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, 2007, 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 * Extending GDB:: Extending @value{GDBN}
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.
2002 @kindex set disable-randomization
2003 @item set disable-randomization
2004 @itemx set disable-randomization on
2005 This option (enabled by default in @value{GDBN}) will turn off the native
2006 randomization of the virtual address space of the started program. This option
2007 is useful for multiple debugging sessions to make the execution better
2008 reproducible and memory addresses reusable across debugging sessions.
2010 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2014 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2017 @item set disable-randomization off
2018 Leave the behavior of the started executable unchanged. Some bugs rear their
2019 ugly heads only when the program is loaded at certain addresses. If your bug
2020 disappears when you run the program under @value{GDBN}, that might be because
2021 @value{GDBN} by default disables the address randomization on platforms, such
2022 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2023 disable-randomization off} to try to reproduce such elusive bugs.
2025 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2026 It protects the programs against some kinds of security attacks. In these
2027 cases the attacker needs to know the exact location of a concrete executable
2028 code. Randomizing its location makes it impossible to inject jumps misusing
2029 a code at its expected addresses.
2031 Prelinking shared libraries provides a startup performance advantage but it
2032 makes addresses in these libraries predictable for privileged processes by
2033 having just unprivileged access at the target system. Reading the shared
2034 library binary gives enough information for assembling the malicious code
2035 misusing it. Still even a prelinked shared library can get loaded at a new
2036 random address just requiring the regular relocation process during the
2037 startup. Shared libraries not already prelinked are always loaded at
2038 a randomly chosen address.
2040 Position independent executables (PIE) contain position independent code
2041 similar to the shared libraries and therefore such executables get loaded at
2042 a randomly chosen address upon startup. PIE executables always load even
2043 already prelinked shared libraries at a random address. You can build such
2044 executable using @command{gcc -fPIE -pie}.
2046 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2047 (as long as the randomization is enabled).
2049 @item show disable-randomization
2050 Show the current setting of the explicit disable of the native randomization of
2051 the virtual address space of the started program.
2056 @section Your Program's Arguments
2058 @cindex arguments (to your program)
2059 The arguments to your program can be specified by the arguments of the
2061 They are passed to a shell, which expands wildcard characters and
2062 performs redirection of I/O, and thence to your program. Your
2063 @code{SHELL} environment variable (if it exists) specifies what shell
2064 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2065 the default shell (@file{/bin/sh} on Unix).
2067 On non-Unix systems, the program is usually invoked directly by
2068 @value{GDBN}, which emulates I/O redirection via the appropriate system
2069 calls, and the wildcard characters are expanded by the startup code of
2070 the program, not by the shell.
2072 @code{run} with no arguments uses the same arguments used by the previous
2073 @code{run}, or those set by the @code{set args} command.
2078 Specify the arguments to be used the next time your program is run. If
2079 @code{set args} has no arguments, @code{run} executes your program
2080 with no arguments. Once you have run your program with arguments,
2081 using @code{set args} before the next @code{run} is the only way to run
2082 it again without arguments.
2086 Show the arguments to give your program when it is started.
2090 @section Your Program's Environment
2092 @cindex environment (of your program)
2093 The @dfn{environment} consists of a set of environment variables and
2094 their values. Environment variables conventionally record such things as
2095 your user name, your home directory, your terminal type, and your search
2096 path for programs to run. Usually you set up environment variables with
2097 the shell and they are inherited by all the other programs you run. When
2098 debugging, it can be useful to try running your program with a modified
2099 environment without having to start @value{GDBN} over again.
2103 @item path @var{directory}
2104 Add @var{directory} to the front of the @code{PATH} environment variable
2105 (the search path for executables) that will be passed to your program.
2106 The value of @code{PATH} used by @value{GDBN} does not change.
2107 You may specify several directory names, separated by whitespace or by a
2108 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2109 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2110 is moved to the front, so it is searched sooner.
2112 You can use the string @samp{$cwd} to refer to whatever is the current
2113 working directory at the time @value{GDBN} searches the path. If you
2114 use @samp{.} instead, it refers to the directory where you executed the
2115 @code{path} command. @value{GDBN} replaces @samp{.} in the
2116 @var{directory} argument (with the current path) before adding
2117 @var{directory} to the search path.
2118 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2119 @c document that, since repeating it would be a no-op.
2123 Display the list of search paths for executables (the @code{PATH}
2124 environment variable).
2126 @kindex show environment
2127 @item show environment @r{[}@var{varname}@r{]}
2128 Print the value of environment variable @var{varname} to be given to
2129 your program when it starts. If you do not supply @var{varname},
2130 print the names and values of all environment variables to be given to
2131 your program. You can abbreviate @code{environment} as @code{env}.
2133 @kindex set environment
2134 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2135 Set environment variable @var{varname} to @var{value}. The value
2136 changes for your program only, not for @value{GDBN} itself. @var{value} may
2137 be any string; the values of environment variables are just strings, and
2138 any interpretation is supplied by your program itself. The @var{value}
2139 parameter is optional; if it is eliminated, the variable is set to a
2141 @c "any string" here does not include leading, trailing
2142 @c blanks. Gnu asks: does anyone care?
2144 For example, this command:
2151 tells the debugged program, when subsequently run, that its user is named
2152 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2153 are not actually required.)
2155 @kindex unset environment
2156 @item unset environment @var{varname}
2157 Remove variable @var{varname} from the environment to be passed to your
2158 program. This is different from @samp{set env @var{varname} =};
2159 @code{unset environment} removes the variable from the environment,
2160 rather than assigning it an empty value.
2163 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2165 by your @code{SHELL} environment variable if it exists (or
2166 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2167 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2168 @file{.bashrc} for BASH---any variables you set in that file affect
2169 your program. You may wish to move setting of environment variables to
2170 files that are only run when you sign on, such as @file{.login} or
2173 @node Working Directory
2174 @section Your Program's Working Directory
2176 @cindex working directory (of your program)
2177 Each time you start your program with @code{run}, it inherits its
2178 working directory from the current working directory of @value{GDBN}.
2179 The @value{GDBN} working directory is initially whatever it inherited
2180 from its parent process (typically the shell), but you can specify a new
2181 working directory in @value{GDBN} with the @code{cd} command.
2183 The @value{GDBN} working directory also serves as a default for the commands
2184 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2189 @cindex change working directory
2190 @item cd @var{directory}
2191 Set the @value{GDBN} working directory to @var{directory}.
2195 Print the @value{GDBN} working directory.
2198 It is generally impossible to find the current working directory of
2199 the process being debugged (since a program can change its directory
2200 during its run). If you work on a system where @value{GDBN} is
2201 configured with the @file{/proc} support, you can use the @code{info
2202 proc} command (@pxref{SVR4 Process Information}) to find out the
2203 current working directory of the debuggee.
2206 @section Your Program's Input and Output
2211 By default, the program you run under @value{GDBN} does input and output to
2212 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2213 to its own terminal modes to interact with you, but it records the terminal
2214 modes your program was using and switches back to them when you continue
2215 running your program.
2218 @kindex info terminal
2220 Displays information recorded by @value{GDBN} about the terminal modes your
2224 You can redirect your program's input and/or output using shell
2225 redirection with the @code{run} command. For example,
2232 starts your program, diverting its output to the file @file{outfile}.
2235 @cindex controlling terminal
2236 Another way to specify where your program should do input and output is
2237 with the @code{tty} command. This command accepts a file name as
2238 argument, and causes this file to be the default for future @code{run}
2239 commands. It also resets the controlling terminal for the child
2240 process, for future @code{run} commands. For example,
2247 directs that processes started with subsequent @code{run} commands
2248 default to do input and output on the terminal @file{/dev/ttyb} and have
2249 that as their controlling terminal.
2251 An explicit redirection in @code{run} overrides the @code{tty} command's
2252 effect on the input/output device, but not its effect on the controlling
2255 When you use the @code{tty} command or redirect input in the @code{run}
2256 command, only the input @emph{for your program} is affected. The input
2257 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2258 for @code{set inferior-tty}.
2260 @cindex inferior tty
2261 @cindex set inferior controlling terminal
2262 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2263 display the name of the terminal that will be used for future runs of your
2267 @item set inferior-tty /dev/ttyb
2268 @kindex set inferior-tty
2269 Set the tty for the program being debugged to /dev/ttyb.
2271 @item show inferior-tty
2272 @kindex show inferior-tty
2273 Show the current tty for the program being debugged.
2277 @section Debugging an Already-running Process
2282 @item attach @var{process-id}
2283 This command attaches to a running process---one that was started
2284 outside @value{GDBN}. (@code{info files} shows your active
2285 targets.) The command takes as argument a process ID. The usual way to
2286 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2287 or with the @samp{jobs -l} shell command.
2289 @code{attach} does not repeat if you press @key{RET} a second time after
2290 executing the command.
2293 To use @code{attach}, your program must be running in an environment
2294 which supports processes; for example, @code{attach} does not work for
2295 programs on bare-board targets that lack an operating system. You must
2296 also have permission to send the process a signal.
2298 When you use @code{attach}, the debugger finds the program running in
2299 the process first by looking in the current working directory, then (if
2300 the program is not found) by using the source file search path
2301 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2302 the @code{file} command to load the program. @xref{Files, ,Commands to
2305 The first thing @value{GDBN} does after arranging to debug the specified
2306 process is to stop it. You can examine and modify an attached process
2307 with all the @value{GDBN} commands that are ordinarily available when
2308 you start processes with @code{run}. You can insert breakpoints; you
2309 can step and continue; you can modify storage. If you would rather the
2310 process continue running, you may use the @code{continue} command after
2311 attaching @value{GDBN} to the process.
2316 When you have finished debugging the attached process, you can use the
2317 @code{detach} command to release it from @value{GDBN} control. Detaching
2318 the process continues its execution. After the @code{detach} command,
2319 that process and @value{GDBN} become completely independent once more, and you
2320 are ready to @code{attach} another process or start one with @code{run}.
2321 @code{detach} does not repeat if you press @key{RET} again after
2322 executing the command.
2325 If you exit @value{GDBN} while you have an attached process, you detach
2326 that process. If you use the @code{run} command, you kill that process.
2327 By default, @value{GDBN} asks for confirmation if you try to do either of these
2328 things; you can control whether or not you need to confirm by using the
2329 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2333 @section Killing the Child Process
2338 Kill the child process in which your program is running under @value{GDBN}.
2341 This command is useful if you wish to debug a core dump instead of a
2342 running process. @value{GDBN} ignores any core dump file while your program
2345 On some operating systems, a program cannot be executed outside @value{GDBN}
2346 while you have breakpoints set on it inside @value{GDBN}. You can use the
2347 @code{kill} command in this situation to permit running your program
2348 outside the debugger.
2350 The @code{kill} command is also useful if you wish to recompile and
2351 relink your program, since on many systems it is impossible to modify an
2352 executable file while it is running in a process. In this case, when you
2353 next type @code{run}, @value{GDBN} notices that the file has changed, and
2354 reads the symbol table again (while trying to preserve your current
2355 breakpoint settings).
2358 @section Debugging Programs with Multiple Threads
2360 @cindex threads of execution
2361 @cindex multiple threads
2362 @cindex switching threads
2363 In some operating systems, such as HP-UX and Solaris, a single program
2364 may have more than one @dfn{thread} of execution. The precise semantics
2365 of threads differ from one operating system to another, but in general
2366 the threads of a single program are akin to multiple processes---except
2367 that they share one address space (that is, they can all examine and
2368 modify the same variables). On the other hand, each thread has its own
2369 registers and execution stack, and perhaps private memory.
2371 @value{GDBN} provides these facilities for debugging multi-thread
2375 @item automatic notification of new threads
2376 @item @samp{thread @var{threadno}}, a command to switch among threads
2377 @item @samp{info threads}, a command to inquire about existing threads
2378 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2379 a command to apply a command to a list of threads
2380 @item thread-specific breakpoints
2381 @item @samp{set print thread-events}, which controls printing of
2382 messages on thread start and exit.
2386 @emph{Warning:} These facilities are not yet available on every
2387 @value{GDBN} configuration where the operating system supports threads.
2388 If your @value{GDBN} does not support threads, these commands have no
2389 effect. For example, a system without thread support shows no output
2390 from @samp{info threads}, and always rejects the @code{thread} command,
2394 (@value{GDBP}) info threads
2395 (@value{GDBP}) thread 1
2396 Thread ID 1 not known. Use the "info threads" command to
2397 see the IDs of currently known threads.
2399 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2400 @c doesn't support threads"?
2403 @cindex focus of debugging
2404 @cindex current thread
2405 The @value{GDBN} thread debugging facility allows you to observe all
2406 threads while your program runs---but whenever @value{GDBN} takes
2407 control, one thread in particular is always the focus of debugging.
2408 This thread is called the @dfn{current thread}. Debugging commands show
2409 program information from the perspective of the current thread.
2411 @cindex @code{New} @var{systag} message
2412 @cindex thread identifier (system)
2413 @c FIXME-implementors!! It would be more helpful if the [New...] message
2414 @c included GDB's numeric thread handle, so you could just go to that
2415 @c thread without first checking `info threads'.
2416 Whenever @value{GDBN} detects a new thread in your program, it displays
2417 the target system's identification for the thread with a message in the
2418 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2419 whose form varies depending on the particular system. For example, on
2420 @sc{gnu}/Linux, you might see
2423 [New Thread 46912507313328 (LWP 25582)]
2427 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2428 the @var{systag} is simply something like @samp{process 368}, with no
2431 @c FIXME!! (1) Does the [New...] message appear even for the very first
2432 @c thread of a program, or does it only appear for the
2433 @c second---i.e.@: when it becomes obvious we have a multithread
2435 @c (2) *Is* there necessarily a first thread always? Or do some
2436 @c multithread systems permit starting a program with multiple
2437 @c threads ab initio?
2439 @cindex thread number
2440 @cindex thread identifier (GDB)
2441 For debugging purposes, @value{GDBN} associates its own thread
2442 number---always a single integer---with each thread in your program.
2445 @kindex info threads
2447 Display a summary of all threads currently in your
2448 program. @value{GDBN} displays for each thread (in this order):
2452 the thread number assigned by @value{GDBN}
2455 the target system's thread identifier (@var{systag})
2458 the current stack frame summary for that thread
2462 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2463 indicates the current thread.
2467 @c end table here to get a little more width for example
2470 (@value{GDBP}) info threads
2471 3 process 35 thread 27 0x34e5 in sigpause ()
2472 2 process 35 thread 23 0x34e5 in sigpause ()
2473 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2479 @cindex debugging multithreaded programs (on HP-UX)
2480 @cindex thread identifier (GDB), on HP-UX
2481 For debugging purposes, @value{GDBN} associates its own thread
2482 number---a small integer assigned in thread-creation order---with each
2483 thread in your program.
2485 @cindex @code{New} @var{systag} message, on HP-UX
2486 @cindex thread identifier (system), on HP-UX
2487 @c FIXME-implementors!! It would be more helpful if the [New...] message
2488 @c included GDB's numeric thread handle, so you could just go to that
2489 @c thread without first checking `info threads'.
2490 Whenever @value{GDBN} detects a new thread in your program, it displays
2491 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2492 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2493 whose form varies depending on the particular system. For example, on
2497 [New thread 2 (system thread 26594)]
2501 when @value{GDBN} notices a new thread.
2504 @kindex info threads (HP-UX)
2506 Display a summary of all threads currently in your
2507 program. @value{GDBN} displays for each thread (in this order):
2510 @item the thread number assigned by @value{GDBN}
2512 @item the target system's thread identifier (@var{systag})
2514 @item the current stack frame summary for that thread
2518 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2519 indicates the current thread.
2523 @c end table here to get a little more width for example
2526 (@value{GDBP}) info threads
2527 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2529 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2530 from /usr/lib/libc.2
2531 1 system thread 27905 0x7b003498 in _brk () \@*
2532 from /usr/lib/libc.2
2535 On Solaris, you can display more information about user threads with a
2536 Solaris-specific command:
2539 @item maint info sol-threads
2540 @kindex maint info sol-threads
2541 @cindex thread info (Solaris)
2542 Display info on Solaris user threads.
2546 @kindex thread @var{threadno}
2547 @item thread @var{threadno}
2548 Make thread number @var{threadno} the current thread. The command
2549 argument @var{threadno} is the internal @value{GDBN} thread number, as
2550 shown in the first field of the @samp{info threads} display.
2551 @value{GDBN} responds by displaying the system identifier of the thread
2552 you selected, and its current stack frame summary:
2555 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2556 (@value{GDBP}) thread 2
2557 [Switching to process 35 thread 23]
2558 0x34e5 in sigpause ()
2562 As with the @samp{[New @dots{}]} message, the form of the text after
2563 @samp{Switching to} depends on your system's conventions for identifying
2566 @kindex thread apply
2567 @cindex apply command to several threads
2568 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2569 The @code{thread apply} command allows you to apply the named
2570 @var{command} to one or more threads. Specify the numbers of the
2571 threads that you want affected with the command argument
2572 @var{threadno}. It can be a single thread number, one of the numbers
2573 shown in the first field of the @samp{info threads} display; or it
2574 could be a range of thread numbers, as in @code{2-4}. To apply a
2575 command to all threads, type @kbd{thread apply all @var{command}}.
2577 @kindex set print thread-events
2578 @cindex print messages on thread start and exit
2579 @item set print thread-events
2580 @itemx set print thread-events on
2581 @itemx set print thread-events off
2582 The @code{set print thread-events} command allows you to enable or
2583 disable printing of messages when @value{GDBN} notices that new threads have
2584 started or that threads have exited. By default, these messages will
2585 be printed if detection of these events is supported by the target.
2586 Note that these messages cannot be disabled on all targets.
2588 @kindex show print thread-events
2589 @item show print thread-events
2590 Show whether messages will be printed when @value{GDBN} detects that threads
2591 have started and exited.
2594 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2595 more information about how @value{GDBN} behaves when you stop and start
2596 programs with multiple threads.
2598 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2599 watchpoints in programs with multiple threads.
2602 @section Debugging Programs with Multiple Processes
2604 @cindex fork, debugging programs which call
2605 @cindex multiple processes
2606 @cindex processes, multiple
2607 On most systems, @value{GDBN} has no special support for debugging
2608 programs which create additional processes using the @code{fork}
2609 function. When a program forks, @value{GDBN} will continue to debug the
2610 parent process and the child process will run unimpeded. If you have
2611 set a breakpoint in any code which the child then executes, the child
2612 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2613 will cause it to terminate.
2615 However, if you want to debug the child process there is a workaround
2616 which isn't too painful. Put a call to @code{sleep} in the code which
2617 the child process executes after the fork. It may be useful to sleep
2618 only if a certain environment variable is set, or a certain file exists,
2619 so that the delay need not occur when you don't want to run @value{GDBN}
2620 on the child. While the child is sleeping, use the @code{ps} program to
2621 get its process ID. Then tell @value{GDBN} (a new invocation of
2622 @value{GDBN} if you are also debugging the parent process) to attach to
2623 the child process (@pxref{Attach}). From that point on you can debug
2624 the child process just like any other process which you attached to.
2626 On some systems, @value{GDBN} provides support for debugging programs that
2627 create additional processes using the @code{fork} or @code{vfork} functions.
2628 Currently, the only platforms with this feature are HP-UX (11.x and later
2629 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2631 By default, when a program forks, @value{GDBN} will continue to debug
2632 the parent process and the child process will run unimpeded.
2634 If you want to follow the child process instead of the parent process,
2635 use the command @w{@code{set follow-fork-mode}}.
2638 @kindex set follow-fork-mode
2639 @item set follow-fork-mode @var{mode}
2640 Set the debugger response to a program call of @code{fork} or
2641 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2642 process. The @var{mode} argument can be:
2646 The original process is debugged after a fork. The child process runs
2647 unimpeded. This is the default.
2650 The new process is debugged after a fork. The parent process runs
2655 @kindex show follow-fork-mode
2656 @item show follow-fork-mode
2657 Display the current debugger response to a @code{fork} or @code{vfork} call.
2660 @cindex debugging multiple processes
2661 On Linux, if you want to debug both the parent and child processes, use the
2662 command @w{@code{set detach-on-fork}}.
2665 @kindex set detach-on-fork
2666 @item set detach-on-fork @var{mode}
2667 Tells gdb whether to detach one of the processes after a fork, or
2668 retain debugger control over them both.
2672 The child process (or parent process, depending on the value of
2673 @code{follow-fork-mode}) will be detached and allowed to run
2674 independently. This is the default.
2677 Both processes will be held under the control of @value{GDBN}.
2678 One process (child or parent, depending on the value of
2679 @code{follow-fork-mode}) is debugged as usual, while the other
2684 @kindex show detach-on-fork
2685 @item show detach-on-fork
2686 Show whether detach-on-fork mode is on/off.
2689 If you choose to set @samp{detach-on-fork} mode off, then
2690 @value{GDBN} will retain control of all forked processes (including
2691 nested forks). You can list the forked processes under the control of
2692 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2693 from one fork to another by using the @w{@code{fork}} command.
2698 Print a list of all forked processes under the control of @value{GDBN}.
2699 The listing will include a fork id, a process id, and the current
2700 position (program counter) of the process.
2702 @kindex fork @var{fork-id}
2703 @item fork @var{fork-id}
2704 Make fork number @var{fork-id} the current process. The argument
2705 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2706 as shown in the first field of the @samp{info forks} display.
2708 @kindex process @var{process-id}
2709 @item process @var{process-id}
2710 Make process number @var{process-id} the current process. The
2711 argument @var{process-id} must be one that is listed in the output of
2716 To quit debugging one of the forked processes, you can either detach
2717 from it by using the @w{@code{detach fork}} command (allowing it to
2718 run independently), or delete (and kill) it using the
2719 @w{@code{delete fork}} command.
2722 @kindex detach fork @var{fork-id}
2723 @item detach fork @var{fork-id}
2724 Detach from the process identified by @value{GDBN} fork number
2725 @var{fork-id}, and remove it from the fork list. The process will be
2726 allowed to run independently.
2728 @kindex delete fork @var{fork-id}
2729 @item delete fork @var{fork-id}
2730 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2731 and remove it from the fork list.
2735 If you ask to debug a child process and a @code{vfork} is followed by an
2736 @code{exec}, @value{GDBN} executes the new target up to the first
2737 breakpoint in the new target. If you have a breakpoint set on
2738 @code{main} in your original program, the breakpoint will also be set on
2739 the child process's @code{main}.
2741 When a child process is spawned by @code{vfork}, you cannot debug the
2742 child or parent until an @code{exec} call completes.
2744 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2745 call executes, the new target restarts. To restart the parent process,
2746 use the @code{file} command with the parent executable name as its
2749 You can use the @code{catch} command to make @value{GDBN} stop whenever
2750 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2751 Catchpoints, ,Setting Catchpoints}.
2753 @node Checkpoint/Restart
2754 @section Setting a @emph{Bookmark} to Return to Later
2759 @cindex snapshot of a process
2760 @cindex rewind program state
2762 On certain operating systems@footnote{Currently, only
2763 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2764 program's state, called a @dfn{checkpoint}, and come back to it
2767 Returning to a checkpoint effectively undoes everything that has
2768 happened in the program since the @code{checkpoint} was saved. This
2769 includes changes in memory, registers, and even (within some limits)
2770 system state. Effectively, it is like going back in time to the
2771 moment when the checkpoint was saved.
2773 Thus, if you're stepping thru a program and you think you're
2774 getting close to the point where things go wrong, you can save
2775 a checkpoint. Then, if you accidentally go too far and miss
2776 the critical statement, instead of having to restart your program
2777 from the beginning, you can just go back to the checkpoint and
2778 start again from there.
2780 This can be especially useful if it takes a lot of time or
2781 steps to reach the point where you think the bug occurs.
2783 To use the @code{checkpoint}/@code{restart} method of debugging:
2788 Save a snapshot of the debugged program's current execution state.
2789 The @code{checkpoint} command takes no arguments, but each checkpoint
2790 is assigned a small integer id, similar to a breakpoint id.
2792 @kindex info checkpoints
2793 @item info checkpoints
2794 List the checkpoints that have been saved in the current debugging
2795 session. For each checkpoint, the following information will be
2802 @item Source line, or label
2805 @kindex restart @var{checkpoint-id}
2806 @item restart @var{checkpoint-id}
2807 Restore the program state that was saved as checkpoint number
2808 @var{checkpoint-id}. All program variables, registers, stack frames
2809 etc.@: will be returned to the values that they had when the checkpoint
2810 was saved. In essence, gdb will ``wind back the clock'' to the point
2811 in time when the checkpoint was saved.
2813 Note that breakpoints, @value{GDBN} variables, command history etc.
2814 are not affected by restoring a checkpoint. In general, a checkpoint
2815 only restores things that reside in the program being debugged, not in
2818 @kindex delete checkpoint @var{checkpoint-id}
2819 @item delete checkpoint @var{checkpoint-id}
2820 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2824 Returning to a previously saved checkpoint will restore the user state
2825 of the program being debugged, plus a significant subset of the system
2826 (OS) state, including file pointers. It won't ``un-write'' data from
2827 a file, but it will rewind the file pointer to the previous location,
2828 so that the previously written data can be overwritten. For files
2829 opened in read mode, the pointer will also be restored so that the
2830 previously read data can be read again.
2832 Of course, characters that have been sent to a printer (or other
2833 external device) cannot be ``snatched back'', and characters received
2834 from eg.@: a serial device can be removed from internal program buffers,
2835 but they cannot be ``pushed back'' into the serial pipeline, ready to
2836 be received again. Similarly, the actual contents of files that have
2837 been changed cannot be restored (at this time).
2839 However, within those constraints, you actually can ``rewind'' your
2840 program to a previously saved point in time, and begin debugging it
2841 again --- and you can change the course of events so as to debug a
2842 different execution path this time.
2844 @cindex checkpoints and process id
2845 Finally, there is one bit of internal program state that will be
2846 different when you return to a checkpoint --- the program's process
2847 id. Each checkpoint will have a unique process id (or @var{pid}),
2848 and each will be different from the program's original @var{pid}.
2849 If your program has saved a local copy of its process id, this could
2850 potentially pose a problem.
2852 @subsection A Non-obvious Benefit of Using Checkpoints
2854 On some systems such as @sc{gnu}/Linux, address space randomization
2855 is performed on new processes for security reasons. This makes it
2856 difficult or impossible to set a breakpoint, or watchpoint, on an
2857 absolute address if you have to restart the program, since the
2858 absolute location of a symbol will change from one execution to the
2861 A checkpoint, however, is an @emph{identical} copy of a process.
2862 Therefore if you create a checkpoint at (eg.@:) the start of main,
2863 and simply return to that checkpoint instead of restarting the
2864 process, you can avoid the effects of address randomization and
2865 your symbols will all stay in the same place.
2868 @chapter Stopping and Continuing
2870 The principal purposes of using a debugger are so that you can stop your
2871 program before it terminates; or so that, if your program runs into
2872 trouble, you can investigate and find out why.
2874 Inside @value{GDBN}, your program may stop for any of several reasons,
2875 such as a signal, a breakpoint, or reaching a new line after a
2876 @value{GDBN} command such as @code{step}. You may then examine and
2877 change variables, set new breakpoints or remove old ones, and then
2878 continue execution. Usually, the messages shown by @value{GDBN} provide
2879 ample explanation of the status of your program---but you can also
2880 explicitly request this information at any time.
2883 @kindex info program
2885 Display information about the status of your program: whether it is
2886 running or not, what process it is, and why it stopped.
2890 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2891 * Continuing and Stepping:: Resuming execution
2893 * Thread Stops:: Stopping and starting multi-thread programs
2897 @section Breakpoints, Watchpoints, and Catchpoints
2900 A @dfn{breakpoint} makes your program stop whenever a certain point in
2901 the program is reached. For each breakpoint, you can add conditions to
2902 control in finer detail whether your program stops. You can set
2903 breakpoints with the @code{break} command and its variants (@pxref{Set
2904 Breaks, ,Setting Breakpoints}), to specify the place where your program
2905 should stop by line number, function name or exact address in the
2908 On some systems, you can set breakpoints in shared libraries before
2909 the executable is run. There is a minor limitation on HP-UX systems:
2910 you must wait until the executable is run in order to set breakpoints
2911 in shared library routines that are not called directly by the program
2912 (for example, routines that are arguments in a @code{pthread_create}
2916 @cindex data breakpoints
2917 @cindex memory tracing
2918 @cindex breakpoint on memory address
2919 @cindex breakpoint on variable modification
2920 A @dfn{watchpoint} is a special breakpoint that stops your program
2921 when the value of an expression changes. The expression may be a value
2922 of a variable, or it could involve values of one or more variables
2923 combined by operators, such as @samp{a + b}. This is sometimes called
2924 @dfn{data breakpoints}. You must use a different command to set
2925 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2926 from that, you can manage a watchpoint like any other breakpoint: you
2927 enable, disable, and delete both breakpoints and watchpoints using the
2930 You can arrange to have values from your program displayed automatically
2931 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2935 @cindex breakpoint on events
2936 A @dfn{catchpoint} is another special breakpoint that stops your program
2937 when a certain kind of event occurs, such as the throwing of a C@t{++}
2938 exception or the loading of a library. As with watchpoints, you use a
2939 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2940 Catchpoints}), but aside from that, you can manage a catchpoint like any
2941 other breakpoint. (To stop when your program receives a signal, use the
2942 @code{handle} command; see @ref{Signals, ,Signals}.)
2944 @cindex breakpoint numbers
2945 @cindex numbers for breakpoints
2946 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2947 catchpoint when you create it; these numbers are successive integers
2948 starting with one. In many of the commands for controlling various
2949 features of breakpoints you use the breakpoint number to say which
2950 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2951 @dfn{disabled}; if disabled, it has no effect on your program until you
2954 @cindex breakpoint ranges
2955 @cindex ranges of breakpoints
2956 Some @value{GDBN} commands accept a range of breakpoints on which to
2957 operate. A breakpoint range is either a single breakpoint number, like
2958 @samp{5}, or two such numbers, in increasing order, separated by a
2959 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2960 all breakpoints in that range are operated on.
2963 * Set Breaks:: Setting breakpoints
2964 * Set Watchpoints:: Setting watchpoints
2965 * Set Catchpoints:: Setting catchpoints
2966 * Delete Breaks:: Deleting breakpoints
2967 * Disabling:: Disabling breakpoints
2968 * Conditions:: Break conditions
2969 * Break Commands:: Breakpoint command lists
2970 * Error in Breakpoints:: ``Cannot insert breakpoints''
2971 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2975 @subsection Setting Breakpoints
2977 @c FIXME LMB what does GDB do if no code on line of breakpt?
2978 @c consider in particular declaration with/without initialization.
2980 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2983 @kindex b @r{(@code{break})}
2984 @vindex $bpnum@r{, convenience variable}
2985 @cindex latest breakpoint
2986 Breakpoints are set with the @code{break} command (abbreviated
2987 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2988 number of the breakpoint you've set most recently; see @ref{Convenience
2989 Vars,, Convenience Variables}, for a discussion of what you can do with
2990 convenience variables.
2993 @item break @var{location}
2994 Set a breakpoint at the given @var{location}, which can specify a
2995 function name, a line number, or an address of an instruction.
2996 (@xref{Specify Location}, for a list of all the possible ways to
2997 specify a @var{location}.) The breakpoint will stop your program just
2998 before it executes any of the code in the specified @var{location}.
3000 When using source languages that permit overloading of symbols, such as
3001 C@t{++}, a function name may refer to more than one possible place to break.
3002 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3006 When called without any arguments, @code{break} sets a breakpoint at
3007 the next instruction to be executed in the selected stack frame
3008 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3009 innermost, this makes your program stop as soon as control
3010 returns to that frame. This is similar to the effect of a
3011 @code{finish} command in the frame inside the selected frame---except
3012 that @code{finish} does not leave an active breakpoint. If you use
3013 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3014 the next time it reaches the current location; this may be useful
3017 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3018 least one instruction has been executed. If it did not do this, you
3019 would be unable to proceed past a breakpoint without first disabling the
3020 breakpoint. This rule applies whether or not the breakpoint already
3021 existed when your program stopped.
3023 @item break @dots{} if @var{cond}
3024 Set a breakpoint with condition @var{cond}; evaluate the expression
3025 @var{cond} each time the breakpoint is reached, and stop only if the
3026 value is nonzero---that is, if @var{cond} evaluates as true.
3027 @samp{@dots{}} stands for one of the possible arguments described
3028 above (or no argument) specifying where to break. @xref{Conditions,
3029 ,Break Conditions}, for more information on breakpoint conditions.
3032 @item tbreak @var{args}
3033 Set a breakpoint enabled only for one stop. @var{args} are the
3034 same as for the @code{break} command, and the breakpoint is set in the same
3035 way, but the breakpoint is automatically deleted after the first time your
3036 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3039 @cindex hardware breakpoints
3040 @item hbreak @var{args}
3041 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3042 @code{break} command and the breakpoint is set in the same way, but the
3043 breakpoint requires hardware support and some target hardware may not
3044 have this support. The main purpose of this is EPROM/ROM code
3045 debugging, so you can set a breakpoint at an instruction without
3046 changing the instruction. This can be used with the new trap-generation
3047 provided by SPARClite DSU and most x86-based targets. These targets
3048 will generate traps when a program accesses some data or instruction
3049 address that is assigned to the debug registers. However the hardware
3050 breakpoint registers can take a limited number of breakpoints. For
3051 example, on the DSU, only two data breakpoints can be set at a time, and
3052 @value{GDBN} will reject this command if more than two are used. Delete
3053 or disable unused hardware breakpoints before setting new ones
3054 (@pxref{Disabling, ,Disabling Breakpoints}).
3055 @xref{Conditions, ,Break Conditions}.
3056 For remote targets, you can restrict the number of hardware
3057 breakpoints @value{GDBN} will use, see @ref{set remote
3058 hardware-breakpoint-limit}.
3061 @item thbreak @var{args}
3062 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3063 are the same as for the @code{hbreak} command and the breakpoint is set in
3064 the same way. However, like the @code{tbreak} command,
3065 the breakpoint is automatically deleted after the
3066 first time your program stops there. Also, like the @code{hbreak}
3067 command, the breakpoint requires hardware support and some target hardware
3068 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3069 See also @ref{Conditions, ,Break Conditions}.
3072 @cindex regular expression
3073 @cindex breakpoints in functions matching a regexp
3074 @cindex set breakpoints in many functions
3075 @item rbreak @var{regex}
3076 Set breakpoints on all functions matching the regular expression
3077 @var{regex}. This command sets an unconditional breakpoint on all
3078 matches, printing a list of all breakpoints it set. Once these
3079 breakpoints are set, they are treated just like the breakpoints set with
3080 the @code{break} command. You can delete them, disable them, or make
3081 them conditional the same way as any other breakpoint.
3083 The syntax of the regular expression is the standard one used with tools
3084 like @file{grep}. Note that this is different from the syntax used by
3085 shells, so for instance @code{foo*} matches all functions that include
3086 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3087 @code{.*} leading and trailing the regular expression you supply, so to
3088 match only functions that begin with @code{foo}, use @code{^foo}.
3090 @cindex non-member C@t{++} functions, set breakpoint in
3091 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3092 breakpoints on overloaded functions that are not members of any special
3095 @cindex set breakpoints on all functions
3096 The @code{rbreak} command can be used to set breakpoints in
3097 @strong{all} the functions in a program, like this:
3100 (@value{GDBP}) rbreak .
3103 @kindex info breakpoints
3104 @cindex @code{$_} and @code{info breakpoints}
3105 @item info breakpoints @r{[}@var{n}@r{]}
3106 @itemx info break @r{[}@var{n}@r{]}
3107 @itemx info watchpoints @r{[}@var{n}@r{]}
3108 Print a table of all breakpoints, watchpoints, and catchpoints set and
3109 not deleted. Optional argument @var{n} means print information only
3110 about the specified breakpoint (or watchpoint or catchpoint). For
3111 each breakpoint, following columns are printed:
3114 @item Breakpoint Numbers
3116 Breakpoint, watchpoint, or catchpoint.
3118 Whether the breakpoint is marked to be disabled or deleted when hit.
3119 @item Enabled or Disabled
3120 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3121 that are not enabled.
3123 Where the breakpoint is in your program, as a memory address. For a
3124 pending breakpoint whose address is not yet known, this field will
3125 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3126 library that has the symbol or line referred by breakpoint is loaded.
3127 See below for details. A breakpoint with several locations will
3128 have @samp{<MULTIPLE>} in this field---see below for details.
3130 Where the breakpoint is in the source for your program, as a file and
3131 line number. For a pending breakpoint, the original string passed to
3132 the breakpoint command will be listed as it cannot be resolved until
3133 the appropriate shared library is loaded in the future.
3137 If a breakpoint is conditional, @code{info break} shows the condition on
3138 the line following the affected breakpoint; breakpoint commands, if any,
3139 are listed after that. A pending breakpoint is allowed to have a condition
3140 specified for it. The condition is not parsed for validity until a shared
3141 library is loaded that allows the pending breakpoint to resolve to a
3145 @code{info break} with a breakpoint
3146 number @var{n} as argument lists only that breakpoint. The
3147 convenience variable @code{$_} and the default examining-address for
3148 the @code{x} command are set to the address of the last breakpoint
3149 listed (@pxref{Memory, ,Examining Memory}).
3152 @code{info break} displays a count of the number of times the breakpoint
3153 has been hit. This is especially useful in conjunction with the
3154 @code{ignore} command. You can ignore a large number of breakpoint
3155 hits, look at the breakpoint info to see how many times the breakpoint
3156 was hit, and then run again, ignoring one less than that number. This
3157 will get you quickly to the last hit of that breakpoint.
3160 @value{GDBN} allows you to set any number of breakpoints at the same place in
3161 your program. There is nothing silly or meaningless about this. When
3162 the breakpoints are conditional, this is even useful
3163 (@pxref{Conditions, ,Break Conditions}).
3165 @cindex multiple locations, breakpoints
3166 @cindex breakpoints, multiple locations
3167 It is possible that a breakpoint corresponds to several locations
3168 in your program. Examples of this situation are:
3172 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3173 instances of the function body, used in different cases.
3176 For a C@t{++} template function, a given line in the function can
3177 correspond to any number of instantiations.
3180 For an inlined function, a given source line can correspond to
3181 several places where that function is inlined.
3184 In all those cases, @value{GDBN} will insert a breakpoint at all
3185 the relevant locations@footnote{
3186 As of this writing, multiple-location breakpoints work only if there's
3187 line number information for all the locations. This means that they
3188 will generally not work in system libraries, unless you have debug
3189 info with line numbers for them.}.
3191 A breakpoint with multiple locations is displayed in the breakpoint
3192 table using several rows---one header row, followed by one row for
3193 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3194 address column. The rows for individual locations contain the actual
3195 addresses for locations, and show the functions to which those
3196 locations belong. The number column for a location is of the form
3197 @var{breakpoint-number}.@var{location-number}.
3202 Num Type Disp Enb Address What
3203 1 breakpoint keep y <MULTIPLE>
3205 breakpoint already hit 1 time
3206 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3207 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3210 Each location can be individually enabled or disabled by passing
3211 @var{breakpoint-number}.@var{location-number} as argument to the
3212 @code{enable} and @code{disable} commands. Note that you cannot
3213 delete the individual locations from the list, you can only delete the
3214 entire list of locations that belong to their parent breakpoint (with
3215 the @kbd{delete @var{num}} command, where @var{num} is the number of
3216 the parent breakpoint, 1 in the above example). Disabling or enabling
3217 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3218 that belong to that breakpoint.
3220 @cindex pending breakpoints
3221 It's quite common to have a breakpoint inside a shared library.
3222 Shared libraries can be loaded and unloaded explicitly,
3223 and possibly repeatedly, as the program is executed. To support
3224 this use case, @value{GDBN} updates breakpoint locations whenever
3225 any shared library is loaded or unloaded. Typically, you would
3226 set a breakpoint in a shared library at the beginning of your
3227 debugging session, when the library is not loaded, and when the
3228 symbols from the library are not available. When you try to set
3229 breakpoint, @value{GDBN} will ask you if you want to set
3230 a so called @dfn{pending breakpoint}---breakpoint whose address
3231 is not yet resolved.
3233 After the program is run, whenever a new shared library is loaded,
3234 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3235 shared library contains the symbol or line referred to by some
3236 pending breakpoint, that breakpoint is resolved and becomes an
3237 ordinary breakpoint. When a library is unloaded, all breakpoints
3238 that refer to its symbols or source lines become pending again.
3240 This logic works for breakpoints with multiple locations, too. For
3241 example, if you have a breakpoint in a C@t{++} template function, and
3242 a newly loaded shared library has an instantiation of that template,
3243 a new location is added to the list of locations for the breakpoint.
3245 Except for having unresolved address, pending breakpoints do not
3246 differ from regular breakpoints. You can set conditions or commands,
3247 enable and disable them and perform other breakpoint operations.
3249 @value{GDBN} provides some additional commands for controlling what
3250 happens when the @samp{break} command cannot resolve breakpoint
3251 address specification to an address:
3253 @kindex set breakpoint pending
3254 @kindex show breakpoint pending
3256 @item set breakpoint pending auto
3257 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3258 location, it queries you whether a pending breakpoint should be created.
3260 @item set breakpoint pending on
3261 This indicates that an unrecognized breakpoint location should automatically
3262 result in a pending breakpoint being created.
3264 @item set breakpoint pending off
3265 This indicates that pending breakpoints are not to be created. Any
3266 unrecognized breakpoint location results in an error. This setting does
3267 not affect any pending breakpoints previously created.
3269 @item show breakpoint pending
3270 Show the current behavior setting for creating pending breakpoints.
3273 The settings above only affect the @code{break} command and its
3274 variants. Once breakpoint is set, it will be automatically updated
3275 as shared libraries are loaded and unloaded.
3277 @cindex automatic hardware breakpoints
3278 For some targets, @value{GDBN} can automatically decide if hardware or
3279 software breakpoints should be used, depending on whether the
3280 breakpoint address is read-only or read-write. This applies to
3281 breakpoints set with the @code{break} command as well as to internal
3282 breakpoints set by commands like @code{next} and @code{finish}. For
3283 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3286 You can control this automatic behaviour with the following commands::
3288 @kindex set breakpoint auto-hw
3289 @kindex show breakpoint auto-hw
3291 @item set breakpoint auto-hw on
3292 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3293 will try to use the target memory map to decide if software or hardware
3294 breakpoint must be used.
3296 @item set breakpoint auto-hw off
3297 This indicates @value{GDBN} should not automatically select breakpoint
3298 type. If the target provides a memory map, @value{GDBN} will warn when
3299 trying to set software breakpoint at a read-only address.
3302 @value{GDBN} normally implements breakpoints by replacing the program code
3303 at the breakpoint address with a special instruction, which, when
3304 executed, given control to the debugger. By default, the program
3305 code is so modified only when the program is resumed. As soon as
3306 the program stops, @value{GDBN} restores the original instructions. This
3307 behaviour guards against leaving breakpoints inserted in the
3308 target should gdb abrubptly disconnect. However, with slow remote
3309 targets, inserting and removing breakpoint can reduce the performance.
3310 This behavior can be controlled with the following commands::
3312 @kindex set breakpoint always-inserted
3313 @kindex show breakpoint always-inserted
3315 @item set breakpoint always-inserted off
3316 All breakpoints, including newly added by the user, are inserted in
3317 the target only when the target is resumed. All breakpoints are
3318 removed from the target when it stops.
3320 @item set breakpoint always-inserted on
3321 Causes all breakpoints to be inserted in the target at all times. If
3322 the user adds a new breakpoint, or changes an existing breakpoint, the
3323 breakpoints in the target are updated immediately. A breakpoint is
3324 removed from the target only when breakpoint itself is removed.
3326 @cindex non-stop mode, and @code{breakpoint always-inserted}
3327 @item set breakpoint always-inserted auto
3328 This is the default mode. If @value{GDBN} is controlling the inferior
3329 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3330 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3331 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3332 @code{breakpoint always-inserted} mode is off.
3335 @cindex negative breakpoint numbers
3336 @cindex internal @value{GDBN} breakpoints
3337 @value{GDBN} itself sometimes sets breakpoints in your program for
3338 special purposes, such as proper handling of @code{longjmp} (in C
3339 programs). These internal breakpoints are assigned negative numbers,
3340 starting with @code{-1}; @samp{info breakpoints} does not display them.
3341 You can see these breakpoints with the @value{GDBN} maintenance command
3342 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3345 @node Set Watchpoints
3346 @subsection Setting Watchpoints
3348 @cindex setting watchpoints
3349 You can use a watchpoint to stop execution whenever the value of an
3350 expression changes, without having to predict a particular place where
3351 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3352 The expression may be as simple as the value of a single variable, or
3353 as complex as many variables combined by operators. Examples include:
3357 A reference to the value of a single variable.
3360 An address cast to an appropriate data type. For example,
3361 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3362 address (assuming an @code{int} occupies 4 bytes).
3365 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3366 expression can use any operators valid in the program's native
3367 language (@pxref{Languages}).
3370 You can set a watchpoint on an expression even if the expression can
3371 not be evaluated yet. For instance, you can set a watchpoint on
3372 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3373 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3374 the expression produces a valid value. If the expression becomes
3375 valid in some other way than changing a variable (e.g.@: if the memory
3376 pointed to by @samp{*global_ptr} becomes readable as the result of a
3377 @code{malloc} call), @value{GDBN} may not stop until the next time
3378 the expression changes.
3380 @cindex software watchpoints
3381 @cindex hardware watchpoints
3382 Depending on your system, watchpoints may be implemented in software or
3383 hardware. @value{GDBN} does software watchpointing by single-stepping your
3384 program and testing the variable's value each time, which is hundreds of
3385 times slower than normal execution. (But this may still be worth it, to
3386 catch errors where you have no clue what part of your program is the
3389 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3390 x86-based targets, @value{GDBN} includes support for hardware
3391 watchpoints, which do not slow down the running of your program.
3395 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3396 Set a watchpoint for an expression. @value{GDBN} will break when the
3397 expression @var{expr} is written into by the program and its value
3398 changes. The simplest (and the most popular) use of this command is
3399 to watch the value of a single variable:
3402 (@value{GDBP}) watch foo
3405 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3406 clause, @value{GDBN} breaks only when the thread identified by
3407 @var{threadnum} changes the value of @var{expr}. If any other threads
3408 change the value of @var{expr}, @value{GDBN} will not break. Note
3409 that watchpoints restricted to a single thread in this way only work
3410 with Hardware Watchpoints.
3413 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3414 Set a watchpoint that will break when the value of @var{expr} is read
3418 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3419 Set a watchpoint that will break when @var{expr} is either read from
3420 or written into by the program.
3422 @kindex info watchpoints @r{[}@var{n}@r{]}
3423 @item info watchpoints
3424 This command prints a list of watchpoints, breakpoints, and catchpoints;
3425 it is the same as @code{info break} (@pxref{Set Breaks}).
3428 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3429 watchpoints execute very quickly, and the debugger reports a change in
3430 value at the exact instruction where the change occurs. If @value{GDBN}
3431 cannot set a hardware watchpoint, it sets a software watchpoint, which
3432 executes more slowly and reports the change in value at the next
3433 @emph{statement}, not the instruction, after the change occurs.
3435 @cindex use only software watchpoints
3436 You can force @value{GDBN} to use only software watchpoints with the
3437 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3438 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3439 the underlying system supports them. (Note that hardware-assisted
3440 watchpoints that were set @emph{before} setting
3441 @code{can-use-hw-watchpoints} to zero will still use the hardware
3442 mechanism of watching expression values.)
3445 @item set can-use-hw-watchpoints
3446 @kindex set can-use-hw-watchpoints
3447 Set whether or not to use hardware watchpoints.
3449 @item show can-use-hw-watchpoints
3450 @kindex show can-use-hw-watchpoints
3451 Show the current mode of using hardware watchpoints.
3454 For remote targets, you can restrict the number of hardware
3455 watchpoints @value{GDBN} will use, see @ref{set remote
3456 hardware-breakpoint-limit}.
3458 When you issue the @code{watch} command, @value{GDBN} reports
3461 Hardware watchpoint @var{num}: @var{expr}
3465 if it was able to set a hardware watchpoint.
3467 Currently, the @code{awatch} and @code{rwatch} commands can only set
3468 hardware watchpoints, because accesses to data that don't change the
3469 value of the watched expression cannot be detected without examining
3470 every instruction as it is being executed, and @value{GDBN} does not do
3471 that currently. If @value{GDBN} finds that it is unable to set a
3472 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3473 will print a message like this:
3476 Expression cannot be implemented with read/access watchpoint.
3479 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3480 data type of the watched expression is wider than what a hardware
3481 watchpoint on the target machine can handle. For example, some systems
3482 can only watch regions that are up to 4 bytes wide; on such systems you
3483 cannot set hardware watchpoints for an expression that yields a
3484 double-precision floating-point number (which is typically 8 bytes
3485 wide). As a work-around, it might be possible to break the large region
3486 into a series of smaller ones and watch them with separate watchpoints.
3488 If you set too many hardware watchpoints, @value{GDBN} might be unable
3489 to insert all of them when you resume the execution of your program.
3490 Since the precise number of active watchpoints is unknown until such
3491 time as the program is about to be resumed, @value{GDBN} might not be
3492 able to warn you about this when you set the watchpoints, and the
3493 warning will be printed only when the program is resumed:
3496 Hardware watchpoint @var{num}: Could not insert watchpoint
3500 If this happens, delete or disable some of the watchpoints.
3502 Watching complex expressions that reference many variables can also
3503 exhaust the resources available for hardware-assisted watchpoints.
3504 That's because @value{GDBN} needs to watch every variable in the
3505 expression with separately allocated resources.
3507 If you call a function interactively using @code{print} or @code{call},
3508 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3509 kind of breakpoint or the call completes.
3511 @value{GDBN} automatically deletes watchpoints that watch local
3512 (automatic) variables, or expressions that involve such variables, when
3513 they go out of scope, that is, when the execution leaves the block in
3514 which these variables were defined. In particular, when the program
3515 being debugged terminates, @emph{all} local variables go out of scope,
3516 and so only watchpoints that watch global variables remain set. If you
3517 rerun the program, you will need to set all such watchpoints again. One
3518 way of doing that would be to set a code breakpoint at the entry to the
3519 @code{main} function and when it breaks, set all the watchpoints.
3521 @cindex watchpoints and threads
3522 @cindex threads and watchpoints
3523 In multi-threaded programs, watchpoints will detect changes to the
3524 watched expression from every thread.
3527 @emph{Warning:} In multi-threaded programs, software watchpoints
3528 have only limited usefulness. If @value{GDBN} creates a software
3529 watchpoint, it can only watch the value of an expression @emph{in a
3530 single thread}. If you are confident that the expression can only
3531 change due to the current thread's activity (and if you are also
3532 confident that no other thread can become current), then you can use
3533 software watchpoints as usual. However, @value{GDBN} may not notice
3534 when a non-current thread's activity changes the expression. (Hardware
3535 watchpoints, in contrast, watch an expression in all threads.)
3538 @xref{set remote hardware-watchpoint-limit}.
3540 @node Set Catchpoints
3541 @subsection Setting Catchpoints
3542 @cindex catchpoints, setting
3543 @cindex exception handlers
3544 @cindex event handling
3546 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3547 kinds of program events, such as C@t{++} exceptions or the loading of a
3548 shared library. Use the @code{catch} command to set a catchpoint.
3552 @item catch @var{event}
3553 Stop when @var{event} occurs. @var{event} can be any of the following:
3556 @cindex stop on C@t{++} exceptions
3557 The throwing of a C@t{++} exception.
3560 The catching of a C@t{++} exception.
3563 @cindex Ada exception catching
3564 @cindex catch Ada exceptions
3565 An Ada exception being raised. If an exception name is specified
3566 at the end of the command (eg @code{catch exception Program_Error}),
3567 the debugger will stop only when this specific exception is raised.
3568 Otherwise, the debugger stops execution when any Ada exception is raised.
3570 @item exception unhandled
3571 An exception that was raised but is not handled by the program.
3574 A failed Ada assertion.
3577 @cindex break on fork/exec
3578 A call to @code{exec}. This is currently only available for HP-UX
3582 A call to @code{fork}. This is currently only available for HP-UX
3586 A call to @code{vfork}. This is currently only available for HP-UX
3590 @itemx load @var{libname}
3591 @cindex break on load/unload of shared library
3592 The dynamic loading of any shared library, or the loading of the library
3593 @var{libname}. This is currently only available for HP-UX.
3596 @itemx unload @var{libname}
3597 The unloading of any dynamically loaded shared library, or the unloading
3598 of the library @var{libname}. This is currently only available for HP-UX.
3601 @item tcatch @var{event}
3602 Set a catchpoint that is enabled only for one stop. The catchpoint is
3603 automatically deleted after the first time the event is caught.
3607 Use the @code{info break} command to list the current catchpoints.
3609 There are currently some limitations to C@t{++} exception handling
3610 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3614 If you call a function interactively, @value{GDBN} normally returns
3615 control to you when the function has finished executing. If the call
3616 raises an exception, however, the call may bypass the mechanism that
3617 returns control to you and cause your program either to abort or to
3618 simply continue running until it hits a breakpoint, catches a signal
3619 that @value{GDBN} is listening for, or exits. This is the case even if
3620 you set a catchpoint for the exception; catchpoints on exceptions are
3621 disabled within interactive calls.
3624 You cannot raise an exception interactively.
3627 You cannot install an exception handler interactively.
3630 @cindex raise exceptions
3631 Sometimes @code{catch} is not the best way to debug exception handling:
3632 if you need to know exactly where an exception is raised, it is better to
3633 stop @emph{before} the exception handler is called, since that way you
3634 can see the stack before any unwinding takes place. If you set a
3635 breakpoint in an exception handler instead, it may not be easy to find
3636 out where the exception was raised.
3638 To stop just before an exception handler is called, you need some
3639 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3640 raised by calling a library function named @code{__raise_exception}
3641 which has the following ANSI C interface:
3644 /* @var{addr} is where the exception identifier is stored.
3645 @var{id} is the exception identifier. */
3646 void __raise_exception (void **addr, void *id);
3650 To make the debugger catch all exceptions before any stack
3651 unwinding takes place, set a breakpoint on @code{__raise_exception}
3652 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3654 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3655 that depends on the value of @var{id}, you can stop your program when
3656 a specific exception is raised. You can use multiple conditional
3657 breakpoints to stop your program when any of a number of exceptions are
3662 @subsection Deleting Breakpoints
3664 @cindex clearing breakpoints, watchpoints, catchpoints
3665 @cindex deleting breakpoints, watchpoints, catchpoints
3666 It is often necessary to eliminate a breakpoint, watchpoint, or
3667 catchpoint once it has done its job and you no longer want your program
3668 to stop there. This is called @dfn{deleting} the breakpoint. A
3669 breakpoint that has been deleted no longer exists; it is forgotten.
3671 With the @code{clear} command you can delete breakpoints according to
3672 where they are in your program. With the @code{delete} command you can
3673 delete individual breakpoints, watchpoints, or catchpoints by specifying
3674 their breakpoint numbers.
3676 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3677 automatically ignores breakpoints on the first instruction to be executed
3678 when you continue execution without changing the execution address.
3683 Delete any breakpoints at the next instruction to be executed in the
3684 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3685 the innermost frame is selected, this is a good way to delete a
3686 breakpoint where your program just stopped.
3688 @item clear @var{location}
3689 Delete any breakpoints set at the specified @var{location}.
3690 @xref{Specify Location}, for the various forms of @var{location}; the
3691 most useful ones are listed below:
3694 @item clear @var{function}
3695 @itemx clear @var{filename}:@var{function}
3696 Delete any breakpoints set at entry to the named @var{function}.
3698 @item clear @var{linenum}
3699 @itemx clear @var{filename}:@var{linenum}
3700 Delete any breakpoints set at or within the code of the specified
3701 @var{linenum} of the specified @var{filename}.
3704 @cindex delete breakpoints
3706 @kindex d @r{(@code{delete})}
3707 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3708 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3709 ranges specified as arguments. If no argument is specified, delete all
3710 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3711 confirm off}). You can abbreviate this command as @code{d}.
3715 @subsection Disabling Breakpoints
3717 @cindex enable/disable a breakpoint
3718 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3719 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3720 it had been deleted, but remembers the information on the breakpoint so
3721 that you can @dfn{enable} it again later.
3723 You disable and enable breakpoints, watchpoints, and catchpoints with
3724 the @code{enable} and @code{disable} commands, optionally specifying one
3725 or more breakpoint numbers as arguments. Use @code{info break} or
3726 @code{info watch} to print a list of breakpoints, watchpoints, and
3727 catchpoints if you do not know which numbers to use.
3729 Disabling and enabling a breakpoint that has multiple locations
3730 affects all of its locations.
3732 A breakpoint, watchpoint, or catchpoint can have any of four different
3733 states of enablement:
3737 Enabled. The breakpoint stops your program. A breakpoint set
3738 with the @code{break} command starts out in this state.
3740 Disabled. The breakpoint has no effect on your program.
3742 Enabled once. The breakpoint stops your program, but then becomes
3745 Enabled for deletion. The breakpoint stops your program, but
3746 immediately after it does so it is deleted permanently. A breakpoint
3747 set with the @code{tbreak} command starts out in this state.
3750 You can use the following commands to enable or disable breakpoints,
3751 watchpoints, and catchpoints:
3755 @kindex dis @r{(@code{disable})}
3756 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3757 Disable the specified breakpoints---or all breakpoints, if none are
3758 listed. A disabled breakpoint has no effect but is not forgotten. All
3759 options such as ignore-counts, conditions and commands are remembered in
3760 case the breakpoint is enabled again later. You may abbreviate
3761 @code{disable} as @code{dis}.
3764 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3765 Enable the specified breakpoints (or all defined breakpoints). They
3766 become effective once again in stopping your program.
3768 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3769 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3770 of these breakpoints immediately after stopping your program.
3772 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3773 Enable the specified breakpoints to work once, then die. @value{GDBN}
3774 deletes any of these breakpoints as soon as your program stops there.
3775 Breakpoints set by the @code{tbreak} command start out in this state.
3778 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3779 @c confusing: tbreak is also initially enabled.
3780 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3781 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3782 subsequently, they become disabled or enabled only when you use one of
3783 the commands above. (The command @code{until} can set and delete a
3784 breakpoint of its own, but it does not change the state of your other
3785 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3789 @subsection Break Conditions
3790 @cindex conditional breakpoints
3791 @cindex breakpoint conditions
3793 @c FIXME what is scope of break condition expr? Context where wanted?
3794 @c in particular for a watchpoint?
3795 The simplest sort of breakpoint breaks every time your program reaches a
3796 specified place. You can also specify a @dfn{condition} for a
3797 breakpoint. A condition is just a Boolean expression in your
3798 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3799 a condition evaluates the expression each time your program reaches it,
3800 and your program stops only if the condition is @emph{true}.
3802 This is the converse of using assertions for program validation; in that
3803 situation, you want to stop when the assertion is violated---that is,
3804 when the condition is false. In C, if you want to test an assertion expressed
3805 by the condition @var{assert}, you should set the condition
3806 @samp{! @var{assert}} on the appropriate breakpoint.
3808 Conditions are also accepted for watchpoints; you may not need them,
3809 since a watchpoint is inspecting the value of an expression anyhow---but
3810 it might be simpler, say, to just set a watchpoint on a variable name,
3811 and specify a condition that tests whether the new value is an interesting
3814 Break conditions can have side effects, and may even call functions in
3815 your program. This can be useful, for example, to activate functions
3816 that log program progress, or to use your own print functions to
3817 format special data structures. The effects are completely predictable
3818 unless there is another enabled breakpoint at the same address. (In
3819 that case, @value{GDBN} might see the other breakpoint first and stop your
3820 program without checking the condition of this one.) Note that
3821 breakpoint commands are usually more convenient and flexible than break
3823 purpose of performing side effects when a breakpoint is reached
3824 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3826 Break conditions can be specified when a breakpoint is set, by using
3827 @samp{if} in the arguments to the @code{break} command. @xref{Set
3828 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3829 with the @code{condition} command.
3831 You can also use the @code{if} keyword with the @code{watch} command.
3832 The @code{catch} command does not recognize the @code{if} keyword;
3833 @code{condition} is the only way to impose a further condition on a
3838 @item condition @var{bnum} @var{expression}
3839 Specify @var{expression} as the break condition for breakpoint,
3840 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3841 breakpoint @var{bnum} stops your program only if the value of
3842 @var{expression} is true (nonzero, in C). When you use
3843 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3844 syntactic correctness, and to determine whether symbols in it have
3845 referents in the context of your breakpoint. If @var{expression} uses
3846 symbols not referenced in the context of the breakpoint, @value{GDBN}
3847 prints an error message:
3850 No symbol "foo" in current context.
3855 not actually evaluate @var{expression} at the time the @code{condition}
3856 command (or a command that sets a breakpoint with a condition, like
3857 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3859 @item condition @var{bnum}
3860 Remove the condition from breakpoint number @var{bnum}. It becomes
3861 an ordinary unconditional breakpoint.
3864 @cindex ignore count (of breakpoint)
3865 A special case of a breakpoint condition is to stop only when the
3866 breakpoint has been reached a certain number of times. This is so
3867 useful that there is a special way to do it, using the @dfn{ignore
3868 count} of the breakpoint. Every breakpoint has an ignore count, which
3869 is an integer. Most of the time, the ignore count is zero, and
3870 therefore has no effect. But if your program reaches a breakpoint whose
3871 ignore count is positive, then instead of stopping, it just decrements
3872 the ignore count by one and continues. As a result, if the ignore count
3873 value is @var{n}, the breakpoint does not stop the next @var{n} times
3874 your program reaches it.
3878 @item ignore @var{bnum} @var{count}
3879 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3880 The next @var{count} times the breakpoint is reached, your program's
3881 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3884 To make the breakpoint stop the next time it is reached, specify
3887 When you use @code{continue} to resume execution of your program from a
3888 breakpoint, you can specify an ignore count directly as an argument to
3889 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3890 Stepping,,Continuing and Stepping}.
3892 If a breakpoint has a positive ignore count and a condition, the
3893 condition is not checked. Once the ignore count reaches zero,
3894 @value{GDBN} resumes checking the condition.
3896 You could achieve the effect of the ignore count with a condition such
3897 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3898 is decremented each time. @xref{Convenience Vars, ,Convenience
3902 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3905 @node Break Commands
3906 @subsection Breakpoint Command Lists
3908 @cindex breakpoint commands
3909 You can give any breakpoint (or watchpoint or catchpoint) a series of
3910 commands to execute when your program stops due to that breakpoint. For
3911 example, you might want to print the values of certain expressions, or
3912 enable other breakpoints.
3916 @kindex end@r{ (breakpoint commands)}
3917 @item commands @r{[}@var{bnum}@r{]}
3918 @itemx @dots{} @var{command-list} @dots{}
3920 Specify a list of commands for breakpoint number @var{bnum}. The commands
3921 themselves appear on the following lines. Type a line containing just
3922 @code{end} to terminate the commands.
3924 To remove all commands from a breakpoint, type @code{commands} and
3925 follow it immediately with @code{end}; that is, give no commands.
3927 With no @var{bnum} argument, @code{commands} refers to the last
3928 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3929 recently encountered).
3932 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3933 disabled within a @var{command-list}.
3935 You can use breakpoint commands to start your program up again. Simply
3936 use the @code{continue} command, or @code{step}, or any other command
3937 that resumes execution.
3939 Any other commands in the command list, after a command that resumes
3940 execution, are ignored. This is because any time you resume execution
3941 (even with a simple @code{next} or @code{step}), you may encounter
3942 another breakpoint---which could have its own command list, leading to
3943 ambiguities about which list to execute.
3946 If the first command you specify in a command list is @code{silent}, the
3947 usual message about stopping at a breakpoint is not printed. This may
3948 be desirable for breakpoints that are to print a specific message and
3949 then continue. If none of the remaining commands print anything, you
3950 see no sign that the breakpoint was reached. @code{silent} is
3951 meaningful only at the beginning of a breakpoint command list.
3953 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3954 print precisely controlled output, and are often useful in silent
3955 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3957 For example, here is how you could use breakpoint commands to print the
3958 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3964 printf "x is %d\n",x
3969 One application for breakpoint commands is to compensate for one bug so
3970 you can test for another. Put a breakpoint just after the erroneous line
3971 of code, give it a condition to detect the case in which something
3972 erroneous has been done, and give it commands to assign correct values
3973 to any variables that need them. End with the @code{continue} command
3974 so that your program does not stop, and start with the @code{silent}
3975 command so that no output is produced. Here is an example:
3986 @c @ifclear BARETARGET
3987 @node Error in Breakpoints
3988 @subsection ``Cannot insert breakpoints''
3990 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3992 Under some operating systems, breakpoints cannot be used in a program if
3993 any other process is running that program. In this situation,
3994 attempting to run or continue a program with a breakpoint causes
3995 @value{GDBN} to print an error message:
3998 Cannot insert breakpoints.
3999 The same program may be running in another process.
4002 When this happens, you have three ways to proceed:
4006 Remove or disable the breakpoints, then continue.
4009 Suspend @value{GDBN}, and copy the file containing your program to a new
4010 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
4011 that @value{GDBN} should run your program under that name.
4012 Then start your program again.
4015 Relink your program so that the text segment is nonsharable, using the
4016 linker option @samp{-N}. The operating system limitation may not apply
4017 to nonsharable executables.
4021 A similar message can be printed if you request too many active
4022 hardware-assisted breakpoints and watchpoints:
4024 @c FIXME: the precise wording of this message may change; the relevant
4025 @c source change is not committed yet (Sep 3, 1999).
4027 Stopped; cannot insert breakpoints.
4028 You may have requested too many hardware breakpoints and watchpoints.
4032 This message is printed when you attempt to resume the program, since
4033 only then @value{GDBN} knows exactly how many hardware breakpoints and
4034 watchpoints it needs to insert.
4036 When this message is printed, you need to disable or remove some of the
4037 hardware-assisted breakpoints and watchpoints, and then continue.
4039 @node Breakpoint-related Warnings
4040 @subsection ``Breakpoint address adjusted...''
4041 @cindex breakpoint address adjusted
4043 Some processor architectures place constraints on the addresses at
4044 which breakpoints may be placed. For architectures thus constrained,
4045 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4046 with the constraints dictated by the architecture.
4048 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4049 a VLIW architecture in which a number of RISC-like instructions may be
4050 bundled together for parallel execution. The FR-V architecture
4051 constrains the location of a breakpoint instruction within such a
4052 bundle to the instruction with the lowest address. @value{GDBN}
4053 honors this constraint by adjusting a breakpoint's address to the
4054 first in the bundle.
4056 It is not uncommon for optimized code to have bundles which contain
4057 instructions from different source statements, thus it may happen that
4058 a breakpoint's address will be adjusted from one source statement to
4059 another. Since this adjustment may significantly alter @value{GDBN}'s
4060 breakpoint related behavior from what the user expects, a warning is
4061 printed when the breakpoint is first set and also when the breakpoint
4064 A warning like the one below is printed when setting a breakpoint
4065 that's been subject to address adjustment:
4068 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4071 Such warnings are printed both for user settable and @value{GDBN}'s
4072 internal breakpoints. If you see one of these warnings, you should
4073 verify that a breakpoint set at the adjusted address will have the
4074 desired affect. If not, the breakpoint in question may be removed and
4075 other breakpoints may be set which will have the desired behavior.
4076 E.g., it may be sufficient to place the breakpoint at a later
4077 instruction. A conditional breakpoint may also be useful in some
4078 cases to prevent the breakpoint from triggering too often.
4080 @value{GDBN} will also issue a warning when stopping at one of these
4081 adjusted breakpoints:
4084 warning: Breakpoint 1 address previously adjusted from 0x00010414
4088 When this warning is encountered, it may be too late to take remedial
4089 action except in cases where the breakpoint is hit earlier or more
4090 frequently than expected.
4092 @node Continuing and Stepping
4093 @section Continuing and Stepping
4097 @cindex resuming execution
4098 @dfn{Continuing} means resuming program execution until your program
4099 completes normally. In contrast, @dfn{stepping} means executing just
4100 one more ``step'' of your program, where ``step'' may mean either one
4101 line of source code, or one machine instruction (depending on what
4102 particular command you use). Either when continuing or when stepping,
4103 your program may stop even sooner, due to a breakpoint or a signal. (If
4104 it stops due to a signal, you may want to use @code{handle}, or use
4105 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4109 @kindex c @r{(@code{continue})}
4110 @kindex fg @r{(resume foreground execution)}
4111 @item continue @r{[}@var{ignore-count}@r{]}
4112 @itemx c @r{[}@var{ignore-count}@r{]}
4113 @itemx fg @r{[}@var{ignore-count}@r{]}
4114 Resume program execution, at the address where your program last stopped;
4115 any breakpoints set at that address are bypassed. The optional argument
4116 @var{ignore-count} allows you to specify a further number of times to
4117 ignore a breakpoint at this location; its effect is like that of
4118 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4120 The argument @var{ignore-count} is meaningful only when your program
4121 stopped due to a breakpoint. At other times, the argument to
4122 @code{continue} is ignored.
4124 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4125 debugged program is deemed to be the foreground program) are provided
4126 purely for convenience, and have exactly the same behavior as
4130 To resume execution at a different place, you can use @code{return}
4131 (@pxref{Returning, ,Returning from a Function}) to go back to the
4132 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4133 Different Address}) to go to an arbitrary location in your program.
4135 A typical technique for using stepping is to set a breakpoint
4136 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4137 beginning of the function or the section of your program where a problem
4138 is believed to lie, run your program until it stops at that breakpoint,
4139 and then step through the suspect area, examining the variables that are
4140 interesting, until you see the problem happen.
4144 @kindex s @r{(@code{step})}
4146 Continue running your program until control reaches a different source
4147 line, then stop it and return control to @value{GDBN}. This command is
4148 abbreviated @code{s}.
4151 @c "without debugging information" is imprecise; actually "without line
4152 @c numbers in the debugging information". (gcc -g1 has debugging info but
4153 @c not line numbers). But it seems complex to try to make that
4154 @c distinction here.
4155 @emph{Warning:} If you use the @code{step} command while control is
4156 within a function that was compiled without debugging information,
4157 execution proceeds until control reaches a function that does have
4158 debugging information. Likewise, it will not step into a function which
4159 is compiled without debugging information. To step through functions
4160 without debugging information, use the @code{stepi} command, described
4164 The @code{step} command only stops at the first instruction of a source
4165 line. This prevents the multiple stops that could otherwise occur in
4166 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4167 to stop if a function that has debugging information is called within
4168 the line. In other words, @code{step} @emph{steps inside} any functions
4169 called within the line.
4171 Also, the @code{step} command only enters a function if there is line
4172 number information for the function. Otherwise it acts like the
4173 @code{next} command. This avoids problems when using @code{cc -gl}
4174 on MIPS machines. Previously, @code{step} entered subroutines if there
4175 was any debugging information about the routine.
4177 @item step @var{count}
4178 Continue running as in @code{step}, but do so @var{count} times. If a
4179 breakpoint is reached, or a signal not related to stepping occurs before
4180 @var{count} steps, stepping stops right away.
4183 @kindex n @r{(@code{next})}
4184 @item next @r{[}@var{count}@r{]}
4185 Continue to the next source line in the current (innermost) stack frame.
4186 This is similar to @code{step}, but function calls that appear within
4187 the line of code are executed without stopping. Execution stops when
4188 control reaches a different line of code at the original stack level
4189 that was executing when you gave the @code{next} command. This command
4190 is abbreviated @code{n}.
4192 An argument @var{count} is a repeat count, as for @code{step}.
4195 @c FIX ME!! Do we delete this, or is there a way it fits in with
4196 @c the following paragraph? --- Vctoria
4198 @c @code{next} within a function that lacks debugging information acts like
4199 @c @code{step}, but any function calls appearing within the code of the
4200 @c function are executed without stopping.
4202 The @code{next} command only stops at the first instruction of a
4203 source line. This prevents multiple stops that could otherwise occur in
4204 @code{switch} statements, @code{for} loops, etc.
4206 @kindex set step-mode
4208 @cindex functions without line info, and stepping
4209 @cindex stepping into functions with no line info
4210 @itemx set step-mode on
4211 The @code{set step-mode on} command causes the @code{step} command to
4212 stop at the first instruction of a function which contains no debug line
4213 information rather than stepping over it.
4215 This is useful in cases where you may be interested in inspecting the
4216 machine instructions of a function which has no symbolic info and do not
4217 want @value{GDBN} to automatically skip over this function.
4219 @item set step-mode off
4220 Causes the @code{step} command to step over any functions which contains no
4221 debug information. This is the default.
4223 @item show step-mode
4224 Show whether @value{GDBN} will stop in or step over functions without
4225 source line debug information.
4228 @kindex fin @r{(@code{finish})}
4230 Continue running until just after function in the selected stack frame
4231 returns. Print the returned value (if any). This command can be
4232 abbreviated as @code{fin}.
4234 Contrast this with the @code{return} command (@pxref{Returning,
4235 ,Returning from a Function}).
4238 @kindex u @r{(@code{until})}
4239 @cindex run until specified location
4242 Continue running until a source line past the current line, in the
4243 current stack frame, is reached. This command is used to avoid single
4244 stepping through a loop more than once. It is like the @code{next}
4245 command, except that when @code{until} encounters a jump, it
4246 automatically continues execution until the program counter is greater
4247 than the address of the jump.
4249 This means that when you reach the end of a loop after single stepping
4250 though it, @code{until} makes your program continue execution until it
4251 exits the loop. In contrast, a @code{next} command at the end of a loop
4252 simply steps back to the beginning of the loop, which forces you to step
4253 through the next iteration.
4255 @code{until} always stops your program if it attempts to exit the current
4258 @code{until} may produce somewhat counterintuitive results if the order
4259 of machine code does not match the order of the source lines. For
4260 example, in the following excerpt from a debugging session, the @code{f}
4261 (@code{frame}) command shows that execution is stopped at line
4262 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4266 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4268 (@value{GDBP}) until
4269 195 for ( ; argc > 0; NEXTARG) @{
4272 This happened because, for execution efficiency, the compiler had
4273 generated code for the loop closure test at the end, rather than the
4274 start, of the loop---even though the test in a C @code{for}-loop is
4275 written before the body of the loop. The @code{until} command appeared
4276 to step back to the beginning of the loop when it advanced to this
4277 expression; however, it has not really gone to an earlier
4278 statement---not in terms of the actual machine code.
4280 @code{until} with no argument works by means of single
4281 instruction stepping, and hence is slower than @code{until} with an
4284 @item until @var{location}
4285 @itemx u @var{location}
4286 Continue running your program until either the specified location is
4287 reached, or the current stack frame returns. @var{location} is any of
4288 the forms described in @ref{Specify Location}.
4289 This form of the command uses temporary breakpoints, and
4290 hence is quicker than @code{until} without an argument. The specified
4291 location is actually reached only if it is in the current frame. This
4292 implies that @code{until} can be used to skip over recursive function
4293 invocations. For instance in the code below, if the current location is
4294 line @code{96}, issuing @code{until 99} will execute the program up to
4295 line @code{99} in the same invocation of factorial, i.e., after the inner
4296 invocations have returned.
4299 94 int factorial (int value)
4301 96 if (value > 1) @{
4302 97 value *= factorial (value - 1);
4309 @kindex advance @var{location}
4310 @itemx advance @var{location}
4311 Continue running the program up to the given @var{location}. An argument is
4312 required, which should be of one of the forms described in
4313 @ref{Specify Location}.
4314 Execution will also stop upon exit from the current stack
4315 frame. This command is similar to @code{until}, but @code{advance} will
4316 not skip over recursive function calls, and the target location doesn't
4317 have to be in the same frame as the current one.
4321 @kindex si @r{(@code{stepi})}
4323 @itemx stepi @var{arg}
4325 Execute one machine instruction, then stop and return to the debugger.
4327 It is often useful to do @samp{display/i $pc} when stepping by machine
4328 instructions. This makes @value{GDBN} automatically display the next
4329 instruction to be executed, each time your program stops. @xref{Auto
4330 Display,, Automatic Display}.
4332 An argument is a repeat count, as in @code{step}.
4336 @kindex ni @r{(@code{nexti})}
4338 @itemx nexti @var{arg}
4340 Execute one machine instruction, but if it is a function call,
4341 proceed until the function returns.
4343 An argument is a repeat count, as in @code{next}.
4350 A signal is an asynchronous event that can happen in a program. The
4351 operating system defines the possible kinds of signals, and gives each
4352 kind a name and a number. For example, in Unix @code{SIGINT} is the
4353 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4354 @code{SIGSEGV} is the signal a program gets from referencing a place in
4355 memory far away from all the areas in use; @code{SIGALRM} occurs when
4356 the alarm clock timer goes off (which happens only if your program has
4357 requested an alarm).
4359 @cindex fatal signals
4360 Some signals, including @code{SIGALRM}, are a normal part of the
4361 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4362 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4363 program has not specified in advance some other way to handle the signal.
4364 @code{SIGINT} does not indicate an error in your program, but it is normally
4365 fatal so it can carry out the purpose of the interrupt: to kill the program.
4367 @value{GDBN} has the ability to detect any occurrence of a signal in your
4368 program. You can tell @value{GDBN} in advance what to do for each kind of
4371 @cindex handling signals
4372 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4373 @code{SIGALRM} be silently passed to your program
4374 (so as not to interfere with their role in the program's functioning)
4375 but to stop your program immediately whenever an error signal happens.
4376 You can change these settings with the @code{handle} command.
4379 @kindex info signals
4383 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4384 handle each one. You can use this to see the signal numbers of all
4385 the defined types of signals.
4387 @item info signals @var{sig}
4388 Similar, but print information only about the specified signal number.
4390 @code{info handle} is an alias for @code{info signals}.
4393 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4394 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4395 can be the number of a signal or its name (with or without the
4396 @samp{SIG} at the beginning); a list of signal numbers of the form
4397 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4398 known signals. Optional arguments @var{keywords}, described below,
4399 say what change to make.
4403 The keywords allowed by the @code{handle} command can be abbreviated.
4404 Their full names are:
4408 @value{GDBN} should not stop your program when this signal happens. It may
4409 still print a message telling you that the signal has come in.
4412 @value{GDBN} should stop your program when this signal happens. This implies
4413 the @code{print} keyword as well.
4416 @value{GDBN} should print a message when this signal happens.
4419 @value{GDBN} should not mention the occurrence of the signal at all. This
4420 implies the @code{nostop} keyword as well.
4424 @value{GDBN} should allow your program to see this signal; your program
4425 can handle the signal, or else it may terminate if the signal is fatal
4426 and not handled. @code{pass} and @code{noignore} are synonyms.
4430 @value{GDBN} should not allow your program to see this signal.
4431 @code{nopass} and @code{ignore} are synonyms.
4435 When a signal stops your program, the signal is not visible to the
4437 continue. Your program sees the signal then, if @code{pass} is in
4438 effect for the signal in question @emph{at that time}. In other words,
4439 after @value{GDBN} reports a signal, you can use the @code{handle}
4440 command with @code{pass} or @code{nopass} to control whether your
4441 program sees that signal when you continue.
4443 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4444 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4445 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4448 You can also use the @code{signal} command to prevent your program from
4449 seeing a signal, or cause it to see a signal it normally would not see,
4450 or to give it any signal at any time. For example, if your program stopped
4451 due to some sort of memory reference error, you might store correct
4452 values into the erroneous variables and continue, hoping to see more
4453 execution; but your program would probably terminate immediately as
4454 a result of the fatal signal once it saw the signal. To prevent this,
4455 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4459 @section Stopping and Starting Multi-thread Programs
4461 @cindex stopped threads
4462 @cindex threads, stopped
4464 @cindex continuing threads
4465 @cindex threads, continuing
4467 @value{GDBN} supports debugging programs with multiple threads
4468 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4469 are two modes of controlling execution of your program within the
4470 debugger. In the default mode, referred to as @dfn{all-stop mode},
4471 when any thread in your program stops (for example, at a breakpoint
4472 or while being stepped), all other threads in the program are also stopped by
4473 @value{GDBN}. On some targets, @value{GDBN} also supports
4474 @dfn{non-stop mode}, in which other threads can continue to run freely while
4475 you examine the stopped thread in the debugger.
4478 * All-Stop Mode:: All threads stop when GDB takes control
4479 * Non-Stop Mode:: Other threads continue to execute
4480 * Background Execution:: Running your program asynchronously
4481 * Thread-Specific Breakpoints:: Controlling breakpoints
4482 * Interrupted System Calls:: GDB may interfere with system calls
4486 @subsection All-Stop Mode
4488 @cindex all-stop mode
4490 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4491 @emph{all} threads of execution stop, not just the current thread. This
4492 allows you to examine the overall state of the program, including
4493 switching between threads, without worrying that things may change
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 @cindex automatic thread selection
4514 @cindex switching threads automatically
4515 @cindex threads, automatic switching
4516 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4517 signal, it automatically selects the thread where that breakpoint or
4518 signal happened. @value{GDBN} alerts you to the context switch with a
4519 message such as @samp{[Switching to Thread @var{n}]} to identify the
4522 On some OSes, you can modify @value{GDBN}'s default behavior by
4523 locking the OS scheduler to allow only a single thread to run.
4526 @item set scheduler-locking @var{mode}
4527 @cindex scheduler locking mode
4528 @cindex lock scheduler
4529 Set the scheduler locking mode. If it is @code{off}, then there is no
4530 locking and any thread may run at any time. If @code{on}, then only the
4531 current thread may run when the inferior is resumed. The @code{step}
4532 mode optimizes for single-stepping; it prevents other threads
4533 from preempting the current thread while you are stepping, so that
4534 the focus of debugging does not change unexpectedly.
4535 Other threads only rarely (or never) get a chance to run
4536 when you step. They are more likely to run when you @samp{next} over a
4537 function call, and they are completely free to run when you use commands
4538 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4539 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4540 the current thread away from the thread that you are debugging.
4542 @item show scheduler-locking
4543 Display the current scheduler locking mode.
4547 @subsection Non-Stop Mode
4549 @cindex non-stop mode
4551 @c This section is really only a place-holder, and needs to be expanded
4552 @c with more details.
4554 For some multi-threaded targets, @value{GDBN} supports an optional
4555 mode of operation in which you can examine stopped program threads in
4556 the debugger while other threads continue to execute freely. This
4557 minimizes intrusion when debugging live systems, such as programs
4558 where some threads have real-time constraints or must continue to
4559 respond to external events. This is referred to as @dfn{non-stop} mode.
4561 In non-stop mode, when a thread stops to report a debugging event,
4562 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4563 threads as well, in contrast to the all-stop mode behavior. Additionally,
4564 execution commands such as @code{continue} and @code{step} apply by default
4565 only to the current thread in non-stop mode, rather than all threads as
4566 in all-stop mode. This allows you to control threads explicitly in
4567 ways that are not possible in all-stop mode --- for example, stepping
4568 one thread while allowing others to run freely, stepping
4569 one thread while holding all others stopped, or stepping several threads
4570 independently and simultaneously.
4572 To enter non-stop mode, use this sequence of commands before you run
4573 or attach to your program:
4576 # Enable the async interface.
4579 # If using the CLI, pagination breaks non-stop.
4582 # Finally, turn it on!
4586 You can use these commands to manipulate the non-stop mode setting:
4589 @kindex set non-stop
4590 @item set non-stop on
4591 Enable selection of non-stop mode.
4592 @item set non-stop off
4593 Disable selection of non-stop mode.
4594 @kindex show non-stop
4596 Show the current non-stop enablement setting.
4599 Note these commands only reflect whether non-stop mode is enabled,
4600 not whether the currently-executing program is being run in non-stop mode.
4601 In particular, the @code{set non-stop} preference is only consulted when
4602 @value{GDBN} starts or connects to the target program, and it is generally
4603 not possible to switch modes once debugging has started. Furthermore,
4604 since not all targets support non-stop mode, even when you have enabled
4605 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4608 In non-stop mode, all execution commands apply only to the current thread
4609 by default. That is, @code{continue} only continues one thread.
4610 To continue all threads, issue @code{continue -a} or @code{c -a}.
4612 You can use @value{GDBN}'s background execution commands
4613 (@pxref{Background Execution}) to run some threads in the background
4614 while you continue to examine or step others from @value{GDBN}.
4615 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4616 always executed asynchronously in non-stop mode.
4618 Suspending execution is done with the @code{interrupt} command when
4619 running in the background, or @kbd{Ctrl-c} during foreground execution.
4620 In all-stop mode, this stops the whole process;
4621 but in non-stop mode the interrupt applies only to the current thread.
4622 To stop the whole program, use @code{interrupt -a}.
4624 Other execution commands do not currently support the @code{-a} option.
4626 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4627 that thread current, as it does in all-stop mode. This is because the
4628 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4629 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4630 changed to a different thread just as you entered a command to operate on the
4631 previously current thread.
4633 @node Background Execution
4634 @subsection Background Execution
4636 @cindex foreground execution
4637 @cindex background execution
4638 @cindex asynchronous execution
4639 @cindex execution, foreground, background and asynchronous
4641 @value{GDBN}'s execution commands have two variants: the normal
4642 foreground (synchronous) behavior, and a background
4643 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4644 the program to report that some thread has stopped before prompting for
4645 another command. In background execution, @value{GDBN} immediately gives
4646 a command prompt so that you can issue other commands while your program runs.
4648 To specify background execution, add a @code{&} to the command. For example,
4649 the background form of the @code{continue} command is @code{continue&}, or
4650 just @code{c&}. The execution commands that accept background execution
4656 @xref{Starting, , Starting your Program}.
4660 @xref{Attach, , Debugging an Already-running Process}.
4664 @xref{Continuing and Stepping, step}.
4668 @xref{Continuing and Stepping, stepi}.
4672 @xref{Continuing and Stepping, next}.
4676 @xref{Continuing and Stepping, continue}.
4680 @xref{Continuing and Stepping, finish}.
4684 @xref{Continuing and Stepping, until}.
4688 Background execution is especially useful in conjunction with non-stop
4689 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4690 However, you can also use these commands in the normal all-stop mode with
4691 the restriction that you cannot issue another execution command until the
4692 previous one finishes. Examples of commands that are valid in all-stop
4693 mode while the program is running include @code{help} and @code{info break}.
4695 You can interrupt your program while it is running in the background by
4696 using the @code{interrupt} command.
4703 Suspend execution of the running program. In all-stop mode,
4704 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4705 only the current thread. To stop the whole program in non-stop mode,
4706 use @code{interrupt -a}.
4709 You may need to explicitly enable async mode before you can use background
4710 execution commands, with the @code{set target-async 1} command. If the
4711 target doesn't support async mode, @value{GDBN} issues an error message
4712 if you attempt to use the background execution commands.
4714 @node Thread-Specific Breakpoints
4715 @subsection Thread-Specific Breakpoints
4717 When your program has multiple threads (@pxref{Threads,, Debugging
4718 Programs with Multiple Threads}), you can choose whether to set
4719 breakpoints on all threads, or on a particular thread.
4722 @cindex breakpoints and threads
4723 @cindex thread breakpoints
4724 @kindex break @dots{} thread @var{threadno}
4725 @item break @var{linespec} thread @var{threadno}
4726 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4727 @var{linespec} specifies source lines; there are several ways of
4728 writing them (@pxref{Specify Location}), but the effect is always to
4729 specify some source line.
4731 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4732 to specify that you only want @value{GDBN} to stop the program when a
4733 particular thread reaches this breakpoint. @var{threadno} is one of the
4734 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4735 column of the @samp{info threads} display.
4737 If you do not specify @samp{thread @var{threadno}} when you set a
4738 breakpoint, the breakpoint applies to @emph{all} threads of your
4741 You can use the @code{thread} qualifier on conditional breakpoints as
4742 well; in this case, place @samp{thread @var{threadno}} before the
4743 breakpoint condition, like this:
4746 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4751 @node Interrupted System Calls
4752 @subsection Interrupted System Calls
4754 @cindex thread breakpoints and system calls
4755 @cindex system calls and thread breakpoints
4756 @cindex premature return from system calls
4757 There is an unfortunate side effect when using @value{GDBN} to debug
4758 multi-threaded programs. If one thread stops for a
4759 breakpoint, or for some other reason, and another thread is blocked in a
4760 system call, then the system call may return prematurely. This is a
4761 consequence of the interaction between multiple threads and the signals
4762 that @value{GDBN} uses to implement breakpoints and other events that
4765 To handle this problem, your program should check the return value of
4766 each system call and react appropriately. This is good programming
4769 For example, do not write code like this:
4775 The call to @code{sleep} will return early if a different thread stops
4776 at a breakpoint or for some other reason.
