blocked in a
4458 system call, then the system call may return prematurely. This is a
4459 consequence of the interaction between multiple threads and the signals
4460 that @value{GDBN} uses to implement breakpoints and other events that
4463 To handle this problem, your program should check the return value of
4464 each system call and react appropriately. This is good programming
4467 For example, do not write code like this:
4473 The call to @code{sleep} will return early if a different thread stops
4474 at a breakpoint or for some other reason.
4476 Instead, write this:
4481 unslept = sleep (unslept);
4484 A system call is allowed to return early, so the system is still
4485 conforming to its specification. But @value{GDBN} does cause your
4486 multi-threaded program to behave differently than it would without
4489 Also, @value{GDBN} uses internal breakpoints in the thread library to
4490 monitor certain events such as thread creation and thread destruction.
4491 When such an event happens, a system call in another thread may return
4492 prematurely, even though your program does not appear to stop.
4494 @cindex continuing threads
4495 @cindex threads, continuing
4496 Conversely, whenever you restart the program, @emph{all} threads start
4497 executing. @emph{This is true even when single-stepping} with commands
4498 like @code{step} or @code{next}.
4500 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4501 Since thread scheduling is up to your debugging target's operating
4502 system (not controlled by @value{GDBN}), other threads may
4503 execute more than one statement while the current thread completes a
4504 single step. Moreover, in general other threads stop in the middle of a
4505 statement, rather than at a clean statement boundary, when the program
4508 You might even find your program stopped in another thread after
4509 continuing or even single-stepping. This happens whenever some other
4510 thread runs into a breakpoint, a signal, or an exception before the
4511 first thread completes whatever you requested.
4513 On some OSes, you can lock the OS scheduler and thus allow only a single
4517 @item set scheduler-locking @var{mode}
4518 @cindex scheduler locking mode
4519 @cindex lock scheduler
4520 Set the scheduler locking mode. If it is @code{off}, then there is no
4521 locking and any thread may run at any time. If @code{on}, then only the
4522 current thread may run when the inferior is resumed. The @code{step}
4523 mode optimizes for single-stepping. It stops other threads from
4524 ``seizing the prompt'' by preempting the current thread while you are
4525 stepping. Other threads will only rarely (or never) get a chance to run
4526 when you step. They are more likely to run when you @samp{next} over a
4527 function call, and they are completely free to run when you use commands
4528 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4529 thread hits a breakpoint during its timeslice, they will never steal the
4530 @value{GDBN} prompt away from the thread that you are debugging.
4532 @item show scheduler-locking
4533 Display the current scheduler locking mode.
4538 @chapter Examining the Stack
4540 When your program has stopped, the first thing you need to know is where it
4541 stopped and how it got there.
4544 Each time your program performs a function call, information about the call
4546 That information includes the location of the call in your program,
4547 the arguments of the call,
4548 and the local variables of the function being called.
4549 The information is saved in a block of data called a @dfn{stack frame}.
4550 The stack frames are allocated in a region of memory called the @dfn{call
4553 When your program stops, the @value{GDBN} commands for examining the
4554 stack allow you to see all of this information.
4556 @cindex selected frame
4557 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4558 @value{GDBN} commands refer implicitly to the selected frame. In
4559 particular, whenever you ask @value{GDBN} for the value of a variable in
4560 your program, the value is found in the selected frame. There are
4561 special @value{GDBN} commands to select whichever frame you are
4562 interested in. @xref{Selection, ,Selecting a Frame}.
4564 When your program stops, @value{GDBN} automatically selects the
4565 currently executing frame and describes it briefly, similar to the
4566 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4569 * Frames:: Stack frames
4570 * Backtrace:: Backtraces
4571 * Selection:: Selecting a frame
4572 * Frame Info:: Information on a frame
4577 @section Stack Frames
4579 @cindex frame, definition
4581 The call stack is divided up into contiguous pieces called @dfn{stack
4582 frames}, or @dfn{frames} for short; each frame is the data associated
4583 with one call to one function. The frame contains the arguments given
4584 to the function, the function's local variables, and the address at
4585 which the function is executing.
4587 @cindex initial frame
4588 @cindex outermost frame
4589 @cindex innermost frame
4590 When your program is started, the stack has only one frame, that of the
4591 function @code{main}. This is called the @dfn{initial} frame or the
4592 @dfn{outermost} frame. Each time a function is called, a new frame is
4593 made. Each time a function returns, the frame for that function invocation
4594 is eliminated. If a function is recursive, there can be many frames for
4595 the same function. The frame for the function in which execution is
4596 actually occurring is called the @dfn{innermost} frame. This is the most
4597 recently created of all the stack frames that still exist.
4599 @cindex frame pointer
4600 Inside your program, stack frames are identified by their addresses. A
4601 stack frame consists of many bytes, each of which has its own address; each
4602 kind of computer has a convention for choosing one byte whose
4603 address serves as the address of the frame. Usually this address is kept
4604 in a register called the @dfn{frame pointer register}
4605 (@pxref{Registers, $fp}) while execution is going on in that frame.
4607 @cindex frame number
4608 @value{GDBN} assigns numbers to all existing stack frames, starting with
4609 zero for the innermost frame, one for the frame that called it,
4610 and so on upward. These numbers do not really exist in your program;
4611 they are assigned by @value{GDBN} to give you a way of designating stack
4612 frames in @value{GDBN} commands.
4614 @c The -fomit-frame-pointer below perennially causes hbox overflow
4615 @c underflow problems.
4616 @cindex frameless execution
4617 Some compilers provide a way to compile functions so that they operate
4618 without stack frames. (For example, the @value{NGCC} option
4620 @samp{-fomit-frame-pointer}
4622 generates functions without a frame.)
4623 This is occasionally done with heavily used library functions to save
4624 the frame setup time. @value{GDBN} has limited facilities for dealing
4625 with these function invocations. If the innermost function invocation
4626 has no stack frame, @value{GDBN} nevertheless regards it as though
4627 it had a separate frame, which is numbered zero as usual, allowing
4628 correct tracing of the function call chain. However, @value{GDBN} has
4629 no provision for frameless functions elsewhere in the stack.
4632 @kindex frame@r{, command}
4633 @cindex current stack frame
4634 @item frame @var{args}
4635 The @code{frame} command allows you to move from one stack frame to another,
4636 and to print the stack frame you select. @var{args} may be either the
4637 address of the frame or the stack frame number. Without an argument,
4638 @code{frame} prints the current stack frame.
4640 @kindex select-frame
4641 @cindex selecting frame silently
4643 The @code{select-frame} command allows you to move from one stack frame
4644 to another without printing the frame. This is the silent version of
4652 @cindex call stack traces
4653 A backtrace is a summary of how your program got where it is. It shows one
4654 line per frame, for many frames, starting with the currently executing
4655 frame (frame zero), followed by its caller (frame one), and on up the
4660 @kindex bt @r{(@code{backtrace})}
4663 Print a backtrace of the entire stack: one line per frame for all
4664 frames in the stack.
4666 You can stop the backtrace at any time by typing the system interrupt
4667 character, normally @kbd{Ctrl-c}.
4669 @item backtrace @var{n}
4671 Similar, but print only the innermost @var{n} frames.
4673 @item backtrace -@var{n}
4675 Similar, but print only the outermost @var{n} frames.
4677 @item backtrace full
4679 @itemx bt full @var{n}
4680 @itemx bt full -@var{n}
4681 Print the values of the local variables also. @var{n} specifies the
4682 number of frames to print, as described above.
4687 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4688 are additional aliases for @code{backtrace}.
4690 @cindex multiple threads, backtrace
4691 In a multi-threaded program, @value{GDBN} by default shows the
4692 backtrace only for the current thread. To display the backtrace for
4693 several or all of the threads, use the command @code{thread apply}
4694 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4695 apply all backtrace}, @value{GDBN} will display the backtrace for all
4696 the threads; this is handy when you debug a core dump of a
4697 multi-threaded program.
4699 Each line in the backtrace shows the frame number and the function name.
4700 The program counter value is also shown---unless you use @code{set
4701 print address off}. The backtrace also shows the source file name and
4702 line number, as well as the arguments to the function. The program
4703 counter value is omitted if it is at the beginning of the code for that
4706 Here is an example of a backtrace. It was made with the command
4707 @samp{bt 3}, so it shows the innermost three frames.
4711 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4713 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4714 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4716 (More stack frames follow...)
4721 The display for frame zero does not begin with a program counter
4722 value, indicating that your program has stopped at the beginning of the
4723 code for line @code{993} of @code{builtin.c}.
4725 @cindex value optimized out, in backtrace
4726 @cindex function call arguments, optimized out
4727 If your program was compiled with optimizations, some compilers will
4728 optimize away arguments passed to functions if those arguments are
4729 never used after the call. Such optimizations generate code that
4730 passes arguments through registers, but doesn't store those arguments
4731 in the stack frame. @value{GDBN} has no way of displaying such
4732 arguments in stack frames other than the innermost one. Here's what
4733 such a backtrace might look like:
4737 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4739 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4740 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4742 (More stack frames follow...)
4747 The values of arguments that were not saved in their stack frames are
4748 shown as @samp{<value optimized out>}.
4750 If you need to display the values of such optimized-out arguments,
4751 either deduce that from other variables whose values depend on the one
4752 you are interested in, or recompile without optimizations.
4754 @cindex backtrace beyond @code{main} function
4755 @cindex program entry point
4756 @cindex startup code, and backtrace
4757 Most programs have a standard user entry point---a place where system
4758 libraries and startup code transition into user code. For C this is
4759 @code{main}@footnote{
4760 Note that embedded programs (the so-called ``free-standing''
4761 environment) are not required to have a @code{main} function as the
4762 entry point. They could even have multiple entry points.}.
4763 When @value{GDBN} finds the entry function in a backtrace
4764 it will terminate the backtrace, to avoid tracing into highly
4765 system-specific (and generally uninteresting) code.
4767 If you need to examine the startup code, or limit the number of levels
4768 in a backtrace, you can change this behavior:
4771 @item set backtrace past-main
4772 @itemx set backtrace past-main on
4773 @kindex set backtrace
4774 Backtraces will continue past the user entry point.
4776 @item set backtrace past-main off
4777 Backtraces will stop when they encounter the user entry point. This is the
4780 @item show backtrace past-main
4781 @kindex show backtrace
4782 Display the current user entry point backtrace policy.
4784 @item set backtrace past-entry
4785 @itemx set backtrace past-entry on
4786 Backtraces will continue past the internal entry point of an application.
4787 This entry point is encoded by the linker when the application is built,
4788 and is likely before the user entry point @code{main} (or equivalent) is called.
4790 @item set backtrace past-entry off
4791 Backtraces will stop when they encounter the internal entry point of an
4792 application. This is the default.
4794 @item show backtrace past-entry
4795 Display the current internal entry point backtrace policy.
4797 @item set backtrace limit @var{n}
4798 @itemx set backtrace limit 0
4799 @cindex backtrace limit
4800 Limit the backtrace to @var{n} levels. A value of zero means
4803 @item show backtrace limit
4804 Display the current limit on backtrace levels.
4808 @section Selecting a Frame
4810 Most commands for examining the stack and other data in your program work on
4811 whichever stack frame is selected at the moment. Here are the commands for
4812 selecting a stack frame; all of them finish by printing a brief description
4813 of the stack frame just selected.
4816 @kindex frame@r{, selecting}
4817 @kindex f @r{(@code{frame})}
4820 Select frame number @var{n}. Recall that frame zero is the innermost
4821 (currently executing) frame, frame one is the frame that called the
4822 innermost one, and so on. The highest-numbered frame is the one for
4825 @item frame @var{addr}
4827 Select the frame at address @var{addr}. This is useful mainly if the
4828 chaining of stack frames has been damaged by a bug, making it
4829 impossible for @value{GDBN} to assign numbers properly to all frames. In
4830 addition, this can be useful when your program has multiple stacks and
4831 switches between them.
4833 On the SPARC architecture, @code{frame} needs two addresses to
4834 select an arbitrary frame: a frame pointer and a stack pointer.
4836 On the MIPS and Alpha architecture, it needs two addresses: a stack
4837 pointer and a program counter.
4839 On the 29k architecture, it needs three addresses: a register stack
4840 pointer, a program counter, and a memory stack pointer.
4844 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4845 advances toward the outermost frame, to higher frame numbers, to frames
4846 that have existed longer. @var{n} defaults to one.
4849 @kindex do @r{(@code{down})}
4851 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4852 advances toward the innermost frame, to lower frame numbers, to frames
4853 that were created more recently. @var{n} defaults to one. You may
4854 abbreviate @code{down} as @code{do}.
4857 All of these commands end by printing two lines of output describing the
4858 frame. The first line shows the frame number, the function name, the
4859 arguments, and the source file and line number of execution in that
4860 frame. The second line shows the text of that source line.
4868 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4870 10 read_input_file (argv[i]);
4874 After such a printout, the @code{list} command with no arguments
4875 prints ten lines centered on the point of execution in the frame.
4876 You can also edit the program at the point of execution with your favorite
4877 editing program by typing @code{edit}.
4878 @xref{List, ,Printing Source Lines},
4882 @kindex down-silently
4884 @item up-silently @var{n}
4885 @itemx down-silently @var{n}
4886 These two commands are variants of @code{up} and @code{down},
4887 respectively; they differ in that they do their work silently, without
4888 causing display of the new frame. They are intended primarily for use
4889 in @value{GDBN} command scripts, where the output might be unnecessary and
4894 @section Information About a Frame
4896 There are several other commands to print information about the selected
4902 When used without any argument, this command does not change which
4903 frame is selected, but prints a brief description of the currently
4904 selected stack frame. It can be abbreviated @code{f}. With an
4905 argument, this command is used to select a stack frame.
4906 @xref{Selection, ,Selecting a Frame}.
4909 @kindex info f @r{(@code{info frame})}
4912 This command prints a verbose description of the selected stack frame,
4917 the address of the frame
4919 the address of the next frame down (called by this frame)
4921 the address of the next frame up (caller of this frame)
4923 the language in which the source code corresponding to this frame is written
4925 the address of the frame's arguments
4927 the address of the frame's local variables
4929 the program counter saved in it (the address of execution in the caller frame)
4931 which registers were saved in the frame
4934 @noindent The verbose description is useful when
4935 something has gone wrong that has made the stack format fail to fit
4936 the usual conventions.
4938 @item info frame @var{addr}
4939 @itemx info f @var{addr}
4940 Print a verbose description of the frame at address @var{addr}, without
4941 selecting that frame. The selected frame remains unchanged by this
4942 command. This requires the same kind of address (more than one for some
4943 architectures) that you specify in the @code{frame} command.
4944 @xref{Selection, ,Selecting a Frame}.
4948 Print the arguments of the selected frame, each on a separate line.
4952 Print the local variables of the selected frame, each on a separate
4953 line. These are all variables (declared either static or automatic)
4954 accessible at the point of execution of the selected frame.
4957 @cindex catch exceptions, list active handlers
4958 @cindex exception handlers, how to list
4960 Print a list of all the exception handlers that are active in the
4961 current stack frame at the current point of execution. To see other
4962 exception handlers, visit the associated frame (using the @code{up},
4963 @code{down}, or @code{frame} commands); then type @code{info catch}.
4964 @xref{Set Catchpoints, , Setting Catchpoints}.
4970 @chapter Examining Source Files
4972 @value{GDBN} can print parts of your program's source, since the debugging
4973 information recorded in the program tells @value{GDBN} what source files were
4974 used to build it. When your program stops, @value{GDBN} spontaneously prints
4975 the line where it stopped. Likewise, when you select a stack frame
4976 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4977 execution in that frame has stopped. You can print other portions of
4978 source files by explicit command.
4980 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4981 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4982 @value{GDBN} under @sc{gnu} Emacs}.
4985 * List:: Printing source lines
4986 * Specify Location:: How to specify code locations
4987 * Edit:: Editing source files
4988 * Search:: Searching source files
4989 * Source Path:: Specifying source directories
4990 * Machine Code:: Source and machine code
4994 @section Printing Source Lines
4997 @kindex l @r{(@code{list})}
4998 To print lines from a source file, use the @code{list} command
4999 (abbreviated @code{l}). By default, ten lines are printed.
5000 There are several ways to specify what part of the file you want to
5001 print; see @ref{Specify Location}, for the full list.
5003 Here are the forms of the @code{list} command most commonly used:
5006 @item list @var{linenum}
5007 Print lines centered around line number @var{linenum} in the
5008 current source file.
5010 @item list @var{function}
5011 Print lines centered around the beginning of function
5015 Print more lines. If the last lines printed were printed with a
5016 @code{list} command, this prints lines following the last lines
5017 printed; however, if the last line printed was a solitary line printed
5018 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5019 Stack}), this prints lines centered around that line.
5022 Print lines just before the lines last printed.
5025 @cindex @code{list}, how many lines to display
5026 By default, @value{GDBN} prints ten source lines with any of these forms of
5027 the @code{list} command. You can change this using @code{set listsize}:
5030 @kindex set listsize
5031 @item set listsize @var{count}
5032 Make the @code{list} command display @var{count} source lines (unless
5033 the @code{list} argument explicitly specifies some other number).
5035 @kindex show listsize
5037 Display the number of lines that @code{list} prints.
5040 Repeating a @code{list} command with @key{RET} discards the argument,
5041 so it is equivalent to typing just @code{list}. This is more useful
5042 than listing the same lines again. An exception is made for an
5043 argument of @samp{-}; that argument is preserved in repetition so that
5044 each repetition moves up in the source file.
5046 In general, the @code{list} command expects you to supply zero, one or two
5047 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5048 of writing them (@pxref{Specify Location}), but the effect is always
5049 to specify some source line.
5051 Here is a complete description of the possible arguments for @code{list}:
5054 @item list @var{linespec}
5055 Print lines centered around the line specified by @var{linespec}.
5057 @item list @var{first},@var{last}
5058 Print lines from @var{first} to @var{last}. Both arguments are
5059 linespecs. When a @code{list} command has two linespecs, and the
5060 source file of the second linespec is omitted, this refers to
5061 the same source file as the first linespec.
5063 @item list ,@var{last}
5064 Print lines ending with @var{last}.
5066 @item list @var{first},
5067 Print lines starting with @var{first}.
5070 Print lines just after the lines last printed.
5073 Print lines just before the lines last printed.
5076 As described in the preceding table.
5079 @node Specify Location
5080 @section Specifying a Location
5081 @cindex specifying location
5084 Several @value{GDBN} commands accept arguments that specify a location
5085 of your program's code. Since @value{GDBN} is a source-level
5086 debugger, a location usually specifies some line in the source code;
5087 for that reason, locations are also known as @dfn{linespecs}.
5089 Here are all the different ways of specifying a code location that
5090 @value{GDBN} understands:
5094 Specifies the line number @var{linenum} of the current source file.
5097 @itemx +@var{offset}
5098 Specifies the line @var{offset} lines before or after the @dfn{current
5099 line}. For the @code{list} command, the current line is the last one
5100 printed; for the breakpoint commands, this is the line at which
5101 execution stopped in the currently selected @dfn{stack frame}
5102 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5103 used as the second of the two linespecs in a @code{list} command,
5104 this specifies the line @var{offset} lines up or down from the first
5107 @item @var{filename}:@var{linenum}
5108 Specifies the line @var{linenum} in the source file @var{filename}.
5110 @item @var{function}
5111 Specifies the line that begins the body of the function @var{function}.
5112 For example, in C, this is the line with the open brace.
5114 @item @var{filename}:@var{function}
5115 Specifies the line that begins the body of the function @var{function}
5116 in the file @var{filename}. You only need the file name with a
5117 function name to avoid ambiguity when there are identically named
5118 functions in different source files.
5120 @item *@var{address}
5121 Specifies the program address @var{address}. For line-oriented
5122 commands, such as @code{list} and @code{edit}, this specifies a source
5123 line that contains @var{address}. For @code{break} and other
5124 breakpoint oriented commands, this can be used to set breakpoints in
5125 parts of your program which do not have debugging information or
5128 Here @var{address} may be any expression valid in the current working
5129 language (@pxref{Languages, working language}) that specifies a code
5130 address. In addition, as a convenience, @value{GDBN} extends the
5131 semantics of expressions used in locations to cover the situations
5132 that frequently happen during debugging. Here are the various forms
5136 @item @var{expression}
5137 Any expression valid in the current working language.
5139 @item @var{funcaddr}
5140 An address of a function or procedure derived from its name. In C,
5141 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5142 simply the function's name @var{function} (and actually a special case
5143 of a valid expression). In Pascal and Modula-2, this is
5144 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5145 (although the Pascal form also works).
5147 This form specifies the address of the function's first instruction,
5148 before the stack frame and arguments have been set up.
5150 @item '@var{filename}'::@var{funcaddr}
5151 Like @var{funcaddr} above, but also specifies the name of the source
5152 file explicitly. This is useful if the name of the function does not
5153 specify the function unambiguously, e.g., if there are several
5154 functions with identical names in different source files.
5161 @section Editing Source Files
5162 @cindex editing source files
5165 @kindex e @r{(@code{edit})}
5166 To edit the lines in a source file, use the @code{edit} command.
5167 The editing program of your choice
5168 is invoked with the current line set to
5169 the active line in the program.
5170 Alternatively, there are several ways to specify what part of the file you
5171 want to print if you want to see other parts of the program:
5174 @item edit @var{location}
5175 Edit the source file specified by @code{location}. Editing starts at
5176 that @var{location}, e.g., at the specified source line of the
5177 specified file. @xref{Specify Location}, for all the possible forms
5178 of the @var{location} argument; here are the forms of the @code{edit}
5179 command most commonly used:
5182 @item edit @var{number}
5183 Edit the current source file with @var{number} as the active line number.
5185 @item edit @var{function}
5186 Edit the file containing @var{function} at the beginning of its definition.
5191 @subsection Choosing your Editor
5192 You can customize @value{GDBN} to use any editor you want
5194 The only restriction is that your editor (say @code{ex}), recognizes the
5195 following command-line syntax:
5197 ex +@var{number} file
5199 The optional numeric value +@var{number} specifies the number of the line in
5200 the file where to start editing.}.
5201 By default, it is @file{@value{EDITOR}}, but you can change this
5202 by setting the environment variable @code{EDITOR} before using
5203 @value{GDBN}. For example, to configure @value{GDBN} to use the
5204 @code{vi} editor, you could use these commands with the @code{sh} shell:
5210 or in the @code{csh} shell,
5212 setenv EDITOR /usr/bin/vi
5217 @section Searching Source Files
5218 @cindex searching source files
5220 There are two commands for searching through the current source file for a
5225 @kindex forward-search
5226 @item forward-search @var{regexp}
5227 @itemx search @var{regexp}
5228 The command @samp{forward-search @var{regexp}} checks each line,
5229 starting with the one following the last line listed, for a match for
5230 @var{regexp}. It lists the line that is found. You can use the
5231 synonym @samp{search @var{regexp}} or abbreviate the command name as
5234 @kindex reverse-search
5235 @item reverse-search @var{regexp}
5236 The command @samp{reverse-search @var{regexp}} checks each line, starting
5237 with the one before the last line listed and going backward, for a match
5238 for @var{regexp}. It lists the line that is found. You can abbreviate
5239 this command as @code{rev}.
5243 @section Specifying Source Directories
5246 @cindex directories for source files
5247 Executable programs sometimes do not record the directories of the source
5248 files from which they were compiled, just the names. Even when they do,
5249 the directories could be moved between the compilation and your debugging
5250 session. @value{GDBN} has a list of directories to search for source files;
5251 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5252 it tries all the directories in the list, in the order they are present
5253 in the list, until it finds a file with the desired name.
5255 For example, suppose an executable references the file
5256 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5257 @file{/mnt/cross}. The file is first looked up literally; if this
5258 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5259 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5260 message is printed. @value{GDBN} does not look up the parts of the
5261 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5262 Likewise, the subdirectories of the source path are not searched: if
5263 the source path is @file{/mnt/cross}, and the binary refers to
5264 @file{foo.c}, @value{GDBN} would not find it under
5265 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5267 Plain file names, relative file names with leading directories, file
5268 names containing dots, etc.@: are all treated as described above; for
5269 instance, if the source path is @file{/mnt/cross}, and the source file
5270 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5271 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5272 that---@file{/mnt/cross/foo.c}.
5274 Note that the executable search path is @emph{not} used to locate the
5277 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5278 any information it has cached about where source files are found and where
5279 each line is in the file.
5283 When you start @value{GDBN}, its source path includes only @samp{cdir}
5284 and @samp{cwd}, in that order.
5285 To add other directories, use the @code{directory} command.
5287 The search path is used to find both program source files and @value{GDBN}
5288 script files (read using the @samp{-command} option and @samp{source} command).
5290 In addition to the source path, @value{GDBN} provides a set of commands
5291 that manage a list of source path substitution rules. A @dfn{substitution
5292 rule} specifies how to rewrite source directories stored in the program's
5293 debug information in case the sources were moved to a different
5294 directory between compilation and debugging. A rule is made of
5295 two strings, the first specifying what needs to be rewritten in
5296 the path, and the second specifying how it should be rewritten.
5297 In @ref{set substitute-path}, we name these two parts @var{from} and
5298 @var{to} respectively. @value{GDBN} does a simple string replacement
5299 of @var{from} with @var{to} at the start of the directory part of the
5300 source file name, and uses that result instead of the original file
5301 name to look up the sources.
5303 Using the previous example, suppose the @file{foo-1.0} tree has been
5304 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5305 @value{GDBN} to replace @file{/usr/src} in all source path names with
5306 @file{/mnt/cross}. The first lookup will then be
5307 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5308 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5309 substitution rule, use the @code{set substitute-path} command
5310 (@pxref{set substitute-path}).
5312 To avoid unexpected substitution results, a rule is applied only if the
5313 @var{from} part of the directory name ends at a directory separator.
5314 For instance, a rule substituting @file{/usr/source} into
5315 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5316 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5317 is applied only at the beginning of the directory name, this rule will
5318 not be applied to @file{/root/usr/source/baz.c} either.
5320 In many cases, you can achieve the same result using the @code{directory}
5321 command. However, @code{set substitute-path} can be more efficient in
5322 the case where the sources are organized in a complex tree with multiple
5323 subdirectories. With the @code{directory} command, you need to add each
5324 subdirectory of your project. If you moved the entire tree while
5325 preserving its internal organization, then @code{set substitute-path}
5326 allows you to direct the debugger to all the sources with one single
5329 @code{set substitute-path} is also more than just a shortcut command.
5330 The source path is only used if the file at the original location no
5331 longer exists. On the other hand, @code{set substitute-path} modifies
5332 the debugger behavior to look at the rewritten location instead. So, if
5333 for any reason a source file that is not relevant to your executable is
5334 located at the original location, a substitution rule is the only
5335 method available to point @value{GDBN} at the new location.
5338 @item directory @var{dirname} @dots{}
5339 @item dir @var{dirname} @dots{}
5340 Add directory @var{dirname} to the front of the source path. Several
5341 directory names may be given to this command, separated by @samp{:}
5342 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5343 part of absolute file names) or
5344 whitespace. You may specify a directory that is already in the source
5345 path; this moves it forward, so @value{GDBN} searches it sooner.
5349 @vindex $cdir@r{, convenience variable}
5350 @vindex $cwd@r{, convenience variable}
5351 @cindex compilation directory
5352 @cindex current directory
5353 @cindex working directory
5354 @cindex directory, current
5355 @cindex directory, compilation
5356 You can use the string @samp{$cdir} to refer to the compilation
5357 directory (if one is recorded), and @samp{$cwd} to refer to the current
5358 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5359 tracks the current working directory as it changes during your @value{GDBN}
5360 session, while the latter is immediately expanded to the current
5361 directory at the time you add an entry to the source path.
5364 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5366 @c RET-repeat for @code{directory} is explicitly disabled, but since
5367 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5369 @item show directories
5370 @kindex show directories
5371 Print the source path: show which directories it contains.
5373 @anchor{set substitute-path}
5374 @item set substitute-path @var{from} @var{to}
5375 @kindex set substitute-path
5376 Define a source path substitution rule, and add it at the end of the
5377 current list of existing substitution rules. If a rule with the same
5378 @var{from} was already defined, then the old rule is also deleted.
5380 For example, if the file @file{/foo/bar/baz.c} was moved to
5381 @file{/mnt/cross/baz.c}, then the command
5384 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5388 will tell @value{GDBN} to replace @samp{/usr/src} with
5389 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5390 @file{baz.c} even though it was moved.
5392 In the case when more than one substitution rule have been defined,
5393 the rules are evaluated one by one in the order where they have been
5394 defined. The first one matching, if any, is selected to perform
5397 For instance, if we had entered the following commands:
5400 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5401 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5405 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5406 @file{/mnt/include/defs.h} by using the first rule. However, it would
5407 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5408 @file{/mnt/src/lib/foo.c}.
5411 @item unset substitute-path [path]
5412 @kindex unset substitute-path
5413 If a path is specified, search the current list of substitution rules
5414 for a rule that would rewrite that path. Delete that rule if found.
5415 A warning is emitted by the debugger if no rule could be found.
5417 If no path is specified, then all substitution rules are deleted.
5419 @item show substitute-path [path]
5420 @kindex show substitute-path
5421 If a path is specified, then print the source path substitution rule
5422 which would rewrite that path, if any.
5424 If no path is specified, then print all existing source path substitution
5429 If your source path is cluttered with directories that are no longer of
5430 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5431 versions of source. You can correct the situation as follows:
5435 Use @code{directory} with no argument to reset the source path to its default value.
5438 Use @code{directory} with suitable arguments to reinstall the
5439 directories you want in the source path. You can add all the
5440 directories in one command.
5444 @section Source and Machine Code
5445 @cindex source line and its code address
5447 You can use the command @code{info line} to map source lines to program
5448 addresses (and vice versa), and the command @code{disassemble} to display
5449 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5450 mode, the @code{info line} command causes the arrow to point to the
5451 line specified. Also, @code{info line} prints addresses in symbolic form as
5456 @item info line @var{linespec}
5457 Print the starting and ending addresses of the compiled code for
5458 source line @var{linespec}. You can specify source lines in any of
5459 the ways documented in @ref{Specify Location}.
5462 For example, we can use @code{info line} to discover the location of
5463 the object code for the first line of function
5464 @code{m4_changequote}:
5466 @c FIXME: I think this example should also show the addresses in
5467 @c symbolic form, as they usually would be displayed.
5469 (@value{GDBP}) info line m4_changequote
5470 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5474 @cindex code address and its source line
5475 We can also inquire (using @code{*@var{addr}} as the form for
5476 @var{linespec}) what source line covers a particular address:
5478 (@value{GDBP}) info line *0x63ff
5479 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5482 @cindex @code{$_} and @code{info line}
5483 @cindex @code{x} command, default address
5484 @kindex x@r{(examine), and} info line
5485 After @code{info line}, the default address for the @code{x} command
5486 is changed to the starting address of the line, so that @samp{x/i} is
5487 sufficient to begin examining the machine code (@pxref{Memory,
5488 ,Examining Memory}). Also, this address is saved as the value of the
5489 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5494 @cindex assembly instructions
5495 @cindex instructions, assembly
5496 @cindex machine instructions
5497 @cindex listing machine instructions
5499 @itemx disassemble /m
5500 This specialized command dumps a range of memory as machine
5501 instructions. It can also print mixed source+disassembly by specifying
5502 the @code{/m} modifier.
5503 The default memory range is the function surrounding the
5504 program counter of the selected frame. A single argument to this
5505 command is a program counter value; @value{GDBN} dumps the function
5506 surrounding this value. Two arguments specify a range of addresses
5507 (first inclusive, second exclusive) to dump.
5510 The following example shows the disassembly of a range of addresses of
5511 HP PA-RISC 2.0 code:
5514 (@value{GDBP}) disas 0x32c4 0x32e4
5515 Dump of assembler code from 0x32c4 to 0x32e4:
5516 0x32c4 <main+204>: addil 0,dp
5517 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5518 0x32cc <main+212>: ldil 0x3000,r31
5519 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5520 0x32d4 <main+220>: ldo 0(r31),rp
5521 0x32d8 <main+224>: addil -0x800,dp
5522 0x32dc <main+228>: ldo 0x588(r1),r26
5523 0x32e0 <main+232>: ldil 0x3000,r31
5524 End of assembler dump.
5527 Here is an example showing mixed source+assembly for Intel x86:
5530 (@value{GDBP}) disas /m main
5531 Dump of assembler code for function main:
5533 0x08048330 <main+0>: push %ebp
5534 0x08048331 <main+1>: mov %esp,%ebp
5535 0x08048333 <main+3>: sub $0x8,%esp
5536 0x08048336 <main+6>: and $0xfffffff0,%esp
5537 0x08048339 <main+9>: sub $0x10,%esp
5539 6 printf ("Hello.\n");
5540 0x0804833c <main+12>: movl $0x8048440,(%esp)
5541 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
5545 0x08048348 <main+24>: mov $0x0,%eax
5546 0x0804834d <main+29>: leave
5547 0x0804834e <main+30>: ret
5549 End of assembler dump.
5552 Some architectures have more than one commonly-used set of instruction
5553 mnemonics or other syntax.
5555 For programs that were dynamically linked and use shared libraries,
5556 instructions that call functions or branch to locations in the shared
5557 libraries might show a seemingly bogus location---it's actually a
5558 location of the relocation table. On some architectures, @value{GDBN}
5559 might be able to resolve these to actual function names.
5562 @kindex set disassembly-flavor
5563 @cindex Intel disassembly flavor
5564 @cindex AT&T disassembly flavor
5565 @item set disassembly-flavor @var{instruction-set}
5566 Select the instruction set to use when disassembling the
5567 program via the @code{disassemble} or @code{x/i} commands.
5569 Currently this command is only defined for the Intel x86 family. You
5570 can set @var{instruction-set} to either @code{intel} or @code{att}.
5571 The default is @code{att}, the AT&T flavor used by default by Unix
5572 assemblers for x86-based targets.
5574 @kindex show disassembly-flavor
5575 @item show disassembly-flavor
5576 Show the current setting of the disassembly flavor.
5581 @chapter Examining Data
5583 @cindex printing data
5584 @cindex examining data
5587 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5588 @c document because it is nonstandard... Under Epoch it displays in a
5589 @c different window or something like that.
5590 The usual way to examine data in your program is with the @code{print}
5591 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5592 evaluates and prints the value of an expression of the language your
5593 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5594 Different Languages}).
5597 @item print @var{expr}
5598 @itemx print /@var{f} @var{expr}
5599 @var{expr} is an expression (in the source language). By default the
5600 value of @var{expr} is printed in a format appropriate to its data type;
5601 you can choose a different format by specifying @samp{/@var{f}}, where
5602 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5606 @itemx print /@var{f}
5607 @cindex reprint the last value
5608 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5609 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5610 conveniently inspect the same value in an alternative format.
5613 A more low-level way of examining data is with the @code{x} command.
5614 It examines data in memory at a specified address and prints it in a
5615 specified format. @xref{Memory, ,Examining Memory}.
5617 If you are interested in information about types, or about how the
5618 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5619 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5623 * Expressions:: Expressions
5624 * Ambiguous Expressions:: Ambiguous Expressions
5625 * Variables:: Program variables
5626 * Arrays:: Artificial arrays
5627 * Output Formats:: Output formats
5628 * Memory:: Examining memory
5629 * Auto Display:: Automatic display
5630 * Print Settings:: Print settings
5631 * Value History:: Value history
5632 * Convenience Vars:: Convenience variables
5633 * Registers:: Registers
5634 * Floating Point Hardware:: Floating point hardware
5635 * Vector Unit:: Vector Unit
5636 * OS Information:: Auxiliary data provided by operating system
5637 * Memory Region Attributes:: Memory region attributes
5638 * Dump/Restore Files:: Copy between memory and a file
5639 * Core File Generation:: Cause a program dump its core
5640 * Character Sets:: Debugging programs that use a different
5641 character set than GDB does
5642 * Caching Remote Data:: Data caching for remote targets
5643 * Searching Memory:: Searching memory for a sequence of bytes
5647 @section Expressions
5650 @code{print} and many other @value{GDBN} commands accept an expression and
5651 compute its value. Any kind of constant, variable or operator defined
5652 by the programming language you are using is valid in an expression in
5653 @value{GDBN}. This includes conditional expressions, function calls,
5654 casts, and string constants. It also includes preprocessor macros, if
5655 you compiled your program to include this information; see
5658 @cindex arrays in expressions
5659 @value{GDBN} supports array constants in expressions input by
5660 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5661 you can use the command @code{print @{1, 2, 3@}} to create an array
5662 of three integers. If you pass an array to a function or assign it
5663 to a program variable, @value{GDBN} copies the array to memory that
5664 is @code{malloc}ed in the target program.
5666 Because C is so widespread, most of the expressions shown in examples in
5667 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5668 Languages}, for information on how to use expressions in other
5671 In this section, we discuss operators that you can use in @value{GDBN}
5672 expressions regardless of your programming language.
5674 @cindex casts, in expressions
5675 Casts are supported in all languages, not just in C, because it is so
5676 useful to cast a number into a pointer in order to examine a structure
5677 at that address in memory.
5678 @c FIXME: casts supported---Mod2 true?
5680 @value{GDBN} supports these operators, in addition to those common
5681 to programming languages:
5685 @samp{@@} is a binary operator for treating parts of memory as arrays.
5686 @xref{Arrays, ,Artificial Arrays}, for more information.
5689 @samp{::} allows you to specify a variable in terms of the file or
5690 function where it is defined. @xref{Variables, ,Program Variables}.
5692 @cindex @{@var{type}@}
5693 @cindex type casting memory
5694 @cindex memory, viewing as typed object
5695 @cindex casts, to view memory
5696 @item @{@var{type}@} @var{addr}
5697 Refers to an object of type @var{type} stored at address @var{addr} in
5698 memory. @var{addr} may be any expression whose value is an integer or
5699 pointer (but parentheses are required around binary operators, just as in
5700 a cast). This construct is allowed regardless of what kind of data is
5701 normally supposed to reside at @var{addr}.
5704 @node Ambiguous Expressions
5705 @section Ambiguous Expressions
5706 @cindex ambiguous expressions
5708 Expressions can sometimes contain some ambiguous elements. For instance,
5709 some programming languages (notably Ada, C@t{++} and Objective-C) permit
5710 a single function name to be defined several times, for application in
5711 different contexts. This is called @dfn{overloading}. Another example
5712 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
5713 templates and is typically instantiated several times, resulting in
5714 the same function name being defined in different contexts.
5716 In some cases and depending on the language, it is possible to adjust
5717 the expression to remove the ambiguity. For instance in C@t{++}, you
5718 can specify the signature of the function you want to break on, as in
5719 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
5720 qualified name of your function often makes the expression unambiguous
5723 When an ambiguity that needs to be resolved is detected, the debugger
5724 has the capability to display a menu of numbered choices for each
5725 possibility, and then waits for the selection with the prompt @samp{>}.
5726 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
5727 aborts the current command. If the command in which the expression was
5728 used allows more than one choice to be selected, the next option in the
5729 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
5732 For example, the following session excerpt shows an attempt to set a
5733 breakpoint at the overloaded symbol @code{String::after}.
5734 We choose three particular definitions of that function name:
5736 @c FIXME! This is likely to change to show arg type lists, at least
5739 (@value{GDBP}) b String::after
5742 [2] file:String.cc; line number:867
5743 [3] file:String.cc; line number:860
5744 [4] file:String.cc; line number:875
5745 [5] file:String.cc; line number:853
5746 [6] file:String.cc; line number:846
5747 [7] file:String.cc; line number:735
5749 Breakpoint 1 at 0xb26c: file String.cc, line 867.
5750 Breakpoint 2 at 0xb344: file String.cc, line 875.
5751 Breakpoint 3 at 0xafcc: file String.cc, line 846.
5752 Multiple breakpoints were set.
5753 Use the "delete" command to delete unwanted
5760 @kindex set multiple-symbols
5761 @item set multiple-symbols @var{mode}
5762 @cindex multiple-symbols menu
5764 This option allows you to adjust the debugger behavior when an expression
5767 By default, @var{mode} is set to @code{all}. If the command with which
5768 the expression is used allows more than one choice, then @value{GDBN}
5769 automatically selects all possible choices. For instance, inserting
5770 a breakpoint on a function using an ambiguous name results in a breakpoint
5771 inserted on each possible match. However, if a unique choice must be made,
5772 then @value{GDBN} uses the menu to help you disambiguate the expression.
5773 For instance, printing the address of an overloaded function will result
5774 in the use of the menu.
5776 When @var{mode} is set to @code{ask}, the debugger always uses the menu
5777 when an ambiguity is detected.
5779 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
5780 an error due to the ambiguity and the command is aborted.
5782 @kindex show multiple-symbols
5783 @item show multiple-symbols
5784 Show the current value of the @code{multiple-symbols} setting.
5788 @section Program Variables
5790 The most common kind of expression to use is the name of a variable
5793 Variables in expressions are understood in the selected stack frame
5794 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5798 global (or file-static)
5805 visible according to the scope rules of the
5806 programming language from the point of execution in that frame
5809 @noindent This means that in the function
5824 you can examine and use the variable @code{a} whenever your program is
5825 executing within the function @code{foo}, but you can only use or
5826 examine the variable @code{b} while your program is executing inside
5827 the block where @code{b} is declared.
5829 @cindex variable name conflict
5830 There is an exception: you can refer to a variable or function whose
5831 scope is a single source file even if the current execution point is not
5832 in this file. But it is possible to have more than one such variable or
5833 function with the same name (in different source files). If that
5834 happens, referring to that name has unpredictable effects. If you wish,
5835 you can specify a static variable in a particular function or file,
5836 using the colon-colon (@code{::}) notation:
5838 @cindex colon-colon, context for variables/functions
5840 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5841 @cindex @code{::}, context for variables/functions
5844 @var{file}::@var{variable}
5845 @var{function}::@var{variable}
5849 Here @var{file} or @var{function} is the name of the context for the
5850 static @var{variable}. In the case of file names, you can use quotes to
5851 make sure @value{GDBN} parses the file name as a single word---for example,
5852 to print a global value of @code{x} defined in @file{f2.c}:
5855 (@value{GDBP}) p 'f2.c'::x
5858 @cindex C@t{++} scope resolution
5859 This use of @samp{::} is very rarely in conflict with the very similar
5860 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5861 scope resolution operator in @value{GDBN} expressions.
5862 @c FIXME: Um, so what happens in one of those rare cases where it's in
5865 @cindex wrong values
5866 @cindex variable values, wrong
5867 @cindex function entry/exit, wrong values of variables
5868 @cindex optimized code, wrong values of variables
5870 @emph{Warning:} Occasionally, a local variable may appear to have the
5871 wrong value at certain points in a function---just after entry to a new
5872 scope, and just before exit.
5874 You may see this problem when you are stepping by machine instructions.
5875 This is because, on most machines, it takes more than one instruction to
5876 set up a stack frame (including local variable definitions); if you are
5877 stepping by machine instructions, variables may appear to have the wrong
5878 values until the stack frame is completely built. On exit, it usually
5879 also takes more than one machine instruction to destroy a stack frame;
5880 after you begin stepping through that group of instructions, local
5881 variable definitions may be gone.
5883 This may also happen when the compiler does significant optimizations.
5884 To be sure of always seeing accurate values, turn off all optimization
5887 @cindex ``No symbol "foo" in current context''
5888 Another possible effect of compiler optimizations is to optimize
5889 unused variables out of existence, or assign variables to registers (as
5890 opposed to memory addresses). Depending on the support for such cases
5891 offered by the debug info format used by the compiler, @value{GDBN}
5892 might not be able to display values for such local variables. If that
5893 happens, @value{GDBN} will print a message like this:
5896 No symbol "foo" in current context.
5899 To solve such problems, either recompile without optimizations, or use a
5900 different debug info format, if the compiler supports several such
5901 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5902 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5903 produces debug info in a format that is superior to formats such as
5904 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5905 an effective form for debug info. @xref{Debugging Options,,Options
5906 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5907 Compiler Collection (GCC)}.
5908 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5909 that are best suited to C@t{++} programs.
5911 If you ask to print an object whose contents are unknown to
5912 @value{GDBN}, e.g., because its data type is not completely specified
5913 by the debug information, @value{GDBN} will say @samp{<incomplete
5914 type>}. @xref{Symbols, incomplete type}, for more about this.
5916 Strings are identified as arrays of @code{char} values without specified
5917 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5918 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5919 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5920 defines literal string type @code{"char"} as @code{char} without a sign.
5925 signed char var1[] = "A";
5928 You get during debugging
5933 $2 = @{65 'A', 0 '\0'@}
5937 @section Artificial Arrays
5939 @cindex artificial array
5941 @kindex @@@r{, referencing memory as an array}
5942 It is often useful to print out several successive objects of the
5943 same type in memory; a section of an array, or an array of
5944 dynamically determined size for which only a pointer exists in the
5947 You can do this by referring to a contiguous span of memory as an
5948 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5949 operand of @samp{@@} should be the first element of the desired array
5950 and be an individual object. The right operand should be the desired length
5951 of the array. The result is an array value whose elements are all of
5952 the type of the left argument. The first element is actually the left
5953 argument; the second element comes from bytes of memory immediately
5954 following those that hold the first element, and so on. Here is an
5955 example. If a program says
5958 int *array = (int *) malloc (len * sizeof (int));
5962 you can print the contents of @code{array} with
5968 The left operand of @samp{@@} must reside in memory. Array values made
5969 with @samp{@@} in this way behave just like other arrays in terms of
5970 subscripting, and are coerced to pointers when used in expressions.
5971 Artificial arrays most often appear in expressions via the value history
5972 (@pxref{Value History, ,Value History}), after printing one out.
5974 Another way to create an artificial array is to use a cast.
5975 This re-interprets a value as if it were an array.
5976 The value need not be in memory:
5978 (@value{GDBP}) p/x (short[2])0x12345678
5979 $1 = @{0x1234, 0x5678@}
5982 As a convenience, if you leave the array length out (as in
5983 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5984 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5986 (@value{GDBP}) p/x (short[])0x12345678
5987 $2 = @{0x1234, 0x5678@}
5990 Sometimes the artificial array mechanism is not quite enough; in
5991 moderately complex data structures, the elements of interest may not
5992 actually be adjacent---for example, if you are interested in the values
5993 of pointers in an array. One useful work-around in this situation is
5994 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5995 Variables}) as a counter in an expression that prints the first
5996 interesting value, and then repeat that expression via @key{RET}. For
5997 instance, suppose you have an array @code{dtab} of pointers to
5998 structures, and you are interested in the values of a field @code{fv}
5999 in each structure. Here is an example of what you might type:
6009 @node Output Formats
6010 @section Output Formats
6012 @cindex formatted output
6013 @cindex output formats
6014 By default, @value{GDBN} prints a value according to its data type. Sometimes
6015 this is not what you want. For example, you might want to print a number
6016 in hex, or a pointer in decimal. Or you might want to view data in memory
6017 at a certain address as a character string or as an instruction. To do
6018 these things, specify an @dfn{output format} when you print a value.
6020 The simplest use of output formats is to say how to print a value
6021 already computed. This is done by starting the arguments of the
6022 @code{print} command with a slash and a format letter. The format
6023 letters supported are:
6027 Regard the bits of the value as an integer, and print the integer in
6031 Print as integer in signed decimal.
6034 Print as integer in unsigned decimal.
6037 Print as integer in octal.
6040 Print as integer in binary. The letter @samp{t} stands for ``two''.
6041 @footnote{@samp{b} cannot be used because these format letters are also
6042 used with the @code{x} command, where @samp{b} stands for ``byte'';
6043 see @ref{Memory,,Examining Memory}.}
6046 @cindex unknown address, locating
6047 @cindex locate address
6048 Print as an address, both absolute in hexadecimal and as an offset from
6049 the nearest preceding symbol. You can use this format used to discover
6050 where (in what function) an unknown address is located:
6053 (@value{GDBP}) p/a 0x54320
6054 $3 = 0x54320 <_initialize_vx+396>
6058 The command @code{info symbol 0x54320} yields similar results.
6059 @xref{Symbols, info symbol}.
6062 Regard as an integer and print it as a character constant. This
6063 prints both the numerical value and its character representation. The
6064 character representation is replaced with the octal escape @samp{\nnn}
6065 for characters outside the 7-bit @sc{ascii} range.
6067 Without this format, @value{GDBN} displays @code{char},
6068 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6069 constants. Single-byte members of vectors are displayed as integer
6073 Regard the bits of the value as a floating point number and print
6074 using typical floating point syntax.
6077 @cindex printing strings
6078 @cindex printing byte arrays
6079 Regard as a string, if possible. With this format, pointers to single-byte
6080 data are displayed as null-terminated strings and arrays of single-byte data
6081 are displayed as fixed-length strings. Other values are displayed in their
6084 Without this format, @value{GDBN} displays pointers to and arrays of
6085 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6086 strings. Single-byte members of a vector are displayed as an integer
6090 For example, to print the program counter in hex (@pxref{Registers}), type
6097 Note that no space is required before the slash; this is because command
6098 names in @value{GDBN} cannot contain a slash.
6100 To reprint the last value in the value history with a different format,
6101 you can use the @code{print} command with just a format and no
6102 expression. For example, @samp{p/x} reprints the last value in hex.
6105 @section Examining Memory
6107 You can use the command @code{x} (for ``examine'') to examine memory in
6108 any of several formats, independently of your program's data types.
6110 @cindex examining memory
6112 @kindex x @r{(examine memory)}
6113 @item x/@var{nfu} @var{addr}
6116 Use the @code{x} command to examine memory.
6119 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6120 much memory to display and how to format it; @var{addr} is an
6121 expression giving the address where you want to start displaying memory.
6122 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6123 Several commands set convenient defaults for @var{addr}.
6126 @item @var{n}, the repeat count
6127 The repeat count is a decimal integer; the default is 1. It specifies
6128 how much memory (counting by units @var{u}) to display.
6129 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6132 @item @var{f}, the display format
6133 The display format is one of the formats used by @code{print}
6134 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6135 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6136 The default is @samp{x} (hexadecimal) initially. The default changes
6137 each time you use either @code{x} or @code{print}.
6139 @item @var{u}, the unit size
6140 The unit size is any of
6146 Halfwords (two bytes).
6148 Words (four bytes). This is the initial default.
6150 Giant words (eight bytes).
6153 Each time you specify a unit size with @code{x}, that size becomes the
6154 default unit the next time you use @code{x}. (For the @samp{s} and
6155 @samp{i} formats, the unit size is ignored and is normally not written.)
6157 @item @var{addr}, starting display address
6158 @var{addr} is the address where you want @value{GDBN} to begin displaying
6159 memory. The expression need not have a pointer value (though it may);
6160 it is always interpreted as an integer address of a byte of memory.
6161 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6162 @var{addr} is usually just after the last address examined---but several
6163 other commands also set the default address: @code{info breakpoints} (to
6164 the address of the last breakpoint listed), @code{info line} (to the
6165 starting address of a line), and @code{print} (if you use it to display
6166 a value from memory).
6169 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6170 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6171 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6172 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6173 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6175 Since the letters indicating unit sizes are all distinct from the
6176 letters specifying output formats, you do not have to remember whether
6177 unit size or format comes first; either order works. The output
6178 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6179 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6181 Even though the unit size @var{u} is ignored for the formats @samp{s}
6182 and @samp{i}, you might still want to use a count @var{n}; for example,
6183 @samp{3i} specifies that you want to see three machine instructions,
6184 including any operands. For convenience, especially when used with
6185 the @code{display} command, the @samp{i} format also prints branch delay
6186 slot instructions, if any, beyond the count specified, which immediately
6187 follow the last instruction that is within the count. The command
6188 @code{disassemble} gives an alternative way of inspecting machine
6189 instructions; see @ref{Machine Code,,Source and Machine Code}.
6191 All the defaults for the arguments to @code{x} are designed to make it
6192 easy to continue scanning memory with minimal specifications each time
6193 you use @code{x}. For example, after you have inspected three machine
6194 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6195 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6196 the repeat count @var{n} is used again; the other arguments default as
6197 for successive uses of @code{x}.
6199 @cindex @code{$_}, @code{$__}, and value history
6200 The addresses and contents printed by the @code{x} command are not saved
6201 in the value history because there is often too much of them and they
6202 would get in the way. Instead, @value{GDBN} makes these values available for
6203 subsequent use in expressions as values of the convenience variables
6204 @code{$_} and @code{$__}. After an @code{x} command, the last address
6205 examined is available for use in expressions in the convenience variable
6206 @code{$_}. The contents of that address, as examined, are available in
6207 the convenience variable @code{$__}.
6209 If the @code{x} command has a repeat count, the address and contents saved
6210 are from the last memory unit printed; this is not the same as the last
6211 address printed if several units were printed on the last line of output.
6213 @cindex remote memory comparison
6214 @cindex verify remote memory image
6215 When you are debugging a program running on a remote target machine
6216 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6217 remote machine's memory against the executable file you downloaded to
6218 the target. The @code{compare-sections} command is provided for such
6222 @kindex compare-sections
6223 @item compare-sections @r{[}@var{section-name}@r{]}
6224 Compare the data of a loadable section @var{section-name} in the
6225 executable file of the program being debugged with the same section in
6226 the remote machine's memory, and report any mismatches. With no
6227 arguments, compares all loadable sections. This command's
6228 availability depends on the target's support for the @code{"qCRC"}
6233 @section Automatic Display
6234 @cindex automatic display
6235 @cindex display of expressions
6237 If you find that you want to print the value of an expression frequently
6238 (to see how it changes), you might want to add it to the @dfn{automatic
6239 display list} so that @value{GDBN} prints its value each time your program stops.
6240 Each expression added to the list is given a number to identify it;
6241 to remove an expression from the list, you specify that number.
6242 The automatic display looks like this:
6246 3: bar[5] = (struct hack *) 0x3804
6250 This display shows item numbers, expressions and their current values. As with
6251 displays you request manually using @code{x} or @code{print}, you can
6252 specify the output format you prefer; in fact, @code{display} decides
6253 whether to use @code{print} or @code{x} depending your format
6254 specification---it uses @code{x} if you specify either the @samp{i}
6255 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6259 @item display @var{expr}
6260 Add the expression @var{expr} to the list of expressions to display
6261 each time your program stops. @xref{Expressions, ,Expressions}.
6263 @code{display} does not repeat if you press @key{RET} again after using it.
6265 @item display/@var{fmt} @var{expr}
6266 For @var{fmt} specifying only a display format and not a size or
6267 count, add the expression @var{expr} to the auto-display list but
6268 arrange to display it each time in the specified format @var{fmt}.
6269 @xref{Output Formats,,Output Formats}.
6271 @item display/@var{fmt} @var{addr}
6272 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6273 number of units, add the expression @var{addr} as a memory address to
6274 be examined each time your program stops. Examining means in effect
6275 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6278 For example, @samp{display/i $pc} can be helpful, to see the machine
6279 instruction about to be executed each time execution stops (@samp{$pc}
6280 is a common name for the program counter; @pxref{Registers, ,Registers}).
6283 @kindex delete display
6285 @item undisplay @var{dnums}@dots{}
6286 @itemx delete display @var{dnums}@dots{}
6287 Remove item numbers @var{dnums} from the list of expressions to display.
6289 @code{undisplay} does not repeat if you press @key{RET} after using it.
6290 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6292 @kindex disable display
6293 @item disable display @var{dnums}@dots{}
6294 Disable the display of item numbers @var{dnums}. A disabled display
6295 item is not printed automatically, but is not forgotten. It may be
6296 enabled again later.
6298 @kindex enable display
6299 @item enable display @var{dnums}@dots{}
6300 Enable display of item numbers @var{dnums}. It becomes effective once
6301 again in auto display of its expression, until you specify otherwise.
6304 Display the current values of the expressions on the list, just as is
6305 done when your program stops.
6307 @kindex info display
6309 Print the list of expressions previously set up to display
6310 automatically, each one with its item number, but without showing the
6311 values. This includes disabled expressions, which are marked as such.
6312 It also includes expressions which would not be displayed right now
6313 because they refer to automatic variables not currently available.
6316 @cindex display disabled out of scope
6317 If a display expression refers to local variables, then it does not make
6318 sense outside the lexical context for which it was set up. Such an
6319 expression is disabled when execution enters a context where one of its
6320 variables is not defined. For example, if you give the command
6321 @code{display last_char} while inside a function with an argument
6322 @code{last_char}, @value{GDBN} displays this argument while your program
6323 continues to stop inside that function. When it stops elsewhere---where
6324 there is no variable @code{last_char}---the display is disabled
6325 automatically. The next time your program stops where @code{last_char}
6326 is meaningful, you can enable the display expression once again.
6328 @node Print Settings
6329 @section Print Settings
6331 @cindex format options
6332 @cindex print settings
6333 @value{GDBN} provides the following ways to control how arrays, structures,
6334 and symbols are printed.
6337 These settings are useful for debugging programs in any language:
6341 @item set print address
6342 @itemx set print address on
6343 @cindex print/don't print memory addresses
6344 @value{GDBN} prints memory addresses showing the location of stack
6345 traces, structure values, pointer values, breakpoints, and so forth,
6346 even when it also displays the contents of those addresses. The default
6347 is @code{on}. For example, this is what a stack frame display looks like with
6348 @code{set print address on}:
6353 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6355 530 if (lquote != def_lquote)
6359 @item set print address off
6360 Do not print addresses when displaying their contents. For example,
6361 this is the same stack frame displayed with @code{set print address off}:
6365 (@value{GDBP}) set print addr off
6367 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6368 530 if (lquote != def_lquote)
6372 You can use @samp{set print address off} to eliminate all machine
6373 dependent displays from the @value{GDBN} interface. For example, with
6374 @code{print address off}, you should get the same text for backtraces on
6375 all machines---whether or not they involve pointer arguments.
6378 @item show print address
6379 Show whether or not addresses are to be printed.
6382 When @value{GDBN} prints a symbolic address, it normally prints the
6383 closest earlier symbol plus an offset. If that symbol does not uniquely
6384 identify the address (for example, it is a name whose scope is a single
6385 source file), you may need to clarify. One way to do this is with
6386 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6387 you can set @value{GDBN} to print the source file and line number when
6388 it prints a symbolic address:
6391 @item set print symbol-filename on
6392 @cindex source file and line of a symbol
6393 @cindex symbol, source file and line
6394 Tell @value{GDBN} to print the source file name and line number of a
6395 symbol in the symbolic form of an address.
6397 @item set print symbol-filename off
6398 Do not print source file name and line number of a symbol. This is the
6401 @item show print symbol-filename
6402 Show whether or not @value{GDBN} will print the source file name and
6403 line number of a symbol in the symbolic form of an address.
6406 Another situation where it is helpful to show symbol filenames and line
6407 numbers is when disassembling code; @value{GDBN} shows you the line
6408 number and source file that corresponds to each instruction.
6410 Also, you may wish to see the symbolic form only if the address being
6411 printed is reasonably close to the closest earlier symbol:
6414 @item set print max-symbolic-offset @var{max-offset}
6415 @cindex maximum value for offset of closest symbol
6416 Tell @value{GDBN} to only display the symbolic form of an address if the
6417 offset between the closest earlier symbol and the address is less than
6418 @var{max-offset}. The default is 0, which tells @value{GDBN}
6419 to always print the symbolic form of an address if any symbol precedes it.
6421 @item show print max-symbolic-offset
6422 Ask how large the maximum offset is that @value{GDBN} prints in a
6426 @cindex wild pointer, interpreting
6427 @cindex pointer, finding referent
6428 If you have a pointer and you are not sure where it points, try
6429 @samp{set print symbol-filename on}. Then you can determine the name
6430 and source file location of the variable where it points, using
6431 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6432 For example, here @value{GDBN} shows that a variable @code{ptt} points
6433 at another variable @code{t}, defined in @file{hi2.c}:
6436 (@value{GDBP}) set print symbol-filename on
6437 (@value{GDBP}) p/a ptt
6438 $4 = 0xe008 <t in hi2.c>
6442 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6443 does not show the symbol name and filename of the referent, even with
6444 the appropriate @code{set print} options turned on.
6447 Other settings control how different kinds of objects are printed:
6450 @item set print array
6451 @itemx set print array on
6452 @cindex pretty print arrays
6453 Pretty print arrays. This format is more convenient to read,
6454 but uses more space. The default is off.
6456 @item set print array off
6457 Return to compressed format for arrays.
6459 @item show print array
6460 Show whether compressed or pretty format is selected for displaying
6463 @cindex print array indexes
6464 @item set print array-indexes
6465 @itemx set print array-indexes on
6466 Print the index of each element when displaying arrays. May be more
6467 convenient to locate a given element in the array or quickly find the
6468 index of a given element in that printed array. The default is off.
6470 @item set print array-indexes off
6471 Stop printing element indexes when displaying arrays.
6473 @item show print array-indexes
6474 Show whether the index of each element is printed when displaying
6477 @item set print elements @var{number-of-elements}
6478 @cindex number of array elements to print
6479 @cindex limit on number of printed array elements
6480 Set a limit on how many elements of an array @value{GDBN} will print.
6481 If @value{GDBN} is printing a large array, it stops printing after it has
6482 printed the number of elements set by the @code{set print elements} command.
6483 This limit also applies to the display of strings.
6484 When @value{GDBN} starts, this limit is set to 200.
6485 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6487 @item show print elements
6488 Display the number of elements of a large array that @value{GDBN} will print.
6489 If the number is 0, then the printing is unlimited.
6491 @item set print frame-arguments @var{value}
6492 @cindex printing frame argument values
6493 @cindex print all frame argument values
6494 @cindex print frame argument values for scalars only
6495 @cindex do not print frame argument values
6496 This command allows to control how the values of arguments are printed
6497 when the debugger prints a frame (@pxref{Frames}). The possible
6502 The values of all arguments are printed. This is the default.
6505 Print the value of an argument only if it is a scalar. The value of more
6506 complex arguments such as arrays, structures, unions, etc, is replaced
6507 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6510 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6515 None of the argument values are printed. Instead, the value of each argument
6516 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6519 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6524 By default, all argument values are always printed. But this command
6525 can be useful in several cases. For instance, it can be used to reduce
6526 the amount of information printed in each frame, making the backtrace
6527 more readable. Also, this command can be used to improve performance
6528 when displaying Ada frames, because the computation of large arguments
6529 can sometimes be CPU-intensive, especiallly in large applications.
6530 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6531 avoids this computation, thus speeding up the display of each Ada frame.
6533 @item show print frame-arguments
6534 Show how the value of arguments should be displayed when printing a frame.
6536 @item set print repeats
6537 @cindex repeated array elements
6538 Set the threshold for suppressing display of repeated array
6539 elements. When the number of consecutive identical elements of an
6540 array exceeds the threshold, @value{GDBN} prints the string
6541 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6542 identical repetitions, instead of displaying the identical elements
6543 themselves. Setting the threshold to zero will cause all elements to
6544 be individually printed. The default threshold is 10.
6546 @item show print repeats
6547 Display the current threshold for printing repeated identical
6550 @item set print null-stop
6551 @cindex @sc{null} elements in arrays
6552 Cause @value{GDBN} to stop printing the characters of an array when the first
6553 @sc{null} is encountered. This is useful when large arrays actually
6554 contain only short strings.
6557 @item show print null-stop
6558 Show whether @value{GDBN} stops printing an array on the first
6559 @sc{null} character.
6561 @item set print pretty on
6562 @cindex print structures in indented form
6563 @cindex indentation in structure display
6564 Cause @value{GDBN} to print structures in an indented format with one member
6565 per line, like this:
6580 @item set print pretty off
6581 Cause @value{GDBN} to print structures in a compact format, like this:
6585 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6586 meat = 0x54 "Pork"@}
6591 This is the default format.
6593 @item show print pretty
6594 Show which format @value{GDBN} is using to print structures.
6596 @item set print sevenbit-strings on
6597 @cindex eight-bit characters in strings
6598 @cindex octal escapes in strings
6599 Print using only seven-bit characters; if this option is set,
6600 @value{GDBN} displays any eight-bit characters (in strings or
6601 character values) using the notation @code{\}@var{nnn}. This setting is
6602 best if you are working in English (@sc{ascii}) and you use the
6603 high-order bit of characters as a marker or ``meta'' bit.
6605 @item set print sevenbit-strings off
6606 Print full eight-bit characters. This allows the use of more
6607 international character sets, and is the default.
6609 @item show print sevenbit-strings
6610 Show whether or not @value{GDBN} is printing only seven-bit characters.
6612 @item set print union on
6613 @cindex unions in structures, printing
6614 Tell @value{GDBN} to print unions which are contained in structures
6615 and other unions. This is the default setting.
6617 @item set print union off
6618 Tell @value{GDBN} not to print unions which are contained in
6619 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6622 @item show print union
6623 Ask @value{GDBN} whether or not it will print unions which are contained in
6624 structures and other unions.
6626 For example, given the declarations
6629 typedef enum @{Tree, Bug@} Species;
6630 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6631 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6642 struct thing foo = @{Tree, @{Acorn@}@};
6646 with @code{set print union on} in effect @samp{p foo} would print
6649 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6653 and with @code{set print union off} in effect it would print
6656 $1 = @{it = Tree, form = @{...@}@}
6660 @code{set print union} affects programs written in C-like languages
6666 These settings are of interest when debugging C@t{++} programs:
6669 @cindex demangling C@t{++} names
6670 @item set print demangle
6671 @itemx set print demangle on
6672 Print C@t{++} names in their source form rather than in the encoded
6673 (``mangled'') form passed to the assembler and linker for type-safe
6674 linkage. The default is on.
6676 @item show print demangle
6677 Show whether C@t{++} names are printed in mangled or demangled form.
6679 @item set print asm-demangle
6680 @itemx set print asm-demangle on
6681 Print C@t{++} names in their source form rather than their mangled form, even
6682 in assembler code printouts such as instruction disassemblies.
6685 @item show print asm-demangle
6686 Show whether C@t{++} names in assembly listings are printed in mangled
6689 @cindex C@t{++} symbol decoding style
6690 @cindex symbol decoding style, C@t{++}
6691 @kindex set demangle-style
6692 @item set demangle-style @var{style}
6693 Choose among several encoding schemes used by different compilers to
6694 represent C@t{++} names. The choices for @var{style} are currently:
6698 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6701 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6702 This is the default.
6705 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6708 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6711 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6712 @strong{Warning:} this setting alone is not sufficient to allow
6713 debugging @code{cfront}-generated executables. @value{GDBN} would
6714 require further enhancement to permit that.
6717 If you omit @var{style}, you will see a list of possible formats.
6719 @item show demangle-style
6720 Display the encoding style currently in use for decoding C@t{++} symbols.
6722 @item set print object
6723 @itemx set print object on
6724 @cindex derived type of an object, printing
6725 @cindex display derived types
6726 When displaying a pointer to an object, identify the @emph{actual}
6727 (derived) type of the object rather than the @emph{declared} type, using
6728 the virtual function table.
6730 @item set print object off
6731 Display only the declared type of objects, without reference to the
6732 virtual function table. This is the default setting.
6734 @item show print object
6735 Show whether actual, or declared, object types are displayed.
6737 @item set print static-members
6738 @itemx set print static-members on
6739 @cindex static members of C@t{++} objects
6740 Print static members when displaying a C@t{++} object. The default is on.
6742 @item set print static-members off
6743 Do not print static members when displaying a C@t{++} object.
6745 @item show print static-members
6746 Show whether C@t{++} static members are printed or not.
6748 @item set print pascal_static-members
6749 @itemx set print pascal_static-members on
6750 @cindex static members of Pascal objects
6751 @cindex Pascal objects, static members display
6752 Print static members when displaying a Pascal object. The default is on.
6754 @item set print pascal_static-members off
6755 Do not print static members when displaying a Pascal object.
6757 @item show print pascal_static-members
6758 Show whether Pascal static members are printed or not.
6760 @c These don't work with HP ANSI C++ yet.
6761 @item set print vtbl
6762 @itemx set print vtbl on
6763 @cindex pretty print C@t{++} virtual function tables
6764 @cindex virtual functions (C@t{++}) display
6765 @cindex VTBL display
6766 Pretty print C@t{++} virtual function tables. The default is off.
6767 (The @code{vtbl} commands do not work on programs compiled with the HP
6768 ANSI C@t{++} compiler (@code{aCC}).)
6770 @item set print vtbl off
6771 Do not pretty print C@t{++} virtual function tables.
6773 @item show print vtbl
6774 Show whether C@t{++} virtual function tables are pretty printed, or not.
6778 @section Value History
6780 @cindex value history
6781 @cindex history of values printed by @value{GDBN}
6782 Values printed by the @code{print} command are saved in the @value{GDBN}
6783 @dfn{value history}. This allows you to refer to them in other expressions.
6784 Values are kept until the symbol table is re-read or discarded
6785 (for example with the @code{file} or @code{symbol-file} commands).
6786 When the symbol table changes, the value history is discarded,
6787 since the values may contain pointers back to the types defined in the
6792 @cindex history number
6793 The values printed are given @dfn{history numbers} by which you can
6794 refer to them. These are successive integers starting with one.
6795 @code{print} shows you the history number assigned to a value by
6796 printing @samp{$@var{num} = } before the value; here @var{num} is the
6799 To refer to any previous value, use @samp{$} followed by the value's
6800 history number. The way @code{print} labels its output is designed to
6801 remind you of this. Just @code{$} refers to the most recent value in
6802 the history, and @code{$$} refers to the value before that.
6803 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6804 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6805 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6807 For example, suppose you have just printed a pointer to a structure and
6808 want to see the contents of the structure. It suffices to type
6814 If you have a chain of structures where the component @code{next} points
6815 to the next one, you can print the contents of the next one with this:
6822 You can print successive links in the chain by repeating this
6823 command---which you can do by just typing @key{RET}.
6825 Note that the history records values, not expressions. If the value of
6826 @code{x} is 4 and you type these commands:
6834 then the value recorded in the value history by the @code{print} command
6835 remains 4 even though the value of @code{x} has changed.
6840 Print the last ten values in the value history, with their item numbers.
6841 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6842 values} does not change the history.
6844 @item show values @var{n}
6845 Print ten history values centered on history item number @var{n}.
6848 Print ten history values just after the values last printed. If no more
6849 values are available, @code{show values +} produces no display.
6852 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6853 same effect as @samp{show values +}.
6855 @node Convenience Vars
6856 @section Convenience Variables
6858 @cindex convenience variables
6859 @cindex user-defined variables
6860 @value{GDBN} provides @dfn{convenience variables} that you can use within
6861 @value{GDBN} to hold on to a value and refer to it later. These variables
6862 exist entirely within @value{GDBN}; they are not part of your program, and
6863 setting a convenience variable has no direct effect on further execution
6864 of your program. That is why you can use them freely.
6866 Convenience variables are prefixed with @samp{$}. Any name preceded by
6867 @samp{$} can be used for a convenience variable, unless it is one of
6868 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6869 (Value history references, in contrast, are @emph{numbers} preceded
6870 by @samp{$}. @xref{Value History, ,Value History}.)
6872 You can save a value in a convenience variable with an assignment
6873 expression, just as you would set a variable in your program.
6877 set $foo = *object_ptr
6881 would save in @code{$foo} the value contained in the object pointed to by
6884 Using a convenience variable for the first time creates it, but its
6885 value is @code{void} until you assign a new value. You can alter the
6886 value with another assignment at any time.
6888 Convenience variables have no fixed types. You can assign a convenience
6889 variable any type of value, including structures and arrays, even if
6890 that variable already has a value of a different type. The convenience
6891 variable, when used as an expression, has the type of its current value.
6894 @kindex show convenience
6895 @cindex show all user variables
6896 @item show convenience
6897 Print a list of convenience variables used so far, and their values.
6898 Abbreviated @code{show conv}.
6900 @kindex init-if-undefined
6901 @cindex convenience variables, initializing
6902 @item init-if-undefined $@var{variable} = @var{expression}
6903 Set a convenience variable if it has not already been set. This is useful
6904 for user-defined commands that keep some state. It is similar, in concept,
6905 to using local static variables with initializers in C (except that
6906 convenience variables are global). It can also be used to allow users to
6907 override default values used in a command script.
6909 If the variable is already defined then the expression is not evaluated so
6910 any side-effects do not occur.
6913 One of the ways to use a convenience variable is as a counter to be
6914 incremented or a pointer to be advanced. For example, to print
6915 a field from successive elements of an array of structures:
6919 print bar[$i++]->contents
6923 Repeat that command by typing @key{RET}.
6925 Some convenience variables are created automatically by @value{GDBN} and given
6926 values likely to be useful.
6929 @vindex $_@r{, convenience variable}
6931 The variable @code{$_} is automatically set by the @code{x} command to
6932 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6933 commands which provide a default address for @code{x} to examine also
6934 set @code{$_} to that address; these commands include @code{info line}
6935 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6936 except when set by the @code{x} command, in which case it is a pointer
6937 to the type of @code{$__}.
6939 @vindex $__@r{, convenience variable}
6941 The variable @code{$__} is automatically set by the @code{x} command
6942 to the value found in the last address examined. Its type is chosen
6943 to match the format in which the data was printed.
6946 @vindex $_exitcode@r{, convenience variable}
6947 The variable @code{$_exitcode} is automatically set to the exit code when
6948 the program being debugged terminates.
6951 On HP-UX systems, if you refer to a function or variable name that
6952 begins with a dollar sign, @value{GDBN} searches for a user or system
6953 name first, before it searches for a convenience variable.
6959 You can refer to machine register contents, in expressions, as variables
6960 with names starting with @samp{$}. The names of registers are different
6961 for each machine; use @code{info registers} to see the names used on
6965 @kindex info registers
6966 @item info registers
6967 Print the names and values of all registers except floating-point
6968 and vector registers (in the selected stack frame).
6970 @kindex info all-registers
6971 @cindex floating point registers
6972 @item info all-registers
6973 Print the names and values of all registers, including floating-point
6974 and vector registers (in the selected stack frame).
6976 @item info registers @var{regname} @dots{}
6977 Print the @dfn{relativized} value of each specified register @var{regname}.
6978 As discussed in detail below, register values are normally relative to
6979 the selected stack frame. @var{regname} may be any register name valid on
6980 the machine you are using, with or without the initial @samp{$}.
6983 @cindex stack pointer register
6984 @cindex program counter register
6985 @cindex process status register
6986 @cindex frame pointer register
6987 @cindex standard registers
6988 @value{GDBN} has four ``standard'' register names that are available (in
6989 expressions) on most machines---whenever they do not conflict with an
6990 architecture's canonical mnemonics for registers. The register names
6991 @code{$pc} and @code{$sp} are used for the program counter register and
6992 the stack pointer. @code{$fp} is used for a register that contains a
6993 pointer to the current stack frame, and @code{$ps} is used for a
6994 register that contains the processor status. For example,
6995 you could print the program counter in hex with
7002 or print the instruction to be executed next with
7009 or add four to the stack pointer@footnote{This is a way of removing
7010 one word from the stack, on machines where stacks grow downward in
7011 memory (most machines, nowadays). This assumes that the innermost
7012 stack frame is selected; setting @code{$sp} is not allowed when other
7013 stack frames are selected. To pop entire frames off the stack,
7014 regardless of machine architecture, use @code{return};
7015 see @ref{Returning, ,Returning from a Function}.} with
7021 Whenever possible, these four standard register names are available on
7022 your machine even though the machine has different canonical mnemonics,
7023 so long as there is no conflict. The @code{info registers} command
7024 shows the canonical names. For example, on the SPARC, @code{info
7025 registers} displays the processor status register as @code{$psr} but you
7026 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7027 is an alias for the @sc{eflags} register.
7029 @value{GDBN} always considers the contents of an ordinary register as an
7030 integer when the register is examined in this way. Some machines have
7031 special registers which can hold nothing but floating point; these
7032 registers are considered to have floating point values. There is no way
7033 to refer to the contents of an ordinary register as floating point value
7034 (although you can @emph{print} it as a floating point value with
7035 @samp{print/f $@var{regname}}).
