1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 @ifset VERSION_PACKAGE
53 @value{VERSION_PACKAGE}
55 Version @value{GDBVN}.
57 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
58 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006@*
59 Free Software Foundation, Inc.
61 Permission is granted to copy, distribute and/or modify this document
62 under the terms of the GNU Free Documentation License, Version 1.1 or
63 any later version published by the Free Software Foundation; with the
64 Invariant Sections being ``Free Software'' and ``Free Software Needs
65 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
66 and with the Back-Cover Texts as in (a) below.
68 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
69 this GNU Manual. Buying copies from GNU Press supports the FSF in
70 developing GNU and promoting software freedom.''
74 @title Debugging with @value{GDBN}
75 @subtitle The @sc{gnu} Source-Level Debugger
77 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
78 @ifset VERSION_PACKAGE
80 @subtitle @value{VERSION_PACKAGE}
82 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
86 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
87 \hfill {\it Debugging with @value{GDBN}}\par
88 \hfill \TeX{}info \texinfoversion\par
92 @vskip 0pt plus 1filll
93 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
94 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
95 Free Software Foundation, Inc.
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
102 Permission is granted to copy, distribute and/or modify this document
103 under the terms of the GNU Free Documentation License, Version 1.1 or
104 any later version published by the Free Software Foundation; with the
105 Invariant Sections being ``Free Software'' and ``Free Software Needs
106 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
107 and with the Back-Cover Texts as in (a) below.
109 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
110 this GNU Manual. Buying copies from GNU Press supports the FSF in
111 developing GNU and promoting software freedom.''
113 This edition of the GDB manual is dedicated to the memory of Fred
114 Fish. Fred was a long-standing contributor to GDB and to Free
115 software in general. We will miss him.
120 @node Top, Summary, (dir), (dir)
122 @top Debugging with @value{GDBN}
124 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
126 This is the @value{EDITION} Edition, for @value{GDBN}
127 @ifset VERSION_PACKAGE
128 @value{VERSION_PACKAGE}
130 Version @value{GDBVN}.
132 Copyright (C) 1988-2006 Free Software Foundation, Inc.
134 This edition of the GDB manual is dedicated to the memory of Fred
135 Fish. Fred was a long-standing contributor to GDB and to Free
136 software in general. We will miss him.
139 * Summary:: Summary of @value{GDBN}
140 * Sample Session:: A sample @value{GDBN} session
142 * Invocation:: Getting in and out of @value{GDBN}
143 * Commands:: @value{GDBN} commands
144 * Running:: Running programs under @value{GDBN}
145 * Stopping:: Stopping and continuing
146 * Stack:: Examining the stack
147 * Source:: Examining source files
148 * Data:: Examining data
149 * Macros:: Preprocessor Macros
150 * Tracepoints:: Debugging remote targets non-intrusively
151 * Overlays:: Debugging programs that use overlays
153 * Languages:: Using @value{GDBN} with different languages
155 * Symbols:: Examining the symbol table
156 * Altering:: Altering execution
157 * GDB Files:: @value{GDBN} files
158 * Targets:: Specifying a debugging target
159 * Remote Debugging:: Debugging remote programs
160 * Configurations:: Configuration-specific information
161 * Controlling GDB:: Controlling @value{GDBN}
162 * Sequences:: Canned sequences of commands
163 * Interpreters:: Command Interpreters
164 * TUI:: @value{GDBN} Text User Interface
165 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
166 * GDB/MI:: @value{GDBN}'s Machine Interface.
167 * Annotations:: @value{GDBN}'s annotation interface.
169 * GDB Bugs:: Reporting bugs in @value{GDBN}
171 * Command Line Editing:: Command Line Editing
172 * Using History Interactively:: Using History Interactively
173 * Formatting Documentation:: How to format and print @value{GDBN} documentation
174 * Installing GDB:: Installing GDB
175 * Maintenance Commands:: Maintenance Commands
176 * Remote Protocol:: GDB Remote Serial Protocol
177 * Agent Expressions:: The GDB Agent Expression Mechanism
178 * Target Descriptions:: How targets can describe themselves to
180 * Copying:: GNU General Public License says
181 how you can copy and share GDB
182 * GNU Free Documentation License:: The license for this documentation
191 @unnumbered Summary of @value{GDBN}
193 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
194 going on ``inside'' another program while it executes---or what another
195 program was doing at the moment it crashed.
197 @value{GDBN} can do four main kinds of things (plus other things in support of
198 these) to help you catch bugs in the act:
202 Start your program, specifying anything that might affect its behavior.
205 Make your program stop on specified conditions.
208 Examine what has happened, when your program has stopped.
211 Change things in your program, so you can experiment with correcting the
212 effects of one bug and go on to learn about another.
215 You can use @value{GDBN} to debug programs written in C and C@t{++}.
216 For more information, see @ref{Supported Languages,,Supported Languages}.
217 For more information, see @ref{C,,C and C++}.
220 Support for Modula-2 is partial. For information on Modula-2, see
221 @ref{Modula-2,,Modula-2}.
224 Debugging Pascal programs which use sets, subranges, file variables, or
225 nested functions does not currently work. @value{GDBN} does not support
226 entering expressions, printing values, or similar features using Pascal
230 @value{GDBN} can be used to debug programs written in Fortran, although
231 it may be necessary to refer to some variables with a trailing
234 @value{GDBN} can be used to debug programs written in Objective-C,
235 using either the Apple/NeXT or the GNU Objective-C runtime.
238 * Free Software:: Freely redistributable software
239 * Contributors:: Contributors to GDB
243 @unnumberedsec Free Software
245 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
246 General Public License
247 (GPL). The GPL gives you the freedom to copy or adapt a licensed
248 program---but every person getting a copy also gets with it the
249 freedom to modify that copy (which means that they must get access to
250 the source code), and the freedom to distribute further copies.
251 Typical software companies use copyrights to limit your freedoms; the
252 Free Software Foundation uses the GPL to preserve these freedoms.
254 Fundamentally, the General Public License is a license which says that
255 you have these freedoms and that you cannot take these freedoms away
258 @unnumberedsec Free Software Needs Free Documentation
260 The biggest deficiency in the free software community today is not in
261 the software---it is the lack of good free documentation that we can
262 include with the free software. Many of our most important
263 programs do not come with free reference manuals and free introductory
264 texts. Documentation is an essential part of any software package;
265 when an important free software package does not come with a free
266 manual and a free tutorial, that is a major gap. We have many such
269 Consider Perl, for instance. The tutorial manuals that people
270 normally use are non-free. How did this come about? Because the
271 authors of those manuals published them with restrictive terms---no
272 copying, no modification, source files not available---which exclude
273 them from the free software world.
275 That wasn't the first time this sort of thing happened, and it was far
276 from the last. Many times we have heard a GNU user eagerly describe a
277 manual that he is writing, his intended contribution to the community,
278 only to learn that he had ruined everything by signing a publication
279 contract to make it non-free.
281 Free documentation, like free software, is a matter of freedom, not
282 price. The problem with the non-free manual is not that publishers
283 charge a price for printed copies---that in itself is fine. (The Free
284 Software Foundation sells printed copies of manuals, too.) The
285 problem is the restrictions on the use of the manual. Free manuals
286 are available in source code form, and give you permission to copy and
287 modify. Non-free manuals do not allow this.
289 The criteria of freedom for a free manual are roughly the same as for
290 free software. Redistribution (including the normal kinds of
291 commercial redistribution) must be permitted, so that the manual can
292 accompany every copy of the program, both on-line and on paper.
294 Permission for modification of the technical content is crucial too.
295 When people modify the software, adding or changing features, if they
296 are conscientious they will change the manual too---so they can
297 provide accurate and clear documentation for the modified program. A
298 manual that leaves you no choice but to write a new manual to document
299 a changed version of the program is not really available to our
302 Some kinds of limits on the way modification is handled are
303 acceptable. For example, requirements to preserve the original
304 author's copyright notice, the distribution terms, or the list of
305 authors, are ok. It is also no problem to require modified versions
306 to include notice that they were modified. Even entire sections that
307 may not be deleted or changed are acceptable, as long as they deal
308 with nontechnical topics (like this one). These kinds of restrictions
309 are acceptable because they don't obstruct the community's normal use
312 However, it must be possible to modify all the @emph{technical}
313 content of the manual, and then distribute the result in all the usual
314 media, through all the usual channels. Otherwise, the restrictions
315 obstruct the use of the manual, it is not free, and we need another
316 manual to replace it.
318 Please spread the word about this issue. Our community continues to
319 lose manuals to proprietary publishing. If we spread the word that
320 free software needs free reference manuals and free tutorials, perhaps
321 the next person who wants to contribute by writing documentation will
322 realize, before it is too late, that only free manuals contribute to
323 the free software community.
325 If you are writing documentation, please insist on publishing it under
326 the GNU Free Documentation License or another free documentation
327 license. Remember that this decision requires your approval---you
328 don't have to let the publisher decide. Some commercial publishers
329 will use a free license if you insist, but they will not propose the
330 option; it is up to you to raise the issue and say firmly that this is
331 what you want. If the publisher you are dealing with refuses, please
332 try other publishers. If you're not sure whether a proposed license
333 is free, write to @email{licensing@@gnu.org}.
335 You can encourage commercial publishers to sell more free, copylefted
336 manuals and tutorials by buying them, and particularly by buying
337 copies from the publishers that paid for their writing or for major
338 improvements. Meanwhile, try to avoid buying non-free documentation
339 at all. Check the distribution terms of a manual before you buy it,
340 and insist that whoever seeks your business must respect your freedom.
341 Check the history of the book, and try to reward the publishers that
342 have paid or pay the authors to work on it.
344 The Free Software Foundation maintains a list of free documentation
345 published by other publishers, at
346 @url{http://www.fsf.org/doc/other-free-books.html}.
349 @unnumberedsec Contributors to @value{GDBN}
351 Richard Stallman was the original author of @value{GDBN}, and of many
352 other @sc{gnu} programs. Many others have contributed to its
353 development. This section attempts to credit major contributors. One
354 of the virtues of free software is that everyone is free to contribute
355 to it; with regret, we cannot actually acknowledge everyone here. The
356 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
357 blow-by-blow account.
359 Changes much prior to version 2.0 are lost in the mists of time.
362 @emph{Plea:} Additions to this section are particularly welcome. If you
363 or your friends (or enemies, to be evenhanded) have been unfairly
364 omitted from this list, we would like to add your names!
367 So that they may not regard their many labors as thankless, we
368 particularly thank those who shepherded @value{GDBN} through major
370 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
371 Jim Blandy (release 4.18);
372 Jason Molenda (release 4.17);
373 Stan Shebs (release 4.14);
374 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
375 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
376 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
377 Jim Kingdon (releases 3.5, 3.4, and 3.3);
378 and Randy Smith (releases 3.2, 3.1, and 3.0).
380 Richard Stallman, assisted at various times by Peter TerMaat, Chris
381 Hanson, and Richard Mlynarik, handled releases through 2.8.
383 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
384 in @value{GDBN}, with significant additional contributions from Per
385 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
386 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
387 much general update work leading to release 3.0).
389 @value{GDBN} uses the BFD subroutine library to examine multiple
390 object-file formats; BFD was a joint project of David V.
391 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
393 David Johnson wrote the original COFF support; Pace Willison did
394 the original support for encapsulated COFF.
396 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
398 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
399 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
401 Jean-Daniel Fekete contributed Sun 386i support.
402 Chris Hanson improved the HP9000 support.
403 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
404 David Johnson contributed Encore Umax support.
405 Jyrki Kuoppala contributed Altos 3068 support.
406 Jeff Law contributed HP PA and SOM support.
407 Keith Packard contributed NS32K support.
408 Doug Rabson contributed Acorn Risc Machine support.
409 Bob Rusk contributed Harris Nighthawk CX-UX support.
410 Chris Smith contributed Convex support (and Fortran debugging).
411 Jonathan Stone contributed Pyramid support.
412 Michael Tiemann contributed SPARC support.
413 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
414 Pace Willison contributed Intel 386 support.
415 Jay Vosburgh contributed Symmetry support.
416 Marko Mlinar contributed OpenRISC 1000 support.
418 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
420 Rich Schaefer and Peter Schauer helped with support of SunOS shared
423 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
424 about several machine instruction sets.
426 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
427 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
428 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
429 and RDI targets, respectively.
431 Brian Fox is the author of the readline libraries providing
432 command-line editing and command history.
434 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
435 Modula-2 support, and contributed the Languages chapter of this manual.
437 Fred Fish wrote most of the support for Unix System Vr4.
438 He also enhanced the command-completion support to cover C@t{++} overloaded
441 Hitachi America (now Renesas America), Ltd. sponsored the support for
442 H8/300, H8/500, and Super-H processors.
444 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
446 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
449 Toshiba sponsored the support for the TX39 Mips processor.
451 Matsushita sponsored the support for the MN10200 and MN10300 processors.
453 Fujitsu sponsored the support for SPARClite and FR30 processors.
455 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
458 Michael Snyder added support for tracepoints.
460 Stu Grossman wrote gdbserver.
462 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
463 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
465 The following people at the Hewlett-Packard Company contributed
466 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
467 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
468 compiler, and the Text User Interface (nee Terminal User Interface):
469 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
470 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
471 provided HP-specific information in this manual.
473 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
474 Robert Hoehne made significant contributions to the DJGPP port.
476 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
477 development since 1991. Cygnus engineers who have worked on @value{GDBN}
478 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
479 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
480 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
481 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
482 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
483 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
484 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
485 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
486 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
487 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
488 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
489 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
490 Zuhn have made contributions both large and small.
492 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
493 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
495 Jim Blandy added support for preprocessor macros, while working for Red
498 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
499 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
500 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
501 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
502 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
503 with the migration of old architectures to this new framework.
505 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
506 unwinder framework, this consisting of a fresh new design featuring
507 frame IDs, independent frame sniffers, and the sentinel frame. Mark
508 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
509 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
510 trad unwinders. The architecture-specific changes, each involving a
511 complete rewrite of the architecture's frame code, were carried out by
512 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
513 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
514 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
515 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
518 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
519 Tensilica, Inc.@: contributed support for Xtensa processors. Others
520 who have worked on the Xtensa port of @value{GDBN} in the past include
521 Steve Tjiang, John Newlin, and Scott Foehner.
524 @chapter A Sample @value{GDBN} Session
526 You can use this manual at your leisure to read all about @value{GDBN}.
527 However, a handful of commands are enough to get started using the
528 debugger. This chapter illustrates those commands.
531 In this sample session, we emphasize user input like this: @b{input},
532 to make it easier to pick out from the surrounding output.
535 @c FIXME: this example may not be appropriate for some configs, where
536 @c FIXME...primary interest is in remote use.
538 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
539 processor) exhibits the following bug: sometimes, when we change its
540 quote strings from the default, the commands used to capture one macro
541 definition within another stop working. In the following short @code{m4}
542 session, we define a macro @code{foo} which expands to @code{0000}; we
543 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
544 same thing. However, when we change the open quote string to
545 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
546 procedure fails to define a new synonym @code{baz}:
555 @b{define(bar,defn(`foo'))}
559 @b{changequote(<QUOTE>,<UNQUOTE>)}
561 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
564 m4: End of input: 0: fatal error: EOF in string
568 Let us use @value{GDBN} to try to see what is going on.
571 $ @b{@value{GDBP} m4}
572 @c FIXME: this falsifies the exact text played out, to permit smallbook
573 @c FIXME... format to come out better.
574 @value{GDBN} is free software and you are welcome to distribute copies
575 of it under certain conditions; type "show copying" to see
577 There is absolutely no warranty for @value{GDBN}; type "show warranty"
580 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
585 @value{GDBN} reads only enough symbol data to know where to find the
586 rest when needed; as a result, the first prompt comes up very quickly.
587 We now tell @value{GDBN} to use a narrower display width than usual, so
588 that examples fit in this manual.
591 (@value{GDBP}) @b{set width 70}
595 We need to see how the @code{m4} built-in @code{changequote} works.
596 Having looked at the source, we know the relevant subroutine is
597 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
598 @code{break} command.
601 (@value{GDBP}) @b{break m4_changequote}
602 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
606 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
607 control; as long as control does not reach the @code{m4_changequote}
608 subroutine, the program runs as usual:
611 (@value{GDBP}) @b{run}
612 Starting program: /work/Editorial/gdb/gnu/m4/m4
620 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
621 suspends execution of @code{m4}, displaying information about the
622 context where it stops.
625 @b{changequote(<QUOTE>,<UNQUOTE>)}
627 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
629 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
633 Now we use the command @code{n} (@code{next}) to advance execution to
634 the next line of the current function.
638 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
643 @code{set_quotes} looks like a promising subroutine. We can go into it
644 by using the command @code{s} (@code{step}) instead of @code{next}.
645 @code{step} goes to the next line to be executed in @emph{any}
646 subroutine, so it steps into @code{set_quotes}.
650 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
652 530 if (lquote != def_lquote)
656 The display that shows the subroutine where @code{m4} is now
657 suspended (and its arguments) is called a stack frame display. It
658 shows a summary of the stack. We can use the @code{backtrace}
659 command (which can also be spelled @code{bt}), to see where we are
660 in the stack as a whole: the @code{backtrace} command displays a
661 stack frame for each active subroutine.
664 (@value{GDBP}) @b{bt}
665 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
667 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
669 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
670 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
672 #4 0x79dc in expand_input () at macro.c:40
673 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
677 We step through a few more lines to see what happens. The first two
678 times, we can use @samp{s}; the next two times we use @code{n} to avoid
679 falling into the @code{xstrdup} subroutine.
683 0x3b5c 532 if (rquote != def_rquote)
685 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
686 def_lquote : xstrdup(lq);
688 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
691 538 len_lquote = strlen(rquote);
695 The last line displayed looks a little odd; we can examine the variables
696 @code{lquote} and @code{rquote} to see if they are in fact the new left
697 and right quotes we specified. We use the command @code{p}
698 (@code{print}) to see their values.
701 (@value{GDBP}) @b{p lquote}
702 $1 = 0x35d40 "<QUOTE>"
703 (@value{GDBP}) @b{p rquote}
704 $2 = 0x35d50 "<UNQUOTE>"
708 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
709 To look at some context, we can display ten lines of source
710 surrounding the current line with the @code{l} (@code{list}) command.
716 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
718 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
721 538 len_lquote = strlen(rquote);
722 539 len_rquote = strlen(lquote);
729 Let us step past the two lines that set @code{len_lquote} and
730 @code{len_rquote}, and then examine the values of those variables.
734 539 len_rquote = strlen(lquote);
737 (@value{GDBP}) @b{p len_lquote}
739 (@value{GDBP}) @b{p len_rquote}
744 That certainly looks wrong, assuming @code{len_lquote} and
745 @code{len_rquote} are meant to be the lengths of @code{lquote} and
746 @code{rquote} respectively. We can set them to better values using
747 the @code{p} command, since it can print the value of
748 any expression---and that expression can include subroutine calls and
752 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
754 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
759 Is that enough to fix the problem of using the new quotes with the
760 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
761 executing with the @code{c} (@code{continue}) command, and then try the
762 example that caused trouble initially:
768 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
775 Success! The new quotes now work just as well as the default ones. The
776 problem seems to have been just the two typos defining the wrong
777 lengths. We allow @code{m4} exit by giving it an EOF as input:
781 Program exited normally.
785 The message @samp{Program exited normally.} is from @value{GDBN}; it
786 indicates @code{m4} has finished executing. We can end our @value{GDBN}
787 session with the @value{GDBN} @code{quit} command.
790 (@value{GDBP}) @b{quit}
794 @chapter Getting In and Out of @value{GDBN}
796 This chapter discusses how to start @value{GDBN}, and how to get out of it.
800 type @samp{@value{GDBP}} to start @value{GDBN}.
802 type @kbd{quit} or @kbd{Ctrl-d} to exit.
806 * Invoking GDB:: How to start @value{GDBN}
807 * Quitting GDB:: How to quit @value{GDBN}
808 * Shell Commands:: How to use shell commands inside @value{GDBN}
809 * Logging Output:: How to log @value{GDBN}'s output to a file
813 @section Invoking @value{GDBN}
815 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
816 @value{GDBN} reads commands from the terminal until you tell it to exit.
818 You can also run @code{@value{GDBP}} with a variety of arguments and options,
819 to specify more of your debugging environment at the outset.
821 The command-line options described here are designed
822 to cover a variety of situations; in some environments, some of these
823 options may effectively be unavailable.
825 The most usual way to start @value{GDBN} is with one argument,
826 specifying an executable program:
829 @value{GDBP} @var{program}
833 You can also start with both an executable program and a core file
837 @value{GDBP} @var{program} @var{core}
840 You can, instead, specify a process ID as a second argument, if you want
841 to debug a running process:
844 @value{GDBP} @var{program} 1234
848 would attach @value{GDBN} to process @code{1234} (unless you also have a file
849 named @file{1234}; @value{GDBN} does check for a core file first).
851 Taking advantage of the second command-line argument requires a fairly
852 complete operating system; when you use @value{GDBN} as a remote
853 debugger attached to a bare board, there may not be any notion of
854 ``process'', and there is often no way to get a core dump. @value{GDBN}
855 will warn you if it is unable to attach or to read core dumps.
857 You can optionally have @code{@value{GDBP}} pass any arguments after the
858 executable file to the inferior using @code{--args}. This option stops
861 @value{GDBP} --args gcc -O2 -c foo.c
863 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
864 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
866 You can run @code{@value{GDBP}} without printing the front material, which describes
867 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
874 You can further control how @value{GDBN} starts up by using command-line
875 options. @value{GDBN} itself can remind you of the options available.
885 to display all available options and briefly describe their use
886 (@samp{@value{GDBP} -h} is a shorter equivalent).
888 All options and command line arguments you give are processed
889 in sequential order. The order makes a difference when the
890 @samp{-x} option is used.
894 * File Options:: Choosing files
895 * Mode Options:: Choosing modes
896 * Startup:: What @value{GDBN} does during startup
900 @subsection Choosing Files
902 When @value{GDBN} starts, it reads any arguments other than options as
903 specifying an executable file and core file (or process ID). This is
904 the same as if the arguments were specified by the @samp{-se} and
905 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
906 first argument that does not have an associated option flag as
907 equivalent to the @samp{-se} option followed by that argument; and the
908 second argument that does not have an associated option flag, if any, as
909 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
910 If the second argument begins with a decimal digit, @value{GDBN} will
911 first attempt to attach to it as a process, and if that fails, attempt
912 to open it as a corefile. If you have a corefile whose name begins with
913 a digit, you can prevent @value{GDBN} from treating it as a pid by
914 prefixing it with @file{./}, e.g.@: @file{./12345}.
916 If @value{GDBN} has not been configured to included core file support,
917 such as for most embedded targets, then it will complain about a second
918 argument and ignore it.
920 Many options have both long and short forms; both are shown in the
921 following list. @value{GDBN} also recognizes the long forms if you truncate
922 them, so long as enough of the option is present to be unambiguous.
923 (If you prefer, you can flag option arguments with @samp{--} rather
924 than @samp{-}, though we illustrate the more usual convention.)
926 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
927 @c way, both those who look for -foo and --foo in the index, will find
931 @item -symbols @var{file}
933 @cindex @code{--symbols}
935 Read symbol table from file @var{file}.
937 @item -exec @var{file}
939 @cindex @code{--exec}
941 Use file @var{file} as the executable file to execute when appropriate,
942 and for examining pure data in conjunction with a core dump.
946 Read symbol table from file @var{file} and use it as the executable
949 @item -core @var{file}
951 @cindex @code{--core}
953 Use file @var{file} as a core dump to examine.
955 @item -pid @var{number}
956 @itemx -p @var{number}
959 Connect to process ID @var{number}, as with the @code{attach} command.
961 @item -command @var{file}
963 @cindex @code{--command}
965 Execute @value{GDBN} commands from file @var{file}. @xref{Command
966 Files,, Command files}.
968 @item -eval-command @var{command}
969 @itemx -ex @var{command}
970 @cindex @code{--eval-command}
972 Execute a single @value{GDBN} command.
974 This option may be used multiple times to call multiple commands. It may
975 also be interleaved with @samp{-command} as required.
978 @value{GDBP} -ex 'target sim' -ex 'load' \
979 -x setbreakpoints -ex 'run' a.out
982 @item -directory @var{directory}
983 @itemx -d @var{directory}
984 @cindex @code{--directory}
986 Add @var{directory} to the path to search for source and script files.
990 @cindex @code{--readnow}
992 Read each symbol file's entire symbol table immediately, rather than
993 the default, which is to read it incrementally as it is needed.
994 This makes startup slower, but makes future operations faster.
999 @subsection Choosing Modes
1001 You can run @value{GDBN} in various alternative modes---for example, in
1002 batch mode or quiet mode.
1009 Do not execute commands found in any initialization files. Normally,
1010 @value{GDBN} executes the commands in these files after all the command
1011 options and arguments have been processed. @xref{Command Files,,Command
1017 @cindex @code{--quiet}
1018 @cindex @code{--silent}
1020 ``Quiet''. Do not print the introductory and copyright messages. These
1021 messages are also suppressed in batch mode.
1024 @cindex @code{--batch}
1025 Run in batch mode. Exit with status @code{0} after processing all the
1026 command files specified with @samp{-x} (and all commands from
1027 initialization files, if not inhibited with @samp{-n}). Exit with
1028 nonzero status if an error occurs in executing the @value{GDBN} commands
1029 in the command files.
1031 Batch mode may be useful for running @value{GDBN} as a filter, for
1032 example to download and run a program on another computer; in order to
1033 make this more useful, the message
1036 Program exited normally.
1040 (which is ordinarily issued whenever a program running under
1041 @value{GDBN} control terminates) is not issued when running in batch
1045 @cindex @code{--batch-silent}
1046 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1047 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1048 unaffected). This is much quieter than @samp{-silent} and would be useless
1049 for an interactive session.
1051 This is particularly useful when using targets that give @samp{Loading section}
1052 messages, for example.
1054 Note that targets that give their output via @value{GDBN}, as opposed to
1055 writing directly to @code{stdout}, will also be made silent.
1057 @item -return-child-result
1058 @cindex @code{--return-child-result}
1059 The return code from @value{GDBN} will be the return code from the child
1060 process (the process being debugged), with the following exceptions:
1064 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1065 internal error. In this case the exit code is the same as it would have been
1066 without @samp{-return-child-result}.
1068 The user quits with an explicit value. E.g., @samp{quit 1}.
1070 The child process never runs, or is not allowed to terminate, in which case
1071 the exit code will be -1.
1074 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1075 when @value{GDBN} is being used as a remote program loader or simulator
1080 @cindex @code{--nowindows}
1082 ``No windows''. If @value{GDBN} comes with a graphical user interface
1083 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1084 interface. If no GUI is available, this option has no effect.
1088 @cindex @code{--windows}
1090 If @value{GDBN} includes a GUI, then this option requires it to be
1093 @item -cd @var{directory}
1095 Run @value{GDBN} using @var{directory} as its working directory,
1096 instead of the current directory.
1100 @cindex @code{--fullname}
1102 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1103 subprocess. It tells @value{GDBN} to output the full file name and line
1104 number in a standard, recognizable fashion each time a stack frame is
1105 displayed (which includes each time your program stops). This
1106 recognizable format looks like two @samp{\032} characters, followed by
1107 the file name, line number and character position separated by colons,
1108 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1109 @samp{\032} characters as a signal to display the source code for the
1113 @cindex @code{--epoch}
1114 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1115 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1116 routines so as to allow Epoch to display values of expressions in a
1119 @item -annotate @var{level}
1120 @cindex @code{--annotate}
1121 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1122 effect is identical to using @samp{set annotate @var{level}}
1123 (@pxref{Annotations}). The annotation @var{level} controls how much
1124 information @value{GDBN} prints together with its prompt, values of
1125 expressions, source lines, and other types of output. Level 0 is the
1126 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1127 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1128 that control @value{GDBN}, and level 2 has been deprecated.
1130 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1134 @cindex @code{--args}
1135 Change interpretation of command line so that arguments following the
1136 executable file are passed as command line arguments to the inferior.
1137 This option stops option processing.
1139 @item -baud @var{bps}
1141 @cindex @code{--baud}
1143 Set the line speed (baud rate or bits per second) of any serial
1144 interface used by @value{GDBN} for remote debugging.
1146 @item -l @var{timeout}
1148 Set the timeout (in seconds) of any communication used by @value{GDBN}
1149 for remote debugging.
1151 @item -tty @var{device}
1152 @itemx -t @var{device}
1153 @cindex @code{--tty}
1155 Run using @var{device} for your program's standard input and output.
1156 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1158 @c resolve the situation of these eventually
1160 @cindex @code{--tui}
1161 Activate the @dfn{Text User Interface} when starting. The Text User
1162 Interface manages several text windows on the terminal, showing
1163 source, assembly, registers and @value{GDBN} command outputs
1164 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1165 Text User Interface can be enabled by invoking the program
1166 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1167 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1170 @c @cindex @code{--xdb}
1171 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1172 @c For information, see the file @file{xdb_trans.html}, which is usually
1173 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1176 @item -interpreter @var{interp}
1177 @cindex @code{--interpreter}
1178 Use the interpreter @var{interp} for interface with the controlling
1179 program or device. This option is meant to be set by programs which
1180 communicate with @value{GDBN} using it as a back end.
1181 @xref{Interpreters, , Command Interpreters}.
1183 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1184 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1185 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1186 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1187 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1188 @sc{gdb/mi} interfaces are no longer supported.
1191 @cindex @code{--write}
1192 Open the executable and core files for both reading and writing. This
1193 is equivalent to the @samp{set write on} command inside @value{GDBN}
1197 @cindex @code{--statistics}
1198 This option causes @value{GDBN} to print statistics about time and
1199 memory usage after it completes each command and returns to the prompt.
1202 @cindex @code{--version}
1203 This option causes @value{GDBN} to print its version number and
1204 no-warranty blurb, and exit.
1209 @subsection What @value{GDBN} Does During Startup
1210 @cindex @value{GDBN} startup
1212 Here's the description of what @value{GDBN} does during session startup:
1216 Sets up the command interpreter as specified by the command line
1217 (@pxref{Mode Options, interpreter}).
1221 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1222 DOS/Windows systems, the home directory is the one pointed to by the
1223 @code{HOME} environment variable.} and executes all the commands in
1227 Processes command line options and operands.
1230 Reads and executes the commands from init file (if any) in the current
1231 working directory. This is only done if the current directory is
1232 different from your home directory. Thus, you can have more than one
1233 init file, one generic in your home directory, and another, specific
1234 to the program you are debugging, in the directory where you invoke
1238 Reads command files specified by the @samp{-x} option. @xref{Command
1239 Files}, for more details about @value{GDBN} command files.
1242 Reads the command history recorded in the @dfn{history file}.
1243 @xref{Command History}, for more details about the command history and the
1244 files where @value{GDBN} records it.
1247 Init files use the same syntax as @dfn{command files} (@pxref{Command
1248 Files}) and are processed by @value{GDBN} in the same way. The init
1249 file in your home directory can set options (such as @samp{set
1250 complaints}) that affect subsequent processing of command line options
1251 and operands. Init files are not executed if you use the @samp{-nx}
1252 option (@pxref{Mode Options, ,Choosing Modes}).
1254 @cindex init file name
1255 @cindex @file{.gdbinit}
1256 @cindex @file{gdb.ini}
1257 The @value{GDBN} init files are normally called @file{.gdbinit}.
1258 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1259 the limitations of file names imposed by DOS filesystems. The Windows
1260 ports of @value{GDBN} use the standard name, but if they find a
1261 @file{gdb.ini} file, they warn you about that and suggest to rename
1262 the file to the standard name.
1266 @section Quitting @value{GDBN}
1267 @cindex exiting @value{GDBN}
1268 @cindex leaving @value{GDBN}
1271 @kindex quit @r{[}@var{expression}@r{]}
1272 @kindex q @r{(@code{quit})}
1273 @item quit @r{[}@var{expression}@r{]}
1275 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1276 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1277 do not supply @var{expression}, @value{GDBN} will terminate normally;
1278 otherwise it will terminate using the result of @var{expression} as the
1283 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1284 terminates the action of any @value{GDBN} command that is in progress and
1285 returns to @value{GDBN} command level. It is safe to type the interrupt
1286 character at any time because @value{GDBN} does not allow it to take effect
1287 until a time when it is safe.
1289 If you have been using @value{GDBN} to control an attached process or
1290 device, you can release it with the @code{detach} command
1291 (@pxref{Attach, ,Debugging an Already-running Process}).
1293 @node Shell Commands
1294 @section Shell Commands
1296 If you need to execute occasional shell commands during your
1297 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1298 just use the @code{shell} command.
1302 @cindex shell escape
1303 @item shell @var{command string}
1304 Invoke a standard shell to execute @var{command string}.
1305 If it exists, the environment variable @code{SHELL} determines which
1306 shell to run. Otherwise @value{GDBN} uses the default shell
1307 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1310 The utility @code{make} is often needed in development environments.
1311 You do not have to use the @code{shell} command for this purpose in
1316 @cindex calling make
1317 @item make @var{make-args}
1318 Execute the @code{make} program with the specified
1319 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1322 @node Logging Output
1323 @section Logging Output
1324 @cindex logging @value{GDBN} output
1325 @cindex save @value{GDBN} output to a file
1327 You may want to save the output of @value{GDBN} commands to a file.
1328 There are several commands to control @value{GDBN}'s logging.
1332 @item set logging on
1334 @item set logging off
1336 @cindex logging file name
1337 @item set logging file @var{file}
1338 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1339 @item set logging overwrite [on|off]
1340 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1341 you want @code{set logging on} to overwrite the logfile instead.
1342 @item set logging redirect [on|off]
1343 By default, @value{GDBN} output will go to both the terminal and the logfile.
1344 Set @code{redirect} if you want output to go only to the log file.
1345 @kindex show logging
1347 Show the current values of the logging settings.
1351 @chapter @value{GDBN} Commands
1353 You can abbreviate a @value{GDBN} command to the first few letters of the command
1354 name, if that abbreviation is unambiguous; and you can repeat certain
1355 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1356 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1357 show you the alternatives available, if there is more than one possibility).
1360 * Command Syntax:: How to give commands to @value{GDBN}
1361 * Completion:: Command completion
1362 * Help:: How to ask @value{GDBN} for help
1365 @node Command Syntax
1366 @section Command Syntax
1368 A @value{GDBN} command is a single line of input. There is no limit on
1369 how long it can be. It starts with a command name, which is followed by
1370 arguments whose meaning depends on the command name. For example, the
1371 command @code{step} accepts an argument which is the number of times to
1372 step, as in @samp{step 5}. You can also use the @code{step} command
1373 with no arguments. Some commands do not allow any arguments.
1375 @cindex abbreviation
1376 @value{GDBN} command names may always be truncated if that abbreviation is
1377 unambiguous. Other possible command abbreviations are listed in the
1378 documentation for individual commands. In some cases, even ambiguous
1379 abbreviations are allowed; for example, @code{s} is specially defined as
1380 equivalent to @code{step} even though there are other commands whose
1381 names start with @code{s}. You can test abbreviations by using them as
1382 arguments to the @code{help} command.
1384 @cindex repeating commands
1385 @kindex RET @r{(repeat last command)}
1386 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1387 repeat the previous command. Certain commands (for example, @code{run})
1388 will not repeat this way; these are commands whose unintentional
1389 repetition might cause trouble and which you are unlikely to want to
1390 repeat. User-defined commands can disable this feature; see
1391 @ref{Define, dont-repeat}.
1393 The @code{list} and @code{x} commands, when you repeat them with
1394 @key{RET}, construct new arguments rather than repeating
1395 exactly as typed. This permits easy scanning of source or memory.
1397 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1398 output, in a way similar to the common utility @code{more}
1399 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1400 @key{RET} too many in this situation, @value{GDBN} disables command
1401 repetition after any command that generates this sort of display.
1403 @kindex # @r{(a comment)}
1405 Any text from a @kbd{#} to the end of the line is a comment; it does
1406 nothing. This is useful mainly in command files (@pxref{Command
1407 Files,,Command Files}).
1409 @cindex repeating command sequences
1410 @kindex Ctrl-o @r{(operate-and-get-next)}
1411 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1412 commands. This command accepts the current line, like @key{RET}, and
1413 then fetches the next line relative to the current line from the history
1417 @section Command Completion
1420 @cindex word completion
1421 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1422 only one possibility; it can also show you what the valid possibilities
1423 are for the next word in a command, at any time. This works for @value{GDBN}
1424 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1426 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1427 of a word. If there is only one possibility, @value{GDBN} fills in the
1428 word, and waits for you to finish the command (or press @key{RET} to
1429 enter it). For example, if you type
1431 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1432 @c complete accuracy in these examples; space introduced for clarity.
1433 @c If texinfo enhancements make it unnecessary, it would be nice to
1434 @c replace " @key" by "@key" in the following...
1436 (@value{GDBP}) info bre @key{TAB}
1440 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1441 the only @code{info} subcommand beginning with @samp{bre}:
1444 (@value{GDBP}) info breakpoints
1448 You can either press @key{RET} at this point, to run the @code{info
1449 breakpoints} command, or backspace and enter something else, if
1450 @samp{breakpoints} does not look like the command you expected. (If you
1451 were sure you wanted @code{info breakpoints} in the first place, you
1452 might as well just type @key{RET} immediately after @samp{info bre},
1453 to exploit command abbreviations rather than command completion).
1455 If there is more than one possibility for the next word when you press
1456 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1457 characters and try again, or just press @key{TAB} a second time;
1458 @value{GDBN} displays all the possible completions for that word. For
1459 example, you might want to set a breakpoint on a subroutine whose name
1460 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1461 just sounds the bell. Typing @key{TAB} again displays all the
1462 function names in your program that begin with those characters, for
1466 (@value{GDBP}) b make_ @key{TAB}
1467 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1468 make_a_section_from_file make_environ
1469 make_abs_section make_function_type
1470 make_blockvector make_pointer_type
1471 make_cleanup make_reference_type
1472 make_command make_symbol_completion_list
1473 (@value{GDBP}) b make_
1477 After displaying the available possibilities, @value{GDBN} copies your
1478 partial input (@samp{b make_} in the example) so you can finish the
1481 If you just want to see the list of alternatives in the first place, you
1482 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1483 means @kbd{@key{META} ?}. You can type this either by holding down a
1484 key designated as the @key{META} shift on your keyboard (if there is
1485 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1487 @cindex quotes in commands
1488 @cindex completion of quoted strings
1489 Sometimes the string you need, while logically a ``word'', may contain
1490 parentheses or other characters that @value{GDBN} normally excludes from
1491 its notion of a word. To permit word completion to work in this
1492 situation, you may enclose words in @code{'} (single quote marks) in
1493 @value{GDBN} commands.
1495 The most likely situation where you might need this is in typing the
1496 name of a C@t{++} function. This is because C@t{++} allows function
1497 overloading (multiple definitions of the same function, distinguished
1498 by argument type). For example, when you want to set a breakpoint you
1499 may need to distinguish whether you mean the version of @code{name}
1500 that takes an @code{int} parameter, @code{name(int)}, or the version
1501 that takes a @code{float} parameter, @code{name(float)}. To use the
1502 word-completion facilities in this situation, type a single quote
1503 @code{'} at the beginning of the function name. This alerts
1504 @value{GDBN} that it may need to consider more information than usual
1505 when you press @key{TAB} or @kbd{M-?} to request word completion:
1508 (@value{GDBP}) b 'bubble( @kbd{M-?}
1509 bubble(double,double) bubble(int,int)
1510 (@value{GDBP}) b 'bubble(
1513 In some cases, @value{GDBN} can tell that completing a name requires using
1514 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1515 completing as much as it can) if you do not type the quote in the first
1519 (@value{GDBP}) b bub @key{TAB}
1520 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1521 (@value{GDBP}) b 'bubble(
1525 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1526 you have not yet started typing the argument list when you ask for
1527 completion on an overloaded symbol.
1529 For more information about overloaded functions, see @ref{C Plus Plus
1530 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1531 overload-resolution off} to disable overload resolution;
1532 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1536 @section Getting Help
1537 @cindex online documentation
1540 You can always ask @value{GDBN} itself for information on its commands,
1541 using the command @code{help}.
1544 @kindex h @r{(@code{help})}
1547 You can use @code{help} (abbreviated @code{h}) with no arguments to
1548 display a short list of named classes of commands:
1552 List of classes of commands:
1554 aliases -- Aliases of other commands
1555 breakpoints -- Making program stop at certain points
1556 data -- Examining data
1557 files -- Specifying and examining files
1558 internals -- Maintenance commands
1559 obscure -- Obscure features
1560 running -- Running the program
1561 stack -- Examining the stack
1562 status -- Status inquiries
1563 support -- Support facilities
1564 tracepoints -- Tracing of program execution without
1565 stopping the program
1566 user-defined -- User-defined commands
1568 Type "help" followed by a class name for a list of
1569 commands in that class.
1570 Type "help" followed by command name for full
1572 Command name abbreviations are allowed if unambiguous.
1575 @c the above line break eliminates huge line overfull...
1577 @item help @var{class}
1578 Using one of the general help classes as an argument, you can get a
1579 list of the individual commands in that class. For example, here is the
1580 help display for the class @code{status}:
1583 (@value{GDBP}) help status
1588 @c Line break in "show" line falsifies real output, but needed
1589 @c to fit in smallbook page size.
1590 info -- Generic command for showing things
1591 about the program being debugged
1592 show -- Generic command for showing things
1595 Type "help" followed by command name for full
1597 Command name abbreviations are allowed if unambiguous.
1601 @item help @var{command}
1602 With a command name as @code{help} argument, @value{GDBN} displays a
1603 short paragraph on how to use that command.
1606 @item apropos @var{args}
1607 The @code{apropos} command searches through all of the @value{GDBN}
1608 commands, and their documentation, for the regular expression specified in
1609 @var{args}. It prints out all matches found. For example:
1620 set symbol-reloading -- Set dynamic symbol table reloading
1621 multiple times in one run
1622 show symbol-reloading -- Show dynamic symbol table reloading
1623 multiple times in one run
1628 @item complete @var{args}
1629 The @code{complete @var{args}} command lists all the possible completions
1630 for the beginning of a command. Use @var{args} to specify the beginning of the
1631 command you want completed. For example:
1637 @noindent results in:
1648 @noindent This is intended for use by @sc{gnu} Emacs.
1651 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1652 and @code{show} to inquire about the state of your program, or the state
1653 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1654 manual introduces each of them in the appropriate context. The listings
1655 under @code{info} and under @code{show} in the Index point to
1656 all the sub-commands. @xref{Index}.
1661 @kindex i @r{(@code{info})}
1663 This command (abbreviated @code{i}) is for describing the state of your
1664 program. For example, you can show the arguments passed to a function
1665 with @code{info args}, list the registers currently in use with @code{info
1666 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1667 You can get a complete list of the @code{info} sub-commands with
1668 @w{@code{help info}}.
1672 You can assign the result of an expression to an environment variable with
1673 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1674 @code{set prompt $}.
1678 In contrast to @code{info}, @code{show} is for describing the state of
1679 @value{GDBN} itself.
1680 You can change most of the things you can @code{show}, by using the
1681 related command @code{set}; for example, you can control what number
1682 system is used for displays with @code{set radix}, or simply inquire
1683 which is currently in use with @code{show radix}.
1686 To display all the settable parameters and their current
1687 values, you can use @code{show} with no arguments; you may also use
1688 @code{info set}. Both commands produce the same display.
1689 @c FIXME: "info set" violates the rule that "info" is for state of
1690 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1691 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1695 Here are three miscellaneous @code{show} subcommands, all of which are
1696 exceptional in lacking corresponding @code{set} commands:
1699 @kindex show version
1700 @cindex @value{GDBN} version number
1702 Show what version of @value{GDBN} is running. You should include this
1703 information in @value{GDBN} bug-reports. If multiple versions of
1704 @value{GDBN} are in use at your site, you may need to determine which
1705 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1706 commands are introduced, and old ones may wither away. Also, many
1707 system vendors ship variant versions of @value{GDBN}, and there are
1708 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1709 The version number is the same as the one announced when you start
1712 @kindex show copying
1713 @kindex info copying
1714 @cindex display @value{GDBN} copyright
1717 Display information about permission for copying @value{GDBN}.
1719 @kindex show warranty
1720 @kindex info warranty
1722 @itemx info warranty
1723 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1724 if your version of @value{GDBN} comes with one.
1729 @chapter Running Programs Under @value{GDBN}
1731 When you run a program under @value{GDBN}, you must first generate
1732 debugging information when you compile it.
1734 You may start @value{GDBN} with its arguments, if any, in an environment
1735 of your choice. If you are doing native debugging, you may redirect
1736 your program's input and output, debug an already running process, or
1737 kill a child process.
1740 * Compilation:: Compiling for debugging
1741 * Starting:: Starting your program
1742 * Arguments:: Your program's arguments
1743 * Environment:: Your program's environment
1745 * Working Directory:: Your program's working directory
1746 * Input/Output:: Your program's input and output
1747 * Attach:: Debugging an already-running process
1748 * Kill Process:: Killing the child process
1750 * Threads:: Debugging programs with multiple threads
1751 * Processes:: Debugging programs with multiple processes
1752 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1756 @section Compiling for Debugging
1758 In order to debug a program effectively, you need to generate
1759 debugging information when you compile it. This debugging information
1760 is stored in the object file; it describes the data type of each
1761 variable or function and the correspondence between source line numbers
1762 and addresses in the executable code.
1764 To request debugging information, specify the @samp{-g} option when you run
1767 Programs that are to be shipped to your customers are compiled with
1768 optimizations, using the @samp{-O} compiler option. However, many
1769 compilers are unable to handle the @samp{-g} and @samp{-O} options
1770 together. Using those compilers, you cannot generate optimized
1771 executables containing debugging information.
1773 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1774 without @samp{-O}, making it possible to debug optimized code. We
1775 recommend that you @emph{always} use @samp{-g} whenever you compile a
1776 program. You may think your program is correct, but there is no sense
1777 in pushing your luck.
1779 @cindex optimized code, debugging
1780 @cindex debugging optimized code
1781 When you debug a program compiled with @samp{-g -O}, remember that the
1782 optimizer is rearranging your code; the debugger shows you what is
1783 really there. Do not be too surprised when the execution path does not
1784 exactly match your source file! An extreme example: if you define a
1785 variable, but never use it, @value{GDBN} never sees that
1786 variable---because the compiler optimizes it out of existence.
1788 Some things do not work as well with @samp{-g -O} as with just
1789 @samp{-g}, particularly on machines with instruction scheduling. If in
1790 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1791 please report it to us as a bug (including a test case!).
1792 @xref{Variables}, for more information about debugging optimized code.
1794 Older versions of the @sc{gnu} C compiler permitted a variant option
1795 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1796 format; if your @sc{gnu} C compiler has this option, do not use it.
1798 @value{GDBN} knows about preprocessor macros and can show you their
1799 expansion (@pxref{Macros}). Most compilers do not include information
1800 about preprocessor macros in the debugging information if you specify
1801 the @option{-g} flag alone, because this information is rather large.
1802 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1803 provides macro information if you specify the options
1804 @option{-gdwarf-2} and @option{-g3}; the former option requests
1805 debugging information in the Dwarf 2 format, and the latter requests
1806 ``extra information''. In the future, we hope to find more compact
1807 ways to represent macro information, so that it can be included with
1812 @section Starting your Program
1818 @kindex r @r{(@code{run})}
1821 Use the @code{run} command to start your program under @value{GDBN}.
1822 You must first specify the program name (except on VxWorks) with an
1823 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1824 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1825 (@pxref{Files, ,Commands to Specify Files}).
1829 If you are running your program in an execution environment that
1830 supports processes, @code{run} creates an inferior process and makes
1831 that process run your program. In some environments without processes,
1832 @code{run} jumps to the start of your program. Other targets,
1833 like @samp{remote}, are always running. If you get an error
1834 message like this one:
1837 The "remote" target does not support "run".
1838 Try "help target" or "continue".
1842 then use @code{continue} to run your program. You may need @code{load}
1843 first (@pxref{load}).
1845 The execution of a program is affected by certain information it
1846 receives from its superior. @value{GDBN} provides ways to specify this
1847 information, which you must do @emph{before} starting your program. (You
1848 can change it after starting your program, but such changes only affect
1849 your program the next time you start it.) This information may be
1850 divided into four categories:
1853 @item The @emph{arguments.}
1854 Specify the arguments to give your program as the arguments of the
1855 @code{run} command. If a shell is available on your target, the shell
1856 is used to pass the arguments, so that you may use normal conventions
1857 (such as wildcard expansion or variable substitution) in describing
1859 In Unix systems, you can control which shell is used with the
1860 @code{SHELL} environment variable.
1861 @xref{Arguments, ,Your Program's Arguments}.
1863 @item The @emph{environment.}
1864 Your program normally inherits its environment from @value{GDBN}, but you can
1865 use the @value{GDBN} commands @code{set environment} and @code{unset
1866 environment} to change parts of the environment that affect
1867 your program. @xref{Environment, ,Your Program's Environment}.
1869 @item The @emph{working directory.}
1870 Your program inherits its working directory from @value{GDBN}. You can set
1871 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1872 @xref{Working Directory, ,Your Program's Working Directory}.
1874 @item The @emph{standard input and output.}
1875 Your program normally uses the same device for standard input and
1876 standard output as @value{GDBN} is using. You can redirect input and output
1877 in the @code{run} command line, or you can use the @code{tty} command to
1878 set a different device for your program.
1879 @xref{Input/Output, ,Your Program's Input and Output}.
1882 @emph{Warning:} While input and output redirection work, you cannot use
1883 pipes to pass the output of the program you are debugging to another
1884 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1888 When you issue the @code{run} command, your program begins to execute
1889 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1890 of how to arrange for your program to stop. Once your program has
1891 stopped, you may call functions in your program, using the @code{print}
1892 or @code{call} commands. @xref{Data, ,Examining Data}.
1894 If the modification time of your symbol file has changed since the last
1895 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1896 table, and reads it again. When it does this, @value{GDBN} tries to retain
1897 your current breakpoints.
1902 @cindex run to main procedure
1903 The name of the main procedure can vary from language to language.
1904 With C or C@t{++}, the main procedure name is always @code{main}, but
1905 other languages such as Ada do not require a specific name for their
1906 main procedure. The debugger provides a convenient way to start the
1907 execution of the program and to stop at the beginning of the main
1908 procedure, depending on the language used.
1910 The @samp{start} command does the equivalent of setting a temporary
1911 breakpoint at the beginning of the main procedure and then invoking
1912 the @samp{run} command.
1914 @cindex elaboration phase
1915 Some programs contain an @dfn{elaboration} phase where some startup code is
1916 executed before the main procedure is called. This depends on the
1917 languages used to write your program. In C@t{++}, for instance,
1918 constructors for static and global objects are executed before
1919 @code{main} is called. It is therefore possible that the debugger stops
1920 before reaching the main procedure. However, the temporary breakpoint
1921 will remain to halt execution.
1923 Specify the arguments to give to your program as arguments to the
1924 @samp{start} command. These arguments will be given verbatim to the
1925 underlying @samp{run} command. Note that the same arguments will be
1926 reused if no argument is provided during subsequent calls to
1927 @samp{start} or @samp{run}.
1929 It is sometimes necessary to debug the program during elaboration. In
1930 these cases, using the @code{start} command would stop the execution of
1931 your program too late, as the program would have already completed the
1932 elaboration phase. Under these circumstances, insert breakpoints in your
1933 elaboration code before running your program.
1935 @kindex set exec-wrapper
1936 @item set exec-wrapper @var{wrapper}
1937 @itemx show exec-wrapper
1938 @itemx unset exec-wrapper
1939 When @samp{exec-wrapper} is set, the specified wrapper is used to
1940 launch programs for debugging. @value{GDBN} starts your program
1941 with a shell command of the form @kbd{exec @var{wrapper}
1942 @var{program}}. Quoting is added to @var{program} and its
1943 arguments, but not to @var{wrapper}, so you should add quotes if
1944 appropriate for your shell. The wrapper runs until it executes
1945 your program, and then @value{GDBN} takes control.
1947 You can use any program that eventually calls @code{execve} with
1948 its arguments as a wrapper. Several standard Unix utilities do
1949 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1950 with @code{exec "$@@"} will also work.
1952 For example, you can use @code{env} to pass an environment variable to
1953 the debugged program, without setting the variable in your shell's
1957 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1961 This command is available when debugging locally on most targets, excluding
1962 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
1967 @section Your Program's Arguments
1969 @cindex arguments (to your program)
1970 The arguments to your program can be specified by the arguments of the
1972 They are passed to a shell, which expands wildcard characters and
1973 performs redirection of I/O, and thence to your program. Your
1974 @code{SHELL} environment variable (if it exists) specifies what shell
1975 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1976 the default shell (@file{/bin/sh} on Unix).
1978 On non-Unix systems, the program is usually invoked directly by
1979 @value{GDBN}, which emulates I/O redirection via the appropriate system
1980 calls, and the wildcard characters are expanded by the startup code of
1981 the program, not by the shell.
1983 @code{run} with no arguments uses the same arguments used by the previous
1984 @code{run}, or those set by the @code{set args} command.
1989 Specify the arguments to be used the next time your program is run. If
1990 @code{set args} has no arguments, @code{run} executes your program
1991 with no arguments. Once you have run your program with arguments,
1992 using @code{set args} before the next @code{run} is the only way to run
1993 it again without arguments.
1997 Show the arguments to give your program when it is started.
2001 @section Your Program's Environment
2003 @cindex environment (of your program)
2004 The @dfn{environment} consists of a set of environment variables and
2005 their values. Environment variables conventionally record such things as
2006 your user name, your home directory, your terminal type, and your search
2007 path for programs to run. Usually you set up environment variables with
2008 the shell and they are inherited by all the other programs you run. When
2009 debugging, it can be useful to try running your program with a modified
2010 environment without having to start @value{GDBN} over again.
2014 @item path @var{directory}
2015 Add @var{directory} to the front of the @code{PATH} environment variable
2016 (the search path for executables) that will be passed to your program.
2017 The value of @code{PATH} used by @value{GDBN} does not change.
2018 You may specify several directory names, separated by whitespace or by a
2019 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2020 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2021 is moved to the front, so it is searched sooner.
2023 You can use the string @samp{$cwd} to refer to whatever is the current
2024 working directory at the time @value{GDBN} searches the path. If you
2025 use @samp{.} instead, it refers to the directory where you executed the
2026 @code{path} command. @value{GDBN} replaces @samp{.} in the
2027 @var{directory} argument (with the current path) before adding
2028 @var{directory} to the search path.
2029 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2030 @c document that, since repeating it would be a no-op.
2034 Display the list of search paths for executables (the @code{PATH}
2035 environment variable).
2037 @kindex show environment
2038 @item show environment @r{[}@var{varname}@r{]}
2039 Print the value of environment variable @var{varname} to be given to
2040 your program when it starts. If you do not supply @var{varname},
2041 print the names and values of all environment variables to be given to
2042 your program. You can abbreviate @code{environment} as @code{env}.
2044 @kindex set environment
2045 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2046 Set environment variable @var{varname} to @var{value}. The value
2047 changes for your program only, not for @value{GDBN} itself. @var{value} may
2048 be any string; the values of environment variables are just strings, and
2049 any interpretation is supplied by your program itself. The @var{value}
2050 parameter is optional; if it is eliminated, the variable is set to a
2052 @c "any string" here does not include leading, trailing
2053 @c blanks. Gnu asks: does anyone care?
2055 For example, this command:
2062 tells the debugged program, when subsequently run, that its user is named
2063 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2064 are not actually required.)
2066 @kindex unset environment
2067 @item unset environment @var{varname}
2068 Remove variable @var{varname} from the environment to be passed to your
2069 program. This is different from @samp{set env @var{varname} =};
2070 @code{unset environment} removes the variable from the environment,
2071 rather than assigning it an empty value.
2074 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2076 by your @code{SHELL} environment variable if it exists (or
2077 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2078 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2079 @file{.bashrc} for BASH---any variables you set in that file affect
2080 your program. You may wish to move setting of environment variables to
2081 files that are only run when you sign on, such as @file{.login} or
2084 @node Working Directory
2085 @section Your Program's Working Directory
2087 @cindex working directory (of your program)
2088 Each time you start your program with @code{run}, it inherits its
2089 working directory from the current working directory of @value{GDBN}.
2090 The @value{GDBN} working directory is initially whatever it inherited
2091 from its parent process (typically the shell), but you can specify a new
2092 working directory in @value{GDBN} with the @code{cd} command.
2094 The @value{GDBN} working directory also serves as a default for the commands
2095 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2100 @cindex change working directory
2101 @item cd @var{directory}
2102 Set the @value{GDBN} working directory to @var{directory}.
2106 Print the @value{GDBN} working directory.
2109 It is generally impossible to find the current working directory of
2110 the process being debugged (since a program can change its directory
2111 during its run). If you work on a system where @value{GDBN} is
2112 configured with the @file{/proc} support, you can use the @code{info
2113 proc} command (@pxref{SVR4 Process Information}) to find out the
2114 current working directory of the debuggee.
2117 @section Your Program's Input and Output
2122 By default, the program you run under @value{GDBN} does input and output to
2123 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2124 to its own terminal modes to interact with you, but it records the terminal
2125 modes your program was using and switches back to them when you continue
2126 running your program.
2129 @kindex info terminal
2131 Displays information recorded by @value{GDBN} about the terminal modes your
2135 You can redirect your program's input and/or output using shell
2136 redirection with the @code{run} command. For example,
2143 starts your program, diverting its output to the file @file{outfile}.
2146 @cindex controlling terminal
2147 Another way to specify where your program should do input and output is
2148 with the @code{tty} command. This command accepts a file name as
2149 argument, and causes this file to be the default for future @code{run}
2150 commands. It also resets the controlling terminal for the child
2151 process, for future @code{run} commands. For example,
2158 directs that processes started with subsequent @code{run} commands
2159 default to do input and output on the terminal @file{/dev/ttyb} and have
2160 that as their controlling terminal.
2162 An explicit redirection in @code{run} overrides the @code{tty} command's
2163 effect on the input/output device, but not its effect on the controlling
2166 When you use the @code{tty} command or redirect input in the @code{run}
2167 command, only the input @emph{for your program} is affected. The input
2168 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2169 for @code{set inferior-tty}.
2171 @cindex inferior tty
2172 @cindex set inferior controlling terminal
2173 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2174 display the name of the terminal that will be used for future runs of your
2178 @item set inferior-tty /dev/ttyb
2179 @kindex set inferior-tty
2180 Set the tty for the program being debugged to /dev/ttyb.
2182 @item show inferior-tty
2183 @kindex show inferior-tty
2184 Show the current tty for the program being debugged.
2188 @section Debugging an Already-running Process
2193 @item attach @var{process-id}
2194 This command attaches to a running process---one that was started
2195 outside @value{GDBN}. (@code{info files} shows your active
2196 targets.) The command takes as argument a process ID. The usual way to
2197 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2198 or with the @samp{jobs -l} shell command.
2200 @code{attach} does not repeat if you press @key{RET} a second time after
2201 executing the command.
2204 To use @code{attach}, your program must be running in an environment
2205 which supports processes; for example, @code{attach} does not work for
2206 programs on bare-board targets that lack an operating system. You must
2207 also have permission to send the process a signal.
2209 When you use @code{attach}, the debugger finds the program running in
2210 the process first by looking in the current working directory, then (if
2211 the program is not found) by using the source file search path
2212 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2213 the @code{file} command to load the program. @xref{Files, ,Commands to
2216 The first thing @value{GDBN} does after arranging to debug the specified
2217 process is to stop it. You can examine and modify an attached process
2218 with all the @value{GDBN} commands that are ordinarily available when
2219 you start processes with @code{run}. You can insert breakpoints; you
2220 can step and continue; you can modify storage. If you would rather the
2221 process continue running, you may use the @code{continue} command after
2222 attaching @value{GDBN} to the process.
2227 When you have finished debugging the attached process, you can use the
2228 @code{detach} command to release it from @value{GDBN} control. Detaching
2229 the process continues its execution. After the @code{detach} command,
2230 that process and @value{GDBN} become completely independent once more, and you
2231 are ready to @code{attach} another process or start one with @code{run}.
2232 @code{detach} does not repeat if you press @key{RET} again after
2233 executing the command.
2236 If you exit @value{GDBN} while you have an attached process, you detach
2237 that process. If you use the @code{run} command, you kill that process.
2238 By default, @value{GDBN} asks for confirmation if you try to do either of these
2239 things; you can control whether or not you need to confirm by using the
2240 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2244 @section Killing the Child Process
2249 Kill the child process in which your program is running under @value{GDBN}.
2252 This command is useful if you wish to debug a core dump instead of a
2253 running process. @value{GDBN} ignores any core dump file while your program
2256 On some operating systems, a program cannot be executed outside @value{GDBN}
2257 while you have breakpoints set on it inside @value{GDBN}. You can use the
2258 @code{kill} command in this situation to permit running your program
2259 outside the debugger.
2261 The @code{kill} command is also useful if you wish to recompile and
2262 relink your program, since on many systems it is impossible to modify an
2263 executable file while it is running in a process. In this case, when you
2264 next type @code{run}, @value{GDBN} notices that the file has changed, and
2265 reads the symbol table again (while trying to preserve your current
2266 breakpoint settings).
2269 @section Debugging Programs with Multiple Threads
2271 @cindex threads of execution
2272 @cindex multiple threads
2273 @cindex switching threads
2274 In some operating systems, such as HP-UX and Solaris, a single program
2275 may have more than one @dfn{thread} of execution. The precise semantics
2276 of threads differ from one operating system to another, but in general
2277 the threads of a single program are akin to multiple processes---except
2278 that they share one address space (that is, they can all examine and
2279 modify the same variables). On the other hand, each thread has its own
2280 registers and execution stack, and perhaps private memory.
2282 @value{GDBN} provides these facilities for debugging multi-thread
2286 @item automatic notification of new threads
2287 @item @samp{thread @var{threadno}}, a command to switch among threads
2288 @item @samp{info threads}, a command to inquire about existing threads
2289 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2290 a command to apply a command to a list of threads
2291 @item thread-specific breakpoints
2292 @item @samp{set print thread-events}, which controls printing of
2293 messages on thread start and exit.
2297 @emph{Warning:} These facilities are not yet available on every
2298 @value{GDBN} configuration where the operating system supports threads.
2299 If your @value{GDBN} does not support threads, these commands have no
2300 effect. For example, a system without thread support shows no output
2301 from @samp{info threads}, and always rejects the @code{thread} command,
2305 (@value{GDBP}) info threads
2306 (@value{GDBP}) thread 1
2307 Thread ID 1 not known. Use the "info threads" command to
2308 see the IDs of currently known threads.
2310 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2311 @c doesn't support threads"?
2314 @cindex focus of debugging
2315 @cindex current thread
2316 The @value{GDBN} thread debugging facility allows you to observe all
2317 threads while your program runs---but whenever @value{GDBN} takes
2318 control, one thread in particular is always the focus of debugging.
2319 This thread is called the @dfn{current thread}. Debugging commands show
2320 program information from the perspective of the current thread.
2322 @cindex @code{New} @var{systag} message
2323 @cindex thread identifier (system)
2324 @c FIXME-implementors!! It would be more helpful if the [New...] message
2325 @c included GDB's numeric thread handle, so you could just go to that
2326 @c thread without first checking `info threads'.
2327 Whenever @value{GDBN} detects a new thread in your program, it displays
2328 the target system's identification for the thread with a message in the
2329 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2330 whose form varies depending on the particular system. For example, on
2331 @sc{gnu}/Linux, you might see
2334 [New Thread 46912507313328 (LWP 25582)]
2338 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2339 the @var{systag} is simply something like @samp{process 368}, with no
2342 @c FIXME!! (1) Does the [New...] message appear even for the very first
2343 @c thread of a program, or does it only appear for the
2344 @c second---i.e.@: when it becomes obvious we have a multithread
2346 @c (2) *Is* there necessarily a first thread always? Or do some
2347 @c multithread systems permit starting a program with multiple
2348 @c threads ab initio?
2350 @cindex thread number
2351 @cindex thread identifier (GDB)
2352 For debugging purposes, @value{GDBN} associates its own thread
2353 number---always a single integer---with each thread in your program.
2356 @kindex info threads
2358 Display a summary of all threads currently in your
2359 program. @value{GDBN} displays for each thread (in this order):
2363 the thread number assigned by @value{GDBN}
2366 the target system's thread identifier (@var{systag})
2369 the current stack frame summary for that thread
2373 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2374 indicates the current thread.
2378 @c end table here to get a little more width for example
2381 (@value{GDBP}) info threads
2382 3 process 35 thread 27 0x34e5 in sigpause ()
2383 2 process 35 thread 23 0x34e5 in sigpause ()
2384 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2390 @cindex debugging multithreaded programs (on HP-UX)
2391 @cindex thread identifier (GDB), on HP-UX
2392 For debugging purposes, @value{GDBN} associates its own thread
2393 number---a small integer assigned in thread-creation order---with each
2394 thread in your program.
2396 @cindex @code{New} @var{systag} message, on HP-UX
2397 @cindex thread identifier (system), on HP-UX
2398 @c FIXME-implementors!! It would be more helpful if the [New...] message
2399 @c included GDB's numeric thread handle, so you could just go to that
2400 @c thread without first checking `info threads'.
2401 Whenever @value{GDBN} detects a new thread in your program, it displays
2402 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2403 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2404 whose form varies depending on the particular system. For example, on
2408 [New thread 2 (system thread 26594)]
2412 when @value{GDBN} notices a new thread.
2415 @kindex info threads (HP-UX)
2417 Display a summary of all threads currently in your
2418 program. @value{GDBN} displays for each thread (in this order):
2421 @item the thread number assigned by @value{GDBN}
2423 @item the target system's thread identifier (@var{systag})
2425 @item the current stack frame summary for that thread
2429 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2430 indicates the current thread.
2434 @c end table here to get a little more width for example
2437 (@value{GDBP}) info threads
2438 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2440 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2441 from /usr/lib/libc.2
2442 1 system thread 27905 0x7b003498 in _brk () \@*
2443 from /usr/lib/libc.2
2446 On Solaris, you can display more information about user threads with a
2447 Solaris-specific command:
2450 @item maint info sol-threads
2451 @kindex maint info sol-threads
2452 @cindex thread info (Solaris)
2453 Display info on Solaris user threads.
2457 @kindex thread @var{threadno}
2458 @item thread @var{threadno}
2459 Make thread number @var{threadno} the current thread. The command
2460 argument @var{threadno} is the internal @value{GDBN} thread number, as
2461 shown in the first field of the @samp{info threads} display.
2462 @value{GDBN} responds by displaying the system identifier of the thread
2463 you selected, and its current stack frame summary:
2466 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2467 (@value{GDBP}) thread 2
2468 [Switching to process 35 thread 23]
2469 0x34e5 in sigpause ()
2473 As with the @samp{[New @dots{}]} message, the form of the text after
2474 @samp{Switching to} depends on your system's conventions for identifying
2477 @kindex thread apply
2478 @cindex apply command to several threads
2479 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2480 The @code{thread apply} command allows you to apply the named
2481 @var{command} to one or more threads. Specify the numbers of the
2482 threads that you want affected with the command argument
2483 @var{threadno}. It can be a single thread number, one of the numbers
2484 shown in the first field of the @samp{info threads} display; or it
2485 could be a range of thread numbers, as in @code{2-4}. To apply a
2486 command to all threads, type @kbd{thread apply all @var{command}}.
2488 @kindex set print thread-events
2489 @cindex print messages on thread start and exit
2490 @item set print thread-events
2491 @itemx set print thread-events on
2492 @itemx set print thread-events off
2493 The @code{set print thread-events} command allows you to enable or
2494 disable printing of messages when @value{GDBN} notices that new threads have
2495 started or that threads have exited. By default, these messages will
2496 be printed if detection of these events is supported by the target.
2497 Note that these messages cannot be disabled on all targets.
2499 @kindex show print thread-events
2500 @item show print thread-events
2501 Show whether messages will be printed when @value{GDBN} detects that threads
2502 have started and exited.
2505 @cindex automatic thread selection
2506 @cindex switching threads automatically
2507 @cindex threads, automatic switching
2508 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2509 signal, it automatically selects the thread where that breakpoint or
2510 signal happened. @value{GDBN} alerts you to the context switch with a
2511 message of the form @samp{[Switching to @var{systag}]} to identify the
2514 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2515 more information about how @value{GDBN} behaves when you stop and start
2516 programs with multiple threads.
2518 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2519 watchpoints in programs with multiple threads.
2522 @section Debugging Programs with Multiple Processes
2524 @cindex fork, debugging programs which call
2525 @cindex multiple processes
2526 @cindex processes, multiple
2527 On most systems, @value{GDBN} has no special support for debugging
2528 programs which create additional processes using the @code{fork}
2529 function. When a program forks, @value{GDBN} will continue to debug the
2530 parent process and the child process will run unimpeded. If you have
2531 set a breakpoint in any code which the child then executes, the child
2532 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2533 will cause it to terminate.
2535 However, if you want to debug the child process there is a workaround
2536 which isn't too painful. Put a call to @code{sleep} in the code which
2537 the child process executes after the fork. It may be useful to sleep
2538 only if a certain environment variable is set, or a certain file exists,
2539 so that the delay need not occur when you don't want to run @value{GDBN}
2540 on the child. While the child is sleeping, use the @code{ps} program to
2541 get its process ID. Then tell @value{GDBN} (a new invocation of
2542 @value{GDBN} if you are also debugging the parent process) to attach to
2543 the child process (@pxref{Attach}). From that point on you can debug
2544 the child process just like any other process which you attached to.
2546 On some systems, @value{GDBN} provides support for debugging programs that
2547 create additional processes using the @code{fork} or @code{vfork} functions.
2548 Currently, the only platforms with this feature are HP-UX (11.x and later
2549 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2551 By default, when a program forks, @value{GDBN} will continue to debug
2552 the parent process and the child process will run unimpeded.
2554 If you want to follow the child process instead of the parent process,
2555 use the command @w{@code{set follow-fork-mode}}.
2558 @kindex set follow-fork-mode
2559 @item set follow-fork-mode @var{mode}
2560 Set the debugger response to a program call of @code{fork} or
2561 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2562 process. The @var{mode} argument can be:
2566 The original process is debugged after a fork. The child process runs
2567 unimpeded. This is the default.
2570 The new process is debugged after a fork. The parent process runs
2575 @kindex show follow-fork-mode
2576 @item show follow-fork-mode
2577 Display the current debugger response to a @code{fork} or @code{vfork} call.
2580 @cindex debugging multiple processes
2581 On Linux, if you want to debug both the parent and child processes, use the
2582 command @w{@code{set detach-on-fork}}.
2585 @kindex set detach-on-fork
2586 @item set detach-on-fork @var{mode}
2587 Tells gdb whether to detach one of the processes after a fork, or
2588 retain debugger control over them both.
2592 The child process (or parent process, depending on the value of
2593 @code{follow-fork-mode}) will be detached and allowed to run
2594 independently. This is the default.
2597 Both processes will be held under the control of @value{GDBN}.
2598 One process (child or parent, depending on the value of
2599 @code{follow-fork-mode}) is debugged as usual, while the other
2604 @kindex show detach-on-fork
2605 @item show detach-on-fork
2606 Show whether detach-on-fork mode is on/off.
2609 If you choose to set @samp{detach-on-fork} mode off, then
2610 @value{GDBN} will retain control of all forked processes (including
2611 nested forks). You can list the forked processes under the control of
2612 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2613 from one fork to another by using the @w{@code{fork}} command.
2618 Print a list of all forked processes under the control of @value{GDBN}.
2619 The listing will include a fork id, a process id, and the current
2620 position (program counter) of the process.
2622 @kindex fork @var{fork-id}
2623 @item fork @var{fork-id}
2624 Make fork number @var{fork-id} the current process. The argument
2625 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2626 as shown in the first field of the @samp{info forks} display.
2628 @kindex process @var{process-id}
2629 @item process @var{process-id}
2630 Make process number @var{process-id} the current process. The
2631 argument @var{process-id} must be one that is listed in the output of
2636 To quit debugging one of the forked processes, you can either detach
2637 from it by using the @w{@code{detach fork}} command (allowing it to
2638 run independently), or delete (and kill) it using the
2639 @w{@code{delete fork}} command.
2642 @kindex detach fork @var{fork-id}
2643 @item detach fork @var{fork-id}
2644 Detach from the process identified by @value{GDBN} fork number
2645 @var{fork-id}, and remove it from the fork list. The process will be
2646 allowed to run independently.
2648 @kindex delete fork @var{fork-id}
2649 @item delete fork @var{fork-id}
2650 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2651 and remove it from the fork list.
2655 If you ask to debug a child process and a @code{vfork} is followed by an
2656 @code{exec}, @value{GDBN} executes the new target up to the first
2657 breakpoint in the new target. If you have a breakpoint set on
2658 @code{main} in your original program, the breakpoint will also be set on
2659 the child process's @code{main}.
2661 When a child process is spawned by @code{vfork}, you cannot debug the
2662 child or parent until an @code{exec} call completes.
2664 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2665 call executes, the new target restarts. To restart the parent process,
2666 use the @code{file} command with the parent executable name as its
2669 You can use the @code{catch} command to make @value{GDBN} stop whenever
2670 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2671 Catchpoints, ,Setting Catchpoints}.
2673 @node Checkpoint/Restart
2674 @section Setting a @emph{Bookmark} to Return to Later
2679 @cindex snapshot of a process
2680 @cindex rewind program state
2682 On certain operating systems@footnote{Currently, only
2683 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2684 program's state, called a @dfn{checkpoint}, and come back to it
2687 Returning to a checkpoint effectively undoes everything that has
2688 happened in the program since the @code{checkpoint} was saved. This
2689 includes changes in memory, registers, and even (within some limits)
2690 system state. Effectively, it is like going back in time to the
2691 moment when the checkpoint was saved.
2693 Thus, if you're stepping thru a program and you think you're
2694 getting close to the point where things go wrong, you can save
2695 a checkpoint. Then, if you accidentally go too far and miss
2696 the critical statement, instead of having to restart your program
2697 from the beginning, you can just go back to the checkpoint and
2698 start again from there.
2700 This can be especially useful if it takes a lot of time or
2701 steps to reach the point where you think the bug occurs.
2703 To use the @code{checkpoint}/@code{restart} method of debugging:
2708 Save a snapshot of the debugged program's current execution state.
2709 The @code{checkpoint} command takes no arguments, but each checkpoint
2710 is assigned a small integer id, similar to a breakpoint id.
2712 @kindex info checkpoints
2713 @item info checkpoints
2714 List the checkpoints that have been saved in the current debugging
2715 session. For each checkpoint, the following information will be
2722 @item Source line, or label
2725 @kindex restart @var{checkpoint-id}
2726 @item restart @var{checkpoint-id}
2727 Restore the program state that was saved as checkpoint number
2728 @var{checkpoint-id}. All program variables, registers, stack frames
2729 etc.@: will be returned to the values that they had when the checkpoint
2730 was saved. In essence, gdb will ``wind back the clock'' to the point
2731 in time when the checkpoint was saved.
2733 Note that breakpoints, @value{GDBN} variables, command history etc.
2734 are not affected by restoring a checkpoint. In general, a checkpoint
2735 only restores things that reside in the program being debugged, not in
2738 @kindex delete checkpoint @var{checkpoint-id}
2739 @item delete checkpoint @var{checkpoint-id}
2740 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2744 Returning to a previously saved checkpoint will restore the user state
2745 of the program being debugged, plus a significant subset of the system
2746 (OS) state, including file pointers. It won't ``un-write'' data from
2747 a file, but it will rewind the file pointer to the previous location,
2748 so that the previously written data can be overwritten. For files
2749 opened in read mode, the pointer will also be restored so that the
2750 previously read data can be read again.
2752 Of course, characters that have been sent to a printer (or other
2753 external device) cannot be ``snatched back'', and characters received
2754 from eg.@: a serial device can be removed from internal program buffers,
2755 but they cannot be ``pushed back'' into the serial pipeline, ready to
2756 be received again. Similarly, the actual contents of files that have
2757 been changed cannot be restored (at this time).
2759 However, within those constraints, you actually can ``rewind'' your
2760 program to a previously saved point in time, and begin debugging it
2761 again --- and you can change the course of events so as to debug a
2762 different execution path this time.
2764 @cindex checkpoints and process id
2765 Finally, there is one bit of internal program state that will be
2766 different when you return to a checkpoint --- the program's process
2767 id. Each checkpoint will have a unique process id (or @var{pid}),
2768 and each will be different from the program's original @var{pid}.
2769 If your program has saved a local copy of its process id, this could
2770 potentially pose a problem.
2772 @subsection A Non-obvious Benefit of Using Checkpoints
2774 On some systems such as @sc{gnu}/Linux, address space randomization
2775 is performed on new processes for security reasons. This makes it
2776 difficult or impossible to set a breakpoint, or watchpoint, on an
2777 absolute address if you have to restart the program, since the
2778 absolute location of a symbol will change from one execution to the
2781 A checkpoint, however, is an @emph{identical} copy of a process.
2782 Therefore if you create a checkpoint at (eg.@:) the start of main,
2783 and simply return to that checkpoint instead of restarting the
2784 process, you can avoid the effects of address randomization and
2785 your symbols will all stay in the same place.
2788 @chapter Stopping and Continuing
2790 The principal purposes of using a debugger are so that you can stop your
2791 program before it terminates; or so that, if your program runs into
2792 trouble, you can investigate and find out why.
2794 Inside @value{GDBN}, your program may stop for any of several reasons,
2795 such as a signal, a breakpoint, or reaching a new line after a
2796 @value{GDBN} command such as @code{step}. You may then examine and
2797 change variables, set new breakpoints or remove old ones, and then
2798 continue execution. Usually, the messages shown by @value{GDBN} provide
2799 ample explanation of the status of your program---but you can also
2800 explicitly request this information at any time.
2803 @kindex info program
2805 Display information about the status of your program: whether it is
2806 running or not, what process it is, and why it stopped.
2810 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2811 * Continuing and Stepping:: Resuming execution
2813 * Thread Stops:: Stopping and starting multi-thread programs
2817 @section Breakpoints, Watchpoints, and Catchpoints
2820 A @dfn{breakpoint} makes your program stop whenever a certain point in
2821 the program is reached. For each breakpoint, you can add conditions to
2822 control in finer detail whether your program stops. You can set
2823 breakpoints with the @code{break} command and its variants (@pxref{Set
2824 Breaks, ,Setting Breakpoints}), to specify the place where your program
2825 should stop by line number, function name or exact address in the
2828 On some systems, you can set breakpoints in shared libraries before
2829 the executable is run. There is a minor limitation on HP-UX systems:
2830 you must wait until the executable is run in order to set breakpoints
2831 in shared library routines that are not called directly by the program
2832 (for example, routines that are arguments in a @code{pthread_create}
2836 @cindex data breakpoints
2837 @cindex memory tracing
2838 @cindex breakpoint on memory address
2839 @cindex breakpoint on variable modification
2840 A @dfn{watchpoint} is a special breakpoint that stops your program
2841 when the value of an expression changes. The expression may be a value
2842 of a variable, or it could involve values of one or more variables
2843 combined by operators, such as @samp{a + b}. This is sometimes called
2844 @dfn{data breakpoints}. You must use a different command to set
2845 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2846 from that, you can manage a watchpoint like any other breakpoint: you
2847 enable, disable, and delete both breakpoints and watchpoints using the
2850 You can arrange to have values from your program displayed automatically
2851 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2855 @cindex breakpoint on events
2856 A @dfn{catchpoint} is another special breakpoint that stops your program
2857 when a certain kind of event occurs, such as the throwing of a C@t{++}
2858 exception or the loading of a library. As with watchpoints, you use a
2859 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2860 Catchpoints}), but aside from that, you can manage a catchpoint like any
2861 other breakpoint. (To stop when your program receives a signal, use the
2862 @code{handle} command; see @ref{Signals, ,Signals}.)
2864 @cindex breakpoint numbers
2865 @cindex numbers for breakpoints
2866 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2867 catchpoint when you create it; these numbers are successive integers
2868 starting with one. In many of the commands for controlling various
2869 features of breakpoints you use the breakpoint number to say which
2870 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2871 @dfn{disabled}; if disabled, it has no effect on your program until you
2874 @cindex breakpoint ranges
2875 @cindex ranges of breakpoints
2876 Some @value{GDBN} commands accept a range of breakpoints on which to
2877 operate. A breakpoint range is either a single breakpoint number, like
2878 @samp{5}, or two such numbers, in increasing order, separated by a
2879 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2880 all breakpoints in that range are operated on.
2883 * Set Breaks:: Setting breakpoints
2884 * Set Watchpoints:: Setting watchpoints
2885 * Set Catchpoints:: Setting catchpoints
2886 * Delete Breaks:: Deleting breakpoints
2887 * Disabling:: Disabling breakpoints
2888 * Conditions:: Break conditions
2889 * Break Commands:: Breakpoint command lists
2890 * Error in Breakpoints:: ``Cannot insert breakpoints''
2891 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2895 @subsection Setting Breakpoints
2897 @c FIXME LMB what does GDB do if no code on line of breakpt?
2898 @c consider in particular declaration with/without initialization.
2900 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2903 @kindex b @r{(@code{break})}
2904 @vindex $bpnum@r{, convenience variable}
2905 @cindex latest breakpoint
2906 Breakpoints are set with the @code{break} command (abbreviated
2907 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2908 number of the breakpoint you've set most recently; see @ref{Convenience
2909 Vars,, Convenience Variables}, for a discussion of what you can do with
2910 convenience variables.
2913 @item break @var{location}
2914 Set a breakpoint at the given @var{location}, which can specify a
2915 function name, a line number, or an address of an instruction.
2916 (@xref{Specify Location}, for a list of all the possible ways to
2917 specify a @var{location}.) The breakpoint will stop your program just
2918 before it executes any of the code in the specified @var{location}.
2920 When using source languages that permit overloading of symbols, such as
2921 C@t{++}, a function name may refer to more than one possible place to break.
2922 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
2926 When called without any arguments, @code{break} sets a breakpoint at
2927 the next instruction to be executed in the selected stack frame
2928 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2929 innermost, this makes your program stop as soon as control
2930 returns to that frame. This is similar to the effect of a
2931 @code{finish} command in the frame inside the selected frame---except
2932 that @code{finish} does not leave an active breakpoint. If you use
2933 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2934 the next time it reaches the current location; this may be useful
2937 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2938 least one instruction has been executed. If it did not do this, you
2939 would be unable to proceed past a breakpoint without first disabling the
2940 breakpoint. This rule applies whether or not the breakpoint already
2941 existed when your program stopped.
2943 @item break @dots{} if @var{cond}
2944 Set a breakpoint with condition @var{cond}; evaluate the expression
2945 @var{cond} each time the breakpoint is reached, and stop only if the
2946 value is nonzero---that is, if @var{cond} evaluates as true.
2947 @samp{@dots{}} stands for one of the possible arguments described
2948 above (or no argument) specifying where to break. @xref{Conditions,
2949 ,Break Conditions}, for more information on breakpoint conditions.
2952 @item tbreak @var{args}
2953 Set a breakpoint enabled only for one stop. @var{args} are the
2954 same as for the @code{break} command, and the breakpoint is set in the same
2955 way, but the breakpoint is automatically deleted after the first time your
2956 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2959 @cindex hardware breakpoints
2960 @item hbreak @var{args}
2961 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2962 @code{break} command and the breakpoint is set in the same way, but the
2963 breakpoint requires hardware support and some target hardware may not
2964 have this support. The main purpose of this is EPROM/ROM code
2965 debugging, so you can set a breakpoint at an instruction without
2966 changing the instruction. This can be used with the new trap-generation
2967 provided by SPARClite DSU and most x86-based targets. These targets
2968 will generate traps when a program accesses some data or instruction
2969 address that is assigned to the debug registers. However the hardware
2970 breakpoint registers can take a limited number of breakpoints. For
2971 example, on the DSU, only two data breakpoints can be set at a time, and
2972 @value{GDBN} will reject this command if more than two are used. Delete
2973 or disable unused hardware breakpoints before setting new ones
2974 (@pxref{Disabling, ,Disabling Breakpoints}).
2975 @xref{Conditions, ,Break Conditions}.
2976 For remote targets, you can restrict the number of hardware
2977 breakpoints @value{GDBN} will use, see @ref{set remote
2978 hardware-breakpoint-limit}.
2981 @item thbreak @var{args}
2982 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2983 are the same as for the @code{hbreak} command and the breakpoint is set in
2984 the same way. However, like the @code{tbreak} command,
2985 the breakpoint is automatically deleted after the
2986 first time your program stops there. Also, like the @code{hbreak}
2987 command, the breakpoint requires hardware support and some target hardware
2988 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2989 See also @ref{Conditions, ,Break Conditions}.
2992 @cindex regular expression
2993 @cindex breakpoints in functions matching a regexp
2994 @cindex set breakpoints in many functions
2995 @item rbreak @var{regex}
2996 Set breakpoints on all functions matching the regular expression
2997 @var{regex}. This command sets an unconditional breakpoint on all
2998 matches, printing a list of all breakpoints it set. Once these
2999 breakpoints are set, they are treated just like the breakpoints set with
3000 the @code{break} command. You can delete them, disable them, or make
3001 them conditional the same way as any other breakpoint.
3003 The syntax of the regular expression is the standard one used with tools
3004 like @file{grep}. Note that this is different from the syntax used by
3005 shells, so for instance @code{foo*} matches all functions that include
3006 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3007 @code{.*} leading and trailing the regular expression you supply, so to
3008 match only functions that begin with @code{foo}, use @code{^foo}.
3010 @cindex non-member C@t{++} functions, set breakpoint in
3011 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3012 breakpoints on overloaded functions that are not members of any special
3015 @cindex set breakpoints on all functions
3016 The @code{rbreak} command can be used to set breakpoints in
3017 @strong{all} the functions in a program, like this:
3020 (@value{GDBP}) rbreak .
3023 @kindex info breakpoints
3024 @cindex @code{$_} and @code{info breakpoints}
3025 @item info breakpoints @r{[}@var{n}@r{]}
3026 @itemx info break @r{[}@var{n}@r{]}
3027 @itemx info watchpoints @r{[}@var{n}@r{]}
3028 Print a table of all breakpoints, watchpoints, and catchpoints set and
3029 not deleted. Optional argument @var{n} means print information only
3030 about the specified breakpoint (or watchpoint or catchpoint). For
3031 each breakpoint, following columns are printed:
3034 @item Breakpoint Numbers
3036 Breakpoint, watchpoint, or catchpoint.
3038 Whether the breakpoint is marked to be disabled or deleted when hit.
3039 @item Enabled or Disabled
3040 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3041 that are not enabled.
3043 Where the breakpoint is in your program, as a memory address. For a
3044 pending breakpoint whose address is not yet known, this field will
3045 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3046 library that has the symbol or line referred by breakpoint is loaded.
3047 See below for details. A breakpoint with several locations will
3048 have @samp{<MULTIPLE>} in this field---see below for details.
3050 Where the breakpoint is in the source for your program, as a file and
3051 line number. For a pending breakpoint, the original string passed to
3052 the breakpoint command will be listed as it cannot be resolved until
3053 the appropriate shared library is loaded in the future.
3057 If a breakpoint is conditional, @code{info break} shows the condition on
3058 the line following the affected breakpoint; breakpoint commands, if any,
3059 are listed after that. A pending breakpoint is allowed to have a condition
3060 specified for it. The condition is not parsed for validity until a shared
3061 library is loaded that allows the pending breakpoint to resolve to a
3065 @code{info break} with a breakpoint
3066 number @var{n} as argument lists only that breakpoint. The
3067 convenience variable @code{$_} and the default examining-address for
3068 the @code{x} command are set to the address of the last breakpoint
3069 listed (@pxref{Memory, ,Examining Memory}).
3072 @code{info break} displays a count of the number of times the breakpoint
3073 has been hit. This is especially useful in conjunction with the
3074 @code{ignore} command. You can ignore a large number of breakpoint
3075 hits, look at the breakpoint info to see how many times the breakpoint
3076 was hit, and then run again, ignoring one less than that number. This
3077 will get you quickly to the last hit of that breakpoint.
3080 @value{GDBN} allows you to set any number of breakpoints at the same place in
3081 your program. There is nothing silly or meaningless about this. When
3082 the breakpoints are conditional, this is even useful
3083 (@pxref{Conditions, ,Break Conditions}).
3085 @cindex multiple locations, breakpoints
3086 @cindex breakpoints, multiple locations
3087 It is possible that a breakpoint corresponds to several locations
3088 in your program. Examples of this situation are:
3092 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3093 instances of the function body, used in different cases.
3096 For a C@t{++} template function, a given line in the function can
3097 correspond to any number of instantiations.
3100 For an inlined function, a given source line can correspond to
3101 several places where that function is inlined.
3104 In all those cases, @value{GDBN} will insert a breakpoint at all
3105 the relevant locations@footnote{
3106 As of this writing, multiple-location breakpoints work only if there's
3107 line number information for all the locations. This means that they
3108 will generally not work in system libraries, unless you have debug
3109 info with line numbers for them.}.
3111 A breakpoint with multiple locations is displayed in the breakpoint
3112 table using several rows---one header row, followed by one row for
3113 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3114 address column. The rows for individual locations contain the actual
3115 addresses for locations, and show the functions to which those
3116 locations belong. The number column for a location is of the form
3117 @var{breakpoint-number}.@var{location-number}.
3122 Num Type Disp Enb Address What
3123 1 breakpoint keep y <MULTIPLE>
3125 breakpoint already hit 1 time
3126 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3127 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3130 Each location can be individually enabled or disabled by passing
3131 @var{breakpoint-number}.@var{location-number} as argument to the
3132 @code{enable} and @code{disable} commands. Note that you cannot
3133 delete the individual locations from the list, you can only delete the
3134 entire list of locations that belong to their parent breakpoint (with
3135 the @kbd{delete @var{num}} command, where @var{num} is the number of
3136 the parent breakpoint, 1 in the above example). Disabling or enabling
3137 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3138 that belong to that breakpoint.
3140 @cindex pending breakpoints
3141 It's quite common to have a breakpoint inside a shared library.
3142 Shared libraries can be loaded and unloaded explicitly,
3143 and possibly repeatedly, as the program is executed. To support
3144 this use case, @value{GDBN} updates breakpoint locations whenever
3145 any shared library is loaded or unloaded. Typically, you would
3146 set a breakpoint in a shared library at the beginning of your
3147 debugging session, when the library is not loaded, and when the
3148 symbols from the library are not available. When you try to set
3149 breakpoint, @value{GDBN} will ask you if you want to set
3150 a so called @dfn{pending breakpoint}---breakpoint whose address
3151 is not yet resolved.
3153 After the program is run, whenever a new shared library is loaded,
3154 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3155 shared library contains the symbol or line referred to by some
3156 pending breakpoint, that breakpoint is resolved and becomes an
3157 ordinary breakpoint. When a library is unloaded, all breakpoints
3158 that refer to its symbols or source lines become pending again.
3160 This logic works for breakpoints with multiple locations, too. For
3161 example, if you have a breakpoint in a C@t{++} template function, and
3162 a newly loaded shared library has an instantiation of that template,
3163 a new location is added to the list of locations for the breakpoint.
3165 Except for having unresolved address, pending breakpoints do not
3166 differ from regular breakpoints. You can set conditions or commands,
3167 enable and disable them and perform other breakpoint operations.
3169 @value{GDBN} provides some additional commands for controlling what
3170 happens when the @samp{break} command cannot resolve breakpoint
3171 address specification to an address:
3173 @kindex set breakpoint pending
3174 @kindex show breakpoint pending
3176 @item set breakpoint pending auto
3177 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3178 location, it queries you whether a pending breakpoint should be created.
3180 @item set breakpoint pending on
3181 This indicates that an unrecognized breakpoint location should automatically
3182 result in a pending breakpoint being created.
3184 @item set breakpoint pending off
3185 This indicates that pending breakpoints are not to be created. Any
3186 unrecognized breakpoint location results in an error. This setting does
3187 not affect any pending breakpoints previously created.
3189 @item show breakpoint pending
3190 Show the current behavior setting for creating pending breakpoints.
3193 The settings above only affect the @code{break} command and its
3194 variants. Once breakpoint is set, it will be automatically updated
3195 as shared libraries are loaded and unloaded.
