1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The Free Software Foundation's Back-Cover Text is: ``You have
66 freedom to copy and modify this GNU Manual, like GNU software. Copies
67 published by the Free Software Foundation raise funds for GNU
72 @title Debugging with @value{GDBN}
73 @subtitle The @sc{gnu} Source-Level Debugger
75 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
76 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
80 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
81 \hfill {\it Debugging with @value{GDBN}}\par
82 \hfill \TeX{}info \texinfoversion\par
86 @vskip 0pt plus 1filll
87 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
88 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
89 Free Software Foundation, Inc.
91 Published by the Free Software Foundation @*
92 51 Franklin Street, Fifth Floor,
93 Boston, MA 02110-1301, USA@*
96 Permission is granted to copy, distribute and/or modify this document
97 under the terms of the GNU Free Documentation License, Version 1.1 or
98 any later version published by the Free Software Foundation; with the
99 Invariant Sections being ``Free Software'' and ``Free Software Needs
100 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
101 and with the Back-Cover Texts as in (a) below.
103 (a) The Free Software Foundation's Back-Cover Text is: ``You have
104 freedom to copy and modify this GNU Manual, like GNU software. Copies
105 published by the Free Software Foundation raise funds for GNU
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN} Version
120 Copyright (C) 1988-2006 Free Software Foundation, Inc.
123 * Summary:: Summary of @value{GDBN}
124 * Sample Session:: A sample @value{GDBN} session
126 * Invocation:: Getting in and out of @value{GDBN}
127 * Commands:: @value{GDBN} commands
128 * Running:: Running programs under @value{GDBN}
129 * Stopping:: Stopping and continuing
130 * Stack:: Examining the stack
131 * Source:: Examining source files
132 * Data:: Examining data
133 * Macros:: Preprocessor Macros
134 * Tracepoints:: Debugging remote targets non-intrusively
135 * Overlays:: Debugging programs that use overlays
137 * Languages:: Using @value{GDBN} with different languages
139 * Symbols:: Examining the symbol table
140 * Altering:: Altering execution
141 * GDB Files:: @value{GDBN} files
142 * Targets:: Specifying a debugging target
143 * Remote Debugging:: Debugging remote programs
144 * Configurations:: Configuration-specific information
145 * Controlling GDB:: Controlling @value{GDBN}
146 * Sequences:: Canned sequences of commands
147 * Interpreters:: Command Interpreters
148 * TUI:: @value{GDBN} Text User Interface
149 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
150 * GDB/MI:: @value{GDBN}'s Machine Interface.
151 * Annotations:: @value{GDBN}'s annotation interface.
153 * GDB Bugs:: Reporting bugs in @value{GDBN}
155 * Command Line Editing:: Command Line Editing
156 * Using History Interactively:: Using History Interactively
157 * Formatting Documentation:: How to format and print @value{GDBN} documentation
158 * Installing GDB:: Installing GDB
159 * Maintenance Commands:: Maintenance Commands
160 * Remote Protocol:: GDB Remote Serial Protocol
161 * Agent Expressions:: The GDB Agent Expression Mechanism
162 * Target Descriptions:: How targets can describe themselves to
164 * Copying:: GNU General Public License says
165 how you can copy and share GDB
166 * GNU Free Documentation License:: The license for this documentation
175 @unnumbered Summary of @value{GDBN}
177 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
178 going on ``inside'' another program while it executes---or what another
179 program was doing at the moment it crashed.
181 @value{GDBN} can do four main kinds of things (plus other things in support of
182 these) to help you catch bugs in the act:
186 Start your program, specifying anything that might affect its behavior.
189 Make your program stop on specified conditions.
192 Examine what has happened, when your program has stopped.
195 Change things in your program, so you can experiment with correcting the
196 effects of one bug and go on to learn about another.
199 You can use @value{GDBN} to debug programs written in C and C@t{++}.
200 For more information, see @ref{Supported Languages,,Supported Languages}.
201 For more information, see @ref{C,,C and C++}.
204 Support for Modula-2 is partial. For information on Modula-2, see
205 @ref{Modula-2,,Modula-2}.
208 Debugging Pascal programs which use sets, subranges, file variables, or
209 nested functions does not currently work. @value{GDBN} does not support
210 entering expressions, printing values, or similar features using Pascal
214 @value{GDBN} can be used to debug programs written in Fortran, although
215 it may be necessary to refer to some variables with a trailing
218 @value{GDBN} can be used to debug programs written in Objective-C,
219 using either the Apple/NeXT or the GNU Objective-C runtime.
222 * Free Software:: Freely redistributable software
223 * Contributors:: Contributors to GDB
227 @unnumberedsec Free Software
229 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
230 General Public License
231 (GPL). The GPL gives you the freedom to copy or adapt a licensed
232 program---but every person getting a copy also gets with it the
233 freedom to modify that copy (which means that they must get access to
234 the source code), and the freedom to distribute further copies.
235 Typical software companies use copyrights to limit your freedoms; the
236 Free Software Foundation uses the GPL to preserve these freedoms.
238 Fundamentally, the General Public License is a license which says that
239 you have these freedoms and that you cannot take these freedoms away
242 @unnumberedsec Free Software Needs Free Documentation
244 The biggest deficiency in the free software community today is not in
245 the software---it is the lack of good free documentation that we can
246 include with the free software. Many of our most important
247 programs do not come with free reference manuals and free introductory
248 texts. Documentation is an essential part of any software package;
249 when an important free software package does not come with a free
250 manual and a free tutorial, that is a major gap. We have many such
253 Consider Perl, for instance. The tutorial manuals that people
254 normally use are non-free. How did this come about? Because the
255 authors of those manuals published them with restrictive terms---no
256 copying, no modification, source files not available---which exclude
257 them from the free software world.
259 That wasn't the first time this sort of thing happened, and it was far
260 from the last. Many times we have heard a GNU user eagerly describe a
261 manual that he is writing, his intended contribution to the community,
262 only to learn that he had ruined everything by signing a publication
263 contract to make it non-free.
265 Free documentation, like free software, is a matter of freedom, not
266 price. The problem with the non-free manual is not that publishers
267 charge a price for printed copies---that in itself is fine. (The Free
268 Software Foundation sells printed copies of manuals, too.) The
269 problem is the restrictions on the use of the manual. Free manuals
270 are available in source code form, and give you permission to copy and
271 modify. Non-free manuals do not allow this.
273 The criteria of freedom for a free manual are roughly the same as for
274 free software. Redistribution (including the normal kinds of
275 commercial redistribution) must be permitted, so that the manual can
276 accompany every copy of the program, both on-line and on paper.
278 Permission for modification of the technical content is crucial too.
279 When people modify the software, adding or changing features, if they
280 are conscientious they will change the manual too---so they can
281 provide accurate and clear documentation for the modified program. A
282 manual that leaves you no choice but to write a new manual to document
283 a changed version of the program is not really available to our
286 Some kinds of limits on the way modification is handled are
287 acceptable. For example, requirements to preserve the original
288 author's copyright notice, the distribution terms, or the list of
289 authors, are ok. It is also no problem to require modified versions
290 to include notice that they were modified. Even entire sections that
291 may not be deleted or changed are acceptable, as long as they deal
292 with nontechnical topics (like this one). These kinds of restrictions
293 are acceptable because they don't obstruct the community's normal use
296 However, it must be possible to modify all the @emph{technical}
297 content of the manual, and then distribute the result in all the usual
298 media, through all the usual channels. Otherwise, the restrictions
299 obstruct the use of the manual, it is not free, and we need another
300 manual to replace it.
302 Please spread the word about this issue. Our community continues to
303 lose manuals to proprietary publishing. If we spread the word that
304 free software needs free reference manuals and free tutorials, perhaps
305 the next person who wants to contribute by writing documentation will
306 realize, before it is too late, that only free manuals contribute to
307 the free software community.
309 If you are writing documentation, please insist on publishing it under
310 the GNU Free Documentation License or another free documentation
311 license. Remember that this decision requires your approval---you
312 don't have to let the publisher decide. Some commercial publishers
313 will use a free license if you insist, but they will not propose the
314 option; it is up to you to raise the issue and say firmly that this is
315 what you want. If the publisher you are dealing with refuses, please
316 try other publishers. If you're not sure whether a proposed license
317 is free, write to @email{licensing@@gnu.org}.
319 You can encourage commercial publishers to sell more free, copylefted
320 manuals and tutorials by buying them, and particularly by buying
321 copies from the publishers that paid for their writing or for major
322 improvements. Meanwhile, try to avoid buying non-free documentation
323 at all. Check the distribution terms of a manual before you buy it,
324 and insist that whoever seeks your business must respect your freedom.
325 Check the history of the book, and try to reward the publishers that
326 have paid or pay the authors to work on it.
328 The Free Software Foundation maintains a list of free documentation
329 published by other publishers, at
330 @url{http://www.fsf.org/doc/other-free-books.html}.
333 @unnumberedsec Contributors to @value{GDBN}
335 Richard Stallman was the original author of @value{GDBN}, and of many
336 other @sc{gnu} programs. Many others have contributed to its
337 development. This section attempts to credit major contributors. One
338 of the virtues of free software is that everyone is free to contribute
339 to it; with regret, we cannot actually acknowledge everyone here. The
340 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
341 blow-by-blow account.
343 Changes much prior to version 2.0 are lost in the mists of time.
346 @emph{Plea:} Additions to this section are particularly welcome. If you
347 or your friends (or enemies, to be evenhanded) have been unfairly
348 omitted from this list, we would like to add your names!
351 So that they may not regard their many labors as thankless, we
352 particularly thank those who shepherded @value{GDBN} through major
354 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
355 Jim Blandy (release 4.18);
356 Jason Molenda (release 4.17);
357 Stan Shebs (release 4.14);
358 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
359 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
360 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
361 Jim Kingdon (releases 3.5, 3.4, and 3.3);
362 and Randy Smith (releases 3.2, 3.1, and 3.0).
364 Richard Stallman, assisted at various times by Peter TerMaat, Chris
365 Hanson, and Richard Mlynarik, handled releases through 2.8.
367 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
368 in @value{GDBN}, with significant additional contributions from Per
369 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
370 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
371 much general update work leading to release 3.0).
373 @value{GDBN} uses the BFD subroutine library to examine multiple
374 object-file formats; BFD was a joint project of David V.
375 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
377 David Johnson wrote the original COFF support; Pace Willison did
378 the original support for encapsulated COFF.
380 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
382 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
383 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
385 Jean-Daniel Fekete contributed Sun 386i support.
386 Chris Hanson improved the HP9000 support.
387 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
388 David Johnson contributed Encore Umax support.
389 Jyrki Kuoppala contributed Altos 3068 support.
390 Jeff Law contributed HP PA and SOM support.
391 Keith Packard contributed NS32K support.
392 Doug Rabson contributed Acorn Risc Machine support.
393 Bob Rusk contributed Harris Nighthawk CX-UX support.
394 Chris Smith contributed Convex support (and Fortran debugging).
395 Jonathan Stone contributed Pyramid support.
396 Michael Tiemann contributed SPARC support.
397 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
398 Pace Willison contributed Intel 386 support.
399 Jay Vosburgh contributed Symmetry support.
400 Marko Mlinar contributed OpenRISC 1000 support.
402 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
404 Rich Schaefer and Peter Schauer helped with support of SunOS shared
407 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
408 about several machine instruction sets.
410 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
411 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
412 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
413 and RDI targets, respectively.
415 Brian Fox is the author of the readline libraries providing
416 command-line editing and command history.
418 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
419 Modula-2 support, and contributed the Languages chapter of this manual.
421 Fred Fish wrote most of the support for Unix System Vr4.
422 He also enhanced the command-completion support to cover C@t{++} overloaded
425 Hitachi America (now Renesas America), Ltd. sponsored the support for
426 H8/300, H8/500, and Super-H processors.
428 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
430 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
433 Toshiba sponsored the support for the TX39 Mips processor.
435 Matsushita sponsored the support for the MN10200 and MN10300 processors.
437 Fujitsu sponsored the support for SPARClite and FR30 processors.
439 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
442 Michael Snyder added support for tracepoints.
444 Stu Grossman wrote gdbserver.
446 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
447 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
449 The following people at the Hewlett-Packard Company contributed
450 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
451 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
452 compiler, and the Text User Interface (nee Terminal User Interface):
453 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
454 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
455 provided HP-specific information in this manual.
457 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
458 Robert Hoehne made significant contributions to the DJGPP port.
460 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
461 development since 1991. Cygnus engineers who have worked on @value{GDBN}
462 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
463 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
464 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
465 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
466 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
467 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
468 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
469 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
470 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
471 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
472 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
473 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
474 Zuhn have made contributions both large and small.
476 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
477 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
479 Jim Blandy added support for preprocessor macros, while working for Red
482 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
483 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
484 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
485 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
486 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
487 with the migration of old architectures to this new framework.
489 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
490 unwinder framework, this consisting of a fresh new design featuring
491 frame IDs, independent frame sniffers, and the sentinel frame. Mark
492 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
493 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
494 trad unwinders. The architecture-specific changes, each involving a
495 complete rewrite of the architecture's frame code, were carried out by
496 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
497 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
498 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
499 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
502 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
503 Tensilica, Inc.@: contributed support for Xtensa processors. Others
504 who have worked on the Xtensa port of @value{GDBN} in the past include
505 Steve Tjiang, John Newlin, and Scott Foehner.
508 @chapter A Sample @value{GDBN} Session
510 You can use this manual at your leisure to read all about @value{GDBN}.
511 However, a handful of commands are enough to get started using the
512 debugger. This chapter illustrates those commands.
515 In this sample session, we emphasize user input like this: @b{input},
516 to make it easier to pick out from the surrounding output.
519 @c FIXME: this example may not be appropriate for some configs, where
520 @c FIXME...primary interest is in remote use.
522 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
523 processor) exhibits the following bug: sometimes, when we change its
524 quote strings from the default, the commands used to capture one macro
525 definition within another stop working. In the following short @code{m4}
526 session, we define a macro @code{foo} which expands to @code{0000}; we
527 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
528 same thing. However, when we change the open quote string to
529 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
530 procedure fails to define a new synonym @code{baz}:
539 @b{define(bar,defn(`foo'))}
543 @b{changequote(<QUOTE>,<UNQUOTE>)}
545 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
548 m4: End of input: 0: fatal error: EOF in string
552 Let us use @value{GDBN} to try to see what is going on.
555 $ @b{@value{GDBP} m4}
556 @c FIXME: this falsifies the exact text played out, to permit smallbook
557 @c FIXME... format to come out better.
558 @value{GDBN} is free software and you are welcome to distribute copies
559 of it under certain conditions; type "show copying" to see
561 There is absolutely no warranty for @value{GDBN}; type "show warranty"
564 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
569 @value{GDBN} reads only enough symbol data to know where to find the
570 rest when needed; as a result, the first prompt comes up very quickly.
571 We now tell @value{GDBN} to use a narrower display width than usual, so
572 that examples fit in this manual.
575 (@value{GDBP}) @b{set width 70}
579 We need to see how the @code{m4} built-in @code{changequote} works.
580 Having looked at the source, we know the relevant subroutine is
581 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
582 @code{break} command.
585 (@value{GDBP}) @b{break m4_changequote}
586 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
590 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
591 control; as long as control does not reach the @code{m4_changequote}
592 subroutine, the program runs as usual:
595 (@value{GDBP}) @b{run}
596 Starting program: /work/Editorial/gdb/gnu/m4/m4
604 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
605 suspends execution of @code{m4}, displaying information about the
606 context where it stops.
609 @b{changequote(<QUOTE>,<UNQUOTE>)}
611 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
613 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
617 Now we use the command @code{n} (@code{next}) to advance execution to
618 the next line of the current function.
622 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
627 @code{set_quotes} looks like a promising subroutine. We can go into it
628 by using the command @code{s} (@code{step}) instead of @code{next}.
629 @code{step} goes to the next line to be executed in @emph{any}
630 subroutine, so it steps into @code{set_quotes}.
634 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
636 530 if (lquote != def_lquote)
640 The display that shows the subroutine where @code{m4} is now
641 suspended (and its arguments) is called a stack frame display. It
642 shows a summary of the stack. We can use the @code{backtrace}
643 command (which can also be spelled @code{bt}), to see where we are
644 in the stack as a whole: the @code{backtrace} command displays a
645 stack frame for each active subroutine.
648 (@value{GDBP}) @b{bt}
649 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
651 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
653 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
654 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
656 #4 0x79dc in expand_input () at macro.c:40
657 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
661 We step through a few more lines to see what happens. The first two
662 times, we can use @samp{s}; the next two times we use @code{n} to avoid
663 falling into the @code{xstrdup} subroutine.
667 0x3b5c 532 if (rquote != def_rquote)
669 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
670 def_lquote : xstrdup(lq);
672 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
675 538 len_lquote = strlen(rquote);
679 The last line displayed looks a little odd; we can examine the variables
680 @code{lquote} and @code{rquote} to see if they are in fact the new left
681 and right quotes we specified. We use the command @code{p}
682 (@code{print}) to see their values.
685 (@value{GDBP}) @b{p lquote}
686 $1 = 0x35d40 "<QUOTE>"
687 (@value{GDBP}) @b{p rquote}
688 $2 = 0x35d50 "<UNQUOTE>"
692 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
693 To look at some context, we can display ten lines of source
694 surrounding the current line with the @code{l} (@code{list}) command.
700 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
702 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
705 538 len_lquote = strlen(rquote);
706 539 len_rquote = strlen(lquote);
713 Let us step past the two lines that set @code{len_lquote} and
714 @code{len_rquote}, and then examine the values of those variables.
718 539 len_rquote = strlen(lquote);
721 (@value{GDBP}) @b{p len_lquote}
723 (@value{GDBP}) @b{p len_rquote}
728 That certainly looks wrong, assuming @code{len_lquote} and
729 @code{len_rquote} are meant to be the lengths of @code{lquote} and
730 @code{rquote} respectively. We can set them to better values using
731 the @code{p} command, since it can print the value of
732 any expression---and that expression can include subroutine calls and
736 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
738 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
743 Is that enough to fix the problem of using the new quotes with the
744 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
745 executing with the @code{c} (@code{continue}) command, and then try the
746 example that caused trouble initially:
752 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
759 Success! The new quotes now work just as well as the default ones. The
760 problem seems to have been just the two typos defining the wrong
761 lengths. We allow @code{m4} exit by giving it an EOF as input:
765 Program exited normally.
769 The message @samp{Program exited normally.} is from @value{GDBN}; it
770 indicates @code{m4} has finished executing. We can end our @value{GDBN}
771 session with the @value{GDBN} @code{quit} command.
774 (@value{GDBP}) @b{quit}
778 @chapter Getting In and Out of @value{GDBN}
780 This chapter discusses how to start @value{GDBN}, and how to get out of it.
784 type @samp{@value{GDBP}} to start @value{GDBN}.
786 type @kbd{quit} or @kbd{Ctrl-d} to exit.
790 * Invoking GDB:: How to start @value{GDBN}
791 * Quitting GDB:: How to quit @value{GDBN}
792 * Shell Commands:: How to use shell commands inside @value{GDBN}
793 * Logging Output:: How to log @value{GDBN}'s output to a file
797 @section Invoking @value{GDBN}
799 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
800 @value{GDBN} reads commands from the terminal until you tell it to exit.
802 You can also run @code{@value{GDBP}} with a variety of arguments and options,
803 to specify more of your debugging environment at the outset.
805 The command-line options described here are designed
806 to cover a variety of situations; in some environments, some of these
807 options may effectively be unavailable.
809 The most usual way to start @value{GDBN} is with one argument,
810 specifying an executable program:
813 @value{GDBP} @var{program}
817 You can also start with both an executable program and a core file
821 @value{GDBP} @var{program} @var{core}
824 You can, instead, specify a process ID as a second argument, if you want
825 to debug a running process:
828 @value{GDBP} @var{program} 1234
832 would attach @value{GDBN} to process @code{1234} (unless you also have a file
833 named @file{1234}; @value{GDBN} does check for a core file first).
835 Taking advantage of the second command-line argument requires a fairly
836 complete operating system; when you use @value{GDBN} as a remote
837 debugger attached to a bare board, there may not be any notion of
838 ``process'', and there is often no way to get a core dump. @value{GDBN}
839 will warn you if it is unable to attach or to read core dumps.
841 You can optionally have @code{@value{GDBP}} pass any arguments after the
842 executable file to the inferior using @code{--args}. This option stops
845 @value{GDBP} --args gcc -O2 -c foo.c
847 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
848 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
850 You can run @code{@value{GDBP}} without printing the front material, which describes
851 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
858 You can further control how @value{GDBN} starts up by using command-line
859 options. @value{GDBN} itself can remind you of the options available.
869 to display all available options and briefly describe their use
870 (@samp{@value{GDBP} -h} is a shorter equivalent).
872 All options and command line arguments you give are processed
873 in sequential order. The order makes a difference when the
874 @samp{-x} option is used.
878 * File Options:: Choosing files
879 * Mode Options:: Choosing modes
880 * Startup:: What @value{GDBN} does during startup
884 @subsection Choosing Files
886 When @value{GDBN} starts, it reads any arguments other than options as
887 specifying an executable file and core file (or process ID). This is
888 the same as if the arguments were specified by the @samp{-se} and
889 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
890 first argument that does not have an associated option flag as
891 equivalent to the @samp{-se} option followed by that argument; and the
892 second argument that does not have an associated option flag, if any, as
893 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
894 If the second argument begins with a decimal digit, @value{GDBN} will
895 first attempt to attach to it as a process, and if that fails, attempt
896 to open it as a corefile. If you have a corefile whose name begins with
897 a digit, you can prevent @value{GDBN} from treating it as a pid by
898 prefixing it with @file{./}, e.g.@: @file{./12345}.