7037 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7038 means that the data format in which the register contents are saved by
7039 the operating system is not the same one that your program normally
7040 sees. For example, the registers of the 68881 floating point
7041 coprocessor are always saved in ``extended'' (raw) format, but all C
7042 programs expect to work with ``double'' (virtual) format. In such
7043 cases, @value{GDBN} normally works with the virtual format only (the format
7044 that makes sense for your program), but the @code{info registers} command
7045 prints the data in both formats.
7047 @cindex SSE registers (x86)
7048 @cindex MMX registers (x86)
7049 Some machines have special registers whose contents can be interpreted
7050 in several different ways. For example, modern x86-based machines
7051 have SSE and MMX registers that can hold several values packed
7052 together in several different formats. @value{GDBN} refers to such
7053 registers in @code{struct} notation:
7056 (@value{GDBP}) print $xmm1
7058 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7059 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7060 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7061 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7062 v4_int32 = @{0, 20657912, 11, 13@},
7063 v2_int64 = @{88725056443645952, 55834574859@},
7064 uint128 = 0x0000000d0000000b013b36f800000000
7069 To set values of such registers, you need to tell @value{GDBN} which
7070 view of the register you wish to change, as if you were assigning
7071 value to a @code{struct} member:
7074 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7077 Normally, register values are relative to the selected stack frame
7078 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7079 value that the register would contain if all stack frames farther in
7080 were exited and their saved registers restored. In order to see the
7081 true contents of hardware registers, you must select the innermost
7082 frame (with @samp{frame 0}).
7084 However, @value{GDBN} must deduce where registers are saved, from the machine
7085 code generated by your compiler. If some registers are not saved, or if
7086 @value{GDBN} is unable to locate the saved registers, the selected stack
7087 frame makes no difference.
7089 @node Floating Point Hardware
7090 @section Floating Point Hardware
7091 @cindex floating point
7093 Depending on the configuration, @value{GDBN} may be able to give
7094 you more information about the status of the floating point hardware.
7099 Display hardware-dependent information about the floating
7100 point unit. The exact contents and layout vary depending on the
7101 floating point chip. Currently, @samp{info float} is supported on
7102 the ARM and x86 machines.
7106 @section Vector Unit
7109 Depending on the configuration, @value{GDBN} may be able to give you
7110 more information about the status of the vector unit.
7115 Display information about the vector unit. The exact contents and
7116 layout vary depending on the hardware.
7119 @node OS Information
7120 @section Operating System Auxiliary Information
7121 @cindex OS information
7123 @value{GDBN} provides interfaces to useful OS facilities that can help
7124 you debug your program.
7126 @cindex @code{ptrace} system call
7127 @cindex @code{struct user} contents
7128 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7129 machines), it interfaces with the inferior via the @code{ptrace}
7130 system call. The operating system creates a special sata structure,
7131 called @code{struct user}, for this interface. You can use the
7132 command @code{info udot} to display the contents of this data
7138 Display the contents of the @code{struct user} maintained by the OS
7139 kernel for the program being debugged. @value{GDBN} displays the
7140 contents of @code{struct user} as a list of hex numbers, similar to
7141 the @code{examine} command.
7144 @cindex auxiliary vector
7145 @cindex vector, auxiliary
7146 Some operating systems supply an @dfn{auxiliary vector} to programs at
7147 startup. This is akin to the arguments and environment that you
7148 specify for a program, but contains a system-dependent variety of
7149 binary values that tell system libraries important details about the
7150 hardware, operating system, and process. Each value's purpose is
7151 identified by an integer tag; the meanings are well-known but system-specific.
7152 Depending on the configuration and operating system facilities,
7153 @value{GDBN} may be able to show you this information. For remote
7154 targets, this functionality may further depend on the remote stub's
7155 support of the @samp{qXfer:auxv:read} packet, see
7156 @ref{qXfer auxiliary vector read}.
7161 Display the auxiliary vector of the inferior, which can be either a
7162 live process or a core dump file. @value{GDBN} prints each tag value
7163 numerically, and also shows names and text descriptions for recognized
7164 tags. Some values in the vector are numbers, some bit masks, and some
7165 pointers to strings or other data. @value{GDBN} displays each value in the
7166 most appropriate form for a recognized tag, and in hexadecimal for
7167 an unrecognized tag.
7171 @node Memory Region Attributes
7172 @section Memory Region Attributes
7173 @cindex memory region attributes
7175 @dfn{Memory region attributes} allow you to describe special handling
7176 required by regions of your target's memory. @value{GDBN} uses
7177 attributes to determine whether to allow certain types of memory
7178 accesses; whether to use specific width accesses; and whether to cache
7179 target memory. By default the description of memory regions is
7180 fetched from the target (if the current target supports this), but the
7181 user can override the fetched regions.
7183 Defined memory regions can be individually enabled and disabled. When a
7184 memory region is disabled, @value{GDBN} uses the default attributes when
7185 accessing memory in that region. Similarly, if no memory regions have
7186 been defined, @value{GDBN} uses the default attributes when accessing
7189 When a memory region is defined, it is given a number to identify it;
7190 to enable, disable, or remove a memory region, you specify that number.
7194 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7195 Define a memory region bounded by @var{lower} and @var{upper} with
7196 attributes @var{attributes}@dots{}, and add it to the list of regions
7197 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7198 case: it is treated as the target's maximum memory address.
7199 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7202 Discard any user changes to the memory regions and use target-supplied
7203 regions, if available, or no regions if the target does not support.
7206 @item delete mem @var{nums}@dots{}
7207 Remove memory regions @var{nums}@dots{} from the list of regions
7208 monitored by @value{GDBN}.
7211 @item disable mem @var{nums}@dots{}
7212 Disable monitoring of memory regions @var{nums}@dots{}.
7213 A disabled memory region is not forgotten.
7214 It may be enabled again later.
7217 @item enable mem @var{nums}@dots{}
7218 Enable monitoring of memory regions @var{nums}@dots{}.
7222 Print a table of all defined memory regions, with the following columns
7226 @item Memory Region Number
7227 @item Enabled or Disabled.
7228 Enabled memory regions are marked with @samp{y}.
7229 Disabled memory regions are marked with @samp{n}.
7232 The address defining the inclusive lower bound of the memory region.
7235 The address defining the exclusive upper bound of the memory region.
7238 The list of attributes set for this memory region.
7243 @subsection Attributes
7245 @subsubsection Memory Access Mode
7246 The access mode attributes set whether @value{GDBN} may make read or
7247 write accesses to a memory region.
7249 While these attributes prevent @value{GDBN} from performing invalid
7250 memory accesses, they do nothing to prevent the target system, I/O DMA,
7251 etc.@: from accessing memory.
7255 Memory is read only.
7257 Memory is write only.
7259 Memory is read/write. This is the default.
7262 @subsubsection Memory Access Size
7263 The access size attribute tells @value{GDBN} to use specific sized
7264 accesses in the memory region. Often memory mapped device registers
7265 require specific sized accesses. If no access size attribute is
7266 specified, @value{GDBN} may use accesses of any size.
7270 Use 8 bit memory accesses.
7272 Use 16 bit memory accesses.
7274 Use 32 bit memory accesses.
7276 Use 64 bit memory accesses.
7279 @c @subsubsection Hardware/Software Breakpoints
7280 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7281 @c will use hardware or software breakpoints for the internal breakpoints
7282 @c used by the step, next, finish, until, etc. commands.
7286 @c Always use hardware breakpoints
7287 @c @item swbreak (default)
7290 @subsubsection Data Cache
7291 The data cache attributes set whether @value{GDBN} will cache target
7292 memory. While this generally improves performance by reducing debug
7293 protocol overhead, it can lead to incorrect results because @value{GDBN}
7294 does not know about volatile variables or memory mapped device
7299 Enable @value{GDBN} to cache target memory.
7301 Disable @value{GDBN} from caching target memory. This is the default.
7304 @subsection Memory Access Checking
7305 @value{GDBN} can be instructed to refuse accesses to memory that is
7306 not explicitly described. This can be useful if accessing such
7307 regions has undesired effects for a specific target, or to provide
7308 better error checking. The following commands control this behaviour.
7311 @kindex set mem inaccessible-by-default
7312 @item set mem inaccessible-by-default [on|off]
7313 If @code{on} is specified, make @value{GDBN} treat memory not
7314 explicitly described by the memory ranges as non-existent and refuse accesses
7315 to such memory. The checks are only performed if there's at least one
7316 memory range defined. If @code{off} is specified, make @value{GDBN}
7317 treat the memory not explicitly described by the memory ranges as RAM.
7318 The default value is @code{on}.
7319 @kindex show mem inaccessible-by-default
7320 @item show mem inaccessible-by-default
7321 Show the current handling of accesses to unknown memory.
7325 @c @subsubsection Memory Write Verification
7326 @c The memory write verification attributes set whether @value{GDBN}
7327 @c will re-reads data after each write to verify the write was successful.
7331 @c @item noverify (default)
7334 @node Dump/Restore Files
7335 @section Copy Between Memory and a File
7336 @cindex dump/restore files
7337 @cindex append data to a file
7338 @cindex dump data to a file
7339 @cindex restore data from a file
7341 You can use the commands @code{dump}, @code{append}, and
7342 @code{restore} to copy data between target memory and a file. The
7343 @code{dump} and @code{append} commands write data to a file, and the
7344 @code{restore} command reads data from a file back into the inferior's
7345 memory. Files may be in binary, Motorola S-record, Intel hex, or
7346 Tektronix Hex format; however, @value{GDBN} can only append to binary
7352 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7353 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7354 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7355 or the value of @var{expr}, to @var{filename} in the given format.
7357 The @var{format} parameter may be any one of:
7364 Motorola S-record format.
7366 Tektronix Hex format.
7369 @value{GDBN} uses the same definitions of these formats as the
7370 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7371 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7375 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7376 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7377 Append the contents of memory from @var{start_addr} to @var{end_addr},
7378 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7379 (@value{GDBN} can only append data to files in raw binary form.)
7382 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7383 Restore the contents of file @var{filename} into memory. The
7384 @code{restore} command can automatically recognize any known @sc{bfd}
7385 file format, except for raw binary. To restore a raw binary file you
7386 must specify the optional keyword @code{binary} after the filename.
7388 If @var{bias} is non-zero, its value will be added to the addresses
7389 contained in the file. Binary files always start at address zero, so
7390 they will be restored at address @var{bias}. Other bfd files have
7391 a built-in location; they will be restored at offset @var{bias}
7394 If @var{start} and/or @var{end} are non-zero, then only data between
7395 file offset @var{start} and file offset @var{end} will be restored.
7396 These offsets are relative to the addresses in the file, before
7397 the @var{bias} argument is applied.
7401 @node Core File Generation
7402 @section How to Produce a Core File from Your Program
7403 @cindex dump core from inferior
7405 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7406 image of a running process and its process status (register values
7407 etc.). Its primary use is post-mortem debugging of a program that
7408 crashed while it ran outside a debugger. A program that crashes
7409 automatically produces a core file, unless this feature is disabled by
7410 the user. @xref{Files}, for information on invoking @value{GDBN} in
7411 the post-mortem debugging mode.
7413 Occasionally, you may wish to produce a core file of the program you
7414 are debugging in order to preserve a snapshot of its state.
7415 @value{GDBN} has a special command for that.
7419 @kindex generate-core-file
7420 @item generate-core-file [@var{file}]
7421 @itemx gcore [@var{file}]
7422 Produce a core dump of the inferior process. The optional argument
7423 @var{file} specifies the file name where to put the core dump. If not
7424 specified, the file name defaults to @file{core.@var{pid}}, where
7425 @var{pid} is the inferior process ID.
7427 Note that this command is implemented only for some systems (as of
7428 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7431 @node Character Sets
7432 @section Character Sets
7433 @cindex character sets
7435 @cindex translating between character sets
7436 @cindex host character set
7437 @cindex target character set
7439 If the program you are debugging uses a different character set to
7440 represent characters and strings than the one @value{GDBN} uses itself,
7441 @value{GDBN} can automatically translate between the character sets for
7442 you. The character set @value{GDBN} uses we call the @dfn{host
7443 character set}; the one the inferior program uses we call the
7444 @dfn{target character set}.
7446 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7447 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7448 remote protocol (@pxref{Remote Debugging}) to debug a program
7449 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7450 then the host character set is Latin-1, and the target character set is
7451 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7452 target-charset EBCDIC-US}, then @value{GDBN} translates between
7453 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7454 character and string literals in expressions.
7456 @value{GDBN} has no way to automatically recognize which character set
7457 the inferior program uses; you must tell it, using the @code{set
7458 target-charset} command, described below.
7460 Here are the commands for controlling @value{GDBN}'s character set
7464 @item set target-charset @var{charset}
7465 @kindex set target-charset
7466 Set the current target character set to @var{charset}. We list the
7467 character set names @value{GDBN} recognizes below, but if you type
7468 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7469 list the target character sets it supports.
7473 @item set host-charset @var{charset}
7474 @kindex set host-charset
7475 Set the current host character set to @var{charset}.
7477 By default, @value{GDBN} uses a host character set appropriate to the
7478 system it is running on; you can override that default using the
7479 @code{set host-charset} command.
7481 @value{GDBN} can only use certain character sets as its host character
7482 set. We list the character set names @value{GDBN} recognizes below, and
7483 indicate which can be host character sets, but if you type
7484 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7485 list the host character sets it supports.
7487 @item set charset @var{charset}
7489 Set the current host and target character sets to @var{charset}. As
7490 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7491 @value{GDBN} will list the name of the character sets that can be used
7492 for both host and target.
7496 @kindex show charset
7497 Show the names of the current host and target charsets.
7499 @itemx show host-charset
7500 @kindex show host-charset
7501 Show the name of the current host charset.
7503 @itemx show target-charset
7504 @kindex show target-charset
7505 Show the name of the current target charset.
7509 @value{GDBN} currently includes support for the following character
7515 @cindex ASCII character set
7516 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7520 @cindex ISO 8859-1 character set
7521 @cindex ISO Latin 1 character set
7522 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7523 characters needed for French, German, and Spanish. @value{GDBN} can use
7524 this as its host character set.
7528 @cindex EBCDIC character set
7529 @cindex IBM1047 character set
7530 Variants of the @sc{ebcdic} character set, used on some of IBM's
7531 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7532 @value{GDBN} cannot use these as its host character set.
7536 Note that these are all single-byte character sets. More work inside
7537 @value{GDBN} is needed to support multi-byte or variable-width character
7538 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7540 Here is an example of @value{GDBN}'s character set support in action.
7541 Assume that the following source code has been placed in the file
7542 @file{charset-test.c}:
7548 = @{72, 101, 108, 108, 111, 44, 32, 119,
7549 111, 114, 108, 100, 33, 10, 0@};
7550 char ibm1047_hello[]
7551 = @{200, 133, 147, 147, 150, 107, 64, 166,
7552 150, 153, 147, 132, 90, 37, 0@};
7556 printf ("Hello, world!\n");
7560 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7561 containing the string @samp{Hello, world!} followed by a newline,
7562 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7564 We compile the program, and invoke the debugger on it:
7567 $ gcc -g charset-test.c -o charset-test
7568 $ gdb -nw charset-test
7569 GNU gdb 2001-12-19-cvs
7570 Copyright 2001 Free Software Foundation, Inc.
7575 We can use the @code{show charset} command to see what character sets
7576 @value{GDBN} is currently using to interpret and display characters and
7580 (@value{GDBP}) show charset
7581 The current host and target character set is `ISO-8859-1'.
7585 For the sake of printing this manual, let's use @sc{ascii} as our
7586 initial character set:
7588 (@value{GDBP}) set charset ASCII
7589 (@value{GDBP}) show charset
7590 The current host and target character set is `ASCII'.
7594 Let's assume that @sc{ascii} is indeed the correct character set for our
7595 host system --- in other words, let's assume that if @value{GDBN} prints
7596 characters using the @sc{ascii} character set, our terminal will display
7597 them properly. Since our current target character set is also
7598 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7601 (@value{GDBP}) print ascii_hello
7602 $1 = 0x401698 "Hello, world!\n"
7603 (@value{GDBP}) print ascii_hello[0]
7608 @value{GDBN} uses the target character set for character and string
7609 literals you use in expressions:
7612 (@value{GDBP}) print '+'
7617 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7620 @value{GDBN} relies on the user to tell it which character set the
7621 target program uses. If we print @code{ibm1047_hello} while our target
7622 character set is still @sc{ascii}, we get jibberish:
7625 (@value{GDBP}) print ibm1047_hello
7626 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7627 (@value{GDBP}) print ibm1047_hello[0]
7632 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7633 @value{GDBN} tells us the character sets it supports:
7636 (@value{GDBP}) set target-charset
7637 ASCII EBCDIC-US IBM1047 ISO-8859-1
7638 (@value{GDBP}) set target-charset
7641 We can select @sc{ibm1047} as our target character set, and examine the
7642 program's strings again. Now the @sc{ascii} string is wrong, but
7643 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7644 target character set, @sc{ibm1047}, to the host character set,
7645 @sc{ascii}, and they display correctly:
7648 (@value{GDBP}) set target-charset IBM1047
7649 (@value{GDBP}) show charset
7650 The current host character set is `ASCII'.
7651 The current target character set is `IBM1047'.
7652 (@value{GDBP}) print ascii_hello
7653 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7654 (@value{GDBP}) print ascii_hello[0]
7656 (@value{GDBP}) print ibm1047_hello
7657 $8 = 0x4016a8 "Hello, world!\n"
7658 (@value{GDBP}) print ibm1047_hello[0]
7663 As above, @value{GDBN} uses the target character set for character and
7664 string literals you use in expressions:
7667 (@value{GDBP}) print '+'
7672 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7675 @node Caching Remote Data
7676 @section Caching Data of Remote Targets
7677 @cindex caching data of remote targets
7679 @value{GDBN} can cache data exchanged between the debugger and a
7680 remote target (@pxref{Remote Debugging}). Such caching generally improves
7681 performance, because it reduces the overhead of the remote protocol by
7682 bundling memory reads and writes into large chunks. Unfortunately,
7683 @value{GDBN} does not currently know anything about volatile
7684 registers, and thus data caching will produce incorrect results when
7685 volatile registers are in use.
7688 @kindex set remotecache
7689 @item set remotecache on
7690 @itemx set remotecache off
7691 Set caching state for remote targets. When @code{ON}, use data
7692 caching. By default, this option is @code{OFF}.
7694 @kindex show remotecache
7695 @item show remotecache
7696 Show the current state of data caching for remote targets.
7700 Print the information about the data cache performance. The
7701 information displayed includes: the dcache width and depth; and for
7702 each cache line, how many times it was referenced, and its data and
7703 state (dirty, bad, ok, etc.). This command is useful for debugging
7704 the data cache operation.
7707 @node Searching Memory
7708 @section Search Memory
7709 @cindex searching memory
7711 Memory can be searched for a particular sequence of bytes with the
7712 @code{find} command.
7716 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
7717 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
7718 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
7719 etc. The search begins at address @var{start_addr} and continues for either
7720 @var{len} bytes or through to @var{end_addr} inclusive.
7723 @var{s} and @var{n} are optional parameters.
7724 They may be specified in either order, apart or together.
7727 @item @var{s}, search query size
7728 The size of each search query value.
7734 halfwords (two bytes)
7738 giant words (eight bytes)
7741 All values are interpreted in the current language.
7742 This means, for example, that if the current source language is C/C@t{++}
7743 then searching for the string ``hello'' includes the trailing '\0'.
7745 If the value size is not specified, it is taken from the
7746 value's type in the current language.
7747 This is useful when one wants to specify the search
7748 pattern as a mixture of types.
7749 Note that this means, for example, that in the case of C-like languages
7750 a search for an untyped 0x42 will search for @samp{(int) 0x42}
7751 which is typically four bytes.
7753 @item @var{n}, maximum number of finds
7754 The maximum number of matches to print. The default is to print all finds.
7757 You can use strings as search values. Quote them with double-quotes
7759 The string value is copied into the search pattern byte by byte,
7760 regardless of the endianness of the target and the size specification.
7762 The address of each match found is printed as well as a count of the
7763 number of matches found.
7765 The address of the last value found is stored in convenience variable
7767 A count of the number of matches is stored in @samp{$numfound}.
7769 For example, if stopped at the @code{printf} in this function:
7775 static char hello[] = "hello-hello";
7776 static struct @{ char c; short s; int i; @}
7777 __attribute__ ((packed)) mixed
7778 = @{ 'c', 0x1234, 0x87654321 @};
7779 printf ("%s\n", hello);
7784 you get during debugging:
7787 (gdb) find &hello[0], +sizeof(hello), "hello"
7788 0x804956d <hello.1620+6>
7790 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
7791 0x8049567 <hello.1620>
7792 0x804956d <hello.1620+6>
7794 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
7795 0x8049567 <hello.1620>
7797 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
7798 0x8049560 <mixed.1625>
7800 (gdb) print $numfound
7803 $2 = (void *) 0x8049560
7807 @chapter C Preprocessor Macros
7809 Some languages, such as C and C@t{++}, provide a way to define and invoke
7810 ``preprocessor macros'' which expand into strings of tokens.
7811 @value{GDBN} can evaluate expressions containing macro invocations, show
7812 the result of macro expansion, and show a macro's definition, including
7813 where it was defined.
7815 You may need to compile your program specially to provide @value{GDBN}
7816 with information about preprocessor macros. Most compilers do not
7817 include macros in their debugging information, even when you compile
7818 with the @option{-g} flag. @xref{Compilation}.
7820 A program may define a macro at one point, remove that definition later,
7821 and then provide a different definition after that. Thus, at different
7822 points in the program, a macro may have different definitions, or have
7823 no definition at all. If there is a current stack frame, @value{GDBN}
7824 uses the macros in scope at that frame's source code line. Otherwise,
7825 @value{GDBN} uses the macros in scope at the current listing location;
7828 At the moment, @value{GDBN} does not support the @code{##}
7829 token-splicing operator, the @code{#} stringification operator, or
7830 variable-arity macros.
7832 Whenever @value{GDBN} evaluates an expression, it always expands any
7833 macro invocations present in the expression. @value{GDBN} also provides
7834 the following commands for working with macros explicitly.
7838 @kindex macro expand
7839 @cindex macro expansion, showing the results of preprocessor
7840 @cindex preprocessor macro expansion, showing the results of
7841 @cindex expanding preprocessor macros
7842 @item macro expand @var{expression}
7843 @itemx macro exp @var{expression}
7844 Show the results of expanding all preprocessor macro invocations in
7845 @var{expression}. Since @value{GDBN} simply expands macros, but does
7846 not parse the result, @var{expression} need not be a valid expression;
7847 it can be any string of tokens.
7850 @item macro expand-once @var{expression}
7851 @itemx macro exp1 @var{expression}
7852 @cindex expand macro once
7853 @i{(This command is not yet implemented.)} Show the results of
7854 expanding those preprocessor macro invocations that appear explicitly in
7855 @var{expression}. Macro invocations appearing in that expansion are
7856 left unchanged. This command allows you to see the effect of a
7857 particular macro more clearly, without being confused by further
7858 expansions. Since @value{GDBN} simply expands macros, but does not
7859 parse the result, @var{expression} need not be a valid expression; it
7860 can be any string of tokens.
7863 @cindex macro definition, showing
7864 @cindex definition, showing a macro's
7865 @item info macro @var{macro}
7866 Show the definition of the macro named @var{macro}, and describe the
7867 source location where that definition was established.
7869 @kindex macro define
7870 @cindex user-defined macros
7871 @cindex defining macros interactively
7872 @cindex macros, user-defined
7873 @item macro define @var{macro} @var{replacement-list}
7874 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7875 @i{(This command is not yet implemented.)} Introduce a definition for a
7876 preprocessor macro named @var{macro}, invocations of which are replaced
7877 by the tokens given in @var{replacement-list}. The first form of this
7878 command defines an ``object-like'' macro, which takes no arguments; the
7879 second form defines a ``function-like'' macro, which takes the arguments
7880 given in @var{arglist}.
7882 A definition introduced by this command is in scope in every expression
7883 evaluated in @value{GDBN}, until it is removed with the @command{macro
7884 undef} command, described below. The definition overrides all
7885 definitions for @var{macro} present in the program being debugged, as
7886 well as any previous user-supplied definition.
7889 @item macro undef @var{macro}
7890 @i{(This command is not yet implemented.)} Remove any user-supplied
7891 definition for the macro named @var{macro}. This command only affects
7892 definitions provided with the @command{macro define} command, described
7893 above; it cannot remove definitions present in the program being
7898 @i{(This command is not yet implemented.)} List all the macros
7899 defined using the @code{macro define} command.
7902 @cindex macros, example of debugging with
7903 Here is a transcript showing the above commands in action. First, we
7904 show our source files:
7912 #define ADD(x) (M + x)
7917 printf ("Hello, world!\n");
7919 printf ("We're so creative.\n");
7921 printf ("Goodbye, world!\n");
7928 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7929 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7930 compiler includes information about preprocessor macros in the debugging
7934 $ gcc -gdwarf-2 -g3 sample.c -o sample
7938 Now, we start @value{GDBN} on our sample program:
7942 GNU gdb 2002-05-06-cvs
7943 Copyright 2002 Free Software Foundation, Inc.
7944 GDB is free software, @dots{}
7948 We can expand macros and examine their definitions, even when the
7949 program is not running. @value{GDBN} uses the current listing position
7950 to decide which macro definitions are in scope:
7953 (@value{GDBP}) list main
7956 5 #define ADD(x) (M + x)
7961 10 printf ("Hello, world!\n");
7963 12 printf ("We're so creative.\n");
7964 (@value{GDBP}) info macro ADD
7965 Defined at /home/jimb/gdb/macros/play/sample.c:5
7966 #define ADD(x) (M + x)
7967 (@value{GDBP}) info macro Q
7968 Defined at /home/jimb/gdb/macros/play/sample.h:1
7969 included at /home/jimb/gdb/macros/play/sample.c:2
7971 (@value{GDBP}) macro expand ADD(1)
7972 expands to: (42 + 1)
7973 (@value{GDBP}) macro expand-once ADD(1)
7974 expands to: once (M + 1)
7978 In the example above, note that @command{macro expand-once} expands only
7979 the macro invocation explicit in the original text --- the invocation of
7980 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7981 which was introduced by @code{ADD}.
7983 Once the program is running, @value{GDBN} uses the macro definitions in
7984 force at the source line of the current stack frame:
7987 (@value{GDBP}) break main
7988 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7990 Starting program: /home/jimb/gdb/macros/play/sample
7992 Breakpoint 1, main () at sample.c:10
7993 10 printf ("Hello, world!\n");
7997 At line 10, the definition of the macro @code{N} at line 9 is in force:
8000 (@value{GDBP}) info macro N
8001 Defined at /home/jimb/gdb/macros/play/sample.c:9
8003 (@value{GDBP}) macro expand N Q M
8005 (@value{GDBP}) print N Q M
8010 As we step over directives that remove @code{N}'s definition, and then
8011 give it a new definition, @value{GDBN} finds the definition (or lack
8012 thereof) in force at each point:
8017 12 printf ("We're so creative.\n");
8018 (@value{GDBP}) info macro N
8019 The symbol `N' has no definition as a C/C++ preprocessor macro
8020 at /home/jimb/gdb/macros/play/sample.c:12
8023 14 printf ("Goodbye, world!\n");
8024 (@value{GDBP}) info macro N
8025 Defined at /home/jimb/gdb/macros/play/sample.c:13
8027 (@value{GDBP}) macro expand N Q M
8028 expands to: 1729 < 42
8029 (@value{GDBP}) print N Q M
8036 @chapter Tracepoints
8037 @c This chapter is based on the documentation written by Michael
8038 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8041 In some applications, it is not feasible for the debugger to interrupt
8042 the program's execution long enough for the developer to learn
8043 anything helpful about its behavior. If the program's correctness
8044 depends on its real-time behavior, delays introduced by a debugger
8045 might cause the program to change its behavior drastically, or perhaps
8046 fail, even when the code itself is correct. It is useful to be able
8047 to observe the program's behavior without interrupting it.
8049 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8050 specify locations in the program, called @dfn{tracepoints}, and
8051 arbitrary expressions to evaluate when those tracepoints are reached.
8052 Later, using the @code{tfind} command, you can examine the values
8053 those expressions had when the program hit the tracepoints. The
8054 expressions may also denote objects in memory---structures or arrays,
8055 for example---whose values @value{GDBN} should record; while visiting
8056 a particular tracepoint, you may inspect those objects as if they were
8057 in memory at that moment. However, because @value{GDBN} records these
8058 values without interacting with you, it can do so quickly and
8059 unobtrusively, hopefully not disturbing the program's behavior.
8061 The tracepoint facility is currently available only for remote
8062 targets. @xref{Targets}. In addition, your remote target must know
8063 how to collect trace data. This functionality is implemented in the
8064 remote stub; however, none of the stubs distributed with @value{GDBN}
8065 support tracepoints as of this writing. The format of the remote
8066 packets used to implement tracepoints are described in @ref{Tracepoint
8069 This chapter describes the tracepoint commands and features.
8073 * Analyze Collected Data::
8074 * Tracepoint Variables::
8077 @node Set Tracepoints
8078 @section Commands to Set Tracepoints
8080 Before running such a @dfn{trace experiment}, an arbitrary number of
8081 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8082 tracepoint has a number assigned to it by @value{GDBN}. Like with
8083 breakpoints, tracepoint numbers are successive integers starting from
8084 one. Many of the commands associated with tracepoints take the
8085 tracepoint number as their argument, to identify which tracepoint to
8088 For each tracepoint, you can specify, in advance, some arbitrary set
8089 of data that you want the target to collect in the trace buffer when
8090 it hits that tracepoint. The collected data can include registers,
8091 local variables, or global data. Later, you can use @value{GDBN}
8092 commands to examine the values these data had at the time the
8095 This section describes commands to set tracepoints and associated
8096 conditions and actions.
8099 * Create and Delete Tracepoints::
8100 * Enable and Disable Tracepoints::
8101 * Tracepoint Passcounts::
8102 * Tracepoint Actions::
8103 * Listing Tracepoints::
8104 * Starting and Stopping Trace Experiments::
8107 @node Create and Delete Tracepoints
8108 @subsection Create and Delete Tracepoints
8111 @cindex set tracepoint
8114 The @code{trace} command is very similar to the @code{break} command.
8115 Its argument can be a source line, a function name, or an address in
8116 the target program. @xref{Set Breaks}. The @code{trace} command
8117 defines a tracepoint, which is a point in the target program where the
8118 debugger will briefly stop, collect some data, and then allow the
8119 program to continue. Setting a tracepoint or changing its commands
8120 doesn't take effect until the next @code{tstart} command; thus, you
8121 cannot change the tracepoint attributes once a trace experiment is
8124 Here are some examples of using the @code{trace} command:
8127 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8129 (@value{GDBP}) @b{trace +2} // 2 lines forward
8131 (@value{GDBP}) @b{trace my_function} // first source line of function
8133 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8135 (@value{GDBP}) @b{trace *0x2117c4} // an address
8139 You can abbreviate @code{trace} as @code{tr}.
8142 @cindex last tracepoint number
8143 @cindex recent tracepoint number
8144 @cindex tracepoint number
8145 The convenience variable @code{$tpnum} records the tracepoint number
8146 of the most recently set tracepoint.
8148 @kindex delete tracepoint
8149 @cindex tracepoint deletion
8150 @item delete tracepoint @r{[}@var{num}@r{]}
8151 Permanently delete one or more tracepoints. With no argument, the
8152 default is to delete all tracepoints.
8157 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8159 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8163 You can abbreviate this command as @code{del tr}.
8166 @node Enable and Disable Tracepoints
8167 @subsection Enable and Disable Tracepoints
8170 @kindex disable tracepoint
8171 @item disable tracepoint @r{[}@var{num}@r{]}
8172 Disable tracepoint @var{num}, or all tracepoints if no argument
8173 @var{num} is given. A disabled tracepoint will have no effect during
8174 the next trace experiment, but it is not forgotten. You can re-enable
8175 a disabled tracepoint using the @code{enable tracepoint} command.
8177 @kindex enable tracepoint
8178 @item enable tracepoint @r{[}@var{num}@r{]}
8179 Enable tracepoint @var{num}, or all tracepoints. The enabled
8180 tracepoints will become effective the next time a trace experiment is
8184 @node Tracepoint Passcounts
8185 @subsection Tracepoint Passcounts
8189 @cindex tracepoint pass count
8190 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8191 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8192 automatically stop a trace experiment. If a tracepoint's passcount is
8193 @var{n}, then the trace experiment will be automatically stopped on
8194 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8195 @var{num} is not specified, the @code{passcount} command sets the
8196 passcount of the most recently defined tracepoint. If no passcount is
8197 given, the trace experiment will run until stopped explicitly by the
8203 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8204 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8206 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8207 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8208 (@value{GDBP}) @b{trace foo}
8209 (@value{GDBP}) @b{pass 3}
8210 (@value{GDBP}) @b{trace bar}
8211 (@value{GDBP}) @b{pass 2}
8212 (@value{GDBP}) @b{trace baz}
8213 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8214 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8215 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8216 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8220 @node Tracepoint Actions
8221 @subsection Tracepoint Action Lists
8225 @cindex tracepoint actions
8226 @item actions @r{[}@var{num}@r{]}
8227 This command will prompt for a list of actions to be taken when the
8228 tracepoint is hit. If the tracepoint number @var{num} is not
8229 specified, this command sets the actions for the one that was most
8230 recently defined (so that you can define a tracepoint and then say
8231 @code{actions} without bothering about its number). You specify the
8232 actions themselves on the following lines, one action at a time, and
8233 terminate the actions list with a line containing just @code{end}. So
8234 far, the only defined actions are @code{collect} and
8235 @code{while-stepping}.
8237 @cindex remove actions from a tracepoint
8238 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8239 and follow it immediately with @samp{end}.
8242 (@value{GDBP}) @b{collect @var{data}} // collect some data
8244 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8246 (@value{GDBP}) @b{end} // signals the end of actions.
8249 In the following example, the action list begins with @code{collect}
8250 commands indicating the things to be collected when the tracepoint is
8251 hit. Then, in order to single-step and collect additional data
8252 following the tracepoint, a @code{while-stepping} command is used,
8253 followed by the list of things to be collected while stepping. The
8254 @code{while-stepping} command is terminated by its own separate
8255 @code{end} command. Lastly, the action list is terminated by an
8259 (@value{GDBP}) @b{trace foo}
8260 (@value{GDBP}) @b{actions}
8261 Enter actions for tracepoint 1, one per line:
8270 @kindex collect @r{(tracepoints)}
8271 @item collect @var{expr1}, @var{expr2}, @dots{}
8272 Collect values of the given expressions when the tracepoint is hit.
8273 This command accepts a comma-separated list of any valid expressions.
8274 In addition to global, static, or local variables, the following
8275 special arguments are supported:
8279 collect all registers
8282 collect all function arguments
8285 collect all local variables.
8288 You can give several consecutive @code{collect} commands, each one
8289 with a single argument, or one @code{collect} command with several
8290 arguments separated by commas: the effect is the same.
8292 The command @code{info scope} (@pxref{Symbols, info scope}) is
8293 particularly useful for figuring out what data to collect.
8295 @kindex while-stepping @r{(tracepoints)}
8296 @item while-stepping @var{n}
8297 Perform @var{n} single-step traces after the tracepoint, collecting
8298 new data at each step. The @code{while-stepping} command is
8299 followed by the list of what to collect while stepping (followed by
8300 its own @code{end} command):
8304 > collect $regs, myglobal
8310 You may abbreviate @code{while-stepping} as @code{ws} or
8314 @node Listing Tracepoints
8315 @subsection Listing Tracepoints
8318 @kindex info tracepoints
8320 @cindex information about tracepoints
8321 @item info tracepoints @r{[}@var{num}@r{]}
8322 Display information about the tracepoint @var{num}. If you don't specify
8323 a tracepoint number, displays information about all the tracepoints
8324 defined so far. For each tracepoint, the following information is
8331 whether it is enabled or disabled
8335 its passcount as given by the @code{passcount @var{n}} command
8337 its step count as given by the @code{while-stepping @var{n}} command
8339 where in the source files is the tracepoint set
8341 its action list as given by the @code{actions} command
8345 (@value{GDBP}) @b{info trace}
8346 Num Enb Address PassC StepC What
8347 1 y 0x002117c4 0 0 <gdb_asm>
8348 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8349 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8354 This command can be abbreviated @code{info tp}.
8357 @node Starting and Stopping Trace Experiments
8358 @subsection Starting and Stopping Trace Experiments
8362 @cindex start a new trace experiment
8363 @cindex collected data discarded
8365 This command takes no arguments. It starts the trace experiment, and
8366 begins collecting data. This has the side effect of discarding all
8367 the data collected in the trace buffer during the previous trace
8371 @cindex stop a running trace experiment
8373 This command takes no arguments. It ends the trace experiment, and
8374 stops collecting data.
8376 @strong{Note}: a trace experiment and data collection may stop
8377 automatically if any tracepoint's passcount is reached
8378 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8381 @cindex status of trace data collection
8382 @cindex trace experiment, status of
8384 This command displays the status of the current trace data
8388 Here is an example of the commands we described so far:
8391 (@value{GDBP}) @b{trace gdb_c_test}
8392 (@value{GDBP}) @b{actions}
8393 Enter actions for tracepoint #1, one per line.
8394 > collect $regs,$locals,$args
8399 (@value{GDBP}) @b{tstart}
8400 [time passes @dots{}]
8401 (@value{GDBP}) @b{tstop}
8405 @node Analyze Collected Data
8406 @section Using the Collected Data
8408 After the tracepoint experiment ends, you use @value{GDBN} commands
8409 for examining the trace data. The basic idea is that each tracepoint
8410 collects a trace @dfn{snapshot} every time it is hit and another
8411 snapshot every time it single-steps. All these snapshots are
8412 consecutively numbered from zero and go into a buffer, and you can
8413 examine them later. The way you examine them is to @dfn{focus} on a
8414 specific trace snapshot. When the remote stub is focused on a trace
8415 snapshot, it will respond to all @value{GDBN} requests for memory and
8416 registers by reading from the buffer which belongs to that snapshot,
8417 rather than from @emph{real} memory or registers of the program being
8418 debugged. This means that @strong{all} @value{GDBN} commands
8419 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8420 behave as if we were currently debugging the program state as it was
8421 when the tracepoint occurred. Any requests for data that are not in
8422 the buffer will fail.
8425 * tfind:: How to select a trace snapshot
8426 * tdump:: How to display all data for a snapshot
8427 * save-tracepoints:: How to save tracepoints for a future run
8431 @subsection @code{tfind @var{n}}
8434 @cindex select trace snapshot
8435 @cindex find trace snapshot
8436 The basic command for selecting a trace snapshot from the buffer is
8437 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8438 counting from zero. If no argument @var{n} is given, the next
8439 snapshot is selected.
8441 Here are the various forms of using the @code{tfind} command.
8445 Find the first snapshot in the buffer. This is a synonym for
8446 @code{tfind 0} (since 0 is the number of the first snapshot).
8449 Stop debugging trace snapshots, resume @emph{live} debugging.
8452 Same as @samp{tfind none}.
8455 No argument means find the next trace snapshot.
8458 Find the previous trace snapshot before the current one. This permits
8459 retracing earlier steps.
8461 @item tfind tracepoint @var{num}
8462 Find the next snapshot associated with tracepoint @var{num}. Search
8463 proceeds forward from the last examined trace snapshot. If no
8464 argument @var{num} is given, it means find the next snapshot collected
8465 for the same tracepoint as the current snapshot.
8467 @item tfind pc @var{addr}
8468 Find the next snapshot associated with the value @var{addr} of the
8469 program counter. Search proceeds forward from the last examined trace
8470 snapshot. If no argument @var{addr} is given, it means find the next
8471 snapshot with the same value of PC as the current snapshot.
8473 @item tfind outside @var{addr1}, @var{addr2}
8474 Find the next snapshot whose PC is outside the given range of
8477 @item tfind range @var{addr1}, @var{addr2}
8478 Find the next snapshot whose PC is between @var{addr1} and
8479 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8481 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8482 Find the next snapshot associated with the source line @var{n}. If
8483 the optional argument @var{file} is given, refer to line @var{n} in
8484 that source file. Search proceeds forward from the last examined
8485 trace snapshot. If no argument @var{n} is given, it means find the
8486 next line other than the one currently being examined; thus saying
8487 @code{tfind line} repeatedly can appear to have the same effect as
8488 stepping from line to line in a @emph{live} debugging session.
8491 The default arguments for the @code{tfind} commands are specifically
8492 designed to make it easy to scan through the trace buffer. For
8493 instance, @code{tfind} with no argument selects the next trace
8494 snapshot, and @code{tfind -} with no argument selects the previous
8495 trace snapshot. So, by giving one @code{tfind} command, and then
8496 simply hitting @key{RET} repeatedly you can examine all the trace
8497 snapshots in order. Or, by saying @code{tfind -} and then hitting
8498 @key{RET} repeatedly you can examine the snapshots in reverse order.
8499 The @code{tfind line} command with no argument selects the snapshot
8500 for the next source line executed. The @code{tfind pc} command with
8501 no argument selects the next snapshot with the same program counter
8502 (PC) as the current frame. The @code{tfind tracepoint} command with
8503 no argument selects the next trace snapshot collected by the same
8504 tracepoint as the current one.
8506 In addition to letting you scan through the trace buffer manually,
8507 these commands make it easy to construct @value{GDBN} scripts that
8508 scan through the trace buffer and print out whatever collected data
8509 you are interested in. Thus, if we want to examine the PC, FP, and SP
8510 registers from each trace frame in the buffer, we can say this:
8513 (@value{GDBP}) @b{tfind start}
8514 (@value{GDBP}) @b{while ($trace_frame != -1)}
8515 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8516 $trace_frame, $pc, $sp, $fp
8520 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8521 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8522 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8523 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8524 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8525 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8526 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8527 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8528 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8529 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8530 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8533 Or, if we want to examine the variable @code{X} at each source line in
8537 (@value{GDBP}) @b{tfind start}
8538 (@value{GDBP}) @b{while ($trace_frame != -1)}
8539 > printf "Frame %d, X == %d\n", $trace_frame, X
8549 @subsection @code{tdump}
8551 @cindex dump all data collected at tracepoint
8552 @cindex tracepoint data, display
8554 This command takes no arguments. It prints all the data collected at
8555 the current trace snapshot.
8558 (@value{GDBP}) @b{trace 444}
8559 (@value{GDBP}) @b{actions}
8560 Enter actions for tracepoint #2, one per line:
8561 > collect $regs, $locals, $args, gdb_long_test
8564 (@value{GDBP}) @b{tstart}
8566 (@value{GDBP}) @b{tfind line 444}
8567 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8569 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8571 (@value{GDBP}) @b{tdump}
8572 Data collected at tracepoint 2, trace frame 1:
8573 d0 0xc4aa0085 -995491707
8577 d4 0x71aea3d 119204413
8582 a1 0x3000668 50333288
8585 a4 0x3000698 50333336
8587 fp 0x30bf3c 0x30bf3c
8588 sp 0x30bf34 0x30bf34
8590 pc 0x20b2c8 0x20b2c8
8594 p = 0x20e5b4 "gdb-test"
8601 gdb_long_test = 17 '\021'
8606 @node save-tracepoints
8607 @subsection @code{save-tracepoints @var{filename}}
8608 @kindex save-tracepoints
8609 @cindex save tracepoints for future sessions
8611 This command saves all current tracepoint definitions together with
8612 their actions and passcounts, into a file @file{@var{filename}}
8613 suitable for use in a later debugging session. To read the saved
8614 tracepoint definitions, use the @code{source} command (@pxref{Command
8617 @node Tracepoint Variables
8618 @section Convenience Variables for Tracepoints
8619 @cindex tracepoint variables
8620 @cindex convenience variables for tracepoints
8623 @vindex $trace_frame
8624 @item (int) $trace_frame
8625 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8626 snapshot is selected.
8629 @item (int) $tracepoint
8630 The tracepoint for the current trace snapshot.
8633 @item (int) $trace_line
8634 The line number for the current trace snapshot.
8637 @item (char []) $trace_file
8638 The source file for the current trace snapshot.
8641 @item (char []) $trace_func
8642 The name of the function containing @code{$tracepoint}.
8645 Note: @code{$trace_file} is not suitable for use in @code{printf},
8646 use @code{output} instead.
8648 Here's a simple example of using these convenience variables for
8649 stepping through all the trace snapshots and printing some of their
8653 (@value{GDBP}) @b{tfind start}
8655 (@value{GDBP}) @b{while $trace_frame != -1}
8656 > output $trace_file
8657 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8663 @chapter Debugging Programs That Use Overlays
8666 If your program is too large to fit completely in your target system's
8667 memory, you can sometimes use @dfn{overlays} to work around this
8668 problem. @value{GDBN} provides some support for debugging programs that
8672 * How Overlays Work:: A general explanation of overlays.
8673 * Overlay Commands:: Managing overlays in @value{GDBN}.
8674 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8675 mapped by asking the inferior.
8676 * Overlay Sample Program:: A sample program using overlays.
8679 @node How Overlays Work
8680 @section How Overlays Work
8681 @cindex mapped overlays
8682 @cindex unmapped overlays
8683 @cindex load address, overlay's
8684 @cindex mapped address
8685 @cindex overlay area
8687 Suppose you have a computer whose instruction address space is only 64
8688 kilobytes long, but which has much more memory which can be accessed by
8689 other means: special instructions, segment registers, or memory
8690 management hardware, for example. Suppose further that you want to
8691 adapt a program which is larger than 64 kilobytes to run on this system.
8693 One solution is to identify modules of your program which are relatively
8694 independent, and need not call each other directly; call these modules
8695 @dfn{overlays}. Separate the overlays from the main program, and place
8696 their machine code in the larger memory. Place your main program in
8697 instruction memory, but leave at least enough space there to hold the
8698 largest overlay as well.
8700 Now, to call a function located in an overlay, you must first copy that
8701 overlay's machine code from the large memory into the space set aside
8702 for it in the instruction memory, and then jump to its entry point
8705 @c NB: In the below the mapped area's size is greater or equal to the
8706 @c size of all overlays. This is intentional to remind the developer
8707 @c that overlays don't necessarily need to be the same size.
8711 Data Instruction Larger
8712 Address Space Address Space Address Space
8713 +-----------+ +-----------+ +-----------+
8715 +-----------+ +-----------+ +-----------+<-- overlay 1
8716 | program | | main | .----| overlay 1 | load address
8717 | variables | | program | | +-----------+
8718 | and heap | | | | | |
8719 +-----------+ | | | +-----------+<-- overlay 2
8720 | | +-----------+ | | | load address
8721 +-----------+ | | | .-| overlay 2 |
8723 mapped --->+-----------+ | | +-----------+
8725 | overlay | <-' | | |
8726 | area | <---' +-----------+<-- overlay 3
8727 | | <---. | | load address
8728 +-----------+ `--| overlay 3 |
8735 @anchor{A code overlay}A code overlay
8739 The diagram (@pxref{A code overlay}) shows a system with separate data
8740 and instruction address spaces. To map an overlay, the program copies
8741 its code from the larger address space to the instruction address space.
8742 Since the overlays shown here all use the same mapped address, only one
8743 may be mapped at a time. For a system with a single address space for
8744 data and instructions, the diagram would be similar, except that the
8745 program variables and heap would share an address space with the main
8746 program and the overlay area.
8748 An overlay loaded into instruction memory and ready for use is called a
8749 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8750 instruction memory. An overlay not present (or only partially present)
8751 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8752 is its address in the larger memory. The mapped address is also called
8753 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8754 called the @dfn{load memory address}, or @dfn{LMA}.
8756 Unfortunately, overlays are not a completely transparent way to adapt a
8757 program to limited instruction memory. They introduce a new set of
8758 global constraints you must keep in mind as you design your program:
8763 Before calling or returning to a function in an overlay, your program
8764 must make sure that overlay is actually mapped. Otherwise, the call or
8765 return will transfer control to the right address, but in the wrong
8766 overlay, and your program will probably crash.
8769 If the process of mapping an overlay is expensive on your system, you
8770 will need to choose your overlays carefully to minimize their effect on
8771 your program's performance.
8774 The executable file you load onto your system must contain each
8775 overlay's instructions, appearing at the overlay's load address, not its
8776 mapped address. However, each overlay's instructions must be relocated
8777 and its symbols defined as if the overlay were at its mapped address.
8778 You can use GNU linker scripts to specify different load and relocation
8779 addresses for pieces of your program; see @ref{Overlay Description,,,
8780 ld.info, Using ld: the GNU linker}.
8783 The procedure for loading executable files onto your system must be able
8784 to load their contents into the larger address space as well as the
8785 instruction and data spaces.
8789 The overlay system described above is rather simple, and could be
8790 improved in many ways:
8795 If your system has suitable bank switch registers or memory management
8796 hardware, you could use those facilities to make an overlay's load area
8797 contents simply appear at their mapped address in instruction space.
8798 This would probably be faster than copying the overlay to its mapped
8799 area in the usual way.
8802 If your overlays are small enough, you could set aside more than one
8803 overlay area, and have more than one overlay mapped at a time.
8806 You can use overlays to manage data, as well as instructions. In
8807 general, data overlays are even less transparent to your design than
8808 code overlays: whereas code overlays only require care when you call or
8809 return to functions, data overlays require care every time you access
8810 the data. Also, if you change the contents of a data overlay, you
8811 must copy its contents back out to its load address before you can copy a
8812 different data overlay into the same mapped area.
8817 @node Overlay Commands
8818 @section Overlay Commands
8820 To use @value{GDBN}'s overlay support, each overlay in your program must
8821 correspond to a separate section of the executable file. The section's
8822 virtual memory address and load memory address must be the overlay's
8823 mapped and load addresses. Identifying overlays with sections allows
8824 @value{GDBN} to determine the appropriate address of a function or
8825 variable, depending on whether the overlay is mapped or not.
8827 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8828 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8833 Disable @value{GDBN}'s overlay support. When overlay support is
8834 disabled, @value{GDBN} assumes that all functions and variables are
8835 always present at their mapped addresses. By default, @value{GDBN}'s
8836 overlay support is disabled.
8838 @item overlay manual
8839 @cindex manual overlay debugging
8840 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8841 relies on you to tell it which overlays are mapped, and which are not,
8842 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8843 commands described below.
8845 @item overlay map-overlay @var{overlay}
8846 @itemx overlay map @var{overlay}
8847 @cindex map an overlay
8848 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8849 be the name of the object file section containing the overlay. When an
8850 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8851 functions and variables at their mapped addresses. @value{GDBN} assumes
8852 that any other overlays whose mapped ranges overlap that of
8853 @var{overlay} are now unmapped.
8855 @item overlay unmap-overlay @var{overlay}
8856 @itemx overlay unmap @var{overlay}
8857 @cindex unmap an overlay
8858 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8859 must be the name of the object file section containing the overlay.
8860 When an overlay is unmapped, @value{GDBN} assumes it can find the
8861 overlay's functions and variables at their load addresses.
8864 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8865 consults a data structure the overlay manager maintains in the inferior
8866 to see which overlays are mapped. For details, see @ref{Automatic
8869 @item overlay load-target
8871 @cindex reloading the overlay table
8872 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8873 re-reads the table @value{GDBN} automatically each time the inferior
8874 stops, so this command should only be necessary if you have changed the
8875 overlay mapping yourself using @value{GDBN}. This command is only
8876 useful when using automatic overlay debugging.
8878 @item overlay list-overlays
8880 @cindex listing mapped overlays
8881 Display a list of the overlays currently mapped, along with their mapped
8882 addresses, load addresses, and sizes.
8886 Normally, when @value{GDBN} prints a code address, it includes the name
8887 of the function the address falls in:
8890 (@value{GDBP}) print main
8891 $3 = @{int ()@} 0x11a0 <main>
8894 When overlay debugging is enabled, @value{GDBN} recognizes code in
8895 unmapped overlays, and prints the names of unmapped functions with
8896 asterisks around them. For example, if @code{foo} is a function in an
8897 unmapped overlay, @value{GDBN} prints it this way:
8900 (@value{GDBP}) overlay list
8901 No sections are mapped.
8902 (@value{GDBP}) print foo
8903 $5 = @{int (int)@} 0x100000 <*foo*>
8906 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8910 (@value{GDBP}) overlay list
8911 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8912 mapped at 0x1016 - 0x104a
8913 (@value{GDBP}) print foo
8914 $6 = @{int (int)@} 0x1016 <foo>
8917 When overlay debugging is enabled, @value{GDBN} can find the correct
8918 address for functions and variables in an overlay, whether or not the
8919 overlay is mapped. This allows most @value{GDBN} commands, like
8920 @code{break} and @code{disassemble}, to work normally, even on unmapped
8921 code. However, @value{GDBN}'s breakpoint support has some limitations:
8925 @cindex breakpoints in overlays
8926 @cindex overlays, setting breakpoints in
8927 You can set breakpoints in functions in unmapped overlays, as long as
8928 @value{GDBN} can write to the overlay at its load address.
8930 @value{GDBN} can not set hardware or simulator-based breakpoints in
8931 unmapped overlays. However, if you set a breakpoint at the end of your
8932 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8933 you are using manual overlay management), @value{GDBN} will re-set its
8934 breakpoints properly.
8938 @node Automatic Overlay Debugging
8939 @section Automatic Overlay Debugging
8940 @cindex automatic overlay debugging
8942 @value{GDBN} can automatically track which overlays are mapped and which
8943 are not, given some simple co-operation from the overlay manager in the
8944 inferior. If you enable automatic overlay debugging with the
8945 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8946 looks in the inferior's memory for certain variables describing the
8947 current state of the overlays.
8949 Here are the variables your overlay manager must define to support
8950 @value{GDBN}'s automatic overlay debugging:
8954 @item @code{_ovly_table}:
8955 This variable must be an array of the following structures:
8960 /* The overlay's mapped address. */
8963 /* The size of the overlay, in bytes. */
8966 /* The overlay's load address. */
8969 /* Non-zero if the overlay is currently mapped;
8971 unsigned long mapped;
8975 @item @code{_novlys}:
8976 This variable must be a four-byte signed integer, holding the total
8977 number of elements in @code{_ovly_table}.
8981 To decide whether a particular overlay is mapped or not, @value{GDBN}
8982 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8983 @code{lma} members equal the VMA and LMA of the overlay's section in the
8984 executable file. When @value{GDBN} finds a matching entry, it consults
8985 the entry's @code{mapped} member to determine whether the overlay is
8988 In addition, your overlay manager may define a function called
8989 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8990 will silently set a breakpoint there. If the overlay manager then
8991 calls this function whenever it has changed the overlay table, this
8992 will enable @value{GDBN} to accurately keep track of which overlays
8993 are in program memory, and update any breakpoints that may be set
8994 in overlays. This will allow breakpoints to work even if the
8995 overlays are kept in ROM or other non-writable memory while they
8996 are not being executed.
8998 @node Overlay Sample Program
8999 @section Overlay Sample Program
9000 @cindex overlay example program
9002 When linking a program which uses overlays, you must place the overlays
9003 at their load addresses, while relocating them to run at their mapped
9004 addresses. To do this, you must write a linker script (@pxref{Overlay
9005 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9006 since linker scripts are specific to a particular host system, target
9007 architecture, and target memory layout, this manual cannot provide
9008 portable sample code demonstrating @value{GDBN}'s overlay support.
9010 However, the @value{GDBN} source distribution does contain an overlaid
9011 program, with linker scripts for a few systems, as part of its test
9012 suite. The program consists of the following files from
9013 @file{gdb/testsuite/gdb.base}:
9017 The main program file.
9019 A simple overlay manager, used by @file{overlays.c}.
9024 Overlay modules, loaded and used by @file{overlays.c}.
9027 Linker scripts for linking the test program on the @code{d10v-elf}
9028 and @code{m32r-elf} targets.
9031 You can build the test program using the @code{d10v-elf} GCC
9032 cross-compiler like this:
9035 $ d10v-elf-gcc -g -c overlays.c
9036 $ d10v-elf-gcc -g -c ovlymgr.c
9037 $ d10v-elf-gcc -g -c foo.c
9038 $ d10v-elf-gcc -g -c bar.c
9039 $ d10v-elf-gcc -g -c baz.c
9040 $ d10v-elf-gcc -g -c grbx.c
9041 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9042 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9045 The build process is identical for any other architecture, except that
9046 you must substitute the appropriate compiler and linker script for the
9047 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9051 @chapter Using @value{GDBN} with Different Languages
9054 Although programming languages generally have common aspects, they are
9055 rarely expressed in the same manner. For instance, in ANSI C,
9056 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9057 Modula-2, it is accomplished by @code{p^}. Values can also be
9058 represented (and displayed) differently. Hex numbers in C appear as
9059 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9061 @cindex working language
9062 Language-specific information is built into @value{GDBN} for some languages,
9063 allowing you to express operations like the above in your program's
9064 native language, and allowing @value{GDBN} to output values in a manner
9065 consistent with the syntax of your program's native language. The
9066 language you use to build expressions is called the @dfn{working
9070 * Setting:: Switching between source languages
9071 * Show:: Displaying the language
9072 * Checks:: Type and range checks
9073 * Supported Languages:: Supported languages
9074 * Unsupported Languages:: Unsupported languages
9078 @section Switching Between Source Languages
9080 There are two ways to control the working language---either have @value{GDBN}
9081 set it automatically, or select it manually yourself. You can use the
9082 @code{set language} command for either purpose. On startup, @value{GDBN}
9083 defaults to setting the language automatically. The working language is
9084 used to determine how expressions you type are interpreted, how values
9087 In addition to the working language, every source file that
9088 @value{GDBN} knows about has its own working language. For some object
9089 file formats, the compiler might indicate which language a particular
9090 source file is in. However, most of the time @value{GDBN} infers the
9091 language from the name of the file. The language of a source file
9092 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9093 show each frame appropriately for its own language. There is no way to
9094 set the language of a source file from within @value{GDBN}, but you can
9095 set the language associated with a filename extension. @xref{Show, ,
9096 Displaying the Language}.
9098 This is most commonly a problem when you use a program, such
9099 as @code{cfront} or @code{f2c}, that generates C but is written in
9100 another language. In that case, make the
9101 program use @code{#line} directives in its C output; that way
9102 @value{GDBN} will know the correct language of the source code of the original
9103 program, and will display that source code, not the generated C code.
9106 * Filenames:: Filename extensions and languages.
9107 * Manually:: Setting the working language manually
9108 * Automatically:: Having @value{GDBN} infer the source language
9112 @subsection List of Filename Extensions and Languages
9114 If a source file name ends in one of the following extensions, then
9115 @value{GDBN} infers that its language is the one indicated.
9136 Objective-C source file
9143 Modula-2 source file
9147 Assembler source file. This actually behaves almost like C, but
9148 @value{GDBN} does not skip over function prologues when stepping.
9151 In addition, you may set the language associated with a filename
9152 extension. @xref{Show, , Displaying the Language}.
9155 @subsection Setting the Working Language
9157 If you allow @value{GDBN} to set the language automatically,
9158 expressions are interpreted the same way in your debugging session and
9161 @kindex set language
9162 If you wish, you may set the language manually. To do this, issue the
9163 command @samp{set language @var{lang}}, where @var{lang} is the name of
9165 @code{c} or @code{modula-2}.
9166 For a list of the supported languages, type @samp{set language}.
9168 Setting the language manually prevents @value{GDBN} from updating the working
9169 language automatically. This can lead to confusion if you try
9170 to debug a program when the working language is not the same as the
9171 source language, when an expression is acceptable to both
9172 languages---but means different things. For instance, if the current
9173 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9181 might not have the effect you intended. In C, this means to add
9182 @code{b} and @code{c} and place the result in @code{a}. The result
9183 printed would be the value of @code{a}. In Modula-2, this means to compare
9184 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9187 @subsection Having @value{GDBN} Infer the Source Language
9189 To have @value{GDBN} set the working language automatically, use
9190 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9191 then infers the working language. That is, when your program stops in a
9192 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9193 working language to the language recorded for the function in that
9194 frame. If the language for a frame is unknown (that is, if the function
9195 or block corresponding to the frame was defined in a source file that
9196 does not have a recognized extension), the current working language is
9197 not changed, and @value{GDBN} issues a warning.
9199 This may not seem necessary for most programs, which are written
9200 entirely in one source language. However, program modules and libraries
9201 written in one source language can be used by a main program written in
9202 a different source language. Using @samp{set language auto} in this
9203 case frees you from having to set the working language manually.
9206 @section Displaying the Language
9208 The following commands help you find out which language is the
9209 working language, and also what language source files were written in.
9213 @kindex show language
9214 Display the current working language. This is the
9215 language you can use with commands such as @code{print} to
9216 build and compute expressions that may involve variables in your program.
9219 @kindex info frame@r{, show the source language}
9220 Display the source language for this frame. This language becomes the
9221 working language if you use an identifier from this frame.
9222 @xref{Frame Info, ,Information about a Frame}, to identify the other
9223 information listed here.
9226 @kindex info source@r{, show the source language}
9227 Display the source language of this source file.
9228 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9229 information listed here.
9232 In unusual circumstances, you may have source files with extensions
9233 not in the standard list. You can then set the extension associated
9234 with a language explicitly:
9237 @item set extension-language @var{ext} @var{language}
9238 @kindex set extension-language
9239 Tell @value{GDBN} that source files with extension @var{ext} are to be
9240 assumed as written in the source language @var{language}.
9242 @item info extensions
9243 @kindex info extensions
9244 List all the filename extensions and the associated languages.
9248 @section Type and Range Checking
9251 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9252 checking are included, but they do not yet have any effect. This
9253 section documents the intended facilities.
9255 @c FIXME remove warning when type/range code added
9257 Some languages are designed to guard you against making seemingly common
9258 errors through a series of compile- and run-time checks. These include
9259 checking the type of arguments to functions and operators, and making
9260 sure mathematical overflows are caught at run time. Checks such as
9261 these help to ensure a program's correctness once it has been compiled
9262 by eliminating type mismatches, and providing active checks for range
9263 errors when your program is running.
9265 @value{GDBN} can check for conditions like the above if you wish.
9266 Although @value{GDBN} does not check the statements in your program,
9267 it can check expressions entered directly into @value{GDBN} for
9268 evaluation via the @code{print} command, for example. As with the
9269 working language, @value{GDBN} can also decide whether or not to check
9270 automatically based on your program's source language.
9271 @xref{Supported Languages, ,Supported Languages}, for the default
9272 settings of supported languages.
9275 * Type Checking:: An overview of type checking
9276 * Range Checking:: An overview of range checking
9279 @cindex type checking
9280 @cindex checks, type
9282 @subsection An Overview of Type Checking
9284 Some languages, such as Modula-2, are strongly typed, meaning that the
9285 arguments to operators and functions have to be of the correct type,
9286 otherwise an error occurs. These checks prevent type mismatch
9287 errors from ever causing any run-time problems. For example,
9295 The second example fails because the @code{CARDINAL} 1 is not
9296 type-compatible with the @code{REAL} 2.3.
9298 For the expressions you use in @value{GDBN} commands, you can tell the
9299 @value{GDBN} type checker to skip checking;
9300 to treat any mismatches as errors and abandon the expression;
9301 or to only issue warnings when type mismatches occur,
9302 but evaluate the expression anyway. When you choose the last of
9303 these, @value{GDBN} evaluates expressions like the second example above, but
9304 also issues a warning.
9306 Even if you turn type checking off, there may be other reasons
9307 related to type that prevent @value{GDBN} from evaluating an expression.
9308 For instance, @value{GDBN} does not know how to add an @code{int} and
9309 a @code{struct foo}. These particular type errors have nothing to do
9310 with the language in use, and usually arise from expressions, such as
9311 the one described above, which make little sense to evaluate anyway.
9313 Each language defines to what degree it is strict about type. For
9314 instance, both Modula-2 and C require the arguments to arithmetical
9315 operators to be numbers. In C, enumerated types and pointers can be
9316 represented as numbers, so that they are valid arguments to mathematical
9317 operators. @xref{Supported Languages, ,Supported Languages}, for further
9318 details on specific languages.
9320 @value{GDBN} provides some additional commands for controlling the type checker:
9322 @kindex set check type
9323 @kindex show check type
9325 @item set check type auto
9326 Set type checking on or off based on the current working language.
9327 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9330 @item set check type on
9331 @itemx set check type off
9332 Set type checking on or off, overriding the default setting for the
9333 current working language. Issue a warning if the setting does not
9334 match the language default. If any type mismatches occur in
9335 evaluating an expression while type checking is on, @value{GDBN} prints a
9336 message and aborts evaluation of the expression.
9338 @item set check type warn
9339 Cause the type checker to issue warnings, but to always attempt to
9340 evaluate the expression. Evaluating the expression may still
9341 be impossible for other reasons. For example, @value{GDBN} cannot add
9342 numbers and structures.
9345 Show the current setting of the type checker, and whether or not @value{GDBN}
9346 is setting it automatically.
9349 @cindex range checking
9350 @cindex checks, range
9351 @node Range Checking
9352 @subsection An Overview of Range Checking
9354 In some languages (such as Modula-2), it is an error to exceed the
9355 bounds of a type; this is enforced with run-time checks. Such range
9356 checking is meant to ensure program correctness by making sure
9357 computations do not overflow, or indices on an array element access do
9358 not exceed the bounds of the array.
9360 For expressions you use in @value{GDBN} commands, you can tell
9361 @value{GDBN} to treat range errors in one of three ways: ignore them,
9362 always treat them as errors and abandon the expression, or issue
9363 warnings but evaluate the expression anyway.
9365 A range error can result from numerical overflow, from exceeding an
9366 array index bound, or when you type a constant that is not a member
9367 of any type. Some languages, however, do not treat overflows as an
9368 error. In many implementations of C, mathematical overflow causes the
9369 result to ``wrap around'' to lower values---for example, if @var{m} is
9370 the largest integer value, and @var{s} is the smallest, then
9373 @var{m} + 1 @result{} @var{s}
9376 This, too, is specific to individual languages, and in some cases
9377 specific to individual compilers or machines. @xref{Supported Languages, ,
9378 Supported Languages}, for further details on specific languages.
9380 @value{GDBN} provides some additional commands for controlling the range checker:
9382 @kindex set check range
9383 @kindex show check range
9385 @item set check range auto
9386 Set range checking on or off based on the current working language.
9387 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9390 @item set check range on
9391 @itemx set check range off
9392 Set range checking on or off, overriding the default setting for the
9393 current working language. A warning is issued if the setting does not
9394 match the language default. If a range error occurs and range checking is on,
9395 then a message is printed and evaluation of the expression is aborted.
9397 @item set check range warn
9398 Output messages when the @value{GDBN} range checker detects a range error,
9399 but attempt to evaluate the expression anyway. Evaluating the
9400 expression may still be impossible for other reasons, such as accessing
9401 memory that the process does not own (a typical example from many Unix
9405 Show the current setting of the range checker, and whether or not it is
9406 being set automatically by @value{GDBN}.
9409 @node Supported Languages
9410 @section Supported Languages
9412 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9413 assembly, Modula-2, and Ada.
9414 @c This is false ...
9415 Some @value{GDBN} features may be used in expressions regardless of the
9416 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9417 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9418 ,Expressions}) can be used with the constructs of any supported
9421 The following sections detail to what degree each source language is
9422 supported by @value{GDBN}. These sections are not meant to be language
9423 tutorials or references, but serve only as a reference guide to what the
9424 @value{GDBN} expression parser accepts, and what input and output
9425 formats should look like for different languages. There are many good
9426 books written on each of these languages; please look to these for a
9427 language reference or tutorial.
9431 * Objective-C:: Objective-C
9434 * Modula-2:: Modula-2
9439 @subsection C and C@t{++}
9441 @cindex C and C@t{++}
9442 @cindex expressions in C or C@t{++}
9444 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9445 to both languages. Whenever this is the case, we discuss those languages
9449 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9450 @cindex @sc{gnu} C@t{++}
9451 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9452 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9453 effectively, you must compile your C@t{++} programs with a supported
9454 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9455 compiler (@code{aCC}).
9457 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9458 format; if it doesn't work on your system, try the stabs+ debugging
9459 format. You can select those formats explicitly with the @code{g++}
9460 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9461 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9462 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9465 * C Operators:: C and C@t{++} operators
9466 * C Constants:: C and C@t{++} constants
9467 * C Plus Plus Expressions:: C@t{++} expressions
9468 * C Defaults:: Default settings for C and C@t{++}
9469 * C Checks:: C and C@t{++} type and range checks
9470 * Debugging C:: @value{GDBN} and C
9471 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9472 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9476 @subsubsection C and C@t{++} Operators
9478 @cindex C and C@t{++} operators
9480 Operators must be defined on values of specific types. For instance,
9481 @code{+} is defined on numbers, but not on structures. Operators are
9482 often defined on groups of types.
9484 For the purposes of C and C@t{++}, the following definitions hold:
9489 @emph{Integral types} include @code{int} with any of its storage-class
9490 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9493 @emph{Floating-point types} include @code{float}, @code{double}, and
9494 @code{long double} (if supported by the target platform).
9497 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9500 @emph{Scalar types} include all of the above.
9505 The following operators are supported. They are listed here
9506 in order of increasing precedence:
9510 The comma or sequencing operator. Expressions in a comma-separated list
9511 are evaluated from left to right, with the result of the entire
9512 expression being the last expression evaluated.
9515 Assignment. The value of an assignment expression is the value
9516 assigned. Defined on scalar types.
9519 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9520 and translated to @w{@code{@var{a} = @var{a op b}}}.
9521 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9522 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9523 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9526 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9527 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9531 Logical @sc{or}. Defined on integral types.
9534 Logical @sc{and}. Defined on integral types.
9537 Bitwise @sc{or}. Defined on integral types.
9540 Bitwise exclusive-@sc{or}. Defined on integral types.
9543 Bitwise @sc{and}. Defined on integral types.
9546 Equality and inequality. Defined on scalar types. The value of these
9547 expressions is 0 for false and non-zero for true.
9549 @item <@r{, }>@r{, }<=@r{, }>=
9550 Less than, greater than, less than or equal, greater than or equal.
9551 Defined on scalar types. The value of these expressions is 0 for false
9552 and non-zero for true.
9555 left shift, and right shift. Defined on integral types.
9558 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9561 Addition and subtraction. Defined on integral types, floating-point types and
9564 @item *@r{, }/@r{, }%
9565 Multiplication, division, and modulus. Multiplication and division are
9566 defined on integral and floating-point types. Modulus is defined on
9570 Increment and decrement. When appearing before a variable, the
9571 operation is performed before the variable is used in an expression;
9572 when appearing after it, the variable's value is used before the
9573 operation takes place.
9576 Pointer dereferencing. Defined on pointer types. Same precedence as
9580 Address operator. Defined on variables. Same precedence as @code{++}.
9582 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9583 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9584 to examine the address
9585 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9589 Negative. Defined on integral and floating-point types. Same
9590 precedence as @code{++}.
9593 Logical negation. Defined on integral types. Same precedence as
9597 Bitwise complement operator. Defined on integral types. Same precedence as
9602 Structure member, and pointer-to-structure member. For convenience,
9603 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9604 pointer based on the stored type information.
9605 Defined on @code{struct} and @code{union} data.
9608 Dereferences of pointers to members.
9611 Array indexing. @code{@var{a}[@var{i}]} is defined as
9612 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9615 Function parameter list. Same precedence as @code{->}.
9618 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9619 and @code{class} types.
9622 Doubled colons also represent the @value{GDBN} scope operator
9623 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9627 If an operator is redefined in the user code, @value{GDBN} usually
9628 attempts to invoke the redefined version instead of using the operator's
9632 @subsubsection C and C@t{++} Constants
9634 @cindex C and C@t{++} constants
9636 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9641 Integer constants are a sequence of digits. Octal constants are
9642 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9643 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9644 @samp{l}, specifying that the constant should be treated as a
9648 Floating point constants are a sequence of digits, followed by a decimal
9649 point, followed by a sequence of digits, and optionally followed by an
9650 exponent. An exponent is of the form:
9651 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9652 sequence of digits. The @samp{+} is optional for positive exponents.
9653 A floating-point constant may also end with a letter @samp{f} or
9654 @samp{F}, specifying that the constant should be treated as being of
9655 the @code{float} (as opposed to the default @code{double}) type; or with
9656 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9660 Enumerated constants consist of enumerated identifiers, or their
9661 integral equivalents.
9664 Character constants are a single character surrounded by single quotes
9665 (@code{'}), or a number---the ordinal value of the corresponding character
9666 (usually its @sc{ascii} value). Within quotes, the single character may
9667 be represented by a letter or by @dfn{escape sequences}, which are of
9668 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9669 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9670 @samp{@var{x}} is a predefined special character---for example,
9671 @samp{\n} for newline.
9674 String constants are a sequence of character constants surrounded by
9675 double quotes (@code{"}). Any valid character constant (as described
9676 above) may appear. Double quotes within the string must be preceded by
9677 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9681 Pointer constants are an integral value. You can also write pointers
9682 to constants using the C operator @samp{&}.
9685 Array constants are comma-separated lists surrounded by braces @samp{@{}
9686 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9687 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9688 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9691 @node C Plus Plus Expressions
9692 @subsubsection C@t{++} Expressions
9694 @cindex expressions in C@t{++}
9695 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9697 @cindex debugging C@t{++} programs
9698 @cindex C@t{++} compilers
9699 @cindex debug formats and C@t{++}
9700 @cindex @value{NGCC} and C@t{++}
9702 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9703 proper compiler and the proper debug format. Currently, @value{GDBN}
9704 works best when debugging C@t{++} code that is compiled with
9705 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9706 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9707 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9708 stabs+ as their default debug format, so you usually don't need to
9709 specify a debug format explicitly. Other compilers and/or debug formats
9710 are likely to work badly or not at all when using @value{GDBN} to debug
9716 @cindex member functions
9718 Member function calls are allowed; you can use expressions like
9721 count = aml->GetOriginal(x, y)
9724 @vindex this@r{, inside C@t{++} member functions}
9725 @cindex namespace in C@t{++}
9727 While a member function is active (in the selected stack frame), your
9728 expressions have the same namespace available as the member function;
9729 that is, @value{GDBN} allows implicit references to the class instance
9730 pointer @code{this} following the same rules as C@t{++}.
9732 @cindex call overloaded functions
9733 @cindex overloaded functions, calling
9734 @cindex type conversions in C@t{++}
9736 You can call overloaded functions; @value{GDBN} resolves the function
9737 call to the right definition, with some restrictions. @value{GDBN} does not
9738 perform overload resolution involving user-defined type conversions,
9739 calls to constructors, or instantiations of templates that do not exist
9740 in the program. It also cannot handle ellipsis argument lists or
9743 It does perform integral conversions and promotions, floating-point
9744 promotions, arithmetic conversions, pointer conversions, conversions of
9745 class objects to base classes, and standard conversions such as those of
9746 functions or arrays to pointers; it requires an exact match on the
9747 number of function arguments.
9749 Overload resolution is always performed, unless you have specified
9750 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9751 ,@value{GDBN} Features for C@t{++}}.
9753 You must specify @code{set overload-resolution off} in order to use an
9754 explicit function signature to call an overloaded function, as in
9756 p 'foo(char,int)'('x', 13)
9759 The @value{GDBN} command-completion facility can simplify this;
9760 see @ref{Completion, ,Command Completion}.
9762 @cindex reference declarations
9764 @value{GDBN} understands variables declared as C@t{++} references; you can use
9765 them in expressions just as you do in C@t{++} source---they are automatically
9768 In the parameter list shown when @value{GDBN} displays a frame, the values of
9769 reference variables are not displayed (unlike other variables); this
9770 avoids clutter, since references are often used for large structures.
9771 The @emph{address} of a reference variable is always shown, unless
9772 you have specified @samp{set print address off}.
9775 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9776 expressions can use it just as expressions in your program do. Since
9777 one scope may be defined in another, you can use @code{::} repeatedly if
9778 necessary, for example in an expression like
9779 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9780 resolving name scope by reference to source files, in both C and C@t{++}
9781 debugging (@pxref{Variables, ,Program Variables}).