4778 Instead, write this:
4783 unslept = sleep (unslept);
4786 A system call is allowed to return early, so the system is still
4787 conforming to its specification. But @value{GDBN} does cause your
4788 multi-threaded program to behave differently than it would without
4791 Also, @value{GDBN} uses internal breakpoints in the thread library to
4792 monitor certain events such as thread creation and thread destruction.
4793 When such an event happens, a system call in another thread may return
4794 prematurely, even though your program does not appear to stop.
4799 @chapter Examining the Stack
4801 When your program has stopped, the first thing you need to know is where it
4802 stopped and how it got there.
4805 Each time your program performs a function call, information about the call
4807 That information includes the location of the call in your program,
4808 the arguments of the call,
4809 and the local variables of the function being called.
4810 The information is saved in a block of data called a @dfn{stack frame}.
4811 The stack frames are allocated in a region of memory called the @dfn{call
4814 When your program stops, the @value{GDBN} commands for examining the
4815 stack allow you to see all of this information.
4817 @cindex selected frame
4818 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4819 @value{GDBN} commands refer implicitly to the selected frame. In
4820 particular, whenever you ask @value{GDBN} for the value of a variable in
4821 your program, the value is found in the selected frame. There are
4822 special @value{GDBN} commands to select whichever frame you are
4823 interested in. @xref{Selection, ,Selecting a Frame}.
4825 When your program stops, @value{GDBN} automatically selects the
4826 currently executing frame and describes it briefly, similar to the
4827 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4830 * Frames:: Stack frames
4831 * Backtrace:: Backtraces
4832 * Selection:: Selecting a frame
4833 * Frame Info:: Information on a frame
4838 @section Stack Frames
4840 @cindex frame, definition
4842 The call stack is divided up into contiguous pieces called @dfn{stack
4843 frames}, or @dfn{frames} for short; each frame is the data associated
4844 with one call to one function. The frame contains the arguments given
4845 to the function, the function's local variables, and the address at
4846 which the function is executing.
4848 @cindex initial frame
4849 @cindex outermost frame
4850 @cindex innermost frame
4851 When your program is started, the stack has only one frame, that of the
4852 function @code{main}. This is called the @dfn{initial} frame or the
4853 @dfn{outermost} frame. Each time a function is called, a new frame is
4854 made. Each time a function returns, the frame for that function invocation
4855 is eliminated. If a function is recursive, there can be many frames for
4856 the same function. The frame for the function in which execution is
4857 actually occurring is called the @dfn{innermost} frame. This is the most
4858 recently created of all the stack frames that still exist.
4860 @cindex frame pointer
4861 Inside your program, stack frames are identified by their addresses. A
4862 stack frame consists of many bytes, each of which has its own address; each
4863 kind of computer has a convention for choosing one byte whose
4864 address serves as the address of the frame. Usually this address is kept
4865 in a register called the @dfn{frame pointer register}
4866 (@pxref{Registers, $fp}) while execution is going on in that frame.
4868 @cindex frame number
4869 @value{GDBN} assigns numbers to all existing stack frames, starting with
4870 zero for the innermost frame, one for the frame that called it,
4871 and so on upward. These numbers do not really exist in your program;
4872 they are assigned by @value{GDBN} to give you a way of designating stack
4873 frames in @value{GDBN} commands.
4875 @c The -fomit-frame-pointer below perennially causes hbox overflow
4876 @c underflow problems.
4877 @cindex frameless execution
4878 Some compilers provide a way to compile functions so that they operate
4879 without stack frames. (For example, the @value{NGCC} option
4881 @samp{-fomit-frame-pointer}
4883 generates functions without a frame.)
4884 This is occasionally done with heavily used library functions to save
4885 the frame setup time. @value{GDBN} has limited facilities for dealing
4886 with these function invocations. If the innermost function invocation
4887 has no stack frame, @value{GDBN} nevertheless regards it as though
4888 it had a separate frame, which is numbered zero as usual, allowing
4889 correct tracing of the function call chain. However, @value{GDBN} has
4890 no provision for frameless functions elsewhere in the stack.
4893 @kindex frame@r{, command}
4894 @cindex current stack frame
4895 @item frame @var{args}
4896 The @code{frame} command allows you to move from one stack frame to another,
4897 and to print the stack frame you select. @var{args} may be either the
4898 address of the frame or the stack frame number. Without an argument,
4899 @code{frame} prints the current stack frame.
4901 @kindex select-frame
4902 @cindex selecting frame silently
4904 The @code{select-frame} command allows you to move from one stack frame
4905 to another without printing the frame. This is the silent version of
4913 @cindex call stack traces
4914 A backtrace is a summary of how your program got where it is. It shows one
4915 line per frame, for many frames, starting with the currently executing
4916 frame (frame zero), followed by its caller (frame one), and on up the
4921 @kindex bt @r{(@code{backtrace})}
4924 Print a backtrace of the entire stack: one line per frame for all
4925 frames in the stack.
4927 You can stop the backtrace at any time by typing the system interrupt
4928 character, normally @kbd{Ctrl-c}.
4930 @item backtrace @var{n}
4932 Similar, but print only the innermost @var{n} frames.
4934 @item backtrace -@var{n}
4936 Similar, but print only the outermost @var{n} frames.
4938 @item backtrace full
4940 @itemx bt full @var{n}
4941 @itemx bt full -@var{n}
4942 Print the values of the local variables also. @var{n} specifies the
4943 number of frames to print, as described above.
4948 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4949 are additional aliases for @code{backtrace}.
4951 @cindex multiple threads, backtrace
4952 In a multi-threaded program, @value{GDBN} by default shows the
4953 backtrace only for the current thread. To display the backtrace for
4954 several or all of the threads, use the command @code{thread apply}
4955 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4956 apply all backtrace}, @value{GDBN} will display the backtrace for all
4957 the threads; this is handy when you debug a core dump of a
4958 multi-threaded program.
4960 Each line in the backtrace shows the frame number and the function name.
4961 The program counter value is also shown---unless you use @code{set
4962 print address off}. The backtrace also shows the source file name and
4963 line number, as well as the arguments to the function. The program
4964 counter value is omitted if it is at the beginning of the code for that
4967 Here is an example of a backtrace. It was made with the command
4968 @samp{bt 3}, so it shows the innermost three frames.
4972 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4974 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4975 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4977 (More stack frames follow...)
4982 The display for frame zero does not begin with a program counter
4983 value, indicating that your program has stopped at the beginning of the
4984 code for line @code{993} of @code{builtin.c}.
4986 @cindex value optimized out, in backtrace
4987 @cindex function call arguments, optimized out
4988 If your program was compiled with optimizations, some compilers will
4989 optimize away arguments passed to functions if those arguments are
4990 never used after the call. Such optimizations generate code that
4991 passes arguments through registers, but doesn't store those arguments
4992 in the stack frame. @value{GDBN} has no way of displaying such
4993 arguments in stack frames other than the innermost one. Here's what
4994 such a backtrace might look like:
4998 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5000 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5001 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5003 (More stack frames follow...)
5008 The values of arguments that were not saved in their stack frames are
5009 shown as @samp{<value optimized out>}.
5011 If you need to display the values of such optimized-out arguments,
5012 either deduce that from other variables whose values depend on the one
5013 you are interested in, or recompile without optimizations.
5015 @cindex backtrace beyond @code{main} function
5016 @cindex program entry point
5017 @cindex startup code, and backtrace
5018 Most programs have a standard user entry point---a place where system
5019 libraries and startup code transition into user code. For C this is
5020 @code{main}@footnote{
5021 Note that embedded programs (the so-called ``free-standing''
5022 environment) are not required to have a @code{main} function as the
5023 entry point. They could even have multiple entry points.}.
5024 When @value{GDBN} finds the entry function in a backtrace
5025 it will terminate the backtrace, to avoid tracing into highly
5026 system-specific (and generally uninteresting) code.
5028 If you need to examine the startup code, or limit the number of levels
5029 in a backtrace, you can change this behavior:
5032 @item set backtrace past-main
5033 @itemx set backtrace past-main on
5034 @kindex set backtrace
5035 Backtraces will continue past the user entry point.
5037 @item set backtrace past-main off
5038 Backtraces will stop when they encounter the user entry point. This is the
5041 @item show backtrace past-main
5042 @kindex show backtrace
5043 Display the current user entry point backtrace policy.
5045 @item set backtrace past-entry
5046 @itemx set backtrace past-entry on
5047 Backtraces will continue past the internal entry point of an application.
5048 This entry point is encoded by the linker when the application is built,
5049 and is likely before the user entry point @code{main} (or equivalent) is called.
5051 @item set backtrace past-entry off
5052 Backtraces will stop when they encounter the internal entry point of an
5053 application. This is the default.
5055 @item show backtrace past-entry
5056 Display the current internal entry point backtrace policy.
5058 @item set backtrace limit @var{n}
5059 @itemx set backtrace limit 0
5060 @cindex backtrace limit
5061 Limit the backtrace to @var{n} levels. A value of zero means
5064 @item show backtrace limit
5065 Display the current limit on backtrace levels.
5069 @section Selecting a Frame
5071 Most commands for examining the stack and other data in your program work on
5072 whichever stack frame is selected at the moment. Here are the commands for
5073 selecting a stack frame; all of them finish by printing a brief description
5074 of the stack frame just selected.
5077 @kindex frame@r{, selecting}
5078 @kindex f @r{(@code{frame})}
5081 Select frame number @var{n}. Recall that frame zero is the innermost
5082 (currently executing) frame, frame one is the frame that called the
5083 innermost one, and so on. The highest-numbered frame is the one for
5086 @item frame @var{addr}
5088 Select the frame at address @var{addr}. This is useful mainly if the
5089 chaining of stack frames has been damaged by a bug, making it
5090 impossible for @value{GDBN} to assign numbers properly to all frames. In
5091 addition, this can be useful when your program has multiple stacks and
5092 switches between them.
5094 On the SPARC architecture, @code{frame} needs two addresses to
5095 select an arbitrary frame: a frame pointer and a stack pointer.
5097 On the MIPS and Alpha architecture, it needs two addresses: a stack
5098 pointer and a program counter.
5100 On the 29k architecture, it needs three addresses: a register stack
5101 pointer, a program counter, and a memory stack pointer.
5105 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5106 advances toward the outermost frame, to higher frame numbers, to frames
5107 that have existed longer. @var{n} defaults to one.
5110 @kindex do @r{(@code{down})}
5112 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5113 advances toward the innermost frame, to lower frame numbers, to frames
5114 that were created more recently. @var{n} defaults to one. You may
5115 abbreviate @code{down} as @code{do}.
5118 All of these commands end by printing two lines of output describing the
5119 frame. The first line shows the frame number, the function name, the
5120 arguments, and the source file and line number of execution in that
5121 frame. The second line shows the text of that source line.
5129 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5131 10 read_input_file (argv[i]);
5135 After such a printout, the @code{list} command with no arguments
5136 prints ten lines centered on the point of execution in the frame.
5137 You can also edit the program at the point of execution with your favorite
5138 editing program by typing @code{edit}.
5139 @xref{List, ,Printing Source Lines},
5143 @kindex down-silently
5145 @item up-silently @var{n}
5146 @itemx down-silently @var{n}
5147 These two commands are variants of @code{up} and @code{down},
5148 respectively; they differ in that they do their work silently, without
5149 causing display of the new frame. They are intended primarily for use
5150 in @value{GDBN} command scripts, where the output might be unnecessary and
5155 @section Information About a Frame
5157 There are several other commands to print information about the selected
5163 When used without any argument, this command does not change which
5164 frame is selected, but prints a brief description of the currently
5165 selected stack frame. It can be abbreviated @code{f}. With an
5166 argument, this command is used to select a stack frame.
5167 @xref{Selection, ,Selecting a Frame}.
5170 @kindex info f @r{(@code{info frame})}
5173 This command prints a verbose description of the selected stack frame,
5178 the address of the frame
5180 the address of the next frame down (called by this frame)
5182 the address of the next frame up (caller of this frame)
5184 the language in which the source code corresponding to this frame is written
5186 the address of the frame's arguments
5188 the address of the frame's local variables
5190 the program counter saved in it (the address of execution in the caller frame)
5192 which registers were saved in the frame
5195 @noindent The verbose description is useful when
5196 something has gone wrong that has made the stack format fail to fit
5197 the usual conventions.
5199 @item info frame @var{addr}
5200 @itemx info f @var{addr}
5201 Print a verbose description of the frame at address @var{addr}, without
5202 selecting that frame. The selected frame remains unchanged by this
5203 command. This requires the same kind of address (more than one for some
5204 architectures) that you specify in the @code{frame} command.
5205 @xref{Selection, ,Selecting a Frame}.
5209 Print the arguments of the selected frame, each on a separate line.
5213 Print the local variables of the selected frame, each on a separate
5214 line. These are all variables (declared either static or automatic)
5215 accessible at the point of execution of the selected frame.
5218 @cindex catch exceptions, list active handlers
5219 @cindex exception handlers, how to list
5221 Print a list of all the exception handlers that are active in the
5222 current stack frame at the current point of execution. To see other
5223 exception handlers, visit the associated frame (using the @code{up},
5224 @code{down}, or @code{frame} commands); then type @code{info catch}.
5225 @xref{Set Catchpoints, , Setting Catchpoints}.
5231 @chapter Examining Source Files
5233 @value{GDBN} can print parts of your program's source, since the debugging
5234 information recorded in the program tells @value{GDBN} what source files were
5235 used to build it. When your program stops, @value{GDBN} spontaneously prints
5236 the line where it stopped. Likewise, when you select a stack frame
5237 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5238 execution in that frame has stopped. You can print other portions of
5239 source files by explicit command.
5241 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5242 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5243 @value{GDBN} under @sc{gnu} Emacs}.
5246 * List:: Printing source lines
5247 * Specify Location:: How to specify code locations
5248 * Edit:: Editing source files
5249 * Search:: Searching source files
5250 * Source Path:: Specifying source directories
5251 * Machine Code:: Source and machine code
5255 @section Printing Source Lines
5258 @kindex l @r{(@code{list})}
5259 To print lines from a source file, use the @code{list} command
5260 (abbreviated @code{l}). By default, ten lines are printed.
5261 There are several ways to specify what part of the file you want to
5262 print; see @ref{Specify Location}, for the full list.
5264 Here are the forms of the @code{list} command most commonly used:
5267 @item list @var{linenum}
5268 Print lines centered around line number @var{linenum} in the
5269 current source file.
5271 @item list @var{function}
5272 Print lines centered around the beginning of function
5276 Print more lines. If the last lines printed were printed with a
5277 @code{list} command, this prints lines following the last lines
5278 printed; however, if the last line printed was a solitary line printed
5279 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5280 Stack}), this prints lines centered around that line.
5283 Print lines just before the lines last printed.
5286 @cindex @code{list}, how many lines to display
5287 By default, @value{GDBN} prints ten source lines with any of these forms of
5288 the @code{list} command. You can change this using @code{set listsize}:
5291 @kindex set listsize
5292 @item set listsize @var{count}
5293 Make the @code{list} command display @var{count} source lines (unless
5294 the @code{list} argument explicitly specifies some other number).
5296 @kindex show listsize
5298 Display the number of lines that @code{list} prints.
5301 Repeating a @code{list} command with @key{RET} discards the argument,
5302 so it is equivalent to typing just @code{list}. This is more useful
5303 than listing the same lines again. An exception is made for an
5304 argument of @samp{-}; that argument is preserved in repetition so that
5305 each repetition moves up in the source file.
5307 In general, the @code{list} command expects you to supply zero, one or two
5308 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5309 of writing them (@pxref{Specify Location}), but the effect is always
5310 to specify some source line.
5312 Here is a complete description of the possible arguments for @code{list}:
5315 @item list @var{linespec}
5316 Print lines centered around the line specified by @var{linespec}.
5318 @item list @var{first},@var{last}
5319 Print lines from @var{first} to @var{last}. Both arguments are
5320 linespecs. When a @code{list} command has two linespecs, and the
5321 source file of the second linespec is omitted, this refers to
5322 the same source file as the first linespec.
5324 @item list ,@var{last}
5325 Print lines ending with @var{last}.
5327 @item list @var{first},
5328 Print lines starting with @var{first}.
5331 Print lines just after the lines last printed.
5334 Print lines just before the lines last printed.
5337 As described in the preceding table.
5340 @node Specify Location
5341 @section Specifying a Location
5342 @cindex specifying location
5345 Several @value{GDBN} commands accept arguments that specify a location
5346 of your program's code. Since @value{GDBN} is a source-level
5347 debugger, a location usually specifies some line in the source code;
5348 for that reason, locations are also known as @dfn{linespecs}.
5350 Here are all the different ways of specifying a code location that
5351 @value{GDBN} understands:
5355 Specifies the line number @var{linenum} of the current source file.
5358 @itemx +@var{offset}
5359 Specifies the line @var{offset} lines before or after the @dfn{current
5360 line}. For the @code{list} command, the current line is the last one
5361 printed; for the breakpoint commands, this is the line at which
5362 execution stopped in the currently selected @dfn{stack frame}
5363 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5364 used as the second of the two linespecs in a @code{list} command,
5365 this specifies the line @var{offset} lines up or down from the first
5368 @item @var{filename}:@var{linenum}
5369 Specifies the line @var{linenum} in the source file @var{filename}.
5371 @item @var{function}
5372 Specifies the line that begins the body of the function @var{function}.
5373 For example, in C, this is the line with the open brace.
5375 @item @var{filename}:@var{function}
5376 Specifies the line that begins the body of the function @var{function}
5377 in the file @var{filename}. You only need the file name with a
5378 function name to avoid ambiguity when there are identically named
5379 functions in different source files.
5381 @item *@var{address}
5382 Specifies the program address @var{address}. For line-oriented
5383 commands, such as @code{list} and @code{edit}, this specifies a source
5384 line that contains @var{address}. For @code{break} and other
5385 breakpoint oriented commands, this can be used to set breakpoints in
5386 parts of your program which do not have debugging information or
5389 Here @var{address} may be any expression valid in the current working
5390 language (@pxref{Languages, working language}) that specifies a code
5391 address. In addition, as a convenience, @value{GDBN} extends the
5392 semantics of expressions used in locations to cover the situations
5393 that frequently happen during debugging. Here are the various forms
5397 @item @var{expression}
5398 Any expression valid in the current working language.
5400 @item @var{funcaddr}
5401 An address of a function or procedure derived from its name. In C,
5402 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5403 simply the function's name @var{function} (and actually a special case
5404 of a valid expression). In Pascal and Modula-2, this is
5405 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5406 (although the Pascal form also works).
5408 This form specifies the address of the function's first instruction,
5409 before the stack frame and arguments have been set up.
5411 @item '@var{filename}'::@var{funcaddr}
5412 Like @var{funcaddr} above, but also specifies the name of the source
5413 file explicitly. This is useful if the name of the function does not
5414 specify the function unambiguously, e.g., if there are several
5415 functions with identical names in different source files.
5422 @section Editing Source Files
5423 @cindex editing source files
5426 @kindex e @r{(@code{edit})}
5427 To edit the lines in a source file, use the @code{edit} command.
5428 The editing program of your choice
5429 is invoked with the current line set to
5430 the active line in the program.
5431 Alternatively, there are several ways to specify what part of the file you
5432 want to print if you want to see other parts of the program:
5435 @item edit @var{location}
5436 Edit the source file specified by @code{location}. Editing starts at
5437 that @var{location}, e.g., at the specified source line of the
5438 specified file. @xref{Specify Location}, for all the possible forms
5439 of the @var{location} argument; here are the forms of the @code{edit}
5440 command most commonly used:
5443 @item edit @var{number}
5444 Edit the current source file with @var{number} as the active line number.
5446 @item edit @var{function}
5447 Edit the file containing @var{function} at the beginning of its definition.
5452 @subsection Choosing your Editor
5453 You can customize @value{GDBN} to use any editor you want
5455 The only restriction is that your editor (say @code{ex}), recognizes the
5456 following command-line syntax:
5458 ex +@var{number} file
5460 The optional numeric value +@var{number} specifies the number of the line in
5461 the file where to start editing.}.
5462 By default, it is @file{@value{EDITOR}}, but you can change this
5463 by setting the environment variable @code{EDITOR} before using
5464 @value{GDBN}. For example, to configure @value{GDBN} to use the
5465 @code{vi} editor, you could use these commands with the @code{sh} shell:
5471 or in the @code{csh} shell,
5473 setenv EDITOR /usr/bin/vi
5478 @section Searching Source Files
5479 @cindex searching source files
5481 There are two commands for searching through the current source file for a
5486 @kindex forward-search
5487 @item forward-search @var{regexp}
5488 @itemx search @var{regexp}
5489 The command @samp{forward-search @var{regexp}} checks each line,
5490 starting with the one following the last line listed, for a match for
5491 @var{regexp}. It lists the line that is found. You can use the
5492 synonym @samp{search @var{regexp}} or abbreviate the command name as
5495 @kindex reverse-search
5496 @item reverse-search @var{regexp}
5497 The command @samp{reverse-search @var{regexp}} checks each line, starting
5498 with the one before the last line listed and going backward, for a match
5499 for @var{regexp}. It lists the line that is found. You can abbreviate
5500 this command as @code{rev}.
5504 @section Specifying Source Directories
5507 @cindex directories for source files
5508 Executable programs sometimes do not record the directories of the source
5509 files from which they were compiled, just the names. Even when they do,
5510 the directories could be moved between the compilation and your debugging
5511 session. @value{GDBN} has a list of directories to search for source files;
5512 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5513 it tries all the directories in the list, in the order they are present
5514 in the list, until it finds a file with the desired name.
5516 For example, suppose an executable references the file
5517 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5518 @file{/mnt/cross}. The file is first looked up literally; if this
5519 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5520 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5521 message is printed. @value{GDBN} does not look up the parts of the
5522 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5523 Likewise, the subdirectories of the source path are not searched: if
5524 the source path is @file{/mnt/cross}, and the binary refers to
5525 @file{foo.c}, @value{GDBN} would not find it under
5526 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5528 Plain file names, relative file names with leading directories, file
5529 names containing dots, etc.@: are all treated as described above; for
5530 instance, if the source path is @file{/mnt/cross}, and the source file
5531 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5532 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5533 that---@file{/mnt/cross/foo.c}.
5535 Note that the executable search path is @emph{not} used to locate the
5538 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5539 any information it has cached about where source files are found and where
5540 each line is in the file.
5544 When you start @value{GDBN}, its source path includes only @samp{cdir}
5545 and @samp{cwd}, in that order.
5546 To add other directories, use the @code{directory} command.
5548 The search path is used to find both program source files and @value{GDBN}
5549 script files (read using the @samp{-command} option and @samp{source} command).
5551 In addition to the source path, @value{GDBN} provides a set of commands
5552 that manage a list of source path substitution rules. A @dfn{substitution
5553 rule} specifies how to rewrite source directories stored in the program's
5554 debug information in case the sources were moved to a different
5555 directory between compilation and debugging. A rule is made of
5556 two strings, the first specifying what needs to be rewritten in
5557 the path, and the second specifying how it should be rewritten.
5558 In @ref{set substitute-path}, we name these two parts @var{from} and
5559 @var{to} respectively. @value{GDBN} does a simple string replacement
5560 of @var{from} with @var{to} at the start of the directory part of the
5561 source file name, and uses that result instead of the original file
5562 name to look up the sources.
5564 Using the previous example, suppose the @file{foo-1.0} tree has been
5565 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5566 @value{GDBN} to replace @file{/usr/src} in all source path names with
5567 @file{/mnt/cross}. The first lookup will then be
5568 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5569 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5570 substitution rule, use the @code{set substitute-path} command
5571 (@pxref{set substitute-path}).
5573 To avoid unexpected substitution results, a rule is applied only if the
5574 @var{from} part of the directory name ends at a directory separator.
5575 For instance, a rule substituting @file{/usr/source} into
5576 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5577 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5578 is applied only at the beginning of the directory name, this rule will
5579 not be applied to @file{/root/usr/source/baz.c} either.
5581 In many cases, you can achieve the same result using the @code{directory}
5582 command. However, @code{set substitute-path} can be more efficient in
5583 the case where the sources are organized in a complex tree with multiple
5584 subdirectories. With the @code{directory} command, you need to add each
5585 subdirectory of your project. If you moved the entire tree while
5586 preserving its internal organization, then @code{set substitute-path}
5587 allows you to direct the debugger to all the sources with one single
5590 @code{set substitute-path} is also more than just a shortcut command.
5591 The source path is only used if the file at the original location no
5592 longer exists. On the other hand, @code{set substitute-path} modifies
5593 the debugger behavior to look at the rewritten location instead. So, if
5594 for any reason a source file that is not relevant to your executable is
5595 located at the original location, a substitution rule is the only
5596 method available to point @value{GDBN} at the new location.
5599 @item directory @var{dirname} @dots{}
5600 @item dir @var{dirname} @dots{}
5601 Add directory @var{dirname} to the front of the source path. Several
5602 directory names may be given to this command, separated by @samp{:}
5603 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5604 part of absolute file names) or
5605 whitespace. You may specify a directory that is already in the source
5606 path; this moves it forward, so @value{GDBN} searches it sooner.
5610 @vindex $cdir@r{, convenience variable}
5611 @vindex $cwd@r{, convenience variable}
5612 @cindex compilation directory
5613 @cindex current directory
5614 @cindex working directory
5615 @cindex directory, current
5616 @cindex directory, compilation
5617 You can use the string @samp{$cdir} to refer to the compilation
5618 directory (if one is recorded), and @samp{$cwd} to refer to the current
5619 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5620 tracks the current working directory as it changes during your @value{GDBN}
5621 session, while the latter is immediately expanded to the current
5622 directory at the time you add an entry to the source path.
5625 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5627 @c RET-repeat for @code{directory} is explicitly disabled, but since
5628 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5630 @item show directories
5631 @kindex show directories
5632 Print the source path: show which directories it contains.
5634 @anchor{set substitute-path}
5635 @item set substitute-path @var{from} @var{to}
5636 @kindex set substitute-path
5637 Define a source path substitution rule, and add it at the end of the
5638 current list of existing substitution rules. If a rule with the same
5639 @var{from} was already defined, then the old rule is also deleted.
5641 For example, if the file @file{/foo/bar/baz.c} was moved to
5642 @file{/mnt/cross/baz.c}, then the command
5645 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5649 will tell @value{GDBN} to replace @samp{/usr/src} with
5650 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5651 @file{baz.c} even though it was moved.
5653 In the case when more than one substitution rule have been defined,
5654 the rules are evaluated one by one in the order where they have been
5655 defined. The first one matching, if any, is selected to perform
5658 For instance, if we had entered the following commands:
5661 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5662 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5666 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5667 @file{/mnt/include/defs.h} by using the first rule. However, it would
5668 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5669 @file{/mnt/src/lib/foo.c}.
5672 @item unset substitute-path [path]
5673 @kindex unset substitute-path
5674 If a path is specified, search the current list of substitution rules
5675 for a rule that would rewrite that path. Delete that rule if found.
5676 A warning is emitted by the debugger if no rule could be found.
5678 If no path is specified, then all substitution rules are deleted.
5680 @item show substitute-path [path]
5681 @kindex show substitute-path
5682 If a path is specified, then print the source path substitution rule
5683 which would rewrite that path, if any.
5685 If no path is specified, then print all existing source path substitution
5690 If your source path is cluttered with directories that are no longer of
5691 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5692 versions of source. You can correct the situation as follows:
5696 Use @code{directory} with no argument to reset the source path to its default value.
5699 Use @code{directory} with suitable arguments to reinstall the
5700 directories you want in the source path. You can add all the
5701 directories in one command.
5705 @section Source and Machine Code
5706 @cindex source line and its code address
5708 You can use the command @code{info line} to map source lines to program
5709 addresses (and vice versa), and the command @code{disassemble} to display
5710 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5711 mode, the @code{info line} command causes the arrow to point to the
5712 line specified. Also, @code{info line} prints addresses in symbolic form as
5717 @item info line @var{linespec}
5718 Print the starting and ending addresses of the compiled code for
5719 source line @var{linespec}. You can specify source lines in any of
5720 the ways documented in @ref{Specify Location}.
5723 For example, we can use @code{info line} to discover the location of
5724 the object code for the first line of function
5725 @code{m4_changequote}:
5727 @c FIXME: I think this example should also show the addresses in
5728 @c symbolic form, as they usually would be displayed.
5730 (@value{GDBP}) info line m4_changequote
5731 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5735 @cindex code address and its source line
5736 We can also inquire (using @code{*@var{addr}} as the form for
5737 @var{linespec}) what source line covers a particular address:
5739 (@value{GDBP}) info line *0x63ff
5740 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5743 @cindex @code{$_} and @code{info line}
5744 @cindex @code{x} command, default address
5745 @kindex x@r{(examine), and} info line
5746 After @code{info line}, the default address for the @code{x} command
5747 is changed to the starting address of the line, so that @samp{x/i} is
5748 sufficient to begin examining the machine code (@pxref{Memory,
5749 ,Examining Memory}). Also, this address is saved as the value of the
5750 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5755 @cindex assembly instructions
5756 @cindex instructions, assembly
5757 @cindex machine instructions
5758 @cindex listing machine instructions
5760 @itemx disassemble /m
5761 This specialized command dumps a range of memory as machine
5762 instructions. It can also print mixed source+disassembly by specifying
5763 the @code{/m} modifier.
5764 The default memory range is the function surrounding the
5765 program counter of the selected frame. A single argument to this
5766 command is a program counter value; @value{GDBN} dumps the function
5767 surrounding this value. Two arguments specify a range of addresses
5768 (first inclusive, second exclusive) to dump.
5771 The following example shows the disassembly of a range of addresses of
5772 HP PA-RISC 2.0 code:
5775 (@value{GDBP}) disas 0x32c4 0x32e4
5776 Dump of assembler code from 0x32c4 to 0x32e4:
5777 0x32c4 <main+204>: addil 0,dp
5778 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5779 0x32cc <main+212>: ldil 0x3000,r31
5780 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5781 0x32d4 <main+220>: ldo 0(r31),rp
5782 0x32d8 <main+224>: addil -0x800,dp
5783 0x32dc <main+228>: ldo 0x588(r1),r26
5784 0x32e0 <main+232>: ldil 0x3000,r31
5785 End of assembler dump.
5788 Here is an example showing mixed source+assembly for Intel x86:
5791 (@value{GDBP}) disas /m main
5792 Dump of assembler code for function main:
5794 0x08048330 <main+0>: push %ebp
5795 0x08048331 <main+1>: mov %esp,%ebp
5796 0x08048333 <main+3>: sub $0x8,%esp
5797 0x08048336 <main+6>: and $0xfffffff0,%esp
5798 0x08048339 <main+9>: sub $0x10,%esp
5800 6 printf ("Hello.\n");
5801 0x0804833c <main+12>: movl $0x8048440,(%esp)
5802 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
5806 0x08048348 <main+24>: mov $0x0,%eax
5807 0x0804834d <main+29>: leave
5808 0x0804834e <main+30>: ret
5810 End of assembler dump.
5813 Some architectures have more than one commonly-used set of instruction
5814 mnemonics or other syntax.
5816 For programs that were dynamically linked and use shared libraries,
5817 instructions that call functions or branch to locations in the shared
5818 libraries might show a seemingly bogus location---it's actually a
5819 location of the relocation table. On some architectures, @value{GDBN}
5820 might be able to resolve these to actual function names.
5823 @kindex set disassembly-flavor
5824 @cindex Intel disassembly flavor
5825 @cindex AT&T disassembly flavor
5826 @item set disassembly-flavor @var{instruction-set}
5827 Select the instruction set to use when disassembling the
5828 program via the @code{disassemble} or @code{x/i} commands.
5830 Currently this command is only defined for the Intel x86 family. You
5831 can set @var{instruction-set} to either @code{intel} or @code{att}.
5832 The default is @code{att}, the AT&T flavor used by default by Unix
5833 assemblers for x86-based targets.
5835 @kindex show disassembly-flavor
5836 @item show disassembly-flavor
5837 Show the current setting of the disassembly flavor.
5842 @chapter Examining Data
5844 @cindex printing data
5845 @cindex examining data
5848 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5849 @c document because it is nonstandard... Under Epoch it displays in a
5850 @c different window or something like that.
5851 The usual way to examine data in your program is with the @code{print}
5852 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5853 evaluates and prints the value of an expression of the language your
5854 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5855 Different Languages}).
5858 @item print @var{expr}
5859 @itemx print /@var{f} @var{expr}
5860 @var{expr} is an expression (in the source language). By default the
5861 value of @var{expr} is printed in a format appropriate to its data type;
5862 you can choose a different format by specifying @samp{/@var{f}}, where
5863 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5867 @itemx print /@var{f}
5868 @cindex reprint the last value
5869 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5870 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5871 conveniently inspect the same value in an alternative format.
5874 A more low-level way of examining data is with the @code{x} command.
5875 It examines data in memory at a specified address and prints it in a
5876 specified format. @xref{Memory, ,Examining Memory}.
5878 If you are interested in information about types, or about how the
5879 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5880 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5884 * Expressions:: Expressions
5885 * Ambiguous Expressions:: Ambiguous Expressions
5886 * Variables:: Program variables
5887 * Arrays:: Artificial arrays
5888 * Output Formats:: Output formats
5889 * Memory:: Examining memory
5890 * Auto Display:: Automatic display
5891 * Print Settings:: Print settings
5892 * Value History:: Value history
5893 * Convenience Vars:: Convenience variables
5894 * Registers:: Registers
5895 * Floating Point Hardware:: Floating point hardware
5896 * Vector Unit:: Vector Unit
5897 * OS Information:: Auxiliary data provided by operating system
5898 * Memory Region Attributes:: Memory region attributes
5899 * Dump/Restore Files:: Copy between memory and a file
5900 * Core File Generation:: Cause a program dump its core
5901 * Character Sets:: Debugging programs that use a different
5902 character set than GDB does
5903 * Caching Remote Data:: Data caching for remote targets
5904 * Searching Memory:: Searching memory for a sequence of bytes
5908 @section Expressions
5911 @code{print} and many other @value{GDBN} commands accept an expression and
5912 compute its value. Any kind of constant, variable or operator defined
5913 by the programming language you are using is valid in an expression in
5914 @value{GDBN}. This includes conditional expressions, function calls,
5915 casts, and string constants. It also includes preprocessor macros, if
5916 you compiled your program to include this information; see
5919 @cindex arrays in expressions
5920 @value{GDBN} supports array constants in expressions input by
5921 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5922 you can use the command @code{print @{1, 2, 3@}} to create an array
5923 of three integers. If you pass an array to a function or assign it
5924 to a program variable, @value{GDBN} copies the array to memory that
5925 is @code{malloc}ed in the target program.
5927 Because C is so widespread, most of the expressions shown in examples in
5928 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5929 Languages}, for information on how to use expressions in other
5932 In this section, we discuss operators that you can use in @value{GDBN}
5933 expressions regardless of your programming language.
5935 @cindex casts, in expressions
5936 Casts are supported in all languages, not just in C, because it is so
5937 useful to cast a number into a pointer in order to examine a structure
5938 at that address in memory.
5939 @c FIXME: casts supported---Mod2 true?
5941 @value{GDBN} supports these operators, in addition to those common
5942 to programming languages:
5946 @samp{@@} is a binary operator for treating parts of memory as arrays.
5947 @xref{Arrays, ,Artificial Arrays}, for more information.
5950 @samp{::} allows you to specify a variable in terms of the file or
5951 function where it is defined. @xref{Variables, ,Program Variables}.
5953 @cindex @{@var{type}@}
5954 @cindex type casting memory
5955 @cindex memory, viewing as typed object
5956 @cindex casts, to view memory
5957 @item @{@var{type}@} @var{addr}
5958 Refers to an object of type @var{type} stored at address @var{addr} in
5959 memory. @var{addr} may be any expression whose value is an integer or
5960 pointer (but parentheses are required around binary operators, just as in
5961 a cast). This construct is allowed regardless of what kind of data is
5962 normally supposed to reside at @var{addr}.
5965 @node Ambiguous Expressions
5966 @section Ambiguous Expressions
5967 @cindex ambiguous expressions
5969 Expressions can sometimes contain some ambiguous elements. For instance,
5970 some programming languages (notably Ada, C@t{++} and Objective-C) permit
5971 a single function name to be defined several times, for application in
5972 different contexts. This is called @dfn{overloading}. Another example
5973 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
5974 templates and is typically instantiated several times, resulting in
5975 the same function name being defined in different contexts.
5977 In some cases and depending on the language, it is possible to adjust
5978 the expression to remove the ambiguity. For instance in C@t{++}, you
5979 can specify the signature of the function you want to break on, as in
5980 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
5981 qualified name of your function often makes the expression unambiguous
5984 When an ambiguity that needs to be resolved is detected, the debugger
5985 has the capability to display a menu of numbered choices for each
5986 possibility, and then waits for the selection with the prompt @samp{>}.
5987 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
5988 aborts the current command. If the command in which the expression was
5989 used allows more than one choice to be selected, the next option in the
5990 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
5993 For example, the following session excerpt shows an attempt to set a
5994 breakpoint at the overloaded symbol @code{String::after}.
5995 We choose three particular definitions of that function name:
5997 @c FIXME! This is likely to change to show arg type lists, at least
6000 (@value{GDBP}) b String::after
6003 [2] file:String.cc; line number:867
6004 [3] file:String.cc; line number:860
6005 [4] file:String.cc; line number:875
6006 [5] file:String.cc; line number:853
6007 [6] file:String.cc; line number:846
6008 [7] file:String.cc; line number:735
6010 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6011 Breakpoint 2 at 0xb344: file String.cc, line 875.
6012 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6013 Multiple breakpoints were set.
6014 Use the "delete" command to delete unwanted
6021 @kindex set multiple-symbols
6022 @item set multiple-symbols @var{mode}
6023 @cindex multiple-symbols menu
6025 This option allows you to adjust the debugger behavior when an expression
6028 By default, @var{mode} is set to @code{all}. If the command with which
6029 the expression is used allows more than one choice, then @value{GDBN}
6030 automatically selects all possible choices. For instance, inserting
6031 a breakpoint on a function using an ambiguous name results in a breakpoint
6032 inserted on each possible match. However, if a unique choice must be made,
6033 then @value{GDBN} uses the menu to help you disambiguate the expression.
6034 For instance, printing the address of an overloaded function will result
6035 in the use of the menu.
6037 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6038 when an ambiguity is detected.
6040 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6041 an error due to the ambiguity and the command is aborted.
6043 @kindex show multiple-symbols
6044 @item show multiple-symbols
6045 Show the current value of the @code{multiple-symbols} setting.
6049 @section Program Variables
6051 The most common kind of expression to use is the name of a variable
6054 Variables in expressions are understood in the selected stack frame
6055 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6059 global (or file-static)
6066 visible according to the scope rules of the
6067 programming language from the point of execution in that frame
6070 @noindent This means that in the function
6085 you can examine and use the variable @code{a} whenever your program is
6086 executing within the function @code{foo}, but you can only use or
6087 examine the variable @code{b} while your program is executing inside
6088 the block where @code{b} is declared.
6090 @cindex variable name conflict
6091 There is an exception: you can refer to a variable or function whose
6092 scope is a single source file even if the current execution point is not
6093 in this file. But it is possible to have more than one such variable or
6094 function with the same name (in different source files). If that
6095 happens, referring to that name has unpredictable effects. If you wish,
6096 you can specify a static variable in a particular function or file,
6097 using the colon-colon (@code{::}) notation:
6099 @cindex colon-colon, context for variables/functions
6101 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6102 @cindex @code{::}, context for variables/functions
6105 @var{file}::@var{variable}
6106 @var{function}::@var{variable}
6110 Here @var{file} or @var{function} is the name of the context for the
6111 static @var{variable}. In the case of file names, you can use quotes to
6112 make sure @value{GDBN} parses the file name as a single word---for example,
6113 to print a global value of @code{x} defined in @file{f2.c}:
6116 (@value{GDBP}) p 'f2.c'::x
6119 @cindex C@t{++} scope resolution
6120 This use of @samp{::} is very rarely in conflict with the very similar
6121 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6122 scope resolution operator in @value{GDBN} expressions.
6123 @c FIXME: Um, so what happens in one of those rare cases where it's in
6126 @cindex wrong values
6127 @cindex variable values, wrong
6128 @cindex function entry/exit, wrong values of variables
6129 @cindex optimized code, wrong values of variables
6131 @emph{Warning:} Occasionally, a local variable may appear to have the
6132 wrong value at certain points in a function---just after entry to a new
6133 scope, and just before exit.
6135 You may see this problem when you are stepping by machine instructions.
6136 This is because, on most machines, it takes more than one instruction to
6137 set up a stack frame (including local variable definitions); if you are
6138 stepping by machine instructions, variables may appear to have the wrong
6139 values until the stack frame is completely built. On exit, it usually
6140 also takes more than one machine instruction to destroy a stack frame;
6141 after you begin stepping through that group of instructions, local
6142 variable definitions may be gone.
6144 This may also happen when the compiler does significant optimizations.
6145 To be sure of always seeing accurate values, turn off all optimization
6148 @cindex ``No symbol "foo" in current context''
6149 Another possible effect of compiler optimizations is to optimize
6150 unused variables out of existence, or assign variables to registers (as
6151 opposed to memory addresses). Depending on the support for such cases
6152 offered by the debug info format used by the compiler, @value{GDBN}
6153 might not be able to display values for such local variables. If that
6154 happens, @value{GDBN} will print a message like this:
6157 No symbol "foo" in current context.
6160 To solve such problems, either recompile without optimizations, or use a
6161 different debug info format, if the compiler supports several such
6162 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6163 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6164 produces debug info in a format that is superior to formats such as
6165 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6166 an effective form for debug info. @xref{Debugging Options,,Options
6167 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6168 Compiler Collection (GCC)}.
6169 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6170 that are best suited to C@t{++} programs.
6172 If you ask to print an object whose contents are unknown to
6173 @value{GDBN}, e.g., because its data type is not completely specified
6174 by the debug information, @value{GDBN} will say @samp{<incomplete
6175 type>}. @xref{Symbols, incomplete type}, for more about this.
6177 Strings are identified as arrays of @code{char} values without specified
6178 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6179 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6180 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6181 defines literal string type @code{"char"} as @code{char} without a sign.
6186 signed char var1[] = "A";
6189 You get during debugging
6194 $2 = @{65 'A', 0 '\0'@}
6198 @section Artificial Arrays
6200 @cindex artificial array
6202 @kindex @@@r{, referencing memory as an array}
6203 It is often useful to print out several successive objects of the
6204 same type in memory; a section of an array, or an array of
6205 dynamically determined size for which only a pointer exists in the
6208 You can do this by referring to a contiguous span of memory as an
6209 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6210 operand of @samp{@@} should be the first element of the desired array
6211 and be an individual object. The right operand should be the desired length
6212 of the array. The result is an array value whose elements are all of
6213 the type of the left argument. The first element is actually the left
6214 argument; the second element comes from bytes of memory immediately
6215 following those that hold the first element, and so on. Here is an
6216 example. If a program says
6219 int *array = (int *) malloc (len * sizeof (int));
6223 you can print the contents of @code{array} with
6229 The left operand of @samp{@@} must reside in memory. Array values made
6230 with @samp{@@} in this way behave just like other arrays in terms of
6231 subscripting, and are coerced to pointers when used in expressions.
6232 Artificial arrays most often appear in expressions via the value history
6233 (@pxref{Value History, ,Value History}), after printing one out.
6235 Another way to create an artificial array is to use a cast.
6236 This re-interprets a value as if it were an array.
6237 The value need not be in memory:
6239 (@value{GDBP}) p/x (short[2])0x12345678
6240 $1 = @{0x1234, 0x5678@}
6243 As a convenience, if you leave the array length out (as in
6244 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6245 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6247 (@value{GDBP}) p/x (short[])0x12345678
6248 $2 = @{0x1234, 0x5678@}
6251 Sometimes the artificial array mechanism is not quite enough; in
6252 moderately complex data structures, the elements of interest may not
6253 actually be adjacent---for example, if you are interested in the values
6254 of pointers in an array. One useful work-around in this situation is
6255 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6256 Variables}) as a counter in an expression that prints the first
6257 interesting value, and then repeat that expression via @key{RET}. For
6258 instance, suppose you have an array @code{dtab} of pointers to
6259 structures, and you are interested in the values of a field @code{fv}
6260 in each structure. Here is an example of what you might type:
6270 @node Output Formats
6271 @section Output Formats
6273 @cindex formatted output
6274 @cindex output formats
6275 By default, @value{GDBN} prints a value according to its data type. Sometimes
6276 this is not what you want. For example, you might want to print a number
6277 in hex, or a pointer in decimal. Or you might want to view data in memory
6278 at a certain address as a character string or as an instruction. To do
6279 these things, specify an @dfn{output format} when you print a value.
6281 The simplest use of output formats is to say how to print a value
6282 already computed. This is done by starting the arguments of the
6283 @code{print} command with a slash and a format letter. The format
6284 letters supported are:
6288 Regard the bits of the value as an integer, and print the integer in
6292 Print as integer in signed decimal.
6295 Print as integer in unsigned decimal.
6298 Print as integer in octal.
6301 Print as integer in binary. The letter @samp{t} stands for ``two''.
6302 @footnote{@samp{b} cannot be used because these format letters are also
6303 used with the @code{x} command, where @samp{b} stands for ``byte'';
6304 see @ref{Memory,,Examining Memory}.}
6307 @cindex unknown address, locating
6308 @cindex locate address
6309 Print as an address, both absolute in hexadecimal and as an offset from
6310 the nearest preceding symbol. You can use this format used to discover
6311 where (in what function) an unknown address is located:
6314 (@value{GDBP}) p/a 0x54320
6315 $3 = 0x54320 <_initialize_vx+396>
6319 The command @code{info symbol 0x54320} yields similar results.
6320 @xref{Symbols, info symbol}.
6323 Regard as an integer and print it as a character constant. This
6324 prints both the numerical value and its character representation. The
6325 character representation is replaced with the octal escape @samp{\nnn}
6326 for characters outside the 7-bit @sc{ascii} range.
6328 Without this format, @value{GDBN} displays @code{char},
6329 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6330 constants. Single-byte members of vectors are displayed as integer
6334 Regard the bits of the value as a floating point number and print
6335 using typical floating point syntax.
6338 @cindex printing strings
6339 @cindex printing byte arrays
6340 Regard as a string, if possible. With this format, pointers to single-byte
6341 data are displayed as null-terminated strings and arrays of single-byte data
6342 are displayed as fixed-length strings. Other values are displayed in their
6345 Without this format, @value{GDBN} displays pointers to and arrays of
6346 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6347 strings. Single-byte members of a vector are displayed as an integer
6351 For example, to print the program counter in hex (@pxref{Registers}), type
6358 Note that no space is required before the slash; this is because command
6359 names in @value{GDBN} cannot contain a slash.
6361 To reprint the last value in the value history with a different format,
6362 you can use the @code{print} command with just a format and no
6363 expression. For example, @samp{p/x} reprints the last value in hex.
6366 @section Examining Memory
6368 You can use the command @code{x} (for ``examine'') to examine memory in
6369 any of several formats, independently of your program's data types.
6371 @cindex examining memory
6373 @kindex x @r{(examine memory)}
6374 @item x/@var{nfu} @var{addr}
6377 Use the @code{x} command to examine memory.
6380 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6381 much memory to display and how to format it; @var{addr} is an
6382 expression giving the address where you want to start displaying memory.
6383 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6384 Several commands set convenient defaults for @var{addr}.
6387 @item @var{n}, the repeat count
6388 The repeat count is a decimal integer; the default is 1. It specifies
6389 how much memory (counting by units @var{u}) to display.
6390 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6393 @item @var{f}, the display format
6394 The display format is one of the formats used by @code{print}
6395 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6396 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6397 The default is @samp{x} (hexadecimal) initially. The default changes
6398 each time you use either @code{x} or @code{print}.
6400 @item @var{u}, the unit size
6401 The unit size is any of
6407 Halfwords (two bytes).
6409 Words (four bytes). This is the initial default.
6411 Giant words (eight bytes).
6414 Each time you specify a unit size with @code{x}, that size becomes the
6415 default unit the next time you use @code{x}. (For the @samp{s} and
6416 @samp{i} formats, the unit size is ignored and is normally not written.)
6418 @item @var{addr}, starting display address
6419 @var{addr} is the address where you want @value{GDBN} to begin displaying
6420 memory. The expression need not have a pointer value (though it may);
6421 it is always interpreted as an integer address of a byte of memory.
6422 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6423 @var{addr} is usually just after the last address examined---but several
6424 other commands also set the default address: @code{info breakpoints} (to
6425 the address of the last breakpoint listed), @code{info line} (to the
6426 starting address of a line), and @code{print} (if you use it to display
6427 a value from memory).
6430 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6431 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6432 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6433 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6434 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6436 Since the letters indicating unit sizes are all distinct from the
6437 letters specifying output formats, you do not have to remember whether
6438 unit size or format comes first; either order works. The output
6439 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6440 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6442 Even though the unit size @var{u} is ignored for the formats @samp{s}
6443 and @samp{i}, you might still want to use a count @var{n}; for example,
6444 @samp{3i} specifies that you want to see three machine instructions,
6445 including any operands. For convenience, especially when used with
6446 the @code{display} command, the @samp{i} format also prints branch delay
6447 slot instructions, if any, beyond the count specified, which immediately
6448 follow the last instruction that is within the count. The command
6449 @code{disassemble} gives an alternative way of inspecting machine
6450 instructions; see @ref{Machine Code,,Source and Machine Code}.
6452 All the defaults for the arguments to @code{x} are designed to make it
6453 easy to continue scanning memory with minimal specifications each time
6454 you use @code{x}. For example, after you have inspected three machine
6455 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6456 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6457 the repeat count @var{n} is used again; the other arguments default as
6458 for successive uses of @code{x}.
6460 @cindex @code{$_}, @code{$__}, and value history
6461 The addresses and contents printed by the @code{x} command are not saved
6462 in the value history because there is often too much of them and they
6463 would get in the way. Instead, @value{GDBN} makes these values available for
6464 subsequent use in expressions as values of the convenience variables
6465 @code{$_} and @code{$__}. After an @code{x} command, the last address
6466 examined is available for use in expressions in the convenience variable
6467 @code{$_}. The contents of that address, as examined, are available in
6468 the convenience variable @code{$__}.
6470 If the @code{x} command has a repeat count, the address and contents saved
6471 are from the last memory unit printed; this is not the same as the last
6472 address printed if several units were printed on the last line of output.
6474 @cindex remote memory comparison
6475 @cindex verify remote memory image
6476 When you are debugging a program running on a remote target machine
6477 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6478 remote machine's memory against the executable file you downloaded to
6479 the target. The @code{compare-sections} command is provided for such
6483 @kindex compare-sections
6484 @item compare-sections @r{[}@var{section-name}@r{]}
6485 Compare the data of a loadable section @var{section-name} in the
6486 executable file of the program being debugged with the same section in
6487 the remote machine's memory, and report any mismatches. With no
6488 arguments, compares all loadable sections. This command's
6489 availability depends on the target's support for the @code{"qCRC"}
6494 @section Automatic Display
6495 @cindex automatic display
6496 @cindex display of expressions
6498 If you find that you want to print the value of an expression frequently
6499 (to see how it changes), you might want to add it to the @dfn{automatic
6500 display list} so that @value{GDBN} prints its value each time your program stops.
6501 Each expression added to the list is given a number to identify it;
6502 to remove an expression from the list, you specify that number.
6503 The automatic display looks like this:
6507 3: bar[5] = (struct hack *) 0x3804
6511 This display shows item numbers, expressions and their current values. As with
6512 displays you request manually using @code{x} or @code{print}, you can
6513 specify the output format you prefer; in fact, @code{display} decides
6514 whether to use @code{print} or @code{x} depending your format
6515 specification---it uses @code{x} if you specify either the @samp{i}
6516 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6520 @item display @var{expr}
6521 Add the expression @var{expr} to the list of expressions to display
6522 each time your program stops. @xref{Expressions, ,Expressions}.
6524 @code{display} does not repeat if you press @key{RET} again after using it.
6526 @item display/@var{fmt} @var{expr}
6527 For @var{fmt} specifying only a display format and not a size or
6528 count, add the expression @var{expr} to the auto-display list but
6529 arrange to display it each time in the specified format @var{fmt}.
6530 @xref{Output Formats,,Output Formats}.
6532 @item display/@var{fmt} @var{addr}
6533 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6534 number of units, add the expression @var{addr} as a memory address to
6535 be examined each time your program stops. Examining means in effect
6536 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6539 For example, @samp{display/i $pc} can be helpful, to see the machine
6540 instruction about to be executed each time execution stops (@samp{$pc}
6541 is a common name for the program counter; @pxref{Registers, ,Registers}).
6544 @kindex delete display
6546 @item undisplay @var{dnums}@dots{}
6547 @itemx delete display @var{dnums}@dots{}
6548 Remove item numbers @var{dnums} from the list of expressions to display.
6550 @code{undisplay} does not repeat if you press @key{RET} after using it.
6551 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6553 @kindex disable display
6554 @item disable display @var{dnums}@dots{}
6555 Disable the display of item numbers @var{dnums}. A disabled display
6556 item is not printed automatically, but is not forgotten. It may be
6557 enabled again later.
6559 @kindex enable display
6560 @item enable display @var{dnums}@dots{}
6561 Enable display of item numbers @var{dnums}. It becomes effective once
6562 again in auto display of its expression, until you specify otherwise.
6565 Display the current values of the expressions on the list, just as is
6566 done when your program stops.
6568 @kindex info display
6570 Print the list of expressions previously set up to display
6571 automatically, each one with its item number, but without showing the
6572 values. This includes disabled expressions, which are marked as such.
6573 It also includes expressions which would not be displayed right now
6574 because they refer to automatic variables not currently available.
6577 @cindex display disabled out of scope
6578 If a display expression refers to local variables, then it does not make
6579 sense outside the lexical context for which it was set up. Such an
6580 expression is disabled when execution enters a context where one of its
6581 variables is not defined. For example, if you give the command
6582 @code{display last_char} while inside a function with an argument
6583 @code{last_char}, @value{GDBN} displays this argument while your program
6584 continues to stop inside that function. When it stops elsewhere---where
6585 there is no variable @code{last_char}---the display is disabled
6586 automatically. The next time your program stops where @code{last_char}
6587 is meaningful, you can enable the display expression once again.
6589 @node Print Settings
6590 @section Print Settings
6592 @cindex format options
6593 @cindex print settings
6594 @value{GDBN} provides the following ways to control how arrays, structures,
6595 and symbols are printed.
6598 These settings are useful for debugging programs in any language:
6602 @item set print address
6603 @itemx set print address on
6604 @cindex print/don't print memory addresses
6605 @value{GDBN} prints memory addresses showing the location of stack
6606 traces, structure values, pointer values, breakpoints, and so forth,
6607 even when it also displays the contents of those addresses. The default
6608 is @code{on}. For example, this is what a stack frame display looks like with
6609 @code{set print address on}:
6614 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6616 530 if (lquote != def_lquote)
6620 @item set print address off
6621 Do not print addresses when displaying their contents. For example,
6622 this is the same stack frame displayed with @code{set print address off}:
6626 (@value{GDBP}) set print addr off
6628 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6629 530 if (lquote != def_lquote)
6633 You can use @samp{set print address off} to eliminate all machine
6634 dependent displays from the @value{GDBN} interface. For example, with
6635 @code{print address off}, you should get the same text for backtraces on
6636 all machines---whether or not they involve pointer arguments.
6639 @item show print address
6640 Show whether or not addresses are to be printed.
6643 When @value{GDBN} prints a symbolic address, it normally prints the
6644 closest earlier symbol plus an offset. If that symbol does not uniquely
6645 identify the address (for example, it is a name whose scope is a single
6646 source file), you may need to clarify. One way to do this is with
6647 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6648 you can set @value{GDBN} to print the source file and line number when
6649 it prints a symbolic address:
6652 @item set print symbol-filename on
6653 @cindex source file and line of a symbol
6654 @cindex symbol, source file and line
6655 Tell @value{GDBN} to print the source file name and line number of a
6656 symbol in the symbolic form of an address.
6658 @item set print symbol-filename off
6659 Do not print source file name and line number of a symbol. This is the
6662 @item show print symbol-filename
6663 Show whether or not @value{GDBN} will print the source file name and
6664 line number of a symbol in the symbolic form of an address.
6667 Another situation where it is helpful to show symbol filenames and line
6668 numbers is when disassembling code; @value{GDBN} shows you the line
6669 number and source file that corresponds to each instruction.
6671 Also, you may wish to see the symbolic form only if the address being
6672 printed is reasonably close to the closest earlier symbol:
6675 @item set print max-symbolic-offset @var{max-offset}
6676 @cindex maximum value for offset of closest symbol
6677 Tell @value{GDBN} to only display the symbolic form of an address if the
6678 offset between the closest earlier symbol and the address is less than
6679 @var{max-offset}. The default is 0, which tells @value{GDBN}
6680 to always print the symbolic form of an address if any symbol precedes it.
6682 @item show print max-symbolic-offset
6683 Ask how large the maximum offset is that @value{GDBN} prints in a
6687 @cindex wild pointer, interpreting
6688 @cindex pointer, finding referent
6689 If you have a pointer and you are not sure where it points, try
6690 @samp{set print symbol-filename on}. Then you can determine the name
6691 and source file location of the variable where it points, using
6692 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6693 For example, here @value{GDBN} shows that a variable @code{ptt} points
6694 at another variable @code{t}, defined in @file{hi2.c}:
6697 (@value{GDBP}) set print symbol-filename on
6698 (@value{GDBP}) p/a ptt
6699 $4 = 0xe008 <t in hi2.c>
6703 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6704 does not show the symbol name and filename of the referent, even with
6705 the appropriate @code{set print} options turned on.
6708 Other settings control how different kinds of objects are printed:
6711 @item set print array
6712 @itemx set print array on
6713 @cindex pretty print arrays
6714 Pretty print arrays. This format is more convenient to read,
6715 but uses more space. The default is off.
6717 @item set print array off
6718 Return to compressed format for arrays.
6720 @item show print array
6721 Show whether compressed or pretty format is selected for displaying
6724 @cindex print array indexes
6725 @item set print array-indexes
6726 @itemx set print array-indexes on
6727 Print the index of each element when displaying arrays. May be more
6728 convenient to locate a given element in the array or quickly find the
6729 index of a given element in that printed array. The default is off.
6731 @item set print array-indexes off
6732 Stop printing element indexes when displaying arrays.
6734 @item show print array-indexes
6735 Show whether the index of each element is printed when displaying
6738 @item set print elements @var{number-of-elements}
6739 @cindex number of array elements to print
6740 @cindex limit on number of printed array elements
6741 Set a limit on how many elements of an array @value{GDBN} will print.
6742 If @value{GDBN} is printing a large array, it stops printing after it has
6743 printed the number of elements set by the @code{set print elements} command.
6744 This limit also applies to the display of strings.
6745 When @value{GDBN} starts, this limit is set to 200.
6746 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6748 @item show print elements
6749 Display the number of elements of a large array that @value{GDBN} will print.
6750 If the number is 0, then the printing is unlimited.
6752 @item set print frame-arguments @var{value}
6753 @cindex printing frame argument values
6754 @cindex print all frame argument values
6755 @cindex print frame argument values for scalars only
6756 @cindex do not print frame argument values
6757 This command allows to control how the values of arguments are printed
6758 when the debugger prints a frame (@pxref{Frames}). The possible
6763 The values of all arguments are printed. This is the default.
6766 Print the value of an argument only if it is a scalar. The value of more
6767 complex arguments such as arrays, structures, unions, etc, is replaced
6768 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6771 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6776 None of the argument values are printed. Instead, the value of each argument
6777 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6780 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6785 By default, all argument values are always printed. But this command
6786 can be useful in several cases. For instance, it can be used to reduce
6787 the amount of information printed in each frame, making the backtrace
6788 more readable. Also, this command can be used to improve performance
6789 when displaying Ada frames, because the computation of large arguments
6790 can sometimes be CPU-intensive, especiallly in large applications.
6791 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6792 avoids this computation, thus speeding up the display of each Ada frame.
6794 @item show print frame-arguments
6795 Show how the value of arguments should be displayed when printing a frame.
6797 @item set print repeats
6798 @cindex repeated array elements
6799 Set the threshold for suppressing display of repeated array
6800 elements. When the number of consecutive identical elements of an
6801 array exceeds the threshold, @value{GDBN} prints the string
6802 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6803 identical repetitions, instead of displaying the identical elements
6804 themselves. Setting the threshold to zero will cause all elements to
6805 be individually printed. The default threshold is 10.
6807 @item show print repeats
6808 Display the current threshold for printing repeated identical
6811 @item set print null-stop
6812 @cindex @sc{null} elements in arrays
6813 Cause @value{GDBN} to stop printing the characters of an array when the first
6814 @sc{null} is encountered. This is useful when large arrays actually
6815 contain only short strings.
6818 @item show print null-stop
6819 Show whether @value{GDBN} stops printing an array on the first
6820 @sc{null} character.
6822 @item set print pretty on
6823 @cindex print structures in indented form
6824 @cindex indentation in structure display
6825 Cause @value{GDBN} to print structures in an indented format with one member
6826 per line, like this:
6841 @item set print pretty off
6842 Cause @value{GDBN} to print structures in a compact format, like this:
6846 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6847 meat = 0x54 "Pork"@}
6852 This is the default format.
6854 @item show print pretty
6855 Show which format @value{GDBN} is using to print structures.
6857 @item set print sevenbit-strings on
6858 @cindex eight-bit characters in strings
6859 @cindex octal escapes in strings
6860 Print using only seven-bit characters; if this option is set,
6861 @value{GDBN} displays any eight-bit characters (in strings or
6862 character values) using the notation @code{\}@var{nnn}. This setting is
6863 best if you are working in English (@sc{ascii}) and you use the
6864 high-order bit of characters as a marker or ``meta'' bit.
6866 @item set print sevenbit-strings off
6867 Print full eight-bit characters. This allows the use of more
6868 international character sets, and is the default.
6870 @item show print sevenbit-strings
6871 Show whether or not @value{GDBN} is printing only seven-bit characters.
6873 @item set print union on
6874 @cindex unions in structures, printing
6875 Tell @value{GDBN} to print unions which are contained in structures
6876 and other unions. This is the default setting.
6878 @item set print union off
6879 Tell @value{GDBN} not to print unions which are contained in
6880 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6883 @item show print union
6884 Ask @value{GDBN} whether or not it will print unions which are contained in
6885 structures and other unions.
6887 For example, given the declarations
6890 typedef enum @{Tree, Bug@} Species;
6891 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6892 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6903 struct thing foo = @{Tree, @{Acorn@}@};
6907 with @code{set print union on} in effect @samp{p foo} would print
6910 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6914 and with @code{set print union off} in effect it would print
6917 $1 = @{it = Tree, form = @{...@}@}
6921 @code{set print union} affects programs written in C-like languages
6927 These settings are of interest when debugging C@t{++} programs:
6930 @cindex demangling C@t{++} names
6931 @item set print demangle
6932 @itemx set print demangle on
6933 Print C@t{++} names in their source form rather than in the encoded
6934 (``mangled'') form passed to the assembler and linker for type-safe
6935 linkage. The default is on.
6937 @item show print demangle
6938 Show whether C@t{++} names are printed in mangled or demangled form.
6940 @item set print asm-demangle
6941 @itemx set print asm-demangle on
6942 Print C@t{++} names in their source form rather than their mangled form, even
6943 in assembler code printouts such as instruction disassemblies.
6946 @item show print asm-demangle
6947 Show whether C@t{++} names in assembly listings are printed in mangled
6950 @cindex C@t{++} symbol decoding style
6951 @cindex symbol decoding style, C@t{++}
6952 @kindex set demangle-style
6953 @item set demangle-style @var{style}
6954 Choose among several encoding schemes used by different compilers to
6955 represent C@t{++} names. The choices for @var{style} are currently:
6959 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6962 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6963 This is the default.
6966 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6969 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6972 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6973 @strong{Warning:} this setting alone is not sufficient to allow
6974 debugging @code{cfront}-generated executables. @value{GDBN} would
6975 require further enhancement to permit that.
6978 If you omit @var{style}, you will see a list of possible formats.
6980 @item show demangle-style
6981 Display the encoding style currently in use for decoding C@t{++} symbols.
6983 @item set print object
6984 @itemx set print object on
6985 @cindex derived type of an object, printing
6986 @cindex display derived types
6987 When displaying a pointer to an object, identify the @emph{actual}
6988 (derived) type of the object rather than the @emph{declared} type, using
6989 the virtual function table.
6991 @item set print object off
6992 Display only the declared type of objects, without reference to the
6993 virtual function table. This is the default setting.
6995 @item show print object
6996 Show whether actual, or declared, object types are displayed.
6998 @item set print static-members
6999 @itemx set print static-members on
7000 @cindex static members of C@t{++} objects
7001 Print static members when displaying a C@t{++} object. The default is on.
7003 @item set print static-members off
7004 Do not print static members when displaying a C@t{++} object.
7006 @item show print static-members
7007 Show whether C@t{++} static members are printed or not.
7009 @item set print pascal_static-members
7010 @itemx set print pascal_static-members on
7011 @cindex static members of Pascal objects
7012 @cindex Pascal objects, static members display
7013 Print static members when displaying a Pascal object. The default is on.
7015 @item set print pascal_static-members off
7016 Do not print static members when displaying a Pascal object.
7018 @item show print pascal_static-members
7019 Show whether Pascal static members are printed or not.
7021 @c These don't work with HP ANSI C++ yet.
7022 @item set print vtbl
7023 @itemx set print vtbl on
7024 @cindex pretty print C@t{++} virtual function tables
7025 @cindex virtual functions (C@t{++}) display
7026 @cindex VTBL display
7027 Pretty print C@t{++} virtual function tables. The default is off.
7028 (The @code{vtbl} commands do not work on programs compiled with the HP
7029 ANSI C@t{++} compiler (@code{aCC}).)
7031 @item set print vtbl off
7032 Do not pretty print C@t{++} virtual function tables.
7034 @item show print vtbl
7035 Show whether C@t{++} virtual function tables are pretty printed, or not.
7039 @section Value History
7041 @cindex value history
7042 @cindex history of values printed by @value{GDBN}
7043 Values printed by the @code{print} command are saved in the @value{GDBN}
7044 @dfn{value history}. This allows you to refer to them in other expressions.
7045 Values are kept until the symbol table is re-read or discarded
7046 (for example with the @code{file} or @code{symbol-file} commands).
7047 When the symbol table changes, the value history is discarded,
7048 since the values may contain pointers back to the types defined in the
7053 @cindex history number
7054 The values printed are given @dfn{history numbers} by which you can
7055 refer to them. These are successive integers starting with one.
7056 @code{print} shows you the history number assigned to a value by
7057 printing @samp{$@var{num} = } before the value; here @var{num} is the
7060 To refer to any previous value, use @samp{$} followed by the value's
7061 history number. The way @code{print} labels its output is designed to
7062 remind you of this. Just @code{$} refers to the most recent value in
7063 the history, and @code{$$} refers to the value before that.
7064 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7065 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7066 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7068 For example, suppose you have just printed a pointer to a structure and
7069 want to see the contents of the structure. It suffices to type
7075 If you have a chain of structures where the component @code{next} points
7076 to the next one, you can print the contents of the next one with this:
7083 You can print successive links in the chain by repeating this
7084 command---which you can do by just typing @key{RET}.
7086 Note that the history records values, not expressions. If the value of
7087 @code{x} is 4 and you type these commands:
7095 then the value recorded in the value history by the @code{print} command
7096 remains 4 even though the value of @code{x} has changed.
7101 Print the last ten values in the value history, with their item numbers.
7102 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7103 values} does not change the history.
7105 @item show values @var{n}
7106 Print ten history values centered on history item number @var{n}.
7109 Print ten history values just after the values last printed. If no more
7110 values are available, @code{show values +} produces no display.
7113 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7114 same effect as @samp{show values +}.
7116 @node Convenience Vars
7117 @section Convenience Variables
7119 @cindex convenience variables
7120 @cindex user-defined variables
7121 @value{GDBN} provides @dfn{convenience variables} that you can use within
7122 @value{GDBN} to hold on to a value and refer to it later. These variables
7123 exist entirely within @value{GDBN}; they are not part of your program, and
7124 setting a convenience variable has no direct effect on further execution
7125 of your program. That is why you can use them freely.
7127 Convenience variables are prefixed with @samp{$}. Any name preceded by
7128 @samp{$} can be used for a convenience variable, unless it is one of
7129 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7130 (Value history references, in contrast, are @emph{numbers} preceded
7131 by @samp{$}. @xref{Value History, ,Value History}.)
7133 You can save a value in a convenience variable with an assignment
7134 expression, just as you would set a variable in your program.
7138 set $foo = *object_ptr
7142 would save in @code{$foo} the value contained in the object pointed to by
7145 Using a convenience variable for the first time creates it, but its
7146 value is @code{void} until you assign a new value. You can alter the
7147 value with another assignment at any time.
7149 Convenience variables have no fixed types. You can assign a convenience
7150 variable any type of value, including structures and arrays, even if
7151 that variable already has a value of a different type. The convenience
7152 variable, when used as an expression, has the type of its current value.
7155 @kindex show convenience
7156 @cindex show all user variables
7157 @item show convenience
7158 Print a list of convenience variables used so far, and their values.
7159 Abbreviated @code{show conv}.
7161 @kindex init-if-undefined
7162 @cindex convenience variables, initializing
7163 @item init-if-undefined $@var{variable} = @var{expression}
7164 Set a convenience variable if it has not already been set. This is useful
7165 for user-defined commands that keep some state. It is similar, in concept,
7166 to using local static variables with initializers in C (except that
7167 convenience variables are global). It can also be used to allow users to
7168 override default values used in a command script.
7170 If the variable is already defined then the expression is not evaluated so
7171 any side-effects do not occur.
7174 One of the ways to use a convenience variable is as a counter to be
7175 incremented or a pointer to be advanced. For example, to print
7176 a field from successive elements of an array of structures:
7180 print bar[$i++]->contents
7184 Repeat that command by typing @key{RET}.
7186 Some convenience variables are created automatically by @value{GDBN} and given
7187 values likely to be useful.
7190 @vindex $_@r{, convenience variable}
7192 The variable @code{$_} is automatically set by the @code{x} command to
7193 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7194 commands which provide a default address for @code{x} to examine also
7195 set @code{$_} to that address; these commands include @code{info line}
7196 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7197 except when set by the @code{x} command, in which case it is a pointer
7198 to the type of @code{$__}.
7200 @vindex $__@r{, convenience variable}
7202 The variable @code{$__} is automatically set by the @code{x} command
7203 to the value found in the last address examined. Its type is chosen
7204 to match the format in which the data was printed.
7207 @vindex $_exitcode@r{, convenience variable}
7208 The variable @code{$_exitcode} is automatically set to the exit code when
7209 the program being debugged terminates.
7212 On HP-UX systems, if you refer to a function or variable name that
7213 begins with a dollar sign, @value{GDBN} searches for a user or system
7214 name first, before it searches for a convenience variable.
7220 You can refer to machine register contents, in expressions, as variables
7221 with names starting with @samp{$}. The names of registers are different
7222 for each machine; use @code{info registers} to see the names used on
7226 @kindex info registers
7227 @item info registers
7228 Print the names and values of all registers except floating-point
7229 and vector registers (in the selected stack frame).
7231 @kindex info all-registers
7232 @cindex floating point registers
7233 @item info all-registers
7234 Print the names and values of all registers, including floating-point
7235 and vector registers (in the selected stack frame).
7237 @item info registers @var{regname} @dots{}
7238 Print the @dfn{relativized} value of each specified register @var{regname}.
7239 As discussed in detail below, register values are normally relative to
7240 the selected stack frame. @var{regname} may be any register name valid on
7241 the machine you are using, with or without the initial @samp{$}.
7244 @cindex stack pointer register
7245 @cindex program counter register
7246 @cindex process status register
7247 @cindex frame pointer register
7248 @cindex standard registers
7249 @value{GDBN} has four ``standard'' register names that are available (in
7250 expressions) on most machines---whenever they do not conflict with an
7251 architecture's canonical mnemonics for registers. The register names
7252 @code{$pc} and @code{$sp} are used for the program counter register and
7253 the stack pointer. @code{$fp} is used for a register that contains a
7254 pointer to the current stack frame, and @code{$ps} is used for a
7255 register that contains the processor status. For example,
7256 you could print the program counter in hex with
7263 or print the instruction to be executed next with
7270 or add four to the stack pointer@footnote{This is a way of removing
7271 one word from the stack, on machines where stacks grow downward in
7272 memory (most machines, nowadays). This assumes that the innermost
7273 stack frame is selected; setting @code{$sp} is not allowed when other
7274 stack frames are selected. To pop entire frames off the stack,
7275 regardless of machine architecture, use @code{return};
7276 see @ref{Returning, ,Returning from a Function}.} with
7282 Whenever possible, these four standard register names are available on
7283 your machine even though the machine has different canonical mnemonics,
7284 so long as there is no conflict. The @code{info registers} command
7285 shows the canonical names. For example, on the SPARC, @code{info
7286 registers} displays the processor status register as @code{$psr} but you
7287 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7288 is an alias for the @sc{eflags} register.
7290 @value{GDBN} always considers the contents of an ordinary register as an
7291 integer when the register is examined in this way. Some machines have
7292 special registers which can hold nothing but floating point; these
7293 registers are considered to have floating point values. There is no way
7294 to refer to the contents of an ordinary register as floating point value
7295 (although you can @emph{print} it as a floating point value with
7296 @samp{print/f $@var{regname}}).
7298 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7299 means that the data format in which the register contents are saved by
7300 the operating system is not the same one that your program normally
7301 sees. For example, the registers of the 68881 floating point
7302 coprocessor are always saved in ``extended'' (raw) format, but all C
7303 programs expect to work with ``double'' (virtual) format. In such
7304 cases, @value{GDBN} normally works with the virtual format only (the format
7305 that makes sense for your program), but the @code{info registers} command
7306 prints the data in both formats.
7308 @cindex SSE registers (x86)
7309 @cindex MMX registers (x86)
7310 Some machines have special registers whose contents can be interpreted
7311 in several different ways. For example, modern x86-based machines
7312 have SSE and MMX registers that can hold several values packed
7313 together in several different formats. @value{GDBN} refers to such
7314 registers in @code{struct} notation:
7317 (@value{GDBP}) print $xmm1
7319 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7320 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7321 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7322 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7323 v4_int32 = @{0, 20657912, 11, 13@},
7324 v2_int64 = @{88725056443645952, 55834574859@},
7325 uint128 = 0x0000000d0000000b013b36f800000000
7330 To set values of such registers, you need to tell @value{GDBN} which
7331 view of the register you wish to change, as if you were assigning
7332 value to a @code{struct} member:
7335 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7338 Normally, register values are relative to the selected stack frame
7339 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7340 value that the register would contain if all stack frames farther in
7341 were exited and their saved registers restored. In order to see the
7342 true contents of hardware registers, you must select the innermost
7343 frame (with @samp{frame 0}).
7345 However, @value{GDBN} must deduce where registers are saved, from the machine
7346 code generated by your compiler. If some registers are not saved, or if
7347 @value{GDBN} is unable to locate the saved registers, the selected stack
7348 frame makes no difference.
7350 @node Floating Point Hardware
7351 @section Floating Point Hardware
7352 @cindex floating point
7354 Depending on the configuration, @value{GDBN} may be able to give
7355 you more information about the status of the floating point hardware.
7360 Display hardware-dependent information about the floating
7361 point unit. The exact contents and layout vary depending on the
7362 floating point chip. Currently, @samp{info float} is supported on
7363 the ARM and x86 machines.
7367 @section Vector Unit
7370 Depending on the configuration, @value{GDBN} may be able to give you
7371 more information about the status of the vector unit.
7376 Display information about the vector unit. The exact contents and
7377 layout vary depending on the hardware.
7380 @node OS Information
7381 @section Operating System Auxiliary Information
7382 @cindex OS information
7384 @value{GDBN} provides interfaces to useful OS facilities that can help
7385 you debug your program.
7387 @cindex @code{ptrace} system call
7388 @cindex @code{struct user} contents
7389 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7390 machines), it interfaces with the inferior via the @code{ptrace}
7391 system call. The operating system creates a special sata structure,
7392 called @code{struct user}, for this interface. You can use the
7393 command @code{info udot} to display the contents of this data
7399 Display the contents of the @code{struct user} maintained by the OS
7400 kernel for the program being debugged. @value{GDBN} displays the
7401 contents of @code{struct user} as a list of hex numbers, similar to
7402 the @code{examine} command.
7405 @cindex auxiliary vector
7406 @cindex vector, auxiliary
7407 Some operating systems supply an @dfn{auxiliary vector} to programs at
7408 startup. This is akin to the arguments and environment that you
7409 specify for a program, but contains a system-dependent variety of
7410 binary values that tell system libraries important details about the
7411 hardware, operating system, and process. Each value's purpose is
7412 identified by an integer tag; the meanings are well-known but system-specific.
7413 Depending on the configuration and operating system facilities,
7414 @value{GDBN} may be able to show you this information. For remote
7415 targets, this functionality may further depend on the remote stub's
7416 support of the @samp{qXfer:auxv:read} packet, see
7417 @ref{qXfer auxiliary vector read}.
7422 Display the auxiliary vector of the inferior, which can be either a
7423 live process or a core dump file. @value{GDBN} prints each tag value
7424 numerically, and also shows names and text descriptions for recognized
7425 tags. Some values in the vector are numbers, some bit masks, and some
7426 pointers to strings or other data. @value{GDBN} displays each value in the
7427 most appropriate form for a recognized tag, and in hexadecimal for
7428 an unrecognized tag.
7432 @node Memory Region Attributes
7433 @section Memory Region Attributes
7434 @cindex memory region attributes
7436 @dfn{Memory region attributes} allow you to describe special handling
7437 required by regions of your target's memory. @value{GDBN} uses
7438 attributes to determine whether to allow certain types of memory
7439 accesses; whether to use specific width accesses; and whether to cache
7440 target memory. By default the description of memory regions is
7441 fetched from the target (if the current target supports this), but the
7442 user can override the fetched regions.
7444 Defined memory regions can be individually enabled and disabled. When a
7445 memory region is disabled, @value{GDBN} uses the default attributes when
7446 accessing memory in that region. Similarly, if no memory regions have
7447 been defined, @value{GDBN} uses the default attributes when accessing
7450 When a memory region is defined, it is given a number to identify it;
7451 to enable, disable, or remove a memory region, you specify that number.
7455 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7456 Define a memory region bounded by @var{lower} and @var{upper} with
7457 attributes @var{attributes}@dots{}, and add it to the list of regions
7458 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7459 case: it is treated as the target's maximum memory address.
7460 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7463 Discard any user changes to the memory regions and use target-supplied
7464 regions, if available, or no regions if the target does not support.
7467 @item delete mem @var{nums}@dots{}
7468 Remove memory regions @var{nums}@dots{} from the list of regions
7469 monitored by @value{GDBN}.
7472 @item disable mem @var{nums}@dots{}
7473 Disable monitoring of memory regions @var{nums}@dots{}.
7474 A disabled memory region is not forgotten.
7475 It may be enabled again later.
7478 @item enable mem @var{nums}@dots{}
7479 Enable monitoring of memory regions @var{nums}@dots{}.
7483 Print a table of all defined memory regions, with the following columns
7487 @item Memory Region Number
7488 @item Enabled or Disabled.
7489 Enabled memory regions are marked with @samp{y}.
7490 Disabled memory regions are marked with @samp{n}.
7493 The address defining the inclusive lower bound of the memory region.
7496 The address defining the exclusive upper bound of the memory region.
7499 The list of attributes set for this memory region.
7504 @subsection Attributes
7506 @subsubsection Memory Access Mode
7507 The access mode attributes set whether @value{GDBN} may make read or
7508 write accesses to a memory region.
7510 While these attributes prevent @value{GDBN} from performing invalid
7511 memory accesses, they do nothing to prevent the target system, I/O DMA,
7512 etc.@: from accessing memory.
7516 Memory is read only.
7518 Memory is write only.
7520 Memory is read/write. This is the default.
7523 @subsubsection Memory Access Size
7524 The access size attribute tells @value{GDBN} to use specific sized
7525 accesses in the memory region. Often memory mapped device registers
7526 require specific sized accesses. If no access size attribute is
7527 specified, @value{GDBN} may use accesses of any size.
7531 Use 8 bit memory accesses.
7533 Use 16 bit memory accesses.
7535 Use 32 bit memory accesses.
7537 Use 64 bit memory accesses.
7540 @c @subsubsection Hardware/Software Breakpoints
7541 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7542 @c will use hardware or software breakpoints for the internal breakpoints
7543 @c used by the step, next, finish, until, etc. commands.
7547 @c Always use hardware breakpoints
7548 @c @item swbreak (default)
7551 @subsubsection Data Cache
7552 The data cache attributes set whether @value{GDBN} will cache target
7553 memory. While this generally improves performance by reducing debug
7554 protocol overhead, it can lead to incorrect results because @value{GDBN}
7555 does not know about volatile variables or memory mapped device
7560 Enable @value{GDBN} to cache target memory.
7562 Disable @value{GDBN} from caching target memory. This is the default.
7565 @subsection Memory Access Checking
7566 @value{GDBN} can be instructed to refuse accesses to memory that is
7567 not explicitly described. This can be useful if accessing such
7568 regions has undesired effects for a specific target, or to provide
7569 better error checking. The following commands control this behaviour.
7572 @kindex set mem inaccessible-by-default
7573 @item set mem inaccessible-by-default [on|off]
7574 If @code{on} is specified, make @value{GDBN} treat memory not
7575 explicitly described by the memory ranges as non-existent and refuse accesses
7576 to such memory. The checks are only performed if there's at least one
7577 memory range defined. If @code{off} is specified, make @value{GDBN}
7578 treat the memory not explicitly described by the memory ranges as RAM.
7579 The default value is @code{on}.
7580 @kindex show mem inaccessible-by-default
7581 @item show mem inaccessible-by-default
7582 Show the current handling of accesses to unknown memory.
7586 @c @subsubsection Memory Write Verification
7587 @c The memory write verification attributes set whether @value{GDBN}
7588 @c will re-reads data after each write to verify the write was successful.
7592 @c @item noverify (default)
7595 @node Dump/Restore Files
7596 @section Copy Between Memory and a File
7597 @cindex dump/restore files
7598 @cindex append data to a file
7599 @cindex dump data to a file
7600 @cindex restore data from a file
7602 You can use the commands @code{dump}, @code{append}, and
7603 @code{restore} to copy data between target memory and a file. The
7604 @code{dump} and @code{append} commands write data to a file, and the
7605 @code{restore} command reads data from a file back into the inferior's
7606 memory. Files may be in binary, Motorola S-record, Intel hex, or
7607 Tektronix Hex format; however, @value{GDBN} can only append to binary
7613 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7614 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7615 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7616 or the value of @var{expr}, to @var{filename} in the given format.
7618 The @var{format} parameter may be any one of:
7625 Motorola S-record format.
7627 Tektronix Hex format.
7630 @value{GDBN} uses the same definitions of these formats as the
7631 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7632 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7636 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7637 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7638 Append the contents of memory from @var{start_addr} to @var{end_addr},
7639 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7640 (@value{GDBN} can only append data to files in raw binary form.)
7643 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7644 Restore the contents of file @var{filename} into memory. The
7645 @code{restore} command can automatically recognize any known @sc{bfd}
7646 file format, except for raw binary. To restore a raw binary file you
7647 must specify the optional keyword @code{binary} after the filename.
7649 If @var{bias} is non-zero, its value will be added to the addresses
7650 contained in the file. Binary files always start at address zero, so
7651 they will be restored at address @var{bias}. Other bfd files have
7652 a built-in location; they will be restored at offset @var{bias}
7655 If @var{start} and/or @var{end} are non-zero, then only data between
7656 file offset @var{start} and file offset @var{end} will be restored.
7657 These offsets are relative to the addresses in the file, before
7658 the @var{bias} argument is applied.
7662 @node Core File Generation
7663 @section How to Produce a Core File from Your Program
7664 @cindex dump core from inferior
7666 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7667 image of a running process and its process status (register values
7668 etc.). Its primary use is post-mortem debugging of a program that
7669 crashed while it ran outside a debugger. A program that crashes
7670 automatically produces a core file, unless this feature is disabled by
7671 the user. @xref{Files}, for information on invoking @value{GDBN} in
7672 the post-mortem debugging mode.
7674 Occasionally, you may wish to produce a core file of the program you
7675 are debugging in order to preserve a snapshot of its state.
7676 @value{GDBN} has a special command for that.
7680 @kindex generate-core-file
7681 @item generate-core-file [@var{file}]
7682 @itemx gcore [@var{file}]
7683 Produce a core dump of the inferior process. The optional argument
7684 @var{file} specifies the file name where to put the core dump. If not
7685 specified, the file name defaults to @file{core.@var{pid}}, where
7686 @var{pid} is the inferior process ID.
7688 Note that this command is implemented only for some systems (as of
7689 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7692 @node Character Sets
7693 @section Character Sets
7694 @cindex character sets
7696 @cindex translating between character sets
7697 @cindex host character set
7698 @cindex target character set
7700 If the program you are debugging uses a different character set to
7701 represent characters and strings than the one @value{GDBN} uses itself,
7702 @value{GDBN} can automatically translate between the character sets for
7703 you. The character set @value{GDBN} uses we call the @dfn{host
7704 character set}; the one the inferior program uses we call the
7705 @dfn{target character set}.
7707 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7708 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7709 remote protocol (@pxref{Remote Debugging}) to debug a program
7710 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7711 then the host character set is Latin-1, and the target character set is
7712 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7713 target-charset EBCDIC-US}, then @value{GDBN} translates between
7714 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7715 character and string literals in expressions.
7717 @value{GDBN} has no way to automatically recognize which character set
7718 the inferior program uses; you must tell it, using the @code{set
7719 target-charset} command, described below.
7721 Here are the commands for controlling @value{GDBN}'s character set
7725 @item set target-charset @var{charset}
7726 @kindex set target-charset
7727 Set the current target character set to @var{charset}. We list the
7728 character set names @value{GDBN} recognizes below, but if you type
7729 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7730 list the target character sets it supports.
7734 @item set host-charset @var{charset}
7735 @kindex set host-charset
7736 Set the current host character set to @var{charset}.
7738 By default, @value{GDBN} uses a host character set appropriate to the
7739 system it is running on; you can override that default using the
7740 @code{set host-charset} command.
7742 @value{GDBN} can only use certain character sets as its host character
7743 set. We list the character set names @value{GDBN} recognizes below, and
7744 indicate which can be host character sets, but if you type
7745 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7746 list the host character sets it supports.
7748 @item set charset @var{charset}
7750 Set the current host and target character sets to @var{charset}. As
7751 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7752 @value{GDBN} will list the name of the character sets that can be used
7753 for both host and target.
7757 @kindex show charset
7758 Show the names of the current host and target charsets.
7760 @itemx show host-charset
7761 @kindex show host-charset
7762 Show the name of the current host charset.
7764 @itemx show target-charset
7765 @kindex show target-charset
7766 Show the name of the current target charset.
7770 @value{GDBN} currently includes support for the following character
7776 @cindex ASCII character set
7777 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7781 @cindex ISO 8859-1 character set
7782 @cindex ISO Latin 1 character set
7783 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7784 characters needed for French, German, and Spanish. @value{GDBN} can use
7785 this as its host character set.
7789 @cindex EBCDIC character set
7790 @cindex IBM1047 character set
7791 Variants of the @sc{ebcdic} character set, used on some of IBM's
7792 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7793 @value{GDBN} cannot use these as its host character set.