900 If @value{GDBN} has not been configured to included core file support,
901 such as for most embedded targets, then it will complain about a second
902 argument and ignore it.
904 Many options have both long and short forms; both are shown in the
905 following list. @value{GDBN} also recognizes the long forms if you truncate
906 them, so long as enough of the option is present to be unambiguous.
907 (If you prefer, you can flag option arguments with @samp{--} rather
908 than @samp{-}, though we illustrate the more usual convention.)
910 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
911 @c way, both those who look for -foo and --foo in the index, will find
915 @item -symbols @var{file}
917 @cindex @code{--symbols}
919 Read symbol table from file @var{file}.
921 @item -exec @var{file}
923 @cindex @code{--exec}
925 Use file @var{file} as the executable file to execute when appropriate,
926 and for examining pure data in conjunction with a core dump.
930 Read symbol table from file @var{file} and use it as the executable
933 @item -core @var{file}
935 @cindex @code{--core}
937 Use file @var{file} as a core dump to examine.
939 @item -c @var{number}
940 @item -pid @var{number}
941 @itemx -p @var{number}
944 Connect to process ID @var{number}, as with the @code{attach} command.
945 If there is no such process, @value{GDBN} will attempt to open a core
946 file named @var{number}.
948 @item -command @var{file}
950 @cindex @code{--command}
952 Execute @value{GDBN} commands from file @var{file}. @xref{Command
953 Files,, Command files}.
955 @item -eval-command @var{command}
956 @itemx -ex @var{command}
957 @cindex @code{--eval-command}
959 Execute a single @value{GDBN} command.
961 This option may be used multiple times to call multiple commands. It may
962 also be interleaved with @samp{-command} as required.
965 @value{GDBP} -ex 'target sim' -ex 'load' \
966 -x setbreakpoints -ex 'run' a.out
969 @item -directory @var{directory}
970 @itemx -d @var{directory}
971 @cindex @code{--directory}
973 Add @var{directory} to the path to search for source and script files.
977 @cindex @code{--readnow}
979 Read each symbol file's entire symbol table immediately, rather than
980 the default, which is to read it incrementally as it is needed.
981 This makes startup slower, but makes future operations faster.
986 @subsection Choosing Modes
988 You can run @value{GDBN} in various alternative modes---for example, in
989 batch mode or quiet mode.
996 Do not execute commands found in any initialization files. Normally,
997 @value{GDBN} executes the commands in these files after all the command
998 options and arguments have been processed. @xref{Command Files,,Command
1004 @cindex @code{--quiet}
1005 @cindex @code{--silent}
1007 ``Quiet''. Do not print the introductory and copyright messages. These
1008 messages are also suppressed in batch mode.
1011 @cindex @code{--batch}
1012 Run in batch mode. Exit with status @code{0} after processing all the
1013 command files specified with @samp{-x} (and all commands from
1014 initialization files, if not inhibited with @samp{-n}). Exit with
1015 nonzero status if an error occurs in executing the @value{GDBN} commands
1016 in the command files.
1018 Batch mode may be useful for running @value{GDBN} as a filter, for
1019 example to download and run a program on another computer; in order to
1020 make this more useful, the message
1023 Program exited normally.
1027 (which is ordinarily issued whenever a program running under
1028 @value{GDBN} control terminates) is not issued when running in batch
1032 @cindex @code{--batch-silent}
1033 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1034 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1035 unaffected). This is much quieter than @samp{-silent} and would be useless
1036 for an interactive session.
1038 This is particularly useful when using targets that give @samp{Loading section}
1039 messages, for example.
1041 Note that targets that give their output via @value{GDBN}, as opposed to
1042 writing directly to @code{stdout}, will also be made silent.
1044 @item -return-child-result
1045 @cindex @code{--return-child-result}
1046 The return code from @value{GDBN} will be the return code from the child
1047 process (the process being debugged), with the following exceptions:
1051 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1052 internal error. In this case the exit code is the same as it would have been
1053 without @samp{-return-child-result}.
1055 The user quits with an explicit value. E.g., @samp{quit 1}.
1057 The child process never runs, or is not allowed to terminate, in which case
1058 the exit code will be -1.
1061 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1062 when @value{GDBN} is being used as a remote program loader or simulator
1067 @cindex @code{--nowindows}
1069 ``No windows''. If @value{GDBN} comes with a graphical user interface
1070 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1071 interface. If no GUI is available, this option has no effect.
1075 @cindex @code{--windows}
1077 If @value{GDBN} includes a GUI, then this option requires it to be
1080 @item -cd @var{directory}
1082 Run @value{GDBN} using @var{directory} as its working directory,
1083 instead of the current directory.
1087 @cindex @code{--fullname}
1089 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1090 subprocess. It tells @value{GDBN} to output the full file name and line
1091 number in a standard, recognizable fashion each time a stack frame is
1092 displayed (which includes each time your program stops). This
1093 recognizable format looks like two @samp{\032} characters, followed by
1094 the file name, line number and character position separated by colons,
1095 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1096 @samp{\032} characters as a signal to display the source code for the
1100 @cindex @code{--epoch}
1101 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1102 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1103 routines so as to allow Epoch to display values of expressions in a
1106 @item -annotate @var{level}
1107 @cindex @code{--annotate}
1108 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1109 effect is identical to using @samp{set annotate @var{level}}
1110 (@pxref{Annotations}). The annotation @var{level} controls how much
1111 information @value{GDBN} prints together with its prompt, values of
1112 expressions, source lines, and other types of output. Level 0 is the
1113 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1114 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1115 that control @value{GDBN}, and level 2 has been deprecated.
1117 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1121 @cindex @code{--args}
1122 Change interpretation of command line so that arguments following the
1123 executable file are passed as command line arguments to the inferior.
1124 This option stops option processing.
1126 @item -baud @var{bps}
1128 @cindex @code{--baud}
1130 Set the line speed (baud rate or bits per second) of any serial
1131 interface used by @value{GDBN} for remote debugging.
1133 @item -l @var{timeout}
1135 Set the timeout (in seconds) of any communication used by @value{GDBN}
1136 for remote debugging.
1138 @item -tty @var{device}
1139 @itemx -t @var{device}
1140 @cindex @code{--tty}
1142 Run using @var{device} for your program's standard input and output.
1143 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1145 @c resolve the situation of these eventually
1147 @cindex @code{--tui}
1148 Activate the @dfn{Text User Interface} when starting. The Text User
1149 Interface manages several text windows on the terminal, showing
1150 source, assembly, registers and @value{GDBN} command outputs
1151 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1152 Text User Interface can be enabled by invoking the program
1153 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1154 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1157 @c @cindex @code{--xdb}
1158 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1159 @c For information, see the file @file{xdb_trans.html}, which is usually
1160 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1163 @item -interpreter @var{interp}
1164 @cindex @code{--interpreter}
1165 Use the interpreter @var{interp} for interface with the controlling
1166 program or device. This option is meant to be set by programs which
1167 communicate with @value{GDBN} using it as a back end.
1168 @xref{Interpreters, , Command Interpreters}.
1170 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1171 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1172 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1173 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1174 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1175 @sc{gdb/mi} interfaces are no longer supported.
1178 @cindex @code{--write}
1179 Open the executable and core files for both reading and writing. This
1180 is equivalent to the @samp{set write on} command inside @value{GDBN}
1184 @cindex @code{--statistics}
1185 This option causes @value{GDBN} to print statistics about time and
1186 memory usage after it completes each command and returns to the prompt.
1189 @cindex @code{--version}
1190 This option causes @value{GDBN} to print its version number and
1191 no-warranty blurb, and exit.
1196 @subsection What @value{GDBN} Does During Startup
1197 @cindex @value{GDBN} startup
1199 Here's the description of what @value{GDBN} does during session startup:
1203 Sets up the command interpreter as specified by the command line
1204 (@pxref{Mode Options, interpreter}).
1208 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1209 DOS/Windows systems, the home directory is the one pointed to by the
1210 @code{HOME} environment variable.} and executes all the commands in
1214 Processes command line options and operands.
1217 Reads and executes the commands from init file (if any) in the current
1218 working directory. This is only done if the current directory is
1219 different from your home directory. Thus, you can have more than one
1220 init file, one generic in your home directory, and another, specific
1221 to the program you are debugging, in the directory where you invoke
1225 Reads command files specified by the @samp{-x} option. @xref{Command
1226 Files}, for more details about @value{GDBN} command files.
1229 Reads the command history recorded in the @dfn{history file}.
1230 @xref{Command History}, for more details about the command history and the
1231 files where @value{GDBN} records it.
1234 Init files use the same syntax as @dfn{command files} (@pxref{Command
1235 Files}) and are processed by @value{GDBN} in the same way. The init
1236 file in your home directory can set options (such as @samp{set
1237 complaints}) that affect subsequent processing of command line options
1238 and operands. Init files are not executed if you use the @samp{-nx}
1239 option (@pxref{Mode Options, ,Choosing Modes}).
1241 @cindex init file name
1242 @cindex @file{.gdbinit}
1243 @cindex @file{gdb.ini}
1244 The @value{GDBN} init files are normally called @file{.gdbinit}.
1245 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1246 the limitations of file names imposed by DOS filesystems. The Windows
1247 ports of @value{GDBN} use the standard name, but if they find a
1248 @file{gdb.ini} file, they warn you about that and suggest to rename
1249 the file to the standard name.
1253 @section Quitting @value{GDBN}
1254 @cindex exiting @value{GDBN}
1255 @cindex leaving @value{GDBN}
1258 @kindex quit @r{[}@var{expression}@r{]}
1259 @kindex q @r{(@code{quit})}
1260 @item quit @r{[}@var{expression}@r{]}
1262 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1263 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1264 do not supply @var{expression}, @value{GDBN} will terminate normally;
1265 otherwise it will terminate using the result of @var{expression} as the
1270 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1271 terminates the action of any @value{GDBN} command that is in progress and
1272 returns to @value{GDBN} command level. It is safe to type the interrupt
1273 character at any time because @value{GDBN} does not allow it to take effect
1274 until a time when it is safe.
1276 If you have been using @value{GDBN} to control an attached process or
1277 device, you can release it with the @code{detach} command
1278 (@pxref{Attach, ,Debugging an Already-running Process}).
1280 @node Shell Commands
1281 @section Shell Commands
1283 If you need to execute occasional shell commands during your
1284 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1285 just use the @code{shell} command.
1289 @cindex shell escape
1290 @item shell @var{command string}
1291 Invoke a standard shell to execute @var{command string}.
1292 If it exists, the environment variable @code{SHELL} determines which
1293 shell to run. Otherwise @value{GDBN} uses the default shell
1294 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1297 The utility @code{make} is often needed in development environments.
1298 You do not have to use the @code{shell} command for this purpose in
1303 @cindex calling make
1304 @item make @var{make-args}
1305 Execute the @code{make} program with the specified
1306 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1309 @node Logging Output
1310 @section Logging Output
1311 @cindex logging @value{GDBN} output
1312 @cindex save @value{GDBN} output to a file
1314 You may want to save the output of @value{GDBN} commands to a file.
1315 There are several commands to control @value{GDBN}'s logging.
1319 @item set logging on
1321 @item set logging off
1323 @cindex logging file name
1324 @item set logging file @var{file}
1325 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1326 @item set logging overwrite [on|off]
1327 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1328 you want @code{set logging on} to overwrite the logfile instead.
1329 @item set logging redirect [on|off]
1330 By default, @value{GDBN} output will go to both the terminal and the logfile.
1331 Set @code{redirect} if you want output to go only to the log file.
1332 @kindex show logging
1334 Show the current values of the logging settings.
1338 @chapter @value{GDBN} Commands
1340 You can abbreviate a @value{GDBN} command to the first few letters of the command
1341 name, if that abbreviation is unambiguous; and you can repeat certain
1342 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1343 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1344 show you the alternatives available, if there is more than one possibility).
1347 * Command Syntax:: How to give commands to @value{GDBN}
1348 * Completion:: Command completion
1349 * Help:: How to ask @value{GDBN} for help
1352 @node Command Syntax
1353 @section Command Syntax
1355 A @value{GDBN} command is a single line of input. There is no limit on
1356 how long it can be. It starts with a command name, which is followed by
1357 arguments whose meaning depends on the command name. For example, the
1358 command @code{step} accepts an argument which is the number of times to
1359 step, as in @samp{step 5}. You can also use the @code{step} command
1360 with no arguments. Some commands do not allow any arguments.
1362 @cindex abbreviation
1363 @value{GDBN} command names may always be truncated if that abbreviation is
1364 unambiguous. Other possible command abbreviations are listed in the
1365 documentation for individual commands. In some cases, even ambiguous
1366 abbreviations are allowed; for example, @code{s} is specially defined as
1367 equivalent to @code{step} even though there are other commands whose
1368 names start with @code{s}. You can test abbreviations by using them as
1369 arguments to the @code{help} command.
1371 @cindex repeating commands
1372 @kindex RET @r{(repeat last command)}
1373 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1374 repeat the previous command. Certain commands (for example, @code{run})
1375 will not repeat this way; these are commands whose unintentional
1376 repetition might cause trouble and which you are unlikely to want to
1377 repeat. User-defined commands can disable this feature; see
1378 @ref{Define, dont-repeat}.
1380 The @code{list} and @code{x} commands, when you repeat them with
1381 @key{RET}, construct new arguments rather than repeating
1382 exactly as typed. This permits easy scanning of source or memory.
1384 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1385 output, in a way similar to the common utility @code{more}
1386 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1387 @key{RET} too many in this situation, @value{GDBN} disables command
1388 repetition after any command that generates this sort of display.
1390 @kindex # @r{(a comment)}
1392 Any text from a @kbd{#} to the end of the line is a comment; it does
1393 nothing. This is useful mainly in command files (@pxref{Command
1394 Files,,Command Files}).
1396 @cindex repeating command sequences
1397 @kindex Ctrl-o @r{(operate-and-get-next)}
1398 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1399 commands. This command accepts the current line, like @key{RET}, and
1400 then fetches the next line relative to the current line from the history
1404 @section Command Completion
1407 @cindex word completion
1408 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1409 only one possibility; it can also show you what the valid possibilities
1410 are for the next word in a command, at any time. This works for @value{GDBN}
1411 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1413 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1414 of a word. If there is only one possibility, @value{GDBN} fills in the
1415 word, and waits for you to finish the command (or press @key{RET} to
1416 enter it). For example, if you type
1418 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1419 @c complete accuracy in these examples; space introduced for clarity.
1420 @c If texinfo enhancements make it unnecessary, it would be nice to
1421 @c replace " @key" by "@key" in the following...
1423 (@value{GDBP}) info bre @key{TAB}
1427 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1428 the only @code{info} subcommand beginning with @samp{bre}:
1431 (@value{GDBP}) info breakpoints
1435 You can either press @key{RET} at this point, to run the @code{info
1436 breakpoints} command, or backspace and enter something else, if
1437 @samp{breakpoints} does not look like the command you expected. (If you
1438 were sure you wanted @code{info breakpoints} in the first place, you
1439 might as well just type @key{RET} immediately after @samp{info bre},
1440 to exploit command abbreviations rather than command completion).
1442 If there is more than one possibility for the next word when you press
1443 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1444 characters and try again, or just press @key{TAB} a second time;
1445 @value{GDBN} displays all the possible completions for that word. For
1446 example, you might want to set a breakpoint on a subroutine whose name
1447 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1448 just sounds the bell. Typing @key{TAB} again displays all the
1449 function names in your program that begin with those characters, for
1453 (@value{GDBP}) b make_ @key{TAB}
1454 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1455 make_a_section_from_file make_environ
1456 make_abs_section make_function_type
1457 make_blockvector make_pointer_type
1458 make_cleanup make_reference_type
1459 make_command make_symbol_completion_list
1460 (@value{GDBP}) b make_
1464 After displaying the available possibilities, @value{GDBN} copies your
1465 partial input (@samp{b make_} in the example) so you can finish the
1468 If you just want to see the list of alternatives in the first place, you
1469 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1470 means @kbd{@key{META} ?}. You can type this either by holding down a
1471 key designated as the @key{META} shift on your keyboard (if there is
1472 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1474 @cindex quotes in commands
1475 @cindex completion of quoted strings
1476 Sometimes the string you need, while logically a ``word'', may contain
1477 parentheses or other characters that @value{GDBN} normally excludes from
1478 its notion of a word. To permit word completion to work in this
1479 situation, you may enclose words in @code{'} (single quote marks) in
1480 @value{GDBN} commands.
1482 The most likely situation where you might need this is in typing the
1483 name of a C@t{++} function. This is because C@t{++} allows function
1484 overloading (multiple definitions of the same function, distinguished
1485 by argument type). For example, when you want to set a breakpoint you
1486 may need to distinguish whether you mean the version of @code{name}
1487 that takes an @code{int} parameter, @code{name(int)}, or the version
1488 that takes a @code{float} parameter, @code{name(float)}. To use the
1489 word-completion facilities in this situation, type a single quote
1490 @code{'} at the beginning of the function name. This alerts
1491 @value{GDBN} that it may need to consider more information than usual
1492 when you press @key{TAB} or @kbd{M-?} to request word completion:
1495 (@value{GDBP}) b 'bubble( @kbd{M-?}
1496 bubble(double,double) bubble(int,int)
1497 (@value{GDBP}) b 'bubble(
1500 In some cases, @value{GDBN} can tell that completing a name requires using
1501 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1502 completing as much as it can) if you do not type the quote in the first
1506 (@value{GDBP}) b bub @key{TAB}
1507 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1508 (@value{GDBP}) b 'bubble(
1512 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1513 you have not yet started typing the argument list when you ask for
1514 completion on an overloaded symbol.
1516 For more information about overloaded functions, see @ref{C Plus Plus
1517 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1518 overload-resolution off} to disable overload resolution;
1519 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1523 @section Getting Help
1524 @cindex online documentation
1527 You can always ask @value{GDBN} itself for information on its commands,
1528 using the command @code{help}.
1531 @kindex h @r{(@code{help})}
1534 You can use @code{help} (abbreviated @code{h}) with no arguments to
1535 display a short list of named classes of commands:
1539 List of classes of commands:
1541 aliases -- Aliases of other commands
1542 breakpoints -- Making program stop at certain points
1543 data -- Examining data
1544 files -- Specifying and examining files
1545 internals -- Maintenance commands
1546 obscure -- Obscure features
1547 running -- Running the program
1548 stack -- Examining the stack
1549 status -- Status inquiries
1550 support -- Support facilities
1551 tracepoints -- Tracing of program execution without
1552 stopping the program
1553 user-defined -- User-defined commands
1555 Type "help" followed by a class name for a list of
1556 commands in that class.
1557 Type "help" followed by command name for full
1559 Command name abbreviations are allowed if unambiguous.
1562 @c the above line break eliminates huge line overfull...
1564 @item help @var{class}
1565 Using one of the general help classes as an argument, you can get a
1566 list of the individual commands in that class. For example, here is the
1567 help display for the class @code{status}:
1570 (@value{GDBP}) help status
1575 @c Line break in "show" line falsifies real output, but needed
1576 @c to fit in smallbook page size.
1577 info -- Generic command for showing things
1578 about the program being debugged
1579 show -- Generic command for showing things
1582 Type "help" followed by command name for full
1584 Command name abbreviations are allowed if unambiguous.
1588 @item help @var{command}
1589 With a command name as @code{help} argument, @value{GDBN} displays a
1590 short paragraph on how to use that command.
1593 @item apropos @var{args}
1594 The @code{apropos} command searches through all of the @value{GDBN}
1595 commands, and their documentation, for the regular expression specified in
1596 @var{args}. It prints out all matches found. For example:
1607 set symbol-reloading -- Set dynamic symbol table reloading
1608 multiple times in one run
1609 show symbol-reloading -- Show dynamic symbol table reloading
1610 multiple times in one run
1615 @item complete @var{args}
1616 The @code{complete @var{args}} command lists all the possible completions
1617 for the beginning of a command. Use @var{args} to specify the beginning of the
1618 command you want completed. For example:
1624 @noindent results in:
1635 @noindent This is intended for use by @sc{gnu} Emacs.
1638 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1639 and @code{show} to inquire about the state of your program, or the state
1640 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1641 manual introduces each of them in the appropriate context. The listings
1642 under @code{info} and under @code{show} in the Index point to
1643 all the sub-commands. @xref{Index}.
1648 @kindex i @r{(@code{info})}
1650 This command (abbreviated @code{i}) is for describing the state of your
1651 program. For example, you can list the arguments given to your program
1652 with @code{info args}, list the registers currently in use with @code{info
1653 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1654 You can get a complete list of the @code{info} sub-commands with
1655 @w{@code{help info}}.
1659 You can assign the result of an expression to an environment variable with
1660 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1661 @code{set prompt $}.
1665 In contrast to @code{info}, @code{show} is for describing the state of
1666 @value{GDBN} itself.
1667 You can change most of the things you can @code{show}, by using the
1668 related command @code{set}; for example, you can control what number
1669 system is used for displays with @code{set radix}, or simply inquire
1670 which is currently in use with @code{show radix}.
1673 To display all the settable parameters and their current
1674 values, you can use @code{show} with no arguments; you may also use
1675 @code{info set}. Both commands produce the same display.