9784 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9785 calling virtual functions correctly, printing out virtual bases of
9786 objects, calling functions in a base subobject, casting objects, and
9787 invoking user-defined operators.
9790 @subsubsection C and C@t{++} Defaults
9792 @cindex C and C@t{++} defaults
9794 If you allow @value{GDBN} to set type and range checking automatically, they
9795 both default to @code{off} whenever the working language changes to
9796 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9797 selects the working language.
9799 If you allow @value{GDBN} to set the language automatically, it
9800 recognizes source files whose names end with @file{.c}, @file{.C}, or
9801 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9802 these files, it sets the working language to C or C@t{++}.
9803 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9804 for further details.
9806 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9807 @c unimplemented. If (b) changes, it might make sense to let this node
9808 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9811 @subsubsection C and C@t{++} Type and Range Checks
9813 @cindex C and C@t{++} checks
9815 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9816 is not used. However, if you turn type checking on, @value{GDBN}
9817 considers two variables type equivalent if:
9821 The two variables are structured and have the same structure, union, or
9825 The two variables have the same type name, or types that have been
9826 declared equivalent through @code{typedef}.
9829 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9832 The two @code{struct}, @code{union}, or @code{enum} variables are
9833 declared in the same declaration. (Note: this may not be true for all C
9838 Range checking, if turned on, is done on mathematical operations. Array
9839 indices are not checked, since they are often used to index a pointer
9840 that is not itself an array.
9843 @subsubsection @value{GDBN} and C
9845 The @code{set print union} and @code{show print union} commands apply to
9846 the @code{union} type. When set to @samp{on}, any @code{union} that is
9847 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9848 appears as @samp{@{...@}}.
9850 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9851 with pointers and a memory allocation function. @xref{Expressions,
9854 @node Debugging C Plus Plus
9855 @subsubsection @value{GDBN} Features for C@t{++}
9857 @cindex commands for C@t{++}
9859 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9860 designed specifically for use with C@t{++}. Here is a summary:
9863 @cindex break in overloaded functions
9864 @item @r{breakpoint menus}
9865 When you want a breakpoint in a function whose name is overloaded,
9866 @value{GDBN} has the capability to display a menu of possible breakpoint
9867 locations to help you specify which function definition you want.
9868 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
9870 @cindex overloading in C@t{++}
9871 @item rbreak @var{regex}
9872 Setting breakpoints using regular expressions is helpful for setting
9873 breakpoints on overloaded functions that are not members of any special
9875 @xref{Set Breaks, ,Setting Breakpoints}.
9877 @cindex C@t{++} exception handling
9880 Debug C@t{++} exception handling using these commands. @xref{Set
9881 Catchpoints, , Setting Catchpoints}.
9884 @item ptype @var{typename}
9885 Print inheritance relationships as well as other information for type
9887 @xref{Symbols, ,Examining the Symbol Table}.
9889 @cindex C@t{++} symbol display
9890 @item set print demangle
9891 @itemx show print demangle
9892 @itemx set print asm-demangle
9893 @itemx show print asm-demangle
9894 Control whether C@t{++} symbols display in their source form, both when
9895 displaying code as C@t{++} source and when displaying disassemblies.
9896 @xref{Print Settings, ,Print Settings}.
9898 @item set print object
9899 @itemx show print object
9900 Choose whether to print derived (actual) or declared types of objects.
9901 @xref{Print Settings, ,Print Settings}.
9903 @item set print vtbl
9904 @itemx show print vtbl
9905 Control the format for printing virtual function tables.
9906 @xref{Print Settings, ,Print Settings}.
9907 (The @code{vtbl} commands do not work on programs compiled with the HP
9908 ANSI C@t{++} compiler (@code{aCC}).)
9910 @kindex set overload-resolution
9911 @cindex overloaded functions, overload resolution
9912 @item set overload-resolution on
9913 Enable overload resolution for C@t{++} expression evaluation. The default
9914 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9915 and searches for a function whose signature matches the argument types,
9916 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9917 Expressions, ,C@t{++} Expressions}, for details).
9918 If it cannot find a match, it emits a message.
9920 @item set overload-resolution off
9921 Disable overload resolution for C@t{++} expression evaluation. For
9922 overloaded functions that are not class member functions, @value{GDBN}
9923 chooses the first function of the specified name that it finds in the
9924 symbol table, whether or not its arguments are of the correct type. For
9925 overloaded functions that are class member functions, @value{GDBN}
9926 searches for a function whose signature @emph{exactly} matches the
9929 @kindex show overload-resolution
9930 @item show overload-resolution
9931 Show the current setting of overload resolution.
9933 @item @r{Overloaded symbol names}
9934 You can specify a particular definition of an overloaded symbol, using
9935 the same notation that is used to declare such symbols in C@t{++}: type
9936 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9937 also use the @value{GDBN} command-line word completion facilities to list the
9938 available choices, or to finish the type list for you.
9939 @xref{Completion,, Command Completion}, for details on how to do this.
9942 @node Decimal Floating Point
9943 @subsubsection Decimal Floating Point format
9944 @cindex decimal floating point format
9946 @value{GDBN} can examine, set and perform computations with numbers in
9947 decimal floating point format, which in the C language correspond to the
9948 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
9949 specified by the extension to support decimal floating-point arithmetic.
9951 There are two encodings in use, depending on the architecture: BID (Binary
9952 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
9953 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
9956 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
9957 to manipulate decimal floating point numbers, it is not possible to convert
9958 (using a cast, for example) integers wider than 32-bit to decimal float.
9960 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
9961 point computations, error checking in decimal float operations ignores
9962 underflow, overflow and divide by zero exceptions.
9964 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
9965 to inspect @code{_Decimal128} values stored in floating point registers. See
9966 @ref{PowerPC,,PowerPC} for more details.
9969 @subsection Objective-C
9972 This section provides information about some commands and command
9973 options that are useful for debugging Objective-C code. See also
9974 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9975 few more commands specific to Objective-C support.
9978 * Method Names in Commands::
9979 * The Print Command with Objective-C::
9982 @node Method Names in Commands
9983 @subsubsection Method Names in Commands
9985 The following commands have been extended to accept Objective-C method
9986 names as line specifications:
9988 @kindex clear@r{, and Objective-C}
9989 @kindex break@r{, and Objective-C}
9990 @kindex info line@r{, and Objective-C}
9991 @kindex jump@r{, and Objective-C}
9992 @kindex list@r{, and Objective-C}
9996 @item @code{info line}
10001 A fully qualified Objective-C method name is specified as
10004 -[@var{Class} @var{methodName}]
10007 where the minus sign is used to indicate an instance method and a
10008 plus sign (not shown) is used to indicate a class method. The class
10009 name @var{Class} and method name @var{methodName} are enclosed in
10010 brackets, similar to the way messages are specified in Objective-C
10011 source code. For example, to set a breakpoint at the @code{create}
10012 instance method of class @code{Fruit} in the program currently being
10016 break -[Fruit create]
10019 To list ten program lines around the @code{initialize} class method,
10023 list +[NSText initialize]
10026 In the current version of @value{GDBN}, the plus or minus sign is
10027 required. In future versions of @value{GDBN}, the plus or minus
10028 sign will be optional, but you can use it to narrow the search. It
10029 is also possible to specify just a method name:
10035 You must specify the complete method name, including any colons. If
10036 your program's source files contain more than one @code{create} method,
10037 you'll be presented with a numbered list of classes that implement that
10038 method. Indicate your choice by number, or type @samp{0} to exit if
10041 As another example, to clear a breakpoint established at the
10042 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10045 clear -[NSWindow makeKeyAndOrderFront:]
10048 @node The Print Command with Objective-C
10049 @subsubsection The Print Command With Objective-C
10050 @cindex Objective-C, print objects
10051 @kindex print-object
10052 @kindex po @r{(@code{print-object})}
10054 The print command has also been extended to accept methods. For example:
10057 print -[@var{object} hash]
10060 @cindex print an Objective-C object description
10061 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10063 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10064 and print the result. Also, an additional command has been added,
10065 @code{print-object} or @code{po} for short, which is meant to print
10066 the description of an object. However, this command may only work
10067 with certain Objective-C libraries that have a particular hook
10068 function, @code{_NSPrintForDebugger}, defined.
10071 @subsection Fortran
10072 @cindex Fortran-specific support in @value{GDBN}
10074 @value{GDBN} can be used to debug programs written in Fortran, but it
10075 currently supports only the features of Fortran 77 language.
10077 @cindex trailing underscore, in Fortran symbols
10078 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10079 among them) append an underscore to the names of variables and
10080 functions. When you debug programs compiled by those compilers, you
10081 will need to refer to variables and functions with a trailing
10085 * Fortran Operators:: Fortran operators and expressions
10086 * Fortran Defaults:: Default settings for Fortran
10087 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10090 @node Fortran Operators
10091 @subsubsection Fortran Operators and Expressions
10093 @cindex Fortran operators and expressions
10095 Operators must be defined on values of specific types. For instance,
10096 @code{+} is defined on numbers, but not on characters or other non-
10097 arithmetic types. Operators are often defined on groups of types.
10101 The exponentiation operator. It raises the first operand to the power
10105 The range operator. Normally used in the form of array(low:high) to
10106 represent a section of array.
10109 The access component operator. Normally used to access elements in derived
10110 types. Also suitable for unions. As unions aren't part of regular Fortran,
10111 this can only happen when accessing a register that uses a gdbarch-defined
10115 @node Fortran Defaults
10116 @subsubsection Fortran Defaults
10118 @cindex Fortran Defaults
10120 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10121 default uses case-insensitive matches for Fortran symbols. You can
10122 change that with the @samp{set case-insensitive} command, see
10123 @ref{Symbols}, for the details.
10125 @node Special Fortran Commands
10126 @subsubsection Special Fortran Commands
10128 @cindex Special Fortran commands
10130 @value{GDBN} has some commands to support Fortran-specific features,
10131 such as displaying common blocks.
10134 @cindex @code{COMMON} blocks, Fortran
10135 @kindex info common
10136 @item info common @r{[}@var{common-name}@r{]}
10137 This command prints the values contained in the Fortran @code{COMMON}
10138 block whose name is @var{common-name}. With no argument, the names of
10139 all @code{COMMON} blocks visible at the current program location are
10146 @cindex Pascal support in @value{GDBN}, limitations
10147 Debugging Pascal programs which use sets, subranges, file variables, or
10148 nested functions does not currently work. @value{GDBN} does not support
10149 entering expressions, printing values, or similar features using Pascal
10152 The Pascal-specific command @code{set print pascal_static-members}
10153 controls whether static members of Pascal objects are displayed.
10154 @xref{Print Settings, pascal_static-members}.
10157 @subsection Modula-2
10159 @cindex Modula-2, @value{GDBN} support
10161 The extensions made to @value{GDBN} to support Modula-2 only support
10162 output from the @sc{gnu} Modula-2 compiler (which is currently being
10163 developed). Other Modula-2 compilers are not currently supported, and
10164 attempting to debug executables produced by them is most likely
10165 to give an error as @value{GDBN} reads in the executable's symbol
10168 @cindex expressions in Modula-2
10170 * M2 Operators:: Built-in operators
10171 * Built-In Func/Proc:: Built-in functions and procedures
10172 * M2 Constants:: Modula-2 constants
10173 * M2 Types:: Modula-2 types
10174 * M2 Defaults:: Default settings for Modula-2
10175 * Deviations:: Deviations from standard Modula-2
10176 * M2 Checks:: Modula-2 type and range checks
10177 * M2 Scope:: The scope operators @code{::} and @code{.}
10178 * GDB/M2:: @value{GDBN} and Modula-2
10182 @subsubsection Operators
10183 @cindex Modula-2 operators
10185 Operators must be defined on values of specific types. For instance,
10186 @code{+} is defined on numbers, but not on structures. Operators are
10187 often defined on groups of types. For the purposes of Modula-2, the
10188 following definitions hold:
10193 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10197 @emph{Character types} consist of @code{CHAR} and its subranges.
10200 @emph{Floating-point types} consist of @code{REAL}.
10203 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10207 @emph{Scalar types} consist of all of the above.
10210 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10213 @emph{Boolean types} consist of @code{BOOLEAN}.
10217 The following operators are supported, and appear in order of
10218 increasing precedence:
10222 Function argument or array index separator.
10225 Assignment. The value of @var{var} @code{:=} @var{value} is
10229 Less than, greater than on integral, floating-point, or enumerated
10233 Less than or equal to, greater than or equal to
10234 on integral, floating-point and enumerated types, or set inclusion on
10235 set types. Same precedence as @code{<}.
10237 @item =@r{, }<>@r{, }#
10238 Equality and two ways of expressing inequality, valid on scalar types.
10239 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10240 available for inequality, since @code{#} conflicts with the script
10244 Set membership. Defined on set types and the types of their members.
10245 Same precedence as @code{<}.
10248 Boolean disjunction. Defined on boolean types.
10251 Boolean conjunction. Defined on boolean types.
10254 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10257 Addition and subtraction on integral and floating-point types, or union
10258 and difference on set types.
10261 Multiplication on integral and floating-point types, or set intersection
10265 Division on floating-point types, or symmetric set difference on set
10266 types. Same precedence as @code{*}.
10269 Integer division and remainder. Defined on integral types. Same
10270 precedence as @code{*}.
10273 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10276 Pointer dereferencing. Defined on pointer types.
10279 Boolean negation. Defined on boolean types. Same precedence as
10283 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10284 precedence as @code{^}.
10287 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10290 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10294 @value{GDBN} and Modula-2 scope operators.
10298 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10299 treats the use of the operator @code{IN}, or the use of operators
10300 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10301 @code{<=}, and @code{>=} on sets as an error.
10305 @node Built-In Func/Proc
10306 @subsubsection Built-in Functions and Procedures
10307 @cindex Modula-2 built-ins
10309 Modula-2 also makes available several built-in procedures and functions.
10310 In describing these, the following metavariables are used:
10315 represents an @code{ARRAY} variable.
10318 represents a @code{CHAR} constant or variable.
10321 represents a variable or constant of integral type.
10324 represents an identifier that belongs to a set. Generally used in the
10325 same function with the metavariable @var{s}. The type of @var{s} should
10326 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10329 represents a variable or constant of integral or floating-point type.
10332 represents a variable or constant of floating-point type.
10338 represents a variable.
10341 represents a variable or constant of one of many types. See the
10342 explanation of the function for details.
10345 All Modula-2 built-in procedures also return a result, described below.
10349 Returns the absolute value of @var{n}.
10352 If @var{c} is a lower case letter, it returns its upper case
10353 equivalent, otherwise it returns its argument.
10356 Returns the character whose ordinal value is @var{i}.
10359 Decrements the value in the variable @var{v} by one. Returns the new value.
10361 @item DEC(@var{v},@var{i})
10362 Decrements the value in the variable @var{v} by @var{i}. Returns the
10365 @item EXCL(@var{m},@var{s})
10366 Removes the element @var{m} from the set @var{s}. Returns the new
10369 @item FLOAT(@var{i})
10370 Returns the floating point equivalent of the integer @var{i}.
10372 @item HIGH(@var{a})
10373 Returns the index of the last member of @var{a}.
10376 Increments the value in the variable @var{v} by one. Returns the new value.
10378 @item INC(@var{v},@var{i})
10379 Increments the value in the variable @var{v} by @var{i}. Returns the
10382 @item INCL(@var{m},@var{s})
10383 Adds the element @var{m} to the set @var{s} if it is not already
10384 there. Returns the new set.
10387 Returns the maximum value of the type @var{t}.
10390 Returns the minimum value of the type @var{t}.
10393 Returns boolean TRUE if @var{i} is an odd number.
10396 Returns the ordinal value of its argument. For example, the ordinal
10397 value of a character is its @sc{ascii} value (on machines supporting the
10398 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10399 integral, character and enumerated types.
10401 @item SIZE(@var{x})
10402 Returns the size of its argument. @var{x} can be a variable or a type.
10404 @item TRUNC(@var{r})
10405 Returns the integral part of @var{r}.
10407 @item TSIZE(@var{x})
10408 Returns the size of its argument. @var{x} can be a variable or a type.
10410 @item VAL(@var{t},@var{i})
10411 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10415 @emph{Warning:} Sets and their operations are not yet supported, so
10416 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10420 @cindex Modula-2 constants
10422 @subsubsection Constants
10424 @value{GDBN} allows you to express the constants of Modula-2 in the following
10430 Integer constants are simply a sequence of digits. When used in an
10431 expression, a constant is interpreted to be type-compatible with the
10432 rest of the expression. Hexadecimal integers are specified by a
10433 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10436 Floating point constants appear as a sequence of digits, followed by a
10437 decimal point and another sequence of digits. An optional exponent can
10438 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10439 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10440 digits of the floating point constant must be valid decimal (base 10)
10444 Character constants consist of a single character enclosed by a pair of
10445 like quotes, either single (@code{'}) or double (@code{"}). They may
10446 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10447 followed by a @samp{C}.
10450 String constants consist of a sequence of characters enclosed by a
10451 pair of like quotes, either single (@code{'}) or double (@code{"}).
10452 Escape sequences in the style of C are also allowed. @xref{C
10453 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10457 Enumerated constants consist of an enumerated identifier.
10460 Boolean constants consist of the identifiers @code{TRUE} and
10464 Pointer constants consist of integral values only.
10467 Set constants are not yet supported.
10471 @subsubsection Modula-2 Types
10472 @cindex Modula-2 types
10474 Currently @value{GDBN} can print the following data types in Modula-2
10475 syntax: array types, record types, set types, pointer types, procedure
10476 types, enumerated types, subrange types and base types. You can also
10477 print the contents of variables declared using these type.
10478 This section gives a number of simple source code examples together with
10479 sample @value{GDBN} sessions.
10481 The first example contains the following section of code:
10490 and you can request @value{GDBN} to interrogate the type and value of
10491 @code{r} and @code{s}.
10494 (@value{GDBP}) print s
10496 (@value{GDBP}) ptype s
10498 (@value{GDBP}) print r
10500 (@value{GDBP}) ptype r
10505 Likewise if your source code declares @code{s} as:
10509 s: SET ['A'..'Z'] ;
10513 then you may query the type of @code{s} by:
10516 (@value{GDBP}) ptype s
10517 type = SET ['A'..'Z']
10521 Note that at present you cannot interactively manipulate set
10522 expressions using the debugger.
10524 The following example shows how you might declare an array in Modula-2
10525 and how you can interact with @value{GDBN} to print its type and contents:
10529 s: ARRAY [-10..10] OF CHAR ;
10533 (@value{GDBP}) ptype s
10534 ARRAY [-10..10] OF CHAR
10537 Note that the array handling is not yet complete and although the type
10538 is printed correctly, expression handling still assumes that all
10539 arrays have a lower bound of zero and not @code{-10} as in the example
10542 Here are some more type related Modula-2 examples:
10546 colour = (blue, red, yellow, green) ;
10547 t = [blue..yellow] ;
10555 The @value{GDBN} interaction shows how you can query the data type
10556 and value of a variable.
10559 (@value{GDBP}) print s
10561 (@value{GDBP}) ptype t
10562 type = [blue..yellow]
10566 In this example a Modula-2 array is declared and its contents
10567 displayed. Observe that the contents are written in the same way as
10568 their @code{C} counterparts.
10572 s: ARRAY [1..5] OF CARDINAL ;
10578 (@value{GDBP}) print s
10579 $1 = @{1, 0, 0, 0, 0@}
10580 (@value{GDBP}) ptype s
10581 type = ARRAY [1..5] OF CARDINAL
10584 The Modula-2 language interface to @value{GDBN} also understands
10585 pointer types as shown in this example:
10589 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10596 and you can request that @value{GDBN} describes the type of @code{s}.
10599 (@value{GDBP}) ptype s
10600 type = POINTER TO ARRAY [1..5] OF CARDINAL
10603 @value{GDBN} handles compound types as we can see in this example.
10604 Here we combine array types, record types, pointer types and subrange
10615 myarray = ARRAY myrange OF CARDINAL ;
10616 myrange = [-2..2] ;
10618 s: POINTER TO ARRAY myrange OF foo ;
10622 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10626 (@value{GDBP}) ptype s
10627 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10630 f3 : ARRAY [-2..2] OF CARDINAL;
10635 @subsubsection Modula-2 Defaults
10636 @cindex Modula-2 defaults
10638 If type and range checking are set automatically by @value{GDBN}, they
10639 both default to @code{on} whenever the working language changes to
10640 Modula-2. This happens regardless of whether you or @value{GDBN}
10641 selected the working language.
10643 If you allow @value{GDBN} to set the language automatically, then entering
10644 code compiled from a file whose name ends with @file{.mod} sets the
10645 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10646 Infer the Source Language}, for further details.
10649 @subsubsection Deviations from Standard Modula-2
10650 @cindex Modula-2, deviations from
10652 A few changes have been made to make Modula-2 programs easier to debug.
10653 This is done primarily via loosening its type strictness:
10657 Unlike in standard Modula-2, pointer constants can be formed by
10658 integers. This allows you to modify pointer variables during
10659 debugging. (In standard Modula-2, the actual address contained in a
10660 pointer variable is hidden from you; it can only be modified
10661 through direct assignment to another pointer variable or expression that
10662 returned a pointer.)
10665 C escape sequences can be used in strings and characters to represent
10666 non-printable characters. @value{GDBN} prints out strings with these
10667 escape sequences embedded. Single non-printable characters are
10668 printed using the @samp{CHR(@var{nnn})} format.
10671 The assignment operator (@code{:=}) returns the value of its right-hand
10675 All built-in procedures both modify @emph{and} return their argument.
10679 @subsubsection Modula-2 Type and Range Checks
10680 @cindex Modula-2 checks
10683 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10686 @c FIXME remove warning when type/range checks added
10688 @value{GDBN} considers two Modula-2 variables type equivalent if:
10692 They are of types that have been declared equivalent via a @code{TYPE
10693 @var{t1} = @var{t2}} statement
10696 They have been declared on the same line. (Note: This is true of the
10697 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10700 As long as type checking is enabled, any attempt to combine variables
10701 whose types are not equivalent is an error.
10703 Range checking is done on all mathematical operations, assignment, array
10704 index bounds, and all built-in functions and procedures.
10707 @subsubsection The Scope Operators @code{::} and @code{.}
10709 @cindex @code{.}, Modula-2 scope operator
10710 @cindex colon, doubled as scope operator
10712 @vindex colon-colon@r{, in Modula-2}
10713 @c Info cannot handle :: but TeX can.
10716 @vindex ::@r{, in Modula-2}
10719 There are a few subtle differences between the Modula-2 scope operator
10720 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10725 @var{module} . @var{id}
10726 @var{scope} :: @var{id}
10730 where @var{scope} is the name of a module or a procedure,
10731 @var{module} the name of a module, and @var{id} is any declared
10732 identifier within your program, except another module.
10734 Using the @code{::} operator makes @value{GDBN} search the scope
10735 specified by @var{scope} for the identifier @var{id}. If it is not
10736 found in the specified scope, then @value{GDBN} searches all scopes
10737 enclosing the one specified by @var{scope}.
10739 Using the @code{.} operator makes @value{GDBN} search the current scope for
10740 the identifier specified by @var{id} that was imported from the
10741 definition module specified by @var{module}. With this operator, it is
10742 an error if the identifier @var{id} was not imported from definition
10743 module @var{module}, or if @var{id} is not an identifier in
10747 @subsubsection @value{GDBN} and Modula-2
10749 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10750 Five subcommands of @code{set print} and @code{show print} apply
10751 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10752 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10753 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10754 analogue in Modula-2.
10756 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10757 with any language, is not useful with Modula-2. Its
10758 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10759 created in Modula-2 as they can in C or C@t{++}. However, because an
10760 address can be specified by an integral constant, the construct
10761 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10763 @cindex @code{#} in Modula-2
10764 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10765 interpreted as the beginning of a comment. Use @code{<>} instead.
10771 The extensions made to @value{GDBN} for Ada only support
10772 output from the @sc{gnu} Ada (GNAT) compiler.
10773 Other Ada compilers are not currently supported, and
10774 attempting to debug executables produced by them is most likely
10778 @cindex expressions in Ada
10780 * Ada Mode Intro:: General remarks on the Ada syntax
10781 and semantics supported by Ada mode
10783 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10784 * Additions to Ada:: Extensions of the Ada expression syntax.
10785 * Stopping Before Main Program:: Debugging the program during elaboration.
10786 * Ada Glitches:: Known peculiarities of Ada mode.
10789 @node Ada Mode Intro
10790 @subsubsection Introduction
10791 @cindex Ada mode, general
10793 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10794 syntax, with some extensions.
10795 The philosophy behind the design of this subset is
10799 That @value{GDBN} should provide basic literals and access to operations for
10800 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10801 leaving more sophisticated computations to subprograms written into the
10802 program (which therefore may be called from @value{GDBN}).
10805 That type safety and strict adherence to Ada language restrictions
10806 are not particularly important to the @value{GDBN} user.
10809 That brevity is important to the @value{GDBN} user.
10812 Thus, for brevity, the debugger acts as if there were
10813 implicit @code{with} and @code{use} clauses in effect for all user-written
10814 packages, making it unnecessary to fully qualify most names with
10815 their packages, regardless of context. Where this causes ambiguity,
10816 @value{GDBN} asks the user's intent.
10818 The debugger will start in Ada mode if it detects an Ada main program.
10819 As for other languages, it will enter Ada mode when stopped in a program that
10820 was translated from an Ada source file.
10822 While in Ada mode, you may use `@t{--}' for comments. This is useful
10823 mostly for documenting command files. The standard @value{GDBN} comment
10824 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10825 middle (to allow based literals).
10827 The debugger supports limited overloading. Given a subprogram call in which
10828 the function symbol has multiple definitions, it will use the number of
10829 actual parameters and some information about their types to attempt to narrow
10830 the set of definitions. It also makes very limited use of context, preferring
10831 procedures to functions in the context of the @code{call} command, and
10832 functions to procedures elsewhere.
10834 @node Omissions from Ada
10835 @subsubsection Omissions from Ada
10836 @cindex Ada, omissions from
10838 Here are the notable omissions from the subset:
10842 Only a subset of the attributes are supported:
10846 @t{'First}, @t{'Last}, and @t{'Length}
10847 on array objects (not on types and subtypes).
10850 @t{'Min} and @t{'Max}.
10853 @t{'Pos} and @t{'Val}.
10859 @t{'Range} on array objects (not subtypes), but only as the right
10860 operand of the membership (@code{in}) operator.
10863 @t{'Access}, @t{'Unchecked_Access}, and
10864 @t{'Unrestricted_Access} (a GNAT extension).
10872 @code{Characters.Latin_1} are not available and
10873 concatenation is not implemented. Thus, escape characters in strings are
10874 not currently available.
10877 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10878 equality of representations. They will generally work correctly
10879 for strings and arrays whose elements have integer or enumeration types.
10880 They may not work correctly for arrays whose element
10881 types have user-defined equality, for arrays of real values
10882 (in particular, IEEE-conformant floating point, because of negative
10883 zeroes and NaNs), and for arrays whose elements contain unused bits with
10884 indeterminate values.
10887 The other component-by-component array operations (@code{and}, @code{or},
10888 @code{xor}, @code{not}, and relational tests other than equality)
10889 are not implemented.
10892 @cindex array aggregates (Ada)
10893 @cindex record aggregates (Ada)
10894 @cindex aggregates (Ada)
10895 There is limited support for array and record aggregates. They are
10896 permitted only on the right sides of assignments, as in these examples:
10899 set An_Array := (1, 2, 3, 4, 5, 6)
10900 set An_Array := (1, others => 0)
10901 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10902 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10903 set A_Record := (1, "Peter", True);
10904 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10908 discriminant's value by assigning an aggregate has an
10909 undefined effect if that discriminant is used within the record.
10910 However, you can first modify discriminants by directly assigning to
10911 them (which normally would not be allowed in Ada), and then performing an
10912 aggregate assignment. For example, given a variable @code{A_Rec}
10913 declared to have a type such as:
10916 type Rec (Len : Small_Integer := 0) is record
10918 Vals : IntArray (1 .. Len);
10922 you can assign a value with a different size of @code{Vals} with two
10927 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10930 As this example also illustrates, @value{GDBN} is very loose about the usual
10931 rules concerning aggregates. You may leave out some of the
10932 components of an array or record aggregate (such as the @code{Len}
10933 component in the assignment to @code{A_Rec} above); they will retain their
10934 original values upon assignment. You may freely use dynamic values as
10935 indices in component associations. You may even use overlapping or
10936 redundant component associations, although which component values are
10937 assigned in such cases is not defined.
10940 Calls to dispatching subprograms are not implemented.
10943 The overloading algorithm is much more limited (i.e., less selective)
10944 than that of real Ada. It makes only limited use of the context in
10945 which a subexpression appears to resolve its meaning, and it is much
10946 looser in its rules for allowing type matches. As a result, some
10947 function calls will be ambiguous, and the user will be asked to choose
10948 the proper resolution.
10951 The @code{new} operator is not implemented.
10954 Entry calls are not implemented.
10957 Aside from printing, arithmetic operations on the native VAX floating-point
10958 formats are not supported.
10961 It is not possible to slice a packed array.
10964 @node Additions to Ada
10965 @subsubsection Additions to Ada
10966 @cindex Ada, deviations from
10968 As it does for other languages, @value{GDBN} makes certain generic
10969 extensions to Ada (@pxref{Expressions}):
10973 If the expression @var{E} is a variable residing in memory (typically
10974 a local variable or array element) and @var{N} is a positive integer,
10975 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10976 @var{N}-1 adjacent variables following it in memory as an array. In
10977 Ada, this operator is generally not necessary, since its prime use is
10978 in displaying parts of an array, and slicing will usually do this in
10979 Ada. However, there are occasional uses when debugging programs in
10980 which certain debugging information has been optimized away.
10983 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10984 appears in function or file @var{B}.'' When @var{B} is a file name,
10985 you must typically surround it in single quotes.
10988 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10989 @var{type} that appears at address @var{addr}.''
10992 A name starting with @samp{$} is a convenience variable
10993 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10996 In addition, @value{GDBN} provides a few other shortcuts and outright
10997 additions specific to Ada:
11001 The assignment statement is allowed as an expression, returning
11002 its right-hand operand as its value. Thus, you may enter
11006 print A(tmp := y + 1)
11010 The semicolon is allowed as an ``operator,'' returning as its value
11011 the value of its right-hand operand.
11012 This allows, for example,
11013 complex conditional breaks:
11017 condition 1 (report(i); k += 1; A(k) > 100)
11021 Rather than use catenation and symbolic character names to introduce special
11022 characters into strings, one may instead use a special bracket notation,
11023 which is also used to print strings. A sequence of characters of the form
11024 @samp{["@var{XX}"]} within a string or character literal denotes the
11025 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11026 sequence of characters @samp{["""]} also denotes a single quotation mark
11027 in strings. For example,
11029 "One line.["0a"]Next line.["0a"]"
11032 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11036 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11037 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11045 When printing arrays, @value{GDBN} uses positional notation when the
11046 array has a lower bound of 1, and uses a modified named notation otherwise.
11047 For example, a one-dimensional array of three integers with a lower bound
11048 of 3 might print as
11055 That is, in contrast to valid Ada, only the first component has a @code{=>}
11059 You may abbreviate attributes in expressions with any unique,
11060 multi-character subsequence of
11061 their names (an exact match gets preference).
11062 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11063 in place of @t{a'length}.
11066 @cindex quoting Ada internal identifiers
11067 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11068 to lower case. The GNAT compiler uses upper-case characters for
11069 some of its internal identifiers, which are normally of no interest to users.
11070 For the rare occasions when you actually have to look at them,
11071 enclose them in angle brackets to avoid the lower-case mapping.
11074 @value{GDBP} print <JMPBUF_SAVE>[0]
11078 Printing an object of class-wide type or dereferencing an
11079 access-to-class-wide value will display all the components of the object's
11080 specific type (as indicated by its run-time tag). Likewise, component
11081 selection on such a value will operate on the specific type of the
11086 @node Stopping Before Main Program
11087 @subsubsection Stopping at the Very Beginning
11089 @cindex breakpointing Ada elaboration code
11090 It is sometimes necessary to debug the program during elaboration, and
11091 before reaching the main procedure.
11092 As defined in the Ada Reference
11093 Manual, the elaboration code is invoked from a procedure called
11094 @code{adainit}. To run your program up to the beginning of
11095 elaboration, simply use the following two commands:
11096 @code{tbreak adainit} and @code{run}.
11099 @subsubsection Known Peculiarities of Ada Mode
11100 @cindex Ada, problems
11102 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11103 we know of several problems with and limitations of Ada mode in
11105 some of which will be fixed with planned future releases of the debugger
11106 and the GNU Ada compiler.
11110 Currently, the debugger
11111 has insufficient information to determine whether certain pointers represent
11112 pointers to objects or the objects themselves.
11113 Thus, the user may have to tack an extra @code{.all} after an expression
11114 to get it printed properly.
11117 Static constants that the compiler chooses not to materialize as objects in
11118 storage are invisible to the debugger.
11121 Named parameter associations in function argument lists are ignored (the
11122 argument lists are treated as positional).
11125 Many useful library packages are currently invisible to the debugger.
11128 Fixed-point arithmetic, conversions, input, and output is carried out using
11129 floating-point arithmetic, and may give results that only approximate those on
11133 The type of the @t{'Address} attribute may not be @code{System.Address}.
11136 The GNAT compiler never generates the prefix @code{Standard} for any of
11137 the standard symbols defined by the Ada language. @value{GDBN} knows about
11138 this: it will strip the prefix from names when you use it, and will never
11139 look for a name you have so qualified among local symbols, nor match against
11140 symbols in other packages or subprograms. If you have
11141 defined entities anywhere in your program other than parameters and
11142 local variables whose simple names match names in @code{Standard},
11143 GNAT's lack of qualification here can cause confusion. When this happens,
11144 you can usually resolve the confusion
11145 by qualifying the problematic names with package
11146 @code{Standard} explicitly.
11149 @node Unsupported Languages
11150 @section Unsupported Languages
11152 @cindex unsupported languages
11153 @cindex minimal language
11154 In addition to the other fully-supported programming languages,
11155 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11156 It does not represent a real programming language, but provides a set
11157 of capabilities close to what the C or assembly languages provide.
11158 This should allow most simple operations to be performed while debugging
11159 an application that uses a language currently not supported by @value{GDBN}.
11161 If the language is set to @code{auto}, @value{GDBN} will automatically
11162 select this language if the current frame corresponds to an unsupported
11166 @chapter Examining the Symbol Table
11168 The commands described in this chapter allow you to inquire about the
11169 symbols (names of variables, functions and types) defined in your
11170 program. This information is inherent in the text of your program and
11171 does not change as your program executes. @value{GDBN} finds it in your
11172 program's symbol table, in the file indicated when you started @value{GDBN}
11173 (@pxref{File Options, ,Choosing Files}), or by one of the
11174 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11176 @cindex symbol names
11177 @cindex names of symbols
11178 @cindex quoting names
11179 Occasionally, you may need to refer to symbols that contain unusual
11180 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11181 most frequent case is in referring to static variables in other
11182 source files (@pxref{Variables,,Program Variables}). File names
11183 are recorded in object files as debugging symbols, but @value{GDBN} would
11184 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11185 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11186 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11193 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11196 @cindex case-insensitive symbol names
11197 @cindex case sensitivity in symbol names
11198 @kindex set case-sensitive
11199 @item set case-sensitive on
11200 @itemx set case-sensitive off
11201 @itemx set case-sensitive auto
11202 Normally, when @value{GDBN} looks up symbols, it matches their names
11203 with case sensitivity determined by the current source language.
11204 Occasionally, you may wish to control that. The command @code{set
11205 case-sensitive} lets you do that by specifying @code{on} for
11206 case-sensitive matches or @code{off} for case-insensitive ones. If
11207 you specify @code{auto}, case sensitivity is reset to the default
11208 suitable for the source language. The default is case-sensitive
11209 matches for all languages except for Fortran, for which the default is
11210 case-insensitive matches.
11212 @kindex show case-sensitive
11213 @item show case-sensitive
11214 This command shows the current setting of case sensitivity for symbols
11217 @kindex info address
11218 @cindex address of a symbol
11219 @item info address @var{symbol}
11220 Describe where the data for @var{symbol} is stored. For a register
11221 variable, this says which register it is kept in. For a non-register
11222 local variable, this prints the stack-frame offset at which the variable
11225 Note the contrast with @samp{print &@var{symbol}}, which does not work
11226 at all for a register variable, and for a stack local variable prints
11227 the exact address of the current instantiation of the variable.
11229 @kindex info symbol
11230 @cindex symbol from address
11231 @cindex closest symbol and offset for an address
11232 @item info symbol @var{addr}
11233 Print the name of a symbol which is stored at the address @var{addr}.
11234 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11235 nearest symbol and an offset from it:
11238 (@value{GDBP}) info symbol 0x54320
11239 _initialize_vx + 396 in section .text
11243 This is the opposite of the @code{info address} command. You can use
11244 it to find out the name of a variable or a function given its address.
11247 @item whatis [@var{arg}]
11248 Print the data type of @var{arg}, which can be either an expression or
11249 a data type. With no argument, print the data type of @code{$}, the
11250 last value in the value history. If @var{arg} is an expression, it is
11251 not actually evaluated, and any side-effecting operations (such as
11252 assignments or function calls) inside it do not take place. If
11253 @var{arg} is a type name, it may be the name of a type or typedef, or
11254 for C code it may have the form @samp{class @var{class-name}},
11255 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11256 @samp{enum @var{enum-tag}}.
11257 @xref{Expressions, ,Expressions}.
11260 @item ptype [@var{arg}]
11261 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11262 detailed description of the type, instead of just the name of the type.
11263 @xref{Expressions, ,Expressions}.
11265 For example, for this variable declaration:
11268 struct complex @{double real; double imag;@} v;
11272 the two commands give this output:
11276 (@value{GDBP}) whatis v
11277 type = struct complex
11278 (@value{GDBP}) ptype v
11279 type = struct complex @{
11287 As with @code{whatis}, using @code{ptype} without an argument refers to
11288 the type of @code{$}, the last value in the value history.
11290 @cindex incomplete type
11291 Sometimes, programs use opaque data types or incomplete specifications
11292 of complex data structure. If the debug information included in the
11293 program does not allow @value{GDBN} to display a full declaration of
11294 the data type, it will say @samp{<incomplete type>}. For example,
11295 given these declarations:
11299 struct foo *fooptr;
11303 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11306 (@value{GDBP}) ptype foo
11307 $1 = <incomplete type>
11311 ``Incomplete type'' is C terminology for data types that are not
11312 completely specified.
11315 @item info types @var{regexp}
11317 Print a brief description of all types whose names match the regular
11318 expression @var{regexp} (or all types in your program, if you supply
11319 no argument). Each complete typename is matched as though it were a
11320 complete line; thus, @samp{i type value} gives information on all
11321 types in your program whose names include the string @code{value}, but
11322 @samp{i type ^value$} gives information only on types whose complete
11323 name is @code{value}.
11325 This command differs from @code{ptype} in two ways: first, like
11326 @code{whatis}, it does not print a detailed description; second, it
11327 lists all source files where a type is defined.
11330 @cindex local variables
11331 @item info scope @var{location}
11332 List all the variables local to a particular scope. This command
11333 accepts a @var{location} argument---a function name, a source line, or
11334 an address preceded by a @samp{*}, and prints all the variables local
11335 to the scope defined by that location. (@xref{Specify Location}, for
11336 details about supported forms of @var{location}.) For example:
11339 (@value{GDBP}) @b{info scope command_line_handler}
11340 Scope for command_line_handler:
11341 Symbol rl is an argument at stack/frame offset 8, length 4.
11342 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11343 Symbol linelength is in static storage at address 0x150a1c, length 4.
11344 Symbol p is a local variable in register $esi, length 4.
11345 Symbol p1 is a local variable in register $ebx, length 4.
11346 Symbol nline is a local variable in register $edx, length 4.
11347 Symbol repeat is a local variable at frame offset -8, length 4.
11351 This command is especially useful for determining what data to collect
11352 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11355 @kindex info source
11357 Show information about the current source file---that is, the source file for
11358 the function containing the current point of execution:
11361 the name of the source file, and the directory containing it,
11363 the directory it was compiled in,
11365 its length, in lines,
11367 which programming language it is written in,
11369 whether the executable includes debugging information for that file, and
11370 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11372 whether the debugging information includes information about
11373 preprocessor macros.
11377 @kindex info sources
11379 Print the names of all source files in your program for which there is
11380 debugging information, organized into two lists: files whose symbols
11381 have already been read, and files whose symbols will be read when needed.
11383 @kindex info functions
11384 @item info functions
11385 Print the names and data types of all defined functions.
11387 @item info functions @var{regexp}
11388 Print the names and data types of all defined functions
11389 whose names contain a match for regular expression @var{regexp}.
11390 Thus, @samp{info fun step} finds all functions whose names
11391 include @code{step}; @samp{info fun ^step} finds those whose names
11392 start with @code{step}. If a function name contains characters
11393 that conflict with the regular expression language (e.g.@:
11394 @samp{operator*()}), they may be quoted with a backslash.
11396 @kindex info variables
11397 @item info variables
11398 Print the names and data types of all variables that are declared
11399 outside of functions (i.e.@: excluding local variables).
11401 @item info variables @var{regexp}
11402 Print the names and data types of all variables (except for local
11403 variables) whose names contain a match for regular expression
11406 @kindex info classes
11407 @cindex Objective-C, classes and selectors
11409 @itemx info classes @var{regexp}
11410 Display all Objective-C classes in your program, or
11411 (with the @var{regexp} argument) all those matching a particular regular
11414 @kindex info selectors
11415 @item info selectors
11416 @itemx info selectors @var{regexp}
11417 Display all Objective-C selectors in your program, or
11418 (with the @var{regexp} argument) all those matching a particular regular
11422 This was never implemented.
11423 @kindex info methods
11425 @itemx info methods @var{regexp}
11426 The @code{info methods} command permits the user to examine all defined
11427 methods within C@t{++} program, or (with the @var{regexp} argument) a
11428 specific set of methods found in the various C@t{++} classes. Many
11429 C@t{++} classes provide a large number of methods. Thus, the output
11430 from the @code{ptype} command can be overwhelming and hard to use. The
11431 @code{info-methods} command filters the methods, printing only those
11432 which match the regular-expression @var{regexp}.
11435 @cindex reloading symbols
11436 Some systems allow individual object files that make up your program to
11437 be replaced without stopping and restarting your program. For example,
11438 in VxWorks you can simply recompile a defective object file and keep on
11439 running. If you are running on one of these systems, you can allow
11440 @value{GDBN} to reload the symbols for automatically relinked modules:
11443 @kindex set symbol-reloading
11444 @item set symbol-reloading on
11445 Replace symbol definitions for the corresponding source file when an
11446 object file with a particular name is seen again.
11448 @item set symbol-reloading off
11449 Do not replace symbol definitions when encountering object files of the
11450 same name more than once. This is the default state; if you are not
11451 running on a system that permits automatic relinking of modules, you
11452 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11453 may discard symbols when linking large programs, that may contain
11454 several modules (from different directories or libraries) with the same
11457 @kindex show symbol-reloading
11458 @item show symbol-reloading
11459 Show the current @code{on} or @code{off} setting.
11462 @cindex opaque data types
11463 @kindex set opaque-type-resolution
11464 @item set opaque-type-resolution on
11465 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11466 declared as a pointer to a @code{struct}, @code{class}, or
11467 @code{union}---for example, @code{struct MyType *}---that is used in one
11468 source file although the full declaration of @code{struct MyType} is in
11469 another source file. The default is on.
11471 A change in the setting of this subcommand will not take effect until
11472 the next time symbols for a file are loaded.
11474 @item set opaque-type-resolution off
11475 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11476 is printed as follows:
11478 @{<no data fields>@}
11481 @kindex show opaque-type-resolution
11482 @item show opaque-type-resolution
11483 Show whether opaque types are resolved or not.
11485 @kindex maint print symbols
11486 @cindex symbol dump
11487 @kindex maint print psymbols
11488 @cindex partial symbol dump
11489 @item maint print symbols @var{filename}
11490 @itemx maint print psymbols @var{filename}
11491 @itemx maint print msymbols @var{filename}
11492 Write a dump of debugging symbol data into the file @var{filename}.
11493 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11494 symbols with debugging data are included. If you use @samp{maint print
11495 symbols}, @value{GDBN} includes all the symbols for which it has already
11496 collected full details: that is, @var{filename} reflects symbols for
11497 only those files whose symbols @value{GDBN} has read. You can use the
11498 command @code{info sources} to find out which files these are. If you
11499 use @samp{maint print psymbols} instead, the dump shows information about
11500 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11501 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11502 @samp{maint print msymbols} dumps just the minimal symbol information
11503 required for each object file from which @value{GDBN} has read some symbols.
11504 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11505 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11507 @kindex maint info symtabs
11508 @kindex maint info psymtabs
11509 @cindex listing @value{GDBN}'s internal symbol tables
11510 @cindex symbol tables, listing @value{GDBN}'s internal
11511 @cindex full symbol tables, listing @value{GDBN}'s internal
11512 @cindex partial symbol tables, listing @value{GDBN}'s internal
11513 @item maint info symtabs @r{[} @var{regexp} @r{]}
11514 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11516 List the @code{struct symtab} or @code{struct partial_symtab}
11517 structures whose names match @var{regexp}. If @var{regexp} is not
11518 given, list them all. The output includes expressions which you can
11519 copy into a @value{GDBN} debugging this one to examine a particular
11520 structure in more detail. For example:
11523 (@value{GDBP}) maint info psymtabs dwarf2read
11524 @{ objfile /home/gnu/build/gdb/gdb
11525 ((struct objfile *) 0x82e69d0)
11526 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11527 ((struct partial_symtab *) 0x8474b10)
11530 text addresses 0x814d3c8 -- 0x8158074
11531 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11532 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11533 dependencies (none)
11536 (@value{GDBP}) maint info symtabs
11540 We see that there is one partial symbol table whose filename contains
11541 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11542 and we see that @value{GDBN} has not read in any symtabs yet at all.
11543 If we set a breakpoint on a function, that will cause @value{GDBN} to
11544 read the symtab for the compilation unit containing that function:
11547 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11548 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11550 (@value{GDBP}) maint info symtabs
11551 @{ objfile /home/gnu/build/gdb/gdb
11552 ((struct objfile *) 0x82e69d0)
11553 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11554 ((struct symtab *) 0x86c1f38)
11557 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11558 linetable ((struct linetable *) 0x8370fa0)
11559 debugformat DWARF 2
11568 @chapter Altering Execution
11570 Once you think you have found an error in your program, you might want to
11571 find out for certain whether correcting the apparent error would lead to
11572 correct results in the rest of the run. You can find the answer by
11573 experiment, using the @value{GDBN} features for altering execution of the
11576 For example, you can store new values into variables or memory
11577 locations, give your program a signal, restart it at a different
11578 address, or even return prematurely from a function.
11581 * Assignment:: Assignment to variables
11582 * Jumping:: Continuing at a different address
11583 * Signaling:: Giving your program a signal
11584 * Returning:: Returning from a function
11585 * Calling:: Calling your program's functions
11586 * Patching:: Patching your program
11590 @section Assignment to Variables
11593 @cindex setting variables
11594 To alter the value of a variable, evaluate an assignment expression.
11595 @xref{Expressions, ,Expressions}. For example,
11602 stores the value 4 into the variable @code{x}, and then prints the
11603 value of the assignment expression (which is 4).
11604 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11605 information on operators in supported languages.
11607 @kindex set variable
11608 @cindex variables, setting
11609 If you are not interested in seeing the value of the assignment, use the
11610 @code{set} command instead of the @code{print} command. @code{set} is
11611 really the same as @code{print} except that the expression's value is
11612 not printed and is not put in the value history (@pxref{Value History,
11613 ,Value History}). The expression is evaluated only for its effects.
11615 If the beginning of the argument string of the @code{set} command
11616 appears identical to a @code{set} subcommand, use the @code{set
11617 variable} command instead of just @code{set}. This command is identical
11618 to @code{set} except for its lack of subcommands. For example, if your
11619 program has a variable @code{width}, you get an error if you try to set
11620 a new value with just @samp{set width=13}, because @value{GDBN} has the
11621 command @code{set width}:
11624 (@value{GDBP}) whatis width
11626 (@value{GDBP}) p width
11628 (@value{GDBP}) set width=47
11629 Invalid syntax in expression.
11633 The invalid expression, of course, is @samp{=47}. In
11634 order to actually set the program's variable @code{width}, use
11637 (@value{GDBP}) set var width=47
11640 Because the @code{set} command has many subcommands that can conflict
11641 with the names of program variables, it is a good idea to use the
11642 @code{set variable} command instead of just @code{set}. For example, if
11643 your program has a variable @code{g}, you run into problems if you try
11644 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11645 the command @code{set gnutarget}, abbreviated @code{set g}:
11649 (@value{GDBP}) whatis g
11653 (@value{GDBP}) set g=4
11657 The program being debugged has been started already.
11658 Start it from the beginning? (y or n) y
11659 Starting program: /home/smith/cc_progs/a.out
11660 "/home/smith/cc_progs/a.out": can't open to read symbols:
11661 Invalid bfd target.
11662 (@value{GDBP}) show g
11663 The current BFD target is "=4".
11668 The program variable @code{g} did not change, and you silently set the
11669 @code{gnutarget} to an invalid value. In order to set the variable
11673 (@value{GDBP}) set var g=4
11676 @value{GDBN} allows more implicit conversions in assignments than C; you can
11677 freely store an integer value into a pointer variable or vice versa,
11678 and you can convert any structure to any other structure that is the
11679 same length or shorter.
11680 @comment FIXME: how do structs align/pad in these conversions?
11681 @comment /doc@cygnus.com 18dec1990
11683 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11684 construct to generate a value of specified type at a specified address
11685 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11686 to memory location @code{0x83040} as an integer (which implies a certain size
11687 and representation in memory), and
11690 set @{int@}0x83040 = 4
11694 stores the value 4 into that memory location.
11697 @section Continuing at a Different Address
11699 Ordinarily, when you continue your program, you do so at the place where
11700 it stopped, with the @code{continue} command. You can instead continue at
11701 an address of your own choosing, with the following commands:
11705 @item jump @var{linespec}
11706 @itemx jump @var{location}
11707 Resume execution at line @var{linespec} or at address given by
11708 @var{location}. Execution stops again immediately if there is a
11709 breakpoint there. @xref{Specify Location}, for a description of the
11710 different forms of @var{linespec} and @var{location}. It is common
11711 practice to use the @code{tbreak} command in conjunction with
11712 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
11714 The @code{jump} command does not change the current stack frame, or
11715 the stack pointer, or the contents of any memory location or any
11716 register other than the program counter. If line @var{linespec} is in
11717 a different function from the one currently executing, the results may
11718 be bizarre if the two functions expect different patterns of arguments or
11719 of local variables. For this reason, the @code{jump} command requests
11720 confirmation if the specified line is not in the function currently
11721 executing. However, even bizarre results are predictable if you are
11722 well acquainted with the machine-language code of your program.
11725 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11726 On many systems, you can get much the same effect as the @code{jump}
11727 command by storing a new value into the register @code{$pc}. The
11728 difference is that this does not start your program running; it only
11729 changes the address of where it @emph{will} run when you continue. For
11737 makes the next @code{continue} command or stepping command execute at
11738 address @code{0x485}, rather than at the address where your program stopped.
11739 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11741 The most common occasion to use the @code{jump} command is to back
11742 up---perhaps with more breakpoints set---over a portion of a program
11743 that has already executed, in order to examine its execution in more
11748 @section Giving your Program a Signal
11749 @cindex deliver a signal to a program
11753 @item signal @var{signal}
11754 Resume execution where your program stopped, but immediately give it the
11755 signal @var{signal}. @var{signal} can be the name or the number of a
11756 signal. For example, on many systems @code{signal 2} and @code{signal
11757 SIGINT} are both ways of sending an interrupt signal.
11759 Alternatively, if @var{signal} is zero, continue execution without
11760 giving a signal. This is useful when your program stopped on account of
11761 a signal and would ordinary see the signal when resumed with the
11762 @code{continue} command; @samp{signal 0} causes it to resume without a
11765 @code{signal} does not repeat when you press @key{RET} a second time
11766 after executing the command.
11770 Invoking the @code{signal} command is not the same as invoking the
11771 @code{kill} utility from the shell. Sending a signal with @code{kill}
11772 causes @value{GDBN} to decide what to do with the signal depending on
11773 the signal handling tables (@pxref{Signals}). The @code{signal} command
11774 passes the signal directly to your program.
11778 @section Returning from a Function
11781 @cindex returning from a function
11784 @itemx return @var{expression}
11785 You can cancel execution of a function call with the @code{return}
11786 command. If you give an
11787 @var{expression} argument, its value is used as the function's return
11791 When you use @code{return}, @value{GDBN} discards the selected stack frame
11792 (and all frames within it). You can think of this as making the
11793 discarded frame return prematurely. If you wish to specify a value to
11794 be returned, give that value as the argument to @code{return}.
11796 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11797 Frame}), and any other frames inside of it, leaving its caller as the
11798 innermost remaining frame. That frame becomes selected. The
11799 specified value is stored in the registers used for returning values
11802 The @code{return} command does not resume execution; it leaves the
11803 program stopped in the state that would exist if the function had just
11804 returned. In contrast, the @code{finish} command (@pxref{Continuing
11805 and Stepping, ,Continuing and Stepping}) resumes execution until the
11806 selected stack frame returns naturally.
11809 @section Calling Program Functions
11812 @cindex calling functions
11813 @cindex inferior functions, calling
11814 @item print @var{expr}
11815 Evaluate the expression @var{expr} and display the resulting value.
11816 @var{expr} may include calls to functions in the program being
11820 @item call @var{expr}
11821 Evaluate the expression @var{expr} without displaying @code{void}
11824 You can use this variant of the @code{print} command if you want to
11825 execute a function from your program that does not return anything
11826 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11827 with @code{void} returned values that @value{GDBN} will otherwise
11828 print. If the result is not void, it is printed and saved in the
11832 It is possible for the function you call via the @code{print} or
11833 @code{call} command to generate a signal (e.g., if there's a bug in
11834 the function, or if you passed it incorrect arguments). What happens
11835 in that case is controlled by the @code{set unwindonsignal} command.
11838 @item set unwindonsignal
11839 @kindex set unwindonsignal
11840 @cindex unwind stack in called functions
11841 @cindex call dummy stack unwinding
11842 Set unwinding of the stack if a signal is received while in a function
11843 that @value{GDBN} called in the program being debugged. If set to on,
11844 @value{GDBN} unwinds the stack it created for the call and restores
11845 the context to what it was before the call. If set to off (the
11846 default), @value{GDBN} stops in the frame where the signal was
11849 @item show unwindonsignal
11850 @kindex show unwindonsignal
11851 Show the current setting of stack unwinding in the functions called by
11855 @cindex weak alias functions
11856 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11857 for another function. In such case, @value{GDBN} might not pick up
11858 the type information, including the types of the function arguments,
11859 which causes @value{GDBN} to call the inferior function incorrectly.
11860 As a result, the called function will function erroneously and may
11861 even crash. A solution to that is to use the name of the aliased
11865 @section Patching Programs
11867 @cindex patching binaries
11868 @cindex writing into executables
11869 @cindex writing into corefiles
11871 By default, @value{GDBN} opens the file containing your program's
11872 executable code (or the corefile) read-only. This prevents accidental
11873 alterations to machine code; but it also prevents you from intentionally
11874 patching your program's binary.
11876 If you'd like to be able to patch the binary, you can specify that
11877 explicitly with the @code{set write} command. For example, you might
11878 want to turn on internal debugging flags, or even to make emergency
11884 @itemx set write off
11885 If you specify @samp{set write on}, @value{GDBN} opens executable and
11886 core files for both reading and writing; if you specify @samp{set write
11887 off} (the default), @value{GDBN} opens them read-only.
11889 If you have already loaded a file, you must load it again (using the
11890 @code{exec-file} or @code{core-file} command) after changing @code{set
11891 write}, for your new setting to take effect.
11895 Display whether executable files and core files are opened for writing
11896 as well as reading.
11900 @chapter @value{GDBN} Files
11902 @value{GDBN} needs to know the file name of the program to be debugged,
11903 both in order to read its symbol table and in order to start your
11904 program. To debug a core dump of a previous run, you must also tell
11905 @value{GDBN} the name of the core dump file.
11908 * Files:: Commands to specify files
11909 * Separate Debug Files:: Debugging information in separate files
11910 * Symbol Errors:: Errors reading symbol files
11914 @section Commands to Specify Files
11916 @cindex symbol table
11917 @cindex core dump file
11919 You may want to specify executable and core dump file names. The usual
11920 way to do this is at start-up time, using the arguments to
11921 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11922 Out of @value{GDBN}}).
11924 Occasionally it is necessary to change to a different file during a
11925 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11926 specify a file you want to use. Or you are debugging a remote target
11927 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11928 Program}). In these situations the @value{GDBN} commands to specify
11929 new files are useful.
11932 @cindex executable file
11934 @item file @var{filename}
11935 Use @var{filename} as the program to be debugged. It is read for its
11936 symbols and for the contents of pure memory. It is also the program
11937 executed when you use the @code{run} command. If you do not specify a
11938 directory and the file is not found in the @value{GDBN} working directory,
11939 @value{GDBN} uses the environment variable @code{PATH} as a list of
11940 directories to search, just as the shell does when looking for a program
11941 to run. You can change the value of this variable, for both @value{GDBN}
11942 and your program, using the @code{path} command.
11944 @cindex unlinked object files
11945 @cindex patching object files
11946 You can load unlinked object @file{.o} files into @value{GDBN} using
11947 the @code{file} command. You will not be able to ``run'' an object
11948 file, but you can disassemble functions and inspect variables. Also,
11949 if the underlying BFD functionality supports it, you could use
11950 @kbd{gdb -write} to patch object files using this technique. Note
11951 that @value{GDBN} can neither interpret nor modify relocations in this
11952 case, so branches and some initialized variables will appear to go to
11953 the wrong place. But this feature is still handy from time to time.
11956 @code{file} with no argument makes @value{GDBN} discard any information it
11957 has on both executable file and the symbol table.
11960 @item exec-file @r{[} @var{filename} @r{]}
11961 Specify that the program to be run (but not the symbol table) is found
11962 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11963 if necessary to locate your program. Omitting @var{filename} means to
11964 discard information on the executable file.
11966 @kindex symbol-file
11967 @item symbol-file @r{[} @var{filename} @r{]}
11968 Read symbol table information from file @var{filename}. @code{PATH} is
11969 searched when necessary. Use the @code{file} command to get both symbol
11970 table and program to run from the same file.
11972 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11973 program's symbol table.
11975 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11976 some breakpoints and auto-display expressions. This is because they may
11977 contain pointers to the internal data recording symbols and data types,
11978 which are part of the old symbol table data being discarded inside
11981 @code{symbol-file} does not repeat if you press @key{RET} again after
11984 When @value{GDBN} is configured for a particular environment, it
11985 understands debugging information in whatever format is the standard
11986 generated for that environment; you may use either a @sc{gnu} compiler, or
11987 other compilers that adhere to the local conventions.
11988 Best results are usually obtained from @sc{gnu} compilers; for example,
11989 using @code{@value{NGCC}} you can generate debugging information for
11992 For most kinds of object files, with the exception of old SVR3 systems
11993 using COFF, the @code{symbol-file} command does not normally read the
11994 symbol table in full right away. Instead, it scans the symbol table
11995 quickly to find which source files and which symbols are present. The
11996 details are read later, one source file at a time, as they are needed.
11998 The purpose of this two-stage reading strategy is to make @value{GDBN}
11999 start up faster. For the most part, it is invisible except for
12000 occasional pauses while the symbol table details for a particular source
12001 file are being read. (The @code{set verbose} command can turn these
12002 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12003 Warnings and Messages}.)
12005 We have not implemented the two-stage strategy for COFF yet. When the
12006 symbol table is stored in COFF format, @code{symbol-file} reads the
12007 symbol table data in full right away. Note that ``stabs-in-COFF''
12008 still does the two-stage strategy, since the debug info is actually
12012 @cindex reading symbols immediately
12013 @cindex symbols, reading immediately
12014 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12015 @itemx file @var{filename} @r{[} -readnow @r{]}
12016 You can override the @value{GDBN} two-stage strategy for reading symbol
12017 tables by using the @samp{-readnow} option with any of the commands that
12018 load symbol table information, if you want to be sure @value{GDBN} has the
12019 entire symbol table available.
12021 @c FIXME: for now no mention of directories, since this seems to be in
12022 @c flux. 13mar1992 status is that in theory GDB would look either in
12023 @c current dir or in same dir as myprog; but issues like competing
12024 @c GDB's, or clutter in system dirs, mean that in practice right now
12025 @c only current dir is used. FFish says maybe a special GDB hierarchy
12026 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12030 @item core-file @r{[}@var{filename}@r{]}
12032 Specify the whereabouts of a core dump file to be used as the ``contents
12033 of memory''. Traditionally, core files contain only some parts of the
12034 address space of the process that generated them; @value{GDBN} can access the
12035 executable file itself for other parts.
12037 @code{core-file} with no argument specifies that no core file is
12040 Note that the core file is ignored when your program is actually running
12041 under @value{GDBN}. So, if you have been running your program and you
12042 wish to debug a core file instead, you must kill the subprocess in which
12043 the program is running. To do this, use the @code{kill} command
12044 (@pxref{Kill Process, ,Killing the Child Process}).
12046 @kindex add-symbol-file
12047 @cindex dynamic linking
12048 @item add-symbol-file @var{filename} @var{address}
12049 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12050 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12051 The @code{add-symbol-file} command reads additional symbol table
12052 information from the file @var{filename}. You would use this command
12053 when @var{filename} has been dynamically loaded (by some other means)
12054 into the program that is running. @var{address} should be the memory
12055 address at which the file has been loaded; @value{GDBN} cannot figure
12056 this out for itself. You can additionally specify an arbitrary number
12057 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12058 section name and base address for that section. You can specify any
12059 @var{address} as an expression.
12061 The symbol table of the file @var{filename} is added to the symbol table
12062 originally read with the @code{symbol-file} command. You can use the
12063 @code{add-symbol-file} command any number of times; the new symbol data
12064 thus read keeps adding to the old. To discard all old symbol data
12065 instead, use the @code{symbol-file} command without any arguments.
12067 @cindex relocatable object files, reading symbols from
12068 @cindex object files, relocatable, reading symbols from
12069 @cindex reading symbols from relocatable object files
12070 @cindex symbols, reading from relocatable object files
12071 @cindex @file{.o} files, reading symbols from
12072 Although @var{filename} is typically a shared library file, an
12073 executable file, or some other object file which has been fully
12074 relocated for loading into a process, you can also load symbolic
12075 information from relocatable @file{.o} files, as long as:
12079 the file's symbolic information refers only to linker symbols defined in
12080 that file, not to symbols defined by other object files,
12082 every section the file's symbolic information refers to has actually
12083 been loaded into the inferior, as it appears in the file, and
12085 you can determine the address at which every section was loaded, and
12086 provide these to the @code{add-symbol-file} command.
12090 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12091 relocatable files into an already running program; such systems
12092 typically make the requirements above easy to meet. However, it's
12093 important to recognize that many native systems use complex link
12094 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12095 assembly, for example) that make the requirements difficult to meet. In
12096 general, one cannot assume that using @code{add-symbol-file} to read a
12097 relocatable object file's symbolic information will have the same effect
12098 as linking the relocatable object file into the program in the normal
12101 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12103 @kindex add-symbol-file-from-memory
12104 @cindex @code{syscall DSO}
12105 @cindex load symbols from memory
12106 @item add-symbol-file-from-memory @var{address}
12107 Load symbols from the given @var{address} in a dynamically loaded
12108 object file whose image is mapped directly into the inferior's memory.
12109 For example, the Linux kernel maps a @code{syscall DSO} into each
12110 process's address space; this DSO provides kernel-specific code for
12111 some system calls. The argument can be any expression whose
12112 evaluation yields the address of the file's shared object file header.
12113 For this command to work, you must have used @code{symbol-file} or
12114 @code{exec-file} commands in advance.
12116 @kindex add-shared-symbol-files
12118 @item add-shared-symbol-files @var{library-file}
12119 @itemx assf @var{library-file}
12120 The @code{add-shared-symbol-files} command can currently be used only
12121 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12122 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12123 @value{GDBN} automatically looks for shared libraries, however if
12124 @value{GDBN} does not find yours, you can invoke
12125 @code{add-shared-symbol-files}. It takes one argument: the shared
12126 library's file name. @code{assf} is a shorthand alias for
12127 @code{add-shared-symbol-files}.
12130 @item section @var{section} @var{addr}
12131 The @code{section} command changes the base address of the named
12132 @var{section} of the exec file to @var{addr}. This can be used if the
12133 exec file does not contain section addresses, (such as in the
12134 @code{a.out} format), or when the addresses specified in the file
12135 itself are wrong. Each section must be changed separately. The
12136 @code{info files} command, described below, lists all the sections and
12140 @kindex info target
12143 @code{info files} and @code{info target} are synonymous; both print the
12144 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12145 including the names of the executable and core dump files currently in
12146 use by @value{GDBN}, and the files from which symbols were loaded. The
12147 command @code{help target} lists all possible targets rather than
12150 @kindex maint info sections
12151 @item maint info sections
12152 Another command that can give you extra information about program sections
12153 is @code{maint info sections}. In addition to the section information
12154 displayed by @code{info files}, this command displays the flags and file
12155 offset of each section in the executable and core dump files. In addition,
12156 @code{maint info sections} provides the following command options (which
12157 may be arbitrarily combined):
12161 Display sections for all loaded object files, including shared libraries.
12162 @item @var{sections}
12163 Display info only for named @var{sections}.
12164 @item @var{section-flags}
12165 Display info only for sections for which @var{section-flags} are true.
12166 The section flags that @value{GDBN} currently knows about are:
12169 Section will have space allocated in the process when loaded.
12170 Set for all sections except those containing debug information.
12172 Section will be loaded from the file into the child process memory.
12173 Set for pre-initialized code and data, clear for @code{.bss} sections.
12175 Section needs to be relocated before loading.
12177 Section cannot be modified by the child process.
12179 Section contains executable code only.
12181 Section contains data only (no executable code).
12183 Section will reside in ROM.
12185 Section contains data for constructor/destructor lists.
12187 Section is not empty.
12189 An instruction to the linker to not output the section.
12190 @item COFF_SHARED_LIBRARY
12191 A notification to the linker that the section contains
12192 COFF shared library information.
12194 Section contains common symbols.
12197 @kindex set trust-readonly-sections
12198 @cindex read-only sections
12199 @item set trust-readonly-sections on
12200 Tell @value{GDBN} that readonly sections in your object file
12201 really are read-only (i.e.@: that their contents will not change).
12202 In that case, @value{GDBN} can fetch values from these sections
12203 out of the object file, rather than from the target program.
12204 For some targets (notably embedded ones), this can be a significant
12205 enhancement to debugging performance.
12207 The default is off.
12209 @item set trust-readonly-sections off
12210 Tell @value{GDBN} not to trust readonly sections. This means that
12211 the contents of the section might change while the program is running,
12212 and must therefore be fetched from the target when needed.
12214 @item show trust-readonly-sections
12215 Show the current setting of trusting readonly sections.
12218 All file-specifying commands allow both absolute and relative file names
12219 as arguments. @value{GDBN} always converts the file name to an absolute file
12220 name and remembers it that way.
12222 @cindex shared libraries
12223 @anchor{Shared Libraries}
12224 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12225 and IBM RS/6000 AIX shared libraries.
12227 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12228 shared libraries. @xref{Expat}.
12230 @value{GDBN} automatically loads symbol definitions from shared libraries
12231 when you use the @code{run} command, or when you examine a core file.
12232 (Before you issue the @code{run} command, @value{GDBN} does not understand
12233 references to a function in a shared library, however---unless you are
12234 debugging a core file).
12236 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12237 automatically loads the symbols at the time of the @code{shl_load} call.
12239 @c FIXME: some @value{GDBN} release may permit some refs to undef
12240 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12241 @c FIXME...lib; check this from time to time when updating manual
12243 There are times, however, when you may wish to not automatically load
12244 symbol definitions from shared libraries, such as when they are
12245 particularly large or there are many of them.
12247 To control the automatic loading of shared library symbols, use the
12251 @kindex set auto-solib-add
12252 @item set auto-solib-add @var{mode}
12253 If @var{mode} is @code{on}, symbols from all shared object libraries
12254 will be loaded automatically when the inferior begins execution, you
12255 attach to an independently started inferior, or when the dynamic linker
12256 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12257 is @code{off}, symbols must be loaded manually, using the
12258 @code{sharedlibrary} command. The default value is @code{on}.
12260 @cindex memory used for symbol tables
12261 If your program uses lots of shared libraries with debug info that
12262 takes large amounts of memory, you can decrease the @value{GDBN}
12263 memory footprint by preventing it from automatically loading the
12264 symbols from shared libraries. To that end, type @kbd{set
12265 auto-solib-add off} before running the inferior, then load each
12266 library whose debug symbols you do need with @kbd{sharedlibrary
12267 @var{regexp}}, where @var{regexp} is a regular expression that matches
12268 the libraries whose symbols you want to be loaded.
12270 @kindex show auto-solib-add
12271 @item show auto-solib-add
12272 Display the current autoloading mode.
12275 @cindex load shared library
12276 To explicitly load shared library symbols, use the @code{sharedlibrary}
12280 @kindex info sharedlibrary
12283 @itemx info sharedlibrary
12284 Print the names of the shared libraries which are currently loaded.
12286 @kindex sharedlibrary
12288 @item sharedlibrary @var{regex}
12289 @itemx share @var{regex}
12290 Load shared object library symbols for files matching a
12291 Unix regular expression.
12292 As with files loaded automatically, it only loads shared libraries
12293 required by your program for a core file or after typing @code{run}. If
12294 @var{regex} is omitted all shared libraries required by your program are
12297 @item nosharedlibrary
12298 @kindex nosharedlibrary
12299 @cindex unload symbols from shared libraries
12300 Unload all shared object library symbols. This discards all symbols
12301 that have been loaded from all shared libraries. Symbols from shared
12302 libraries that were loaded by explicit user requests are not
12306 Sometimes you may wish that @value{GDBN} stops and gives you control
12307 when any of shared library events happen. Use the @code{set
12308 stop-on-solib-events} command for this:
12311 @item set stop-on-solib-events
12312 @kindex set stop-on-solib-events
12313 This command controls whether @value{GDBN} should give you control
12314 when the dynamic linker notifies it about some shared library event.
12315 The most common event of interest is loading or unloading of a new
12318 @item show stop-on-solib-events
12319 @kindex show stop-on-solib-events
12320 Show whether @value{GDBN} stops and gives you control when shared
12321 library events happen.
12324 Shared libraries are also supported in many cross or remote debugging
12325 configurations. A copy of the target's libraries need to be present on the
12326 host system; they need to be the same as the target libraries, although the
12327 copies on the target can be stripped as long as the copies on the host are
12330 @cindex where to look for shared libraries
12331 For remote debugging, you need to tell @value{GDBN} where the target
12332 libraries are, so that it can load the correct copies---otherwise, it
12333 may try to load the host's libraries. @value{GDBN} has two variables
12334 to specify the search directories for target libraries.
12337 @cindex prefix for shared library file names
12338 @cindex system root, alternate
12339 @kindex set solib-absolute-prefix
12340 @kindex set sysroot
12341 @item set sysroot @var{path}
12342 Use @var{path} as the system root for the program being debugged. Any
12343 absolute shared library paths will be prefixed with @var{path}; many
12344 runtime loaders store the absolute paths to the shared library in the
12345 target program's memory. If you use @code{set sysroot} to find shared
12346 libraries, they need to be laid out in the same way that they are on
12347 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12350 The @code{set solib-absolute-prefix} command is an alias for @code{set
12353 @cindex default system root
12354 @cindex @samp{--with-sysroot}
12355 You can set the default system root by using the configure-time
12356 @samp{--with-sysroot} option. If the system root is inside
12357 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12358 @samp{--exec-prefix}), then the default system root will be updated
12359 automatically if the installed @value{GDBN} is moved to a new
12362 @kindex show sysroot
12364 Display the current shared library prefix.
12366 @kindex set solib-search-path
12367 @item set solib-search-path @var{path}
12368 If this variable is set, @var{path} is a colon-separated list of
12369 directories to search for shared libraries. @samp{solib-search-path}
12370 is used after @samp{sysroot} fails to locate the library, or if the
12371 path to the library is relative instead of absolute. If you want to
12372 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12373 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12374 finding your host's libraries. @samp{sysroot} is preferred; setting
12375 it to a nonexistent directory may interfere with automatic loading
12376 of shared library symbols.
12378 @kindex show solib-search-path
12379 @item show solib-search-path
12380 Display the current shared library search path.
12384 @node Separate Debug Files
12385 @section Debugging Information in Separate Files
12386 @cindex separate debugging information files
12387 @cindex debugging information in separate files
12388 @cindex @file{.debug} subdirectories
12389 @cindex debugging information directory, global
12390 @cindex global debugging information directory
12391 @cindex build ID, and separate debugging files
12392 @cindex @file{.build-id} directory
12394 @value{GDBN} allows you to put a program's debugging information in a
12395 file separate from the executable itself, in a way that allows
12396 @value{GDBN} to find and load the debugging information automatically.
12397 Since debugging information can be very large---sometimes larger
12398 than the executable code itself---some systems distribute debugging
12399 information for their executables in separate files, which users can
12400 install only when they need to debug a problem.
12402 @value{GDBN} supports two ways of specifying the separate debug info
12407 The executable contains a @dfn{debug link} that specifies the name of
12408 the separate debug info file. The separate debug file's name is
12409 usually @file{@var{executable}.debug}, where @var{executable} is the
12410 name of the corresponding executable file without leading directories
12411 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12412 debug link specifies a CRC32 checksum for the debug file, which
12413 @value{GDBN} uses to validate that the executable and the debug file
12414 came from the same build.
12417 The executable contains a @dfn{build ID}, a unique bit string that is
12418 also present in the corresponding debug info file. (This is supported
12419 only on some operating systems, notably those which use the ELF format
12420 for binary files and the @sc{gnu} Binutils.) For more details about
12421 this feature, see the description of the @option{--build-id}
12422 command-line option in @ref{Options, , Command Line Options, ld.info,
12423 The GNU Linker}. The debug info file's name is not specified
12424 explicitly by the build ID, but can be computed from the build ID, see
12428 Depending on the way the debug info file is specified, @value{GDBN}
12429 uses two different methods of looking for the debug file:
12433 For the ``debug link'' method, @value{GDBN} looks up the named file in
12434 the directory of the executable file, then in a subdirectory of that
12435 directory named @file{.debug}, and finally under the global debug
12436 directory, in a subdirectory whose name is identical to the leading
12437 directories of the executable's absolute file name.
12440 For the ``build ID'' method, @value{GDBN} looks in the
12441 @file{.build-id} subdirectory of the global debug directory for a file
12442 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12443 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12444 are the rest of the bit string. (Real build ID strings are 32 or more
12445 hex characters, not 10.)
12448 So, for example, suppose you ask @value{GDBN} to debug
12449 @file{/usr/bin/ls}, which has a debug link that specifies the
12450 file @file{ls.debug}, and a build ID whose value in hex is
12451 @code{abcdef1234}. If the global debug directory is
12452 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12453 debug information files, in the indicated order:
12457 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12459 @file{/usr/bin/ls.debug}
12461 @file{/usr/bin/.debug/ls.debug}
12463 @file{/usr/lib/debug/usr/bin/ls.debug}.
12466 You can set the global debugging info directory's name, and view the
12467 name @value{GDBN} is currently using.
