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 This is the default behaviour. All breakpoints, including newly added
3317 by the user, are inserted in the target only when the target is
3318 resumed. All breakpoints are 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.
3327 @cindex negative breakpoint numbers
3328 @cindex internal @value{GDBN} breakpoints
3329 @value{GDBN} itself sometimes sets breakpoints in your program for
3330 special purposes, such as proper handling of @code{longjmp} (in C
3331 programs). These internal breakpoints are assigned negative numbers,
3332 starting with @code{-1}; @samp{info breakpoints} does not display them.
3333 You can see these breakpoints with the @value{GDBN} maintenance command
3334 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3337 @node Set Watchpoints
3338 @subsection Setting Watchpoints
3340 @cindex setting watchpoints
3341 You can use a watchpoint to stop execution whenever the value of an
3342 expression changes, without having to predict a particular place where
3343 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3344 The expression may be as simple as the value of a single variable, or
3345 as complex as many variables combined by operators. Examples include:
3349 A reference to the value of a single variable.
3352 An address cast to an appropriate data type. For example,
3353 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3354 address (assuming an @code{int} occupies 4 bytes).
3357 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3358 expression can use any operators valid in the program's native
3359 language (@pxref{Languages}).
3362 You can set a watchpoint on an expression even if the expression can
3363 not be evaluated yet. For instance, you can set a watchpoint on
3364 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3365 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3366 the expression produces a valid value. If the expression becomes
3367 valid in some other way than changing a variable (e.g.@: if the memory
3368 pointed to by @samp{*global_ptr} becomes readable as the result of a
3369 @code{malloc} call), @value{GDBN} may not stop until the next time
3370 the expression changes.
3372 @cindex software watchpoints
3373 @cindex hardware watchpoints
3374 Depending on your system, watchpoints may be implemented in software or
3375 hardware. @value{GDBN} does software watchpointing by single-stepping your
3376 program and testing the variable's value each time, which is hundreds of
3377 times slower than normal execution. (But this may still be worth it, to
3378 catch errors where you have no clue what part of your program is the
3381 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3382 x86-based targets, @value{GDBN} includes support for hardware
3383 watchpoints, which do not slow down the running of your program.
3387 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3388 Set a watchpoint for an expression. @value{GDBN} will break when the
3389 expression @var{expr} is written into by the program and its value
3390 changes. The simplest (and the most popular) use of this command is
3391 to watch the value of a single variable:
3394 (@value{GDBP}) watch foo
3397 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3398 clause, @value{GDBN} breaks only when the thread identified by
3399 @var{threadnum} changes the value of @var{expr}. If any other threads
3400 change the value of @var{expr}, @value{GDBN} will not break. Note
3401 that watchpoints restricted to a single thread in this way only work
3402 with Hardware Watchpoints.
3405 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3406 Set a watchpoint that will break when the value of @var{expr} is read
3410 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3411 Set a watchpoint that will break when @var{expr} is either read from
3412 or written into by the program.
3414 @kindex info watchpoints @r{[}@var{n}@r{]}
3415 @item info watchpoints
3416 This command prints a list of watchpoints, breakpoints, and catchpoints;
3417 it is the same as @code{info break} (@pxref{Set Breaks}).
3420 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3421 watchpoints execute very quickly, and the debugger reports a change in
3422 value at the exact instruction where the change occurs. If @value{GDBN}
3423 cannot set a hardware watchpoint, it sets a software watchpoint, which
3424 executes more slowly and reports the change in value at the next
3425 @emph{statement}, not the instruction, after the change occurs.
3427 @cindex use only software watchpoints
3428 You can force @value{GDBN} to use only software watchpoints with the
3429 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3430 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3431 the underlying system supports them. (Note that hardware-assisted
3432 watchpoints that were set @emph{before} setting
3433 @code{can-use-hw-watchpoints} to zero will still use the hardware
3434 mechanism of watching expression values.)
3437 @item set can-use-hw-watchpoints
3438 @kindex set can-use-hw-watchpoints
3439 Set whether or not to use hardware watchpoints.
3441 @item show can-use-hw-watchpoints
3442 @kindex show can-use-hw-watchpoints
3443 Show the current mode of using hardware watchpoints.
3446 For remote targets, you can restrict the number of hardware
3447 watchpoints @value{GDBN} will use, see @ref{set remote
3448 hardware-breakpoint-limit}.
3450 When you issue the @code{watch} command, @value{GDBN} reports
3453 Hardware watchpoint @var{num}: @var{expr}
3457 if it was able to set a hardware watchpoint.
3459 Currently, the @code{awatch} and @code{rwatch} commands can only set
3460 hardware watchpoints, because accesses to data that don't change the
3461 value of the watched expression cannot be detected without examining
3462 every instruction as it is being executed, and @value{GDBN} does not do
3463 that currently. If @value{GDBN} finds that it is unable to set a
3464 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3465 will print a message like this:
3468 Expression cannot be implemented with read/access watchpoint.
3471 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3472 data type of the watched expression is wider than what a hardware
3473 watchpoint on the target machine can handle. For example, some systems
3474 can only watch regions that are up to 4 bytes wide; on such systems you
3475 cannot set hardware watchpoints for an expression that yields a
3476 double-precision floating-point number (which is typically 8 bytes
3477 wide). As a work-around, it might be possible to break the large region
3478 into a series of smaller ones and watch them with separate watchpoints.
3480 If you set too many hardware watchpoints, @value{GDBN} might be unable
3481 to insert all of them when you resume the execution of your program.
3482 Since the precise number of active watchpoints is unknown until such
3483 time as the program is about to be resumed, @value{GDBN} might not be
3484 able to warn you about this when you set the watchpoints, and the
3485 warning will be printed only when the program is resumed:
3488 Hardware watchpoint @var{num}: Could not insert watchpoint
3492 If this happens, delete or disable some of the watchpoints.
3494 Watching complex expressions that reference many variables can also
3495 exhaust the resources available for hardware-assisted watchpoints.
3496 That's because @value{GDBN} needs to watch every variable in the
3497 expression with separately allocated resources.
3499 If you call a function interactively using @code{print} or @code{call},
3500 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3501 kind of breakpoint or the call completes.
3503 @value{GDBN} automatically deletes watchpoints that watch local
3504 (automatic) variables, or expressions that involve such variables, when
3505 they go out of scope, that is, when the execution leaves the block in
3506 which these variables were defined. In particular, when the program
3507 being debugged terminates, @emph{all} local variables go out of scope,
3508 and so only watchpoints that watch global variables remain set. If you
3509 rerun the program, you will need to set all such watchpoints again. One
3510 way of doing that would be to set a code breakpoint at the entry to the
3511 @code{main} function and when it breaks, set all the watchpoints.
3513 @cindex watchpoints and threads
3514 @cindex threads and watchpoints
3515 In multi-threaded programs, watchpoints will detect changes to the
3516 watched expression from every thread.
3519 @emph{Warning:} In multi-threaded programs, software watchpoints
3520 have only limited usefulness. If @value{GDBN} creates a software
3521 watchpoint, it can only watch the value of an expression @emph{in a
3522 single thread}. If you are confident that the expression can only
3523 change due to the current thread's activity (and if you are also
3524 confident that no other thread can become current), then you can use
3525 software watchpoints as usual. However, @value{GDBN} may not notice
3526 when a non-current thread's activity changes the expression. (Hardware
3527 watchpoints, in contrast, watch an expression in all threads.)
3530 @xref{set remote hardware-watchpoint-limit}.
3532 @node Set Catchpoints
3533 @subsection Setting Catchpoints
3534 @cindex catchpoints, setting
3535 @cindex exception handlers
3536 @cindex event handling
3538 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3539 kinds of program events, such as C@t{++} exceptions or the loading of a
3540 shared library. Use the @code{catch} command to set a catchpoint.
3544 @item catch @var{event}
3545 Stop when @var{event} occurs. @var{event} can be any of the following:
3548 @cindex stop on C@t{++} exceptions
3549 The throwing of a C@t{++} exception.
3552 The catching of a C@t{++} exception.
3555 @cindex Ada exception catching
3556 @cindex catch Ada exceptions
3557 An Ada exception being raised. If an exception name is specified
3558 at the end of the command (eg @code{catch exception Program_Error}),
3559 the debugger will stop only when this specific exception is raised.
3560 Otherwise, the debugger stops execution when any Ada exception is raised.
3562 @item exception unhandled
3563 An exception that was raised but is not handled by the program.
3566 A failed Ada assertion.
3569 @cindex break on fork/exec
3570 A call to @code{exec}. This is currently only available for HP-UX
3574 A call to @code{fork}. This is currently only available for HP-UX
3578 A call to @code{vfork}. This is currently only available for HP-UX
3582 @itemx load @var{libname}
3583 @cindex break on load/unload of shared library
3584 The dynamic loading of any shared library, or the loading of the library
3585 @var{libname}. This is currently only available for HP-UX.
3588 @itemx unload @var{libname}
3589 The unloading of any dynamically loaded shared library, or the unloading
3590 of the library @var{libname}. This is currently only available for HP-UX.
3593 @item tcatch @var{event}
3594 Set a catchpoint that is enabled only for one stop. The catchpoint is
3595 automatically deleted after the first time the event is caught.
3599 Use the @code{info break} command to list the current catchpoints.
3601 There are currently some limitations to C@t{++} exception handling
3602 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3606 If you call a function interactively, @value{GDBN} normally returns
3607 control to you when the function has finished executing. If the call
3608 raises an exception, however, the call may bypass the mechanism that
3609 returns control to you and cause your program either to abort or to
3610 simply continue running until it hits a breakpoint, catches a signal
3611 that @value{GDBN} is listening for, or exits. This is the case even if
3612 you set a catchpoint for the exception; catchpoints on exceptions are
3613 disabled within interactive calls.
3616 You cannot raise an exception interactively.
3619 You cannot install an exception handler interactively.
3622 @cindex raise exceptions
3623 Sometimes @code{catch} is not the best way to debug exception handling:
3624 if you need to know exactly where an exception is raised, it is better to
3625 stop @emph{before} the exception handler is called, since that way you
3626 can see the stack before any unwinding takes place. If you set a
3627 breakpoint in an exception handler instead, it may not be easy to find
3628 out where the exception was raised.
3630 To stop just before an exception handler is called, you need some
3631 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3632 raised by calling a library function named @code{__raise_exception}
3633 which has the following ANSI C interface:
3636 /* @var{addr} is where the exception identifier is stored.
3637 @var{id} is the exception identifier. */
3638 void __raise_exception (void **addr, void *id);
3642 To make the debugger catch all exceptions before any stack
3643 unwinding takes place, set a breakpoint on @code{__raise_exception}
3644 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3646 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3647 that depends on the value of @var{id}, you can stop your program when
3648 a specific exception is raised. You can use multiple conditional
3649 breakpoints to stop your program when any of a number of exceptions are
3654 @subsection Deleting Breakpoints
3656 @cindex clearing breakpoints, watchpoints, catchpoints
3657 @cindex deleting breakpoints, watchpoints, catchpoints
3658 It is often necessary to eliminate a breakpoint, watchpoint, or
3659 catchpoint once it has done its job and you no longer want your program
3660 to stop there. This is called @dfn{deleting} the breakpoint. A
3661 breakpoint that has been deleted no longer exists; it is forgotten.
3663 With the @code{clear} command you can delete breakpoints according to
3664 where they are in your program. With the @code{delete} command you can
3665 delete individual breakpoints, watchpoints, or catchpoints by specifying
3666 their breakpoint numbers.
3668 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3669 automatically ignores breakpoints on the first instruction to be executed
3670 when you continue execution without changing the execution address.
3675 Delete any breakpoints at the next instruction to be executed in the
3676 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3677 the innermost frame is selected, this is a good way to delete a
3678 breakpoint where your program just stopped.
3680 @item clear @var{location}
3681 Delete any breakpoints set at the specified @var{location}.
3682 @xref{Specify Location}, for the various forms of @var{location}; the
3683 most useful ones are listed below:
3686 @item clear @var{function}
3687 @itemx clear @var{filename}:@var{function}
3688 Delete any breakpoints set at entry to the named @var{function}.
3690 @item clear @var{linenum}
3691 @itemx clear @var{filename}:@var{linenum}
3692 Delete any breakpoints set at or within the code of the specified
3693 @var{linenum} of the specified @var{filename}.
3696 @cindex delete breakpoints
3698 @kindex d @r{(@code{delete})}
3699 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3700 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3701 ranges specified as arguments. If no argument is specified, delete all
3702 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3703 confirm off}). You can abbreviate this command as @code{d}.
3707 @subsection Disabling Breakpoints
3709 @cindex enable/disable a breakpoint
3710 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3711 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3712 it had been deleted, but remembers the information on the breakpoint so
3713 that you can @dfn{enable} it again later.
3715 You disable and enable breakpoints, watchpoints, and catchpoints with
3716 the @code{enable} and @code{disable} commands, optionally specifying one
3717 or more breakpoint numbers as arguments. Use @code{info break} or
3718 @code{info watch} to print a list of breakpoints, watchpoints, and
3719 catchpoints if you do not know which numbers to use.
3721 Disabling and enabling a breakpoint that has multiple locations
3722 affects all of its locations.
3724 A breakpoint, watchpoint, or catchpoint can have any of four different
3725 states of enablement:
3729 Enabled. The breakpoint stops your program. A breakpoint set
3730 with the @code{break} command starts out in this state.
3732 Disabled. The breakpoint has no effect on your program.
3734 Enabled once. The breakpoint stops your program, but then becomes
3737 Enabled for deletion. The breakpoint stops your program, but
3738 immediately after it does so it is deleted permanently. A breakpoint
3739 set with the @code{tbreak} command starts out in this state.
3742 You can use the following commands to enable or disable breakpoints,
3743 watchpoints, and catchpoints:
3747 @kindex dis @r{(@code{disable})}
3748 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3749 Disable the specified breakpoints---or all breakpoints, if none are
3750 listed. A disabled breakpoint has no effect but is not forgotten. All
3751 options such as ignore-counts, conditions and commands are remembered in
3752 case the breakpoint is enabled again later. You may abbreviate
3753 @code{disable} as @code{dis}.
3756 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3757 Enable the specified breakpoints (or all defined breakpoints). They
3758 become effective once again in stopping your program.
3760 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3761 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3762 of these breakpoints immediately after stopping your program.
3764 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3765 Enable the specified breakpoints to work once, then die. @value{GDBN}
3766 deletes any of these breakpoints as soon as your program stops there.
3767 Breakpoints set by the @code{tbreak} command start out in this state.
3770 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3771 @c confusing: tbreak is also initially enabled.
3772 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3773 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3774 subsequently, they become disabled or enabled only when you use one of
3775 the commands above. (The command @code{until} can set and delete a
3776 breakpoint of its own, but it does not change the state of your other
3777 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3781 @subsection Break Conditions
3782 @cindex conditional breakpoints
3783 @cindex breakpoint conditions
3785 @c FIXME what is scope of break condition expr? Context where wanted?
3786 @c in particular for a watchpoint?
3787 The simplest sort of breakpoint breaks every time your program reaches a
3788 specified place. You can also specify a @dfn{condition} for a
3789 breakpoint. A condition is just a Boolean expression in your
3790 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3791 a condition evaluates the expression each time your program reaches it,
3792 and your program stops only if the condition is @emph{true}.
3794 This is the converse of using assertions for program validation; in that
3795 situation, you want to stop when the assertion is violated---that is,
3796 when the condition is false. In C, if you want to test an assertion expressed
3797 by the condition @var{assert}, you should set the condition
3798 @samp{! @var{assert}} on the appropriate breakpoint.
3800 Conditions are also accepted for watchpoints; you may not need them,
3801 since a watchpoint is inspecting the value of an expression anyhow---but
3802 it might be simpler, say, to just set a watchpoint on a variable name,
3803 and specify a condition that tests whether the new value is an interesting
3806 Break conditions can have side effects, and may even call functions in
3807 your program. This can be useful, for example, to activate functions
3808 that log program progress, or to use your own print functions to
3809 format special data structures. The effects are completely predictable
3810 unless there is another enabled breakpoint at the same address. (In
3811 that case, @value{GDBN} might see the other breakpoint first and stop your
3812 program without checking the condition of this one.) Note that
3813 breakpoint commands are usually more convenient and flexible than break
3815 purpose of performing side effects when a breakpoint is reached
3816 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3818 Break conditions can be specified when a breakpoint is set, by using
3819 @samp{if} in the arguments to the @code{break} command. @xref{Set
3820 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3821 with the @code{condition} command.
3823 You can also use the @code{if} keyword with the @code{watch} command.
3824 The @code{catch} command does not recognize the @code{if} keyword;
3825 @code{condition} is the only way to impose a further condition on a
3830 @item condition @var{bnum} @var{expression}
3831 Specify @var{expression} as the break condition for breakpoint,
3832 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3833 breakpoint @var{bnum} stops your program only if the value of
3834 @var{expression} is true (nonzero, in C). When you use
3835 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3836 syntactic correctness, and to determine whether symbols in it have
3837 referents in the context of your breakpoint. If @var{expression} uses
3838 symbols not referenced in the context of the breakpoint, @value{GDBN}
3839 prints an error message:
3842 No symbol "foo" in current context.
3847 not actually evaluate @var{expression} at the time the @code{condition}
3848 command (or a command that sets a breakpoint with a condition, like
3849 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3851 @item condition @var{bnum}
3852 Remove the condition from breakpoint number @var{bnum}. It becomes
3853 an ordinary unconditional breakpoint.
3856 @cindex ignore count (of breakpoint)
3857 A special case of a breakpoint condition is to stop only when the
3858 breakpoint has been reached a certain number of times. This is so
3859 useful that there is a special way to do it, using the @dfn{ignore
3860 count} of the breakpoint. Every breakpoint has an ignore count, which
3861 is an integer. Most of the time, the ignore count is zero, and
3862 therefore has no effect. But if your program reaches a breakpoint whose
3863 ignore count is positive, then instead of stopping, it just decrements
3864 the ignore count by one and continues. As a result, if the ignore count
3865 value is @var{n}, the breakpoint does not stop the next @var{n} times
3866 your program reaches it.
3870 @item ignore @var{bnum} @var{count}
3871 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3872 The next @var{count} times the breakpoint is reached, your program's
3873 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3876 To make the breakpoint stop the next time it is reached, specify
3879 When you use @code{continue} to resume execution of your program from a
3880 breakpoint, you can specify an ignore count directly as an argument to
3881 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3882 Stepping,,Continuing and Stepping}.
3884 If a breakpoint has a positive ignore count and a condition, the
3885 condition is not checked. Once the ignore count reaches zero,
3886 @value{GDBN} resumes checking the condition.
3888 You could achieve the effect of the ignore count with a condition such
3889 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3890 is decremented each time. @xref{Convenience Vars, ,Convenience
3894 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3897 @node Break Commands
3898 @subsection Breakpoint Command Lists
3900 @cindex breakpoint commands
3901 You can give any breakpoint (or watchpoint or catchpoint) a series of
3902 commands to execute when your program stops due to that breakpoint. For
3903 example, you might want to print the values of certain expressions, or
3904 enable other breakpoints.
3908 @kindex end@r{ (breakpoint commands)}
3909 @item commands @r{[}@var{bnum}@r{]}
3910 @itemx @dots{} @var{command-list} @dots{}
3912 Specify a list of commands for breakpoint number @var{bnum}. The commands
3913 themselves appear on the following lines. Type a line containing just
3914 @code{end} to terminate the commands.
3916 To remove all commands from a breakpoint, type @code{commands} and
3917 follow it immediately with @code{end}; that is, give no commands.
3919 With no @var{bnum} argument, @code{commands} refers to the last
3920 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3921 recently encountered).
3924 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3925 disabled within a @var{command-list}.
3927 You can use breakpoint commands to start your program up again. Simply
3928 use the @code{continue} command, or @code{step}, or any other command
3929 that resumes execution.
3931 Any other commands in the command list, after a command that resumes
3932 execution, are ignored. This is because any time you resume execution
3933 (even with a simple @code{next} or @code{step}), you may encounter
3934 another breakpoint---which could have its own command list, leading to
3935 ambiguities about which list to execute.
3938 If the first command you specify in a command list is @code{silent}, the
3939 usual message about stopping at a breakpoint is not printed. This may
3940 be desirable for breakpoints that are to print a specific message and
3941 then continue. If none of the remaining commands print anything, you
3942 see no sign that the breakpoint was reached. @code{silent} is
3943 meaningful only at the beginning of a breakpoint command list.
3945 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3946 print precisely controlled output, and are often useful in silent
3947 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3949 For example, here is how you could use breakpoint commands to print the
3950 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3956 printf "x is %d\n",x
3961 One application for breakpoint commands is to compensate for one bug so
3962 you can test for another. Put a breakpoint just after the erroneous line
3963 of code, give it a condition to detect the case in which something
3964 erroneous has been done, and give it commands to assign correct values
3965 to any variables that need them. End with the @code{continue} command
3966 so that your program does not stop, and start with the @code{silent}
3967 command so that no output is produced. Here is an example:
3978 @c @ifclear BARETARGET
3979 @node Error in Breakpoints
3980 @subsection ``Cannot insert breakpoints''
3982 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3984 Under some operating systems, breakpoints cannot be used in a program if
3985 any other process is running that program. In this situation,
3986 attempting to run or continue a program with a breakpoint causes
3987 @value{GDBN} to print an error message:
3990 Cannot insert breakpoints.
3991 The same program may be running in another process.
3994 When this happens, you have three ways to proceed:
3998 Remove or disable the breakpoints, then continue.
4001 Suspend @value{GDBN}, and copy the file containing your program to a new
4002 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
4003 that @value{GDBN} should run your program under that name.
4004 Then start your program again.
4007 Relink your program so that the text segment is nonsharable, using the
4008 linker option @samp{-N}. The operating system limitation may not apply
4009 to nonsharable executables.
4013 A similar message can be printed if you request too many active
4014 hardware-assisted breakpoints and watchpoints:
4016 @c FIXME: the precise wording of this message may change; the relevant
4017 @c source change is not committed yet (Sep 3, 1999).
4019 Stopped; cannot insert breakpoints.
4020 You may have requested too many hardware breakpoints and watchpoints.
4024 This message is printed when you attempt to resume the program, since
4025 only then @value{GDBN} knows exactly how many hardware breakpoints and
4026 watchpoints it needs to insert.
4028 When this message is printed, you need to disable or remove some of the
4029 hardware-assisted breakpoints and watchpoints, and then continue.
4031 @node Breakpoint-related Warnings
4032 @subsection ``Breakpoint address adjusted...''
4033 @cindex breakpoint address adjusted
4035 Some processor architectures place constraints on the addresses at
4036 which breakpoints may be placed. For architectures thus constrained,
4037 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4038 with the constraints dictated by the architecture.
4040 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4041 a VLIW architecture in which a number of RISC-like instructions may be
4042 bundled together for parallel execution. The FR-V architecture
4043 constrains the location of a breakpoint instruction within such a
4044 bundle to the instruction with the lowest address. @value{GDBN}
4045 honors this constraint by adjusting a breakpoint's address to the
4046 first in the bundle.
4048 It is not uncommon for optimized code to have bundles which contain
4049 instructions from different source statements, thus it may happen that
4050 a breakpoint's address will be adjusted from one source statement to
4051 another. Since this adjustment may significantly alter @value{GDBN}'s
4052 breakpoint related behavior from what the user expects, a warning is
4053 printed when the breakpoint is first set and also when the breakpoint
4056 A warning like the one below is printed when setting a breakpoint
4057 that's been subject to address adjustment:
4060 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4063 Such warnings are printed both for user settable and @value{GDBN}'s
4064 internal breakpoints. If you see one of these warnings, you should
4065 verify that a breakpoint set at the adjusted address will have the
4066 desired affect. If not, the breakpoint in question may be removed and
4067 other breakpoints may be set which will have the desired behavior.
4068 E.g., it may be sufficient to place the breakpoint at a later
4069 instruction. A conditional breakpoint may also be useful in some
4070 cases to prevent the breakpoint from triggering too often.
4072 @value{GDBN} will also issue a warning when stopping at one of these
4073 adjusted breakpoints:
4076 warning: Breakpoint 1 address previously adjusted from 0x00010414
4080 When this warning is encountered, it may be too late to take remedial
4081 action except in cases where the breakpoint is hit earlier or more
4082 frequently than expected.
4084 @node Continuing and Stepping
4085 @section Continuing and Stepping
4089 @cindex resuming execution
4090 @dfn{Continuing} means resuming program execution until your program
4091 completes normally. In contrast, @dfn{stepping} means executing just
4092 one more ``step'' of your program, where ``step'' may mean either one
4093 line of source code, or one machine instruction (depending on what
4094 particular command you use). Either when continuing or when stepping,
4095 your program may stop even sooner, due to a breakpoint or a signal. (If
4096 it stops due to a signal, you may want to use @code{handle}, or use
4097 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4101 @kindex c @r{(@code{continue})}
4102 @kindex fg @r{(resume foreground execution)}
4103 @item continue @r{[}@var{ignore-count}@r{]}
4104 @itemx c @r{[}@var{ignore-count}@r{]}
4105 @itemx fg @r{[}@var{ignore-count}@r{]}
4106 Resume program execution, at the address where your program last stopped;
4107 any breakpoints set at that address are bypassed. The optional argument
4108 @var{ignore-count} allows you to specify a further number of times to
4109 ignore a breakpoint at this location; its effect is like that of
4110 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4112 The argument @var{ignore-count} is meaningful only when your program
4113 stopped due to a breakpoint. At other times, the argument to
4114 @code{continue} is ignored.
4116 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4117 debugged program is deemed to be the foreground program) are provided
4118 purely for convenience, and have exactly the same behavior as
4122 To resume execution at a different place, you can use @code{return}
4123 (@pxref{Returning, ,Returning from a Function}) to go back to the
4124 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4125 Different Address}) to go to an arbitrary location in your program.
4127 A typical technique for using stepping is to set a breakpoint
4128 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4129 beginning of the function or the section of your program where a problem
4130 is believed to lie, run your program until it stops at that breakpoint,
4131 and then step through the suspect area, examining the variables that are
4132 interesting, until you see the problem happen.
4136 @kindex s @r{(@code{step})}
4138 Continue running your program until control reaches a different source
4139 line, then stop it and return control to @value{GDBN}. This command is
4140 abbreviated @code{s}.
4143 @c "without debugging information" is imprecise; actually "without line
4144 @c numbers in the debugging information". (gcc -g1 has debugging info but
4145 @c not line numbers). But it seems complex to try to make that
4146 @c distinction here.
4147 @emph{Warning:} If you use the @code{step} command while control is
4148 within a function that was compiled without debugging information,
4149 execution proceeds until control reaches a function that does have
4150 debugging information. Likewise, it will not step into a function which
4151 is compiled without debugging information. To step through functions
4152 without debugging information, use the @code{stepi} command, described
4156 The @code{step} command only stops at the first instruction of a source
4157 line. This prevents the multiple stops that could otherwise occur in
4158 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4159 to stop if a function that has debugging information is called within
4160 the line. In other words, @code{step} @emph{steps inside} any functions
4161 called within the line.
4163 Also, the @code{step} command only enters a function if there is line
4164 number information for the function. Otherwise it acts like the
4165 @code{next} command. This avoids problems when using @code{cc -gl}
4166 on MIPS machines. Previously, @code{step} entered subroutines if there
4167 was any debugging information about the routine.
4169 @item step @var{count}
4170 Continue running as in @code{step}, but do so @var{count} times. If a
4171 breakpoint is reached, or a signal not related to stepping occurs before
4172 @var{count} steps, stepping stops right away.
4175 @kindex n @r{(@code{next})}
4176 @item next @r{[}@var{count}@r{]}
4177 Continue to the next source line in the current (innermost) stack frame.
4178 This is similar to @code{step}, but function calls that appear within
4179 the line of code are executed without stopping. Execution stops when
4180 control reaches a different line of code at the original stack level
4181 that was executing when you gave the @code{next} command. This command
4182 is abbreviated @code{n}.
4184 An argument @var{count} is a repeat count, as for @code{step}.
4187 @c FIX ME!! Do we delete this, or is there a way it fits in with
4188 @c the following paragraph? --- Vctoria
4190 @c @code{next} within a function that lacks debugging information acts like
4191 @c @code{step}, but any function calls appearing within the code of the
4192 @c function are executed without stopping.
4194 The @code{next} command only stops at the first instruction of a
4195 source line. This prevents multiple stops that could otherwise occur in
4196 @code{switch} statements, @code{for} loops, etc.
4198 @kindex set step-mode
4200 @cindex functions without line info, and stepping
4201 @cindex stepping into functions with no line info
4202 @itemx set step-mode on
4203 The @code{set step-mode on} command causes the @code{step} command to
4204 stop at the first instruction of a function which contains no debug line
4205 information rather than stepping over it.
4207 This is useful in cases where you may be interested in inspecting the
4208 machine instructions of a function which has no symbolic info and do not
4209 want @value{GDBN} to automatically skip over this function.
4211 @item set step-mode off
4212 Causes the @code{step} command to step over any functions which contains no
4213 debug information. This is the default.
4215 @item show step-mode
4216 Show whether @value{GDBN} will stop in or step over functions without
4217 source line debug information.
4220 @kindex fin @r{(@code{finish})}
4222 Continue running until just after function in the selected stack frame
4223 returns. Print the returned value (if any). This command can be
4224 abbreviated as @code{fin}.
4226 Contrast this with the @code{return} command (@pxref{Returning,
4227 ,Returning from a Function}).
4230 @kindex u @r{(@code{until})}
4231 @cindex run until specified location
4234 Continue running until a source line past the current line, in the
4235 current stack frame, is reached. This command is used to avoid single
4236 stepping through a loop more than once. It is like the @code{next}
4237 command, except that when @code{until} encounters a jump, it
4238 automatically continues execution until the program counter is greater
4239 than the address of the jump.
4241 This means that when you reach the end of a loop after single stepping
4242 though it, @code{until} makes your program continue execution until it
4243 exits the loop. In contrast, a @code{next} command at the end of a loop
4244 simply steps back to the beginning of the loop, which forces you to step
4245 through the next iteration.
4247 @code{until} always stops your program if it attempts to exit the current
4250 @code{until} may produce somewhat counterintuitive results if the order
4251 of machine code does not match the order of the source lines. For
4252 example, in the following excerpt from a debugging session, the @code{f}
4253 (@code{frame}) command shows that execution is stopped at line
4254 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4258 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4260 (@value{GDBP}) until
4261 195 for ( ; argc > 0; NEXTARG) @{
4264 This happened because, for execution efficiency, the compiler had
4265 generated code for the loop closure test at the end, rather than the
4266 start, of the loop---even though the test in a C @code{for}-loop is
4267 written before the body of the loop. The @code{until} command appeared
4268 to step back to the beginning of the loop when it advanced to this
4269 expression; however, it has not really gone to an earlier
4270 statement---not in terms of the actual machine code.
4272 @code{until} with no argument works by means of single
4273 instruction stepping, and hence is slower than @code{until} with an
4276 @item until @var{location}
4277 @itemx u @var{location}
4278 Continue running your program until either the specified location is
4279 reached, or the current stack frame returns. @var{location} is any of
4280 the forms described in @ref{Specify Location}.
4281 This form of the command uses temporary breakpoints, and
4282 hence is quicker than @code{until} without an argument. The specified
4283 location is actually reached only if it is in the current frame. This
4284 implies that @code{until} can be used to skip over recursive function
4285 invocations. For instance in the code below, if the current location is
4286 line @code{96}, issuing @code{until 99} will execute the program up to
4287 line @code{99} in the same invocation of factorial, i.e., after the inner
4288 invocations have returned.
4291 94 int factorial (int value)
4293 96 if (value > 1) @{
4294 97 value *= factorial (value - 1);
4301 @kindex advance @var{location}
4302 @itemx advance @var{location}
4303 Continue running the program up to the given @var{location}. An argument is
4304 required, which should be of one of the forms described in
4305 @ref{Specify Location}.
4306 Execution will also stop upon exit from the current stack
4307 frame. This command is similar to @code{until}, but @code{advance} will
4308 not skip over recursive function calls, and the target location doesn't
4309 have to be in the same frame as the current one.
4313 @kindex si @r{(@code{stepi})}
4315 @itemx stepi @var{arg}
4317 Execute one machine instruction, then stop and return to the debugger.
4319 It is often useful to do @samp{display/i $pc} when stepping by machine
4320 instructions. This makes @value{GDBN} automatically display the next
4321 instruction to be executed, each time your program stops. @xref{Auto
4322 Display,, Automatic Display}.
4324 An argument is a repeat count, as in @code{step}.
4328 @kindex ni @r{(@code{nexti})}
4330 @itemx nexti @var{arg}
4332 Execute one machine instruction, but if it is a function call,
4333 proceed until the function returns.
4335 An argument is a repeat count, as in @code{next}.
4342 A signal is an asynchronous event that can happen in a program. The
4343 operating system defines the possible kinds of signals, and gives each
4344 kind a name and a number. For example, in Unix @code{SIGINT} is the
4345 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4346 @code{SIGSEGV} is the signal a program gets from referencing a place in
4347 memory far away from all the areas in use; @code{SIGALRM} occurs when
4348 the alarm clock timer goes off (which happens only if your program has
4349 requested an alarm).
4351 @cindex fatal signals
4352 Some signals, including @code{SIGALRM}, are a normal part of the
4353 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4354 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4355 program has not specified in advance some other way to handle the signal.
4356 @code{SIGINT} does not indicate an error in your program, but it is normally
4357 fatal so it can carry out the purpose of the interrupt: to kill the program.
4359 @value{GDBN} has the ability to detect any occurrence of a signal in your
4360 program. You can tell @value{GDBN} in advance what to do for each kind of
4363 @cindex handling signals
4364 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4365 @code{SIGALRM} be silently passed to your program
4366 (so as not to interfere with their role in the program's functioning)
4367 but to stop your program immediately whenever an error signal happens.
4368 You can change these settings with the @code{handle} command.
4371 @kindex info signals
4375 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4376 handle each one. You can use this to see the signal numbers of all
4377 the defined types of signals.
4379 @item info signals @var{sig}
4380 Similar, but print information only about the specified signal number.
4382 @code{info handle} is an alias for @code{info signals}.
4385 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4386 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4387 can be the number of a signal or its name (with or without the
4388 @samp{SIG} at the beginning); a list of signal numbers of the form
4389 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4390 known signals. Optional arguments @var{keywords}, described below,
4391 say what change to make.
4395 The keywords allowed by the @code{handle} command can be abbreviated.
4396 Their full names are:
4400 @value{GDBN} should not stop your program when this signal happens. It may
4401 still print a message telling you that the signal has come in.
4404 @value{GDBN} should stop your program when this signal happens. This implies
4405 the @code{print} keyword as well.
4408 @value{GDBN} should print a message when this signal happens.
4411 @value{GDBN} should not mention the occurrence of the signal at all. This
4412 implies the @code{nostop} keyword as well.
4416 @value{GDBN} should allow your program to see this signal; your program
4417 can handle the signal, or else it may terminate if the signal is fatal
4418 and not handled. @code{pass} and @code{noignore} are synonyms.
4422 @value{GDBN} should not allow your program to see this signal.
4423 @code{nopass} and @code{ignore} are synonyms.
4427 When a signal stops your program, the signal is not visible to the
4429 continue. Your program sees the signal then, if @code{pass} is in
4430 effect for the signal in question @emph{at that time}. In other words,
4431 after @value{GDBN} reports a signal, you can use the @code{handle}
4432 command with @code{pass} or @code{nopass} to control whether your
4433 program sees that signal when you continue.
4435 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4436 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4437 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4440 You can also use the @code{signal} command to prevent your program from
4441 seeing a signal, or cause it to see a signal it normally would not see,
4442 or to give it any signal at any time. For example, if your program stopped
4443 due to some sort of memory reference error, you might store correct
4444 values into the erroneous variables and continue, hoping to see more
4445 execution; but your program would probably terminate immediately as
4446 a result of the fatal signal once it saw the signal. To prevent this,
4447 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4451 @section Stopping and Starting Multi-thread Programs
4453 @cindex stopped threads
4454 @cindex threads, stopped
4456 @cindex continuing threads
4457 @cindex threads, continuing
4459 @value{GDBN} supports debugging programs with multiple threads
4460 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4461 are two modes of controlling execution of your program within the
4462 debugger. In the default mode, referred to as @dfn{all-stop mode},
4463 when any thread in your program stops (for example, at a breakpoint
4464 or while being stepped), all other threads in the program are also stopped by
4465 @value{GDBN}. On some targets, @value{GDBN} also supports
4466 @dfn{non-stop mode}, in which other threads can continue to run freely while
4467 you examine the stopped thread in the debugger.
4470 * All-Stop Mode:: All threads stop when GDB takes control
4471 * Non-Stop Mode:: Other threads continue to execute
4472 * Background Execution:: Running your program asynchronously
4473 * Thread-Specific Breakpoints:: Controlling breakpoints
4474 * Interrupted System Calls:: GDB may interfere with system calls
4478 @subsection All-Stop Mode
4480 @cindex all-stop mode
4482 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4483 @emph{all} threads of execution stop, not just the current thread. This
4484 allows you to examine the overall state of the program, including
4485 switching between threads, without worrying that things may change
4488 Conversely, whenever you restart the program, @emph{all} threads start
4489 executing. @emph{This is true even when single-stepping} with commands
4490 like @code{step} or @code{next}.
4492 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4493 Since thread scheduling is up to your debugging target's operating
4494 system (not controlled by @value{GDBN}), other threads may
4495 execute more than one statement while the current thread completes a
4496 single step. Moreover, in general other threads stop in the middle of a
4497 statement, rather than at a clean statement boundary, when the program
4500 You might even find your program stopped in another thread after
4501 continuing or even single-stepping. This happens whenever some other
4502 thread runs into a breakpoint, a signal, or an exception before the
4503 first thread completes whatever you requested.
4505 @cindex automatic thread selection
4506 @cindex switching threads automatically
4507 @cindex threads, automatic switching
4508 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4509 signal, it automatically selects the thread where that breakpoint or
4510 signal happened. @value{GDBN} alerts you to the context switch with a
4511 message such as @samp{[Switching to Thread @var{n}]} to identify the
4514 On some OSes, you can modify @value{GDBN}'s default behavior by
4515 locking the OS scheduler to allow only a single thread to run.
4518 @item set scheduler-locking @var{mode}
4519 @cindex scheduler locking mode
4520 @cindex lock scheduler
4521 Set the scheduler locking mode. If it is @code{off}, then there is no
4522 locking and any thread may run at any time. If @code{on}, then only the
4523 current thread may run when the inferior is resumed. The @code{step}
4524 mode optimizes for single-stepping; it prevents other threads
4525 from preempting the current thread while you are stepping, so that
4526 the focus of debugging does not change unexpectedly.
4527 Other threads only rarely (or never) get a chance to run
4528 when you step. They are more likely to run when you @samp{next} over a
4529 function call, and they are completely free to run when you use commands
4530 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4531 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4532 the current thread away from the thread that you are debugging.
4534 @item show scheduler-locking
4535 Display the current scheduler locking mode.
4539 @subsection Non-Stop Mode
4541 @cindex non-stop mode
4543 @c This section is really only a place-holder, and needs to be expanded
4544 @c with more details.
4546 For some multi-threaded targets, @value{GDBN} supports an optional
4547 mode of operation in which you can examine stopped program threads in
4548 the debugger while other threads continue to execute freely. This
4549 minimizes intrusion when debugging live systems, such as programs
4550 where some threads have real-time constraints or must continue to
4551 respond to external events. This is referred to as @dfn{non-stop} mode.
4553 In non-stop mode, when a thread stops to report a debugging event,
4554 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4555 threads as well, in contrast to the all-stop mode behavior. Additionally,
4556 execution commands such as @code{continue} and @code{step} apply by default
4557 only to the current thread in non-stop mode, rather than all threads as
4558 in all-stop mode. This allows you to control threads explicitly in
4559 ways that are not possible in all-stop mode --- for example, stepping
4560 one thread while allowing others to run freely, stepping
4561 one thread while holding all others stopped, or stepping several threads
4562 independently and simultaneously.
4564 To enter non-stop mode, use this sequence of commands before you run
4565 or attach to your program:
4567 @c FIXME: can we fix this recipe to avoid the linux-async/remote-async details?
4570 # Enable the async interface.
4571 # For target remote, use remote-async instead of linux-async.
4572 maint set linux-async 1
4574 # With non-stop, breakpoints have to be always inserted.
4575 set breakpoint always-inserted 1
4577 # If using the CLI, pagination breaks non-stop.
4580 # Finally, turn it on!
4584 You can use these commands to manipulate the non-stop mode setting:
4587 @kindex set non-stop
4588 @item set non-stop on
4589 Enable selection of non-stop mode.
4590 @item set non-stop off
4591 Disable selection of non-stop mode.
4592 @kindex show non-stop
4594 Show the current non-stop enablement setting.
4597 Note these commands only reflect whether non-stop mode is enabled,
4598 not whether the currently-executing program is being run in non-stop mode.
4599 In particular, the @code{set non-stop} preference is only consulted when
4600 @value{GDBN} starts or connects to the target program, and it is generally
4601 not possible to switch modes once debugging has started. Furthermore,
4602 since not all targets support non-stop mode, even when you have enabled
4603 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4606 In non-stop mode, all execution commands apply only to the current thread
4607 by default. That is, @code{continue} only continues one thread.
4608 To continue all threads, issue @code{continue -a} or @code{c -a}.
4610 You can use @value{GDBN}'s background execution commands
4611 (@pxref{Background Execution}) to run some threads in the background
4612 while you continue to examine or step others from @value{GDBN}.
4613 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4614 always executed asynchronously in non-stop mode.
4616 Suspending execution is done with the @code{interrupt} command when
4617 running in the background, or @kbd{Ctrl-c} during foreground execution.
4618 In all-stop mode, this stops the whole process;
4619 but in non-stop mode the interrupt applies only to the current thread.
4620 To stop the whole program, use @code{interrupt -a}.
4622 Other execution commands do not currently support the @code{-a} option.
4624 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4625 that thread current, as it does in all-stop mode. This is because the
4626 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4627 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4628 changed to a different thread just as you entered a command to operate on the
4629 previously current thread.
4631 @node Background Execution
4632 @subsection Background Execution
4634 @cindex foreground execution
4635 @cindex background execution
4636 @cindex asynchronous execution
4637 @cindex execution, foreground, background and asynchronous
4639 @value{GDBN}'s execution commands have two variants: the normal
4640 foreground (synchronous) behavior, and a background
4641 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4642 the program to report that some thread has stopped before prompting for
4643 another command. In background execution, @value{GDBN} immediately gives
4644 a command prompt so that you can issue other commands while your program runs.
4646 To specify background execution, add a @code{&} to the command. For example,
4647 the background form of the @code{continue} command is @code{continue&}, or
4648 just @code{c&}. The execution commands that accept background execution
4654 @xref{Starting, , Starting your Program}.
4658 @xref{Attach, , Debugging an Already-running Process}.
4662 @xref{Continuing and Stepping, step}.
4666 @xref{Continuing and Stepping, stepi}.
4670 @xref{Continuing and Stepping, next}.
4674 @xref{Continuing and Stepping, continue}.
4678 @xref{Continuing and Stepping, finish}.
4682 @xref{Continuing and Stepping, until}.
4686 Background execution is especially useful in conjunction with non-stop
4687 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4688 However, you can also use these commands in the normal all-stop mode with
4689 the restriction that you cannot issue another execution command until the
4690 previous one finishes. Examples of commands that are valid in all-stop
4691 mode while the program is running include @code{help} and @code{info break}.
4693 You can interrupt your program while it is running in the background by
4694 using the @code{interrupt} command.
4701 Suspend execution of the running program. In all-stop mode,
4702 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4703 only the current thread. To stop the whole program in non-stop mode,
4704 use @code{interrupt -a}.
4707 You may need to explicitly enable async mode before you can use background
4708 execution commands. @xref{Maintenance Commands}, for details. If the
4709 target doesn't support async mode, @value{GDBN} issues an error message
4710 if you attempt to use the background execution commands.
4712 @node Thread-Specific Breakpoints
4713 @subsection Thread-Specific Breakpoints
4715 When your program has multiple threads (@pxref{Threads,, Debugging
4716 Programs with Multiple Threads}), you can choose whether to set
4717 breakpoints on all threads, or on a particular thread.
4720 @cindex breakpoints and threads
4721 @cindex thread breakpoints
4722 @kindex break @dots{} thread @var{threadno}
4723 @item break @var{linespec} thread @var{threadno}
4724 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4725 @var{linespec} specifies source lines; there are several ways of
4726 writing them (@pxref{Specify Location}), but the effect is always to
4727 specify some source line.
4729 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4730 to specify that you only want @value{GDBN} to stop the program when a
4731 particular thread reaches this breakpoint. @var{threadno} is one of the
4732 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4733 column of the @samp{info threads} display.
4735 If you do not specify @samp{thread @var{threadno}} when you set a
4736 breakpoint, the breakpoint applies to @emph{all} threads of your
4739 You can use the @code{thread} qualifier on conditional breakpoints as
4740 well; in this case, place @samp{thread @var{threadno}} before the
4741 breakpoint condition, like this:
4744 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4749 @node Interrupted System Calls
4750 @subsection Interrupted System Calls
4752 @cindex thread breakpoints and system calls
4753 @cindex system calls and thread breakpoints
4754 @cindex premature return from system calls
4755 There is an unfortunate side effect when using @value{GDBN} to debug
4756 multi-threaded programs. If one thread stops for a
4757 breakpoint, or for some other reason, and another thread is blocked in a
4758 system call, then the system call may return prematurely. This is a
4759 consequence of the interaction between multiple threads and the signals
4760 that @value{GDBN} uses to implement breakpoints and other events that
4763 To handle this problem, your program should check the return value of
4764 each system call and react appropriately. This is good programming
4767 For example, do not write code like this:
4773 The call to @code{sleep} will return early if a different thread stops
4774 at a breakpoint or for some other reason.
4776 Instead, write this:
4781 unslept = sleep (unslept);
4784 A system call is allowed to return early, so the system is still
4785 conforming to its specification. But @value{GDBN} does cause your
4786 multi-threaded program to behave differently than it would without
4789 Also, @value{GDBN} uses internal breakpoints in the thread library to
4790 monitor certain events such as thread creation and thread destruction.
4791 When such an event happens, a system call in another thread may return
4792 prematurely, even though your program does not appear to stop.
4797 @chapter Examining the Stack
4799 When your program has stopped, the first thing you need to know is where it
4800 stopped and how it got there.
4803 Each time your program performs a function call, information about the call
4805 That information includes the location of the call in your program,
4806 the arguments of the call,
4807 and the local variables of the function being called.
4808 The information is saved in a block of data called a @dfn{stack frame}.
4809 The stack frames are allocated in a region of memory called the @dfn{call
4812 When your program stops, the @value{GDBN} commands for examining the
4813 stack allow you to see all of this information.
4815 @cindex selected frame
4816 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4817 @value{GDBN} commands refer implicitly to the selected frame. In
4818 particular, whenever you ask @value{GDBN} for the value of a variable in
4819 your program, the value is found in the selected frame. There are
4820 special @value{GDBN} commands to select whichever frame you are
4821 interested in. @xref{Selection, ,Selecting a Frame}.
4823 When your program stops, @value{GDBN} automatically selects the
4824 currently executing frame and describes it briefly, similar to the
4825 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4828 * Frames:: Stack frames
4829 * Backtrace:: Backtraces
4830 * Selection:: Selecting a frame
4831 * Frame Info:: Information on a frame
4836 @section Stack Frames
4838 @cindex frame, definition
4840 The call stack is divided up into contiguous pieces called @dfn{stack
4841 frames}, or @dfn{frames} for short; each frame is the data associated
4842 with one call to one function. The frame contains the arguments given
4843 to the function, the function's local variables, and the address at
4844 which the function is executing.
4846 @cindex initial frame
4847 @cindex outermost frame
4848 @cindex innermost frame
4849 When your program is started, the stack has only one frame, that of the
4850 function @code{main}. This is called the @dfn{initial} frame or the
4851 @dfn{outermost} frame. Each time a function is called, a new frame is
4852 made. Each time a function returns, the frame for that function invocation
4853 is eliminated. If a function is recursive, there can be many frames for
4854 the same function. The frame for the function in which execution is
4855 actually occurring is called the @dfn{innermost} frame. This is the most
4856 recently created of all the stack frames that still exist.
4858 @cindex frame pointer
4859 Inside your program, stack frames are identified by their addresses. A
4860 stack frame consists of many bytes, each of which has its own address; each
4861 kind of computer has a convention for choosing one byte whose
4862 address serves as the address of the frame. Usually this address is kept
4863 in a register called the @dfn{frame pointer register}
4864 (@pxref{Registers, $fp}) while execution is going on in that frame.
4866 @cindex frame number
4867 @value{GDBN} assigns numbers to all existing stack frames, starting with
4868 zero for the innermost frame, one for the frame that called it,
4869 and so on upward. These numbers do not really exist in your program;
4870 they are assigned by @value{GDBN} to give you a way of designating stack
4871 frames in @value{GDBN} commands.
4873 @c The -fomit-frame-pointer below perennially causes hbox overflow
4874 @c underflow problems.
4875 @cindex frameless execution
4876 Some compilers provide a way to compile functions so that they operate
4877 without stack frames. (For example, the @value{NGCC} option
4879 @samp{-fomit-frame-pointer}
4881 generates functions without a frame.)
4882 This is occasionally done with heavily used library functions to save
4883 the frame setup time. @value{GDBN} has limited facilities for dealing
4884 with these function invocations. If the innermost function invocation
4885 has no stack frame, @value{GDBN} nevertheless regards it as though
4886 it had a separate frame, which is numbered zero as usual, allowing
4887 correct tracing of the function call chain. However, @value{GDBN} has
4888 no provision for frameless functions elsewhere in the stack.
4891 @kindex frame@r{, command}
4892 @cindex current stack frame
4893 @item frame @var{args}
4894 The @code{frame} command allows you to move from one stack frame to another,
4895 and to print the stack frame you select. @var{args} may be either the
4896 address of the frame or the stack frame number. Without an argument,
4897 @code{frame} prints the current stack frame.
4899 @kindex select-frame
4900 @cindex selecting frame silently
4902 The @code{select-frame} command allows you to move from one stack frame
4903 to another without printing the frame. This is the silent version of
4911 @cindex call stack traces
4912 A backtrace is a summary of how your program got where it is. It shows one
4913 line per frame, for many frames, starting with the currently executing
4914 frame (frame zero), followed by its caller (frame one), and on up the
4919 @kindex bt @r{(@code{backtrace})}
4922 Print a backtrace of the entire stack: one line per frame for all
4923 frames in the stack.
4925 You can stop the backtrace at any time by typing the system interrupt
4926 character, normally @kbd{Ctrl-c}.
4928 @item backtrace @var{n}
4930 Similar, but print only the innermost @var{n} frames.
4932 @item backtrace -@var{n}
4934 Similar, but print only the outermost @var{n} frames.
4936 @item backtrace full
4938 @itemx bt full @var{n}
4939 @itemx bt full -@var{n}
4940 Print the values of the local variables also. @var{n} specifies the
4941 number of frames to print, as described above.
4946 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4947 are additional aliases for @code{backtrace}.
4949 @cindex multiple threads, backtrace
4950 In a multi-threaded program, @value{GDBN} by default shows the
4951 backtrace only for the current thread. To display the backtrace for
4952 several or all of the threads, use the command @code{thread apply}
4953 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4954 apply all backtrace}, @value{GDBN} will display the backtrace for all
4955 the threads; this is handy when you debug a core dump of a
4956 multi-threaded program.
4958 Each line in the backtrace shows the frame number and the function name.
4959 The program counter value is also shown---unless you use @code{set
4960 print address off}. The backtrace also shows the source file name and
4961 line number, as well as the arguments to the function. The program
4962 counter value is omitted if it is at the beginning of the code for that
4965 Here is an example of a backtrace. It was made with the command
4966 @samp{bt 3}, so it shows the innermost three frames.
4970 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4972 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4973 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4975 (More stack frames follow...)
4980 The display for frame zero does not begin with a program counter
4981 value, indicating that your program has stopped at the beginning of the
4982 code for line @code{993} of @code{builtin.c}.
4984 @cindex value optimized out, in backtrace
4985 @cindex function call arguments, optimized out
4986 If your program was compiled with optimizations, some compilers will
4987 optimize away arguments passed to functions if those arguments are
4988 never used after the call. Such optimizations generate code that
4989 passes arguments through registers, but doesn't store those arguments
4990 in the stack frame. @value{GDBN} has no way of displaying such
4991 arguments in stack frames other than the innermost one. Here's what
4992 such a backtrace might look like:
4996 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4998 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4999 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5001 (More stack frames follow...)
5006 The values of arguments that were not saved in their stack frames are
5007 shown as @samp{<value optimized out>}.
5009 If you need to display the values of such optimized-out arguments,
5010 either deduce that from other variables whose values depend on the one
5011 you are interested in, or recompile without optimizations.
5013 @cindex backtrace beyond @code{main} function
5014 @cindex program entry point
5015 @cindex startup code, and backtrace
5016 Most programs have a standard user entry point---a place where system
5017 libraries and startup code transition into user code. For C this is
5018 @code{main}@footnote{
5019 Note that embedded programs (the so-called ``free-standing''
5020 environment) are not required to have a @code{main} function as the
5021 entry point. They could even have multiple entry points.}.
5022 When @value{GDBN} finds the entry function in a backtrace
5023 it will terminate the backtrace, to avoid tracing into highly
5024 system-specific (and generally uninteresting) code.
5026 If you need to examine the startup code, or limit the number of levels
5027 in a backtrace, you can change this behavior:
5030 @item set backtrace past-main
5031 @itemx set backtrace past-main on
5032 @kindex set backtrace
5033 Backtraces will continue past the user entry point.
5035 @item set backtrace past-main off
5036 Backtraces will stop when they encounter the user entry point. This is the
5039 @item show backtrace past-main
5040 @kindex show backtrace
5041 Display the current user entry point backtrace policy.
5043 @item set backtrace past-entry
5044 @itemx set backtrace past-entry on
5045 Backtraces will continue past the internal entry point of an application.
5046 This entry point is encoded by the linker when the application is built,
5047 and is likely before the user entry point @code{main} (or equivalent) is called.
5049 @item set backtrace past-entry off
5050 Backtraces will stop when they encounter the internal entry point of an
5051 application. This is the default.
5053 @item show backtrace past-entry
5054 Display the current internal entry point backtrace policy.
5056 @item set backtrace limit @var{n}
5057 @itemx set backtrace limit 0
5058 @cindex backtrace limit
5059 Limit the backtrace to @var{n} levels. A value of zero means
5062 @item show backtrace limit
5063 Display the current limit on backtrace levels.
5067 @section Selecting a Frame
5069 Most commands for examining the stack and other data in your program work on
5070 whichever stack frame is selected at the moment. Here are the commands for
5071 selecting a stack frame; all of them finish by printing a brief description
5072 of the stack frame just selected.
5075 @kindex frame@r{, selecting}
5076 @kindex f @r{(@code{frame})}
5079 Select frame number @var{n}. Recall that frame zero is the innermost
5080 (currently executing) frame, frame one is the frame that called the
5081 innermost one, and so on. The highest-numbered frame is the one for
5084 @item frame @var{addr}
5086 Select the frame at address @var{addr}. This is useful mainly if the
5087 chaining of stack frames has been damaged by a bug, making it
5088 impossible for @value{GDBN} to assign numbers properly to all frames. In
5089 addition, this can be useful when your program has multiple stacks and
5090 switches between them.
5092 On the SPARC architecture, @code{frame} needs two addresses to
5093 select an arbitrary frame: a frame pointer and a stack pointer.
5095 On the MIPS and Alpha architecture, it needs two addresses: a stack
5096 pointer and a program counter.
5098 On the 29k architecture, it needs three addresses: a register stack
5099 pointer, a program counter, and a memory stack pointer.
5103 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5104 advances toward the outermost frame, to higher frame numbers, to frames
5105 that have existed longer. @var{n} defaults to one.
5108 @kindex do @r{(@code{down})}
5110 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5111 advances toward the innermost frame, to lower frame numbers, to frames
5112 that were created more recently. @var{n} defaults to one. You may
5113 abbreviate @code{down} as @code{do}.
5116 All of these commands end by printing two lines of output describing the
5117 frame. The first line shows the frame number, the function name, the
5118 arguments, and the source file and line number of execution in that
5119 frame. The second line shows the text of that source line.
5127 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5129 10 read_input_file (argv[i]);
5133 After such a printout, the @code{list} command with no arguments
5134 prints ten lines centered on the point of execution in the frame.
5135 You can also edit the program at the point of execution with your favorite
5136 editing program by typing @code{edit}.
5137 @xref{List, ,Printing Source Lines},
5141 @kindex down-silently
5143 @item up-silently @var{n}
5144 @itemx down-silently @var{n}
5145 These two commands are variants of @code{up} and @code{down},
5146 respectively; they differ in that they do their work silently, without
5147 causing display of the new frame. They are intended primarily for use
5148 in @value{GDBN} command scripts, where the output might be unnecessary and
5153 @section Information About a Frame
5155 There are several other commands to print information about the selected
5161 When used without any argument, this command does not change which
5162 frame is selected, but prints a brief description of the currently
5163 selected stack frame. It can be abbreviated @code{f}. With an
5164 argument, this command is used to select a stack frame.
5165 @xref{Selection, ,Selecting a Frame}.
5168 @kindex info f @r{(@code{info frame})}
5171 This command prints a verbose description of the selected stack frame,
5176 the address of the frame
5178 the address of the next frame down (called by this frame)
5180 the address of the next frame up (caller of this frame)
5182 the language in which the source code corresponding to this frame is written
5184 the address of the frame's arguments
5186 the address of the frame's local variables
5188 the program counter saved in it (the address of execution in the caller frame)
5190 which registers were saved in the frame
5193 @noindent The verbose description is useful when
5194 something has gone wrong that has made the stack format fail to fit
5195 the usual conventions.
5197 @item info frame @var{addr}
5198 @itemx info f @var{addr}
5199 Print a verbose description of the frame at address @var{addr}, without
5200 selecting that frame. The selected frame remains unchanged by this
5201 command. This requires the same kind of address (more than one for some
5202 architectures) that you specify in the @code{frame} command.
5203 @xref{Selection, ,Selecting a Frame}.
5207 Print the arguments of the selected frame, each on a separate line.
5211 Print the local variables of the selected frame, each on a separate
5212 line. These are all variables (declared either static or automatic)
5213 accessible at the point of execution of the selected frame.
5216 @cindex catch exceptions, list active handlers
5217 @cindex exception handlers, how to list
5219 Print a list of all the exception handlers that are active in the
5220 current stack frame at the current point of execution. To see other
5221 exception handlers, visit the associated frame (using the @code{up},
5222 @code{down}, or @code{frame} commands); then type @code{info catch}.
5223 @xref{Set Catchpoints, , Setting Catchpoints}.
5229 @chapter Examining Source Files
5231 @value{GDBN} can print parts of your program's source, since the debugging
5232 information recorded in the program tells @value{GDBN} what source files were
5233 used to build it. When your program stops, @value{GDBN} spontaneously prints
5234 the line where it stopped. Likewise, when you select a stack frame
5235 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5236 execution in that frame has stopped. You can print other portions of
5237 source files by explicit command.
5239 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5240 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5241 @value{GDBN} under @sc{gnu} Emacs}.
5244 * List:: Printing source lines
5245 * Specify Location:: How to specify code locations
5246 * Edit:: Editing source files
5247 * Search:: Searching source files
5248 * Source Path:: Specifying source directories
5249 * Machine Code:: Source and machine code
5253 @section Printing Source Lines
5256 @kindex l @r{(@code{list})}
5257 To print lines from a source file, use the @code{list} command
5258 (abbreviated @code{l}). By default, ten lines are printed.
5259 There are several ways to specify what part of the file you want to
5260 print; see @ref{Specify Location}, for the full list.
5262 Here are the forms of the @code{list} command most commonly used:
5265 @item list @var{linenum}
5266 Print lines centered around line number @var{linenum} in the
5267 current source file.
5269 @item list @var{function}
5270 Print lines centered around the beginning of function
5274 Print more lines. If the last lines printed were printed with a
5275 @code{list} command, this prints lines following the last lines
5276 printed; however, if the last line printed was a solitary line printed
5277 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5278 Stack}), this prints lines centered around that line.
5281 Print lines just before the lines last printed.
5284 @cindex @code{list}, how many lines to display
5285 By default, @value{GDBN} prints ten source lines with any of these forms of
5286 the @code{list} command. You can change this using @code{set listsize}:
5289 @kindex set listsize
5290 @item set listsize @var{count}
5291 Make the @code{list} command display @var{count} source lines (unless
5292 the @code{list} argument explicitly specifies some other number).
5294 @kindex show listsize
5296 Display the number of lines that @code{list} prints.
5299 Repeating a @code{list} command with @key{RET} discards the argument,
5300 so it is equivalent to typing just @code{list}. This is more useful
5301 than listing the same lines again. An exception is made for an
5302 argument of @samp{-}; that argument is preserved in repetition so that
5303 each repetition moves up in the source file.
5305 In general, the @code{list} command expects you to supply zero, one or two
5306 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5307 of writing them (@pxref{Specify Location}), but the effect is always
5308 to specify some source line.
5310 Here is a complete description of the possible arguments for @code{list}:
5313 @item list @var{linespec}
5314 Print lines centered around the line specified by @var{linespec}.
5316 @item list @var{first},@var{last}
5317 Print lines from @var{first} to @var{last}. Both arguments are
5318 linespecs. When a @code{list} command has two linespecs, and the
5319 source file of the second linespec is omitted, this refers to
5320 the same source file as the first linespec.
5322 @item list ,@var{last}
5323 Print lines ending with @var{last}.
5325 @item list @var{first},
5326 Print lines starting with @var{first}.
5329 Print lines just after the lines last printed.
5332 Print lines just before the lines last printed.
5335 As described in the preceding table.
5338 @node Specify Location
5339 @section Specifying a Location
5340 @cindex specifying location
5343 Several @value{GDBN} commands accept arguments that specify a location
5344 of your program's code. Since @value{GDBN} is a source-level
5345 debugger, a location usually specifies some line in the source code;
5346 for that reason, locations are also known as @dfn{linespecs}.
5348 Here are all the different ways of specifying a code location that
5349 @value{GDBN} understands:
5353 Specifies the line number @var{linenum} of the current source file.
5356 @itemx +@var{offset}
5357 Specifies the line @var{offset} lines before or after the @dfn{current
5358 line}. For the @code{list} command, the current line is the last one
5359 printed; for the breakpoint commands, this is the line at which
5360 execution stopped in the currently selected @dfn{stack frame}
5361 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5362 used as the second of the two linespecs in a @code{list} command,
5363 this specifies the line @var{offset} lines up or down from the first
5366 @item @var{filename}:@var{linenum}
5367 Specifies the line @var{linenum} in the source file @var{filename}.
5369 @item @var{function}
5370 Specifies the line that begins the body of the function @var{function}.
5371 For example, in C, this is the line with the open brace.
5373 @item @var{filename}:@var{function}
5374 Specifies the line that begins the body of the function @var{function}
5375 in the file @var{filename}. You only need the file name with a
5376 function name to avoid ambiguity when there are identically named
5377 functions in different source files.
5379 @item *@var{address}
5380 Specifies the program address @var{address}. For line-oriented
5381 commands, such as @code{list} and @code{edit}, this specifies a source
5382 line that contains @var{address}. For @code{break} and other
5383 breakpoint oriented commands, this can be used to set breakpoints in
5384 parts of your program which do not have debugging information or
5387 Here @var{address} may be any expression valid in the current working
5388 language (@pxref{Languages, working language}) that specifies a code
5389 address. In addition, as a convenience, @value{GDBN} extends the
5390 semantics of expressions used in locations to cover the situations
5391 that frequently happen during debugging. Here are the various forms
5395 @item @var{expression}
5396 Any expression valid in the current working language.
5398 @item @var{funcaddr}
5399 An address of a function or procedure derived from its name. In C,
5400 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5401 simply the function's name @var{function} (and actually a special case
5402 of a valid expression). In Pascal and Modula-2, this is
5403 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5404 (although the Pascal form also works).
5406 This form specifies the address of the function's first instruction,
5407 before the stack frame and arguments have been set up.
5409 @item '@var{filename}'::@var{funcaddr}
5410 Like @var{funcaddr} above, but also specifies the name of the source
5411 file explicitly. This is useful if the name of the function does not
5412 specify the function unambiguously, e.g., if there are several
5413 functions with identical names in different source files.
5420 @section Editing Source Files
5421 @cindex editing source files
5424 @kindex e @r{(@code{edit})}
5425 To edit the lines in a source file, use the @code{edit} command.
5426 The editing program of your choice
5427 is invoked with the current line set to
5428 the active line in the program.
5429 Alternatively, there are several ways to specify what part of the file you
5430 want to print if you want to see other parts of the program:
5433 @item edit @var{location}
5434 Edit the source file specified by @code{location}. Editing starts at
5435 that @var{location}, e.g., at the specified source line of the
5436 specified file. @xref{Specify Location}, for all the possible forms
5437 of the @var{location} argument; here are the forms of the @code{edit}
5438 command most commonly used:
5441 @item edit @var{number}
5442 Edit the current source file with @var{number} as the active line number.
5444 @item edit @var{function}
5445 Edit the file containing @var{function} at the beginning of its definition.
5450 @subsection Choosing your Editor
5451 You can customize @value{GDBN} to use any editor you want
5453 The only restriction is that your editor (say @code{ex}), recognizes the
5454 following command-line syntax:
5456 ex +@var{number} file
5458 The optional numeric value +@var{number} specifies the number of the line in
5459 the file where to start editing.}.
5460 By default, it is @file{@value{EDITOR}}, but you can change this
5461 by setting the environment variable @code{EDITOR} before using
5462 @value{GDBN}. For example, to configure @value{GDBN} to use the
5463 @code{vi} editor, you could use these commands with the @code{sh} shell:
5469 or in the @code{csh} shell,
5471 setenv EDITOR /usr/bin/vi
5476 @section Searching Source Files
5477 @cindex searching source files
5479 There are two commands for searching through the current source file for a
5484 @kindex forward-search
5485 @item forward-search @var{regexp}
5486 @itemx search @var{regexp}
5487 The command @samp{forward-search @var{regexp}} checks each line,
5488 starting with the one following the last line listed, for a match for
5489 @var{regexp}. It lists the line that is found. You can use the
5490 synonym @samp{search @var{regexp}} or abbreviate the command name as
5493 @kindex reverse-search
5494 @item reverse-search @var{regexp}
5495 The command @samp{reverse-search @var{regexp}} checks each line, starting
5496 with the one before the last line listed and going backward, for a match
5497 for @var{regexp}. It lists the line that is found. You can abbreviate
5498 this command as @code{rev}.
5502 @section Specifying Source Directories
5505 @cindex directories for source files
5506 Executable programs sometimes do not record the directories of the source
5507 files from which they were compiled, just the names. Even when they do,
5508 the directories could be moved between the compilation and your debugging
5509 session. @value{GDBN} has a list of directories to search for source files;
5510 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5511 it tries all the directories in the list, in the order they are present
5512 in the list, until it finds a file with the desired name.
5514 For example, suppose an executable references the file
5515 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5516 @file{/mnt/cross}. The file is first looked up literally; if this
5517 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5518 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5519 message is printed. @value{GDBN} does not look up the parts of the
5520 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5521 Likewise, the subdirectories of the source path are not searched: if
5522 the source path is @file{/mnt/cross}, and the binary refers to
5523 @file{foo.c}, @value{GDBN} would not find it under
5524 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5526 Plain file names, relative file names with leading directories, file
5527 names containing dots, etc.@: are all treated as described above; for
5528 instance, if the source path is @file{/mnt/cross}, and the source file
5529 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5530 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5531 that---@file{/mnt/cross/foo.c}.
5533 Note that the executable search path is @emph{not} used to locate the
5536 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5537 any information it has cached about where source files are found and where
5538 each line is in the file.
5542 When you start @value{GDBN}, its source path includes only @samp{cdir}
5543 and @samp{cwd}, in that order.
5544 To add other directories, use the @code{directory} command.
5546 The search path is used to find both program source files and @value{GDBN}
5547 script files (read using the @samp{-command} option and @samp{source} command).
5549 In addition to the source path, @value{GDBN} provides a set of commands
5550 that manage a list of source path substitution rules. A @dfn{substitution
5551 rule} specifies how to rewrite source directories stored in the program's
5552 debug information in case the sources were moved to a different
5553 directory between compilation and debugging. A rule is made of
5554 two strings, the first specifying what needs to be rewritten in
5555 the path, and the second specifying how it should be rewritten.
5556 In @ref{set substitute-path}, we name these two parts @var{from} and
5557 @var{to} respectively. @value{GDBN} does a simple string replacement
5558 of @var{from} with @var{to} at the start of the directory part of the
5559 source file name, and uses that result instead of the original file
5560 name to look up the sources.
5562 Using the previous example, suppose the @file{foo-1.0} tree has been
5563 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5564 @value{GDBN} to replace @file{/usr/src} in all source path names with
5565 @file{/mnt/cross}. The first lookup will then be
5566 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5567 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5568 substitution rule, use the @code{set substitute-path} command
5569 (@pxref{set substitute-path}).
5571 To avoid unexpected substitution results, a rule is applied only if the
5572 @var{from} part of the directory name ends at a directory separator.
5573 For instance, a rule substituting @file{/usr/source} into
5574 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5575 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5576 is applied only at the beginning of the directory name, this rule will
5577 not be applied to @file{/root/usr/source/baz.c} either.
5579 In many cases, you can achieve the same result using the @code{directory}
5580 command. However, @code{set substitute-path} can be more efficient in
5581 the case where the sources are organized in a complex tree with multiple
5582 subdirectories. With the @code{directory} command, you need to add each
5583 subdirectory of your project. If you moved the entire tree while
5584 preserving its internal organization, then @code{set substitute-path}
5585 allows you to direct the debugger to all the sources with one single
5588 @code{set substitute-path} is also more than just a shortcut command.
5589 The source path is only used if the file at the original location no
5590 longer exists. On the other hand, @code{set substitute-path} modifies
5591 the debugger behavior to look at the rewritten location instead. So, if
5592 for any reason a source file that is not relevant to your executable is
5593 located at the original location, a substitution rule is the only
5594 method available to point @value{GDBN} at the new location.
5597 @item directory @var{dirname} @dots{}
5598 @item dir @var{dirname} @dots{}
5599 Add directory @var{dirname} to the front of the source path. Several
5600 directory names may be given to this command, separated by @samp{:}
5601 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5602 part of absolute file names) or
5603 whitespace. You may specify a directory that is already in the source
5604 path; this moves it forward, so @value{GDBN} searches it sooner.
5608 @vindex $cdir@r{, convenience variable}
5609 @vindex $cwd@r{, convenience variable}
5610 @cindex compilation directory
5611 @cindex current directory
5612 @cindex working directory
5613 @cindex directory, current
5614 @cindex directory, compilation
5615 You can use the string @samp{$cdir} to refer to the compilation
5616 directory (if one is recorded), and @samp{$cwd} to refer to the current
5617 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5618 tracks the current working directory as it changes during your @value{GDBN}
5619 session, while the latter is immediately expanded to the current
5620 directory at the time you add an entry to the source path.
5623 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5625 @c RET-repeat for @code{directory} is explicitly disabled, but since
5626 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5628 @item show directories
5629 @kindex show directories
5630 Print the source path: show which directories it contains.
5632 @anchor{set substitute-path}
5633 @item set substitute-path @var{from} @var{to}
5634 @kindex set substitute-path
5635 Define a source path substitution rule, and add it at the end of the
5636 current list of existing substitution rules. If a rule with the same
5637 @var{from} was already defined, then the old rule is also deleted.
5639 For example, if the file @file{/foo/bar/baz.c} was moved to
5640 @file{/mnt/cross/baz.c}, then the command
5643 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5647 will tell @value{GDBN} to replace @samp{/usr/src} with
5648 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5649 @file{baz.c} even though it was moved.
5651 In the case when more than one substitution rule have been defined,
5652 the rules are evaluated one by one in the order where they have been
5653 defined. The first one matching, if any, is selected to perform
5656 For instance, if we had entered the following commands:
5659 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5660 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5664 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5665 @file{/mnt/include/defs.h} by using the first rule. However, it would
5666 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5667 @file{/mnt/src/lib/foo.c}.
5670 @item unset substitute-path [path]
5671 @kindex unset substitute-path
5672 If a path is specified, search the current list of substitution rules
5673 for a rule that would rewrite that path. Delete that rule if found.
5674 A warning is emitted by the debugger if no rule could be found.
5676 If no path is specified, then all substitution rules are deleted.
5678 @item show substitute-path [path]
5679 @kindex show substitute-path
5680 If a path is specified, then print the source path substitution rule
5681 which would rewrite that path, if any.
5683 If no path is specified, then print all existing source path substitution
5688 If your source path is cluttered with directories that are no longer of
5689 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5690 versions of source. You can correct the situation as follows:
5694 Use @code{directory} with no argument to reset the source path to its default value.
5697 Use @code{directory} with suitable arguments to reinstall the
5698 directories you want in the source path. You can add all the
5699 directories in one command.
5703 @section Source and Machine Code
5704 @cindex source line and its code address
5706 You can use the command @code{info line} to map source lines to program
5707 addresses (and vice versa), and the command @code{disassemble} to display
5708 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5709 mode, the @code{info line} command causes the arrow to point to the
5710 line specified. Also, @code{info line} prints addresses in symbolic form as
5715 @item info line @var{linespec}
5716 Print the starting and ending addresses of the compiled code for
5717 source line @var{linespec}. You can specify source lines in any of
5718 the ways documented in @ref{Specify Location}.
5721 For example, we can use @code{info line} to discover the location of
5722 the object code for the first line of function
5723 @code{m4_changequote}:
5725 @c FIXME: I think this example should also show the addresses in
5726 @c symbolic form, as they usually would be displayed.
5728 (@value{GDBP}) info line m4_changequote
5729 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5733 @cindex code address and its source line
5734 We can also inquire (using @code{*@var{addr}} as the form for
5735 @var{linespec}) what source line covers a particular address:
5737 (@value{GDBP}) info line *0x63ff
5738 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5741 @cindex @code{$_} and @code{info line}
5742 @cindex @code{x} command, default address
5743 @kindex x@r{(examine), and} info line
5744 After @code{info line}, the default address for the @code{x} command
5745 is changed to the starting address of the line, so that @samp{x/i} is
5746 sufficient to begin examining the machine code (@pxref{Memory,
5747 ,Examining Memory}). Also, this address is saved as the value of the
5748 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5753 @cindex assembly instructions
5754 @cindex instructions, assembly
5755 @cindex machine instructions
5756 @cindex listing machine instructions
5758 @itemx disassemble /m
5759 This specialized command dumps a range of memory as machine
5760 instructions. It can also print mixed source+disassembly by specifying
5761 the @code{/m} modifier.
5762 The default memory range is the function surrounding the
5763 program counter of the selected frame. A single argument to this
5764 command is a program counter value; @value{GDBN} dumps the function
5765 surrounding this value. Two arguments specify a range of addresses
5766 (first inclusive, second exclusive) to dump.
5769 The following example shows the disassembly of a range of addresses of
5770 HP PA-RISC 2.0 code:
5773 (@value{GDBP}) disas 0x32c4 0x32e4
5774 Dump of assembler code from 0x32c4 to 0x32e4:
5775 0x32c4 <main+204>: addil 0,dp
5776 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5777 0x32cc <main+212>: ldil 0x3000,r31
5778 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5779 0x32d4 <main+220>: ldo 0(r31),rp
5780 0x32d8 <main+224>: addil -0x800,dp
5781 0x32dc <main+228>: ldo 0x588(r1),r26
5782 0x32e0 <main+232>: ldil 0x3000,r31
5783 End of assembler dump.
5786 Here is an example showing mixed source+assembly for Intel x86:
5789 (@value{GDBP}) disas /m main
5790 Dump of assembler code for function main:
5792 0x08048330 <main+0>: push %ebp
5793 0x08048331 <main+1>: mov %esp,%ebp
5794 0x08048333 <main+3>: sub $0x8,%esp
5795 0x08048336 <main+6>: and $0xfffffff0,%esp
5796 0x08048339 <main+9>: sub $0x10,%esp
5798 6 printf ("Hello.\n");
5799 0x0804833c <main+12>: movl $0x8048440,(%esp)
5800 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
5804 0x08048348 <main+24>: mov $0x0,%eax
5805 0x0804834d <main+29>: leave
5806 0x0804834e <main+30>: ret
5808 End of assembler dump.
5811 Some architectures have more than one commonly-used set of instruction
5812 mnemonics or other syntax.
5814 For programs that were dynamically linked and use shared libraries,
5815 instructions that call functions or branch to locations in the shared
5816 libraries might show a seemingly bogus location---it's actually a
5817 location of the relocation table. On some architectures, @value{GDBN}
5818 might be able to resolve these to actual function names.
5821 @kindex set disassembly-flavor
5822 @cindex Intel disassembly flavor
5823 @cindex AT&T disassembly flavor
5824 @item set disassembly-flavor @var{instruction-set}
5825 Select the instruction set to use when disassembling the
5826 program via the @code{disassemble} or @code{x/i} commands.
5828 Currently this command is only defined for the Intel x86 family. You
5829 can set @var{instruction-set} to either @code{intel} or @code{att}.
5830 The default is @code{att}, the AT&T flavor used by default by Unix
5831 assemblers for x86-based targets.
5833 @kindex show disassembly-flavor
5834 @item show disassembly-flavor
5835 Show the current setting of the disassembly flavor.
5840 @chapter Examining Data
5842 @cindex printing data
5843 @cindex examining data
5846 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5847 @c document because it is nonstandard... Under Epoch it displays in a
5848 @c different window or something like that.
5849 The usual way to examine data in your program is with the @code{print}
5850 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5851 evaluates and prints the value of an expression of the language your
5852 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5853 Different Languages}).
5856 @item print @var{expr}
5857 @itemx print /@var{f} @var{expr}
5858 @var{expr} is an expression (in the source language). By default the
5859 value of @var{expr} is printed in a format appropriate to its data type;
5860 you can choose a different format by specifying @samp{/@var{f}}, where
5861 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5865 @itemx print /@var{f}
5866 @cindex reprint the last value
5867 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5868 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5869 conveniently inspect the same value in an alternative format.
5872 A more low-level way of examining data is with the @code{x} command.
5873 It examines data in memory at a specified address and prints it in a
5874 specified format. @xref{Memory, ,Examining Memory}.
5876 If you are interested in information about types, or about how the
5877 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5878 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5882 * Expressions:: Expressions
5883 * Ambiguous Expressions:: Ambiguous Expressions
5884 * Variables:: Program variables
5885 * Arrays:: Artificial arrays
5886 * Output Formats:: Output formats
5887 * Memory:: Examining memory
5888 * Auto Display:: Automatic display
5889 * Print Settings:: Print settings
5890 * Value History:: Value history
5891 * Convenience Vars:: Convenience variables
5892 * Registers:: Registers
5893 * Floating Point Hardware:: Floating point hardware
5894 * Vector Unit:: Vector Unit
5895 * OS Information:: Auxiliary data provided by operating system
5896 * Memory Region Attributes:: Memory region attributes
5897 * Dump/Restore Files:: Copy between memory and a file
5898 * Core File Generation:: Cause a program dump its core
5899 * Character Sets:: Debugging programs that use a different
5900 character set than GDB does
5901 * Caching Remote Data:: Data caching for remote targets
5902 * Searching Memory:: Searching memory for a sequence of bytes
5906 @section Expressions
5909 @code{print} and many other @value{GDBN} commands accept an expression and
5910 compute its value. Any kind of constant, variable or operator defined
5911 by the programming language you are using is valid in an expression in
5912 @value{GDBN}. This includes conditional expressions, function calls,
5913 casts, and string constants. It also includes preprocessor macros, if
5914 you compiled your program to include this information; see
5917 @cindex arrays in expressions
5918 @value{GDBN} supports array constants in expressions input by
5919 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5920 you can use the command @code{print @{1, 2, 3@}} to create an array
5921 of three integers. If you pass an array to a function or assign it
5922 to a program variable, @value{GDBN} copies the array to memory that
5923 is @code{malloc}ed in the target program.
5925 Because C is so widespread, most of the expressions shown in examples in
5926 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5927 Languages}, for information on how to use expressions in other
5930 In this section, we discuss operators that you can use in @value{GDBN}
5931 expressions regardless of your programming language.
5933 @cindex casts, in expressions
5934 Casts are supported in all languages, not just in C, because it is so
5935 useful to cast a number into a pointer in order to examine a structure
5936 at that address in memory.
5937 @c FIXME: casts supported---Mod2 true?
5939 @value{GDBN} supports these operators, in addition to those common
5940 to programming languages:
5944 @samp{@@} is a binary operator for treating parts of memory as arrays.
5945 @xref{Arrays, ,Artificial Arrays}, for more information.
5948 @samp{::} allows you to specify a variable in terms of the file or
5949 function where it is defined. @xref{Variables, ,Program Variables}.
5951 @cindex @{@var{type}@}
5952 @cindex type casting memory
5953 @cindex memory, viewing as typed object
5954 @cindex casts, to view memory
5955 @item @{@var{type}@} @var{addr}
5956 Refers to an object of type @var{type} stored at address @var{addr} in
5957 memory. @var{addr} may be any expression whose value is an integer or
5958 pointer (but parentheses are required around binary operators, just as in
5959 a cast). This construct is allowed regardless of what kind of data is
5960 normally supposed to reside at @var{addr}.
5963 @node Ambiguous Expressions
5964 @section Ambiguous Expressions
5965 @cindex ambiguous expressions
5967 Expressions can sometimes contain some ambiguous elements. For instance,
5968 some programming languages (notably Ada, C@t{++} and Objective-C) permit
5969 a single function name to be defined several times, for application in
5970 different contexts. This is called @dfn{overloading}. Another example
5971 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
5972 templates and is typically instantiated several times, resulting in
5973 the same function name being defined in different contexts.