1676 @c FIXME: "info set" violates the rule that "info" is for state of
1677 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1678 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1682 Here are three miscellaneous @code{show} subcommands, all of which are
1683 exceptional in lacking corresponding @code{set} commands:
1686 @kindex show version
1687 @cindex @value{GDBN} version number
1689 Show what version of @value{GDBN} is running. You should include this
1690 information in @value{GDBN} bug-reports. If multiple versions of
1691 @value{GDBN} are in use at your site, you may need to determine which
1692 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1693 commands are introduced, and old ones may wither away. Also, many
1694 system vendors ship variant versions of @value{GDBN}, and there are
1695 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1696 The version number is the same as the one announced when you start
1699 @kindex show copying
1700 @kindex info copying
1701 @cindex display @value{GDBN} copyright
1704 Display information about permission for copying @value{GDBN}.
1706 @kindex show warranty
1707 @kindex info warranty
1709 @itemx info warranty
1710 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1711 if your version of @value{GDBN} comes with one.
1716 @chapter Running Programs Under @value{GDBN}
1718 When you run a program under @value{GDBN}, you must first generate
1719 debugging information when you compile it.
1721 You may start @value{GDBN} with its arguments, if any, in an environment
1722 of your choice. If you are doing native debugging, you may redirect
1723 your program's input and output, debug an already running process, or
1724 kill a child process.
1727 * Compilation:: Compiling for debugging
1728 * Starting:: Starting your program
1729 * Arguments:: Your program's arguments
1730 * Environment:: Your program's environment
1732 * Working Directory:: Your program's working directory
1733 * Input/Output:: Your program's input and output
1734 * Attach:: Debugging an already-running process
1735 * Kill Process:: Killing the child process
1737 * Threads:: Debugging programs with multiple threads
1738 * Processes:: Debugging programs with multiple processes
1739 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1743 @section Compiling for Debugging
1745 In order to debug a program effectively, you need to generate
1746 debugging information when you compile it. This debugging information
1747 is stored in the object file; it describes the data type of each
1748 variable or function and the correspondence between source line numbers
1749 and addresses in the executable code.
1751 To request debugging information, specify the @samp{-g} option when you run
1754 Programs that are to be shipped to your customers are compiled with
1755 optimizations, using the @samp{-O} compiler option. However, many
1756 compilers are unable to handle the @samp{-g} and @samp{-O} options
1757 together. Using those compilers, you cannot generate optimized
1758 executables containing debugging information.
1760 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1761 without @samp{-O}, making it possible to debug optimized code. We
1762 recommend that you @emph{always} use @samp{-g} whenever you compile a
1763 program. You may think your program is correct, but there is no sense
1764 in pushing your luck.
1766 @cindex optimized code, debugging
1767 @cindex debugging optimized code
1768 When you debug a program compiled with @samp{-g -O}, remember that the
1769 optimizer is rearranging your code; the debugger shows you what is
1770 really there. Do not be too surprised when the execution path does not
1771 exactly match your source file! An extreme example: if you define a
1772 variable, but never use it, @value{GDBN} never sees that
1773 variable---because the compiler optimizes it out of existence.
1775 Some things do not work as well with @samp{-g -O} as with just
1776 @samp{-g}, particularly on machines with instruction scheduling. If in
1777 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1778 please report it to us as a bug (including a test case!).
1779 @xref{Variables}, for more information about debugging optimized code.
1781 Older versions of the @sc{gnu} C compiler permitted a variant option
1782 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1783 format; if your @sc{gnu} C compiler has this option, do not use it.
1785 @value{GDBN} knows about preprocessor macros and can show you their
1786 expansion (@pxref{Macros}). Most compilers do not include information
1787 about preprocessor macros in the debugging information if you specify
1788 the @option{-g} flag alone, because this information is rather large.
1789 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1790 provides macro information if you specify the options
1791 @option{-gdwarf-2} and @option{-g3}; the former option requests
1792 debugging information in the Dwarf 2 format, and the latter requests
1793 ``extra information''. In the future, we hope to find more compact
1794 ways to represent macro information, so that it can be included with
1799 @section Starting your Program
1805 @kindex r @r{(@code{run})}
1808 Use the @code{run} command to start your program under @value{GDBN}.
1809 You must first specify the program name (except on VxWorks) with an
1810 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1811 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1812 (@pxref{Files, ,Commands to Specify Files}).
1816 If you are running your program in an execution environment that
1817 supports processes, @code{run} creates an inferior process and makes
1818 that process run your program. (In environments without processes,
1819 @code{run} jumps to the start of your program.)
1821 The execution of a program is affected by certain information it
1822 receives from its superior. @value{GDBN} provides ways to specify this
1823 information, which you must do @emph{before} starting your program. (You
1824 can change it after starting your program, but such changes only affect
1825 your program the next time you start it.) This information may be
1826 divided into four categories:
1829 @item The @emph{arguments.}
1830 Specify the arguments to give your program as the arguments of the
1831 @code{run} command. If a shell is available on your target, the shell
1832 is used to pass the arguments, so that you may use normal conventions
1833 (such as wildcard expansion or variable substitution) in describing
1835 In Unix systems, you can control which shell is used with the
1836 @code{SHELL} environment variable.
1837 @xref{Arguments, ,Your Program's Arguments}.
1839 @item The @emph{environment.}
1840 Your program normally inherits its environment from @value{GDBN}, but you can
1841 use the @value{GDBN} commands @code{set environment} and @code{unset
1842 environment} to change parts of the environment that affect
1843 your program. @xref{Environment, ,Your Program's Environment}.
1845 @item The @emph{working directory.}
1846 Your program inherits its working directory from @value{GDBN}. You can set
1847 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1848 @xref{Working Directory, ,Your Program's Working Directory}.
1850 @item The @emph{standard input and output.}
1851 Your program normally uses the same device for standard input and
1852 standard output as @value{GDBN} is using. You can redirect input and output
1853 in the @code{run} command line, or you can use the @code{tty} command to
1854 set a different device for your program.
1855 @xref{Input/Output, ,Your Program's Input and Output}.
1858 @emph{Warning:} While input and output redirection work, you cannot use
1859 pipes to pass the output of the program you are debugging to another
1860 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1864 When you issue the @code{run} command, your program begins to execute
1865 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1866 of how to arrange for your program to stop. Once your program has
1867 stopped, you may call functions in your program, using the @code{print}
1868 or @code{call} commands. @xref{Data, ,Examining Data}.
1870 If the modification time of your symbol file has changed since the last
1871 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1872 table, and reads it again. When it does this, @value{GDBN} tries to retain
1873 your current breakpoints.
1878 @cindex run to main procedure
1879 The name of the main procedure can vary from language to language.
1880 With C or C@t{++}, the main procedure name is always @code{main}, but
1881 other languages such as Ada do not require a specific name for their
1882 main procedure. The debugger provides a convenient way to start the
1883 execution of the program and to stop at the beginning of the main
1884 procedure, depending on the language used.
1886 The @samp{start} command does the equivalent of setting a temporary
1887 breakpoint at the beginning of the main procedure and then invoking
1888 the @samp{run} command.
1890 @cindex elaboration phase
1891 Some programs contain an @dfn{elaboration} phase where some startup code is
1892 executed before the main procedure is called. This depends on the
1893 languages used to write your program. In C@t{++}, for instance,
1894 constructors for static and global objects are executed before
1895 @code{main} is called. It is therefore possible that the debugger stops
1896 before reaching the main procedure. However, the temporary breakpoint
1897 will remain to halt execution.
1899 Specify the arguments to give to your program as arguments to the
1900 @samp{start} command. These arguments will be given verbatim to the
1901 underlying @samp{run} command. Note that the same arguments will be
1902 reused if no argument is provided during subsequent calls to
1903 @samp{start} or @samp{run}.
1905 It is sometimes necessary to debug the program during elaboration. In
1906 these cases, using the @code{start} command would stop the execution of
1907 your program too late, as the program would have already completed the
1908 elaboration phase. Under these circumstances, insert breakpoints in your
1909 elaboration code before running your program.
1913 @section Your Program's Arguments
1915 @cindex arguments (to your program)
1916 The arguments to your program can be specified by the arguments of the
1918 They are passed to a shell, which expands wildcard characters and
1919 performs redirection of I/O, and thence to your program. Your
1920 @code{SHELL} environment variable (if it exists) specifies what shell
1921 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1922 the default shell (@file{/bin/sh} on Unix).
1924 On non-Unix systems, the program is usually invoked directly by
1925 @value{GDBN}, which emulates I/O redirection via the appropriate system
1926 calls, and the wildcard characters are expanded by the startup code of
1927 the program, not by the shell.
1929 @code{run} with no arguments uses the same arguments used by the previous
1930 @code{run}, or those set by the @code{set args} command.
1935 Specify the arguments to be used the next time your program is run. If
1936 @code{set args} has no arguments, @code{run} executes your program
1937 with no arguments. Once you have run your program with arguments,
1938 using @code{set args} before the next @code{run} is the only way to run
1939 it again without arguments.
1943 Show the arguments to give your program when it is started.
1947 @section Your Program's Environment
1949 @cindex environment (of your program)
1950 The @dfn{environment} consists of a set of environment variables and
1951 their values. Environment variables conventionally record such things as
1952 your user name, your home directory, your terminal type, and your search
1953 path for programs to run. Usually you set up environment variables with
1954 the shell and they are inherited by all the other programs you run. When
1955 debugging, it can be useful to try running your program with a modified
1956 environment without having to start @value{GDBN} over again.
1960 @item path @var{directory}
1961 Add @var{directory} to the front of the @code{PATH} environment variable
1962 (the search path for executables) that will be passed to your program.
1963 The value of @code{PATH} used by @value{GDBN} does not change.
1964 You may specify several directory names, separated by whitespace or by a
1965 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1966 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1967 is moved to the front, so it is searched sooner.
1969 You can use the string @samp{$cwd} to refer to whatever is the current
1970 working directory at the time @value{GDBN} searches the path. If you
1971 use @samp{.} instead, it refers to the directory where you executed the
1972 @code{path} command. @value{GDBN} replaces @samp{.} in the
1973 @var{directory} argument (with the current path) before adding
1974 @var{directory} to the search path.
1975 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1976 @c document that, since repeating it would be a no-op.
1980 Display the list of search paths for executables (the @code{PATH}
1981 environment variable).
1983 @kindex show environment
1984 @item show environment @r{[}@var{varname}@r{]}
1985 Print the value of environment variable @var{varname} to be given to
1986 your program when it starts. If you do not supply @var{varname},
1987 print the names and values of all environment variables to be given to
1988 your program. You can abbreviate @code{environment} as @code{env}.
1990 @kindex set environment
1991 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1992 Set environment variable @var{varname} to @var{value}. The value
1993 changes for your program only, not for @value{GDBN} itself. @var{value} may
1994 be any string; the values of environment variables are just strings, and
1995 any interpretation is supplied by your program itself. The @var{value}
1996 parameter is optional; if it is eliminated, the variable is set to a
1998 @c "any string" here does not include leading, trailing
1999 @c blanks. Gnu asks: does anyone care?
2001 For example, this command:
2008 tells the debugged program, when subsequently run, that its user is named
2009 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2010 are not actually required.)
2012 @kindex unset environment
2013 @item unset environment @var{varname}
2014 Remove variable @var{varname} from the environment to be passed to your
2015 program. This is different from @samp{set env @var{varname} =};
2016 @code{unset environment} removes the variable from the environment,
2017 rather than assigning it an empty value.
2020 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2022 by your @code{SHELL} environment variable if it exists (or
2023 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2024 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2025 @file{.bashrc} for BASH---any variables you set in that file affect
2026 your program. You may wish to move setting of environment variables to
2027 files that are only run when you sign on, such as @file{.login} or
2030 @node Working Directory
2031 @section Your Program's Working Directory
2033 @cindex working directory (of your program)
2034 Each time you start your program with @code{run}, it inherits its
2035 working directory from the current working directory of @value{GDBN}.
2036 The @value{GDBN} working directory is initially whatever it inherited
2037 from its parent process (typically the shell), but you can specify a new
2038 working directory in @value{GDBN} with the @code{cd} command.
2040 The @value{GDBN} working directory also serves as a default for the commands
2041 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2046 @cindex change working directory
2047 @item cd @var{directory}
2048 Set the @value{GDBN} working directory to @var{directory}.
2052 Print the @value{GDBN} working directory.
2055 It is generally impossible to find the current working directory of
2056 the process being debugged (since a program can change its directory
2057 during its run). If you work on a system where @value{GDBN} is
2058 configured with the @file{/proc} support, you can use the @code{info
2059 proc} command (@pxref{SVR4 Process Information}) to find out the
2060 current working directory of the debuggee.
2063 @section Your Program's Input and Output
2068 By default, the program you run under @value{GDBN} does input and output to
2069 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2070 to its own terminal modes to interact with you, but it records the terminal
2071 modes your program was using and switches back to them when you continue
2072 running your program.
2075 @kindex info terminal
2077 Displays information recorded by @value{GDBN} about the terminal modes your
2081 You can redirect your program's input and/or output using shell
2082 redirection with the @code{run} command. For example,
2089 starts your program, diverting its output to the file @file{outfile}.
2092 @cindex controlling terminal
2093 Another way to specify where your program should do input and output is
2094 with the @code{tty} command. This command accepts a file name as
2095 argument, and causes this file to be the default for future @code{run}
2096 commands. It also resets the controlling terminal for the child
2097 process, for future @code{run} commands. For example,
2104 directs that processes started with subsequent @code{run} commands
2105 default to do input and output on the terminal @file{/dev/ttyb} and have
2106 that as their controlling terminal.
2108 An explicit redirection in @code{run} overrides the @code{tty} command's
2109 effect on the input/output device, but not its effect on the controlling
2112 When you use the @code{tty} command or redirect input in the @code{run}
2113 command, only the input @emph{for your program} is affected. The input
2114 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2115 for @code{set inferior-tty}.
2117 @cindex inferior tty
2118 @cindex set inferior controlling terminal
2119 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2120 display the name of the terminal that will be used for future runs of your
2124 @item set inferior-tty /dev/ttyb
2125 @kindex set inferior-tty
2126 Set the tty for the program being debugged to /dev/ttyb.
2128 @item show inferior-tty
2129 @kindex show inferior-tty
2130 Show the current tty for the program being debugged.
2134 @section Debugging an Already-running Process
2139 @item attach @var{process-id}
2140 This command attaches to a running process---one that was started
2141 outside @value{GDBN}. (@code{info files} shows your active
2142 targets.) The command takes as argument a process ID. The usual way to
2143 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2144 or with the @samp{jobs -l} shell command.
2146 @code{attach} does not repeat if you press @key{RET} a second time after
2147 executing the command.
2150 To use @code{attach}, your program must be running in an environment
2151 which supports processes; for example, @code{attach} does not work for
2152 programs on bare-board targets that lack an operating system. You must
2153 also have permission to send the process a signal.
2155 When you use @code{attach}, the debugger finds the program running in
2156 the process first by looking in the current working directory, then (if
2157 the program is not found) by using the source file search path
2158 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2159 the @code{file} command to load the program. @xref{Files, ,Commands to
2162 The first thing @value{GDBN} does after arranging to debug the specified
2163 process is to stop it. You can examine and modify an attached process
2164 with all the @value{GDBN} commands that are ordinarily available when
2165 you start processes with @code{run}. You can insert breakpoints; you
2166 can step and continue; you can modify storage. If you would rather the
2167 process continue running, you may use the @code{continue} command after
2168 attaching @value{GDBN} to the process.
2173 When you have finished debugging the attached process, you can use the
2174 @code{detach} command to release it from @value{GDBN} control. Detaching
2175 the process continues its execution. After the @code{detach} command,
2176 that process and @value{GDBN} become completely independent once more, and you
2177 are ready to @code{attach} another process or start one with @code{run}.
2178 @code{detach} does not repeat if you press @key{RET} again after
2179 executing the command.
2182 If you exit @value{GDBN} or use the @code{run} command while you have an
2183 attached process, you kill that process. By default, @value{GDBN} asks
2184 for confirmation if you try to do either of these things; you can
2185 control whether or not you need to confirm by using the @code{set
2186 confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2190 @section Killing the Child Process
2195 Kill the child process in which your program is running under @value{GDBN}.
2198 This command is useful if you wish to debug a core dump instead of a
2199 running process. @value{GDBN} ignores any core dump file while your program
2202 On some operating systems, a program cannot be executed outside @value{GDBN}
2203 while you have breakpoints set on it inside @value{GDBN}. You can use the
2204 @code{kill} command in this situation to permit running your program
2205 outside the debugger.
2207 The @code{kill} command is also useful if you wish to recompile and
2208 relink your program, since on many systems it is impossible to modify an
2209 executable file while it is running in a process. In this case, when you
2210 next type @code{run}, @value{GDBN} notices that the file has changed, and
2211 reads the symbol table again (while trying to preserve your current
2212 breakpoint settings).
2215 @section Debugging Programs with Multiple Threads
2217 @cindex threads of execution
2218 @cindex multiple threads
2219 @cindex switching threads
2220 In some operating systems, such as HP-UX and Solaris, a single program
2221 may have more than one @dfn{thread} of execution. The precise semantics
2222 of threads differ from one operating system to another, but in general
2223 the threads of a single program are akin to multiple processes---except
2224 that they share one address space (that is, they can all examine and
2225 modify the same variables). On the other hand, each thread has its own
2226 registers and execution stack, and perhaps private memory.
2228 @value{GDBN} provides these facilities for debugging multi-thread
2232 @item automatic notification of new threads
2233 @item @samp{thread @var{threadno}}, a command to switch among threads
2234 @item @samp{info threads}, a command to inquire about existing threads
2235 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2236 a command to apply a command to a list of threads
2237 @item thread-specific breakpoints
2241 @emph{Warning:} These facilities are not yet available on every
2242 @value{GDBN} configuration where the operating system supports threads.
2243 If your @value{GDBN} does not support threads, these commands have no
2244 effect. For example, a system without thread support shows no output
2245 from @samp{info threads}, and always rejects the @code{thread} command,
2249 (@value{GDBP}) info threads
2250 (@value{GDBP}) thread 1
2251 Thread ID 1 not known. Use the "info threads" command to
2252 see the IDs of currently known threads.
2254 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2255 @c doesn't support threads"?
2258 @cindex focus of debugging
2259 @cindex current thread
2260 The @value{GDBN} thread debugging facility allows you to observe all
2261 threads while your program runs---but whenever @value{GDBN} takes
2262 control, one thread in particular is always the focus of debugging.
2263 This thread is called the @dfn{current thread}. Debugging commands show
2264 program information from the perspective of the current thread.
2266 @cindex @code{New} @var{systag} message
2267 @cindex thread identifier (system)
2268 @c FIXME-implementors!! It would be more helpful if the [New...] message
2269 @c included GDB's numeric thread handle, so you could just go to that
2270 @c thread without first checking `info threads'.
2271 Whenever @value{GDBN} detects a new thread in your program, it displays
2272 the target system's identification for the thread with a message in the
2273 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2274 whose form varies depending on the particular system. For example, on
2275 @sc{gnu}/Linux, you might see
2278 [New Thread 46912507313328 (LWP 25582)]
2282 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2283 the @var{systag} is simply something like @samp{process 368}, with no
2286 @c FIXME!! (1) Does the [New...] message appear even for the very first
2287 @c thread of a program, or does it only appear for the
2288 @c second---i.e.@: when it becomes obvious we have a multithread
2290 @c (2) *Is* there necessarily a first thread always? Or do some
2291 @c multithread systems permit starting a program with multiple
2292 @c threads ab initio?
2294 @cindex thread number
2295 @cindex thread identifier (GDB)
2296 For debugging purposes, @value{GDBN} associates its own thread
2297 number---always a single integer---with each thread in your program.
2300 @kindex info threads
2302 Display a summary of all threads currently in your
2303 program. @value{GDBN} displays for each thread (in this order):
2307 the thread number assigned by @value{GDBN}
2310 the target system's thread identifier (@var{systag})
2313 the current stack frame summary for that thread
2317 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2318 indicates the current thread.
2322 @c end table here to get a little more width for example
2325 (@value{GDBP}) info threads
2326 3 process 35 thread 27 0x34e5 in sigpause ()
2327 2 process 35 thread 23 0x34e5 in sigpause ()
2328 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2334 @cindex debugging multithreaded programs (on HP-UX)
2335 @cindex thread identifier (GDB), on HP-UX
2336 For debugging purposes, @value{GDBN} associates its own thread
2337 number---a small integer assigned in thread-creation order---with each
2338 thread in your program.
2340 @cindex @code{New} @var{systag} message, on HP-UX
2341 @cindex thread identifier (system), on HP-UX
2342 @c FIXME-implementors!! It would be more helpful if the [New...] message
2343 @c included GDB's numeric thread handle, so you could just go to that
2344 @c thread without first checking `info threads'.
2345 Whenever @value{GDBN} detects a new thread in your program, it displays
2346 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2347 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2348 whose form varies depending on the particular system. For example, on
2352 [New thread 2 (system thread 26594)]
2356 when @value{GDBN} notices a new thread.
2359 @kindex info threads (HP-UX)
2361 Display a summary of all threads currently in your
2362 program. @value{GDBN} displays for each thread (in this order):
2365 @item the thread number assigned by @value{GDBN}
2367 @item the target system's thread identifier (@var{systag})
2369 @item 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 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2384 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2385 from /usr/lib/libc.2
2386 1 system thread 27905 0x7b003498 in _brk () \@*
2387 from /usr/lib/libc.2
2390 On Solaris, you can display more information about user threads with a
2391 Solaris-specific command:
2394 @item maint info sol-threads
2395 @kindex maint info sol-threads
2396 @cindex thread info (Solaris)
2397 Display info on Solaris user threads.
2401 @kindex thread @var{threadno}
2402 @item thread @var{threadno}
2403 Make thread number @var{threadno} the current thread. The command
2404 argument @var{threadno} is the internal @value{GDBN} thread number, as
2405 shown in the first field of the @samp{info threads} display.