3197 @cindex automatic hardware breakpoints
3198 For some targets, @value{GDBN} can automatically decide if hardware or
3199 software breakpoints should be used, depending on whether the
3200 breakpoint address is read-only or read-write. This applies to
3201 breakpoints set with the @code{break} command as well as to internal
3202 breakpoints set by commands like @code{next} and @code{finish}. For
3203 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3206 You can control this automatic behaviour with the following commands::
3208 @kindex set breakpoint auto-hw
3209 @kindex show breakpoint auto-hw
3211 @item set breakpoint auto-hw on
3212 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3213 will try to use the target memory map to decide if software or hardware
3214 breakpoint must be used.
3216 @item set breakpoint auto-hw off
3217 This indicates @value{GDBN} should not automatically select breakpoint
3218 type. If the target provides a memory map, @value{GDBN} will warn when
3219 trying to set software breakpoint at a read-only address.
3222 @value{GDBN} normally implements breakpoints by replacing the program code
3223 at the breakpoint address with a special instruction, which, when
3224 executed, given control to the debugger. By default, the program
3225 code is so modified only when the program is resumed. As soon as
3226 the program stops, @value{GDBN} restores the original instructions. This
3227 behaviour guards against leaving breakpoints inserted in the
3228 target should gdb abrubptly disconnect. However, with slow remote
3229 targets, inserting and removing breakpoint can reduce the performance.
3230 This behavior can be controlled with the following commands::
3232 @kindex set breakpoint always-inserted
3233 @kindex show breakpoint always-inserted
3235 @item set breakpoint always-inserted off
3236 This is the default behaviour. All breakpoints, including newly added
3237 by the user, are inserted in the target only when the target is
3238 resumed. All breakpoints are removed from the target when it stops.
3240 @item set breakpoint always-inserted on
3241 Causes all breakpoints to be inserted in the target at all times. If
3242 the user adds a new breakpoint, or changes an existing breakpoint, the
3243 breakpoints in the target are updated immediately. A breakpoint is
3244 removed from the target only when breakpoint itself is removed.
3247 @cindex negative breakpoint numbers
3248 @cindex internal @value{GDBN} breakpoints
3249 @value{GDBN} itself sometimes sets breakpoints in your program for
3250 special purposes, such as proper handling of @code{longjmp} (in C
3251 programs). These internal breakpoints are assigned negative numbers,
3252 starting with @code{-1}; @samp{info breakpoints} does not display them.
3253 You can see these breakpoints with the @value{GDBN} maintenance command
3254 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3257 @node Set Watchpoints
3258 @subsection Setting Watchpoints
3260 @cindex setting watchpoints
3261 You can use a watchpoint to stop execution whenever the value of an
3262 expression changes, without having to predict a particular place where
3263 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3264 The expression may be as simple as the value of a single variable, or
3265 as complex as many variables combined by operators. Examples include:
3269 A reference to the value of a single variable.
3272 An address cast to an appropriate data type. For example,
3273 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3274 address (assuming an @code{int} occupies 4 bytes).
3277 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3278 expression can use any operators valid in the program's native
3279 language (@pxref{Languages}).
3282 You can set a watchpoint on an expression even if the expression can
3283 not be evaluated yet. For instance, you can set a watchpoint on
3284 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3285 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3286 the expression produces a valid value. If the expression becomes
3287 valid in some other way than changing a variable (e.g.@: if the memory
3288 pointed to by @samp{*global_ptr} becomes readable as the result of a
3289 @code{malloc} call), @value{GDBN} may not stop until the next time
3290 the expression changes.
3292 @cindex software watchpoints
3293 @cindex hardware watchpoints
3294 Depending on your system, watchpoints may be implemented in software or
3295 hardware. @value{GDBN} does software watchpointing by single-stepping your
3296 program and testing the variable's value each time, which is hundreds of
3297 times slower than normal execution. (But this may still be worth it, to
3298 catch errors where you have no clue what part of your program is the
3301 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3302 x86-based targets, @value{GDBN} includes support for hardware
3303 watchpoints, which do not slow down the running of your program.
3307 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3308 Set a watchpoint for an expression. @value{GDBN} will break when the
3309 expression @var{expr} is written into by the program and its value
3310 changes. The simplest (and the most popular) use of this command is
3311 to watch the value of a single variable:
3314 (@value{GDBP}) watch foo
3317 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3318 clause, @value{GDBN} breaks only when the thread identified by
3319 @var{threadnum} changes the value of @var{expr}. If any other threads
3320 change the value of @var{expr}, @value{GDBN} will not break. Note
3321 that watchpoints restricted to a single thread in this way only work
3322 with Hardware Watchpoints.
3325 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3326 Set a watchpoint that will break when the value of @var{expr} is read
3330 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3331 Set a watchpoint that will break when @var{expr} is either read from
3332 or written into by the program.
3334 @kindex info watchpoints @r{[}@var{n}@r{]}
3335 @item info watchpoints
3336 This command prints a list of watchpoints, breakpoints, and catchpoints;
3337 it is the same as @code{info break} (@pxref{Set Breaks}).
3340 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3341 watchpoints execute very quickly, and the debugger reports a change in
3342 value at the exact instruction where the change occurs. If @value{GDBN}
3343 cannot set a hardware watchpoint, it sets a software watchpoint, which
3344 executes more slowly and reports the change in value at the next
3345 @emph{statement}, not the instruction, after the change occurs.
3347 @cindex use only software watchpoints
3348 You can force @value{GDBN} to use only software watchpoints with the
3349 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3350 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3351 the underlying system supports them. (Note that hardware-assisted
3352 watchpoints that were set @emph{before} setting
3353 @code{can-use-hw-watchpoints} to zero will still use the hardware
3354 mechanism of watching expression values.)
3357 @item set can-use-hw-watchpoints
3358 @kindex set can-use-hw-watchpoints
3359 Set whether or not to use hardware watchpoints.
3361 @item show can-use-hw-watchpoints
3362 @kindex show can-use-hw-watchpoints
3363 Show the current mode of using hardware watchpoints.
3366 For remote targets, you can restrict the number of hardware
3367 watchpoints @value{GDBN} will use, see @ref{set remote
3368 hardware-breakpoint-limit}.
3370 When you issue the @code{watch} command, @value{GDBN} reports
3373 Hardware watchpoint @var{num}: @var{expr}
3377 if it was able to set a hardware watchpoint.
3379 Currently, the @code{awatch} and @code{rwatch} commands can only set
3380 hardware watchpoints, because accesses to data that don't change the
3381 value of the watched expression cannot be detected without examining
3382 every instruction as it is being executed, and @value{GDBN} does not do
3383 that currently. If @value{GDBN} finds that it is unable to set a
3384 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3385 will print a message like this:
3388 Expression cannot be implemented with read/access watchpoint.
3391 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3392 data type of the watched expression is wider than what a hardware
3393 watchpoint on the target machine can handle. For example, some systems
3394 can only watch regions that are up to 4 bytes wide; on such systems you
3395 cannot set hardware watchpoints for an expression that yields a
3396 double-precision floating-point number (which is typically 8 bytes
3397 wide). As a work-around, it might be possible to break the large region
3398 into a series of smaller ones and watch them with separate watchpoints.
3400 If you set too many hardware watchpoints, @value{GDBN} might be unable
3401 to insert all of them when you resume the execution of your program.
3402 Since the precise number of active watchpoints is unknown until such
3403 time as the program is about to be resumed, @value{GDBN} might not be
3404 able to warn you about this when you set the watchpoints, and the
3405 warning will be printed only when the program is resumed:
3408 Hardware watchpoint @var{num}: Could not insert watchpoint
3412 If this happens, delete or disable some of the watchpoints.
3414 Watching complex expressions that reference many variables can also
3415 exhaust the resources available for hardware-assisted watchpoints.
3416 That's because @value{GDBN} needs to watch every variable in the
3417 expression with separately allocated resources.
3419 If you call a function interactively using @code{print} or @code{call},
3420 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3421 kind of breakpoint or the call completes.
3423 @value{GDBN} automatically deletes watchpoints that watch local
3424 (automatic) variables, or expressions that involve such variables, when
3425 they go out of scope, that is, when the execution leaves the block in
3426 which these variables were defined. In particular, when the program
3427 being debugged terminates, @emph{all} local variables go out of scope,
3428 and so only watchpoints that watch global variables remain set. If you
3429 rerun the program, you will need to set all such watchpoints again. One
3430 way of doing that would be to set a code breakpoint at the entry to the
3431 @code{main} function and when it breaks, set all the watchpoints.
3433 @cindex watchpoints and threads
3434 @cindex threads and watchpoints
3435 In multi-threaded programs, watchpoints will detect changes to the
3436 watched expression from every thread.
3439 @emph{Warning:} In multi-threaded programs, software watchpoints
3440 have only limited usefulness. If @value{GDBN} creates a software
3441 watchpoint, it can only watch the value of an expression @emph{in a
3442 single thread}. If you are confident that the expression can only
3443 change due to the current thread's activity (and if you are also
3444 confident that no other thread can become current), then you can use
3445 software watchpoints as usual. However, @value{GDBN} may not notice
3446 when a non-current thread's activity changes the expression. (Hardware
3447 watchpoints, in contrast, watch an expression in all threads.)
3450 @xref{set remote hardware-watchpoint-limit}.
3452 @node Set Catchpoints
3453 @subsection Setting Catchpoints
3454 @cindex catchpoints, setting
3455 @cindex exception handlers
3456 @cindex event handling
3458 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3459 kinds of program events, such as C@t{++} exceptions or the loading of a
3460 shared library. Use the @code{catch} command to set a catchpoint.
3464 @item catch @var{event}
3465 Stop when @var{event} occurs. @var{event} can be any of the following:
3468 @cindex stop on C@t{++} exceptions
3469 The throwing of a C@t{++} exception.
3472 The catching of a C@t{++} exception.
3475 @cindex Ada exception catching
3476 @cindex catch Ada exceptions
3477 An Ada exception being raised. If an exception name is specified
3478 at the end of the command (eg @code{catch exception Program_Error}),
3479 the debugger will stop only when this specific exception is raised.
3480 Otherwise, the debugger stops execution when any Ada exception is raised.
3482 @item exception unhandled
3483 An exception that was raised but is not handled by the program.
3486 A failed Ada assertion.
3489 @cindex break on fork/exec
3490 A call to @code{exec}. This is currently only available for HP-UX
3494 A call to @code{fork}. This is currently only available for HP-UX
3498 A call to @code{vfork}. This is currently only available for HP-UX
3502 @itemx load @var{libname}
3503 @cindex break on load/unload of shared library
3504 The dynamic loading of any shared library, or the loading of the library
3505 @var{libname}. This is currently only available for HP-UX.
3508 @itemx unload @var{libname}
3509 The unloading of any dynamically loaded shared library, or the unloading
3510 of the library @var{libname}. This is currently only available for HP-UX.
3513 @item tcatch @var{event}
3514 Set a catchpoint that is enabled only for one stop. The catchpoint is
3515 automatically deleted after the first time the event is caught.
3519 Use the @code{info break} command to list the current catchpoints.
3521 There are currently some limitations to C@t{++} exception handling
3522 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3526 If you call a function interactively, @value{GDBN} normally returns
3527 control to you when the function has finished executing. If the call
3528 raises an exception, however, the call may bypass the mechanism that
3529 returns control to you and cause your program either to abort or to
3530 simply continue running until it hits a breakpoint, catches a signal
3531 that @value{GDBN} is listening for, or exits. This is the case even if
3532 you set a catchpoint for the exception; catchpoints on exceptions are
3533 disabled within interactive calls.
3536 You cannot raise an exception interactively.
3539 You cannot install an exception handler interactively.
3542 @cindex raise exceptions
3543 Sometimes @code{catch} is not the best way to debug exception handling:
3544 if you need to know exactly where an exception is raised, it is better to
3545 stop @emph{before} the exception handler is called, since that way you
3546 can see the stack before any unwinding takes place. If you set a
3547 breakpoint in an exception handler instead, it may not be easy to find
3548 out where the exception was raised.
3550 To stop just before an exception handler is called, you need some
3551 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3552 raised by calling a library function named @code{__raise_exception}
3553 which has the following ANSI C interface:
3556 /* @var{addr} is where the exception identifier is stored.
3557 @var{id} is the exception identifier. */
3558 void __raise_exception (void **addr, void *id);
3562 To make the debugger catch all exceptions before any stack
3563 unwinding takes place, set a breakpoint on @code{__raise_exception}
3564 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3566 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3567 that depends on the value of @var{id}, you can stop your program when
3568 a specific exception is raised. You can use multiple conditional
3569 breakpoints to stop your program when any of a number of exceptions are
3574 @subsection Deleting Breakpoints
3576 @cindex clearing breakpoints, watchpoints, catchpoints
3577 @cindex deleting breakpoints, watchpoints, catchpoints
3578 It is often necessary to eliminate a breakpoint, watchpoint, or
3579 catchpoint once it has done its job and you no longer want your program
3580 to stop there. This is called @dfn{deleting} the breakpoint. A
3581 breakpoint that has been deleted no longer exists; it is forgotten.
3583 With the @code{clear} command you can delete breakpoints according to
3584 where they are in your program. With the @code{delete} command you can
3585 delete individual breakpoints, watchpoints, or catchpoints by specifying
3586 their breakpoint numbers.
3588 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3589 automatically ignores breakpoints on the first instruction to be executed
3590 when you continue execution without changing the execution address.
3595 Delete any breakpoints at the next instruction to be executed in the
3596 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3597 the innermost frame is selected, this is a good way to delete a
3598 breakpoint where your program just stopped.
3600 @item clear @var{location}
3601 Delete any breakpoints set at the specified @var{location}.
3602 @xref{Specify Location}, for the various forms of @var{location}; the
3603 most useful ones are listed below:
3606 @item clear @var{function}
3607 @itemx clear @var{filename}:@var{function}
3608 Delete any breakpoints set at entry to the named @var{function}.
3610 @item clear @var{linenum}
3611 @itemx clear @var{filename}:@var{linenum}
3612 Delete any breakpoints set at or within the code of the specified
3613 @var{linenum} of the specified @var{filename}.
3616 @cindex delete breakpoints
3618 @kindex d @r{(@code{delete})}
3619 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3620 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3621 ranges specified as arguments. If no argument is specified, delete all
3622 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3623 confirm off}). You can abbreviate this command as @code{d}.
3627 @subsection Disabling Breakpoints
3629 @cindex enable/disable a breakpoint
3630 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3631 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3632 it had been deleted, but remembers the information on the breakpoint so
3633 that you can @dfn{enable} it again later.
3635 You disable and enable breakpoints, watchpoints, and catchpoints with
3636 the @code{enable} and @code{disable} commands, optionally specifying one
3637 or more breakpoint numbers as arguments. Use @code{info break} or
3638 @code{info watch} to print a list of breakpoints, watchpoints, and
3639 catchpoints if you do not know which numbers to use.
3641 Disabling and enabling a breakpoint that has multiple locations
3642 affects all of its locations.
3644 A breakpoint, watchpoint, or catchpoint can have any of four different
3645 states of enablement:
3649 Enabled. The breakpoint stops your program. A breakpoint set
3650 with the @code{break} command starts out in this state.
3652 Disabled. The breakpoint has no effect on your program.
3654 Enabled once. The breakpoint stops your program, but then becomes
3657 Enabled for deletion. The breakpoint stops your program, but
3658 immediately after it does so it is deleted permanently. A breakpoint
3659 set with the @code{tbreak} command starts out in this state.
3662 You can use the following commands to enable or disable breakpoints,
3663 watchpoints, and catchpoints:
3667 @kindex dis @r{(@code{disable})}
3668 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3669 Disable the specified breakpoints---or all breakpoints, if none are
3670 listed. A disabled breakpoint has no effect but is not forgotten. All
3671 options such as ignore-counts, conditions and commands are remembered in
3672 case the breakpoint is enabled again later. You may abbreviate
3673 @code{disable} as @code{dis}.
3676 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3677 Enable the specified breakpoints (or all defined breakpoints). They
3678 become effective once again in stopping your program.
3680 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3681 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3682 of these breakpoints immediately after stopping your program.
3684 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3685 Enable the specified breakpoints to work once, then die. @value{GDBN}
3686 deletes any of these breakpoints as soon as your program stops there.
3687 Breakpoints set by the @code{tbreak} command start out in this state.
3690 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3691 @c confusing: tbreak is also initially enabled.
3692 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3693 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3694 subsequently, they become disabled or enabled only when you use one of
3695 the commands above. (The command @code{until} can set and delete a
3696 breakpoint of its own, but it does not change the state of your other
3697 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3701 @subsection Break Conditions
3702 @cindex conditional breakpoints
3703 @cindex breakpoint conditions
3705 @c FIXME what is scope of break condition expr? Context where wanted?
3706 @c in particular for a watchpoint?
3707 The simplest sort of breakpoint breaks every time your program reaches a
3708 specified place. You can also specify a @dfn{condition} for a
3709 breakpoint. A condition is just a Boolean expression in your
3710 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3711 a condition evaluates the expression each time your program reaches it,
3712 and your program stops only if the condition is @emph{true}.
3714 This is the converse of using assertions for program validation; in that
3715 situation, you want to stop when the assertion is violated---that is,
3716 when the condition is false. In C, if you want to test an assertion expressed
3717 by the condition @var{assert}, you should set the condition
3718 @samp{! @var{assert}} on the appropriate breakpoint.
3720 Conditions are also accepted for watchpoints; you may not need them,
3721 since a watchpoint is inspecting the value of an expression anyhow---but
3722 it might be simpler, say, to just set a watchpoint on a variable name,
3723 and specify a condition that tests whether the new value is an interesting
3726 Break conditions can have side effects, and may even call functions in
3727 your program. This can be useful, for example, to activate functions
3728 that log program progress, or to use your own print functions to
3729 format special data structures. The effects are completely predictable
3730 unless there is another enabled breakpoint at the same address. (In
3731 that case, @value{GDBN} might see the other breakpoint first and stop your
3732 program without checking the condition of this one.) Note that
3733 breakpoint commands are usually more convenient and flexible than break
3735 purpose of performing side effects when a breakpoint is reached
3736 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3738 Break conditions can be specified when a breakpoint is set, by using
3739 @samp{if} in the arguments to the @code{break} command. @xref{Set
3740 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3741 with the @code{condition} command.
3743 You can also use the @code{if} keyword with the @code{watch} command.
3744 The @code{catch} command does not recognize the @code{if} keyword;
3745 @code{condition} is the only way to impose a further condition on a
3750 @item condition @var{bnum} @var{expression}
3751 Specify @var{expression} as the break condition for breakpoint,
3752 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3753 breakpoint @var{bnum} stops your program only if the value of
3754 @var{expression} is true (nonzero, in C). When you use
3755 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3756 syntactic correctness, and to determine whether symbols in it have
3757 referents in the context of your breakpoint. If @var{expression} uses
3758 symbols not referenced in the context of the breakpoint, @value{GDBN}
3759 prints an error message:
3762 No symbol "foo" in current context.
3767 not actually evaluate @var{expression} at the time the @code{condition}
3768 command (or a command that sets a breakpoint with a condition, like
3769 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3771 @item condition @var{bnum}
3772 Remove the condition from breakpoint number @var{bnum}. It becomes
3773 an ordinary unconditional breakpoint.
3776 @cindex ignore count (of breakpoint)
3777 A special case of a breakpoint condition is to stop only when the
3778 breakpoint has been reached a certain number of times. This is so
3779 useful that there is a special way to do it, using the @dfn{ignore
3780 count} of the breakpoint. Every breakpoint has an ignore count, which
3781 is an integer. Most of the time, the ignore count is zero, and
3782 therefore has no effect. But if your program reaches a breakpoint whose
3783 ignore count is positive, then instead of stopping, it just decrements
3784 the ignore count by one and continues. As a result, if the ignore count
3785 value is @var{n}, the breakpoint does not stop the next @var{n} times
3786 your program reaches it.
3790 @item ignore @var{bnum} @var{count}
3791 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3792 The next @var{count} times the breakpoint is reached, your program's
3793 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3796 To make the breakpoint stop the next time it is reached, specify
3799 When you use @code{continue} to resume execution of your program from a
3800 breakpoint, you can specify an ignore count directly as an argument to
3801 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3802 Stepping,,Continuing and Stepping}.
3804 If a breakpoint has a positive ignore count and a condition, the
3805 condition is not checked. Once the ignore count reaches zero,
3806 @value{GDBN} resumes checking the condition.
3808 You could achieve the effect of the ignore count with a condition such
3809 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3810 is decremented each time. @xref{Convenience Vars, ,Convenience
3814 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3817 @node Break Commands
3818 @subsection Breakpoint Command Lists
3820 @cindex breakpoint commands
3821 You can give any breakpoint (or watchpoint or catchpoint) a series of
3822 commands to execute when your program stops due to that breakpoint. For
3823 example, you might want to print the values of certain expressions, or
3824 enable other breakpoints.
3828 @kindex end@r{ (breakpoint commands)}
3829 @item commands @r{[}@var{bnum}@r{]}
3830 @itemx @dots{} @var{command-list} @dots{}
3832 Specify a list of commands for breakpoint number @var{bnum}. The commands
3833 themselves appear on the following lines. Type a line containing just
3834 @code{end} to terminate the commands.
3836 To remove all commands from a breakpoint, type @code{commands} and
3837 follow it immediately with @code{end}; that is, give no commands.
3839 With no @var{bnum} argument, @code{commands} refers to the last
3840 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3841 recently encountered).
3844 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3845 disabled within a @var{command-list}.
3847 You can use breakpoint commands to start your program up again. Simply
3848 use the @code{continue} command, or @code{step}, or any other command
3849 that resumes execution.
3851 Any other commands in the command list, after a command that resumes
3852 execution, are ignored. This is because any time you resume execution
3853 (even with a simple @code{next} or @code{step}), you may encounter
3854 another breakpoint---which could have its own command list, leading to
3855 ambiguities about which list to execute.
3858 If the first command you specify in a command list is @code{silent}, the
3859 usual message about stopping at a breakpoint is not printed. This may
3860 be desirable for breakpoints that are to print a specific message and
3861 then continue. If none of the remaining commands print anything, you
3862 see no sign that the breakpoint was reached. @code{silent} is
3863 meaningful only at the beginning of a breakpoint command list.
3865 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3866 print precisely controlled output, and are often useful in silent
3867 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3869 For example, here is how you could use breakpoint commands to print the
3870 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3876 printf "x is %d\n",x
3881 One application for breakpoint commands is to compensate for one bug so
3882 you can test for another. Put a breakpoint just after the erroneous line
3883 of code, give it a condition to detect the case in which something
3884 erroneous has been done, and give it commands to assign correct values
3885 to any variables that need them. End with the @code{continue} command
3886 so that your program does not stop, and start with the @code{silent}
3887 command so that no output is produced. Here is an example:
3898 @c @ifclear BARETARGET
3899 @node Error in Breakpoints
3900 @subsection ``Cannot insert breakpoints''
3902 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3904 Under some operating systems, breakpoints cannot be used in a program if
3905 any other process is running that program. In this situation,
3906 attempting to run or continue a program with a breakpoint causes
3907 @value{GDBN} to print an error message:
3910 Cannot insert breakpoints.
3911 The same program may be running in another process.
3914 When this happens, you have three ways to proceed:
3918 Remove or disable the breakpoints, then continue.
3921 Suspend @value{GDBN}, and copy the file containing your program to a new
3922 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3923 that @value{GDBN} should run your program under that name.
3924 Then start your program again.
3927 Relink your program so that the text segment is nonsharable, using the
3928 linker option @samp{-N}. The operating system limitation may not apply
3929 to nonsharable executables.
3933 A similar message can be printed if you request too many active
3934 hardware-assisted breakpoints and watchpoints:
3936 @c FIXME: the precise wording of this message may change; the relevant
3937 @c source change is not committed yet (Sep 3, 1999).
3939 Stopped; cannot insert breakpoints.
3940 You may have requested too many hardware breakpoints and watchpoints.
3944 This message is printed when you attempt to resume the program, since
3945 only then @value{GDBN} knows exactly how many hardware breakpoints and
3946 watchpoints it needs to insert.
3948 When this message is printed, you need to disable or remove some of the
3949 hardware-assisted breakpoints and watchpoints, and then continue.
3951 @node Breakpoint-related Warnings
3952 @subsection ``Breakpoint address adjusted...''
3953 @cindex breakpoint address adjusted
3955 Some processor architectures place constraints on the addresses at
3956 which breakpoints may be placed. For architectures thus constrained,
3957 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3958 with the constraints dictated by the architecture.
3960 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3961 a VLIW architecture in which a number of RISC-like instructions may be
3962 bundled together for parallel execution. The FR-V architecture
3963 constrains the location of a breakpoint instruction within such a
3964 bundle to the instruction with the lowest address. @value{GDBN}
3965 honors this constraint by adjusting a breakpoint's address to the
3966 first in the bundle.
3968 It is not uncommon for optimized code to have bundles which contain
3969 instructions from different source statements, thus it may happen that
3970 a breakpoint's address will be adjusted from one source statement to
3971 another. Since this adjustment may significantly alter @value{GDBN}'s
3972 breakpoint related behavior from what the user expects, a warning is
3973 printed when the breakpoint is first set and also when the breakpoint
3976 A warning like the one below is printed when setting a breakpoint
3977 that's been subject to address adjustment:
3980 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3983 Such warnings are printed both for user settable and @value{GDBN}'s
3984 internal breakpoints. If you see one of these warnings, you should
3985 verify that a breakpoint set at the adjusted address will have the
3986 desired affect. If not, the breakpoint in question may be removed and
3987 other breakpoints may be set which will have the desired behavior.
3988 E.g., it may be sufficient to place the breakpoint at a later
3989 instruction. A conditional breakpoint may also be useful in some
3990 cases to prevent the breakpoint from triggering too often.
3992 @value{GDBN} will also issue a warning when stopping at one of these
3993 adjusted breakpoints:
3996 warning: Breakpoint 1 address previously adjusted from 0x00010414
4000 When this warning is encountered, it may be too late to take remedial
4001 action except in cases where the breakpoint is hit earlier or more
4002 frequently than expected.
4004 @node Continuing and Stepping
4005 @section Continuing and Stepping
4009 @cindex resuming execution
4010 @dfn{Continuing} means resuming program execution until your program
4011 completes normally. In contrast, @dfn{stepping} means executing just
4012 one more ``step'' of your program, where ``step'' may mean either one
4013 line of source code, or one machine instruction (depending on what
4014 particular command you use). Either when continuing or when stepping,
4015 your program may stop even sooner, due to a breakpoint or a signal. (If
4016 it stops due to a signal, you may want to use @code{handle}, or use
4017 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4021 @kindex c @r{(@code{continue})}
4022 @kindex fg @r{(resume foreground execution)}
4023 @item continue @r{[}@var{ignore-count}@r{]}
4024 @itemx c @r{[}@var{ignore-count}@r{]}
4025 @itemx fg @r{[}@var{ignore-count}@r{]}
4026 Resume program execution, at the address where your program last stopped;
4027 any breakpoints set at that address are bypassed. The optional argument
4028 @var{ignore-count} allows you to specify a further number of times to
4029 ignore a breakpoint at this location; its effect is like that of
4030 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4032 The argument @var{ignore-count} is meaningful only when your program
4033 stopped due to a breakpoint. At other times, the argument to
4034 @code{continue} is ignored.
4036 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4037 debugged program is deemed to be the foreground program) are provided
4038 purely for convenience, and have exactly the same behavior as
4042 To resume execution at a different place, you can use @code{return}
4043 (@pxref{Returning, ,Returning from a Function}) to go back to the
4044 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4045 Different Address}) to go to an arbitrary location in your program.
4047 A typical technique for using stepping is to set a breakpoint
4048 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4049 beginning of the function or the section of your program where a problem
4050 is believed to lie, run your program until it stops at that breakpoint,
4051 and then step through the suspect area, examining the variables that are
4052 interesting, until you see the problem happen.
4056 @kindex s @r{(@code{step})}
4058 Continue running your program until control reaches a different source
4059 line, then stop it and return control to @value{GDBN}. This command is
4060 abbreviated @code{s}.
4063 @c "without debugging information" is imprecise; actually "without line
4064 @c numbers in the debugging information". (gcc -g1 has debugging info but
4065 @c not line numbers). But it seems complex to try to make that
4066 @c distinction here.
4067 @emph{Warning:} If you use the @code{step} command while control is
4068 within a function that was compiled without debugging information,
4069 execution proceeds until control reaches a function that does have
4070 debugging information. Likewise, it will not step into a function which
4071 is compiled without debugging information. To step through functions
4072 without debugging information, use the @code{stepi} command, described
4076 The @code{step} command only stops at the first instruction of a source
4077 line. This prevents the multiple stops that could otherwise occur in
4078 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4079 to stop if a function that has debugging information is called within
4080 the line. In other words, @code{step} @emph{steps inside} any functions
4081 called within the line.
4083 Also, the @code{step} command only enters a function if there is line
4084 number information for the function. Otherwise it acts like the
4085 @code{next} command. This avoids problems when using @code{cc -gl}
4086 on MIPS machines. Previously, @code{step} entered subroutines if there
4087 was any debugging information about the routine.
4089 @item step @var{count}
4090 Continue running as in @code{step}, but do so @var{count} times. If a
4091 breakpoint is reached, or a signal not related to stepping occurs before
4092 @var{count} steps, stepping stops right away.
4095 @kindex n @r{(@code{next})}
4096 @item next @r{[}@var{count}@r{]}
4097 Continue to the next source line in the current (innermost) stack frame.
4098 This is similar to @code{step}, but function calls that appear within
4099 the line of code are executed without stopping. Execution stops when
4100 control reaches a different line of code at the original stack level
4101 that was executing when you gave the @code{next} command. This command
4102 is abbreviated @code{n}.
4104 An argument @var{count} is a repeat count, as for @code{step}.
4107 @c FIX ME!! Do we delete this, or is there a way it fits in with
4108 @c the following paragraph? --- Vctoria
4110 @c @code{next} within a function that lacks debugging information acts like
4111 @c @code{step}, but any function calls appearing within the code of the
4112 @c function are executed without stopping.
4114 The @code{next} command only stops at the first instruction of a
4115 source line. This prevents multiple stops that could otherwise occur in
4116 @code{switch} statements, @code{for} loops, etc.
4118 @kindex set step-mode
4120 @cindex functions without line info, and stepping
4121 @cindex stepping into functions with no line info
4122 @itemx set step-mode on
4123 The @code{set step-mode on} command causes the @code{step} command to
4124 stop at the first instruction of a function which contains no debug line
4125 information rather than stepping over it.
4127 This is useful in cases where you may be interested in inspecting the
4128 machine instructions of a function which has no symbolic info and do not
4129 want @value{GDBN} to automatically skip over this function.
4131 @item set step-mode off
4132 Causes the @code{step} command to step over any functions which contains no
4133 debug information. This is the default.
4135 @item show step-mode
4136 Show whether @value{GDBN} will stop in or step over functions without
4137 source line debug information.
4140 @kindex fin @r{(@code{finish})}
4142 Continue running until just after function in the selected stack frame
4143 returns. Print the returned value (if any). This command can be
4144 abbreviated as @code{fin}.
4146 Contrast this with the @code{return} command (@pxref{Returning,
4147 ,Returning from a Function}).
4150 @kindex u @r{(@code{until})}
4151 @cindex run until specified location
4154 Continue running until a source line past the current line, in the
4155 current stack frame, is reached. This command is used to avoid single
4156 stepping through a loop more than once. It is like the @code{next}
4157 command, except that when @code{until} encounters a jump, it
4158 automatically continues execution until the program counter is greater
4159 than the address of the jump.
4161 This means that when you reach the end of a loop after single stepping
4162 though it, @code{until} makes your program continue execution until it
4163 exits the loop. In contrast, a @code{next} command at the end of a loop
4164 simply steps back to the beginning of the loop, which forces you to step
4165 through the next iteration.
4167 @code{until} always stops your program if it attempts to exit the current
4170 @code{until} may produce somewhat counterintuitive results if the order
4171 of machine code does not match the order of the source lines. For
4172 example, in the following excerpt from a debugging session, the @code{f}
4173 (@code{frame}) command shows that execution is stopped at line
4174 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4178 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4180 (@value{GDBP}) until
4181 195 for ( ; argc > 0; NEXTARG) @{
4184 This happened because, for execution efficiency, the compiler had
4185 generated code for the loop closure test at the end, rather than the
4186 start, of the loop---even though the test in a C @code{for}-loop is
4187 written before the body of the loop. The @code{until} command appeared
4188 to step back to the beginning of the loop when it advanced to this
4189 expression; however, it has not really gone to an earlier
4190 statement---not in terms of the actual machine code.
4192 @code{until} with no argument works by means of single
4193 instruction stepping, and hence is slower than @code{until} with an
4196 @item until @var{location}
4197 @itemx u @var{location}
4198 Continue running your program until either the specified location is
4199 reached, or the current stack frame returns. @var{location} is any of
4200 the forms described in @ref{Specify Location}.
4201 This form of the command uses temporary breakpoints, and
4202 hence is quicker than @code{until} without an argument. The specified
4203 location is actually reached only if it is in the current frame. This
4204 implies that @code{until} can be used to skip over recursive function
4205 invocations. For instance in the code below, if the current location is
4206 line @code{96}, issuing @code{until 99} will execute the program up to
4207 line @code{99} in the same invocation of factorial, i.e., after the inner
4208 invocations have returned.
4211 94 int factorial (int value)
4213 96 if (value > 1) @{
4214 97 value *= factorial (value - 1);
4221 @kindex advance @var{location}
4222 @itemx advance @var{location}
4223 Continue running the program up to the given @var{location}. An argument is
4224 required, which should be of one of the forms described in
4225 @ref{Specify Location}.
4226 Execution will also stop upon exit from the current stack
4227 frame. This command is similar to @code{until}, but @code{advance} will
4228 not skip over recursive function calls, and the target location doesn't
4229 have to be in the same frame as the current one.
4233 @kindex si @r{(@code{stepi})}
4235 @itemx stepi @var{arg}
4237 Execute one machine instruction, then stop and return to the debugger.
4239 It is often useful to do @samp{display/i $pc} when stepping by machine
4240 instructions. This makes @value{GDBN} automatically display the next
4241 instruction to be executed, each time your program stops. @xref{Auto
4242 Display,, Automatic Display}.
4244 An argument is a repeat count, as in @code{step}.
4248 @kindex ni @r{(@code{nexti})}
4250 @itemx nexti @var{arg}
4252 Execute one machine instruction, but if it is a function call,
4253 proceed until the function returns.
4255 An argument is a repeat count, as in @code{next}.
4262 A signal is an asynchronous event that can happen in a program. The
4263 operating system defines the possible kinds of signals, and gives each
4264 kind a name and a number. For example, in Unix @code{SIGINT} is the
4265 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4266 @code{SIGSEGV} is the signal a program gets from referencing a place in
4267 memory far away from all the areas in use; @code{SIGALRM} occurs when
4268 the alarm clock timer goes off (which happens only if your program has
4269 requested an alarm).
4271 @cindex fatal signals
4272 Some signals, including @code{SIGALRM}, are a normal part of the
4273 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4274 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4275 program has not specified in advance some other way to handle the signal.
4276 @code{SIGINT} does not indicate an error in your program, but it is normally
4277 fatal so it can carry out the purpose of the interrupt: to kill the program.
4279 @value{GDBN} has the ability to detect any occurrence of a signal in your
4280 program. You can tell @value{GDBN} in advance what to do for each kind of
4283 @cindex handling signals
4284 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4285 @code{SIGALRM} be silently passed to your program
4286 (so as not to interfere with their role in the program's functioning)
4287 but to stop your program immediately whenever an error signal happens.
4288 You can change these settings with the @code{handle} command.
4291 @kindex info signals
4295 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4296 handle each one. You can use this to see the signal numbers of all
4297 the defined types of signals.
4299 @item info signals @var{sig}
4300 Similar, but print information only about the specified signal number.
4302 @code{info handle} is an alias for @code{info signals}.
4305 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4306 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4307 can be the number of a signal or its name (with or without the
4308 @samp{SIG} at the beginning); a list of signal numbers of the form
4309 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4310 known signals. Optional arguments @var{keywords}, described below,
4311 say what change to make.
4315 The keywords allowed by the @code{handle} command can be abbreviated.
4316 Their full names are:
4320 @value{GDBN} should not stop your program when this signal happens. It may
4321 still print a message telling you that the signal has come in.
4324 @value{GDBN} should stop your program when this signal happens. This implies
4325 the @code{print} keyword as well.
4328 @value{GDBN} should print a message when this signal happens.
4331 @value{GDBN} should not mention the occurrence of the signal at all. This
4332 implies the @code{nostop} keyword as well.
4336 @value{GDBN} should allow your program to see this signal; your program
4337 can handle the signal, or else it may terminate if the signal is fatal
4338 and not handled. @code{pass} and @code{noignore} are synonyms.
4342 @value{GDBN} should not allow your program to see this signal.
4343 @code{nopass} and @code{ignore} are synonyms.
4347 When a signal stops your program, the signal is not visible to the
4349 continue. Your program sees the signal then, if @code{pass} is in
4350 effect for the signal in question @emph{at that time}. In other words,
4351 after @value{GDBN} reports a signal, you can use the @code{handle}
4352 command with @code{pass} or @code{nopass} to control whether your
4353 program sees that signal when you continue.
4355 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4356 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4357 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4360 You can also use the @code{signal} command to prevent your program from
4361 seeing a signal, or cause it to see a signal it normally would not see,
4362 or to give it any signal at any time. For example, if your program stopped
4363 due to some sort of memory reference error, you might store correct
4364 values into the erroneous variables and continue, hoping to see more
4365 execution; but your program would probably terminate immediately as
4366 a result of the fatal signal once it saw the signal. To prevent this,
4367 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4371 @section Stopping and Starting Multi-thread Programs
4373 When your program has multiple threads (@pxref{Threads,, Debugging
4374 Programs with Multiple Threads}), you can choose whether to set
4375 breakpoints on all threads, or on a particular thread.
4378 @cindex breakpoints and threads
4379 @cindex thread breakpoints
4380 @kindex break @dots{} thread @var{threadno}
4381 @item break @var{linespec} thread @var{threadno}
4382 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4383 @var{linespec} specifies source lines; there are several ways of
4384 writing them (@pxref{Specify Location}), but the effect is always to
4385 specify some source line.
4387 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4388 to specify that you only want @value{GDBN} to stop the program when a
4389 particular thread reaches this breakpoint. @var{threadno} is one of the
4390 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4391 column of the @samp{info threads} display.
4393 If you do not specify @samp{thread @var{threadno}} when you set a
4394 breakpoint, the breakpoint applies to @emph{all} threads of your
4397 You can use the @code{thread} qualifier on conditional breakpoints as
4398 well; in this case, place @samp{thread @var{threadno}} before the
4399 breakpoint condition, like this:
4402 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4407 @cindex stopped threads
4408 @cindex threads, stopped
4409 Whenever your program stops under @value{GDBN} for any reason,
4410 @emph{all} threads of execution stop, not just the current thread. This
4411 allows you to examine the overall state of the program, including
4412 switching between threads, without worrying that things may change
4415 @cindex thread breakpoints and system calls
4416 @cindex system calls and thread breakpoints
4417 @cindex premature return from system calls
4418 There is an unfortunate side effect. If one thread stops for a
4419 breakpoint, or for some other reason, and another thread is blocked in a
4420 system call, then the system call may return prematurely. This is a
4421 consequence of the interaction between multiple threads and the signals
4422 that @value{GDBN} uses to implement breakpoints and other events that
4425 To handle this problem, your program should check the return value of
4426 each system call and react appropriately. This is good programming
4429 For example, do not write code like this:
4435 The call to @code{sleep} will return early if a different thread stops
4436 at a breakpoint or for some other reason.
4438 Instead, write this:
4443 unslept = sleep (unslept);
4446 A system call is allowed to return early, so the system is still
4447 conforming to its specification. But @value{GDBN} does cause your
4448 multi-threaded program to behave differently than it would without
4451 Also, @value{GDBN} uses internal breakpoints in the thread library to
4452 monitor certain events such as thread creation and thread destruction.
4453 When such an event happens, a system call in another thread may return
4454 prematurely, even though your program does not appear to stop.
4456 @cindex continuing threads
4457 @cindex threads, continuing
4458 Conversely, whenever you restart the program, @emph{all} threads start
4459 executing. @emph{This is true even when single-stepping} with commands
4460 like @code{step} or @code{next}.
4462 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4463 Since thread scheduling is up to your debugging target's operating
4464 system (not controlled by @value{GDBN}), other threads may
4465 execute more than one statement while the current thread completes a
4466 single step. Moreover, in general other threads stop in the middle of a
4467 statement, rather than at a clean statement boundary, when the program
4470 You might even find your program stopped in another thread after
4471 continuing or even single-stepping. This happens whenever some other
4472 thread runs into a breakpoint, a signal, or an exception before the
4473 first thread completes whatever you requested.
4475 On some OSes, you can lock the OS scheduler and thus allow only a single
4479 @item set scheduler-locking @var{mode}
4480 @cindex scheduler locking mode
4481 @cindex lock scheduler
4482 Set the scheduler locking mode. If it is @code{off}, then there is no
4483 locking and any thread may run at any time. If @code{on}, then only the
4484 current thread may run when the inferior is resumed. The @code{step}
4485 mode optimizes for single-stepping. It stops other threads from
4486 ``seizing the prompt'' by preempting the current thread while you are
4487 stepping. Other threads will only rarely (or never) get a chance to run
4488 when you step. They are more likely to run when you @samp{next} over a
4489 function call, and they are completely free to run when you use commands
4490 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4491 thread hits a breakpoint during its timeslice, they will never steal the
4492 @value{GDBN} prompt away from the thread that you are debugging.
4494 @item show scheduler-locking
4495 Display the current scheduler locking mode.
4500 @chapter Examining the Stack
4502 When your program has stopped, the first thing you need to know is where it
4503 stopped and how it got there.
4506 Each time your program performs a function call, information about the call
4508 That information includes the location of the call in your program,
4509 the arguments of the call,
4510 and the local variables of the function being called.
4511 The information is saved in a block of data called a @dfn{stack frame}.
4512 The stack frames are allocated in a region of memory called the @dfn{call
4515 When your program stops, the @value{GDBN} commands for examining the
4516 stack allow you to see all of this information.
4518 @cindex selected frame
4519 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4520 @value{GDBN} commands refer implicitly to the selected frame. In
4521 particular, whenever you ask @value{GDBN} for the value of a variable in
4522 your program, the value is found in the selected frame. There are
4523 special @value{GDBN} commands to select whichever frame you are
4524 interested in. @xref{Selection, ,Selecting a Frame}.
4526 When your program stops, @value{GDBN} automatically selects the
4527 currently executing frame and describes it briefly, similar to the
4528 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4531 * Frames:: Stack frames
4532 * Backtrace:: Backtraces
4533 * Selection:: Selecting a frame
4534 * Frame Info:: Information on a frame
4539 @section Stack Frames
4541 @cindex frame, definition
4543 The call stack is divided up into contiguous pieces called @dfn{stack
4544 frames}, or @dfn{frames} for short; each frame is the data associated
4545 with one call to one function. The frame contains the arguments given
4546 to the function, the function's local variables, and the address at
4547 which the function is executing.
4549 @cindex initial frame
4550 @cindex outermost frame
4551 @cindex innermost frame
4552 When your program is started, the stack has only one frame, that of the
4553 function @code{main}. This is called the @dfn{initial} frame or the
4554 @dfn{outermost} frame. Each time a function is called, a new frame is
4555 made. Each time a function returns, the frame for that function invocation
4556 is eliminated. If a function is recursive, there can be many frames for
4557 the same function. The frame for the function in which execution is
4558 actually occurring is called the @dfn{innermost} frame. This is the most
4559 recently created of all the stack frames that still exist.
4561 @cindex frame pointer
4562 Inside your program, stack frames are identified by their addresses. A
4563 stack frame consists of many bytes, each of which has its own address; each
4564 kind of computer has a convention for choosing one byte whose
4565 address serves as the address of the frame. Usually this address is kept
4566 in a register called the @dfn{frame pointer register}
4567 (@pxref{Registers, $fp}) while execution is going on in that frame.
4569 @cindex frame number
4570 @value{GDBN} assigns numbers to all existing stack frames, starting with
4571 zero for the innermost frame, one for the frame that called it,
4572 and so on upward. These numbers do not really exist in your program;
4573 they are assigned by @value{GDBN} to give you a way of designating stack
4574 frames in @value{GDBN} commands.
4576 @c The -fomit-frame-pointer below perennially causes hbox overflow
4577 @c underflow problems.
4578 @cindex frameless execution
4579 Some compilers provide a way to compile functions so that they operate
4580 without stack frames. (For example, the @value{NGCC} option
4582 @samp{-fomit-frame-pointer}
4584 generates functions without a frame.)
4585 This is occasionally done with heavily used library functions to save
4586 the frame setup time. @value{GDBN} has limited facilities for dealing
4587 with these function invocations. If the innermost function invocation
4588 has no stack frame, @value{GDBN} nevertheless regards it as though
4589 it had a separate frame, which is numbered zero as usual, allowing
4590 correct tracing of the function call chain. However, @value{GDBN} has
4591 no provision for frameless functions elsewhere in the stack.
4594 @kindex frame@r{, command}
4595 @cindex current stack frame
4596 @item frame @var{args}
4597 The @code{frame} command allows you to move from one stack frame to another,
4598 and to print the stack frame you select. @var{args} may be either the
4599 address of the frame or the stack frame number. Without an argument,
4600 @code{frame} prints the current stack frame.
4602 @kindex select-frame
4603 @cindex selecting frame silently
4605 The @code{select-frame} command allows you to move from one stack frame
4606 to another without printing the frame. This is the silent version of
4614 @cindex call stack traces
4615 A backtrace is a summary of how your program got where it is. It shows one
4616 line per frame, for many frames, starting with the currently executing
4617 frame (frame zero), followed by its caller (frame one), and on up the
4622 @kindex bt @r{(@code{backtrace})}
4625 Print a backtrace of the entire stack: one line per frame for all
4626 frames in the stack.
4628 You can stop the backtrace at any time by typing the system interrupt
4629 character, normally @kbd{Ctrl-c}.
4631 @item backtrace @var{n}
4633 Similar, but print only the innermost @var{n} frames.
4635 @item backtrace -@var{n}
4637 Similar, but print only the outermost @var{n} frames.
4639 @item backtrace full
4641 @itemx bt full @var{n}
4642 @itemx bt full -@var{n}
4643 Print the values of the local variables also. @var{n} specifies the
4644 number of frames to print, as described above.
4649 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4650 are additional aliases for @code{backtrace}.
4652 @cindex multiple threads, backtrace
4653 In a multi-threaded program, @value{GDBN} by default shows the
4654 backtrace only for the current thread. To display the backtrace for
4655 several or all of the threads, use the command @code{thread apply}
4656 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4657 apply all backtrace}, @value{GDBN} will display the backtrace for all
4658 the threads; this is handy when you debug a core dump of a
4659 multi-threaded program.
4661 Each line in the backtrace shows the frame number and the function name.
4662 The program counter value is also shown---unless you use @code{set
4663 print address off}. The backtrace also shows the source file name and
4664 line number, as well as the arguments to the function. The program
4665 counter value is omitted if it is at the beginning of the code for that
4668 Here is an example of a backtrace. It was made with the command
4669 @samp{bt 3}, so it shows the innermost three frames.
4673 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4675 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4676 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4678 (More stack frames follow...)
4683 The display for frame zero does not begin with a program counter
4684 value, indicating that your program has stopped at the beginning of the
4685 code for line @code{993} of @code{builtin.c}.
4687 @cindex value optimized out, in backtrace
4688 @cindex function call arguments, optimized out
4689 If your program was compiled with optimizations, some compilers will
4690 optimize away arguments passed to functions if those arguments are
4691 never used after the call. Such optimizations generate code that
4692 passes arguments through registers, but doesn't store those arguments
4693 in the stack frame. @value{GDBN} has no way of displaying such
4694 arguments in stack frames other than the innermost one. Here's what
4695 such a backtrace might look like:
4699 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4701 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4702 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4704 (More stack frames follow...)
4709 The values of arguments that were not saved in their stack frames are
4710 shown as @samp{<value optimized out>}.
4712 If you need to display the values of such optimized-out arguments,
4713 either deduce that from other variables whose values depend on the one
4714 you are interested in, or recompile without optimizations.
4716 @cindex backtrace beyond @code{main} function
4717 @cindex program entry point
4718 @cindex startup code, and backtrace
4719 Most programs have a standard user entry point---a place where system
4720 libraries and startup code transition into user code. For C this is
4721 @code{main}@footnote{
4722 Note that embedded programs (the so-called ``free-standing''
4723 environment) are not required to have a @code{main} function as the
4724 entry point. They could even have multiple entry points.}.
4725 When @value{GDBN} finds the entry function in a backtrace
4726 it will terminate the backtrace, to avoid tracing into highly
4727 system-specific (and generally uninteresting) code.
4729 If you need to examine the startup code, or limit the number of levels
4730 in a backtrace, you can change this behavior:
4733 @item set backtrace past-main
4734 @itemx set backtrace past-main on
4735 @kindex set backtrace
4736 Backtraces will continue past the user entry point.
4738 @item set backtrace past-main off
4739 Backtraces will stop when they encounter the user entry point. This is the
4742 @item show backtrace past-main
4743 @kindex show backtrace
4744 Display the current user entry point backtrace policy.
4746 @item set backtrace past-entry
4747 @itemx set backtrace past-entry on
4748 Backtraces will continue past the internal entry point of an application.
4749 This entry point is encoded by the linker when the application is built,
4750 and is likely before the user entry point @code{main} (or equivalent) is called.
4752 @item set backtrace past-entry off
4753 Backtraces will stop when they encounter the internal entry point of an
4754 application. This is the default.
4756 @item show backtrace past-entry
4757 Display the current internal entry point backtrace policy.
4759 @item set backtrace limit @var{n}
4760 @itemx set backtrace limit 0
4761 @cindex backtrace limit
4762 Limit the backtrace to @var{n} levels. A value of zero means
4765 @item show backtrace limit
4766 Display the current limit on backtrace levels.
4770 @section Selecting a Frame
4772 Most commands for examining the stack and other data in your program work on
4773 whichever stack frame is selected at the moment. Here are the commands for
4774 selecting a stack frame; all of them finish by printing a brief description
4775 of the stack frame just selected.
4778 @kindex frame@r{, selecting}
4779 @kindex f @r{(@code{frame})}
4782 Select frame number @var{n}. Recall that frame zero is the innermost
4783 (currently executing) frame, frame one is the frame that called the
4784 innermost one, and so on. The highest-numbered frame is the one for
4787 @item frame @var{addr}
4789 Select the frame at address @var{addr}. This is useful mainly if the
4790 chaining of stack frames has been damaged by a bug, making it
4791 impossible for @value{GDBN} to assign numbers properly to all frames. In
4792 addition, this can be useful when your program has multiple stacks and
4793 switches between them.
4795 On the SPARC architecture, @code{frame} needs two addresses to
4796 select an arbitrary frame: a frame pointer and a stack pointer.
4798 On the MIPS and Alpha architecture, it needs two addresses: a stack
4799 pointer and a program counter.
4801 On the 29k architecture, it needs three addresses: a register stack
4802 pointer, a program counter, and a memory stack pointer.
4806 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4807 advances toward the outermost frame, to higher frame numbers, to frames
4808 that have existed longer. @var{n} defaults to one.
4811 @kindex do @r{(@code{down})}
4813 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4814 advances toward the innermost frame, to lower frame numbers, to frames
4815 that were created more recently. @var{n} defaults to one. You may
4816 abbreviate @code{down} as @code{do}.
4819 All of these commands end by printing two lines of output describing the
4820 frame. The first line shows the frame number, the function name, the
4821 arguments, and the source file and line number of execution in that
4822 frame. The second line shows the text of that source line.
4830 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4832 10 read_input_file (argv[i]);
4836 After such a printout, the @code{list} command with no arguments
4837 prints ten lines centered on the point of execution in the frame.
4838 You can also edit the program at the point of execution with your favorite
4839 editing program by typing @code{edit}.
4840 @xref{List, ,Printing Source Lines},
4844 @kindex down-silently
4846 @item up-silently @var{n}
4847 @itemx down-silently @var{n}
4848 These two commands are variants of @code{up} and @code{down},
4849 respectively; they differ in that they do their work silently, without
4850 causing display of the new frame. They are intended primarily for use
4851 in @value{GDBN} command scripts, where the output might be unnecessary and
4856 @section Information About a Frame
4858 There are several other commands to print information about the selected
4864 When used without any argument, this command does not change which
4865 frame is selected, but prints a brief description of the currently
4866 selected stack frame. It can be abbreviated @code{f}. With an
4867 argument, this command is used to select a stack frame.
4868 @xref{Selection, ,Selecting a Frame}.
4871 @kindex info f @r{(@code{info frame})}
4874 This command prints a verbose description of the selected stack frame,
4879 the address of the frame
4881 the address of the next frame down (called by this frame)
4883 the address of the next frame up (caller of this frame)
4885 the language in which the source code corresponding to this frame is written
4887 the address of the frame's arguments
4889 the address of the frame's local variables
4891 the program counter saved in it (the address of execution in the caller frame)
4893 which registers were saved in the frame
4896 @noindent The verbose description is useful when
4897 something has gone wrong that has made the stack format fail to fit
4898 the usual conventions.
4900 @item info frame @var{addr}
4901 @itemx info f @var{addr}
4902 Print a verbose description of the frame at address @var{addr}, without
4903 selecting that frame. The selected frame remains unchanged by this
4904 command. This requires the same kind of address (more than one for some
4905 architectures) that you specify in the @code{frame} command.
4906 @xref{Selection, ,Selecting a Frame}.
4910 Print the arguments of the selected frame, each on a separate line.
4914 Print the local variables of the selected frame, each on a separate
4915 line. These are all variables (declared either static or automatic)
4916 accessible at the point of execution of the selected frame.
4919 @cindex catch exceptions, list active handlers
4920 @cindex exception handlers, how to list
4922 Print a list of all the exception handlers that are active in the
4923 current stack frame at the current point of execution. To see other
4924 exception handlers, visit the associated frame (using the @code{up},
4925 @code{down}, or @code{frame} commands); then type @code{info catch}.
4926 @xref{Set Catchpoints, , Setting Catchpoints}.
4932 @chapter Examining Source Files
4934 @value{GDBN} can print parts of your program's source, since the debugging
4935 information recorded in the program tells @value{GDBN} what source files were
4936 used to build it. When your program stops, @value{GDBN} spontaneously prints
4937 the line where it stopped. Likewise, when you select a stack frame
4938 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4939 execution in that frame has stopped. You can print other portions of
4940 source files by explicit command.
4942 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4943 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4944 @value{GDBN} under @sc{gnu} Emacs}.
4947 * List:: Printing source lines
4948 * Specify Location:: How to specify code locations
4949 * Edit:: Editing source files
4950 * Search:: Searching source files
4951 * Source Path:: Specifying source directories
4952 * Machine Code:: Source and machine code
4956 @section Printing Source Lines
4959 @kindex l @r{(@code{list})}
4960 To print lines from a source file, use the @code{list} command
4961 (abbreviated @code{l}). By default, ten lines are printed.
4962 There are several ways to specify what part of the file you want to
4963 print; see @ref{Specify Location}, for the full list.
4965 Here are the forms of the @code{list} command most commonly used:
4968 @item list @var{linenum}
4969 Print lines centered around line number @var{linenum} in the
4970 current source file.
4972 @item list @var{function}
4973 Print lines centered around the beginning of function
4977 Print more lines. If the last lines printed were printed with a
4978 @code{list} command, this prints lines following the last lines
4979 printed; however, if the last line printed was a solitary line printed
4980 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4981 Stack}), this prints lines centered around that line.
4984 Print lines just before the lines last printed.
4987 @cindex @code{list}, how many lines to display
4988 By default, @value{GDBN} prints ten source lines with any of these forms of
4989 the @code{list} command. You can change this using @code{set listsize}:
4992 @kindex set listsize
4993 @item set listsize @var{count}
4994 Make the @code{list} command display @var{count} source lines (unless
4995 the @code{list} argument explicitly specifies some other number).
4997 @kindex show listsize
4999 Display the number of lines that @code{list} prints.
5002 Repeating a @code{list} command with @key{RET} discards the argument,
5003 so it is equivalent to typing just @code{list}. This is more useful
5004 than listing the same lines again. An exception is made for an
5005 argument of @samp{-}; that argument is preserved in repetition so that
5006 each repetition moves up in the source file.
5008 In general, the @code{list} command expects you to supply zero, one or two
5009 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5010 of writing them (@pxref{Specify Location}), but the effect is always
5011 to specify some source line.
5013 Here is a complete description of the possible arguments for @code{list}:
5016 @item list @var{linespec}
5017 Print lines centered around the line specified by @var{linespec}.
5019 @item list @var{first},@var{last}
5020 Print lines from @var{first} to @var{last}. Both arguments are
5021 linespecs. When a @code{list} command has two linespecs, and the
5022 source file of the second linespec is omitted, this refers to
5023 the same source file as the first linespec.
5025 @item list ,@var{last}
5026 Print lines ending with @var{last}.
5028 @item list @var{first},
5029 Print lines starting with @var{first}.
5032 Print lines just after the lines last printed.
5035 Print lines just before the lines last printed.
5038 As described in the preceding table.
5041 @node Specify Location
5042 @section Specifying a Location
5043 @cindex specifying location
5046 Several @value{GDBN} commands accept arguments that specify a location
5047 of your program's code. Since @value{GDBN} is a source-level
5048 debugger, a location usually specifies some line in the source code;
5049 for that reason, locations are also known as @dfn{linespecs}.
5051 Here are all the different ways of specifying a code location that
5052 @value{GDBN} understands:
5056 Specifies the line number @var{linenum} of the current source file.
5059 @itemx +@var{offset}
5060 Specifies the line @var{offset} lines before or after the @dfn{current
5061 line}. For the @code{list} command, the current line is the last one
5062 printed; for the breakpoint commands, this is the line at which
5063 execution stopped in the currently selected @dfn{stack frame}
5064 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5065 used as the second of the two linespecs in a @code{list} command,
5066 this specifies the line @var{offset} lines up or down from the first
5069 @item @var{filename}:@var{linenum}
5070 Specifies the line @var{linenum} in the source file @var{filename}.
5072 @item @var{function}
5073 Specifies the line that begins the body of the function @var{function}.
5074 For example, in C, this is the line with the open brace.
5076 @item @var{filename}:@var{function}
5077 Specifies the line that begins the body of the function @var{function}
5078 in the file @var{filename}. You only need the file name with a
5079 function name to avoid ambiguity when there are identically named
5080 functions in different source files.
5082 @item *@var{address}
5083 Specifies the program address @var{address}. For line-oriented
5084 commands, such as @code{list} and @code{edit}, this specifies a source
5085 line that contains @var{address}. For @code{break} and other
5086 breakpoint oriented commands, this can be used to set breakpoints in
5087 parts of your program which do not have debugging information or
5090 Here @var{address} may be any expression valid in the current working
5091 language (@pxref{Languages, working language}) that specifies a code
5092 address. In addition, as a convenience, @value{GDBN} extends the
5093 semantics of expressions used in locations to cover the situations
5094 that frequently happen during debugging. Here are the various forms
5098 @item @var{expression}
5099 Any expression valid in the current working language.
5101 @item @var{funcaddr}
5102 An address of a function or procedure derived from its name. In C,
5103 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5104 simply the function's name @var{function} (and actually a special case
5105 of a valid expression). In Pascal and Modula-2, this is
5106 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5107 (although the Pascal form also works).
5109 This form specifies the address of the function's first instruction,
5110 before the stack frame and arguments have been set up.
5112 @item '@var{filename}'::@var{funcaddr}
5113 Like @var{funcaddr} above, but also specifies the name of the source
5114 file explicitly. This is useful if the name of the function does not
5115 specify the function unambiguously, e.g., if there are several
5116 functions with identical names in different source files.
5123 @section Editing Source Files
5124 @cindex editing source files
5127 @kindex e @r{(@code{edit})}
5128 To edit the lines in a source file, use the @code{edit} command.
5129 The editing program of your choice
5130 is invoked with the current line set to
5131 the active line in the program.
5132 Alternatively, there are several ways to specify what part of the file you
5133 want to print if you want to see other parts of the program:
5136 @item edit @var{location}
5137 Edit the source file specified by @code{location}. Editing starts at
5138 that @var{location}, e.g., at the specified source line of the
5139 specified file. @xref{Specify Location}, for all the possible forms
5140 of the @var{location} argument; here are the forms of the @code{edit}
5141 command most commonly used:
5144 @item edit @var{number}
5145 Edit the current source file with @var{number} as the active line number.
5147 @item edit @var{function}
5148 Edit the file containing @var{function} at the beginning of its definition.
5153 @subsection Choosing your Editor
5154 You can customize @value{GDBN} to use any editor you want
5156 The only restriction is that your editor (say @code{ex}), recognizes the
5157 following command-line syntax:
5159 ex +@var{number} file
5161 The optional numeric value +@var{number} specifies the number of the line in
5162 the file where to start editing.}.
5163 By default, it is @file{@value{EDITOR}}, but you can change this
5164 by setting the environment variable @code{EDITOR} before using
5165 @value{GDBN}. For example, to configure @value{GDBN} to use the
5166 @code{vi} editor, you could use these commands with the @code{sh} shell:
5172 or in the @code{csh} shell,
5174 setenv EDITOR /usr/bin/vi
5179 @section Searching Source Files
5180 @cindex searching source files
5182 There are two commands for searching through the current source file for a
5187 @kindex forward-search
5188 @item forward-search @var{regexp}
5189 @itemx search @var{regexp}
5190 The command @samp{forward-search @var{regexp}} checks each line,
5191 starting with the one following the last line listed, for a match for
5192 @var{regexp}. It lists the line that is found. You can use the
5193 synonym @samp{search @var{regexp}} or abbreviate the command name as
5196 @kindex reverse-search
5197 @item reverse-search @var{regexp}
5198 The command @samp{reverse-search @var{regexp}} checks each line, starting
5199 with the one before the last line listed and going backward, for a match
5200 for @var{regexp}. It lists the line that is found. You can abbreviate
5201 this command as @code{rev}.
5205 @section Specifying Source Directories
5208 @cindex directories for source files
5209 Executable programs sometimes do not record the directories of the source
5210 files from which they were compiled, just the names. Even when they do,
5211 the directories could be moved between the compilation and your debugging
5212 session. @value{GDBN} has a list of directories to search for source files;
5213 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5214 it tries all the directories in the list, in the order they are present
5215 in the list, until it finds a file with the desired name.
5217 For example, suppose an executable references the file
5218 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5219 @file{/mnt/cross}. The file is first looked up literally; if this
5220 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5221 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5222 message is printed. @value{GDBN} does not look up the parts of the
5223 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5224 Likewise, the subdirectories of the source path are not searched: if
5225 the source path is @file{/mnt/cross}, and the binary refers to
5226 @file{foo.c}, @value{GDBN} would not find it under
5227 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5229 Plain file names, relative file names with leading directories, file
5230 names containing dots, etc.@: are all treated as described above; for
5231 instance, if the source path is @file{/mnt/cross}, and the source file
5232 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5233 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5234 that---@file{/mnt/cross/foo.c}.
5236 Note that the executable search path is @emph{not} used to locate the
5239 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5240 any information it has cached about where source files are found and where
5241 each line is in the file.
5245 When you start @value{GDBN}, its source path includes only @samp{cdir}
5246 and @samp{cwd}, in that order.
5247 To add other directories, use the @code{directory} command.
5249 The search path is used to find both program source files and @value{GDBN}
5250 script files (read using the @samp{-command} option and @samp{source} command).
5252 In addition to the source path, @value{GDBN} provides a set of commands
5253 that manage a list of source path substitution rules. A @dfn{substitution
5254 rule} specifies how to rewrite source directories stored in the program's
5255 debug information in case the sources were moved to a different
5256 directory between compilation and debugging. A rule is made of
5257 two strings, the first specifying what needs to be rewritten in
5258 the path, and the second specifying how it should be rewritten.
5259 In @ref{set substitute-path}, we name these two parts @var{from} and
5260 @var{to} respectively. @value{GDBN} does a simple string replacement
5261 of @var{from} with @var{to} at the start of the directory part of the
5262 source file name, and uses that result instead of the original file
5263 name to look up the sources.
5265 Using the previous example, suppose the @file{foo-1.0} tree has been
5266 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5267 @value{GDBN} to replace @file{/usr/src} in all source path names with
5268 @file{/mnt/cross}. The first lookup will then be
5269 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5270 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5271 substitution rule, use the @code{set substitute-path} command
5272 (@pxref{set substitute-path}).
5274 To avoid unexpected substitution results, a rule is applied only if the
5275 @var{from} part of the directory name ends at a directory separator.
5276 For instance, a rule substituting @file{/usr/source} into
5277 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5278 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5279 is applied only at the beginning of the directory name, this rule will
5280 not be applied to @file{/root/usr/source/baz.c} either.
5282 In many cases, you can achieve the same result using the @code{directory}
5283 command. However, @code{set substitute-path} can be more efficient in
5284 the case where the sources are organized in a complex tree with multiple
5285 subdirectories. With the @code{directory} command, you need to add each
5286 subdirectory of your project. If you moved the entire tree while
5287 preserving its internal organization, then @code{set substitute-path}
5288 allows you to direct the debugger to all the sources with one single
5291 @code{set substitute-path} is also more than just a shortcut command.
5292 The source path is only used if the file at the original location no
5293 longer exists. On the other hand, @code{set substitute-path} modifies
5294 the debugger behavior to look at the rewritten location instead. So, if
5295 for any reason a source file that is not relevant to your executable is
5296 located at the original location, a substitution rule is the only
5297 method available to point @value{GDBN} at the new location.
5300 @item directory @var{dirname} @dots{}
5301 @item dir @var{dirname} @dots{}
5302 Add directory @var{dirname} to the front of the source path. Several
5303 directory names may be given to this command, separated by @samp{:}
5304 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5305 part of absolute file names) or
5306 whitespace. You may specify a directory that is already in the source
5307 path; this moves it forward, so @value{GDBN} searches it sooner.
5311 @vindex $cdir@r{, convenience variable}
5312 @vindex $cwd@r{, convenience variable}
5313 @cindex compilation directory
5314 @cindex current directory
5315 @cindex working directory
5316 @cindex directory, current
5317 @cindex directory, compilation
5318 You can use the string @samp{$cdir} to refer to the compilation
5319 directory (if one is recorded), and @samp{$cwd} to refer to the current
5320 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5321 tracks the current working directory as it changes during your @value{GDBN}
5322 session, while the latter is immediately expanded to the current
5323 directory at the time you add an entry to the source path.
5326 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5328 @c RET-repeat for @code{directory} is explicitly disabled, but since
5329 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5331 @item show directories
5332 @kindex show directories
5333 Print the source path: show which directories it contains.
5335 @anchor{set substitute-path}
5336 @item set substitute-path @var{from} @var{to}
5337 @kindex set substitute-path
5338 Define a source path substitution rule, and add it at the end of the
5339 current list of existing substitution rules. If a rule with the same
5340 @var{from} was already defined, then the old rule is also deleted.
5342 For example, if the file @file{/foo/bar/baz.c} was moved to
5343 @file{/mnt/cross/baz.c}, then the command
5346 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5350 will tell @value{GDBN} to replace @samp{/usr/src} with
5351 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5352 @file{baz.c} even though it was moved.
5354 In the case when more than one substitution rule have been defined,
5355 the rules are evaluated one by one in the order where they have been
5356 defined. The first one matching, if any, is selected to perform
5359 For instance, if we had entered the following commands:
5362 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5363 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5367 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5368 @file{/mnt/include/defs.h} by using the first rule. However, it would
5369 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5370 @file{/mnt/src/lib/foo.c}.
5373 @item unset substitute-path [path]
5374 @kindex unset substitute-path
5375 If a path is specified, search the current list of substitution rules
5376 for a rule that would rewrite that path. Delete that rule if found.
5377 A warning is emitted by the debugger if no rule could be found.
5379 If no path is specified, then all substitution rules are deleted.
5381 @item show substitute-path [path]
5382 @kindex show substitute-path
5383 If a path is specified, then print the source path substitution rule
5384 which would rewrite that path, if any.
5386 If no path is specified, then print all existing source path substitution
5391 If your source path is cluttered with directories that are no longer of
5392 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5393 versions of source. You can correct the situation as follows:
5397 Use @code{directory} with no argument to reset the source path to its default value.
5400 Use @code{directory} with suitable arguments to reinstall the
5401 directories you want in the source path. You can add all the
5402 directories in one command.
5406 @section Source and Machine Code
5407 @cindex source line and its code address
5409 You can use the command @code{info line} to map source lines to program
5410 addresses (and vice versa), and the command @code{disassemble} to display
5411 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5412 mode, the @code{info line} command causes the arrow to point to the
5413 line specified. Also, @code{info line} prints addresses in symbolic form as
5418 @item info line @var{linespec}
5419 Print the starting and ending addresses of the compiled code for
5420 source line @var{linespec}. You can specify source lines in any of
5421 the ways documented in @ref{Specify Location}.
5424 For example, we can use @code{info line} to discover the location of
5425 the object code for the first line of function
5426 @code{m4_changequote}:
5428 @c FIXME: I think this example should also show the addresses in
5429 @c symbolic form, as they usually would be displayed.
5431 (@value{GDBP}) info line m4_changequote
5432 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5436 @cindex code address and its source line
5437 We can also inquire (using @code{*@var{addr}} as the form for
5438 @var{linespec}) what source line covers a particular address:
5440 (@value{GDBP}) info line *0x63ff
5441 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5444 @cindex @code{$_} and @code{info line}
5445 @cindex @code{x} command, default address
5446 @kindex x@r{(examine), and} info line
5447 After @code{info line}, the default address for the @code{x} command
5448 is changed to the starting address of the line, so that @samp{x/i} is
5449 sufficient to begin examining the machine code (@pxref{Memory,
5450 ,Examining Memory}). Also, this address is saved as the value of the
5451 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5456 @cindex assembly instructions
5457 @cindex instructions, assembly
5458 @cindex machine instructions
5459 @cindex listing machine instructions
5461 @itemx disassemble /m
5462 This specialized command dumps a range of memory as machine
5463 instructions. It can also print mixed source+disassembly by specifying
5464 the @code{/m} modifier.
5465 The default memory range is the function surrounding the
5466 program counter of the selected frame. A single argument to this
5467 command is a program counter value; @value{GDBN} dumps the function
5468 surrounding this value. Two arguments specify a range of addresses
5469 (first inclusive, second exclusive) to dump.
5472 The following example shows the disassembly of a range of addresses of
5473 HP PA-RISC 2.0 code:
5476 (@value{GDBP}) disas 0x32c4 0x32e4
5477 Dump of assembler code from 0x32c4 to 0x32e4:
5478 0x32c4 <main+204>: addil 0,dp
5479 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5480 0x32cc <main+212>: ldil 0x3000,r31
5481 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5482 0x32d4 <main+220>: ldo 0(r31),rp
5483 0x32d8 <main+224>: addil -0x800,dp
5484 0x32dc <main+228>: ldo 0x588(r1),r26
5485 0x32e0 <main+232>: ldil 0x3000,r31
5486 End of assembler dump.
5489 Here is an example showing mixed source+assembly for Intel x86:
5492 (@value{GDBP}) disas /m main
5493 Dump of assembler code for function main:
5495 0x08048330 <main+0>: push %ebp
5496 0x08048331 <main+1>: mov %esp,%ebp
5497 0x08048333 <main+3>: sub $0x8,%esp
5498 0x08048336 <main+6>: and $0xfffffff0,%esp
5499 0x08048339 <main+9>: sub $0x10,%esp
5501 6 printf ("Hello.\n");
5502 0x0804833c <main+12>: movl $0x8048440,(%esp)
5503 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
5507 0x08048348 <main+24>: mov $0x0,%eax
5508 0x0804834d <main+29>: leave
5509 0x0804834e <main+30>: ret
5511 End of assembler dump.
5514 Some architectures have more than one commonly-used set of instruction
5515 mnemonics or other syntax.
5517 For programs that were dynamically linked and use shared libraries,
5518 instructions that call functions or branch to locations in the shared
5519 libraries might show a seemingly bogus location---it's actually a
5520 location of the relocation table. On some architectures, @value{GDBN}
5521 might be able to resolve these to actual function names.
5524 @kindex set disassembly-flavor
5525 @cindex Intel disassembly flavor
5526 @cindex AT&T disassembly flavor
5527 @item set disassembly-flavor @var{instruction-set}
5528 Select the instruction set to use when disassembling the
5529 program via the @code{disassemble} or @code{x/i} commands.
5531 Currently this command is only defined for the Intel x86 family. You
5532 can set @var{instruction-set} to either @code{intel} or @code{att}.
5533 The default is @code{att}, the AT&T flavor used by default by Unix
5534 assemblers for x86-based targets.
5536 @kindex show disassembly-flavor
5537 @item show disassembly-flavor
5538 Show the current setting of the disassembly flavor.
5543 @chapter Examining Data
5545 @cindex printing data
5546 @cindex examining data
5549 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5550 @c document because it is nonstandard... Under Epoch it displays in a
5551 @c different window or something like that.
5552 The usual way to examine data in your program is with the @code{print}
5553 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5554 evaluates and prints the value of an expression of the language your
5555 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5556 Different Languages}).
5559 @item print @var{expr}
5560 @itemx print /@var{f} @var{expr}
5561 @var{expr} is an expression (in the source language). By default the
5562 value of @var{expr} is printed in a format appropriate to its data type;
5563 you can choose a different format by specifying @samp{/@var{f}}, where
5564 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5568 @itemx print /@var{f}
5569 @cindex reprint the last value
5570 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5571 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5572 conveniently inspect the same value in an alternative format.
5575 A more low-level way of examining data is with the @code{x} command.
5576 It examines data in memory at a specified address and prints it in a
5577 specified format. @xref{Memory, ,Examining Memory}.
5579 If you are interested in information about types, or about how the
5580 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5581 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5585 * Expressions:: Expressions
5586 * Ambiguous Expressions:: Ambiguous Expressions
5587 * Variables:: Program variables
5588 * Arrays:: Artificial arrays
5589 * Output Formats:: Output formats
5590 * Memory:: Examining memory
5591 * Auto Display:: Automatic display
5592 * Print Settings:: Print settings
5593 * Value History:: Value history
5594 * Convenience Vars:: Convenience variables
5595 * Registers:: Registers
5596 * Floating Point Hardware:: Floating point hardware
5597 * Vector Unit:: Vector Unit
5598 * OS Information:: Auxiliary data provided by operating system
5599 * Memory Region Attributes:: Memory region attributes
5600 * Dump/Restore Files:: Copy between memory and a file
5601 * Core File Generation:: Cause a program dump its core
5602 * Character Sets:: Debugging programs that use a different
5603 character set than GDB does
5604 * Caching Remote Data:: Data caching for remote targets
5605 * Searching Memory:: Searching memory for a sequence of bytes
5609 @section Expressions
5612 @code{print} and many other @value{GDBN} commands accept an expression and
5613 compute its value. Any kind of constant, variable or operator defined
5614 by the programming language you are using is valid in an expression in
5615 @value{GDBN}. This includes conditional expressions, function calls,
5616 casts, and string constants. It also includes preprocessor macros, if
5617 you compiled your program to include this information; see
5620 @cindex arrays in expressions
5621 @value{GDBN} supports array constants in expressions input by
5622 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5623 you can use the command @code{print @{1, 2, 3@}} to create an array
5624 of three integers. If you pass an array to a function or assign it
5625 to a program variable, @value{GDBN} copies the array to memory that
5626 is @code{malloc}ed in the target program.
5628 Because C is so widespread, most of the expressions shown in examples in
5629 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5630 Languages}, for information on how to use expressions in other
5633 In this section, we discuss operators that you can use in @value{GDBN}
5634 expressions regardless of your programming language.
5636 @cindex casts, in expressions
5637 Casts are supported in all languages, not just in C, because it is so
5638 useful to cast a number into a pointer in order to examine a structure
5639 at that address in memory.
5640 @c FIXME: casts supported---Mod2 true?
5642 @value{GDBN} supports these operators, in addition to those common
5643 to programming languages:
5647 @samp{@@} is a binary operator for treating parts of memory as arrays.
5648 @xref{Arrays, ,Artificial Arrays}, for more information.
5651 @samp{::} allows you to specify a variable in terms of the file or
5652 function where it is defined. @xref{Variables, ,Program Variables}.
5654 @cindex @{@var{type}@}
5655 @cindex type casting memory
5656 @cindex memory, viewing as typed object
5657 @cindex casts, to view memory
5658 @item @{@var{type}@} @var{addr}
5659 Refers to an object of type @var{type} stored at address @var{addr} in
5660 memory. @var{addr} may be any expression whose value is an integer or
5661 pointer (but parentheses are required around binary operators, just as in
5662 a cast). This construct is allowed regardless of what kind of data is
5663 normally supposed to reside at @var{addr}.
5666 @node Ambiguous Expressions
5667 @section Ambiguous Expressions
5668 @cindex ambiguous expressions
5670 Expressions can sometimes contain some ambiguous elements. For instance,
5671 some programming languages (notably Ada, C@t{++} and Objective-C) permit
5672 a single function name to be defined several times, for application in
5673 different contexts. This is called @dfn{overloading}. Another example
5674 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
5675 templates and is typically instantiated several times, resulting in
5676 the same function name being defined in different contexts.
5678 In some cases and depending on the language, it is possible to adjust
5679 the expression to remove the ambiguity. For instance in C@t{++}, you
5680 can specify the signature of the function you want to break on, as in
5681 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
5682 qualified name of your function often makes the expression unambiguous
5685 When an ambiguity that needs to be resolved is detected, the debugger
5686 has the capability to display a menu of numbered choices for each
5687 possibility, and then waits for the selection with the prompt @samp{>}.
5688 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
5689 aborts the current command. If the command in which the expression was
5690 used allows more than one choice to be selected, the next option in the
5691 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
5694 For example, the following session excerpt shows an attempt to set a
5695 breakpoint at the overloaded symbol @code{String::after}.
5696 We choose three particular definitions of that function name:
5698 @c FIXME! This is likely to change to show arg type lists, at least
5701 (@value{GDBP}) b String::after
5704 [2] file:String.cc; line number:867
5705 [3] file:String.cc; line number:860
5706 [4] file:String.cc; line number:875
5707 [5] file:String.cc; line number:853
5708 [6] file:String.cc; line number:846
5709 [7] file:String.cc; line number:735
5711 Breakpoint 1 at 0xb26c: file String.cc, line 867.
5712 Breakpoint 2 at 0xb344: file String.cc, line 875.
5713 Breakpoint 3 at 0xafcc: file String.cc, line 846.
5714 Multiple breakpoints were set.
5715 Use the "delete" command to delete unwanted
5722 @kindex set multiple-symbols
5723 @item set multiple-symbols @var{mode}
5724 @cindex multiple-symbols menu
5726 This option allows you to adjust the debugger behavior when an expression
5729 By default, @var{mode} is set to @code{all}. If the command with which
5730 the expression is used allows more than one choice, then @value{GDBN}
5731 automatically selects all possible choices. For instance, inserting
5732 a breakpoint on a function using an ambiguous name results in a breakpoint
5733 inserted on each possible match. However, if a unique choice must be made,
5734 then @value{GDBN} uses the menu to help you disambiguate the expression.
5735 For instance, printing the address of an overloaded function will result
5736 in the use of the menu.
5738 When @var{mode} is set to @code{ask}, the debugger always uses the menu
5739 when an ambiguity is detected.
5741 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
5742 an error due to the ambiguity and the command is aborted.
5744 @kindex show multiple-symbols
5745 @item show multiple-symbols
5746 Show the current value of the @code{multiple-symbols} setting.
5750 @section Program Variables
5752 The most common kind of expression to use is the name of a variable
5755 Variables in expressions are understood in the selected stack frame
5756 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5760 global (or file-static)
5767 visible according to the scope rules of the
5768 programming language from the point of execution in that frame
5771 @noindent This means that in the function
5786 you can examine and use the variable @code{a} whenever your program is
5787 executing within the function @code{foo}, but you can only use or
5788 examine the variable @code{b} while your program is executing inside
5789 the block where @code{b} is declared.
5791 @cindex variable name conflict
5792 There is an exception: you can refer to a variable or function whose
5793 scope is a single source file even if the current execution point is not
5794 in this file. But it is possible to have more than one such variable or
5795 function with the same name (in different source files). If that
5796 happens, referring to that name has unpredictable effects. If you wish,
5797 you can specify a static variable in a particular function or file,
5798 using the colon-colon (@code{::}) notation:
5800 @cindex colon-colon, context for variables/functions
5802 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5803 @cindex @code{::}, context for variables/functions
5806 @var{file}::@var{variable}
5807 @var{function}::@var{variable}
5811 Here @var{file} or @var{function} is the name of the context for the
5812 static @var{variable}. In the case of file names, you can use quotes to
5813 make sure @value{GDBN} parses the file name as a single word---for example,
5814 to print a global value of @code{x} defined in @file{f2.c}:
5817 (@value{GDBP}) p 'f2.c'::x
5820 @cindex C@t{++} scope resolution
5821 This use of @samp{::} is very rarely in conflict with the very similar
5822 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5823 scope resolution operator in @value{GDBN} expressions.
5824 @c FIXME: Um, so what happens in one of those rare cases where it's in
5827 @cindex wrong values
5828 @cindex variable values, wrong
5829 @cindex function entry/exit, wrong values of variables
5830 @cindex optimized code, wrong values of variables
5832 @emph{Warning:} Occasionally, a local variable may appear to have the
5833 wrong value at certain points in a function---just after entry to a new
5834 scope, and just before exit.
5836 You may see this problem when you are stepping by machine instructions.
5837 This is because, on most machines, it takes more than one instruction to
5838 set up a stack frame (including local variable definitions); if you are
5839 stepping by machine instructions, variables may appear to have the wrong
5840 values until the stack frame is completely built. On exit, it usually
5841 also takes more than one machine instruction to destroy a stack frame;
5842 after you begin stepping through that group of instructions, local
5843 variable definitions may be gone.
5845 This may also happen when the compiler does significant optimizations.
5846 To be sure of always seeing accurate values, turn off all optimization
5849 @cindex ``No symbol "foo" in current context''
5850 Another possible effect of compiler optimizations is to optimize
5851 unused variables out of existence, or assign variables to registers (as
5852 opposed to memory addresses). Depending on the support for such cases
5853 offered by the debug info format used by the compiler, @value{GDBN}
5854 might not be able to display values for such local variables. If that
5855 happens, @value{GDBN} will print a message like this:
5858 No symbol "foo" in current context.
5861 To solve such problems, either recompile without optimizations, or use a
5862 different debug info format, if the compiler supports several such
5863 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5864 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5865 produces debug info in a format that is superior to formats such as
5866 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5867 an effective form for debug info. @xref{Debugging Options,,Options
5868 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5869 Compiler Collection (GCC)}.
5870 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5871 that are best suited to C@t{++} programs.
5873 If you ask to print an object whose contents are unknown to
5874 @value{GDBN}, e.g., because its data type is not completely specified
5875 by the debug information, @value{GDBN} will say @samp{<incomplete
5876 type>}. @xref{Symbols, incomplete type}, for more about this.
5878 Strings are identified as arrays of @code{char} values without specified
5879 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5880 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5881 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5882 defines literal string type @code{"char"} as @code{char} without a sign.
5887 signed char var1[] = "A";
5890 You get during debugging
5895 $2 = @{65 'A', 0 '\0'@}
5899 @section Artificial Arrays
5901 @cindex artificial array
5903 @kindex @@@r{, referencing memory as an array}
5904 It is often useful to print out several successive objects of the
5905 same type in memory; a section of an array, or an array of
5906 dynamically determined size for which only a pointer exists in the
5909 You can do this by referring to a contiguous span of memory as an
5910 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5911 operand of @samp{@@} should be the first element of the desired array
5912 and be an individual object. The right operand should be the desired length
5913 of the array. The result is an array value whose elements are all of
5914 the type of the left argument. The first element is actually the left
5915 argument; the second element comes from bytes of memory immediately
5916 following those that hold the first element, and so on. Here is an
5917 example. If a program says
5920 int *array = (int *) malloc (len * sizeof (int));
5924 you can print the contents of @code{array} with
5930 The left operand of @samp{@@} must reside in memory. Array values made
5931 with @samp{@@} in this way behave just like other arrays in terms of
5932 subscripting, and are coerced to pointers when used in expressions.
5933 Artificial arrays most often appear in expressions via the value history
5934 (@pxref{Value History, ,Value History}), after printing one out.
5936 Another way to create an artificial array is to use a cast.
5937 This re-interprets a value as if it were an array.
5938 The value need not be in memory:
5940 (@value{GDBP}) p/x (short[2])0x12345678
5941 $1 = @{0x1234, 0x5678@}
5944 As a convenience, if you leave the array length out (as in
5945 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5946 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5948 (@value{GDBP}) p/x (short[])0x12345678
5949 $2 = @{0x1234, 0x5678@}
5952 Sometimes the artificial array mechanism is not quite enough; in
5953 moderately complex data structures, the elements of interest may not
5954 actually be adjacent---for example, if you are interested in the values
5955 of pointers in an array. One useful work-around in this situation is
5956 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5957 Variables}) as a counter in an expression that prints the first
5958 interesting value, and then repeat that expression via @key{RET}. For
5959 instance, suppose you have an array @code{dtab} of pointers to
5960 structures, and you are interested in the values of a field @code{fv}
5961 in each structure. Here is an example of what you might type:
5971 @node Output Formats
5972 @section Output Formats
5974 @cindex formatted output
5975 @cindex output formats
5976 By default, @value{GDBN} prints a value according to its data type. Sometimes
5977 this is not what you want. For example, you might want to print a number
5978 in hex, or a pointer in decimal. Or you might want to view data in memory
5979 at a certain address as a character string or as an instruction. To do
5980 these things, specify an @dfn{output format} when you print a value.
5982 The simplest use of output formats is to say how to print a value
5983 already computed. This is done by starting the arguments of the
5984 @code{print} command with a slash and a format letter. The format
5985 letters supported are:
5989 Regard the bits of the value as an integer, and print the integer in
5993 Print as integer in signed decimal.
5996 Print as integer in unsigned decimal.
5999 Print as integer in octal.
6002 Print as integer in binary. The letter @samp{t} stands for ``two''.
6003 @footnote{@samp{b} cannot be used because these format letters are also
6004 used with the @code{x} command, where @samp{b} stands for ``byte'';
6005 see @ref{Memory,,Examining Memory}.}
6008 @cindex unknown address, locating
6009 @cindex locate address
6010 Print as an address, both absolute in hexadecimal and as an offset from
6011 the nearest preceding symbol. You can use this format used to discover
6012 where (in what function) an unknown address is located:
6015 (@value{GDBP}) p/a 0x54320
6016 $3 = 0x54320 <_initialize_vx+396>
6020 The command @code{info symbol 0x54320} yields similar results.
6021 @xref{Symbols, info symbol}.
6024 Regard as an integer and print it as a character constant. This
6025 prints both the numerical value and its character representation. The
6026 character representation is replaced with the octal escape @samp{\nnn}
6027 for characters outside the 7-bit @sc{ascii} range.
6029 Without this format, @value{GDBN} displays @code{char},
6030 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6031 constants. Single-byte members of vectors are displayed as integer
6035 Regard the bits of the value as a floating point number and print
6036 using typical floating point syntax.
6039 @cindex printing strings
6040 @cindex printing byte arrays
6041 Regard as a string, if possible. With this format, pointers to single-byte
6042 data are displayed as null-terminated strings and arrays of single-byte data
6043 are displayed as fixed-length strings. Other values are displayed in their
6046 Without this format, @value{GDBN} displays pointers to and arrays of
6047 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6048 strings. Single-byte members of a vector are displayed as an integer
6052 For example, to print the program counter in hex (@pxref{Registers}), type
6059 Note that no space is required before the slash; this is because command
6060 names in @value{GDBN} cannot contain a slash.
6062 To reprint the last value in the value history with a different format,
6063 you can use the @code{print} command with just a format and no
6064 expression. For example, @samp{p/x} reprints the last value in hex.
6067 @section Examining Memory
6069 You can use the command @code{x} (for ``examine'') to examine memory in
6070 any of several formats, independently of your program's data types.
6072 @cindex examining memory
6074 @kindex x @r{(examine memory)}
6075 @item x/@var{nfu} @var{addr}
6078 Use the @code{x} command to examine memory.
6081 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6082 much memory to display and how to format it; @var{addr} is an
6083 expression giving the address where you want to start displaying memory.
6084 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6085 Several commands set convenient defaults for @var{addr}.
6088 @item @var{n}, the repeat count
6089 The repeat count is a decimal integer; the default is 1. It specifies
6090 how much memory (counting by units @var{u}) to display.
6091 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6094 @item @var{f}, the display format
6095 The display format is one of the formats used by @code{print}
6096 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6097 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6098 The default is @samp{x} (hexadecimal) initially. The default changes
6099 each time you use either @code{x} or @code{print}.
6101 @item @var{u}, the unit size
6102 The unit size is any of
6108 Halfwords (two bytes).
6110 Words (four bytes). This is the initial default.
6112 Giant words (eight bytes).
6115 Each time you specify a unit size with @code{x}, that size becomes the
6116 default unit the next time you use @code{x}. (For the @samp{s} and
6117 @samp{i} formats, the unit size is ignored and is normally not written.)
6119 @item @var{addr}, starting display address
6120 @var{addr} is the address where you want @value{GDBN} to begin displaying
6121 memory. The expression need not have a pointer value (though it may);
6122 it is always interpreted as an integer address of a byte of memory.
6123 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6124 @var{addr} is usually just after the last address examined---but several
6125 other commands also set the default address: @code{info breakpoints} (to
6126 the address of the last breakpoint listed), @code{info line} (to the
6127 starting address of a line), and @code{print} (if you use it to display
6128 a value from memory).
6131 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6132 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6133 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6134 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6135 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6137 Since the letters indicating unit sizes are all distinct from the
6138 letters specifying output formats, you do not have to remember whether
6139 unit size or format comes first; either order works. The output
6140 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6141 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6143 Even though the unit size @var{u} is ignored for the formats @samp{s}
6144 and @samp{i}, you might still want to use a count @var{n}; for example,
6145 @samp{3i} specifies that you want to see three machine instructions,
6146 including any operands. For convenience, especially when used with
6147 the @code{display} command, the @samp{i} format also prints branch delay
6148 slot instructions, if any, beyond the count specified, which immediately
6149 follow the last instruction that is within the count. The command
6150 @code{disassemble} gives an alternative way of inspecting machine
6151 instructions; see @ref{Machine Code,,Source and Machine Code}.
6153 All the defaults for the arguments to @code{x} are designed to make it
6154 easy to continue scanning memory with minimal specifications each time
6155 you use @code{x}. For example, after you have inspected three machine
6156 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6157 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6158 the repeat count @var{n} is used again; the other arguments default as
6159 for successive uses of @code{x}.
6161 @cindex @code{$_}, @code{$__}, and value history
6162 The addresses and contents printed by the @code{x} command are not saved
6163 in the value history because there is often too much of them and they
6164 would get in the way. Instead, @value{GDBN} makes these values available for
6165 subsequent use in expressions as values of the convenience variables
6166 @code{$_} and @code{$__}. After an @code{x} command, the last address
6167 examined is available for use in expressions in the convenience variable
6168 @code{$_}. The contents of that address, as examined, are available in
6169 the convenience variable @code{$__}.
6171 If the @code{x} command has a repeat count, the address and contents saved
6172 are from the last memory unit printed; this is not the same as the last
6173 address printed if several units were printed on the last line of output.