7797 Note that these are all single-byte character sets. More work inside
7798 @value{GDBN} is needed to support multi-byte or variable-width character
7799 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7801 Here is an example of @value{GDBN}'s character set support in action.
7802 Assume that the following source code has been placed in the file
7803 @file{charset-test.c}:
7809 = @{72, 101, 108, 108, 111, 44, 32, 119,
7810 111, 114, 108, 100, 33, 10, 0@};
7811 char ibm1047_hello[]
7812 = @{200, 133, 147, 147, 150, 107, 64, 166,
7813 150, 153, 147, 132, 90, 37, 0@};
7817 printf ("Hello, world!\n");
7821 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7822 containing the string @samp{Hello, world!} followed by a newline,
7823 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7825 We compile the program, and invoke the debugger on it:
7828 $ gcc -g charset-test.c -o charset-test
7829 $ gdb -nw charset-test
7830 GNU gdb 2001-12-19-cvs
7831 Copyright 2001 Free Software Foundation, Inc.
7836 We can use the @code{show charset} command to see what character sets
7837 @value{GDBN} is currently using to interpret and display characters and
7841 (@value{GDBP}) show charset
7842 The current host and target character set is `ISO-8859-1'.
7846 For the sake of printing this manual, let's use @sc{ascii} as our
7847 initial character set:
7849 (@value{GDBP}) set charset ASCII
7850 (@value{GDBP}) show charset
7851 The current host and target character set is `ASCII'.
7855 Let's assume that @sc{ascii} is indeed the correct character set for our
7856 host system --- in other words, let's assume that if @value{GDBN} prints
7857 characters using the @sc{ascii} character set, our terminal will display
7858 them properly. Since our current target character set is also
7859 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7862 (@value{GDBP}) print ascii_hello
7863 $1 = 0x401698 "Hello, world!\n"
7864 (@value{GDBP}) print ascii_hello[0]
7869 @value{GDBN} uses the target character set for character and string
7870 literals you use in expressions:
7873 (@value{GDBP}) print '+'
7878 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7881 @value{GDBN} relies on the user to tell it which character set the
7882 target program uses. If we print @code{ibm1047_hello} while our target
7883 character set is still @sc{ascii}, we get jibberish:
7886 (@value{GDBP}) print ibm1047_hello
7887 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7888 (@value{GDBP}) print ibm1047_hello[0]
7893 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7894 @value{GDBN} tells us the character sets it supports:
7897 (@value{GDBP}) set target-charset
7898 ASCII EBCDIC-US IBM1047 ISO-8859-1
7899 (@value{GDBP}) set target-charset
7902 We can select @sc{ibm1047} as our target character set, and examine the
7903 program's strings again. Now the @sc{ascii} string is wrong, but
7904 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7905 target character set, @sc{ibm1047}, to the host character set,
7906 @sc{ascii}, and they display correctly:
7909 (@value{GDBP}) set target-charset IBM1047
7910 (@value{GDBP}) show charset
7911 The current host character set is `ASCII'.
7912 The current target character set is `IBM1047'.
7913 (@value{GDBP}) print ascii_hello
7914 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7915 (@value{GDBP}) print ascii_hello[0]
7917 (@value{GDBP}) print ibm1047_hello
7918 $8 = 0x4016a8 "Hello, world!\n"
7919 (@value{GDBP}) print ibm1047_hello[0]
7924 As above, @value{GDBN} uses the target character set for character and
7925 string literals you use in expressions:
7928 (@value{GDBP}) print '+'
7933 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7936 @node Caching Remote Data
7937 @section Caching Data of Remote Targets
7938 @cindex caching data of remote targets
7940 @value{GDBN} can cache data exchanged between the debugger and a
7941 remote target (@pxref{Remote Debugging}). Such caching generally improves
7942 performance, because it reduces the overhead of the remote protocol by
7943 bundling memory reads and writes into large chunks. Unfortunately,
7944 @value{GDBN} does not currently know anything about volatile
7945 registers, and thus data caching will produce incorrect results when
7946 volatile registers are in use.
7949 @kindex set remotecache
7950 @item set remotecache on
7951 @itemx set remotecache off
7952 Set caching state for remote targets. When @code{ON}, use data
7953 caching. By default, this option is @code{OFF}.
7955 @kindex show remotecache
7956 @item show remotecache
7957 Show the current state of data caching for remote targets.
7961 Print the information about the data cache performance. The
7962 information displayed includes: the dcache width and depth; and for
7963 each cache line, how many times it was referenced, and its data and
7964 state (dirty, bad, ok, etc.). This command is useful for debugging
7965 the data cache operation.
7968 @node Searching Memory
7969 @section Search Memory
7970 @cindex searching memory
7972 Memory can be searched for a particular sequence of bytes with the
7973 @code{find} command.
7977 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
7978 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
7979 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
7980 etc. The search begins at address @var{start_addr} and continues for either
7981 @var{len} bytes or through to @var{end_addr} inclusive.
7984 @var{s} and @var{n} are optional parameters.
7985 They may be specified in either order, apart or together.
7988 @item @var{s}, search query size
7989 The size of each search query value.
7995 halfwords (two bytes)
7999 giant words (eight bytes)
8002 All values are interpreted in the current language.
8003 This means, for example, that if the current source language is C/C@t{++}
8004 then searching for the string ``hello'' includes the trailing '\0'.
8006 If the value size is not specified, it is taken from the
8007 value's type in the current language.
8008 This is useful when one wants to specify the search
8009 pattern as a mixture of types.
8010 Note that this means, for example, that in the case of C-like languages
8011 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8012 which is typically four bytes.
8014 @item @var{n}, maximum number of finds
8015 The maximum number of matches to print. The default is to print all finds.
8018 You can use strings as search values. Quote them with double-quotes
8020 The string value is copied into the search pattern byte by byte,
8021 regardless of the endianness of the target and the size specification.
8023 The address of each match found is printed as well as a count of the
8024 number of matches found.
8026 The address of the last value found is stored in convenience variable
8028 A count of the number of matches is stored in @samp{$numfound}.
8030 For example, if stopped at the @code{printf} in this function:
8036 static char hello[] = "hello-hello";
8037 static struct @{ char c; short s; int i; @}
8038 __attribute__ ((packed)) mixed
8039 = @{ 'c', 0x1234, 0x87654321 @};
8040 printf ("%s\n", hello);
8045 you get during debugging:
8048 (gdb) find &hello[0], +sizeof(hello), "hello"
8049 0x804956d <hello.1620+6>
8051 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8052 0x8049567 <hello.1620>
8053 0x804956d <hello.1620+6>
8055 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8056 0x8049567 <hello.1620>
8058 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8059 0x8049560 <mixed.1625>
8061 (gdb) print $numfound
8064 $2 = (void *) 0x8049560
8068 @chapter C Preprocessor Macros
8070 Some languages, such as C and C@t{++}, provide a way to define and invoke
8071 ``preprocessor macros'' which expand into strings of tokens.
8072 @value{GDBN} can evaluate expressions containing macro invocations, show
8073 the result of macro expansion, and show a macro's definition, including
8074 where it was defined.
8076 You may need to compile your program specially to provide @value{GDBN}
8077 with information about preprocessor macros. Most compilers do not
8078 include macros in their debugging information, even when you compile
8079 with the @option{-g} flag. @xref{Compilation}.
8081 A program may define a macro at one point, remove that definition later,
8082 and then provide a different definition after that. Thus, at different
8083 points in the program, a macro may have different definitions, or have
8084 no definition at all. If there is a current stack frame, @value{GDBN}
8085 uses the macros in scope at that frame's source code line. Otherwise,
8086 @value{GDBN} uses the macros in scope at the current listing location;
8089 At the moment, @value{GDBN} does not support the @code{##}
8090 token-splicing operator, the @code{#} stringification operator, or
8091 variable-arity macros.
8093 Whenever @value{GDBN} evaluates an expression, it always expands any
8094 macro invocations present in the expression. @value{GDBN} also provides
8095 the following commands for working with macros explicitly.
8099 @kindex macro expand
8100 @cindex macro expansion, showing the results of preprocessor
8101 @cindex preprocessor macro expansion, showing the results of
8102 @cindex expanding preprocessor macros
8103 @item macro expand @var{expression}
8104 @itemx macro exp @var{expression}
8105 Show the results of expanding all preprocessor macro invocations in
8106 @var{expression}. Since @value{GDBN} simply expands macros, but does
8107 not parse the result, @var{expression} need not be a valid expression;
8108 it can be any string of tokens.
8111 @item macro expand-once @var{expression}
8112 @itemx macro exp1 @var{expression}
8113 @cindex expand macro once
8114 @i{(This command is not yet implemented.)} Show the results of
8115 expanding those preprocessor macro invocations that appear explicitly in
8116 @var{expression}. Macro invocations appearing in that expansion are
8117 left unchanged. This command allows you to see the effect of a
8118 particular macro more clearly, without being confused by further
8119 expansions. Since @value{GDBN} simply expands macros, but does not
8120 parse the result, @var{expression} need not be a valid expression; it
8121 can be any string of tokens.
8124 @cindex macro definition, showing
8125 @cindex definition, showing a macro's
8126 @item info macro @var{macro}
8127 Show the definition of the macro named @var{macro}, and describe the
8128 source location where that definition was established.
8130 @kindex macro define
8131 @cindex user-defined macros
8132 @cindex defining macros interactively
8133 @cindex macros, user-defined
8134 @item macro define @var{macro} @var{replacement-list}
8135 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8136 Introduce a definition for a preprocessor macro named @var{macro},
8137 invocations of which are replaced by the tokens given in
8138 @var{replacement-list}. The first form of this command defines an
8139 ``object-like'' macro, which takes no arguments; the second form
8140 defines a ``function-like'' macro, which takes the arguments given in
8143 A definition introduced by this command is in scope in every
8144 expression evaluated in @value{GDBN}, until it is removed with the
8145 @code{macro undef} command, described below. The definition overrides
8146 all definitions for @var{macro} present in the program being debugged,
8147 as well as any previous user-supplied definition.
8150 @item macro undef @var{macro}
8151 Remove any user-supplied definition for the macro named @var{macro}.
8152 This command only affects definitions provided with the @code{macro
8153 define} command, described above; it cannot remove definitions present
8154 in the program being debugged.
8158 List all the macros defined using the @code{macro define} command.
8161 @cindex macros, example of debugging with
8162 Here is a transcript showing the above commands in action. First, we
8163 show our source files:
8171 #define ADD(x) (M + x)
8176 printf ("Hello, world!\n");
8178 printf ("We're so creative.\n");
8180 printf ("Goodbye, world!\n");
8187 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8188 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8189 compiler includes information about preprocessor macros in the debugging
8193 $ gcc -gdwarf-2 -g3 sample.c -o sample
8197 Now, we start @value{GDBN} on our sample program:
8201 GNU gdb 2002-05-06-cvs
8202 Copyright 2002 Free Software Foundation, Inc.
8203 GDB is free software, @dots{}
8207 We can expand macros and examine their definitions, even when the
8208 program is not running. @value{GDBN} uses the current listing position
8209 to decide which macro definitions are in scope:
8212 (@value{GDBP}) list main
8215 5 #define ADD(x) (M + x)
8220 10 printf ("Hello, world!\n");
8222 12 printf ("We're so creative.\n");
8223 (@value{GDBP}) info macro ADD
8224 Defined at /home/jimb/gdb/macros/play/sample.c:5
8225 #define ADD(x) (M + x)
8226 (@value{GDBP}) info macro Q
8227 Defined at /home/jimb/gdb/macros/play/sample.h:1
8228 included at /home/jimb/gdb/macros/play/sample.c:2
8230 (@value{GDBP}) macro expand ADD(1)
8231 expands to: (42 + 1)
8232 (@value{GDBP}) macro expand-once ADD(1)
8233 expands to: once (M + 1)
8237 In the example above, note that @code{macro expand-once} expands only
8238 the macro invocation explicit in the original text --- the invocation of
8239 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8240 which was introduced by @code{ADD}.
8242 Once the program is running, @value{GDBN} uses the macro definitions in
8243 force at the source line of the current stack frame:
8246 (@value{GDBP}) break main
8247 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8249 Starting program: /home/jimb/gdb/macros/play/sample
8251 Breakpoint 1, main () at sample.c:10
8252 10 printf ("Hello, world!\n");
8256 At line 10, the definition of the macro @code{N} at line 9 is in force:
8259 (@value{GDBP}) info macro N
8260 Defined at /home/jimb/gdb/macros/play/sample.c:9
8262 (@value{GDBP}) macro expand N Q M
8264 (@value{GDBP}) print N Q M
8269 As we step over directives that remove @code{N}'s definition, and then
8270 give it a new definition, @value{GDBN} finds the definition (or lack
8271 thereof) in force at each point:
8276 12 printf ("We're so creative.\n");
8277 (@value{GDBP}) info macro N
8278 The symbol `N' has no definition as a C/C++ preprocessor macro
8279 at /home/jimb/gdb/macros/play/sample.c:12
8282 14 printf ("Goodbye, world!\n");
8283 (@value{GDBP}) info macro N
8284 Defined at /home/jimb/gdb/macros/play/sample.c:13
8286 (@value{GDBP}) macro expand N Q M
8287 expands to: 1729 < 42
8288 (@value{GDBP}) print N Q M
8295 @chapter Tracepoints
8296 @c This chapter is based on the documentation written by Michael
8297 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8300 In some applications, it is not feasible for the debugger to interrupt
8301 the program's execution long enough for the developer to learn
8302 anything helpful about its behavior. If the program's correctness
8303 depends on its real-time behavior, delays introduced by a debugger
8304 might cause the program to change its behavior drastically, or perhaps
8305 fail, even when the code itself is correct. It is useful to be able
8306 to observe the program's behavior without interrupting it.
8308 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8309 specify locations in the program, called @dfn{tracepoints}, and
8310 arbitrary expressions to evaluate when those tracepoints are reached.
8311 Later, using the @code{tfind} command, you can examine the values
8312 those expressions had when the program hit the tracepoints. The
8313 expressions may also denote objects in memory---structures or arrays,
8314 for example---whose values @value{GDBN} should record; while visiting
8315 a particular tracepoint, you may inspect those objects as if they were
8316 in memory at that moment. However, because @value{GDBN} records these
8317 values without interacting with you, it can do so quickly and
8318 unobtrusively, hopefully not disturbing the program's behavior.
8320 The tracepoint facility is currently available only for remote
8321 targets. @xref{Targets}. In addition, your remote target must know
8322 how to collect trace data. This functionality is implemented in the
8323 remote stub; however, none of the stubs distributed with @value{GDBN}
8324 support tracepoints as of this writing. The format of the remote
8325 packets used to implement tracepoints are described in @ref{Tracepoint
8328 This chapter describes the tracepoint commands and features.
8332 * Analyze Collected Data::
8333 * Tracepoint Variables::
8336 @node Set Tracepoints
8337 @section Commands to Set Tracepoints
8339 Before running such a @dfn{trace experiment}, an arbitrary number of
8340 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8341 tracepoint has a number assigned to it by @value{GDBN}. Like with
8342 breakpoints, tracepoint numbers are successive integers starting from
8343 one. Many of the commands associated with tracepoints take the
8344 tracepoint number as their argument, to identify which tracepoint to
8347 For each tracepoint, you can specify, in advance, some arbitrary set
8348 of data that you want the target to collect in the trace buffer when
8349 it hits that tracepoint. The collected data can include registers,
8350 local variables, or global data. Later, you can use @value{GDBN}
8351 commands to examine the values these data had at the time the
8354 This section describes commands to set tracepoints and associated
8355 conditions and actions.
8358 * Create and Delete Tracepoints::
8359 * Enable and Disable Tracepoints::
8360 * Tracepoint Passcounts::
8361 * Tracepoint Actions::
8362 * Listing Tracepoints::
8363 * Starting and Stopping Trace Experiments::
8366 @node Create and Delete Tracepoints
8367 @subsection Create and Delete Tracepoints
8370 @cindex set tracepoint
8373 The @code{trace} command is very similar to the @code{break} command.
8374 Its argument can be a source line, a function name, or an address in
8375 the target program. @xref{Set Breaks}. The @code{trace} command
8376 defines a tracepoint, which is a point in the target program where the
8377 debugger will briefly stop, collect some data, and then allow the
8378 program to continue. Setting a tracepoint or changing its commands
8379 doesn't take effect until the next @code{tstart} command; thus, you
8380 cannot change the tracepoint attributes once a trace experiment is
8383 Here are some examples of using the @code{trace} command:
8386 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8388 (@value{GDBP}) @b{trace +2} // 2 lines forward
8390 (@value{GDBP}) @b{trace my_function} // first source line of function
8392 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8394 (@value{GDBP}) @b{trace *0x2117c4} // an address
8398 You can abbreviate @code{trace} as @code{tr}.
8401 @cindex last tracepoint number
8402 @cindex recent tracepoint number
8403 @cindex tracepoint number
8404 The convenience variable @code{$tpnum} records the tracepoint number
8405 of the most recently set tracepoint.
8407 @kindex delete tracepoint
8408 @cindex tracepoint deletion
8409 @item delete tracepoint @r{[}@var{num}@r{]}
8410 Permanently delete one or more tracepoints. With no argument, the
8411 default is to delete all tracepoints.
8416 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8418 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8422 You can abbreviate this command as @code{del tr}.
8425 @node Enable and Disable Tracepoints
8426 @subsection Enable and Disable Tracepoints
8429 @kindex disable tracepoint
8430 @item disable tracepoint @r{[}@var{num}@r{]}
8431 Disable tracepoint @var{num}, or all tracepoints if no argument
8432 @var{num} is given. A disabled tracepoint will have no effect during
8433 the next trace experiment, but it is not forgotten. You can re-enable
8434 a disabled tracepoint using the @code{enable tracepoint} command.
8436 @kindex enable tracepoint
8437 @item enable tracepoint @r{[}@var{num}@r{]}
8438 Enable tracepoint @var{num}, or all tracepoints. The enabled
8439 tracepoints will become effective the next time a trace experiment is
8443 @node Tracepoint Passcounts
8444 @subsection Tracepoint Passcounts
8448 @cindex tracepoint pass count
8449 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8450 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8451 automatically stop a trace experiment. If a tracepoint's passcount is
8452 @var{n}, then the trace experiment will be automatically stopped on
8453 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8454 @var{num} is not specified, the @code{passcount} command sets the
8455 passcount of the most recently defined tracepoint. If no passcount is
8456 given, the trace experiment will run until stopped explicitly by the
8462 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8463 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8465 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8466 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8467 (@value{GDBP}) @b{trace foo}
8468 (@value{GDBP}) @b{pass 3}
8469 (@value{GDBP}) @b{trace bar}
8470 (@value{GDBP}) @b{pass 2}
8471 (@value{GDBP}) @b{trace baz}
8472 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8473 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8474 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8475 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8479 @node Tracepoint Actions
8480 @subsection Tracepoint Action Lists
8484 @cindex tracepoint actions
8485 @item actions @r{[}@var{num}@r{]}
8486 This command will prompt for a list of actions to be taken when the
8487 tracepoint is hit. If the tracepoint number @var{num} is not
8488 specified, this command sets the actions for the one that was most
8489 recently defined (so that you can define a tracepoint and then say
8490 @code{actions} without bothering about its number). You specify the
8491 actions themselves on the following lines, one action at a time, and
8492 terminate the actions list with a line containing just @code{end}. So
8493 far, the only defined actions are @code{collect} and
8494 @code{while-stepping}.
8496 @cindex remove actions from a tracepoint
8497 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8498 and follow it immediately with @samp{end}.
8501 (@value{GDBP}) @b{collect @var{data}} // collect some data
8503 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8505 (@value{GDBP}) @b{end} // signals the end of actions.
8508 In the following example, the action list begins with @code{collect}
8509 commands indicating the things to be collected when the tracepoint is
8510 hit. Then, in order to single-step and collect additional data
8511 following the tracepoint, a @code{while-stepping} command is used,
8512 followed by the list of things to be collected while stepping. The
8513 @code{while-stepping} command is terminated by its own separate
8514 @code{end} command. Lastly, the action list is terminated by an
8518 (@value{GDBP}) @b{trace foo}
8519 (@value{GDBP}) @b{actions}
8520 Enter actions for tracepoint 1, one per line:
8529 @kindex collect @r{(tracepoints)}
8530 @item collect @var{expr1}, @var{expr2}, @dots{}
8531 Collect values of the given expressions when the tracepoint is hit.
8532 This command accepts a comma-separated list of any valid expressions.
8533 In addition to global, static, or local variables, the following
8534 special arguments are supported:
8538 collect all registers
8541 collect all function arguments
8544 collect all local variables.
8547 You can give several consecutive @code{collect} commands, each one
8548 with a single argument, or one @code{collect} command with several
8549 arguments separated by commas: the effect is the same.
8551 The command @code{info scope} (@pxref{Symbols, info scope}) is
8552 particularly useful for figuring out what data to collect.
8554 @kindex while-stepping @r{(tracepoints)}
8555 @item while-stepping @var{n}
8556 Perform @var{n} single-step traces after the tracepoint, collecting
8557 new data at each step. The @code{while-stepping} command is
8558 followed by the list of what to collect while stepping (followed by
8559 its own @code{end} command):
8563 > collect $regs, myglobal
8569 You may abbreviate @code{while-stepping} as @code{ws} or
8573 @node Listing Tracepoints
8574 @subsection Listing Tracepoints
8577 @kindex info tracepoints
8579 @cindex information about tracepoints
8580 @item info tracepoints @r{[}@var{num}@r{]}
8581 Display information about the tracepoint @var{num}. If you don't specify
8582 a tracepoint number, displays information about all the tracepoints
8583 defined so far. For each tracepoint, the following information is
8590 whether it is enabled or disabled
8594 its passcount as given by the @code{passcount @var{n}} command
8596 its step count as given by the @code{while-stepping @var{n}} command
8598 where in the source files is the tracepoint set
8600 its action list as given by the @code{actions} command
8604 (@value{GDBP}) @b{info trace}
8605 Num Enb Address PassC StepC What
8606 1 y 0x002117c4 0 0 <gdb_asm>
8607 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8608 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8613 This command can be abbreviated @code{info tp}.
8616 @node Starting and Stopping Trace Experiments
8617 @subsection Starting and Stopping Trace Experiments
8621 @cindex start a new trace experiment
8622 @cindex collected data discarded
8624 This command takes no arguments. It starts the trace experiment, and
8625 begins collecting data. This has the side effect of discarding all
8626 the data collected in the trace buffer during the previous trace
8630 @cindex stop a running trace experiment
8632 This command takes no arguments. It ends the trace experiment, and
8633 stops collecting data.
8635 @strong{Note}: a trace experiment and data collection may stop
8636 automatically if any tracepoint's passcount is reached
8637 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8640 @cindex status of trace data collection
8641 @cindex trace experiment, status of
8643 This command displays the status of the current trace data
8647 Here is an example of the commands we described so far:
8650 (@value{GDBP}) @b{trace gdb_c_test}
8651 (@value{GDBP}) @b{actions}
8652 Enter actions for tracepoint #1, one per line.
8653 > collect $regs,$locals,$args
8658 (@value{GDBP}) @b{tstart}
8659 [time passes @dots{}]
8660 (@value{GDBP}) @b{tstop}
8664 @node Analyze Collected Data
8665 @section Using the Collected Data
8667 After the tracepoint experiment ends, you use @value{GDBN} commands
8668 for examining the trace data. The basic idea is that each tracepoint
8669 collects a trace @dfn{snapshot} every time it is hit and another
8670 snapshot every time it single-steps. All these snapshots are
8671 consecutively numbered from zero and go into a buffer, and you can
8672 examine them later. The way you examine them is to @dfn{focus} on a
8673 specific trace snapshot. When the remote stub is focused on a trace
8674 snapshot, it will respond to all @value{GDBN} requests for memory and
8675 registers by reading from the buffer which belongs to that snapshot,
8676 rather than from @emph{real} memory or registers of the program being
8677 debugged. This means that @strong{all} @value{GDBN} commands
8678 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8679 behave as if we were currently debugging the program state as it was
8680 when the tracepoint occurred. Any requests for data that are not in
8681 the buffer will fail.
8684 * tfind:: How to select a trace snapshot
8685 * tdump:: How to display all data for a snapshot
8686 * save-tracepoints:: How to save tracepoints for a future run
8690 @subsection @code{tfind @var{n}}
8693 @cindex select trace snapshot
8694 @cindex find trace snapshot
8695 The basic command for selecting a trace snapshot from the buffer is
8696 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8697 counting from zero. If no argument @var{n} is given, the next
8698 snapshot is selected.
8700 Here are the various forms of using the @code{tfind} command.
8704 Find the first snapshot in the buffer. This is a synonym for
8705 @code{tfind 0} (since 0 is the number of the first snapshot).
8708 Stop debugging trace snapshots, resume @emph{live} debugging.
8711 Same as @samp{tfind none}.
8714 No argument means find the next trace snapshot.
8717 Find the previous trace snapshot before the current one. This permits
8718 retracing earlier steps.
8720 @item tfind tracepoint @var{num}
8721 Find the next snapshot associated with tracepoint @var{num}. Search
8722 proceeds forward from the last examined trace snapshot. If no
8723 argument @var{num} is given, it means find the next snapshot collected
8724 for the same tracepoint as the current snapshot.
8726 @item tfind pc @var{addr}
8727 Find the next snapshot associated with the value @var{addr} of the
8728 program counter. Search proceeds forward from the last examined trace
8729 snapshot. If no argument @var{addr} is given, it means find the next
8730 snapshot with the same value of PC as the current snapshot.
8732 @item tfind outside @var{addr1}, @var{addr2}
8733 Find the next snapshot whose PC is outside the given range of
8736 @item tfind range @var{addr1}, @var{addr2}
8737 Find the next snapshot whose PC is between @var{addr1} and
8738 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8740 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8741 Find the next snapshot associated with the source line @var{n}. If
8742 the optional argument @var{file} is given, refer to line @var{n} in
8743 that source file. Search proceeds forward from the last examined
8744 trace snapshot. If no argument @var{n} is given, it means find the
8745 next line other than the one currently being examined; thus saying
8746 @code{tfind line} repeatedly can appear to have the same effect as
8747 stepping from line to line in a @emph{live} debugging session.
8750 The default arguments for the @code{tfind} commands are specifically
8751 designed to make it easy to scan through the trace buffer. For
8752 instance, @code{tfind} with no argument selects the next trace
8753 snapshot, and @code{tfind -} with no argument selects the previous
8754 trace snapshot. So, by giving one @code{tfind} command, and then
8755 simply hitting @key{RET} repeatedly you can examine all the trace
8756 snapshots in order. Or, by saying @code{tfind -} and then hitting
8757 @key{RET} repeatedly you can examine the snapshots in reverse order.
8758 The @code{tfind line} command with no argument selects the snapshot
8759 for the next source line executed. The @code{tfind pc} command with
8760 no argument selects the next snapshot with the same program counter
8761 (PC) as the current frame. The @code{tfind tracepoint} command with
8762 no argument selects the next trace snapshot collected by the same
8763 tracepoint as the current one.
8765 In addition to letting you scan through the trace buffer manually,
8766 these commands make it easy to construct @value{GDBN} scripts that
8767 scan through the trace buffer and print out whatever collected data
8768 you are interested in. Thus, if we want to examine the PC, FP, and SP
8769 registers from each trace frame in the buffer, we can say this:
8772 (@value{GDBP}) @b{tfind start}
8773 (@value{GDBP}) @b{while ($trace_frame != -1)}
8774 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8775 $trace_frame, $pc, $sp, $fp
8779 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8780 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8781 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8782 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8783 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8784 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8785 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8786 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8787 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8788 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8789 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8792 Or, if we want to examine the variable @code{X} at each source line in
8796 (@value{GDBP}) @b{tfind start}
8797 (@value{GDBP}) @b{while ($trace_frame != -1)}
8798 > printf "Frame %d, X == %d\n", $trace_frame, X
8808 @subsection @code{tdump}
8810 @cindex dump all data collected at tracepoint
8811 @cindex tracepoint data, display
8813 This command takes no arguments. It prints all the data collected at
8814 the current trace snapshot.
8817 (@value{GDBP}) @b{trace 444}
8818 (@value{GDBP}) @b{actions}
8819 Enter actions for tracepoint #2, one per line:
8820 > collect $regs, $locals, $args, gdb_long_test
8823 (@value{GDBP}) @b{tstart}
8825 (@value{GDBP}) @b{tfind line 444}
8826 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8828 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8830 (@value{GDBP}) @b{tdump}
8831 Data collected at tracepoint 2, trace frame 1:
8832 d0 0xc4aa0085 -995491707
8836 d4 0x71aea3d 119204413
8841 a1 0x3000668 50333288
8844 a4 0x3000698 50333336
8846 fp 0x30bf3c 0x30bf3c
8847 sp 0x30bf34 0x30bf34
8849 pc 0x20b2c8 0x20b2c8
8853 p = 0x20e5b4 "gdb-test"
8860 gdb_long_test = 17 '\021'
8865 @node save-tracepoints
8866 @subsection @code{save-tracepoints @var{filename}}
8867 @kindex save-tracepoints
8868 @cindex save tracepoints for future sessions
8870 This command saves all current tracepoint definitions together with
8871 their actions and passcounts, into a file @file{@var{filename}}
8872 suitable for use in a later debugging session. To read the saved
8873 tracepoint definitions, use the @code{source} command (@pxref{Command
8876 @node Tracepoint Variables
8877 @section Convenience Variables for Tracepoints
8878 @cindex tracepoint variables
8879 @cindex convenience variables for tracepoints
8882 @vindex $trace_frame
8883 @item (int) $trace_frame
8884 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8885 snapshot is selected.
8888 @item (int) $tracepoint
8889 The tracepoint for the current trace snapshot.
8892 @item (int) $trace_line
8893 The line number for the current trace snapshot.
8896 @item (char []) $trace_file
8897 The source file for the current trace snapshot.
8900 @item (char []) $trace_func
8901 The name of the function containing @code{$tracepoint}.
8904 Note: @code{$trace_file} is not suitable for use in @code{printf},
8905 use @code{output} instead.
8907 Here's a simple example of using these convenience variables for
8908 stepping through all the trace snapshots and printing some of their
8912 (@value{GDBP}) @b{tfind start}
8914 (@value{GDBP}) @b{while $trace_frame != -1}
8915 > output $trace_file
8916 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8922 @chapter Debugging Programs That Use Overlays
8925 If your program is too large to fit completely in your target system's
8926 memory, you can sometimes use @dfn{overlays} to work around this
8927 problem. @value{GDBN} provides some support for debugging programs that
8931 * How Overlays Work:: A general explanation of overlays.
8932 * Overlay Commands:: Managing overlays in @value{GDBN}.
8933 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8934 mapped by asking the inferior.
8935 * Overlay Sample Program:: A sample program using overlays.
8938 @node How Overlays Work
8939 @section How Overlays Work
8940 @cindex mapped overlays
8941 @cindex unmapped overlays
8942 @cindex load address, overlay's
8943 @cindex mapped address
8944 @cindex overlay area
8946 Suppose you have a computer whose instruction address space is only 64
8947 kilobytes long, but which has much more memory which can be accessed by
8948 other means: special instructions, segment registers, or memory
8949 management hardware, for example. Suppose further that you want to
8950 adapt a program which is larger than 64 kilobytes to run on this system.
8952 One solution is to identify modules of your program which are relatively
8953 independent, and need not call each other directly; call these modules
8954 @dfn{overlays}. Separate the overlays from the main program, and place
8955 their machine code in the larger memory. Place your main program in
8956 instruction memory, but leave at least enough space there to hold the
8957 largest overlay as well.
8959 Now, to call a function located in an overlay, you must first copy that
8960 overlay's machine code from the large memory into the space set aside
8961 for it in the instruction memory, and then jump to its entry point
8964 @c NB: In the below the mapped area's size is greater or equal to the
8965 @c size of all overlays. This is intentional to remind the developer
8966 @c that overlays don't necessarily need to be the same size.
8970 Data Instruction Larger
8971 Address Space Address Space Address Space
8972 +-----------+ +-----------+ +-----------+
8974 +-----------+ +-----------+ +-----------+<-- overlay 1
8975 | program | | main | .----| overlay 1 | load address
8976 | variables | | program | | +-----------+
8977 | and heap | | | | | |
8978 +-----------+ | | | +-----------+<-- overlay 2
8979 | | +-----------+ | | | load address
8980 +-----------+ | | | .-| overlay 2 |
8982 mapped --->+-----------+ | | +-----------+
8984 | overlay | <-' | | |
8985 | area | <---' +-----------+<-- overlay 3
8986 | | <---. | | load address
8987 +-----------+ `--| overlay 3 |
8994 @anchor{A code overlay}A code overlay
8998 The diagram (@pxref{A code overlay}) shows a system with separate data
8999 and instruction address spaces. To map an overlay, the program copies
9000 its code from the larger address space to the instruction address space.
9001 Since the overlays shown here all use the same mapped address, only one
9002 may be mapped at a time. For a system with a single address space for
9003 data and instructions, the diagram would be similar, except that the
9004 program variables and heap would share an address space with the main
9005 program and the overlay area.
9007 An overlay loaded into instruction memory and ready for use is called a
9008 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9009 instruction memory. An overlay not present (or only partially present)
9010 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9011 is its address in the larger memory. The mapped address is also called
9012 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9013 called the @dfn{load memory address}, or @dfn{LMA}.
9015 Unfortunately, overlays are not a completely transparent way to adapt a
9016 program to limited instruction memory. They introduce a new set of
9017 global constraints you must keep in mind as you design your program:
9022 Before calling or returning to a function in an overlay, your program
9023 must make sure that overlay is actually mapped. Otherwise, the call or
9024 return will transfer control to the right address, but in the wrong
9025 overlay, and your program will probably crash.
9028 If the process of mapping an overlay is expensive on your system, you
9029 will need to choose your overlays carefully to minimize their effect on
9030 your program's performance.
9033 The executable file you load onto your system must contain each
9034 overlay's instructions, appearing at the overlay's load address, not its
9035 mapped address. However, each overlay's instructions must be relocated
9036 and its symbols defined as if the overlay were at its mapped address.
9037 You can use GNU linker scripts to specify different load and relocation
9038 addresses for pieces of your program; see @ref{Overlay Description,,,
9039 ld.info, Using ld: the GNU linker}.
9042 The procedure for loading executable files onto your system must be able
9043 to load their contents into the larger address space as well as the
9044 instruction and data spaces.
9048 The overlay system described above is rather simple, and could be
9049 improved in many ways:
9054 If your system has suitable bank switch registers or memory management
9055 hardware, you could use those facilities to make an overlay's load area
9056 contents simply appear at their mapped address in instruction space.
9057 This would probably be faster than copying the overlay to its mapped
9058 area in the usual way.
9061 If your overlays are small enough, you could set aside more than one
9062 overlay area, and have more than one overlay mapped at a time.
9065 You can use overlays to manage data, as well as instructions. In
9066 general, data overlays are even less transparent to your design than
9067 code overlays: whereas code overlays only require care when you call or
9068 return to functions, data overlays require care every time you access
9069 the data. Also, if you change the contents of a data overlay, you
9070 must copy its contents back out to its load address before you can copy a
9071 different data overlay into the same mapped area.
9076 @node Overlay Commands
9077 @section Overlay Commands
9079 To use @value{GDBN}'s overlay support, each overlay in your program must
9080 correspond to a separate section of the executable file. The section's
9081 virtual memory address and load memory address must be the overlay's
9082 mapped and load addresses. Identifying overlays with sections allows
9083 @value{GDBN} to determine the appropriate address of a function or
9084 variable, depending on whether the overlay is mapped or not.
9086 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9087 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9092 Disable @value{GDBN}'s overlay support. When overlay support is
9093 disabled, @value{GDBN} assumes that all functions and variables are
9094 always present at their mapped addresses. By default, @value{GDBN}'s
9095 overlay support is disabled.
9097 @item overlay manual
9098 @cindex manual overlay debugging
9099 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9100 relies on you to tell it which overlays are mapped, and which are not,
9101 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9102 commands described below.
9104 @item overlay map-overlay @var{overlay}
9105 @itemx overlay map @var{overlay}
9106 @cindex map an overlay
9107 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9108 be the name of the object file section containing the overlay. When an
9109 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9110 functions and variables at their mapped addresses. @value{GDBN} assumes
9111 that any other overlays whose mapped ranges overlap that of
9112 @var{overlay} are now unmapped.
9114 @item overlay unmap-overlay @var{overlay}
9115 @itemx overlay unmap @var{overlay}
9116 @cindex unmap an overlay
9117 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9118 must be the name of the object file section containing the overlay.
9119 When an overlay is unmapped, @value{GDBN} assumes it can find the
9120 overlay's functions and variables at their load addresses.
9123 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9124 consults a data structure the overlay manager maintains in the inferior
9125 to see which overlays are mapped. For details, see @ref{Automatic
9128 @item overlay load-target
9130 @cindex reloading the overlay table
9131 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9132 re-reads the table @value{GDBN} automatically each time the inferior
9133 stops, so this command should only be necessary if you have changed the
9134 overlay mapping yourself using @value{GDBN}. This command is only
9135 useful when using automatic overlay debugging.
9137 @item overlay list-overlays
9139 @cindex listing mapped overlays
9140 Display a list of the overlays currently mapped, along with their mapped
9141 addresses, load addresses, and sizes.
9145 Normally, when @value{GDBN} prints a code address, it includes the name
9146 of the function the address falls in:
9149 (@value{GDBP}) print main
9150 $3 = @{int ()@} 0x11a0 <main>
9153 When overlay debugging is enabled, @value{GDBN} recognizes code in
9154 unmapped overlays, and prints the names of unmapped functions with
9155 asterisks around them. For example, if @code{foo} is a function in an
9156 unmapped overlay, @value{GDBN} prints it this way:
9159 (@value{GDBP}) overlay list
9160 No sections are mapped.
9161 (@value{GDBP}) print foo
9162 $5 = @{int (int)@} 0x100000 <*foo*>
9165 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9169 (@value{GDBP}) overlay list
9170 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9171 mapped at 0x1016 - 0x104a
9172 (@value{GDBP}) print foo
9173 $6 = @{int (int)@} 0x1016 <foo>
9176 When overlay debugging is enabled, @value{GDBN} can find the correct
9177 address for functions and variables in an overlay, whether or not the
9178 overlay is mapped. This allows most @value{GDBN} commands, like
9179 @code{break} and @code{disassemble}, to work normally, even on unmapped
9180 code. However, @value{GDBN}'s breakpoint support has some limitations:
9184 @cindex breakpoints in overlays
9185 @cindex overlays, setting breakpoints in
9186 You can set breakpoints in functions in unmapped overlays, as long as
9187 @value{GDBN} can write to the overlay at its load address.
9189 @value{GDBN} can not set hardware or simulator-based breakpoints in
9190 unmapped overlays. However, if you set a breakpoint at the end of your
9191 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9192 you are using manual overlay management), @value{GDBN} will re-set its
9193 breakpoints properly.
9197 @node Automatic Overlay Debugging
9198 @section Automatic Overlay Debugging
9199 @cindex automatic overlay debugging
9201 @value{GDBN} can automatically track which overlays are mapped and which
9202 are not, given some simple co-operation from the overlay manager in the
9203 inferior. If you enable automatic overlay debugging with the
9204 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9205 looks in the inferior's memory for certain variables describing the
9206 current state of the overlays.
9208 Here are the variables your overlay manager must define to support
9209 @value{GDBN}'s automatic overlay debugging:
9213 @item @code{_ovly_table}:
9214 This variable must be an array of the following structures:
9219 /* The overlay's mapped address. */
9222 /* The size of the overlay, in bytes. */
9225 /* The overlay's load address. */
9228 /* Non-zero if the overlay is currently mapped;
9230 unsigned long mapped;
9234 @item @code{_novlys}:
9235 This variable must be a four-byte signed integer, holding the total
9236 number of elements in @code{_ovly_table}.
9240 To decide whether a particular overlay is mapped or not, @value{GDBN}
9241 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9242 @code{lma} members equal the VMA and LMA of the overlay's section in the
9243 executable file. When @value{GDBN} finds a matching entry, it consults
9244 the entry's @code{mapped} member to determine whether the overlay is
9247 In addition, your overlay manager may define a function called
9248 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9249 will silently set a breakpoint there. If the overlay manager then
9250 calls this function whenever it has changed the overlay table, this
9251 will enable @value{GDBN} to accurately keep track of which overlays
9252 are in program memory, and update any breakpoints that may be set
9253 in overlays. This will allow breakpoints to work even if the
9254 overlays are kept in ROM or other non-writable memory while they
9255 are not being executed.
9257 @node Overlay Sample Program
9258 @section Overlay Sample Program
9259 @cindex overlay example program
9261 When linking a program which uses overlays, you must place the overlays
9262 at their load addresses, while relocating them to run at their mapped
9263 addresses. To do this, you must write a linker script (@pxref{Overlay
9264 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9265 since linker scripts are specific to a particular host system, target
9266 architecture, and target memory layout, this manual cannot provide
9267 portable sample code demonstrating @value{GDBN}'s overlay support.
9269 However, the @value{GDBN} source distribution does contain an overlaid
9270 program, with linker scripts for a few systems, as part of its test
9271 suite. The program consists of the following files from
9272 @file{gdb/testsuite/gdb.base}:
9276 The main program file.
9278 A simple overlay manager, used by @file{overlays.c}.
9283 Overlay modules, loaded and used by @file{overlays.c}.
9286 Linker scripts for linking the test program on the @code{d10v-elf}
9287 and @code{m32r-elf} targets.
9290 You can build the test program using the @code{d10v-elf} GCC
9291 cross-compiler like this:
9294 $ d10v-elf-gcc -g -c overlays.c
9295 $ d10v-elf-gcc -g -c ovlymgr.c
9296 $ d10v-elf-gcc -g -c foo.c
9297 $ d10v-elf-gcc -g -c bar.c
9298 $ d10v-elf-gcc -g -c baz.c
9299 $ d10v-elf-gcc -g -c grbx.c
9300 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9301 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9304 The build process is identical for any other architecture, except that
9305 you must substitute the appropriate compiler and linker script for the
9306 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9310 @chapter Using @value{GDBN} with Different Languages
9313 Although programming languages generally have common aspects, they are
9314 rarely expressed in the same manner. For instance, in ANSI C,
9315 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9316 Modula-2, it is accomplished by @code{p^}. Values can also be
9317 represented (and displayed) differently. Hex numbers in C appear as
9318 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9320 @cindex working language
9321 Language-specific information is built into @value{GDBN} for some languages,
9322 allowing you to express operations like the above in your program's
9323 native language, and allowing @value{GDBN} to output values in a manner
9324 consistent with the syntax of your program's native language. The
9325 language you use to build expressions is called the @dfn{working
9329 * Setting:: Switching between source languages
9330 * Show:: Displaying the language
9331 * Checks:: Type and range checks
9332 * Supported Languages:: Supported languages
9333 * Unsupported Languages:: Unsupported languages
9337 @section Switching Between Source Languages
9339 There are two ways to control the working language---either have @value{GDBN}
9340 set it automatically, or select it manually yourself. You can use the
9341 @code{set language} command for either purpose. On startup, @value{GDBN}
9342 defaults to setting the language automatically. The working language is
9343 used to determine how expressions you type are interpreted, how values
9346 In addition to the working language, every source file that
9347 @value{GDBN} knows about has its own working language. For some object
9348 file formats, the compiler might indicate which language a particular
9349 source file is in. However, most of the time @value{GDBN} infers the
9350 language from the name of the file. The language of a source file
9351 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9352 show each frame appropriately for its own language. There is no way to
9353 set the language of a source file from within @value{GDBN}, but you can
9354 set the language associated with a filename extension. @xref{Show, ,
9355 Displaying the Language}.
9357 This is most commonly a problem when you use a program, such
9358 as @code{cfront} or @code{f2c}, that generates C but is written in
9359 another language. In that case, make the
9360 program use @code{#line} directives in its C output; that way
9361 @value{GDBN} will know the correct language of the source code of the original
9362 program, and will display that source code, not the generated C code.
9365 * Filenames:: Filename extensions and languages.
9366 * Manually:: Setting the working language manually
9367 * Automatically:: Having @value{GDBN} infer the source language
9371 @subsection List of Filename Extensions and Languages
9373 If a source file name ends in one of the following extensions, then
9374 @value{GDBN} infers that its language is the one indicated.
9395 Objective-C source file
9402 Modula-2 source file
9406 Assembler source file. This actually behaves almost like C, but
9407 @value{GDBN} does not skip over function prologues when stepping.
9410 In addition, you may set the language associated with a filename
9411 extension. @xref{Show, , Displaying the Language}.
9414 @subsection Setting the Working Language
9416 If you allow @value{GDBN} to set the language automatically,
9417 expressions are interpreted the same way in your debugging session and
9420 @kindex set language
9421 If you wish, you may set the language manually. To do this, issue the
9422 command @samp{set language @var{lang}}, where @var{lang} is the name of
9424 @code{c} or @code{modula-2}.
9425 For a list of the supported languages, type @samp{set language}.
9427 Setting the language manually prevents @value{GDBN} from updating the working
9428 language automatically. This can lead to confusion if you try
9429 to debug a program when the working language is not the same as the
9430 source language, when an expression is acceptable to both
9431 languages---but means different things. For instance, if the current
9432 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9440 might not have the effect you intended. In C, this means to add
9441 @code{b} and @code{c} and place the result in @code{a}. The result
9442 printed would be the value of @code{a}. In Modula-2, this means to compare
9443 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9446 @subsection Having @value{GDBN} Infer the Source Language
9448 To have @value{GDBN} set the working language automatically, use
9449 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9450 then infers the working language. That is, when your program stops in a
9451 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9452 working language to the language recorded for the function in that
9453 frame. If the language for a frame is unknown (that is, if the function
9454 or block corresponding to the frame was defined in a source file that
9455 does not have a recognized extension), the current working language is
9456 not changed, and @value{GDBN} issues a warning.
9458 This may not seem necessary for most programs, which are written
9459 entirely in one source language. However, program modules and libraries
9460 written in one source language can be used by a main program written in
9461 a different source language. Using @samp{set language auto} in this
9462 case frees you from having to set the working language manually.
9465 @section Displaying the Language
9467 The following commands help you find out which language is the
9468 working language, and also what language source files were written in.
9472 @kindex show language
9473 Display the current working language. This is the
9474 language you can use with commands such as @code{print} to
9475 build and compute expressions that may involve variables in your program.
9478 @kindex info frame@r{, show the source language}
9479 Display the source language for this frame. This language becomes the
9480 working language if you use an identifier from this frame.
9481 @xref{Frame Info, ,Information about a Frame}, to identify the other
9482 information listed here.
9485 @kindex info source@r{, show the source language}
9486 Display the source language of this source file.
9487 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9488 information listed here.
9491 In unusual circumstances, you may have source files with extensions
9492 not in the standard list. You can then set the extension associated
9493 with a language explicitly:
9496 @item set extension-language @var{ext} @var{language}
9497 @kindex set extension-language
9498 Tell @value{GDBN} that source files with extension @var{ext} are to be
9499 assumed as written in the source language @var{language}.
9501 @item info extensions
9502 @kindex info extensions
9503 List all the filename extensions and the associated languages.
9507 @section Type and Range Checking
9510 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9511 checking are included, but they do not yet have any effect. This
9512 section documents the intended facilities.
9514 @c FIXME remove warning when type/range code added
9516 Some languages are designed to guard you against making seemingly common
9517 errors through a series of compile- and run-time checks. These include
9518 checking the type of arguments to functions and operators, and making
9519 sure mathematical overflows are caught at run time. Checks such as
9520 these help to ensure a program's correctness once it has been compiled
9521 by eliminating type mismatches, and providing active checks for range
9522 errors when your program is running.
9524 @value{GDBN} can check for conditions like the above if you wish.
9525 Although @value{GDBN} does not check the statements in your program,
9526 it can check expressions entered directly into @value{GDBN} for
9527 evaluation via the @code{print} command, for example. As with the
9528 working language, @value{GDBN} can also decide whether or not to check
9529 automatically based on your program's source language.
9530 @xref{Supported Languages, ,Supported Languages}, for the default
9531 settings of supported languages.
9534 * Type Checking:: An overview of type checking
9535 * Range Checking:: An overview of range checking
9538 @cindex type checking
9539 @cindex checks, type
9541 @subsection An Overview of Type Checking
9543 Some languages, such as Modula-2, are strongly typed, meaning that the
9544 arguments to operators and functions have to be of the correct type,
9545 otherwise an error occurs. These checks prevent type mismatch
9546 errors from ever causing any run-time problems. For example,
9554 The second example fails because the @code{CARDINAL} 1 is not
9555 type-compatible with the @code{REAL} 2.3.
9557 For the expressions you use in @value{GDBN} commands, you can tell the
9558 @value{GDBN} type checker to skip checking;
9559 to treat any mismatches as errors and abandon the expression;
9560 or to only issue warnings when type mismatches occur,
9561 but evaluate the expression anyway. When you choose the last of
9562 these, @value{GDBN} evaluates expressions like the second example above, but
9563 also issues a warning.
9565 Even if you turn type checking off, there may be other reasons
9566 related to type that prevent @value{GDBN} from evaluating an expression.
9567 For instance, @value{GDBN} does not know how to add an @code{int} and
9568 a @code{struct foo}. These particular type errors have nothing to do
9569 with the language in use, and usually arise from expressions, such as
9570 the one described above, which make little sense to evaluate anyway.
9572 Each language defines to what degree it is strict about type. For
9573 instance, both Modula-2 and C require the arguments to arithmetical
9574 operators to be numbers. In C, enumerated types and pointers can be
9575 represented as numbers, so that they are valid arguments to mathematical
9576 operators. @xref{Supported Languages, ,Supported Languages}, for further
9577 details on specific languages.
9579 @value{GDBN} provides some additional commands for controlling the type checker:
9581 @kindex set check type
9582 @kindex show check type
9584 @item set check type auto
9585 Set type checking on or off based on the current working language.
9586 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9589 @item set check type on
9590 @itemx set check type off
9591 Set type checking on or off, overriding the default setting for the
9592 current working language. Issue a warning if the setting does not
9593 match the language default. If any type mismatches occur in
9594 evaluating an expression while type checking is on, @value{GDBN} prints a
9595 message and aborts evaluation of the expression.
9597 @item set check type warn
9598 Cause the type checker to issue warnings, but to always attempt to
9599 evaluate the expression. Evaluating the expression may still
9600 be impossible for other reasons. For example, @value{GDBN} cannot add
9601 numbers and structures.
9604 Show the current setting of the type checker, and whether or not @value{GDBN}
9605 is setting it automatically.
9608 @cindex range checking
9609 @cindex checks, range
9610 @node Range Checking
9611 @subsection An Overview of Range Checking
9613 In some languages (such as Modula-2), it is an error to exceed the
9614 bounds of a type; this is enforced with run-time checks. Such range
9615 checking is meant to ensure program correctness by making sure
9616 computations do not overflow, or indices on an array element access do
9617 not exceed the bounds of the array.
9619 For expressions you use in @value{GDBN} commands, you can tell
9620 @value{GDBN} to treat range errors in one of three ways: ignore them,
9621 always treat them as errors and abandon the expression, or issue
9622 warnings but evaluate the expression anyway.
9624 A range error can result from numerical overflow, from exceeding an
9625 array index bound, or when you type a constant that is not a member
9626 of any type. Some languages, however, do not treat overflows as an
9627 error. In many implementations of C, mathematical overflow causes the
9628 result to ``wrap around'' to lower values---for example, if @var{m} is
9629 the largest integer value, and @var{s} is the smallest, then
9632 @var{m} + 1 @result{} @var{s}
9635 This, too, is specific to individual languages, and in some cases
9636 specific to individual compilers or machines. @xref{Supported Languages, ,
9637 Supported Languages}, for further details on specific languages.
9639 @value{GDBN} provides some additional commands for controlling the range checker:
9641 @kindex set check range
9642 @kindex show check range
9644 @item set check range auto
9645 Set range checking on or off based on the current working language.
9646 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9649 @item set check range on
9650 @itemx set check range off
9651 Set range checking on or off, overriding the default setting for the
9652 current working language. A warning is issued if the setting does not
9653 match the language default. If a range error occurs and range checking is on,
9654 then a message is printed and evaluation of the expression is aborted.
9656 @item set check range warn
9657 Output messages when the @value{GDBN} range checker detects a range error,
9658 but attempt to evaluate the expression anyway. Evaluating the
9659 expression may still be impossible for other reasons, such as accessing
9660 memory that the process does not own (a typical example from many Unix
9664 Show the current setting of the range checker, and whether or not it is
9665 being set automatically by @value{GDBN}.
9668 @node Supported Languages
9669 @section Supported Languages
9671 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9672 assembly, Modula-2, and Ada.
9673 @c This is false ...
9674 Some @value{GDBN} features may be used in expressions regardless of the
9675 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9676 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9677 ,Expressions}) can be used with the constructs of any supported
9680 The following sections detail to what degree each source language is
9681 supported by @value{GDBN}. These sections are not meant to be language
9682 tutorials or references, but serve only as a reference guide to what the
9683 @value{GDBN} expression parser accepts, and what input and output
9684 formats should look like for different languages. There are many good
9685 books written on each of these languages; please look to these for a
9686 language reference or tutorial.
9690 * Objective-C:: Objective-C
9693 * Modula-2:: Modula-2
9698 @subsection C and C@t{++}
9700 @cindex C and C@t{++}
9701 @cindex expressions in C or C@t{++}
9703 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9704 to both languages. Whenever this is the case, we discuss those languages
9708 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9709 @cindex @sc{gnu} C@t{++}
9710 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9711 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9712 effectively, you must compile your C@t{++} programs with a supported
9713 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9714 compiler (@code{aCC}).
9716 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9717 format; if it doesn't work on your system, try the stabs+ debugging
9718 format. You can select those formats explicitly with the @code{g++}
9719 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9720 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9721 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9724 * C Operators:: C and C@t{++} operators
9725 * C Constants:: C and C@t{++} constants
9726 * C Plus Plus Expressions:: C@t{++} expressions
9727 * C Defaults:: Default settings for C and C@t{++}
9728 * C Checks:: C and C@t{++} type and range checks
9729 * Debugging C:: @value{GDBN} and C
9730 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9731 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9735 @subsubsection C and C@t{++} Operators
9737 @cindex C and C@t{++} operators
9739 Operators must be defined on values of specific types. For instance,
9740 @code{+} is defined on numbers, but not on structures. Operators are
9741 often defined on groups of types.
9743 For the purposes of C and C@t{++}, the following definitions hold:
9748 @emph{Integral types} include @code{int} with any of its storage-class
9749 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9752 @emph{Floating-point types} include @code{float}, @code{double}, and
9753 @code{long double} (if supported by the target platform).
9756 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9759 @emph{Scalar types} include all of the above.
9764 The following operators are supported. They are listed here
9765 in order of increasing precedence:
9769 The comma or sequencing operator. Expressions in a comma-separated list
9770 are evaluated from left to right, with the result of the entire
9771 expression being the last expression evaluated.
9774 Assignment. The value of an assignment expression is the value
9775 assigned. Defined on scalar types.
9778 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9779 and translated to @w{@code{@var{a} = @var{a op b}}}.
9780 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9781 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9782 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9785 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9786 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9790 Logical @sc{or}. Defined on integral types.
9793 Logical @sc{and}. Defined on integral types.
9796 Bitwise @sc{or}. Defined on integral types.
9799 Bitwise exclusive-@sc{or}. Defined on integral types.
9802 Bitwise @sc{and}. Defined on integral types.
9805 Equality and inequality. Defined on scalar types. The value of these
9806 expressions is 0 for false and non-zero for true.
9808 @item <@r{, }>@r{, }<=@r{, }>=
9809 Less than, greater than, less than or equal, greater than or equal.
9810 Defined on scalar types. The value of these expressions is 0 for false
9811 and non-zero for true.
9814 left shift, and right shift. Defined on integral types.
9817 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9820 Addition and subtraction. Defined on integral types, floating-point types and
9823 @item *@r{, }/@r{, }%
9824 Multiplication, division, and modulus. Multiplication and division are
9825 defined on integral and floating-point types. Modulus is defined on
9829 Increment and decrement. When appearing before a variable, the
9830 operation is performed before the variable is used in an expression;
9831 when appearing after it, the variable's value is used before the
9832 operation takes place.
9835 Pointer dereferencing. Defined on pointer types. Same precedence as
9839 Address operator. Defined on variables. Same precedence as @code{++}.
9841 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9842 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9843 to examine the address
9844 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9848 Negative. Defined on integral and floating-point types. Same
9849 precedence as @code{++}.
9852 Logical negation. Defined on integral types. Same precedence as
9856 Bitwise complement operator. Defined on integral types. Same precedence as
9861 Structure member, and pointer-to-structure member. For convenience,
9862 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9863 pointer based on the stored type information.
9864 Defined on @code{struct} and @code{union} data.
9867 Dereferences of pointers to members.
9870 Array indexing. @code{@var{a}[@var{i}]} is defined as
9871 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9874 Function parameter list. Same precedence as @code{->}.
9877 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9878 and @code{class} types.
9881 Doubled colons also represent the @value{GDBN} scope operator
9882 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9886 If an operator is redefined in the user code, @value{GDBN} usually
9887 attempts to invoke the redefined version instead of using the operator's
9891 @subsubsection C and C@t{++} Constants
9893 @cindex C and C@t{++} constants
9895 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9900 Integer constants are a sequence of digits. Octal constants are
9901 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9902 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9903 @samp{l}, specifying that the constant should be treated as a
9907 Floating point constants are a sequence of digits, followed by a decimal
9908 point, followed by a sequence of digits, and optionally followed by an
9909 exponent. An exponent is of the form:
9910 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9911 sequence of digits. The @samp{+} is optional for positive exponents.
9912 A floating-point constant may also end with a letter @samp{f} or
9913 @samp{F}, specifying that the constant should be treated as being of
9914 the @code{float} (as opposed to the default @code{double}) type; or with
9915 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9919 Enumerated constants consist of enumerated identifiers, or their
9920 integral equivalents.
9923 Character constants are a single character surrounded by single quotes
9924 (@code{'}), or a number---the ordinal value of the corresponding character
9925 (usually its @sc{ascii} value). Within quotes, the single character may
9926 be represented by a letter or by @dfn{escape sequences}, which are of
9927 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9928 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9929 @samp{@var{x}} is a predefined special character---for example,
9930 @samp{\n} for newline.
9933 String constants are a sequence of character constants surrounded by
9934 double quotes (@code{"}). Any valid character constant (as described
9935 above) may appear. Double quotes within the string must be preceded by
9936 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9940 Pointer constants are an integral value. You can also write pointers
9941 to constants using the C operator @samp{&}.
9944 Array constants are comma-separated lists surrounded by braces @samp{@{}
9945 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9946 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9947 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9950 @node C Plus Plus Expressions
9951 @subsubsection C@t{++} Expressions
9953 @cindex expressions in C@t{++}
9954 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9956 @cindex debugging C@t{++} programs
9957 @cindex C@t{++} compilers
9958 @cindex debug formats and C@t{++}
9959 @cindex @value{NGCC} and C@t{++}
9961 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9962 proper compiler and the proper debug format. Currently, @value{GDBN}
9963 works best when debugging C@t{++} code that is compiled with
9964 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9965 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9966 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9967 stabs+ as their default debug format, so you usually don't need to
9968 specify a debug format explicitly. Other compilers and/or debug formats
9969 are likely to work badly or not at all when using @value{GDBN} to debug
9975 @cindex member functions
9977 Member function calls are allowed; you can use expressions like
9980 count = aml->GetOriginal(x, y)
9983 @vindex this@r{, inside C@t{++} member functions}
9984 @cindex namespace in C@t{++}
9986 While a member function is active (in the selected stack frame), your
9987 expressions have the same namespace available as the member function;
9988 that is, @value{GDBN} allows implicit references to the class instance
9989 pointer @code{this} following the same rules as C@t{++}.
9991 @cindex call overloaded functions
9992 @cindex overloaded functions, calling
9993 @cindex type conversions in C@t{++}
9995 You can call overloaded functions; @value{GDBN} resolves the function
9996 call to the right definition, with some restrictions. @value{GDBN} does not
9997 perform overload resolution involving user-defined type conversions,
9998 calls to constructors, or instantiations of templates that do not exist
9999 in the program. It also cannot handle ellipsis argument lists or
10002 It does perform integral conversions and promotions, floating-point
10003 promotions, arithmetic conversions, pointer conversions, conversions of
10004 class objects to base classes, and standard conversions such as those of
10005 functions or arrays to pointers; it requires an exact match on the
10006 number of function arguments.
10008 Overload resolution is always performed, unless you have specified
10009 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10010 ,@value{GDBN} Features for C@t{++}}.
10012 You must specify @code{set overload-resolution off} in order to use an
10013 explicit function signature to call an overloaded function, as in
10015 p 'foo(char,int)'('x', 13)
10018 The @value{GDBN} command-completion facility can simplify this;
10019 see @ref{Completion, ,Command Completion}.
10021 @cindex reference declarations
10023 @value{GDBN} understands variables declared as C@t{++} references; you can use
10024 them in expressions just as you do in C@t{++} source---they are automatically
10027 In the parameter list shown when @value{GDBN} displays a frame, the values of
10028 reference variables are not displayed (unlike other variables); this
10029 avoids clutter, since references are often used for large structures.
10030 The @emph{address} of a reference variable is always shown, unless
10031 you have specified @samp{set print address off}.
10034 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10035 expressions can use it just as expressions in your program do. Since
10036 one scope may be defined in another, you can use @code{::} repeatedly if
10037 necessary, for example in an expression like
10038 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10039 resolving name scope by reference to source files, in both C and C@t{++}
10040 debugging (@pxref{Variables, ,Program Variables}).
10043 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10044 calling virtual functions correctly, printing out virtual bases of
10045 objects, calling functions in a base subobject, casting objects, and
10046 invoking user-defined operators.
10049 @subsubsection C and C@t{++} Defaults
10051 @cindex C and C@t{++} defaults
10053 If you allow @value{GDBN} to set type and range checking automatically, they
10054 both default to @code{off} whenever the working language changes to
10055 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10056 selects the working language.
10058 If you allow @value{GDBN} to set the language automatically, it
10059 recognizes source files whose names end with @file{.c}, @file{.C}, or
10060 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10061 these files, it sets the working language to C or C@t{++}.
10062 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10063 for further details.
10065 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10066 @c unimplemented. If (b) changes, it might make sense to let this node
10067 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10070 @subsubsection C and C@t{++} Type and Range Checks
10072 @cindex C and C@t{++} checks
10074 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10075 is not used. However, if you turn type checking on, @value{GDBN}
10076 considers two variables type equivalent if:
10080 The two variables are structured and have the same structure, union, or
10084 The two variables have the same type name, or types that have been
10085 declared equivalent through @code{typedef}.
10088 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10091 The two @code{struct}, @code{union}, or @code{enum} variables are
10092 declared in the same declaration. (Note: this may not be true for all C
10097 Range checking, if turned on, is done on mathematical operations. Array
10098 indices are not checked, since they are often used to index a pointer
10099 that is not itself an array.
10102 @subsubsection @value{GDBN} and C
10104 The @code{set print union} and @code{show print union} commands apply to
10105 the @code{union} type. When set to @samp{on}, any @code{union} that is
10106 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10107 appears as @samp{@{...@}}.
10109 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10110 with pointers and a memory allocation function. @xref{Expressions,
10113 @node Debugging C Plus Plus
10114 @subsubsection @value{GDBN} Features for C@t{++}
10116 @cindex commands for C@t{++}
10118 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10119 designed specifically for use with C@t{++}. Here is a summary:
10122 @cindex break in overloaded functions
10123 @item @r{breakpoint menus}
10124 When you want a breakpoint in a function whose name is overloaded,
10125 @value{GDBN} has the capability to display a menu of possible breakpoint
10126 locations to help you specify which function definition you want.
10127 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10129 @cindex overloading in C@t{++}
10130 @item rbreak @var{regex}
10131 Setting breakpoints using regular expressions is helpful for setting
10132 breakpoints on overloaded functions that are not members of any special
10134 @xref{Set Breaks, ,Setting Breakpoints}.
10136 @cindex C@t{++} exception handling
10139 Debug C@t{++} exception handling using these commands. @xref{Set
10140 Catchpoints, , Setting Catchpoints}.
10142 @cindex inheritance
10143 @item ptype @var{typename}
10144 Print inheritance relationships as well as other information for type
10146 @xref{Symbols, ,Examining the Symbol Table}.
10148 @cindex C@t{++} symbol display
10149 @item set print demangle
10150 @itemx show print demangle
10151 @itemx set print asm-demangle
10152 @itemx show print asm-demangle
10153 Control whether C@t{++} symbols display in their source form, both when
10154 displaying code as C@t{++} source and when displaying disassemblies.
10155 @xref{Print Settings, ,Print Settings}.
10157 @item set print object
10158 @itemx show print object
10159 Choose whether to print derived (actual) or declared types of objects.
10160 @xref{Print Settings, ,Print Settings}.
10162 @item set print vtbl
10163 @itemx show print vtbl
10164 Control the format for printing virtual function tables.
10165 @xref{Print Settings, ,Print Settings}.
10166 (The @code{vtbl} commands do not work on programs compiled with the HP
10167 ANSI C@t{++} compiler (@code{aCC}).)
10169 @kindex set overload-resolution
10170 @cindex overloaded functions, overload resolution
10171 @item set overload-resolution on
10172 Enable overload resolution for C@t{++} expression evaluation. The default
10173 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10174 and searches for a function whose signature matches the argument types,
10175 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10176 Expressions, ,C@t{++} Expressions}, for details).
10177 If it cannot find a match, it emits a message.
10179 @item set overload-resolution off
10180 Disable overload resolution for C@t{++} expression evaluation. For
10181 overloaded functions that are not class member functions, @value{GDBN}
10182 chooses the first function of the specified name that it finds in the
10183 symbol table, whether or not its arguments are of the correct type. For
10184 overloaded functions that are class member functions, @value{GDBN}
10185 searches for a function whose signature @emph{exactly} matches the
10188 @kindex show overload-resolution
10189 @item show overload-resolution
10190 Show the current setting of overload resolution.
10192 @item @r{Overloaded symbol names}
10193 You can specify a particular definition of an overloaded symbol, using
10194 the same notation that is used to declare such symbols in C@t{++}: type
10195 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10196 also use the @value{GDBN} command-line word completion facilities to list the
10197 available choices, or to finish the type list for you.
10198 @xref{Completion,, Command Completion}, for details on how to do this.
10201 @node Decimal Floating Point
10202 @subsubsection Decimal Floating Point format
10203 @cindex decimal floating point format
10205 @value{GDBN} can examine, set and perform computations with numbers in
10206 decimal floating point format, which in the C language correspond to the
10207 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10208 specified by the extension to support decimal floating-point arithmetic.
10210 There are two encodings in use, depending on the architecture: BID (Binary
10211 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10212 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10215 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10216 to manipulate decimal floating point numbers, it is not possible to convert
10217 (using a cast, for example) integers wider than 32-bit to decimal float.
10219 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10220 point computations, error checking in decimal float operations ignores
10221 underflow, overflow and divide by zero exceptions.
10223 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10224 to inspect @code{_Decimal128} values stored in floating point registers. See
10225 @ref{PowerPC,,PowerPC} for more details.
10228 @subsection Objective-C
10230 @cindex Objective-C
10231 This section provides information about some commands and command
10232 options that are useful for debugging Objective-C code. See also
10233 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10234 few more commands specific to Objective-C support.
10237 * Method Names in Commands::
10238 * The Print Command with Objective-C::
10241 @node Method Names in Commands
10242 @subsubsection Method Names in Commands
10244 The following commands have been extended to accept Objective-C method
10245 names as line specifications:
10247 @kindex clear@r{, and Objective-C}
10248 @kindex break@r{, and Objective-C}
10249 @kindex info line@r{, and Objective-C}
10250 @kindex jump@r{, and Objective-C}
10251 @kindex list@r{, and Objective-C}
10255 @item @code{info line}
10260 A fully qualified Objective-C method name is specified as
10263 -[@var{Class} @var{methodName}]
10266 where the minus sign is used to indicate an instance method and a
10267 plus sign (not shown) is used to indicate a class method. The class
10268 name @var{Class} and method name @var{methodName} are enclosed in
10269 brackets, similar to the way messages are specified in Objective-C
10270 source code. For example, to set a breakpoint at the @code{create}
10271 instance method of class @code{Fruit} in the program currently being
10275 break -[Fruit create]
10278 To list ten program lines around the @code{initialize} class method,
10282 list +[NSText initialize]
10285 In the current version of @value{GDBN}, the plus or minus sign is
10286 required. In future versions of @value{GDBN}, the plus or minus
10287 sign will be optional, but you can use it to narrow the search. It
10288 is also possible to specify just a method name:
10294 You must specify the complete method name, including any colons. If
10295 your program's source files contain more than one @code{create} method,
10296 you'll be presented with a numbered list of classes that implement that
10297 method. Indicate your choice by number, or type @samp{0} to exit if
10300 As another example, to clear a breakpoint established at the
10301 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10304 clear -[NSWindow makeKeyAndOrderFront:]
10307 @node The Print Command with Objective-C
10308 @subsubsection The Print Command With Objective-C
10309 @cindex Objective-C, print objects
10310 @kindex print-object
10311 @kindex po @r{(@code{print-object})}
10313 The print command has also been extended to accept methods. For example:
10316 print -[@var{object} hash]
10319 @cindex print an Objective-C object description
10320 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10322 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10323 and print the result. Also, an additional command has been added,
10324 @code{print-object} or @code{po} for short, which is meant to print
10325 the description of an object. However, this command may only work
10326 with certain Objective-C libraries that have a particular hook
10327 function, @code{_NSPrintForDebugger}, defined.
10330 @subsection Fortran
10331 @cindex Fortran-specific support in @value{GDBN}
10333 @value{GDBN} can be used to debug programs written in Fortran, but it
10334 currently supports only the features of Fortran 77 language.
10336 @cindex trailing underscore, in Fortran symbols
10337 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10338 among them) append an underscore to the names of variables and
10339 functions. When you debug programs compiled by those compilers, you
10340 will need to refer to variables and functions with a trailing
10344 * Fortran Operators:: Fortran operators and expressions
10345 * Fortran Defaults:: Default settings for Fortran
10346 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10349 @node Fortran Operators
10350 @subsubsection Fortran Operators and Expressions
10352 @cindex Fortran operators and expressions
10354 Operators must be defined on values of specific types. For instance,
10355 @code{+} is defined on numbers, but not on characters or other non-
10356 arithmetic types. Operators are often defined on groups of types.
10360 The exponentiation operator. It raises the first operand to the power
10364 The range operator. Normally used in the form of array(low:high) to
10365 represent a section of array.
10368 The access component operator. Normally used to access elements in derived
10369 types. Also suitable for unions. As unions aren't part of regular Fortran,
10370 this can only happen when accessing a register that uses a gdbarch-defined
10374 @node Fortran Defaults
10375 @subsubsection Fortran Defaults
10377 @cindex Fortran Defaults
10379 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10380 default uses case-insensitive matches for Fortran symbols. You can
10381 change that with the @samp{set case-insensitive} command, see
10382 @ref{Symbols}, for the details.
10384 @node Special Fortran Commands
10385 @subsubsection Special Fortran Commands
10387 @cindex Special Fortran commands
10389 @value{GDBN} has some commands to support Fortran-specific features,
10390 such as displaying common blocks.
10393 @cindex @code{COMMON} blocks, Fortran
10394 @kindex info common
10395 @item info common @r{[}@var{common-name}@r{]}
10396 This command prints the values contained in the Fortran @code{COMMON}
10397 block whose name is @var{common-name}. With no argument, the names of
10398 all @code{COMMON} blocks visible at the current program location are
10405 @cindex Pascal support in @value{GDBN}, limitations
10406 Debugging Pascal programs which use sets, subranges, file variables, or
10407 nested functions does not currently work. @value{GDBN} does not support
10408 entering expressions, printing values, or similar features using Pascal
10411 The Pascal-specific command @code{set print pascal_static-members}
10412 controls whether static members of Pascal objects are displayed.
10413 @xref{Print Settings, pascal_static-members}.
10416 @subsection Modula-2
10418 @cindex Modula-2, @value{GDBN} support
10420 The extensions made to @value{GDBN} to support Modula-2 only support
10421 output from the @sc{gnu} Modula-2 compiler (which is currently being
10422 developed). Other Modula-2 compilers are not currently supported, and
10423 attempting to debug executables produced by them is most likely
10424 to give an error as @value{GDBN} reads in the executable's symbol
10427 @cindex expressions in Modula-2
10429 * M2 Operators:: Built-in operators
10430 * Built-In Func/Proc:: Built-in functions and procedures
10431 * M2 Constants:: Modula-2 constants
10432 * M2 Types:: Modula-2 types
10433 * M2 Defaults:: Default settings for Modula-2
10434 * Deviations:: Deviations from standard Modula-2
10435 * M2 Checks:: Modula-2 type and range checks
10436 * M2 Scope:: The scope operators @code{::} and @code{.}
10437 * GDB/M2:: @value{GDBN} and Modula-2
10441 @subsubsection Operators
10442 @cindex Modula-2 operators
10444 Operators must be defined on values of specific types. For instance,
10445 @code{+} is defined on numbers, but not on structures. Operators are
10446 often defined on groups of types. For the purposes of Modula-2, the
10447 following definitions hold:
10452 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10456 @emph{Character types} consist of @code{CHAR} and its subranges.
10459 @emph{Floating-point types} consist of @code{REAL}.
10462 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10466 @emph{Scalar types} consist of all of the above.
10469 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10472 @emph{Boolean types} consist of @code{BOOLEAN}.
10476 The following operators are supported, and appear in order of
10477 increasing precedence:
10481 Function argument or array index separator.
10484 Assignment. The value of @var{var} @code{:=} @var{value} is
10488 Less than, greater than on integral, floating-point, or enumerated
10492 Less than or equal to, greater than or equal to
10493 on integral, floating-point and enumerated types, or set inclusion on
10494 set types. Same precedence as @code{<}.
10496 @item =@r{, }<>@r{, }#
10497 Equality and two ways of expressing inequality, valid on scalar types.
10498 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10499 available for inequality, since @code{#} conflicts with the script
10503 Set membership. Defined on set types and the types of their members.
10504 Same precedence as @code{<}.
10507 Boolean disjunction. Defined on boolean types.
10510 Boolean conjunction. Defined on boolean types.
10513 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10516 Addition and subtraction on integral and floating-point types, or union
10517 and difference on set types.
10520 Multiplication on integral and floating-point types, or set intersection
10524 Division on floating-point types, or symmetric set difference on set
10525 types. Same precedence as @code{*}.
10528 Integer division and remainder. Defined on integral types. Same
10529 precedence as @code{*}.
10532 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10535 Pointer dereferencing. Defined on pointer types.
10538 Boolean negation. Defined on boolean types. Same precedence as
10542 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10543 precedence as @code{^}.
10546 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10549 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10553 @value{GDBN} and Modula-2 scope operators.
10557 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10558 treats the use of the operator @code{IN}, or the use of operators
10559 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10560 @code{<=}, and @code{>=} on sets as an error.
10564 @node Built-In Func/Proc
10565 @subsubsection Built-in Functions and Procedures
10566 @cindex Modula-2 built-ins
10568 Modula-2 also makes available several built-in procedures and functions.
10569 In describing these, the following metavariables are used:
10574 represents an @code{ARRAY} variable.
10577 represents a @code{CHAR} constant or variable.
10580 represents a variable or constant of integral type.
10583 represents an identifier that belongs to a set. Generally used in the
10584 same function with the metavariable @var{s}. The type of @var{s} should
10585 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10588 represents a variable or constant of integral or floating-point type.
10591 represents a variable or constant of floating-point type.
10597 represents a variable.
10600 represents a variable or constant of one of many types. See the
10601 explanation of the function for details.
10604 All Modula-2 built-in procedures also return a result, described below.
10608 Returns the absolute value of @var{n}.
10611 If @var{c} is a lower case letter, it returns its upper case
10612 equivalent, otherwise it returns its argument.
10615 Returns the character whose ordinal value is @var{i}.
10618 Decrements the value in the variable @var{v} by one. Returns the new value.
10620 @item DEC(@var{v},@var{i})
10621 Decrements the value in the variable @var{v} by @var{i}. Returns the
10624 @item EXCL(@var{m},@var{s})
10625 Removes the element @var{m} from the set @var{s}. Returns the new
10628 @item FLOAT(@var{i})
10629 Returns the floating point equivalent of the integer @var{i}.
10631 @item HIGH(@var{a})
10632 Returns the index of the last member of @var{a}.
10635 Increments the value in the variable @var{v} by one. Returns the new value.
10637 @item INC(@var{v},@var{i})
10638 Increments the value in the variable @var{v} by @var{i}. Returns the
10641 @item INCL(@var{m},@var{s})
10642 Adds the element @var{m} to the set @var{s} if it is not already
10643 there. Returns the new set.
10646 Returns the maximum value of the type @var{t}.
10649 Returns the minimum value of the type @var{t}.
10652 Returns boolean TRUE if @var{i} is an odd number.
10655 Returns the ordinal value of its argument. For example, the ordinal
10656 value of a character is its @sc{ascii} value (on machines supporting the
10657 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10658 integral, character and enumerated types.
10660 @item SIZE(@var{x})
10661 Returns the size of its argument. @var{x} can be a variable or a type.
10663 @item TRUNC(@var{r})
10664 Returns the integral part of @var{r}.
10666 @item TSIZE(@var{x})
10667 Returns the size of its argument. @var{x} can be a variable or a type.
10669 @item VAL(@var{t},@var{i})
10670 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10674 @emph{Warning:} Sets and their operations are not yet supported, so
10675 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10679 @cindex Modula-2 constants
10681 @subsubsection Constants
10683 @value{GDBN} allows you to express the constants of Modula-2 in the following
10689 Integer constants are simply a sequence of digits. When used in an
10690 expression, a constant is interpreted to be type-compatible with the
10691 rest of the expression. Hexadecimal integers are specified by a
10692 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10695 Floating point constants appear as a sequence of digits, followed by a
10696 decimal point and another sequence of digits. An optional exponent can
10697 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10698 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10699 digits of the floating point constant must be valid decimal (base 10)
10703 Character constants consist of a single character enclosed by a pair of
10704 like quotes, either single (@code{'}) or double (@code{"}). They may
10705 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10706 followed by a @samp{C}.
10709 String constants consist of a sequence of characters enclosed by a
10710 pair of like quotes, either single (@code{'}) or double (@code{"}).
10711 Escape sequences in the style of C are also allowed. @xref{C
10712 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10716 Enumerated constants consist of an enumerated identifier.
10719 Boolean constants consist of the identifiers @code{TRUE} and
10723 Pointer constants consist of integral values only.
10726 Set constants are not yet supported.
10730 @subsubsection Modula-2 Types
10731 @cindex Modula-2 types
10733 Currently @value{GDBN} can print the following data types in Modula-2
10734 syntax: array types, record types, set types, pointer types, procedure
10735 types, enumerated types, subrange types and base types. You can also
10736 print the contents of variables declared using these type.
10737 This section gives a number of simple source code examples together with
10738 sample @value{GDBN} sessions.
10740 The first example contains the following section of code:
10749 and you can request @value{GDBN} to interrogate the type and value of
10750 @code{r} and @code{s}.
10753 (@value{GDBP}) print s
10755 (@value{GDBP}) ptype s
10757 (@value{GDBP}) print r
10759 (@value{GDBP}) ptype r
10764 Likewise if your source code declares @code{s} as:
10768 s: SET ['A'..'Z'] ;
10772 then you may query the type of @code{s} by:
10775 (@value{GDBP}) ptype s
10776 type = SET ['A'..'Z']
10780 Note that at present you cannot interactively manipulate set
10781 expressions using the debugger.
10783 The following example shows how you might declare an array in Modula-2
10784 and how you can interact with @value{GDBN} to print its type and contents:
10788 s: ARRAY [-10..10] OF CHAR ;
10792 (@value{GDBP}) ptype s
10793 ARRAY [-10..10] OF CHAR
10796 Note that the array handling is not yet complete and although the type
10797 is printed correctly, expression handling still assumes that all
10798 arrays have a lower bound of zero and not @code{-10} as in the example
10801 Here are some more type related Modula-2 examples:
10805 colour = (blue, red, yellow, green) ;
10806 t = [blue..yellow] ;
10814 The @value{GDBN} interaction shows how you can query the data type
10815 and value of a variable.
10818 (@value{GDBP}) print s
10820 (@value{GDBP}) ptype t
10821 type = [blue..yellow]
10825 In this example a Modula-2 array is declared and its contents
10826 displayed. Observe that the contents are written in the same way as
10827 their @code{C} counterparts.
10831 s: ARRAY [1..5] OF CARDINAL ;
10837 (@value{GDBP}) print s
10838 $1 = @{1, 0, 0, 0, 0@}
10839 (@value{GDBP}) ptype s
10840 type = ARRAY [1..5] OF CARDINAL
10843 The Modula-2 language interface to @value{GDBN} also understands
10844 pointer types as shown in this example:
10848 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10855 and you can request that @value{GDBN} describes the type of @code{s}.
10858 (@value{GDBP}) ptype s
10859 type = POINTER TO ARRAY [1..5] OF CARDINAL
10862 @value{GDBN} handles compound types as we can see in this example.
10863 Here we combine array types, record types, pointer types and subrange
10874 myarray = ARRAY myrange OF CARDINAL ;
10875 myrange = [-2..2] ;
10877 s: POINTER TO ARRAY myrange OF foo ;
10881 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10885 (@value{GDBP}) ptype s
10886 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10889 f3 : ARRAY [-2..2] OF CARDINAL;
10894 @subsubsection Modula-2 Defaults
10895 @cindex Modula-2 defaults
10897 If type and range checking are set automatically by @value{GDBN}, they
10898 both default to @code{on} whenever the working language changes to
10899 Modula-2. This happens regardless of whether you or @value{GDBN}
10900 selected the working language.
10902 If you allow @value{GDBN} to set the language automatically, then entering
10903 code compiled from a file whose name ends with @file{.mod} sets the
10904 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10905 Infer the Source Language}, for further details.
10908 @subsubsection Deviations from Standard Modula-2
10909 @cindex Modula-2, deviations from
10911 A few changes have been made to make Modula-2 programs easier to debug.
10912 This is done primarily via loosening its type strictness:
10916 Unlike in standard Modula-2, pointer constants can be formed by
10917 integers. This allows you to modify pointer variables during
10918 debugging. (In standard Modula-2, the actual address contained in a
10919 pointer variable is hidden from you; it can only be modified
10920 through direct assignment to another pointer variable or expression that
10921 returned a pointer.)
10924 C escape sequences can be used in strings and characters to represent
10925 non-printable characters. @value{GDBN} prints out strings with these
10926 escape sequences embedded. Single non-printable characters are
10927 printed using the @samp{CHR(@var{nnn})} format.
10930 The assignment operator (@code{:=}) returns the value of its right-hand
10934 All built-in procedures both modify @emph{and} return their argument.
10938 @subsubsection Modula-2 Type and Range Checks
10939 @cindex Modula-2 checks
10942 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10945 @c FIXME remove warning when type/range checks added
10947 @value{GDBN} considers two Modula-2 variables type equivalent if:
10951 They are of types that have been declared equivalent via a @code{TYPE
10952 @var{t1} = @var{t2}} statement
10955 They have been declared on the same line. (Note: This is true of the
10956 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10959 As long as type checking is enabled, any attempt to combine variables
10960 whose types are not equivalent is an error.
10962 Range checking is done on all mathematical operations, assignment, array
10963 index bounds, and all built-in functions and procedures.
10966 @subsubsection The Scope Operators @code{::} and @code{.}
10968 @cindex @code{.}, Modula-2 scope operator
10969 @cindex colon, doubled as scope operator
10971 @vindex colon-colon@r{, in Modula-2}
10972 @c Info cannot handle :: but TeX can.
10975 @vindex ::@r{, in Modula-2}
10978 There are a few subtle differences between the Modula-2 scope operator
10979 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10984 @var{module} . @var{id}
10985 @var{scope} :: @var{id}
10989 where @var{scope} is the name of a module or a procedure,
10990 @var{module} the name of a module, and @var{id} is any declared
10991 identifier within your program, except another module.
10993 Using the @code{::} operator makes @value{GDBN} search the scope
10994 specified by @var{scope} for the identifier @var{id}. If it is not
10995 found in the specified scope, then @value{GDBN} searches all scopes
10996 enclosing the one specified by @var{scope}.
10998 Using the @code{.} operator makes @value{GDBN} search the current scope for
10999 the identifier specified by @var{id} that was imported from the
11000 definition module specified by @var{module}. With this operator, it is
11001 an error if the identifier @var{id} was not imported from definition
11002 module @var{module}, or if @var{id} is not an identifier in
11006 @subsubsection @value{GDBN} and Modula-2
11008 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11009 Five subcommands of @code{set print} and @code{show print} apply
11010 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11011 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11012 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11013 analogue in Modula-2.
11015 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11016 with any language, is not useful with Modula-2. Its
11017 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11018 created in Modula-2 as they can in C or C@t{++}. However, because an
11019 address can be specified by an integral constant, the construct
11020 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11022 @cindex @code{#} in Modula-2
11023 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11024 interpreted as the beginning of a comment. Use @code{<>} instead.
11030 The extensions made to @value{GDBN} for Ada only support
11031 output from the @sc{gnu} Ada (GNAT) compiler.
11032 Other Ada compilers are not currently supported, and
11033 attempting to debug executables produced by them is most likely
11037 @cindex expressions in Ada
11039 * Ada Mode Intro:: General remarks on the Ada syntax
11040 and semantics supported by Ada mode
11042 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11043 * Additions to Ada:: Extensions of the Ada expression syntax.
11044 * Stopping Before Main Program:: Debugging the program during elaboration.
11045 * Ada Glitches:: Known peculiarities of Ada mode.
11048 @node Ada Mode Intro
11049 @subsubsection Introduction
11050 @cindex Ada mode, general
11052 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11053 syntax, with some extensions.
11054 The philosophy behind the design of this subset is
11058 That @value{GDBN} should provide basic literals and access to operations for
11059 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11060 leaving more sophisticated computations to subprograms written into the
11061 program (which therefore may be called from @value{GDBN}).
11064 That type safety and strict adherence to Ada language restrictions
11065 are not particularly important to the @value{GDBN} user.
11068 That brevity is important to the @value{GDBN} user.
11071 Thus, for brevity, the debugger acts as if all names declared in
11072 user-written packages are directly visible, even if they are not visible
11073 according to Ada rules, thus making it unnecessary to fully qualify most
11074 names with their packages, regardless of context. Where this causes
11075 ambiguity, @value{GDBN} asks the user's intent.
11077 The debugger will start in Ada mode if it detects an Ada main program.
11078 As for other languages, it will enter Ada mode when stopped in a program that
11079 was translated from an Ada source file.
11081 While in Ada mode, you may use `@t{--}' for comments. This is useful
11082 mostly for documenting command files. The standard @value{GDBN} comment
11083 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11084 middle (to allow based literals).
11086 The debugger supports limited overloading. Given a subprogram call in which
11087 the function symbol has multiple definitions, it will use the number of
11088 actual parameters and some information about their types to attempt to narrow
11089 the set of definitions. It also makes very limited use of context, preferring
11090 procedures to functions in the context of the @code{call} command, and
11091 functions to procedures elsewhere.
11093 @node Omissions from Ada
11094 @subsubsection Omissions from Ada
11095 @cindex Ada, omissions from
11097 Here are the notable omissions from the subset:
11101 Only a subset of the attributes are supported:
11105 @t{'First}, @t{'Last}, and @t{'Length}
11106 on array objects (not on types and subtypes).
11109 @t{'Min} and @t{'Max}.
11112 @t{'Pos} and @t{'Val}.
11118 @t{'Range} on array objects (not subtypes), but only as the right
11119 operand of the membership (@code{in}) operator.
11122 @t{'Access}, @t{'Unchecked_Access}, and
11123 @t{'Unrestricted_Access} (a GNAT extension).
11131 @code{Characters.Latin_1} are not available and
11132 concatenation is not implemented. Thus, escape characters in strings are
11133 not currently available.