2406 @value{GDBN} responds by displaying the system identifier of the thread
2407 you selected, and its current stack frame summary:
2410 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2411 (@value{GDBP}) thread 2
2412 [Switching to process 35 thread 23]
2413 0x34e5 in sigpause ()
2417 As with the @samp{[New @dots{}]} message, the form of the text after
2418 @samp{Switching to} depends on your system's conventions for identifying
2421 @kindex thread apply
2422 @cindex apply command to several threads
2423 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2424 The @code{thread apply} command allows you to apply the named
2425 @var{command} to one or more threads. Specify the numbers of the
2426 threads that you want affected with the command argument
2427 @var{threadno}. It can be a single thread number, one of the numbers
2428 shown in the first field of the @samp{info threads} display; or it
2429 could be a range of thread numbers, as in @code{2-4}. To apply a
2430 command to all threads, type @kbd{thread apply all @var{command}}.
2433 @cindex automatic thread selection
2434 @cindex switching threads automatically
2435 @cindex threads, automatic switching
2436 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2437 signal, it automatically selects the thread where that breakpoint or
2438 signal happened. @value{GDBN} alerts you to the context switch with a
2439 message of the form @samp{[Switching to @var{systag}]} to identify the
2442 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2443 more information about how @value{GDBN} behaves when you stop and start
2444 programs with multiple threads.
2446 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2447 watchpoints in programs with multiple threads.
2450 @section Debugging Programs with Multiple Processes
2452 @cindex fork, debugging programs which call
2453 @cindex multiple processes
2454 @cindex processes, multiple
2455 On most systems, @value{GDBN} has no special support for debugging
2456 programs which create additional processes using the @code{fork}
2457 function. When a program forks, @value{GDBN} will continue to debug the
2458 parent process and the child process will run unimpeded. If you have
2459 set a breakpoint in any code which the child then executes, the child
2460 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2461 will cause it to terminate.
2463 However, if you want to debug the child process there is a workaround
2464 which isn't too painful. Put a call to @code{sleep} in the code which
2465 the child process executes after the fork. It may be useful to sleep
2466 only if a certain environment variable is set, or a certain file exists,
2467 so that the delay need not occur when you don't want to run @value{GDBN}
2468 on the child. While the child is sleeping, use the @code{ps} program to
2469 get its process ID. Then tell @value{GDBN} (a new invocation of
2470 @value{GDBN} if you are also debugging the parent process) to attach to
2471 the child process (@pxref{Attach}). From that point on you can debug
2472 the child process just like any other process which you attached to.
2474 On some systems, @value{GDBN} provides support for debugging programs that
2475 create additional processes using the @code{fork} or @code{vfork} functions.
2476 Currently, the only platforms with this feature are HP-UX (11.x and later
2477 only?) and GNU/Linux (kernel version 2.5.60 and later).
2479 By default, when a program forks, @value{GDBN} will continue to debug
2480 the parent process and the child process will run unimpeded.
2482 If you want to follow the child process instead of the parent process,
2483 use the command @w{@code{set follow-fork-mode}}.
2486 @kindex set follow-fork-mode
2487 @item set follow-fork-mode @var{mode}
2488 Set the debugger response to a program call of @code{fork} or
2489 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2490 process. The @var{mode} argument can be:
2494 The original process is debugged after a fork. The child process runs
2495 unimpeded. This is the default.
2498 The new process is debugged after a fork. The parent process runs
2503 @kindex show follow-fork-mode
2504 @item show follow-fork-mode
2505 Display the current debugger response to a @code{fork} or @code{vfork} call.
2508 @cindex debugging multiple processes
2509 On Linux, if you want to debug both the parent and child processes, use the
2510 command @w{@code{set detach-on-fork}}.
2513 @kindex set detach-on-fork
2514 @item set detach-on-fork @var{mode}
2515 Tells gdb whether to detach one of the processes after a fork, or
2516 retain debugger control over them both.
2520 The child process (or parent process, depending on the value of
2521 @code{follow-fork-mode}) will be detached and allowed to run
2522 independently. This is the default.
2525 Both processes will be held under the control of @value{GDBN}.
2526 One process (child or parent, depending on the value of
2527 @code{follow-fork-mode}) is debugged as usual, while the other
2532 @kindex show detach-on-follow
2533 @item show detach-on-follow
2534 Show whether detach-on-follow mode is on/off.
2537 If you choose to set @var{detach-on-follow} mode off, then
2538 @value{GDBN} will retain control of all forked processes (including
2539 nested forks). You can list the forked processes under the control of
2540 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2541 from one fork to another by using the @w{@code{fork}} command.
2546 Print a list of all forked processes under the control of @value{GDBN}.
2547 The listing will include a fork id, a process id, and the current
2548 position (program counter) of the process.
2551 @kindex fork @var{fork-id}
2552 @item fork @var{fork-id}
2553 Make fork number @var{fork-id} the current process. The argument
2554 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2555 as shown in the first field of the @samp{info forks} display.
2559 To quit debugging one of the forked processes, you can either detach
2560 from it by using the @w{@code{detach fork}} command (allowing it to
2561 run independently), or delete (and kill) it using the
2562 @w{@code{delete fork}} command.
2565 @kindex detach fork @var{fork-id}
2566 @item detach fork @var{fork-id}
2567 Detach from the process identified by @value{GDBN} fork number
2568 @var{fork-id}, and remove it from the fork list. The process will be
2569 allowed to run independently.
2571 @kindex delete fork @var{fork-id}
2572 @item delete fork @var{fork-id}
2573 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2574 and remove it from the fork list.
2578 If you ask to debug a child process and a @code{vfork} is followed by an
2579 @code{exec}, @value{GDBN} executes the new target up to the first
2580 breakpoint in the new target. If you have a breakpoint set on
2581 @code{main} in your original program, the breakpoint will also be set on
2582 the child process's @code{main}.
2584 When a child process is spawned by @code{vfork}, you cannot debug the
2585 child or parent until an @code{exec} call completes.
2587 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2588 call executes, the new target restarts. To restart the parent process,
2589 use the @code{file} command with the parent executable name as its
2592 You can use the @code{catch} command to make @value{GDBN} stop whenever
2593 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2594 Catchpoints, ,Setting Catchpoints}.
2596 @node Checkpoint/Restart
2597 @section Setting a @emph{Bookmark} to Return to Later
2602 @cindex snapshot of a process
2603 @cindex rewind program state
2605 On certain operating systems@footnote{Currently, only
2606 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2607 program's state, called a @dfn{checkpoint}, and come back to it
2610 Returning to a checkpoint effectively undoes everything that has
2611 happened in the program since the @code{checkpoint} was saved. This
2612 includes changes in memory, registers, and even (within some limits)
2613 system state. Effectively, it is like going back in time to the
2614 moment when the checkpoint was saved.
2616 Thus, if you're stepping thru a program and you think you're
2617 getting close to the point where things go wrong, you can save
2618 a checkpoint. Then, if you accidentally go too far and miss
2619 the critical statement, instead of having to restart your program
2620 from the beginning, you can just go back to the checkpoint and
2621 start again from there.
2623 This can be especially useful if it takes a lot of time or
2624 steps to reach the point where you think the bug occurs.
2626 To use the @code{checkpoint}/@code{restart} method of debugging:
2631 Save a snapshot of the debugged program's current execution state.
2632 The @code{checkpoint} command takes no arguments, but each checkpoint
2633 is assigned a small integer id, similar to a breakpoint id.
2635 @kindex info checkpoints
2636 @item info checkpoints
2637 List the checkpoints that have been saved in the current debugging
2638 session. For each checkpoint, the following information will be
2645 @item Source line, or label
2648 @kindex restart @var{checkpoint-id}
2649 @item restart @var{checkpoint-id}
2650 Restore the program state that was saved as checkpoint number
2651 @var{checkpoint-id}. All program variables, registers, stack frames
2652 etc.@: will be returned to the values that they had when the checkpoint
2653 was saved. In essence, gdb will ``wind back the clock'' to the point
2654 in time when the checkpoint was saved.
2656 Note that breakpoints, @value{GDBN} variables, command history etc.
2657 are not affected by restoring a checkpoint. In general, a checkpoint
2658 only restores things that reside in the program being debugged, not in
2661 @kindex delete checkpoint @var{checkpoint-id}
2662 @item delete checkpoint @var{checkpoint-id}
2663 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2667 Returning to a previously saved checkpoint will restore the user state
2668 of the program being debugged, plus a significant subset of the system
2669 (OS) state, including file pointers. It won't ``un-write'' data from
2670 a file, but it will rewind the file pointer to the previous location,
2671 so that the previously written data can be overwritten. For files
2672 opened in read mode, the pointer will also be restored so that the
2673 previously read data can be read again.
2675 Of course, characters that have been sent to a printer (or other
2676 external device) cannot be ``snatched back'', and characters received
2677 from eg.@: a serial device can be removed from internal program buffers,
2678 but they cannot be ``pushed back'' into the serial pipeline, ready to
2679 be received again. Similarly, the actual contents of files that have
2680 been changed cannot be restored (at this time).
2682 However, within those constraints, you actually can ``rewind'' your
2683 program to a previously saved point in time, and begin debugging it
2684 again --- and you can change the course of events so as to debug a
2685 different execution path this time.
2687 @cindex checkpoints and process id
2688 Finally, there is one bit of internal program state that will be
2689 different when you return to a checkpoint --- the program's process
2690 id. Each checkpoint will have a unique process id (or @var{pid}),
2691 and each will be different from the program's original @var{pid}.
2692 If your program has saved a local copy of its process id, this could
2693 potentially pose a problem.
2695 @subsection A Non-obvious Benefit of Using Checkpoints
2697 On some systems such as @sc{gnu}/Linux, address space randomization
2698 is performed on new processes for security reasons. This makes it
2699 difficult or impossible to set a breakpoint, or watchpoint, on an
2700 absolute address if you have to restart the program, since the
2701 absolute location of a symbol will change from one execution to the
2704 A checkpoint, however, is an @emph{identical} copy of a process.
2705 Therefore if you create a checkpoint at (eg.@:) the start of main,
2706 and simply return to that checkpoint instead of restarting the
2707 process, you can avoid the effects of address randomization and
2708 your symbols will all stay in the same place.
2711 @chapter Stopping and Continuing
2713 The principal purposes of using a debugger are so that you can stop your
2714 program before it terminates; or so that, if your program runs into
2715 trouble, you can investigate and find out why.
2717 Inside @value{GDBN}, your program may stop for any of several reasons,
2718 such as a signal, a breakpoint, or reaching a new line after a
2719 @value{GDBN} command such as @code{step}. You may then examine and
2720 change variables, set new breakpoints or remove old ones, and then
2721 continue execution. Usually, the messages shown by @value{GDBN} provide
2722 ample explanation of the status of your program---but you can also
2723 explicitly request this information at any time.
2726 @kindex info program
2728 Display information about the status of your program: whether it is
2729 running or not, what process it is, and why it stopped.
2733 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2734 * Continuing and Stepping:: Resuming execution
2736 * Thread Stops:: Stopping and starting multi-thread programs
2740 @section Breakpoints, Watchpoints, and Catchpoints
2743 A @dfn{breakpoint} makes your program stop whenever a certain point in
2744 the program is reached. For each breakpoint, you can add conditions to
2745 control in finer detail whether your program stops. You can set
2746 breakpoints with the @code{break} command and its variants (@pxref{Set
2747 Breaks, ,Setting Breakpoints}), to specify the place where your program
2748 should stop by line number, function name or exact address in the
2751 On some systems, you can set breakpoints in shared libraries before
2752 the executable is run. There is a minor limitation on HP-UX systems:
2753 you must wait until the executable is run in order to set breakpoints
2754 in shared library routines that are not called directly by the program
2755 (for example, routines that are arguments in a @code{pthread_create}
2759 @cindex data breakpoints
2760 @cindex memory tracing
2761 @cindex breakpoint on memory address
2762 @cindex breakpoint on variable modification
2763 A @dfn{watchpoint} is a special breakpoint that stops your program
2764 when the value of an expression changes. The expression may be a value
2765 of a variable, or it could involve values of one or more variables
2766 combined by operators, such as @samp{a + b}. This is sometimes called
2767 @dfn{data breakpoints}. You must use a different command to set
2768 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2769 from that, you can manage a watchpoint like any other breakpoint: you
2770 enable, disable, and delete both breakpoints and watchpoints using the
2773 You can arrange to have values from your program displayed automatically
2774 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2778 @cindex breakpoint on events
2779 A @dfn{catchpoint} is another special breakpoint that stops your program
2780 when a certain kind of event occurs, such as the throwing of a C@t{++}
2781 exception or the loading of a library. As with watchpoints, you use a
2782 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2783 Catchpoints}), but aside from that, you can manage a catchpoint like any
2784 other breakpoint. (To stop when your program receives a signal, use the
2785 @code{handle} command; see @ref{Signals, ,Signals}.)
2787 @cindex breakpoint numbers
2788 @cindex numbers for breakpoints
2789 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2790 catchpoint when you create it; these numbers are successive integers
2791 starting with one. In many of the commands for controlling various
2792 features of breakpoints you use the breakpoint number to say which
2793 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2794 @dfn{disabled}; if disabled, it has no effect on your program until you
2797 @cindex breakpoint ranges
2798 @cindex ranges of breakpoints
2799 Some @value{GDBN} commands accept a range of breakpoints on which to
2800 operate. A breakpoint range is either a single breakpoint number, like
2801 @samp{5}, or two such numbers, in increasing order, separated by a
2802 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2803 all breakpoints in that range are operated on.
2806 * Set Breaks:: Setting breakpoints
2807 * Set Watchpoints:: Setting watchpoints
2808 * Set Catchpoints:: Setting catchpoints
2809 * Delete Breaks:: Deleting breakpoints
2810 * Disabling:: Disabling breakpoints
2811 * Conditions:: Break conditions
2812 * Break Commands:: Breakpoint command lists
2813 * Breakpoint Menus:: Breakpoint menus
2814 * Error in Breakpoints:: ``Cannot insert breakpoints''
2815 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2819 @subsection Setting Breakpoints
2821 @c FIXME LMB what does GDB do if no code on line of breakpt?
2822 @c consider in particular declaration with/without initialization.
2824 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2827 @kindex b @r{(@code{break})}
2828 @vindex $bpnum@r{, convenience variable}
2829 @cindex latest breakpoint
2830 Breakpoints are set with the @code{break} command (abbreviated
2831 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2832 number of the breakpoint you've set most recently; see @ref{Convenience
2833 Vars,, Convenience Variables}, for a discussion of what you can do with
2834 convenience variables.
2836 You have several ways to say where the breakpoint should go.
2839 @item break @var{function}
2840 Set a breakpoint at entry to function @var{function}.
2841 When using source languages that permit overloading of symbols, such as
2842 C@t{++}, @var{function} may refer to more than one possible place to break.
2843 @xref{Breakpoint Menus,,Breakpoint Menus}, for a discussion of that situation.
2845 @item break +@var{offset}
2846 @itemx break -@var{offset}
2847 Set a breakpoint some number of lines forward or back from the position
2848 at which execution stopped in the currently selected @dfn{stack frame}.
2849 (@xref{Frames, ,Frames}, for a description of stack frames.)
2851 @item break @var{linenum}
2852 Set a breakpoint at line @var{linenum} in the current source file.
2853 The current source file is the last file whose source text was printed.
2854 The breakpoint will stop your program just before it executes any of the
2857 @item break @var{filename}:@var{linenum}
2858 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2860 @item break @var{filename}:@var{function}
2861 Set a breakpoint at entry to function @var{function} found in file
2862 @var{filename}. Specifying a file name as well as a function name is
2863 superfluous except when multiple files contain similarly named
2866 @item break *@var{address}
2867 Set a breakpoint at address @var{address}. You can use this to set
2868 breakpoints in parts of your program which do not have debugging
2869 information or source files.
2872 When called without any arguments, @code{break} sets a breakpoint at
2873 the next instruction to be executed in the selected stack frame
2874 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2875 innermost, this makes your program stop as soon as control
2876 returns to that frame. This is similar to the effect of a
2877 @code{finish} command in the frame inside the selected frame---except
2878 that @code{finish} does not leave an active breakpoint. If you use
2879 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2880 the next time it reaches the current location; this may be useful
2883 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2884 least one instruction has been executed. If it did not do this, you
2885 would be unable to proceed past a breakpoint without first disabling the
2886 breakpoint. This rule applies whether or not the breakpoint already
2887 existed when your program stopped.
2889 @item break @dots{} if @var{cond}
2890 Set a breakpoint with condition @var{cond}; evaluate the expression
2891 @var{cond} each time the breakpoint is reached, and stop only if the
2892 value is nonzero---that is, if @var{cond} evaluates as true.
2893 @samp{@dots{}} stands for one of the possible arguments described
2894 above (or no argument) specifying where to break. @xref{Conditions,
2895 ,Break Conditions}, for more information on breakpoint conditions.
2898 @item tbreak @var{args}
2899 Set a breakpoint enabled only for one stop. @var{args} are the
2900 same as for the @code{break} command, and the breakpoint is set in the same
2901 way, but the breakpoint is automatically deleted after the first time your
2902 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2905 @cindex hardware breakpoints
2906 @item hbreak @var{args}
2907 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2908 @code{break} command and the breakpoint is set in the same way, but the
2909 breakpoint requires hardware support and some target hardware may not
2910 have this support. The main purpose of this is EPROM/ROM code
2911 debugging, so you can set a breakpoint at an instruction without
2912 changing the instruction. This can be used with the new trap-generation
2913 provided by SPARClite DSU and most x86-based targets. These targets
2914 will generate traps when a program accesses some data or instruction
2915 address that is assigned to the debug registers. However the hardware
2916 breakpoint registers can take a limited number of breakpoints. For
2917 example, on the DSU, only two data breakpoints can be set at a time, and
2918 @value{GDBN} will reject this command if more than two are used. Delete
2919 or disable unused hardware breakpoints before setting new ones
2920 (@pxref{Disabling, ,Disabling Breakpoints}).
2921 @xref{Conditions, ,Break Conditions}.
2922 For remote targets, you can restrict the number of hardware
2923 breakpoints @value{GDBN} will use, see @ref{set remote
2924 hardware-breakpoint-limit}.
2928 @item thbreak @var{args}
2929 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2930 are the same as for the @code{hbreak} command and the breakpoint is set in
2931 the same way. However, like the @code{tbreak} command,
2932 the breakpoint is automatically deleted after the
2933 first time your program stops there. Also, like the @code{hbreak}
2934 command, the breakpoint requires hardware support and some target hardware
2935 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2936 See also @ref{Conditions, ,Break Conditions}.
2939 @cindex regular expression
2940 @cindex breakpoints in functions matching a regexp
2941 @cindex set breakpoints in many functions
2942 @item rbreak @var{regex}
2943 Set breakpoints on all functions matching the regular expression
2944 @var{regex}. This command sets an unconditional breakpoint on all
2945 matches, printing a list of all breakpoints it set. Once these
2946 breakpoints are set, they are treated just like the breakpoints set with
2947 the @code{break} command. You can delete them, disable them, or make
2948 them conditional the same way as any other breakpoint.
2950 The syntax of the regular expression is the standard one used with tools
2951 like @file{grep}. Note that this is different from the syntax used by
2952 shells, so for instance @code{foo*} matches all functions that include
2953 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2954 @code{.*} leading and trailing the regular expression you supply, so to
2955 match only functions that begin with @code{foo}, use @code{^foo}.
2957 @cindex non-member C@t{++} functions, set breakpoint in
2958 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2959 breakpoints on overloaded functions that are not members of any special
2962 @cindex set breakpoints on all functions
2963 The @code{rbreak} command can be used to set breakpoints in
2964 @strong{all} the functions in a program, like this:
2967 (@value{GDBP}) rbreak .
2970 @kindex info breakpoints
2971 @cindex @code{$_} and @code{info breakpoints}
2972 @item info breakpoints @r{[}@var{n}@r{]}
2973 @itemx info break @r{[}@var{n}@r{]}
2974 @itemx info watchpoints @r{[}@var{n}@r{]}
2975 Print a table of all breakpoints, watchpoints, and catchpoints set and
2976 not deleted. Optional argument @var{n} means print information only
2977 about the specified breakpoint (or watchpoint or catchpoint). For
2978 each breakpoint, following columns are printed:
2981 @item Breakpoint Numbers
2983 Breakpoint, watchpoint, or catchpoint.
2985 Whether the breakpoint is marked to be disabled or deleted when hit.
2986 @item Enabled or Disabled
2987 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2988 that are not enabled.
2990 Where the breakpoint is in your program, as a memory address. If the
2991 breakpoint is pending (see below for details) on a future load of a shared library, the address
2992 will be listed as @samp{<PENDING>}.
2994 Where the breakpoint is in the source for your program, as a file and
2995 line number. For a pending breakpoint, the original string passed to
2996 the breakpoint command will be listed as it cannot be resolved until
2997 the appropriate shared library is loaded in the future.