12471 @kindex set debug-file-directory
12472 @item set debug-file-directory @var{directory}
12473 Set the directory which @value{GDBN} searches for separate debugging
12474 information files to @var{directory}.
12476 @kindex show debug-file-directory
12477 @item show debug-file-directory
12478 Show the directory @value{GDBN} searches for separate debugging
12483 @cindex @code{.gnu_debuglink} sections
12484 @cindex debug link sections
12485 A debug link is a special section of the executable file named
12486 @code{.gnu_debuglink}. The section must contain:
12490 A filename, with any leading directory components removed, followed by
12493 zero to three bytes of padding, as needed to reach the next four-byte
12494 boundary within the section, and
12496 a four-byte CRC checksum, stored in the same endianness used for the
12497 executable file itself. The checksum is computed on the debugging
12498 information file's full contents by the function given below, passing
12499 zero as the @var{crc} argument.
12502 Any executable file format can carry a debug link, as long as it can
12503 contain a section named @code{.gnu_debuglink} with the contents
12506 @cindex @code{.note.gnu.build-id} sections
12507 @cindex build ID sections
12508 The build ID is a special section in the executable file (and in other
12509 ELF binary files that @value{GDBN} may consider). This section is
12510 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12511 It contains unique identification for the built files---the ID remains
12512 the same across multiple builds of the same build tree. The default
12513 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12514 content for the build ID string. The same section with an identical
12515 value is present in the original built binary with symbols, in its
12516 stripped variant, and in the separate debugging information file.
12518 The debugging information file itself should be an ordinary
12519 executable, containing a full set of linker symbols, sections, and
12520 debugging information. The sections of the debugging information file
12521 should have the same names, addresses, and sizes as the original file,
12522 but they need not contain any data---much like a @code{.bss} section
12523 in an ordinary executable.
12525 The @sc{gnu} binary utilities (Binutils) package includes the
12526 @samp{objcopy} utility that can produce
12527 the separated executable / debugging information file pairs using the
12528 following commands:
12531 @kbd{objcopy --only-keep-debug foo foo.debug}
12536 These commands remove the debugging
12537 information from the executable file @file{foo} and place it in the file
12538 @file{foo.debug}. You can use the first, second or both methods to link the
12543 The debug link method needs the following additional command to also leave
12544 behind a debug link in @file{foo}:
12547 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12550 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12551 a version of the @code{strip} command such that the command @kbd{strip foo -f
12552 foo.debug} has the same functionality as the two @code{objcopy} commands and
12553 the @code{ln -s} command above, together.
12556 Build ID gets embedded into the main executable using @code{ld --build-id} or
12557 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12558 compatibility fixes for debug files separation are present in @sc{gnu} binary
12559 utilities (Binutils) package since version 2.18.
12564 Since there are many different ways to compute CRC's for the debug
12565 link (different polynomials, reversals, byte ordering, etc.), the
12566 simplest way to describe the CRC used in @code{.gnu_debuglink}
12567 sections is to give the complete code for a function that computes it:
12569 @kindex gnu_debuglink_crc32
12572 gnu_debuglink_crc32 (unsigned long crc,
12573 unsigned char *buf, size_t len)
12575 static const unsigned long crc32_table[256] =
12577 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12578 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12579 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12580 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12581 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12582 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12583 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12584 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12585 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12586 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12587 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12588 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12589 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12590 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12591 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12592 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12593 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12594 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12595 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12596 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12597 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12598 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12599 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12600 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12601 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12602 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12603 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12604 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12605 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12606 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12607 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12608 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12609 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12610 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12611 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12612 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12613 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12614 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12615 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12616 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12617 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12618 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12619 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12620 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12621 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12622 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12623 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12624 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12625 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12626 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12627 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12630 unsigned char *end;
12632 crc = ~crc & 0xffffffff;
12633 for (end = buf + len; buf < end; ++buf)
12634 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12635 return ~crc & 0xffffffff;
12640 This computation does not apply to the ``build ID'' method.
12643 @node Symbol Errors
12644 @section Errors Reading Symbol Files
12646 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12647 such as symbol types it does not recognize, or known bugs in compiler
12648 output. By default, @value{GDBN} does not notify you of such problems, since
12649 they are relatively common and primarily of interest to people
12650 debugging compilers. If you are interested in seeing information
12651 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12652 only one message about each such type of problem, no matter how many
12653 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12654 to see how many times the problems occur, with the @code{set
12655 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12658 The messages currently printed, and their meanings, include:
12661 @item inner block not inside outer block in @var{symbol}
12663 The symbol information shows where symbol scopes begin and end
12664 (such as at the start of a function or a block of statements). This
12665 error indicates that an inner scope block is not fully contained
12666 in its outer scope blocks.
12668 @value{GDBN} circumvents the problem by treating the inner block as if it had
12669 the same scope as the outer block. In the error message, @var{symbol}
12670 may be shown as ``@code{(don't know)}'' if the outer block is not a
12673 @item block at @var{address} out of order
12675 The symbol information for symbol scope blocks should occur in
12676 order of increasing addresses. This error indicates that it does not
12679 @value{GDBN} does not circumvent this problem, and has trouble
12680 locating symbols in the source file whose symbols it is reading. (You
12681 can often determine what source file is affected by specifying
12682 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12685 @item bad block start address patched
12687 The symbol information for a symbol scope block has a start address
12688 smaller than the address of the preceding source line. This is known
12689 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12691 @value{GDBN} circumvents the problem by treating the symbol scope block as
12692 starting on the previous source line.
12694 @item bad string table offset in symbol @var{n}
12697 Symbol number @var{n} contains a pointer into the string table which is
12698 larger than the size of the string table.
12700 @value{GDBN} circumvents the problem by considering the symbol to have the
12701 name @code{foo}, which may cause other problems if many symbols end up
12704 @item unknown symbol type @code{0x@var{nn}}
12706 The symbol information contains new data types that @value{GDBN} does
12707 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12708 uncomprehended information, in hexadecimal.
12710 @value{GDBN} circumvents the error by ignoring this symbol information.
12711 This usually allows you to debug your program, though certain symbols
12712 are not accessible. If you encounter such a problem and feel like
12713 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12714 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12715 and examine @code{*bufp} to see the symbol.
12717 @item stub type has NULL name
12719 @value{GDBN} could not find the full definition for a struct or class.
12721 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12722 The symbol information for a C@t{++} member function is missing some
12723 information that recent versions of the compiler should have output for
12726 @item info mismatch between compiler and debugger
12728 @value{GDBN} could not parse a type specification output by the compiler.
12733 @chapter Specifying a Debugging Target
12735 @cindex debugging target
12736 A @dfn{target} is the execution environment occupied by your program.
12738 Often, @value{GDBN} runs in the same host environment as your program;
12739 in that case, the debugging target is specified as a side effect when
12740 you use the @code{file} or @code{core} commands. When you need more
12741 flexibility---for example, running @value{GDBN} on a physically separate
12742 host, or controlling a standalone system over a serial port or a
12743 realtime system over a TCP/IP connection---you can use the @code{target}
12744 command to specify one of the target types configured for @value{GDBN}
12745 (@pxref{Target Commands, ,Commands for Managing Targets}).
12747 @cindex target architecture
12748 It is possible to build @value{GDBN} for several different @dfn{target
12749 architectures}. When @value{GDBN} is built like that, you can choose
12750 one of the available architectures with the @kbd{set architecture}
12754 @kindex set architecture
12755 @kindex show architecture
12756 @item set architecture @var{arch}
12757 This command sets the current target architecture to @var{arch}. The
12758 value of @var{arch} can be @code{"auto"}, in addition to one of the
12759 supported architectures.
12761 @item show architecture
12762 Show the current target architecture.
12764 @item set processor
12766 @kindex set processor
12767 @kindex show processor
12768 These are alias commands for, respectively, @code{set architecture}
12769 and @code{show architecture}.
12773 * Active Targets:: Active targets
12774 * Target Commands:: Commands for managing targets
12775 * Byte Order:: Choosing target byte order
12778 @node Active Targets
12779 @section Active Targets
12781 @cindex stacking targets
12782 @cindex active targets
12783 @cindex multiple targets
12785 There are three classes of targets: processes, core files, and
12786 executable files. @value{GDBN} can work concurrently on up to three
12787 active targets, one in each class. This allows you to (for example)
12788 start a process and inspect its activity without abandoning your work on
12791 For example, if you execute @samp{gdb a.out}, then the executable file
12792 @code{a.out} is the only active target. If you designate a core file as
12793 well---presumably from a prior run that crashed and coredumped---then
12794 @value{GDBN} has two active targets and uses them in tandem, looking
12795 first in the corefile target, then in the executable file, to satisfy
12796 requests for memory addresses. (Typically, these two classes of target
12797 are complementary, since core files contain only a program's
12798 read-write memory---variables and so on---plus machine status, while
12799 executable files contain only the program text and initialized data.)
12801 When you type @code{run}, your executable file becomes an active process
12802 target as well. When a process target is active, all @value{GDBN}
12803 commands requesting memory addresses refer to that target; addresses in
12804 an active core file or executable file target are obscured while the
12805 process target is active.
12807 Use the @code{core-file} and @code{exec-file} commands to select a new
12808 core file or executable target (@pxref{Files, ,Commands to Specify
12809 Files}). To specify as a target a process that is already running, use
12810 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12813 @node Target Commands
12814 @section Commands for Managing Targets
12817 @item target @var{type} @var{parameters}
12818 Connects the @value{GDBN} host environment to a target machine or
12819 process. A target is typically a protocol for talking to debugging
12820 facilities. You use the argument @var{type} to specify the type or
12821 protocol of the target machine.
12823 Further @var{parameters} are interpreted by the target protocol, but
12824 typically include things like device names or host names to connect
12825 with, process numbers, and baud rates.
12827 The @code{target} command does not repeat if you press @key{RET} again
12828 after executing the command.
12830 @kindex help target
12832 Displays the names of all targets available. To display targets
12833 currently selected, use either @code{info target} or @code{info files}
12834 (@pxref{Files, ,Commands to Specify Files}).
12836 @item help target @var{name}
12837 Describe a particular target, including any parameters necessary to
12840 @kindex set gnutarget
12841 @item set gnutarget @var{args}
12842 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12843 knows whether it is reading an @dfn{executable},
12844 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12845 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12846 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12849 @emph{Warning:} To specify a file format with @code{set gnutarget},
12850 you must know the actual BFD name.
12854 @xref{Files, , Commands to Specify Files}.
12856 @kindex show gnutarget
12857 @item show gnutarget
12858 Use the @code{show gnutarget} command to display what file format
12859 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12860 @value{GDBN} will determine the file format for each file automatically,
12861 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12864 @cindex common targets
12865 Here are some common targets (available, or not, depending on the GDB
12870 @item target exec @var{program}
12871 @cindex executable file target
12872 An executable file. @samp{target exec @var{program}} is the same as
12873 @samp{exec-file @var{program}}.
12875 @item target core @var{filename}
12876 @cindex core dump file target
12877 A core dump file. @samp{target core @var{filename}} is the same as
12878 @samp{core-file @var{filename}}.
12880 @item target remote @var{medium}
12881 @cindex remote target
12882 A remote system connected to @value{GDBN} via a serial line or network
12883 connection. This command tells @value{GDBN} to use its own remote
12884 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12886 For example, if you have a board connected to @file{/dev/ttya} on the
12887 machine running @value{GDBN}, you could say:
12890 target remote /dev/ttya
12893 @code{target remote} supports the @code{load} command. This is only
12894 useful if you have some other way of getting the stub to the target
12895 system, and you can put it somewhere in memory where it won't get
12896 clobbered by the download.
12899 @cindex built-in simulator target
12900 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12908 works; however, you cannot assume that a specific memory map, device
12909 drivers, or even basic I/O is available, although some simulators do
12910 provide these. For info about any processor-specific simulator details,
12911 see the appropriate section in @ref{Embedded Processors, ,Embedded
12916 Some configurations may include these targets as well:
12920 @item target nrom @var{dev}
12921 @cindex NetROM ROM emulator target
12922 NetROM ROM emulator. This target only supports downloading.
12926 Different targets are available on different configurations of @value{GDBN};
12927 your configuration may have more or fewer targets.
12929 Many remote targets require you to download the executable's code once
12930 you've successfully established a connection. You may wish to control
12931 various aspects of this process.
12936 @kindex set hash@r{, for remote monitors}
12937 @cindex hash mark while downloading
12938 This command controls whether a hash mark @samp{#} is displayed while
12939 downloading a file to the remote monitor. If on, a hash mark is
12940 displayed after each S-record is successfully downloaded to the
12944 @kindex show hash@r{, for remote monitors}
12945 Show the current status of displaying the hash mark.
12947 @item set debug monitor
12948 @kindex set debug monitor
12949 @cindex display remote monitor communications
12950 Enable or disable display of communications messages between
12951 @value{GDBN} and the remote monitor.
12953 @item show debug monitor
12954 @kindex show debug monitor
12955 Show the current status of displaying communications between
12956 @value{GDBN} and the remote monitor.
12961 @kindex load @var{filename}
12962 @item load @var{filename}
12964 Depending on what remote debugging facilities are configured into
12965 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12966 is meant to make @var{filename} (an executable) available for debugging
12967 on the remote system---by downloading, or dynamic linking, for example.
12968 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12969 the @code{add-symbol-file} command.
12971 If your @value{GDBN} does not have a @code{load} command, attempting to
12972 execute it gets the error message ``@code{You can't do that when your
12973 target is @dots{}}''
12975 The file is loaded at whatever address is specified in the executable.
12976 For some object file formats, you can specify the load address when you
12977 link the program; for other formats, like a.out, the object file format
12978 specifies a fixed address.
12979 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12981 Depending on the remote side capabilities, @value{GDBN} may be able to
12982 load programs into flash memory.
12984 @code{load} does not repeat if you press @key{RET} again after using it.
12988 @section Choosing Target Byte Order
12990 @cindex choosing target byte order
12991 @cindex target byte order
12993 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12994 offer the ability to run either big-endian or little-endian byte
12995 orders. Usually the executable or symbol will include a bit to
12996 designate the endian-ness, and you will not need to worry about
12997 which to use. However, you may still find it useful to adjust
12998 @value{GDBN}'s idea of processor endian-ness manually.
13002 @item set endian big
13003 Instruct @value{GDBN} to assume the target is big-endian.
13005 @item set endian little
13006 Instruct @value{GDBN} to assume the target is little-endian.
13008 @item set endian auto
13009 Instruct @value{GDBN} to use the byte order associated with the
13013 Display @value{GDBN}'s current idea of the target byte order.
13017 Note that these commands merely adjust interpretation of symbolic
13018 data on the host, and that they have absolutely no effect on the
13022 @node Remote Debugging
13023 @chapter Debugging Remote Programs
13024 @cindex remote debugging
13026 If you are trying to debug a program running on a machine that cannot run
13027 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13028 For example, you might use remote debugging on an operating system kernel,
13029 or on a small system which does not have a general purpose operating system
13030 powerful enough to run a full-featured debugger.
13032 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13033 to make this work with particular debugging targets. In addition,
13034 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13035 but not specific to any particular target system) which you can use if you
13036 write the remote stubs---the code that runs on the remote system to
13037 communicate with @value{GDBN}.
13039 Other remote targets may be available in your
13040 configuration of @value{GDBN}; use @code{help target} to list them.
13043 * Connecting:: Connecting to a remote target
13044 * File Transfer:: Sending files to a remote system
13045 * Server:: Using the gdbserver program
13046 * Remote Configuration:: Remote configuration
13047 * Remote Stub:: Implementing a remote stub
13051 @section Connecting to a Remote Target
13053 On the @value{GDBN} host machine, you will need an unstripped copy of
13054 your program, since @value{GDBN} needs symbol and debugging information.
13055 Start up @value{GDBN} as usual, using the name of the local copy of your
13056 program as the first argument.
13058 @cindex @code{target remote}
13059 @value{GDBN} can communicate with the target over a serial line, or
13060 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13061 each case, @value{GDBN} uses the same protocol for debugging your
13062 program; only the medium carrying the debugging packets varies. The
13063 @code{target remote} command establishes a connection to the target.
13064 Its arguments indicate which medium to use:
13068 @item target remote @var{serial-device}
13069 @cindex serial line, @code{target remote}
13070 Use @var{serial-device} to communicate with the target. For example,
13071 to use a serial line connected to the device named @file{/dev/ttyb}:
13074 target remote /dev/ttyb
13077 If you're using a serial line, you may want to give @value{GDBN} the
13078 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13079 (@pxref{Remote Configuration, set remotebaud}) before the
13080 @code{target} command.
13082 @item target remote @code{@var{host}:@var{port}}
13083 @itemx target remote @code{tcp:@var{host}:@var{port}}
13084 @cindex @acronym{TCP} port, @code{target remote}
13085 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13086 The @var{host} may be either a host name or a numeric @acronym{IP}
13087 address; @var{port} must be a decimal number. The @var{host} could be
13088 the target machine itself, if it is directly connected to the net, or
13089 it might be a terminal server which in turn has a serial line to the
13092 For example, to connect to port 2828 on a terminal server named
13096 target remote manyfarms:2828
13099 If your remote target is actually running on the same machine as your
13100 debugger session (e.g.@: a simulator for your target running on the
13101 same host), you can omit the hostname. For example, to connect to
13102 port 1234 on your local machine:
13105 target remote :1234
13109 Note that the colon is still required here.
13111 @item target remote @code{udp:@var{host}:@var{port}}
13112 @cindex @acronym{UDP} port, @code{target remote}
13113 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13114 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13117 target remote udp:manyfarms:2828
13120 When using a @acronym{UDP} connection for remote debugging, you should
13121 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13122 can silently drop packets on busy or unreliable networks, which will
13123 cause havoc with your debugging session.
13125 @item target remote | @var{command}
13126 @cindex pipe, @code{target remote} to
13127 Run @var{command} in the background and communicate with it using a
13128 pipe. The @var{command} is a shell command, to be parsed and expanded
13129 by the system's command shell, @code{/bin/sh}; it should expect remote
13130 protocol packets on its standard input, and send replies on its
13131 standard output. You could use this to run a stand-alone simulator
13132 that speaks the remote debugging protocol, to make net connections
13133 using programs like @code{ssh}, or for other similar tricks.
13135 If @var{command} closes its standard output (perhaps by exiting),
13136 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13137 program has already exited, this will have no effect.)
13141 Once the connection has been established, you can use all the usual
13142 commands to examine and change data. The remote program is already
13143 running; you can use @kbd{step} and @kbd{continue}, and you do not
13144 need to use @kbd{run}.
13146 @cindex interrupting remote programs
13147 @cindex remote programs, interrupting
13148 Whenever @value{GDBN} is waiting for the remote program, if you type the
13149 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13150 program. This may or may not succeed, depending in part on the hardware
13151 and the serial drivers the remote system uses. If you type the
13152 interrupt character once again, @value{GDBN} displays this prompt:
13155 Interrupted while waiting for the program.
13156 Give up (and stop debugging it)? (y or n)
13159 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13160 (If you decide you want to try again later, you can use @samp{target
13161 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13162 goes back to waiting.
13165 @kindex detach (remote)
13167 When you have finished debugging the remote program, you can use the
13168 @code{detach} command to release it from @value{GDBN} control.
13169 Detaching from the target normally resumes its execution, but the results
13170 will depend on your particular remote stub. After the @code{detach}
13171 command, @value{GDBN} is free to connect to another target.
13175 The @code{disconnect} command behaves like @code{detach}, except that
13176 the target is generally not resumed. It will wait for @value{GDBN}
13177 (this instance or another one) to connect and continue debugging. After
13178 the @code{disconnect} command, @value{GDBN} is again free to connect to
13181 @cindex send command to remote monitor
13182 @cindex extend @value{GDBN} for remote targets
13183 @cindex add new commands for external monitor
13185 @item monitor @var{cmd}
13186 This command allows you to send arbitrary commands directly to the
13187 remote monitor. Since @value{GDBN} doesn't care about the commands it
13188 sends like this, this command is the way to extend @value{GDBN}---you
13189 can add new commands that only the external monitor will understand
13193 @node File Transfer
13194 @section Sending files to a remote system
13195 @cindex remote target, file transfer
13196 @cindex file transfer
13197 @cindex sending files to remote systems
13199 Some remote targets offer the ability to transfer files over the same
13200 connection used to communicate with @value{GDBN}. This is convenient
13201 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13202 running @code{gdbserver} over a network interface. For other targets,
13203 e.g.@: embedded devices with only a single serial port, this may be
13204 the only way to upload or download files.
13206 Not all remote targets support these commands.
13210 @item remote put @var{hostfile} @var{targetfile}
13211 Copy file @var{hostfile} from the host system (the machine running
13212 @value{GDBN}) to @var{targetfile} on the target system.
13215 @item remote get @var{targetfile} @var{hostfile}
13216 Copy file @var{targetfile} from the target system to @var{hostfile}
13217 on the host system.
13219 @kindex remote delete
13220 @item remote delete @var{targetfile}
13221 Delete @var{targetfile} from the target system.
13226 @section Using the @code{gdbserver} Program
13229 @cindex remote connection without stubs
13230 @code{gdbserver} is a control program for Unix-like systems, which
13231 allows you to connect your program with a remote @value{GDBN} via
13232 @code{target remote}---but without linking in the usual debugging stub.
13234 @code{gdbserver} is not a complete replacement for the debugging stubs,
13235 because it requires essentially the same operating-system facilities
13236 that @value{GDBN} itself does. In fact, a system that can run
13237 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13238 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13239 because it is a much smaller program than @value{GDBN} itself. It is
13240 also easier to port than all of @value{GDBN}, so you may be able to get
13241 started more quickly on a new system by using @code{gdbserver}.
13242 Finally, if you develop code for real-time systems, you may find that
13243 the tradeoffs involved in real-time operation make it more convenient to
13244 do as much development work as possible on another system, for example
13245 by cross-compiling. You can use @code{gdbserver} to make a similar
13246 choice for debugging.
13248 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13249 or a TCP connection, using the standard @value{GDBN} remote serial
13253 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13254 Do not run @code{gdbserver} connected to any public network; a
13255 @value{GDBN} connection to @code{gdbserver} provides access to the
13256 target system with the same privileges as the user running
13260 @subsection Running @code{gdbserver}
13261 @cindex arguments, to @code{gdbserver}
13263 Run @code{gdbserver} on the target system. You need a copy of the
13264 program you want to debug, including any libraries it requires.
13265 @code{gdbserver} does not need your program's symbol table, so you can
13266 strip the program if necessary to save space. @value{GDBN} on the host
13267 system does all the symbol handling.
13269 To use the server, you must tell it how to communicate with @value{GDBN};
13270 the name of your program; and the arguments for your program. The usual
13274 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13277 @var{comm} is either a device name (to use a serial line) or a TCP
13278 hostname and portnumber. For example, to debug Emacs with the argument
13279 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13283 target> gdbserver /dev/com1 emacs foo.txt
13286 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13289 To use a TCP connection instead of a serial line:
13292 target> gdbserver host:2345 emacs foo.txt
13295 The only difference from the previous example is the first argument,
13296 specifying that you are communicating with the host @value{GDBN} via
13297 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13298 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13299 (Currently, the @samp{host} part is ignored.) You can choose any number
13300 you want for the port number as long as it does not conflict with any
13301 TCP ports already in use on the target system (for example, @code{23} is
13302 reserved for @code{telnet}).@footnote{If you choose a port number that
13303 conflicts with another service, @code{gdbserver} prints an error message
13304 and exits.} You must use the same port number with the host @value{GDBN}
13305 @code{target remote} command.
13307 @subsubsection Attaching to a Running Program
13309 On some targets, @code{gdbserver} can also attach to running programs.
13310 This is accomplished via the @code{--attach} argument. The syntax is:
13313 target> gdbserver --attach @var{comm} @var{pid}
13316 @var{pid} is the process ID of a currently running process. It isn't necessary
13317 to point @code{gdbserver} at a binary for the running process.
13320 @cindex attach to a program by name
13321 You can debug processes by name instead of process ID if your target has the
13322 @code{pidof} utility:
13325 target> gdbserver --attach @var{comm} `pidof @var{program}`
13328 In case more than one copy of @var{program} is running, or @var{program}
13329 has multiple threads, most versions of @code{pidof} support the
13330 @code{-s} option to only return the first process ID.
13332 @subsubsection Multi-Process Mode for @code{gdbserver}
13333 @cindex gdbserver, multiple processes
13334 @cindex multiple processes with gdbserver
13336 When you connect to @code{gdbserver} using @code{target remote},
13337 @code{gdbserver} debugs the specified program only once. When the
13338 program exits, or you detach from it, @value{GDBN} closes the connection
13339 and @code{gdbserver} exits.
13341 If you connect using @kbd{target extended-remote}, @code{gdbserver}
13342 enters multi-process mode. When the debugged program exits, or you
13343 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
13344 though no program is running. The @code{run} and @code{attach}
13345 commands instruct @code{gdbserver} to run or attach to a new program.
13346 The @code{run} command uses @code{set remote exec-file} (@pxref{set
13347 remote exec-file}) to select the program to run. Command line
13348 arguments are supported, except for wildcard expansion and I/O
13349 redirection (@pxref{Arguments}).
13351 To start @code{gdbserver} without supplying an initial command to run
13352 or process ID to attach, use the @option{--multi} command line option.
13353 Then you can connect using @kbd{target extended-remote} and start
13354 the program you want to debug.
13356 @code{gdbserver} does not automatically exit in multi-process mode.
13357 You can terminate it by using @code{monitor exit}
13358 (@pxref{Monitor Commands for gdbserver}).
13360 @subsubsection Other Command-Line Arguments for @code{gdbserver}
13362 You can include @option{--debug} on the @code{gdbserver} command line.
13363 @code{gdbserver} will display extra status information about the debugging
13364 process. This option is intended for @code{gdbserver} development and
13365 for bug reports to the developers.
13367 The @option{--wrapper} option specifies a wrapper to launch programs
13368 for debugging. The option should be followed by the name of the
13369 wrapper, then any command-line arguments to pass to the wrapper, then
13370 @kbd{--} indicating the end of the wrapper arguments.
13372 @code{gdbserver} runs the specified wrapper program with a combined
13373 command line including the wrapper arguments, then the name of the
13374 program to debug, then any arguments to the program. The wrapper
13375 runs until it executes your program, and then @value{GDBN} gains control.
13377 You can use any program that eventually calls @code{execve} with
13378 its arguments as a wrapper. Several standard Unix utilities do
13379 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
13380 with @code{exec "$@@"} will also work.
13382 For example, you can use @code{env} to pass an environment variable to
13383 the debugged program, without setting the variable in @code{gdbserver}'s
13387 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
13390 @subsection Connecting to @code{gdbserver}
13392 Run @value{GDBN} on the host system.
13394 First make sure you have the necessary symbol files. Load symbols for
13395 your application using the @code{file} command before you connect. Use
13396 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
13397 was compiled with the correct sysroot using @code{--with-sysroot}).
13399 The symbol file and target libraries must exactly match the executable
13400 and libraries on the target, with one exception: the files on the host
13401 system should not be stripped, even if the files on the target system
13402 are. Mismatched or missing files will lead to confusing results
13403 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
13404 files may also prevent @code{gdbserver} from debugging multi-threaded
13407 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
13408 For TCP connections, you must start up @code{gdbserver} prior to using
13409 the @code{target remote} command. Otherwise you may get an error whose
13410 text depends on the host system, but which usually looks something like
13411 @samp{Connection refused}. Don't use the @code{load}
13412 command in @value{GDBN} when using @code{gdbserver}, since the program is
13413 already on the target.
13415 @subsection Monitor Commands for @code{gdbserver}
13416 @cindex monitor commands, for @code{gdbserver}
13417 @anchor{Monitor Commands for gdbserver}
13419 During a @value{GDBN} session using @code{gdbserver}, you can use the
13420 @code{monitor} command to send special requests to @code{gdbserver}.
13421 Here are the available commands.
13425 List the available monitor commands.
13427 @item monitor set debug 0
13428 @itemx monitor set debug 1
13429 Disable or enable general debugging messages.
13431 @item monitor set remote-debug 0
13432 @itemx monitor set remote-debug 1
13433 Disable or enable specific debugging messages associated with the remote
13434 protocol (@pxref{Remote Protocol}).
13437 Tell gdbserver to exit immediately. This command should be followed by
13438 @code{disconnect} to close the debugging session. @code{gdbserver} will
13439 detach from any attached processes and kill any processes it created.
13440 Use @code{monitor exit} to terminate @code{gdbserver} at the end
13441 of a multi-process mode debug session.
13445 @node Remote Configuration
13446 @section Remote Configuration
13449 @kindex show remote
13450 This section documents the configuration options available when
13451 debugging remote programs. For the options related to the File I/O
13452 extensions of the remote protocol, see @ref{system,
13453 system-call-allowed}.
13456 @item set remoteaddresssize @var{bits}
13457 @cindex address size for remote targets
13458 @cindex bits in remote address
13459 Set the maximum size of address in a memory packet to the specified
13460 number of bits. @value{GDBN} will mask off the address bits above
13461 that number, when it passes addresses to the remote target. The
13462 default value is the number of bits in the target's address.
13464 @item show remoteaddresssize
13465 Show the current value of remote address size in bits.
13467 @item set remotebaud @var{n}
13468 @cindex baud rate for remote targets
13469 Set the baud rate for the remote serial I/O to @var{n} baud. The
13470 value is used to set the speed of the serial port used for debugging
13473 @item show remotebaud
13474 Show the current speed of the remote connection.
13476 @item set remotebreak
13477 @cindex interrupt remote programs
13478 @cindex BREAK signal instead of Ctrl-C
13479 @anchor{set remotebreak}
13480 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13481 when you type @kbd{Ctrl-c} to interrupt the program running
13482 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13483 character instead. The default is off, since most remote systems
13484 expect to see @samp{Ctrl-C} as the interrupt signal.
13486 @item show remotebreak
13487 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13488 interrupt the remote program.
13490 @item set remoteflow on
13491 @itemx set remoteflow off
13492 @kindex set remoteflow
13493 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13494 on the serial port used to communicate to the remote target.
13496 @item show remoteflow
13497 @kindex show remoteflow
13498 Show the current setting of hardware flow control.
13500 @item set remotelogbase @var{base}
13501 Set the base (a.k.a.@: radix) of logging serial protocol
13502 communications to @var{base}. Supported values of @var{base} are:
13503 @code{ascii}, @code{octal}, and @code{hex}. The default is
13506 @item show remotelogbase
13507 Show the current setting of the radix for logging remote serial
13510 @item set remotelogfile @var{file}
13511 @cindex record serial communications on file
13512 Record remote serial communications on the named @var{file}. The
13513 default is not to record at all.
13515 @item show remotelogfile.
13516 Show the current setting of the file name on which to record the
13517 serial communications.
13519 @item set remotetimeout @var{num}
13520 @cindex timeout for serial communications
13521 @cindex remote timeout
13522 Set the timeout limit to wait for the remote target to respond to
13523 @var{num} seconds. The default is 2 seconds.
13525 @item show remotetimeout
13526 Show the current number of seconds to wait for the remote target
13529 @cindex limit hardware breakpoints and watchpoints
13530 @cindex remote target, limit break- and watchpoints
13531 @anchor{set remote hardware-watchpoint-limit}
13532 @anchor{set remote hardware-breakpoint-limit}
13533 @item set remote hardware-watchpoint-limit @var{limit}
13534 @itemx set remote hardware-breakpoint-limit @var{limit}
13535 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13536 watchpoints. A limit of -1, the default, is treated as unlimited.
13538 @item set remote exec-file @var{filename}
13539 @itemx show remote exec-file
13540 @anchor{set remote exec-file}
13541 @cindex executable file, for remote target
13542 Select the file used for @code{run} with @code{target
13543 extended-remote}. This should be set to a filename valid on the
13544 target system. If it is not set, the target will use a default
13545 filename (e.g.@: the last program run).
13548 @cindex remote packets, enabling and disabling
13549 The @value{GDBN} remote protocol autodetects the packets supported by
13550 your debugging stub. If you need to override the autodetection, you
13551 can use these commands to enable or disable individual packets. Each
13552 packet can be set to @samp{on} (the remote target supports this
13553 packet), @samp{off} (the remote target does not support this packet),
13554 or @samp{auto} (detect remote target support for this packet). They
13555 all default to @samp{auto}. For more information about each packet,
13556 see @ref{Remote Protocol}.
13558 During normal use, you should not have to use any of these commands.
13559 If you do, that may be a bug in your remote debugging stub, or a bug
13560 in @value{GDBN}. You may want to report the problem to the
13561 @value{GDBN} developers.
13563 For each packet @var{name}, the command to enable or disable the
13564 packet is @code{set remote @var{name}-packet}. The available settings
13567 @multitable @columnfractions 0.28 0.32 0.25
13570 @tab Related Features
13572 @item @code{fetch-register}
13574 @tab @code{info registers}
13576 @item @code{set-register}
13580 @item @code{binary-download}
13582 @tab @code{load}, @code{set}
13584 @item @code{read-aux-vector}
13585 @tab @code{qXfer:auxv:read}
13586 @tab @code{info auxv}
13588 @item @code{symbol-lookup}
13589 @tab @code{qSymbol}
13590 @tab Detecting multiple threads
13592 @item @code{attach}
13593 @tab @code{vAttach}
13596 @item @code{verbose-resume}
13598 @tab Stepping or resuming multiple threads
13604 @item @code{software-breakpoint}
13608 @item @code{hardware-breakpoint}
13612 @item @code{write-watchpoint}
13616 @item @code{read-watchpoint}
13620 @item @code{access-watchpoint}
13624 @item @code{target-features}
13625 @tab @code{qXfer:features:read}
13626 @tab @code{set architecture}
13628 @item @code{library-info}
13629 @tab @code{qXfer:libraries:read}
13630 @tab @code{info sharedlibrary}
13632 @item @code{memory-map}
13633 @tab @code{qXfer:memory-map:read}
13634 @tab @code{info mem}
13636 @item @code{read-spu-object}
13637 @tab @code{qXfer:spu:read}
13638 @tab @code{info spu}
13640 @item @code{write-spu-object}
13641 @tab @code{qXfer:spu:write}
13642 @tab @code{info spu}
13644 @item @code{get-thread-local-@*storage-address}
13645 @tab @code{qGetTLSAddr}
13646 @tab Displaying @code{__thread} variables
13648 @item @code{search-memory}
13649 @tab @code{qSearch:memory}
13652 @item @code{supported-packets}
13653 @tab @code{qSupported}
13654 @tab Remote communications parameters
13656 @item @code{pass-signals}
13657 @tab @code{QPassSignals}
13658 @tab @code{handle @var{signal}}
13660 @item @code{hostio-close-packet}
13661 @tab @code{vFile:close}
13662 @tab @code{remote get}, @code{remote put}
13664 @item @code{hostio-open-packet}
13665 @tab @code{vFile:open}
13666 @tab @code{remote get}, @code{remote put}
13668 @item @code{hostio-pread-packet}
13669 @tab @code{vFile:pread}
13670 @tab @code{remote get}, @code{remote put}
13672 @item @code{hostio-pwrite-packet}
13673 @tab @code{vFile:pwrite}
13674 @tab @code{remote get}, @code{remote put}
13676 @item @code{hostio-unlink-packet}
13677 @tab @code{vFile:unlink}
13678 @tab @code{remote delete}
13682 @section Implementing a Remote Stub
13684 @cindex debugging stub, example
13685 @cindex remote stub, example
13686 @cindex stub example, remote debugging
13687 The stub files provided with @value{GDBN} implement the target side of the
13688 communication protocol, and the @value{GDBN} side is implemented in the
13689 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13690 these subroutines to communicate, and ignore the details. (If you're
13691 implementing your own stub file, you can still ignore the details: start
13692 with one of the existing stub files. @file{sparc-stub.c} is the best
13693 organized, and therefore the easiest to read.)
13695 @cindex remote serial debugging, overview
13696 To debug a program running on another machine (the debugging
13697 @dfn{target} machine), you must first arrange for all the usual
13698 prerequisites for the program to run by itself. For example, for a C
13703 A startup routine to set up the C runtime environment; these usually
13704 have a name like @file{crt0}. The startup routine may be supplied by
13705 your hardware supplier, or you may have to write your own.
13708 A C subroutine library to support your program's
13709 subroutine calls, notably managing input and output.
13712 A way of getting your program to the other machine---for example, a
13713 download program. These are often supplied by the hardware
13714 manufacturer, but you may have to write your own from hardware
13718 The next step is to arrange for your program to use a serial port to
13719 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13720 machine). In general terms, the scheme looks like this:
13724 @value{GDBN} already understands how to use this protocol; when everything
13725 else is set up, you can simply use the @samp{target remote} command
13726 (@pxref{Targets,,Specifying a Debugging Target}).
13728 @item On the target,
13729 you must link with your program a few special-purpose subroutines that
13730 implement the @value{GDBN} remote serial protocol. The file containing these
13731 subroutines is called a @dfn{debugging stub}.
13733 On certain remote targets, you can use an auxiliary program
13734 @code{gdbserver} instead of linking a stub into your program.
13735 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13738 The debugging stub is specific to the architecture of the remote
13739 machine; for example, use @file{sparc-stub.c} to debug programs on
13742 @cindex remote serial stub list
13743 These working remote stubs are distributed with @value{GDBN}:
13748 @cindex @file{i386-stub.c}
13751 For Intel 386 and compatible architectures.
13754 @cindex @file{m68k-stub.c}
13755 @cindex Motorola 680x0
13757 For Motorola 680x0 architectures.
13760 @cindex @file{sh-stub.c}
13763 For Renesas SH architectures.
13766 @cindex @file{sparc-stub.c}
13768 For @sc{sparc} architectures.
13770 @item sparcl-stub.c
13771 @cindex @file{sparcl-stub.c}
13774 For Fujitsu @sc{sparclite} architectures.
13778 The @file{README} file in the @value{GDBN} distribution may list other
13779 recently added stubs.
13782 * Stub Contents:: What the stub can do for you
13783 * Bootstrapping:: What you must do for the stub
13784 * Debug Session:: Putting it all together
13787 @node Stub Contents
13788 @subsection What the Stub Can Do for You
13790 @cindex remote serial stub
13791 The debugging stub for your architecture supplies these three
13795 @item set_debug_traps
13796 @findex set_debug_traps
13797 @cindex remote serial stub, initialization
13798 This routine arranges for @code{handle_exception} to run when your
13799 program stops. You must call this subroutine explicitly near the
13800 beginning of your program.
13802 @item handle_exception
13803 @findex handle_exception
13804 @cindex remote serial stub, main routine
13805 This is the central workhorse, but your program never calls it
13806 explicitly---the setup code arranges for @code{handle_exception} to
13807 run when a trap is triggered.
13809 @code{handle_exception} takes control when your program stops during
13810 execution (for example, on a breakpoint), and mediates communications
13811 with @value{GDBN} on the host machine. This is where the communications
13812 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13813 representative on the target machine. It begins by sending summary
13814 information on the state of your program, then continues to execute,
13815 retrieving and transmitting any information @value{GDBN} needs, until you
13816 execute a @value{GDBN} command that makes your program resume; at that point,
13817 @code{handle_exception} returns control to your own code on the target
13821 @cindex @code{breakpoint} subroutine, remote
13822 Use this auxiliary subroutine to make your program contain a
13823 breakpoint. Depending on the particular situation, this may be the only
13824 way for @value{GDBN} to get control. For instance, if your target
13825 machine has some sort of interrupt button, you won't need to call this;
13826 pressing the interrupt button transfers control to
13827 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13828 simply receiving characters on the serial port may also trigger a trap;
13829 again, in that situation, you don't need to call @code{breakpoint} from
13830 your own program---simply running @samp{target remote} from the host
13831 @value{GDBN} session gets control.
13833 Call @code{breakpoint} if none of these is true, or if you simply want
13834 to make certain your program stops at a predetermined point for the
13835 start of your debugging session.
13838 @node Bootstrapping
13839 @subsection What You Must Do for the Stub
13841 @cindex remote stub, support routines
13842 The debugging stubs that come with @value{GDBN} are set up for a particular
13843 chip architecture, but they have no information about the rest of your
13844 debugging target machine.
13846 First of all you need to tell the stub how to communicate with the
13850 @item int getDebugChar()
13851 @findex getDebugChar
13852 Write this subroutine to read a single character from the serial port.
13853 It may be identical to @code{getchar} for your target system; a
13854 different name is used to allow you to distinguish the two if you wish.
13856 @item void putDebugChar(int)
13857 @findex putDebugChar
13858 Write this subroutine to write a single character to the serial port.
13859 It may be identical to @code{putchar} for your target system; a
13860 different name is used to allow you to distinguish the two if you wish.
13863 @cindex control C, and remote debugging
13864 @cindex interrupting remote targets
13865 If you want @value{GDBN} to be able to stop your program while it is
13866 running, you need to use an interrupt-driven serial driver, and arrange
13867 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13868 character). That is the character which @value{GDBN} uses to tell the
13869 remote system to stop.
13871 Getting the debugging target to return the proper status to @value{GDBN}
13872 probably requires changes to the standard stub; one quick and dirty way
13873 is to just execute a breakpoint instruction (the ``dirty'' part is that
13874 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13876 Other routines you need to supply are:
13879 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13880 @findex exceptionHandler
13881 Write this function to install @var{exception_address} in the exception
13882 handling tables. You need to do this because the stub does not have any
13883 way of knowing what the exception handling tables on your target system
13884 are like (for example, the processor's table might be in @sc{rom},
13885 containing entries which point to a table in @sc{ram}).
13886 @var{exception_number} is the exception number which should be changed;
13887 its meaning is architecture-dependent (for example, different numbers
13888 might represent divide by zero, misaligned access, etc). When this
13889 exception occurs, control should be transferred directly to
13890 @var{exception_address}, and the processor state (stack, registers,
13891 and so on) should be just as it is when a processor exception occurs. So if
13892 you want to use a jump instruction to reach @var{exception_address}, it
13893 should be a simple jump, not a jump to subroutine.
13895 For the 386, @var{exception_address} should be installed as an interrupt
13896 gate so that interrupts are masked while the handler runs. The gate
13897 should be at privilege level 0 (the most privileged level). The
13898 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13899 help from @code{exceptionHandler}.
13901 @item void flush_i_cache()
13902 @findex flush_i_cache
13903 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13904 instruction cache, if any, on your target machine. If there is no
13905 instruction cache, this subroutine may be a no-op.
13907 On target machines that have instruction caches, @value{GDBN} requires this
13908 function to make certain that the state of your program is stable.
13912 You must also make sure this library routine is available:
13915 @item void *memset(void *, int, int)
13917 This is the standard library function @code{memset} that sets an area of
13918 memory to a known value. If you have one of the free versions of
13919 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13920 either obtain it from your hardware manufacturer, or write your own.
13923 If you do not use the GNU C compiler, you may need other standard
13924 library subroutines as well; this varies from one stub to another,
13925 but in general the stubs are likely to use any of the common library
13926 subroutines which @code{@value{NGCC}} generates as inline code.
13929 @node Debug Session
13930 @subsection Putting it All Together
13932 @cindex remote serial debugging summary
13933 In summary, when your program is ready to debug, you must follow these
13938 Make sure you have defined the supporting low-level routines
13939 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13941 @code{getDebugChar}, @code{putDebugChar},
13942 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13946 Insert these lines near the top of your program:
13954 For the 680x0 stub only, you need to provide a variable called
13955 @code{exceptionHook}. Normally you just use:
13958 void (*exceptionHook)() = 0;
13962 but if before calling @code{set_debug_traps}, you set it to point to a
13963 function in your program, that function is called when
13964 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13965 error). The function indicated by @code{exceptionHook} is called with
13966 one parameter: an @code{int} which is the exception number.
13969 Compile and link together: your program, the @value{GDBN} debugging stub for
13970 your target architecture, and the supporting subroutines.
13973 Make sure you have a serial connection between your target machine and
13974 the @value{GDBN} host, and identify the serial port on the host.
13977 @c The "remote" target now provides a `load' command, so we should
13978 @c document that. FIXME.
13979 Download your program to your target machine (or get it there by
13980 whatever means the manufacturer provides), and start it.
13983 Start @value{GDBN} on the host, and connect to the target
13984 (@pxref{Connecting,,Connecting to a Remote Target}).
13988 @node Configurations
13989 @chapter Configuration-Specific Information
13991 While nearly all @value{GDBN} commands are available for all native and
13992 cross versions of the debugger, there are some exceptions. This chapter
13993 describes things that are only available in certain configurations.
13995 There are three major categories of configurations: native
13996 configurations, where the host and target are the same, embedded
13997 operating system configurations, which are usually the same for several
13998 different processor architectures, and bare embedded processors, which
13999 are quite different from each other.
14004 * Embedded Processors::
14011 This section describes details specific to particular native
14016 * BSD libkvm Interface:: Debugging BSD kernel memory images
14017 * SVR4 Process Information:: SVR4 process information
14018 * DJGPP Native:: Features specific to the DJGPP port
14019 * Cygwin Native:: Features specific to the Cygwin port
14020 * Hurd Native:: Features specific to @sc{gnu} Hurd
14021 * Neutrino:: Features specific to QNX Neutrino
14027 On HP-UX systems, if you refer to a function or variable name that
14028 begins with a dollar sign, @value{GDBN} searches for a user or system
14029 name first, before it searches for a convenience variable.
14032 @node BSD libkvm Interface
14033 @subsection BSD libkvm Interface
14036 @cindex kernel memory image
14037 @cindex kernel crash dump
14039 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14040 interface that provides a uniform interface for accessing kernel virtual
14041 memory images, including live systems and crash dumps. @value{GDBN}
14042 uses this interface to allow you to debug live kernels and kernel crash
14043 dumps on many native BSD configurations. This is implemented as a
14044 special @code{kvm} debugging target. For debugging a live system, load
14045 the currently running kernel into @value{GDBN} and connect to the
14049 (@value{GDBP}) @b{target kvm}
14052 For debugging crash dumps, provide the file name of the crash dump as an
14056 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14059 Once connected to the @code{kvm} target, the following commands are
14065 Set current context from the @dfn{Process Control Block} (PCB) address.
14068 Set current context from proc address. This command isn't available on
14069 modern FreeBSD systems.
14072 @node SVR4 Process Information
14073 @subsection SVR4 Process Information
14075 @cindex examine process image
14076 @cindex process info via @file{/proc}
14078 Many versions of SVR4 and compatible systems provide a facility called
14079 @samp{/proc} that can be used to examine the image of a running
14080 process using file-system subroutines. If @value{GDBN} is configured
14081 for an operating system with this facility, the command @code{info
14082 proc} is available to report information about the process running
14083 your program, or about any process running on your system. @code{info
14084 proc} works only on SVR4 systems that include the @code{procfs} code.
14085 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14086 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14092 @itemx info proc @var{process-id}
14093 Summarize available information about any running process. If a
14094 process ID is specified by @var{process-id}, display information about
14095 that process; otherwise display information about the program being
14096 debugged. The summary includes the debugged process ID, the command
14097 line used to invoke it, its current working directory, and its
14098 executable file's absolute file name.
14100 On some systems, @var{process-id} can be of the form
14101 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14102 within a process. If the optional @var{pid} part is missing, it means
14103 a thread from the process being debugged (the leading @samp{/} still
14104 needs to be present, or else @value{GDBN} will interpret the number as
14105 a process ID rather than a thread ID).
14107 @item info proc mappings
14108 @cindex memory address space mappings
14109 Report the memory address space ranges accessible in the program, with
14110 information on whether the process has read, write, or execute access
14111 rights to each range. On @sc{gnu}/Linux systems, each memory range
14112 includes the object file which is mapped to that range, instead of the
14113 memory access rights to that range.
14115 @item info proc stat
14116 @itemx info proc status
14117 @cindex process detailed status information
14118 These subcommands are specific to @sc{gnu}/Linux systems. They show
14119 the process-related information, including the user ID and group ID;
14120 how many threads are there in the process; its virtual memory usage;
14121 the signals that are pending, blocked, and ignored; its TTY; its
14122 consumption of system and user time; its stack size; its @samp{nice}
14123 value; etc. For more information, see the @samp{proc} man page
14124 (type @kbd{man 5 proc} from your shell prompt).
14126 @item info proc all
14127 Show all the information about the process described under all of the
14128 above @code{info proc} subcommands.
14131 @comment These sub-options of 'info proc' were not included when
14132 @comment procfs.c was re-written. Keep their descriptions around
14133 @comment against the day when someone finds the time to put them back in.
14134 @kindex info proc times
14135 @item info proc times
14136 Starting time, user CPU time, and system CPU time for your program and
14139 @kindex info proc id
14141 Report on the process IDs related to your program: its own process ID,
14142 the ID of its parent, the process group ID, and the session ID.
14145 @item set procfs-trace
14146 @kindex set procfs-trace
14147 @cindex @code{procfs} API calls
14148 This command enables and disables tracing of @code{procfs} API calls.
14150 @item show procfs-trace
14151 @kindex show procfs-trace
14152 Show the current state of @code{procfs} API call tracing.
14154 @item set procfs-file @var{file}
14155 @kindex set procfs-file
14156 Tell @value{GDBN} to write @code{procfs} API trace to the named
14157 @var{file}. @value{GDBN} appends the trace info to the previous
14158 contents of the file. The default is to display the trace on the
14161 @item show procfs-file
14162 @kindex show procfs-file
14163 Show the file to which @code{procfs} API trace is written.
14165 @item proc-trace-entry
14166 @itemx proc-trace-exit
14167 @itemx proc-untrace-entry
14168 @itemx proc-untrace-exit
14169 @kindex proc-trace-entry
14170 @kindex proc-trace-exit
14171 @kindex proc-untrace-entry
14172 @kindex proc-untrace-exit
14173 These commands enable and disable tracing of entries into and exits
14174 from the @code{syscall} interface.
14177 @kindex info pidlist
14178 @cindex process list, QNX Neutrino
14179 For QNX Neutrino only, this command displays the list of all the
14180 processes and all the threads within each process.
14183 @kindex info meminfo
14184 @cindex mapinfo list, QNX Neutrino
14185 For QNX Neutrino only, this command displays the list of all mapinfos.
14189 @subsection Features for Debugging @sc{djgpp} Programs
14190 @cindex @sc{djgpp} debugging
14191 @cindex native @sc{djgpp} debugging
14192 @cindex MS-DOS-specific commands
14195 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14196 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14197 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14198 top of real-mode DOS systems and their emulations.
14200 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14201 defines a few commands specific to the @sc{djgpp} port. This
14202 subsection describes those commands.
14207 This is a prefix of @sc{djgpp}-specific commands which print
14208 information about the target system and important OS structures.
14211 @cindex MS-DOS system info
14212 @cindex free memory information (MS-DOS)
14213 @item info dos sysinfo
14214 This command displays assorted information about the underlying
14215 platform: the CPU type and features, the OS version and flavor, the
14216 DPMI version, and the available conventional and DPMI memory.
14221 @cindex segment descriptor tables
14222 @cindex descriptor tables display
14224 @itemx info dos ldt
14225 @itemx info dos idt
14226 These 3 commands display entries from, respectively, Global, Local,
14227 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14228 tables are data structures which store a descriptor for each segment
14229 that is currently in use. The segment's selector is an index into a
14230 descriptor table; the table entry for that index holds the
14231 descriptor's base address and limit, and its attributes and access
14234 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14235 segment (used for both data and the stack), and a DOS segment (which
14236 allows access to DOS/BIOS data structures and absolute addresses in
14237 conventional memory). However, the DPMI host will usually define
14238 additional segments in order to support the DPMI environment.
14240 @cindex garbled pointers
14241 These commands allow to display entries from the descriptor tables.
14242 Without an argument, all entries from the specified table are
14243 displayed. An argument, which should be an integer expression, means
14244 display a single entry whose index is given by the argument. For
14245 example, here's a convenient way to display information about the
14246 debugged program's data segment:
14249 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14250 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14254 This comes in handy when you want to see whether a pointer is outside
14255 the data segment's limit (i.e.@: @dfn{garbled}).
14257 @cindex page tables display (MS-DOS)
14259 @itemx info dos pte
14260 These two commands display entries from, respectively, the Page
14261 Directory and the Page Tables. Page Directories and Page Tables are
14262 data structures which control how virtual memory addresses are mapped
14263 into physical addresses. A Page Table includes an entry for every
14264 page of memory that is mapped into the program's address space; there
14265 may be several Page Tables, each one holding up to 4096 entries. A
14266 Page Directory has up to 4096 entries, one each for every Page Table
14267 that is currently in use.
14269 Without an argument, @kbd{info dos pde} displays the entire Page
14270 Directory, and @kbd{info dos pte} displays all the entries in all of
14271 the Page Tables. An argument, an integer expression, given to the
14272 @kbd{info dos pde} command means display only that entry from the Page
14273 Directory table. An argument given to the @kbd{info dos pte} command
14274 means display entries from a single Page Table, the one pointed to by
14275 the specified entry in the Page Directory.
14277 @cindex direct memory access (DMA) on MS-DOS
14278 These commands are useful when your program uses @dfn{DMA} (Direct
14279 Memory Access), which needs physical addresses to program the DMA
14282 These commands are supported only with some DPMI servers.
14284 @cindex physical address from linear address
14285 @item info dos address-pte @var{addr}
14286 This command displays the Page Table entry for a specified linear
14287 address. The argument @var{addr} is a linear address which should
14288 already have the appropriate segment's base address added to it,
14289 because this command accepts addresses which may belong to @emph{any}
14290 segment. For example, here's how to display the Page Table entry for
14291 the page where a variable @code{i} is stored:
14294 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14295 @exdent @code{Page Table entry for address 0x11a00d30:}
14296 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14300 This says that @code{i} is stored at offset @code{0xd30} from the page
14301 whose physical base address is @code{0x02698000}, and shows all the
14302 attributes of that page.
14304 Note that you must cast the addresses of variables to a @code{char *},
14305 since otherwise the value of @code{__djgpp_base_address}, the base
14306 address of all variables and functions in a @sc{djgpp} program, will
14307 be added using the rules of C pointer arithmetics: if @code{i} is
14308 declared an @code{int}, @value{GDBN} will add 4 times the value of
14309 @code{__djgpp_base_address} to the address of @code{i}.
14311 Here's another example, it displays the Page Table entry for the
14315 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14316 @exdent @code{Page Table entry for address 0x29110:}
14317 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14321 (The @code{+ 3} offset is because the transfer buffer's address is the
14322 3rd member of the @code{_go32_info_block} structure.) The output
14323 clearly shows that this DPMI server maps the addresses in conventional
14324 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
14325 linear (@code{0x29110}) addresses are identical.
14327 This command is supported only with some DPMI servers.
14330 @cindex DOS serial data link, remote debugging
14331 In addition to native debugging, the DJGPP port supports remote
14332 debugging via a serial data link. The following commands are specific
14333 to remote serial debugging in the DJGPP port of @value{GDBN}.
14336 @kindex set com1base
14337 @kindex set com1irq
14338 @kindex set com2base
14339 @kindex set com2irq
14340 @kindex set com3base
14341 @kindex set com3irq
14342 @kindex set com4base
14343 @kindex set com4irq
14344 @item set com1base @var{addr}
14345 This command sets the base I/O port address of the @file{COM1} serial
14348 @item set com1irq @var{irq}
14349 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
14350 for the @file{COM1} serial port.
14352 There are similar commands @samp{set com2base}, @samp{set com3irq},
14353 etc.@: for setting the port address and the @code{IRQ} lines for the
14356 @kindex show com1base
14357 @kindex show com1irq
14358 @kindex show com2base
14359 @kindex show com2irq
14360 @kindex show com3base
14361 @kindex show com3irq
14362 @kindex show com4base
14363 @kindex show com4irq
14364 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
14365 display the current settings of the base address and the @code{IRQ}
14366 lines used by the COM ports.
14369 @kindex info serial
14370 @cindex DOS serial port status
14371 This command prints the status of the 4 DOS serial ports. For each
14372 port, it prints whether it's active or not, its I/O base address and
14373 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
14374 counts of various errors encountered so far.
14378 @node Cygwin Native
14379 @subsection Features for Debugging MS Windows PE Executables
14380 @cindex MS Windows debugging
14381 @cindex native Cygwin debugging
14382 @cindex Cygwin-specific commands
14384 @value{GDBN} supports native debugging of MS Windows programs, including
14385 DLLs with and without symbolic debugging information. There are various
14386 additional Cygwin-specific commands, described in this section.
14387 Working with DLLs that have no debugging symbols is described in
14388 @ref{Non-debug DLL Symbols}.
14393 This is a prefix of MS Windows-specific commands which print
14394 information about the target system and important OS structures.
14396 @item info w32 selector
14397 This command displays information returned by
14398 the Win32 API @code{GetThreadSelectorEntry} function.
14399 It takes an optional argument that is evaluated to
14400 a long value to give the information about this given selector.
14401 Without argument, this command displays information
14402 about the six segment registers.
14406 This is a Cygwin-specific alias of @code{info shared}.
14408 @kindex dll-symbols
14410 This command loads symbols from a dll similarly to
14411 add-sym command but without the need to specify a base address.
14413 @kindex set cygwin-exceptions
14414 @cindex debugging the Cygwin DLL
14415 @cindex Cygwin DLL, debugging
14416 @item set cygwin-exceptions @var{mode}
14417 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
14418 happen inside the Cygwin DLL. If @var{mode} is @code{off},
14419 @value{GDBN} will delay recognition of exceptions, and may ignore some
14420 exceptions which seem to be caused by internal Cygwin DLL
14421 ``bookkeeping''. This option is meant primarily for debugging the
14422 Cygwin DLL itself; the default value is @code{off} to avoid annoying
14423 @value{GDBN} users with false @code{SIGSEGV} signals.
14425 @kindex show cygwin-exceptions
14426 @item show cygwin-exceptions
14427 Displays whether @value{GDBN} will break on exceptions that happen
14428 inside the Cygwin DLL itself.
14430 @kindex set new-console
14431 @item set new-console @var{mode}
14432 If @var{mode} is @code{on} the debuggee will
14433 be started in a new console on next start.
14434 If @var{mode} is @code{off}i, the debuggee will
14435 be started in the same console as the debugger.
14437 @kindex show new-console
14438 @item show new-console
14439 Displays whether a new console is used
14440 when the debuggee is started.
14442 @kindex set new-group
14443 @item set new-group @var{mode}
14444 This boolean value controls whether the debuggee should
14445 start a new group or stay in the same group as the debugger.
14446 This affects the way the Windows OS handles
14449 @kindex show new-group
14450 @item show new-group
14451 Displays current value of new-group boolean.
14453 @kindex set debugevents
14454 @item set debugevents
14455 This boolean value adds debug output concerning kernel events related
14456 to the debuggee seen by the debugger. This includes events that
14457 signal thread and process creation and exit, DLL loading and
14458 unloading, console interrupts, and debugging messages produced by the
14459 Windows @code{OutputDebugString} API call.
14461 @kindex set debugexec
14462 @item set debugexec
14463 This boolean value adds debug output concerning execute events
14464 (such as resume thread) seen by the debugger.
14466 @kindex set debugexceptions
14467 @item set debugexceptions
14468 This boolean value adds debug output concerning exceptions in the
14469 debuggee seen by the debugger.
14471 @kindex set debugmemory
14472 @item set debugmemory
14473 This boolean value adds debug output concerning debuggee memory reads
14474 and writes by the debugger.
14478 This boolean values specifies whether the debuggee is called
14479 via a shell or directly (default value is on).
14483 Displays if the debuggee will be started with a shell.
14488 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14491 @node Non-debug DLL Symbols
14492 @subsubsection Support for DLLs without Debugging Symbols
14493 @cindex DLLs with no debugging symbols
14494 @cindex Minimal symbols and DLLs
14496 Very often on windows, some of the DLLs that your program relies on do
14497 not include symbolic debugging information (for example,
14498 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14499 symbols in a DLL, it relies on the minimal amount of symbolic
14500 information contained in the DLL's export table. This section
14501 describes working with such symbols, known internally to @value{GDBN} as
14502 ``minimal symbols''.
14504 Note that before the debugged program has started execution, no DLLs
14505 will have been loaded. The easiest way around this problem is simply to
14506 start the program --- either by setting a breakpoint or letting the
14507 program run once to completion. It is also possible to force
14508 @value{GDBN} to load a particular DLL before starting the executable ---
14509 see the shared library information in @ref{Files}, or the
14510 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14511 explicitly loading symbols from a DLL with no debugging information will
14512 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14513 which may adversely affect symbol lookup performance.
14515 @subsubsection DLL Name Prefixes
14517 In keeping with the naming conventions used by the Microsoft debugging
14518 tools, DLL export symbols are made available with a prefix based on the
14519 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14520 also entered into the symbol table, so @code{CreateFileA} is often
14521 sufficient. In some cases there will be name clashes within a program
14522 (particularly if the executable itself includes full debugging symbols)
14523 necessitating the use of the fully qualified name when referring to the
14524 contents of the DLL. Use single-quotes around the name to avoid the
14525 exclamation mark (``!'') being interpreted as a language operator.
14527 Note that the internal name of the DLL may be all upper-case, even
14528 though the file name of the DLL is lower-case, or vice-versa. Since
14529 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14530 some confusion. If in doubt, try the @code{info functions} and
14531 @code{info variables} commands or even @code{maint print msymbols}
14532 (@pxref{Symbols}). Here's an example:
14535 (@value{GDBP}) info function CreateFileA
14536 All functions matching regular expression "CreateFileA":
14538 Non-debugging symbols:
14539 0x77e885f4 CreateFileA
14540 0x77e885f4 KERNEL32!CreateFileA
14544 (@value{GDBP}) info function !
14545 All functions matching regular expression "!":
14547 Non-debugging symbols:
14548 0x6100114c cygwin1!__assert
14549 0x61004034 cygwin1!_dll_crt0@@0
14550 0x61004240 cygwin1!dll_crt0(per_process *)
14554 @subsubsection Working with Minimal Symbols
14556 Symbols extracted from a DLL's export table do not contain very much
14557 type information. All that @value{GDBN} can do is guess whether a symbol
14558 refers to a function or variable depending on the linker section that
14559 contains the symbol. Also note that the actual contents of the memory
14560 contained in a DLL are not available unless the program is running. This
14561 means that you cannot examine the contents of a variable or disassemble
14562 a function within a DLL without a running program.
14564 Variables are generally treated as pointers and dereferenced
14565 automatically. For this reason, it is often necessary to prefix a
14566 variable name with the address-of operator (``&'') and provide explicit
14567 type information in the command. Here's an example of the type of
14571 (@value{GDBP}) print 'cygwin1!__argv'
14576 (@value{GDBP}) x 'cygwin1!__argv'
14577 0x10021610: "\230y\""
14580 And two possible solutions:
14583 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14584 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14588 (@value{GDBP}) x/2x &'cygwin1!__argv'
14589 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14590 (@value{GDBP}) x/x 0x10021608
14591 0x10021608: 0x0022fd98
14592 (@value{GDBP}) x/s 0x0022fd98
14593 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14596 Setting a break point within a DLL is possible even before the program
14597 starts execution. However, under these circumstances, @value{GDBN} can't
14598 examine the initial instructions of the function in order to skip the
14599 function's frame set-up code. You can work around this by using ``*&''
14600 to set the breakpoint at a raw memory address:
14603 (@value{GDBP}) break *&'python22!PyOS_Readline'
14604 Breakpoint 1 at 0x1e04eff0
14607 The author of these extensions is not entirely convinced that setting a
14608 break point within a shared DLL like @file{kernel32.dll} is completely
14612 @subsection Commands Specific to @sc{gnu} Hurd Systems
14613 @cindex @sc{gnu} Hurd debugging
14615 This subsection describes @value{GDBN} commands specific to the
14616 @sc{gnu} Hurd native debugging.
14621 @kindex set signals@r{, Hurd command}
14622 @kindex set sigs@r{, Hurd command}
14623 This command toggles the state of inferior signal interception by
14624 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14625 affected by this command. @code{sigs} is a shorthand alias for
14630 @kindex show signals@r{, Hurd command}
14631 @kindex show sigs@r{, Hurd command}
14632 Show the current state of intercepting inferior's signals.
14634 @item set signal-thread
14635 @itemx set sigthread
14636 @kindex set signal-thread
14637 @kindex set sigthread
14638 This command tells @value{GDBN} which thread is the @code{libc} signal
14639 thread. That thread is run when a signal is delivered to a running
14640 process. @code{set sigthread} is the shorthand alias of @code{set
14643 @item show signal-thread
14644 @itemx show sigthread
14645 @kindex show signal-thread
14646 @kindex show sigthread
14647 These two commands show which thread will run when the inferior is
14648 delivered a signal.
14651 @kindex set stopped@r{, Hurd command}
14652 This commands tells @value{GDBN} that the inferior process is stopped,
14653 as with the @code{SIGSTOP} signal. The stopped process can be
14654 continued by delivering a signal to it.
14657 @kindex show stopped@r{, Hurd command}
14658 This command shows whether @value{GDBN} thinks the debuggee is
14661 @item set exceptions
14662 @kindex set exceptions@r{, Hurd command}
14663 Use this command to turn off trapping of exceptions in the inferior.
14664 When exception trapping is off, neither breakpoints nor
14665 single-stepping will work. To restore the default, set exception
14668 @item show exceptions
14669 @kindex show exceptions@r{, Hurd command}
14670 Show the current state of trapping exceptions in the inferior.
14672 @item set task pause
14673 @kindex set task@r{, Hurd commands}
14674 @cindex task attributes (@sc{gnu} Hurd)
14675 @cindex pause current task (@sc{gnu} Hurd)
14676 This command toggles task suspension when @value{GDBN} has control.
14677 Setting it to on takes effect immediately, and the task is suspended
14678 whenever @value{GDBN} gets control. Setting it to off will take
14679 effect the next time the inferior is continued. If this option is set
14680 to off, you can use @code{set thread default pause on} or @code{set
14681 thread pause on} (see below) to pause individual threads.
14683 @item show task pause
14684 @kindex show task@r{, Hurd commands}
14685 Show the current state of task suspension.
14687 @item set task detach-suspend-count
14688 @cindex task suspend count
14689 @cindex detach from task, @sc{gnu} Hurd
14690 This command sets the suspend count the task will be left with when
14691 @value{GDBN} detaches from it.
14693 @item show task detach-suspend-count
14694 Show the suspend count the task will be left with when detaching.
14696 @item set task exception-port
14697 @itemx set task excp
14698 @cindex task exception port, @sc{gnu} Hurd
14699 This command sets the task exception port to which @value{GDBN} will
14700 forward exceptions. The argument should be the value of the @dfn{send
14701 rights} of the task. @code{set task excp} is a shorthand alias.
14703 @item set noninvasive
14704 @cindex noninvasive task options
14705 This command switches @value{GDBN} to a mode that is the least
14706 invasive as far as interfering with the inferior is concerned. This
14707 is the same as using @code{set task pause}, @code{set exceptions}, and
14708 @code{set signals} to values opposite to the defaults.
14710 @item info send-rights
14711 @itemx info receive-rights
14712 @itemx info port-rights
14713 @itemx info port-sets
14714 @itemx info dead-names
14717 @cindex send rights, @sc{gnu} Hurd
14718 @cindex receive rights, @sc{gnu} Hurd
14719 @cindex port rights, @sc{gnu} Hurd
14720 @cindex port sets, @sc{gnu} Hurd
14721 @cindex dead names, @sc{gnu} Hurd
14722 These commands display information about, respectively, send rights,
14723 receive rights, port rights, port sets, and dead names of a task.
14724 There are also shorthand aliases: @code{info ports} for @code{info
14725 port-rights} and @code{info psets} for @code{info port-sets}.
14727 @item set thread pause
14728 @kindex set thread@r{, Hurd command}
14729 @cindex thread properties, @sc{gnu} Hurd
14730 @cindex pause current thread (@sc{gnu} Hurd)
14731 This command toggles current thread suspension when @value{GDBN} has
14732 control. Setting it to on takes effect immediately, and the current
14733 thread is suspended whenever @value{GDBN} gets control. Setting it to
14734 off will take effect the next time the inferior is continued.
14735 Normally, this command has no effect, since when @value{GDBN} has
14736 control, the whole task is suspended. However, if you used @code{set
14737 task pause off} (see above), this command comes in handy to suspend
14738 only the current thread.
14740 @item show thread pause
14741 @kindex show thread@r{, Hurd command}
14742 This command shows the state of current thread suspension.
14744 @item set thread run
14745 This command sets whether the current thread is allowed to run.
14747 @item show thread run
14748 Show whether the current thread is allowed to run.
14750 @item set thread detach-suspend-count
14751 @cindex thread suspend count, @sc{gnu} Hurd
14752 @cindex detach from thread, @sc{gnu} Hurd
14753 This command sets the suspend count @value{GDBN} will leave on a
14754 thread when detaching. This number is relative to the suspend count
14755 found by @value{GDBN} when it notices the thread; use @code{set thread
14756 takeover-suspend-count} to force it to an absolute value.
14758 @item show thread detach-suspend-count
14759 Show the suspend count @value{GDBN} will leave on the thread when
14762 @item set thread exception-port
14763 @itemx set thread excp
14764 Set the thread exception port to which to forward exceptions. This
14765 overrides the port set by @code{set task exception-port} (see above).
14766 @code{set thread excp} is the shorthand alias.
14768 @item set thread takeover-suspend-count
14769 Normally, @value{GDBN}'s thread suspend counts are relative to the
14770 value @value{GDBN} finds when it notices each thread. This command
14771 changes the suspend counts to be absolute instead.
14773 @item set thread default
14774 @itemx show thread default
14775 @cindex thread default settings, @sc{gnu} Hurd
14776 Each of the above @code{set thread} commands has a @code{set thread
14777 default} counterpart (e.g., @code{set thread default pause}, @code{set
14778 thread default exception-port}, etc.). The @code{thread default}
14779 variety of commands sets the default thread properties for all
14780 threads; you can then change the properties of individual threads with
14781 the non-default commands.
14786 @subsection QNX Neutrino
14787 @cindex QNX Neutrino
14789 @value{GDBN} provides the following commands specific to the QNX
14793 @item set debug nto-debug
14794 @kindex set debug nto-debug
14795 When set to on, enables debugging messages specific to the QNX
14798 @item show debug nto-debug
14799 @kindex show debug nto-debug
14800 Show the current state of QNX Neutrino messages.
14805 @section Embedded Operating Systems
14807 This section describes configurations involving the debugging of
14808 embedded operating systems that are available for several different
14812 * VxWorks:: Using @value{GDBN} with VxWorks
14815 @value{GDBN} includes the ability to debug programs running on
14816 various real-time operating systems.
14819 @subsection Using @value{GDBN} with VxWorks
14825 @kindex target vxworks
14826 @item target vxworks @var{machinename}
14827 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14828 is the target system's machine name or IP address.
14832 On VxWorks, @code{load} links @var{filename} dynamically on the
14833 current target system as well as adding its symbols in @value{GDBN}.
14835 @value{GDBN} enables developers to spawn and debug tasks running on networked
14836 VxWorks targets from a Unix host. Already-running tasks spawned from
14837 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14838 both the Unix host and on the VxWorks target. The program
14839 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14840 installed with the name @code{vxgdb}, to distinguish it from a
14841 @value{GDBN} for debugging programs on the host itself.)
14844 @item VxWorks-timeout @var{args}
14845 @kindex vxworks-timeout
14846 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14847 This option is set by the user, and @var{args} represents the number of
14848 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14849 your VxWorks target is a slow software simulator or is on the far side
14850 of a thin network line.
14853 The following information on connecting to VxWorks was current when
14854 this manual was produced; newer releases of VxWorks may use revised
14857 @findex INCLUDE_RDB
14858 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14859 to include the remote debugging interface routines in the VxWorks
14860 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14861 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14862 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14863 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14864 information on configuring and remaking VxWorks, see the manufacturer's
14866 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14868 Once you have included @file{rdb.a} in your VxWorks system image and set
14869 your Unix execution search path to find @value{GDBN}, you are ready to
14870 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14871 @code{vxgdb}, depending on your installation).
14873 @value{GDBN} comes up showing the prompt:
14880 * VxWorks Connection:: Connecting to VxWorks
14881 * VxWorks Download:: VxWorks download
14882 * VxWorks Attach:: Running tasks
14885 @node VxWorks Connection
14886 @subsubsection Connecting to VxWorks
14888 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14889 network. To connect to a target whose host name is ``@code{tt}'', type:
14892 (vxgdb) target vxworks tt
14896 @value{GDBN} displays messages like these:
14899 Attaching remote machine across net...
14904 @value{GDBN} then attempts to read the symbol tables of any object modules
14905 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14906 these files by searching the directories listed in the command search
14907 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14908 to find an object file, it displays a message such as:
14911 prog.o: No such file or directory.
14914 When this happens, add the appropriate directory to the search path with
14915 the @value{GDBN} command @code{path}, and execute the @code{target}
14918 @node VxWorks Download
14919 @subsubsection VxWorks Download
14921 @cindex download to VxWorks
14922 If you have connected to the VxWorks target and you want to debug an
14923 object that has not yet been loaded, you can use the @value{GDBN}
14924 @code{load} command to download a file from Unix to VxWorks
14925 incrementally. The object file given as an argument to the @code{load}
14926 command is actually opened twice: first by the VxWorks target in order
14927 to download the code, then by @value{GDBN} in order to read the symbol
14928 table. This can lead to problems if the current working directories on
14929 the two systems differ. If both systems have NFS mounted the same
14930 filesystems, you can avoid these problems by using absolute paths.
14931 Otherwise, it is simplest to set the working directory on both systems
14932 to the directory in which the object file resides, and then to reference
14933 the file by its name, without any path. For instance, a program
14934 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14935 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14936 program, type this on VxWorks:
14939 -> cd "@var{vxpath}/vw/demo/rdb"
14943 Then, in @value{GDBN}, type:
14946 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14947 (vxgdb) load prog.o
14950 @value{GDBN} displays a response similar to this:
14953 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14956 You can also use the @code{load} command to reload an object module
14957 after editing and recompiling the corresponding source file. Note that
14958 this makes @value{GDBN} delete all currently-defined breakpoints,
14959 auto-displays, and convenience variables, and to clear the value
14960 history. (This is necessary in order to preserve the integrity of
14961 debugger's data structures that reference the target system's symbol
14964 @node VxWorks Attach
14965 @subsubsection Running Tasks
14967 @cindex running VxWorks tasks
14968 You can also attach to an existing task using the @code{attach} command as
14972 (vxgdb) attach @var{task}
14976 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14977 or suspended when you attach to it. Running tasks are suspended at
14978 the time of attachment.
14980 @node Embedded Processors
14981 @section Embedded Processors
14983 This section goes into details specific to particular embedded
14986 @cindex send command to simulator
14987 Whenever a specific embedded processor has a simulator, @value{GDBN}
14988 allows to send an arbitrary command to the simulator.
14991 @item sim @var{command}
14992 @kindex sim@r{, a command}
14993 Send an arbitrary @var{command} string to the simulator. Consult the
14994 documentation for the specific simulator in use for information about
14995 acceptable commands.
15001 * M32R/D:: Renesas M32R/D
15002 * M68K:: Motorola M68K
15003 * MIPS Embedded:: MIPS Embedded
15004 * OpenRISC 1000:: OpenRisc 1000
15005 * PA:: HP PA Embedded
15006 * PowerPC Embedded:: PowerPC Embedded
15007 * Sparclet:: Tsqware Sparclet
15008 * Sparclite:: Fujitsu Sparclite
15009 * Z8000:: Zilog Z8000
15012 * Super-H:: Renesas Super-H
15021 @item target rdi @var{dev}
15022 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15023 use this target to communicate with both boards running the Angel
15024 monitor, or with the EmbeddedICE JTAG debug device.
15027 @item target rdp @var{dev}
15032 @value{GDBN} provides the following ARM-specific commands:
15035 @item set arm disassembler
15037 This commands selects from a list of disassembly styles. The
15038 @code{"std"} style is the standard style.