11136 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11137 equality of representations. They will generally work correctly
11138 for strings and arrays whose elements have integer or enumeration types.
11139 They may not work correctly for arrays whose element
11140 types have user-defined equality, for arrays of real values
11141 (in particular, IEEE-conformant floating point, because of negative
11142 zeroes and NaNs), and for arrays whose elements contain unused bits with
11143 indeterminate values.
11146 The other component-by-component array operations (@code{and}, @code{or},
11147 @code{xor}, @code{not}, and relational tests other than equality)
11148 are not implemented.
11151 @cindex array aggregates (Ada)
11152 @cindex record aggregates (Ada)
11153 @cindex aggregates (Ada)
11154 There is limited support for array and record aggregates. They are
11155 permitted only on the right sides of assignments, as in these examples:
11158 set An_Array := (1, 2, 3, 4, 5, 6)
11159 set An_Array := (1, others => 0)
11160 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11161 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11162 set A_Record := (1, "Peter", True);
11163 set A_Record := (Name => "Peter", Id => 1, Alive => True)
11167 discriminant's value by assigning an aggregate has an
11168 undefined effect if that discriminant is used within the record.
11169 However, you can first modify discriminants by directly assigning to
11170 them (which normally would not be allowed in Ada), and then performing an
11171 aggregate assignment. For example, given a variable @code{A_Rec}
11172 declared to have a type such as:
11175 type Rec (Len : Small_Integer := 0) is record
11177 Vals : IntArray (1 .. Len);
11181 you can assign a value with a different size of @code{Vals} with two
11186 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11189 As this example also illustrates, @value{GDBN} is very loose about the usual
11190 rules concerning aggregates. You may leave out some of the
11191 components of an array or record aggregate (such as the @code{Len}
11192 component in the assignment to @code{A_Rec} above); they will retain their
11193 original values upon assignment. You may freely use dynamic values as
11194 indices in component associations. You may even use overlapping or
11195 redundant component associations, although which component values are
11196 assigned in such cases is not defined.
11199 Calls to dispatching subprograms are not implemented.
11202 The overloading algorithm is much more limited (i.e., less selective)
11203 than that of real Ada. It makes only limited use of the context in
11204 which a subexpression appears to resolve its meaning, and it is much
11205 looser in its rules for allowing type matches. As a result, some
11206 function calls will be ambiguous, and the user will be asked to choose
11207 the proper resolution.
11210 The @code{new} operator is not implemented.
11213 Entry calls are not implemented.
11216 Aside from printing, arithmetic operations on the native VAX floating-point
11217 formats are not supported.
11220 It is not possible to slice a packed array.
11223 The names @code{True} and @code{False}, when not part of a qualified name,
11224 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11226 Should your program
11227 redefine these names in a package or procedure (at best a dubious practice),
11228 you will have to use fully qualified names to access their new definitions.
11231 @node Additions to Ada
11232 @subsubsection Additions to Ada
11233 @cindex Ada, deviations from
11235 As it does for other languages, @value{GDBN} makes certain generic
11236 extensions to Ada (@pxref{Expressions}):
11240 If the expression @var{E} is a variable residing in memory (typically
11241 a local variable or array element) and @var{N} is a positive integer,
11242 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11243 @var{N}-1 adjacent variables following it in memory as an array. In
11244 Ada, this operator is generally not necessary, since its prime use is
11245 in displaying parts of an array, and slicing will usually do this in
11246 Ada. However, there are occasional uses when debugging programs in
11247 which certain debugging information has been optimized away.
11250 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11251 appears in function or file @var{B}.'' When @var{B} is a file name,
11252 you must typically surround it in single quotes.
11255 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11256 @var{type} that appears at address @var{addr}.''
11259 A name starting with @samp{$} is a convenience variable
11260 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11263 In addition, @value{GDBN} provides a few other shortcuts and outright
11264 additions specific to Ada:
11268 The assignment statement is allowed as an expression, returning
11269 its right-hand operand as its value. Thus, you may enter
11273 print A(tmp := y + 1)
11277 The semicolon is allowed as an ``operator,'' returning as its value
11278 the value of its right-hand operand.
11279 This allows, for example,
11280 complex conditional breaks:
11284 condition 1 (report(i); k += 1; A(k) > 100)
11288 Rather than use catenation and symbolic character names to introduce special
11289 characters into strings, one may instead use a special bracket notation,
11290 which is also used to print strings. A sequence of characters of the form
11291 @samp{["@var{XX}"]} within a string or character literal denotes the
11292 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11293 sequence of characters @samp{["""]} also denotes a single quotation mark
11294 in strings. For example,
11296 "One line.["0a"]Next line.["0a"]"
11299 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11303 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11304 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11312 When printing arrays, @value{GDBN} uses positional notation when the
11313 array has a lower bound of 1, and uses a modified named notation otherwise.
11314 For example, a one-dimensional array of three integers with a lower bound
11315 of 3 might print as
11322 That is, in contrast to valid Ada, only the first component has a @code{=>}
11326 You may abbreviate attributes in expressions with any unique,
11327 multi-character subsequence of
11328 their names (an exact match gets preference).
11329 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11330 in place of @t{a'length}.
11333 @cindex quoting Ada internal identifiers
11334 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11335 to lower case. The GNAT compiler uses upper-case characters for
11336 some of its internal identifiers, which are normally of no interest to users.
11337 For the rare occasions when you actually have to look at them,
11338 enclose them in angle brackets to avoid the lower-case mapping.
11341 @value{GDBP} print <JMPBUF_SAVE>[0]
11345 Printing an object of class-wide type or dereferencing an
11346 access-to-class-wide value will display all the components of the object's
11347 specific type (as indicated by its run-time tag). Likewise, component
11348 selection on such a value will operate on the specific type of the
11353 @node Stopping Before Main Program
11354 @subsubsection Stopping at the Very Beginning
11356 @cindex breakpointing Ada elaboration code
11357 It is sometimes necessary to debug the program during elaboration, and
11358 before reaching the main procedure.
11359 As defined in the Ada Reference
11360 Manual, the elaboration code is invoked from a procedure called
11361 @code{adainit}. To run your program up to the beginning of
11362 elaboration, simply use the following two commands:
11363 @code{tbreak adainit} and @code{run}.
11366 @subsubsection Known Peculiarities of Ada Mode
11367 @cindex Ada, problems
11369 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11370 we know of several problems with and limitations of Ada mode in
11372 some of which will be fixed with planned future releases of the debugger
11373 and the GNU Ada compiler.
11377 Currently, the debugger
11378 has insufficient information to determine whether certain pointers represent
11379 pointers to objects or the objects themselves.
11380 Thus, the user may have to tack an extra @code{.all} after an expression
11381 to get it printed properly.
11384 Static constants that the compiler chooses not to materialize as objects in
11385 storage are invisible to the debugger.
11388 Named parameter associations in function argument lists are ignored (the
11389 argument lists are treated as positional).
11392 Many useful library packages are currently invisible to the debugger.
11395 Fixed-point arithmetic, conversions, input, and output is carried out using
11396 floating-point arithmetic, and may give results that only approximate those on
11400 The type of the @t{'Address} attribute may not be @code{System.Address}.
11403 The GNAT compiler never generates the prefix @code{Standard} for any of
11404 the standard symbols defined by the Ada language. @value{GDBN} knows about
11405 this: it will strip the prefix from names when you use it, and will never
11406 look for a name you have so qualified among local symbols, nor match against
11407 symbols in other packages or subprograms. If you have
11408 defined entities anywhere in your program other than parameters and
11409 local variables whose simple names match names in @code{Standard},
11410 GNAT's lack of qualification here can cause confusion. When this happens,
11411 you can usually resolve the confusion
11412 by qualifying the problematic names with package
11413 @code{Standard} explicitly.
11416 @node Unsupported Languages
11417 @section Unsupported Languages
11419 @cindex unsupported languages
11420 @cindex minimal language
11421 In addition to the other fully-supported programming languages,
11422 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11423 It does not represent a real programming language, but provides a set
11424 of capabilities close to what the C or assembly languages provide.
11425 This should allow most simple operations to be performed while debugging
11426 an application that uses a language currently not supported by @value{GDBN}.
11428 If the language is set to @code{auto}, @value{GDBN} will automatically
11429 select this language if the current frame corresponds to an unsupported
11433 @chapter Examining the Symbol Table
11435 The commands described in this chapter allow you to inquire about the
11436 symbols (names of variables, functions and types) defined in your
11437 program. This information is inherent in the text of your program and
11438 does not change as your program executes. @value{GDBN} finds it in your
11439 program's symbol table, in the file indicated when you started @value{GDBN}
11440 (@pxref{File Options, ,Choosing Files}), or by one of the
11441 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11443 @cindex symbol names
11444 @cindex names of symbols
11445 @cindex quoting names
11446 Occasionally, you may need to refer to symbols that contain unusual
11447 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11448 most frequent case is in referring to static variables in other
11449 source files (@pxref{Variables,,Program Variables}). File names
11450 are recorded in object files as debugging symbols, but @value{GDBN} would
11451 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11452 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11453 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11460 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11463 @cindex case-insensitive symbol names
11464 @cindex case sensitivity in symbol names
11465 @kindex set case-sensitive
11466 @item set case-sensitive on
11467 @itemx set case-sensitive off
11468 @itemx set case-sensitive auto
11469 Normally, when @value{GDBN} looks up symbols, it matches their names
11470 with case sensitivity determined by the current source language.
11471 Occasionally, you may wish to control that. The command @code{set
11472 case-sensitive} lets you do that by specifying @code{on} for
11473 case-sensitive matches or @code{off} for case-insensitive ones. If
11474 you specify @code{auto}, case sensitivity is reset to the default
11475 suitable for the source language. The default is case-sensitive
11476 matches for all languages except for Fortran, for which the default is
11477 case-insensitive matches.
11479 @kindex show case-sensitive
11480 @item show case-sensitive
11481 This command shows the current setting of case sensitivity for symbols
11484 @kindex info address
11485 @cindex address of a symbol
11486 @item info address @var{symbol}
11487 Describe where the data for @var{symbol} is stored. For a register
11488 variable, this says which register it is kept in. For a non-register
11489 local variable, this prints the stack-frame offset at which the variable
11492 Note the contrast with @samp{print &@var{symbol}}, which does not work
11493 at all for a register variable, and for a stack local variable prints
11494 the exact address of the current instantiation of the variable.
11496 @kindex info symbol
11497 @cindex symbol from address
11498 @cindex closest symbol and offset for an address
11499 @item info symbol @var{addr}
11500 Print the name of a symbol which is stored at the address @var{addr}.
11501 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11502 nearest symbol and an offset from it:
11505 (@value{GDBP}) info symbol 0x54320
11506 _initialize_vx + 396 in section .text
11510 This is the opposite of the @code{info address} command. You can use
11511 it to find out the name of a variable or a function given its address.
11514 @item whatis [@var{arg}]
11515 Print the data type of @var{arg}, which can be either an expression or
11516 a data type. With no argument, print the data type of @code{$}, the
11517 last value in the value history. If @var{arg} is an expression, it is
11518 not actually evaluated, and any side-effecting operations (such as
11519 assignments or function calls) inside it do not take place. If
11520 @var{arg} is a type name, it may be the name of a type or typedef, or
11521 for C code it may have the form @samp{class @var{class-name}},
11522 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11523 @samp{enum @var{enum-tag}}.
11524 @xref{Expressions, ,Expressions}.
11527 @item ptype [@var{arg}]
11528 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11529 detailed description of the type, instead of just the name of the type.
11530 @xref{Expressions, ,Expressions}.
11532 For example, for this variable declaration:
11535 struct complex @{double real; double imag;@} v;
11539 the two commands give this output:
11543 (@value{GDBP}) whatis v
11544 type = struct complex
11545 (@value{GDBP}) ptype v
11546 type = struct complex @{
11554 As with @code{whatis}, using @code{ptype} without an argument refers to
11555 the type of @code{$}, the last value in the value history.
11557 @cindex incomplete type
11558 Sometimes, programs use opaque data types or incomplete specifications
11559 of complex data structure. If the debug information included in the
11560 program does not allow @value{GDBN} to display a full declaration of
11561 the data type, it will say @samp{<incomplete type>}. For example,
11562 given these declarations:
11566 struct foo *fooptr;
11570 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11573 (@value{GDBP}) ptype foo
11574 $1 = <incomplete type>
11578 ``Incomplete type'' is C terminology for data types that are not
11579 completely specified.
11582 @item info types @var{regexp}
11584 Print a brief description of all types whose names match the regular
11585 expression @var{regexp} (or all types in your program, if you supply
11586 no argument). Each complete typename is matched as though it were a
11587 complete line; thus, @samp{i type value} gives information on all
11588 types in your program whose names include the string @code{value}, but
11589 @samp{i type ^value$} gives information only on types whose complete
11590 name is @code{value}.
11592 This command differs from @code{ptype} in two ways: first, like
11593 @code{whatis}, it does not print a detailed description; second, it
11594 lists all source files where a type is defined.
11597 @cindex local variables
11598 @item info scope @var{location}
11599 List all the variables local to a particular scope. This command
11600 accepts a @var{location} argument---a function name, a source line, or
11601 an address preceded by a @samp{*}, and prints all the variables local
11602 to the scope defined by that location. (@xref{Specify Location}, for
11603 details about supported forms of @var{location}.) For example:
11606 (@value{GDBP}) @b{info scope command_line_handler}
11607 Scope for command_line_handler:
11608 Symbol rl is an argument at stack/frame offset 8, length 4.
11609 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11610 Symbol linelength is in static storage at address 0x150a1c, length 4.
11611 Symbol p is a local variable in register $esi, length 4.
11612 Symbol p1 is a local variable in register $ebx, length 4.
11613 Symbol nline is a local variable in register $edx, length 4.
11614 Symbol repeat is a local variable at frame offset -8, length 4.
11618 This command is especially useful for determining what data to collect
11619 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11622 @kindex info source
11624 Show information about the current source file---that is, the source file for
11625 the function containing the current point of execution:
11628 the name of the source file, and the directory containing it,
11630 the directory it was compiled in,
11632 its length, in lines,
11634 which programming language it is written in,
11636 whether the executable includes debugging information for that file, and
11637 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11639 whether the debugging information includes information about
11640 preprocessor macros.
11644 @kindex info sources
11646 Print the names of all source files in your program for which there is
11647 debugging information, organized into two lists: files whose symbols
11648 have already been read, and files whose symbols will be read when needed.
11650 @kindex info functions
11651 @item info functions
11652 Print the names and data types of all defined functions.
11654 @item info functions @var{regexp}
11655 Print the names and data types of all defined functions
11656 whose names contain a match for regular expression @var{regexp}.
11657 Thus, @samp{info fun step} finds all functions whose names
11658 include @code{step}; @samp{info fun ^step} finds those whose names
11659 start with @code{step}. If a function name contains characters
11660 that conflict with the regular expression language (e.g.@:
11661 @samp{operator*()}), they may be quoted with a backslash.
11663 @kindex info variables
11664 @item info variables
11665 Print the names and data types of all variables that are declared
11666 outside of functions (i.e.@: excluding local variables).
11668 @item info variables @var{regexp}
11669 Print the names and data types of all variables (except for local
11670 variables) whose names contain a match for regular expression
11673 @kindex info classes
11674 @cindex Objective-C, classes and selectors
11676 @itemx info classes @var{regexp}
11677 Display all Objective-C classes in your program, or
11678 (with the @var{regexp} argument) all those matching a particular regular
11681 @kindex info selectors
11682 @item info selectors
11683 @itemx info selectors @var{regexp}
11684 Display all Objective-C selectors in your program, or
11685 (with the @var{regexp} argument) all those matching a particular regular
11689 This was never implemented.
11690 @kindex info methods
11692 @itemx info methods @var{regexp}
11693 The @code{info methods} command permits the user to examine all defined
11694 methods within C@t{++} program, or (with the @var{regexp} argument) a
11695 specific set of methods found in the various C@t{++} classes. Many
11696 C@t{++} classes provide a large number of methods. Thus, the output
11697 from the @code{ptype} command can be overwhelming and hard to use. The
11698 @code{info-methods} command filters the methods, printing only those
11699 which match the regular-expression @var{regexp}.
11702 @cindex reloading symbols
11703 Some systems allow individual object files that make up your program to
11704 be replaced without stopping and restarting your program. For example,
11705 in VxWorks you can simply recompile a defective object file and keep on
11706 running. If you are running on one of these systems, you can allow
11707 @value{GDBN} to reload the symbols for automatically relinked modules:
11710 @kindex set symbol-reloading
11711 @item set symbol-reloading on
11712 Replace symbol definitions for the corresponding source file when an
11713 object file with a particular name is seen again.
11715 @item set symbol-reloading off
11716 Do not replace symbol definitions when encountering object files of the
11717 same name more than once. This is the default state; if you are not
11718 running on a system that permits automatic relinking of modules, you
11719 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11720 may discard symbols when linking large programs, that may contain
11721 several modules (from different directories or libraries) with the same
11724 @kindex show symbol-reloading
11725 @item show symbol-reloading
11726 Show the current @code{on} or @code{off} setting.
11729 @cindex opaque data types
11730 @kindex set opaque-type-resolution
11731 @item set opaque-type-resolution on
11732 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11733 declared as a pointer to a @code{struct}, @code{class}, or
11734 @code{union}---for example, @code{struct MyType *}---that is used in one
11735 source file although the full declaration of @code{struct MyType} is in
11736 another source file. The default is on.
11738 A change in the setting of this subcommand will not take effect until
11739 the next time symbols for a file are loaded.
11741 @item set opaque-type-resolution off
11742 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11743 is printed as follows:
11745 @{<no data fields>@}
11748 @kindex show opaque-type-resolution
11749 @item show opaque-type-resolution
11750 Show whether opaque types are resolved or not.
11752 @kindex set print symbol-loading
11753 @cindex print messages when symbols are loaded
11754 @item set print symbol-loading
11755 @itemx set print symbol-loading on
11756 @itemx set print symbol-loading off
11757 The @code{set print symbol-loading} command allows you to enable or
11758 disable printing of messages when @value{GDBN} loads symbols.
11759 By default, these messages will be printed, and normally this is what
11760 you want. Disabling these messages is useful when debugging applications
11761 with lots of shared libraries where the quantity of output can be more
11762 annoying than useful.
11764 @kindex show print symbol-loading
11765 @item show print symbol-loading
11766 Show whether messages will be printed when @value{GDBN} loads symbols.
11768 @kindex maint print symbols
11769 @cindex symbol dump
11770 @kindex maint print psymbols
11771 @cindex partial symbol dump
11772 @item maint print symbols @var{filename}
11773 @itemx maint print psymbols @var{filename}
11774 @itemx maint print msymbols @var{filename}
11775 Write a dump of debugging symbol data into the file @var{filename}.
11776 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11777 symbols with debugging data are included. If you use @samp{maint print
11778 symbols}, @value{GDBN} includes all the symbols for which it has already
11779 collected full details: that is, @var{filename} reflects symbols for
11780 only those files whose symbols @value{GDBN} has read. You can use the
11781 command @code{info sources} to find out which files these are. If you
11782 use @samp{maint print psymbols} instead, the dump shows information about
11783 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11784 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11785 @samp{maint print msymbols} dumps just the minimal symbol information
11786 required for each object file from which @value{GDBN} has read some symbols.
11787 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11788 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11790 @kindex maint info symtabs
11791 @kindex maint info psymtabs
11792 @cindex listing @value{GDBN}'s internal symbol tables
11793 @cindex symbol tables, listing @value{GDBN}'s internal
11794 @cindex full symbol tables, listing @value{GDBN}'s internal
11795 @cindex partial symbol tables, listing @value{GDBN}'s internal
11796 @item maint info symtabs @r{[} @var{regexp} @r{]}
11797 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11799 List the @code{struct symtab} or @code{struct partial_symtab}
11800 structures whose names match @var{regexp}. If @var{regexp} is not
11801 given, list them all. The output includes expressions which you can
11802 copy into a @value{GDBN} debugging this one to examine a particular
11803 structure in more detail. For example:
11806 (@value{GDBP}) maint info psymtabs dwarf2read
11807 @{ objfile /home/gnu/build/gdb/gdb
11808 ((struct objfile *) 0x82e69d0)
11809 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11810 ((struct partial_symtab *) 0x8474b10)
11813 text addresses 0x814d3c8 -- 0x8158074
11814 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11815 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11816 dependencies (none)
11819 (@value{GDBP}) maint info symtabs
11823 We see that there is one partial symbol table whose filename contains
11824 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11825 and we see that @value{GDBN} has not read in any symtabs yet at all.
11826 If we set a breakpoint on a function, that will cause @value{GDBN} to
11827 read the symtab for the compilation unit containing that function:
11830 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11831 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11833 (@value{GDBP}) maint info symtabs
11834 @{ objfile /home/gnu/build/gdb/gdb
11835 ((struct objfile *) 0x82e69d0)
11836 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11837 ((struct symtab *) 0x86c1f38)
11840 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11841 linetable ((struct linetable *) 0x8370fa0)
11842 debugformat DWARF 2
11851 @chapter Altering Execution
11853 Once you think you have found an error in your program, you might want to
11854 find out for certain whether correcting the apparent error would lead to
11855 correct results in the rest of the run. You can find the answer by
11856 experiment, using the @value{GDBN} features for altering execution of the
11859 For example, you can store new values into variables or memory
11860 locations, give your program a signal, restart it at a different
11861 address, or even return prematurely from a function.
11864 * Assignment:: Assignment to variables
11865 * Jumping:: Continuing at a different address
11866 * Signaling:: Giving your program a signal
11867 * Returning:: Returning from a function
11868 * Calling:: Calling your program's functions
11869 * Patching:: Patching your program
11873 @section Assignment to Variables
11876 @cindex setting variables
11877 To alter the value of a variable, evaluate an assignment expression.
11878 @xref{Expressions, ,Expressions}. For example,
11885 stores the value 4 into the variable @code{x}, and then prints the
11886 value of the assignment expression (which is 4).
11887 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11888 information on operators in supported languages.
11890 @kindex set variable
11891 @cindex variables, setting
11892 If you are not interested in seeing the value of the assignment, use the
11893 @code{set} command instead of the @code{print} command. @code{set} is
11894 really the same as @code{print} except that the expression's value is
11895 not printed and is not put in the value history (@pxref{Value History,
11896 ,Value History}). The expression is evaluated only for its effects.
11898 If the beginning of the argument string of the @code{set} command
11899 appears identical to a @code{set} subcommand, use the @code{set
11900 variable} command instead of just @code{set}. This command is identical
11901 to @code{set} except for its lack of subcommands. For example, if your
11902 program has a variable @code{width}, you get an error if you try to set
11903 a new value with just @samp{set width=13}, because @value{GDBN} has the
11904 command @code{set width}:
11907 (@value{GDBP}) whatis width
11909 (@value{GDBP}) p width
11911 (@value{GDBP}) set width=47
11912 Invalid syntax in expression.
11916 The invalid expression, of course, is @samp{=47}. In
11917 order to actually set the program's variable @code{width}, use
11920 (@value{GDBP}) set var width=47
11923 Because the @code{set} command has many subcommands that can conflict
11924 with the names of program variables, it is a good idea to use the
11925 @code{set variable} command instead of just @code{set}. For example, if
11926 your program has a variable @code{g}, you run into problems if you try
11927 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11928 the command @code{set gnutarget}, abbreviated @code{set g}:
11932 (@value{GDBP}) whatis g
11936 (@value{GDBP}) set g=4
11940 The program being debugged has been started already.
11941 Start it from the beginning? (y or n) y
11942 Starting program: /home/smith/cc_progs/a.out
11943 "/home/smith/cc_progs/a.out": can't open to read symbols:
11944 Invalid bfd target.
11945 (@value{GDBP}) show g
11946 The current BFD target is "=4".
11951 The program variable @code{g} did not change, and you silently set the
11952 @code{gnutarget} to an invalid value. In order to set the variable
11956 (@value{GDBP}) set var g=4
11959 @value{GDBN} allows more implicit conversions in assignments than C; you can
11960 freely store an integer value into a pointer variable or vice versa,
11961 and you can convert any structure to any other structure that is the
11962 same length or shorter.
11963 @comment FIXME: how do structs align/pad in these conversions?
11964 @comment /doc@cygnus.com 18dec1990
11966 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11967 construct to generate a value of specified type at a specified address
11968 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11969 to memory location @code{0x83040} as an integer (which implies a certain size
11970 and representation in memory), and
11973 set @{int@}0x83040 = 4
11977 stores the value 4 into that memory location.
11980 @section Continuing at a Different Address
11982 Ordinarily, when you continue your program, you do so at the place where
11983 it stopped, with the @code{continue} command. You can instead continue at
11984 an address of your own choosing, with the following commands:
11988 @item jump @var{linespec}
11989 @itemx jump @var{location}
11990 Resume execution at line @var{linespec} or at address given by
11991 @var{location}. Execution stops again immediately if there is a
11992 breakpoint there. @xref{Specify Location}, for a description of the
11993 different forms of @var{linespec} and @var{location}. It is common
11994 practice to use the @code{tbreak} command in conjunction with
11995 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
11997 The @code{jump} command does not change the current stack frame, or
11998 the stack pointer, or the contents of any memory location or any
11999 register other than the program counter. If line @var{linespec} is in
12000 a different function from the one currently executing, the results may
12001 be bizarre if the two functions expect different patterns of arguments or
12002 of local variables. For this reason, the @code{jump} command requests
12003 confirmation if the specified line is not in the function currently
12004 executing. However, even bizarre results are predictable if you are
12005 well acquainted with the machine-language code of your program.
12008 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12009 On many systems, you can get much the same effect as the @code{jump}
12010 command by storing a new value into the register @code{$pc}. The
12011 difference is that this does not start your program running; it only
12012 changes the address of where it @emph{will} run when you continue. For
12020 makes the next @code{continue} command or stepping command execute at
12021 address @code{0x485}, rather than at the address where your program stopped.
12022 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12024 The most common occasion to use the @code{jump} command is to back
12025 up---perhaps with more breakpoints set---over a portion of a program
12026 that has already executed, in order to examine its execution in more
12031 @section Giving your Program a Signal
12032 @cindex deliver a signal to a program
12036 @item signal @var{signal}
12037 Resume execution where your program stopped, but immediately give it the
12038 signal @var{signal}. @var{signal} can be the name or the number of a
12039 signal. For example, on many systems @code{signal 2} and @code{signal
12040 SIGINT} are both ways of sending an interrupt signal.
12042 Alternatively, if @var{signal} is zero, continue execution without
12043 giving a signal. This is useful when your program stopped on account of
12044 a signal and would ordinary see the signal when resumed with the
12045 @code{continue} command; @samp{signal 0} causes it to resume without a
12048 @code{signal} does not repeat when you press @key{RET} a second time
12049 after executing the command.
12053 Invoking the @code{signal} command is not the same as invoking the
12054 @code{kill} utility from the shell. Sending a signal with @code{kill}
12055 causes @value{GDBN} to decide what to do with the signal depending on
12056 the signal handling tables (@pxref{Signals}). The @code{signal} command
12057 passes the signal directly to your program.
12061 @section Returning from a Function
12064 @cindex returning from a function
12067 @itemx return @var{expression}
12068 You can cancel execution of a function call with the @code{return}
12069 command. If you give an
12070 @var{expression} argument, its value is used as the function's return
12074 When you use @code{return}, @value{GDBN} discards the selected stack frame
12075 (and all frames within it). You can think of this as making the
12076 discarded frame return prematurely. If you wish to specify a value to
12077 be returned, give that value as the argument to @code{return}.
12079 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12080 Frame}), and any other frames inside of it, leaving its caller as the
12081 innermost remaining frame. That frame becomes selected. The
12082 specified value is stored in the registers used for returning values
12085 The @code{return} command does not resume execution; it leaves the
12086 program stopped in the state that would exist if the function had just
12087 returned. In contrast, the @code{finish} command (@pxref{Continuing
12088 and Stepping, ,Continuing and Stepping}) resumes execution until the
12089 selected stack frame returns naturally.
12092 @section Calling Program Functions
12095 @cindex calling functions
12096 @cindex inferior functions, calling
12097 @item print @var{expr}
12098 Evaluate the expression @var{expr} and display the resulting value.
12099 @var{expr} may include calls to functions in the program being
12103 @item call @var{expr}
12104 Evaluate the expression @var{expr} without displaying @code{void}
12107 You can use this variant of the @code{print} command if you want to
12108 execute a function from your program that does not return anything
12109 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12110 with @code{void} returned values that @value{GDBN} will otherwise
12111 print. If the result is not void, it is printed and saved in the
12115 It is possible for the function you call via the @code{print} or
12116 @code{call} command to generate a signal (e.g., if there's a bug in
12117 the function, or if you passed it incorrect arguments). What happens
12118 in that case is controlled by the @code{set unwindonsignal} command.
12121 @item set unwindonsignal
12122 @kindex set unwindonsignal
12123 @cindex unwind stack in called functions
12124 @cindex call dummy stack unwinding
12125 Set unwinding of the stack if a signal is received while in a function
12126 that @value{GDBN} called in the program being debugged. If set to on,
12127 @value{GDBN} unwinds the stack it created for the call and restores
12128 the context to what it was before the call. If set to off (the
12129 default), @value{GDBN} stops in the frame where the signal was
12132 @item show unwindonsignal
12133 @kindex show unwindonsignal
12134 Show the current setting of stack unwinding in the functions called by
12138 @cindex weak alias functions
12139 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12140 for another function. In such case, @value{GDBN} might not pick up
12141 the type information, including the types of the function arguments,
12142 which causes @value{GDBN} to call the inferior function incorrectly.
12143 As a result, the called function will function erroneously and may
12144 even crash. A solution to that is to use the name of the aliased
12148 @section Patching Programs
12150 @cindex patching binaries
12151 @cindex writing into executables
12152 @cindex writing into corefiles
12154 By default, @value{GDBN} opens the file containing your program's
12155 executable code (or the corefile) read-only. This prevents accidental
12156 alterations to machine code; but it also prevents you from intentionally
12157 patching your program's binary.
12159 If you'd like to be able to patch the binary, you can specify that
12160 explicitly with the @code{set write} command. For example, you might
12161 want to turn on internal debugging flags, or even to make emergency
12167 @itemx set write off
12168 If you specify @samp{set write on}, @value{GDBN} opens executable and
12169 core files for both reading and writing; if you specify @samp{set write
12170 off} (the default), @value{GDBN} opens them read-only.
12172 If you have already loaded a file, you must load it again (using the
12173 @code{exec-file} or @code{core-file} command) after changing @code{set
12174 write}, for your new setting to take effect.
12178 Display whether executable files and core files are opened for writing
12179 as well as reading.
12183 @chapter @value{GDBN} Files
12185 @value{GDBN} needs to know the file name of the program to be debugged,
12186 both in order to read its symbol table and in order to start your
12187 program. To debug a core dump of a previous run, you must also tell
12188 @value{GDBN} the name of the core dump file.
12191 * Files:: Commands to specify files
12192 * Separate Debug Files:: Debugging information in separate files
12193 * Symbol Errors:: Errors reading symbol files
12197 @section Commands to Specify Files
12199 @cindex symbol table
12200 @cindex core dump file
12202 You may want to specify executable and core dump file names. The usual
12203 way to do this is at start-up time, using the arguments to
12204 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12205 Out of @value{GDBN}}).
12207 Occasionally it is necessary to change to a different file during a
12208 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12209 specify a file you want to use. Or you are debugging a remote target
12210 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12211 Program}). In these situations the @value{GDBN} commands to specify
12212 new files are useful.
12215 @cindex executable file
12217 @item file @var{filename}
12218 Use @var{filename} as the program to be debugged. It is read for its
12219 symbols and for the contents of pure memory. It is also the program
12220 executed when you use the @code{run} command. If you do not specify a
12221 directory and the file is not found in the @value{GDBN} working directory,
12222 @value{GDBN} uses the environment variable @code{PATH} as a list of
12223 directories to search, just as the shell does when looking for a program
12224 to run. You can change the value of this variable, for both @value{GDBN}
12225 and your program, using the @code{path} command.
12227 @cindex unlinked object files
12228 @cindex patching object files
12229 You can load unlinked object @file{.o} files into @value{GDBN} using
12230 the @code{file} command. You will not be able to ``run'' an object
12231 file, but you can disassemble functions and inspect variables. Also,
12232 if the underlying BFD functionality supports it, you could use
12233 @kbd{gdb -write} to patch object files using this technique. Note
12234 that @value{GDBN} can neither interpret nor modify relocations in this
12235 case, so branches and some initialized variables will appear to go to
12236 the wrong place. But this feature is still handy from time to time.
12239 @code{file} with no argument makes @value{GDBN} discard any information it
12240 has on both executable file and the symbol table.
12243 @item exec-file @r{[} @var{filename} @r{]}
12244 Specify that the program to be run (but not the symbol table) is found
12245 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12246 if necessary to locate your program. Omitting @var{filename} means to
12247 discard information on the executable file.
12249 @kindex symbol-file
12250 @item symbol-file @r{[} @var{filename} @r{]}
12251 Read symbol table information from file @var{filename}. @code{PATH} is
12252 searched when necessary. Use the @code{file} command to get both symbol
12253 table and program to run from the same file.
12255 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12256 program's symbol table.
12258 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12259 some breakpoints and auto-display expressions. This is because they may
12260 contain pointers to the internal data recording symbols and data types,
12261 which are part of the old symbol table data being discarded inside
12264 @code{symbol-file} does not repeat if you press @key{RET} again after
12267 When @value{GDBN} is configured for a particular environment, it
12268 understands debugging information in whatever format is the standard
12269 generated for that environment; you may use either a @sc{gnu} compiler, or
12270 other compilers that adhere to the local conventions.
12271 Best results are usually obtained from @sc{gnu} compilers; for example,
12272 using @code{@value{NGCC}} you can generate debugging information for
12275 For most kinds of object files, with the exception of old SVR3 systems
12276 using COFF, the @code{symbol-file} command does not normally read the
12277 symbol table in full right away. Instead, it scans the symbol table
12278 quickly to find which source files and which symbols are present. The
12279 details are read later, one source file at a time, as they are needed.
12281 The purpose of this two-stage reading strategy is to make @value{GDBN}
12282 start up faster. For the most part, it is invisible except for
12283 occasional pauses while the symbol table details for a particular source
12284 file are being read. (The @code{set verbose} command can turn these
12285 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12286 Warnings and Messages}.)
12288 We have not implemented the two-stage strategy for COFF yet. When the
12289 symbol table is stored in COFF format, @code{symbol-file} reads the
12290 symbol table data in full right away. Note that ``stabs-in-COFF''
12291 still does the two-stage strategy, since the debug info is actually
12295 @cindex reading symbols immediately
12296 @cindex symbols, reading immediately
12297 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12298 @itemx file @var{filename} @r{[} -readnow @r{]}
12299 You can override the @value{GDBN} two-stage strategy for reading symbol
12300 tables by using the @samp{-readnow} option with any of the commands that
12301 load symbol table information, if you want to be sure @value{GDBN} has the
12302 entire symbol table available.
12304 @c FIXME: for now no mention of directories, since this seems to be in
12305 @c flux. 13mar1992 status is that in theory GDB would look either in
12306 @c current dir or in same dir as myprog; but issues like competing
12307 @c GDB's, or clutter in system dirs, mean that in practice right now
12308 @c only current dir is used. FFish says maybe a special GDB hierarchy
12309 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12313 @item core-file @r{[}@var{filename}@r{]}
12315 Specify the whereabouts of a core dump file to be used as the ``contents
12316 of memory''. Traditionally, core files contain only some parts of the
12317 address space of the process that generated them; @value{GDBN} can access the
12318 executable file itself for other parts.
12320 @code{core-file} with no argument specifies that no core file is
12323 Note that the core file is ignored when your program is actually running
12324 under @value{GDBN}. So, if you have been running your program and you
12325 wish to debug a core file instead, you must kill the subprocess in which
12326 the program is running. To do this, use the @code{kill} command
12327 (@pxref{Kill Process, ,Killing the Child Process}).
12329 @kindex add-symbol-file
12330 @cindex dynamic linking
12331 @item add-symbol-file @var{filename} @var{address}
12332 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12333 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12334 The @code{add-symbol-file} command reads additional symbol table
12335 information from the file @var{filename}. You would use this command
12336 when @var{filename} has been dynamically loaded (by some other means)
12337 into the program that is running. @var{address} should be the memory
12338 address at which the file has been loaded; @value{GDBN} cannot figure
12339 this out for itself. You can additionally specify an arbitrary number
12340 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12341 section name and base address for that section. You can specify any
12342 @var{address} as an expression.
12344 The symbol table of the file @var{filename} is added to the symbol table
12345 originally read with the @code{symbol-file} command. You can use the
12346 @code{add-symbol-file} command any number of times; the new symbol data
12347 thus read keeps adding to the old. To discard all old symbol data
12348 instead, use the @code{symbol-file} command without any arguments.
12350 @cindex relocatable object files, reading symbols from
12351 @cindex object files, relocatable, reading symbols from
12352 @cindex reading symbols from relocatable object files
12353 @cindex symbols, reading from relocatable object files
12354 @cindex @file{.o} files, reading symbols from
12355 Although @var{filename} is typically a shared library file, an
12356 executable file, or some other object file which has been fully
12357 relocated for loading into a process, you can also load symbolic
12358 information from relocatable @file{.o} files, as long as:
12362 the file's symbolic information refers only to linker symbols defined in
12363 that file, not to symbols defined by other object files,
12365 every section the file's symbolic information refers to has actually
12366 been loaded into the inferior, as it appears in the file, and
12368 you can determine the address at which every section was loaded, and
12369 provide these to the @code{add-symbol-file} command.
12373 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12374 relocatable files into an already running program; such systems
12375 typically make the requirements above easy to meet. However, it's
12376 important to recognize that many native systems use complex link
12377 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12378 assembly, for example) that make the requirements difficult to meet. In
12379 general, one cannot assume that using @code{add-symbol-file} to read a
12380 relocatable object file's symbolic information will have the same effect
12381 as linking the relocatable object file into the program in the normal
12384 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12386 @kindex add-symbol-file-from-memory
12387 @cindex @code{syscall DSO}
12388 @cindex load symbols from memory
12389 @item add-symbol-file-from-memory @var{address}
12390 Load symbols from the given @var{address} in a dynamically loaded
12391 object file whose image is mapped directly into the inferior's memory.
12392 For example, the Linux kernel maps a @code{syscall DSO} into each
12393 process's address space; this DSO provides kernel-specific code for
12394 some system calls. The argument can be any expression whose
12395 evaluation yields the address of the file's shared object file header.
12396 For this command to work, you must have used @code{symbol-file} or
12397 @code{exec-file} commands in advance.
12399 @kindex add-shared-symbol-files
12401 @item add-shared-symbol-files @var{library-file}
12402 @itemx assf @var{library-file}
12403 The @code{add-shared-symbol-files} command can currently be used only
12404 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12405 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12406 @value{GDBN} automatically looks for shared libraries, however if
12407 @value{GDBN} does not find yours, you can invoke
12408 @code{add-shared-symbol-files}. It takes one argument: the shared
12409 library's file name. @code{assf} is a shorthand alias for
12410 @code{add-shared-symbol-files}.
12413 @item section @var{section} @var{addr}
12414 The @code{section} command changes the base address of the named
12415 @var{section} of the exec file to @var{addr}. This can be used if the
12416 exec file does not contain section addresses, (such as in the
12417 @code{a.out} format), or when the addresses specified in the file
12418 itself are wrong. Each section must be changed separately. The
12419 @code{info files} command, described below, lists all the sections and
12423 @kindex info target
12426 @code{info files} and @code{info target} are synonymous; both print the
12427 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12428 including the names of the executable and core dump files currently in
12429 use by @value{GDBN}, and the files from which symbols were loaded. The
12430 command @code{help target} lists all possible targets rather than
12433 @kindex maint info sections
12434 @item maint info sections
12435 Another command that can give you extra information about program sections
12436 is @code{maint info sections}. In addition to the section information
12437 displayed by @code{info files}, this command displays the flags and file
12438 offset of each section in the executable and core dump files. In addition,
12439 @code{maint info sections} provides the following command options (which
12440 may be arbitrarily combined):
12444 Display sections for all loaded object files, including shared libraries.
12445 @item @var{sections}
12446 Display info only for named @var{sections}.
12447 @item @var{section-flags}
12448 Display info only for sections for which @var{section-flags} are true.
12449 The section flags that @value{GDBN} currently knows about are:
12452 Section will have space allocated in the process when loaded.
12453 Set for all sections except those containing debug information.
12455 Section will be loaded from the file into the child process memory.
12456 Set for pre-initialized code and data, clear for @code{.bss} sections.
12458 Section needs to be relocated before loading.
12460 Section cannot be modified by the child process.
12462 Section contains executable code only.
12464 Section contains data only (no executable code).
12466 Section will reside in ROM.
12468 Section contains data for constructor/destructor lists.
12470 Section is not empty.
12472 An instruction to the linker to not output the section.
12473 @item COFF_SHARED_LIBRARY
12474 A notification to the linker that the section contains
12475 COFF shared library information.
12477 Section contains common symbols.
12480 @kindex set trust-readonly-sections
12481 @cindex read-only sections
12482 @item set trust-readonly-sections on
12483 Tell @value{GDBN} that readonly sections in your object file
12484 really are read-only (i.e.@: that their contents will not change).
12485 In that case, @value{GDBN} can fetch values from these sections
12486 out of the object file, rather than from the target program.
12487 For some targets (notably embedded ones), this can be a significant
12488 enhancement to debugging performance.
12490 The default is off.
12492 @item set trust-readonly-sections off
12493 Tell @value{GDBN} not to trust readonly sections. This means that
12494 the contents of the section might change while the program is running,
12495 and must therefore be fetched from the target when needed.
12497 @item show trust-readonly-sections
12498 Show the current setting of trusting readonly sections.
12501 All file-specifying commands allow both absolute and relative file names
12502 as arguments. @value{GDBN} always converts the file name to an absolute file
12503 name and remembers it that way.
12505 @cindex shared libraries
12506 @anchor{Shared Libraries}
12507 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12508 and IBM RS/6000 AIX shared libraries.
12510 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12511 shared libraries. @xref{Expat}.
12513 @value{GDBN} automatically loads symbol definitions from shared libraries
12514 when you use the @code{run} command, or when you examine a core file.
12515 (Before you issue the @code{run} command, @value{GDBN} does not understand
12516 references to a function in a shared library, however---unless you are
12517 debugging a core file).
12519 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12520 automatically loads the symbols at the time of the @code{shl_load} call.
12522 @c FIXME: some @value{GDBN} release may permit some refs to undef
12523 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12524 @c FIXME...lib; check this from time to time when updating manual
12526 There are times, however, when you may wish to not automatically load
12527 symbol definitions from shared libraries, such as when they are
12528 particularly large or there are many of them.
12530 To control the automatic loading of shared library symbols, use the
12534 @kindex set auto-solib-add
12535 @item set auto-solib-add @var{mode}
12536 If @var{mode} is @code{on}, symbols from all shared object libraries
12537 will be loaded automatically when the inferior begins execution, you
12538 attach to an independently started inferior, or when the dynamic linker
12539 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12540 is @code{off}, symbols must be loaded manually, using the
12541 @code{sharedlibrary} command. The default value is @code{on}.
12543 @cindex memory used for symbol tables
12544 If your program uses lots of shared libraries with debug info that
12545 takes large amounts of memory, you can decrease the @value{GDBN}
12546 memory footprint by preventing it from automatically loading the
12547 symbols from shared libraries. To that end, type @kbd{set
12548 auto-solib-add off} before running the inferior, then load each
12549 library whose debug symbols you do need with @kbd{sharedlibrary
12550 @var{regexp}}, where @var{regexp} is a regular expression that matches
12551 the libraries whose symbols you want to be loaded.
12553 @kindex show auto-solib-add
12554 @item show auto-solib-add
12555 Display the current autoloading mode.
12558 @cindex load shared library
12559 To explicitly load shared library symbols, use the @code{sharedlibrary}
12563 @kindex info sharedlibrary
12566 @itemx info sharedlibrary
12567 Print the names of the shared libraries which are currently loaded.
12569 @kindex sharedlibrary
12571 @item sharedlibrary @var{regex}
12572 @itemx share @var{regex}
12573 Load shared object library symbols for files matching a
12574 Unix regular expression.
12575 As with files loaded automatically, it only loads shared libraries
12576 required by your program for a core file or after typing @code{run}. If
12577 @var{regex} is omitted all shared libraries required by your program are
12580 @item nosharedlibrary
12581 @kindex nosharedlibrary
12582 @cindex unload symbols from shared libraries
12583 Unload all shared object library symbols. This discards all symbols
12584 that have been loaded from all shared libraries. Symbols from shared
12585 libraries that were loaded by explicit user requests are not
12589 Sometimes you may wish that @value{GDBN} stops and gives you control
12590 when any of shared library events happen. Use the @code{set
12591 stop-on-solib-events} command for this:
12594 @item set stop-on-solib-events
12595 @kindex set stop-on-solib-events
12596 This command controls whether @value{GDBN} should give you control
12597 when the dynamic linker notifies it about some shared library event.
12598 The most common event of interest is loading or unloading of a new
12601 @item show stop-on-solib-events
12602 @kindex show stop-on-solib-events
12603 Show whether @value{GDBN} stops and gives you control when shared
12604 library events happen.
12607 Shared libraries are also supported in many cross or remote debugging
12608 configurations. @value{GDBN} needs to have access to the target's libraries;
12609 this can be accomplished either by providing copies of the libraries
12610 on the host system, or by asking @value{GDBN} to automatically retrieve the
12611 libraries from the target. If copies of the target libraries are
12612 provided, they need to be the same as the target libraries, although the
12613 copies on the target can be stripped as long as the copies on the host are
12616 @cindex where to look for shared libraries
12617 For remote debugging, you need to tell @value{GDBN} where the target
12618 libraries are, so that it can load the correct copies---otherwise, it
12619 may try to load the host's libraries. @value{GDBN} has two variables
12620 to specify the search directories for target libraries.
12623 @cindex prefix for shared library file names
12624 @cindex system root, alternate
12625 @kindex set solib-absolute-prefix
12626 @kindex set sysroot
12627 @item set sysroot @var{path}
12628 Use @var{path} as the system root for the program being debugged. Any
12629 absolute shared library paths will be prefixed with @var{path}; many
12630 runtime loaders store the absolute paths to the shared library in the
12631 target program's memory. If you use @code{set sysroot} to find shared
12632 libraries, they need to be laid out in the same way that they are on
12633 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12636 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
12637 retrieve the target libraries from the remote system. This is only
12638 supported when using a remote target that supports the @code{remote get}
12639 command (@pxref{File Transfer,,Sending files to a remote system}).
12640 The part of @var{path} following the initial @file{remote:}
12641 (if present) is used as system root prefix on the remote file system.
12642 @footnote{If you want to specify a local system root using a directory
12643 that happens to be named @file{remote:}, you need to use some equivalent
12644 variant of the name like @file{./remote:}.}
12646 The @code{set solib-absolute-prefix} command is an alias for @code{set
12649 @cindex default system root
12650 @cindex @samp{--with-sysroot}
12651 You can set the default system root by using the configure-time
12652 @samp{--with-sysroot} option. If the system root is inside
12653 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12654 @samp{--exec-prefix}), then the default system root will be updated
12655 automatically if the installed @value{GDBN} is moved to a new
12658 @kindex show sysroot
12660 Display the current shared library prefix.
12662 @kindex set solib-search-path
12663 @item set solib-search-path @var{path}
12664 If this variable is set, @var{path} is a colon-separated list of
12665 directories to search for shared libraries. @samp{solib-search-path}
12666 is used after @samp{sysroot} fails to locate the library, or if the
12667 path to the library is relative instead of absolute. If you want to
12668 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12669 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12670 finding your host's libraries. @samp{sysroot} is preferred; setting
12671 it to a nonexistent directory may interfere with automatic loading
12672 of shared library symbols.
12674 @kindex show solib-search-path
12675 @item show solib-search-path
12676 Display the current shared library search path.
12680 @node Separate Debug Files
12681 @section Debugging Information in Separate Files
12682 @cindex separate debugging information files
12683 @cindex debugging information in separate files
12684 @cindex @file{.debug} subdirectories
12685 @cindex debugging information directory, global
12686 @cindex global debugging information directory
12687 @cindex build ID, and separate debugging files
12688 @cindex @file{.build-id} directory
12690 @value{GDBN} allows you to put a program's debugging information in a
12691 file separate from the executable itself, in a way that allows
12692 @value{GDBN} to find and load the debugging information automatically.
12693 Since debugging information can be very large---sometimes larger
12694 than the executable code itself---some systems distribute debugging
12695 information for their executables in separate files, which users can
12696 install only when they need to debug a problem.
12698 @value{GDBN} supports two ways of specifying the separate debug info
12703 The executable contains a @dfn{debug link} that specifies the name of
12704 the separate debug info file. The separate debug file's name is
12705 usually @file{@var{executable}.debug}, where @var{executable} is the
12706 name of the corresponding executable file without leading directories
12707 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12708 debug link specifies a CRC32 checksum for the debug file, which
12709 @value{GDBN} uses to validate that the executable and the debug file
12710 came from the same build.
12713 The executable contains a @dfn{build ID}, a unique bit string that is
12714 also present in the corresponding debug info file. (This is supported
12715 only on some operating systems, notably those which use the ELF format
12716 for binary files and the @sc{gnu} Binutils.) For more details about
12717 this feature, see the description of the @option{--build-id}
12718 command-line option in @ref{Options, , Command Line Options, ld.info,
12719 The GNU Linker}. The debug info file's name is not specified
12720 explicitly by the build ID, but can be computed from the build ID, see
12724 Depending on the way the debug info file is specified, @value{GDBN}
12725 uses two different methods of looking for the debug file:
12729 For the ``debug link'' method, @value{GDBN} looks up the named file in
12730 the directory of the executable file, then in a subdirectory of that
12731 directory named @file{.debug}, and finally under the global debug
12732 directory, in a subdirectory whose name is identical to the leading
12733 directories of the executable's absolute file name.
12736 For the ``build ID'' method, @value{GDBN} looks in the
12737 @file{.build-id} subdirectory of the global debug directory for a file
12738 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12739 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12740 are the rest of the bit string. (Real build ID strings are 32 or more
12741 hex characters, not 10.)
12744 So, for example, suppose you ask @value{GDBN} to debug
12745 @file{/usr/bin/ls}, which has a debug link that specifies the
12746 file @file{ls.debug}, and a build ID whose value in hex is
12747 @code{abcdef1234}. If the global debug directory is
12748 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12749 debug information files, in the indicated order:
12753 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12755 @file{/usr/bin/ls.debug}
12757 @file{/usr/bin/.debug/ls.debug}
12759 @file{/usr/lib/debug/usr/bin/ls.debug}.
12762 You can set the global debugging info directory's name, and view the
12763 name @value{GDBN} is currently using.
12767 @kindex set debug-file-directory
12768 @item set debug-file-directory @var{directory}
12769 Set the directory which @value{GDBN} searches for separate debugging
12770 information files to @var{directory}.
12772 @kindex show debug-file-directory
12773 @item show debug-file-directory
12774 Show the directory @value{GDBN} searches for separate debugging
12779 @cindex @code{.gnu_debuglink} sections
12780 @cindex debug link sections
12781 A debug link is a special section of the executable file named
12782 @code{.gnu_debuglink}. The section must contain:
12786 A filename, with any leading directory components removed, followed by
12789 zero to three bytes of padding, as needed to reach the next four-byte
12790 boundary within the section, and
12792 a four-byte CRC checksum, stored in the same endianness used for the
12793 executable file itself. The checksum is computed on the debugging
12794 information file's full contents by the function given below, passing
12795 zero as the @var{crc} argument.
12798 Any executable file format can carry a debug link, as long as it can
12799 contain a section named @code{.gnu_debuglink} with the contents
12802 @cindex @code{.note.gnu.build-id} sections
12803 @cindex build ID sections
12804 The build ID is a special section in the executable file (and in other
12805 ELF binary files that @value{GDBN} may consider). This section is
12806 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12807 It contains unique identification for the built files---the ID remains
12808 the same across multiple builds of the same build tree. The default
12809 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12810 content for the build ID string. The same section with an identical
12811 value is present in the original built binary with symbols, in its
12812 stripped variant, and in the separate debugging information file.
12814 The debugging information file itself should be an ordinary
12815 executable, containing a full set of linker symbols, sections, and
12816 debugging information. The sections of the debugging information file
12817 should have the same names, addresses, and sizes as the original file,
12818 but they need not contain any data---much like a @code{.bss} section
12819 in an ordinary executable.
12821 The @sc{gnu} binary utilities (Binutils) package includes the
12822 @samp{objcopy} utility that can produce
12823 the separated executable / debugging information file pairs using the
12824 following commands:
12827 @kbd{objcopy --only-keep-debug foo foo.debug}
12832 These commands remove the debugging
12833 information from the executable file @file{foo} and place it in the file
12834 @file{foo.debug}. You can use the first, second or both methods to link the
12839 The debug link method needs the following additional command to also leave
12840 behind a debug link in @file{foo}:
12843 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12846 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12847 a version of the @code{strip} command such that the command @kbd{strip foo -f
12848 foo.debug} has the same functionality as the two @code{objcopy} commands and
12849 the @code{ln -s} command above, together.
12852 Build ID gets embedded into the main executable using @code{ld --build-id} or
12853 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12854 compatibility fixes for debug files separation are present in @sc{gnu} binary
12855 utilities (Binutils) package since version 2.18.
12860 Since there are many different ways to compute CRC's for the debug
12861 link (different polynomials, reversals, byte ordering, etc.), the
12862 simplest way to describe the CRC used in @code{.gnu_debuglink}
12863 sections is to give the complete code for a function that computes it:
12865 @kindex gnu_debuglink_crc32
12868 gnu_debuglink_crc32 (unsigned long crc,
12869 unsigned char *buf, size_t len)
12871 static const unsigned long crc32_table[256] =
12873 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12874 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12875 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12876 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12877 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12878 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12879 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12880 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12881 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12882 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12883 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12884 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12885 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12886 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12887 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12888 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12889 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12890 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12891 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12892 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12893 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12894 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12895 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12896 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12897 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12898 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12899 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12900 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12901 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12902 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12903 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12904 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12905 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12906 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12907 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12908 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12909 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12910 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12911 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12912 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12913 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12914 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12915 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12916 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12917 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12918 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12919 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12920 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12921 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12922 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12923 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12926 unsigned char *end;
12928 crc = ~crc & 0xffffffff;
12929 for (end = buf + len; buf < end; ++buf)
12930 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12931 return ~crc & 0xffffffff;
12936 This computation does not apply to the ``build ID'' method.
12939 @node Symbol Errors
12940 @section Errors Reading Symbol Files
12942 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12943 such as symbol types it does not recognize, or known bugs in compiler
12944 output. By default, @value{GDBN} does not notify you of such problems, since
12945 they are relatively common and primarily of interest to people
12946 debugging compilers. If you are interested in seeing information
12947 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12948 only one message about each such type of problem, no matter how many
12949 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12950 to see how many times the problems occur, with the @code{set
12951 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12954 The messages currently printed, and their meanings, include:
12957 @item inner block not inside outer block in @var{symbol}
12959 The symbol information shows where symbol scopes begin and end
12960 (such as at the start of a function or a block of statements). This
12961 error indicates that an inner scope block is not fully contained
12962 in its outer scope blocks.
12964 @value{GDBN} circumvents the problem by treating the inner block as if it had
12965 the same scope as the outer block. In the error message, @var{symbol}
12966 may be shown as ``@code{(don't know)}'' if the outer block is not a
12969 @item block at @var{address} out of order
12971 The symbol information for symbol scope blocks should occur in
12972 order of increasing addresses. This error indicates that it does not
12975 @value{GDBN} does not circumvent this problem, and has trouble
12976 locating symbols in the source file whose symbols it is reading. (You
12977 can often determine what source file is affected by specifying
12978 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12981 @item bad block start address patched
12983 The symbol information for a symbol scope block has a start address
12984 smaller than the address of the preceding source line. This is known
12985 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12987 @value{GDBN} circumvents the problem by treating the symbol scope block as
12988 starting on the previous source line.
12990 @item bad string table offset in symbol @var{n}
12993 Symbol number @var{n} contains a pointer into the string table which is
12994 larger than the size of the string table.
12996 @value{GDBN} circumvents the problem by considering the symbol to have the
12997 name @code{foo}, which may cause other problems if many symbols end up
13000 @item unknown symbol type @code{0x@var{nn}}
13002 The symbol information contains new data types that @value{GDBN} does
13003 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13004 uncomprehended information, in hexadecimal.
13006 @value{GDBN} circumvents the error by ignoring this symbol information.
13007 This usually allows you to debug your program, though certain symbols
13008 are not accessible. If you encounter such a problem and feel like
13009 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13010 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13011 and examine @code{*bufp} to see the symbol.
13013 @item stub type has NULL name
13015 @value{GDBN} could not find the full definition for a struct or class.
13017 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13018 The symbol information for a C@t{++} member function is missing some
13019 information that recent versions of the compiler should have output for
13022 @item info mismatch between compiler and debugger
13024 @value{GDBN} could not parse a type specification output by the compiler.
13029 @chapter Specifying a Debugging Target
13031 @cindex debugging target
13032 A @dfn{target} is the execution environment occupied by your program.
13034 Often, @value{GDBN} runs in the same host environment as your program;
13035 in that case, the debugging target is specified as a side effect when
13036 you use the @code{file} or @code{core} commands. When you need more
13037 flexibility---for example, running @value{GDBN} on a physically separate
13038 host, or controlling a standalone system over a serial port or a
13039 realtime system over a TCP/IP connection---you can use the @code{target}
13040 command to specify one of the target types configured for @value{GDBN}
13041 (@pxref{Target Commands, ,Commands for Managing Targets}).
13043 @cindex target architecture
13044 It is possible to build @value{GDBN} for several different @dfn{target
13045 architectures}. When @value{GDBN} is built like that, you can choose
13046 one of the available architectures with the @kbd{set architecture}
13050 @kindex set architecture
13051 @kindex show architecture
13052 @item set architecture @var{arch}
13053 This command sets the current target architecture to @var{arch}. The
13054 value of @var{arch} can be @code{"auto"}, in addition to one of the
13055 supported architectures.
13057 @item show architecture
13058 Show the current target architecture.
13060 @item set processor
13062 @kindex set processor
13063 @kindex show processor
13064 These are alias commands for, respectively, @code{set architecture}
13065 and @code{show architecture}.
13069 * Active Targets:: Active targets
13070 * Target Commands:: Commands for managing targets
13071 * Byte Order:: Choosing target byte order
13074 @node Active Targets
13075 @section Active Targets
13077 @cindex stacking targets
13078 @cindex active targets
13079 @cindex multiple targets
13081 There are three classes of targets: processes, core files, and
13082 executable files. @value{GDBN} can work concurrently on up to three
13083 active targets, one in each class. This allows you to (for example)
13084 start a process and inspect its activity without abandoning your work on
13087 For example, if you execute @samp{gdb a.out}, then the executable file
13088 @code{a.out} is the only active target. If you designate a core file as
13089 well---presumably from a prior run that crashed and coredumped---then
13090 @value{GDBN} has two active targets and uses them in tandem, looking
13091 first in the corefile target, then in the executable file, to satisfy
13092 requests for memory addresses. (Typically, these two classes of target
13093 are complementary, since core files contain only a program's
13094 read-write memory---variables and so on---plus machine status, while
13095 executable files contain only the program text and initialized data.)
13097 When you type @code{run}, your executable file becomes an active process
13098 target as well. When a process target is active, all @value{GDBN}
13099 commands requesting memory addresses refer to that target; addresses in
13100 an active core file or executable file target are obscured while the
13101 process target is active.
13103 Use the @code{core-file} and @code{exec-file} commands to select a new
13104 core file or executable target (@pxref{Files, ,Commands to Specify
13105 Files}). To specify as a target a process that is already running, use
13106 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13109 @node Target Commands
13110 @section Commands for Managing Targets
13113 @item target @var{type} @var{parameters}
13114 Connects the @value{GDBN} host environment to a target machine or
13115 process. A target is typically a protocol for talking to debugging
13116 facilities. You use the argument @var{type} to specify the type or
13117 protocol of the target machine.
13119 Further @var{parameters} are interpreted by the target protocol, but
13120 typically include things like device names or host names to connect
13121 with, process numbers, and baud rates.
13123 The @code{target} command does not repeat if you press @key{RET} again
13124 after executing the command.
13126 @kindex help target
13128 Displays the names of all targets available. To display targets
13129 currently selected, use either @code{info target} or @code{info files}
13130 (@pxref{Files, ,Commands to Specify Files}).
13132 @item help target @var{name}
13133 Describe a particular target, including any parameters necessary to
13136 @kindex set gnutarget
13137 @item set gnutarget @var{args}
13138 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13139 knows whether it is reading an @dfn{executable},
13140 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13141 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13142 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13145 @emph{Warning:} To specify a file format with @code{set gnutarget},
13146 you must know the actual BFD name.
13150 @xref{Files, , Commands to Specify Files}.
13152 @kindex show gnutarget
13153 @item show gnutarget
13154 Use the @code{show gnutarget} command to display what file format
13155 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13156 @value{GDBN} will determine the file format for each file automatically,
13157 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13160 @cindex common targets
13161 Here are some common targets (available, or not, depending on the GDB
13166 @item target exec @var{program}
13167 @cindex executable file target
13168 An executable file. @samp{target exec @var{program}} is the same as
13169 @samp{exec-file @var{program}}.
13171 @item target core @var{filename}
13172 @cindex core dump file target
13173 A core dump file. @samp{target core @var{filename}} is the same as
13174 @samp{core-file @var{filename}}.
13176 @item target remote @var{medium}
13177 @cindex remote target
13178 A remote system connected to @value{GDBN} via a serial line or network
13179 connection. This command tells @value{GDBN} to use its own remote
13180 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13182 For example, if you have a board connected to @file{/dev/ttya} on the
13183 machine running @value{GDBN}, you could say:
13186 target remote /dev/ttya
13189 @code{target remote} supports the @code{load} command. This is only
13190 useful if you have some other way of getting the stub to the target
13191 system, and you can put it somewhere in memory where it won't get
13192 clobbered by the download.
13195 @cindex built-in simulator target
13196 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13204 works; however, you cannot assume that a specific memory map, device
13205 drivers, or even basic I/O is available, although some simulators do
13206 provide these. For info about any processor-specific simulator details,
13207 see the appropriate section in @ref{Embedded Processors, ,Embedded
13212 Some configurations may include these targets as well:
13216 @item target nrom @var{dev}
13217 @cindex NetROM ROM emulator target
13218 NetROM ROM emulator. This target only supports downloading.
13222 Different targets are available on different configurations of @value{GDBN};
13223 your configuration may have more or fewer targets.
13225 Many remote targets require you to download the executable's code once
13226 you've successfully established a connection. You may wish to control
13227 various aspects of this process.
13232 @kindex set hash@r{, for remote monitors}
13233 @cindex hash mark while downloading
13234 This command controls whether a hash mark @samp{#} is displayed while
13235 downloading a file to the remote monitor. If on, a hash mark is
13236 displayed after each S-record is successfully downloaded to the
13240 @kindex show hash@r{, for remote monitors}
13241 Show the current status of displaying the hash mark.
13243 @item set debug monitor
13244 @kindex set debug monitor
13245 @cindex display remote monitor communications
13246 Enable or disable display of communications messages between
13247 @value{GDBN} and the remote monitor.
13249 @item show debug monitor
13250 @kindex show debug monitor
13251 Show the current status of displaying communications between
13252 @value{GDBN} and the remote monitor.
13257 @kindex load @var{filename}
13258 @item load @var{filename}
13260 Depending on what remote debugging facilities are configured into
13261 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13262 is meant to make @var{filename} (an executable) available for debugging
13263 on the remote system---by downloading, or dynamic linking, for example.
13264 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13265 the @code{add-symbol-file} command.
13267 If your @value{GDBN} does not have a @code{load} command, attempting to
13268 execute it gets the error message ``@code{You can't do that when your
13269 target is @dots{}}''
13271 The file is loaded at whatever address is specified in the executable.
13272 For some object file formats, you can specify the load address when you
13273 link the program; for other formats, like a.out, the object file format
13274 specifies a fixed address.
13275 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13277 Depending on the remote side capabilities, @value{GDBN} may be able to
13278 load programs into flash memory.
13280 @code{load} does not repeat if you press @key{RET} again after using it.
13284 @section Choosing Target Byte Order
13286 @cindex choosing target byte order
13287 @cindex target byte order
13289 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13290 offer the ability to run either big-endian or little-endian byte
13291 orders. Usually the executable or symbol will include a bit to
13292 designate the endian-ness, and you will not need to worry about
13293 which to use. However, you may still find it useful to adjust
13294 @value{GDBN}'s idea of processor endian-ness manually.
13298 @item set endian big
13299 Instruct @value{GDBN} to assume the target is big-endian.
13301 @item set endian little
13302 Instruct @value{GDBN} to assume the target is little-endian.
13304 @item set endian auto
13305 Instruct @value{GDBN} to use the byte order associated with the
13309 Display @value{GDBN}'s current idea of the target byte order.
13313 Note that these commands merely adjust interpretation of symbolic
13314 data on the host, and that they have absolutely no effect on the
13318 @node Remote Debugging
13319 @chapter Debugging Remote Programs
13320 @cindex remote debugging
13322 If you are trying to debug a program running on a machine that cannot run
13323 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13324 For example, you might use remote debugging on an operating system kernel,
13325 or on a small system which does not have a general purpose operating system
13326 powerful enough to run a full-featured debugger.
13328 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13329 to make this work with particular debugging targets. In addition,
13330 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13331 but not specific to any particular target system) which you can use if you
13332 write the remote stubs---the code that runs on the remote system to
13333 communicate with @value{GDBN}.
13335 Other remote targets may be available in your
13336 configuration of @value{GDBN}; use @code{help target} to list them.
13339 * Connecting:: Connecting to a remote target
13340 * File Transfer:: Sending files to a remote system
13341 * Server:: Using the gdbserver program
13342 * Remote Configuration:: Remote configuration
13343 * Remote Stub:: Implementing a remote stub
13347 @section Connecting to a Remote Target
13349 On the @value{GDBN} host machine, you will need an unstripped copy of
13350 your program, since @value{GDBN} needs symbol and debugging information.
13351 Start up @value{GDBN} as usual, using the name of the local copy of your
13352 program as the first argument.
13354 @cindex @code{target remote}
13355 @value{GDBN} can communicate with the target over a serial line, or
13356 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13357 each case, @value{GDBN} uses the same protocol for debugging your
13358 program; only the medium carrying the debugging packets varies. The
13359 @code{target remote} command establishes a connection to the target.
13360 Its arguments indicate which medium to use:
13364 @item target remote @var{serial-device}
13365 @cindex serial line, @code{target remote}
13366 Use @var{serial-device} to communicate with the target. For example,
13367 to use a serial line connected to the device named @file{/dev/ttyb}:
13370 target remote /dev/ttyb
13373 If you're using a serial line, you may want to give @value{GDBN} the
13374 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13375 (@pxref{Remote Configuration, set remotebaud}) before the
13376 @code{target} command.
13378 @item target remote @code{@var{host}:@var{port}}
13379 @itemx target remote @code{tcp:@var{host}:@var{port}}
13380 @cindex @acronym{TCP} port, @code{target remote}
13381 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13382 The @var{host} may be either a host name or a numeric @acronym{IP}
13383 address; @var{port} must be a decimal number. The @var{host} could be
13384 the target machine itself, if it is directly connected to the net, or
13385 it might be a terminal server which in turn has a serial line to the
13388 For example, to connect to port 2828 on a terminal server named
13392 target remote manyfarms:2828
13395 If your remote target is actually running on the same machine as your
13396 debugger session (e.g.@: a simulator for your target running on the
13397 same host), you can omit the hostname. For example, to connect to
13398 port 1234 on your local machine:
13401 target remote :1234
13405 Note that the colon is still required here.
13407 @item target remote @code{udp:@var{host}:@var{port}}
13408 @cindex @acronym{UDP} port, @code{target remote}
13409 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13410 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13413 target remote udp:manyfarms:2828
13416 When using a @acronym{UDP} connection for remote debugging, you should
13417 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13418 can silently drop packets on busy or unreliable networks, which will
13419 cause havoc with your debugging session.
13421 @item target remote | @var{command}
13422 @cindex pipe, @code{target remote} to
13423 Run @var{command} in the background and communicate with it using a
13424 pipe. The @var{command} is a shell command, to be parsed and expanded
13425 by the system's command shell, @code{/bin/sh}; it should expect remote
13426 protocol packets on its standard input, and send replies on its
13427 standard output. You could use this to run a stand-alone simulator
13428 that speaks the remote debugging protocol, to make net connections
13429 using programs like @code{ssh}, or for other similar tricks.
13431 If @var{command} closes its standard output (perhaps by exiting),
13432 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13433 program has already exited, this will have no effect.)
13437 Once the connection has been established, you can use all the usual
13438 commands to examine and change data. The remote program is already
13439 running; you can use @kbd{step} and @kbd{continue}, and you do not
13440 need to use @kbd{run}.
13442 @cindex interrupting remote programs
13443 @cindex remote programs, interrupting
13444 Whenever @value{GDBN} is waiting for the remote program, if you type the
13445 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13446 program. This may or may not succeed, depending in part on the hardware
13447 and the serial drivers the remote system uses. If you type the
13448 interrupt character once again, @value{GDBN} displays this prompt:
13451 Interrupted while waiting for the program.
13452 Give up (and stop debugging it)? (y or n)
13455 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13456 (If you decide you want to try again later, you can use @samp{target
13457 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13458 goes back to waiting.
13461 @kindex detach (remote)
13463 When you have finished debugging the remote program, you can use the
13464 @code{detach} command to release it from @value{GDBN} control.
13465 Detaching from the target normally resumes its execution, but the results
13466 will depend on your particular remote stub. After the @code{detach}
13467 command, @value{GDBN} is free to connect to another target.
13471 The @code{disconnect} command behaves like @code{detach}, except that
13472 the target is generally not resumed. It will wait for @value{GDBN}
13473 (this instance or another one) to connect and continue debugging. After
13474 the @code{disconnect} command, @value{GDBN} is again free to connect to
13477 @cindex send command to remote monitor
13478 @cindex extend @value{GDBN} for remote targets
13479 @cindex add new commands for external monitor
13481 @item monitor @var{cmd}
13482 This command allows you to send arbitrary commands directly to the
13483 remote monitor. Since @value{GDBN} doesn't care about the commands it
13484 sends like this, this command is the way to extend @value{GDBN}---you
13485 can add new commands that only the external monitor will understand
13489 @node File Transfer
13490 @section Sending files to a remote system
13491 @cindex remote target, file transfer
13492 @cindex file transfer
13493 @cindex sending files to remote systems
13495 Some remote targets offer the ability to transfer files over the same
13496 connection used to communicate with @value{GDBN}. This is convenient
13497 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13498 running @code{gdbserver} over a network interface. For other targets,
13499 e.g.@: embedded devices with only a single serial port, this may be
13500 the only way to upload or download files.
13502 Not all remote targets support these commands.
13506 @item remote put @var{hostfile} @var{targetfile}
13507 Copy file @var{hostfile} from the host system (the machine running
13508 @value{GDBN}) to @var{targetfile} on the target system.
13511 @item remote get @var{targetfile} @var{hostfile}
13512 Copy file @var{targetfile} from the target system to @var{hostfile}
13513 on the host system.
13515 @kindex remote delete
13516 @item remote delete @var{targetfile}
13517 Delete @var{targetfile} from the target system.
13522 @section Using the @code{gdbserver} Program
13525 @cindex remote connection without stubs
13526 @code{gdbserver} is a control program for Unix-like systems, which
13527 allows you to connect your program with a remote @value{GDBN} via
13528 @code{target remote}---but without linking in the usual debugging stub.
13530 @code{gdbserver} is not a complete replacement for the debugging stubs,
13531 because it requires essentially the same operating-system facilities
13532 that @value{GDBN} itself does. In fact, a system that can run
13533 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13534 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13535 because it is a much smaller program than @value{GDBN} itself. It is
13536 also easier to port than all of @value{GDBN}, so you may be able to get
13537 started more quickly on a new system by using @code{gdbserver}.
13538 Finally, if you develop code for real-time systems, you may find that
13539 the tradeoffs involved in real-time operation make it more convenient to
13540 do as much development work as possible on another system, for example
13541 by cross-compiling. You can use @code{gdbserver} to make a similar
13542 choice for debugging.
13544 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13545 or a TCP connection, using the standard @value{GDBN} remote serial
13549 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13550 Do not run @code{gdbserver} connected to any public network; a
13551 @value{GDBN} connection to @code{gdbserver} provides access to the
13552 target system with the same privileges as the user running
13556 @subsection Running @code{gdbserver}
13557 @cindex arguments, to @code{gdbserver}
13559 Run @code{gdbserver} on the target system. You need a copy of the
13560 program you want to debug, including any libraries it requires.
13561 @code{gdbserver} does not need your program's symbol table, so you can
13562 strip the program if necessary to save space. @value{GDBN} on the host
13563 system does all the symbol handling.
13565 To use the server, you must tell it how to communicate with @value{GDBN};
13566 the name of your program; and the arguments for your program. The usual
13570 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13573 @var{comm} is either a device name (to use a serial line) or a TCP
13574 hostname and portnumber. For example, to debug Emacs with the argument
13575 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13579 target> gdbserver /dev/com1 emacs foo.txt
13582 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13585 To use a TCP connection instead of a serial line:
13588 target> gdbserver host:2345 emacs foo.txt
13591 The only difference from the previous example is the first argument,
13592 specifying that you are communicating with the host @value{GDBN} via
13593 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13594 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13595 (Currently, the @samp{host} part is ignored.) You can choose any number
13596 you want for the port number as long as it does not conflict with any
13597 TCP ports already in use on the target system (for example, @code{23} is
13598 reserved for @code{telnet}).@footnote{If you choose a port number that
13599 conflicts with another service, @code{gdbserver} prints an error message
13600 and exits.} You must use the same port number with the host @value{GDBN}
13601 @code{target remote} command.
13603 @subsubsection Attaching to a Running Program
13605 On some targets, @code{gdbserver} can also attach to running programs.
13606 This is accomplished via the @code{--attach} argument. The syntax is:
13609 target> gdbserver --attach @var{comm} @var{pid}
13612 @var{pid} is the process ID of a currently running process. It isn't necessary
13613 to point @code{gdbserver} at a binary for the running process.
13616 @cindex attach to a program by name
13617 You can debug processes by name instead of process ID if your target has the
13618 @code{pidof} utility:
13621 target> gdbserver --attach @var{comm} `pidof @var{program}`
13624 In case more than one copy of @var{program} is running, or @var{program}
13625 has multiple threads, most versions of @code{pidof} support the
13626 @code{-s} option to only return the first process ID.
13628 @subsubsection Multi-Process Mode for @code{gdbserver}
13629 @cindex gdbserver, multiple processes
13630 @cindex multiple processes with gdbserver
13632 When you connect to @code{gdbserver} using @code{target remote},
13633 @code{gdbserver} debugs the specified program only once. When the
13634 program exits, or you detach from it, @value{GDBN} closes the connection
13635 and @code{gdbserver} exits.
13637 If you connect using @kbd{target extended-remote}, @code{gdbserver}
13638 enters multi-process mode. When the debugged program exits, or you
13639 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
13640 though no program is running. The @code{run} and @code{attach}
13641 commands instruct @code{gdbserver} to run or attach to a new program.
13642 The @code{run} command uses @code{set remote exec-file} (@pxref{set
13643 remote exec-file}) to select the program to run. Command line
13644 arguments are supported, except for wildcard expansion and I/O
13645 redirection (@pxref{Arguments}).
13647 To start @code{gdbserver} without supplying an initial command to run
13648 or process ID to attach, use the @option{--multi} command line option.
13649 Then you can connect using @kbd{target extended-remote} and start
13650 the program you want to debug.
13652 @code{gdbserver} does not automatically exit in multi-process mode.
13653 You can terminate it by using @code{monitor exit}
13654 (@pxref{Monitor Commands for gdbserver}).
13656 @subsubsection Other Command-Line Arguments for @code{gdbserver}
13658 You can include @option{--debug} on the @code{gdbserver} command line.
13659 @code{gdbserver} will display extra status information about the debugging
13660 process. This option is intended for @code{gdbserver} development and
13661 for bug reports to the developers.
13663 The @option{--wrapper} option specifies a wrapper to launch programs
13664 for debugging. The option should be followed by the name of the
13665 wrapper, then any command-line arguments to pass to the wrapper, then
13666 @kbd{--} indicating the end of the wrapper arguments.
13668 @code{gdbserver} runs the specified wrapper program with a combined
13669 command line including the wrapper arguments, then the name of the
13670 program to debug, then any arguments to the program. The wrapper
13671 runs until it executes your program, and then @value{GDBN} gains control.
13673 You can use any program that eventually calls @code{execve} with
13674 its arguments as a wrapper. Several standard Unix utilities do
13675 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
13676 with @code{exec "$@@"} will also work.
13678 For example, you can use @code{env} to pass an environment variable to
13679 the debugged program, without setting the variable in @code{gdbserver}'s
13683 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
13686 @subsection Connecting to @code{gdbserver}
13688 Run @value{GDBN} on the host system.
13690 First make sure you have the necessary symbol files. Load symbols for
13691 your application using the @code{file} command before you connect. Use
13692 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
13693 was compiled with the correct sysroot using @code{--with-sysroot}).
13695 The symbol file and target libraries must exactly match the executable
13696 and libraries on the target, with one exception: the files on the host
13697 system should not be stripped, even if the files on the target system
13698 are. Mismatched or missing files will lead to confusing results
13699 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
13700 files may also prevent @code{gdbserver} from debugging multi-threaded
13703 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
13704 For TCP connections, you must start up @code{gdbserver} prior to using
13705 the @code{target remote} command. Otherwise you may get an error whose
13706 text depends on the host system, but which usually looks something like
13707 @samp{Connection refused}. Don't use the @code{load}
13708 command in @value{GDBN} when using @code{gdbserver}, since the program is
13709 already on the target.
13711 @subsection Monitor Commands for @code{gdbserver}
13712 @cindex monitor commands, for @code{gdbserver}
13713 @anchor{Monitor Commands for gdbserver}
13715 During a @value{GDBN} session using @code{gdbserver}, you can use the
13716 @code{monitor} command to send special requests to @code{gdbserver}.
13717 Here are the available commands.
13721 List the available monitor commands.
13723 @item monitor set debug 0
13724 @itemx monitor set debug 1
13725 Disable or enable general debugging messages.
13727 @item monitor set remote-debug 0
13728 @itemx monitor set remote-debug 1
13729 Disable or enable specific debugging messages associated with the remote
13730 protocol (@pxref{Remote Protocol}).
13733 Tell gdbserver to exit immediately. This command should be followed by
13734 @code{disconnect} to close the debugging session. @code{gdbserver} will
13735 detach from any attached processes and kill any processes it created.
13736 Use @code{monitor exit} to terminate @code{gdbserver} at the end
13737 of a multi-process mode debug session.
13741 @node Remote Configuration
13742 @section Remote Configuration
13745 @kindex show remote
13746 This section documents the configuration options available when
13747 debugging remote programs. For the options related to the File I/O
13748 extensions of the remote protocol, see @ref{system,
13749 system-call-allowed}.
13752 @item set remoteaddresssize @var{bits}
13753 @cindex address size for remote targets
13754 @cindex bits in remote address
13755 Set the maximum size of address in a memory packet to the specified
13756 number of bits. @value{GDBN} will mask off the address bits above
13757 that number, when it passes addresses to the remote target. The
13758 default value is the number of bits in the target's address.
13760 @item show remoteaddresssize
13761 Show the current value of remote address size in bits.
13763 @item set remotebaud @var{n}
13764 @cindex baud rate for remote targets
13765 Set the baud rate for the remote serial I/O to @var{n} baud. The
13766 value is used to set the speed of the serial port used for debugging
13769 @item show remotebaud
13770 Show the current speed of the remote connection.
13772 @item set remotebreak
13773 @cindex interrupt remote programs
13774 @cindex BREAK signal instead of Ctrl-C
13775 @anchor{set remotebreak}
13776 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13777 when you type @kbd{Ctrl-c} to interrupt the program running
13778 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13779 character instead. The default is off, since most remote systems
13780 expect to see @samp{Ctrl-C} as the interrupt signal.
13782 @item show remotebreak
13783 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13784 interrupt the remote program.
13786 @item set remoteflow on
13787 @itemx set remoteflow off
13788 @kindex set remoteflow
13789 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13790 on the serial port used to communicate to the remote target.
13792 @item show remoteflow
13793 @kindex show remoteflow
13794 Show the current setting of hardware flow control.
13796 @item set remotelogbase @var{base}
13797 Set the base (a.k.a.@: radix) of logging serial protocol
13798 communications to @var{base}. Supported values of @var{base} are:
13799 @code{ascii}, @code{octal}, and @code{hex}. The default is
13802 @item show remotelogbase
13803 Show the current setting of the radix for logging remote serial
13806 @item set remotelogfile @var{file}
13807 @cindex record serial communications on file
13808 Record remote serial communications on the named @var{file}. The
13809 default is not to record at all.
13811 @item show remotelogfile.
13812 Show the current setting of the file name on which to record the
13813 serial communications.
13815 @item set remotetimeout @var{num}
13816 @cindex timeout for serial communications
13817 @cindex remote timeout
13818 Set the timeout limit to wait for the remote target to respond to
13819 @var{num} seconds. The default is 2 seconds.
13821 @item show remotetimeout
13822 Show the current number of seconds to wait for the remote target
13825 @cindex limit hardware breakpoints and watchpoints
13826 @cindex remote target, limit break- and watchpoints
13827 @anchor{set remote hardware-watchpoint-limit}
13828 @anchor{set remote hardware-breakpoint-limit}
13829 @item set remote hardware-watchpoint-limit @var{limit}
13830 @itemx set remote hardware-breakpoint-limit @var{limit}
13831 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13832 watchpoints. A limit of -1, the default, is treated as unlimited.
13834 @item set remote exec-file @var{filename}
13835 @itemx show remote exec-file
13836 @anchor{set remote exec-file}
13837 @cindex executable file, for remote target
13838 Select the file used for @code{run} with @code{target
13839 extended-remote}. This should be set to a filename valid on the
13840 target system. If it is not set, the target will use a default
13841 filename (e.g.@: the last program run).
13844 @cindex remote packets, enabling and disabling
13845 The @value{GDBN} remote protocol autodetects the packets supported by
13846 your debugging stub. If you need to override the autodetection, you
13847 can use these commands to enable or disable individual packets. Each
13848 packet can be set to @samp{on} (the remote target supports this
13849 packet), @samp{off} (the remote target does not support this packet),
13850 or @samp{auto} (detect remote target support for this packet). They
13851 all default to @samp{auto}. For more information about each packet,
13852 see @ref{Remote Protocol}.
13854 During normal use, you should not have to use any of these commands.
13855 If you do, that may be a bug in your remote debugging stub, or a bug
13856 in @value{GDBN}. You may want to report the problem to the
13857 @value{GDBN} developers.
13859 For each packet @var{name}, the command to enable or disable the
13860 packet is @code{set remote @var{name}-packet}. The available settings
13863 @multitable @columnfractions 0.28 0.32 0.25
13866 @tab Related Features
13868 @item @code{fetch-register}
13870 @tab @code{info registers}
13872 @item @code{set-register}
13876 @item @code{binary-download}
13878 @tab @code{load}, @code{set}
13880 @item @code{read-aux-vector}
13881 @tab @code{qXfer:auxv:read}
13882 @tab @code{info auxv}
13884 @item @code{symbol-lookup}
13885 @tab @code{qSymbol}
13886 @tab Detecting multiple threads
13888 @item @code{attach}
13889 @tab @code{vAttach}
13892 @item @code{verbose-resume}
13894 @tab Stepping or resuming multiple threads
13900 @item @code{software-breakpoint}
13904 @item @code{hardware-breakpoint}
13908 @item @code{write-watchpoint}
13912 @item @code{read-watchpoint}
13916 @item @code{access-watchpoint}
13920 @item @code{target-features}
13921 @tab @code{qXfer:features:read}
13922 @tab @code{set architecture}
13924 @item @code{library-info}
13925 @tab @code{qXfer:libraries:read}
13926 @tab @code{info sharedlibrary}
13928 @item @code{memory-map}
13929 @tab @code{qXfer:memory-map:read}
13930 @tab @code{info mem}
13932 @item @code{read-spu-object}
13933 @tab @code{qXfer:spu:read}
13934 @tab @code{info spu}
13936 @item @code{write-spu-object}
13937 @tab @code{qXfer:spu:write}
13938 @tab @code{info spu}
13940 @item @code{get-thread-local-@*storage-address}
13941 @tab @code{qGetTLSAddr}
13942 @tab Displaying @code{__thread} variables
13944 @item @code{search-memory}
13945 @tab @code{qSearch:memory}
13948 @item @code{supported-packets}
13949 @tab @code{qSupported}
13950 @tab Remote communications parameters
13952 @item @code{pass-signals}
13953 @tab @code{QPassSignals}
13954 @tab @code{handle @var{signal}}
13956 @item @code{hostio-close-packet}
13957 @tab @code{vFile:close}
13958 @tab @code{remote get}, @code{remote put}
13960 @item @code{hostio-open-packet}
13961 @tab @code{vFile:open}
13962 @tab @code{remote get}, @code{remote put}
13964 @item @code{hostio-pread-packet}
13965 @tab @code{vFile:pread}
13966 @tab @code{remote get}, @code{remote put}
13968 @item @code{hostio-pwrite-packet}
13969 @tab @code{vFile:pwrite}
13970 @tab @code{remote get}, @code{remote put}
13972 @item @code{hostio-unlink-packet}
13973 @tab @code{vFile:unlink}
13974 @tab @code{remote delete}
13976 @item @code{noack-packet}
13977 @tab @code{QStartNoAckMode}
13978 @tab Packet acknowledgment
13982 @section Implementing a Remote Stub
13984 @cindex debugging stub, example
13985 @cindex remote stub, example
13986 @cindex stub example, remote debugging
13987 The stub files provided with @value{GDBN} implement the target side of the
13988 communication protocol, and the @value{GDBN} side is implemented in the
13989 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13990 these subroutines to communicate, and ignore the details. (If you're
13991 implementing your own stub file, you can still ignore the details: start
13992 with one of the existing stub files. @file{sparc-stub.c} is the best
13993 organized, and therefore the easiest to read.)
13995 @cindex remote serial debugging, overview
13996 To debug a program running on another machine (the debugging
13997 @dfn{target} machine), you must first arrange for all the usual
13998 prerequisites for the program to run by itself. For example, for a C
14003 A startup routine to set up the C runtime environment; these usually
14004 have a name like @file{crt0}. The startup routine may be supplied by
14005 your hardware supplier, or you may have to write your own.
14008 A C subroutine library to support your program's
14009 subroutine calls, notably managing input and output.
14012 A way of getting your program to the other machine---for example, a
14013 download program. These are often supplied by the hardware
14014 manufacturer, but you may have to write your own from hardware
14018 The next step is to arrange for your program to use a serial port to
14019 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14020 machine). In general terms, the scheme looks like this:
14024 @value{GDBN} already understands how to use this protocol; when everything
14025 else is set up, you can simply use the @samp{target remote} command
14026 (@pxref{Targets,,Specifying a Debugging Target}).
14028 @item On the target,
14029 you must link with your program a few special-purpose subroutines that
14030 implement the @value{GDBN} remote serial protocol. The file containing these
14031 subroutines is called a @dfn{debugging stub}.
14033 On certain remote targets, you can use an auxiliary program
14034 @code{gdbserver} instead of linking a stub into your program.