5975 In some cases and depending on the language, it is possible to adjust
5976 the expression to remove the ambiguity. For instance in C@t{++}, you
5977 can specify the signature of the function you want to break on, as in
5978 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
5979 qualified name of your function often makes the expression unambiguous
5982 When an ambiguity that needs to be resolved is detected, the debugger
5983 has the capability to display a menu of numbered choices for each
5984 possibility, and then waits for the selection with the prompt @samp{>}.
5985 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
5986 aborts the current command. If the command in which the expression was
5987 used allows more than one choice to be selected, the next option in the
5988 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
5991 For example, the following session excerpt shows an attempt to set a
5992 breakpoint at the overloaded symbol @code{String::after}.
5993 We choose three particular definitions of that function name:
5995 @c FIXME! This is likely to change to show arg type lists, at least
5998 (@value{GDBP}) b String::after
6001 [2] file:String.cc; line number:867
6002 [3] file:String.cc; line number:860
6003 [4] file:String.cc; line number:875
6004 [5] file:String.cc; line number:853
6005 [6] file:String.cc; line number:846
6006 [7] file:String.cc; line number:735
6008 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6009 Breakpoint 2 at 0xb344: file String.cc, line 875.
6010 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6011 Multiple breakpoints were set.
6012 Use the "delete" command to delete unwanted
6019 @kindex set multiple-symbols
6020 @item set multiple-symbols @var{mode}
6021 @cindex multiple-symbols menu
6023 This option allows you to adjust the debugger behavior when an expression
6026 By default, @var{mode} is set to @code{all}. If the command with which
6027 the expression is used allows more than one choice, then @value{GDBN}
6028 automatically selects all possible choices. For instance, inserting
6029 a breakpoint on a function using an ambiguous name results in a breakpoint
6030 inserted on each possible match. However, if a unique choice must be made,
6031 then @value{GDBN} uses the menu to help you disambiguate the expression.
6032 For instance, printing the address of an overloaded function will result
6033 in the use of the menu.
6035 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6036 when an ambiguity is detected.
6038 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6039 an error due to the ambiguity and the command is aborted.
6041 @kindex show multiple-symbols
6042 @item show multiple-symbols
6043 Show the current value of the @code{multiple-symbols} setting.
6047 @section Program Variables
6049 The most common kind of expression to use is the name of a variable
6052 Variables in expressions are understood in the selected stack frame
6053 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6057 global (or file-static)
6064 visible according to the scope rules of the
6065 programming language from the point of execution in that frame
6068 @noindent This means that in the function
6083 you can examine and use the variable @code{a} whenever your program is
6084 executing within the function @code{foo}, but you can only use or
6085 examine the variable @code{b} while your program is executing inside
6086 the block where @code{b} is declared.
6088 @cindex variable name conflict
6089 There is an exception: you can refer to a variable or function whose
6090 scope is a single source file even if the current execution point is not
6091 in this file. But it is possible to have more than one such variable or
6092 function with the same name (in different source files). If that
6093 happens, referring to that name has unpredictable effects. If you wish,
6094 you can specify a static variable in a particular function or file,
6095 using the colon-colon (@code{::}) notation:
6097 @cindex colon-colon, context for variables/functions
6099 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6100 @cindex @code{::}, context for variables/functions
6103 @var{file}::@var{variable}
6104 @var{function}::@var{variable}
6108 Here @var{file} or @var{function} is the name of the context for the
6109 static @var{variable}. In the case of file names, you can use quotes to
6110 make sure @value{GDBN} parses the file name as a single word---for example,
6111 to print a global value of @code{x} defined in @file{f2.c}:
6114 (@value{GDBP}) p 'f2.c'::x
6117 @cindex C@t{++} scope resolution
6118 This use of @samp{::} is very rarely in conflict with the very similar
6119 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6120 scope resolution operator in @value{GDBN} expressions.
6121 @c FIXME: Um, so what happens in one of those rare cases where it's in
6124 @cindex wrong values
6125 @cindex variable values, wrong
6126 @cindex function entry/exit, wrong values of variables
6127 @cindex optimized code, wrong values of variables
6129 @emph{Warning:} Occasionally, a local variable may appear to have the
6130 wrong value at certain points in a function---just after entry to a new
6131 scope, and just before exit.
6133 You may see this problem when you are stepping by machine instructions.
6134 This is because, on most machines, it takes more than one instruction to
6135 set up a stack frame (including local variable definitions); if you are
6136 stepping by machine instructions, variables may appear to have the wrong
6137 values until the stack frame is completely built. On exit, it usually
6138 also takes more than one machine instruction to destroy a stack frame;
6139 after you begin stepping through that group of instructions, local
6140 variable definitions may be gone.
6142 This may also happen when the compiler does significant optimizations.
6143 To be sure of always seeing accurate values, turn off all optimization
6146 @cindex ``No symbol "foo" in current context''
6147 Another possible effect of compiler optimizations is to optimize
6148 unused variables out of existence, or assign variables to registers (as
6149 opposed to memory addresses). Depending on the support for such cases
6150 offered by the debug info format used by the compiler, @value{GDBN}
6151 might not be able to display values for such local variables. If that
6152 happens, @value{GDBN} will print a message like this:
6155 No symbol "foo" in current context.
6158 To solve such problems, either recompile without optimizations, or use a
6159 different debug info format, if the compiler supports several such
6160 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6161 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6162 produces debug info in a format that is superior to formats such as
6163 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6164 an effective form for debug info. @xref{Debugging Options,,Options
6165 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6166 Compiler Collection (GCC)}.
6167 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6168 that are best suited to C@t{++} programs.
6170 If you ask to print an object whose contents are unknown to
6171 @value{GDBN}, e.g., because its data type is not completely specified
6172 by the debug information, @value{GDBN} will say @samp{<incomplete
6173 type>}. @xref{Symbols, incomplete type}, for more about this.
6175 Strings are identified as arrays of @code{char} values without specified
6176 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6177 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6178 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6179 defines literal string type @code{"char"} as @code{char} without a sign.
6184 signed char var1[] = "A";
6187 You get during debugging
6192 $2 = @{65 'A', 0 '\0'@}
6196 @section Artificial Arrays
6198 @cindex artificial array
6200 @kindex @@@r{, referencing memory as an array}
6201 It is often useful to print out several successive objects of the
6202 same type in memory; a section of an array, or an array of
6203 dynamically determined size for which only a pointer exists in the
6206 You can do this by referring to a contiguous span of memory as an
6207 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6208 operand of @samp{@@} should be the first element of the desired array
6209 and be an individual object. The right operand should be the desired length
6210 of the array. The result is an array value whose elements are all of
6211 the type of the left argument. The first element is actually the left
6212 argument; the second element comes from bytes of memory immediately
6213 following those that hold the first element, and so on. Here is an
6214 example. If a program says
6217 int *array = (int *) malloc (len * sizeof (int));
6221 you can print the contents of @code{array} with
6227 The left operand of @samp{@@} must reside in memory. Array values made
6228 with @samp{@@} in this way behave just like other arrays in terms of
6229 subscripting, and are coerced to pointers when used in expressions.
6230 Artificial arrays most often appear in expressions via the value history
6231 (@pxref{Value History, ,Value History}), after printing one out.
6233 Another way to create an artificial array is to use a cast.
6234 This re-interprets a value as if it were an array.
6235 The value need not be in memory:
6237 (@value{GDBP}) p/x (short[2])0x12345678
6238 $1 = @{0x1234, 0x5678@}
6241 As a convenience, if you leave the array length out (as in
6242 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6243 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6245 (@value{GDBP}) p/x (short[])0x12345678
6246 $2 = @{0x1234, 0x5678@}
6249 Sometimes the artificial array mechanism is not quite enough; in
6250 moderately complex data structures, the elements of interest may not
6251 actually be adjacent---for example, if you are interested in the values
6252 of pointers in an array. One useful work-around in this situation is
6253 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6254 Variables}) as a counter in an expression that prints the first
6255 interesting value, and then repeat that expression via @key{RET}. For
6256 instance, suppose you have an array @code{dtab} of pointers to
6257 structures, and you are interested in the values of a field @code{fv}
6258 in each structure. Here is an example of what you might type:
6268 @node Output Formats
6269 @section Output Formats
6271 @cindex formatted output
6272 @cindex output formats
6273 By default, @value{GDBN} prints a value according to its data type. Sometimes
6274 this is not what you want. For example, you might want to print a number
6275 in hex, or a pointer in decimal. Or you might want to view data in memory
6276 at a certain address as a character string or as an instruction. To do
6277 these things, specify an @dfn{output format} when you print a value.
6279 The simplest use of output formats is to say how to print a value
6280 already computed. This is done by starting the arguments of the
6281 @code{print} command with a slash and a format letter. The format
6282 letters supported are:
6286 Regard the bits of the value as an integer, and print the integer in
6290 Print as integer in signed decimal.
6293 Print as integer in unsigned decimal.
6296 Print as integer in octal.
6299 Print as integer in binary. The letter @samp{t} stands for ``two''.
6300 @footnote{@samp{b} cannot be used because these format letters are also
6301 used with the @code{x} command, where @samp{b} stands for ``byte'';
6302 see @ref{Memory,,Examining Memory}.}
6305 @cindex unknown address, locating
6306 @cindex locate address
6307 Print as an address, both absolute in hexadecimal and as an offset from
6308 the nearest preceding symbol. You can use this format used to discover
6309 where (in what function) an unknown address is located:
6312 (@value{GDBP}) p/a 0x54320
6313 $3 = 0x54320 <_initialize_vx+396>
6317 The command @code{info symbol 0x54320} yields similar results.
6318 @xref{Symbols, info symbol}.
6321 Regard as an integer and print it as a character constant. This
6322 prints both the numerical value and its character representation. The
6323 character representation is replaced with the octal escape @samp{\nnn}
6324 for characters outside the 7-bit @sc{ascii} range.
6326 Without this format, @value{GDBN} displays @code{char},
6327 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6328 constants. Single-byte members of vectors are displayed as integer
6332 Regard the bits of the value as a floating point number and print
6333 using typical floating point syntax.
6336 @cindex printing strings
6337 @cindex printing byte arrays
6338 Regard as a string, if possible. With this format, pointers to single-byte
6339 data are displayed as null-terminated strings and arrays of single-byte data
6340 are displayed as fixed-length strings. Other values are displayed in their
6343 Without this format, @value{GDBN} displays pointers to and arrays of
6344 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6345 strings. Single-byte members of a vector are displayed as an integer
6349 For example, to print the program counter in hex (@pxref{Registers}), type
6356 Note that no space is required before the slash; this is because command
6357 names in @value{GDBN} cannot contain a slash.
6359 To reprint the last value in the value history with a different format,
6360 you can use the @code{print} command with just a format and no
6361 expression. For example, @samp{p/x} reprints the last value in hex.
6364 @section Examining Memory
6366 You can use the command @code{x} (for ``examine'') to examine memory in
6367 any of several formats, independently of your program's data types.
6369 @cindex examining memory
6371 @kindex x @r{(examine memory)}
6372 @item x/@var{nfu} @var{addr}
6375 Use the @code{x} command to examine memory.
6378 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6379 much memory to display and how to format it; @var{addr} is an
6380 expression giving the address where you want to start displaying memory.
6381 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6382 Several commands set convenient defaults for @var{addr}.
6385 @item @var{n}, the repeat count
6386 The repeat count is a decimal integer; the default is 1. It specifies
6387 how much memory (counting by units @var{u}) to display.
6388 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6391 @item @var{f}, the display format
6392 The display format is one of the formats used by @code{print}
6393 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6394 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6395 The default is @samp{x} (hexadecimal) initially. The default changes
6396 each time you use either @code{x} or @code{print}.
6398 @item @var{u}, the unit size
6399 The unit size is any of
6405 Halfwords (two bytes).
6407 Words (four bytes). This is the initial default.
6409 Giant words (eight bytes).
6412 Each time you specify a unit size with @code{x}, that size becomes the
6413 default unit the next time you use @code{x}. (For the @samp{s} and
6414 @samp{i} formats, the unit size is ignored and is normally not written.)
6416 @item @var{addr}, starting display address
6417 @var{addr} is the address where you want @value{GDBN} to begin displaying
6418 memory. The expression need not have a pointer value (though it may);
6419 it is always interpreted as an integer address of a byte of memory.
6420 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6421 @var{addr} is usually just after the last address examined---but several
6422 other commands also set the default address: @code{info breakpoints} (to
6423 the address of the last breakpoint listed), @code{info line} (to the
6424 starting address of a line), and @code{print} (if you use it to display
6425 a value from memory).
6428 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6429 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6430 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6431 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6432 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6434 Since the letters indicating unit sizes are all distinct from the
6435 letters specifying output formats, you do not have to remember whether
6436 unit size or format comes first; either order works. The output
6437 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6438 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6440 Even though the unit size @var{u} is ignored for the formats @samp{s}
6441 and @samp{i}, you might still want to use a count @var{n}; for example,
6442 @samp{3i} specifies that you want to see three machine instructions,
6443 including any operands. For convenience, especially when used with
6444 the @code{display} command, the @samp{i} format also prints branch delay
6445 slot instructions, if any, beyond the count specified, which immediately
6446 follow the last instruction that is within the count. The command
6447 @code{disassemble} gives an alternative way of inspecting machine
6448 instructions; see @ref{Machine Code,,Source and Machine Code}.
6450 All the defaults for the arguments to @code{x} are designed to make it
6451 easy to continue scanning memory with minimal specifications each time
6452 you use @code{x}. For example, after you have inspected three machine
6453 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6454 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6455 the repeat count @var{n} is used again; the other arguments default as
6456 for successive uses of @code{x}.
6458 @cindex @code{$_}, @code{$__}, and value history
6459 The addresses and contents printed by the @code{x} command are not saved
6460 in the value history because there is often too much of them and they
6461 would get in the way. Instead, @value{GDBN} makes these values available for
6462 subsequent use in expressions as values of the convenience variables
6463 @code{$_} and @code{$__}. After an @code{x} command, the last address
6464 examined is available for use in expressions in the convenience variable
6465 @code{$_}. The contents of that address, as examined, are available in
6466 the convenience variable @code{$__}.
6468 If the @code{x} command has a repeat count, the address and contents saved
6469 are from the last memory unit printed; this is not the same as the last
6470 address printed if several units were printed on the last line of output.
6472 @cindex remote memory comparison
6473 @cindex verify remote memory image
6474 When you are debugging a program running on a remote target machine
6475 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6476 remote machine's memory against the executable file you downloaded to
6477 the target. The @code{compare-sections} command is provided for such
6481 @kindex compare-sections
6482 @item compare-sections @r{[}@var{section-name}@r{]}
6483 Compare the data of a loadable section @var{section-name} in the
6484 executable file of the program being debugged with the same section in
6485 the remote machine's memory, and report any mismatches. With no
6486 arguments, compares all loadable sections. This command's
6487 availability depends on the target's support for the @code{"qCRC"}
6492 @section Automatic Display
6493 @cindex automatic display
6494 @cindex display of expressions
6496 If you find that you want to print the value of an expression frequently
6497 (to see how it changes), you might want to add it to the @dfn{automatic
6498 display list} so that @value{GDBN} prints its value each time your program stops.
6499 Each expression added to the list is given a number to identify it;
6500 to remove an expression from the list, you specify that number.
6501 The automatic display looks like this:
6505 3: bar[5] = (struct hack *) 0x3804
6509 This display shows item numbers, expressions and their current values. As with
6510 displays you request manually using @code{x} or @code{print}, you can
6511 specify the output format you prefer; in fact, @code{display} decides
6512 whether to use @code{print} or @code{x} depending your format
6513 specification---it uses @code{x} if you specify either the @samp{i}
6514 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6518 @item display @var{expr}
6519 Add the expression @var{expr} to the list of expressions to display
6520 each time your program stops. @xref{Expressions, ,Expressions}.
6522 @code{display} does not repeat if you press @key{RET} again after using it.
6524 @item display/@var{fmt} @var{expr}
6525 For @var{fmt} specifying only a display format and not a size or
6526 count, add the expression @var{expr} to the auto-display list but
6527 arrange to display it each time in the specified format @var{fmt}.
6528 @xref{Output Formats,,Output Formats}.
6530 @item display/@var{fmt} @var{addr}
6531 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6532 number of units, add the expression @var{addr} as a memory address to
6533 be examined each time your program stops. Examining means in effect
6534 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6537 For example, @samp{display/i $pc} can be helpful, to see the machine
6538 instruction about to be executed each time execution stops (@samp{$pc}
6539 is a common name for the program counter; @pxref{Registers, ,Registers}).
6542 @kindex delete display
6544 @item undisplay @var{dnums}@dots{}
6545 @itemx delete display @var{dnums}@dots{}
6546 Remove item numbers @var{dnums} from the list of expressions to display.
6548 @code{undisplay} does not repeat if you press @key{RET} after using it.
6549 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6551 @kindex disable display
6552 @item disable display @var{dnums}@dots{}
6553 Disable the display of item numbers @var{dnums}. A disabled display
6554 item is not printed automatically, but is not forgotten. It may be
6555 enabled again later.
6557 @kindex enable display
6558 @item enable display @var{dnums}@dots{}
6559 Enable display of item numbers @var{dnums}. It becomes effective once
6560 again in auto display of its expression, until you specify otherwise.
6563 Display the current values of the expressions on the list, just as is
6564 done when your program stops.
6566 @kindex info display
6568 Print the list of expressions previously set up to display
6569 automatically, each one with its item number, but without showing the
6570 values. This includes disabled expressions, which are marked as such.
6571 It also includes expressions which would not be displayed right now
6572 because they refer to automatic variables not currently available.
6575 @cindex display disabled out of scope
6576 If a display expression refers to local variables, then it does not make
6577 sense outside the lexical context for which it was set up. Such an
6578 expression is disabled when execution enters a context where one of its
6579 variables is not defined. For example, if you give the command
6580 @code{display last_char} while inside a function with an argument
6581 @code{last_char}, @value{GDBN} displays this argument while your program
6582 continues to stop inside that function. When it stops elsewhere---where
6583 there is no variable @code{last_char}---the display is disabled
6584 automatically. The next time your program stops where @code{last_char}
6585 is meaningful, you can enable the display expression once again.
6587 @node Print Settings
6588 @section Print Settings
6590 @cindex format options
6591 @cindex print settings
6592 @value{GDBN} provides the following ways to control how arrays, structures,
6593 and symbols are printed.
6596 These settings are useful for debugging programs in any language:
6600 @item set print address
6601 @itemx set print address on
6602 @cindex print/don't print memory addresses
6603 @value{GDBN} prints memory addresses showing the location of stack
6604 traces, structure values, pointer values, breakpoints, and so forth,
6605 even when it also displays the contents of those addresses. The default
6606 is @code{on}. For example, this is what a stack frame display looks like with
6607 @code{set print address on}:
6612 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6614 530 if (lquote != def_lquote)
6618 @item set print address off
6619 Do not print addresses when displaying their contents. For example,
6620 this is the same stack frame displayed with @code{set print address off}:
6624 (@value{GDBP}) set print addr off
6626 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6627 530 if (lquote != def_lquote)
6631 You can use @samp{set print address off} to eliminate all machine
6632 dependent displays from the @value{GDBN} interface. For example, with
6633 @code{print address off}, you should get the same text for backtraces on
6634 all machines---whether or not they involve pointer arguments.
6637 @item show print address
6638 Show whether or not addresses are to be printed.
6641 When @value{GDBN} prints a symbolic address, it normally prints the
6642 closest earlier symbol plus an offset. If that symbol does not uniquely
6643 identify the address (for example, it is a name whose scope is a single
6644 source file), you may need to clarify. One way to do this is with
6645 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6646 you can set @value{GDBN} to print the source file and line number when
6647 it prints a symbolic address:
6650 @item set print symbol-filename on
6651 @cindex source file and line of a symbol
6652 @cindex symbol, source file and line
6653 Tell @value{GDBN} to print the source file name and line number of a
6654 symbol in the symbolic form of an address.
6656 @item set print symbol-filename off
6657 Do not print source file name and line number of a symbol. This is the
6660 @item show print symbol-filename
6661 Show whether or not @value{GDBN} will print the source file name and
6662 line number of a symbol in the symbolic form of an address.
6665 Another situation where it is helpful to show symbol filenames and line
6666 numbers is when disassembling code; @value{GDBN} shows you the line
6667 number and source file that corresponds to each instruction.
6669 Also, you may wish to see the symbolic form only if the address being
6670 printed is reasonably close to the closest earlier symbol:
6673 @item set print max-symbolic-offset @var{max-offset}
6674 @cindex maximum value for offset of closest symbol
6675 Tell @value{GDBN} to only display the symbolic form of an address if the
6676 offset between the closest earlier symbol and the address is less than
6677 @var{max-offset}. The default is 0, which tells @value{GDBN}
6678 to always print the symbolic form of an address if any symbol precedes it.
6680 @item show print max-symbolic-offset
6681 Ask how large the maximum offset is that @value{GDBN} prints in a
6685 @cindex wild pointer, interpreting
6686 @cindex pointer, finding referent
6687 If you have a pointer and you are not sure where it points, try
6688 @samp{set print symbol-filename on}. Then you can determine the name
6689 and source file location of the variable where it points, using
6690 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6691 For example, here @value{GDBN} shows that a variable @code{ptt} points
6692 at another variable @code{t}, defined in @file{hi2.c}:
6695 (@value{GDBP}) set print symbol-filename on
6696 (@value{GDBP}) p/a ptt
6697 $4 = 0xe008 <t in hi2.c>
6701 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6702 does not show the symbol name and filename of the referent, even with
6703 the appropriate @code{set print} options turned on.
6706 Other settings control how different kinds of objects are printed:
6709 @item set print array
6710 @itemx set print array on
6711 @cindex pretty print arrays
6712 Pretty print arrays. This format is more convenient to read,
6713 but uses more space. The default is off.
6715 @item set print array off
6716 Return to compressed format for arrays.
6718 @item show print array
6719 Show whether compressed or pretty format is selected for displaying
6722 @cindex print array indexes
6723 @item set print array-indexes
6724 @itemx set print array-indexes on
6725 Print the index of each element when displaying arrays. May be more
6726 convenient to locate a given element in the array or quickly find the
6727 index of a given element in that printed array. The default is off.
6729 @item set print array-indexes off
6730 Stop printing element indexes when displaying arrays.
6732 @item show print array-indexes
6733 Show whether the index of each element is printed when displaying
6736 @item set print elements @var{number-of-elements}
6737 @cindex number of array elements to print
6738 @cindex limit on number of printed array elements
6739 Set a limit on how many elements of an array @value{GDBN} will print.
6740 If @value{GDBN} is printing a large array, it stops printing after it has
6741 printed the number of elements set by the @code{set print elements} command.
6742 This limit also applies to the display of strings.
6743 When @value{GDBN} starts, this limit is set to 200.
6744 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6746 @item show print elements
6747 Display the number of elements of a large array that @value{GDBN} will print.
6748 If the number is 0, then the printing is unlimited.
6750 @item set print frame-arguments @var{value}
6751 @cindex printing frame argument values
6752 @cindex print all frame argument values
6753 @cindex print frame argument values for scalars only
6754 @cindex do not print frame argument values
6755 This command allows to control how the values of arguments are printed
6756 when the debugger prints a frame (@pxref{Frames}). The possible
6761 The values of all arguments are printed. This is the default.
6764 Print the value of an argument only if it is a scalar. The value of more
6765 complex arguments such as arrays, structures, unions, etc, is replaced
6766 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6769 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6774 None of the argument values are printed. Instead, the value of each argument
6775 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6778 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6783 By default, all argument values are always printed. But this command
6784 can be useful in several cases. For instance, it can be used to reduce
6785 the amount of information printed in each frame, making the backtrace
6786 more readable. Also, this command can be used to improve performance
6787 when displaying Ada frames, because the computation of large arguments
6788 can sometimes be CPU-intensive, especiallly in large applications.
6789 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6790 avoids this computation, thus speeding up the display of each Ada frame.
6792 @item show print frame-arguments
6793 Show how the value of arguments should be displayed when printing a frame.
6795 @item set print repeats
6796 @cindex repeated array elements
6797 Set the threshold for suppressing display of repeated array
6798 elements. When the number of consecutive identical elements of an
6799 array exceeds the threshold, @value{GDBN} prints the string
6800 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6801 identical repetitions, instead of displaying the identical elements
6802 themselves. Setting the threshold to zero will cause all elements to
6803 be individually printed. The default threshold is 10.
6805 @item show print repeats
6806 Display the current threshold for printing repeated identical
6809 @item set print null-stop
6810 @cindex @sc{null} elements in arrays
6811 Cause @value{GDBN} to stop printing the characters of an array when the first
6812 @sc{null} is encountered. This is useful when large arrays actually
6813 contain only short strings.
6816 @item show print null-stop
6817 Show whether @value{GDBN} stops printing an array on the first
6818 @sc{null} character.
6820 @item set print pretty on
6821 @cindex print structures in indented form
6822 @cindex indentation in structure display
6823 Cause @value{GDBN} to print structures in an indented format with one member
6824 per line, like this:
6839 @item set print pretty off
6840 Cause @value{GDBN} to print structures in a compact format, like this:
6844 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6845 meat = 0x54 "Pork"@}
6850 This is the default format.
6852 @item show print pretty
6853 Show which format @value{GDBN} is using to print structures.
6855 @item set print sevenbit-strings on
6856 @cindex eight-bit characters in strings
6857 @cindex octal escapes in strings
6858 Print using only seven-bit characters; if this option is set,
6859 @value{GDBN} displays any eight-bit characters (in strings or
6860 character values) using the notation @code{\}@var{nnn}. This setting is
6861 best if you are working in English (@sc{ascii}) and you use the
6862 high-order bit of characters as a marker or ``meta'' bit.
6864 @item set print sevenbit-strings off
6865 Print full eight-bit characters. This allows the use of more
6866 international character sets, and is the default.
6868 @item show print sevenbit-strings
6869 Show whether or not @value{GDBN} is printing only seven-bit characters.
6871 @item set print union on
6872 @cindex unions in structures, printing
6873 Tell @value{GDBN} to print unions which are contained in structures
6874 and other unions. This is the default setting.
6876 @item set print union off
6877 Tell @value{GDBN} not to print unions which are contained in
6878 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6881 @item show print union
6882 Ask @value{GDBN} whether or not it will print unions which are contained in
6883 structures and other unions.
6885 For example, given the declarations
6888 typedef enum @{Tree, Bug@} Species;
6889 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6890 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6901 struct thing foo = @{Tree, @{Acorn@}@};
6905 with @code{set print union on} in effect @samp{p foo} would print
6908 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6912 and with @code{set print union off} in effect it would print
6915 $1 = @{it = Tree, form = @{...@}@}
6919 @code{set print union} affects programs written in C-like languages
6925 These settings are of interest when debugging C@t{++} programs:
6928 @cindex demangling C@t{++} names
6929 @item set print demangle
6930 @itemx set print demangle on
6931 Print C@t{++} names in their source form rather than in the encoded
6932 (``mangled'') form passed to the assembler and linker for type-safe
6933 linkage. The default is on.
6935 @item show print demangle
6936 Show whether C@t{++} names are printed in mangled or demangled form.
6938 @item set print asm-demangle
6939 @itemx set print asm-demangle on
6940 Print C@t{++} names in their source form rather than their mangled form, even
6941 in assembler code printouts such as instruction disassemblies.
6944 @item show print asm-demangle
6945 Show whether C@t{++} names in assembly listings are printed in mangled
6948 @cindex C@t{++} symbol decoding style
6949 @cindex symbol decoding style, C@t{++}
6950 @kindex set demangle-style
6951 @item set demangle-style @var{style}
6952 Choose among several encoding schemes used by different compilers to
6953 represent C@t{++} names. The choices for @var{style} are currently:
6957 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6960 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6961 This is the default.
6964 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6967 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6970 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6971 @strong{Warning:} this setting alone is not sufficient to allow
6972 debugging @code{cfront}-generated executables. @value{GDBN} would
6973 require further enhancement to permit that.
6976 If you omit @var{style}, you will see a list of possible formats.
6978 @item show demangle-style
6979 Display the encoding style currently in use for decoding C@t{++} symbols.
6981 @item set print object
6982 @itemx set print object on
6983 @cindex derived type of an object, printing
6984 @cindex display derived types
6985 When displaying a pointer to an object, identify the @emph{actual}
6986 (derived) type of the object rather than the @emph{declared} type, using
6987 the virtual function table.
6989 @item set print object off
6990 Display only the declared type of objects, without reference to the
6991 virtual function table. This is the default setting.
6993 @item show print object
6994 Show whether actual, or declared, object types are displayed.
6996 @item set print static-members
6997 @itemx set print static-members on
6998 @cindex static members of C@t{++} objects
6999 Print static members when displaying a C@t{++} object. The default is on.
7001 @item set print static-members off
7002 Do not print static members when displaying a C@t{++} object.
7004 @item show print static-members
7005 Show whether C@t{++} static members are printed or not.
7007 @item set print pascal_static-members
7008 @itemx set print pascal_static-members on
7009 @cindex static members of Pascal objects
7010 @cindex Pascal objects, static members display
7011 Print static members when displaying a Pascal object. The default is on.
7013 @item set print pascal_static-members off
7014 Do not print static members when displaying a Pascal object.
7016 @item show print pascal_static-members
7017 Show whether Pascal static members are printed or not.
7019 @c These don't work with HP ANSI C++ yet.
7020 @item set print vtbl
7021 @itemx set print vtbl on
7022 @cindex pretty print C@t{++} virtual function tables
7023 @cindex virtual functions (C@t{++}) display
7024 @cindex VTBL display
7025 Pretty print C@t{++} virtual function tables. The default is off.
7026 (The @code{vtbl} commands do not work on programs compiled with the HP
7027 ANSI C@t{++} compiler (@code{aCC}).)
7029 @item set print vtbl off
7030 Do not pretty print C@t{++} virtual function tables.
7032 @item show print vtbl
7033 Show whether C@t{++} virtual function tables are pretty printed, or not.
7037 @section Value History
7039 @cindex value history
7040 @cindex history of values printed by @value{GDBN}
7041 Values printed by the @code{print} command are saved in the @value{GDBN}
7042 @dfn{value history}. This allows you to refer to them in other expressions.
7043 Values are kept until the symbol table is re-read or discarded
7044 (for example with the @code{file} or @code{symbol-file} commands).
7045 When the symbol table changes, the value history is discarded,
7046 since the values may contain pointers back to the types defined in the
7051 @cindex history number
7052 The values printed are given @dfn{history numbers} by which you can
7053 refer to them. These are successive integers starting with one.
7054 @code{print} shows you the history number assigned to a value by
7055 printing @samp{$@var{num} = } before the value; here @var{num} is the
7058 To refer to any previous value, use @samp{$} followed by the value's
7059 history number. The way @code{print} labels its output is designed to
7060 remind you of this. Just @code{$} refers to the most recent value in
7061 the history, and @code{$$} refers to the value before that.
7062 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7063 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7064 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7066 For example, suppose you have just printed a pointer to a structure and
7067 want to see the contents of the structure. It suffices to type
7073 If you have a chain of structures where the component @code{next} points
7074 to the next one, you can print the contents of the next one with this:
7081 You can print successive links in the chain by repeating this
7082 command---which you can do by just typing @key{RET}.
7084 Note that the history records values, not expressions. If the value of
7085 @code{x} is 4 and you type these commands:
7093 then the value recorded in the value history by the @code{print} command
7094 remains 4 even though the value of @code{x} has changed.
7099 Print the last ten values in the value history, with their item numbers.
7100 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7101 values} does not change the history.
7103 @item show values @var{n}
7104 Print ten history values centered on history item number @var{n}.
7107 Print ten history values just after the values last printed. If no more
7108 values are available, @code{show values +} produces no display.
7111 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7112 same effect as @samp{show values +}.
7114 @node Convenience Vars
7115 @section Convenience Variables
7117 @cindex convenience variables
7118 @cindex user-defined variables
7119 @value{GDBN} provides @dfn{convenience variables} that you can use within
7120 @value{GDBN} to hold on to a value and refer to it later. These variables
7121 exist entirely within @value{GDBN}; they are not part of your program, and
7122 setting a convenience variable has no direct effect on further execution
7123 of your program. That is why you can use them freely.
7125 Convenience variables are prefixed with @samp{$}. Any name preceded by
7126 @samp{$} can be used for a convenience variable, unless it is one of
7127 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7128 (Value history references, in contrast, are @emph{numbers} preceded
7129 by @samp{$}. @xref{Value History, ,Value History}.)
7131 You can save a value in a convenience variable with an assignment
7132 expression, just as you would set a variable in your program.
7136 set $foo = *object_ptr
7140 would save in @code{$foo} the value contained in the object pointed to by
7143 Using a convenience variable for the first time creates it, but its
7144 value is @code{void} until you assign a new value. You can alter the
7145 value with another assignment at any time.
7147 Convenience variables have no fixed types. You can assign a convenience
7148 variable any type of value, including structures and arrays, even if
7149 that variable already has a value of a different type. The convenience
7150 variable, when used as an expression, has the type of its current value.
7153 @kindex show convenience
7154 @cindex show all user variables
7155 @item show convenience
7156 Print a list of convenience variables used so far, and their values.
7157 Abbreviated @code{show conv}.
7159 @kindex init-if-undefined
7160 @cindex convenience variables, initializing
7161 @item init-if-undefined $@var{variable} = @var{expression}
7162 Set a convenience variable if it has not already been set. This is useful
7163 for user-defined commands that keep some state. It is similar, in concept,
7164 to using local static variables with initializers in C (except that
7165 convenience variables are global). It can also be used to allow users to
7166 override default values used in a command script.
7168 If the variable is already defined then the expression is not evaluated so
7169 any side-effects do not occur.
7172 One of the ways to use a convenience variable is as a counter to be
7173 incremented or a pointer to be advanced. For example, to print
7174 a field from successive elements of an array of structures:
7178 print bar[$i++]->contents
7182 Repeat that command by typing @key{RET}.
7184 Some convenience variables are created automatically by @value{GDBN} and given
7185 values likely to be useful.
7188 @vindex $_@r{, convenience variable}
7190 The variable @code{$_} is automatically set by the @code{x} command to
7191 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7192 commands which provide a default address for @code{x} to examine also
7193 set @code{$_} to that address; these commands include @code{info line}
7194 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7195 except when set by the @code{x} command, in which case it is a pointer
7196 to the type of @code{$__}.
7198 @vindex $__@r{, convenience variable}
7200 The variable @code{$__} is automatically set by the @code{x} command
7201 to the value found in the last address examined. Its type is chosen
7202 to match the format in which the data was printed.
7205 @vindex $_exitcode@r{, convenience variable}
7206 The variable @code{$_exitcode} is automatically set to the exit code when
7207 the program being debugged terminates.
7210 On HP-UX systems, if you refer to a function or variable name that
7211 begins with a dollar sign, @value{GDBN} searches for a user or system
7212 name first, before it searches for a convenience variable.
7218 You can refer to machine register contents, in expressions, as variables
7219 with names starting with @samp{$}. The names of registers are different
7220 for each machine; use @code{info registers} to see the names used on
7224 @kindex info registers
7225 @item info registers
7226 Print the names and values of all registers except floating-point
7227 and vector registers (in the selected stack frame).
7229 @kindex info all-registers
7230 @cindex floating point registers
7231 @item info all-registers
7232 Print the names and values of all registers, including floating-point
7233 and vector registers (in the selected stack frame).
7235 @item info registers @var{regname} @dots{}
7236 Print the @dfn{relativized} value of each specified register @var{regname}.
7237 As discussed in detail below, register values are normally relative to
7238 the selected stack frame. @var{regname} may be any register name valid on
7239 the machine you are using, with or without the initial @samp{$}.
7242 @cindex stack pointer register
7243 @cindex program counter register
7244 @cindex process status register
7245 @cindex frame pointer register
7246 @cindex standard registers
7247 @value{GDBN} has four ``standard'' register names that are available (in
7248 expressions) on most machines---whenever they do not conflict with an
7249 architecture's canonical mnemonics for registers. The register names
7250 @code{$pc} and @code{$sp} are used for the program counter register and
7251 the stack pointer. @code{$fp} is used for a register that contains a
7252 pointer to the current stack frame, and @code{$ps} is used for a
7253 register that contains the processor status. For example,
7254 you could print the program counter in hex with
7261 or print the instruction to be executed next with
7268 or add four to the stack pointer@footnote{This is a way of removing
7269 one word from the stack, on machines where stacks grow downward in
7270 memory (most machines, nowadays). This assumes that the innermost
7271 stack frame is selected; setting @code{$sp} is not allowed when other
7272 stack frames are selected. To pop entire frames off the stack,
7273 regardless of machine architecture, use @code{return};
7274 see @ref{Returning, ,Returning from a Function}.} with
7280 Whenever possible, these four standard register names are available on
7281 your machine even though the machine has different canonical mnemonics,
7282 so long as there is no conflict. The @code{info registers} command
7283 shows the canonical names. For example, on the SPARC, @code{info
7284 registers} displays the processor status register as @code{$psr} but you
7285 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7286 is an alias for the @sc{eflags} register.
7288 @value{GDBN} always considers the contents of an ordinary register as an
7289 integer when the register is examined in this way. Some machines have
7290 special registers which can hold nothing but floating point; these
7291 registers are considered to have floating point values. There is no way
7292 to refer to the contents of an ordinary register as floating point value
7293 (although you can @emph{print} it as a floating point value with
7294 @samp{print/f $@var{regname}}).
7296 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7297 means that the data format in which the register contents are saved by
7298 the operating system is not the same one that your program normally
7299 sees. For example, the registers of the 68881 floating point
7300 coprocessor are always saved in ``extended'' (raw) format, but all C
7301 programs expect to work with ``double'' (virtual) format. In such
7302 cases, @value{GDBN} normally works with the virtual format only (the format
7303 that makes sense for your program), but the @code{info registers} command
7304 prints the data in both formats.
7306 @cindex SSE registers (x86)
7307 @cindex MMX registers (x86)
7308 Some machines have special registers whose contents can be interpreted
7309 in several different ways. For example, modern x86-based machines
7310 have SSE and MMX registers that can hold several values packed
7311 together in several different formats. @value{GDBN} refers to such
7312 registers in @code{struct} notation:
7315 (@value{GDBP}) print $xmm1
7317 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7318 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7319 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7320 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7321 v4_int32 = @{0, 20657912, 11, 13@},
7322 v2_int64 = @{88725056443645952, 55834574859@},
7323 uint128 = 0x0000000d0000000b013b36f800000000
7328 To set values of such registers, you need to tell @value{GDBN} which
7329 view of the register you wish to change, as if you were assigning
7330 value to a @code{struct} member:
7333 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7336 Normally, register values are relative to the selected stack frame
7337 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7338 value that the register would contain if all stack frames farther in
7339 were exited and their saved registers restored. In order to see the
7340 true contents of hardware registers, you must select the innermost
7341 frame (with @samp{frame 0}).
7343 However, @value{GDBN} must deduce where registers are saved, from the machine
7344 code generated by your compiler. If some registers are not saved, or if
7345 @value{GDBN} is unable to locate the saved registers, the selected stack
7346 frame makes no difference.
7348 @node Floating Point Hardware
7349 @section Floating Point Hardware
7350 @cindex floating point
7352 Depending on the configuration, @value{GDBN} may be able to give
7353 you more information about the status of the floating point hardware.
7358 Display hardware-dependent information about the floating
7359 point unit. The exact contents and layout vary depending on the
7360 floating point chip. Currently, @samp{info float} is supported on
7361 the ARM and x86 machines.
7365 @section Vector Unit
7368 Depending on the configuration, @value{GDBN} may be able to give you
7369 more information about the status of the vector unit.
7374 Display information about the vector unit. The exact contents and
7375 layout vary depending on the hardware.
7378 @node OS Information
7379 @section Operating System Auxiliary Information
7380 @cindex OS information
7382 @value{GDBN} provides interfaces to useful OS facilities that can help
7383 you debug your program.
7385 @cindex @code{ptrace} system call
7386 @cindex @code{struct user} contents
7387 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7388 machines), it interfaces with the inferior via the @code{ptrace}
7389 system call. The operating system creates a special sata structure,
7390 called @code{struct user}, for this interface. You can use the
7391 command @code{info udot} to display the contents of this data
7397 Display the contents of the @code{struct user} maintained by the OS
7398 kernel for the program being debugged. @value{GDBN} displays the
7399 contents of @code{struct user} as a list of hex numbers, similar to
7400 the @code{examine} command.
7403 @cindex auxiliary vector
7404 @cindex vector, auxiliary
7405 Some operating systems supply an @dfn{auxiliary vector} to programs at
7406 startup. This is akin to the arguments and environment that you
7407 specify for a program, but contains a system-dependent variety of
7408 binary values that tell system libraries important details about the
7409 hardware, operating system, and process. Each value's purpose is
7410 identified by an integer tag; the meanings are well-known but system-specific.
7411 Depending on the configuration and operating system facilities,
7412 @value{GDBN} may be able to show you this information. For remote
7413 targets, this functionality may further depend on the remote stub's
7414 support of the @samp{qXfer:auxv:read} packet, see
7415 @ref{qXfer auxiliary vector read}.
7420 Display the auxiliary vector of the inferior, which can be either a
7421 live process or a core dump file. @value{GDBN} prints each tag value
7422 numerically, and also shows names and text descriptions for recognized
7423 tags. Some values in the vector are numbers, some bit masks, and some
7424 pointers to strings or other data. @value{GDBN} displays each value in the
7425 most appropriate form for a recognized tag, and in hexadecimal for
7426 an unrecognized tag.
7430 @node Memory Region Attributes
7431 @section Memory Region Attributes
7432 @cindex memory region attributes
7434 @dfn{Memory region attributes} allow you to describe special handling
7435 required by regions of your target's memory. @value{GDBN} uses
7436 attributes to determine whether to allow certain types of memory
7437 accesses; whether to use specific width accesses; and whether to cache
7438 target memory. By default the description of memory regions is
7439 fetched from the target (if the current target supports this), but the
7440 user can override the fetched regions.
7442 Defined memory regions can be individually enabled and disabled. When a
7443 memory region is disabled, @value{GDBN} uses the default attributes when
7444 accessing memory in that region. Similarly, if no memory regions have
7445 been defined, @value{GDBN} uses the default attributes when accessing
7448 When a memory region is defined, it is given a number to identify it;
7449 to enable, disable, or remove a memory region, you specify that number.
7453 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7454 Define a memory region bounded by @var{lower} and @var{upper} with
7455 attributes @var{attributes}@dots{}, and add it to the list of regions
7456 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7457 case: it is treated as the target's maximum memory address.
7458 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7461 Discard any user changes to the memory regions and use target-supplied
7462 regions, if available, or no regions if the target does not support.
7465 @item delete mem @var{nums}@dots{}
7466 Remove memory regions @var{nums}@dots{} from the list of regions
7467 monitored by @value{GDBN}.
7470 @item disable mem @var{nums}@dots{}
7471 Disable monitoring of memory regions @var{nums}@dots{}.
7472 A disabled memory region is not forgotten.
7473 It may be enabled again later.
7476 @item enable mem @var{nums}@dots{}
7477 Enable monitoring of memory regions @var{nums}@dots{}.
7481 Print a table of all defined memory regions, with the following columns
7485 @item Memory Region Number
7486 @item Enabled or Disabled.
7487 Enabled memory regions are marked with @samp{y}.
7488 Disabled memory regions are marked with @samp{n}.
7491 The address defining the inclusive lower bound of the memory region.
7494 The address defining the exclusive upper bound of the memory region.
7497 The list of attributes set for this memory region.
7502 @subsection Attributes
7504 @subsubsection Memory Access Mode
7505 The access mode attributes set whether @value{GDBN} may make read or
7506 write accesses to a memory region.
7508 While these attributes prevent @value{GDBN} from performing invalid
7509 memory accesses, they do nothing to prevent the target system, I/O DMA,
7510 etc.@: from accessing memory.
7514 Memory is read only.
7516 Memory is write only.
7518 Memory is read/write. This is the default.
7521 @subsubsection Memory Access Size
7522 The access size attribute tells @value{GDBN} to use specific sized
7523 accesses in the memory region. Often memory mapped device registers
7524 require specific sized accesses. If no access size attribute is
7525 specified, @value{GDBN} may use accesses of any size.
7529 Use 8 bit memory accesses.
7531 Use 16 bit memory accesses.
7533 Use 32 bit memory accesses.
7535 Use 64 bit memory accesses.
7538 @c @subsubsection Hardware/Software Breakpoints
7539 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7540 @c will use hardware or software breakpoints for the internal breakpoints
7541 @c used by the step, next, finish, until, etc. commands.
7545 @c Always use hardware breakpoints
7546 @c @item swbreak (default)
7549 @subsubsection Data Cache
7550 The data cache attributes set whether @value{GDBN} will cache target
7551 memory. While this generally improves performance by reducing debug
7552 protocol overhead, it can lead to incorrect results because @value{GDBN}
7553 does not know about volatile variables or memory mapped device
7558 Enable @value{GDBN} to cache target memory.
7560 Disable @value{GDBN} from caching target memory. This is the default.
7563 @subsection Memory Access Checking
7564 @value{GDBN} can be instructed to refuse accesses to memory that is
7565 not explicitly described. This can be useful if accessing such
7566 regions has undesired effects for a specific target, or to provide
7567 better error checking. The following commands control this behaviour.
7570 @kindex set mem inaccessible-by-default
7571 @item set mem inaccessible-by-default [on|off]
7572 If @code{on} is specified, make @value{GDBN} treat memory not
7573 explicitly described by the memory ranges as non-existent and refuse accesses
7574 to such memory. The checks are only performed if there's at least one
7575 memory range defined. If @code{off} is specified, make @value{GDBN}
7576 treat the memory not explicitly described by the memory ranges as RAM.
7577 The default value is @code{on}.
7578 @kindex show mem inaccessible-by-default
7579 @item show mem inaccessible-by-default
7580 Show the current handling of accesses to unknown memory.
7584 @c @subsubsection Memory Write Verification
7585 @c The memory write verification attributes set whether @value{GDBN}
7586 @c will re-reads data after each write to verify the write was successful.
7590 @c @item noverify (default)
7593 @node Dump/Restore Files
7594 @section Copy Between Memory and a File
7595 @cindex dump/restore files
7596 @cindex append data to a file
7597 @cindex dump data to a file
7598 @cindex restore data from a file
7600 You can use the commands @code{dump}, @code{append}, and
7601 @code{restore} to copy data between target memory and a file. The
7602 @code{dump} and @code{append} commands write data to a file, and the
7603 @code{restore} command reads data from a file back into the inferior's
7604 memory. Files may be in binary, Motorola S-record, Intel hex, or
7605 Tektronix Hex format; however, @value{GDBN} can only append to binary
7611 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7612 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7613 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7614 or the value of @var{expr}, to @var{filename} in the given format.
7616 The @var{format} parameter may be any one of:
7623 Motorola S-record format.
7625 Tektronix Hex format.
7628 @value{GDBN} uses the same definitions of these formats as the
7629 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7630 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7634 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7635 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7636 Append the contents of memory from @var{start_addr} to @var{end_addr},
7637 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7638 (@value{GDBN} can only append data to files in raw binary form.)
7641 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7642 Restore the contents of file @var{filename} into memory. The
7643 @code{restore} command can automatically recognize any known @sc{bfd}
7644 file format, except for raw binary. To restore a raw binary file you
7645 must specify the optional keyword @code{binary} after the filename.
7647 If @var{bias} is non-zero, its value will be added to the addresses
7648 contained in the file. Binary files always start at address zero, so
7649 they will be restored at address @var{bias}. Other bfd files have
7650 a built-in location; they will be restored at offset @var{bias}
7653 If @var{start} and/or @var{end} are non-zero, then only data between
7654 file offset @var{start} and file offset @var{end} will be restored.
7655 These offsets are relative to the addresses in the file, before
7656 the @var{bias} argument is applied.
7660 @node Core File Generation
7661 @section How to Produce a Core File from Your Program
7662 @cindex dump core from inferior
7664 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7665 image of a running process and its process status (register values
7666 etc.). Its primary use is post-mortem debugging of a program that
7667 crashed while it ran outside a debugger. A program that crashes
7668 automatically produces a core file, unless this feature is disabled by
7669 the user. @xref{Files}, for information on invoking @value{GDBN} in
7670 the post-mortem debugging mode.
7672 Occasionally, you may wish to produce a core file of the program you
7673 are debugging in order to preserve a snapshot of its state.
7674 @value{GDBN} has a special command for that.
7678 @kindex generate-core-file
7679 @item generate-core-file [@var{file}]
7680 @itemx gcore [@var{file}]
7681 Produce a core dump of the inferior process. The optional argument
7682 @var{file} specifies the file name where to put the core dump. If not
7683 specified, the file name defaults to @file{core.@var{pid}}, where
7684 @var{pid} is the inferior process ID.
7686 Note that this command is implemented only for some systems (as of
7687 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7690 @node Character Sets
7691 @section Character Sets
7692 @cindex character sets
7694 @cindex translating between character sets
7695 @cindex host character set
7696 @cindex target character set
7698 If the program you are debugging uses a different character set to
7699 represent characters and strings than the one @value{GDBN} uses itself,
7700 @value{GDBN} can automatically translate between the character sets for
7701 you. The character set @value{GDBN} uses we call the @dfn{host
7702 character set}; the one the inferior program uses we call the
7703 @dfn{target character set}.
7705 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7706 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7707 remote protocol (@pxref{Remote Debugging}) to debug a program
7708 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7709 then the host character set is Latin-1, and the target character set is
7710 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7711 target-charset EBCDIC-US}, then @value{GDBN} translates between
7712 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7713 character and string literals in expressions.
7715 @value{GDBN} has no way to automatically recognize which character set
7716 the inferior program uses; you must tell it, using the @code{set
7717 target-charset} command, described below.
7719 Here are the commands for controlling @value{GDBN}'s character set
7723 @item set target-charset @var{charset}
7724 @kindex set target-charset
7725 Set the current target character set to @var{charset}. We list the
7726 character set names @value{GDBN} recognizes below, but if you type
7727 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7728 list the target character sets it supports.
7732 @item set host-charset @var{charset}
7733 @kindex set host-charset
7734 Set the current host character set to @var{charset}.
7736 By default, @value{GDBN} uses a host character set appropriate to the
7737 system it is running on; you can override that default using the
7738 @code{set host-charset} command.
7740 @value{GDBN} can only use certain character sets as its host character
7741 set. We list the character set names @value{GDBN} recognizes below, and
7742 indicate which can be host character sets, but if you type
7743 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7744 list the host character sets it supports.
7746 @item set charset @var{charset}
7748 Set the current host and target character sets to @var{charset}. As
7749 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7750 @value{GDBN} will list the name of the character sets that can be used
7751 for both host and target.
7755 @kindex show charset
7756 Show the names of the current host and target charsets.
7758 @itemx show host-charset
7759 @kindex show host-charset
7760 Show the name of the current host charset.
7762 @itemx show target-charset
7763 @kindex show target-charset
7764 Show the name of the current target charset.
7768 @value{GDBN} currently includes support for the following character
7774 @cindex ASCII character set
7775 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7779 @cindex ISO 8859-1 character set
7780 @cindex ISO Latin 1 character set
7781 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7782 characters needed for French, German, and Spanish. @value{GDBN} can use
7783 this as its host character set.
7787 @cindex EBCDIC character set
7788 @cindex IBM1047 character set
7789 Variants of the @sc{ebcdic} character set, used on some of IBM's
7790 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7791 @value{GDBN} cannot use these as its host character set.
7795 Note that these are all single-byte character sets. More work inside
7796 @value{GDBN} is needed to support multi-byte or variable-width character
7797 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7799 Here is an example of @value{GDBN}'s character set support in action.
7800 Assume that the following source code has been placed in the file
7801 @file{charset-test.c}:
7807 = @{72, 101, 108, 108, 111, 44, 32, 119,
7808 111, 114, 108, 100, 33, 10, 0@};
7809 char ibm1047_hello[]
7810 = @{200, 133, 147, 147, 150, 107, 64, 166,
7811 150, 153, 147, 132, 90, 37, 0@};
7815 printf ("Hello, world!\n");
7819 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7820 containing the string @samp{Hello, world!} followed by a newline,
7821 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7823 We compile the program, and invoke the debugger on it:
7826 $ gcc -g charset-test.c -o charset-test
7827 $ gdb -nw charset-test
7828 GNU gdb 2001-12-19-cvs
7829 Copyright 2001 Free Software Foundation, Inc.
7834 We can use the @code{show charset} command to see what character sets
7835 @value{GDBN} is currently using to interpret and display characters and
7839 (@value{GDBP}) show charset
7840 The current host and target character set is `ISO-8859-1'.
7844 For the sake of printing this manual, let's use @sc{ascii} as our
7845 initial character set:
7847 (@value{GDBP}) set charset ASCII
7848 (@value{GDBP}) show charset
7849 The current host and target character set is `ASCII'.
7853 Let's assume that @sc{ascii} is indeed the correct character set for our
7854 host system --- in other words, let's assume that if @value{GDBN} prints
7855 characters using the @sc{ascii} character set, our terminal will display
7856 them properly. Since our current target character set is also
7857 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7860 (@value{GDBP}) print ascii_hello
7861 $1 = 0x401698 "Hello, world!\n"
7862 (@value{GDBP}) print ascii_hello[0]
7867 @value{GDBN} uses the target character set for character and string
7868 literals you use in expressions:
7871 (@value{GDBP}) print '+'
7876 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7879 @value{GDBN} relies on the user to tell it which character set the
7880 target program uses. If we print @code{ibm1047_hello} while our target
7881 character set is still @sc{ascii}, we get jibberish:
7884 (@value{GDBP}) print ibm1047_hello
7885 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7886 (@value{GDBP}) print ibm1047_hello[0]
7891 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7892 @value{GDBN} tells us the character sets it supports:
7895 (@value{GDBP}) set target-charset
7896 ASCII EBCDIC-US IBM1047 ISO-8859-1
7897 (@value{GDBP}) set target-charset
7900 We can select @sc{ibm1047} as our target character set, and examine the
7901 program's strings again. Now the @sc{ascii} string is wrong, but
7902 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7903 target character set, @sc{ibm1047}, to the host character set,
7904 @sc{ascii}, and they display correctly:
7907 (@value{GDBP}) set target-charset IBM1047
7908 (@value{GDBP}) show charset
7909 The current host character set is `ASCII'.
7910 The current target character set is `IBM1047'.
7911 (@value{GDBP}) print ascii_hello
7912 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7913 (@value{GDBP}) print ascii_hello[0]
7915 (@value{GDBP}) print ibm1047_hello
7916 $8 = 0x4016a8 "Hello, world!\n"
7917 (@value{GDBP}) print ibm1047_hello[0]
7922 As above, @value{GDBN} uses the target character set for character and
7923 string literals you use in expressions:
7926 (@value{GDBP}) print '+'
7931 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7934 @node Caching Remote Data
7935 @section Caching Data of Remote Targets
7936 @cindex caching data of remote targets
7938 @value{GDBN} can cache data exchanged between the debugger and a
7939 remote target (@pxref{Remote Debugging}). Such caching generally improves
7940 performance, because it reduces the overhead of the remote protocol by
7941 bundling memory reads and writes into large chunks. Unfortunately,
7942 @value{GDBN} does not currently know anything about volatile
7943 registers, and thus data caching will produce incorrect results when
7944 volatile registers are in use.
7947 @kindex set remotecache
7948 @item set remotecache on
7949 @itemx set remotecache off
7950 Set caching state for remote targets. When @code{ON}, use data
7951 caching. By default, this option is @code{OFF}.
7953 @kindex show remotecache
7954 @item show remotecache
7955 Show the current state of data caching for remote targets.
7959 Print the information about the data cache performance. The
7960 information displayed includes: the dcache width and depth; and for
7961 each cache line, how many times it was referenced, and its data and
7962 state (dirty, bad, ok, etc.). This command is useful for debugging
7963 the data cache operation.
7966 @node Searching Memory
7967 @section Search Memory
7968 @cindex searching memory
7970 Memory can be searched for a particular sequence of bytes with the
7971 @code{find} command.
7975 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
7976 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
7977 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
7978 etc. The search begins at address @var{start_addr} and continues for either
7979 @var{len} bytes or through to @var{end_addr} inclusive.
7982 @var{s} and @var{n} are optional parameters.
7983 They may be specified in either order, apart or together.
7986 @item @var{s}, search query size
7987 The size of each search query value.
7993 halfwords (two bytes)
7997 giant words (eight bytes)
8000 All values are interpreted in the current language.
8001 This means, for example, that if the current source language is C/C@t{++}
8002 then searching for the string ``hello'' includes the trailing '\0'.
8004 If the value size is not specified, it is taken from the
8005 value's type in the current language.
8006 This is useful when one wants to specify the search
8007 pattern as a mixture of types.
8008 Note that this means, for example, that in the case of C-like languages
8009 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8010 which is typically four bytes.
8012 @item @var{n}, maximum number of finds
8013 The maximum number of matches to print. The default is to print all finds.
8016 You can use strings as search values. Quote them with double-quotes
8018 The string value is copied into the search pattern byte by byte,
8019 regardless of the endianness of the target and the size specification.
8021 The address of each match found is printed as well as a count of the
8022 number of matches found.
8024 The address of the last value found is stored in convenience variable
8026 A count of the number of matches is stored in @samp{$numfound}.
8028 For example, if stopped at the @code{printf} in this function:
8034 static char hello[] = "hello-hello";
8035 static struct @{ char c; short s; int i; @}
8036 __attribute__ ((packed)) mixed
8037 = @{ 'c', 0x1234, 0x87654321 @};
8038 printf ("%s\n", hello);
8043 you get during debugging:
8046 (gdb) find &hello[0], +sizeof(hello), "hello"
8047 0x804956d <hello.1620+6>
8049 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8050 0x8049567 <hello.1620>
8051 0x804956d <hello.1620+6>
8053 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8054 0x8049567 <hello.1620>
8056 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8057 0x8049560 <mixed.1625>
8059 (gdb) print $numfound
8062 $2 = (void *) 0x8049560
8066 @chapter C Preprocessor Macros
8068 Some languages, such as C and C@t{++}, provide a way to define and invoke
8069 ``preprocessor macros'' which expand into strings of tokens.
8070 @value{GDBN} can evaluate expressions containing macro invocations, show
8071 the result of macro expansion, and show a macro's definition, including
8072 where it was defined.
8074 You may need to compile your program specially to provide @value{GDBN}
8075 with information about preprocessor macros. Most compilers do not
8076 include macros in their debugging information, even when you compile
8077 with the @option{-g} flag. @xref{Compilation}.
8079 A program may define a macro at one point, remove that definition later,
8080 and then provide a different definition after that. Thus, at different
8081 points in the program, a macro may have different definitions, or have
8082 no definition at all. If there is a current stack frame, @value{GDBN}
8083 uses the macros in scope at that frame's source code line. Otherwise,
8084 @value{GDBN} uses the macros in scope at the current listing location;
8087 At the moment, @value{GDBN} does not support the @code{##}
8088 token-splicing operator, the @code{#} stringification operator, or
8089 variable-arity macros.
8091 Whenever @value{GDBN} evaluates an expression, it always expands any
8092 macro invocations present in the expression. @value{GDBN} also provides
8093 the following commands for working with macros explicitly.
8097 @kindex macro expand
8098 @cindex macro expansion, showing the results of preprocessor
8099 @cindex preprocessor macro expansion, showing the results of
8100 @cindex expanding preprocessor macros
8101 @item macro expand @var{expression}
8102 @itemx macro exp @var{expression}
8103 Show the results of expanding all preprocessor macro invocations in
8104 @var{expression}. Since @value{GDBN} simply expands macros, but does
8105 not parse the result, @var{expression} need not be a valid expression;
8106 it can be any string of tokens.
8109 @item macro expand-once @var{expression}
8110 @itemx macro exp1 @var{expression}
8111 @cindex expand macro once
8112 @i{(This command is not yet implemented.)} Show the results of
8113 expanding those preprocessor macro invocations that appear explicitly in
8114 @var{expression}. Macro invocations appearing in that expansion are
8115 left unchanged. This command allows you to see the effect of a
8116 particular macro more clearly, without being confused by further
8117 expansions. Since @value{GDBN} simply expands macros, but does not
8118 parse the result, @var{expression} need not be a valid expression; it
8119 can be any string of tokens.
8122 @cindex macro definition, showing
8123 @cindex definition, showing a macro's
8124 @item info macro @var{macro}
8125 Show the definition of the macro named @var{macro}, and describe the
8126 source location where that definition was established.
8128 @kindex macro define
8129 @cindex user-defined macros
8130 @cindex defining macros interactively
8131 @cindex macros, user-defined
8132 @item macro define @var{macro} @var{replacement-list}
8133 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8134 Introduce a definition for a preprocessor macro named @var{macro},
8135 invocations of which are replaced by the tokens given in
8136 @var{replacement-list}. The first form of this command defines an
8137 ``object-like'' macro, which takes no arguments; the second form
8138 defines a ``function-like'' macro, which takes the arguments given in
8141 A definition introduced by this command is in scope in every
8142 expression evaluated in @value{GDBN}, until it is removed with the
8143 @code{macro undef} command, described below. The definition overrides
8144 all definitions for @var{macro} present in the program being debugged,
8145 as well as any previous user-supplied definition.
8148 @item macro undef @var{macro}
8149 Remove any user-supplied definition for the macro named @var{macro}.
8150 This command only affects definitions provided with the @code{macro
8151 define} command, described above; it cannot remove definitions present
8152 in the program being debugged.
8156 List all the macros defined using the @code{macro define} command.
8159 @cindex macros, example of debugging with
8160 Here is a transcript showing the above commands in action. First, we
8161 show our source files:
8169 #define ADD(x) (M + x)
8174 printf ("Hello, world!\n");
8176 printf ("We're so creative.\n");
8178 printf ("Goodbye, world!\n");
8185 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8186 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8187 compiler includes information about preprocessor macros in the debugging
8191 $ gcc -gdwarf-2 -g3 sample.c -o sample
8195 Now, we start @value{GDBN} on our sample program:
8199 GNU gdb 2002-05-06-cvs
8200 Copyright 2002 Free Software Foundation, Inc.
8201 GDB is free software, @dots{}
8205 We can expand macros and examine their definitions, even when the
8206 program is not running. @value{GDBN} uses the current listing position
8207 to decide which macro definitions are in scope:
8210 (@value{GDBP}) list main
8213 5 #define ADD(x) (M + x)
8218 10 printf ("Hello, world!\n");
8220 12 printf ("We're so creative.\n");
8221 (@value{GDBP}) info macro ADD
8222 Defined at /home/jimb/gdb/macros/play/sample.c:5
8223 #define ADD(x) (M + x)
8224 (@value{GDBP}) info macro Q
8225 Defined at /home/jimb/gdb/macros/play/sample.h:1
8226 included at /home/jimb/gdb/macros/play/sample.c:2
8228 (@value{GDBP}) macro expand ADD(1)
8229 expands to: (42 + 1)
8230 (@value{GDBP}) macro expand-once ADD(1)
8231 expands to: once (M + 1)
8235 In the example above, note that @code{macro expand-once} expands only
8236 the macro invocation explicit in the original text --- the invocation of
8237 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8238 which was introduced by @code{ADD}.
8240 Once the program is running, @value{GDBN} uses the macro definitions in
8241 force at the source line of the current stack frame:
8244 (@value{GDBP}) break main
8245 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8247 Starting program: /home/jimb/gdb/macros/play/sample
8249 Breakpoint 1, main () at sample.c:10
8250 10 printf ("Hello, world!\n");
8254 At line 10, the definition of the macro @code{N} at line 9 is in force:
8257 (@value{GDBP}) info macro N
8258 Defined at /home/jimb/gdb/macros/play/sample.c:9
8260 (@value{GDBP}) macro expand N Q M
8262 (@value{GDBP}) print N Q M
8267 As we step over directives that remove @code{N}'s definition, and then
8268 give it a new definition, @value{GDBN} finds the definition (or lack
8269 thereof) in force at each point:
8274 12 printf ("We're so creative.\n");
8275 (@value{GDBP}) info macro N
8276 The symbol `N' has no definition as a C/C++ preprocessor macro
8277 at /home/jimb/gdb/macros/play/sample.c:12
8280 14 printf ("Goodbye, world!\n");
8281 (@value{GDBP}) info macro N
8282 Defined at /home/jimb/gdb/macros/play/sample.c:13
8284 (@value{GDBP}) macro expand N Q M
8285 expands to: 1729 < 42
8286 (@value{GDBP}) print N Q M
8293 @chapter Tracepoints
8294 @c This chapter is based on the documentation written by Michael
8295 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8298 In some applications, it is not feasible for the debugger to interrupt
8299 the program's execution long enough for the developer to learn
8300 anything helpful about its behavior. If the program's correctness
8301 depends on its real-time behavior, delays introduced by a debugger
8302 might cause the program to change its behavior drastically, or perhaps
8303 fail, even when the code itself is correct. It is useful to be able
8304 to observe the program's behavior without interrupting it.
8306 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8307 specify locations in the program, called @dfn{tracepoints}, and
8308 arbitrary expressions to evaluate when those tracepoints are reached.
8309 Later, using the @code{tfind} command, you can examine the values
8310 those expressions had when the program hit the tracepoints. The
8311 expressions may also denote objects in memory---structures or arrays,
8312 for example---whose values @value{GDBN} should record; while visiting
8313 a particular tracepoint, you may inspect those objects as if they were
8314 in memory at that moment. However, because @value{GDBN} records these
8315 values without interacting with you, it can do so quickly and
8316 unobtrusively, hopefully not disturbing the program's behavior.
8318 The tracepoint facility is currently available only for remote
8319 targets. @xref{Targets}. In addition, your remote target must know
8320 how to collect trace data. This functionality is implemented in the
8321 remote stub; however, none of the stubs distributed with @value{GDBN}
8322 support tracepoints as of this writing. The format of the remote
8323 packets used to implement tracepoints are described in @ref{Tracepoint
8326 This chapter describes the tracepoint commands and features.
8330 * Analyze Collected Data::
8331 * Tracepoint Variables::
8334 @node Set Tracepoints
8335 @section Commands to Set Tracepoints
8337 Before running such a @dfn{trace experiment}, an arbitrary number of
8338 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8339 tracepoint has a number assigned to it by @value{GDBN}. Like with
8340 breakpoints, tracepoint numbers are successive integers starting from
8341 one. Many of the commands associated with tracepoints take the
8342 tracepoint number as their argument, to identify which tracepoint to
8345 For each tracepoint, you can specify, in advance, some arbitrary set
8346 of data that you want the target to collect in the trace buffer when
8347 it hits that tracepoint. The collected data can include registers,
8348 local variables, or global data. Later, you can use @value{GDBN}
8349 commands to examine the values these data had at the time the
8352 This section describes commands to set tracepoints and associated
8353 conditions and actions.
8356 * Create and Delete Tracepoints::
8357 * Enable and Disable Tracepoints::
8358 * Tracepoint Passcounts::
8359 * Tracepoint Actions::
8360 * Listing Tracepoints::
8361 * Starting and Stopping Trace Experiments::
8364 @node Create and Delete Tracepoints
8365 @subsection Create and Delete Tracepoints
8368 @cindex set tracepoint
8371 The @code{trace} command is very similar to the @code{break} command.
8372 Its argument can be a source line, a function name, or an address in
8373 the target program. @xref{Set Breaks}. The @code{trace} command
8374 defines a tracepoint, which is a point in the target program where the
8375 debugger will briefly stop, collect some data, and then allow the
8376 program to continue. Setting a tracepoint or changing its commands
8377 doesn't take effect until the next @code{tstart} command; thus, you
8378 cannot change the tracepoint attributes once a trace experiment is
8381 Here are some examples of using the @code{trace} command:
8384 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8386 (@value{GDBP}) @b{trace +2} // 2 lines forward
8388 (@value{GDBP}) @b{trace my_function} // first source line of function
8390 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8392 (@value{GDBP}) @b{trace *0x2117c4} // an address
8396 You can abbreviate @code{trace} as @code{tr}.
8399 @cindex last tracepoint number
8400 @cindex recent tracepoint number
8401 @cindex tracepoint number
8402 The convenience variable @code{$tpnum} records the tracepoint number
8403 of the most recently set tracepoint.
8405 @kindex delete tracepoint
8406 @cindex tracepoint deletion
8407 @item delete tracepoint @r{[}@var{num}@r{]}
8408 Permanently delete one or more tracepoints. With no argument, the
8409 default is to delete all tracepoints.
8414 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8416 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8420 You can abbreviate this command as @code{del tr}.
8423 @node Enable and Disable Tracepoints
8424 @subsection Enable and Disable Tracepoints
8427 @kindex disable tracepoint
8428 @item disable tracepoint @r{[}@var{num}@r{]}
8429 Disable tracepoint @var{num}, or all tracepoints if no argument
8430 @var{num} is given. A disabled tracepoint will have no effect during
8431 the next trace experiment, but it is not forgotten. You can re-enable
8432 a disabled tracepoint using the @code{enable tracepoint} command.
8434 @kindex enable tracepoint
8435 @item enable tracepoint @r{[}@var{num}@r{]}
8436 Enable tracepoint @var{num}, or all tracepoints. The enabled
8437 tracepoints will become effective the next time a trace experiment is
8441 @node Tracepoint Passcounts
8442 @subsection Tracepoint Passcounts
8446 @cindex tracepoint pass count
8447 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8448 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8449 automatically stop a trace experiment. If a tracepoint's passcount is
8450 @var{n}, then the trace experiment will be automatically stopped on
8451 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8452 @var{num} is not specified, the @code{passcount} command sets the
8453 passcount of the most recently defined tracepoint. If no passcount is
8454 given, the trace experiment will run until stopped explicitly by the
8460 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8461 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8463 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8464 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8465 (@value{GDBP}) @b{trace foo}
8466 (@value{GDBP}) @b{pass 3}
8467 (@value{GDBP}) @b{trace bar}
8468 (@value{GDBP}) @b{pass 2}
8469 (@value{GDBP}) @b{trace baz}
8470 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8471 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8472 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8473 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8477 @node Tracepoint Actions
8478 @subsection Tracepoint Action Lists
8482 @cindex tracepoint actions
8483 @item actions @r{[}@var{num}@r{]}
8484 This command will prompt for a list of actions to be taken when the
8485 tracepoint is hit. If the tracepoint number @var{num} is not
8486 specified, this command sets the actions for the one that was most
8487 recently defined (so that you can define a tracepoint and then say
8488 @code{actions} without bothering about its number). You specify the
8489 actions themselves on the following lines, one action at a time, and
8490 terminate the actions list with a line containing just @code{end}. So
8491 far, the only defined actions are @code{collect} and
8492 @code{while-stepping}.
8494 @cindex remove actions from a tracepoint
8495 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8496 and follow it immediately with @samp{end}.
8499 (@value{GDBP}) @b{collect @var{data}} // collect some data
8501 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8503 (@value{GDBP}) @b{end} // signals the end of actions.
8506 In the following example, the action list begins with @code{collect}
8507 commands indicating the things to be collected when the tracepoint is
8508 hit. Then, in order to single-step and collect additional data
8509 following the tracepoint, a @code{while-stepping} command is used,
8510 followed by the list of things to be collected while stepping. The
8511 @code{while-stepping} command is terminated by its own separate
8512 @code{end} command. Lastly, the action list is terminated by an
8516 (@value{GDBP}) @b{trace foo}
8517 (@value{GDBP}) @b{actions}
8518 Enter actions for tracepoint 1, one per line:
8527 @kindex collect @r{(tracepoints)}
8528 @item collect @var{expr1}, @var{expr2}, @dots{}
8529 Collect values of the given expressions when the tracepoint is hit.
8530 This command accepts a comma-separated list of any valid expressions.
8531 In addition to global, static, or local variables, the following
8532 special arguments are supported:
8536 collect all registers
8539 collect all function arguments
8542 collect all local variables.
8545 You can give several consecutive @code{collect} commands, each one
8546 with a single argument, or one @code{collect} command with several
8547 arguments separated by commas: the effect is the same.
8549 The command @code{info scope} (@pxref{Symbols, info scope}) is
8550 particularly useful for figuring out what data to collect.
8552 @kindex while-stepping @r{(tracepoints)}
8553 @item while-stepping @var{n}
8554 Perform @var{n} single-step traces after the tracepoint, collecting
8555 new data at each step. The @code{while-stepping} command is
8556 followed by the list of what to collect while stepping (followed by
8557 its own @code{end} command):
8561 > collect $regs, myglobal
8567 You may abbreviate @code{while-stepping} as @code{ws} or
8571 @node Listing Tracepoints
8572 @subsection Listing Tracepoints
8575 @kindex info tracepoints
8577 @cindex information about tracepoints
8578 @item info tracepoints @r{[}@var{num}@r{]}
8579 Display information about the tracepoint @var{num}. If you don't specify
8580 a tracepoint number, displays information about all the tracepoints
8581 defined so far. For each tracepoint, the following information is
8588 whether it is enabled or disabled
8592 its passcount as given by the @code{passcount @var{n}} command
8594 its step count as given by the @code{while-stepping @var{n}} command
8596 where in the source files is the tracepoint set
8598 its action list as given by the @code{actions} command
8602 (@value{GDBP}) @b{info trace}
8603 Num Enb Address PassC StepC What
8604 1 y 0x002117c4 0 0 <gdb_asm>
8605 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8606 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8611 This command can be abbreviated @code{info tp}.
8614 @node Starting and Stopping Trace Experiments
8615 @subsection Starting and Stopping Trace Experiments
8619 @cindex start a new trace experiment
8620 @cindex collected data discarded
8622 This command takes no arguments. It starts the trace experiment, and
8623 begins collecting data. This has the side effect of discarding all
8624 the data collected in the trace buffer during the previous trace
8628 @cindex stop a running trace experiment
8630 This command takes no arguments. It ends the trace experiment, and
8631 stops collecting data.
8633 @strong{Note}: a trace experiment and data collection may stop
8634 automatically if any tracepoint's passcount is reached
8635 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8638 @cindex status of trace data collection
8639 @cindex trace experiment, status of
8641 This command displays the status of the current trace data
8645 Here is an example of the commands we described so far:
8648 (@value{GDBP}) @b{trace gdb_c_test}
8649 (@value{GDBP}) @b{actions}
8650 Enter actions for tracepoint #1, one per line.
8651 > collect $regs,$locals,$args
8656 (@value{GDBP}) @b{tstart}
8657 [time passes @dots{}]
8658 (@value{GDBP}) @b{tstop}
8662 @node Analyze Collected Data
8663 @section Using the Collected Data
8665 After the tracepoint experiment ends, you use @value{GDBN} commands
8666 for examining the trace data. The basic idea is that each tracepoint
8667 collects a trace @dfn{snapshot} every time it is hit and another
8668 snapshot every time it single-steps. All these snapshots are
8669 consecutively numbered from zero and go into a buffer, and you can
8670 examine them later. The way you examine them is to @dfn{focus} on a
8671 specific trace snapshot. When the remote stub is focused on a trace
8672 snapshot, it will respond to all @value{GDBN} requests for memory and
8673 registers by reading from the buffer which belongs to that snapshot,
8674 rather than from @emph{real} memory or registers of the program being
8675 debugged. This means that @strong{all} @value{GDBN} commands
8676 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8677 behave as if we were currently debugging the program state as it was
8678 when the tracepoint occurred. Any requests for data that are not in
8679 the buffer will fail.
8682 * tfind:: How to select a trace snapshot
8683 * tdump:: How to display all data for a snapshot
8684 * save-tracepoints:: How to save tracepoints for a future run
8688 @subsection @code{tfind @var{n}}
8691 @cindex select trace snapshot
8692 @cindex find trace snapshot
8693 The basic command for selecting a trace snapshot from the buffer is
8694 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8695 counting from zero. If no argument @var{n} is given, the next
8696 snapshot is selected.
8698 Here are the various forms of using the @code{tfind} command.
8702 Find the first snapshot in the buffer. This is a synonym for
8703 @code{tfind 0} (since 0 is the number of the first snapshot).
8706 Stop debugging trace snapshots, resume @emph{live} debugging.
8709 Same as @samp{tfind none}.
8712 No argument means find the next trace snapshot.
8715 Find the previous trace snapshot before the current one. This permits
8716 retracing earlier steps.
8718 @item tfind tracepoint @var{num}
8719 Find the next snapshot associated with tracepoint @var{num}. Search
8720 proceeds forward from the last examined trace snapshot. If no
8721 argument @var{num} is given, it means find the next snapshot collected
8722 for the same tracepoint as the current snapshot.
8724 @item tfind pc @var{addr}
8725 Find the next snapshot associated with the value @var{addr} of the
8726 program counter. Search proceeds forward from the last examined trace
8727 snapshot. If no argument @var{addr} is given, it means find the next
8728 snapshot with the same value of PC as the current snapshot.
8730 @item tfind outside @var{addr1}, @var{addr2}
8731 Find the next snapshot whose PC is outside the given range of
8734 @item tfind range @var{addr1}, @var{addr2}
8735 Find the next snapshot whose PC is between @var{addr1} and
8736 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8738 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8739 Find the next snapshot associated with the source line @var{n}. If
8740 the optional argument @var{file} is given, refer to line @var{n} in
8741 that source file. Search proceeds forward from the last examined
8742 trace snapshot. If no argument @var{n} is given, it means find the
8743 next line other than the one currently being examined; thus saying
8744 @code{tfind line} repeatedly can appear to have the same effect as
8745 stepping from line to line in a @emph{live} debugging session.
8748 The default arguments for the @code{tfind} commands are specifically
8749 designed to make it easy to scan through the trace buffer. For
8750 instance, @code{tfind} with no argument selects the next trace
8751 snapshot, and @code{tfind -} with no argument selects the previous
8752 trace snapshot. So, by giving one @code{tfind} command, and then
8753 simply hitting @key{RET} repeatedly you can examine all the trace
8754 snapshots in order. Or, by saying @code{tfind -} and then hitting
8755 @key{RET} repeatedly you can examine the snapshots in reverse order.
8756 The @code{tfind line} command with no argument selects the snapshot
8757 for the next source line executed. The @code{tfind pc} command with
8758 no argument selects the next snapshot with the same program counter
8759 (PC) as the current frame. The @code{tfind tracepoint} command with
8760 no argument selects the next trace snapshot collected by the same
8761 tracepoint as the current one.
8763 In addition to letting you scan through the trace buffer manually,
8764 these commands make it easy to construct @value{GDBN} scripts that
8765 scan through the trace buffer and print out whatever collected data
8766 you are interested in. Thus, if we want to examine the PC, FP, and SP
8767 registers from each trace frame in the buffer, we can say this:
8770 (@value{GDBP}) @b{tfind start}
8771 (@value{GDBP}) @b{while ($trace_frame != -1)}
8772 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8773 $trace_frame, $pc, $sp, $fp
8777 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8778 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8779 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8780 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8781 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8782 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8783 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8784 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8785 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8786 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8787 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8790 Or, if we want to examine the variable @code{X} at each source line in
8794 (@value{GDBP}) @b{tfind start}
8795 (@value{GDBP}) @b{while ($trace_frame != -1)}
8796 > printf "Frame %d, X == %d\n", $trace_frame, X
8806 @subsection @code{tdump}
8808 @cindex dump all data collected at tracepoint
8809 @cindex tracepoint data, display
8811 This command takes no arguments. It prints all the data collected at
8812 the current trace snapshot.
8815 (@value{GDBP}) @b{trace 444}
8816 (@value{GDBP}) @b{actions}
8817 Enter actions for tracepoint #2, one per line:
8818 > collect $regs, $locals, $args, gdb_long_test
8821 (@value{GDBP}) @b{tstart}
8823 (@value{GDBP}) @b{tfind line 444}
8824 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8826 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8828 (@value{GDBP}) @b{tdump}
8829 Data collected at tracepoint 2, trace frame 1:
8830 d0 0xc4aa0085 -995491707
8834 d4 0x71aea3d 119204413
8839 a1 0x3000668 50333288
8842 a4 0x3000698 50333336
8844 fp 0x30bf3c 0x30bf3c
8845 sp 0x30bf34 0x30bf34
8847 pc 0x20b2c8 0x20b2c8
8851 p = 0x20e5b4 "gdb-test"
8858 gdb_long_test = 17 '\021'
8863 @node save-tracepoints
8864 @subsection @code{save-tracepoints @var{filename}}
8865 @kindex save-tracepoints
8866 @cindex save tracepoints for future sessions
8868 This command saves all current tracepoint definitions together with
8869 their actions and passcounts, into a file @file{@var{filename}}
8870 suitable for use in a later debugging session. To read the saved
8871 tracepoint definitions, use the @code{source} command (@pxref{Command
8874 @node Tracepoint Variables
8875 @section Convenience Variables for Tracepoints
8876 @cindex tracepoint variables
8877 @cindex convenience variables for tracepoints
8880 @vindex $trace_frame
8881 @item (int) $trace_frame
8882 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8883 snapshot is selected.
8886 @item (int) $tracepoint
8887 The tracepoint for the current trace snapshot.
8890 @item (int) $trace_line
8891 The line number for the current trace snapshot.
8894 @item (char []) $trace_file
8895 The source file for the current trace snapshot.
8898 @item (char []) $trace_func
8899 The name of the function containing @code{$tracepoint}.
8902 Note: @code{$trace_file} is not suitable for use in @code{printf},
8903 use @code{output} instead.
8905 Here's a simple example of using these convenience variables for
8906 stepping through all the trace snapshots and printing some of their
8910 (@value{GDBP}) @b{tfind start}
8912 (@value{GDBP}) @b{while $trace_frame != -1}
8913 > output $trace_file
8914 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8920 @chapter Debugging Programs That Use Overlays
8923 If your program is too large to fit completely in your target system's
8924 memory, you can sometimes use @dfn{overlays} to work around this
8925 problem. @value{GDBN} provides some support for debugging programs that
8929 * How Overlays Work:: A general explanation of overlays.
8930 * Overlay Commands:: Managing overlays in @value{GDBN}.
8931 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8932 mapped by asking the inferior.
8933 * Overlay Sample Program:: A sample program using overlays.
8936 @node How Overlays Work
8937 @section How Overlays Work
8938 @cindex mapped overlays
8939 @cindex unmapped overlays
8940 @cindex load address, overlay's
8941 @cindex mapped address
8942 @cindex overlay area
8944 Suppose you have a computer whose instruction address space is only 64
8945 kilobytes long, but which has much more memory which can be accessed by
8946 other means: special instructions, segment registers, or memory
8947 management hardware, for example. Suppose further that you want to
8948 adapt a program which is larger than 64 kilobytes to run on this system.