15040 @item show arm disassembler
15042 Show the current disassembly style.
15044 @item set arm apcs32
15045 @cindex ARM 32-bit mode
15046 This command toggles ARM operation mode between 32-bit and 26-bit.
15048 @item show arm apcs32
15049 Display the current usage of the ARM 32-bit mode.
15051 @item set arm fpu @var{fputype}
15052 This command sets the ARM floating-point unit (FPU) type. The
15053 argument @var{fputype} can be one of these:
15057 Determine the FPU type by querying the OS ABI.
15059 Software FPU, with mixed-endian doubles on little-endian ARM
15062 GCC-compiled FPA co-processor.
15064 Software FPU with pure-endian doubles.
15070 Show the current type of the FPU.
15073 This command forces @value{GDBN} to use the specified ABI.
15076 Show the currently used ABI.
15078 @item set arm fallback-mode (arm|thumb|auto)
15079 @value{GDBN} uses the symbol table, when available, to determine
15080 whether instructions are ARM or Thumb. This command controls
15081 @value{GDBN}'s default behavior when the symbol table is not
15082 available. The default is @samp{auto}, which causes @value{GDBN} to
15083 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15086 @item show arm fallback-mode
15087 Show the current fallback instruction mode.
15089 @item set arm force-mode (arm|thumb|auto)
15090 This command overrides use of the symbol table to determine whether
15091 instructions are ARM or Thumb. The default is @samp{auto}, which
15092 causes @value{GDBN} to use the symbol table and then the setting
15093 of @samp{set arm fallback-mode}.
15095 @item show arm force-mode
15096 Show the current forced instruction mode.
15098 @item set debug arm
15099 Toggle whether to display ARM-specific debugging messages from the ARM
15100 target support subsystem.
15102 @item show debug arm
15103 Show whether ARM-specific debugging messages are enabled.
15106 The following commands are available when an ARM target is debugged
15107 using the RDI interface:
15110 @item rdilogfile @r{[}@var{file}@r{]}
15112 @cindex ADP (Angel Debugger Protocol) logging
15113 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15114 With an argument, sets the log file to the specified @var{file}. With
15115 no argument, show the current log file name. The default log file is
15118 @item rdilogenable @r{[}@var{arg}@r{]}
15119 @kindex rdilogenable
15120 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15121 enables logging, with an argument 0 or @code{"no"} disables it. With
15122 no arguments displays the current setting. When logging is enabled,
15123 ADP packets exchanged between @value{GDBN} and the RDI target device
15124 are logged to a file.
15126 @item set rdiromatzero
15127 @kindex set rdiromatzero
15128 @cindex ROM at zero address, RDI
15129 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15130 vector catching is disabled, so that zero address can be used. If off
15131 (the default), vector catching is enabled. For this command to take
15132 effect, it needs to be invoked prior to the @code{target rdi} command.
15134 @item show rdiromatzero
15135 @kindex show rdiromatzero
15136 Show the current setting of ROM at zero address.
15138 @item set rdiheartbeat
15139 @kindex set rdiheartbeat
15140 @cindex RDI heartbeat
15141 Enable or disable RDI heartbeat packets. It is not recommended to
15142 turn on this option, since it confuses ARM and EPI JTAG interface, as
15143 well as the Angel monitor.
15145 @item show rdiheartbeat
15146 @kindex show rdiheartbeat
15147 Show the setting of RDI heartbeat packets.
15152 @subsection Renesas M32R/D and M32R/SDI
15155 @kindex target m32r
15156 @item target m32r @var{dev}
15157 Renesas M32R/D ROM monitor.
15159 @kindex target m32rsdi
15160 @item target m32rsdi @var{dev}
15161 Renesas M32R SDI server, connected via parallel port to the board.
15164 The following @value{GDBN} commands are specific to the M32R monitor:
15167 @item set download-path @var{path}
15168 @kindex set download-path
15169 @cindex find downloadable @sc{srec} files (M32R)
15170 Set the default path for finding downloadable @sc{srec} files.
15172 @item show download-path
15173 @kindex show download-path
15174 Show the default path for downloadable @sc{srec} files.
15176 @item set board-address @var{addr}
15177 @kindex set board-address
15178 @cindex M32-EVA target board address
15179 Set the IP address for the M32R-EVA target board.
15181 @item show board-address
15182 @kindex show board-address
15183 Show the current IP address of the target board.
15185 @item set server-address @var{addr}
15186 @kindex set server-address
15187 @cindex download server address (M32R)
15188 Set the IP address for the download server, which is the @value{GDBN}'s
15191 @item show server-address
15192 @kindex show server-address
15193 Display the IP address of the download server.
15195 @item upload @r{[}@var{file}@r{]}
15196 @kindex upload@r{, M32R}
15197 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
15198 upload capability. If no @var{file} argument is given, the current
15199 executable file is uploaded.
15201 @item tload @r{[}@var{file}@r{]}
15202 @kindex tload@r{, M32R}
15203 Test the @code{upload} command.
15206 The following commands are available for M32R/SDI:
15211 @cindex reset SDI connection, M32R
15212 This command resets the SDI connection.
15216 This command shows the SDI connection status.
15219 @kindex debug_chaos
15220 @cindex M32R/Chaos debugging
15221 Instructs the remote that M32R/Chaos debugging is to be used.
15223 @item use_debug_dma
15224 @kindex use_debug_dma
15225 Instructs the remote to use the DEBUG_DMA method of accessing memory.
15228 @kindex use_mon_code
15229 Instructs the remote to use the MON_CODE method of accessing memory.
15232 @kindex use_ib_break
15233 Instructs the remote to set breakpoints by IB break.
15235 @item use_dbt_break
15236 @kindex use_dbt_break
15237 Instructs the remote to set breakpoints by DBT.
15243 The Motorola m68k configuration includes ColdFire support, and a
15244 target command for the following ROM monitor.
15248 @kindex target dbug
15249 @item target dbug @var{dev}
15250 dBUG ROM monitor for Motorola ColdFire.
15254 @node MIPS Embedded
15255 @subsection MIPS Embedded
15257 @cindex MIPS boards
15258 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15259 MIPS board attached to a serial line. This is available when
15260 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15263 Use these @value{GDBN} commands to specify the connection to your target board:
15266 @item target mips @var{port}
15267 @kindex target mips @var{port}
15268 To run a program on the board, start up @code{@value{GDBP}} with the
15269 name of your program as the argument. To connect to the board, use the
15270 command @samp{target mips @var{port}}, where @var{port} is the name of
15271 the serial port connected to the board. If the program has not already
15272 been downloaded to the board, you may use the @code{load} command to
15273 download it. You can then use all the usual @value{GDBN} commands.
15275 For example, this sequence connects to the target board through a serial
15276 port, and loads and runs a program called @var{prog} through the
15280 host$ @value{GDBP} @var{prog}
15281 @value{GDBN} is free software and @dots{}
15282 (@value{GDBP}) target mips /dev/ttyb
15283 (@value{GDBP}) load @var{prog}
15287 @item target mips @var{hostname}:@var{portnumber}
15288 On some @value{GDBN} host configurations, you can specify a TCP
15289 connection (for instance, to a serial line managed by a terminal
15290 concentrator) instead of a serial port, using the syntax
15291 @samp{@var{hostname}:@var{portnumber}}.
15293 @item target pmon @var{port}
15294 @kindex target pmon @var{port}
15297 @item target ddb @var{port}
15298 @kindex target ddb @var{port}
15299 NEC's DDB variant of PMON for Vr4300.
15301 @item target lsi @var{port}
15302 @kindex target lsi @var{port}
15303 LSI variant of PMON.
15305 @kindex target r3900
15306 @item target r3900 @var{dev}
15307 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
15309 @kindex target array
15310 @item target array @var{dev}
15311 Array Tech LSI33K RAID controller board.
15317 @value{GDBN} also supports these special commands for MIPS targets:
15320 @item set mipsfpu double
15321 @itemx set mipsfpu single
15322 @itemx set mipsfpu none
15323 @itemx set mipsfpu auto
15324 @itemx show mipsfpu
15325 @kindex set mipsfpu
15326 @kindex show mipsfpu
15327 @cindex MIPS remote floating point
15328 @cindex floating point, MIPS remote
15329 If your target board does not support the MIPS floating point
15330 coprocessor, you should use the command @samp{set mipsfpu none} (if you
15331 need this, you may wish to put the command in your @value{GDBN} init
15332 file). This tells @value{GDBN} how to find the return value of
15333 functions which return floating point values. It also allows
15334 @value{GDBN} to avoid saving the floating point registers when calling
15335 functions on the board. If you are using a floating point coprocessor
15336 with only single precision floating point support, as on the @sc{r4650}
15337 processor, use the command @samp{set mipsfpu single}. The default
15338 double precision floating point coprocessor may be selected using
15339 @samp{set mipsfpu double}.
15341 In previous versions the only choices were double precision or no
15342 floating point, so @samp{set mipsfpu on} will select double precision
15343 and @samp{set mipsfpu off} will select no floating point.
15345 As usual, you can inquire about the @code{mipsfpu} variable with
15346 @samp{show mipsfpu}.
15348 @item set timeout @var{seconds}
15349 @itemx set retransmit-timeout @var{seconds}
15350 @itemx show timeout
15351 @itemx show retransmit-timeout
15352 @cindex @code{timeout}, MIPS protocol
15353 @cindex @code{retransmit-timeout}, MIPS protocol
15354 @kindex set timeout
15355 @kindex show timeout
15356 @kindex set retransmit-timeout
15357 @kindex show retransmit-timeout
15358 You can control the timeout used while waiting for a packet, in the MIPS
15359 remote protocol, with the @code{set timeout @var{seconds}} command. The
15360 default is 5 seconds. Similarly, you can control the timeout used while
15361 waiting for an acknowledgement of a packet with the @code{set
15362 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
15363 You can inspect both values with @code{show timeout} and @code{show
15364 retransmit-timeout}. (These commands are @emph{only} available when
15365 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
15367 The timeout set by @code{set timeout} does not apply when @value{GDBN}
15368 is waiting for your program to stop. In that case, @value{GDBN} waits
15369 forever because it has no way of knowing how long the program is going
15370 to run before stopping.
15372 @item set syn-garbage-limit @var{num}
15373 @kindex set syn-garbage-limit@r{, MIPS remote}
15374 @cindex synchronize with remote MIPS target
15375 Limit the maximum number of characters @value{GDBN} should ignore when
15376 it tries to synchronize with the remote target. The default is 10
15377 characters. Setting the limit to -1 means there's no limit.
15379 @item show syn-garbage-limit
15380 @kindex show syn-garbage-limit@r{, MIPS remote}
15381 Show the current limit on the number of characters to ignore when
15382 trying to synchronize with the remote system.
15384 @item set monitor-prompt @var{prompt}
15385 @kindex set monitor-prompt@r{, MIPS remote}
15386 @cindex remote monitor prompt
15387 Tell @value{GDBN} to expect the specified @var{prompt} string from the
15388 remote monitor. The default depends on the target:
15398 @item show monitor-prompt
15399 @kindex show monitor-prompt@r{, MIPS remote}
15400 Show the current strings @value{GDBN} expects as the prompt from the
15403 @item set monitor-warnings
15404 @kindex set monitor-warnings@r{, MIPS remote}
15405 Enable or disable monitor warnings about hardware breakpoints. This
15406 has effect only for the @code{lsi} target. When on, @value{GDBN} will
15407 display warning messages whose codes are returned by the @code{lsi}
15408 PMON monitor for breakpoint commands.
15410 @item show monitor-warnings
15411 @kindex show monitor-warnings@r{, MIPS remote}
15412 Show the current setting of printing monitor warnings.
15414 @item pmon @var{command}
15415 @kindex pmon@r{, MIPS remote}
15416 @cindex send PMON command
15417 This command allows sending an arbitrary @var{command} string to the
15418 monitor. The monitor must be in debug mode for this to work.
15421 @node OpenRISC 1000
15422 @subsection OpenRISC 1000
15423 @cindex OpenRISC 1000
15425 @cindex or1k boards
15426 See OR1k Architecture document (@uref{www.opencores.org}) for more information
15427 about platform and commands.
15431 @kindex target jtag
15432 @item target jtag jtag://@var{host}:@var{port}
15434 Connects to remote JTAG server.
15435 JTAG remote server can be either an or1ksim or JTAG server,
15436 connected via parallel port to the board.
15438 Example: @code{target jtag jtag://localhost:9999}
15441 @item or1ksim @var{command}
15442 If connected to @code{or1ksim} OpenRISC 1000 Architectural
15443 Simulator, proprietary commands can be executed.
15445 @kindex info or1k spr
15446 @item info or1k spr
15447 Displays spr groups.
15449 @item info or1k spr @var{group}
15450 @itemx info or1k spr @var{groupno}
15451 Displays register names in selected group.
15453 @item info or1k spr @var{group} @var{register}
15454 @itemx info or1k spr @var{register}
15455 @itemx info or1k spr @var{groupno} @var{registerno}
15456 @itemx info or1k spr @var{registerno}
15457 Shows information about specified spr register.
15460 @item spr @var{group} @var{register} @var{value}
15461 @itemx spr @var{register @var{value}}
15462 @itemx spr @var{groupno} @var{registerno @var{value}}
15463 @itemx spr @var{registerno @var{value}}
15464 Writes @var{value} to specified spr register.
15467 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15468 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15469 program execution and is thus much faster. Hardware breakpoints/watchpoint
15470 triggers can be set using:
15473 Load effective address/data
15475 Store effective address/data
15477 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15482 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15483 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15485 @code{htrace} commands:
15486 @cindex OpenRISC 1000 htrace
15489 @item hwatch @var{conditional}
15490 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15491 or Data. For example:
15493 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15495 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15499 Display information about current HW trace configuration.
15501 @item htrace trigger @var{conditional}
15502 Set starting criteria for HW trace.
15504 @item htrace qualifier @var{conditional}
15505 Set acquisition qualifier for HW trace.
15507 @item htrace stop @var{conditional}
15508 Set HW trace stopping criteria.
15510 @item htrace record [@var{data}]*
15511 Selects the data to be recorded, when qualifier is met and HW trace was
15514 @item htrace enable
15515 @itemx htrace disable
15516 Enables/disables the HW trace.
15518 @item htrace rewind [@var{filename}]
15519 Clears currently recorded trace data.
15521 If filename is specified, new trace file is made and any newly collected data
15522 will be written there.
15524 @item htrace print [@var{start} [@var{len}]]
15525 Prints trace buffer, using current record configuration.
15527 @item htrace mode continuous
15528 Set continuous trace mode.
15530 @item htrace mode suspend
15531 Set suspend trace mode.
15535 @node PowerPC Embedded
15536 @subsection PowerPC Embedded
15538 @value{GDBN} provides the following PowerPC-specific commands:
15541 @kindex set powerpc
15542 @item set powerpc soft-float
15543 @itemx show powerpc soft-float
15544 Force @value{GDBN} to use (or not use) a software floating point calling
15545 convention. By default, @value{GDBN} selects the calling convention based
15546 on the selected architecture and the provided executable file.
15548 @item set powerpc vector-abi
15549 @itemx show powerpc vector-abi
15550 Force @value{GDBN} to use the specified calling convention for vector
15551 arguments and return values. The valid options are @samp{auto};
15552 @samp{generic}, to avoid vector registers even if they are present;
15553 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15554 registers. By default, @value{GDBN} selects the calling convention
15555 based on the selected architecture and the provided executable file.
15557 @kindex target dink32
15558 @item target dink32 @var{dev}
15559 DINK32 ROM monitor.
15561 @kindex target ppcbug
15562 @item target ppcbug @var{dev}
15563 @kindex target ppcbug1
15564 @item target ppcbug1 @var{dev}
15565 PPCBUG ROM monitor for PowerPC.
15568 @item target sds @var{dev}
15569 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15572 @cindex SDS protocol
15573 The following commands specific to the SDS protocol are supported
15577 @item set sdstimeout @var{nsec}
15578 @kindex set sdstimeout
15579 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15580 default is 2 seconds.
15582 @item show sdstimeout
15583 @kindex show sdstimeout
15584 Show the current value of the SDS timeout.
15586 @item sds @var{command}
15587 @kindex sds@r{, a command}
15588 Send the specified @var{command} string to the SDS monitor.
15593 @subsection HP PA Embedded
15597 @kindex target op50n
15598 @item target op50n @var{dev}
15599 OP50N monitor, running on an OKI HPPA board.
15601 @kindex target w89k
15602 @item target w89k @var{dev}
15603 W89K monitor, running on a Winbond HPPA board.
15608 @subsection Tsqware Sparclet
15612 @value{GDBN} enables developers to debug tasks running on
15613 Sparclet targets from a Unix host.
15614 @value{GDBN} uses code that runs on
15615 both the Unix host and on the Sparclet target. The program
15616 @code{@value{GDBP}} is installed and executed on the Unix host.
15619 @item remotetimeout @var{args}
15620 @kindex remotetimeout
15621 @value{GDBN} supports the option @code{remotetimeout}.
15622 This option is set by the user, and @var{args} represents the number of
15623 seconds @value{GDBN} waits for responses.
15626 @cindex compiling, on Sparclet
15627 When compiling for debugging, include the options @samp{-g} to get debug
15628 information and @samp{-Ttext} to relocate the program to where you wish to
15629 load it on the target. You may also want to add the options @samp{-n} or
15630 @samp{-N} in order to reduce the size of the sections. Example:
15633 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15636 You can use @code{objdump} to verify that the addresses are what you intended:
15639 sparclet-aout-objdump --headers --syms prog
15642 @cindex running, on Sparclet
15644 your Unix execution search path to find @value{GDBN}, you are ready to
15645 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15646 (or @code{sparclet-aout-gdb}, depending on your installation).
15648 @value{GDBN} comes up showing the prompt:
15655 * Sparclet File:: Setting the file to debug
15656 * Sparclet Connection:: Connecting to Sparclet
15657 * Sparclet Download:: Sparclet download
15658 * Sparclet Execution:: Running and debugging
15661 @node Sparclet File
15662 @subsubsection Setting File to Debug
15664 The @value{GDBN} command @code{file} lets you choose with program to debug.
15667 (gdbslet) file prog
15671 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15672 @value{GDBN} locates
15673 the file by searching the directories listed in the command search
15675 If the file was compiled with debug information (option @samp{-g}), source
15676 files will be searched as well.
15677 @value{GDBN} locates
15678 the source files by searching the directories listed in the directory search
15679 path (@pxref{Environment, ,Your Program's Environment}).
15681 to find a file, it displays a message such as:
15684 prog: No such file or directory.
15687 When this happens, add the appropriate directories to the search paths with
15688 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15689 @code{target} command again.
15691 @node Sparclet Connection
15692 @subsubsection Connecting to Sparclet
15694 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15695 To connect to a target on serial port ``@code{ttya}'', type:
15698 (gdbslet) target sparclet /dev/ttya
15699 Remote target sparclet connected to /dev/ttya
15700 main () at ../prog.c:3
15704 @value{GDBN} displays messages like these:
15710 @node Sparclet Download
15711 @subsubsection Sparclet Download
15713 @cindex download to Sparclet
15714 Once connected to the Sparclet target,
15715 you can use the @value{GDBN}
15716 @code{load} command to download the file from the host to the target.
15717 The file name and load offset should be given as arguments to the @code{load}
15719 Since the file format is aout, the program must be loaded to the starting
15720 address. You can use @code{objdump} to find out what this value is. The load
15721 offset is an offset which is added to the VMA (virtual memory address)
15722 of each of the file's sections.
15723 For instance, if the program
15724 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15725 and bss at 0x12010170, in @value{GDBN}, type:
15728 (gdbslet) load prog 0x12010000
15729 Loading section .text, size 0xdb0 vma 0x12010000
15732 If the code is loaded at a different address then what the program was linked
15733 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15734 to tell @value{GDBN} where to map the symbol table.
15736 @node Sparclet Execution
15737 @subsubsection Running and Debugging
15739 @cindex running and debugging Sparclet programs
15740 You can now begin debugging the task using @value{GDBN}'s execution control
15741 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15742 manual for the list of commands.
15746 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15748 Starting program: prog
15749 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15750 3 char *symarg = 0;
15752 4 char *execarg = "hello!";
15757 @subsection Fujitsu Sparclite
15761 @kindex target sparclite
15762 @item target sparclite @var{dev}
15763 Fujitsu sparclite boards, used only for the purpose of loading.
15764 You must use an additional command to debug the program.
15765 For example: target remote @var{dev} using @value{GDBN} standard
15771 @subsection Zilog Z8000
15774 @cindex simulator, Z8000
15775 @cindex Zilog Z8000 simulator
15777 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15780 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15781 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15782 segmented variant). The simulator recognizes which architecture is
15783 appropriate by inspecting the object code.
15786 @item target sim @var{args}
15788 @kindex target sim@r{, with Z8000}
15789 Debug programs on a simulated CPU. If the simulator supports setup
15790 options, specify them via @var{args}.
15794 After specifying this target, you can debug programs for the simulated
15795 CPU in the same style as programs for your host computer; use the
15796 @code{file} command to load a new program image, the @code{run} command
15797 to run your program, and so on.
15799 As well as making available all the usual machine registers
15800 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15801 additional items of information as specially named registers:
15806 Counts clock-ticks in the simulator.
15809 Counts instructions run in the simulator.
15812 Execution time in 60ths of a second.
15816 You can refer to these values in @value{GDBN} expressions with the usual
15817 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15818 conditional breakpoint that suspends only after at least 5000
15819 simulated clock ticks.
15822 @subsection Atmel AVR
15825 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15826 following AVR-specific commands:
15829 @item info io_registers
15830 @kindex info io_registers@r{, AVR}
15831 @cindex I/O registers (Atmel AVR)
15832 This command displays information about the AVR I/O registers. For
15833 each register, @value{GDBN} prints its number and value.
15840 When configured for debugging CRIS, @value{GDBN} provides the
15841 following CRIS-specific commands:
15844 @item set cris-version @var{ver}
15845 @cindex CRIS version
15846 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15847 The CRIS version affects register names and sizes. This command is useful in
15848 case autodetection of the CRIS version fails.
15850 @item show cris-version
15851 Show the current CRIS version.
15853 @item set cris-dwarf2-cfi
15854 @cindex DWARF-2 CFI and CRIS
15855 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15856 Change to @samp{off} when using @code{gcc-cris} whose version is below
15859 @item show cris-dwarf2-cfi
15860 Show the current state of using DWARF-2 CFI.
15862 @item set cris-mode @var{mode}
15864 Set the current CRIS mode to @var{mode}. It should only be changed when
15865 debugging in guru mode, in which case it should be set to
15866 @samp{guru} (the default is @samp{normal}).
15868 @item show cris-mode
15869 Show the current CRIS mode.
15873 @subsection Renesas Super-H
15876 For the Renesas Super-H processor, @value{GDBN} provides these
15881 @kindex regs@r{, Super-H}
15882 Show the values of all Super-H registers.
15884 @item set sh calling-convention @var{convention}
15885 @kindex set sh calling-convention
15886 Set the calling-convention used when calling functions from @value{GDBN}.
15887 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
15888 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
15889 convention. If the DWARF-2 information of the called function specifies
15890 that the function follows the Renesas calling convention, the function
15891 is called using the Renesas calling convention. If the calling convention
15892 is set to @samp{renesas}, the Renesas calling convention is always used,
15893 regardless of the DWARF-2 information. This can be used to override the
15894 default of @samp{gcc} if debug information is missing, or the compiler
15895 does not emit the DWARF-2 calling convention entry for a function.
15897 @item show sh calling-convention
15898 @kindex show sh calling-convention
15899 Show the current calling convention setting.
15904 @node Architectures
15905 @section Architectures
15907 This section describes characteristics of architectures that affect
15908 all uses of @value{GDBN} with the architecture, both native and cross.
15915 * HPPA:: HP PA architecture
15916 * SPU:: Cell Broadband Engine SPU architecture
15921 @subsection x86 Architecture-specific Issues
15924 @item set struct-convention @var{mode}
15925 @kindex set struct-convention
15926 @cindex struct return convention
15927 @cindex struct/union returned in registers
15928 Set the convention used by the inferior to return @code{struct}s and
15929 @code{union}s from functions to @var{mode}. Possible values of
15930 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15931 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15932 are returned on the stack, while @code{"reg"} means that a
15933 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15934 be returned in a register.
15936 @item show struct-convention
15937 @kindex show struct-convention
15938 Show the current setting of the convention to return @code{struct}s
15947 @kindex set rstack_high_address
15948 @cindex AMD 29K register stack
15949 @cindex register stack, AMD29K
15950 @item set rstack_high_address @var{address}
15951 On AMD 29000 family processors, registers are saved in a separate
15952 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15953 extent of this stack. Normally, @value{GDBN} just assumes that the
15954 stack is ``large enough''. This may result in @value{GDBN} referencing
15955 memory locations that do not exist. If necessary, you can get around
15956 this problem by specifying the ending address of the register stack with
15957 the @code{set rstack_high_address} command. The argument should be an
15958 address, which you probably want to precede with @samp{0x} to specify in
15961 @kindex show rstack_high_address
15962 @item show rstack_high_address
15963 Display the current limit of the register stack, on AMD 29000 family
15971 See the following section.
15976 @cindex stack on Alpha
15977 @cindex stack on MIPS
15978 @cindex Alpha stack
15980 Alpha- and MIPS-based computers use an unusual stack frame, which
15981 sometimes requires @value{GDBN} to search backward in the object code to
15982 find the beginning of a function.
15984 @cindex response time, MIPS debugging
15985 To improve response time (especially for embedded applications, where
15986 @value{GDBN} may be restricted to a slow serial line for this search)
15987 you may want to limit the size of this search, using one of these
15991 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15992 @item set heuristic-fence-post @var{limit}
15993 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15994 search for the beginning of a function. A value of @var{0} (the
15995 default) means there is no limit. However, except for @var{0}, the
15996 larger the limit the more bytes @code{heuristic-fence-post} must search
15997 and therefore the longer it takes to run. You should only need to use
15998 this command when debugging a stripped executable.
16000 @item show heuristic-fence-post
16001 Display the current limit.
16005 These commands are available @emph{only} when @value{GDBN} is configured
16006 for debugging programs on Alpha or MIPS processors.
16008 Several MIPS-specific commands are available when debugging MIPS
16012 @item set mips abi @var{arg}
16013 @kindex set mips abi
16014 @cindex set ABI for MIPS
16015 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16016 values of @var{arg} are:
16020 The default ABI associated with the current binary (this is the
16031 @item show mips abi
16032 @kindex show mips abi
16033 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16036 @itemx show mipsfpu
16037 @xref{MIPS Embedded, set mipsfpu}.
16039 @item set mips mask-address @var{arg}
16040 @kindex set mips mask-address
16041 @cindex MIPS addresses, masking
16042 This command determines whether the most-significant 32 bits of 64-bit
16043 MIPS addresses are masked off. The argument @var{arg} can be
16044 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16045 setting, which lets @value{GDBN} determine the correct value.
16047 @item show mips mask-address
16048 @kindex show mips mask-address
16049 Show whether the upper 32 bits of MIPS addresses are masked off or
16052 @item set remote-mips64-transfers-32bit-regs
16053 @kindex set remote-mips64-transfers-32bit-regs
16054 This command controls compatibility with 64-bit MIPS targets that
16055 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16056 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16057 and 64 bits for other registers, set this option to @samp{on}.
16059 @item show remote-mips64-transfers-32bit-regs
16060 @kindex show remote-mips64-transfers-32bit-regs
16061 Show the current setting of compatibility with older MIPS 64 targets.
16063 @item set debug mips
16064 @kindex set debug mips
16065 This command turns on and off debugging messages for the MIPS-specific
16066 target code in @value{GDBN}.
16068 @item show debug mips
16069 @kindex show debug mips
16070 Show the current setting of MIPS debugging messages.
16076 @cindex HPPA support
16078 When @value{GDBN} is debugging the HP PA architecture, it provides the
16079 following special commands:
16082 @item set debug hppa
16083 @kindex set debug hppa
16084 This command determines whether HPPA architecture-specific debugging
16085 messages are to be displayed.
16087 @item show debug hppa
16088 Show whether HPPA debugging messages are displayed.
16090 @item maint print unwind @var{address}
16091 @kindex maint print unwind@r{, HPPA}
16092 This command displays the contents of the unwind table entry at the
16093 given @var{address}.
16099 @subsection Cell Broadband Engine SPU architecture
16100 @cindex Cell Broadband Engine
16103 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16104 it provides the following special commands:
16107 @item info spu event
16109 Display SPU event facility status. Shows current event mask
16110 and pending event status.
16112 @item info spu signal
16113 Display SPU signal notification facility status. Shows pending
16114 signal-control word and signal notification mode of both signal
16115 notification channels.
16117 @item info spu mailbox
16118 Display SPU mailbox facility status. Shows all pending entries,
16119 in order of processing, in each of the SPU Write Outbound,
16120 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16123 Display MFC DMA status. Shows all pending commands in the MFC
16124 DMA queue. For each entry, opcode, tag, class IDs, effective
16125 and local store addresses and transfer size are shown.
16127 @item info spu proxydma
16128 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16129 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16130 and local store addresses and transfer size are shown.
16135 @subsection PowerPC
16136 @cindex PowerPC architecture
16138 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16139 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16140 numbers stored in the floating point registers. These values must be stored
16141 in two consecutive registers, always starting at an even register like
16142 @code{f0} or @code{f2}.
16144 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16145 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16146 @code{f2} and @code{f3} for @code{$dl1} and so on.
16149 @node Controlling GDB
16150 @chapter Controlling @value{GDBN}
16152 You can alter the way @value{GDBN} interacts with you by using the
16153 @code{set} command. For commands controlling how @value{GDBN} displays
16154 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16159 * Editing:: Command editing
16160 * Command History:: Command history
16161 * Screen Size:: Screen size
16162 * Numbers:: Numbers
16163 * ABI:: Configuring the current ABI
16164 * Messages/Warnings:: Optional warnings and messages
16165 * Debugging Output:: Optional messages about internal happenings
16173 @value{GDBN} indicates its readiness to read a command by printing a string
16174 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
16175 can change the prompt string with the @code{set prompt} command. For
16176 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
16177 the prompt in one of the @value{GDBN} sessions so that you can always tell
16178 which one you are talking to.
16180 @emph{Note:} @code{set prompt} does not add a space for you after the
16181 prompt you set. This allows you to set a prompt which ends in a space
16182 or a prompt that does not.
16186 @item set prompt @var{newprompt}
16187 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
16189 @kindex show prompt
16191 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
16195 @section Command Editing
16197 @cindex command line editing
16199 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
16200 @sc{gnu} library provides consistent behavior for programs which provide a
16201 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16202 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16203 substitution, and a storage and recall of command history across
16204 debugging sessions.
16206 You may control the behavior of command line editing in @value{GDBN} with the
16207 command @code{set}.
16210 @kindex set editing
16213 @itemx set editing on
16214 Enable command line editing (enabled by default).
16216 @item set editing off
16217 Disable command line editing.
16219 @kindex show editing
16221 Show whether command line editing is enabled.
16224 @xref{Command Line Editing}, for more details about the Readline
16225 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
16226 encouraged to read that chapter.
16228 @node Command History
16229 @section Command History
16230 @cindex command history
16232 @value{GDBN} can keep track of the commands you type during your
16233 debugging sessions, so that you can be certain of precisely what
16234 happened. Use these commands to manage the @value{GDBN} command
16237 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
16238 package, to provide the history facility. @xref{Using History
16239 Interactively}, for the detailed description of the History library.
16241 To issue a command to @value{GDBN} without affecting certain aspects of
16242 the state which is seen by users, prefix it with @samp{server }
16243 (@pxref{Server Prefix}). This
16244 means that this command will not affect the command history, nor will it
16245 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
16246 pressed on a line by itself.
16248 @cindex @code{server}, command prefix
16249 The server prefix does not affect the recording of values into the value
16250 history; to print a value without recording it into the value history,
16251 use the @code{output} command instead of the @code{print} command.
16253 Here is the description of @value{GDBN} commands related to command
16257 @cindex history substitution
16258 @cindex history file
16259 @kindex set history filename
16260 @cindex @env{GDBHISTFILE}, environment variable
16261 @item set history filename @var{fname}
16262 Set the name of the @value{GDBN} command history file to @var{fname}.
16263 This is the file where @value{GDBN} reads an initial command history
16264 list, and where it writes the command history from this session when it
16265 exits. You can access this list through history expansion or through
16266 the history command editing characters listed below. This file defaults
16267 to the value of the environment variable @code{GDBHISTFILE}, or to
16268 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16271 @cindex save command history
16272 @kindex set history save
16273 @item set history save
16274 @itemx set history save on
16275 Record command history in a file, whose name may be specified with the
16276 @code{set history filename} command. By default, this option is disabled.
16278 @item set history save off
16279 Stop recording command history in a file.
16281 @cindex history size
16282 @kindex set history size
16283 @cindex @env{HISTSIZE}, environment variable
16284 @item set history size @var{size}
16285 Set the number of commands which @value{GDBN} keeps in its history list.
16286 This defaults to the value of the environment variable
16287 @code{HISTSIZE}, or to 256 if this variable is not set.
16290 History expansion assigns special meaning to the character @kbd{!}.
16291 @xref{Event Designators}, for more details.
16293 @cindex history expansion, turn on/off
16294 Since @kbd{!} is also the logical not operator in C, history expansion
16295 is off by default. If you decide to enable history expansion with the
16296 @code{set history expansion on} command, you may sometimes need to
16297 follow @kbd{!} (when it is used as logical not, in an expression) with
16298 a space or a tab to prevent it from being expanded. The readline
16299 history facilities do not attempt substitution on the strings
16300 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
16302 The commands to control history expansion are:
16305 @item set history expansion on
16306 @itemx set history expansion
16307 @kindex set history expansion
16308 Enable history expansion. History expansion is off by default.
16310 @item set history expansion off
16311 Disable history expansion.
16314 @kindex show history
16316 @itemx show history filename
16317 @itemx show history save
16318 @itemx show history size
16319 @itemx show history expansion
16320 These commands display the state of the @value{GDBN} history parameters.
16321 @code{show history} by itself displays all four states.
16326 @kindex show commands
16327 @cindex show last commands
16328 @cindex display command history
16329 @item show commands
16330 Display the last ten commands in the command history.
16332 @item show commands @var{n}
16333 Print ten commands centered on command number @var{n}.
16335 @item show commands +
16336 Print ten commands just after the commands last printed.
16340 @section Screen Size
16341 @cindex size of screen
16342 @cindex pauses in output
16344 Certain commands to @value{GDBN} may produce large amounts of
16345 information output to the screen. To help you read all of it,
16346 @value{GDBN} pauses and asks you for input at the end of each page of
16347 output. Type @key{RET} when you want to continue the output, or @kbd{q}
16348 to discard the remaining output. Also, the screen width setting
16349 determines when to wrap lines of output. Depending on what is being
16350 printed, @value{GDBN} tries to break the line at a readable place,
16351 rather than simply letting it overflow onto the following line.
16353 Normally @value{GDBN} knows the size of the screen from the terminal
16354 driver software. For example, on Unix @value{GDBN} uses the termcap data base
16355 together with the value of the @code{TERM} environment variable and the
16356 @code{stty rows} and @code{stty cols} settings. If this is not correct,
16357 you can override it with the @code{set height} and @code{set
16364 @kindex show height
16365 @item set height @var{lpp}
16367 @itemx set width @var{cpl}
16369 These @code{set} commands specify a screen height of @var{lpp} lines and
16370 a screen width of @var{cpl} characters. The associated @code{show}
16371 commands display the current settings.
16373 If you specify a height of zero lines, @value{GDBN} does not pause during
16374 output no matter how long the output is. This is useful if output is to a
16375 file or to an editor buffer.
16377 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
16378 from wrapping its output.
16380 @item set pagination on
16381 @itemx set pagination off
16382 @kindex set pagination
16383 Turn the output pagination on or off; the default is on. Turning
16384 pagination off is the alternative to @code{set height 0}.
16386 @item show pagination
16387 @kindex show pagination
16388 Show the current pagination mode.
16393 @cindex number representation
16394 @cindex entering numbers
16396 You can always enter numbers in octal, decimal, or hexadecimal in
16397 @value{GDBN} by the usual conventions: octal numbers begin with
16398 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
16399 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
16400 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
16401 10; likewise, the default display for numbers---when no particular
16402 format is specified---is base 10. You can change the default base for
16403 both input and output with the commands described below.
16406 @kindex set input-radix
16407 @item set input-radix @var{base}
16408 Set the default base for numeric input. Supported choices
16409 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16410 specified either unambiguously or using the current input radix; for
16414 set input-radix 012
16415 set input-radix 10.
16416 set input-radix 0xa
16420 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
16421 leaves the input radix unchanged, no matter what it was, since
16422 @samp{10}, being without any leading or trailing signs of its base, is
16423 interpreted in the current radix. Thus, if the current radix is 16,
16424 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
16427 @kindex set output-radix
16428 @item set output-radix @var{base}
16429 Set the default base for numeric display. Supported choices
16430 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16431 specified either unambiguously or using the current input radix.
16433 @kindex show input-radix
16434 @item show input-radix
16435 Display the current default base for numeric input.
16437 @kindex show output-radix
16438 @item show output-radix
16439 Display the current default base for numeric display.
16441 @item set radix @r{[}@var{base}@r{]}
16445 These commands set and show the default base for both input and output
16446 of numbers. @code{set radix} sets the radix of input and output to
16447 the same base; without an argument, it resets the radix back to its
16448 default value of 10.
16453 @section Configuring the Current ABI
16455 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
16456 application automatically. However, sometimes you need to override its
16457 conclusions. Use these commands to manage @value{GDBN}'s view of the
16464 One @value{GDBN} configuration can debug binaries for multiple operating
16465 system targets, either via remote debugging or native emulation.
16466 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
16467 but you can override its conclusion using the @code{set osabi} command.
16468 One example where this is useful is in debugging of binaries which use
16469 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16470 not have the same identifying marks that the standard C library for your
16475 Show the OS ABI currently in use.
16478 With no argument, show the list of registered available OS ABI's.
16480 @item set osabi @var{abi}
16481 Set the current OS ABI to @var{abi}.
16484 @cindex float promotion
16486 Generally, the way that an argument of type @code{float} is passed to a
16487 function depends on whether the function is prototyped. For a prototyped
16488 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16489 according to the architecture's convention for @code{float}. For unprototyped
16490 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16491 @code{double} and then passed.
16493 Unfortunately, some forms of debug information do not reliably indicate whether
16494 a function is prototyped. If @value{GDBN} calls a function that is not marked
16495 as prototyped, it consults @kbd{set coerce-float-to-double}.
16498 @kindex set coerce-float-to-double
16499 @item set coerce-float-to-double
16500 @itemx set coerce-float-to-double on
16501 Arguments of type @code{float} will be promoted to @code{double} when passed
16502 to an unprototyped function. This is the default setting.
16504 @item set coerce-float-to-double off
16505 Arguments of type @code{float} will be passed directly to unprototyped
16508 @kindex show coerce-float-to-double
16509 @item show coerce-float-to-double
16510 Show the current setting of promoting @code{float} to @code{double}.
16514 @kindex show cp-abi
16515 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16516 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16517 used to build your application. @value{GDBN} only fully supports
16518 programs with a single C@t{++} ABI; if your program contains code using
16519 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16520 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16521 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16522 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16523 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16524 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16529 Show the C@t{++} ABI currently in use.
16532 With no argument, show the list of supported C@t{++} ABI's.
16534 @item set cp-abi @var{abi}
16535 @itemx set cp-abi auto
16536 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16539 @node Messages/Warnings
16540 @section Optional Warnings and Messages
16542 @cindex verbose operation
16543 @cindex optional warnings
16544 By default, @value{GDBN} is silent about its inner workings. If you are
16545 running on a slow machine, you may want to use the @code{set verbose}
16546 command. This makes @value{GDBN} tell you when it does a lengthy
16547 internal operation, so you will not think it has crashed.
16549 Currently, the messages controlled by @code{set verbose} are those
16550 which announce that the symbol table for a source file is being read;
16551 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16554 @kindex set verbose
16555 @item set verbose on
16556 Enables @value{GDBN} output of certain informational messages.
16558 @item set verbose off
16559 Disables @value{GDBN} output of certain informational messages.
16561 @kindex show verbose
16563 Displays whether @code{set verbose} is on or off.
16566 By default, if @value{GDBN} encounters bugs in the symbol table of an
16567 object file, it is silent; but if you are debugging a compiler, you may
16568 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16573 @kindex set complaints
16574 @item set complaints @var{limit}
16575 Permits @value{GDBN} to output @var{limit} complaints about each type of
16576 unusual symbols before becoming silent about the problem. Set
16577 @var{limit} to zero to suppress all complaints; set it to a large number
16578 to prevent complaints from being suppressed.
16580 @kindex show complaints
16581 @item show complaints
16582 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16586 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16587 lot of stupid questions to confirm certain commands. For example, if
16588 you try to run a program which is already running:
16592 The program being debugged has been started already.
16593 Start it from the beginning? (y or n)
16596 If you are willing to unflinchingly face the consequences of your own
16597 commands, you can disable this ``feature'':
16601 @kindex set confirm
16603 @cindex confirmation
16604 @cindex stupid questions
16605 @item set confirm off
16606 Disables confirmation requests.
16608 @item set confirm on
16609 Enables confirmation requests (the default).
16611 @kindex show confirm
16613 Displays state of confirmation requests.
16617 @cindex command tracing
16618 If you need to debug user-defined commands or sourced files you may find it
16619 useful to enable @dfn{command tracing}. In this mode each command will be
16620 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16621 quantity denoting the call depth of each command.
16624 @kindex set trace-commands
16625 @cindex command scripts, debugging
16626 @item set trace-commands on
16627 Enable command tracing.
16628 @item set trace-commands off
16629 Disable command tracing.
16630 @item show trace-commands
16631 Display the current state of command tracing.
16634 @node Debugging Output
16635 @section Optional Messages about Internal Happenings
16636 @cindex optional debugging messages
16638 @value{GDBN} has commands that enable optional debugging messages from
16639 various @value{GDBN} subsystems; normally these commands are of
16640 interest to @value{GDBN} maintainers, or when reporting a bug. This
16641 section documents those commands.
16644 @kindex set exec-done-display
16645 @item set exec-done-display
16646 Turns on or off the notification of asynchronous commands'
16647 completion. When on, @value{GDBN} will print a message when an
16648 asynchronous command finishes its execution. The default is off.
16649 @kindex show exec-done-display
16650 @item show exec-done-display
16651 Displays the current setting of asynchronous command completion
16654 @cindex gdbarch debugging info
16655 @cindex architecture debugging info
16656 @item set debug arch
16657 Turns on or off display of gdbarch debugging info. The default is off
16659 @item show debug arch
16660 Displays the current state of displaying gdbarch debugging info.
16661 @item set debug aix-thread
16662 @cindex AIX threads
16663 Display debugging messages about inner workings of the AIX thread
16665 @item show debug aix-thread
16666 Show the current state of AIX thread debugging info display.
16667 @item set debug displaced
16668 @cindex displaced stepping debugging info
16669 Turns on or off display of @value{GDBN} debugging info for the
16670 displaced stepping support. The default is off.
16671 @item show debug displaced
16672 Displays the current state of displaying @value{GDBN} debugging info
16673 related to displaced stepping.
16674 @item set debug event
16675 @cindex event debugging info
16676 Turns on or off display of @value{GDBN} event debugging info. The
16678 @item show debug event
16679 Displays the current state of displaying @value{GDBN} event debugging
16681 @item set debug expression
16682 @cindex expression debugging info
16683 Turns on or off display of debugging info about @value{GDBN}
16684 expression parsing. The default is off.
16685 @item show debug expression
16686 Displays the current state of displaying debugging info about
16687 @value{GDBN} expression parsing.
16688 @item set debug frame
16689 @cindex frame debugging info
16690 Turns on or off display of @value{GDBN} frame debugging info. The
16692 @item show debug frame
16693 Displays the current state of displaying @value{GDBN} frame debugging
16695 @item set debug infrun
16696 @cindex inferior debugging info
16697 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16698 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16699 for implementing operations such as single-stepping the inferior.
16700 @item show debug infrun
16701 Displays the current state of @value{GDBN} inferior debugging.
16702 @item set debug lin-lwp
16703 @cindex @sc{gnu}/Linux LWP debug messages
16704 @cindex Linux lightweight processes
16705 Turns on or off debugging messages from the Linux LWP debug support.
16706 @item show debug lin-lwp
16707 Show the current state of Linux LWP debugging messages.
16708 @item set debug lin-lwp-async
16709 @cindex @sc{gnu}/Linux LWP async debug messages
16710 @cindex Linux lightweight processes
16711 Turns on or off debugging messages from the Linux LWP async debug support.
16712 @item show debug lin-lwp-async
16713 Show the current state of Linux LWP async debugging messages.
16714 @item set debug observer
16715 @cindex observer debugging info
16716 Turns on or off display of @value{GDBN} observer debugging. This
16717 includes info such as the notification of observable events.
16718 @item show debug observer
16719 Displays the current state of observer debugging.
16720 @item set debug overload
16721 @cindex C@t{++} overload debugging info
16722 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16723 info. This includes info such as ranking of functions, etc. The default
16725 @item show debug overload
16726 Displays the current state of displaying @value{GDBN} C@t{++} overload
16728 @cindex packets, reporting on stdout
16729 @cindex serial connections, debugging
16730 @cindex debug remote protocol
16731 @cindex remote protocol debugging
16732 @cindex display remote packets
16733 @item set debug remote
16734 Turns on or off display of reports on all packets sent back and forth across
16735 the serial line to the remote machine. The info is printed on the
16736 @value{GDBN} standard output stream. The default is off.
16737 @item show debug remote
16738 Displays the state of display of remote packets.
16739 @item set debug serial
16740 Turns on or off display of @value{GDBN} serial debugging info. The
16742 @item show debug serial
16743 Displays the current state of displaying @value{GDBN} serial debugging
16745 @item set debug solib-frv
16746 @cindex FR-V shared-library debugging
16747 Turns on or off debugging messages for FR-V shared-library code.
16748 @item show debug solib-frv
16749 Display the current state of FR-V shared-library code debugging
16751 @item set debug target
16752 @cindex target debugging info
16753 Turns on or off display of @value{GDBN} target debugging info. This info
16754 includes what is going on at the target level of GDB, as it happens. The
16755 default is 0. Set it to 1 to track events, and to 2 to also track the
16756 value of large memory transfers. Changes to this flag do not take effect
16757 until the next time you connect to a target or use the @code{run} command.
16758 @item show debug target
16759 Displays the current state of displaying @value{GDBN} target debugging
16761 @item set debug timestamp
16762 @cindex timestampping debugging info
16763 Turns on or off display of timestamps with @value{GDBN} debugging info.
16764 When enabled, seconds and microseconds are displayed before each debugging
16766 @item show debug timestamp
16767 Displays the current state of displaying timestamps with @value{GDBN}
16769 @item set debugvarobj
16770 @cindex variable object debugging info
16771 Turns on or off display of @value{GDBN} variable object debugging
16772 info. The default is off.
16773 @item show debugvarobj
16774 Displays the current state of displaying @value{GDBN} variable object
16776 @item set debug xml
16777 @cindex XML parser debugging
16778 Turns on or off debugging messages for built-in XML parsers.
16779 @item show debug xml
16780 Displays the current state of XML debugging messages.
16784 @chapter Canned Sequences of Commands
16786 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16787 Command Lists}), @value{GDBN} provides two ways to store sequences of
16788 commands for execution as a unit: user-defined commands and command
16792 * Define:: How to define your own commands
16793 * Hooks:: Hooks for user-defined commands
16794 * Command Files:: How to write scripts of commands to be stored in a file
16795 * Output:: Commands for controlled output
16799 @section User-defined Commands
16801 @cindex user-defined command
16802 @cindex arguments, to user-defined commands
16803 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16804 which you assign a new name as a command. This is done with the
16805 @code{define} command. User commands may accept up to 10 arguments
16806 separated by whitespace. Arguments are accessed within the user command
16807 via @code{$arg0@dots{}$arg9}. A trivial example:
16811 print $arg0 + $arg1 + $arg2
16816 To execute the command use:
16823 This defines the command @code{adder}, which prints the sum of
16824 its three arguments. Note the arguments are text substitutions, so they may
16825 reference variables, use complex expressions, or even perform inferior
16828 @cindex argument count in user-defined commands
16829 @cindex how many arguments (user-defined commands)
16830 In addition, @code{$argc} may be used to find out how many arguments have
16831 been passed. This expands to a number in the range 0@dots{}10.
16836 print $arg0 + $arg1
16839 print $arg0 + $arg1 + $arg2
16847 @item define @var{commandname}
16848 Define a command named @var{commandname}. If there is already a command
16849 by that name, you are asked to confirm that you want to redefine it.
16851 The definition of the command is made up of other @value{GDBN} command lines,
16852 which are given following the @code{define} command. The end of these
16853 commands is marked by a line containing @code{end}.
16856 @kindex end@r{ (user-defined commands)}
16857 @item document @var{commandname}
16858 Document the user-defined command @var{commandname}, so that it can be
16859 accessed by @code{help}. The command @var{commandname} must already be
16860 defined. This command reads lines of documentation just as @code{define}
16861 reads the lines of the command definition, ending with @code{end}.
16862 After the @code{document} command is finished, @code{help} on command
16863 @var{commandname} displays the documentation you have written.
16865 You may use the @code{document} command again to change the
16866 documentation of a command. Redefining the command with @code{define}
16867 does not change the documentation.
16869 @kindex dont-repeat
16870 @cindex don't repeat command
16872 Used inside a user-defined command, this tells @value{GDBN} that this
16873 command should not be repeated when the user hits @key{RET}
16874 (@pxref{Command Syntax, repeat last command}).
16876 @kindex help user-defined
16877 @item help user-defined
16878 List all user-defined commands, with the first line of the documentation
16883 @itemx show user @var{commandname}
16884 Display the @value{GDBN} commands used to define @var{commandname} (but
16885 not its documentation). If no @var{commandname} is given, display the
16886 definitions for all user-defined commands.
16888 @cindex infinite recursion in user-defined commands
16889 @kindex show max-user-call-depth
16890 @kindex set max-user-call-depth
16891 @item show max-user-call-depth
16892 @itemx set max-user-call-depth
16893 The value of @code{max-user-call-depth} controls how many recursion
16894 levels are allowed in user-defined commands before @value{GDBN} suspects an
16895 infinite recursion and aborts the command.
16898 In addition to the above commands, user-defined commands frequently
16899 use control flow commands, described in @ref{Command Files}.
16901 When user-defined commands are executed, the
16902 commands of the definition are not printed. An error in any command
16903 stops execution of the user-defined command.
16905 If used interactively, commands that would ask for confirmation proceed
16906 without asking when used inside a user-defined command. Many @value{GDBN}
16907 commands that normally print messages to say what they are doing omit the
16908 messages when used in a user-defined command.
16911 @section User-defined Command Hooks
16912 @cindex command hooks
16913 @cindex hooks, for commands
16914 @cindex hooks, pre-command
16917 You may define @dfn{hooks}, which are a special kind of user-defined
16918 command. Whenever you run the command @samp{foo}, if the user-defined
16919 command @samp{hook-foo} exists, it is executed (with no arguments)
16920 before that command.
16922 @cindex hooks, post-command
16924 A hook may also be defined which is run after the command you executed.
16925 Whenever you run the command @samp{foo}, if the user-defined command
16926 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16927 that command. Post-execution hooks may exist simultaneously with
16928 pre-execution hooks, for the same command.
16930 It is valid for a hook to call the command which it hooks. If this
16931 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16933 @c It would be nice if hookpost could be passed a parameter indicating
16934 @c if the command it hooks executed properly or not. FIXME!
16936 @kindex stop@r{, a pseudo-command}
16937 In addition, a pseudo-command, @samp{stop} exists. Defining
16938 (@samp{hook-stop}) makes the associated commands execute every time
16939 execution stops in your program: before breakpoint commands are run,
16940 displays are printed, or the stack frame is printed.
16942 For example, to ignore @code{SIGALRM} signals while
16943 single-stepping, but treat them normally during normal execution,
16948 handle SIGALRM nopass
16952 handle SIGALRM pass
16955 define hook-continue
16956 handle SIGALRM pass
16960 As a further example, to hook at the beginning and end of the @code{echo}
16961 command, and to add extra text to the beginning and end of the message,
16969 define hookpost-echo
16973 (@value{GDBP}) echo Hello World
16974 <<<---Hello World--->>>
16979 You can define a hook for any single-word command in @value{GDBN}, but
16980 not for command aliases; you should define a hook for the basic command
16981 name, e.g.@: @code{backtrace} rather than @code{bt}.
16982 @c FIXME! So how does Joe User discover whether a command is an alias
16984 If an error occurs during the execution of your hook, execution of
16985 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16986 (before the command that you actually typed had a chance to run).
16988 If you try to define a hook which does not match any known command, you
16989 get a warning from the @code{define} command.
16991 @node Command Files
16992 @section Command Files
16994 @cindex command files
16995 @cindex scripting commands
16996 A command file for @value{GDBN} is a text file made of lines that are
16997 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16998 also be included. An empty line in a command file does nothing; it
16999 does not mean to repeat the last command, as it would from the
17002 You can request the execution of a command file with the @code{source}
17007 @cindex execute commands from a file
17008 @item source [@code{-v}] @var{filename}
17009 Execute the command file @var{filename}.
17012 The lines in a command file are generally executed sequentially,
17013 unless the order of execution is changed by one of the
17014 @emph{flow-control commands} described below. The commands are not
17015 printed as they are executed. An error in any command terminates
17016 execution of the command file and control is returned to the console.
17018 @value{GDBN} searches for @var{filename} in the current directory and then
17019 on the search path (specified with the @samp{directory} command).
17021 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17022 each command as it is executed. The option must be given before
17023 @var{filename}, and is interpreted as part of the filename anywhere else.
17025 Commands that would ask for confirmation if used interactively proceed
17026 without asking when used in a command file. Many @value{GDBN} commands that
17027 normally print messages to say what they are doing omit the messages
17028 when called from command files.
17030 @value{GDBN} also accepts command input from standard input. In this
17031 mode, normal output goes to standard output and error output goes to
17032 standard error. Errors in a command file supplied on standard input do
17033 not terminate execution of the command file---execution continues with
17037 gdb < cmds > log 2>&1
17040 (The syntax above will vary depending on the shell used.) This example
17041 will execute commands from the file @file{cmds}. All output and errors
17042 would be directed to @file{log}.
17044 Since commands stored on command files tend to be more general than
17045 commands typed interactively, they frequently need to deal with
17046 complicated situations, such as different or unexpected values of
17047 variables and symbols, changes in how the program being debugged is
17048 built, etc. @value{GDBN} provides a set of flow-control commands to
17049 deal with these complexities. Using these commands, you can write
17050 complex scripts that loop over data structures, execute commands
17051 conditionally, etc.
17058 This command allows to include in your script conditionally executed
17059 commands. The @code{if} command takes a single argument, which is an
17060 expression to evaluate. It is followed by a series of commands that
17061 are executed only if the expression is true (its value is nonzero).
17062 There can then optionally be an @code{else} line, followed by a series
17063 of commands that are only executed if the expression was false. The
17064 end of the list is marked by a line containing @code{end}.
17068 This command allows to write loops. Its syntax is similar to
17069 @code{if}: the command takes a single argument, which is an expression
17070 to evaluate, and must be followed by the commands to execute, one per
17071 line, terminated by an @code{end}. These commands are called the
17072 @dfn{body} of the loop. The commands in the body of @code{while} are
17073 executed repeatedly as long as the expression evaluates to true.
17077 This command exits the @code{while} loop in whose body it is included.
17078 Execution of the script continues after that @code{while}s @code{end}
17081 @kindex loop_continue
17082 @item loop_continue
17083 This command skips the execution of the rest of the body of commands
17084 in the @code{while} loop in whose body it is included. Execution
17085 branches to the beginning of the @code{while} loop, where it evaluates
17086 the controlling expression.
17088 @kindex end@r{ (if/else/while commands)}
17090 Terminate the block of commands that are the body of @code{if},
17091 @code{else}, or @code{while} flow-control commands.
17096 @section Commands for Controlled Output
17098 During the execution of a command file or a user-defined command, normal
17099 @value{GDBN} output is suppressed; the only output that appears is what is
17100 explicitly printed by the commands in the definition. This section
17101 describes three commands useful for generating exactly the output you
17106 @item echo @var{text}
17107 @c I do not consider backslash-space a standard C escape sequence
17108 @c because it is not in ANSI.
17109 Print @var{text}. Nonprinting characters can be included in
17110 @var{text} using C escape sequences, such as @samp{\n} to print a
17111 newline. @strong{No newline is printed unless you specify one.}
17112 In addition to the standard C escape sequences, a backslash followed
17113 by a space stands for a space. This is useful for displaying a
17114 string with spaces at the beginning or the end, since leading and
17115 trailing spaces are otherwise trimmed from all arguments.
17116 To print @samp{@w{ }and foo =@w{ }}, use the command
17117 @samp{echo \@w{ }and foo = \@w{ }}.
17119 A backslash at the end of @var{text} can be used, as in C, to continue
17120 the command onto subsequent lines. For example,
17123 echo This is some text\n\
17124 which is continued\n\
17125 onto several lines.\n
17128 produces the same output as
17131 echo This is some text\n
17132 echo which is continued\n
17133 echo onto several lines.\n
17137 @item output @var{expression}
17138 Print the value of @var{expression} and nothing but that value: no
17139 newlines, no @samp{$@var{nn} = }. The value is not entered in the
17140 value history either. @xref{Expressions, ,Expressions}, for more information
17143 @item output/@var{fmt} @var{expression}
17144 Print the value of @var{expression} in format @var{fmt}. You can use
17145 the same formats as for @code{print}. @xref{Output Formats,,Output
17146 Formats}, for more information.
17149 @item printf @var{template}, @var{expressions}@dots{}
17150 Print the values of one or more @var{expressions} under the control of
17151 the string @var{template}. To print several values, make
17152 @var{expressions} be a comma-separated list of individual expressions,
17153 which may be either numbers or pointers. Their values are printed as
17154 specified by @var{template}, exactly as a C program would do by
17155 executing the code below:
17158 printf (@var{template}, @var{expressions}@dots{});
17161 As in @code{C} @code{printf}, ordinary characters in @var{template}
17162 are printed verbatim, while @dfn{conversion specification} introduced
17163 by the @samp{%} character cause subsequent @var{expressions} to be
17164 evaluated, their values converted and formatted according to type and
17165 style information encoded in the conversion specifications, and then
17168 For example, you can print two values in hex like this:
17171 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
17174 @code{printf} supports all the standard @code{C} conversion
17175 specifications, including the flags and modifiers between the @samp{%}
17176 character and the conversion letter, with the following exceptions:
17180 The argument-ordering modifiers, such as @samp{2$}, are not supported.
17183 The modifier @samp{*} is not supported for specifying precision or
17187 The @samp{'} flag (for separation of digits into groups according to
17188 @code{LC_NUMERIC'}) is not supported.
17191 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
17195 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
17198 The conversion letters @samp{a} and @samp{A} are not supported.
17202 Note that the @samp{ll} type modifier is supported only if the
17203 underlying @code{C} implementation used to build @value{GDBN} supports
17204 the @code{long long int} type, and the @samp{L} type modifier is
17205 supported only if @code{long double} type is available.
17207 As in @code{C}, @code{printf} supports simple backslash-escape
17208 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
17209 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
17210 single character. Octal and hexadecimal escape sequences are not
17213 Additionally, @code{printf} supports conversion specifications for DFP
17214 (@dfn{Decimal Floating Point}) types using the following length modifiers
17215 together with a floating point specifier.
17220 @samp{H} for printing @code{Decimal32} types.
17223 @samp{D} for printing @code{Decimal64} types.
17226 @samp{DD} for printing @code{Decimal128} types.
17229 If the underlying @code{C} implementation used to build @value{GDBN} has
17230 support for the three length modifiers for DFP types, other modifiers
17231 such as width and precision will also be available for @value{GDBN} to use.
17233 In case there is no such @code{C} support, no additional modifiers will be
17234 available and the value will be printed in the standard way.
17236 Here's an example of printing DFP types using the above conversion letters:
17238 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
17244 @chapter Command Interpreters
17245 @cindex command interpreters
17247 @value{GDBN} supports multiple command interpreters, and some command
17248 infrastructure to allow users or user interface writers to switch
17249 between interpreters or run commands in other interpreters.
17251 @value{GDBN} currently supports two command interpreters, the console
17252 interpreter (sometimes called the command-line interpreter or @sc{cli})
17253 and the machine interface interpreter (or @sc{gdb/mi}). This manual
17254 describes both of these interfaces in great detail.
17256 By default, @value{GDBN} will start with the console interpreter.
17257 However, the user may choose to start @value{GDBN} with another
17258 interpreter by specifying the @option{-i} or @option{--interpreter}
17259 startup options. Defined interpreters include:
17263 @cindex console interpreter
17264 The traditional console or command-line interpreter. This is the most often
17265 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
17266 @value{GDBN} will use this interpreter.
17269 @cindex mi interpreter
17270 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
17271 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
17272 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
17276 @cindex mi2 interpreter
17277 The current @sc{gdb/mi} interface.
17280 @cindex mi1 interpreter
17281 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
17285 @cindex invoke another interpreter
17286 The interpreter being used by @value{GDBN} may not be dynamically
17287 switched at runtime. Although possible, this could lead to a very
17288 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
17289 enters the command "interpreter-set console" in a console view,
17290 @value{GDBN} would switch to using the console interpreter, rendering
17291 the IDE inoperable!
17293 @kindex interpreter-exec
17294 Although you may only choose a single interpreter at startup, you may execute
17295 commands in any interpreter from the current interpreter using the appropriate
17296 command. If you are running the console interpreter, simply use the
17297 @code{interpreter-exec} command:
17300 interpreter-exec mi "-data-list-register-names"
17303 @sc{gdb/mi} has a similar command, although it is only available in versions of
17304 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
17307 @chapter @value{GDBN} Text User Interface
17309 @cindex Text User Interface
17312 * TUI Overview:: TUI overview
17313 * TUI Keys:: TUI key bindings
17314 * TUI Single Key Mode:: TUI single key mode
17315 * TUI Commands:: TUI-specific commands
17316 * TUI Configuration:: TUI configuration variables
17319 The @value{GDBN} Text User Interface (TUI) is a terminal
17320 interface which uses the @code{curses} library to show the source
17321 file, the assembly output, the program registers and @value{GDBN}
17322 commands in separate text windows. The TUI mode is supported only
17323 on platforms where a suitable version of the @code{curses} library
17326 @pindex @value{GDBTUI}
17327 The TUI mode is enabled by default when you invoke @value{GDBN} as
17328 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
17329 You can also switch in and out of TUI mode while @value{GDBN} runs by
17330 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
17331 @xref{TUI Keys, ,TUI Key Bindings}.
17334 @section TUI Overview
17336 In TUI mode, @value{GDBN} can display several text windows:
17340 This window is the @value{GDBN} command window with the @value{GDBN}
17341 prompt and the @value{GDBN} output. The @value{GDBN} input is still
17342 managed using readline.
17345 The source window shows the source file of the program. The current
17346 line and active breakpoints are displayed in this window.
17349 The assembly window shows the disassembly output of the program.
17352 This window shows the processor registers. Registers are highlighted
17353 when their values change.
17356 The source and assembly windows show the current program position
17357 by highlighting the current line and marking it with a @samp{>} marker.
17358 Breakpoints are indicated with two markers. The first marker
17359 indicates the breakpoint type:
17363 Breakpoint which was hit at least once.
17366 Breakpoint which was never hit.
17369 Hardware breakpoint which was hit at least once.
17372 Hardware breakpoint which was never hit.
17375 The second marker indicates whether the breakpoint is enabled or not:
17379 Breakpoint is enabled.
17382 Breakpoint is disabled.
17385 The source, assembly and register windows are updated when the current
17386 thread changes, when the frame changes, or when the program counter
17389 These windows are not all visible at the same time. The command
17390 window is always visible. The others can be arranged in several
17401 source and assembly,
17404 source and registers, or
17407 assembly and registers.
17410 A status line above the command window shows the following information:
17414 Indicates the current @value{GDBN} target.
17415 (@pxref{Targets, ,Specifying a Debugging Target}).
17418 Gives the current process or thread number.
17419 When no process is being debugged, this field is set to @code{No process}.
17422 Gives the current function name for the selected frame.
17423 The name is demangled if demangling is turned on (@pxref{Print Settings}).
17424 When there is no symbol corresponding to the current program counter,
17425 the string @code{??} is displayed.
17428 Indicates the current line number for the selected frame.
17429 When the current line number is not known, the string @code{??} is displayed.
17432 Indicates the current program counter address.
17436 @section TUI Key Bindings
17437 @cindex TUI key bindings
17439 The TUI installs several key bindings in the readline keymaps
17440 (@pxref{Command Line Editing}). The following key bindings
17441 are installed for both TUI mode and the @value{GDBN} standard mode.
17450 Enter or leave the TUI mode. When leaving the TUI mode,
17451 the curses window management stops and @value{GDBN} operates using
17452 its standard mode, writing on the terminal directly. When reentering
17453 the TUI mode, control is given back to the curses windows.
17454 The screen is then refreshed.
17458 Use a TUI layout with only one window. The layout will
17459 either be @samp{source} or @samp{assembly}. When the TUI mode
17460 is not active, it will switch to the TUI mode.
17462 Think of this key binding as the Emacs @kbd{C-x 1} binding.
17466 Use a TUI layout with at least two windows. When the current
17467 layout already has two windows, the next layout with two windows is used.
17468 When a new layout is chosen, one window will always be common to the
17469 previous layout and the new one.
17471 Think of it as the Emacs @kbd{C-x 2} binding.
17475 Change the active window. The TUI associates several key bindings
17476 (like scrolling and arrow keys) with the active window. This command
17477 gives the focus to the next TUI window.
17479 Think of it as the Emacs @kbd{C-x o} binding.
17483 Switch in and out of the TUI SingleKey mode that binds single
17484 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
17487 The following key bindings only work in the TUI mode:
17492 Scroll the active window one page up.
17496 Scroll the active window one page down.
17500 Scroll the active window one line up.
17504 Scroll the active window one line down.
17508 Scroll the active window one column left.
17512 Scroll the active window one column right.
17516 Refresh the screen.
17519 Because the arrow keys scroll the active window in the TUI mode, they
17520 are not available for their normal use by readline unless the command
17521 window has the focus. When another window is active, you must use
17522 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
17523 and @kbd{C-f} to control the command window.
17525 @node TUI Single Key Mode
17526 @section TUI Single Key Mode
17527 @cindex TUI single key mode
17529 The TUI also provides a @dfn{SingleKey} mode, which binds several
17530 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
17531 switch into this mode, where the following key bindings are used:
17534 @kindex c @r{(SingleKey TUI key)}
17538 @kindex d @r{(SingleKey TUI key)}
17542 @kindex f @r{(SingleKey TUI key)}
17546 @kindex n @r{(SingleKey TUI key)}
17550 @kindex q @r{(SingleKey TUI key)}
17552 exit the SingleKey mode.
17554 @kindex r @r{(SingleKey TUI key)}
17558 @kindex s @r{(SingleKey TUI key)}
17562 @kindex u @r{(SingleKey TUI key)}
17566 @kindex v @r{(SingleKey TUI key)}
17570 @kindex w @r{(SingleKey TUI key)}
17575 Other keys temporarily switch to the @value{GDBN} command prompt.
17576 The key that was pressed is inserted in the editing buffer so that
17577 it is possible to type most @value{GDBN} commands without interaction
17578 with the TUI SingleKey mode. Once the command is entered the TUI
17579 SingleKey mode is restored. The only way to permanently leave
17580 this mode is by typing @kbd{q} or @kbd{C-x s}.
17584 @section TUI-specific Commands
17585 @cindex TUI commands
17587 The TUI has specific commands to control the text windows.
17588 These commands are always available, even when @value{GDBN} is not in
17589 the TUI mode. When @value{GDBN} is in the standard mode, most
17590 of these commands will automatically switch to the TUI mode.
17595 List and give the size of all displayed windows.
17599 Display the next layout.
17602 Display the previous layout.
17605 Display the source window only.
17608 Display the assembly window only.
17611 Display the source and assembly window.
17614 Display the register window together with the source or assembly window.
17618 Make the next window active for scrolling.
17621 Make the previous window active for scrolling.
17624 Make the source window active for scrolling.
17627 Make the assembly window active for scrolling.
17630 Make the register window active for scrolling.
17633 Make the command window active for scrolling.
17637 Refresh the screen. This is similar to typing @kbd{C-L}.
17639 @item tui reg float
17641 Show the floating point registers in the register window.
17643 @item tui reg general
17644 Show the general registers in the register window.
17647 Show the next register group. The list of register groups as well as
17648 their order is target specific. The predefined register groups are the
17649 following: @code{general}, @code{float}, @code{system}, @code{vector},
17650 @code{all}, @code{save}, @code{restore}.
17652 @item tui reg system
17653 Show the system registers in the register window.
17657 Update the source window and the current execution point.
17659 @item winheight @var{name} +@var{count}
17660 @itemx winheight @var{name} -@var{count}
17662 Change the height of the window @var{name} by @var{count}
17663 lines. Positive counts increase the height, while negative counts
17666 @item tabset @var{nchars}
17668 Set the width of tab stops to be @var{nchars} characters.
17671 @node TUI Configuration
17672 @section TUI Configuration Variables
17673 @cindex TUI configuration variables
17675 Several configuration variables control the appearance of TUI windows.
17678 @item set tui border-kind @var{kind}
17679 @kindex set tui border-kind
17680 Select the border appearance for the source, assembly and register windows.
17681 The possible values are the following:
17684 Use a space character to draw the border.
17687 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
17690 Use the Alternate Character Set to draw the border. The border is
17691 drawn using character line graphics if the terminal supports them.
17694 @item set tui border-mode @var{mode}
17695 @kindex set tui border-mode
17696 @itemx set tui active-border-mode @var{mode}
17697 @kindex set tui active-border-mode
17698 Select the display attributes for the borders of the inactive windows
17699 or the active window. The @var{mode} can be one of the following:
17702 Use normal attributes to display the border.
17708 Use reverse video mode.
17711 Use half bright mode.
17713 @item half-standout
17714 Use half bright and standout mode.
17717 Use extra bright or bold mode.
17719 @item bold-standout
17720 Use extra bright or bold and standout mode.
17725 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17728 @cindex @sc{gnu} Emacs
17729 A special interface allows you to use @sc{gnu} Emacs to view (and
17730 edit) the source files for the program you are debugging with
17733 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17734 executable file you want to debug as an argument. This command starts
17735 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17736 created Emacs buffer.
17737 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17739 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17744 All ``terminal'' input and output goes through an Emacs buffer, called
17747 This applies both to @value{GDBN} commands and their output, and to the input
17748 and output done by the program you are debugging.
17750 This is useful because it means that you can copy the text of previous
17751 commands and input them again; you can even use parts of the output
17754 All the facilities of Emacs' Shell mode are available for interacting
17755 with your program. In particular, you can send signals the usual
17756 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17760 @value{GDBN} displays source code through Emacs.
17762 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17763 source file for that frame and puts an arrow (@samp{=>}) at the
17764 left margin of the current line. Emacs uses a separate buffer for
17765 source display, and splits the screen to show both your @value{GDBN} session
17768 Explicit @value{GDBN} @code{list} or search commands still produce output as
17769 usual, but you probably have no reason to use them from Emacs.
17772 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17773 a graphical mode, enabled by default, which provides further buffers
17774 that can control the execution and describe the state of your program.
17775 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17777 If you specify an absolute file name when prompted for the @kbd{M-x
17778 gdb} argument, then Emacs sets your current working directory to where
17779 your program resides. If you only specify the file name, then Emacs
17780 sets your current working directory to to the directory associated
17781 with the previous buffer. In this case, @value{GDBN} may find your
17782 program by searching your environment's @code{PATH} variable, but on
17783 some operating systems it might not find the source. So, although the
17784 @value{GDBN} input and output session proceeds normally, the auxiliary
17785 buffer does not display the current source and line of execution.
17787 The initial working directory of @value{GDBN} is printed on the top
17788 line of the GUD buffer and this serves as a default for the commands
17789 that specify files for @value{GDBN} to operate on. @xref{Files,
17790 ,Commands to Specify Files}.
17792 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17793 need to call @value{GDBN} by a different name (for example, if you
17794 keep several configurations around, with different names) you can
17795 customize the Emacs variable @code{gud-gdb-command-name} to run the
17798 In the GUD buffer, you can use these special Emacs commands in
17799 addition to the standard Shell mode commands:
17803 Describe the features of Emacs' GUD Mode.
17806 Execute to another source line, like the @value{GDBN} @code{step} command; also
17807 update the display window to show the current file and location.
17810 Execute to next source line in this function, skipping all function
17811 calls, like the @value{GDBN} @code{next} command. Then update the display window
17812 to show the current file and location.
17815 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17816 display window accordingly.
17819 Execute until exit from the selected stack frame, like the @value{GDBN}
17820 @code{finish} command.
17823 Continue execution of your program, like the @value{GDBN} @code{continue}
17827 Go up the number of frames indicated by the numeric argument
17828 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17829 like the @value{GDBN} @code{up} command.
17832 Go down the number of frames indicated by the numeric argument, like the
17833 @value{GDBN} @code{down} command.
17836 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17837 tells @value{GDBN} to set a breakpoint on the source line point is on.
17839 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17840 separate frame which shows a backtrace when the GUD buffer is current.
17841 Move point to any frame in the stack and type @key{RET} to make it
17842 become the current frame and display the associated source in the
17843 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17844 selected frame become the current one. In graphical mode, the
17845 speedbar displays watch expressions.
17847 If you accidentally delete the source-display buffer, an easy way to get
17848 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17849 request a frame display; when you run under Emacs, this recreates
17850 the source buffer if necessary to show you the context of the current
17853 The source files displayed in Emacs are in ordinary Emacs buffers
17854 which are visiting the source files in the usual way. You can edit
17855 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17856 communicates with Emacs in terms of line numbers. If you add or
17857 delete lines from the text, the line numbers that @value{GDBN} knows cease
17858 to correspond properly with the code.
17860 A more detailed description of Emacs' interaction with @value{GDBN} is
17861 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17864 @c The following dropped because Epoch is nonstandard. Reactivate
17865 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17867 @kindex Emacs Epoch environment
17871 Version 18 of @sc{gnu} Emacs has a built-in window system
17872 called the @code{epoch}
17873 environment. Users of this environment can use a new command,
17874 @code{inspect} which performs identically to @code{print} except that
17875 each value is printed in its own window.
17880 @chapter The @sc{gdb/mi} Interface
17882 @unnumberedsec Function and Purpose
17884 @cindex @sc{gdb/mi}, its purpose
17885 @sc{gdb/mi} is a line based machine oriented text interface to
17886 @value{GDBN} and is activated by specifying using the
17887 @option{--interpreter} command line option (@pxref{Mode Options}). It
17888 is specifically intended to support the development of systems which
17889 use the debugger as just one small component of a larger system.
17891 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17892 in the form of a reference manual.
17894 Note that @sc{gdb/mi} is still under construction, so some of the
17895 features described below are incomplete and subject to change
17896 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17898 @unnumberedsec Notation and Terminology
17900 @cindex notational conventions, for @sc{gdb/mi}
17901 This chapter uses the following notation:
17905 @code{|} separates two alternatives.
17908 @code{[ @var{something} ]} indicates that @var{something} is optional:
17909 it may or may not be given.
17912 @code{( @var{group} )*} means that @var{group} inside the parentheses
17913 may repeat zero or more times.
17916 @code{( @var{group} )+} means that @var{group} inside the parentheses
17917 may repeat one or more times.
17920 @code{"@var{string}"} means a literal @var{string}.