14035 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14038 The debugging stub is specific to the architecture of the remote
14039 machine; for example, use @file{sparc-stub.c} to debug programs on
14042 @cindex remote serial stub list
14043 These working remote stubs are distributed with @value{GDBN}:
14048 @cindex @file{i386-stub.c}
14051 For Intel 386 and compatible architectures.
14054 @cindex @file{m68k-stub.c}
14055 @cindex Motorola 680x0
14057 For Motorola 680x0 architectures.
14060 @cindex @file{sh-stub.c}
14063 For Renesas SH architectures.
14066 @cindex @file{sparc-stub.c}
14068 For @sc{sparc} architectures.
14070 @item sparcl-stub.c
14071 @cindex @file{sparcl-stub.c}
14074 For Fujitsu @sc{sparclite} architectures.
14078 The @file{README} file in the @value{GDBN} distribution may list other
14079 recently added stubs.
14082 * Stub Contents:: What the stub can do for you
14083 * Bootstrapping:: What you must do for the stub
14084 * Debug Session:: Putting it all together
14087 @node Stub Contents
14088 @subsection What the Stub Can Do for You
14090 @cindex remote serial stub
14091 The debugging stub for your architecture supplies these three
14095 @item set_debug_traps
14096 @findex set_debug_traps
14097 @cindex remote serial stub, initialization
14098 This routine arranges for @code{handle_exception} to run when your
14099 program stops. You must call this subroutine explicitly near the
14100 beginning of your program.
14102 @item handle_exception
14103 @findex handle_exception
14104 @cindex remote serial stub, main routine
14105 This is the central workhorse, but your program never calls it
14106 explicitly---the setup code arranges for @code{handle_exception} to
14107 run when a trap is triggered.
14109 @code{handle_exception} takes control when your program stops during
14110 execution (for example, on a breakpoint), and mediates communications
14111 with @value{GDBN} on the host machine. This is where the communications
14112 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14113 representative on the target machine. It begins by sending summary
14114 information on the state of your program, then continues to execute,
14115 retrieving and transmitting any information @value{GDBN} needs, until you
14116 execute a @value{GDBN} command that makes your program resume; at that point,
14117 @code{handle_exception} returns control to your own code on the target
14121 @cindex @code{breakpoint} subroutine, remote
14122 Use this auxiliary subroutine to make your program contain a
14123 breakpoint. Depending on the particular situation, this may be the only
14124 way for @value{GDBN} to get control. For instance, if your target
14125 machine has some sort of interrupt button, you won't need to call this;
14126 pressing the interrupt button transfers control to
14127 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14128 simply receiving characters on the serial port may also trigger a trap;
14129 again, in that situation, you don't need to call @code{breakpoint} from
14130 your own program---simply running @samp{target remote} from the host
14131 @value{GDBN} session gets control.
14133 Call @code{breakpoint} if none of these is true, or if you simply want
14134 to make certain your program stops at a predetermined point for the
14135 start of your debugging session.
14138 @node Bootstrapping
14139 @subsection What You Must Do for the Stub
14141 @cindex remote stub, support routines
14142 The debugging stubs that come with @value{GDBN} are set up for a particular
14143 chip architecture, but they have no information about the rest of your
14144 debugging target machine.
14146 First of all you need to tell the stub how to communicate with the
14150 @item int getDebugChar()
14151 @findex getDebugChar
14152 Write this subroutine to read a single character from the serial port.
14153 It may be identical to @code{getchar} for your target system; a
14154 different name is used to allow you to distinguish the two if you wish.
14156 @item void putDebugChar(int)
14157 @findex putDebugChar
14158 Write this subroutine to write a single character to the serial port.
14159 It may be identical to @code{putchar} for your target system; a
14160 different name is used to allow you to distinguish the two if you wish.
14163 @cindex control C, and remote debugging
14164 @cindex interrupting remote targets
14165 If you want @value{GDBN} to be able to stop your program while it is
14166 running, you need to use an interrupt-driven serial driver, and arrange
14167 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14168 character). That is the character which @value{GDBN} uses to tell the
14169 remote system to stop.
14171 Getting the debugging target to return the proper status to @value{GDBN}
14172 probably requires changes to the standard stub; one quick and dirty way
14173 is to just execute a breakpoint instruction (the ``dirty'' part is that
14174 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14176 Other routines you need to supply are:
14179 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14180 @findex exceptionHandler
14181 Write this function to install @var{exception_address} in the exception
14182 handling tables. You need to do this because the stub does not have any
14183 way of knowing what the exception handling tables on your target system
14184 are like (for example, the processor's table might be in @sc{rom},
14185 containing entries which point to a table in @sc{ram}).
14186 @var{exception_number} is the exception number which should be changed;
14187 its meaning is architecture-dependent (for example, different numbers
14188 might represent divide by zero, misaligned access, etc). When this
14189 exception occurs, control should be transferred directly to
14190 @var{exception_address}, and the processor state (stack, registers,
14191 and so on) should be just as it is when a processor exception occurs. So if
14192 you want to use a jump instruction to reach @var{exception_address}, it
14193 should be a simple jump, not a jump to subroutine.
14195 For the 386, @var{exception_address} should be installed as an interrupt
14196 gate so that interrupts are masked while the handler runs. The gate
14197 should be at privilege level 0 (the most privileged level). The
14198 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14199 help from @code{exceptionHandler}.
14201 @item void flush_i_cache()
14202 @findex flush_i_cache
14203 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14204 instruction cache, if any, on your target machine. If there is no
14205 instruction cache, this subroutine may be a no-op.
14207 On target machines that have instruction caches, @value{GDBN} requires this
14208 function to make certain that the state of your program is stable.
14212 You must also make sure this library routine is available:
14215 @item void *memset(void *, int, int)
14217 This is the standard library function @code{memset} that sets an area of
14218 memory to a known value. If you have one of the free versions of
14219 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14220 either obtain it from your hardware manufacturer, or write your own.
14223 If you do not use the GNU C compiler, you may need other standard
14224 library subroutines as well; this varies from one stub to another,
14225 but in general the stubs are likely to use any of the common library
14226 subroutines which @code{@value{NGCC}} generates as inline code.
14229 @node Debug Session
14230 @subsection Putting it All Together
14232 @cindex remote serial debugging summary
14233 In summary, when your program is ready to debug, you must follow these
14238 Make sure you have defined the supporting low-level routines
14239 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14241 @code{getDebugChar}, @code{putDebugChar},
14242 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14246 Insert these lines near the top of your program:
14254 For the 680x0 stub only, you need to provide a variable called
14255 @code{exceptionHook}. Normally you just use:
14258 void (*exceptionHook)() = 0;
14262 but if before calling @code{set_debug_traps}, you set it to point to a
14263 function in your program, that function is called when
14264 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14265 error). The function indicated by @code{exceptionHook} is called with
14266 one parameter: an @code{int} which is the exception number.
14269 Compile and link together: your program, the @value{GDBN} debugging stub for
14270 your target architecture, and the supporting subroutines.
14273 Make sure you have a serial connection between your target machine and
14274 the @value{GDBN} host, and identify the serial port on the host.
14277 @c The "remote" target now provides a `load' command, so we should
14278 @c document that. FIXME.
14279 Download your program to your target machine (or get it there by
14280 whatever means the manufacturer provides), and start it.
14283 Start @value{GDBN} on the host, and connect to the target
14284 (@pxref{Connecting,,Connecting to a Remote Target}).
14288 @node Configurations
14289 @chapter Configuration-Specific Information
14291 While nearly all @value{GDBN} commands are available for all native and
14292 cross versions of the debugger, there are some exceptions. This chapter
14293 describes things that are only available in certain configurations.
14295 There are three major categories of configurations: native
14296 configurations, where the host and target are the same, embedded
14297 operating system configurations, which are usually the same for several
14298 different processor architectures, and bare embedded processors, which
14299 are quite different from each other.
14304 * Embedded Processors::
14311 This section describes details specific to particular native
14316 * BSD libkvm Interface:: Debugging BSD kernel memory images
14317 * SVR4 Process Information:: SVR4 process information
14318 * DJGPP Native:: Features specific to the DJGPP port
14319 * Cygwin Native:: Features specific to the Cygwin port
14320 * Hurd Native:: Features specific to @sc{gnu} Hurd
14321 * Neutrino:: Features specific to QNX Neutrino
14327 On HP-UX systems, if you refer to a function or variable name that
14328 begins with a dollar sign, @value{GDBN} searches for a user or system
14329 name first, before it searches for a convenience variable.
14332 @node BSD libkvm Interface
14333 @subsection BSD libkvm Interface
14336 @cindex kernel memory image
14337 @cindex kernel crash dump
14339 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14340 interface that provides a uniform interface for accessing kernel virtual
14341 memory images, including live systems and crash dumps. @value{GDBN}
14342 uses this interface to allow you to debug live kernels and kernel crash
14343 dumps on many native BSD configurations. This is implemented as a
14344 special @code{kvm} debugging target. For debugging a live system, load
14345 the currently running kernel into @value{GDBN} and connect to the
14349 (@value{GDBP}) @b{target kvm}
14352 For debugging crash dumps, provide the file name of the crash dump as an
14356 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14359 Once connected to the @code{kvm} target, the following commands are
14365 Set current context from the @dfn{Process Control Block} (PCB) address.
14368 Set current context from proc address. This command isn't available on
14369 modern FreeBSD systems.
14372 @node SVR4 Process Information
14373 @subsection SVR4 Process Information
14375 @cindex examine process image
14376 @cindex process info via @file{/proc}
14378 Many versions of SVR4 and compatible systems provide a facility called
14379 @samp{/proc} that can be used to examine the image of a running
14380 process using file-system subroutines. If @value{GDBN} is configured
14381 for an operating system with this facility, the command @code{info
14382 proc} is available to report information about the process running
14383 your program, or about any process running on your system. @code{info
14384 proc} works only on SVR4 systems that include the @code{procfs} code.
14385 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14386 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14392 @itemx info proc @var{process-id}
14393 Summarize available information about any running process. If a
14394 process ID is specified by @var{process-id}, display information about
14395 that process; otherwise display information about the program being
14396 debugged. The summary includes the debugged process ID, the command
14397 line used to invoke it, its current working directory, and its
14398 executable file's absolute file name.
14400 On some systems, @var{process-id} can be of the form
14401 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14402 within a process. If the optional @var{pid} part is missing, it means
14403 a thread from the process being debugged (the leading @samp{/} still
14404 needs to be present, or else @value{GDBN} will interpret the number as
14405 a process ID rather than a thread ID).
14407 @item info proc mappings
14408 @cindex memory address space mappings
14409 Report the memory address space ranges accessible in the program, with
14410 information on whether the process has read, write, or execute access
14411 rights to each range. On @sc{gnu}/Linux systems, each memory range
14412 includes the object file which is mapped to that range, instead of the
14413 memory access rights to that range.
14415 @item info proc stat
14416 @itemx info proc status
14417 @cindex process detailed status information
14418 These subcommands are specific to @sc{gnu}/Linux systems. They show
14419 the process-related information, including the user ID and group ID;
14420 how many threads are there in the process; its virtual memory usage;
14421 the signals that are pending, blocked, and ignored; its TTY; its
14422 consumption of system and user time; its stack size; its @samp{nice}
14423 value; etc. For more information, see the @samp{proc} man page
14424 (type @kbd{man 5 proc} from your shell prompt).
14426 @item info proc all
14427 Show all the information about the process described under all of the
14428 above @code{info proc} subcommands.
14431 @comment These sub-options of 'info proc' were not included when
14432 @comment procfs.c was re-written. Keep their descriptions around
14433 @comment against the day when someone finds the time to put them back in.
14434 @kindex info proc times
14435 @item info proc times
14436 Starting time, user CPU time, and system CPU time for your program and
14439 @kindex info proc id
14441 Report on the process IDs related to your program: its own process ID,
14442 the ID of its parent, the process group ID, and the session ID.
14445 @item set procfs-trace
14446 @kindex set procfs-trace
14447 @cindex @code{procfs} API calls
14448 This command enables and disables tracing of @code{procfs} API calls.
14450 @item show procfs-trace
14451 @kindex show procfs-trace
14452 Show the current state of @code{procfs} API call tracing.
14454 @item set procfs-file @var{file}
14455 @kindex set procfs-file
14456 Tell @value{GDBN} to write @code{procfs} API trace to the named
14457 @var{file}. @value{GDBN} appends the trace info to the previous
14458 contents of the file. The default is to display the trace on the
14461 @item show procfs-file
14462 @kindex show procfs-file
14463 Show the file to which @code{procfs} API trace is written.
14465 @item proc-trace-entry
14466 @itemx proc-trace-exit
14467 @itemx proc-untrace-entry
14468 @itemx proc-untrace-exit
14469 @kindex proc-trace-entry
14470 @kindex proc-trace-exit
14471 @kindex proc-untrace-entry
14472 @kindex proc-untrace-exit
14473 These commands enable and disable tracing of entries into and exits
14474 from the @code{syscall} interface.
14477 @kindex info pidlist
14478 @cindex process list, QNX Neutrino
14479 For QNX Neutrino only, this command displays the list of all the
14480 processes and all the threads within each process.
14483 @kindex info meminfo
14484 @cindex mapinfo list, QNX Neutrino
14485 For QNX Neutrino only, this command displays the list of all mapinfos.
14489 @subsection Features for Debugging @sc{djgpp} Programs
14490 @cindex @sc{djgpp} debugging
14491 @cindex native @sc{djgpp} debugging
14492 @cindex MS-DOS-specific commands
14495 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14496 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14497 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14498 top of real-mode DOS systems and their emulations.
14500 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14501 defines a few commands specific to the @sc{djgpp} port. This
14502 subsection describes those commands.
14507 This is a prefix of @sc{djgpp}-specific commands which print
14508 information about the target system and important OS structures.
14511 @cindex MS-DOS system info
14512 @cindex free memory information (MS-DOS)
14513 @item info dos sysinfo
14514 This command displays assorted information about the underlying
14515 platform: the CPU type and features, the OS version and flavor, the
14516 DPMI version, and the available conventional and DPMI memory.
14521 @cindex segment descriptor tables
14522 @cindex descriptor tables display
14524 @itemx info dos ldt
14525 @itemx info dos idt
14526 These 3 commands display entries from, respectively, Global, Local,
14527 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14528 tables are data structures which store a descriptor for each segment
14529 that is currently in use. The segment's selector is an index into a
14530 descriptor table; the table entry for that index holds the
14531 descriptor's base address and limit, and its attributes and access
14534 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14535 segment (used for both data and the stack), and a DOS segment (which
14536 allows access to DOS/BIOS data structures and absolute addresses in
14537 conventional memory). However, the DPMI host will usually define
14538 additional segments in order to support the DPMI environment.
14540 @cindex garbled pointers
14541 These commands allow to display entries from the descriptor tables.
14542 Without an argument, all entries from the specified table are
14543 displayed. An argument, which should be an integer expression, means
14544 display a single entry whose index is given by the argument. For
14545 example, here's a convenient way to display information about the
14546 debugged program's data segment:
14549 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14550 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14554 This comes in handy when you want to see whether a pointer is outside
14555 the data segment's limit (i.e.@: @dfn{garbled}).
14557 @cindex page tables display (MS-DOS)
14559 @itemx info dos pte
14560 These two commands display entries from, respectively, the Page
14561 Directory and the Page Tables. Page Directories and Page Tables are
14562 data structures which control how virtual memory addresses are mapped
14563 into physical addresses. A Page Table includes an entry for every
14564 page of memory that is mapped into the program's address space; there
14565 may be several Page Tables, each one holding up to 4096 entries. A
14566 Page Directory has up to 4096 entries, one each for every Page Table
14567 that is currently in use.
14569 Without an argument, @kbd{info dos pde} displays the entire Page
14570 Directory, and @kbd{info dos pte} displays all the entries in all of
14571 the Page Tables. An argument, an integer expression, given to the
14572 @kbd{info dos pde} command means display only that entry from the Page
14573 Directory table. An argument given to the @kbd{info dos pte} command
14574 means display entries from a single Page Table, the one pointed to by
14575 the specified entry in the Page Directory.
14577 @cindex direct memory access (DMA) on MS-DOS
14578 These commands are useful when your program uses @dfn{DMA} (Direct
14579 Memory Access), which needs physical addresses to program the DMA
14582 These commands are supported only with some DPMI servers.
14584 @cindex physical address from linear address
14585 @item info dos address-pte @var{addr}
14586 This command displays the Page Table entry for a specified linear
14587 address. The argument @var{addr} is a linear address which should
14588 already have the appropriate segment's base address added to it,
14589 because this command accepts addresses which may belong to @emph{any}
14590 segment. For example, here's how to display the Page Table entry for
14591 the page where a variable @code{i} is stored:
14594 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14595 @exdent @code{Page Table entry for address 0x11a00d30:}
14596 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14600 This says that @code{i} is stored at offset @code{0xd30} from the page
14601 whose physical base address is @code{0x02698000}, and shows all the
14602 attributes of that page.
14604 Note that you must cast the addresses of variables to a @code{char *},
14605 since otherwise the value of @code{__djgpp_base_address}, the base
14606 address of all variables and functions in a @sc{djgpp} program, will
14607 be added using the rules of C pointer arithmetics: if @code{i} is
14608 declared an @code{int}, @value{GDBN} will add 4 times the value of
14609 @code{__djgpp_base_address} to the address of @code{i}.
14611 Here's another example, it displays the Page Table entry for the
14615 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14616 @exdent @code{Page Table entry for address 0x29110:}
14617 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14621 (The @code{+ 3} offset is because the transfer buffer's address is the
14622 3rd member of the @code{_go32_info_block} structure.) The output
14623 clearly shows that this DPMI server maps the addresses in conventional
14624 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
14625 linear (@code{0x29110}) addresses are identical.
14627 This command is supported only with some DPMI servers.
14630 @cindex DOS serial data link, remote debugging
14631 In addition to native debugging, the DJGPP port supports remote
14632 debugging via a serial data link. The following commands are specific
14633 to remote serial debugging in the DJGPP port of @value{GDBN}.
14636 @kindex set com1base
14637 @kindex set com1irq
14638 @kindex set com2base
14639 @kindex set com2irq
14640 @kindex set com3base
14641 @kindex set com3irq
14642 @kindex set com4base
14643 @kindex set com4irq
14644 @item set com1base @var{addr}
14645 This command sets the base I/O port address of the @file{COM1} serial
14648 @item set com1irq @var{irq}
14649 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
14650 for the @file{COM1} serial port.
14652 There are similar commands @samp{set com2base}, @samp{set com3irq},
14653 etc.@: for setting the port address and the @code{IRQ} lines for the
14656 @kindex show com1base
14657 @kindex show com1irq
14658 @kindex show com2base
14659 @kindex show com2irq
14660 @kindex show com3base
14661 @kindex show com3irq
14662 @kindex show com4base
14663 @kindex show com4irq
14664 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
14665 display the current settings of the base address and the @code{IRQ}
14666 lines used by the COM ports.
14669 @kindex info serial
14670 @cindex DOS serial port status
14671 This command prints the status of the 4 DOS serial ports. For each
14672 port, it prints whether it's active or not, its I/O base address and
14673 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
14674 counts of various errors encountered so far.
14678 @node Cygwin Native
14679 @subsection Features for Debugging MS Windows PE Executables
14680 @cindex MS Windows debugging
14681 @cindex native Cygwin debugging
14682 @cindex Cygwin-specific commands
14684 @value{GDBN} supports native debugging of MS Windows programs, including
14685 DLLs with and without symbolic debugging information. There are various
14686 additional Cygwin-specific commands, described in this section.
14687 Working with DLLs that have no debugging symbols is described in
14688 @ref{Non-debug DLL Symbols}.
14693 This is a prefix of MS Windows-specific commands which print
14694 information about the target system and important OS structures.
14696 @item info w32 selector
14697 This command displays information returned by
14698 the Win32 API @code{GetThreadSelectorEntry} function.
14699 It takes an optional argument that is evaluated to
14700 a long value to give the information about this given selector.
14701 Without argument, this command displays information
14702 about the six segment registers.
14706 This is a Cygwin-specific alias of @code{info shared}.
14708 @kindex dll-symbols
14710 This command loads symbols from a dll similarly to
14711 add-sym command but without the need to specify a base address.
14713 @kindex set cygwin-exceptions
14714 @cindex debugging the Cygwin DLL
14715 @cindex Cygwin DLL, debugging
14716 @item set cygwin-exceptions @var{mode}
14717 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
14718 happen inside the Cygwin DLL. If @var{mode} is @code{off},
14719 @value{GDBN} will delay recognition of exceptions, and may ignore some
14720 exceptions which seem to be caused by internal Cygwin DLL
14721 ``bookkeeping''. This option is meant primarily for debugging the
14722 Cygwin DLL itself; the default value is @code{off} to avoid annoying
14723 @value{GDBN} users with false @code{SIGSEGV} signals.
14725 @kindex show cygwin-exceptions
14726 @item show cygwin-exceptions
14727 Displays whether @value{GDBN} will break on exceptions that happen
14728 inside the Cygwin DLL itself.
14730 @kindex set new-console
14731 @item set new-console @var{mode}
14732 If @var{mode} is @code{on} the debuggee will
14733 be started in a new console on next start.
14734 If @var{mode} is @code{off}i, the debuggee will
14735 be started in the same console as the debugger.
14737 @kindex show new-console
14738 @item show new-console
14739 Displays whether a new console is used
14740 when the debuggee is started.
14742 @kindex set new-group
14743 @item set new-group @var{mode}
14744 This boolean value controls whether the debuggee should
14745 start a new group or stay in the same group as the debugger.
14746 This affects the way the Windows OS handles
14749 @kindex show new-group
14750 @item show new-group
14751 Displays current value of new-group boolean.
14753 @kindex set debugevents
14754 @item set debugevents
14755 This boolean value adds debug output concerning kernel events related
14756 to the debuggee seen by the debugger. This includes events that
14757 signal thread and process creation and exit, DLL loading and
14758 unloading, console interrupts, and debugging messages produced by the
14759 Windows @code{OutputDebugString} API call.
14761 @kindex set debugexec
14762 @item set debugexec
14763 This boolean value adds debug output concerning execute events
14764 (such as resume thread) seen by the debugger.
14766 @kindex set debugexceptions
14767 @item set debugexceptions
14768 This boolean value adds debug output concerning exceptions in the
14769 debuggee seen by the debugger.
14771 @kindex set debugmemory
14772 @item set debugmemory
14773 This boolean value adds debug output concerning debuggee memory reads
14774 and writes by the debugger.
14778 This boolean values specifies whether the debuggee is called
14779 via a shell or directly (default value is on).
14783 Displays if the debuggee will be started with a shell.
14788 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14791 @node Non-debug DLL Symbols
14792 @subsubsection Support for DLLs without Debugging Symbols
14793 @cindex DLLs with no debugging symbols
14794 @cindex Minimal symbols and DLLs
14796 Very often on windows, some of the DLLs that your program relies on do
14797 not include symbolic debugging information (for example,
14798 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14799 symbols in a DLL, it relies on the minimal amount of symbolic
14800 information contained in the DLL's export table. This section
14801 describes working with such symbols, known internally to @value{GDBN} as
14802 ``minimal symbols''.
14804 Note that before the debugged program has started execution, no DLLs
14805 will have been loaded. The easiest way around this problem is simply to
14806 start the program --- either by setting a breakpoint or letting the
14807 program run once to completion. It is also possible to force
14808 @value{GDBN} to load a particular DLL before starting the executable ---
14809 see the shared library information in @ref{Files}, or the
14810 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14811 explicitly loading symbols from a DLL with no debugging information will
14812 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14813 which may adversely affect symbol lookup performance.
14815 @subsubsection DLL Name Prefixes
14817 In keeping with the naming conventions used by the Microsoft debugging
14818 tools, DLL export symbols are made available with a prefix based on the
14819 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14820 also entered into the symbol table, so @code{CreateFileA} is often
14821 sufficient. In some cases there will be name clashes within a program
14822 (particularly if the executable itself includes full debugging symbols)
14823 necessitating the use of the fully qualified name when referring to the
14824 contents of the DLL. Use single-quotes around the name to avoid the
14825 exclamation mark (``!'') being interpreted as a language operator.
14827 Note that the internal name of the DLL may be all upper-case, even
14828 though the file name of the DLL is lower-case, or vice-versa. Since
14829 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14830 some confusion. If in doubt, try the @code{info functions} and
14831 @code{info variables} commands or even @code{maint print msymbols}
14832 (@pxref{Symbols}). Here's an example:
14835 (@value{GDBP}) info function CreateFileA
14836 All functions matching regular expression "CreateFileA":
14838 Non-debugging symbols:
14839 0x77e885f4 CreateFileA
14840 0x77e885f4 KERNEL32!CreateFileA
14844 (@value{GDBP}) info function !
14845 All functions matching regular expression "!":
14847 Non-debugging symbols:
14848 0x6100114c cygwin1!__assert
14849 0x61004034 cygwin1!_dll_crt0@@0
14850 0x61004240 cygwin1!dll_crt0(per_process *)
14854 @subsubsection Working with Minimal Symbols
14856 Symbols extracted from a DLL's export table do not contain very much
14857 type information. All that @value{GDBN} can do is guess whether a symbol
14858 refers to a function or variable depending on the linker section that
14859 contains the symbol. Also note that the actual contents of the memory
14860 contained in a DLL are not available unless the program is running. This
14861 means that you cannot examine the contents of a variable or disassemble
14862 a function within a DLL without a running program.
14864 Variables are generally treated as pointers and dereferenced
14865 automatically. For this reason, it is often necessary to prefix a
14866 variable name with the address-of operator (``&'') and provide explicit
14867 type information in the command. Here's an example of the type of
14871 (@value{GDBP}) print 'cygwin1!__argv'
14876 (@value{GDBP}) x 'cygwin1!__argv'
14877 0x10021610: "\230y\""
14880 And two possible solutions:
14883 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14884 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14888 (@value{GDBP}) x/2x &'cygwin1!__argv'
14889 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14890 (@value{GDBP}) x/x 0x10021608
14891 0x10021608: 0x0022fd98
14892 (@value{GDBP}) x/s 0x0022fd98
14893 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14896 Setting a break point within a DLL is possible even before the program
14897 starts execution. However, under these circumstances, @value{GDBN} can't
14898 examine the initial instructions of the function in order to skip the
14899 function's frame set-up code. You can work around this by using ``*&''
14900 to set the breakpoint at a raw memory address:
14903 (@value{GDBP}) break *&'python22!PyOS_Readline'
14904 Breakpoint 1 at 0x1e04eff0
14907 The author of these extensions is not entirely convinced that setting a
14908 break point within a shared DLL like @file{kernel32.dll} is completely
14912 @subsection Commands Specific to @sc{gnu} Hurd Systems
14913 @cindex @sc{gnu} Hurd debugging
14915 This subsection describes @value{GDBN} commands specific to the
14916 @sc{gnu} Hurd native debugging.
14921 @kindex set signals@r{, Hurd command}
14922 @kindex set sigs@r{, Hurd command}
14923 This command toggles the state of inferior signal interception by
14924 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14925 affected by this command. @code{sigs} is a shorthand alias for
14930 @kindex show signals@r{, Hurd command}
14931 @kindex show sigs@r{, Hurd command}
14932 Show the current state of intercepting inferior's signals.
14934 @item set signal-thread
14935 @itemx set sigthread
14936 @kindex set signal-thread
14937 @kindex set sigthread
14938 This command tells @value{GDBN} which thread is the @code{libc} signal
14939 thread. That thread is run when a signal is delivered to a running
14940 process. @code{set sigthread} is the shorthand alias of @code{set
14943 @item show signal-thread
14944 @itemx show sigthread
14945 @kindex show signal-thread
14946 @kindex show sigthread
14947 These two commands show which thread will run when the inferior is
14948 delivered a signal.
14951 @kindex set stopped@r{, Hurd command}
14952 This commands tells @value{GDBN} that the inferior process is stopped,
14953 as with the @code{SIGSTOP} signal. The stopped process can be
14954 continued by delivering a signal to it.
14957 @kindex show stopped@r{, Hurd command}
14958 This command shows whether @value{GDBN} thinks the debuggee is
14961 @item set exceptions
14962 @kindex set exceptions@r{, Hurd command}
14963 Use this command to turn off trapping of exceptions in the inferior.
14964 When exception trapping is off, neither breakpoints nor
14965 single-stepping will work. To restore the default, set exception
14968 @item show exceptions
14969 @kindex show exceptions@r{, Hurd command}
14970 Show the current state of trapping exceptions in the inferior.
14972 @item set task pause
14973 @kindex set task@r{, Hurd commands}
14974 @cindex task attributes (@sc{gnu} Hurd)
14975 @cindex pause current task (@sc{gnu} Hurd)
14976 This command toggles task suspension when @value{GDBN} has control.
14977 Setting it to on takes effect immediately, and the task is suspended
14978 whenever @value{GDBN} gets control. Setting it to off will take
14979 effect the next time the inferior is continued. If this option is set
14980 to off, you can use @code{set thread default pause on} or @code{set
14981 thread pause on} (see below) to pause individual threads.
14983 @item show task pause
14984 @kindex show task@r{, Hurd commands}
14985 Show the current state of task suspension.
14987 @item set task detach-suspend-count
14988 @cindex task suspend count
14989 @cindex detach from task, @sc{gnu} Hurd
14990 This command sets the suspend count the task will be left with when
14991 @value{GDBN} detaches from it.
14993 @item show task detach-suspend-count
14994 Show the suspend count the task will be left with when detaching.
14996 @item set task exception-port
14997 @itemx set task excp
14998 @cindex task exception port, @sc{gnu} Hurd
14999 This command sets the task exception port to which @value{GDBN} will
15000 forward exceptions. The argument should be the value of the @dfn{send
15001 rights} of the task. @code{set task excp} is a shorthand alias.
15003 @item set noninvasive
15004 @cindex noninvasive task options
15005 This command switches @value{GDBN} to a mode that is the least
15006 invasive as far as interfering with the inferior is concerned. This
15007 is the same as using @code{set task pause}, @code{set exceptions}, and
15008 @code{set signals} to values opposite to the defaults.
15010 @item info send-rights
15011 @itemx info receive-rights
15012 @itemx info port-rights
15013 @itemx info port-sets
15014 @itemx info dead-names
15017 @cindex send rights, @sc{gnu} Hurd
15018 @cindex receive rights, @sc{gnu} Hurd
15019 @cindex port rights, @sc{gnu} Hurd
15020 @cindex port sets, @sc{gnu} Hurd
15021 @cindex dead names, @sc{gnu} Hurd
15022 These commands display information about, respectively, send rights,
15023 receive rights, port rights, port sets, and dead names of a task.
15024 There are also shorthand aliases: @code{info ports} for @code{info
15025 port-rights} and @code{info psets} for @code{info port-sets}.
15027 @item set thread pause
15028 @kindex set thread@r{, Hurd command}
15029 @cindex thread properties, @sc{gnu} Hurd
15030 @cindex pause current thread (@sc{gnu} Hurd)
15031 This command toggles current thread suspension when @value{GDBN} has
15032 control. Setting it to on takes effect immediately, and the current
15033 thread is suspended whenever @value{GDBN} gets control. Setting it to
15034 off will take effect the next time the inferior is continued.
15035 Normally, this command has no effect, since when @value{GDBN} has
15036 control, the whole task is suspended. However, if you used @code{set
15037 task pause off} (see above), this command comes in handy to suspend
15038 only the current thread.
15040 @item show thread pause
15041 @kindex show thread@r{, Hurd command}
15042 This command shows the state of current thread suspension.
15044 @item set thread run
15045 This command sets whether the current thread is allowed to run.
15047 @item show thread run
15048 Show whether the current thread is allowed to run.
15050 @item set thread detach-suspend-count
15051 @cindex thread suspend count, @sc{gnu} Hurd
15052 @cindex detach from thread, @sc{gnu} Hurd
15053 This command sets the suspend count @value{GDBN} will leave on a
15054 thread when detaching. This number is relative to the suspend count
15055 found by @value{GDBN} when it notices the thread; use @code{set thread
15056 takeover-suspend-count} to force it to an absolute value.
15058 @item show thread detach-suspend-count
15059 Show the suspend count @value{GDBN} will leave on the thread when
15062 @item set thread exception-port
15063 @itemx set thread excp
15064 Set the thread exception port to which to forward exceptions. This
15065 overrides the port set by @code{set task exception-port} (see above).
15066 @code{set thread excp} is the shorthand alias.
15068 @item set thread takeover-suspend-count
15069 Normally, @value{GDBN}'s thread suspend counts are relative to the
15070 value @value{GDBN} finds when it notices each thread. This command
15071 changes the suspend counts to be absolute instead.
15073 @item set thread default
15074 @itemx show thread default
15075 @cindex thread default settings, @sc{gnu} Hurd
15076 Each of the above @code{set thread} commands has a @code{set thread
15077 default} counterpart (e.g., @code{set thread default pause}, @code{set
15078 thread default exception-port}, etc.). The @code{thread default}
15079 variety of commands sets the default thread properties for all
15080 threads; you can then change the properties of individual threads with
15081 the non-default commands.
15086 @subsection QNX Neutrino
15087 @cindex QNX Neutrino
15089 @value{GDBN} provides the following commands specific to the QNX
15093 @item set debug nto-debug
15094 @kindex set debug nto-debug
15095 When set to on, enables debugging messages specific to the QNX
15098 @item show debug nto-debug
15099 @kindex show debug nto-debug
15100 Show the current state of QNX Neutrino messages.
15105 @section Embedded Operating Systems
15107 This section describes configurations involving the debugging of
15108 embedded operating systems that are available for several different
15112 * VxWorks:: Using @value{GDBN} with VxWorks
15115 @value{GDBN} includes the ability to debug programs running on
15116 various real-time operating systems.
15119 @subsection Using @value{GDBN} with VxWorks
15125 @kindex target vxworks
15126 @item target vxworks @var{machinename}
15127 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15128 is the target system's machine name or IP address.
15132 On VxWorks, @code{load} links @var{filename} dynamically on the
15133 current target system as well as adding its symbols in @value{GDBN}.
15135 @value{GDBN} enables developers to spawn and debug tasks running on networked
15136 VxWorks targets from a Unix host. Already-running tasks spawned from
15137 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15138 both the Unix host and on the VxWorks target. The program
15139 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15140 installed with the name @code{vxgdb}, to distinguish it from a
15141 @value{GDBN} for debugging programs on the host itself.)
15144 @item VxWorks-timeout @var{args}
15145 @kindex vxworks-timeout
15146 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15147 This option is set by the user, and @var{args} represents the number of
15148 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15149 your VxWorks target is a slow software simulator or is on the far side
15150 of a thin network line.
15153 The following information on connecting to VxWorks was current when
15154 this manual was produced; newer releases of VxWorks may use revised
15157 @findex INCLUDE_RDB
15158 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15159 to include the remote debugging interface routines in the VxWorks
15160 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15161 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15162 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15163 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15164 information on configuring and remaking VxWorks, see the manufacturer's
15166 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15168 Once you have included @file{rdb.a} in your VxWorks system image and set
15169 your Unix execution search path to find @value{GDBN}, you are ready to
15170 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15171 @code{vxgdb}, depending on your installation).
15173 @value{GDBN} comes up showing the prompt:
15180 * VxWorks Connection:: Connecting to VxWorks
15181 * VxWorks Download:: VxWorks download
15182 * VxWorks Attach:: Running tasks
15185 @node VxWorks Connection
15186 @subsubsection Connecting to VxWorks
15188 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15189 network. To connect to a target whose host name is ``@code{tt}'', type:
15192 (vxgdb) target vxworks tt
15196 @value{GDBN} displays messages like these:
15199 Attaching remote machine across net...
15204 @value{GDBN} then attempts to read the symbol tables of any object modules
15205 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15206 these files by searching the directories listed in the command search
15207 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15208 to find an object file, it displays a message such as:
15211 prog.o: No such file or directory.
15214 When this happens, add the appropriate directory to the search path with
15215 the @value{GDBN} command @code{path}, and execute the @code{target}
15218 @node VxWorks Download
15219 @subsubsection VxWorks Download
15221 @cindex download to VxWorks
15222 If you have connected to the VxWorks target and you want to debug an
15223 object that has not yet been loaded, you can use the @value{GDBN}
15224 @code{load} command to download a file from Unix to VxWorks
15225 incrementally. The object file given as an argument to the @code{load}
15226 command is actually opened twice: first by the VxWorks target in order
15227 to download the code, then by @value{GDBN} in order to read the symbol
15228 table. This can lead to problems if the current working directories on
15229 the two systems differ. If both systems have NFS mounted the same
15230 filesystems, you can avoid these problems by using absolute paths.
15231 Otherwise, it is simplest to set the working directory on both systems
15232 to the directory in which the object file resides, and then to reference
15233 the file by its name, without any path. For instance, a program
15234 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15235 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15236 program, type this on VxWorks:
15239 -> cd "@var{vxpath}/vw/demo/rdb"
15243 Then, in @value{GDBN}, type:
15246 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15247 (vxgdb) load prog.o
15250 @value{GDBN} displays a response similar to this:
15253 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15256 You can also use the @code{load} command to reload an object module
15257 after editing and recompiling the corresponding source file. Note that
15258 this makes @value{GDBN} delete all currently-defined breakpoints,
15259 auto-displays, and convenience variables, and to clear the value
15260 history. (This is necessary in order to preserve the integrity of
15261 debugger's data structures that reference the target system's symbol
15264 @node VxWorks Attach
15265 @subsubsection Running Tasks
15267 @cindex running VxWorks tasks
15268 You can also attach to an existing task using the @code{attach} command as
15272 (vxgdb) attach @var{task}
15276 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15277 or suspended when you attach to it. Running tasks are suspended at
15278 the time of attachment.
15280 @node Embedded Processors
15281 @section Embedded Processors
15283 This section goes into details specific to particular embedded
15286 @cindex send command to simulator
15287 Whenever a specific embedded processor has a simulator, @value{GDBN}
15288 allows to send an arbitrary command to the simulator.
15291 @item sim @var{command}
15292 @kindex sim@r{, a command}
15293 Send an arbitrary @var{command} string to the simulator. Consult the
15294 documentation for the specific simulator in use for information about
15295 acceptable commands.
15301 * M32R/D:: Renesas M32R/D
15302 * M68K:: Motorola M68K
15303 * MIPS Embedded:: MIPS Embedded
15304 * OpenRISC 1000:: OpenRisc 1000
15305 * PA:: HP PA Embedded
15306 * PowerPC Embedded:: PowerPC Embedded
15307 * Sparclet:: Tsqware Sparclet
15308 * Sparclite:: Fujitsu Sparclite
15309 * Z8000:: Zilog Z8000
15312 * Super-H:: Renesas Super-H
15321 @item target rdi @var{dev}
15322 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15323 use this target to communicate with both boards running the Angel
15324 monitor, or with the EmbeddedICE JTAG debug device.
15327 @item target rdp @var{dev}
15332 @value{GDBN} provides the following ARM-specific commands:
15335 @item set arm disassembler
15337 This commands selects from a list of disassembly styles. The
15338 @code{"std"} style is the standard style.
15340 @item show arm disassembler
15342 Show the current disassembly style.
15344 @item set arm apcs32
15345 @cindex ARM 32-bit mode
15346 This command toggles ARM operation mode between 32-bit and 26-bit.
15348 @item show arm apcs32
15349 Display the current usage of the ARM 32-bit mode.
15351 @item set arm fpu @var{fputype}
15352 This command sets the ARM floating-point unit (FPU) type. The
15353 argument @var{fputype} can be one of these:
15357 Determine the FPU type by querying the OS ABI.
15359 Software FPU, with mixed-endian doubles on little-endian ARM
15362 GCC-compiled FPA co-processor.
15364 Software FPU with pure-endian doubles.
15370 Show the current type of the FPU.
15373 This command forces @value{GDBN} to use the specified ABI.
15376 Show the currently used ABI.
15378 @item set arm fallback-mode (arm|thumb|auto)
15379 @value{GDBN} uses the symbol table, when available, to determine
15380 whether instructions are ARM or Thumb. This command controls
15381 @value{GDBN}'s default behavior when the symbol table is not
15382 available. The default is @samp{auto}, which causes @value{GDBN} to
15383 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15386 @item show arm fallback-mode
15387 Show the current fallback instruction mode.
15389 @item set arm force-mode (arm|thumb|auto)
15390 This command overrides use of the symbol table to determine whether
15391 instructions are ARM or Thumb. The default is @samp{auto}, which
15392 causes @value{GDBN} to use the symbol table and then the setting
15393 of @samp{set arm fallback-mode}.
15395 @item show arm force-mode
15396 Show the current forced instruction mode.
15398 @item set debug arm
15399 Toggle whether to display ARM-specific debugging messages from the ARM
15400 target support subsystem.
15402 @item show debug arm
15403 Show whether ARM-specific debugging messages are enabled.
15406 The following commands are available when an ARM target is debugged
15407 using the RDI interface:
15410 @item rdilogfile @r{[}@var{file}@r{]}
15412 @cindex ADP (Angel Debugger Protocol) logging
15413 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15414 With an argument, sets the log file to the specified @var{file}. With
15415 no argument, show the current log file name. The default log file is
15418 @item rdilogenable @r{[}@var{arg}@r{]}
15419 @kindex rdilogenable
15420 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15421 enables logging, with an argument 0 or @code{"no"} disables it. With
15422 no arguments displays the current setting. When logging is enabled,
15423 ADP packets exchanged between @value{GDBN} and the RDI target device
15424 are logged to a file.
15426 @item set rdiromatzero
15427 @kindex set rdiromatzero
15428 @cindex ROM at zero address, RDI
15429 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15430 vector catching is disabled, so that zero address can be used. If off
15431 (the default), vector catching is enabled. For this command to take
15432 effect, it needs to be invoked prior to the @code{target rdi} command.
15434 @item show rdiromatzero
15435 @kindex show rdiromatzero
15436 Show the current setting of ROM at zero address.
15438 @item set rdiheartbeat
15439 @kindex set rdiheartbeat
15440 @cindex RDI heartbeat
15441 Enable or disable RDI heartbeat packets. It is not recommended to
15442 turn on this option, since it confuses ARM and EPI JTAG interface, as
15443 well as the Angel monitor.
15445 @item show rdiheartbeat
15446 @kindex show rdiheartbeat
15447 Show the setting of RDI heartbeat packets.
15452 @subsection Renesas M32R/D and M32R/SDI
15455 @kindex target m32r
15456 @item target m32r @var{dev}
15457 Renesas M32R/D ROM monitor.
15459 @kindex target m32rsdi
15460 @item target m32rsdi @var{dev}
15461 Renesas M32R SDI server, connected via parallel port to the board.
15464 The following @value{GDBN} commands are specific to the M32R monitor:
15467 @item set download-path @var{path}
15468 @kindex set download-path
15469 @cindex find downloadable @sc{srec} files (M32R)
15470 Set the default path for finding downloadable @sc{srec} files.
15472 @item show download-path
15473 @kindex show download-path
15474 Show the default path for downloadable @sc{srec} files.
15476 @item set board-address @var{addr}
15477 @kindex set board-address
15478 @cindex M32-EVA target board address
15479 Set the IP address for the M32R-EVA target board.
15481 @item show board-address
15482 @kindex show board-address
15483 Show the current IP address of the target board.
15485 @item set server-address @var{addr}
15486 @kindex set server-address
15487 @cindex download server address (M32R)
15488 Set the IP address for the download server, which is the @value{GDBN}'s
15491 @item show server-address
15492 @kindex show server-address
15493 Display the IP address of the download server.
15495 @item upload @r{[}@var{file}@r{]}
15496 @kindex upload@r{, M32R}
15497 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
15498 upload capability. If no @var{file} argument is given, the current
15499 executable file is uploaded.
15501 @item tload @r{[}@var{file}@r{]}
15502 @kindex tload@r{, M32R}
15503 Test the @code{upload} command.
15506 The following commands are available for M32R/SDI:
15511 @cindex reset SDI connection, M32R
15512 This command resets the SDI connection.
15516 This command shows the SDI connection status.
15519 @kindex debug_chaos
15520 @cindex M32R/Chaos debugging
15521 Instructs the remote that M32R/Chaos debugging is to be used.
15523 @item use_debug_dma
15524 @kindex use_debug_dma
15525 Instructs the remote to use the DEBUG_DMA method of accessing memory.
15528 @kindex use_mon_code
15529 Instructs the remote to use the MON_CODE method of accessing memory.
15532 @kindex use_ib_break
15533 Instructs the remote to set breakpoints by IB break.
15535 @item use_dbt_break
15536 @kindex use_dbt_break
15537 Instructs the remote to set breakpoints by DBT.
15543 The Motorola m68k configuration includes ColdFire support, and a
15544 target command for the following ROM monitor.
15548 @kindex target dbug
15549 @item target dbug @var{dev}
15550 dBUG ROM monitor for Motorola ColdFire.
15554 @node MIPS Embedded
15555 @subsection MIPS Embedded
15557 @cindex MIPS boards
15558 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15559 MIPS board attached to a serial line. This is available when
15560 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15563 Use these @value{GDBN} commands to specify the connection to your target board:
15566 @item target mips @var{port}
15567 @kindex target mips @var{port}
15568 To run a program on the board, start up @code{@value{GDBP}} with the
15569 name of your program as the argument. To connect to the board, use the
15570 command @samp{target mips @var{port}}, where @var{port} is the name of
15571 the serial port connected to the board. If the program has not already
15572 been downloaded to the board, you may use the @code{load} command to
15573 download it. You can then use all the usual @value{GDBN} commands.
15575 For example, this sequence connects to the target board through a serial
15576 port, and loads and runs a program called @var{prog} through the
15580 host$ @value{GDBP} @var{prog}
15581 @value{GDBN} is free software and @dots{}
15582 (@value{GDBP}) target mips /dev/ttyb
15583 (@value{GDBP}) load @var{prog}
15587 @item target mips @var{hostname}:@var{portnumber}
15588 On some @value{GDBN} host configurations, you can specify a TCP
15589 connection (for instance, to a serial line managed by a terminal
15590 concentrator) instead of a serial port, using the syntax
15591 @samp{@var{hostname}:@var{portnumber}}.
15593 @item target pmon @var{port}
15594 @kindex target pmon @var{port}
15597 @item target ddb @var{port}
15598 @kindex target ddb @var{port}
15599 NEC's DDB variant of PMON for Vr4300.
15601 @item target lsi @var{port}
15602 @kindex target lsi @var{port}
15603 LSI variant of PMON.
15605 @kindex target r3900
15606 @item target r3900 @var{dev}
15607 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
15609 @kindex target array
15610 @item target array @var{dev}
15611 Array Tech LSI33K RAID controller board.
15617 @value{GDBN} also supports these special commands for MIPS targets:
15620 @item set mipsfpu double
15621 @itemx set mipsfpu single
15622 @itemx set mipsfpu none
15623 @itemx set mipsfpu auto
15624 @itemx show mipsfpu
15625 @kindex set mipsfpu
15626 @kindex show mipsfpu
15627 @cindex MIPS remote floating point
15628 @cindex floating point, MIPS remote
15629 If your target board does not support the MIPS floating point
15630 coprocessor, you should use the command @samp{set mipsfpu none} (if you
15631 need this, you may wish to put the command in your @value{GDBN} init
15632 file). This tells @value{GDBN} how to find the return value of
15633 functions which return floating point values. It also allows
15634 @value{GDBN} to avoid saving the floating point registers when calling
15635 functions on the board. If you are using a floating point coprocessor
15636 with only single precision floating point support, as on the @sc{r4650}
15637 processor, use the command @samp{set mipsfpu single}. The default
15638 double precision floating point coprocessor may be selected using
15639 @samp{set mipsfpu double}.
15641 In previous versions the only choices were double precision or no
15642 floating point, so @samp{set mipsfpu on} will select double precision
15643 and @samp{set mipsfpu off} will select no floating point.
15645 As usual, you can inquire about the @code{mipsfpu} variable with
15646 @samp{show mipsfpu}.
15648 @item set timeout @var{seconds}
15649 @itemx set retransmit-timeout @var{seconds}
15650 @itemx show timeout
15651 @itemx show retransmit-timeout
15652 @cindex @code{timeout}, MIPS protocol
15653 @cindex @code{retransmit-timeout}, MIPS protocol
15654 @kindex set timeout
15655 @kindex show timeout
15656 @kindex set retransmit-timeout
15657 @kindex show retransmit-timeout
15658 You can control the timeout used while waiting for a packet, in the MIPS
15659 remote protocol, with the @code{set timeout @var{seconds}} command. The
15660 default is 5 seconds. Similarly, you can control the timeout used while
15661 waiting for an acknowledgment of a packet with the @code{set
15662 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
15663 You can inspect both values with @code{show timeout} and @code{show
15664 retransmit-timeout}. (These commands are @emph{only} available when
15665 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
15667 The timeout set by @code{set timeout} does not apply when @value{GDBN}
15668 is waiting for your program to stop. In that case, @value{GDBN} waits
15669 forever because it has no way of knowing how long the program is going
15670 to run before stopping.
15672 @item set syn-garbage-limit @var{num}
15673 @kindex set syn-garbage-limit@r{, MIPS remote}
15674 @cindex synchronize with remote MIPS target
15675 Limit the maximum number of characters @value{GDBN} should ignore when
15676 it tries to synchronize with the remote target. The default is 10
15677 characters. Setting the limit to -1 means there's no limit.
15679 @item show syn-garbage-limit
15680 @kindex show syn-garbage-limit@r{, MIPS remote}
15681 Show the current limit on the number of characters to ignore when
15682 trying to synchronize with the remote system.
15684 @item set monitor-prompt @var{prompt}
15685 @kindex set monitor-prompt@r{, MIPS remote}
15686 @cindex remote monitor prompt
15687 Tell @value{GDBN} to expect the specified @var{prompt} string from the
15688 remote monitor. The default depends on the target:
15698 @item show monitor-prompt
15699 @kindex show monitor-prompt@r{, MIPS remote}
15700 Show the current strings @value{GDBN} expects as the prompt from the
15703 @item set monitor-warnings
15704 @kindex set monitor-warnings@r{, MIPS remote}
15705 Enable or disable monitor warnings about hardware breakpoints. This
15706 has effect only for the @code{lsi} target. When on, @value{GDBN} will
15707 display warning messages whose codes are returned by the @code{lsi}
15708 PMON monitor for breakpoint commands.
15710 @item show monitor-warnings
15711 @kindex show monitor-warnings@r{, MIPS remote}
15712 Show the current setting of printing monitor warnings.
15714 @item pmon @var{command}
15715 @kindex pmon@r{, MIPS remote}
15716 @cindex send PMON command
15717 This command allows sending an arbitrary @var{command} string to the
15718 monitor. The monitor must be in debug mode for this to work.
15721 @node OpenRISC 1000
15722 @subsection OpenRISC 1000
15723 @cindex OpenRISC 1000
15725 @cindex or1k boards
15726 See OR1k Architecture document (@uref{www.opencores.org}) for more information
15727 about platform and commands.
15731 @kindex target jtag
15732 @item target jtag jtag://@var{host}:@var{port}
15734 Connects to remote JTAG server.
15735 JTAG remote server can be either an or1ksim or JTAG server,
15736 connected via parallel port to the board.
15738 Example: @code{target jtag jtag://localhost:9999}
15741 @item or1ksim @var{command}
15742 If connected to @code{or1ksim} OpenRISC 1000 Architectural
15743 Simulator, proprietary commands can be executed.
15745 @kindex info or1k spr
15746 @item info or1k spr
15747 Displays spr groups.
15749 @item info or1k spr @var{group}
15750 @itemx info or1k spr @var{groupno}
15751 Displays register names in selected group.
15753 @item info or1k spr @var{group} @var{register}
15754 @itemx info or1k spr @var{register}
15755 @itemx info or1k spr @var{groupno} @var{registerno}
15756 @itemx info or1k spr @var{registerno}
15757 Shows information about specified spr register.
15760 @item spr @var{group} @var{register} @var{value}
15761 @itemx spr @var{register @var{value}}
15762 @itemx spr @var{groupno} @var{registerno @var{value}}
15763 @itemx spr @var{registerno @var{value}}
15764 Writes @var{value} to specified spr register.
15767 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15768 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15769 program execution and is thus much faster. Hardware breakpoints/watchpoint
15770 triggers can be set using:
15773 Load effective address/data
15775 Store effective address/data
15777 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15782 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15783 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15785 @code{htrace} commands:
15786 @cindex OpenRISC 1000 htrace
15789 @item hwatch @var{conditional}
15790 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15791 or Data. For example:
15793 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15795 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15799 Display information about current HW trace configuration.
15801 @item htrace trigger @var{conditional}
15802 Set starting criteria for HW trace.
15804 @item htrace qualifier @var{conditional}
15805 Set acquisition qualifier for HW trace.
15807 @item htrace stop @var{conditional}
15808 Set HW trace stopping criteria.
15810 @item htrace record [@var{data}]*
15811 Selects the data to be recorded, when qualifier is met and HW trace was
15814 @item htrace enable
15815 @itemx htrace disable
15816 Enables/disables the HW trace.
15818 @item htrace rewind [@var{filename}]
15819 Clears currently recorded trace data.
15821 If filename is specified, new trace file is made and any newly collected data
15822 will be written there.
15824 @item htrace print [@var{start} [@var{len}]]
15825 Prints trace buffer, using current record configuration.
15827 @item htrace mode continuous
15828 Set continuous trace mode.
15830 @item htrace mode suspend
15831 Set suspend trace mode.
15835 @node PowerPC Embedded
15836 @subsection PowerPC Embedded
15838 @value{GDBN} provides the following PowerPC-specific commands:
15841 @kindex set powerpc
15842 @item set powerpc soft-float
15843 @itemx show powerpc soft-float
15844 Force @value{GDBN} to use (or not use) a software floating point calling
15845 convention. By default, @value{GDBN} selects the calling convention based
15846 on the selected architecture and the provided executable file.
15848 @item set powerpc vector-abi
15849 @itemx show powerpc vector-abi
15850 Force @value{GDBN} to use the specified calling convention for vector
15851 arguments and return values. The valid options are @samp{auto};
15852 @samp{generic}, to avoid vector registers even if they are present;
15853 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15854 registers. By default, @value{GDBN} selects the calling convention
15855 based on the selected architecture and the provided executable file.
15857 @kindex target dink32
15858 @item target dink32 @var{dev}
15859 DINK32 ROM monitor.
15861 @kindex target ppcbug
15862 @item target ppcbug @var{dev}
15863 @kindex target ppcbug1
15864 @item target ppcbug1 @var{dev}
15865 PPCBUG ROM monitor for PowerPC.
15868 @item target sds @var{dev}
15869 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15872 @cindex SDS protocol
15873 The following commands specific to the SDS protocol are supported
15877 @item set sdstimeout @var{nsec}
15878 @kindex set sdstimeout
15879 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15880 default is 2 seconds.
15882 @item show sdstimeout
15883 @kindex show sdstimeout
15884 Show the current value of the SDS timeout.
15886 @item sds @var{command}
15887 @kindex sds@r{, a command}
15888 Send the specified @var{command} string to the SDS monitor.
15893 @subsection HP PA Embedded
15897 @kindex target op50n
15898 @item target op50n @var{dev}
15899 OP50N monitor, running on an OKI HPPA board.
15901 @kindex target w89k
15902 @item target w89k @var{dev}
15903 W89K monitor, running on a Winbond HPPA board.
15908 @subsection Tsqware Sparclet
15912 @value{GDBN} enables developers to debug tasks running on
15913 Sparclet targets from a Unix host.
15914 @value{GDBN} uses code that runs on
15915 both the Unix host and on the Sparclet target. The program
15916 @code{@value{GDBP}} is installed and executed on the Unix host.
15919 @item remotetimeout @var{args}
15920 @kindex remotetimeout
15921 @value{GDBN} supports the option @code{remotetimeout}.
15922 This option is set by the user, and @var{args} represents the number of
15923 seconds @value{GDBN} waits for responses.
15926 @cindex compiling, on Sparclet
15927 When compiling for debugging, include the options @samp{-g} to get debug
15928 information and @samp{-Ttext} to relocate the program to where you wish to
15929 load it on the target. You may also want to add the options @samp{-n} or
15930 @samp{-N} in order to reduce the size of the sections. Example:
15933 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15936 You can use @code{objdump} to verify that the addresses are what you intended:
15939 sparclet-aout-objdump --headers --syms prog
15942 @cindex running, on Sparclet
15944 your Unix execution search path to find @value{GDBN}, you are ready to
15945 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15946 (or @code{sparclet-aout-gdb}, depending on your installation).
15948 @value{GDBN} comes up showing the prompt:
15955 * Sparclet File:: Setting the file to debug
15956 * Sparclet Connection:: Connecting to Sparclet
15957 * Sparclet Download:: Sparclet download
15958 * Sparclet Execution:: Running and debugging
15961 @node Sparclet File
15962 @subsubsection Setting File to Debug
15964 The @value{GDBN} command @code{file} lets you choose with program to debug.
15967 (gdbslet) file prog
15971 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15972 @value{GDBN} locates
15973 the file by searching the directories listed in the command search
15975 If the file was compiled with debug information (option @samp{-g}), source
15976 files will be searched as well.
15977 @value{GDBN} locates
15978 the source files by searching the directories listed in the directory search
15979 path (@pxref{Environment, ,Your Program's Environment}).
15981 to find a file, it displays a message such as:
15984 prog: No such file or directory.
15987 When this happens, add the appropriate directories to the search paths with
15988 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15989 @code{target} command again.
15991 @node Sparclet Connection
15992 @subsubsection Connecting to Sparclet
15994 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15995 To connect to a target on serial port ``@code{ttya}'', type:
15998 (gdbslet) target sparclet /dev/ttya
15999 Remote target sparclet connected to /dev/ttya
16000 main () at ../prog.c:3
16004 @value{GDBN} displays messages like these:
16010 @node Sparclet Download
16011 @subsubsection Sparclet Download
16013 @cindex download to Sparclet
16014 Once connected to the Sparclet target,
16015 you can use the @value{GDBN}
16016 @code{load} command to download the file from the host to the target.
16017 The file name and load offset should be given as arguments to the @code{load}
16019 Since the file format is aout, the program must be loaded to the starting
16020 address. You can use @code{objdump} to find out what this value is. The load
16021 offset is an offset which is added to the VMA (virtual memory address)
16022 of each of the file's sections.
16023 For instance, if the program
16024 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16025 and bss at 0x12010170, in @value{GDBN}, type:
16028 (gdbslet) load prog 0x12010000
16029 Loading section .text, size 0xdb0 vma 0x12010000
16032 If the code is loaded at a different address then what the program was linked
16033 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16034 to tell @value{GDBN} where to map the symbol table.
16036 @node Sparclet Execution
16037 @subsubsection Running and Debugging
16039 @cindex running and debugging Sparclet programs
16040 You can now begin debugging the task using @value{GDBN}'s execution control
16041 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16042 manual for the list of commands.
16046 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16048 Starting program: prog
16049 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16050 3 char *symarg = 0;
16052 4 char *execarg = "hello!";
16057 @subsection Fujitsu Sparclite
16061 @kindex target sparclite
16062 @item target sparclite @var{dev}
16063 Fujitsu sparclite boards, used only for the purpose of loading.
16064 You must use an additional command to debug the program.
16065 For example: target remote @var{dev} using @value{GDBN} standard
16071 @subsection Zilog Z8000
16074 @cindex simulator, Z8000
16075 @cindex Zilog Z8000 simulator
16077 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16080 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16081 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16082 segmented variant). The simulator recognizes which architecture is
16083 appropriate by inspecting the object code.
16086 @item target sim @var{args}
16088 @kindex target sim@r{, with Z8000}
16089 Debug programs on a simulated CPU. If the simulator supports setup
16090 options, specify them via @var{args}.
16094 After specifying this target, you can debug programs for the simulated
16095 CPU in the same style as programs for your host computer; use the
16096 @code{file} command to load a new program image, the @code{run} command
16097 to run your program, and so on.
16099 As well as making available all the usual machine registers
16100 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16101 additional items of information as specially named registers:
16106 Counts clock-ticks in the simulator.
16109 Counts instructions run in the simulator.
16112 Execution time in 60ths of a second.
16116 You can refer to these values in @value{GDBN} expressions with the usual
16117 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16118 conditional breakpoint that suspends only after at least 5000
16119 simulated clock ticks.
16122 @subsection Atmel AVR
16125 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16126 following AVR-specific commands:
16129 @item info io_registers
16130 @kindex info io_registers@r{, AVR}
16131 @cindex I/O registers (Atmel AVR)
16132 This command displays information about the AVR I/O registers. For
16133 each register, @value{GDBN} prints its number and value.
16140 When configured for debugging CRIS, @value{GDBN} provides the
16141 following CRIS-specific commands:
16144 @item set cris-version @var{ver}
16145 @cindex CRIS version
16146 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16147 The CRIS version affects register names and sizes. This command is useful in
16148 case autodetection of the CRIS version fails.
16150 @item show cris-version
16151 Show the current CRIS version.
16153 @item set cris-dwarf2-cfi
16154 @cindex DWARF-2 CFI and CRIS
16155 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16156 Change to @samp{off} when using @code{gcc-cris} whose version is below
16159 @item show cris-dwarf2-cfi
16160 Show the current state of using DWARF-2 CFI.
16162 @item set cris-mode @var{mode}
16164 Set the current CRIS mode to @var{mode}. It should only be changed when
16165 debugging in guru mode, in which case it should be set to
16166 @samp{guru} (the default is @samp{normal}).
16168 @item show cris-mode
16169 Show the current CRIS mode.
16173 @subsection Renesas Super-H
16176 For the Renesas Super-H processor, @value{GDBN} provides these
16181 @kindex regs@r{, Super-H}
16182 Show the values of all Super-H registers.
16184 @item set sh calling-convention @var{convention}
16185 @kindex set sh calling-convention
16186 Set the calling-convention used when calling functions from @value{GDBN}.
16187 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16188 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16189 convention. If the DWARF-2 information of the called function specifies
16190 that the function follows the Renesas calling convention, the function
16191 is called using the Renesas calling convention. If the calling convention
16192 is set to @samp{renesas}, the Renesas calling convention is always used,
16193 regardless of the DWARF-2 information. This can be used to override the
16194 default of @samp{gcc} if debug information is missing, or the compiler
16195 does not emit the DWARF-2 calling convention entry for a function.
16197 @item show sh calling-convention
16198 @kindex show sh calling-convention
16199 Show the current calling convention setting.
16204 @node Architectures
16205 @section Architectures
16207 This section describes characteristics of architectures that affect
16208 all uses of @value{GDBN} with the architecture, both native and cross.
16215 * HPPA:: HP PA architecture
16216 * SPU:: Cell Broadband Engine SPU architecture
16221 @subsection x86 Architecture-specific Issues
16224 @item set struct-convention @var{mode}
16225 @kindex set struct-convention
16226 @cindex struct return convention
16227 @cindex struct/union returned in registers
16228 Set the convention used by the inferior to return @code{struct}s and
16229 @code{union}s from functions to @var{mode}. Possible values of
16230 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16231 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16232 are returned on the stack, while @code{"reg"} means that a
16233 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16234 be returned in a register.
16236 @item show struct-convention
16237 @kindex show struct-convention
16238 Show the current setting of the convention to return @code{struct}s
16247 @kindex set rstack_high_address
16248 @cindex AMD 29K register stack
16249 @cindex register stack, AMD29K
16250 @item set rstack_high_address @var{address}
16251 On AMD 29000 family processors, registers are saved in a separate
16252 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16253 extent of this stack. Normally, @value{GDBN} just assumes that the
16254 stack is ``large enough''. This may result in @value{GDBN} referencing
16255 memory locations that do not exist. If necessary, you can get around
16256 this problem by specifying the ending address of the register stack with
16257 the @code{set rstack_high_address} command. The argument should be an
16258 address, which you probably want to precede with @samp{0x} to specify in
16261 @kindex show rstack_high_address
16262 @item show rstack_high_address
16263 Display the current limit of the register stack, on AMD 29000 family
16271 See the following section.
16276 @cindex stack on Alpha
16277 @cindex stack on MIPS
16278 @cindex Alpha stack
16280 Alpha- and MIPS-based computers use an unusual stack frame, which
16281 sometimes requires @value{GDBN} to search backward in the object code to
16282 find the beginning of a function.
16284 @cindex response time, MIPS debugging
16285 To improve response time (especially for embedded applications, where
16286 @value{GDBN} may be restricted to a slow serial line for this search)
16287 you may want to limit the size of this search, using one of these
16291 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16292 @item set heuristic-fence-post @var{limit}
16293 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16294 search for the beginning of a function. A value of @var{0} (the
16295 default) means there is no limit. However, except for @var{0}, the
16296 larger the limit the more bytes @code{heuristic-fence-post} must search
16297 and therefore the longer it takes to run. You should only need to use
16298 this command when debugging a stripped executable.
16300 @item show heuristic-fence-post
16301 Display the current limit.
16305 These commands are available @emph{only} when @value{GDBN} is configured
16306 for debugging programs on Alpha or MIPS processors.
16308 Several MIPS-specific commands are available when debugging MIPS
16312 @item set mips abi @var{arg}
16313 @kindex set mips abi
16314 @cindex set ABI for MIPS
16315 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16316 values of @var{arg} are:
16320 The default ABI associated with the current binary (this is the
16331 @item show mips abi
16332 @kindex show mips abi
16333 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16336 @itemx show mipsfpu
16337 @xref{MIPS Embedded, set mipsfpu}.
16339 @item set mips mask-address @var{arg}
16340 @kindex set mips mask-address
16341 @cindex MIPS addresses, masking
16342 This command determines whether the most-significant 32 bits of 64-bit
16343 MIPS addresses are masked off. The argument @var{arg} can be
16344 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16345 setting, which lets @value{GDBN} determine the correct value.
16347 @item show mips mask-address
16348 @kindex show mips mask-address
16349 Show whether the upper 32 bits of MIPS addresses are masked off or
16352 @item set remote-mips64-transfers-32bit-regs
16353 @kindex set remote-mips64-transfers-32bit-regs
16354 This command controls compatibility with 64-bit MIPS targets that
16355 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16356 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16357 and 64 bits for other registers, set this option to @samp{on}.
16359 @item show remote-mips64-transfers-32bit-regs
16360 @kindex show remote-mips64-transfers-32bit-regs
16361 Show the current setting of compatibility with older MIPS 64 targets.
16363 @item set debug mips
16364 @kindex set debug mips
16365 This command turns on and off debugging messages for the MIPS-specific
16366 target code in @value{GDBN}.
16368 @item show debug mips
16369 @kindex show debug mips
16370 Show the current setting of MIPS debugging messages.
16376 @cindex HPPA support
16378 When @value{GDBN} is debugging the HP PA architecture, it provides the
16379 following special commands:
16382 @item set debug hppa
16383 @kindex set debug hppa
16384 This command determines whether HPPA architecture-specific debugging
16385 messages are to be displayed.
16387 @item show debug hppa
16388 Show whether HPPA debugging messages are displayed.
16390 @item maint print unwind @var{address}
16391 @kindex maint print unwind@r{, HPPA}
16392 This command displays the contents of the unwind table entry at the
16393 given @var{address}.
16399 @subsection Cell Broadband Engine SPU architecture
16400 @cindex Cell Broadband Engine
16403 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16404 it provides the following special commands:
16407 @item info spu event
16409 Display SPU event facility status. Shows current event mask
16410 and pending event status.
16412 @item info spu signal
16413 Display SPU signal notification facility status. Shows pending
16414 signal-control word and signal notification mode of both signal
16415 notification channels.
16417 @item info spu mailbox
16418 Display SPU mailbox facility status. Shows all pending entries,
16419 in order of processing, in each of the SPU Write Outbound,
16420 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16423 Display MFC DMA status. Shows all pending commands in the MFC
16424 DMA queue. For each entry, opcode, tag, class IDs, effective
16425 and local store addresses and transfer size are shown.
16427 @item info spu proxydma
16428 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16429 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16430 and local store addresses and transfer size are shown.
16435 @subsection PowerPC
16436 @cindex PowerPC architecture
16438 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16439 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16440 numbers stored in the floating point registers. These values must be stored
16441 in two consecutive registers, always starting at an even register like
16442 @code{f0} or @code{f2}.
16444 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16445 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16446 @code{f2} and @code{f3} for @code{$dl1} and so on.
16448 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
16449 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
16452 @node Controlling GDB
16453 @chapter Controlling @value{GDBN}
16455 You can alter the way @value{GDBN} interacts with you by using the
16456 @code{set} command. For commands controlling how @value{GDBN} displays
16457 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16462 * Editing:: Command editing
16463 * Command History:: Command history
16464 * Screen Size:: Screen size
16465 * Numbers:: Numbers
16466 * ABI:: Configuring the current ABI
16467 * Messages/Warnings:: Optional warnings and messages
16468 * Debugging Output:: Optional messages about internal happenings
16476 @value{GDBN} indicates its readiness to read a command by printing a string
16477 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
16478 can change the prompt string with the @code{set prompt} command. For
16479 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
16480 the prompt in one of the @value{GDBN} sessions so that you can always tell
16481 which one you are talking to.
16483 @emph{Note:} @code{set prompt} does not add a space for you after the
16484 prompt you set. This allows you to set a prompt which ends in a space
16485 or a prompt that does not.
16489 @item set prompt @var{newprompt}
16490 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
16492 @kindex show prompt
16494 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
16498 @section Command Editing
16500 @cindex command line editing
16502 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
16503 @sc{gnu} library provides consistent behavior for programs which provide a
16504 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16505 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16506 substitution, and a storage and recall of command history across
16507 debugging sessions.
16509 You may control the behavior of command line editing in @value{GDBN} with the
16510 command @code{set}.
16513 @kindex set editing
16516 @itemx set editing on
16517 Enable command line editing (enabled by default).
16519 @item set editing off
16520 Disable command line editing.
16522 @kindex show editing
16524 Show whether command line editing is enabled.
16527 @xref{Command Line Editing}, for more details about the Readline
16528 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
16529 encouraged to read that chapter.
16531 @node Command History
16532 @section Command History
16533 @cindex command history
16535 @value{GDBN} can keep track of the commands you type during your
16536 debugging sessions, so that you can be certain of precisely what
16537 happened. Use these commands to manage the @value{GDBN} command
16540 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
16541 package, to provide the history facility. @xref{Using History
16542 Interactively}, for the detailed description of the History library.
16544 To issue a command to @value{GDBN} without affecting certain aspects of
16545 the state which is seen by users, prefix it with @samp{server }
16546 (@pxref{Server Prefix}). This
16547 means that this command will not affect the command history, nor will it
16548 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
16549 pressed on a line by itself.
16551 @cindex @code{server}, command prefix
16552 The server prefix does not affect the recording of values into the value
16553 history; to print a value without recording it into the value history,
16554 use the @code{output} command instead of the @code{print} command.
16556 Here is the description of @value{GDBN} commands related to command
16560 @cindex history substitution
16561 @cindex history file
16562 @kindex set history filename
16563 @cindex @env{GDBHISTFILE}, environment variable
16564 @item set history filename @var{fname}
16565 Set the name of the @value{GDBN} command history file to @var{fname}.
16566 This is the file where @value{GDBN} reads an initial command history
16567 list, and where it writes the command history from this session when it
16568 exits. You can access this list through history expansion or through
16569 the history command editing characters listed below. This file defaults
16570 to the value of the environment variable @code{GDBHISTFILE}, or to
16571 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16574 @cindex save command history
16575 @kindex set history save
16576 @item set history save
16577 @itemx set history save on
16578 Record command history in a file, whose name may be specified with the
16579 @code{set history filename} command. By default, this option is disabled.
16581 @item set history save off
16582 Stop recording command history in a file.
16584 @cindex history size
16585 @kindex set history size
16586 @cindex @env{HISTSIZE}, environment variable
16587 @item set history size @var{size}
16588 Set the number of commands which @value{GDBN} keeps in its history list.
16589 This defaults to the value of the environment variable
16590 @code{HISTSIZE}, or to 256 if this variable is not set.
16593 History expansion assigns special meaning to the character @kbd{!}.
16594 @xref{Event Designators}, for more details.
16596 @cindex history expansion, turn on/off
16597 Since @kbd{!} is also the logical not operator in C, history expansion
16598 is off by default. If you decide to enable history expansion with the
16599 @code{set history expansion on} command, you may sometimes need to
16600 follow @kbd{!} (when it is used as logical not, in an expression) with
16601 a space or a tab to prevent it from being expanded. The readline
16602 history facilities do not attempt substitution on the strings
16603 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
16605 The commands to control history expansion are:
16608 @item set history expansion on
16609 @itemx set history expansion
16610 @kindex set history expansion
16611 Enable history expansion. History expansion is off by default.
16613 @item set history expansion off
16614 Disable history expansion.
16617 @kindex show history
16619 @itemx show history filename
16620 @itemx show history save
16621 @itemx show history size
16622 @itemx show history expansion
16623 These commands display the state of the @value{GDBN} history parameters.
16624 @code{show history} by itself displays all four states.
16629 @kindex show commands
16630 @cindex show last commands
16631 @cindex display command history
16632 @item show commands
16633 Display the last ten commands in the command history.
16635 @item show commands @var{n}
16636 Print ten commands centered on command number @var{n}.
16638 @item show commands +
16639 Print ten commands just after the commands last printed.
16643 @section Screen Size
16644 @cindex size of screen
16645 @cindex pauses in output
16647 Certain commands to @value{GDBN} may produce large amounts of
16648 information output to the screen. To help you read all of it,
16649 @value{GDBN} pauses and asks you for input at the end of each page of
16650 output. Type @key{RET} when you want to continue the output, or @kbd{q}
16651 to discard the remaining output. Also, the screen width setting
16652 determines when to wrap lines of output. Depending on what is being
16653 printed, @value{GDBN} tries to break the line at a readable place,
16654 rather than simply letting it overflow onto the following line.
16656 Normally @value{GDBN} knows the size of the screen from the terminal
16657 driver software. For example, on Unix @value{GDBN} uses the termcap data base
16658 together with the value of the @code{TERM} environment variable and the
16659 @code{stty rows} and @code{stty cols} settings. If this is not correct,
16660 you can override it with the @code{set height} and @code{set
16667 @kindex show height
16668 @item set height @var{lpp}
16670 @itemx set width @var{cpl}
16672 These @code{set} commands specify a screen height of @var{lpp} lines and
16673 a screen width of @var{cpl} characters. The associated @code{show}
16674 commands display the current settings.
16676 If you specify a height of zero lines, @value{GDBN} does not pause during
16677 output no matter how long the output is. This is useful if output is to a
16678 file or to an editor buffer.
16680 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
16681 from wrapping its output.
16683 @item set pagination on
16684 @itemx set pagination off
16685 @kindex set pagination
16686 Turn the output pagination on or off; the default is on. Turning
16687 pagination off is the alternative to @code{set height 0}.
16689 @item show pagination
16690 @kindex show pagination
16691 Show the current pagination mode.
16696 @cindex number representation
16697 @cindex entering numbers
16699 You can always enter numbers in octal, decimal, or hexadecimal in
16700 @value{GDBN} by the usual conventions: octal numbers begin with
16701 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
16702 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
16703 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
16704 10; likewise, the default display for numbers---when no particular
16705 format is specified---is base 10. You can change the default base for
16706 both input and output with the commands described below.
16709 @kindex set input-radix
16710 @item set input-radix @var{base}
16711 Set the default base for numeric input. Supported choices
16712 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16713 specified either unambiguously or using the current input radix; for
16717 set input-radix 012
16718 set input-radix 10.
16719 set input-radix 0xa
16723 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
16724 leaves the input radix unchanged, no matter what it was, since
16725 @samp{10}, being without any leading or trailing signs of its base, is
16726 interpreted in the current radix. Thus, if the current radix is 16,
16727 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
16730 @kindex set output-radix
16731 @item set output-radix @var{base}
16732 Set the default base for numeric display. Supported choices
16733 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16734 specified either unambiguously or using the current input radix.
16736 @kindex show input-radix
16737 @item show input-radix
16738 Display the current default base for numeric input.
16740 @kindex show output-radix
16741 @item show output-radix
16742 Display the current default base for numeric display.
16744 @item set radix @r{[}@var{base}@r{]}
16748 These commands set and show the default base for both input and output
16749 of numbers. @code{set radix} sets the radix of input and output to
16750 the same base; without an argument, it resets the radix back to its
16751 default value of 10.
16756 @section Configuring the Current ABI
16758 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
16759 application automatically. However, sometimes you need to override its
16760 conclusions. Use these commands to manage @value{GDBN}'s view of the
16767 One @value{GDBN} configuration can debug binaries for multiple operating
16768 system targets, either via remote debugging or native emulation.
16769 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
16770 but you can override its conclusion using the @code{set osabi} command.
16771 One example where this is useful is in debugging of binaries which use
16772 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16773 not have the same identifying marks that the standard C library for your
16778 Show the OS ABI currently in use.
16781 With no argument, show the list of registered available OS ABI's.
16783 @item set osabi @var{abi}
16784 Set the current OS ABI to @var{abi}.
16787 @cindex float promotion
16789 Generally, the way that an argument of type @code{float} is passed to a
16790 function depends on whether the function is prototyped. For a prototyped
16791 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16792 according to the architecture's convention for @code{float}. For unprototyped
16793 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16794 @code{double} and then passed.
16796 Unfortunately, some forms of debug information do not reliably indicate whether
16797 a function is prototyped. If @value{GDBN} calls a function that is not marked
16798 as prototyped, it consults @kbd{set coerce-float-to-double}.
16801 @kindex set coerce-float-to-double
16802 @item set coerce-float-to-double
16803 @itemx set coerce-float-to-double on
16804 Arguments of type @code{float} will be promoted to @code{double} when passed
16805 to an unprototyped function. This is the default setting.
16807 @item set coerce-float-to-double off
16808 Arguments of type @code{float} will be passed directly to unprototyped
16811 @kindex show coerce-float-to-double
16812 @item show coerce-float-to-double
16813 Show the current setting of promoting @code{float} to @code{double}.
16817 @kindex show cp-abi
16818 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16819 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16820 used to build your application. @value{GDBN} only fully supports
16821 programs with a single C@t{++} ABI; if your program contains code using
16822 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16823 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16824 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16825 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16826 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16827 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16832 Show the C@t{++} ABI currently in use.
16835 With no argument, show the list of supported C@t{++} ABI's.
16837 @item set cp-abi @var{abi}
16838 @itemx set cp-abi auto
16839 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16842 @node Messages/Warnings
16843 @section Optional Warnings and Messages
16845 @cindex verbose operation
16846 @cindex optional warnings
16847 By default, @value{GDBN} is silent about its inner workings. If you are
16848 running on a slow machine, you may want to use the @code{set verbose}
16849 command. This makes @value{GDBN} tell you when it does a lengthy
16850 internal operation, so you will not think it has crashed.
16852 Currently, the messages controlled by @code{set verbose} are those
16853 which announce that the symbol table for a source file is being read;
16854 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16857 @kindex set verbose
16858 @item set verbose on
16859 Enables @value{GDBN} output of certain informational messages.
16861 @item set verbose off
16862 Disables @value{GDBN} output of certain informational messages.
16864 @kindex show verbose
16866 Displays whether @code{set verbose} is on or off.
16869 By default, if @value{GDBN} encounters bugs in the symbol table of an
16870 object file, it is silent; but if you are debugging a compiler, you may
16871 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16876 @kindex set complaints
16877 @item set complaints @var{limit}
16878 Permits @value{GDBN} to output @var{limit} complaints about each type of
16879 unusual symbols before becoming silent about the problem. Set
16880 @var{limit} to zero to suppress all complaints; set it to a large number
16881 to prevent complaints from being suppressed.
16883 @kindex show complaints
16884 @item show complaints
16885 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16889 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16890 lot of stupid questions to confirm certain commands. For example, if
16891 you try to run a program which is already running:
16895 The program being debugged has been started already.
16896 Start it from the beginning? (y or n)
16899 If you are willing to unflinchingly face the consequences of your own
16900 commands, you can disable this ``feature'':
16904 @kindex set confirm
16906 @cindex confirmation
16907 @cindex stupid questions
16908 @item set confirm off
16909 Disables confirmation requests.
16911 @item set confirm on
16912 Enables confirmation requests (the default).
16914 @kindex show confirm
16916 Displays state of confirmation requests.
16920 @cindex command tracing
16921 If you need to debug user-defined commands or sourced files you may find it
16922 useful to enable @dfn{command tracing}. In this mode each command will be
16923 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16924 quantity denoting the call depth of each command.
16927 @kindex set trace-commands
16928 @cindex command scripts, debugging
16929 @item set trace-commands on
16930 Enable command tracing.
16931 @item set trace-commands off
16932 Disable command tracing.
16933 @item show trace-commands
16934 Display the current state of command tracing.
16937 @node Debugging Output
16938 @section Optional Messages about Internal Happenings
16939 @cindex optional debugging messages
16941 @value{GDBN} has commands that enable optional debugging messages from
16942 various @value{GDBN} subsystems; normally these commands are of
16943 interest to @value{GDBN} maintainers, or when reporting a bug. This
16944 section documents those commands.
16947 @kindex set exec-done-display
16948 @item set exec-done-display
16949 Turns on or off the notification of asynchronous commands'
16950 completion. When on, @value{GDBN} will print a message when an
16951 asynchronous command finishes its execution. The default is off.
16952 @kindex show exec-done-display
16953 @item show exec-done-display
16954 Displays the current setting of asynchronous command completion
16957 @cindex gdbarch debugging info
16958 @cindex architecture debugging info
16959 @item set debug arch
16960 Turns on or off display of gdbarch debugging info. The default is off
16962 @item show debug arch
16963 Displays the current state of displaying gdbarch debugging info.
16964 @item set debug aix-thread
16965 @cindex AIX threads
16966 Display debugging messages about inner workings of the AIX thread
16968 @item show debug aix-thread
16969 Show the current state of AIX thread debugging info display.
16970 @item set debug displaced
16971 @cindex displaced stepping debugging info
16972 Turns on or off display of @value{GDBN} debugging info for the
16973 displaced stepping support. The default is off.
16974 @item show debug displaced
16975 Displays the current state of displaying @value{GDBN} debugging info
16976 related to displaced stepping.
16977 @item set debug event
16978 @cindex event debugging info
16979 Turns on or off display of @value{GDBN} event debugging info. The
16981 @item show debug event
16982 Displays the current state of displaying @value{GDBN} event debugging
16984 @item set debug expression
16985 @cindex expression debugging info
16986 Turns on or off display of debugging info about @value{GDBN}
16987 expression parsing. The default is off.
16988 @item show debug expression
16989 Displays the current state of displaying debugging info about
16990 @value{GDBN} expression parsing.
16991 @item set debug frame
16992 @cindex frame debugging info
16993 Turns on or off display of @value{GDBN} frame debugging info. The
16995 @item show debug frame
16996 Displays the current state of displaying @value{GDBN} frame debugging
16998 @item set debug infrun
16999 @cindex inferior debugging info
17000 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17001 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17002 for implementing operations such as single-stepping the inferior.
17003 @item show debug infrun
17004 Displays the current state of @value{GDBN} inferior debugging.
17005 @item set debug lin-lwp
17006 @cindex @sc{gnu}/Linux LWP debug messages
17007 @cindex Linux lightweight processes
17008 Turns on or off debugging messages from the Linux LWP debug support.
17009 @item show debug lin-lwp
17010 Show the current state of Linux LWP debugging messages.
17011 @item set debug lin-lwp-async
17012 @cindex @sc{gnu}/Linux LWP async debug messages
17013 @cindex Linux lightweight processes
17014 Turns on or off debugging messages from the Linux LWP async debug support.
17015 @item show debug lin-lwp-async
17016 Show the current state of Linux LWP async debugging messages.
17017 @item set debug observer
17018 @cindex observer debugging info
17019 Turns on or off display of @value{GDBN} observer debugging. This
17020 includes info such as the notification of observable events.
17021 @item show debug observer
17022 Displays the current state of observer debugging.
17023 @item set debug overload
17024 @cindex C@t{++} overload debugging info
17025 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17026 info. This includes info such as ranking of functions, etc. The default
17028 @item show debug overload
17029 Displays the current state of displaying @value{GDBN} C@t{++} overload
17031 @cindex packets, reporting on stdout
17032 @cindex serial connections, debugging
17033 @cindex debug remote protocol
17034 @cindex remote protocol debugging
17035 @cindex display remote packets
17036 @item set debug remote
17037 Turns on or off display of reports on all packets sent back and forth across
17038 the serial line to the remote machine. The info is printed on the
17039 @value{GDBN} standard output stream. The default is off.
17040 @item show debug remote
17041 Displays the state of display of remote packets.
17042 @item set debug serial
17043 Turns on or off display of @value{GDBN} serial debugging info. The
17045 @item show debug serial
17046 Displays the current state of displaying @value{GDBN} serial debugging
17048 @item set debug solib-frv
17049 @cindex FR-V shared-library debugging
17050 Turns on or off debugging messages for FR-V shared-library code.
17051 @item show debug solib-frv
17052 Display the current state of FR-V shared-library code debugging
17054 @item set debug target
17055 @cindex target debugging info
17056 Turns on or off display of @value{GDBN} target debugging info. This info
17057 includes what is going on at the target level of GDB, as it happens. The
17058 default is 0. Set it to 1 to track events, and to 2 to also track the
17059 value of large memory transfers. Changes to this flag do not take effect
17060 until the next time you connect to a target or use the @code{run} command.
17061 @item show debug target
17062 Displays the current state of displaying @value{GDBN} target debugging
17064 @item set debug timestamp
17065 @cindex timestampping debugging info
17066 Turns on or off display of timestamps with @value{GDBN} debugging info.
17067 When enabled, seconds and microseconds are displayed before each debugging
17069 @item show debug timestamp
17070 Displays the current state of displaying timestamps with @value{GDBN}
17072 @item set debugvarobj
17073 @cindex variable object debugging info
17074 Turns on or off display of @value{GDBN} variable object debugging
17075 info. The default is off.
17076 @item show debugvarobj
17077 Displays the current state of displaying @value{GDBN} variable object
17079 @item set debug xml
17080 @cindex XML parser debugging
17081 Turns on or off debugging messages for built-in XML parsers.
17082 @item show debug xml
17083 Displays the current state of XML debugging messages.
17086 @node Extending GDB
17087 @chapter Extending @value{GDBN}
17088 @cindex extending GDB
17090 @value{GDBN} provides two mechanisms for extension. The first is based
17091 on composition of @value{GDBN} commands, and the second is based on the
17092 Python scripting language.
17095 * Sequences:: Canned Sequences of Commands
17096 * Python:: Scripting @value{GDBN} using Python
17100 @section Canned Sequences of Commands
17102 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17103 Command Lists}), @value{GDBN} provides two ways to store sequences of
17104 commands for execution as a unit: user-defined commands and command
17108 * Define:: How to define your own commands
17109 * Hooks:: Hooks for user-defined commands
17110 * Command Files:: How to write scripts of commands to be stored in a file
17111 * Output:: Commands for controlled output
17115 @subsection User-defined Commands
17117 @cindex user-defined command
17118 @cindex arguments, to user-defined commands
17119 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17120 which you assign a new name as a command. This is done with the
17121 @code{define} command. User commands may accept up to 10 arguments
17122 separated by whitespace. Arguments are accessed within the user command
17123 via @code{$arg0@dots{}$arg9}. A trivial example:
17127 print $arg0 + $arg1 + $arg2
17132 To execute the command use:
17139 This defines the command @code{adder}, which prints the sum of
17140 its three arguments. Note the arguments are text substitutions, so they may
17141 reference variables, use complex expressions, or even perform inferior
17144 @cindex argument count in user-defined commands
17145 @cindex how many arguments (user-defined commands)
17146 In addition, @code{$argc} may be used to find out how many arguments have
17147 been passed. This expands to a number in the range 0@dots{}10.
17152 print $arg0 + $arg1
17155 print $arg0 + $arg1 + $arg2
17163 @item define @var{commandname}
17164 Define a command named @var{commandname}. If there is already a command
17165 by that name, you are asked to confirm that you want to redefine it.
17167 The definition of the command is made up of other @value{GDBN} command lines,
17168 which are given following the @code{define} command. The end of these
17169 commands is marked by a line containing @code{end}.
17172 @kindex end@r{ (user-defined commands)}
17173 @item document @var{commandname}
17174 Document the user-defined command @var{commandname}, so that it can be
17175 accessed by @code{help}. The command @var{commandname} must already be
17176 defined. This command reads lines of documentation just as @code{define}
17177 reads the lines of the command definition, ending with @code{end}.