8950 One solution is to identify modules of your program which are relatively
8951 independent, and need not call each other directly; call these modules
8952 @dfn{overlays}. Separate the overlays from the main program, and place
8953 their machine code in the larger memory. Place your main program in
8954 instruction memory, but leave at least enough space there to hold the
8955 largest overlay as well.
8957 Now, to call a function located in an overlay, you must first copy that
8958 overlay's machine code from the large memory into the space set aside
8959 for it in the instruction memory, and then jump to its entry point
8962 @c NB: In the below the mapped area's size is greater or equal to the
8963 @c size of all overlays. This is intentional to remind the developer
8964 @c that overlays don't necessarily need to be the same size.
8968 Data Instruction Larger
8969 Address Space Address Space Address Space
8970 +-----------+ +-----------+ +-----------+
8972 +-----------+ +-----------+ +-----------+<-- overlay 1
8973 | program | | main | .----| overlay 1 | load address
8974 | variables | | program | | +-----------+
8975 | and heap | | | | | |
8976 +-----------+ | | | +-----------+<-- overlay 2
8977 | | +-----------+ | | | load address
8978 +-----------+ | | | .-| overlay 2 |
8980 mapped --->+-----------+ | | +-----------+
8982 | overlay | <-' | | |
8983 | area | <---' +-----------+<-- overlay 3
8984 | | <---. | | load address
8985 +-----------+ `--| overlay 3 |
8992 @anchor{A code overlay}A code overlay
8996 The diagram (@pxref{A code overlay}) shows a system with separate data
8997 and instruction address spaces. To map an overlay, the program copies
8998 its code from the larger address space to the instruction address space.
8999 Since the overlays shown here all use the same mapped address, only one
9000 may be mapped at a time. For a system with a single address space for
9001 data and instructions, the diagram would be similar, except that the
9002 program variables and heap would share an address space with the main
9003 program and the overlay area.
9005 An overlay loaded into instruction memory and ready for use is called a
9006 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9007 instruction memory. An overlay not present (or only partially present)
9008 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9009 is its address in the larger memory. The mapped address is also called
9010 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9011 called the @dfn{load memory address}, or @dfn{LMA}.
9013 Unfortunately, overlays are not a completely transparent way to adapt a
9014 program to limited instruction memory. They introduce a new set of
9015 global constraints you must keep in mind as you design your program:
9020 Before calling or returning to a function in an overlay, your program
9021 must make sure that overlay is actually mapped. Otherwise, the call or
9022 return will transfer control to the right address, but in the wrong
9023 overlay, and your program will probably crash.
9026 If the process of mapping an overlay is expensive on your system, you
9027 will need to choose your overlays carefully to minimize their effect on
9028 your program's performance.
9031 The executable file you load onto your system must contain each
9032 overlay's instructions, appearing at the overlay's load address, not its
9033 mapped address. However, each overlay's instructions must be relocated
9034 and its symbols defined as if the overlay were at its mapped address.
9035 You can use GNU linker scripts to specify different load and relocation
9036 addresses for pieces of your program; see @ref{Overlay Description,,,
9037 ld.info, Using ld: the GNU linker}.
9040 The procedure for loading executable files onto your system must be able
9041 to load their contents into the larger address space as well as the
9042 instruction and data spaces.
9046 The overlay system described above is rather simple, and could be
9047 improved in many ways:
9052 If your system has suitable bank switch registers or memory management
9053 hardware, you could use those facilities to make an overlay's load area
9054 contents simply appear at their mapped address in instruction space.
9055 This would probably be faster than copying the overlay to its mapped
9056 area in the usual way.
9059 If your overlays are small enough, you could set aside more than one
9060 overlay area, and have more than one overlay mapped at a time.
9063 You can use overlays to manage data, as well as instructions. In
9064 general, data overlays are even less transparent to your design than
9065 code overlays: whereas code overlays only require care when you call or
9066 return to functions, data overlays require care every time you access
9067 the data. Also, if you change the contents of a data overlay, you
9068 must copy its contents back out to its load address before you can copy a
9069 different data overlay into the same mapped area.
9074 @node Overlay Commands
9075 @section Overlay Commands
9077 To use @value{GDBN}'s overlay support, each overlay in your program must
9078 correspond to a separate section of the executable file. The section's
9079 virtual memory address and load memory address must be the overlay's
9080 mapped and load addresses. Identifying overlays with sections allows
9081 @value{GDBN} to determine the appropriate address of a function or
9082 variable, depending on whether the overlay is mapped or not.
9084 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9085 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9090 Disable @value{GDBN}'s overlay support. When overlay support is
9091 disabled, @value{GDBN} assumes that all functions and variables are
9092 always present at their mapped addresses. By default, @value{GDBN}'s
9093 overlay support is disabled.
9095 @item overlay manual
9096 @cindex manual overlay debugging
9097 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9098 relies on you to tell it which overlays are mapped, and which are not,
9099 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9100 commands described below.
9102 @item overlay map-overlay @var{overlay}
9103 @itemx overlay map @var{overlay}
9104 @cindex map an overlay
9105 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9106 be the name of the object file section containing the overlay. When an
9107 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9108 functions and variables at their mapped addresses. @value{GDBN} assumes
9109 that any other overlays whose mapped ranges overlap that of
9110 @var{overlay} are now unmapped.
9112 @item overlay unmap-overlay @var{overlay}
9113 @itemx overlay unmap @var{overlay}
9114 @cindex unmap an overlay
9115 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9116 must be the name of the object file section containing the overlay.
9117 When an overlay is unmapped, @value{GDBN} assumes it can find the
9118 overlay's functions and variables at their load addresses.
9121 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9122 consults a data structure the overlay manager maintains in the inferior
9123 to see which overlays are mapped. For details, see @ref{Automatic
9126 @item overlay load-target
9128 @cindex reloading the overlay table
9129 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9130 re-reads the table @value{GDBN} automatically each time the inferior
9131 stops, so this command should only be necessary if you have changed the
9132 overlay mapping yourself using @value{GDBN}. This command is only
9133 useful when using automatic overlay debugging.
9135 @item overlay list-overlays
9137 @cindex listing mapped overlays
9138 Display a list of the overlays currently mapped, along with their mapped
9139 addresses, load addresses, and sizes.
9143 Normally, when @value{GDBN} prints a code address, it includes the name
9144 of the function the address falls in:
9147 (@value{GDBP}) print main
9148 $3 = @{int ()@} 0x11a0 <main>
9151 When overlay debugging is enabled, @value{GDBN} recognizes code in
9152 unmapped overlays, and prints the names of unmapped functions with
9153 asterisks around them. For example, if @code{foo} is a function in an
9154 unmapped overlay, @value{GDBN} prints it this way:
9157 (@value{GDBP}) overlay list
9158 No sections are mapped.
9159 (@value{GDBP}) print foo
9160 $5 = @{int (int)@} 0x100000 <*foo*>
9163 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9167 (@value{GDBP}) overlay list
9168 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9169 mapped at 0x1016 - 0x104a
9170 (@value{GDBP}) print foo
9171 $6 = @{int (int)@} 0x1016 <foo>
9174 When overlay debugging is enabled, @value{GDBN} can find the correct
9175 address for functions and variables in an overlay, whether or not the
9176 overlay is mapped. This allows most @value{GDBN} commands, like
9177 @code{break} and @code{disassemble}, to work normally, even on unmapped
9178 code. However, @value{GDBN}'s breakpoint support has some limitations:
9182 @cindex breakpoints in overlays
9183 @cindex overlays, setting breakpoints in
9184 You can set breakpoints in functions in unmapped overlays, as long as
9185 @value{GDBN} can write to the overlay at its load address.
9187 @value{GDBN} can not set hardware or simulator-based breakpoints in
9188 unmapped overlays. However, if you set a breakpoint at the end of your
9189 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9190 you are using manual overlay management), @value{GDBN} will re-set its
9191 breakpoints properly.
9195 @node Automatic Overlay Debugging
9196 @section Automatic Overlay Debugging
9197 @cindex automatic overlay debugging
9199 @value{GDBN} can automatically track which overlays are mapped and which
9200 are not, given some simple co-operation from the overlay manager in the
9201 inferior. If you enable automatic overlay debugging with the
9202 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9203 looks in the inferior's memory for certain variables describing the
9204 current state of the overlays.
9206 Here are the variables your overlay manager must define to support
9207 @value{GDBN}'s automatic overlay debugging:
9211 @item @code{_ovly_table}:
9212 This variable must be an array of the following structures:
9217 /* The overlay's mapped address. */
9220 /* The size of the overlay, in bytes. */
9223 /* The overlay's load address. */
9226 /* Non-zero if the overlay is currently mapped;
9228 unsigned long mapped;
9232 @item @code{_novlys}:
9233 This variable must be a four-byte signed integer, holding the total
9234 number of elements in @code{_ovly_table}.
9238 To decide whether a particular overlay is mapped or not, @value{GDBN}
9239 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9240 @code{lma} members equal the VMA and LMA of the overlay's section in the
9241 executable file. When @value{GDBN} finds a matching entry, it consults
9242 the entry's @code{mapped} member to determine whether the overlay is
9245 In addition, your overlay manager may define a function called
9246 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9247 will silently set a breakpoint there. If the overlay manager then
9248 calls this function whenever it has changed the overlay table, this
9249 will enable @value{GDBN} to accurately keep track of which overlays
9250 are in program memory, and update any breakpoints that may be set
9251 in overlays. This will allow breakpoints to work even if the
9252 overlays are kept in ROM or other non-writable memory while they
9253 are not being executed.
9255 @node Overlay Sample Program
9256 @section Overlay Sample Program
9257 @cindex overlay example program
9259 When linking a program which uses overlays, you must place the overlays
9260 at their load addresses, while relocating them to run at their mapped
9261 addresses. To do this, you must write a linker script (@pxref{Overlay
9262 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9263 since linker scripts are specific to a particular host system, target
9264 architecture, and target memory layout, this manual cannot provide
9265 portable sample code demonstrating @value{GDBN}'s overlay support.
9267 However, the @value{GDBN} source distribution does contain an overlaid
9268 program, with linker scripts for a few systems, as part of its test
9269 suite. The program consists of the following files from
9270 @file{gdb/testsuite/gdb.base}:
9274 The main program file.
9276 A simple overlay manager, used by @file{overlays.c}.
9281 Overlay modules, loaded and used by @file{overlays.c}.
9284 Linker scripts for linking the test program on the @code{d10v-elf}
9285 and @code{m32r-elf} targets.
9288 You can build the test program using the @code{d10v-elf} GCC
9289 cross-compiler like this:
9292 $ d10v-elf-gcc -g -c overlays.c
9293 $ d10v-elf-gcc -g -c ovlymgr.c
9294 $ d10v-elf-gcc -g -c foo.c
9295 $ d10v-elf-gcc -g -c bar.c
9296 $ d10v-elf-gcc -g -c baz.c
9297 $ d10v-elf-gcc -g -c grbx.c
9298 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9299 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9302 The build process is identical for any other architecture, except that
9303 you must substitute the appropriate compiler and linker script for the
9304 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9308 @chapter Using @value{GDBN} with Different Languages
9311 Although programming languages generally have common aspects, they are
9312 rarely expressed in the same manner. For instance, in ANSI C,
9313 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9314 Modula-2, it is accomplished by @code{p^}. Values can also be
9315 represented (and displayed) differently. Hex numbers in C appear as
9316 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9318 @cindex working language
9319 Language-specific information is built into @value{GDBN} for some languages,
9320 allowing you to express operations like the above in your program's
9321 native language, and allowing @value{GDBN} to output values in a manner
9322 consistent with the syntax of your program's native language. The
9323 language you use to build expressions is called the @dfn{working
9327 * Setting:: Switching between source languages
9328 * Show:: Displaying the language
9329 * Checks:: Type and range checks
9330 * Supported Languages:: Supported languages
9331 * Unsupported Languages:: Unsupported languages
9335 @section Switching Between Source Languages
9337 There are two ways to control the working language---either have @value{GDBN}
9338 set it automatically, or select it manually yourself. You can use the
9339 @code{set language} command for either purpose. On startup, @value{GDBN}
9340 defaults to setting the language automatically. The working language is
9341 used to determine how expressions you type are interpreted, how values
9344 In addition to the working language, every source file that
9345 @value{GDBN} knows about has its own working language. For some object
9346 file formats, the compiler might indicate which language a particular
9347 source file is in. However, most of the time @value{GDBN} infers the
9348 language from the name of the file. The language of a source file
9349 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9350 show each frame appropriately for its own language. There is no way to
9351 set the language of a source file from within @value{GDBN}, but you can
9352 set the language associated with a filename extension. @xref{Show, ,
9353 Displaying the Language}.
9355 This is most commonly a problem when you use a program, such
9356 as @code{cfront} or @code{f2c}, that generates C but is written in
9357 another language. In that case, make the
9358 program use @code{#line} directives in its C output; that way
9359 @value{GDBN} will know the correct language of the source code of the original
9360 program, and will display that source code, not the generated C code.
9363 * Filenames:: Filename extensions and languages.
9364 * Manually:: Setting the working language manually
9365 * Automatically:: Having @value{GDBN} infer the source language
9369 @subsection List of Filename Extensions and Languages
9371 If a source file name ends in one of the following extensions, then
9372 @value{GDBN} infers that its language is the one indicated.
9393 Objective-C source file
9400 Modula-2 source file
9404 Assembler source file. This actually behaves almost like C, but
9405 @value{GDBN} does not skip over function prologues when stepping.
9408 In addition, you may set the language associated with a filename
9409 extension. @xref{Show, , Displaying the Language}.
9412 @subsection Setting the Working Language
9414 If you allow @value{GDBN} to set the language automatically,
9415 expressions are interpreted the same way in your debugging session and
9418 @kindex set language
9419 If you wish, you may set the language manually. To do this, issue the
9420 command @samp{set language @var{lang}}, where @var{lang} is the name of
9422 @code{c} or @code{modula-2}.
9423 For a list of the supported languages, type @samp{set language}.
9425 Setting the language manually prevents @value{GDBN} from updating the working
9426 language automatically. This can lead to confusion if you try
9427 to debug a program when the working language is not the same as the
9428 source language, when an expression is acceptable to both
9429 languages---but means different things. For instance, if the current
9430 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9438 might not have the effect you intended. In C, this means to add
9439 @code{b} and @code{c} and place the result in @code{a}. The result
9440 printed would be the value of @code{a}. In Modula-2, this means to compare
9441 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9444 @subsection Having @value{GDBN} Infer the Source Language
9446 To have @value{GDBN} set the working language automatically, use
9447 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9448 then infers the working language. That is, when your program stops in a
9449 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9450 working language to the language recorded for the function in that
9451 frame. If the language for a frame is unknown (that is, if the function
9452 or block corresponding to the frame was defined in a source file that
9453 does not have a recognized extension), the current working language is
9454 not changed, and @value{GDBN} issues a warning.
9456 This may not seem necessary for most programs, which are written
9457 entirely in one source language. However, program modules and libraries
9458 written in one source language can be used by a main program written in
9459 a different source language. Using @samp{set language auto} in this
9460 case frees you from having to set the working language manually.
9463 @section Displaying the Language
9465 The following commands help you find out which language is the
9466 working language, and also what language source files were written in.
9470 @kindex show language
9471 Display the current working language. This is the
9472 language you can use with commands such as @code{print} to
9473 build and compute expressions that may involve variables in your program.
9476 @kindex info frame@r{, show the source language}
9477 Display the source language for this frame. This language becomes the
9478 working language if you use an identifier from this frame.
9479 @xref{Frame Info, ,Information about a Frame}, to identify the other
9480 information listed here.
9483 @kindex info source@r{, show the source language}
9484 Display the source language of this source file.
9485 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9486 information listed here.
9489 In unusual circumstances, you may have source files with extensions
9490 not in the standard list. You can then set the extension associated
9491 with a language explicitly:
9494 @item set extension-language @var{ext} @var{language}
9495 @kindex set extension-language
9496 Tell @value{GDBN} that source files with extension @var{ext} are to be
9497 assumed as written in the source language @var{language}.
9499 @item info extensions
9500 @kindex info extensions
9501 List all the filename extensions and the associated languages.
9505 @section Type and Range Checking
9508 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9509 checking are included, but they do not yet have any effect. This
9510 section documents the intended facilities.
9512 @c FIXME remove warning when type/range code added
9514 Some languages are designed to guard you against making seemingly common
9515 errors through a series of compile- and run-time checks. These include
9516 checking the type of arguments to functions and operators, and making
9517 sure mathematical overflows are caught at run time. Checks such as
9518 these help to ensure a program's correctness once it has been compiled
9519 by eliminating type mismatches, and providing active checks for range
9520 errors when your program is running.
9522 @value{GDBN} can check for conditions like the above if you wish.
9523 Although @value{GDBN} does not check the statements in your program,
9524 it can check expressions entered directly into @value{GDBN} for
9525 evaluation via the @code{print} command, for example. As with the
9526 working language, @value{GDBN} can also decide whether or not to check
9527 automatically based on your program's source language.
9528 @xref{Supported Languages, ,Supported Languages}, for the default
9529 settings of supported languages.
9532 * Type Checking:: An overview of type checking
9533 * Range Checking:: An overview of range checking
9536 @cindex type checking
9537 @cindex checks, type
9539 @subsection An Overview of Type Checking
9541 Some languages, such as Modula-2, are strongly typed, meaning that the
9542 arguments to operators and functions have to be of the correct type,
9543 otherwise an error occurs. These checks prevent type mismatch
9544 errors from ever causing any run-time problems. For example,
9552 The second example fails because the @code{CARDINAL} 1 is not
9553 type-compatible with the @code{REAL} 2.3.
9555 For the expressions you use in @value{GDBN} commands, you can tell the
9556 @value{GDBN} type checker to skip checking;
9557 to treat any mismatches as errors and abandon the expression;
9558 or to only issue warnings when type mismatches occur,
9559 but evaluate the expression anyway. When you choose the last of
9560 these, @value{GDBN} evaluates expressions like the second example above, but
9561 also issues a warning.
9563 Even if you turn type checking off, there may be other reasons
9564 related to type that prevent @value{GDBN} from evaluating an expression.
9565 For instance, @value{GDBN} does not know how to add an @code{int} and
9566 a @code{struct foo}. These particular type errors have nothing to do
9567 with the language in use, and usually arise from expressions, such as
9568 the one described above, which make little sense to evaluate anyway.
9570 Each language defines to what degree it is strict about type. For
9571 instance, both Modula-2 and C require the arguments to arithmetical
9572 operators to be numbers. In C, enumerated types and pointers can be
9573 represented as numbers, so that they are valid arguments to mathematical
9574 operators. @xref{Supported Languages, ,Supported Languages}, for further
9575 details on specific languages.
9577 @value{GDBN} provides some additional commands for controlling the type checker:
9579 @kindex set check type
9580 @kindex show check type
9582 @item set check type auto
9583 Set type checking on or off based on the current working language.
9584 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9587 @item set check type on
9588 @itemx set check type off
9589 Set type checking on or off, overriding the default setting for the
9590 current working language. Issue a warning if the setting does not
9591 match the language default. If any type mismatches occur in
9592 evaluating an expression while type checking is on, @value{GDBN} prints a
9593 message and aborts evaluation of the expression.
9595 @item set check type warn
9596 Cause the type checker to issue warnings, but to always attempt to
9597 evaluate the expression. Evaluating the expression may still
9598 be impossible for other reasons. For example, @value{GDBN} cannot add
9599 numbers and structures.
9602 Show the current setting of the type checker, and whether or not @value{GDBN}
9603 is setting it automatically.
9606 @cindex range checking
9607 @cindex checks, range
9608 @node Range Checking
9609 @subsection An Overview of Range Checking
9611 In some languages (such as Modula-2), it is an error to exceed the
9612 bounds of a type; this is enforced with run-time checks. Such range
9613 checking is meant to ensure program correctness by making sure
9614 computations do not overflow, or indices on an array element access do
9615 not exceed the bounds of the array.
9617 For expressions you use in @value{GDBN} commands, you can tell
9618 @value{GDBN} to treat range errors in one of three ways: ignore them,
9619 always treat them as errors and abandon the expression, or issue
9620 warnings but evaluate the expression anyway.
9622 A range error can result from numerical overflow, from exceeding an
9623 array index bound, or when you type a constant that is not a member
9624 of any type. Some languages, however, do not treat overflows as an
9625 error. In many implementations of C, mathematical overflow causes the
9626 result to ``wrap around'' to lower values---for example, if @var{m} is
9627 the largest integer value, and @var{s} is the smallest, then
9630 @var{m} + 1 @result{} @var{s}
9633 This, too, is specific to individual languages, and in some cases
9634 specific to individual compilers or machines. @xref{Supported Languages, ,
9635 Supported Languages}, for further details on specific languages.
9637 @value{GDBN} provides some additional commands for controlling the range checker:
9639 @kindex set check range
9640 @kindex show check range
9642 @item set check range auto
9643 Set range checking on or off based on the current working language.
9644 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9647 @item set check range on
9648 @itemx set check range off
9649 Set range checking on or off, overriding the default setting for the
9650 current working language. A warning is issued if the setting does not
9651 match the language default. If a range error occurs and range checking is on,
9652 then a message is printed and evaluation of the expression is aborted.
9654 @item set check range warn
9655 Output messages when the @value{GDBN} range checker detects a range error,
9656 but attempt to evaluate the expression anyway. Evaluating the
9657 expression may still be impossible for other reasons, such as accessing
9658 memory that the process does not own (a typical example from many Unix
9662 Show the current setting of the range checker, and whether or not it is
9663 being set automatically by @value{GDBN}.
9666 @node Supported Languages
9667 @section Supported Languages
9669 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9670 assembly, Modula-2, and Ada.
9671 @c This is false ...
9672 Some @value{GDBN} features may be used in expressions regardless of the
9673 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9674 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9675 ,Expressions}) can be used with the constructs of any supported
9678 The following sections detail to what degree each source language is
9679 supported by @value{GDBN}. These sections are not meant to be language
9680 tutorials or references, but serve only as a reference guide to what the
9681 @value{GDBN} expression parser accepts, and what input and output
9682 formats should look like for different languages. There are many good
9683 books written on each of these languages; please look to these for a
9684 language reference or tutorial.
9688 * Objective-C:: Objective-C
9691 * Modula-2:: Modula-2
9696 @subsection C and C@t{++}
9698 @cindex C and C@t{++}
9699 @cindex expressions in C or C@t{++}
9701 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9702 to both languages. Whenever this is the case, we discuss those languages
9706 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9707 @cindex @sc{gnu} C@t{++}
9708 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9709 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9710 effectively, you must compile your C@t{++} programs with a supported
9711 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9712 compiler (@code{aCC}).
9714 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9715 format; if it doesn't work on your system, try the stabs+ debugging
9716 format. You can select those formats explicitly with the @code{g++}
9717 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9718 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9719 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9722 * C Operators:: C and C@t{++} operators
9723 * C Constants:: C and C@t{++} constants
9724 * C Plus Plus Expressions:: C@t{++} expressions
9725 * C Defaults:: Default settings for C and C@t{++}
9726 * C Checks:: C and C@t{++} type and range checks
9727 * Debugging C:: @value{GDBN} and C
9728 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9729 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9733 @subsubsection C and C@t{++} Operators
9735 @cindex C and C@t{++} operators
9737 Operators must be defined on values of specific types. For instance,
9738 @code{+} is defined on numbers, but not on structures. Operators are
9739 often defined on groups of types.
9741 For the purposes of C and C@t{++}, the following definitions hold:
9746 @emph{Integral types} include @code{int} with any of its storage-class
9747 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9750 @emph{Floating-point types} include @code{float}, @code{double}, and
9751 @code{long double} (if supported by the target platform).
9754 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9757 @emph{Scalar types} include all of the above.
9762 The following operators are supported. They are listed here
9763 in order of increasing precedence:
9767 The comma or sequencing operator. Expressions in a comma-separated list
9768 are evaluated from left to right, with the result of the entire
9769 expression being the last expression evaluated.
9772 Assignment. The value of an assignment expression is the value
9773 assigned. Defined on scalar types.
9776 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9777 and translated to @w{@code{@var{a} = @var{a op b}}}.
9778 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9779 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9780 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9783 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9784 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9788 Logical @sc{or}. Defined on integral types.
9791 Logical @sc{and}. Defined on integral types.
9794 Bitwise @sc{or}. Defined on integral types.
9797 Bitwise exclusive-@sc{or}. Defined on integral types.
9800 Bitwise @sc{and}. Defined on integral types.
9803 Equality and inequality. Defined on scalar types. The value of these
9804 expressions is 0 for false and non-zero for true.
9806 @item <@r{, }>@r{, }<=@r{, }>=
9807 Less than, greater than, less than or equal, greater than or equal.
9808 Defined on scalar types. The value of these expressions is 0 for false
9809 and non-zero for true.
9812 left shift, and right shift. Defined on integral types.
9815 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9818 Addition and subtraction. Defined on integral types, floating-point types and
9821 @item *@r{, }/@r{, }%
9822 Multiplication, division, and modulus. Multiplication and division are
9823 defined on integral and floating-point types. Modulus is defined on
9827 Increment and decrement. When appearing before a variable, the
9828 operation is performed before the variable is used in an expression;
9829 when appearing after it, the variable's value is used before the
9830 operation takes place.
9833 Pointer dereferencing. Defined on pointer types. Same precedence as
9837 Address operator. Defined on variables. Same precedence as @code{++}.
9839 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9840 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9841 to examine the address
9842 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9846 Negative. Defined on integral and floating-point types. Same
9847 precedence as @code{++}.
9850 Logical negation. Defined on integral types. Same precedence as
9854 Bitwise complement operator. Defined on integral types. Same precedence as
9859 Structure member, and pointer-to-structure member. For convenience,
9860 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9861 pointer based on the stored type information.
9862 Defined on @code{struct} and @code{union} data.
9865 Dereferences of pointers to members.
9868 Array indexing. @code{@var{a}[@var{i}]} is defined as
9869 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9872 Function parameter list. Same precedence as @code{->}.
9875 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9876 and @code{class} types.
9879 Doubled colons also represent the @value{GDBN} scope operator
9880 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9884 If an operator is redefined in the user code, @value{GDBN} usually
9885 attempts to invoke the redefined version instead of using the operator's
9889 @subsubsection C and C@t{++} Constants
9891 @cindex C and C@t{++} constants
9893 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9898 Integer constants are a sequence of digits. Octal constants are
9899 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9900 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9901 @samp{l}, specifying that the constant should be treated as a
9905 Floating point constants are a sequence of digits, followed by a decimal
9906 point, followed by a sequence of digits, and optionally followed by an
9907 exponent. An exponent is of the form:
9908 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9909 sequence of digits. The @samp{+} is optional for positive exponents.
9910 A floating-point constant may also end with a letter @samp{f} or
9911 @samp{F}, specifying that the constant should be treated as being of
9912 the @code{float} (as opposed to the default @code{double}) type; or with
9913 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9917 Enumerated constants consist of enumerated identifiers, or their
9918 integral equivalents.
9921 Character constants are a single character surrounded by single quotes
9922 (@code{'}), or a number---the ordinal value of the corresponding character
9923 (usually its @sc{ascii} value). Within quotes, the single character may
9924 be represented by a letter or by @dfn{escape sequences}, which are of
9925 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9926 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9927 @samp{@var{x}} is a predefined special character---for example,
9928 @samp{\n} for newline.
9931 String constants are a sequence of character constants surrounded by
9932 double quotes (@code{"}). Any valid character constant (as described
9933 above) may appear. Double quotes within the string must be preceded by
9934 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9938 Pointer constants are an integral value. You can also write pointers
9939 to constants using the C operator @samp{&}.
9942 Array constants are comma-separated lists surrounded by braces @samp{@{}
9943 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9944 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9945 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9948 @node C Plus Plus Expressions
9949 @subsubsection C@t{++} Expressions
9951 @cindex expressions in C@t{++}
9952 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9954 @cindex debugging C@t{++} programs
9955 @cindex C@t{++} compilers
9956 @cindex debug formats and C@t{++}
9957 @cindex @value{NGCC} and C@t{++}
9959 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9960 proper compiler and the proper debug format. Currently, @value{GDBN}
9961 works best when debugging C@t{++} code that is compiled with
9962 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9963 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9964 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9965 stabs+ as their default debug format, so you usually don't need to
9966 specify a debug format explicitly. Other compilers and/or debug formats
9967 are likely to work badly or not at all when using @value{GDBN} to debug
9973 @cindex member functions
9975 Member function calls are allowed; you can use expressions like
9978 count = aml->GetOriginal(x, y)
9981 @vindex this@r{, inside C@t{++} member functions}
9982 @cindex namespace in C@t{++}
9984 While a member function is active (in the selected stack frame), your
9985 expressions have the same namespace available as the member function;
9986 that is, @value{GDBN} allows implicit references to the class instance
9987 pointer @code{this} following the same rules as C@t{++}.
9989 @cindex call overloaded functions
9990 @cindex overloaded functions, calling
9991 @cindex type conversions in C@t{++}
9993 You can call overloaded functions; @value{GDBN} resolves the function
9994 call to the right definition, with some restrictions. @value{GDBN} does not
9995 perform overload resolution involving user-defined type conversions,
9996 calls to constructors, or instantiations of templates that do not exist
9997 in the program. It also cannot handle ellipsis argument lists or
10000 It does perform integral conversions and promotions, floating-point
10001 promotions, arithmetic conversions, pointer conversions, conversions of
10002 class objects to base classes, and standard conversions such as those of
10003 functions or arrays to pointers; it requires an exact match on the
10004 number of function arguments.
10006 Overload resolution is always performed, unless you have specified
10007 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10008 ,@value{GDBN} Features for C@t{++}}.
10010 You must specify @code{set overload-resolution off} in order to use an
10011 explicit function signature to call an overloaded function, as in
10013 p 'foo(char,int)'('x', 13)
10016 The @value{GDBN} command-completion facility can simplify this;
10017 see @ref{Completion, ,Command Completion}.
10019 @cindex reference declarations
10021 @value{GDBN} understands variables declared as C@t{++} references; you can use
10022 them in expressions just as you do in C@t{++} source---they are automatically
10025 In the parameter list shown when @value{GDBN} displays a frame, the values of
10026 reference variables are not displayed (unlike other variables); this
10027 avoids clutter, since references are often used for large structures.
10028 The @emph{address} of a reference variable is always shown, unless
10029 you have specified @samp{set print address off}.
10032 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10033 expressions can use it just as expressions in your program do. Since
10034 one scope may be defined in another, you can use @code{::} repeatedly if
10035 necessary, for example in an expression like
10036 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10037 resolving name scope by reference to source files, in both C and C@t{++}
10038 debugging (@pxref{Variables, ,Program Variables}).
10041 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10042 calling virtual functions correctly, printing out virtual bases of
10043 objects, calling functions in a base subobject, casting objects, and
10044 invoking user-defined operators.
10047 @subsubsection C and C@t{++} Defaults
10049 @cindex C and C@t{++} defaults
10051 If you allow @value{GDBN} to set type and range checking automatically, they
10052 both default to @code{off} whenever the working language changes to
10053 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10054 selects the working language.
10056 If you allow @value{GDBN} to set the language automatically, it
10057 recognizes source files whose names end with @file{.c}, @file{.C}, or
10058 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10059 these files, it sets the working language to C or C@t{++}.
10060 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10061 for further details.
10063 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10064 @c unimplemented. If (b) changes, it might make sense to let this node
10065 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10068 @subsubsection C and C@t{++} Type and Range Checks
10070 @cindex C and C@t{++} checks
10072 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10073 is not used. However, if you turn type checking on, @value{GDBN}
10074 considers two variables type equivalent if:
10078 The two variables are structured and have the same structure, union, or
10082 The two variables have the same type name, or types that have been
10083 declared equivalent through @code{typedef}.
10086 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10089 The two @code{struct}, @code{union}, or @code{enum} variables are
10090 declared in the same declaration. (Note: this may not be true for all C
10095 Range checking, if turned on, is done on mathematical operations. Array
10096 indices are not checked, since they are often used to index a pointer
10097 that is not itself an array.
10100 @subsubsection @value{GDBN} and C
10102 The @code{set print union} and @code{show print union} commands apply to
10103 the @code{union} type. When set to @samp{on}, any @code{union} that is
10104 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10105 appears as @samp{@{...@}}.
10107 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10108 with pointers and a memory allocation function. @xref{Expressions,
10111 @node Debugging C Plus Plus
10112 @subsubsection @value{GDBN} Features for C@t{++}
10114 @cindex commands for C@t{++}
10116 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10117 designed specifically for use with C@t{++}. Here is a summary:
10120 @cindex break in overloaded functions
10121 @item @r{breakpoint menus}
10122 When you want a breakpoint in a function whose name is overloaded,
10123 @value{GDBN} has the capability to display a menu of possible breakpoint
10124 locations to help you specify which function definition you want.
10125 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10127 @cindex overloading in C@t{++}
10128 @item rbreak @var{regex}
10129 Setting breakpoints using regular expressions is helpful for setting
10130 breakpoints on overloaded functions that are not members of any special
10132 @xref{Set Breaks, ,Setting Breakpoints}.
10134 @cindex C@t{++} exception handling
10137 Debug C@t{++} exception handling using these commands. @xref{Set
10138 Catchpoints, , Setting Catchpoints}.
10140 @cindex inheritance
10141 @item ptype @var{typename}
10142 Print inheritance relationships as well as other information for type
10144 @xref{Symbols, ,Examining the Symbol Table}.
10146 @cindex C@t{++} symbol display
10147 @item set print demangle
10148 @itemx show print demangle
10149 @itemx set print asm-demangle
10150 @itemx show print asm-demangle
10151 Control whether C@t{++} symbols display in their source form, both when
10152 displaying code as C@t{++} source and when displaying disassemblies.
10153 @xref{Print Settings, ,Print Settings}.
10155 @item set print object
10156 @itemx show print object
10157 Choose whether to print derived (actual) or declared types of objects.
10158 @xref{Print Settings, ,Print Settings}.
10160 @item set print vtbl
10161 @itemx show print vtbl
10162 Control the format for printing virtual function tables.
10163 @xref{Print Settings, ,Print Settings}.
10164 (The @code{vtbl} commands do not work on programs compiled with the HP
10165 ANSI C@t{++} compiler (@code{aCC}).)
10167 @kindex set overload-resolution
10168 @cindex overloaded functions, overload resolution
10169 @item set overload-resolution on
10170 Enable overload resolution for C@t{++} expression evaluation. The default
10171 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10172 and searches for a function whose signature matches the argument types,
10173 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10174 Expressions, ,C@t{++} Expressions}, for details).
10175 If it cannot find a match, it emits a message.
10177 @item set overload-resolution off
10178 Disable overload resolution for C@t{++} expression evaluation. For
10179 overloaded functions that are not class member functions, @value{GDBN}
10180 chooses the first function of the specified name that it finds in the
10181 symbol table, whether or not its arguments are of the correct type. For
10182 overloaded functions that are class member functions, @value{GDBN}
10183 searches for a function whose signature @emph{exactly} matches the
10186 @kindex show overload-resolution
10187 @item show overload-resolution
10188 Show the current setting of overload resolution.
10190 @item @r{Overloaded symbol names}
10191 You can specify a particular definition of an overloaded symbol, using
10192 the same notation that is used to declare such symbols in C@t{++}: type
10193 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10194 also use the @value{GDBN} command-line word completion facilities to list the
10195 available choices, or to finish the type list for you.
10196 @xref{Completion,, Command Completion}, for details on how to do this.
10199 @node Decimal Floating Point
10200 @subsubsection Decimal Floating Point format
10201 @cindex decimal floating point format
10203 @value{GDBN} can examine, set and perform computations with numbers in
10204 decimal floating point format, which in the C language correspond to the
10205 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10206 specified by the extension to support decimal floating-point arithmetic.
10208 There are two encodings in use, depending on the architecture: BID (Binary
10209 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10210 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10213 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10214 to manipulate decimal floating point numbers, it is not possible to convert
10215 (using a cast, for example) integers wider than 32-bit to decimal float.
10217 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10218 point computations, error checking in decimal float operations ignores
10219 underflow, overflow and divide by zero exceptions.
10221 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10222 to inspect @code{_Decimal128} values stored in floating point registers. See
10223 @ref{PowerPC,,PowerPC} for more details.
10226 @subsection Objective-C
10228 @cindex Objective-C
10229 This section provides information about some commands and command
10230 options that are useful for debugging Objective-C code. See also
10231 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10232 few more commands specific to Objective-C support.
10235 * Method Names in Commands::
10236 * The Print Command with Objective-C::
10239 @node Method Names in Commands
10240 @subsubsection Method Names in Commands
10242 The following commands have been extended to accept Objective-C method
10243 names as line specifications:
10245 @kindex clear@r{, and Objective-C}
10246 @kindex break@r{, and Objective-C}
10247 @kindex info line@r{, and Objective-C}
10248 @kindex jump@r{, and Objective-C}
10249 @kindex list@r{, and Objective-C}
10253 @item @code{info line}
10258 A fully qualified Objective-C method name is specified as
10261 -[@var{Class} @var{methodName}]
10264 where the minus sign is used to indicate an instance method and a
10265 plus sign (not shown) is used to indicate a class method. The class
10266 name @var{Class} and method name @var{methodName} are enclosed in
10267 brackets, similar to the way messages are specified in Objective-C
10268 source code. For example, to set a breakpoint at the @code{create}
10269 instance method of class @code{Fruit} in the program currently being
10273 break -[Fruit create]
10276 To list ten program lines around the @code{initialize} class method,
10280 list +[NSText initialize]
10283 In the current version of @value{GDBN}, the plus or minus sign is
10284 required. In future versions of @value{GDBN}, the plus or minus
10285 sign will be optional, but you can use it to narrow the search. It
10286 is also possible to specify just a method name:
10292 You must specify the complete method name, including any colons. If
10293 your program's source files contain more than one @code{create} method,
10294 you'll be presented with a numbered list of classes that implement that
10295 method. Indicate your choice by number, or type @samp{0} to exit if
10298 As another example, to clear a breakpoint established at the
10299 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10302 clear -[NSWindow makeKeyAndOrderFront:]
10305 @node The Print Command with Objective-C
10306 @subsubsection The Print Command With Objective-C
10307 @cindex Objective-C, print objects
10308 @kindex print-object
10309 @kindex po @r{(@code{print-object})}
10311 The print command has also been extended to accept methods. For example:
10314 print -[@var{object} hash]
10317 @cindex print an Objective-C object description
10318 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10320 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10321 and print the result. Also, an additional command has been added,
10322 @code{print-object} or @code{po} for short, which is meant to print
10323 the description of an object. However, this command may only work
10324 with certain Objective-C libraries that have a particular hook
10325 function, @code{_NSPrintForDebugger}, defined.
10328 @subsection Fortran
10329 @cindex Fortran-specific support in @value{GDBN}
10331 @value{GDBN} can be used to debug programs written in Fortran, but it
10332 currently supports only the features of Fortran 77 language.
10334 @cindex trailing underscore, in Fortran symbols
10335 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10336 among them) append an underscore to the names of variables and
10337 functions. When you debug programs compiled by those compilers, you
10338 will need to refer to variables and functions with a trailing
10342 * Fortran Operators:: Fortran operators and expressions
10343 * Fortran Defaults:: Default settings for Fortran
10344 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10347 @node Fortran Operators
10348 @subsubsection Fortran Operators and Expressions
10350 @cindex Fortran operators and expressions
10352 Operators must be defined on values of specific types. For instance,
10353 @code{+} is defined on numbers, but not on characters or other non-
10354 arithmetic types. Operators are often defined on groups of types.
10358 The exponentiation operator. It raises the first operand to the power
10362 The range operator. Normally used in the form of array(low:high) to
10363 represent a section of array.
10366 The access component operator. Normally used to access elements in derived
10367 types. Also suitable for unions. As unions aren't part of regular Fortran,
10368 this can only happen when accessing a register that uses a gdbarch-defined
10372 @node Fortran Defaults
10373 @subsubsection Fortran Defaults
10375 @cindex Fortran Defaults
10377 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10378 default uses case-insensitive matches for Fortran symbols. You can
10379 change that with the @samp{set case-insensitive} command, see
10380 @ref{Symbols}, for the details.
10382 @node Special Fortran Commands
10383 @subsubsection Special Fortran Commands
10385 @cindex Special Fortran commands
10387 @value{GDBN} has some commands to support Fortran-specific features,
10388 such as displaying common blocks.
10391 @cindex @code{COMMON} blocks, Fortran
10392 @kindex info common
10393 @item info common @r{[}@var{common-name}@r{]}
10394 This command prints the values contained in the Fortran @code{COMMON}
10395 block whose name is @var{common-name}. With no argument, the names of
10396 all @code{COMMON} blocks visible at the current program location are
10403 @cindex Pascal support in @value{GDBN}, limitations
10404 Debugging Pascal programs which use sets, subranges, file variables, or
10405 nested functions does not currently work. @value{GDBN} does not support
10406 entering expressions, printing values, or similar features using Pascal
10409 The Pascal-specific command @code{set print pascal_static-members}
10410 controls whether static members of Pascal objects are displayed.
10411 @xref{Print Settings, pascal_static-members}.
10414 @subsection Modula-2
10416 @cindex Modula-2, @value{GDBN} support
10418 The extensions made to @value{GDBN} to support Modula-2 only support
10419 output from the @sc{gnu} Modula-2 compiler (which is currently being
10420 developed). Other Modula-2 compilers are not currently supported, and
10421 attempting to debug executables produced by them is most likely
10422 to give an error as @value{GDBN} reads in the executable's symbol
10425 @cindex expressions in Modula-2
10427 * M2 Operators:: Built-in operators
10428 * Built-In Func/Proc:: Built-in functions and procedures
10429 * M2 Constants:: Modula-2 constants
10430 * M2 Types:: Modula-2 types
10431 * M2 Defaults:: Default settings for Modula-2
10432 * Deviations:: Deviations from standard Modula-2
10433 * M2 Checks:: Modula-2 type and range checks
10434 * M2 Scope:: The scope operators @code{::} and @code{.}
10435 * GDB/M2:: @value{GDBN} and Modula-2
10439 @subsubsection Operators
10440 @cindex Modula-2 operators
10442 Operators must be defined on values of specific types. For instance,
10443 @code{+} is defined on numbers, but not on structures. Operators are
10444 often defined on groups of types. For the purposes of Modula-2, the
10445 following definitions hold:
10450 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10454 @emph{Character types} consist of @code{CHAR} and its subranges.
10457 @emph{Floating-point types} consist of @code{REAL}.
10460 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10464 @emph{Scalar types} consist of all of the above.
10467 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10470 @emph{Boolean types} consist of @code{BOOLEAN}.
10474 The following operators are supported, and appear in order of
10475 increasing precedence:
10479 Function argument or array index separator.
10482 Assignment. The value of @var{var} @code{:=} @var{value} is
10486 Less than, greater than on integral, floating-point, or enumerated
10490 Less than or equal to, greater than or equal to
10491 on integral, floating-point and enumerated types, or set inclusion on
10492 set types. Same precedence as @code{<}.
10494 @item =@r{, }<>@r{, }#
10495 Equality and two ways of expressing inequality, valid on scalar types.
10496 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10497 available for inequality, since @code{#} conflicts with the script
10501 Set membership. Defined on set types and the types of their members.
10502 Same precedence as @code{<}.
10505 Boolean disjunction. Defined on boolean types.
10508 Boolean conjunction. Defined on boolean types.
10511 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10514 Addition and subtraction on integral and floating-point types, or union
10515 and difference on set types.
10518 Multiplication on integral and floating-point types, or set intersection
10522 Division on floating-point types, or symmetric set difference on set
10523 types. Same precedence as @code{*}.
10526 Integer division and remainder. Defined on integral types. Same
10527 precedence as @code{*}.
10530 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10533 Pointer dereferencing. Defined on pointer types.
10536 Boolean negation. Defined on boolean types. Same precedence as
10540 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10541 precedence as @code{^}.
10544 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10547 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10551 @value{GDBN} and Modula-2 scope operators.
10555 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10556 treats the use of the operator @code{IN}, or the use of operators
10557 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10558 @code{<=}, and @code{>=} on sets as an error.
10562 @node Built-In Func/Proc
10563 @subsubsection Built-in Functions and Procedures
10564 @cindex Modula-2 built-ins
10566 Modula-2 also makes available several built-in procedures and functions.
10567 In describing these, the following metavariables are used:
10572 represents an @code{ARRAY} variable.
10575 represents a @code{CHAR} constant or variable.
10578 represents a variable or constant of integral type.
10581 represents an identifier that belongs to a set. Generally used in the
10582 same function with the metavariable @var{s}. The type of @var{s} should
10583 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10586 represents a variable or constant of integral or floating-point type.
10589 represents a variable or constant of floating-point type.
10595 represents a variable.
10598 represents a variable or constant of one of many types. See the
10599 explanation of the function for details.
10602 All Modula-2 built-in procedures also return a result, described below.
10606 Returns the absolute value of @var{n}.
10609 If @var{c} is a lower case letter, it returns its upper case
10610 equivalent, otherwise it returns its argument.
10613 Returns the character whose ordinal value is @var{i}.
10616 Decrements the value in the variable @var{v} by one. Returns the new value.
10618 @item DEC(@var{v},@var{i})
10619 Decrements the value in the variable @var{v} by @var{i}. Returns the
10622 @item EXCL(@var{m},@var{s})
10623 Removes the element @var{m} from the set @var{s}. Returns the new
10626 @item FLOAT(@var{i})
10627 Returns the floating point equivalent of the integer @var{i}.
10629 @item HIGH(@var{a})
10630 Returns the index of the last member of @var{a}.
10633 Increments the value in the variable @var{v} by one. Returns the new value.
10635 @item INC(@var{v},@var{i})
10636 Increments the value in the variable @var{v} by @var{i}. Returns the
10639 @item INCL(@var{m},@var{s})
10640 Adds the element @var{m} to the set @var{s} if it is not already
10641 there. Returns the new set.
10644 Returns the maximum value of the type @var{t}.
10647 Returns the minimum value of the type @var{t}.
10650 Returns boolean TRUE if @var{i} is an odd number.
10653 Returns the ordinal value of its argument. For example, the ordinal
10654 value of a character is its @sc{ascii} value (on machines supporting the
10655 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10656 integral, character and enumerated types.
10658 @item SIZE(@var{x})
10659 Returns the size of its argument. @var{x} can be a variable or a type.
10661 @item TRUNC(@var{r})
10662 Returns the integral part of @var{r}.
10664 @item TSIZE(@var{x})
10665 Returns the size of its argument. @var{x} can be a variable or a type.
10667 @item VAL(@var{t},@var{i})
10668 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10672 @emph{Warning:} Sets and their operations are not yet supported, so
10673 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10677 @cindex Modula-2 constants
10679 @subsubsection Constants
10681 @value{GDBN} allows you to express the constants of Modula-2 in the following
10687 Integer constants are simply a sequence of digits. When used in an
10688 expression, a constant is interpreted to be type-compatible with the
10689 rest of the expression. Hexadecimal integers are specified by a
10690 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10693 Floating point constants appear as a sequence of digits, followed by a
10694 decimal point and another sequence of digits. An optional exponent can
10695 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10696 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10697 digits of the floating point constant must be valid decimal (base 10)
10701 Character constants consist of a single character enclosed by a pair of
10702 like quotes, either single (@code{'}) or double (@code{"}). They may
10703 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10704 followed by a @samp{C}.
10707 String constants consist of a sequence of characters enclosed by a
10708 pair of like quotes, either single (@code{'}) or double (@code{"}).
10709 Escape sequences in the style of C are also allowed. @xref{C
10710 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10714 Enumerated constants consist of an enumerated identifier.
10717 Boolean constants consist of the identifiers @code{TRUE} and
10721 Pointer constants consist of integral values only.
10724 Set constants are not yet supported.
10728 @subsubsection Modula-2 Types
10729 @cindex Modula-2 types
10731 Currently @value{GDBN} can print the following data types in Modula-2
10732 syntax: array types, record types, set types, pointer types, procedure
10733 types, enumerated types, subrange types and base types. You can also
10734 print the contents of variables declared using these type.
10735 This section gives a number of simple source code examples together with
10736 sample @value{GDBN} sessions.
10738 The first example contains the following section of code:
10747 and you can request @value{GDBN} to interrogate the type and value of
10748 @code{r} and @code{s}.
10751 (@value{GDBP}) print s
10753 (@value{GDBP}) ptype s
10755 (@value{GDBP}) print r
10757 (@value{GDBP}) ptype r
10762 Likewise if your source code declares @code{s} as:
10766 s: SET ['A'..'Z'] ;
10770 then you may query the type of @code{s} by:
10773 (@value{GDBP}) ptype s
10774 type = SET ['A'..'Z']
10778 Note that at present you cannot interactively manipulate set
10779 expressions using the debugger.
10781 The following example shows how you might declare an array in Modula-2
10782 and how you can interact with @value{GDBN} to print its type and contents:
10786 s: ARRAY [-10..10] OF CHAR ;
10790 (@value{GDBP}) ptype s
10791 ARRAY [-10..10] OF CHAR
10794 Note that the array handling is not yet complete and although the type
10795 is printed correctly, expression handling still assumes that all
10796 arrays have a lower bound of zero and not @code{-10} as in the example
10799 Here are some more type related Modula-2 examples:
10803 colour = (blue, red, yellow, green) ;
10804 t = [blue..yellow] ;
10812 The @value{GDBN} interaction shows how you can query the data type
10813 and value of a variable.
10816 (@value{GDBP}) print s
10818 (@value{GDBP}) ptype t
10819 type = [blue..yellow]
10823 In this example a Modula-2 array is declared and its contents
10824 displayed. Observe that the contents are written in the same way as
10825 their @code{C} counterparts.
10829 s: ARRAY [1..5] OF CARDINAL ;
10835 (@value{GDBP}) print s
10836 $1 = @{1, 0, 0, 0, 0@}
10837 (@value{GDBP}) ptype s
10838 type = ARRAY [1..5] OF CARDINAL
10841 The Modula-2 language interface to @value{GDBN} also understands
10842 pointer types as shown in this example:
10846 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10853 and you can request that @value{GDBN} describes the type of @code{s}.
10856 (@value{GDBP}) ptype s
10857 type = POINTER TO ARRAY [1..5] OF CARDINAL
10860 @value{GDBN} handles compound types as we can see in this example.
10861 Here we combine array types, record types, pointer types and subrange
10872 myarray = ARRAY myrange OF CARDINAL ;
10873 myrange = [-2..2] ;
10875 s: POINTER TO ARRAY myrange OF foo ;
10879 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10883 (@value{GDBP}) ptype s
10884 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10887 f3 : ARRAY [-2..2] OF CARDINAL;
10892 @subsubsection Modula-2 Defaults
10893 @cindex Modula-2 defaults
10895 If type and range checking are set automatically by @value{GDBN}, they
10896 both default to @code{on} whenever the working language changes to
10897 Modula-2. This happens regardless of whether you or @value{GDBN}
10898 selected the working language.
10900 If you allow @value{GDBN} to set the language automatically, then entering
10901 code compiled from a file whose name ends with @file{.mod} sets the
10902 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10903 Infer the Source Language}, for further details.
10906 @subsubsection Deviations from Standard Modula-2
10907 @cindex Modula-2, deviations from
10909 A few changes have been made to make Modula-2 programs easier to debug.
10910 This is done primarily via loosening its type strictness:
10914 Unlike in standard Modula-2, pointer constants can be formed by
10915 integers. This allows you to modify pointer variables during
10916 debugging. (In standard Modula-2, the actual address contained in a
10917 pointer variable is hidden from you; it can only be modified
10918 through direct assignment to another pointer variable or expression that
10919 returned a pointer.)
10922 C escape sequences can be used in strings and characters to represent
10923 non-printable characters. @value{GDBN} prints out strings with these
10924 escape sequences embedded. Single non-printable characters are
10925 printed using the @samp{CHR(@var{nnn})} format.
10928 The assignment operator (@code{:=}) returns the value of its right-hand
10932 All built-in procedures both modify @emph{and} return their argument.
10936 @subsubsection Modula-2 Type and Range Checks
10937 @cindex Modula-2 checks
10940 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10943 @c FIXME remove warning when type/range checks added
10945 @value{GDBN} considers two Modula-2 variables type equivalent if:
10949 They are of types that have been declared equivalent via a @code{TYPE
10950 @var{t1} = @var{t2}} statement
10953 They have been declared on the same line. (Note: This is true of the
10954 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10957 As long as type checking is enabled, any attempt to combine variables
10958 whose types are not equivalent is an error.
10960 Range checking is done on all mathematical operations, assignment, array
10961 index bounds, and all built-in functions and procedures.
10964 @subsubsection The Scope Operators @code{::} and @code{.}
10966 @cindex @code{.}, Modula-2 scope operator
10967 @cindex colon, doubled as scope operator
10969 @vindex colon-colon@r{, in Modula-2}
10970 @c Info cannot handle :: but TeX can.
10973 @vindex ::@r{, in Modula-2}
10976 There are a few subtle differences between the Modula-2 scope operator
10977 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10982 @var{module} . @var{id}
10983 @var{scope} :: @var{id}
10987 where @var{scope} is the name of a module or a procedure,
10988 @var{module} the name of a module, and @var{id} is any declared
10989 identifier within your program, except another module.
10991 Using the @code{::} operator makes @value{GDBN} search the scope
10992 specified by @var{scope} for the identifier @var{id}. If it is not
10993 found in the specified scope, then @value{GDBN} searches all scopes
10994 enclosing the one specified by @var{scope}.
10996 Using the @code{.} operator makes @value{GDBN} search the current scope for
10997 the identifier specified by @var{id} that was imported from the
10998 definition module specified by @var{module}. With this operator, it is
10999 an error if the identifier @var{id} was not imported from definition
11000 module @var{module}, or if @var{id} is not an identifier in
11004 @subsubsection @value{GDBN} and Modula-2
11006 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11007 Five subcommands of @code{set print} and @code{show print} apply
11008 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11009 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11010 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11011 analogue in Modula-2.
11013 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11014 with any language, is not useful with Modula-2. Its
11015 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11016 created in Modula-2 as they can in C or C@t{++}. However, because an
11017 address can be specified by an integral constant, the construct
11018 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11020 @cindex @code{#} in Modula-2
11021 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11022 interpreted as the beginning of a comment. Use @code{<>} instead.
11028 The extensions made to @value{GDBN} for Ada only support
11029 output from the @sc{gnu} Ada (GNAT) compiler.
11030 Other Ada compilers are not currently supported, and
11031 attempting to debug executables produced by them is most likely
11035 @cindex expressions in Ada
11037 * Ada Mode Intro:: General remarks on the Ada syntax
11038 and semantics supported by Ada mode
11040 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11041 * Additions to Ada:: Extensions of the Ada expression syntax.
11042 * Stopping Before Main Program:: Debugging the program during elaboration.
11043 * Ada Glitches:: Known peculiarities of Ada mode.
11046 @node Ada Mode Intro
11047 @subsubsection Introduction
11048 @cindex Ada mode, general
11050 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11051 syntax, with some extensions.
11052 The philosophy behind the design of this subset is
11056 That @value{GDBN} should provide basic literals and access to operations for
11057 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11058 leaving more sophisticated computations to subprograms written into the
11059 program (which therefore may be called from @value{GDBN}).
11062 That type safety and strict adherence to Ada language restrictions
11063 are not particularly important to the @value{GDBN} user.
11066 That brevity is important to the @value{GDBN} user.
11069 Thus, for brevity, the debugger acts as if there were
11070 implicit @code{with} and @code{use} clauses in effect for all user-written
11071 packages, making it unnecessary to fully qualify most names with
11072 their packages, regardless of context. Where this causes ambiguity,
11073 @value{GDBN} asks the user's intent.
11075 The debugger will start in Ada mode if it detects an Ada main program.
11076 As for other languages, it will enter Ada mode when stopped in a program that
11077 was translated from an Ada source file.
11079 While in Ada mode, you may use `@t{--}' for comments. This is useful
11080 mostly for documenting command files. The standard @value{GDBN} comment
11081 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11082 middle (to allow based literals).
11084 The debugger supports limited overloading. Given a subprogram call in which
11085 the function symbol has multiple definitions, it will use the number of
11086 actual parameters and some information about their types to attempt to narrow
11087 the set of definitions. It also makes very limited use of context, preferring
11088 procedures to functions in the context of the @code{call} command, and
11089 functions to procedures elsewhere.
11091 @node Omissions from Ada
11092 @subsubsection Omissions from Ada
11093 @cindex Ada, omissions from
11095 Here are the notable omissions from the subset:
11099 Only a subset of the attributes are supported:
11103 @t{'First}, @t{'Last}, and @t{'Length}
11104 on array objects (not on types and subtypes).
11107 @t{'Min} and @t{'Max}.
11110 @t{'Pos} and @t{'Val}.
11116 @t{'Range} on array objects (not subtypes), but only as the right
11117 operand of the membership (@code{in}) operator.
11120 @t{'Access}, @t{'Unchecked_Access}, and
11121 @t{'Unrestricted_Access} (a GNAT extension).
11129 @code{Characters.Latin_1} are not available and
11130 concatenation is not implemented. Thus, escape characters in strings are
11131 not currently available.
11134 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11135 equality of representations. They will generally work correctly
11136 for strings and arrays whose elements have integer or enumeration types.
11137 They may not work correctly for arrays whose element
11138 types have user-defined equality, for arrays of real values
11139 (in particular, IEEE-conformant floating point, because of negative
11140 zeroes and NaNs), and for arrays whose elements contain unused bits with
11141 indeterminate values.
11144 The other component-by-component array operations (@code{and}, @code{or},
11145 @code{xor}, @code{not}, and relational tests other than equality)
11146 are not implemented.
11149 @cindex array aggregates (Ada)
11150 @cindex record aggregates (Ada)
11151 @cindex aggregates (Ada)
11152 There is limited support for array and record aggregates. They are
11153 permitted only on the right sides of assignments, as in these examples:
11156 set An_Array := (1, 2, 3, 4, 5, 6)
11157 set An_Array := (1, others => 0)
11158 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11159 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11160 set A_Record := (1, "Peter", True);
11161 set A_Record := (Name => "Peter", Id => 1, Alive => True)
11165 discriminant's value by assigning an aggregate has an
11166 undefined effect if that discriminant is used within the record.
11167 However, you can first modify discriminants by directly assigning to
11168 them (which normally would not be allowed in Ada), and then performing an
11169 aggregate assignment. For example, given a variable @code{A_Rec}
11170 declared to have a type such as:
11173 type Rec (Len : Small_Integer := 0) is record
11175 Vals : IntArray (1 .. Len);
11179 you can assign a value with a different size of @code{Vals} with two
11184 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11187 As this example also illustrates, @value{GDBN} is very loose about the usual
11188 rules concerning aggregates. You may leave out some of the
11189 components of an array or record aggregate (such as the @code{Len}
11190 component in the assignment to @code{A_Rec} above); they will retain their
11191 original values upon assignment. You may freely use dynamic values as
11192 indices in component associations. You may even use overlapping or
11193 redundant component associations, although which component values are
11194 assigned in such cases is not defined.
11197 Calls to dispatching subprograms are not implemented.
11200 The overloading algorithm is much more limited (i.e., less selective)
11201 than that of real Ada. It makes only limited use of the context in
11202 which a subexpression appears to resolve its meaning, and it is much
11203 looser in its rules for allowing type matches. As a result, some
11204 function calls will be ambiguous, and the user will be asked to choose
11205 the proper resolution.
11208 The @code{new} operator is not implemented.
11211 Entry calls are not implemented.
11214 Aside from printing, arithmetic operations on the native VAX floating-point
11215 formats are not supported.
11218 It is not possible to slice a packed array.
11221 @node Additions to Ada
11222 @subsubsection Additions to Ada
11223 @cindex Ada, deviations from
11225 As it does for other languages, @value{GDBN} makes certain generic
11226 extensions to Ada (@pxref{Expressions}):
11230 If the expression @var{E} is a variable residing in memory (typically
11231 a local variable or array element) and @var{N} is a positive integer,
11232 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11233 @var{N}-1 adjacent variables following it in memory as an array. In
11234 Ada, this operator is generally not necessary, since its prime use is
11235 in displaying parts of an array, and slicing will usually do this in
11236 Ada. However, there are occasional uses when debugging programs in
11237 which certain debugging information has been optimized away.
11240 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11241 appears in function or file @var{B}.'' When @var{B} is a file name,
11242 you must typically surround it in single quotes.
11245 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11246 @var{type} that appears at address @var{addr}.''
11249 A name starting with @samp{$} is a convenience variable
11250 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11253 In addition, @value{GDBN} provides a few other shortcuts and outright
11254 additions specific to Ada:
11258 The assignment statement is allowed as an expression, returning
11259 its right-hand operand as its value. Thus, you may enter
11263 print A(tmp := y + 1)
11267 The semicolon is allowed as an ``operator,'' returning as its value
11268 the value of its right-hand operand.
11269 This allows, for example,
11270 complex conditional breaks:
11274 condition 1 (report(i); k += 1; A(k) > 100)
11278 Rather than use catenation and symbolic character names to introduce special
11279 characters into strings, one may instead use a special bracket notation,
11280 which is also used to print strings. A sequence of characters of the form
11281 @samp{["@var{XX}"]} within a string or character literal denotes the
11282 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11283 sequence of characters @samp{["""]} also denotes a single quotation mark
11284 in strings. For example,
11286 "One line.["0a"]Next line.["0a"]"
11289 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11293 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11294 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11302 When printing arrays, @value{GDBN} uses positional notation when the
11303 array has a lower bound of 1, and uses a modified named notation otherwise.
11304 For example, a one-dimensional array of three integers with a lower bound
11305 of 3 might print as
11312 That is, in contrast to valid Ada, only the first component has a @code{=>}
11316 You may abbreviate attributes in expressions with any unique,
11317 multi-character subsequence of
11318 their names (an exact match gets preference).
11319 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11320 in place of @t{a'length}.
11323 @cindex quoting Ada internal identifiers
11324 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11325 to lower case. The GNAT compiler uses upper-case characters for
11326 some of its internal identifiers, which are normally of no interest to users.
11327 For the rare occasions when you actually have to look at them,
11328 enclose them in angle brackets to avoid the lower-case mapping.
11331 @value{GDBP} print <JMPBUF_SAVE>[0]
11335 Printing an object of class-wide type or dereferencing an
11336 access-to-class-wide value will display all the components of the object's
11337 specific type (as indicated by its run-time tag). Likewise, component
11338 selection on such a value will operate on the specific type of the
11343 @node Stopping Before Main Program
11344 @subsubsection Stopping at the Very Beginning
11346 @cindex breakpointing Ada elaboration code
11347 It is sometimes necessary to debug the program during elaboration, and
11348 before reaching the main procedure.
11349 As defined in the Ada Reference
11350 Manual, the elaboration code is invoked from a procedure called
11351 @code{adainit}. To run your program up to the beginning of
11352 elaboration, simply use the following two commands:
11353 @code{tbreak adainit} and @code{run}.
11356 @subsubsection Known Peculiarities of Ada Mode
11357 @cindex Ada, problems
11359 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11360 we know of several problems with and limitations of Ada mode in
11362 some of which will be fixed with planned future releases of the debugger
11363 and the GNU Ada compiler.
11367 Currently, the debugger
11368 has insufficient information to determine whether certain pointers represent
11369 pointers to objects or the objects themselves.
11370 Thus, the user may have to tack an extra @code{.all} after an expression
11371 to get it printed properly.
11374 Static constants that the compiler chooses not to materialize as objects in
11375 storage are invisible to the debugger.
11378 Named parameter associations in function argument lists are ignored (the
11379 argument lists are treated as positional).
11382 Many useful library packages are currently invisible to the debugger.
11385 Fixed-point arithmetic, conversions, input, and output is carried out using
11386 floating-point arithmetic, and may give results that only approximate those on
11390 The type of the @t{'Address} attribute may not be @code{System.Address}.
11393 The GNAT compiler never generates the prefix @code{Standard} for any of
11394 the standard symbols defined by the Ada language. @value{GDBN} knows about
11395 this: it will strip the prefix from names when you use it, and will never
11396 look for a name you have so qualified among local symbols, nor match against
11397 symbols in other packages or subprograms. If you have
11398 defined entities anywhere in your program other than parameters and
11399 local variables whose simple names match names in @code{Standard},
11400 GNAT's lack of qualification here can cause confusion. When this happens,
11401 you can usually resolve the confusion
11402 by qualifying the problematic names with package
11403 @code{Standard} explicitly.
11406 @node Unsupported Languages
11407 @section Unsupported Languages
11409 @cindex unsupported languages
11410 @cindex minimal language
11411 In addition to the other fully-supported programming languages,
11412 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11413 It does not represent a real programming language, but provides a set
11414 of capabilities close to what the C or assembly languages provide.
11415 This should allow most simple operations to be performed while debugging
11416 an application that uses a language currently not supported by @value{GDBN}.
11418 If the language is set to @code{auto}, @value{GDBN} will automatically
11419 select this language if the current frame corresponds to an unsupported
11423 @chapter Examining the Symbol Table
11425 The commands described in this chapter allow you to inquire about the
11426 symbols (names of variables, functions and types) defined in your
11427 program. This information is inherent in the text of your program and
11428 does not change as your program executes. @value{GDBN} finds it in your
11429 program's symbol table, in the file indicated when you started @value{GDBN}
11430 (@pxref{File Options, ,Choosing Files}), or by one of the
11431 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11433 @cindex symbol names
11434 @cindex names of symbols
11435 @cindex quoting names
11436 Occasionally, you may need to refer to symbols that contain unusual
11437 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11438 most frequent case is in referring to static variables in other
11439 source files (@pxref{Variables,,Program Variables}). File names
11440 are recorded in object files as debugging symbols, but @value{GDBN} would
11441 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11442 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11443 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11450 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11453 @cindex case-insensitive symbol names
11454 @cindex case sensitivity in symbol names
11455 @kindex set case-sensitive
11456 @item set case-sensitive on
11457 @itemx set case-sensitive off
11458 @itemx set case-sensitive auto
11459 Normally, when @value{GDBN} looks up symbols, it matches their names
11460 with case sensitivity determined by the current source language.
11461 Occasionally, you may wish to control that. The command @code{set
11462 case-sensitive} lets you do that by specifying @code{on} for
11463 case-sensitive matches or @code{off} for case-insensitive ones. If
11464 you specify @code{auto}, case sensitivity is reset to the default
11465 suitable for the source language. The default is case-sensitive
11466 matches for all languages except for Fortran, for which the default is
11467 case-insensitive matches.
11469 @kindex show case-sensitive
11470 @item show case-sensitive
11471 This command shows the current setting of case sensitivity for symbols
11474 @kindex info address
11475 @cindex address of a symbol
11476 @item info address @var{symbol}
11477 Describe where the data for @var{symbol} is stored. For a register
11478 variable, this says which register it is kept in. For a non-register
11479 local variable, this prints the stack-frame offset at which the variable
11482 Note the contrast with @samp{print &@var{symbol}}, which does not work
11483 at all for a register variable, and for a stack local variable prints
11484 the exact address of the current instantiation of the variable.
11486 @kindex info symbol
11487 @cindex symbol from address
11488 @cindex closest symbol and offset for an address
11489 @item info symbol @var{addr}
11490 Print the name of a symbol which is stored at the address @var{addr}.
11491 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11492 nearest symbol and an offset from it:
11495 (@value{GDBP}) info symbol 0x54320
11496 _initialize_vx + 396 in section .text
11500 This is the opposite of the @code{info address} command. You can use
11501 it to find out the name of a variable or a function given its address.
11504 @item whatis [@var{arg}]
11505 Print the data type of @var{arg}, which can be either an expression or
11506 a data type. With no argument, print the data type of @code{$}, the
11507 last value in the value history. If @var{arg} is an expression, it is
11508 not actually evaluated, and any side-effecting operations (such as
11509 assignments or function calls) inside it do not take place. If
11510 @var{arg} is a type name, it may be the name of a type or typedef, or
11511 for C code it may have the form @samp{class @var{class-name}},
11512 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11513 @samp{enum @var{enum-tag}}.
11514 @xref{Expressions, ,Expressions}.
11517 @item ptype [@var{arg}]
11518 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11519 detailed description of the type, instead of just the name of the type.
11520 @xref{Expressions, ,Expressions}.
11522 For example, for this variable declaration:
11525 struct complex @{double real; double imag;@} v;
11529 the two commands give this output:
11533 (@value{GDBP}) whatis v
11534 type = struct complex
11535 (@value{GDBP}) ptype v
11536 type = struct complex @{
11544 As with @code{whatis}, using @code{ptype} without an argument refers to
11545 the type of @code{$}, the last value in the value history.
11547 @cindex incomplete type
11548 Sometimes, programs use opaque data types or incomplete specifications
11549 of complex data structure. If the debug information included in the
11550 program does not allow @value{GDBN} to display a full declaration of
11551 the data type, it will say @samp{<incomplete type>}. For example,
11552 given these declarations:
11556 struct foo *fooptr;
11560 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11563 (@value{GDBP}) ptype foo
11564 $1 = <incomplete type>
11568 ``Incomplete type'' is C terminology for data types that are not
11569 completely specified.
11572 @item info types @var{regexp}
11574 Print a brief description of all types whose names match the regular
11575 expression @var{regexp} (or all types in your program, if you supply
11576 no argument). Each complete typename is matched as though it were a
11577 complete line; thus, @samp{i type value} gives information on all
11578 types in your program whose names include the string @code{value}, but
11579 @samp{i type ^value$} gives information only on types whose complete
11580 name is @code{value}.
11582 This command differs from @code{ptype} in two ways: first, like
11583 @code{whatis}, it does not print a detailed description; second, it
11584 lists all source files where a type is defined.
11587 @cindex local variables
11588 @item info scope @var{location}
11589 List all the variables local to a particular scope. This command
11590 accepts a @var{location} argument---a function name, a source line, or
11591 an address preceded by a @samp{*}, and prints all the variables local
11592 to the scope defined by that location. (@xref{Specify Location}, for
11593 details about supported forms of @var{location}.) For example:
11596 (@value{GDBP}) @b{info scope command_line_handler}
11597 Scope for command_line_handler:
11598 Symbol rl is an argument at stack/frame offset 8, length 4.
11599 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11600 Symbol linelength is in static storage at address 0x150a1c, length 4.
11601 Symbol p is a local variable in register $esi, length 4.
11602 Symbol p1 is a local variable in register $ebx, length 4.
11603 Symbol nline is a local variable in register $edx, length 4.
11604 Symbol repeat is a local variable at frame offset -8, length 4.
11608 This command is especially useful for determining what data to collect
11609 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11612 @kindex info source
11614 Show information about the current source file---that is, the source file for
11615 the function containing the current point of execution:
11618 the name of the source file, and the directory containing it,
11620 the directory it was compiled in,
11622 its length, in lines,
11624 which programming language it is written in,
11626 whether the executable includes debugging information for that file, and
11627 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11629 whether the debugging information includes information about
11630 preprocessor macros.
11634 @kindex info sources
11636 Print the names of all source files in your program for which there is
11637 debugging information, organized into two lists: files whose symbols
11638 have already been read, and files whose symbols will be read when needed.
11640 @kindex info functions
11641 @item info functions
11642 Print the names and data types of all defined functions.
11644 @item info functions @var{regexp}
11645 Print the names and data types of all defined functions
11646 whose names contain a match for regular expression @var{regexp}.
11647 Thus, @samp{info fun step} finds all functions whose names
11648 include @code{step}; @samp{info fun ^step} finds those whose names
11649 start with @code{step}. If a function name contains characters
11650 that conflict with the regular expression language (e.g.@:
11651 @samp{operator*()}), they may be quoted with a backslash.
11653 @kindex info variables
11654 @item info variables
11655 Print the names and data types of all variables that are declared
11656 outside of functions (i.e.@: excluding local variables).
11658 @item info variables @var{regexp}
11659 Print the names and data types of all variables (except for local
11660 variables) whose names contain a match for regular expression
11663 @kindex info classes
11664 @cindex Objective-C, classes and selectors
11666 @itemx info classes @var{regexp}
11667 Display all Objective-C classes in your program, or
11668 (with the @var{regexp} argument) all those matching a particular regular
11671 @kindex info selectors
11672 @item info selectors
11673 @itemx info selectors @var{regexp}
11674 Display all Objective-C selectors in your program, or
11675 (with the @var{regexp} argument) all those matching a particular regular
11679 This was never implemented.
11680 @kindex info methods
11682 @itemx info methods @var{regexp}
11683 The @code{info methods} command permits the user to examine all defined
11684 methods within C@t{++} program, or (with the @var{regexp} argument) a
11685 specific set of methods found in the various C@t{++} classes. Many
11686 C@t{++} classes provide a large number of methods. Thus, the output
11687 from the @code{ptype} command can be overwhelming and hard to use. The
11688 @code{info-methods} command filters the methods, printing only those
11689 which match the regular-expression @var{regexp}.
11692 @cindex reloading symbols
11693 Some systems allow individual object files that make up your program to
11694 be replaced without stopping and restarting your program. For example,
11695 in VxWorks you can simply recompile a defective object file and keep on
11696 running. If you are running on one of these systems, you can allow
11697 @value{GDBN} to reload the symbols for automatically relinked modules:
11700 @kindex set symbol-reloading
11701 @item set symbol-reloading on
11702 Replace symbol definitions for the corresponding source file when an
11703 object file with a particular name is seen again.
11705 @item set symbol-reloading off
11706 Do not replace symbol definitions when encountering object files of the
11707 same name more than once. This is the default state; if you are not
11708 running on a system that permits automatic relinking of modules, you
11709 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11710 may discard symbols when linking large programs, that may contain
11711 several modules (from different directories or libraries) with the same
11714 @kindex show symbol-reloading
11715 @item show symbol-reloading
11716 Show the current @code{on} or @code{off} setting.
11719 @cindex opaque data types
11720 @kindex set opaque-type-resolution
11721 @item set opaque-type-resolution on
11722 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11723 declared as a pointer to a @code{struct}, @code{class}, or
11724 @code{union}---for example, @code{struct MyType *}---that is used in one
11725 source file although the full declaration of @code{struct MyType} is in
11726 another source file. The default is on.
11728 A change in the setting of this subcommand will not take effect until
11729 the next time symbols for a file are loaded.
11731 @item set opaque-type-resolution off
11732 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11733 is printed as follows:
11735 @{<no data fields>@}
11738 @kindex show opaque-type-resolution
11739 @item show opaque-type-resolution
11740 Show whether opaque types are resolved or not.
11742 @kindex set print symbol-loading
11743 @cindex print messages when symbols are loaded
11744 @item set print symbol-loading
11745 @itemx set print symbol-loading on
11746 @itemx set print symbol-loading off
11747 The @code{set print symbol-loading} command allows you to enable or
11748 disable printing of messages when @value{GDBN} loads symbols.
11749 By default, these messages will be printed, and normally this is what
11750 you want. Disabling these messages is useful when debugging applications
11751 with lots of shared libraries where the quantity of output can be more
11752 annoying than useful.
11754 @kindex show print symbol-loading
11755 @item show print symbol-loading
11756 Show whether messages will be printed when @value{GDBN} loads symbols.
11758 @kindex maint print symbols
11759 @cindex symbol dump
11760 @kindex maint print psymbols
11761 @cindex partial symbol dump
11762 @item maint print symbols @var{filename}
11763 @itemx maint print psymbols @var{filename}
11764 @itemx maint print msymbols @var{filename}
11765 Write a dump of debugging symbol data into the file @var{filename}.
11766 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11767 symbols with debugging data are included. If you use @samp{maint print
11768 symbols}, @value{GDBN} includes all the symbols for which it has already
11769 collected full details: that is, @var{filename} reflects symbols for
11770 only those files whose symbols @value{GDBN} has read. You can use the
11771 command @code{info sources} to find out which files these are. If you
11772 use @samp{maint print psymbols} instead, the dump shows information about
11773 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11774 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11775 @samp{maint print msymbols} dumps just the minimal symbol information
11776 required for each object file from which @value{GDBN} has read some symbols.
11777 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11778 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11780 @kindex maint info symtabs
11781 @kindex maint info psymtabs
11782 @cindex listing @value{GDBN}'s internal symbol tables
11783 @cindex symbol tables, listing @value{GDBN}'s internal
11784 @cindex full symbol tables, listing @value{GDBN}'s internal
11785 @cindex partial symbol tables, listing @value{GDBN}'s internal
11786 @item maint info symtabs @r{[} @var{regexp} @r{]}
11787 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11789 List the @code{struct symtab} or @code{struct partial_symtab}
11790 structures whose names match @var{regexp}. If @var{regexp} is not
11791 given, list them all. The output includes expressions which you can
11792 copy into a @value{GDBN} debugging this one to examine a particular
11793 structure in more detail. For example:
11796 (@value{GDBP}) maint info psymtabs dwarf2read
11797 @{ objfile /home/gnu/build/gdb/gdb
11798 ((struct objfile *) 0x82e69d0)
11799 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11800 ((struct partial_symtab *) 0x8474b10)
11803 text addresses 0x814d3c8 -- 0x8158074
11804 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11805 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11806 dependencies (none)
11809 (@value{GDBP}) maint info symtabs
11813 We see that there is one partial symbol table whose filename contains
11814 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11815 and we see that @value{GDBN} has not read in any symtabs yet at all.
11816 If we set a breakpoint on a function, that will cause @value{GDBN} to
11817 read the symtab for the compilation unit containing that function:
11820 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11821 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11823 (@value{GDBP}) maint info symtabs
11824 @{ objfile /home/gnu/build/gdb/gdb
11825 ((struct objfile *) 0x82e69d0)
11826 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11827 ((struct symtab *) 0x86c1f38)
11830 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11831 linetable ((struct linetable *) 0x8370fa0)
11832 debugformat DWARF 2
11841 @chapter Altering Execution
11843 Once you think you have found an error in your program, you might want to
11844 find out for certain whether correcting the apparent error would lead to
11845 correct results in the rest of the run. You can find the answer by
11846 experiment, using the @value{GDBN} features for altering execution of the
11849 For example, you can store new values into variables or memory
11850 locations, give your program a signal, restart it at a different
11851 address, or even return prematurely from a function.
11854 * Assignment:: Assignment to variables
11855 * Jumping:: Continuing at a different address
11856 * Signaling:: Giving your program a signal
11857 * Returning:: Returning from a function
11858 * Calling:: Calling your program's functions
11859 * Patching:: Patching your program
11863 @section Assignment to Variables
11866 @cindex setting variables
11867 To alter the value of a variable, evaluate an assignment expression.
11868 @xref{Expressions, ,Expressions}. For example,
11875 stores the value 4 into the variable @code{x}, and then prints the
11876 value of the assignment expression (which is 4).
11877 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11878 information on operators in supported languages.
11880 @kindex set variable
11881 @cindex variables, setting
11882 If you are not interested in seeing the value of the assignment, use the
11883 @code{set} command instead of the @code{print} command. @code{set} is
11884 really the same as @code{print} except that the expression's value is
11885 not printed and is not put in the value history (@pxref{Value History,
11886 ,Value History}). The expression is evaluated only for its effects.
11888 If the beginning of the argument string of the @code{set} command
11889 appears identical to a @code{set} subcommand, use the @code{set
11890 variable} command instead of just @code{set}. This command is identical
11891 to @code{set} except for its lack of subcommands. For example, if your
11892 program has a variable @code{width}, you get an error if you try to set
11893 a new value with just @samp{set width=13}, because @value{GDBN} has the
11894 command @code{set width}:
11897 (@value{GDBP}) whatis width
11899 (@value{GDBP}) p width
11901 (@value{GDBP}) set width=47
11902 Invalid syntax in expression.
11906 The invalid expression, of course, is @samp{=47}. In
11907 order to actually set the program's variable @code{width}, use
11910 (@value{GDBP}) set var width=47
11913 Because the @code{set} command has many subcommands that can conflict
11914 with the names of program variables, it is a good idea to use the
11915 @code{set variable} command instead of just @code{set}. For example, if
11916 your program has a variable @code{g}, you run into problems if you try
11917 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11918 the command @code{set gnutarget}, abbreviated @code{set g}:
11922 (@value{GDBP}) whatis g
11926 (@value{GDBP}) set g=4
11930 The program being debugged has been started already.
11931 Start it from the beginning? (y or n) y
11932 Starting program: /home/smith/cc_progs/a.out
11933 "/home/smith/cc_progs/a.out": can't open to read symbols:
11934 Invalid bfd target.
11935 (@value{GDBP}) show g
11936 The current BFD target is "=4".
11941 The program variable @code{g} did not change, and you silently set the
11942 @code{gnutarget} to an invalid value. In order to set the variable
11946 (@value{GDBP}) set var g=4
11949 @value{GDBN} allows more implicit conversions in assignments than C; you can
11950 freely store an integer value into a pointer variable or vice versa,
11951 and you can convert any structure to any other structure that is the
11952 same length or shorter.
11953 @comment FIXME: how do structs align/pad in these conversions?
11954 @comment /doc@cygnus.com 18dec1990
11956 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11957 construct to generate a value of specified type at a specified address
11958 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11959 to memory location @code{0x83040} as an integer (which implies a certain size
11960 and representation in memory), and
11963 set @{int@}0x83040 = 4
11967 stores the value 4 into that memory location.
11970 @section Continuing at a Different Address
11972 Ordinarily, when you continue your program, you do so at the place where
11973 it stopped, with the @code{continue} command. You can instead continue at
11974 an address of your own choosing, with the following commands:
11978 @item jump @var{linespec}
11979 @itemx jump @var{location}
11980 Resume execution at line @var{linespec} or at address given by
11981 @var{location}. Execution stops again immediately if there is a
11982 breakpoint there. @xref{Specify Location}, for a description of the
11983 different forms of @var{linespec} and @var{location}. It is common
11984 practice to use the @code{tbreak} command in conjunction with
11985 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
11987 The @code{jump} command does not change the current stack frame, or
11988 the stack pointer, or the contents of any memory location or any
11989 register other than the program counter. If line @var{linespec} is in
11990 a different function from the one currently executing, the results may
11991 be bizarre if the two functions expect different patterns of arguments or
11992 of local variables. For this reason, the @code{jump} command requests
11993 confirmation if the specified line is not in the function currently
11994 executing. However, even bizarre results are predictable if you are
11995 well acquainted with the machine-language code of your program.