3001 If a breakpoint is conditional, @code{info break} shows the condition on
3002 the line following the affected breakpoint; breakpoint commands, if any,
3003 are listed after that. A pending breakpoint is allowed to have a condition
3004 specified for it. The condition is not parsed for validity until a shared
3005 library is loaded that allows the pending breakpoint to resolve to a
3009 @code{info break} with a breakpoint
3010 number @var{n} as argument lists only that breakpoint. The
3011 convenience variable @code{$_} and the default examining-address for
3012 the @code{x} command are set to the address of the last breakpoint
3013 listed (@pxref{Memory, ,Examining Memory}).
3016 @code{info break} displays a count of the number of times the breakpoint
3017 has been hit. This is especially useful in conjunction with the
3018 @code{ignore} command. You can ignore a large number of breakpoint
3019 hits, look at the breakpoint info to see how many times the breakpoint
3020 was hit, and then run again, ignoring one less than that number. This
3021 will get you quickly to the last hit of that breakpoint.
3024 @value{GDBN} allows you to set any number of breakpoints at the same place in
3025 your program. There is nothing silly or meaningless about this. When
3026 the breakpoints are conditional, this is even useful
3027 (@pxref{Conditions, ,Break Conditions}).
3029 @cindex pending breakpoints
3030 If a specified breakpoint location cannot be found, it may be due to the fact
3031 that the location is in a shared library that is yet to be loaded. In such
3032 a case, you may want @value{GDBN} to create a special breakpoint (known as
3033 a @dfn{pending breakpoint}) that
3034 attempts to resolve itself in the future when an appropriate shared library
3037 Pending breakpoints are useful to set at the start of your
3038 @value{GDBN} session for locations that you know will be dynamically loaded
3039 later by the program being debugged. When shared libraries are loaded,
3040 a check is made to see if the load resolves any pending breakpoint locations.
3041 If a pending breakpoint location gets resolved,
3042 a regular breakpoint is created and the original pending breakpoint is removed.
3044 @value{GDBN} provides some additional commands for controlling pending
3047 @kindex set breakpoint pending
3048 @kindex show breakpoint pending
3050 @item set breakpoint pending auto
3051 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3052 location, it queries you whether a pending breakpoint should be created.
3054 @item set breakpoint pending on
3055 This indicates that an unrecognized breakpoint location should automatically
3056 result in a pending breakpoint being created.
3058 @item set breakpoint pending off
3059 This indicates that pending breakpoints are not to be created. Any
3060 unrecognized breakpoint location results in an error. This setting does
3061 not affect any pending breakpoints previously created.
3063 @item show breakpoint pending
3064 Show the current behavior setting for creating pending breakpoints.
3067 @cindex operations allowed on pending breakpoints
3068 Normal breakpoint operations apply to pending breakpoints as well. You may
3069 specify a condition for a pending breakpoint and/or commands to run when the
3070 breakpoint is reached. You can also enable or disable
3071 the pending breakpoint. When you specify a condition for a pending breakpoint,
3072 the parsing of the condition will be deferred until the point where the
3073 pending breakpoint location is resolved. Disabling a pending breakpoint
3074 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
3075 shared library load. When a pending breakpoint is re-enabled,
3076 @value{GDBN} checks to see if the location is already resolved.
3077 This is done because any number of shared library loads could have
3078 occurred since the time the breakpoint was disabled and one or more
3079 of these loads could resolve the location.
3081 @cindex automatic hardware breakpoints
3082 For some targets, @value{GDBN} can automatically decide if hardware or
3083 software breakpoints should be used, depending on whether the
3084 breakpoint address is read-only or read-write. This applies to
3085 breakpoints set with the @code{break} command as well as to internal
3086 breakpoints set by commands like @code{next} and @code{finish}. For
3087 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3090 You can control this automatic behaviour with the following commands::
3092 @kindex set breakpoint auto-hw
3093 @kindex show breakpoint auto-hw
3095 @item set breakpoint auto-hw on
3096 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3097 will try to use the target memory map to decide if software or hardware
3098 breakpoint must be used.
3100 @item set breakpoint auto-hw off
3101 This indicates @value{GDBN} should not automatically select breakpoint
3102 type. If the target provides a memory map, @value{GDBN} will warn when
3103 trying to set software breakpoint at a read-only address.
3107 @cindex negative breakpoint numbers
3108 @cindex internal @value{GDBN} breakpoints
3109 @value{GDBN} itself sometimes sets breakpoints in your program for
3110 special purposes, such as proper handling of @code{longjmp} (in C
3111 programs). These internal breakpoints are assigned negative numbers,
3112 starting with @code{-1}; @samp{info breakpoints} does not display them.
3113 You can see these breakpoints with the @value{GDBN} maintenance command
3114 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3117 @node Set Watchpoints
3118 @subsection Setting Watchpoints
3120 @cindex setting watchpoints
3121 You can use a watchpoint to stop execution whenever the value of an
3122 expression changes, without having to predict a particular place where
3123 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3124 The expression may be as simple as the value of a single variable, or
3125 as complex as many variables combined by operators. Examples include:
3129 A reference to the value of a single variable.
3132 An address cast to an appropriate data type. For example,
3133 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3134 address (assuming an @code{int} occupies 4 bytes).
3137 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3138 expression can use any operators valid in the program's native
3139 language (@pxref{Languages}).
3142 @cindex software watchpoints
3143 @cindex hardware watchpoints
3144 Depending on your system, watchpoints may be implemented in software or
3145 hardware. @value{GDBN} does software watchpointing by single-stepping your
3146 program and testing the variable's value each time, which is hundreds of
3147 times slower than normal execution. (But this may still be worth it, to
3148 catch errors where you have no clue what part of your program is the
3151 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
3152 x86-based targets, @value{GDBN} includes support for hardware
3153 watchpoints, which do not slow down the running of your program.
3157 @item watch @var{expr}
3158 Set a watchpoint for an expression. @value{GDBN} will break when the
3159 expression @var{expr} is written into by the program and its value
3160 changes. The simplest (and the most popular) use of this command is
3161 to watch the value of a single variable:
3164 (@value{GDBP}) watch foo
3168 @item rwatch @var{expr}
3169 Set a watchpoint that will break when the value of @var{expr} is read
3173 @item awatch @var{expr}
3174 Set a watchpoint that will break when @var{expr} is either read from
3175 or written into by the program.
3177 @kindex info watchpoints @r{[}@var{n}@r{]}
3178 @item info watchpoints
3179 This command prints a list of watchpoints, breakpoints, and catchpoints;
3180 it is the same as @code{info break} (@pxref{Set Breaks}).
3183 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3184 watchpoints execute very quickly, and the debugger reports a change in
3185 value at the exact instruction where the change occurs. If @value{GDBN}
3186 cannot set a hardware watchpoint, it sets a software watchpoint, which
3187 executes more slowly and reports the change in value at the next
3188 @emph{statement}, not the instruction, after the change occurs.
3190 @cindex use only software watchpoints
3191 You can force @value{GDBN} to use only software watchpoints with the
3192 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3193 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3194 the underlying system supports them. (Note that hardware-assisted
3195 watchpoints that were set @emph{before} setting
3196 @code{can-use-hw-watchpoints} to zero will still use the hardware
3197 mechanism of watching expression values.)
3200 @item set can-use-hw-watchpoints
3201 @kindex set can-use-hw-watchpoints
3202 Set whether or not to use hardware watchpoints.
3204 @item show can-use-hw-watchpoints
3205 @kindex show can-use-hw-watchpoints
3206 Show the current mode of using hardware watchpoints.
3209 For remote targets, you can restrict the number of hardware
3210 watchpoints @value{GDBN} will use, see @ref{set remote
3211 hardware-breakpoint-limit}.
3213 When you issue the @code{watch} command, @value{GDBN} reports
3216 Hardware watchpoint @var{num}: @var{expr}
3220 if it was able to set a hardware watchpoint.
3222 Currently, the @code{awatch} and @code{rwatch} commands can only set
3223 hardware watchpoints, because accesses to data that don't change the
3224 value of the watched expression cannot be detected without examining
3225 every instruction as it is being executed, and @value{GDBN} does not do
3226 that currently. If @value{GDBN} finds that it is unable to set a
3227 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3228 will print a message like this:
3231 Expression cannot be implemented with read/access watchpoint.
3234 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3235 data type of the watched expression is wider than what a hardware
3236 watchpoint on the target machine can handle. For example, some systems
3237 can only watch regions that are up to 4 bytes wide; on such systems you
3238 cannot set hardware watchpoints for an expression that yields a
3239 double-precision floating-point number (which is typically 8 bytes
3240 wide). As a work-around, it might be possible to break the large region
3241 into a series of smaller ones and watch them with separate watchpoints.
3243 If you set too many hardware watchpoints, @value{GDBN} might be unable
3244 to insert all of them when you resume the execution of your program.
3245 Since the precise number of active watchpoints is unknown until such
3246 time as the program is about to be resumed, @value{GDBN} might not be
3247 able to warn you about this when you set the watchpoints, and the
3248 warning will be printed only when the program is resumed:
3251 Hardware watchpoint @var{num}: Could not insert watchpoint
3255 If this happens, delete or disable some of the watchpoints.
3257 Watching complex expressions that reference many variables can also
3258 exhaust the resources available for hardware-assisted watchpoints.
3259 That's because @value{GDBN} needs to watch every variable in the
3260 expression with separately allocated resources.
3262 The SPARClite DSU will generate traps when a program accesses some data
3263 or instruction address that is assigned to the debug registers. For the
3264 data addresses, DSU facilitates the @code{watch} command. However the
3265 hardware breakpoint registers can only take two data watchpoints, and
3266 both watchpoints must be the same kind. For example, you can set two
3267 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3268 @strong{or} two with @code{awatch} commands, but you cannot set one
3269 watchpoint with one command and the other with a different command.
3270 @value{GDBN} will reject the command if you try to mix watchpoints.
3271 Delete or disable unused watchpoint commands before setting new ones.
3273 If you call a function interactively using @code{print} or @code{call},
3274 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3275 kind of breakpoint or the call completes.
3277 @value{GDBN} automatically deletes watchpoints that watch local
3278 (automatic) variables, or expressions that involve such variables, when
3279 they go out of scope, that is, when the execution leaves the block in
3280 which these variables were defined. In particular, when the program
3281 being debugged terminates, @emph{all} local variables go out of scope,
3282 and so only watchpoints that watch global variables remain set. If you
3283 rerun the program, you will need to set all such watchpoints again. One
3284 way of doing that would be to set a code breakpoint at the entry to the
3285 @code{main} function and when it breaks, set all the watchpoints.
3288 @cindex watchpoints and threads
3289 @cindex threads and watchpoints
3290 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3291 usefulness. With the current watchpoint implementation, @value{GDBN}
3292 can only watch the value of an expression @emph{in a single thread}. If
3293 you are confident that the expression can only change due to the current
3294 thread's activity (and if you are also confident that no other thread
3295 can become current), then you can use watchpoints as usual. However,
3296 @value{GDBN} may not notice when a non-current thread's activity changes
3299 @c FIXME: this is almost identical to the previous paragraph.
3300 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3301 have only limited usefulness. If @value{GDBN} creates a software
3302 watchpoint, it can only watch the value of an expression @emph{in a
3303 single thread}. If you are confident that the expression can only
3304 change due to the current thread's activity (and if you are also
3305 confident that no other thread can become current), then you can use
3306 software watchpoints as usual. However, @value{GDBN} may not notice
3307 when a non-current thread's activity changes the expression. (Hardware
3308 watchpoints, in contrast, watch an expression in all threads.)
3311 @xref{set remote hardware-watchpoint-limit}.
3313 @node Set Catchpoints
3314 @subsection Setting Catchpoints
3315 @cindex catchpoints, setting
3316 @cindex exception handlers
3317 @cindex event handling
3319 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3320 kinds of program events, such as C@t{++} exceptions or the loading of a
3321 shared library. Use the @code{catch} command to set a catchpoint.
3325 @item catch @var{event}
3326 Stop when @var{event} occurs. @var{event} can be any of the following:
3329 @cindex stop on C@t{++} exceptions
3330 The throwing of a C@t{++} exception.
3333 The catching of a C@t{++} exception.
3336 @cindex Ada exception catching
3337 @cindex catch Ada exceptions
3338 An Ada exception being raised. If an exception name is specified
3339 at the end of the command (eg @code{catch exception Program_Error}),
3340 the debugger will stop only when this specific exception is raised.
3341 Otherwise, the debugger stops execution when any Ada exception is raised.
3343 @item exception unhandled
3344 An exception that was raised but is not handled by the program.
3347 A failed Ada assertion.
3350 @cindex break on fork/exec
3351 A call to @code{exec}. This is currently only available for HP-UX.
3354 A call to @code{fork}. This is currently only available for HP-UX.
3357 A call to @code{vfork}. This is currently only available for HP-UX.
3360 @itemx load @var{libname}
3361 @cindex break on load/unload of shared library
3362 The dynamic loading of any shared library, or the loading of the library
3363 @var{libname}. This is currently only available for HP-UX.
3366 @itemx unload @var{libname}
3367 The unloading of any dynamically loaded shared library, or the unloading
3368 of the library @var{libname}. This is currently only available for HP-UX.
3371 @item tcatch @var{event}
3372 Set a catchpoint that is enabled only for one stop. The catchpoint is
3373 automatically deleted after the first time the event is caught.
3377 Use the @code{info break} command to list the current catchpoints.
3379 There are currently some limitations to C@t{++} exception handling
3380 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3384 If you call a function interactively, @value{GDBN} normally returns
3385 control to you when the function has finished executing. If the call
3386 raises an exception, however, the call may bypass the mechanism that
3387 returns control to you and cause your program either to abort or to
3388 simply continue running until it hits a breakpoint, catches a signal
3389 that @value{GDBN} is listening for, or exits. This is the case even if
3390 you set a catchpoint for the exception; catchpoints on exceptions are
3391 disabled within interactive calls.
3394 You cannot raise an exception interactively.
3397 You cannot install an exception handler interactively.
3400 @cindex raise exceptions
3401 Sometimes @code{catch} is not the best way to debug exception handling:
3402 if you need to know exactly where an exception is raised, it is better to
3403 stop @emph{before} the exception handler is called, since that way you
3404 can see the stack before any unwinding takes place. If you set a
3405 breakpoint in an exception handler instead, it may not be easy to find
3406 out where the exception was raised.
3408 To stop just before an exception handler is called, you need some
3409 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3410 raised by calling a library function named @code{__raise_exception}
3411 which has the following ANSI C interface:
3414 /* @var{addr} is where the exception identifier is stored.
3415 @var{id} is the exception identifier. */
3416 void __raise_exception (void **addr, void *id);
3420 To make the debugger catch all exceptions before any stack
3421 unwinding takes place, set a breakpoint on @code{__raise_exception}
3422 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3424 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3425 that depends on the value of @var{id}, you can stop your program when
3426 a specific exception is raised. You can use multiple conditional
3427 breakpoints to stop your program when any of a number of exceptions are
3432 @subsection Deleting Breakpoints
3434 @cindex clearing breakpoints, watchpoints, catchpoints
3435 @cindex deleting breakpoints, watchpoints, catchpoints
3436 It is often necessary to eliminate a breakpoint, watchpoint, or
3437 catchpoint once it has done its job and you no longer want your program
3438 to stop there. This is called @dfn{deleting} the breakpoint. A
3439 breakpoint that has been deleted no longer exists; it is forgotten.
3441 With the @code{clear} command you can delete breakpoints according to
3442 where they are in your program. With the @code{delete} command you can
3443 delete individual breakpoints, watchpoints, or catchpoints by specifying
3444 their breakpoint numbers.
3446 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3447 automatically ignores breakpoints on the first instruction to be executed
3448 when you continue execution without changing the execution address.
3453 Delete any breakpoints at the next instruction to be executed in the
3454 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3455 the innermost frame is selected, this is a good way to delete a
3456 breakpoint where your program just stopped.
3458 @item clear @var{function}
3459 @itemx clear @var{filename}:@var{function}
3460 Delete any breakpoints set at entry to the named @var{function}.
3462 @item clear @var{linenum}
3463 @itemx clear @var{filename}:@var{linenum}
3464 Delete any breakpoints set at or within the code of the specified
3465 @var{linenum} of the specified @var{filename}.
3467 @cindex delete breakpoints
3469 @kindex d @r{(@code{delete})}
3470 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3471 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3472 ranges specified as arguments. If no argument is specified, delete all
3473 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3474 confirm off}). You can abbreviate this command as @code{d}.
3478 @subsection Disabling Breakpoints
3480 @cindex enable/disable a breakpoint
3481 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3482 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3483 it had been deleted, but remembers the information on the breakpoint so
3484 that you can @dfn{enable} it again later.
3486 You disable and enable breakpoints, watchpoints, and catchpoints with
3487 the @code{enable} and @code{disable} commands, optionally specifying one
3488 or more breakpoint numbers as arguments. Use @code{info break} or
3489 @code{info watch} to print a list of breakpoints, watchpoints, and
3490 catchpoints if you do not know which numbers to use.
3492 A breakpoint, watchpoint, or catchpoint can have any of four different
3493 states of enablement:
3497 Enabled. The breakpoint stops your program. A breakpoint set
3498 with the @code{break} command starts out in this state.
3500 Disabled. The breakpoint has no effect on your program.
3502 Enabled once. The breakpoint stops your program, but then becomes
3505 Enabled for deletion. The breakpoint stops your program, but
3506 immediately after it does so it is deleted permanently. A breakpoint
3507 set with the @code{tbreak} command starts out in this state.
3510 You can use the following commands to enable or disable breakpoints,
3511 watchpoints, and catchpoints:
3515 @kindex dis @r{(@code{disable})}
3516 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3517 Disable the specified breakpoints---or all breakpoints, if none are
3518 listed. A disabled breakpoint has no effect but is not forgotten. All
3519 options such as ignore-counts, conditions and commands are remembered in
3520 case the breakpoint is enabled again later. You may abbreviate
3521 @code{disable} as @code{dis}.
3524 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3525 Enable the specified breakpoints (or all defined breakpoints). They
3526 become effective once again in stopping your program.
3528 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3529 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3530 of these breakpoints immediately after stopping your program.
3532 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3533 Enable the specified breakpoints to work once, then die. @value{GDBN}
3534 deletes any of these breakpoints as soon as your program stops there.
3535 Breakpoints set by the @code{tbreak} command start out in this state.
3538 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3539 @c confusing: tbreak is also initially enabled.
3540 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3541 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3542 subsequently, they become disabled or enabled only when you use one of
3543 the commands above. (The command @code{until} can set and delete a
3544 breakpoint of its own, but it does not change the state of your other
3545 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3549 @subsection Break Conditions
3550 @cindex conditional breakpoints
3551 @cindex breakpoint conditions
3553 @c FIXME what is scope of break condition expr? Context where wanted?
3554 @c in particular for a watchpoint?
3555 The simplest sort of breakpoint breaks every time your program reaches a
3556 specified place. You can also specify a @dfn{condition} for a
3557 breakpoint. A condition is just a Boolean expression in your
3558 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3559 a condition evaluates the expression each time your program reaches it,
3560 and your program stops only if the condition is @emph{true}.
3562 This is the converse of using assertions for program validation; in that
3563 situation, you want to stop when the assertion is violated---that is,
3564 when the condition is false. In C, if you want to test an assertion expressed
3565 by the condition @var{assert}, you should set the condition
3566 @samp{! @var{assert}} on the appropriate breakpoint.
3568 Conditions are also accepted for watchpoints; you may not need them,
3569 since a watchpoint is inspecting the value of an expression anyhow---but
3570 it might be simpler, say, to just set a watchpoint on a variable name,
3571 and specify a condition that tests whether the new value is an interesting
3574 Break conditions can have side effects, and may even call functions in
3575 your program. This can be useful, for example, to activate functions
3576 that log program progress, or to use your own print functions to
3577 format special data structures. The effects are completely predictable
3578 unless there is another enabled breakpoint at the same address. (In
3579 that case, @value{GDBN} might see the other breakpoint first and stop your
3580 program without checking the condition of this one.) Note that
3581 breakpoint commands are usually more convenient and flexible than break
3583 purpose of performing side effects when a breakpoint is reached
3584 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3586 Break conditions can be specified when a breakpoint is set, by using
3587 @samp{if} in the arguments to the @code{break} command. @xref{Set
3588 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3589 with the @code{condition} command.
3591 You can also use the @code{if} keyword with the @code{watch} command.
3592 The @code{catch} command does not recognize the @code{if} keyword;
3593 @code{condition} is the only way to impose a further condition on a
3598 @item condition @var{bnum} @var{expression}
3599 Specify @var{expression} as the break condition for breakpoint,
3600 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3601 breakpoint @var{bnum} stops your program only if the value of
3602 @var{expression} is true (nonzero, in C). When you use
3603 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3604 syntactic correctness, and to determine whether symbols in it have
3605 referents in the context of your breakpoint. If @var{expression} uses
3606 symbols not referenced in the context of the breakpoint, @value{GDBN}
3607 prints an error message:
3610 No symbol "foo" in current context.
3615 not actually evaluate @var{expression} at the time the @code{condition}
3616 command (or a command that sets a breakpoint with a condition, like
3617 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3619 @item condition @var{bnum}
3620 Remove the condition from breakpoint number @var{bnum}. It becomes
3621 an ordinary unconditional breakpoint.
3624 @cindex ignore count (of breakpoint)
3625 A special case of a breakpoint condition is to stop only when the
3626 breakpoint has been reached a certain number of times. This is so
3627 useful that there is a special way to do it, using the @dfn{ignore
3628 count} of the breakpoint. Every breakpoint has an ignore count, which
3629 is an integer. Most of the time, the ignore count is zero, and
3630 therefore has no effect. But if your program reaches a breakpoint whose
3631 ignore count is positive, then instead of stopping, it just decrements
3632 the ignore count by one and continues. As a result, if the ignore count
3633 value is @var{n}, the breakpoint does not stop the next @var{n} times
3634 your program reaches it.