6175 @cindex remote memory comparison
6176 @cindex verify remote memory image
6177 When you are debugging a program running on a remote target machine
6178 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6179 remote machine's memory against the executable file you downloaded to
6180 the target. The @code{compare-sections} command is provided for such
6184 @kindex compare-sections
6185 @item compare-sections @r{[}@var{section-name}@r{]}
6186 Compare the data of a loadable section @var{section-name} in the
6187 executable file of the program being debugged with the same section in
6188 the remote machine's memory, and report any mismatches. With no
6189 arguments, compares all loadable sections. This command's
6190 availability depends on the target's support for the @code{"qCRC"}
6195 @section Automatic Display
6196 @cindex automatic display
6197 @cindex display of expressions
6199 If you find that you want to print the value of an expression frequently
6200 (to see how it changes), you might want to add it to the @dfn{automatic
6201 display list} so that @value{GDBN} prints its value each time your program stops.
6202 Each expression added to the list is given a number to identify it;
6203 to remove an expression from the list, you specify that number.
6204 The automatic display looks like this:
6208 3: bar[5] = (struct hack *) 0x3804
6212 This display shows item numbers, expressions and their current values. As with
6213 displays you request manually using @code{x} or @code{print}, you can
6214 specify the output format you prefer; in fact, @code{display} decides
6215 whether to use @code{print} or @code{x} depending your format
6216 specification---it uses @code{x} if you specify either the @samp{i}
6217 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6221 @item display @var{expr}
6222 Add the expression @var{expr} to the list of expressions to display
6223 each time your program stops. @xref{Expressions, ,Expressions}.
6225 @code{display} does not repeat if you press @key{RET} again after using it.
6227 @item display/@var{fmt} @var{expr}
6228 For @var{fmt} specifying only a display format and not a size or
6229 count, add the expression @var{expr} to the auto-display list but
6230 arrange to display it each time in the specified format @var{fmt}.
6231 @xref{Output Formats,,Output Formats}.
6233 @item display/@var{fmt} @var{addr}
6234 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6235 number of units, add the expression @var{addr} as a memory address to
6236 be examined each time your program stops. Examining means in effect
6237 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6240 For example, @samp{display/i $pc} can be helpful, to see the machine
6241 instruction about to be executed each time execution stops (@samp{$pc}
6242 is a common name for the program counter; @pxref{Registers, ,Registers}).
6245 @kindex delete display
6247 @item undisplay @var{dnums}@dots{}
6248 @itemx delete display @var{dnums}@dots{}
6249 Remove item numbers @var{dnums} from the list of expressions to display.
6251 @code{undisplay} does not repeat if you press @key{RET} after using it.
6252 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6254 @kindex disable display
6255 @item disable display @var{dnums}@dots{}
6256 Disable the display of item numbers @var{dnums}. A disabled display
6257 item is not printed automatically, but is not forgotten. It may be
6258 enabled again later.
6260 @kindex enable display
6261 @item enable display @var{dnums}@dots{}
6262 Enable display of item numbers @var{dnums}. It becomes effective once
6263 again in auto display of its expression, until you specify otherwise.
6266 Display the current values of the expressions on the list, just as is
6267 done when your program stops.
6269 @kindex info display
6271 Print the list of expressions previously set up to display
6272 automatically, each one with its item number, but without showing the
6273 values. This includes disabled expressions, which are marked as such.
6274 It also includes expressions which would not be displayed right now
6275 because they refer to automatic variables not currently available.
6278 @cindex display disabled out of scope
6279 If a display expression refers to local variables, then it does not make
6280 sense outside the lexical context for which it was set up. Such an
6281 expression is disabled when execution enters a context where one of its
6282 variables is not defined. For example, if you give the command
6283 @code{display last_char} while inside a function with an argument
6284 @code{last_char}, @value{GDBN} displays this argument while your program
6285 continues to stop inside that function. When it stops elsewhere---where
6286 there is no variable @code{last_char}---the display is disabled
6287 automatically. The next time your program stops where @code{last_char}
6288 is meaningful, you can enable the display expression once again.
6290 @node Print Settings
6291 @section Print Settings
6293 @cindex format options
6294 @cindex print settings
6295 @value{GDBN} provides the following ways to control how arrays, structures,
6296 and symbols are printed.
6299 These settings are useful for debugging programs in any language:
6303 @item set print address
6304 @itemx set print address on
6305 @cindex print/don't print memory addresses
6306 @value{GDBN} prints memory addresses showing the location of stack
6307 traces, structure values, pointer values, breakpoints, and so forth,
6308 even when it also displays the contents of those addresses. The default
6309 is @code{on}. For example, this is what a stack frame display looks like with
6310 @code{set print address on}:
6315 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6317 530 if (lquote != def_lquote)
6321 @item set print address off
6322 Do not print addresses when displaying their contents. For example,
6323 this is the same stack frame displayed with @code{set print address off}:
6327 (@value{GDBP}) set print addr off
6329 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6330 530 if (lquote != def_lquote)
6334 You can use @samp{set print address off} to eliminate all machine
6335 dependent displays from the @value{GDBN} interface. For example, with
6336 @code{print address off}, you should get the same text for backtraces on
6337 all machines---whether or not they involve pointer arguments.
6340 @item show print address
6341 Show whether or not addresses are to be printed.
6344 When @value{GDBN} prints a symbolic address, it normally prints the
6345 closest earlier symbol plus an offset. If that symbol does not uniquely
6346 identify the address (for example, it is a name whose scope is a single
6347 source file), you may need to clarify. One way to do this is with
6348 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6349 you can set @value{GDBN} to print the source file and line number when
6350 it prints a symbolic address:
6353 @item set print symbol-filename on
6354 @cindex source file and line of a symbol
6355 @cindex symbol, source file and line
6356 Tell @value{GDBN} to print the source file name and line number of a
6357 symbol in the symbolic form of an address.
6359 @item set print symbol-filename off
6360 Do not print source file name and line number of a symbol. This is the
6363 @item show print symbol-filename
6364 Show whether or not @value{GDBN} will print the source file name and
6365 line number of a symbol in the symbolic form of an address.
6368 Another situation where it is helpful to show symbol filenames and line
6369 numbers is when disassembling code; @value{GDBN} shows you the line
6370 number and source file that corresponds to each instruction.
6372 Also, you may wish to see the symbolic form only if the address being
6373 printed is reasonably close to the closest earlier symbol:
6376 @item set print max-symbolic-offset @var{max-offset}
6377 @cindex maximum value for offset of closest symbol
6378 Tell @value{GDBN} to only display the symbolic form of an address if the
6379 offset between the closest earlier symbol and the address is less than
6380 @var{max-offset}. The default is 0, which tells @value{GDBN}
6381 to always print the symbolic form of an address if any symbol precedes it.
6383 @item show print max-symbolic-offset
6384 Ask how large the maximum offset is that @value{GDBN} prints in a
6388 @cindex wild pointer, interpreting
6389 @cindex pointer, finding referent
6390 If you have a pointer and you are not sure where it points, try
6391 @samp{set print symbol-filename on}. Then you can determine the name
6392 and source file location of the variable where it points, using
6393 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6394 For example, here @value{GDBN} shows that a variable @code{ptt} points
6395 at another variable @code{t}, defined in @file{hi2.c}:
6398 (@value{GDBP}) set print symbol-filename on
6399 (@value{GDBP}) p/a ptt
6400 $4 = 0xe008 <t in hi2.c>
6404 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6405 does not show the symbol name and filename of the referent, even with
6406 the appropriate @code{set print} options turned on.
6409 Other settings control how different kinds of objects are printed:
6412 @item set print array
6413 @itemx set print array on
6414 @cindex pretty print arrays
6415 Pretty print arrays. This format is more convenient to read,
6416 but uses more space. The default is off.
6418 @item set print array off
6419 Return to compressed format for arrays.
6421 @item show print array
6422 Show whether compressed or pretty format is selected for displaying
6425 @cindex print array indexes
6426 @item set print array-indexes
6427 @itemx set print array-indexes on
6428 Print the index of each element when displaying arrays. May be more
6429 convenient to locate a given element in the array or quickly find the
6430 index of a given element in that printed array. The default is off.
6432 @item set print array-indexes off
6433 Stop printing element indexes when displaying arrays.
6435 @item show print array-indexes
6436 Show whether the index of each element is printed when displaying
6439 @item set print elements @var{number-of-elements}
6440 @cindex number of array elements to print
6441 @cindex limit on number of printed array elements
6442 Set a limit on how many elements of an array @value{GDBN} will print.
6443 If @value{GDBN} is printing a large array, it stops printing after it has
6444 printed the number of elements set by the @code{set print elements} command.
6445 This limit also applies to the display of strings.
6446 When @value{GDBN} starts, this limit is set to 200.
6447 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6449 @item show print elements
6450 Display the number of elements of a large array that @value{GDBN} will print.
6451 If the number is 0, then the printing is unlimited.
6453 @item set print frame-arguments @var{value}
6454 @cindex printing frame argument values
6455 @cindex print all frame argument values
6456 @cindex print frame argument values for scalars only
6457 @cindex do not print frame argument values
6458 This command allows to control how the values of arguments are printed
6459 when the debugger prints a frame (@pxref{Frames}). The possible
6464 The values of all arguments are printed. This is the default.
6467 Print the value of an argument only if it is a scalar. The value of more
6468 complex arguments such as arrays, structures, unions, etc, is replaced
6469 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6472 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6477 None of the argument values are printed. Instead, the value of each argument
6478 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6481 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6486 By default, all argument values are always printed. But this command
6487 can be useful in several cases. For instance, it can be used to reduce
6488 the amount of information printed in each frame, making the backtrace
6489 more readable. Also, this command can be used to improve performance
6490 when displaying Ada frames, because the computation of large arguments
6491 can sometimes be CPU-intensive, especiallly in large applications.
6492 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6493 avoids this computation, thus speeding up the display of each Ada frame.
6495 @item show print frame-arguments
6496 Show how the value of arguments should be displayed when printing a frame.
6498 @item set print repeats
6499 @cindex repeated array elements
6500 Set the threshold for suppressing display of repeated array
6501 elements. When the number of consecutive identical elements of an
6502 array exceeds the threshold, @value{GDBN} prints the string
6503 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6504 identical repetitions, instead of displaying the identical elements
6505 themselves. Setting the threshold to zero will cause all elements to
6506 be individually printed. The default threshold is 10.
6508 @item show print repeats
6509 Display the current threshold for printing repeated identical
6512 @item set print null-stop
6513 @cindex @sc{null} elements in arrays
6514 Cause @value{GDBN} to stop printing the characters of an array when the first
6515 @sc{null} is encountered. This is useful when large arrays actually
6516 contain only short strings.
6519 @item show print null-stop
6520 Show whether @value{GDBN} stops printing an array on the first
6521 @sc{null} character.
6523 @item set print pretty on
6524 @cindex print structures in indented form
6525 @cindex indentation in structure display
6526 Cause @value{GDBN} to print structures in an indented format with one member
6527 per line, like this:
6542 @item set print pretty off
6543 Cause @value{GDBN} to print structures in a compact format, like this:
6547 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6548 meat = 0x54 "Pork"@}
6553 This is the default format.
6555 @item show print pretty
6556 Show which format @value{GDBN} is using to print structures.
6558 @item set print sevenbit-strings on
6559 @cindex eight-bit characters in strings
6560 @cindex octal escapes in strings
6561 Print using only seven-bit characters; if this option is set,
6562 @value{GDBN} displays any eight-bit characters (in strings or
6563 character values) using the notation @code{\}@var{nnn}. This setting is
6564 best if you are working in English (@sc{ascii}) and you use the
6565 high-order bit of characters as a marker or ``meta'' bit.
6567 @item set print sevenbit-strings off
6568 Print full eight-bit characters. This allows the use of more
6569 international character sets, and is the default.
6571 @item show print sevenbit-strings
6572 Show whether or not @value{GDBN} is printing only seven-bit characters.
6574 @item set print union on
6575 @cindex unions in structures, printing
6576 Tell @value{GDBN} to print unions which are contained in structures
6577 and other unions. This is the default setting.
6579 @item set print union off
6580 Tell @value{GDBN} not to print unions which are contained in
6581 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6584 @item show print union
6585 Ask @value{GDBN} whether or not it will print unions which are contained in
6586 structures and other unions.
6588 For example, given the declarations
6591 typedef enum @{Tree, Bug@} Species;
6592 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6593 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6604 struct thing foo = @{Tree, @{Acorn@}@};
6608 with @code{set print union on} in effect @samp{p foo} would print
6611 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6615 and with @code{set print union off} in effect it would print
6618 $1 = @{it = Tree, form = @{...@}@}
6622 @code{set print union} affects programs written in C-like languages
6628 These settings are of interest when debugging C@t{++} programs:
6631 @cindex demangling C@t{++} names
6632 @item set print demangle
6633 @itemx set print demangle on
6634 Print C@t{++} names in their source form rather than in the encoded
6635 (``mangled'') form passed to the assembler and linker for type-safe
6636 linkage. The default is on.
6638 @item show print demangle
6639 Show whether C@t{++} names are printed in mangled or demangled form.
6641 @item set print asm-demangle
6642 @itemx set print asm-demangle on
6643 Print C@t{++} names in their source form rather than their mangled form, even
6644 in assembler code printouts such as instruction disassemblies.
6647 @item show print asm-demangle
6648 Show whether C@t{++} names in assembly listings are printed in mangled
6651 @cindex C@t{++} symbol decoding style
6652 @cindex symbol decoding style, C@t{++}
6653 @kindex set demangle-style
6654 @item set demangle-style @var{style}
6655 Choose among several encoding schemes used by different compilers to
6656 represent C@t{++} names. The choices for @var{style} are currently:
6660 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6663 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6664 This is the default.
6667 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6670 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6673 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6674 @strong{Warning:} this setting alone is not sufficient to allow
6675 debugging @code{cfront}-generated executables. @value{GDBN} would
6676 require further enhancement to permit that.
6679 If you omit @var{style}, you will see a list of possible formats.
6681 @item show demangle-style
6682 Display the encoding style currently in use for decoding C@t{++} symbols.
6684 @item set print object
6685 @itemx set print object on
6686 @cindex derived type of an object, printing
6687 @cindex display derived types
6688 When displaying a pointer to an object, identify the @emph{actual}
6689 (derived) type of the object rather than the @emph{declared} type, using
6690 the virtual function table.
6692 @item set print object off
6693 Display only the declared type of objects, without reference to the
6694 virtual function table. This is the default setting.
6696 @item show print object
6697 Show whether actual, or declared, object types are displayed.
6699 @item set print static-members
6700 @itemx set print static-members on
6701 @cindex static members of C@t{++} objects
6702 Print static members when displaying a C@t{++} object. The default is on.
6704 @item set print static-members off
6705 Do not print static members when displaying a C@t{++} object.
6707 @item show print static-members
6708 Show whether C@t{++} static members are printed or not.
6710 @item set print pascal_static-members
6711 @itemx set print pascal_static-members on
6712 @cindex static members of Pascal objects
6713 @cindex Pascal objects, static members display
6714 Print static members when displaying a Pascal object. The default is on.
6716 @item set print pascal_static-members off
6717 Do not print static members when displaying a Pascal object.
6719 @item show print pascal_static-members
6720 Show whether Pascal static members are printed or not.
6722 @c These don't work with HP ANSI C++ yet.
6723 @item set print vtbl
6724 @itemx set print vtbl on
6725 @cindex pretty print C@t{++} virtual function tables
6726 @cindex virtual functions (C@t{++}) display
6727 @cindex VTBL display
6728 Pretty print C@t{++} virtual function tables. The default is off.
6729 (The @code{vtbl} commands do not work on programs compiled with the HP
6730 ANSI C@t{++} compiler (@code{aCC}).)
6732 @item set print vtbl off
6733 Do not pretty print C@t{++} virtual function tables.
6735 @item show print vtbl
6736 Show whether C@t{++} virtual function tables are pretty printed, or not.
6740 @section Value History
6742 @cindex value history
6743 @cindex history of values printed by @value{GDBN}
6744 Values printed by the @code{print} command are saved in the @value{GDBN}
6745 @dfn{value history}. This allows you to refer to them in other expressions.
6746 Values are kept until the symbol table is re-read or discarded
6747 (for example with the @code{file} or @code{symbol-file} commands).
6748 When the symbol table changes, the value history is discarded,
6749 since the values may contain pointers back to the types defined in the
6754 @cindex history number
6755 The values printed are given @dfn{history numbers} by which you can
6756 refer to them. These are successive integers starting with one.
6757 @code{print} shows you the history number assigned to a value by
6758 printing @samp{$@var{num} = } before the value; here @var{num} is the
6761 To refer to any previous value, use @samp{$} followed by the value's
6762 history number. The way @code{print} labels its output is designed to
6763 remind you of this. Just @code{$} refers to the most recent value in
6764 the history, and @code{$$} refers to the value before that.
6765 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6766 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6767 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6769 For example, suppose you have just printed a pointer to a structure and
6770 want to see the contents of the structure. It suffices to type
6776 If you have a chain of structures where the component @code{next} points
6777 to the next one, you can print the contents of the next one with this:
6784 You can print successive links in the chain by repeating this
6785 command---which you can do by just typing @key{RET}.
6787 Note that the history records values, not expressions. If the value of
6788 @code{x} is 4 and you type these commands:
6796 then the value recorded in the value history by the @code{print} command
6797 remains 4 even though the value of @code{x} has changed.
6802 Print the last ten values in the value history, with their item numbers.
6803 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6804 values} does not change the history.
6806 @item show values @var{n}
6807 Print ten history values centered on history item number @var{n}.
6810 Print ten history values just after the values last printed. If no more
6811 values are available, @code{show values +} produces no display.
6814 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6815 same effect as @samp{show values +}.
6817 @node Convenience Vars
6818 @section Convenience Variables
6820 @cindex convenience variables
6821 @cindex user-defined variables
6822 @value{GDBN} provides @dfn{convenience variables} that you can use within
6823 @value{GDBN} to hold on to a value and refer to it later. These variables
6824 exist entirely within @value{GDBN}; they are not part of your program, and
6825 setting a convenience variable has no direct effect on further execution
6826 of your program. That is why you can use them freely.
6828 Convenience variables are prefixed with @samp{$}. Any name preceded by
6829 @samp{$} can be used for a convenience variable, unless it is one of
6830 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6831 (Value history references, in contrast, are @emph{numbers} preceded
6832 by @samp{$}. @xref{Value History, ,Value History}.)
6834 You can save a value in a convenience variable with an assignment
6835 expression, just as you would set a variable in your program.
6839 set $foo = *object_ptr
6843 would save in @code{$foo} the value contained in the object pointed to by
6846 Using a convenience variable for the first time creates it, but its
6847 value is @code{void} until you assign a new value. You can alter the
6848 value with another assignment at any time.
6850 Convenience variables have no fixed types. You can assign a convenience
6851 variable any type of value, including structures and arrays, even if
6852 that variable already has a value of a different type. The convenience
6853 variable, when used as an expression, has the type of its current value.
6856 @kindex show convenience
6857 @cindex show all user variables
6858 @item show convenience
6859 Print a list of convenience variables used so far, and their values.
6860 Abbreviated @code{show conv}.
6862 @kindex init-if-undefined
6863 @cindex convenience variables, initializing
6864 @item init-if-undefined $@var{variable} = @var{expression}
6865 Set a convenience variable if it has not already been set. This is useful
6866 for user-defined commands that keep some state. It is similar, in concept,
6867 to using local static variables with initializers in C (except that
6868 convenience variables are global). It can also be used to allow users to
6869 override default values used in a command script.
6871 If the variable is already defined then the expression is not evaluated so
6872 any side-effects do not occur.
6875 One of the ways to use a convenience variable is as a counter to be
6876 incremented or a pointer to be advanced. For example, to print
6877 a field from successive elements of an array of structures:
6881 print bar[$i++]->contents
6885 Repeat that command by typing @key{RET}.
6887 Some convenience variables are created automatically by @value{GDBN} and given
6888 values likely to be useful.
6891 @vindex $_@r{, convenience variable}
6893 The variable @code{$_} is automatically set by the @code{x} command to
6894 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6895 commands which provide a default address for @code{x} to examine also
6896 set @code{$_} to that address; these commands include @code{info line}
6897 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6898 except when set by the @code{x} command, in which case it is a pointer
6899 to the type of @code{$__}.
6901 @vindex $__@r{, convenience variable}
6903 The variable @code{$__} is automatically set by the @code{x} command
6904 to the value found in the last address examined. Its type is chosen
6905 to match the format in which the data was printed.
6908 @vindex $_exitcode@r{, convenience variable}
6909 The variable @code{$_exitcode} is automatically set to the exit code when
6910 the program being debugged terminates.
6913 On HP-UX systems, if you refer to a function or variable name that
6914 begins with a dollar sign, @value{GDBN} searches for a user or system
6915 name first, before it searches for a convenience variable.
6921 You can refer to machine register contents, in expressions, as variables
6922 with names starting with @samp{$}. The names of registers are different
6923 for each machine; use @code{info registers} to see the names used on
6927 @kindex info registers
6928 @item info registers
6929 Print the names and values of all registers except floating-point
6930 and vector registers (in the selected stack frame).
6932 @kindex info all-registers
6933 @cindex floating point registers
6934 @item info all-registers
6935 Print the names and values of all registers, including floating-point
6936 and vector registers (in the selected stack frame).
6938 @item info registers @var{regname} @dots{}
6939 Print the @dfn{relativized} value of each specified register @var{regname}.
6940 As discussed in detail below, register values are normally relative to
6941 the selected stack frame. @var{regname} may be any register name valid on
6942 the machine you are using, with or without the initial @samp{$}.
6945 @cindex stack pointer register
6946 @cindex program counter register
6947 @cindex process status register
6948 @cindex frame pointer register
6949 @cindex standard registers
6950 @value{GDBN} has four ``standard'' register names that are available (in
6951 expressions) on most machines---whenever they do not conflict with an
6952 architecture's canonical mnemonics for registers. The register names
6953 @code{$pc} and @code{$sp} are used for the program counter register and
6954 the stack pointer. @code{$fp} is used for a register that contains a
6955 pointer to the current stack frame, and @code{$ps} is used for a
6956 register that contains the processor status. For example,
6957 you could print the program counter in hex with
6964 or print the instruction to be executed next with
6971 or add four to the stack pointer@footnote{This is a way of removing
6972 one word from the stack, on machines where stacks grow downward in
6973 memory (most machines, nowadays). This assumes that the innermost
6974 stack frame is selected; setting @code{$sp} is not allowed when other
6975 stack frames are selected. To pop entire frames off the stack,
6976 regardless of machine architecture, use @code{return};
6977 see @ref{Returning, ,Returning from a Function}.} with
6983 Whenever possible, these four standard register names are available on
6984 your machine even though the machine has different canonical mnemonics,
6985 so long as there is no conflict. The @code{info registers} command
6986 shows the canonical names. For example, on the SPARC, @code{info
6987 registers} displays the processor status register as @code{$psr} but you
6988 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6989 is an alias for the @sc{eflags} register.
6991 @value{GDBN} always considers the contents of an ordinary register as an
6992 integer when the register is examined in this way. Some machines have
6993 special registers which can hold nothing but floating point; these
6994 registers are considered to have floating point values. There is no way
6995 to refer to the contents of an ordinary register as floating point value
6996 (although you can @emph{print} it as a floating point value with
6997 @samp{print/f $@var{regname}}).
6999 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7000 means that the data format in which the register contents are saved by
7001 the operating system is not the same one that your program normally
7002 sees. For example, the registers of the 68881 floating point
7003 coprocessor are always saved in ``extended'' (raw) format, but all C
7004 programs expect to work with ``double'' (virtual) format. In such
7005 cases, @value{GDBN} normally works with the virtual format only (the format
7006 that makes sense for your program), but the @code{info registers} command
7007 prints the data in both formats.
7009 @cindex SSE registers (x86)
7010 @cindex MMX registers (x86)
7011 Some machines have special registers whose contents can be interpreted
7012 in several different ways. For example, modern x86-based machines
7013 have SSE and MMX registers that can hold several values packed
7014 together in several different formats. @value{GDBN} refers to such
7015 registers in @code{struct} notation:
7018 (@value{GDBP}) print $xmm1
7020 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7021 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7022 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7023 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7024 v4_int32 = @{0, 20657912, 11, 13@},
7025 v2_int64 = @{88725056443645952, 55834574859@},
7026 uint128 = 0x0000000d0000000b013b36f800000000
7031 To set values of such registers, you need to tell @value{GDBN} which
7032 view of the register you wish to change, as if you were assigning
7033 value to a @code{struct} member:
7036 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7039 Normally, register values are relative to the selected stack frame
7040 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7041 value that the register would contain if all stack frames farther in
7042 were exited and their saved registers restored. In order to see the
7043 true contents of hardware registers, you must select the innermost
7044 frame (with @samp{frame 0}).
7046 However, @value{GDBN} must deduce where registers are saved, from the machine
7047 code generated by your compiler. If some registers are not saved, or if
7048 @value{GDBN} is unable to locate the saved registers, the selected stack
7049 frame makes no difference.
7051 @node Floating Point Hardware
7052 @section Floating Point Hardware
7053 @cindex floating point
7055 Depending on the configuration, @value{GDBN} may be able to give
7056 you more information about the status of the floating point hardware.
7061 Display hardware-dependent information about the floating
7062 point unit. The exact contents and layout vary depending on the
7063 floating point chip. Currently, @samp{info float} is supported on
7064 the ARM and x86 machines.
7068 @section Vector Unit
7071 Depending on the configuration, @value{GDBN} may be able to give you
7072 more information about the status of the vector unit.
7077 Display information about the vector unit. The exact contents and
7078 layout vary depending on the hardware.
7081 @node OS Information
7082 @section Operating System Auxiliary Information
7083 @cindex OS information
7085 @value{GDBN} provides interfaces to useful OS facilities that can help
7086 you debug your program.
7088 @cindex @code{ptrace} system call
7089 @cindex @code{struct user} contents
7090 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7091 machines), it interfaces with the inferior via the @code{ptrace}
7092 system call. The operating system creates a special sata structure,
7093 called @code{struct user}, for this interface. You can use the
7094 command @code{info udot} to display the contents of this data
7100 Display the contents of the @code{struct user} maintained by the OS
7101 kernel for the program being debugged. @value{GDBN} displays the
7102 contents of @code{struct user} as a list of hex numbers, similar to
7103 the @code{examine} command.
7106 @cindex auxiliary vector
7107 @cindex vector, auxiliary
7108 Some operating systems supply an @dfn{auxiliary vector} to programs at
7109 startup. This is akin to the arguments and environment that you
7110 specify for a program, but contains a system-dependent variety of
7111 binary values that tell system libraries important details about the
7112 hardware, operating system, and process. Each value's purpose is
7113 identified by an integer tag; the meanings are well-known but system-specific.
7114 Depending on the configuration and operating system facilities,
7115 @value{GDBN} may be able to show you this information. For remote
7116 targets, this functionality may further depend on the remote stub's
7117 support of the @samp{qXfer:auxv:read} packet, see
7118 @ref{qXfer auxiliary vector read}.
7123 Display the auxiliary vector of the inferior, which can be either a
7124 live process or a core dump file. @value{GDBN} prints each tag value
7125 numerically, and also shows names and text descriptions for recognized
7126 tags. Some values in the vector are numbers, some bit masks, and some
7127 pointers to strings or other data. @value{GDBN} displays each value in the
7128 most appropriate form for a recognized tag, and in hexadecimal for
7129 an unrecognized tag.
7133 @node Memory Region Attributes
7134 @section Memory Region Attributes
7135 @cindex memory region attributes
7137 @dfn{Memory region attributes} allow you to describe special handling
7138 required by regions of your target's memory. @value{GDBN} uses
7139 attributes to determine whether to allow certain types of memory
7140 accesses; whether to use specific width accesses; and whether to cache
7141 target memory. By default the description of memory regions is
7142 fetched from the target (if the current target supports this), but the
7143 user can override the fetched regions.
7145 Defined memory regions can be individually enabled and disabled. When a
7146 memory region is disabled, @value{GDBN} uses the default attributes when
7147 accessing memory in that region. Similarly, if no memory regions have
7148 been defined, @value{GDBN} uses the default attributes when accessing
7151 When a memory region is defined, it is given a number to identify it;
7152 to enable, disable, or remove a memory region, you specify that number.
7156 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7157 Define a memory region bounded by @var{lower} and @var{upper} with
7158 attributes @var{attributes}@dots{}, and add it to the list of regions
7159 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7160 case: it is treated as the target's maximum memory address.
7161 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7164 Discard any user changes to the memory regions and use target-supplied
7165 regions, if available, or no regions if the target does not support.
7168 @item delete mem @var{nums}@dots{}
7169 Remove memory regions @var{nums}@dots{} from the list of regions
7170 monitored by @value{GDBN}.
7173 @item disable mem @var{nums}@dots{}
7174 Disable monitoring of memory regions @var{nums}@dots{}.
7175 A disabled memory region is not forgotten.
7176 It may be enabled again later.
7179 @item enable mem @var{nums}@dots{}
7180 Enable monitoring of memory regions @var{nums}@dots{}.
7184 Print a table of all defined memory regions, with the following columns
7188 @item Memory Region Number
7189 @item Enabled or Disabled.
7190 Enabled memory regions are marked with @samp{y}.
7191 Disabled memory regions are marked with @samp{n}.
7194 The address defining the inclusive lower bound of the memory region.
7197 The address defining the exclusive upper bound of the memory region.
7200 The list of attributes set for this memory region.
7205 @subsection Attributes
7207 @subsubsection Memory Access Mode
7208 The access mode attributes set whether @value{GDBN} may make read or
7209 write accesses to a memory region.
7211 While these attributes prevent @value{GDBN} from performing invalid
7212 memory accesses, they do nothing to prevent the target system, I/O DMA,
7213 etc.@: from accessing memory.
7217 Memory is read only.
7219 Memory is write only.
7221 Memory is read/write. This is the default.
7224 @subsubsection Memory Access Size
7225 The access size attribute tells @value{GDBN} to use specific sized
7226 accesses in the memory region. Often memory mapped device registers
7227 require specific sized accesses. If no access size attribute is
7228 specified, @value{GDBN} may use accesses of any size.
7232 Use 8 bit memory accesses.
7234 Use 16 bit memory accesses.
7236 Use 32 bit memory accesses.
7238 Use 64 bit memory accesses.
7241 @c @subsubsection Hardware/Software Breakpoints
7242 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7243 @c will use hardware or software breakpoints for the internal breakpoints
7244 @c used by the step, next, finish, until, etc. commands.
7248 @c Always use hardware breakpoints
7249 @c @item swbreak (default)
7252 @subsubsection Data Cache
7253 The data cache attributes set whether @value{GDBN} will cache target
7254 memory. While this generally improves performance by reducing debug
7255 protocol overhead, it can lead to incorrect results because @value{GDBN}
7256 does not know about volatile variables or memory mapped device
7261 Enable @value{GDBN} to cache target memory.
7263 Disable @value{GDBN} from caching target memory. This is the default.
7266 @subsection Memory Access Checking
7267 @value{GDBN} can be instructed to refuse accesses to memory that is
7268 not explicitly described. This can be useful if accessing such
7269 regions has undesired effects for a specific target, or to provide
7270 better error checking. The following commands control this behaviour.
7273 @kindex set mem inaccessible-by-default
7274 @item set mem inaccessible-by-default [on|off]
7275 If @code{on} is specified, make @value{GDBN} treat memory not
7276 explicitly described by the memory ranges as non-existent and refuse accesses
7277 to such memory. The checks are only performed if there's at least one
7278 memory range defined. If @code{off} is specified, make @value{GDBN}
7279 treat the memory not explicitly described by the memory ranges as RAM.
7280 The default value is @code{on}.
7281 @kindex show mem inaccessible-by-default
7282 @item show mem inaccessible-by-default
7283 Show the current handling of accesses to unknown memory.
7287 @c @subsubsection Memory Write Verification
7288 @c The memory write verification attributes set whether @value{GDBN}
7289 @c will re-reads data after each write to verify the write was successful.
7293 @c @item noverify (default)
7296 @node Dump/Restore Files
7297 @section Copy Between Memory and a File
7298 @cindex dump/restore files
7299 @cindex append data to a file
7300 @cindex dump data to a file
7301 @cindex restore data from a file
7303 You can use the commands @code{dump}, @code{append}, and
7304 @code{restore} to copy data between target memory and a file. The
7305 @code{dump} and @code{append} commands write data to a file, and the
7306 @code{restore} command reads data from a file back into the inferior's
7307 memory. Files may be in binary, Motorola S-record, Intel hex, or
7308 Tektronix Hex format; however, @value{GDBN} can only append to binary
7314 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7315 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7316 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7317 or the value of @var{expr}, to @var{filename} in the given format.
7319 The @var{format} parameter may be any one of:
7326 Motorola S-record format.
7328 Tektronix Hex format.
7331 @value{GDBN} uses the same definitions of these formats as the
7332 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7333 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7337 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7338 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7339 Append the contents of memory from @var{start_addr} to @var{end_addr},
7340 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7341 (@value{GDBN} can only append data to files in raw binary form.)
7344 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7345 Restore the contents of file @var{filename} into memory. The
7346 @code{restore} command can automatically recognize any known @sc{bfd}
7347 file format, except for raw binary. To restore a raw binary file you
7348 must specify the optional keyword @code{binary} after the filename.
7350 If @var{bias} is non-zero, its value will be added to the addresses
7351 contained in the file. Binary files always start at address zero, so
7352 they will be restored at address @var{bias}. Other bfd files have
7353 a built-in location; they will be restored at offset @var{bias}
7356 If @var{start} and/or @var{end} are non-zero, then only data between
7357 file offset @var{start} and file offset @var{end} will be restored.
7358 These offsets are relative to the addresses in the file, before
7359 the @var{bias} argument is applied.
7363 @node Core File Generation
7364 @section How to Produce a Core File from Your Program
7365 @cindex dump core from inferior
7367 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7368 image of a running process and its process status (register values
7369 etc.). Its primary use is post-mortem debugging of a program that
7370 crashed while it ran outside a debugger. A program that crashes
7371 automatically produces a core file, unless this feature is disabled by
7372 the user. @xref{Files}, for information on invoking @value{GDBN} in
7373 the post-mortem debugging mode.
7375 Occasionally, you may wish to produce a core file of the program you
7376 are debugging in order to preserve a snapshot of its state.
7377 @value{GDBN} has a special command for that.
7381 @kindex generate-core-file
7382 @item generate-core-file [@var{file}]
7383 @itemx gcore [@var{file}]
7384 Produce a core dump of the inferior process. The optional argument
7385 @var{file} specifies the file name where to put the core dump. If not
7386 specified, the file name defaults to @file{core.@var{pid}}, where
7387 @var{pid} is the inferior process ID.
7389 Note that this command is implemented only for some systems (as of
7390 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7393 @node Character Sets
7394 @section Character Sets
7395 @cindex character sets
7397 @cindex translating between character sets
7398 @cindex host character set
7399 @cindex target character set
7401 If the program you are debugging uses a different character set to
7402 represent characters and strings than the one @value{GDBN} uses itself,
7403 @value{GDBN} can automatically translate between the character sets for
7404 you. The character set @value{GDBN} uses we call the @dfn{host
7405 character set}; the one the inferior program uses we call the
7406 @dfn{target character set}.
7408 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7409 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7410 remote protocol (@pxref{Remote Debugging}) to debug a program
7411 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7412 then the host character set is Latin-1, and the target character set is
7413 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7414 target-charset EBCDIC-US}, then @value{GDBN} translates between
7415 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7416 character and string literals in expressions.
7418 @value{GDBN} has no way to automatically recognize which character set
7419 the inferior program uses; you must tell it, using the @code{set
7420 target-charset} command, described below.
7422 Here are the commands for controlling @value{GDBN}'s character set
7426 @item set target-charset @var{charset}
7427 @kindex set target-charset
7428 Set the current target character set to @var{charset}. We list the
7429 character set names @value{GDBN} recognizes below, but if you type
7430 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7431 list the target character sets it supports.
7435 @item set host-charset @var{charset}
7436 @kindex set host-charset
7437 Set the current host character set to @var{charset}.
7439 By default, @value{GDBN} uses a host character set appropriate to the
7440 system it is running on; you can override that default using the
7441 @code{set host-charset} command.
7443 @value{GDBN} can only use certain character sets as its host character
7444 set. We list the character set names @value{GDBN} recognizes below, and
7445 indicate which can be host character sets, but if you type
7446 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7447 list the host character sets it supports.
7449 @item set charset @var{charset}
7451 Set the current host and target character sets to @var{charset}. As
7452 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7453 @value{GDBN} will list the name of the character sets that can be used
7454 for both host and target.
7458 @kindex show charset
7459 Show the names of the current host and target charsets.
7461 @itemx show host-charset
7462 @kindex show host-charset
7463 Show the name of the current host charset.
7465 @itemx show target-charset
7466 @kindex show target-charset
7467 Show the name of the current target charset.
7471 @value{GDBN} currently includes support for the following character
7477 @cindex ASCII character set
7478 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7482 @cindex ISO 8859-1 character set
7483 @cindex ISO Latin 1 character set
7484 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7485 characters needed for French, German, and Spanish. @value{GDBN} can use
7486 this as its host character set.
7490 @cindex EBCDIC character set
7491 @cindex IBM1047 character set
7492 Variants of the @sc{ebcdic} character set, used on some of IBM's
7493 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7494 @value{GDBN} cannot use these as its host character set.
7498 Note that these are all single-byte character sets. More work inside
7499 @value{GDBN} is needed to support multi-byte or variable-width character
7500 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7502 Here is an example of @value{GDBN}'s character set support in action.
7503 Assume that the following source code has been placed in the file
7504 @file{charset-test.c}:
7510 = @{72, 101, 108, 108, 111, 44, 32, 119,
7511 111, 114, 108, 100, 33, 10, 0@};
7512 char ibm1047_hello[]
7513 = @{200, 133, 147, 147, 150, 107, 64, 166,
7514 150, 153, 147, 132, 90, 37, 0@};
7518 printf ("Hello, world!\n");
7522 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7523 containing the string @samp{Hello, world!} followed by a newline,
7524 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7526 We compile the program, and invoke the debugger on it:
7529 $ gcc -g charset-test.c -o charset-test
7530 $ gdb -nw charset-test
7531 GNU gdb 2001-12-19-cvs
7532 Copyright 2001 Free Software Foundation, Inc.
7537 We can use the @code{show charset} command to see what character sets
7538 @value{GDBN} is currently using to interpret and display characters and
7542 (@value{GDBP}) show charset
7543 The current host and target character set is `ISO-8859-1'.
7547 For the sake of printing this manual, let's use @sc{ascii} as our
7548 initial character set:
7550 (@value{GDBP}) set charset ASCII
7551 (@value{GDBP}) show charset
7552 The current host and target character set is `ASCII'.
7556 Let's assume that @sc{ascii} is indeed the correct character set for our
7557 host system --- in other words, let's assume that if @value{GDBN} prints
7558 characters using the @sc{ascii} character set, our terminal will display
7559 them properly. Since our current target character set is also
7560 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7563 (@value{GDBP}) print ascii_hello
7564 $1 = 0x401698 "Hello, world!\n"
7565 (@value{GDBP}) print ascii_hello[0]
7570 @value{GDBN} uses the target character set for character and string
7571 literals you use in expressions:
7574 (@value{GDBP}) print '+'
7579 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7582 @value{GDBN} relies on the user to tell it which character set the
7583 target program uses. If we print @code{ibm1047_hello} while our target
7584 character set is still @sc{ascii}, we get jibberish:
7587 (@value{GDBP}) print ibm1047_hello
7588 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7589 (@value{GDBP}) print ibm1047_hello[0]
7594 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7595 @value{GDBN} tells us the character sets it supports:
7598 (@value{GDBP}) set target-charset
7599 ASCII EBCDIC-US IBM1047 ISO-8859-1
7600 (@value{GDBP}) set target-charset
7603 We can select @sc{ibm1047} as our target character set, and examine the
7604 program's strings again. Now the @sc{ascii} string is wrong, but
7605 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7606 target character set, @sc{ibm1047}, to the host character set,
7607 @sc{ascii}, and they display correctly:
7610 (@value{GDBP}) set target-charset IBM1047
7611 (@value{GDBP}) show charset
7612 The current host character set is `ASCII'.
7613 The current target character set is `IBM1047'.
7614 (@value{GDBP}) print ascii_hello
7615 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7616 (@value{GDBP}) print ascii_hello[0]
7618 (@value{GDBP}) print ibm1047_hello
7619 $8 = 0x4016a8 "Hello, world!\n"
7620 (@value{GDBP}) print ibm1047_hello[0]
7625 As above, @value{GDBN} uses the target character set for character and
7626 string literals you use in expressions:
7629 (@value{GDBP}) print '+'
7634 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7637 @node Caching Remote Data
7638 @section Caching Data of Remote Targets
7639 @cindex caching data of remote targets
7641 @value{GDBN} can cache data exchanged between the debugger and a
7642 remote target (@pxref{Remote Debugging}). Such caching generally improves
7643 performance, because it reduces the overhead of the remote protocol by
7644 bundling memory reads and writes into large chunks. Unfortunately,
7645 @value{GDBN} does not currently know anything about volatile
7646 registers, and thus data caching will produce incorrect results when
7647 volatile registers are in use.
7650 @kindex set remotecache
7651 @item set remotecache on
7652 @itemx set remotecache off
7653 Set caching state for remote targets. When @code{ON}, use data
7654 caching. By default, this option is @code{OFF}.
7656 @kindex show remotecache
7657 @item show remotecache
7658 Show the current state of data caching for remote targets.
7662 Print the information about the data cache performance. The
7663 information displayed includes: the dcache width and depth; and for
7664 each cache line, how many times it was referenced, and its data and
7665 state (dirty, bad, ok, etc.). This command is useful for debugging
7666 the data cache operation.
7669 @node Searching Memory
7670 @section Search Memory
7671 @cindex searching memory
7673 Memory can be searched for a particular sequence of bytes with the
7674 @code{find} command.
7678 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
7679 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
7680 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
7681 etc. The search begins at address @var{start_addr} and continues for either
7682 @var{len} bytes or through to @var{end_addr} inclusive.
7685 @var{s} and @var{n} are optional parameters.
7686 They may be specified in either order, apart or together.
7689 @item @var{s}, search query size
7690 The size of each search query value.
7696 halfwords (two bytes)
7700 giant words (eight bytes)
7703 All values are interpreted in the current language.
7704 This means, for example, that if the current source language is C/C@t{++}
7705 then searching for the string ``hello'' includes the trailing '\0'.
7707 If the value size is not specified, it is taken from the
7708 value's type in the current language.
7709 This is useful when one wants to specify the search
7710 pattern as a mixture of types.
7711 Note that this means, for example, that in the case of C-like languages
7712 a search for an untyped 0x42 will search for @samp{(int) 0x42}
7713 which is typically four bytes.
7715 @item @var{n}, maximum number of finds
7716 The maximum number of matches to print. The default is to print all finds.
7719 You can use strings as search values. Quote them with double-quotes
7721 The string value is copied into the search pattern byte by byte,
7722 regardless of the endianness of the target and the size specification.
7724 The address of each match found is printed as well as a count of the
7725 number of matches found.
7727 The address of the last value found is stored in convenience variable
7729 A count of the number of matches is stored in @samp{$numfound}.
7731 For example, if stopped at the @code{printf} in this function:
7737 static char hello[] = "hello-hello";
7738 static struct @{ char c; short s; int i; @}
7739 __attribute__ ((packed)) mixed
7740 = @{ 'c', 0x1234, 0x87654321 @};
7741 printf ("%s\n", hello);
7746 you get during debugging:
7749 (gdb) find &hello[0], +sizeof(hello), "hello"
7750 0x804956d <hello.1620+6>
7752 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
7753 0x8049567 <hello.1620>
7754 0x804956d <hello.1620+6>
7756 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
7757 0x8049567 <hello.1620>
7759 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
7760 0x8049560 <mixed.1625>
7762 (gdb) print $numfound
7765 $2 = (void *) 0x8049560
7769 @chapter C Preprocessor Macros
7771 Some languages, such as C and C@t{++}, provide a way to define and invoke
7772 ``preprocessor macros'' which expand into strings of tokens.
7773 @value{GDBN} can evaluate expressions containing macro invocations, show
7774 the result of macro expansion, and show a macro's definition, including
7775 where it was defined.
7777 You may need to compile your program specially to provide @value{GDBN}
7778 with information about preprocessor macros. Most compilers do not
7779 include macros in their debugging information, even when you compile
7780 with the @option{-g} flag. @xref{Compilation}.
7782 A program may define a macro at one point, remove that definition later,
7783 and then provide a different definition after that. Thus, at different
7784 points in the program, a macro may have different definitions, or have
7785 no definition at all. If there is a current stack frame, @value{GDBN}
7786 uses the macros in scope at that frame's source code line. Otherwise,
7787 @value{GDBN} uses the macros in scope at the current listing location;
7790 At the moment, @value{GDBN} does not support the @code{##}
7791 token-splicing operator, the @code{#} stringification operator, or
7792 variable-arity macros.
7794 Whenever @value{GDBN} evaluates an expression, it always expands any
7795 macro invocations present in the expression. @value{GDBN} also provides
7796 the following commands for working with macros explicitly.
7800 @kindex macro expand
7801 @cindex macro expansion, showing the results of preprocessor
7802 @cindex preprocessor macro expansion, showing the results of
7803 @cindex expanding preprocessor macros
7804 @item macro expand @var{expression}
7805 @itemx macro exp @var{expression}
7806 Show the results of expanding all preprocessor macro invocations in
7807 @var{expression}. Since @value{GDBN} simply expands macros, but does
7808 not parse the result, @var{expression} need not be a valid expression;
7809 it can be any string of tokens.
7812 @item macro expand-once @var{expression}
7813 @itemx macro exp1 @var{expression}
7814 @cindex expand macro once
7815 @i{(This command is not yet implemented.)} Show the results of
7816 expanding those preprocessor macro invocations that appear explicitly in
7817 @var{expression}. Macro invocations appearing in that expansion are
7818 left unchanged. This command allows you to see the effect of a
7819 particular macro more clearly, without being confused by further
7820 expansions. Since @value{GDBN} simply expands macros, but does not
7821 parse the result, @var{expression} need not be a valid expression; it
7822 can be any string of tokens.
7825 @cindex macro definition, showing
7826 @cindex definition, showing a macro's
7827 @item info macro @var{macro}
7828 Show the definition of the macro named @var{macro}, and describe the
7829 source location where that definition was established.
7831 @kindex macro define
7832 @cindex user-defined macros
7833 @cindex defining macros interactively
7834 @cindex macros, user-defined
7835 @item macro define @var{macro} @var{replacement-list}
7836 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7837 @i{(This command is not yet implemented.)} Introduce a definition for a
7838 preprocessor macro named @var{macro}, invocations of which are replaced
7839 by the tokens given in @var{replacement-list}. The first form of this
7840 command defines an ``object-like'' macro, which takes no arguments; the
7841 second form defines a ``function-like'' macro, which takes the arguments
7842 given in @var{arglist}.
7844 A definition introduced by this command is in scope in every expression
7845 evaluated in @value{GDBN}, until it is removed with the @command{macro
7846 undef} command, described below. The definition overrides all
7847 definitions for @var{macro} present in the program being debugged, as
7848 well as any previous user-supplied definition.
7851 @item macro undef @var{macro}
7852 @i{(This command is not yet implemented.)} Remove any user-supplied
7853 definition for the macro named @var{macro}. This command only affects
7854 definitions provided with the @command{macro define} command, described
7855 above; it cannot remove definitions present in the program being
7860 @i{(This command is not yet implemented.)} List all the macros
7861 defined using the @code{macro define} command.
7864 @cindex macros, example of debugging with
7865 Here is a transcript showing the above commands in action. First, we
7866 show our source files:
7874 #define ADD(x) (M + x)
7879 printf ("Hello, world!\n");
7881 printf ("We're so creative.\n");
7883 printf ("Goodbye, world!\n");
7890 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7891 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7892 compiler includes information about preprocessor macros in the debugging
7896 $ gcc -gdwarf-2 -g3 sample.c -o sample
7900 Now, we start @value{GDBN} on our sample program:
7904 GNU gdb 2002-05-06-cvs
7905 Copyright 2002 Free Software Foundation, Inc.
7906 GDB is free software, @dots{}
7910 We can expand macros and examine their definitions, even when the
7911 program is not running. @value{GDBN} uses the current listing position
7912 to decide which macro definitions are in scope:
7915 (@value{GDBP}) list main
7918 5 #define ADD(x) (M + x)
7923 10 printf ("Hello, world!\n");
7925 12 printf ("We're so creative.\n");
7926 (@value{GDBP}) info macro ADD
7927 Defined at /home/jimb/gdb/macros/play/sample.c:5
7928 #define ADD(x) (M + x)
7929 (@value{GDBP}) info macro Q
7930 Defined at /home/jimb/gdb/macros/play/sample.h:1
7931 included at /home/jimb/gdb/macros/play/sample.c:2
7933 (@value{GDBP}) macro expand ADD(1)
7934 expands to: (42 + 1)
7935 (@value{GDBP}) macro expand-once ADD(1)
7936 expands to: once (M + 1)
7940 In the example above, note that @command{macro expand-once} expands only
7941 the macro invocation explicit in the original text --- the invocation of
7942 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7943 which was introduced by @code{ADD}.
7945 Once the program is running, @value{GDBN} uses the macro definitions in
7946 force at the source line of the current stack frame:
7949 (@value{GDBP}) break main
7950 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7952 Starting program: /home/jimb/gdb/macros/play/sample
7954 Breakpoint 1, main () at sample.c:10
7955 10 printf ("Hello, world!\n");
7959 At line 10, the definition of the macro @code{N} at line 9 is in force:
7962 (@value{GDBP}) info macro N
7963 Defined at /home/jimb/gdb/macros/play/sample.c:9
7965 (@value{GDBP}) macro expand N Q M
7967 (@value{GDBP}) print N Q M
7972 As we step over directives that remove @code{N}'s definition, and then
7973 give it a new definition, @value{GDBN} finds the definition (or lack
7974 thereof) in force at each point:
7979 12 printf ("We're so creative.\n");
7980 (@value{GDBP}) info macro N
7981 The symbol `N' has no definition as a C/C++ preprocessor macro
7982 at /home/jimb/gdb/macros/play/sample.c:12
7985 14 printf ("Goodbye, world!\n");
7986 (@value{GDBP}) info macro N
7987 Defined at /home/jimb/gdb/macros/play/sample.c:13
7989 (@value{GDBP}) macro expand N Q M
7990 expands to: 1729 < 42
7991 (@value{GDBP}) print N Q M
7998 @chapter Tracepoints
7999 @c This chapter is based on the documentation written by Michael
8000 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8003 In some applications, it is not feasible for the debugger to interrupt
8004 the program's execution long enough for the developer to learn
8005 anything helpful about its behavior. If the program's correctness
8006 depends on its real-time behavior, delays introduced by a debugger
8007 might cause the program to change its behavior drastically, or perhaps
8008 fail, even when the code itself is correct. It is useful to be able
8009 to observe the program's behavior without interrupting it.
8011 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8012 specify locations in the program, called @dfn{tracepoints}, and
8013 arbitrary expressions to evaluate when those tracepoints are reached.
8014 Later, using the @code{tfind} command, you can examine the values
8015 those expressions had when the program hit the tracepoints. The
8016 expressions may also denote objects in memory---structures or arrays,
8017 for example---whose values @value{GDBN} should record; while visiting
8018 a particular tracepoint, you may inspect those objects as if they were
8019 in memory at that moment. However, because @value{GDBN} records these
8020 values without interacting with you, it can do so quickly and
8021 unobtrusively, hopefully not disturbing the program's behavior.
8023 The tracepoint facility is currently available only for remote
8024 targets. @xref{Targets}. In addition, your remote target must know
8025 how to collect trace data. This functionality is implemented in the
8026 remote stub; however, none of the stubs distributed with @value{GDBN}
8027 support tracepoints as of this writing. The format of the remote
8028 packets used to implement tracepoints are described in @ref{Tracepoint
8031 This chapter describes the tracepoint commands and features.
8035 * Analyze Collected Data::
8036 * Tracepoint Variables::
8039 @node Set Tracepoints
8040 @section Commands to Set Tracepoints
8042 Before running such a @dfn{trace experiment}, an arbitrary number of
8043 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8044 tracepoint has a number assigned to it by @value{GDBN}. Like with
8045 breakpoints, tracepoint numbers are successive integers starting from
8046 one. Many of the commands associated with tracepoints take the
8047 tracepoint number as their argument, to identify which tracepoint to
8050 For each tracepoint, you can specify, in advance, some arbitrary set
8051 of data that you want the target to collect in the trace buffer when
8052 it hits that tracepoint. The collected data can include registers,
8053 local variables, or global data. Later, you can use @value{GDBN}
8054 commands to examine the values these data had at the time the
8057 This section describes commands to set tracepoints and associated
8058 conditions and actions.
8061 * Create and Delete Tracepoints::
8062 * Enable and Disable Tracepoints::
8063 * Tracepoint Passcounts::
8064 * Tracepoint Actions::
8065 * Listing Tracepoints::
8066 * Starting and Stopping Trace Experiments::
8069 @node Create and Delete Tracepoints
8070 @subsection Create and Delete Tracepoints
8073 @cindex set tracepoint
8076 The @code{trace} command is very similar to the @code{break} command.
8077 Its argument can be a source line, a function name, or an address in
8078 the target program. @xref{Set Breaks}. The @code{trace} command
8079 defines a tracepoint, which is a point in the target program where the
8080 debugger will briefly stop, collect some data, and then allow the
8081 program to continue. Setting a tracepoint or changing its commands
8082 doesn't take effect until the next @code{tstart} command; thus, you
8083 cannot change the tracepoint attributes once a trace experiment is
8086 Here are some examples of using the @code{trace} command:
8089 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8091 (@value{GDBP}) @b{trace +2} // 2 lines forward
8093 (@value{GDBP}) @b{trace my_function} // first source line of function
8095 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8097 (@value{GDBP}) @b{trace *0x2117c4} // an address
8101 You can abbreviate @code{trace} as @code{tr}.
8104 @cindex last tracepoint number
8105 @cindex recent tracepoint number
8106 @cindex tracepoint number
8107 The convenience variable @code{$tpnum} records the tracepoint number
8108 of the most recently set tracepoint.
8110 @kindex delete tracepoint
8111 @cindex tracepoint deletion
8112 @item delete tracepoint @r{[}@var{num}@r{]}
8113 Permanently delete one or more tracepoints. With no argument, the
8114 default is to delete all tracepoints.
8119 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8121 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8125 You can abbreviate this command as @code{del tr}.
8128 @node Enable and Disable Tracepoints
8129 @subsection Enable and Disable Tracepoints
8132 @kindex disable tracepoint
8133 @item disable tracepoint @r{[}@var{num}@r{]}
8134 Disable tracepoint @var{num}, or all tracepoints if no argument
8135 @var{num} is given. A disabled tracepoint will have no effect during
8136 the next trace experiment, but it is not forgotten. You can re-enable
8137 a disabled tracepoint using the @code{enable tracepoint} command.
8139 @kindex enable tracepoint
8140 @item enable tracepoint @r{[}@var{num}@r{]}
8141 Enable tracepoint @var{num}, or all tracepoints. The enabled
8142 tracepoints will become effective the next time a trace experiment is
8146 @node Tracepoint Passcounts
8147 @subsection Tracepoint Passcounts
8151 @cindex tracepoint pass count
8152 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8153 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8154 automatically stop a trace experiment. If a tracepoint's passcount is
8155 @var{n}, then the trace experiment will be automatically stopped on
8156 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8157 @var{num} is not specified, the @code{passcount} command sets the
8158 passcount of the most recently defined tracepoint. If no passcount is
8159 given, the trace experiment will run until stopped explicitly by the
8165 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8166 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8168 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8169 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8170 (@value{GDBP}) @b{trace foo}
8171 (@value{GDBP}) @b{pass 3}
8172 (@value{GDBP}) @b{trace bar}
8173 (@value{GDBP}) @b{pass 2}
8174 (@value{GDBP}) @b{trace baz}
8175 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8176 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8177 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8178 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8182 @node Tracepoint Actions
8183 @subsection Tracepoint Action Lists
8187 @cindex tracepoint actions
8188 @item actions @r{[}@var{num}@r{]}
8189 This command will prompt for a list of actions to be taken when the
8190 tracepoint is hit. If the tracepoint number @var{num} is not
8191 specified, this command sets the actions for the one that was most
8192 recently defined (so that you can define a tracepoint and then say
8193 @code{actions} without bothering about its number). You specify the
8194 actions themselves on the following lines, one action at a time, and
8195 terminate the actions list with a line containing just @code{end}. So
8196 far, the only defined actions are @code{collect} and
8197 @code{while-stepping}.
8199 @cindex remove actions from a tracepoint
8200 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8201 and follow it immediately with @samp{end}.
8204 (@value{GDBP}) @b{collect @var{data}} // collect some data
8206 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8208 (@value{GDBP}) @b{end} // signals the end of actions.
8211 In the following example, the action list begins with @code{collect}
8212 commands indicating the things to be collected when the tracepoint is
8213 hit. Then, in order to single-step and collect additional data
8214 following the tracepoint, a @code{while-stepping} command is used,
8215 followed by the list of things to be collected while stepping. The
8216 @code{while-stepping} command is terminated by its own separate
8217 @code{end} command. Lastly, the action list is terminated by an
8221 (@value{GDBP}) @b{trace foo}
8222 (@value{GDBP}) @b{actions}
8223 Enter actions for tracepoint 1, one per line:
8232 @kindex collect @r{(tracepoints)}
8233 @item collect @var{expr1}, @var{expr2}, @dots{}
8234 Collect values of the given expressions when the tracepoint is hit.
8235 This command accepts a comma-separated list of any valid expressions.
8236 In addition to global, static, or local variables, the following
8237 special arguments are supported:
8241 collect all registers
8244 collect all function arguments
8247 collect all local variables.
8250 You can give several consecutive @code{collect} commands, each one
8251 with a single argument, or one @code{collect} command with several
8252 arguments separated by commas: the effect is the same.
8254 The command @code{info scope} (@pxref{Symbols, info scope}) is
8255 particularly useful for figuring out what data to collect.
8257 @kindex while-stepping @r{(tracepoints)}
8258 @item while-stepping @var{n}
8259 Perform @var{n} single-step traces after the tracepoint, collecting
8260 new data at each step. The @code{while-stepping} command is
8261 followed by the list of what to collect while stepping (followed by
8262 its own @code{end} command):
8266 > collect $regs, myglobal
8272 You may abbreviate @code{while-stepping} as @code{ws} or
8276 @node Listing Tracepoints
8277 @subsection Listing Tracepoints
8280 @kindex info tracepoints
8282 @cindex information about tracepoints
8283 @item info tracepoints @r{[}@var{num}@r{]}
8284 Display information about the tracepoint @var{num}. If you don't specify
8285 a tracepoint number, displays information about all the tracepoints
8286 defined so far. For each tracepoint, the following information is
8293 whether it is enabled or disabled
8297 its passcount as given by the @code{passcount @var{n}} command
8299 its step count as given by the @code{while-stepping @var{n}} command
8301 where in the source files is the tracepoint set
8303 its action list as given by the @code{actions} command
8307 (@value{GDBP}) @b{info trace}
8308 Num Enb Address PassC StepC What
8309 1 y 0x002117c4 0 0 <gdb_asm>
8310 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8311 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8316 This command can be abbreviated @code{info tp}.
8319 @node Starting and Stopping Trace Experiments
8320 @subsection Starting and Stopping Trace Experiments
8324 @cindex start a new trace experiment
8325 @cindex collected data discarded
8327 This command takes no arguments. It starts the trace experiment, and
8328 begins collecting data. This has the side effect of discarding all
8329 the data collected in the trace buffer during the previous trace
8333 @cindex stop a running trace experiment
8335 This command takes no arguments. It ends the trace experiment, and
8336 stops collecting data.
8338 @strong{Note}: a trace experiment and data collection may stop
8339 automatically if any tracepoint's passcount is reached
8340 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8343 @cindex status of trace data collection
8344 @cindex trace experiment, status of
8346 This command displays the status of the current trace data
8350 Here is an example of the commands we described so far:
8353 (@value{GDBP}) @b{trace gdb_c_test}
8354 (@value{GDBP}) @b{actions}
8355 Enter actions for tracepoint #1, one per line.
8356 > collect $regs,$locals,$args
8361 (@value{GDBP}) @b{tstart}
8362 [time passes @dots{}]
8363 (@value{GDBP}) @b{tstop}
8367 @node Analyze Collected Data
8368 @section Using the Collected Data
8370 After the tracepoint experiment ends, you use @value{GDBN} commands
8371 for examining the trace data. The basic idea is that each tracepoint
8372 collects a trace @dfn{snapshot} every time it is hit and another
8373 snapshot every time it single-steps. All these snapshots are
8374 consecutively numbered from zero and go into a buffer, and you can
8375 examine them later. The way you examine them is to @dfn{focus} on a
8376 specific trace snapshot. When the remote stub is focused on a trace
8377 snapshot, it will respond to all @value{GDBN} requests for memory and
8378 registers by reading from the buffer which belongs to that snapshot,
8379 rather than from @emph{real} memory or registers of the program being
8380 debugged. This means that @strong{all} @value{GDBN} commands
8381 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8382 behave as if we were currently debugging the program state as it was
8383 when the tracepoint occurred. Any requests for data that are not in
8384 the buffer will fail.
8387 * tfind:: How to select a trace snapshot
8388 * tdump:: How to display all data for a snapshot
8389 * save-tracepoints:: How to save tracepoints for a future run
8393 @subsection @code{tfind @var{n}}
8396 @cindex select trace snapshot
8397 @cindex find trace snapshot
8398 The basic command for selecting a trace snapshot from the buffer is
8399 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8400 counting from zero. If no argument @var{n} is given, the next
8401 snapshot is selected.
8403 Here are the various forms of using the @code{tfind} command.
8407 Find the first snapshot in the buffer. This is a synonym for
8408 @code{tfind 0} (since 0 is the number of the first snapshot).
8411 Stop debugging trace snapshots, resume @emph{live} debugging.
8414 Same as @samp{tfind none}.
8417 No argument means find the next trace snapshot.
8420 Find the previous trace snapshot before the current one. This permits
8421 retracing earlier steps.
8423 @item tfind tracepoint @var{num}
8424 Find the next snapshot associated with tracepoint @var{num}. Search
8425 proceeds forward from the last examined trace snapshot. If no
8426 argument @var{num} is given, it means find the next snapshot collected
8427 for the same tracepoint as the current snapshot.
8429 @item tfind pc @var{addr}
8430 Find the next snapshot associated with the value @var{addr} of the
8431 program counter. Search proceeds forward from the last examined trace
8432 snapshot. If no argument @var{addr} is given, it means find the next
8433 snapshot with the same value of PC as the current snapshot.
8435 @item tfind outside @var{addr1}, @var{addr2}
8436 Find the next snapshot whose PC is outside the given range of
8439 @item tfind range @var{addr1}, @var{addr2}
8440 Find the next snapshot whose PC is between @var{addr1} and
8441 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8443 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8444 Find the next snapshot associated with the source line @var{n}. If
8445 the optional argument @var{file} is given, refer to line @var{n} in
8446 that source file. Search proceeds forward from the last examined
8447 trace snapshot. If no argument @var{n} is given, it means find the
8448 next line other than the one currently being examined; thus saying
8449 @code{tfind line} repeatedly can appear to have the same effect as
8450 stepping from line to line in a @emph{live} debugging session.
8453 The default arguments for the @code{tfind} commands are specifically
8454 designed to make it easy to scan through the trace buffer. For
8455 instance, @code{tfind} with no argument selects the next trace
8456 snapshot, and @code{tfind -} with no argument selects the previous
8457 trace snapshot. So, by giving one @code{tfind} command, and then
8458 simply hitting @key{RET} repeatedly you can examine all the trace
8459 snapshots in order. Or, by saying @code{tfind -} and then hitting
8460 @key{RET} repeatedly you can examine the snapshots in reverse order.
8461 The @code{tfind line} command with no argument selects the snapshot
8462 for the next source line executed. The @code{tfind pc} command with
8463 no argument selects the next snapshot with the same program counter
8464 (PC) as the current frame. The @code{tfind tracepoint} command with
8465 no argument selects the next trace snapshot collected by the same
8466 tracepoint as the current one.
8468 In addition to letting you scan through the trace buffer manually,
8469 these commands make it easy to construct @value{GDBN} scripts that
8470 scan through the trace buffer and print out whatever collected data
8471 you are interested in. Thus, if we want to examine the PC, FP, and SP
8472 registers from each trace frame in the buffer, we can say this:
8475 (@value{GDBP}) @b{tfind start}
8476 (@value{GDBP}) @b{while ($trace_frame != -1)}
8477 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8478 $trace_frame, $pc, $sp, $fp
8482 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8483 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8484 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8485 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8486 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8487 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8488 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8489 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8490 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8491 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8492 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8495 Or, if we want to examine the variable @code{X} at each source line in
8499 (@value{GDBP}) @b{tfind start}
8500 (@value{GDBP}) @b{while ($trace_frame != -1)}
8501 > printf "Frame %d, X == %d\n", $trace_frame, X
8511 @subsection @code{tdump}
8513 @cindex dump all data collected at tracepoint
8514 @cindex tracepoint data, display
8516 This command takes no arguments. It prints all the data collected at
8517 the current trace snapshot.
8520 (@value{GDBP}) @b{trace 444}
8521 (@value{GDBP}) @b{actions}
8522 Enter actions for tracepoint #2, one per line:
8523 > collect $regs, $locals, $args, gdb_long_test
8526 (@value{GDBP}) @b{tstart}
8528 (@value{GDBP}) @b{tfind line 444}
8529 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8531 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8533 (@value{GDBP}) @b{tdump}
8534 Data collected at tracepoint 2, trace frame 1:
8535 d0 0xc4aa0085 -995491707
8539 d4 0x71aea3d 119204413
8544 a1 0x3000668 50333288
8547 a4 0x3000698 50333336
8549 fp 0x30bf3c 0x30bf3c
8550 sp 0x30bf34 0x30bf34
8552 pc 0x20b2c8 0x20b2c8
8556 p = 0x20e5b4 "gdb-test"
8563 gdb_long_test = 17 '\021'
8568 @node save-tracepoints
8569 @subsection @code{save-tracepoints @var{filename}}
8570 @kindex save-tracepoints
8571 @cindex save tracepoints for future sessions
8573 This command saves all current tracepoint definitions together with
8574 their actions and passcounts, into a file @file{@var{filename}}
8575 suitable for use in a later debugging session. To read the saved
8576 tracepoint definitions, use the @code{source} command (@pxref{Command
8579 @node Tracepoint Variables
8580 @section Convenience Variables for Tracepoints
8581 @cindex tracepoint variables
8582 @cindex convenience variables for tracepoints
8585 @vindex $trace_frame
8586 @item (int) $trace_frame
8587 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8588 snapshot is selected.
8591 @item (int) $tracepoint
8592 The tracepoint for the current trace snapshot.
8595 @item (int) $trace_line
8596 The line number for the current trace snapshot.
8599 @item (char []) $trace_file
8600 The source file for the current trace snapshot.
8603 @item (char []) $trace_func
8604 The name of the function containing @code{$tracepoint}.
8607 Note: @code{$trace_file} is not suitable for use in @code{printf},
8608 use @code{output} instead.
8610 Here's a simple example of using these convenience variables for
8611 stepping through all the trace snapshots and printing some of their
8615 (@value{GDBP}) @b{tfind start}
8617 (@value{GDBP}) @b{while $trace_frame != -1}
8618 > output $trace_file
8619 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8625 @chapter Debugging Programs That Use Overlays
8628 If your program is too large to fit completely in your target system's
8629 memory, you can sometimes use @dfn{overlays} to work around this
8630 problem. @value{GDBN} provides some support for debugging programs that
8634 * How Overlays Work:: A general explanation of overlays.
8635 * Overlay Commands:: Managing overlays in @value{GDBN}.
8636 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8637 mapped by asking the inferior.
8638 * Overlay Sample Program:: A sample program using overlays.
8641 @node How Overlays Work
8642 @section How Overlays Work
8643 @cindex mapped overlays
8644 @cindex unmapped overlays
8645 @cindex load address, overlay's
8646 @cindex mapped address
8647 @cindex overlay area
8649 Suppose you have a computer whose instruction address space is only 64
8650 kilobytes long, but which has much more memory which can be accessed by
8651 other means: special instructions, segment registers, or memory
8652 management hardware, for example. Suppose further that you want to
8653 adapt a program which is larger than 64 kilobytes to run on this system.
8655 One solution is to identify modules of your program which are relatively
8656 independent, and need not call each other directly; call these modules
8657 @dfn{overlays}. Separate the overlays from the main program, and place
8658 their machine code in the larger memory. Place your main program in
8659 instruction memory, but leave at least enough space there to hold the
8660 largest overlay as well.
8662 Now, to call a function located in an overlay, you must first copy that
8663 overlay's machine code from the large memory into the space set aside
8664 for it in the instruction memory, and then jump to its entry point
8667 @c NB: In the below the mapped area's size is greater or equal to the
8668 @c size of all overlays. This is intentional to remind the developer
8669 @c that overlays don't necessarily need to be the same size.
8673 Data Instruction Larger
8674 Address Space Address Space Address Space
8675 +-----------+ +-----------+ +-----------+
8677 +-----------+ +-----------+ +-----------+<-- overlay 1
8678 | program | | main | .----| overlay 1 | load address
8679 | variables | | program | | +-----------+
8680 | and heap | | | | | |
8681 +-----------+ | | | +-----------+<-- overlay 2
8682 | | +-----------+ | | | load address
8683 +-----------+ | | | .-| overlay 2 |
8685 mapped --->+-----------+ | | +-----------+
8687 | overlay | <-' | | |
8688 | area | <---' +-----------+<-- overlay 3
8689 | | <---. | | load address
8690 +-----------+ `--| overlay 3 |
8697 @anchor{A code overlay}A code overlay
8701 The diagram (@pxref{A code overlay}) shows a system with separate data
8702 and instruction address spaces. To map an overlay, the program copies
8703 its code from the larger address space to the instruction address space.
8704 Since the overlays shown here all use the same mapped address, only one
8705 may be mapped at a time. For a system with a single address space for
8706 data and instructions, the diagram would be similar, except that the
8707 program variables and heap would share an address space with the main
8708 program and the overlay area.
8710 An overlay loaded into instruction memory and ready for use is called a
8711 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8712 instruction memory. An overlay not present (or only partially present)
8713 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8714 is its address in the larger memory. The mapped address is also called
8715 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8716 called the @dfn{load memory address}, or @dfn{LMA}.
8718 Unfortunately, overlays are not a completely transparent way to adapt a
8719 program to limited instruction memory. They introduce a new set of
8720 global constraints you must keep in mind as you design your program:
8725 Before calling or returning to a function in an overlay, your program
8726 must make sure that overlay is actually mapped. Otherwise, the call or
8727 return will transfer control to the right address, but in the wrong
8728 overlay, and your program will probably crash.
8731 If the process of mapping an overlay is expensive on your system, you
8732 will need to choose your overlays carefully to minimize their effect on
8733 your program's performance.
8736 The executable file you load onto your system must contain each
8737 overlay's instructions, appearing at the overlay's load address, not its
8738 mapped address. However, each overlay's instructions must be relocated
8739 and its symbols defined as if the overlay were at its mapped address.
8740 You can use GNU linker scripts to specify different load and relocation
8741 addresses for pieces of your program; see @ref{Overlay Description,,,
8742 ld.info, Using ld: the GNU linker}.
8745 The procedure for loading executable files onto your system must be able
8746 to load their contents into the larger address space as well as the
8747 instruction and data spaces.
8751 The overlay system described above is rather simple, and could be
8752 improved in many ways:
8757 If your system has suitable bank switch registers or memory management
8758 hardware, you could use those facilities to make an overlay's load area
8759 contents simply appear at their mapped address in instruction space.
8760 This would probably be faster than copying the overlay to its mapped
8761 area in the usual way.
8764 If your overlays are small enough, you could set aside more than one
8765 overlay area, and have more than one overlay mapped at a time.
8768 You can use overlays to manage data, as well as instructions. In
8769 general, data overlays are even less transparent to your design than
8770 code overlays: whereas code overlays only require care when you call or
8771 return to functions, data overlays require care every time you access
8772 the data. Also, if you change the contents of a data overlay, you
8773 must copy its contents back out to its load address before you can copy a
8774 different data overlay into the same mapped area.
8779 @node Overlay Commands
8780 @section Overlay Commands
8782 To use @value{GDBN}'s overlay support, each overlay in your program must
8783 correspond to a separate section of the executable file. The section's
8784 virtual memory address and load memory address must be the overlay's
8785 mapped and load addresses. Identifying overlays with sections allows
8786 @value{GDBN} to determine the appropriate address of a function or
8787 variable, depending on whether the overlay is mapped or not.
8789 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8790 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8795 Disable @value{GDBN}'s overlay support. When overlay support is
8796 disabled, @value{GDBN} assumes that all functions and variables are
8797 always present at their mapped addresses. By default, @value{GDBN}'s
8798 overlay support is disabled.
8800 @item overlay manual
8801 @cindex manual overlay debugging
8802 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8803 relies on you to tell it which overlays are mapped, and which are not,
8804 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8805 commands described below.
8807 @item overlay map-overlay @var{overlay}
8808 @itemx overlay map @var{overlay}
8809 @cindex map an overlay
8810 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8811 be the name of the object file section containing the overlay. When an
8812 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8813 functions and variables at their mapped addresses. @value{GDBN} assumes
8814 that any other overlays whose mapped ranges overlap that of
8815 @var{overlay} are now unmapped.
8817 @item overlay unmap-overlay @var{overlay}
8818 @itemx overlay unmap @var{overlay}
8819 @cindex unmap an overlay
8820 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8821 must be the name of the object file section containing the overlay.
8822 When an overlay is unmapped, @value{GDBN} assumes it can find the
8823 overlay's functions and variables at their load addresses.
8826 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8827 consults a data structure the overlay manager maintains in the inferior
8828 to see which overlays are mapped. For details, see @ref{Automatic
8831 @item overlay load-target
8833 @cindex reloading the overlay table
8834 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8835 re-reads the table @value{GDBN} automatically each time the inferior
8836 stops, so this command should only be necessary if you have changed the
8837 overlay mapping yourself using @value{GDBN}. This command is only
8838 useful when using automatic overlay debugging.
8840 @item overlay list-overlays
8842 @cindex listing mapped overlays
8843 Display a list of the overlays currently mapped, along with their mapped
8844 addresses, load addresses, and sizes.
8848 Normally, when @value{GDBN} prints a code address, it includes the name
8849 of the function the address falls in:
8852 (@value{GDBP}) print main
8853 $3 = @{int ()@} 0x11a0 <main>
8856 When overlay debugging is enabled, @value{GDBN} recognizes code in
8857 unmapped overlays, and prints the names of unmapped functions with
8858 asterisks around them. For example, if @code{foo} is a function in an
8859 unmapped overlay, @value{GDBN} prints it this way:
8862 (@value{GDBP}) overlay list
8863 No sections are mapped.
8864 (@value{GDBP}) print foo
8865 $5 = @{int (int)@} 0x100000 <*foo*>
8868 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8872 (@value{GDBP}) overlay list
8873 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8874 mapped at 0x1016 - 0x104a
8875 (@value{GDBP}) print foo
8876 $6 = @{int (int)@} 0x1016 <foo>
8879 When overlay debugging is enabled, @value{GDBN} can find the correct
8880 address for functions and variables in an overlay, whether or not the
8881 overlay is mapped. This allows most @value{GDBN} commands, like
8882 @code{break} and @code{disassemble}, to work normally, even on unmapped
8883 code. However, @value{GDBN}'s breakpoint support has some limitations:
8887 @cindex breakpoints in overlays
8888 @cindex overlays, setting breakpoints in
8889 You can set breakpoints in functions in unmapped overlays, as long as
8890 @value{GDBN} can write to the overlay at its load address.
8892 @value{GDBN} can not set hardware or simulator-based breakpoints in
8893 unmapped overlays. However, if you set a breakpoint at the end of your
8894 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8895 you are using manual overlay management), @value{GDBN} will re-set its
8896 breakpoints properly.
8900 @node Automatic Overlay Debugging
8901 @section Automatic Overlay Debugging
8902 @cindex automatic overlay debugging
8904 @value{GDBN} can automatically track which overlays are mapped and which
8905 are not, given some simple co-operation from the overlay manager in the
8906 inferior. If you enable automatic overlay debugging with the
8907 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8908 looks in the inferior's memory for certain variables describing the
8909 current state of the overlays.
8911 Here are the variables your overlay manager must define to support
8912 @value{GDBN}'s automatic overlay debugging:
8916 @item @code{_ovly_table}:
8917 This variable must be an array of the following structures:
8922 /* The overlay's mapped address. */
8925 /* The size of the overlay, in bytes. */
8928 /* The overlay's load address. */
8931 /* Non-zero if the overlay is currently mapped;
8933 unsigned long mapped;
8937 @item @code{_novlys}:
8938 This variable must be a four-byte signed integer, holding the total
8939 number of elements in @code{_ovly_table}.
8943 To decide whether a particular overlay is mapped or not, @value{GDBN}
8944 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8945 @code{lma} members equal the VMA and LMA of the overlay's section in the
8946 executable file. When @value{GDBN} finds a matching entry, it consults
8947 the entry's @code{mapped} member to determine whether the overlay is
8950 In addition, your overlay manager may define a function called
8951 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8952 will silently set a breakpoint there. If the overlay manager then
8953 calls this function whenever it has changed the overlay table, this
8954 will enable @value{GDBN} to accurately keep track of which overlays
8955 are in program memory, and update any breakpoints that may be set
8956 in overlays. This will allow breakpoints to work even if the
8957 overlays are kept in ROM or other non-writable memory while they
8958 are not being executed.
8960 @node Overlay Sample Program
8961 @section Overlay Sample Program
8962 @cindex overlay example program
8964 When linking a program which uses overlays, you must place the overlays
8965 at their load addresses, while relocating them to run at their mapped
8966 addresses. To do this, you must write a linker script (@pxref{Overlay
8967 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8968 since linker scripts are specific to a particular host system, target
8969 architecture, and target memory layout, this manual cannot provide
8970 portable sample code demonstrating @value{GDBN}'s overlay support.
8972 However, the @value{GDBN} source distribution does contain an overlaid
8973 program, with linker scripts for a few systems, as part of its test
8974 suite. The program consists of the following files from
8975 @file{gdb/testsuite/gdb.base}:
8979 The main program file.
8981 A simple overlay manager, used by @file{overlays.c}.
8986 Overlay modules, loaded and used by @file{overlays.c}.
8989 Linker scripts for linking the test program on the @code{d10v-elf}
8990 and @code{m32r-elf} targets.
8993 You can build the test program using the @code{d10v-elf} GCC
8994 cross-compiler like this:
8997 $ d10v-elf-gcc -g -c overlays.c
8998 $ d10v-elf-gcc -g -c ovlymgr.c
8999 $ d10v-elf-gcc -g -c foo.c
9000 $ d10v-elf-gcc -g -c bar.c
9001 $ d10v-elf-gcc -g -c baz.c
9002 $ d10v-elf-gcc -g -c grbx.c
9003 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9004 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9007 The build process is identical for any other architecture, except that
9008 you must substitute the appropriate compiler and linker script for the
9009 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9013 @chapter Using @value{GDBN} with Different Languages
9016 Although programming languages generally have common aspects, they are
9017 rarely expressed in the same manner. For instance, in ANSI C,
9018 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9019 Modula-2, it is accomplished by @code{p^}. Values can also be
9020 represented (and displayed) differently. Hex numbers in C appear as
9021 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9023 @cindex working language
9024 Language-specific information is built into @value{GDBN} for some languages,
9025 allowing you to express operations like the above in your program's
9026 native language, and allowing @value{GDBN} to output values in a manner
9027 consistent with the syntax of your program's native language. The
9028 language you use to build expressions is called the @dfn{working
9032 * Setting:: Switching between source languages
9033 * Show:: Displaying the language
9034 * Checks:: Type and range checks
9035 * Supported Languages:: Supported languages
9036 * Unsupported Languages:: Unsupported languages
9040 @section Switching Between Source Languages
9042 There are two ways to control the working language---either have @value{GDBN}
9043 set it automatically, or select it manually yourself. You can use the
9044 @code{set language} command for either purpose. On startup, @value{GDBN}
9045 defaults to setting the language automatically. The working language is
9046 used to determine how expressions you type are interpreted, how values
9049 In addition to the working language, every source file that
9050 @value{GDBN} knows about has its own working language. For some object
9051 file formats, the compiler might indicate which language a particular
9052 source file is in. However, most of the time @value{GDBN} infers the
9053 language from the name of the file. The language of a source file
9054 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9055 show each frame appropriately for its own language. There is no way to
9056 set the language of a source file from within @value{GDBN}, but you can
9057 set the language associated with a filename extension. @xref{Show, ,
9058 Displaying the Language}.
9060 This is most commonly a problem when you use a program, such
9061 as @code{cfront} or @code{f2c}, that generates C but is written in
9062 another language. In that case, make the
9063 program use @code{#line} directives in its C output; that way
9064 @value{GDBN} will know the correct language of the source code of the original
9065 program, and will display that source code, not the generated C code.
9068 * Filenames:: Filename extensions and languages.
9069 * Manually:: Setting the working language manually
9070 * Automatically:: Having @value{GDBN} infer the source language
9074 @subsection List of Filename Extensions and Languages
9076 If a source file name ends in one of the following extensions, then
9077 @value{GDBN} infers that its language is the one indicated.
9098 Objective-C source file
9105 Modula-2 source file
9109 Assembler source file. This actually behaves almost like C, but
9110 @value{GDBN} does not skip over function prologues when stepping.
9113 In addition, you may set the language associated with a filename
9114 extension. @xref{Show, , Displaying the Language}.
9117 @subsection Setting the Working Language
9119 If you allow @value{GDBN} to set the language automatically,
9120 expressions are interpreted the same way in your debugging session and
9123 @kindex set language
9124 If you wish, you may set the language manually. To do this, issue the
9125 command @samp{set language @var{lang}}, where @var{lang} is the name of
9127 @code{c} or @code{modula-2}.
9128 For a list of the supported languages, type @samp{set language}.
9130 Setting the language manually prevents @value{GDBN} from updating the working
9131 language automatically. This can lead to confusion if you try
9132 to debug a program when the working language is not the same as the
9133 source language, when an expression is acceptable to both
9134 languages---but means different things. For instance, if the current
9135 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9143 might not have the effect you intended. In C, this means to add
9144 @code{b} and @code{c} and place the result in @code{a}. The result
9145 printed would be the value of @code{a}. In Modula-2, this means to compare
9146 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9149 @subsection Having @value{GDBN} Infer the Source Language
9151 To have @value{GDBN} set the working language automatically, use
9152 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9153 then infers the working language. That is, when your program stops in a
9154 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9155 working language to the language recorded for the function in that
9156 frame. If the language for a frame is unknown (that is, if the function
9157 or block corresponding to the frame was defined in a source file that
9158 does not have a recognized extension), the current working language is
9159 not changed, and @value{GDBN} issues a warning.
9161 This may not seem necessary for most programs, which are written
9162 entirely in one source language. However, program modules and libraries
9163 written in one source language can be used by a main program written in
9164 a different source language. Using @samp{set language auto} in this
9165 case frees you from having to set the working language manually.
9168 @section Displaying the Language
9170 The following commands help you find out which language is the
9171 working language, and also what language source files were written in.
9175 @kindex show language
9176 Display the current working language. This is the
9177 language you can use with commands such as @code{print} to
9178 build and compute expressions that may involve variables in your program.
9181 @kindex info frame@r{, show the source language}
9182 Display the source language for this frame. This language becomes the
9183 working language if you use an identifier from this frame.
9184 @xref{Frame Info, ,Information about a Frame}, to identify the other
9185 information listed here.
9188 @kindex info source@r{, show the source language}
9189 Display the source language of this source file.
9190 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9191 information listed here.
9194 In unusual circumstances, you may have source files with extensions
9195 not in the standard list. You can then set the extension associated
9196 with a language explicitly:
9199 @item set extension-language @var{ext} @var{language}
9200 @kindex set extension-language
9201 Tell @value{GDBN} that source files with extension @var{ext} are to be
9202 assumed as written in the source language @var{language}.
9204 @item info extensions
9205 @kindex info extensions
9206 List all the filename extensions and the associated languages.
9210 @section Type and Range Checking
9213 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9214 checking are included, but they do not yet have any effect. This
9215 section documents the intended facilities.
9217 @c FIXME remove warning when type/range code added
9219 Some languages are designed to guard you against making seemingly common
9220 errors through a series of compile- and run-time checks. These include
9221 checking the type of arguments to functions and operators, and making
9222 sure mathematical overflows are caught at run time. Checks such as
9223 these help to ensure a program's correctness once it has been compiled
9224 by eliminating type mismatches, and providing active checks for range
9225 errors when your program is running.
9227 @value{GDBN} can check for conditions like the above if you wish.
9228 Although @value{GDBN} does not check the statements in your program,
9229 it can check expressions entered directly into @value{GDBN} for
9230 evaluation via the @code{print} command, for example. As with the
9231 working language, @value{GDBN} can also decide whether or not to check
9232 automatically based on your program's source language.
9233 @xref{Supported Languages, ,Supported Languages}, for the default
9234 settings of supported languages.
9237 * Type Checking:: An overview of type checking
9238 * Range Checking:: An overview of range checking
9241 @cindex type checking
9242 @cindex checks, type
9244 @subsection An Overview of Type Checking
9246 Some languages, such as Modula-2, are strongly typed, meaning that the
9247 arguments to operators and functions have to be of the correct type,
9248 otherwise an error occurs. These checks prevent type mismatch
9249 errors from ever causing any run-time problems. For example,
9257 The second example fails because the @code{CARDINAL} 1 is not
9258 type-compatible with the @code{REAL} 2.3.
9260 For the expressions you use in @value{GDBN} commands, you can tell the
9261 @value{GDBN} type checker to skip checking;
9262 to treat any mismatches as errors and abandon the expression;
9263 or to only issue warnings when type mismatches occur,
9264 but evaluate the expression anyway. When you choose the last of
9265 these, @value{GDBN} evaluates expressions like the second example above, but
9266 also issues a warning.
9268 Even if you turn type checking off, there may be other reasons
9269 related to type that prevent @value{GDBN} from evaluating an expression.
9270 For instance, @value{GDBN} does not know how to add an @code{int} and
9271 a @code{struct foo}. These particular type errors have nothing to do
9272 with the language in use, and usually arise from expressions, such as
9273 the one described above, which make little sense to evaluate anyway.
9275 Each language defines to what degree it is strict about type. For
9276 instance, both Modula-2 and C require the arguments to arithmetical
9277 operators to be numbers. In C, enumerated types and pointers can be
9278 represented as numbers, so that they are valid arguments to mathematical
9279 operators. @xref{Supported Languages, ,Supported Languages}, for further
9280 details on specific languages.
9282 @value{GDBN} provides some additional commands for controlling the type checker:
9284 @kindex set check type
9285 @kindex show check type
9287 @item set check type auto
9288 Set type checking on or off based on the current working language.
9289 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9292 @item set check type on
9293 @itemx set check type off
9294 Set type checking on or off, overriding the default setting for the
9295 current working language. Issue a warning if the setting does not
9296 match the language default. If any type mismatches occur in
9297 evaluating an expression while type checking is on, @value{GDBN} prints a
9298 message and aborts evaluation of the expression.
9300 @item set check type warn
9301 Cause the type checker to issue warnings, but to always attempt to
9302 evaluate the expression. Evaluating the expression may still
9303 be impossible for other reasons. For example, @value{GDBN} cannot add
9304 numbers and structures.
9307 Show the current setting of the type checker, and whether or not @value{GDBN}
9308 is setting it automatically.
9311 @cindex range checking
9312 @cindex checks, range
9313 @node Range Checking
9314 @subsection An Overview of Range Checking
9316 In some languages (such as Modula-2), it is an error to exceed the
9317 bounds of a type; this is enforced with run-time checks. Such range
9318 checking is meant to ensure program correctness by making sure
9319 computations do not overflow, or indices on an array element access do
9320 not exceed the bounds of the array.
9322 For expressions you use in @value{GDBN} commands, you can tell
9323 @value{GDBN} to treat range errors in one of three ways: ignore them,
9324 always treat them as errors and abandon the expression, or issue
9325 warnings but evaluate the expression anyway.
9327 A range error can result from numerical overflow, from exceeding an
9328 array index bound, or when you type a constant that is not a member
9329 of any type. Some languages, however, do not treat overflows as an
9330 error. In many implementations of C, mathematical overflow causes the
9331 result to ``wrap around'' to lower values---for example, if @var{m} is
9332 the largest integer value, and @var{s} is the smallest, then
9335 @var{m} + 1 @result{} @var{s}
9338 This, too, is specific to individual languages, and in some cases
9339 specific to individual compilers or machines. @xref{Supported Languages, ,
9340 Supported Languages}, for further details on specific languages.
9342 @value{GDBN} provides some additional commands for controlling the range checker:
9344 @kindex set check range
9345 @kindex show check range
9347 @item set check range auto
9348 Set range checking on or off based on the current working language.
9349 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9352 @item set check range on
9353 @itemx set check range off
9354 Set range checking on or off, overriding the default setting for the
9355 current working language. A warning is issued if the setting does not
9356 match the language default. If a range error occurs and range checking is on,
9357 then a message is printed and evaluation of the expression is aborted.
9359 @item set check range warn
9360 Output messages when the @value{GDBN} range checker detects a range error,
9361 but attempt to evaluate the expression anyway. Evaluating the
9362 expression may still be impossible for other reasons, such as accessing
9363 memory that the process does not own (a typical example from many Unix
9367 Show the current setting of the range checker, and whether or not it is
9368 being set automatically by @value{GDBN}.
9371 @node Supported Languages
9372 @section Supported Languages
9374 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9375 assembly, Modula-2, and Ada.
9376 @c This is false ...
9377 Some @value{GDBN} features may be used in expressions regardless of the
9378 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9379 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9380 ,Expressions}) can be used with the constructs of any supported
9383 The following sections detail to what degree each source language is
9384 supported by @value{GDBN}. These sections are not meant to be language
9385 tutorials or references, but serve only as a reference guide to what the
9386 @value{GDBN} expression parser accepts, and what input and output
9387 formats should look like for different languages. There are many good
9388 books written on each of these languages; please look to these for a
9389 language reference or tutorial.
9393 * Objective-C:: Objective-C
9396 * Modula-2:: Modula-2
9401 @subsection C and C@t{++}
9403 @cindex C and C@t{++}
9404 @cindex expressions in C or C@t{++}
9406 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9407 to both languages. Whenever this is the case, we discuss those languages
9411 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9412 @cindex @sc{gnu} C@t{++}
9413 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9414 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9415 effectively, you must compile your C@t{++} programs with a supported
9416 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9417 compiler (@code{aCC}).
9419 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9420 format; if it doesn't work on your system, try the stabs+ debugging
9421 format. You can select those formats explicitly with the @code{g++}
9422 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9423 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9424 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9427 * C Operators:: C and C@t{++} operators
9428 * C Constants:: C and C@t{++} constants
9429 * C Plus Plus Expressions:: C@t{++} expressions
9430 * C Defaults:: Default settings for C and C@t{++}
9431 * C Checks:: C and C@t{++} type and range checks
9432 * Debugging C:: @value{GDBN} and C
9433 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9434 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9438 @subsubsection C and C@t{++} Operators
9440 @cindex C and C@t{++} operators
9442 Operators must be defined on values of specific types. For instance,
9443 @code{+} is defined on numbers, but not on structures. Operators are
9444 often defined on groups of types.
9446 For the purposes of C and C@t{++}, the following definitions hold:
9451 @emph{Integral types} include @code{int} with any of its storage-class
9452 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9455 @emph{Floating-point types} include @code{float}, @code{double}, and
9456 @code{long double} (if supported by the target platform).
9459 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9462 @emph{Scalar types} include all of the above.
9467 The following operators are supported. They are listed here
9468 in order of increasing precedence:
9472 The comma or sequencing operator. Expressions in a comma-separated list
9473 are evaluated from left to right, with the result of the entire
9474 expression being the last expression evaluated.
9477 Assignment. The value of an assignment expression is the value
9478 assigned. Defined on scalar types.
9481 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9482 and translated to @w{@code{@var{a} = @var{a op b}}}.