11998 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11999 On many systems, you can get much the same effect as the @code{jump}
12000 command by storing a new value into the register @code{$pc}. The
12001 difference is that this does not start your program running; it only
12002 changes the address of where it @emph{will} run when you continue. For
12010 makes the next @code{continue} command or stepping command execute at
12011 address @code{0x485}, rather than at the address where your program stopped.
12012 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12014 The most common occasion to use the @code{jump} command is to back
12015 up---perhaps with more breakpoints set---over a portion of a program
12016 that has already executed, in order to examine its execution in more
12021 @section Giving your Program a Signal
12022 @cindex deliver a signal to a program
12026 @item signal @var{signal}
12027 Resume execution where your program stopped, but immediately give it the
12028 signal @var{signal}. @var{signal} can be the name or the number of a
12029 signal. For example, on many systems @code{signal 2} and @code{signal
12030 SIGINT} are both ways of sending an interrupt signal.
12032 Alternatively, if @var{signal} is zero, continue execution without
12033 giving a signal. This is useful when your program stopped on account of
12034 a signal and would ordinary see the signal when resumed with the
12035 @code{continue} command; @samp{signal 0} causes it to resume without a
12038 @code{signal} does not repeat when you press @key{RET} a second time
12039 after executing the command.
12043 Invoking the @code{signal} command is not the same as invoking the
12044 @code{kill} utility from the shell. Sending a signal with @code{kill}
12045 causes @value{GDBN} to decide what to do with the signal depending on
12046 the signal handling tables (@pxref{Signals}). The @code{signal} command
12047 passes the signal directly to your program.
12051 @section Returning from a Function
12054 @cindex returning from a function
12057 @itemx return @var{expression}
12058 You can cancel execution of a function call with the @code{return}
12059 command. If you give an
12060 @var{expression} argument, its value is used as the function's return
12064 When you use @code{return}, @value{GDBN} discards the selected stack frame
12065 (and all frames within it). You can think of this as making the
12066 discarded frame return prematurely. If you wish to specify a value to
12067 be returned, give that value as the argument to @code{return}.
12069 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12070 Frame}), and any other frames inside of it, leaving its caller as the
12071 innermost remaining frame. That frame becomes selected. The
12072 specified value is stored in the registers used for returning values
12075 The @code{return} command does not resume execution; it leaves the
12076 program stopped in the state that would exist if the function had just
12077 returned. In contrast, the @code{finish} command (@pxref{Continuing
12078 and Stepping, ,Continuing and Stepping}) resumes execution until the
12079 selected stack frame returns naturally.
12082 @section Calling Program Functions
12085 @cindex calling functions
12086 @cindex inferior functions, calling
12087 @item print @var{expr}
12088 Evaluate the expression @var{expr} and display the resulting value.
12089 @var{expr} may include calls to functions in the program being
12093 @item call @var{expr}
12094 Evaluate the expression @var{expr} without displaying @code{void}
12097 You can use this variant of the @code{print} command if you want to
12098 execute a function from your program that does not return anything
12099 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12100 with @code{void} returned values that @value{GDBN} will otherwise
12101 print. If the result is not void, it is printed and saved in the
12105 It is possible for the function you call via the @code{print} or
12106 @code{call} command to generate a signal (e.g., if there's a bug in
12107 the function, or if you passed it incorrect arguments). What happens
12108 in that case is controlled by the @code{set unwindonsignal} command.
12111 @item set unwindonsignal
12112 @kindex set unwindonsignal
12113 @cindex unwind stack in called functions
12114 @cindex call dummy stack unwinding
12115 Set unwinding of the stack if a signal is received while in a function
12116 that @value{GDBN} called in the program being debugged. If set to on,
12117 @value{GDBN} unwinds the stack it created for the call and restores
12118 the context to what it was before the call. If set to off (the
12119 default), @value{GDBN} stops in the frame where the signal was
12122 @item show unwindonsignal
12123 @kindex show unwindonsignal
12124 Show the current setting of stack unwinding in the functions called by
12128 @cindex weak alias functions
12129 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12130 for another function. In such case, @value{GDBN} might not pick up
12131 the type information, including the types of the function arguments,
12132 which causes @value{GDBN} to call the inferior function incorrectly.
12133 As a result, the called function will function erroneously and may
12134 even crash. A solution to that is to use the name of the aliased
12138 @section Patching Programs
12140 @cindex patching binaries
12141 @cindex writing into executables
12142 @cindex writing into corefiles
12144 By default, @value{GDBN} opens the file containing your program's
12145 executable code (or the corefile) read-only. This prevents accidental
12146 alterations to machine code; but it also prevents you from intentionally
12147 patching your program's binary.
12149 If you'd like to be able to patch the binary, you can specify that
12150 explicitly with the @code{set write} command. For example, you might
12151 want to turn on internal debugging flags, or even to make emergency
12157 @itemx set write off
12158 If you specify @samp{set write on}, @value{GDBN} opens executable and
12159 core files for both reading and writing; if you specify @samp{set write
12160 off} (the default), @value{GDBN} opens them read-only.
12162 If you have already loaded a file, you must load it again (using the
12163 @code{exec-file} or @code{core-file} command) after changing @code{set
12164 write}, for your new setting to take effect.
12168 Display whether executable files and core files are opened for writing
12169 as well as reading.
12173 @chapter @value{GDBN} Files
12175 @value{GDBN} needs to know the file name of the program to be debugged,
12176 both in order to read its symbol table and in order to start your
12177 program. To debug a core dump of a previous run, you must also tell
12178 @value{GDBN} the name of the core dump file.
12181 * Files:: Commands to specify files
12182 * Separate Debug Files:: Debugging information in separate files
12183 * Symbol Errors:: Errors reading symbol files
12187 @section Commands to Specify Files
12189 @cindex symbol table
12190 @cindex core dump file
12192 You may want to specify executable and core dump file names. The usual
12193 way to do this is at start-up time, using the arguments to
12194 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12195 Out of @value{GDBN}}).
12197 Occasionally it is necessary to change to a different file during a
12198 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12199 specify a file you want to use. Or you are debugging a remote target
12200 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12201 Program}). In these situations the @value{GDBN} commands to specify
12202 new files are useful.
12205 @cindex executable file
12207 @item file @var{filename}
12208 Use @var{filename} as the program to be debugged. It is read for its
12209 symbols and for the contents of pure memory. It is also the program
12210 executed when you use the @code{run} command. If you do not specify a
12211 directory and the file is not found in the @value{GDBN} working directory,
12212 @value{GDBN} uses the environment variable @code{PATH} as a list of
12213 directories to search, just as the shell does when looking for a program
12214 to run. You can change the value of this variable, for both @value{GDBN}
12215 and your program, using the @code{path} command.
12217 @cindex unlinked object files
12218 @cindex patching object files
12219 You can load unlinked object @file{.o} files into @value{GDBN} using
12220 the @code{file} command. You will not be able to ``run'' an object
12221 file, but you can disassemble functions and inspect variables. Also,
12222 if the underlying BFD functionality supports it, you could use
12223 @kbd{gdb -write} to patch object files using this technique. Note
12224 that @value{GDBN} can neither interpret nor modify relocations in this
12225 case, so branches and some initialized variables will appear to go to
12226 the wrong place. But this feature is still handy from time to time.
12229 @code{file} with no argument makes @value{GDBN} discard any information it
12230 has on both executable file and the symbol table.
12233 @item exec-file @r{[} @var{filename} @r{]}
12234 Specify that the program to be run (but not the symbol table) is found
12235 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12236 if necessary to locate your program. Omitting @var{filename} means to
12237 discard information on the executable file.
12239 @kindex symbol-file
12240 @item symbol-file @r{[} @var{filename} @r{]}
12241 Read symbol table information from file @var{filename}. @code{PATH} is
12242 searched when necessary. Use the @code{file} command to get both symbol
12243 table and program to run from the same file.
12245 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12246 program's symbol table.
12248 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12249 some breakpoints and auto-display expressions. This is because they may
12250 contain pointers to the internal data recording symbols and data types,
12251 which are part of the old symbol table data being discarded inside
12254 @code{symbol-file} does not repeat if you press @key{RET} again after
12257 When @value{GDBN} is configured for a particular environment, it
12258 understands debugging information in whatever format is the standard
12259 generated for that environment; you may use either a @sc{gnu} compiler, or
12260 other compilers that adhere to the local conventions.
12261 Best results are usually obtained from @sc{gnu} compilers; for example,
12262 using @code{@value{NGCC}} you can generate debugging information for
12265 For most kinds of object files, with the exception of old SVR3 systems
12266 using COFF, the @code{symbol-file} command does not normally read the
12267 symbol table in full right away. Instead, it scans the symbol table
12268 quickly to find which source files and which symbols are present. The
12269 details are read later, one source file at a time, as they are needed.
12271 The purpose of this two-stage reading strategy is to make @value{GDBN}
12272 start up faster. For the most part, it is invisible except for
12273 occasional pauses while the symbol table details for a particular source
12274 file are being read. (The @code{set verbose} command can turn these
12275 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12276 Warnings and Messages}.)
12278 We have not implemented the two-stage strategy for COFF yet. When the
12279 symbol table is stored in COFF format, @code{symbol-file} reads the
12280 symbol table data in full right away. Note that ``stabs-in-COFF''
12281 still does the two-stage strategy, since the debug info is actually
12285 @cindex reading symbols immediately
12286 @cindex symbols, reading immediately
12287 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12288 @itemx file @var{filename} @r{[} -readnow @r{]}
12289 You can override the @value{GDBN} two-stage strategy for reading symbol
12290 tables by using the @samp{-readnow} option with any of the commands that
12291 load symbol table information, if you want to be sure @value{GDBN} has the
12292 entire symbol table available.
12294 @c FIXME: for now no mention of directories, since this seems to be in
12295 @c flux. 13mar1992 status is that in theory GDB would look either in
12296 @c current dir or in same dir as myprog; but issues like competing
12297 @c GDB's, or clutter in system dirs, mean that in practice right now
12298 @c only current dir is used. FFish says maybe a special GDB hierarchy
12299 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12303 @item core-file @r{[}@var{filename}@r{]}
12305 Specify the whereabouts of a core dump file to be used as the ``contents
12306 of memory''. Traditionally, core files contain only some parts of the
12307 address space of the process that generated them; @value{GDBN} can access the
12308 executable file itself for other parts.
12310 @code{core-file} with no argument specifies that no core file is
12313 Note that the core file is ignored when your program is actually running
12314 under @value{GDBN}. So, if you have been running your program and you
12315 wish to debug a core file instead, you must kill the subprocess in which
12316 the program is running. To do this, use the @code{kill} command
12317 (@pxref{Kill Process, ,Killing the Child Process}).
12319 @kindex add-symbol-file
12320 @cindex dynamic linking
12321 @item add-symbol-file @var{filename} @var{address}
12322 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12323 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12324 The @code{add-symbol-file} command reads additional symbol table
12325 information from the file @var{filename}. You would use this command
12326 when @var{filename} has been dynamically loaded (by some other means)
12327 into the program that is running. @var{address} should be the memory
12328 address at which the file has been loaded; @value{GDBN} cannot figure
12329 this out for itself. You can additionally specify an arbitrary number
12330 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12331 section name and base address for that section. You can specify any
12332 @var{address} as an expression.
12334 The symbol table of the file @var{filename} is added to the symbol table
12335 originally read with the @code{symbol-file} command. You can use the
12336 @code{add-symbol-file} command any number of times; the new symbol data
12337 thus read keeps adding to the old. To discard all old symbol data
12338 instead, use the @code{symbol-file} command without any arguments.
12340 @cindex relocatable object files, reading symbols from
12341 @cindex object files, relocatable, reading symbols from
12342 @cindex reading symbols from relocatable object files
12343 @cindex symbols, reading from relocatable object files
12344 @cindex @file{.o} files, reading symbols from
12345 Although @var{filename} is typically a shared library file, an
12346 executable file, or some other object file which has been fully
12347 relocated for loading into a process, you can also load symbolic
12348 information from relocatable @file{.o} files, as long as:
12352 the file's symbolic information refers only to linker symbols defined in
12353 that file, not to symbols defined by other object files,
12355 every section the file's symbolic information refers to has actually
12356 been loaded into the inferior, as it appears in the file, and
12358 you can determine the address at which every section was loaded, and
12359 provide these to the @code{add-symbol-file} command.
12363 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12364 relocatable files into an already running program; such systems
12365 typically make the requirements above easy to meet. However, it's
12366 important to recognize that many native systems use complex link
12367 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12368 assembly, for example) that make the requirements difficult to meet. In
12369 general, one cannot assume that using @code{add-symbol-file} to read a
12370 relocatable object file's symbolic information will have the same effect
12371 as linking the relocatable object file into the program in the normal
12374 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12376 @kindex add-symbol-file-from-memory
12377 @cindex @code{syscall DSO}
12378 @cindex load symbols from memory
12379 @item add-symbol-file-from-memory @var{address}
12380 Load symbols from the given @var{address} in a dynamically loaded
12381 object file whose image is mapped directly into the inferior's memory.
12382 For example, the Linux kernel maps a @code{syscall DSO} into each
12383 process's address space; this DSO provides kernel-specific code for
12384 some system calls. The argument can be any expression whose
12385 evaluation yields the address of the file's shared object file header.
12386 For this command to work, you must have used @code{symbol-file} or
12387 @code{exec-file} commands in advance.
12389 @kindex add-shared-symbol-files
12391 @item add-shared-symbol-files @var{library-file}
12392 @itemx assf @var{library-file}
12393 The @code{add-shared-symbol-files} command can currently be used only
12394 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12395 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12396 @value{GDBN} automatically looks for shared libraries, however if
12397 @value{GDBN} does not find yours, you can invoke
12398 @code{add-shared-symbol-files}. It takes one argument: the shared
12399 library's file name. @code{assf} is a shorthand alias for
12400 @code{add-shared-symbol-files}.
12403 @item section @var{section} @var{addr}
12404 The @code{section} command changes the base address of the named
12405 @var{section} of the exec file to @var{addr}. This can be used if the
12406 exec file does not contain section addresses, (such as in the
12407 @code{a.out} format), or when the addresses specified in the file
12408 itself are wrong. Each section must be changed separately. The
12409 @code{info files} command, described below, lists all the sections and
12413 @kindex info target
12416 @code{info files} and @code{info target} are synonymous; both print the
12417 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12418 including the names of the executable and core dump files currently in
12419 use by @value{GDBN}, and the files from which symbols were loaded. The
12420 command @code{help target} lists all possible targets rather than
12423 @kindex maint info sections
12424 @item maint info sections
12425 Another command that can give you extra information about program sections
12426 is @code{maint info sections}. In addition to the section information
12427 displayed by @code{info files}, this command displays the flags and file
12428 offset of each section in the executable and core dump files. In addition,
12429 @code{maint info sections} provides the following command options (which
12430 may be arbitrarily combined):
12434 Display sections for all loaded object files, including shared libraries.
12435 @item @var{sections}
12436 Display info only for named @var{sections}.
12437 @item @var{section-flags}
12438 Display info only for sections for which @var{section-flags} are true.
12439 The section flags that @value{GDBN} currently knows about are:
12442 Section will have space allocated in the process when loaded.
12443 Set for all sections except those containing debug information.
12445 Section will be loaded from the file into the child process memory.
12446 Set for pre-initialized code and data, clear for @code{.bss} sections.
12448 Section needs to be relocated before loading.
12450 Section cannot be modified by the child process.
12452 Section contains executable code only.
12454 Section contains data only (no executable code).
12456 Section will reside in ROM.
12458 Section contains data for constructor/destructor lists.
12460 Section is not empty.
12462 An instruction to the linker to not output the section.
12463 @item COFF_SHARED_LIBRARY
12464 A notification to the linker that the section contains
12465 COFF shared library information.
12467 Section contains common symbols.
12470 @kindex set trust-readonly-sections
12471 @cindex read-only sections
12472 @item set trust-readonly-sections on
12473 Tell @value{GDBN} that readonly sections in your object file
12474 really are read-only (i.e.@: that their contents will not change).
12475 In that case, @value{GDBN} can fetch values from these sections
12476 out of the object file, rather than from the target program.
12477 For some targets (notably embedded ones), this can be a significant
12478 enhancement to debugging performance.
12480 The default is off.
12482 @item set trust-readonly-sections off
12483 Tell @value{GDBN} not to trust readonly sections. This means that
12484 the contents of the section might change while the program is running,
12485 and must therefore be fetched from the target when needed.
12487 @item show trust-readonly-sections
12488 Show the current setting of trusting readonly sections.
12491 All file-specifying commands allow both absolute and relative file names
12492 as arguments. @value{GDBN} always converts the file name to an absolute file
12493 name and remembers it that way.
12495 @cindex shared libraries
12496 @anchor{Shared Libraries}
12497 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12498 and IBM RS/6000 AIX shared libraries.
12500 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12501 shared libraries. @xref{Expat}.
12503 @value{GDBN} automatically loads symbol definitions from shared libraries
12504 when you use the @code{run} command, or when you examine a core file.
12505 (Before you issue the @code{run} command, @value{GDBN} does not understand
12506 references to a function in a shared library, however---unless you are
12507 debugging a core file).
12509 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12510 automatically loads the symbols at the time of the @code{shl_load} call.
12512 @c FIXME: some @value{GDBN} release may permit some refs to undef
12513 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12514 @c FIXME...lib; check this from time to time when updating manual
12516 There are times, however, when you may wish to not automatically load
12517 symbol definitions from shared libraries, such as when they are
12518 particularly large or there are many of them.
12520 To control the automatic loading of shared library symbols, use the
12524 @kindex set auto-solib-add
12525 @item set auto-solib-add @var{mode}
12526 If @var{mode} is @code{on}, symbols from all shared object libraries
12527 will be loaded automatically when the inferior begins execution, you
12528 attach to an independently started inferior, or when the dynamic linker
12529 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12530 is @code{off}, symbols must be loaded manually, using the
12531 @code{sharedlibrary} command. The default value is @code{on}.
12533 @cindex memory used for symbol tables
12534 If your program uses lots of shared libraries with debug info that
12535 takes large amounts of memory, you can decrease the @value{GDBN}
12536 memory footprint by preventing it from automatically loading the
12537 symbols from shared libraries. To that end, type @kbd{set
12538 auto-solib-add off} before running the inferior, then load each
12539 library whose debug symbols you do need with @kbd{sharedlibrary
12540 @var{regexp}}, where @var{regexp} is a regular expression that matches
12541 the libraries whose symbols you want to be loaded.
12543 @kindex show auto-solib-add
12544 @item show auto-solib-add
12545 Display the current autoloading mode.
12548 @cindex load shared library
12549 To explicitly load shared library symbols, use the @code{sharedlibrary}
12553 @kindex info sharedlibrary
12556 @itemx info sharedlibrary
12557 Print the names of the shared libraries which are currently loaded.
12559 @kindex sharedlibrary
12561 @item sharedlibrary @var{regex}
12562 @itemx share @var{regex}
12563 Load shared object library symbols for files matching a
12564 Unix regular expression.
12565 As with files loaded automatically, it only loads shared libraries
12566 required by your program for a core file or after typing @code{run}. If
12567 @var{regex} is omitted all shared libraries required by your program are
12570 @item nosharedlibrary
12571 @kindex nosharedlibrary
12572 @cindex unload symbols from shared libraries
12573 Unload all shared object library symbols. This discards all symbols
12574 that have been loaded from all shared libraries. Symbols from shared
12575 libraries that were loaded by explicit user requests are not
12579 Sometimes you may wish that @value{GDBN} stops and gives you control
12580 when any of shared library events happen. Use the @code{set
12581 stop-on-solib-events} command for this:
12584 @item set stop-on-solib-events
12585 @kindex set stop-on-solib-events
12586 This command controls whether @value{GDBN} should give you control
12587 when the dynamic linker notifies it about some shared library event.
12588 The most common event of interest is loading or unloading of a new
12591 @item show stop-on-solib-events
12592 @kindex show stop-on-solib-events
12593 Show whether @value{GDBN} stops and gives you control when shared
12594 library events happen.
12597 Shared libraries are also supported in many cross or remote debugging
12598 configurations. A copy of the target's libraries need to be present on the
12599 host system; they need to be the same as the target libraries, although the
12600 copies on the target can be stripped as long as the copies on the host are
12603 @cindex where to look for shared libraries
12604 For remote debugging, you need to tell @value{GDBN} where the target
12605 libraries are, so that it can load the correct copies---otherwise, it
12606 may try to load the host's libraries. @value{GDBN} has two variables
12607 to specify the search directories for target libraries.
12610 @cindex prefix for shared library file names
12611 @cindex system root, alternate
12612 @kindex set solib-absolute-prefix
12613 @kindex set sysroot
12614 @item set sysroot @var{path}
12615 Use @var{path} as the system root for the program being debugged. Any
12616 absolute shared library paths will be prefixed with @var{path}; many
12617 runtime loaders store the absolute paths to the shared library in the
12618 target program's memory. If you use @code{set sysroot} to find shared
12619 libraries, they need to be laid out in the same way that they are on
12620 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12623 The @code{set solib-absolute-prefix} command is an alias for @code{set
12626 @cindex default system root
12627 @cindex @samp{--with-sysroot}
12628 You can set the default system root by using the configure-time
12629 @samp{--with-sysroot} option. If the system root is inside
12630 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12631 @samp{--exec-prefix}), then the default system root will be updated
12632 automatically if the installed @value{GDBN} is moved to a new
12635 @kindex show sysroot
12637 Display the current shared library prefix.
12639 @kindex set solib-search-path
12640 @item set solib-search-path @var{path}
12641 If this variable is set, @var{path} is a colon-separated list of
12642 directories to search for shared libraries. @samp{solib-search-path}
12643 is used after @samp{sysroot} fails to locate the library, or if the
12644 path to the library is relative instead of absolute. If you want to
12645 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12646 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12647 finding your host's libraries. @samp{sysroot} is preferred; setting
12648 it to a nonexistent directory may interfere with automatic loading
12649 of shared library symbols.
12651 @kindex show solib-search-path
12652 @item show solib-search-path
12653 Display the current shared library search path.
12657 @node Separate Debug Files
12658 @section Debugging Information in Separate Files
12659 @cindex separate debugging information files
12660 @cindex debugging information in separate files
12661 @cindex @file{.debug} subdirectories
12662 @cindex debugging information directory, global
12663 @cindex global debugging information directory
12664 @cindex build ID, and separate debugging files
12665 @cindex @file{.build-id} directory
12667 @value{GDBN} allows you to put a program's debugging information in a
12668 file separate from the executable itself, in a way that allows
12669 @value{GDBN} to find and load the debugging information automatically.
12670 Since debugging information can be very large---sometimes larger
12671 than the executable code itself---some systems distribute debugging
12672 information for their executables in separate files, which users can
12673 install only when they need to debug a problem.
12675 @value{GDBN} supports two ways of specifying the separate debug info
12680 The executable contains a @dfn{debug link} that specifies the name of
12681 the separate debug info file. The separate debug file's name is
12682 usually @file{@var{executable}.debug}, where @var{executable} is the
12683 name of the corresponding executable file without leading directories
12684 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12685 debug link specifies a CRC32 checksum for the debug file, which
12686 @value{GDBN} uses to validate that the executable and the debug file
12687 came from the same build.
12690 The executable contains a @dfn{build ID}, a unique bit string that is
12691 also present in the corresponding debug info file. (This is supported
12692 only on some operating systems, notably those which use the ELF format
12693 for binary files and the @sc{gnu} Binutils.) For more details about
12694 this feature, see the description of the @option{--build-id}
12695 command-line option in @ref{Options, , Command Line Options, ld.info,
12696 The GNU Linker}. The debug info file's name is not specified
12697 explicitly by the build ID, but can be computed from the build ID, see
12701 Depending on the way the debug info file is specified, @value{GDBN}
12702 uses two different methods of looking for the debug file:
12706 For the ``debug link'' method, @value{GDBN} looks up the named file in
12707 the directory of the executable file, then in a subdirectory of that
12708 directory named @file{.debug}, and finally under the global debug
12709 directory, in a subdirectory whose name is identical to the leading
12710 directories of the executable's absolute file name.
12713 For the ``build ID'' method, @value{GDBN} looks in the
12714 @file{.build-id} subdirectory of the global debug directory for a file
12715 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12716 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12717 are the rest of the bit string. (Real build ID strings are 32 or more
12718 hex characters, not 10.)
12721 So, for example, suppose you ask @value{GDBN} to debug
12722 @file{/usr/bin/ls}, which has a debug link that specifies the
12723 file @file{ls.debug}, and a build ID whose value in hex is
12724 @code{abcdef1234}. If the global debug directory is
12725 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12726 debug information files, in the indicated order:
12730 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12732 @file{/usr/bin/ls.debug}
12734 @file{/usr/bin/.debug/ls.debug}
12736 @file{/usr/lib/debug/usr/bin/ls.debug}.
12739 You can set the global debugging info directory's name, and view the
12740 name @value{GDBN} is currently using.
12744 @kindex set debug-file-directory
12745 @item set debug-file-directory @var{directory}
12746 Set the directory which @value{GDBN} searches for separate debugging
12747 information files to @var{directory}.
12749 @kindex show debug-file-directory
12750 @item show debug-file-directory
12751 Show the directory @value{GDBN} searches for separate debugging
12756 @cindex @code{.gnu_debuglink} sections
12757 @cindex debug link sections
12758 A debug link is a special section of the executable file named
12759 @code{.gnu_debuglink}. The section must contain:
12763 A filename, with any leading directory components removed, followed by
12766 zero to three bytes of padding, as needed to reach the next four-byte
12767 boundary within the section, and
12769 a four-byte CRC checksum, stored in the same endianness used for the
12770 executable file itself. The checksum is computed on the debugging
12771 information file's full contents by the function given below, passing
12772 zero as the @var{crc} argument.
12775 Any executable file format can carry a debug link, as long as it can
12776 contain a section named @code{.gnu_debuglink} with the contents
12779 @cindex @code{.note.gnu.build-id} sections
12780 @cindex build ID sections
12781 The build ID is a special section in the executable file (and in other
12782 ELF binary files that @value{GDBN} may consider). This section is
12783 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12784 It contains unique identification for the built files---the ID remains
12785 the same across multiple builds of the same build tree. The default
12786 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12787 content for the build ID string. The same section with an identical
12788 value is present in the original built binary with symbols, in its
12789 stripped variant, and in the separate debugging information file.
12791 The debugging information file itself should be an ordinary
12792 executable, containing a full set of linker symbols, sections, and
12793 debugging information. The sections of the debugging information file
12794 should have the same names, addresses, and sizes as the original file,
12795 but they need not contain any data---much like a @code{.bss} section
12796 in an ordinary executable.
12798 The @sc{gnu} binary utilities (Binutils) package includes the
12799 @samp{objcopy} utility that can produce
12800 the separated executable / debugging information file pairs using the
12801 following commands:
12804 @kbd{objcopy --only-keep-debug foo foo.debug}
12809 These commands remove the debugging
12810 information from the executable file @file{foo} and place it in the file
12811 @file{foo.debug}. You can use the first, second or both methods to link the
12816 The debug link method needs the following additional command to also leave
12817 behind a debug link in @file{foo}:
12820 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12823 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12824 a version of the @code{strip} command such that the command @kbd{strip foo -f
12825 foo.debug} has the same functionality as the two @code{objcopy} commands and
12826 the @code{ln -s} command above, together.
12829 Build ID gets embedded into the main executable using @code{ld --build-id} or
12830 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12831 compatibility fixes for debug files separation are present in @sc{gnu} binary
12832 utilities (Binutils) package since version 2.18.
12837 Since there are many different ways to compute CRC's for the debug
12838 link (different polynomials, reversals, byte ordering, etc.), the
12839 simplest way to describe the CRC used in @code{.gnu_debuglink}
12840 sections is to give the complete code for a function that computes it:
12842 @kindex gnu_debuglink_crc32
12845 gnu_debuglink_crc32 (unsigned long crc,
12846 unsigned char *buf, size_t len)
12848 static const unsigned long crc32_table[256] =
12850 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12851 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12852 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12853 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12854 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12855 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12856 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12857 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12858 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12859 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12860 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12861 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12862 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12863 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12864 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12865 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12866 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12867 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12868 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12869 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12870 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12871 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12872 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12873 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12874 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12875 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12876 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12877 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12878 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12879 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12880 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12881 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12882 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12883 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12884 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12885 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12886 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12887 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12888 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12889 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12890 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12891 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12892 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12893 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12894 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12895 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12896 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12897 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12898 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12899 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12900 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12903 unsigned char *end;
12905 crc = ~crc & 0xffffffff;
12906 for (end = buf + len; buf < end; ++buf)
12907 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12908 return ~crc & 0xffffffff;
12913 This computation does not apply to the ``build ID'' method.
12916 @node Symbol Errors
12917 @section Errors Reading Symbol Files
12919 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12920 such as symbol types it does not recognize, or known bugs in compiler
12921 output. By default, @value{GDBN} does not notify you of such problems, since
12922 they are relatively common and primarily of interest to people
12923 debugging compilers. If you are interested in seeing information
12924 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12925 only one message about each such type of problem, no matter how many
12926 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12927 to see how many times the problems occur, with the @code{set
12928 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12931 The messages currently printed, and their meanings, include:
12934 @item inner block not inside outer block in @var{symbol}
12936 The symbol information shows where symbol scopes begin and end
12937 (such as at the start of a function or a block of statements). This
12938 error indicates that an inner scope block is not fully contained
12939 in its outer scope blocks.
12941 @value{GDBN} circumvents the problem by treating the inner block as if it had
12942 the same scope as the outer block. In the error message, @var{symbol}
12943 may be shown as ``@code{(don't know)}'' if the outer block is not a
12946 @item block at @var{address} out of order
12948 The symbol information for symbol scope blocks should occur in
12949 order of increasing addresses. This error indicates that it does not
12952 @value{GDBN} does not circumvent this problem, and has trouble
12953 locating symbols in the source file whose symbols it is reading. (You
12954 can often determine what source file is affected by specifying
12955 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12958 @item bad block start address patched
12960 The symbol information for a symbol scope block has a start address
12961 smaller than the address of the preceding source line. This is known
12962 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12964 @value{GDBN} circumvents the problem by treating the symbol scope block as
12965 starting on the previous source line.
12967 @item bad string table offset in symbol @var{n}
12970 Symbol number @var{n} contains a pointer into the string table which is
12971 larger than the size of the string table.
12973 @value{GDBN} circumvents the problem by considering the symbol to have the
12974 name @code{foo}, which may cause other problems if many symbols end up
12977 @item unknown symbol type @code{0x@var{nn}}
12979 The symbol information contains new data types that @value{GDBN} does
12980 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12981 uncomprehended information, in hexadecimal.
12983 @value{GDBN} circumvents the error by ignoring this symbol information.
12984 This usually allows you to debug your program, though certain symbols
12985 are not accessible. If you encounter such a problem and feel like
12986 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12987 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12988 and examine @code{*bufp} to see the symbol.
12990 @item stub type has NULL name
12992 @value{GDBN} could not find the full definition for a struct or class.
12994 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12995 The symbol information for a C@t{++} member function is missing some
12996 information that recent versions of the compiler should have output for
12999 @item info mismatch between compiler and debugger
13001 @value{GDBN} could not parse a type specification output by the compiler.
13006 @chapter Specifying a Debugging Target
13008 @cindex debugging target
13009 A @dfn{target} is the execution environment occupied by your program.
13011 Often, @value{GDBN} runs in the same host environment as your program;
13012 in that case, the debugging target is specified as a side effect when
13013 you use the @code{file} or @code{core} commands. When you need more
13014 flexibility---for example, running @value{GDBN} on a physically separate
13015 host, or controlling a standalone system over a serial port or a
13016 realtime system over a TCP/IP connection---you can use the @code{target}
13017 command to specify one of the target types configured for @value{GDBN}
13018 (@pxref{Target Commands, ,Commands for Managing Targets}).
13020 @cindex target architecture
13021 It is possible to build @value{GDBN} for several different @dfn{target
13022 architectures}. When @value{GDBN} is built like that, you can choose
13023 one of the available architectures with the @kbd{set architecture}
13027 @kindex set architecture
13028 @kindex show architecture
13029 @item set architecture @var{arch}
13030 This command sets the current target architecture to @var{arch}. The
13031 value of @var{arch} can be @code{"auto"}, in addition to one of the
13032 supported architectures.
13034 @item show architecture
13035 Show the current target architecture.
13037 @item set processor
13039 @kindex set processor
13040 @kindex show processor
13041 These are alias commands for, respectively, @code{set architecture}
13042 and @code{show architecture}.
13046 * Active Targets:: Active targets
13047 * Target Commands:: Commands for managing targets
13048 * Byte Order:: Choosing target byte order
13051 @node Active Targets
13052 @section Active Targets
13054 @cindex stacking targets
13055 @cindex active targets
13056 @cindex multiple targets
13058 There are three classes of targets: processes, core files, and
13059 executable files. @value{GDBN} can work concurrently on up to three
13060 active targets, one in each class. This allows you to (for example)
13061 start a process and inspect its activity without abandoning your work on
13064 For example, if you execute @samp{gdb a.out}, then the executable file
13065 @code{a.out} is the only active target. If you designate a core file as
13066 well---presumably from a prior run that crashed and coredumped---then
13067 @value{GDBN} has two active targets and uses them in tandem, looking
13068 first in the corefile target, then in the executable file, to satisfy
13069 requests for memory addresses. (Typically, these two classes of target
13070 are complementary, since core files contain only a program's
13071 read-write memory---variables and so on---plus machine status, while
13072 executable files contain only the program text and initialized data.)
13074 When you type @code{run}, your executable file becomes an active process
13075 target as well. When a process target is active, all @value{GDBN}
13076 commands requesting memory addresses refer to that target; addresses in
13077 an active core file or executable file target are obscured while the
13078 process target is active.
13080 Use the @code{core-file} and @code{exec-file} commands to select a new
13081 core file or executable target (@pxref{Files, ,Commands to Specify
13082 Files}). To specify as a target a process that is already running, use
13083 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13086 @node Target Commands
13087 @section Commands for Managing Targets
13090 @item target @var{type} @var{parameters}
13091 Connects the @value{GDBN} host environment to a target machine or
13092 process. A target is typically a protocol for talking to debugging
13093 facilities. You use the argument @var{type} to specify the type or
13094 protocol of the target machine.
13096 Further @var{parameters} are interpreted by the target protocol, but
13097 typically include things like device names or host names to connect
13098 with, process numbers, and baud rates.
13100 The @code{target} command does not repeat if you press @key{RET} again
13101 after executing the command.
13103 @kindex help target
13105 Displays the names of all targets available. To display targets
13106 currently selected, use either @code{info target} or @code{info files}
13107 (@pxref{Files, ,Commands to Specify Files}).
13109 @item help target @var{name}
13110 Describe a particular target, including any parameters necessary to
13113 @kindex set gnutarget
13114 @item set gnutarget @var{args}
13115 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13116 knows whether it is reading an @dfn{executable},
13117 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13118 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13119 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13122 @emph{Warning:} To specify a file format with @code{set gnutarget},
13123 you must know the actual BFD name.
13127 @xref{Files, , Commands to Specify Files}.
13129 @kindex show gnutarget
13130 @item show gnutarget
13131 Use the @code{show gnutarget} command to display what file format
13132 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13133 @value{GDBN} will determine the file format for each file automatically,
13134 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13137 @cindex common targets
13138 Here are some common targets (available, or not, depending on the GDB
13143 @item target exec @var{program}
13144 @cindex executable file target
13145 An executable file. @samp{target exec @var{program}} is the same as
13146 @samp{exec-file @var{program}}.
13148 @item target core @var{filename}
13149 @cindex core dump file target
13150 A core dump file. @samp{target core @var{filename}} is the same as
13151 @samp{core-file @var{filename}}.
13153 @item target remote @var{medium}
13154 @cindex remote target
13155 A remote system connected to @value{GDBN} via a serial line or network
13156 connection. This command tells @value{GDBN} to use its own remote
13157 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13159 For example, if you have a board connected to @file{/dev/ttya} on the
13160 machine running @value{GDBN}, you could say:
13163 target remote /dev/ttya
13166 @code{target remote} supports the @code{load} command. This is only
13167 useful if you have some other way of getting the stub to the target
13168 system, and you can put it somewhere in memory where it won't get
13169 clobbered by the download.
13172 @cindex built-in simulator target
13173 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13181 works; however, you cannot assume that a specific memory map, device
13182 drivers, or even basic I/O is available, although some simulators do
13183 provide these. For info about any processor-specific simulator details,
13184 see the appropriate section in @ref{Embedded Processors, ,Embedded
13189 Some configurations may include these targets as well:
13193 @item target nrom @var{dev}
13194 @cindex NetROM ROM emulator target
13195 NetROM ROM emulator. This target only supports downloading.
13199 Different targets are available on different configurations of @value{GDBN};
13200 your configuration may have more or fewer targets.
13202 Many remote targets require you to download the executable's code once
13203 you've successfully established a connection. You may wish to control
13204 various aspects of this process.
13209 @kindex set hash@r{, for remote monitors}
13210 @cindex hash mark while downloading
13211 This command controls whether a hash mark @samp{#} is displayed while
13212 downloading a file to the remote monitor. If on, a hash mark is
13213 displayed after each S-record is successfully downloaded to the
13217 @kindex show hash@r{, for remote monitors}
13218 Show the current status of displaying the hash mark.
13220 @item set debug monitor
13221 @kindex set debug monitor
13222 @cindex display remote monitor communications
13223 Enable or disable display of communications messages between
13224 @value{GDBN} and the remote monitor.
13226 @item show debug monitor
13227 @kindex show debug monitor
13228 Show the current status of displaying communications between
13229 @value{GDBN} and the remote monitor.
13234 @kindex load @var{filename}
13235 @item load @var{filename}
13237 Depending on what remote debugging facilities are configured into
13238 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13239 is meant to make @var{filename} (an executable) available for debugging
13240 on the remote system---by downloading, or dynamic linking, for example.
13241 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13242 the @code{add-symbol-file} command.
13244 If your @value{GDBN} does not have a @code{load} command, attempting to
13245 execute it gets the error message ``@code{You can't do that when your
13246 target is @dots{}}''
13248 The file is loaded at whatever address is specified in the executable.
13249 For some object file formats, you can specify the load address when you
13250 link the program; for other formats, like a.out, the object file format
13251 specifies a fixed address.
13252 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13254 Depending on the remote side capabilities, @value{GDBN} may be able to
13255 load programs into flash memory.
13257 @code{load} does not repeat if you press @key{RET} again after using it.
13261 @section Choosing Target Byte Order
13263 @cindex choosing target byte order
13264 @cindex target byte order
13266 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13267 offer the ability to run either big-endian or little-endian byte
13268 orders. Usually the executable or symbol will include a bit to
13269 designate the endian-ness, and you will not need to worry about
13270 which to use. However, you may still find it useful to adjust
13271 @value{GDBN}'s idea of processor endian-ness manually.
13275 @item set endian big
13276 Instruct @value{GDBN} to assume the target is big-endian.
13278 @item set endian little
13279 Instruct @value{GDBN} to assume the target is little-endian.
13281 @item set endian auto
13282 Instruct @value{GDBN} to use the byte order associated with the
13286 Display @value{GDBN}'s current idea of the target byte order.
13290 Note that these commands merely adjust interpretation of symbolic
13291 data on the host, and that they have absolutely no effect on the
13295 @node Remote Debugging
13296 @chapter Debugging Remote Programs
13297 @cindex remote debugging
13299 If you are trying to debug a program running on a machine that cannot run
13300 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13301 For example, you might use remote debugging on an operating system kernel,
13302 or on a small system which does not have a general purpose operating system
13303 powerful enough to run a full-featured debugger.
13305 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13306 to make this work with particular debugging targets. In addition,
13307 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13308 but not specific to any particular target system) which you can use if you
13309 write the remote stubs---the code that runs on the remote system to
13310 communicate with @value{GDBN}.
13312 Other remote targets may be available in your
13313 configuration of @value{GDBN}; use @code{help target} to list them.
13316 * Connecting:: Connecting to a remote target
13317 * File Transfer:: Sending files to a remote system
13318 * Server:: Using the gdbserver program
13319 * Remote Configuration:: Remote configuration
13320 * Remote Stub:: Implementing a remote stub
13324 @section Connecting to a Remote Target
13326 On the @value{GDBN} host machine, you will need an unstripped copy of
13327 your program, since @value{GDBN} needs symbol and debugging information.
13328 Start up @value{GDBN} as usual, using the name of the local copy of your
13329 program as the first argument.
13331 @cindex @code{target remote}
13332 @value{GDBN} can communicate with the target over a serial line, or
13333 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13334 each case, @value{GDBN} uses the same protocol for debugging your
13335 program; only the medium carrying the debugging packets varies. The
13336 @code{target remote} command establishes a connection to the target.
13337 Its arguments indicate which medium to use:
13341 @item target remote @var{serial-device}
13342 @cindex serial line, @code{target remote}
13343 Use @var{serial-device} to communicate with the target. For example,
13344 to use a serial line connected to the device named @file{/dev/ttyb}:
13347 target remote /dev/ttyb
13350 If you're using a serial line, you may want to give @value{GDBN} the
13351 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13352 (@pxref{Remote Configuration, set remotebaud}) before the
13353 @code{target} command.
13355 @item target remote @code{@var{host}:@var{port}}
13356 @itemx target remote @code{tcp:@var{host}:@var{port}}
13357 @cindex @acronym{TCP} port, @code{target remote}
13358 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13359 The @var{host} may be either a host name or a numeric @acronym{IP}
13360 address; @var{port} must be a decimal number. The @var{host} could be
13361 the target machine itself, if it is directly connected to the net, or
13362 it might be a terminal server which in turn has a serial line to the
13365 For example, to connect to port 2828 on a terminal server named
13369 target remote manyfarms:2828
13372 If your remote target is actually running on the same machine as your
13373 debugger session (e.g.@: a simulator for your target running on the
13374 same host), you can omit the hostname. For example, to connect to
13375 port 1234 on your local machine:
13378 target remote :1234
13382 Note that the colon is still required here.
13384 @item target remote @code{udp:@var{host}:@var{port}}
13385 @cindex @acronym{UDP} port, @code{target remote}
13386 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13387 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13390 target remote udp:manyfarms:2828
13393 When using a @acronym{UDP} connection for remote debugging, you should
13394 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13395 can silently drop packets on busy or unreliable networks, which will
13396 cause havoc with your debugging session.
13398 @item target remote | @var{command}
13399 @cindex pipe, @code{target remote} to
13400 Run @var{command} in the background and communicate with it using a
13401 pipe. The @var{command} is a shell command, to be parsed and expanded
13402 by the system's command shell, @code{/bin/sh}; it should expect remote
13403 protocol packets on its standard input, and send replies on its
13404 standard output. You could use this to run a stand-alone simulator
13405 that speaks the remote debugging protocol, to make net connections
13406 using programs like @code{ssh}, or for other similar tricks.
13408 If @var{command} closes its standard output (perhaps by exiting),
13409 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13410 program has already exited, this will have no effect.)
13414 Once the connection has been established, you can use all the usual
13415 commands to examine and change data. The remote program is already
13416 running; you can use @kbd{step} and @kbd{continue}, and you do not
13417 need to use @kbd{run}.
13419 @cindex interrupting remote programs
13420 @cindex remote programs, interrupting
13421 Whenever @value{GDBN} is waiting for the remote program, if you type the
13422 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13423 program. This may or may not succeed, depending in part on the hardware
13424 and the serial drivers the remote system uses. If you type the
13425 interrupt character once again, @value{GDBN} displays this prompt:
13428 Interrupted while waiting for the program.
13429 Give up (and stop debugging it)? (y or n)
13432 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13433 (If you decide you want to try again later, you can use @samp{target
13434 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13435 goes back to waiting.
13438 @kindex detach (remote)
13440 When you have finished debugging the remote program, you can use the
13441 @code{detach} command to release it from @value{GDBN} control.
13442 Detaching from the target normally resumes its execution, but the results
13443 will depend on your particular remote stub. After the @code{detach}
13444 command, @value{GDBN} is free to connect to another target.
13448 The @code{disconnect} command behaves like @code{detach}, except that
13449 the target is generally not resumed. It will wait for @value{GDBN}
13450 (this instance or another one) to connect and continue debugging. After
13451 the @code{disconnect} command, @value{GDBN} is again free to connect to
13454 @cindex send command to remote monitor
13455 @cindex extend @value{GDBN} for remote targets
13456 @cindex add new commands for external monitor
13458 @item monitor @var{cmd}
13459 This command allows you to send arbitrary commands directly to the
13460 remote monitor. Since @value{GDBN} doesn't care about the commands it
13461 sends like this, this command is the way to extend @value{GDBN}---you
13462 can add new commands that only the external monitor will understand
13466 @node File Transfer
13467 @section Sending files to a remote system
13468 @cindex remote target, file transfer
13469 @cindex file transfer
13470 @cindex sending files to remote systems
13472 Some remote targets offer the ability to transfer files over the same
13473 connection used to communicate with @value{GDBN}. This is convenient
13474 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13475 running @code{gdbserver} over a network interface. For other targets,
13476 e.g.@: embedded devices with only a single serial port, this may be
13477 the only way to upload or download files.
13479 Not all remote targets support these commands.
13483 @item remote put @var{hostfile} @var{targetfile}
13484 Copy file @var{hostfile} from the host system (the machine running
13485 @value{GDBN}) to @var{targetfile} on the target system.
13488 @item remote get @var{targetfile} @var{hostfile}
13489 Copy file @var{targetfile} from the target system to @var{hostfile}
13490 on the host system.
13492 @kindex remote delete
13493 @item remote delete @var{targetfile}
13494 Delete @var{targetfile} from the target system.
13499 @section Using the @code{gdbserver} Program
13502 @cindex remote connection without stubs
13503 @code{gdbserver} is a control program for Unix-like systems, which
13504 allows you to connect your program with a remote @value{GDBN} via
13505 @code{target remote}---but without linking in the usual debugging stub.
13507 @code{gdbserver} is not a complete replacement for the debugging stubs,
13508 because it requires essentially the same operating-system facilities
13509 that @value{GDBN} itself does. In fact, a system that can run
13510 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13511 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13512 because it is a much smaller program than @value{GDBN} itself. It is
13513 also easier to port than all of @value{GDBN}, so you may be able to get
13514 started more quickly on a new system by using @code{gdbserver}.
13515 Finally, if you develop code for real-time systems, you may find that
13516 the tradeoffs involved in real-time operation make it more convenient to
13517 do as much development work as possible on another system, for example
13518 by cross-compiling. You can use @code{gdbserver} to make a similar
13519 choice for debugging.
13521 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13522 or a TCP connection, using the standard @value{GDBN} remote serial
13526 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13527 Do not run @code{gdbserver} connected to any public network; a
13528 @value{GDBN} connection to @code{gdbserver} provides access to the
13529 target system with the same privileges as the user running
13533 @subsection Running @code{gdbserver}
13534 @cindex arguments, to @code{gdbserver}
13536 Run @code{gdbserver} on the target system. You need a copy of the
13537 program you want to debug, including any libraries it requires.
13538 @code{gdbserver} does not need your program's symbol table, so you can
13539 strip the program if necessary to save space. @value{GDBN} on the host
13540 system does all the symbol handling.
13542 To use the server, you must tell it how to communicate with @value{GDBN};
13543 the name of your program; and the arguments for your program. The usual
13547 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13550 @var{comm} is either a device name (to use a serial line) or a TCP
13551 hostname and portnumber. For example, to debug Emacs with the argument
13552 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13556 target> gdbserver /dev/com1 emacs foo.txt
13559 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13562 To use a TCP connection instead of a serial line:
13565 target> gdbserver host:2345 emacs foo.txt
13568 The only difference from the previous example is the first argument,
13569 specifying that you are communicating with the host @value{GDBN} via
13570 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13571 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13572 (Currently, the @samp{host} part is ignored.) You can choose any number
13573 you want for the port number as long as it does not conflict with any
13574 TCP ports already in use on the target system (for example, @code{23} is
13575 reserved for @code{telnet}).@footnote{If you choose a port number that
13576 conflicts with another service, @code{gdbserver} prints an error message
13577 and exits.} You must use the same port number with the host @value{GDBN}
13578 @code{target remote} command.
13580 @subsubsection Attaching to a Running Program
13582 On some targets, @code{gdbserver} can also attach to running programs.
13583 This is accomplished via the @code{--attach} argument. The syntax is:
13586 target> gdbserver --attach @var{comm} @var{pid}
13589 @var{pid} is the process ID of a currently running process. It isn't necessary
13590 to point @code{gdbserver} at a binary for the running process.
13593 @cindex attach to a program by name
13594 You can debug processes by name instead of process ID if your target has the
13595 @code{pidof} utility:
13598 target> gdbserver --attach @var{comm} `pidof @var{program}`
13601 In case more than one copy of @var{program} is running, or @var{program}
13602 has multiple threads, most versions of @code{pidof} support the
13603 @code{-s} option to only return the first process ID.
13605 @subsubsection Multi-Process Mode for @code{gdbserver}
13606 @cindex gdbserver, multiple processes
13607 @cindex multiple processes with gdbserver
13609 When you connect to @code{gdbserver} using @code{target remote},
13610 @code{gdbserver} debugs the specified program only once. When the
13611 program exits, or you detach from it, @value{GDBN} closes the connection
13612 and @code{gdbserver} exits.
13614 If you connect using @kbd{target extended-remote}, @code{gdbserver}
13615 enters multi-process mode. When the debugged program exits, or you
13616 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
13617 though no program is running. The @code{run} and @code{attach}
13618 commands instruct @code{gdbserver} to run or attach to a new program.
13619 The @code{run} command uses @code{set remote exec-file} (@pxref{set
13620 remote exec-file}) to select the program to run. Command line
13621 arguments are supported, except for wildcard expansion and I/O
13622 redirection (@pxref{Arguments}).
13624 To start @code{gdbserver} without supplying an initial command to run
13625 or process ID to attach, use the @option{--multi} command line option.
13626 Then you can connect using @kbd{target extended-remote} and start
13627 the program you want to debug.
13629 @code{gdbserver} does not automatically exit in multi-process mode.
13630 You can terminate it by using @code{monitor exit}
13631 (@pxref{Monitor Commands for gdbserver}).
13633 @subsubsection Other Command-Line Arguments for @code{gdbserver}
13635 You can include @option{--debug} on the @code{gdbserver} command line.
13636 @code{gdbserver} will display extra status information about the debugging
13637 process. This option is intended for @code{gdbserver} development and
13638 for bug reports to the developers.
13640 The @option{--wrapper} option specifies a wrapper to launch programs
13641 for debugging. The option should be followed by the name of the
13642 wrapper, then any command-line arguments to pass to the wrapper, then
13643 @kbd{--} indicating the end of the wrapper arguments.
13645 @code{gdbserver} runs the specified wrapper program with a combined
13646 command line including the wrapper arguments, then the name of the
13647 program to debug, then any arguments to the program. The wrapper
13648 runs until it executes your program, and then @value{GDBN} gains control.
13650 You can use any program that eventually calls @code{execve} with
13651 its arguments as a wrapper. Several standard Unix utilities do
13652 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
13653 with @code{exec "$@@"} will also work.
13655 For example, you can use @code{env} to pass an environment variable to
13656 the debugged program, without setting the variable in @code{gdbserver}'s
13660 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
13663 @subsection Connecting to @code{gdbserver}
13665 Run @value{GDBN} on the host system.
13667 First make sure you have the necessary symbol files. Load symbols for
13668 your application using the @code{file} command before you connect. Use
13669 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
13670 was compiled with the correct sysroot using @code{--with-sysroot}).
13672 The symbol file and target libraries must exactly match the executable
13673 and libraries on the target, with one exception: the files on the host
13674 system should not be stripped, even if the files on the target system
13675 are. Mismatched or missing files will lead to confusing results
13676 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
13677 files may also prevent @code{gdbserver} from debugging multi-threaded
13680 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
13681 For TCP connections, you must start up @code{gdbserver} prior to using
13682 the @code{target remote} command. Otherwise you may get an error whose
13683 text depends on the host system, but which usually looks something like
13684 @samp{Connection refused}. Don't use the @code{load}
13685 command in @value{GDBN} when using @code{gdbserver}, since the program is
13686 already on the target.
13688 @subsection Monitor Commands for @code{gdbserver}
13689 @cindex monitor commands, for @code{gdbserver}
13690 @anchor{Monitor Commands for gdbserver}
13692 During a @value{GDBN} session using @code{gdbserver}, you can use the
13693 @code{monitor} command to send special requests to @code{gdbserver}.
13694 Here are the available commands.
13698 List the available monitor commands.
13700 @item monitor set debug 0
13701 @itemx monitor set debug 1
13702 Disable or enable general debugging messages.
13704 @item monitor set remote-debug 0
13705 @itemx monitor set remote-debug 1
13706 Disable or enable specific debugging messages associated with the remote
13707 protocol (@pxref{Remote Protocol}).
13710 Tell gdbserver to exit immediately. This command should be followed by
13711 @code{disconnect} to close the debugging session. @code{gdbserver} will
13712 detach from any attached processes and kill any processes it created.
13713 Use @code{monitor exit} to terminate @code{gdbserver} at the end
13714 of a multi-process mode debug session.
13718 @node Remote Configuration
13719 @section Remote Configuration
13722 @kindex show remote
13723 This section documents the configuration options available when
13724 debugging remote programs. For the options related to the File I/O
13725 extensions of the remote protocol, see @ref{system,
13726 system-call-allowed}.
13729 @item set remoteaddresssize @var{bits}
13730 @cindex address size for remote targets
13731 @cindex bits in remote address
13732 Set the maximum size of address in a memory packet to the specified
13733 number of bits. @value{GDBN} will mask off the address bits above
13734 that number, when it passes addresses to the remote target. The
13735 default value is the number of bits in the target's address.
13737 @item show remoteaddresssize
13738 Show the current value of remote address size in bits.
13740 @item set remotebaud @var{n}
13741 @cindex baud rate for remote targets
13742 Set the baud rate for the remote serial I/O to @var{n} baud. The
13743 value is used to set the speed of the serial port used for debugging
13746 @item show remotebaud
13747 Show the current speed of the remote connection.
13749 @item set remotebreak
13750 @cindex interrupt remote programs
13751 @cindex BREAK signal instead of Ctrl-C
13752 @anchor{set remotebreak}
13753 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13754 when you type @kbd{Ctrl-c} to interrupt the program running
13755 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13756 character instead. The default is off, since most remote systems
13757 expect to see @samp{Ctrl-C} as the interrupt signal.
13759 @item show remotebreak
13760 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13761 interrupt the remote program.
13763 @item set remoteflow on
13764 @itemx set remoteflow off
13765 @kindex set remoteflow
13766 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13767 on the serial port used to communicate to the remote target.
13769 @item show remoteflow
13770 @kindex show remoteflow
13771 Show the current setting of hardware flow control.
13773 @item set remotelogbase @var{base}
13774 Set the base (a.k.a.@: radix) of logging serial protocol
13775 communications to @var{base}. Supported values of @var{base} are:
13776 @code{ascii}, @code{octal}, and @code{hex}. The default is
13779 @item show remotelogbase
13780 Show the current setting of the radix for logging remote serial
13783 @item set remotelogfile @var{file}
13784 @cindex record serial communications on file
13785 Record remote serial communications on the named @var{file}. The
13786 default is not to record at all.
13788 @item show remotelogfile.
13789 Show the current setting of the file name on which to record the
13790 serial communications.
13792 @item set remotetimeout @var{num}
13793 @cindex timeout for serial communications
13794 @cindex remote timeout
13795 Set the timeout limit to wait for the remote target to respond to
13796 @var{num} seconds. The default is 2 seconds.
13798 @item show remotetimeout
13799 Show the current number of seconds to wait for the remote target
13802 @cindex limit hardware breakpoints and watchpoints
13803 @cindex remote target, limit break- and watchpoints
13804 @anchor{set remote hardware-watchpoint-limit}
13805 @anchor{set remote hardware-breakpoint-limit}
13806 @item set remote hardware-watchpoint-limit @var{limit}
13807 @itemx set remote hardware-breakpoint-limit @var{limit}
13808 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13809 watchpoints. A limit of -1, the default, is treated as unlimited.
13811 @item set remote exec-file @var{filename}
13812 @itemx show remote exec-file
13813 @anchor{set remote exec-file}
13814 @cindex executable file, for remote target
13815 Select the file used for @code{run} with @code{target
13816 extended-remote}. This should be set to a filename valid on the
13817 target system. If it is not set, the target will use a default
13818 filename (e.g.@: the last program run).
13821 @cindex remote packets, enabling and disabling
13822 The @value{GDBN} remote protocol autodetects the packets supported by
13823 your debugging stub. If you need to override the autodetection, you
13824 can use these commands to enable or disable individual packets. Each
13825 packet can be set to @samp{on} (the remote target supports this
13826 packet), @samp{off} (the remote target does not support this packet),
13827 or @samp{auto} (detect remote target support for this packet). They
13828 all default to @samp{auto}. For more information about each packet,
13829 see @ref{Remote Protocol}.
13831 During normal use, you should not have to use any of these commands.
13832 If you do, that may be a bug in your remote debugging stub, or a bug
13833 in @value{GDBN}. You may want to report the problem to the
13834 @value{GDBN} developers.
13836 For each packet @var{name}, the command to enable or disable the
13837 packet is @code{set remote @var{name}-packet}. The available settings
13840 @multitable @columnfractions 0.28 0.32 0.25
13843 @tab Related Features
13845 @item @code{fetch-register}
13847 @tab @code{info registers}
13849 @item @code{set-register}
13853 @item @code{binary-download}
13855 @tab @code{load}, @code{set}
13857 @item @code{read-aux-vector}
13858 @tab @code{qXfer:auxv:read}
13859 @tab @code{info auxv}
13861 @item @code{symbol-lookup}
13862 @tab @code{qSymbol}
13863 @tab Detecting multiple threads
13865 @item @code{attach}
13866 @tab @code{vAttach}
13869 @item @code{verbose-resume}
13871 @tab Stepping or resuming multiple threads
13877 @item @code{software-breakpoint}
13881 @item @code{hardware-breakpoint}
13885 @item @code{write-watchpoint}
13889 @item @code{read-watchpoint}
13893 @item @code{access-watchpoint}
13897 @item @code{target-features}
13898 @tab @code{qXfer:features:read}
13899 @tab @code{set architecture}
13901 @item @code{library-info}
13902 @tab @code{qXfer:libraries:read}
13903 @tab @code{info sharedlibrary}
13905 @item @code{memory-map}
13906 @tab @code{qXfer:memory-map:read}
13907 @tab @code{info mem}
13909 @item @code{read-spu-object}
13910 @tab @code{qXfer:spu:read}
13911 @tab @code{info spu}
13913 @item @code{write-spu-object}
13914 @tab @code{qXfer:spu:write}
13915 @tab @code{info spu}
13917 @item @code{get-thread-local-@*storage-address}
13918 @tab @code{qGetTLSAddr}
13919 @tab Displaying @code{__thread} variables
13921 @item @code{search-memory}
13922 @tab @code{qSearch:memory}
13925 @item @code{supported-packets}
13926 @tab @code{qSupported}
13927 @tab Remote communications parameters
13929 @item @code{pass-signals}
13930 @tab @code{QPassSignals}
13931 @tab @code{handle @var{signal}}
13933 @item @code{hostio-close-packet}
13934 @tab @code{vFile:close}
13935 @tab @code{remote get}, @code{remote put}
13937 @item @code{hostio-open-packet}
13938 @tab @code{vFile:open}
13939 @tab @code{remote get}, @code{remote put}
13941 @item @code{hostio-pread-packet}
13942 @tab @code{vFile:pread}
13943 @tab @code{remote get}, @code{remote put}
13945 @item @code{hostio-pwrite-packet}
13946 @tab @code{vFile:pwrite}
13947 @tab @code{remote get}, @code{remote put}
13949 @item @code{hostio-unlink-packet}
13950 @tab @code{vFile:unlink}
13951 @tab @code{remote delete}
13955 @section Implementing a Remote Stub
13957 @cindex debugging stub, example
13958 @cindex remote stub, example
13959 @cindex stub example, remote debugging
13960 The stub files provided with @value{GDBN} implement the target side of the
13961 communication protocol, and the @value{GDBN} side is implemented in the
13962 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13963 these subroutines to communicate, and ignore the details. (If you're
13964 implementing your own stub file, you can still ignore the details: start
13965 with one of the existing stub files. @file{sparc-stub.c} is the best
13966 organized, and therefore the easiest to read.)
13968 @cindex remote serial debugging, overview
13969 To debug a program running on another machine (the debugging
13970 @dfn{target} machine), you must first arrange for all the usual
13971 prerequisites for the program to run by itself. For example, for a C
13976 A startup routine to set up the C runtime environment; these usually
13977 have a name like @file{crt0}. The startup routine may be supplied by
13978 your hardware supplier, or you may have to write your own.
13981 A C subroutine library to support your program's
13982 subroutine calls, notably managing input and output.
13985 A way of getting your program to the other machine---for example, a
13986 download program. These are often supplied by the hardware
13987 manufacturer, but you may have to write your own from hardware
13991 The next step is to arrange for your program to use a serial port to
13992 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13993 machine). In general terms, the scheme looks like this:
13997 @value{GDBN} already understands how to use this protocol; when everything
13998 else is set up, you can simply use the @samp{target remote} command
13999 (@pxref{Targets,,Specifying a Debugging Target}).
14001 @item On the target,
14002 you must link with your program a few special-purpose subroutines that
14003 implement the @value{GDBN} remote serial protocol. The file containing these
14004 subroutines is called a @dfn{debugging stub}.
14006 On certain remote targets, you can use an auxiliary program
14007 @code{gdbserver} instead of linking a stub into your program.
14008 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14011 The debugging stub is specific to the architecture of the remote
14012 machine; for example, use @file{sparc-stub.c} to debug programs on
14015 @cindex remote serial stub list
14016 These working remote stubs are distributed with @value{GDBN}:
14021 @cindex @file{i386-stub.c}
14024 For Intel 386 and compatible architectures.
14027 @cindex @file{m68k-stub.c}
14028 @cindex Motorola 680x0
14030 For Motorola 680x0 architectures.
14033 @cindex @file{sh-stub.c}
14036 For Renesas SH architectures.
14039 @cindex @file{sparc-stub.c}
14041 For @sc{sparc} architectures.
14043 @item sparcl-stub.c
14044 @cindex @file{sparcl-stub.c}
14047 For Fujitsu @sc{sparclite} architectures.
14051 The @file{README} file in the @value{GDBN} distribution may list other
14052 recently added stubs.
14055 * Stub Contents:: What the stub can do for you
14056 * Bootstrapping:: What you must do for the stub
14057 * Debug Session:: Putting it all together
14060 @node Stub Contents
14061 @subsection What the Stub Can Do for You
14063 @cindex remote serial stub
14064 The debugging stub for your architecture supplies these three
14068 @item set_debug_traps
14069 @findex set_debug_traps
14070 @cindex remote serial stub, initialization
14071 This routine arranges for @code{handle_exception} to run when your
14072 program stops. You must call this subroutine explicitly near the
14073 beginning of your program.
14075 @item handle_exception
14076 @findex handle_exception
14077 @cindex remote serial stub, main routine
14078 This is the central workhorse, but your program never calls it
14079 explicitly---the setup code arranges for @code{handle_exception} to
14080 run when a trap is triggered.
14082 @code{handle_exception} takes control when your program stops during
14083 execution (for example, on a breakpoint), and mediates communications
14084 with @value{GDBN} on the host machine. This is where the communications
14085 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14086 representative on the target machine. It begins by sending summary
14087 information on the state of your program, then continues to execute,
14088 retrieving and transmitting any information @value{GDBN} needs, until you
14089 execute a @value{GDBN} command that makes your program resume; at that point,
14090 @code{handle_exception} returns control to your own code on the target
14094 @cindex @code{breakpoint} subroutine, remote
14095 Use this auxiliary subroutine to make your program contain a
14096 breakpoint. Depending on the particular situation, this may be the only
14097 way for @value{GDBN} to get control. For instance, if your target
14098 machine has some sort of interrupt button, you won't need to call this;
14099 pressing the interrupt button transfers control to
14100 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14101 simply receiving characters on the serial port may also trigger a trap;
14102 again, in that situation, you don't need to call @code{breakpoint} from
14103 your own program---simply running @samp{target remote} from the host
14104 @value{GDBN} session gets control.
14106 Call @code{breakpoint} if none of these is true, or if you simply want
14107 to make certain your program stops at a predetermined point for the
14108 start of your debugging session.
14111 @node Bootstrapping
14112 @subsection What You Must Do for the Stub
14114 @cindex remote stub, support routines
14115 The debugging stubs that come with @value{GDBN} are set up for a particular
14116 chip architecture, but they have no information about the rest of your
14117 debugging target machine.
14119 First of all you need to tell the stub how to communicate with the
14123 @item int getDebugChar()
14124 @findex getDebugChar
14125 Write this subroutine to read a single character from the serial port.
14126 It may be identical to @code{getchar} for your target system; a
14127 different name is used to allow you to distinguish the two if you wish.
14129 @item void putDebugChar(int)
14130 @findex putDebugChar
14131 Write this subroutine to write a single character to the serial port.
14132 It may be identical to @code{putchar} for your target system; a
14133 different name is used to allow you to distinguish the two if you wish.
14136 @cindex control C, and remote debugging
14137 @cindex interrupting remote targets
14138 If you want @value{GDBN} to be able to stop your program while it is
14139 running, you need to use an interrupt-driven serial driver, and arrange
14140 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14141 character). That is the character which @value{GDBN} uses to tell the
14142 remote system to stop.
14144 Getting the debugging target to return the proper status to @value{GDBN}
14145 probably requires changes to the standard stub; one quick and dirty way
14146 is to just execute a breakpoint instruction (the ``dirty'' part is that
14147 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14149 Other routines you need to supply are:
14152 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14153 @findex exceptionHandler
14154 Write this function to install @var{exception_address} in the exception
14155 handling tables. You need to do this because the stub does not have any
14156 way of knowing what the exception handling tables on your target system
14157 are like (for example, the processor's table might be in @sc{rom},
14158 containing entries which point to a table in @sc{ram}).
14159 @var{exception_number} is the exception number which should be changed;
14160 its meaning is architecture-dependent (for example, different numbers
14161 might represent divide by zero, misaligned access, etc). When this
14162 exception occurs, control should be transferred directly to
14163 @var{exception_address}, and the processor state (stack, registers,
14164 and so on) should be just as it is when a processor exception occurs. So if
14165 you want to use a jump instruction to reach @var{exception_address}, it
14166 should be a simple jump, not a jump to subroutine.
14168 For the 386, @var{exception_address} should be installed as an interrupt
14169 gate so that interrupts are masked while the handler runs. The gate
14170 should be at privilege level 0 (the most privileged level). The
14171 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14172 help from @code{exceptionHandler}.
14174 @item void flush_i_cache()
14175 @findex flush_i_cache
14176 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14177 instruction cache, if any, on your target machine. If there is no
14178 instruction cache, this subroutine may be a no-op.
14180 On target machines that have instruction caches, @value{GDBN} requires this
14181 function to make certain that the state of your program is stable.
14185 You must also make sure this library routine is available:
14188 @item void *memset(void *, int, int)
14190 This is the standard library function @code{memset} that sets an area of
14191 memory to a known value. If you have one of the free versions of
14192 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14193 either obtain it from your hardware manufacturer, or write your own.
14196 If you do not use the GNU C compiler, you may need other standard
14197 library subroutines as well; this varies from one stub to another,
14198 but in general the stubs are likely to use any of the common library
14199 subroutines which @code{@value{NGCC}} generates as inline code.
14202 @node Debug Session
14203 @subsection Putting it All Together
14205 @cindex remote serial debugging summary
14206 In summary, when your program is ready to debug, you must follow these
14211 Make sure you have defined the supporting low-level routines
14212 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14214 @code{getDebugChar}, @code{putDebugChar},
14215 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14219 Insert these lines near the top of your program:
14227 For the 680x0 stub only, you need to provide a variable called
14228 @code{exceptionHook}. Normally you just use:
14231 void (*exceptionHook)() = 0;
14235 but if before calling @code{set_debug_traps}, you set it to point to a
14236 function in your program, that function is called when
14237 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14238 error). The function indicated by @code{exceptionHook} is called with
14239 one parameter: an @code{int} which is the exception number.
14242 Compile and link together: your program, the @value{GDBN} debugging stub for
14243 your target architecture, and the supporting subroutines.
14246 Make sure you have a serial connection between your target machine and
14247 the @value{GDBN} host, and identify the serial port on the host.
14250 @c The "remote" target now provides a `load' command, so we should
14251 @c document that. FIXME.
14252 Download your program to your target machine (or get it there by
14253 whatever means the manufacturer provides), and start it.
14256 Start @value{GDBN} on the host, and connect to the target
14257 (@pxref{Connecting,,Connecting to a Remote Target}).
14261 @node Configurations
14262 @chapter Configuration-Specific Information
14264 While nearly all @value{GDBN} commands are available for all native and
14265 cross versions of the debugger, there are some exceptions. This chapter
14266 describes things that are only available in certain configurations.
14268 There are three major categories of configurations: native
14269 configurations, where the host and target are the same, embedded
14270 operating system configurations, which are usually the same for several
14271 different processor architectures, and bare embedded processors, which
14272 are quite different from each other.
14277 * Embedded Processors::
14284 This section describes details specific to particular native
14289 * BSD libkvm Interface:: Debugging BSD kernel memory images
14290 * SVR4 Process Information:: SVR4 process information
14291 * DJGPP Native:: Features specific to the DJGPP port
14292 * Cygwin Native:: Features specific to the Cygwin port
14293 * Hurd Native:: Features specific to @sc{gnu} Hurd
14294 * Neutrino:: Features specific to QNX Neutrino
14300 On HP-UX systems, if you refer to a function or variable name that
14301 begins with a dollar sign, @value{GDBN} searches for a user or system
14302 name first, before it searches for a convenience variable.
14305 @node BSD libkvm Interface
14306 @subsection BSD libkvm Interface
14309 @cindex kernel memory image
14310 @cindex kernel crash dump
14312 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14313 interface that provides a uniform interface for accessing kernel virtual
14314 memory images, including live systems and crash dumps. @value{GDBN}
14315 uses this interface to allow you to debug live kernels and kernel crash
14316 dumps on many native BSD configurations. This is implemented as a
14317 special @code{kvm} debugging target. For debugging a live system, load
14318 the currently running kernel into @value{GDBN} and connect to the
14322 (@value{GDBP}) @b{target kvm}
14325 For debugging crash dumps, provide the file name of the crash dump as an
14329 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14332 Once connected to the @code{kvm} target, the following commands are
14338 Set current context from the @dfn{Process Control Block} (PCB) address.
14341 Set current context from proc address. This command isn't available on
14342 modern FreeBSD systems.
14345 @node SVR4 Process Information
14346 @subsection SVR4 Process Information
14348 @cindex examine process image
14349 @cindex process info via @file{/proc}
14351 Many versions of SVR4 and compatible systems provide a facility called
14352 @samp{/proc} that can be used to examine the image of a running
14353 process using file-system subroutines. If @value{GDBN} is configured
14354 for an operating system with this facility, the command @code{info
14355 proc} is available to report information about the process running
14356 your program, or about any process running on your system. @code{info
14357 proc} works only on SVR4 systems that include the @code{procfs} code.
14358 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14359 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14365 @itemx info proc @var{process-id}
14366 Summarize available information about any running process. If a
14367 process ID is specified by @var{process-id}, display information about
14368 that process; otherwise display information about the program being
14369 debugged. The summary includes the debugged process ID, the command
14370 line used to invoke it, its current working directory, and its
14371 executable file's absolute file name.
14373 On some systems, @var{process-id} can be of the form
14374 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14375 within a process. If the optional @var{pid} part is missing, it means
14376 a thread from the process being debugged (the leading @samp{/} still
14377 needs to be present, or else @value{GDBN} will interpret the number as
14378 a process ID rather than a thread ID).
14380 @item info proc mappings
14381 @cindex memory address space mappings
14382 Report the memory address space ranges accessible in the program, with
14383 information on whether the process has read, write, or execute access
14384 rights to each range. On @sc{gnu}/Linux systems, each memory range
14385 includes the object file which is mapped to that range, instead of the
14386 memory access rights to that range.
14388 @item info proc stat
14389 @itemx info proc status
14390 @cindex process detailed status information
14391 These subcommands are specific to @sc{gnu}/Linux systems. They show
14392 the process-related information, including the user ID and group ID;
14393 how many threads are there in the process; its virtual memory usage;
14394 the signals that are pending, blocked, and ignored; its TTY; its
14395 consumption of system and user time; its stack size; its @samp{nice}
14396 value; etc. For more information, see the @samp{proc} man page
14397 (type @kbd{man 5 proc} from your shell prompt).
14399 @item info proc all
14400 Show all the information about the process described under all of the
14401 above @code{info proc} subcommands.
14404 @comment These sub-options of 'info proc' were not included when
14405 @comment procfs.c was re-written. Keep their descriptions around
14406 @comment against the day when someone finds the time to put them back in.
14407 @kindex info proc times
14408 @item info proc times
14409 Starting time, user CPU time, and system CPU time for your program and
14412 @kindex info proc id
14414 Report on the process IDs related to your program: its own process ID,
14415 the ID of its parent, the process group ID, and the session ID.
14418 @item set procfs-trace
14419 @kindex set procfs-trace
14420 @cindex @code{procfs} API calls
14421 This command enables and disables tracing of @code{procfs} API calls.
14423 @item show procfs-trace
14424 @kindex show procfs-trace
14425 Show the current state of @code{procfs} API call tracing.
14427 @item set procfs-file @var{file}
14428 @kindex set procfs-file
14429 Tell @value{GDBN} to write @code{procfs} API trace to the named
14430 @var{file}. @value{GDBN} appends the trace info to the previous
14431 contents of the file. The default is to display the trace on the
14434 @item show procfs-file
14435 @kindex show procfs-file
14436 Show the file to which @code{procfs} API trace is written.
14438 @item proc-trace-entry
14439 @itemx proc-trace-exit
14440 @itemx proc-untrace-entry
14441 @itemx proc-untrace-exit
14442 @kindex proc-trace-entry
14443 @kindex proc-trace-exit
14444 @kindex proc-untrace-entry
14445 @kindex proc-untrace-exit
14446 These commands enable and disable tracing of entries into and exits
14447 from the @code{syscall} interface.
14450 @kindex info pidlist
14451 @cindex process list, QNX Neutrino
14452 For QNX Neutrino only, this command displays the list of all the
14453 processes and all the threads within each process.
14456 @kindex info meminfo
14457 @cindex mapinfo list, QNX Neutrino
14458 For QNX Neutrino only, this command displays the list of all mapinfos.
14462 @subsection Features for Debugging @sc{djgpp} Programs
14463 @cindex @sc{djgpp} debugging
14464 @cindex native @sc{djgpp} debugging
14465 @cindex MS-DOS-specific commands
14468 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14469 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14470 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14471 top of real-mode DOS systems and their emulations.
14473 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14474 defines a few commands specific to the @sc{djgpp} port. This
14475 subsection describes those commands.
14480 This is a prefix of @sc{djgpp}-specific commands which print
14481 information about the target system and important OS structures.
14484 @cindex MS-DOS system info
14485 @cindex free memory information (MS-DOS)
14486 @item info dos sysinfo
14487 This command displays assorted information about the underlying
14488 platform: the CPU type and features, the OS version and flavor, the
14489 DPMI version, and the available conventional and DPMI memory.
14494 @cindex segment descriptor tables
14495 @cindex descriptor tables display
14497 @itemx info dos ldt
14498 @itemx info dos idt
14499 These 3 commands display entries from, respectively, Global, Local,
14500 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14501 tables are data structures which store a descriptor for each segment
14502 that is currently in use. The segment's selector is an index into a
14503 descriptor table; the table entry for that index holds the
14504 descriptor's base address and limit, and its attributes and access
14507 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14508 segment (used for both data and the stack), and a DOS segment (which
14509 allows access to DOS/BIOS data structures and absolute addresses in
14510 conventional memory). However, the DPMI host will usually define
14511 additional segments in order to support the DPMI environment.
14513 @cindex garbled pointers
14514 These commands allow to display entries from the descriptor tables.
14515 Without an argument, all entries from the specified table are
14516 displayed. An argument, which should be an integer expression, means
14517 display a single entry whose index is given by the argument. For
14518 example, here's a convenient way to display information about the
14519 debugged program's data segment:
14522 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14523 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14527 This comes in handy when you want to see whether a pointer is outside
14528 the data segment's limit (i.e.@: @dfn{garbled}).
14530 @cindex page tables display (MS-DOS)
14532 @itemx info dos pte
14533 These two commands display entries from, respectively, the Page
14534 Directory and the Page Tables. Page Directories and Page Tables are
14535 data structures which control how virtual memory addresses are mapped
14536 into physical addresses. A Page Table includes an entry for every
14537 page of memory that is mapped into the program's address space; there
14538 may be several Page Tables, each one holding up to 4096 entries. A
14539 Page Directory has up to 4096 entries, one each for every Page Table
14540 that is currently in use.
14542 Without an argument, @kbd{info dos pde} displays the entire Page
14543 Directory, and @kbd{info dos pte} displays all the entries in all of
14544 the Page Tables. An argument, an integer expression, given to the
14545 @kbd{info dos pde} command means display only that entry from the Page
14546 Directory table. An argument given to the @kbd{info dos pte} command
14547 means display entries from a single Page Table, the one pointed to by
14548 the specified entry in the Page Directory.
14550 @cindex direct memory access (DMA) on MS-DOS
14551 These commands are useful when your program uses @dfn{DMA} (Direct
14552 Memory Access), which needs physical addresses to program the DMA
14555 These commands are supported only with some DPMI servers.
14557 @cindex physical address from linear address
14558 @item info dos address-pte @var{addr}
14559 This command displays the Page Table entry for a specified linear
14560 address. The argument @var{addr} is a linear address which should
14561 already have the appropriate segment's base address added to it,
14562 because this command accepts addresses which may belong to @emph{any}
14563 segment. For example, here's how to display the Page Table entry for
14564 the page where a variable @code{i} is stored:
14567 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14568 @exdent @code{Page Table entry for address 0x11a00d30:}
14569 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14573 This says that @code{i} is stored at offset @code{0xd30} from the page
14574 whose physical base address is @code{0x02698000}, and shows all the
14575 attributes of that page.
14577 Note that you must cast the addresses of variables to a @code{char *},
14578 since otherwise the value of @code{__djgpp_base_address}, the base
14579 address of all variables and functions in a @sc{djgpp} program, will
14580 be added using the rules of C pointer arithmetics: if @code{i} is
14581 declared an @code{int}, @value{GDBN} will add 4 times the value of
14582 @code{__djgpp_base_address} to the address of @code{i}.
14584 Here's another example, it displays the Page Table entry for the
14588 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14589 @exdent @code{Page Table entry for address 0x29110:}
14590 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14594 (The @code{+ 3} offset is because the transfer buffer's address is the
14595 3rd member of the @code{_go32_info_block} structure.) The output
14596 clearly shows that this DPMI server maps the addresses in conventional
14597 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
14598 linear (@code{0x29110}) addresses are identical.
14600 This command is supported only with some DPMI servers.
14603 @cindex DOS serial data link, remote debugging
14604 In addition to native debugging, the DJGPP port supports remote
14605 debugging via a serial data link. The following commands are specific
14606 to remote serial debugging in the DJGPP port of @value{GDBN}.
14609 @kindex set com1base
14610 @kindex set com1irq
14611 @kindex set com2base
14612 @kindex set com2irq
14613 @kindex set com3base
14614 @kindex set com3irq
14615 @kindex set com4base
14616 @kindex set com4irq
14617 @item set com1base @var{addr}
14618 This command sets the base I/O port address of the @file{COM1} serial
14621 @item set com1irq @var{irq}
14622 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
14623 for the @file{COM1} serial port.
14625 There are similar commands @samp{set com2base}, @samp{set com3irq},
14626 etc.@: for setting the port address and the @code{IRQ} lines for the
14629 @kindex show com1base
14630 @kindex show com1irq
14631 @kindex show com2base
14632 @kindex show com2irq
14633 @kindex show com3base
14634 @kindex show com3irq
14635 @kindex show com4base
14636 @kindex show com4irq
14637 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
14638 display the current settings of the base address and the @code{IRQ}
14639 lines used by the COM ports.
14642 @kindex info serial
14643 @cindex DOS serial port status
14644 This command prints the status of the 4 DOS serial ports. For each
14645 port, it prints whether it's active or not, its I/O base address and
14646 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
14647 counts of various errors encountered so far.
14651 @node Cygwin Native
14652 @subsection Features for Debugging MS Windows PE Executables
14653 @cindex MS Windows debugging
14654 @cindex native Cygwin debugging
14655 @cindex Cygwin-specific commands
14657 @value{GDBN} supports native debugging of MS Windows programs, including
14658 DLLs with and without symbolic debugging information. There are various
14659 additional Cygwin-specific commands, described in this section.
14660 Working with DLLs that have no debugging symbols is described in
14661 @ref{Non-debug DLL Symbols}.
14666 This is a prefix of MS Windows-specific commands which print
14667 information about the target system and important OS structures.
14669 @item info w32 selector
14670 This command displays information returned by
14671 the Win32 API @code{GetThreadSelectorEntry} function.
14672 It takes an optional argument that is evaluated to
14673 a long value to give the information about this given selector.
14674 Without argument, this command displays information
14675 about the six segment registers.
14679 This is a Cygwin-specific alias of @code{info shared}.
14681 @kindex dll-symbols
14683 This command loads symbols from a dll similarly to
14684 add-sym command but without the need to specify a base address.
14686 @kindex set cygwin-exceptions
14687 @cindex debugging the Cygwin DLL
14688 @cindex Cygwin DLL, debugging
14689 @item set cygwin-exceptions @var{mode}
14690 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
14691 happen inside the Cygwin DLL. If @var{mode} is @code{off},
14692 @value{GDBN} will delay recognition of exceptions, and may ignore some
14693 exceptions which seem to be caused by internal Cygwin DLL
14694 ``bookkeeping''. This option is meant primarily for debugging the
14695 Cygwin DLL itself; the default value is @code{off} to avoid annoying
14696 @value{GDBN} users with false @code{SIGSEGV} signals.