3638 @item ignore @var{bnum} @var{count}
3639 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3640 The next @var{count} times the breakpoint is reached, your program's
3641 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3644 To make the breakpoint stop the next time it is reached, specify
3647 When you use @code{continue} to resume execution of your program from a
3648 breakpoint, you can specify an ignore count directly as an argument to
3649 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3650 Stepping,,Continuing and Stepping}.
3652 If a breakpoint has a positive ignore count and a condition, the
3653 condition is not checked. Once the ignore count reaches zero,
3654 @value{GDBN} resumes checking the condition.
3656 You could achieve the effect of the ignore count with a condition such
3657 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3658 is decremented each time. @xref{Convenience Vars, ,Convenience
3662 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3665 @node Break Commands
3666 @subsection Breakpoint Command Lists
3668 @cindex breakpoint commands
3669 You can give any breakpoint (or watchpoint or catchpoint) a series of
3670 commands to execute when your program stops due to that breakpoint. For
3671 example, you might want to print the values of certain expressions, or
3672 enable other breakpoints.
3676 @kindex end@r{ (breakpoint commands)}
3677 @item commands @r{[}@var{bnum}@r{]}
3678 @itemx @dots{} @var{command-list} @dots{}
3680 Specify a list of commands for breakpoint number @var{bnum}. The commands
3681 themselves appear on the following lines. Type a line containing just
3682 @code{end} to terminate the commands.
3684 To remove all commands from a breakpoint, type @code{commands} and
3685 follow it immediately with @code{end}; that is, give no commands.
3687 With no @var{bnum} argument, @code{commands} refers to the last
3688 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3689 recently encountered).
3692 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3693 disabled within a @var{command-list}.
3695 You can use breakpoint commands to start your program up again. Simply
3696 use the @code{continue} command, or @code{step}, or any other command
3697 that resumes execution.
3699 Any other commands in the command list, after a command that resumes
3700 execution, are ignored. This is because any time you resume execution
3701 (even with a simple @code{next} or @code{step}), you may encounter
3702 another breakpoint---which could have its own command list, leading to
3703 ambiguities about which list to execute.
3706 If the first command you specify in a command list is @code{silent}, the
3707 usual message about stopping at a breakpoint is not printed. This may
3708 be desirable for breakpoints that are to print a specific message and
3709 then continue. If none of the remaining commands print anything, you
3710 see no sign that the breakpoint was reached. @code{silent} is
3711 meaningful only at the beginning of a breakpoint command list.
3713 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3714 print precisely controlled output, and are often useful in silent
3715 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3717 For example, here is how you could use breakpoint commands to print the
3718 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3724 printf "x is %d\n",x
3729 One application for breakpoint commands is to compensate for one bug so
3730 you can test for another. Put a breakpoint just after the erroneous line
3731 of code, give it a condition to detect the case in which something
3732 erroneous has been done, and give it commands to assign correct values
3733 to any variables that need them. End with the @code{continue} command
3734 so that your program does not stop, and start with the @code{silent}
3735 command so that no output is produced. Here is an example:
3746 @node Breakpoint Menus
3747 @subsection Breakpoint Menus
3749 @cindex symbol overloading
3751 Some programming languages (notably C@t{++} and Objective-C) permit a
3752 single function name
3753 to be defined several times, for application in different contexts.
3754 This is called @dfn{overloading}. When a function name is overloaded,
3755 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3756 a breakpoint. If you realize this is a problem, you can use
3757 something like @samp{break @var{function}(@var{types})} to specify which
3758 particular version of the function you want. Otherwise, @value{GDBN} offers
3759 you a menu of numbered choices for different possible breakpoints, and
3760 waits for your selection with the prompt @samp{>}. The first two
3761 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3762 sets a breakpoint at each definition of @var{function}, and typing
3763 @kbd{0} aborts the @code{break} command without setting any new
3766 For example, the following session excerpt shows an attempt to set a
3767 breakpoint at the overloaded symbol @code{String::after}.
3768 We choose three particular definitions of that function name:
3770 @c FIXME! This is likely to change to show arg type lists, at least
3773 (@value{GDBP}) b String::after
3776 [2] file:String.cc; line number:867
3777 [3] file:String.cc; line number:860
3778 [4] file:String.cc; line number:875
3779 [5] file:String.cc; line number:853
3780 [6] file:String.cc; line number:846
3781 [7] file:String.cc; line number:735
3783 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3784 Breakpoint 2 at 0xb344: file String.cc, line 875.
3785 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3786 Multiple breakpoints were set.
3787 Use the "delete" command to delete unwanted
3793 @c @ifclear BARETARGET
3794 @node Error in Breakpoints
3795 @subsection ``Cannot insert breakpoints''
3797 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3799 Under some operating systems, breakpoints cannot be used in a program if
3800 any other process is running that program. In this situation,
3801 attempting to run or continue a program with a breakpoint causes
3802 @value{GDBN} to print an error message:
3805 Cannot insert breakpoints.
3806 The same program may be running in another process.
3809 When this happens, you have three ways to proceed:
3813 Remove or disable the breakpoints, then continue.
3816 Suspend @value{GDBN}, and copy the file containing your program to a new
3817 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3818 that @value{GDBN} should run your program under that name.
3819 Then start your program again.
3822 Relink your program so that the text segment is nonsharable, using the
3823 linker option @samp{-N}. The operating system limitation may not apply
3824 to nonsharable executables.
3828 A similar message can be printed if you request too many active
3829 hardware-assisted breakpoints and watchpoints:
3831 @c FIXME: the precise wording of this message may change; the relevant
3832 @c source change is not committed yet (Sep 3, 1999).
3834 Stopped; cannot insert breakpoints.
3835 You may have requested too many hardware breakpoints and watchpoints.
3839 This message is printed when you attempt to resume the program, since
3840 only then @value{GDBN} knows exactly how many hardware breakpoints and
3841 watchpoints it needs to insert.
3843 When this message is printed, you need to disable or remove some of the
3844 hardware-assisted breakpoints and watchpoints, and then continue.
3846 @node Breakpoint-related Warnings
3847 @subsection ``Breakpoint address adjusted...''
3848 @cindex breakpoint address adjusted
3850 Some processor architectures place constraints on the addresses at
3851 which breakpoints may be placed. For architectures thus constrained,
3852 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3853 with the constraints dictated by the architecture.
3855 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3856 a VLIW architecture in which a number of RISC-like instructions may be
3857 bundled together for parallel execution. The FR-V architecture
3858 constrains the location of a breakpoint instruction within such a
3859 bundle to the instruction with the lowest address. @value{GDBN}
3860 honors this constraint by adjusting a breakpoint's address to the
3861 first in the bundle.
3863 It is not uncommon for optimized code to have bundles which contain
3864 instructions from different source statements, thus it may happen that
3865 a breakpoint's address will be adjusted from one source statement to
3866 another. Since this adjustment may significantly alter @value{GDBN}'s
3867 breakpoint related behavior from what the user expects, a warning is
3868 printed when the breakpoint is first set and also when the breakpoint
3871 A warning like the one below is printed when setting a breakpoint
3872 that's been subject to address adjustment:
3875 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3878 Such warnings are printed both for user settable and @value{GDBN}'s
3879 internal breakpoints. If you see one of these warnings, you should
3880 verify that a breakpoint set at the adjusted address will have the
3881 desired affect. If not, the breakpoint in question may be removed and
3882 other breakpoints may be set which will have the desired behavior.
3883 E.g., it may be sufficient to place the breakpoint at a later
3884 instruction. A conditional breakpoint may also be useful in some
3885 cases to prevent the breakpoint from triggering too often.
3887 @value{GDBN} will also issue a warning when stopping at one of these
3888 adjusted breakpoints:
3891 warning: Breakpoint 1 address previously adjusted from 0x00010414
3895 When this warning is encountered, it may be too late to take remedial
3896 action except in cases where the breakpoint is hit earlier or more
3897 frequently than expected.
3899 @node Continuing and Stepping
3900 @section Continuing and Stepping
3904 @cindex resuming execution
3905 @dfn{Continuing} means resuming program execution until your program
3906 completes normally. In contrast, @dfn{stepping} means executing just
3907 one more ``step'' of your program, where ``step'' may mean either one
3908 line of source code, or one machine instruction (depending on what
3909 particular command you use). Either when continuing or when stepping,
3910 your program may stop even sooner, due to a breakpoint or a signal. (If
3911 it stops due to a signal, you may want to use @code{handle}, or use
3912 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3916 @kindex c @r{(@code{continue})}
3917 @kindex fg @r{(resume foreground execution)}
3918 @item continue @r{[}@var{ignore-count}@r{]}
3919 @itemx c @r{[}@var{ignore-count}@r{]}
3920 @itemx fg @r{[}@var{ignore-count}@r{]}
3921 Resume program execution, at the address where your program last stopped;
3922 any breakpoints set at that address are bypassed. The optional argument
3923 @var{ignore-count} allows you to specify a further number of times to
3924 ignore a breakpoint at this location; its effect is like that of
3925 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
3927 The argument @var{ignore-count} is meaningful only when your program
3928 stopped due to a breakpoint. At other times, the argument to
3929 @code{continue} is ignored.
3931 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3932 debugged program is deemed to be the foreground program) are provided
3933 purely for convenience, and have exactly the same behavior as
3937 To resume execution at a different place, you can use @code{return}
3938 (@pxref{Returning, ,Returning from a Function}) to go back to the
3939 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3940 Different Address}) to go to an arbitrary location in your program.
3942 A typical technique for using stepping is to set a breakpoint
3943 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
3944 beginning of the function or the section of your program where a problem
3945 is believed to lie, run your program until it stops at that breakpoint,
3946 and then step through the suspect area, examining the variables that are
3947 interesting, until you see the problem happen.
3951 @kindex s @r{(@code{step})}
3953 Continue running your program until control reaches a different source
3954 line, then stop it and return control to @value{GDBN}. This command is
3955 abbreviated @code{s}.
3958 @c "without debugging information" is imprecise; actually "without line
3959 @c numbers in the debugging information". (gcc -g1 has debugging info but
3960 @c not line numbers). But it seems complex to try to make that
3961 @c distinction here.
3962 @emph{Warning:} If you use the @code{step} command while control is
3963 within a function that was compiled without debugging information,
3964 execution proceeds until control reaches a function that does have
3965 debugging information. Likewise, it will not step into a function which
3966 is compiled without debugging information. To step through functions
3967 without debugging information, use the @code{stepi} command, described
3971 The @code{step} command only stops at the first instruction of a source
3972 line. This prevents the multiple stops that could otherwise occur in
3973 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3974 to stop if a function that has debugging information is called within
3975 the line. In other words, @code{step} @emph{steps inside} any functions
3976 called within the line.
3978 Also, the @code{step} command only enters a function if there is line
3979 number information for the function. Otherwise it acts like the
3980 @code{next} command. This avoids problems when using @code{cc -gl}
3981 on MIPS machines. Previously, @code{step} entered subroutines if there
3982 was any debugging information about the routine.
3984 @item step @var{count}
3985 Continue running as in @code{step}, but do so @var{count} times. If a
3986 breakpoint is reached, or a signal not related to stepping occurs before
3987 @var{count} steps, stepping stops right away.
3990 @kindex n @r{(@code{next})}
3991 @item next @r{[}@var{count}@r{]}
3992 Continue to the next source line in the current (innermost) stack frame.
3993 This is similar to @code{step}, but function calls that appear within
3994 the line of code are executed without stopping. Execution stops when
3995 control reaches a different line of code at the original stack level
3996 that was executing when you gave the @code{next} command. This command
3997 is abbreviated @code{n}.
3999 An argument @var{count} is a repeat count, as for @code{step}.
4002 @c FIX ME!! Do we delete this, or is there a way it fits in with
4003 @c the following paragraph? --- Vctoria
4005 @c @code{next} within a function that lacks debugging information acts like
4006 @c @code{step}, but any function calls appearing within the code of the
4007 @c function are executed without stopping.
4009 The @code{next} command only stops at the first instruction of a
4010 source line. This prevents multiple stops that could otherwise occur in
4011 @code{switch} statements, @code{for} loops, etc.
4013 @kindex set step-mode
4015 @cindex functions without line info, and stepping
4016 @cindex stepping into functions with no line info
4017 @itemx set step-mode on
4018 The @code{set step-mode on} command causes the @code{step} command to
4019 stop at the first instruction of a function which contains no debug line
4020 information rather than stepping over it.
4022 This is useful in cases where you may be interested in inspecting the
4023 machine instructions of a function which has no symbolic info and do not
4024 want @value{GDBN} to automatically skip over this function.
4026 @item set step-mode off
4027 Causes the @code{step} command to step over any functions which contains no
4028 debug information. This is the default.
4030 @item show step-mode
4031 Show whether @value{GDBN} will stop in or step over functions without
4032 source line debug information.
4036 Continue running until just after function in the selected stack frame
4037 returns. Print the returned value (if any).
4039 Contrast this with the @code{return} command (@pxref{Returning,
4040 ,Returning from a Function}).
4043 @kindex u @r{(@code{until})}
4044 @cindex run until specified location
4047 Continue running until a source line past the current line, in the
4048 current stack frame, is reached. This command is used to avoid single
4049 stepping through a loop more than once. It is like the @code{next}
4050 command, except that when @code{until} encounters a jump, it
4051 automatically continues execution until the program counter is greater
4052 than the address of the jump.
4054 This means that when you reach the end of a loop after single stepping
4055 though it, @code{until} makes your program continue execution until it
4056 exits the loop. In contrast, a @code{next} command at the end of a loop
4057 simply steps back to the beginning of the loop, which forces you to step
4058 through the next iteration.
4060 @code{until} always stops your program if it attempts to exit the current
4063 @code{until} may produce somewhat counterintuitive results if the order
4064 of machine code does not match the order of the source lines. For
4065 example, in the following excerpt from a debugging session, the @code{f}
4066 (@code{frame}) command shows that execution is stopped at line
4067 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4071 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4073 (@value{GDBP}) until
4074 195 for ( ; argc > 0; NEXTARG) @{
4077 This happened because, for execution efficiency, the compiler had
4078 generated code for the loop closure test at the end, rather than the
4079 start, of the loop---even though the test in a C @code{for}-loop is
4080 written before the body of the loop. The @code{until} command appeared
4081 to step back to the beginning of the loop when it advanced to this
4082 expression; however, it has not really gone to an earlier
4083 statement---not in terms of the actual machine code.
4085 @code{until} with no argument works by means of single
4086 instruction stepping, and hence is slower than @code{until} with an
4089 @item until @var{location}
4090 @itemx u @var{location}
4091 Continue running your program until either the specified location is
4092 reached, or the current stack frame returns. @var{location} is any of
4093 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4094 ,Setting Breakpoints}). This form of the command uses breakpoints, and
4095 hence is quicker than @code{until} without an argument. The specified
4096 location is actually reached only if it is in the current frame. This
4097 implies that @code{until} can be used to skip over recursive function
4098 invocations. For instance in the code below, if the current location is
4099 line @code{96}, issuing @code{until 99} will execute the program up to
4100 line @code{99} in the same invocation of factorial, i.e., after the inner
4101 invocations have returned.
4104 94 int factorial (int value)
4106 96 if (value > 1) @{
4107 97 value *= factorial (value - 1);
4114 @kindex advance @var{location}
4115 @itemx advance @var{location}
4116 Continue running the program up to the given @var{location}. An argument is
4117 required, which should be of the same form as arguments for the @code{break}
4118 command. Execution will also stop upon exit from the current stack
4119 frame. This command is similar to @code{until}, but @code{advance} will
4120 not skip over recursive function calls, and the target location doesn't
4121 have to be in the same frame as the current one.
4125 @kindex si @r{(@code{stepi})}
4127 @itemx stepi @var{arg}
4129 Execute one machine instruction, then stop and return to the debugger.
4131 It is often useful to do @samp{display/i $pc} when stepping by machine
4132 instructions. This makes @value{GDBN} automatically display the next
4133 instruction to be executed, each time your program stops. @xref{Auto
4134 Display,, Automatic Display}.
4136 An argument is a repeat count, as in @code{step}.
4140 @kindex ni @r{(@code{nexti})}
4142 @itemx nexti @var{arg}
4144 Execute one machine instruction, but if it is a function call,
4145 proceed until the function returns.
4147 An argument is a repeat count, as in @code{next}.
4154 A signal is an asynchronous event that can happen in a program. The
4155 operating system defines the possible kinds of signals, and gives each
4156 kind a name and a number. For example, in Unix @code{SIGINT} is the
4157 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4158 @code{SIGSEGV} is the signal a program gets from referencing a place in
4159 memory far away from all the areas in use; @code{SIGALRM} occurs when
4160 the alarm clock timer goes off (which happens only if your program has
4161 requested an alarm).
4163 @cindex fatal signals
4164 Some signals, including @code{SIGALRM}, are a normal part of the
4165 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4166 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4167 program has not specified in advance some other way to handle the signal.
4168 @code{SIGINT} does not indicate an error in your program, but it is normally
4169 fatal so it can carry out the purpose of the interrupt: to kill the program.
4171 @value{GDBN} has the ability to detect any occurrence of a signal in your
4172 program. You can tell @value{GDBN} in advance what to do for each kind of
4175 @cindex handling signals
4176 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4177 @code{SIGALRM} be silently passed to your program
4178 (so as not to interfere with their role in the program's functioning)
4179 but to stop your program immediately whenever an error signal happens.
4180 You can change these settings with the @code{handle} command.
4183 @kindex info signals
4187 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4188 handle each one. You can use this to see the signal numbers of all
4189 the defined types of signals.
4191 @item info signals @var{sig}
4192 Similar, but print information only about the specified signal number.
4194 @code{info handle} is an alias for @code{info signals}.
4197 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4198 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4199 can be the number of a signal or its name (with or without the
4200 @samp{SIG} at the beginning); a list of signal numbers of the form
4201 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4202 known signals. Optional arguments @var{keywords}, described below,
4203 say what change to make.
4207 The keywords allowed by the @code{handle} command can be abbreviated.
4208 Their full names are:
4212 @value{GDBN} should not stop your program when this signal happens. It may
4213 still print a message telling you that the signal has come in.
4216 @value{GDBN} should stop your program when this signal happens. This implies
4217 the @code{print} keyword as well.
4220 @value{GDBN} should print a message when this signal happens.
4223 @value{GDBN} should not mention the occurrence of the signal at all. This
4224 implies the @code{nostop} keyword as well.
4228 @value{GDBN} should allow your program to see this signal; your program
4229 can handle the signal, or else it may terminate if the signal is fatal
4230 and not handled. @code{pass} and @code{noignore} are synonyms.
4234 @value{GDBN} should not allow your program to see this signal.
4235 @code{nopass} and @code{ignore} are synonyms.
4239 When a signal stops your program, the signal is not visible to the
4241 continue. Your program sees the signal then, if @code{pass} is in
4242 effect for the signal in question @emph{at that time}. In other words,
4243 after @value{GDBN} reports a signal, you can use the @code{handle}
4244 command with @code{pass} or @code{nopass} to control whether your
4245 program sees that signal when you continue.
4247 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4248 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4249 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4252 You can also use the @code{signal} command to prevent your program from
4253 seeing a signal, or cause it to see a signal it normally would not see,
4254 or to give it any signal at any time. For example, if your program stopped
4255 due to some sort of memory reference error, you might store correct
4256 values into the erroneous variables and continue, hoping to see more
4257 execution; but your program would probably terminate immediately as
4258 a result of the fatal signal once it saw the signal. To prevent this,
4259 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4263 @section Stopping and Starting Multi-thread Programs
4265 When your program has multiple threads (@pxref{Threads,, Debugging
4266 Programs with Multiple Threads}), you can choose whether to set
4267 breakpoints on all threads, or on a particular thread.
4270 @cindex breakpoints and threads
4271 @cindex thread breakpoints
4272 @kindex break @dots{} thread @var{threadno}
4273 @item break @var{linespec} thread @var{threadno}
4274 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4275 @var{linespec} specifies source lines; there are several ways of
4276 writing them, but the effect is always to specify some source line.
4278 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4279 to specify that you only want @value{GDBN} to stop the program when a
4280 particular thread reaches this breakpoint. @var{threadno} is one of the
4281 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4282 column of the @samp{info threads} display.
4284 If you do not specify @samp{thread @var{threadno}} when you set a
4285 breakpoint, the breakpoint applies to @emph{all} threads of your
4288 You can use the @code{thread} qualifier on conditional breakpoints as
4289 well; in this case, place @samp{thread @var{threadno}} before the
4290 breakpoint condition, like this:
4293 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4298 @cindex stopped threads
4299 @cindex threads, stopped
4300 Whenever your program stops under @value{GDBN} for any reason,
4301 @emph{all} threads of execution stop, not just the current thread. This
4302 allows you to examine the overall state of the program, including
4303 switching between threads, without worrying that things may change
4306 @cindex thread breakpoints and system calls
4307 @cindex system calls and thread breakpoints
4308 @cindex premature return from system calls
4309 There is an unfortunate side effect. If one thread stops for a
4310 breakpoint, or for some other reason, and another thread is blocked in a
4311 system call, then the system call may return prematurely. This is a
4312 consequence of the interaction between multiple threads and the signals
4313 that @value{GDBN} uses to implement breakpoints and other events that
4316 To handle this problem, your program should check the return value of
4317 each system call and react appropriately. This is good programming
4320 For example, do not write code like this:
4326 The call to @code{sleep} will return early if a different thread stops
4327 at a breakpoint or for some other reason.