9483 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9484 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9485 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9488 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9489 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9493 Logical @sc{or}. Defined on integral types.
9496 Logical @sc{and}. Defined on integral types.
9499 Bitwise @sc{or}. Defined on integral types.
9502 Bitwise exclusive-@sc{or}. Defined on integral types.
9505 Bitwise @sc{and}. Defined on integral types.
9508 Equality and inequality. Defined on scalar types. The value of these
9509 expressions is 0 for false and non-zero for true.
9511 @item <@r{, }>@r{, }<=@r{, }>=
9512 Less than, greater than, less than or equal, greater than or equal.
9513 Defined on scalar types. The value of these expressions is 0 for false
9514 and non-zero for true.
9517 left shift, and right shift. Defined on integral types.
9520 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9523 Addition and subtraction. Defined on integral types, floating-point types and
9526 @item *@r{, }/@r{, }%
9527 Multiplication, division, and modulus. Multiplication and division are
9528 defined on integral and floating-point types. Modulus is defined on
9532 Increment and decrement. When appearing before a variable, the
9533 operation is performed before the variable is used in an expression;
9534 when appearing after it, the variable's value is used before the
9535 operation takes place.
9538 Pointer dereferencing. Defined on pointer types. Same precedence as
9542 Address operator. Defined on variables. Same precedence as @code{++}.
9544 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9545 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9546 to examine the address
9547 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9551 Negative. Defined on integral and floating-point types. Same
9552 precedence as @code{++}.
9555 Logical negation. Defined on integral types. Same precedence as
9559 Bitwise complement operator. Defined on integral types. Same precedence as
9564 Structure member, and pointer-to-structure member. For convenience,
9565 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9566 pointer based on the stored type information.
9567 Defined on @code{struct} and @code{union} data.
9570 Dereferences of pointers to members.
9573 Array indexing. @code{@var{a}[@var{i}]} is defined as
9574 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9577 Function parameter list. Same precedence as @code{->}.
9580 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9581 and @code{class} types.
9584 Doubled colons also represent the @value{GDBN} scope operator
9585 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9589 If an operator is redefined in the user code, @value{GDBN} usually
9590 attempts to invoke the redefined version instead of using the operator's
9594 @subsubsection C and C@t{++} Constants
9596 @cindex C and C@t{++} constants
9598 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9603 Integer constants are a sequence of digits. Octal constants are
9604 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9605 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9606 @samp{l}, specifying that the constant should be treated as a
9610 Floating point constants are a sequence of digits, followed by a decimal
9611 point, followed by a sequence of digits, and optionally followed by an
9612 exponent. An exponent is of the form:
9613 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9614 sequence of digits. The @samp{+} is optional for positive exponents.
9615 A floating-point constant may also end with a letter @samp{f} or
9616 @samp{F}, specifying that the constant should be treated as being of
9617 the @code{float} (as opposed to the default @code{double}) type; or with
9618 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9622 Enumerated constants consist of enumerated identifiers, or their
9623 integral equivalents.
9626 Character constants are a single character surrounded by single quotes
9627 (@code{'}), or a number---the ordinal value of the corresponding character
9628 (usually its @sc{ascii} value). Within quotes, the single character may
9629 be represented by a letter or by @dfn{escape sequences}, which are of
9630 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9631 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9632 @samp{@var{x}} is a predefined special character---for example,
9633 @samp{\n} for newline.
9636 String constants are a sequence of character constants surrounded by
9637 double quotes (@code{"}). Any valid character constant (as described
9638 above) may appear. Double quotes within the string must be preceded by
9639 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9643 Pointer constants are an integral value. You can also write pointers
9644 to constants using the C operator @samp{&}.
9647 Array constants are comma-separated lists surrounded by braces @samp{@{}
9648 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9649 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9650 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9653 @node C Plus Plus Expressions
9654 @subsubsection C@t{++} Expressions
9656 @cindex expressions in C@t{++}
9657 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9659 @cindex debugging C@t{++} programs
9660 @cindex C@t{++} compilers
9661 @cindex debug formats and C@t{++}
9662 @cindex @value{NGCC} and C@t{++}
9664 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9665 proper compiler and the proper debug format. Currently, @value{GDBN}
9666 works best when debugging C@t{++} code that is compiled with
9667 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9668 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9669 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9670 stabs+ as their default debug format, so you usually don't need to
9671 specify a debug format explicitly. Other compilers and/or debug formats
9672 are likely to work badly or not at all when using @value{GDBN} to debug
9678 @cindex member functions
9680 Member function calls are allowed; you can use expressions like
9683 count = aml->GetOriginal(x, y)
9686 @vindex this@r{, inside C@t{++} member functions}
9687 @cindex namespace in C@t{++}
9689 While a member function is active (in the selected stack frame), your
9690 expressions have the same namespace available as the member function;
9691 that is, @value{GDBN} allows implicit references to the class instance
9692 pointer @code{this} following the same rules as C@t{++}.
9694 @cindex call overloaded functions
9695 @cindex overloaded functions, calling
9696 @cindex type conversions in C@t{++}
9698 You can call overloaded functions; @value{GDBN} resolves the function
9699 call to the right definition, with some restrictions. @value{GDBN} does not
9700 perform overload resolution involving user-defined type conversions,
9701 calls to constructors, or instantiations of templates that do not exist
9702 in the program. It also cannot handle ellipsis argument lists or
9705 It does perform integral conversions and promotions, floating-point
9706 promotions, arithmetic conversions, pointer conversions, conversions of
9707 class objects to base classes, and standard conversions such as those of
9708 functions or arrays to pointers; it requires an exact match on the
9709 number of function arguments.
9711 Overload resolution is always performed, unless you have specified
9712 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9713 ,@value{GDBN} Features for C@t{++}}.
9715 You must specify @code{set overload-resolution off} in order to use an
9716 explicit function signature to call an overloaded function, as in
9718 p 'foo(char,int)'('x', 13)
9721 The @value{GDBN} command-completion facility can simplify this;
9722 see @ref{Completion, ,Command Completion}.
9724 @cindex reference declarations
9726 @value{GDBN} understands variables declared as C@t{++} references; you can use
9727 them in expressions just as you do in C@t{++} source---they are automatically
9730 In the parameter list shown when @value{GDBN} displays a frame, the values of
9731 reference variables are not displayed (unlike other variables); this
9732 avoids clutter, since references are often used for large structures.
9733 The @emph{address} of a reference variable is always shown, unless
9734 you have specified @samp{set print address off}.
9737 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9738 expressions can use it just as expressions in your program do. Since
9739 one scope may be defined in another, you can use @code{::} repeatedly if
9740 necessary, for example in an expression like
9741 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9742 resolving name scope by reference to source files, in both C and C@t{++}
9743 debugging (@pxref{Variables, ,Program Variables}).
9746 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9747 calling virtual functions correctly, printing out virtual bases of
9748 objects, calling functions in a base subobject, casting objects, and
9749 invoking user-defined operators.
9752 @subsubsection C and C@t{++} Defaults
9754 @cindex C and C@t{++} defaults
9756 If you allow @value{GDBN} to set type and range checking automatically, they
9757 both default to @code{off} whenever the working language changes to
9758 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9759 selects the working language.
9761 If you allow @value{GDBN} to set the language automatically, it
9762 recognizes source files whose names end with @file{.c}, @file{.C}, or
9763 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9764 these files, it sets the working language to C or C@t{++}.
9765 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9766 for further details.
9768 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9769 @c unimplemented. If (b) changes, it might make sense to let this node
9770 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9773 @subsubsection C and C@t{++} Type and Range Checks
9775 @cindex C and C@t{++} checks
9777 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9778 is not used. However, if you turn type checking on, @value{GDBN}
9779 considers two variables type equivalent if:
9783 The two variables are structured and have the same structure, union, or
9787 The two variables have the same type name, or types that have been
9788 declared equivalent through @code{typedef}.
9791 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9794 The two @code{struct}, @code{union}, or @code{enum} variables are
9795 declared in the same declaration. (Note: this may not be true for all C
9800 Range checking, if turned on, is done on mathematical operations. Array
9801 indices are not checked, since they are often used to index a pointer
9802 that is not itself an array.
9805 @subsubsection @value{GDBN} and C
9807 The @code{set print union} and @code{show print union} commands apply to
9808 the @code{union} type. When set to @samp{on}, any @code{union} that is
9809 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9810 appears as @samp{@{...@}}.
9812 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9813 with pointers and a memory allocation function. @xref{Expressions,
9816 @node Debugging C Plus Plus
9817 @subsubsection @value{GDBN} Features for C@t{++}
9819 @cindex commands for C@t{++}
9821 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9822 designed specifically for use with C@t{++}. Here is a summary:
9825 @cindex break in overloaded functions
9826 @item @r{breakpoint menus}
9827 When you want a breakpoint in a function whose name is overloaded,
9828 @value{GDBN} has the capability to display a menu of possible breakpoint
9829 locations to help you specify which function definition you want.
9830 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
9832 @cindex overloading in C@t{++}
9833 @item rbreak @var{regex}
9834 Setting breakpoints using regular expressions is helpful for setting
9835 breakpoints on overloaded functions that are not members of any special
9837 @xref{Set Breaks, ,Setting Breakpoints}.
9839 @cindex C@t{++} exception handling
9842 Debug C@t{++} exception handling using these commands. @xref{Set
9843 Catchpoints, , Setting Catchpoints}.
9846 @item ptype @var{typename}
9847 Print inheritance relationships as well as other information for type
9849 @xref{Symbols, ,Examining the Symbol Table}.
9851 @cindex C@t{++} symbol display
9852 @item set print demangle
9853 @itemx show print demangle
9854 @itemx set print asm-demangle
9855 @itemx show print asm-demangle
9856 Control whether C@t{++} symbols display in their source form, both when
9857 displaying code as C@t{++} source and when displaying disassemblies.
9858 @xref{Print Settings, ,Print Settings}.
9860 @item set print object
9861 @itemx show print object
9862 Choose whether to print derived (actual) or declared types of objects.
9863 @xref{Print Settings, ,Print Settings}.
9865 @item set print vtbl
9866 @itemx show print vtbl
9867 Control the format for printing virtual function tables.
9868 @xref{Print Settings, ,Print Settings}.
9869 (The @code{vtbl} commands do not work on programs compiled with the HP
9870 ANSI C@t{++} compiler (@code{aCC}).)
9872 @kindex set overload-resolution
9873 @cindex overloaded functions, overload resolution
9874 @item set overload-resolution on
9875 Enable overload resolution for C@t{++} expression evaluation. The default
9876 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9877 and searches for a function whose signature matches the argument types,
9878 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9879 Expressions, ,C@t{++} Expressions}, for details).
9880 If it cannot find a match, it emits a message.
9882 @item set overload-resolution off
9883 Disable overload resolution for C@t{++} expression evaluation. For
9884 overloaded functions that are not class member functions, @value{GDBN}
9885 chooses the first function of the specified name that it finds in the
9886 symbol table, whether or not its arguments are of the correct type. For
9887 overloaded functions that are class member functions, @value{GDBN}
9888 searches for a function whose signature @emph{exactly} matches the
9891 @kindex show overload-resolution
9892 @item show overload-resolution
9893 Show the current setting of overload resolution.
9895 @item @r{Overloaded symbol names}
9896 You can specify a particular definition of an overloaded symbol, using
9897 the same notation that is used to declare such symbols in C@t{++}: type
9898 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9899 also use the @value{GDBN} command-line word completion facilities to list the
9900 available choices, or to finish the type list for you.
9901 @xref{Completion,, Command Completion}, for details on how to do this.
9904 @node Decimal Floating Point
9905 @subsubsection Decimal Floating Point format
9906 @cindex decimal floating point format
9908 @value{GDBN} can examine, set and perform computations with numbers in
9909 decimal floating point format, which in the C language correspond to the
9910 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
9911 specified by the extension to support decimal floating-point arithmetic.
9913 There are two encodings in use, depending on the architecture: BID (Binary
9914 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
9915 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
9918 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
9919 to manipulate decimal floating point numbers, it is not possible to convert
9920 (using a cast, for example) integers wider than 32-bit to decimal float.
9922 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
9923 point computations, error checking in decimal float operations ignores
9924 underflow, overflow and divide by zero exceptions.
9926 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
9927 to inspect @code{_Decimal128} values stored in floating point registers. See
9928 @ref{PowerPC,,PowerPC} for more details.
9931 @subsection Objective-C
9934 This section provides information about some commands and command
9935 options that are useful for debugging Objective-C code. See also
9936 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9937 few more commands specific to Objective-C support.
9940 * Method Names in Commands::
9941 * The Print Command with Objective-C::
9944 @node Method Names in Commands
9945 @subsubsection Method Names in Commands
9947 The following commands have been extended to accept Objective-C method
9948 names as line specifications:
9950 @kindex clear@r{, and Objective-C}
9951 @kindex break@r{, and Objective-C}
9952 @kindex info line@r{, and Objective-C}
9953 @kindex jump@r{, and Objective-C}
9954 @kindex list@r{, and Objective-C}
9958 @item @code{info line}
9963 A fully qualified Objective-C method name is specified as
9966 -[@var{Class} @var{methodName}]
9969 where the minus sign is used to indicate an instance method and a
9970 plus sign (not shown) is used to indicate a class method. The class
9971 name @var{Class} and method name @var{methodName} are enclosed in
9972 brackets, similar to the way messages are specified in Objective-C
9973 source code. For example, to set a breakpoint at the @code{create}
9974 instance method of class @code{Fruit} in the program currently being
9978 break -[Fruit create]
9981 To list ten program lines around the @code{initialize} class method,
9985 list +[NSText initialize]
9988 In the current version of @value{GDBN}, the plus or minus sign is
9989 required. In future versions of @value{GDBN}, the plus or minus
9990 sign will be optional, but you can use it to narrow the search. It
9991 is also possible to specify just a method name:
9997 You must specify the complete method name, including any colons. If
9998 your program's source files contain more than one @code{create} method,
9999 you'll be presented with a numbered list of classes that implement that
10000 method. Indicate your choice by number, or type @samp{0} to exit if
10003 As another example, to clear a breakpoint established at the
10004 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10007 clear -[NSWindow makeKeyAndOrderFront:]
10010 @node The Print Command with Objective-C
10011 @subsubsection The Print Command With Objective-C
10012 @cindex Objective-C, print objects
10013 @kindex print-object
10014 @kindex po @r{(@code{print-object})}
10016 The print command has also been extended to accept methods. For example:
10019 print -[@var{object} hash]
10022 @cindex print an Objective-C object description
10023 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10025 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10026 and print the result. Also, an additional command has been added,
10027 @code{print-object} or @code{po} for short, which is meant to print
10028 the description of an object. However, this command may only work
10029 with certain Objective-C libraries that have a particular hook
10030 function, @code{_NSPrintForDebugger}, defined.
10033 @subsection Fortran
10034 @cindex Fortran-specific support in @value{GDBN}
10036 @value{GDBN} can be used to debug programs written in Fortran, but it
10037 currently supports only the features of Fortran 77 language.
10039 @cindex trailing underscore, in Fortran symbols
10040 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10041 among them) append an underscore to the names of variables and
10042 functions. When you debug programs compiled by those compilers, you
10043 will need to refer to variables and functions with a trailing
10047 * Fortran Operators:: Fortran operators and expressions
10048 * Fortran Defaults:: Default settings for Fortran
10049 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10052 @node Fortran Operators
10053 @subsubsection Fortran Operators and Expressions
10055 @cindex Fortran operators and expressions
10057 Operators must be defined on values of specific types. For instance,
10058 @code{+} is defined on numbers, but not on characters or other non-
10059 arithmetic types. Operators are often defined on groups of types.
10063 The exponentiation operator. It raises the first operand to the power
10067 The range operator. Normally used in the form of array(low:high) to
10068 represent a section of array.
10071 The access component operator. Normally used to access elements in derived
10072 types. Also suitable for unions. As unions aren't part of regular Fortran,
10073 this can only happen when accessing a register that uses a gdbarch-defined
10077 @node Fortran Defaults
10078 @subsubsection Fortran Defaults
10080 @cindex Fortran Defaults
10082 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10083 default uses case-insensitive matches for Fortran symbols. You can
10084 change that with the @samp{set case-insensitive} command, see
10085 @ref{Symbols}, for the details.
10087 @node Special Fortran Commands
10088 @subsubsection Special Fortran Commands
10090 @cindex Special Fortran commands
10092 @value{GDBN} has some commands to support Fortran-specific features,
10093 such as displaying common blocks.
10096 @cindex @code{COMMON} blocks, Fortran
10097 @kindex info common
10098 @item info common @r{[}@var{common-name}@r{]}
10099 This command prints the values contained in the Fortran @code{COMMON}
10100 block whose name is @var{common-name}. With no argument, the names of
10101 all @code{COMMON} blocks visible at the current program location are
10108 @cindex Pascal support in @value{GDBN}, limitations
10109 Debugging Pascal programs which use sets, subranges, file variables, or
10110 nested functions does not currently work. @value{GDBN} does not support
10111 entering expressions, printing values, or similar features using Pascal
10114 The Pascal-specific command @code{set print pascal_static-members}
10115 controls whether static members of Pascal objects are displayed.
10116 @xref{Print Settings, pascal_static-members}.
10119 @subsection Modula-2
10121 @cindex Modula-2, @value{GDBN} support
10123 The extensions made to @value{GDBN} to support Modula-2 only support
10124 output from the @sc{gnu} Modula-2 compiler (which is currently being
10125 developed). Other Modula-2 compilers are not currently supported, and
10126 attempting to debug executables produced by them is most likely
10127 to give an error as @value{GDBN} reads in the executable's symbol
10130 @cindex expressions in Modula-2
10132 * M2 Operators:: Built-in operators
10133 * Built-In Func/Proc:: Built-in functions and procedures
10134 * M2 Constants:: Modula-2 constants
10135 * M2 Types:: Modula-2 types
10136 * M2 Defaults:: Default settings for Modula-2
10137 * Deviations:: Deviations from standard Modula-2
10138 * M2 Checks:: Modula-2 type and range checks
10139 * M2 Scope:: The scope operators @code{::} and @code{.}
10140 * GDB/M2:: @value{GDBN} and Modula-2
10144 @subsubsection Operators
10145 @cindex Modula-2 operators
10147 Operators must be defined on values of specific types. For instance,
10148 @code{+} is defined on numbers, but not on structures. Operators are
10149 often defined on groups of types. For the purposes of Modula-2, the
10150 following definitions hold:
10155 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10159 @emph{Character types} consist of @code{CHAR} and its subranges.
10162 @emph{Floating-point types} consist of @code{REAL}.
10165 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10169 @emph{Scalar types} consist of all of the above.
10172 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10175 @emph{Boolean types} consist of @code{BOOLEAN}.
10179 The following operators are supported, and appear in order of
10180 increasing precedence:
10184 Function argument or array index separator.
10187 Assignment. The value of @var{var} @code{:=} @var{value} is
10191 Less than, greater than on integral, floating-point, or enumerated
10195 Less than or equal to, greater than or equal to
10196 on integral, floating-point and enumerated types, or set inclusion on
10197 set types. Same precedence as @code{<}.
10199 @item =@r{, }<>@r{, }#
10200 Equality and two ways of expressing inequality, valid on scalar types.
10201 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10202 available for inequality, since @code{#} conflicts with the script
10206 Set membership. Defined on set types and the types of their members.
10207 Same precedence as @code{<}.
10210 Boolean disjunction. Defined on boolean types.
10213 Boolean conjunction. Defined on boolean types.
10216 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10219 Addition and subtraction on integral and floating-point types, or union
10220 and difference on set types.
10223 Multiplication on integral and floating-point types, or set intersection
10227 Division on floating-point types, or symmetric set difference on set
10228 types. Same precedence as @code{*}.
10231 Integer division and remainder. Defined on integral types. Same
10232 precedence as @code{*}.
10235 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10238 Pointer dereferencing. Defined on pointer types.
10241 Boolean negation. Defined on boolean types. Same precedence as
10245 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10246 precedence as @code{^}.
10249 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10252 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10256 @value{GDBN} and Modula-2 scope operators.
10260 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10261 treats the use of the operator @code{IN}, or the use of operators
10262 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10263 @code{<=}, and @code{>=} on sets as an error.
10267 @node Built-In Func/Proc
10268 @subsubsection Built-in Functions and Procedures
10269 @cindex Modula-2 built-ins
10271 Modula-2 also makes available several built-in procedures and functions.
10272 In describing these, the following metavariables are used:
10277 represents an @code{ARRAY} variable.
10280 represents a @code{CHAR} constant or variable.
10283 represents a variable or constant of integral type.
10286 represents an identifier that belongs to a set. Generally used in the
10287 same function with the metavariable @var{s}. The type of @var{s} should
10288 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10291 represents a variable or constant of integral or floating-point type.
10294 represents a variable or constant of floating-point type.
10300 represents a variable.
10303 represents a variable or constant of one of many types. See the
10304 explanation of the function for details.
10307 All Modula-2 built-in procedures also return a result, described below.
10311 Returns the absolute value of @var{n}.
10314 If @var{c} is a lower case letter, it returns its upper case
10315 equivalent, otherwise it returns its argument.
10318 Returns the character whose ordinal value is @var{i}.
10321 Decrements the value in the variable @var{v} by one. Returns the new value.
10323 @item DEC(@var{v},@var{i})
10324 Decrements the value in the variable @var{v} by @var{i}. Returns the
10327 @item EXCL(@var{m},@var{s})
10328 Removes the element @var{m} from the set @var{s}. Returns the new
10331 @item FLOAT(@var{i})
10332 Returns the floating point equivalent of the integer @var{i}.
10334 @item HIGH(@var{a})
10335 Returns the index of the last member of @var{a}.
10338 Increments the value in the variable @var{v} by one. Returns the new value.
10340 @item INC(@var{v},@var{i})
10341 Increments the value in the variable @var{v} by @var{i}. Returns the
10344 @item INCL(@var{m},@var{s})
10345 Adds the element @var{m} to the set @var{s} if it is not already
10346 there. Returns the new set.
10349 Returns the maximum value of the type @var{t}.
10352 Returns the minimum value of the type @var{t}.
10355 Returns boolean TRUE if @var{i} is an odd number.
10358 Returns the ordinal value of its argument. For example, the ordinal
10359 value of a character is its @sc{ascii} value (on machines supporting the
10360 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10361 integral, character and enumerated types.
10363 @item SIZE(@var{x})
10364 Returns the size of its argument. @var{x} can be a variable or a type.
10366 @item TRUNC(@var{r})
10367 Returns the integral part of @var{r}.
10369 @item TSIZE(@var{x})
10370 Returns the size of its argument. @var{x} can be a variable or a type.
10372 @item VAL(@var{t},@var{i})
10373 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10377 @emph{Warning:} Sets and their operations are not yet supported, so
10378 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10382 @cindex Modula-2 constants
10384 @subsubsection Constants
10386 @value{GDBN} allows you to express the constants of Modula-2 in the following
10392 Integer constants are simply a sequence of digits. When used in an
10393 expression, a constant is interpreted to be type-compatible with the
10394 rest of the expression. Hexadecimal integers are specified by a
10395 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10398 Floating point constants appear as a sequence of digits, followed by a
10399 decimal point and another sequence of digits. An optional exponent can
10400 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10401 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10402 digits of the floating point constant must be valid decimal (base 10)
10406 Character constants consist of a single character enclosed by a pair of
10407 like quotes, either single (@code{'}) or double (@code{"}). They may
10408 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10409 followed by a @samp{C}.
10412 String constants consist of a sequence of characters enclosed by a
10413 pair of like quotes, either single (@code{'}) or double (@code{"}).
10414 Escape sequences in the style of C are also allowed. @xref{C
10415 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10419 Enumerated constants consist of an enumerated identifier.
10422 Boolean constants consist of the identifiers @code{TRUE} and
10426 Pointer constants consist of integral values only.
10429 Set constants are not yet supported.
10433 @subsubsection Modula-2 Types
10434 @cindex Modula-2 types
10436 Currently @value{GDBN} can print the following data types in Modula-2
10437 syntax: array types, record types, set types, pointer types, procedure
10438 types, enumerated types, subrange types and base types. You can also
10439 print the contents of variables declared using these type.
10440 This section gives a number of simple source code examples together with
10441 sample @value{GDBN} sessions.
10443 The first example contains the following section of code:
10452 and you can request @value{GDBN} to interrogate the type and value of
10453 @code{r} and @code{s}.
10456 (@value{GDBP}) print s
10458 (@value{GDBP}) ptype s
10460 (@value{GDBP}) print r
10462 (@value{GDBP}) ptype r
10467 Likewise if your source code declares @code{s} as:
10471 s: SET ['A'..'Z'] ;
10475 then you may query the type of @code{s} by:
10478 (@value{GDBP}) ptype s
10479 type = SET ['A'..'Z']
10483 Note that at present you cannot interactively manipulate set
10484 expressions using the debugger.
10486 The following example shows how you might declare an array in Modula-2
10487 and how you can interact with @value{GDBN} to print its type and contents:
10491 s: ARRAY [-10..10] OF CHAR ;
10495 (@value{GDBP}) ptype s
10496 ARRAY [-10..10] OF CHAR
10499 Note that the array handling is not yet complete and although the type
10500 is printed correctly, expression handling still assumes that all
10501 arrays have a lower bound of zero and not @code{-10} as in the example
10504 Here are some more type related Modula-2 examples:
10508 colour = (blue, red, yellow, green) ;
10509 t = [blue..yellow] ;
10517 The @value{GDBN} interaction shows how you can query the data type
10518 and value of a variable.
10521 (@value{GDBP}) print s
10523 (@value{GDBP}) ptype t
10524 type = [blue..yellow]
10528 In this example a Modula-2 array is declared and its contents
10529 displayed. Observe that the contents are written in the same way as
10530 their @code{C} counterparts.
10534 s: ARRAY [1..5] OF CARDINAL ;
10540 (@value{GDBP}) print s
10541 $1 = @{1, 0, 0, 0, 0@}
10542 (@value{GDBP}) ptype s
10543 type = ARRAY [1..5] OF CARDINAL
10546 The Modula-2 language interface to @value{GDBN} also understands
10547 pointer types as shown in this example:
10551 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10558 and you can request that @value{GDBN} describes the type of @code{s}.
10561 (@value{GDBP}) ptype s
10562 type = POINTER TO ARRAY [1..5] OF CARDINAL
10565 @value{GDBN} handles compound types as we can see in this example.
10566 Here we combine array types, record types, pointer types and subrange
10577 myarray = ARRAY myrange OF CARDINAL ;
10578 myrange = [-2..2] ;
10580 s: POINTER TO ARRAY myrange OF foo ;
10584 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10588 (@value{GDBP}) ptype s
10589 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10592 f3 : ARRAY [-2..2] OF CARDINAL;
10597 @subsubsection Modula-2 Defaults
10598 @cindex Modula-2 defaults
10600 If type and range checking are set automatically by @value{GDBN}, they
10601 both default to @code{on} whenever the working language changes to
10602 Modula-2. This happens regardless of whether you or @value{GDBN}
10603 selected the working language.
10605 If you allow @value{GDBN} to set the language automatically, then entering
10606 code compiled from a file whose name ends with @file{.mod} sets the
10607 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10608 Infer the Source Language}, for further details.
10611 @subsubsection Deviations from Standard Modula-2
10612 @cindex Modula-2, deviations from
10614 A few changes have been made to make Modula-2 programs easier to debug.
10615 This is done primarily via loosening its type strictness:
10619 Unlike in standard Modula-2, pointer constants can be formed by
10620 integers. This allows you to modify pointer variables during
10621 debugging. (In standard Modula-2, the actual address contained in a
10622 pointer variable is hidden from you; it can only be modified
10623 through direct assignment to another pointer variable or expression that
10624 returned a pointer.)
10627 C escape sequences can be used in strings and characters to represent
10628 non-printable characters. @value{GDBN} prints out strings with these
10629 escape sequences embedded. Single non-printable characters are
10630 printed using the @samp{CHR(@var{nnn})} format.
10633 The assignment operator (@code{:=}) returns the value of its right-hand
10637 All built-in procedures both modify @emph{and} return their argument.
10641 @subsubsection Modula-2 Type and Range Checks
10642 @cindex Modula-2 checks
10645 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10648 @c FIXME remove warning when type/range checks added
10650 @value{GDBN} considers two Modula-2 variables type equivalent if:
10654 They are of types that have been declared equivalent via a @code{TYPE
10655 @var{t1} = @var{t2}} statement
10658 They have been declared on the same line. (Note: This is true of the
10659 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10662 As long as type checking is enabled, any attempt to combine variables
10663 whose types are not equivalent is an error.
10665 Range checking is done on all mathematical operations, assignment, array
10666 index bounds, and all built-in functions and procedures.
10669 @subsubsection The Scope Operators @code{::} and @code{.}
10671 @cindex @code{.}, Modula-2 scope operator
10672 @cindex colon, doubled as scope operator
10674 @vindex colon-colon@r{, in Modula-2}
10675 @c Info cannot handle :: but TeX can.
10678 @vindex ::@r{, in Modula-2}
10681 There are a few subtle differences between the Modula-2 scope operator
10682 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10687 @var{module} . @var{id}
10688 @var{scope} :: @var{id}
10692 where @var{scope} is the name of a module or a procedure,
10693 @var{module} the name of a module, and @var{id} is any declared
10694 identifier within your program, except another module.
10696 Using the @code{::} operator makes @value{GDBN} search the scope
10697 specified by @var{scope} for the identifier @var{id}. If it is not
10698 found in the specified scope, then @value{GDBN} searches all scopes
10699 enclosing the one specified by @var{scope}.
10701 Using the @code{.} operator makes @value{GDBN} search the current scope for
10702 the identifier specified by @var{id} that was imported from the
10703 definition module specified by @var{module}. With this operator, it is
10704 an error if the identifier @var{id} was not imported from definition
10705 module @var{module}, or if @var{id} is not an identifier in
10709 @subsubsection @value{GDBN} and Modula-2
10711 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10712 Five subcommands of @code{set print} and @code{show print} apply
10713 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10714 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10715 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10716 analogue in Modula-2.
10718 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10719 with any language, is not useful with Modula-2. Its
10720 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10721 created in Modula-2 as they can in C or C@t{++}. However, because an
10722 address can be specified by an integral constant, the construct
10723 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10725 @cindex @code{#} in Modula-2
10726 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10727 interpreted as the beginning of a comment. Use @code{<>} instead.
10733 The extensions made to @value{GDBN} for Ada only support
10734 output from the @sc{gnu} Ada (GNAT) compiler.
10735 Other Ada compilers are not currently supported, and
10736 attempting to debug executables produced by them is most likely
10740 @cindex expressions in Ada
10742 * Ada Mode Intro:: General remarks on the Ada syntax
10743 and semantics supported by Ada mode
10745 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10746 * Additions to Ada:: Extensions of the Ada expression syntax.
10747 * Stopping Before Main Program:: Debugging the program during elaboration.
10748 * Ada Glitches:: Known peculiarities of Ada mode.
10751 @node Ada Mode Intro
10752 @subsubsection Introduction
10753 @cindex Ada mode, general
10755 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10756 syntax, with some extensions.
10757 The philosophy behind the design of this subset is
10761 That @value{GDBN} should provide basic literals and access to operations for
10762 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10763 leaving more sophisticated computations to subprograms written into the
10764 program (which therefore may be called from @value{GDBN}).
10767 That type safety and strict adherence to Ada language restrictions
10768 are not particularly important to the @value{GDBN} user.
10771 That brevity is important to the @value{GDBN} user.
10774 Thus, for brevity, the debugger acts as if there were
10775 implicit @code{with} and @code{use} clauses in effect for all user-written
10776 packages, making it unnecessary to fully qualify most names with
10777 their packages, regardless of context. Where this causes ambiguity,
10778 @value{GDBN} asks the user's intent.
10780 The debugger will start in Ada mode if it detects an Ada main program.
10781 As for other languages, it will enter Ada mode when stopped in a program that
10782 was translated from an Ada source file.
10784 While in Ada mode, you may use `@t{--}' for comments. This is useful
10785 mostly for documenting command files. The standard @value{GDBN} comment
10786 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10787 middle (to allow based literals).
10789 The debugger supports limited overloading. Given a subprogram call in which
10790 the function symbol has multiple definitions, it will use the number of
10791 actual parameters and some information about their types to attempt to narrow
10792 the set of definitions. It also makes very limited use of context, preferring
10793 procedures to functions in the context of the @code{call} command, and
10794 functions to procedures elsewhere.
10796 @node Omissions from Ada
10797 @subsubsection Omissions from Ada
10798 @cindex Ada, omissions from
10800 Here are the notable omissions from the subset:
10804 Only a subset of the attributes are supported:
10808 @t{'First}, @t{'Last}, and @t{'Length}
10809 on array objects (not on types and subtypes).
10812 @t{'Min} and @t{'Max}.
10815 @t{'Pos} and @t{'Val}.
10821 @t{'Range} on array objects (not subtypes), but only as the right
10822 operand of the membership (@code{in}) operator.
10825 @t{'Access}, @t{'Unchecked_Access}, and
10826 @t{'Unrestricted_Access} (a GNAT extension).
10834 @code{Characters.Latin_1} are not available and
10835 concatenation is not implemented. Thus, escape characters in strings are
10836 not currently available.
10839 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10840 equality of representations. They will generally work correctly
10841 for strings and arrays whose elements have integer or enumeration types.
10842 They may not work correctly for arrays whose element
10843 types have user-defined equality, for arrays of real values
10844 (in particular, IEEE-conformant floating point, because of negative
10845 zeroes and NaNs), and for arrays whose elements contain unused bits with
10846 indeterminate values.
10849 The other component-by-component array operations (@code{and}, @code{or},
10850 @code{xor}, @code{not}, and relational tests other than equality)
10851 are not implemented.
10854 @cindex array aggregates (Ada)
10855 @cindex record aggregates (Ada)
10856 @cindex aggregates (Ada)
10857 There is limited support for array and record aggregates. They are
10858 permitted only on the right sides of assignments, as in these examples:
10861 set An_Array := (1, 2, 3, 4, 5, 6)
10862 set An_Array := (1, others => 0)
10863 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10864 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10865 set A_Record := (1, "Peter", True);
10866 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10870 discriminant's value by assigning an aggregate has an
10871 undefined effect if that discriminant is used within the record.
10872 However, you can first modify discriminants by directly assigning to
10873 them (which normally would not be allowed in Ada), and then performing an
10874 aggregate assignment. For example, given a variable @code{A_Rec}
10875 declared to have a type such as:
10878 type Rec (Len : Small_Integer := 0) is record
10880 Vals : IntArray (1 .. Len);
10884 you can assign a value with a different size of @code{Vals} with two
10889 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10892 As this example also illustrates, @value{GDBN} is very loose about the usual
10893 rules concerning aggregates. You may leave out some of the
10894 components of an array or record aggregate (such as the @code{Len}
10895 component in the assignment to @code{A_Rec} above); they will retain their
10896 original values upon assignment. You may freely use dynamic values as
10897 indices in component associations. You may even use overlapping or
10898 redundant component associations, although which component values are
10899 assigned in such cases is not defined.
10902 Calls to dispatching subprograms are not implemented.
10905 The overloading algorithm is much more limited (i.e., less selective)
10906 than that of real Ada. It makes only limited use of the context in
10907 which a subexpression appears to resolve its meaning, and it is much
10908 looser in its rules for allowing type matches. As a result, some
10909 function calls will be ambiguous, and the user will be asked to choose
10910 the proper resolution.
10913 The @code{new} operator is not implemented.
10916 Entry calls are not implemented.
10919 Aside from printing, arithmetic operations on the native VAX floating-point
10920 formats are not supported.
10923 It is not possible to slice a packed array.
10926 @node Additions to Ada
10927 @subsubsection Additions to Ada
10928 @cindex Ada, deviations from
10930 As it does for other languages, @value{GDBN} makes certain generic
10931 extensions to Ada (@pxref{Expressions}):
10935 If the expression @var{E} is a variable residing in memory (typically
10936 a local variable or array element) and @var{N} is a positive integer,
10937 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10938 @var{N}-1 adjacent variables following it in memory as an array. In
10939 Ada, this operator is generally not necessary, since its prime use is
10940 in displaying parts of an array, and slicing will usually do this in
10941 Ada. However, there are occasional uses when debugging programs in
10942 which certain debugging information has been optimized away.
10945 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10946 appears in function or file @var{B}.'' When @var{B} is a file name,
10947 you must typically surround it in single quotes.
10950 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10951 @var{type} that appears at address @var{addr}.''
10954 A name starting with @samp{$} is a convenience variable
10955 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10958 In addition, @value{GDBN} provides a few other shortcuts and outright
10959 additions specific to Ada:
10963 The assignment statement is allowed as an expression, returning
10964 its right-hand operand as its value. Thus, you may enter
10968 print A(tmp := y + 1)
10972 The semicolon is allowed as an ``operator,'' returning as its value
10973 the value of its right-hand operand.
10974 This allows, for example,
10975 complex conditional breaks:
10979 condition 1 (report(i); k += 1; A(k) > 100)
10983 Rather than use catenation and symbolic character names to introduce special
10984 characters into strings, one may instead use a special bracket notation,
10985 which is also used to print strings. A sequence of characters of the form
10986 @samp{["@var{XX}"]} within a string or character literal denotes the
10987 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10988 sequence of characters @samp{["""]} also denotes a single quotation mark
10989 in strings. For example,
10991 "One line.["0a"]Next line.["0a"]"
10994 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10998 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10999 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11007 When printing arrays, @value{GDBN} uses positional notation when the
11008 array has a lower bound of 1, and uses a modified named notation otherwise.
11009 For example, a one-dimensional array of three integers with a lower bound
11010 of 3 might print as
11017 That is, in contrast to valid Ada, only the first component has a @code{=>}
11021 You may abbreviate attributes in expressions with any unique,
11022 multi-character subsequence of
11023 their names (an exact match gets preference).
11024 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11025 in place of @t{a'length}.
11028 @cindex quoting Ada internal identifiers
11029 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11030 to lower case. The GNAT compiler uses upper-case characters for
11031 some of its internal identifiers, which are normally of no interest to users.
11032 For the rare occasions when you actually have to look at them,
11033 enclose them in angle brackets to avoid the lower-case mapping.
11036 @value{GDBP} print <JMPBUF_SAVE>[0]
11040 Printing an object of class-wide type or dereferencing an
11041 access-to-class-wide value will display all the components of the object's
11042 specific type (as indicated by its run-time tag). Likewise, component
11043 selection on such a value will operate on the specific type of the
11048 @node Stopping Before Main Program
11049 @subsubsection Stopping at the Very Beginning
11051 @cindex breakpointing Ada elaboration code
11052 It is sometimes necessary to debug the program during elaboration, and
11053 before reaching the main procedure.
11054 As defined in the Ada Reference
11055 Manual, the elaboration code is invoked from a procedure called
11056 @code{adainit}. To run your program up to the beginning of
11057 elaboration, simply use the following two commands:
11058 @code{tbreak adainit} and @code{run}.
11061 @subsubsection Known Peculiarities of Ada Mode
11062 @cindex Ada, problems
11064 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11065 we know of several problems with and limitations of Ada mode in
11067 some of which will be fixed with planned future releases of the debugger
11068 and the GNU Ada compiler.
11072 Currently, the debugger
11073 has insufficient information to determine whether certain pointers represent
11074 pointers to objects or the objects themselves.
11075 Thus, the user may have to tack an extra @code{.all} after an expression
11076 to get it printed properly.
11079 Static constants that the compiler chooses not to materialize as objects in
11080 storage are invisible to the debugger.
11083 Named parameter associations in function argument lists are ignored (the
11084 argument lists are treated as positional).
11087 Many useful library packages are currently invisible to the debugger.
11090 Fixed-point arithmetic, conversions, input, and output is carried out using
11091 floating-point arithmetic, and may give results that only approximate those on
11095 The type of the @t{'Address} attribute may not be @code{System.Address}.
11098 The GNAT compiler never generates the prefix @code{Standard} for any of
11099 the standard symbols defined by the Ada language. @value{GDBN} knows about
11100 this: it will strip the prefix from names when you use it, and will never
11101 look for a name you have so qualified among local symbols, nor match against
11102 symbols in other packages or subprograms. If you have
11103 defined entities anywhere in your program other than parameters and
11104 local variables whose simple names match names in @code{Standard},
11105 GNAT's lack of qualification here can cause confusion. When this happens,
11106 you can usually resolve the confusion
11107 by qualifying the problematic names with package
11108 @code{Standard} explicitly.
11111 @node Unsupported Languages
11112 @section Unsupported Languages
11114 @cindex unsupported languages
11115 @cindex minimal language
11116 In addition to the other fully-supported programming languages,
11117 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11118 It does not represent a real programming language, but provides a set
11119 of capabilities close to what the C or assembly languages provide.
11120 This should allow most simple operations to be performed while debugging
11121 an application that uses a language currently not supported by @value{GDBN}.
11123 If the language is set to @code{auto}, @value{GDBN} will automatically
11124 select this language if the current frame corresponds to an unsupported
11128 @chapter Examining the Symbol Table
11130 The commands described in this chapter allow you to inquire about the
11131 symbols (names of variables, functions and types) defined in your
11132 program. This information is inherent in the text of your program and
11133 does not change as your program executes. @value{GDBN} finds it in your
11134 program's symbol table, in the file indicated when you started @value{GDBN}
11135 (@pxref{File Options, ,Choosing Files}), or by one of the
11136 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11138 @cindex symbol names
11139 @cindex names of symbols
11140 @cindex quoting names
11141 Occasionally, you may need to refer to symbols that contain unusual
11142 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11143 most frequent case is in referring to static variables in other
11144 source files (@pxref{Variables,,Program Variables}). File names
11145 are recorded in object files as debugging symbols, but @value{GDBN} would
11146 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11147 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11148 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11155 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11158 @cindex case-insensitive symbol names
11159 @cindex case sensitivity in symbol names
11160 @kindex set case-sensitive
11161 @item set case-sensitive on
11162 @itemx set case-sensitive off
11163 @itemx set case-sensitive auto
11164 Normally, when @value{GDBN} looks up symbols, it matches their names
11165 with case sensitivity determined by the current source language.
11166 Occasionally, you may wish to control that. The command @code{set
11167 case-sensitive} lets you do that by specifying @code{on} for
11168 case-sensitive matches or @code{off} for case-insensitive ones. If
11169 you specify @code{auto}, case sensitivity is reset to the default
11170 suitable for the source language. The default is case-sensitive
11171 matches for all languages except for Fortran, for which the default is
11172 case-insensitive matches.
11174 @kindex show case-sensitive
11175 @item show case-sensitive
11176 This command shows the current setting of case sensitivity for symbols
11179 @kindex info address
11180 @cindex address of a symbol
11181 @item info address @var{symbol}
11182 Describe where the data for @var{symbol} is stored. For a register
11183 variable, this says which register it is kept in. For a non-register
11184 local variable, this prints the stack-frame offset at which the variable
11187 Note the contrast with @samp{print &@var{symbol}}, which does not work
11188 at all for a register variable, and for a stack local variable prints
11189 the exact address of the current instantiation of the variable.
11191 @kindex info symbol
11192 @cindex symbol from address
11193 @cindex closest symbol and offset for an address
11194 @item info symbol @var{addr}
11195 Print the name of a symbol which is stored at the address @var{addr}.
11196 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11197 nearest symbol and an offset from it:
11200 (@value{GDBP}) info symbol 0x54320
11201 _initialize_vx + 396 in section .text
11205 This is the opposite of the @code{info address} command. You can use
11206 it to find out the name of a variable or a function given its address.
11209 @item whatis [@var{arg}]
11210 Print the data type of @var{arg}, which can be either an expression or
11211 a data type. With no argument, print the data type of @code{$}, the
11212 last value in the value history. If @var{arg} is an expression, it is
11213 not actually evaluated, and any side-effecting operations (such as
11214 assignments or function calls) inside it do not take place. If
11215 @var{arg} is a type name, it may be the name of a type or typedef, or
11216 for C code it may have the form @samp{class @var{class-name}},
11217 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11218 @samp{enum @var{enum-tag}}.
11219 @xref{Expressions, ,Expressions}.
11222 @item ptype [@var{arg}]
11223 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11224 detailed description of the type, instead of just the name of the type.
11225 @xref{Expressions, ,Expressions}.
11227 For example, for this variable declaration:
11230 struct complex @{double real; double imag;@} v;
11234 the two commands give this output:
11238 (@value{GDBP}) whatis v
11239 type = struct complex
11240 (@value{GDBP}) ptype v
11241 type = struct complex @{
11249 As with @code{whatis}, using @code{ptype} without an argument refers to
11250 the type of @code{$}, the last value in the value history.
11252 @cindex incomplete type
11253 Sometimes, programs use opaque data types or incomplete specifications
11254 of complex data structure. If the debug information included in the
11255 program does not allow @value{GDBN} to display a full declaration of
11256 the data type, it will say @samp{<incomplete type>}. For example,
11257 given these declarations:
11261 struct foo *fooptr;
11265 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11268 (@value{GDBP}) ptype foo
11269 $1 = <incomplete type>
11273 ``Incomplete type'' is C terminology for data types that are not
11274 completely specified.
11277 @item info types @var{regexp}
11279 Print a brief description of all types whose names match the regular
11280 expression @var{regexp} (or all types in your program, if you supply
11281 no argument). Each complete typename is matched as though it were a
11282 complete line; thus, @samp{i type value} gives information on all
11283 types in your program whose names include the string @code{value}, but
11284 @samp{i type ^value$} gives information only on types whose complete
11285 name is @code{value}.
11287 This command differs from @code{ptype} in two ways: first, like
11288 @code{whatis}, it does not print a detailed description; second, it
11289 lists all source files where a type is defined.
11292 @cindex local variables
11293 @item info scope @var{location}
11294 List all the variables local to a particular scope. This command
11295 accepts a @var{location} argument---a function name, a source line, or
11296 an address preceded by a @samp{*}, and prints all the variables local
11297 to the scope defined by that location. (@xref{Specify Location}, for
11298 details about supported forms of @var{location}.) For example:
11301 (@value{GDBP}) @b{info scope command_line_handler}
11302 Scope for command_line_handler:
11303 Symbol rl is an argument at stack/frame offset 8, length 4.
11304 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11305 Symbol linelength is in static storage at address 0x150a1c, length 4.
11306 Symbol p is a local variable in register $esi, length 4.
11307 Symbol p1 is a local variable in register $ebx, length 4.
11308 Symbol nline is a local variable in register $edx, length 4.
11309 Symbol repeat is a local variable at frame offset -8, length 4.
11313 This command is especially useful for determining what data to collect
11314 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11317 @kindex info source
11319 Show information about the current source file---that is, the source file for
11320 the function containing the current point of execution:
11323 the name of the source file, and the directory containing it,
11325 the directory it was compiled in,
11327 its length, in lines,
11329 which programming language it is written in,
11331 whether the executable includes debugging information for that file, and
11332 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11334 whether the debugging information includes information about
11335 preprocessor macros.
11339 @kindex info sources
11341 Print the names of all source files in your program for which there is
11342 debugging information, organized into two lists: files whose symbols
11343 have already been read, and files whose symbols will be read when needed.
11345 @kindex info functions
11346 @item info functions
11347 Print the names and data types of all defined functions.
11349 @item info functions @var{regexp}
11350 Print the names and data types of all defined functions
11351 whose names contain a match for regular expression @var{regexp}.
11352 Thus, @samp{info fun step} finds all functions whose names
11353 include @code{step}; @samp{info fun ^step} finds those whose names
11354 start with @code{step}. If a function name contains characters
11355 that conflict with the regular expression language (e.g.@:
11356 @samp{operator*()}), they may be quoted with a backslash.
11358 @kindex info variables
11359 @item info variables
11360 Print the names and data types of all variables that are declared
11361 outside of functions (i.e.@: excluding local variables).
11363 @item info variables @var{regexp}
11364 Print the names and data types of all variables (except for local
11365 variables) whose names contain a match for regular expression
11368 @kindex info classes
11369 @cindex Objective-C, classes and selectors
11371 @itemx info classes @var{regexp}
11372 Display all Objective-C classes in your program, or
11373 (with the @var{regexp} argument) all those matching a particular regular
11376 @kindex info selectors
11377 @item info selectors
11378 @itemx info selectors @var{regexp}
11379 Display all Objective-C selectors in your program, or
11380 (with the @var{regexp} argument) all those matching a particular regular
11384 This was never implemented.
11385 @kindex info methods
11387 @itemx info methods @var{regexp}
11388 The @code{info methods} command permits the user to examine all defined
11389 methods within C@t{++} program, or (with the @var{regexp} argument) a
11390 specific set of methods found in the various C@t{++} classes. Many
11391 C@t{++} classes provide a large number of methods. Thus, the output
11392 from the @code{ptype} command can be overwhelming and hard to use. The
11393 @code{info-methods} command filters the methods, printing only those
11394 which match the regular-expression @var{regexp}.
11397 @cindex reloading symbols
11398 Some systems allow individual object files that make up your program to
11399 be replaced without stopping and restarting your program. For example,
11400 in VxWorks you can simply recompile a defective object file and keep on
11401 running. If you are running on one of these systems, you can allow
11402 @value{GDBN} to reload the symbols for automatically relinked modules:
11405 @kindex set symbol-reloading
11406 @item set symbol-reloading on
11407 Replace symbol definitions for the corresponding source file when an
11408 object file with a particular name is seen again.
11410 @item set symbol-reloading off
11411 Do not replace symbol definitions when encountering object files of the
11412 same name more than once. This is the default state; if you are not
11413 running on a system that permits automatic relinking of modules, you
11414 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11415 may discard symbols when linking large programs, that may contain
11416 several modules (from different directories or libraries) with the same
11419 @kindex show symbol-reloading
11420 @item show symbol-reloading
11421 Show the current @code{on} or @code{off} setting.
11424 @cindex opaque data types
11425 @kindex set opaque-type-resolution
11426 @item set opaque-type-resolution on
11427 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11428 declared as a pointer to a @code{struct}, @code{class}, or
11429 @code{union}---for example, @code{struct MyType *}---that is used in one
11430 source file although the full declaration of @code{struct MyType} is in
11431 another source file. The default is on.
11433 A change in the setting of this subcommand will not take effect until
11434 the next time symbols for a file are loaded.
11436 @item set opaque-type-resolution off
11437 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11438 is printed as follows:
11440 @{<no data fields>@}
11443 @kindex show opaque-type-resolution
11444 @item show opaque-type-resolution
11445 Show whether opaque types are resolved or not.
11447 @kindex maint print symbols
11448 @cindex symbol dump
11449 @kindex maint print psymbols
11450 @cindex partial symbol dump
11451 @item maint print symbols @var{filename}
11452 @itemx maint print psymbols @var{filename}
11453 @itemx maint print msymbols @var{filename}
11454 Write a dump of debugging symbol data into the file @var{filename}.
11455 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11456 symbols with debugging data are included. If you use @samp{maint print
11457 symbols}, @value{GDBN} includes all the symbols for which it has already
11458 collected full details: that is, @var{filename} reflects symbols for
11459 only those files whose symbols @value{GDBN} has read. You can use the
11460 command @code{info sources} to find out which files these are. If you
11461 use @samp{maint print psymbols} instead, the dump shows information about
11462 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11463 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11464 @samp{maint print msymbols} dumps just the minimal symbol information
11465 required for each object file from which @value{GDBN} has read some symbols.
11466 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11467 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11469 @kindex maint info symtabs
11470 @kindex maint info psymtabs
11471 @cindex listing @value{GDBN}'s internal symbol tables
11472 @cindex symbol tables, listing @value{GDBN}'s internal
11473 @cindex full symbol tables, listing @value{GDBN}'s internal
11474 @cindex partial symbol tables, listing @value{GDBN}'s internal
11475 @item maint info symtabs @r{[} @var{regexp} @r{]}
11476 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11478 List the @code{struct symtab} or @code{struct partial_symtab}
11479 structures whose names match @var{regexp}. If @var{regexp} is not
11480 given, list them all. The output includes expressions which you can
11481 copy into a @value{GDBN} debugging this one to examine a particular
11482 structure in more detail. For example:
11485 (@value{GDBP}) maint info psymtabs dwarf2read
11486 @{ objfile /home/gnu/build/gdb/gdb
11487 ((struct objfile *) 0x82e69d0)
11488 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11489 ((struct partial_symtab *) 0x8474b10)
11492 text addresses 0x814d3c8 -- 0x8158074
11493 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11494 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11495 dependencies (none)
11498 (@value{GDBP}) maint info symtabs
11502 We see that there is one partial symbol table whose filename contains
11503 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11504 and we see that @value{GDBN} has not read in any symtabs yet at all.
11505 If we set a breakpoint on a function, that will cause @value{GDBN} to
11506 read the symtab for the compilation unit containing that function:
11509 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11510 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11512 (@value{GDBP}) maint info symtabs
11513 @{ objfile /home/gnu/build/gdb/gdb
11514 ((struct objfile *) 0x82e69d0)
11515 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11516 ((struct symtab *) 0x86c1f38)
11519 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11520 linetable ((struct linetable *) 0x8370fa0)
11521 debugformat DWARF 2
11530 @chapter Altering Execution
11532 Once you think you have found an error in your program, you might want to
11533 find out for certain whether correcting the apparent error would lead to
11534 correct results in the rest of the run. You can find the answer by
11535 experiment, using the @value{GDBN} features for altering execution of the
11538 For example, you can store new values into variables or memory
11539 locations, give your program a signal, restart it at a different
11540 address, or even return prematurely from a function.
11543 * Assignment:: Assignment to variables
11544 * Jumping:: Continuing at a different address
11545 * Signaling:: Giving your program a signal
11546 * Returning:: Returning from a function
11547 * Calling:: Calling your program's functions
11548 * Patching:: Patching your program
11552 @section Assignment to Variables
11555 @cindex setting variables
11556 To alter the value of a variable, evaluate an assignment expression.
11557 @xref{Expressions, ,Expressions}. For example,
11564 stores the value 4 into the variable @code{x}, and then prints the
11565 value of the assignment expression (which is 4).
11566 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11567 information on operators in supported languages.
11569 @kindex set variable
11570 @cindex variables, setting
11571 If you are not interested in seeing the value of the assignment, use the
11572 @code{set} command instead of the @code{print} command. @code{set} is
11573 really the same as @code{print} except that the expression's value is
11574 not printed and is not put in the value history (@pxref{Value History,
11575 ,Value History}). The expression is evaluated only for its effects.
11577 If the beginning of the argument string of the @code{set} command
11578 appears identical to a @code{set} subcommand, use the @code{set
11579 variable} command instead of just @code{set}. This command is identical
11580 to @code{set} except for its lack of subcommands. For example, if your
11581 program has a variable @code{width}, you get an error if you try to set
11582 a new value with just @samp{set width=13}, because @value{GDBN} has the
11583 command @code{set width}:
11586 (@value{GDBP}) whatis width
11588 (@value{GDBP}) p width
11590 (@value{GDBP}) set width=47
11591 Invalid syntax in expression.
11595 The invalid expression, of course, is @samp{=47}. In
11596 order to actually set the program's variable @code{width}, use
11599 (@value{GDBP}) set var width=47
11602 Because the @code{set} command has many subcommands that can conflict
11603 with the names of program variables, it is a good idea to use the
11604 @code{set variable} command instead of just @code{set}. For example, if
11605 your program has a variable @code{g}, you run into problems if you try
11606 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11607 the command @code{set gnutarget}, abbreviated @code{set g}:
11611 (@value{GDBP}) whatis g
11615 (@value{GDBP}) set g=4
11619 The program being debugged has been started already.
11620 Start it from the beginning? (y or n) y
11621 Starting program: /home/smith/cc_progs/a.out
11622 "/home/smith/cc_progs/a.out": can't open to read symbols:
11623 Invalid bfd target.
11624 (@value{GDBP}) show g
11625 The current BFD target is "=4".
11630 The program variable @code{g} did not change, and you silently set the
11631 @code{gnutarget} to an invalid value. In order to set the variable
11635 (@value{GDBP}) set var g=4
11638 @value{GDBN} allows more implicit conversions in assignments than C; you can
11639 freely store an integer value into a pointer variable or vice versa,
11640 and you can convert any structure to any other structure that is the
11641 same length or shorter.
11642 @comment FIXME: how do structs align/pad in these conversions?
11643 @comment /doc@cygnus.com 18dec1990
11645 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11646 construct to generate a value of specified type at a specified address
11647 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11648 to memory location @code{0x83040} as an integer (which implies a certain size
11649 and representation in memory), and
11652 set @{int@}0x83040 = 4
11656 stores the value 4 into that memory location.
11659 @section Continuing at a Different Address
11661 Ordinarily, when you continue your program, you do so at the place where
11662 it stopped, with the @code{continue} command. You can instead continue at
11663 an address of your own choosing, with the following commands:
11667 @item jump @var{linespec}
11668 @itemx jump @var{location}
11669 Resume execution at line @var{linespec} or at address given by
11670 @var{location}. Execution stops again immediately if there is a
11671 breakpoint there. @xref{Specify Location}, for a description of the
11672 different forms of @var{linespec} and @var{location}. It is common
11673 practice to use the @code{tbreak} command in conjunction with
11674 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
11676 The @code{jump} command does not change the current stack frame, or
11677 the stack pointer, or the contents of any memory location or any
11678 register other than the program counter. If line @var{linespec} is in
11679 a different function from the one currently executing, the results may
11680 be bizarre if the two functions expect different patterns of arguments or
11681 of local variables. For this reason, the @code{jump} command requests
11682 confirmation if the specified line is not in the function currently
11683 executing. However, even bizarre results are predictable if you are
11684 well acquainted with the machine-language code of your program.
11687 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11688 On many systems, you can get much the same effect as the @code{jump}
11689 command by storing a new value into the register @code{$pc}. The
11690 difference is that this does not start your program running; it only
11691 changes the address of where it @emph{will} run when you continue. For
11699 makes the next @code{continue} command or stepping command execute at
11700 address @code{0x485}, rather than at the address where your program stopped.
11701 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11703 The most common occasion to use the @code{jump} command is to back
11704 up---perhaps with more breakpoints set---over a portion of a program
11705 that has already executed, in order to examine its execution in more
11710 @section Giving your Program a Signal
11711 @cindex deliver a signal to a program
11715 @item signal @var{signal}
11716 Resume execution where your program stopped, but immediately give it the
11717 signal @var{signal}. @var{signal} can be the name or the number of a
11718 signal. For example, on many systems @code{signal 2} and @code{signal
11719 SIGINT} are both ways of sending an interrupt signal.
11721 Alternatively, if @var{signal} is zero, continue execution without
11722 giving a signal. This is useful when your program stopped on account of
11723 a signal and would ordinary see the signal when resumed with the
11724 @code{continue} command; @samp{signal 0} causes it to resume without a
11727 @code{signal} does not repeat when you press @key{RET} a second time
11728 after executing the command.
11732 Invoking the @code{signal} command is not the same as invoking the
11733 @code{kill} utility from the shell. Sending a signal with @code{kill}
11734 causes @value{GDBN} to decide what to do with the signal depending on
11735 the signal handling tables (@pxref{Signals}). The @code{signal} command
11736 passes the signal directly to your program.
11740 @section Returning from a Function
11743 @cindex returning from a function
11746 @itemx return @var{expression}
11747 You can cancel execution of a function call with the @code{return}
11748 command. If you give an
11749 @var{expression} argument, its value is used as the function's return
11753 When you use @code{return}, @value{GDBN} discards the selected stack frame
11754 (and all frames within it). You can think of this as making the
11755 discarded frame return prematurely. If you wish to specify a value to
11756 be returned, give that value as the argument to @code{return}.
11758 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11759 Frame}), and any other frames inside of it, leaving its caller as the
11760 innermost remaining frame. That frame becomes selected. The
11761 specified value is stored in the registers used for returning values
11764 The @code{return} command does not resume execution; it leaves the
11765 program stopped in the state that would exist if the function had just
11766 returned. In contrast, the @code{finish} command (@pxref{Continuing
11767 and Stepping, ,Continuing and Stepping}) resumes execution until the
11768 selected stack frame returns naturally.
11771 @section Calling Program Functions
11774 @cindex calling functions
11775 @cindex inferior functions, calling
11776 @item print @var{expr}
11777 Evaluate the expression @var{expr} and display the resulting value.
11778 @var{expr} may include calls to functions in the program being
11782 @item call @var{expr}
11783 Evaluate the expression @var{expr} without displaying @code{void}
11786 You can use this variant of the @code{print} command if you want to
11787 execute a function from your program that does not return anything
11788 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11789 with @code{void} returned values that @value{GDBN} will otherwise
11790 print. If the result is not void, it is printed and saved in the
11794 It is possible for the function you call via the @code{print} or
11795 @code{call} command to generate a signal (e.g., if there's a bug in
11796 the function, or if you passed it incorrect arguments). What happens
11797 in that case is controlled by the @code{set unwindonsignal} command.
11800 @item set unwindonsignal
11801 @kindex set unwindonsignal
11802 @cindex unwind stack in called functions
11803 @cindex call dummy stack unwinding
11804 Set unwinding of the stack if a signal is received while in a function
11805 that @value{GDBN} called in the program being debugged. If set to on,
11806 @value{GDBN} unwinds the stack it created for the call and restores
11807 the context to what it was before the call. If set to off (the
11808 default), @value{GDBN} stops in the frame where the signal was
11811 @item show unwindonsignal
11812 @kindex show unwindonsignal
11813 Show the current setting of stack unwinding in the functions called by
11817 @cindex weak alias functions
11818 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11819 for another function. In such case, @value{GDBN} might not pick up
11820 the type information, including the types of the function arguments,
11821 which causes @value{GDBN} to call the inferior function incorrectly.
11822 As a result, the called function will function erroneously and may
11823 even crash. A solution to that is to use the name of the aliased
11827 @section Patching Programs
11829 @cindex patching binaries
11830 @cindex writing into executables
11831 @cindex writing into corefiles
11833 By default, @value{GDBN} opens the file containing your program's
11834 executable code (or the corefile) read-only. This prevents accidental
11835 alterations to machine code; but it also prevents you from intentionally
11836 patching your program's binary.
11838 If you'd like to be able to patch the binary, you can specify that
11839 explicitly with the @code{set write} command. For example, you might
11840 want to turn on internal debugging flags, or even to make emergency
11846 @itemx set write off
11847 If you specify @samp{set write on}, @value{GDBN} opens executable and
11848 core files for both reading and writing; if you specify @samp{set write
11849 off} (the default), @value{GDBN} opens them read-only.
11851 If you have already loaded a file, you must load it again (using the
11852 @code{exec-file} or @code{core-file} command) after changing @code{set
11853 write}, for your new setting to take effect.
11857 Display whether executable files and core files are opened for writing
11858 as well as reading.
11862 @chapter @value{GDBN} Files
11864 @value{GDBN} needs to know the file name of the program to be debugged,
11865 both in order to read its symbol table and in order to start your
11866 program. To debug a core dump of a previous run, you must also tell
11867 @value{GDBN} the name of the core dump file.
11870 * Files:: Commands to specify files
11871 * Separate Debug Files:: Debugging information in separate files
11872 * Symbol Errors:: Errors reading symbol files
11876 @section Commands to Specify Files
11878 @cindex symbol table
11879 @cindex core dump file
11881 You may want to specify executable and core dump file names. The usual
11882 way to do this is at start-up time, using the arguments to
11883 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11884 Out of @value{GDBN}}).
11886 Occasionally it is necessary to change to a different file during a
11887 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11888 specify a file you want to use. Or you are debugging a remote target
11889 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11890 Program}). In these situations the @value{GDBN} commands to specify
11891 new files are useful.
11894 @cindex executable file
11896 @item file @var{filename}
11897 Use @var{filename} as the program to be debugged. It is read for its
11898 symbols and for the contents of pure memory. It is also the program
11899 executed when you use the @code{run} command. If you do not specify a
11900 directory and the file is not found in the @value{GDBN} working directory,
11901 @value{GDBN} uses the environment variable @code{PATH} as a list of
11902 directories to search, just as the shell does when looking for a program
11903 to run. You can change the value of this variable, for both @value{GDBN}
11904 and your program, using the @code{path} command.
11906 @cindex unlinked object files
11907 @cindex patching object files
11908 You can load unlinked object @file{.o} files into @value{GDBN} using
11909 the @code{file} command. You will not be able to ``run'' an object
11910 file, but you can disassemble functions and inspect variables. Also,
11911 if the underlying BFD functionality supports it, you could use
11912 @kbd{gdb -write} to patch object files using this technique. Note
11913 that @value{GDBN} can neither interpret nor modify relocations in this
11914 case, so branches and some initialized variables will appear to go to
11915 the wrong place. But this feature is still handy from time to time.
11918 @code{file} with no argument makes @value{GDBN} discard any information it
11919 has on both executable file and the symbol table.
11922 @item exec-file @r{[} @var{filename} @r{]}
11923 Specify that the program to be run (but not the symbol table) is found
11924 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11925 if necessary to locate your program. Omitting @var{filename} means to
11926 discard information on the executable file.
11928 @kindex symbol-file
11929 @item symbol-file @r{[} @var{filename} @r{]}
11930 Read symbol table information from file @var{filename}. @code{PATH} is
11931 searched when necessary. Use the @code{file} command to get both symbol
11932 table and program to run from the same file.
11934 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11935 program's symbol table.
11937 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11938 some breakpoints and auto-display expressions. This is because they may
11939 contain pointers to the internal data recording symbols and data types,
11940 which are part of the old symbol table data being discarded inside
11943 @code{symbol-file} does not repeat if you press @key{RET} again after
11946 When @value{GDBN} is configured for a particular environment, it
11947 understands debugging information in whatever format is the standard
11948 generated for that environment; you may use either a @sc{gnu} compiler, or
11949 other compilers that adhere to the local conventions.
11950 Best results are usually obtained from @sc{gnu} compilers; for example,
11951 using @code{@value{NGCC}} you can generate debugging information for
11954 For most kinds of object files, with the exception of old SVR3 systems
11955 using COFF, the @code{symbol-file} command does not normally read the
11956 symbol table in full right away. Instead, it scans the symbol table
11957 quickly to find which source files and which symbols are present. The
11958 details are read later, one source file at a time, as they are needed.
11960 The purpose of this two-stage reading strategy is to make @value{GDBN}
11961 start up faster. For the most part, it is invisible except for
11962 occasional pauses while the symbol table details for a particular source
11963 file are being read. (The @code{set verbose} command can turn these
11964 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11965 Warnings and Messages}.)
11967 We have not implemented the two-stage strategy for COFF yet. When the
11968 symbol table is stored in COFF format, @code{symbol-file} reads the
11969 symbol table data in full right away. Note that ``stabs-in-COFF''
11970 still does the two-stage strategy, since the debug info is actually
11974 @cindex reading symbols immediately
11975 @cindex symbols, reading immediately
11976 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11977 @itemx file @var{filename} @r{[} -readnow @r{]}
11978 You can override the @value{GDBN} two-stage strategy for reading symbol
11979 tables by using the @samp{-readnow} option with any of the commands that
11980 load symbol table information, if you want to be sure @value{GDBN} has the
11981 entire symbol table available.
11983 @c FIXME: for now no mention of directories, since this seems to be in
11984 @c flux. 13mar1992 status is that in theory GDB would look either in
11985 @c current dir or in same dir as myprog; but issues like competing
11986 @c GDB's, or clutter in system dirs, mean that in practice right now
11987 @c only current dir is used. FFish says maybe a special GDB hierarchy
11988 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11992 @item core-file @r{[}@var{filename}@r{]}
11994 Specify the whereabouts of a core dump file to be used as the ``contents
11995 of memory''. Traditionally, core files contain only some parts of the
11996 address space of the process that generated them; @value{GDBN} can access the
11997 executable file itself for other parts.
11999 @code{core-file} with no argument specifies that no core file is
12002 Note that the core file is ignored when your program is actually running
12003 under @value{GDBN}. So, if you have been running your program and you
12004 wish to debug a core file instead, you must kill the subprocess in which
12005 the program is running. To do this, use the @code{kill} command
12006 (@pxref{Kill Process, ,Killing the Child Process}).
12008 @kindex add-symbol-file
12009 @cindex dynamic linking
12010 @item add-symbol-file @var{filename} @var{address}
12011 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12012 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12013 The @code{add-symbol-file} command reads additional symbol table
12014 information from the file @var{filename}. You would use this command
12015 when @var{filename} has been dynamically loaded (by some other means)
12016 into the program that is running. @var{address} should be the memory
12017 address at which the file has been loaded; @value{GDBN} cannot figure
12018 this out for itself. You can additionally specify an arbitrary number
12019 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12020 section name and base address for that section. You can specify any
12021 @var{address} as an expression.
12023 The symbol table of the file @var{filename} is added to the symbol table
12024 originally read with the @code{symbol-file} command. You can use the
12025 @code{add-symbol-file} command any number of times; the new symbol data
12026 thus read keeps adding to the old. To discard all old symbol data
12027 instead, use the @code{symbol-file} command without any arguments.
12029 @cindex relocatable object files, reading symbols from
12030 @cindex object files, relocatable, reading symbols from
12031 @cindex reading symbols from relocatable object files
12032 @cindex symbols, reading from relocatable object files
12033 @cindex @file{.o} files, reading symbols from
12034 Although @var{filename} is typically a shared library file, an
12035 executable file, or some other object file which has been fully
12036 relocated for loading into a process, you can also load symbolic
12037 information from relocatable @file{.o} files, as long as:
12041 the file's symbolic information refers only to linker symbols defined in
12042 that file, not to symbols defined by other object files,
12044 every section the file's symbolic information refers to has actually
12045 been loaded into the inferior, as it appears in the file, and
12047 you can determine the address at which every section was loaded, and
12048 provide these to the @code{add-symbol-file} command.
12052 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12053 relocatable files into an already running program; such systems
12054 typically make the requirements above easy to meet. However, it's
12055 important to recognize that many native systems use complex link
12056 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12057 assembly, for example) that make the requirements difficult to meet. In
12058 general, one cannot assume that using @code{add-symbol-file} to read a
12059 relocatable object file's symbolic information will have the same effect
12060 as linking the relocatable object file into the program in the normal
12063 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12065 @kindex add-symbol-file-from-memory
12066 @cindex @code{syscall DSO}
12067 @cindex load symbols from memory
12068 @item add-symbol-file-from-memory @var{address}
12069 Load symbols from the given @var{address} in a dynamically loaded
12070 object file whose image is mapped directly into the inferior's memory.
12071 For example, the Linux kernel maps a @code{syscall DSO} into each
12072 process's address space; this DSO provides kernel-specific code for
12073 some system calls. The argument can be any expression whose
12074 evaluation yields the address of the file's shared object file header.
12075 For this command to work, you must have used @code{symbol-file} or
12076 @code{exec-file} commands in advance.
12078 @kindex add-shared-symbol-files
12080 @item add-shared-symbol-files @var{library-file}
12081 @itemx assf @var{library-file}
12082 The @code{add-shared-symbol-files} command can currently be used only
12083 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12084 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12085 @value{GDBN} automatically looks for shared libraries, however if
12086 @value{GDBN} does not find yours, you can invoke
12087 @code{add-shared-symbol-files}. It takes one argument: the shared
12088 library's file name. @code{assf} is a shorthand alias for
12089 @code{add-shared-symbol-files}.
12092 @item section @var{section} @var{addr}
12093 The @code{section} command changes the base address of the named
12094 @var{section} of the exec file to @var{addr}. This can be used if the
12095 exec file does not contain section addresses, (such as in the
12096 @code{a.out} format), or when the addresses specified in the file
12097 itself are wrong. Each section must be changed separately. The
12098 @code{info files} command, described below, lists all the sections and
12102 @kindex info target
12105 @code{info files} and @code{info target} are synonymous; both print the
12106 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12107 including the names of the executable and core dump files currently in
12108 use by @value{GDBN}, and the files from which symbols were loaded. The
12109 command @code{help target} lists all possible targets rather than
12112 @kindex maint info sections
12113 @item maint info sections
12114 Another command that can give you extra information about program sections
12115 is @code{maint info sections}. In addition to the section information
12116 displayed by @code{info files}, this command displays the flags and file
12117 offset of each section in the executable and core dump files. In addition,
12118 @code{maint info sections} provides the following command options (which
12119 may be arbitrarily combined):
12123 Display sections for all loaded object files, including shared libraries.
12124 @item @var{sections}
12125 Display info only for named @var{sections}.
12126 @item @var{section-flags}
12127 Display info only for sections for which @var{section-flags} are true.
12128 The section flags that @value{GDBN} currently knows about are:
12131 Section will have space allocated in the process when loaded.
12132 Set for all sections except those containing debug information.
12134 Section will be loaded from the file into the child process memory.
12135 Set for pre-initialized code and data, clear for @code{.bss} sections.
12137 Section needs to be relocated before loading.
12139 Section cannot be modified by the child process.
12141 Section contains executable code only.
12143 Section contains data only (no executable code).
12145 Section will reside in ROM.
12147 Section contains data for constructor/destructor lists.
12149 Section is not empty.
12151 An instruction to the linker to not output the section.
12152 @item COFF_SHARED_LIBRARY
12153 A notification to the linker that the section contains
12154 COFF shared library information.
12156 Section contains common symbols.
12159 @kindex set trust-readonly-sections
12160 @cindex read-only sections
12161 @item set trust-readonly-sections on
12162 Tell @value{GDBN} that readonly sections in your object file
12163 really are read-only (i.e.@: that their contents will not change).
12164 In that case, @value{GDBN} can fetch values from these sections
12165 out of the object file, rather than from the target program.
12166 For some targets (notably embedded ones), this can be a significant
12167 enhancement to debugging performance.
12169 The default is off.
12171 @item set trust-readonly-sections off
12172 Tell @value{GDBN} not to trust readonly sections. This means that
12173 the contents of the section might change while the program is running,
12174 and must therefore be fetched from the target when needed.
12176 @item show trust-readonly-sections
12177 Show the current setting of trusting readonly sections.
12180 All file-specifying commands allow both absolute and relative file names
12181 as arguments. @value{GDBN} always converts the file name to an absolute file
12182 name and remembers it that way.
12184 @cindex shared libraries
12185 @anchor{Shared Libraries}
12186 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12187 and IBM RS/6000 AIX shared libraries.
12189 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12190 shared libraries. @xref{Expat}.
12192 @value{GDBN} automatically loads symbol definitions from shared libraries
12193 when you use the @code{run} command, or when you examine a core file.
12194 (Before you issue the @code{run} command, @value{GDBN} does not understand
12195 references to a function in a shared library, however---unless you are
12196 debugging a core file).
12198 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12199 automatically loads the symbols at the time of the @code{shl_load} call.
12201 @c FIXME: some @value{GDBN} release may permit some refs to undef
12202 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12203 @c FIXME...lib; check this from time to time when updating manual
12205 There are times, however, when you may wish to not automatically load
12206 symbol definitions from shared libraries, such as when they are
12207 particularly large or there are many of them.
12209 To control the automatic loading of shared library symbols, use the
12213 @kindex set auto-solib-add
12214 @item set auto-solib-add @var{mode}
12215 If @var{mode} is @code{on}, symbols from all shared object libraries
12216 will be loaded automatically when the inferior begins execution, you
12217 attach to an independently started inferior, or when the dynamic linker
12218 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12219 is @code{off}, symbols must be loaded manually, using the
12220 @code{sharedlibrary} command. The default value is @code{on}.
12222 @cindex memory used for symbol tables
12223 If your program uses lots of shared libraries with debug info that
12224 takes large amounts of memory, you can decrease the @value{GDBN}
12225 memory footprint by preventing it from automatically loading the
12226 symbols from shared libraries. To that end, type @kbd{set
12227 auto-solib-add off} before running the inferior, then load each
12228 library whose debug symbols you do need with @kbd{sharedlibrary
12229 @var{regexp}}, where @var{regexp} is a regular expression that matches
12230 the libraries whose symbols you want to be loaded.
12232 @kindex show auto-solib-add
12233 @item show auto-solib-add
12234 Display the current autoloading mode.
12237 @cindex load shared library
12238 To explicitly load shared library symbols, use the @code{sharedlibrary}
12242 @kindex info sharedlibrary
12245 @itemx info sharedlibrary
12246 Print the names of the shared libraries which are currently loaded.
12248 @kindex sharedlibrary
12250 @item sharedlibrary @var{regex}
12251 @itemx share @var{regex}
12252 Load shared object library symbols for files matching a
12253 Unix regular expression.
12254 As with files loaded automatically, it only loads shared libraries
12255 required by your program for a core file or after typing @code{run}. If
12256 @var{regex} is omitted all shared libraries required by your program are
12259 @item nosharedlibrary
12260 @kindex nosharedlibrary
12261 @cindex unload symbols from shared libraries
12262 Unload all shared object library symbols. This discards all symbols
12263 that have been loaded from all shared libraries. Symbols from shared
12264 libraries that were loaded by explicit user requests are not
12268 Sometimes you may wish that @value{GDBN} stops and gives you control
12269 when any of shared library events happen. Use the @code{set
12270 stop-on-solib-events} command for this:
12273 @item set stop-on-solib-events
12274 @kindex set stop-on-solib-events
12275 This command controls whether @value{GDBN} should give you control
12276 when the dynamic linker notifies it about some shared library event.
12277 The most common event of interest is loading or unloading of a new
12280 @item show stop-on-solib-events
12281 @kindex show stop-on-solib-events
12282 Show whether @value{GDBN} stops and gives you control when shared
12283 library events happen.
12286 Shared libraries are also supported in many cross or remote debugging
12287 configurations. A copy of the target's libraries need to be present on the
12288 host system; they need to be the same as the target libraries, although the
12289 copies on the target can be stripped as long as the copies on the host are
12292 @cindex where to look for shared libraries
12293 For remote debugging, you need to tell @value{GDBN} where the target
12294 libraries are, so that it can load the correct copies---otherwise, it
12295 may try to load the host's libraries. @value{GDBN} has two variables
12296 to specify the search directories for target libraries.
12299 @cindex prefix for shared library file names
12300 @cindex system root, alternate
12301 @kindex set solib-absolute-prefix
12302 @kindex set sysroot
12303 @item set sysroot @var{path}
12304 Use @var{path} as the system root for the program being debugged. Any
12305 absolute shared library paths will be prefixed with @var{path}; many
12306 runtime loaders store the absolute paths to the shared library in the
12307 target program's memory. If you use @code{set sysroot} to find shared
12308 libraries, they need to be laid out in the same way that they are on
12309 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12312 The @code{set solib-absolute-prefix} command is an alias for @code{set
12315 @cindex default system root
12316 @cindex @samp{--with-sysroot}
12317 You can set the default system root by using the configure-time
12318 @samp{--with-sysroot} option. If the system root is inside
12319 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12320 @samp{--exec-prefix}), then the default system root will be updated
12321 automatically if the installed @value{GDBN} is moved to a new
12324 @kindex show sysroot
12326 Display the current shared library prefix.
12328 @kindex set solib-search-path
12329 @item set solib-search-path @var{path}
12330 If this variable is set, @var{path} is a colon-separated list of
12331 directories to search for shared libraries. @samp{solib-search-path}
12332 is used after @samp{sysroot} fails to locate the library, or if the
12333 path to the library is relative instead of absolute. If you want to
12334 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12335 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12336 finding your host's libraries. @samp{sysroot} is preferred; setting
12337 it to a nonexistent directory may interfere with automatic loading
12338 of shared library symbols.
12340 @kindex show solib-search-path
12341 @item show solib-search-path
12342 Display the current shared library search path.
12346 @node Separate Debug Files
12347 @section Debugging Information in Separate Files
12348 @cindex separate debugging information files
12349 @cindex debugging information in separate files
12350 @cindex @file{.debug} subdirectories
12351 @cindex debugging information directory, global
12352 @cindex global debugging information directory
12353 @cindex build ID, and separate debugging files
12354 @cindex @file{.build-id} directory
12356 @value{GDBN} allows you to put a program's debugging information in a
12357 file separate from the executable itself, in a way that allows
12358 @value{GDBN} to find and load the debugging information automatically.
12359 Since debugging information can be very large---sometimes larger
12360 than the executable code itself---some systems distribute debugging
12361 information for their executables in separate files, which users can
12362 install only when they need to debug a problem.
12364 @value{GDBN} supports two ways of specifying the separate debug info
12369 The executable contains a @dfn{debug link} that specifies the name of
12370 the separate debug info file. The separate debug file's name is
12371 usually @file{@var{executable}.debug}, where @var{executable} is the
12372 name of the corresponding executable file without leading directories
12373 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12374 debug link specifies a CRC32 checksum for the debug file, which
12375 @value{GDBN} uses to validate that the executable and the debug file
12376 came from the same build.
12379 The executable contains a @dfn{build ID}, a unique bit string that is
12380 also present in the corresponding debug info file. (This is supported
12381 only on some operating systems, notably those which use the ELF format
12382 for binary files and the @sc{gnu} Binutils.) For more details about
12383 this feature, see the description of the @option{--build-id}
12384 command-line option in @ref{Options, , Command Line Options, ld.info,
12385 The GNU Linker}. The debug info file's name is not specified
12386 explicitly by the build ID, but can be computed from the build ID, see
12390 Depending on the way the debug info file is specified, @value{GDBN}
12391 uses two different methods of looking for the debug file:
12395 For the ``debug link'' method, @value{GDBN} looks up the named file in
12396 the directory of the executable file, then in a subdirectory of that
12397 directory named @file{.debug}, and finally under the global debug
12398 directory, in a subdirectory whose name is identical to the leading
12399 directories of the executable's absolute file name.
12402 For the ``build ID'' method, @value{GDBN} looks in the
12403 @file{.build-id} subdirectory of the global debug directory for a file
12404 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12405 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12406 are the rest of the bit string. (Real build ID strings are 32 or more
12407 hex characters, not 10.)
12410 So, for example, suppose you ask @value{GDBN} to debug
12411 @file{/usr/bin/ls}, which has a debug link that specifies the
12412 file @file{ls.debug}, and a build ID whose value in hex is
12413 @code{abcdef1234}. If the global debug directory is
12414 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12415 debug information files, in the indicated order:
12419 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12421 @file{/usr/bin/ls.debug}
12423 @file{/usr/bin/.debug/ls.debug}
12425 @file{/usr/lib/debug/usr/bin/ls.debug}.
12428 You can set the global debugging info directory's name, and view the
12429 name @value{GDBN} is currently using.
12433 @kindex set debug-file-directory
12434 @item set debug-file-directory @var{directory}
12435 Set the directory which @value{GDBN} searches for separate debugging
12436 information files to @var{directory}.
12438 @kindex show debug-file-directory
12439 @item show debug-file-directory
12440 Show the directory @value{GDBN} searches for separate debugging
12445 @cindex @code{.gnu_debuglink} sections
12446 @cindex debug link sections
12447 A debug link is a special section of the executable file named
12448 @code{.gnu_debuglink}. The section must contain:
12452 A filename, with any leading directory components removed, followed by
12455 zero to three bytes of padding, as needed to reach the next four-byte
12456 boundary within the section, and
12458 a four-byte CRC checksum, stored in the same endianness used for the
12459 executable file itself. The checksum is computed on the debugging
12460 information file's full contents by the function given below, passing
12461 zero as the @var{crc} argument.
12464 Any executable file format can carry a debug link, as long as it can
12465 contain a section named @code{.gnu_debuglink} with the contents
12468 @cindex @code{.note.gnu.build-id} sections
12469 @cindex build ID sections
12470 The build ID is a special section in the executable file (and in other
12471 ELF binary files that @value{GDBN} may consider). This section is
12472 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12473 It contains unique identification for the built files---the ID remains
12474 the same across multiple builds of the same build tree. The default
12475 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12476 content for the build ID string. The same section with an identical
12477 value is present in the original built binary with symbols, in its
12478 stripped variant, and in the separate debugging information file.
12480 The debugging information file itself should be an ordinary
12481 executable, containing a full set of linker symbols, sections, and
12482 debugging information. The sections of the debugging information file
12483 should have the same names, addresses, and sizes as the original file,
12484 but they need not contain any data---much like a @code{.bss} section
12485 in an ordinary executable.
12487 The @sc{gnu} binary utilities (Binutils) package includes the
12488 @samp{objcopy} utility that can produce
12489 the separated executable / debugging information file pairs using the
12490 following commands:
12493 @kbd{objcopy --only-keep-debug foo foo.debug}
12498 These commands remove the debugging
12499 information from the executable file @file{foo} and place it in the file
12500 @file{foo.debug}. You can use the first, second or both methods to link the
12505 The debug link method needs the following additional command to also leave
12506 behind a debug link in @file{foo}:
12509 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12512 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12513 a version of the @code{strip} command such that the command @kbd{strip foo -f
12514 foo.debug} has the same functionality as the two @code{objcopy} commands and
12515 the @code{ln -s} command above, together.
12518 Build ID gets embedded into the main executable using @code{ld --build-id} or
12519 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12520 compatibility fixes for debug files separation are present in @sc{gnu} binary
12521 utilities (Binutils) package since version 2.18.
12526 Since there are many different ways to compute CRC's for the debug
12527 link (different polynomials, reversals, byte ordering, etc.), the
12528 simplest way to describe the CRC used in @code{.gnu_debuglink}
12529 sections is to give the complete code for a function that computes it:
12531 @kindex gnu_debuglink_crc32
12534 gnu_debuglink_crc32 (unsigned long crc,
12535 unsigned char *buf, size_t len)
12537 static const unsigned long crc32_table[256] =
12539 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12540 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12541 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12542 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12543 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12544 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12545 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12546 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12547 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12548 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12549 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12550 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12551 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12552 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12553 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12554 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12555 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12556 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12557 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12558 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12559 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12560 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12561 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12562 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12563 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12564 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12565 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12566 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12567 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12568 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12569 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12570 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12571 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12572 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12573 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12574 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12575 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12576 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12577 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12578 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12579 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12580 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12581 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12582 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12583 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12584 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12585 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12586 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12587 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12588 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12589 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12592 unsigned char *end;
12594 crc = ~crc & 0xffffffff;
12595 for (end = buf + len; buf < end; ++buf)
12596 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12597 return ~crc & 0xffffffff;
12602 This computation does not apply to the ``build ID'' method.
12605 @node Symbol Errors
12606 @section Errors Reading Symbol Files
12608 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12609 such as symbol types it does not recognize, or known bugs in compiler
12610 output. By default, @value{GDBN} does not notify you of such problems, since
12611 they are relatively common and primarily of interest to people
12612 debugging compilers. If you are interested in seeing information
12613 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12614 only one message about each such type of problem, no matter how many
12615 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12616 to see how many times the problems occur, with the @code{set
12617 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12620 The messages currently printed, and their meanings, include:
12623 @item inner block not inside outer block in @var{symbol}
12625 The symbol information shows where symbol scopes begin and end
12626 (such as at the start of a function or a block of statements). This
12627 error indicates that an inner scope block is not fully contained
12628 in its outer scope blocks.
12630 @value{GDBN} circumvents the problem by treating the inner block as if it had
12631 the same scope as the outer block. In the error message, @var{symbol}
12632 may be shown as ``@code{(don't know)}'' if the outer block is not a
12635 @item block at @var{address} out of order
12637 The symbol information for symbol scope blocks should occur in
12638 order of increasing addresses. This error indicates that it does not
12641 @value{GDBN} does not circumvent this problem, and has trouble
12642 locating symbols in the source file whose symbols it is reading. (You
12643 can often determine what source file is affected by specifying
12644 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12647 @item bad block start address patched
12649 The symbol information for a symbol scope block has a start address
12650 smaller than the address of the preceding source line. This is known
12651 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12653 @value{GDBN} circumvents the problem by treating the symbol scope block as
12654 starting on the previous source line.
12656 @item bad string table offset in symbol @var{n}
12659 Symbol number @var{n} contains a pointer into the string table which is
12660 larger than the size of the string table.
12662 @value{GDBN} circumvents the problem by considering the symbol to have the
12663 name @code{foo}, which may cause other problems if many symbols end up
12666 @item unknown symbol type @code{0x@var{nn}}
12668 The symbol information contains new data types that @value{GDBN} does
12669 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12670 uncomprehended information, in hexadecimal.
12672 @value{GDBN} circumvents the error by ignoring this symbol information.
12673 This usually allows you to debug your program, though certain symbols
12674 are not accessible. If you encounter such a problem and feel like
12675 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12676 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12677 and examine @code{*bufp} to see the symbol.
12679 @item stub type has NULL name
12681 @value{GDBN} could not find the full definition for a struct or class.
12683 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12684 The symbol information for a C@t{++} member function is missing some
12685 information that recent versions of the compiler should have output for
12688 @item info mismatch between compiler and debugger
12690 @value{GDBN} could not parse a type specification output by the compiler.
12695 @chapter Specifying a Debugging Target
12697 @cindex debugging target
12698 A @dfn{target} is the execution environment occupied by your program.
12700 Often, @value{GDBN} runs in the same host environment as your program;
12701 in that case, the debugging target is specified as a side effect when
12702 you use the @code{file} or @code{core} commands. When you need more
12703 flexibility---for example, running @value{GDBN} on a physically separate
12704 host, or controlling a standalone system over a serial port or a
12705 realtime system over a TCP/IP connection---you can use the @code{target}
12706 command to specify one of the target types configured for @value{GDBN}
12707 (@pxref{Target Commands, ,Commands for Managing Targets}).
12709 @cindex target architecture
12710 It is possible to build @value{GDBN} for several different @dfn{target
12711 architectures}. When @value{GDBN} is built like that, you can choose
12712 one of the available architectures with the @kbd{set architecture}
12716 @kindex set architecture
12717 @kindex show architecture
12718 @item set architecture @var{arch}
12719 This command sets the current target architecture to @var{arch}. The
12720 value of @var{arch} can be @code{"auto"}, in addition to one of the
12721 supported architectures.
12723 @item show architecture
12724 Show the current target architecture.
12726 @item set processor
12728 @kindex set processor
12729 @kindex show processor
12730 These are alias commands for, respectively, @code{set architecture}
12731 and @code{show architecture}.
12735 * Active Targets:: Active targets
12736 * Target Commands:: Commands for managing targets
12737 * Byte Order:: Choosing target byte order
12740 @node Active Targets
12741 @section Active Targets
12743 @cindex stacking targets
12744 @cindex active targets
12745 @cindex multiple targets
12747 There are three classes of targets: processes, core files, and
12748 executable files. @value{GDBN} can work concurrently on up to three
12749 active targets, one in each class. This allows you to (for example)
12750 start a process and inspect its activity without abandoning your work on
12753 For example, if you execute @samp{gdb a.out}, then the executable file
12754 @code{a.out} is the only active target. If you designate a core file as
12755 well---presumably from a prior run that crashed and coredumped---then
12756 @value{GDBN} has two active targets and uses them in tandem, looking
12757 first in the corefile target, then in the executable file, to satisfy
12758 requests for memory addresses. (Typically, these two classes of target
12759 are complementary, since core files contain only a program's
12760 read-write memory---variables and so on---plus machine status, while
12761 executable files contain only the program text and initialized data.)
12763 When you type @code{run}, your executable file becomes an active process
12764 target as well. When a process target is active, all @value{GDBN}
12765 commands requesting memory addresses refer to that target; addresses in
12766 an active core file or executable file target are obscured while the
12767 process target is active.
12769 Use the @code{core-file} and @code{exec-file} commands to select a new
12770 core file or executable target (@pxref{Files, ,Commands to Specify
12771 Files}). To specify as a target a process that is already running, use
12772 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12775 @node Target Commands
12776 @section Commands for Managing Targets
12779 @item target @var{type} @var{parameters}
12780 Connects the @value{GDBN} host environment to a target machine or
12781 process. A target is typically a protocol for talking to debugging
12782 facilities. You use the argument @var{type} to specify the type or
12783 protocol of the target machine.
12785 Further @var{parameters} are interpreted by the target protocol, but
12786 typically include things like device names or host names to connect
12787 with, process numbers, and baud rates.
12789 The @code{target} command does not repeat if you press @key{RET} again
12790 after executing the command.
12792 @kindex help target
12794 Displays the names of all targets available. To display targets
12795 currently selected, use either @code{info target} or @code{info files}
12796 (@pxref{Files, ,Commands to Specify Files}).