14698 @kindex show cygwin-exceptions
14699 @item show cygwin-exceptions
14700 Displays whether @value{GDBN} will break on exceptions that happen
14701 inside the Cygwin DLL itself.
14703 @kindex set new-console
14704 @item set new-console @var{mode}
14705 If @var{mode} is @code{on} the debuggee will
14706 be started in a new console on next start.
14707 If @var{mode} is @code{off}i, the debuggee will
14708 be started in the same console as the debugger.
14710 @kindex show new-console
14711 @item show new-console
14712 Displays whether a new console is used
14713 when the debuggee is started.
14715 @kindex set new-group
14716 @item set new-group @var{mode}
14717 This boolean value controls whether the debuggee should
14718 start a new group or stay in the same group as the debugger.
14719 This affects the way the Windows OS handles
14722 @kindex show new-group
14723 @item show new-group
14724 Displays current value of new-group boolean.
14726 @kindex set debugevents
14727 @item set debugevents
14728 This boolean value adds debug output concerning kernel events related
14729 to the debuggee seen by the debugger. This includes events that
14730 signal thread and process creation and exit, DLL loading and
14731 unloading, console interrupts, and debugging messages produced by the
14732 Windows @code{OutputDebugString} API call.
14734 @kindex set debugexec
14735 @item set debugexec
14736 This boolean value adds debug output concerning execute events
14737 (such as resume thread) seen by the debugger.
14739 @kindex set debugexceptions
14740 @item set debugexceptions
14741 This boolean value adds debug output concerning exceptions in the
14742 debuggee seen by the debugger.
14744 @kindex set debugmemory
14745 @item set debugmemory
14746 This boolean value adds debug output concerning debuggee memory reads
14747 and writes by the debugger.
14751 This boolean values specifies whether the debuggee is called
14752 via a shell or directly (default value is on).
14756 Displays if the debuggee will be started with a shell.
14761 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14764 @node Non-debug DLL Symbols
14765 @subsubsection Support for DLLs without Debugging Symbols
14766 @cindex DLLs with no debugging symbols
14767 @cindex Minimal symbols and DLLs
14769 Very often on windows, some of the DLLs that your program relies on do
14770 not include symbolic debugging information (for example,
14771 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14772 symbols in a DLL, it relies on the minimal amount of symbolic
14773 information contained in the DLL's export table. This section
14774 describes working with such symbols, known internally to @value{GDBN} as
14775 ``minimal symbols''.
14777 Note that before the debugged program has started execution, no DLLs
14778 will have been loaded. The easiest way around this problem is simply to
14779 start the program --- either by setting a breakpoint or letting the
14780 program run once to completion. It is also possible to force
14781 @value{GDBN} to load a particular DLL before starting the executable ---
14782 see the shared library information in @ref{Files}, or the
14783 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14784 explicitly loading symbols from a DLL with no debugging information will
14785 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14786 which may adversely affect symbol lookup performance.
14788 @subsubsection DLL Name Prefixes
14790 In keeping with the naming conventions used by the Microsoft debugging
14791 tools, DLL export symbols are made available with a prefix based on the
14792 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14793 also entered into the symbol table, so @code{CreateFileA} is often
14794 sufficient. In some cases there will be name clashes within a program
14795 (particularly if the executable itself includes full debugging symbols)
14796 necessitating the use of the fully qualified name when referring to the
14797 contents of the DLL. Use single-quotes around the name to avoid the
14798 exclamation mark (``!'') being interpreted as a language operator.
14800 Note that the internal name of the DLL may be all upper-case, even
14801 though the file name of the DLL is lower-case, or vice-versa. Since
14802 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14803 some confusion. If in doubt, try the @code{info functions} and
14804 @code{info variables} commands or even @code{maint print msymbols}
14805 (@pxref{Symbols}). Here's an example:
14808 (@value{GDBP}) info function CreateFileA
14809 All functions matching regular expression "CreateFileA":
14811 Non-debugging symbols:
14812 0x77e885f4 CreateFileA
14813 0x77e885f4 KERNEL32!CreateFileA
14817 (@value{GDBP}) info function !
14818 All functions matching regular expression "!":
14820 Non-debugging symbols:
14821 0x6100114c cygwin1!__assert
14822 0x61004034 cygwin1!_dll_crt0@@0
14823 0x61004240 cygwin1!dll_crt0(per_process *)
14827 @subsubsection Working with Minimal Symbols
14829 Symbols extracted from a DLL's export table do not contain very much
14830 type information. All that @value{GDBN} can do is guess whether a symbol
14831 refers to a function or variable depending on the linker section that
14832 contains the symbol. Also note that the actual contents of the memory
14833 contained in a DLL are not available unless the program is running. This
14834 means that you cannot examine the contents of a variable or disassemble
14835 a function within a DLL without a running program.
14837 Variables are generally treated as pointers and dereferenced
14838 automatically. For this reason, it is often necessary to prefix a
14839 variable name with the address-of operator (``&'') and provide explicit
14840 type information in the command. Here's an example of the type of
14844 (@value{GDBP}) print 'cygwin1!__argv'
14849 (@value{GDBP}) x 'cygwin1!__argv'
14850 0x10021610: "\230y\""
14853 And two possible solutions:
14856 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14857 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14861 (@value{GDBP}) x/2x &'cygwin1!__argv'
14862 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14863 (@value{GDBP}) x/x 0x10021608
14864 0x10021608: 0x0022fd98
14865 (@value{GDBP}) x/s 0x0022fd98
14866 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14869 Setting a break point within a DLL is possible even before the program
14870 starts execution. However, under these circumstances, @value{GDBN} can't
14871 examine the initial instructions of the function in order to skip the
14872 function's frame set-up code. You can work around this by using ``*&''
14873 to set the breakpoint at a raw memory address:
14876 (@value{GDBP}) break *&'python22!PyOS_Readline'
14877 Breakpoint 1 at 0x1e04eff0
14880 The author of these extensions is not entirely convinced that setting a
14881 break point within a shared DLL like @file{kernel32.dll} is completely
14885 @subsection Commands Specific to @sc{gnu} Hurd Systems
14886 @cindex @sc{gnu} Hurd debugging
14888 This subsection describes @value{GDBN} commands specific to the
14889 @sc{gnu} Hurd native debugging.
14894 @kindex set signals@r{, Hurd command}
14895 @kindex set sigs@r{, Hurd command}
14896 This command toggles the state of inferior signal interception by
14897 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14898 affected by this command. @code{sigs} is a shorthand alias for
14903 @kindex show signals@r{, Hurd command}
14904 @kindex show sigs@r{, Hurd command}
14905 Show the current state of intercepting inferior's signals.
14907 @item set signal-thread
14908 @itemx set sigthread
14909 @kindex set signal-thread
14910 @kindex set sigthread
14911 This command tells @value{GDBN} which thread is the @code{libc} signal
14912 thread. That thread is run when a signal is delivered to a running
14913 process. @code{set sigthread} is the shorthand alias of @code{set
14916 @item show signal-thread
14917 @itemx show sigthread
14918 @kindex show signal-thread
14919 @kindex show sigthread
14920 These two commands show which thread will run when the inferior is
14921 delivered a signal.
14924 @kindex set stopped@r{, Hurd command}
14925 This commands tells @value{GDBN} that the inferior process is stopped,
14926 as with the @code{SIGSTOP} signal. The stopped process can be
14927 continued by delivering a signal to it.
14930 @kindex show stopped@r{, Hurd command}
14931 This command shows whether @value{GDBN} thinks the debuggee is
14934 @item set exceptions
14935 @kindex set exceptions@r{, Hurd command}
14936 Use this command to turn off trapping of exceptions in the inferior.
14937 When exception trapping is off, neither breakpoints nor
14938 single-stepping will work. To restore the default, set exception
14941 @item show exceptions
14942 @kindex show exceptions@r{, Hurd command}
14943 Show the current state of trapping exceptions in the inferior.
14945 @item set task pause
14946 @kindex set task@r{, Hurd commands}
14947 @cindex task attributes (@sc{gnu} Hurd)
14948 @cindex pause current task (@sc{gnu} Hurd)
14949 This command toggles task suspension when @value{GDBN} has control.
14950 Setting it to on takes effect immediately, and the task is suspended
14951 whenever @value{GDBN} gets control. Setting it to off will take
14952 effect the next time the inferior is continued. If this option is set
14953 to off, you can use @code{set thread default pause on} or @code{set
14954 thread pause on} (see below) to pause individual threads.
14956 @item show task pause
14957 @kindex show task@r{, Hurd commands}
14958 Show the current state of task suspension.
14960 @item set task detach-suspend-count
14961 @cindex task suspend count
14962 @cindex detach from task, @sc{gnu} Hurd
14963 This command sets the suspend count the task will be left with when
14964 @value{GDBN} detaches from it.
14966 @item show task detach-suspend-count
14967 Show the suspend count the task will be left with when detaching.
14969 @item set task exception-port
14970 @itemx set task excp
14971 @cindex task exception port, @sc{gnu} Hurd
14972 This command sets the task exception port to which @value{GDBN} will
14973 forward exceptions. The argument should be the value of the @dfn{send
14974 rights} of the task. @code{set task excp} is a shorthand alias.
14976 @item set noninvasive
14977 @cindex noninvasive task options
14978 This command switches @value{GDBN} to a mode that is the least
14979 invasive as far as interfering with the inferior is concerned. This
14980 is the same as using @code{set task pause}, @code{set exceptions}, and
14981 @code{set signals} to values opposite to the defaults.
14983 @item info send-rights
14984 @itemx info receive-rights
14985 @itemx info port-rights
14986 @itemx info port-sets
14987 @itemx info dead-names
14990 @cindex send rights, @sc{gnu} Hurd
14991 @cindex receive rights, @sc{gnu} Hurd
14992 @cindex port rights, @sc{gnu} Hurd
14993 @cindex port sets, @sc{gnu} Hurd
14994 @cindex dead names, @sc{gnu} Hurd
14995 These commands display information about, respectively, send rights,
14996 receive rights, port rights, port sets, and dead names of a task.
14997 There are also shorthand aliases: @code{info ports} for @code{info
14998 port-rights} and @code{info psets} for @code{info port-sets}.
15000 @item set thread pause
15001 @kindex set thread@r{, Hurd command}
15002 @cindex thread properties, @sc{gnu} Hurd
15003 @cindex pause current thread (@sc{gnu} Hurd)
15004 This command toggles current thread suspension when @value{GDBN} has
15005 control. Setting it to on takes effect immediately, and the current
15006 thread is suspended whenever @value{GDBN} gets control. Setting it to
15007 off will take effect the next time the inferior is continued.
15008 Normally, this command has no effect, since when @value{GDBN} has
15009 control, the whole task is suspended. However, if you used @code{set
15010 task pause off} (see above), this command comes in handy to suspend
15011 only the current thread.
15013 @item show thread pause
15014 @kindex show thread@r{, Hurd command}
15015 This command shows the state of current thread suspension.
15017 @item set thread run
15018 This command sets whether the current thread is allowed to run.
15020 @item show thread run
15021 Show whether the current thread is allowed to run.
15023 @item set thread detach-suspend-count
15024 @cindex thread suspend count, @sc{gnu} Hurd
15025 @cindex detach from thread, @sc{gnu} Hurd
15026 This command sets the suspend count @value{GDBN} will leave on a
15027 thread when detaching. This number is relative to the suspend count
15028 found by @value{GDBN} when it notices the thread; use @code{set thread
15029 takeover-suspend-count} to force it to an absolute value.
15031 @item show thread detach-suspend-count
15032 Show the suspend count @value{GDBN} will leave on the thread when
15035 @item set thread exception-port
15036 @itemx set thread excp
15037 Set the thread exception port to which to forward exceptions. This
15038 overrides the port set by @code{set task exception-port} (see above).
15039 @code{set thread excp} is the shorthand alias.
15041 @item set thread takeover-suspend-count
15042 Normally, @value{GDBN}'s thread suspend counts are relative to the
15043 value @value{GDBN} finds when it notices each thread. This command
15044 changes the suspend counts to be absolute instead.
15046 @item set thread default
15047 @itemx show thread default
15048 @cindex thread default settings, @sc{gnu} Hurd
15049 Each of the above @code{set thread} commands has a @code{set thread
15050 default} counterpart (e.g., @code{set thread default pause}, @code{set
15051 thread default exception-port}, etc.). The @code{thread default}
15052 variety of commands sets the default thread properties for all
15053 threads; you can then change the properties of individual threads with
15054 the non-default commands.
15059 @subsection QNX Neutrino
15060 @cindex QNX Neutrino
15062 @value{GDBN} provides the following commands specific to the QNX
15066 @item set debug nto-debug
15067 @kindex set debug nto-debug
15068 When set to on, enables debugging messages specific to the QNX
15071 @item show debug nto-debug
15072 @kindex show debug nto-debug
15073 Show the current state of QNX Neutrino messages.
15078 @section Embedded Operating Systems
15080 This section describes configurations involving the debugging of
15081 embedded operating systems that are available for several different
15085 * VxWorks:: Using @value{GDBN} with VxWorks
15088 @value{GDBN} includes the ability to debug programs running on
15089 various real-time operating systems.
15092 @subsection Using @value{GDBN} with VxWorks
15098 @kindex target vxworks
15099 @item target vxworks @var{machinename}
15100 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15101 is the target system's machine name or IP address.
15105 On VxWorks, @code{load} links @var{filename} dynamically on the
15106 current target system as well as adding its symbols in @value{GDBN}.
15108 @value{GDBN} enables developers to spawn and debug tasks running on networked
15109 VxWorks targets from a Unix host. Already-running tasks spawned from
15110 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15111 both the Unix host and on the VxWorks target. The program
15112 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15113 installed with the name @code{vxgdb}, to distinguish it from a
15114 @value{GDBN} for debugging programs on the host itself.)
15117 @item VxWorks-timeout @var{args}
15118 @kindex vxworks-timeout
15119 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15120 This option is set by the user, and @var{args} represents the number of
15121 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15122 your VxWorks target is a slow software simulator or is on the far side
15123 of a thin network line.
15126 The following information on connecting to VxWorks was current when
15127 this manual was produced; newer releases of VxWorks may use revised
15130 @findex INCLUDE_RDB
15131 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15132 to include the remote debugging interface routines in the VxWorks
15133 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15134 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15135 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15136 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15137 information on configuring and remaking VxWorks, see the manufacturer's
15139 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15141 Once you have included @file{rdb.a} in your VxWorks system image and set
15142 your Unix execution search path to find @value{GDBN}, you are ready to
15143 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15144 @code{vxgdb}, depending on your installation).
15146 @value{GDBN} comes up showing the prompt:
15153 * VxWorks Connection:: Connecting to VxWorks
15154 * VxWorks Download:: VxWorks download
15155 * VxWorks Attach:: Running tasks
15158 @node VxWorks Connection
15159 @subsubsection Connecting to VxWorks
15161 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15162 network. To connect to a target whose host name is ``@code{tt}'', type:
15165 (vxgdb) target vxworks tt
15169 @value{GDBN} displays messages like these:
15172 Attaching remote machine across net...
15177 @value{GDBN} then attempts to read the symbol tables of any object modules
15178 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15179 these files by searching the directories listed in the command search
15180 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15181 to find an object file, it displays a message such as:
15184 prog.o: No such file or directory.
15187 When this happens, add the appropriate directory to the search path with
15188 the @value{GDBN} command @code{path}, and execute the @code{target}
15191 @node VxWorks Download
15192 @subsubsection VxWorks Download
15194 @cindex download to VxWorks
15195 If you have connected to the VxWorks target and you want to debug an
15196 object that has not yet been loaded, you can use the @value{GDBN}
15197 @code{load} command to download a file from Unix to VxWorks
15198 incrementally. The object file given as an argument to the @code{load}
15199 command is actually opened twice: first by the VxWorks target in order
15200 to download the code, then by @value{GDBN} in order to read the symbol
15201 table. This can lead to problems if the current working directories on
15202 the two systems differ. If both systems have NFS mounted the same
15203 filesystems, you can avoid these problems by using absolute paths.
15204 Otherwise, it is simplest to set the working directory on both systems
15205 to the directory in which the object file resides, and then to reference
15206 the file by its name, without any path. For instance, a program
15207 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15208 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15209 program, type this on VxWorks:
15212 -> cd "@var{vxpath}/vw/demo/rdb"
15216 Then, in @value{GDBN}, type:
15219 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15220 (vxgdb) load prog.o
15223 @value{GDBN} displays a response similar to this:
15226 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15229 You can also use the @code{load} command to reload an object module
15230 after editing and recompiling the corresponding source file. Note that
15231 this makes @value{GDBN} delete all currently-defined breakpoints,
15232 auto-displays, and convenience variables, and to clear the value
15233 history. (This is necessary in order to preserve the integrity of
15234 debugger's data structures that reference the target system's symbol
15237 @node VxWorks Attach
15238 @subsubsection Running Tasks
15240 @cindex running VxWorks tasks
15241 You can also attach to an existing task using the @code{attach} command as
15245 (vxgdb) attach @var{task}
15249 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15250 or suspended when you attach to it. Running tasks are suspended at
15251 the time of attachment.
15253 @node Embedded Processors
15254 @section Embedded Processors
15256 This section goes into details specific to particular embedded
15259 @cindex send command to simulator
15260 Whenever a specific embedded processor has a simulator, @value{GDBN}
15261 allows to send an arbitrary command to the simulator.
15264 @item sim @var{command}
15265 @kindex sim@r{, a command}
15266 Send an arbitrary @var{command} string to the simulator. Consult the
15267 documentation for the specific simulator in use for information about
15268 acceptable commands.
15274 * M32R/D:: Renesas M32R/D
15275 * M68K:: Motorola M68K
15276 * MIPS Embedded:: MIPS Embedded
15277 * OpenRISC 1000:: OpenRisc 1000
15278 * PA:: HP PA Embedded
15279 * PowerPC Embedded:: PowerPC Embedded
15280 * Sparclet:: Tsqware Sparclet
15281 * Sparclite:: Fujitsu Sparclite
15282 * Z8000:: Zilog Z8000
15285 * Super-H:: Renesas Super-H
15294 @item target rdi @var{dev}
15295 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15296 use this target to communicate with both boards running the Angel
15297 monitor, or with the EmbeddedICE JTAG debug device.
15300 @item target rdp @var{dev}
15305 @value{GDBN} provides the following ARM-specific commands:
15308 @item set arm disassembler
15310 This commands selects from a list of disassembly styles. The
15311 @code{"std"} style is the standard style.
15313 @item show arm disassembler
15315 Show the current disassembly style.
15317 @item set arm apcs32
15318 @cindex ARM 32-bit mode
15319 This command toggles ARM operation mode between 32-bit and 26-bit.
15321 @item show arm apcs32
15322 Display the current usage of the ARM 32-bit mode.
15324 @item set arm fpu @var{fputype}
15325 This command sets the ARM floating-point unit (FPU) type. The
15326 argument @var{fputype} can be one of these:
15330 Determine the FPU type by querying the OS ABI.
15332 Software FPU, with mixed-endian doubles on little-endian ARM
15335 GCC-compiled FPA co-processor.
15337 Software FPU with pure-endian doubles.
15343 Show the current type of the FPU.
15346 This command forces @value{GDBN} to use the specified ABI.
15349 Show the currently used ABI.
15351 @item set arm fallback-mode (arm|thumb|auto)
15352 @value{GDBN} uses the symbol table, when available, to determine
15353 whether instructions are ARM or Thumb. This command controls
15354 @value{GDBN}'s default behavior when the symbol table is not
15355 available. The default is @samp{auto}, which causes @value{GDBN} to
15356 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15359 @item show arm fallback-mode
15360 Show the current fallback instruction mode.
15362 @item set arm force-mode (arm|thumb|auto)
15363 This command overrides use of the symbol table to determine whether
15364 instructions are ARM or Thumb. The default is @samp{auto}, which
15365 causes @value{GDBN} to use the symbol table and then the setting
15366 of @samp{set arm fallback-mode}.
15368 @item show arm force-mode
15369 Show the current forced instruction mode.
15371 @item set debug arm
15372 Toggle whether to display ARM-specific debugging messages from the ARM
15373 target support subsystem.
15375 @item show debug arm
15376 Show whether ARM-specific debugging messages are enabled.
15379 The following commands are available when an ARM target is debugged
15380 using the RDI interface:
15383 @item rdilogfile @r{[}@var{file}@r{]}
15385 @cindex ADP (Angel Debugger Protocol) logging
15386 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15387 With an argument, sets the log file to the specified @var{file}. With
15388 no argument, show the current log file name. The default log file is
15391 @item rdilogenable @r{[}@var{arg}@r{]}
15392 @kindex rdilogenable
15393 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15394 enables logging, with an argument 0 or @code{"no"} disables it. With
15395 no arguments displays the current setting. When logging is enabled,
15396 ADP packets exchanged between @value{GDBN} and the RDI target device
15397 are logged to a file.
15399 @item set rdiromatzero
15400 @kindex set rdiromatzero
15401 @cindex ROM at zero address, RDI
15402 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15403 vector catching is disabled, so that zero address can be used. If off
15404 (the default), vector catching is enabled. For this command to take
15405 effect, it needs to be invoked prior to the @code{target rdi} command.
15407 @item show rdiromatzero
15408 @kindex show rdiromatzero
15409 Show the current setting of ROM at zero address.
15411 @item set rdiheartbeat
15412 @kindex set rdiheartbeat
15413 @cindex RDI heartbeat
15414 Enable or disable RDI heartbeat packets. It is not recommended to
15415 turn on this option, since it confuses ARM and EPI JTAG interface, as
15416 well as the Angel monitor.
15418 @item show rdiheartbeat
15419 @kindex show rdiheartbeat
15420 Show the setting of RDI heartbeat packets.
15425 @subsection Renesas M32R/D and M32R/SDI
15428 @kindex target m32r
15429 @item target m32r @var{dev}
15430 Renesas M32R/D ROM monitor.
15432 @kindex target m32rsdi
15433 @item target m32rsdi @var{dev}
15434 Renesas M32R SDI server, connected via parallel port to the board.
15437 The following @value{GDBN} commands are specific to the M32R monitor:
15440 @item set download-path @var{path}
15441 @kindex set download-path
15442 @cindex find downloadable @sc{srec} files (M32R)
15443 Set the default path for finding downloadable @sc{srec} files.
15445 @item show download-path
15446 @kindex show download-path
15447 Show the default path for downloadable @sc{srec} files.
15449 @item set board-address @var{addr}
15450 @kindex set board-address
15451 @cindex M32-EVA target board address
15452 Set the IP address for the M32R-EVA target board.
15454 @item show board-address
15455 @kindex show board-address
15456 Show the current IP address of the target board.
15458 @item set server-address @var{addr}
15459 @kindex set server-address
15460 @cindex download server address (M32R)
15461 Set the IP address for the download server, which is the @value{GDBN}'s
15464 @item show server-address
15465 @kindex show server-address
15466 Display the IP address of the download server.
15468 @item upload @r{[}@var{file}@r{]}
15469 @kindex upload@r{, M32R}
15470 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
15471 upload capability. If no @var{file} argument is given, the current
15472 executable file is uploaded.
15474 @item tload @r{[}@var{file}@r{]}
15475 @kindex tload@r{, M32R}
15476 Test the @code{upload} command.
15479 The following commands are available for M32R/SDI:
15484 @cindex reset SDI connection, M32R
15485 This command resets the SDI connection.
15489 This command shows the SDI connection status.
15492 @kindex debug_chaos
15493 @cindex M32R/Chaos debugging
15494 Instructs the remote that M32R/Chaos debugging is to be used.
15496 @item use_debug_dma
15497 @kindex use_debug_dma
15498 Instructs the remote to use the DEBUG_DMA method of accessing memory.
15501 @kindex use_mon_code
15502 Instructs the remote to use the MON_CODE method of accessing memory.
15505 @kindex use_ib_break
15506 Instructs the remote to set breakpoints by IB break.
15508 @item use_dbt_break
15509 @kindex use_dbt_break
15510 Instructs the remote to set breakpoints by DBT.
15516 The Motorola m68k configuration includes ColdFire support, and a
15517 target command for the following ROM monitor.
15521 @kindex target dbug
15522 @item target dbug @var{dev}
15523 dBUG ROM monitor for Motorola ColdFire.
15527 @node MIPS Embedded
15528 @subsection MIPS Embedded
15530 @cindex MIPS boards
15531 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15532 MIPS board attached to a serial line. This is available when
15533 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15536 Use these @value{GDBN} commands to specify the connection to your target board:
15539 @item target mips @var{port}
15540 @kindex target mips @var{port}
15541 To run a program on the board, start up @code{@value{GDBP}} with the
15542 name of your program as the argument. To connect to the board, use the
15543 command @samp{target mips @var{port}}, where @var{port} is the name of
15544 the serial port connected to the board. If the program has not already
15545 been downloaded to the board, you may use the @code{load} command to
15546 download it. You can then use all the usual @value{GDBN} commands.
15548 For example, this sequence connects to the target board through a serial
15549 port, and loads and runs a program called @var{prog} through the
15553 host$ @value{GDBP} @var{prog}
15554 @value{GDBN} is free software and @dots{}
15555 (@value{GDBP}) target mips /dev/ttyb
15556 (@value{GDBP}) load @var{prog}
15560 @item target mips @var{hostname}:@var{portnumber}
15561 On some @value{GDBN} host configurations, you can specify a TCP
15562 connection (for instance, to a serial line managed by a terminal
15563 concentrator) instead of a serial port, using the syntax
15564 @samp{@var{hostname}:@var{portnumber}}.
15566 @item target pmon @var{port}
15567 @kindex target pmon @var{port}
15570 @item target ddb @var{port}
15571 @kindex target ddb @var{port}
15572 NEC's DDB variant of PMON for Vr4300.
15574 @item target lsi @var{port}
15575 @kindex target lsi @var{port}
15576 LSI variant of PMON.
15578 @kindex target r3900
15579 @item target r3900 @var{dev}
15580 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
15582 @kindex target array
15583 @item target array @var{dev}
15584 Array Tech LSI33K RAID controller board.
15590 @value{GDBN} also supports these special commands for MIPS targets:
15593 @item set mipsfpu double
15594 @itemx set mipsfpu single
15595 @itemx set mipsfpu none
15596 @itemx set mipsfpu auto
15597 @itemx show mipsfpu
15598 @kindex set mipsfpu
15599 @kindex show mipsfpu
15600 @cindex MIPS remote floating point
15601 @cindex floating point, MIPS remote
15602 If your target board does not support the MIPS floating point
15603 coprocessor, you should use the command @samp{set mipsfpu none} (if you
15604 need this, you may wish to put the command in your @value{GDBN} init
15605 file). This tells @value{GDBN} how to find the return value of
15606 functions which return floating point values. It also allows
15607 @value{GDBN} to avoid saving the floating point registers when calling
15608 functions on the board. If you are using a floating point coprocessor
15609 with only single precision floating point support, as on the @sc{r4650}
15610 processor, use the command @samp{set mipsfpu single}. The default
15611 double precision floating point coprocessor may be selected using
15612 @samp{set mipsfpu double}.
15614 In previous versions the only choices were double precision or no
15615 floating point, so @samp{set mipsfpu on} will select double precision
15616 and @samp{set mipsfpu off} will select no floating point.
15618 As usual, you can inquire about the @code{mipsfpu} variable with
15619 @samp{show mipsfpu}.
15621 @item set timeout @var{seconds}
15622 @itemx set retransmit-timeout @var{seconds}
15623 @itemx show timeout
15624 @itemx show retransmit-timeout
15625 @cindex @code{timeout}, MIPS protocol
15626 @cindex @code{retransmit-timeout}, MIPS protocol
15627 @kindex set timeout
15628 @kindex show timeout
15629 @kindex set retransmit-timeout
15630 @kindex show retransmit-timeout
15631 You can control the timeout used while waiting for a packet, in the MIPS
15632 remote protocol, with the @code{set timeout @var{seconds}} command. The
15633 default is 5 seconds. Similarly, you can control the timeout used while
15634 waiting for an acknowledgement of a packet with the @code{set
15635 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
15636 You can inspect both values with @code{show timeout} and @code{show
15637 retransmit-timeout}. (These commands are @emph{only} available when
15638 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
15640 The timeout set by @code{set timeout} does not apply when @value{GDBN}
15641 is waiting for your program to stop. In that case, @value{GDBN} waits
15642 forever because it has no way of knowing how long the program is going
15643 to run before stopping.
15645 @item set syn-garbage-limit @var{num}
15646 @kindex set syn-garbage-limit@r{, MIPS remote}
15647 @cindex synchronize with remote MIPS target
15648 Limit the maximum number of characters @value{GDBN} should ignore when
15649 it tries to synchronize with the remote target. The default is 10
15650 characters. Setting the limit to -1 means there's no limit.
15652 @item show syn-garbage-limit
15653 @kindex show syn-garbage-limit@r{, MIPS remote}
15654 Show the current limit on the number of characters to ignore when
15655 trying to synchronize with the remote system.
15657 @item set monitor-prompt @var{prompt}
15658 @kindex set monitor-prompt@r{, MIPS remote}
15659 @cindex remote monitor prompt
15660 Tell @value{GDBN} to expect the specified @var{prompt} string from the
15661 remote monitor. The default depends on the target:
15671 @item show monitor-prompt
15672 @kindex show monitor-prompt@r{, MIPS remote}
15673 Show the current strings @value{GDBN} expects as the prompt from the
15676 @item set monitor-warnings
15677 @kindex set monitor-warnings@r{, MIPS remote}
15678 Enable or disable monitor warnings about hardware breakpoints. This
15679 has effect only for the @code{lsi} target. When on, @value{GDBN} will
15680 display warning messages whose codes are returned by the @code{lsi}
15681 PMON monitor for breakpoint commands.
15683 @item show monitor-warnings
15684 @kindex show monitor-warnings@r{, MIPS remote}
15685 Show the current setting of printing monitor warnings.
15687 @item pmon @var{command}
15688 @kindex pmon@r{, MIPS remote}
15689 @cindex send PMON command
15690 This command allows sending an arbitrary @var{command} string to the
15691 monitor. The monitor must be in debug mode for this to work.
15694 @node OpenRISC 1000
15695 @subsection OpenRISC 1000
15696 @cindex OpenRISC 1000
15698 @cindex or1k boards
15699 See OR1k Architecture document (@uref{www.opencores.org}) for more information
15700 about platform and commands.
15704 @kindex target jtag
15705 @item target jtag jtag://@var{host}:@var{port}
15707 Connects to remote JTAG server.
15708 JTAG remote server can be either an or1ksim or JTAG server,
15709 connected via parallel port to the board.
15711 Example: @code{target jtag jtag://localhost:9999}
15714 @item or1ksim @var{command}
15715 If connected to @code{or1ksim} OpenRISC 1000 Architectural
15716 Simulator, proprietary commands can be executed.
15718 @kindex info or1k spr
15719 @item info or1k spr
15720 Displays spr groups.
15722 @item info or1k spr @var{group}
15723 @itemx info or1k spr @var{groupno}
15724 Displays register names in selected group.
15726 @item info or1k spr @var{group} @var{register}
15727 @itemx info or1k spr @var{register}
15728 @itemx info or1k spr @var{groupno} @var{registerno}
15729 @itemx info or1k spr @var{registerno}
15730 Shows information about specified spr register.
15733 @item spr @var{group} @var{register} @var{value}
15734 @itemx spr @var{register @var{value}}
15735 @itemx spr @var{groupno} @var{registerno @var{value}}
15736 @itemx spr @var{registerno @var{value}}
15737 Writes @var{value} to specified spr register.
15740 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15741 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15742 program execution and is thus much faster. Hardware breakpoints/watchpoint
15743 triggers can be set using:
15746 Load effective address/data
15748 Store effective address/data
15750 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15755 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15756 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15758 @code{htrace} commands:
15759 @cindex OpenRISC 1000 htrace
15762 @item hwatch @var{conditional}
15763 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15764 or Data. For example:
15766 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15768 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15772 Display information about current HW trace configuration.
15774 @item htrace trigger @var{conditional}
15775 Set starting criteria for HW trace.
15777 @item htrace qualifier @var{conditional}
15778 Set acquisition qualifier for HW trace.
15780 @item htrace stop @var{conditional}
15781 Set HW trace stopping criteria.
15783 @item htrace record [@var{data}]*
15784 Selects the data to be recorded, when qualifier is met and HW trace was
15787 @item htrace enable
15788 @itemx htrace disable
15789 Enables/disables the HW trace.
15791 @item htrace rewind [@var{filename}]
15792 Clears currently recorded trace data.
15794 If filename is specified, new trace file is made and any newly collected data
15795 will be written there.
15797 @item htrace print [@var{start} [@var{len}]]
15798 Prints trace buffer, using current record configuration.
15800 @item htrace mode continuous
15801 Set continuous trace mode.
15803 @item htrace mode suspend
15804 Set suspend trace mode.
15808 @node PowerPC Embedded
15809 @subsection PowerPC Embedded
15811 @value{GDBN} provides the following PowerPC-specific commands:
15814 @kindex set powerpc
15815 @item set powerpc soft-float
15816 @itemx show powerpc soft-float
15817 Force @value{GDBN} to use (or not use) a software floating point calling
15818 convention. By default, @value{GDBN} selects the calling convention based
15819 on the selected architecture and the provided executable file.
15821 @item set powerpc vector-abi
15822 @itemx show powerpc vector-abi
15823 Force @value{GDBN} to use the specified calling convention for vector
15824 arguments and return values. The valid options are @samp{auto};
15825 @samp{generic}, to avoid vector registers even if they are present;
15826 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15827 registers. By default, @value{GDBN} selects the calling convention
15828 based on the selected architecture and the provided executable file.
15830 @kindex target dink32
15831 @item target dink32 @var{dev}
15832 DINK32 ROM monitor.
15834 @kindex target ppcbug
15835 @item target ppcbug @var{dev}
15836 @kindex target ppcbug1
15837 @item target ppcbug1 @var{dev}
15838 PPCBUG ROM monitor for PowerPC.
15841 @item target sds @var{dev}
15842 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15845 @cindex SDS protocol
15846 The following commands specific to the SDS protocol are supported
15850 @item set sdstimeout @var{nsec}
15851 @kindex set sdstimeout
15852 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15853 default is 2 seconds.
15855 @item show sdstimeout
15856 @kindex show sdstimeout
15857 Show the current value of the SDS timeout.
15859 @item sds @var{command}
15860 @kindex sds@r{, a command}
15861 Send the specified @var{command} string to the SDS monitor.
15866 @subsection HP PA Embedded
15870 @kindex target op50n
15871 @item target op50n @var{dev}
15872 OP50N monitor, running on an OKI HPPA board.
15874 @kindex target w89k
15875 @item target w89k @var{dev}
15876 W89K monitor, running on a Winbond HPPA board.
15881 @subsection Tsqware Sparclet
15885 @value{GDBN} enables developers to debug tasks running on
15886 Sparclet targets from a Unix host.
15887 @value{GDBN} uses code that runs on
15888 both the Unix host and on the Sparclet target. The program
15889 @code{@value{GDBP}} is installed and executed on the Unix host.
15892 @item remotetimeout @var{args}
15893 @kindex remotetimeout
15894 @value{GDBN} supports the option @code{remotetimeout}.
15895 This option is set by the user, and @var{args} represents the number of
15896 seconds @value{GDBN} waits for responses.
15899 @cindex compiling, on Sparclet
15900 When compiling for debugging, include the options @samp{-g} to get debug
15901 information and @samp{-Ttext} to relocate the program to where you wish to
15902 load it on the target. You may also want to add the options @samp{-n} or
15903 @samp{-N} in order to reduce the size of the sections. Example:
15906 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15909 You can use @code{objdump} to verify that the addresses are what you intended:
15912 sparclet-aout-objdump --headers --syms prog
15915 @cindex running, on Sparclet
15917 your Unix execution search path to find @value{GDBN}, you are ready to
15918 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15919 (or @code{sparclet-aout-gdb}, depending on your installation).
15921 @value{GDBN} comes up showing the prompt:
15928 * Sparclet File:: Setting the file to debug
15929 * Sparclet Connection:: Connecting to Sparclet
15930 * Sparclet Download:: Sparclet download
15931 * Sparclet Execution:: Running and debugging
15934 @node Sparclet File
15935 @subsubsection Setting File to Debug
15937 The @value{GDBN} command @code{file} lets you choose with program to debug.
15940 (gdbslet) file prog
15944 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15945 @value{GDBN} locates
15946 the file by searching the directories listed in the command search
15948 If the file was compiled with debug information (option @samp{-g}), source
15949 files will be searched as well.
15950 @value{GDBN} locates
15951 the source files by searching the directories listed in the directory search
15952 path (@pxref{Environment, ,Your Program's Environment}).
15954 to find a file, it displays a message such as:
15957 prog: No such file or directory.
15960 When this happens, add the appropriate directories to the search paths with
15961 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15962 @code{target} command again.
15964 @node Sparclet Connection
15965 @subsubsection Connecting to Sparclet
15967 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15968 To connect to a target on serial port ``@code{ttya}'', type:
15971 (gdbslet) target sparclet /dev/ttya
15972 Remote target sparclet connected to /dev/ttya
15973 main () at ../prog.c:3
15977 @value{GDBN} displays messages like these:
15983 @node Sparclet Download
15984 @subsubsection Sparclet Download
15986 @cindex download to Sparclet
15987 Once connected to the Sparclet target,
15988 you can use the @value{GDBN}
15989 @code{load} command to download the file from the host to the target.
15990 The file name and load offset should be given as arguments to the @code{load}
15992 Since the file format is aout, the program must be loaded to the starting
15993 address. You can use @code{objdump} to find out what this value is. The load
15994 offset is an offset which is added to the VMA (virtual memory address)
15995 of each of the file's sections.
15996 For instance, if the program
15997 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15998 and bss at 0x12010170, in @value{GDBN}, type:
16001 (gdbslet) load prog 0x12010000
16002 Loading section .text, size 0xdb0 vma 0x12010000
16005 If the code is loaded at a different address then what the program was linked
16006 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16007 to tell @value{GDBN} where to map the symbol table.
16009 @node Sparclet Execution
16010 @subsubsection Running and Debugging
16012 @cindex running and debugging Sparclet programs
16013 You can now begin debugging the task using @value{GDBN}'s execution control
16014 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16015 manual for the list of commands.
16019 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16021 Starting program: prog
16022 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16023 3 char *symarg = 0;
16025 4 char *execarg = "hello!";
16030 @subsection Fujitsu Sparclite
16034 @kindex target sparclite
16035 @item target sparclite @var{dev}
16036 Fujitsu sparclite boards, used only for the purpose of loading.
16037 You must use an additional command to debug the program.
16038 For example: target remote @var{dev} using @value{GDBN} standard
16044 @subsection Zilog Z8000
16047 @cindex simulator, Z8000
16048 @cindex Zilog Z8000 simulator
16050 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16053 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16054 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16055 segmented variant). The simulator recognizes which architecture is
16056 appropriate by inspecting the object code.
16059 @item target sim @var{args}
16061 @kindex target sim@r{, with Z8000}
16062 Debug programs on a simulated CPU. If the simulator supports setup
16063 options, specify them via @var{args}.
16067 After specifying this target, you can debug programs for the simulated
16068 CPU in the same style as programs for your host computer; use the
16069 @code{file} command to load a new program image, the @code{run} command
16070 to run your program, and so on.
16072 As well as making available all the usual machine registers
16073 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16074 additional items of information as specially named registers:
16079 Counts clock-ticks in the simulator.
16082 Counts instructions run in the simulator.
16085 Execution time in 60ths of a second.
16089 You can refer to these values in @value{GDBN} expressions with the usual
16090 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16091 conditional breakpoint that suspends only after at least 5000
16092 simulated clock ticks.
16095 @subsection Atmel AVR
16098 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16099 following AVR-specific commands:
16102 @item info io_registers
16103 @kindex info io_registers@r{, AVR}
16104 @cindex I/O registers (Atmel AVR)
16105 This command displays information about the AVR I/O registers. For
16106 each register, @value{GDBN} prints its number and value.
16113 When configured for debugging CRIS, @value{GDBN} provides the
16114 following CRIS-specific commands:
16117 @item set cris-version @var{ver}
16118 @cindex CRIS version
16119 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16120 The CRIS version affects register names and sizes. This command is useful in
16121 case autodetection of the CRIS version fails.
16123 @item show cris-version
16124 Show the current CRIS version.
16126 @item set cris-dwarf2-cfi
16127 @cindex DWARF-2 CFI and CRIS
16128 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16129 Change to @samp{off} when using @code{gcc-cris} whose version is below
16132 @item show cris-dwarf2-cfi
16133 Show the current state of using DWARF-2 CFI.
16135 @item set cris-mode @var{mode}
16137 Set the current CRIS mode to @var{mode}. It should only be changed when
16138 debugging in guru mode, in which case it should be set to
16139 @samp{guru} (the default is @samp{normal}).
16141 @item show cris-mode
16142 Show the current CRIS mode.
16146 @subsection Renesas Super-H
16149 For the Renesas Super-H processor, @value{GDBN} provides these
16154 @kindex regs@r{, Super-H}
16155 Show the values of all Super-H registers.
16157 @item set sh calling-convention @var{convention}
16158 @kindex set sh calling-convention
16159 Set the calling-convention used when calling functions from @value{GDBN}.
16160 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16161 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16162 convention. If the DWARF-2 information of the called function specifies
16163 that the function follows the Renesas calling convention, the function
16164 is called using the Renesas calling convention. If the calling convention
16165 is set to @samp{renesas}, the Renesas calling convention is always used,
16166 regardless of the DWARF-2 information. This can be used to override the
16167 default of @samp{gcc} if debug information is missing, or the compiler
16168 does not emit the DWARF-2 calling convention entry for a function.
16170 @item show sh calling-convention
16171 @kindex show sh calling-convention
16172 Show the current calling convention setting.
16177 @node Architectures
16178 @section Architectures
16180 This section describes characteristics of architectures that affect
16181 all uses of @value{GDBN} with the architecture, both native and cross.
16188 * HPPA:: HP PA architecture
16189 * SPU:: Cell Broadband Engine SPU architecture
16194 @subsection x86 Architecture-specific Issues
16197 @item set struct-convention @var{mode}
16198 @kindex set struct-convention
16199 @cindex struct return convention
16200 @cindex struct/union returned in registers
16201 Set the convention used by the inferior to return @code{struct}s and
16202 @code{union}s from functions to @var{mode}. Possible values of
16203 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16204 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16205 are returned on the stack, while @code{"reg"} means that a
16206 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16207 be returned in a register.
16209 @item show struct-convention
16210 @kindex show struct-convention
16211 Show the current setting of the convention to return @code{struct}s
16220 @kindex set rstack_high_address
16221 @cindex AMD 29K register stack
16222 @cindex register stack, AMD29K
16223 @item set rstack_high_address @var{address}
16224 On AMD 29000 family processors, registers are saved in a separate
16225 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16226 extent of this stack. Normally, @value{GDBN} just assumes that the
16227 stack is ``large enough''. This may result in @value{GDBN} referencing
16228 memory locations that do not exist. If necessary, you can get around
16229 this problem by specifying the ending address of the register stack with
16230 the @code{set rstack_high_address} command. The argument should be an
16231 address, which you probably want to precede with @samp{0x} to specify in
16234 @kindex show rstack_high_address
16235 @item show rstack_high_address
16236 Display the current limit of the register stack, on AMD 29000 family
16244 See the following section.
16249 @cindex stack on Alpha
16250 @cindex stack on MIPS
16251 @cindex Alpha stack
16253 Alpha- and MIPS-based computers use an unusual stack frame, which
16254 sometimes requires @value{GDBN} to search backward in the object code to
16255 find the beginning of a function.
16257 @cindex response time, MIPS debugging
16258 To improve response time (especially for embedded applications, where
16259 @value{GDBN} may be restricted to a slow serial line for this search)
16260 you may want to limit the size of this search, using one of these
16264 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16265 @item set heuristic-fence-post @var{limit}
16266 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16267 search for the beginning of a function. A value of @var{0} (the
16268 default) means there is no limit. However, except for @var{0}, the
16269 larger the limit the more bytes @code{heuristic-fence-post} must search
16270 and therefore the longer it takes to run. You should only need to use
16271 this command when debugging a stripped executable.
16273 @item show heuristic-fence-post
16274 Display the current limit.
16278 These commands are available @emph{only} when @value{GDBN} is configured
16279 for debugging programs on Alpha or MIPS processors.
16281 Several MIPS-specific commands are available when debugging MIPS
16285 @item set mips abi @var{arg}
16286 @kindex set mips abi
16287 @cindex set ABI for MIPS
16288 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16289 values of @var{arg} are:
16293 The default ABI associated with the current binary (this is the
16304 @item show mips abi
16305 @kindex show mips abi
16306 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16309 @itemx show mipsfpu
16310 @xref{MIPS Embedded, set mipsfpu}.
16312 @item set mips mask-address @var{arg}
16313 @kindex set mips mask-address
16314 @cindex MIPS addresses, masking
16315 This command determines whether the most-significant 32 bits of 64-bit
16316 MIPS addresses are masked off. The argument @var{arg} can be
16317 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16318 setting, which lets @value{GDBN} determine the correct value.
16320 @item show mips mask-address
16321 @kindex show mips mask-address
16322 Show whether the upper 32 bits of MIPS addresses are masked off or
16325 @item set remote-mips64-transfers-32bit-regs
16326 @kindex set remote-mips64-transfers-32bit-regs
16327 This command controls compatibility with 64-bit MIPS targets that
16328 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16329 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16330 and 64 bits for other registers, set this option to @samp{on}.
16332 @item show remote-mips64-transfers-32bit-regs
16333 @kindex show remote-mips64-transfers-32bit-regs
16334 Show the current setting of compatibility with older MIPS 64 targets.
16336 @item set debug mips
16337 @kindex set debug mips
16338 This command turns on and off debugging messages for the MIPS-specific
16339 target code in @value{GDBN}.
16341 @item show debug mips
16342 @kindex show debug mips
16343 Show the current setting of MIPS debugging messages.
16349 @cindex HPPA support
16351 When @value{GDBN} is debugging the HP PA architecture, it provides the
16352 following special commands:
16355 @item set debug hppa
16356 @kindex set debug hppa
16357 This command determines whether HPPA architecture-specific debugging
16358 messages are to be displayed.
16360 @item show debug hppa
16361 Show whether HPPA debugging messages are displayed.
16363 @item maint print unwind @var{address}
16364 @kindex maint print unwind@r{, HPPA}
16365 This command displays the contents of the unwind table entry at the
16366 given @var{address}.
16372 @subsection Cell Broadband Engine SPU architecture
16373 @cindex Cell Broadband Engine
16376 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16377 it provides the following special commands:
16380 @item info spu event
16382 Display SPU event facility status. Shows current event mask
16383 and pending event status.
16385 @item info spu signal
16386 Display SPU signal notification facility status. Shows pending
16387 signal-control word and signal notification mode of both signal
16388 notification channels.
16390 @item info spu mailbox
16391 Display SPU mailbox facility status. Shows all pending entries,
16392 in order of processing, in each of the SPU Write Outbound,
16393 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16396 Display MFC DMA status. Shows all pending commands in the MFC
16397 DMA queue. For each entry, opcode, tag, class IDs, effective
16398 and local store addresses and transfer size are shown.
16400 @item info spu proxydma
16401 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16402 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16403 and local store addresses and transfer size are shown.
16408 @subsection PowerPC
16409 @cindex PowerPC architecture
16411 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16412 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16413 numbers stored in the floating point registers. These values must be stored
16414 in two consecutive registers, always starting at an even register like
16415 @code{f0} or @code{f2}.
16417 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16418 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16419 @code{f2} and @code{f3} for @code{$dl1} and so on.
16422 @node Controlling GDB
16423 @chapter Controlling @value{GDBN}
16425 You can alter the way @value{GDBN} interacts with you by using the
16426 @code{set} command. For commands controlling how @value{GDBN} displays
16427 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16432 * Editing:: Command editing
16433 * Command History:: Command history
16434 * Screen Size:: Screen size
16435 * Numbers:: Numbers
16436 * ABI:: Configuring the current ABI
16437 * Messages/Warnings:: Optional warnings and messages
16438 * Debugging Output:: Optional messages about internal happenings
16446 @value{GDBN} indicates its readiness to read a command by printing a string
16447 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
16448 can change the prompt string with the @code{set prompt} command. For
16449 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
16450 the prompt in one of the @value{GDBN} sessions so that you can always tell
16451 which one you are talking to.
16453 @emph{Note:} @code{set prompt} does not add a space for you after the
16454 prompt you set. This allows you to set a prompt which ends in a space
16455 or a prompt that does not.
16459 @item set prompt @var{newprompt}
16460 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
16462 @kindex show prompt
16464 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
16468 @section Command Editing
16470 @cindex command line editing
16472 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
16473 @sc{gnu} library provides consistent behavior for programs which provide a
16474 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16475 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16476 substitution, and a storage and recall of command history across
16477 debugging sessions.
16479 You may control the behavior of command line editing in @value{GDBN} with the
16480 command @code{set}.
16483 @kindex set editing
16486 @itemx set editing on
16487 Enable command line editing (enabled by default).
16489 @item set editing off
16490 Disable command line editing.
16492 @kindex show editing
16494 Show whether command line editing is enabled.
16497 @xref{Command Line Editing}, for more details about the Readline
16498 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
16499 encouraged to read that chapter.
16501 @node Command History
16502 @section Command History
16503 @cindex command history
16505 @value{GDBN} can keep track of the commands you type during your
16506 debugging sessions, so that you can be certain of precisely what
16507 happened. Use these commands to manage the @value{GDBN} command
16510 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
16511 package, to provide the history facility. @xref{Using History
16512 Interactively}, for the detailed description of the History library.
16514 To issue a command to @value{GDBN} without affecting certain aspects of
16515 the state which is seen by users, prefix it with @samp{server }
16516 (@pxref{Server Prefix}). This
16517 means that this command will not affect the command history, nor will it
16518 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
16519 pressed on a line by itself.
16521 @cindex @code{server}, command prefix
16522 The server prefix does not affect the recording of values into the value
16523 history; to print a value without recording it into the value history,
16524 use the @code{output} command instead of the @code{print} command.
16526 Here is the description of @value{GDBN} commands related to command
16530 @cindex history substitution
16531 @cindex history file
16532 @kindex set history filename
16533 @cindex @env{GDBHISTFILE}, environment variable
16534 @item set history filename @var{fname}
16535 Set the name of the @value{GDBN} command history file to @var{fname}.
16536 This is the file where @value{GDBN} reads an initial command history
16537 list, and where it writes the command history from this session when it
16538 exits. You can access this list through history expansion or through
16539 the history command editing characters listed below. This file defaults
16540 to the value of the environment variable @code{GDBHISTFILE}, or to
16541 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16544 @cindex save command history
16545 @kindex set history save
16546 @item set history save
16547 @itemx set history save on
16548 Record command history in a file, whose name may be specified with the
16549 @code{set history filename} command. By default, this option is disabled.
16551 @item set history save off
16552 Stop recording command history in a file.
16554 @cindex history size
16555 @kindex set history size
16556 @cindex @env{HISTSIZE}, environment variable
16557 @item set history size @var{size}
16558 Set the number of commands which @value{GDBN} keeps in its history list.
16559 This defaults to the value of the environment variable
16560 @code{HISTSIZE}, or to 256 if this variable is not set.
16563 History expansion assigns special meaning to the character @kbd{!}.
16564 @xref{Event Designators}, for more details.
16566 @cindex history expansion, turn on/off
16567 Since @kbd{!} is also the logical not operator in C, history expansion
16568 is off by default. If you decide to enable history expansion with the
16569 @code{set history expansion on} command, you may sometimes need to
16570 follow @kbd{!} (when it is used as logical not, in an expression) with
16571 a space or a tab to prevent it from being expanded. The readline
16572 history facilities do not attempt substitution on the strings
16573 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
16575 The commands to control history expansion are:
16578 @item set history expansion on
16579 @itemx set history expansion
16580 @kindex set history expansion
16581 Enable history expansion. History expansion is off by default.
16583 @item set history expansion off
16584 Disable history expansion.
16587 @kindex show history
16589 @itemx show history filename
16590 @itemx show history save
16591 @itemx show history size
16592 @itemx show history expansion
16593 These commands display the state of the @value{GDBN} history parameters.
16594 @code{show history} by itself displays all four states.
16599 @kindex show commands
16600 @cindex show last commands
16601 @cindex display command history
16602 @item show commands
16603 Display the last ten commands in the command history.
16605 @item show commands @var{n}
16606 Print ten commands centered on command number @var{n}.
16608 @item show commands +
16609 Print ten commands just after the commands last printed.
16613 @section Screen Size
16614 @cindex size of screen
16615 @cindex pauses in output
16617 Certain commands to @value{GDBN} may produce large amounts of
16618 information output to the screen. To help you read all of it,
16619 @value{GDBN} pauses and asks you for input at the end of each page of
16620 output. Type @key{RET} when you want to continue the output, or @kbd{q}
16621 to discard the remaining output. Also, the screen width setting
16622 determines when to wrap lines of output. Depending on what is being
16623 printed, @value{GDBN} tries to break the line at a readable place,
16624 rather than simply letting it overflow onto the following line.
16626 Normally @value{GDBN} knows the size of the screen from the terminal
16627 driver software. For example, on Unix @value{GDBN} uses the termcap data base
16628 together with the value of the @code{TERM} environment variable and the
16629 @code{stty rows} and @code{stty cols} settings. If this is not correct,
16630 you can override it with the @code{set height} and @code{set
16637 @kindex show height
16638 @item set height @var{lpp}
16640 @itemx set width @var{cpl}
16642 These @code{set} commands specify a screen height of @var{lpp} lines and
16643 a screen width of @var{cpl} characters. The associated @code{show}
16644 commands display the current settings.
16646 If you specify a height of zero lines, @value{GDBN} does not pause during
16647 output no matter how long the output is. This is useful if output is to a
16648 file or to an editor buffer.
16650 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
16651 from wrapping its output.
16653 @item set pagination on
16654 @itemx set pagination off
16655 @kindex set pagination
16656 Turn the output pagination on or off; the default is on. Turning
16657 pagination off is the alternative to @code{set height 0}.
16659 @item show pagination
16660 @kindex show pagination
16661 Show the current pagination mode.
16666 @cindex number representation
16667 @cindex entering numbers
16669 You can always enter numbers in octal, decimal, or hexadecimal in
16670 @value{GDBN} by the usual conventions: octal numbers begin with
16671 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
16672 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
16673 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
16674 10; likewise, the default display for numbers---when no particular
16675 format is specified---is base 10. You can change the default base for
16676 both input and output with the commands described below.
16679 @kindex set input-radix
16680 @item set input-radix @var{base}
16681 Set the default base for numeric input. Supported choices
16682 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16683 specified either unambiguously or using the current input radix; for
16687 set input-radix 012
16688 set input-radix 10.
16689 set input-radix 0xa
16693 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
16694 leaves the input radix unchanged, no matter what it was, since
16695 @samp{10}, being without any leading or trailing signs of its base, is
16696 interpreted in the current radix. Thus, if the current radix is 16,
16697 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
16700 @kindex set output-radix
16701 @item set output-radix @var{base}
16702 Set the default base for numeric display. Supported choices
16703 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16704 specified either unambiguously or using the current input radix.
16706 @kindex show input-radix
16707 @item show input-radix
16708 Display the current default base for numeric input.
16710 @kindex show output-radix
16711 @item show output-radix
16712 Display the current default base for numeric display.
16714 @item set radix @r{[}@var{base}@r{]}
16718 These commands set and show the default base for both input and output
16719 of numbers. @code{set radix} sets the radix of input and output to
16720 the same base; without an argument, it resets the radix back to its
16721 default value of 10.
16726 @section Configuring the Current ABI
16728 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
16729 application automatically. However, sometimes you need to override its
16730 conclusions. Use these commands to manage @value{GDBN}'s view of the
16737 One @value{GDBN} configuration can debug binaries for multiple operating
16738 system targets, either via remote debugging or native emulation.
16739 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
16740 but you can override its conclusion using the @code{set osabi} command.
16741 One example where this is useful is in debugging of binaries which use
16742 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16743 not have the same identifying marks that the standard C library for your
16748 Show the OS ABI currently in use.
16751 With no argument, show the list of registered available OS ABI's.
16753 @item set osabi @var{abi}
16754 Set the current OS ABI to @var{abi}.
16757 @cindex float promotion
16759 Generally, the way that an argument of type @code{float} is passed to a
16760 function depends on whether the function is prototyped. For a prototyped
16761 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16762 according to the architecture's convention for @code{float}. For unprototyped
16763 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16764 @code{double} and then passed.
16766 Unfortunately, some forms of debug information do not reliably indicate whether
16767 a function is prototyped. If @value{GDBN} calls a function that is not marked
16768 as prototyped, it consults @kbd{set coerce-float-to-double}.
16771 @kindex set coerce-float-to-double
16772 @item set coerce-float-to-double
16773 @itemx set coerce-float-to-double on
16774 Arguments of type @code{float} will be promoted to @code{double} when passed
16775 to an unprototyped function. This is the default setting.
16777 @item set coerce-float-to-double off
16778 Arguments of type @code{float} will be passed directly to unprototyped
16781 @kindex show coerce-float-to-double
16782 @item show coerce-float-to-double
16783 Show the current setting of promoting @code{float} to @code{double}.
16787 @kindex show cp-abi
16788 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16789 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16790 used to build your application. @value{GDBN} only fully supports
16791 programs with a single C@t{++} ABI; if your program contains code using
16792 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16793 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16794 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16795 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16796 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16797 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16802 Show the C@t{++} ABI currently in use.
16805 With no argument, show the list of supported C@t{++} ABI's.
16807 @item set cp-abi @var{abi}
16808 @itemx set cp-abi auto
16809 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16812 @node Messages/Warnings
16813 @section Optional Warnings and Messages
16815 @cindex verbose operation
16816 @cindex optional warnings
16817 By default, @value{GDBN} is silent about its inner workings. If you are
16818 running on a slow machine, you may want to use the @code{set verbose}
16819 command. This makes @value{GDBN} tell you when it does a lengthy
16820 internal operation, so you will not think it has crashed.
16822 Currently, the messages controlled by @code{set verbose} are those
16823 which announce that the symbol table for a source file is being read;
16824 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16827 @kindex set verbose
16828 @item set verbose on
16829 Enables @value{GDBN} output of certain informational messages.
16831 @item set verbose off
16832 Disables @value{GDBN} output of certain informational messages.
16834 @kindex show verbose
16836 Displays whether @code{set verbose} is on or off.
16839 By default, if @value{GDBN} encounters bugs in the symbol table of an
16840 object file, it is silent; but if you are debugging a compiler, you may
16841 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16846 @kindex set complaints
16847 @item set complaints @var{limit}
16848 Permits @value{GDBN} to output @var{limit} complaints about each type of
16849 unusual symbols before becoming silent about the problem. Set
16850 @var{limit} to zero to suppress all complaints; set it to a large number
16851 to prevent complaints from being suppressed.
16853 @kindex show complaints
16854 @item show complaints
16855 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16859 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16860 lot of stupid questions to confirm certain commands. For example, if
16861 you try to run a program which is already running:
16865 The program being debugged has been started already.
16866 Start it from the beginning? (y or n)
16869 If you are willing to unflinchingly face the consequences of your own
16870 commands, you can disable this ``feature'':
16874 @kindex set confirm
16876 @cindex confirmation
16877 @cindex stupid questions
16878 @item set confirm off
16879 Disables confirmation requests.
16881 @item set confirm on
16882 Enables confirmation requests (the default).
16884 @kindex show confirm
16886 Displays state of confirmation requests.
16890 @cindex command tracing
16891 If you need to debug user-defined commands or sourced files you may find it
16892 useful to enable @dfn{command tracing}. In this mode each command will be
16893 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16894 quantity denoting the call depth of each command.
16897 @kindex set trace-commands
16898 @cindex command scripts, debugging
16899 @item set trace-commands on
16900 Enable command tracing.
16901 @item set trace-commands off
16902 Disable command tracing.
16903 @item show trace-commands
16904 Display the current state of command tracing.
16907 @node Debugging Output
16908 @section Optional Messages about Internal Happenings
16909 @cindex optional debugging messages
16911 @value{GDBN} has commands that enable optional debugging messages from
16912 various @value{GDBN} subsystems; normally these commands are of
16913 interest to @value{GDBN} maintainers, or when reporting a bug. This
16914 section documents those commands.
16917 @kindex set exec-done-display
16918 @item set exec-done-display
16919 Turns on or off the notification of asynchronous commands'
16920 completion. When on, @value{GDBN} will print a message when an
16921 asynchronous command finishes its execution. The default is off.
16922 @kindex show exec-done-display
16923 @item show exec-done-display
16924 Displays the current setting of asynchronous command completion
16927 @cindex gdbarch debugging info
16928 @cindex architecture debugging info
16929 @item set debug arch
16930 Turns on or off display of gdbarch debugging info. The default is off
16932 @item show debug arch
16933 Displays the current state of displaying gdbarch debugging info.
16934 @item set debug aix-thread
16935 @cindex AIX threads
16936 Display debugging messages about inner workings of the AIX thread
16938 @item show debug aix-thread
16939 Show the current state of AIX thread debugging info display.
16940 @item set debug displaced
16941 @cindex displaced stepping debugging info
16942 Turns on or off display of @value{GDBN} debugging info for the
16943 displaced stepping support. The default is off.
16944 @item show debug displaced
16945 Displays the current state of displaying @value{GDBN} debugging info
16946 related to displaced stepping.
16947 @item set debug event
16948 @cindex event debugging info
16949 Turns on or off display of @value{GDBN} event debugging info. The
16951 @item show debug event
16952 Displays the current state of displaying @value{GDBN} event debugging
16954 @item set debug expression
16955 @cindex expression debugging info
16956 Turns on or off display of debugging info about @value{GDBN}
16957 expression parsing. The default is off.
16958 @item show debug expression
16959 Displays the current state of displaying debugging info about
16960 @value{GDBN} expression parsing.
16961 @item set debug frame
16962 @cindex frame debugging info
16963 Turns on or off display of @value{GDBN} frame debugging info. The
16965 @item show debug frame
16966 Displays the current state of displaying @value{GDBN} frame debugging
16968 @item set debug infrun
16969 @cindex inferior debugging info
16970 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16971 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16972 for implementing operations such as single-stepping the inferior.
16973 @item show debug infrun
16974 Displays the current state of @value{GDBN} inferior debugging.
16975 @item set debug lin-lwp
16976 @cindex @sc{gnu}/Linux LWP debug messages
16977 @cindex Linux lightweight processes
16978 Turns on or off debugging messages from the Linux LWP debug support.
16979 @item show debug lin-lwp
16980 Show the current state of Linux LWP debugging messages.
16981 @item set debug lin-lwp-async
16982 @cindex @sc{gnu}/Linux LWP async debug messages
16983 @cindex Linux lightweight processes
16984 Turns on or off debugging messages from the Linux LWP async debug support.
16985 @item show debug lin-lwp-async
16986 Show the current state of Linux LWP async debugging messages.
16987 @item set debug observer
16988 @cindex observer debugging info
16989 Turns on or off display of @value{GDBN} observer debugging. This
16990 includes info such as the notification of observable events.
16991 @item show debug observer
16992 Displays the current state of observer debugging.
16993 @item set debug overload
16994 @cindex C@t{++} overload debugging info
16995 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16996 info. This includes info such as ranking of functions, etc. The default
16998 @item show debug overload
16999 Displays the current state of displaying @value{GDBN} C@t{++} overload
17001 @cindex packets, reporting on stdout
17002 @cindex serial connections, debugging
17003 @cindex debug remote protocol
17004 @cindex remote protocol debugging
17005 @cindex display remote packets
17006 @item set debug remote
17007 Turns on or off display of reports on all packets sent back and forth across
17008 the serial line to the remote machine. The info is printed on the
17009 @value{GDBN} standard output stream. The default is off.
17010 @item show debug remote
17011 Displays the state of display of remote packets.
17012 @item set debug serial
17013 Turns on or off display of @value{GDBN} serial debugging info. The
17015 @item show debug serial
17016 Displays the current state of displaying @value{GDBN} serial debugging
17018 @item set debug solib-frv
17019 @cindex FR-V shared-library debugging
17020 Turns on or off debugging messages for FR-V shared-library code.
17021 @item show debug solib-frv
17022 Display the current state of FR-V shared-library code debugging
17024 @item set debug target
17025 @cindex target debugging info
17026 Turns on or off display of @value{GDBN} target debugging info. This info
17027 includes what is going on at the target level of GDB, as it happens. The
17028 default is 0. Set it to 1 to track events, and to 2 to also track the
17029 value of large memory transfers. Changes to this flag do not take effect
17030 until the next time you connect to a target or use the @code{run} command.
17031 @item show debug target
17032 Displays the current state of displaying @value{GDBN} target debugging
17034 @item set debug timestamp
17035 @cindex timestampping debugging info
17036 Turns on or off display of timestamps with @value{GDBN} debugging info.
17037 When enabled, seconds and microseconds are displayed before each debugging
17039 @item show debug timestamp
17040 Displays the current state of displaying timestamps with @value{GDBN}
17042 @item set debugvarobj
17043 @cindex variable object debugging info
17044 Turns on or off display of @value{GDBN} variable object debugging
17045 info. The default is off.
17046 @item show debugvarobj
17047 Displays the current state of displaying @value{GDBN} variable object
17049 @item set debug xml
17050 @cindex XML parser debugging
17051 Turns on or off debugging messages for built-in XML parsers.
17052 @item show debug xml
17053 Displays the current state of XML debugging messages.
17056 @node Extending GDB
17057 @chapter Extending @value{GDBN}
17058 @cindex extending GDB
17060 @value{GDBN} provides two mechanisms for extension. The first is based
17061 on composition of @value{GDBN} commands, and the second is based on the
17062 Python scripting language.
17065 * Sequences:: Canned Sequences of Commands
17066 * Python:: Scripting @value{GDBN} using Python
17070 @section Canned Sequences of Commands
17072 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17073 Command Lists}), @value{GDBN} provides two ways to store sequences of
17074 commands for execution as a unit: user-defined commands and command
17078 * Define:: How to define your own commands
17079 * Hooks:: Hooks for user-defined commands
17080 * Command Files:: How to write scripts of commands to be stored in a file
17081 * Output:: Commands for controlled output
17085 @subsection User-defined Commands
17087 @cindex user-defined command
17088 @cindex arguments, to user-defined commands
17089 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17090 which you assign a new name as a command. This is done with the
17091 @code{define} command. User commands may accept up to 10 arguments
17092 separated by whitespace. Arguments are accessed within the user command
17093 via @code{$arg0@dots{}$arg9}. A trivial example:
17097 print $arg0 + $arg1 + $arg2
17102 To execute the command use:
17109 This defines the command @code{adder}, which prints the sum of
17110 its three arguments. Note the arguments are text substitutions, so they may
17111 reference variables, use complex expressions, or even perform inferior
17114 @cindex argument count in user-defined commands
17115 @cindex how many arguments (user-defined commands)
17116 In addition, @code{$argc} may be used to find out how many arguments have
17117 been passed. This expands to a number in the range 0@dots{}10.
17122 print $arg0 + $arg1
17125 print $arg0 + $arg1 + $arg2
17133 @item define @var{commandname}
17134 Define a command named @var{commandname}. If there is already a command
17135 by that name, you are asked to confirm that you want to redefine it.
17137 The definition of the command is made up of other @value{GDBN} command lines,
17138 which are given following the @code{define} command. The end of these
17139 commands is marked by a line containing @code{end}.
17142 @kindex end@r{ (user-defined commands)}
17143 @item document @var{commandname}
17144 Document the user-defined command @var{commandname}, so that it can be
17145 accessed by @code{help}. The command @var{commandname} must already be
17146 defined. This command reads lines of documentation just as @code{define}
17147 reads the lines of the command definition, ending with @code{end}.
17148 After the @code{document} command is finished, @code{help} on command
17149 @var{commandname} displays the documentation you have written.
17151 You may use the @code{document} command again to change the
17152 documentation of a command. Redefining the command with @code{define}
17153 does not change the documentation.
17155 @kindex dont-repeat
17156 @cindex don't repeat command
17158 Used inside a user-defined command, this tells @value{GDBN} that this
17159 command should not be repeated when the user hits @key{RET}
17160 (@pxref{Command Syntax, repeat last command}).
17162 @kindex help user-defined
17163 @item help user-defined
17164 List all user-defined commands, with the first line of the documentation
17169 @itemx show user @var{commandname}
17170 Display the @value{GDBN} commands used to define @var{commandname} (but
17171 not its documentation). If no @var{commandname} is given, display the
17172 definitions for all user-defined commands.
17174 @cindex infinite recursion in user-defined commands
17175 @kindex show max-user-call-depth
17176 @kindex set max-user-call-depth
17177 @item show max-user-call-depth
17178 @itemx set max-user-call-depth
17179 The value of @code{max-user-call-depth} controls how many recursion
17180 levels are allowed in user-defined commands before @value{GDBN} suspects an
17181 infinite recursion and aborts the command.
17184 In addition to the above commands, user-defined commands frequently
17185 use control flow commands, described in @ref{Command Files}.
17187 When user-defined commands are executed, the
17188 commands of the definition are not printed. An error in any command
17189 stops execution of the user-defined command.
17191 If used interactively, commands that would ask for confirmation proceed
17192 without asking when used inside a user-defined command. Many @value{GDBN}
17193 commands that normally print messages to say what they are doing omit the
17194 messages when used in a user-defined command.
17197 @subsection User-defined Command Hooks
17198 @cindex command hooks
17199 @cindex hooks, for commands
17200 @cindex hooks, pre-command
17203 You may define @dfn{hooks}, which are a special kind of user-defined
17204 command. Whenever you run the command @samp{foo}, if the user-defined
17205 command @samp{hook-foo} exists, it is executed (with no arguments)
17206 before that command.
17208 @cindex hooks, post-command
17210 A hook may also be defined which is run after the command you executed.
17211 Whenever you run the command @samp{foo}, if the user-defined command
17212 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17213 that command. Post-execution hooks may exist simultaneously with
17214 pre-execution hooks, for the same command.
17216 It is valid for a hook to call the command which it hooks. If this
17217 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17219 @c It would be nice if hookpost could be passed a parameter indicating
17220 @c if the command it hooks executed properly or not. FIXME!
17222 @kindex stop@r{, a pseudo-command}
17223 In addition, a pseudo-command, @samp{stop} exists. Defining
17224 (@samp{hook-stop}) makes the associated commands execute every time
17225 execution stops in your program: before breakpoint commands are run,
17226 displays are printed, or the stack frame is printed.
17228 For example, to ignore @code{SIGALRM} signals while
17229 single-stepping, but treat them normally during normal execution,
17234 handle SIGALRM nopass
17238 handle SIGALRM pass
17241 define hook-continue
17242 handle SIGALRM pass
17246 As a further example, to hook at the beginning and end of the @code{echo}
17247 command, and to add extra text to the beginning and end of the message,
17255 define hookpost-echo
17259 (@value{GDBP}) echo Hello World
17260 <<<---Hello World--->>>
17265 You can define a hook for any single-word command in @value{GDBN}, but
17266 not for command aliases; you should define a hook for the basic command
17267 name, e.g.@: @code{backtrace} rather than @code{bt}.
17268 @c FIXME! So how does Joe User discover whether a command is an alias
17270 If an error occurs during the execution of your hook, execution of
17271 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17272 (before the command that you actually typed had a chance to run).
17274 If you try to define a hook which does not match any known command, you
17275 get a warning from the @code{define} command.
17277 @node Command Files
17278 @subsection Command Files
17280 @cindex command files
17281 @cindex scripting commands
17282 A command file for @value{GDBN} is a text file made of lines that are
17283 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17284 also be included. An empty line in a command file does nothing; it
17285 does not mean to repeat the last command, as it would from the
17288 You can request the execution of a command file with the @code{source}
17293 @cindex execute commands from a file
17294 @item source [@code{-v}] @var{filename}
17295 Execute the command file @var{filename}.
17298 The lines in a command file are generally executed sequentially,
17299 unless the order of execution is changed by one of the
17300 @emph{flow-control commands} described below. The commands are not
17301 printed as they are executed. An error in any command terminates
17302 execution of the command file and control is returned to the console.
17304 @value{GDBN} searches for @var{filename} in the current directory and then
17305 on the search path (specified with the @samp{directory} command).
17307 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17308 each command as it is executed. The option must be given before
17309 @var{filename}, and is interpreted as part of the filename anywhere else.
17311 Commands that would ask for confirmation if used interactively proceed
17312 without asking when used in a command file. Many @value{GDBN} commands that
17313 normally print messages to say what they are doing omit the messages
17314 when called from command files.
17316 @value{GDBN} also accepts command input from standard input. In this
17317 mode, normal output goes to standard output and error output goes to
17318 standard error. Errors in a command file supplied on standard input do
17319 not terminate execution of the command file---execution continues with
17323 gdb < cmds > log 2>&1
17326 (The syntax above will vary depending on the shell used.) This example
17327 will execute commands from the file @file{cmds}. All output and errors
17328 would be directed to @file{log}.
17330 Since commands stored on command files tend to be more general than
17331 commands typed interactively, they frequently need to deal with
17332 complicated situations, such as different or unexpected values of
17333 variables and symbols, changes in how the program being debugged is
17334 built, etc. @value{GDBN} provides a set of flow-control commands to
17335 deal with these complexities. Using these commands, you can write
17336 complex scripts that loop over data structures, execute commands
17337 conditionally, etc.
17344 This command allows to include in your script conditionally executed
17345 commands. The @code{if} command takes a single argument, which is an
17346 expression to evaluate. It is followed by a series of commands that
17347 are executed only if the expression is true (its value is nonzero).
17348 There can then optionally be an @code{else} line, followed by a series
17349 of commands that are only executed if the expression was false. The
17350 end of the list is marked by a line containing @code{end}.
17354 This command allows to write loops. Its syntax is similar to
17355 @code{if}: the command takes a single argument, which is an expression
17356 to evaluate, and must be followed by the commands to execute, one per
17357 line, terminated by an @code{end}. These commands are called the
17358 @dfn{body} of the loop. The commands in the body of @code{while} are
17359 executed repeatedly as long as the expression evaluates to true.
17363 This command exits the @code{while} loop in whose body it is included.
17364 Execution of the script continues after that @code{while}s @code{end}
17367 @kindex loop_continue
17368 @item loop_continue
17369 This command skips the execution of the rest of the body of commands
17370 in the @code{while} loop in whose body it is included. Execution
17371 branches to the beginning of the @code{while} loop, where it evaluates
17372 the controlling expression.
17374 @kindex end@r{ (if/else/while commands)}
17376 Terminate the block of commands that are the body of @code{if},
17377 @code{else}, or @code{while} flow-control commands.
17382 @subsection Commands for Controlled Output
17384 During the execution of a command file or a user-defined command, normal
17385 @value{GDBN} output is suppressed; the only output that appears is what is
17386 explicitly printed by the commands in the definition. This section
17387 describes three commands useful for generating exactly the output you
17392 @item echo @var{text}
17393 @c I do not consider backslash-space a standard C escape sequence
17394 @c because it is not in ANSI.
17395 Print @var{text}. Nonprinting characters can be included in
17396 @var{text} using C escape sequences, such as @samp{\n} to print a
17397 newline. @strong{No newline is printed unless you specify one.}
17398 In addition to the standard C escape sequences, a backslash followed
17399 by a space stands for a space. This is useful for displaying a
17400 string with spaces at the beginning or the end, since leading and
17401 trailing spaces are otherwise trimmed from all arguments.
17402 To print @samp{@w{ }and foo =@w{ }}, use the command
17403 @samp{echo \@w{ }and foo = \@w{ }}.
17405 A backslash at the end of @var{text} can be used, as in C, to continue
17406 the command onto subsequent lines. For example,
17409 echo This is some text\n\
17410 which is continued\n\
17411 onto several lines.\n
17414 produces the same output as
17417 echo This is some text\n
17418 echo which is continued\n
17419 echo onto several lines.\n
17423 @item output @var{expression}
17424 Print the value of @var{expression} and nothing but that value: no
17425 newlines, no @samp{$@var{nn} = }. The value is not entered in the
17426 value history either. @xref{Expressions, ,Expressions}, for more information
17429 @item output/@var{fmt} @var{expression}
17430 Print the value of @var{expression} in format @var{fmt}. You can use
17431 the same formats as for @code{print}. @xref{Output Formats,,Output
17432 Formats}, for more information.
17435 @item printf @var{template}, @var{expressions}@dots{}
17436 Print the values of one or more @var{expressions} under the control of
17437 the string @var{template}. To print several values, make
17438 @var{expressions} be a comma-separated list of individual expressions,
17439 which may be either numbers or pointers. Their values are printed as
17440 specified by @var{template}, exactly as a C program would do by
17441 executing the code below:
17444 printf (@var{template}, @var{expressions}@dots{});
17447 As in @code{C} @code{printf}, ordinary characters in @var{template}
17448 are printed verbatim, while @dfn{conversion specification} introduced
17449 by the @samp{%} character cause subsequent @var{expressions} to be
17450 evaluated, their values converted and formatted according to type and
17451 style information encoded in the conversion specifications, and then
17454 For example, you can print two values in hex like this:
17457 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
17460 @code{printf} supports all the standard @code{C} conversion
17461 specifications, including the flags and modifiers between the @samp{%}
17462 character and the conversion letter, with the following exceptions:
17466 The argument-ordering modifiers, such as @samp{2$}, are not supported.
17469 The modifier @samp{*} is not supported for specifying precision or
17473 The @samp{'} flag (for separation of digits into groups according to
17474 @code{LC_NUMERIC'}) is not supported.
17477 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
17481 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
17484 The conversion letters @samp{a} and @samp{A} are not supported.
17488 Note that the @samp{ll} type modifier is supported only if the
17489 underlying @code{C} implementation used to build @value{GDBN} supports
17490 the @code{long long int} type, and the @samp{L} type modifier is
17491 supported only if @code{long double} type is available.
17493 As in @code{C}, @code{printf} supports simple backslash-escape
17494 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
17495 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
17496 single character. Octal and hexadecimal escape sequences are not
17499 Additionally, @code{printf} supports conversion specifications for DFP
17500 (@dfn{Decimal Floating Point}) types using the following length modifiers
17501 together with a floating point specifier.
17506 @samp{H} for printing @code{Decimal32} types.
17509 @samp{D} for printing @code{Decimal64} types.
17512 @samp{DD} for printing @code{Decimal128} types.
17515 If the underlying @code{C} implementation used to build @value{GDBN} has
17516 support for the three length modifiers for DFP types, other modifiers
17517 such as width and precision will also be available for @value{GDBN} to use.
17519 In case there is no such @code{C} support, no additional modifiers will be
17520 available and the value will be printed in the standard way.
17522 Here's an example of printing DFP types using the above conversion letters:
17524 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
17530 @section Scripting @value{GDBN} using Python
17531 @cindex python scripting
17532 @cindex scripting with python
17534 You can script @value{GDBN} using the @uref{http://www.python.org/,
17535 Python programming language}. This feature is available only if
17536 @value{GDBN} was configured using @option{--with-python}.
17539 * Python Commands:: Accessing Python from @value{GDBN}.
17540 * Python API:: Accessing @value{GDBN} from Python.
17543 @node Python Commands
17544 @subsection Python Commands
17545 @cindex python commands
17546 @cindex commands to access python
17548 @value{GDBN} provides one command for accessing the Python interpreter,
17549 and one related setting:
17553 @item python @r{[}@var{code}@r{]}
17554 The @code{python} command can be used to evaluate Python code.
17556 If given an argument, the @code{python} command will evaluate the
17557 argument as a Python command. For example:
17560 (@value{GDBP}) python print 23
17564 If you do not provide an argument to @code{python}, it will act as a
17565 multi-line command, like @code{define}. In this case, the Python
17566 script is made up of subsequent command lines, given after the
17567 @code{python} command. This command list is terminated using a line
17568 containing @code{end}. For example:
17571 (@value{GDBP}) python
17573 End with a line saying just "end".
17579 @kindex maint set python print-stack
17580 @item maint set python print-stack
17581 By default, @value{GDBN} will print a stack trace when an error occurs
17582 in a Python script. This can be controlled using @code{maint set
17583 python print-stack}: if @code{on}, the default, then Python stack
17584 printing is enabled; if @code{off}, then Python stack printing is
17589 @subsection Python API
17591 @cindex programming in python
17593 @cindex python stdout
17594 @cindex python pagination
17595 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
17596 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
17597 A Python program which outputs to one of these streams may have its
17598 output interrupted by the user (@pxref{Screen Size}). In this
17599 situation, a Python @code{KeyboardInterrupt} exception is thrown.
17602 * Basic Python:: Basic Python Functions.
17603 * Exception Handling::
17607 @subsubsection Basic Python
17609 @cindex python functions
17610 @cindex python module
17612 @value{GDBN} introduces a new Python module, named @code{gdb}. All
17613 methods and classes added by @value{GDBN} are placed in this module.
17614 @value{GDBN} automatically @code{import}s the @code{gdb} module for
17615 use in all scripts evaluated by the @code{python} command.
17617 @findex gdb.execute
17618 @defun execute command
17619 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
17620 If a GDB exception happens while @var{command} runs, it is
17621 translated as described in @ref{Exception Handling,,Exception Handling}.
17622 If no exceptions occur, this function returns @code{None}.
17625 @findex gdb.get_parameter
17626 @defun get_parameter parameter
17627 Return the value of a @value{GDBN} parameter. @var{parameter} is a
17628 string naming the parameter to look up; @var{parameter} may contain
17629 spaces if the parameter has a multi-part name. For example,
17630 @samp{print object} is a valid parameter name.
17632 If the named parameter does not exist, this function throws a
17633 @code{RuntimeError}. Otherwise, the parameter's value is converted to
17634 a Python value of the appropriate type, and returned.
17638 @defun write string
17639 Print a string to @value{GDBN}'s paginated standard output stream.
17640 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
17641 call this function.