4329 Instead, write this:
4334 unslept = sleep (unslept);
4337 A system call is allowed to return early, so the system is still
4338 conforming to its specification. But @value{GDBN} does cause your
4339 multi-threaded program to behave differently than it would without
4342 Also, @value{GDBN} uses internal breakpoints in the thread library to
4343 monitor certain events such as thread creation and thread destruction.
4344 When such an event happens, a system call in another thread may return
4345 prematurely, even though your program does not appear to stop.
4347 @cindex continuing threads
4348 @cindex threads, continuing
4349 Conversely, whenever you restart the program, @emph{all} threads start
4350 executing. @emph{This is true even when single-stepping} with commands
4351 like @code{step} or @code{next}.
4353 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4354 Since thread scheduling is up to your debugging target's operating
4355 system (not controlled by @value{GDBN}), other threads may
4356 execute more than one statement while the current thread completes a
4357 single step. Moreover, in general other threads stop in the middle of a
4358 statement, rather than at a clean statement boundary, when the program
4361 You might even find your program stopped in another thread after
4362 continuing or even single-stepping. This happens whenever some other
4363 thread runs into a breakpoint, a signal, or an exception before the
4364 first thread completes whatever you requested.
4366 On some OSes, you can lock the OS scheduler and thus allow only a single
4370 @item set scheduler-locking @var{mode}
4371 @cindex scheduler locking mode
4372 @cindex lock scheduler
4373 Set the scheduler locking mode. If it is @code{off}, then there is no
4374 locking and any thread may run at any time. If @code{on}, then only the
4375 current thread may run when the inferior is resumed. The @code{step}
4376 mode optimizes for single-stepping. It stops other threads from
4377 ``seizing the prompt'' by preempting the current thread while you are
4378 stepping. Other threads will only rarely (or never) get a chance to run
4379 when you step. They are more likely to run when you @samp{next} over a
4380 function call, and they are completely free to run when you use commands
4381 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4382 thread hits a breakpoint during its timeslice, they will never steal the
4383 @value{GDBN} prompt away from the thread that you are debugging.
4385 @item show scheduler-locking
4386 Display the current scheduler locking mode.
4391 @chapter Examining the Stack
4393 When your program has stopped, the first thing you need to know is where it
4394 stopped and how it got there.
4397 Each time your program performs a function call, information about the call
4399 That information includes the location of the call in your program,
4400 the arguments of the call,
4401 and the local variables of the function being called.
4402 The information is saved in a block of data called a @dfn{stack frame}.
4403 The stack frames are allocated in a region of memory called the @dfn{call
4406 When your program stops, the @value{GDBN} commands for examining the
4407 stack allow you to see all of this information.
4409 @cindex selected frame
4410 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4411 @value{GDBN} commands refer implicitly to the selected frame. In
4412 particular, whenever you ask @value{GDBN} for the value of a variable in
4413 your program, the value is found in the selected frame. There are
4414 special @value{GDBN} commands to select whichever frame you are
4415 interested in. @xref{Selection, ,Selecting a Frame}.
4417 When your program stops, @value{GDBN} automatically selects the
4418 currently executing frame and describes it briefly, similar to the
4419 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4422 * Frames:: Stack frames
4423 * Backtrace:: Backtraces
4424 * Selection:: Selecting a frame
4425 * Frame Info:: Information on a frame
4430 @section Stack Frames
4432 @cindex frame, definition
4434 The call stack is divided up into contiguous pieces called @dfn{stack
4435 frames}, or @dfn{frames} for short; each frame is the data associated
4436 with one call to one function. The frame contains the arguments given
4437 to the function, the function's local variables, and the address at
4438 which the function is executing.
4440 @cindex initial frame
4441 @cindex outermost frame
4442 @cindex innermost frame
4443 When your program is started, the stack has only one frame, that of the
4444 function @code{main}. This is called the @dfn{initial} frame or the
4445 @dfn{outermost} frame. Each time a function is called, a new frame is
4446 made. Each time a function returns, the frame for that function invocation
4447 is eliminated. If a function is recursive, there can be many frames for
4448 the same function. The frame for the function in which execution is
4449 actually occurring is called the @dfn{innermost} frame. This is the most
4450 recently created of all the stack frames that still exist.
4452 @cindex frame pointer
4453 Inside your program, stack frames are identified by their addresses. A
4454 stack frame consists of many bytes, each of which has its own address; each
4455 kind of computer has a convention for choosing one byte whose
4456 address serves as the address of the frame. Usually this address is kept
4457 in a register called the @dfn{frame pointer register}
4458 (@pxref{Registers, $fp}) while execution is going on in that frame.
4460 @cindex frame number
4461 @value{GDBN} assigns numbers to all existing stack frames, starting with
4462 zero for the innermost frame, one for the frame that called it,
4463 and so on upward. These numbers do not really exist in your program;
4464 they are assigned by @value{GDBN} to give you a way of designating stack
4465 frames in @value{GDBN} commands.
4467 @c The -fomit-frame-pointer below perennially causes hbox overflow
4468 @c underflow problems.
4469 @cindex frameless execution
4470 Some compilers provide a way to compile functions so that they operate
4471 without stack frames. (For example, the @value{NGCC} option
4473 @samp{-fomit-frame-pointer}
4475 generates functions without a frame.)
4476 This is occasionally done with heavily used library functions to save
4477 the frame setup time. @value{GDBN} has limited facilities for dealing
4478 with these function invocations. If the innermost function invocation
4479 has no stack frame, @value{GDBN} nevertheless regards it as though
4480 it had a separate frame, which is numbered zero as usual, allowing
4481 correct tracing of the function call chain. However, @value{GDBN} has
4482 no provision for frameless functions elsewhere in the stack.
4485 @kindex frame@r{, command}
4486 @cindex current stack frame
4487 @item frame @var{args}
4488 The @code{frame} command allows you to move from one stack frame to another,
4489 and to print the stack frame you select. @var{args} may be either the
4490 address of the frame or the stack frame number. Without an argument,
4491 @code{frame} prints the current stack frame.
4493 @kindex select-frame
4494 @cindex selecting frame silently
4496 The @code{select-frame} command allows you to move from one stack frame
4497 to another without printing the frame. This is the silent version of
4505 @cindex call stack traces
4506 A backtrace is a summary of how your program got where it is. It shows one
4507 line per frame, for many frames, starting with the currently executing
4508 frame (frame zero), followed by its caller (frame one), and on up the
4513 @kindex bt @r{(@code{backtrace})}
4516 Print a backtrace of the entire stack: one line per frame for all
4517 frames in the stack.
4519 You can stop the backtrace at any time by typing the system interrupt
4520 character, normally @kbd{Ctrl-c}.
4522 @item backtrace @var{n}
4524 Similar, but print only the innermost @var{n} frames.
4526 @item backtrace -@var{n}
4528 Similar, but print only the outermost @var{n} frames.
4530 @item backtrace full
4532 @itemx bt full @var{n}
4533 @itemx bt full -@var{n}
4534 Print the values of the local variables also. @var{n} specifies the
4535 number of frames to print, as described above.
4540 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4541 are additional aliases for @code{backtrace}.
4543 @cindex multiple threads, backtrace
4544 In a multi-threaded program, @value{GDBN} by default shows the
4545 backtrace only for the current thread. To display the backtrace for
4546 several or all of the threads, use the command @code{thread apply}
4547 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4548 apply all backtrace}, @value{GDBN} will display the backtrace for all
4549 the threads; this is handy when you debug a core dump of a
4550 multi-threaded program.
4552 Each line in the backtrace shows the frame number and the function name.
4553 The program counter value is also shown---unless you use @code{set
4554 print address off}. The backtrace also shows the source file name and
4555 line number, as well as the arguments to the function. The program
4556 counter value is omitted if it is at the beginning of the code for that
4559 Here is an example of a backtrace. It was made with the command
4560 @samp{bt 3}, so it shows the innermost three frames.
4564 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4566 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4567 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4569 (More stack frames follow...)
4574 The display for frame zero does not begin with a program counter
4575 value, indicating that your program has stopped at the beginning of the
4576 code for line @code{993} of @code{builtin.c}.
4578 @cindex value optimized out, in backtrace
4579 @cindex function call arguments, optimized out
4580 If your program was compiled with optimizations, some compilers will
4581 optimize away arguments passed to functions if those arguments are
4582 never used after the call. Such optimizations generate code that
4583 passes arguments through registers, but doesn't store those arguments
4584 in the stack frame. @value{GDBN} has no way of displaying such
4585 arguments in stack frames other than the innermost one. Here's what
4586 such a backtrace might look like:
4590 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4592 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4593 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4595 (More stack frames follow...)
4600 The values of arguments that were not saved in their stack frames are
4601 shown as @samp{<value optimized out>}.
4603 If you need to display the values of such optimized-out arguments,
4604 either deduce that from other variables whose values depend on the one
4605 you are interested in, or recompile without optimizations.
4607 @cindex backtrace beyond @code{main} function
4608 @cindex program entry point
4609 @cindex startup code, and backtrace
4610 Most programs have a standard user entry point---a place where system
4611 libraries and startup code transition into user code. For C this is
4612 @code{main}@footnote{
4613 Note that embedded programs (the so-called ``free-standing''
4614 environment) are not required to have a @code{main} function as the
4615 entry point. They could even have multiple entry points.}.
4616 When @value{GDBN} finds the entry function in a backtrace
4617 it will terminate the backtrace, to avoid tracing into highly
4618 system-specific (and generally uninteresting) code.
4620 If you need to examine the startup code, or limit the number of levels
4621 in a backtrace, you can change this behavior:
4624 @item set backtrace past-main
4625 @itemx set backtrace past-main on
4626 @kindex set backtrace
4627 Backtraces will continue past the user entry point.
4629 @item set backtrace past-main off
4630 Backtraces will stop when they encounter the user entry point. This is the
4633 @item show backtrace past-main
4634 @kindex show backtrace
4635 Display the current user entry point backtrace policy.
4637 @item set backtrace past-entry
4638 @itemx set backtrace past-entry on
4639 Backtraces will continue past the internal entry point of an application.
4640 This entry point is encoded by the linker when the application is built,
4641 and is likely before the user entry point @code{main} (or equivalent) is called.
4643 @item set backtrace past-entry off
4644 Backtraces will stop when they encounter the internal entry point of an
4645 application. This is the default.
4647 @item show backtrace past-entry
4648 Display the current internal entry point backtrace policy.
4650 @item set backtrace limit @var{n}
4651 @itemx set backtrace limit 0
4652 @cindex backtrace limit
4653 Limit the backtrace to @var{n} levels. A value of zero means
4656 @item show backtrace limit
4657 Display the current limit on backtrace levels.
4661 @section Selecting a Frame
4663 Most commands for examining the stack and other data in your program work on
4664 whichever stack frame is selected at the moment. Here are the commands for
4665 selecting a stack frame; all of them finish by printing a brief description
4666 of the stack frame just selected.
4669 @kindex frame@r{, selecting}
4670 @kindex f @r{(@code{frame})}
4673 Select frame number @var{n}. Recall that frame zero is the innermost
4674 (currently executing) frame, frame one is the frame that called the
4675 innermost one, and so on. The highest-numbered frame is the one for
4678 @item frame @var{addr}
4680 Select the frame at address @var{addr}. This is useful mainly if the
4681 chaining of stack frames has been damaged by a bug, making it
4682 impossible for @value{GDBN} to assign numbers properly to all frames. In
4683 addition, this can be useful when your program has multiple stacks and
4684 switches between them.
4686 On the SPARC architecture, @code{frame} needs two addresses to
4687 select an arbitrary frame: a frame pointer and a stack pointer.
4689 On the MIPS and Alpha architecture, it needs two addresses: a stack
4690 pointer and a program counter.
4692 On the 29k architecture, it needs three addresses: a register stack
4693 pointer, a program counter, and a memory stack pointer.
4697 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4698 advances toward the outermost frame, to higher frame numbers, to frames
4699 that have existed longer. @var{n} defaults to one.
4702 @kindex do @r{(@code{down})}
4704 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4705 advances toward the innermost frame, to lower frame numbers, to frames
4706 that were created more recently. @var{n} defaults to one. You may
4707 abbreviate @code{down} as @code{do}.
4710 All of these commands end by printing two lines of output describing the
4711 frame. The first line shows the frame number, the function name, the
4712 arguments, and the source file and line number of execution in that
4713 frame. The second line shows the text of that source line.
4721 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4723 10 read_input_file (argv[i]);
4727 After such a printout, the @code{list} command with no arguments
4728 prints ten lines centered on the point of execution in the frame.
4729 You can also edit the program at the point of execution with your favorite
4730 editing program by typing @code{edit}.
4731 @xref{List, ,Printing Source Lines},
4735 @kindex down-silently
4737 @item up-silently @var{n}
4738 @itemx down-silently @var{n}
4739 These two commands are variants of @code{up} and @code{down},
4740 respectively; they differ in that they do their work silently, without
4741 causing display of the new frame. They are intended primarily for use
4742 in @value{GDBN} command scripts, where the output might be unnecessary and
4747 @section Information About a Frame
4749 There are several other commands to print information about the selected
4755 When used without any argument, this command does not change which
4756 frame is selected, but prints a brief description of the currently
4757 selected stack frame. It can be abbreviated @code{f}. With an
4758 argument, this command is used to select a stack frame.
4759 @xref{Selection, ,Selecting a Frame}.
4762 @kindex info f @r{(@code{info frame})}
4765 This command prints a verbose description of the selected stack frame,
4770 the address of the frame
4772 the address of the next frame down (called by this frame)
4774 the address of the next frame up (caller of this frame)
4776 the language in which the source code corresponding to this frame is written
4778 the address of the frame's arguments
4780 the address of the frame's local variables
4782 the program counter saved in it (the address of execution in the caller frame)
4784 which registers were saved in the frame
4787 @noindent The verbose description is useful when
4788 something has gone wrong that has made the stack format fail to fit
4789 the usual conventions.
4791 @item info frame @var{addr}
4792 @itemx info f @var{addr}
4793 Print a verbose description of the frame at address @var{addr}, without
4794 selecting that frame. The selected frame remains unchanged by this
4795 command. This requires the same kind of address (more than one for some
4796 architectures) that you specify in the @code{frame} command.
4797 @xref{Selection, ,Selecting a Frame}.
4801 Print the arguments of the selected frame, each on a separate line.
4805 Print the local variables of the selected frame, each on a separate
4806 line. These are all variables (declared either static or automatic)
4807 accessible at the point of execution of the selected frame.
4810 @cindex catch exceptions, list active handlers
4811 @cindex exception handlers, how to list
4813 Print a list of all the exception handlers that are active in the
4814 current stack frame at the current point of execution. To see other
4815 exception handlers, visit the associated frame (using the @code{up},
4816 @code{down}, or @code{frame} commands); then type @code{info catch}.
4817 @xref{Set Catchpoints, , Setting Catchpoints}.
4823 @chapter Examining Source Files
4825 @value{GDBN} can print parts of your program's source, since the debugging
4826 information recorded in the program tells @value{GDBN} what source files were
4827 used to build it. When your program stops, @value{GDBN} spontaneously prints
4828 the line where it stopped. Likewise, when you select a stack frame
4829 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4830 execution in that frame has stopped. You can print other portions of
4831 source files by explicit command.
4833 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4834 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4835 @value{GDBN} under @sc{gnu} Emacs}.
4838 * List:: Printing source lines
4839 * Edit:: Editing source files
4840 * Search:: Searching source files
4841 * Source Path:: Specifying source directories
4842 * Machine Code:: Source and machine code
4846 @section Printing Source Lines
4849 @kindex l @r{(@code{list})}
4850 To print lines from a source file, use the @code{list} command
4851 (abbreviated @code{l}). By default, ten lines are printed.
4852 There are several ways to specify what part of the file you want to print.
4854 Here are the forms of the @code{list} command most commonly used:
4857 @item list @var{linenum}
4858 Print lines centered around line number @var{linenum} in the
4859 current source file.
4861 @item list @var{function}
4862 Print lines centered around the beginning of function
4866 Print more lines. If the last lines printed were printed with a
4867 @code{list} command, this prints lines following the last lines
4868 printed; however, if the last line printed was a solitary line printed
4869 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4870 Stack}), this prints lines centered around that line.
4873 Print lines just before the lines last printed.
4876 @cindex @code{list}, how many lines to display
4877 By default, @value{GDBN} prints ten source lines with any of these forms of
4878 the @code{list} command. You can change this using @code{set listsize}:
4881 @kindex set listsize
4882 @item set listsize @var{count}
4883 Make the @code{list} command display @var{count} source lines (unless
4884 the @code{list} argument explicitly specifies some other number).
4886 @kindex show listsize
4888 Display the number of lines that @code{list} prints.
4891 Repeating a @code{list} command with @key{RET} discards the argument,
4892 so it is equivalent to typing just @code{list}. This is more useful
4893 than listing the same lines again. An exception is made for an
4894 argument of @samp{-}; that argument is preserved in repetition so that
4895 each repetition moves up in the source file.
4898 In general, the @code{list} command expects you to supply zero, one or two
4899 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4900 of writing them, but the effect is always to specify some source line.
4901 Here is a complete description of the possible arguments for @code{list}:
4904 @item list @var{linespec}
4905 Print lines centered around the line specified by @var{linespec}.
4907 @item list @var{first},@var{last}
4908 Print lines from @var{first} to @var{last}. Both arguments are
4911 @item list ,@var{last}
4912 Print lines ending with @var{last}.
4914 @item list @var{first},
4915 Print lines starting with @var{first}.
4918 Print lines just after the lines last printed.
4921 Print lines just before the lines last printed.
4924 As described in the preceding table.
4927 Here are the ways of specifying a single source line---all the
4932 Specifies line @var{number} of the current source file.
4933 When a @code{list} command has two linespecs, this refers to
4934 the same source file as the first linespec.
4937 Specifies the line @var{offset} lines after the last line printed.
4938 When used as the second linespec in a @code{list} command that has
4939 two, this specifies the line @var{offset} lines down from the
4943 Specifies the line @var{offset} lines before the last line printed.
4945 @item @var{filename}:@var{number}
4946 Specifies line @var{number} in the source file @var{filename}.
4948 @item @var{function}
4949 Specifies the line that begins the body of the function @var{function}.
4950 For example: in C, this is the line with the open brace.
4952 @item @var{filename}:@var{function}
4953 Specifies the line of the open-brace that begins the body of the
4954 function @var{function} in the file @var{filename}. You only need the
4955 file name with a function name to avoid ambiguity when there are
4956 identically named functions in different source files.
4958 @item *@var{address}
4959 Specifies the line containing the program address @var{address}.
4960 @var{address} may be any expression.
4964 @section Editing Source Files
4965 @cindex editing source files
4968 @kindex e @r{(@code{edit})}
4969 To edit the lines in a source file, use the @code{edit} command.
4970 The editing program of your choice
4971 is invoked with the current line set to
4972 the active line in the program.
4973 Alternatively, there are several ways to specify what part of the file you
4974 want to print if you want to see other parts of the program.
4976 Here are the forms of the @code{edit} command most commonly used:
4980 Edit the current source file at the active line number in the program.
4982 @item edit @var{number}
4983 Edit the current source file with @var{number} as the active line number.
4985 @item edit @var{function}
4986 Edit the file containing @var{function} at the beginning of its definition.
4988 @item edit @var{filename}:@var{number}
4989 Specifies line @var{number} in the source file @var{filename}.
4991 @item edit @var{filename}:@var{function}
4992 Specifies the line that begins the body of the
4993 function @var{function} in the file @var{filename}. You only need the
4994 file name with a function name to avoid ambiguity when there are
4995 identically named functions in different source files.
4997 @item edit *@var{address}
4998 Specifies the line containing the program address @var{address}.
4999 @var{address} may be any expression.
5002 @subsection Choosing your Editor
5003 You can customize @value{GDBN} to use any editor you want
5005 The only restriction is that your editor (say @code{ex}), recognizes the
5006 following command-line syntax:
5008 ex +@var{number} file
5010 The optional numeric value +@var{number} specifies the number of the line in
5011 the file where to start editing.}.
5012 By default, it is @file{@value{EDITOR}}, but you can change this
5013 by setting the environment variable @code{EDITOR} before using
5014 @value{GDBN}. For example, to configure @value{GDBN} to use the
5015 @code{vi} editor, you could use these commands with the @code{sh} shell:
5021 or in the @code{csh} shell,
5023 setenv EDITOR /usr/bin/vi
5028 @section Searching Source Files
5029 @cindex searching source files
5031 There are two commands for searching through the current source file for a
5036 @kindex forward-search
5037 @item forward-search @var{regexp}
5038 @itemx search @var{regexp}
5039 The command @samp{forward-search @var{regexp}} checks each line,
5040 starting with the one following the last line listed, for a match for
5041 @var{regexp}. It lists the line that is found. You can use the
5042 synonym @samp{search @var{regexp}} or abbreviate the command name as
5045 @kindex reverse-search
5046 @item reverse-search @var{regexp}
5047 The command @samp{reverse-search @var{regexp}} checks each line, starting
5048 with the one before the last line listed and going backward, for a match
5049 for @var{regexp}. It lists the line that is found. You can abbreviate
5050 this command as @code{rev}.
5054 @section Specifying Source Directories
5057 @cindex directories for source files
5058 Executable programs sometimes do not record the directories of the source
5059 files from which they were compiled, just the names. Even when they do,
5060 the directories could be moved between the compilation and your debugging
5061 session. @value{GDBN} has a list of directories to search for source files;
5062 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5063 it tries all the directories in the list, in the order they are present
5064 in the list, until it finds a file with the desired name.