12798 @item help target @var{name}
12799 Describe a particular target, including any parameters necessary to
12802 @kindex set gnutarget
12803 @item set gnutarget @var{args}
12804 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12805 knows whether it is reading an @dfn{executable},
12806 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12807 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12808 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12811 @emph{Warning:} To specify a file format with @code{set gnutarget},
12812 you must know the actual BFD name.
12816 @xref{Files, , Commands to Specify Files}.
12818 @kindex show gnutarget
12819 @item show gnutarget
12820 Use the @code{show gnutarget} command to display what file format
12821 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12822 @value{GDBN} will determine the file format for each file automatically,
12823 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12826 @cindex common targets
12827 Here are some common targets (available, or not, depending on the GDB
12832 @item target exec @var{program}
12833 @cindex executable file target
12834 An executable file. @samp{target exec @var{program}} is the same as
12835 @samp{exec-file @var{program}}.
12837 @item target core @var{filename}
12838 @cindex core dump file target
12839 A core dump file. @samp{target core @var{filename}} is the same as
12840 @samp{core-file @var{filename}}.
12842 @item target remote @var{medium}
12843 @cindex remote target
12844 A remote system connected to @value{GDBN} via a serial line or network
12845 connection. This command tells @value{GDBN} to use its own remote
12846 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12848 For example, if you have a board connected to @file{/dev/ttya} on the
12849 machine running @value{GDBN}, you could say:
12852 target remote /dev/ttya
12855 @code{target remote} supports the @code{load} command. This is only
12856 useful if you have some other way of getting the stub to the target
12857 system, and you can put it somewhere in memory where it won't get
12858 clobbered by the download.
12861 @cindex built-in simulator target
12862 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12870 works; however, you cannot assume that a specific memory map, device
12871 drivers, or even basic I/O is available, although some simulators do
12872 provide these. For info about any processor-specific simulator details,
12873 see the appropriate section in @ref{Embedded Processors, ,Embedded
12878 Some configurations may include these targets as well:
12882 @item target nrom @var{dev}
12883 @cindex NetROM ROM emulator target
12884 NetROM ROM emulator. This target only supports downloading.
12888 Different targets are available on different configurations of @value{GDBN};
12889 your configuration may have more or fewer targets.
12891 Many remote targets require you to download the executable's code once
12892 you've successfully established a connection. You may wish to control
12893 various aspects of this process.
12898 @kindex set hash@r{, for remote monitors}
12899 @cindex hash mark while downloading
12900 This command controls whether a hash mark @samp{#} is displayed while
12901 downloading a file to the remote monitor. If on, a hash mark is
12902 displayed after each S-record is successfully downloaded to the
12906 @kindex show hash@r{, for remote monitors}
12907 Show the current status of displaying the hash mark.
12909 @item set debug monitor
12910 @kindex set debug monitor
12911 @cindex display remote monitor communications
12912 Enable or disable display of communications messages between
12913 @value{GDBN} and the remote monitor.
12915 @item show debug monitor
12916 @kindex show debug monitor
12917 Show the current status of displaying communications between
12918 @value{GDBN} and the remote monitor.
12923 @kindex load @var{filename}
12924 @item load @var{filename}
12926 Depending on what remote debugging facilities are configured into
12927 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12928 is meant to make @var{filename} (an executable) available for debugging
12929 on the remote system---by downloading, or dynamic linking, for example.
12930 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12931 the @code{add-symbol-file} command.
12933 If your @value{GDBN} does not have a @code{load} command, attempting to
12934 execute it gets the error message ``@code{You can't do that when your
12935 target is @dots{}}''
12937 The file is loaded at whatever address is specified in the executable.
12938 For some object file formats, you can specify the load address when you
12939 link the program; for other formats, like a.out, the object file format
12940 specifies a fixed address.
12941 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12943 Depending on the remote side capabilities, @value{GDBN} may be able to
12944 load programs into flash memory.
12946 @code{load} does not repeat if you press @key{RET} again after using it.
12950 @section Choosing Target Byte Order
12952 @cindex choosing target byte order
12953 @cindex target byte order
12955 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12956 offer the ability to run either big-endian or little-endian byte
12957 orders. Usually the executable or symbol will include a bit to
12958 designate the endian-ness, and you will not need to worry about
12959 which to use. However, you may still find it useful to adjust
12960 @value{GDBN}'s idea of processor endian-ness manually.
12964 @item set endian big
12965 Instruct @value{GDBN} to assume the target is big-endian.
12967 @item set endian little
12968 Instruct @value{GDBN} to assume the target is little-endian.
12970 @item set endian auto
12971 Instruct @value{GDBN} to use the byte order associated with the
12975 Display @value{GDBN}'s current idea of the target byte order.
12979 Note that these commands merely adjust interpretation of symbolic
12980 data on the host, and that they have absolutely no effect on the
12984 @node Remote Debugging
12985 @chapter Debugging Remote Programs
12986 @cindex remote debugging
12988 If you are trying to debug a program running on a machine that cannot run
12989 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12990 For example, you might use remote debugging on an operating system kernel,
12991 or on a small system which does not have a general purpose operating system
12992 powerful enough to run a full-featured debugger.
12994 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12995 to make this work with particular debugging targets. In addition,
12996 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12997 but not specific to any particular target system) which you can use if you
12998 write the remote stubs---the code that runs on the remote system to
12999 communicate with @value{GDBN}.
13001 Other remote targets may be available in your
13002 configuration of @value{GDBN}; use @code{help target} to list them.
13005 * Connecting:: Connecting to a remote target
13006 * File Transfer:: Sending files to a remote system
13007 * Server:: Using the gdbserver program
13008 * Remote Configuration:: Remote configuration
13009 * Remote Stub:: Implementing a remote stub
13013 @section Connecting to a Remote Target
13015 On the @value{GDBN} host machine, you will need an unstripped copy of
13016 your program, since @value{GDBN} needs symbol and debugging information.
13017 Start up @value{GDBN} as usual, using the name of the local copy of your
13018 program as the first argument.
13020 @cindex @code{target remote}
13021 @value{GDBN} can communicate with the target over a serial line, or
13022 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13023 each case, @value{GDBN} uses the same protocol for debugging your
13024 program; only the medium carrying the debugging packets varies. The
13025 @code{target remote} command establishes a connection to the target.
13026 Its arguments indicate which medium to use:
13030 @item target remote @var{serial-device}
13031 @cindex serial line, @code{target remote}
13032 Use @var{serial-device} to communicate with the target. For example,
13033 to use a serial line connected to the device named @file{/dev/ttyb}:
13036 target remote /dev/ttyb
13039 If you're using a serial line, you may want to give @value{GDBN} the
13040 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13041 (@pxref{Remote Configuration, set remotebaud}) before the
13042 @code{target} command.
13044 @item target remote @code{@var{host}:@var{port}}
13045 @itemx target remote @code{tcp:@var{host}:@var{port}}
13046 @cindex @acronym{TCP} port, @code{target remote}
13047 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13048 The @var{host} may be either a host name or a numeric @acronym{IP}
13049 address; @var{port} must be a decimal number. The @var{host} could be
13050 the target machine itself, if it is directly connected to the net, or
13051 it might be a terminal server which in turn has a serial line to the
13054 For example, to connect to port 2828 on a terminal server named
13058 target remote manyfarms:2828
13061 If your remote target is actually running on the same machine as your
13062 debugger session (e.g.@: a simulator for your target running on the
13063 same host), you can omit the hostname. For example, to connect to
13064 port 1234 on your local machine:
13067 target remote :1234
13071 Note that the colon is still required here.
13073 @item target remote @code{udp:@var{host}:@var{port}}
13074 @cindex @acronym{UDP} port, @code{target remote}
13075 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13076 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13079 target remote udp:manyfarms:2828
13082 When using a @acronym{UDP} connection for remote debugging, you should
13083 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13084 can silently drop packets on busy or unreliable networks, which will
13085 cause havoc with your debugging session.
13087 @item target remote | @var{command}
13088 @cindex pipe, @code{target remote} to
13089 Run @var{command} in the background and communicate with it using a
13090 pipe. The @var{command} is a shell command, to be parsed and expanded
13091 by the system's command shell, @code{/bin/sh}; it should expect remote
13092 protocol packets on its standard input, and send replies on its
13093 standard output. You could use this to run a stand-alone simulator
13094 that speaks the remote debugging protocol, to make net connections
13095 using programs like @code{ssh}, or for other similar tricks.
13097 If @var{command} closes its standard output (perhaps by exiting),
13098 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13099 program has already exited, this will have no effect.)
13103 Once the connection has been established, you can use all the usual
13104 commands to examine and change data. The remote program is already
13105 running; you can use @kbd{step} and @kbd{continue}, and you do not
13106 need to use @kbd{run}.
13108 @cindex interrupting remote programs
13109 @cindex remote programs, interrupting
13110 Whenever @value{GDBN} is waiting for the remote program, if you type the
13111 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13112 program. This may or may not succeed, depending in part on the hardware
13113 and the serial drivers the remote system uses. If you type the
13114 interrupt character once again, @value{GDBN} displays this prompt:
13117 Interrupted while waiting for the program.
13118 Give up (and stop debugging it)? (y or n)
13121 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13122 (If you decide you want to try again later, you can use @samp{target
13123 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13124 goes back to waiting.
13127 @kindex detach (remote)
13129 When you have finished debugging the remote program, you can use the
13130 @code{detach} command to release it from @value{GDBN} control.
13131 Detaching from the target normally resumes its execution, but the results
13132 will depend on your particular remote stub. After the @code{detach}
13133 command, @value{GDBN} is free to connect to another target.
13137 The @code{disconnect} command behaves like @code{detach}, except that
13138 the target is generally not resumed. It will wait for @value{GDBN}
13139 (this instance or another one) to connect and continue debugging. After
13140 the @code{disconnect} command, @value{GDBN} is again free to connect to
13143 @cindex send command to remote monitor
13144 @cindex extend @value{GDBN} for remote targets
13145 @cindex add new commands for external monitor
13147 @item monitor @var{cmd}
13148 This command allows you to send arbitrary commands directly to the
13149 remote monitor. Since @value{GDBN} doesn't care about the commands it
13150 sends like this, this command is the way to extend @value{GDBN}---you
13151 can add new commands that only the external monitor will understand
13155 @node File Transfer
13156 @section Sending files to a remote system
13157 @cindex remote target, file transfer
13158 @cindex file transfer
13159 @cindex sending files to remote systems
13161 Some remote targets offer the ability to transfer files over the same
13162 connection used to communicate with @value{GDBN}. This is convenient
13163 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13164 running @code{gdbserver} over a network interface. For other targets,
13165 e.g.@: embedded devices with only a single serial port, this may be
13166 the only way to upload or download files.
13168 Not all remote targets support these commands.
13172 @item remote put @var{hostfile} @var{targetfile}
13173 Copy file @var{hostfile} from the host system (the machine running
13174 @value{GDBN}) to @var{targetfile} on the target system.
13177 @item remote get @var{targetfile} @var{hostfile}
13178 Copy file @var{targetfile} from the target system to @var{hostfile}
13179 on the host system.
13181 @kindex remote delete
13182 @item remote delete @var{targetfile}
13183 Delete @var{targetfile} from the target system.
13188 @section Using the @code{gdbserver} Program
13191 @cindex remote connection without stubs
13192 @code{gdbserver} is a control program for Unix-like systems, which
13193 allows you to connect your program with a remote @value{GDBN} via
13194 @code{target remote}---but without linking in the usual debugging stub.
13196 @code{gdbserver} is not a complete replacement for the debugging stubs,
13197 because it requires essentially the same operating-system facilities
13198 that @value{GDBN} itself does. In fact, a system that can run
13199 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13200 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13201 because it is a much smaller program than @value{GDBN} itself. It is
13202 also easier to port than all of @value{GDBN}, so you may be able to get
13203 started more quickly on a new system by using @code{gdbserver}.
13204 Finally, if you develop code for real-time systems, you may find that
13205 the tradeoffs involved in real-time operation make it more convenient to
13206 do as much development work as possible on another system, for example
13207 by cross-compiling. You can use @code{gdbserver} to make a similar
13208 choice for debugging.
13210 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13211 or a TCP connection, using the standard @value{GDBN} remote serial
13215 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13216 Do not run @code{gdbserver} connected to any public network; a
13217 @value{GDBN} connection to @code{gdbserver} provides access to the
13218 target system with the same privileges as the user running
13222 @subsection Running @code{gdbserver}
13223 @cindex arguments, to @code{gdbserver}
13225 Run @code{gdbserver} on the target system. You need a copy of the
13226 program you want to debug, including any libraries it requires.
13227 @code{gdbserver} does not need your program's symbol table, so you can
13228 strip the program if necessary to save space. @value{GDBN} on the host
13229 system does all the symbol handling.
13231 To use the server, you must tell it how to communicate with @value{GDBN};
13232 the name of your program; and the arguments for your program. The usual
13236 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13239 @var{comm} is either a device name (to use a serial line) or a TCP
13240 hostname and portnumber. For example, to debug Emacs with the argument
13241 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13245 target> gdbserver /dev/com1 emacs foo.txt
13248 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13251 To use a TCP connection instead of a serial line:
13254 target> gdbserver host:2345 emacs foo.txt
13257 The only difference from the previous example is the first argument,
13258 specifying that you are communicating with the host @value{GDBN} via
13259 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13260 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13261 (Currently, the @samp{host} part is ignored.) You can choose any number
13262 you want for the port number as long as it does not conflict with any
13263 TCP ports already in use on the target system (for example, @code{23} is
13264 reserved for @code{telnet}).@footnote{If you choose a port number that
13265 conflicts with another service, @code{gdbserver} prints an error message
13266 and exits.} You must use the same port number with the host @value{GDBN}
13267 @code{target remote} command.
13269 @subsubsection Attaching to a Running Program
13271 On some targets, @code{gdbserver} can also attach to running programs.
13272 This is accomplished via the @code{--attach} argument. The syntax is:
13275 target> gdbserver --attach @var{comm} @var{pid}
13278 @var{pid} is the process ID of a currently running process. It isn't necessary
13279 to point @code{gdbserver} at a binary for the running process.
13282 @cindex attach to a program by name
13283 You can debug processes by name instead of process ID if your target has the
13284 @code{pidof} utility:
13287 target> gdbserver --attach @var{comm} `pidof @var{program}`
13290 In case more than one copy of @var{program} is running, or @var{program}
13291 has multiple threads, most versions of @code{pidof} support the
13292 @code{-s} option to only return the first process ID.
13294 @subsubsection Multi-Process Mode for @code{gdbserver}
13295 @cindex gdbserver, multiple processes
13296 @cindex multiple processes with gdbserver
13298 When you connect to @code{gdbserver} using @code{target remote},
13299 @code{gdbserver} debugs the specified program only once. When the
13300 program exits, or you detach from it, @value{GDBN} closes the connection
13301 and @code{gdbserver} exits.
13303 If you connect using @kbd{target extended-remote}, @code{gdbserver}
13304 enters multi-process mode. When the debugged program exits, or you
13305 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
13306 though no program is running. The @code{run} and @code{attach}
13307 commands instruct @code{gdbserver} to run or attach to a new program.
13308 The @code{run} command uses @code{set remote exec-file} (@pxref{set
13309 remote exec-file}) to select the program to run. Command line
13310 arguments are supported, except for wildcard expansion and I/O
13311 redirection (@pxref{Arguments}).
13313 To start @code{gdbserver} without supplying an initial command to run
13314 or process ID to attach, use the @option{--multi} command line option.
13315 Then you can connect using @kbd{target extended-remote} and start
13316 the program you want to debug.
13318 @code{gdbserver} does not automatically exit in multi-process mode.
13319 You can terminate it by using @code{monitor exit}
13320 (@pxref{Monitor Commands for gdbserver}).
13322 @subsubsection Other Command-Line Arguments for @code{gdbserver}
13324 You can include @option{--debug} on the @code{gdbserver} command line.
13325 @code{gdbserver} will display extra status information about the debugging
13326 process. This option is intended for @code{gdbserver} development and
13327 for bug reports to the developers.
13329 The @option{--wrapper} option specifies a wrapper to launch programs
13330 for debugging. The option should be followed by the name of the
13331 wrapper, then any command-line arguments to pass to the wrapper, then
13332 @kbd{--} indicating the end of the wrapper arguments.
13334 @code{gdbserver} runs the specified wrapper program with a combined
13335 command line including the wrapper arguments, then the name of the
13336 program to debug, then any arguments to the program. The wrapper
13337 runs until it executes your program, and then @value{GDBN} gains control.
13339 You can use any program that eventually calls @code{execve} with
13340 its arguments as a wrapper. Several standard Unix utilities do
13341 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
13342 with @code{exec "$@@"} will also work.
13344 For example, you can use @code{env} to pass an environment variable to
13345 the debugged program, without setting the variable in @code{gdbserver}'s
13349 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
13352 @subsection Connecting to @code{gdbserver}
13354 Run @value{GDBN} on the host system.
13356 First make sure you have the necessary symbol files. Load symbols for
13357 your application using the @code{file} command before you connect. Use
13358 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
13359 was compiled with the correct sysroot using @code{--with-sysroot}).
13361 The symbol file and target libraries must exactly match the executable
13362 and libraries on the target, with one exception: the files on the host
13363 system should not be stripped, even if the files on the target system
13364 are. Mismatched or missing files will lead to confusing results
13365 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
13366 files may also prevent @code{gdbserver} from debugging multi-threaded
13369 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
13370 For TCP connections, you must start up @code{gdbserver} prior to using
13371 the @code{target remote} command. Otherwise you may get an error whose
13372 text depends on the host system, but which usually looks something like
13373 @samp{Connection refused}. Don't use the @code{load}
13374 command in @value{GDBN} when using @code{gdbserver}, since the program is
13375 already on the target.
13377 @subsection Monitor Commands for @code{gdbserver}
13378 @cindex monitor commands, for @code{gdbserver}
13379 @anchor{Monitor Commands for gdbserver}
13381 During a @value{GDBN} session using @code{gdbserver}, you can use the
13382 @code{monitor} command to send special requests to @code{gdbserver}.
13383 Here are the available commands.
13387 List the available monitor commands.
13389 @item monitor set debug 0
13390 @itemx monitor set debug 1
13391 Disable or enable general debugging messages.
13393 @item monitor set remote-debug 0
13394 @itemx monitor set remote-debug 1
13395 Disable or enable specific debugging messages associated with the remote
13396 protocol (@pxref{Remote Protocol}).
13399 Tell gdbserver to exit immediately. This command should be followed by
13400 @code{disconnect} to close the debugging session. @code{gdbserver} will
13401 detach from any attached processes and kill any processes it created.
13402 Use @code{monitor exit} to terminate @code{gdbserver} at the end
13403 of a multi-process mode debug session.
13407 @node Remote Configuration
13408 @section Remote Configuration
13411 @kindex show remote
13412 This section documents the configuration options available when
13413 debugging remote programs. For the options related to the File I/O
13414 extensions of the remote protocol, see @ref{system,
13415 system-call-allowed}.
13418 @item set remoteaddresssize @var{bits}
13419 @cindex address size for remote targets
13420 @cindex bits in remote address
13421 Set the maximum size of address in a memory packet to the specified
13422 number of bits. @value{GDBN} will mask off the address bits above
13423 that number, when it passes addresses to the remote target. The
13424 default value is the number of bits in the target's address.
13426 @item show remoteaddresssize
13427 Show the current value of remote address size in bits.
13429 @item set remotebaud @var{n}
13430 @cindex baud rate for remote targets
13431 Set the baud rate for the remote serial I/O to @var{n} baud. The
13432 value is used to set the speed of the serial port used for debugging
13435 @item show remotebaud
13436 Show the current speed of the remote connection.
13438 @item set remotebreak
13439 @cindex interrupt remote programs
13440 @cindex BREAK signal instead of Ctrl-C
13441 @anchor{set remotebreak}
13442 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13443 when you type @kbd{Ctrl-c} to interrupt the program running
13444 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13445 character instead. The default is off, since most remote systems
13446 expect to see @samp{Ctrl-C} as the interrupt signal.
13448 @item show remotebreak
13449 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13450 interrupt the remote program.
13452 @item set remoteflow on
13453 @itemx set remoteflow off
13454 @kindex set remoteflow
13455 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13456 on the serial port used to communicate to the remote target.
13458 @item show remoteflow
13459 @kindex show remoteflow
13460 Show the current setting of hardware flow control.
13462 @item set remotelogbase @var{base}
13463 Set the base (a.k.a.@: radix) of logging serial protocol
13464 communications to @var{base}. Supported values of @var{base} are:
13465 @code{ascii}, @code{octal}, and @code{hex}. The default is
13468 @item show remotelogbase
13469 Show the current setting of the radix for logging remote serial
13472 @item set remotelogfile @var{file}
13473 @cindex record serial communications on file
13474 Record remote serial communications on the named @var{file}. The
13475 default is not to record at all.
13477 @item show remotelogfile.
13478 Show the current setting of the file name on which to record the
13479 serial communications.
13481 @item set remotetimeout @var{num}
13482 @cindex timeout for serial communications
13483 @cindex remote timeout
13484 Set the timeout limit to wait for the remote target to respond to
13485 @var{num} seconds. The default is 2 seconds.
13487 @item show remotetimeout
13488 Show the current number of seconds to wait for the remote target
13491 @cindex limit hardware breakpoints and watchpoints
13492 @cindex remote target, limit break- and watchpoints
13493 @anchor{set remote hardware-watchpoint-limit}
13494 @anchor{set remote hardware-breakpoint-limit}
13495 @item set remote hardware-watchpoint-limit @var{limit}
13496 @itemx set remote hardware-breakpoint-limit @var{limit}
13497 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13498 watchpoints. A limit of -1, the default, is treated as unlimited.
13500 @item set remote exec-file @var{filename}
13501 @itemx show remote exec-file
13502 @anchor{set remote exec-file}
13503 @cindex executable file, for remote target
13504 Select the file used for @code{run} with @code{target
13505 extended-remote}. This should be set to a filename valid on the
13506 target system. If it is not set, the target will use a default
13507 filename (e.g.@: the last program run).
13510 @cindex remote packets, enabling and disabling
13511 The @value{GDBN} remote protocol autodetects the packets supported by
13512 your debugging stub. If you need to override the autodetection, you
13513 can use these commands to enable or disable individual packets. Each
13514 packet can be set to @samp{on} (the remote target supports this
13515 packet), @samp{off} (the remote target does not support this packet),
13516 or @samp{auto} (detect remote target support for this packet). They
13517 all default to @samp{auto}. For more information about each packet,
13518 see @ref{Remote Protocol}.
13520 During normal use, you should not have to use any of these commands.
13521 If you do, that may be a bug in your remote debugging stub, or a bug
13522 in @value{GDBN}. You may want to report the problem to the
13523 @value{GDBN} developers.
13525 For each packet @var{name}, the command to enable or disable the
13526 packet is @code{set remote @var{name}-packet}. The available settings
13529 @multitable @columnfractions 0.28 0.32 0.25
13532 @tab Related Features
13534 @item @code{fetch-register}
13536 @tab @code{info registers}
13538 @item @code{set-register}
13542 @item @code{binary-download}
13544 @tab @code{load}, @code{set}
13546 @item @code{read-aux-vector}
13547 @tab @code{qXfer:auxv:read}
13548 @tab @code{info auxv}
13550 @item @code{symbol-lookup}
13551 @tab @code{qSymbol}
13552 @tab Detecting multiple threads
13554 @item @code{attach}
13555 @tab @code{vAttach}
13558 @item @code{verbose-resume}
13560 @tab Stepping or resuming multiple threads
13566 @item @code{software-breakpoint}
13570 @item @code{hardware-breakpoint}
13574 @item @code{write-watchpoint}
13578 @item @code{read-watchpoint}
13582 @item @code{access-watchpoint}
13586 @item @code{target-features}
13587 @tab @code{qXfer:features:read}
13588 @tab @code{set architecture}
13590 @item @code{library-info}
13591 @tab @code{qXfer:libraries:read}
13592 @tab @code{info sharedlibrary}
13594 @item @code{memory-map}
13595 @tab @code{qXfer:memory-map:read}
13596 @tab @code{info mem}
13598 @item @code{read-spu-object}
13599 @tab @code{qXfer:spu:read}
13600 @tab @code{info spu}
13602 @item @code{write-spu-object}
13603 @tab @code{qXfer:spu:write}
13604 @tab @code{info spu}
13606 @item @code{get-thread-local-@*storage-address}
13607 @tab @code{qGetTLSAddr}
13608 @tab Displaying @code{__thread} variables
13610 @item @code{search-memory}
13611 @tab @code{qSearch:memory}
13614 @item @code{supported-packets}
13615 @tab @code{qSupported}
13616 @tab Remote communications parameters
13618 @item @code{pass-signals}
13619 @tab @code{QPassSignals}
13620 @tab @code{handle @var{signal}}
13622 @item @code{hostio-close-packet}
13623 @tab @code{vFile:close}
13624 @tab @code{remote get}, @code{remote put}
13626 @item @code{hostio-open-packet}
13627 @tab @code{vFile:open}
13628 @tab @code{remote get}, @code{remote put}
13630 @item @code{hostio-pread-packet}
13631 @tab @code{vFile:pread}
13632 @tab @code{remote get}, @code{remote put}
13634 @item @code{hostio-pwrite-packet}
13635 @tab @code{vFile:pwrite}
13636 @tab @code{remote get}, @code{remote put}
13638 @item @code{hostio-unlink-packet}
13639 @tab @code{vFile:unlink}
13640 @tab @code{remote delete}
13644 @section Implementing a Remote Stub
13646 @cindex debugging stub, example
13647 @cindex remote stub, example
13648 @cindex stub example, remote debugging
13649 The stub files provided with @value{GDBN} implement the target side of the
13650 communication protocol, and the @value{GDBN} side is implemented in the
13651 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13652 these subroutines to communicate, and ignore the details. (If you're
13653 implementing your own stub file, you can still ignore the details: start
13654 with one of the existing stub files. @file{sparc-stub.c} is the best
13655 organized, and therefore the easiest to read.)
13657 @cindex remote serial debugging, overview
13658 To debug a program running on another machine (the debugging
13659 @dfn{target} machine), you must first arrange for all the usual
13660 prerequisites for the program to run by itself. For example, for a C
13665 A startup routine to set up the C runtime environment; these usually
13666 have a name like @file{crt0}. The startup routine may be supplied by
13667 your hardware supplier, or you may have to write your own.
13670 A C subroutine library to support your program's
13671 subroutine calls, notably managing input and output.
13674 A way of getting your program to the other machine---for example, a
13675 download program. These are often supplied by the hardware
13676 manufacturer, but you may have to write your own from hardware
13680 The next step is to arrange for your program to use a serial port to
13681 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13682 machine). In general terms, the scheme looks like this:
13686 @value{GDBN} already understands how to use this protocol; when everything
13687 else is set up, you can simply use the @samp{target remote} command
13688 (@pxref{Targets,,Specifying a Debugging Target}).
13690 @item On the target,
13691 you must link with your program a few special-purpose subroutines that
13692 implement the @value{GDBN} remote serial protocol. The file containing these
13693 subroutines is called a @dfn{debugging stub}.
13695 On certain remote targets, you can use an auxiliary program
13696 @code{gdbserver} instead of linking a stub into your program.
13697 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13700 The debugging stub is specific to the architecture of the remote
13701 machine; for example, use @file{sparc-stub.c} to debug programs on
13704 @cindex remote serial stub list
13705 These working remote stubs are distributed with @value{GDBN}:
13710 @cindex @file{i386-stub.c}
13713 For Intel 386 and compatible architectures.
13716 @cindex @file{m68k-stub.c}
13717 @cindex Motorola 680x0
13719 For Motorola 680x0 architectures.
13722 @cindex @file{sh-stub.c}
13725 For Renesas SH architectures.
13728 @cindex @file{sparc-stub.c}
13730 For @sc{sparc} architectures.
13732 @item sparcl-stub.c
13733 @cindex @file{sparcl-stub.c}
13736 For Fujitsu @sc{sparclite} architectures.
13740 The @file{README} file in the @value{GDBN} distribution may list other
13741 recently added stubs.
13744 * Stub Contents:: What the stub can do for you
13745 * Bootstrapping:: What you must do for the stub
13746 * Debug Session:: Putting it all together
13749 @node Stub Contents
13750 @subsection What the Stub Can Do for You
13752 @cindex remote serial stub
13753 The debugging stub for your architecture supplies these three
13757 @item set_debug_traps
13758 @findex set_debug_traps
13759 @cindex remote serial stub, initialization
13760 This routine arranges for @code{handle_exception} to run when your
13761 program stops. You must call this subroutine explicitly near the
13762 beginning of your program.
13764 @item handle_exception
13765 @findex handle_exception
13766 @cindex remote serial stub, main routine
13767 This is the central workhorse, but your program never calls it
13768 explicitly---the setup code arranges for @code{handle_exception} to
13769 run when a trap is triggered.
13771 @code{handle_exception} takes control when your program stops during
13772 execution (for example, on a breakpoint), and mediates communications
13773 with @value{GDBN} on the host machine. This is where the communications
13774 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13775 representative on the target machine. It begins by sending summary
13776 information on the state of your program, then continues to execute,
13777 retrieving and transmitting any information @value{GDBN} needs, until you
13778 execute a @value{GDBN} command that makes your program resume; at that point,
13779 @code{handle_exception} returns control to your own code on the target
13783 @cindex @code{breakpoint} subroutine, remote
13784 Use this auxiliary subroutine to make your program contain a
13785 breakpoint. Depending on the particular situation, this may be the only
13786 way for @value{GDBN} to get control. For instance, if your target
13787 machine has some sort of interrupt button, you won't need to call this;
13788 pressing the interrupt button transfers control to
13789 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13790 simply receiving characters on the serial port may also trigger a trap;
13791 again, in that situation, you don't need to call @code{breakpoint} from
13792 your own program---simply running @samp{target remote} from the host
13793 @value{GDBN} session gets control.
13795 Call @code{breakpoint} if none of these is true, or if you simply want
13796 to make certain your program stops at a predetermined point for the
13797 start of your debugging session.
13800 @node Bootstrapping
13801 @subsection What You Must Do for the Stub
13803 @cindex remote stub, support routines
13804 The debugging stubs that come with @value{GDBN} are set up for a particular
13805 chip architecture, but they have no information about the rest of your
13806 debugging target machine.
13808 First of all you need to tell the stub how to communicate with the
13812 @item int getDebugChar()
13813 @findex getDebugChar
13814 Write this subroutine to read a single character from the serial port.
13815 It may be identical to @code{getchar} for your target system; a
13816 different name is used to allow you to distinguish the two if you wish.
13818 @item void putDebugChar(int)
13819 @findex putDebugChar
13820 Write this subroutine to write a single character to the serial port.
13821 It may be identical to @code{putchar} for your target system; a
13822 different name is used to allow you to distinguish the two if you wish.
13825 @cindex control C, and remote debugging
13826 @cindex interrupting remote targets
13827 If you want @value{GDBN} to be able to stop your program while it is
13828 running, you need to use an interrupt-driven serial driver, and arrange
13829 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13830 character). That is the character which @value{GDBN} uses to tell the
13831 remote system to stop.
13833 Getting the debugging target to return the proper status to @value{GDBN}
13834 probably requires changes to the standard stub; one quick and dirty way
13835 is to just execute a breakpoint instruction (the ``dirty'' part is that
13836 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13838 Other routines you need to supply are:
13841 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13842 @findex exceptionHandler
13843 Write this function to install @var{exception_address} in the exception
13844 handling tables. You need to do this because the stub does not have any
13845 way of knowing what the exception handling tables on your target system
13846 are like (for example, the processor's table might be in @sc{rom},
13847 containing entries which point to a table in @sc{ram}).
13848 @var{exception_number} is the exception number which should be changed;
13849 its meaning is architecture-dependent (for example, different numbers
13850 might represent divide by zero, misaligned access, etc). When this
13851 exception occurs, control should be transferred directly to
13852 @var{exception_address}, and the processor state (stack, registers,
13853 and so on) should be just as it is when a processor exception occurs. So if
13854 you want to use a jump instruction to reach @var{exception_address}, it
13855 should be a simple jump, not a jump to subroutine.
13857 For the 386, @var{exception_address} should be installed as an interrupt
13858 gate so that interrupts are masked while the handler runs. The gate
13859 should be at privilege level 0 (the most privileged level). The
13860 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13861 help from @code{exceptionHandler}.
13863 @item void flush_i_cache()
13864 @findex flush_i_cache
13865 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13866 instruction cache, if any, on your target machine. If there is no
13867 instruction cache, this subroutine may be a no-op.
13869 On target machines that have instruction caches, @value{GDBN} requires this
13870 function to make certain that the state of your program is stable.
13874 You must also make sure this library routine is available:
13877 @item void *memset(void *, int, int)
13879 This is the standard library function @code{memset} that sets an area of
13880 memory to a known value. If you have one of the free versions of
13881 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13882 either obtain it from your hardware manufacturer, or write your own.
13885 If you do not use the GNU C compiler, you may need other standard
13886 library subroutines as well; this varies from one stub to another,
13887 but in general the stubs are likely to use any of the common library
13888 subroutines which @code{@value{NGCC}} generates as inline code.
13891 @node Debug Session
13892 @subsection Putting it All Together
13894 @cindex remote serial debugging summary
13895 In summary, when your program is ready to debug, you must follow these
13900 Make sure you have defined the supporting low-level routines
13901 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13903 @code{getDebugChar}, @code{putDebugChar},
13904 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13908 Insert these lines near the top of your program:
13916 For the 680x0 stub only, you need to provide a variable called
13917 @code{exceptionHook}. Normally you just use:
13920 void (*exceptionHook)() = 0;
13924 but if before calling @code{set_debug_traps}, you set it to point to a
13925 function in your program, that function is called when
13926 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13927 error). The function indicated by @code{exceptionHook} is called with
13928 one parameter: an @code{int} which is the exception number.
13931 Compile and link together: your program, the @value{GDBN} debugging stub for
13932 your target architecture, and the supporting subroutines.
13935 Make sure you have a serial connection between your target machine and
13936 the @value{GDBN} host, and identify the serial port on the host.
13939 @c The "remote" target now provides a `load' command, so we should
13940 @c document that. FIXME.
13941 Download your program to your target machine (or get it there by
13942 whatever means the manufacturer provides), and start it.
13945 Start @value{GDBN} on the host, and connect to the target
13946 (@pxref{Connecting,,Connecting to a Remote Target}).
13950 @node Configurations
13951 @chapter Configuration-Specific Information
13953 While nearly all @value{GDBN} commands are available for all native and
13954 cross versions of the debugger, there are some exceptions. This chapter
13955 describes things that are only available in certain configurations.
13957 There are three major categories of configurations: native
13958 configurations, where the host and target are the same, embedded
13959 operating system configurations, which are usually the same for several
13960 different processor architectures, and bare embedded processors, which
13961 are quite different from each other.
13966 * Embedded Processors::
13973 This section describes details specific to particular native
13978 * BSD libkvm Interface:: Debugging BSD kernel memory images
13979 * SVR4 Process Information:: SVR4 process information
13980 * DJGPP Native:: Features specific to the DJGPP port
13981 * Cygwin Native:: Features specific to the Cygwin port
13982 * Hurd Native:: Features specific to @sc{gnu} Hurd
13983 * Neutrino:: Features specific to QNX Neutrino
13989 On HP-UX systems, if you refer to a function or variable name that
13990 begins with a dollar sign, @value{GDBN} searches for a user or system
13991 name first, before it searches for a convenience variable.
13994 @node BSD libkvm Interface
13995 @subsection BSD libkvm Interface
13998 @cindex kernel memory image
13999 @cindex kernel crash dump
14001 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14002 interface that provides a uniform interface for accessing kernel virtual
14003 memory images, including live systems and crash dumps. @value{GDBN}
14004 uses this interface to allow you to debug live kernels and kernel crash
14005 dumps on many native BSD configurations. This is implemented as a
14006 special @code{kvm} debugging target. For debugging a live system, load
14007 the currently running kernel into @value{GDBN} and connect to the
14011 (@value{GDBP}) @b{target kvm}
14014 For debugging crash dumps, provide the file name of the crash dump as an
14018 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14021 Once connected to the @code{kvm} target, the following commands are
14027 Set current context from the @dfn{Process Control Block} (PCB) address.
14030 Set current context from proc address. This command isn't available on
14031 modern FreeBSD systems.
14034 @node SVR4 Process Information
14035 @subsection SVR4 Process Information
14037 @cindex examine process image
14038 @cindex process info via @file{/proc}
14040 Many versions of SVR4 and compatible systems provide a facility called
14041 @samp{/proc} that can be used to examine the image of a running
14042 process using file-system subroutines. If @value{GDBN} is configured
14043 for an operating system with this facility, the command @code{info
14044 proc} is available to report information about the process running
14045 your program, or about any process running on your system. @code{info
14046 proc} works only on SVR4 systems that include the @code{procfs} code.
14047 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14048 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14054 @itemx info proc @var{process-id}
14055 Summarize available information about any running process. If a
14056 process ID is specified by @var{process-id}, display information about
14057 that process; otherwise display information about the program being
14058 debugged. The summary includes the debugged process ID, the command
14059 line used to invoke it, its current working directory, and its
14060 executable file's absolute file name.
14062 On some systems, @var{process-id} can be of the form
14063 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14064 within a process. If the optional @var{pid} part is missing, it means
14065 a thread from the process being debugged (the leading @samp{/} still
14066 needs to be present, or else @value{GDBN} will interpret the number as
14067 a process ID rather than a thread ID).
14069 @item info proc mappings
14070 @cindex memory address space mappings
14071 Report the memory address space ranges accessible in the program, with
14072 information on whether the process has read, write, or execute access
14073 rights to each range. On @sc{gnu}/Linux systems, each memory range
14074 includes the object file which is mapped to that range, instead of the
14075 memory access rights to that range.
14077 @item info proc stat
14078 @itemx info proc status
14079 @cindex process detailed status information
14080 These subcommands are specific to @sc{gnu}/Linux systems. They show
14081 the process-related information, including the user ID and group ID;
14082 how many threads are there in the process; its virtual memory usage;
14083 the signals that are pending, blocked, and ignored; its TTY; its
14084 consumption of system and user time; its stack size; its @samp{nice}
14085 value; etc. For more information, see the @samp{proc} man page
14086 (type @kbd{man 5 proc} from your shell prompt).
14088 @item info proc all
14089 Show all the information about the process described under all of the
14090 above @code{info proc} subcommands.
14093 @comment These sub-options of 'info proc' were not included when
14094 @comment procfs.c was re-written. Keep their descriptions around
14095 @comment against the day when someone finds the time to put them back in.
14096 @kindex info proc times
14097 @item info proc times
14098 Starting time, user CPU time, and system CPU time for your program and
14101 @kindex info proc id
14103 Report on the process IDs related to your program: its own process ID,
14104 the ID of its parent, the process group ID, and the session ID.
14107 @item set procfs-trace
14108 @kindex set procfs-trace
14109 @cindex @code{procfs} API calls
14110 This command enables and disables tracing of @code{procfs} API calls.
14112 @item show procfs-trace
14113 @kindex show procfs-trace
14114 Show the current state of @code{procfs} API call tracing.
14116 @item set procfs-file @var{file}
14117 @kindex set procfs-file
14118 Tell @value{GDBN} to write @code{procfs} API trace to the named
14119 @var{file}. @value{GDBN} appends the trace info to the previous
14120 contents of the file. The default is to display the trace on the
14123 @item show procfs-file
14124 @kindex show procfs-file
14125 Show the file to which @code{procfs} API trace is written.
14127 @item proc-trace-entry
14128 @itemx proc-trace-exit
14129 @itemx proc-untrace-entry
14130 @itemx proc-untrace-exit
14131 @kindex proc-trace-entry
14132 @kindex proc-trace-exit
14133 @kindex proc-untrace-entry
14134 @kindex proc-untrace-exit
14135 These commands enable and disable tracing of entries into and exits
14136 from the @code{syscall} interface.
14139 @kindex info pidlist
14140 @cindex process list, QNX Neutrino
14141 For QNX Neutrino only, this command displays the list of all the
14142 processes and all the threads within each process.
14145 @kindex info meminfo
14146 @cindex mapinfo list, QNX Neutrino
14147 For QNX Neutrino only, this command displays the list of all mapinfos.
14151 @subsection Features for Debugging @sc{djgpp} Programs
14152 @cindex @sc{djgpp} debugging
14153 @cindex native @sc{djgpp} debugging
14154 @cindex MS-DOS-specific commands
14157 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14158 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14159 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14160 top of real-mode DOS systems and their emulations.
14162 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14163 defines a few commands specific to the @sc{djgpp} port. This
14164 subsection describes those commands.
14169 This is a prefix of @sc{djgpp}-specific commands which print
14170 information about the target system and important OS structures.
14173 @cindex MS-DOS system info
14174 @cindex free memory information (MS-DOS)
14175 @item info dos sysinfo
14176 This command displays assorted information about the underlying
14177 platform: the CPU type and features, the OS version and flavor, the
14178 DPMI version, and the available conventional and DPMI memory.
14183 @cindex segment descriptor tables
14184 @cindex descriptor tables display
14186 @itemx info dos ldt
14187 @itemx info dos idt
14188 These 3 commands display entries from, respectively, Global, Local,
14189 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14190 tables are data structures which store a descriptor for each segment
14191 that is currently in use. The segment's selector is an index into a
14192 descriptor table; the table entry for that index holds the
14193 descriptor's base address and limit, and its attributes and access
14196 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14197 segment (used for both data and the stack), and a DOS segment (which
14198 allows access to DOS/BIOS data structures and absolute addresses in
14199 conventional memory). However, the DPMI host will usually define
14200 additional segments in order to support the DPMI environment.
14202 @cindex garbled pointers
14203 These commands allow to display entries from the descriptor tables.
14204 Without an argument, all entries from the specified table are
14205 displayed. An argument, which should be an integer expression, means
14206 display a single entry whose index is given by the argument. For
14207 example, here's a convenient way to display information about the
14208 debugged program's data segment:
14211 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14212 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14216 This comes in handy when you want to see whether a pointer is outside
14217 the data segment's limit (i.e.@: @dfn{garbled}).
14219 @cindex page tables display (MS-DOS)
14221 @itemx info dos pte
14222 These two commands display entries from, respectively, the Page
14223 Directory and the Page Tables. Page Directories and Page Tables are
14224 data structures which control how virtual memory addresses are mapped
14225 into physical addresses. A Page Table includes an entry for every
14226 page of memory that is mapped into the program's address space; there
14227 may be several Page Tables, each one holding up to 4096 entries. A
14228 Page Directory has up to 4096 entries, one each for every Page Table
14229 that is currently in use.
14231 Without an argument, @kbd{info dos pde} displays the entire Page
14232 Directory, and @kbd{info dos pte} displays all the entries in all of
14233 the Page Tables. An argument, an integer expression, given to the
14234 @kbd{info dos pde} command means display only that entry from the Page
14235 Directory table. An argument given to the @kbd{info dos pte} command
14236 means display entries from a single Page Table, the one pointed to by
14237 the specified entry in the Page Directory.
14239 @cindex direct memory access (DMA) on MS-DOS
14240 These commands are useful when your program uses @dfn{DMA} (Direct
14241 Memory Access), which needs physical addresses to program the DMA
14244 These commands are supported only with some DPMI servers.
14246 @cindex physical address from linear address
14247 @item info dos address-pte @var{addr}
14248 This command displays the Page Table entry for a specified linear
14249 address. The argument @var{addr} is a linear address which should
14250 already have the appropriate segment's base address added to it,
14251 because this command accepts addresses which may belong to @emph{any}
14252 segment. For example, here's how to display the Page Table entry for
14253 the page where a variable @code{i} is stored:
14256 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14257 @exdent @code{Page Table entry for address 0x11a00d30:}
14258 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14262 This says that @code{i} is stored at offset @code{0xd30} from the page
14263 whose physical base address is @code{0x02698000}, and shows all the
14264 attributes of that page.
14266 Note that you must cast the addresses of variables to a @code{char *},
14267 since otherwise the value of @code{__djgpp_base_address}, the base
14268 address of all variables and functions in a @sc{djgpp} program, will
14269 be added using the rules of C pointer arithmetics: if @code{i} is
14270 declared an @code{int}, @value{GDBN} will add 4 times the value of
14271 @code{__djgpp_base_address} to the address of @code{i}.
14273 Here's another example, it displays the Page Table entry for the
14277 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14278 @exdent @code{Page Table entry for address 0x29110:}
14279 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14283 (The @code{+ 3} offset is because the transfer buffer's address is the
14284 3rd member of the @code{_go32_info_block} structure.) The output
14285 clearly shows that this DPMI server maps the addresses in conventional
14286 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
14287 linear (@code{0x29110}) addresses are identical.
14289 This command is supported only with some DPMI servers.
14292 @cindex DOS serial data link, remote debugging
14293 In addition to native debugging, the DJGPP port supports remote
14294 debugging via a serial data link. The following commands are specific
14295 to remote serial debugging in the DJGPP port of @value{GDBN}.
14298 @kindex set com1base
14299 @kindex set com1irq
14300 @kindex set com2base
14301 @kindex set com2irq
14302 @kindex set com3base
14303 @kindex set com3irq
14304 @kindex set com4base
14305 @kindex set com4irq
14306 @item set com1base @var{addr}
14307 This command sets the base I/O port address of the @file{COM1} serial
14310 @item set com1irq @var{irq}
14311 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
14312 for the @file{COM1} serial port.
14314 There are similar commands @samp{set com2base}, @samp{set com3irq},
14315 etc.@: for setting the port address and the @code{IRQ} lines for the
14318 @kindex show com1base
14319 @kindex show com1irq
14320 @kindex show com2base
14321 @kindex show com2irq
14322 @kindex show com3base
14323 @kindex show com3irq
14324 @kindex show com4base
14325 @kindex show com4irq
14326 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
14327 display the current settings of the base address and the @code{IRQ}
14328 lines used by the COM ports.
14331 @kindex info serial
14332 @cindex DOS serial port status
14333 This command prints the status of the 4 DOS serial ports. For each
14334 port, it prints whether it's active or not, its I/O base address and
14335 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
14336 counts of various errors encountered so far.
14340 @node Cygwin Native
14341 @subsection Features for Debugging MS Windows PE Executables
14342 @cindex MS Windows debugging
14343 @cindex native Cygwin debugging
14344 @cindex Cygwin-specific commands
14346 @value{GDBN} supports native debugging of MS Windows programs, including
14347 DLLs with and without symbolic debugging information. There are various
14348 additional Cygwin-specific commands, described in this section.
14349 Working with DLLs that have no debugging symbols is described in
14350 @ref{Non-debug DLL Symbols}.
14355 This is a prefix of MS Windows-specific commands which print
14356 information about the target system and important OS structures.
14358 @item info w32 selector
14359 This command displays information returned by
14360 the Win32 API @code{GetThreadSelectorEntry} function.
14361 It takes an optional argument that is evaluated to
14362 a long value to give the information about this given selector.
14363 Without argument, this command displays information
14364 about the six segment registers.
14368 This is a Cygwin-specific alias of @code{info shared}.
14370 @kindex dll-symbols
14372 This command loads symbols from a dll similarly to
14373 add-sym command but without the need to specify a base address.
14375 @kindex set cygwin-exceptions
14376 @cindex debugging the Cygwin DLL
14377 @cindex Cygwin DLL, debugging
14378 @item set cygwin-exceptions @var{mode}
14379 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
14380 happen inside the Cygwin DLL. If @var{mode} is @code{off},
14381 @value{GDBN} will delay recognition of exceptions, and may ignore some
14382 exceptions which seem to be caused by internal Cygwin DLL
14383 ``bookkeeping''. This option is meant primarily for debugging the
14384 Cygwin DLL itself; the default value is @code{off} to avoid annoying
14385 @value{GDBN} users with false @code{SIGSEGV} signals.
14387 @kindex show cygwin-exceptions
14388 @item show cygwin-exceptions
14389 Displays whether @value{GDBN} will break on exceptions that happen
14390 inside the Cygwin DLL itself.
14392 @kindex set new-console
14393 @item set new-console @var{mode}
14394 If @var{mode} is @code{on} the debuggee will
14395 be started in a new console on next start.
14396 If @var{mode} is @code{off}i, the debuggee will
14397 be started in the same console as the debugger.
14399 @kindex show new-console
14400 @item show new-console
14401 Displays whether a new console is used
14402 when the debuggee is started.
14404 @kindex set new-group
14405 @item set new-group @var{mode}
14406 This boolean value controls whether the debuggee should
14407 start a new group or stay in the same group as the debugger.
14408 This affects the way the Windows OS handles
14411 @kindex show new-group
14412 @item show new-group
14413 Displays current value of new-group boolean.
14415 @kindex set debugevents
14416 @item set debugevents
14417 This boolean value adds debug output concerning kernel events related
14418 to the debuggee seen by the debugger. This includes events that
14419 signal thread and process creation and exit, DLL loading and
14420 unloading, console interrupts, and debugging messages produced by the
14421 Windows @code{OutputDebugString} API call.
14423 @kindex set debugexec
14424 @item set debugexec
14425 This boolean value adds debug output concerning execute events
14426 (such as resume thread) seen by the debugger.
14428 @kindex set debugexceptions
14429 @item set debugexceptions
14430 This boolean value adds debug output concerning exceptions in the
14431 debuggee seen by the debugger.
14433 @kindex set debugmemory
14434 @item set debugmemory
14435 This boolean value adds debug output concerning debuggee memory reads
14436 and writes by the debugger.
14440 This boolean values specifies whether the debuggee is called
14441 via a shell or directly (default value is on).
14445 Displays if the debuggee will be started with a shell.
14450 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14453 @node Non-debug DLL Symbols
14454 @subsubsection Support for DLLs without Debugging Symbols
14455 @cindex DLLs with no debugging symbols
14456 @cindex Minimal symbols and DLLs
14458 Very often on windows, some of the DLLs that your program relies on do
14459 not include symbolic debugging information (for example,
14460 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14461 symbols in a DLL, it relies on the minimal amount of symbolic
14462 information contained in the DLL's export table. This section
14463 describes working with such symbols, known internally to @value{GDBN} as
14464 ``minimal symbols''.
14466 Note that before the debugged program has started execution, no DLLs
14467 will have been loaded. The easiest way around this problem is simply to
14468 start the program --- either by setting a breakpoint or letting the
14469 program run once to completion. It is also possible to force
14470 @value{GDBN} to load a particular DLL before starting the executable ---
14471 see the shared library information in @ref{Files}, or the
14472 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14473 explicitly loading symbols from a DLL with no debugging information will
14474 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14475 which may adversely affect symbol lookup performance.
14477 @subsubsection DLL Name Prefixes
14479 In keeping with the naming conventions used by the Microsoft debugging
14480 tools, DLL export symbols are made available with a prefix based on the
14481 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14482 also entered into the symbol table, so @code{CreateFileA} is often
14483 sufficient. In some cases there will be name clashes within a program
14484 (particularly if the executable itself includes full debugging symbols)
14485 necessitating the use of the fully qualified name when referring to the
14486 contents of the DLL. Use single-quotes around the name to avoid the
14487 exclamation mark (``!'') being interpreted as a language operator.
14489 Note that the internal name of the DLL may be all upper-case, even
14490 though the file name of the DLL is lower-case, or vice-versa. Since
14491 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14492 some confusion. If in doubt, try the @code{info functions} and
14493 @code{info variables} commands or even @code{maint print msymbols}
14494 (@pxref{Symbols}). Here's an example:
14497 (@value{GDBP}) info function CreateFileA
14498 All functions matching regular expression "CreateFileA":
14500 Non-debugging symbols:
14501 0x77e885f4 CreateFileA
14502 0x77e885f4 KERNEL32!CreateFileA
14506 (@value{GDBP}) info function !
14507 All functions matching regular expression "!":
14509 Non-debugging symbols:
14510 0x6100114c cygwin1!__assert
14511 0x61004034 cygwin1!_dll_crt0@@0
14512 0x61004240 cygwin1!dll_crt0(per_process *)
14516 @subsubsection Working with Minimal Symbols
14518 Symbols extracted from a DLL's export table do not contain very much
14519 type information. All that @value{GDBN} can do is guess whether a symbol
14520 refers to a function or variable depending on the linker section that
14521 contains the symbol. Also note that the actual contents of the memory
14522 contained in a DLL are not available unless the program is running. This
14523 means that you cannot examine the contents of a variable or disassemble
14524 a function within a DLL without a running program.
14526 Variables are generally treated as pointers and dereferenced
14527 automatically. For this reason, it is often necessary to prefix a
14528 variable name with the address-of operator (``&'') and provide explicit
14529 type information in the command. Here's an example of the type of
14533 (@value{GDBP}) print 'cygwin1!__argv'
14538 (@value{GDBP}) x 'cygwin1!__argv'
14539 0x10021610: "\230y\""
14542 And two possible solutions:
14545 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14546 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14550 (@value{GDBP}) x/2x &'cygwin1!__argv'
14551 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14552 (@value{GDBP}) x/x 0x10021608
14553 0x10021608: 0x0022fd98
14554 (@value{GDBP}) x/s 0x0022fd98
14555 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14558 Setting a break point within a DLL is possible even before the program
14559 starts execution. However, under these circumstances, @value{GDBN} can't
14560 examine the initial instructions of the function in order to skip the
14561 function's frame set-up code. You can work around this by using ``*&''
14562 to set the breakpoint at a raw memory address:
14565 (@value{GDBP}) break *&'python22!PyOS_Readline'
14566 Breakpoint 1 at 0x1e04eff0
14569 The author of these extensions is not entirely convinced that setting a
14570 break point within a shared DLL like @file{kernel32.dll} is completely
14574 @subsection Commands Specific to @sc{gnu} Hurd Systems
14575 @cindex @sc{gnu} Hurd debugging
14577 This subsection describes @value{GDBN} commands specific to the
14578 @sc{gnu} Hurd native debugging.
14583 @kindex set signals@r{, Hurd command}
14584 @kindex set sigs@r{, Hurd command}
14585 This command toggles the state of inferior signal interception by
14586 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14587 affected by this command. @code{sigs} is a shorthand alias for
14592 @kindex show signals@r{, Hurd command}
14593 @kindex show sigs@r{, Hurd command}
14594 Show the current state of intercepting inferior's signals.
14596 @item set signal-thread
14597 @itemx set sigthread
14598 @kindex set signal-thread
14599 @kindex set sigthread
14600 This command tells @value{GDBN} which thread is the @code{libc} signal
14601 thread. That thread is run when a signal is delivered to a running
14602 process. @code{set sigthread} is the shorthand alias of @code{set
14605 @item show signal-thread
14606 @itemx show sigthread
14607 @kindex show signal-thread
14608 @kindex show sigthread
14609 These two commands show which thread will run when the inferior is
14610 delivered a signal.
14613 @kindex set stopped@r{, Hurd command}
14614 This commands tells @value{GDBN} that the inferior process is stopped,
14615 as with the @code{SIGSTOP} signal. The stopped process can be
14616 continued by delivering a signal to it.
14619 @kindex show stopped@r{, Hurd command}
14620 This command shows whether @value{GDBN} thinks the debuggee is
14623 @item set exceptions
14624 @kindex set exceptions@r{, Hurd command}
14625 Use this command to turn off trapping of exceptions in the inferior.
14626 When exception trapping is off, neither breakpoints nor
14627 single-stepping will work. To restore the default, set exception
14630 @item show exceptions
14631 @kindex show exceptions@r{, Hurd command}
14632 Show the current state of trapping exceptions in the inferior.
14634 @item set task pause
14635 @kindex set task@r{, Hurd commands}
14636 @cindex task attributes (@sc{gnu} Hurd)
14637 @cindex pause current task (@sc{gnu} Hurd)
14638 This command toggles task suspension when @value{GDBN} has control.
14639 Setting it to on takes effect immediately, and the task is suspended
14640 whenever @value{GDBN} gets control. Setting it to off will take
14641 effect the next time the inferior is continued. If this option is set
14642 to off, you can use @code{set thread default pause on} or @code{set
14643 thread pause on} (see below) to pause individual threads.
14645 @item show task pause
14646 @kindex show task@r{, Hurd commands}
14647 Show the current state of task suspension.
14649 @item set task detach-suspend-count
14650 @cindex task suspend count
14651 @cindex detach from task, @sc{gnu} Hurd
14652 This command sets the suspend count the task will be left with when
14653 @value{GDBN} detaches from it.
14655 @item show task detach-suspend-count
14656 Show the suspend count the task will be left with when detaching.
14658 @item set task exception-port
14659 @itemx set task excp
14660 @cindex task exception port, @sc{gnu} Hurd
14661 This command sets the task exception port to which @value{GDBN} will
14662 forward exceptions. The argument should be the value of the @dfn{send
14663 rights} of the task. @code{set task excp} is a shorthand alias.
14665 @item set noninvasive
14666 @cindex noninvasive task options
14667 This command switches @value{GDBN} to a mode that is the least
14668 invasive as far as interfering with the inferior is concerned. This
14669 is the same as using @code{set task pause}, @code{set exceptions}, and
14670 @code{set signals} to values opposite to the defaults.
14672 @item info send-rights
14673 @itemx info receive-rights
14674 @itemx info port-rights
14675 @itemx info port-sets
14676 @itemx info dead-names
14679 @cindex send rights, @sc{gnu} Hurd
14680 @cindex receive rights, @sc{gnu} Hurd
14681 @cindex port rights, @sc{gnu} Hurd
14682 @cindex port sets, @sc{gnu} Hurd
14683 @cindex dead names, @sc{gnu} Hurd
14684 These commands display information about, respectively, send rights,
14685 receive rights, port rights, port sets, and dead names of a task.
14686 There are also shorthand aliases: @code{info ports} for @code{info
14687 port-rights} and @code{info psets} for @code{info port-sets}.
14689 @item set thread pause
14690 @kindex set thread@r{, Hurd command}
14691 @cindex thread properties, @sc{gnu} Hurd
14692 @cindex pause current thread (@sc{gnu} Hurd)
14693 This command toggles current thread suspension when @value{GDBN} has
14694 control. Setting it to on takes effect immediately, and the current
14695 thread is suspended whenever @value{GDBN} gets control. Setting it to
14696 off will take effect the next time the inferior is continued.
14697 Normally, this command has no effect, since when @value{GDBN} has
14698 control, the whole task is suspended. However, if you used @code{set
14699 task pause off} (see above), this command comes in handy to suspend
14700 only the current thread.
14702 @item show thread pause
14703 @kindex show thread@r{, Hurd command}
14704 This command shows the state of current thread suspension.
14706 @item set thread run
14707 This command sets whether the current thread is allowed to run.
14709 @item show thread run
14710 Show whether the current thread is allowed to run.
14712 @item set thread detach-suspend-count
14713 @cindex thread suspend count, @sc{gnu} Hurd
14714 @cindex detach from thread, @sc{gnu} Hurd
14715 This command sets the suspend count @value{GDBN} will leave on a
14716 thread when detaching. This number is relative to the suspend count
14717 found by @value{GDBN} when it notices the thread; use @code{set thread
14718 takeover-suspend-count} to force it to an absolute value.
14720 @item show thread detach-suspend-count
14721 Show the suspend count @value{GDBN} will leave on the thread when
14724 @item set thread exception-port
14725 @itemx set thread excp
14726 Set the thread exception port to which to forward exceptions. This
14727 overrides the port set by @code{set task exception-port} (see above).
14728 @code{set thread excp} is the shorthand alias.
14730 @item set thread takeover-suspend-count
14731 Normally, @value{GDBN}'s thread suspend counts are relative to the
14732 value @value{GDBN} finds when it notices each thread. This command
14733 changes the suspend counts to be absolute instead.
14735 @item set thread default
14736 @itemx show thread default
14737 @cindex thread default settings, @sc{gnu} Hurd
14738 Each of the above @code{set thread} commands has a @code{set thread
14739 default} counterpart (e.g., @code{set thread default pause}, @code{set
14740 thread default exception-port}, etc.). The @code{thread default}
14741 variety of commands sets the default thread properties for all
14742 threads; you can then change the properties of individual threads with
14743 the non-default commands.
14748 @subsection QNX Neutrino
14749 @cindex QNX Neutrino
14751 @value{GDBN} provides the following commands specific to the QNX
14755 @item set debug nto-debug
14756 @kindex set debug nto-debug
14757 When set to on, enables debugging messages specific to the QNX
14760 @item show debug nto-debug
14761 @kindex show debug nto-debug
14762 Show the current state of QNX Neutrino messages.
14767 @section Embedded Operating Systems
14769 This section describes configurations involving the debugging of
14770 embedded operating systems that are available for several different
14774 * VxWorks:: Using @value{GDBN} with VxWorks
14777 @value{GDBN} includes the ability to debug programs running on
14778 various real-time operating systems.
14781 @subsection Using @value{GDBN} with VxWorks
14787 @kindex target vxworks
14788 @item target vxworks @var{machinename}
14789 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14790 is the target system's machine name or IP address.
14794 On VxWorks, @code{load} links @var{filename} dynamically on the
14795 current target system as well as adding its symbols in @value{GDBN}.
14797 @value{GDBN} enables developers to spawn and debug tasks running on networked
14798 VxWorks targets from a Unix host. Already-running tasks spawned from
14799 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14800 both the Unix host and on the VxWorks target. The program
14801 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14802 installed with the name @code{vxgdb}, to distinguish it from a
14803 @value{GDBN} for debugging programs on the host itself.)
14806 @item VxWorks-timeout @var{args}
14807 @kindex vxworks-timeout
14808 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14809 This option is set by the user, and @var{args} represents the number of
14810 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14811 your VxWorks target is a slow software simulator or is on the far side
14812 of a thin network line.
14815 The following information on connecting to VxWorks was current when
14816 this manual was produced; newer releases of VxWorks may use revised
14819 @findex INCLUDE_RDB
14820 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14821 to include the remote debugging interface routines in the VxWorks
14822 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14823 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14824 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14825 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14826 information on configuring and remaking VxWorks, see the manufacturer's
14828 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14830 Once you have included @file{rdb.a} in your VxWorks system image and set
14831 your Unix execution search path to find @value{GDBN}, you are ready to
14832 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14833 @code{vxgdb}, depending on your installation).
14835 @value{GDBN} comes up showing the prompt:
14842 * VxWorks Connection:: Connecting to VxWorks
14843 * VxWorks Download:: VxWorks download
14844 * VxWorks Attach:: Running tasks
14847 @node VxWorks Connection
14848 @subsubsection Connecting to VxWorks
14850 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14851 network. To connect to a target whose host name is ``@code{tt}'', type:
14854 (vxgdb) target vxworks tt
14858 @value{GDBN} displays messages like these:
14861 Attaching remote machine across net...
14866 @value{GDBN} then attempts to read the symbol tables of any object modules
14867 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14868 these files by searching the directories listed in the command search
14869 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14870 to find an object file, it displays a message such as:
14873 prog.o: No such file or directory.
14876 When this happens, add the appropriate directory to the search path with
14877 the @value{GDBN} command @code{path}, and execute the @code{target}
14880 @node VxWorks Download
14881 @subsubsection VxWorks Download
14883 @cindex download to VxWorks
14884 If you have connected to the VxWorks target and you want to debug an
14885 object that has not yet been loaded, you can use the @value{GDBN}
14886 @code{load} command to download a file from Unix to VxWorks
14887 incrementally. The object file given as an argument to the @code{load}
14888 command is actually opened twice: first by the VxWorks target in order
14889 to download the code, then by @value{GDBN} in order to read the symbol
14890 table. This can lead to problems if the current working directories on
14891 the two systems differ. If both systems have NFS mounted the same
14892 filesystems, you can avoid these problems by using absolute paths.
14893 Otherwise, it is simplest to set the working directory on both systems
14894 to the directory in which the object file resides, and then to reference
14895 the file by its name, without any path. For instance, a program
14896 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14897 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14898 program, type this on VxWorks:
14901 -> cd "@var{vxpath}/vw/demo/rdb"
14905 Then, in @value{GDBN}, type:
14908 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14909 (vxgdb) load prog.o
14912 @value{GDBN} displays a response similar to this:
14915 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14918 You can also use the @code{load} command to reload an object module
14919 after editing and recompiling the corresponding source file. Note that
14920 this makes @value{GDBN} delete all currently-defined breakpoints,
14921 auto-displays, and convenience variables, and to clear the value
14922 history. (This is necessary in order to preserve the integrity of
14923 debugger's data structures that reference the target system's symbol
14926 @node VxWorks Attach
14927 @subsubsection Running Tasks
14929 @cindex running VxWorks tasks
14930 You can also attach to an existing task using the @code{attach} command as
14934 (vxgdb) attach @var{task}
14938 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14939 or suspended when you attach to it. Running tasks are suspended at
14940 the time of attachment.
14942 @node Embedded Processors
14943 @section Embedded Processors
14945 This section goes into details specific to particular embedded
14948 @cindex send command to simulator
14949 Whenever a specific embedded processor has a simulator, @value{GDBN}
14950 allows to send an arbitrary command to the simulator.
14953 @item sim @var{command}
14954 @kindex sim@r{, a command}
14955 Send an arbitrary @var{command} string to the simulator. Consult the
14956 documentation for the specific simulator in use for information about
14957 acceptable commands.
14963 * M32R/D:: Renesas M32R/D
14964 * M68K:: Motorola M68K
14965 * MIPS Embedded:: MIPS Embedded
14966 * OpenRISC 1000:: OpenRisc 1000
14967 * PA:: HP PA Embedded
14968 * PowerPC Embedded:: PowerPC Embedded
14969 * Sparclet:: Tsqware Sparclet
14970 * Sparclite:: Fujitsu Sparclite
14971 * Z8000:: Zilog Z8000
14974 * Super-H:: Renesas Super-H
14983 @item target rdi @var{dev}
14984 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14985 use this target to communicate with both boards running the Angel
14986 monitor, or with the EmbeddedICE JTAG debug device.
14989 @item target rdp @var{dev}
14994 @value{GDBN} provides the following ARM-specific commands:
14997 @item set arm disassembler
14999 This commands selects from a list of disassembly styles. The
15000 @code{"std"} style is the standard style.
15002 @item show arm disassembler
15004 Show the current disassembly style.
15006 @item set arm apcs32
15007 @cindex ARM 32-bit mode
15008 This command toggles ARM operation mode between 32-bit and 26-bit.
15010 @item show arm apcs32
15011 Display the current usage of the ARM 32-bit mode.
15013 @item set arm fpu @var{fputype}
15014 This command sets the ARM floating-point unit (FPU) type. The
15015 argument @var{fputype} can be one of these:
15019 Determine the FPU type by querying the OS ABI.
15021 Software FPU, with mixed-endian doubles on little-endian ARM
15024 GCC-compiled FPA co-processor.
15026 Software FPU with pure-endian doubles.
15032 Show the current type of the FPU.
15035 This command forces @value{GDBN} to use the specified ABI.
15038 Show the currently used ABI.
15040 @item set arm fallback-mode (arm|thumb|auto)
15041 @value{GDBN} uses the symbol table, when available, to determine
15042 whether instructions are ARM or Thumb. This command controls
15043 @value{GDBN}'s default behavior when the symbol table is not
15044 available. The default is @samp{auto}, which causes @value{GDBN} to
15045 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15048 @item show arm fallback-mode
15049 Show the current fallback instruction mode.
15051 @item set arm force-mode (arm|thumb|auto)
15052 This command overrides use of the symbol table to determine whether
15053 instructions are ARM or Thumb. The default is @samp{auto}, which
15054 causes @value{GDBN} to use the symbol table and then the setting
15055 of @samp{set arm fallback-mode}.
15057 @item show arm force-mode
15058 Show the current forced instruction mode.
15060 @item set debug arm
15061 Toggle whether to display ARM-specific debugging messages from the ARM
15062 target support subsystem.
15064 @item show debug arm
15065 Show whether ARM-specific debugging messages are enabled.
15068 The following commands are available when an ARM target is debugged
15069 using the RDI interface:
15072 @item rdilogfile @r{[}@var{file}@r{]}
15074 @cindex ADP (Angel Debugger Protocol) logging
15075 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15076 With an argument, sets the log file to the specified @var{file}. With
15077 no argument, show the current log file name. The default log file is
15080 @item rdilogenable @r{[}@var{arg}@r{]}
15081 @kindex rdilogenable
15082 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15083 enables logging, with an argument 0 or @code{"no"} disables it. With
15084 no arguments displays the current setting. When logging is enabled,
15085 ADP packets exchanged between @value{GDBN} and the RDI target device
15086 are logged to a file.
15088 @item set rdiromatzero
15089 @kindex set rdiromatzero
15090 @cindex ROM at zero address, RDI
15091 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15092 vector catching is disabled, so that zero address can be used. If off
15093 (the default), vector catching is enabled. For this command to take
15094 effect, it needs to be invoked prior to the @code{target rdi} command.
15096 @item show rdiromatzero
15097 @kindex show rdiromatzero
15098 Show the current setting of ROM at zero address.
15100 @item set rdiheartbeat
15101 @kindex set rdiheartbeat
15102 @cindex RDI heartbeat
15103 Enable or disable RDI heartbeat packets. It is not recommended to
15104 turn on this option, since it confuses ARM and EPI JTAG interface, as
15105 well as the Angel monitor.
15107 @item show rdiheartbeat
15108 @kindex show rdiheartbeat
15109 Show the setting of RDI heartbeat packets.
15114 @subsection Renesas M32R/D and M32R/SDI
15117 @kindex target m32r
15118 @item target m32r @var{dev}
15119 Renesas M32R/D ROM monitor.
15121 @kindex target m32rsdi
15122 @item target m32rsdi @var{dev}
15123 Renesas M32R SDI server, connected via parallel port to the board.
15126 The following @value{GDBN} commands are specific to the M32R monitor:
15129 @item set download-path @var{path}
15130 @kindex set download-path
15131 @cindex find downloadable @sc{srec} files (M32R)
15132 Set the default path for finding downloadable @sc{srec} files.
15134 @item show download-path
15135 @kindex show download-path
15136 Show the default path for downloadable @sc{srec} files.
15138 @item set board-address @var{addr}
15139 @kindex set board-address
15140 @cindex M32-EVA target board address
15141 Set the IP address for the M32R-EVA target board.
15143 @item show board-address
15144 @kindex show board-address
15145 Show the current IP address of the target board.
15147 @item set server-address @var{addr}
15148 @kindex set server-address
15149 @cindex download server address (M32R)
15150 Set the IP address for the download server, which is the @value{GDBN}'s
15153 @item show server-address
15154 @kindex show server-address
15155 Display the IP address of the download server.
15157 @item upload @r{[}@var{file}@r{]}
15158 @kindex upload@r{, M32R}
15159 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
15160 upload capability. If no @var{file} argument is given, the current
15161 executable file is uploaded.
15163 @item tload @r{[}@var{file}@r{]}
15164 @kindex tload@r{, M32R}
15165 Test the @code{upload} command.
15168 The following commands are available for M32R/SDI:
15173 @cindex reset SDI connection, M32R
15174 This command resets the SDI connection.
15178 This command shows the SDI connection status.
15181 @kindex debug_chaos
15182 @cindex M32R/Chaos debugging
15183 Instructs the remote that M32R/Chaos debugging is to be used.
15185 @item use_debug_dma
15186 @kindex use_debug_dma
15187 Instructs the remote to use the DEBUG_DMA method of accessing memory.
15190 @kindex use_mon_code
15191 Instructs the remote to use the MON_CODE method of accessing memory.
15194 @kindex use_ib_break
15195 Instructs the remote to set breakpoints by IB break.
15197 @item use_dbt_break
15198 @kindex use_dbt_break
15199 Instructs the remote to set breakpoints by DBT.
15205 The Motorola m68k configuration includes ColdFire support, and a
15206 target command for the following ROM monitor.
15210 @kindex target dbug
15211 @item target dbug @var{dev}
15212 dBUG ROM monitor for Motorola ColdFire.
15216 @node MIPS Embedded
15217 @subsection MIPS Embedded
15219 @cindex MIPS boards
15220 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15221 MIPS board attached to a serial line. This is available when
15222 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15225 Use these @value{GDBN} commands to specify the connection to your target board:
15228 @item target mips @var{port}
15229 @kindex target mips @var{port}
15230 To run a program on the board, start up @code{@value{GDBP}} with the
15231 name of your program as the argument. To connect to the board, use the
15232 command @samp{target mips @var{port}}, where @var{port} is the name of
15233 the serial port connected to the board. If the program has not already
15234 been downloaded to the board, you may use the @code{load} command to
15235 download it. You can then use all the usual @value{GDBN} commands.
15237 For example, this sequence connects to the target board through a serial
15238 port, and loads and runs a program called @var{prog} through the
15242 host$ @value{GDBP} @var{prog}
15243 @value{GDBN} is free software and @dots{}
15244 (@value{GDBP}) target mips /dev/ttyb
15245 (@value{GDBP}) load @var{prog}
15249 @item target mips @var{hostname}:@var{portnumber}
15250 On some @value{GDBN} host configurations, you can specify a TCP
15251 connection (for instance, to a serial line managed by a terminal
15252 concentrator) instead of a serial port, using the syntax
15253 @samp{@var{hostname}:@var{portnumber}}.
15255 @item target pmon @var{port}
15256 @kindex target pmon @var{port}
15259 @item target ddb @var{port}
15260 @kindex target ddb @var{port}
15261 NEC's DDB variant of PMON for Vr4300.
15263 @item target lsi @var{port}
15264 @kindex target lsi @var{port}
15265 LSI variant of PMON.
15267 @kindex target r3900
15268 @item target r3900 @var{dev}
15269 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
15271 @kindex target array
15272 @item target array @var{dev}
15273 Array Tech LSI33K RAID controller board.
15279 @value{GDBN} also supports these special commands for MIPS targets:
15282 @item set mipsfpu double
15283 @itemx set mipsfpu single
15284 @itemx set mipsfpu none
15285 @itemx set mipsfpu auto
15286 @itemx show mipsfpu
15287 @kindex set mipsfpu
15288 @kindex show mipsfpu
15289 @cindex MIPS remote floating point
15290 @cindex floating point, MIPS remote
15291 If your target board does not support the MIPS floating point
15292 coprocessor, you should use the command @samp{set mipsfpu none} (if you
15293 need this, you may wish to put the command in your @value{GDBN} init
15294 file). This tells @value{GDBN} how to find the return value of
15295 functions which return floating point values. It also allows
15296 @value{GDBN} to avoid saving the floating point registers when calling
15297 functions on the board. If you are using a floating point coprocessor
15298 with only single precision floating point support, as on the @sc{r4650}
15299 processor, use the command @samp{set mipsfpu single}. The default
15300 double precision floating point coprocessor may be selected using
15301 @samp{set mipsfpu double}.
15303 In previous versions the only choices were double precision or no
15304 floating point, so @samp{set mipsfpu on} will select double precision
15305 and @samp{set mipsfpu off} will select no floating point.
15307 As usual, you can inquire about the @code{mipsfpu} variable with
15308 @samp{show mipsfpu}.
15310 @item set timeout @var{seconds}
15311 @itemx set retransmit-timeout @var{seconds}
15312 @itemx show timeout
15313 @itemx show retransmit-timeout
15314 @cindex @code{timeout}, MIPS protocol
15315 @cindex @code{retransmit-timeout}, MIPS protocol
15316 @kindex set timeout
15317 @kindex show timeout
15318 @kindex set retransmit-timeout
15319 @kindex show retransmit-timeout
15320 You can control the timeout used while waiting for a packet, in the MIPS
15321 remote protocol, with the @code{set timeout @var{seconds}} command. The
15322 default is 5 seconds. Similarly, you can control the timeout used while
15323 waiting for an acknowledgement of a packet with the @code{set
15324 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
15325 You can inspect both values with @code{show timeout} and @code{show
15326 retransmit-timeout}. (These commands are @emph{only} available when
15327 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
15329 The timeout set by @code{set timeout} does not apply when @value{GDBN}
15330 is waiting for your program to stop. In that case, @value{GDBN} waits
15331 forever because it has no way of knowing how long the program is going
15332 to run before stopping.
15334 @item set syn-garbage-limit @var{num}
15335 @kindex set syn-garbage-limit@r{, MIPS remote}
15336 @cindex synchronize with remote MIPS target
15337 Limit the maximum number of characters @value{GDBN} should ignore when
15338 it tries to synchronize with the remote target. The default is 10
15339 characters. Setting the limit to -1 means there's no limit.
15341 @item show syn-garbage-limit
15342 @kindex show syn-garbage-limit@r{, MIPS remote}
15343 Show the current limit on the number of characters to ignore when
15344 trying to synchronize with the remote system.
15346 @item set monitor-prompt @var{prompt}
15347 @kindex set monitor-prompt@r{, MIPS remote}
15348 @cindex remote monitor prompt
15349 Tell @value{GDBN} to expect the specified @var{prompt} string from the
15350 remote monitor. The default depends on the target:
15360 @item show monitor-prompt
15361 @kindex show monitor-prompt@r{, MIPS remote}
15362 Show the current strings @value{GDBN} expects as the prompt from the
15365 @item set monitor-warnings
15366 @kindex set monitor-warnings@r{, MIPS remote}
15367 Enable or disable monitor warnings about hardware breakpoints. This
15368 has effect only for the @code{lsi} target. When on, @value{GDBN} will
15369 display warning messages whose codes are returned by the @code{lsi}
15370 PMON monitor for breakpoint commands.
15372 @item show monitor-warnings
15373 @kindex show monitor-warnings@r{, MIPS remote}
15374 Show the current setting of printing monitor warnings.
15376 @item pmon @var{command}
15377 @kindex pmon@r{, MIPS remote}
15378 @cindex send PMON command
15379 This command allows sending an arbitrary @var{command} string to the
15380 monitor. The monitor must be in debug mode for this to work.
15383 @node OpenRISC 1000
15384 @subsection OpenRISC 1000
15385 @cindex OpenRISC 1000
15387 @cindex or1k boards
15388 See OR1k Architecture document (@uref{www.opencores.org}) for more information
15389 about platform and commands.
15393 @kindex target jtag
15394 @item target jtag jtag://@var{host}:@var{port}
15396 Connects to remote JTAG server.
15397 JTAG remote server can be either an or1ksim or JTAG server,
15398 connected via parallel port to the board.
15400 Example: @code{target jtag jtag://localhost:9999}
15403 @item or1ksim @var{command}
15404 If connected to @code{or1ksim} OpenRISC 1000 Architectural
15405 Simulator, proprietary commands can be executed.
15407 @kindex info or1k spr
15408 @item info or1k spr
15409 Displays spr groups.
15411 @item info or1k spr @var{group}
15412 @itemx info or1k spr @var{groupno}
15413 Displays register names in selected group.
15415 @item info or1k spr @var{group} @var{register}
15416 @itemx info or1k spr @var{register}
15417 @itemx info or1k spr @var{groupno} @var{registerno}
15418 @itemx info or1k spr @var{registerno}
15419 Shows information about specified spr register.
15422 @item spr @var{group} @var{register} @var{value}
15423 @itemx spr @var{register @var{value}}
15424 @itemx spr @var{groupno} @var{registerno @var{value}}
15425 @itemx spr @var{registerno @var{value}}
15426 Writes @var{value} to specified spr register.
15429 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15430 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15431 program execution and is thus much faster. Hardware breakpoints/watchpoint
15432 triggers can be set using:
15435 Load effective address/data
15437 Store effective address/data
15439 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15444 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15445 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15447 @code{htrace} commands:
15448 @cindex OpenRISC 1000 htrace
15451 @item hwatch @var{conditional}
15452 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15453 or Data. For example:
15455 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15457 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15461 Display information about current HW trace configuration.
15463 @item htrace trigger @var{conditional}
15464 Set starting criteria for HW trace.
15466 @item htrace qualifier @var{conditional}
15467 Set acquisition qualifier for HW trace.
15469 @item htrace stop @var{conditional}
15470 Set HW trace stopping criteria.
15472 @item htrace record [@var{data}]*
15473 Selects the data to be recorded, when qualifier is met and HW trace was
15476 @item htrace enable
15477 @itemx htrace disable
15478 Enables/disables the HW trace.
15480 @item htrace rewind [@var{filename}]
15481 Clears currently recorded trace data.
15483 If filename is specified, new trace file is made and any newly collected data
15484 will be written there.
15486 @item htrace print [@var{start} [@var{len}]]
15487 Prints trace buffer, using current record configuration.
15489 @item htrace mode continuous
15490 Set continuous trace mode.
15492 @item htrace mode suspend
15493 Set suspend trace mode.
15497 @node PowerPC Embedded
15498 @subsection PowerPC Embedded
15500 @value{GDBN} provides the following PowerPC-specific commands:
15503 @kindex set powerpc
15504 @item set powerpc soft-float
15505 @itemx show powerpc soft-float
15506 Force @value{GDBN} to use (or not use) a software floating point calling
15507 convention. By default, @value{GDBN} selects the calling convention based
15508 on the selected architecture and the provided executable file.
15510 @item set powerpc vector-abi
15511 @itemx show powerpc vector-abi
15512 Force @value{GDBN} to use the specified calling convention for vector
15513 arguments and return values. The valid options are @samp{auto};
15514 @samp{generic}, to avoid vector registers even if they are present;
15515 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15516 registers. By default, @value{GDBN} selects the calling convention
15517 based on the selected architecture and the provided executable file.
15519 @kindex target dink32
15520 @item target dink32 @var{dev}
15521 DINK32 ROM monitor.
15523 @kindex target ppcbug
15524 @item target ppcbug @var{dev}
15525 @kindex target ppcbug1
15526 @item target ppcbug1 @var{dev}
15527 PPCBUG ROM monitor for PowerPC.
15530 @item target sds @var{dev}
15531 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15534 @cindex SDS protocol
15535 The following commands specific to the SDS protocol are supported
15539 @item set sdstimeout @var{nsec}
15540 @kindex set sdstimeout
15541 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15542 default is 2 seconds.
15544 @item show sdstimeout
15545 @kindex show sdstimeout
15546 Show the current value of the SDS timeout.
15548 @item sds @var{command}
15549 @kindex sds@r{, a command}
15550 Send the specified @var{command} string to the SDS monitor.
15555 @subsection HP PA Embedded
15559 @kindex target op50n
15560 @item target op50n @var{dev}
15561 OP50N monitor, running on an OKI HPPA board.
15563 @kindex target w89k
15564 @item target w89k @var{dev}
15565 W89K monitor, running on a Winbond HPPA board.
15570 @subsection Tsqware Sparclet
15574 @value{GDBN} enables developers to debug tasks running on
15575 Sparclet targets from a Unix host.
15576 @value{GDBN} uses code that runs on
15577 both the Unix host and on the Sparclet target. The program
15578 @code{@value{GDBP}} is installed and executed on the Unix host.
15581 @item remotetimeout @var{args}
15582 @kindex remotetimeout
15583 @value{GDBN} supports the option @code{remotetimeout}.
15584 This option is set by the user, and @var{args} represents the number of
15585 seconds @value{GDBN} waits for responses.
15588 @cindex compiling, on Sparclet
15589 When compiling for debugging, include the options @samp{-g} to get debug
15590 information and @samp{-Ttext} to relocate the program to where you wish to
15591 load it on the target. You may also want to add the options @samp{-n} or
15592 @samp{-N} in order to reduce the size of the sections. Example:
15595 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15598 You can use @code{objdump} to verify that the addresses are what you intended:
15601 sparclet-aout-objdump --headers --syms prog
15604 @cindex running, on Sparclet
15606 your Unix execution search path to find @value{GDBN}, you are ready to
15607 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15608 (or @code{sparclet-aout-gdb}, depending on your installation).
15610 @value{GDBN} comes up showing the prompt:
15617 * Sparclet File:: Setting the file to debug
15618 * Sparclet Connection:: Connecting to Sparclet
15619 * Sparclet Download:: Sparclet download
15620 * Sparclet Execution:: Running and debugging
15623 @node Sparclet File
15624 @subsubsection Setting File to Debug
15626 The @value{GDBN} command @code{file} lets you choose with program to debug.
15629 (gdbslet) file prog
15633 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15634 @value{GDBN} locates
15635 the file by searching the directories listed in the command search
15637 If the file was compiled with debug information (option @samp{-g}), source
15638 files will be searched as well.
15639 @value{GDBN} locates
15640 the source files by searching the directories listed in the directory search
15641 path (@pxref{Environment, ,Your Program's Environment}).
15643 to find a file, it displays a message such as:
15646 prog: No such file or directory.
15649 When this happens, add the appropriate directories to the search paths with
15650 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15651 @code{target} command again.
15653 @node Sparclet Connection
15654 @subsubsection Connecting to Sparclet
15656 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15657 To connect to a target on serial port ``@code{ttya}'', type:
15660 (gdbslet) target sparclet /dev/ttya
15661 Remote target sparclet connected to /dev/ttya
15662 main () at ../prog.c:3
15666 @value{GDBN} displays messages like these:
15672 @node Sparclet Download
15673 @subsubsection Sparclet Download
15675 @cindex download to Sparclet
15676 Once connected to the Sparclet target,
15677 you can use the @value{GDBN}
15678 @code{load} command to download the file from the host to the target.
15679 The file name and load offset should be given as arguments to the @code{load}
15681 Since the file format is aout, the program must be loaded to the starting
15682 address. You can use @code{objdump} to find out what this value is. The load
15683 offset is an offset which is added to the VMA (virtual memory address)
15684 of each of the file's sections.
15685 For instance, if the program
15686 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15687 and bss at 0x12010170, in @value{GDBN}, type:
15690 (gdbslet) load prog 0x12010000
15691 Loading section .text, size 0xdb0 vma 0x12010000
15694 If the code is loaded at a different address then what the program was linked
15695 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15696 to tell @value{GDBN} where to map the symbol table.
15698 @node Sparclet Execution
15699 @subsubsection Running and Debugging
15701 @cindex running and debugging Sparclet programs
15702 You can now begin debugging the task using @value{GDBN}'s execution control
15703 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15704 manual for the list of commands.
15708 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15710 Starting program: prog
15711 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15712 3 char *symarg = 0;
15714 4 char *execarg = "hello!";
15719 @subsection Fujitsu Sparclite
15723 @kindex target sparclite
15724 @item target sparclite @var{dev}
15725 Fujitsu sparclite boards, used only for the purpose of loading.
15726 You must use an additional command to debug the program.
15727 For example: target remote @var{dev} using @value{GDBN} standard
15733 @subsection Zilog Z8000
15736 @cindex simulator, Z8000
15737 @cindex Zilog Z8000 simulator
15739 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15742 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15743 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15744 segmented variant). The simulator recognizes which architecture is
15745 appropriate by inspecting the object code.
15748 @item target sim @var{args}
15750 @kindex target sim@r{, with Z8000}
15751 Debug programs on a simulated CPU. If the simulator supports setup
15752 options, specify them via @var{args}.
15756 After specifying this target, you can debug programs for the simulated
15757 CPU in the same style as programs for your host computer; use the
15758 @code{file} command to load a new program image, the @code{run} command
15759 to run your program, and so on.
15761 As well as making available all the usual machine registers
15762 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15763 additional items of information as specially named registers:
15768 Counts clock-ticks in the simulator.
15771 Counts instructions run in the simulator.
15774 Execution time in 60ths of a second.
15778 You can refer to these values in @value{GDBN} expressions with the usual
15779 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15780 conditional breakpoint that suspends only after at least 5000
15781 simulated clock ticks.
15784 @subsection Atmel AVR
15787 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15788 following AVR-specific commands:
15791 @item info io_registers
15792 @kindex info io_registers@r{, AVR}
15793 @cindex I/O registers (Atmel AVR)
15794 This command displays information about the AVR I/O registers. For
15795 each register, @value{GDBN} prints its number and value.
15802 When configured for debugging CRIS, @value{GDBN} provides the
15803 following CRIS-specific commands:
15806 @item set cris-version @var{ver}
15807 @cindex CRIS version
15808 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15809 The CRIS version affects register names and sizes. This command is useful in
15810 case autodetection of the CRIS version fails.
15812 @item show cris-version
15813 Show the current CRIS version.
15815 @item set cris-dwarf2-cfi
15816 @cindex DWARF-2 CFI and CRIS
15817 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15818 Change to @samp{off} when using @code{gcc-cris} whose version is below
15821 @item show cris-dwarf2-cfi
15822 Show the current state of using DWARF-2 CFI.
15824 @item set cris-mode @var{mode}
15826 Set the current CRIS mode to @var{mode}. It should only be changed when
15827 debugging in guru mode, in which case it should be set to
15828 @samp{guru} (the default is @samp{normal}).
15830 @item show cris-mode
15831 Show the current CRIS mode.
15835 @subsection Renesas Super-H
15838 For the Renesas Super-H processor, @value{GDBN} provides these
15843 @kindex regs@r{, Super-H}
15844 Show the values of all Super-H registers.
15846 @item set sh calling-convention @var{convention}
15847 @kindex set sh calling-convention
15848 Set the calling-convention used when calling functions from @value{GDBN}.
15849 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
15850 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
15851 convention. If the DWARF-2 information of the called function specifies
15852 that the function follows the Renesas calling convention, the function
15853 is called using the Renesas calling convention. If the calling convention
15854 is set to @samp{renesas}, the Renesas calling convention is always used,
15855 regardless of the DWARF-2 information. This can be used to override the
15856 default of @samp{gcc} if debug information is missing, or the compiler
15857 does not emit the DWARF-2 calling convention entry for a function.
15859 @item show sh calling-convention
15860 @kindex show sh calling-convention
15861 Show the current calling convention setting.
15866 @node Architectures
15867 @section Architectures
15869 This section describes characteristics of architectures that affect
15870 all uses of @value{GDBN} with the architecture, both native and cross.
15877 * HPPA:: HP PA architecture
15878 * SPU:: Cell Broadband Engine SPU architecture
15883 @subsection x86 Architecture-specific Issues
15886 @item set struct-convention @var{mode}
15887 @kindex set struct-convention
15888 @cindex struct return convention
15889 @cindex struct/union returned in registers
15890 Set the convention used by the inferior to return @code{struct}s and
15891 @code{union}s from functions to @var{mode}. Possible values of
15892 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15893 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15894 are returned on the stack, while @code{"reg"} means that a
15895 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15896 be returned in a register.
15898 @item show struct-convention
15899 @kindex show struct-convention
15900 Show the current setting of the convention to return @code{struct}s
15909 @kindex set rstack_high_address
15910 @cindex AMD 29K register stack
15911 @cindex register stack, AMD29K
15912 @item set rstack_high_address @var{address}
15913 On AMD 29000 family processors, registers are saved in a separate
15914 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15915 extent of this stack. Normally, @value{GDBN} just assumes that the
15916 stack is ``large enough''. This may result in @value{GDBN} referencing
15917 memory locations that do not exist. If necessary, you can get around
15918 this problem by specifying the ending address of the register stack with
15919 the @code{set rstack_high_address} command. The argument should be an
15920 address, which you probably want to precede with @samp{0x} to specify in
15923 @kindex show rstack_high_address
15924 @item show rstack_high_address
15925 Display the current limit of the register stack, on AMD 29000 family
15933 See the following section.
15938 @cindex stack on Alpha
15939 @cindex stack on MIPS
15940 @cindex Alpha stack
15942 Alpha- and MIPS-based computers use an unusual stack frame, which
15943 sometimes requires @value{GDBN} to search backward in the object code to
15944 find the beginning of a function.
15946 @cindex response time, MIPS debugging
15947 To improve response time (especially for embedded applications, where
15948 @value{GDBN} may be restricted to a slow serial line for this search)
15949 you may want to limit the size of this search, using one of these
15953 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15954 @item set heuristic-fence-post @var{limit}
15955 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15956 search for the beginning of a function. A value of @var{0} (the
15957 default) means there is no limit. However, except for @var{0}, the
15958 larger the limit the more bytes @code{heuristic-fence-post} must search
15959 and therefore the longer it takes to run. You should only need to use
15960 this command when debugging a stripped executable.
15962 @item show heuristic-fence-post
15963 Display the current limit.
15967 These commands are available @emph{only} when @value{GDBN} is configured
15968 for debugging programs on Alpha or MIPS processors.
15970 Several MIPS-specific commands are available when debugging MIPS
15974 @item set mips abi @var{arg}
15975 @kindex set mips abi
15976 @cindex set ABI for MIPS
15977 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15978 values of @var{arg} are:
15982 The default ABI associated with the current binary (this is the
15993 @item show mips abi
15994 @kindex show mips abi
15995 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15998 @itemx show mipsfpu
15999 @xref{MIPS Embedded, set mipsfpu}.