17646 Flush @value{GDBN}'s paginated standard output stream. Flushing
17647 @code{sys.stdout} or @code{sys.stderr} will automatically call this
17651 @node Exception Handling
17652 @subsubsection Exception Handling
17653 @cindex python exceptions
17654 @cindex exceptions, python
17656 When executing the @code{python} command, Python exceptions
17657 uncaught within the Python code are translated to calls to
17658 @value{GDBN} error-reporting mechanism. If the command that called
17659 @code{python} does not handle the error, @value{GDBN} will
17660 terminate it and print an error message containing the Python
17661 exception name, the associated value, and the Python call stack
17662 backtrace at the point where the exception was raised. Example:
17665 (@value{GDBP}) python print foo
17666 Traceback (most recent call last):
17667 File "<string>", line 1, in <module>
17668 NameError: name 'foo' is not defined
17671 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
17672 code are converted to Python @code{RuntimeError} exceptions. User
17673 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
17674 prompt) is translated to a Python @code{KeyboardInterrupt}
17675 exception. If you catch these exceptions in your Python code, your
17676 exception handler will see @code{RuntimeError} or
17677 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
17678 message as its value, and the Python call stack backtrace at the
17679 Python statement closest to where the @value{GDBN} error occured as the
17683 @chapter Command Interpreters
17684 @cindex command interpreters
17686 @value{GDBN} supports multiple command interpreters, and some command
17687 infrastructure to allow users or user interface writers to switch
17688 between interpreters or run commands in other interpreters.
17690 @value{GDBN} currently supports two command interpreters, the console
17691 interpreter (sometimes called the command-line interpreter or @sc{cli})
17692 and the machine interface interpreter (or @sc{gdb/mi}). This manual
17693 describes both of these interfaces in great detail.
17695 By default, @value{GDBN} will start with the console interpreter.
17696 However, the user may choose to start @value{GDBN} with another
17697 interpreter by specifying the @option{-i} or @option{--interpreter}
17698 startup options. Defined interpreters include:
17702 @cindex console interpreter
17703 The traditional console or command-line interpreter. This is the most often
17704 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
17705 @value{GDBN} will use this interpreter.
17708 @cindex mi interpreter
17709 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
17710 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
17711 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
17715 @cindex mi2 interpreter
17716 The current @sc{gdb/mi} interface.
17719 @cindex mi1 interpreter
17720 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
17724 @cindex invoke another interpreter
17725 The interpreter being used by @value{GDBN} may not be dynamically
17726 switched at runtime. Although possible, this could lead to a very
17727 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
17728 enters the command "interpreter-set console" in a console view,
17729 @value{GDBN} would switch to using the console interpreter, rendering
17730 the IDE inoperable!
17732 @kindex interpreter-exec
17733 Although you may only choose a single interpreter at startup, you may execute
17734 commands in any interpreter from the current interpreter using the appropriate
17735 command. If you are running the console interpreter, simply use the
17736 @code{interpreter-exec} command:
17739 interpreter-exec mi "-data-list-register-names"
17742 @sc{gdb/mi} has a similar command, although it is only available in versions of
17743 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
17746 @chapter @value{GDBN} Text User Interface
17748 @cindex Text User Interface
17751 * TUI Overview:: TUI overview
17752 * TUI Keys:: TUI key bindings
17753 * TUI Single Key Mode:: TUI single key mode
17754 * TUI Commands:: TUI-specific commands
17755 * TUI Configuration:: TUI configuration variables
17758 The @value{GDBN} Text User Interface (TUI) is a terminal
17759 interface which uses the @code{curses} library to show the source
17760 file, the assembly output, the program registers and @value{GDBN}
17761 commands in separate text windows. The TUI mode is supported only
17762 on platforms where a suitable version of the @code{curses} library
17765 @pindex @value{GDBTUI}
17766 The TUI mode is enabled by default when you invoke @value{GDBN} as
17767 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
17768 You can also switch in and out of TUI mode while @value{GDBN} runs by
17769 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
17770 @xref{TUI Keys, ,TUI Key Bindings}.
17773 @section TUI Overview
17775 In TUI mode, @value{GDBN} can display several text windows:
17779 This window is the @value{GDBN} command window with the @value{GDBN}
17780 prompt and the @value{GDBN} output. The @value{GDBN} input is still
17781 managed using readline.
17784 The source window shows the source file of the program. The current
17785 line and active breakpoints are displayed in this window.
17788 The assembly window shows the disassembly output of the program.
17791 This window shows the processor registers. Registers are highlighted
17792 when their values change.
17795 The source and assembly windows show the current program position
17796 by highlighting the current line and marking it with a @samp{>} marker.
17797 Breakpoints are indicated with two markers. The first marker
17798 indicates the breakpoint type:
17802 Breakpoint which was hit at least once.
17805 Breakpoint which was never hit.
17808 Hardware breakpoint which was hit at least once.
17811 Hardware breakpoint which was never hit.
17814 The second marker indicates whether the breakpoint is enabled or not:
17818 Breakpoint is enabled.
17821 Breakpoint is disabled.
17824 The source, assembly and register windows are updated when the current
17825 thread changes, when the frame changes, or when the program counter
17828 These windows are not all visible at the same time. The command
17829 window is always visible. The others can be arranged in several
17840 source and assembly,
17843 source and registers, or
17846 assembly and registers.
17849 A status line above the command window shows the following information:
17853 Indicates the current @value{GDBN} target.
17854 (@pxref{Targets, ,Specifying a Debugging Target}).
17857 Gives the current process or thread number.
17858 When no process is being debugged, this field is set to @code{No process}.
17861 Gives the current function name for the selected frame.
17862 The name is demangled if demangling is turned on (@pxref{Print Settings}).
17863 When there is no symbol corresponding to the current program counter,
17864 the string @code{??} is displayed.
17867 Indicates the current line number for the selected frame.
17868 When the current line number is not known, the string @code{??} is displayed.
17871 Indicates the current program counter address.
17875 @section TUI Key Bindings
17876 @cindex TUI key bindings
17878 The TUI installs several key bindings in the readline keymaps
17879 (@pxref{Command Line Editing}). The following key bindings
17880 are installed for both TUI mode and the @value{GDBN} standard mode.
17889 Enter or leave the TUI mode. When leaving the TUI mode,
17890 the curses window management stops and @value{GDBN} operates using
17891 its standard mode, writing on the terminal directly. When reentering
17892 the TUI mode, control is given back to the curses windows.
17893 The screen is then refreshed.
17897 Use a TUI layout with only one window. The layout will
17898 either be @samp{source} or @samp{assembly}. When the TUI mode
17899 is not active, it will switch to the TUI mode.
17901 Think of this key binding as the Emacs @kbd{C-x 1} binding.
17905 Use a TUI layout with at least two windows. When the current
17906 layout already has two windows, the next layout with two windows is used.
17907 When a new layout is chosen, one window will always be common to the
17908 previous layout and the new one.
17910 Think of it as the Emacs @kbd{C-x 2} binding.
17914 Change the active window. The TUI associates several key bindings
17915 (like scrolling and arrow keys) with the active window. This command
17916 gives the focus to the next TUI window.
17918 Think of it as the Emacs @kbd{C-x o} binding.
17922 Switch in and out of the TUI SingleKey mode that binds single
17923 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
17926 The following key bindings only work in the TUI mode:
17931 Scroll the active window one page up.
17935 Scroll the active window one page down.
17939 Scroll the active window one line up.
17943 Scroll the active window one line down.
17947 Scroll the active window one column left.
17951 Scroll the active window one column right.
17955 Refresh the screen.
17958 Because the arrow keys scroll the active window in the TUI mode, they
17959 are not available for their normal use by readline unless the command
17960 window has the focus. When another window is active, you must use
17961 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
17962 and @kbd{C-f} to control the command window.
17964 @node TUI Single Key Mode
17965 @section TUI Single Key Mode
17966 @cindex TUI single key mode
17968 The TUI also provides a @dfn{SingleKey} mode, which binds several
17969 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
17970 switch into this mode, where the following key bindings are used:
17973 @kindex c @r{(SingleKey TUI key)}
17977 @kindex d @r{(SingleKey TUI key)}
17981 @kindex f @r{(SingleKey TUI key)}
17985 @kindex n @r{(SingleKey TUI key)}
17989 @kindex q @r{(SingleKey TUI key)}
17991 exit the SingleKey mode.
17993 @kindex r @r{(SingleKey TUI key)}
17997 @kindex s @r{(SingleKey TUI key)}
18001 @kindex u @r{(SingleKey TUI key)}
18005 @kindex v @r{(SingleKey TUI key)}
18009 @kindex w @r{(SingleKey TUI key)}
18014 Other keys temporarily switch to the @value{GDBN} command prompt.
18015 The key that was pressed is inserted in the editing buffer so that
18016 it is possible to type most @value{GDBN} commands without interaction
18017 with the TUI SingleKey mode. Once the command is entered the TUI
18018 SingleKey mode is restored. The only way to permanently leave
18019 this mode is by typing @kbd{q} or @kbd{C-x s}.
18023 @section TUI-specific Commands
18024 @cindex TUI commands
18026 The TUI has specific commands to control the text windows.
18027 These commands are always available, even when @value{GDBN} is not in
18028 the TUI mode. When @value{GDBN} is in the standard mode, most
18029 of these commands will automatically switch to the TUI mode.
18034 List and give the size of all displayed windows.
18038 Display the next layout.
18041 Display the previous layout.
18044 Display the source window only.
18047 Display the assembly window only.
18050 Display the source and assembly window.
18053 Display the register window together with the source or assembly window.
18057 Make the next window active for scrolling.
18060 Make the previous window active for scrolling.
18063 Make the source window active for scrolling.
18066 Make the assembly window active for scrolling.
18069 Make the register window active for scrolling.
18072 Make the command window active for scrolling.
18076 Refresh the screen. This is similar to typing @kbd{C-L}.
18078 @item tui reg float
18080 Show the floating point registers in the register window.
18082 @item tui reg general
18083 Show the general registers in the register window.
18086 Show the next register group. The list of register groups as well as
18087 their order is target specific. The predefined register groups are the
18088 following: @code{general}, @code{float}, @code{system}, @code{vector},
18089 @code{all}, @code{save}, @code{restore}.
18091 @item tui reg system
18092 Show the system registers in the register window.
18096 Update the source window and the current execution point.
18098 @item winheight @var{name} +@var{count}
18099 @itemx winheight @var{name} -@var{count}
18101 Change the height of the window @var{name} by @var{count}
18102 lines. Positive counts increase the height, while negative counts
18105 @item tabset @var{nchars}
18107 Set the width of tab stops to be @var{nchars} characters.
18110 @node TUI Configuration
18111 @section TUI Configuration Variables
18112 @cindex TUI configuration variables
18114 Several configuration variables control the appearance of TUI windows.
18117 @item set tui border-kind @var{kind}
18118 @kindex set tui border-kind
18119 Select the border appearance for the source, assembly and register windows.
18120 The possible values are the following:
18123 Use a space character to draw the border.
18126 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
18129 Use the Alternate Character Set to draw the border. The border is
18130 drawn using character line graphics if the terminal supports them.
18133 @item set tui border-mode @var{mode}
18134 @kindex set tui border-mode
18135 @itemx set tui active-border-mode @var{mode}
18136 @kindex set tui active-border-mode
18137 Select the display attributes for the borders of the inactive windows
18138 or the active window. The @var{mode} can be one of the following:
18141 Use normal attributes to display the border.
18147 Use reverse video mode.
18150 Use half bright mode.
18152 @item half-standout
18153 Use half bright and standout mode.
18156 Use extra bright or bold mode.
18158 @item bold-standout
18159 Use extra bright or bold and standout mode.
18164 @chapter Using @value{GDBN} under @sc{gnu} Emacs
18167 @cindex @sc{gnu} Emacs
18168 A special interface allows you to use @sc{gnu} Emacs to view (and
18169 edit) the source files for the program you are debugging with
18172 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
18173 executable file you want to debug as an argument. This command starts
18174 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
18175 created Emacs buffer.
18176 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
18178 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
18183 All ``terminal'' input and output goes through an Emacs buffer, called
18186 This applies both to @value{GDBN} commands and their output, and to the input
18187 and output done by the program you are debugging.
18189 This is useful because it means that you can copy the text of previous
18190 commands and input them again; you can even use parts of the output
18193 All the facilities of Emacs' Shell mode are available for interacting
18194 with your program. In particular, you can send signals the usual
18195 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
18199 @value{GDBN} displays source code through Emacs.
18201 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
18202 source file for that frame and puts an arrow (@samp{=>}) at the
18203 left margin of the current line. Emacs uses a separate buffer for
18204 source display, and splits the screen to show both your @value{GDBN} session
18207 Explicit @value{GDBN} @code{list} or search commands still produce output as
18208 usual, but you probably have no reason to use them from Emacs.
18211 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
18212 a graphical mode, enabled by default, which provides further buffers
18213 that can control the execution and describe the state of your program.
18214 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
18216 If you specify an absolute file name when prompted for the @kbd{M-x
18217 gdb} argument, then Emacs sets your current working directory to where
18218 your program resides. If you only specify the file name, then Emacs
18219 sets your current working directory to to the directory associated
18220 with the previous buffer. In this case, @value{GDBN} may find your
18221 program by searching your environment's @code{PATH} variable, but on
18222 some operating systems it might not find the source. So, although the
18223 @value{GDBN} input and output session proceeds normally, the auxiliary
18224 buffer does not display the current source and line of execution.
18226 The initial working directory of @value{GDBN} is printed on the top
18227 line of the GUD buffer and this serves as a default for the commands
18228 that specify files for @value{GDBN} to operate on. @xref{Files,
18229 ,Commands to Specify Files}.
18231 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
18232 need to call @value{GDBN} by a different name (for example, if you
18233 keep several configurations around, with different names) you can
18234 customize the Emacs variable @code{gud-gdb-command-name} to run the
18237 In the GUD buffer, you can use these special Emacs commands in
18238 addition to the standard Shell mode commands:
18242 Describe the features of Emacs' GUD Mode.
18245 Execute to another source line, like the @value{GDBN} @code{step} command; also
18246 update the display window to show the current file and location.
18249 Execute to next source line in this function, skipping all function
18250 calls, like the @value{GDBN} @code{next} command. Then update the display window
18251 to show the current file and location.
18254 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
18255 display window accordingly.
18258 Execute until exit from the selected stack frame, like the @value{GDBN}
18259 @code{finish} command.
18262 Continue execution of your program, like the @value{GDBN} @code{continue}
18266 Go up the number of frames indicated by the numeric argument
18267 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
18268 like the @value{GDBN} @code{up} command.
18271 Go down the number of frames indicated by the numeric argument, like the
18272 @value{GDBN} @code{down} command.
18275 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
18276 tells @value{GDBN} to set a breakpoint on the source line point is on.
18278 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
18279 separate frame which shows a backtrace when the GUD buffer is current.
18280 Move point to any frame in the stack and type @key{RET} to make it
18281 become the current frame and display the associated source in the
18282 source buffer. Alternatively, click @kbd{Mouse-2} to make the
18283 selected frame become the current one. In graphical mode, the
18284 speedbar displays watch expressions.
18286 If you accidentally delete the source-display buffer, an easy way to get
18287 it back is to type the command @code{f} in the @value{GDBN} buffer, to
18288 request a frame display; when you run under Emacs, this recreates
18289 the source buffer if necessary to show you the context of the current
18292 The source files displayed in Emacs are in ordinary Emacs buffers
18293 which are visiting the source files in the usual way. You can edit
18294 the files with these buffers if you wish; but keep in mind that @value{GDBN}
18295 communicates with Emacs in terms of line numbers. If you add or
18296 delete lines from the text, the line numbers that @value{GDBN} knows cease
18297 to correspond properly with the code.
18299 A more detailed description of Emacs' interaction with @value{GDBN} is
18300 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
18303 @c The following dropped because Epoch is nonstandard. Reactivate
18304 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
18306 @kindex Emacs Epoch environment
18310 Version 18 of @sc{gnu} Emacs has a built-in window system
18311 called the @code{epoch}
18312 environment. Users of this environment can use a new command,
18313 @code{inspect} which performs identically to @code{print} except that
18314 each value is printed in its own window.
18319 @chapter The @sc{gdb/mi} Interface
18321 @unnumberedsec Function and Purpose
18323 @cindex @sc{gdb/mi}, its purpose
18324 @sc{gdb/mi} is a line based machine oriented text interface to
18325 @value{GDBN} and is activated by specifying using the
18326 @option{--interpreter} command line option (@pxref{Mode Options}). It
18327 is specifically intended to support the development of systems which
18328 use the debugger as just one small component of a larger system.
18330 This chapter is a specification of the @sc{gdb/mi} interface. It is written
18331 in the form of a reference manual.
18333 Note that @sc{gdb/mi} is still under construction, so some of the
18334 features described below are incomplete and subject to change
18335 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
18337 @unnumberedsec Notation and Terminology
18339 @cindex notational conventions, for @sc{gdb/mi}
18340 This chapter uses the following notation:
18344 @code{|} separates two alternatives.
18347 @code{[ @var{something} ]} indicates that @var{something} is optional:
18348 it may or may not be given.
18351 @code{( @var{group} )*} means that @var{group} inside the parentheses
18352 may repeat zero or more times.
18355 @code{( @var{group} )+} means that @var{group} inside the parentheses
18356 may repeat one or more times.
18359 @code{"@var{string}"} means a literal @var{string}.
18363 @heading Dependencies
18367 * GDB/MI Command Syntax::
18368 * GDB/MI Compatibility with CLI::
18369 * GDB/MI Development and Front Ends::
18370 * GDB/MI Output Records::
18371 * GDB/MI Simple Examples::
18372 * GDB/MI Command Description Format::
18373 * GDB/MI Breakpoint Commands::
18374 * GDB/MI Program Context::
18375 * GDB/MI Thread Commands::
18376 * GDB/MI Program Execution::
18377 * GDB/MI Stack Manipulation::
18378 * GDB/MI Variable Objects::
18379 * GDB/MI Data Manipulation::
18380 * GDB/MI Tracepoint Commands::
18381 * GDB/MI Symbol Query::
18382 * GDB/MI File Commands::
18384 * GDB/MI Kod Commands::
18385 * GDB/MI Memory Overlay Commands::
18386 * GDB/MI Signal Handling Commands::
18388 * GDB/MI Target Manipulation::
18389 * GDB/MI File Transfer Commands::
18390 * GDB/MI Miscellaneous Commands::
18393 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18394 @node GDB/MI Command Syntax
18395 @section @sc{gdb/mi} Command Syntax
18398 * GDB/MI Input Syntax::
18399 * GDB/MI Output Syntax::
18402 @node GDB/MI Input Syntax
18403 @subsection @sc{gdb/mi} Input Syntax
18405 @cindex input syntax for @sc{gdb/mi}
18406 @cindex @sc{gdb/mi}, input syntax
18408 @item @var{command} @expansion{}
18409 @code{@var{cli-command} | @var{mi-command}}
18411 @item @var{cli-command} @expansion{}
18412 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
18413 @var{cli-command} is any existing @value{GDBN} CLI command.
18415 @item @var{mi-command} @expansion{}
18416 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
18417 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
18419 @item @var{token} @expansion{}
18420 "any sequence of digits"
18422 @item @var{option} @expansion{}
18423 @code{"-" @var{parameter} [ " " @var{parameter} ]}
18425 @item @var{parameter} @expansion{}
18426 @code{@var{non-blank-sequence} | @var{c-string}}
18428 @item @var{operation} @expansion{}
18429 @emph{any of the operations described in this chapter}
18431 @item @var{non-blank-sequence} @expansion{}
18432 @emph{anything, provided it doesn't contain special characters such as
18433 "-", @var{nl}, """ and of course " "}
18435 @item @var{c-string} @expansion{}
18436 @code{""" @var{seven-bit-iso-c-string-content} """}
18438 @item @var{nl} @expansion{}
18447 The CLI commands are still handled by the @sc{mi} interpreter; their
18448 output is described below.
18451 The @code{@var{token}}, when present, is passed back when the command
18455 Some @sc{mi} commands accept optional arguments as part of the parameter
18456 list. Each option is identified by a leading @samp{-} (dash) and may be
18457 followed by an optional argument parameter. Options occur first in the
18458 parameter list and can be delimited from normal parameters using
18459 @samp{--} (this is useful when some parameters begin with a dash).
18466 We want easy access to the existing CLI syntax (for debugging).
18469 We want it to be easy to spot a @sc{mi} operation.
18472 @node GDB/MI Output Syntax
18473 @subsection @sc{gdb/mi} Output Syntax
18475 @cindex output syntax of @sc{gdb/mi}
18476 @cindex @sc{gdb/mi}, output syntax
18477 The output from @sc{gdb/mi} consists of zero or more out-of-band records
18478 followed, optionally, by a single result record. This result record
18479 is for the most recent command. The sequence of output records is
18480 terminated by @samp{(gdb)}.
18482 If an input command was prefixed with a @code{@var{token}} then the
18483 corresponding output for that command will also be prefixed by that same
18487 @item @var{output} @expansion{}
18488 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
18490 @item @var{result-record} @expansion{}
18491 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
18493 @item @var{out-of-band-record} @expansion{}
18494 @code{@var{async-record} | @var{stream-record}}
18496 @item @var{async-record} @expansion{}
18497 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
18499 @item @var{exec-async-output} @expansion{}
18500 @code{[ @var{token} ] "*" @var{async-output}}
18502 @item @var{status-async-output} @expansion{}
18503 @code{[ @var{token} ] "+" @var{async-output}}
18505 @item @var{notify-async-output} @expansion{}
18506 @code{[ @var{token} ] "=" @var{async-output}}
18508 @item @var{async-output} @expansion{}
18509 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
18511 @item @var{result-class} @expansion{}
18512 @code{"done" | "running" | "connected" | "error" | "exit"}
18514 @item @var{async-class} @expansion{}
18515 @code{"stopped" | @var{others}} (where @var{others} will be added
18516 depending on the needs---this is still in development).
18518 @item @var{result} @expansion{}
18519 @code{ @var{variable} "=" @var{value}}
18521 @item @var{variable} @expansion{}
18522 @code{ @var{string} }
18524 @item @var{value} @expansion{}
18525 @code{ @var{const} | @var{tuple} | @var{list} }
18527 @item @var{const} @expansion{}
18528 @code{@var{c-string}}
18530 @item @var{tuple} @expansion{}
18531 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
18533 @item @var{list} @expansion{}
18534 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
18535 @var{result} ( "," @var{result} )* "]" }
18537 @item @var{stream-record} @expansion{}
18538 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
18540 @item @var{console-stream-output} @expansion{}
18541 @code{"~" @var{c-string}}
18543 @item @var{target-stream-output} @expansion{}
18544 @code{"@@" @var{c-string}}
18546 @item @var{log-stream-output} @expansion{}
18547 @code{"&" @var{c-string}}
18549 @item @var{nl} @expansion{}
18552 @item @var{token} @expansion{}
18553 @emph{any sequence of digits}.
18561 All output sequences end in a single line containing a period.
18564 The @code{@var{token}} is from the corresponding request. Note that
18565 for all async output, while the token is allowed by the grammar and
18566 may be output by future versions of @value{GDBN} for select async
18567 output messages, it is generally omitted. Frontends should treat
18568 all async output as reporting general changes in the state of the
18569 target and there should be no need to associate async output to any
18573 @cindex status output in @sc{gdb/mi}
18574 @var{status-async-output} contains on-going status information about the
18575 progress of a slow operation. It can be discarded. All status output is
18576 prefixed by @samp{+}.
18579 @cindex async output in @sc{gdb/mi}
18580 @var{exec-async-output} contains asynchronous state change on the target
18581 (stopped, started, disappeared). All async output is prefixed by
18585 @cindex notify output in @sc{gdb/mi}
18586 @var{notify-async-output} contains supplementary information that the
18587 client should handle (e.g., a new breakpoint information). All notify
18588 output is prefixed by @samp{=}.
18591 @cindex console output in @sc{gdb/mi}
18592 @var{console-stream-output} is output that should be displayed as is in the
18593 console. It is the textual response to a CLI command. All the console
18594 output is prefixed by @samp{~}.
18597 @cindex target output in @sc{gdb/mi}
18598 @var{target-stream-output} is the output produced by the target program.
18599 All the target output is prefixed by @samp{@@}.
18602 @cindex log output in @sc{gdb/mi}
18603 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
18604 instance messages that should be displayed as part of an error log. All
18605 the log output is prefixed by @samp{&}.
18608 @cindex list output in @sc{gdb/mi}
18609 New @sc{gdb/mi} commands should only output @var{lists} containing
18615 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
18616 details about the various output records.
18618 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18619 @node GDB/MI Compatibility with CLI
18620 @section @sc{gdb/mi} Compatibility with CLI
18622 @cindex compatibility, @sc{gdb/mi} and CLI
18623 @cindex @sc{gdb/mi}, compatibility with CLI
18625 For the developers convenience CLI commands can be entered directly,
18626 but there may be some unexpected behaviour. For example, commands
18627 that query the user will behave as if the user replied yes, breakpoint
18628 command lists are not executed and some CLI commands, such as
18629 @code{if}, @code{when} and @code{define}, prompt for further input with
18630 @samp{>}, which is not valid MI output.
18632 This feature may be removed at some stage in the future and it is
18633 recommended that front ends use the @code{-interpreter-exec} command
18634 (@pxref{-interpreter-exec}).
18636 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18637 @node GDB/MI Development and Front Ends
18638 @section @sc{gdb/mi} Development and Front Ends
18639 @cindex @sc{gdb/mi} development
18641 The application which takes the MI output and presents the state of the
18642 program being debugged to the user is called a @dfn{front end}.
18644 Although @sc{gdb/mi} is still incomplete, it is currently being used
18645 by a variety of front ends to @value{GDBN}. This makes it difficult
18646 to introduce new functionality without breaking existing usage. This
18647 section tries to minimize the problems by describing how the protocol
18650 Some changes in MI need not break a carefully designed front end, and
18651 for these the MI version will remain unchanged. The following is a
18652 list of changes that may occur within one level, so front ends should
18653 parse MI output in a way that can handle them:
18657 New MI commands may be added.
18660 New fields may be added to the output of any MI command.
18663 The range of values for fields with specified values, e.g.,
18664 @code{in_scope} (@pxref{-var-update}) may be extended.
18666 @c The format of field's content e.g type prefix, may change so parse it
18667 @c at your own risk. Yes, in general?
18669 @c The order of fields may change? Shouldn't really matter but it might
18670 @c resolve inconsistencies.
18673 If the changes are likely to break front ends, the MI version level
18674 will be increased by one. This will allow the front end to parse the
18675 output according to the MI version. Apart from mi0, new versions of
18676 @value{GDBN} will not support old versions of MI and it will be the
18677 responsibility of the front end to work with the new one.
18679 @c Starting with mi3, add a new command -mi-version that prints the MI
18682 The best way to avoid unexpected changes in MI that might break your front
18683 end is to make your project known to @value{GDBN} developers and
18684 follow development on @email{gdb@@sourceware.org} and
18685 @email{gdb-patches@@sourceware.org}.
18686 @cindex mailing lists
18688 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18689 @node GDB/MI Output Records
18690 @section @sc{gdb/mi} Output Records
18693 * GDB/MI Result Records::
18694 * GDB/MI Stream Records::
18695 * GDB/MI Async Records::
18698 @node GDB/MI Result Records
18699 @subsection @sc{gdb/mi} Result Records
18701 @cindex result records in @sc{gdb/mi}
18702 @cindex @sc{gdb/mi}, result records
18703 In addition to a number of out-of-band notifications, the response to a
18704 @sc{gdb/mi} command includes one of the following result indications:
18708 @item "^done" [ "," @var{results} ]
18709 The synchronous operation was successful, @code{@var{results}} are the return
18714 @c Is this one correct? Should it be an out-of-band notification?
18715 The asynchronous operation was successfully started. The target is
18720 @value{GDBN} has connected to a remote target.
18722 @item "^error" "," @var{c-string}
18724 The operation failed. The @code{@var{c-string}} contains the corresponding
18729 @value{GDBN} has terminated.
18733 @node GDB/MI Stream Records
18734 @subsection @sc{gdb/mi} Stream Records
18736 @cindex @sc{gdb/mi}, stream records
18737 @cindex stream records in @sc{gdb/mi}
18738 @value{GDBN} internally maintains a number of output streams: the console, the
18739 target, and the log. The output intended for each of these streams is
18740 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
18742 Each stream record begins with a unique @dfn{prefix character} which
18743 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
18744 Syntax}). In addition to the prefix, each stream record contains a
18745 @code{@var{string-output}}. This is either raw text (with an implicit new
18746 line) or a quoted C string (which does not contain an implicit newline).
18749 @item "~" @var{string-output}
18750 The console output stream contains text that should be displayed in the
18751 CLI console window. It contains the textual responses to CLI commands.
18753 @item "@@" @var{string-output}
18754 The target output stream contains any textual output from the running
18755 target. This is only present when GDB's event loop is truly
18756 asynchronous, which is currently only the case for remote targets.
18758 @item "&" @var{string-output}
18759 The log stream contains debugging messages being produced by @value{GDBN}'s
18763 @node GDB/MI Async Records
18764 @subsection @sc{gdb/mi} Async Records
18766 @cindex async records in @sc{gdb/mi}
18767 @cindex @sc{gdb/mi}, async records
18768 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
18769 additional changes that have occurred. Those changes can either be a
18770 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
18771 target activity (e.g., target stopped).
18773 The following is the list of possible async records:
18777 @item *running,thread-id="@var{thread}"
18778 The target is now running. The @var{thread} field tells which
18779 specific thread is now running, and can be @samp{all} if all threads
18780 are running. The frontend should assume that no interaction with a
18781 running thread is possible after this notification is produced.
18782 The frontend should not assume that this notification is output
18783 only once for any command. @value{GDBN} may emit this notification
18784 several times, either for different threads, because it cannot resume
18785 all threads together, or even for a single thread, if the thread must
18786 be stepped though some code before letting it run freely.
18788 @item *stopped,reason="@var{reason}"
18789 The target has stopped. The @var{reason} field can have one of the
18793 @item breakpoint-hit
18794 A breakpoint was reached.
18795 @item watchpoint-trigger
18796 A watchpoint was triggered.
18797 @item read-watchpoint-trigger
18798 A read watchpoint was triggered.
18799 @item access-watchpoint-trigger
18800 An access watchpoint was triggered.
18801 @item function-finished
18802 An -exec-finish or similar CLI command was accomplished.
18803 @item location-reached
18804 An -exec-until or similar CLI command was accomplished.
18805 @item watchpoint-scope
18806 A watchpoint has gone out of scope.
18807 @item end-stepping-range
18808 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
18809 similar CLI command was accomplished.
18810 @item exited-signalled
18811 The inferior exited because of a signal.
18813 The inferior exited.
18814 @item exited-normally
18815 The inferior exited normally.
18816 @item signal-received
18817 A signal was received by the inferior.
18820 @item =thread-created,id="@var{id}"
18821 @itemx =thread-exited,id="@var{id}"
18822 A thread either was created, or has exited. The @var{id} field
18823 contains the @value{GDBN} identifier of the thread.
18828 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18829 @node GDB/MI Simple Examples
18830 @section Simple Examples of @sc{gdb/mi} Interaction
18831 @cindex @sc{gdb/mi}, simple examples
18833 This subsection presents several simple examples of interaction using
18834 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
18835 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
18836 the output received from @sc{gdb/mi}.
18838 Note the line breaks shown in the examples are here only for
18839 readability, they don't appear in the real output.
18841 @subheading Setting a Breakpoint
18843 Setting a breakpoint generates synchronous output which contains detailed
18844 information of the breakpoint.
18847 -> -break-insert main
18848 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18849 enabled="y",addr="0x08048564",func="main",file="myprog.c",
18850 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
18854 @subheading Program Execution
18856 Program execution generates asynchronous records and MI gives the
18857 reason that execution stopped.
18863 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
18864 frame=@{addr="0x08048564",func="main",
18865 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
18866 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
18871 <- *stopped,reason="exited-normally"
18875 @subheading Quitting @value{GDBN}
18877 Quitting @value{GDBN} just prints the result class @samp{^exit}.
18885 @subheading A Bad Command
18887 Here's what happens if you pass a non-existent command:
18891 <- ^error,msg="Undefined MI command: rubbish"
18896 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18897 @node GDB/MI Command Description Format
18898 @section @sc{gdb/mi} Command Description Format
18900 The remaining sections describe blocks of commands. Each block of
18901 commands is laid out in a fashion similar to this section.
18903 @subheading Motivation
18905 The motivation for this collection of commands.
18907 @subheading Introduction
18909 A brief introduction to this collection of commands as a whole.
18911 @subheading Commands
18913 For each command in the block, the following is described:
18915 @subsubheading Synopsis
18918 -command @var{args}@dots{}
18921 @subsubheading Result
18923 @subsubheading @value{GDBN} Command
18925 The corresponding @value{GDBN} CLI command(s), if any.
18927 @subsubheading Example
18929 Example(s) formatted for readability. Some of the described commands have
18930 not been implemented yet and these are labeled N.A.@: (not available).
18933 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18934 @node GDB/MI Breakpoint Commands
18935 @section @sc{gdb/mi} Breakpoint Commands
18937 @cindex breakpoint commands for @sc{gdb/mi}
18938 @cindex @sc{gdb/mi}, breakpoint commands
18939 This section documents @sc{gdb/mi} commands for manipulating
18942 @subheading The @code{-break-after} Command
18943 @findex -break-after
18945 @subsubheading Synopsis
18948 -break-after @var{number} @var{count}
18951 The breakpoint number @var{number} is not in effect until it has been
18952 hit @var{count} times. To see how this is reflected in the output of
18953 the @samp{-break-list} command, see the description of the
18954 @samp{-break-list} command below.
18956 @subsubheading @value{GDBN} Command
18958 The corresponding @value{GDBN} command is @samp{ignore}.
18960 @subsubheading Example
18965 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18966 enabled="y",addr="0x000100d0",func="main",file="hello.c",
18967 fullname="/home/foo/hello.c",line="5",times="0"@}
18974 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18975 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18976 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18977 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18978 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18979 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18980 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18981 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18982 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18983 line="5",times="0",ignore="3"@}]@}
18988 @subheading The @code{-break-catch} Command
18989 @findex -break-catch
18991 @subheading The @code{-break-commands} Command
18992 @findex -break-commands
18996 @subheading The @code{-break-condition} Command
18997 @findex -break-condition
18999 @subsubheading Synopsis
19002 -break-condition @var{number} @var{expr}
19005 Breakpoint @var{number} will stop the program only if the condition in
19006 @var{expr} is true. The condition becomes part of the
19007 @samp{-break-list} output (see the description of the @samp{-break-list}
19010 @subsubheading @value{GDBN} Command
19012 The corresponding @value{GDBN} command is @samp{condition}.
19014 @subsubheading Example
19018 -break-condition 1 1
19022 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19023 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19024 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19025 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19026 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19027 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19028 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19029 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19030 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19031 line="5",cond="1",times="0",ignore="3"@}]@}
19035 @subheading The @code{-break-delete} Command
19036 @findex -break-delete
19038 @subsubheading Synopsis
19041 -break-delete ( @var{breakpoint} )+
19044 Delete the breakpoint(s) whose number(s) are specified in the argument
19045 list. This is obviously reflected in the breakpoint list.
19047 @subsubheading @value{GDBN} Command
19049 The corresponding @value{GDBN} command is @samp{delete}.
19051 @subsubheading Example
19059 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
19060 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19061 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19062 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19063 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19064 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19065 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19070 @subheading The @code{-break-disable} Command
19071 @findex -break-disable
19073 @subsubheading Synopsis
19076 -break-disable ( @var{breakpoint} )+
19079 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
19080 break list is now set to @samp{n} for the named @var{breakpoint}(s).
19082 @subsubheading @value{GDBN} Command
19084 The corresponding @value{GDBN} command is @samp{disable}.
19086 @subsubheading Example
19094 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19095 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19096 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19097 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19098 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19099 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19100 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19101 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
19102 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19103 line="5",times="0"@}]@}
19107 @subheading The @code{-break-enable} Command
19108 @findex -break-enable
19110 @subsubheading Synopsis
19113 -break-enable ( @var{breakpoint} )+
19116 Enable (previously disabled) @var{breakpoint}(s).
19118 @subsubheading @value{GDBN} Command
19120 The corresponding @value{GDBN} command is @samp{enable}.
19122 @subsubheading Example
19130 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19131 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19132 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19133 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19134 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19135 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19136 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19137 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
19138 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19139 line="5",times="0"@}]@}
19143 @subheading The @code{-break-info} Command
19144 @findex -break-info
19146 @subsubheading Synopsis
19149 -break-info @var{breakpoint}
19153 Get information about a single breakpoint.
19155 @subsubheading @value{GDBN} Command
19157 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
19159 @subsubheading Example
19162 @subheading The @code{-break-insert} Command
19163 @findex -break-insert
19165 @subsubheading Synopsis
19168 -break-insert [ -t ] [ -h ] [ -f ]
19169 [ -c @var{condition} ] [ -i @var{ignore-count} ]
19170 [ -p @var{thread} ] [ @var{location} ]
19174 If specified, @var{location}, can be one of:
19181 @item filename:linenum
19182 @item filename:function
19186 The possible optional parameters of this command are:
19190 Insert a temporary breakpoint.
19192 Insert a hardware breakpoint.
19193 @item -c @var{condition}
19194 Make the breakpoint conditional on @var{condition}.
19195 @item -i @var{ignore-count}
19196 Initialize the @var{ignore-count}.
19198 If @var{location} cannot be parsed (for example if it
19199 refers to unknown files or functions), create a pending
19200 breakpoint. Without this flag, @value{GDBN} will report
19201 an error, and won't create a breakpoint, if @var{location}
19205 @subsubheading Result
19207 The result is in the form:
19210 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
19211 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
19212 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
19213 times="@var{times}"@}
19217 where @var{number} is the @value{GDBN} number for this breakpoint,
19218 @var{funcname} is the name of the function where the breakpoint was
19219 inserted, @var{filename} is the name of the source file which contains
19220 this function, @var{lineno} is the source line number within that file
19221 and @var{times} the number of times that the breakpoint has been hit
19222 (always 0 for -break-insert but may be greater for -break-info or -break-list
19223 which use the same output).
19225 Note: this format is open to change.
19226 @c An out-of-band breakpoint instead of part of the result?
19228 @subsubheading @value{GDBN} Command
19230 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
19231 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
19233 @subsubheading Example
19238 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
19239 fullname="/home/foo/recursive2.c,line="4",times="0"@}
19241 -break-insert -t foo
19242 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
19243 fullname="/home/foo/recursive2.c,line="11",times="0"@}
19246 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19247 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19248 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19249 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19250 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19251 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19252 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19253 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19254 addr="0x0001072c", func="main",file="recursive2.c",
19255 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
19256 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
19257 addr="0x00010774",func="foo",file="recursive2.c",
19258 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
19260 -break-insert -r foo.*
19261 ~int foo(int, int);
19262 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
19263 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
19267 @subheading The @code{-break-list} Command
19268 @findex -break-list
19270 @subsubheading Synopsis
19276 Displays the list of inserted breakpoints, showing the following fields:
19280 number of the breakpoint
19282 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
19284 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
19287 is the breakpoint enabled or no: @samp{y} or @samp{n}
19289 memory location at which the breakpoint is set
19291 logical location of the breakpoint, expressed by function name, file
19294 number of times the breakpoint has been hit
19297 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
19298 @code{body} field is an empty list.
19300 @subsubheading @value{GDBN} Command
19302 The corresponding @value{GDBN} command is @samp{info break}.
19304 @subsubheading Example
19309 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19310 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19311 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19312 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19313 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19314 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19315 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19316 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19317 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
19318 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
19319 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
19320 line="13",times="0"@}]@}
19324 Here's an example of the result when there are no breakpoints:
19329 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
19330 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19331 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19332 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19333 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19334 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19335 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19340 @subheading The @code{-break-watch} Command
19341 @findex -break-watch
19343 @subsubheading Synopsis
19346 -break-watch [ -a | -r ]
19349 Create a watchpoint. With the @samp{-a} option it will create an
19350 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
19351 read from or on a write to the memory location. With the @samp{-r}
19352 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
19353 trigger only when the memory location is accessed for reading. Without
19354 either of the options, the watchpoint created is a regular watchpoint,
19355 i.e., it will trigger when the memory location is accessed for writing.
19356 @xref{Set Watchpoints, , Setting Watchpoints}.
19358 Note that @samp{-break-list} will report a single list of watchpoints and
19359 breakpoints inserted.
19361 @subsubheading @value{GDBN} Command
19363 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
19366 @subsubheading Example
19368 Setting a watchpoint on a variable in the @code{main} function:
19373 ^done,wpt=@{number="2",exp="x"@}
19378 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
19379 value=@{old="-268439212",new="55"@},
19380 frame=@{func="main",args=[],file="recursive2.c",
19381 fullname="/home/foo/bar/recursive2.c",line="5"@}
19385 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
19386 the program execution twice: first for the variable changing value, then
19387 for the watchpoint going out of scope.
19392 ^done,wpt=@{number="5",exp="C"@}
19397 *stopped,reason="watchpoint-trigger",
19398 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
19399 frame=@{func="callee4",args=[],
19400 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19401 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
19406 *stopped,reason="watchpoint-scope",wpnum="5",
19407 frame=@{func="callee3",args=[@{name="strarg",
19408 value="0x11940 \"A string argument.\""@}],
19409 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19410 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19414 Listing breakpoints and watchpoints, at different points in the program
19415 execution. Note that once the watchpoint goes out of scope, it is
19421 ^done,wpt=@{number="2",exp="C"@}
19424 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19425 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19426 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19427 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19428 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19429 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19430 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19431 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19432 addr="0x00010734",func="callee4",
19433 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19434 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
19435 bkpt=@{number="2",type="watchpoint",disp="keep",
19436 enabled="y",addr="",what="C",times="0"@}]@}
19441 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
19442 value=@{old="-276895068",new="3"@},
19443 frame=@{func="callee4",args=[],
19444 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19445 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
19448 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19449 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19450 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19451 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19452 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19453 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19454 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19455 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19456 addr="0x00010734",func="callee4",
19457 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19458 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
19459 bkpt=@{number="2",type="watchpoint",disp="keep",
19460 enabled="y",addr="",what="C",times="-5"@}]@}
19464 ^done,reason="watchpoint-scope",wpnum="2",
19465 frame=@{func="callee3",args=[@{name="strarg",
19466 value="0x11940 \"A string argument.\""@}],
19467 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19468 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19471 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19472 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19473 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19474 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19475 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19476 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19477 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19478 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19479 addr="0x00010734",func="callee4",
19480 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19481 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
19486 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19487 @node GDB/MI Program Context
19488 @section @sc{gdb/mi} Program Context
19490 @subheading The @code{-exec-arguments} Command
19491 @findex -exec-arguments
19494 @subsubheading Synopsis
19497 -exec-arguments @var{args}
19500 Set the inferior program arguments, to be used in the next
19503 @subsubheading @value{GDBN} Command
19505 The corresponding @value{GDBN} command is @samp{set args}.
19507 @subsubheading Example
19511 -exec-arguments -v word
19517 @subheading The @code{-exec-show-arguments} Command
19518 @findex -exec-show-arguments
19520 @subsubheading Synopsis
19523 -exec-show-arguments
19526 Print the arguments of the program.
19528 @subsubheading @value{GDBN} Command
19530 The corresponding @value{GDBN} command is @samp{show args}.
19532 @subsubheading Example
19536 @subheading The @code{-environment-cd} Command
19537 @findex -environment-cd
19539 @subsubheading Synopsis
19542 -environment-cd @var{pathdir}
19545 Set @value{GDBN}'s working directory.
19547 @subsubheading @value{GDBN} Command
19549 The corresponding @value{GDBN} command is @samp{cd}.
19551 @subsubheading Example
19555 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19561 @subheading The @code{-environment-directory} Command
19562 @findex -environment-directory
19564 @subsubheading Synopsis
19567 -environment-directory [ -r ] [ @var{pathdir} ]+
19570 Add directories @var{pathdir} to beginning of search path for source files.
19571 If the @samp{-r} option is used, the search path is reset to the default
19572 search path. If directories @var{pathdir} are supplied in addition to the
19573 @samp{-r} option, the search path is first reset and then addition
19575 Multiple directories may be specified, separated by blanks. Specifying
19576 multiple directories in a single command
19577 results in the directories added to the beginning of the
19578 search path in the same order they were presented in the command.
19579 If blanks are needed as
19580 part of a directory name, double-quotes should be used around
19581 the name. In the command output, the path will show up separated
19582 by the system directory-separator character. The directory-separator
19583 character must not be used
19584 in any directory name.
19585 If no directories are specified, the current search path is displayed.
19587 @subsubheading @value{GDBN} Command
19589 The corresponding @value{GDBN} command is @samp{dir}.
19591 @subsubheading Example
19595 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19596 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19598 -environment-directory ""
19599 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19601 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
19602 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
19604 -environment-directory -r
19605 ^done,source-path="$cdir:$cwd"
19610 @subheading The @code{-environment-path} Command
19611 @findex -environment-path
19613 @subsubheading Synopsis
19616 -environment-path [ -r ] [ @var{pathdir} ]+
19619 Add directories @var{pathdir} to beginning of search path for object files.
19620 If the @samp{-r} option is used, the search path is reset to the original
19621 search path that existed at gdb start-up. If directories @var{pathdir} are
19622 supplied in addition to the
19623 @samp{-r} option, the search path is first reset and then addition
19625 Multiple directories may be specified, separated by blanks. Specifying
19626 multiple directories in a single command
19627 results in the directories added to the beginning of the
19628 search path in the same order they were presented in the command.
19629 If blanks are needed as
19630 part of a directory name, double-quotes should be used around
19631 the name. In the command output, the path will show up separated
19632 by the system directory-separator character. The directory-separator
19633 character must not be used
19634 in any directory name.
19635 If no directories are specified, the current path is displayed.
19638 @subsubheading @value{GDBN} Command
19640 The corresponding @value{GDBN} command is @samp{path}.
19642 @subsubheading Example
19647 ^done,path="/usr/bin"
19649 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
19650 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
19652 -environment-path -r /usr/local/bin
19653 ^done,path="/usr/local/bin:/usr/bin"
19658 @subheading The @code{-environment-pwd} Command
19659 @findex -environment-pwd
19661 @subsubheading Synopsis
19667 Show the current working directory.
19669 @subsubheading @value{GDBN} Command
19671 The corresponding @value{GDBN} command is @samp{pwd}.
19673 @subsubheading Example
19678 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
19682 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19683 @node GDB/MI Thread Commands
19684 @section @sc{gdb/mi} Thread Commands
19687 @subheading The @code{-thread-info} Command
19688 @findex -thread-info
19690 @subsubheading Synopsis
19693 -thread-info [ @var{thread-id} ]
19696 Reports information about either a specific thread, if
19697 the @var{thread-id} parameter is present, or about all
19698 threads. When printing information about all threads,
19699 also reports the current thread.
19701 @subsubheading @value{GDBN} Command
19703 The @samp{info thread} command prints the same information
19706 @subsubheading Example
19711 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
19712 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},
19713 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
19714 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
19715 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}@}],
19716 current-thread-id="1"
19720 @subheading The @code{-thread-list-ids} Command
19721 @findex -thread-list-ids
19723 @subsubheading Synopsis
19729 Produces a list of the currently known @value{GDBN} thread ids. At the
19730 end of the list it also prints the total number of such threads.
19732 @subsubheading @value{GDBN} Command
19734 Part of @samp{info threads} supplies the same information.
19736 @subsubheading Example
19738 No threads present, besides the main process:
19743 ^done,thread-ids=@{@},number-of-threads="0"
19753 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19754 number-of-threads="3"
19759 @subheading The @code{-thread-select} Command
19760 @findex -thread-select
19762 @subsubheading Synopsis
19765 -thread-select @var{threadnum}
19768 Make @var{threadnum} the current thread. It prints the number of the new
19769 current thread, and the topmost frame for that thread.
19771 @subsubheading @value{GDBN} Command
19773 The corresponding @value{GDBN} command is @samp{thread}.
19775 @subsubheading Example
19782 *stopped,reason="end-stepping-range",thread-id="2",line="187",
19783 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
19787 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19788 number-of-threads="3"
19791 ^done,new-thread-id="3",
19792 frame=@{level="0",func="vprintf",
19793 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
19794 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
19798 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19799 @node GDB/MI Program Execution
19800 @section @sc{gdb/mi} Program Execution
19802 These are the asynchronous commands which generate the out-of-band
19803 record @samp{*stopped}. Currently @value{GDBN} only really executes
19804 asynchronously with remote targets and this interaction is mimicked in
19807 @subheading The @code{-exec-continue} Command
19808 @findex -exec-continue
19810 @subsubheading Synopsis
19816 Resumes the execution of the inferior program until a breakpoint is
19817 encountered, or until the inferior exits.
19819 @subsubheading @value{GDBN} Command
19821 The corresponding @value{GDBN} corresponding is @samp{continue}.
19823 @subsubheading Example
19830 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
19831 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
19837 @subheading The @code{-exec-finish} Command
19838 @findex -exec-finish
19840 @subsubheading Synopsis
19846 Resumes the execution of the inferior program until the current
19847 function is exited. Displays the results returned by the function.
19849 @subsubheading @value{GDBN} Command
19851 The corresponding @value{GDBN} command is @samp{finish}.
19853 @subsubheading Example
19855 Function returning @code{void}.
19862 *stopped,reason="function-finished",frame=@{func="main",args=[],
19863 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
19867 Function returning other than @code{void}. The name of the internal
19868 @value{GDBN} variable storing the result is printed, together with the
19875 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
19876 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
19877 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19878 gdb-result-var="$1",return-value="0"
19883 @subheading The @code{-exec-interrupt} Command
19884 @findex -exec-interrupt
19886 @subsubheading Synopsis
19892 Interrupts the background execution of the target. Note how the token
19893 associated with the stop message is the one for the execution command
19894 that has been interrupted. The token for the interrupt itself only
19895 appears in the @samp{^done} output. If the user is trying to
19896 interrupt a non-running program, an error message will be printed.
19898 @subsubheading @value{GDBN} Command
19900 The corresponding @value{GDBN} command is @samp{interrupt}.
19902 @subsubheading Example
19913 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
19914 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
19915 fullname="/home/foo/bar/try.c",line="13"@}
19920 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
19925 @subheading The @code{-exec-next} Command
19928 @subsubheading Synopsis
19934 Resumes execution of the inferior program, stopping when the beginning
19935 of the next source line is reached.
19937 @subsubheading @value{GDBN} Command
19939 The corresponding @value{GDBN} command is @samp{next}.
19941 @subsubheading Example
19947 *stopped,reason="end-stepping-range",line="8",file="hello.c"
19952 @subheading The @code{-exec-next-instruction} Command
19953 @findex -exec-next-instruction
19955 @subsubheading Synopsis
19958 -exec-next-instruction
19961 Executes one machine instruction. If the instruction is a function
19962 call, continues until the function returns. If the program stops at an
19963 instruction in the middle of a source line, the address will be
19966 @subsubheading @value{GDBN} Command
19968 The corresponding @value{GDBN} command is @samp{nexti}.
19970 @subsubheading Example
19974 -exec-next-instruction
19978 *stopped,reason="end-stepping-range",
19979 addr="0x000100d4",line="5",file="hello.c"
19984 @subheading The @code{-exec-return} Command
19985 @findex -exec-return
19987 @subsubheading Synopsis
19993 Makes current function return immediately. Doesn't execute the inferior.
19994 Displays the new current frame.
19996 @subsubheading @value{GDBN} Command
19998 The corresponding @value{GDBN} command is @samp{return}.
20000 @subsubheading Example
20004 200-break-insert callee4
20005 200^done,bkpt=@{number="1",addr="0x00010734",
20006 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
20011 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
20012 frame=@{func="callee4",args=[],
20013 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20014 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
20020 111^done,frame=@{level="0",func="callee3",
20021 args=[@{name="strarg",
20022 value="0x11940 \"A string argument.\""@}],
20023 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20024 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20029 @subheading The @code{-exec-run} Command
20032 @subsubheading Synopsis
20038 Starts execution of the inferior from the beginning. The inferior
20039 executes until either a breakpoint is encountered or the program
20040 exits. In the latter case the output will include an exit code, if
20041 the program has exited exceptionally.
20043 @subsubheading @value{GDBN} Command
20045 The corresponding @value{GDBN} command is @samp{run}.
20047 @subsubheading Examples
20052 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
20057 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
20058 frame=@{func="main",args=[],file="recursive2.c",
20059 fullname="/home/foo/bar/recursive2.c",line="4"@}
20064 Program exited normally:
20072 *stopped,reason="exited-normally"
20077 Program exited exceptionally:
20085 *stopped,reason="exited",exit-code="01"
20089 Another way the program can terminate is if it receives a signal such as
20090 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
20094 *stopped,reason="exited-signalled",signal-name="SIGINT",
20095 signal-meaning="Interrupt"
20099 @c @subheading -exec-signal
20102 @subheading The @code{-exec-step} Command
20105 @subsubheading Synopsis
20111 Resumes execution of the inferior program, stopping when the beginning
20112 of the next source line is reached, if the next source line is not a
20113 function call. If it is, stop at the first instruction of the called
20116 @subsubheading @value{GDBN} Command
20118 The corresponding @value{GDBN} command is @samp{step}.
20120 @subsubheading Example
20122 Stepping into a function:
20128 *stopped,reason="end-stepping-range",
20129 frame=@{func="foo",args=[@{name="a",value="10"@},
20130 @{name="b",value="0"@}],file="recursive2.c",
20131 fullname="/home/foo/bar/recursive2.c",line="11"@}
20141 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
20146 @subheading The @code{-exec-step-instruction} Command
20147 @findex -exec-step-instruction
20149 @subsubheading Synopsis
20152 -exec-step-instruction
20155 Resumes the inferior which executes one machine instruction. The
20156 output, once @value{GDBN} has stopped, will vary depending on whether
20157 we have stopped in the middle of a source line or not. In the former
20158 case, the address at which the program stopped will be printed as
20161 @subsubheading @value{GDBN} Command
20163 The corresponding @value{GDBN} command is @samp{stepi}.
20165 @subsubheading Example
20169 -exec-step-instruction
20173 *stopped,reason="end-stepping-range",
20174 frame=@{func="foo",args=[],file="try.c",
20175 fullname="/home/foo/bar/try.c",line="10"@}
20177 -exec-step-instruction
20181 *stopped,reason="end-stepping-range",
20182 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
20183 fullname="/home/foo/bar/try.c",line="10"@}
20188 @subheading The @code{-exec-until} Command
20189 @findex -exec-until
20191 @subsubheading Synopsis
20194 -exec-until [ @var{location} ]
20197 Executes the inferior until the @var{location} specified in the
20198 argument is reached. If there is no argument, the inferior executes
20199 until a source line greater than the current one is reached. The
20200 reason for stopping in this case will be @samp{location-reached}.
20202 @subsubheading @value{GDBN} Command
20204 The corresponding @value{GDBN} command is @samp{until}.
20206 @subsubheading Example
20210 -exec-until recursive2.c:6
20214 *stopped,reason="location-reached",frame=@{func="main",args=[],
20215 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
20220 @subheading -file-clear
20221 Is this going away????
20224 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20225 @node GDB/MI Stack Manipulation
20226 @section @sc{gdb/mi} Stack Manipulation Commands
20229 @subheading The @code{-stack-info-frame} Command
20230 @findex -stack-info-frame
20232 @subsubheading Synopsis
20238 Get info on the selected frame.
20240 @subsubheading @value{GDBN} Command
20242 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
20243 (without arguments).
20245 @subsubheading Example
20250 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
20251 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20252 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
20256 @subheading The @code{-stack-info-depth} Command
20257 @findex -stack-info-depth
20259 @subsubheading Synopsis
20262 -stack-info-depth [ @var{max-depth} ]
20265 Return the depth of the stack. If the integer argument @var{max-depth}
20266 is specified, do not count beyond @var{max-depth} frames.
20268 @subsubheading @value{GDBN} Command
20270 There's no equivalent @value{GDBN} command.
20272 @subsubheading Example
20274 For a stack with frame levels 0 through 11:
20281 -stack-info-depth 4
20284 -stack-info-depth 12
20287 -stack-info-depth 11
20290 -stack-info-depth 13
20295 @subheading The @code{-stack-list-arguments} Command
20296 @findex -stack-list-arguments
20298 @subsubheading Synopsis
20301 -stack-list-arguments @var{show-values}
20302 [ @var{low-frame} @var{high-frame} ]
20305 Display a list of the arguments for the frames between @var{low-frame}
20306 and @var{high-frame} (inclusive). If @var{low-frame} and
20307 @var{high-frame} are not provided, list the arguments for the whole
20308 call stack. If the two arguments are equal, show the single frame
20309 at the corresponding level. It is an error if @var{low-frame} is
20310 larger than the actual number of frames. On the other hand,
20311 @var{high-frame} may be larger than the actual number of frames, in
20312 which case only existing frames will be returned.
20314 The @var{show-values} argument must have a value of 0 or 1. A value of
20315 0 means that only the names of the arguments are listed, a value of 1
20316 means that both names and values of the arguments are printed.
20318 @subsubheading @value{GDBN} Command
20320 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
20321 @samp{gdb_get_args} command which partially overlaps with the
20322 functionality of @samp{-stack-list-arguments}.
20324 @subsubheading Example
20331 frame=@{level="0",addr="0x00010734",func="callee4",
20332 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20333 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
20334 frame=@{level="1",addr="0x0001076c",func="callee3",
20335 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20336 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
20337 frame=@{level="2",addr="0x0001078c",func="callee2",
20338 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20339 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
20340 frame=@{level="3",addr="0x000107b4",func="callee1",
20341 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20342 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
20343 frame=@{level="4",addr="0x000107e0",func="main",
20344 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20345 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
20347 -stack-list-arguments 0
20350 frame=@{level="0",args=[]@},
20351 frame=@{level="1",args=[name="strarg"]@},
20352 frame=@{level="2",args=[name="intarg",name="strarg"]@},
20353 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
20354 frame=@{level="4",args=[]@}]
20356 -stack-list-arguments 1
20359 frame=@{level="0",args=[]@},
20361 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
20362 frame=@{level="2",args=[
20363 @{name="intarg",value="2"@},
20364 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
20365 @{frame=@{level="3",args=[
20366 @{name="intarg",value="2"@},
20367 @{name="strarg",value="0x11940 \"A string argument.\""@},
20368 @{name="fltarg",value="3.5"@}]@},
20369 frame=@{level="4",args=[]@}]
20371 -stack-list-arguments 0 2 2
20372 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
20374 -stack-list-arguments 1 2 2
20375 ^done,stack-args=[frame=@{level="2",
20376 args=[@{name="intarg",value="2"@},
20377 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
20381 @c @subheading -stack-list-exception-handlers
20384 @subheading The @code{-stack-list-frames} Command
20385 @findex -stack-list-frames
20387 @subsubheading Synopsis
20390 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
20393 List the frames currently on the stack. For each frame it displays the
20398 The frame number, 0 being the topmost frame, i.e., the innermost function.
20400 The @code{$pc} value for that frame.
20404 File name of the source file where the function lives.
20406 Line number corresponding to the @code{$pc}.
20409 If invoked without arguments, this command prints a backtrace for the
20410 whole stack. If given two integer arguments, it shows the frames whose
20411 levels are between the two arguments (inclusive). If the two arguments
20412 are equal, it shows the single frame at the corresponding level. It is
20413 an error if @var{low-frame} is larger than the actual number of
20414 frames. On the other hand, @var{high-frame} may be larger than the
20415 actual number of frames, in which case only existing frames will be returned.
20417 @subsubheading @value{GDBN} Command
20419 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
20421 @subsubheading Example
20423 Full stack backtrace:
20429 [frame=@{level="0",addr="0x0001076c",func="foo",
20430 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
20431 frame=@{level="1",addr="0x000107a4",func="foo",
20432 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20433 frame=@{level="2",addr="0x000107a4",func="foo",
20434 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20435 frame=@{level="3",addr="0x000107a4",func="foo",
20436 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20437 frame=@{level="4",addr="0x000107a4",func="foo",
20438 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20439 frame=@{level="5",addr="0x000107a4",func="foo",
20440 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20441 frame=@{level="6",addr="0x000107a4",func="foo",
20442 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20443 frame=@{level="7",addr="0x000107a4",func="foo",
20444 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20445 frame=@{level="8",addr="0x000107a4",func="foo",
20446 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20447 frame=@{level="9",addr="0x000107a4",func="foo",
20448 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20449 frame=@{level="10",addr="0x000107a4",func="foo",
20450 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20451 frame=@{level="11",addr="0x00010738",func="main",
20452 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
20456 Show frames between @var{low_frame} and @var{high_frame}:
20460 -stack-list-frames 3 5
20462 [frame=@{level="3",addr="0x000107a4",func="foo",
20463 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20464 frame=@{level="4",addr="0x000107a4",func="foo",
20465 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20466 frame=@{level="5",addr="0x000107a4",func="foo",
20467 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20471 Show a single frame:
20475 -stack-list-frames 3 3
20477 [frame=@{level="3",addr="0x000107a4",func="foo",
20478 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20483 @subheading The @code{-stack-list-locals} Command
20484 @findex -stack-list-locals
20486 @subsubheading Synopsis
20489 -stack-list-locals @var{print-values}
20492 Display the local variable names for the selected frame. If
20493 @var{print-values} is 0 or @code{--no-values}, print only the names of
20494 the variables; if it is 1 or @code{--all-values}, print also their
20495 values; and if it is 2 or @code{--simple-values}, print the name,
20496 type and value for simple data types and the name and type for arrays,
20497 structures and unions. In this last case, a frontend can immediately
20498 display the value of simple data types and create variable objects for
20499 other data types when the user wishes to explore their values in
20502 @subsubheading @value{GDBN} Command
20504 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
20506 @subsubheading Example
20510 -stack-list-locals 0
20511 ^done,locals=[name="A",name="B",name="C"]
20513 -stack-list-locals --all-values
20514 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
20515 @{name="C",value="@{1, 2, 3@}"@}]
20516 -stack-list-locals --simple-values
20517 ^done,locals=[@{name="A",type="int",value="1"@},
20518 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
20523 @subheading The @code{-stack-select-frame} Command
20524 @findex -stack-select-frame
20526 @subsubheading Synopsis
20529 -stack-select-frame @var{framenum}
20532 Change the selected frame. Select a different frame @var{framenum} on
20535 @subsubheading @value{GDBN} Command
20537 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
20538 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
20540 @subsubheading Example
20544 -stack-select-frame 2
20549 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20550 @node GDB/MI Variable Objects
20551 @section @sc{gdb/mi} Variable Objects
20555 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20557 For the implementation of a variable debugger window (locals, watched
20558 expressions, etc.), we are proposing the adaptation of the existing code
20559 used by @code{Insight}.
20561 The two main reasons for that are:
20565 It has been proven in practice (it is already on its second generation).
20568 It will shorten development time (needless to say how important it is
20572 The original interface was designed to be used by Tcl code, so it was
20573 slightly changed so it could be used through @sc{gdb/mi}. This section
20574 describes the @sc{gdb/mi} operations that will be available and gives some
20575 hints about their use.
20577 @emph{Note}: In addition to the set of operations described here, we
20578 expect the @sc{gui} implementation of a variable window to require, at
20579 least, the following operations:
20582 @item @code{-gdb-show} @code{output-radix}
20583 @item @code{-stack-list-arguments}
20584 @item @code{-stack-list-locals}
20585 @item @code{-stack-select-frame}
20590 @subheading Introduction to Variable Objects
20592 @cindex variable objects in @sc{gdb/mi}
20594 Variable objects are "object-oriented" MI interface for examining and
20595 changing values of expressions. Unlike some other MI interfaces that
20596 work with expressions, variable objects are specifically designed for
20597 simple and efficient presentation in the frontend. A variable object
20598 is identified by string name. When a variable object is created, the
20599 frontend specifies the expression for that variable object. The
20600 expression can be a simple variable, or it can be an arbitrary complex
20601 expression, and can even involve CPU registers. After creating a
20602 variable object, the frontend can invoke other variable object
20603 operations---for example to obtain or change the value of a variable
20604 object, or to change display format.
20606 Variable objects have hierarchical tree structure. Any variable object
20607 that corresponds to a composite type, such as structure in C, has
20608 a number of child variable objects, for example corresponding to each
20609 element of a structure. A child variable object can itself have
20610 children, recursively. Recursion ends when we reach
20611 leaf variable objects, which always have built-in types. Child variable
20612 objects are created only by explicit request, so if a frontend
20613 is not interested in the children of a particular variable object, no
20614 child will be created.
20616 For a leaf variable object it is possible to obtain its value as a
20617 string, or set the value from a string. String value can be also
20618 obtained for a non-leaf variable object, but it's generally a string
20619 that only indicates the type of the object, and does not list its
20620 contents. Assignment to a non-leaf variable object is not allowed.
20622 A frontend does not need to read the values of all variable objects each time
20623 the program stops. Instead, MI provides an update command that lists all
20624 variable objects whose values has changed since the last update
20625 operation. This considerably reduces the amount of data that must
20626 be transferred to the frontend. As noted above, children variable
20627 objects are created on demand, and only leaf variable objects have a
20628 real value. As result, gdb will read target memory only for leaf
20629 variables that frontend has created.
20631 The automatic update is not always desirable. For example, a frontend
20632 might want to keep a value of some expression for future reference,
20633 and never update it. For another example, fetching memory is
20634 relatively slow for embedded targets, so a frontend might want
20635 to disable automatic update for the variables that are either not
20636 visible on the screen, or ``closed''. This is possible using so
20637 called ``frozen variable objects''. Such variable objects are never
20638 implicitly updated.
20640 The following is the complete set of @sc{gdb/mi} operations defined to
20641 access this functionality:
20643 @multitable @columnfractions .4 .6
20644 @item @strong{Operation}
20645 @tab @strong{Description}
20647 @item @code{-var-create}
20648 @tab create a variable object
20649 @item @code{-var-delete}
20650 @tab delete the variable object and/or its children
20651 @item @code{-var-set-format}
20652 @tab set the display format of this variable
20653 @item @code{-var-show-format}
20654 @tab show the display format of this variable
20655 @item @code{-var-info-num-children}
20656 @tab tells how many children this object has
20657 @item @code{-var-list-children}
20658 @tab return a list of the object's children
20659 @item @code{-var-info-type}
20660 @tab show the type of this variable object
20661 @item @code{-var-info-expression}
20662 @tab print parent-relative expression that this variable object represents
20663 @item @code{-var-info-path-expression}
20664 @tab print full expression that this variable object represents
20665 @item @code{-var-show-attributes}
20666 @tab is this variable editable? does it exist here?
20667 @item @code{-var-evaluate-expression}
20668 @tab get the value of this variable
20669 @item @code{-var-assign}
20670 @tab set the value of this variable
20671 @item @code{-var-update}
20672 @tab update the variable and its children
20673 @item @code{-var-set-frozen}
20674 @tab set frozeness attribute
20677 In the next subsection we describe each operation in detail and suggest
20678 how it can be used.
20680 @subheading Description And Use of Operations on Variable Objects
20682 @subheading The @code{-var-create} Command
20683 @findex -var-create
20685 @subsubheading Synopsis
20688 -var-create @{@var{name} | "-"@}
20689 @{@var{frame-addr} | "*"@} @var{expression}
20692 This operation creates a variable object, which allows the monitoring of
20693 a variable, the result of an expression, a memory cell or a CPU
20696 The @var{name} parameter is the string by which the object can be
20697 referenced. It must be unique. If @samp{-} is specified, the varobj
20698 system will generate a string ``varNNNNNN'' automatically. It will be
20699 unique provided that one does not specify @var{name} on that format.
20700 The command fails if a duplicate name is found.
20702 The frame under which the expression should be evaluated can be
20703 specified by @var{frame-addr}. A @samp{*} indicates that the current
20704 frame should be used.
20706 @var{expression} is any expression valid on the current language set (must not
20707 begin with a @samp{*}), or one of the following:
20711 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20714 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20717 @samp{$@var{regname}} --- a CPU register name
20720 @subsubheading Result
20722 This operation returns the name, number of children and the type of the
20723 object created. Type is returned as a string as the ones generated by
20724 the @value{GDBN} CLI:
20727 name="@var{name}",numchild="N",type="@var{type}"
20731 @subheading The @code{-var-delete} Command
20732 @findex -var-delete
20734 @subsubheading Synopsis
20737 -var-delete [ -c ] @var{name}
20740 Deletes a previously created variable object and all of its children.
20741 With the @samp{-c} option, just deletes the children.
20743 Returns an error if the object @var{name} is not found.
20746 @subheading The @code{-var-set-format} Command
20747 @findex -var-set-format
20749 @subsubheading Synopsis
20752 -var-set-format @var{name} @var{format-spec}
20755 Sets the output format for the value of the object @var{name} to be
20758 @anchor{-var-set-format}
20759 The syntax for the @var{format-spec} is as follows:
20762 @var{format-spec} @expansion{}
20763 @{binary | decimal | hexadecimal | octal | natural@}
20766 The natural format is the default format choosen automatically
20767 based on the variable type (like decimal for an @code{int}, hex
20768 for pointers, etc.).
20770 For a variable with children, the format is set only on the
20771 variable itself, and the children are not affected.
20773 @subheading The @code{-var-show-format} Command
20774 @findex -var-show-format
20776 @subsubheading Synopsis
20779 -var-show-format @var{name}
20782 Returns the format used to display the value of the object @var{name}.
20785 @var{format} @expansion{}
20790 @subheading The @code{-var-info-num-children} Command
20791 @findex -var-info-num-children
20793 @subsubheading Synopsis
20796 -var-info-num-children @var{name}
20799 Returns the number of children of a variable object @var{name}:
20806 @subheading The @code{-var-list-children} Command
20807 @findex -var-list-children
20809 @subsubheading Synopsis
20812 -var-list-children [@var{print-values}] @var{name}
20814 @anchor{-var-list-children}
20816 Return a list of the children of the specified variable object and
20817 create variable objects for them, if they do not already exist. With
20818 a single argument or if @var{print-values} has a value for of 0 or
20819 @code{--no-values}, print only the names of the variables; if
20820 @var{print-values} is 1 or @code{--all-values}, also print their
20821 values; and if it is 2 or @code{--simple-values} print the name and
20822 value for simple data types and just the name for arrays, structures
20825 @subsubheading Example
20829 -var-list-children n
20830 ^done,numchild=@var{n},children=[@{name=@var{name},
20831 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20833 -var-list-children --all-values n
20834 ^done,numchild=@var{n},children=[@{name=@var{name},
20835 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20839 @subheading The @code{-var-info-type} Command
20840 @findex -var-info-type
20842 @subsubheading Synopsis
20845 -var-info-type @var{name}
20848 Returns the type of the specified variable @var{name}. The type is
20849 returned as a string in the same format as it is output by the
20853 type=@var{typename}
20857 @subheading The @code{-var-info-expression} Command
20858 @findex -var-info-expression
20860 @subsubheading Synopsis
20863 -var-info-expression @var{name}
20866 Returns a string that is suitable for presenting this
20867 variable object in user interface. The string is generally
20868 not valid expression in the current language, and cannot be evaluated.
20870 For example, if @code{a} is an array, and variable object
20871 @code{A} was created for @code{a}, then we'll get this output:
20874 (gdb) -var-info-expression A.1
20875 ^done,lang="C",exp="1"
20879 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
20881 Note that the output of the @code{-var-list-children} command also
20882 includes those expressions, so the @code{-var-info-expression} command
20885 @subheading The @code{-var-info-path-expression} Command
20886 @findex -var-info-path-expression
20888 @subsubheading Synopsis
20891 -var-info-path-expression @var{name}
20894 Returns an expression that can be evaluated in the current
20895 context and will yield the same value that a variable object has.
20896 Compare this with the @code{-var-info-expression} command, which
20897 result can be used only for UI presentation. Typical use of
20898 the @code{-var-info-path-expression} command is creating a
20899 watchpoint from a variable object.
20901 For example, suppose @code{C} is a C@t{++} class, derived from class
20902 @code{Base}, and that the @code{Base} class has a member called
20903 @code{m_size}. Assume a variable @code{c} is has the type of
20904 @code{C} and a variable object @code{C} was created for variable
20905 @code{c}. Then, we'll get this output:
20907 (gdb) -var-info-path-expression C.Base.public.m_size
20908 ^done,path_expr=((Base)c).m_size)
20911 @subheading The @code{-var-show-attributes} Command
20912 @findex -var-show-attributes
20914 @subsubheading Synopsis
20917 -var-show-attributes @var{name}
20920 List attributes of the specified variable object @var{name}:
20923 status=@var{attr} [ ( ,@var{attr} )* ]
20927 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20929 @subheading The @code{-var-evaluate-expression} Command
20930 @findex -var-evaluate-expression
20932 @subsubheading Synopsis
20935 -var-evaluate-expression [-f @var{format-spec}] @var{name}
20938 Evaluates the expression that is represented by the specified variable
20939 object and returns its value as a string. The format of the string
20940 can be specified with the @samp{-f} option. The possible values of
20941 this option are the same as for @code{-var-set-format}
20942 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
20943 the current display format will be used. The current display format
20944 can be changed using the @code{-var-set-format} command.
20950 Note that one must invoke @code{-var-list-children} for a variable
20951 before the value of a child variable can be evaluated.
20953 @subheading The @code{-var-assign} Command
20954 @findex -var-assign
20956 @subsubheading Synopsis
20959 -var-assign @var{name} @var{expression}
20962 Assigns the value of @var{expression} to the variable object specified
20963 by @var{name}. The object must be @samp{editable}. If the variable's
20964 value is altered by the assign, the variable will show up in any
20965 subsequent @code{-var-update} list.
20967 @subsubheading Example
20975 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20979 @subheading The @code{-var-update} Command
20980 @findex -var-update
20982 @subsubheading Synopsis
20985 -var-update [@var{print-values}] @{@var{name} | "*"@}
20988 Reevaluate the expressions corresponding to the variable object
20989 @var{name} and all its direct and indirect children, and return the
20990 list of variable objects whose values have changed; @var{name} must
20991 be a root variable object. Here, ``changed'' means that the result of
20992 @code{-var-evaluate-expression} before and after the
20993 @code{-var-update} is different. If @samp{*} is used as the variable
20994 object names, all existing variable objects are updated, except
20995 for frozen ones (@pxref{-var-set-frozen}). The option
20996 @var{print-values} determines whether both names and values, or just
20997 names are printed. The possible values of this option are the same
20998 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
20999 recommended to use the @samp{--all-values} option, to reduce the
21000 number of MI commands needed on each program stop.
21003 @subsubheading Example
21010 -var-update --all-values var1
21011 ^done,changelist=[@{name="var1",value="3",in_scope="true",
21012 type_changed="false"@}]
21016 @anchor{-var-update}
21017 The field in_scope may take three values:
21021 The variable object's current value is valid.
21024 The variable object does not currently hold a valid value but it may
21025 hold one in the future if its associated expression comes back into
21029 The variable object no longer holds a valid value.
21030 This can occur when the executable file being debugged has changed,
21031 either through recompilation or by using the @value{GDBN} @code{file}
21032 command. The front end should normally choose to delete these variable
21036 In the future new values may be added to this list so the front should
21037 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
21039 @subheading The @code{-var-set-frozen} Command
21040 @findex -var-set-frozen
21041 @anchor{-var-set-frozen}
21043 @subsubheading Synopsis
21046 -var-set-frozen @var{name} @var{flag}
21049 Set the frozenness flag on the variable object @var{name}. The
21050 @var{flag} parameter should be either @samp{1} to make the variable
21051 frozen or @samp{0} to make it unfrozen. If a variable object is
21052 frozen, then neither itself, nor any of its children, are
21053 implicitly updated by @code{-var-update} of
21054 a parent variable or by @code{-var-update *}. Only
21055 @code{-var-update} of the variable itself will update its value and
21056 values of its children. After a variable object is unfrozen, it is
21057 implicitly updated by all subsequent @code{-var-update} operations.
21058 Unfreezing a variable does not update it, only subsequent
21059 @code{-var-update} does.
21061 @subsubheading Example
21065 -var-set-frozen V 1
21071 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21072 @node GDB/MI Data Manipulation
21073 @section @sc{gdb/mi} Data Manipulation
21075 @cindex data manipulation, in @sc{gdb/mi}
21076 @cindex @sc{gdb/mi}, data manipulation
21077 This section describes the @sc{gdb/mi} commands that manipulate data:
21078 examine memory and registers, evaluate expressions, etc.
21080 @c REMOVED FROM THE INTERFACE.
21081 @c @subheading -data-assign
21082 @c Change the value of a program variable. Plenty of side effects.
21083 @c @subsubheading GDB Command
21085 @c @subsubheading Example
21088 @subheading The @code{-data-disassemble} Command
21089 @findex -data-disassemble
21091 @subsubheading Synopsis
21095 [ -s @var{start-addr} -e @var{end-addr} ]
21096 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
21104 @item @var{start-addr}
21105 is the beginning address (or @code{$pc})
21106 @item @var{end-addr}
21108 @item @var{filename}
21109 is the name of the file to disassemble
21110 @item @var{linenum}
21111 is the line number to disassemble around
21113 is the number of disassembly lines to be produced. If it is -1,
21114 the whole function will be disassembled, in case no @var{end-addr} is
21115 specified. If @var{end-addr} is specified as a non-zero value, and
21116 @var{lines} is lower than the number of disassembly lines between
21117 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
21118 displayed; if @var{lines} is higher than the number of lines between
21119 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
21122 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
21126 @subsubheading Result
21128 The output for each instruction is composed of four fields:
21137 Note that whatever included in the instruction field, is not manipulated
21138 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
21140 @subsubheading @value{GDBN} Command
21142 There's no direct mapping from this command to the CLI.
21144 @subsubheading Example
21146 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
21150 -data-disassemble -s $pc -e "$pc + 20" -- 0
21153 @{address="0x000107c0",func-name="main",offset="4",
21154 inst="mov 2, %o0"@},
21155 @{address="0x000107c4",func-name="main",offset="8",
21156 inst="sethi %hi(0x11800), %o2"@},
21157 @{address="0x000107c8",func-name="main",offset="12",
21158 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
21159 @{address="0x000107cc",func-name="main",offset="16",
21160 inst="sethi %hi(0x11800), %o2"@},
21161 @{address="0x000107d0",func-name="main",offset="20",
21162 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
21166 Disassemble the whole @code{main} function. Line 32 is part of
21170 -data-disassemble -f basics.c -l 32 -- 0
21172 @{address="0x000107bc",func-name="main",offset="0",
21173 inst="save %sp, -112, %sp"@},
21174 @{address="0x000107c0",func-name="main",offset="4",
21175 inst="mov 2, %o0"@},
21176 @{address="0x000107c4",func-name="main",offset="8",
21177 inst="sethi %hi(0x11800), %o2"@},
21179 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
21180 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
21184 Disassemble 3 instructions from the start of @code{main}:
21188 -data-disassemble -f basics.c -l 32 -n 3 -- 0
21190 @{address="0x000107bc",func-name="main",offset="0",
21191 inst="save %sp, -112, %sp"@},
21192 @{address="0x000107c0",func-name="main",offset="4",
21193 inst="mov 2, %o0"@},
21194 @{address="0x000107c4",func-name="main",offset="8",
21195 inst="sethi %hi(0x11800), %o2"@}]
21199 Disassemble 3 instructions from the start of @code{main} in mixed mode:
21203 -data-disassemble -f basics.c -l 32 -n 3 -- 1
21205 src_and_asm_line=@{line="31",
21206 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
21207 testsuite/gdb.mi/basics.c",line_asm_insn=[
21208 @{address="0x000107bc",func-name="main",offset="0",
21209 inst="save %sp, -112, %sp"@}]@},
21210 src_and_asm_line=@{line="32",
21211 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
21212 testsuite/gdb.mi/basics.c",line_asm_insn=[
21213 @{address="0x000107c0",func-name="main",offset="4",
21214 inst="mov 2, %o0"@},
21215 @{address="0x000107c4",func-name="main",offset="8",
21216 inst="sethi %hi(0x11800), %o2"@}]@}]
21221 @subheading The @code{-data-evaluate-expression} Command
21222 @findex -data-evaluate-expression
21224 @subsubheading Synopsis
21227 -data-evaluate-expression @var{expr}
21230 Evaluate @var{expr} as an expression. The expression could contain an
21231 inferior function call. The function call will execute synchronously.
21232 If the expression contains spaces, it must be enclosed in double quotes.
21234 @subsubheading @value{GDBN} Command
21236 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
21237 @samp{call}. In @code{gdbtk} only, there's a corresponding
21238 @samp{gdb_eval} command.
21240 @subsubheading Example
21242 In the following example, the numbers that precede the commands are the
21243 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
21244 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
21248 211-data-evaluate-expression A
21251 311-data-evaluate-expression &A
21252 311^done,value="0xefffeb7c"
21254 411-data-evaluate-expression A+3
21257 511-data-evaluate-expression "A + 3"
21263 @subheading The @code{-data-list-changed-registers} Command
21264 @findex -data-list-changed-registers
21266 @subsubheading Synopsis
21269 -data-list-changed-registers
21272 Display a list of the registers that have changed.
21274 @subsubheading @value{GDBN} Command
21276 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
21277 has the corresponding command @samp{gdb_changed_register_list}.
21279 @subsubheading Example
21281 On a PPC MBX board:
21289 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
21290 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
21293 -data-list-changed-registers
21294 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
21295 "10","11","13","14","15","16","17","18","19","20","21","22","23",
21296 "24","25","26","27","28","30","31","64","65","66","67","69"]
21301 @subheading The @code{-data-list-register-names} Command
21302 @findex -data-list-register-names
21304 @subsubheading Synopsis
21307 -data-list-register-names [ ( @var{regno} )+ ]
21310 Show a list of register names for the current target. If no arguments
21311 are given, it shows a list of the names of all the registers. If
21312 integer numbers are given as arguments, it will print a list of the
21313 names of the registers corresponding to the arguments. To ensure
21314 consistency between a register name and its number, the output list may
21315 include empty register names.
21317 @subsubheading @value{GDBN} Command
21319 @value{GDBN} does not have a command which corresponds to
21320 @samp{-data-list-register-names}. In @code{gdbtk} there is a
21321 corresponding command @samp{gdb_regnames}.