17178 After the @code{document} command is finished, @code{help} on command
17179 @var{commandname} displays the documentation you have written.
17181 You may use the @code{document} command again to change the
17182 documentation of a command. Redefining the command with @code{define}
17183 does not change the documentation.
17185 @kindex dont-repeat
17186 @cindex don't repeat command
17188 Used inside a user-defined command, this tells @value{GDBN} that this
17189 command should not be repeated when the user hits @key{RET}
17190 (@pxref{Command Syntax, repeat last command}).
17192 @kindex help user-defined
17193 @item help user-defined
17194 List all user-defined commands, with the first line of the documentation
17199 @itemx show user @var{commandname}
17200 Display the @value{GDBN} commands used to define @var{commandname} (but
17201 not its documentation). If no @var{commandname} is given, display the
17202 definitions for all user-defined commands.
17204 @cindex infinite recursion in user-defined commands
17205 @kindex show max-user-call-depth
17206 @kindex set max-user-call-depth
17207 @item show max-user-call-depth
17208 @itemx set max-user-call-depth
17209 The value of @code{max-user-call-depth} controls how many recursion
17210 levels are allowed in user-defined commands before @value{GDBN} suspects an
17211 infinite recursion and aborts the command.
17214 In addition to the above commands, user-defined commands frequently
17215 use control flow commands, described in @ref{Command Files}.
17217 When user-defined commands are executed, the
17218 commands of the definition are not printed. An error in any command
17219 stops execution of the user-defined command.
17221 If used interactively, commands that would ask for confirmation proceed
17222 without asking when used inside a user-defined command. Many @value{GDBN}
17223 commands that normally print messages to say what they are doing omit the
17224 messages when used in a user-defined command.
17227 @subsection User-defined Command Hooks
17228 @cindex command hooks
17229 @cindex hooks, for commands
17230 @cindex hooks, pre-command
17233 You may define @dfn{hooks}, which are a special kind of user-defined
17234 command. Whenever you run the command @samp{foo}, if the user-defined
17235 command @samp{hook-foo} exists, it is executed (with no arguments)
17236 before that command.
17238 @cindex hooks, post-command
17240 A hook may also be defined which is run after the command you executed.
17241 Whenever you run the command @samp{foo}, if the user-defined command
17242 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17243 that command. Post-execution hooks may exist simultaneously with
17244 pre-execution hooks, for the same command.
17246 It is valid for a hook to call the command which it hooks. If this
17247 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17249 @c It would be nice if hookpost could be passed a parameter indicating
17250 @c if the command it hooks executed properly or not. FIXME!
17252 @kindex stop@r{, a pseudo-command}
17253 In addition, a pseudo-command, @samp{stop} exists. Defining
17254 (@samp{hook-stop}) makes the associated commands execute every time
17255 execution stops in your program: before breakpoint commands are run,
17256 displays are printed, or the stack frame is printed.
17258 For example, to ignore @code{SIGALRM} signals while
17259 single-stepping, but treat them normally during normal execution,
17264 handle SIGALRM nopass
17268 handle SIGALRM pass
17271 define hook-continue
17272 handle SIGALRM pass
17276 As a further example, to hook at the beginning and end of the @code{echo}
17277 command, and to add extra text to the beginning and end of the message,
17285 define hookpost-echo
17289 (@value{GDBP}) echo Hello World
17290 <<<---Hello World--->>>
17295 You can define a hook for any single-word command in @value{GDBN}, but
17296 not for command aliases; you should define a hook for the basic command
17297 name, e.g.@: @code{backtrace} rather than @code{bt}.
17298 @c FIXME! So how does Joe User discover whether a command is an alias
17300 If an error occurs during the execution of your hook, execution of
17301 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17302 (before the command that you actually typed had a chance to run).
17304 If you try to define a hook which does not match any known command, you
17305 get a warning from the @code{define} command.
17307 @node Command Files
17308 @subsection Command Files
17310 @cindex command files
17311 @cindex scripting commands
17312 A command file for @value{GDBN} is a text file made of lines that are
17313 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17314 also be included. An empty line in a command file does nothing; it
17315 does not mean to repeat the last command, as it would from the
17318 You can request the execution of a command file with the @code{source}
17323 @cindex execute commands from a file
17324 @item source [@code{-v}] @var{filename}
17325 Execute the command file @var{filename}.
17328 The lines in a command file are generally executed sequentially,
17329 unless the order of execution is changed by one of the
17330 @emph{flow-control commands} described below. The commands are not
17331 printed as they are executed. An error in any command terminates
17332 execution of the command file and control is returned to the console.
17334 @value{GDBN} searches for @var{filename} in the current directory and then
17335 on the search path (specified with the @samp{directory} command).
17337 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17338 each command as it is executed. The option must be given before
17339 @var{filename}, and is interpreted as part of the filename anywhere else.
17341 Commands that would ask for confirmation if used interactively proceed
17342 without asking when used in a command file. Many @value{GDBN} commands that
17343 normally print messages to say what they are doing omit the messages
17344 when called from command files.
17346 @value{GDBN} also accepts command input from standard input. In this
17347 mode, normal output goes to standard output and error output goes to
17348 standard error. Errors in a command file supplied on standard input do
17349 not terminate execution of the command file---execution continues with
17353 gdb < cmds > log 2>&1
17356 (The syntax above will vary depending on the shell used.) This example
17357 will execute commands from the file @file{cmds}. All output and errors
17358 would be directed to @file{log}.
17360 Since commands stored on command files tend to be more general than
17361 commands typed interactively, they frequently need to deal with
17362 complicated situations, such as different or unexpected values of
17363 variables and symbols, changes in how the program being debugged is
17364 built, etc. @value{GDBN} provides a set of flow-control commands to
17365 deal with these complexities. Using these commands, you can write
17366 complex scripts that loop over data structures, execute commands
17367 conditionally, etc.
17374 This command allows to include in your script conditionally executed
17375 commands. The @code{if} command takes a single argument, which is an
17376 expression to evaluate. It is followed by a series of commands that
17377 are executed only if the expression is true (its value is nonzero).
17378 There can then optionally be an @code{else} line, followed by a series
17379 of commands that are only executed if the expression was false. The
17380 end of the list is marked by a line containing @code{end}.
17384 This command allows to write loops. Its syntax is similar to
17385 @code{if}: the command takes a single argument, which is an expression
17386 to evaluate, and must be followed by the commands to execute, one per
17387 line, terminated by an @code{end}. These commands are called the
17388 @dfn{body} of the loop. The commands in the body of @code{while} are
17389 executed repeatedly as long as the expression evaluates to true.
17393 This command exits the @code{while} loop in whose body it is included.
17394 Execution of the script continues after that @code{while}s @code{end}
17397 @kindex loop_continue
17398 @item loop_continue
17399 This command skips the execution of the rest of the body of commands
17400 in the @code{while} loop in whose body it is included. Execution
17401 branches to the beginning of the @code{while} loop, where it evaluates
17402 the controlling expression.
17404 @kindex end@r{ (if/else/while commands)}
17406 Terminate the block of commands that are the body of @code{if},
17407 @code{else}, or @code{while} flow-control commands.
17412 @subsection Commands for Controlled Output
17414 During the execution of a command file or a user-defined command, normal
17415 @value{GDBN} output is suppressed; the only output that appears is what is
17416 explicitly printed by the commands in the definition. This section
17417 describes three commands useful for generating exactly the output you
17422 @item echo @var{text}
17423 @c I do not consider backslash-space a standard C escape sequence
17424 @c because it is not in ANSI.
17425 Print @var{text}. Nonprinting characters can be included in
17426 @var{text} using C escape sequences, such as @samp{\n} to print a
17427 newline. @strong{No newline is printed unless you specify one.}
17428 In addition to the standard C escape sequences, a backslash followed
17429 by a space stands for a space. This is useful for displaying a
17430 string with spaces at the beginning or the end, since leading and
17431 trailing spaces are otherwise trimmed from all arguments.
17432 To print @samp{@w{ }and foo =@w{ }}, use the command
17433 @samp{echo \@w{ }and foo = \@w{ }}.
17435 A backslash at the end of @var{text} can be used, as in C, to continue
17436 the command onto subsequent lines. For example,
17439 echo This is some text\n\
17440 which is continued\n\
17441 onto several lines.\n
17444 produces the same output as
17447 echo This is some text\n
17448 echo which is continued\n
17449 echo onto several lines.\n
17453 @item output @var{expression}
17454 Print the value of @var{expression} and nothing but that value: no
17455 newlines, no @samp{$@var{nn} = }. The value is not entered in the
17456 value history either. @xref{Expressions, ,Expressions}, for more information
17459 @item output/@var{fmt} @var{expression}
17460 Print the value of @var{expression} in format @var{fmt}. You can use
17461 the same formats as for @code{print}. @xref{Output Formats,,Output
17462 Formats}, for more information.
17465 @item printf @var{template}, @var{expressions}@dots{}
17466 Print the values of one or more @var{expressions} under the control of
17467 the string @var{template}. To print several values, make
17468 @var{expressions} be a comma-separated list of individual expressions,
17469 which may be either numbers or pointers. Their values are printed as
17470 specified by @var{template}, exactly as a C program would do by
17471 executing the code below:
17474 printf (@var{template}, @var{expressions}@dots{});
17477 As in @code{C} @code{printf}, ordinary characters in @var{template}
17478 are printed verbatim, while @dfn{conversion specification} introduced
17479 by the @samp{%} character cause subsequent @var{expressions} to be
17480 evaluated, their values converted and formatted according to type and
17481 style information encoded in the conversion specifications, and then
17484 For example, you can print two values in hex like this:
17487 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
17490 @code{printf} supports all the standard @code{C} conversion
17491 specifications, including the flags and modifiers between the @samp{%}
17492 character and the conversion letter, with the following exceptions:
17496 The argument-ordering modifiers, such as @samp{2$}, are not supported.
17499 The modifier @samp{*} is not supported for specifying precision or
17503 The @samp{'} flag (for separation of digits into groups according to
17504 @code{LC_NUMERIC'}) is not supported.
17507 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
17511 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
17514 The conversion letters @samp{a} and @samp{A} are not supported.
17518 Note that the @samp{ll} type modifier is supported only if the
17519 underlying @code{C} implementation used to build @value{GDBN} supports
17520 the @code{long long int} type, and the @samp{L} type modifier is
17521 supported only if @code{long double} type is available.
17523 As in @code{C}, @code{printf} supports simple backslash-escape
17524 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
17525 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
17526 single character. Octal and hexadecimal escape sequences are not
17529 Additionally, @code{printf} supports conversion specifications for DFP
17530 (@dfn{Decimal Floating Point}) types using the following length modifiers
17531 together with a floating point specifier.
17536 @samp{H} for printing @code{Decimal32} types.
17539 @samp{D} for printing @code{Decimal64} types.
17542 @samp{DD} for printing @code{Decimal128} types.
17545 If the underlying @code{C} implementation used to build @value{GDBN} has
17546 support for the three length modifiers for DFP types, other modifiers
17547 such as width and precision will also be available for @value{GDBN} to use.
17549 In case there is no such @code{C} support, no additional modifiers will be
17550 available and the value will be printed in the standard way.
17552 Here's an example of printing DFP types using the above conversion letters:
17554 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
17560 @section Scripting @value{GDBN} using Python
17561 @cindex python scripting
17562 @cindex scripting with python
17564 You can script @value{GDBN} using the @uref{http://www.python.org/,
17565 Python programming language}. This feature is available only if
17566 @value{GDBN} was configured using @option{--with-python}.
17569 * Python Commands:: Accessing Python from @value{GDBN}.
17570 * Python API:: Accessing @value{GDBN} from Python.
17573 @node Python Commands
17574 @subsection Python Commands
17575 @cindex python commands
17576 @cindex commands to access python
17578 @value{GDBN} provides one command for accessing the Python interpreter,
17579 and one related setting:
17583 @item python @r{[}@var{code}@r{]}
17584 The @code{python} command can be used to evaluate Python code.
17586 If given an argument, the @code{python} command will evaluate the
17587 argument as a Python command. For example:
17590 (@value{GDBP}) python print 23
17594 If you do not provide an argument to @code{python}, it will act as a
17595 multi-line command, like @code{define}. In this case, the Python
17596 script is made up of subsequent command lines, given after the
17597 @code{python} command. This command list is terminated using a line
17598 containing @code{end}. For example:
17601 (@value{GDBP}) python
17603 End with a line saying just "end".
17609 @kindex maint set python print-stack
17610 @item maint set python print-stack
17611 By default, @value{GDBN} will print a stack trace when an error occurs
17612 in a Python script. This can be controlled using @code{maint set
17613 python print-stack}: if @code{on}, the default, then Python stack
17614 printing is enabled; if @code{off}, then Python stack printing is
17619 @subsection Python API
17621 @cindex programming in python
17623 @cindex python stdout
17624 @cindex python pagination
17625 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
17626 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
17627 A Python program which outputs to one of these streams may have its
17628 output interrupted by the user (@pxref{Screen Size}). In this
17629 situation, a Python @code{KeyboardInterrupt} exception is thrown.
17632 * Basic Python:: Basic Python Functions.
17633 * Exception Handling::
17637 @subsubsection Basic Python
17639 @cindex python functions
17640 @cindex python module
17642 @value{GDBN} introduces a new Python module, named @code{gdb}. All
17643 methods and classes added by @value{GDBN} are placed in this module.
17644 @value{GDBN} automatically @code{import}s the @code{gdb} module for
17645 use in all scripts evaluated by the @code{python} command.
17647 @findex gdb.execute
17648 @defun execute command
17649 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
17650 If a GDB exception happens while @var{command} runs, it is
17651 translated as described in @ref{Exception Handling,,Exception Handling}.
17652 If no exceptions occur, this function returns @code{None}.
17655 @findex gdb.get_parameter
17656 @defun get_parameter parameter
17657 Return the value of a @value{GDBN} parameter. @var{parameter} is a
17658 string naming the parameter to look up; @var{parameter} may contain
17659 spaces if the parameter has a multi-part name. For example,
17660 @samp{print object} is a valid parameter name.
17662 If the named parameter does not exist, this function throws a
17663 @code{RuntimeError}. Otherwise, the parameter's value is converted to
17664 a Python value of the appropriate type, and returned.
17668 @defun write string
17669 Print a string to @value{GDBN}'s paginated standard output stream.
17670 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
17671 call this function.
17676 Flush @value{GDBN}'s paginated standard output stream. Flushing
17677 @code{sys.stdout} or @code{sys.stderr} will automatically call this
17681 @node Exception Handling
17682 @subsubsection Exception Handling
17683 @cindex python exceptions
17684 @cindex exceptions, python
17686 When executing the @code{python} command, Python exceptions
17687 uncaught within the Python code are translated to calls to
17688 @value{GDBN} error-reporting mechanism. If the command that called
17689 @code{python} does not handle the error, @value{GDBN} will
17690 terminate it and print an error message containing the Python
17691 exception name, the associated value, and the Python call stack
17692 backtrace at the point where the exception was raised. Example:
17695 (@value{GDBP}) python print foo
17696 Traceback (most recent call last):
17697 File "<string>", line 1, in <module>
17698 NameError: name 'foo' is not defined
17701 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
17702 code are converted to Python @code{RuntimeError} exceptions. User
17703 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
17704 prompt) is translated to a Python @code{KeyboardInterrupt}
17705 exception. If you catch these exceptions in your Python code, your
17706 exception handler will see @code{RuntimeError} or
17707 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
17708 message as its value, and the Python call stack backtrace at the
17709 Python statement closest to where the @value{GDBN} error occured as the
17713 @chapter Command Interpreters
17714 @cindex command interpreters
17716 @value{GDBN} supports multiple command interpreters, and some command
17717 infrastructure to allow users or user interface writers to switch
17718 between interpreters or run commands in other interpreters.
17720 @value{GDBN} currently supports two command interpreters, the console
17721 interpreter (sometimes called the command-line interpreter or @sc{cli})
17722 and the machine interface interpreter (or @sc{gdb/mi}). This manual
17723 describes both of these interfaces in great detail.
17725 By default, @value{GDBN} will start with the console interpreter.
17726 However, the user may choose to start @value{GDBN} with another
17727 interpreter by specifying the @option{-i} or @option{--interpreter}
17728 startup options. Defined interpreters include:
17732 @cindex console interpreter
17733 The traditional console or command-line interpreter. This is the most often
17734 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
17735 @value{GDBN} will use this interpreter.
17738 @cindex mi interpreter
17739 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
17740 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
17741 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
17745 @cindex mi2 interpreter
17746 The current @sc{gdb/mi} interface.
17749 @cindex mi1 interpreter
17750 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
17754 @cindex invoke another interpreter
17755 The interpreter being used by @value{GDBN} may not be dynamically
17756 switched at runtime. Although possible, this could lead to a very
17757 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
17758 enters the command "interpreter-set console" in a console view,
17759 @value{GDBN} would switch to using the console interpreter, rendering
17760 the IDE inoperable!
17762 @kindex interpreter-exec
17763 Although you may only choose a single interpreter at startup, you may execute
17764 commands in any interpreter from the current interpreter using the appropriate
17765 command. If you are running the console interpreter, simply use the
17766 @code{interpreter-exec} command:
17769 interpreter-exec mi "-data-list-register-names"
17772 @sc{gdb/mi} has a similar command, although it is only available in versions of
17773 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
17776 @chapter @value{GDBN} Text User Interface
17778 @cindex Text User Interface
17781 * TUI Overview:: TUI overview
17782 * TUI Keys:: TUI key bindings
17783 * TUI Single Key Mode:: TUI single key mode
17784 * TUI Commands:: TUI-specific commands
17785 * TUI Configuration:: TUI configuration variables
17788 The @value{GDBN} Text User Interface (TUI) is a terminal
17789 interface which uses the @code{curses} library to show the source
17790 file, the assembly output, the program registers and @value{GDBN}
17791 commands in separate text windows. The TUI mode is supported only
17792 on platforms where a suitable version of the @code{curses} library
17795 @pindex @value{GDBTUI}
17796 The TUI mode is enabled by default when you invoke @value{GDBN} as
17797 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
17798 You can also switch in and out of TUI mode while @value{GDBN} runs by
17799 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
17800 @xref{TUI Keys, ,TUI Key Bindings}.
17803 @section TUI Overview
17805 In TUI mode, @value{GDBN} can display several text windows:
17809 This window is the @value{GDBN} command window with the @value{GDBN}
17810 prompt and the @value{GDBN} output. The @value{GDBN} input is still
17811 managed using readline.
17814 The source window shows the source file of the program. The current
17815 line and active breakpoints are displayed in this window.
17818 The assembly window shows the disassembly output of the program.
17821 This window shows the processor registers. Registers are highlighted
17822 when their values change.
17825 The source and assembly windows show the current program position
17826 by highlighting the current line and marking it with a @samp{>} marker.
17827 Breakpoints are indicated with two markers. The first marker
17828 indicates the breakpoint type:
17832 Breakpoint which was hit at least once.
17835 Breakpoint which was never hit.
17838 Hardware breakpoint which was hit at least once.
17841 Hardware breakpoint which was never hit.
17844 The second marker indicates whether the breakpoint is enabled or not:
17848 Breakpoint is enabled.
17851 Breakpoint is disabled.
17854 The source, assembly and register windows are updated when the current
17855 thread changes, when the frame changes, or when the program counter
17858 These windows are not all visible at the same time. The command
17859 window is always visible. The others can be arranged in several
17870 source and assembly,
17873 source and registers, or
17876 assembly and registers.
17879 A status line above the command window shows the following information:
17883 Indicates the current @value{GDBN} target.
17884 (@pxref{Targets, ,Specifying a Debugging Target}).
17887 Gives the current process or thread number.
17888 When no process is being debugged, this field is set to @code{No process}.
17891 Gives the current function name for the selected frame.
17892 The name is demangled if demangling is turned on (@pxref{Print Settings}).
17893 When there is no symbol corresponding to the current program counter,
17894 the string @code{??} is displayed.
17897 Indicates the current line number for the selected frame.
17898 When the current line number is not known, the string @code{??} is displayed.
17901 Indicates the current program counter address.
17905 @section TUI Key Bindings
17906 @cindex TUI key bindings
17908 The TUI installs several key bindings in the readline keymaps
17909 (@pxref{Command Line Editing}). The following key bindings
17910 are installed for both TUI mode and the @value{GDBN} standard mode.
17919 Enter or leave the TUI mode. When leaving the TUI mode,
17920 the curses window management stops and @value{GDBN} operates using
17921 its standard mode, writing on the terminal directly. When reentering
17922 the TUI mode, control is given back to the curses windows.
17923 The screen is then refreshed.
17927 Use a TUI layout with only one window. The layout will
17928 either be @samp{source} or @samp{assembly}. When the TUI mode
17929 is not active, it will switch to the TUI mode.
17931 Think of this key binding as the Emacs @kbd{C-x 1} binding.
17935 Use a TUI layout with at least two windows. When the current
17936 layout already has two windows, the next layout with two windows is used.
17937 When a new layout is chosen, one window will always be common to the
17938 previous layout and the new one.
17940 Think of it as the Emacs @kbd{C-x 2} binding.
17944 Change the active window. The TUI associates several key bindings
17945 (like scrolling and arrow keys) with the active window. This command
17946 gives the focus to the next TUI window.
17948 Think of it as the Emacs @kbd{C-x o} binding.
17952 Switch in and out of the TUI SingleKey mode that binds single
17953 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
17956 The following key bindings only work in the TUI mode:
17961 Scroll the active window one page up.
17965 Scroll the active window one page down.
17969 Scroll the active window one line up.
17973 Scroll the active window one line down.
17977 Scroll the active window one column left.
17981 Scroll the active window one column right.
17985 Refresh the screen.
17988 Because the arrow keys scroll the active window in the TUI mode, they
17989 are not available for their normal use by readline unless the command
17990 window has the focus. When another window is active, you must use
17991 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
17992 and @kbd{C-f} to control the command window.
17994 @node TUI Single Key Mode
17995 @section TUI Single Key Mode
17996 @cindex TUI single key mode
17998 The TUI also provides a @dfn{SingleKey} mode, which binds several
17999 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
18000 switch into this mode, where the following key bindings are used:
18003 @kindex c @r{(SingleKey TUI key)}
18007 @kindex d @r{(SingleKey TUI key)}
18011 @kindex f @r{(SingleKey TUI key)}
18015 @kindex n @r{(SingleKey TUI key)}
18019 @kindex q @r{(SingleKey TUI key)}
18021 exit the SingleKey mode.
18023 @kindex r @r{(SingleKey TUI key)}
18027 @kindex s @r{(SingleKey TUI key)}
18031 @kindex u @r{(SingleKey TUI key)}
18035 @kindex v @r{(SingleKey TUI key)}
18039 @kindex w @r{(SingleKey TUI key)}
18044 Other keys temporarily switch to the @value{GDBN} command prompt.
18045 The key that was pressed is inserted in the editing buffer so that
18046 it is possible to type most @value{GDBN} commands without interaction
18047 with the TUI SingleKey mode. Once the command is entered the TUI
18048 SingleKey mode is restored. The only way to permanently leave
18049 this mode is by typing @kbd{q} or @kbd{C-x s}.
18053 @section TUI-specific Commands
18054 @cindex TUI commands
18056 The TUI has specific commands to control the text windows.
18057 These commands are always available, even when @value{GDBN} is not in
18058 the TUI mode. When @value{GDBN} is in the standard mode, most
18059 of these commands will automatically switch to the TUI mode.
18064 List and give the size of all displayed windows.
18068 Display the next layout.
18071 Display the previous layout.
18074 Display the source window only.
18077 Display the assembly window only.
18080 Display the source and assembly window.
18083 Display the register window together with the source or assembly window.
18087 Make the next window active for scrolling.
18090 Make the previous window active for scrolling.
18093 Make the source window active for scrolling.
18096 Make the assembly window active for scrolling.
18099 Make the register window active for scrolling.
18102 Make the command window active for scrolling.
18106 Refresh the screen. This is similar to typing @kbd{C-L}.
18108 @item tui reg float
18110 Show the floating point registers in the register window.
18112 @item tui reg general
18113 Show the general registers in the register window.
18116 Show the next register group. The list of register groups as well as
18117 their order is target specific. The predefined register groups are the
18118 following: @code{general}, @code{float}, @code{system}, @code{vector},
18119 @code{all}, @code{save}, @code{restore}.
18121 @item tui reg system
18122 Show the system registers in the register window.
18126 Update the source window and the current execution point.
18128 @item winheight @var{name} +@var{count}
18129 @itemx winheight @var{name} -@var{count}
18131 Change the height of the window @var{name} by @var{count}
18132 lines. Positive counts increase the height, while negative counts
18135 @item tabset @var{nchars}
18137 Set the width of tab stops to be @var{nchars} characters.
18140 @node TUI Configuration
18141 @section TUI Configuration Variables
18142 @cindex TUI configuration variables
18144 Several configuration variables control the appearance of TUI windows.
18147 @item set tui border-kind @var{kind}
18148 @kindex set tui border-kind
18149 Select the border appearance for the source, assembly and register windows.
18150 The possible values are the following:
18153 Use a space character to draw the border.
18156 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
18159 Use the Alternate Character Set to draw the border. The border is
18160 drawn using character line graphics if the terminal supports them.
18163 @item set tui border-mode @var{mode}
18164 @kindex set tui border-mode
18165 @itemx set tui active-border-mode @var{mode}
18166 @kindex set tui active-border-mode
18167 Select the display attributes for the borders of the inactive windows
18168 or the active window. The @var{mode} can be one of the following:
18171 Use normal attributes to display the border.
18177 Use reverse video mode.
18180 Use half bright mode.
18182 @item half-standout
18183 Use half bright and standout mode.
18186 Use extra bright or bold mode.
18188 @item bold-standout
18189 Use extra bright or bold and standout mode.
18194 @chapter Using @value{GDBN} under @sc{gnu} Emacs
18197 @cindex @sc{gnu} Emacs
18198 A special interface allows you to use @sc{gnu} Emacs to view (and
18199 edit) the source files for the program you are debugging with
18202 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
18203 executable file you want to debug as an argument. This command starts
18204 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
18205 created Emacs buffer.
18206 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
18208 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
18213 All ``terminal'' input and output goes through an Emacs buffer, called
18216 This applies both to @value{GDBN} commands and their output, and to the input
18217 and output done by the program you are debugging.
18219 This is useful because it means that you can copy the text of previous
18220 commands and input them again; you can even use parts of the output
18223 All the facilities of Emacs' Shell mode are available for interacting
18224 with your program. In particular, you can send signals the usual
18225 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
18229 @value{GDBN} displays source code through Emacs.
18231 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
18232 source file for that frame and puts an arrow (@samp{=>}) at the
18233 left margin of the current line. Emacs uses a separate buffer for
18234 source display, and splits the screen to show both your @value{GDBN} session
18237 Explicit @value{GDBN} @code{list} or search commands still produce output as
18238 usual, but you probably have no reason to use them from Emacs.
18241 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
18242 a graphical mode, enabled by default, which provides further buffers
18243 that can control the execution and describe the state of your program.
18244 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
18246 If you specify an absolute file name when prompted for the @kbd{M-x
18247 gdb} argument, then Emacs sets your current working directory to where
18248 your program resides. If you only specify the file name, then Emacs
18249 sets your current working directory to to the directory associated
18250 with the previous buffer. In this case, @value{GDBN} may find your
18251 program by searching your environment's @code{PATH} variable, but on
18252 some operating systems it might not find the source. So, although the
18253 @value{GDBN} input and output session proceeds normally, the auxiliary
18254 buffer does not display the current source and line of execution.
18256 The initial working directory of @value{GDBN} is printed on the top
18257 line of the GUD buffer and this serves as a default for the commands
18258 that specify files for @value{GDBN} to operate on. @xref{Files,
18259 ,Commands to Specify Files}.
18261 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
18262 need to call @value{GDBN} by a different name (for example, if you
18263 keep several configurations around, with different names) you can
18264 customize the Emacs variable @code{gud-gdb-command-name} to run the
18267 In the GUD buffer, you can use these special Emacs commands in
18268 addition to the standard Shell mode commands:
18272 Describe the features of Emacs' GUD Mode.
18275 Execute to another source line, like the @value{GDBN} @code{step} command; also
18276 update the display window to show the current file and location.
18279 Execute to next source line in this function, skipping all function
18280 calls, like the @value{GDBN} @code{next} command. Then update the display window
18281 to show the current file and location.
18284 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
18285 display window accordingly.
18288 Execute until exit from the selected stack frame, like the @value{GDBN}
18289 @code{finish} command.
18292 Continue execution of your program, like the @value{GDBN} @code{continue}
18296 Go up the number of frames indicated by the numeric argument
18297 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
18298 like the @value{GDBN} @code{up} command.
18301 Go down the number of frames indicated by the numeric argument, like the
18302 @value{GDBN} @code{down} command.
18305 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
18306 tells @value{GDBN} to set a breakpoint on the source line point is on.
18308 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
18309 separate frame which shows a backtrace when the GUD buffer is current.
18310 Move point to any frame in the stack and type @key{RET} to make it
18311 become the current frame and display the associated source in the
18312 source buffer. Alternatively, click @kbd{Mouse-2} to make the
18313 selected frame become the current one. In graphical mode, the
18314 speedbar displays watch expressions.
18316 If you accidentally delete the source-display buffer, an easy way to get
18317 it back is to type the command @code{f} in the @value{GDBN} buffer, to
18318 request a frame display; when you run under Emacs, this recreates
18319 the source buffer if necessary to show you the context of the current
18322 The source files displayed in Emacs are in ordinary Emacs buffers
18323 which are visiting the source files in the usual way. You can edit
18324 the files with these buffers if you wish; but keep in mind that @value{GDBN}
18325 communicates with Emacs in terms of line numbers. If you add or
18326 delete lines from the text, the line numbers that @value{GDBN} knows cease
18327 to correspond properly with the code.
18329 A more detailed description of Emacs' interaction with @value{GDBN} is
18330 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
18333 @c The following dropped because Epoch is nonstandard. Reactivate
18334 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
18336 @kindex Emacs Epoch environment
18340 Version 18 of @sc{gnu} Emacs has a built-in window system
18341 called the @code{epoch}
18342 environment. Users of this environment can use a new command,
18343 @code{inspect} which performs identically to @code{print} except that
18344 each value is printed in its own window.
18349 @chapter The @sc{gdb/mi} Interface
18351 @unnumberedsec Function and Purpose
18353 @cindex @sc{gdb/mi}, its purpose
18354 @sc{gdb/mi} is a line based machine oriented text interface to
18355 @value{GDBN} and is activated by specifying using the
18356 @option{--interpreter} command line option (@pxref{Mode Options}). It
18357 is specifically intended to support the development of systems which
18358 use the debugger as just one small component of a larger system.
18360 This chapter is a specification of the @sc{gdb/mi} interface. It is written
18361 in the form of a reference manual.
18363 Note that @sc{gdb/mi} is still under construction, so some of the
18364 features described below are incomplete and subject to change
18365 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
18367 @unnumberedsec Notation and Terminology
18369 @cindex notational conventions, for @sc{gdb/mi}
18370 This chapter uses the following notation:
18374 @code{|} separates two alternatives.
18377 @code{[ @var{something} ]} indicates that @var{something} is optional:
18378 it may or may not be given.
18381 @code{( @var{group} )*} means that @var{group} inside the parentheses
18382 may repeat zero or more times.
18385 @code{( @var{group} )+} means that @var{group} inside the parentheses
18386 may repeat one or more times.
18389 @code{"@var{string}"} means a literal @var{string}.
18393 @heading Dependencies
18397 * GDB/MI Command Syntax::
18398 * GDB/MI Compatibility with CLI::
18399 * GDB/MI Development and Front Ends::
18400 * GDB/MI Output Records::
18401 * GDB/MI Simple Examples::
18402 * GDB/MI Command Description Format::
18403 * GDB/MI Breakpoint Commands::
18404 * GDB/MI Program Context::
18405 * GDB/MI Thread Commands::
18406 * GDB/MI Program Execution::
18407 * GDB/MI Stack Manipulation::
18408 * GDB/MI Variable Objects::
18409 * GDB/MI Data Manipulation::
18410 * GDB/MI Tracepoint Commands::
18411 * GDB/MI Symbol Query::
18412 * GDB/MI File Commands::
18414 * GDB/MI Kod Commands::
18415 * GDB/MI Memory Overlay Commands::
18416 * GDB/MI Signal Handling Commands::
18418 * GDB/MI Target Manipulation::
18419 * GDB/MI File Transfer Commands::
18420 * GDB/MI Miscellaneous Commands::
18423 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18424 @node GDB/MI Command Syntax
18425 @section @sc{gdb/mi} Command Syntax
18428 * GDB/MI Input Syntax::
18429 * GDB/MI Output Syntax::
18432 @node GDB/MI Input Syntax
18433 @subsection @sc{gdb/mi} Input Syntax
18435 @cindex input syntax for @sc{gdb/mi}
18436 @cindex @sc{gdb/mi}, input syntax
18438 @item @var{command} @expansion{}
18439 @code{@var{cli-command} | @var{mi-command}}
18441 @item @var{cli-command} @expansion{}
18442 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
18443 @var{cli-command} is any existing @value{GDBN} CLI command.
18445 @item @var{mi-command} @expansion{}
18446 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
18447 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
18449 @item @var{token} @expansion{}
18450 "any sequence of digits"
18452 @item @var{option} @expansion{}
18453 @code{"-" @var{parameter} [ " " @var{parameter} ]}
18455 @item @var{parameter} @expansion{}
18456 @code{@var{non-blank-sequence} | @var{c-string}}
18458 @item @var{operation} @expansion{}
18459 @emph{any of the operations described in this chapter}
18461 @item @var{non-blank-sequence} @expansion{}
18462 @emph{anything, provided it doesn't contain special characters such as
18463 "-", @var{nl}, """ and of course " "}
18465 @item @var{c-string} @expansion{}
18466 @code{""" @var{seven-bit-iso-c-string-content} """}
18468 @item @var{nl} @expansion{}
18477 The CLI commands are still handled by the @sc{mi} interpreter; their
18478 output is described below.
18481 The @code{@var{token}}, when present, is passed back when the command
18485 Some @sc{mi} commands accept optional arguments as part of the parameter
18486 list. Each option is identified by a leading @samp{-} (dash) and may be
18487 followed by an optional argument parameter. Options occur first in the
18488 parameter list and can be delimited from normal parameters using
18489 @samp{--} (this is useful when some parameters begin with a dash).
18496 We want easy access to the existing CLI syntax (for debugging).
18499 We want it to be easy to spot a @sc{mi} operation.
18502 @node GDB/MI Output Syntax
18503 @subsection @sc{gdb/mi} Output Syntax
18505 @cindex output syntax of @sc{gdb/mi}
18506 @cindex @sc{gdb/mi}, output syntax
18507 The output from @sc{gdb/mi} consists of zero or more out-of-band records
18508 followed, optionally, by a single result record. This result record
18509 is for the most recent command. The sequence of output records is
18510 terminated by @samp{(gdb)}.
18512 If an input command was prefixed with a @code{@var{token}} then the
18513 corresponding output for that command will also be prefixed by that same
18517 @item @var{output} @expansion{}
18518 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
18520 @item @var{result-record} @expansion{}
18521 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
18523 @item @var{out-of-band-record} @expansion{}
18524 @code{@var{async-record} | @var{stream-record}}
18526 @item @var{async-record} @expansion{}
18527 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
18529 @item @var{exec-async-output} @expansion{}
18530 @code{[ @var{token} ] "*" @var{async-output}}
18532 @item @var{status-async-output} @expansion{}
18533 @code{[ @var{token} ] "+" @var{async-output}}
18535 @item @var{notify-async-output} @expansion{}
18536 @code{[ @var{token} ] "=" @var{async-output}}
18538 @item @var{async-output} @expansion{}
18539 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
18541 @item @var{result-class} @expansion{}
18542 @code{"done" | "running" | "connected" | "error" | "exit"}
18544 @item @var{async-class} @expansion{}
18545 @code{"stopped" | @var{others}} (where @var{others} will be added
18546 depending on the needs---this is still in development).
18548 @item @var{result} @expansion{}
18549 @code{ @var{variable} "=" @var{value}}
18551 @item @var{variable} @expansion{}
18552 @code{ @var{string} }
18554 @item @var{value} @expansion{}
18555 @code{ @var{const} | @var{tuple} | @var{list} }
18557 @item @var{const} @expansion{}
18558 @code{@var{c-string}}
18560 @item @var{tuple} @expansion{}
18561 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
18563 @item @var{list} @expansion{}
18564 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
18565 @var{result} ( "," @var{result} )* "]" }
18567 @item @var{stream-record} @expansion{}
18568 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
18570 @item @var{console-stream-output} @expansion{}
18571 @code{"~" @var{c-string}}
18573 @item @var{target-stream-output} @expansion{}
18574 @code{"@@" @var{c-string}}
18576 @item @var{log-stream-output} @expansion{}
18577 @code{"&" @var{c-string}}
18579 @item @var{nl} @expansion{}
18582 @item @var{token} @expansion{}
18583 @emph{any sequence of digits}.
18591 All output sequences end in a single line containing a period.
18594 The @code{@var{token}} is from the corresponding request. Note that
18595 for all async output, while the token is allowed by the grammar and
18596 may be output by future versions of @value{GDBN} for select async
18597 output messages, it is generally omitted. Frontends should treat
18598 all async output as reporting general changes in the state of the
18599 target and there should be no need to associate async output to any
18603 @cindex status output in @sc{gdb/mi}
18604 @var{status-async-output} contains on-going status information about the
18605 progress of a slow operation. It can be discarded. All status output is
18606 prefixed by @samp{+}.
18609 @cindex async output in @sc{gdb/mi}
18610 @var{exec-async-output} contains asynchronous state change on the target
18611 (stopped, started, disappeared). All async output is prefixed by
18615 @cindex notify output in @sc{gdb/mi}
18616 @var{notify-async-output} contains supplementary information that the
18617 client should handle (e.g., a new breakpoint information). All notify
18618 output is prefixed by @samp{=}.
18621 @cindex console output in @sc{gdb/mi}
18622 @var{console-stream-output} is output that should be displayed as is in the
18623 console. It is the textual response to a CLI command. All the console
18624 output is prefixed by @samp{~}.
18627 @cindex target output in @sc{gdb/mi}
18628 @var{target-stream-output} is the output produced by the target program.
18629 All the target output is prefixed by @samp{@@}.
18632 @cindex log output in @sc{gdb/mi}
18633 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
18634 instance messages that should be displayed as part of an error log. All
18635 the log output is prefixed by @samp{&}.
18638 @cindex list output in @sc{gdb/mi}
18639 New @sc{gdb/mi} commands should only output @var{lists} containing
18645 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
18646 details about the various output records.
18648 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18649 @node GDB/MI Compatibility with CLI
18650 @section @sc{gdb/mi} Compatibility with CLI
18652 @cindex compatibility, @sc{gdb/mi} and CLI
18653 @cindex @sc{gdb/mi}, compatibility with CLI
18655 For the developers convenience CLI commands can be entered directly,
18656 but there may be some unexpected behaviour. For example, commands
18657 that query the user will behave as if the user replied yes, breakpoint
18658 command lists are not executed and some CLI commands, such as
18659 @code{if}, @code{when} and @code{define}, prompt for further input with
18660 @samp{>}, which is not valid MI output.
18662 This feature may be removed at some stage in the future and it is
18663 recommended that front ends use the @code{-interpreter-exec} command
18664 (@pxref{-interpreter-exec}).
18666 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18667 @node GDB/MI Development and Front Ends
18668 @section @sc{gdb/mi} Development and Front Ends
18669 @cindex @sc{gdb/mi} development
18671 The application which takes the MI output and presents the state of the
18672 program being debugged to the user is called a @dfn{front end}.
18674 Although @sc{gdb/mi} is still incomplete, it is currently being used
18675 by a variety of front ends to @value{GDBN}. This makes it difficult
18676 to introduce new functionality without breaking existing usage. This
18677 section tries to minimize the problems by describing how the protocol
18680 Some changes in MI need not break a carefully designed front end, and
18681 for these the MI version will remain unchanged. The following is a
18682 list of changes that may occur within one level, so front ends should
18683 parse MI output in a way that can handle them:
18687 New MI commands may be added.
18690 New fields may be added to the output of any MI command.
18693 The range of values for fields with specified values, e.g.,
18694 @code{in_scope} (@pxref{-var-update}) may be extended.
18696 @c The format of field's content e.g type prefix, may change so parse it
18697 @c at your own risk. Yes, in general?
18699 @c The order of fields may change? Shouldn't really matter but it might
18700 @c resolve inconsistencies.
18703 If the changes are likely to break front ends, the MI version level
18704 will be increased by one. This will allow the front end to parse the
18705 output according to the MI version. Apart from mi0, new versions of
18706 @value{GDBN} will not support old versions of MI and it will be the
18707 responsibility of the front end to work with the new one.
18709 @c Starting with mi3, add a new command -mi-version that prints the MI
18712 The best way to avoid unexpected changes in MI that might break your front
18713 end is to make your project known to @value{GDBN} developers and
18714 follow development on @email{gdb@@sourceware.org} and
18715 @email{gdb-patches@@sourceware.org}.
18716 @cindex mailing lists
18718 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18719 @node GDB/MI Output Records
18720 @section @sc{gdb/mi} Output Records
18723 * GDB/MI Result Records::
18724 * GDB/MI Stream Records::
18725 * GDB/MI Async Records::
18728 @node GDB/MI Result Records
18729 @subsection @sc{gdb/mi} Result Records
18731 @cindex result records in @sc{gdb/mi}
18732 @cindex @sc{gdb/mi}, result records
18733 In addition to a number of out-of-band notifications, the response to a
18734 @sc{gdb/mi} command includes one of the following result indications:
18738 @item "^done" [ "," @var{results} ]
18739 The synchronous operation was successful, @code{@var{results}} are the return
18744 @c Is this one correct? Should it be an out-of-band notification?
18745 The asynchronous operation was successfully started. The target is
18750 @value{GDBN} has connected to a remote target.
18752 @item "^error" "," @var{c-string}
18754 The operation failed. The @code{@var{c-string}} contains the corresponding
18759 @value{GDBN} has terminated.
18763 @node GDB/MI Stream Records
18764 @subsection @sc{gdb/mi} Stream Records
18766 @cindex @sc{gdb/mi}, stream records
18767 @cindex stream records in @sc{gdb/mi}
18768 @value{GDBN} internally maintains a number of output streams: the console, the
18769 target, and the log. The output intended for each of these streams is
18770 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
18772 Each stream record begins with a unique @dfn{prefix character} which
18773 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
18774 Syntax}). In addition to the prefix, each stream record contains a
18775 @code{@var{string-output}}. This is either raw text (with an implicit new
18776 line) or a quoted C string (which does not contain an implicit newline).
18779 @item "~" @var{string-output}
18780 The console output stream contains text that should be displayed in the
18781 CLI console window. It contains the textual responses to CLI commands.
18783 @item "@@" @var{string-output}
18784 The target output stream contains any textual output from the running
18785 target. This is only present when GDB's event loop is truly
18786 asynchronous, which is currently only the case for remote targets.
18788 @item "&" @var{string-output}
18789 The log stream contains debugging messages being produced by @value{GDBN}'s
18793 @node GDB/MI Async Records
18794 @subsection @sc{gdb/mi} Async Records
18796 @cindex async records in @sc{gdb/mi}
18797 @cindex @sc{gdb/mi}, async records
18798 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
18799 additional changes that have occurred. Those changes can either be a
18800 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
18801 target activity (e.g., target stopped).
18803 The following is the list of possible async records:
18807 @item *running,thread-id="@var{thread}"
18808 The target is now running. The @var{thread} field tells which
18809 specific thread is now running, and can be @samp{all} if all threads
18810 are running. The frontend should assume that no interaction with a
18811 running thread is possible after this notification is produced.
18812 The frontend should not assume that this notification is output
18813 only once for any command. @value{GDBN} may emit this notification
18814 several times, either for different threads, because it cannot resume
18815 all threads together, or even for a single thread, if the thread must
18816 be stepped though some code before letting it run freely.
18818 @item *stopped,reason="@var{reason}"
18819 The target has stopped. The @var{reason} field can have one of the
18823 @item breakpoint-hit
18824 A breakpoint was reached.
18825 @item watchpoint-trigger
18826 A watchpoint was triggered.
18827 @item read-watchpoint-trigger
18828 A read watchpoint was triggered.
18829 @item access-watchpoint-trigger
18830 An access watchpoint was triggered.
18831 @item function-finished
18832 An -exec-finish or similar CLI command was accomplished.
18833 @item location-reached
18834 An -exec-until or similar CLI command was accomplished.
18835 @item watchpoint-scope
18836 A watchpoint has gone out of scope.
18837 @item end-stepping-range
18838 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
18839 similar CLI command was accomplished.
18840 @item exited-signalled
18841 The inferior exited because of a signal.
18843 The inferior exited.
18844 @item exited-normally
18845 The inferior exited normally.
18846 @item signal-received
18847 A signal was received by the inferior.
18850 @item =thread-created,id="@var{id}"
18851 @itemx =thread-exited,id="@var{id}"
18852 A thread either was created, or has exited. The @var{id} field
18853 contains the @value{GDBN} identifier of the thread.
18858 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18859 @node GDB/MI Simple Examples
18860 @section Simple Examples of @sc{gdb/mi} Interaction
18861 @cindex @sc{gdb/mi}, simple examples
18863 This subsection presents several simple examples of interaction using
18864 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
18865 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
18866 the output received from @sc{gdb/mi}.
18868 Note the line breaks shown in the examples are here only for
18869 readability, they don't appear in the real output.
18871 @subheading Setting a Breakpoint
18873 Setting a breakpoint generates synchronous output which contains detailed
18874 information of the breakpoint.
18877 -> -break-insert main
18878 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18879 enabled="y",addr="0x08048564",func="main",file="myprog.c",
18880 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
18884 @subheading Program Execution
18886 Program execution generates asynchronous records and MI gives the
18887 reason that execution stopped.
18893 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
18894 frame=@{addr="0x08048564",func="main",
18895 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
18896 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
18901 <- *stopped,reason="exited-normally"
18905 @subheading Quitting @value{GDBN}
18907 Quitting @value{GDBN} just prints the result class @samp{^exit}.
18915 @subheading A Bad Command
18917 Here's what happens if you pass a non-existent command:
18921 <- ^error,msg="Undefined MI command: rubbish"
18926 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18927 @node GDB/MI Command Description Format
18928 @section @sc{gdb/mi} Command Description Format
18930 The remaining sections describe blocks of commands. Each block of
18931 commands is laid out in a fashion similar to this section.
18933 @subheading Motivation
18935 The motivation for this collection of commands.
18937 @subheading Introduction
18939 A brief introduction to this collection of commands as a whole.
18941 @subheading Commands
18943 For each command in the block, the following is described:
18945 @subsubheading Synopsis
18948 -command @var{args}@dots{}
18951 @subsubheading Result
18953 @subsubheading @value{GDBN} Command
18955 The corresponding @value{GDBN} CLI command(s), if any.
18957 @subsubheading Example
18959 Example(s) formatted for readability. Some of the described commands have
18960 not been implemented yet and these are labeled N.A.@: (not available).
18963 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18964 @node GDB/MI Breakpoint Commands
18965 @section @sc{gdb/mi} Breakpoint Commands
18967 @cindex breakpoint commands for @sc{gdb/mi}
18968 @cindex @sc{gdb/mi}, breakpoint commands
18969 This section documents @sc{gdb/mi} commands for manipulating
18972 @subheading The @code{-break-after} Command
18973 @findex -break-after
18975 @subsubheading Synopsis
18978 -break-after @var{number} @var{count}
18981 The breakpoint number @var{number} is not in effect until it has been
18982 hit @var{count} times. To see how this is reflected in the output of
18983 the @samp{-break-list} command, see the description of the
18984 @samp{-break-list} command below.
18986 @subsubheading @value{GDBN} Command
18988 The corresponding @value{GDBN} command is @samp{ignore}.
18990 @subsubheading Example
18995 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18996 enabled="y",addr="0x000100d0",func="main",file="hello.c",
18997 fullname="/home/foo/hello.c",line="5",times="0"@}
19004 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19005 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19006 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19007 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19008 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19009 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19010 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19011 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19012 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19013 line="5",times="0",ignore="3"@}]@}
19018 @subheading The @code{-break-catch} Command
19019 @findex -break-catch
19021 @subheading The @code{-break-commands} Command
19022 @findex -break-commands
19026 @subheading The @code{-break-condition} Command
19027 @findex -break-condition
19029 @subsubheading Synopsis
19032 -break-condition @var{number} @var{expr}
19035 Breakpoint @var{number} will stop the program only if the condition in
19036 @var{expr} is true. The condition becomes part of the
19037 @samp{-break-list} output (see the description of the @samp{-break-list}
19040 @subsubheading @value{GDBN} Command
19042 The corresponding @value{GDBN} command is @samp{condition}.
19044 @subsubheading Example
19048 -break-condition 1 1
19052 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19053 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19054 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19055 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19056 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19057 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19058 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19059 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19060 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19061 line="5",cond="1",times="0",ignore="3"@}]@}
19065 @subheading The @code{-break-delete} Command
19066 @findex -break-delete
19068 @subsubheading Synopsis
19071 -break-delete ( @var{breakpoint} )+
19074 Delete the breakpoint(s) whose number(s) are specified in the argument
19075 list. This is obviously reflected in the breakpoint list.
19077 @subsubheading @value{GDBN} Command
19079 The corresponding @value{GDBN} command is @samp{delete}.
19081 @subsubheading Example
19089 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
19090 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19091 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19092 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19093 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19094 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19095 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19100 @subheading The @code{-break-disable} Command
19101 @findex -break-disable
19103 @subsubheading Synopsis
19106 -break-disable ( @var{breakpoint} )+
19109 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
19110 break list is now set to @samp{n} for the named @var{breakpoint}(s).
19112 @subsubheading @value{GDBN} Command
19114 The corresponding @value{GDBN} command is @samp{disable}.
19116 @subsubheading Example
19124 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19125 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19126 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19127 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19128 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19129 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19130 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19131 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
19132 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19133 line="5",times="0"@}]@}
19137 @subheading The @code{-break-enable} Command
19138 @findex -break-enable
19140 @subsubheading Synopsis
19143 -break-enable ( @var{breakpoint} )+
19146 Enable (previously disabled) @var{breakpoint}(s).
19148 @subsubheading @value{GDBN} Command
19150 The corresponding @value{GDBN} command is @samp{enable}.
19152 @subsubheading Example
19160 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19161 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19162 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19163 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19164 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19165 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19166 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19167 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
19168 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19169 line="5",times="0"@}]@}
19173 @subheading The @code{-break-info} Command
19174 @findex -break-info
19176 @subsubheading Synopsis
19179 -break-info @var{breakpoint}
19183 Get information about a single breakpoint.
19185 @subsubheading @value{GDBN} Command
19187 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
19189 @subsubheading Example
19192 @subheading The @code{-break-insert} Command
19193 @findex -break-insert
19195 @subsubheading Synopsis
19198 -break-insert [ -t ] [ -h ] [ -f ]
19199 [ -c @var{condition} ] [ -i @var{ignore-count} ]
19200 [ -p @var{thread} ] [ @var{location} ]
19204 If specified, @var{location}, can be one of:
19211 @item filename:linenum
19212 @item filename:function
19216 The possible optional parameters of this command are:
19220 Insert a temporary breakpoint.
19222 Insert a hardware breakpoint.
19223 @item -c @var{condition}
19224 Make the breakpoint conditional on @var{condition}.
19225 @item -i @var{ignore-count}
19226 Initialize the @var{ignore-count}.
19228 If @var{location} cannot be parsed (for example if it
19229 refers to unknown files or functions), create a pending
19230 breakpoint. Without this flag, @value{GDBN} will report
19231 an error, and won't create a breakpoint, if @var{location}
19235 @subsubheading Result
19237 The result is in the form:
19240 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
19241 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
19242 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
19243 times="@var{times}"@}
19247 where @var{number} is the @value{GDBN} number for this breakpoint,
19248 @var{funcname} is the name of the function where the breakpoint was
19249 inserted, @var{filename} is the name of the source file which contains
19250 this function, @var{lineno} is the source line number within that file
19251 and @var{times} the number of times that the breakpoint has been hit
19252 (always 0 for -break-insert but may be greater for -break-info or -break-list
19253 which use the same output).
19255 Note: this format is open to change.
19256 @c An out-of-band breakpoint instead of part of the result?
19258 @subsubheading @value{GDBN} Command
19260 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
19261 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
19263 @subsubheading Example
19268 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
19269 fullname="/home/foo/recursive2.c,line="4",times="0"@}
19271 -break-insert -t foo
19272 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
19273 fullname="/home/foo/recursive2.c,line="11",times="0"@}
19276 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19277 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19278 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19279 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19280 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19281 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19282 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19283 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19284 addr="0x0001072c", func="main",file="recursive2.c",
19285 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
19286 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
19287 addr="0x00010774",func="foo",file="recursive2.c",
19288 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
19290 -break-insert -r foo.*
19291 ~int foo(int, int);
19292 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
19293 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
19297 @subheading The @code{-break-list} Command
19298 @findex -break-list
19300 @subsubheading Synopsis
19306 Displays the list of inserted breakpoints, showing the following fields:
19310 number of the breakpoint
19312 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
19314 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
19317 is the breakpoint enabled or no: @samp{y} or @samp{n}
19319 memory location at which the breakpoint is set
19321 logical location of the breakpoint, expressed by function name, file
19324 number of times the breakpoint has been hit
19327 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
19328 @code{body} field is an empty list.
19330 @subsubheading @value{GDBN} Command
19332 The corresponding @value{GDBN} command is @samp{info break}.
19334 @subsubheading Example
19339 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19340 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19341 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19342 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19343 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19344 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19345 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19346 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19347 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
19348 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
19349 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
19350 line="13",times="0"@}]@}
19354 Here's an example of the result when there are no breakpoints:
19359 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
19360 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19361 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19362 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19363 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19364 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19365 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19370 @subheading The @code{-break-watch} Command
19371 @findex -break-watch
19373 @subsubheading Synopsis
19376 -break-watch [ -a | -r ]
19379 Create a watchpoint. With the @samp{-a} option it will create an
19380 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
19381 read from or on a write to the memory location. With the @samp{-r}
19382 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
19383 trigger only when the memory location is accessed for reading. Without
19384 either of the options, the watchpoint created is a regular watchpoint,
19385 i.e., it will trigger when the memory location is accessed for writing.
19386 @xref{Set Watchpoints, , Setting Watchpoints}.
19388 Note that @samp{-break-list} will report a single list of watchpoints and
19389 breakpoints inserted.
19391 @subsubheading @value{GDBN} Command
19393 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
19396 @subsubheading Example
19398 Setting a watchpoint on a variable in the @code{main} function:
19403 ^done,wpt=@{number="2",exp="x"@}
19408 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
19409 value=@{old="-268439212",new="55"@},
19410 frame=@{func="main",args=[],file="recursive2.c",
19411 fullname="/home/foo/bar/recursive2.c",line="5"@}
19415 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
19416 the program execution twice: first for the variable changing value, then
19417 for the watchpoint going out of scope.
19422 ^done,wpt=@{number="5",exp="C"@}
19427 *stopped,reason="watchpoint-trigger",
19428 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
19429 frame=@{func="callee4",args=[],
19430 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19431 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
19436 *stopped,reason="watchpoint-scope",wpnum="5",
19437 frame=@{func="callee3",args=[@{name="strarg",
19438 value="0x11940 \"A string argument.\""@}],
19439 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19440 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19444 Listing breakpoints and watchpoints, at different points in the program
19445 execution. Note that once the watchpoint goes out of scope, it is
19451 ^done,wpt=@{number="2",exp="C"@}
19454 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19455 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19456 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19457 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19458 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19459 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19460 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19461 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19462 addr="0x00010734",func="callee4",
19463 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19464 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
19465 bkpt=@{number="2",type="watchpoint",disp="keep",
19466 enabled="y",addr="",what="C",times="0"@}]@}
19471 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
19472 value=@{old="-276895068",new="3"@},
19473 frame=@{func="callee4",args=[],
19474 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19475 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
19478 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19479 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19480 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19481 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19482 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19483 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19484 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19485 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19486 addr="0x00010734",func="callee4",
19487 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19488 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
19489 bkpt=@{number="2",type="watchpoint",disp="keep",
19490 enabled="y",addr="",what="C",times="-5"@}]@}
19494 ^done,reason="watchpoint-scope",wpnum="2",
19495 frame=@{func="callee3",args=[@{name="strarg",
19496 value="0x11940 \"A string argument.\""@}],
19497 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19498 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19501 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19502 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19503 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19504 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19505 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19506 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19507 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19508 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19509 addr="0x00010734",func="callee4",
19510 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19511 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
19516 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19517 @node GDB/MI Program Context
19518 @section @sc{gdb/mi} Program Context
19520 @subheading The @code{-exec-arguments} Command
19521 @findex -exec-arguments
19524 @subsubheading Synopsis
19527 -exec-arguments @var{args}
19530 Set the inferior program arguments, to be used in the next
19533 @subsubheading @value{GDBN} Command
19535 The corresponding @value{GDBN} command is @samp{set args}.
19537 @subsubheading Example
19541 -exec-arguments -v word
19547 @subheading The @code{-exec-show-arguments} Command
19548 @findex -exec-show-arguments
19550 @subsubheading Synopsis
19553 -exec-show-arguments
19556 Print the arguments of the program.
19558 @subsubheading @value{GDBN} Command
19560 The corresponding @value{GDBN} command is @samp{show args}.
19562 @subsubheading Example
19566 @subheading The @code{-environment-cd} Command
19567 @findex -environment-cd
19569 @subsubheading Synopsis
19572 -environment-cd @var{pathdir}
19575 Set @value{GDBN}'s working directory.
19577 @subsubheading @value{GDBN} Command
19579 The corresponding @value{GDBN} command is @samp{cd}.
19581 @subsubheading Example
19585 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19591 @subheading The @code{-environment-directory} Command
19592 @findex -environment-directory
19594 @subsubheading Synopsis
19597 -environment-directory [ -r ] [ @var{pathdir} ]+
19600 Add directories @var{pathdir} to beginning of search path for source files.
19601 If the @samp{-r} option is used, the search path is reset to the default
19602 search path. If directories @var{pathdir} are supplied in addition to the
19603 @samp{-r} option, the search path is first reset and then addition
19605 Multiple directories may be specified, separated by blanks. Specifying
19606 multiple directories in a single command
19607 results in the directories added to the beginning of the
19608 search path in the same order they were presented in the command.
19609 If blanks are needed as
19610 part of a directory name, double-quotes should be used around
19611 the name. In the command output, the path will show up separated
19612 by the system directory-separator character. The directory-separator
19613 character must not be used
19614 in any directory name.
19615 If no directories are specified, the current search path is displayed.
19617 @subsubheading @value{GDBN} Command
19619 The corresponding @value{GDBN} command is @samp{dir}.
19621 @subsubheading Example
19625 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19626 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19628 -environment-directory ""
19629 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19631 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
19632 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
19634 -environment-directory -r
19635 ^done,source-path="$cdir:$cwd"
19640 @subheading The @code{-environment-path} Command
19641 @findex -environment-path
19643 @subsubheading Synopsis
19646 -environment-path [ -r ] [ @var{pathdir} ]+
19649 Add directories @var{pathdir} to beginning of search path for object files.
19650 If the @samp{-r} option is used, the search path is reset to the original
19651 search path that existed at gdb start-up. If directories @var{pathdir} are
19652 supplied in addition to the
19653 @samp{-r} option, the search path is first reset and then addition
19655 Multiple directories may be specified, separated by blanks. Specifying
19656 multiple directories in a single command
19657 results in the directories added to the beginning of the
19658 search path in the same order they were presented in the command.
19659 If blanks are needed as
19660 part of a directory name, double-quotes should be used around
19661 the name. In the command output, the path will show up separated
19662 by the system directory-separator character. The directory-separator
19663 character must not be used
19664 in any directory name.
19665 If no directories are specified, the current path is displayed.
19668 @subsubheading @value{GDBN} Command
19670 The corresponding @value{GDBN} command is @samp{path}.
19672 @subsubheading Example
19677 ^done,path="/usr/bin"
19679 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
19680 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
19682 -environment-path -r /usr/local/bin
19683 ^done,path="/usr/local/bin:/usr/bin"
19688 @subheading The @code{-environment-pwd} Command
19689 @findex -environment-pwd
19691 @subsubheading Synopsis
19697 Show the current working directory.
19699 @subsubheading @value{GDBN} Command
19701 The corresponding @value{GDBN} command is @samp{pwd}.
19703 @subsubheading Example
19708 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
19712 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19713 @node GDB/MI Thread Commands
19714 @section @sc{gdb/mi} Thread Commands
19717 @subheading The @code{-thread-info} Command
19718 @findex -thread-info
19720 @subsubheading Synopsis
19723 -thread-info [ @var{thread-id} ]
19726 Reports information about either a specific thread, if
19727 the @var{thread-id} parameter is present, or about all
19728 threads. When printing information about all threads,
19729 also reports the current thread.
19731 @subsubheading @value{GDBN} Command
19733 The @samp{info thread} command prints the same information
19736 @subsubheading Example
19741 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
19742 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},
19743 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
19744 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
19745 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}@}],
19746 current-thread-id="1"
19750 @subheading The @code{-thread-list-ids} Command
19751 @findex -thread-list-ids
19753 @subsubheading Synopsis
19759 Produces a list of the currently known @value{GDBN} thread ids. At the
19760 end of the list it also prints the total number of such threads.
19762 @subsubheading @value{GDBN} Command
19764 Part of @samp{info threads} supplies the same information.
19766 @subsubheading Example
19768 No threads present, besides the main process:
19773 ^done,thread-ids=@{@},number-of-threads="0"
19783 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19784 number-of-threads="3"
19789 @subheading The @code{-thread-select} Command
19790 @findex -thread-select
19792 @subsubheading Synopsis
19795 -thread-select @var{threadnum}
19798 Make @var{threadnum} the current thread. It prints the number of the new
19799 current thread, and the topmost frame for that thread.
19801 @subsubheading @value{GDBN} Command
19803 The corresponding @value{GDBN} command is @samp{thread}.
19805 @subsubheading Example
19812 *stopped,reason="end-stepping-range",thread-id="2",line="187",
19813 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
19817 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19818 number-of-threads="3"
19821 ^done,new-thread-id="3",
19822 frame=@{level="0",func="vprintf",
19823 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
19824 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
19828 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19829 @node GDB/MI Program Execution
19830 @section @sc{gdb/mi} Program Execution
19832 These are the asynchronous commands which generate the out-of-band
19833 record @samp{*stopped}. Currently @value{GDBN} only really executes
19834 asynchronously with remote targets and this interaction is mimicked in
19837 @subheading The @code{-exec-continue} Command
19838 @findex -exec-continue
19840 @subsubheading Synopsis
19846 Resumes the execution of the inferior program until a breakpoint is
19847 encountered, or until the inferior exits.
19849 @subsubheading @value{GDBN} Command
19851 The corresponding @value{GDBN} corresponding is @samp{continue}.
19853 @subsubheading Example
19860 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
19861 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
19867 @subheading The @code{-exec-finish} Command
19868 @findex -exec-finish
19870 @subsubheading Synopsis
19876 Resumes the execution of the inferior program until the current
19877 function is exited. Displays the results returned by the function.
19879 @subsubheading @value{GDBN} Command
19881 The corresponding @value{GDBN} command is @samp{finish}.
19883 @subsubheading Example
19885 Function returning @code{void}.
19892 *stopped,reason="function-finished",frame=@{func="main",args=[],
19893 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
19897 Function returning other than @code{void}. The name of the internal
19898 @value{GDBN} variable storing the result is printed, together with the
19905 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
19906 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
19907 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19908 gdb-result-var="$1",return-value="0"
19913 @subheading The @code{-exec-interrupt} Command
19914 @findex -exec-interrupt
19916 @subsubheading Synopsis
19922 Interrupts the background execution of the target. Note how the token
19923 associated with the stop message is the one for the execution command
19924 that has been interrupted. The token for the interrupt itself only
19925 appears in the @samp{^done} output. If the user is trying to
19926 interrupt a non-running program, an error message will be printed.
19928 @subsubheading @value{GDBN} Command
19930 The corresponding @value{GDBN} command is @samp{interrupt}.
19932 @subsubheading Example
19943 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
19944 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
19945 fullname="/home/foo/bar/try.c",line="13"@}
19950 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
19955 @subheading The @code{-exec-next} Command
19958 @subsubheading Synopsis
19964 Resumes execution of the inferior program, stopping when the beginning
19965 of the next source line is reached.
19967 @subsubheading @value{GDBN} Command
19969 The corresponding @value{GDBN} command is @samp{next}.
19971 @subsubheading Example
19977 *stopped,reason="end-stepping-range",line="8",file="hello.c"
19982 @subheading The @code{-exec-next-instruction} Command
19983 @findex -exec-next-instruction
19985 @subsubheading Synopsis
19988 -exec-next-instruction
19991 Executes one machine instruction. If the instruction is a function
19992 call, continues until the function returns. If the program stops at an
19993 instruction in the middle of a source line, the address will be
19996 @subsubheading @value{GDBN} Command
19998 The corresponding @value{GDBN} command is @samp{nexti}.
20000 @subsubheading Example
20004 -exec-next-instruction
20008 *stopped,reason="end-stepping-range",
20009 addr="0x000100d4",line="5",file="hello.c"
20014 @subheading The @code{-exec-return} Command
20015 @findex -exec-return
20017 @subsubheading Synopsis
20023 Makes current function return immediately. Doesn't execute the inferior.
20024 Displays the new current frame.
20026 @subsubheading @value{GDBN} Command
20028 The corresponding @value{GDBN} command is @samp{return}.
20030 @subsubheading Example
20034 200-break-insert callee4
20035 200^done,bkpt=@{number="1",addr="0x00010734",
20036 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
20041 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
20042 frame=@{func="callee4",args=[],
20043 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20044 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
20050 111^done,frame=@{level="0",func="callee3",
20051 args=[@{name="strarg",
20052 value="0x11940 \"A string argument.\""@}],
20053 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20054 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20059 @subheading The @code{-exec-run} Command
20062 @subsubheading Synopsis
20068 Starts execution of the inferior from the beginning. The inferior
20069 executes until either a breakpoint is encountered or the program
20070 exits. In the latter case the output will include an exit code, if
20071 the program has exited exceptionally.
20073 @subsubheading @value{GDBN} Command
20075 The corresponding @value{GDBN} command is @samp{run}.
20077 @subsubheading Examples
20082 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
20087 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
20088 frame=@{func="main",args=[],file="recursive2.c",
20089 fullname="/home/foo/bar/recursive2.c",line="4"@}
20094 Program exited normally:
20102 *stopped,reason="exited-normally"
20107 Program exited exceptionally:
20115 *stopped,reason="exited",exit-code="01"
20119 Another way the program can terminate is if it receives a signal such as
20120 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
20124 *stopped,reason="exited-signalled",signal-name="SIGINT",
20125 signal-meaning="Interrupt"
20129 @c @subheading -exec-signal
20132 @subheading The @code{-exec-step} Command
20135 @subsubheading Synopsis
20141 Resumes execution of the inferior program, stopping when the beginning
20142 of the next source line is reached, if the next source line is not a
20143 function call. If it is, stop at the first instruction of the called
20146 @subsubheading @value{GDBN} Command
20148 The corresponding @value{GDBN} command is @samp{step}.
20150 @subsubheading Example
20152 Stepping into a function:
20158 *stopped,reason="end-stepping-range",
20159 frame=@{func="foo",args=[@{name="a",value="10"@},
20160 @{name="b",value="0"@}],file="recursive2.c",
20161 fullname="/home/foo/bar/recursive2.c",line="11"@}
20171 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
20176 @subheading The @code{-exec-step-instruction} Command
20177 @findex -exec-step-instruction
20179 @subsubheading Synopsis
20182 -exec-step-instruction
20185 Resumes the inferior which executes one machine instruction. The
20186 output, once @value{GDBN} has stopped, will vary depending on whether
20187 we have stopped in the middle of a source line or not. In the former
20188 case, the address at which the program stopped will be printed as
20191 @subsubheading @value{GDBN} Command
20193 The corresponding @value{GDBN} command is @samp{stepi}.
20195 @subsubheading Example
20199 -exec-step-instruction
20203 *stopped,reason="end-stepping-range",
20204 frame=@{func="foo",args=[],file="try.c",
20205 fullname="/home/foo/bar/try.c",line="10"@}
20207 -exec-step-instruction
20211 *stopped,reason="end-stepping-range",
20212 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
20213 fullname="/home/foo/bar/try.c",line="10"@}
20218 @subheading The @code{-exec-until} Command
20219 @findex -exec-until
20221 @subsubheading Synopsis
20224 -exec-until [ @var{location} ]
20227 Executes the inferior until the @var{location} specified in the
20228 argument is reached. If there is no argument, the inferior executes
20229 until a source line greater than the current one is reached. The
20230 reason for stopping in this case will be @samp{location-reached}.
20232 @subsubheading @value{GDBN} Command
20234 The corresponding @value{GDBN} command is @samp{until}.
20236 @subsubheading Example
20240 -exec-until recursive2.c:6
20244 *stopped,reason="location-reached",frame=@{func="main",args=[],
20245 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
20250 @subheading -file-clear
20251 Is this going away????
20254 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20255 @node GDB/MI Stack Manipulation
20256 @section @sc{gdb/mi} Stack Manipulation Commands
20259 @subheading The @code{-stack-info-frame} Command
20260 @findex -stack-info-frame
20262 @subsubheading Synopsis
20268 Get info on the selected frame.
20270 @subsubheading @value{GDBN} Command
20272 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
20273 (without arguments).
20275 @subsubheading Example
20280 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
20281 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20282 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
20286 @subheading The @code{-stack-info-depth} Command
20287 @findex -stack-info-depth
20289 @subsubheading Synopsis
20292 -stack-info-depth [ @var{max-depth} ]
20295 Return the depth of the stack. If the integer argument @var{max-depth}
20296 is specified, do not count beyond @var{max-depth} frames.
20298 @subsubheading @value{GDBN} Command
20300 There's no equivalent @value{GDBN} command.
20302 @subsubheading Example
20304 For a stack with frame levels 0 through 11:
20311 -stack-info-depth 4
20314 -stack-info-depth 12
20317 -stack-info-depth 11
20320 -stack-info-depth 13
20325 @subheading The @code{-stack-list-arguments} Command
20326 @findex -stack-list-arguments
20328 @subsubheading Synopsis
20331 -stack-list-arguments @var{show-values}
20332 [ @var{low-frame} @var{high-frame} ]
20335 Display a list of the arguments for the frames between @var{low-frame}
20336 and @var{high-frame} (inclusive). If @var{low-frame} and
20337 @var{high-frame} are not provided, list the arguments for the whole
20338 call stack. If the two arguments are equal, show the single frame
20339 at the corresponding level. It is an error if @var{low-frame} is
20340 larger than the actual number of frames. On the other hand,
20341 @var{high-frame} may be larger than the actual number of frames, in
20342 which case only existing frames will be returned.
20344 The @var{show-values} argument must have a value of 0 or 1. A value of
20345 0 means that only the names of the arguments are listed, a value of 1
20346 means that both names and values of the arguments are printed.
20348 @subsubheading @value{GDBN} Command
20350 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
20351 @samp{gdb_get_args} command which partially overlaps with the
20352 functionality of @samp{-stack-list-arguments}.
20354 @subsubheading Example
20361 frame=@{level="0",addr="0x00010734",func="callee4",
20362 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20363 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
20364 frame=@{level="1",addr="0x0001076c",func="callee3",
20365 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20366 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
20367 frame=@{level="2",addr="0x0001078c",func="callee2",
20368 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20369 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
20370 frame=@{level="3",addr="0x000107b4",func="callee1",
20371 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20372 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
20373 frame=@{level="4",addr="0x000107e0",func="main",
20374 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20375 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
20377 -stack-list-arguments 0
20380 frame=@{level="0",args=[]@},
20381 frame=@{level="1",args=[name="strarg"]@},
20382 frame=@{level="2",args=[name="intarg",name="strarg"]@},
20383 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
20384 frame=@{level="4",args=[]@}]
20386 -stack-list-arguments 1
20389 frame=@{level="0",args=[]@},
20391 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
20392 frame=@{level="2",args=[
20393 @{name="intarg",value="2"@},
20394 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
20395 @{frame=@{level="3",args=[
20396 @{name="intarg",value="2"@},
20397 @{name="strarg",value="0x11940 \"A string argument.\""@},
20398 @{name="fltarg",value="3.5"@}]@},
20399 frame=@{level="4",args=[]@}]
20401 -stack-list-arguments 0 2 2
20402 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
20404 -stack-list-arguments 1 2 2
20405 ^done,stack-args=[frame=@{level="2",
20406 args=[@{name="intarg",value="2"@},
20407 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
20411 @c @subheading -stack-list-exception-handlers
20414 @subheading The @code{-stack-list-frames} Command
20415 @findex -stack-list-frames
20417 @subsubheading Synopsis
20420 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
20423 List the frames currently on the stack. For each frame it displays the
20428 The frame number, 0 being the topmost frame, i.e., the innermost function.
20430 The @code{$pc} value for that frame.
20434 File name of the source file where the function lives.
20436 Line number corresponding to the @code{$pc}.
20439 If invoked without arguments, this command prints a backtrace for the
20440 whole stack. If given two integer arguments, it shows the frames whose
20441 levels are between the two arguments (inclusive). If the two arguments
20442 are equal, it shows the single frame at the corresponding level. It is
20443 an error if @var{low-frame} is larger than the actual number of
20444 frames. On the other hand, @var{high-frame} may be larger than the
20445 actual number of frames, in which case only existing frames will be returned.
20447 @subsubheading @value{GDBN} Command
20449 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
20451 @subsubheading Example
20453 Full stack backtrace:
20459 [frame=@{level="0",addr="0x0001076c",func="foo",
20460 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
20461 frame=@{level="1",addr="0x000107a4",func="foo",
20462 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20463 frame=@{level="2",addr="0x000107a4",func="foo",
20464 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20465 frame=@{level="3",addr="0x000107a4",func="foo",
20466 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20467 frame=@{level="4",addr="0x000107a4",func="foo",
20468 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20469 frame=@{level="5",addr="0x000107a4",func="foo",
20470 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20471 frame=@{level="6",addr="0x000107a4",func="foo",
20472 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20473 frame=@{level="7",addr="0x000107a4",func="foo",
20474 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20475 frame=@{level="8",addr="0x000107a4",func="foo",
20476 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20477 frame=@{level="9",addr="0x000107a4",func="foo",
20478 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20479 frame=@{level="10",addr="0x000107a4",func="foo",
20480 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20481 frame=@{level="11",addr="0x00010738",func="main",
20482 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
20486 Show frames between @var{low_frame} and @var{high_frame}:
20490 -stack-list-frames 3 5
20492 [frame=@{level="3",addr="0x000107a4",func="foo",
20493 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20494 frame=@{level="4",addr="0x000107a4",func="foo",
20495 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20496 frame=@{level="5",addr="0x000107a4",func="foo",
20497 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20501 Show a single frame:
20505 -stack-list-frames 3 3
20507 [frame=@{level="3",addr="0x000107a4",func="foo",
20508 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20513 @subheading The @code{-stack-list-locals} Command
20514 @findex -stack-list-locals
20516 @subsubheading Synopsis
20519 -stack-list-locals @var{print-values}
20522 Display the local variable names for the selected frame. If
20523 @var{print-values} is 0 or @code{--no-values}, print only the names of
20524 the variables; if it is 1 or @code{--all-values}, print also their
20525 values; and if it is 2 or @code{--simple-values}, print the name,
20526 type and value for simple data types and the name and type for arrays,
20527 structures and unions. In this last case, a frontend can immediately
20528 display the value of simple data types and create variable objects for
20529 other data types when the user wishes to explore their values in
20532 @subsubheading @value{GDBN} Command
20534 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
20536 @subsubheading Example
20540 -stack-list-locals 0
20541 ^done,locals=[name="A",name="B",name="C"]
20543 -stack-list-locals --all-values
20544 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
20545 @{name="C",value="@{1, 2, 3@}"@}]
20546 -stack-list-locals --simple-values
20547 ^done,locals=[@{name="A",type="int",value="1"@},
20548 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
20553 @subheading The @code{-stack-select-frame} Command
20554 @findex -stack-select-frame
20556 @subsubheading Synopsis
20559 -stack-select-frame @var{framenum}
20562 Change the selected frame. Select a different frame @var{framenum} on
20565 @subsubheading @value{GDBN} Command
20567 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
20568 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
20570 @subsubheading Example
20574 -stack-select-frame 2
20579 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20580 @node GDB/MI Variable Objects
20581 @section @sc{gdb/mi} Variable Objects
20585 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20587 For the implementation of a variable debugger window (locals, watched
20588 expressions, etc.), we are proposing the adaptation of the existing code
20589 used by @code{Insight}.
20591 The two main reasons for that are:
20595 It has been proven in practice (it is already on its second generation).
20598 It will shorten development time (needless to say how important it is
20602 The original interface was designed to be used by Tcl code, so it was
20603 slightly changed so it could be used through @sc{gdb/mi}. This section
20604 describes the @sc{gdb/mi} operations that will be available and gives some
20605 hints about their use.
20607 @emph{Note}: In addition to the set of operations described here, we
20608 expect the @sc{gui} implementation of a variable window to require, at
20609 least, the following operations:
20612 @item @code{-gdb-show} @code{output-radix}
20613 @item @code{-stack-list-arguments}
20614 @item @code{-stack-list-locals}
20615 @item @code{-stack-select-frame}
20620 @subheading Introduction to Variable Objects
20622 @cindex variable objects in @sc{gdb/mi}
20624 Variable objects are "object-oriented" MI interface for examining and
20625 changing values of expressions. Unlike some other MI interfaces that
20626 work with expressions, variable objects are specifically designed for
20627 simple and efficient presentation in the frontend. A variable object
20628 is identified by string name. When a variable object is created, the
20629 frontend specifies the expression for that variable object. The
20630 expression can be a simple variable, or it can be an arbitrary complex
20631 expression, and can even involve CPU registers. After creating a
20632 variable object, the frontend can invoke other variable object
20633 operations---for example to obtain or change the value of a variable
20634 object, or to change display format.
20636 Variable objects have hierarchical tree structure. Any variable object
20637 that corresponds to a composite type, such as structure in C, has
20638 a number of child variable objects, for example corresponding to each
20639 element of a structure. A child variable object can itself have
20640 children, recursively. Recursion ends when we reach
20641 leaf variable objects, which always have built-in types. Child variable
20642 objects are created only by explicit request, so if a frontend
20643 is not interested in the children of a particular variable object, no
20644 child will be created.
20646 For a leaf variable object it is possible to obtain its value as a
20647 string, or set the value from a string. String value can be also
20648 obtained for a non-leaf variable object, but it's generally a string
20649 that only indicates the type of the object, and does not list its
20650 contents. Assignment to a non-leaf variable object is not allowed.
20652 A frontend does not need to read the values of all variable objects each time
20653 the program stops. Instead, MI provides an update command that lists all
20654 variable objects whose values has changed since the last update
20655 operation. This considerably reduces the amount of data that must
20656 be transferred to the frontend. As noted above, children variable
20657 objects are created on demand, and only leaf variable objects have a
20658 real value. As result, gdb will read target memory only for leaf
20659 variables that frontend has created.
20661 The automatic update is not always desirable. For example, a frontend
20662 might want to keep a value of some expression for future reference,
20663 and never update it. For another example, fetching memory is
20664 relatively slow for embedded targets, so a frontend might want
20665 to disable automatic update for the variables that are either not
20666 visible on the screen, or ``closed''. This is possible using so
20667 called ``frozen variable objects''. Such variable objects are never
20668 implicitly updated.
20670 The following is the complete set of @sc{gdb/mi} operations defined to
20671 access this functionality:
20673 @multitable @columnfractions .4 .6
20674 @item @strong{Operation}
20675 @tab @strong{Description}
20677 @item @code{-var-create}
20678 @tab create a variable object
20679 @item @code{-var-delete}
20680 @tab delete the variable object and/or its children
20681 @item @code{-var-set-format}
20682 @tab set the display format of this variable
20683 @item @code{-var-show-format}
20684 @tab show the display format of this variable
20685 @item @code{-var-info-num-children}
20686 @tab tells how many children this object has
20687 @item @code{-var-list-children}
20688 @tab return a list of the object's children
20689 @item @code{-var-info-type}
20690 @tab show the type of this variable object
20691 @item @code{-var-info-expression}
20692 @tab print parent-relative expression that this variable object represents
20693 @item @code{-var-info-path-expression}
20694 @tab print full expression that this variable object represents
20695 @item @code{-var-show-attributes}
20696 @tab is this variable editable? does it exist here?
20697 @item @code{-var-evaluate-expression}
20698 @tab get the value of this variable
20699 @item @code{-var-assign}
20700 @tab set the value of this variable
20701 @item @code{-var-update}
20702 @tab update the variable and its children
20703 @item @code{-var-set-frozen}
20704 @tab set frozeness attribute
20707 In the next subsection we describe each operation in detail and suggest
20708 how it can be used.
20710 @subheading Description And Use of Operations on Variable Objects
20712 @subheading The @code{-var-create} Command
20713 @findex -var-create
20715 @subsubheading Synopsis
20718 -var-create @{@var{name} | "-"@}
20719 @{@var{frame-addr} | "*"@} @var{expression}
20722 This operation creates a variable object, which allows the monitoring of
20723 a variable, the result of an expression, a memory cell or a CPU
20726 The @var{name} parameter is the string by which the object can be
20727 referenced. It must be unique. If @samp{-} is specified, the varobj
20728 system will generate a string ``varNNNNNN'' automatically. It will be
20729 unique provided that one does not specify @var{name} on that format.
20730 The command fails if a duplicate name is found.
20732 The frame under which the expression should be evaluated can be
20733 specified by @var{frame-addr}. A @samp{*} indicates that the current
20734 frame should be used.
20736 @var{expression} is any expression valid on the current language set (must not
20737 begin with a @samp{*}), or one of the following:
20741 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20744 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20747 @samp{$@var{regname}} --- a CPU register name
20750 @subsubheading Result
20752 This operation returns the name, number of children and the type of the
20753 object created. Type is returned as a string as the ones generated by
20754 the @value{GDBN} CLI:
20757 name="@var{name}",numchild="N",type="@var{type}"
20761 @subheading The @code{-var-delete} Command
20762 @findex -var-delete
20764 @subsubheading Synopsis
20767 -var-delete [ -c ] @var{name}
20770 Deletes a previously created variable object and all of its children.
20771 With the @samp{-c} option, just deletes the children.
20773 Returns an error if the object @var{name} is not found.
20776 @subheading The @code{-var-set-format} Command
20777 @findex -var-set-format
20779 @subsubheading Synopsis
20782 -var-set-format @var{name} @var{format-spec}
20785 Sets the output format for the value of the object @var{name} to be
20788 @anchor{-var-set-format}
20789 The syntax for the @var{format-spec} is as follows:
20792 @var{format-spec} @expansion{}
20793 @{binary | decimal | hexadecimal | octal | natural@}
20796 The natural format is the default format choosen automatically
20797 based on the variable type (like decimal for an @code{int}, hex
20798 for pointers, etc.).
20800 For a variable with children, the format is set only on the
20801 variable itself, and the children are not affected.
20803 @subheading The @code{-var-show-format} Command
20804 @findex -var-show-format
20806 @subsubheading Synopsis
20809 -var-show-format @var{name}
20812 Returns the format used to display the value of the object @var{name}.
20815 @var{format} @expansion{}
20820 @subheading The @code{-var-info-num-children} Command
20821 @findex -var-info-num-children
20823 @subsubheading Synopsis
20826 -var-info-num-children @var{name}
20829 Returns the number of children of a variable object @var{name}:
20836 @subheading The @code{-var-list-children} Command
20837 @findex -var-list-children
20839 @subsubheading Synopsis
20842 -var-list-children [@var{print-values}] @var{name}
20844 @anchor{-var-list-children}
20846 Return a list of the children of the specified variable object and
20847 create variable objects for them, if they do not already exist. With
20848 a single argument or if @var{print-values} has a value for of 0 or
20849 @code{--no-values}, print only the names of the variables; if
20850 @var{print-values} is 1 or @code{--all-values}, also print their
20851 values; and if it is 2 or @code{--simple-values} print the name and
20852 value for simple data types and just the name for arrays, structures
20855 @subsubheading Example
20859 -var-list-children n
20860 ^done,numchild=@var{n},children=[@{name=@var{name},
20861 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20863 -var-list-children --all-values n
20864 ^done,numchild=@var{n},children=[@{name=@var{name},
20865 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20869 @subheading The @code{-var-info-type} Command
20870 @findex -var-info-type
20872 @subsubheading Synopsis
20875 -var-info-type @var{name}
20878 Returns the type of the specified variable @var{name}. The type is
20879 returned as a string in the same format as it is output by the
20883 type=@var{typename}
20887 @subheading The @code{-var-info-expression} Command
20888 @findex -var-info-expression
20890 @subsubheading Synopsis
20893 -var-info-expression @var{name}
20896 Returns a string that is suitable for presenting this
20897 variable object in user interface. The string is generally
20898 not valid expression in the current language, and cannot be evaluated.
20900 For example, if @code{a} is an array, and variable object
20901 @code{A} was created for @code{a}, then we'll get this output:
20904 (gdb) -var-info-expression A.1
20905 ^done,lang="C",exp="1"
20909 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
20911 Note that the output of the @code{-var-list-children} command also
20912 includes those expressions, so the @code{-var-info-expression} command
20915 @subheading The @code{-var-info-path-expression} Command
20916 @findex -var-info-path-expression
20918 @subsubheading Synopsis
20921 -var-info-path-expression @var{name}
20924 Returns an expression that can be evaluated in the current
20925 context and will yield the same value that a variable object has.
20926 Compare this with the @code{-var-info-expression} command, which
20927 result can be used only for UI presentation. Typical use of
20928 the @code{-var-info-path-expression} command is creating a
20929 watchpoint from a variable object.
20931 For example, suppose @code{C} is a C@t{++} class, derived from class
20932 @code{Base}, and that the @code{Base} class has a member called
20933 @code{m_size}. Assume a variable @code{c} is has the type of
20934 @code{C} and a variable object @code{C} was created for variable
20935 @code{c}. Then, we'll get this output:
20937 (gdb) -var-info-path-expression C.Base.public.m_size
20938 ^done,path_expr=((Base)c).m_size)
20941 @subheading The @code{-var-show-attributes} Command
20942 @findex -var-show-attributes
20944 @subsubheading Synopsis
20947 -var-show-attributes @var{name}
20950 List attributes of the specified variable object @var{name}:
20953 status=@var{attr} [ ( ,@var{attr} )* ]
20957 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20959 @subheading The @code{-var-evaluate-expression} Command
20960 @findex -var-evaluate-expression
20962 @subsubheading Synopsis
20965 -var-evaluate-expression [-f @var{format-spec}] @var{name}
20968 Evaluates the expression that is represented by the specified variable
20969 object and returns its value as a string. The format of the string
20970 can be specified with the @samp{-f} option. The possible values of
20971 this option are the same as for @code{-var-set-format}
20972 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
20973 the current display format will be used. The current display format
20974 can be changed using the @code{-var-set-format} command.
20980 Note that one must invoke @code{-var-list-children} for a variable
20981 before the value of a child variable can be evaluated.
20983 @subheading The @code{-var-assign} Command
20984 @findex -var-assign
20986 @subsubheading Synopsis
20989 -var-assign @var{name} @var{expression}
20992 Assigns the value of @var{expression} to the variable object specified
20993 by @var{name}. The object must be @samp{editable}. If the variable's
20994 value is altered by the assign, the variable will show up in any
20995 subsequent @code{-var-update} list.