16001 @item set mips mask-address @var{arg}
16002 @kindex set mips mask-address
16003 @cindex MIPS addresses, masking
16004 This command determines whether the most-significant 32 bits of 64-bit
16005 MIPS addresses are masked off. The argument @var{arg} can be
16006 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16007 setting, which lets @value{GDBN} determine the correct value.
16009 @item show mips mask-address
16010 @kindex show mips mask-address
16011 Show whether the upper 32 bits of MIPS addresses are masked off or
16014 @item set remote-mips64-transfers-32bit-regs
16015 @kindex set remote-mips64-transfers-32bit-regs
16016 This command controls compatibility with 64-bit MIPS targets that
16017 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16018 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16019 and 64 bits for other registers, set this option to @samp{on}.
16021 @item show remote-mips64-transfers-32bit-regs
16022 @kindex show remote-mips64-transfers-32bit-regs
16023 Show the current setting of compatibility with older MIPS 64 targets.
16025 @item set debug mips
16026 @kindex set debug mips
16027 This command turns on and off debugging messages for the MIPS-specific
16028 target code in @value{GDBN}.
16030 @item show debug mips
16031 @kindex show debug mips
16032 Show the current setting of MIPS debugging messages.
16038 @cindex HPPA support
16040 When @value{GDBN} is debugging the HP PA architecture, it provides the
16041 following special commands:
16044 @item set debug hppa
16045 @kindex set debug hppa
16046 This command determines whether HPPA architecture-specific debugging
16047 messages are to be displayed.
16049 @item show debug hppa
16050 Show whether HPPA debugging messages are displayed.
16052 @item maint print unwind @var{address}
16053 @kindex maint print unwind@r{, HPPA}
16054 This command displays the contents of the unwind table entry at the
16055 given @var{address}.
16061 @subsection Cell Broadband Engine SPU architecture
16062 @cindex Cell Broadband Engine
16065 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16066 it provides the following special commands:
16069 @item info spu event
16071 Display SPU event facility status. Shows current event mask
16072 and pending event status.
16074 @item info spu signal
16075 Display SPU signal notification facility status. Shows pending
16076 signal-control word and signal notification mode of both signal
16077 notification channels.
16079 @item info spu mailbox
16080 Display SPU mailbox facility status. Shows all pending entries,
16081 in order of processing, in each of the SPU Write Outbound,
16082 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16085 Display MFC DMA status. Shows all pending commands in the MFC
16086 DMA queue. For each entry, opcode, tag, class IDs, effective
16087 and local store addresses and transfer size are shown.
16089 @item info spu proxydma
16090 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16091 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16092 and local store addresses and transfer size are shown.
16097 @subsection PowerPC
16098 @cindex PowerPC architecture
16100 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16101 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16102 numbers stored in the floating point registers. These values must be stored
16103 in two consecutive registers, always starting at an even register like
16104 @code{f0} or @code{f2}.
16106 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16107 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16108 @code{f2} and @code{f3} for @code{$dl1} and so on.
16111 @node Controlling GDB
16112 @chapter Controlling @value{GDBN}
16114 You can alter the way @value{GDBN} interacts with you by using the
16115 @code{set} command. For commands controlling how @value{GDBN} displays
16116 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16121 * Editing:: Command editing
16122 * Command History:: Command history
16123 * Screen Size:: Screen size
16124 * Numbers:: Numbers
16125 * ABI:: Configuring the current ABI
16126 * Messages/Warnings:: Optional warnings and messages
16127 * Debugging Output:: Optional messages about internal happenings
16135 @value{GDBN} indicates its readiness to read a command by printing a string
16136 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
16137 can change the prompt string with the @code{set prompt} command. For
16138 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
16139 the prompt in one of the @value{GDBN} sessions so that you can always tell
16140 which one you are talking to.
16142 @emph{Note:} @code{set prompt} does not add a space for you after the
16143 prompt you set. This allows you to set a prompt which ends in a space
16144 or a prompt that does not.
16148 @item set prompt @var{newprompt}
16149 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
16151 @kindex show prompt
16153 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
16157 @section Command Editing
16159 @cindex command line editing
16161 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
16162 @sc{gnu} library provides consistent behavior for programs which provide a
16163 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16164 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16165 substitution, and a storage and recall of command history across
16166 debugging sessions.
16168 You may control the behavior of command line editing in @value{GDBN} with the
16169 command @code{set}.
16172 @kindex set editing
16175 @itemx set editing on
16176 Enable command line editing (enabled by default).
16178 @item set editing off
16179 Disable command line editing.
16181 @kindex show editing
16183 Show whether command line editing is enabled.
16186 @xref{Command Line Editing}, for more details about the Readline
16187 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
16188 encouraged to read that chapter.
16190 @node Command History
16191 @section Command History
16192 @cindex command history
16194 @value{GDBN} can keep track of the commands you type during your
16195 debugging sessions, so that you can be certain of precisely what
16196 happened. Use these commands to manage the @value{GDBN} command
16199 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
16200 package, to provide the history facility. @xref{Using History
16201 Interactively}, for the detailed description of the History library.
16203 To issue a command to @value{GDBN} without affecting certain aspects of
16204 the state which is seen by users, prefix it with @samp{server }
16205 (@pxref{Server Prefix}). This
16206 means that this command will not affect the command history, nor will it
16207 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
16208 pressed on a line by itself.
16210 @cindex @code{server}, command prefix
16211 The server prefix does not affect the recording of values into the value
16212 history; to print a value without recording it into the value history,
16213 use the @code{output} command instead of the @code{print} command.
16215 Here is the description of @value{GDBN} commands related to command
16219 @cindex history substitution
16220 @cindex history file
16221 @kindex set history filename
16222 @cindex @env{GDBHISTFILE}, environment variable
16223 @item set history filename @var{fname}
16224 Set the name of the @value{GDBN} command history file to @var{fname}.
16225 This is the file where @value{GDBN} reads an initial command history
16226 list, and where it writes the command history from this session when it
16227 exits. You can access this list through history expansion or through
16228 the history command editing characters listed below. This file defaults
16229 to the value of the environment variable @code{GDBHISTFILE}, or to
16230 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16233 @cindex save command history
16234 @kindex set history save
16235 @item set history save
16236 @itemx set history save on
16237 Record command history in a file, whose name may be specified with the
16238 @code{set history filename} command. By default, this option is disabled.
16240 @item set history save off
16241 Stop recording command history in a file.
16243 @cindex history size
16244 @kindex set history size
16245 @cindex @env{HISTSIZE}, environment variable
16246 @item set history size @var{size}
16247 Set the number of commands which @value{GDBN} keeps in its history list.
16248 This defaults to the value of the environment variable
16249 @code{HISTSIZE}, or to 256 if this variable is not set.
16252 History expansion assigns special meaning to the character @kbd{!}.
16253 @xref{Event Designators}, for more details.
16255 @cindex history expansion, turn on/off
16256 Since @kbd{!} is also the logical not operator in C, history expansion
16257 is off by default. If you decide to enable history expansion with the
16258 @code{set history expansion on} command, you may sometimes need to
16259 follow @kbd{!} (when it is used as logical not, in an expression) with
16260 a space or a tab to prevent it from being expanded. The readline
16261 history facilities do not attempt substitution on the strings
16262 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
16264 The commands to control history expansion are:
16267 @item set history expansion on
16268 @itemx set history expansion
16269 @kindex set history expansion
16270 Enable history expansion. History expansion is off by default.
16272 @item set history expansion off
16273 Disable history expansion.
16276 @kindex show history
16278 @itemx show history filename
16279 @itemx show history save
16280 @itemx show history size
16281 @itemx show history expansion
16282 These commands display the state of the @value{GDBN} history parameters.
16283 @code{show history} by itself displays all four states.
16288 @kindex show commands
16289 @cindex show last commands
16290 @cindex display command history
16291 @item show commands
16292 Display the last ten commands in the command history.
16294 @item show commands @var{n}
16295 Print ten commands centered on command number @var{n}.
16297 @item show commands +
16298 Print ten commands just after the commands last printed.
16302 @section Screen Size
16303 @cindex size of screen
16304 @cindex pauses in output
16306 Certain commands to @value{GDBN} may produce large amounts of
16307 information output to the screen. To help you read all of it,
16308 @value{GDBN} pauses and asks you for input at the end of each page of
16309 output. Type @key{RET} when you want to continue the output, or @kbd{q}
16310 to discard the remaining output. Also, the screen width setting
16311 determines when to wrap lines of output. Depending on what is being
16312 printed, @value{GDBN} tries to break the line at a readable place,
16313 rather than simply letting it overflow onto the following line.
16315 Normally @value{GDBN} knows the size of the screen from the terminal
16316 driver software. For example, on Unix @value{GDBN} uses the termcap data base
16317 together with the value of the @code{TERM} environment variable and the
16318 @code{stty rows} and @code{stty cols} settings. If this is not correct,
16319 you can override it with the @code{set height} and @code{set
16326 @kindex show height
16327 @item set height @var{lpp}
16329 @itemx set width @var{cpl}
16331 These @code{set} commands specify a screen height of @var{lpp} lines and
16332 a screen width of @var{cpl} characters. The associated @code{show}
16333 commands display the current settings.
16335 If you specify a height of zero lines, @value{GDBN} does not pause during
16336 output no matter how long the output is. This is useful if output is to a
16337 file or to an editor buffer.
16339 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
16340 from wrapping its output.
16342 @item set pagination on
16343 @itemx set pagination off
16344 @kindex set pagination
16345 Turn the output pagination on or off; the default is on. Turning
16346 pagination off is the alternative to @code{set height 0}.
16348 @item show pagination
16349 @kindex show pagination
16350 Show the current pagination mode.
16355 @cindex number representation
16356 @cindex entering numbers
16358 You can always enter numbers in octal, decimal, or hexadecimal in
16359 @value{GDBN} by the usual conventions: octal numbers begin with
16360 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
16361 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
16362 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
16363 10; likewise, the default display for numbers---when no particular
16364 format is specified---is base 10. You can change the default base for
16365 both input and output with the commands described below.
16368 @kindex set input-radix
16369 @item set input-radix @var{base}
16370 Set the default base for numeric input. Supported choices
16371 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16372 specified either unambiguously or using the current input radix; for
16376 set input-radix 012
16377 set input-radix 10.
16378 set input-radix 0xa
16382 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
16383 leaves the input radix unchanged, no matter what it was, since
16384 @samp{10}, being without any leading or trailing signs of its base, is
16385 interpreted in the current radix. Thus, if the current radix is 16,
16386 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
16389 @kindex set output-radix
16390 @item set output-radix @var{base}
16391 Set the default base for numeric display. Supported choices
16392 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16393 specified either unambiguously or using the current input radix.
16395 @kindex show input-radix
16396 @item show input-radix
16397 Display the current default base for numeric input.
16399 @kindex show output-radix
16400 @item show output-radix
16401 Display the current default base for numeric display.
16403 @item set radix @r{[}@var{base}@r{]}
16407 These commands set and show the default base for both input and output
16408 of numbers. @code{set radix} sets the radix of input and output to
16409 the same base; without an argument, it resets the radix back to its
16410 default value of 10.
16415 @section Configuring the Current ABI
16417 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
16418 application automatically. However, sometimes you need to override its
16419 conclusions. Use these commands to manage @value{GDBN}'s view of the
16426 One @value{GDBN} configuration can debug binaries for multiple operating
16427 system targets, either via remote debugging or native emulation.
16428 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
16429 but you can override its conclusion using the @code{set osabi} command.
16430 One example where this is useful is in debugging of binaries which use
16431 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16432 not have the same identifying marks that the standard C library for your
16437 Show the OS ABI currently in use.
16440 With no argument, show the list of registered available OS ABI's.
16442 @item set osabi @var{abi}
16443 Set the current OS ABI to @var{abi}.
16446 @cindex float promotion
16448 Generally, the way that an argument of type @code{float} is passed to a
16449 function depends on whether the function is prototyped. For a prototyped
16450 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16451 according to the architecture's convention for @code{float}. For unprototyped
16452 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16453 @code{double} and then passed.
16455 Unfortunately, some forms of debug information do not reliably indicate whether
16456 a function is prototyped. If @value{GDBN} calls a function that is not marked
16457 as prototyped, it consults @kbd{set coerce-float-to-double}.
16460 @kindex set coerce-float-to-double
16461 @item set coerce-float-to-double
16462 @itemx set coerce-float-to-double on
16463 Arguments of type @code{float} will be promoted to @code{double} when passed
16464 to an unprototyped function. This is the default setting.
16466 @item set coerce-float-to-double off
16467 Arguments of type @code{float} will be passed directly to unprototyped
16470 @kindex show coerce-float-to-double
16471 @item show coerce-float-to-double
16472 Show the current setting of promoting @code{float} to @code{double}.
16476 @kindex show cp-abi
16477 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16478 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16479 used to build your application. @value{GDBN} only fully supports
16480 programs with a single C@t{++} ABI; if your program contains code using
16481 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16482 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16483 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16484 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16485 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16486 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16491 Show the C@t{++} ABI currently in use.
16494 With no argument, show the list of supported C@t{++} ABI's.
16496 @item set cp-abi @var{abi}
16497 @itemx set cp-abi auto
16498 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16501 @node Messages/Warnings
16502 @section Optional Warnings and Messages
16504 @cindex verbose operation
16505 @cindex optional warnings
16506 By default, @value{GDBN} is silent about its inner workings. If you are
16507 running on a slow machine, you may want to use the @code{set verbose}
16508 command. This makes @value{GDBN} tell you when it does a lengthy
16509 internal operation, so you will not think it has crashed.
16511 Currently, the messages controlled by @code{set verbose} are those
16512 which announce that the symbol table for a source file is being read;
16513 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16516 @kindex set verbose
16517 @item set verbose on
16518 Enables @value{GDBN} output of certain informational messages.
16520 @item set verbose off
16521 Disables @value{GDBN} output of certain informational messages.
16523 @kindex show verbose
16525 Displays whether @code{set verbose} is on or off.
16528 By default, if @value{GDBN} encounters bugs in the symbol table of an
16529 object file, it is silent; but if you are debugging a compiler, you may
16530 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16535 @kindex set complaints
16536 @item set complaints @var{limit}
16537 Permits @value{GDBN} to output @var{limit} complaints about each type of
16538 unusual symbols before becoming silent about the problem. Set
16539 @var{limit} to zero to suppress all complaints; set it to a large number
16540 to prevent complaints from being suppressed.
16542 @kindex show complaints
16543 @item show complaints
16544 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16548 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16549 lot of stupid questions to confirm certain commands. For example, if
16550 you try to run a program which is already running:
16554 The program being debugged has been started already.
16555 Start it from the beginning? (y or n)
16558 If you are willing to unflinchingly face the consequences of your own
16559 commands, you can disable this ``feature'':
16563 @kindex set confirm
16565 @cindex confirmation
16566 @cindex stupid questions
16567 @item set confirm off
16568 Disables confirmation requests.
16570 @item set confirm on
16571 Enables confirmation requests (the default).
16573 @kindex show confirm
16575 Displays state of confirmation requests.
16579 @cindex command tracing
16580 If you need to debug user-defined commands or sourced files you may find it
16581 useful to enable @dfn{command tracing}. In this mode each command will be
16582 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16583 quantity denoting the call depth of each command.
16586 @kindex set trace-commands
16587 @cindex command scripts, debugging
16588 @item set trace-commands on
16589 Enable command tracing.
16590 @item set trace-commands off
16591 Disable command tracing.
16592 @item show trace-commands
16593 Display the current state of command tracing.
16596 @node Debugging Output
16597 @section Optional Messages about Internal Happenings
16598 @cindex optional debugging messages
16600 @value{GDBN} has commands that enable optional debugging messages from
16601 various @value{GDBN} subsystems; normally these commands are of
16602 interest to @value{GDBN} maintainers, or when reporting a bug. This
16603 section documents those commands.
16606 @kindex set exec-done-display
16607 @item set exec-done-display
16608 Turns on or off the notification of asynchronous commands'
16609 completion. When on, @value{GDBN} will print a message when an
16610 asynchronous command finishes its execution. The default is off.
16611 @kindex show exec-done-display
16612 @item show exec-done-display
16613 Displays the current setting of asynchronous command completion
16616 @cindex gdbarch debugging info
16617 @cindex architecture debugging info
16618 @item set debug arch
16619 Turns on or off display of gdbarch debugging info. The default is off
16621 @item show debug arch
16622 Displays the current state of displaying gdbarch debugging info.
16623 @item set debug aix-thread
16624 @cindex AIX threads
16625 Display debugging messages about inner workings of the AIX thread
16627 @item show debug aix-thread
16628 Show the current state of AIX thread debugging info display.
16629 @item set debug displaced
16630 @cindex displaced stepping debugging info
16631 Turns on or off display of @value{GDBN} debugging info for the
16632 displaced stepping support. The default is off.
16633 @item show debug displaced
16634 Displays the current state of displaying @value{GDBN} debugging info
16635 related to displaced stepping.
16636 @item set debug event
16637 @cindex event debugging info
16638 Turns on or off display of @value{GDBN} event debugging info. The
16640 @item show debug event
16641 Displays the current state of displaying @value{GDBN} event debugging
16643 @item set debug expression
16644 @cindex expression debugging info
16645 Turns on or off display of debugging info about @value{GDBN}
16646 expression parsing. The default is off.
16647 @item show debug expression
16648 Displays the current state of displaying debugging info about
16649 @value{GDBN} expression parsing.
16650 @item set debug frame
16651 @cindex frame debugging info
16652 Turns on or off display of @value{GDBN} frame debugging info. The
16654 @item show debug frame
16655 Displays the current state of displaying @value{GDBN} frame debugging
16657 @item set debug infrun
16658 @cindex inferior debugging info
16659 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16660 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16661 for implementing operations such as single-stepping the inferior.
16662 @item show debug infrun
16663 Displays the current state of @value{GDBN} inferior debugging.
16664 @item set debug lin-lwp
16665 @cindex @sc{gnu}/Linux LWP debug messages
16666 @cindex Linux lightweight processes
16667 Turns on or off debugging messages from the Linux LWP debug support.
16668 @item show debug lin-lwp
16669 Show the current state of Linux LWP debugging messages.
16670 @item set debug lin-lwp-async
16671 @cindex @sc{gnu}/Linux LWP async debug messages
16672 @cindex Linux lightweight processes
16673 Turns on or off debugging messages from the Linux LWP async debug support.
16674 @item show debug lin-lwp-async
16675 Show the current state of Linux LWP async debugging messages.
16676 @item set debug observer
16677 @cindex observer debugging info
16678 Turns on or off display of @value{GDBN} observer debugging. This
16679 includes info such as the notification of observable events.
16680 @item show debug observer
16681 Displays the current state of observer debugging.
16682 @item set debug overload
16683 @cindex C@t{++} overload debugging info
16684 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16685 info. This includes info such as ranking of functions, etc. The default
16687 @item show debug overload
16688 Displays the current state of displaying @value{GDBN} C@t{++} overload
16690 @cindex packets, reporting on stdout
16691 @cindex serial connections, debugging
16692 @cindex debug remote protocol
16693 @cindex remote protocol debugging
16694 @cindex display remote packets
16695 @item set debug remote
16696 Turns on or off display of reports on all packets sent back and forth across
16697 the serial line to the remote machine. The info is printed on the
16698 @value{GDBN} standard output stream. The default is off.
16699 @item show debug remote
16700 Displays the state of display of remote packets.
16701 @item set debug serial
16702 Turns on or off display of @value{GDBN} serial debugging info. The
16704 @item show debug serial
16705 Displays the current state of displaying @value{GDBN} serial debugging
16707 @item set debug solib-frv
16708 @cindex FR-V shared-library debugging
16709 Turns on or off debugging messages for FR-V shared-library code.
16710 @item show debug solib-frv
16711 Display the current state of FR-V shared-library code debugging
16713 @item set debug target
16714 @cindex target debugging info
16715 Turns on or off display of @value{GDBN} target debugging info. This info
16716 includes what is going on at the target level of GDB, as it happens. The
16717 default is 0. Set it to 1 to track events, and to 2 to also track the
16718 value of large memory transfers. Changes to this flag do not take effect
16719 until the next time you connect to a target or use the @code{run} command.
16720 @item show debug target
16721 Displays the current state of displaying @value{GDBN} target debugging
16723 @item set debug timestamp
16724 @cindex timestampping debugging info
16725 Turns on or off display of timestamps with @value{GDBN} debugging info.
16726 When enabled, seconds and microseconds are displayed before each debugging
16728 @item show debug timestamp
16729 Displays the current state of displaying timestamps with @value{GDBN}
16731 @item set debugvarobj
16732 @cindex variable object debugging info
16733 Turns on or off display of @value{GDBN} variable object debugging
16734 info. The default is off.
16735 @item show debugvarobj
16736 Displays the current state of displaying @value{GDBN} variable object
16738 @item set debug xml
16739 @cindex XML parser debugging
16740 Turns on or off debugging messages for built-in XML parsers.
16741 @item show debug xml
16742 Displays the current state of XML debugging messages.
16746 @chapter Canned Sequences of Commands
16748 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16749 Command Lists}), @value{GDBN} provides two ways to store sequences of
16750 commands for execution as a unit: user-defined commands and command
16754 * Define:: How to define your own commands
16755 * Hooks:: Hooks for user-defined commands
16756 * Command Files:: How to write scripts of commands to be stored in a file
16757 * Output:: Commands for controlled output
16761 @section User-defined Commands
16763 @cindex user-defined command
16764 @cindex arguments, to user-defined commands
16765 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16766 which you assign a new name as a command. This is done with the
16767 @code{define} command. User commands may accept up to 10 arguments
16768 separated by whitespace. Arguments are accessed within the user command
16769 via @code{$arg0@dots{}$arg9}. A trivial example:
16773 print $arg0 + $arg1 + $arg2
16778 To execute the command use:
16785 This defines the command @code{adder}, which prints the sum of
16786 its three arguments. Note the arguments are text substitutions, so they may
16787 reference variables, use complex expressions, or even perform inferior
16790 @cindex argument count in user-defined commands
16791 @cindex how many arguments (user-defined commands)
16792 In addition, @code{$argc} may be used to find out how many arguments have
16793 been passed. This expands to a number in the range 0@dots{}10.
16798 print $arg0 + $arg1
16801 print $arg0 + $arg1 + $arg2
16809 @item define @var{commandname}
16810 Define a command named @var{commandname}. If there is already a command
16811 by that name, you are asked to confirm that you want to redefine it.
16813 The definition of the command is made up of other @value{GDBN} command lines,
16814 which are given following the @code{define} command. The end of these
16815 commands is marked by a line containing @code{end}.
16818 @kindex end@r{ (user-defined commands)}
16819 @item document @var{commandname}
16820 Document the user-defined command @var{commandname}, so that it can be
16821 accessed by @code{help}. The command @var{commandname} must already be
16822 defined. This command reads lines of documentation just as @code{define}
16823 reads the lines of the command definition, ending with @code{end}.
16824 After the @code{document} command is finished, @code{help} on command
16825 @var{commandname} displays the documentation you have written.
16827 You may use the @code{document} command again to change the
16828 documentation of a command. Redefining the command with @code{define}
16829 does not change the documentation.
16831 @kindex dont-repeat
16832 @cindex don't repeat command
16834 Used inside a user-defined command, this tells @value{GDBN} that this
16835 command should not be repeated when the user hits @key{RET}
16836 (@pxref{Command Syntax, repeat last command}).
16838 @kindex help user-defined
16839 @item help user-defined
16840 List all user-defined commands, with the first line of the documentation
16845 @itemx show user @var{commandname}
16846 Display the @value{GDBN} commands used to define @var{commandname} (but
16847 not its documentation). If no @var{commandname} is given, display the
16848 definitions for all user-defined commands.
16850 @cindex infinite recursion in user-defined commands
16851 @kindex show max-user-call-depth
16852 @kindex set max-user-call-depth
16853 @item show max-user-call-depth
16854 @itemx set max-user-call-depth
16855 The value of @code{max-user-call-depth} controls how many recursion
16856 levels are allowed in user-defined commands before @value{GDBN} suspects an
16857 infinite recursion and aborts the command.
16860 In addition to the above commands, user-defined commands frequently
16861 use control flow commands, described in @ref{Command Files}.
16863 When user-defined commands are executed, the
16864 commands of the definition are not printed. An error in any command
16865 stops execution of the user-defined command.
16867 If used interactively, commands that would ask for confirmation proceed
16868 without asking when used inside a user-defined command. Many @value{GDBN}
16869 commands that normally print messages to say what they are doing omit the
16870 messages when used in a user-defined command.
16873 @section User-defined Command Hooks
16874 @cindex command hooks
16875 @cindex hooks, for commands
16876 @cindex hooks, pre-command
16879 You may define @dfn{hooks}, which are a special kind of user-defined
16880 command. Whenever you run the command @samp{foo}, if the user-defined
16881 command @samp{hook-foo} exists, it is executed (with no arguments)
16882 before that command.
16884 @cindex hooks, post-command
16886 A hook may also be defined which is run after the command you executed.
16887 Whenever you run the command @samp{foo}, if the user-defined command
16888 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16889 that command. Post-execution hooks may exist simultaneously with
16890 pre-execution hooks, for the same command.
16892 It is valid for a hook to call the command which it hooks. If this
16893 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16895 @c It would be nice if hookpost could be passed a parameter indicating
16896 @c if the command it hooks executed properly or not. FIXME!
16898 @kindex stop@r{, a pseudo-command}
16899 In addition, a pseudo-command, @samp{stop} exists. Defining
16900 (@samp{hook-stop}) makes the associated commands execute every time
16901 execution stops in your program: before breakpoint commands are run,
16902 displays are printed, or the stack frame is printed.
16904 For example, to ignore @code{SIGALRM} signals while
16905 single-stepping, but treat them normally during normal execution,
16910 handle SIGALRM nopass
16914 handle SIGALRM pass
16917 define hook-continue
16918 handle SIGALRM pass
16922 As a further example, to hook at the beginning and end of the @code{echo}
16923 command, and to add extra text to the beginning and end of the message,
16931 define hookpost-echo
16935 (@value{GDBP}) echo Hello World
16936 <<<---Hello World--->>>
16941 You can define a hook for any single-word command in @value{GDBN}, but
16942 not for command aliases; you should define a hook for the basic command
16943 name, e.g.@: @code{backtrace} rather than @code{bt}.
16944 @c FIXME! So how does Joe User discover whether a command is an alias
16946 If an error occurs during the execution of your hook, execution of
16947 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16948 (before the command that you actually typed had a chance to run).
16950 If you try to define a hook which does not match any known command, you
16951 get a warning from the @code{define} command.
16953 @node Command Files
16954 @section Command Files
16956 @cindex command files
16957 @cindex scripting commands
16958 A command file for @value{GDBN} is a text file made of lines that are
16959 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16960 also be included. An empty line in a command file does nothing; it
16961 does not mean to repeat the last command, as it would from the
16964 You can request the execution of a command file with the @code{source}
16969 @cindex execute commands from a file
16970 @item source [@code{-v}] @var{filename}
16971 Execute the command file @var{filename}.
16974 The lines in a command file are generally executed sequentially,
16975 unless the order of execution is changed by one of the
16976 @emph{flow-control commands} described below. The commands are not
16977 printed as they are executed. An error in any command terminates
16978 execution of the command file and control is returned to the console.
16980 @value{GDBN} searches for @var{filename} in the current directory and then
16981 on the search path (specified with the @samp{directory} command).
16983 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16984 each command as it is executed. The option must be given before
16985 @var{filename}, and is interpreted as part of the filename anywhere else.
16987 Commands that would ask for confirmation if used interactively proceed
16988 without asking when used in a command file. Many @value{GDBN} commands that
16989 normally print messages to say what they are doing omit the messages
16990 when called from command files.
16992 @value{GDBN} also accepts command input from standard input. In this
16993 mode, normal output goes to standard output and error output goes to
16994 standard error. Errors in a command file supplied on standard input do
16995 not terminate execution of the command file---execution continues with
16999 gdb < cmds > log 2>&1
17002 (The syntax above will vary depending on the shell used.) This example
17003 will execute commands from the file @file{cmds}. All output and errors
17004 would be directed to @file{log}.
17006 Since commands stored on command files tend to be more general than
17007 commands typed interactively, they frequently need to deal with
17008 complicated situations, such as different or unexpected values of
17009 variables and symbols, changes in how the program being debugged is
17010 built, etc. @value{GDBN} provides a set of flow-control commands to
17011 deal with these complexities. Using these commands, you can write
17012 complex scripts that loop over data structures, execute commands
17013 conditionally, etc.
17020 This command allows to include in your script conditionally executed
17021 commands. The @code{if} command takes a single argument, which is an
17022 expression to evaluate. It is followed by a series of commands that
17023 are executed only if the expression is true (its value is nonzero).
17024 There can then optionally be an @code{else} line, followed by a series
17025 of commands that are only executed if the expression was false. The
17026 end of the list is marked by a line containing @code{end}.
17030 This command allows to write loops. Its syntax is similar to
17031 @code{if}: the command takes a single argument, which is an expression
17032 to evaluate, and must be followed by the commands to execute, one per
17033 line, terminated by an @code{end}. These commands are called the
17034 @dfn{body} of the loop. The commands in the body of @code{while} are
17035 executed repeatedly as long as the expression evaluates to true.
17039 This command exits the @code{while} loop in whose body it is included.
17040 Execution of the script continues after that @code{while}s @code{end}
17043 @kindex loop_continue
17044 @item loop_continue
17045 This command skips the execution of the rest of the body of commands
17046 in the @code{while} loop in whose body it is included. Execution
17047 branches to the beginning of the @code{while} loop, where it evaluates
17048 the controlling expression.
17050 @kindex end@r{ (if/else/while commands)}
17052 Terminate the block of commands that are the body of @code{if},
17053 @code{else}, or @code{while} flow-control commands.
17058 @section Commands for Controlled Output
17060 During the execution of a command file or a user-defined command, normal
17061 @value{GDBN} output is suppressed; the only output that appears is what is
17062 explicitly printed by the commands in the definition. This section
17063 describes three commands useful for generating exactly the output you
17068 @item echo @var{text}
17069 @c I do not consider backslash-space a standard C escape sequence
17070 @c because it is not in ANSI.
17071 Print @var{text}. Nonprinting characters can be included in
17072 @var{text} using C escape sequences, such as @samp{\n} to print a
17073 newline. @strong{No newline is printed unless you specify one.}
17074 In addition to the standard C escape sequences, a backslash followed
17075 by a space stands for a space. This is useful for displaying a
17076 string with spaces at the beginning or the end, since leading and
17077 trailing spaces are otherwise trimmed from all arguments.
17078 To print @samp{@w{ }and foo =@w{ }}, use the command
17079 @samp{echo \@w{ }and foo = \@w{ }}.
17081 A backslash at the end of @var{text} can be used, as in C, to continue
17082 the command onto subsequent lines. For example,
17085 echo This is some text\n\
17086 which is continued\n\
17087 onto several lines.\n
17090 produces the same output as
17093 echo This is some text\n
17094 echo which is continued\n
17095 echo onto several lines.\n
17099 @item output @var{expression}
17100 Print the value of @var{expression} and nothing but that value: no
17101 newlines, no @samp{$@var{nn} = }. The value is not entered in the
17102 value history either. @xref{Expressions, ,Expressions}, for more information
17105 @item output/@var{fmt} @var{expression}
17106 Print the value of @var{expression} in format @var{fmt}. You can use
17107 the same formats as for @code{print}. @xref{Output Formats,,Output
17108 Formats}, for more information.
17111 @item printf @var{template}, @var{expressions}@dots{}
17112 Print the values of one or more @var{expressions} under the control of
17113 the string @var{template}. To print several values, make
17114 @var{expressions} be a comma-separated list of individual expressions,
17115 which may be either numbers or pointers. Their values are printed as
17116 specified by @var{template}, exactly as a C program would do by
17117 executing the code below:
17120 printf (@var{template}, @var{expressions}@dots{});
17123 As in @code{C} @code{printf}, ordinary characters in @var{template}
17124 are printed verbatim, while @dfn{conversion specification} introduced
17125 by the @samp{%} character cause subsequent @var{expressions} to be
17126 evaluated, their values converted and formatted according to type and
17127 style information encoded in the conversion specifications, and then
17130 For example, you can print two values in hex like this:
17133 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
17136 @code{printf} supports all the standard @code{C} conversion
17137 specifications, including the flags and modifiers between the @samp{%}
17138 character and the conversion letter, with the following exceptions:
17142 The argument-ordering modifiers, such as @samp{2$}, are not supported.
17145 The modifier @samp{*} is not supported for specifying precision or
17149 The @samp{'} flag (for separation of digits into groups according to
17150 @code{LC_NUMERIC'}) is not supported.
17153 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
17157 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
17160 The conversion letters @samp{a} and @samp{A} are not supported.
17164 Note that the @samp{ll} type modifier is supported only if the
17165 underlying @code{C} implementation used to build @value{GDBN} supports
17166 the @code{long long int} type, and the @samp{L} type modifier is
17167 supported only if @code{long double} type is available.
17169 As in @code{C}, @code{printf} supports simple backslash-escape
17170 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
17171 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
17172 single character. Octal and hexadecimal escape sequences are not
17175 Additionally, @code{printf} supports conversion specifications for DFP
17176 (@dfn{Decimal Floating Point}) types using the following length modifiers
17177 together with a floating point specifier.
17182 @samp{H} for printing @code{Decimal32} types.
17185 @samp{D} for printing @code{Decimal64} types.
17188 @samp{DD} for printing @code{Decimal128} types.
17191 If the underlying @code{C} implementation used to build @value{GDBN} has
17192 support for the three length modifiers for DFP types, other modifiers
17193 such as width and precision will also be available for @value{GDBN} to use.
17195 In case there is no such @code{C} support, no additional modifiers will be
17196 available and the value will be printed in the standard way.
17198 Here's an example of printing DFP types using the above conversion letters:
17200 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
17206 @chapter Command Interpreters
17207 @cindex command interpreters
17209 @value{GDBN} supports multiple command interpreters, and some command
17210 infrastructure to allow users or user interface writers to switch
17211 between interpreters or run commands in other interpreters.
17213 @value{GDBN} currently supports two command interpreters, the console
17214 interpreter (sometimes called the command-line interpreter or @sc{cli})
17215 and the machine interface interpreter (or @sc{gdb/mi}). This manual
17216 describes both of these interfaces in great detail.
17218 By default, @value{GDBN} will start with the console interpreter.
17219 However, the user may choose to start @value{GDBN} with another
17220 interpreter by specifying the @option{-i} or @option{--interpreter}
17221 startup options. Defined interpreters include:
17225 @cindex console interpreter
17226 The traditional console or command-line interpreter. This is the most often
17227 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
17228 @value{GDBN} will use this interpreter.
17231 @cindex mi interpreter
17232 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
17233 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
17234 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
17238 @cindex mi2 interpreter
17239 The current @sc{gdb/mi} interface.
17242 @cindex mi1 interpreter
17243 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
17247 @cindex invoke another interpreter
17248 The interpreter being used by @value{GDBN} may not be dynamically
17249 switched at runtime. Although possible, this could lead to a very
17250 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
17251 enters the command "interpreter-set console" in a console view,
17252 @value{GDBN} would switch to using the console interpreter, rendering
17253 the IDE inoperable!
17255 @kindex interpreter-exec
17256 Although you may only choose a single interpreter at startup, you may execute
17257 commands in any interpreter from the current interpreter using the appropriate
17258 command. If you are running the console interpreter, simply use the
17259 @code{interpreter-exec} command:
17262 interpreter-exec mi "-data-list-register-names"
17265 @sc{gdb/mi} has a similar command, although it is only available in versions of
17266 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
17269 @chapter @value{GDBN} Text User Interface
17271 @cindex Text User Interface
17274 * TUI Overview:: TUI overview
17275 * TUI Keys:: TUI key bindings
17276 * TUI Single Key Mode:: TUI single key mode
17277 * TUI Commands:: TUI-specific commands
17278 * TUI Configuration:: TUI configuration variables
17281 The @value{GDBN} Text User Interface (TUI) is a terminal
17282 interface which uses the @code{curses} library to show the source
17283 file, the assembly output, the program registers and @value{GDBN}
17284 commands in separate text windows. The TUI mode is supported only
17285 on platforms where a suitable version of the @code{curses} library
17288 @pindex @value{GDBTUI}
17289 The TUI mode is enabled by default when you invoke @value{GDBN} as
17290 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
17291 You can also switch in and out of TUI mode while @value{GDBN} runs by
17292 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
17293 @xref{TUI Keys, ,TUI Key Bindings}.
17296 @section TUI Overview
17298 In TUI mode, @value{GDBN} can display several text windows:
17302 This window is the @value{GDBN} command window with the @value{GDBN}
17303 prompt and the @value{GDBN} output. The @value{GDBN} input is still
17304 managed using readline.
17307 The source window shows the source file of the program. The current
17308 line and active breakpoints are displayed in this window.
17311 The assembly window shows the disassembly output of the program.
17314 This window shows the processor registers. Registers are highlighted
17315 when their values change.
17318 The source and assembly windows show the current program position
17319 by highlighting the current line and marking it with a @samp{>} marker.
17320 Breakpoints are indicated with two markers. The first marker
17321 indicates the breakpoint type:
17325 Breakpoint which was hit at least once.
17328 Breakpoint which was never hit.
17331 Hardware breakpoint which was hit at least once.
17334 Hardware breakpoint which was never hit.
17337 The second marker indicates whether the breakpoint is enabled or not:
17341 Breakpoint is enabled.
17344 Breakpoint is disabled.
17347 The source, assembly and register windows are updated when the current
17348 thread changes, when the frame changes, or when the program counter
17351 These windows are not all visible at the same time. The command
17352 window is always visible. The others can be arranged in several
17363 source and assembly,
17366 source and registers, or
17369 assembly and registers.
17372 A status line above the command window shows the following information:
17376 Indicates the current @value{GDBN} target.
17377 (@pxref{Targets, ,Specifying a Debugging Target}).
17380 Gives the current process or thread number.
17381 When no process is being debugged, this field is set to @code{No process}.
17384 Gives the current function name for the selected frame.
17385 The name is demangled if demangling is turned on (@pxref{Print Settings}).
17386 When there is no symbol corresponding to the current program counter,
17387 the string @code{??} is displayed.
17390 Indicates the current line number for the selected frame.
17391 When the current line number is not known, the string @code{??} is displayed.
17394 Indicates the current program counter address.
17398 @section TUI Key Bindings
17399 @cindex TUI key bindings
17401 The TUI installs several key bindings in the readline keymaps
17402 (@pxref{Command Line Editing}). The following key bindings
17403 are installed for both TUI mode and the @value{GDBN} standard mode.
17412 Enter or leave the TUI mode. When leaving the TUI mode,
17413 the curses window management stops and @value{GDBN} operates using
17414 its standard mode, writing on the terminal directly. When reentering
17415 the TUI mode, control is given back to the curses windows.
17416 The screen is then refreshed.
17420 Use a TUI layout with only one window. The layout will
17421 either be @samp{source} or @samp{assembly}. When the TUI mode
17422 is not active, it will switch to the TUI mode.
17424 Think of this key binding as the Emacs @kbd{C-x 1} binding.
17428 Use a TUI layout with at least two windows. When the current
17429 layout already has two windows, the next layout with two windows is used.
17430 When a new layout is chosen, one window will always be common to the
17431 previous layout and the new one.
17433 Think of it as the Emacs @kbd{C-x 2} binding.
17437 Change the active window. The TUI associates several key bindings
17438 (like scrolling and arrow keys) with the active window. This command
17439 gives the focus to the next TUI window.
17441 Think of it as the Emacs @kbd{C-x o} binding.
17445 Switch in and out of the TUI SingleKey mode that binds single
17446 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
17449 The following key bindings only work in the TUI mode:
17454 Scroll the active window one page up.
17458 Scroll the active window one page down.
17462 Scroll the active window one line up.
17466 Scroll the active window one line down.
17470 Scroll the active window one column left.
17474 Scroll the active window one column right.
17478 Refresh the screen.
17481 Because the arrow keys scroll the active window in the TUI mode, they
17482 are not available for their normal use by readline unless the command
17483 window has the focus. When another window is active, you must use
17484 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
17485 and @kbd{C-f} to control the command window.
17487 @node TUI Single Key Mode
17488 @section TUI Single Key Mode
17489 @cindex TUI single key mode
17491 The TUI also provides a @dfn{SingleKey} mode, which binds several
17492 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
17493 switch into this mode, where the following key bindings are used:
17496 @kindex c @r{(SingleKey TUI key)}
17500 @kindex d @r{(SingleKey TUI key)}
17504 @kindex f @r{(SingleKey TUI key)}
17508 @kindex n @r{(SingleKey TUI key)}
17512 @kindex q @r{(SingleKey TUI key)}
17514 exit the SingleKey mode.
17516 @kindex r @r{(SingleKey TUI key)}
17520 @kindex s @r{(SingleKey TUI key)}
17524 @kindex u @r{(SingleKey TUI key)}
17528 @kindex v @r{(SingleKey TUI key)}
17532 @kindex w @r{(SingleKey TUI key)}
17537 Other keys temporarily switch to the @value{GDBN} command prompt.
17538 The key that was pressed is inserted in the editing buffer so that
17539 it is possible to type most @value{GDBN} commands without interaction
17540 with the TUI SingleKey mode. Once the command is entered the TUI
17541 SingleKey mode is restored. The only way to permanently leave
17542 this mode is by typing @kbd{q} or @kbd{C-x s}.
17546 @section TUI-specific Commands
17547 @cindex TUI commands
17549 The TUI has specific commands to control the text windows.
17550 These commands are always available, even when @value{GDBN} is not in
17551 the TUI mode. When @value{GDBN} is in the standard mode, most
17552 of these commands will automatically switch to the TUI mode.
17557 List and give the size of all displayed windows.
17561 Display the next layout.
17564 Display the previous layout.
17567 Display the source window only.
17570 Display the assembly window only.
17573 Display the source and assembly window.
17576 Display the register window together with the source or assembly window.
17580 Make the next window active for scrolling.
17583 Make the previous window active for scrolling.
17586 Make the source window active for scrolling.
17589 Make the assembly window active for scrolling.
17592 Make the register window active for scrolling.
17595 Make the command window active for scrolling.
17599 Refresh the screen. This is similar to typing @kbd{C-L}.
17601 @item tui reg float
17603 Show the floating point registers in the register window.
17605 @item tui reg general
17606 Show the general registers in the register window.
17609 Show the next register group. The list of register groups as well as
17610 their order is target specific. The predefined register groups are the
17611 following: @code{general}, @code{float}, @code{system}, @code{vector},
17612 @code{all}, @code{save}, @code{restore}.
17614 @item tui reg system
17615 Show the system registers in the register window.
17619 Update the source window and the current execution point.
17621 @item winheight @var{name} +@var{count}
17622 @itemx winheight @var{name} -@var{count}
17624 Change the height of the window @var{name} by @var{count}
17625 lines. Positive counts increase the height, while negative counts
17628 @item tabset @var{nchars}
17630 Set the width of tab stops to be @var{nchars} characters.
17633 @node TUI Configuration
17634 @section TUI Configuration Variables
17635 @cindex TUI configuration variables
17637 Several configuration variables control the appearance of TUI windows.
17640 @item set tui border-kind @var{kind}
17641 @kindex set tui border-kind
17642 Select the border appearance for the source, assembly and register windows.
17643 The possible values are the following:
17646 Use a space character to draw the border.
17649 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
17652 Use the Alternate Character Set to draw the border. The border is
17653 drawn using character line graphics if the terminal supports them.
17656 @item set tui border-mode @var{mode}
17657 @kindex set tui border-mode
17658 @itemx set tui active-border-mode @var{mode}
17659 @kindex set tui active-border-mode
17660 Select the display attributes for the borders of the inactive windows
17661 or the active window. The @var{mode} can be one of the following:
17664 Use normal attributes to display the border.
17670 Use reverse video mode.
17673 Use half bright mode.
17675 @item half-standout
17676 Use half bright and standout mode.
17679 Use extra bright or bold mode.
17681 @item bold-standout
17682 Use extra bright or bold and standout mode.
17687 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17690 @cindex @sc{gnu} Emacs
17691 A special interface allows you to use @sc{gnu} Emacs to view (and
17692 edit) the source files for the program you are debugging with
17695 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17696 executable file you want to debug as an argument. This command starts
17697 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17698 created Emacs buffer.
17699 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17701 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17706 All ``terminal'' input and output goes through an Emacs buffer, called
17709 This applies both to @value{GDBN} commands and their output, and to the input
17710 and output done by the program you are debugging.
17712 This is useful because it means that you can copy the text of previous
17713 commands and input them again; you can even use parts of the output
17716 All the facilities of Emacs' Shell mode are available for interacting
17717 with your program. In particular, you can send signals the usual
17718 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17722 @value{GDBN} displays source code through Emacs.
17724 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17725 source file for that frame and puts an arrow (@samp{=>}) at the
17726 left margin of the current line. Emacs uses a separate buffer for
17727 source display, and splits the screen to show both your @value{GDBN} session
17730 Explicit @value{GDBN} @code{list} or search commands still produce output as
17731 usual, but you probably have no reason to use them from Emacs.
17734 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17735 a graphical mode, enabled by default, which provides further buffers
17736 that can control the execution and describe the state of your program.
17737 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17739 If you specify an absolute file name when prompted for the @kbd{M-x
17740 gdb} argument, then Emacs sets your current working directory to where
17741 your program resides. If you only specify the file name, then Emacs
17742 sets your current working directory to to the directory associated
17743 with the previous buffer. In this case, @value{GDBN} may find your
17744 program by searching your environment's @code{PATH} variable, but on
17745 some operating systems it might not find the source. So, although the
17746 @value{GDBN} input and output session proceeds normally, the auxiliary
17747 buffer does not display the current source and line of execution.
17749 The initial working directory of @value{GDBN} is printed on the top
17750 line of the GUD buffer and this serves as a default for the commands
17751 that specify files for @value{GDBN} to operate on. @xref{Files,
17752 ,Commands to Specify Files}.
17754 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17755 need to call @value{GDBN} by a different name (for example, if you
17756 keep several configurations around, with different names) you can
17757 customize the Emacs variable @code{gud-gdb-command-name} to run the
17760 In the GUD buffer, you can use these special Emacs commands in
17761 addition to the standard Shell mode commands:
17765 Describe the features of Emacs' GUD Mode.
17768 Execute to another source line, like the @value{GDBN} @code{step} command; also
17769 update the display window to show the current file and location.
17772 Execute to next source line in this function, skipping all function
17773 calls, like the @value{GDBN} @code{next} command. Then update the display window
17774 to show the current file and location.
17777 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17778 display window accordingly.
17781 Execute until exit from the selected stack frame, like the @value{GDBN}
17782 @code{finish} command.
17785 Continue execution of your program, like the @value{GDBN} @code{continue}
17789 Go up the number of frames indicated by the numeric argument
17790 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17791 like the @value{GDBN} @code{up} command.
17794 Go down the number of frames indicated by the numeric argument, like the
17795 @value{GDBN} @code{down} command.
17798 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17799 tells @value{GDBN} to set a breakpoint on the source line point is on.
17801 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17802 separate frame which shows a backtrace when the GUD buffer is current.
17803 Move point to any frame in the stack and type @key{RET} to make it
17804 become the current frame and display the associated source in the
17805 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17806 selected frame become the current one. In graphical mode, the
17807 speedbar displays watch expressions.
17809 If you accidentally delete the source-display buffer, an easy way to get
17810 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17811 request a frame display; when you run under Emacs, this recreates
17812 the source buffer if necessary to show you the context of the current
17815 The source files displayed in Emacs are in ordinary Emacs buffers
17816 which are visiting the source files in the usual way. You can edit
17817 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17818 communicates with Emacs in terms of line numbers. If you add or
17819 delete lines from the text, the line numbers that @value{GDBN} knows cease
17820 to correspond properly with the code.
17822 A more detailed description of Emacs' interaction with @value{GDBN} is
17823 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17826 @c The following dropped because Epoch is nonstandard. Reactivate
17827 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17829 @kindex Emacs Epoch environment
17833 Version 18 of @sc{gnu} Emacs has a built-in window system
17834 called the @code{epoch}
17835 environment. Users of this environment can use a new command,
17836 @code{inspect} which performs identically to @code{print} except that
17837 each value is printed in its own window.
17842 @chapter The @sc{gdb/mi} Interface
17844 @unnumberedsec Function and Purpose
17846 @cindex @sc{gdb/mi}, its purpose
17847 @sc{gdb/mi} is a line based machine oriented text interface to
17848 @value{GDBN} and is activated by specifying using the
17849 @option{--interpreter} command line option (@pxref{Mode Options}). It
17850 is specifically intended to support the development of systems which
17851 use the debugger as just one small component of a larger system.
17853 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17854 in the form of a reference manual.
17856 Note that @sc{gdb/mi} is still under construction, so some of the
17857 features described below are incomplete and subject to change
17858 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17860 @unnumberedsec Notation and Terminology
17862 @cindex notational conventions, for @sc{gdb/mi}
17863 This chapter uses the following notation:
17867 @code{|} separates two alternatives.
17870 @code{[ @var{something} ]} indicates that @var{something} is optional:
17871 it may or may not be given.
17874 @code{( @var{group} )*} means that @var{group} inside the parentheses
17875 may repeat zero or more times.
17878 @code{( @var{group} )+} means that @var{group} inside the parentheses
17879 may repeat one or more times.
17882 @code{"@var{string}"} means a literal @var{string}.
17886 @heading Dependencies
17890 * GDB/MI Command Syntax::
17891 * GDB/MI Compatibility with CLI::
17892 * GDB/MI Development and Front Ends::
17893 * GDB/MI Output Records::
17894 * GDB/MI Simple Examples::
17895 * GDB/MI Command Description Format::
17896 * GDB/MI Breakpoint Commands::
17897 * GDB/MI Program Context::
17898 * GDB/MI Thread Commands::
17899 * GDB/MI Program Execution::
17900 * GDB/MI Stack Manipulation::
17901 * GDB/MI Variable Objects::
17902 * GDB/MI Data Manipulation::
17903 * GDB/MI Tracepoint Commands::
17904 * GDB/MI Symbol Query::
17905 * GDB/MI File Commands::
17907 * GDB/MI Kod Commands::
17908 * GDB/MI Memory Overlay Commands::
17909 * GDB/MI Signal Handling Commands::
17911 * GDB/MI Target Manipulation::
17912 * GDB/MI File Transfer Commands::
17913 * GDB/MI Miscellaneous Commands::
17916 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17917 @node GDB/MI Command Syntax
17918 @section @sc{gdb/mi} Command Syntax
17921 * GDB/MI Input Syntax::
17922 * GDB/MI Output Syntax::
17925 @node GDB/MI Input Syntax
17926 @subsection @sc{gdb/mi} Input Syntax
17928 @cindex input syntax for @sc{gdb/mi}
17929 @cindex @sc{gdb/mi}, input syntax
17931 @item @var{command} @expansion{}
17932 @code{@var{cli-command} | @var{mi-command}}
17934 @item @var{cli-command} @expansion{}
17935 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17936 @var{cli-command} is any existing @value{GDBN} CLI command.
17938 @item @var{mi-command} @expansion{}
17939 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17940 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17942 @item @var{token} @expansion{}
17943 "any sequence of digits"
17945 @item @var{option} @expansion{}
17946 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17948 @item @var{parameter} @expansion{}
17949 @code{@var{non-blank-sequence} | @var{c-string}}
17951 @item @var{operation} @expansion{}
17952 @emph{any of the operations described in this chapter}
17954 @item @var{non-blank-sequence} @expansion{}
17955 @emph{anything, provided it doesn't contain special characters such as
17956 "-", @var{nl}, """ and of course " "}
17958 @item @var{c-string} @expansion{}
17959 @code{""" @var{seven-bit-iso-c-string-content} """}
17961 @item @var{nl} @expansion{}
17970 The CLI commands are still handled by the @sc{mi} interpreter; their
17971 output is described below.
17974 The @code{@var{token}}, when present, is passed back when the command
17978 Some @sc{mi} commands accept optional arguments as part of the parameter
17979 list. Each option is identified by a leading @samp{-} (dash) and may be
17980 followed by an optional argument parameter. Options occur first in the
17981 parameter list and can be delimited from normal parameters using
17982 @samp{--} (this is useful when some parameters begin with a dash).
17989 We want easy access to the existing CLI syntax (for debugging).
17992 We want it to be easy to spot a @sc{mi} operation.
17995 @node GDB/MI Output Syntax
17996 @subsection @sc{gdb/mi} Output Syntax
17998 @cindex output syntax of @sc{gdb/mi}
17999 @cindex @sc{gdb/mi}, output syntax
18000 The output from @sc{gdb/mi} consists of zero or more out-of-band records
18001 followed, optionally, by a single result record. This result record
18002 is for the most recent command. The sequence of output records is
18003 terminated by @samp{(gdb)}.
18005 If an input command was prefixed with a @code{@var{token}} then the
18006 corresponding output for that command will also be prefixed by that same
18010 @item @var{output} @expansion{}
18011 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
18013 @item @var{result-record} @expansion{}
18014 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
18016 @item @var{out-of-band-record} @expansion{}
18017 @code{@var{async-record} | @var{stream-record}}
18019 @item @var{async-record} @expansion{}
18020 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
18022 @item @var{exec-async-output} @expansion{}
18023 @code{[ @var{token} ] "*" @var{async-output}}
18025 @item @var{status-async-output} @expansion{}
18026 @code{[ @var{token} ] "+" @var{async-output}}
18028 @item @var{notify-async-output} @expansion{}
18029 @code{[ @var{token} ] "=" @var{async-output}}
18031 @item @var{async-output} @expansion{}
18032 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
18034 @item @var{result-class} @expansion{}
18035 @code{"done" | "running" | "connected" | "error" | "exit"}
18037 @item @var{async-class} @expansion{}
18038 @code{"stopped" | @var{others}} (where @var{others} will be added
18039 depending on the needs---this is still in development).
18041 @item @var{result} @expansion{}
18042 @code{ @var{variable} "=" @var{value}}
18044 @item @var{variable} @expansion{}
18045 @code{ @var{string} }
18047 @item @var{value} @expansion{}
18048 @code{ @var{const} | @var{tuple} | @var{list} }
18050 @item @var{const} @expansion{}
18051 @code{@var{c-string}}
18053 @item @var{tuple} @expansion{}
18054 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
18056 @item @var{list} @expansion{}
18057 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
18058 @var{result} ( "," @var{result} )* "]" }
18060 @item @var{stream-record} @expansion{}
18061 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
18063 @item @var{console-stream-output} @expansion{}
18064 @code{"~" @var{c-string}}
18066 @item @var{target-stream-output} @expansion{}
18067 @code{"@@" @var{c-string}}
18069 @item @var{log-stream-output} @expansion{}
18070 @code{"&" @var{c-string}}
18072 @item @var{nl} @expansion{}
18075 @item @var{token} @expansion{}
18076 @emph{any sequence of digits}.
18084 All output sequences end in a single line containing a period.
18087 The @code{@var{token}} is from the corresponding request. Note that
18088 for all async output, while the token is allowed by the grammar and
18089 may be output by future versions of @value{GDBN} for select async
18090 output messages, it is generally omitted. Frontends should treat
18091 all async output as reporting general changes in the state of the
18092 target and there should be no need to associate async output to any
18096 @cindex status output in @sc{gdb/mi}
18097 @var{status-async-output} contains on-going status information about the
18098 progress of a slow operation. It can be discarded. All status output is
18099 prefixed by @samp{+}.
18102 @cindex async output in @sc{gdb/mi}
18103 @var{exec-async-output} contains asynchronous state change on the target
18104 (stopped, started, disappeared). All async output is prefixed by
18108 @cindex notify output in @sc{gdb/mi}
18109 @var{notify-async-output} contains supplementary information that the
18110 client should handle (e.g., a new breakpoint information). All notify
18111 output is prefixed by @samp{=}.
18114 @cindex console output in @sc{gdb/mi}
18115 @var{console-stream-output} is output that should be displayed as is in the
18116 console. It is the textual response to a CLI command. All the console
18117 output is prefixed by @samp{~}.
18120 @cindex target output in @sc{gdb/mi}
18121 @var{target-stream-output} is the output produced by the target program.
18122 All the target output is prefixed by @samp{@@}.
18125 @cindex log output in @sc{gdb/mi}
18126 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
18127 instance messages that should be displayed as part of an error log. All
18128 the log output is prefixed by @samp{&}.
18131 @cindex list output in @sc{gdb/mi}
18132 New @sc{gdb/mi} commands should only output @var{lists} containing
18138 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
18139 details about the various output records.
18141 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18142 @node GDB/MI Compatibility with CLI
18143 @section @sc{gdb/mi} Compatibility with CLI
18145 @cindex compatibility, @sc{gdb/mi} and CLI
18146 @cindex @sc{gdb/mi}, compatibility with CLI
18148 For the developers convenience CLI commands can be entered directly,
18149 but there may be some unexpected behaviour. For example, commands
18150 that query the user will behave as if the user replied yes, breakpoint
18151 command lists are not executed and some CLI commands, such as
18152 @code{if}, @code{when} and @code{define}, prompt for further input with
18153 @samp{>}, which is not valid MI output.
18155 This feature may be removed at some stage in the future and it is
18156 recommended that front ends use the @code{-interpreter-exec} command
18157 (@pxref{-interpreter-exec}).
18159 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18160 @node GDB/MI Development and Front Ends
18161 @section @sc{gdb/mi} Development and Front Ends
18162 @cindex @sc{gdb/mi} development
18164 The application which takes the MI output and presents the state of the
18165 program being debugged to the user is called a @dfn{front end}.
18167 Although @sc{gdb/mi} is still incomplete, it is currently being used
18168 by a variety of front ends to @value{GDBN}. This makes it difficult
18169 to introduce new functionality without breaking existing usage. This
18170 section tries to minimize the problems by describing how the protocol
18173 Some changes in MI need not break a carefully designed front end, and
18174 for these the MI version will remain unchanged. The following is a
18175 list of changes that may occur within one level, so front ends should
18176 parse MI output in a way that can handle them:
18180 New MI commands may be added.
18183 New fields may be added to the output of any MI command.
18186 The range of values for fields with specified values, e.g.,
18187 @code{in_scope} (@pxref{-var-update}) may be extended.
18189 @c The format of field's content e.g type prefix, may change so parse it
18190 @c at your own risk. Yes, in general?
18192 @c The order of fields may change? Shouldn't really matter but it might
18193 @c resolve inconsistencies.
18196 If the changes are likely to break front ends, the MI version level
18197 will be increased by one. This will allow the front end to parse the
18198 output according to the MI version. Apart from mi0, new versions of
18199 @value{GDBN} will not support old versions of MI and it will be the
18200 responsibility of the front end to work with the new one.
18202 @c Starting with mi3, add a new command -mi-version that prints the MI
18205 The best way to avoid unexpected changes in MI that might break your front
18206 end is to make your project known to @value{GDBN} developers and
18207 follow development on @email{gdb@@sourceware.org} and
18208 @email{gdb-patches@@sourceware.org}.
18209 @cindex mailing lists
18211 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18212 @node GDB/MI Output Records
18213 @section @sc{gdb/mi} Output Records
18216 * GDB/MI Result Records::
18217 * GDB/MI Stream Records::
18218 * GDB/MI Async Records::
18221 @node GDB/MI Result Records
18222 @subsection @sc{gdb/mi} Result Records
18224 @cindex result records in @sc{gdb/mi}
18225 @cindex @sc{gdb/mi}, result records
18226 In addition to a number of out-of-band notifications, the response to a
18227 @sc{gdb/mi} command includes one of the following result indications:
18231 @item "^done" [ "," @var{results} ]
18232 The synchronous operation was successful, @code{@var{results}} are the return
18237 @c Is this one correct? Should it be an out-of-band notification?
18238 The asynchronous operation was successfully started. The target is
18243 @value{GDBN} has connected to a remote target.
18245 @item "^error" "," @var{c-string}
18247 The operation failed. The @code{@var{c-string}} contains the corresponding
18252 @value{GDBN} has terminated.
18256 @node GDB/MI Stream Records
18257 @subsection @sc{gdb/mi} Stream Records
18259 @cindex @sc{gdb/mi}, stream records
18260 @cindex stream records in @sc{gdb/mi}
18261 @value{GDBN} internally maintains a number of output streams: the console, the
18262 target, and the log. The output intended for each of these streams is
18263 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
18265 Each stream record begins with a unique @dfn{prefix character} which
18266 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
18267 Syntax}). In addition to the prefix, each stream record contains a
18268 @code{@var{string-output}}. This is either raw text (with an implicit new
18269 line) or a quoted C string (which does not contain an implicit newline).
18272 @item "~" @var{string-output}
18273 The console output stream contains text that should be displayed in the
18274 CLI console window. It contains the textual responses to CLI commands.
18276 @item "@@" @var{string-output}
18277 The target output stream contains any textual output from the running
18278 target. This is only present when GDB's event loop is truly
18279 asynchronous, which is currently only the case for remote targets.
18281 @item "&" @var{string-output}
18282 The log stream contains debugging messages being produced by @value{GDBN}'s
18286 @node GDB/MI Async Records
18287 @subsection @sc{gdb/mi} Async Records
18289 @cindex async records in @sc{gdb/mi}
18290 @cindex @sc{gdb/mi}, async records
18291 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
18292 additional changes that have occurred. Those changes can either be a
18293 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
18294 target activity (e.g., target stopped).
18296 The following is the list of possible async records:
18300 @item *stopped,reason="@var{reason}"
18301 The target has stopped. The @var{reason} field can have one of the
18305 @item breakpoint-hit
18306 A breakpoint was reached.
18307 @item watchpoint-trigger
18308 A watchpoint was triggered.
18309 @item read-watchpoint-trigger
18310 A read watchpoint was triggered.
18311 @item access-watchpoint-trigger
18312 An access watchpoint was triggered.
18313 @item function-finished
18314 An -exec-finish or similar CLI command was accomplished.
18315 @item location-reached
18316 An -exec-until or similar CLI command was accomplished.
18317 @item watchpoint-scope
18318 A watchpoint has gone out of scope.
18319 @item end-stepping-range
18320 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
18321 similar CLI command was accomplished.
18322 @item exited-signalled
18323 The inferior exited because of a signal.
18325 The inferior exited.
18326 @item exited-normally
18327 The inferior exited normally.
18328 @item signal-received
18329 A signal was received by the inferior.
18332 @item =thread-created,id="@var{id}"
18333 @itemx =thread-exited,id="@var{id}"
18334 A thread either was created, or has exited. The @var{id} field
18335 contains the @value{GDBN} identifier of the thread.
18340 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18341 @node GDB/MI Simple Examples
18342 @section Simple Examples of @sc{gdb/mi} Interaction
18343 @cindex @sc{gdb/mi}, simple examples
18345 This subsection presents several simple examples of interaction using
18346 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
18347 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
18348 the output received from @sc{gdb/mi}.
18350 Note the line breaks shown in the examples are here only for
18351 readability, they don't appear in the real output.
18353 @subheading Setting a Breakpoint
18355 Setting a breakpoint generates synchronous output which contains detailed
18356 information of the breakpoint.
18359 -> -break-insert main
18360 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18361 enabled="y",addr="0x08048564",func="main",file="myprog.c",
18362 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
18366 @subheading Program Execution
18368 Program execution generates asynchronous records and MI gives the
18369 reason that execution stopped.
18375 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
18376 frame=@{addr="0x08048564",func="main",
18377 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
18378 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
18383 <- *stopped,reason="exited-normally"
18387 @subheading Quitting @value{GDBN}
18389 Quitting @value{GDBN} just prints the result class @samp{^exit}.
18397 @subheading A Bad Command
18399 Here's what happens if you pass a non-existent command:
18403 <- ^error,msg="Undefined MI command: rubbish"
18408 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18409 @node GDB/MI Command Description Format
18410 @section @sc{gdb/mi} Command Description Format
18412 The remaining sections describe blocks of commands. Each block of
18413 commands is laid out in a fashion similar to this section.
18415 @subheading Motivation
18417 The motivation for this collection of commands.
18419 @subheading Introduction
18421 A brief introduction to this collection of commands as a whole.
18423 @subheading Commands
18425 For each command in the block, the following is described:
18427 @subsubheading Synopsis
18430 -command @var{args}@dots{}
18433 @subsubheading Result
18435 @subsubheading @value{GDBN} Command
18437 The corresponding @value{GDBN} CLI command(s), if any.
18439 @subsubheading Example
18441 Example(s) formatted for readability. Some of the described commands have
18442 not been implemented yet and these are labeled N.A.@: (not available).
18445 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18446 @node GDB/MI Breakpoint Commands
18447 @section @sc{gdb/mi} Breakpoint Commands
18449 @cindex breakpoint commands for @sc{gdb/mi}
18450 @cindex @sc{gdb/mi}, breakpoint commands
18451 This section documents @sc{gdb/mi} commands for manipulating
18454 @subheading The @code{-break-after} Command
18455 @findex -break-after
18457 @subsubheading Synopsis
18460 -break-after @var{number} @var{count}
18463 The breakpoint number @var{number} is not in effect until it has been
18464 hit @var{count} times. To see how this is reflected in the output of
18465 the @samp{-break-list} command, see the description of the
18466 @samp{-break-list} command below.
18468 @subsubheading @value{GDBN} Command
18470 The corresponding @value{GDBN} command is @samp{ignore}.
18472 @subsubheading Example
18477 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18478 enabled="y",addr="0x000100d0",func="main",file="hello.c",
18479 fullname="/home/foo/hello.c",line="5",times="0"@}
18486 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18487 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18488 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18489 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18490 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18491 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18492 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18493 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18494 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18495 line="5",times="0",ignore="3"@}]@}
18500 @subheading The @code{-break-catch} Command
18501 @findex -break-catch
18503 @subheading The @code{-break-commands} Command
18504 @findex -break-commands
18508 @subheading The @code{-break-condition} Command
18509 @findex -break-condition
18511 @subsubheading Synopsis
18514 -break-condition @var{number} @var{expr}
18517 Breakpoint @var{number} will stop the program only if the condition in
18518 @var{expr} is true. The condition becomes part of the
18519 @samp{-break-list} output (see the description of the @samp{-break-list}
18522 @subsubheading @value{GDBN} Command
18524 The corresponding @value{GDBN} command is @samp{condition}.
18526 @subsubheading Example
18530 -break-condition 1 1
18534 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18535 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18536 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18537 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18538 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18539 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18540 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18541 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18542 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18543 line="5",cond="1",times="0",ignore="3"@}]@}
18547 @subheading The @code{-break-delete} Command
18548 @findex -break-delete
18550 @subsubheading Synopsis
18553 -break-delete ( @var{breakpoint} )+
18556 Delete the breakpoint(s) whose number(s) are specified in the argument
18557 list. This is obviously reflected in the breakpoint list.
18559 @subsubheading @value{GDBN} Command
18561 The corresponding @value{GDBN} command is @samp{delete}.
18563 @subsubheading Example
18571 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18572 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18573 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18574 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18575 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18576 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18577 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18582 @subheading The @code{-break-disable} Command
18583 @findex -break-disable
18585 @subsubheading Synopsis
18588 -break-disable ( @var{breakpoint} )+
18591 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18592 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18594 @subsubheading @value{GDBN} Command
18596 The corresponding @value{GDBN} command is @samp{disable}.
18598 @subsubheading Example
18606 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18607 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18608 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18609 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18610 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18611 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18612 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18613 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18614 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18615 line="5",times="0"@}]@}
18619 @subheading The @code{-break-enable} Command
18620 @findex -break-enable
18622 @subsubheading Synopsis
18625 -break-enable ( @var{breakpoint} )+
18628 Enable (previously disabled) @var{breakpoint}(s).
18630 @subsubheading @value{GDBN} Command
18632 The corresponding @value{GDBN} command is @samp{enable}.
18634 @subsubheading Example
18642 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18643 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18644 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18645 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18646 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18647 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18648 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18649 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18650 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18651 line="5",times="0"@}]@}
18655 @subheading The @code{-break-info} Command
18656 @findex -break-info
18658 @subsubheading Synopsis
18661 -break-info @var{breakpoint}
18665 Get information about a single breakpoint.
18667 @subsubheading @value{GDBN} Command
18669 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18671 @subsubheading Example
18674 @subheading The @code{-break-insert} Command
18675 @findex -break-insert
18677 @subsubheading Synopsis
18680 -break-insert [ -t ] [ -h ] [ -f ]
18681 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18682 [ -p @var{thread} ] [ @var{location} ]
18686 If specified, @var{location}, can be one of:
18693 @item filename:linenum
18694 @item filename:function
18698 The possible optional parameters of this command are:
18702 Insert a temporary breakpoint.
18704 Insert a hardware breakpoint.
18705 @item -c @var{condition}
18706 Make the breakpoint conditional on @var{condition}.
18707 @item -i @var{ignore-count}
18708 Initialize the @var{ignore-count}.
18710 If @var{location} cannot be parsed (for example if it
18711 refers to unknown files or functions), create a pending
18712 breakpoint. Without this flag, @value{GDBN} will report
18713 an error, and won't create a breakpoint, if @var{location}
18717 @subsubheading Result
18719 The result is in the form:
18722 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18723 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18724 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18725 times="@var{times}"@}
18729 where @var{number} is the @value{GDBN} number for this breakpoint,
18730 @var{funcname} is the name of the function where the breakpoint was
18731 inserted, @var{filename} is the name of the source file which contains
18732 this function, @var{lineno} is the source line number within that file
18733 and @var{times} the number of times that the breakpoint has been hit
18734 (always 0 for -break-insert but may be greater for -break-info or -break-list
18735 which use the same output).
18737 Note: this format is open to change.
18738 @c An out-of-band breakpoint instead of part of the result?
18740 @subsubheading @value{GDBN} Command
18742 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18743 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18745 @subsubheading Example
18750 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18751 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18753 -break-insert -t foo
18754 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18755 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18758 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18759 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18760 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18761 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18762 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18763 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18764 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18765 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18766 addr="0x0001072c", func="main",file="recursive2.c",
18767 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18768 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18769 addr="0x00010774",func="foo",file="recursive2.c",
18770 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18772 -break-insert -r foo.*
18773 ~int foo(int, int);
18774 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18775 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18779 @subheading The @code{-break-list} Command
18780 @findex -break-list
18782 @subsubheading Synopsis
18788 Displays the list of inserted breakpoints, showing the following fields:
18792 number of the breakpoint
18794 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18796 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18799 is the breakpoint enabled or no: @samp{y} or @samp{n}
18801 memory location at which the breakpoint is set
18803 logical location of the breakpoint, expressed by function name, file
18806 number of times the breakpoint has been hit
18809 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18810 @code{body} field is an empty list.
18812 @subsubheading @value{GDBN} Command
18814 The corresponding @value{GDBN} command is @samp{info break}.
18816 @subsubheading Example
18821 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18822 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18823 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18824 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18825 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18826 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18827 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18828 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18829 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18830 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18831 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18832 line="13",times="0"@}]@}
18836 Here's an example of the result when there are no breakpoints:
18841 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18842 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18843 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18844 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18845 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18846 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18847 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18852 @subheading The @code{-break-watch} Command
18853 @findex -break-watch
18855 @subsubheading Synopsis
18858 -break-watch [ -a | -r ]
18861 Create a watchpoint. With the @samp{-a} option it will create an
18862 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18863 read from or on a write to the memory location. With the @samp{-r}
18864 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18865 trigger only when the memory location is accessed for reading. Without
18866 either of the options, the watchpoint created is a regular watchpoint,
18867 i.e., it will trigger when the memory location is accessed for writing.
18868 @xref{Set Watchpoints, , Setting Watchpoints}.
18870 Note that @samp{-break-list} will report a single list of watchpoints and
18871 breakpoints inserted.
18873 @subsubheading @value{GDBN} Command
18875 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18878 @subsubheading Example
18880 Setting a watchpoint on a variable in the @code{main} function:
18885 ^done,wpt=@{number="2",exp="x"@}
18890 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18891 value=@{old="-268439212",new="55"@},
18892 frame=@{func="main",args=[],file="recursive2.c",
18893 fullname="/home/foo/bar/recursive2.c",line="5"@}
18897 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18898 the program execution twice: first for the variable changing value, then
18899 for the watchpoint going out of scope.
18904 ^done,wpt=@{number="5",exp="C"@}
18909 *stopped,reason="watchpoint-trigger",
18910 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18911 frame=@{func="callee4",args=[],
18912 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18913 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18918 *stopped,reason="watchpoint-scope",wpnum="5",
18919 frame=@{func="callee3",args=[@{name="strarg",
18920 value="0x11940 \"A string argument.\""@}],
18921 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18922 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18926 Listing breakpoints and watchpoints, at different points in the program
18927 execution. Note that once the watchpoint goes out of scope, it is
18933 ^done,wpt=@{number="2",exp="C"@}
18936 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18937 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18938 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18939 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18940 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18941 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18942 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18943 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18944 addr="0x00010734",func="callee4",
18945 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18946 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18947 bkpt=@{number="2",type="watchpoint",disp="keep",
18948 enabled="y",addr="",what="C",times="0"@}]@}
18953 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18954 value=@{old="-276895068",new="3"@},
18955 frame=@{func="callee4",args=[],
18956 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18957 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18960 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18961 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18962 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18963 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18964 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18965 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18966 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18967 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18968 addr="0x00010734",func="callee4",
18969 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18970 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18971 bkpt=@{number="2",type="watchpoint",disp="keep",
18972 enabled="y",addr="",what="C",times="-5"@}]@}
18976 ^done,reason="watchpoint-scope",wpnum="2",
18977 frame=@{func="callee3",args=[@{name="strarg",
18978 value="0x11940 \"A string argument.\""@}],
18979 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18980 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18983 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18984 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18985 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18986 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18987 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18988 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18989 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18990 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18991 addr="0x00010734",func="callee4",
18992 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18993 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18998 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18999 @node GDB/MI Program Context
19000 @section @sc{gdb/mi} Program Context
19002 @subheading The @code{-exec-arguments} Command
19003 @findex -exec-arguments
19006 @subsubheading Synopsis
19009 -exec-arguments @var{args}
19012 Set the inferior program arguments, to be used in the next
19015 @subsubheading @value{GDBN} Command
19017 The corresponding @value{GDBN} command is @samp{set args}.
19019 @subsubheading Example
19022 Don't have one around.
19025 @subheading The @code{-exec-show-arguments} Command
19026 @findex -exec-show-arguments
19028 @subsubheading Synopsis
19031 -exec-show-arguments
19034 Print the arguments of the program.
19036 @subsubheading @value{GDBN} Command
19038 The corresponding @value{GDBN} command is @samp{show args}.
19040 @subsubheading Example
19044 @subheading The @code{-environment-cd} Command
19045 @findex -environment-cd
19047 @subsubheading Synopsis
19050 -environment-cd @var{pathdir}
19053 Set @value{GDBN}'s working directory.
19055 @subsubheading @value{GDBN} Command
19057 The corresponding @value{GDBN} command is @samp{cd}.
19059 @subsubheading Example
19063 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19069 @subheading The @code{-environment-directory} Command
19070 @findex -environment-directory
19072 @subsubheading Synopsis
19075 -environment-directory [ -r ] [ @var{pathdir} ]+
19078 Add directories @var{pathdir} to beginning of search path for source files.
19079 If the @samp{-r} option is used, the search path is reset to the default
19080 search path. If directories @var{pathdir} are supplied in addition to the
19081 @samp{-r} option, the search path is first reset and then addition
19083 Multiple directories may be specified, separated by blanks. Specifying
19084 multiple directories in a single command
19085 results in the directories added to the beginning of the
19086 search path in the same order they were presented in the command.
19087 If blanks are needed as
19088 part of a directory name, double-quotes should be used around
19089 the name. In the command output, the path will show up separated
19090 by the system directory-separator character. The directory-separator
19091 character must not be used
19092 in any directory name.
19093 If no directories are specified, the current search path is displayed.
19095 @subsubheading @value{GDBN} Command
19097 The corresponding @value{GDBN} command is @samp{dir}.
19099 @subsubheading Example
19103 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19104 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19106 -environment-directory ""
19107 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19109 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
19110 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
19112 -environment-directory -r
19113 ^done,source-path="$cdir:$cwd"
19118 @subheading The @code{-environment-path} Command
19119 @findex -environment-path
19121 @subsubheading Synopsis
19124 -environment-path [ -r ] [ @var{pathdir} ]+
19127 Add directories @var{pathdir} to beginning of search path for object files.
19128 If the @samp{-r} option is used, the search path is reset to the original
19129 search path that existed at gdb start-up. If directories @var{pathdir} are
19130 supplied in addition to the
19131 @samp{-r} option, the search path is first reset and then addition
19133 Multiple directories may be specified, separated by blanks. Specifying
19134 multiple directories in a single command
19135 results in the directories added to the beginning of the
19136 search path in the same order they were presented in the command.
19137 If blanks are needed as
19138 part of a directory name, double-quotes should be used around
19139 the name. In the command output, the path will show up separated
19140 by the system directory-separator character. The directory-separator
19141 character must not be used
19142 in any directory name.
19143 If no directories are specified, the current path is displayed.
19146 @subsubheading @value{GDBN} Command
19148 The corresponding @value{GDBN} command is @samp{path}.
19150 @subsubheading Example
19155 ^done,path="/usr/bin"
19157 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
19158 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
19160 -environment-path -r /usr/local/bin
19161 ^done,path="/usr/local/bin:/usr/bin"
19166 @subheading The @code{-environment-pwd} Command
19167 @findex -environment-pwd
19169 @subsubheading Synopsis
19175 Show the current working directory.
19177 @subsubheading @value{GDBN} Command
19179 The corresponding @value{GDBN} command is @samp{pwd}.
19181 @subsubheading Example
19186 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
19190 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19191 @node GDB/MI Thread Commands
19192 @section @sc{gdb/mi} Thread Commands
19195 @subheading The @code{-thread-info} Command
19196 @findex -thread-info
19198 @subsubheading Synopsis
19201 -thread-info [ @var{thread-id} ]
19204 Reports information about either a specific thread, if
19205 the @var{thread-id} parameter is present, or about all
19206 threads. When printing information about all threads,
19207 also reports the current thread.
19209 @subsubheading @value{GDBN} Command
19211 The @samp{info thread} command prints the same information
19214 @subsubheading Example
19219 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
19220 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},
19221 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
19222 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
19223 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}@}],
19224 current-thread-id="1"
19228 @subheading The @code{-thread-list-ids} Command
19229 @findex -thread-list-ids
19231 @subsubheading Synopsis
19237 Produces a list of the currently known @value{GDBN} thread ids. At the
19238 end of the list it also prints the total number of such threads.
19240 @subsubheading @value{GDBN} Command
19242 Part of @samp{info threads} supplies the same information.
19244 @subsubheading Example
19246 No threads present, besides the main process:
19251 ^done,thread-ids=@{@},number-of-threads="0"
19261 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19262 number-of-threads="3"
19267 @subheading The @code{-thread-select} Command
19268 @findex -thread-select
19270 @subsubheading Synopsis
19273 -thread-select @var{threadnum}
19276 Make @var{threadnum} the current thread. It prints the number of the new
19277 current thread, and the topmost frame for that thread.
19279 @subsubheading @value{GDBN} Command
19281 The corresponding @value{GDBN} command is @samp{thread}.
19283 @subsubheading Example
19290 *stopped,reason="end-stepping-range",thread-id="2",line="187",
19291 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
19295 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19296 number-of-threads="3"
19299 ^done,new-thread-id="3",
19300 frame=@{level="0",func="vprintf",
19301 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
19302 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
19306 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19307 @node GDB/MI Program Execution
19308 @section @sc{gdb/mi} Program Execution
19310 These are the asynchronous commands which generate the out-of-band
19311 record @samp{*stopped}. Currently @value{GDBN} only really executes
19312 asynchronously with remote targets and this interaction is mimicked in
19315 @subheading The @code{-exec-continue} Command
19316 @findex -exec-continue
19318 @subsubheading Synopsis
19324 Resumes the execution of the inferior program until a breakpoint is
19325 encountered, or until the inferior exits.
19327 @subsubheading @value{GDBN} Command
19329 The corresponding @value{GDBN} corresponding is @samp{continue}.
19331 @subsubheading Example
19338 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
19339 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
19345 @subheading The @code{-exec-finish} Command
19346 @findex -exec-finish
19348 @subsubheading Synopsis
19354 Resumes the execution of the inferior program until the current
19355 function is exited. Displays the results returned by the function.
19357 @subsubheading @value{GDBN} Command
19359 The corresponding @value{GDBN} command is @samp{finish}.
19361 @subsubheading Example
19363 Function returning @code{void}.
19370 *stopped,reason="function-finished",frame=@{func="main",args=[],
19371 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
19375 Function returning other than @code{void}. The name of the internal
19376 @value{GDBN} variable storing the result is printed, together with the
19383 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
19384 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
19385 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19386 gdb-result-var="$1",return-value="0"
19391 @subheading The @code{-exec-interrupt} Command
19392 @findex -exec-interrupt
19394 @subsubheading Synopsis
19400 Interrupts the background execution of the target. Note how the token
19401 associated with the stop message is the one for the execution command
19402 that has been interrupted. The token for the interrupt itself only
19403 appears in the @samp{^done} output. If the user is trying to
19404 interrupt a non-running program, an error message will be printed.
19406 @subsubheading @value{GDBN} Command
19408 The corresponding @value{GDBN} command is @samp{interrupt}.
19410 @subsubheading Example
19421 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
19422 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
19423 fullname="/home/foo/bar/try.c",line="13"@}
19428 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
19433 @subheading The @code{-exec-next} Command
19436 @subsubheading Synopsis
19442 Resumes execution of the inferior program, stopping when the beginning
19443 of the next source line is reached.
19445 @subsubheading @value{GDBN} Command
19447 The corresponding @value{GDBN} command is @samp{next}.
19449 @subsubheading Example
19455 *stopped,reason="end-stepping-range",line="8",file="hello.c"
19460 @subheading The @code{-exec-next-instruction} Command
19461 @findex -exec-next-instruction
19463 @subsubheading Synopsis
19466 -exec-next-instruction
19469 Executes one machine instruction. If the instruction is a function
19470 call, continues until the function returns. If the program stops at an
19471 instruction in the middle of a source line, the address will be
19474 @subsubheading @value{GDBN} Command
19476 The corresponding @value{GDBN} command is @samp{nexti}.
19478 @subsubheading Example
19482 -exec-next-instruction
19486 *stopped,reason="end-stepping-range",
19487 addr="0x000100d4",line="5",file="hello.c"
19492 @subheading The @code{-exec-return} Command
19493 @findex -exec-return
19495 @subsubheading Synopsis
19501 Makes current function return immediately. Doesn't execute the inferior.
19502 Displays the new current frame.
19504 @subsubheading @value{GDBN} Command
19506 The corresponding @value{GDBN} command is @samp{return}.
19508 @subsubheading Example
19512 200-break-insert callee4
19513 200^done,bkpt=@{number="1",addr="0x00010734",
19514 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19519 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
19520 frame=@{func="callee4",args=[],
19521 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19522 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19528 111^done,frame=@{level="0",func="callee3",
19529 args=[@{name="strarg",
19530 value="0x11940 \"A string argument.\""@}],
19531 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19532 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19537 @subheading The @code{-exec-run} Command
19540 @subsubheading Synopsis
19546 Starts execution of the inferior from the beginning. The inferior
19547 executes until either a breakpoint is encountered or the program
19548 exits. In the latter case the output will include an exit code, if
19549 the program has exited exceptionally.
19551 @subsubheading @value{GDBN} Command
19553 The corresponding @value{GDBN} command is @samp{run}.
19555 @subsubheading Examples
19560 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19565 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
19566 frame=@{func="main",args=[],file="recursive2.c",
19567 fullname="/home/foo/bar/recursive2.c",line="4"@}
19572 Program exited normally:
19580 *stopped,reason="exited-normally"
19585 Program exited exceptionally:
19593 *stopped,reason="exited",exit-code="01"
19597 Another way the program can terminate is if it receives a signal such as
19598 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19602 *stopped,reason="exited-signalled",signal-name="SIGINT",
19603 signal-meaning="Interrupt"
19607 @c @subheading -exec-signal
19610 @subheading The @code{-exec-step} Command
19613 @subsubheading Synopsis
19619 Resumes execution of the inferior program, stopping when the beginning
19620 of the next source line is reached, if the next source line is not a
19621 function call. If it is, stop at the first instruction of the called
19624 @subsubheading @value{GDBN} Command
19626 The corresponding @value{GDBN} command is @samp{step}.
19628 @subsubheading Example
19630 Stepping into a function:
19636 *stopped,reason="end-stepping-range",
19637 frame=@{func="foo",args=[@{name="a",value="10"@},
19638 @{name="b",value="0"@}],file="recursive2.c",
19639 fullname="/home/foo/bar/recursive2.c",line="11"@}
19649 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19654 @subheading The @code{-exec-step-instruction} Command
19655 @findex -exec-step-instruction
19657 @subsubheading Synopsis
19660 -exec-step-instruction
19663 Resumes the inferior which executes one machine instruction. The
19664 output, once @value{GDBN} has stopped, will vary depending on whether
19665 we have stopped in the middle of a source line or not. In the former
19666 case, the address at which the program stopped will be printed as
19669 @subsubheading @value{GDBN} Command
19671 The corresponding @value{GDBN} command is @samp{stepi}.
19673 @subsubheading Example
19677 -exec-step-instruction
19681 *stopped,reason="end-stepping-range",
19682 frame=@{func="foo",args=[],file="try.c",
19683 fullname="/home/foo/bar/try.c",line="10"@}
19685 -exec-step-instruction
19689 *stopped,reason="end-stepping-range",
19690 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19691 fullname="/home/foo/bar/try.c",line="10"@}
19696 @subheading The @code{-exec-until} Command
19697 @findex -exec-until
19699 @subsubheading Synopsis
19702 -exec-until [ @var{location} ]
19705 Executes the inferior until the @var{location} specified in the
19706 argument is reached. If there is no argument, the inferior executes
19707 until a source line greater than the current one is reached. The
19708 reason for stopping in this case will be @samp{location-reached}.
19710 @subsubheading @value{GDBN} Command
19712 The corresponding @value{GDBN} command is @samp{until}.
19714 @subsubheading Example
19718 -exec-until recursive2.c:6
19722 *stopped,reason="location-reached",frame=@{func="main",args=[],
19723 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19728 @subheading -file-clear
19729 Is this going away????
19732 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19733 @node GDB/MI Stack Manipulation
19734 @section @sc{gdb/mi} Stack Manipulation Commands
19737 @subheading The @code{-stack-info-frame} Command
19738 @findex -stack-info-frame
19740 @subsubheading Synopsis
19746 Get info on the selected frame.
19748 @subsubheading @value{GDBN} Command
19750 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19751 (without arguments).
19753 @subsubheading Example
19758 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19759 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19760 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19764 @subheading The @code{-stack-info-depth} Command
19765 @findex -stack-info-depth
19767 @subsubheading Synopsis
19770 -stack-info-depth [ @var{max-depth} ]
19773 Return the depth of the stack. If the integer argument @var{max-depth}
19774 is specified, do not count beyond @var{max-depth} frames.
19776 @subsubheading @value{GDBN} Command
19778 There's no equivalent @value{GDBN} command.
19780 @subsubheading Example
19782 For a stack with frame levels 0 through 11:
19789 -stack-info-depth 4
19792 -stack-info-depth 12
19795 -stack-info-depth 11
19798 -stack-info-depth 13
19803 @subheading The @code{-stack-list-arguments} Command
19804 @findex -stack-list-arguments
19806 @subsubheading Synopsis
19809 -stack-list-arguments @var{show-values}
19810 [ @var{low-frame} @var{high-frame} ]
19813 Display a list of the arguments for the frames between @var{low-frame}
19814 and @var{high-frame} (inclusive). If @var{low-frame} and
19815 @var{high-frame} are not provided, list the arguments for the whole
19816 call stack. If the two arguments are equal, show the single frame
19817 at the corresponding level. It is an error if @var{low-frame} is
19818 larger than the actual number of frames. On the other hand,
19819 @var{high-frame} may be larger than the actual number of frames, in
19820 which case only existing frames will be returned.
19822 The @var{show-values} argument must have a value of 0 or 1. A value of
19823 0 means that only the names of the arguments are listed, a value of 1
19824 means that both names and values of the arguments are printed.
19826 @subsubheading @value{GDBN} Command
19828 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19829 @samp{gdb_get_args} command which partially overlaps with the
19830 functionality of @samp{-stack-list-arguments}.
19832 @subsubheading Example
19839 frame=@{level="0",addr="0x00010734",func="callee4",
19840 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19841 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19842 frame=@{level="1",addr="0x0001076c",func="callee3",
19843 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19844 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19845 frame=@{level="2",addr="0x0001078c",func="callee2",
19846 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19847 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19848 frame=@{level="3",addr="0x000107b4",func="callee1",
19849 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19850 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19851 frame=@{level="4",addr="0x000107e0",func="main",
19852 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19853 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19855 -stack-list-arguments 0
19858 frame=@{level="0",args=[]@},
19859 frame=@{level="1",args=[name="strarg"]@},
19860 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19861 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19862 frame=@{level="4",args=[]@}]
19864 -stack-list-arguments 1
19867 frame=@{level="0",args=[]@},
19869 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19870 frame=@{level="2",args=[
19871 @{name="intarg",value="2"@},
19872 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19873 @{frame=@{level="3",args=[
19874 @{name="intarg",value="2"@},
19875 @{name="strarg",value="0x11940 \"A string argument.\""@},
19876 @{name="fltarg",value="3.5"@}]@},
19877 frame=@{level="4",args=[]@}]
19879 -stack-list-arguments 0 2 2
19880 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19882 -stack-list-arguments 1 2 2
19883 ^done,stack-args=[frame=@{level="2",
19884 args=[@{name="intarg",value="2"@},
19885 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19889 @c @subheading -stack-list-exception-handlers
19892 @subheading The @code{-stack-list-frames} Command
19893 @findex -stack-list-frames
19895 @subsubheading Synopsis
19898 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19901 List the frames currently on the stack. For each frame it displays the
19906 The frame number, 0 being the topmost frame, i.e., the innermost function.
19908 The @code{$pc} value for that frame.
19912 File name of the source file where the function lives.
19914 Line number corresponding to the @code{$pc}.
19917 If invoked without arguments, this command prints a backtrace for the
19918 whole stack. If given two integer arguments, it shows the frames whose
19919 levels are between the two arguments (inclusive). If the two arguments
19920 are equal, it shows the single frame at the corresponding level. It is
19921 an error if @var{low-frame} is larger than the actual number of
19922 frames. On the other hand, @var{high-frame} may be larger than the
19923 actual number of frames, in which case only existing frames will be returned.