21323 @subsubheading Example
21325 For the PPC MBX board:
21328 -data-list-register-names
21329 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
21330 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
21331 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
21332 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
21333 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
21334 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
21335 "", "pc","ps","cr","lr","ctr","xer"]
21337 -data-list-register-names 1 2 3
21338 ^done,register-names=["r1","r2","r3"]
21342 @subheading The @code{-data-list-register-values} Command
21343 @findex -data-list-register-values
21345 @subsubheading Synopsis
21348 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
21351 Display the registers' contents. @var{fmt} is the format according to
21352 which the registers' contents are to be returned, followed by an optional
21353 list of numbers specifying the registers to display. A missing list of
21354 numbers indicates that the contents of all the registers must be returned.
21356 Allowed formats for @var{fmt} are:
21373 @subsubheading @value{GDBN} Command
21375 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
21376 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
21378 @subsubheading Example
21380 For a PPC MBX board (note: line breaks are for readability only, they
21381 don't appear in the actual output):
21385 -data-list-register-values r 64 65
21386 ^done,register-values=[@{number="64",value="0xfe00a300"@},
21387 @{number="65",value="0x00029002"@}]
21389 -data-list-register-values x
21390 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
21391 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
21392 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
21393 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
21394 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
21395 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
21396 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
21397 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
21398 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
21399 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
21400 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
21401 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
21402 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
21403 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
21404 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
21405 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
21406 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
21407 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
21408 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
21409 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
21410 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
21411 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
21412 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
21413 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
21414 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
21415 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
21416 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
21417 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
21418 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
21419 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
21420 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
21421 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
21422 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
21423 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
21424 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
21425 @{number="69",value="0x20002b03"@}]
21430 @subheading The @code{-data-read-memory} Command
21431 @findex -data-read-memory
21433 @subsubheading Synopsis
21436 -data-read-memory [ -o @var{byte-offset} ]
21437 @var{address} @var{word-format} @var{word-size}
21438 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
21445 @item @var{address}
21446 An expression specifying the address of the first memory word to be
21447 read. Complex expressions containing embedded white space should be
21448 quoted using the C convention.
21450 @item @var{word-format}
21451 The format to be used to print the memory words. The notation is the
21452 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
21455 @item @var{word-size}
21456 The size of each memory word in bytes.
21458 @item @var{nr-rows}
21459 The number of rows in the output table.
21461 @item @var{nr-cols}
21462 The number of columns in the output table.
21465 If present, indicates that each row should include an @sc{ascii} dump. The
21466 value of @var{aschar} is used as a padding character when a byte is not a
21467 member of the printable @sc{ascii} character set (printable @sc{ascii}
21468 characters are those whose code is between 32 and 126, inclusively).
21470 @item @var{byte-offset}
21471 An offset to add to the @var{address} before fetching memory.
21474 This command displays memory contents as a table of @var{nr-rows} by
21475 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
21476 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
21477 (returned as @samp{total-bytes}). Should less than the requested number
21478 of bytes be returned by the target, the missing words are identified
21479 using @samp{N/A}. The number of bytes read from the target is returned
21480 in @samp{nr-bytes} and the starting address used to read memory in
21483 The address of the next/previous row or page is available in
21484 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
21487 @subsubheading @value{GDBN} Command
21489 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
21490 @samp{gdb_get_mem} memory read command.
21492 @subsubheading Example
21494 Read six bytes of memory starting at @code{bytes+6} but then offset by
21495 @code{-6} bytes. Format as three rows of two columns. One byte per
21496 word. Display each word in hex.
21500 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
21501 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
21502 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
21503 prev-page="0x0000138a",memory=[
21504 @{addr="0x00001390",data=["0x00","0x01"]@},
21505 @{addr="0x00001392",data=["0x02","0x03"]@},
21506 @{addr="0x00001394",data=["0x04","0x05"]@}]
21510 Read two bytes of memory starting at address @code{shorts + 64} and
21511 display as a single word formatted in decimal.
21515 5-data-read-memory shorts+64 d 2 1 1
21516 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
21517 next-row="0x00001512",prev-row="0x0000150e",
21518 next-page="0x00001512",prev-page="0x0000150e",memory=[
21519 @{addr="0x00001510",data=["128"]@}]
21523 Read thirty two bytes of memory starting at @code{bytes+16} and format
21524 as eight rows of four columns. Include a string encoding with @samp{x}
21525 used as the non-printable character.
21529 4-data-read-memory bytes+16 x 1 8 4 x
21530 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
21531 next-row="0x000013c0",prev-row="0x0000139c",
21532 next-page="0x000013c0",prev-page="0x00001380",memory=[
21533 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
21534 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
21535 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
21536 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
21537 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
21538 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
21539 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
21540 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
21544 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21545 @node GDB/MI Tracepoint Commands
21546 @section @sc{gdb/mi} Tracepoint Commands
21548 The tracepoint commands are not yet implemented.
21550 @c @subheading -trace-actions
21552 @c @subheading -trace-delete
21554 @c @subheading -trace-disable
21556 @c @subheading -trace-dump
21558 @c @subheading -trace-enable
21560 @c @subheading -trace-exists
21562 @c @subheading -trace-find
21564 @c @subheading -trace-frame-number
21566 @c @subheading -trace-info
21568 @c @subheading -trace-insert
21570 @c @subheading -trace-list
21572 @c @subheading -trace-pass-count
21574 @c @subheading -trace-save
21576 @c @subheading -trace-start
21578 @c @subheading -trace-stop
21581 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21582 @node GDB/MI Symbol Query
21583 @section @sc{gdb/mi} Symbol Query Commands
21586 @subheading The @code{-symbol-info-address} Command
21587 @findex -symbol-info-address
21589 @subsubheading Synopsis
21592 -symbol-info-address @var{symbol}
21595 Describe where @var{symbol} is stored.
21597 @subsubheading @value{GDBN} Command
21599 The corresponding @value{GDBN} command is @samp{info address}.
21601 @subsubheading Example
21605 @subheading The @code{-symbol-info-file} Command
21606 @findex -symbol-info-file
21608 @subsubheading Synopsis
21614 Show the file for the symbol.
21616 @subsubheading @value{GDBN} Command
21618 There's no equivalent @value{GDBN} command. @code{gdbtk} has
21619 @samp{gdb_find_file}.
21621 @subsubheading Example
21625 @subheading The @code{-symbol-info-function} Command
21626 @findex -symbol-info-function
21628 @subsubheading Synopsis
21631 -symbol-info-function
21634 Show which function the symbol lives in.
21636 @subsubheading @value{GDBN} Command
21638 @samp{gdb_get_function} in @code{gdbtk}.
21640 @subsubheading Example
21644 @subheading The @code{-symbol-info-line} Command
21645 @findex -symbol-info-line
21647 @subsubheading Synopsis
21653 Show the core addresses of the code for a source line.
21655 @subsubheading @value{GDBN} Command
21657 The corresponding @value{GDBN} command is @samp{info line}.
21658 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
21660 @subsubheading Example
21664 @subheading The @code{-symbol-info-symbol} Command
21665 @findex -symbol-info-symbol
21667 @subsubheading Synopsis
21670 -symbol-info-symbol @var{addr}
21673 Describe what symbol is at location @var{addr}.
21675 @subsubheading @value{GDBN} Command
21677 The corresponding @value{GDBN} command is @samp{info symbol}.
21679 @subsubheading Example
21683 @subheading The @code{-symbol-list-functions} Command
21684 @findex -symbol-list-functions
21686 @subsubheading Synopsis
21689 -symbol-list-functions
21692 List the functions in the executable.
21694 @subsubheading @value{GDBN} Command
21696 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
21697 @samp{gdb_search} in @code{gdbtk}.
21699 @subsubheading Example
21703 @subheading The @code{-symbol-list-lines} Command
21704 @findex -symbol-list-lines
21706 @subsubheading Synopsis
21709 -symbol-list-lines @var{filename}
21712 Print the list of lines that contain code and their associated program
21713 addresses for the given source filename. The entries are sorted in
21714 ascending PC order.
21716 @subsubheading @value{GDBN} Command
21718 There is no corresponding @value{GDBN} command.
21720 @subsubheading Example
21723 -symbol-list-lines basics.c
21724 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
21729 @subheading The @code{-symbol-list-types} Command
21730 @findex -symbol-list-types
21732 @subsubheading Synopsis
21738 List all the type names.
21740 @subsubheading @value{GDBN} Command
21742 The corresponding commands are @samp{info types} in @value{GDBN},
21743 @samp{gdb_search} in @code{gdbtk}.
21745 @subsubheading Example
21749 @subheading The @code{-symbol-list-variables} Command
21750 @findex -symbol-list-variables
21752 @subsubheading Synopsis
21755 -symbol-list-variables
21758 List all the global and static variable names.
21760 @subsubheading @value{GDBN} Command
21762 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
21764 @subsubheading Example
21768 @subheading The @code{-symbol-locate} Command
21769 @findex -symbol-locate
21771 @subsubheading Synopsis
21777 @subsubheading @value{GDBN} Command
21779 @samp{gdb_loc} in @code{gdbtk}.
21781 @subsubheading Example
21785 @subheading The @code{-symbol-type} Command
21786 @findex -symbol-type
21788 @subsubheading Synopsis
21791 -symbol-type @var{variable}
21794 Show type of @var{variable}.
21796 @subsubheading @value{GDBN} Command
21798 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
21799 @samp{gdb_obj_variable}.
21801 @subsubheading Example
21805 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21806 @node GDB/MI File Commands
21807 @section @sc{gdb/mi} File Commands
21809 This section describes the GDB/MI commands to specify executable file names
21810 and to read in and obtain symbol table information.
21812 @subheading The @code{-file-exec-and-symbols} Command
21813 @findex -file-exec-and-symbols
21815 @subsubheading Synopsis
21818 -file-exec-and-symbols @var{file}
21821 Specify the executable file to be debugged. This file is the one from
21822 which the symbol table is also read. If no file is specified, the
21823 command clears the executable and symbol information. If breakpoints
21824 are set when using this command with no arguments, @value{GDBN} will produce
21825 error messages. Otherwise, no output is produced, except a completion
21828 @subsubheading @value{GDBN} Command
21830 The corresponding @value{GDBN} command is @samp{file}.
21832 @subsubheading Example
21836 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21842 @subheading The @code{-file-exec-file} Command
21843 @findex -file-exec-file
21845 @subsubheading Synopsis
21848 -file-exec-file @var{file}
21851 Specify the executable file to be debugged. Unlike
21852 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
21853 from this file. If used without argument, @value{GDBN} clears the information
21854 about the executable file. No output is produced, except a completion
21857 @subsubheading @value{GDBN} Command
21859 The corresponding @value{GDBN} command is @samp{exec-file}.
21861 @subsubheading Example
21865 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21871 @subheading The @code{-file-list-exec-sections} Command
21872 @findex -file-list-exec-sections
21874 @subsubheading Synopsis
21877 -file-list-exec-sections
21880 List the sections of the current executable file.
21882 @subsubheading @value{GDBN} Command
21884 The @value{GDBN} command @samp{info file} shows, among the rest, the same
21885 information as this command. @code{gdbtk} has a corresponding command
21886 @samp{gdb_load_info}.
21888 @subsubheading Example
21892 @subheading The @code{-file-list-exec-source-file} Command
21893 @findex -file-list-exec-source-file
21895 @subsubheading Synopsis
21898 -file-list-exec-source-file
21901 List the line number, the current source file, and the absolute path
21902 to the current source file for the current executable. The macro
21903 information field has a value of @samp{1} or @samp{0} depending on
21904 whether or not the file includes preprocessor macro information.
21906 @subsubheading @value{GDBN} Command
21908 The @value{GDBN} equivalent is @samp{info source}
21910 @subsubheading Example
21914 123-file-list-exec-source-file
21915 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
21920 @subheading The @code{-file-list-exec-source-files} Command
21921 @findex -file-list-exec-source-files
21923 @subsubheading Synopsis
21926 -file-list-exec-source-files
21929 List the source files for the current executable.
21931 It will always output the filename, but only when @value{GDBN} can find
21932 the absolute file name of a source file, will it output the fullname.
21934 @subsubheading @value{GDBN} Command
21936 The @value{GDBN} equivalent is @samp{info sources}.
21937 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
21939 @subsubheading Example
21942 -file-list-exec-source-files
21944 @{file=foo.c,fullname=/home/foo.c@},
21945 @{file=/home/bar.c,fullname=/home/bar.c@},
21946 @{file=gdb_could_not_find_fullpath.c@}]
21950 @subheading The @code{-file-list-shared-libraries} Command
21951 @findex -file-list-shared-libraries
21953 @subsubheading Synopsis
21956 -file-list-shared-libraries
21959 List the shared libraries in the program.
21961 @subsubheading @value{GDBN} Command
21963 The corresponding @value{GDBN} command is @samp{info shared}.
21965 @subsubheading Example
21969 @subheading The @code{-file-list-symbol-files} Command
21970 @findex -file-list-symbol-files
21972 @subsubheading Synopsis
21975 -file-list-symbol-files
21980 @subsubheading @value{GDBN} Command
21982 The corresponding @value{GDBN} command is @samp{info file} (part of it).
21984 @subsubheading Example
21988 @subheading The @code{-file-symbol-file} Command
21989 @findex -file-symbol-file
21991 @subsubheading Synopsis
21994 -file-symbol-file @var{file}
21997 Read symbol table info from the specified @var{file} argument. When
21998 used without arguments, clears @value{GDBN}'s symbol table info. No output is
21999 produced, except for a completion notification.
22001 @subsubheading @value{GDBN} Command
22003 The corresponding @value{GDBN} command is @samp{symbol-file}.
22005 @subsubheading Example
22009 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22015 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22016 @node GDB/MI Memory Overlay Commands
22017 @section @sc{gdb/mi} Memory Overlay Commands
22019 The memory overlay commands are not implemented.
22021 @c @subheading -overlay-auto
22023 @c @subheading -overlay-list-mapping-state
22025 @c @subheading -overlay-list-overlays
22027 @c @subheading -overlay-map
22029 @c @subheading -overlay-off
22031 @c @subheading -overlay-on
22033 @c @subheading -overlay-unmap
22035 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22036 @node GDB/MI Signal Handling Commands
22037 @section @sc{gdb/mi} Signal Handling Commands
22039 Signal handling commands are not implemented.
22041 @c @subheading -signal-handle
22043 @c @subheading -signal-list-handle-actions
22045 @c @subheading -signal-list-signal-types
22049 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22050 @node GDB/MI Target Manipulation
22051 @section @sc{gdb/mi} Target Manipulation Commands
22054 @subheading The @code{-target-attach} Command
22055 @findex -target-attach
22057 @subsubheading Synopsis
22060 -target-attach @var{pid} | @var{file}
22063 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
22065 @subsubheading @value{GDBN} Command
22067 The corresponding @value{GDBN} command is @samp{attach}.
22069 @subsubheading Example
22073 =thread-created,id="1"
22074 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
22079 @subheading The @code{-target-compare-sections} Command
22080 @findex -target-compare-sections
22082 @subsubheading Synopsis
22085 -target-compare-sections [ @var{section} ]
22088 Compare data of section @var{section} on target to the exec file.
22089 Without the argument, all sections are compared.
22091 @subsubheading @value{GDBN} Command
22093 The @value{GDBN} equivalent is @samp{compare-sections}.
22095 @subsubheading Example
22099 @subheading The @code{-target-detach} Command
22100 @findex -target-detach
22102 @subsubheading Synopsis
22108 Detach from the remote target which normally resumes its execution.
22111 @subsubheading @value{GDBN} Command
22113 The corresponding @value{GDBN} command is @samp{detach}.
22115 @subsubheading Example
22125 @subheading The @code{-target-disconnect} Command
22126 @findex -target-disconnect
22128 @subsubheading Synopsis
22134 Disconnect from the remote target. There's no output and the target is
22135 generally not resumed.
22137 @subsubheading @value{GDBN} Command
22139 The corresponding @value{GDBN} command is @samp{disconnect}.
22141 @subsubheading Example
22151 @subheading The @code{-target-download} Command
22152 @findex -target-download
22154 @subsubheading Synopsis
22160 Loads the executable onto the remote target.
22161 It prints out an update message every half second, which includes the fields:
22165 The name of the section.
22167 The size of what has been sent so far for that section.
22169 The size of the section.
22171 The total size of what was sent so far (the current and the previous sections).
22173 The size of the overall executable to download.
22177 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
22178 @sc{gdb/mi} Output Syntax}).
22180 In addition, it prints the name and size of the sections, as they are
22181 downloaded. These messages include the following fields:
22185 The name of the section.
22187 The size of the section.
22189 The size of the overall executable to download.
22193 At the end, a summary is printed.
22195 @subsubheading @value{GDBN} Command
22197 The corresponding @value{GDBN} command is @samp{load}.
22199 @subsubheading Example
22201 Note: each status message appears on a single line. Here the messages
22202 have been broken down so that they can fit onto a page.
22207 +download,@{section=".text",section-size="6668",total-size="9880"@}
22208 +download,@{section=".text",section-sent="512",section-size="6668",
22209 total-sent="512",total-size="9880"@}
22210 +download,@{section=".text",section-sent="1024",section-size="6668",
22211 total-sent="1024",total-size="9880"@}
22212 +download,@{section=".text",section-sent="1536",section-size="6668",
22213 total-sent="1536",total-size="9880"@}
22214 +download,@{section=".text",section-sent="2048",section-size="6668",
22215 total-sent="2048",total-size="9880"@}
22216 +download,@{section=".text",section-sent="2560",section-size="6668",
22217 total-sent="2560",total-size="9880"@}
22218 +download,@{section=".text",section-sent="3072",section-size="6668",
22219 total-sent="3072",total-size="9880"@}
22220 +download,@{section=".text",section-sent="3584",section-size="6668",
22221 total-sent="3584",total-size="9880"@}
22222 +download,@{section=".text",section-sent="4096",section-size="6668",
22223 total-sent="4096",total-size="9880"@}
22224 +download,@{section=".text",section-sent="4608",section-size="6668",
22225 total-sent="4608",total-size="9880"@}
22226 +download,@{section=".text",section-sent="5120",section-size="6668",
22227 total-sent="5120",total-size="9880"@}
22228 +download,@{section=".text",section-sent="5632",section-size="6668",
22229 total-sent="5632",total-size="9880"@}
22230 +download,@{section=".text",section-sent="6144",section-size="6668",
22231 total-sent="6144",total-size="9880"@}
22232 +download,@{section=".text",section-sent="6656",section-size="6668",
22233 total-sent="6656",total-size="9880"@}
22234 +download,@{section=".init",section-size="28",total-size="9880"@}
22235 +download,@{section=".fini",section-size="28",total-size="9880"@}
22236 +download,@{section=".data",section-size="3156",total-size="9880"@}
22237 +download,@{section=".data",section-sent="512",section-size="3156",
22238 total-sent="7236",total-size="9880"@}
22239 +download,@{section=".data",section-sent="1024",section-size="3156",
22240 total-sent="7748",total-size="9880"@}
22241 +download,@{section=".data",section-sent="1536",section-size="3156",
22242 total-sent="8260",total-size="9880"@}
22243 +download,@{section=".data",section-sent="2048",section-size="3156",
22244 total-sent="8772",total-size="9880"@}
22245 +download,@{section=".data",section-sent="2560",section-size="3156",
22246 total-sent="9284",total-size="9880"@}
22247 +download,@{section=".data",section-sent="3072",section-size="3156",
22248 total-sent="9796",total-size="9880"@}
22249 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
22255 @subheading The @code{-target-exec-status} Command
22256 @findex -target-exec-status
22258 @subsubheading Synopsis
22261 -target-exec-status
22264 Provide information on the state of the target (whether it is running or
22265 not, for instance).
22267 @subsubheading @value{GDBN} Command
22269 There's no equivalent @value{GDBN} command.
22271 @subsubheading Example
22275 @subheading The @code{-target-list-available-targets} Command
22276 @findex -target-list-available-targets
22278 @subsubheading Synopsis
22281 -target-list-available-targets
22284 List the possible targets to connect to.
22286 @subsubheading @value{GDBN} Command
22288 The corresponding @value{GDBN} command is @samp{help target}.
22290 @subsubheading Example
22294 @subheading The @code{-target-list-current-targets} Command
22295 @findex -target-list-current-targets
22297 @subsubheading Synopsis
22300 -target-list-current-targets
22303 Describe the current target.
22305 @subsubheading @value{GDBN} Command
22307 The corresponding information is printed by @samp{info file} (among
22310 @subsubheading Example
22314 @subheading The @code{-target-list-parameters} Command
22315 @findex -target-list-parameters
22317 @subsubheading Synopsis
22320 -target-list-parameters
22325 @subsubheading @value{GDBN} Command
22329 @subsubheading Example
22333 @subheading The @code{-target-select} Command
22334 @findex -target-select
22336 @subsubheading Synopsis
22339 -target-select @var{type} @var{parameters @dots{}}
22342 Connect @value{GDBN} to the remote target. This command takes two args:
22346 The type of target, for instance @samp{remote}, etc.
22347 @item @var{parameters}
22348 Device names, host names and the like. @xref{Target Commands, ,
22349 Commands for Managing Targets}, for more details.
22352 The output is a connection notification, followed by the address at
22353 which the target program is, in the following form:
22356 ^connected,addr="@var{address}",func="@var{function name}",
22357 args=[@var{arg list}]
22360 @subsubheading @value{GDBN} Command
22362 The corresponding @value{GDBN} command is @samp{target}.
22364 @subsubheading Example
22368 -target-select remote /dev/ttya
22369 ^connected,addr="0xfe00a300",func="??",args=[]
22373 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22374 @node GDB/MI File Transfer Commands
22375 @section @sc{gdb/mi} File Transfer Commands
22378 @subheading The @code{-target-file-put} Command
22379 @findex -target-file-put
22381 @subsubheading Synopsis
22384 -target-file-put @var{hostfile} @var{targetfile}
22387 Copy file @var{hostfile} from the host system (the machine running
22388 @value{GDBN}) to @var{targetfile} on the target system.
22390 @subsubheading @value{GDBN} Command
22392 The corresponding @value{GDBN} command is @samp{remote put}.
22394 @subsubheading Example
22398 -target-file-put localfile remotefile
22404 @subheading The @code{-target-file-get} Command
22405 @findex -target-file-get
22407 @subsubheading Synopsis
22410 -target-file-get @var{targetfile} @var{hostfile}
22413 Copy file @var{targetfile} from the target system to @var{hostfile}
22414 on the host system.
22416 @subsubheading @value{GDBN} Command
22418 The corresponding @value{GDBN} command is @samp{remote get}.
22420 @subsubheading Example
22424 -target-file-get remotefile localfile
22430 @subheading The @code{-target-file-delete} Command
22431 @findex -target-file-delete
22433 @subsubheading Synopsis
22436 -target-file-delete @var{targetfile}
22439 Delete @var{targetfile} from the target system.
22441 @subsubheading @value{GDBN} Command
22443 The corresponding @value{GDBN} command is @samp{remote delete}.
22445 @subsubheading Example
22449 -target-file-delete remotefile
22455 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22456 @node GDB/MI Miscellaneous Commands
22457 @section Miscellaneous @sc{gdb/mi} Commands
22459 @c @subheading -gdb-complete
22461 @subheading The @code{-gdb-exit} Command
22464 @subsubheading Synopsis
22470 Exit @value{GDBN} immediately.
22472 @subsubheading @value{GDBN} Command
22474 Approximately corresponds to @samp{quit}.
22476 @subsubheading Example
22485 @subheading The @code{-exec-abort} Command
22486 @findex -exec-abort
22488 @subsubheading Synopsis
22494 Kill the inferior running program.
22496 @subsubheading @value{GDBN} Command
22498 The corresponding @value{GDBN} command is @samp{kill}.
22500 @subsubheading Example
22504 @subheading The @code{-gdb-set} Command
22507 @subsubheading Synopsis
22513 Set an internal @value{GDBN} variable.
22514 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
22516 @subsubheading @value{GDBN} Command
22518 The corresponding @value{GDBN} command is @samp{set}.
22520 @subsubheading Example
22530 @subheading The @code{-gdb-show} Command
22533 @subsubheading Synopsis
22539 Show the current value of a @value{GDBN} variable.
22541 @subsubheading @value{GDBN} Command
22543 The corresponding @value{GDBN} command is @samp{show}.
22545 @subsubheading Example
22554 @c @subheading -gdb-source
22557 @subheading The @code{-gdb-version} Command
22558 @findex -gdb-version
22560 @subsubheading Synopsis
22566 Show version information for @value{GDBN}. Used mostly in testing.
22568 @subsubheading @value{GDBN} Command
22570 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
22571 default shows this information when you start an interactive session.
22573 @subsubheading Example
22575 @c This example modifies the actual output from GDB to avoid overfull
22581 ~Copyright 2000 Free Software Foundation, Inc.
22582 ~GDB is free software, covered by the GNU General Public License, and
22583 ~you are welcome to change it and/or distribute copies of it under
22584 ~ certain conditions.
22585 ~Type "show copying" to see the conditions.
22586 ~There is absolutely no warranty for GDB. Type "show warranty" for
22588 ~This GDB was configured as
22589 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
22594 @subheading The @code{-list-features} Command
22595 @findex -list-features
22597 Returns a list of particular features of the MI protocol that
22598 this version of gdb implements. A feature can be a command,
22599 or a new field in an output of some command, or even an
22600 important bugfix. While a frontend can sometimes detect presence
22601 of a feature at runtime, it is easier to perform detection at debugger
22604 The command returns a list of strings, with each string naming an
22605 available feature. Each returned string is just a name, it does not
22606 have any internal structure. The list of possible feature names
22612 (gdb) -list-features
22613 ^done,result=["feature1","feature2"]
22616 The current list of features is:
22620 @samp{frozen-varobjs}---indicates presence of the
22621 @code{-var-set-frozen} command, as well as possible presense of the
22622 @code{frozen} field in the output of @code{-varobj-create}.
22624 @samp{pending-breakpoints}---indicates presence of the @code{-f}
22625 option to the @code{-break-insert} command.
22627 @samp{thread-info}---indicates presence of the @code{-thread-info} command.
22631 @subheading The @code{-interpreter-exec} Command
22632 @findex -interpreter-exec
22634 @subheading Synopsis
22637 -interpreter-exec @var{interpreter} @var{command}
22639 @anchor{-interpreter-exec}
22641 Execute the specified @var{command} in the given @var{interpreter}.
22643 @subheading @value{GDBN} Command
22645 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
22647 @subheading Example
22651 -interpreter-exec console "break main"
22652 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
22653 &"During symbol reading, bad structure-type format.\n"
22654 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
22659 @subheading The @code{-inferior-tty-set} Command
22660 @findex -inferior-tty-set
22662 @subheading Synopsis
22665 -inferior-tty-set /dev/pts/1
22668 Set terminal for future runs of the program being debugged.
22670 @subheading @value{GDBN} Command
22672 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
22674 @subheading Example
22678 -inferior-tty-set /dev/pts/1
22683 @subheading The @code{-inferior-tty-show} Command
22684 @findex -inferior-tty-show
22686 @subheading Synopsis
22692 Show terminal for future runs of program being debugged.
22694 @subheading @value{GDBN} Command
22696 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
22698 @subheading Example
22702 -inferior-tty-set /dev/pts/1
22706 ^done,inferior_tty_terminal="/dev/pts/1"
22710 @subheading The @code{-enable-timings} Command
22711 @findex -enable-timings
22713 @subheading Synopsis
22716 -enable-timings [yes | no]
22719 Toggle the printing of the wallclock, user and system times for an MI
22720 command as a field in its output. This command is to help frontend
22721 developers optimize the performance of their code. No argument is
22722 equivalent to @samp{yes}.
22724 @subheading @value{GDBN} Command
22728 @subheading Example
22736 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22737 addr="0x080484ed",func="main",file="myprog.c",
22738 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
22739 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
22747 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22748 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
22749 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
22750 fullname="/home/nickrob/myprog.c",line="73"@}
22755 @chapter @value{GDBN} Annotations
22757 This chapter describes annotations in @value{GDBN}. Annotations were
22758 designed to interface @value{GDBN} to graphical user interfaces or other
22759 similar programs which want to interact with @value{GDBN} at a
22760 relatively high level.
22762 The annotation mechanism has largely been superseded by @sc{gdb/mi}
22766 This is Edition @value{EDITION}, @value{DATE}.
22770 * Annotations Overview:: What annotations are; the general syntax.
22771 * Server Prefix:: Issuing a command without affecting user state.
22772 * Prompting:: Annotations marking @value{GDBN}'s need for input.
22773 * Errors:: Annotations for error messages.
22774 * Invalidation:: Some annotations describe things now invalid.
22775 * Annotations for Running::
22776 Whether the program is running, how it stopped, etc.
22777 * Source Annotations:: Annotations describing source code.
22780 @node Annotations Overview
22781 @section What is an Annotation?
22782 @cindex annotations
22784 Annotations start with a newline character, two @samp{control-z}
22785 characters, and the name of the annotation. If there is no additional
22786 information associated with this annotation, the name of the annotation
22787 is followed immediately by a newline. If there is additional
22788 information, the name of the annotation is followed by a space, the
22789 additional information, and a newline. The additional information
22790 cannot contain newline characters.
22792 Any output not beginning with a newline and two @samp{control-z}
22793 characters denotes literal output from @value{GDBN}. Currently there is
22794 no need for @value{GDBN} to output a newline followed by two
22795 @samp{control-z} characters, but if there was such a need, the
22796 annotations could be extended with an @samp{escape} annotation which
22797 means those three characters as output.
22799 The annotation @var{level}, which is specified using the
22800 @option{--annotate} command line option (@pxref{Mode Options}), controls
22801 how much information @value{GDBN} prints together with its prompt,
22802 values of expressions, source lines, and other types of output. Level 0
22803 is for no annotations, level 1 is for use when @value{GDBN} is run as a
22804 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
22805 for programs that control @value{GDBN}, and level 2 annotations have
22806 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
22807 Interface, annotate, GDB's Obsolete Annotations}).
22810 @kindex set annotate
22811 @item set annotate @var{level}
22812 The @value{GDBN} command @code{set annotate} sets the level of
22813 annotations to the specified @var{level}.
22815 @item show annotate
22816 @kindex show annotate
22817 Show the current annotation level.
22820 This chapter describes level 3 annotations.
22822 A simple example of starting up @value{GDBN} with annotations is:
22825 $ @kbd{gdb --annotate=3}
22827 Copyright 2003 Free Software Foundation, Inc.
22828 GDB is free software, covered by the GNU General Public License,
22829 and you are welcome to change it and/or distribute copies of it
22830 under certain conditions.
22831 Type "show copying" to see the conditions.
22832 There is absolutely no warranty for GDB. Type "show warranty"
22834 This GDB was configured as "i386-pc-linux-gnu"
22845 Here @samp{quit} is input to @value{GDBN}; the rest is output from
22846 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
22847 denotes a @samp{control-z} character) are annotations; the rest is
22848 output from @value{GDBN}.
22850 @node Server Prefix
22851 @section The Server Prefix
22852 @cindex server prefix
22854 If you prefix a command with @samp{server } then it will not affect
22855 the command history, nor will it affect @value{GDBN}'s notion of which
22856 command to repeat if @key{RET} is pressed on a line by itself. This
22857 means that commands can be run behind a user's back by a front-end in
22858 a transparent manner.
22860 The server prefix does not affect the recording of values into the value
22861 history; to print a value without recording it into the value history,
22862 use the @code{output} command instead of the @code{print} command.
22865 @section Annotation for @value{GDBN} Input
22867 @cindex annotations for prompts
22868 When @value{GDBN} prompts for input, it annotates this fact so it is possible
22869 to know when to send output, when the output from a given command is
22872 Different kinds of input each have a different @dfn{input type}. Each
22873 input type has three annotations: a @code{pre-} annotation, which
22874 denotes the beginning of any prompt which is being output, a plain
22875 annotation, which denotes the end of the prompt, and then a @code{post-}
22876 annotation which denotes the end of any echo which may (or may not) be
22877 associated with the input. For example, the @code{prompt} input type
22878 features the following annotations:
22886 The input types are
22889 @findex pre-prompt annotation
22890 @findex prompt annotation
22891 @findex post-prompt annotation
22893 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
22895 @findex pre-commands annotation
22896 @findex commands annotation
22897 @findex post-commands annotation
22899 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
22900 command. The annotations are repeated for each command which is input.
22902 @findex pre-overload-choice annotation
22903 @findex overload-choice annotation
22904 @findex post-overload-choice annotation
22905 @item overload-choice
22906 When @value{GDBN} wants the user to select between various overloaded functions.
22908 @findex pre-query annotation
22909 @findex query annotation
22910 @findex post-query annotation
22912 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
22914 @findex pre-prompt-for-continue annotation
22915 @findex prompt-for-continue annotation
22916 @findex post-prompt-for-continue annotation
22917 @item prompt-for-continue
22918 When @value{GDBN} is asking the user to press return to continue. Note: Don't
22919 expect this to work well; instead use @code{set height 0} to disable
22920 prompting. This is because the counting of lines is buggy in the
22921 presence of annotations.
22926 @cindex annotations for errors, warnings and interrupts
22928 @findex quit annotation
22933 This annotation occurs right before @value{GDBN} responds to an interrupt.
22935 @findex error annotation
22940 This annotation occurs right before @value{GDBN} responds to an error.
22942 Quit and error annotations indicate that any annotations which @value{GDBN} was
22943 in the middle of may end abruptly. For example, if a
22944 @code{value-history-begin} annotation is followed by a @code{error}, one
22945 cannot expect to receive the matching @code{value-history-end}. One
22946 cannot expect not to receive it either, however; an error annotation
22947 does not necessarily mean that @value{GDBN} is immediately returning all the way
22950 @findex error-begin annotation
22951 A quit or error annotation may be preceded by
22957 Any output between that and the quit or error annotation is the error
22960 Warning messages are not yet annotated.
22961 @c If we want to change that, need to fix warning(), type_error(),
22962 @c range_error(), and possibly other places.
22965 @section Invalidation Notices
22967 @cindex annotations for invalidation messages
22968 The following annotations say that certain pieces of state may have
22972 @findex frames-invalid annotation
22973 @item ^Z^Zframes-invalid
22975 The frames (for example, output from the @code{backtrace} command) may
22978 @findex breakpoints-invalid annotation
22979 @item ^Z^Zbreakpoints-invalid
22981 The breakpoints may have changed. For example, the user just added or
22982 deleted a breakpoint.
22985 @node Annotations for Running
22986 @section Running the Program
22987 @cindex annotations for running programs
22989 @findex starting annotation
22990 @findex stopping annotation
22991 When the program starts executing due to a @value{GDBN} command such as
22992 @code{step} or @code{continue},
22998 is output. When the program stops,
23004 is output. Before the @code{stopped} annotation, a variety of
23005 annotations describe how the program stopped.
23008 @findex exited annotation
23009 @item ^Z^Zexited @var{exit-status}
23010 The program exited, and @var{exit-status} is the exit status (zero for
23011 successful exit, otherwise nonzero).
23013 @findex signalled annotation
23014 @findex signal-name annotation
23015 @findex signal-name-end annotation
23016 @findex signal-string annotation
23017 @findex signal-string-end annotation
23018 @item ^Z^Zsignalled
23019 The program exited with a signal. After the @code{^Z^Zsignalled}, the
23020 annotation continues:
23026 ^Z^Zsignal-name-end
23030 ^Z^Zsignal-string-end
23035 where @var{name} is the name of the signal, such as @code{SIGILL} or
23036 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
23037 as @code{Illegal Instruction} or @code{Segmentation fault}.
23038 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
23039 user's benefit and have no particular format.
23041 @findex signal annotation
23043 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
23044 just saying that the program received the signal, not that it was
23045 terminated with it.
23047 @findex breakpoint annotation
23048 @item ^Z^Zbreakpoint @var{number}
23049 The program hit breakpoint number @var{number}.
23051 @findex watchpoint annotation
23052 @item ^Z^Zwatchpoint @var{number}
23053 The program hit watchpoint number @var{number}.
23056 @node Source Annotations
23057 @section Displaying Source
23058 @cindex annotations for source display
23060 @findex source annotation
23061 The following annotation is used instead of displaying source code:
23064 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
23067 where @var{filename} is an absolute file name indicating which source
23068 file, @var{line} is the line number within that file (where 1 is the
23069 first line in the file), @var{character} is the character position
23070 within the file (where 0 is the first character in the file) (for most
23071 debug formats this will necessarily point to the beginning of a line),
23072 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
23073 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
23074 @var{addr} is the address in the target program associated with the
23075 source which is being displayed. @var{addr} is in the form @samp{0x}
23076 followed by one or more lowercase hex digits (note that this does not
23077 depend on the language).
23080 @chapter Reporting Bugs in @value{GDBN}
23081 @cindex bugs in @value{GDBN}
23082 @cindex reporting bugs in @value{GDBN}
23084 Your bug reports play an essential role in making @value{GDBN} reliable.
23086 Reporting a bug may help you by bringing a solution to your problem, or it
23087 may not. But in any case the principal function of a bug report is to help
23088 the entire community by making the next version of @value{GDBN} work better. Bug
23089 reports are your contribution to the maintenance of @value{GDBN}.
23091 In order for a bug report to serve its purpose, you must include the
23092 information that enables us to fix the bug.
23095 * Bug Criteria:: Have you found a bug?
23096 * Bug Reporting:: How to report bugs
23100 @section Have You Found a Bug?
23101 @cindex bug criteria
23103 If you are not sure whether you have found a bug, here are some guidelines:
23106 @cindex fatal signal
23107 @cindex debugger crash
23108 @cindex crash of debugger
23110 If the debugger gets a fatal signal, for any input whatever, that is a
23111 @value{GDBN} bug. Reliable debuggers never crash.
23113 @cindex error on valid input
23115 If @value{GDBN} produces an error message for valid input, that is a
23116 bug. (Note that if you're cross debugging, the problem may also be
23117 somewhere in the connection to the target.)
23119 @cindex invalid input
23121 If @value{GDBN} does not produce an error message for invalid input,
23122 that is a bug. However, you should note that your idea of
23123 ``invalid input'' might be our idea of ``an extension'' or ``support
23124 for traditional practice''.
23127 If you are an experienced user of debugging tools, your suggestions
23128 for improvement of @value{GDBN} are welcome in any case.
23131 @node Bug Reporting
23132 @section How to Report Bugs
23133 @cindex bug reports
23134 @cindex @value{GDBN} bugs, reporting
23136 A number of companies and individuals offer support for @sc{gnu} products.
23137 If you obtained @value{GDBN} from a support organization, we recommend you
23138 contact that organization first.
23140 You can find contact information for many support companies and
23141 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
23143 @c should add a web page ref...
23146 @ifset BUGURL_DEFAULT
23147 In any event, we also recommend that you submit bug reports for
23148 @value{GDBN}. The preferred method is to submit them directly using
23149 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
23150 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
23153 @strong{Do not send bug reports to @samp{info-gdb}, or to
23154 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
23155 not want to receive bug reports. Those that do have arranged to receive
23158 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
23159 serves as a repeater. The mailing list and the newsgroup carry exactly
23160 the same messages. Often people think of posting bug reports to the
23161 newsgroup instead of mailing them. This appears to work, but it has one
23162 problem which can be crucial: a newsgroup posting often lacks a mail
23163 path back to the sender. Thus, if we need to ask for more information,
23164 we may be unable to reach you. For this reason, it is better to send
23165 bug reports to the mailing list.
23167 @ifclear BUGURL_DEFAULT
23168 In any event, we also recommend that you submit bug reports for
23169 @value{GDBN} to @value{BUGURL}.
23173 The fundamental principle of reporting bugs usefully is this:
23174 @strong{report all the facts}. If you are not sure whether to state a
23175 fact or leave it out, state it!
23177 Often people omit facts because they think they know what causes the
23178 problem and assume that some details do not matter. Thus, you might
23179 assume that the name of the variable you use in an example does not matter.
23180 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
23181 stray memory reference which happens to fetch from the location where that
23182 name is stored in memory; perhaps, if the name were different, the contents
23183 of that location would fool the debugger into doing the right thing despite
23184 the bug. Play it safe and give a specific, complete example. That is the
23185 easiest thing for you to do, and the most helpful.
23187 Keep in mind that the purpose of a bug report is to enable us to fix the
23188 bug. It may be that the bug has been reported previously, but neither
23189 you nor we can know that unless your bug report is complete and
23192 Sometimes people give a few sketchy facts and ask, ``Does this ring a
23193 bell?'' Those bug reports are useless, and we urge everyone to
23194 @emph{refuse to respond to them} except to chide the sender to report
23197 To enable us to fix the bug, you should include all these things:
23201 The version of @value{GDBN}. @value{GDBN} announces it if you start
23202 with no arguments; you can also print it at any time using @code{show
23205 Without this, we will not know whether there is any point in looking for
23206 the bug in the current version of @value{GDBN}.
23209 The type of machine you are using, and the operating system name and
23213 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
23214 ``@value{GCC}--2.8.1''.
23217 What compiler (and its version) was used to compile the program you are
23218 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
23219 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
23220 to get this information; for other compilers, see the documentation for
23224 The command arguments you gave the compiler to compile your example and
23225 observe the bug. For example, did you use @samp{-O}? To guarantee
23226 you will not omit something important, list them all. A copy of the
23227 Makefile (or the output from make) is sufficient.
23229 If we were to try to guess the arguments, we would probably guess wrong
23230 and then we might not encounter the bug.
23233 A complete input script, and all necessary source files, that will
23237 A description of what behavior you observe that you believe is
23238 incorrect. For example, ``It gets a fatal signal.''
23240 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
23241 will certainly notice it. But if the bug is incorrect output, we might
23242 not notice unless it is glaringly wrong. You might as well not give us
23243 a chance to make a mistake.
23245 Even if the problem you experience is a fatal signal, you should still
23246 say so explicitly. Suppose something strange is going on, such as, your
23247 copy of @value{GDBN} is out of synch, or you have encountered a bug in
23248 the C library on your system. (This has happened!) Your copy might
23249 crash and ours would not. If you told us to expect a crash, then when
23250 ours fails to crash, we would know that the bug was not happening for
23251 us. If you had not told us to expect a crash, then we would not be able
23252 to draw any conclusion from our observations.
23255 @cindex recording a session script
23256 To collect all this information, you can use a session recording program
23257 such as @command{script}, which is available on many Unix systems.
23258 Just run your @value{GDBN} session inside @command{script} and then
23259 include the @file{typescript} file with your bug report.
23261 Another way to record a @value{GDBN} session is to run @value{GDBN}
23262 inside Emacs and then save the entire buffer to a file.
23265 If you wish to suggest changes to the @value{GDBN} source, send us context
23266 diffs. If you even discuss something in the @value{GDBN} source, refer to
23267 it by context, not by line number.
23269 The line numbers in our development sources will not match those in your
23270 sources. Your line numbers would convey no useful information to us.
23274 Here are some things that are not necessary:
23278 A description of the envelope of the bug.
23280 Often people who encounter a bug spend a lot of time investigating
23281 which changes to the input file will make the bug go away and which
23282 changes will not affect it.
23284 This is often time consuming and not very useful, because the way we
23285 will find the bug is by running a single example under the debugger
23286 with breakpoints, not by pure deduction from a series of examples.
23287 We recommend that you save your time for something else.
23289 Of course, if you can find a simpler example to report @emph{instead}
23290 of the original one, that is a convenience for us. Errors in the
23291 output will be easier to spot, running under the debugger will take
23292 less time, and so on.
23294 However, simplification is not vital; if you do not want to do this,
23295 report the bug anyway and send us the entire test case you used.
23298 A patch for the bug.
23300 A patch for the bug does help us if it is a good one. But do not omit
23301 the necessary information, such as the test case, on the assumption that
23302 a patch is all we need. We might see problems with your patch and decide
23303 to fix the problem another way, or we might not understand it at all.
23305 Sometimes with a program as complicated as @value{GDBN} it is very hard to
23306 construct an example that will make the program follow a certain path
23307 through the code. If you do not send us the example, we will not be able
23308 to construct one, so we will not be able to verify that the bug is fixed.
23310 And if we cannot understand what bug you are trying to fix, or why your
23311 patch should be an improvement, we will not install it. A test case will
23312 help us to understand.
23315 A guess about what the bug is or what it depends on.
23317 Such guesses are usually wrong. Even we cannot guess right about such
23318 things without first using the debugger to find the facts.
23321 @c The readline documentation is distributed with the readline code
23322 @c and consists of the two following files:
23324 @c inc-hist.texinfo
23325 @c Use -I with makeinfo to point to the appropriate directory,
23326 @c environment var TEXINPUTS with TeX.
23327 @include rluser.texi
23328 @include inc-hist.texinfo
23331 @node Formatting Documentation
23332 @appendix Formatting Documentation
23334 @cindex @value{GDBN} reference card
23335 @cindex reference card
23336 The @value{GDBN} 4 release includes an already-formatted reference card, ready
23337 for printing with PostScript or Ghostscript, in the @file{gdb}
23338 subdirectory of the main source directory@footnote{In
23339 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
23340 release.}. If you can use PostScript or Ghostscript with your printer,
23341 you can print the reference card immediately with @file{refcard.ps}.
23343 The release also includes the source for the reference card. You
23344 can format it, using @TeX{}, by typing:
23350 The @value{GDBN} reference card is designed to print in @dfn{landscape}
23351 mode on US ``letter'' size paper;
23352 that is, on a sheet 11 inches wide by 8.5 inches
23353 high. You will need to specify this form of printing as an option to
23354 your @sc{dvi} output program.
23356 @cindex documentation
23358 All the documentation for @value{GDBN} comes as part of the machine-readable
23359 distribution. The documentation is written in Texinfo format, which is
23360 a documentation system that uses a single source file to produce both
23361 on-line information and a printed manual. You can use one of the Info
23362 formatting commands to create the on-line version of the documentation
23363 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
23365 @value{GDBN} includes an already formatted copy of the on-line Info
23366 version of this manual in the @file{gdb} subdirectory. The main Info
23367 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
23368 subordinate files matching @samp{gdb.info*} in the same directory. If
23369 necessary, you can print out these files, or read them with any editor;
23370 but they are easier to read using the @code{info} subsystem in @sc{gnu}
23371 Emacs or the standalone @code{info} program, available as part of the
23372 @sc{gnu} Texinfo distribution.
23374 If you want to format these Info files yourself, you need one of the
23375 Info formatting programs, such as @code{texinfo-format-buffer} or
23378 If you have @code{makeinfo} installed, and are in the top level
23379 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
23380 version @value{GDBVN}), you can make the Info file by typing:
23387 If you want to typeset and print copies of this manual, you need @TeX{},
23388 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
23389 Texinfo definitions file.
23391 @TeX{} is a typesetting program; it does not print files directly, but
23392 produces output files called @sc{dvi} files. To print a typeset
23393 document, you need a program to print @sc{dvi} files. If your system
23394 has @TeX{} installed, chances are it has such a program. The precise
23395 command to use depends on your system; @kbd{lpr -d} is common; another
23396 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
23397 require a file name without any extension or a @samp{.dvi} extension.
23399 @TeX{} also requires a macro definitions file called
23400 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
23401 written in Texinfo format. On its own, @TeX{} cannot either read or
23402 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
23403 and is located in the @file{gdb-@var{version-number}/texinfo}
23406 If you have @TeX{} and a @sc{dvi} printer program installed, you can
23407 typeset and print this manual. First switch to the @file{gdb}
23408 subdirectory of the main source directory (for example, to
23409 @file{gdb-@value{GDBVN}/gdb}) and type:
23415 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
23417 @node Installing GDB
23418 @appendix Installing @value{GDBN}
23419 @cindex installation
23422 * Requirements:: Requirements for building @value{GDBN}
23423 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
23424 * Separate Objdir:: Compiling @value{GDBN} in another directory
23425 * Config Names:: Specifying names for hosts and targets
23426 * Configure Options:: Summary of options for configure
23430 @section Requirements for Building @value{GDBN}
23431 @cindex building @value{GDBN}, requirements for
23433 Building @value{GDBN} requires various tools and packages to be available.
23434 Other packages will be used only if they are found.
23436 @heading Tools/Packages Necessary for Building @value{GDBN}
23438 @item ISO C90 compiler
23439 @value{GDBN} is written in ISO C90. It should be buildable with any
23440 working C90 compiler, e.g.@: GCC.
23444 @heading Tools/Packages Optional for Building @value{GDBN}
23448 @value{GDBN} can use the Expat XML parsing library. This library may be
23449 included with your operating system distribution; if it is not, you
23450 can get the latest version from @url{http://expat.sourceforge.net}.
23451 The @file{configure} script will search for this library in several
23452 standard locations; if it is installed in an unusual path, you can
23453 use the @option{--with-libexpat-prefix} option to specify its location.
23459 Remote protocol memory maps (@pxref{Memory Map Format})
23461 Target descriptions (@pxref{Target Descriptions})
23463 Remote shared library lists (@pxref{Library List Format})
23465 MS-Windows shared libraries (@pxref{Shared Libraries})
23469 @cindex compressed debug sections
23470 @value{GDBN} will use the @samp{zlib} library, if available, to read
23471 compressed debug sections. Some linkers, such as GNU gold, are capable
23472 of producing binaries with compressed debug sections. If @value{GDBN}
23473 is compiled with @samp{zlib}, it will be able to read the debug
23474 information in such binaries.
23476 The @samp{zlib} library is likely included with your operating system
23477 distribution; if it is not, you can get the latest version from
23478 @url{http://zlib.net}.
23482 @node Running Configure
23483 @section Invoking the @value{GDBN} @file{configure} Script
23484 @cindex configuring @value{GDBN}
23485 @value{GDBN} comes with a @file{configure} script that automates the process
23486 of preparing @value{GDBN} for installation; you can then use @code{make} to
23487 build the @code{gdb} program.
23489 @c irrelevant in info file; it's as current as the code it lives with.
23490 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
23491 look at the @file{README} file in the sources; we may have improved the
23492 installation procedures since publishing this manual.}
23495 The @value{GDBN} distribution includes all the source code you need for
23496 @value{GDBN} in a single directory, whose name is usually composed by
23497 appending the version number to @samp{gdb}.
23499 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
23500 @file{gdb-@value{GDBVN}} directory. That directory contains:
23503 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
23504 script for configuring @value{GDBN} and all its supporting libraries
23506 @item gdb-@value{GDBVN}/gdb
23507 the source specific to @value{GDBN} itself
23509 @item gdb-@value{GDBVN}/bfd
23510 source for the Binary File Descriptor library
23512 @item gdb-@value{GDBVN}/include
23513 @sc{gnu} include files
23515 @item gdb-@value{GDBVN}/libiberty
23516 source for the @samp{-liberty} free software library
23518 @item gdb-@value{GDBVN}/opcodes
23519 source for the library of opcode tables and disassemblers
23521 @item gdb-@value{GDBVN}/readline
23522 source for the @sc{gnu} command-line interface
23524 @item gdb-@value{GDBVN}/glob
23525 source for the @sc{gnu} filename pattern-matching subroutine
23527 @item gdb-@value{GDBVN}/mmalloc
23528 source for the @sc{gnu} memory-mapped malloc package
23531 The simplest way to configure and build @value{GDBN} is to run @file{configure}
23532 from the @file{gdb-@var{version-number}} source directory, which in
23533 this example is the @file{gdb-@value{GDBVN}} directory.
23535 First switch to the @file{gdb-@var{version-number}} source directory
23536 if you are not already in it; then run @file{configure}. Pass the
23537 identifier for the platform on which @value{GDBN} will run as an
23543 cd gdb-@value{GDBVN}
23544 ./configure @var{host}
23549 where @var{host} is an identifier such as @samp{sun4} or
23550 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
23551 (You can often leave off @var{host}; @file{configure} tries to guess the
23552 correct value by examining your system.)
23554 Running @samp{configure @var{host}} and then running @code{make} builds the
23555 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
23556 libraries, then @code{gdb} itself. The configured source files, and the
23557 binaries, are left in the corresponding source directories.
23560 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
23561 system does not recognize this automatically when you run a different
23562 shell, you may need to run @code{sh} on it explicitly:
23565 sh configure @var{host}
23568 If you run @file{configure} from a directory that contains source
23569 directories for multiple libraries or programs, such as the
23570 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
23572 creates configuration files for every directory level underneath (unless
23573 you tell it not to, with the @samp{--norecursion} option).
23575 You should run the @file{configure} script from the top directory in the
23576 source tree, the @file{gdb-@var{version-number}} directory. If you run
23577 @file{configure} from one of the subdirectories, you will configure only
23578 that subdirectory. That is usually not what you want. In particular,
23579 if you run the first @file{configure} from the @file{gdb} subdirectory
23580 of the @file{gdb-@var{version-number}} directory, you will omit the
23581 configuration of @file{bfd}, @file{readline}, and other sibling
23582 directories of the @file{gdb} subdirectory. This leads to build errors
23583 about missing include files such as @file{bfd/bfd.h}.
23585 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
23586 However, you should make sure that the shell on your path (named by
23587 the @samp{SHELL} environment variable) is publicly readable. Remember
23588 that @value{GDBN} uses the shell to start your program---some systems refuse to
23589 let @value{GDBN} debug child processes whose programs are not readable.
23591 @node Separate Objdir
23592 @section Compiling @value{GDBN} in Another Directory
23594 If you want to run @value{GDBN} versions for several host or target machines,
23595 you need a different @code{gdb} compiled for each combination of
23596 host and target. @file{configure} is designed to make this easy by
23597 allowing you to generate each configuration in a separate subdirectory,
23598 rather than in the source directory. If your @code{make} program
23599 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
23600 @code{make} in each of these directories builds the @code{gdb}
23601 program specified there.
23603 To build @code{gdb} in a separate directory, run @file{configure}
23604 with the @samp{--srcdir} option to specify where to find the source.
23605 (You also need to specify a path to find @file{configure}
23606 itself from your working directory. If the path to @file{configure}
23607 would be the same as the argument to @samp{--srcdir}, you can leave out
23608 the @samp{--srcdir} option; it is assumed.)
23610 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
23611 separate directory for a Sun 4 like this:
23615 cd gdb-@value{GDBVN}
23618 ../gdb-@value{GDBVN}/configure sun4
23623 When @file{configure} builds a configuration using a remote source
23624 directory, it creates a tree for the binaries with the same structure
23625 (and using the same names) as the tree under the source directory. In
23626 the example, you'd find the Sun 4 library @file{libiberty.a} in the
23627 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
23628 @file{gdb-sun4/gdb}.
23630 Make sure that your path to the @file{configure} script has just one
23631 instance of @file{gdb} in it. If your path to @file{configure} looks
23632 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
23633 one subdirectory of @value{GDBN}, not the whole package. This leads to
23634 build errors about missing include files such as @file{bfd/bfd.h}.
23636 One popular reason to build several @value{GDBN} configurations in separate
23637 directories is to configure @value{GDBN} for cross-compiling (where
23638 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
23639 programs that run on another machine---the @dfn{target}).
23640 You specify a cross-debugging target by
23641 giving the @samp{--target=@var{target}} option to @file{configure}.
23643 When you run @code{make} to build a program or library, you must run
23644 it in a configured directory---whatever directory you were in when you
23645 called @file{configure} (or one of its subdirectories).
23647 The @code{Makefile} that @file{configure} generates in each source
23648 directory also runs recursively. If you type @code{make} in a source
23649 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
23650 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
23651 will build all the required libraries, and then build GDB.
23653 When you have multiple hosts or targets configured in separate
23654 directories, you can run @code{make} on them in parallel (for example,
23655 if they are NFS-mounted on each of the hosts); they will not interfere
23659 @section Specifying Names for Hosts and Targets
23661 The specifications used for hosts and targets in the @file{configure}
23662 script are based on a three-part naming scheme, but some short predefined
23663 aliases are also supported. The full naming scheme encodes three pieces
23664 of information in the following pattern:
23667 @var{architecture}-@var{vendor}-@var{os}
23670 For example, you can use the alias @code{sun4} as a @var{host} argument,
23671 or as the value for @var{target} in a @code{--target=@var{target}}
23672 option. The equivalent full name is @samp{sparc-sun-sunos4}.
23674 The @file{configure} script accompanying @value{GDBN} does not provide
23675 any query facility to list all supported host and target names or
23676 aliases. @file{configure} calls the Bourne shell script
23677 @code{config.sub} to map abbreviations to full names; you can read the
23678 script, if you wish, or you can use it to test your guesses on
23679 abbreviations---for example:
23682 % sh config.sub i386-linux
23684 % sh config.sub alpha-linux
23685 alpha-unknown-linux-gnu
23686 % sh config.sub hp9k700
23688 % sh config.sub sun4
23689 sparc-sun-sunos4.1.1
23690 % sh config.sub sun3
23691 m68k-sun-sunos4.1.1
23692 % sh config.sub i986v
23693 Invalid configuration `i986v': machine `i986v' not recognized
23697 @code{config.sub} is also distributed in the @value{GDBN} source
23698 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
23700 @node Configure Options
23701 @section @file{configure} Options
23703 Here is a summary of the @file{configure} options and arguments that
23704 are most often useful for building @value{GDBN}. @file{configure} also has
23705 several other options not listed here. @inforef{What Configure
23706 Does,,configure.info}, for a full explanation of @file{configure}.
23709 configure @r{[}--help@r{]}
23710 @r{[}--prefix=@var{dir}@r{]}
23711 @r{[}--exec-prefix=@var{dir}@r{]}
23712 @r{[}--srcdir=@var{dirname}@r{]}
23713 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
23714 @r{[}--target=@var{target}@r{]}
23719 You may introduce options with a single @samp{-} rather than
23720 @samp{--} if you prefer; but you may abbreviate option names if you use
23725 Display a quick summary of how to invoke @file{configure}.
23727 @item --prefix=@var{dir}
23728 Configure the source to install programs and files under directory
23731 @item --exec-prefix=@var{dir}
23732 Configure the source to install programs under directory
23735 @c avoid splitting the warning from the explanation:
23737 @item --srcdir=@var{dirname}
23738 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
23739 @code{make} that implements the @code{VPATH} feature.}@*
23740 Use this option to make configurations in directories separate from the
23741 @value{GDBN} source directories. Among other things, you can use this to
23742 build (or maintain) several configurations simultaneously, in separate
23743 directories. @file{configure} writes configuration-specific files in
23744 the current directory, but arranges for them to use the source in the
23745 directory @var{dirname}. @file{configure} creates directories under
23746 the working directory in parallel to the source directories below
23749 @item --norecursion
23750 Configure only the directory level where @file{configure} is executed; do not
23751 propagate configuration to subdirectories.
23753 @item --target=@var{target}
23754 Configure @value{GDBN} for cross-debugging programs running on the specified
23755 @var{target}. Without this option, @value{GDBN} is configured to debug
23756 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
23758 There is no convenient way to generate a list of all available targets.
23760 @item @var{host} @dots{}
23761 Configure @value{GDBN} to run on the specified @var{host}.
23763 There is no convenient way to generate a list of all available hosts.
23766 There are many other options available as well, but they are generally
23767 needed for special purposes only.
23769 @node Maintenance Commands
23770 @appendix Maintenance Commands
23771 @cindex maintenance commands
23772 @cindex internal commands
23774 In addition to commands intended for @value{GDBN} users, @value{GDBN}
23775 includes a number of commands intended for @value{GDBN} developers,
23776 that are not documented elsewhere in this manual. These commands are
23777 provided here for reference. (For commands that turn on debugging
23778 messages, see @ref{Debugging Output}.)
23781 @kindex maint agent
23782 @item maint agent @var{expression}
23783 Translate the given @var{expression} into remote agent bytecodes.
23784 This command is useful for debugging the Agent Expression mechanism
23785 (@pxref{Agent Expressions}).
23787 @kindex maint info breakpoints
23788 @item @anchor{maint info breakpoints}maint info breakpoints
23789 Using the same format as @samp{info breakpoints}, display both the
23790 breakpoints you've set explicitly, and those @value{GDBN} is using for
23791 internal purposes. Internal breakpoints are shown with negative
23792 breakpoint numbers. The type column identifies what kind of breakpoint
23797 Normal, explicitly set breakpoint.
23800 Normal, explicitly set watchpoint.
23803 Internal breakpoint, used to handle correctly stepping through
23804 @code{longjmp} calls.
23806 @item longjmp resume
23807 Internal breakpoint at the target of a @code{longjmp}.
23810 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
23813 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
23816 Shared library events.
23820 @kindex maint set can-use-displaced-stepping
23821 @kindex maint show can-use-displaced-stepping
23822 @cindex displaced stepping support
23823 @cindex out-of-line single-stepping
23824 @item maint set can-use-displaced-stepping
23825 @itemx maint show can-use-displaced-stepping
23826 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
23827 if the target supports it. The default is on. Displaced stepping is
23828 a way to single-step over breakpoints without removing them from the
23829 inferior, by executing an out-of-line copy of the instruction that was
23830 originally at the breakpoint location. It is also known as
23831 out-of-line single-stepping.
23833 @kindex maint check-symtabs
23834 @item maint check-symtabs
23835 Check the consistency of psymtabs and symtabs.
23837 @kindex maint cplus first_component
23838 @item maint cplus first_component @var{name}
23839 Print the first C@t{++} class/namespace component of @var{name}.
23841 @kindex maint cplus namespace
23842 @item maint cplus namespace
23843 Print the list of possible C@t{++} namespaces.
23845 @kindex maint demangle
23846 @item maint demangle @var{name}
23847 Demangle a C@t{++} or Objective-C mangled @var{name}.
23849 @kindex maint deprecate
23850 @kindex maint undeprecate
23851 @cindex deprecated commands
23852 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
23853 @itemx maint undeprecate @var{command}
23854 Deprecate or undeprecate the named @var{command}. Deprecated commands
23855 cause @value{GDBN} to issue a warning when you use them. The optional
23856 argument @var{replacement} says which newer command should be used in
23857 favor of the deprecated one; if it is given, @value{GDBN} will mention
23858 the replacement as part of the warning.
23860 @kindex maint dump-me
23861 @item maint dump-me
23862 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
23863 Cause a fatal signal in the debugger and force it to dump its core.
23864 This is supported only on systems which support aborting a program
23865 with the @code{SIGQUIT} signal.
23867 @kindex maint internal-error
23868 @kindex maint internal-warning
23869 @item maint internal-error @r{[}@var{message-text}@r{]}
23870 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
23871 Cause @value{GDBN} to call the internal function @code{internal_error}
23872 or @code{internal_warning} and hence behave as though an internal error
23873 or internal warning has been detected. In addition to reporting the
23874 internal problem, these functions give the user the opportunity to
23875 either quit @value{GDBN} or create a core file of the current
23876 @value{GDBN} session.
23878 These commands take an optional parameter @var{message-text} that is
23879 used as the text of the error or warning message.
23881 Here's an example of using @code{internal-error}:
23884 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
23885 @dots{}/maint.c:121: internal-error: testing, 1, 2
23886 A problem internal to GDB has been detected. Further
23887 debugging may prove unreliable.
23888 Quit this debugging session? (y or n) @kbd{n}
23889 Create a core file? (y or n) @kbd{n}
23893 @kindex maint packet
23894 @item maint packet @var{text}
23895 If @value{GDBN} is talking to an inferior via the serial protocol,
23896 then this command sends the string @var{text} to the inferior, and
23897 displays the response packet. @value{GDBN} supplies the initial
23898 @samp{$} character, the terminating @samp{#} character, and the
23901 @kindex maint print architecture
23902 @item maint print architecture @r{[}@var{file}@r{]}
23903 Print the entire architecture configuration. The optional argument
23904 @var{file} names the file where the output goes.
23906 @kindex maint print c-tdesc
23907 @item maint print c-tdesc
23908 Print the current target description (@pxref{Target Descriptions}) as
23909 a C source file. The created source file can be used in @value{GDBN}
23910 when an XML parser is not available to parse the description.
23912 @kindex maint print dummy-frames
23913 @item maint print dummy-frames
23914 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
23917 (@value{GDBP}) @kbd{b add}
23919 (@value{GDBP}) @kbd{print add(2,3)}
23920 Breakpoint 2, add (a=2, b=3) at @dots{}
23922 The program being debugged stopped while in a function called from GDB.
23924 (@value{GDBP}) @kbd{maint print dummy-frames}
23925 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
23926 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
23927 call_lo=0x01014000 call_hi=0x01014001
23931 Takes an optional file parameter.
23933 @kindex maint print registers
23934 @kindex maint print raw-registers
23935 @kindex maint print cooked-registers
23936 @kindex maint print register-groups
23937 @item maint print registers @r{[}@var{file}@r{]}
23938 @itemx maint print raw-registers @r{[}@var{file}@r{]}
23939 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
23940 @itemx maint print register-groups @r{[}@var{file}@r{]}
23941 Print @value{GDBN}'s internal register data structures.
23943 The command @code{maint print raw-registers} includes the contents of
23944 the raw register cache; the command @code{maint print cooked-registers}
23945 includes the (cooked) value of all registers; and the command
23946 @code{maint print register-groups} includes the groups that each
23947 register is a member of. @xref{Registers,, Registers, gdbint,
23948 @value{GDBN} Internals}.
23950 These commands take an optional parameter, a file name to which to
23951 write the information.
23953 @kindex maint print reggroups
23954 @item maint print reggroups @r{[}@var{file}@r{]}
23955 Print @value{GDBN}'s internal register group data structures. The
23956 optional argument @var{file} tells to what file to write the
23959 The register groups info looks like this:
23962 (@value{GDBP}) @kbd{maint print reggroups}
23975 This command forces @value{GDBN} to flush its internal register cache.
23977 @kindex maint print objfiles
23978 @cindex info for known object files
23979 @item maint print objfiles
23980 Print a dump of all known object files. For each object file, this
23981 command prints its name, address in memory, and all of its psymtabs
23984 @kindex maint print statistics
23985 @cindex bcache statistics
23986 @item maint print statistics
23987 This command prints, for each object file in the program, various data
23988 about that object file followed by the byte cache (@dfn{bcache})
23989 statistics for the object file. The objfile data includes the number
23990 of minimal, partial, full, and stabs symbols, the number of types
23991 defined by the objfile, the number of as yet unexpanded psym tables,
23992 the number of line tables and string tables, and the amount of memory
23993 used by the various tables. The bcache statistics include the counts,
23994 sizes, and counts of duplicates of all and unique objects, max,
23995 average, and median entry size, total memory used and its overhead and
23996 savings, and various measures of the hash table size and chain
23999 @kindex maint print target-stack
24000 @cindex target stack description
24001 @item maint print target-stack
24002 A @dfn{target} is an interface between the debugger and a particular
24003 kind of file or process. Targets can be stacked in @dfn{strata},
24004 so that more than one target can potentially respond to a request.
24005 In particular, memory accesses will walk down the stack of targets
24006 until they find a target that is interested in handling that particular
24009 This command prints a short description of each layer that was pushed on
24010 the @dfn{target stack}, starting from the top layer down to the bottom one.
24012 @kindex maint print type
24013 @cindex type chain of a data type
24014 @item maint print type @var{expr}
24015 Print the type chain for a type specified by @var{expr}. The argument
24016 can be either a type name or a symbol. If it is a symbol, the type of
24017 that symbol is described. The type chain produced by this command is
24018 a recursive definition of the data type as stored in @value{GDBN}'s
24019 data structures, including its flags and contained types.
24021 @kindex maint set dwarf2 max-cache-age
24022 @kindex maint show dwarf2 max-cache-age
24023 @item maint set dwarf2 max-cache-age
24024 @itemx maint show dwarf2 max-cache-age
24025 Control the DWARF 2 compilation unit cache.
24027 @cindex DWARF 2 compilation units cache
24028 In object files with inter-compilation-unit references, such as those
24029 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
24030 reader needs to frequently refer to previously read compilation units.
24031 This setting controls how long a compilation unit will remain in the
24032 cache if it is not referenced. A higher limit means that cached
24033 compilation units will be stored in memory longer, and more total
24034 memory will be used. Setting it to zero disables caching, which will
24035 slow down @value{GDBN} startup, but reduce memory consumption.
24037 @kindex maint set profile
24038 @kindex maint show profile
24039 @cindex profiling GDB
24040 @item maint set profile
24041 @itemx maint show profile
24042 Control profiling of @value{GDBN}.
24044 Profiling will be disabled until you use the @samp{maint set profile}
24045 command to enable it. When you enable profiling, the system will begin
24046 collecting timing and execution count data; when you disable profiling or
24047 exit @value{GDBN}, the results will be written to a log file. Remember that
24048 if you use profiling, @value{GDBN} will overwrite the profiling log file
24049 (often called @file{gmon.out}). If you have a record of important profiling
24050 data in a @file{gmon.out} file, be sure to move it to a safe location.
24052 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
24053 compiled with the @samp{-pg} compiler option.
24055 @kindex maint set linux-async
24056 @kindex maint show linux-async
24057 @cindex asynchronous support
24058 @item maint set linux-async
24059 @itemx maint show linux-async
24060 Control the GNU/Linux native asynchronous support
24061 (@pxref{Background Execution}) of @value{GDBN}.
24063 GNU/Linux native asynchronous support will be disabled until you use
24064 the @samp{maint set linux-async} command to enable it.
24066 @kindex maint set remote-async
24067 @kindex maint show remote-async
24068 @cindex asynchronous support
24069 @item maint set remote-async
24070 @itemx maint show remote-async
24071 Control the remote asynchronous support
24072 (@pxref{Background Execution}) of @value{GDBN}.
24074 Remote asynchronous support will be disabled until you use
24075 the @samp{maint set remote-async} command to enable it.
24077 @kindex maint show-debug-regs
24078 @cindex x86 hardware debug registers
24079 @item maint show-debug-regs
24080 Control whether to show variables that mirror the x86 hardware debug
24081 registers. Use @code{ON} to enable, @code{OFF} to disable. If
24082 enabled, the debug registers values are shown when @value{GDBN} inserts or
24083 removes a hardware breakpoint or watchpoint, and when the inferior
24084 triggers a hardware-assisted breakpoint or watchpoint.
24086 @kindex maint space
24087 @cindex memory used by commands
24089 Control whether to display memory usage for each command. If set to a
24090 nonzero value, @value{GDBN} will display how much memory each command
24091 took, following the command's own output. This can also be requested
24092 by invoking @value{GDBN} with the @option{--statistics} command-line
24093 switch (@pxref{Mode Options}).
24096 @cindex time of command execution
24098 Control whether to display the execution time for each command. If
24099 set to a nonzero value, @value{GDBN} will display how much time it
24100 took to execute each command, following the command's own output.
24101 The time is not printed for the commands that run the target, since
24102 there's no mechanism currently to compute how much time was spend
24103 by @value{GDBN} and how much time was spend by the program been debugged.
24104 it's not possibly currently
24105 This can also be requested by invoking @value{GDBN} with the
24106 @option{--statistics} command-line switch (@pxref{Mode Options}).
24108 @kindex maint translate-address
24109 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
24110 Find the symbol stored at the location specified by the address
24111 @var{addr} and an optional section name @var{section}. If found,
24112 @value{GDBN} prints the name of the closest symbol and an offset from
24113 the symbol's location to the specified address. This is similar to
24114 the @code{info address} command (@pxref{Symbols}), except that this
24115 command also allows to find symbols in other sections.
24119 The following command is useful for non-interactive invocations of
24120 @value{GDBN}, such as in the test suite.
24123 @item set watchdog @var{nsec}
24124 @kindex set watchdog
24125 @cindex watchdog timer
24126 @cindex timeout for commands
24127 Set the maximum number of seconds @value{GDBN} will wait for the
24128 target operation to finish. If this time expires, @value{GDBN}
24129 reports and error and the command is aborted.
24131 @item show watchdog
24132 Show the current setting of the target wait timeout.
24135 @node Remote Protocol
24136 @appendix @value{GDBN} Remote Serial Protocol
24141 * Stop Reply Packets::
24142 * General Query Packets::
24143 * Register Packet Format::
24144 * Tracepoint Packets::
24145 * Host I/O Packets::
24148 * File-I/O Remote Protocol Extension::
24149 * Library List Format::
24150 * Memory Map Format::
24156 There may be occasions when you need to know something about the
24157 protocol---for example, if there is only one serial port to your target
24158 machine, you might want your program to do something special if it
24159 recognizes a packet meant for @value{GDBN}.
24161 In the examples below, @samp{->} and @samp{<-} are used to indicate
24162 transmitted and received data, respectively.
24164 @cindex protocol, @value{GDBN} remote serial
24165 @cindex serial protocol, @value{GDBN} remote
24166 @cindex remote serial protocol
24167 All @value{GDBN} commands and responses (other than acknowledgments) are
24168 sent as a @var{packet}. A @var{packet} is introduced with the character
24169 @samp{$}, the actual @var{packet-data}, and the terminating character
24170 @samp{#} followed by a two-digit @var{checksum}:
24173 @code{$}@var{packet-data}@code{#}@var{checksum}
24177 @cindex checksum, for @value{GDBN} remote
24179 The two-digit @var{checksum} is computed as the modulo 256 sum of all
24180 characters between the leading @samp{$} and the trailing @samp{#} (an
24181 eight bit unsigned checksum).
24183 Implementors should note that prior to @value{GDBN} 5.0 the protocol
24184 specification also included an optional two-digit @var{sequence-id}:
24187 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
24190 @cindex sequence-id, for @value{GDBN} remote
24192 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
24193 has never output @var{sequence-id}s. Stubs that handle packets added
24194 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
24196 @cindex acknowledgment, for @value{GDBN} remote
24197 When either the host or the target machine receives a packet, the first
24198 response expected is an acknowledgment: either @samp{+} (to indicate
24199 the package was received correctly) or @samp{-} (to request
24203 -> @code{$}@var{packet-data}@code{#}@var{checksum}
24208 The host (@value{GDBN}) sends @var{command}s, and the target (the
24209 debugging stub incorporated in your program) sends a @var{response}. In
24210 the case of step and continue @var{command}s, the response is only sent
24211 when the operation has completed (the target has again stopped).
24213 @var{packet-data} consists of a sequence of characters with the
24214 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
24217 @cindex remote protocol, field separator
24218 Fields within the packet should be separated using @samp{,} @samp{;} or
24219 @samp{:}. Except where otherwise noted all numbers are represented in
24220 @sc{hex} with leading zeros suppressed.
24222 Implementors should note that prior to @value{GDBN} 5.0, the character
24223 @samp{:} could not appear as the third character in a packet (as it
24224 would potentially conflict with the @var{sequence-id}).
24226 @cindex remote protocol, binary data
24227 @anchor{Binary Data}
24228 Binary data in most packets is encoded either as two hexadecimal
24229 digits per byte of binary data. This allowed the traditional remote
24230 protocol to work over connections which were only seven-bit clean.
24231 Some packets designed more recently assume an eight-bit clean
24232 connection, and use a more efficient encoding to send and receive
24235 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
24236 as an escape character. Any escaped byte is transmitted as the escape
24237 character followed by the original character XORed with @code{0x20}.
24238 For example, the byte @code{0x7d} would be transmitted as the two
24239 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
24240 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
24241 @samp{@}}) must always be escaped. Responses sent by the stub
24242 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
24243 is not interpreted as the start of a run-length encoded sequence
24246 Response @var{data} can be run-length encoded to save space.
24247 Run-length encoding replaces runs of identical characters with one
24248 instance of the repeated character, followed by a @samp{*} and a
24249 repeat count. The repeat count is itself sent encoded, to avoid
24250 binary characters in @var{data}: a value of @var{n} is sent as
24251 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
24252 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
24253 code 32) for a repeat count of 3. (This is because run-length
24254 encoding starts to win for counts 3 or more.) Thus, for example,
24255 @samp{0* } is a run-length encoding of ``0000'': the space character
24256 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
24259 The printable characters @samp{#} and @samp{$} or with a numeric value
24260 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
24261 seven repeats (@samp{$}) can be expanded using a repeat count of only
24262 five (@samp{"}). For example, @samp{00000000} can be encoded as
24265 The error response returned for some packets includes a two character
24266 error number. That number is not well defined.
24268 @cindex empty response, for unsupported packets
24269 For any @var{command} not supported by the stub, an empty response
24270 (@samp{$#00}) should be returned. That way it is possible to extend the
24271 protocol. A newer @value{GDBN} can tell if a packet is supported based
24274 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
24275 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
24281 The following table provides a complete list of all currently defined
24282 @var{command}s and their corresponding response @var{data}.
24283 @xref{File-I/O Remote Protocol Extension}, for details about the File
24284 I/O extension of the remote protocol.
24286 Each packet's description has a template showing the packet's overall
24287 syntax, followed by an explanation of the packet's meaning. We
24288 include spaces in some of the templates for clarity; these are not
24289 part of the packet's syntax. No @value{GDBN} packet uses spaces to
24290 separate its components. For example, a template like @samp{foo
24291 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
24292 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
24293 @var{baz}. @value{GDBN} does not transmit a space character between the
24294 @samp{foo} and the @var{bar}, or between the @var{bar} and the
24297 Note that all packet forms beginning with an upper- or lower-case
24298 letter, other than those described here, are reserved for future use.
24300 Here are the packet descriptions.
24305 @cindex @samp{!} packet
24306 @anchor{extended mode}
24307 Enable extended mode. In extended mode, the remote server is made
24308 persistent. The @samp{R} packet is used to restart the program being
24314 The remote target both supports and has enabled extended mode.
24318 @cindex @samp{?} packet
24319 Indicate the reason the target halted. The reply is the same as for
24323 @xref{Stop Reply Packets}, for the reply specifications.
24325 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
24326 @cindex @samp{A} packet
24327 Initialized @code{argv[]} array passed into program. @var{arglen}
24328 specifies the number of bytes in the hex encoded byte stream
24329 @var{arg}. See @code{gdbserver} for more details.
24334 The arguments were set.
24340 @cindex @samp{b} packet
24341 (Don't use this packet; its behavior is not well-defined.)
24342 Change the serial line speed to @var{baud}.
24344 JTC: @emph{When does the transport layer state change? When it's
24345 received, or after the ACK is transmitted. In either case, there are
24346 problems if the command or the acknowledgment packet is dropped.}
24348 Stan: @emph{If people really wanted to add something like this, and get
24349 it working for the first time, they ought to modify ser-unix.c to send
24350 some kind of out-of-band message to a specially-setup stub and have the
24351 switch happen "in between" packets, so that from remote protocol's point
24352 of view, nothing actually happened.}
24354 @item B @var{addr},@var{mode}
24355 @cindex @samp{B} packet
24356 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
24357 breakpoint at @var{addr}.
24359 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
24360 (@pxref{insert breakpoint or watchpoint packet}).
24362 @item c @r{[}@var{addr}@r{]}
24363 @cindex @samp{c} packet
24364 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
24365 resume at current address.
24368 @xref{Stop Reply Packets}, for the reply specifications.
24370 @item C @var{sig}@r{[};@var{addr}@r{]}
24371 @cindex @samp{C} packet
24372 Continue with signal @var{sig} (hex signal number). If
24373 @samp{;@var{addr}} is omitted, resume at same address.
24376 @xref{Stop Reply Packets}, for the reply specifications.
24379 @cindex @samp{d} packet
24382 Don't use this packet; instead, define a general set packet
24383 (@pxref{General Query Packets}).
24386 @cindex @samp{D} packet
24387 Detach @value{GDBN} from the remote system. Sent to the remote target
24388 before @value{GDBN} disconnects via the @code{detach} command.
24398 @item F @var{RC},@var{EE},@var{CF};@var{XX}
24399 @cindex @samp{F} packet
24400 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
24401 This is part of the File-I/O protocol extension. @xref{File-I/O
24402 Remote Protocol Extension}, for the specification.
24405 @anchor{read registers packet}
24406 @cindex @samp{g} packet
24407 Read general registers.
24411 @item @var{XX@dots{}}
24412 Each byte of register data is described by two hex digits. The bytes
24413 with the register are transmitted in target byte order. The size of
24414 each register and their position within the @samp{g} packet are
24415 determined by the @value{GDBN} internal gdbarch functions
24416 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
24417 specification of several standard @samp{g} packets is specified below.
24422 @item G @var{XX@dots{}}
24423 @cindex @samp{G} packet
24424 Write general registers. @xref{read registers packet}, for a
24425 description of the @var{XX@dots{}} data.
24435 @item H @var{c} @var{t}
24436 @cindex @samp{H} packet
24437 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
24438 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
24439 should be @samp{c} for step and continue operations, @samp{g} for other
24440 operations. The thread designator @var{t} may be @samp{-1}, meaning all
24441 the threads, a thread number, or @samp{0} which means pick any thread.
24452 @c 'H': How restrictive (or permissive) is the thread model. If a
24453 @c thread is selected and stopped, are other threads allowed
24454 @c to continue to execute? As I mentioned above, I think the
24455 @c semantics of each command when a thread is selected must be
24456 @c described. For example:
24458 @c 'g': If the stub supports threads and a specific thread is
24459 @c selected, returns the register block from that thread;
24460 @c otherwise returns current registers.
24462 @c 'G' If the stub supports threads and a specific thread is
24463 @c selected, sets the registers of the register block of
24464 @c that thread; otherwise sets current registers.
24466 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
24467 @anchor{cycle step packet}
24468 @cindex @samp{i} packet
24469 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
24470 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
24471 step starting at that address.
24474 @cindex @samp{I} packet
24475 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
24479 @cindex @samp{k} packet
24482 FIXME: @emph{There is no description of how to operate when a specific
24483 thread context has been selected (i.e.@: does 'k' kill only that
24486 @item m @var{addr},@var{length}
24487 @cindex @samp{m} packet
24488 Read @var{length} bytes of memory starting at address @var{addr}.
24489 Note that @var{addr} may not be aligned to any particular boundary.
24491 The stub need not use any particular size or alignment when gathering
24492 data from memory for the response; even if @var{addr} is word-aligned
24493 and @var{length} is a multiple of the word size, the stub is free to
24494 use byte accesses, or not. For this reason, this packet may not be
24495 suitable for accessing memory-mapped I/O devices.
24496 @cindex alignment of remote memory accesses
24497 @cindex size of remote memory accesses
24498 @cindex memory, alignment and size of remote accesses
24502 @item @var{XX@dots{}}
24503 Memory contents; each byte is transmitted as a two-digit hexadecimal
24504 number. The reply may contain fewer bytes than requested if the
24505 server was able to read only part of the region of memory.
24510 @item M @var{addr},@var{length}:@var{XX@dots{}}
24511 @cindex @samp{M} packet
24512 Write @var{length} bytes of memory starting at address @var{addr}.
24513 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
24514 hexadecimal number.