17924 @heading Dependencies
17928 * GDB/MI Command Syntax::
17929 * GDB/MI Compatibility with CLI::
17930 * GDB/MI Development and Front Ends::
17931 * GDB/MI Output Records::
17932 * GDB/MI Simple Examples::
17933 * GDB/MI Command Description Format::
17934 * GDB/MI Breakpoint Commands::
17935 * GDB/MI Program Context::
17936 * GDB/MI Thread Commands::
17937 * GDB/MI Program Execution::
17938 * GDB/MI Stack Manipulation::
17939 * GDB/MI Variable Objects::
17940 * GDB/MI Data Manipulation::
17941 * GDB/MI Tracepoint Commands::
17942 * GDB/MI Symbol Query::
17943 * GDB/MI File Commands::
17945 * GDB/MI Kod Commands::
17946 * GDB/MI Memory Overlay Commands::
17947 * GDB/MI Signal Handling Commands::
17949 * GDB/MI Target Manipulation::
17950 * GDB/MI File Transfer Commands::
17951 * GDB/MI Miscellaneous Commands::
17954 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17955 @node GDB/MI Command Syntax
17956 @section @sc{gdb/mi} Command Syntax
17959 * GDB/MI Input Syntax::
17960 * GDB/MI Output Syntax::
17963 @node GDB/MI Input Syntax
17964 @subsection @sc{gdb/mi} Input Syntax
17966 @cindex input syntax for @sc{gdb/mi}
17967 @cindex @sc{gdb/mi}, input syntax
17969 @item @var{command} @expansion{}
17970 @code{@var{cli-command} | @var{mi-command}}
17972 @item @var{cli-command} @expansion{}
17973 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17974 @var{cli-command} is any existing @value{GDBN} CLI command.
17976 @item @var{mi-command} @expansion{}
17977 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17978 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17980 @item @var{token} @expansion{}
17981 "any sequence of digits"
17983 @item @var{option} @expansion{}
17984 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17986 @item @var{parameter} @expansion{}
17987 @code{@var{non-blank-sequence} | @var{c-string}}
17989 @item @var{operation} @expansion{}
17990 @emph{any of the operations described in this chapter}
17992 @item @var{non-blank-sequence} @expansion{}
17993 @emph{anything, provided it doesn't contain special characters such as
17994 "-", @var{nl}, """ and of course " "}
17996 @item @var{c-string} @expansion{}
17997 @code{""" @var{seven-bit-iso-c-string-content} """}
17999 @item @var{nl} @expansion{}
18008 The CLI commands are still handled by the @sc{mi} interpreter; their
18009 output is described below.
18012 The @code{@var{token}}, when present, is passed back when the command
18016 Some @sc{mi} commands accept optional arguments as part of the parameter
18017 list. Each option is identified by a leading @samp{-} (dash) and may be
18018 followed by an optional argument parameter. Options occur first in the
18019 parameter list and can be delimited from normal parameters using
18020 @samp{--} (this is useful when some parameters begin with a dash).
18027 We want easy access to the existing CLI syntax (for debugging).
18030 We want it to be easy to spot a @sc{mi} operation.
18033 @node GDB/MI Output Syntax
18034 @subsection @sc{gdb/mi} Output Syntax
18036 @cindex output syntax of @sc{gdb/mi}
18037 @cindex @sc{gdb/mi}, output syntax
18038 The output from @sc{gdb/mi} consists of zero or more out-of-band records
18039 followed, optionally, by a single result record. This result record
18040 is for the most recent command. The sequence of output records is
18041 terminated by @samp{(gdb)}.
18043 If an input command was prefixed with a @code{@var{token}} then the
18044 corresponding output for that command will also be prefixed by that same
18048 @item @var{output} @expansion{}
18049 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
18051 @item @var{result-record} @expansion{}
18052 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
18054 @item @var{out-of-band-record} @expansion{}
18055 @code{@var{async-record} | @var{stream-record}}
18057 @item @var{async-record} @expansion{}
18058 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
18060 @item @var{exec-async-output} @expansion{}
18061 @code{[ @var{token} ] "*" @var{async-output}}
18063 @item @var{status-async-output} @expansion{}
18064 @code{[ @var{token} ] "+" @var{async-output}}
18066 @item @var{notify-async-output} @expansion{}
18067 @code{[ @var{token} ] "=" @var{async-output}}
18069 @item @var{async-output} @expansion{}
18070 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
18072 @item @var{result-class} @expansion{}
18073 @code{"done" | "running" | "connected" | "error" | "exit"}
18075 @item @var{async-class} @expansion{}
18076 @code{"stopped" | @var{others}} (where @var{others} will be added
18077 depending on the needs---this is still in development).
18079 @item @var{result} @expansion{}
18080 @code{ @var{variable} "=" @var{value}}
18082 @item @var{variable} @expansion{}
18083 @code{ @var{string} }
18085 @item @var{value} @expansion{}
18086 @code{ @var{const} | @var{tuple} | @var{list} }
18088 @item @var{const} @expansion{}
18089 @code{@var{c-string}}
18091 @item @var{tuple} @expansion{}
18092 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
18094 @item @var{list} @expansion{}
18095 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
18096 @var{result} ( "," @var{result} )* "]" }
18098 @item @var{stream-record} @expansion{}
18099 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
18101 @item @var{console-stream-output} @expansion{}
18102 @code{"~" @var{c-string}}
18104 @item @var{target-stream-output} @expansion{}
18105 @code{"@@" @var{c-string}}
18107 @item @var{log-stream-output} @expansion{}
18108 @code{"&" @var{c-string}}
18110 @item @var{nl} @expansion{}
18113 @item @var{token} @expansion{}
18114 @emph{any sequence of digits}.
18122 All output sequences end in a single line containing a period.
18125 The @code{@var{token}} is from the corresponding request. Note that
18126 for all async output, while the token is allowed by the grammar and
18127 may be output by future versions of @value{GDBN} for select async
18128 output messages, it is generally omitted. Frontends should treat
18129 all async output as reporting general changes in the state of the
18130 target and there should be no need to associate async output to any
18134 @cindex status output in @sc{gdb/mi}
18135 @var{status-async-output} contains on-going status information about the
18136 progress of a slow operation. It can be discarded. All status output is
18137 prefixed by @samp{+}.
18140 @cindex async output in @sc{gdb/mi}
18141 @var{exec-async-output} contains asynchronous state change on the target
18142 (stopped, started, disappeared). All async output is prefixed by
18146 @cindex notify output in @sc{gdb/mi}
18147 @var{notify-async-output} contains supplementary information that the
18148 client should handle (e.g., a new breakpoint information). All notify
18149 output is prefixed by @samp{=}.
18152 @cindex console output in @sc{gdb/mi}
18153 @var{console-stream-output} is output that should be displayed as is in the
18154 console. It is the textual response to a CLI command. All the console
18155 output is prefixed by @samp{~}.
18158 @cindex target output in @sc{gdb/mi}
18159 @var{target-stream-output} is the output produced by the target program.
18160 All the target output is prefixed by @samp{@@}.
18163 @cindex log output in @sc{gdb/mi}
18164 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
18165 instance messages that should be displayed as part of an error log. All
18166 the log output is prefixed by @samp{&}.
18169 @cindex list output in @sc{gdb/mi}
18170 New @sc{gdb/mi} commands should only output @var{lists} containing
18176 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
18177 details about the various output records.
18179 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18180 @node GDB/MI Compatibility with CLI
18181 @section @sc{gdb/mi} Compatibility with CLI
18183 @cindex compatibility, @sc{gdb/mi} and CLI
18184 @cindex @sc{gdb/mi}, compatibility with CLI
18186 For the developers convenience CLI commands can be entered directly,
18187 but there may be some unexpected behaviour. For example, commands
18188 that query the user will behave as if the user replied yes, breakpoint
18189 command lists are not executed and some CLI commands, such as
18190 @code{if}, @code{when} and @code{define}, prompt for further input with
18191 @samp{>}, which is not valid MI output.
18193 This feature may be removed at some stage in the future and it is
18194 recommended that front ends use the @code{-interpreter-exec} command
18195 (@pxref{-interpreter-exec}).
18197 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18198 @node GDB/MI Development and Front Ends
18199 @section @sc{gdb/mi} Development and Front Ends
18200 @cindex @sc{gdb/mi} development
18202 The application which takes the MI output and presents the state of the
18203 program being debugged to the user is called a @dfn{front end}.
18205 Although @sc{gdb/mi} is still incomplete, it is currently being used
18206 by a variety of front ends to @value{GDBN}. This makes it difficult
18207 to introduce new functionality without breaking existing usage. This
18208 section tries to minimize the problems by describing how the protocol
18211 Some changes in MI need not break a carefully designed front end, and
18212 for these the MI version will remain unchanged. The following is a
18213 list of changes that may occur within one level, so front ends should
18214 parse MI output in a way that can handle them:
18218 New MI commands may be added.
18221 New fields may be added to the output of any MI command.
18224 The range of values for fields with specified values, e.g.,
18225 @code{in_scope} (@pxref{-var-update}) may be extended.
18227 @c The format of field's content e.g type prefix, may change so parse it
18228 @c at your own risk. Yes, in general?
18230 @c The order of fields may change? Shouldn't really matter but it might
18231 @c resolve inconsistencies.
18234 If the changes are likely to break front ends, the MI version level
18235 will be increased by one. This will allow the front end to parse the
18236 output according to the MI version. Apart from mi0, new versions of
18237 @value{GDBN} will not support old versions of MI and it will be the
18238 responsibility of the front end to work with the new one.
18240 @c Starting with mi3, add a new command -mi-version that prints the MI
18243 The best way to avoid unexpected changes in MI that might break your front
18244 end is to make your project known to @value{GDBN} developers and
18245 follow development on @email{gdb@@sourceware.org} and
18246 @email{gdb-patches@@sourceware.org}.
18247 @cindex mailing lists
18249 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18250 @node GDB/MI Output Records
18251 @section @sc{gdb/mi} Output Records
18254 * GDB/MI Result Records::
18255 * GDB/MI Stream Records::
18256 * GDB/MI Async Records::
18259 @node GDB/MI Result Records
18260 @subsection @sc{gdb/mi} Result Records
18262 @cindex result records in @sc{gdb/mi}
18263 @cindex @sc{gdb/mi}, result records
18264 In addition to a number of out-of-band notifications, the response to a
18265 @sc{gdb/mi} command includes one of the following result indications:
18269 @item "^done" [ "," @var{results} ]
18270 The synchronous operation was successful, @code{@var{results}} are the return
18275 @c Is this one correct? Should it be an out-of-band notification?
18276 The asynchronous operation was successfully started. The target is
18281 @value{GDBN} has connected to a remote target.
18283 @item "^error" "," @var{c-string}
18285 The operation failed. The @code{@var{c-string}} contains the corresponding
18290 @value{GDBN} has terminated.
18294 @node GDB/MI Stream Records
18295 @subsection @sc{gdb/mi} Stream Records
18297 @cindex @sc{gdb/mi}, stream records
18298 @cindex stream records in @sc{gdb/mi}
18299 @value{GDBN} internally maintains a number of output streams: the console, the
18300 target, and the log. The output intended for each of these streams is
18301 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
18303 Each stream record begins with a unique @dfn{prefix character} which
18304 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
18305 Syntax}). In addition to the prefix, each stream record contains a
18306 @code{@var{string-output}}. This is either raw text (with an implicit new
18307 line) or a quoted C string (which does not contain an implicit newline).
18310 @item "~" @var{string-output}
18311 The console output stream contains text that should be displayed in the
18312 CLI console window. It contains the textual responses to CLI commands.
18314 @item "@@" @var{string-output}
18315 The target output stream contains any textual output from the running
18316 target. This is only present when GDB's event loop is truly
18317 asynchronous, which is currently only the case for remote targets.
18319 @item "&" @var{string-output}
18320 The log stream contains debugging messages being produced by @value{GDBN}'s
18324 @node GDB/MI Async Records
18325 @subsection @sc{gdb/mi} Async Records
18327 @cindex async records in @sc{gdb/mi}
18328 @cindex @sc{gdb/mi}, async records
18329 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
18330 additional changes that have occurred. Those changes can either be a
18331 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
18332 target activity (e.g., target stopped).
18334 The following is the list of possible async records:
18338 @item *stopped,reason="@var{reason}"
18339 The target has stopped. The @var{reason} field can have one of the
18343 @item breakpoint-hit
18344 A breakpoint was reached.
18345 @item watchpoint-trigger
18346 A watchpoint was triggered.
18347 @item read-watchpoint-trigger
18348 A read watchpoint was triggered.
18349 @item access-watchpoint-trigger
18350 An access watchpoint was triggered.
18351 @item function-finished
18352 An -exec-finish or similar CLI command was accomplished.
18353 @item location-reached
18354 An -exec-until or similar CLI command was accomplished.
18355 @item watchpoint-scope
18356 A watchpoint has gone out of scope.
18357 @item end-stepping-range
18358 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
18359 similar CLI command was accomplished.
18360 @item exited-signalled
18361 The inferior exited because of a signal.
18363 The inferior exited.
18364 @item exited-normally
18365 The inferior exited normally.
18366 @item signal-received
18367 A signal was received by the inferior.
18370 @item =thread-created,id="@var{id}"
18371 @itemx =thread-exited,id="@var{id}"
18372 A thread either was created, or has exited. The @var{id} field
18373 contains the @value{GDBN} identifier of the thread.
18378 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18379 @node GDB/MI Simple Examples
18380 @section Simple Examples of @sc{gdb/mi} Interaction
18381 @cindex @sc{gdb/mi}, simple examples
18383 This subsection presents several simple examples of interaction using
18384 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
18385 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
18386 the output received from @sc{gdb/mi}.
18388 Note the line breaks shown in the examples are here only for
18389 readability, they don't appear in the real output.
18391 @subheading Setting a Breakpoint
18393 Setting a breakpoint generates synchronous output which contains detailed
18394 information of the breakpoint.
18397 -> -break-insert main
18398 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18399 enabled="y",addr="0x08048564",func="main",file="myprog.c",
18400 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
18404 @subheading Program Execution
18406 Program execution generates asynchronous records and MI gives the
18407 reason that execution stopped.
18413 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
18414 frame=@{addr="0x08048564",func="main",
18415 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
18416 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
18421 <- *stopped,reason="exited-normally"
18425 @subheading Quitting @value{GDBN}
18427 Quitting @value{GDBN} just prints the result class @samp{^exit}.
18435 @subheading A Bad Command
18437 Here's what happens if you pass a non-existent command:
18441 <- ^error,msg="Undefined MI command: rubbish"
18446 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18447 @node GDB/MI Command Description Format
18448 @section @sc{gdb/mi} Command Description Format
18450 The remaining sections describe blocks of commands. Each block of
18451 commands is laid out in a fashion similar to this section.
18453 @subheading Motivation
18455 The motivation for this collection of commands.
18457 @subheading Introduction
18459 A brief introduction to this collection of commands as a whole.
18461 @subheading Commands
18463 For each command in the block, the following is described:
18465 @subsubheading Synopsis
18468 -command @var{args}@dots{}
18471 @subsubheading Result
18473 @subsubheading @value{GDBN} Command
18475 The corresponding @value{GDBN} CLI command(s), if any.
18477 @subsubheading Example
18479 Example(s) formatted for readability. Some of the described commands have
18480 not been implemented yet and these are labeled N.A.@: (not available).
18483 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18484 @node GDB/MI Breakpoint Commands
18485 @section @sc{gdb/mi} Breakpoint Commands
18487 @cindex breakpoint commands for @sc{gdb/mi}
18488 @cindex @sc{gdb/mi}, breakpoint commands
18489 This section documents @sc{gdb/mi} commands for manipulating
18492 @subheading The @code{-break-after} Command
18493 @findex -break-after
18495 @subsubheading Synopsis
18498 -break-after @var{number} @var{count}
18501 The breakpoint number @var{number} is not in effect until it has been
18502 hit @var{count} times. To see how this is reflected in the output of
18503 the @samp{-break-list} command, see the description of the
18504 @samp{-break-list} command below.
18506 @subsubheading @value{GDBN} Command
18508 The corresponding @value{GDBN} command is @samp{ignore}.
18510 @subsubheading Example
18515 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18516 enabled="y",addr="0x000100d0",func="main",file="hello.c",
18517 fullname="/home/foo/hello.c",line="5",times="0"@}
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",times="0",ignore="3"@}]@}
18538 @subheading The @code{-break-catch} Command
18539 @findex -break-catch
18541 @subheading The @code{-break-commands} Command
18542 @findex -break-commands
18546 @subheading The @code{-break-condition} Command
18547 @findex -break-condition
18549 @subsubheading Synopsis
18552 -break-condition @var{number} @var{expr}
18555 Breakpoint @var{number} will stop the program only if the condition in
18556 @var{expr} is true. The condition becomes part of the
18557 @samp{-break-list} output (see the description of the @samp{-break-list}
18560 @subsubheading @value{GDBN} Command
18562 The corresponding @value{GDBN} command is @samp{condition}.
18564 @subsubheading Example
18568 -break-condition 1 1
18572 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18573 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18574 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18575 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18576 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18577 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18578 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18579 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18580 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18581 line="5",cond="1",times="0",ignore="3"@}]@}
18585 @subheading The @code{-break-delete} Command
18586 @findex -break-delete
18588 @subsubheading Synopsis
18591 -break-delete ( @var{breakpoint} )+
18594 Delete the breakpoint(s) whose number(s) are specified in the argument
18595 list. This is obviously reflected in the breakpoint list.
18597 @subsubheading @value{GDBN} Command
18599 The corresponding @value{GDBN} command is @samp{delete}.
18601 @subsubheading Example
18609 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18610 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18611 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18612 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18613 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18614 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18615 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18620 @subheading The @code{-break-disable} Command
18621 @findex -break-disable
18623 @subsubheading Synopsis
18626 -break-disable ( @var{breakpoint} )+
18629 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18630 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18632 @subsubheading @value{GDBN} Command
18634 The corresponding @value{GDBN} command is @samp{disable}.
18636 @subsubheading Example
18644 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18645 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18646 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18647 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18648 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18649 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18650 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18651 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18652 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18653 line="5",times="0"@}]@}
18657 @subheading The @code{-break-enable} Command
18658 @findex -break-enable
18660 @subsubheading Synopsis
18663 -break-enable ( @var{breakpoint} )+
18666 Enable (previously disabled) @var{breakpoint}(s).
18668 @subsubheading @value{GDBN} Command
18670 The corresponding @value{GDBN} command is @samp{enable}.
18672 @subsubheading Example
18680 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18681 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18682 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18683 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18684 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18685 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18686 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18687 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18688 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18689 line="5",times="0"@}]@}
18693 @subheading The @code{-break-info} Command
18694 @findex -break-info
18696 @subsubheading Synopsis
18699 -break-info @var{breakpoint}
18703 Get information about a single breakpoint.
18705 @subsubheading @value{GDBN} Command
18707 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18709 @subsubheading Example
18712 @subheading The @code{-break-insert} Command
18713 @findex -break-insert
18715 @subsubheading Synopsis
18718 -break-insert [ -t ] [ -h ] [ -f ]
18719 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18720 [ -p @var{thread} ] [ @var{location} ]
18724 If specified, @var{location}, can be one of:
18731 @item filename:linenum
18732 @item filename:function
18736 The possible optional parameters of this command are:
18740 Insert a temporary breakpoint.
18742 Insert a hardware breakpoint.
18743 @item -c @var{condition}
18744 Make the breakpoint conditional on @var{condition}.
18745 @item -i @var{ignore-count}
18746 Initialize the @var{ignore-count}.
18748 If @var{location} cannot be parsed (for example if it
18749 refers to unknown files or functions), create a pending
18750 breakpoint. Without this flag, @value{GDBN} will report
18751 an error, and won't create a breakpoint, if @var{location}
18755 @subsubheading Result
18757 The result is in the form:
18760 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18761 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18762 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18763 times="@var{times}"@}
18767 where @var{number} is the @value{GDBN} number for this breakpoint,
18768 @var{funcname} is the name of the function where the breakpoint was
18769 inserted, @var{filename} is the name of the source file which contains
18770 this function, @var{lineno} is the source line number within that file
18771 and @var{times} the number of times that the breakpoint has been hit
18772 (always 0 for -break-insert but may be greater for -break-info or -break-list
18773 which use the same output).
18775 Note: this format is open to change.
18776 @c An out-of-band breakpoint instead of part of the result?
18778 @subsubheading @value{GDBN} Command
18780 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18781 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18783 @subsubheading Example
18788 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18789 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18791 -break-insert -t foo
18792 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18793 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18796 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18797 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18798 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18799 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18800 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18801 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18802 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18803 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18804 addr="0x0001072c", func="main",file="recursive2.c",
18805 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18806 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18807 addr="0x00010774",func="foo",file="recursive2.c",
18808 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18810 -break-insert -r foo.*
18811 ~int foo(int, int);
18812 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18813 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18817 @subheading The @code{-break-list} Command
18818 @findex -break-list
18820 @subsubheading Synopsis
18826 Displays the list of inserted breakpoints, showing the following fields:
18830 number of the breakpoint
18832 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18834 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18837 is the breakpoint enabled or no: @samp{y} or @samp{n}
18839 memory location at which the breakpoint is set
18841 logical location of the breakpoint, expressed by function name, file
18844 number of times the breakpoint has been hit
18847 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18848 @code{body} field is an empty list.
18850 @subsubheading @value{GDBN} Command
18852 The corresponding @value{GDBN} command is @samp{info break}.
18854 @subsubheading Example
18859 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18860 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18861 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18862 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18863 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18864 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18865 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18866 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18867 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18868 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18869 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18870 line="13",times="0"@}]@}
18874 Here's an example of the result when there are no breakpoints:
18879 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18880 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18881 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18882 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18883 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18884 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18885 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18890 @subheading The @code{-break-watch} Command
18891 @findex -break-watch
18893 @subsubheading Synopsis
18896 -break-watch [ -a | -r ]
18899 Create a watchpoint. With the @samp{-a} option it will create an
18900 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18901 read from or on a write to the memory location. With the @samp{-r}
18902 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18903 trigger only when the memory location is accessed for reading. Without
18904 either of the options, the watchpoint created is a regular watchpoint,
18905 i.e., it will trigger when the memory location is accessed for writing.
18906 @xref{Set Watchpoints, , Setting Watchpoints}.
18908 Note that @samp{-break-list} will report a single list of watchpoints and
18909 breakpoints inserted.
18911 @subsubheading @value{GDBN} Command
18913 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18916 @subsubheading Example
18918 Setting a watchpoint on a variable in the @code{main} function:
18923 ^done,wpt=@{number="2",exp="x"@}
18928 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18929 value=@{old="-268439212",new="55"@},
18930 frame=@{func="main",args=[],file="recursive2.c",
18931 fullname="/home/foo/bar/recursive2.c",line="5"@}
18935 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18936 the program execution twice: first for the variable changing value, then
18937 for the watchpoint going out of scope.
18942 ^done,wpt=@{number="5",exp="C"@}
18947 *stopped,reason="watchpoint-trigger",
18948 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18949 frame=@{func="callee4",args=[],
18950 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18951 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18956 *stopped,reason="watchpoint-scope",wpnum="5",
18957 frame=@{func="callee3",args=[@{name="strarg",
18958 value="0x11940 \"A string argument.\""@}],
18959 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18960 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18964 Listing breakpoints and watchpoints, at different points in the program
18965 execution. Note that once the watchpoint goes out of scope, it is
18971 ^done,wpt=@{number="2",exp="C"@}
18974 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18975 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18976 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18977 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18978 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18979 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18980 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18981 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18982 addr="0x00010734",func="callee4",
18983 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18984 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18985 bkpt=@{number="2",type="watchpoint",disp="keep",
18986 enabled="y",addr="",what="C",times="0"@}]@}
18991 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18992 value=@{old="-276895068",new="3"@},
18993 frame=@{func="callee4",args=[],
18994 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18995 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18998 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18999 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19000 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19001 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19002 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19003 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19004 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19005 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19006 addr="0x00010734",func="callee4",
19007 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19008 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
19009 bkpt=@{number="2",type="watchpoint",disp="keep",
19010 enabled="y",addr="",what="C",times="-5"@}]@}
19014 ^done,reason="watchpoint-scope",wpnum="2",
19015 frame=@{func="callee3",args=[@{name="strarg",
19016 value="0x11940 \"A string argument.\""@}],
19017 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19018 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19021 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19022 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19023 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19024 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19025 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19026 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19027 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19028 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19029 addr="0x00010734",func="callee4",
19030 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19031 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
19036 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19037 @node GDB/MI Program Context
19038 @section @sc{gdb/mi} Program Context
19040 @subheading The @code{-exec-arguments} Command
19041 @findex -exec-arguments
19044 @subsubheading Synopsis
19047 -exec-arguments @var{args}
19050 Set the inferior program arguments, to be used in the next
19053 @subsubheading @value{GDBN} Command
19055 The corresponding @value{GDBN} command is @samp{set args}.
19057 @subsubheading Example
19061 -exec-arguments -v word
19067 @subheading The @code{-exec-show-arguments} Command
19068 @findex -exec-show-arguments
19070 @subsubheading Synopsis
19073 -exec-show-arguments
19076 Print the arguments of the program.
19078 @subsubheading @value{GDBN} Command
19080 The corresponding @value{GDBN} command is @samp{show args}.
19082 @subsubheading Example
19086 @subheading The @code{-environment-cd} Command
19087 @findex -environment-cd
19089 @subsubheading Synopsis
19092 -environment-cd @var{pathdir}
19095 Set @value{GDBN}'s working directory.
19097 @subsubheading @value{GDBN} Command
19099 The corresponding @value{GDBN} command is @samp{cd}.
19101 @subsubheading Example
19105 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19111 @subheading The @code{-environment-directory} Command
19112 @findex -environment-directory
19114 @subsubheading Synopsis
19117 -environment-directory [ -r ] [ @var{pathdir} ]+
19120 Add directories @var{pathdir} to beginning of search path for source files.
19121 If the @samp{-r} option is used, the search path is reset to the default
19122 search path. If directories @var{pathdir} are supplied in addition to the
19123 @samp{-r} option, the search path is first reset and then addition
19125 Multiple directories may be specified, separated by blanks. Specifying
19126 multiple directories in a single command
19127 results in the directories added to the beginning of the
19128 search path in the same order they were presented in the command.
19129 If blanks are needed as
19130 part of a directory name, double-quotes should be used around
19131 the name. In the command output, the path will show up separated
19132 by the system directory-separator character. The directory-separator
19133 character must not be used
19134 in any directory name.
19135 If no directories are specified, the current search path is displayed.
19137 @subsubheading @value{GDBN} Command
19139 The corresponding @value{GDBN} command is @samp{dir}.
19141 @subsubheading Example
19145 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19146 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19148 -environment-directory ""
19149 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19151 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
19152 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
19154 -environment-directory -r
19155 ^done,source-path="$cdir:$cwd"
19160 @subheading The @code{-environment-path} Command
19161 @findex -environment-path
19163 @subsubheading Synopsis
19166 -environment-path [ -r ] [ @var{pathdir} ]+
19169 Add directories @var{pathdir} to beginning of search path for object files.
19170 If the @samp{-r} option is used, the search path is reset to the original
19171 search path that existed at gdb start-up. If directories @var{pathdir} are
19172 supplied in addition to the
19173 @samp{-r} option, the search path is first reset and then addition
19175 Multiple directories may be specified, separated by blanks. Specifying
19176 multiple directories in a single command
19177 results in the directories added to the beginning of the
19178 search path in the same order they were presented in the command.
19179 If blanks are needed as
19180 part of a directory name, double-quotes should be used around
19181 the name. In the command output, the path will show up separated
19182 by the system directory-separator character. The directory-separator
19183 character must not be used
19184 in any directory name.
19185 If no directories are specified, the current path is displayed.
19188 @subsubheading @value{GDBN} Command
19190 The corresponding @value{GDBN} command is @samp{path}.
19192 @subsubheading Example
19197 ^done,path="/usr/bin"
19199 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
19200 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
19202 -environment-path -r /usr/local/bin
19203 ^done,path="/usr/local/bin:/usr/bin"
19208 @subheading The @code{-environment-pwd} Command
19209 @findex -environment-pwd
19211 @subsubheading Synopsis
19217 Show the current working directory.
19219 @subsubheading @value{GDBN} Command
19221 The corresponding @value{GDBN} command is @samp{pwd}.
19223 @subsubheading Example
19228 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
19232 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19233 @node GDB/MI Thread Commands
19234 @section @sc{gdb/mi} Thread Commands
19237 @subheading The @code{-thread-info} Command
19238 @findex -thread-info
19240 @subsubheading Synopsis
19243 -thread-info [ @var{thread-id} ]
19246 Reports information about either a specific thread, if
19247 the @var{thread-id} parameter is present, or about all
19248 threads. When printing information about all threads,
19249 also reports the current thread.
19251 @subsubheading @value{GDBN} Command
19253 The @samp{info thread} command prints the same information
19256 @subsubheading Example
19261 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
19262 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},
19263 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
19264 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
19265 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}@}],
19266 current-thread-id="1"
19270 @subheading The @code{-thread-list-ids} Command
19271 @findex -thread-list-ids
19273 @subsubheading Synopsis
19279 Produces a list of the currently known @value{GDBN} thread ids. At the
19280 end of the list it also prints the total number of such threads.
19282 @subsubheading @value{GDBN} Command
19284 Part of @samp{info threads} supplies the same information.
19286 @subsubheading Example
19288 No threads present, besides the main process:
19293 ^done,thread-ids=@{@},number-of-threads="0"
19303 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19304 number-of-threads="3"
19309 @subheading The @code{-thread-select} Command
19310 @findex -thread-select
19312 @subsubheading Synopsis
19315 -thread-select @var{threadnum}
19318 Make @var{threadnum} the current thread. It prints the number of the new
19319 current thread, and the topmost frame for that thread.
19321 @subsubheading @value{GDBN} Command
19323 The corresponding @value{GDBN} command is @samp{thread}.
19325 @subsubheading Example
19332 *stopped,reason="end-stepping-range",thread-id="2",line="187",
19333 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
19337 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19338 number-of-threads="3"
19341 ^done,new-thread-id="3",
19342 frame=@{level="0",func="vprintf",
19343 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
19344 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
19348 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19349 @node GDB/MI Program Execution
19350 @section @sc{gdb/mi} Program Execution
19352 These are the asynchronous commands which generate the out-of-band
19353 record @samp{*stopped}. Currently @value{GDBN} only really executes
19354 asynchronously with remote targets and this interaction is mimicked in
19357 @subheading The @code{-exec-continue} Command
19358 @findex -exec-continue
19360 @subsubheading Synopsis
19366 Resumes the execution of the inferior program until a breakpoint is
19367 encountered, or until the inferior exits.
19369 @subsubheading @value{GDBN} Command
19371 The corresponding @value{GDBN} corresponding is @samp{continue}.
19373 @subsubheading Example
19380 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
19381 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
19387 @subheading The @code{-exec-finish} Command
19388 @findex -exec-finish
19390 @subsubheading Synopsis
19396 Resumes the execution of the inferior program until the current
19397 function is exited. Displays the results returned by the function.
19399 @subsubheading @value{GDBN} Command
19401 The corresponding @value{GDBN} command is @samp{finish}.
19403 @subsubheading Example
19405 Function returning @code{void}.
19412 *stopped,reason="function-finished",frame=@{func="main",args=[],
19413 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
19417 Function returning other than @code{void}. The name of the internal
19418 @value{GDBN} variable storing the result is printed, together with the
19425 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
19426 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
19427 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19428 gdb-result-var="$1",return-value="0"
19433 @subheading The @code{-exec-interrupt} Command
19434 @findex -exec-interrupt
19436 @subsubheading Synopsis
19442 Interrupts the background execution of the target. Note how the token
19443 associated with the stop message is the one for the execution command
19444 that has been interrupted. The token for the interrupt itself only
19445 appears in the @samp{^done} output. If the user is trying to
19446 interrupt a non-running program, an error message will be printed.
19448 @subsubheading @value{GDBN} Command
19450 The corresponding @value{GDBN} command is @samp{interrupt}.
19452 @subsubheading Example
19463 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
19464 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
19465 fullname="/home/foo/bar/try.c",line="13"@}
19470 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
19475 @subheading The @code{-exec-next} Command
19478 @subsubheading Synopsis
19484 Resumes execution of the inferior program, stopping when the beginning
19485 of the next source line is reached.
19487 @subsubheading @value{GDBN} Command
19489 The corresponding @value{GDBN} command is @samp{next}.
19491 @subsubheading Example
19497 *stopped,reason="end-stepping-range",line="8",file="hello.c"
19502 @subheading The @code{-exec-next-instruction} Command
19503 @findex -exec-next-instruction
19505 @subsubheading Synopsis
19508 -exec-next-instruction
19511 Executes one machine instruction. If the instruction is a function
19512 call, continues until the function returns. If the program stops at an
19513 instruction in the middle of a source line, the address will be
19516 @subsubheading @value{GDBN} Command
19518 The corresponding @value{GDBN} command is @samp{nexti}.
19520 @subsubheading Example
19524 -exec-next-instruction
19528 *stopped,reason="end-stepping-range",
19529 addr="0x000100d4",line="5",file="hello.c"
19534 @subheading The @code{-exec-return} Command
19535 @findex -exec-return
19537 @subsubheading Synopsis
19543 Makes current function return immediately. Doesn't execute the inferior.
19544 Displays the new current frame.
19546 @subsubheading @value{GDBN} Command
19548 The corresponding @value{GDBN} command is @samp{return}.
19550 @subsubheading Example
19554 200-break-insert callee4
19555 200^done,bkpt=@{number="1",addr="0x00010734",
19556 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19561 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
19562 frame=@{func="callee4",args=[],
19563 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19564 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19570 111^done,frame=@{level="0",func="callee3",
19571 args=[@{name="strarg",
19572 value="0x11940 \"A string argument.\""@}],
19573 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19574 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19579 @subheading The @code{-exec-run} Command
19582 @subsubheading Synopsis
19588 Starts execution of the inferior from the beginning. The inferior
19589 executes until either a breakpoint is encountered or the program
19590 exits. In the latter case the output will include an exit code, if
19591 the program has exited exceptionally.
19593 @subsubheading @value{GDBN} Command
19595 The corresponding @value{GDBN} command is @samp{run}.
19597 @subsubheading Examples
19602 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19607 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
19608 frame=@{func="main",args=[],file="recursive2.c",
19609 fullname="/home/foo/bar/recursive2.c",line="4"@}
19614 Program exited normally:
19622 *stopped,reason="exited-normally"
19627 Program exited exceptionally:
19635 *stopped,reason="exited",exit-code="01"
19639 Another way the program can terminate is if it receives a signal such as
19640 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19644 *stopped,reason="exited-signalled",signal-name="SIGINT",
19645 signal-meaning="Interrupt"
19649 @c @subheading -exec-signal
19652 @subheading The @code{-exec-step} Command
19655 @subsubheading Synopsis
19661 Resumes execution of the inferior program, stopping when the beginning
19662 of the next source line is reached, if the next source line is not a
19663 function call. If it is, stop at the first instruction of the called
19666 @subsubheading @value{GDBN} Command
19668 The corresponding @value{GDBN} command is @samp{step}.
19670 @subsubheading Example
19672 Stepping into a function:
19678 *stopped,reason="end-stepping-range",
19679 frame=@{func="foo",args=[@{name="a",value="10"@},
19680 @{name="b",value="0"@}],file="recursive2.c",
19681 fullname="/home/foo/bar/recursive2.c",line="11"@}
19691 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19696 @subheading The @code{-exec-step-instruction} Command
19697 @findex -exec-step-instruction
19699 @subsubheading Synopsis
19702 -exec-step-instruction
19705 Resumes the inferior which executes one machine instruction. The
19706 output, once @value{GDBN} has stopped, will vary depending on whether
19707 we have stopped in the middle of a source line or not. In the former
19708 case, the address at which the program stopped will be printed as
19711 @subsubheading @value{GDBN} Command
19713 The corresponding @value{GDBN} command is @samp{stepi}.
19715 @subsubheading Example
19719 -exec-step-instruction
19723 *stopped,reason="end-stepping-range",
19724 frame=@{func="foo",args=[],file="try.c",
19725 fullname="/home/foo/bar/try.c",line="10"@}
19727 -exec-step-instruction
19731 *stopped,reason="end-stepping-range",
19732 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19733 fullname="/home/foo/bar/try.c",line="10"@}
19738 @subheading The @code{-exec-until} Command
19739 @findex -exec-until
19741 @subsubheading Synopsis
19744 -exec-until [ @var{location} ]
19747 Executes the inferior until the @var{location} specified in the
19748 argument is reached. If there is no argument, the inferior executes
19749 until a source line greater than the current one is reached. The
19750 reason for stopping in this case will be @samp{location-reached}.
19752 @subsubheading @value{GDBN} Command
19754 The corresponding @value{GDBN} command is @samp{until}.
19756 @subsubheading Example
19760 -exec-until recursive2.c:6
19764 *stopped,reason="location-reached",frame=@{func="main",args=[],
19765 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19770 @subheading -file-clear
19771 Is this going away????
19774 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19775 @node GDB/MI Stack Manipulation
19776 @section @sc{gdb/mi} Stack Manipulation Commands
19779 @subheading The @code{-stack-info-frame} Command
19780 @findex -stack-info-frame
19782 @subsubheading Synopsis
19788 Get info on the selected frame.
19790 @subsubheading @value{GDBN} Command
19792 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19793 (without arguments).
19795 @subsubheading Example
19800 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19801 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19802 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19806 @subheading The @code{-stack-info-depth} Command
19807 @findex -stack-info-depth
19809 @subsubheading Synopsis
19812 -stack-info-depth [ @var{max-depth} ]
19815 Return the depth of the stack. If the integer argument @var{max-depth}
19816 is specified, do not count beyond @var{max-depth} frames.
19818 @subsubheading @value{GDBN} Command
19820 There's no equivalent @value{GDBN} command.
19822 @subsubheading Example
19824 For a stack with frame levels 0 through 11:
19831 -stack-info-depth 4
19834 -stack-info-depth 12
19837 -stack-info-depth 11
19840 -stack-info-depth 13
19845 @subheading The @code{-stack-list-arguments} Command
19846 @findex -stack-list-arguments
19848 @subsubheading Synopsis
19851 -stack-list-arguments @var{show-values}
19852 [ @var{low-frame} @var{high-frame} ]
19855 Display a list of the arguments for the frames between @var{low-frame}
19856 and @var{high-frame} (inclusive). If @var{low-frame} and
19857 @var{high-frame} are not provided, list the arguments for the whole
19858 call stack. If the two arguments are equal, show the single frame
19859 at the corresponding level. It is an error if @var{low-frame} is
19860 larger than the actual number of frames. On the other hand,
19861 @var{high-frame} may be larger than the actual number of frames, in
19862 which case only existing frames will be returned.
19864 The @var{show-values} argument must have a value of 0 or 1. A value of
19865 0 means that only the names of the arguments are listed, a value of 1
19866 means that both names and values of the arguments are printed.
19868 @subsubheading @value{GDBN} Command
19870 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19871 @samp{gdb_get_args} command which partially overlaps with the
19872 functionality of @samp{-stack-list-arguments}.
19874 @subsubheading Example
19881 frame=@{level="0",addr="0x00010734",func="callee4",
19882 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19883 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19884 frame=@{level="1",addr="0x0001076c",func="callee3",
19885 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19886 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19887 frame=@{level="2",addr="0x0001078c",func="callee2",
19888 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19889 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19890 frame=@{level="3",addr="0x000107b4",func="callee1",
19891 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19892 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19893 frame=@{level="4",addr="0x000107e0",func="main",
19894 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19895 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19897 -stack-list-arguments 0
19900 frame=@{level="0",args=[]@},
19901 frame=@{level="1",args=[name="strarg"]@},
19902 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19903 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19904 frame=@{level="4",args=[]@}]
19906 -stack-list-arguments 1
19909 frame=@{level="0",args=[]@},
19911 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19912 frame=@{level="2",args=[
19913 @{name="intarg",value="2"@},
19914 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19915 @{frame=@{level="3",args=[
19916 @{name="intarg",value="2"@},
19917 @{name="strarg",value="0x11940 \"A string argument.\""@},
19918 @{name="fltarg",value="3.5"@}]@},
19919 frame=@{level="4",args=[]@}]
19921 -stack-list-arguments 0 2 2
19922 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19924 -stack-list-arguments 1 2 2
19925 ^done,stack-args=[frame=@{level="2",
19926 args=[@{name="intarg",value="2"@},
19927 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19931 @c @subheading -stack-list-exception-handlers
19934 @subheading The @code{-stack-list-frames} Command
19935 @findex -stack-list-frames
19937 @subsubheading Synopsis
19940 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19943 List the frames currently on the stack. For each frame it displays the
19948 The frame number, 0 being the topmost frame, i.e., the innermost function.
19950 The @code{$pc} value for that frame.
19954 File name of the source file where the function lives.
19956 Line number corresponding to the @code{$pc}.
19959 If invoked without arguments, this command prints a backtrace for the
19960 whole stack. If given two integer arguments, it shows the frames whose
19961 levels are between the two arguments (inclusive). If the two arguments
19962 are equal, it shows the single frame at the corresponding level. It is
19963 an error if @var{low-frame} is larger than the actual number of
19964 frames. On the other hand, @var{high-frame} may be larger than the
19965 actual number of frames, in which case only existing frames will be returned.
19967 @subsubheading @value{GDBN} Command
19969 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19971 @subsubheading Example
19973 Full stack backtrace:
19979 [frame=@{level="0",addr="0x0001076c",func="foo",
19980 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19981 frame=@{level="1",addr="0x000107a4",func="foo",
19982 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19983 frame=@{level="2",addr="0x000107a4",func="foo",
19984 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19985 frame=@{level="3",addr="0x000107a4",func="foo",
19986 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19987 frame=@{level="4",addr="0x000107a4",func="foo",
19988 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19989 frame=@{level="5",addr="0x000107a4",func="foo",
19990 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19991 frame=@{level="6",addr="0x000107a4",func="foo",
19992 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19993 frame=@{level="7",addr="0x000107a4",func="foo",
19994 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19995 frame=@{level="8",addr="0x000107a4",func="foo",
19996 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19997 frame=@{level="9",addr="0x000107a4",func="foo",
19998 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19999 frame=@{level="10",addr="0x000107a4",func="foo",
20000 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20001 frame=@{level="11",addr="0x00010738",func="main",
20002 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
20006 Show frames between @var{low_frame} and @var{high_frame}:
20010 -stack-list-frames 3 5
20012 [frame=@{level="3",addr="0x000107a4",func="foo",
20013 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20014 frame=@{level="4",addr="0x000107a4",func="foo",
20015 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20016 frame=@{level="5",addr="0x000107a4",func="foo",
20017 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20021 Show a single frame:
20025 -stack-list-frames 3 3
20027 [frame=@{level="3",addr="0x000107a4",func="foo",
20028 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20033 @subheading The @code{-stack-list-locals} Command
20034 @findex -stack-list-locals
20036 @subsubheading Synopsis
20039 -stack-list-locals @var{print-values}
20042 Display the local variable names for the selected frame. If
20043 @var{print-values} is 0 or @code{--no-values}, print only the names of
20044 the variables; if it is 1 or @code{--all-values}, print also their
20045 values; and if it is 2 or @code{--simple-values}, print the name,
20046 type and value for simple data types and the name and type for arrays,
20047 structures and unions. In this last case, a frontend can immediately
20048 display the value of simple data types and create variable objects for
20049 other data types when the user wishes to explore their values in
20052 @subsubheading @value{GDBN} Command
20054 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
20056 @subsubheading Example
20060 -stack-list-locals 0
20061 ^done,locals=[name="A",name="B",name="C"]
20063 -stack-list-locals --all-values
20064 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
20065 @{name="C",value="@{1, 2, 3@}"@}]
20066 -stack-list-locals --simple-values
20067 ^done,locals=[@{name="A",type="int",value="1"@},
20068 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
20073 @subheading The @code{-stack-select-frame} Command
20074 @findex -stack-select-frame
20076 @subsubheading Synopsis
20079 -stack-select-frame @var{framenum}
20082 Change the selected frame. Select a different frame @var{framenum} on
20085 @subsubheading @value{GDBN} Command
20087 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
20088 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
20090 @subsubheading Example
20094 -stack-select-frame 2
20099 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20100 @node GDB/MI Variable Objects
20101 @section @sc{gdb/mi} Variable Objects
20105 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20107 For the implementation of a variable debugger window (locals, watched
20108 expressions, etc.), we are proposing the adaptation of the existing code
20109 used by @code{Insight}.
20111 The two main reasons for that are:
20115 It has been proven in practice (it is already on its second generation).
20118 It will shorten development time (needless to say how important it is
20122 The original interface was designed to be used by Tcl code, so it was
20123 slightly changed so it could be used through @sc{gdb/mi}. This section
20124 describes the @sc{gdb/mi} operations that will be available and gives some
20125 hints about their use.
20127 @emph{Note}: In addition to the set of operations described here, we
20128 expect the @sc{gui} implementation of a variable window to require, at
20129 least, the following operations:
20132 @item @code{-gdb-show} @code{output-radix}
20133 @item @code{-stack-list-arguments}
20134 @item @code{-stack-list-locals}
20135 @item @code{-stack-select-frame}
20140 @subheading Introduction to Variable Objects
20142 @cindex variable objects in @sc{gdb/mi}
20144 Variable objects are "object-oriented" MI interface for examining and
20145 changing values of expressions. Unlike some other MI interfaces that
20146 work with expressions, variable objects are specifically designed for
20147 simple and efficient presentation in the frontend. A variable object
20148 is identified by string name. When a variable object is created, the
20149 frontend specifies the expression for that variable object. The
20150 expression can be a simple variable, or it can be an arbitrary complex
20151 expression, and can even involve CPU registers. After creating a
20152 variable object, the frontend can invoke other variable object
20153 operations---for example to obtain or change the value of a variable
20154 object, or to change display format.
20156 Variable objects have hierarchical tree structure. Any variable object
20157 that corresponds to a composite type, such as structure in C, has
20158 a number of child variable objects, for example corresponding to each
20159 element of a structure. A child variable object can itself have
20160 children, recursively. Recursion ends when we reach
20161 leaf variable objects, which always have built-in types. Child variable
20162 objects are created only by explicit request, so if a frontend
20163 is not interested in the children of a particular variable object, no
20164 child will be created.
20166 For a leaf variable object it is possible to obtain its value as a
20167 string, or set the value from a string. String value can be also
20168 obtained for a non-leaf variable object, but it's generally a string
20169 that only indicates the type of the object, and does not list its
20170 contents. Assignment to a non-leaf variable object is not allowed.
20172 A frontend does not need to read the values of all variable objects each time
20173 the program stops. Instead, MI provides an update command that lists all
20174 variable objects whose values has changed since the last update
20175 operation. This considerably reduces the amount of data that must
20176 be transferred to the frontend. As noted above, children variable
20177 objects are created on demand, and only leaf variable objects have a
20178 real value. As result, gdb will read target memory only for leaf
20179 variables that frontend has created.
20181 The automatic update is not always desirable. For example, a frontend
20182 might want to keep a value of some expression for future reference,
20183 and never update it. For another example, fetching memory is
20184 relatively slow for embedded targets, so a frontend might want
20185 to disable automatic update for the variables that are either not
20186 visible on the screen, or ``closed''. This is possible using so
20187 called ``frozen variable objects''. Such variable objects are never
20188 implicitly updated.
20190 The following is the complete set of @sc{gdb/mi} operations defined to
20191 access this functionality:
20193 @multitable @columnfractions .4 .6
20194 @item @strong{Operation}
20195 @tab @strong{Description}
20197 @item @code{-var-create}
20198 @tab create a variable object
20199 @item @code{-var-delete}
20200 @tab delete the variable object and/or its children
20201 @item @code{-var-set-format}
20202 @tab set the display format of this variable
20203 @item @code{-var-show-format}
20204 @tab show the display format of this variable
20205 @item @code{-var-info-num-children}
20206 @tab tells how many children this object has
20207 @item @code{-var-list-children}
20208 @tab return a list of the object's children
20209 @item @code{-var-info-type}
20210 @tab show the type of this variable object
20211 @item @code{-var-info-expression}
20212 @tab print parent-relative expression that this variable object represents
20213 @item @code{-var-info-path-expression}
20214 @tab print full expression that this variable object represents
20215 @item @code{-var-show-attributes}
20216 @tab is this variable editable? does it exist here?
20217 @item @code{-var-evaluate-expression}
20218 @tab get the value of this variable
20219 @item @code{-var-assign}
20220 @tab set the value of this variable
20221 @item @code{-var-update}
20222 @tab update the variable and its children
20223 @item @code{-var-set-frozen}
20224 @tab set frozeness attribute
20227 In the next subsection we describe each operation in detail and suggest
20228 how it can be used.
20230 @subheading Description And Use of Operations on Variable Objects
20232 @subheading The @code{-var-create} Command
20233 @findex -var-create
20235 @subsubheading Synopsis
20238 -var-create @{@var{name} | "-"@}
20239 @{@var{frame-addr} | "*"@} @var{expression}
20242 This operation creates a variable object, which allows the monitoring of
20243 a variable, the result of an expression, a memory cell or a CPU
20246 The @var{name} parameter is the string by which the object can be
20247 referenced. It must be unique. If @samp{-} is specified, the varobj
20248 system will generate a string ``varNNNNNN'' automatically. It will be
20249 unique provided that one does not specify @var{name} on that format.
20250 The command fails if a duplicate name is found.
20252 The frame under which the expression should be evaluated can be
20253 specified by @var{frame-addr}. A @samp{*} indicates that the current
20254 frame should be used.
20256 @var{expression} is any expression valid on the current language set (must not
20257 begin with a @samp{*}), or one of the following:
20261 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20264 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20267 @samp{$@var{regname}} --- a CPU register name
20270 @subsubheading Result
20272 This operation returns the name, number of children and the type of the
20273 object created. Type is returned as a string as the ones generated by
20274 the @value{GDBN} CLI:
20277 name="@var{name}",numchild="N",type="@var{type}"
20281 @subheading The @code{-var-delete} Command
20282 @findex -var-delete
20284 @subsubheading Synopsis
20287 -var-delete [ -c ] @var{name}
20290 Deletes a previously created variable object and all of its children.
20291 With the @samp{-c} option, just deletes the children.
20293 Returns an error if the object @var{name} is not found.
20296 @subheading The @code{-var-set-format} Command
20297 @findex -var-set-format
20299 @subsubheading Synopsis
20302 -var-set-format @var{name} @var{format-spec}
20305 Sets the output format for the value of the object @var{name} to be
20308 @anchor{-var-set-format}
20309 The syntax for the @var{format-spec} is as follows:
20312 @var{format-spec} @expansion{}
20313 @{binary | decimal | hexadecimal | octal | natural@}
20316 The natural format is the default format choosen automatically
20317 based on the variable type (like decimal for an @code{int}, hex
20318 for pointers, etc.).
20320 For a variable with children, the format is set only on the
20321 variable itself, and the children are not affected.
20323 @subheading The @code{-var-show-format} Command
20324 @findex -var-show-format
20326 @subsubheading Synopsis
20329 -var-show-format @var{name}
20332 Returns the format used to display the value of the object @var{name}.
20335 @var{format} @expansion{}
20340 @subheading The @code{-var-info-num-children} Command
20341 @findex -var-info-num-children
20343 @subsubheading Synopsis
20346 -var-info-num-children @var{name}
20349 Returns the number of children of a variable object @var{name}:
20356 @subheading The @code{-var-list-children} Command
20357 @findex -var-list-children
20359 @subsubheading Synopsis
20362 -var-list-children [@var{print-values}] @var{name}
20364 @anchor{-var-list-children}
20366 Return a list of the children of the specified variable object and
20367 create variable objects for them, if they do not already exist. With
20368 a single argument or if @var{print-values} has a value for of 0 or
20369 @code{--no-values}, print only the names of the variables; if
20370 @var{print-values} is 1 or @code{--all-values}, also print their
20371 values; and if it is 2 or @code{--simple-values} print the name and
20372 value for simple data types and just the name for arrays, structures
20375 @subsubheading Example
20379 -var-list-children n
20380 ^done,numchild=@var{n},children=[@{name=@var{name},
20381 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20383 -var-list-children --all-values n
20384 ^done,numchild=@var{n},children=[@{name=@var{name},
20385 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20389 @subheading The @code{-var-info-type} Command
20390 @findex -var-info-type
20392 @subsubheading Synopsis
20395 -var-info-type @var{name}
20398 Returns the type of the specified variable @var{name}. The type is
20399 returned as a string in the same format as it is output by the
20403 type=@var{typename}
20407 @subheading The @code{-var-info-expression} Command
20408 @findex -var-info-expression
20410 @subsubheading Synopsis
20413 -var-info-expression @var{name}
20416 Returns a string that is suitable for presenting this
20417 variable object in user interface. The string is generally
20418 not valid expression in the current language, and cannot be evaluated.
20420 For example, if @code{a} is an array, and variable object
20421 @code{A} was created for @code{a}, then we'll get this output:
20424 (gdb) -var-info-expression A.1
20425 ^done,lang="C",exp="1"
20429 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
20431 Note that the output of the @code{-var-list-children} command also
20432 includes those expressions, so the @code{-var-info-expression} command
20435 @subheading The @code{-var-info-path-expression} Command
20436 @findex -var-info-path-expression
20438 @subsubheading Synopsis
20441 -var-info-path-expression @var{name}
20444 Returns an expression that can be evaluated in the current
20445 context and will yield the same value that a variable object has.
20446 Compare this with the @code{-var-info-expression} command, which
20447 result can be used only for UI presentation. Typical use of
20448 the @code{-var-info-path-expression} command is creating a
20449 watchpoint from a variable object.
20451 For example, suppose @code{C} is a C@t{++} class, derived from class
20452 @code{Base}, and that the @code{Base} class has a member called
20453 @code{m_size}. Assume a variable @code{c} is has the type of
20454 @code{C} and a variable object @code{C} was created for variable
20455 @code{c}. Then, we'll get this output:
20457 (gdb) -var-info-path-expression C.Base.public.m_size
20458 ^done,path_expr=((Base)c).m_size)
20461 @subheading The @code{-var-show-attributes} Command
20462 @findex -var-show-attributes
20464 @subsubheading Synopsis
20467 -var-show-attributes @var{name}
20470 List attributes of the specified variable object @var{name}:
20473 status=@var{attr} [ ( ,@var{attr} )* ]
20477 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20479 @subheading The @code{-var-evaluate-expression} Command
20480 @findex -var-evaluate-expression
20482 @subsubheading Synopsis
20485 -var-evaluate-expression [-f @var{format-spec}] @var{name}
20488 Evaluates the expression that is represented by the specified variable
20489 object and returns its value as a string. The format of the string
20490 can be specified with the @samp{-f} option. The possible values of
20491 this option are the same as for @code{-var-set-format}
20492 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
20493 the current display format will be used. The current display format
20494 can be changed using the @code{-var-set-format} command.
20500 Note that one must invoke @code{-var-list-children} for a variable
20501 before the value of a child variable can be evaluated.
20503 @subheading The @code{-var-assign} Command
20504 @findex -var-assign
20506 @subsubheading Synopsis
20509 -var-assign @var{name} @var{expression}
20512 Assigns the value of @var{expression} to the variable object specified
20513 by @var{name}. The object must be @samp{editable}. If the variable's
20514 value is altered by the assign, the variable will show up in any
20515 subsequent @code{-var-update} list.
20517 @subsubheading Example
20525 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20529 @subheading The @code{-var-update} Command
20530 @findex -var-update
20532 @subsubheading Synopsis
20535 -var-update [@var{print-values}] @{@var{name} | "*"@}
20538 Reevaluate the expressions corresponding to the variable object
20539 @var{name} and all its direct and indirect children, and return the
20540 list of variable objects whose values have changed; @var{name} must
20541 be a root variable object. Here, ``changed'' means that the result of
20542 @code{-var-evaluate-expression} before and after the
20543 @code{-var-update} is different. If @samp{*} is used as the variable
20544 object names, all existing variable objects are updated, except
20545 for frozen ones (@pxref{-var-set-frozen}). The option
20546 @var{print-values} determines whether both names and values, or just
20547 names are printed. The possible values of this option are the same
20548 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
20549 recommended to use the @samp{--all-values} option, to reduce the
20550 number of MI commands needed on each program stop.
20553 @subsubheading Example
20560 -var-update --all-values var1
20561 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20562 type_changed="false"@}]
20566 @anchor{-var-update}
20567 The field in_scope may take three values:
20571 The variable object's current value is valid.
20574 The variable object does not currently hold a valid value but it may
20575 hold one in the future if its associated expression comes back into
20579 The variable object no longer holds a valid value.
20580 This can occur when the executable file being debugged has changed,
20581 either through recompilation or by using the @value{GDBN} @code{file}
20582 command. The front end should normally choose to delete these variable
20586 In the future new values may be added to this list so the front should
20587 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
20589 @subheading The @code{-var-set-frozen} Command
20590 @findex -var-set-frozen
20591 @anchor{-var-set-frozen}
20593 @subsubheading Synopsis
20596 -var-set-frozen @var{name} @var{flag}
20599 Set the frozenness flag on the variable object @var{name}. The
20600 @var{flag} parameter should be either @samp{1} to make the variable
20601 frozen or @samp{0} to make it unfrozen. If a variable object is
20602 frozen, then neither itself, nor any of its children, are
20603 implicitly updated by @code{-var-update} of
20604 a parent variable or by @code{-var-update *}. Only
20605 @code{-var-update} of the variable itself will update its value and
20606 values of its children. After a variable object is unfrozen, it is
20607 implicitly updated by all subsequent @code{-var-update} operations.
20608 Unfreezing a variable does not update it, only subsequent
20609 @code{-var-update} does.
20611 @subsubheading Example
20615 -var-set-frozen V 1
20621 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20622 @node GDB/MI Data Manipulation
20623 @section @sc{gdb/mi} Data Manipulation
20625 @cindex data manipulation, in @sc{gdb/mi}
20626 @cindex @sc{gdb/mi}, data manipulation
20627 This section describes the @sc{gdb/mi} commands that manipulate data:
20628 examine memory and registers, evaluate expressions, etc.
20630 @c REMOVED FROM THE INTERFACE.
20631 @c @subheading -data-assign
20632 @c Change the value of a program variable. Plenty of side effects.
20633 @c @subsubheading GDB Command
20635 @c @subsubheading Example
20638 @subheading The @code{-data-disassemble} Command
20639 @findex -data-disassemble
20641 @subsubheading Synopsis
20645 [ -s @var{start-addr} -e @var{end-addr} ]
20646 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20654 @item @var{start-addr}
20655 is the beginning address (or @code{$pc})
20656 @item @var{end-addr}
20658 @item @var{filename}
20659 is the name of the file to disassemble
20660 @item @var{linenum}
20661 is the line number to disassemble around
20663 is the number of disassembly lines to be produced. If it is -1,
20664 the whole function will be disassembled, in case no @var{end-addr} is
20665 specified. If @var{end-addr} is specified as a non-zero value, and
20666 @var{lines} is lower than the number of disassembly lines between
20667 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20668 displayed; if @var{lines} is higher than the number of lines between
20669 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20672 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20676 @subsubheading Result
20678 The output for each instruction is composed of four fields:
20687 Note that whatever included in the instruction field, is not manipulated
20688 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20690 @subsubheading @value{GDBN} Command
20692 There's no direct mapping from this command to the CLI.
20694 @subsubheading Example
20696 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20700 -data-disassemble -s $pc -e "$pc + 20" -- 0
20703 @{address="0x000107c0",func-name="main",offset="4",
20704 inst="mov 2, %o0"@},
20705 @{address="0x000107c4",func-name="main",offset="8",
20706 inst="sethi %hi(0x11800), %o2"@},
20707 @{address="0x000107c8",func-name="main",offset="12",
20708 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20709 @{address="0x000107cc",func-name="main",offset="16",
20710 inst="sethi %hi(0x11800), %o2"@},
20711 @{address="0x000107d0",func-name="main",offset="20",
20712 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20716 Disassemble the whole @code{main} function. Line 32 is part of
20720 -data-disassemble -f basics.c -l 32 -- 0
20722 @{address="0x000107bc",func-name="main",offset="0",
20723 inst="save %sp, -112, %sp"@},
20724 @{address="0x000107c0",func-name="main",offset="4",
20725 inst="mov 2, %o0"@},
20726 @{address="0x000107c4",func-name="main",offset="8",
20727 inst="sethi %hi(0x11800), %o2"@},
20729 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20730 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20734 Disassemble 3 instructions from the start of @code{main}:
20738 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20740 @{address="0x000107bc",func-name="main",offset="0",
20741 inst="save %sp, -112, %sp"@},
20742 @{address="0x000107c0",func-name="main",offset="4",
20743 inst="mov 2, %o0"@},
20744 @{address="0x000107c4",func-name="main",offset="8",
20745 inst="sethi %hi(0x11800), %o2"@}]
20749 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20753 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20755 src_and_asm_line=@{line="31",
20756 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20757 testsuite/gdb.mi/basics.c",line_asm_insn=[
20758 @{address="0x000107bc",func-name="main",offset="0",
20759 inst="save %sp, -112, %sp"@}]@},
20760 src_and_asm_line=@{line="32",
20761 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20762 testsuite/gdb.mi/basics.c",line_asm_insn=[
20763 @{address="0x000107c0",func-name="main",offset="4",
20764 inst="mov 2, %o0"@},
20765 @{address="0x000107c4",func-name="main",offset="8",
20766 inst="sethi %hi(0x11800), %o2"@}]@}]
20771 @subheading The @code{-data-evaluate-expression} Command
20772 @findex -data-evaluate-expression
20774 @subsubheading Synopsis
20777 -data-evaluate-expression @var{expr}
20780 Evaluate @var{expr} as an expression. The expression could contain an
20781 inferior function call. The function call will execute synchronously.
20782 If the expression contains spaces, it must be enclosed in double quotes.
20784 @subsubheading @value{GDBN} Command
20786 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20787 @samp{call}. In @code{gdbtk} only, there's a corresponding
20788 @samp{gdb_eval} command.
20790 @subsubheading Example
20792 In the following example, the numbers that precede the commands are the
20793 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20794 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20798 211-data-evaluate-expression A
20801 311-data-evaluate-expression &A
20802 311^done,value="0xefffeb7c"
20804 411-data-evaluate-expression A+3
20807 511-data-evaluate-expression "A + 3"
20813 @subheading The @code{-data-list-changed-registers} Command
20814 @findex -data-list-changed-registers
20816 @subsubheading Synopsis
20819 -data-list-changed-registers
20822 Display a list of the registers that have changed.
20824 @subsubheading @value{GDBN} Command
20826 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20827 has the corresponding command @samp{gdb_changed_register_list}.
20829 @subsubheading Example
20831 On a PPC MBX board:
20839 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
20840 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
20843 -data-list-changed-registers
20844 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20845 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20846 "24","25","26","27","28","30","31","64","65","66","67","69"]
20851 @subheading The @code{-data-list-register-names} Command
20852 @findex -data-list-register-names
20854 @subsubheading Synopsis
20857 -data-list-register-names [ ( @var{regno} )+ ]
20860 Show a list of register names for the current target. If no arguments
20861 are given, it shows a list of the names of all the registers. If
20862 integer numbers are given as arguments, it will print a list of the
20863 names of the registers corresponding to the arguments. To ensure
20864 consistency between a register name and its number, the output list may
20865 include empty register names.
20867 @subsubheading @value{GDBN} Command
20869 @value{GDBN} does not have a command which corresponds to
20870 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20871 corresponding command @samp{gdb_regnames}.
20873 @subsubheading Example
20875 For the PPC MBX board:
20878 -data-list-register-names
20879 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20880 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20881 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20882 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20883 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20884 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20885 "", "pc","ps","cr","lr","ctr","xer"]
20887 -data-list-register-names 1 2 3
20888 ^done,register-names=["r1","r2","r3"]
20892 @subheading The @code{-data-list-register-values} Command
20893 @findex -data-list-register-values
20895 @subsubheading Synopsis
20898 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20901 Display the registers' contents. @var{fmt} is the format according to
20902 which the registers' contents are to be returned, followed by an optional
20903 list of numbers specifying the registers to display. A missing list of
20904 numbers indicates that the contents of all the registers must be returned.
20906 Allowed formats for @var{fmt} are:
20923 @subsubheading @value{GDBN} Command
20925 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20926 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20928 @subsubheading Example
20930 For a PPC MBX board (note: line breaks are for readability only, they
20931 don't appear in the actual output):
20935 -data-list-register-values r 64 65
20936 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20937 @{number="65",value="0x00029002"@}]
20939 -data-list-register-values x
20940 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20941 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20942 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20943 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20944 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20945 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20946 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20947 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20948 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20949 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20950 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20951 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20952 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20953 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20954 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20955 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20956 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20957 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20958 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20959 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20960 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20961 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20962 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20963 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20964 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20965 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20966 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20967 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20968 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20969 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20970 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20971 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20972 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20973 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20974 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20975 @{number="69",value="0x20002b03"@}]
20980 @subheading The @code{-data-read-memory} Command
20981 @findex -data-read-memory
20983 @subsubheading Synopsis
20986 -data-read-memory [ -o @var{byte-offset} ]
20987 @var{address} @var{word-format} @var{word-size}
20988 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20995 @item @var{address}
20996 An expression specifying the address of the first memory word to be
20997 read. Complex expressions containing embedded white space should be
20998 quoted using the C convention.
21000 @item @var{word-format}
21001 The format to be used to print the memory words. The notation is the
21002 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
21005 @item @var{word-size}
21006 The size of each memory word in bytes.
21008 @item @var{nr-rows}
21009 The number of rows in the output table.
21011 @item @var{nr-cols}
21012 The number of columns in the output table.
21015 If present, indicates that each row should include an @sc{ascii} dump. The
21016 value of @var{aschar} is used as a padding character when a byte is not a
21017 member of the printable @sc{ascii} character set (printable @sc{ascii}
21018 characters are those whose code is between 32 and 126, inclusively).
21020 @item @var{byte-offset}
21021 An offset to add to the @var{address} before fetching memory.
21024 This command displays memory contents as a table of @var{nr-rows} by
21025 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
21026 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
21027 (returned as @samp{total-bytes}). Should less than the requested number
21028 of bytes be returned by the target, the missing words are identified
21029 using @samp{N/A}. The number of bytes read from the target is returned
21030 in @samp{nr-bytes} and the starting address used to read memory in
21033 The address of the next/previous row or page is available in
21034 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
21037 @subsubheading @value{GDBN} Command
21039 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
21040 @samp{gdb_get_mem} memory read command.
21042 @subsubheading Example
21044 Read six bytes of memory starting at @code{bytes+6} but then offset by
21045 @code{-6} bytes. Format as three rows of two columns. One byte per
21046 word. Display each word in hex.
21050 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
21051 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
21052 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
21053 prev-page="0x0000138a",memory=[
21054 @{addr="0x00001390",data=["0x00","0x01"]@},
21055 @{addr="0x00001392",data=["0x02","0x03"]@},
21056 @{addr="0x00001394",data=["0x04","0x05"]@}]
21060 Read two bytes of memory starting at address @code{shorts + 64} and
21061 display as a single word formatted in decimal.
21065 5-data-read-memory shorts+64 d 2 1 1
21066 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
21067 next-row="0x00001512",prev-row="0x0000150e",
21068 next-page="0x00001512",prev-page="0x0000150e",memory=[
21069 @{addr="0x00001510",data=["128"]@}]
21073 Read thirty two bytes of memory starting at @code{bytes+16} and format
21074 as eight rows of four columns. Include a string encoding with @samp{x}
21075 used as the non-printable character.
21079 4-data-read-memory bytes+16 x 1 8 4 x
21080 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
21081 next-row="0x000013c0",prev-row="0x0000139c",
21082 next-page="0x000013c0",prev-page="0x00001380",memory=[
21083 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
21084 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
21085 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
21086 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
21087 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
21088 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
21089 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
21090 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
21094 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21095 @node GDB/MI Tracepoint Commands
21096 @section @sc{gdb/mi} Tracepoint Commands
21098 The tracepoint commands are not yet implemented.
21100 @c @subheading -trace-actions
21102 @c @subheading -trace-delete
21104 @c @subheading -trace-disable
21106 @c @subheading -trace-dump
21108 @c @subheading -trace-enable
21110 @c @subheading -trace-exists
21112 @c @subheading -trace-find
21114 @c @subheading -trace-frame-number
21116 @c @subheading -trace-info
21118 @c @subheading -trace-insert
21120 @c @subheading -trace-list
21122 @c @subheading -trace-pass-count
21124 @c @subheading -trace-save
21126 @c @subheading -trace-start
21128 @c @subheading -trace-stop
21131 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21132 @node GDB/MI Symbol Query
21133 @section @sc{gdb/mi} Symbol Query Commands
21136 @subheading The @code{-symbol-info-address} Command
21137 @findex -symbol-info-address
21139 @subsubheading Synopsis
21142 -symbol-info-address @var{symbol}
21145 Describe where @var{symbol} is stored.
21147 @subsubheading @value{GDBN} Command
21149 The corresponding @value{GDBN} command is @samp{info address}.
21151 @subsubheading Example
21155 @subheading The @code{-symbol-info-file} Command
21156 @findex -symbol-info-file
21158 @subsubheading Synopsis
21164 Show the file for the symbol.
21166 @subsubheading @value{GDBN} Command
21168 There's no equivalent @value{GDBN} command. @code{gdbtk} has
21169 @samp{gdb_find_file}.
21171 @subsubheading Example
21175 @subheading The @code{-symbol-info-function} Command
21176 @findex -symbol-info-function
21178 @subsubheading Synopsis
21181 -symbol-info-function
21184 Show which function the symbol lives in.
21186 @subsubheading @value{GDBN} Command
21188 @samp{gdb_get_function} in @code{gdbtk}.
21190 @subsubheading Example
21194 @subheading The @code{-symbol-info-line} Command
21195 @findex -symbol-info-line
21197 @subsubheading Synopsis
21203 Show the core addresses of the code for a source line.
21205 @subsubheading @value{GDBN} Command
21207 The corresponding @value{GDBN} command is @samp{info line}.
21208 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
21210 @subsubheading Example
21214 @subheading The @code{-symbol-info-symbol} Command
21215 @findex -symbol-info-symbol
21217 @subsubheading Synopsis
21220 -symbol-info-symbol @var{addr}
21223 Describe what symbol is at location @var{addr}.
21225 @subsubheading @value{GDBN} Command
21227 The corresponding @value{GDBN} command is @samp{info symbol}.
21229 @subsubheading Example
21233 @subheading The @code{-symbol-list-functions} Command
21234 @findex -symbol-list-functions
21236 @subsubheading Synopsis
21239 -symbol-list-functions
21242 List the functions in the executable.
21244 @subsubheading @value{GDBN} Command
21246 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
21247 @samp{gdb_search} in @code{gdbtk}.
21249 @subsubheading Example
21253 @subheading The @code{-symbol-list-lines} Command
21254 @findex -symbol-list-lines
21256 @subsubheading Synopsis
21259 -symbol-list-lines @var{filename}
21262 Print the list of lines that contain code and their associated program
21263 addresses for the given source filename. The entries are sorted in
21264 ascending PC order.
21266 @subsubheading @value{GDBN} Command
21268 There is no corresponding @value{GDBN} command.
21270 @subsubheading Example
21273 -symbol-list-lines basics.c
21274 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
21279 @subheading The @code{-symbol-list-types} Command
21280 @findex -symbol-list-types
21282 @subsubheading Synopsis
21288 List all the type names.
21290 @subsubheading @value{GDBN} Command
21292 The corresponding commands are @samp{info types} in @value{GDBN},
21293 @samp{gdb_search} in @code{gdbtk}.
21295 @subsubheading Example
21299 @subheading The @code{-symbol-list-variables} Command
21300 @findex -symbol-list-variables
21302 @subsubheading Synopsis
21305 -symbol-list-variables
21308 List all the global and static variable names.
21310 @subsubheading @value{GDBN} Command
21312 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
21314 @subsubheading Example
21318 @subheading The @code{-symbol-locate} Command
21319 @findex -symbol-locate
21321 @subsubheading Synopsis
21327 @subsubheading @value{GDBN} Command
21329 @samp{gdb_loc} in @code{gdbtk}.
21331 @subsubheading Example
21335 @subheading The @code{-symbol-type} Command
21336 @findex -symbol-type
21338 @subsubheading Synopsis
21341 -symbol-type @var{variable}
21344 Show type of @var{variable}.
21346 @subsubheading @value{GDBN} Command
21348 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
21349 @samp{gdb_obj_variable}.
21351 @subsubheading Example
21355 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21356 @node GDB/MI File Commands
21357 @section @sc{gdb/mi} File Commands
21359 This section describes the GDB/MI commands to specify executable file names
21360 and to read in and obtain symbol table information.
21362 @subheading The @code{-file-exec-and-symbols} Command
21363 @findex -file-exec-and-symbols
21365 @subsubheading Synopsis
21368 -file-exec-and-symbols @var{file}
21371 Specify the executable file to be debugged. This file is the one from
21372 which the symbol table is also read. If no file is specified, the
21373 command clears the executable and symbol information. If breakpoints
21374 are set when using this command with no arguments, @value{GDBN} will produce
21375 error messages. Otherwise, no output is produced, except a completion
21378 @subsubheading @value{GDBN} Command
21380 The corresponding @value{GDBN} command is @samp{file}.
21382 @subsubheading Example
21386 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21392 @subheading The @code{-file-exec-file} Command
21393 @findex -file-exec-file
21395 @subsubheading Synopsis
21398 -file-exec-file @var{file}
21401 Specify the executable file to be debugged. Unlike
21402 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
21403 from this file. If used without argument, @value{GDBN} clears the information
21404 about the executable file. No output is produced, except a completion
21407 @subsubheading @value{GDBN} Command
21409 The corresponding @value{GDBN} command is @samp{exec-file}.
21411 @subsubheading Example
21415 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21421 @subheading The @code{-file-list-exec-sections} Command
21422 @findex -file-list-exec-sections
21424 @subsubheading Synopsis
21427 -file-list-exec-sections
21430 List the sections of the current executable file.
21432 @subsubheading @value{GDBN} Command
21434 The @value{GDBN} command @samp{info file} shows, among the rest, the same
21435 information as this command. @code{gdbtk} has a corresponding command
21436 @samp{gdb_load_info}.
21438 @subsubheading Example
21442 @subheading The @code{-file-list-exec-source-file} Command
21443 @findex -file-list-exec-source-file
21445 @subsubheading Synopsis
21448 -file-list-exec-source-file
21451 List the line number, the current source file, and the absolute path
21452 to the current source file for the current executable. The macro
21453 information field has a value of @samp{1} or @samp{0} depending on
21454 whether or not the file includes preprocessor macro information.
21456 @subsubheading @value{GDBN} Command
21458 The @value{GDBN} equivalent is @samp{info source}
21460 @subsubheading Example
21464 123-file-list-exec-source-file
21465 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
21470 @subheading The @code{-file-list-exec-source-files} Command
21471 @findex -file-list-exec-source-files
21473 @subsubheading Synopsis
21476 -file-list-exec-source-files
21479 List the source files for the current executable.
21481 It will always output the filename, but only when @value{GDBN} can find
21482 the absolute file name of a source file, will it output the fullname.