20997 @subsubheading Example
21005 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
21009 @subheading The @code{-var-update} Command
21010 @findex -var-update
21012 @subsubheading Synopsis
21015 -var-update [@var{print-values}] @{@var{name} | "*"@}
21018 Reevaluate the expressions corresponding to the variable object
21019 @var{name} and all its direct and indirect children, and return the
21020 list of variable objects whose values have changed; @var{name} must
21021 be a root variable object. Here, ``changed'' means that the result of
21022 @code{-var-evaluate-expression} before and after the
21023 @code{-var-update} is different. If @samp{*} is used as the variable
21024 object names, all existing variable objects are updated, except
21025 for frozen ones (@pxref{-var-set-frozen}). The option
21026 @var{print-values} determines whether both names and values, or just
21027 names are printed. The possible values of this option are the same
21028 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
21029 recommended to use the @samp{--all-values} option, to reduce the
21030 number of MI commands needed on each program stop.
21033 @subsubheading Example
21040 -var-update --all-values var1
21041 ^done,changelist=[@{name="var1",value="3",in_scope="true",
21042 type_changed="false"@}]
21046 @anchor{-var-update}
21047 The field in_scope may take three values:
21051 The variable object's current value is valid.
21054 The variable object does not currently hold a valid value but it may
21055 hold one in the future if its associated expression comes back into
21059 The variable object no longer holds a valid value.
21060 This can occur when the executable file being debugged has changed,
21061 either through recompilation or by using the @value{GDBN} @code{file}
21062 command. The front end should normally choose to delete these variable
21066 In the future new values may be added to this list so the front should
21067 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
21069 @subheading The @code{-var-set-frozen} Command
21070 @findex -var-set-frozen
21071 @anchor{-var-set-frozen}
21073 @subsubheading Synopsis
21076 -var-set-frozen @var{name} @var{flag}
21079 Set the frozenness flag on the variable object @var{name}. The
21080 @var{flag} parameter should be either @samp{1} to make the variable
21081 frozen or @samp{0} to make it unfrozen. If a variable object is
21082 frozen, then neither itself, nor any of its children, are
21083 implicitly updated by @code{-var-update} of
21084 a parent variable or by @code{-var-update *}. Only
21085 @code{-var-update} of the variable itself will update its value and
21086 values of its children. After a variable object is unfrozen, it is
21087 implicitly updated by all subsequent @code{-var-update} operations.
21088 Unfreezing a variable does not update it, only subsequent
21089 @code{-var-update} does.
21091 @subsubheading Example
21095 -var-set-frozen V 1
21101 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21102 @node GDB/MI Data Manipulation
21103 @section @sc{gdb/mi} Data Manipulation
21105 @cindex data manipulation, in @sc{gdb/mi}
21106 @cindex @sc{gdb/mi}, data manipulation
21107 This section describes the @sc{gdb/mi} commands that manipulate data:
21108 examine memory and registers, evaluate expressions, etc.
21110 @c REMOVED FROM THE INTERFACE.
21111 @c @subheading -data-assign
21112 @c Change the value of a program variable. Plenty of side effects.
21113 @c @subsubheading GDB Command
21115 @c @subsubheading Example
21118 @subheading The @code{-data-disassemble} Command
21119 @findex -data-disassemble
21121 @subsubheading Synopsis
21125 [ -s @var{start-addr} -e @var{end-addr} ]
21126 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
21134 @item @var{start-addr}
21135 is the beginning address (or @code{$pc})
21136 @item @var{end-addr}
21138 @item @var{filename}
21139 is the name of the file to disassemble
21140 @item @var{linenum}
21141 is the line number to disassemble around
21143 is the number of disassembly lines to be produced. If it is -1,
21144 the whole function will be disassembled, in case no @var{end-addr} is
21145 specified. If @var{end-addr} is specified as a non-zero value, and
21146 @var{lines} is lower than the number of disassembly lines between
21147 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
21148 displayed; if @var{lines} is higher than the number of lines between
21149 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
21152 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
21156 @subsubheading Result
21158 The output for each instruction is composed of four fields:
21167 Note that whatever included in the instruction field, is not manipulated
21168 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
21170 @subsubheading @value{GDBN} Command
21172 There's no direct mapping from this command to the CLI.
21174 @subsubheading Example
21176 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
21180 -data-disassemble -s $pc -e "$pc + 20" -- 0
21183 @{address="0x000107c0",func-name="main",offset="4",
21184 inst="mov 2, %o0"@},
21185 @{address="0x000107c4",func-name="main",offset="8",
21186 inst="sethi %hi(0x11800), %o2"@},
21187 @{address="0x000107c8",func-name="main",offset="12",
21188 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
21189 @{address="0x000107cc",func-name="main",offset="16",
21190 inst="sethi %hi(0x11800), %o2"@},
21191 @{address="0x000107d0",func-name="main",offset="20",
21192 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
21196 Disassemble the whole @code{main} function. Line 32 is part of
21200 -data-disassemble -f basics.c -l 32 -- 0
21202 @{address="0x000107bc",func-name="main",offset="0",
21203 inst="save %sp, -112, %sp"@},
21204 @{address="0x000107c0",func-name="main",offset="4",
21205 inst="mov 2, %o0"@},
21206 @{address="0x000107c4",func-name="main",offset="8",
21207 inst="sethi %hi(0x11800), %o2"@},
21209 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
21210 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
21214 Disassemble 3 instructions from the start of @code{main}:
21218 -data-disassemble -f basics.c -l 32 -n 3 -- 0
21220 @{address="0x000107bc",func-name="main",offset="0",
21221 inst="save %sp, -112, %sp"@},
21222 @{address="0x000107c0",func-name="main",offset="4",
21223 inst="mov 2, %o0"@},
21224 @{address="0x000107c4",func-name="main",offset="8",
21225 inst="sethi %hi(0x11800), %o2"@}]
21229 Disassemble 3 instructions from the start of @code{main} in mixed mode:
21233 -data-disassemble -f basics.c -l 32 -n 3 -- 1
21235 src_and_asm_line=@{line="31",
21236 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
21237 testsuite/gdb.mi/basics.c",line_asm_insn=[
21238 @{address="0x000107bc",func-name="main",offset="0",
21239 inst="save %sp, -112, %sp"@}]@},
21240 src_and_asm_line=@{line="32",
21241 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
21242 testsuite/gdb.mi/basics.c",line_asm_insn=[
21243 @{address="0x000107c0",func-name="main",offset="4",
21244 inst="mov 2, %o0"@},
21245 @{address="0x000107c4",func-name="main",offset="8",
21246 inst="sethi %hi(0x11800), %o2"@}]@}]
21251 @subheading The @code{-data-evaluate-expression} Command
21252 @findex -data-evaluate-expression
21254 @subsubheading Synopsis
21257 -data-evaluate-expression @var{expr}
21260 Evaluate @var{expr} as an expression. The expression could contain an
21261 inferior function call. The function call will execute synchronously.
21262 If the expression contains spaces, it must be enclosed in double quotes.
21264 @subsubheading @value{GDBN} Command
21266 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
21267 @samp{call}. In @code{gdbtk} only, there's a corresponding
21268 @samp{gdb_eval} command.
21270 @subsubheading Example
21272 In the following example, the numbers that precede the commands are the
21273 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
21274 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
21278 211-data-evaluate-expression A
21281 311-data-evaluate-expression &A
21282 311^done,value="0xefffeb7c"
21284 411-data-evaluate-expression A+3
21287 511-data-evaluate-expression "A + 3"
21293 @subheading The @code{-data-list-changed-registers} Command
21294 @findex -data-list-changed-registers
21296 @subsubheading Synopsis
21299 -data-list-changed-registers
21302 Display a list of the registers that have changed.
21304 @subsubheading @value{GDBN} Command
21306 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
21307 has the corresponding command @samp{gdb_changed_register_list}.
21309 @subsubheading Example
21311 On a PPC MBX board:
21319 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
21320 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
21323 -data-list-changed-registers
21324 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
21325 "10","11","13","14","15","16","17","18","19","20","21","22","23",
21326 "24","25","26","27","28","30","31","64","65","66","67","69"]
21331 @subheading The @code{-data-list-register-names} Command
21332 @findex -data-list-register-names
21334 @subsubheading Synopsis
21337 -data-list-register-names [ ( @var{regno} )+ ]
21340 Show a list of register names for the current target. If no arguments
21341 are given, it shows a list of the names of all the registers. If
21342 integer numbers are given as arguments, it will print a list of the
21343 names of the registers corresponding to the arguments. To ensure
21344 consistency between a register name and its number, the output list may
21345 include empty register names.
21347 @subsubheading @value{GDBN} Command
21349 @value{GDBN} does not have a command which corresponds to
21350 @samp{-data-list-register-names}. In @code{gdbtk} there is a
21351 corresponding command @samp{gdb_regnames}.
21353 @subsubheading Example
21355 For the PPC MBX board:
21358 -data-list-register-names
21359 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
21360 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
21361 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
21362 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
21363 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
21364 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
21365 "", "pc","ps","cr","lr","ctr","xer"]
21367 -data-list-register-names 1 2 3
21368 ^done,register-names=["r1","r2","r3"]
21372 @subheading The @code{-data-list-register-values} Command
21373 @findex -data-list-register-values
21375 @subsubheading Synopsis
21378 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
21381 Display the registers' contents. @var{fmt} is the format according to
21382 which the registers' contents are to be returned, followed by an optional
21383 list of numbers specifying the registers to display. A missing list of
21384 numbers indicates that the contents of all the registers must be returned.
21386 Allowed formats for @var{fmt} are:
21403 @subsubheading @value{GDBN} Command
21405 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
21406 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
21408 @subsubheading Example
21410 For a PPC MBX board (note: line breaks are for readability only, they
21411 don't appear in the actual output):
21415 -data-list-register-values r 64 65
21416 ^done,register-values=[@{number="64",value="0xfe00a300"@},
21417 @{number="65",value="0x00029002"@}]
21419 -data-list-register-values x
21420 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
21421 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
21422 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
21423 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
21424 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
21425 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
21426 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
21427 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
21428 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
21429 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
21430 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
21431 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
21432 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
21433 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
21434 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
21435 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
21436 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
21437 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
21438 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
21439 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
21440 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
21441 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
21442 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
21443 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
21444 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
21445 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
21446 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
21447 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
21448 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
21449 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
21450 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
21451 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
21452 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
21453 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
21454 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
21455 @{number="69",value="0x20002b03"@}]
21460 @subheading The @code{-data-read-memory} Command
21461 @findex -data-read-memory
21463 @subsubheading Synopsis
21466 -data-read-memory [ -o @var{byte-offset} ]
21467 @var{address} @var{word-format} @var{word-size}
21468 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
21475 @item @var{address}
21476 An expression specifying the address of the first memory word to be
21477 read. Complex expressions containing embedded white space should be
21478 quoted using the C convention.
21480 @item @var{word-format}
21481 The format to be used to print the memory words. The notation is the
21482 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
21485 @item @var{word-size}
21486 The size of each memory word in bytes.
21488 @item @var{nr-rows}
21489 The number of rows in the output table.
21491 @item @var{nr-cols}
21492 The number of columns in the output table.
21495 If present, indicates that each row should include an @sc{ascii} dump. The
21496 value of @var{aschar} is used as a padding character when a byte is not a
21497 member of the printable @sc{ascii} character set (printable @sc{ascii}
21498 characters are those whose code is between 32 and 126, inclusively).
21500 @item @var{byte-offset}
21501 An offset to add to the @var{address} before fetching memory.
21504 This command displays memory contents as a table of @var{nr-rows} by
21505 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
21506 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
21507 (returned as @samp{total-bytes}). Should less than the requested number
21508 of bytes be returned by the target, the missing words are identified
21509 using @samp{N/A}. The number of bytes read from the target is returned
21510 in @samp{nr-bytes} and the starting address used to read memory in
21513 The address of the next/previous row or page is available in
21514 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
21517 @subsubheading @value{GDBN} Command
21519 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
21520 @samp{gdb_get_mem} memory read command.
21522 @subsubheading Example
21524 Read six bytes of memory starting at @code{bytes+6} but then offset by
21525 @code{-6} bytes. Format as three rows of two columns. One byte per
21526 word. Display each word in hex.
21530 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
21531 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
21532 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
21533 prev-page="0x0000138a",memory=[
21534 @{addr="0x00001390",data=["0x00","0x01"]@},
21535 @{addr="0x00001392",data=["0x02","0x03"]@},
21536 @{addr="0x00001394",data=["0x04","0x05"]@}]
21540 Read two bytes of memory starting at address @code{shorts + 64} and
21541 display as a single word formatted in decimal.
21545 5-data-read-memory shorts+64 d 2 1 1
21546 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
21547 next-row="0x00001512",prev-row="0x0000150e",
21548 next-page="0x00001512",prev-page="0x0000150e",memory=[
21549 @{addr="0x00001510",data=["128"]@}]
21553 Read thirty two bytes of memory starting at @code{bytes+16} and format
21554 as eight rows of four columns. Include a string encoding with @samp{x}
21555 used as the non-printable character.
21559 4-data-read-memory bytes+16 x 1 8 4 x
21560 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
21561 next-row="0x000013c0",prev-row="0x0000139c",
21562 next-page="0x000013c0",prev-page="0x00001380",memory=[
21563 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
21564 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
21565 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
21566 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
21567 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
21568 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
21569 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
21570 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
21574 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21575 @node GDB/MI Tracepoint Commands
21576 @section @sc{gdb/mi} Tracepoint Commands
21578 The tracepoint commands are not yet implemented.
21580 @c @subheading -trace-actions
21582 @c @subheading -trace-delete
21584 @c @subheading -trace-disable
21586 @c @subheading -trace-dump
21588 @c @subheading -trace-enable
21590 @c @subheading -trace-exists
21592 @c @subheading -trace-find
21594 @c @subheading -trace-frame-number
21596 @c @subheading -trace-info
21598 @c @subheading -trace-insert
21600 @c @subheading -trace-list
21602 @c @subheading -trace-pass-count
21604 @c @subheading -trace-save
21606 @c @subheading -trace-start
21608 @c @subheading -trace-stop
21611 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21612 @node GDB/MI Symbol Query
21613 @section @sc{gdb/mi} Symbol Query Commands
21616 @subheading The @code{-symbol-info-address} Command
21617 @findex -symbol-info-address
21619 @subsubheading Synopsis
21622 -symbol-info-address @var{symbol}
21625 Describe where @var{symbol} is stored.
21627 @subsubheading @value{GDBN} Command
21629 The corresponding @value{GDBN} command is @samp{info address}.
21631 @subsubheading Example
21635 @subheading The @code{-symbol-info-file} Command
21636 @findex -symbol-info-file
21638 @subsubheading Synopsis
21644 Show the file for the symbol.
21646 @subsubheading @value{GDBN} Command
21648 There's no equivalent @value{GDBN} command. @code{gdbtk} has
21649 @samp{gdb_find_file}.
21651 @subsubheading Example
21655 @subheading The @code{-symbol-info-function} Command
21656 @findex -symbol-info-function
21658 @subsubheading Synopsis
21661 -symbol-info-function
21664 Show which function the symbol lives in.
21666 @subsubheading @value{GDBN} Command
21668 @samp{gdb_get_function} in @code{gdbtk}.
21670 @subsubheading Example
21674 @subheading The @code{-symbol-info-line} Command
21675 @findex -symbol-info-line
21677 @subsubheading Synopsis
21683 Show the core addresses of the code for a source line.
21685 @subsubheading @value{GDBN} Command
21687 The corresponding @value{GDBN} command is @samp{info line}.
21688 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
21690 @subsubheading Example
21694 @subheading The @code{-symbol-info-symbol} Command
21695 @findex -symbol-info-symbol
21697 @subsubheading Synopsis
21700 -symbol-info-symbol @var{addr}
21703 Describe what symbol is at location @var{addr}.
21705 @subsubheading @value{GDBN} Command
21707 The corresponding @value{GDBN} command is @samp{info symbol}.
21709 @subsubheading Example
21713 @subheading The @code{-symbol-list-functions} Command
21714 @findex -symbol-list-functions
21716 @subsubheading Synopsis
21719 -symbol-list-functions
21722 List the functions in the executable.
21724 @subsubheading @value{GDBN} Command
21726 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
21727 @samp{gdb_search} in @code{gdbtk}.
21729 @subsubheading Example
21733 @subheading The @code{-symbol-list-lines} Command
21734 @findex -symbol-list-lines
21736 @subsubheading Synopsis
21739 -symbol-list-lines @var{filename}
21742 Print the list of lines that contain code and their associated program
21743 addresses for the given source filename. The entries are sorted in
21744 ascending PC order.
21746 @subsubheading @value{GDBN} Command
21748 There is no corresponding @value{GDBN} command.
21750 @subsubheading Example
21753 -symbol-list-lines basics.c
21754 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
21759 @subheading The @code{-symbol-list-types} Command
21760 @findex -symbol-list-types
21762 @subsubheading Synopsis
21768 List all the type names.
21770 @subsubheading @value{GDBN} Command
21772 The corresponding commands are @samp{info types} in @value{GDBN},
21773 @samp{gdb_search} in @code{gdbtk}.
21775 @subsubheading Example
21779 @subheading The @code{-symbol-list-variables} Command
21780 @findex -symbol-list-variables
21782 @subsubheading Synopsis
21785 -symbol-list-variables
21788 List all the global and static variable names.
21790 @subsubheading @value{GDBN} Command
21792 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
21794 @subsubheading Example
21798 @subheading The @code{-symbol-locate} Command
21799 @findex -symbol-locate
21801 @subsubheading Synopsis
21807 @subsubheading @value{GDBN} Command
21809 @samp{gdb_loc} in @code{gdbtk}.
21811 @subsubheading Example
21815 @subheading The @code{-symbol-type} Command
21816 @findex -symbol-type
21818 @subsubheading Synopsis
21821 -symbol-type @var{variable}
21824 Show type of @var{variable}.
21826 @subsubheading @value{GDBN} Command
21828 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
21829 @samp{gdb_obj_variable}.
21831 @subsubheading Example
21835 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21836 @node GDB/MI File Commands
21837 @section @sc{gdb/mi} File Commands
21839 This section describes the GDB/MI commands to specify executable file names
21840 and to read in and obtain symbol table information.
21842 @subheading The @code{-file-exec-and-symbols} Command
21843 @findex -file-exec-and-symbols
21845 @subsubheading Synopsis
21848 -file-exec-and-symbols @var{file}
21851 Specify the executable file to be debugged. This file is the one from
21852 which the symbol table is also read. If no file is specified, the
21853 command clears the executable and symbol information. If breakpoints
21854 are set when using this command with no arguments, @value{GDBN} will produce
21855 error messages. Otherwise, no output is produced, except a completion
21858 @subsubheading @value{GDBN} Command
21860 The corresponding @value{GDBN} command is @samp{file}.
21862 @subsubheading Example
21866 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21872 @subheading The @code{-file-exec-file} Command
21873 @findex -file-exec-file
21875 @subsubheading Synopsis
21878 -file-exec-file @var{file}
21881 Specify the executable file to be debugged. Unlike
21882 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
21883 from this file. If used without argument, @value{GDBN} clears the information
21884 about the executable file. No output is produced, except a completion
21887 @subsubheading @value{GDBN} Command
21889 The corresponding @value{GDBN} command is @samp{exec-file}.
21891 @subsubheading Example
21895 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21901 @subheading The @code{-file-list-exec-sections} Command
21902 @findex -file-list-exec-sections
21904 @subsubheading Synopsis
21907 -file-list-exec-sections
21910 List the sections of the current executable file.
21912 @subsubheading @value{GDBN} Command
21914 The @value{GDBN} command @samp{info file} shows, among the rest, the same
21915 information as this command. @code{gdbtk} has a corresponding command
21916 @samp{gdb_load_info}.
21918 @subsubheading Example
21922 @subheading The @code{-file-list-exec-source-file} Command
21923 @findex -file-list-exec-source-file
21925 @subsubheading Synopsis
21928 -file-list-exec-source-file
21931 List the line number, the current source file, and the absolute path
21932 to the current source file for the current executable. The macro
21933 information field has a value of @samp{1} or @samp{0} depending on
21934 whether or not the file includes preprocessor macro information.
21936 @subsubheading @value{GDBN} Command
21938 The @value{GDBN} equivalent is @samp{info source}
21940 @subsubheading Example
21944 123-file-list-exec-source-file
21945 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
21950 @subheading The @code{-file-list-exec-source-files} Command
21951 @findex -file-list-exec-source-files
21953 @subsubheading Synopsis
21956 -file-list-exec-source-files
21959 List the source files for the current executable.
21961 It will always output the filename, but only when @value{GDBN} can find
21962 the absolute file name of a source file, will it output the fullname.
21964 @subsubheading @value{GDBN} Command
21966 The @value{GDBN} equivalent is @samp{info sources}.
21967 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
21969 @subsubheading Example
21972 -file-list-exec-source-files
21974 @{file=foo.c,fullname=/home/foo.c@},
21975 @{file=/home/bar.c,fullname=/home/bar.c@},
21976 @{file=gdb_could_not_find_fullpath.c@}]
21980 @subheading The @code{-file-list-shared-libraries} Command
21981 @findex -file-list-shared-libraries
21983 @subsubheading Synopsis
21986 -file-list-shared-libraries
21989 List the shared libraries in the program.
21991 @subsubheading @value{GDBN} Command
21993 The corresponding @value{GDBN} command is @samp{info shared}.
21995 @subsubheading Example
21999 @subheading The @code{-file-list-symbol-files} Command
22000 @findex -file-list-symbol-files
22002 @subsubheading Synopsis
22005 -file-list-symbol-files
22010 @subsubheading @value{GDBN} Command
22012 The corresponding @value{GDBN} command is @samp{info file} (part of it).
22014 @subsubheading Example
22018 @subheading The @code{-file-symbol-file} Command
22019 @findex -file-symbol-file
22021 @subsubheading Synopsis
22024 -file-symbol-file @var{file}
22027 Read symbol table info from the specified @var{file} argument. When
22028 used without arguments, clears @value{GDBN}'s symbol table info. No output is
22029 produced, except for a completion notification.
22031 @subsubheading @value{GDBN} Command
22033 The corresponding @value{GDBN} command is @samp{symbol-file}.
22035 @subsubheading Example
22039 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22045 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22046 @node GDB/MI Memory Overlay Commands
22047 @section @sc{gdb/mi} Memory Overlay Commands
22049 The memory overlay commands are not implemented.
22051 @c @subheading -overlay-auto
22053 @c @subheading -overlay-list-mapping-state
22055 @c @subheading -overlay-list-overlays
22057 @c @subheading -overlay-map
22059 @c @subheading -overlay-off
22061 @c @subheading -overlay-on
22063 @c @subheading -overlay-unmap
22065 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22066 @node GDB/MI Signal Handling Commands
22067 @section @sc{gdb/mi} Signal Handling Commands
22069 Signal handling commands are not implemented.
22071 @c @subheading -signal-handle
22073 @c @subheading -signal-list-handle-actions
22075 @c @subheading -signal-list-signal-types
22079 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22080 @node GDB/MI Target Manipulation
22081 @section @sc{gdb/mi} Target Manipulation Commands
22084 @subheading The @code{-target-attach} Command
22085 @findex -target-attach
22087 @subsubheading Synopsis
22090 -target-attach @var{pid} | @var{file}
22093 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
22095 @subsubheading @value{GDBN} Command
22097 The corresponding @value{GDBN} command is @samp{attach}.
22099 @subsubheading Example
22103 =thread-created,id="1"
22104 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
22109 @subheading The @code{-target-compare-sections} Command
22110 @findex -target-compare-sections
22112 @subsubheading Synopsis
22115 -target-compare-sections [ @var{section} ]
22118 Compare data of section @var{section} on target to the exec file.
22119 Without the argument, all sections are compared.
22121 @subsubheading @value{GDBN} Command
22123 The @value{GDBN} equivalent is @samp{compare-sections}.
22125 @subsubheading Example
22129 @subheading The @code{-target-detach} Command
22130 @findex -target-detach
22132 @subsubheading Synopsis
22138 Detach from the remote target which normally resumes its execution.
22141 @subsubheading @value{GDBN} Command
22143 The corresponding @value{GDBN} command is @samp{detach}.
22145 @subsubheading Example
22155 @subheading The @code{-target-disconnect} Command
22156 @findex -target-disconnect
22158 @subsubheading Synopsis
22164 Disconnect from the remote target. There's no output and the target is
22165 generally not resumed.
22167 @subsubheading @value{GDBN} Command
22169 The corresponding @value{GDBN} command is @samp{disconnect}.
22171 @subsubheading Example
22181 @subheading The @code{-target-download} Command
22182 @findex -target-download
22184 @subsubheading Synopsis
22190 Loads the executable onto the remote target.
22191 It prints out an update message every half second, which includes the fields:
22195 The name of the section.
22197 The size of what has been sent so far for that section.
22199 The size of the section.
22201 The total size of what was sent so far (the current and the previous sections).
22203 The size of the overall executable to download.
22207 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
22208 @sc{gdb/mi} Output Syntax}).
22210 In addition, it prints the name and size of the sections, as they are
22211 downloaded. These messages include the following fields:
22215 The name of the section.
22217 The size of the section.
22219 The size of the overall executable to download.
22223 At the end, a summary is printed.
22225 @subsubheading @value{GDBN} Command
22227 The corresponding @value{GDBN} command is @samp{load}.
22229 @subsubheading Example
22231 Note: each status message appears on a single line. Here the messages
22232 have been broken down so that they can fit onto a page.
22237 +download,@{section=".text",section-size="6668",total-size="9880"@}
22238 +download,@{section=".text",section-sent="512",section-size="6668",
22239 total-sent="512",total-size="9880"@}
22240 +download,@{section=".text",section-sent="1024",section-size="6668",
22241 total-sent="1024",total-size="9880"@}
22242 +download,@{section=".text",section-sent="1536",section-size="6668",
22243 total-sent="1536",total-size="9880"@}
22244 +download,@{section=".text",section-sent="2048",section-size="6668",
22245 total-sent="2048",total-size="9880"@}
22246 +download,@{section=".text",section-sent="2560",section-size="6668",
22247 total-sent="2560",total-size="9880"@}
22248 +download,@{section=".text",section-sent="3072",section-size="6668",
22249 total-sent="3072",total-size="9880"@}
22250 +download,@{section=".text",section-sent="3584",section-size="6668",
22251 total-sent="3584",total-size="9880"@}
22252 +download,@{section=".text",section-sent="4096",section-size="6668",
22253 total-sent="4096",total-size="9880"@}
22254 +download,@{section=".text",section-sent="4608",section-size="6668",
22255 total-sent="4608",total-size="9880"@}
22256 +download,@{section=".text",section-sent="5120",section-size="6668",
22257 total-sent="5120",total-size="9880"@}
22258 +download,@{section=".text",section-sent="5632",section-size="6668",
22259 total-sent="5632",total-size="9880"@}
22260 +download,@{section=".text",section-sent="6144",section-size="6668",
22261 total-sent="6144",total-size="9880"@}
22262 +download,@{section=".text",section-sent="6656",section-size="6668",
22263 total-sent="6656",total-size="9880"@}
22264 +download,@{section=".init",section-size="28",total-size="9880"@}
22265 +download,@{section=".fini",section-size="28",total-size="9880"@}
22266 +download,@{section=".data",section-size="3156",total-size="9880"@}
22267 +download,@{section=".data",section-sent="512",section-size="3156",
22268 total-sent="7236",total-size="9880"@}
22269 +download,@{section=".data",section-sent="1024",section-size="3156",
22270 total-sent="7748",total-size="9880"@}
22271 +download,@{section=".data",section-sent="1536",section-size="3156",
22272 total-sent="8260",total-size="9880"@}
22273 +download,@{section=".data",section-sent="2048",section-size="3156",
22274 total-sent="8772",total-size="9880"@}
22275 +download,@{section=".data",section-sent="2560",section-size="3156",
22276 total-sent="9284",total-size="9880"@}
22277 +download,@{section=".data",section-sent="3072",section-size="3156",
22278 total-sent="9796",total-size="9880"@}
22279 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
22285 @subheading The @code{-target-exec-status} Command
22286 @findex -target-exec-status
22288 @subsubheading Synopsis
22291 -target-exec-status
22294 Provide information on the state of the target (whether it is running or
22295 not, for instance).
22297 @subsubheading @value{GDBN} Command
22299 There's no equivalent @value{GDBN} command.
22301 @subsubheading Example
22305 @subheading The @code{-target-list-available-targets} Command
22306 @findex -target-list-available-targets
22308 @subsubheading Synopsis
22311 -target-list-available-targets
22314 List the possible targets to connect to.
22316 @subsubheading @value{GDBN} Command
22318 The corresponding @value{GDBN} command is @samp{help target}.
22320 @subsubheading Example
22324 @subheading The @code{-target-list-current-targets} Command
22325 @findex -target-list-current-targets
22327 @subsubheading Synopsis
22330 -target-list-current-targets
22333 Describe the current target.
22335 @subsubheading @value{GDBN} Command
22337 The corresponding information is printed by @samp{info file} (among
22340 @subsubheading Example
22344 @subheading The @code{-target-list-parameters} Command
22345 @findex -target-list-parameters
22347 @subsubheading Synopsis
22350 -target-list-parameters
22355 @subsubheading @value{GDBN} Command
22359 @subsubheading Example
22363 @subheading The @code{-target-select} Command
22364 @findex -target-select
22366 @subsubheading Synopsis
22369 -target-select @var{type} @var{parameters @dots{}}
22372 Connect @value{GDBN} to the remote target. This command takes two args:
22376 The type of target, for instance @samp{remote}, etc.
22377 @item @var{parameters}
22378 Device names, host names and the like. @xref{Target Commands, ,
22379 Commands for Managing Targets}, for more details.
22382 The output is a connection notification, followed by the address at
22383 which the target program is, in the following form:
22386 ^connected,addr="@var{address}",func="@var{function name}",
22387 args=[@var{arg list}]
22390 @subsubheading @value{GDBN} Command
22392 The corresponding @value{GDBN} command is @samp{target}.
22394 @subsubheading Example
22398 -target-select remote /dev/ttya
22399 ^connected,addr="0xfe00a300",func="??",args=[]
22403 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22404 @node GDB/MI File Transfer Commands
22405 @section @sc{gdb/mi} File Transfer Commands
22408 @subheading The @code{-target-file-put} Command
22409 @findex -target-file-put
22411 @subsubheading Synopsis
22414 -target-file-put @var{hostfile} @var{targetfile}
22417 Copy file @var{hostfile} from the host system (the machine running
22418 @value{GDBN}) to @var{targetfile} on the target system.
22420 @subsubheading @value{GDBN} Command
22422 The corresponding @value{GDBN} command is @samp{remote put}.
22424 @subsubheading Example
22428 -target-file-put localfile remotefile
22434 @subheading The @code{-target-file-get} Command
22435 @findex -target-file-get
22437 @subsubheading Synopsis
22440 -target-file-get @var{targetfile} @var{hostfile}
22443 Copy file @var{targetfile} from the target system to @var{hostfile}
22444 on the host system.
22446 @subsubheading @value{GDBN} Command
22448 The corresponding @value{GDBN} command is @samp{remote get}.
22450 @subsubheading Example
22454 -target-file-get remotefile localfile
22460 @subheading The @code{-target-file-delete} Command
22461 @findex -target-file-delete
22463 @subsubheading Synopsis
22466 -target-file-delete @var{targetfile}
22469 Delete @var{targetfile} from the target system.
22471 @subsubheading @value{GDBN} Command
22473 The corresponding @value{GDBN} command is @samp{remote delete}.
22475 @subsubheading Example
22479 -target-file-delete remotefile
22485 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22486 @node GDB/MI Miscellaneous Commands
22487 @section Miscellaneous @sc{gdb/mi} Commands
22489 @c @subheading -gdb-complete
22491 @subheading The @code{-gdb-exit} Command
22494 @subsubheading Synopsis
22500 Exit @value{GDBN} immediately.
22502 @subsubheading @value{GDBN} Command
22504 Approximately corresponds to @samp{quit}.
22506 @subsubheading Example
22515 @subheading The @code{-exec-abort} Command
22516 @findex -exec-abort
22518 @subsubheading Synopsis
22524 Kill the inferior running program.
22526 @subsubheading @value{GDBN} Command
22528 The corresponding @value{GDBN} command is @samp{kill}.
22530 @subsubheading Example
22534 @subheading The @code{-gdb-set} Command
22537 @subsubheading Synopsis
22543 Set an internal @value{GDBN} variable.
22544 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
22546 @subsubheading @value{GDBN} Command
22548 The corresponding @value{GDBN} command is @samp{set}.
22550 @subsubheading Example
22560 @subheading The @code{-gdb-show} Command
22563 @subsubheading Synopsis
22569 Show the current value of a @value{GDBN} variable.
22571 @subsubheading @value{GDBN} Command
22573 The corresponding @value{GDBN} command is @samp{show}.
22575 @subsubheading Example
22584 @c @subheading -gdb-source
22587 @subheading The @code{-gdb-version} Command
22588 @findex -gdb-version
22590 @subsubheading Synopsis
22596 Show version information for @value{GDBN}. Used mostly in testing.
22598 @subsubheading @value{GDBN} Command
22600 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
22601 default shows this information when you start an interactive session.
22603 @subsubheading Example
22605 @c This example modifies the actual output from GDB to avoid overfull
22611 ~Copyright 2000 Free Software Foundation, Inc.
22612 ~GDB is free software, covered by the GNU General Public License, and
22613 ~you are welcome to change it and/or distribute copies of it under
22614 ~ certain conditions.
22615 ~Type "show copying" to see the conditions.
22616 ~There is absolutely no warranty for GDB. Type "show warranty" for
22618 ~This GDB was configured as
22619 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
22624 @subheading The @code{-list-features} Command
22625 @findex -list-features
22627 Returns a list of particular features of the MI protocol that
22628 this version of gdb implements. A feature can be a command,
22629 or a new field in an output of some command, or even an
22630 important bugfix. While a frontend can sometimes detect presence
22631 of a feature at runtime, it is easier to perform detection at debugger
22634 The command returns a list of strings, with each string naming an
22635 available feature. Each returned string is just a name, it does not
22636 have any internal structure. The list of possible feature names
22642 (gdb) -list-features
22643 ^done,result=["feature1","feature2"]
22646 The current list of features is:
22649 @item frozen-varobjs
22650 Indicates presence of the @code{-var-set-frozen} command, as well
22651 as possible presense of the @code{frozen} field in the output
22652 of @code{-varobj-create}.
22653 @item pending-breakpoints
22654 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
22656 Indicates presence of the @code{-thread-info} command.
22660 @subheading The @code{-list-target-features} Command
22661 @findex -list-target-features
22663 Returns a list of particular features that are supported by the
22664 target. Those features affect the permitted MI commands, but
22665 unlike the features reported by the @code{-list-features} command, the
22666 features depend on which target GDB is using at the moment. Whenever
22667 a target can change, due to commands such as @code{-target-select},
22668 @code{-target-attach} or @code{-exec-run}, the list of target features
22669 may change, and the frontend should obtain it again.
22673 (gdb) -list-features
22674 ^done,result=["async"]
22677 The current list of features is:
22681 Indicates that the target is capable of asynchronous command
22682 execution, which means that @value{GDBN} will accept further commands
22683 while the target is running.
22688 @subheading The @code{-interpreter-exec} Command
22689 @findex -interpreter-exec
22691 @subheading Synopsis
22694 -interpreter-exec @var{interpreter} @var{command}
22696 @anchor{-interpreter-exec}
22698 Execute the specified @var{command} in the given @var{interpreter}.
22700 @subheading @value{GDBN} Command
22702 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
22704 @subheading Example
22708 -interpreter-exec console "break main"
22709 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
22710 &"During symbol reading, bad structure-type format.\n"
22711 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
22716 @subheading The @code{-inferior-tty-set} Command
22717 @findex -inferior-tty-set
22719 @subheading Synopsis
22722 -inferior-tty-set /dev/pts/1
22725 Set terminal for future runs of the program being debugged.
22727 @subheading @value{GDBN} Command
22729 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
22731 @subheading Example
22735 -inferior-tty-set /dev/pts/1
22740 @subheading The @code{-inferior-tty-show} Command
22741 @findex -inferior-tty-show
22743 @subheading Synopsis
22749 Show terminal for future runs of program being debugged.
22751 @subheading @value{GDBN} Command
22753 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
22755 @subheading Example
22759 -inferior-tty-set /dev/pts/1
22763 ^done,inferior_tty_terminal="/dev/pts/1"
22767 @subheading The @code{-enable-timings} Command
22768 @findex -enable-timings
22770 @subheading Synopsis
22773 -enable-timings [yes | no]
22776 Toggle the printing of the wallclock, user and system times for an MI
22777 command as a field in its output. This command is to help frontend
22778 developers optimize the performance of their code. No argument is
22779 equivalent to @samp{yes}.
22781 @subheading @value{GDBN} Command
22785 @subheading Example
22793 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22794 addr="0x080484ed",func="main",file="myprog.c",
22795 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
22796 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
22804 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22805 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
22806 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
22807 fullname="/home/nickrob/myprog.c",line="73"@}
22812 @chapter @value{GDBN} Annotations
22814 This chapter describes annotations in @value{GDBN}. Annotations were
22815 designed to interface @value{GDBN} to graphical user interfaces or other
22816 similar programs which want to interact with @value{GDBN} at a
22817 relatively high level.
22819 The annotation mechanism has largely been superseded by @sc{gdb/mi}
22823 This is Edition @value{EDITION}, @value{DATE}.
22827 * Annotations Overview:: What annotations are; the general syntax.
22828 * Server Prefix:: Issuing a command without affecting user state.
22829 * Prompting:: Annotations marking @value{GDBN}'s need for input.
22830 * Errors:: Annotations for error messages.
22831 * Invalidation:: Some annotations describe things now invalid.
22832 * Annotations for Running::
22833 Whether the program is running, how it stopped, etc.
22834 * Source Annotations:: Annotations describing source code.
22837 @node Annotations Overview
22838 @section What is an Annotation?
22839 @cindex annotations
22841 Annotations start with a newline character, two @samp{control-z}
22842 characters, and the name of the annotation. If there is no additional
22843 information associated with this annotation, the name of the annotation
22844 is followed immediately by a newline. If there is additional
22845 information, the name of the annotation is followed by a space, the
22846 additional information, and a newline. The additional information
22847 cannot contain newline characters.
22849 Any output not beginning with a newline and two @samp{control-z}
22850 characters denotes literal output from @value{GDBN}. Currently there is
22851 no need for @value{GDBN} to output a newline followed by two
22852 @samp{control-z} characters, but if there was such a need, the
22853 annotations could be extended with an @samp{escape} annotation which
22854 means those three characters as output.
22856 The annotation @var{level}, which is specified using the
22857 @option{--annotate} command line option (@pxref{Mode Options}), controls
22858 how much information @value{GDBN} prints together with its prompt,
22859 values of expressions, source lines, and other types of output. Level 0
22860 is for no annotations, level 1 is for use when @value{GDBN} is run as a
22861 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
22862 for programs that control @value{GDBN}, and level 2 annotations have
22863 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
22864 Interface, annotate, GDB's Obsolete Annotations}).
22867 @kindex set annotate
22868 @item set annotate @var{level}
22869 The @value{GDBN} command @code{set annotate} sets the level of
22870 annotations to the specified @var{level}.
22872 @item show annotate
22873 @kindex show annotate
22874 Show the current annotation level.
22877 This chapter describes level 3 annotations.
22879 A simple example of starting up @value{GDBN} with annotations is:
22882 $ @kbd{gdb --annotate=3}
22884 Copyright 2003 Free Software Foundation, Inc.
22885 GDB is free software, covered by the GNU General Public License,
22886 and you are welcome to change it and/or distribute copies of it
22887 under certain conditions.
22888 Type "show copying" to see the conditions.
22889 There is absolutely no warranty for GDB. Type "show warranty"
22891 This GDB was configured as "i386-pc-linux-gnu"
22902 Here @samp{quit} is input to @value{GDBN}; the rest is output from
22903 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
22904 denotes a @samp{control-z} character) are annotations; the rest is
22905 output from @value{GDBN}.
22907 @node Server Prefix
22908 @section The Server Prefix
22909 @cindex server prefix
22911 If you prefix a command with @samp{server } then it will not affect
22912 the command history, nor will it affect @value{GDBN}'s notion of which
22913 command to repeat if @key{RET} is pressed on a line by itself. This
22914 means that commands can be run behind a user's back by a front-end in
22915 a transparent manner.
22917 The server prefix does not affect the recording of values into the value
22918 history; to print a value without recording it into the value history,
22919 use the @code{output} command instead of the @code{print} command.
22922 @section Annotation for @value{GDBN} Input
22924 @cindex annotations for prompts
22925 When @value{GDBN} prompts for input, it annotates this fact so it is possible
22926 to know when to send output, when the output from a given command is
22929 Different kinds of input each have a different @dfn{input type}. Each
22930 input type has three annotations: a @code{pre-} annotation, which
22931 denotes the beginning of any prompt which is being output, a plain
22932 annotation, which denotes the end of the prompt, and then a @code{post-}
22933 annotation which denotes the end of any echo which may (or may not) be
22934 associated with the input. For example, the @code{prompt} input type
22935 features the following annotations:
22943 The input types are
22946 @findex pre-prompt annotation
22947 @findex prompt annotation
22948 @findex post-prompt annotation
22950 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
22952 @findex pre-commands annotation
22953 @findex commands annotation
22954 @findex post-commands annotation
22956 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
22957 command. The annotations are repeated for each command which is input.
22959 @findex pre-overload-choice annotation
22960 @findex overload-choice annotation
22961 @findex post-overload-choice annotation
22962 @item overload-choice
22963 When @value{GDBN} wants the user to select between various overloaded functions.
22965 @findex pre-query annotation
22966 @findex query annotation
22967 @findex post-query annotation
22969 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
22971 @findex pre-prompt-for-continue annotation
22972 @findex prompt-for-continue annotation
22973 @findex post-prompt-for-continue annotation
22974 @item prompt-for-continue
22975 When @value{GDBN} is asking the user to press return to continue. Note: Don't
22976 expect this to work well; instead use @code{set height 0} to disable
22977 prompting. This is because the counting of lines is buggy in the
22978 presence of annotations.
22983 @cindex annotations for errors, warnings and interrupts
22985 @findex quit annotation
22990 This annotation occurs right before @value{GDBN} responds to an interrupt.
22992 @findex error annotation
22997 This annotation occurs right before @value{GDBN} responds to an error.
22999 Quit and error annotations indicate that any annotations which @value{GDBN} was
23000 in the middle of may end abruptly. For example, if a
23001 @code{value-history-begin} annotation is followed by a @code{error}, one
23002 cannot expect to receive the matching @code{value-history-end}. One
23003 cannot expect not to receive it either, however; an error annotation
23004 does not necessarily mean that @value{GDBN} is immediately returning all the way
23007 @findex error-begin annotation
23008 A quit or error annotation may be preceded by
23014 Any output between that and the quit or error annotation is the error
23017 Warning messages are not yet annotated.
23018 @c If we want to change that, need to fix warning(), type_error(),
23019 @c range_error(), and possibly other places.
23022 @section Invalidation Notices
23024 @cindex annotations for invalidation messages
23025 The following annotations say that certain pieces of state may have
23029 @findex frames-invalid annotation
23030 @item ^Z^Zframes-invalid
23032 The frames (for example, output from the @code{backtrace} command) may
23035 @findex breakpoints-invalid annotation
23036 @item ^Z^Zbreakpoints-invalid
23038 The breakpoints may have changed. For example, the user just added or
23039 deleted a breakpoint.
23042 @node Annotations for Running
23043 @section Running the Program
23044 @cindex annotations for running programs
23046 @findex starting annotation
23047 @findex stopping annotation
23048 When the program starts executing due to a @value{GDBN} command such as
23049 @code{step} or @code{continue},
23055 is output. When the program stops,
23061 is output. Before the @code{stopped} annotation, a variety of
23062 annotations describe how the program stopped.
23065 @findex exited annotation
23066 @item ^Z^Zexited @var{exit-status}
23067 The program exited, and @var{exit-status} is the exit status (zero for
23068 successful exit, otherwise nonzero).
23070 @findex signalled annotation
23071 @findex signal-name annotation
23072 @findex signal-name-end annotation
23073 @findex signal-string annotation
23074 @findex signal-string-end annotation
23075 @item ^Z^Zsignalled
23076 The program exited with a signal. After the @code{^Z^Zsignalled}, the
23077 annotation continues:
23083 ^Z^Zsignal-name-end
23087 ^Z^Zsignal-string-end
23092 where @var{name} is the name of the signal, such as @code{SIGILL} or
23093 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
23094 as @code{Illegal Instruction} or @code{Segmentation fault}.
23095 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
23096 user's benefit and have no particular format.
23098 @findex signal annotation
23100 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
23101 just saying that the program received the signal, not that it was
23102 terminated with it.
23104 @findex breakpoint annotation
23105 @item ^Z^Zbreakpoint @var{number}
23106 The program hit breakpoint number @var{number}.
23108 @findex watchpoint annotation
23109 @item ^Z^Zwatchpoint @var{number}
23110 The program hit watchpoint number @var{number}.
23113 @node Source Annotations
23114 @section Displaying Source
23115 @cindex annotations for source display
23117 @findex source annotation
23118 The following annotation is used instead of displaying source code:
23121 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
23124 where @var{filename} is an absolute file name indicating which source
23125 file, @var{line} is the line number within that file (where 1 is the
23126 first line in the file), @var{character} is the character position
23127 within the file (where 0 is the first character in the file) (for most
23128 debug formats this will necessarily point to the beginning of a line),
23129 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
23130 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
23131 @var{addr} is the address in the target program associated with the
23132 source which is being displayed. @var{addr} is in the form @samp{0x}
23133 followed by one or more lowercase hex digits (note that this does not
23134 depend on the language).
23137 @chapter Reporting Bugs in @value{GDBN}
23138 @cindex bugs in @value{GDBN}
23139 @cindex reporting bugs in @value{GDBN}
23141 Your bug reports play an essential role in making @value{GDBN} reliable.
23143 Reporting a bug may help you by bringing a solution to your problem, or it
23144 may not. But in any case the principal function of a bug report is to help
23145 the entire community by making the next version of @value{GDBN} work better. Bug
23146 reports are your contribution to the maintenance of @value{GDBN}.
23148 In order for a bug report to serve its purpose, you must include the
23149 information that enables us to fix the bug.
23152 * Bug Criteria:: Have you found a bug?
23153 * Bug Reporting:: How to report bugs
23157 @section Have You Found a Bug?
23158 @cindex bug criteria
23160 If you are not sure whether you have found a bug, here are some guidelines:
23163 @cindex fatal signal
23164 @cindex debugger crash
23165 @cindex crash of debugger
23167 If the debugger gets a fatal signal, for any input whatever, that is a
23168 @value{GDBN} bug. Reliable debuggers never crash.
23170 @cindex error on valid input
23172 If @value{GDBN} produces an error message for valid input, that is a
23173 bug. (Note that if you're cross debugging, the problem may also be
23174 somewhere in the connection to the target.)
23176 @cindex invalid input
23178 If @value{GDBN} does not produce an error message for invalid input,
23179 that is a bug. However, you should note that your idea of
23180 ``invalid input'' might be our idea of ``an extension'' or ``support
23181 for traditional practice''.
23184 If you are an experienced user of debugging tools, your suggestions
23185 for improvement of @value{GDBN} are welcome in any case.
23188 @node Bug Reporting
23189 @section How to Report Bugs
23190 @cindex bug reports
23191 @cindex @value{GDBN} bugs, reporting
23193 A number of companies and individuals offer support for @sc{gnu} products.
23194 If you obtained @value{GDBN} from a support organization, we recommend you
23195 contact that organization first.
23197 You can find contact information for many support companies and
23198 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
23200 @c should add a web page ref...
23203 @ifset BUGURL_DEFAULT
23204 In any event, we also recommend that you submit bug reports for
23205 @value{GDBN}. The preferred method is to submit them directly using
23206 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
23207 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
23210 @strong{Do not send bug reports to @samp{info-gdb}, or to
23211 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
23212 not want to receive bug reports. Those that do have arranged to receive
23215 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
23216 serves as a repeater. The mailing list and the newsgroup carry exactly
23217 the same messages. Often people think of posting bug reports to the
23218 newsgroup instead of mailing them. This appears to work, but it has one
23219 problem which can be crucial: a newsgroup posting often lacks a mail
23220 path back to the sender. Thus, if we need to ask for more information,
23221 we may be unable to reach you. For this reason, it is better to send
23222 bug reports to the mailing list.
23224 @ifclear BUGURL_DEFAULT
23225 In any event, we also recommend that you submit bug reports for
23226 @value{GDBN} to @value{BUGURL}.
23230 The fundamental principle of reporting bugs usefully is this:
23231 @strong{report all the facts}. If you are not sure whether to state a
23232 fact or leave it out, state it!
23234 Often people omit facts because they think they know what causes the
23235 problem and assume that some details do not matter. Thus, you might
23236 assume that the name of the variable you use in an example does not matter.
23237 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
23238 stray memory reference which happens to fetch from the location where that
23239 name is stored in memory; perhaps, if the name were different, the contents
23240 of that location would fool the debugger into doing the right thing despite
23241 the bug. Play it safe and give a specific, complete example. That is the
23242 easiest thing for you to do, and the most helpful.
23244 Keep in mind that the purpose of a bug report is to enable us to fix the
23245 bug. It may be that the bug has been reported previously, but neither
23246 you nor we can know that unless your bug report is complete and
23249 Sometimes people give a few sketchy facts and ask, ``Does this ring a
23250 bell?'' Those bug reports are useless, and we urge everyone to
23251 @emph{refuse to respond to them} except to chide the sender to report
23254 To enable us to fix the bug, you should include all these things:
23258 The version of @value{GDBN}. @value{GDBN} announces it if you start
23259 with no arguments; you can also print it at any time using @code{show
23262 Without this, we will not know whether there is any point in looking for
23263 the bug in the current version of @value{GDBN}.
23266 The type of machine you are using, and the operating system name and
23270 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
23271 ``@value{GCC}--2.8.1''.
23274 What compiler (and its version) was used to compile the program you are
23275 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
23276 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
23277 to get this information; for other compilers, see the documentation for
23281 The command arguments you gave the compiler to compile your example and
23282 observe the bug. For example, did you use @samp{-O}? To guarantee
23283 you will not omit something important, list them all. A copy of the
23284 Makefile (or the output from make) is sufficient.
23286 If we were to try to guess the arguments, we would probably guess wrong
23287 and then we might not encounter the bug.
23290 A complete input script, and all necessary source files, that will
23294 A description of what behavior you observe that you believe is
23295 incorrect. For example, ``It gets a fatal signal.''
23297 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
23298 will certainly notice it. But if the bug is incorrect output, we might
23299 not notice unless it is glaringly wrong. You might as well not give us
23300 a chance to make a mistake.
23302 Even if the problem you experience is a fatal signal, you should still
23303 say so explicitly. Suppose something strange is going on, such as, your
23304 copy of @value{GDBN} is out of synch, or you have encountered a bug in
23305 the C library on your system. (This has happened!) Your copy might
23306 crash and ours would not. If you told us to expect a crash, then when
23307 ours fails to crash, we would know that the bug was not happening for
23308 us. If you had not told us to expect a crash, then we would not be able
23309 to draw any conclusion from our observations.
23312 @cindex recording a session script
23313 To collect all this information, you can use a session recording program
23314 such as @command{script}, which is available on many Unix systems.
23315 Just run your @value{GDBN} session inside @command{script} and then
23316 include the @file{typescript} file with your bug report.
23318 Another way to record a @value{GDBN} session is to run @value{GDBN}
23319 inside Emacs and then save the entire buffer to a file.
23322 If you wish to suggest changes to the @value{GDBN} source, send us context
23323 diffs. If you even discuss something in the @value{GDBN} source, refer to
23324 it by context, not by line number.
23326 The line numbers in our development sources will not match those in your
23327 sources. Your line numbers would convey no useful information to us.
23331 Here are some things that are not necessary:
23335 A description of the envelope of the bug.
23337 Often people who encounter a bug spend a lot of time investigating
23338 which changes to the input file will make the bug go away and which
23339 changes will not affect it.
23341 This is often time consuming and not very useful, because the way we
23342 will find the bug is by running a single example under the debugger
23343 with breakpoints, not by pure deduction from a series of examples.
23344 We recommend that you save your time for something else.
23346 Of course, if you can find a simpler example to report @emph{instead}
23347 of the original one, that is a convenience for us. Errors in the
23348 output will be easier to spot, running under the debugger will take
23349 less time, and so on.
23351 However, simplification is not vital; if you do not want to do this,
23352 report the bug anyway and send us the entire test case you used.
23355 A patch for the bug.
23357 A patch for the bug does help us if it is a good one. But do not omit
23358 the necessary information, such as the test case, on the assumption that
23359 a patch is all we need. We might see problems with your patch and decide
23360 to fix the problem another way, or we might not understand it at all.
23362 Sometimes with a program as complicated as @value{GDBN} it is very hard to
23363 construct an example that will make the program follow a certain path
23364 through the code. If you do not send us the example, we will not be able
23365 to construct one, so we will not be able to verify that the bug is fixed.
23367 And if we cannot understand what bug you are trying to fix, or why your
23368 patch should be an improvement, we will not install it. A test case will
23369 help us to understand.
23372 A guess about what the bug is or what it depends on.
23374 Such guesses are usually wrong. Even we cannot guess right about such
23375 things without first using the debugger to find the facts.
23378 @c The readline documentation is distributed with the readline code
23379 @c and consists of the two following files:
23381 @c inc-hist.texinfo
23382 @c Use -I with makeinfo to point to the appropriate directory,
23383 @c environment var TEXINPUTS with TeX.
23384 @include rluser.texi
23385 @include inc-hist.texinfo
23388 @node Formatting Documentation
23389 @appendix Formatting Documentation
23391 @cindex @value{GDBN} reference card
23392 @cindex reference card
23393 The @value{GDBN} 4 release includes an already-formatted reference card, ready
23394 for printing with PostScript or Ghostscript, in the @file{gdb}
23395 subdirectory of the main source directory@footnote{In
23396 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
23397 release.}. If you can use PostScript or Ghostscript with your printer,
23398 you can print the reference card immediately with @file{refcard.ps}.
23400 The release also includes the source for the reference card. You
23401 can format it, using @TeX{}, by typing:
23407 The @value{GDBN} reference card is designed to print in @dfn{landscape}
23408 mode on US ``letter'' size paper;
23409 that is, on a sheet 11 inches wide by 8.5 inches
23410 high. You will need to specify this form of printing as an option to
23411 your @sc{dvi} output program.
23413 @cindex documentation
23415 All the documentation for @value{GDBN} comes as part of the machine-readable
23416 distribution. The documentation is written in Texinfo format, which is
23417 a documentation system that uses a single source file to produce both
23418 on-line information and a printed manual. You can use one of the Info
23419 formatting commands to create the on-line version of the documentation
23420 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
23422 @value{GDBN} includes an already formatted copy of the on-line Info
23423 version of this manual in the @file{gdb} subdirectory. The main Info
23424 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
23425 subordinate files matching @samp{gdb.info*} in the same directory. If
23426 necessary, you can print out these files, or read them with any editor;
23427 but they are easier to read using the @code{info} subsystem in @sc{gnu}
23428 Emacs or the standalone @code{info} program, available as part of the
23429 @sc{gnu} Texinfo distribution.
23431 If you want to format these Info files yourself, you need one of the
23432 Info formatting programs, such as @code{texinfo-format-buffer} or
23435 If you have @code{makeinfo} installed, and are in the top level
23436 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
23437 version @value{GDBVN}), you can make the Info file by typing:
23444 If you want to typeset and print copies of this manual, you need @TeX{},
23445 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
23446 Texinfo definitions file.
23448 @TeX{} is a typesetting program; it does not print files directly, but
23449 produces output files called @sc{dvi} files. To print a typeset
23450 document, you need a program to print @sc{dvi} files. If your system
23451 has @TeX{} installed, chances are it has such a program. The precise
23452 command to use depends on your system; @kbd{lpr -d} is common; another
23453 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
23454 require a file name without any extension or a @samp{.dvi} extension.
23456 @TeX{} also requires a macro definitions file called
23457 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
23458 written in Texinfo format. On its own, @TeX{} cannot either read or
23459 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
23460 and is located in the @file{gdb-@var{version-number}/texinfo}
23463 If you have @TeX{} and a @sc{dvi} printer program installed, you can
23464 typeset and print this manual. First switch to the @file{gdb}
23465 subdirectory of the main source directory (for example, to
23466 @file{gdb-@value{GDBVN}/gdb}) and type:
23472 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
23474 @node Installing GDB
23475 @appendix Installing @value{GDBN}
23476 @cindex installation
23479 * Requirements:: Requirements for building @value{GDBN}
23480 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
23481 * Separate Objdir:: Compiling @value{GDBN} in another directory
23482 * Config Names:: Specifying names for hosts and targets
23483 * Configure Options:: Summary of options for configure
23487 @section Requirements for Building @value{GDBN}
23488 @cindex building @value{GDBN}, requirements for
23490 Building @value{GDBN} requires various tools and packages to be available.
23491 Other packages will be used only if they are found.
23493 @heading Tools/Packages Necessary for Building @value{GDBN}
23495 @item ISO C90 compiler
23496 @value{GDBN} is written in ISO C90. It should be buildable with any
23497 working C90 compiler, e.g.@: GCC.
23501 @heading Tools/Packages Optional for Building @value{GDBN}
23505 @value{GDBN} can use the Expat XML parsing library. This library may be
23506 included with your operating system distribution; if it is not, you
23507 can get the latest version from @url{http://expat.sourceforge.net}.
23508 The @file{configure} script will search for this library in several
23509 standard locations; if it is installed in an unusual path, you can
23510 use the @option{--with-libexpat-prefix} option to specify its location.
23516 Remote protocol memory maps (@pxref{Memory Map Format})
23518 Target descriptions (@pxref{Target Descriptions})
23520 Remote shared library lists (@pxref{Library List Format})
23522 MS-Windows shared libraries (@pxref{Shared Libraries})
23526 @cindex compressed debug sections
23527 @value{GDBN} will use the @samp{zlib} library, if available, to read
23528 compressed debug sections. Some linkers, such as GNU gold, are capable
23529 of producing binaries with compressed debug sections. If @value{GDBN}
23530 is compiled with @samp{zlib}, it will be able to read the debug
23531 information in such binaries.
23533 The @samp{zlib} library is likely included with your operating system
23534 distribution; if it is not, you can get the latest version from
23535 @url{http://zlib.net}.
23539 @node Running Configure
23540 @section Invoking the @value{GDBN} @file{configure} Script
23541 @cindex configuring @value{GDBN}
23542 @value{GDBN} comes with a @file{configure} script that automates the process
23543 of preparing @value{GDBN} for installation; you can then use @code{make} to
23544 build the @code{gdb} program.
23546 @c irrelevant in info file; it's as current as the code it lives with.
23547 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
23548 look at the @file{README} file in the sources; we may have improved the
23549 installation procedures since publishing this manual.}
23552 The @value{GDBN} distribution includes all the source code you need for
23553 @value{GDBN} in a single directory, whose name is usually composed by
23554 appending the version number to @samp{gdb}.
23556 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
23557 @file{gdb-@value{GDBVN}} directory. That directory contains:
23560 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
23561 script for configuring @value{GDBN} and all its supporting libraries
23563 @item gdb-@value{GDBVN}/gdb
23564 the source specific to @value{GDBN} itself
23566 @item gdb-@value{GDBVN}/bfd
23567 source for the Binary File Descriptor library
23569 @item gdb-@value{GDBVN}/include
23570 @sc{gnu} include files
23572 @item gdb-@value{GDBVN}/libiberty
23573 source for the @samp{-liberty} free software library
23575 @item gdb-@value{GDBVN}/opcodes
23576 source for the library of opcode tables and disassemblers
23578 @item gdb-@value{GDBVN}/readline
23579 source for the @sc{gnu} command-line interface
23581 @item gdb-@value{GDBVN}/glob
23582 source for the @sc{gnu} filename pattern-matching subroutine
23584 @item gdb-@value{GDBVN}/mmalloc
23585 source for the @sc{gnu} memory-mapped malloc package
23588 The simplest way to configure and build @value{GDBN} is to run @file{configure}
23589 from the @file{gdb-@var{version-number}} source directory, which in
23590 this example is the @file{gdb-@value{GDBVN}} directory.
23592 First switch to the @file{gdb-@var{version-number}} source directory
23593 if you are not already in it; then run @file{configure}. Pass the
23594 identifier for the platform on which @value{GDBN} will run as an
23600 cd gdb-@value{GDBVN}
23601 ./configure @var{host}
23606 where @var{host} is an identifier such as @samp{sun4} or
23607 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
23608 (You can often leave off @var{host}; @file{configure} tries to guess the
23609 correct value by examining your system.)
23611 Running @samp{configure @var{host}} and then running @code{make} builds the
23612 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
23613 libraries, then @code{gdb} itself. The configured source files, and the
23614 binaries, are left in the corresponding source directories.
23617 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
23618 system does not recognize this automatically when you run a different
23619 shell, you may need to run @code{sh} on it explicitly:
23622 sh configure @var{host}
23625 If you run @file{configure} from a directory that contains source
23626 directories for multiple libraries or programs, such as the
23627 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
23629 creates configuration files for every directory level underneath (unless
23630 you tell it not to, with the @samp{--norecursion} option).
23632 You should run the @file{configure} script from the top directory in the
23633 source tree, the @file{gdb-@var{version-number}} directory. If you run
23634 @file{configure} from one of the subdirectories, you will configure only
23635 that subdirectory. That is usually not what you want. In particular,
23636 if you run the first @file{configure} from the @file{gdb} subdirectory
23637 of the @file{gdb-@var{version-number}} directory, you will omit the
23638 configuration of @file{bfd}, @file{readline}, and other sibling
23639 directories of the @file{gdb} subdirectory. This leads to build errors
23640 about missing include files such as @file{bfd/bfd.h}.
23642 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
23643 However, you should make sure that the shell on your path (named by
23644 the @samp{SHELL} environment variable) is publicly readable. Remember
23645 that @value{GDBN} uses the shell to start your program---some systems refuse to
23646 let @value{GDBN} debug child processes whose programs are not readable.
23648 @node Separate Objdir
23649 @section Compiling @value{GDBN} in Another Directory
23651 If you want to run @value{GDBN} versions for several host or target machines,
23652 you need a different @code{gdb} compiled for each combination of
23653 host and target. @file{configure} is designed to make this easy by
23654 allowing you to generate each configuration in a separate subdirectory,
23655 rather than in the source directory. If your @code{make} program
23656 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
23657 @code{make} in each of these directories builds the @code{gdb}
23658 program specified there.
23660 To build @code{gdb} in a separate directory, run @file{configure}
23661 with the @samp{--srcdir} option to specify where to find the source.
23662 (You also need to specify a path to find @file{configure}
23663 itself from your working directory. If the path to @file{configure}
23664 would be the same as the argument to @samp{--srcdir}, you can leave out
23665 the @samp{--srcdir} option; it is assumed.)
23667 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
23668 separate directory for a Sun 4 like this:
23672 cd gdb-@value{GDBVN}
23675 ../gdb-@value{GDBVN}/configure sun4
23680 When @file{configure} builds a configuration using a remote source
23681 directory, it creates a tree for the binaries with the same structure
23682 (and using the same names) as the tree under the source directory. In
23683 the example, you'd find the Sun 4 library @file{libiberty.a} in the
23684 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
23685 @file{gdb-sun4/gdb}.
23687 Make sure that your path to the @file{configure} script has just one
23688 instance of @file{gdb} in it. If your path to @file{configure} looks
23689 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
23690 one subdirectory of @value{GDBN}, not the whole package. This leads to
23691 build errors about missing include files such as @file{bfd/bfd.h}.
23693 One popular reason to build several @value{GDBN} configurations in separate
23694 directories is to configure @value{GDBN} for cross-compiling (where
23695 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
23696 programs that run on another machine---the @dfn{target}).
23697 You specify a cross-debugging target by
23698 giving the @samp{--target=@var{target}} option to @file{configure}.
23700 When you run @code{make} to build a program or library, you must run
23701 it in a configured directory---whatever directory you were in when you
23702 called @file{configure} (or one of its subdirectories).
23704 The @code{Makefile} that @file{configure} generates in each source
23705 directory also runs recursively. If you type @code{make} in a source
23706 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
23707 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
23708 will build all the required libraries, and then build GDB.
23710 When you have multiple hosts or targets configured in separate
23711 directories, you can run @code{make} on them in parallel (for example,
23712 if they are NFS-mounted on each of the hosts); they will not interfere
23716 @section Specifying Names for Hosts and Targets
23718 The specifications used for hosts and targets in the @file{configure}
23719 script are based on a three-part naming scheme, but some short predefined
23720 aliases are also supported. The full naming scheme encodes three pieces
23721 of information in the following pattern:
23724 @var{architecture}-@var{vendor}-@var{os}
23727 For example, you can use the alias @code{sun4} as a @var{host} argument,
23728 or as the value for @var{target} in a @code{--target=@var{target}}
23729 option. The equivalent full name is @samp{sparc-sun-sunos4}.
23731 The @file{configure} script accompanying @value{GDBN} does not provide
23732 any query facility to list all supported host and target names or
23733 aliases. @file{configure} calls the Bourne shell script
23734 @code{config.sub} to map abbreviations to full names; you can read the
23735 script, if you wish, or you can use it to test your guesses on
23736 abbreviations---for example:
23739 % sh config.sub i386-linux
23741 % sh config.sub alpha-linux
23742 alpha-unknown-linux-gnu
23743 % sh config.sub hp9k700
23745 % sh config.sub sun4
23746 sparc-sun-sunos4.1.1
23747 % sh config.sub sun3
23748 m68k-sun-sunos4.1.1
23749 % sh config.sub i986v
23750 Invalid configuration `i986v': machine `i986v' not recognized
23754 @code{config.sub} is also distributed in the @value{GDBN} source
23755 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
23757 @node Configure Options
23758 @section @file{configure} Options
23760 Here is a summary of the @file{configure} options and arguments that
23761 are most often useful for building @value{GDBN}. @file{configure} also has
23762 several other options not listed here. @inforef{What Configure
23763 Does,,configure.info}, for a full explanation of @file{configure}.
23766 configure @r{[}--help@r{]}
23767 @r{[}--prefix=@var{dir}@r{]}
23768 @r{[}--exec-prefix=@var{dir}@r{]}
23769 @r{[}--srcdir=@var{dirname}@r{]}
23770 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
23771 @r{[}--target=@var{target}@r{]}
23776 You may introduce options with a single @samp{-} rather than
23777 @samp{--} if you prefer; but you may abbreviate option names if you use
23782 Display a quick summary of how to invoke @file{configure}.
23784 @item --prefix=@var{dir}
23785 Configure the source to install programs and files under directory
23788 @item --exec-prefix=@var{dir}
23789 Configure the source to install programs under directory
23792 @c avoid splitting the warning from the explanation:
23794 @item --srcdir=@var{dirname}
23795 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
23796 @code{make} that implements the @code{VPATH} feature.}@*
23797 Use this option to make configurations in directories separate from the
23798 @value{GDBN} source directories. Among other things, you can use this to
23799 build (or maintain) several configurations simultaneously, in separate
23800 directories. @file{configure} writes configuration-specific files in
23801 the current directory, but arranges for them to use the source in the
23802 directory @var{dirname}. @file{configure} creates directories under
23803 the working directory in parallel to the source directories below
23806 @item --norecursion
23807 Configure only the directory level where @file{configure} is executed; do not
23808 propagate configuration to subdirectories.
23810 @item --target=@var{target}
23811 Configure @value{GDBN} for cross-debugging programs running on the specified
23812 @var{target}. Without this option, @value{GDBN} is configured to debug
23813 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
23815 There is no convenient way to generate a list of all available targets.
23817 @item @var{host} @dots{}
23818 Configure @value{GDBN} to run on the specified @var{host}.
23820 There is no convenient way to generate a list of all available hosts.
23823 There are many other options available as well, but they are generally
23824 needed for special purposes only.
23826 @node Maintenance Commands
23827 @appendix Maintenance Commands
23828 @cindex maintenance commands
23829 @cindex internal commands
23831 In addition to commands intended for @value{GDBN} users, @value{GDBN}
23832 includes a number of commands intended for @value{GDBN} developers,
23833 that are not documented elsewhere in this manual. These commands are
23834 provided here for reference. (For commands that turn on debugging
23835 messages, see @ref{Debugging Output}.)
23838 @kindex maint agent
23839 @item maint agent @var{expression}
23840 Translate the given @var{expression} into remote agent bytecodes.
23841 This command is useful for debugging the Agent Expression mechanism
23842 (@pxref{Agent Expressions}).
23844 @kindex maint info breakpoints
23845 @item @anchor{maint info breakpoints}maint info breakpoints
23846 Using the same format as @samp{info breakpoints}, display both the
23847 breakpoints you've set explicitly, and those @value{GDBN} is using for
23848 internal purposes. Internal breakpoints are shown with negative
23849 breakpoint numbers. The type column identifies what kind of breakpoint
23854 Normal, explicitly set breakpoint.
23857 Normal, explicitly set watchpoint.
23860 Internal breakpoint, used to handle correctly stepping through
23861 @code{longjmp} calls.
23863 @item longjmp resume
23864 Internal breakpoint at the target of a @code{longjmp}.
23867 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
23870 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
23873 Shared library events.
23877 @kindex maint set can-use-displaced-stepping
23878 @kindex maint show can-use-displaced-stepping
23879 @cindex displaced stepping support
23880 @cindex out-of-line single-stepping
23881 @item maint set can-use-displaced-stepping
23882 @itemx maint show can-use-displaced-stepping
23883 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
23884 if the target supports it. The default is on. Displaced stepping is
23885 a way to single-step over breakpoints without removing them from the
23886 inferior, by executing an out-of-line copy of the instruction that was
23887 originally at the breakpoint location. It is also known as
23888 out-of-line single-stepping.
23890 @kindex maint check-symtabs
23891 @item maint check-symtabs
23892 Check the consistency of psymtabs and symtabs.
23894 @kindex maint cplus first_component
23895 @item maint cplus first_component @var{name}
23896 Print the first C@t{++} class/namespace component of @var{name}.
23898 @kindex maint cplus namespace
23899 @item maint cplus namespace
23900 Print the list of possible C@t{++} namespaces.
23902 @kindex maint demangle
23903 @item maint demangle @var{name}
23904 Demangle a C@t{++} or Objective-C mangled @var{name}.
23906 @kindex maint deprecate
23907 @kindex maint undeprecate
23908 @cindex deprecated commands
23909 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
23910 @itemx maint undeprecate @var{command}
23911 Deprecate or undeprecate the named @var{command}. Deprecated commands
23912 cause @value{GDBN} to issue a warning when you use them. The optional
23913 argument @var{replacement} says which newer command should be used in
23914 favor of the deprecated one; if it is given, @value{GDBN} will mention
23915 the replacement as part of the warning.
23917 @kindex maint dump-me
23918 @item maint dump-me
23919 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
23920 Cause a fatal signal in the debugger and force it to dump its core.
23921 This is supported only on systems which support aborting a program
23922 with the @code{SIGQUIT} signal.
23924 @kindex maint internal-error
23925 @kindex maint internal-warning
23926 @item maint internal-error @r{[}@var{message-text}@r{]}
23927 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
23928 Cause @value{GDBN} to call the internal function @code{internal_error}
23929 or @code{internal_warning} and hence behave as though an internal error
23930 or internal warning has been detected. In addition to reporting the
23931 internal problem, these functions give the user the opportunity to
23932 either quit @value{GDBN} or create a core file of the current
23933 @value{GDBN} session.
23935 These commands take an optional parameter @var{message-text} that is
23936 used as the text of the error or warning message.
23938 Here's an example of using @code{internal-error}:
23941 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
23942 @dots{}/maint.c:121: internal-error: testing, 1, 2
23943 A problem internal to GDB has been detected. Further
23944 debugging may prove unreliable.
23945 Quit this debugging session? (y or n) @kbd{n}
23946 Create a core file? (y or n) @kbd{n}
23950 @kindex maint packet
23951 @item maint packet @var{text}
23952 If @value{GDBN} is talking to an inferior via the serial protocol,
23953 then this command sends the string @var{text} to the inferior, and
23954 displays the response packet. @value{GDBN} supplies the initial
23955 @samp{$} character, the terminating @samp{#} character, and the
23958 @kindex maint print architecture
23959 @item maint print architecture @r{[}@var{file}@r{]}
23960 Print the entire architecture configuration. The optional argument
23961 @var{file} names the file where the output goes.
23963 @kindex maint print c-tdesc
23964 @item maint print c-tdesc
23965 Print the current target description (@pxref{Target Descriptions}) as
23966 a C source file. The created source file can be used in @value{GDBN}
23967 when an XML parser is not available to parse the description.
23969 @kindex maint print dummy-frames
23970 @item maint print dummy-frames
23971 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
23974 (@value{GDBP}) @kbd{b add}
23976 (@value{GDBP}) @kbd{print add(2,3)}
23977 Breakpoint 2, add (a=2, b=3) at @dots{}
23979 The program being debugged stopped while in a function called from GDB.
23981 (@value{GDBP}) @kbd{maint print dummy-frames}
23982 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
23983 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
23984 call_lo=0x01014000 call_hi=0x01014001
23988 Takes an optional file parameter.
23990 @kindex maint print registers
23991 @kindex maint print raw-registers
23992 @kindex maint print cooked-registers
23993 @kindex maint print register-groups
23994 @item maint print registers @r{[}@var{file}@r{]}
23995 @itemx maint print raw-registers @r{[}@var{file}@r{]}
23996 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
23997 @itemx maint print register-groups @r{[}@var{file}@r{]}
23998 Print @value{GDBN}'s internal register data structures.
24000 The command @code{maint print raw-registers} includes the contents of
24001 the raw register cache; the command @code{maint print cooked-registers}
24002 includes the (cooked) value of all registers; and the command
24003 @code{maint print register-groups} includes the groups that each
24004 register is a member of. @xref{Registers,, Registers, gdbint,
24005 @value{GDBN} Internals}.
24007 These commands take an optional parameter, a file name to which to
24008 write the information.
24010 @kindex maint print reggroups
24011 @item maint print reggroups @r{[}@var{file}@r{]}
24012 Print @value{GDBN}'s internal register group data structures. The
24013 optional argument @var{file} tells to what file to write the
24016 The register groups info looks like this:
24019 (@value{GDBP}) @kbd{maint print reggroups}
24032 This command forces @value{GDBN} to flush its internal register cache.
24034 @kindex maint print objfiles
24035 @cindex info for known object files
24036 @item maint print objfiles
24037 Print a dump of all known object files. For each object file, this
24038 command prints its name, address in memory, and all of its psymtabs
24041 @kindex maint print statistics
24042 @cindex bcache statistics
24043 @item maint print statistics
24044 This command prints, for each object file in the program, various data
24045 about that object file followed by the byte cache (@dfn{bcache})
24046 statistics for the object file. The objfile data includes the number
24047 of minimal, partial, full, and stabs symbols, the number of types
24048 defined by the objfile, the number of as yet unexpanded psym tables,
24049 the number of line tables and string tables, and the amount of memory
24050 used by the various tables. The bcache statistics include the counts,
24051 sizes, and counts of duplicates of all and unique objects, max,
24052 average, and median entry size, total memory used and its overhead and
24053 savings, and various measures of the hash table size and chain
24056 @kindex maint print target-stack
24057 @cindex target stack description
24058 @item maint print target-stack
24059 A @dfn{target} is an interface between the debugger and a particular
24060 kind of file or process. Targets can be stacked in @dfn{strata},
24061 so that more than one target can potentially respond to a request.
24062 In particular, memory accesses will walk down the stack of targets
24063 until they find a target that is interested in handling that particular
24066 This command prints a short description of each layer that was pushed on
24067 the @dfn{target stack}, starting from the top layer down to the bottom one.
24069 @kindex maint print type
24070 @cindex type chain of a data type
24071 @item maint print type @var{expr}
24072 Print the type chain for a type specified by @var{expr}. The argument
24073 can be either a type name or a symbol. If it is a symbol, the type of
24074 that symbol is described. The type chain produced by this command is
24075 a recursive definition of the data type as stored in @value{GDBN}'s
24076 data structures, including its flags and contained types.
24078 @kindex maint set dwarf2 max-cache-age
24079 @kindex maint show dwarf2 max-cache-age
24080 @item maint set dwarf2 max-cache-age
24081 @itemx maint show dwarf2 max-cache-age
24082 Control the DWARF 2 compilation unit cache.
24084 @cindex DWARF 2 compilation units cache
24085 In object files with inter-compilation-unit references, such as those
24086 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
24087 reader needs to frequently refer to previously read compilation units.
24088 This setting controls how long a compilation unit will remain in the
24089 cache if it is not referenced. A higher limit means that cached
24090 compilation units will be stored in memory longer, and more total
24091 memory will be used. Setting it to zero disables caching, which will
24092 slow down @value{GDBN} startup, but reduce memory consumption.
24094 @kindex maint set profile
24095 @kindex maint show profile
24096 @cindex profiling GDB
24097 @item maint set profile
24098 @itemx maint show profile
24099 Control profiling of @value{GDBN}.
24101 Profiling will be disabled until you use the @samp{maint set profile}
24102 command to enable it. When you enable profiling, the system will begin
24103 collecting timing and execution count data; when you disable profiling or
24104 exit @value{GDBN}, the results will be written to a log file. Remember that
24105 if you use profiling, @value{GDBN} will overwrite the profiling log file
24106 (often called @file{gmon.out}). If you have a record of important profiling
24107 data in a @file{gmon.out} file, be sure to move it to a safe location.
24109 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
24110 compiled with the @samp{-pg} compiler option.
24112 @kindex maint set linux-async
24113 @kindex maint show linux-async
24114 @cindex asynchronous support
24115 @item maint set linux-async
24116 @itemx maint show linux-async
24117 Control the GNU/Linux native asynchronous support
24118 (@pxref{Background Execution}) of @value{GDBN}.
24120 GNU/Linux native asynchronous support will be disabled until you use
24121 the @samp{maint set linux-async} command to enable it.
24123 @kindex maint set remote-async
24124 @kindex maint show remote-async
24125 @cindex asynchronous support
24126 @item maint set remote-async
24127 @itemx maint show remote-async
24128 Control the remote asynchronous support
24129 (@pxref{Background Execution}) of @value{GDBN}.
24131 Remote asynchronous support will be disabled until you use
24132 the @samp{maint set remote-async} command to enable it.
24134 @kindex maint show-debug-regs
24135 @cindex x86 hardware debug registers
24136 @item maint show-debug-regs
24137 Control whether to show variables that mirror the x86 hardware debug
24138 registers. Use @code{ON} to enable, @code{OFF} to disable. If
24139 enabled, the debug registers values are shown when @value{GDBN} inserts or
24140 removes a hardware breakpoint or watchpoint, and when the inferior
24141 triggers a hardware-assisted breakpoint or watchpoint.
24143 @kindex maint space
24144 @cindex memory used by commands
24146 Control whether to display memory usage for each command. If set to a
24147 nonzero value, @value{GDBN} will display how much memory each command
24148 took, following the command's own output. This can also be requested
24149 by invoking @value{GDBN} with the @option{--statistics} command-line
24150 switch (@pxref{Mode Options}).
24153 @cindex time of command execution
24155 Control whether to display the execution time for each command. If
24156 set to a nonzero value, @value{GDBN} will display how much time it
24157 took to execute each command, following the command's own output.
24158 The time is not printed for the commands that run the target, since
24159 there's no mechanism currently to compute how much time was spend
24160 by @value{GDBN} and how much time was spend by the program been debugged.
24161 it's not possibly currently
24162 This can also be requested by invoking @value{GDBN} with the
24163 @option{--statistics} command-line switch (@pxref{Mode Options}).
24165 @kindex maint translate-address
24166 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
24167 Find the symbol stored at the location specified by the address
24168 @var{addr} and an optional section name @var{section}. If found,
24169 @value{GDBN} prints the name of the closest symbol and an offset from
24170 the symbol's location to the specified address. This is similar to
24171 the @code{info address} command (@pxref{Symbols}), except that this
24172 command also allows to find symbols in other sections.
24176 The following command is useful for non-interactive invocations of
24177 @value{GDBN}, such as in the test suite.
24180 @item set watchdog @var{nsec}
24181 @kindex set watchdog
24182 @cindex watchdog timer
24183 @cindex timeout for commands
24184 Set the maximum number of seconds @value{GDBN} will wait for the
24185 target operation to finish. If this time expires, @value{GDBN}
24186 reports and error and the command is aborted.
24188 @item show watchdog
24189 Show the current setting of the target wait timeout.
24192 @node Remote Protocol
24193 @appendix @value{GDBN} Remote Serial Protocol
24198 * Stop Reply Packets::
24199 * General Query Packets::
24200 * Register Packet Format::
24201 * Tracepoint Packets::
24202 * Host I/O Packets::
24204 * Packet Acknowledgment::
24206 * File-I/O Remote Protocol Extension::
24207 * Library List Format::
24208 * Memory Map Format::
24214 There may be occasions when you need to know something about the
24215 protocol---for example, if there is only one serial port to your target
24216 machine, you might want your program to do something special if it
24217 recognizes a packet meant for @value{GDBN}.
24219 In the examples below, @samp{->} and @samp{<-} are used to indicate
24220 transmitted and received data, respectively.
24222 @cindex protocol, @value{GDBN} remote serial
24223 @cindex serial protocol, @value{GDBN} remote
24224 @cindex remote serial protocol
24225 All @value{GDBN} commands and responses (other than acknowledgments) are
24226 sent as a @var{packet}. A @var{packet} is introduced with the character
24227 @samp{$}, the actual @var{packet-data}, and the terminating character
24228 @samp{#} followed by a two-digit @var{checksum}:
24231 @code{$}@var{packet-data}@code{#}@var{checksum}
24235 @cindex checksum, for @value{GDBN} remote
24237 The two-digit @var{checksum} is computed as the modulo 256 sum of all
24238 characters between the leading @samp{$} and the trailing @samp{#} (an
24239 eight bit unsigned checksum).
24241 Implementors should note that prior to @value{GDBN} 5.0 the protocol
24242 specification also included an optional two-digit @var{sequence-id}:
24245 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
24248 @cindex sequence-id, for @value{GDBN} remote
24250 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
24251 has never output @var{sequence-id}s. Stubs that handle packets added
24252 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
24254 When either the host or the target machine receives a packet, the first
24255 response expected is an acknowledgment: either @samp{+} (to indicate
24256 the package was received correctly) or @samp{-} (to request
24260 -> @code{$}@var{packet-data}@code{#}@var{checksum}
24265 The @samp{+}/@samp{-} acknowledgments can be disabled
24266 once a connection is established.
24267 @xref{Packet Acknowledgment}, for details.
24269 The host (@value{GDBN}) sends @var{command}s, and the target (the
24270 debugging stub incorporated in your program) sends a @var{response}. In
24271 the case of step and continue @var{command}s, the response is only sent
24272 when the operation has completed (the target has again stopped).
24274 @var{packet-data} consists of a sequence of characters with the
24275 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
24278 @cindex remote protocol, field separator
24279 Fields within the packet should be separated using @samp{,} @samp{;} or
24280 @samp{:}. Except where otherwise noted all numbers are represented in
24281 @sc{hex} with leading zeros suppressed.
24283 Implementors should note that prior to @value{GDBN} 5.0, the character
24284 @samp{:} could not appear as the third character in a packet (as it
24285 would potentially conflict with the @var{sequence-id}).
24287 @cindex remote protocol, binary data
24288 @anchor{Binary Data}
24289 Binary data in most packets is encoded either as two hexadecimal
24290 digits per byte of binary data. This allowed the traditional remote
24291 protocol to work over connections which were only seven-bit clean.
24292 Some packets designed more recently assume an eight-bit clean
24293 connection, and use a more efficient encoding to send and receive
24296 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
24297 as an escape character. Any escaped byte is transmitted as the escape
24298 character followed by the original character XORed with @code{0x20}.
24299 For example, the byte @code{0x7d} would be transmitted as the two
24300 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
24301 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
24302 @samp{@}}) must always be escaped. Responses sent by the stub
24303 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
24304 is not interpreted as the start of a run-length encoded sequence
24307 Response @var{data} can be run-length encoded to save space.
24308 Run-length encoding replaces runs of identical characters with one
24309 instance of the repeated character, followed by a @samp{*} and a
24310 repeat count. The repeat count is itself sent encoded, to avoid
24311 binary characters in @var{data}: a value of @var{n} is sent as
24312 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
24313 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
24314 code 32) for a repeat count of 3. (This is because run-length
24315 encoding starts to win for counts 3 or more.) Thus, for example,
24316 @samp{0* } is a run-length encoding of ``0000'': the space character
24317 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
24320 The printable characters @samp{#} and @samp{$} or with a numeric value
24321 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
24322 seven repeats (@samp{$}) can be expanded using a repeat count of only
24323 five (@samp{"}). For example, @samp{00000000} can be encoded as
24326 The error response returned for some packets includes a two character
24327 error number. That number is not well defined.
24329 @cindex empty response, for unsupported packets
24330 For any @var{command} not supported by the stub, an empty response
24331 (@samp{$#00}) should be returned. That way it is possible to extend the
24332 protocol. A newer @value{GDBN} can tell if a packet is supported based
24335 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
24336 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
24342 The following table provides a complete list of all currently defined
24343 @var{command}s and their corresponding response @var{data}.
24344 @xref{File-I/O Remote Protocol Extension}, for details about the File
24345 I/O extension of the remote protocol.
24347 Each packet's description has a template showing the packet's overall
24348 syntax, followed by an explanation of the packet's meaning. We
24349 include spaces in some of the templates for clarity; these are not
24350 part of the packet's syntax. No @value{GDBN} packet uses spaces to
24351 separate its components. For example, a template like @samp{foo
24352 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
24353 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
24354 @var{baz}. @value{GDBN} does not transmit a space character between the
24355 @samp{foo} and the @var{bar}, or between the @var{bar} and the
24358 Note that all packet forms beginning with an upper- or lower-case
24359 letter, other than those described here, are reserved for future use.
24361 Here are the packet descriptions.
24366 @cindex @samp{!} packet
24367 @anchor{extended mode}
24368 Enable extended mode. In extended mode, the remote server is made
24369 persistent. The @samp{R} packet is used to restart the program being
24375 The remote target both supports and has enabled extended mode.
24379 @cindex @samp{?} packet
24380 Indicate the reason the target halted. The reply is the same as for
24384 @xref{Stop Reply Packets}, for the reply specifications.
24386 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
24387 @cindex @samp{A} packet
24388 Initialized @code{argv[]} array passed into program. @var{arglen}
24389 specifies the number of bytes in the hex encoded byte stream
24390 @var{arg}. See @code{gdbserver} for more details.
24395 The arguments were set.
24401 @cindex @samp{b} packet
24402 (Don't use this packet; its behavior is not well-defined.)
24403 Change the serial line speed to @var{baud}.
24405 JTC: @emph{When does the transport layer state change? When it's
24406 received, or after the ACK is transmitted. In either case, there are
24407 problems if the command or the acknowledgment packet is dropped.}
24409 Stan: @emph{If people really wanted to add something like this, and get
24410 it working for the first time, they ought to modify ser-unix.c to send
24411 some kind of out-of-band message to a specially-setup stub and have the
24412 switch happen "in between" packets, so that from remote protocol's point
24413 of view, nothing actually happened.}
24415 @item B @var{addr},@var{mode}
24416 @cindex @samp{B} packet
24417 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
24418 breakpoint at @var{addr}.
24420 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
24421 (@pxref{insert breakpoint or watchpoint packet}).
24423 @item c @r{[}@var{addr}@r{]}
24424 @cindex @samp{c} packet
24425 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
24426 resume at current address.
24429 @xref{Stop Reply Packets}, for the reply specifications.
24431 @item C @var{sig}@r{[};@var{addr}@r{]}
24432 @cindex @samp{C} packet
24433 Continue with signal @var{sig} (hex signal number). If
24434 @samp{;@var{addr}} is omitted, resume at same address.
24437 @xref{Stop Reply Packets}, for the reply specifications.
24440 @cindex @samp{d} packet
24443 Don't use this packet; instead, define a general set packet
24444 (@pxref{General Query Packets}).
24447 @cindex @samp{D} packet
24448 Detach @value{GDBN} from the remote system. Sent to the remote target
24449 before @value{GDBN} disconnects via the @code{detach} command.