24521 for an error (this includes the case where only part of the data was
24526 @cindex @samp{p} packet
24527 Read the value of register @var{n}; @var{n} is in hex.
24528 @xref{read registers packet}, for a description of how the returned
24529 register value is encoded.
24533 @item @var{XX@dots{}}
24534 the register's value
24538 Indicating an unrecognized @var{query}.
24541 @item P @var{n@dots{}}=@var{r@dots{}}
24542 @anchor{write register packet}
24543 @cindex @samp{P} packet
24544 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
24545 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
24546 digits for each byte in the register (target byte order).
24556 @item q @var{name} @var{params}@dots{}
24557 @itemx Q @var{name} @var{params}@dots{}
24558 @cindex @samp{q} packet
24559 @cindex @samp{Q} packet
24560 General query (@samp{q}) and set (@samp{Q}). These packets are
24561 described fully in @ref{General Query Packets}.
24564 @cindex @samp{r} packet
24565 Reset the entire system.
24567 Don't use this packet; use the @samp{R} packet instead.
24570 @cindex @samp{R} packet
24571 Restart the program being debugged. @var{XX}, while needed, is ignored.
24572 This packet is only available in extended mode (@pxref{extended mode}).
24574 The @samp{R} packet has no reply.
24576 @item s @r{[}@var{addr}@r{]}
24577 @cindex @samp{s} packet
24578 Single step. @var{addr} is the address at which to resume. If
24579 @var{addr} is omitted, resume at same address.
24582 @xref{Stop Reply Packets}, for the reply specifications.
24584 @item S @var{sig}@r{[};@var{addr}@r{]}
24585 @anchor{step with signal packet}
24586 @cindex @samp{S} packet
24587 Step with signal. This is analogous to the @samp{C} packet, but
24588 requests a single-step, rather than a normal resumption of execution.
24591 @xref{Stop Reply Packets}, for the reply specifications.
24593 @item t @var{addr}:@var{PP},@var{MM}
24594 @cindex @samp{t} packet
24595 Search backwards starting at address @var{addr} for a match with pattern
24596 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
24597 @var{addr} must be at least 3 digits.
24600 @cindex @samp{T} packet
24601 Find out if the thread XX is alive.
24606 thread is still alive
24612 Packets starting with @samp{v} are identified by a multi-letter name,
24613 up to the first @samp{;} or @samp{?} (or the end of the packet).
24615 @item vAttach;@var{pid}
24616 @cindex @samp{vAttach} packet
24617 Attach to a new process with the specified process ID. @var{pid} is a
24618 hexadecimal integer identifying the process. The attached process is
24621 This packet is only available in extended mode (@pxref{extended mode}).
24627 @item @r{Any stop packet}
24628 for success (@pxref{Stop Reply Packets})
24631 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
24632 @cindex @samp{vCont} packet
24633 Resume the inferior, specifying different actions for each thread.
24634 If an action is specified with no @var{tid}, then it is applied to any
24635 threads that don't have a specific action specified; if no default action is
24636 specified then other threads should remain stopped. Specifying multiple
24637 default actions is an error; specifying no actions is also an error.
24638 Thread IDs are specified in hexadecimal. Currently supported actions are:
24644 Continue with signal @var{sig}. @var{sig} should be two hex digits.
24648 Step with signal @var{sig}. @var{sig} should be two hex digits.
24651 The optional @var{addr} argument normally associated with these packets is
24652 not supported in @samp{vCont}.
24655 @xref{Stop Reply Packets}, for the reply specifications.
24658 @cindex @samp{vCont?} packet
24659 Request a list of actions supported by the @samp{vCont} packet.
24663 @item vCont@r{[};@var{action}@dots{}@r{]}
24664 The @samp{vCont} packet is supported. Each @var{action} is a supported
24665 command in the @samp{vCont} packet.
24667 The @samp{vCont} packet is not supported.
24670 @item vFile:@var{operation}:@var{parameter}@dots{}
24671 @cindex @samp{vFile} packet
24672 Perform a file operation on the target system. For details,
24673 see @ref{Host I/O Packets}.
24675 @item vFlashErase:@var{addr},@var{length}
24676 @cindex @samp{vFlashErase} packet
24677 Direct the stub to erase @var{length} bytes of flash starting at
24678 @var{addr}. The region may enclose any number of flash blocks, but
24679 its start and end must fall on block boundaries, as indicated by the
24680 flash block size appearing in the memory map (@pxref{Memory Map
24681 Format}). @value{GDBN} groups flash memory programming operations
24682 together, and sends a @samp{vFlashDone} request after each group; the
24683 stub is allowed to delay erase operation until the @samp{vFlashDone}
24684 packet is received.
24694 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
24695 @cindex @samp{vFlashWrite} packet
24696 Direct the stub to write data to flash address @var{addr}. The data
24697 is passed in binary form using the same encoding as for the @samp{X}
24698 packet (@pxref{Binary Data}). The memory ranges specified by
24699 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
24700 not overlap, and must appear in order of increasing addresses
24701 (although @samp{vFlashErase} packets for higher addresses may already
24702 have been received; the ordering is guaranteed only between
24703 @samp{vFlashWrite} packets). If a packet writes to an address that was
24704 neither erased by a preceding @samp{vFlashErase} packet nor by some other
24705 target-specific method, the results are unpredictable.
24713 for vFlashWrite addressing non-flash memory
24719 @cindex @samp{vFlashDone} packet
24720 Indicate to the stub that flash programming operation is finished.
24721 The stub is permitted to delay or batch the effects of a group of
24722 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
24723 @samp{vFlashDone} packet is received. The contents of the affected
24724 regions of flash memory are unpredictable until the @samp{vFlashDone}
24725 request is completed.
24727 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
24728 @cindex @samp{vRun} packet
24729 Run the program @var{filename}, passing it each @var{argument} on its
24730 command line. The file and arguments are hex-encoded strings. If
24731 @var{filename} is an empty string, the stub may use a default program
24732 (e.g.@: the last program run). The program is created in the stopped
24735 This packet is only available in extended mode (@pxref{extended mode}).
24741 @item @r{Any stop packet}
24742 for success (@pxref{Stop Reply Packets})
24745 @item X @var{addr},@var{length}:@var{XX@dots{}}
24747 @cindex @samp{X} packet
24748 Write data to memory, where the data is transmitted in binary.
24749 @var{addr} is address, @var{length} is number of bytes,
24750 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
24760 @item z @var{type},@var{addr},@var{length}
24761 @itemx Z @var{type},@var{addr},@var{length}
24762 @anchor{insert breakpoint or watchpoint packet}
24763 @cindex @samp{z} packet
24764 @cindex @samp{Z} packets
24765 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
24766 watchpoint starting at address @var{address} and covering the next
24767 @var{length} bytes.
24769 Each breakpoint and watchpoint packet @var{type} is documented
24772 @emph{Implementation notes: A remote target shall return an empty string
24773 for an unrecognized breakpoint or watchpoint packet @var{type}. A
24774 remote target shall support either both or neither of a given
24775 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
24776 avoid potential problems with duplicate packets, the operations should
24777 be implemented in an idempotent way.}
24779 @item z0,@var{addr},@var{length}
24780 @itemx Z0,@var{addr},@var{length}
24781 @cindex @samp{z0} packet
24782 @cindex @samp{Z0} packet
24783 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
24784 @var{addr} of size @var{length}.
24786 A memory breakpoint is implemented by replacing the instruction at
24787 @var{addr} with a software breakpoint or trap instruction. The
24788 @var{length} is used by targets that indicates the size of the
24789 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
24790 @sc{mips} can insert either a 2 or 4 byte breakpoint).
24792 @emph{Implementation note: It is possible for a target to copy or move
24793 code that contains memory breakpoints (e.g., when implementing
24794 overlays). The behavior of this packet, in the presence of such a
24795 target, is not defined.}
24807 @item z1,@var{addr},@var{length}
24808 @itemx Z1,@var{addr},@var{length}
24809 @cindex @samp{z1} packet
24810 @cindex @samp{Z1} packet
24811 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
24812 address @var{addr} of size @var{length}.
24814 A hardware breakpoint is implemented using a mechanism that is not
24815 dependant on being able to modify the target's memory.
24817 @emph{Implementation note: A hardware breakpoint is not affected by code
24830 @item z2,@var{addr},@var{length}
24831 @itemx Z2,@var{addr},@var{length}
24832 @cindex @samp{z2} packet
24833 @cindex @samp{Z2} packet
24834 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
24846 @item z3,@var{addr},@var{length}
24847 @itemx Z3,@var{addr},@var{length}
24848 @cindex @samp{z3} packet
24849 @cindex @samp{Z3} packet
24850 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
24862 @item z4,@var{addr},@var{length}
24863 @itemx Z4,@var{addr},@var{length}
24864 @cindex @samp{z4} packet
24865 @cindex @samp{Z4} packet
24866 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
24880 @node Stop Reply Packets
24881 @section Stop Reply Packets
24882 @cindex stop reply packets
24884 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
24885 receive any of the below as a reply. In the case of the @samp{C},
24886 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
24887 when the target halts. In the below the exact meaning of @dfn{signal
24888 number} is defined by the header @file{include/gdb/signals.h} in the
24889 @value{GDBN} source code.
24891 As in the description of request packets, we include spaces in the
24892 reply templates for clarity; these are not part of the reply packet's
24893 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
24899 The program received signal number @var{AA} (a two-digit hexadecimal
24900 number). This is equivalent to a @samp{T} response with no
24901 @var{n}:@var{r} pairs.
24903 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
24904 @cindex @samp{T} packet reply
24905 The program received signal number @var{AA} (a two-digit hexadecimal
24906 number). This is equivalent to an @samp{S} response, except that the
24907 @samp{@var{n}:@var{r}} pairs can carry values of important registers
24908 and other information directly in the stop reply packet, reducing
24909 round-trip latency. Single-step and breakpoint traps are reported
24910 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
24914 If @var{n} is a hexadecimal number, it is a register number, and the
24915 corresponding @var{r} gives that register's value. @var{r} is a
24916 series of bytes in target byte order, with each byte given by a
24917 two-digit hex number.
24920 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
24924 If @var{n} is a recognized @dfn{stop reason}, it describes a more
24925 specific event that stopped the target. The currently defined stop
24926 reasons are listed below. @var{aa} should be @samp{05}, the trap
24927 signal. At most one stop reason should be present.
24930 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
24931 and go on to the next; this allows us to extend the protocol in the
24935 The currently defined stop reasons are:
24941 The packet indicates a watchpoint hit, and @var{r} is the data address, in
24944 @cindex shared library events, remote reply
24946 The packet indicates that the loaded libraries have changed.
24947 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
24948 list of loaded libraries. @var{r} is ignored.
24952 The process exited, and @var{AA} is the exit status. This is only
24953 applicable to certain targets.
24956 The process terminated with signal @var{AA}.
24958 @item O @var{XX}@dots{}
24959 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
24960 written as the program's console output. This can happen at any time
24961 while the program is running and the debugger should continue to wait
24962 for @samp{W}, @samp{T}, etc.
24964 @item F @var{call-id},@var{parameter}@dots{}
24965 @var{call-id} is the identifier which says which host system call should
24966 be called. This is just the name of the function. Translation into the
24967 correct system call is only applicable as it's defined in @value{GDBN}.
24968 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
24971 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
24972 this very system call.
24974 The target replies with this packet when it expects @value{GDBN} to
24975 call a host system call on behalf of the target. @value{GDBN} replies
24976 with an appropriate @samp{F} packet and keeps up waiting for the next
24977 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
24978 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
24979 Protocol Extension}, for more details.
24983 @node General Query Packets
24984 @section General Query Packets
24985 @cindex remote query requests
24987 Packets starting with @samp{q} are @dfn{general query packets};
24988 packets starting with @samp{Q} are @dfn{general set packets}. General
24989 query and set packets are a semi-unified form for retrieving and
24990 sending information to and from the stub.
24992 The initial letter of a query or set packet is followed by a name
24993 indicating what sort of thing the packet applies to. For example,
24994 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
24995 definitions with the stub. These packet names follow some
25000 The name must not contain commas, colons or semicolons.
25002 Most @value{GDBN} query and set packets have a leading upper case
25005 The names of custom vendor packets should use a company prefix, in
25006 lower case, followed by a period. For example, packets designed at
25007 the Acme Corporation might begin with @samp{qacme.foo} (for querying
25008 foos) or @samp{Qacme.bar} (for setting bars).
25011 The name of a query or set packet should be separated from any
25012 parameters by a @samp{:}; the parameters themselves should be
25013 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
25014 full packet name, and check for a separator or the end of the packet,
25015 in case two packet names share a common prefix. New packets should not begin
25016 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
25017 packets predate these conventions, and have arguments without any terminator
25018 for the packet name; we suspect they are in widespread use in places that
25019 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
25020 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
25023 Like the descriptions of the other packets, each description here
25024 has a template showing the packet's overall syntax, followed by an
25025 explanation of the packet's meaning. We include spaces in some of the
25026 templates for clarity; these are not part of the packet's syntax. No
25027 @value{GDBN} packet uses spaces to separate its components.
25029 Here are the currently defined query and set packets:
25034 @cindex current thread, remote request
25035 @cindex @samp{qC} packet
25036 Return the current thread id.
25041 Where @var{pid} is an unsigned hexadecimal process id.
25042 @item @r{(anything else)}
25043 Any other reply implies the old pid.
25046 @item qCRC:@var{addr},@var{length}
25047 @cindex CRC of memory block, remote request
25048 @cindex @samp{qCRC} packet
25049 Compute the CRC checksum of a block of memory.
25053 An error (such as memory fault)
25054 @item C @var{crc32}
25055 The specified memory region's checksum is @var{crc32}.
25059 @itemx qsThreadInfo
25060 @cindex list active threads, remote request
25061 @cindex @samp{qfThreadInfo} packet
25062 @cindex @samp{qsThreadInfo} packet
25063 Obtain a list of all active thread ids from the target (OS). Since there
25064 may be too many active threads to fit into one reply packet, this query
25065 works iteratively: it may require more than one query/reply sequence to
25066 obtain the entire list of threads. The first query of the sequence will
25067 be the @samp{qfThreadInfo} query; subsequent queries in the
25068 sequence will be the @samp{qsThreadInfo} query.
25070 NOTE: This packet replaces the @samp{qL} query (see below).
25076 @item m @var{id},@var{id}@dots{}
25077 a comma-separated list of thread ids
25079 (lower case letter @samp{L}) denotes end of list.
25082 In response to each query, the target will reply with a list of one or
25083 more thread ids, in big-endian unsigned hex, separated by commas.
25084 @value{GDBN} will respond to each reply with a request for more thread
25085 ids (using the @samp{qs} form of the query), until the target responds
25086 with @samp{l} (lower-case el, for @dfn{last}).
25088 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
25089 @cindex get thread-local storage address, remote request
25090 @cindex @samp{qGetTLSAddr} packet
25091 Fetch the address associated with thread local storage specified
25092 by @var{thread-id}, @var{offset}, and @var{lm}.
25094 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
25095 thread for which to fetch the TLS address.
25097 @var{offset} is the (big endian, hex encoded) offset associated with the
25098 thread local variable. (This offset is obtained from the debug
25099 information associated with the variable.)
25101 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
25102 the load module associated with the thread local storage. For example,
25103 a @sc{gnu}/Linux system will pass the link map address of the shared
25104 object associated with the thread local storage under consideration.
25105 Other operating environments may choose to represent the load module
25106 differently, so the precise meaning of this parameter will vary.
25110 @item @var{XX}@dots{}
25111 Hex encoded (big endian) bytes representing the address of the thread
25112 local storage requested.
25115 An error occurred. @var{nn} are hex digits.
25118 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
25121 @item qL @var{startflag} @var{threadcount} @var{nextthread}
25122 Obtain thread information from RTOS. Where: @var{startflag} (one hex
25123 digit) is one to indicate the first query and zero to indicate a
25124 subsequent query; @var{threadcount} (two hex digits) is the maximum
25125 number of threads the response packet can contain; and @var{nextthread}
25126 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
25127 returned in the response as @var{argthread}.
25129 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
25133 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
25134 Where: @var{count} (two hex digits) is the number of threads being
25135 returned; @var{done} (one hex digit) is zero to indicate more threads
25136 and one indicates no further threads; @var{argthreadid} (eight hex
25137 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
25138 is a sequence of thread IDs from the target. @var{threadid} (eight hex
25139 digits). See @code{remote.c:parse_threadlist_response()}.
25143 @cindex section offsets, remote request
25144 @cindex @samp{qOffsets} packet
25145 Get section offsets that the target used when relocating the downloaded
25150 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
25151 Relocate the @code{Text} section by @var{xxx} from its original address.
25152 Relocate the @code{Data} section by @var{yyy} from its original address.
25153 If the object file format provides segment information (e.g.@: @sc{elf}
25154 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
25155 segments by the supplied offsets.
25157 @emph{Note: while a @code{Bss} offset may be included in the response,
25158 @value{GDBN} ignores this and instead applies the @code{Data} offset
25159 to the @code{Bss} section.}
25161 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
25162 Relocate the first segment of the object file, which conventionally
25163 contains program code, to a starting address of @var{xxx}. If
25164 @samp{DataSeg} is specified, relocate the second segment, which
25165 conventionally contains modifiable data, to a starting address of
25166 @var{yyy}. @value{GDBN} will report an error if the object file
25167 does not contain segment information, or does not contain at least
25168 as many segments as mentioned in the reply. Extra segments are
25169 kept at fixed offsets relative to the last relocated segment.
25172 @item qP @var{mode} @var{threadid}
25173 @cindex thread information, remote request
25174 @cindex @samp{qP} packet
25175 Returns information on @var{threadid}. Where: @var{mode} is a hex
25176 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
25178 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
25181 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
25183 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
25184 @cindex pass signals to inferior, remote request
25185 @cindex @samp{QPassSignals} packet
25186 @anchor{QPassSignals}
25187 Each listed @var{signal} should be passed directly to the inferior process.
25188 Signals are numbered identically to continue packets and stop replies
25189 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
25190 strictly greater than the previous item. These signals do not need to stop
25191 the inferior, or be reported to @value{GDBN}. All other signals should be
25192 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
25193 combine; any earlier @samp{QPassSignals} list is completely replaced by the
25194 new list. This packet improves performance when using @samp{handle
25195 @var{signal} nostop noprint pass}.
25200 The request succeeded.
25203 An error occurred. @var{nn} are hex digits.
25206 An empty reply indicates that @samp{QPassSignals} is not supported by
25210 Use of this packet is controlled by the @code{set remote pass-signals}
25211 command (@pxref{Remote Configuration, set remote pass-signals}).
25212 This packet is not probed by default; the remote stub must request it,
25213 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25215 @item qRcmd,@var{command}
25216 @cindex execute remote command, remote request
25217 @cindex @samp{qRcmd} packet
25218 @var{command} (hex encoded) is passed to the local interpreter for
25219 execution. Invalid commands should be reported using the output
25220 string. Before the final result packet, the target may also respond
25221 with a number of intermediate @samp{O@var{output}} console output
25222 packets. @emph{Implementors should note that providing access to a
25223 stubs's interpreter may have security implications}.
25228 A command response with no output.
25230 A command response with the hex encoded output string @var{OUTPUT}.
25232 Indicate a badly formed request.
25234 An empty reply indicates that @samp{qRcmd} is not recognized.
25237 (Note that the @code{qRcmd} packet's name is separated from the
25238 command by a @samp{,}, not a @samp{:}, contrary to the naming
25239 conventions above. Please don't use this packet as a model for new
25242 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
25243 @cindex searching memory, in remote debugging
25244 @cindex @samp{qSearch:memory} packet
25245 @anchor{qSearch memory}
25246 Search @var{length} bytes at @var{address} for @var{search-pattern}.
25247 @var{address} and @var{length} are encoded in hex.
25248 @var{search-pattern} is a sequence of bytes, hex encoded.
25253 The pattern was not found.
25255 The pattern was found at @var{address}.
25257 A badly formed request or an error was encountered while searching memory.
25259 An empty reply indicates that @samp{qSearch:memory} is not recognized.
25262 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
25263 @cindex supported packets, remote query
25264 @cindex features of the remote protocol
25265 @cindex @samp{qSupported} packet
25266 @anchor{qSupported}
25267 Tell the remote stub about features supported by @value{GDBN}, and
25268 query the stub for features it supports. This packet allows
25269 @value{GDBN} and the remote stub to take advantage of each others'
25270 features. @samp{qSupported} also consolidates multiple feature probes
25271 at startup, to improve @value{GDBN} performance---a single larger
25272 packet performs better than multiple smaller probe packets on
25273 high-latency links. Some features may enable behavior which must not
25274 be on by default, e.g.@: because it would confuse older clients or
25275 stubs. Other features may describe packets which could be
25276 automatically probed for, but are not. These features must be
25277 reported before @value{GDBN} will use them. This ``default
25278 unsupported'' behavior is not appropriate for all packets, but it
25279 helps to keep the initial connection time under control with new
25280 versions of @value{GDBN} which support increasing numbers of packets.
25284 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
25285 The stub supports or does not support each returned @var{stubfeature},
25286 depending on the form of each @var{stubfeature} (see below for the
25289 An empty reply indicates that @samp{qSupported} is not recognized,
25290 or that no features needed to be reported to @value{GDBN}.
25293 The allowed forms for each feature (either a @var{gdbfeature} in the
25294 @samp{qSupported} packet, or a @var{stubfeature} in the response)
25298 @item @var{name}=@var{value}
25299 The remote protocol feature @var{name} is supported, and associated
25300 with the specified @var{value}. The format of @var{value} depends
25301 on the feature, but it must not include a semicolon.
25303 The remote protocol feature @var{name} is supported, and does not
25304 need an associated value.
25306 The remote protocol feature @var{name} is not supported.
25308 The remote protocol feature @var{name} may be supported, and
25309 @value{GDBN} should auto-detect support in some other way when it is
25310 needed. This form will not be used for @var{gdbfeature} notifications,
25311 but may be used for @var{stubfeature} responses.
25314 Whenever the stub receives a @samp{qSupported} request, the
25315 supplied set of @value{GDBN} features should override any previous
25316 request. This allows @value{GDBN} to put the stub in a known
25317 state, even if the stub had previously been communicating with
25318 a different version of @value{GDBN}.
25320 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
25321 are defined yet. Stubs should ignore any unknown values for
25322 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
25323 packet supports receiving packets of unlimited length (earlier
25324 versions of @value{GDBN} may reject overly long responses). Values
25325 for @var{gdbfeature} may be defined in the future to let the stub take
25326 advantage of new features in @value{GDBN}, e.g.@: incompatible
25327 improvements in the remote protocol---support for unlimited length
25328 responses would be a @var{gdbfeature} example, if it were not implied by
25329 the @samp{qSupported} query. The stub's reply should be independent
25330 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
25331 describes all the features it supports, and then the stub replies with
25332 all the features it supports.
25334 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
25335 responses, as long as each response uses one of the standard forms.
25337 Some features are flags. A stub which supports a flag feature
25338 should respond with a @samp{+} form response. Other features
25339 require values, and the stub should respond with an @samp{=}
25342 Each feature has a default value, which @value{GDBN} will use if
25343 @samp{qSupported} is not available or if the feature is not mentioned
25344 in the @samp{qSupported} response. The default values are fixed; a
25345 stub is free to omit any feature responses that match the defaults.
25347 Not all features can be probed, but for those which can, the probing
25348 mechanism is useful: in some cases, a stub's internal
25349 architecture may not allow the protocol layer to know some information
25350 about the underlying target in advance. This is especially common in
25351 stubs which may be configured for multiple targets.
25353 These are the currently defined stub features and their properties:
25355 @multitable @columnfractions 0.35 0.2 0.12 0.2
25356 @c NOTE: The first row should be @headitem, but we do not yet require
25357 @c a new enough version of Texinfo (4.7) to use @headitem.
25359 @tab Value Required
25363 @item @samp{PacketSize}
25368 @item @samp{qXfer:auxv:read}
25373 @item @samp{qXfer:features:read}
25378 @item @samp{qXfer:libraries:read}
25383 @item @samp{qXfer:memory-map:read}
25388 @item @samp{qXfer:spu:read}
25393 @item @samp{qXfer:spu:write}
25398 @item @samp{QPassSignals}
25405 These are the currently defined stub features, in more detail:
25408 @cindex packet size, remote protocol
25409 @item PacketSize=@var{bytes}
25410 The remote stub can accept packets up to at least @var{bytes} in
25411 length. @value{GDBN} will send packets up to this size for bulk
25412 transfers, and will never send larger packets. This is a limit on the
25413 data characters in the packet, including the frame and checksum.
25414 There is no trailing NUL byte in a remote protocol packet; if the stub
25415 stores packets in a NUL-terminated format, it should allow an extra
25416 byte in its buffer for the NUL. If this stub feature is not supported,
25417 @value{GDBN} guesses based on the size of the @samp{g} packet response.
25419 @item qXfer:auxv:read
25420 The remote stub understands the @samp{qXfer:auxv:read} packet
25421 (@pxref{qXfer auxiliary vector read}).
25423 @item qXfer:features:read
25424 The remote stub understands the @samp{qXfer:features:read} packet
25425 (@pxref{qXfer target description read}).
25427 @item qXfer:libraries:read
25428 The remote stub understands the @samp{qXfer:libraries:read} packet
25429 (@pxref{qXfer library list read}).
25431 @item qXfer:memory-map:read
25432 The remote stub understands the @samp{qXfer:memory-map:read} packet
25433 (@pxref{qXfer memory map read}).
25435 @item qXfer:spu:read
25436 The remote stub understands the @samp{qXfer:spu:read} packet
25437 (@pxref{qXfer spu read}).
25439 @item qXfer:spu:write
25440 The remote stub understands the @samp{qXfer:spu:write} packet
25441 (@pxref{qXfer spu write}).
25444 The remote stub understands the @samp{QPassSignals} packet
25445 (@pxref{QPassSignals}).
25450 @cindex symbol lookup, remote request
25451 @cindex @samp{qSymbol} packet
25452 Notify the target that @value{GDBN} is prepared to serve symbol lookup
25453 requests. Accept requests from the target for the values of symbols.
25458 The target does not need to look up any (more) symbols.
25459 @item qSymbol:@var{sym_name}
25460 The target requests the value of symbol @var{sym_name} (hex encoded).
25461 @value{GDBN} may provide the value by using the
25462 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
25466 @item qSymbol:@var{sym_value}:@var{sym_name}
25467 Set the value of @var{sym_name} to @var{sym_value}.
25469 @var{sym_name} (hex encoded) is the name of a symbol whose value the
25470 target has previously requested.
25472 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
25473 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
25479 The target does not need to look up any (more) symbols.
25480 @item qSymbol:@var{sym_name}
25481 The target requests the value of a new symbol @var{sym_name} (hex
25482 encoded). @value{GDBN} will continue to supply the values of symbols
25483 (if available), until the target ceases to request them.
25488 @xref{Tracepoint Packets}.
25490 @item qThreadExtraInfo,@var{id}
25491 @cindex thread attributes info, remote request
25492 @cindex @samp{qThreadExtraInfo} packet
25493 Obtain a printable string description of a thread's attributes from
25494 the target OS. @var{id} is a thread-id in big-endian hex. This
25495 string may contain anything that the target OS thinks is interesting
25496 for @value{GDBN} to tell the user about the thread. The string is
25497 displayed in @value{GDBN}'s @code{info threads} display. Some
25498 examples of possible thread extra info strings are @samp{Runnable}, or
25499 @samp{Blocked on Mutex}.
25503 @item @var{XX}@dots{}
25504 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
25505 comprising the printable string containing the extra information about
25506 the thread's attributes.
25509 (Note that the @code{qThreadExtraInfo} packet's name is separated from
25510 the command by a @samp{,}, not a @samp{:}, contrary to the naming
25511 conventions above. Please don't use this packet as a model for new
25519 @xref{Tracepoint Packets}.
25521 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
25522 @cindex read special object, remote request
25523 @cindex @samp{qXfer} packet
25524 @anchor{qXfer read}
25525 Read uninterpreted bytes from the target's special data area
25526 identified by the keyword @var{object}. Request @var{length} bytes
25527 starting at @var{offset} bytes into the data. The content and
25528 encoding of @var{annex} is specific to @var{object}; it can supply
25529 additional details about what data to access.
25531 Here are the specific requests of this form defined so far. All
25532 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
25533 formats, listed below.
25536 @item qXfer:auxv:read::@var{offset},@var{length}
25537 @anchor{qXfer auxiliary vector read}
25538 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
25539 auxiliary vector}. Note @var{annex} must be empty.
25541 This packet is not probed by default; the remote stub must request it,
25542 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25544 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
25545 @anchor{qXfer target description read}
25546 Access the @dfn{target description}. @xref{Target Descriptions}. The
25547 annex specifies which XML document to access. The main description is
25548 always loaded from the @samp{target.xml} annex.
25550 This packet is not probed by default; the remote stub must request it,
25551 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25553 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
25554 @anchor{qXfer library list read}
25555 Access the target's list of loaded libraries. @xref{Library List Format}.
25556 The annex part of the generic @samp{qXfer} packet must be empty
25557 (@pxref{qXfer read}).
25559 Targets which maintain a list of libraries in the program's memory do
25560 not need to implement this packet; it is designed for platforms where
25561 the operating system manages the list of loaded libraries.
25563 This packet is not probed by default; the remote stub must request it,
25564 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25566 @item qXfer:memory-map:read::@var{offset},@var{length}
25567 @anchor{qXfer memory map read}
25568 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
25569 annex part of the generic @samp{qXfer} packet must be empty
25570 (@pxref{qXfer read}).
25572 This packet is not probed by default; the remote stub must request it,
25573 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25575 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
25576 @anchor{qXfer spu read}
25577 Read contents of an @code{spufs} file on the target system. The
25578 annex specifies which file to read; it must be of the form
25579 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25580 in the target process, and @var{name} identifes the @code{spufs} file
25581 in that context to be accessed.
25583 This packet is not probed by default; the remote stub must request it,
25584 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25590 Data @var{data} (@pxref{Binary Data}) has been read from the
25591 target. There may be more data at a higher address (although
25592 it is permitted to return @samp{m} even for the last valid
25593 block of data, as long as at least one byte of data was read).
25594 @var{data} may have fewer bytes than the @var{length} in the
25598 Data @var{data} (@pxref{Binary Data}) has been read from the target.
25599 There is no more data to be read. @var{data} may have fewer bytes
25600 than the @var{length} in the request.
25603 The @var{offset} in the request is at the end of the data.
25604 There is no more data to be read.
25607 The request was malformed, or @var{annex} was invalid.
25610 The offset was invalid, or there was an error encountered reading the data.
25611 @var{nn} is a hex-encoded @code{errno} value.
25614 An empty reply indicates the @var{object} string was not recognized by
25615 the stub, or that the object does not support reading.
25618 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25619 @cindex write data into object, remote request
25620 Write uninterpreted bytes into the target's special data area
25621 identified by the keyword @var{object}, starting at @var{offset} bytes
25622 into the data. @var{data}@dots{} is the binary-encoded data
25623 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
25624 is specific to @var{object}; it can supply additional details about what data
25627 Here are the specific requests of this form defined so far. All
25628 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
25629 formats, listed below.
25632 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25633 @anchor{qXfer spu write}
25634 Write @var{data} to an @code{spufs} file on the target system. The
25635 annex specifies which file to write; it must be of the form
25636 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25637 in the target process, and @var{name} identifes the @code{spufs} file
25638 in that context to be accessed.
25640 This packet is not probed by default; the remote stub must request it,
25641 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25647 @var{nn} (hex encoded) is the number of bytes written.
25648 This may be fewer bytes than supplied in the request.
25651 The request was malformed, or @var{annex} was invalid.
25654 The offset was invalid, or there was an error encountered writing the data.
25655 @var{nn} is a hex-encoded @code{errno} value.
25658 An empty reply indicates the @var{object} string was not
25659 recognized by the stub, or that the object does not support writing.
25662 @item qXfer:@var{object}:@var{operation}:@dots{}
25663 Requests of this form may be added in the future. When a stub does
25664 not recognize the @var{object} keyword, or its support for
25665 @var{object} does not recognize the @var{operation} keyword, the stub
25666 must respond with an empty packet.
25670 @node Register Packet Format
25671 @section Register Packet Format
25673 The following @code{g}/@code{G} packets have previously been defined.
25674 In the below, some thirty-two bit registers are transferred as
25675 sixty-four bits. Those registers should be zero/sign extended (which?)
25676 to fill the space allocated. Register bytes are transferred in target
25677 byte order. The two nibbles within a register byte are transferred
25678 most-significant - least-significant.
25684 All registers are transferred as thirty-two bit quantities in the order:
25685 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
25686 registers; fsr; fir; fp.
25690 All registers are transferred as sixty-four bit quantities (including
25691 thirty-two bit registers such as @code{sr}). The ordering is the same
25696 @node Tracepoint Packets
25697 @section Tracepoint Packets
25698 @cindex tracepoint packets
25699 @cindex packets, tracepoint
25701 Here we describe the packets @value{GDBN} uses to implement
25702 tracepoints (@pxref{Tracepoints}).
25706 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
25707 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
25708 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
25709 the tracepoint is disabled. @var{step} is the tracepoint's step
25710 count, and @var{pass} is its pass count. If the trailing @samp{-} is
25711 present, further @samp{QTDP} packets will follow to specify this
25712 tracepoint's actions.
25717 The packet was understood and carried out.
25719 The packet was not recognized.
25722 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
25723 Define actions to be taken when a tracepoint is hit. @var{n} and
25724 @var{addr} must be the same as in the initial @samp{QTDP} packet for
25725 this tracepoint. This packet may only be sent immediately after
25726 another @samp{QTDP} packet that ended with a @samp{-}. If the
25727 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
25728 specifying more actions for this tracepoint.
25730 In the series of action packets for a given tracepoint, at most one
25731 can have an @samp{S} before its first @var{action}. If such a packet
25732 is sent, it and the following packets define ``while-stepping''
25733 actions. Any prior packets define ordinary actions --- that is, those
25734 taken when the tracepoint is first hit. If no action packet has an
25735 @samp{S}, then all the packets in the series specify ordinary
25736 tracepoint actions.
25738 The @samp{@var{action}@dots{}} portion of the packet is a series of
25739 actions, concatenated without separators. Each action has one of the
25745 Collect the registers whose bits are set in @var{mask}. @var{mask} is
25746 a hexadecimal number whose @var{i}'th bit is set if register number
25747 @var{i} should be collected. (The least significant bit is numbered
25748 zero.) Note that @var{mask} may be any number of digits long; it may
25749 not fit in a 32-bit word.
25751 @item M @var{basereg},@var{offset},@var{len}
25752 Collect @var{len} bytes of memory starting at the address in register
25753 number @var{basereg}, plus @var{offset}. If @var{basereg} is
25754 @samp{-1}, then the range has a fixed address: @var{offset} is the
25755 address of the lowest byte to collect. The @var{basereg},
25756 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
25757 values (the @samp{-1} value for @var{basereg} is a special case).
25759 @item X @var{len},@var{expr}
25760 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
25761 it directs. @var{expr} is an agent expression, as described in
25762 @ref{Agent Expressions}. Each byte of the expression is encoded as a
25763 two-digit hex number in the packet; @var{len} is the number of bytes
25764 in the expression (and thus one-half the number of hex digits in the
25769 Any number of actions may be packed together in a single @samp{QTDP}
25770 packet, as long as the packet does not exceed the maximum packet
25771 length (400 bytes, for many stubs). There may be only one @samp{R}
25772 action per tracepoint, and it must precede any @samp{M} or @samp{X}
25773 actions. Any registers referred to by @samp{M} and @samp{X} actions
25774 must be collected by a preceding @samp{R} action. (The
25775 ``while-stepping'' actions are treated as if they were attached to a
25776 separate tracepoint, as far as these restrictions are concerned.)
25781 The packet was understood and carried out.
25783 The packet was not recognized.
25786 @item QTFrame:@var{n}
25787 Select the @var{n}'th tracepoint frame from the buffer, and use the
25788 register and memory contents recorded there to answer subsequent
25789 request packets from @value{GDBN}.
25791 A successful reply from the stub indicates that the stub has found the
25792 requested frame. The response is a series of parts, concatenated
25793 without separators, describing the frame we selected. Each part has
25794 one of the following forms:
25798 The selected frame is number @var{n} in the trace frame buffer;
25799 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
25800 was no frame matching the criteria in the request packet.
25803 The selected trace frame records a hit of tracepoint number @var{t};
25804 @var{t} is a hexadecimal number.
25808 @item QTFrame:pc:@var{addr}
25809 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25810 currently selected frame whose PC is @var{addr};
25811 @var{addr} is a hexadecimal number.
25813 @item QTFrame:tdp:@var{t}
25814 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25815 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
25816 is a hexadecimal number.
25818 @item QTFrame:range:@var{start}:@var{end}
25819 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25820 currently selected frame whose PC is between @var{start} (inclusive)
25821 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
25824 @item QTFrame:outside:@var{start}:@var{end}
25825 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
25826 frame @emph{outside} the given range of addresses.
25829 Begin the tracepoint experiment. Begin collecting data from tracepoint
25830 hits in the trace frame buffer.
25833 End the tracepoint experiment. Stop collecting trace frames.
25836 Clear the table of tracepoints, and empty the trace frame buffer.
25838 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
25839 Establish the given ranges of memory as ``transparent''. The stub
25840 will answer requests for these ranges from memory's current contents,
25841 if they were not collected as part of the tracepoint hit.
25843 @value{GDBN} uses this to mark read-only regions of memory, like those
25844 containing program code. Since these areas never change, they should
25845 still have the same contents they did when the tracepoint was hit, so
25846 there's no reason for the stub to refuse to provide their contents.
25849 Ask the stub if there is a trace experiment running right now.
25854 There is no trace experiment running.
25856 There is a trace experiment running.
25862 @node Host I/O Packets
25863 @section Host I/O Packets
25864 @cindex Host I/O, remote protocol
25865 @cindex file transfer, remote protocol
25867 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
25868 operations on the far side of a remote link. For example, Host I/O is
25869 used to upload and download files to a remote target with its own
25870 filesystem. Host I/O uses the same constant values and data structure
25871 layout as the target-initiated File-I/O protocol. However, the
25872 Host I/O packets are structured differently. The target-initiated
25873 protocol relies on target memory to store parameters and buffers.
25874 Host I/O requests are initiated by @value{GDBN}, and the
25875 target's memory is not involved. @xref{File-I/O Remote Protocol
25876 Extension}, for more details on the target-initiated protocol.
25878 The Host I/O request packets all encode a single operation along with
25879 its arguments. They have this format:
25883 @item vFile:@var{operation}: @var{parameter}@dots{}
25884 @var{operation} is the name of the particular request; the target
25885 should compare the entire packet name up to the second colon when checking
25886 for a supported operation. The format of @var{parameter} depends on
25887 the operation. Numbers are always passed in hexadecimal. Negative
25888 numbers have an explicit minus sign (i.e.@: two's complement is not
25889 used). Strings (e.g.@: filenames) are encoded as a series of
25890 hexadecimal bytes. The last argument to a system call may be a
25891 buffer of escaped binary data (@pxref{Binary Data}).
25895 The valid responses to Host I/O packets are:
25899 @item F @var{result} [, @var{errno}] [; @var{attachment}]
25900 @var{result} is the integer value returned by this operation, usually
25901 non-negative for success and -1 for errors. If an error has occured,
25902 @var{errno} will be included in the result. @var{errno} will have a
25903 value defined by the File-I/O protocol (@pxref{Errno Values}). For
25904 operations which return data, @var{attachment} supplies the data as a
25905 binary buffer. Binary buffers in response packets are escaped in the
25906 normal way (@pxref{Binary Data}). See the individual packet
25907 documentation for the interpretation of @var{result} and
25911 An empty response indicates that this operation is not recognized.
25915 These are the supported Host I/O operations:
25918 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
25919 Open a file at @var{pathname} and return a file descriptor for it, or
25920 return -1 if an error occurs. @var{pathname} is a string,
25921 @var{flags} is an integer indicating a mask of open flags
25922 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
25923 of mode bits to use if the file is created (@pxref{mode_t Values}).
25924 @xref{open}, for details of the open flags and mode values.
25926 @item vFile:close: @var{fd}
25927 Close the open file corresponding to @var{fd} and return 0, or
25928 -1 if an error occurs.
25930 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
25931 Read data from the open file corresponding to @var{fd}. Up to
25932 @var{count} bytes will be read from the file, starting at @var{offset}
25933 relative to the start of the file. The target may read fewer bytes;
25934 common reasons include packet size limits and an end-of-file
25935 condition. The number of bytes read is returned. Zero should only be
25936 returned for a successful read at the end of the file, or if
25937 @var{count} was zero.
25939 The data read should be returned as a binary attachment on success.
25940 If zero bytes were read, the response should include an empty binary
25941 attachment (i.e.@: a trailing semicolon). The return value is the
25942 number of target bytes read; the binary attachment may be longer if
25943 some characters were escaped.
25945 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
25946 Write @var{data} (a binary buffer) to the open file corresponding
25947 to @var{fd}. Start the write at @var{offset} from the start of the
25948 file. Unlike many @code{write} system calls, there is no
25949 separate @var{count} argument; the length of @var{data} in the
25950 packet is used. @samp{vFile:write} returns the number of bytes written,
25951 which may be shorter than the length of @var{data}, or -1 if an
25954 @item vFile:unlink: @var{pathname}
25955 Delete the file at @var{pathname} on the target. Return 0,
25956 or -1 if an error occurs. @var{pathname} is a string.
25961 @section Interrupts
25962 @cindex interrupts (remote protocol)
25964 When a program on the remote target is running, @value{GDBN} may
25965 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
25966 control of which is specified via @value{GDBN}'s @samp{remotebreak}
25967 setting (@pxref{set remotebreak}).
25969 The precise meaning of @code{BREAK} is defined by the transport
25970 mechanism and may, in fact, be undefined. @value{GDBN} does
25971 not currently define a @code{BREAK} mechanism for any of the network
25974 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
25975 transport mechanisms. It is represented by sending the single byte
25976 @code{0x03} without any of the usual packet overhead described in
25977 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
25978 transmitted as part of a packet, it is considered to be packet data
25979 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
25980 (@pxref{X packet}), used for binary downloads, may include an unescaped
25981 @code{0x03} as part of its packet.
25983 Stubs are not required to recognize these interrupt mechanisms and the
25984 precise meaning associated with receipt of the interrupt is
25985 implementation defined. If the stub is successful at interrupting the
25986 running program, it is expected that it will send one of the Stop
25987 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
25988 of successfully stopping the program. Interrupts received while the
25989 program is stopped will be discarded.
25994 Example sequence of a target being re-started. Notice how the restart
25995 does not get any direct output:
26000 @emph{target restarts}
26003 <- @code{T001:1234123412341234}
26007 Example sequence of a target being stepped by a single instruction:
26010 -> @code{G1445@dots{}}
26015 <- @code{T001:1234123412341234}
26019 <- @code{1455@dots{}}
26023 @node File-I/O Remote Protocol Extension
26024 @section File-I/O Remote Protocol Extension
26025 @cindex File-I/O remote protocol extension
26028 * File-I/O Overview::
26029 * Protocol Basics::
26030 * The F Request Packet::
26031 * The F Reply Packet::
26032 * The Ctrl-C Message::
26034 * List of Supported Calls::
26035 * Protocol-specific Representation of Datatypes::
26037 * File-I/O Examples::
26040 @node File-I/O Overview
26041 @subsection File-I/O Overview
26042 @cindex file-i/o overview
26044 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
26045 target to use the host's file system and console I/O to perform various
26046 system calls. System calls on the target system are translated into a
26047 remote protocol packet to the host system, which then performs the needed
26048 actions and returns a response packet to the target system.
26049 This simulates file system operations even on targets that lack file systems.
26051 The protocol is defined to be independent of both the host and target systems.
26052 It uses its own internal representation of datatypes and values. Both
26053 @value{GDBN} and the target's @value{GDBN} stub are responsible for
26054 translating the system-dependent value representations into the internal
26055 protocol representations when data is transmitted.
26057 The communication is synchronous. A system call is possible only when
26058 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
26059 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
26060 the target is stopped to allow deterministic access to the target's
26061 memory. Therefore File-I/O is not interruptible by target signals. On
26062 the other hand, it is possible to interrupt File-I/O by a user interrupt
26063 (@samp{Ctrl-C}) within @value{GDBN}.
26065 The target's request to perform a host system call does not finish
26066 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
26067 after finishing the system call, the target returns to continuing the
26068 previous activity (continue, step). No additional continue or step
26069 request from @value{GDBN} is required.
26072 (@value{GDBP}) continue
26073 <- target requests 'system call X'
26074 target is stopped, @value{GDBN} executes system call
26075 -> @value{GDBN} returns result
26076 ... target continues, @value{GDBN} returns to wait for the target
26077 <- target hits breakpoint and sends a Txx packet
26080 The protocol only supports I/O on the console and to regular files on
26081 the host file system. Character or block special devices, pipes,
26082 named pipes, sockets or any other communication method on the host
26083 system are not supported by this protocol.
26085 @node Protocol Basics
26086 @subsection Protocol Basics
26087 @cindex protocol basics, file-i/o
26089 The File-I/O protocol uses the @code{F} packet as the request as well
26090 as reply packet. Since a File-I/O system call can only occur when
26091 @value{GDBN} is waiting for a response from the continuing or stepping target,
26092 the File-I/O request is a reply that @value{GDBN} has to expect as a result
26093 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
26094 This @code{F} packet contains all information needed to allow @value{GDBN}
26095 to call the appropriate host system call:
26099 A unique identifier for the requested system call.
26102 All parameters to the system call. Pointers are given as addresses
26103 in the target memory address space. Pointers to strings are given as
26104 pointer/length pair. Numerical values are given as they are.
26105 Numerical control flags are given in a protocol-specific representation.
26109 At this point, @value{GDBN} has to perform the following actions.
26113 If the parameters include pointer values to data needed as input to a
26114 system call, @value{GDBN} requests this data from the target with a
26115 standard @code{m} packet request. This additional communication has to be
26116 expected by the target implementation and is handled as any other @code{m}
26120 @value{GDBN} translates all value from protocol representation to host
26121 representation as needed. Datatypes are coerced into the host types.
26124 @value{GDBN} calls the system call.
26127 It then coerces datatypes back to protocol representation.
26130 If the system call is expected to return data in buffer space specified
26131 by pointer parameters to the call, the data is transmitted to the
26132 target using a @code{M} or @code{X} packet. This packet has to be expected
26133 by the target implementation and is handled as any other @code{M} or @code{X}
26138 Eventually @value{GDBN} replies with another @code{F} packet which contains all
26139 necessary information for the target to continue. This at least contains
26146 @code{errno}, if has been changed by the system call.
26153 After having done the needed type and value coercion, the target continues
26154 the latest continue or step action.
26156 @node The F Request Packet
26157 @subsection The @code{F} Request Packet
26158 @cindex file-i/o request packet
26159 @cindex @code{F} request packet
26161 The @code{F} request packet has the following format:
26164 @item F@var{call-id},@var{parameter@dots{}}
26166 @var{call-id} is the identifier to indicate the host system call to be called.
26167 This is just the name of the function.
26169 @var{parameter@dots{}} are the parameters to the system call.
26170 Parameters are hexadecimal integer values, either the actual values in case
26171 of scalar datatypes, pointers to target buffer space in case of compound
26172 datatypes and unspecified memory areas, or pointer/length pairs in case
26173 of string parameters. These are appended to the @var{call-id} as a
26174 comma-delimited list. All values are transmitted in ASCII
26175 string representation, pointer/length pairs separated by a slash.
26181 @node The F Reply Packet
26182 @subsection The @code{F} Reply Packet
26183 @cindex file-i/o reply packet
26184 @cindex @code{F} reply packet
26186 The @code{F} reply packet has the following format:
26190 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
26192 @var{retcode} is the return code of the system call as hexadecimal value.
26194 @var{errno} is the @code{errno} set by the call, in protocol-specific
26196 This parameter can be omitted if the call was successful.
26198 @var{Ctrl-C flag} is only sent if the user requested a break. In this
26199 case, @var{errno} must be sent as well, even if the call was successful.
26200 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
26207 or, if the call was interrupted before the host call has been performed:
26214 assuming 4 is the protocol-specific representation of @code{EINTR}.
26219 @node The Ctrl-C Message
26220 @subsection The @samp{Ctrl-C} Message
26221 @cindex ctrl-c message, in file-i/o protocol
26223 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
26224 reply packet (@pxref{The F Reply Packet}),
26225 the target should behave as if it had
26226 gotten a break message. The meaning for the target is ``system call
26227 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
26228 (as with a break message) and return to @value{GDBN} with a @code{T02}
26231 It's important for the target to know in which
26232 state the system call was interrupted. There are two possible cases:
26236 The system call hasn't been performed on the host yet.
26239 The system call on the host has been finished.
26243 These two states can be distinguished by the target by the value of the
26244 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
26245 call hasn't been performed. This is equivalent to the @code{EINTR} handling
26246 on POSIX systems. In any other case, the target may presume that the
26247 system call has been finished --- successfully or not --- and should behave
26248 as if the break message arrived right after the system call.
26250 @value{GDBN} must behave reliably. If the system call has not been called
26251 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
26252 @code{errno} in the packet. If the system call on the host has been finished
26253 before the user requests a break, the full action must be finished by
26254 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
26255 The @code{F} packet may only be sent when either nothing has happened
26256 or the full action has been completed.
26259 @subsection Console I/O
26260 @cindex console i/o as part of file-i/o
26262 By default and if not explicitly closed by the target system, the file
26263 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
26264 on the @value{GDBN} console is handled as any other file output operation
26265 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
26266 by @value{GDBN} so that after the target read request from file descriptor
26267 0 all following typing is buffered until either one of the following
26272 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
26274 system call is treated as finished.
26277 The user presses @key{RET}. This is treated as end of input with a trailing
26281 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
26282 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
26286 If the user has typed more characters than fit in the buffer given to
26287 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
26288 either another @code{read(0, @dots{})} is requested by the target, or debugging
26289 is stopped at the user's request.
26292 @node List of Supported Calls
26293 @subsection List of Supported Calls
26294 @cindex list of supported file-i/o calls
26311 @unnumberedsubsubsec open
26312 @cindex open, file-i/o system call
26317 int open(const char *pathname, int flags);
26318 int open(const char *pathname, int flags, mode_t mode);
26322 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
26325 @var{flags} is the bitwise @code{OR} of the following values:
26329 If the file does not exist it will be created. The host
26330 rules apply as far as file ownership and time stamps
26334 When used with @code{O_CREAT}, if the file already exists it is
26335 an error and open() fails.
26338 If the file already exists and the open mode allows
26339 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
26340 truncated to zero length.
26343 The file is opened in append mode.
26346 The file is opened for reading only.
26349 The file is opened for writing only.
26352 The file is opened for reading and writing.
26356 Other bits are silently ignored.
26360 @var{mode} is the bitwise @code{OR} of the following values:
26364 User has read permission.
26367 User has write permission.
26370 Group has read permission.
26373 Group has write permission.
26376 Others have read permission.
26379 Others have write permission.
26383 Other bits are silently ignored.
26386 @item Return value:
26387 @code{open} returns the new file descriptor or -1 if an error
26394 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
26397 @var{pathname} refers to a directory.
26400 The requested access is not allowed.
26403 @var{pathname} was too long.
26406 A directory component in @var{pathname} does not exist.
26409 @var{pathname} refers to a device, pipe, named pipe or socket.
26412 @var{pathname} refers to a file on a read-only filesystem and
26413 write access was requested.
26416 @var{pathname} is an invalid pointer value.
26419 No space on device to create the file.
26422 The process already has the maximum number of files open.
26425 The limit on the total number of files open on the system
26429 The call was interrupted by the user.
26435 @unnumberedsubsubsec close
26436 @cindex close, file-i/o system call
26445 @samp{Fclose,@var{fd}}
26447 @item Return value:
26448 @code{close} returns zero on success, or -1 if an error occurred.
26454 @var{fd} isn't a valid open file descriptor.
26457 The call was interrupted by the user.
26463 @unnumberedsubsubsec read
26464 @cindex read, file-i/o system call
26469 int read(int fd, void *buf, unsigned int count);
26473 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
26475 @item Return value:
26476 On success, the number of bytes read is returned.
26477 Zero indicates end of file. If count is zero, read
26478 returns zero as well. On error, -1 is returned.
26484 @var{fd} is not a valid file descriptor or is not open for
26488 @var{bufptr} is an invalid pointer value.
26491 The call was interrupted by the user.
26497 @unnumberedsubsubsec write
26498 @cindex write, file-i/o system call
26503 int write(int fd, const void *buf, unsigned int count);
26507 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
26509 @item Return value:
26510 On success, the number of bytes written are returned.
26511 Zero indicates nothing was written. On error, -1
26518 @var{fd} is not a valid file descriptor or is not open for
26522 @var{bufptr} is an invalid pointer value.
26525 An attempt was made to write a file that exceeds the
26526 host-specific maximum file size allowed.
26529 No space on device to write the data.
26532 The call was interrupted by the user.
26538 @unnumberedsubsubsec lseek
26539 @cindex lseek, file-i/o system call
26544 long lseek (int fd, long offset, int flag);
26548 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
26550 @var{flag} is one of:
26554 The offset is set to @var{offset} bytes.
26557 The offset is set to its current location plus @var{offset}
26561 The offset is set to the size of the file plus @var{offset}
26565 @item Return value:
26566 On success, the resulting unsigned offset in bytes from
26567 the beginning of the file is returned. Otherwise, a
26568 value of -1 is returned.
26574 @var{fd} is not a valid open file descriptor.
26577 @var{fd} is associated with the @value{GDBN} console.
26580 @var{flag} is not a proper value.
26583 The call was interrupted by the user.
26589 @unnumberedsubsubsec rename
26590 @cindex rename, file-i/o system call
26595 int rename(const char *oldpath, const char *newpath);
26599 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
26601 @item Return value:
26602 On success, zero is returned. On error, -1 is returned.
26608 @var{newpath} is an existing directory, but @var{oldpath} is not a
26612 @var{newpath} is a non-empty directory.
26615 @var{oldpath} or @var{newpath} is a directory that is in use by some
26619 An attempt was made to make a directory a subdirectory
26623 A component used as a directory in @var{oldpath} or new
26624 path is not a directory. Or @var{oldpath} is a directory
26625 and @var{newpath} exists but is not a directory.
26628 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
26631 No access to the file or the path of the file.
26635 @var{oldpath} or @var{newpath} was too long.
26638 A directory component in @var{oldpath} or @var{newpath} does not exist.
26641 The file is on a read-only filesystem.
26644 The device containing the file has no room for the new
26648 The call was interrupted by the user.
26654 @unnumberedsubsubsec unlink
26655 @cindex unlink, file-i/o system call
26660 int unlink(const char *pathname);
26664 @samp{Funlink,@var{pathnameptr}/@var{len}}
26666 @item Return value:
26667 On success, zero is returned. On error, -1 is returned.
26673 No access to the file or the path of the file.
26676 The system does not allow unlinking of directories.
26679 The file @var{pathname} cannot be unlinked because it's
26680 being used by another process.
26683 @var{pathnameptr} is an invalid pointer value.
26686 @var{pathname} was too long.
26689 A directory component in @var{pathname} does not exist.
26692 A component of the path is not a directory.
26695 The file is on a read-only filesystem.
26698 The call was interrupted by the user.
26704 @unnumberedsubsubsec stat/fstat
26705 @cindex fstat, file-i/o system call
26706 @cindex stat, file-i/o system call
26711 int stat(const char *pathname, struct stat *buf);
26712 int fstat(int fd, struct stat *buf);
26716 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
26717 @samp{Ffstat,@var{fd},@var{bufptr}}
26719 @item Return value:
26720 On success, zero is returned. On error, -1 is returned.
26726 @var{fd} is not a valid open file.
26729 A directory component in @var{pathname} does not exist or the
26730 path is an empty string.
26733 A component of the path is not a directory.
26736 @var{pathnameptr} is an invalid pointer value.
26739 No access to the file or the path of the file.
26742 @var{pathname} was too long.
26745 The call was interrupted by the user.
26751 @unnumberedsubsubsec gettimeofday
26752 @cindex gettimeofday, file-i/o system call
26757 int gettimeofday(struct timeval *tv, void *tz);
26761 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
26763 @item Return value:
26764 On success, 0 is returned, -1 otherwise.
26770 @var{tz} is a non-NULL pointer.
26773 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
26779 @unnumberedsubsubsec isatty
26780 @cindex isatty, file-i/o system call
26785 int isatty(int fd);
26789 @samp{Fisatty,@var{fd}}
26791 @item Return value:
26792 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
26798 The call was interrupted by the user.
26803 Note that the @code{isatty} call is treated as a special case: it returns
26804 1 to the target if the file descriptor is attached
26805 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
26806 would require implementing @code{ioctl} and would be more complex than
26811 @unnumberedsubsubsec system
26812 @cindex system, file-i/o system call
26817 int system(const char *command);
26821 @samp{Fsystem,@var{commandptr}/@var{len}}
26823 @item Return value:
26824 If @var{len} is zero, the return value indicates whether a shell is
26825 available. A zero return value indicates a shell is not available.
26826 For non-zero @var{len}, the value returned is -1 on error and the
26827 return status of the command otherwise. Only the exit status of the
26828 command is returned, which is extracted from the host's @code{system}
26829 return value by calling @code{WEXITSTATUS(retval)}. In case
26830 @file{/bin/sh} could not be executed, 127 is returned.
26836 The call was interrupted by the user.
26841 @value{GDBN} takes over the full task of calling the necessary host calls
26842 to perform the @code{system} call. The return value of @code{system} on
26843 the host is simplified before it's returned
26844 to the target. Any termination signal information from the child process
26845 is discarded, and the return value consists
26846 entirely of the exit status of the called command.
26848 Due to security concerns, the @code{system} call is by default refused
26849 by @value{GDBN}. The user has to allow this call explicitly with the
26850 @code{set remote system-call-allowed 1} command.
26853 @item set remote system-call-allowed
26854 @kindex set remote system-call-allowed
26855 Control whether to allow the @code{system} calls in the File I/O
26856 protocol for the remote target. The default is zero (disabled).
26858 @item show remote system-call-allowed
26859 @kindex show remote system-call-allowed
26860 Show whether the @code{system} calls are allowed in the File I/O
26864 @node Protocol-specific Representation of Datatypes
26865 @subsection Protocol-specific Representation of Datatypes
26866 @cindex protocol-specific representation of datatypes, in file-i/o protocol
26869 * Integral Datatypes::
26871 * Memory Transfer::
26876 @node Integral Datatypes
26877 @unnumberedsubsubsec Integral Datatypes
26878 @cindex integral datatypes, in file-i/o protocol
26880 The integral datatypes used in the system calls are @code{int},
26881 @code{unsigned int}, @code{long}, @code{unsigned long},
26882 @code{mode_t}, and @code{time_t}.
26884 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
26885 implemented as 32 bit values in this protocol.
26887 @code{long} and @code{unsigned long} are implemented as 64 bit types.
26889 @xref{Limits}, for corresponding MIN and MAX values (similar to those
26890 in @file{limits.h}) to allow range checking on host and target.
26892 @code{time_t} datatypes are defined as seconds since the Epoch.
26894 All integral datatypes transferred as part of a memory read or write of a
26895 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
26898 @node Pointer Values
26899 @unnumberedsubsubsec Pointer Values
26900 @cindex pointer values, in file-i/o protocol
26902 Pointers to target data are transmitted as they are. An exception
26903 is made for pointers to buffers for which the length isn't
26904 transmitted as part of the function call, namely strings. Strings
26905 are transmitted as a pointer/length pair, both as hex values, e.g.@:
26912 which is a pointer to data of length 18 bytes at position 0x1aaf.
26913 The length is defined as the full string length in bytes, including
26914 the trailing null byte. For example, the string @code{"hello world"}
26915 at address 0x123456 is transmitted as
26921 @node Memory Transfer
26922 @unnumberedsubsubsec Memory Transfer
26923 @cindex memory transfer, in file-i/o protocol
26925 Structured data which is transferred using a memory read or write (for
26926 example, a @code{struct stat}) is expected to be in a protocol-specific format
26927 with all scalar multibyte datatypes being big endian. Translation to
26928 this representation needs to be done both by the target before the @code{F}
26929 packet is sent, and by @value{GDBN} before
26930 it transfers memory to the target. Transferred pointers to structured
26931 data should point to the already-coerced data at any time.
26935 @unnumberedsubsubsec struct stat
26936 @cindex struct stat, in file-i/o protocol
26938 The buffer of type @code{struct stat} used by the target and @value{GDBN}
26939 is defined as follows:
26943 unsigned int st_dev; /* device */
26944 unsigned int st_ino; /* inode */
26945 mode_t st_mode; /* protection */
26946 unsigned int st_nlink; /* number of hard links */
26947 unsigned int st_uid; /* user ID of owner */
26948 unsigned int st_gid; /* group ID of owner */
26949 unsigned int st_rdev; /* device type (if inode device) */
26950 unsigned long st_size; /* total size, in bytes */
26951 unsigned long st_blksize; /* blocksize for filesystem I/O */
26952 unsigned long st_blocks; /* number of blocks allocated */
26953 time_t st_atime; /* time of last access */
26954 time_t st_mtime; /* time of last modification */
26955 time_t st_ctime; /* time of last change */
26959 The integral datatypes conform to the definitions given in the
26960 appropriate section (see @ref{Integral Datatypes}, for details) so this
26961 structure is of size 64 bytes.
26963 The values of several fields have a restricted meaning and/or
26969 A value of 0 represents a file, 1 the console.
26972 No valid meaning for the target. Transmitted unchanged.
26975 Valid mode bits are described in @ref{Constants}. Any other
26976 bits have currently no meaning for the target.
26981 No valid meaning for the target. Transmitted unchanged.
26986 These values have a host and file system dependent
26987 accuracy. Especially on Windows hosts, the file system may not
26988 support exact timing values.
26991 The target gets a @code{struct stat} of the above representation and is
26992 responsible for coercing it to the target representation before
26995 Note that due to size differences between the host, target, and protocol
26996 representations of @code{struct stat} members, these members could eventually
26997 get truncated on the target.
26999 @node struct timeval
27000 @unnumberedsubsubsec struct timeval
27001 @cindex struct timeval, in file-i/o protocol
27003 The buffer of type @code{struct timeval} used by the File-I/O protocol
27004 is defined as follows:
27008 time_t tv_sec; /* second */
27009 long tv_usec; /* microsecond */
27013 The integral datatypes conform to the definitions given in the
27014 appropriate section (see @ref{Integral Datatypes}, for details) so this
27015 structure is of size 8 bytes.
27018 @subsection Constants
27019 @cindex constants, in file-i/o protocol
27021 The following values are used for the constants inside of the
27022 protocol. @value{GDBN} and target are responsible for translating these
27023 values before and after the call as needed.
27034 @unnumberedsubsubsec Open Flags
27035 @cindex open flags, in file-i/o protocol
27037 All values are given in hexadecimal representation.
27049 @node mode_t Values
27050 @unnumberedsubsubsec mode_t Values
27051 @cindex mode_t values, in file-i/o protocol
27053 All values are given in octal representation.
27070 @unnumberedsubsubsec Errno Values
27071 @cindex errno values, in file-i/o protocol
27073 All values are given in decimal representation.
27098 @code{EUNKNOWN} is used as a fallback error value if a host system returns
27099 any error value not in the list of supported error numbers.
27102 @unnumberedsubsubsec Lseek Flags
27103 @cindex lseek flags, in file-i/o protocol
27112 @unnumberedsubsubsec Limits
27113 @cindex limits, in file-i/o protocol
27115 All values are given in decimal representation.
27118 INT_MIN -2147483648
27120 UINT_MAX 4294967295
27121 LONG_MIN -9223372036854775808
27122 LONG_MAX 9223372036854775807
27123 ULONG_MAX 18446744073709551615
27126 @node File-I/O Examples
27127 @subsection File-I/O Examples
27128 @cindex file-i/o examples
27130 Example sequence of a write call, file descriptor 3, buffer is at target
27131 address 0x1234, 6 bytes should be written:
27134 <- @code{Fwrite,3,1234,6}
27135 @emph{request memory read from target}
27138 @emph{return "6 bytes written"}
27142 Example sequence of a read call, file descriptor 3, buffer is at target
27143 address 0x1234, 6 bytes should be read:
27146 <- @code{Fread,3,1234,6}
27147 @emph{request memory write to target}
27148 -> @code{X1234,6:XXXXXX}
27149 @emph{return "6 bytes read"}
27153 Example sequence of a read call, call fails on the host due to invalid
27154 file descriptor (@code{EBADF}):
27157 <- @code{Fread,3,1234,6}
27161 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
27165 <- @code{Fread,3,1234,6}
27170 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
27174 <- @code{Fread,3,1234,6}
27175 -> @code{X1234,6:XXXXXX}
27179 @node Library List Format
27180 @section Library List Format
27181 @cindex library list format, remote protocol
27183 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
27184 same process as your application to manage libraries. In this case,
27185 @value{GDBN} can use the loader's symbol table and normal memory
27186 operations to maintain a list of shared libraries. On other
27187 platforms, the operating system manages loaded libraries.
27188 @value{GDBN} can not retrieve the list of currently loaded libraries
27189 through memory operations, so it uses the @samp{qXfer:libraries:read}
27190 packet (@pxref{qXfer library list read}) instead. The remote stub
27191 queries the target's operating system and reports which libraries
27194 The @samp{qXfer:libraries:read} packet returns an XML document which
27195 lists loaded libraries and their offsets. Each library has an
27196 associated name and one or more segment or section base addresses,
27197 which report where the library was loaded in memory.
27199 For the common case of libraries that are fully linked binaries, the
27200 library should have a list of segments. If the target supports
27201 dynamic linking of a relocatable object file, its library XML element
27202 should instead include a list of allocated sections. The segment or
27203 section bases are start addresses, not relocation offsets; they do not
27204 depend on the library's link-time base addresses.
27206 @value{GDBN} must be linked with the Expat library to support XML
27207 library lists. @xref{Expat}.
27209 A simple memory map, with one loaded library relocated by a single
27210 offset, looks like this:
27214 <library name="/lib/libc.so.6">
27215 <segment address="0x10000000"/>
27220 Another simple memory map, with one loaded library with three
27221 allocated sections (.text, .data, .bss), looks like this:
27225 <library name="sharedlib.o">
27226 <section address="0x10000000"/>
27227 <section address="0x20000000"/>
27228 <section address="0x30000000"/>
27233 The format of a library list is described by this DTD:
27236 <!-- library-list: Root element with versioning -->
27237 <!ELEMENT library-list (library)*>
27238 <!ATTLIST library-list version CDATA #FIXED "1.0">
27239 <!ELEMENT library (segment*, section*)>
27240 <!ATTLIST library name CDATA #REQUIRED>
27241 <!ELEMENT segment EMPTY>
27242 <!ATTLIST segment address CDATA #REQUIRED>
27243 <!ELEMENT section EMPTY>
27244 <!ATTLIST section address CDATA #REQUIRED>
27247 In addition, segments and section descriptors cannot be mixed within a
27248 single library element, and you must supply at least one segment or
27249 section for each library.
27251 @node Memory Map Format
27252 @section Memory Map Format
27253 @cindex memory map format
27255 To be able to write into flash memory, @value{GDBN} needs to obtain a
27256 memory map from the target. This section describes the format of the
27259 The memory map is obtained using the @samp{qXfer:memory-map:read}
27260 (@pxref{qXfer memory map read}) packet and is an XML document that
27261 lists memory regions.
27263 @value{GDBN} must be linked with the Expat library to support XML
27264 memory maps. @xref{Expat}.
27266 The top-level structure of the document is shown below:
27269 <?xml version="1.0"?>
27270 <!DOCTYPE memory-map
27271 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
27272 "http://sourceware.org/gdb/gdb-memory-map.dtd">
27278 Each region can be either:
27283 A region of RAM starting at @var{addr} and extending for @var{length}
27287 <memory type="ram" start="@var{addr}" length="@var{length}"/>
27292 A region of read-only memory:
27295 <memory type="rom" start="@var{addr}" length="@var{length}"/>
27300 A region of flash memory, with erasure blocks @var{blocksize}
27304 <memory type="flash" start="@var{addr}" length="@var{length}">
27305 <property name="blocksize">@var{blocksize}</property>
27311 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
27312 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
27313 packets to write to addresses in such ranges.
27315 The formal DTD for memory map format is given below:
27318 <!-- ................................................... -->
27319 <!-- Memory Map XML DTD ................................ -->
27320 <!-- File: memory-map.dtd .............................. -->
27321 <!-- .................................... .............. -->
27322 <!-- memory-map.dtd -->
27323 <!-- memory-map: Root element with versioning -->
27324 <!ELEMENT memory-map (memory | property)>
27325 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
27326 <!ELEMENT memory (property)>
27327 <!-- memory: Specifies a memory region,
27328 and its type, or device. -->
27329 <!ATTLIST memory type CDATA #REQUIRED
27330 start CDATA #REQUIRED
27331 length CDATA #REQUIRED
27332 device CDATA #IMPLIED>
27333 <!-- property: Generic attribute tag -->
27334 <!ELEMENT property (#PCDATA | property)*>
27335 <!ATTLIST property name CDATA #REQUIRED>
27338 @include agentexpr.texi
27340 @node Target Descriptions
27341 @appendix Target Descriptions
27342 @cindex target descriptions
27344 @strong{Warning:} target descriptions are still under active development,
27345 and the contents and format may change between @value{GDBN} releases.
27346 The format is expected to stabilize in the future.
27348 One of the challenges of using @value{GDBN} to debug embedded systems
27349 is that there are so many minor variants of each processor
27350 architecture in use. It is common practice for vendors to start with
27351 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
27352 and then make changes to adapt it to a particular market niche. Some
27353 architectures have hundreds of variants, available from dozens of
27354 vendors. This leads to a number of problems:
27358 With so many different customized processors, it is difficult for
27359 the @value{GDBN} maintainers to keep up with the changes.
27361 Since individual variants may have short lifetimes or limited
27362 audiences, it may not be worthwhile to carry information about every
27363 variant in the @value{GDBN} source tree.
27365 When @value{GDBN} does support the architecture of the embedded system
27366 at hand, the task of finding the correct architecture name to give the
27367 @command{set architecture} command can be error-prone.
27370 To address these problems, the @value{GDBN} remote protocol allows a
27371 target system to not only identify itself to @value{GDBN}, but to
27372 actually describe its own features. This lets @value{GDBN} support
27373 processor variants it has never seen before --- to the extent that the
27374 descriptions are accurate, and that @value{GDBN} understands them.
27376 @value{GDBN} must be linked with the Expat library to support XML
27377 target descriptions. @xref{Expat}.
27380 * Retrieving Descriptions:: How descriptions are fetched from a target.
27381 * Target Description Format:: The contents of a target description.
27382 * Predefined Target Types:: Standard types available for target
27384 * Standard Target Features:: Features @value{GDBN} knows about.
27387 @node Retrieving Descriptions
27388 @section Retrieving Descriptions
27390 Target descriptions can be read from the target automatically, or
27391 specified by the user manually. The default behavior is to read the
27392 description from the target. @value{GDBN} retrieves it via the remote
27393 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
27394 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
27395 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
27396 XML document, of the form described in @ref{Target Description
27399 Alternatively, you can specify a file to read for the target description.
27400 If a file is set, the target will not be queried. The commands to
27401 specify a file are:
27404 @cindex set tdesc filename
27405 @item set tdesc filename @var{path}
27406 Read the target description from @var{path}.
27408 @cindex unset tdesc filename
27409 @item unset tdesc filename
27410 Do not read the XML target description from a file. @value{GDBN}
27411 will use the description supplied by the current target.
27413 @cindex show tdesc filename
27414 @item show tdesc filename
27415 Show the filename to read for a target description, if any.
27419 @node Target Description Format
27420 @section Target Description Format
27421 @cindex target descriptions, XML format
27423 A target description annex is an @uref{http://www.w3.org/XML/, XML}
27424 document which complies with the Document Type Definition provided in
27425 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
27426 means you can use generally available tools like @command{xmllint} to
27427 check that your feature descriptions are well-formed and valid.
27428 However, to help people unfamiliar with XML write descriptions for
27429 their targets, we also describe the grammar here.
27431 Target descriptions can identify the architecture of the remote target
27432 and (for some architectures) provide information about custom register
27433 sets. @value{GDBN} can use this information to autoconfigure for your
27434 target, or to warn you if you connect to an unsupported target.
27436 Here is a simple target description:
27439 <target version="1.0">
27440 <architecture>i386:x86-64</architecture>
27445 This minimal description only says that the target uses
27446 the x86-64 architecture.
27448 A target description has the following overall form, with [ ] marking
27449 optional elements and @dots{} marking repeatable elements. The elements
27450 are explained further below.
27453 <?xml version="1.0"?>
27454 <!DOCTYPE target SYSTEM "gdb-target.dtd">
27455 <target version="1.0">
27456 @r{[}@var{architecture}@r{]}
27457 @r{[}@var{feature}@dots{}@r{]}
27462 The description is generally insensitive to whitespace and line
27463 breaks, under the usual common-sense rules. The XML version
27464 declaration and document type declaration can generally be omitted
27465 (@value{GDBN} does not require them), but specifying them may be
27466 useful for XML validation tools. The @samp{version} attribute for
27467 @samp{<target>} may also be omitted, but we recommend
27468 including it; if future versions of @value{GDBN} use an incompatible
27469 revision of @file{gdb-target.dtd}, they will detect and report
27470 the version mismatch.
27472 @subsection Inclusion
27473 @cindex target descriptions, inclusion
27476 @cindex <xi:include>
27479 It can sometimes be valuable to split a target description up into
27480 several different annexes, either for organizational purposes, or to
27481 share files between different possible target descriptions. You can
27482 divide a description into multiple files by replacing any element of
27483 the target description with an inclusion directive of the form:
27486 <xi:include href="@var{document}"/>
27490 When @value{GDBN} encounters an element of this form, it will retrieve
27491 the named XML @var{document}, and replace the inclusion directive with
27492 the contents of that document. If the current description was read
27493 using @samp{qXfer}, then so will be the included document;
27494 @var{document} will be interpreted as the name of an annex. If the
27495 current description was read from a file, @value{GDBN} will look for
27496 @var{document} as a file in the same directory where it found the
27497 original description.
27499 @subsection Architecture
27500 @cindex <architecture>
27502 An @samp{<architecture>} element has this form:
27505 <architecture>@var{arch}</architecture>
27508 @var{arch} is an architecture name from the same selection
27509 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
27510 Debugging Target}).
27512 @subsection Features
27515 Each @samp{<feature>} describes some logical portion of the target
27516 system. Features are currently used to describe available CPU
27517 registers and the types of their contents. A @samp{<feature>} element
27521 <feature name="@var{name}">
27522 @r{[}@var{type}@dots{}@r{]}
27528 Each feature's name should be unique within the description. The name
27529 of a feature does not matter unless @value{GDBN} has some special
27530 knowledge of the contents of that feature; if it does, the feature
27531 should have its standard name. @xref{Standard Target Features}.
27535 Any register's value is a collection of bits which @value{GDBN} must
27536 interpret. The default interpretation is a two's complement integer,
27537 but other types can be requested by name in the register description.
27538 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
27539 Target Types}), and the description can define additional composite types.
27541 Each type element must have an @samp{id} attribute, which gives
27542 a unique (within the containing @samp{<feature>}) name to the type.
27543 Types must be defined before they are used.
27546 Some targets offer vector registers, which can be treated as arrays
27547 of scalar elements. These types are written as @samp{<vector>} elements,
27548 specifying the array element type, @var{type}, and the number of elements,
27552 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
27556 If a register's value is usefully viewed in multiple ways, define it
27557 with a union type containing the useful representations. The
27558 @samp{<union>} element contains one or more @samp{<field>} elements,
27559 each of which has a @var{name} and a @var{type}:
27562 <union id="@var{id}">
27563 <field name="@var{name}" type="@var{type}"/>
27568 @subsection Registers
27571 Each register is represented as an element with this form:
27574 <reg name="@var{name}"
27575 bitsize="@var{size}"
27576 @r{[}regnum="@var{num}"@r{]}
27577 @r{[}save-restore="@var{save-restore}"@r{]}
27578 @r{[}type="@var{type}"@r{]}
27579 @r{[}group="@var{group}"@r{]}/>
27583 The components are as follows:
27588 The register's name; it must be unique within the target description.
27591 The register's size, in bits.
27594 The register's number. If omitted, a register's number is one greater
27595 than that of the previous register (either in the current feature or in
27596 a preceeding feature); the first register in the target description
27597 defaults to zero. This register number is used to read or write
27598 the register; e.g.@: it is used in the remote @code{p} and @code{P}
27599 packets, and registers appear in the @code{g} and @code{G} packets
27600 in order of increasing register number.
27603 Whether the register should be preserved across inferior function
27604 calls; this must be either @code{yes} or @code{no}. The default is
27605 @code{yes}, which is appropriate for most registers except for
27606 some system control registers; this is not related to the target's
27610 The type of the register. @var{type} may be a predefined type, a type
27611 defined in the current feature, or one of the special types @code{int}
27612 and @code{float}. @code{int} is an integer type of the correct size
27613 for @var{bitsize}, and @code{float} is a floating point type (in the
27614 architecture's normal floating point format) of the correct size for
27615 @var{bitsize}. The default is @code{int}.
27618 The register group to which this register belongs. @var{group} must
27619 be either @code{general}, @code{float}, or @code{vector}. If no
27620 @var{group} is specified, @value{GDBN} will not display the register
27621 in @code{info registers}.
27625 @node Predefined Target Types
27626 @section Predefined Target Types
27627 @cindex target descriptions, predefined types
27629 Type definitions in the self-description can build up composite types
27630 from basic building blocks, but can not define fundamental types. Instead,
27631 standard identifiers are provided by @value{GDBN} for the fundamental
27632 types. The currently supported types are:
27641 Signed integer types holding the specified number of bits.
27648 Unsigned integer types holding the specified number of bits.
27652 Pointers to unspecified code and data. The program counter and
27653 any dedicated return address register may be marked as code
27654 pointers; printing a code pointer converts it into a symbolic
27655 address. The stack pointer and any dedicated address registers
27656 may be marked as data pointers.
27659 Single precision IEEE floating point.
27662 Double precision IEEE floating point.
27665 The 12-byte extended precision format used by ARM FPA registers.
27669 @node Standard Target Features
27670 @section Standard Target Features
27671 @cindex target descriptions, standard features
27673 A target description must contain either no registers or all the
27674 target's registers. If the description contains no registers, then
27675 @value{GDBN} will assume a default register layout, selected based on
27676 the architecture. If the description contains any registers, the
27677 default layout will not be used; the standard registers must be
27678 described in the target description, in such a way that @value{GDBN}
27679 can recognize them.
27681 This is accomplished by giving specific names to feature elements
27682 which contain standard registers. @value{GDBN} will look for features
27683 with those names and verify that they contain the expected registers;
27684 if any known feature is missing required registers, or if any required
27685 feature is missing, @value{GDBN} will reject the target
27686 description. You can add additional registers to any of the
27687 standard features --- @value{GDBN} will display them just as if
27688 they were added to an unrecognized feature.
27690 This section lists the known features and their expected contents.
27691 Sample XML documents for these features are included in the
27692 @value{GDBN} source tree, in the directory @file{gdb/features}.
27694 Names recognized by @value{GDBN} should include the name of the
27695 company or organization which selected the name, and the overall
27696 architecture to which the feature applies; so e.g.@: the feature
27697 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
27699 The names of registers are not case sensitive for the purpose
27700 of recognizing standard features, but @value{GDBN} will only display
27701 registers using the capitalization used in the description.
27707 * PowerPC Features::
27712 @subsection ARM Features
27713 @cindex target descriptions, ARM features
27715 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
27716 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
27717 @samp{lr}, @samp{pc}, and @samp{cpsr}.
27719 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
27720 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
27722 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
27723 it should contain at least registers @samp{wR0} through @samp{wR15} and
27724 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
27725 @samp{wCSSF}, and @samp{wCASF} registers are optional.
27727 @node MIPS Features
27728 @subsection MIPS Features
27729 @cindex target descriptions, MIPS features
27731 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
27732 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
27733 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
27736 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
27737 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
27738 registers. They may be 32-bit or 64-bit depending on the target.
27740 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
27741 it may be optional in a future version of @value{GDBN}. It should
27742 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
27743 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
27745 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
27746 contain a single register, @samp{restart}, which is used by the
27747 Linux kernel to control restartable syscalls.
27749 @node M68K Features
27750 @subsection M68K Features
27751 @cindex target descriptions, M68K features
27754 @item @samp{org.gnu.gdb.m68k.core}
27755 @itemx @samp{org.gnu.gdb.coldfire.core}
27756 @itemx @samp{org.gnu.gdb.fido.core}
27757 One of those features must be always present.
27758 The feature that is present determines which flavor of m86k is
27759 used. The feature that is present should contain registers
27760 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
27761 @samp{sp}, @samp{ps} and @samp{pc}.
27763 @item @samp{org.gnu.gdb.coldfire.fp}
27764 This feature is optional. If present, it should contain registers
27765 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
27769 @node PowerPC Features
27770 @subsection PowerPC Features
27771 @cindex target descriptions, PowerPC features
27773 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
27774 targets. It should contain registers @samp{r0} through @samp{r31},
27775 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
27776 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
27778 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
27779 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
27781 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
27782 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
27785 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
27786 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
27787 @samp{spefscr}. SPE targets should provide 32-bit registers in
27788 @samp{org.gnu.gdb.power.core} and provide the upper halves in
27789 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
27790 these to present registers @samp{ev0} through @samp{ev31} to the
27805 % I think something like @colophon should be in texinfo. In the
27807 \long\def\colophon{\hbox to0pt{}\vfill
27808 \centerline{The body of this manual is set in}
27809 \centerline{\fontname\tenrm,}
27810 \centerline{with headings in {\bf\fontname\tenbf}}
27811 \centerline{and examples in {\tt\fontname\tentt}.}
27812 \centerline{{\it\fontname\tenit\/},}
27813 \centerline{{\bf\fontname\tenbf}, and}
27814 \centerline{{\sl\fontname\tensl\/}}
27815 \centerline{are used for emphasis.}\vfill}
27817 % Blame: doc@cygnus.com, 1991.