19925 @subsubheading @value{GDBN} Command
19927 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19929 @subsubheading Example
19931 Full stack backtrace:
19937 [frame=@{level="0",addr="0x0001076c",func="foo",
19938 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19939 frame=@{level="1",addr="0x000107a4",func="foo",
19940 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19941 frame=@{level="2",addr="0x000107a4",func="foo",
19942 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19943 frame=@{level="3",addr="0x000107a4",func="foo",
19944 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19945 frame=@{level="4",addr="0x000107a4",func="foo",
19946 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19947 frame=@{level="5",addr="0x000107a4",func="foo",
19948 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19949 frame=@{level="6",addr="0x000107a4",func="foo",
19950 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19951 frame=@{level="7",addr="0x000107a4",func="foo",
19952 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19953 frame=@{level="8",addr="0x000107a4",func="foo",
19954 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19955 frame=@{level="9",addr="0x000107a4",func="foo",
19956 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19957 frame=@{level="10",addr="0x000107a4",func="foo",
19958 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19959 frame=@{level="11",addr="0x00010738",func="main",
19960 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19964 Show frames between @var{low_frame} and @var{high_frame}:
19968 -stack-list-frames 3 5
19970 [frame=@{level="3",addr="0x000107a4",func="foo",
19971 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19972 frame=@{level="4",addr="0x000107a4",func="foo",
19973 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19974 frame=@{level="5",addr="0x000107a4",func="foo",
19975 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19979 Show a single frame:
19983 -stack-list-frames 3 3
19985 [frame=@{level="3",addr="0x000107a4",func="foo",
19986 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19991 @subheading The @code{-stack-list-locals} Command
19992 @findex -stack-list-locals
19994 @subsubheading Synopsis
19997 -stack-list-locals @var{print-values}
20000 Display the local variable names for the selected frame. If
20001 @var{print-values} is 0 or @code{--no-values}, print only the names of
20002 the variables; if it is 1 or @code{--all-values}, print also their
20003 values; and if it is 2 or @code{--simple-values}, print the name,
20004 type and value for simple data types and the name and type for arrays,
20005 structures and unions. In this last case, a frontend can immediately
20006 display the value of simple data types and create variable objects for
20007 other data types when the user wishes to explore their values in
20010 @subsubheading @value{GDBN} Command
20012 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
20014 @subsubheading Example
20018 -stack-list-locals 0
20019 ^done,locals=[name="A",name="B",name="C"]
20021 -stack-list-locals --all-values
20022 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
20023 @{name="C",value="@{1, 2, 3@}"@}]
20024 -stack-list-locals --simple-values
20025 ^done,locals=[@{name="A",type="int",value="1"@},
20026 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
20031 @subheading The @code{-stack-select-frame} Command
20032 @findex -stack-select-frame
20034 @subsubheading Synopsis
20037 -stack-select-frame @var{framenum}
20040 Change the selected frame. Select a different frame @var{framenum} on
20043 @subsubheading @value{GDBN} Command
20045 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
20046 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
20048 @subsubheading Example
20052 -stack-select-frame 2
20057 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20058 @node GDB/MI Variable Objects
20059 @section @sc{gdb/mi} Variable Objects
20063 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20065 For the implementation of a variable debugger window (locals, watched
20066 expressions, etc.), we are proposing the adaptation of the existing code
20067 used by @code{Insight}.
20069 The two main reasons for that are:
20073 It has been proven in practice (it is already on its second generation).
20076 It will shorten development time (needless to say how important it is
20080 The original interface was designed to be used by Tcl code, so it was
20081 slightly changed so it could be used through @sc{gdb/mi}. This section
20082 describes the @sc{gdb/mi} operations that will be available and gives some
20083 hints about their use.
20085 @emph{Note}: In addition to the set of operations described here, we
20086 expect the @sc{gui} implementation of a variable window to require, at
20087 least, the following operations:
20090 @item @code{-gdb-show} @code{output-radix}
20091 @item @code{-stack-list-arguments}
20092 @item @code{-stack-list-locals}
20093 @item @code{-stack-select-frame}
20098 @subheading Introduction to Variable Objects
20100 @cindex variable objects in @sc{gdb/mi}
20102 Variable objects are "object-oriented" MI interface for examining and
20103 changing values of expressions. Unlike some other MI interfaces that
20104 work with expressions, variable objects are specifically designed for
20105 simple and efficient presentation in the frontend. A variable object
20106 is identified by string name. When a variable object is created, the
20107 frontend specifies the expression for that variable object. The
20108 expression can be a simple variable, or it can be an arbitrary complex
20109 expression, and can even involve CPU registers. After creating a
20110 variable object, the frontend can invoke other variable object
20111 operations---for example to obtain or change the value of a variable
20112 object, or to change display format.
20114 Variable objects have hierarchical tree structure. Any variable object
20115 that corresponds to a composite type, such as structure in C, has
20116 a number of child variable objects, for example corresponding to each
20117 element of a structure. A child variable object can itself have
20118 children, recursively. Recursion ends when we reach
20119 leaf variable objects, which always have built-in types. Child variable
20120 objects are created only by explicit request, so if a frontend
20121 is not interested in the children of a particular variable object, no
20122 child will be created.
20124 For a leaf variable object it is possible to obtain its value as a
20125 string, or set the value from a string. String value can be also
20126 obtained for a non-leaf variable object, but it's generally a string
20127 that only indicates the type of the object, and does not list its
20128 contents. Assignment to a non-leaf variable object is not allowed.
20130 A frontend does not need to read the values of all variable objects each time
20131 the program stops. Instead, MI provides an update command that lists all
20132 variable objects whose values has changed since the last update
20133 operation. This considerably reduces the amount of data that must
20134 be transferred to the frontend. As noted above, children variable
20135 objects are created on demand, and only leaf variable objects have a
20136 real value. As result, gdb will read target memory only for leaf
20137 variables that frontend has created.
20139 The automatic update is not always desirable. For example, a frontend
20140 might want to keep a value of some expression for future reference,
20141 and never update it. For another example, fetching memory is
20142 relatively slow for embedded targets, so a frontend might want
20143 to disable automatic update for the variables that are either not
20144 visible on the screen, or ``closed''. This is possible using so
20145 called ``frozen variable objects''. Such variable objects are never
20146 implicitly updated.
20148 The following is the complete set of @sc{gdb/mi} operations defined to
20149 access this functionality:
20151 @multitable @columnfractions .4 .6
20152 @item @strong{Operation}
20153 @tab @strong{Description}
20155 @item @code{-var-create}
20156 @tab create a variable object
20157 @item @code{-var-delete}
20158 @tab delete the variable object and/or its children
20159 @item @code{-var-set-format}
20160 @tab set the display format of this variable
20161 @item @code{-var-show-format}
20162 @tab show the display format of this variable
20163 @item @code{-var-info-num-children}
20164 @tab tells how many children this object has
20165 @item @code{-var-list-children}
20166 @tab return a list of the object's children
20167 @item @code{-var-info-type}
20168 @tab show the type of this variable object
20169 @item @code{-var-info-expression}
20170 @tab print parent-relative expression that this variable object represents
20171 @item @code{-var-info-path-expression}
20172 @tab print full expression that this variable object represents
20173 @item @code{-var-show-attributes}
20174 @tab is this variable editable? does it exist here?
20175 @item @code{-var-evaluate-expression}
20176 @tab get the value of this variable
20177 @item @code{-var-assign}
20178 @tab set the value of this variable
20179 @item @code{-var-update}
20180 @tab update the variable and its children
20181 @item @code{-var-set-frozen}
20182 @tab set frozeness attribute
20185 In the next subsection we describe each operation in detail and suggest
20186 how it can be used.
20188 @subheading Description And Use of Operations on Variable Objects
20190 @subheading The @code{-var-create} Command
20191 @findex -var-create
20193 @subsubheading Synopsis
20196 -var-create @{@var{name} | "-"@}
20197 @{@var{frame-addr} | "*"@} @var{expression}
20200 This operation creates a variable object, which allows the monitoring of
20201 a variable, the result of an expression, a memory cell or a CPU
20204 The @var{name} parameter is the string by which the object can be
20205 referenced. It must be unique. If @samp{-} is specified, the varobj
20206 system will generate a string ``varNNNNNN'' automatically. It will be
20207 unique provided that one does not specify @var{name} on that format.
20208 The command fails if a duplicate name is found.
20210 The frame under which the expression should be evaluated can be
20211 specified by @var{frame-addr}. A @samp{*} indicates that the current
20212 frame should be used.
20214 @var{expression} is any expression valid on the current language set (must not
20215 begin with a @samp{*}), or one of the following:
20219 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20222 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20225 @samp{$@var{regname}} --- a CPU register name
20228 @subsubheading Result
20230 This operation returns the name, number of children and the type of the
20231 object created. Type is returned as a string as the ones generated by
20232 the @value{GDBN} CLI:
20235 name="@var{name}",numchild="N",type="@var{type}"
20239 @subheading The @code{-var-delete} Command
20240 @findex -var-delete
20242 @subsubheading Synopsis
20245 -var-delete [ -c ] @var{name}
20248 Deletes a previously created variable object and all of its children.
20249 With the @samp{-c} option, just deletes the children.
20251 Returns an error if the object @var{name} is not found.
20254 @subheading The @code{-var-set-format} Command
20255 @findex -var-set-format
20257 @subsubheading Synopsis
20260 -var-set-format @var{name} @var{format-spec}
20263 Sets the output format for the value of the object @var{name} to be
20266 @anchor{-var-set-format}
20267 The syntax for the @var{format-spec} is as follows:
20270 @var{format-spec} @expansion{}
20271 @{binary | decimal | hexadecimal | octal | natural@}
20274 The natural format is the default format choosen automatically
20275 based on the variable type (like decimal for an @code{int}, hex
20276 for pointers, etc.).
20278 For a variable with children, the format is set only on the
20279 variable itself, and the children are not affected.
20281 @subheading The @code{-var-show-format} Command
20282 @findex -var-show-format
20284 @subsubheading Synopsis
20287 -var-show-format @var{name}
20290 Returns the format used to display the value of the object @var{name}.
20293 @var{format} @expansion{}
20298 @subheading The @code{-var-info-num-children} Command
20299 @findex -var-info-num-children
20301 @subsubheading Synopsis
20304 -var-info-num-children @var{name}
20307 Returns the number of children of a variable object @var{name}:
20314 @subheading The @code{-var-list-children} Command
20315 @findex -var-list-children
20317 @subsubheading Synopsis
20320 -var-list-children [@var{print-values}] @var{name}
20322 @anchor{-var-list-children}
20324 Return a list of the children of the specified variable object and
20325 create variable objects for them, if they do not already exist. With
20326 a single argument or if @var{print-values} has a value for of 0 or
20327 @code{--no-values}, print only the names of the variables; if
20328 @var{print-values} is 1 or @code{--all-values}, also print their
20329 values; and if it is 2 or @code{--simple-values} print the name and
20330 value for simple data types and just the name for arrays, structures
20333 @subsubheading Example
20337 -var-list-children n
20338 ^done,numchild=@var{n},children=[@{name=@var{name},
20339 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20341 -var-list-children --all-values n
20342 ^done,numchild=@var{n},children=[@{name=@var{name},
20343 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20347 @subheading The @code{-var-info-type} Command
20348 @findex -var-info-type
20350 @subsubheading Synopsis
20353 -var-info-type @var{name}
20356 Returns the type of the specified variable @var{name}. The type is
20357 returned as a string in the same format as it is output by the
20361 type=@var{typename}
20365 @subheading The @code{-var-info-expression} Command
20366 @findex -var-info-expression
20368 @subsubheading Synopsis
20371 -var-info-expression @var{name}
20374 Returns a string that is suitable for presenting this
20375 variable object in user interface. The string is generally
20376 not valid expression in the current language, and cannot be evaluated.
20378 For example, if @code{a} is an array, and variable object
20379 @code{A} was created for @code{a}, then we'll get this output:
20382 (gdb) -var-info-expression A.1
20383 ^done,lang="C",exp="1"
20387 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
20389 Note that the output of the @code{-var-list-children} command also
20390 includes those expressions, so the @code{-var-info-expression} command
20393 @subheading The @code{-var-info-path-expression} Command
20394 @findex -var-info-path-expression
20396 @subsubheading Synopsis
20399 -var-info-path-expression @var{name}
20402 Returns an expression that can be evaluated in the current
20403 context and will yield the same value that a variable object has.
20404 Compare this with the @code{-var-info-expression} command, which
20405 result can be used only for UI presentation. Typical use of
20406 the @code{-var-info-path-expression} command is creating a
20407 watchpoint from a variable object.
20409 For example, suppose @code{C} is a C@t{++} class, derived from class
20410 @code{Base}, and that the @code{Base} class has a member called
20411 @code{m_size}. Assume a variable @code{c} is has the type of
20412 @code{C} and a variable object @code{C} was created for variable
20413 @code{c}. Then, we'll get this output:
20415 (gdb) -var-info-path-expression C.Base.public.m_size
20416 ^done,path_expr=((Base)c).m_size)
20419 @subheading The @code{-var-show-attributes} Command
20420 @findex -var-show-attributes
20422 @subsubheading Synopsis
20425 -var-show-attributes @var{name}
20428 List attributes of the specified variable object @var{name}:
20431 status=@var{attr} [ ( ,@var{attr} )* ]
20435 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20437 @subheading The @code{-var-evaluate-expression} Command
20438 @findex -var-evaluate-expression
20440 @subsubheading Synopsis
20443 -var-evaluate-expression [-f @var{format-spec}] @var{name}
20446 Evaluates the expression that is represented by the specified variable
20447 object and returns its value as a string. The format of the string
20448 can be specified with the @samp{-f} option. The possible values of
20449 this option are the same as for @code{-var-set-format}
20450 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
20451 the current display format will be used. The current display format
20452 can be changed using the @code{-var-set-format} command.
20458 Note that one must invoke @code{-var-list-children} for a variable
20459 before the value of a child variable can be evaluated.
20461 @subheading The @code{-var-assign} Command
20462 @findex -var-assign
20464 @subsubheading Synopsis
20467 -var-assign @var{name} @var{expression}
20470 Assigns the value of @var{expression} to the variable object specified
20471 by @var{name}. The object must be @samp{editable}. If the variable's
20472 value is altered by the assign, the variable will show up in any
20473 subsequent @code{-var-update} list.
20475 @subsubheading Example
20483 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20487 @subheading The @code{-var-update} Command
20488 @findex -var-update
20490 @subsubheading Synopsis
20493 -var-update [@var{print-values}] @{@var{name} | "*"@}
20496 Reevaluate the expressions corresponding to the variable object
20497 @var{name} and all its direct and indirect children, and return the
20498 list of variable objects whose values have changed; @var{name} must
20499 be a root variable object. Here, ``changed'' means that the result of
20500 @code{-var-evaluate-expression} before and after the
20501 @code{-var-update} is different. If @samp{*} is used as the variable
20502 object names, all existing variable objects are updated, except
20503 for frozen ones (@pxref{-var-set-frozen}). The option
20504 @var{print-values} determines whether both names and values, or just
20505 names are printed. The possible values of this option are the same
20506 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
20507 recommended to use the @samp{--all-values} option, to reduce the
20508 number of MI commands needed on each program stop.
20511 @subsubheading Example
20518 -var-update --all-values var1
20519 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20520 type_changed="false"@}]
20524 @anchor{-var-update}
20525 The field in_scope may take three values:
20529 The variable object's current value is valid.
20532 The variable object does not currently hold a valid value but it may
20533 hold one in the future if its associated expression comes back into
20537 The variable object no longer holds a valid value.
20538 This can occur when the executable file being debugged has changed,
20539 either through recompilation or by using the @value{GDBN} @code{file}
20540 command. The front end should normally choose to delete these variable
20544 In the future new values may be added to this list so the front should
20545 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
20547 @subheading The @code{-var-set-frozen} Command
20548 @findex -var-set-frozen
20549 @anchor{-var-set-frozen}
20551 @subsubheading Synopsis
20554 -var-set-frozen @var{name} @var{flag}
20557 Set the frozenness flag on the variable object @var{name}. The
20558 @var{flag} parameter should be either @samp{1} to make the variable
20559 frozen or @samp{0} to make it unfrozen. If a variable object is
20560 frozen, then neither itself, nor any of its children, are
20561 implicitly updated by @code{-var-update} of
20562 a parent variable or by @code{-var-update *}. Only
20563 @code{-var-update} of the variable itself will update its value and
20564 values of its children. After a variable object is unfrozen, it is
20565 implicitly updated by all subsequent @code{-var-update} operations.
20566 Unfreezing a variable does not update it, only subsequent
20567 @code{-var-update} does.
20569 @subsubheading Example
20573 -var-set-frozen V 1
20579 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20580 @node GDB/MI Data Manipulation
20581 @section @sc{gdb/mi} Data Manipulation
20583 @cindex data manipulation, in @sc{gdb/mi}
20584 @cindex @sc{gdb/mi}, data manipulation
20585 This section describes the @sc{gdb/mi} commands that manipulate data:
20586 examine memory and registers, evaluate expressions, etc.
20588 @c REMOVED FROM THE INTERFACE.
20589 @c @subheading -data-assign
20590 @c Change the value of a program variable. Plenty of side effects.
20591 @c @subsubheading GDB Command
20593 @c @subsubheading Example
20596 @subheading The @code{-data-disassemble} Command
20597 @findex -data-disassemble
20599 @subsubheading Synopsis
20603 [ -s @var{start-addr} -e @var{end-addr} ]
20604 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20612 @item @var{start-addr}
20613 is the beginning address (or @code{$pc})
20614 @item @var{end-addr}
20616 @item @var{filename}
20617 is the name of the file to disassemble
20618 @item @var{linenum}
20619 is the line number to disassemble around
20621 is the number of disassembly lines to be produced. If it is -1,
20622 the whole function will be disassembled, in case no @var{end-addr} is
20623 specified. If @var{end-addr} is specified as a non-zero value, and
20624 @var{lines} is lower than the number of disassembly lines between
20625 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20626 displayed; if @var{lines} is higher than the number of lines between
20627 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20630 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20634 @subsubheading Result
20636 The output for each instruction is composed of four fields:
20645 Note that whatever included in the instruction field, is not manipulated
20646 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20648 @subsubheading @value{GDBN} Command
20650 There's no direct mapping from this command to the CLI.
20652 @subsubheading Example
20654 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20658 -data-disassemble -s $pc -e "$pc + 20" -- 0
20661 @{address="0x000107c0",func-name="main",offset="4",
20662 inst="mov 2, %o0"@},
20663 @{address="0x000107c4",func-name="main",offset="8",
20664 inst="sethi %hi(0x11800), %o2"@},
20665 @{address="0x000107c8",func-name="main",offset="12",
20666 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20667 @{address="0x000107cc",func-name="main",offset="16",
20668 inst="sethi %hi(0x11800), %o2"@},
20669 @{address="0x000107d0",func-name="main",offset="20",
20670 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20674 Disassemble the whole @code{main} function. Line 32 is part of
20678 -data-disassemble -f basics.c -l 32 -- 0
20680 @{address="0x000107bc",func-name="main",offset="0",
20681 inst="save %sp, -112, %sp"@},
20682 @{address="0x000107c0",func-name="main",offset="4",
20683 inst="mov 2, %o0"@},
20684 @{address="0x000107c4",func-name="main",offset="8",
20685 inst="sethi %hi(0x11800), %o2"@},
20687 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20688 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20692 Disassemble 3 instructions from the start of @code{main}:
20696 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20698 @{address="0x000107bc",func-name="main",offset="0",
20699 inst="save %sp, -112, %sp"@},
20700 @{address="0x000107c0",func-name="main",offset="4",
20701 inst="mov 2, %o0"@},
20702 @{address="0x000107c4",func-name="main",offset="8",
20703 inst="sethi %hi(0x11800), %o2"@}]
20707 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20711 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20713 src_and_asm_line=@{line="31",
20714 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20715 testsuite/gdb.mi/basics.c",line_asm_insn=[
20716 @{address="0x000107bc",func-name="main",offset="0",
20717 inst="save %sp, -112, %sp"@}]@},
20718 src_and_asm_line=@{line="32",
20719 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20720 testsuite/gdb.mi/basics.c",line_asm_insn=[
20721 @{address="0x000107c0",func-name="main",offset="4",
20722 inst="mov 2, %o0"@},
20723 @{address="0x000107c4",func-name="main",offset="8",
20724 inst="sethi %hi(0x11800), %o2"@}]@}]
20729 @subheading The @code{-data-evaluate-expression} Command
20730 @findex -data-evaluate-expression
20732 @subsubheading Synopsis
20735 -data-evaluate-expression @var{expr}
20738 Evaluate @var{expr} as an expression. The expression could contain an
20739 inferior function call. The function call will execute synchronously.
20740 If the expression contains spaces, it must be enclosed in double quotes.
20742 @subsubheading @value{GDBN} Command
20744 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20745 @samp{call}. In @code{gdbtk} only, there's a corresponding
20746 @samp{gdb_eval} command.
20748 @subsubheading Example
20750 In the following example, the numbers that precede the commands are the
20751 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20752 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20756 211-data-evaluate-expression A
20759 311-data-evaluate-expression &A
20760 311^done,value="0xefffeb7c"
20762 411-data-evaluate-expression A+3
20765 511-data-evaluate-expression "A + 3"
20771 @subheading The @code{-data-list-changed-registers} Command
20772 @findex -data-list-changed-registers
20774 @subsubheading Synopsis
20777 -data-list-changed-registers
20780 Display a list of the registers that have changed.
20782 @subsubheading @value{GDBN} Command
20784 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20785 has the corresponding command @samp{gdb_changed_register_list}.
20787 @subsubheading Example
20789 On a PPC MBX board:
20797 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
20798 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
20801 -data-list-changed-registers
20802 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20803 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20804 "24","25","26","27","28","30","31","64","65","66","67","69"]
20809 @subheading The @code{-data-list-register-names} Command
20810 @findex -data-list-register-names
20812 @subsubheading Synopsis
20815 -data-list-register-names [ ( @var{regno} )+ ]
20818 Show a list of register names for the current target. If no arguments
20819 are given, it shows a list of the names of all the registers. If
20820 integer numbers are given as arguments, it will print a list of the
20821 names of the registers corresponding to the arguments. To ensure
20822 consistency between a register name and its number, the output list may
20823 include empty register names.
20825 @subsubheading @value{GDBN} Command
20827 @value{GDBN} does not have a command which corresponds to
20828 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20829 corresponding command @samp{gdb_regnames}.
20831 @subsubheading Example
20833 For the PPC MBX board:
20836 -data-list-register-names
20837 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20838 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20839 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20840 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20841 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20842 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20843 "", "pc","ps","cr","lr","ctr","xer"]
20845 -data-list-register-names 1 2 3
20846 ^done,register-names=["r1","r2","r3"]
20850 @subheading The @code{-data-list-register-values} Command
20851 @findex -data-list-register-values
20853 @subsubheading Synopsis
20856 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20859 Display the registers' contents. @var{fmt} is the format according to
20860 which the registers' contents are to be returned, followed by an optional
20861 list of numbers specifying the registers to display. A missing list of
20862 numbers indicates that the contents of all the registers must be returned.
20864 Allowed formats for @var{fmt} are:
20881 @subsubheading @value{GDBN} Command
20883 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20884 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20886 @subsubheading Example
20888 For a PPC MBX board (note: line breaks are for readability only, they
20889 don't appear in the actual output):
20893 -data-list-register-values r 64 65
20894 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20895 @{number="65",value="0x00029002"@}]
20897 -data-list-register-values x
20898 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20899 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20900 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20901 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20902 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20903 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20904 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20905 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20906 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20907 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20908 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20909 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20910 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20911 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20912 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20913 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20914 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20915 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20916 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20917 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20918 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20919 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20920 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20921 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20922 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20923 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20924 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20925 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20926 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20927 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20928 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20929 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20930 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20931 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20932 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20933 @{number="69",value="0x20002b03"@}]
20938 @subheading The @code{-data-read-memory} Command
20939 @findex -data-read-memory
20941 @subsubheading Synopsis
20944 -data-read-memory [ -o @var{byte-offset} ]
20945 @var{address} @var{word-format} @var{word-size}
20946 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20953 @item @var{address}
20954 An expression specifying the address of the first memory word to be
20955 read. Complex expressions containing embedded white space should be
20956 quoted using the C convention.
20958 @item @var{word-format}
20959 The format to be used to print the memory words. The notation is the
20960 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20963 @item @var{word-size}
20964 The size of each memory word in bytes.
20966 @item @var{nr-rows}
20967 The number of rows in the output table.
20969 @item @var{nr-cols}
20970 The number of columns in the output table.
20973 If present, indicates that each row should include an @sc{ascii} dump. The
20974 value of @var{aschar} is used as a padding character when a byte is not a
20975 member of the printable @sc{ascii} character set (printable @sc{ascii}
20976 characters are those whose code is between 32 and 126, inclusively).
20978 @item @var{byte-offset}
20979 An offset to add to the @var{address} before fetching memory.
20982 This command displays memory contents as a table of @var{nr-rows} by
20983 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20984 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20985 (returned as @samp{total-bytes}). Should less than the requested number
20986 of bytes be returned by the target, the missing words are identified
20987 using @samp{N/A}. The number of bytes read from the target is returned
20988 in @samp{nr-bytes} and the starting address used to read memory in
20991 The address of the next/previous row or page is available in
20992 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20995 @subsubheading @value{GDBN} Command
20997 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20998 @samp{gdb_get_mem} memory read command.
21000 @subsubheading Example
21002 Read six bytes of memory starting at @code{bytes+6} but then offset by
21003 @code{-6} bytes. Format as three rows of two columns. One byte per
21004 word. Display each word in hex.
21008 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
21009 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
21010 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
21011 prev-page="0x0000138a",memory=[
21012 @{addr="0x00001390",data=["0x00","0x01"]@},
21013 @{addr="0x00001392",data=["0x02","0x03"]@},
21014 @{addr="0x00001394",data=["0x04","0x05"]@}]
21018 Read two bytes of memory starting at address @code{shorts + 64} and
21019 display as a single word formatted in decimal.
21023 5-data-read-memory shorts+64 d 2 1 1
21024 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
21025 next-row="0x00001512",prev-row="0x0000150e",
21026 next-page="0x00001512",prev-page="0x0000150e",memory=[
21027 @{addr="0x00001510",data=["128"]@}]
21031 Read thirty two bytes of memory starting at @code{bytes+16} and format
21032 as eight rows of four columns. Include a string encoding with @samp{x}
21033 used as the non-printable character.
21037 4-data-read-memory bytes+16 x 1 8 4 x
21038 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
21039 next-row="0x000013c0",prev-row="0x0000139c",
21040 next-page="0x000013c0",prev-page="0x00001380",memory=[
21041 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
21042 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
21043 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
21044 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
21045 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
21046 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
21047 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
21048 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
21052 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21053 @node GDB/MI Tracepoint Commands
21054 @section @sc{gdb/mi} Tracepoint Commands
21056 The tracepoint commands are not yet implemented.
21058 @c @subheading -trace-actions
21060 @c @subheading -trace-delete
21062 @c @subheading -trace-disable
21064 @c @subheading -trace-dump
21066 @c @subheading -trace-enable
21068 @c @subheading -trace-exists
21070 @c @subheading -trace-find
21072 @c @subheading -trace-frame-number
21074 @c @subheading -trace-info
21076 @c @subheading -trace-insert
21078 @c @subheading -trace-list
21080 @c @subheading -trace-pass-count
21082 @c @subheading -trace-save
21084 @c @subheading -trace-start
21086 @c @subheading -trace-stop
21089 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21090 @node GDB/MI Symbol Query
21091 @section @sc{gdb/mi} Symbol Query Commands
21094 @subheading The @code{-symbol-info-address} Command
21095 @findex -symbol-info-address
21097 @subsubheading Synopsis
21100 -symbol-info-address @var{symbol}
21103 Describe where @var{symbol} is stored.
21105 @subsubheading @value{GDBN} Command
21107 The corresponding @value{GDBN} command is @samp{info address}.
21109 @subsubheading Example
21113 @subheading The @code{-symbol-info-file} Command
21114 @findex -symbol-info-file
21116 @subsubheading Synopsis
21122 Show the file for the symbol.
21124 @subsubheading @value{GDBN} Command
21126 There's no equivalent @value{GDBN} command. @code{gdbtk} has
21127 @samp{gdb_find_file}.
21129 @subsubheading Example
21133 @subheading The @code{-symbol-info-function} Command
21134 @findex -symbol-info-function
21136 @subsubheading Synopsis
21139 -symbol-info-function
21142 Show which function the symbol lives in.
21144 @subsubheading @value{GDBN} Command
21146 @samp{gdb_get_function} in @code{gdbtk}.
21148 @subsubheading Example
21152 @subheading The @code{-symbol-info-line} Command
21153 @findex -symbol-info-line
21155 @subsubheading Synopsis
21161 Show the core addresses of the code for a source line.
21163 @subsubheading @value{GDBN} Command
21165 The corresponding @value{GDBN} command is @samp{info line}.
21166 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
21168 @subsubheading Example
21172 @subheading The @code{-symbol-info-symbol} Command
21173 @findex -symbol-info-symbol
21175 @subsubheading Synopsis
21178 -symbol-info-symbol @var{addr}
21181 Describe what symbol is at location @var{addr}.
21183 @subsubheading @value{GDBN} Command
21185 The corresponding @value{GDBN} command is @samp{info symbol}.
21187 @subsubheading Example
21191 @subheading The @code{-symbol-list-functions} Command
21192 @findex -symbol-list-functions
21194 @subsubheading Synopsis
21197 -symbol-list-functions
21200 List the functions in the executable.
21202 @subsubheading @value{GDBN} Command
21204 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
21205 @samp{gdb_search} in @code{gdbtk}.
21207 @subsubheading Example
21211 @subheading The @code{-symbol-list-lines} Command
21212 @findex -symbol-list-lines
21214 @subsubheading Synopsis
21217 -symbol-list-lines @var{filename}
21220 Print the list of lines that contain code and their associated program
21221 addresses for the given source filename. The entries are sorted in
21222 ascending PC order.
21224 @subsubheading @value{GDBN} Command
21226 There is no corresponding @value{GDBN} command.
21228 @subsubheading Example
21231 -symbol-list-lines basics.c
21232 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
21237 @subheading The @code{-symbol-list-types} Command
21238 @findex -symbol-list-types
21240 @subsubheading Synopsis
21246 List all the type names.
21248 @subsubheading @value{GDBN} Command
21250 The corresponding commands are @samp{info types} in @value{GDBN},
21251 @samp{gdb_search} in @code{gdbtk}.
21253 @subsubheading Example
21257 @subheading The @code{-symbol-list-variables} Command
21258 @findex -symbol-list-variables
21260 @subsubheading Synopsis
21263 -symbol-list-variables
21266 List all the global and static variable names.
21268 @subsubheading @value{GDBN} Command
21270 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
21272 @subsubheading Example
21276 @subheading The @code{-symbol-locate} Command
21277 @findex -symbol-locate
21279 @subsubheading Synopsis
21285 @subsubheading @value{GDBN} Command
21287 @samp{gdb_loc} in @code{gdbtk}.
21289 @subsubheading Example
21293 @subheading The @code{-symbol-type} Command
21294 @findex -symbol-type
21296 @subsubheading Synopsis
21299 -symbol-type @var{variable}
21302 Show type of @var{variable}.
21304 @subsubheading @value{GDBN} Command
21306 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
21307 @samp{gdb_obj_variable}.
21309 @subsubheading Example
21313 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21314 @node GDB/MI File Commands
21315 @section @sc{gdb/mi} File Commands
21317 This section describes the GDB/MI commands to specify executable file names
21318 and to read in and obtain symbol table information.
21320 @subheading The @code{-file-exec-and-symbols} Command
21321 @findex -file-exec-and-symbols
21323 @subsubheading Synopsis
21326 -file-exec-and-symbols @var{file}
21329 Specify the executable file to be debugged. This file is the one from
21330 which the symbol table is also read. If no file is specified, the
21331 command clears the executable and symbol information. If breakpoints
21332 are set when using this command with no arguments, @value{GDBN} will produce
21333 error messages. Otherwise, no output is produced, except a completion
21336 @subsubheading @value{GDBN} Command
21338 The corresponding @value{GDBN} command is @samp{file}.
21340 @subsubheading Example
21344 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21350 @subheading The @code{-file-exec-file} Command
21351 @findex -file-exec-file
21353 @subsubheading Synopsis
21356 -file-exec-file @var{file}
21359 Specify the executable file to be debugged. Unlike
21360 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
21361 from this file. If used without argument, @value{GDBN} clears the information
21362 about the executable file. No output is produced, except a completion
21365 @subsubheading @value{GDBN} Command
21367 The corresponding @value{GDBN} command is @samp{exec-file}.
21369 @subsubheading Example
21373 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21379 @subheading The @code{-file-list-exec-sections} Command
21380 @findex -file-list-exec-sections
21382 @subsubheading Synopsis
21385 -file-list-exec-sections
21388 List the sections of the current executable file.
21390 @subsubheading @value{GDBN} Command
21392 The @value{GDBN} command @samp{info file} shows, among the rest, the same
21393 information as this command. @code{gdbtk} has a corresponding command
21394 @samp{gdb_load_info}.
21396 @subsubheading Example
21400 @subheading The @code{-file-list-exec-source-file} Command
21401 @findex -file-list-exec-source-file
21403 @subsubheading Synopsis
21406 -file-list-exec-source-file
21409 List the line number, the current source file, and the absolute path
21410 to the current source file for the current executable. The macro
21411 information field has a value of @samp{1} or @samp{0} depending on
21412 whether or not the file includes preprocessor macro information.
21414 @subsubheading @value{GDBN} Command
21416 The @value{GDBN} equivalent is @samp{info source}
21418 @subsubheading Example
21422 123-file-list-exec-source-file
21423 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
21428 @subheading The @code{-file-list-exec-source-files} Command
21429 @findex -file-list-exec-source-files
21431 @subsubheading Synopsis
21434 -file-list-exec-source-files
21437 List the source files for the current executable.
21439 It will always output the filename, but only when @value{GDBN} can find
21440 the absolute file name of a source file, will it output the fullname.
21442 @subsubheading @value{GDBN} Command
21444 The @value{GDBN} equivalent is @samp{info sources}.
21445 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
21447 @subsubheading Example
21450 -file-list-exec-source-files
21452 @{file=foo.c,fullname=/home/foo.c@},
21453 @{file=/home/bar.c,fullname=/home/bar.c@},
21454 @{file=gdb_could_not_find_fullpath.c@}]
21458 @subheading The @code{-file-list-shared-libraries} Command
21459 @findex -file-list-shared-libraries
21461 @subsubheading Synopsis
21464 -file-list-shared-libraries
21467 List the shared libraries in the program.
21469 @subsubheading @value{GDBN} Command
21471 The corresponding @value{GDBN} command is @samp{info shared}.
21473 @subsubheading Example
21477 @subheading The @code{-file-list-symbol-files} Command
21478 @findex -file-list-symbol-files
21480 @subsubheading Synopsis
21483 -file-list-symbol-files
21488 @subsubheading @value{GDBN} Command
21490 The corresponding @value{GDBN} command is @samp{info file} (part of it).
21492 @subsubheading Example
21496 @subheading The @code{-file-symbol-file} Command
21497 @findex -file-symbol-file
21499 @subsubheading Synopsis
21502 -file-symbol-file @var{file}
21505 Read symbol table info from the specified @var{file} argument. When
21506 used without arguments, clears @value{GDBN}'s symbol table info. No output is
21507 produced, except for a completion notification.
21509 @subsubheading @value{GDBN} Command
21511 The corresponding @value{GDBN} command is @samp{symbol-file}.
21513 @subsubheading Example
21517 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21523 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21524 @node GDB/MI Memory Overlay Commands
21525 @section @sc{gdb/mi} Memory Overlay Commands
21527 The memory overlay commands are not implemented.
21529 @c @subheading -overlay-auto
21531 @c @subheading -overlay-list-mapping-state
21533 @c @subheading -overlay-list-overlays
21535 @c @subheading -overlay-map
21537 @c @subheading -overlay-off
21539 @c @subheading -overlay-on
21541 @c @subheading -overlay-unmap
21543 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21544 @node GDB/MI Signal Handling Commands
21545 @section @sc{gdb/mi} Signal Handling Commands
21547 Signal handling commands are not implemented.
21549 @c @subheading -signal-handle
21551 @c @subheading -signal-list-handle-actions
21553 @c @subheading -signal-list-signal-types
21557 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21558 @node GDB/MI Target Manipulation
21559 @section @sc{gdb/mi} Target Manipulation Commands
21562 @subheading The @code{-target-attach} Command
21563 @findex -target-attach
21565 @subsubheading Synopsis
21568 -target-attach @var{pid} | @var{file}
21571 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
21573 @subsubheading @value{GDBN} Command
21575 The corresponding @value{GDBN} command is @samp{attach}.
21577 @subsubheading Example
21581 @subheading The @code{-target-compare-sections} Command
21582 @findex -target-compare-sections
21584 @subsubheading Synopsis
21587 -target-compare-sections [ @var{section} ]
21590 Compare data of section @var{section} on target to the exec file.
21591 Without the argument, all sections are compared.
21593 @subsubheading @value{GDBN} Command
21595 The @value{GDBN} equivalent is @samp{compare-sections}.
21597 @subsubheading Example
21601 @subheading The @code{-target-detach} Command
21602 @findex -target-detach
21604 @subsubheading Synopsis
21610 Detach from the remote target which normally resumes its execution.
21613 @subsubheading @value{GDBN} Command
21615 The corresponding @value{GDBN} command is @samp{detach}.
21617 @subsubheading Example
21627 @subheading The @code{-target-disconnect} Command
21628 @findex -target-disconnect
21630 @subsubheading Synopsis
21636 Disconnect from the remote target. There's no output and the target is
21637 generally not resumed.
21639 @subsubheading @value{GDBN} Command
21641 The corresponding @value{GDBN} command is @samp{disconnect}.
21643 @subsubheading Example
21653 @subheading The @code{-target-download} Command
21654 @findex -target-download
21656 @subsubheading Synopsis
21662 Loads the executable onto the remote target.
21663 It prints out an update message every half second, which includes the fields:
21667 The name of the section.
21669 The size of what has been sent so far for that section.
21671 The size of the section.
21673 The total size of what was sent so far (the current and the previous sections).
21675 The size of the overall executable to download.
21679 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21680 @sc{gdb/mi} Output Syntax}).
21682 In addition, it prints the name and size of the sections, as they are
21683 downloaded. These messages include the following fields:
21687 The name of the section.
21689 The size of the section.
21691 The size of the overall executable to download.
21695 At the end, a summary is printed.
21697 @subsubheading @value{GDBN} Command
21699 The corresponding @value{GDBN} command is @samp{load}.
21701 @subsubheading Example
21703 Note: each status message appears on a single line. Here the messages
21704 have been broken down so that they can fit onto a page.
21709 +download,@{section=".text",section-size="6668",total-size="9880"@}
21710 +download,@{section=".text",section-sent="512",section-size="6668",
21711 total-sent="512",total-size="9880"@}
21712 +download,@{section=".text",section-sent="1024",section-size="6668",
21713 total-sent="1024",total-size="9880"@}
21714 +download,@{section=".text",section-sent="1536",section-size="6668",
21715 total-sent="1536",total-size="9880"@}
21716 +download,@{section=".text",section-sent="2048",section-size="6668",
21717 total-sent="2048",total-size="9880"@}
21718 +download,@{section=".text",section-sent="2560",section-size="6668",
21719 total-sent="2560",total-size="9880"@}
21720 +download,@{section=".text",section-sent="3072",section-size="6668",
21721 total-sent="3072",total-size="9880"@}
21722 +download,@{section=".text",section-sent="3584",section-size="6668",
21723 total-sent="3584",total-size="9880"@}
21724 +download,@{section=".text",section-sent="4096",section-size="6668",
21725 total-sent="4096",total-size="9880"@}
21726 +download,@{section=".text",section-sent="4608",section-size="6668",
21727 total-sent="4608",total-size="9880"@}
21728 +download,@{section=".text",section-sent="5120",section-size="6668",
21729 total-sent="5120",total-size="9880"@}
21730 +download,@{section=".text",section-sent="5632",section-size="6668",
21731 total-sent="5632",total-size="9880"@}
21732 +download,@{section=".text",section-sent="6144",section-size="6668",
21733 total-sent="6144",total-size="9880"@}
21734 +download,@{section=".text",section-sent="6656",section-size="6668",
21735 total-sent="6656",total-size="9880"@}
21736 +download,@{section=".init",section-size="28",total-size="9880"@}
21737 +download,@{section=".fini",section-size="28",total-size="9880"@}
21738 +download,@{section=".data",section-size="3156",total-size="9880"@}
21739 +download,@{section=".data",section-sent="512",section-size="3156",
21740 total-sent="7236",total-size="9880"@}
21741 +download,@{section=".data",section-sent="1024",section-size="3156",
21742 total-sent="7748",total-size="9880"@}
21743 +download,@{section=".data",section-sent="1536",section-size="3156",
21744 total-sent="8260",total-size="9880"@}
21745 +download,@{section=".data",section-sent="2048",section-size="3156",
21746 total-sent="8772",total-size="9880"@}
21747 +download,@{section=".data",section-sent="2560",section-size="3156",
21748 total-sent="9284",total-size="9880"@}
21749 +download,@{section=".data",section-sent="3072",section-size="3156",
21750 total-sent="9796",total-size="9880"@}
21751 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21757 @subheading The @code{-target-exec-status} Command
21758 @findex -target-exec-status
21760 @subsubheading Synopsis
21763 -target-exec-status
21766 Provide information on the state of the target (whether it is running or
21767 not, for instance).
21769 @subsubheading @value{GDBN} Command
21771 There's no equivalent @value{GDBN} command.
21773 @subsubheading Example
21777 @subheading The @code{-target-list-available-targets} Command
21778 @findex -target-list-available-targets
21780 @subsubheading Synopsis
21783 -target-list-available-targets
21786 List the possible targets to connect to.
21788 @subsubheading @value{GDBN} Command
21790 The corresponding @value{GDBN} command is @samp{help target}.
21792 @subsubheading Example
21796 @subheading The @code{-target-list-current-targets} Command
21797 @findex -target-list-current-targets
21799 @subsubheading Synopsis
21802 -target-list-current-targets
21805 Describe the current target.
21807 @subsubheading @value{GDBN} Command
21809 The corresponding information is printed by @samp{info file} (among
21812 @subsubheading Example
21816 @subheading The @code{-target-list-parameters} Command
21817 @findex -target-list-parameters
21819 @subsubheading Synopsis
21822 -target-list-parameters
21827 @subsubheading @value{GDBN} Command
21831 @subsubheading Example
21835 @subheading The @code{-target-select} Command
21836 @findex -target-select
21838 @subsubheading Synopsis
21841 -target-select @var{type} @var{parameters @dots{}}
21844 Connect @value{GDBN} to the remote target. This command takes two args:
21848 The type of target, for instance @samp{remote}, etc.
21849 @item @var{parameters}
21850 Device names, host names and the like. @xref{Target Commands, ,
21851 Commands for Managing Targets}, for more details.
21854 The output is a connection notification, followed by the address at
21855 which the target program is, in the following form:
21858 ^connected,addr="@var{address}",func="@var{function name}",
21859 args=[@var{arg list}]
21862 @subsubheading @value{GDBN} Command
21864 The corresponding @value{GDBN} command is @samp{target}.
21866 @subsubheading Example
21870 -target-select remote /dev/ttya
21871 ^connected,addr="0xfe00a300",func="??",args=[]
21875 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21876 @node GDB/MI File Transfer Commands
21877 @section @sc{gdb/mi} File Transfer Commands
21880 @subheading The @code{-target-file-put} Command
21881 @findex -target-file-put
21883 @subsubheading Synopsis
21886 -target-file-put @var{hostfile} @var{targetfile}
21889 Copy file @var{hostfile} from the host system (the machine running
21890 @value{GDBN}) to @var{targetfile} on the target system.
21892 @subsubheading @value{GDBN} Command
21894 The corresponding @value{GDBN} command is @samp{remote put}.
21896 @subsubheading Example
21900 -target-file-put localfile remotefile
21906 @subheading The @code{-target-file-get} Command
21907 @findex -target-file-get
21909 @subsubheading Synopsis
21912 -target-file-get @var{targetfile} @var{hostfile}
21915 Copy file @var{targetfile} from the target system to @var{hostfile}
21916 on the host system.
21918 @subsubheading @value{GDBN} Command
21920 The corresponding @value{GDBN} command is @samp{remote get}.
21922 @subsubheading Example
21926 -target-file-get remotefile localfile
21932 @subheading The @code{-target-file-delete} Command
21933 @findex -target-file-delete
21935 @subsubheading Synopsis
21938 -target-file-delete @var{targetfile}
21941 Delete @var{targetfile} from the target system.
21943 @subsubheading @value{GDBN} Command
21945 The corresponding @value{GDBN} command is @samp{remote delete}.
21947 @subsubheading Example
21951 -target-file-delete remotefile
21957 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21958 @node GDB/MI Miscellaneous Commands
21959 @section Miscellaneous @sc{gdb/mi} Commands
21961 @c @subheading -gdb-complete
21963 @subheading The @code{-gdb-exit} Command
21966 @subsubheading Synopsis
21972 Exit @value{GDBN} immediately.
21974 @subsubheading @value{GDBN} Command
21976 Approximately corresponds to @samp{quit}.
21978 @subsubheading Example
21987 @subheading The @code{-exec-abort} Command
21988 @findex -exec-abort
21990 @subsubheading Synopsis
21996 Kill the inferior running program.
21998 @subsubheading @value{GDBN} Command
22000 The corresponding @value{GDBN} command is @samp{kill}.
22002 @subsubheading Example
22006 @subheading The @code{-gdb-set} Command
22009 @subsubheading Synopsis
22015 Set an internal @value{GDBN} variable.
22016 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
22018 @subsubheading @value{GDBN} Command
22020 The corresponding @value{GDBN} command is @samp{set}.
22022 @subsubheading Example
22032 @subheading The @code{-gdb-show} Command
22035 @subsubheading Synopsis
22041 Show the current value of a @value{GDBN} variable.
22043 @subsubheading @value{GDBN} Command
22045 The corresponding @value{GDBN} command is @samp{show}.
22047 @subsubheading Example
22056 @c @subheading -gdb-source
22059 @subheading The @code{-gdb-version} Command
22060 @findex -gdb-version
22062 @subsubheading Synopsis
22068 Show version information for @value{GDBN}. Used mostly in testing.
22070 @subsubheading @value{GDBN} Command
22072 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
22073 default shows this information when you start an interactive session.
22075 @subsubheading Example
22077 @c This example modifies the actual output from GDB to avoid overfull
22083 ~Copyright 2000 Free Software Foundation, Inc.
22084 ~GDB is free software, covered by the GNU General Public License, and
22085 ~you are welcome to change it and/or distribute copies of it under
22086 ~ certain conditions.
22087 ~Type "show copying" to see the conditions.
22088 ~There is absolutely no warranty for GDB. Type "show warranty" for
22090 ~This GDB was configured as
22091 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
22096 @subheading The @code{-list-features} Command
22097 @findex -list-features
22099 Returns a list of particular features of the MI protocol that
22100 this version of gdb implements. A feature can be a command,
22101 or a new field in an output of some command, or even an
22102 important bugfix. While a frontend can sometimes detect presence
22103 of a feature at runtime, it is easier to perform detection at debugger
22106 The command returns a list of strings, with each string naming an
22107 available feature. Each returned string is just a name, it does not
22108 have any internal structure. The list of possible feature names
22114 (gdb) -list-features
22115 ^done,result=["feature1","feature2"]
22118 The current list of features is:
22122 @samp{frozen-varobjs}---indicates presence of the
22123 @code{-var-set-frozen} command, as well as possible presense of the
22124 @code{frozen} field in the output of @code{-varobj-create}.
22126 @samp{pending-breakpoints}---indicates presence of the @code{-f}
22127 option to the @code{-break-insert} command.
22129 @samp{thread-info}---indicates presence of the @code{-thread-info} command.
22133 @subheading The @code{-interpreter-exec} Command
22134 @findex -interpreter-exec
22136 @subheading Synopsis
22139 -interpreter-exec @var{interpreter} @var{command}
22141 @anchor{-interpreter-exec}
22143 Execute the specified @var{command} in the given @var{interpreter}.
22145 @subheading @value{GDBN} Command
22147 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
22149 @subheading Example
22153 -interpreter-exec console "break main"
22154 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
22155 &"During symbol reading, bad structure-type format.\n"
22156 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
22161 @subheading The @code{-inferior-tty-set} Command
22162 @findex -inferior-tty-set
22164 @subheading Synopsis
22167 -inferior-tty-set /dev/pts/1
22170 Set terminal for future runs of the program being debugged.
22172 @subheading @value{GDBN} Command
22174 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
22176 @subheading Example
22180 -inferior-tty-set /dev/pts/1
22185 @subheading The @code{-inferior-tty-show} Command
22186 @findex -inferior-tty-show
22188 @subheading Synopsis
22194 Show terminal for future runs of program being debugged.
22196 @subheading @value{GDBN} Command
22198 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
22200 @subheading Example
22204 -inferior-tty-set /dev/pts/1
22208 ^done,inferior_tty_terminal="/dev/pts/1"
22212 @subheading The @code{-enable-timings} Command
22213 @findex -enable-timings
22215 @subheading Synopsis
22218 -enable-timings [yes | no]
22221 Toggle the printing of the wallclock, user and system times for an MI
22222 command as a field in its output. This command is to help frontend
22223 developers optimize the performance of their code. No argument is
22224 equivalent to @samp{yes}.
22226 @subheading @value{GDBN} Command
22230 @subheading Example
22238 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22239 addr="0x080484ed",func="main",file="myprog.c",
22240 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
22241 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
22249 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22250 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
22251 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
22252 fullname="/home/nickrob/myprog.c",line="73"@}
22257 @chapter @value{GDBN} Annotations
22259 This chapter describes annotations in @value{GDBN}. Annotations were
22260 designed to interface @value{GDBN} to graphical user interfaces or other
22261 similar programs which want to interact with @value{GDBN} at a
22262 relatively high level.
22264 The annotation mechanism has largely been superseded by @sc{gdb/mi}
22268 This is Edition @value{EDITION}, @value{DATE}.
22272 * Annotations Overview:: What annotations are; the general syntax.
22273 * Server Prefix:: Issuing a command without affecting user state.
22274 * Prompting:: Annotations marking @value{GDBN}'s need for input.
22275 * Errors:: Annotations for error messages.
22276 * Invalidation:: Some annotations describe things now invalid.
22277 * Annotations for Running::
22278 Whether the program is running, how it stopped, etc.
22279 * Source Annotations:: Annotations describing source code.
22282 @node Annotations Overview
22283 @section What is an Annotation?
22284 @cindex annotations
22286 Annotations start with a newline character, two @samp{control-z}
22287 characters, and the name of the annotation. If there is no additional
22288 information associated with this annotation, the name of the annotation
22289 is followed immediately by a newline. If there is additional
22290 information, the name of the annotation is followed by a space, the
22291 additional information, and a newline. The additional information
22292 cannot contain newline characters.
22294 Any output not beginning with a newline and two @samp{control-z}
22295 characters denotes literal output from @value{GDBN}. Currently there is
22296 no need for @value{GDBN} to output a newline followed by two
22297 @samp{control-z} characters, but if there was such a need, the
22298 annotations could be extended with an @samp{escape} annotation which
22299 means those three characters as output.
22301 The annotation @var{level}, which is specified using the
22302 @option{--annotate} command line option (@pxref{Mode Options}), controls
22303 how much information @value{GDBN} prints together with its prompt,
22304 values of expressions, source lines, and other types of output. Level 0
22305 is for no annotations, level 1 is for use when @value{GDBN} is run as a
22306 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
22307 for programs that control @value{GDBN}, and level 2 annotations have
22308 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
22309 Interface, annotate, GDB's Obsolete Annotations}).
22312 @kindex set annotate
22313 @item set annotate @var{level}
22314 The @value{GDBN} command @code{set annotate} sets the level of
22315 annotations to the specified @var{level}.
22317 @item show annotate
22318 @kindex show annotate
22319 Show the current annotation level.
22322 This chapter describes level 3 annotations.
22324 A simple example of starting up @value{GDBN} with annotations is:
22327 $ @kbd{gdb --annotate=3}
22329 Copyright 2003 Free Software Foundation, Inc.
22330 GDB is free software, covered by the GNU General Public License,
22331 and you are welcome to change it and/or distribute copies of it
22332 under certain conditions.
22333 Type "show copying" to see the conditions.
22334 There is absolutely no warranty for GDB. Type "show warranty"
22336 This GDB was configured as "i386-pc-linux-gnu"
22347 Here @samp{quit} is input to @value{GDBN}; the rest is output from
22348 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
22349 denotes a @samp{control-z} character) are annotations; the rest is
22350 output from @value{GDBN}.
22352 @node Server Prefix
22353 @section The Server Prefix
22354 @cindex server prefix
22356 If you prefix a command with @samp{server } then it will not affect
22357 the command history, nor will it affect @value{GDBN}'s notion of which
22358 command to repeat if @key{RET} is pressed on a line by itself. This
22359 means that commands can be run behind a user's back by a front-end in
22360 a transparent manner.
22362 The server prefix does not affect the recording of values into the value
22363 history; to print a value without recording it into the value history,
22364 use the @code{output} command instead of the @code{print} command.
22367 @section Annotation for @value{GDBN} Input
22369 @cindex annotations for prompts
22370 When @value{GDBN} prompts for input, it annotates this fact so it is possible
22371 to know when to send output, when the output from a given command is
22374 Different kinds of input each have a different @dfn{input type}. Each
22375 input type has three annotations: a @code{pre-} annotation, which
22376 denotes the beginning of any prompt which is being output, a plain
22377 annotation, which denotes the end of the prompt, and then a @code{post-}
22378 annotation which denotes the end of any echo which may (or may not) be
22379 associated with the input. For example, the @code{prompt} input type
22380 features the following annotations:
22388 The input types are
22391 @findex pre-prompt annotation
22392 @findex prompt annotation
22393 @findex post-prompt annotation
22395 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
22397 @findex pre-commands annotation
22398 @findex commands annotation
22399 @findex post-commands annotation
22401 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
22402 command. The annotations are repeated for each command which is input.
22404 @findex pre-overload-choice annotation
22405 @findex overload-choice annotation
22406 @findex post-overload-choice annotation
22407 @item overload-choice
22408 When @value{GDBN} wants the user to select between various overloaded functions.
22410 @findex pre-query annotation
22411 @findex query annotation
22412 @findex post-query annotation
22414 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
22416 @findex pre-prompt-for-continue annotation
22417 @findex prompt-for-continue annotation
22418 @findex post-prompt-for-continue annotation
22419 @item prompt-for-continue
22420 When @value{GDBN} is asking the user to press return to continue. Note: Don't
22421 expect this to work well; instead use @code{set height 0} to disable
22422 prompting. This is because the counting of lines is buggy in the
22423 presence of annotations.
22428 @cindex annotations for errors, warnings and interrupts
22430 @findex quit annotation
22435 This annotation occurs right before @value{GDBN} responds to an interrupt.
22437 @findex error annotation
22442 This annotation occurs right before @value{GDBN} responds to an error.
22444 Quit and error annotations indicate that any annotations which @value{GDBN} was
22445 in the middle of may end abruptly. For example, if a
22446 @code{value-history-begin} annotation is followed by a @code{error}, one
22447 cannot expect to receive the matching @code{value-history-end}. One
22448 cannot expect not to receive it either, however; an error annotation
22449 does not necessarily mean that @value{GDBN} is immediately returning all the way
22452 @findex error-begin annotation
22453 A quit or error annotation may be preceded by
22459 Any output between that and the quit or error annotation is the error
22462 Warning messages are not yet annotated.
22463 @c If we want to change that, need to fix warning(), type_error(),
22464 @c range_error(), and possibly other places.
22467 @section Invalidation Notices
22469 @cindex annotations for invalidation messages
22470 The following annotations say that certain pieces of state may have
22474 @findex frames-invalid annotation
22475 @item ^Z^Zframes-invalid
22477 The frames (for example, output from the @code{backtrace} command) may
22480 @findex breakpoints-invalid annotation
22481 @item ^Z^Zbreakpoints-invalid
22483 The breakpoints may have changed. For example, the user just added or
22484 deleted a breakpoint.
22487 @node Annotations for Running
22488 @section Running the Program
22489 @cindex annotations for running programs
22491 @findex starting annotation
22492 @findex stopping annotation
22493 When the program starts executing due to a @value{GDBN} command such as
22494 @code{step} or @code{continue},
22500 is output. When the program stops,
22506 is output. Before the @code{stopped} annotation, a variety of
22507 annotations describe how the program stopped.
22510 @findex exited annotation
22511 @item ^Z^Zexited @var{exit-status}
22512 The program exited, and @var{exit-status} is the exit status (zero for
22513 successful exit, otherwise nonzero).
22515 @findex signalled annotation
22516 @findex signal-name annotation
22517 @findex signal-name-end annotation
22518 @findex signal-string annotation
22519 @findex signal-string-end annotation
22520 @item ^Z^Zsignalled
22521 The program exited with a signal. After the @code{^Z^Zsignalled}, the
22522 annotation continues:
22528 ^Z^Zsignal-name-end
22532 ^Z^Zsignal-string-end
22537 where @var{name} is the name of the signal, such as @code{SIGILL} or
22538 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
22539 as @code{Illegal Instruction} or @code{Segmentation fault}.
22540 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
22541 user's benefit and have no particular format.
22543 @findex signal annotation
22545 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
22546 just saying that the program received the signal, not that it was
22547 terminated with it.
22549 @findex breakpoint annotation
22550 @item ^Z^Zbreakpoint @var{number}
22551 The program hit breakpoint number @var{number}.
22553 @findex watchpoint annotation
22554 @item ^Z^Zwatchpoint @var{number}
22555 The program hit watchpoint number @var{number}.
22558 @node Source Annotations
22559 @section Displaying Source
22560 @cindex annotations for source display
22562 @findex source annotation
22563 The following annotation is used instead of displaying source code:
22566 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
22569 where @var{filename} is an absolute file name indicating which source
22570 file, @var{line} is the line number within that file (where 1 is the
22571 first line in the file), @var{character} is the character position
22572 within the file (where 0 is the first character in the file) (for most
22573 debug formats this will necessarily point to the beginning of a line),
22574 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
22575 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
22576 @var{addr} is the address in the target program associated with the
22577 source which is being displayed. @var{addr} is in the form @samp{0x}
22578 followed by one or more lowercase hex digits (note that this does not
22579 depend on the language).
22582 @chapter Reporting Bugs in @value{GDBN}
22583 @cindex bugs in @value{GDBN}
22584 @cindex reporting bugs in @value{GDBN}
22586 Your bug reports play an essential role in making @value{GDBN} reliable.
22588 Reporting a bug may help you by bringing a solution to your problem, or it
22589 may not. But in any case the principal function of a bug report is to help
22590 the entire community by making the next version of @value{GDBN} work better. Bug
22591 reports are your contribution to the maintenance of @value{GDBN}.
22593 In order for a bug report to serve its purpose, you must include the
22594 information that enables us to fix the bug.
22597 * Bug Criteria:: Have you found a bug?
22598 * Bug Reporting:: How to report bugs
22602 @section Have You Found a Bug?
22603 @cindex bug criteria
22605 If you are not sure whether you have found a bug, here are some guidelines:
22608 @cindex fatal signal
22609 @cindex debugger crash
22610 @cindex crash of debugger
22612 If the debugger gets a fatal signal, for any input whatever, that is a
22613 @value{GDBN} bug. Reliable debuggers never crash.
22615 @cindex error on valid input
22617 If @value{GDBN} produces an error message for valid input, that is a
22618 bug. (Note that if you're cross debugging, the problem may also be
22619 somewhere in the connection to the target.)
22621 @cindex invalid input
22623 If @value{GDBN} does not produce an error message for invalid input,
22624 that is a bug. However, you should note that your idea of
22625 ``invalid input'' might be our idea of ``an extension'' or ``support
22626 for traditional practice''.
22629 If you are an experienced user of debugging tools, your suggestions
22630 for improvement of @value{GDBN} are welcome in any case.
22633 @node Bug Reporting
22634 @section How to Report Bugs
22635 @cindex bug reports
22636 @cindex @value{GDBN} bugs, reporting
22638 A number of companies and individuals offer support for @sc{gnu} products.
22639 If you obtained @value{GDBN} from a support organization, we recommend you
22640 contact that organization first.
22642 You can find contact information for many support companies and
22643 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
22645 @c should add a web page ref...
22648 @ifset BUGURL_DEFAULT
22649 In any event, we also recommend that you submit bug reports for
22650 @value{GDBN}. The preferred method is to submit them directly using
22651 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
22652 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
22655 @strong{Do not send bug reports to @samp{info-gdb}, or to
22656 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
22657 not want to receive bug reports. Those that do have arranged to receive
22660 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
22661 serves as a repeater. The mailing list and the newsgroup carry exactly
22662 the same messages. Often people think of posting bug reports to the
22663 newsgroup instead of mailing them. This appears to work, but it has one
22664 problem which can be crucial: a newsgroup posting often lacks a mail
22665 path back to the sender. Thus, if we need to ask for more information,
22666 we may be unable to reach you. For this reason, it is better to send
22667 bug reports to the mailing list.
22669 @ifclear BUGURL_DEFAULT
22670 In any event, we also recommend that you submit bug reports for
22671 @value{GDBN} to @value{BUGURL}.
22675 The fundamental principle of reporting bugs usefully is this:
22676 @strong{report all the facts}. If you are not sure whether to state a
22677 fact or leave it out, state it!
22679 Often people omit facts because they think they know what causes the
22680 problem and assume that some details do not matter. Thus, you might
22681 assume that the name of the variable you use in an example does not matter.
22682 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
22683 stray memory reference which happens to fetch from the location where that
22684 name is stored in memory; perhaps, if the name were different, the contents
22685 of that location would fool the debugger into doing the right thing despite
22686 the bug. Play it safe and give a specific, complete example. That is the
22687 easiest thing for you to do, and the most helpful.
22689 Keep in mind that the purpose of a bug report is to enable us to fix the
22690 bug. It may be that the bug has been reported previously, but neither
22691 you nor we can know that unless your bug report is complete and
22694 Sometimes people give a few sketchy facts and ask, ``Does this ring a
22695 bell?'' Those bug reports are useless, and we urge everyone to
22696 @emph{refuse to respond to them} except to chide the sender to report
22699 To enable us to fix the bug, you should include all these things:
22703 The version of @value{GDBN}. @value{GDBN} announces it if you start
22704 with no arguments; you can also print it at any time using @code{show
22707 Without this, we will not know whether there is any point in looking for
22708 the bug in the current version of @value{GDBN}.
22711 The type of machine you are using, and the operating system name and
22715 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
22716 ``@value{GCC}--2.8.1''.
22719 What compiler (and its version) was used to compile the program you are
22720 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
22721 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
22722 to get this information; for other compilers, see the documentation for
22726 The command arguments you gave the compiler to compile your example and
22727 observe the bug. For example, did you use @samp{-O}? To guarantee
22728 you will not omit something important, list them all. A copy of the
22729 Makefile (or the output from make) is sufficient.
22731 If we were to try to guess the arguments, we would probably guess wrong
22732 and then we might not encounter the bug.
22735 A complete input script, and all necessary source files, that will
22739 A description of what behavior you observe that you believe is
22740 incorrect. For example, ``It gets a fatal signal.''
22742 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
22743 will certainly notice it. But if the bug is incorrect output, we might
22744 not notice unless it is glaringly wrong. You might as well not give us
22745 a chance to make a mistake.
22747 Even if the problem you experience is a fatal signal, you should still
22748 say so explicitly. Suppose something strange is going on, such as, your
22749 copy of @value{GDBN} is out of synch, or you have encountered a bug in
22750 the C library on your system. (This has happened!) Your copy might
22751 crash and ours would not. If you told us to expect a crash, then when
22752 ours fails to crash, we would know that the bug was not happening for
22753 us. If you had not told us to expect a crash, then we would not be able
22754 to draw any conclusion from our observations.
22757 @cindex recording a session script
22758 To collect all this information, you can use a session recording program
22759 such as @command{script}, which is available on many Unix systems.
22760 Just run your @value{GDBN} session inside @command{script} and then
22761 include the @file{typescript} file with your bug report.
22763 Another way to record a @value{GDBN} session is to run @value{GDBN}
22764 inside Emacs and then save the entire buffer to a file.
22767 If you wish to suggest changes to the @value{GDBN} source, send us context
22768 diffs. If you even discuss something in the @value{GDBN} source, refer to
22769 it by context, not by line number.
22771 The line numbers in our development sources will not match those in your
22772 sources. Your line numbers would convey no useful information to us.
22776 Here are some things that are not necessary:
22780 A description of the envelope of the bug.
22782 Often people who encounter a bug spend a lot of time investigating
22783 which changes to the input file will make the bug go away and which
22784 changes will not affect it.
22786 This is often time consuming and not very useful, because the way we
22787 will find the bug is by running a single example under the debugger
22788 with breakpoints, not by pure deduction from a series of examples.
22789 We recommend that you save your time for something else.
22791 Of course, if you can find a simpler example to report @emph{instead}
22792 of the original one, that is a convenience for us. Errors in the
22793 output will be easier to spot, running under the debugger will take
22794 less time, and so on.
22796 However, simplification is not vital; if you do not want to do this,
22797 report the bug anyway and send us the entire test case you used.
22800 A patch for the bug.
22802 A patch for the bug does help us if it is a good one. But do not omit
22803 the necessary information, such as the test case, on the assumption that
22804 a patch is all we need. We might see problems with your patch and decide
22805 to fix the problem another way, or we might not understand it at all.
22807 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22808 construct an example that will make the program follow a certain path
22809 through the code. If you do not send us the example, we will not be able
22810 to construct one, so we will not be able to verify that the bug is fixed.
22812 And if we cannot understand what bug you are trying to fix, or why your
22813 patch should be an improvement, we will not install it. A test case will
22814 help us to understand.
22817 A guess about what the bug is or what it depends on.
22819 Such guesses are usually wrong. Even we cannot guess right about such
22820 things without first using the debugger to find the facts.
22823 @c The readline documentation is distributed with the readline code
22824 @c and consists of the two following files:
22826 @c inc-hist.texinfo
22827 @c Use -I with makeinfo to point to the appropriate directory,
22828 @c environment var TEXINPUTS with TeX.
22829 @include rluser.texi
22830 @include inc-hist.texinfo
22833 @node Formatting Documentation
22834 @appendix Formatting Documentation
22836 @cindex @value{GDBN} reference card
22837 @cindex reference card
22838 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22839 for printing with PostScript or Ghostscript, in the @file{gdb}
22840 subdirectory of the main source directory@footnote{In
22841 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22842 release.}. If you can use PostScript or Ghostscript with your printer,
22843 you can print the reference card immediately with @file{refcard.ps}.
22845 The release also includes the source for the reference card. You
22846 can format it, using @TeX{}, by typing:
22852 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22853 mode on US ``letter'' size paper;
22854 that is, on a sheet 11 inches wide by 8.5 inches
22855 high. You will need to specify this form of printing as an option to
22856 your @sc{dvi} output program.
22858 @cindex documentation
22860 All the documentation for @value{GDBN} comes as part of the machine-readable
22861 distribution. The documentation is written in Texinfo format, which is
22862 a documentation system that uses a single source file to produce both
22863 on-line information and a printed manual. You can use one of the Info
22864 formatting commands to create the on-line version of the documentation
22865 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22867 @value{GDBN} includes an already formatted copy of the on-line Info
22868 version of this manual in the @file{gdb} subdirectory. The main Info
22869 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22870 subordinate files matching @samp{gdb.info*} in the same directory. If
22871 necessary, you can print out these files, or read them with any editor;
22872 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22873 Emacs or the standalone @code{info} program, available as part of the
22874 @sc{gnu} Texinfo distribution.
22876 If you want to format these Info files yourself, you need one of the
22877 Info formatting programs, such as @code{texinfo-format-buffer} or
22880 If you have @code{makeinfo} installed, and are in the top level
22881 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22882 version @value{GDBVN}), you can make the Info file by typing:
22889 If you want to typeset and print copies of this manual, you need @TeX{},
22890 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22891 Texinfo definitions file.
22893 @TeX{} is a typesetting program; it does not print files directly, but
22894 produces output files called @sc{dvi} files. To print a typeset
22895 document, you need a program to print @sc{dvi} files. If your system
22896 has @TeX{} installed, chances are it has such a program. The precise
22897 command to use depends on your system; @kbd{lpr -d} is common; another
22898 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22899 require a file name without any extension or a @samp{.dvi} extension.
22901 @TeX{} also requires a macro definitions file called
22902 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22903 written in Texinfo format. On its own, @TeX{} cannot either read or
22904 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22905 and is located in the @file{gdb-@var{version-number}/texinfo}
22908 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22909 typeset and print this manual. First switch to the @file{gdb}
22910 subdirectory of the main source directory (for example, to
22911 @file{gdb-@value{GDBVN}/gdb}) and type:
22917 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22919 @node Installing GDB
22920 @appendix Installing @value{GDBN}
22921 @cindex installation
22924 * Requirements:: Requirements for building @value{GDBN}
22925 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22926 * Separate Objdir:: Compiling @value{GDBN} in another directory
22927 * Config Names:: Specifying names for hosts and targets
22928 * Configure Options:: Summary of options for configure
22932 @section Requirements for Building @value{GDBN}
22933 @cindex building @value{GDBN}, requirements for
22935 Building @value{GDBN} requires various tools and packages to be available.
22936 Other packages will be used only if they are found.
22938 @heading Tools/Packages Necessary for Building @value{GDBN}
22940 @item ISO C90 compiler
22941 @value{GDBN} is written in ISO C90. It should be buildable with any
22942 working C90 compiler, e.g.@: GCC.
22946 @heading Tools/Packages Optional for Building @value{GDBN}
22950 @value{GDBN} can use the Expat XML parsing library. This library may be
22951 included with your operating system distribution; if it is not, you
22952 can get the latest version from @url{http://expat.sourceforge.net}.
22953 The @file{configure} script will search for this library in several
22954 standard locations; if it is installed in an unusual path, you can
22955 use the @option{--with-libexpat-prefix} option to specify its location.
22961 Remote protocol memory maps (@pxref{Memory Map Format})
22963 Target descriptions (@pxref{Target Descriptions})
22965 Remote shared library lists (@pxref{Library List Format})
22967 MS-Windows shared libraries (@pxref{Shared Libraries})
22971 @cindex compressed debug sections
22972 @value{GDBN} will use the @samp{zlib} library, if available, to read
22973 compressed debug sections. Some linkers, such as GNU gold, are capable
22974 of producing binaries with compressed debug sections. If @value{GDBN}
22975 is compiled with @samp{zlib}, it will be able to read the debug
22976 information in such binaries.
22978 The @samp{zlib} library is likely included with your operating system
22979 distribution; if it is not, you can get the latest version from
22980 @url{http://zlib.net}.
22984 @node Running Configure
22985 @section Invoking the @value{GDBN} @file{configure} Script
22986 @cindex configuring @value{GDBN}
22987 @value{GDBN} comes with a @file{configure} script that automates the process
22988 of preparing @value{GDBN} for installation; you can then use @code{make} to
22989 build the @code{gdb} program.
22991 @c irrelevant in info file; it's as current as the code it lives with.
22992 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22993 look at the @file{README} file in the sources; we may have improved the
22994 installation procedures since publishing this manual.}
22997 The @value{GDBN} distribution includes all the source code you need for
22998 @value{GDBN} in a single directory, whose name is usually composed by
22999 appending the version number to @samp{gdb}.
23001 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
23002 @file{gdb-@value{GDBVN}} directory. That directory contains:
23005 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
23006 script for configuring @value{GDBN} and all its supporting libraries
23008 @item gdb-@value{GDBVN}/gdb
23009 the source specific to @value{GDBN} itself
23011 @item gdb-@value{GDBVN}/bfd
23012 source for the Binary File Descriptor library
23014 @item gdb-@value{GDBVN}/include
23015 @sc{gnu} include files
23017 @item gdb-@value{GDBVN}/libiberty
23018 source for the @samp{-liberty} free software library
23020 @item gdb-@value{GDBVN}/opcodes
23021 source for the library of opcode tables and disassemblers
23023 @item gdb-@value{GDBVN}/readline
23024 source for the @sc{gnu} command-line interface
23026 @item gdb-@value{GDBVN}/glob
23027 source for the @sc{gnu} filename pattern-matching subroutine
23029 @item gdb-@value{GDBVN}/mmalloc
23030 source for the @sc{gnu} memory-mapped malloc package
23033 The simplest way to configure and build @value{GDBN} is to run @file{configure}
23034 from the @file{gdb-@var{version-number}} source directory, which in
23035 this example is the @file{gdb-@value{GDBVN}} directory.
23037 First switch to the @file{gdb-@var{version-number}} source directory
23038 if you are not already in it; then run @file{configure}. Pass the
23039 identifier for the platform on which @value{GDBN} will run as an
23045 cd gdb-@value{GDBVN}
23046 ./configure @var{host}
23051 where @var{host} is an identifier such as @samp{sun4} or
23052 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
23053 (You can often leave off @var{host}; @file{configure} tries to guess the
23054 correct value by examining your system.)
23056 Running @samp{configure @var{host}} and then running @code{make} builds the
23057 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
23058 libraries, then @code{gdb} itself. The configured source files, and the
23059 binaries, are left in the corresponding source directories.
23062 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
23063 system does not recognize this automatically when you run a different
23064 shell, you may need to run @code{sh} on it explicitly:
23067 sh configure @var{host}
23070 If you run @file{configure} from a directory that contains source
23071 directories for multiple libraries or programs, such as the
23072 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
23074 creates configuration files for every directory level underneath (unless
23075 you tell it not to, with the @samp{--norecursion} option).
23077 You should run the @file{configure} script from the top directory in the
23078 source tree, the @file{gdb-@var{version-number}} directory. If you run
23079 @file{configure} from one of the subdirectories, you will configure only
23080 that subdirectory. That is usually not what you want. In particular,
23081 if you run the first @file{configure} from the @file{gdb} subdirectory
23082 of the @file{gdb-@var{version-number}} directory, you will omit the
23083 configuration of @file{bfd}, @file{readline}, and other sibling
23084 directories of the @file{gdb} subdirectory. This leads to build errors
23085 about missing include files such as @file{bfd/bfd.h}.
23087 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
23088 However, you should make sure that the shell on your path (named by
23089 the @samp{SHELL} environment variable) is publicly readable. Remember
23090 that @value{GDBN} uses the shell to start your program---some systems refuse to
23091 let @value{GDBN} debug child processes whose programs are not readable.
23093 @node Separate Objdir
23094 @section Compiling @value{GDBN} in Another Directory
23096 If you want to run @value{GDBN} versions for several host or target machines,
23097 you need a different @code{gdb} compiled for each combination of
23098 host and target. @file{configure} is designed to make this easy by
23099 allowing you to generate each configuration in a separate subdirectory,
23100 rather than in the source directory. If your @code{make} program
23101 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
23102 @code{make} in each of these directories builds the @code{gdb}
23103 program specified there.
23105 To build @code{gdb} in a separate directory, run @file{configure}
23106 with the @samp{--srcdir} option to specify where to find the source.
23107 (You also need to specify a path to find @file{configure}
23108 itself from your working directory. If the path to @file{configure}
23109 would be the same as the argument to @samp{--srcdir}, you can leave out
23110 the @samp{--srcdir} option; it is assumed.)
23112 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
23113 separate directory for a Sun 4 like this:
23117 cd gdb-@value{GDBVN}
23120 ../gdb-@value{GDBVN}/configure sun4
23125 When @file{configure} builds a configuration using a remote source
23126 directory, it creates a tree for the binaries with the same structure
23127 (and using the same names) as the tree under the source directory. In
23128 the example, you'd find the Sun 4 library @file{libiberty.a} in the
23129 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
23130 @file{gdb-sun4/gdb}.
23132 Make sure that your path to the @file{configure} script has just one
23133 instance of @file{gdb} in it. If your path to @file{configure} looks
23134 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
23135 one subdirectory of @value{GDBN}, not the whole package. This leads to
23136 build errors about missing include files such as @file{bfd/bfd.h}.
23138 One popular reason to build several @value{GDBN} configurations in separate
23139 directories is to configure @value{GDBN} for cross-compiling (where
23140 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
23141 programs that run on another machine---the @dfn{target}).
23142 You specify a cross-debugging target by
23143 giving the @samp{--target=@var{target}} option to @file{configure}.
23145 When you run @code{make} to build a program or library, you must run
23146 it in a configured directory---whatever directory you were in when you
23147 called @file{configure} (or one of its subdirectories).
23149 The @code{Makefile} that @file{configure} generates in each source
23150 directory also runs recursively. If you type @code{make} in a source
23151 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
23152 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
23153 will build all the required libraries, and then build GDB.
23155 When you have multiple hosts or targets configured in separate
23156 directories, you can run @code{make} on them in parallel (for example,
23157 if they are NFS-mounted on each of the hosts); they will not interfere
23161 @section Specifying Names for Hosts and Targets
23163 The specifications used for hosts and targets in the @file{configure}
23164 script are based on a three-part naming scheme, but some short predefined
23165 aliases are also supported. The full naming scheme encodes three pieces
23166 of information in the following pattern:
23169 @var{architecture}-@var{vendor}-@var{os}
23172 For example, you can use the alias @code{sun4} as a @var{host} argument,
23173 or as the value for @var{target} in a @code{--target=@var{target}}
23174 option. The equivalent full name is @samp{sparc-sun-sunos4}.
23176 The @file{configure} script accompanying @value{GDBN} does not provide
23177 any query facility to list all supported host and target names or
23178 aliases. @file{configure} calls the Bourne shell script
23179 @code{config.sub} to map abbreviations to full names; you can read the
23180 script, if you wish, or you can use it to test your guesses on
23181 abbreviations---for example:
23184 % sh config.sub i386-linux
23186 % sh config.sub alpha-linux
23187 alpha-unknown-linux-gnu
23188 % sh config.sub hp9k700
23190 % sh config.sub sun4
23191 sparc-sun-sunos4.1.1
23192 % sh config.sub sun3
23193 m68k-sun-sunos4.1.1
23194 % sh config.sub i986v
23195 Invalid configuration `i986v': machine `i986v' not recognized
23199 @code{config.sub} is also distributed in the @value{GDBN} source
23200 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
23202 @node Configure Options
23203 @section @file{configure} Options
23205 Here is a summary of the @file{configure} options and arguments that
23206 are most often useful for building @value{GDBN}. @file{configure} also has
23207 several other options not listed here. @inforef{What Configure
23208 Does,,configure.info}, for a full explanation of @file{configure}.
23211 configure @r{[}--help@r{]}
23212 @r{[}--prefix=@var{dir}@r{]}
23213 @r{[}--exec-prefix=@var{dir}@r{]}
23214 @r{[}--srcdir=@var{dirname}@r{]}
23215 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
23216 @r{[}--target=@var{target}@r{]}
23221 You may introduce options with a single @samp{-} rather than
23222 @samp{--} if you prefer; but you may abbreviate option names if you use
23227 Display a quick summary of how to invoke @file{configure}.
23229 @item --prefix=@var{dir}
23230 Configure the source to install programs and files under directory
23233 @item --exec-prefix=@var{dir}
23234 Configure the source to install programs under directory
23237 @c avoid splitting the warning from the explanation:
23239 @item --srcdir=@var{dirname}
23240 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
23241 @code{make} that implements the @code{VPATH} feature.}@*
23242 Use this option to make configurations in directories separate from the
23243 @value{GDBN} source directories. Among other things, you can use this to
23244 build (or maintain) several configurations simultaneously, in separate
23245 directories. @file{configure} writes configuration-specific files in
23246 the current directory, but arranges for them to use the source in the
23247 directory @var{dirname}. @file{configure} creates directories under
23248 the working directory in parallel to the source directories below
23251 @item --norecursion
23252 Configure only the directory level where @file{configure} is executed; do not
23253 propagate configuration to subdirectories.
23255 @item --target=@var{target}
23256 Configure @value{GDBN} for cross-debugging programs running on the specified
23257 @var{target}. Without this option, @value{GDBN} is configured to debug
23258 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
23260 There is no convenient way to generate a list of all available targets.
23262 @item @var{host} @dots{}
23263 Configure @value{GDBN} to run on the specified @var{host}.
23265 There is no convenient way to generate a list of all available hosts.
23268 There are many other options available as well, but they are generally
23269 needed for special purposes only.
23271 @node Maintenance Commands
23272 @appendix Maintenance Commands
23273 @cindex maintenance commands
23274 @cindex internal commands
23276 In addition to commands intended for @value{GDBN} users, @value{GDBN}
23277 includes a number of commands intended for @value{GDBN} developers,
23278 that are not documented elsewhere in this manual. These commands are
23279 provided here for reference. (For commands that turn on debugging
23280 messages, see @ref{Debugging Output}.)
23283 @kindex maint agent
23284 @item maint agent @var{expression}
23285 Translate the given @var{expression} into remote agent bytecodes.
23286 This command is useful for debugging the Agent Expression mechanism
23287 (@pxref{Agent Expressions}).
23289 @kindex maint info breakpoints
23290 @item @anchor{maint info breakpoints}maint info breakpoints
23291 Using the same format as @samp{info breakpoints}, display both the
23292 breakpoints you've set explicitly, and those @value{GDBN} is using for
23293 internal purposes. Internal breakpoints are shown with negative
23294 breakpoint numbers. The type column identifies what kind of breakpoint
23299 Normal, explicitly set breakpoint.
23302 Normal, explicitly set watchpoint.
23305 Internal breakpoint, used to handle correctly stepping through
23306 @code{longjmp} calls.
23308 @item longjmp resume
23309 Internal breakpoint at the target of a @code{longjmp}.
23312 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
23315 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
23318 Shared library events.
23322 @kindex maint set can-use-displaced-stepping
23323 @kindex maint show can-use-displaced-stepping
23324 @cindex displaced stepping support
23325 @cindex out-of-line single-stepping
23326 @item maint set can-use-displaced-stepping
23327 @itemx maint show can-use-displaced-stepping
23328 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
23329 if the target supports it. The default is on. Displaced stepping is
23330 a way to single-step over breakpoints without removing them from the
23331 inferior, by executing an out-of-line copy of the instruction that was
23332 originally at the breakpoint location. It is also known as
23333 out-of-line single-stepping.
23335 @kindex maint check-symtabs
23336 @item maint check-symtabs
23337 Check the consistency of psymtabs and symtabs.
23339 @kindex maint cplus first_component
23340 @item maint cplus first_component @var{name}
23341 Print the first C@t{++} class/namespace component of @var{name}.
23343 @kindex maint cplus namespace
23344 @item maint cplus namespace
23345 Print the list of possible C@t{++} namespaces.
23347 @kindex maint demangle
23348 @item maint demangle @var{name}
23349 Demangle a C@t{++} or Objective-C mangled @var{name}.
23351 @kindex maint deprecate
23352 @kindex maint undeprecate
23353 @cindex deprecated commands
23354 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
23355 @itemx maint undeprecate @var{command}
23356 Deprecate or undeprecate the named @var{command}. Deprecated commands
23357 cause @value{GDBN} to issue a warning when you use them. The optional
23358 argument @var{replacement} says which newer command should be used in
23359 favor of the deprecated one; if it is given, @value{GDBN} will mention
23360 the replacement as part of the warning.
23362 @kindex maint dump-me
23363 @item maint dump-me
23364 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
23365 Cause a fatal signal in the debugger and force it to dump its core.
23366 This is supported only on systems which support aborting a program
23367 with the @code{SIGQUIT} signal.
23369 @kindex maint internal-error
23370 @kindex maint internal-warning
23371 @item maint internal-error @r{[}@var{message-text}@r{]}
23372 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
23373 Cause @value{GDBN} to call the internal function @code{internal_error}
23374 or @code{internal_warning} and hence behave as though an internal error
23375 or internal warning has been detected. In addition to reporting the
23376 internal problem, these functions give the user the opportunity to
23377 either quit @value{GDBN} or create a core file of the current
23378 @value{GDBN} session.
23380 These commands take an optional parameter @var{message-text} that is
23381 used as the text of the error or warning message.
23383 Here's an example of using @code{internal-error}:
23386 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
23387 @dots{}/maint.c:121: internal-error: testing, 1, 2
23388 A problem internal to GDB has been detected. Further
23389 debugging may prove unreliable.
23390 Quit this debugging session? (y or n) @kbd{n}
23391 Create a core file? (y or n) @kbd{n}
23395 @kindex maint packet
23396 @item maint packet @var{text}
23397 If @value{GDBN} is talking to an inferior via the serial protocol,
23398 then this command sends the string @var{text} to the inferior, and
23399 displays the response packet. @value{GDBN} supplies the initial
23400 @samp{$} character, the terminating @samp{#} character, and the
23403 @kindex maint print architecture
23404 @item maint print architecture @r{[}@var{file}@r{]}
23405 Print the entire architecture configuration. The optional argument
23406 @var{file} names the file where the output goes.
23408 @kindex maint print c-tdesc
23409 @item maint print c-tdesc
23410 Print the current target description (@pxref{Target Descriptions}) as
23411 a C source file. The created source file can be used in @value{GDBN}
23412 when an XML parser is not available to parse the description.
23414 @kindex maint print dummy-frames
23415 @item maint print dummy-frames
23416 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
23419 (@value{GDBP}) @kbd{b add}
23421 (@value{GDBP}) @kbd{print add(2,3)}
23422 Breakpoint 2, add (a=2, b=3) at @dots{}
23424 The program being debugged stopped while in a function called from GDB.
23426 (@value{GDBP}) @kbd{maint print dummy-frames}
23427 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
23428 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
23429 call_lo=0x01014000 call_hi=0x01014001
23433 Takes an optional file parameter.
23435 @kindex maint print registers
23436 @kindex maint print raw-registers
23437 @kindex maint print cooked-registers
23438 @kindex maint print register-groups
23439 @item maint print registers @r{[}@var{file}@r{]}
23440 @itemx maint print raw-registers @r{[}@var{file}@r{]}
23441 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
23442 @itemx maint print register-groups @r{[}@var{file}@r{]}
23443 Print @value{GDBN}'s internal register data structures.
23445 The command @code{maint print raw-registers} includes the contents of
23446 the raw register cache; the command @code{maint print cooked-registers}
23447 includes the (cooked) value of all registers; and the command
23448 @code{maint print register-groups} includes the groups that each
23449 register is a member of. @xref{Registers,, Registers, gdbint,
23450 @value{GDBN} Internals}.
23452 These commands take an optional parameter, a file name to which to
23453 write the information.
23455 @kindex maint print reggroups
23456 @item maint print reggroups @r{[}@var{file}@r{]}
23457 Print @value{GDBN}'s internal register group data structures. The
23458 optional argument @var{file} tells to what file to write the
23461 The register groups info looks like this:
23464 (@value{GDBP}) @kbd{maint print reggroups}
23477 This command forces @value{GDBN} to flush its internal register cache.
23479 @kindex maint print objfiles
23480 @cindex info for known object files
23481 @item maint print objfiles
23482 Print a dump of all known object files. For each object file, this
23483 command prints its name, address in memory, and all of its psymtabs
23486 @kindex maint print statistics
23487 @cindex bcache statistics
23488 @item maint print statistics
23489 This command prints, for each object file in the program, various data
23490 about that object file followed by the byte cache (@dfn{bcache})
23491 statistics for the object file. The objfile data includes the number
23492 of minimal, partial, full, and stabs symbols, the number of types
23493 defined by the objfile, the number of as yet unexpanded psym tables,
23494 the number of line tables and string tables, and the amount of memory
23495 used by the various tables. The bcache statistics include the counts,
23496 sizes, and counts of duplicates of all and unique objects, max,
23497 average, and median entry size, total memory used and its overhead and
23498 savings, and various measures of the hash table size and chain
23501 @kindex maint print target-stack
23502 @cindex target stack description
23503 @item maint print target-stack
23504 A @dfn{target} is an interface between the debugger and a particular
23505 kind of file or process. Targets can be stacked in @dfn{strata},
23506 so that more than one target can potentially respond to a request.
23507 In particular, memory accesses will walk down the stack of targets
23508 until they find a target that is interested in handling that particular
23511 This command prints a short description of each layer that was pushed on
23512 the @dfn{target stack}, starting from the top layer down to the bottom one.
23514 @kindex maint print type
23515 @cindex type chain of a data type
23516 @item maint print type @var{expr}
23517 Print the type chain for a type specified by @var{expr}. The argument
23518 can be either a type name or a symbol. If it is a symbol, the type of
23519 that symbol is described. The type chain produced by this command is
23520 a recursive definition of the data type as stored in @value{GDBN}'s
23521 data structures, including its flags and contained types.
23523 @kindex maint set dwarf2 max-cache-age
23524 @kindex maint show dwarf2 max-cache-age
23525 @item maint set dwarf2 max-cache-age
23526 @itemx maint show dwarf2 max-cache-age
23527 Control the DWARF 2 compilation unit cache.
23529 @cindex DWARF 2 compilation units cache
23530 In object files with inter-compilation-unit references, such as those
23531 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
23532 reader needs to frequently refer to previously read compilation units.
23533 This setting controls how long a compilation unit will remain in the
23534 cache if it is not referenced. A higher limit means that cached
23535 compilation units will be stored in memory longer, and more total
23536 memory will be used. Setting it to zero disables caching, which will
23537 slow down @value{GDBN} startup, but reduce memory consumption.
23539 @kindex maint set profile
23540 @kindex maint show profile
23541 @cindex profiling GDB
23542 @item maint set profile
23543 @itemx maint show profile
23544 Control profiling of @value{GDBN}.
23546 Profiling will be disabled until you use the @samp{maint set profile}
23547 command to enable it. When you enable profiling, the system will begin
23548 collecting timing and execution count data; when you disable profiling or
23549 exit @value{GDBN}, the results will be written to a log file. Remember that
23550 if you use profiling, @value{GDBN} will overwrite the profiling log file
23551 (often called @file{gmon.out}). If you have a record of important profiling
23552 data in a @file{gmon.out} file, be sure to move it to a safe location.
23554 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
23555 compiled with the @samp{-pg} compiler option.
23557 @kindex maint set linux-async
23558 @kindex maint show linux-async
23559 @cindex asynchronous support
23560 @item maint set linux-async
23561 @itemx maint show linux-async
23562 Control the GNU/Linux native asynchronous support of @value{GDBN}.
23564 GNU/Linux native asynchronous support will be disabled until you use
23565 the @samp{maint set linux-async} command to enable it.
23567 @kindex maint set remote-async
23568 @kindex maint show remote-async
23569 @cindex asynchronous support
23570 @item maint set remote-async
23571 @itemx maint show remote-async
23572 Control the remote asynchronous support of @value{GDBN}.
23574 Remote asynchronous support will be disabled until you use
23575 the @samp{maint set remote-async} command to enable it.
23577 @kindex maint show-debug-regs
23578 @cindex x86 hardware debug registers
23579 @item maint show-debug-regs
23580 Control whether to show variables that mirror the x86 hardware debug
23581 registers. Use @code{ON} to enable, @code{OFF} to disable. If
23582 enabled, the debug registers values are shown when @value{GDBN} inserts or
23583 removes a hardware breakpoint or watchpoint, and when the inferior
23584 triggers a hardware-assisted breakpoint or watchpoint.
23586 @kindex maint space
23587 @cindex memory used by commands
23589 Control whether to display memory usage for each command. If set to a
23590 nonzero value, @value{GDBN} will display how much memory each command
23591 took, following the command's own output. This can also be requested
23592 by invoking @value{GDBN} with the @option{--statistics} command-line
23593 switch (@pxref{Mode Options}).
23596 @cindex time of command execution
23598 Control whether to display the execution time for each command. If
23599 set to a nonzero value, @value{GDBN} will display how much time it
23600 took to execute each command, following the command's own output.
23601 The time is not printed for the commands that run the target, since
23602 there's no mechanism currently to compute how much time was spend
23603 by @value{GDBN} and how much time was spend by the program been debugged.
23604 it's not possibly currently
23605 This can also be requested by invoking @value{GDBN} with the
23606 @option{--statistics} command-line switch (@pxref{Mode Options}).
23608 @kindex maint translate-address
23609 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
23610 Find the symbol stored at the location specified by the address
23611 @var{addr} and an optional section name @var{section}. If found,
23612 @value{GDBN} prints the name of the closest symbol and an offset from
23613 the symbol's location to the specified address. This is similar to
23614 the @code{info address} command (@pxref{Symbols}), except that this
23615 command also allows to find symbols in other sections.
23619 The following command is useful for non-interactive invocations of
23620 @value{GDBN}, such as in the test suite.
23623 @item set watchdog @var{nsec}
23624 @kindex set watchdog
23625 @cindex watchdog timer
23626 @cindex timeout for commands
23627 Set the maximum number of seconds @value{GDBN} will wait for the
23628 target operation to finish. If this time expires, @value{GDBN}
23629 reports and error and the command is aborted.
23631 @item show watchdog
23632 Show the current setting of the target wait timeout.
23635 @node Remote Protocol
23636 @appendix @value{GDBN} Remote Serial Protocol
23641 * Stop Reply Packets::
23642 * General Query Packets::
23643 * Register Packet Format::
23644 * Tracepoint Packets::
23645 * Host I/O Packets::
23648 * File-I/O Remote Protocol Extension::
23649 * Library List Format::
23650 * Memory Map Format::
23656 There may be occasions when you need to know something about the
23657 protocol---for example, if there is only one serial port to your target
23658 machine, you might want your program to do something special if it
23659 recognizes a packet meant for @value{GDBN}.