21484 @subsubheading @value{GDBN} Command
21486 The @value{GDBN} equivalent is @samp{info sources}.
21487 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
21489 @subsubheading Example
21492 -file-list-exec-source-files
21494 @{file=foo.c,fullname=/home/foo.c@},
21495 @{file=/home/bar.c,fullname=/home/bar.c@},
21496 @{file=gdb_could_not_find_fullpath.c@}]
21500 @subheading The @code{-file-list-shared-libraries} Command
21501 @findex -file-list-shared-libraries
21503 @subsubheading Synopsis
21506 -file-list-shared-libraries
21509 List the shared libraries in the program.
21511 @subsubheading @value{GDBN} Command
21513 The corresponding @value{GDBN} command is @samp{info shared}.
21515 @subsubheading Example
21519 @subheading The @code{-file-list-symbol-files} Command
21520 @findex -file-list-symbol-files
21522 @subsubheading Synopsis
21525 -file-list-symbol-files
21530 @subsubheading @value{GDBN} Command
21532 The corresponding @value{GDBN} command is @samp{info file} (part of it).
21534 @subsubheading Example
21538 @subheading The @code{-file-symbol-file} Command
21539 @findex -file-symbol-file
21541 @subsubheading Synopsis
21544 -file-symbol-file @var{file}
21547 Read symbol table info from the specified @var{file} argument. When
21548 used without arguments, clears @value{GDBN}'s symbol table info. No output is
21549 produced, except for a completion notification.
21551 @subsubheading @value{GDBN} Command
21553 The corresponding @value{GDBN} command is @samp{symbol-file}.
21555 @subsubheading Example
21559 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21565 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21566 @node GDB/MI Memory Overlay Commands
21567 @section @sc{gdb/mi} Memory Overlay Commands
21569 The memory overlay commands are not implemented.
21571 @c @subheading -overlay-auto
21573 @c @subheading -overlay-list-mapping-state
21575 @c @subheading -overlay-list-overlays
21577 @c @subheading -overlay-map
21579 @c @subheading -overlay-off
21581 @c @subheading -overlay-on
21583 @c @subheading -overlay-unmap
21585 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21586 @node GDB/MI Signal Handling Commands
21587 @section @sc{gdb/mi} Signal Handling Commands
21589 Signal handling commands are not implemented.
21591 @c @subheading -signal-handle
21593 @c @subheading -signal-list-handle-actions
21595 @c @subheading -signal-list-signal-types
21599 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21600 @node GDB/MI Target Manipulation
21601 @section @sc{gdb/mi} Target Manipulation Commands
21604 @subheading The @code{-target-attach} Command
21605 @findex -target-attach
21607 @subsubheading Synopsis
21610 -target-attach @var{pid} | @var{file}
21613 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
21615 @subsubheading @value{GDBN} Command
21617 The corresponding @value{GDBN} command is @samp{attach}.
21619 @subsubheading Example
21623 @subheading The @code{-target-compare-sections} Command
21624 @findex -target-compare-sections
21626 @subsubheading Synopsis
21629 -target-compare-sections [ @var{section} ]
21632 Compare data of section @var{section} on target to the exec file.
21633 Without the argument, all sections are compared.
21635 @subsubheading @value{GDBN} Command
21637 The @value{GDBN} equivalent is @samp{compare-sections}.
21639 @subsubheading Example
21643 @subheading The @code{-target-detach} Command
21644 @findex -target-detach
21646 @subsubheading Synopsis
21652 Detach from the remote target which normally resumes its execution.
21655 @subsubheading @value{GDBN} Command
21657 The corresponding @value{GDBN} command is @samp{detach}.
21659 @subsubheading Example
21669 @subheading The @code{-target-disconnect} Command
21670 @findex -target-disconnect
21672 @subsubheading Synopsis
21678 Disconnect from the remote target. There's no output and the target is
21679 generally not resumed.
21681 @subsubheading @value{GDBN} Command
21683 The corresponding @value{GDBN} command is @samp{disconnect}.
21685 @subsubheading Example
21695 @subheading The @code{-target-download} Command
21696 @findex -target-download
21698 @subsubheading Synopsis
21704 Loads the executable onto the remote target.
21705 It prints out an update message every half second, which includes the fields:
21709 The name of the section.
21711 The size of what has been sent so far for that section.
21713 The size of the section.
21715 The total size of what was sent so far (the current and the previous sections).
21717 The size of the overall executable to download.
21721 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21722 @sc{gdb/mi} Output Syntax}).
21724 In addition, it prints the name and size of the sections, as they are
21725 downloaded. These messages include the following fields:
21729 The name of the section.
21731 The size of the section.
21733 The size of the overall executable to download.
21737 At the end, a summary is printed.
21739 @subsubheading @value{GDBN} Command
21741 The corresponding @value{GDBN} command is @samp{load}.
21743 @subsubheading Example
21745 Note: each status message appears on a single line. Here the messages
21746 have been broken down so that they can fit onto a page.
21751 +download,@{section=".text",section-size="6668",total-size="9880"@}
21752 +download,@{section=".text",section-sent="512",section-size="6668",
21753 total-sent="512",total-size="9880"@}
21754 +download,@{section=".text",section-sent="1024",section-size="6668",
21755 total-sent="1024",total-size="9880"@}
21756 +download,@{section=".text",section-sent="1536",section-size="6668",
21757 total-sent="1536",total-size="9880"@}
21758 +download,@{section=".text",section-sent="2048",section-size="6668",
21759 total-sent="2048",total-size="9880"@}
21760 +download,@{section=".text",section-sent="2560",section-size="6668",
21761 total-sent="2560",total-size="9880"@}
21762 +download,@{section=".text",section-sent="3072",section-size="6668",
21763 total-sent="3072",total-size="9880"@}
21764 +download,@{section=".text",section-sent="3584",section-size="6668",
21765 total-sent="3584",total-size="9880"@}
21766 +download,@{section=".text",section-sent="4096",section-size="6668",
21767 total-sent="4096",total-size="9880"@}
21768 +download,@{section=".text",section-sent="4608",section-size="6668",
21769 total-sent="4608",total-size="9880"@}
21770 +download,@{section=".text",section-sent="5120",section-size="6668",
21771 total-sent="5120",total-size="9880"@}
21772 +download,@{section=".text",section-sent="5632",section-size="6668",
21773 total-sent="5632",total-size="9880"@}
21774 +download,@{section=".text",section-sent="6144",section-size="6668",
21775 total-sent="6144",total-size="9880"@}
21776 +download,@{section=".text",section-sent="6656",section-size="6668",
21777 total-sent="6656",total-size="9880"@}
21778 +download,@{section=".init",section-size="28",total-size="9880"@}
21779 +download,@{section=".fini",section-size="28",total-size="9880"@}
21780 +download,@{section=".data",section-size="3156",total-size="9880"@}
21781 +download,@{section=".data",section-sent="512",section-size="3156",
21782 total-sent="7236",total-size="9880"@}
21783 +download,@{section=".data",section-sent="1024",section-size="3156",
21784 total-sent="7748",total-size="9880"@}
21785 +download,@{section=".data",section-sent="1536",section-size="3156",
21786 total-sent="8260",total-size="9880"@}
21787 +download,@{section=".data",section-sent="2048",section-size="3156",
21788 total-sent="8772",total-size="9880"@}
21789 +download,@{section=".data",section-sent="2560",section-size="3156",
21790 total-sent="9284",total-size="9880"@}
21791 +download,@{section=".data",section-sent="3072",section-size="3156",
21792 total-sent="9796",total-size="9880"@}
21793 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21799 @subheading The @code{-target-exec-status} Command
21800 @findex -target-exec-status
21802 @subsubheading Synopsis
21805 -target-exec-status
21808 Provide information on the state of the target (whether it is running or
21809 not, for instance).
21811 @subsubheading @value{GDBN} Command
21813 There's no equivalent @value{GDBN} command.
21815 @subsubheading Example
21819 @subheading The @code{-target-list-available-targets} Command
21820 @findex -target-list-available-targets
21822 @subsubheading Synopsis
21825 -target-list-available-targets
21828 List the possible targets to connect to.
21830 @subsubheading @value{GDBN} Command
21832 The corresponding @value{GDBN} command is @samp{help target}.
21834 @subsubheading Example
21838 @subheading The @code{-target-list-current-targets} Command
21839 @findex -target-list-current-targets
21841 @subsubheading Synopsis
21844 -target-list-current-targets
21847 Describe the current target.
21849 @subsubheading @value{GDBN} Command
21851 The corresponding information is printed by @samp{info file} (among
21854 @subsubheading Example
21858 @subheading The @code{-target-list-parameters} Command
21859 @findex -target-list-parameters
21861 @subsubheading Synopsis
21864 -target-list-parameters
21869 @subsubheading @value{GDBN} Command
21873 @subsubheading Example
21877 @subheading The @code{-target-select} Command
21878 @findex -target-select
21880 @subsubheading Synopsis
21883 -target-select @var{type} @var{parameters @dots{}}
21886 Connect @value{GDBN} to the remote target. This command takes two args:
21890 The type of target, for instance @samp{remote}, etc.
21891 @item @var{parameters}
21892 Device names, host names and the like. @xref{Target Commands, ,
21893 Commands for Managing Targets}, for more details.
21896 The output is a connection notification, followed by the address at
21897 which the target program is, in the following form:
21900 ^connected,addr="@var{address}",func="@var{function name}",
21901 args=[@var{arg list}]
21904 @subsubheading @value{GDBN} Command
21906 The corresponding @value{GDBN} command is @samp{target}.
21908 @subsubheading Example
21912 -target-select remote /dev/ttya
21913 ^connected,addr="0xfe00a300",func="??",args=[]
21917 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21918 @node GDB/MI File Transfer Commands
21919 @section @sc{gdb/mi} File Transfer Commands
21922 @subheading The @code{-target-file-put} Command
21923 @findex -target-file-put
21925 @subsubheading Synopsis
21928 -target-file-put @var{hostfile} @var{targetfile}
21931 Copy file @var{hostfile} from the host system (the machine running
21932 @value{GDBN}) to @var{targetfile} on the target system.
21934 @subsubheading @value{GDBN} Command
21936 The corresponding @value{GDBN} command is @samp{remote put}.
21938 @subsubheading Example
21942 -target-file-put localfile remotefile
21948 @subheading The @code{-target-file-get} Command
21949 @findex -target-file-get
21951 @subsubheading Synopsis
21954 -target-file-get @var{targetfile} @var{hostfile}
21957 Copy file @var{targetfile} from the target system to @var{hostfile}
21958 on the host system.
21960 @subsubheading @value{GDBN} Command
21962 The corresponding @value{GDBN} command is @samp{remote get}.
21964 @subsubheading Example
21968 -target-file-get remotefile localfile
21974 @subheading The @code{-target-file-delete} Command
21975 @findex -target-file-delete
21977 @subsubheading Synopsis
21980 -target-file-delete @var{targetfile}
21983 Delete @var{targetfile} from the target system.
21985 @subsubheading @value{GDBN} Command
21987 The corresponding @value{GDBN} command is @samp{remote delete}.
21989 @subsubheading Example
21993 -target-file-delete remotefile
21999 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22000 @node GDB/MI Miscellaneous Commands
22001 @section Miscellaneous @sc{gdb/mi} Commands
22003 @c @subheading -gdb-complete
22005 @subheading The @code{-gdb-exit} Command
22008 @subsubheading Synopsis
22014 Exit @value{GDBN} immediately.
22016 @subsubheading @value{GDBN} Command
22018 Approximately corresponds to @samp{quit}.
22020 @subsubheading Example
22029 @subheading The @code{-exec-abort} Command
22030 @findex -exec-abort
22032 @subsubheading Synopsis
22038 Kill the inferior running program.
22040 @subsubheading @value{GDBN} Command
22042 The corresponding @value{GDBN} command is @samp{kill}.
22044 @subsubheading Example
22048 @subheading The @code{-gdb-set} Command
22051 @subsubheading Synopsis
22057 Set an internal @value{GDBN} variable.
22058 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
22060 @subsubheading @value{GDBN} Command
22062 The corresponding @value{GDBN} command is @samp{set}.
22064 @subsubheading Example
22074 @subheading The @code{-gdb-show} Command
22077 @subsubheading Synopsis
22083 Show the current value of a @value{GDBN} variable.
22085 @subsubheading @value{GDBN} Command
22087 The corresponding @value{GDBN} command is @samp{show}.
22089 @subsubheading Example
22098 @c @subheading -gdb-source
22101 @subheading The @code{-gdb-version} Command
22102 @findex -gdb-version
22104 @subsubheading Synopsis
22110 Show version information for @value{GDBN}. Used mostly in testing.
22112 @subsubheading @value{GDBN} Command
22114 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
22115 default shows this information when you start an interactive session.
22117 @subsubheading Example
22119 @c This example modifies the actual output from GDB to avoid overfull
22125 ~Copyright 2000 Free Software Foundation, Inc.
22126 ~GDB is free software, covered by the GNU General Public License, and
22127 ~you are welcome to change it and/or distribute copies of it under
22128 ~ certain conditions.
22129 ~Type "show copying" to see the conditions.
22130 ~There is absolutely no warranty for GDB. Type "show warranty" for
22132 ~This GDB was configured as
22133 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
22138 @subheading The @code{-list-features} Command
22139 @findex -list-features
22141 Returns a list of particular features of the MI protocol that
22142 this version of gdb implements. A feature can be a command,
22143 or a new field in an output of some command, or even an
22144 important bugfix. While a frontend can sometimes detect presence
22145 of a feature at runtime, it is easier to perform detection at debugger
22148 The command returns a list of strings, with each string naming an
22149 available feature. Each returned string is just a name, it does not
22150 have any internal structure. The list of possible feature names
22156 (gdb) -list-features
22157 ^done,result=["feature1","feature2"]
22160 The current list of features is:
22164 @samp{frozen-varobjs}---indicates presence of the
22165 @code{-var-set-frozen} command, as well as possible presense of the
22166 @code{frozen} field in the output of @code{-varobj-create}.
22168 @samp{pending-breakpoints}---indicates presence of the @code{-f}
22169 option to the @code{-break-insert} command.
22171 @samp{thread-info}---indicates presence of the @code{-thread-info} command.
22175 @subheading The @code{-interpreter-exec} Command
22176 @findex -interpreter-exec
22178 @subheading Synopsis
22181 -interpreter-exec @var{interpreter} @var{command}
22183 @anchor{-interpreter-exec}
22185 Execute the specified @var{command} in the given @var{interpreter}.
22187 @subheading @value{GDBN} Command
22189 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
22191 @subheading Example
22195 -interpreter-exec console "break main"
22196 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
22197 &"During symbol reading, bad structure-type format.\n"
22198 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
22203 @subheading The @code{-inferior-tty-set} Command
22204 @findex -inferior-tty-set
22206 @subheading Synopsis
22209 -inferior-tty-set /dev/pts/1
22212 Set terminal for future runs of the program being debugged.
22214 @subheading @value{GDBN} Command
22216 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
22218 @subheading Example
22222 -inferior-tty-set /dev/pts/1
22227 @subheading The @code{-inferior-tty-show} Command
22228 @findex -inferior-tty-show
22230 @subheading Synopsis
22236 Show terminal for future runs of program being debugged.
22238 @subheading @value{GDBN} Command
22240 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
22242 @subheading Example
22246 -inferior-tty-set /dev/pts/1
22250 ^done,inferior_tty_terminal="/dev/pts/1"
22254 @subheading The @code{-enable-timings} Command
22255 @findex -enable-timings
22257 @subheading Synopsis
22260 -enable-timings [yes | no]
22263 Toggle the printing of the wallclock, user and system times for an MI
22264 command as a field in its output. This command is to help frontend
22265 developers optimize the performance of their code. No argument is
22266 equivalent to @samp{yes}.
22268 @subheading @value{GDBN} Command
22272 @subheading Example
22280 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22281 addr="0x080484ed",func="main",file="myprog.c",
22282 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
22283 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
22291 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22292 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
22293 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
22294 fullname="/home/nickrob/myprog.c",line="73"@}
22299 @chapter @value{GDBN} Annotations
22301 This chapter describes annotations in @value{GDBN}. Annotations were
22302 designed to interface @value{GDBN} to graphical user interfaces or other
22303 similar programs which want to interact with @value{GDBN} at a
22304 relatively high level.
22306 The annotation mechanism has largely been superseded by @sc{gdb/mi}
22310 This is Edition @value{EDITION}, @value{DATE}.
22314 * Annotations Overview:: What annotations are; the general syntax.
22315 * Server Prefix:: Issuing a command without affecting user state.
22316 * Prompting:: Annotations marking @value{GDBN}'s need for input.
22317 * Errors:: Annotations for error messages.
22318 * Invalidation:: Some annotations describe things now invalid.
22319 * Annotations for Running::
22320 Whether the program is running, how it stopped, etc.
22321 * Source Annotations:: Annotations describing source code.
22324 @node Annotations Overview
22325 @section What is an Annotation?
22326 @cindex annotations
22328 Annotations start with a newline character, two @samp{control-z}
22329 characters, and the name of the annotation. If there is no additional
22330 information associated with this annotation, the name of the annotation
22331 is followed immediately by a newline. If there is additional
22332 information, the name of the annotation is followed by a space, the
22333 additional information, and a newline. The additional information
22334 cannot contain newline characters.
22336 Any output not beginning with a newline and two @samp{control-z}
22337 characters denotes literal output from @value{GDBN}. Currently there is
22338 no need for @value{GDBN} to output a newline followed by two
22339 @samp{control-z} characters, but if there was such a need, the
22340 annotations could be extended with an @samp{escape} annotation which
22341 means those three characters as output.
22343 The annotation @var{level}, which is specified using the
22344 @option{--annotate} command line option (@pxref{Mode Options}), controls
22345 how much information @value{GDBN} prints together with its prompt,
22346 values of expressions, source lines, and other types of output. Level 0
22347 is for no annotations, level 1 is for use when @value{GDBN} is run as a
22348 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
22349 for programs that control @value{GDBN}, and level 2 annotations have
22350 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
22351 Interface, annotate, GDB's Obsolete Annotations}).
22354 @kindex set annotate
22355 @item set annotate @var{level}
22356 The @value{GDBN} command @code{set annotate} sets the level of
22357 annotations to the specified @var{level}.
22359 @item show annotate
22360 @kindex show annotate
22361 Show the current annotation level.
22364 This chapter describes level 3 annotations.
22366 A simple example of starting up @value{GDBN} with annotations is:
22369 $ @kbd{gdb --annotate=3}
22371 Copyright 2003 Free Software Foundation, Inc.
22372 GDB is free software, covered by the GNU General Public License,
22373 and you are welcome to change it and/or distribute copies of it
22374 under certain conditions.
22375 Type "show copying" to see the conditions.
22376 There is absolutely no warranty for GDB. Type "show warranty"
22378 This GDB was configured as "i386-pc-linux-gnu"
22389 Here @samp{quit} is input to @value{GDBN}; the rest is output from
22390 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
22391 denotes a @samp{control-z} character) are annotations; the rest is
22392 output from @value{GDBN}.
22394 @node Server Prefix
22395 @section The Server Prefix
22396 @cindex server prefix
22398 If you prefix a command with @samp{server } then it will not affect
22399 the command history, nor will it affect @value{GDBN}'s notion of which
22400 command to repeat if @key{RET} is pressed on a line by itself. This
22401 means that commands can be run behind a user's back by a front-end in
22402 a transparent manner.
22404 The server prefix does not affect the recording of values into the value
22405 history; to print a value without recording it into the value history,
22406 use the @code{output} command instead of the @code{print} command.
22409 @section Annotation for @value{GDBN} Input
22411 @cindex annotations for prompts
22412 When @value{GDBN} prompts for input, it annotates this fact so it is possible
22413 to know when to send output, when the output from a given command is
22416 Different kinds of input each have a different @dfn{input type}. Each
22417 input type has three annotations: a @code{pre-} annotation, which
22418 denotes the beginning of any prompt which is being output, a plain
22419 annotation, which denotes the end of the prompt, and then a @code{post-}
22420 annotation which denotes the end of any echo which may (or may not) be
22421 associated with the input. For example, the @code{prompt} input type
22422 features the following annotations:
22430 The input types are
22433 @findex pre-prompt annotation
22434 @findex prompt annotation
22435 @findex post-prompt annotation
22437 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
22439 @findex pre-commands annotation
22440 @findex commands annotation
22441 @findex post-commands annotation
22443 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
22444 command. The annotations are repeated for each command which is input.
22446 @findex pre-overload-choice annotation
22447 @findex overload-choice annotation
22448 @findex post-overload-choice annotation
22449 @item overload-choice
22450 When @value{GDBN} wants the user to select between various overloaded functions.
22452 @findex pre-query annotation
22453 @findex query annotation
22454 @findex post-query annotation
22456 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
22458 @findex pre-prompt-for-continue annotation
22459 @findex prompt-for-continue annotation
22460 @findex post-prompt-for-continue annotation
22461 @item prompt-for-continue
22462 When @value{GDBN} is asking the user to press return to continue. Note: Don't
22463 expect this to work well; instead use @code{set height 0} to disable
22464 prompting. This is because the counting of lines is buggy in the
22465 presence of annotations.
22470 @cindex annotations for errors, warnings and interrupts
22472 @findex quit annotation
22477 This annotation occurs right before @value{GDBN} responds to an interrupt.
22479 @findex error annotation
22484 This annotation occurs right before @value{GDBN} responds to an error.
22486 Quit and error annotations indicate that any annotations which @value{GDBN} was
22487 in the middle of may end abruptly. For example, if a
22488 @code{value-history-begin} annotation is followed by a @code{error}, one
22489 cannot expect to receive the matching @code{value-history-end}. One
22490 cannot expect not to receive it either, however; an error annotation
22491 does not necessarily mean that @value{GDBN} is immediately returning all the way
22494 @findex error-begin annotation
22495 A quit or error annotation may be preceded by
22501 Any output between that and the quit or error annotation is the error
22504 Warning messages are not yet annotated.
22505 @c If we want to change that, need to fix warning(), type_error(),
22506 @c range_error(), and possibly other places.
22509 @section Invalidation Notices
22511 @cindex annotations for invalidation messages
22512 The following annotations say that certain pieces of state may have
22516 @findex frames-invalid annotation
22517 @item ^Z^Zframes-invalid
22519 The frames (for example, output from the @code{backtrace} command) may
22522 @findex breakpoints-invalid annotation
22523 @item ^Z^Zbreakpoints-invalid
22525 The breakpoints may have changed. For example, the user just added or
22526 deleted a breakpoint.
22529 @node Annotations for Running
22530 @section Running the Program
22531 @cindex annotations for running programs
22533 @findex starting annotation
22534 @findex stopping annotation
22535 When the program starts executing due to a @value{GDBN} command such as
22536 @code{step} or @code{continue},
22542 is output. When the program stops,
22548 is output. Before the @code{stopped} annotation, a variety of
22549 annotations describe how the program stopped.
22552 @findex exited annotation
22553 @item ^Z^Zexited @var{exit-status}
22554 The program exited, and @var{exit-status} is the exit status (zero for
22555 successful exit, otherwise nonzero).
22557 @findex signalled annotation
22558 @findex signal-name annotation
22559 @findex signal-name-end annotation
22560 @findex signal-string annotation
22561 @findex signal-string-end annotation
22562 @item ^Z^Zsignalled
22563 The program exited with a signal. After the @code{^Z^Zsignalled}, the
22564 annotation continues:
22570 ^Z^Zsignal-name-end
22574 ^Z^Zsignal-string-end
22579 where @var{name} is the name of the signal, such as @code{SIGILL} or
22580 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
22581 as @code{Illegal Instruction} or @code{Segmentation fault}.
22582 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
22583 user's benefit and have no particular format.
22585 @findex signal annotation
22587 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
22588 just saying that the program received the signal, not that it was
22589 terminated with it.
22591 @findex breakpoint annotation
22592 @item ^Z^Zbreakpoint @var{number}
22593 The program hit breakpoint number @var{number}.
22595 @findex watchpoint annotation
22596 @item ^Z^Zwatchpoint @var{number}
22597 The program hit watchpoint number @var{number}.
22600 @node Source Annotations
22601 @section Displaying Source
22602 @cindex annotations for source display
22604 @findex source annotation
22605 The following annotation is used instead of displaying source code:
22608 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
22611 where @var{filename} is an absolute file name indicating which source
22612 file, @var{line} is the line number within that file (where 1 is the
22613 first line in the file), @var{character} is the character position
22614 within the file (where 0 is the first character in the file) (for most
22615 debug formats this will necessarily point to the beginning of a line),
22616 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
22617 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
22618 @var{addr} is the address in the target program associated with the
22619 source which is being displayed. @var{addr} is in the form @samp{0x}
22620 followed by one or more lowercase hex digits (note that this does not
22621 depend on the language).
22624 @chapter Reporting Bugs in @value{GDBN}
22625 @cindex bugs in @value{GDBN}
22626 @cindex reporting bugs in @value{GDBN}
22628 Your bug reports play an essential role in making @value{GDBN} reliable.
22630 Reporting a bug may help you by bringing a solution to your problem, or it
22631 may not. But in any case the principal function of a bug report is to help
22632 the entire community by making the next version of @value{GDBN} work better. Bug
22633 reports are your contribution to the maintenance of @value{GDBN}.
22635 In order for a bug report to serve its purpose, you must include the
22636 information that enables us to fix the bug.
22639 * Bug Criteria:: Have you found a bug?
22640 * Bug Reporting:: How to report bugs
22644 @section Have You Found a Bug?
22645 @cindex bug criteria
22647 If you are not sure whether you have found a bug, here are some guidelines:
22650 @cindex fatal signal
22651 @cindex debugger crash
22652 @cindex crash of debugger
22654 If the debugger gets a fatal signal, for any input whatever, that is a
22655 @value{GDBN} bug. Reliable debuggers never crash.
22657 @cindex error on valid input
22659 If @value{GDBN} produces an error message for valid input, that is a
22660 bug. (Note that if you're cross debugging, the problem may also be
22661 somewhere in the connection to the target.)
22663 @cindex invalid input
22665 If @value{GDBN} does not produce an error message for invalid input,
22666 that is a bug. However, you should note that your idea of
22667 ``invalid input'' might be our idea of ``an extension'' or ``support
22668 for traditional practice''.
22671 If you are an experienced user of debugging tools, your suggestions
22672 for improvement of @value{GDBN} are welcome in any case.
22675 @node Bug Reporting
22676 @section How to Report Bugs
22677 @cindex bug reports
22678 @cindex @value{GDBN} bugs, reporting
22680 A number of companies and individuals offer support for @sc{gnu} products.
22681 If you obtained @value{GDBN} from a support organization, we recommend you
22682 contact that organization first.
22684 You can find contact information for many support companies and
22685 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
22687 @c should add a web page ref...
22690 @ifset BUGURL_DEFAULT
22691 In any event, we also recommend that you submit bug reports for
22692 @value{GDBN}. The preferred method is to submit them directly using
22693 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
22694 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
22697 @strong{Do not send bug reports to @samp{info-gdb}, or to
22698 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
22699 not want to receive bug reports. Those that do have arranged to receive
22702 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
22703 serves as a repeater. The mailing list and the newsgroup carry exactly
22704 the same messages. Often people think of posting bug reports to the
22705 newsgroup instead of mailing them. This appears to work, but it has one
22706 problem which can be crucial: a newsgroup posting often lacks a mail
22707 path back to the sender. Thus, if we need to ask for more information,
22708 we may be unable to reach you. For this reason, it is better to send
22709 bug reports to the mailing list.
22711 @ifclear BUGURL_DEFAULT
22712 In any event, we also recommend that you submit bug reports for
22713 @value{GDBN} to @value{BUGURL}.
22717 The fundamental principle of reporting bugs usefully is this:
22718 @strong{report all the facts}. If you are not sure whether to state a
22719 fact or leave it out, state it!
22721 Often people omit facts because they think they know what causes the
22722 problem and assume that some details do not matter. Thus, you might
22723 assume that the name of the variable you use in an example does not matter.
22724 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
22725 stray memory reference which happens to fetch from the location where that
22726 name is stored in memory; perhaps, if the name were different, the contents
22727 of that location would fool the debugger into doing the right thing despite
22728 the bug. Play it safe and give a specific, complete example. That is the
22729 easiest thing for you to do, and the most helpful.
22731 Keep in mind that the purpose of a bug report is to enable us to fix the
22732 bug. It may be that the bug has been reported previously, but neither
22733 you nor we can know that unless your bug report is complete and
22736 Sometimes people give a few sketchy facts and ask, ``Does this ring a
22737 bell?'' Those bug reports are useless, and we urge everyone to
22738 @emph{refuse to respond to them} except to chide the sender to report
22741 To enable us to fix the bug, you should include all these things:
22745 The version of @value{GDBN}. @value{GDBN} announces it if you start
22746 with no arguments; you can also print it at any time using @code{show
22749 Without this, we will not know whether there is any point in looking for
22750 the bug in the current version of @value{GDBN}.
22753 The type of machine you are using, and the operating system name and
22757 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
22758 ``@value{GCC}--2.8.1''.
22761 What compiler (and its version) was used to compile the program you are
22762 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
22763 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
22764 to get this information; for other compilers, see the documentation for
22768 The command arguments you gave the compiler to compile your example and
22769 observe the bug. For example, did you use @samp{-O}? To guarantee
22770 you will not omit something important, list them all. A copy of the
22771 Makefile (or the output from make) is sufficient.
22773 If we were to try to guess the arguments, we would probably guess wrong
22774 and then we might not encounter the bug.
22777 A complete input script, and all necessary source files, that will
22781 A description of what behavior you observe that you believe is
22782 incorrect. For example, ``It gets a fatal signal.''
22784 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
22785 will certainly notice it. But if the bug is incorrect output, we might
22786 not notice unless it is glaringly wrong. You might as well not give us
22787 a chance to make a mistake.
22789 Even if the problem you experience is a fatal signal, you should still
22790 say so explicitly. Suppose something strange is going on, such as, your
22791 copy of @value{GDBN} is out of synch, or you have encountered a bug in
22792 the C library on your system. (This has happened!) Your copy might
22793 crash and ours would not. If you told us to expect a crash, then when
22794 ours fails to crash, we would know that the bug was not happening for
22795 us. If you had not told us to expect a crash, then we would not be able
22796 to draw any conclusion from our observations.
22799 @cindex recording a session script
22800 To collect all this information, you can use a session recording program
22801 such as @command{script}, which is available on many Unix systems.
22802 Just run your @value{GDBN} session inside @command{script} and then
22803 include the @file{typescript} file with your bug report.
22805 Another way to record a @value{GDBN} session is to run @value{GDBN}
22806 inside Emacs and then save the entire buffer to a file.
22809 If you wish to suggest changes to the @value{GDBN} source, send us context
22810 diffs. If you even discuss something in the @value{GDBN} source, refer to
22811 it by context, not by line number.
22813 The line numbers in our development sources will not match those in your
22814 sources. Your line numbers would convey no useful information to us.
22818 Here are some things that are not necessary:
22822 A description of the envelope of the bug.
22824 Often people who encounter a bug spend a lot of time investigating
22825 which changes to the input file will make the bug go away and which
22826 changes will not affect it.
22828 This is often time consuming and not very useful, because the way we
22829 will find the bug is by running a single example under the debugger
22830 with breakpoints, not by pure deduction from a series of examples.
22831 We recommend that you save your time for something else.
22833 Of course, if you can find a simpler example to report @emph{instead}
22834 of the original one, that is a convenience for us. Errors in the
22835 output will be easier to spot, running under the debugger will take
22836 less time, and so on.
22838 However, simplification is not vital; if you do not want to do this,
22839 report the bug anyway and send us the entire test case you used.
22842 A patch for the bug.
22844 A patch for the bug does help us if it is a good one. But do not omit
22845 the necessary information, such as the test case, on the assumption that
22846 a patch is all we need. We might see problems with your patch and decide
22847 to fix the problem another way, or we might not understand it at all.
22849 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22850 construct an example that will make the program follow a certain path
22851 through the code. If you do not send us the example, we will not be able
22852 to construct one, so we will not be able to verify that the bug is fixed.
22854 And if we cannot understand what bug you are trying to fix, or why your
22855 patch should be an improvement, we will not install it. A test case will
22856 help us to understand.
22859 A guess about what the bug is or what it depends on.
22861 Such guesses are usually wrong. Even we cannot guess right about such
22862 things without first using the debugger to find the facts.
22865 @c The readline documentation is distributed with the readline code
22866 @c and consists of the two following files:
22868 @c inc-hist.texinfo
22869 @c Use -I with makeinfo to point to the appropriate directory,
22870 @c environment var TEXINPUTS with TeX.
22871 @include rluser.texi
22872 @include inc-hist.texinfo
22875 @node Formatting Documentation
22876 @appendix Formatting Documentation
22878 @cindex @value{GDBN} reference card
22879 @cindex reference card
22880 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22881 for printing with PostScript or Ghostscript, in the @file{gdb}
22882 subdirectory of the main source directory@footnote{In
22883 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22884 release.}. If you can use PostScript or Ghostscript with your printer,
22885 you can print the reference card immediately with @file{refcard.ps}.
22887 The release also includes the source for the reference card. You
22888 can format it, using @TeX{}, by typing:
22894 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22895 mode on US ``letter'' size paper;
22896 that is, on a sheet 11 inches wide by 8.5 inches
22897 high. You will need to specify this form of printing as an option to
22898 your @sc{dvi} output program.
22900 @cindex documentation
22902 All the documentation for @value{GDBN} comes as part of the machine-readable
22903 distribution. The documentation is written in Texinfo format, which is
22904 a documentation system that uses a single source file to produce both
22905 on-line information and a printed manual. You can use one of the Info
22906 formatting commands to create the on-line version of the documentation
22907 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22909 @value{GDBN} includes an already formatted copy of the on-line Info
22910 version of this manual in the @file{gdb} subdirectory. The main Info
22911 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22912 subordinate files matching @samp{gdb.info*} in the same directory. If
22913 necessary, you can print out these files, or read them with any editor;
22914 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22915 Emacs or the standalone @code{info} program, available as part of the
22916 @sc{gnu} Texinfo distribution.
22918 If you want to format these Info files yourself, you need one of the
22919 Info formatting programs, such as @code{texinfo-format-buffer} or
22922 If you have @code{makeinfo} installed, and are in the top level
22923 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22924 version @value{GDBVN}), you can make the Info file by typing:
22931 If you want to typeset and print copies of this manual, you need @TeX{},
22932 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22933 Texinfo definitions file.
22935 @TeX{} is a typesetting program; it does not print files directly, but
22936 produces output files called @sc{dvi} files. To print a typeset
22937 document, you need a program to print @sc{dvi} files. If your system
22938 has @TeX{} installed, chances are it has such a program. The precise
22939 command to use depends on your system; @kbd{lpr -d} is common; another
22940 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22941 require a file name without any extension or a @samp{.dvi} extension.
22943 @TeX{} also requires a macro definitions file called
22944 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22945 written in Texinfo format. On its own, @TeX{} cannot either read or
22946 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22947 and is located in the @file{gdb-@var{version-number}/texinfo}
22950 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22951 typeset and print this manual. First switch to the @file{gdb}
22952 subdirectory of the main source directory (for example, to
22953 @file{gdb-@value{GDBVN}/gdb}) and type:
22959 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22961 @node Installing GDB
22962 @appendix Installing @value{GDBN}
22963 @cindex installation
22966 * Requirements:: Requirements for building @value{GDBN}
22967 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22968 * Separate Objdir:: Compiling @value{GDBN} in another directory
22969 * Config Names:: Specifying names for hosts and targets
22970 * Configure Options:: Summary of options for configure
22974 @section Requirements for Building @value{GDBN}
22975 @cindex building @value{GDBN}, requirements for
22977 Building @value{GDBN} requires various tools and packages to be available.
22978 Other packages will be used only if they are found.
22980 @heading Tools/Packages Necessary for Building @value{GDBN}
22982 @item ISO C90 compiler
22983 @value{GDBN} is written in ISO C90. It should be buildable with any
22984 working C90 compiler, e.g.@: GCC.
22988 @heading Tools/Packages Optional for Building @value{GDBN}
22992 @value{GDBN} can use the Expat XML parsing library. This library may be
22993 included with your operating system distribution; if it is not, you
22994 can get the latest version from @url{http://expat.sourceforge.net}.
22995 The @file{configure} script will search for this library in several
22996 standard locations; if it is installed in an unusual path, you can
22997 use the @option{--with-libexpat-prefix} option to specify its location.
23003 Remote protocol memory maps (@pxref{Memory Map Format})
23005 Target descriptions (@pxref{Target Descriptions})
23007 Remote shared library lists (@pxref{Library List Format})
23009 MS-Windows shared libraries (@pxref{Shared Libraries})
23013 @cindex compressed debug sections
23014 @value{GDBN} will use the @samp{zlib} library, if available, to read
23015 compressed debug sections. Some linkers, such as GNU gold, are capable
23016 of producing binaries with compressed debug sections. If @value{GDBN}
23017 is compiled with @samp{zlib}, it will be able to read the debug
23018 information in such binaries.
23020 The @samp{zlib} library is likely included with your operating system
23021 distribution; if it is not, you can get the latest version from
23022 @url{http://zlib.net}.
23026 @node Running Configure
23027 @section Invoking the @value{GDBN} @file{configure} Script
23028 @cindex configuring @value{GDBN}
23029 @value{GDBN} comes with a @file{configure} script that automates the process
23030 of preparing @value{GDBN} for installation; you can then use @code{make} to
23031 build the @code{gdb} program.
23033 @c irrelevant in info file; it's as current as the code it lives with.
23034 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
23035 look at the @file{README} file in the sources; we may have improved the
23036 installation procedures since publishing this manual.}
23039 The @value{GDBN} distribution includes all the source code you need for
23040 @value{GDBN} in a single directory, whose name is usually composed by
23041 appending the version number to @samp{gdb}.
23043 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
23044 @file{gdb-@value{GDBVN}} directory. That directory contains:
23047 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
23048 script for configuring @value{GDBN} and all its supporting libraries
23050 @item gdb-@value{GDBVN}/gdb
23051 the source specific to @value{GDBN} itself
23053 @item gdb-@value{GDBVN}/bfd
23054 source for the Binary File Descriptor library
23056 @item gdb-@value{GDBVN}/include
23057 @sc{gnu} include files
23059 @item gdb-@value{GDBVN}/libiberty
23060 source for the @samp{-liberty} free software library
23062 @item gdb-@value{GDBVN}/opcodes
23063 source for the library of opcode tables and disassemblers
23065 @item gdb-@value{GDBVN}/readline
23066 source for the @sc{gnu} command-line interface
23068 @item gdb-@value{GDBVN}/glob
23069 source for the @sc{gnu} filename pattern-matching subroutine
23071 @item gdb-@value{GDBVN}/mmalloc
23072 source for the @sc{gnu} memory-mapped malloc package
23075 The simplest way to configure and build @value{GDBN} is to run @file{configure}
23076 from the @file{gdb-@var{version-number}} source directory, which in
23077 this example is the @file{gdb-@value{GDBVN}} directory.
23079 First switch to the @file{gdb-@var{version-number}} source directory
23080 if you are not already in it; then run @file{configure}. Pass the
23081 identifier for the platform on which @value{GDBN} will run as an
23087 cd gdb-@value{GDBVN}
23088 ./configure @var{host}
23093 where @var{host} is an identifier such as @samp{sun4} or
23094 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
23095 (You can often leave off @var{host}; @file{configure} tries to guess the
23096 correct value by examining your system.)
23098 Running @samp{configure @var{host}} and then running @code{make} builds the
23099 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
23100 libraries, then @code{gdb} itself. The configured source files, and the
23101 binaries, are left in the corresponding source directories.
23104 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
23105 system does not recognize this automatically when you run a different
23106 shell, you may need to run @code{sh} on it explicitly:
23109 sh configure @var{host}
23112 If you run @file{configure} from a directory that contains source
23113 directories for multiple libraries or programs, such as the
23114 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
23116 creates configuration files for every directory level underneath (unless
23117 you tell it not to, with the @samp{--norecursion} option).
23119 You should run the @file{configure} script from the top directory in the
23120 source tree, the @file{gdb-@var{version-number}} directory. If you run
23121 @file{configure} from one of the subdirectories, you will configure only
23122 that subdirectory. That is usually not what you want. In particular,
23123 if you run the first @file{configure} from the @file{gdb} subdirectory
23124 of the @file{gdb-@var{version-number}} directory, you will omit the
23125 configuration of @file{bfd}, @file{readline}, and other sibling
23126 directories of the @file{gdb} subdirectory. This leads to build errors
23127 about missing include files such as @file{bfd/bfd.h}.
23129 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
23130 However, you should make sure that the shell on your path (named by
23131 the @samp{SHELL} environment variable) is publicly readable. Remember
23132 that @value{GDBN} uses the shell to start your program---some systems refuse to
23133 let @value{GDBN} debug child processes whose programs are not readable.
23135 @node Separate Objdir
23136 @section Compiling @value{GDBN} in Another Directory
23138 If you want to run @value{GDBN} versions for several host or target machines,
23139 you need a different @code{gdb} compiled for each combination of
23140 host and target. @file{configure} is designed to make this easy by
23141 allowing you to generate each configuration in a separate subdirectory,
23142 rather than in the source directory. If your @code{make} program
23143 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
23144 @code{make} in each of these directories builds the @code{gdb}
23145 program specified there.
23147 To build @code{gdb} in a separate directory, run @file{configure}
23148 with the @samp{--srcdir} option to specify where to find the source.
23149 (You also need to specify a path to find @file{configure}
23150 itself from your working directory. If the path to @file{configure}
23151 would be the same as the argument to @samp{--srcdir}, you can leave out
23152 the @samp{--srcdir} option; it is assumed.)
23154 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
23155 separate directory for a Sun 4 like this:
23159 cd gdb-@value{GDBVN}
23162 ../gdb-@value{GDBVN}/configure sun4
23167 When @file{configure} builds a configuration using a remote source
23168 directory, it creates a tree for the binaries with the same structure
23169 (and using the same names) as the tree under the source directory. In
23170 the example, you'd find the Sun 4 library @file{libiberty.a} in the
23171 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
23172 @file{gdb-sun4/gdb}.
23174 Make sure that your path to the @file{configure} script has just one
23175 instance of @file{gdb} in it. If your path to @file{configure} looks
23176 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
23177 one subdirectory of @value{GDBN}, not the whole package. This leads to
23178 build errors about missing include files such as @file{bfd/bfd.h}.
23180 One popular reason to build several @value{GDBN} configurations in separate
23181 directories is to configure @value{GDBN} for cross-compiling (where
23182 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
23183 programs that run on another machine---the @dfn{target}).
23184 You specify a cross-debugging target by
23185 giving the @samp{--target=@var{target}} option to @file{configure}.
23187 When you run @code{make} to build a program or library, you must run
23188 it in a configured directory---whatever directory you were in when you
23189 called @file{configure} (or one of its subdirectories).
23191 The @code{Makefile} that @file{configure} generates in each source
23192 directory also runs recursively. If you type @code{make} in a source
23193 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
23194 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
23195 will build all the required libraries, and then build GDB.
23197 When you have multiple hosts or targets configured in separate
23198 directories, you can run @code{make} on them in parallel (for example,
23199 if they are NFS-mounted on each of the hosts); they will not interfere
23203 @section Specifying Names for Hosts and Targets
23205 The specifications used for hosts and targets in the @file{configure}
23206 script are based on a three-part naming scheme, but some short predefined
23207 aliases are also supported. The full naming scheme encodes three pieces
23208 of information in the following pattern:
23211 @var{architecture}-@var{vendor}-@var{os}
23214 For example, you can use the alias @code{sun4} as a @var{host} argument,
23215 or as the value for @var{target} in a @code{--target=@var{target}}
23216 option. The equivalent full name is @samp{sparc-sun-sunos4}.
23218 The @file{configure} script accompanying @value{GDBN} does not provide
23219 any query facility to list all supported host and target names or
23220 aliases. @file{configure} calls the Bourne shell script
23221 @code{config.sub} to map abbreviations to full names; you can read the
23222 script, if you wish, or you can use it to test your guesses on
23223 abbreviations---for example:
23226 % sh config.sub i386-linux
23228 % sh config.sub alpha-linux
23229 alpha-unknown-linux-gnu
23230 % sh config.sub hp9k700
23232 % sh config.sub sun4
23233 sparc-sun-sunos4.1.1
23234 % sh config.sub sun3
23235 m68k-sun-sunos4.1.1
23236 % sh config.sub i986v
23237 Invalid configuration `i986v': machine `i986v' not recognized
23241 @code{config.sub} is also distributed in the @value{GDBN} source
23242 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
23244 @node Configure Options
23245 @section @file{configure} Options
23247 Here is a summary of the @file{configure} options and arguments that
23248 are most often useful for building @value{GDBN}. @file{configure} also has
23249 several other options not listed here. @inforef{What Configure
23250 Does,,configure.info}, for a full explanation of @file{configure}.
23253 configure @r{[}--help@r{]}
23254 @r{[}--prefix=@var{dir}@r{]}
23255 @r{[}--exec-prefix=@var{dir}@r{]}
23256 @r{[}--srcdir=@var{dirname}@r{]}
23257 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
23258 @r{[}--target=@var{target}@r{]}
23263 You may introduce options with a single @samp{-} rather than
23264 @samp{--} if you prefer; but you may abbreviate option names if you use
23269 Display a quick summary of how to invoke @file{configure}.
23271 @item --prefix=@var{dir}
23272 Configure the source to install programs and files under directory
23275 @item --exec-prefix=@var{dir}
23276 Configure the source to install programs under directory
23279 @c avoid splitting the warning from the explanation:
23281 @item --srcdir=@var{dirname}
23282 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
23283 @code{make} that implements the @code{VPATH} feature.}@*
23284 Use this option to make configurations in directories separate from the
23285 @value{GDBN} source directories. Among other things, you can use this to
23286 build (or maintain) several configurations simultaneously, in separate
23287 directories. @file{configure} writes configuration-specific files in
23288 the current directory, but arranges for them to use the source in the
23289 directory @var{dirname}. @file{configure} creates directories under
23290 the working directory in parallel to the source directories below
23293 @item --norecursion
23294 Configure only the directory level where @file{configure} is executed; do not
23295 propagate configuration to subdirectories.
23297 @item --target=@var{target}
23298 Configure @value{GDBN} for cross-debugging programs running on the specified
23299 @var{target}. Without this option, @value{GDBN} is configured to debug
23300 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
23302 There is no convenient way to generate a list of all available targets.
23304 @item @var{host} @dots{}
23305 Configure @value{GDBN} to run on the specified @var{host}.
23307 There is no convenient way to generate a list of all available hosts.
23310 There are many other options available as well, but they are generally
23311 needed for special purposes only.
23313 @node Maintenance Commands
23314 @appendix Maintenance Commands
23315 @cindex maintenance commands
23316 @cindex internal commands
23318 In addition to commands intended for @value{GDBN} users, @value{GDBN}
23319 includes a number of commands intended for @value{GDBN} developers,
23320 that are not documented elsewhere in this manual. These commands are
23321 provided here for reference. (For commands that turn on debugging
23322 messages, see @ref{Debugging Output}.)
23325 @kindex maint agent
23326 @item maint agent @var{expression}
23327 Translate the given @var{expression} into remote agent bytecodes.
23328 This command is useful for debugging the Agent Expression mechanism
23329 (@pxref{Agent Expressions}).
23331 @kindex maint info breakpoints
23332 @item @anchor{maint info breakpoints}maint info breakpoints
23333 Using the same format as @samp{info breakpoints}, display both the
23334 breakpoints you've set explicitly, and those @value{GDBN} is using for
23335 internal purposes. Internal breakpoints are shown with negative
23336 breakpoint numbers. The type column identifies what kind of breakpoint
23341 Normal, explicitly set breakpoint.
23344 Normal, explicitly set watchpoint.
23347 Internal breakpoint, used to handle correctly stepping through
23348 @code{longjmp} calls.
23350 @item longjmp resume
23351 Internal breakpoint at the target of a @code{longjmp}.
23354 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
23357 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
23360 Shared library events.
23364 @kindex maint set can-use-displaced-stepping
23365 @kindex maint show can-use-displaced-stepping
23366 @cindex displaced stepping support
23367 @cindex out-of-line single-stepping
23368 @item maint set can-use-displaced-stepping
23369 @itemx maint show can-use-displaced-stepping
23370 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
23371 if the target supports it. The default is on. Displaced stepping is
23372 a way to single-step over breakpoints without removing them from the
23373 inferior, by executing an out-of-line copy of the instruction that was
23374 originally at the breakpoint location. It is also known as
23375 out-of-line single-stepping.
23377 @kindex maint check-symtabs
23378 @item maint check-symtabs
23379 Check the consistency of psymtabs and symtabs.
23381 @kindex maint cplus first_component
23382 @item maint cplus first_component @var{name}
23383 Print the first C@t{++} class/namespace component of @var{name}.
23385 @kindex maint cplus namespace
23386 @item maint cplus namespace
23387 Print the list of possible C@t{++} namespaces.
23389 @kindex maint demangle
23390 @item maint demangle @var{name}
23391 Demangle a C@t{++} or Objective-C mangled @var{name}.
23393 @kindex maint deprecate
23394 @kindex maint undeprecate
23395 @cindex deprecated commands
23396 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
23397 @itemx maint undeprecate @var{command}
23398 Deprecate or undeprecate the named @var{command}. Deprecated commands
23399 cause @value{GDBN} to issue a warning when you use them. The optional
23400 argument @var{replacement} says which newer command should be used in
23401 favor of the deprecated one; if it is given, @value{GDBN} will mention
23402 the replacement as part of the warning.
23404 @kindex maint dump-me
23405 @item maint dump-me
23406 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
23407 Cause a fatal signal in the debugger and force it to dump its core.
23408 This is supported only on systems which support aborting a program
23409 with the @code{SIGQUIT} signal.
23411 @kindex maint internal-error
23412 @kindex maint internal-warning
23413 @item maint internal-error @r{[}@var{message-text}@r{]}
23414 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
23415 Cause @value{GDBN} to call the internal function @code{internal_error}
23416 or @code{internal_warning} and hence behave as though an internal error
23417 or internal warning has been detected. In addition to reporting the
23418 internal problem, these functions give the user the opportunity to
23419 either quit @value{GDBN} or create a core file of the current
23420 @value{GDBN} session.
23422 These commands take an optional parameter @var{message-text} that is
23423 used as the text of the error or warning message.
23425 Here's an example of using @code{internal-error}:
23428 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
23429 @dots{}/maint.c:121: internal-error: testing, 1, 2
23430 A problem internal to GDB has been detected. Further
23431 debugging may prove unreliable.
23432 Quit this debugging session? (y or n) @kbd{n}
23433 Create a core file? (y or n) @kbd{n}
23437 @kindex maint packet
23438 @item maint packet @var{text}
23439 If @value{GDBN} is talking to an inferior via the serial protocol,
23440 then this command sends the string @var{text} to the inferior, and
23441 displays the response packet. @value{GDBN} supplies the initial
23442 @samp{$} character, the terminating @samp{#} character, and the
23445 @kindex maint print architecture
23446 @item maint print architecture @r{[}@var{file}@r{]}
23447 Print the entire architecture configuration. The optional argument
23448 @var{file} names the file where the output goes.
23450 @kindex maint print c-tdesc
23451 @item maint print c-tdesc
23452 Print the current target description (@pxref{Target Descriptions}) as
23453 a C source file. The created source file can be used in @value{GDBN}
23454 when an XML parser is not available to parse the description.
23456 @kindex maint print dummy-frames
23457 @item maint print dummy-frames
23458 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
23461 (@value{GDBP}) @kbd{b add}
23463 (@value{GDBP}) @kbd{print add(2,3)}
23464 Breakpoint 2, add (a=2, b=3) at @dots{}
23466 The program being debugged stopped while in a function called from GDB.
23468 (@value{GDBP}) @kbd{maint print dummy-frames}
23469 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
23470 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
23471 call_lo=0x01014000 call_hi=0x01014001
23475 Takes an optional file parameter.
23477 @kindex maint print registers
23478 @kindex maint print raw-registers
23479 @kindex maint print cooked-registers
23480 @kindex maint print register-groups
23481 @item maint print registers @r{[}@var{file}@r{]}
23482 @itemx maint print raw-registers @r{[}@var{file}@r{]}
23483 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
23484 @itemx maint print register-groups @r{[}@var{file}@r{]}
23485 Print @value{GDBN}'s internal register data structures.
23487 The command @code{maint print raw-registers} includes the contents of
23488 the raw register cache; the command @code{maint print cooked-registers}
23489 includes the (cooked) value of all registers; and the command
23490 @code{maint print register-groups} includes the groups that each
23491 register is a member of. @xref{Registers,, Registers, gdbint,
23492 @value{GDBN} Internals}.
23494 These commands take an optional parameter, a file name to which to
23495 write the information.
23497 @kindex maint print reggroups
23498 @item maint print reggroups @r{[}@var{file}@r{]}
23499 Print @value{GDBN}'s internal register group data structures. The
23500 optional argument @var{file} tells to what file to write the
23503 The register groups info looks like this:
23506 (@value{GDBP}) @kbd{maint print reggroups}
23519 This command forces @value{GDBN} to flush its internal register cache.
23521 @kindex maint print objfiles
23522 @cindex info for known object files
23523 @item maint print objfiles
23524 Print a dump of all known object files. For each object file, this
23525 command prints its name, address in memory, and all of its psymtabs
23528 @kindex maint print statistics
23529 @cindex bcache statistics
23530 @item maint print statistics
23531 This command prints, for each object file in the program, various data
23532 about that object file followed by the byte cache (@dfn{bcache})
23533 statistics for the object file. The objfile data includes the number
23534 of minimal, partial, full, and stabs symbols, the number of types
23535 defined by the objfile, the number of as yet unexpanded psym tables,
23536 the number of line tables and string tables, and the amount of memory
23537 used by the various tables. The bcache statistics include the counts,
23538 sizes, and counts of duplicates of all and unique objects, max,
23539 average, and median entry size, total memory used and its overhead and
23540 savings, and various measures of the hash table size and chain
23543 @kindex maint print target-stack
23544 @cindex target stack description
23545 @item maint print target-stack
23546 A @dfn{target} is an interface between the debugger and a particular
23547 kind of file or process. Targets can be stacked in @dfn{strata},
23548 so that more than one target can potentially respond to a request.
23549 In particular, memory accesses will walk down the stack of targets
23550 until they find a target that is interested in handling that particular
23553 This command prints a short description of each layer that was pushed on
23554 the @dfn{target stack}, starting from the top layer down to the bottom one.
23556 @kindex maint print type
23557 @cindex type chain of a data type
23558 @item maint print type @var{expr}
23559 Print the type chain for a type specified by @var{expr}. The argument
23560 can be either a type name or a symbol. If it is a symbol, the type of
23561 that symbol is described. The type chain produced by this command is
23562 a recursive definition of the data type as stored in @value{GDBN}'s
23563 data structures, including its flags and contained types.
23565 @kindex maint set dwarf2 max-cache-age
23566 @kindex maint show dwarf2 max-cache-age
23567 @item maint set dwarf2 max-cache-age
23568 @itemx maint show dwarf2 max-cache-age
23569 Control the DWARF 2 compilation unit cache.
23571 @cindex DWARF 2 compilation units cache
23572 In object files with inter-compilation-unit references, such as those
23573 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
23574 reader needs to frequently refer to previously read compilation units.
23575 This setting controls how long a compilation unit will remain in the
23576 cache if it is not referenced. A higher limit means that cached
23577 compilation units will be stored in memory longer, and more total
23578 memory will be used. Setting it to zero disables caching, which will
23579 slow down @value{GDBN} startup, but reduce memory consumption.
23581 @kindex maint set profile
23582 @kindex maint show profile
23583 @cindex profiling GDB
23584 @item maint set profile
23585 @itemx maint show profile
23586 Control profiling of @value{GDBN}.
23588 Profiling will be disabled until you use the @samp{maint set profile}
23589 command to enable it. When you enable profiling, the system will begin
23590 collecting timing and execution count data; when you disable profiling or
23591 exit @value{GDBN}, the results will be written to a log file. Remember that
23592 if you use profiling, @value{GDBN} will overwrite the profiling log file
23593 (often called @file{gmon.out}). If you have a record of important profiling
23594 data in a @file{gmon.out} file, be sure to move it to a safe location.
23596 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
23597 compiled with the @samp{-pg} compiler option.
23599 @kindex maint set linux-async
23600 @kindex maint show linux-async
23601 @cindex asynchronous support
23602 @item maint set linux-async
23603 @itemx maint show linux-async
23604 Control the GNU/Linux native asynchronous support of @value{GDBN}.
23606 GNU/Linux native asynchronous support will be disabled until you use
23607 the @samp{maint set linux-async} command to enable it.
23609 @kindex maint set remote-async
23610 @kindex maint show remote-async
23611 @cindex asynchronous support
23612 @item maint set remote-async
23613 @itemx maint show remote-async
23614 Control the remote asynchronous support of @value{GDBN}.
23616 Remote asynchronous support will be disabled until you use
23617 the @samp{maint set remote-async} command to enable it.
23619 @kindex maint show-debug-regs
23620 @cindex x86 hardware debug registers
23621 @item maint show-debug-regs
23622 Control whether to show variables that mirror the x86 hardware debug
23623 registers. Use @code{ON} to enable, @code{OFF} to disable. If
23624 enabled, the debug registers values are shown when @value{GDBN} inserts or
23625 removes a hardware breakpoint or watchpoint, and when the inferior
23626 triggers a hardware-assisted breakpoint or watchpoint.
23628 @kindex maint space
23629 @cindex memory used by commands
23631 Control whether to display memory usage for each command. If set to a
23632 nonzero value, @value{GDBN} will display how much memory each command
23633 took, following the command's own output. This can also be requested
23634 by invoking @value{GDBN} with the @option{--statistics} command-line
23635 switch (@pxref{Mode Options}).
23638 @cindex time of command execution
23640 Control whether to display the execution time for each command. If
23641 set to a nonzero value, @value{GDBN} will display how much time it
23642 took to execute each command, following the command's own output.
23643 The time is not printed for the commands that run the target, since
23644 there's no mechanism currently to compute how much time was spend
23645 by @value{GDBN} and how much time was spend by the program been debugged.
23646 it's not possibly currently
23647 This can also be requested by invoking @value{GDBN} with the
23648 @option{--statistics} command-line switch (@pxref{Mode Options}).
23650 @kindex maint translate-address
23651 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
23652 Find the symbol stored at the location specified by the address
23653 @var{addr} and an optional section name @var{section}. If found,
23654 @value{GDBN} prints the name of the closest symbol and an offset from
23655 the symbol's location to the specified address. This is similar to
23656 the @code{info address} command (@pxref{Symbols}), except that this
23657 command also allows to find symbols in other sections.
23661 The following command is useful for non-interactive invocations of
23662 @value{GDBN}, such as in the test suite.
23665 @item set watchdog @var{nsec}
23666 @kindex set watchdog
23667 @cindex watchdog timer
23668 @cindex timeout for commands
23669 Set the maximum number of seconds @value{GDBN} will wait for the
23670 target operation to finish. If this time expires, @value{GDBN}
23671 reports and error and the command is aborted.
23673 @item show watchdog
23674 Show the current setting of the target wait timeout.
23677 @node Remote Protocol
23678 @appendix @value{GDBN} Remote Serial Protocol
23683 * Stop Reply Packets::
23684 * General Query Packets::
23685 * Register Packet Format::
23686 * Tracepoint Packets::
23687 * Host I/O Packets::
23690 * File-I/O Remote Protocol Extension::
23691 * Library List Format::
23692 * Memory Map Format::
23698 There may be occasions when you need to know something about the
23699 protocol---for example, if there is only one serial port to your target
23700 machine, you might want your program to do something special if it
23701 recognizes a packet meant for @value{GDBN}.
23703 In the examples below, @samp{->} and @samp{<-} are used to indicate
23704 transmitted and received data, respectively.
23706 @cindex protocol, @value{GDBN} remote serial
23707 @cindex serial protocol, @value{GDBN} remote
23708 @cindex remote serial protocol
23709 All @value{GDBN} commands and responses (other than acknowledgments) are
23710 sent as a @var{packet}. A @var{packet} is introduced with the character
23711 @samp{$}, the actual @var{packet-data}, and the terminating character
23712 @samp{#} followed by a two-digit @var{checksum}:
23715 @code{$}@var{packet-data}@code{#}@var{checksum}
23719 @cindex checksum, for @value{GDBN} remote
23721 The two-digit @var{checksum} is computed as the modulo 256 sum of all
23722 characters between the leading @samp{$} and the trailing @samp{#} (an
23723 eight bit unsigned checksum).
23725 Implementors should note that prior to @value{GDBN} 5.0 the protocol
23726 specification also included an optional two-digit @var{sequence-id}:
23729 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
23732 @cindex sequence-id, for @value{GDBN} remote
23734 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
23735 has never output @var{sequence-id}s. Stubs that handle packets added
23736 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
23738 @cindex acknowledgment, for @value{GDBN} remote
23739 When either the host or the target machine receives a packet, the first
23740 response expected is an acknowledgment: either @samp{+} (to indicate
23741 the package was received correctly) or @samp{-} (to request
23745 -> @code{$}@var{packet-data}@code{#}@var{checksum}
23750 The host (@value{GDBN}) sends @var{command}s, and the target (the
23751 debugging stub incorporated in your program) sends a @var{response}. In
23752 the case of step and continue @var{command}s, the response is only sent
23753 when the operation has completed (the target has again stopped).
23755 @var{packet-data} consists of a sequence of characters with the
23756 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
23759 @cindex remote protocol, field separator
23760 Fields within the packet should be separated using @samp{,} @samp{;} or
23761 @samp{:}. Except where otherwise noted all numbers are represented in
23762 @sc{hex} with leading zeros suppressed.
23764 Implementors should note that prior to @value{GDBN} 5.0, the character
23765 @samp{:} could not appear as the third character in a packet (as it
23766 would potentially conflict with the @var{sequence-id}).
23768 @cindex remote protocol, binary data
23769 @anchor{Binary Data}
23770 Binary data in most packets is encoded either as two hexadecimal
23771 digits per byte of binary data. This allowed the traditional remote
23772 protocol to work over connections which were only seven-bit clean.
23773 Some packets designed more recently assume an eight-bit clean
23774 connection, and use a more efficient encoding to send and receive
23777 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
23778 as an escape character. Any escaped byte is transmitted as the escape
23779 character followed by the original character XORed with @code{0x20}.
23780 For example, the byte @code{0x7d} would be transmitted as the two
23781 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
23782 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
23783 @samp{@}}) must always be escaped. Responses sent by the stub
23784 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
23785 is not interpreted as the start of a run-length encoded sequence
23788 Response @var{data} can be run-length encoded to save space.
23789 Run-length encoding replaces runs of identical characters with one
23790 instance of the repeated character, followed by a @samp{*} and a
23791 repeat count. The repeat count is itself sent encoded, to avoid
23792 binary characters in @var{data}: a value of @var{n} is sent as
23793 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
23794 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
23795 code 32) for a repeat count of 3. (This is because run-length
23796 encoding starts to win for counts 3 or more.) Thus, for example,
23797 @samp{0* } is a run-length encoding of ``0000'': the space character
23798 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
23801 The printable characters @samp{#} and @samp{$} or with a numeric value
23802 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
23803 seven repeats (@samp{$}) can be expanded using a repeat count of only
23804 five (@samp{"}). For example, @samp{00000000} can be encoded as
23807 The error response returned for some packets includes a two character
23808 error number. That number is not well defined.
23810 @cindex empty response, for unsupported packets
23811 For any @var{command} not supported by the stub, an empty response
23812 (@samp{$#00}) should be returned. That way it is possible to extend the
23813 protocol. A newer @value{GDBN} can tell if a packet is supported based
23816 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
23817 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
23823 The following table provides a complete list of all currently defined
23824 @var{command}s and their corresponding response @var{data}.
23825 @xref{File-I/O Remote Protocol Extension}, for details about the File
23826 I/O extension of the remote protocol.
23828 Each packet's description has a template showing the packet's overall
23829 syntax, followed by an explanation of the packet's meaning. We
23830 include spaces in some of the templates for clarity; these are not
23831 part of the packet's syntax. No @value{GDBN} packet uses spaces to
23832 separate its components. For example, a template like @samp{foo
23833 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
23834 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
23835 @var{baz}. @value{GDBN} does not transmit a space character between the
23836 @samp{foo} and the @var{bar}, or between the @var{bar} and the
23839 Note that all packet forms beginning with an upper- or lower-case
23840 letter, other than those described here, are reserved for future use.
23842 Here are the packet descriptions.
23847 @cindex @samp{!} packet
23848 @anchor{extended mode}
23849 Enable extended mode. In extended mode, the remote server is made
23850 persistent. The @samp{R} packet is used to restart the program being
23856 The remote target both supports and has enabled extended mode.
23860 @cindex @samp{?} packet
23861 Indicate the reason the target halted. The reply is the same as for
23865 @xref{Stop Reply Packets}, for the reply specifications.
23867 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
23868 @cindex @samp{A} packet
23869 Initialized @code{argv[]} array passed into program. @var{arglen}
23870 specifies the number of bytes in the hex encoded byte stream
23871 @var{arg}. See @code{gdbserver} for more details.
23876 The arguments were set.
23882 @cindex @samp{b} packet
23883 (Don't use this packet; its behavior is not well-defined.)
23884 Change the serial line speed to @var{baud}.
23886 JTC: @emph{When does the transport layer state change? When it's
23887 received, or after the ACK is transmitted. In either case, there are
23888 problems if the command or the acknowledgment packet is dropped.}
23890 Stan: @emph{If people really wanted to add something like this, and get
23891 it working for the first time, they ought to modify ser-unix.c to send
23892 some kind of out-of-band message to a specially-setup stub and have the
23893 switch happen "in between" packets, so that from remote protocol's point
23894 of view, nothing actually happened.}
23896 @item B @var{addr},@var{mode}
23897 @cindex @samp{B} packet
23898 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23899 breakpoint at @var{addr}.
23901 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23902 (@pxref{insert breakpoint or watchpoint packet}).
23904 @item c @r{[}@var{addr}@r{]}
23905 @cindex @samp{c} packet
23906 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23907 resume at current address.
23910 @xref{Stop Reply Packets}, for the reply specifications.
23912 @item C @var{sig}@r{[};@var{addr}@r{]}
23913 @cindex @samp{C} packet
23914 Continue with signal @var{sig} (hex signal number). If
23915 @samp{;@var{addr}} is omitted, resume at same address.
23918 @xref{Stop Reply Packets}, for the reply specifications.
23921 @cindex @samp{d} packet
23924 Don't use this packet; instead, define a general set packet
23925 (@pxref{General Query Packets}).
23928 @cindex @samp{D} packet
23929 Detach @value{GDBN} from the remote system. Sent to the remote target
23930 before @value{GDBN} disconnects via the @code{detach} command.
23940 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23941 @cindex @samp{F} packet
23942 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23943 This is part of the File-I/O protocol extension. @xref{File-I/O
23944 Remote Protocol Extension}, for the specification.
23947 @anchor{read registers packet}
23948 @cindex @samp{g} packet
23949 Read general registers.
23953 @item @var{XX@dots{}}
23954 Each byte of register data is described by two hex digits. The bytes
23955 with the register are transmitted in target byte order. The size of
23956 each register and their position within the @samp{g} packet are
23957 determined by the @value{GDBN} internal gdbarch functions
23958 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
23959 specification of several standard @samp{g} packets is specified below.
23964 @item G @var{XX@dots{}}
23965 @cindex @samp{G} packet
23966 Write general registers. @xref{read registers packet}, for a
23967 description of the @var{XX@dots{}} data.
23977 @item H @var{c} @var{t}
23978 @cindex @samp{H} packet
23979 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23980 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23981 should be @samp{c} for step and continue operations, @samp{g} for other
23982 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23983 the threads, a thread number, or @samp{0} which means pick any thread.
23994 @c 'H': How restrictive (or permissive) is the thread model. If a
23995 @c thread is selected and stopped, are other threads allowed
23996 @c to continue to execute? As I mentioned above, I think the
23997 @c semantics of each command when a thread is selected must be
23998 @c described. For example:
24000 @c 'g': If the stub supports threads and a specific thread is
24001 @c selected, returns the register block from that thread;
24002 @c otherwise returns current registers.
24004 @c 'G' If the stub supports threads and a specific thread is
24005 @c selected, sets the registers of the register block of
24006 @c that thread; otherwise sets current registers.
24008 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
24009 @anchor{cycle step packet}
24010 @cindex @samp{i} packet
24011 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
24012 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
24013 step starting at that address.
24016 @cindex @samp{I} packet
24017 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
24021 @cindex @samp{k} packet
24024 FIXME: @emph{There is no description of how to operate when a specific
24025 thread context has been selected (i.e.@: does 'k' kill only that
24028 @item m @var{addr},@var{length}
24029 @cindex @samp{m} packet
24030 Read @var{length} bytes of memory starting at address @var{addr}.
24031 Note that @var{addr} may not be aligned to any particular boundary.
24033 The stub need not use any particular size or alignment when gathering
24034 data from memory for the response; even if @var{addr} is word-aligned
24035 and @var{length} is a multiple of the word size, the stub is free to
24036 use byte accesses, or not. For this reason, this packet may not be
24037 suitable for accessing memory-mapped I/O devices.
24038 @cindex alignment of remote memory accesses
24039 @cindex size of remote memory accesses
24040 @cindex memory, alignment and size of remote accesses
24044 @item @var{XX@dots{}}
24045 Memory contents; each byte is transmitted as a two-digit hexadecimal
24046 number. The reply may contain fewer bytes than requested if the
24047 server was able to read only part of the region of memory.
24052 @item M @var{addr},@var{length}:@var{XX@dots{}}
24053 @cindex @samp{M} packet
24054 Write @var{length} bytes of memory starting at address @var{addr}.
24055 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
24056 hexadecimal number.
24063 for an error (this includes the case where only part of the data was
24068 @cindex @samp{p} packet
24069 Read the value of register @var{n}; @var{n} is in hex.
24070 @xref{read registers packet}, for a description of how the returned
24071 register value is encoded.
24075 @item @var{XX@dots{}}
24076 the register's value
24080 Indicating an unrecognized @var{query}.
24083 @item P @var{n@dots{}}=@var{r@dots{}}
24084 @anchor{write register packet}
24085 @cindex @samp{P} packet
24086 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
24087 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
24088 digits for each byte in the register (target byte order).
24098 @item q @var{name} @var{params}@dots{}
24099 @itemx Q @var{name} @var{params}@dots{}
24100 @cindex @samp{q} packet
24101 @cindex @samp{Q} packet
24102 General query (@samp{q}) and set (@samp{Q}). These packets are
24103 described fully in @ref{General Query Packets}.
24106 @cindex @samp{r} packet
24107 Reset the entire system.
24109 Don't use this packet; use the @samp{R} packet instead.
24112 @cindex @samp{R} packet
24113 Restart the program being debugged. @var{XX}, while needed, is ignored.
24114 This packet is only available in extended mode (@pxref{extended mode}).
24116 The @samp{R} packet has no reply.
24118 @item s @r{[}@var{addr}@r{]}
24119 @cindex @samp{s} packet
24120 Single step. @var{addr} is the address at which to resume. If
24121 @var{addr} is omitted, resume at same address.
24124 @xref{Stop Reply Packets}, for the reply specifications.
24126 @item S @var{sig}@r{[};@var{addr}@r{]}
24127 @anchor{step with signal packet}
24128 @cindex @samp{S} packet
24129 Step with signal. This is analogous to the @samp{C} packet, but
24130 requests a single-step, rather than a normal resumption of execution.
24133 @xref{Stop Reply Packets}, for the reply specifications.
24135 @item t @var{addr}:@var{PP},@var{MM}
24136 @cindex @samp{t} packet
24137 Search backwards starting at address @var{addr} for a match with pattern
24138 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
24139 @var{addr} must be at least 3 digits.
24142 @cindex @samp{T} packet
24143 Find out if the thread XX is alive.
24148 thread is still alive
24154 Packets starting with @samp{v} are identified by a multi-letter name,
24155 up to the first @samp{;} or @samp{?} (or the end of the packet).
24157 @item vAttach;@var{pid}
24158 @cindex @samp{vAttach} packet
24159 Attach to a new process with the specified process ID. @var{pid} is a
24160 hexadecimal integer identifying the process. The attached process is
24163 This packet is only available in extended mode (@pxref{extended mode}).
24169 @item @r{Any stop packet}
24170 for success (@pxref{Stop Reply Packets})
24173 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
24174 @cindex @samp{vCont} packet
24175 Resume the inferior, specifying different actions for each thread.
24176 If an action is specified with no @var{tid}, then it is applied to any
24177 threads that don't have a specific action specified; if no default action is
24178 specified then other threads should remain stopped. Specifying multiple
24179 default actions is an error; specifying no actions is also an error.
24180 Thread IDs are specified in hexadecimal. Currently supported actions are:
24186 Continue with signal @var{sig}. @var{sig} should be two hex digits.
24190 Step with signal @var{sig}. @var{sig} should be two hex digits.
24193 The optional @var{addr} argument normally associated with these packets is
24194 not supported in @samp{vCont}.
24197 @xref{Stop Reply Packets}, for the reply specifications.
24200 @cindex @samp{vCont?} packet
24201 Request a list of actions supported by the @samp{vCont} packet.
24205 @item vCont@r{[};@var{action}@dots{}@r{]}
24206 The @samp{vCont} packet is supported. Each @var{action} is a supported
24207 command in the @samp{vCont} packet.
24209 The @samp{vCont} packet is not supported.
24212 @item vFile:@var{operation}:@var{parameter}@dots{}
24213 @cindex @samp{vFile} packet
24214 Perform a file operation on the target system. For details,
24215 see @ref{Host I/O Packets}.
24217 @item vFlashErase:@var{addr},@var{length}
24218 @cindex @samp{vFlashErase} packet
24219 Direct the stub to erase @var{length} bytes of flash starting at
24220 @var{addr}. The region may enclose any number of flash blocks, but
24221 its start and end must fall on block boundaries, as indicated by the
24222 flash block size appearing in the memory map (@pxref{Memory Map
24223 Format}). @value{GDBN} groups flash memory programming operations
24224 together, and sends a @samp{vFlashDone} request after each group; the
24225 stub is allowed to delay erase operation until the @samp{vFlashDone}
24226 packet is received.
24236 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
24237 @cindex @samp{vFlashWrite} packet
24238 Direct the stub to write data to flash address @var{addr}. The data
24239 is passed in binary form using the same encoding as for the @samp{X}
24240 packet (@pxref{Binary Data}). The memory ranges specified by
24241 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
24242 not overlap, and must appear in order of increasing addresses
24243 (although @samp{vFlashErase} packets for higher addresses may already
24244 have been received; the ordering is guaranteed only between
24245 @samp{vFlashWrite} packets). If a packet writes to an address that was
24246 neither erased by a preceding @samp{vFlashErase} packet nor by some other
24247 target-specific method, the results are unpredictable.
24255 for vFlashWrite addressing non-flash memory
24261 @cindex @samp{vFlashDone} packet
24262 Indicate to the stub that flash programming operation is finished.
24263 The stub is permitted to delay or batch the effects of a group of
24264 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
24265 @samp{vFlashDone} packet is received. The contents of the affected
24266 regions of flash memory are unpredictable until the @samp{vFlashDone}
24267 request is completed.
24269 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
24270 @cindex @samp{vRun} packet
24271 Run the program @var{filename}, passing it each @var{argument} on its
24272 command line. The file and arguments are hex-encoded strings. If
24273 @var{filename} is an empty string, the stub may use a default program
24274 (e.g.@: the last program run). The program is created in the stopped
24277 This packet is only available in extended mode (@pxref{extended mode}).
24283 @item @r{Any stop packet}
24284 for success (@pxref{Stop Reply Packets})
24287 @item X @var{addr},@var{length}:@var{XX@dots{}}
24289 @cindex @samp{X} packet
24290 Write data to memory, where the data is transmitted in binary.
24291 @var{addr} is address, @var{length} is number of bytes,
24292 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
24302 @item z @var{type},@var{addr},@var{length}
24303 @itemx Z @var{type},@var{addr},@var{length}
24304 @anchor{insert breakpoint or watchpoint packet}
24305 @cindex @samp{z} packet
24306 @cindex @samp{Z} packets
24307 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
24308 watchpoint starting at address @var{address} and covering the next
24309 @var{length} bytes.