24459 @item F @var{RC},@var{EE},@var{CF};@var{XX}
24460 @cindex @samp{F} packet
24461 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
24462 This is part of the File-I/O protocol extension. @xref{File-I/O
24463 Remote Protocol Extension}, for the specification.
24466 @anchor{read registers packet}
24467 @cindex @samp{g} packet
24468 Read general registers.
24472 @item @var{XX@dots{}}
24473 Each byte of register data is described by two hex digits. The bytes
24474 with the register are transmitted in target byte order. The size of
24475 each register and their position within the @samp{g} packet are
24476 determined by the @value{GDBN} internal gdbarch functions
24477 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
24478 specification of several standard @samp{g} packets is specified below.
24483 @item G @var{XX@dots{}}
24484 @cindex @samp{G} packet
24485 Write general registers. @xref{read registers packet}, for a
24486 description of the @var{XX@dots{}} data.
24496 @item H @var{c} @var{t}
24497 @cindex @samp{H} packet
24498 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
24499 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
24500 should be @samp{c} for step and continue operations, @samp{g} for other
24501 operations. The thread designator @var{t} may be @samp{-1}, meaning all
24502 the threads, a thread number, or @samp{0} which means pick any thread.
24513 @c 'H': How restrictive (or permissive) is the thread model. If a
24514 @c thread is selected and stopped, are other threads allowed
24515 @c to continue to execute? As I mentioned above, I think the
24516 @c semantics of each command when a thread is selected must be
24517 @c described. For example:
24519 @c 'g': If the stub supports threads and a specific thread is
24520 @c selected, returns the register block from that thread;
24521 @c otherwise returns current registers.
24523 @c 'G' If the stub supports threads and a specific thread is
24524 @c selected, sets the registers of the register block of
24525 @c that thread; otherwise sets current registers.
24527 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
24528 @anchor{cycle step packet}
24529 @cindex @samp{i} packet
24530 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
24531 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
24532 step starting at that address.
24535 @cindex @samp{I} packet
24536 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
24540 @cindex @samp{k} packet
24543 FIXME: @emph{There is no description of how to operate when a specific
24544 thread context has been selected (i.e.@: does 'k' kill only that
24547 @item m @var{addr},@var{length}
24548 @cindex @samp{m} packet
24549 Read @var{length} bytes of memory starting at address @var{addr}.
24550 Note that @var{addr} may not be aligned to any particular boundary.
24552 The stub need not use any particular size or alignment when gathering
24553 data from memory for the response; even if @var{addr} is word-aligned
24554 and @var{length} is a multiple of the word size, the stub is free to
24555 use byte accesses, or not. For this reason, this packet may not be
24556 suitable for accessing memory-mapped I/O devices.
24557 @cindex alignment of remote memory accesses
24558 @cindex size of remote memory accesses
24559 @cindex memory, alignment and size of remote accesses
24563 @item @var{XX@dots{}}
24564 Memory contents; each byte is transmitted as a two-digit hexadecimal
24565 number. The reply may contain fewer bytes than requested if the
24566 server was able to read only part of the region of memory.
24571 @item M @var{addr},@var{length}:@var{XX@dots{}}
24572 @cindex @samp{M} packet
24573 Write @var{length} bytes of memory starting at address @var{addr}.
24574 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
24575 hexadecimal number.
24582 for an error (this includes the case where only part of the data was
24587 @cindex @samp{p} packet
24588 Read the value of register @var{n}; @var{n} is in hex.
24589 @xref{read registers packet}, for a description of how the returned
24590 register value is encoded.
24594 @item @var{XX@dots{}}
24595 the register's value
24599 Indicating an unrecognized @var{query}.
24602 @item P @var{n@dots{}}=@var{r@dots{}}
24603 @anchor{write register packet}
24604 @cindex @samp{P} packet
24605 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
24606 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
24607 digits for each byte in the register (target byte order).
24617 @item q @var{name} @var{params}@dots{}
24618 @itemx Q @var{name} @var{params}@dots{}
24619 @cindex @samp{q} packet
24620 @cindex @samp{Q} packet
24621 General query (@samp{q}) and set (@samp{Q}). These packets are
24622 described fully in @ref{General Query Packets}.
24625 @cindex @samp{r} packet
24626 Reset the entire system.
24628 Don't use this packet; use the @samp{R} packet instead.
24631 @cindex @samp{R} packet
24632 Restart the program being debugged. @var{XX}, while needed, is ignored.
24633 This packet is only available in extended mode (@pxref{extended mode}).
24635 The @samp{R} packet has no reply.
24637 @item s @r{[}@var{addr}@r{]}
24638 @cindex @samp{s} packet
24639 Single step. @var{addr} is the address at which to resume. If
24640 @var{addr} is omitted, resume at same address.
24643 @xref{Stop Reply Packets}, for the reply specifications.
24645 @item S @var{sig}@r{[};@var{addr}@r{]}
24646 @anchor{step with signal packet}
24647 @cindex @samp{S} packet
24648 Step with signal. This is analogous to the @samp{C} packet, but
24649 requests a single-step, rather than a normal resumption of execution.
24652 @xref{Stop Reply Packets}, for the reply specifications.
24654 @item t @var{addr}:@var{PP},@var{MM}
24655 @cindex @samp{t} packet
24656 Search backwards starting at address @var{addr} for a match with pattern
24657 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
24658 @var{addr} must be at least 3 digits.
24661 @cindex @samp{T} packet
24662 Find out if the thread XX is alive.
24667 thread is still alive
24673 Packets starting with @samp{v} are identified by a multi-letter name,
24674 up to the first @samp{;} or @samp{?} (or the end of the packet).
24676 @item vAttach;@var{pid}
24677 @cindex @samp{vAttach} packet
24678 Attach to a new process with the specified process ID. @var{pid} is a
24679 hexadecimal integer identifying the process. The attached process is
24682 This packet is only available in extended mode (@pxref{extended mode}).
24688 @item @r{Any stop packet}
24689 for success (@pxref{Stop Reply Packets})
24692 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
24693 @cindex @samp{vCont} packet
24694 Resume the inferior, specifying different actions for each thread.
24695 If an action is specified with no @var{tid}, then it is applied to any
24696 threads that don't have a specific action specified; if no default action is
24697 specified then other threads should remain stopped. Specifying multiple
24698 default actions is an error; specifying no actions is also an error.
24699 Thread IDs are specified in hexadecimal. Currently supported actions are:
24705 Continue with signal @var{sig}. @var{sig} should be two hex digits.
24709 Step with signal @var{sig}. @var{sig} should be two hex digits.
24712 The optional @var{addr} argument normally associated with these packets is
24713 not supported in @samp{vCont}.
24716 @xref{Stop Reply Packets}, for the reply specifications.
24719 @cindex @samp{vCont?} packet
24720 Request a list of actions supported by the @samp{vCont} packet.
24724 @item vCont@r{[};@var{action}@dots{}@r{]}
24725 The @samp{vCont} packet is supported. Each @var{action} is a supported
24726 command in the @samp{vCont} packet.
24728 The @samp{vCont} packet is not supported.
24731 @item vFile:@var{operation}:@var{parameter}@dots{}
24732 @cindex @samp{vFile} packet
24733 Perform a file operation on the target system. For details,
24734 see @ref{Host I/O Packets}.
24736 @item vFlashErase:@var{addr},@var{length}
24737 @cindex @samp{vFlashErase} packet
24738 Direct the stub to erase @var{length} bytes of flash starting at
24739 @var{addr}. The region may enclose any number of flash blocks, but
24740 its start and end must fall on block boundaries, as indicated by the
24741 flash block size appearing in the memory map (@pxref{Memory Map
24742 Format}). @value{GDBN} groups flash memory programming operations
24743 together, and sends a @samp{vFlashDone} request after each group; the
24744 stub is allowed to delay erase operation until the @samp{vFlashDone}
24745 packet is received.
24755 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
24756 @cindex @samp{vFlashWrite} packet
24757 Direct the stub to write data to flash address @var{addr}. The data
24758 is passed in binary form using the same encoding as for the @samp{X}
24759 packet (@pxref{Binary Data}). The memory ranges specified by
24760 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
24761 not overlap, and must appear in order of increasing addresses
24762 (although @samp{vFlashErase} packets for higher addresses may already
24763 have been received; the ordering is guaranteed only between
24764 @samp{vFlashWrite} packets). If a packet writes to an address that was
24765 neither erased by a preceding @samp{vFlashErase} packet nor by some other
24766 target-specific method, the results are unpredictable.
24774 for vFlashWrite addressing non-flash memory
24780 @cindex @samp{vFlashDone} packet
24781 Indicate to the stub that flash programming operation is finished.
24782 The stub is permitted to delay or batch the effects of a group of
24783 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
24784 @samp{vFlashDone} packet is received. The contents of the affected
24785 regions of flash memory are unpredictable until the @samp{vFlashDone}
24786 request is completed.
24788 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
24789 @cindex @samp{vRun} packet
24790 Run the program @var{filename}, passing it each @var{argument} on its
24791 command line. The file and arguments are hex-encoded strings. If
24792 @var{filename} is an empty string, the stub may use a default program
24793 (e.g.@: the last program run). The program is created in the stopped
24796 This packet is only available in extended mode (@pxref{extended mode}).
24802 @item @r{Any stop packet}
24803 for success (@pxref{Stop Reply Packets})
24806 @item X @var{addr},@var{length}:@var{XX@dots{}}
24808 @cindex @samp{X} packet
24809 Write data to memory, where the data is transmitted in binary.
24810 @var{addr} is address, @var{length} is number of bytes,
24811 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
24821 @item z @var{type},@var{addr},@var{length}
24822 @itemx Z @var{type},@var{addr},@var{length}
24823 @anchor{insert breakpoint or watchpoint packet}
24824 @cindex @samp{z} packet
24825 @cindex @samp{Z} packets
24826 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
24827 watchpoint starting at address @var{address} and covering the next
24828 @var{length} bytes.
24830 Each breakpoint and watchpoint packet @var{type} is documented
24833 @emph{Implementation notes: A remote target shall return an empty string
24834 for an unrecognized breakpoint or watchpoint packet @var{type}. A
24835 remote target shall support either both or neither of a given
24836 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
24837 avoid potential problems with duplicate packets, the operations should
24838 be implemented in an idempotent way.}
24840 @item z0,@var{addr},@var{length}
24841 @itemx Z0,@var{addr},@var{length}
24842 @cindex @samp{z0} packet
24843 @cindex @samp{Z0} packet
24844 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
24845 @var{addr} of size @var{length}.
24847 A memory breakpoint is implemented by replacing the instruction at
24848 @var{addr} with a software breakpoint or trap instruction. The
24849 @var{length} is used by targets that indicates the size of the
24850 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
24851 @sc{mips} can insert either a 2 or 4 byte breakpoint).
24853 @emph{Implementation note: It is possible for a target to copy or move
24854 code that contains memory breakpoints (e.g., when implementing
24855 overlays). The behavior of this packet, in the presence of such a
24856 target, is not defined.}
24868 @item z1,@var{addr},@var{length}
24869 @itemx Z1,@var{addr},@var{length}
24870 @cindex @samp{z1} packet
24871 @cindex @samp{Z1} packet
24872 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
24873 address @var{addr} of size @var{length}.
24875 A hardware breakpoint is implemented using a mechanism that is not
24876 dependant on being able to modify the target's memory.
24878 @emph{Implementation note: A hardware breakpoint is not affected by code
24891 @item z2,@var{addr},@var{length}
24892 @itemx Z2,@var{addr},@var{length}
24893 @cindex @samp{z2} packet
24894 @cindex @samp{Z2} packet
24895 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
24907 @item z3,@var{addr},@var{length}
24908 @itemx Z3,@var{addr},@var{length}
24909 @cindex @samp{z3} packet
24910 @cindex @samp{Z3} packet
24911 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
24923 @item z4,@var{addr},@var{length}
24924 @itemx Z4,@var{addr},@var{length}
24925 @cindex @samp{z4} packet
24926 @cindex @samp{Z4} packet
24927 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
24941 @node Stop Reply Packets
24942 @section Stop Reply Packets
24943 @cindex stop reply packets
24945 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
24946 receive any of the below as a reply. In the case of the @samp{C},
24947 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
24948 when the target halts. In the below the exact meaning of @dfn{signal
24949 number} is defined by the header @file{include/gdb/signals.h} in the
24950 @value{GDBN} source code.
24952 As in the description of request packets, we include spaces in the
24953 reply templates for clarity; these are not part of the reply packet's
24954 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
24960 The program received signal number @var{AA} (a two-digit hexadecimal
24961 number). This is equivalent to a @samp{T} response with no
24962 @var{n}:@var{r} pairs.
24964 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
24965 @cindex @samp{T} packet reply
24966 The program received signal number @var{AA} (a two-digit hexadecimal
24967 number). This is equivalent to an @samp{S} response, except that the
24968 @samp{@var{n}:@var{r}} pairs can carry values of important registers
24969 and other information directly in the stop reply packet, reducing
24970 round-trip latency. Single-step and breakpoint traps are reported
24971 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
24975 If @var{n} is a hexadecimal number, it is a register number, and the
24976 corresponding @var{r} gives that register's value. @var{r} is a
24977 series of bytes in target byte order, with each byte given by a
24978 two-digit hex number.
24981 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
24985 If @var{n} is a recognized @dfn{stop reason}, it describes a more
24986 specific event that stopped the target. The currently defined stop
24987 reasons are listed below. @var{aa} should be @samp{05}, the trap
24988 signal. At most one stop reason should be present.
24991 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
24992 and go on to the next; this allows us to extend the protocol in the
24996 The currently defined stop reasons are:
25002 The packet indicates a watchpoint hit, and @var{r} is the data address, in
25005 @cindex shared library events, remote reply
25007 The packet indicates that the loaded libraries have changed.
25008 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
25009 list of loaded libraries. @var{r} is ignored.
25013 The process exited, and @var{AA} is the exit status. This is only
25014 applicable to certain targets.
25017 The process terminated with signal @var{AA}.
25019 @item O @var{XX}@dots{}
25020 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
25021 written as the program's console output. This can happen at any time
25022 while the program is running and the debugger should continue to wait
25023 for @samp{W}, @samp{T}, etc.
25025 @item F @var{call-id},@var{parameter}@dots{}
25026 @var{call-id} is the identifier which says which host system call should
25027 be called. This is just the name of the function. Translation into the
25028 correct system call is only applicable as it's defined in @value{GDBN}.
25029 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
25032 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
25033 this very system call.
25035 The target replies with this packet when it expects @value{GDBN} to
25036 call a host system call on behalf of the target. @value{GDBN} replies
25037 with an appropriate @samp{F} packet and keeps up waiting for the next
25038 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
25039 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
25040 Protocol Extension}, for more details.
25044 @node General Query Packets
25045 @section General Query Packets
25046 @cindex remote query requests
25048 Packets starting with @samp{q} are @dfn{general query packets};
25049 packets starting with @samp{Q} are @dfn{general set packets}. General
25050 query and set packets are a semi-unified form for retrieving and
25051 sending information to and from the stub.
25053 The initial letter of a query or set packet is followed by a name
25054 indicating what sort of thing the packet applies to. For example,
25055 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
25056 definitions with the stub. These packet names follow some
25061 The name must not contain commas, colons or semicolons.
25063 Most @value{GDBN} query and set packets have a leading upper case
25066 The names of custom vendor packets should use a company prefix, in
25067 lower case, followed by a period. For example, packets designed at
25068 the Acme Corporation might begin with @samp{qacme.foo} (for querying
25069 foos) or @samp{Qacme.bar} (for setting bars).
25072 The name of a query or set packet should be separated from any
25073 parameters by a @samp{:}; the parameters themselves should be
25074 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
25075 full packet name, and check for a separator or the end of the packet,
25076 in case two packet names share a common prefix. New packets should not begin
25077 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
25078 packets predate these conventions, and have arguments without any terminator
25079 for the packet name; we suspect they are in widespread use in places that
25080 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
25081 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
25084 Like the descriptions of the other packets, each description here
25085 has a template showing the packet's overall syntax, followed by an
25086 explanation of the packet's meaning. We include spaces in some of the
25087 templates for clarity; these are not part of the packet's syntax. No
25088 @value{GDBN} packet uses spaces to separate its components.
25090 Here are the currently defined query and set packets:
25095 @cindex current thread, remote request
25096 @cindex @samp{qC} packet
25097 Return the current thread id.
25102 Where @var{pid} is an unsigned hexadecimal process id.
25103 @item @r{(anything else)}
25104 Any other reply implies the old pid.
25107 @item qCRC:@var{addr},@var{length}
25108 @cindex CRC of memory block, remote request
25109 @cindex @samp{qCRC} packet
25110 Compute the CRC checksum of a block of memory.
25114 An error (such as memory fault)
25115 @item C @var{crc32}
25116 The specified memory region's checksum is @var{crc32}.
25120 @itemx qsThreadInfo
25121 @cindex list active threads, remote request
25122 @cindex @samp{qfThreadInfo} packet
25123 @cindex @samp{qsThreadInfo} packet
25124 Obtain a list of all active thread ids from the target (OS). Since there
25125 may be too many active threads to fit into one reply packet, this query
25126 works iteratively: it may require more than one query/reply sequence to
25127 obtain the entire list of threads. The first query of the sequence will
25128 be the @samp{qfThreadInfo} query; subsequent queries in the
25129 sequence will be the @samp{qsThreadInfo} query.
25131 NOTE: This packet replaces the @samp{qL} query (see below).
25137 @item m @var{id},@var{id}@dots{}
25138 a comma-separated list of thread ids
25140 (lower case letter @samp{L}) denotes end of list.
25143 In response to each query, the target will reply with a list of one or
25144 more thread ids, in big-endian unsigned hex, separated by commas.
25145 @value{GDBN} will respond to each reply with a request for more thread
25146 ids (using the @samp{qs} form of the query), until the target responds
25147 with @samp{l} (lower-case el, for @dfn{last}).
25149 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
25150 @cindex get thread-local storage address, remote request
25151 @cindex @samp{qGetTLSAddr} packet
25152 Fetch the address associated with thread local storage specified
25153 by @var{thread-id}, @var{offset}, and @var{lm}.
25155 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
25156 thread for which to fetch the TLS address.
25158 @var{offset} is the (big endian, hex encoded) offset associated with the
25159 thread local variable. (This offset is obtained from the debug
25160 information associated with the variable.)
25162 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
25163 the load module associated with the thread local storage. For example,
25164 a @sc{gnu}/Linux system will pass the link map address of the shared
25165 object associated with the thread local storage under consideration.
25166 Other operating environments may choose to represent the load module
25167 differently, so the precise meaning of this parameter will vary.
25171 @item @var{XX}@dots{}
25172 Hex encoded (big endian) bytes representing the address of the thread
25173 local storage requested.
25176 An error occurred. @var{nn} are hex digits.
25179 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
25182 @item qL @var{startflag} @var{threadcount} @var{nextthread}
25183 Obtain thread information from RTOS. Where: @var{startflag} (one hex
25184 digit) is one to indicate the first query and zero to indicate a
25185 subsequent query; @var{threadcount} (two hex digits) is the maximum
25186 number of threads the response packet can contain; and @var{nextthread}
25187 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
25188 returned in the response as @var{argthread}.
25190 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
25194 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
25195 Where: @var{count} (two hex digits) is the number of threads being
25196 returned; @var{done} (one hex digit) is zero to indicate more threads
25197 and one indicates no further threads; @var{argthreadid} (eight hex
25198 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
25199 is a sequence of thread IDs from the target. @var{threadid} (eight hex
25200 digits). See @code{remote.c:parse_threadlist_response()}.
25204 @cindex section offsets, remote request
25205 @cindex @samp{qOffsets} packet
25206 Get section offsets that the target used when relocating the downloaded
25211 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
25212 Relocate the @code{Text} section by @var{xxx} from its original address.
25213 Relocate the @code{Data} section by @var{yyy} from its original address.
25214 If the object file format provides segment information (e.g.@: @sc{elf}
25215 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
25216 segments by the supplied offsets.
25218 @emph{Note: while a @code{Bss} offset may be included in the response,
25219 @value{GDBN} ignores this and instead applies the @code{Data} offset
25220 to the @code{Bss} section.}
25222 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
25223 Relocate the first segment of the object file, which conventionally
25224 contains program code, to a starting address of @var{xxx}. If
25225 @samp{DataSeg} is specified, relocate the second segment, which
25226 conventionally contains modifiable data, to a starting address of
25227 @var{yyy}. @value{GDBN} will report an error if the object file
25228 does not contain segment information, or does not contain at least
25229 as many segments as mentioned in the reply. Extra segments are
25230 kept at fixed offsets relative to the last relocated segment.
25233 @item qP @var{mode} @var{threadid}
25234 @cindex thread information, remote request
25235 @cindex @samp{qP} packet
25236 Returns information on @var{threadid}. Where: @var{mode} is a hex
25237 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
25239 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
25242 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
25244 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
25245 @cindex pass signals to inferior, remote request
25246 @cindex @samp{QPassSignals} packet
25247 @anchor{QPassSignals}
25248 Each listed @var{signal} should be passed directly to the inferior process.
25249 Signals are numbered identically to continue packets and stop replies
25250 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
25251 strictly greater than the previous item. These signals do not need to stop
25252 the inferior, or be reported to @value{GDBN}. All other signals should be
25253 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
25254 combine; any earlier @samp{QPassSignals} list is completely replaced by the
25255 new list. This packet improves performance when using @samp{handle
25256 @var{signal} nostop noprint pass}.
25261 The request succeeded.
25264 An error occurred. @var{nn} are hex digits.
25267 An empty reply indicates that @samp{QPassSignals} is not supported by
25271 Use of this packet is controlled by the @code{set remote pass-signals}
25272 command (@pxref{Remote Configuration, set remote pass-signals}).
25273 This packet is not probed by default; the remote stub must request it,
25274 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25276 @item qRcmd,@var{command}
25277 @cindex execute remote command, remote request
25278 @cindex @samp{qRcmd} packet
25279 @var{command} (hex encoded) is passed to the local interpreter for
25280 execution. Invalid commands should be reported using the output
25281 string. Before the final result packet, the target may also respond
25282 with a number of intermediate @samp{O@var{output}} console output
25283 packets. @emph{Implementors should note that providing access to a
25284 stubs's interpreter may have security implications}.
25289 A command response with no output.
25291 A command response with the hex encoded output string @var{OUTPUT}.
25293 Indicate a badly formed request.
25295 An empty reply indicates that @samp{qRcmd} is not recognized.
25298 (Note that the @code{qRcmd} packet's name is separated from the
25299 command by a @samp{,}, not a @samp{:}, contrary to the naming
25300 conventions above. Please don't use this packet as a model for new
25303 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
25304 @cindex searching memory, in remote debugging
25305 @cindex @samp{qSearch:memory} packet
25306 @anchor{qSearch memory}
25307 Search @var{length} bytes at @var{address} for @var{search-pattern}.
25308 @var{address} and @var{length} are encoded in hex.
25309 @var{search-pattern} is a sequence of bytes, hex encoded.
25314 The pattern was not found.
25316 The pattern was found at @var{address}.
25318 A badly formed request or an error was encountered while searching memory.
25320 An empty reply indicates that @samp{qSearch:memory} is not recognized.
25323 @item QStartNoAckMode
25324 @cindex @samp{QStartNoAckMode} packet
25325 @anchor{QStartNoAckMode}
25326 Request that the remote stub disable the normal @samp{+}/@samp{-}
25327 protocol acknowledgments (@pxref{Packet Acknowledgment}).
25332 The stub has switched to no-acknowledgment mode.
25333 @value{GDBN} acknowledges this reponse,
25334 but neither the stub nor @value{GDBN} shall send or expect further
25335 @samp{+}/@samp{-} acknowledgments in the current connection.
25337 An empty reply indicates that the stub does not support no-acknowledgment mode.
25340 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
25341 @cindex supported packets, remote query
25342 @cindex features of the remote protocol
25343 @cindex @samp{qSupported} packet
25344 @anchor{qSupported}
25345 Tell the remote stub about features supported by @value{GDBN}, and
25346 query the stub for features it supports. This packet allows
25347 @value{GDBN} and the remote stub to take advantage of each others'
25348 features. @samp{qSupported} also consolidates multiple feature probes
25349 at startup, to improve @value{GDBN} performance---a single larger
25350 packet performs better than multiple smaller probe packets on
25351 high-latency links. Some features may enable behavior which must not
25352 be on by default, e.g.@: because it would confuse older clients or
25353 stubs. Other features may describe packets which could be
25354 automatically probed for, but are not. These features must be
25355 reported before @value{GDBN} will use them. This ``default
25356 unsupported'' behavior is not appropriate for all packets, but it
25357 helps to keep the initial connection time under control with new
25358 versions of @value{GDBN} which support increasing numbers of packets.
25362 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
25363 The stub supports or does not support each returned @var{stubfeature},
25364 depending on the form of each @var{stubfeature} (see below for the
25367 An empty reply indicates that @samp{qSupported} is not recognized,
25368 or that no features needed to be reported to @value{GDBN}.
25371 The allowed forms for each feature (either a @var{gdbfeature} in the
25372 @samp{qSupported} packet, or a @var{stubfeature} in the response)
25376 @item @var{name}=@var{value}
25377 The remote protocol feature @var{name} is supported, and associated
25378 with the specified @var{value}. The format of @var{value} depends
25379 on the feature, but it must not include a semicolon.
25381 The remote protocol feature @var{name} is supported, and does not
25382 need an associated value.
25384 The remote protocol feature @var{name} is not supported.
25386 The remote protocol feature @var{name} may be supported, and
25387 @value{GDBN} should auto-detect support in some other way when it is
25388 needed. This form will not be used for @var{gdbfeature} notifications,
25389 but may be used for @var{stubfeature} responses.
25392 Whenever the stub receives a @samp{qSupported} request, the
25393 supplied set of @value{GDBN} features should override any previous
25394 request. This allows @value{GDBN} to put the stub in a known
25395 state, even if the stub had previously been communicating with
25396 a different version of @value{GDBN}.
25398 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
25399 are defined yet. Stubs should ignore any unknown values for
25400 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
25401 packet supports receiving packets of unlimited length (earlier
25402 versions of @value{GDBN} may reject overly long responses). Values
25403 for @var{gdbfeature} may be defined in the future to let the stub take
25404 advantage of new features in @value{GDBN}, e.g.@: incompatible
25405 improvements in the remote protocol---support for unlimited length
25406 responses would be a @var{gdbfeature} example, if it were not implied by
25407 the @samp{qSupported} query. The stub's reply should be independent
25408 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
25409 describes all the features it supports, and then the stub replies with
25410 all the features it supports.
25412 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
25413 responses, as long as each response uses one of the standard forms.
25415 Some features are flags. A stub which supports a flag feature
25416 should respond with a @samp{+} form response. Other features
25417 require values, and the stub should respond with an @samp{=}
25420 Each feature has a default value, which @value{GDBN} will use if
25421 @samp{qSupported} is not available or if the feature is not mentioned
25422 in the @samp{qSupported} response. The default values are fixed; a
25423 stub is free to omit any feature responses that match the defaults.
25425 Not all features can be probed, but for those which can, the probing
25426 mechanism is useful: in some cases, a stub's internal
25427 architecture may not allow the protocol layer to know some information
25428 about the underlying target in advance. This is especially common in
25429 stubs which may be configured for multiple targets.
25431 These are the currently defined stub features and their properties:
25433 @multitable @columnfractions 0.35 0.2 0.12 0.2
25434 @c NOTE: The first row should be @headitem, but we do not yet require
25435 @c a new enough version of Texinfo (4.7) to use @headitem.
25437 @tab Value Required
25441 @item @samp{PacketSize}
25446 @item @samp{qXfer:auxv:read}
25451 @item @samp{qXfer:features:read}
25456 @item @samp{qXfer:libraries:read}
25461 @item @samp{qXfer:memory-map:read}
25466 @item @samp{qXfer:spu:read}
25471 @item @samp{qXfer:spu:write}
25476 @item @samp{QPassSignals}
25481 @item @samp{QStartNoAckMode}
25488 These are the currently defined stub features, in more detail:
25491 @cindex packet size, remote protocol
25492 @item PacketSize=@var{bytes}
25493 The remote stub can accept packets up to at least @var{bytes} in
25494 length. @value{GDBN} will send packets up to this size for bulk
25495 transfers, and will never send larger packets. This is a limit on the
25496 data characters in the packet, including the frame and checksum.
25497 There is no trailing NUL byte in a remote protocol packet; if the stub
25498 stores packets in a NUL-terminated format, it should allow an extra
25499 byte in its buffer for the NUL. If this stub feature is not supported,
25500 @value{GDBN} guesses based on the size of the @samp{g} packet response.
25502 @item qXfer:auxv:read
25503 The remote stub understands the @samp{qXfer:auxv:read} packet
25504 (@pxref{qXfer auxiliary vector read}).
25506 @item qXfer:features:read
25507 The remote stub understands the @samp{qXfer:features:read} packet
25508 (@pxref{qXfer target description read}).
25510 @item qXfer:libraries:read
25511 The remote stub understands the @samp{qXfer:libraries:read} packet
25512 (@pxref{qXfer library list read}).
25514 @item qXfer:memory-map:read
25515 The remote stub understands the @samp{qXfer:memory-map:read} packet
25516 (@pxref{qXfer memory map read}).
25518 @item qXfer:spu:read
25519 The remote stub understands the @samp{qXfer:spu:read} packet
25520 (@pxref{qXfer spu read}).
25522 @item qXfer:spu:write
25523 The remote stub understands the @samp{qXfer:spu:write} packet
25524 (@pxref{qXfer spu write}).
25527 The remote stub understands the @samp{QPassSignals} packet
25528 (@pxref{QPassSignals}).
25530 @item QStartNoAckMode
25531 The remote stub understands the @samp{QStartNoAckMode} packet and
25532 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
25537 @cindex symbol lookup, remote request
25538 @cindex @samp{qSymbol} packet
25539 Notify the target that @value{GDBN} is prepared to serve symbol lookup
25540 requests. Accept requests from the target for the values of symbols.
25545 The target does not need to look up any (more) symbols.
25546 @item qSymbol:@var{sym_name}
25547 The target requests the value of symbol @var{sym_name} (hex encoded).
25548 @value{GDBN} may provide the value by using the
25549 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
25553 @item qSymbol:@var{sym_value}:@var{sym_name}
25554 Set the value of @var{sym_name} to @var{sym_value}.
25556 @var{sym_name} (hex encoded) is the name of a symbol whose value the
25557 target has previously requested.
25559 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
25560 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
25566 The target does not need to look up any (more) symbols.
25567 @item qSymbol:@var{sym_name}
25568 The target requests the value of a new symbol @var{sym_name} (hex
25569 encoded). @value{GDBN} will continue to supply the values of symbols
25570 (if available), until the target ceases to request them.
25575 @xref{Tracepoint Packets}.
25577 @item qThreadExtraInfo,@var{id}
25578 @cindex thread attributes info, remote request
25579 @cindex @samp{qThreadExtraInfo} packet
25580 Obtain a printable string description of a thread's attributes from
25581 the target OS. @var{id} is a thread-id in big-endian hex. This
25582 string may contain anything that the target OS thinks is interesting
25583 for @value{GDBN} to tell the user about the thread. The string is
25584 displayed in @value{GDBN}'s @code{info threads} display. Some
25585 examples of possible thread extra info strings are @samp{Runnable}, or
25586 @samp{Blocked on Mutex}.
25590 @item @var{XX}@dots{}
25591 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
25592 comprising the printable string containing the extra information about
25593 the thread's attributes.
25596 (Note that the @code{qThreadExtraInfo} packet's name is separated from
25597 the command by a @samp{,}, not a @samp{:}, contrary to the naming
25598 conventions above. Please don't use this packet as a model for new
25606 @xref{Tracepoint Packets}.
25608 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
25609 @cindex read special object, remote request
25610 @cindex @samp{qXfer} packet
25611 @anchor{qXfer read}
25612 Read uninterpreted bytes from the target's special data area
25613 identified by the keyword @var{object}. Request @var{length} bytes
25614 starting at @var{offset} bytes into the data. The content and
25615 encoding of @var{annex} is specific to @var{object}; it can supply
25616 additional details about what data to access.
25618 Here are the specific requests of this form defined so far. All
25619 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
25620 formats, listed below.
25623 @item qXfer:auxv:read::@var{offset},@var{length}
25624 @anchor{qXfer auxiliary vector read}
25625 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
25626 auxiliary vector}. Note @var{annex} must be empty.
25628 This packet is not probed by default; the remote stub must request it,
25629 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25631 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
25632 @anchor{qXfer target description read}
25633 Access the @dfn{target description}. @xref{Target Descriptions}. The
25634 annex specifies which XML document to access. The main description is
25635 always loaded from the @samp{target.xml} annex.
25637 This packet is not probed by default; the remote stub must request it,
25638 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25640 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
25641 @anchor{qXfer library list read}
25642 Access the target's list of loaded libraries. @xref{Library List Format}.
25643 The annex part of the generic @samp{qXfer} packet must be empty
25644 (@pxref{qXfer read}).
25646 Targets which maintain a list of libraries in the program's memory do
25647 not need to implement this packet; it is designed for platforms where
25648 the operating system manages the list of loaded libraries.
25650 This packet is not probed by default; the remote stub must request it,
25651 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25653 @item qXfer:memory-map:read::@var{offset},@var{length}
25654 @anchor{qXfer memory map read}
25655 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
25656 annex part of the generic @samp{qXfer} packet must be empty
25657 (@pxref{qXfer read}).
25659 This packet is not probed by default; the remote stub must request it,
25660 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25662 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
25663 @anchor{qXfer spu read}
25664 Read contents of an @code{spufs} file on the target system. The
25665 annex specifies which file to read; it must be of the form
25666 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25667 in the target process, and @var{name} identifes the @code{spufs} file
25668 in that context to be accessed.
25670 This packet is not probed by default; the remote stub must request it,
25671 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25677 Data @var{data} (@pxref{Binary Data}) has been read from the
25678 target. There may be more data at a higher address (although
25679 it is permitted to return @samp{m} even for the last valid
25680 block of data, as long as at least one byte of data was read).
25681 @var{data} may have fewer bytes than the @var{length} in the
25685 Data @var{data} (@pxref{Binary Data}) has been read from the target.
25686 There is no more data to be read. @var{data} may have fewer bytes
25687 than the @var{length} in the request.
25690 The @var{offset} in the request is at the end of the data.
25691 There is no more data to be read.
25694 The request was malformed, or @var{annex} was invalid.
25697 The offset was invalid, or there was an error encountered reading the data.
25698 @var{nn} is a hex-encoded @code{errno} value.
25701 An empty reply indicates the @var{object} string was not recognized by
25702 the stub, or that the object does not support reading.
25705 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25706 @cindex write data into object, remote request
25707 Write uninterpreted bytes into the target's special data area
25708 identified by the keyword @var{object}, starting at @var{offset} bytes
25709 into the data. @var{data}@dots{} is the binary-encoded data
25710 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
25711 is specific to @var{object}; it can supply additional details about what data
25714 Here are the specific requests of this form defined so far. All
25715 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
25716 formats, listed below.
25719 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25720 @anchor{qXfer spu write}
25721 Write @var{data} to an @code{spufs} file on the target system. The
25722 annex specifies which file to write; it must be of the form
25723 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25724 in the target process, and @var{name} identifes the @code{spufs} file
25725 in that context to be accessed.
25727 This packet is not probed by default; the remote stub must request it,
25728 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25734 @var{nn} (hex encoded) is the number of bytes written.
25735 This may be fewer bytes than supplied in the request.
25738 The request was malformed, or @var{annex} was invalid.
25741 The offset was invalid, or there was an error encountered writing the data.
25742 @var{nn} is a hex-encoded @code{errno} value.
25745 An empty reply indicates the @var{object} string was not
25746 recognized by the stub, or that the object does not support writing.
25749 @item qXfer:@var{object}:@var{operation}:@dots{}
25750 Requests of this form may be added in the future. When a stub does
25751 not recognize the @var{object} keyword, or its support for
25752 @var{object} does not recognize the @var{operation} keyword, the stub
25753 must respond with an empty packet.
25757 @node Register Packet Format
25758 @section Register Packet Format
25760 The following @code{g}/@code{G} packets have previously been defined.
25761 In the below, some thirty-two bit registers are transferred as
25762 sixty-four bits. Those registers should be zero/sign extended (which?)
25763 to fill the space allocated. Register bytes are transferred in target
25764 byte order. The two nibbles within a register byte are transferred
25765 most-significant - least-significant.
25771 All registers are transferred as thirty-two bit quantities in the order:
25772 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
25773 registers; fsr; fir; fp.
25777 All registers are transferred as sixty-four bit quantities (including
25778 thirty-two bit registers such as @code{sr}). The ordering is the same
25783 @node Tracepoint Packets
25784 @section Tracepoint Packets
25785 @cindex tracepoint packets
25786 @cindex packets, tracepoint
25788 Here we describe the packets @value{GDBN} uses to implement
25789 tracepoints (@pxref{Tracepoints}).
25793 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
25794 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
25795 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
25796 the tracepoint is disabled. @var{step} is the tracepoint's step
25797 count, and @var{pass} is its pass count. If the trailing @samp{-} is
25798 present, further @samp{QTDP} packets will follow to specify this
25799 tracepoint's actions.
25804 The packet was understood and carried out.
25806 The packet was not recognized.
25809 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
25810 Define actions to be taken when a tracepoint is hit. @var{n} and
25811 @var{addr} must be the same as in the initial @samp{QTDP} packet for
25812 this tracepoint. This packet may only be sent immediately after
25813 another @samp{QTDP} packet that ended with a @samp{-}. If the
25814 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
25815 specifying more actions for this tracepoint.
25817 In the series of action packets for a given tracepoint, at most one
25818 can have an @samp{S} before its first @var{action}. If such a packet
25819 is sent, it and the following packets define ``while-stepping''
25820 actions. Any prior packets define ordinary actions --- that is, those
25821 taken when the tracepoint is first hit. If no action packet has an
25822 @samp{S}, then all the packets in the series specify ordinary
25823 tracepoint actions.
25825 The @samp{@var{action}@dots{}} portion of the packet is a series of
25826 actions, concatenated without separators. Each action has one of the
25832 Collect the registers whose bits are set in @var{mask}. @var{mask} is
25833 a hexadecimal number whose @var{i}'th bit is set if register number
25834 @var{i} should be collected. (The least significant bit is numbered
25835 zero.) Note that @var{mask} may be any number of digits long; it may
25836 not fit in a 32-bit word.
25838 @item M @var{basereg},@var{offset},@var{len}
25839 Collect @var{len} bytes of memory starting at the address in register
25840 number @var{basereg}, plus @var{offset}. If @var{basereg} is
25841 @samp{-1}, then the range has a fixed address: @var{offset} is the
25842 address of the lowest byte to collect. The @var{basereg},
25843 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
25844 values (the @samp{-1} value for @var{basereg} is a special case).
25846 @item X @var{len},@var{expr}
25847 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
25848 it directs. @var{expr} is an agent expression, as described in
25849 @ref{Agent Expressions}. Each byte of the expression is encoded as a
25850 two-digit hex number in the packet; @var{len} is the number of bytes
25851 in the expression (and thus one-half the number of hex digits in the
25856 Any number of actions may be packed together in a single @samp{QTDP}
25857 packet, as long as the packet does not exceed the maximum packet
25858 length (400 bytes, for many stubs). There may be only one @samp{R}
25859 action per tracepoint, and it must precede any @samp{M} or @samp{X}
25860 actions. Any registers referred to by @samp{M} and @samp{X} actions
25861 must be collected by a preceding @samp{R} action. (The
25862 ``while-stepping'' actions are treated as if they were attached to a
25863 separate tracepoint, as far as these restrictions are concerned.)
25868 The packet was understood and carried out.
25870 The packet was not recognized.
25873 @item QTFrame:@var{n}
25874 Select the @var{n}'th tracepoint frame from the buffer, and use the
25875 register and memory contents recorded there to answer subsequent
25876 request packets from @value{GDBN}.
25878 A successful reply from the stub indicates that the stub has found the
25879 requested frame. The response is a series of parts, concatenated
25880 without separators, describing the frame we selected. Each part has
25881 one of the following forms:
25885 The selected frame is number @var{n} in the trace frame buffer;
25886 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
25887 was no frame matching the criteria in the request packet.
25890 The selected trace frame records a hit of tracepoint number @var{t};
25891 @var{t} is a hexadecimal number.
25895 @item QTFrame:pc:@var{addr}
25896 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25897 currently selected frame whose PC is @var{addr};
25898 @var{addr} is a hexadecimal number.
25900 @item QTFrame:tdp:@var{t}
25901 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25902 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
25903 is a hexadecimal number.
25905 @item QTFrame:range:@var{start}:@var{end}
25906 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25907 currently selected frame whose PC is between @var{start} (inclusive)
25908 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
25911 @item QTFrame:outside:@var{start}:@var{end}
25912 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
25913 frame @emph{outside} the given range of addresses.
25916 Begin the tracepoint experiment. Begin collecting data from tracepoint
25917 hits in the trace frame buffer.
25920 End the tracepoint experiment. Stop collecting trace frames.
25923 Clear the table of tracepoints, and empty the trace frame buffer.
25925 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
25926 Establish the given ranges of memory as ``transparent''. The stub
25927 will answer requests for these ranges from memory's current contents,
25928 if they were not collected as part of the tracepoint hit.
25930 @value{GDBN} uses this to mark read-only regions of memory, like those
25931 containing program code. Since these areas never change, they should
25932 still have the same contents they did when the tracepoint was hit, so
25933 there's no reason for the stub to refuse to provide their contents.
25936 Ask the stub if there is a trace experiment running right now.
25941 There is no trace experiment running.
25943 There is a trace experiment running.
25949 @node Host I/O Packets
25950 @section Host I/O Packets
25951 @cindex Host I/O, remote protocol
25952 @cindex file transfer, remote protocol
25954 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
25955 operations on the far side of a remote link. For example, Host I/O is
25956 used to upload and download files to a remote target with its own
25957 filesystem. Host I/O uses the same constant values and data structure
25958 layout as the target-initiated File-I/O protocol. However, the
25959 Host I/O packets are structured differently. The target-initiated
25960 protocol relies on target memory to store parameters and buffers.
25961 Host I/O requests are initiated by @value{GDBN}, and the
25962 target's memory is not involved. @xref{File-I/O Remote Protocol
25963 Extension}, for more details on the target-initiated protocol.
25965 The Host I/O request packets all encode a single operation along with
25966 its arguments. They have this format:
25970 @item vFile:@var{operation}: @var{parameter}@dots{}
25971 @var{operation} is the name of the particular request; the target
25972 should compare the entire packet name up to the second colon when checking
25973 for a supported operation. The format of @var{parameter} depends on
25974 the operation. Numbers are always passed in hexadecimal. Negative
25975 numbers have an explicit minus sign (i.e.@: two's complement is not
25976 used). Strings (e.g.@: filenames) are encoded as a series of
25977 hexadecimal bytes. The last argument to a system call may be a
25978 buffer of escaped binary data (@pxref{Binary Data}).
25982 The valid responses to Host I/O packets are:
25986 @item F @var{result} [, @var{errno}] [; @var{attachment}]
25987 @var{result} is the integer value returned by this operation, usually
25988 non-negative for success and -1 for errors. If an error has occured,
25989 @var{errno} will be included in the result. @var{errno} will have a
25990 value defined by the File-I/O protocol (@pxref{Errno Values}). For
25991 operations which return data, @var{attachment} supplies the data as a
25992 binary buffer. Binary buffers in response packets are escaped in the
25993 normal way (@pxref{Binary Data}). See the individual packet
25994 documentation for the interpretation of @var{result} and
25998 An empty response indicates that this operation is not recognized.
26002 These are the supported Host I/O operations:
26005 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
26006 Open a file at @var{pathname} and return a file descriptor for it, or
26007 return -1 if an error occurs. @var{pathname} is a string,
26008 @var{flags} is an integer indicating a mask of open flags
26009 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
26010 of mode bits to use if the file is created (@pxref{mode_t Values}).
26011 @xref{open}, for details of the open flags and mode values.
26013 @item vFile:close: @var{fd}
26014 Close the open file corresponding to @var{fd} and return 0, or
26015 -1 if an error occurs.
26017 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
26018 Read data from the open file corresponding to @var{fd}. Up to
26019 @var{count} bytes will be read from the file, starting at @var{offset}
26020 relative to the start of the file. The target may read fewer bytes;
26021 common reasons include packet size limits and an end-of-file
26022 condition. The number of bytes read is returned. Zero should only be
26023 returned for a successful read at the end of the file, or if
26024 @var{count} was zero.
26026 The data read should be returned as a binary attachment on success.
26027 If zero bytes were read, the response should include an empty binary
26028 attachment (i.e.@: a trailing semicolon). The return value is the
26029 number of target bytes read; the binary attachment may be longer if
26030 some characters were escaped.
26032 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
26033 Write @var{data} (a binary buffer) to the open file corresponding
26034 to @var{fd}. Start the write at @var{offset} from the start of the
26035 file. Unlike many @code{write} system calls, there is no
26036 separate @var{count} argument; the length of @var{data} in the
26037 packet is used. @samp{vFile:write} returns the number of bytes written,
26038 which may be shorter than the length of @var{data}, or -1 if an
26041 @item vFile:unlink: @var{pathname}
26042 Delete the file at @var{pathname} on the target. Return 0,
26043 or -1 if an error occurs. @var{pathname} is a string.
26048 @section Interrupts
26049 @cindex interrupts (remote protocol)
26051 When a program on the remote target is running, @value{GDBN} may
26052 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
26053 control of which is specified via @value{GDBN}'s @samp{remotebreak}
26054 setting (@pxref{set remotebreak}).
26056 The precise meaning of @code{BREAK} is defined by the transport
26057 mechanism and may, in fact, be undefined. @value{GDBN} does not
26058 currently define a @code{BREAK} mechanism for any of the network
26059 interfaces except for TCP, in which case @value{GDBN} sends the
26060 @code{telnet} BREAK sequence.
26062 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
26063 transport mechanisms. It is represented by sending the single byte
26064 @code{0x03} without any of the usual packet overhead described in
26065 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
26066 transmitted as part of a packet, it is considered to be packet data
26067 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
26068 (@pxref{X packet}), used for binary downloads, may include an unescaped
26069 @code{0x03} as part of its packet.
26071 Stubs are not required to recognize these interrupt mechanisms and the
26072 precise meaning associated with receipt of the interrupt is
26073 implementation defined. If the stub is successful at interrupting the
26074 running program, it is expected that it will send one of the Stop
26075 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
26076 of successfully stopping the program. Interrupts received while the
26077 program is stopped will be discarded.
26079 @node Packet Acknowledgment
26080 @section Packet Acknowledgment
26082 @cindex acknowledgment, for @value{GDBN} remote
26083 @cindex packet acknowledgment, for @value{GDBN} remote
26084 By default, when either the host or the target machine receives a packet,
26085 the first response expected is an acknowledgment: either @samp{+} (to indicate
26086 the package was received correctly) or @samp{-} (to request retransmission).
26087 This mechanism allows the @value{GDBN} remote protocol to operate over
26088 unreliable transport mechanisms, such as a serial line.
26090 In cases where the transport mechanism is itself reliable (such as a pipe or
26091 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
26092 It may be desirable to disable them in that case to reduce communication
26093 overhead, or for other reasons. This can be accomplished by means of the
26094 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
26096 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
26097 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
26098 and response format still includes the normal checksum, as described in
26099 @ref{Overview}, but the checksum may be ignored by the receiver.
26101 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
26102 no-acknowledgment mode, it should report that to @value{GDBN}
26103 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
26104 @pxref{qSupported}.
26105 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
26106 disabled via the @code{set remote noack-packet off} command
26107 (@pxref{Remote Configuration}),
26108 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
26109 Only then may the stub actually turn off packet acknowledgments.
26110 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
26111 response, which can be safely ignored by the stub.
26113 Note that @code{set remote noack-packet} command only affects negotiation
26114 between @value{GDBN} and the stub when subsequent connections are made;
26115 it does not affect the protocol acknowledgment state for any current
26117 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
26118 new connection is established,
26119 there is also no protocol request to re-enable the acknowledgments
26120 for the current connection, once disabled.
26126 Example sequence of a target being re-started. Notice how the restart
26127 does not get any direct output:
26132 @emph{target restarts}
26135 <- @code{T001:1234123412341234}
26139 Example sequence of a target being stepped by a single instruction:
26142 -> @code{G1445@dots{}}
26147 <- @code{T001:1234123412341234}
26151 <- @code{1455@dots{}}
26155 @node File-I/O Remote Protocol Extension
26156 @section File-I/O Remote Protocol Extension
26157 @cindex File-I/O remote protocol extension
26160 * File-I/O Overview::
26161 * Protocol Basics::
26162 * The F Request Packet::
26163 * The F Reply Packet::
26164 * The Ctrl-C Message::
26166 * List of Supported Calls::
26167 * Protocol-specific Representation of Datatypes::
26169 * File-I/O Examples::
26172 @node File-I/O Overview
26173 @subsection File-I/O Overview
26174 @cindex file-i/o overview
26176 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
26177 target to use the host's file system and console I/O to perform various
26178 system calls. System calls on the target system are translated into a
26179 remote protocol packet to the host system, which then performs the needed
26180 actions and returns a response packet to the target system.
26181 This simulates file system operations even on targets that lack file systems.
26183 The protocol is defined to be independent of both the host and target systems.
26184 It uses its own internal representation of datatypes and values. Both
26185 @value{GDBN} and the target's @value{GDBN} stub are responsible for
26186 translating the system-dependent value representations into the internal
26187 protocol representations when data is transmitted.
26189 The communication is synchronous. A system call is possible only when
26190 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
26191 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
26192 the target is stopped to allow deterministic access to the target's
26193 memory. Therefore File-I/O is not interruptible by target signals. On
26194 the other hand, it is possible to interrupt File-I/O by a user interrupt
26195 (@samp{Ctrl-C}) within @value{GDBN}.
26197 The target's request to perform a host system call does not finish
26198 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
26199 after finishing the system call, the target returns to continuing the
26200 previous activity (continue, step). No additional continue or step
26201 request from @value{GDBN} is required.
26204 (@value{GDBP}) continue
26205 <- target requests 'system call X'
26206 target is stopped, @value{GDBN} executes system call
26207 -> @value{GDBN} returns result
26208 ... target continues, @value{GDBN} returns to wait for the target
26209 <- target hits breakpoint and sends a Txx packet
26212 The protocol only supports I/O on the console and to regular files on
26213 the host file system. Character or block special devices, pipes,
26214 named pipes, sockets or any other communication method on the host
26215 system are not supported by this protocol.
26217 @node Protocol Basics
26218 @subsection Protocol Basics
26219 @cindex protocol basics, file-i/o
26221 The File-I/O protocol uses the @code{F} packet as the request as well
26222 as reply packet. Since a File-I/O system call can only occur when
26223 @value{GDBN} is waiting for a response from the continuing or stepping target,
26224 the File-I/O request is a reply that @value{GDBN} has to expect as a result
26225 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
26226 This @code{F} packet contains all information needed to allow @value{GDBN}
26227 to call the appropriate host system call:
26231 A unique identifier for the requested system call.
26234 All parameters to the system call. Pointers are given as addresses
26235 in the target memory address space. Pointers to strings are given as
26236 pointer/length pair. Numerical values are given as they are.
26237 Numerical control flags are given in a protocol-specific representation.
26241 At this point, @value{GDBN} has to perform the following actions.
26245 If the parameters include pointer values to data needed as input to a
26246 system call, @value{GDBN} requests this data from the target with a
26247 standard @code{m} packet request. This additional communication has to be
26248 expected by the target implementation and is handled as any other @code{m}
26252 @value{GDBN} translates all value from protocol representation to host
26253 representation as needed. Datatypes are coerced into the host types.
26256 @value{GDBN} calls the system call.
26259 It then coerces datatypes back to protocol representation.
26262 If the system call is expected to return data in buffer space specified
26263 by pointer parameters to the call, the data is transmitted to the
26264 target using a @code{M} or @code{X} packet. This packet has to be expected
26265 by the target implementation and is handled as any other @code{M} or @code{X}
26270 Eventually @value{GDBN} replies with another @code{F} packet which contains all
26271 necessary information for the target to continue. This at least contains
26278 @code{errno}, if has been changed by the system call.
26285 After having done the needed type and value coercion, the target continues
26286 the latest continue or step action.
26288 @node The F Request Packet
26289 @subsection The @code{F} Request Packet
26290 @cindex file-i/o request packet
26291 @cindex @code{F} request packet
26293 The @code{F} request packet has the following format:
26296 @item F@var{call-id},@var{parameter@dots{}}
26298 @var{call-id} is the identifier to indicate the host system call to be called.
26299 This is just the name of the function.
26301 @var{parameter@dots{}} are the parameters to the system call.
26302 Parameters are hexadecimal integer values, either the actual values in case
26303 of scalar datatypes, pointers to target buffer space in case of compound
26304 datatypes and unspecified memory areas, or pointer/length pairs in case
26305 of string parameters. These are appended to the @var{call-id} as a
26306 comma-delimited list. All values are transmitted in ASCII
26307 string representation, pointer/length pairs separated by a slash.
26313 @node The F Reply Packet
26314 @subsection The @code{F} Reply Packet
26315 @cindex file-i/o reply packet
26316 @cindex @code{F} reply packet
26318 The @code{F} reply packet has the following format:
26322 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
26324 @var{retcode} is the return code of the system call as hexadecimal value.
26326 @var{errno} is the @code{errno} set by the call, in protocol-specific
26328 This parameter can be omitted if the call was successful.
26330 @var{Ctrl-C flag} is only sent if the user requested a break. In this
26331 case, @var{errno} must be sent as well, even if the call was successful.
26332 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
26339 or, if the call was interrupted before the host call has been performed:
26346 assuming 4 is the protocol-specific representation of @code{EINTR}.
26351 @node The Ctrl-C Message
26352 @subsection The @samp{Ctrl-C} Message
26353 @cindex ctrl-c message, in file-i/o protocol
26355 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
26356 reply packet (@pxref{The F Reply Packet}),
26357 the target should behave as if it had
26358 gotten a break message. The meaning for the target is ``system call
26359 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
26360 (as with a break message) and return to @value{GDBN} with a @code{T02}
26363 It's important for the target to know in which
26364 state the system call was interrupted. There are two possible cases:
26368 The system call hasn't been performed on the host yet.
26371 The system call on the host has been finished.
26375 These two states can be distinguished by the target by the value of the
26376 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
26377 call hasn't been performed. This is equivalent to the @code{EINTR} handling
26378 on POSIX systems. In any other case, the target may presume that the
26379 system call has been finished --- successfully or not --- and should behave
26380 as if the break message arrived right after the system call.
26382 @value{GDBN} must behave reliably. If the system call has not been called
26383 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
26384 @code{errno} in the packet. If the system call on the host has been finished
26385 before the user requests a break, the full action must be finished by
26386 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
26387 The @code{F} packet may only be sent when either nothing has happened
26388 or the full action has been completed.
26391 @subsection Console I/O
26392 @cindex console i/o as part of file-i/o
26394 By default and if not explicitly closed by the target system, the file
26395 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
26396 on the @value{GDBN} console is handled as any other file output operation
26397 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
26398 by @value{GDBN} so that after the target read request from file descriptor
26399 0 all following typing is buffered until either one of the following
26404 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
26406 system call is treated as finished.
26409 The user presses @key{RET}. This is treated as end of input with a trailing
26413 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
26414 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
26418 If the user has typed more characters than fit in the buffer given to
26419 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
26420 either another @code{read(0, @dots{})} is requested by the target, or debugging
26421 is stopped at the user's request.
26424 @node List of Supported Calls
26425 @subsection List of Supported Calls
26426 @cindex list of supported file-i/o calls
26443 @unnumberedsubsubsec open
26444 @cindex open, file-i/o system call
26449 int open(const char *pathname, int flags);
26450 int open(const char *pathname, int flags, mode_t mode);
26454 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
26457 @var{flags} is the bitwise @code{OR} of the following values:
26461 If the file does not exist it will be created. The host
26462 rules apply as far as file ownership and time stamps
26466 When used with @code{O_CREAT}, if the file already exists it is
26467 an error and open() fails.
26470 If the file already exists and the open mode allows
26471 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
26472 truncated to zero length.
26475 The file is opened in append mode.
26478 The file is opened for reading only.
26481 The file is opened for writing only.
26484 The file is opened for reading and writing.
26488 Other bits are silently ignored.
26492 @var{mode} is the bitwise @code{OR} of the following values:
26496 User has read permission.
26499 User has write permission.
26502 Group has read permission.
26505 Group has write permission.
26508 Others have read permission.
26511 Others have write permission.
26515 Other bits are silently ignored.
26518 @item Return value:
26519 @code{open} returns the new file descriptor or -1 if an error
26526 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
26529 @var{pathname} refers to a directory.
26532 The requested access is not allowed.
26535 @var{pathname} was too long.
26538 A directory component in @var{pathname} does not exist.
26541 @var{pathname} refers to a device, pipe, named pipe or socket.
26544 @var{pathname} refers to a file on a read-only filesystem and
26545 write access was requested.
26548 @var{pathname} is an invalid pointer value.
26551 No space on device to create the file.
26554 The process already has the maximum number of files open.
26557 The limit on the total number of files open on the system
26561 The call was interrupted by the user.
26567 @unnumberedsubsubsec close
26568 @cindex close, file-i/o system call
26577 @samp{Fclose,@var{fd}}
26579 @item Return value:
26580 @code{close} returns zero on success, or -1 if an error occurred.
26586 @var{fd} isn't a valid open file descriptor.
26589 The call was interrupted by the user.
26595 @unnumberedsubsubsec read
26596 @cindex read, file-i/o system call
26601 int read(int fd, void *buf, unsigned int count);
26605 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
26607 @item Return value:
26608 On success, the number of bytes read is returned.
26609 Zero indicates end of file. If count is zero, read
26610 returns zero as well. On error, -1 is returned.
26616 @var{fd} is not a valid file descriptor or is not open for
26620 @var{bufptr} is an invalid pointer value.
26623 The call was interrupted by the user.
26629 @unnumberedsubsubsec write
26630 @cindex write, file-i/o system call
26635 int write(int fd, const void *buf, unsigned int count);
26639 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
26641 @item Return value:
26642 On success, the number of bytes written are returned.
26643 Zero indicates nothing was written. On error, -1
26650 @var{fd} is not a valid file descriptor or is not open for
26654 @var{bufptr} is an invalid pointer value.
26657 An attempt was made to write a file that exceeds the
26658 host-specific maximum file size allowed.
26661 No space on device to write the data.
26664 The call was interrupted by the user.
26670 @unnumberedsubsubsec lseek
26671 @cindex lseek, file-i/o system call
26676 long lseek (int fd, long offset, int flag);
26680 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
26682 @var{flag} is one of:
26686 The offset is set to @var{offset} bytes.
26689 The offset is set to its current location plus @var{offset}
26693 The offset is set to the size of the file plus @var{offset}
26697 @item Return value:
26698 On success, the resulting unsigned offset in bytes from
26699 the beginning of the file is returned. Otherwise, a
26700 value of -1 is returned.
26706 @var{fd} is not a valid open file descriptor.
26709 @var{fd} is associated with the @value{GDBN} console.
26712 @var{flag} is not a proper value.
26715 The call was interrupted by the user.
26721 @unnumberedsubsubsec rename
26722 @cindex rename, file-i/o system call
26727 int rename(const char *oldpath, const char *newpath);
26731 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
26733 @item Return value:
26734 On success, zero is returned. On error, -1 is returned.
26740 @var{newpath} is an existing directory, but @var{oldpath} is not a
26744 @var{newpath} is a non-empty directory.
26747 @var{oldpath} or @var{newpath} is a directory that is in use by some
26751 An attempt was made to make a directory a subdirectory
26755 A component used as a directory in @var{oldpath} or new
26756 path is not a directory. Or @var{oldpath} is a directory
26757 and @var{newpath} exists but is not a directory.
26760 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
26763 No access to the file or the path of the file.
26767 @var{oldpath} or @var{newpath} was too long.
26770 A directory component in @var{oldpath} or @var{newpath} does not exist.
26773 The file is on a read-only filesystem.
26776 The device containing the file has no room for the new
26780 The call was interrupted by the user.
26786 @unnumberedsubsubsec unlink
26787 @cindex unlink, file-i/o system call
26792 int unlink(const char *pathname);
26796 @samp{Funlink,@var{pathnameptr}/@var{len}}
26798 @item Return value:
26799 On success, zero is returned. On error, -1 is returned.
26805 No access to the file or the path of the file.
26808 The system does not allow unlinking of directories.
26811 The file @var{pathname} cannot be unlinked because it's
26812 being used by another process.
26815 @var{pathnameptr} is an invalid pointer value.
26818 @var{pathname} was too long.
26821 A directory component in @var{pathname} does not exist.
26824 A component of the path is not a directory.
26827 The file is on a read-only filesystem.
26830 The call was interrupted by the user.
26836 @unnumberedsubsubsec stat/fstat
26837 @cindex fstat, file-i/o system call
26838 @cindex stat, file-i/o system call
26843 int stat(const char *pathname, struct stat *buf);
26844 int fstat(int fd, struct stat *buf);
26848 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
26849 @samp{Ffstat,@var{fd},@var{bufptr}}
26851 @item Return value:
26852 On success, zero is returned. On error, -1 is returned.
26858 @var{fd} is not a valid open file.
26861 A directory component in @var{pathname} does not exist or the
26862 path is an empty string.
26865 A component of the path is not a directory.
26868 @var{pathnameptr} is an invalid pointer value.
26871 No access to the file or the path of the file.
26874 @var{pathname} was too long.
26877 The call was interrupted by the user.
26883 @unnumberedsubsubsec gettimeofday
26884 @cindex gettimeofday, file-i/o system call
26889 int gettimeofday(struct timeval *tv, void *tz);
26893 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
26895 @item Return value:
26896 On success, 0 is returned, -1 otherwise.
26902 @var{tz} is a non-NULL pointer.
26905 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
26911 @unnumberedsubsubsec isatty
26912 @cindex isatty, file-i/o system call
26917 int isatty(int fd);
26921 @samp{Fisatty,@var{fd}}
26923 @item Return value:
26924 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
26930 The call was interrupted by the user.
26935 Note that the @code{isatty} call is treated as a special case: it returns
26936 1 to the target if the file descriptor is attached
26937 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
26938 would require implementing @code{ioctl} and would be more complex than
26943 @unnumberedsubsubsec system
26944 @cindex system, file-i/o system call
26949 int system(const char *command);
26953 @samp{Fsystem,@var{commandptr}/@var{len}}
26955 @item Return value:
26956 If @var{len} is zero, the return value indicates whether a shell is
26957 available. A zero return value indicates a shell is not available.
26958 For non-zero @var{len}, the value returned is -1 on error and the
26959 return status of the command otherwise. Only the exit status of the
26960 command is returned, which is extracted from the host's @code{system}
26961 return value by calling @code{WEXITSTATUS(retval)}. In case
26962 @file{/bin/sh} could not be executed, 127 is returned.
26968 The call was interrupted by the user.
26973 @value{GDBN} takes over the full task of calling the necessary host calls
26974 to perform the @code{system} call. The return value of @code{system} on
26975 the host is simplified before it's returned
26976 to the target. Any termination signal information from the child process
26977 is discarded, and the return value consists
26978 entirely of the exit status of the called command.
26980 Due to security concerns, the @code{system} call is by default refused
26981 by @value{GDBN}. The user has to allow this call explicitly with the
26982 @code{set remote system-call-allowed 1} command.
26985 @item set remote system-call-allowed
26986 @kindex set remote system-call-allowed
26987 Control whether to allow the @code{system} calls in the File I/O
26988 protocol for the remote target. The default is zero (disabled).
26990 @item show remote system-call-allowed
26991 @kindex show remote system-call-allowed
26992 Show whether the @code{system} calls are allowed in the File I/O
26996 @node Protocol-specific Representation of Datatypes
26997 @subsection Protocol-specific Representation of Datatypes
26998 @cindex protocol-specific representation of datatypes, in file-i/o protocol
27001 * Integral Datatypes::
27003 * Memory Transfer::
27008 @node Integral Datatypes
27009 @unnumberedsubsubsec Integral Datatypes
27010 @cindex integral datatypes, in file-i/o protocol
27012 The integral datatypes used in the system calls are @code{int},
27013 @code{unsigned int}, @code{long}, @code{unsigned long},
27014 @code{mode_t}, and @code{time_t}.
27016 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
27017 implemented as 32 bit values in this protocol.
27019 @code{long} and @code{unsigned long} are implemented as 64 bit types.
27021 @xref{Limits}, for corresponding MIN and MAX values (similar to those
27022 in @file{limits.h}) to allow range checking on host and target.
27024 @code{time_t} datatypes are defined as seconds since the Epoch.
27026 All integral datatypes transferred as part of a memory read or write of a
27027 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
27030 @node Pointer Values
27031 @unnumberedsubsubsec Pointer Values
27032 @cindex pointer values, in file-i/o protocol
27034 Pointers to target data are transmitted as they are. An exception
27035 is made for pointers to buffers for which the length isn't
27036 transmitted as part of the function call, namely strings. Strings
27037 are transmitted as a pointer/length pair, both as hex values, e.g.@:
27044 which is a pointer to data of length 18 bytes at position 0x1aaf.
27045 The length is defined as the full string length in bytes, including
27046 the trailing null byte. For example, the string @code{"hello world"}
27047 at address 0x123456 is transmitted as
27053 @node Memory Transfer
27054 @unnumberedsubsubsec Memory Transfer
27055 @cindex memory transfer, in file-i/o protocol
27057 Structured data which is transferred using a memory read or write (for
27058 example, a @code{struct stat}) is expected to be in a protocol-specific format
27059 with all scalar multibyte datatypes being big endian. Translation to
27060 this representation needs to be done both by the target before the @code{F}
27061 packet is sent, and by @value{GDBN} before
27062 it transfers memory to the target. Transferred pointers to structured
27063 data should point to the already-coerced data at any time.
27067 @unnumberedsubsubsec struct stat
27068 @cindex struct stat, in file-i/o protocol
27070 The buffer of type @code{struct stat} used by the target and @value{GDBN}
27071 is defined as follows:
27075 unsigned int st_dev; /* device */
27076 unsigned int st_ino; /* inode */
27077 mode_t st_mode; /* protection */
27078 unsigned int st_nlink; /* number of hard links */
27079 unsigned int st_uid; /* user ID of owner */
27080 unsigned int st_gid; /* group ID of owner */
27081 unsigned int st_rdev; /* device type (if inode device) */
27082 unsigned long st_size; /* total size, in bytes */
27083 unsigned long st_blksize; /* blocksize for filesystem I/O */
27084 unsigned long st_blocks; /* number of blocks allocated */
27085 time_t st_atime; /* time of last access */
27086 time_t st_mtime; /* time of last modification */
27087 time_t st_ctime; /* time of last change */
27091 The integral datatypes conform to the definitions given in the
27092 appropriate section (see @ref{Integral Datatypes}, for details) so this
27093 structure is of size 64 bytes.
27095 The values of several fields have a restricted meaning and/or
27101 A value of 0 represents a file, 1 the console.
27104 No valid meaning for the target. Transmitted unchanged.
27107 Valid mode bits are described in @ref{Constants}. Any other
27108 bits have currently no meaning for the target.
27113 No valid meaning for the target. Transmitted unchanged.
27118 These values have a host and file system dependent
27119 accuracy. Especially on Windows hosts, the file system may not
27120 support exact timing values.
27123 The target gets a @code{struct stat} of the above representation and is
27124 responsible for coercing it to the target representation before
27127 Note that due to size differences between the host, target, and protocol
27128 representations of @code{struct stat} members, these members could eventually
27129 get truncated on the target.
27131 @node struct timeval
27132 @unnumberedsubsubsec struct timeval
27133 @cindex struct timeval, in file-i/o protocol
27135 The buffer of type @code{struct timeval} used by the File-I/O protocol
27136 is defined as follows:
27140 time_t tv_sec; /* second */
27141 long tv_usec; /* microsecond */
27145 The integral datatypes conform to the definitions given in the
27146 appropriate section (see @ref{Integral Datatypes}, for details) so this
27147 structure is of size 8 bytes.
27150 @subsection Constants
27151 @cindex constants, in file-i/o protocol
27153 The following values are used for the constants inside of the
27154 protocol. @value{GDBN} and target are responsible for translating these
27155 values before and after the call as needed.
27166 @unnumberedsubsubsec Open Flags
27167 @cindex open flags, in file-i/o protocol
27169 All values are given in hexadecimal representation.
27181 @node mode_t Values
27182 @unnumberedsubsubsec mode_t Values
27183 @cindex mode_t values, in file-i/o protocol
27185 All values are given in octal representation.
27202 @unnumberedsubsubsec Errno Values
27203 @cindex errno values, in file-i/o protocol
27205 All values are given in decimal representation.
27230 @code{EUNKNOWN} is used as a fallback error value if a host system returns
27231 any error value not in the list of supported error numbers.
27234 @unnumberedsubsubsec Lseek Flags
27235 @cindex lseek flags, in file-i/o protocol
27244 @unnumberedsubsubsec Limits
27245 @cindex limits, in file-i/o protocol
27247 All values are given in decimal representation.
27250 INT_MIN -2147483648
27252 UINT_MAX 4294967295
27253 LONG_MIN -9223372036854775808
27254 LONG_MAX 9223372036854775807
27255 ULONG_MAX 18446744073709551615
27258 @node File-I/O Examples
27259 @subsection File-I/O Examples
27260 @cindex file-i/o examples
27262 Example sequence of a write call, file descriptor 3, buffer is at target
27263 address 0x1234, 6 bytes should be written:
27266 <- @code{Fwrite,3,1234,6}
27267 @emph{request memory read from target}
27270 @emph{return "6 bytes written"}
27274 Example sequence of a read call, file descriptor 3, buffer is at target
27275 address 0x1234, 6 bytes should be read:
27278 <- @code{Fread,3,1234,6}
27279 @emph{request memory write to target}
27280 -> @code{X1234,6:XXXXXX}
27281 @emph{return "6 bytes read"}
27285 Example sequence of a read call, call fails on the host due to invalid
27286 file descriptor (@code{EBADF}):
27289 <- @code{Fread,3,1234,6}
27293 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
27297 <- @code{Fread,3,1234,6}
27302 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
27306 <- @code{Fread,3,1234,6}
27307 -> @code{X1234,6:XXXXXX}
27311 @node Library List Format
27312 @section Library List Format
27313 @cindex library list format, remote protocol
27315 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
27316 same process as your application to manage libraries. In this case,
27317 @value{GDBN} can use the loader's symbol table and normal memory
27318 operations to maintain a list of shared libraries. On other
27319 platforms, the operating system manages loaded libraries.
27320 @value{GDBN} can not retrieve the list of currently loaded libraries
27321 through memory operations, so it uses the @samp{qXfer:libraries:read}
27322 packet (@pxref{qXfer library list read}) instead. The remote stub
27323 queries the target's operating system and reports which libraries
27326 The @samp{qXfer:libraries:read} packet returns an XML document which
27327 lists loaded libraries and their offsets. Each library has an
27328 associated name and one or more segment or section base addresses,
27329 which report where the library was loaded in memory.
27331 For the common case of libraries that are fully linked binaries, the
27332 library should have a list of segments. If the target supports
27333 dynamic linking of a relocatable object file, its library XML element
27334 should instead include a list of allocated sections. The segment or
27335 section bases are start addresses, not relocation offsets; they do not
27336 depend on the library's link-time base addresses.
27338 @value{GDBN} must be linked with the Expat library to support XML
27339 library lists. @xref{Expat}.
27341 A simple memory map, with one loaded library relocated by a single
27342 offset, looks like this:
27346 <library name="/lib/libc.so.6">
27347 <segment address="0x10000000"/>
27352 Another simple memory map, with one loaded library with three
27353 allocated sections (.text, .data, .bss), looks like this:
27357 <library name="sharedlib.o">
27358 <section address="0x10000000"/>
27359 <section address="0x20000000"/>
27360 <section address="0x30000000"/>
27365 The format of a library list is described by this DTD:
27368 <!-- library-list: Root element with versioning -->
27369 <!ELEMENT library-list (library)*>
27370 <!ATTLIST library-list version CDATA #FIXED "1.0">
27371 <!ELEMENT library (segment*, section*)>
27372 <!ATTLIST library name CDATA #REQUIRED>
27373 <!ELEMENT segment EMPTY>
27374 <!ATTLIST segment address CDATA #REQUIRED>
27375 <!ELEMENT section EMPTY>
27376 <!ATTLIST section address CDATA #REQUIRED>
27379 In addition, segments and section descriptors cannot be mixed within a
27380 single library element, and you must supply at least one segment or
27381 section for each library.
27383 @node Memory Map Format
27384 @section Memory Map Format
27385 @cindex memory map format
27387 To be able to write into flash memory, @value{GDBN} needs to obtain a
27388 memory map from the target. This section describes the format of the
27391 The memory map is obtained using the @samp{qXfer:memory-map:read}
27392 (@pxref{qXfer memory map read}) packet and is an XML document that
27393 lists memory regions.
27395 @value{GDBN} must be linked with the Expat library to support XML
27396 memory maps. @xref{Expat}.
27398 The top-level structure of the document is shown below:
27401 <?xml version="1.0"?>
27402 <!DOCTYPE memory-map
27403 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
27404 "http://sourceware.org/gdb/gdb-memory-map.dtd">
27410 Each region can be either:
27415 A region of RAM starting at @var{addr} and extending for @var{length}
27419 <memory type="ram" start="@var{addr}" length="@var{length}"/>
27424 A region of read-only memory:
27427 <memory type="rom" start="@var{addr}" length="@var{length}"/>
27432 A region of flash memory, with erasure blocks @var{blocksize}
27436 <memory type="flash" start="@var{addr}" length="@var{length}">
27437 <property name="blocksize">@var{blocksize}</property>
27443 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
27444 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
27445 packets to write to addresses in such ranges.
27447 The formal DTD for memory map format is given below:
27450 <!-- ................................................... -->
27451 <!-- Memory Map XML DTD ................................ -->
27452 <!-- File: memory-map.dtd .............................. -->
27453 <!-- .................................... .............. -->
27454 <!-- memory-map.dtd -->
27455 <!-- memory-map: Root element with versioning -->
27456 <!ELEMENT memory-map (memory | property)>
27457 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
27458 <!ELEMENT memory (property)>
27459 <!-- memory: Specifies a memory region,
27460 and its type, or device. -->
27461 <!ATTLIST memory type CDATA #REQUIRED
27462 start CDATA #REQUIRED
27463 length CDATA #REQUIRED
27464 device CDATA #IMPLIED>
27465 <!-- property: Generic attribute tag -->
27466 <!ELEMENT property (#PCDATA | property)*>
27467 <!ATTLIST property name CDATA #REQUIRED>
27470 @include agentexpr.texi
27472 @node Target Descriptions
27473 @appendix Target Descriptions
27474 @cindex target descriptions
27476 @strong{Warning:} target descriptions are still under active development,
27477 and the contents and format may change between @value{GDBN} releases.
27478 The format is expected to stabilize in the future.
27480 One of the challenges of using @value{GDBN} to debug embedded systems
27481 is that there are so many minor variants of each processor
27482 architecture in use. It is common practice for vendors to start with
27483 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
27484 and then make changes to adapt it to a particular market niche. Some
27485 architectures have hundreds of variants, available from dozens of
27486 vendors. This leads to a number of problems:
27490 With so many different customized processors, it is difficult for
27491 the @value{GDBN} maintainers to keep up with the changes.
27493 Since individual variants may have short lifetimes or limited
27494 audiences, it may not be worthwhile to carry information about every
27495 variant in the @value{GDBN} source tree.
27497 When @value{GDBN} does support the architecture of the embedded system
27498 at hand, the task of finding the correct architecture name to give the
27499 @command{set architecture} command can be error-prone.
27502 To address these problems, the @value{GDBN} remote protocol allows a
27503 target system to not only identify itself to @value{GDBN}, but to
27504 actually describe its own features. This lets @value{GDBN} support
27505 processor variants it has never seen before --- to the extent that the
27506 descriptions are accurate, and that @value{GDBN} understands them.
27508 @value{GDBN} must be linked with the Expat library to support XML
27509 target descriptions. @xref{Expat}.
27512 * Retrieving Descriptions:: How descriptions are fetched from a target.
27513 * Target Description Format:: The contents of a target description.
27514 * Predefined Target Types:: Standard types available for target
27516 * Standard Target Features:: Features @value{GDBN} knows about.
27519 @node Retrieving Descriptions
27520 @section Retrieving Descriptions
27522 Target descriptions can be read from the target automatically, or
27523 specified by the user manually. The default behavior is to read the
27524 description from the target. @value{GDBN} retrieves it via the remote
27525 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
27526 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
27527 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
27528 XML document, of the form described in @ref{Target Description
27531 Alternatively, you can specify a file to read for the target description.
27532 If a file is set, the target will not be queried. The commands to
27533 specify a file are:
27536 @cindex set tdesc filename
27537 @item set tdesc filename @var{path}
27538 Read the target description from @var{path}.
27540 @cindex unset tdesc filename
27541 @item unset tdesc filename
27542 Do not read the XML target description from a file. @value{GDBN}
27543 will use the description supplied by the current target.
27545 @cindex show tdesc filename
27546 @item show tdesc filename
27547 Show the filename to read for a target description, if any.
27551 @node Target Description Format
27552 @section Target Description Format
27553 @cindex target descriptions, XML format
27555 A target description annex is an @uref{http://www.w3.org/XML/, XML}
27556 document which complies with the Document Type Definition provided in
27557 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
27558 means you can use generally available tools like @command{xmllint} to
27559 check that your feature descriptions are well-formed and valid.
27560 However, to help people unfamiliar with XML write descriptions for
27561 their targets, we also describe the grammar here.
27563 Target descriptions can identify the architecture of the remote target
27564 and (for some architectures) provide information about custom register
27565 sets. @value{GDBN} can use this information to autoconfigure for your
27566 target, or to warn you if you connect to an unsupported target.
27568 Here is a simple target description:
27571 <target version="1.0">
27572 <architecture>i386:x86-64</architecture>
27577 This minimal description only says that the target uses
27578 the x86-64 architecture.
27580 A target description has the following overall form, with [ ] marking
27581 optional elements and @dots{} marking repeatable elements. The elements
27582 are explained further below.
27585 <?xml version="1.0"?>
27586 <!DOCTYPE target SYSTEM "gdb-target.dtd">
27587 <target version="1.0">
27588 @r{[}@var{architecture}@r{]}
27589 @r{[}@var{feature}@dots{}@r{]}
27594 The description is generally insensitive to whitespace and line
27595 breaks, under the usual common-sense rules. The XML version
27596 declaration and document type declaration can generally be omitted
27597 (@value{GDBN} does not require them), but specifying them may be
27598 useful for XML validation tools. The @samp{version} attribute for
27599 @samp{<target>} may also be omitted, but we recommend
27600 including it; if future versions of @value{GDBN} use an incompatible
27601 revision of @file{gdb-target.dtd}, they will detect and report
27602 the version mismatch.
27604 @subsection Inclusion
27605 @cindex target descriptions, inclusion
27608 @cindex <xi:include>
27611 It can sometimes be valuable to split a target description up into
27612 several different annexes, either for organizational purposes, or to
27613 share files between different possible target descriptions. You can
27614 divide a description into multiple files by replacing any element of
27615 the target description with an inclusion directive of the form:
27618 <xi:include href="@var{document}"/>
27622 When @value{GDBN} encounters an element of this form, it will retrieve
27623 the named XML @var{document}, and replace the inclusion directive with
27624 the contents of that document. If the current description was read
27625 using @samp{qXfer}, then so will be the included document;
27626 @var{document} will be interpreted as the name of an annex. If the
27627 current description was read from a file, @value{GDBN} will look for
27628 @var{document} as a file in the same directory where it found the
27629 original description.
27631 @subsection Architecture
27632 @cindex <architecture>
27634 An @samp{<architecture>} element has this form:
27637 <architecture>@var{arch}</architecture>
27640 @var{arch} is an architecture name from the same selection
27641 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
27642 Debugging Target}).
27644 @subsection Features
27647 Each @samp{<feature>} describes some logical portion of the target
27648 system. Features are currently used to describe available CPU
27649 registers and the types of their contents. A @samp{<feature>} element
27653 <feature name="@var{name}">
27654 @r{[}@var{type}@dots{}@r{]}
27660 Each feature's name should be unique within the description. The name
27661 of a feature does not matter unless @value{GDBN} has some special
27662 knowledge of the contents of that feature; if it does, the feature
27663 should have its standard name. @xref{Standard Target Features}.
27667 Any register's value is a collection of bits which @value{GDBN} must
27668 interpret. The default interpretation is a two's complement integer,
27669 but other types can be requested by name in the register description.
27670 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
27671 Target Types}), and the description can define additional composite types.
27673 Each type element must have an @samp{id} attribute, which gives
27674 a unique (within the containing @samp{<feature>}) name to the type.
27675 Types must be defined before they are used.
27678 Some targets offer vector registers, which can be treated as arrays
27679 of scalar elements. These types are written as @samp{<vector>} elements,
27680 specifying the array element type, @var{type}, and the number of elements,
27684 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
27688 If a register's value is usefully viewed in multiple ways, define it
27689 with a union type containing the useful representations. The
27690 @samp{<union>} element contains one or more @samp{<field>} elements,
27691 each of which has a @var{name} and a @var{type}:
27694 <union id="@var{id}">
27695 <field name="@var{name}" type="@var{type}"/>
27700 @subsection Registers
27703 Each register is represented as an element with this form:
27706 <reg name="@var{name}"
27707 bitsize="@var{size}"
27708 @r{[}regnum="@var{num}"@r{]}
27709 @r{[}save-restore="@var{save-restore}"@r{]}
27710 @r{[}type="@var{type}"@r{]}
27711 @r{[}group="@var{group}"@r{]}/>
27715 The components are as follows:
27720 The register's name; it must be unique within the target description.
27723 The register's size, in bits.
27726 The register's number. If omitted, a register's number is one greater
27727 than that of the previous register (either in the current feature or in
27728 a preceeding feature); the first register in the target description
27729 defaults to zero. This register number is used to read or write
27730 the register; e.g.@: it is used in the remote @code{p} and @code{P}
27731 packets, and registers appear in the @code{g} and @code{G} packets
27732 in order of increasing register number.
27735 Whether the register should be preserved across inferior function
27736 calls; this must be either @code{yes} or @code{no}. The default is
27737 @code{yes}, which is appropriate for most registers except for
27738 some system control registers; this is not related to the target's
27742 The type of the register. @var{type} may be a predefined type, a type
27743 defined in the current feature, or one of the special types @code{int}
27744 and @code{float}. @code{int} is an integer type of the correct size
27745 for @var{bitsize}, and @code{float} is a floating point type (in the
27746 architecture's normal floating point format) of the correct size for
27747 @var{bitsize}. The default is @code{int}.
27750 The register group to which this register belongs. @var{group} must
27751 be either @code{general}, @code{float}, or @code{vector}. If no
27752 @var{group} is specified, @value{GDBN} will not display the register
27753 in @code{info registers}.
27757 @node Predefined Target Types
27758 @section Predefined Target Types
27759 @cindex target descriptions, predefined types
27761 Type definitions in the self-description can build up composite types
27762 from basic building blocks, but can not define fundamental types. Instead,
27763 standard identifiers are provided by @value{GDBN} for the fundamental
27764 types. The currently supported types are:
27773 Signed integer types holding the specified number of bits.
27780 Unsigned integer types holding the specified number of bits.
27784 Pointers to unspecified code and data. The program counter and
27785 any dedicated return address register may be marked as code
27786 pointers; printing a code pointer converts it into a symbolic
27787 address. The stack pointer and any dedicated address registers
27788 may be marked as data pointers.
27791 Single precision IEEE floating point.
27794 Double precision IEEE floating point.
27797 The 12-byte extended precision format used by ARM FPA registers.
27801 @node Standard Target Features
27802 @section Standard Target Features
27803 @cindex target descriptions, standard features
27805 A target description must contain either no registers or all the
27806 target's registers. If the description contains no registers, then
27807 @value{GDBN} will assume a default register layout, selected based on
27808 the architecture. If the description contains any registers, the
27809 default layout will not be used; the standard registers must be
27810 described in the target description, in such a way that @value{GDBN}
27811 can recognize them.
27813 This is accomplished by giving specific names to feature elements
27814 which contain standard registers. @value{GDBN} will look for features
27815 with those names and verify that they contain the expected registers;
27816 if any known feature is missing required registers, or if any required
27817 feature is missing, @value{GDBN} will reject the target
27818 description. You can add additional registers to any of the
27819 standard features --- @value{GDBN} will display them just as if
27820 they were added to an unrecognized feature.
27822 This section lists the known features and their expected contents.
27823 Sample XML documents for these features are included in the
27824 @value{GDBN} source tree, in the directory @file{gdb/features}.
27826 Names recognized by @value{GDBN} should include the name of the
27827 company or organization which selected the name, and the overall
27828 architecture to which the feature applies; so e.g.@: the feature
27829 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
27831 The names of registers are not case sensitive for the purpose
27832 of recognizing standard features, but @value{GDBN} will only display
27833 registers using the capitalization used in the description.
27839 * PowerPC Features::
27844 @subsection ARM Features
27845 @cindex target descriptions, ARM features
27847 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
27848 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
27849 @samp{lr}, @samp{pc}, and @samp{cpsr}.
27851 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
27852 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
27854 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
27855 it should contain at least registers @samp{wR0} through @samp{wR15} and
27856 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
27857 @samp{wCSSF}, and @samp{wCASF} registers are optional.
27859 @node MIPS Features
27860 @subsection MIPS Features
27861 @cindex target descriptions, MIPS features
27863 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
27864 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
27865 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
27868 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
27869 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
27870 registers. They may be 32-bit or 64-bit depending on the target.
27872 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
27873 it may be optional in a future version of @value{GDBN}. It should
27874 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
27875 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
27877 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
27878 contain a single register, @samp{restart}, which is used by the
27879 Linux kernel to control restartable syscalls.
27881 @node M68K Features
27882 @subsection M68K Features
27883 @cindex target descriptions, M68K features
27886 @item @samp{org.gnu.gdb.m68k.core}
27887 @itemx @samp{org.gnu.gdb.coldfire.core}
27888 @itemx @samp{org.gnu.gdb.fido.core}
27889 One of those features must be always present.
27890 The feature that is present determines which flavor of m86k is
27891 used. The feature that is present should contain registers
27892 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
27893 @samp{sp}, @samp{ps} and @samp{pc}.
27895 @item @samp{org.gnu.gdb.coldfire.fp}
27896 This feature is optional. If present, it should contain registers
27897 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
27901 @node PowerPC Features
27902 @subsection PowerPC Features
27903 @cindex target descriptions, PowerPC features
27905 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
27906 targets. It should contain registers @samp{r0} through @samp{r31},
27907 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
27908 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
27910 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
27911 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
27913 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
27914 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
27917 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
27918 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
27919 will combine these registers with the floating point registers
27920 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
27921 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
27922 through @samp{vs63}, the set of vector registers for POWER7.
27924 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
27925 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
27926 @samp{spefscr}. SPE targets should provide 32-bit registers in
27927 @samp{org.gnu.gdb.power.core} and provide the upper halves in
27928 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
27929 these to present registers @samp{ev0} through @samp{ev31} to the
27944 % I think something like @colophon should be in texinfo. In the
27946 \long\def\colophon{\hbox to0pt{}\vfill
27947 \centerline{The body of this manual is set in}
27948 \centerline{\fontname\tenrm,}
27949 \centerline{with headings in {\bf\fontname\tenbf}}
27950 \centerline{and examples in {\tt\fontname\tentt}.}
27951 \centerline{{\it\fontname\tenit\/},}
27952 \centerline{{\bf\fontname\tenbf}, and}
27953 \centerline{{\sl\fontname\tensl\/}}
27954 \centerline{are used for emphasis.}\vfill}
27956 % Blame: doc@cygnus.com, 1991.