23661 In the examples below, @samp{->} and @samp{<-} are used to indicate
23662 transmitted and received data, respectively.
23664 @cindex protocol, @value{GDBN} remote serial
23665 @cindex serial protocol, @value{GDBN} remote
23666 @cindex remote serial protocol
23667 All @value{GDBN} commands and responses (other than acknowledgments) are
23668 sent as a @var{packet}. A @var{packet} is introduced with the character
23669 @samp{$}, the actual @var{packet-data}, and the terminating character
23670 @samp{#} followed by a two-digit @var{checksum}:
23673 @code{$}@var{packet-data}@code{#}@var{checksum}
23677 @cindex checksum, for @value{GDBN} remote
23679 The two-digit @var{checksum} is computed as the modulo 256 sum of all
23680 characters between the leading @samp{$} and the trailing @samp{#} (an
23681 eight bit unsigned checksum).
23683 Implementors should note that prior to @value{GDBN} 5.0 the protocol
23684 specification also included an optional two-digit @var{sequence-id}:
23687 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
23690 @cindex sequence-id, for @value{GDBN} remote
23692 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
23693 has never output @var{sequence-id}s. Stubs that handle packets added
23694 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
23696 @cindex acknowledgment, for @value{GDBN} remote
23697 When either the host or the target machine receives a packet, the first
23698 response expected is an acknowledgment: either @samp{+} (to indicate
23699 the package was received correctly) or @samp{-} (to request
23703 -> @code{$}@var{packet-data}@code{#}@var{checksum}
23708 The host (@value{GDBN}) sends @var{command}s, and the target (the
23709 debugging stub incorporated in your program) sends a @var{response}. In
23710 the case of step and continue @var{command}s, the response is only sent
23711 when the operation has completed (the target has again stopped).
23713 @var{packet-data} consists of a sequence of characters with the
23714 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
23717 @cindex remote protocol, field separator
23718 Fields within the packet should be separated using @samp{,} @samp{;} or
23719 @samp{:}. Except where otherwise noted all numbers are represented in
23720 @sc{hex} with leading zeros suppressed.
23722 Implementors should note that prior to @value{GDBN} 5.0, the character
23723 @samp{:} could not appear as the third character in a packet (as it
23724 would potentially conflict with the @var{sequence-id}).
23726 @cindex remote protocol, binary data
23727 @anchor{Binary Data}
23728 Binary data in most packets is encoded either as two hexadecimal
23729 digits per byte of binary data. This allowed the traditional remote
23730 protocol to work over connections which were only seven-bit clean.
23731 Some packets designed more recently assume an eight-bit clean
23732 connection, and use a more efficient encoding to send and receive
23735 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
23736 as an escape character. Any escaped byte is transmitted as the escape
23737 character followed by the original character XORed with @code{0x20}.
23738 For example, the byte @code{0x7d} would be transmitted as the two
23739 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
23740 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
23741 @samp{@}}) must always be escaped. Responses sent by the stub
23742 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
23743 is not interpreted as the start of a run-length encoded sequence
23746 Response @var{data} can be run-length encoded to save space.
23747 Run-length encoding replaces runs of identical characters with one
23748 instance of the repeated character, followed by a @samp{*} and a
23749 repeat count. The repeat count is itself sent encoded, to avoid
23750 binary characters in @var{data}: a value of @var{n} is sent as
23751 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
23752 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
23753 code 32) for a repeat count of 3. (This is because run-length
23754 encoding starts to win for counts 3 or more.) Thus, for example,
23755 @samp{0* } is a run-length encoding of ``0000'': the space character
23756 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
23759 The printable characters @samp{#} and @samp{$} or with a numeric value
23760 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
23761 seven repeats (@samp{$}) can be expanded using a repeat count of only
23762 five (@samp{"}). For example, @samp{00000000} can be encoded as
23765 The error response returned for some packets includes a two character
23766 error number. That number is not well defined.
23768 @cindex empty response, for unsupported packets
23769 For any @var{command} not supported by the stub, an empty response
23770 (@samp{$#00}) should be returned. That way it is possible to extend the
23771 protocol. A newer @value{GDBN} can tell if a packet is supported based
23774 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
23775 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
23781 The following table provides a complete list of all currently defined
23782 @var{command}s and their corresponding response @var{data}.
23783 @xref{File-I/O Remote Protocol Extension}, for details about the File
23784 I/O extension of the remote protocol.
23786 Each packet's description has a template showing the packet's overall
23787 syntax, followed by an explanation of the packet's meaning. We
23788 include spaces in some of the templates for clarity; these are not
23789 part of the packet's syntax. No @value{GDBN} packet uses spaces to
23790 separate its components. For example, a template like @samp{foo
23791 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
23792 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
23793 @var{baz}. @value{GDBN} does not transmit a space character between the
23794 @samp{foo} and the @var{bar}, or between the @var{bar} and the
23797 Note that all packet forms beginning with an upper- or lower-case
23798 letter, other than those described here, are reserved for future use.
23800 Here are the packet descriptions.
23805 @cindex @samp{!} packet
23806 @anchor{extended mode}
23807 Enable extended mode. In extended mode, the remote server is made
23808 persistent. The @samp{R} packet is used to restart the program being
23814 The remote target both supports and has enabled extended mode.
23818 @cindex @samp{?} packet
23819 Indicate the reason the target halted. The reply is the same as for
23823 @xref{Stop Reply Packets}, for the reply specifications.
23825 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
23826 @cindex @samp{A} packet
23827 Initialized @code{argv[]} array passed into program. @var{arglen}
23828 specifies the number of bytes in the hex encoded byte stream
23829 @var{arg}. See @code{gdbserver} for more details.
23834 The arguments were set.
23840 @cindex @samp{b} packet
23841 (Don't use this packet; its behavior is not well-defined.)
23842 Change the serial line speed to @var{baud}.
23844 JTC: @emph{When does the transport layer state change? When it's
23845 received, or after the ACK is transmitted. In either case, there are
23846 problems if the command or the acknowledgment packet is dropped.}
23848 Stan: @emph{If people really wanted to add something like this, and get
23849 it working for the first time, they ought to modify ser-unix.c to send
23850 some kind of out-of-band message to a specially-setup stub and have the
23851 switch happen "in between" packets, so that from remote protocol's point
23852 of view, nothing actually happened.}
23854 @item B @var{addr},@var{mode}
23855 @cindex @samp{B} packet
23856 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23857 breakpoint at @var{addr}.
23859 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23860 (@pxref{insert breakpoint or watchpoint packet}).
23862 @item c @r{[}@var{addr}@r{]}
23863 @cindex @samp{c} packet
23864 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23865 resume at current address.
23868 @xref{Stop Reply Packets}, for the reply specifications.
23870 @item C @var{sig}@r{[};@var{addr}@r{]}
23871 @cindex @samp{C} packet
23872 Continue with signal @var{sig} (hex signal number). If
23873 @samp{;@var{addr}} is omitted, resume at same address.
23876 @xref{Stop Reply Packets}, for the reply specifications.
23879 @cindex @samp{d} packet
23882 Don't use this packet; instead, define a general set packet
23883 (@pxref{General Query Packets}).
23886 @cindex @samp{D} packet
23887 Detach @value{GDBN} from the remote system. Sent to the remote target
23888 before @value{GDBN} disconnects via the @code{detach} command.
23898 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23899 @cindex @samp{F} packet
23900 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23901 This is part of the File-I/O protocol extension. @xref{File-I/O
23902 Remote Protocol Extension}, for the specification.
23905 @anchor{read registers packet}
23906 @cindex @samp{g} packet
23907 Read general registers.
23911 @item @var{XX@dots{}}
23912 Each byte of register data is described by two hex digits. The bytes
23913 with the register are transmitted in target byte order. The size of
23914 each register and their position within the @samp{g} packet are
23915 determined by the @value{GDBN} internal gdbarch functions
23916 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
23917 specification of several standard @samp{g} packets is specified below.
23922 @item G @var{XX@dots{}}
23923 @cindex @samp{G} packet
23924 Write general registers. @xref{read registers packet}, for a
23925 description of the @var{XX@dots{}} data.
23935 @item H @var{c} @var{t}
23936 @cindex @samp{H} packet
23937 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23938 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23939 should be @samp{c} for step and continue operations, @samp{g} for other
23940 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23941 the threads, a thread number, or @samp{0} which means pick any thread.
23952 @c 'H': How restrictive (or permissive) is the thread model. If a
23953 @c thread is selected and stopped, are other threads allowed
23954 @c to continue to execute? As I mentioned above, I think the
23955 @c semantics of each command when a thread is selected must be
23956 @c described. For example:
23958 @c 'g': If the stub supports threads and a specific thread is
23959 @c selected, returns the register block from that thread;
23960 @c otherwise returns current registers.
23962 @c 'G' If the stub supports threads and a specific thread is
23963 @c selected, sets the registers of the register block of
23964 @c that thread; otherwise sets current registers.
23966 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23967 @anchor{cycle step packet}
23968 @cindex @samp{i} packet
23969 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23970 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23971 step starting at that address.
23974 @cindex @samp{I} packet
23975 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23979 @cindex @samp{k} packet
23982 FIXME: @emph{There is no description of how to operate when a specific
23983 thread context has been selected (i.e.@: does 'k' kill only that
23986 @item m @var{addr},@var{length}
23987 @cindex @samp{m} packet
23988 Read @var{length} bytes of memory starting at address @var{addr}.
23989 Note that @var{addr} may not be aligned to any particular boundary.
23991 The stub need not use any particular size or alignment when gathering
23992 data from memory for the response; even if @var{addr} is word-aligned
23993 and @var{length} is a multiple of the word size, the stub is free to
23994 use byte accesses, or not. For this reason, this packet may not be
23995 suitable for accessing memory-mapped I/O devices.
23996 @cindex alignment of remote memory accesses
23997 @cindex size of remote memory accesses
23998 @cindex memory, alignment and size of remote accesses
24002 @item @var{XX@dots{}}
24003 Memory contents; each byte is transmitted as a two-digit hexadecimal
24004 number. The reply may contain fewer bytes than requested if the
24005 server was able to read only part of the region of memory.
24010 @item M @var{addr},@var{length}:@var{XX@dots{}}
24011 @cindex @samp{M} packet
24012 Write @var{length} bytes of memory starting at address @var{addr}.
24013 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
24014 hexadecimal number.
24021 for an error (this includes the case where only part of the data was
24026 @cindex @samp{p} packet
24027 Read the value of register @var{n}; @var{n} is in hex.
24028 @xref{read registers packet}, for a description of how the returned
24029 register value is encoded.
24033 @item @var{XX@dots{}}
24034 the register's value
24038 Indicating an unrecognized @var{query}.
24041 @item P @var{n@dots{}}=@var{r@dots{}}
24042 @anchor{write register packet}
24043 @cindex @samp{P} packet
24044 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
24045 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
24046 digits for each byte in the register (target byte order).
24056 @item q @var{name} @var{params}@dots{}
24057 @itemx Q @var{name} @var{params}@dots{}
24058 @cindex @samp{q} packet
24059 @cindex @samp{Q} packet
24060 General query (@samp{q}) and set (@samp{Q}). These packets are
24061 described fully in @ref{General Query Packets}.
24064 @cindex @samp{r} packet
24065 Reset the entire system.
24067 Don't use this packet; use the @samp{R} packet instead.
24070 @cindex @samp{R} packet
24071 Restart the program being debugged. @var{XX}, while needed, is ignored.
24072 This packet is only available in extended mode (@pxref{extended mode}).
24074 The @samp{R} packet has no reply.
24076 @item s @r{[}@var{addr}@r{]}
24077 @cindex @samp{s} packet
24078 Single step. @var{addr} is the address at which to resume. If
24079 @var{addr} is omitted, resume at same address.
24082 @xref{Stop Reply Packets}, for the reply specifications.
24084 @item S @var{sig}@r{[};@var{addr}@r{]}
24085 @anchor{step with signal packet}
24086 @cindex @samp{S} packet
24087 Step with signal. This is analogous to the @samp{C} packet, but
24088 requests a single-step, rather than a normal resumption of execution.
24091 @xref{Stop Reply Packets}, for the reply specifications.
24093 @item t @var{addr}:@var{PP},@var{MM}
24094 @cindex @samp{t} packet
24095 Search backwards starting at address @var{addr} for a match with pattern
24096 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
24097 @var{addr} must be at least 3 digits.
24100 @cindex @samp{T} packet
24101 Find out if the thread XX is alive.
24106 thread is still alive
24112 Packets starting with @samp{v} are identified by a multi-letter name,
24113 up to the first @samp{;} or @samp{?} (or the end of the packet).
24115 @item vAttach;@var{pid}
24116 @cindex @samp{vAttach} packet
24117 Attach to a new process with the specified process ID. @var{pid} is a
24118 hexadecimal integer identifying the process. The attached process is
24121 This packet is only available in extended mode (@pxref{extended mode}).
24127 @item @r{Any stop packet}
24128 for success (@pxref{Stop Reply Packets})
24131 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
24132 @cindex @samp{vCont} packet
24133 Resume the inferior, specifying different actions for each thread.
24134 If an action is specified with no @var{tid}, then it is applied to any
24135 threads that don't have a specific action specified; if no default action is
24136 specified then other threads should remain stopped. Specifying multiple
24137 default actions is an error; specifying no actions is also an error.
24138 Thread IDs are specified in hexadecimal. Currently supported actions are:
24144 Continue with signal @var{sig}. @var{sig} should be two hex digits.
24148 Step with signal @var{sig}. @var{sig} should be two hex digits.
24151 The optional @var{addr} argument normally associated with these packets is
24152 not supported in @samp{vCont}.
24155 @xref{Stop Reply Packets}, for the reply specifications.
24158 @cindex @samp{vCont?} packet
24159 Request a list of actions supported by the @samp{vCont} packet.
24163 @item vCont@r{[};@var{action}@dots{}@r{]}
24164 The @samp{vCont} packet is supported. Each @var{action} is a supported
24165 command in the @samp{vCont} packet.
24167 The @samp{vCont} packet is not supported.
24170 @item vFile:@var{operation}:@var{parameter}@dots{}
24171 @cindex @samp{vFile} packet
24172 Perform a file operation on the target system. For details,
24173 see @ref{Host I/O Packets}.
24175 @item vFlashErase:@var{addr},@var{length}
24176 @cindex @samp{vFlashErase} packet
24177 Direct the stub to erase @var{length} bytes of flash starting at
24178 @var{addr}. The region may enclose any number of flash blocks, but
24179 its start and end must fall on block boundaries, as indicated by the
24180 flash block size appearing in the memory map (@pxref{Memory Map
24181 Format}). @value{GDBN} groups flash memory programming operations
24182 together, and sends a @samp{vFlashDone} request after each group; the
24183 stub is allowed to delay erase operation until the @samp{vFlashDone}
24184 packet is received.
24194 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
24195 @cindex @samp{vFlashWrite} packet
24196 Direct the stub to write data to flash address @var{addr}. The data
24197 is passed in binary form using the same encoding as for the @samp{X}
24198 packet (@pxref{Binary Data}). The memory ranges specified by
24199 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
24200 not overlap, and must appear in order of increasing addresses
24201 (although @samp{vFlashErase} packets for higher addresses may already
24202 have been received; the ordering is guaranteed only between
24203 @samp{vFlashWrite} packets). If a packet writes to an address that was
24204 neither erased by a preceding @samp{vFlashErase} packet nor by some other
24205 target-specific method, the results are unpredictable.
24213 for vFlashWrite addressing non-flash memory
24219 @cindex @samp{vFlashDone} packet
24220 Indicate to the stub that flash programming operation is finished.
24221 The stub is permitted to delay or batch the effects of a group of
24222 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
24223 @samp{vFlashDone} packet is received. The contents of the affected
24224 regions of flash memory are unpredictable until the @samp{vFlashDone}
24225 request is completed.
24227 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
24228 @cindex @samp{vRun} packet
24229 Run the program @var{filename}, passing it each @var{argument} on its
24230 command line. The file and arguments are hex-encoded strings. If
24231 @var{filename} is an empty string, the stub may use a default program
24232 (e.g.@: the last program run). The program is created in the stopped
24235 This packet is only available in extended mode (@pxref{extended mode}).
24241 @item @r{Any stop packet}
24242 for success (@pxref{Stop Reply Packets})
24245 @item X @var{addr},@var{length}:@var{XX@dots{}}
24247 @cindex @samp{X} packet
24248 Write data to memory, where the data is transmitted in binary.
24249 @var{addr} is address, @var{length} is number of bytes,
24250 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
24260 @item z @var{type},@var{addr},@var{length}
24261 @itemx Z @var{type},@var{addr},@var{length}
24262 @anchor{insert breakpoint or watchpoint packet}
24263 @cindex @samp{z} packet
24264 @cindex @samp{Z} packets
24265 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
24266 watchpoint starting at address @var{address} and covering the next
24267 @var{length} bytes.
24269 Each breakpoint and watchpoint packet @var{type} is documented
24272 @emph{Implementation notes: A remote target shall return an empty string
24273 for an unrecognized breakpoint or watchpoint packet @var{type}. A
24274 remote target shall support either both or neither of a given
24275 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
24276 avoid potential problems with duplicate packets, the operations should
24277 be implemented in an idempotent way.}
24279 @item z0,@var{addr},@var{length}
24280 @itemx Z0,@var{addr},@var{length}
24281 @cindex @samp{z0} packet
24282 @cindex @samp{Z0} packet
24283 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
24284 @var{addr} of size @var{length}.
24286 A memory breakpoint is implemented by replacing the instruction at
24287 @var{addr} with a software breakpoint or trap instruction. The
24288 @var{length} is used by targets that indicates the size of the
24289 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
24290 @sc{mips} can insert either a 2 or 4 byte breakpoint).
24292 @emph{Implementation note: It is possible for a target to copy or move
24293 code that contains memory breakpoints (e.g., when implementing
24294 overlays). The behavior of this packet, in the presence of such a
24295 target, is not defined.}
24307 @item z1,@var{addr},@var{length}
24308 @itemx Z1,@var{addr},@var{length}
24309 @cindex @samp{z1} packet
24310 @cindex @samp{Z1} packet
24311 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
24312 address @var{addr} of size @var{length}.
24314 A hardware breakpoint is implemented using a mechanism that is not
24315 dependant on being able to modify the target's memory.
24317 @emph{Implementation note: A hardware breakpoint is not affected by code
24330 @item z2,@var{addr},@var{length}
24331 @itemx Z2,@var{addr},@var{length}
24332 @cindex @samp{z2} packet
24333 @cindex @samp{Z2} packet
24334 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
24346 @item z3,@var{addr},@var{length}
24347 @itemx Z3,@var{addr},@var{length}
24348 @cindex @samp{z3} packet
24349 @cindex @samp{Z3} packet
24350 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
24362 @item z4,@var{addr},@var{length}
24363 @itemx Z4,@var{addr},@var{length}
24364 @cindex @samp{z4} packet
24365 @cindex @samp{Z4} packet
24366 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
24380 @node Stop Reply Packets
24381 @section Stop Reply Packets
24382 @cindex stop reply packets
24384 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
24385 receive any of the below as a reply. In the case of the @samp{C},
24386 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
24387 when the target halts. In the below the exact meaning of @dfn{signal
24388 number} is defined by the header @file{include/gdb/signals.h} in the
24389 @value{GDBN} source code.
24391 As in the description of request packets, we include spaces in the
24392 reply templates for clarity; these are not part of the reply packet's
24393 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
24399 The program received signal number @var{AA} (a two-digit hexadecimal
24400 number). This is equivalent to a @samp{T} response with no
24401 @var{n}:@var{r} pairs.
24403 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
24404 @cindex @samp{T} packet reply
24405 The program received signal number @var{AA} (a two-digit hexadecimal
24406 number). This is equivalent to an @samp{S} response, except that the
24407 @samp{@var{n}:@var{r}} pairs can carry values of important registers
24408 and other information directly in the stop reply packet, reducing
24409 round-trip latency. Single-step and breakpoint traps are reported
24410 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
24414 If @var{n} is a hexadecimal number, it is a register number, and the
24415 corresponding @var{r} gives that register's value. @var{r} is a
24416 series of bytes in target byte order, with each byte given by a
24417 two-digit hex number.
24420 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
24424 If @var{n} is a recognized @dfn{stop reason}, it describes a more
24425 specific event that stopped the target. The currently defined stop
24426 reasons are listed below. @var{aa} should be @samp{05}, the trap
24427 signal. At most one stop reason should be present.
24430 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
24431 and go on to the next; this allows us to extend the protocol in the
24435 The currently defined stop reasons are:
24441 The packet indicates a watchpoint hit, and @var{r} is the data address, in
24444 @cindex shared library events, remote reply
24446 The packet indicates that the loaded libraries have changed.
24447 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
24448 list of loaded libraries. @var{r} is ignored.
24452 The process exited, and @var{AA} is the exit status. This is only
24453 applicable to certain targets.
24456 The process terminated with signal @var{AA}.
24458 @item O @var{XX}@dots{}
24459 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
24460 written as the program's console output. This can happen at any time
24461 while the program is running and the debugger should continue to wait
24462 for @samp{W}, @samp{T}, etc.
24464 @item F @var{call-id},@var{parameter}@dots{}
24465 @var{call-id} is the identifier which says which host system call should
24466 be called. This is just the name of the function. Translation into the
24467 correct system call is only applicable as it's defined in @value{GDBN}.
24468 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
24471 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
24472 this very system call.
24474 The target replies with this packet when it expects @value{GDBN} to
24475 call a host system call on behalf of the target. @value{GDBN} replies
24476 with an appropriate @samp{F} packet and keeps up waiting for the next
24477 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
24478 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
24479 Protocol Extension}, for more details.
24483 @node General Query Packets
24484 @section General Query Packets
24485 @cindex remote query requests
24487 Packets starting with @samp{q} are @dfn{general query packets};
24488 packets starting with @samp{Q} are @dfn{general set packets}. General
24489 query and set packets are a semi-unified form for retrieving and
24490 sending information to and from the stub.
24492 The initial letter of a query or set packet is followed by a name
24493 indicating what sort of thing the packet applies to. For example,
24494 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
24495 definitions with the stub. These packet names follow some
24500 The name must not contain commas, colons or semicolons.
24502 Most @value{GDBN} query and set packets have a leading upper case
24505 The names of custom vendor packets should use a company prefix, in
24506 lower case, followed by a period. For example, packets designed at
24507 the Acme Corporation might begin with @samp{qacme.foo} (for querying
24508 foos) or @samp{Qacme.bar} (for setting bars).
24511 The name of a query or set packet should be separated from any
24512 parameters by a @samp{:}; the parameters themselves should be
24513 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
24514 full packet name, and check for a separator or the end of the packet,
24515 in case two packet names share a common prefix. New packets should not begin
24516 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
24517 packets predate these conventions, and have arguments without any terminator
24518 for the packet name; we suspect they are in widespread use in places that
24519 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
24520 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
24523 Like the descriptions of the other packets, each description here
24524 has a template showing the packet's overall syntax, followed by an
24525 explanation of the packet's meaning. We include spaces in some of the
24526 templates for clarity; these are not part of the packet's syntax. No
24527 @value{GDBN} packet uses spaces to separate its components.
24529 Here are the currently defined query and set packets:
24534 @cindex current thread, remote request
24535 @cindex @samp{qC} packet
24536 Return the current thread id.
24541 Where @var{pid} is an unsigned hexadecimal process id.
24542 @item @r{(anything else)}
24543 Any other reply implies the old pid.
24546 @item qCRC:@var{addr},@var{length}
24547 @cindex CRC of memory block, remote request
24548 @cindex @samp{qCRC} packet
24549 Compute the CRC checksum of a block of memory.
24553 An error (such as memory fault)
24554 @item C @var{crc32}
24555 The specified memory region's checksum is @var{crc32}.
24559 @itemx qsThreadInfo
24560 @cindex list active threads, remote request
24561 @cindex @samp{qfThreadInfo} packet
24562 @cindex @samp{qsThreadInfo} packet
24563 Obtain a list of all active thread ids from the target (OS). Since there
24564 may be too many active threads to fit into one reply packet, this query
24565 works iteratively: it may require more than one query/reply sequence to
24566 obtain the entire list of threads. The first query of the sequence will
24567 be the @samp{qfThreadInfo} query; subsequent queries in the
24568 sequence will be the @samp{qsThreadInfo} query.
24570 NOTE: This packet replaces the @samp{qL} query (see below).
24576 @item m @var{id},@var{id}@dots{}
24577 a comma-separated list of thread ids
24579 (lower case letter @samp{L}) denotes end of list.
24582 In response to each query, the target will reply with a list of one or
24583 more thread ids, in big-endian unsigned hex, separated by commas.
24584 @value{GDBN} will respond to each reply with a request for more thread
24585 ids (using the @samp{qs} form of the query), until the target responds
24586 with @samp{l} (lower-case el, for @dfn{last}).
24588 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
24589 @cindex get thread-local storage address, remote request
24590 @cindex @samp{qGetTLSAddr} packet
24591 Fetch the address associated with thread local storage specified
24592 by @var{thread-id}, @var{offset}, and @var{lm}.
24594 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
24595 thread for which to fetch the TLS address.
24597 @var{offset} is the (big endian, hex encoded) offset associated with the
24598 thread local variable. (This offset is obtained from the debug
24599 information associated with the variable.)
24601 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
24602 the load module associated with the thread local storage. For example,
24603 a @sc{gnu}/Linux system will pass the link map address of the shared
24604 object associated with the thread local storage under consideration.
24605 Other operating environments may choose to represent the load module
24606 differently, so the precise meaning of this parameter will vary.
24610 @item @var{XX}@dots{}
24611 Hex encoded (big endian) bytes representing the address of the thread
24612 local storage requested.
24615 An error occurred. @var{nn} are hex digits.
24618 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
24621 @item qL @var{startflag} @var{threadcount} @var{nextthread}
24622 Obtain thread information from RTOS. Where: @var{startflag} (one hex
24623 digit) is one to indicate the first query and zero to indicate a
24624 subsequent query; @var{threadcount} (two hex digits) is the maximum
24625 number of threads the response packet can contain; and @var{nextthread}
24626 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
24627 returned in the response as @var{argthread}.
24629 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
24633 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
24634 Where: @var{count} (two hex digits) is the number of threads being
24635 returned; @var{done} (one hex digit) is zero to indicate more threads
24636 and one indicates no further threads; @var{argthreadid} (eight hex
24637 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
24638 is a sequence of thread IDs from the target. @var{threadid} (eight hex
24639 digits). See @code{remote.c:parse_threadlist_response()}.
24643 @cindex section offsets, remote request
24644 @cindex @samp{qOffsets} packet
24645 Get section offsets that the target used when relocating the downloaded
24650 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
24651 Relocate the @code{Text} section by @var{xxx} from its original address.
24652 Relocate the @code{Data} section by @var{yyy} from its original address.
24653 If the object file format provides segment information (e.g.@: @sc{elf}
24654 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
24655 segments by the supplied offsets.
24657 @emph{Note: while a @code{Bss} offset may be included in the response,
24658 @value{GDBN} ignores this and instead applies the @code{Data} offset
24659 to the @code{Bss} section.}
24661 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
24662 Relocate the first segment of the object file, which conventionally
24663 contains program code, to a starting address of @var{xxx}. If
24664 @samp{DataSeg} is specified, relocate the second segment, which
24665 conventionally contains modifiable data, to a starting address of
24666 @var{yyy}. @value{GDBN} will report an error if the object file
24667 does not contain segment information, or does not contain at least
24668 as many segments as mentioned in the reply. Extra segments are
24669 kept at fixed offsets relative to the last relocated segment.
24672 @item qP @var{mode} @var{threadid}
24673 @cindex thread information, remote request
24674 @cindex @samp{qP} packet
24675 Returns information on @var{threadid}. Where: @var{mode} is a hex
24676 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
24678 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
24681 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
24683 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
24684 @cindex pass signals to inferior, remote request
24685 @cindex @samp{QPassSignals} packet
24686 @anchor{QPassSignals}
24687 Each listed @var{signal} should be passed directly to the inferior process.
24688 Signals are numbered identically to continue packets and stop replies
24689 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
24690 strictly greater than the previous item. These signals do not need to stop
24691 the inferior, or be reported to @value{GDBN}. All other signals should be
24692 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
24693 combine; any earlier @samp{QPassSignals} list is completely replaced by the
24694 new list. This packet improves performance when using @samp{handle
24695 @var{signal} nostop noprint pass}.
24700 The request succeeded.
24703 An error occurred. @var{nn} are hex digits.
24706 An empty reply indicates that @samp{QPassSignals} is not supported by
24710 Use of this packet is controlled by the @code{set remote pass-signals}
24711 command (@pxref{Remote Configuration, set remote pass-signals}).
24712 This packet is not probed by default; the remote stub must request it,
24713 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24715 @item qRcmd,@var{command}
24716 @cindex execute remote command, remote request
24717 @cindex @samp{qRcmd} packet
24718 @var{command} (hex encoded) is passed to the local interpreter for
24719 execution. Invalid commands should be reported using the output
24720 string. Before the final result packet, the target may also respond
24721 with a number of intermediate @samp{O@var{output}} console output
24722 packets. @emph{Implementors should note that providing access to a
24723 stubs's interpreter may have security implications}.
24728 A command response with no output.
24730 A command response with the hex encoded output string @var{OUTPUT}.
24732 Indicate a badly formed request.
24734 An empty reply indicates that @samp{qRcmd} is not recognized.
24737 (Note that the @code{qRcmd} packet's name is separated from the
24738 command by a @samp{,}, not a @samp{:}, contrary to the naming
24739 conventions above. Please don't use this packet as a model for new
24742 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
24743 @cindex searching memory, in remote debugging
24744 @cindex @samp{qSearch:memory} packet
24745 @anchor{qSearch memory}
24746 Search @var{length} bytes at @var{address} for @var{search-pattern}.
24747 @var{address} and @var{length} are encoded in hex.
24748 @var{search-pattern} is a sequence of bytes, hex encoded.
24753 The pattern was not found.
24755 The pattern was found at @var{address}.
24757 A badly formed request or an error was encountered while searching memory.
24759 An empty reply indicates that @samp{qSearch:memory} is not recognized.
24762 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
24763 @cindex supported packets, remote query
24764 @cindex features of the remote protocol
24765 @cindex @samp{qSupported} packet
24766 @anchor{qSupported}
24767 Tell the remote stub about features supported by @value{GDBN}, and
24768 query the stub for features it supports. This packet allows
24769 @value{GDBN} and the remote stub to take advantage of each others'
24770 features. @samp{qSupported} also consolidates multiple feature probes
24771 at startup, to improve @value{GDBN} performance---a single larger
24772 packet performs better than multiple smaller probe packets on
24773 high-latency links. Some features may enable behavior which must not
24774 be on by default, e.g.@: because it would confuse older clients or
24775 stubs. Other features may describe packets which could be
24776 automatically probed for, but are not. These features must be
24777 reported before @value{GDBN} will use them. This ``default
24778 unsupported'' behavior is not appropriate for all packets, but it
24779 helps to keep the initial connection time under control with new
24780 versions of @value{GDBN} which support increasing numbers of packets.
24784 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
24785 The stub supports or does not support each returned @var{stubfeature},
24786 depending on the form of each @var{stubfeature} (see below for the
24789 An empty reply indicates that @samp{qSupported} is not recognized,
24790 or that no features needed to be reported to @value{GDBN}.
24793 The allowed forms for each feature (either a @var{gdbfeature} in the
24794 @samp{qSupported} packet, or a @var{stubfeature} in the response)
24798 @item @var{name}=@var{value}
24799 The remote protocol feature @var{name} is supported, and associated
24800 with the specified @var{value}. The format of @var{value} depends
24801 on the feature, but it must not include a semicolon.
24803 The remote protocol feature @var{name} is supported, and does not
24804 need an associated value.
24806 The remote protocol feature @var{name} is not supported.
24808 The remote protocol feature @var{name} may be supported, and
24809 @value{GDBN} should auto-detect support in some other way when it is
24810 needed. This form will not be used for @var{gdbfeature} notifications,
24811 but may be used for @var{stubfeature} responses.
24814 Whenever the stub receives a @samp{qSupported} request, the
24815 supplied set of @value{GDBN} features should override any previous
24816 request. This allows @value{GDBN} to put the stub in a known
24817 state, even if the stub had previously been communicating with
24818 a different version of @value{GDBN}.
24820 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
24821 are defined yet. Stubs should ignore any unknown values for
24822 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
24823 packet supports receiving packets of unlimited length (earlier
24824 versions of @value{GDBN} may reject overly long responses). Values
24825 for @var{gdbfeature} may be defined in the future to let the stub take
24826 advantage of new features in @value{GDBN}, e.g.@: incompatible
24827 improvements in the remote protocol---support for unlimited length
24828 responses would be a @var{gdbfeature} example, if it were not implied by
24829 the @samp{qSupported} query. The stub's reply should be independent
24830 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
24831 describes all the features it supports, and then the stub replies with
24832 all the features it supports.
24834 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
24835 responses, as long as each response uses one of the standard forms.
24837 Some features are flags. A stub which supports a flag feature
24838 should respond with a @samp{+} form response. Other features
24839 require values, and the stub should respond with an @samp{=}
24842 Each feature has a default value, which @value{GDBN} will use if
24843 @samp{qSupported} is not available or if the feature is not mentioned
24844 in the @samp{qSupported} response. The default values are fixed; a
24845 stub is free to omit any feature responses that match the defaults.
24847 Not all features can be probed, but for those which can, the probing
24848 mechanism is useful: in some cases, a stub's internal
24849 architecture may not allow the protocol layer to know some information
24850 about the underlying target in advance. This is especially common in
24851 stubs which may be configured for multiple targets.
24853 These are the currently defined stub features and their properties:
24855 @multitable @columnfractions 0.35 0.2 0.12 0.2
24856 @c NOTE: The first row should be @headitem, but we do not yet require
24857 @c a new enough version of Texinfo (4.7) to use @headitem.
24859 @tab Value Required
24863 @item @samp{PacketSize}
24868 @item @samp{qXfer:auxv:read}
24873 @item @samp{qXfer:features:read}
24878 @item @samp{qXfer:libraries:read}
24883 @item @samp{qXfer:memory-map:read}
24888 @item @samp{qXfer:spu:read}
24893 @item @samp{qXfer:spu:write}
24898 @item @samp{QPassSignals}
24905 These are the currently defined stub features, in more detail:
24908 @cindex packet size, remote protocol
24909 @item PacketSize=@var{bytes}
24910 The remote stub can accept packets up to at least @var{bytes} in
24911 length. @value{GDBN} will send packets up to this size for bulk
24912 transfers, and will never send larger packets. This is a limit on the
24913 data characters in the packet, including the frame and checksum.
24914 There is no trailing NUL byte in a remote protocol packet; if the stub
24915 stores packets in a NUL-terminated format, it should allow an extra
24916 byte in its buffer for the NUL. If this stub feature is not supported,
24917 @value{GDBN} guesses based on the size of the @samp{g} packet response.
24919 @item qXfer:auxv:read
24920 The remote stub understands the @samp{qXfer:auxv:read} packet
24921 (@pxref{qXfer auxiliary vector read}).
24923 @item qXfer:features:read
24924 The remote stub understands the @samp{qXfer:features:read} packet
24925 (@pxref{qXfer target description read}).
24927 @item qXfer:libraries:read
24928 The remote stub understands the @samp{qXfer:libraries:read} packet
24929 (@pxref{qXfer library list read}).
24931 @item qXfer:memory-map:read
24932 The remote stub understands the @samp{qXfer:memory-map:read} packet
24933 (@pxref{qXfer memory map read}).
24935 @item qXfer:spu:read
24936 The remote stub understands the @samp{qXfer:spu:read} packet
24937 (@pxref{qXfer spu read}).
24939 @item qXfer:spu:write
24940 The remote stub understands the @samp{qXfer:spu:write} packet
24941 (@pxref{qXfer spu write}).
24944 The remote stub understands the @samp{QPassSignals} packet
24945 (@pxref{QPassSignals}).
24950 @cindex symbol lookup, remote request
24951 @cindex @samp{qSymbol} packet
24952 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24953 requests. Accept requests from the target for the values of symbols.
24958 The target does not need to look up any (more) symbols.
24959 @item qSymbol:@var{sym_name}
24960 The target requests the value of symbol @var{sym_name} (hex encoded).
24961 @value{GDBN} may provide the value by using the
24962 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24966 @item qSymbol:@var{sym_value}:@var{sym_name}
24967 Set the value of @var{sym_name} to @var{sym_value}.
24969 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24970 target has previously requested.
24972 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24973 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24979 The target does not need to look up any (more) symbols.
24980 @item qSymbol:@var{sym_name}
24981 The target requests the value of a new symbol @var{sym_name} (hex
24982 encoded). @value{GDBN} will continue to supply the values of symbols
24983 (if available), until the target ceases to request them.
24988 @xref{Tracepoint Packets}.
24990 @item qThreadExtraInfo,@var{id}
24991 @cindex thread attributes info, remote request
24992 @cindex @samp{qThreadExtraInfo} packet
24993 Obtain a printable string description of a thread's attributes from
24994 the target OS. @var{id} is a thread-id in big-endian hex. This
24995 string may contain anything that the target OS thinks is interesting
24996 for @value{GDBN} to tell the user about the thread. The string is
24997 displayed in @value{GDBN}'s @code{info threads} display. Some
24998 examples of possible thread extra info strings are @samp{Runnable}, or
24999 @samp{Blocked on Mutex}.
25003 @item @var{XX}@dots{}
25004 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
25005 comprising the printable string containing the extra information about
25006 the thread's attributes.
25009 (Note that the @code{qThreadExtraInfo} packet's name is separated from
25010 the command by a @samp{,}, not a @samp{:}, contrary to the naming
25011 conventions above. Please don't use this packet as a model for new
25019 @xref{Tracepoint Packets}.
25021 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
25022 @cindex read special object, remote request
25023 @cindex @samp{qXfer} packet
25024 @anchor{qXfer read}
25025 Read uninterpreted bytes from the target's special data area
25026 identified by the keyword @var{object}. Request @var{length} bytes
25027 starting at @var{offset} bytes into the data. The content and
25028 encoding of @var{annex} is specific to @var{object}; it can supply
25029 additional details about what data to access.
25031 Here are the specific requests of this form defined so far. All
25032 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
25033 formats, listed below.
25036 @item qXfer:auxv:read::@var{offset},@var{length}
25037 @anchor{qXfer auxiliary vector read}
25038 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
25039 auxiliary vector}. Note @var{annex} must be empty.
25041 This packet is not probed by default; the remote stub must request it,
25042 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25044 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
25045 @anchor{qXfer target description read}
25046 Access the @dfn{target description}. @xref{Target Descriptions}. The
25047 annex specifies which XML document to access. The main description is
25048 always loaded from the @samp{target.xml} annex.
25050 This packet is not probed by default; the remote stub must request it,
25051 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25053 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
25054 @anchor{qXfer library list read}
25055 Access the target's list of loaded libraries. @xref{Library List Format}.
25056 The annex part of the generic @samp{qXfer} packet must be empty
25057 (@pxref{qXfer read}).
25059 Targets which maintain a list of libraries in the program's memory do
25060 not need to implement this packet; it is designed for platforms where
25061 the operating system manages the list of loaded libraries.
25063 This packet is not probed by default; the remote stub must request it,
25064 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25066 @item qXfer:memory-map:read::@var{offset},@var{length}
25067 @anchor{qXfer memory map read}
25068 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
25069 annex part of the generic @samp{qXfer} packet must be empty
25070 (@pxref{qXfer read}).
25072 This packet is not probed by default; the remote stub must request it,
25073 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25075 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
25076 @anchor{qXfer spu read}
25077 Read contents of an @code{spufs} file on the target system. The
25078 annex specifies which file to read; it must be of the form
25079 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25080 in the target process, and @var{name} identifes the @code{spufs} file
25081 in that context to be accessed.
25083 This packet is not probed by default; the remote stub must request it,
25084 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25090 Data @var{data} (@pxref{Binary Data}) has been read from the
25091 target. There may be more data at a higher address (although
25092 it is permitted to return @samp{m} even for the last valid
25093 block of data, as long as at least one byte of data was read).
25094 @var{data} may have fewer bytes than the @var{length} in the
25098 Data @var{data} (@pxref{Binary Data}) has been read from the target.
25099 There is no more data to be read. @var{data} may have fewer bytes
25100 than the @var{length} in the request.
25103 The @var{offset} in the request is at the end of the data.
25104 There is no more data to be read.
25107 The request was malformed, or @var{annex} was invalid.
25110 The offset was invalid, or there was an error encountered reading the data.
25111 @var{nn} is a hex-encoded @code{errno} value.
25114 An empty reply indicates the @var{object} string was not recognized by
25115 the stub, or that the object does not support reading.
25118 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25119 @cindex write data into object, remote request
25120 Write uninterpreted bytes into the target's special data area
25121 identified by the keyword @var{object}, starting at @var{offset} bytes
25122 into the data. @var{data}@dots{} is the binary-encoded data
25123 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
25124 is specific to @var{object}; it can supply additional details about what data
25127 Here are the specific requests of this form defined so far. All
25128 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
25129 formats, listed below.
25132 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25133 @anchor{qXfer spu write}
25134 Write @var{data} to an @code{spufs} file on the target system. The
25135 annex specifies which file to write; it must be of the form
25136 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25137 in the target process, and @var{name} identifes the @code{spufs} file
25138 in that context to be accessed.
25140 This packet is not probed by default; the remote stub must request it,
25141 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25147 @var{nn} (hex encoded) is the number of bytes written.
25148 This may be fewer bytes than supplied in the request.
25151 The request was malformed, or @var{annex} was invalid.
25154 The offset was invalid, or there was an error encountered writing the data.
25155 @var{nn} is a hex-encoded @code{errno} value.
25158 An empty reply indicates the @var{object} string was not
25159 recognized by the stub, or that the object does not support writing.
25162 @item qXfer:@var{object}:@var{operation}:@dots{}
25163 Requests of this form may be added in the future. When a stub does
25164 not recognize the @var{object} keyword, or its support for
25165 @var{object} does not recognize the @var{operation} keyword, the stub
25166 must respond with an empty packet.
25170 @node Register Packet Format
25171 @section Register Packet Format
25173 The following @code{g}/@code{G} packets have previously been defined.
25174 In the below, some thirty-two bit registers are transferred as
25175 sixty-four bits. Those registers should be zero/sign extended (which?)
25176 to fill the space allocated. Register bytes are transferred in target
25177 byte order. The two nibbles within a register byte are transferred
25178 most-significant - least-significant.
25184 All registers are transferred as thirty-two bit quantities in the order:
25185 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
25186 registers; fsr; fir; fp.
25190 All registers are transferred as sixty-four bit quantities (including
25191 thirty-two bit registers such as @code{sr}). The ordering is the same
25196 @node Tracepoint Packets
25197 @section Tracepoint Packets
25198 @cindex tracepoint packets
25199 @cindex packets, tracepoint
25201 Here we describe the packets @value{GDBN} uses to implement
25202 tracepoints (@pxref{Tracepoints}).
25206 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
25207 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
25208 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
25209 the tracepoint is disabled. @var{step} is the tracepoint's step
25210 count, and @var{pass} is its pass count. If the trailing @samp{-} is
25211 present, further @samp{QTDP} packets will follow to specify this
25212 tracepoint's actions.
25217 The packet was understood and carried out.
25219 The packet was not recognized.
25222 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
25223 Define actions to be taken when a tracepoint is hit. @var{n} and
25224 @var{addr} must be the same as in the initial @samp{QTDP} packet for
25225 this tracepoint. This packet may only be sent immediately after
25226 another @samp{QTDP} packet that ended with a @samp{-}. If the
25227 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
25228 specifying more actions for this tracepoint.
25230 In the series of action packets for a given tracepoint, at most one
25231 can have an @samp{S} before its first @var{action}. If such a packet
25232 is sent, it and the following packets define ``while-stepping''
25233 actions. Any prior packets define ordinary actions --- that is, those
25234 taken when the tracepoint is first hit. If no action packet has an
25235 @samp{S}, then all the packets in the series specify ordinary
25236 tracepoint actions.
25238 The @samp{@var{action}@dots{}} portion of the packet is a series of
25239 actions, concatenated without separators. Each action has one of the
25245 Collect the registers whose bits are set in @var{mask}. @var{mask} is
25246 a hexadecimal number whose @var{i}'th bit is set if register number
25247 @var{i} should be collected. (The least significant bit is numbered
25248 zero.) Note that @var{mask} may be any number of digits long; it may
25249 not fit in a 32-bit word.
25251 @item M @var{basereg},@var{offset},@var{len}
25252 Collect @var{len} bytes of memory starting at the address in register
25253 number @var{basereg}, plus @var{offset}. If @var{basereg} is
25254 @samp{-1}, then the range has a fixed address: @var{offset} is the
25255 address of the lowest byte to collect. The @var{basereg},
25256 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
25257 values (the @samp{-1} value for @var{basereg} is a special case).
25259 @item X @var{len},@var{expr}
25260 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
25261 it directs. @var{expr} is an agent expression, as described in
25262 @ref{Agent Expressions}. Each byte of the expression is encoded as a
25263 two-digit hex number in the packet; @var{len} is the number of bytes
25264 in the expression (and thus one-half the number of hex digits in the
25269 Any number of actions may be packed together in a single @samp{QTDP}
25270 packet, as long as the packet does not exceed the maximum packet
25271 length (400 bytes, for many stubs). There may be only one @samp{R}
25272 action per tracepoint, and it must precede any @samp{M} or @samp{X}
25273 actions. Any registers referred to by @samp{M} and @samp{X} actions
25274 must be collected by a preceding @samp{R} action. (The
25275 ``while-stepping'' actions are treated as if they were attached to a
25276 separate tracepoint, as far as these restrictions are concerned.)
25281 The packet was understood and carried out.
25283 The packet was not recognized.
25286 @item QTFrame:@var{n}
25287 Select the @var{n}'th tracepoint frame from the buffer, and use the
25288 register and memory contents recorded there to answer subsequent
25289 request packets from @value{GDBN}.
25291 A successful reply from the stub indicates that the stub has found the
25292 requested frame. The response is a series of parts, concatenated
25293 without separators, describing the frame we selected. Each part has
25294 one of the following forms:
25298 The selected frame is number @var{n} in the trace frame buffer;
25299 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
25300 was no frame matching the criteria in the request packet.
25303 The selected trace frame records a hit of tracepoint number @var{t};
25304 @var{t} is a hexadecimal number.
25308 @item QTFrame:pc:@var{addr}
25309 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25310 currently selected frame whose PC is @var{addr};
25311 @var{addr} is a hexadecimal number.
25313 @item QTFrame:tdp:@var{t}
25314 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25315 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
25316 is a hexadecimal number.
25318 @item QTFrame:range:@var{start}:@var{end}
25319 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25320 currently selected frame whose PC is between @var{start} (inclusive)
25321 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
25324 @item QTFrame:outside:@var{start}:@var{end}
25325 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
25326 frame @emph{outside} the given range of addresses.
25329 Begin the tracepoint experiment. Begin collecting data from tracepoint
25330 hits in the trace frame buffer.
25333 End the tracepoint experiment. Stop collecting trace frames.
25336 Clear the table of tracepoints, and empty the trace frame buffer.
25338 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
25339 Establish the given ranges of memory as ``transparent''. The stub
25340 will answer requests for these ranges from memory's current contents,
25341 if they were not collected as part of the tracepoint hit.
25343 @value{GDBN} uses this to mark read-only regions of memory, like those
25344 containing program code. Since these areas never change, they should
25345 still have the same contents they did when the tracepoint was hit, so
25346 there's no reason for the stub to refuse to provide their contents.
25349 Ask the stub if there is a trace experiment running right now.
25354 There is no trace experiment running.
25356 There is a trace experiment running.
25362 @node Host I/O Packets
25363 @section Host I/O Packets
25364 @cindex Host I/O, remote protocol
25365 @cindex file transfer, remote protocol
25367 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
25368 operations on the far side of a remote link. For example, Host I/O is
25369 used to upload and download files to a remote target with its own
25370 filesystem. Host I/O uses the same constant values and data structure
25371 layout as the target-initiated File-I/O protocol. However, the
25372 Host I/O packets are structured differently. The target-initiated
25373 protocol relies on target memory to store parameters and buffers.
25374 Host I/O requests are initiated by @value{GDBN}, and the
25375 target's memory is not involved. @xref{File-I/O Remote Protocol
25376 Extension}, for more details on the target-initiated protocol.
25378 The Host I/O request packets all encode a single operation along with
25379 its arguments. They have this format:
25383 @item vFile:@var{operation}: @var{parameter}@dots{}
25384 @var{operation} is the name of the particular request; the target
25385 should compare the entire packet name up to the second colon when checking
25386 for a supported operation. The format of @var{parameter} depends on
25387 the operation. Numbers are always passed in hexadecimal. Negative
25388 numbers have an explicit minus sign (i.e.@: two's complement is not
25389 used). Strings (e.g.@: filenames) are encoded as a series of
25390 hexadecimal bytes. The last argument to a system call may be a
25391 buffer of escaped binary data (@pxref{Binary Data}).
25395 The valid responses to Host I/O packets are:
25399 @item F @var{result} [, @var{errno}] [; @var{attachment}]
25400 @var{result} is the integer value returned by this operation, usually
25401 non-negative for success and -1 for errors. If an error has occured,
25402 @var{errno} will be included in the result. @var{errno} will have a
25403 value defined by the File-I/O protocol (@pxref{Errno Values}). For
25404 operations which return data, @var{attachment} supplies the data as a
25405 binary buffer. Binary buffers in response packets are escaped in the
25406 normal way (@pxref{Binary Data}). See the individual packet
25407 documentation for the interpretation of @var{result} and
25411 An empty response indicates that this operation is not recognized.
25415 These are the supported Host I/O operations:
25418 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
25419 Open a file at @var{pathname} and return a file descriptor for it, or
25420 return -1 if an error occurs. @var{pathname} is a string,
25421 @var{flags} is an integer indicating a mask of open flags
25422 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
25423 of mode bits to use if the file is created (@pxref{mode_t Values}).
25424 @xref{open}, for details of the open flags and mode values.
25426 @item vFile:close: @var{fd}
25427 Close the open file corresponding to @var{fd} and return 0, or
25428 -1 if an error occurs.
25430 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
25431 Read data from the open file corresponding to @var{fd}. Up to
25432 @var{count} bytes will be read from the file, starting at @var{offset}
25433 relative to the start of the file. The target may read fewer bytes;
25434 common reasons include packet size limits and an end-of-file
25435 condition. The number of bytes read is returned. Zero should only be
25436 returned for a successful read at the end of the file, or if
25437 @var{count} was zero.
25439 The data read should be returned as a binary attachment on success.
25440 If zero bytes were read, the response should include an empty binary
25441 attachment (i.e.@: a trailing semicolon). The return value is the
25442 number of target bytes read; the binary attachment may be longer if
25443 some characters were escaped.
25445 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
25446 Write @var{data} (a binary buffer) to the open file corresponding
25447 to @var{fd}. Start the write at @var{offset} from the start of the
25448 file. Unlike many @code{write} system calls, there is no
25449 separate @var{count} argument; the length of @var{data} in the
25450 packet is used. @samp{vFile:write} returns the number of bytes written,
25451 which may be shorter than the length of @var{data}, or -1 if an
25454 @item vFile:unlink: @var{pathname}
25455 Delete the file at @var{pathname} on the target. Return 0,
25456 or -1 if an error occurs. @var{pathname} is a string.
25461 @section Interrupts
25462 @cindex interrupts (remote protocol)
25464 When a program on the remote target is running, @value{GDBN} may
25465 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
25466 control of which is specified via @value{GDBN}'s @samp{remotebreak}
25467 setting (@pxref{set remotebreak}).
25469 The precise meaning of @code{BREAK} is defined by the transport
25470 mechanism and may, in fact, be undefined. @value{GDBN} does
25471 not currently define a @code{BREAK} mechanism for any of the network
25474 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
25475 transport mechanisms. It is represented by sending the single byte
25476 @code{0x03} without any of the usual packet overhead described in
25477 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
25478 transmitted as part of a packet, it is considered to be packet data
25479 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
25480 (@pxref{X packet}), used for binary downloads, may include an unescaped
25481 @code{0x03} as part of its packet.
25483 Stubs are not required to recognize these interrupt mechanisms and the
25484 precise meaning associated with receipt of the interrupt is
25485 implementation defined. If the stub is successful at interrupting the
25486 running program, it is expected that it will send one of the Stop
25487 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
25488 of successfully stopping the program. Interrupts received while the
25489 program is stopped will be discarded.
25494 Example sequence of a target being re-started. Notice how the restart
25495 does not get any direct output:
25500 @emph{target restarts}
25503 <- @code{T001:1234123412341234}
25507 Example sequence of a target being stepped by a single instruction:
25510 -> @code{G1445@dots{}}
25515 <- @code{T001:1234123412341234}
25519 <- @code{1455@dots{}}
25523 @node File-I/O Remote Protocol Extension
25524 @section File-I/O Remote Protocol Extension
25525 @cindex File-I/O remote protocol extension
25528 * File-I/O Overview::
25529 * Protocol Basics::
25530 * The F Request Packet::
25531 * The F Reply Packet::
25532 * The Ctrl-C Message::
25534 * List of Supported Calls::
25535 * Protocol-specific Representation of Datatypes::
25537 * File-I/O Examples::
25540 @node File-I/O Overview
25541 @subsection File-I/O Overview
25542 @cindex file-i/o overview
25544 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
25545 target to use the host's file system and console I/O to perform various
25546 system calls. System calls on the target system are translated into a
25547 remote protocol packet to the host system, which then performs the needed
25548 actions and returns a response packet to the target system.
25549 This simulates file system operations even on targets that lack file systems.
25551 The protocol is defined to be independent of both the host and target systems.
25552 It uses its own internal representation of datatypes and values. Both
25553 @value{GDBN} and the target's @value{GDBN} stub are responsible for
25554 translating the system-dependent value representations into the internal
25555 protocol representations when data is transmitted.
25557 The communication is synchronous. A system call is possible only when
25558 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
25559 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
25560 the target is stopped to allow deterministic access to the target's
25561 memory. Therefore File-I/O is not interruptible by target signals. On
25562 the other hand, it is possible to interrupt File-I/O by a user interrupt
25563 (@samp{Ctrl-C}) within @value{GDBN}.
25565 The target's request to perform a host system call does not finish
25566 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
25567 after finishing the system call, the target returns to continuing the
25568 previous activity (continue, step). No additional continue or step
25569 request from @value{GDBN} is required.
25572 (@value{GDBP}) continue
25573 <- target requests 'system call X'
25574 target is stopped, @value{GDBN} executes system call
25575 -> @value{GDBN} returns result
25576 ... target continues, @value{GDBN} returns to wait for the target
25577 <- target hits breakpoint and sends a Txx packet
25580 The protocol only supports I/O on the console and to regular files on
25581 the host file system. Character or block special devices, pipes,
25582 named pipes, sockets or any other communication method on the host
25583 system are not supported by this protocol.
25585 @node Protocol Basics
25586 @subsection Protocol Basics
25587 @cindex protocol basics, file-i/o
25589 The File-I/O protocol uses the @code{F} packet as the request as well
25590 as reply packet. Since a File-I/O system call can only occur when
25591 @value{GDBN} is waiting for a response from the continuing or stepping target,
25592 the File-I/O request is a reply that @value{GDBN} has to expect as a result
25593 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
25594 This @code{F} packet contains all information needed to allow @value{GDBN}
25595 to call the appropriate host system call:
25599 A unique identifier for the requested system call.
25602 All parameters to the system call. Pointers are given as addresses
25603 in the target memory address space. Pointers to strings are given as
25604 pointer/length pair. Numerical values are given as they are.
25605 Numerical control flags are given in a protocol-specific representation.
25609 At this point, @value{GDBN} has to perform the following actions.
25613 If the parameters include pointer values to data needed as input to a
25614 system call, @value{GDBN} requests this data from the target with a
25615 standard @code{m} packet request. This additional communication has to be
25616 expected by the target implementation and is handled as any other @code{m}
25620 @value{GDBN} translates all value from protocol representation to host
25621 representation as needed. Datatypes are coerced into the host types.
25624 @value{GDBN} calls the system call.
25627 It then coerces datatypes back to protocol representation.
25630 If the system call is expected to return data in buffer space specified
25631 by pointer parameters to the call, the data is transmitted to the
25632 target using a @code{M} or @code{X} packet. This packet has to be expected
25633 by the target implementation and is handled as any other @code{M} or @code{X}
25638 Eventually @value{GDBN} replies with another @code{F} packet which contains all
25639 necessary information for the target to continue. This at least contains
25646 @code{errno}, if has been changed by the system call.
25653 After having done the needed type and value coercion, the target continues
25654 the latest continue or step action.
25656 @node The F Request Packet
25657 @subsection The @code{F} Request Packet
25658 @cindex file-i/o request packet
25659 @cindex @code{F} request packet
25661 The @code{F} request packet has the following format:
25664 @item F@var{call-id},@var{parameter@dots{}}
25666 @var{call-id} is the identifier to indicate the host system call to be called.
25667 This is just the name of the function.
25669 @var{parameter@dots{}} are the parameters to the system call.
25670 Parameters are hexadecimal integer values, either the actual values in case
25671 of scalar datatypes, pointers to target buffer space in case of compound
25672 datatypes and unspecified memory areas, or pointer/length pairs in case
25673 of string parameters. These are appended to the @var{call-id} as a
25674 comma-delimited list. All values are transmitted in ASCII
25675 string representation, pointer/length pairs separated by a slash.
25681 @node The F Reply Packet
25682 @subsection The @code{F} Reply Packet
25683 @cindex file-i/o reply packet
25684 @cindex @code{F} reply packet
25686 The @code{F} reply packet has the following format:
25690 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
25692 @var{retcode} is the return code of the system call as hexadecimal value.
25694 @var{errno} is the @code{errno} set by the call, in protocol-specific
25696 This parameter can be omitted if the call was successful.
25698 @var{Ctrl-C flag} is only sent if the user requested a break. In this
25699 case, @var{errno} must be sent as well, even if the call was successful.
25700 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
25707 or, if the call was interrupted before the host call has been performed:
25714 assuming 4 is the protocol-specific representation of @code{EINTR}.
25719 @node The Ctrl-C Message
25720 @subsection The @samp{Ctrl-C} Message
25721 @cindex ctrl-c message, in file-i/o protocol
25723 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
25724 reply packet (@pxref{The F Reply Packet}),
25725 the target should behave as if it had
25726 gotten a break message. The meaning for the target is ``system call
25727 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
25728 (as with a break message) and return to @value{GDBN} with a @code{T02}
25731 It's important for the target to know in which
25732 state the system call was interrupted. There are two possible cases:
25736 The system call hasn't been performed on the host yet.
25739 The system call on the host has been finished.
25743 These two states can be distinguished by the target by the value of the
25744 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
25745 call hasn't been performed. This is equivalent to the @code{EINTR} handling
25746 on POSIX systems. In any other case, the target may presume that the
25747 system call has been finished --- successfully or not --- and should behave
25748 as if the break message arrived right after the system call.
25750 @value{GDBN} must behave reliably. If the system call has not been called
25751 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
25752 @code{errno} in the packet. If the system call on the host has been finished
25753 before the user requests a break, the full action must be finished by
25754 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
25755 The @code{F} packet may only be sent when either nothing has happened
25756 or the full action has been completed.
25759 @subsection Console I/O
25760 @cindex console i/o as part of file-i/o
25762 By default and if not explicitly closed by the target system, the file
25763 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
25764 on the @value{GDBN} console is handled as any other file output operation
25765 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
25766 by @value{GDBN} so that after the target read request from file descriptor
25767 0 all following typing is buffered until either one of the following
25772 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
25774 system call is treated as finished.
25777 The user presses @key{RET}. This is treated as end of input with a trailing
25781 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
25782 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
25786 If the user has typed more characters than fit in the buffer given to
25787 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
25788 either another @code{read(0, @dots{})} is requested by the target, or debugging
25789 is stopped at the user's request.
25792 @node List of Supported Calls
25793 @subsection List of Supported Calls
25794 @cindex list of supported file-i/o calls
25811 @unnumberedsubsubsec open
25812 @cindex open, file-i/o system call
25817 int open(const char *pathname, int flags);
25818 int open(const char *pathname, int flags, mode_t mode);
25822 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
25825 @var{flags} is the bitwise @code{OR} of the following values:
25829 If the file does not exist it will be created. The host
25830 rules apply as far as file ownership and time stamps
25834 When used with @code{O_CREAT}, if the file already exists it is
25835 an error and open() fails.
25838 If the file already exists and the open mode allows
25839 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
25840 truncated to zero length.
25843 The file is opened in append mode.
25846 The file is opened for reading only.
25849 The file is opened for writing only.
25852 The file is opened for reading and writing.
25856 Other bits are silently ignored.
25860 @var{mode} is the bitwise @code{OR} of the following values:
25864 User has read permission.
25867 User has write permission.
25870 Group has read permission.
25873 Group has write permission.
25876 Others have read permission.
25879 Others have write permission.
25883 Other bits are silently ignored.
25886 @item Return value:
25887 @code{open} returns the new file descriptor or -1 if an error
25894 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
25897 @var{pathname} refers to a directory.
25900 The requested access is not allowed.
25903 @var{pathname} was too long.
25906 A directory component in @var{pathname} does not exist.
25909 @var{pathname} refers to a device, pipe, named pipe or socket.
25912 @var{pathname} refers to a file on a read-only filesystem and
25913 write access was requested.
25916 @var{pathname} is an invalid pointer value.
25919 No space on device to create the file.
25922 The process already has the maximum number of files open.
25925 The limit on the total number of files open on the system
25929 The call was interrupted by the user.
25935 @unnumberedsubsubsec close
25936 @cindex close, file-i/o system call
25945 @samp{Fclose,@var{fd}}
25947 @item Return value:
25948 @code{close} returns zero on success, or -1 if an error occurred.
25954 @var{fd} isn't a valid open file descriptor.
25957 The call was interrupted by the user.
25963 @unnumberedsubsubsec read
25964 @cindex read, file-i/o system call
25969 int read(int fd, void *buf, unsigned int count);
25973 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
25975 @item Return value:
25976 On success, the number of bytes read is returned.
25977 Zero indicates end of file. If count is zero, read
25978 returns zero as well. On error, -1 is returned.
25984 @var{fd} is not a valid file descriptor or is not open for
25988 @var{bufptr} is an invalid pointer value.
25991 The call was interrupted by the user.
25997 @unnumberedsubsubsec write
25998 @cindex write, file-i/o system call
26003 int write(int fd, const void *buf, unsigned int count);
26007 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
26009 @item Return value:
26010 On success, the number of bytes written are returned.
26011 Zero indicates nothing was written. On error, -1
26018 @var{fd} is not a valid file descriptor or is not open for
26022 @var{bufptr} is an invalid pointer value.
26025 An attempt was made to write a file that exceeds the
26026 host-specific maximum file size allowed.
26029 No space on device to write the data.
26032 The call was interrupted by the user.
26038 @unnumberedsubsubsec lseek
26039 @cindex lseek, file-i/o system call
26044 long lseek (int fd, long offset, int flag);
26048 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
26050 @var{flag} is one of:
26054 The offset is set to @var{offset} bytes.
26057 The offset is set to its current location plus @var{offset}
26061 The offset is set to the size of the file plus @var{offset}
26065 @item Return value:
26066 On success, the resulting unsigned offset in bytes from
26067 the beginning of the file is returned. Otherwise, a
26068 value of -1 is returned.
26074 @var{fd} is not a valid open file descriptor.
26077 @var{fd} is associated with the @value{GDBN} console.
26080 @var{flag} is not a proper value.
26083 The call was interrupted by the user.
26089 @unnumberedsubsubsec rename
26090 @cindex rename, file-i/o system call
26095 int rename(const char *oldpath, const char *newpath);
26099 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
26101 @item Return value:
26102 On success, zero is returned. On error, -1 is returned.
26108 @var{newpath} is an existing directory, but @var{oldpath} is not a
26112 @var{newpath} is a non-empty directory.
26115 @var{oldpath} or @var{newpath} is a directory that is in use by some
26119 An attempt was made to make a directory a subdirectory
26123 A component used as a directory in @var{oldpath} or new
26124 path is not a directory. Or @var{oldpath} is a directory
26125 and @var{newpath} exists but is not a directory.
26128 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
26131 No access to the file or the path of the file.
26135 @var{oldpath} or @var{newpath} was too long.
26138 A directory component in @var{oldpath} or @var{newpath} does not exist.
26141 The file is on a read-only filesystem.
26144 The device containing the file has no room for the new
26148 The call was interrupted by the user.
26154 @unnumberedsubsubsec unlink
26155 @cindex unlink, file-i/o system call
26160 int unlink(const char *pathname);
26164 @samp{Funlink,@var{pathnameptr}/@var{len}}
26166 @item Return value:
26167 On success, zero is returned. On error, -1 is returned.
26173 No access to the file or the path of the file.
26176 The system does not allow unlinking of directories.
26179 The file @var{pathname} cannot be unlinked because it's
26180 being used by another process.
26183 @var{pathnameptr} is an invalid pointer value.
26186 @var{pathname} was too long.
26189 A directory component in @var{pathname} does not exist.
26192 A component of the path is not a directory.
26195 The file is on a read-only filesystem.
26198 The call was interrupted by the user.
26204 @unnumberedsubsubsec stat/fstat
26205 @cindex fstat, file-i/o system call
26206 @cindex stat, file-i/o system call
26211 int stat(const char *pathname, struct stat *buf);
26212 int fstat(int fd, struct stat *buf);
26216 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
26217 @samp{Ffstat,@var{fd},@var{bufptr}}
26219 @item Return value:
26220 On success, zero is returned. On error, -1 is returned.
26226 @var{fd} is not a valid open file.
26229 A directory component in @var{pathname} does not exist or the
26230 path is an empty string.
26233 A component of the path is not a directory.
26236 @var{pathnameptr} is an invalid pointer value.
26239 No access to the file or the path of the file.
26242 @var{pathname} was too long.
26245 The call was interrupted by the user.
26251 @unnumberedsubsubsec gettimeofday
26252 @cindex gettimeofday, file-i/o system call
26257 int gettimeofday(struct timeval *tv, void *tz);
26261 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
26263 @item Return value:
26264 On success, 0 is returned, -1 otherwise.
26270 @var{tz} is a non-NULL pointer.
26273 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
26279 @unnumberedsubsubsec isatty
26280 @cindex isatty, file-i/o system call
26285 int isatty(int fd);
26289 @samp{Fisatty,@var{fd}}
26291 @item Return value:
26292 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
26298 The call was interrupted by the user.
26303 Note that the @code{isatty} call is treated as a special case: it returns
26304 1 to the target if the file descriptor is attached
26305 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
26306 would require implementing @code{ioctl} and would be more complex than
26311 @unnumberedsubsubsec system
26312 @cindex system, file-i/o system call
26317 int system(const char *command);
26321 @samp{Fsystem,@var{commandptr}/@var{len}}
26323 @item Return value:
26324 If @var{len} is zero, the return value indicates whether a shell is
26325 available. A zero return value indicates a shell is not available.
26326 For non-zero @var{len}, the value returned is -1 on error and the
26327 return status of the command otherwise. Only the exit status of the
26328 command is returned, which is extracted from the host's @code{system}
26329 return value by calling @code{WEXITSTATUS(retval)}. In case
26330 @file{/bin/sh} could not be executed, 127 is returned.
26336 The call was interrupted by the user.
26341 @value{GDBN} takes over the full task of calling the necessary host calls
26342 to perform the @code{system} call. The return value of @code{system} on
26343 the host is simplified before it's returned
26344 to the target. Any termination signal information from the child process
26345 is discarded, and the return value consists
26346 entirely of the exit status of the called command.
26348 Due to security concerns, the @code{system} call is by default refused
26349 by @value{GDBN}. The user has to allow this call explicitly with the
26350 @code{set remote system-call-allowed 1} command.
26353 @item set remote system-call-allowed
26354 @kindex set remote system-call-allowed
26355 Control whether to allow the @code{system} calls in the File I/O
26356 protocol for the remote target. The default is zero (disabled).
26358 @item show remote system-call-allowed
26359 @kindex show remote system-call-allowed
26360 Show whether the @code{system} calls are allowed in the File I/O
26364 @node Protocol-specific Representation of Datatypes
26365 @subsection Protocol-specific Representation of Datatypes
26366 @cindex protocol-specific representation of datatypes, in file-i/o protocol
26369 * Integral Datatypes::
26371 * Memory Transfer::
26376 @node Integral Datatypes
26377 @unnumberedsubsubsec Integral Datatypes
26378 @cindex integral datatypes, in file-i/o protocol
26380 The integral datatypes used in the system calls are @code{int},
26381 @code{unsigned int}, @code{long}, @code{unsigned long},
26382 @code{mode_t}, and @code{time_t}.
26384 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
26385 implemented as 32 bit values in this protocol.
26387 @code{long} and @code{unsigned long} are implemented as 64 bit types.
26389 @xref{Limits}, for corresponding MIN and MAX values (similar to those
26390 in @file{limits.h}) to allow range checking on host and target.
26392 @code{time_t} datatypes are defined as seconds since the Epoch.
26394 All integral datatypes transferred as part of a memory read or write of a
26395 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
26398 @node Pointer Values
26399 @unnumberedsubsubsec Pointer Values
26400 @cindex pointer values, in file-i/o protocol
26402 Pointers to target data are transmitted as they are. An exception
26403 is made for pointers to buffers for which the length isn't
26404 transmitted as part of the function call, namely strings. Strings
26405 are transmitted as a pointer/length pair, both as hex values, e.g.@:
26412 which is a pointer to data of length 18 bytes at position 0x1aaf.
26413 The length is defined as the full string length in bytes, including
26414 the trailing null byte. For example, the string @code{"hello world"}
26415 at address 0x123456 is transmitted as
26421 @node Memory Transfer
26422 @unnumberedsubsubsec Memory Transfer
26423 @cindex memory transfer, in file-i/o protocol
26425 Structured data which is transferred using a memory read or write (for
26426 example, a @code{struct stat}) is expected to be in a protocol-specific format
26427 with all scalar multibyte datatypes being big endian. Translation to
26428 this representation needs to be done both by the target before the @code{F}
26429 packet is sent, and by @value{GDBN} before
26430 it transfers memory to the target. Transferred pointers to structured
26431 data should point to the already-coerced data at any time.
26435 @unnumberedsubsubsec struct stat
26436 @cindex struct stat, in file-i/o protocol
26438 The buffer of type @code{struct stat} used by the target and @value{GDBN}
26439 is defined as follows:
26443 unsigned int st_dev; /* device */
26444 unsigned int st_ino; /* inode */
26445 mode_t st_mode; /* protection */
26446 unsigned int st_nlink; /* number of hard links */
26447 unsigned int st_uid; /* user ID of owner */
26448 unsigned int st_gid; /* group ID of owner */
26449 unsigned int st_rdev; /* device type (if inode device) */
26450 unsigned long st_size; /* total size, in bytes */
26451 unsigned long st_blksize; /* blocksize for filesystem I/O */
26452 unsigned long st_blocks; /* number of blocks allocated */
26453 time_t st_atime; /* time of last access */
26454 time_t st_mtime; /* time of last modification */
26455 time_t st_ctime; /* time of last change */
26459 The integral datatypes conform to the definitions given in the
26460 appropriate section (see @ref{Integral Datatypes}, for details) so this
26461 structure is of size 64 bytes.
26463 The values of several fields have a restricted meaning and/or
26469 A value of 0 represents a file, 1 the console.
26472 No valid meaning for the target. Transmitted unchanged.
26475 Valid mode bits are described in @ref{Constants}. Any other
26476 bits have currently no meaning for the target.
26481 No valid meaning for the target. Transmitted unchanged.
26486 These values have a host and file system dependent
26487 accuracy. Especially on Windows hosts, the file system may not
26488 support exact timing values.
26491 The target gets a @code{struct stat} of the above representation and is
26492 responsible for coercing it to the target representation before
26495 Note that due to size differences between the host, target, and protocol
26496 representations of @code{struct stat} members, these members could eventually
26497 get truncated on the target.
26499 @node struct timeval
26500 @unnumberedsubsubsec struct timeval
26501 @cindex struct timeval, in file-i/o protocol
26503 The buffer of type @code{struct timeval} used by the File-I/O protocol
26504 is defined as follows:
26508 time_t tv_sec; /* second */
26509 long tv_usec; /* microsecond */
26513 The integral datatypes conform to the definitions given in the
26514 appropriate section (see @ref{Integral Datatypes}, for details) so this
26515 structure is of size 8 bytes.
26518 @subsection Constants
26519 @cindex constants, in file-i/o protocol
26521 The following values are used for the constants inside of the
26522 protocol. @value{GDBN} and target are responsible for translating these
26523 values before and after the call as needed.
26534 @unnumberedsubsubsec Open Flags
26535 @cindex open flags, in file-i/o protocol
26537 All values are given in hexadecimal representation.
26549 @node mode_t Values
26550 @unnumberedsubsubsec mode_t Values
26551 @cindex mode_t values, in file-i/o protocol
26553 All values are given in octal representation.
26570 @unnumberedsubsubsec Errno Values
26571 @cindex errno values, in file-i/o protocol
26573 All values are given in decimal representation.
26598 @code{EUNKNOWN} is used as a fallback error value if a host system returns
26599 any error value not in the list of supported error numbers.
26602 @unnumberedsubsubsec Lseek Flags
26603 @cindex lseek flags, in file-i/o protocol
26612 @unnumberedsubsubsec Limits
26613 @cindex limits, in file-i/o protocol
26615 All values are given in decimal representation.
26618 INT_MIN -2147483648
26620 UINT_MAX 4294967295
26621 LONG_MIN -9223372036854775808
26622 LONG_MAX 9223372036854775807
26623 ULONG_MAX 18446744073709551615
26626 @node File-I/O Examples
26627 @subsection File-I/O Examples
26628 @cindex file-i/o examples
26630 Example sequence of a write call, file descriptor 3, buffer is at target
26631 address 0x1234, 6 bytes should be written:
26634 <- @code{Fwrite,3,1234,6}
26635 @emph{request memory read from target}
26638 @emph{return "6 bytes written"}
26642 Example sequence of a read call, file descriptor 3, buffer is at target
26643 address 0x1234, 6 bytes should be read:
26646 <- @code{Fread,3,1234,6}
26647 @emph{request memory write to target}
26648 -> @code{X1234,6:XXXXXX}
26649 @emph{return "6 bytes read"}
26653 Example sequence of a read call, call fails on the host due to invalid
26654 file descriptor (@code{EBADF}):
26657 <- @code{Fread,3,1234,6}
26661 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
26665 <- @code{Fread,3,1234,6}
26670 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
26674 <- @code{Fread,3,1234,6}
26675 -> @code{X1234,6:XXXXXX}
26679 @node Library List Format
26680 @section Library List Format
26681 @cindex library list format, remote protocol
26683 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
26684 same process as your application to manage libraries. In this case,
26685 @value{GDBN} can use the loader's symbol table and normal memory
26686 operations to maintain a list of shared libraries. On other
26687 platforms, the operating system manages loaded libraries.
26688 @value{GDBN} can not retrieve the list of currently loaded libraries
26689 through memory operations, so it uses the @samp{qXfer:libraries:read}
26690 packet (@pxref{qXfer library list read}) instead. The remote stub
26691 queries the target's operating system and reports which libraries
26694 The @samp{qXfer:libraries:read} packet returns an XML document which
26695 lists loaded libraries and their offsets. Each library has an
26696 associated name and one or more segment or section base addresses,
26697 which report where the library was loaded in memory.
26699 For the common case of libraries that are fully linked binaries, the
26700 library should have a list of segments. If the target supports
26701 dynamic linking of a relocatable object file, its library XML element
26702 should instead include a list of allocated sections. The segment or
26703 section bases are start addresses, not relocation offsets; they do not
26704 depend on the library's link-time base addresses.
26706 @value{GDBN} must be linked with the Expat library to support XML
26707 library lists. @xref{Expat}.
26709 A simple memory map, with one loaded library relocated by a single
26710 offset, looks like this:
26714 <library name="/lib/libc.so.6">
26715 <segment address="0x10000000"/>
26720 Another simple memory map, with one loaded library with three
26721 allocated sections (.text, .data, .bss), looks like this:
26725 <library name="sharedlib.o">
26726 <section address="0x10000000"/>
26727 <section address="0x20000000"/>
26728 <section address="0x30000000"/>
26733 The format of a library list is described by this DTD:
26736 <!-- library-list: Root element with versioning -->
26737 <!ELEMENT library-list (library)*>
26738 <!ATTLIST library-list version CDATA #FIXED "1.0">
26739 <!ELEMENT library (segment*, section*)>
26740 <!ATTLIST library name CDATA #REQUIRED>
26741 <!ELEMENT segment EMPTY>
26742 <!ATTLIST segment address CDATA #REQUIRED>
26743 <!ELEMENT section EMPTY>
26744 <!ATTLIST section address CDATA #REQUIRED>
26747 In addition, segments and section descriptors cannot be mixed within a
26748 single library element, and you must supply at least one segment or
26749 section for each library.
26751 @node Memory Map Format
26752 @section Memory Map Format
26753 @cindex memory map format
26755 To be able to write into flash memory, @value{GDBN} needs to obtain a
26756 memory map from the target. This section describes the format of the
26759 The memory map is obtained using the @samp{qXfer:memory-map:read}
26760 (@pxref{qXfer memory map read}) packet and is an XML document that
26761 lists memory regions.
26763 @value{GDBN} must be linked with the Expat library to support XML
26764 memory maps. @xref{Expat}.
26766 The top-level structure of the document is shown below:
26769 <?xml version="1.0"?>
26770 <!DOCTYPE memory-map
26771 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
26772 "http://sourceware.org/gdb/gdb-memory-map.dtd">
26778 Each region can be either:
26783 A region of RAM starting at @var{addr} and extending for @var{length}
26787 <memory type="ram" start="@var{addr}" length="@var{length}"/>
26792 A region of read-only memory:
26795 <memory type="rom" start="@var{addr}" length="@var{length}"/>
26800 A region of flash memory, with erasure blocks @var{blocksize}
26804 <memory type="flash" start="@var{addr}" length="@var{length}">
26805 <property name="blocksize">@var{blocksize}</property>
26811 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
26812 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
26813 packets to write to addresses in such ranges.
26815 The formal DTD for memory map format is given below:
26818 <!-- ................................................... -->
26819 <!-- Memory Map XML DTD ................................ -->
26820 <!-- File: memory-map.dtd .............................. -->
26821 <!-- .................................... .............. -->
26822 <!-- memory-map.dtd -->
26823 <!-- memory-map: Root element with versioning -->
26824 <!ELEMENT memory-map (memory | property)>
26825 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
26826 <!ELEMENT memory (property)>
26827 <!-- memory: Specifies a memory region,
26828 and its type, or device. -->
26829 <!ATTLIST memory type CDATA #REQUIRED
26830 start CDATA #REQUIRED
26831 length CDATA #REQUIRED
26832 device CDATA #IMPLIED>
26833 <!-- property: Generic attribute tag -->
26834 <!ELEMENT property (#PCDATA | property)*>
26835 <!ATTLIST property name CDATA #REQUIRED>
26838 @include agentexpr.texi
26840 @node Target Descriptions
26841 @appendix Target Descriptions
26842 @cindex target descriptions
26844 @strong{Warning:} target descriptions are still under active development,
26845 and the contents and format may change between @value{GDBN} releases.
26846 The format is expected to stabilize in the future.
26848 One of the challenges of using @value{GDBN} to debug embedded systems
26849 is that there are so many minor variants of each processor
26850 architecture in use. It is common practice for vendors to start with
26851 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
26852 and then make changes to adapt it to a particular market niche. Some
26853 architectures have hundreds of variants, available from dozens of
26854 vendors. This leads to a number of problems:
26858 With so many different customized processors, it is difficult for
26859 the @value{GDBN} maintainers to keep up with the changes.
26861 Since individual variants may have short lifetimes or limited
26862 audiences, it may not be worthwhile to carry information about every
26863 variant in the @value{GDBN} source tree.
26865 When @value{GDBN} does support the architecture of the embedded system
26866 at hand, the task of finding the correct architecture name to give the
26867 @command{set architecture} command can be error-prone.
26870 To address these problems, the @value{GDBN} remote protocol allows a
26871 target system to not only identify itself to @value{GDBN}, but to
26872 actually describe its own features. This lets @value{GDBN} support
26873 processor variants it has never seen before --- to the extent that the
26874 descriptions are accurate, and that @value{GDBN} understands them.
26876 @value{GDBN} must be linked with the Expat library to support XML
26877 target descriptions. @xref{Expat}.
26880 * Retrieving Descriptions:: How descriptions are fetched from a target.
26881 * Target Description Format:: The contents of a target description.
26882 * Predefined Target Types:: Standard types available for target
26884 * Standard Target Features:: Features @value{GDBN} knows about.
26887 @node Retrieving Descriptions
26888 @section Retrieving Descriptions
26890 Target descriptions can be read from the target automatically, or
26891 specified by the user manually. The default behavior is to read the
26892 description from the target. @value{GDBN} retrieves it via the remote
26893 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
26894 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
26895 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
26896 XML document, of the form described in @ref{Target Description
26899 Alternatively, you can specify a file to read for the target description.
26900 If a file is set, the target will not be queried. The commands to
26901 specify a file are:
26904 @cindex set tdesc filename
26905 @item set tdesc filename @var{path}
26906 Read the target description from @var{path}.
26908 @cindex unset tdesc filename
26909 @item unset tdesc filename
26910 Do not read the XML target description from a file. @value{GDBN}
26911 will use the description supplied by the current target.
26913 @cindex show tdesc filename
26914 @item show tdesc filename
26915 Show the filename to read for a target description, if any.
26919 @node Target Description Format
26920 @section Target Description Format
26921 @cindex target descriptions, XML format
26923 A target description annex is an @uref{http://www.w3.org/XML/, XML}
26924 document which complies with the Document Type Definition provided in
26925 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
26926 means you can use generally available tools like @command{xmllint} to
26927 check that your feature descriptions are well-formed and valid.
26928 However, to help people unfamiliar with XML write descriptions for
26929 their targets, we also describe the grammar here.
26931 Target descriptions can identify the architecture of the remote target
26932 and (for some architectures) provide information about custom register
26933 sets. @value{GDBN} can use this information to autoconfigure for your
26934 target, or to warn you if you connect to an unsupported target.
26936 Here is a simple target description:
26939 <target version="1.0">
26940 <architecture>i386:x86-64</architecture>
26945 This minimal description only says that the target uses
26946 the x86-64 architecture.
26948 A target description has the following overall form, with [ ] marking
26949 optional elements and @dots{} marking repeatable elements. The elements
26950 are explained further below.
26953 <?xml version="1.0"?>
26954 <!DOCTYPE target SYSTEM "gdb-target.dtd">
26955 <target version="1.0">
26956 @r{[}@var{architecture}@r{]}
26957 @r{[}@var{feature}@dots{}@r{]}
26962 The description is generally insensitive to whitespace and line
26963 breaks, under the usual common-sense rules. The XML version
26964 declaration and document type declaration can generally be omitted
26965 (@value{GDBN} does not require them), but specifying them may be
26966 useful for XML validation tools. The @samp{version} attribute for
26967 @samp{<target>} may also be omitted, but we recommend
26968 including it; if future versions of @value{GDBN} use an incompatible
26969 revision of @file{gdb-target.dtd}, they will detect and report
26970 the version mismatch.
26972 @subsection Inclusion
26973 @cindex target descriptions, inclusion
26976 @cindex <xi:include>
26979 It can sometimes be valuable to split a target description up into
26980 several different annexes, either for organizational purposes, or to
26981 share files between different possible target descriptions. You can
26982 divide a description into multiple files by replacing any element of
26983 the target description with an inclusion directive of the form:
26986 <xi:include href="@var{document}"/>
26990 When @value{GDBN} encounters an element of this form, it will retrieve
26991 the named XML @var{document}, and replace the inclusion directive with
26992 the contents of that document. If the current description was read
26993 using @samp{qXfer}, then so will be the included document;
26994 @var{document} will be interpreted as the name of an annex. If the
26995 current description was read from a file, @value{GDBN} will look for
26996 @var{document} as a file in the same directory where it found the
26997 original description.
26999 @subsection Architecture
27000 @cindex <architecture>
27002 An @samp{<architecture>} element has this form:
27005 <architecture>@var{arch}</architecture>
27008 @var{arch} is an architecture name from the same selection
27009 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
27010 Debugging Target}).
27012 @subsection Features
27015 Each @samp{<feature>} describes some logical portion of the target
27016 system. Features are currently used to describe available CPU
27017 registers and the types of their contents. A @samp{<feature>} element
27021 <feature name="@var{name}">
27022 @r{[}@var{type}@dots{}@r{]}
27028 Each feature's name should be unique within the description. The name
27029 of a feature does not matter unless @value{GDBN} has some special
27030 knowledge of the contents of that feature; if it does, the feature
27031 should have its standard name. @xref{Standard Target Features}.
27035 Any register's value is a collection of bits which @value{GDBN} must
27036 interpret. The default interpretation is a two's complement integer,
27037 but other types can be requested by name in the register description.
27038 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
27039 Target Types}), and the description can define additional composite types.
27041 Each type element must have an @samp{id} attribute, which gives
27042 a unique (within the containing @samp{<feature>}) name to the type.
27043 Types must be defined before they are used.
27046 Some targets offer vector registers, which can be treated as arrays
27047 of scalar elements. These types are written as @samp{<vector>} elements,
27048 specifying the array element type, @var{type}, and the number of elements,
27052 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
27056 If a register's value is usefully viewed in multiple ways, define it
27057 with a union type containing the useful representations. The
27058 @samp{<union>} element contains one or more @samp{<field>} elements,
27059 each of which has a @var{name} and a @var{type}:
27062 <union id="@var{id}">
27063 <field name="@var{name}" type="@var{type}"/>
27068 @subsection Registers
27071 Each register is represented as an element with this form:
27074 <reg name="@var{name}"
27075 bitsize="@var{size}"
27076 @r{[}regnum="@var{num}"@r{]}
27077 @r{[}save-restore="@var{save-restore}"@r{]}
27078 @r{[}type="@var{type}"@r{]}
27079 @r{[}group="@var{group}"@r{]}/>
27083 The components are as follows:
27088 The register's name; it must be unique within the target description.
27091 The register's size, in bits.
27094 The register's number. If omitted, a register's number is one greater
27095 than that of the previous register (either in the current feature or in
27096 a preceeding feature); the first register in the target description
27097 defaults to zero. This register number is used to read or write
27098 the register; e.g.@: it is used in the remote @code{p} and @code{P}
27099 packets, and registers appear in the @code{g} and @code{G} packets
27100 in order of increasing register number.
27103 Whether the register should be preserved across inferior function
27104 calls; this must be either @code{yes} or @code{no}. The default is
27105 @code{yes}, which is appropriate for most registers except for
27106 some system control registers; this is not related to the target's
27110 The type of the register. @var{type} may be a predefined type, a type
27111 defined in the current feature, or one of the special types @code{int}
27112 and @code{float}. @code{int} is an integer type of the correct size
27113 for @var{bitsize}, and @code{float} is a floating point type (in the
27114 architecture's normal floating point format) of the correct size for
27115 @var{bitsize}. The default is @code{int}.
27118 The register group to which this register belongs. @var{group} must
27119 be either @code{general}, @code{float}, or @code{vector}. If no
27120 @var{group} is specified, @value{GDBN} will not display the register
27121 in @code{info registers}.
27125 @node Predefined Target Types
27126 @section Predefined Target Types
27127 @cindex target descriptions, predefined types
27129 Type definitions in the self-description can build up composite types
27130 from basic building blocks, but can not define fundamental types. Instead,
27131 standard identifiers are provided by @value{GDBN} for the fundamental
27132 types. The currently supported types are:
27141 Signed integer types holding the specified number of bits.
27148 Unsigned integer types holding the specified number of bits.
27152 Pointers to unspecified code and data. The program counter and
27153 any dedicated return address register may be marked as code
27154 pointers; printing a code pointer converts it into a symbolic
27155 address. The stack pointer and any dedicated address registers
27156 may be marked as data pointers.
27159 Single precision IEEE floating point.
27162 Double precision IEEE floating point.
27165 The 12-byte extended precision format used by ARM FPA registers.
27169 @node Standard Target Features
27170 @section Standard Target Features
27171 @cindex target descriptions, standard features
27173 A target description must contain either no registers or all the
27174 target's registers. If the description contains no registers, then
27175 @value{GDBN} will assume a default register layout, selected based on
27176 the architecture. If the description contains any registers, the
27177 default layout will not be used; the standard registers must be
27178 described in the target description, in such a way that @value{GDBN}
27179 can recognize them.
27181 This is accomplished by giving specific names to feature elements
27182 which contain standard registers. @value{GDBN} will look for features
27183 with those names and verify that they contain the expected registers;
27184 if any known feature is missing required registers, or if any required
27185 feature is missing, @value{GDBN} will reject the target
27186 description. You can add additional registers to any of the
27187 standard features --- @value{GDBN} will display them just as if
27188 they were added to an unrecognized feature.
27190 This section lists the known features and their expected contents.
27191 Sample XML documents for these features are included in the
27192 @value{GDBN} source tree, in the directory @file{gdb/features}.
27194 Names recognized by @value{GDBN} should include the name of the
27195 company or organization which selected the name, and the overall
27196 architecture to which the feature applies; so e.g.@: the feature
27197 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
27199 The names of registers are not case sensitive for the purpose
27200 of recognizing standard features, but @value{GDBN} will only display
27201 registers using the capitalization used in the description.
27207 * PowerPC Features::
27212 @subsection ARM Features
27213 @cindex target descriptions, ARM features
27215 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
27216 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
27217 @samp{lr}, @samp{pc}, and @samp{cpsr}.
27219 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
27220 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
27222 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
27223 it should contain at least registers @samp{wR0} through @samp{wR15} and
27224 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
27225 @samp{wCSSF}, and @samp{wCASF} registers are optional.
27227 @node MIPS Features
27228 @subsection MIPS Features
27229 @cindex target descriptions, MIPS features
27231 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
27232 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
27233 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
27236 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
27237 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
27238 registers. They may be 32-bit or 64-bit depending on the target.
27240 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
27241 it may be optional in a future version of @value{GDBN}. It should
27242 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
27243 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
27245 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
27246 contain a single register, @samp{restart}, which is used by the
27247 Linux kernel to control restartable syscalls.
27249 @node M68K Features
27250 @subsection M68K Features
27251 @cindex target descriptions, M68K features
27254 @item @samp{org.gnu.gdb.m68k.core}
27255 @itemx @samp{org.gnu.gdb.coldfire.core}
27256 @itemx @samp{org.gnu.gdb.fido.core}
27257 One of those features must be always present.
27258 The feature that is present determines which flavor of m86k is
27259 used. The feature that is present should contain registers
27260 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
27261 @samp{sp}, @samp{ps} and @samp{pc}.
27263 @item @samp{org.gnu.gdb.coldfire.fp}
27264 This feature is optional. If present, it should contain registers
27265 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
27269 @node PowerPC Features
27270 @subsection PowerPC Features
27271 @cindex target descriptions, PowerPC features
27273 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
27274 targets. It should contain registers @samp{r0} through @samp{r31},
27275 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
27276 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
27278 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
27279 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
27281 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
27282 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
27285 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
27286 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
27287 @samp{spefscr}. SPE targets should provide 32-bit registers in
27288 @samp{org.gnu.gdb.power.core} and provide the upper halves in
27289 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
27290 these to present registers @samp{ev0} through @samp{ev31} to the
27305 % I think something like @colophon should be in texinfo. In the
27307 \long\def\colophon{\hbox to0pt{}\vfill
27308 \centerline{The body of this manual is set in}
27309 \centerline{\fontname\tenrm,}
27310 \centerline{with headings in {\bf\fontname\tenbf}}
27311 \centerline{and examples in {\tt\fontname\tentt}.}
27312 \centerline{{\it\fontname\tenit\/},}
27313 \centerline{{\bf\fontname\tenbf}, and}
27314 \centerline{{\sl\fontname\tensl\/}}
27315 \centerline{are used for emphasis.}\vfill}
27317 % Blame: doc@cygnus.com, 1991.