24311 Each breakpoint and watchpoint packet @var{type} is documented
24314 @emph{Implementation notes: A remote target shall return an empty string
24315 for an unrecognized breakpoint or watchpoint packet @var{type}. A
24316 remote target shall support either both or neither of a given
24317 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
24318 avoid potential problems with duplicate packets, the operations should
24319 be implemented in an idempotent way.}
24321 @item z0,@var{addr},@var{length}
24322 @itemx Z0,@var{addr},@var{length}
24323 @cindex @samp{z0} packet
24324 @cindex @samp{Z0} packet
24325 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
24326 @var{addr} of size @var{length}.
24328 A memory breakpoint is implemented by replacing the instruction at
24329 @var{addr} with a software breakpoint or trap instruction. The
24330 @var{length} is used by targets that indicates the size of the
24331 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
24332 @sc{mips} can insert either a 2 or 4 byte breakpoint).
24334 @emph{Implementation note: It is possible for a target to copy or move
24335 code that contains memory breakpoints (e.g., when implementing
24336 overlays). The behavior of this packet, in the presence of such a
24337 target, is not defined.}
24349 @item z1,@var{addr},@var{length}
24350 @itemx Z1,@var{addr},@var{length}
24351 @cindex @samp{z1} packet
24352 @cindex @samp{Z1} packet
24353 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
24354 address @var{addr} of size @var{length}.
24356 A hardware breakpoint is implemented using a mechanism that is not
24357 dependant on being able to modify the target's memory.
24359 @emph{Implementation note: A hardware breakpoint is not affected by code
24372 @item z2,@var{addr},@var{length}
24373 @itemx Z2,@var{addr},@var{length}
24374 @cindex @samp{z2} packet
24375 @cindex @samp{Z2} packet
24376 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
24388 @item z3,@var{addr},@var{length}
24389 @itemx Z3,@var{addr},@var{length}
24390 @cindex @samp{z3} packet
24391 @cindex @samp{Z3} packet
24392 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
24404 @item z4,@var{addr},@var{length}
24405 @itemx Z4,@var{addr},@var{length}
24406 @cindex @samp{z4} packet
24407 @cindex @samp{Z4} packet
24408 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
24422 @node Stop Reply Packets
24423 @section Stop Reply Packets
24424 @cindex stop reply packets
24426 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
24427 receive any of the below as a reply. In the case of the @samp{C},
24428 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
24429 when the target halts. In the below the exact meaning of @dfn{signal
24430 number} is defined by the header @file{include/gdb/signals.h} in the
24431 @value{GDBN} source code.
24433 As in the description of request packets, we include spaces in the
24434 reply templates for clarity; these are not part of the reply packet's
24435 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
24441 The program received signal number @var{AA} (a two-digit hexadecimal
24442 number). This is equivalent to a @samp{T} response with no
24443 @var{n}:@var{r} pairs.
24445 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
24446 @cindex @samp{T} packet reply
24447 The program received signal number @var{AA} (a two-digit hexadecimal
24448 number). This is equivalent to an @samp{S} response, except that the
24449 @samp{@var{n}:@var{r}} pairs can carry values of important registers
24450 and other information directly in the stop reply packet, reducing
24451 round-trip latency. Single-step and breakpoint traps are reported
24452 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
24456 If @var{n} is a hexadecimal number, it is a register number, and the
24457 corresponding @var{r} gives that register's value. @var{r} is a
24458 series of bytes in target byte order, with each byte given by a
24459 two-digit hex number.
24462 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
24466 If @var{n} is a recognized @dfn{stop reason}, it describes a more
24467 specific event that stopped the target. The currently defined stop
24468 reasons are listed below. @var{aa} should be @samp{05}, the trap
24469 signal. At most one stop reason should be present.
24472 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
24473 and go on to the next; this allows us to extend the protocol in the
24477 The currently defined stop reasons are:
24483 The packet indicates a watchpoint hit, and @var{r} is the data address, in
24486 @cindex shared library events, remote reply
24488 The packet indicates that the loaded libraries have changed.
24489 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
24490 list of loaded libraries. @var{r} is ignored.
24494 The process exited, and @var{AA} is the exit status. This is only
24495 applicable to certain targets.
24498 The process terminated with signal @var{AA}.
24500 @item O @var{XX}@dots{}
24501 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
24502 written as the program's console output. This can happen at any time
24503 while the program is running and the debugger should continue to wait
24504 for @samp{W}, @samp{T}, etc.
24506 @item F @var{call-id},@var{parameter}@dots{}
24507 @var{call-id} is the identifier which says which host system call should
24508 be called. This is just the name of the function. Translation into the
24509 correct system call is only applicable as it's defined in @value{GDBN}.
24510 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
24513 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
24514 this very system call.
24516 The target replies with this packet when it expects @value{GDBN} to
24517 call a host system call on behalf of the target. @value{GDBN} replies
24518 with an appropriate @samp{F} packet and keeps up waiting for the next
24519 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
24520 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
24521 Protocol Extension}, for more details.
24525 @node General Query Packets
24526 @section General Query Packets
24527 @cindex remote query requests
24529 Packets starting with @samp{q} are @dfn{general query packets};
24530 packets starting with @samp{Q} are @dfn{general set packets}. General
24531 query and set packets are a semi-unified form for retrieving and
24532 sending information to and from the stub.
24534 The initial letter of a query or set packet is followed by a name
24535 indicating what sort of thing the packet applies to. For example,
24536 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
24537 definitions with the stub. These packet names follow some
24542 The name must not contain commas, colons or semicolons.
24544 Most @value{GDBN} query and set packets have a leading upper case
24547 The names of custom vendor packets should use a company prefix, in
24548 lower case, followed by a period. For example, packets designed at
24549 the Acme Corporation might begin with @samp{qacme.foo} (for querying
24550 foos) or @samp{Qacme.bar} (for setting bars).
24553 The name of a query or set packet should be separated from any
24554 parameters by a @samp{:}; the parameters themselves should be
24555 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
24556 full packet name, and check for a separator or the end of the packet,
24557 in case two packet names share a common prefix. New packets should not begin
24558 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
24559 packets predate these conventions, and have arguments without any terminator
24560 for the packet name; we suspect they are in widespread use in places that
24561 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
24562 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
24565 Like the descriptions of the other packets, each description here
24566 has a template showing the packet's overall syntax, followed by an
24567 explanation of the packet's meaning. We include spaces in some of the
24568 templates for clarity; these are not part of the packet's syntax. No
24569 @value{GDBN} packet uses spaces to separate its components.
24571 Here are the currently defined query and set packets:
24576 @cindex current thread, remote request
24577 @cindex @samp{qC} packet
24578 Return the current thread id.
24583 Where @var{pid} is an unsigned hexadecimal process id.
24584 @item @r{(anything else)}
24585 Any other reply implies the old pid.
24588 @item qCRC:@var{addr},@var{length}
24589 @cindex CRC of memory block, remote request
24590 @cindex @samp{qCRC} packet
24591 Compute the CRC checksum of a block of memory.
24595 An error (such as memory fault)
24596 @item C @var{crc32}
24597 The specified memory region's checksum is @var{crc32}.
24601 @itemx qsThreadInfo
24602 @cindex list active threads, remote request
24603 @cindex @samp{qfThreadInfo} packet
24604 @cindex @samp{qsThreadInfo} packet
24605 Obtain a list of all active thread ids from the target (OS). Since there
24606 may be too many active threads to fit into one reply packet, this query
24607 works iteratively: it may require more than one query/reply sequence to
24608 obtain the entire list of threads. The first query of the sequence will
24609 be the @samp{qfThreadInfo} query; subsequent queries in the
24610 sequence will be the @samp{qsThreadInfo} query.
24612 NOTE: This packet replaces the @samp{qL} query (see below).
24618 @item m @var{id},@var{id}@dots{}
24619 a comma-separated list of thread ids
24621 (lower case letter @samp{L}) denotes end of list.
24624 In response to each query, the target will reply with a list of one or
24625 more thread ids, in big-endian unsigned hex, separated by commas.
24626 @value{GDBN} will respond to each reply with a request for more thread
24627 ids (using the @samp{qs} form of the query), until the target responds
24628 with @samp{l} (lower-case el, for @dfn{last}).
24630 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
24631 @cindex get thread-local storage address, remote request
24632 @cindex @samp{qGetTLSAddr} packet
24633 Fetch the address associated with thread local storage specified
24634 by @var{thread-id}, @var{offset}, and @var{lm}.
24636 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
24637 thread for which to fetch the TLS address.
24639 @var{offset} is the (big endian, hex encoded) offset associated with the
24640 thread local variable. (This offset is obtained from the debug
24641 information associated with the variable.)
24643 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
24644 the load module associated with the thread local storage. For example,
24645 a @sc{gnu}/Linux system will pass the link map address of the shared
24646 object associated with the thread local storage under consideration.
24647 Other operating environments may choose to represent the load module
24648 differently, so the precise meaning of this parameter will vary.
24652 @item @var{XX}@dots{}
24653 Hex encoded (big endian) bytes representing the address of the thread
24654 local storage requested.
24657 An error occurred. @var{nn} are hex digits.
24660 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
24663 @item qL @var{startflag} @var{threadcount} @var{nextthread}
24664 Obtain thread information from RTOS. Where: @var{startflag} (one hex
24665 digit) is one to indicate the first query and zero to indicate a
24666 subsequent query; @var{threadcount} (two hex digits) is the maximum
24667 number of threads the response packet can contain; and @var{nextthread}
24668 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
24669 returned in the response as @var{argthread}.
24671 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
24675 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
24676 Where: @var{count} (two hex digits) is the number of threads being
24677 returned; @var{done} (one hex digit) is zero to indicate more threads
24678 and one indicates no further threads; @var{argthreadid} (eight hex
24679 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
24680 is a sequence of thread IDs from the target. @var{threadid} (eight hex
24681 digits). See @code{remote.c:parse_threadlist_response()}.
24685 @cindex section offsets, remote request
24686 @cindex @samp{qOffsets} packet
24687 Get section offsets that the target used when relocating the downloaded
24692 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
24693 Relocate the @code{Text} section by @var{xxx} from its original address.
24694 Relocate the @code{Data} section by @var{yyy} from its original address.
24695 If the object file format provides segment information (e.g.@: @sc{elf}
24696 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
24697 segments by the supplied offsets.
24699 @emph{Note: while a @code{Bss} offset may be included in the response,
24700 @value{GDBN} ignores this and instead applies the @code{Data} offset
24701 to the @code{Bss} section.}
24703 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
24704 Relocate the first segment of the object file, which conventionally
24705 contains program code, to a starting address of @var{xxx}. If
24706 @samp{DataSeg} is specified, relocate the second segment, which
24707 conventionally contains modifiable data, to a starting address of
24708 @var{yyy}. @value{GDBN} will report an error if the object file
24709 does not contain segment information, or does not contain at least
24710 as many segments as mentioned in the reply. Extra segments are
24711 kept at fixed offsets relative to the last relocated segment.
24714 @item qP @var{mode} @var{threadid}
24715 @cindex thread information, remote request
24716 @cindex @samp{qP} packet
24717 Returns information on @var{threadid}. Where: @var{mode} is a hex
24718 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
24720 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
24723 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
24725 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
24726 @cindex pass signals to inferior, remote request
24727 @cindex @samp{QPassSignals} packet
24728 @anchor{QPassSignals}
24729 Each listed @var{signal} should be passed directly to the inferior process.
24730 Signals are numbered identically to continue packets and stop replies
24731 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
24732 strictly greater than the previous item. These signals do not need to stop
24733 the inferior, or be reported to @value{GDBN}. All other signals should be
24734 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
24735 combine; any earlier @samp{QPassSignals} list is completely replaced by the
24736 new list. This packet improves performance when using @samp{handle
24737 @var{signal} nostop noprint pass}.
24742 The request succeeded.
24745 An error occurred. @var{nn} are hex digits.
24748 An empty reply indicates that @samp{QPassSignals} is not supported by
24752 Use of this packet is controlled by the @code{set remote pass-signals}
24753 command (@pxref{Remote Configuration, set remote pass-signals}).
24754 This packet is not probed by default; the remote stub must request it,
24755 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24757 @item qRcmd,@var{command}
24758 @cindex execute remote command, remote request
24759 @cindex @samp{qRcmd} packet
24760 @var{command} (hex encoded) is passed to the local interpreter for
24761 execution. Invalid commands should be reported using the output
24762 string. Before the final result packet, the target may also respond
24763 with a number of intermediate @samp{O@var{output}} console output
24764 packets. @emph{Implementors should note that providing access to a
24765 stubs's interpreter may have security implications}.
24770 A command response with no output.
24772 A command response with the hex encoded output string @var{OUTPUT}.
24774 Indicate a badly formed request.
24776 An empty reply indicates that @samp{qRcmd} is not recognized.
24779 (Note that the @code{qRcmd} packet's name is separated from the
24780 command by a @samp{,}, not a @samp{:}, contrary to the naming
24781 conventions above. Please don't use this packet as a model for new
24784 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
24785 @cindex searching memory, in remote debugging
24786 @cindex @samp{qSearch:memory} packet
24787 @anchor{qSearch memory}
24788 Search @var{length} bytes at @var{address} for @var{search-pattern}.
24789 @var{address} and @var{length} are encoded in hex.
24790 @var{search-pattern} is a sequence of bytes, hex encoded.
24795 The pattern was not found.
24797 The pattern was found at @var{address}.
24799 A badly formed request or an error was encountered while searching memory.
24801 An empty reply indicates that @samp{qSearch:memory} is not recognized.
24804 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
24805 @cindex supported packets, remote query
24806 @cindex features of the remote protocol
24807 @cindex @samp{qSupported} packet
24808 @anchor{qSupported}
24809 Tell the remote stub about features supported by @value{GDBN}, and
24810 query the stub for features it supports. This packet allows
24811 @value{GDBN} and the remote stub to take advantage of each others'
24812 features. @samp{qSupported} also consolidates multiple feature probes
24813 at startup, to improve @value{GDBN} performance---a single larger
24814 packet performs better than multiple smaller probe packets on
24815 high-latency links. Some features may enable behavior which must not
24816 be on by default, e.g.@: because it would confuse older clients or
24817 stubs. Other features may describe packets which could be
24818 automatically probed for, but are not. These features must be
24819 reported before @value{GDBN} will use them. This ``default
24820 unsupported'' behavior is not appropriate for all packets, but it
24821 helps to keep the initial connection time under control with new
24822 versions of @value{GDBN} which support increasing numbers of packets.
24826 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
24827 The stub supports or does not support each returned @var{stubfeature},
24828 depending on the form of each @var{stubfeature} (see below for the
24831 An empty reply indicates that @samp{qSupported} is not recognized,
24832 or that no features needed to be reported to @value{GDBN}.
24835 The allowed forms for each feature (either a @var{gdbfeature} in the
24836 @samp{qSupported} packet, or a @var{stubfeature} in the response)
24840 @item @var{name}=@var{value}
24841 The remote protocol feature @var{name} is supported, and associated
24842 with the specified @var{value}. The format of @var{value} depends
24843 on the feature, but it must not include a semicolon.
24845 The remote protocol feature @var{name} is supported, and does not
24846 need an associated value.
24848 The remote protocol feature @var{name} is not supported.
24850 The remote protocol feature @var{name} may be supported, and
24851 @value{GDBN} should auto-detect support in some other way when it is
24852 needed. This form will not be used for @var{gdbfeature} notifications,
24853 but may be used for @var{stubfeature} responses.
24856 Whenever the stub receives a @samp{qSupported} request, the
24857 supplied set of @value{GDBN} features should override any previous
24858 request. This allows @value{GDBN} to put the stub in a known
24859 state, even if the stub had previously been communicating with
24860 a different version of @value{GDBN}.
24862 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
24863 are defined yet. Stubs should ignore any unknown values for
24864 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
24865 packet supports receiving packets of unlimited length (earlier
24866 versions of @value{GDBN} may reject overly long responses). Values
24867 for @var{gdbfeature} may be defined in the future to let the stub take
24868 advantage of new features in @value{GDBN}, e.g.@: incompatible
24869 improvements in the remote protocol---support for unlimited length
24870 responses would be a @var{gdbfeature} example, if it were not implied by
24871 the @samp{qSupported} query. The stub's reply should be independent
24872 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
24873 describes all the features it supports, and then the stub replies with
24874 all the features it supports.
24876 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
24877 responses, as long as each response uses one of the standard forms.
24879 Some features are flags. A stub which supports a flag feature
24880 should respond with a @samp{+} form response. Other features
24881 require values, and the stub should respond with an @samp{=}
24884 Each feature has a default value, which @value{GDBN} will use if
24885 @samp{qSupported} is not available or if the feature is not mentioned
24886 in the @samp{qSupported} response. The default values are fixed; a
24887 stub is free to omit any feature responses that match the defaults.
24889 Not all features can be probed, but for those which can, the probing
24890 mechanism is useful: in some cases, a stub's internal
24891 architecture may not allow the protocol layer to know some information
24892 about the underlying target in advance. This is especially common in
24893 stubs which may be configured for multiple targets.
24895 These are the currently defined stub features and their properties:
24897 @multitable @columnfractions 0.35 0.2 0.12 0.2
24898 @c NOTE: The first row should be @headitem, but we do not yet require
24899 @c a new enough version of Texinfo (4.7) to use @headitem.
24901 @tab Value Required
24905 @item @samp{PacketSize}
24910 @item @samp{qXfer:auxv:read}
24915 @item @samp{qXfer:features:read}
24920 @item @samp{qXfer:libraries:read}
24925 @item @samp{qXfer:memory-map:read}
24930 @item @samp{qXfer:spu:read}
24935 @item @samp{qXfer:spu:write}
24940 @item @samp{QPassSignals}
24947 These are the currently defined stub features, in more detail:
24950 @cindex packet size, remote protocol
24951 @item PacketSize=@var{bytes}
24952 The remote stub can accept packets up to at least @var{bytes} in
24953 length. @value{GDBN} will send packets up to this size for bulk
24954 transfers, and will never send larger packets. This is a limit on the
24955 data characters in the packet, including the frame and checksum.
24956 There is no trailing NUL byte in a remote protocol packet; if the stub
24957 stores packets in a NUL-terminated format, it should allow an extra
24958 byte in its buffer for the NUL. If this stub feature is not supported,
24959 @value{GDBN} guesses based on the size of the @samp{g} packet response.
24961 @item qXfer:auxv:read
24962 The remote stub understands the @samp{qXfer:auxv:read} packet
24963 (@pxref{qXfer auxiliary vector read}).
24965 @item qXfer:features:read
24966 The remote stub understands the @samp{qXfer:features:read} packet
24967 (@pxref{qXfer target description read}).
24969 @item qXfer:libraries:read
24970 The remote stub understands the @samp{qXfer:libraries:read} packet
24971 (@pxref{qXfer library list read}).
24973 @item qXfer:memory-map:read
24974 The remote stub understands the @samp{qXfer:memory-map:read} packet
24975 (@pxref{qXfer memory map read}).
24977 @item qXfer:spu:read
24978 The remote stub understands the @samp{qXfer:spu:read} packet
24979 (@pxref{qXfer spu read}).
24981 @item qXfer:spu:write
24982 The remote stub understands the @samp{qXfer:spu:write} packet
24983 (@pxref{qXfer spu write}).
24986 The remote stub understands the @samp{QPassSignals} packet
24987 (@pxref{QPassSignals}).
24992 @cindex symbol lookup, remote request
24993 @cindex @samp{qSymbol} packet
24994 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24995 requests. Accept requests from the target for the values of symbols.
25000 The target does not need to look up any (more) symbols.
25001 @item qSymbol:@var{sym_name}
25002 The target requests the value of symbol @var{sym_name} (hex encoded).
25003 @value{GDBN} may provide the value by using the
25004 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
25008 @item qSymbol:@var{sym_value}:@var{sym_name}
25009 Set the value of @var{sym_name} to @var{sym_value}.
25011 @var{sym_name} (hex encoded) is the name of a symbol whose value the
25012 target has previously requested.
25014 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
25015 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
25021 The target does not need to look up any (more) symbols.
25022 @item qSymbol:@var{sym_name}
25023 The target requests the value of a new symbol @var{sym_name} (hex
25024 encoded). @value{GDBN} will continue to supply the values of symbols
25025 (if available), until the target ceases to request them.
25030 @xref{Tracepoint Packets}.
25032 @item qThreadExtraInfo,@var{id}
25033 @cindex thread attributes info, remote request
25034 @cindex @samp{qThreadExtraInfo} packet
25035 Obtain a printable string description of a thread's attributes from
25036 the target OS. @var{id} is a thread-id in big-endian hex. This
25037 string may contain anything that the target OS thinks is interesting
25038 for @value{GDBN} to tell the user about the thread. The string is
25039 displayed in @value{GDBN}'s @code{info threads} display. Some
25040 examples of possible thread extra info strings are @samp{Runnable}, or
25041 @samp{Blocked on Mutex}.
25045 @item @var{XX}@dots{}
25046 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
25047 comprising the printable string containing the extra information about
25048 the thread's attributes.
25051 (Note that the @code{qThreadExtraInfo} packet's name is separated from
25052 the command by a @samp{,}, not a @samp{:}, contrary to the naming
25053 conventions above. Please don't use this packet as a model for new
25061 @xref{Tracepoint Packets}.
25063 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
25064 @cindex read special object, remote request
25065 @cindex @samp{qXfer} packet
25066 @anchor{qXfer read}
25067 Read uninterpreted bytes from the target's special data area
25068 identified by the keyword @var{object}. Request @var{length} bytes
25069 starting at @var{offset} bytes into the data. The content and
25070 encoding of @var{annex} is specific to @var{object}; it can supply
25071 additional details about what data to access.
25073 Here are the specific requests of this form defined so far. All
25074 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
25075 formats, listed below.
25078 @item qXfer:auxv:read::@var{offset},@var{length}
25079 @anchor{qXfer auxiliary vector read}
25080 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
25081 auxiliary vector}. Note @var{annex} must be empty.
25083 This packet is not probed by default; the remote stub must request it,
25084 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25086 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
25087 @anchor{qXfer target description read}
25088 Access the @dfn{target description}. @xref{Target Descriptions}. The
25089 annex specifies which XML document to access. The main description is
25090 always loaded from the @samp{target.xml} annex.
25092 This packet is not probed by default; the remote stub must request it,
25093 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25095 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
25096 @anchor{qXfer library list read}
25097 Access the target's list of loaded libraries. @xref{Library List Format}.
25098 The annex part of the generic @samp{qXfer} packet must be empty
25099 (@pxref{qXfer read}).
25101 Targets which maintain a list of libraries in the program's memory do
25102 not need to implement this packet; it is designed for platforms where
25103 the operating system manages the list of loaded libraries.
25105 This packet is not probed by default; the remote stub must request it,
25106 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25108 @item qXfer:memory-map:read::@var{offset},@var{length}
25109 @anchor{qXfer memory map read}
25110 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
25111 annex part of the generic @samp{qXfer} packet must be empty
25112 (@pxref{qXfer read}).
25114 This packet is not probed by default; the remote stub must request it,
25115 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25117 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
25118 @anchor{qXfer spu read}
25119 Read contents of an @code{spufs} file on the target system. The
25120 annex specifies which file to read; it must be of the form
25121 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25122 in the target process, and @var{name} identifes the @code{spufs} file
25123 in that context to be accessed.
25125 This packet is not probed by default; the remote stub must request it,
25126 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25132 Data @var{data} (@pxref{Binary Data}) has been read from the
25133 target. There may be more data at a higher address (although
25134 it is permitted to return @samp{m} even for the last valid
25135 block of data, as long as at least one byte of data was read).
25136 @var{data} may have fewer bytes than the @var{length} in the
25140 Data @var{data} (@pxref{Binary Data}) has been read from the target.
25141 There is no more data to be read. @var{data} may have fewer bytes
25142 than the @var{length} in the request.
25145 The @var{offset} in the request is at the end of the data.
25146 There is no more data to be read.
25149 The request was malformed, or @var{annex} was invalid.
25152 The offset was invalid, or there was an error encountered reading the data.
25153 @var{nn} is a hex-encoded @code{errno} value.
25156 An empty reply indicates the @var{object} string was not recognized by
25157 the stub, or that the object does not support reading.
25160 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25161 @cindex write data into object, remote request
25162 Write uninterpreted bytes into the target's special data area
25163 identified by the keyword @var{object}, starting at @var{offset} bytes
25164 into the data. @var{data}@dots{} is the binary-encoded data
25165 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
25166 is specific to @var{object}; it can supply additional details about what data
25169 Here are the specific requests of this form defined so far. All
25170 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
25171 formats, listed below.
25174 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25175 @anchor{qXfer spu write}
25176 Write @var{data} to an @code{spufs} file on the target system. The
25177 annex specifies which file to write; it must be of the form
25178 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25179 in the target process, and @var{name} identifes the @code{spufs} file
25180 in that context to be accessed.
25182 This packet is not probed by default; the remote stub must request it,
25183 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25189 @var{nn} (hex encoded) is the number of bytes written.
25190 This may be fewer bytes than supplied in the request.
25193 The request was malformed, or @var{annex} was invalid.
25196 The offset was invalid, or there was an error encountered writing the data.
25197 @var{nn} is a hex-encoded @code{errno} value.
25200 An empty reply indicates the @var{object} string was not
25201 recognized by the stub, or that the object does not support writing.
25204 @item qXfer:@var{object}:@var{operation}:@dots{}
25205 Requests of this form may be added in the future. When a stub does
25206 not recognize the @var{object} keyword, or its support for
25207 @var{object} does not recognize the @var{operation} keyword, the stub
25208 must respond with an empty packet.
25212 @node Register Packet Format
25213 @section Register Packet Format
25215 The following @code{g}/@code{G} packets have previously been defined.
25216 In the below, some thirty-two bit registers are transferred as
25217 sixty-four bits. Those registers should be zero/sign extended (which?)
25218 to fill the space allocated. Register bytes are transferred in target
25219 byte order. The two nibbles within a register byte are transferred
25220 most-significant - least-significant.
25226 All registers are transferred as thirty-two bit quantities in the order:
25227 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
25228 registers; fsr; fir; fp.
25232 All registers are transferred as sixty-four bit quantities (including
25233 thirty-two bit registers such as @code{sr}). The ordering is the same
25238 @node Tracepoint Packets
25239 @section Tracepoint Packets
25240 @cindex tracepoint packets
25241 @cindex packets, tracepoint
25243 Here we describe the packets @value{GDBN} uses to implement
25244 tracepoints (@pxref{Tracepoints}).
25248 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
25249 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
25250 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
25251 the tracepoint is disabled. @var{step} is the tracepoint's step
25252 count, and @var{pass} is its pass count. If the trailing @samp{-} is
25253 present, further @samp{QTDP} packets will follow to specify this
25254 tracepoint's actions.
25259 The packet was understood and carried out.
25261 The packet was not recognized.
25264 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
25265 Define actions to be taken when a tracepoint is hit. @var{n} and
25266 @var{addr} must be the same as in the initial @samp{QTDP} packet for
25267 this tracepoint. This packet may only be sent immediately after
25268 another @samp{QTDP} packet that ended with a @samp{-}. If the
25269 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
25270 specifying more actions for this tracepoint.
25272 In the series of action packets for a given tracepoint, at most one
25273 can have an @samp{S} before its first @var{action}. If such a packet
25274 is sent, it and the following packets define ``while-stepping''
25275 actions. Any prior packets define ordinary actions --- that is, those
25276 taken when the tracepoint is first hit. If no action packet has an
25277 @samp{S}, then all the packets in the series specify ordinary
25278 tracepoint actions.
25280 The @samp{@var{action}@dots{}} portion of the packet is a series of
25281 actions, concatenated without separators. Each action has one of the
25287 Collect the registers whose bits are set in @var{mask}. @var{mask} is
25288 a hexadecimal number whose @var{i}'th bit is set if register number
25289 @var{i} should be collected. (The least significant bit is numbered
25290 zero.) Note that @var{mask} may be any number of digits long; it may
25291 not fit in a 32-bit word.
25293 @item M @var{basereg},@var{offset},@var{len}
25294 Collect @var{len} bytes of memory starting at the address in register
25295 number @var{basereg}, plus @var{offset}. If @var{basereg} is
25296 @samp{-1}, then the range has a fixed address: @var{offset} is the
25297 address of the lowest byte to collect. The @var{basereg},
25298 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
25299 values (the @samp{-1} value for @var{basereg} is a special case).
25301 @item X @var{len},@var{expr}
25302 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
25303 it directs. @var{expr} is an agent expression, as described in
25304 @ref{Agent Expressions}. Each byte of the expression is encoded as a
25305 two-digit hex number in the packet; @var{len} is the number of bytes
25306 in the expression (and thus one-half the number of hex digits in the
25311 Any number of actions may be packed together in a single @samp{QTDP}
25312 packet, as long as the packet does not exceed the maximum packet
25313 length (400 bytes, for many stubs). There may be only one @samp{R}
25314 action per tracepoint, and it must precede any @samp{M} or @samp{X}
25315 actions. Any registers referred to by @samp{M} and @samp{X} actions
25316 must be collected by a preceding @samp{R} action. (The
25317 ``while-stepping'' actions are treated as if they were attached to a
25318 separate tracepoint, as far as these restrictions are concerned.)
25323 The packet was understood and carried out.
25325 The packet was not recognized.
25328 @item QTFrame:@var{n}
25329 Select the @var{n}'th tracepoint frame from the buffer, and use the
25330 register and memory contents recorded there to answer subsequent
25331 request packets from @value{GDBN}.
25333 A successful reply from the stub indicates that the stub has found the
25334 requested frame. The response is a series of parts, concatenated
25335 without separators, describing the frame we selected. Each part has
25336 one of the following forms:
25340 The selected frame is number @var{n} in the trace frame buffer;
25341 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
25342 was no frame matching the criteria in the request packet.
25345 The selected trace frame records a hit of tracepoint number @var{t};
25346 @var{t} is a hexadecimal number.
25350 @item QTFrame:pc:@var{addr}
25351 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25352 currently selected frame whose PC is @var{addr};
25353 @var{addr} is a hexadecimal number.
25355 @item QTFrame:tdp:@var{t}
25356 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25357 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
25358 is a hexadecimal number.
25360 @item QTFrame:range:@var{start}:@var{end}
25361 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25362 currently selected frame whose PC is between @var{start} (inclusive)
25363 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
25366 @item QTFrame:outside:@var{start}:@var{end}
25367 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
25368 frame @emph{outside} the given range of addresses.
25371 Begin the tracepoint experiment. Begin collecting data from tracepoint
25372 hits in the trace frame buffer.
25375 End the tracepoint experiment. Stop collecting trace frames.
25378 Clear the table of tracepoints, and empty the trace frame buffer.
25380 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
25381 Establish the given ranges of memory as ``transparent''. The stub
25382 will answer requests for these ranges from memory's current contents,
25383 if they were not collected as part of the tracepoint hit.
25385 @value{GDBN} uses this to mark read-only regions of memory, like those
25386 containing program code. Since these areas never change, they should
25387 still have the same contents they did when the tracepoint was hit, so
25388 there's no reason for the stub to refuse to provide their contents.
25391 Ask the stub if there is a trace experiment running right now.
25396 There is no trace experiment running.
25398 There is a trace experiment running.
25404 @node Host I/O Packets
25405 @section Host I/O Packets
25406 @cindex Host I/O, remote protocol
25407 @cindex file transfer, remote protocol
25409 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
25410 operations on the far side of a remote link. For example, Host I/O is
25411 used to upload and download files to a remote target with its own
25412 filesystem. Host I/O uses the same constant values and data structure
25413 layout as the target-initiated File-I/O protocol. However, the
25414 Host I/O packets are structured differently. The target-initiated
25415 protocol relies on target memory to store parameters and buffers.
25416 Host I/O requests are initiated by @value{GDBN}, and the
25417 target's memory is not involved. @xref{File-I/O Remote Protocol
25418 Extension}, for more details on the target-initiated protocol.
25420 The Host I/O request packets all encode a single operation along with
25421 its arguments. They have this format:
25425 @item vFile:@var{operation}: @var{parameter}@dots{}
25426 @var{operation} is the name of the particular request; the target
25427 should compare the entire packet name up to the second colon when checking
25428 for a supported operation. The format of @var{parameter} depends on
25429 the operation. Numbers are always passed in hexadecimal. Negative
25430 numbers have an explicit minus sign (i.e.@: two's complement is not
25431 used). Strings (e.g.@: filenames) are encoded as a series of
25432 hexadecimal bytes. The last argument to a system call may be a
25433 buffer of escaped binary data (@pxref{Binary Data}).
25437 The valid responses to Host I/O packets are:
25441 @item F @var{result} [, @var{errno}] [; @var{attachment}]
25442 @var{result} is the integer value returned by this operation, usually
25443 non-negative for success and -1 for errors. If an error has occured,
25444 @var{errno} will be included in the result. @var{errno} will have a
25445 value defined by the File-I/O protocol (@pxref{Errno Values}). For
25446 operations which return data, @var{attachment} supplies the data as a
25447 binary buffer. Binary buffers in response packets are escaped in the
25448 normal way (@pxref{Binary Data}). See the individual packet
25449 documentation for the interpretation of @var{result} and
25453 An empty response indicates that this operation is not recognized.
25457 These are the supported Host I/O operations:
25460 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
25461 Open a file at @var{pathname} and return a file descriptor for it, or
25462 return -1 if an error occurs. @var{pathname} is a string,
25463 @var{flags} is an integer indicating a mask of open flags
25464 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
25465 of mode bits to use if the file is created (@pxref{mode_t Values}).
25466 @xref{open}, for details of the open flags and mode values.
25468 @item vFile:close: @var{fd}
25469 Close the open file corresponding to @var{fd} and return 0, or
25470 -1 if an error occurs.
25472 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
25473 Read data from the open file corresponding to @var{fd}. Up to
25474 @var{count} bytes will be read from the file, starting at @var{offset}
25475 relative to the start of the file. The target may read fewer bytes;
25476 common reasons include packet size limits and an end-of-file
25477 condition. The number of bytes read is returned. Zero should only be
25478 returned for a successful read at the end of the file, or if
25479 @var{count} was zero.
25481 The data read should be returned as a binary attachment on success.
25482 If zero bytes were read, the response should include an empty binary
25483 attachment (i.e.@: a trailing semicolon). The return value is the
25484 number of target bytes read; the binary attachment may be longer if
25485 some characters were escaped.
25487 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
25488 Write @var{data} (a binary buffer) to the open file corresponding
25489 to @var{fd}. Start the write at @var{offset} from the start of the
25490 file. Unlike many @code{write} system calls, there is no
25491 separate @var{count} argument; the length of @var{data} in the
25492 packet is used. @samp{vFile:write} returns the number of bytes written,
25493 which may be shorter than the length of @var{data}, or -1 if an
25496 @item vFile:unlink: @var{pathname}
25497 Delete the file at @var{pathname} on the target. Return 0,
25498 or -1 if an error occurs. @var{pathname} is a string.
25503 @section Interrupts
25504 @cindex interrupts (remote protocol)
25506 When a program on the remote target is running, @value{GDBN} may
25507 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
25508 control of which is specified via @value{GDBN}'s @samp{remotebreak}
25509 setting (@pxref{set remotebreak}).
25511 The precise meaning of @code{BREAK} is defined by the transport
25512 mechanism and may, in fact, be undefined. @value{GDBN} does
25513 not currently define a @code{BREAK} mechanism for any of the network
25516 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
25517 transport mechanisms. It is represented by sending the single byte
25518 @code{0x03} without any of the usual packet overhead described in
25519 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
25520 transmitted as part of a packet, it is considered to be packet data
25521 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
25522 (@pxref{X packet}), used for binary downloads, may include an unescaped
25523 @code{0x03} as part of its packet.
25525 Stubs are not required to recognize these interrupt mechanisms and the
25526 precise meaning associated with receipt of the interrupt is
25527 implementation defined. If the stub is successful at interrupting the
25528 running program, it is expected that it will send one of the Stop
25529 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
25530 of successfully stopping the program. Interrupts received while the
25531 program is stopped will be discarded.
25536 Example sequence of a target being re-started. Notice how the restart
25537 does not get any direct output:
25542 @emph{target restarts}
25545 <- @code{T001:1234123412341234}
25549 Example sequence of a target being stepped by a single instruction:
25552 -> @code{G1445@dots{}}
25557 <- @code{T001:1234123412341234}
25561 <- @code{1455@dots{}}
25565 @node File-I/O Remote Protocol Extension
25566 @section File-I/O Remote Protocol Extension
25567 @cindex File-I/O remote protocol extension
25570 * File-I/O Overview::
25571 * Protocol Basics::
25572 * The F Request Packet::
25573 * The F Reply Packet::
25574 * The Ctrl-C Message::
25576 * List of Supported Calls::
25577 * Protocol-specific Representation of Datatypes::
25579 * File-I/O Examples::
25582 @node File-I/O Overview
25583 @subsection File-I/O Overview
25584 @cindex file-i/o overview
25586 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
25587 target to use the host's file system and console I/O to perform various
25588 system calls. System calls on the target system are translated into a
25589 remote protocol packet to the host system, which then performs the needed
25590 actions and returns a response packet to the target system.
25591 This simulates file system operations even on targets that lack file systems.
25593 The protocol is defined to be independent of both the host and target systems.
25594 It uses its own internal representation of datatypes and values. Both
25595 @value{GDBN} and the target's @value{GDBN} stub are responsible for
25596 translating the system-dependent value representations into the internal
25597 protocol representations when data is transmitted.
25599 The communication is synchronous. A system call is possible only when
25600 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
25601 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
25602 the target is stopped to allow deterministic access to the target's
25603 memory. Therefore File-I/O is not interruptible by target signals. On
25604 the other hand, it is possible to interrupt File-I/O by a user interrupt
25605 (@samp{Ctrl-C}) within @value{GDBN}.
25607 The target's request to perform a host system call does not finish
25608 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
25609 after finishing the system call, the target returns to continuing the
25610 previous activity (continue, step). No additional continue or step
25611 request from @value{GDBN} is required.
25614 (@value{GDBP}) continue
25615 <- target requests 'system call X'
25616 target is stopped, @value{GDBN} executes system call
25617 -> @value{GDBN} returns result
25618 ... target continues, @value{GDBN} returns to wait for the target
25619 <- target hits breakpoint and sends a Txx packet
25622 The protocol only supports I/O on the console and to regular files on
25623 the host file system. Character or block special devices, pipes,
25624 named pipes, sockets or any other communication method on the host
25625 system are not supported by this protocol.
25627 @node Protocol Basics
25628 @subsection Protocol Basics
25629 @cindex protocol basics, file-i/o
25631 The File-I/O protocol uses the @code{F} packet as the request as well
25632 as reply packet. Since a File-I/O system call can only occur when
25633 @value{GDBN} is waiting for a response from the continuing or stepping target,
25634 the File-I/O request is a reply that @value{GDBN} has to expect as a result
25635 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
25636 This @code{F} packet contains all information needed to allow @value{GDBN}
25637 to call the appropriate host system call:
25641 A unique identifier for the requested system call.
25644 All parameters to the system call. Pointers are given as addresses
25645 in the target memory address space. Pointers to strings are given as
25646 pointer/length pair. Numerical values are given as they are.
25647 Numerical control flags are given in a protocol-specific representation.
25651 At this point, @value{GDBN} has to perform the following actions.
25655 If the parameters include pointer values to data needed as input to a
25656 system call, @value{GDBN} requests this data from the target with a
25657 standard @code{m} packet request. This additional communication has to be
25658 expected by the target implementation and is handled as any other @code{m}
25662 @value{GDBN} translates all value from protocol representation to host
25663 representation as needed. Datatypes are coerced into the host types.
25666 @value{GDBN} calls the system call.
25669 It then coerces datatypes back to protocol representation.
25672 If the system call is expected to return data in buffer space specified
25673 by pointer parameters to the call, the data is transmitted to the
25674 target using a @code{M} or @code{X} packet. This packet has to be expected
25675 by the target implementation and is handled as any other @code{M} or @code{X}
25680 Eventually @value{GDBN} replies with another @code{F} packet which contains all
25681 necessary information for the target to continue. This at least contains
25688 @code{errno}, if has been changed by the system call.
25695 After having done the needed type and value coercion, the target continues
25696 the latest continue or step action.
25698 @node The F Request Packet
25699 @subsection The @code{F} Request Packet
25700 @cindex file-i/o request packet
25701 @cindex @code{F} request packet
25703 The @code{F} request packet has the following format:
25706 @item F@var{call-id},@var{parameter@dots{}}
25708 @var{call-id} is the identifier to indicate the host system call to be called.
25709 This is just the name of the function.
25711 @var{parameter@dots{}} are the parameters to the system call.
25712 Parameters are hexadecimal integer values, either the actual values in case
25713 of scalar datatypes, pointers to target buffer space in case of compound
25714 datatypes and unspecified memory areas, or pointer/length pairs in case
25715 of string parameters. These are appended to the @var{call-id} as a
25716 comma-delimited list. All values are transmitted in ASCII
25717 string representation, pointer/length pairs separated by a slash.
25723 @node The F Reply Packet
25724 @subsection The @code{F} Reply Packet
25725 @cindex file-i/o reply packet
25726 @cindex @code{F} reply packet
25728 The @code{F} reply packet has the following format:
25732 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
25734 @var{retcode} is the return code of the system call as hexadecimal value.
25736 @var{errno} is the @code{errno} set by the call, in protocol-specific
25738 This parameter can be omitted if the call was successful.
25740 @var{Ctrl-C flag} is only sent if the user requested a break. In this
25741 case, @var{errno} must be sent as well, even if the call was successful.
25742 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
25749 or, if the call was interrupted before the host call has been performed:
25756 assuming 4 is the protocol-specific representation of @code{EINTR}.
25761 @node The Ctrl-C Message
25762 @subsection The @samp{Ctrl-C} Message
25763 @cindex ctrl-c message, in file-i/o protocol
25765 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
25766 reply packet (@pxref{The F Reply Packet}),
25767 the target should behave as if it had
25768 gotten a break message. The meaning for the target is ``system call
25769 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
25770 (as with a break message) and return to @value{GDBN} with a @code{T02}
25773 It's important for the target to know in which
25774 state the system call was interrupted. There are two possible cases:
25778 The system call hasn't been performed on the host yet.
25781 The system call on the host has been finished.
25785 These two states can be distinguished by the target by the value of the
25786 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
25787 call hasn't been performed. This is equivalent to the @code{EINTR} handling
25788 on POSIX systems. In any other case, the target may presume that the
25789 system call has been finished --- successfully or not --- and should behave
25790 as if the break message arrived right after the system call.
25792 @value{GDBN} must behave reliably. If the system call has not been called
25793 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
25794 @code{errno} in the packet. If the system call on the host has been finished
25795 before the user requests a break, the full action must be finished by
25796 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
25797 The @code{F} packet may only be sent when either nothing has happened
25798 or the full action has been completed.
25801 @subsection Console I/O
25802 @cindex console i/o as part of file-i/o
25804 By default and if not explicitly closed by the target system, the file
25805 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
25806 on the @value{GDBN} console is handled as any other file output operation
25807 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
25808 by @value{GDBN} so that after the target read request from file descriptor
25809 0 all following typing is buffered until either one of the following
25814 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
25816 system call is treated as finished.
25819 The user presses @key{RET}. This is treated as end of input with a trailing
25823 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
25824 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
25828 If the user has typed more characters than fit in the buffer given to
25829 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
25830 either another @code{read(0, @dots{})} is requested by the target, or debugging
25831 is stopped at the user's request.
25834 @node List of Supported Calls
25835 @subsection List of Supported Calls
25836 @cindex list of supported file-i/o calls
25853 @unnumberedsubsubsec open
25854 @cindex open, file-i/o system call
25859 int open(const char *pathname, int flags);
25860 int open(const char *pathname, int flags, mode_t mode);
25864 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
25867 @var{flags} is the bitwise @code{OR} of the following values:
25871 If the file does not exist it will be created. The host
25872 rules apply as far as file ownership and time stamps
25876 When used with @code{O_CREAT}, if the file already exists it is
25877 an error and open() fails.
25880 If the file already exists and the open mode allows
25881 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
25882 truncated to zero length.
25885 The file is opened in append mode.
25888 The file is opened for reading only.
25891 The file is opened for writing only.
25894 The file is opened for reading and writing.
25898 Other bits are silently ignored.
25902 @var{mode} is the bitwise @code{OR} of the following values:
25906 User has read permission.
25909 User has write permission.
25912 Group has read permission.
25915 Group has write permission.
25918 Others have read permission.
25921 Others have write permission.
25925 Other bits are silently ignored.
25928 @item Return value:
25929 @code{open} returns the new file descriptor or -1 if an error
25936 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
25939 @var{pathname} refers to a directory.
25942 The requested access is not allowed.
25945 @var{pathname} was too long.
25948 A directory component in @var{pathname} does not exist.
25951 @var{pathname} refers to a device, pipe, named pipe or socket.
25954 @var{pathname} refers to a file on a read-only filesystem and
25955 write access was requested.
25958 @var{pathname} is an invalid pointer value.
25961 No space on device to create the file.
25964 The process already has the maximum number of files open.
25967 The limit on the total number of files open on the system
25971 The call was interrupted by the user.
25977 @unnumberedsubsubsec close
25978 @cindex close, file-i/o system call
25987 @samp{Fclose,@var{fd}}
25989 @item Return value:
25990 @code{close} returns zero on success, or -1 if an error occurred.
25996 @var{fd} isn't a valid open file descriptor.
25999 The call was interrupted by the user.
26005 @unnumberedsubsubsec read
26006 @cindex read, file-i/o system call
26011 int read(int fd, void *buf, unsigned int count);
26015 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
26017 @item Return value:
26018 On success, the number of bytes read is returned.
26019 Zero indicates end of file. If count is zero, read
26020 returns zero as well. On error, -1 is returned.
26026 @var{fd} is not a valid file descriptor or is not open for
26030 @var{bufptr} is an invalid pointer value.
26033 The call was interrupted by the user.
26039 @unnumberedsubsubsec write
26040 @cindex write, file-i/o system call
26045 int write(int fd, const void *buf, unsigned int count);
26049 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
26051 @item Return value:
26052 On success, the number of bytes written are returned.
26053 Zero indicates nothing was written. On error, -1
26060 @var{fd} is not a valid file descriptor or is not open for
26064 @var{bufptr} is an invalid pointer value.
26067 An attempt was made to write a file that exceeds the
26068 host-specific maximum file size allowed.
26071 No space on device to write the data.
26074 The call was interrupted by the user.
26080 @unnumberedsubsubsec lseek
26081 @cindex lseek, file-i/o system call
26086 long lseek (int fd, long offset, int flag);
26090 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
26092 @var{flag} is one of:
26096 The offset is set to @var{offset} bytes.
26099 The offset is set to its current location plus @var{offset}
26103 The offset is set to the size of the file plus @var{offset}
26107 @item Return value:
26108 On success, the resulting unsigned offset in bytes from
26109 the beginning of the file is returned. Otherwise, a
26110 value of -1 is returned.
26116 @var{fd} is not a valid open file descriptor.
26119 @var{fd} is associated with the @value{GDBN} console.
26122 @var{flag} is not a proper value.
26125 The call was interrupted by the user.
26131 @unnumberedsubsubsec rename
26132 @cindex rename, file-i/o system call
26137 int rename(const char *oldpath, const char *newpath);
26141 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
26143 @item Return value:
26144 On success, zero is returned. On error, -1 is returned.
26150 @var{newpath} is an existing directory, but @var{oldpath} is not a
26154 @var{newpath} is a non-empty directory.
26157 @var{oldpath} or @var{newpath} is a directory that is in use by some
26161 An attempt was made to make a directory a subdirectory
26165 A component used as a directory in @var{oldpath} or new
26166 path is not a directory. Or @var{oldpath} is a directory
26167 and @var{newpath} exists but is not a directory.
26170 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
26173 No access to the file or the path of the file.
26177 @var{oldpath} or @var{newpath} was too long.
26180 A directory component in @var{oldpath} or @var{newpath} does not exist.
26183 The file is on a read-only filesystem.
26186 The device containing the file has no room for the new
26190 The call was interrupted by the user.
26196 @unnumberedsubsubsec unlink
26197 @cindex unlink, file-i/o system call
26202 int unlink(const char *pathname);
26206 @samp{Funlink,@var{pathnameptr}/@var{len}}
26208 @item Return value:
26209 On success, zero is returned. On error, -1 is returned.
26215 No access to the file or the path of the file.
26218 The system does not allow unlinking of directories.
26221 The file @var{pathname} cannot be unlinked because it's
26222 being used by another process.
26225 @var{pathnameptr} is an invalid pointer value.
26228 @var{pathname} was too long.
26231 A directory component in @var{pathname} does not exist.
26234 A component of the path is not a directory.
26237 The file is on a read-only filesystem.
26240 The call was interrupted by the user.
26246 @unnumberedsubsubsec stat/fstat
26247 @cindex fstat, file-i/o system call
26248 @cindex stat, file-i/o system call
26253 int stat(const char *pathname, struct stat *buf);
26254 int fstat(int fd, struct stat *buf);
26258 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
26259 @samp{Ffstat,@var{fd},@var{bufptr}}
26261 @item Return value:
26262 On success, zero is returned. On error, -1 is returned.
26268 @var{fd} is not a valid open file.
26271 A directory component in @var{pathname} does not exist or the
26272 path is an empty string.
26275 A component of the path is not a directory.
26278 @var{pathnameptr} is an invalid pointer value.
26281 No access to the file or the path of the file.
26284 @var{pathname} was too long.
26287 The call was interrupted by the user.
26293 @unnumberedsubsubsec gettimeofday
26294 @cindex gettimeofday, file-i/o system call
26299 int gettimeofday(struct timeval *tv, void *tz);
26303 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
26305 @item Return value:
26306 On success, 0 is returned, -1 otherwise.
26312 @var{tz} is a non-NULL pointer.
26315 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
26321 @unnumberedsubsubsec isatty
26322 @cindex isatty, file-i/o system call
26327 int isatty(int fd);
26331 @samp{Fisatty,@var{fd}}
26333 @item Return value:
26334 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
26340 The call was interrupted by the user.
26345 Note that the @code{isatty} call is treated as a special case: it returns
26346 1 to the target if the file descriptor is attached
26347 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
26348 would require implementing @code{ioctl} and would be more complex than
26353 @unnumberedsubsubsec system
26354 @cindex system, file-i/o system call
26359 int system(const char *command);
26363 @samp{Fsystem,@var{commandptr}/@var{len}}
26365 @item Return value:
26366 If @var{len} is zero, the return value indicates whether a shell is
26367 available. A zero return value indicates a shell is not available.
26368 For non-zero @var{len}, the value returned is -1 on error and the
26369 return status of the command otherwise. Only the exit status of the
26370 command is returned, which is extracted from the host's @code{system}
26371 return value by calling @code{WEXITSTATUS(retval)}. In case
26372 @file{/bin/sh} could not be executed, 127 is returned.
26378 The call was interrupted by the user.
26383 @value{GDBN} takes over the full task of calling the necessary host calls
26384 to perform the @code{system} call. The return value of @code{system} on
26385 the host is simplified before it's returned
26386 to the target. Any termination signal information from the child process
26387 is discarded, and the return value consists
26388 entirely of the exit status of the called command.
26390 Due to security concerns, the @code{system} call is by default refused
26391 by @value{GDBN}. The user has to allow this call explicitly with the
26392 @code{set remote system-call-allowed 1} command.
26395 @item set remote system-call-allowed
26396 @kindex set remote system-call-allowed
26397 Control whether to allow the @code{system} calls in the File I/O
26398 protocol for the remote target. The default is zero (disabled).
26400 @item show remote system-call-allowed
26401 @kindex show remote system-call-allowed
26402 Show whether the @code{system} calls are allowed in the File I/O
26406 @node Protocol-specific Representation of Datatypes
26407 @subsection Protocol-specific Representation of Datatypes
26408 @cindex protocol-specific representation of datatypes, in file-i/o protocol
26411 * Integral Datatypes::
26413 * Memory Transfer::
26418 @node Integral Datatypes
26419 @unnumberedsubsubsec Integral Datatypes
26420 @cindex integral datatypes, in file-i/o protocol
26422 The integral datatypes used in the system calls are @code{int},
26423 @code{unsigned int}, @code{long}, @code{unsigned long},
26424 @code{mode_t}, and @code{time_t}.
26426 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
26427 implemented as 32 bit values in this protocol.
26429 @code{long} and @code{unsigned long} are implemented as 64 bit types.
26431 @xref{Limits}, for corresponding MIN and MAX values (similar to those
26432 in @file{limits.h}) to allow range checking on host and target.
26434 @code{time_t} datatypes are defined as seconds since the Epoch.
26436 All integral datatypes transferred as part of a memory read or write of a
26437 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
26440 @node Pointer Values
26441 @unnumberedsubsubsec Pointer Values
26442 @cindex pointer values, in file-i/o protocol
26444 Pointers to target data are transmitted as they are. An exception
26445 is made for pointers to buffers for which the length isn't
26446 transmitted as part of the function call, namely strings. Strings
26447 are transmitted as a pointer/length pair, both as hex values, e.g.@:
26454 which is a pointer to data of length 18 bytes at position 0x1aaf.
26455 The length is defined as the full string length in bytes, including
26456 the trailing null byte. For example, the string @code{"hello world"}
26457 at address 0x123456 is transmitted as
26463 @node Memory Transfer
26464 @unnumberedsubsubsec Memory Transfer
26465 @cindex memory transfer, in file-i/o protocol
26467 Structured data which is transferred using a memory read or write (for
26468 example, a @code{struct stat}) is expected to be in a protocol-specific format
26469 with all scalar multibyte datatypes being big endian. Translation to
26470 this representation needs to be done both by the target before the @code{F}
26471 packet is sent, and by @value{GDBN} before
26472 it transfers memory to the target. Transferred pointers to structured
26473 data should point to the already-coerced data at any time.
26477 @unnumberedsubsubsec struct stat
26478 @cindex struct stat, in file-i/o protocol
26480 The buffer of type @code{struct stat} used by the target and @value{GDBN}
26481 is defined as follows:
26485 unsigned int st_dev; /* device */
26486 unsigned int st_ino; /* inode */
26487 mode_t st_mode; /* protection */
26488 unsigned int st_nlink; /* number of hard links */
26489 unsigned int st_uid; /* user ID of owner */
26490 unsigned int st_gid; /* group ID of owner */
26491 unsigned int st_rdev; /* device type (if inode device) */
26492 unsigned long st_size; /* total size, in bytes */
26493 unsigned long st_blksize; /* blocksize for filesystem I/O */
26494 unsigned long st_blocks; /* number of blocks allocated */
26495 time_t st_atime; /* time of last access */
26496 time_t st_mtime; /* time of last modification */
26497 time_t st_ctime; /* time of last change */
26501 The integral datatypes conform to the definitions given in the
26502 appropriate section (see @ref{Integral Datatypes}, for details) so this
26503 structure is of size 64 bytes.
26505 The values of several fields have a restricted meaning and/or
26511 A value of 0 represents a file, 1 the console.
26514 No valid meaning for the target. Transmitted unchanged.
26517 Valid mode bits are described in @ref{Constants}. Any other
26518 bits have currently no meaning for the target.
26523 No valid meaning for the target. Transmitted unchanged.
26528 These values have a host and file system dependent
26529 accuracy. Especially on Windows hosts, the file system may not
26530 support exact timing values.
26533 The target gets a @code{struct stat} of the above representation and is
26534 responsible for coercing it to the target representation before
26537 Note that due to size differences between the host, target, and protocol
26538 representations of @code{struct stat} members, these members could eventually
26539 get truncated on the target.
26541 @node struct timeval
26542 @unnumberedsubsubsec struct timeval
26543 @cindex struct timeval, in file-i/o protocol
26545 The buffer of type @code{struct timeval} used by the File-I/O protocol
26546 is defined as follows:
26550 time_t tv_sec; /* second */
26551 long tv_usec; /* microsecond */
26555 The integral datatypes conform to the definitions given in the
26556 appropriate section (see @ref{Integral Datatypes}, for details) so this
26557 structure is of size 8 bytes.
26560 @subsection Constants
26561 @cindex constants, in file-i/o protocol
26563 The following values are used for the constants inside of the
26564 protocol. @value{GDBN} and target are responsible for translating these
26565 values before and after the call as needed.
26576 @unnumberedsubsubsec Open Flags
26577 @cindex open flags, in file-i/o protocol
26579 All values are given in hexadecimal representation.
26591 @node mode_t Values
26592 @unnumberedsubsubsec mode_t Values
26593 @cindex mode_t values, in file-i/o protocol
26595 All values are given in octal representation.
26612 @unnumberedsubsubsec Errno Values
26613 @cindex errno values, in file-i/o protocol
26615 All values are given in decimal representation.
26640 @code{EUNKNOWN} is used as a fallback error value if a host system returns
26641 any error value not in the list of supported error numbers.
26644 @unnumberedsubsubsec Lseek Flags
26645 @cindex lseek flags, in file-i/o protocol
26654 @unnumberedsubsubsec Limits
26655 @cindex limits, in file-i/o protocol
26657 All values are given in decimal representation.
26660 INT_MIN -2147483648
26662 UINT_MAX 4294967295
26663 LONG_MIN -9223372036854775808
26664 LONG_MAX 9223372036854775807
26665 ULONG_MAX 18446744073709551615
26668 @node File-I/O Examples
26669 @subsection File-I/O Examples
26670 @cindex file-i/o examples
26672 Example sequence of a write call, file descriptor 3, buffer is at target
26673 address 0x1234, 6 bytes should be written:
26676 <- @code{Fwrite,3,1234,6}
26677 @emph{request memory read from target}
26680 @emph{return "6 bytes written"}
26684 Example sequence of a read call, file descriptor 3, buffer is at target
26685 address 0x1234, 6 bytes should be read:
26688 <- @code{Fread,3,1234,6}
26689 @emph{request memory write to target}
26690 -> @code{X1234,6:XXXXXX}
26691 @emph{return "6 bytes read"}
26695 Example sequence of a read call, call fails on the host due to invalid
26696 file descriptor (@code{EBADF}):
26699 <- @code{Fread,3,1234,6}
26703 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
26707 <- @code{Fread,3,1234,6}
26712 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
26716 <- @code{Fread,3,1234,6}
26717 -> @code{X1234,6:XXXXXX}
26721 @node Library List Format
26722 @section Library List Format
26723 @cindex library list format, remote protocol
26725 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
26726 same process as your application to manage libraries. In this case,
26727 @value{GDBN} can use the loader's symbol table and normal memory
26728 operations to maintain a list of shared libraries. On other
26729 platforms, the operating system manages loaded libraries.
26730 @value{GDBN} can not retrieve the list of currently loaded libraries
26731 through memory operations, so it uses the @samp{qXfer:libraries:read}
26732 packet (@pxref{qXfer library list read}) instead. The remote stub
26733 queries the target's operating system and reports which libraries
26736 The @samp{qXfer:libraries:read} packet returns an XML document which
26737 lists loaded libraries and their offsets. Each library has an
26738 associated name and one or more segment or section base addresses,
26739 which report where the library was loaded in memory.
26741 For the common case of libraries that are fully linked binaries, the
26742 library should have a list of segments. If the target supports
26743 dynamic linking of a relocatable object file, its library XML element
26744 should instead include a list of allocated sections. The segment or
26745 section bases are start addresses, not relocation offsets; they do not
26746 depend on the library's link-time base addresses.
26748 @value{GDBN} must be linked with the Expat library to support XML
26749 library lists. @xref{Expat}.
26751 A simple memory map, with one loaded library relocated by a single
26752 offset, looks like this:
26756 <library name="/lib/libc.so.6">
26757 <segment address="0x10000000"/>
26762 Another simple memory map, with one loaded library with three
26763 allocated sections (.text, .data, .bss), looks like this:
26767 <library name="sharedlib.o">
26768 <section address="0x10000000"/>
26769 <section address="0x20000000"/>
26770 <section address="0x30000000"/>
26775 The format of a library list is described by this DTD:
26778 <!-- library-list: Root element with versioning -->
26779 <!ELEMENT library-list (library)*>
26780 <!ATTLIST library-list version CDATA #FIXED "1.0">
26781 <!ELEMENT library (segment*, section*)>
26782 <!ATTLIST library name CDATA #REQUIRED>
26783 <!ELEMENT segment EMPTY>
26784 <!ATTLIST segment address CDATA #REQUIRED>
26785 <!ELEMENT section EMPTY>
26786 <!ATTLIST section address CDATA #REQUIRED>
26789 In addition, segments and section descriptors cannot be mixed within a
26790 single library element, and you must supply at least one segment or
26791 section for each library.
26793 @node Memory Map Format
26794 @section Memory Map Format
26795 @cindex memory map format
26797 To be able to write into flash memory, @value{GDBN} needs to obtain a
26798 memory map from the target. This section describes the format of the
26801 The memory map is obtained using the @samp{qXfer:memory-map:read}
26802 (@pxref{qXfer memory map read}) packet and is an XML document that
26803 lists memory regions.
26805 @value{GDBN} must be linked with the Expat library to support XML
26806 memory maps. @xref{Expat}.
26808 The top-level structure of the document is shown below:
26811 <?xml version="1.0"?>
26812 <!DOCTYPE memory-map
26813 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
26814 "http://sourceware.org/gdb/gdb-memory-map.dtd">
26820 Each region can be either:
26825 A region of RAM starting at @var{addr} and extending for @var{length}
26829 <memory type="ram" start="@var{addr}" length="@var{length}"/>
26834 A region of read-only memory:
26837 <memory type="rom" start="@var{addr}" length="@var{length}"/>
26842 A region of flash memory, with erasure blocks @var{blocksize}
26846 <memory type="flash" start="@var{addr}" length="@var{length}">
26847 <property name="blocksize">@var{blocksize}</property>
26853 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
26854 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
26855 packets to write to addresses in such ranges.
26857 The formal DTD for memory map format is given below:
26860 <!-- ................................................... -->
26861 <!-- Memory Map XML DTD ................................ -->
26862 <!-- File: memory-map.dtd .............................. -->
26863 <!-- .................................... .............. -->
26864 <!-- memory-map.dtd -->
26865 <!-- memory-map: Root element with versioning -->
26866 <!ELEMENT memory-map (memory | property)>
26867 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
26868 <!ELEMENT memory (property)>
26869 <!-- memory: Specifies a memory region,
26870 and its type, or device. -->
26871 <!ATTLIST memory type CDATA #REQUIRED
26872 start CDATA #REQUIRED
26873 length CDATA #REQUIRED
26874 device CDATA #IMPLIED>
26875 <!-- property: Generic attribute tag -->
26876 <!ELEMENT property (#PCDATA | property)*>
26877 <!ATTLIST property name CDATA #REQUIRED>
26880 @include agentexpr.texi
26882 @node Target Descriptions
26883 @appendix Target Descriptions
26884 @cindex target descriptions
26886 @strong{Warning:} target descriptions are still under active development,
26887 and the contents and format may change between @value{GDBN} releases.
26888 The format is expected to stabilize in the future.
26890 One of the challenges of using @value{GDBN} to debug embedded systems
26891 is that there are so many minor variants of each processor
26892 architecture in use. It is common practice for vendors to start with
26893 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
26894 and then make changes to adapt it to a particular market niche. Some
26895 architectures have hundreds of variants, available from dozens of
26896 vendors. This leads to a number of problems:
26900 With so many different customized processors, it is difficult for
26901 the @value{GDBN} maintainers to keep up with the changes.
26903 Since individual variants may have short lifetimes or limited
26904 audiences, it may not be worthwhile to carry information about every
26905 variant in the @value{GDBN} source tree.
26907 When @value{GDBN} does support the architecture of the embedded system
26908 at hand, the task of finding the correct architecture name to give the
26909 @command{set architecture} command can be error-prone.
26912 To address these problems, the @value{GDBN} remote protocol allows a
26913 target system to not only identify itself to @value{GDBN}, but to
26914 actually describe its own features. This lets @value{GDBN} support
26915 processor variants it has never seen before --- to the extent that the
26916 descriptions are accurate, and that @value{GDBN} understands them.
26918 @value{GDBN} must be linked with the Expat library to support XML
26919 target descriptions. @xref{Expat}.
26922 * Retrieving Descriptions:: How descriptions are fetched from a target.
26923 * Target Description Format:: The contents of a target description.
26924 * Predefined Target Types:: Standard types available for target
26926 * Standard Target Features:: Features @value{GDBN} knows about.
26929 @node Retrieving Descriptions
26930 @section Retrieving Descriptions
26932 Target descriptions can be read from the target automatically, or
26933 specified by the user manually. The default behavior is to read the
26934 description from the target. @value{GDBN} retrieves it via the remote
26935 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
26936 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
26937 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
26938 XML document, of the form described in @ref{Target Description
26941 Alternatively, you can specify a file to read for the target description.
26942 If a file is set, the target will not be queried. The commands to
26943 specify a file are:
26946 @cindex set tdesc filename
26947 @item set tdesc filename @var{path}
26948 Read the target description from @var{path}.
26950 @cindex unset tdesc filename
26951 @item unset tdesc filename
26952 Do not read the XML target description from a file. @value{GDBN}
26953 will use the description supplied by the current target.
26955 @cindex show tdesc filename
26956 @item show tdesc filename
26957 Show the filename to read for a target description, if any.
26961 @node Target Description Format
26962 @section Target Description Format
26963 @cindex target descriptions, XML format
26965 A target description annex is an @uref{http://www.w3.org/XML/, XML}
26966 document which complies with the Document Type Definition provided in
26967 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
26968 means you can use generally available tools like @command{xmllint} to
26969 check that your feature descriptions are well-formed and valid.
26970 However, to help people unfamiliar with XML write descriptions for
26971 their targets, we also describe the grammar here.
26973 Target descriptions can identify the architecture of the remote target
26974 and (for some architectures) provide information about custom register
26975 sets. @value{GDBN} can use this information to autoconfigure for your
26976 target, or to warn you if you connect to an unsupported target.
26978 Here is a simple target description:
26981 <target version="1.0">
26982 <architecture>i386:x86-64</architecture>
26987 This minimal description only says that the target uses
26988 the x86-64 architecture.
26990 A target description has the following overall form, with [ ] marking
26991 optional elements and @dots{} marking repeatable elements. The elements
26992 are explained further below.
26995 <?xml version="1.0"?>
26996 <!DOCTYPE target SYSTEM "gdb-target.dtd">
26997 <target version="1.0">
26998 @r{[}@var{architecture}@r{]}
26999 @r{[}@var{feature}@dots{}@r{]}
27004 The description is generally insensitive to whitespace and line
27005 breaks, under the usual common-sense rules. The XML version
27006 declaration and document type declaration can generally be omitted
27007 (@value{GDBN} does not require them), but specifying them may be
27008 useful for XML validation tools. The @samp{version} attribute for
27009 @samp{<target>} may also be omitted, but we recommend
27010 including it; if future versions of @value{GDBN} use an incompatible
27011 revision of @file{gdb-target.dtd}, they will detect and report
27012 the version mismatch.
27014 @subsection Inclusion
27015 @cindex target descriptions, inclusion
27018 @cindex <xi:include>
27021 It can sometimes be valuable to split a target description up into
27022 several different annexes, either for organizational purposes, or to
27023 share files between different possible target descriptions. You can
27024 divide a description into multiple files by replacing any element of
27025 the target description with an inclusion directive of the form:
27028 <xi:include href="@var{document}"/>
27032 When @value{GDBN} encounters an element of this form, it will retrieve
27033 the named XML @var{document}, and replace the inclusion directive with
27034 the contents of that document. If the current description was read
27035 using @samp{qXfer}, then so will be the included document;
27036 @var{document} will be interpreted as the name of an annex. If the
27037 current description was read from a file, @value{GDBN} will look for
27038 @var{document} as a file in the same directory where it found the
27039 original description.
27041 @subsection Architecture
27042 @cindex <architecture>
27044 An @samp{<architecture>} element has this form:
27047 <architecture>@var{arch}</architecture>
27050 @var{arch} is an architecture name from the same selection
27051 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
27052 Debugging Target}).
27054 @subsection Features
27057 Each @samp{<feature>} describes some logical portion of the target
27058 system. Features are currently used to describe available CPU
27059 registers and the types of their contents. A @samp{<feature>} element
27063 <feature name="@var{name}">
27064 @r{[}@var{type}@dots{}@r{]}
27070 Each feature's name should be unique within the description. The name
27071 of a feature does not matter unless @value{GDBN} has some special
27072 knowledge of the contents of that feature; if it does, the feature
27073 should have its standard name. @xref{Standard Target Features}.
27077 Any register's value is a collection of bits which @value{GDBN} must
27078 interpret. The default interpretation is a two's complement integer,
27079 but other types can be requested by name in the register description.
27080 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
27081 Target Types}), and the description can define additional composite types.
27083 Each type element must have an @samp{id} attribute, which gives
27084 a unique (within the containing @samp{<feature>}) name to the type.
27085 Types must be defined before they are used.
27088 Some targets offer vector registers, which can be treated as arrays
27089 of scalar elements. These types are written as @samp{<vector>} elements,
27090 specifying the array element type, @var{type}, and the number of elements,
27094 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
27098 If a register's value is usefully viewed in multiple ways, define it
27099 with a union type containing the useful representations. The
27100 @samp{<union>} element contains one or more @samp{<field>} elements,
27101 each of which has a @var{name} and a @var{type}:
27104 <union id="@var{id}">
27105 <field name="@var{name}" type="@var{type}"/>
27110 @subsection Registers
27113 Each register is represented as an element with this form:
27116 <reg name="@var{name}"
27117 bitsize="@var{size}"
27118 @r{[}regnum="@var{num}"@r{]}
27119 @r{[}save-restore="@var{save-restore}"@r{]}
27120 @r{[}type="@var{type}"@r{]}
27121 @r{[}group="@var{group}"@r{]}/>
27125 The components are as follows:
27130 The register's name; it must be unique within the target description.
27133 The register's size, in bits.
27136 The register's number. If omitted, a register's number is one greater
27137 than that of the previous register (either in the current feature or in
27138 a preceeding feature); the first register in the target description
27139 defaults to zero. This register number is used to read or write
27140 the register; e.g.@: it is used in the remote @code{p} and @code{P}
27141 packets, and registers appear in the @code{g} and @code{G} packets
27142 in order of increasing register number.
27145 Whether the register should be preserved across inferior function
27146 calls; this must be either @code{yes} or @code{no}. The default is
27147 @code{yes}, which is appropriate for most registers except for
27148 some system control registers; this is not related to the target's
27152 The type of the register. @var{type} may be a predefined type, a type
27153 defined in the current feature, or one of the special types @code{int}
27154 and @code{float}. @code{int} is an integer type of the correct size
27155 for @var{bitsize}, and @code{float} is a floating point type (in the
27156 architecture's normal floating point format) of the correct size for
27157 @var{bitsize}. The default is @code{int}.
27160 The register group to which this register belongs. @var{group} must
27161 be either @code{general}, @code{float}, or @code{vector}. If no
27162 @var{group} is specified, @value{GDBN} will not display the register
27163 in @code{info registers}.
27167 @node Predefined Target Types
27168 @section Predefined Target Types
27169 @cindex target descriptions, predefined types
27171 Type definitions in the self-description can build up composite types
27172 from basic building blocks, but can not define fundamental types. Instead,
27173 standard identifiers are provided by @value{GDBN} for the fundamental
27174 types. The currently supported types are:
27183 Signed integer types holding the specified number of bits.
27190 Unsigned integer types holding the specified number of bits.
27194 Pointers to unspecified code and data. The program counter and
27195 any dedicated return address register may be marked as code
27196 pointers; printing a code pointer converts it into a symbolic
27197 address. The stack pointer and any dedicated address registers
27198 may be marked as data pointers.
27201 Single precision IEEE floating point.
27204 Double precision IEEE floating point.
27207 The 12-byte extended precision format used by ARM FPA registers.
27211 @node Standard Target Features
27212 @section Standard Target Features
27213 @cindex target descriptions, standard features
27215 A target description must contain either no registers or all the
27216 target's registers. If the description contains no registers, then
27217 @value{GDBN} will assume a default register layout, selected based on
27218 the architecture. If the description contains any registers, the
27219 default layout will not be used; the standard registers must be
27220 described in the target description, in such a way that @value{GDBN}
27221 can recognize them.
27223 This is accomplished by giving specific names to feature elements
27224 which contain standard registers. @value{GDBN} will look for features
27225 with those names and verify that they contain the expected registers;
27226 if any known feature is missing required registers, or if any required
27227 feature is missing, @value{GDBN} will reject the target
27228 description. You can add additional registers to any of the
27229 standard features --- @value{GDBN} will display them just as if
27230 they were added to an unrecognized feature.
27232 This section lists the known features and their expected contents.
27233 Sample XML documents for these features are included in the
27234 @value{GDBN} source tree, in the directory @file{gdb/features}.
27236 Names recognized by @value{GDBN} should include the name of the
27237 company or organization which selected the name, and the overall
27238 architecture to which the feature applies; so e.g.@: the feature
27239 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
27241 The names of registers are not case sensitive for the purpose
27242 of recognizing standard features, but @value{GDBN} will only display
27243 registers using the capitalization used in the description.
27249 * PowerPC Features::
27254 @subsection ARM Features
27255 @cindex target descriptions, ARM features
27257 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
27258 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
27259 @samp{lr}, @samp{pc}, and @samp{cpsr}.
27261 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
27262 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
27264 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
27265 it should contain at least registers @samp{wR0} through @samp{wR15} and
27266 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
27267 @samp{wCSSF}, and @samp{wCASF} registers are optional.
27269 @node MIPS Features
27270 @subsection MIPS Features
27271 @cindex target descriptions, MIPS features
27273 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
27274 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
27275 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
27278 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
27279 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
27280 registers. They may be 32-bit or 64-bit depending on the target.
27282 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
27283 it may be optional in a future version of @value{GDBN}. It should
27284 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
27285 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
27287 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
27288 contain a single register, @samp{restart}, which is used by the
27289 Linux kernel to control restartable syscalls.
27291 @node M68K Features
27292 @subsection M68K Features
27293 @cindex target descriptions, M68K features
27296 @item @samp{org.gnu.gdb.m68k.core}
27297 @itemx @samp{org.gnu.gdb.coldfire.core}
27298 @itemx @samp{org.gnu.gdb.fido.core}
27299 One of those features must be always present.
27300 The feature that is present determines which flavor of m86k is
27301 used. The feature that is present should contain registers
27302 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
27303 @samp{sp}, @samp{ps} and @samp{pc}.
27305 @item @samp{org.gnu.gdb.coldfire.fp}
27306 This feature is optional. If present, it should contain registers
27307 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
27311 @node PowerPC Features
27312 @subsection PowerPC Features
27313 @cindex target descriptions, PowerPC features
27315 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
27316 targets. It should contain registers @samp{r0} through @samp{r31},
27317 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
27318 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
27320 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
27321 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
27323 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
27324 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
27327 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
27328 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
27329 @samp{spefscr}. SPE targets should provide 32-bit registers in
27330 @samp{org.gnu.gdb.power.core} and provide the upper halves in
27331 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
27332 these to present registers @samp{ev0} through @samp{ev31} to the
27347 % I think something like @colophon should be in texinfo. In the
27349 \long\def\colophon{\hbox to0pt{}\vfill
27350 \centerline{The body of this manual is set in}
27351 \centerline{\fontname\tenrm,}
27352 \centerline{with headings in {\bf\fontname\tenbf}}
27353 \centerline{and examples in {\tt\fontname\tentt}.}
27354 \centerline{{\it\fontname\tenit\/},}
27355 \centerline{{\bf\fontname\tenbf}, and}
27356 \centerline{{\sl\fontname\tensl\/}}
27357 \centerline{are used for emphasis.}\vfill}
27359 % Blame: doc@cygnus.com, 1991.