5066 For example, suppose an executable references the file
5067 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5068 @file{/mnt/cross}. The file is first looked up literally; if this
5069 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5070 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5071 message is printed. @value{GDBN} does not look up the parts of the
5072 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5073 Likewise, the subdirectories of the source path are not searched: if
5074 the source path is @file{/mnt/cross}, and the binary refers to
5075 @file{foo.c}, @value{GDBN} would not find it under
5076 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5078 Plain file names, relative file names with leading directories, file
5079 names containing dots, etc.@: are all treated as described above; for
5080 instance, if the source path is @file{/mnt/cross}, and the source file
5081 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5082 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5083 that---@file{/mnt/cross/foo.c}.
5085 Note that the executable search path is @emph{not} used to locate the
5088 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5089 any information it has cached about where source files are found and where
5090 each line is in the file.
5094 When you start @value{GDBN}, its source path includes only @samp{cdir}
5095 and @samp{cwd}, in that order.
5096 To add other directories, use the @code{directory} command.
5098 The search path is used to find both program source files and @value{GDBN}
5099 script files (read using the @samp{-command} option and @samp{source} command).
5101 In addition to the source path, @value{GDBN} provides a set of commands
5102 that manage a list of source path substitution rules. A @dfn{substitution
5103 rule} specifies how to rewrite source directories stored in the program's
5104 debug information in case the sources were moved to a different
5105 directory between compilation and debugging. A rule is made of
5106 two strings, the first specifying what needs to be rewritten in
5107 the path, and the second specifying how it should be rewritten.
5108 In @ref{set substitute-path}, we name these two parts @var{from} and
5109 @var{to} respectively. @value{GDBN} does a simple string replacement
5110 of @var{from} with @var{to} at the start of the directory part of the
5111 source file name, and uses that result instead of the original file
5112 name to look up the sources.
5114 Using the previous example, suppose the @file{foo-1.0} tree has been
5115 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5116 @value{GDBN} to replace @file{/usr/src} in all source path names with
5117 @file{/mnt/cross}. The first lookup will then be
5118 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5119 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5120 substitution rule, use the @code{set substitute-path} command
5121 (@pxref{set substitute-path}).
5123 To avoid unexpected substitution results, a rule is applied only if the
5124 @var{from} part of the directory name ends at a directory separator.
5125 For instance, a rule substituting @file{/usr/source} into
5126 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5127 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5128 is applied only at the beginning of the directory name, this rule will
5129 not be applied to @file{/root/usr/source/baz.c} either.
5131 In many cases, you can achieve the same result using the @code{directory}
5132 command. However, @code{set substitute-path} can be more efficient in
5133 the case where the sources are organized in a complex tree with multiple
5134 subdirectories. With the @code{directory} command, you need to add each
5135 subdirectory of your project. If you moved the entire tree while
5136 preserving its internal organization, then @code{set substitute-path}
5137 allows you to direct the debugger to all the sources with one single
5140 @code{set substitute-path} is also more than just a shortcut command.
5141 The source path is only used if the file at the original location no
5142 longer exists. On the other hand, @code{set substitute-path} modifies
5143 the debugger behavior to look at the rewritten location instead. So, if
5144 for any reason a source file that is not relevant to your executable is
5145 located at the original location, a substitution rule is the only
5146 method available to point @value{GDBN} at the new location.
5149 @item directory @var{dirname} @dots{}
5150 @item dir @var{dirname} @dots{}
5151 Add directory @var{dirname} to the front of the source path. Several
5152 directory names may be given to this command, separated by @samp{:}
5153 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5154 part of absolute file names) or
5155 whitespace. You may specify a directory that is already in the source
5156 path; this moves it forward, so @value{GDBN} searches it sooner.
5160 @vindex $cdir@r{, convenience variable}
5161 @vindex $cwd@r{, convenience variable}
5162 @cindex compilation directory
5163 @cindex current directory
5164 @cindex working directory
5165 @cindex directory, current
5166 @cindex directory, compilation
5167 You can use the string @samp{$cdir} to refer to the compilation
5168 directory (if one is recorded), and @samp{$cwd} to refer to the current
5169 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5170 tracks the current working directory as it changes during your @value{GDBN}
5171 session, while the latter is immediately expanded to the current
5172 directory at the time you add an entry to the source path.
5175 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5177 @c RET-repeat for @code{directory} is explicitly disabled, but since
5178 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5180 @item show directories
5181 @kindex show directories
5182 Print the source path: show which directories it contains.
5184 @anchor{set substitute-path}
5185 @item set substitute-path @var{from} @var{to}
5186 @kindex set substitute-path
5187 Define a source path substitution rule, and add it at the end of the
5188 current list of existing substitution rules. If a rule with the same
5189 @var{from} was already defined, then the old rule is also deleted.
5191 For example, if the file @file{/foo/bar/baz.c} was moved to
5192 @file{/mnt/cross/baz.c}, then the command
5195 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5199 will tell @value{GDBN} to replace @samp{/usr/src} with
5200 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5201 @file{baz.c} even though it was moved.
5203 In the case when more than one substitution rule have been defined,
5204 the rules are evaluated one by one in the order where they have been
5205 defined. The first one matching, if any, is selected to perform
5208 For instance, if we had entered the following commands:
5211 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5212 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5216 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5217 @file{/mnt/include/defs.h} by using the first rule. However, it would
5218 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5219 @file{/mnt/src/lib/foo.c}.
5222 @item unset substitute-path [path]
5223 @kindex unset substitute-path
5224 If a path is specified, search the current list of substitution rules
5225 for a rule that would rewrite that path. Delete that rule if found.
5226 A warning is emitted by the debugger if no rule could be found.
5228 If no path is specified, then all substitution rules are deleted.
5230 @item show substitute-path [path]
5231 @kindex show substitute-path
5232 If a path is specified, then print the source path substitution rule
5233 which would rewrite that path, if any.
5235 If no path is specified, then print all existing source path substitution
5240 If your source path is cluttered with directories that are no longer of
5241 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5242 versions of source. You can correct the situation as follows:
5246 Use @code{directory} with no argument to reset the source path to its default value.
5249 Use @code{directory} with suitable arguments to reinstall the
5250 directories you want in the source path. You can add all the
5251 directories in one command.
5255 @section Source and Machine Code
5256 @cindex source line and its code address
5258 You can use the command @code{info line} to map source lines to program
5259 addresses (and vice versa), and the command @code{disassemble} to display
5260 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5261 mode, the @code{info line} command causes the arrow to point to the
5262 line specified. Also, @code{info line} prints addresses in symbolic form as
5267 @item info line @var{linespec}
5268 Print the starting and ending addresses of the compiled code for
5269 source line @var{linespec}. You can specify source lines in any of
5270 the ways understood by the @code{list} command (@pxref{List, ,Printing
5274 For example, we can use @code{info line} to discover the location of
5275 the object code for the first line of function
5276 @code{m4_changequote}:
5278 @c FIXME: I think this example should also show the addresses in
5279 @c symbolic form, as they usually would be displayed.
5281 (@value{GDBP}) info line m4_changequote
5282 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5286 @cindex code address and its source line
5287 We can also inquire (using @code{*@var{addr}} as the form for
5288 @var{linespec}) what source line covers a particular address:
5290 (@value{GDBP}) info line *0x63ff
5291 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5294 @cindex @code{$_} and @code{info line}
5295 @cindex @code{x} command, default address
5296 @kindex x@r{(examine), and} info line
5297 After @code{info line}, the default address for the @code{x} command
5298 is changed to the starting address of the line, so that @samp{x/i} is
5299 sufficient to begin examining the machine code (@pxref{Memory,
5300 ,Examining Memory}). Also, this address is saved as the value of the
5301 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5306 @cindex assembly instructions
5307 @cindex instructions, assembly
5308 @cindex machine instructions
5309 @cindex listing machine instructions
5311 This specialized command dumps a range of memory as machine
5312 instructions. The default memory range is the function surrounding the
5313 program counter of the selected frame. A single argument to this
5314 command is a program counter value; @value{GDBN} dumps the function
5315 surrounding this value. Two arguments specify a range of addresses
5316 (first inclusive, second exclusive) to dump.
5319 The following example shows the disassembly of a range of addresses of
5320 HP PA-RISC 2.0 code:
5323 (@value{GDBP}) disas 0x32c4 0x32e4
5324 Dump of assembler code from 0x32c4 to 0x32e4:
5325 0x32c4 <main+204>: addil 0,dp
5326 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5327 0x32cc <main+212>: ldil 0x3000,r31
5328 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5329 0x32d4 <main+220>: ldo 0(r31),rp
5330 0x32d8 <main+224>: addil -0x800,dp
5331 0x32dc <main+228>: ldo 0x588(r1),r26
5332 0x32e0 <main+232>: ldil 0x3000,r31
5333 End of assembler dump.
5336 Some architectures have more than one commonly-used set of instruction
5337 mnemonics or other syntax.
5339 For programs that were dynamically linked and use shared libraries,
5340 instructions that call functions or branch to locations in the shared
5341 libraries might show a seemingly bogus location---it's actually a
5342 location of the relocation table. On some architectures, @value{GDBN}
5343 might be able to resolve these to actual function names.
5346 @kindex set disassembly-flavor
5347 @cindex Intel disassembly flavor
5348 @cindex AT&T disassembly flavor
5349 @item set disassembly-flavor @var{instruction-set}
5350 Select the instruction set to use when disassembling the
5351 program via the @code{disassemble} or @code{x/i} commands.
5353 Currently this command is only defined for the Intel x86 family. You
5354 can set @var{instruction-set} to either @code{intel} or @code{att}.
5355 The default is @code{att}, the AT&T flavor used by default by Unix
5356 assemblers for x86-based targets.
5358 @kindex show disassembly-flavor
5359 @item show disassembly-flavor
5360 Show the current setting of the disassembly flavor.
5365 @chapter Examining Data
5367 @cindex printing data
5368 @cindex examining data
5371 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5372 @c document because it is nonstandard... Under Epoch it displays in a
5373 @c different window or something like that.
5374 The usual way to examine data in your program is with the @code{print}
5375 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5376 evaluates and prints the value of an expression of the language your
5377 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5378 Different Languages}).
5381 @item print @var{expr}
5382 @itemx print /@var{f} @var{expr}
5383 @var{expr} is an expression (in the source language). By default the
5384 value of @var{expr} is printed in a format appropriate to its data type;
5385 you can choose a different format by specifying @samp{/@var{f}}, where
5386 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5390 @itemx print /@var{f}
5391 @cindex reprint the last value
5392 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5393 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5394 conveniently inspect the same value in an alternative format.
5397 A more low-level way of examining data is with the @code{x} command.
5398 It examines data in memory at a specified address and prints it in a
5399 specified format. @xref{Memory, ,Examining Memory}.
5401 If you are interested in information about types, or about how the
5402 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5403 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5407 * Expressions:: Expressions
5408 * Variables:: Program variables
5409 * Arrays:: Artificial arrays
5410 * Output Formats:: Output formats
5411 * Memory:: Examining memory
5412 * Auto Display:: Automatic display
5413 * Print Settings:: Print settings
5414 * Value History:: Value history
5415 * Convenience Vars:: Convenience variables
5416 * Registers:: Registers
5417 * Floating Point Hardware:: Floating point hardware
5418 * Vector Unit:: Vector Unit
5419 * OS Information:: Auxiliary data provided by operating system
5420 * Memory Region Attributes:: Memory region attributes
5421 * Dump/Restore Files:: Copy between memory and a file
5422 * Core File Generation:: Cause a program dump its core
5423 * Character Sets:: Debugging programs that use a different
5424 character set than GDB does
5425 * Caching Remote Data:: Data caching for remote targets
5429 @section Expressions
5432 @code{print} and many other @value{GDBN} commands accept an expression and
5433 compute its value. Any kind of constant, variable or operator defined
5434 by the programming language you are using is valid in an expression in
5435 @value{GDBN}. This includes conditional expressions, function calls,
5436 casts, and string constants. It also includes preprocessor macros, if
5437 you compiled your program to include this information; see
5440 @cindex arrays in expressions
5441 @value{GDBN} supports array constants in expressions input by
5442 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5443 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5444 memory that is @code{malloc}ed in the target program.
5446 Because C is so widespread, most of the expressions shown in examples in
5447 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5448 Languages}, for information on how to use expressions in other
5451 In this section, we discuss operators that you can use in @value{GDBN}
5452 expressions regardless of your programming language.
5454 @cindex casts, in expressions
5455 Casts are supported in all languages, not just in C, because it is so
5456 useful to cast a number into a pointer in order to examine a structure
5457 at that address in memory.
5458 @c FIXME: casts supported---Mod2 true?
5460 @value{GDBN} supports these operators, in addition to those common
5461 to programming languages:
5465 @samp{@@} is a binary operator for treating parts of memory as arrays.
5466 @xref{Arrays, ,Artificial Arrays}, for more information.
5469 @samp{::} allows you to specify a variable in terms of the file or
5470 function where it is defined. @xref{Variables, ,Program Variables}.
5472 @cindex @{@var{type}@}
5473 @cindex type casting memory
5474 @cindex memory, viewing as typed object
5475 @cindex casts, to view memory
5476 @item @{@var{type}@} @var{addr}
5477 Refers to an object of type @var{type} stored at address @var{addr} in
5478 memory. @var{addr} may be any expression whose value is an integer or
5479 pointer (but parentheses are required around binary operators, just as in
5480 a cast). This construct is allowed regardless of what kind of data is
5481 normally supposed to reside at @var{addr}.
5485 @section Program Variables
5487 The most common kind of expression to use is the name of a variable
5490 Variables in expressions are understood in the selected stack frame
5491 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5495 global (or file-static)
5502 visible according to the scope rules of the
5503 programming language from the point of execution in that frame
5506 @noindent This means that in the function
5521 you can examine and use the variable @code{a} whenever your program is
5522 executing within the function @code{foo}, but you can only use or
5523 examine the variable @code{b} while your program is executing inside
5524 the block where @code{b} is declared.
5526 @cindex variable name conflict
5527 There is an exception: you can refer to a variable or function whose
5528 scope is a single source file even if the current execution point is not
5529 in this file. But it is possible to have more than one such variable or
5530 function with the same name (in different source files). If that
5531 happens, referring to that name has unpredictable effects. If you wish,
5532 you can specify a static variable in a particular function or file,
5533 using the colon-colon (@code{::}) notation:
5535 @cindex colon-colon, context for variables/functions
5537 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5538 @cindex @code{::}, context for variables/functions
5541 @var{file}::@var{variable}
5542 @var{function}::@var{variable}
5546 Here @var{file} or @var{function} is the name of the context for the
5547 static @var{variable}. In the case of file names, you can use quotes to
5548 make sure @value{GDBN} parses the file name as a single word---for example,
5549 to print a global value of @code{x} defined in @file{f2.c}:
5552 (@value{GDBP}) p 'f2.c'::x
5555 @cindex C@t{++} scope resolution
5556 This use of @samp{::} is very rarely in conflict with the very similar
5557 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5558 scope resolution operator in @value{GDBN} expressions.
5559 @c FIXME: Um, so what happens in one of those rare cases where it's in
5562 @cindex wrong values
5563 @cindex variable values, wrong
5564 @cindex function entry/exit, wrong values of variables
5565 @cindex optimized code, wrong values of variables
5567 @emph{Warning:} Occasionally, a local variable may appear to have the
5568 wrong value at certain points in a function---just after entry to a new
5569 scope, and just before exit.
5571 You may see this problem when you are stepping by machine instructions.
5572 This is because, on most machines, it takes more than one instruction to
5573 set up a stack frame (including local variable definitions); if you are
5574 stepping by machine instructions, variables may appear to have the wrong
5575 values until the stack frame is completely built. On exit, it usually
5576 also takes more than one machine instruction to destroy a stack frame;
5577 after you begin stepping through that group of instructions, local
5578 variable definitions may be gone.
5580 This may also happen when the compiler does significant optimizations.
5581 To be sure of always seeing accurate values, turn off all optimization
5584 @cindex ``No symbol "foo" in current context''
5585 Another possible effect of compiler optimizations is to optimize
5586 unused variables out of existence, or assign variables to registers (as
5587 opposed to memory addresses). Depending on the support for such cases
5588 offered by the debug info format used by the compiler, @value{GDBN}
5589 might not be able to display values for such local variables. If that
5590 happens, @value{GDBN} will print a message like this:
5593 No symbol "foo" in current context.
5596 To solve such problems, either recompile without optimizations, or use a
5597 different debug info format, if the compiler supports several such
5598 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5599 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5600 produces debug info in a format that is superior to formats such as
5601 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5602 an effective form for debug info. @xref{Debugging Options,,Options
5603 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5604 Compiler Collection (GCC)}.
5605 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5606 that are best suited to C@t{++} programs.
5608 If you ask to print an object whose contents are unknown to
5609 @value{GDBN}, e.g., because its data type is not completely specified
5610 by the debug information, @value{GDBN} will say @samp{<incomplete
5611 type>}. @xref{Symbols, incomplete type}, for more about this.
5613 Strings are identified as arrays of @code{char} values without specified
5614 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5615 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5616 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5617 defines literal string type @code{"char"} as @code{char} without a sign.
5622 signed char var1[] = "A";
5625 You get during debugging
5630 $2 = @{65 'A', 0 '\0'@}
5634 @section Artificial Arrays
5636 @cindex artificial array
5638 @kindex @@@r{, referencing memory as an array}
5639 It is often useful to print out several successive objects of the
5640 same type in memory; a section of an array, or an array of
5641 dynamically determined size for which only a pointer exists in the
5644 You can do this by referring to a contiguous span of memory as an
5645 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5646 operand of @samp{@@} should be the first element of the desired array
5647 and be an individual object. The right operand should be the desired length
5648 of the array. The result is an array value whose elements are all of
5649 the type of the left argument. The first element is actually the left
5650 argument; the second element comes from bytes of memory immediately
5651 following those that hold the first element, and so on. Here is an
5652 example. If a program says
5655 int *array = (int *) malloc (len * sizeof (int));
5659 you can print the contents of @code{array} with
5665 The left operand of @samp{@@} must reside in memory. Array values made
5666 with @samp{@@} in this way behave just like other arrays in terms of
5667 subscripting, and are coerced to pointers when used in expressions.
5668 Artificial arrays most often appear in expressions via the value history
5669 (@pxref{Value History, ,Value History}), after printing one out.
5671 Another way to create an artificial array is to use a cast.
5672 This re-interprets a value as if it were an array.
5673 The value need not be in memory:
5675 (@value{GDBP}) p/x (short[2])0x12345678
5676 $1 = @{0x1234, 0x5678@}
5679 As a convenience, if you leave the array length out (as in
5680 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5681 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5683 (@value{GDBP}) p/x (short[])0x12345678
5684 $2 = @{0x1234, 0x5678@}
5687 Sometimes the artificial array mechanism is not quite enough; in
5688 moderately complex data structures, the elements of interest may not
5689 actually be adjacent---for example, if you are interested in the values
5690 of pointers in an array. One useful work-around in this situation is
5691 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5692 Variables}) as a counter in an expression that prints the first
5693 interesting value, and then repeat that expression via @key{RET}. For
5694 instance, suppose you have an array @code{dtab} of pointers to
5695 structures, and you are interested in the values of a field @code{fv}
5696 in each structure. Here is an example of what you might type:
5706 @node Output Formats
5707 @section Output Formats
5709 @cindex formatted output
5710 @cindex output formats
5711 By default, @value{GDBN} prints a value according to its data type. Sometimes
5712 this is not what you want. For example, you might want to print a number
5713 in hex, or a pointer in decimal. Or you might want to view data in memory
5714 at a certain address as a character string or as an instruction. To do
5715 these things, specify an @dfn{output format} when you print a value.
5717 The simplest use of output formats is to say how to print a value
5718 already computed. This is done by starting the arguments of the
5719 @code{print} command with a slash and a format letter. The format
5720 letters supported are:
5724 Regard the bits of the value as an integer, and print the integer in
5728 Print as integer in signed decimal.
5731 Print as integer in unsigned decimal.
5734 Print as integer in octal.
5737 Print as integer in binary. The letter @samp{t} stands for ``two''.
5738 @footnote{@samp{b} cannot be used because these format letters are also
5739 used with the @code{x} command, where @samp{b} stands for ``byte'';
5740 see @ref{Memory,,Examining Memory}.}
5743 @cindex unknown address, locating
5744 @cindex locate address
5745 Print as an address, both absolute in hexadecimal and as an offset from
5746 the nearest preceding symbol. You can use this format used to discover
5747 where (in what function) an unknown address is located:
5750 (@value{GDBP}) p/a 0x54320
5751 $3 = 0x54320 <_initialize_vx+396>
5755 The command @code{info symbol 0x54320} yields similar results.
5756 @xref{Symbols, info symbol}.
5759 Regard as an integer and print it as a character constant. This
5760 prints both the numerical value and its character representation. The
5761 character representation is replaced with the octal escape @samp{\nnn}
5762 for characters outside the 7-bit @sc{ascii} range.
5765 Regard the bits of the value as a floating point number and print
5766 using typical floating point syntax.
5769 For example, to print the program counter in hex (@pxref{Registers}), type
5776 Note that no space is required before the slash; this is because command
5777 names in @value{GDBN} cannot contain a slash.
5779 To reprint the last value in the value history with a different format,
5780 you can use the @code{print} command with just a format and no
5781 expression. For example, @samp{p/x} reprints the last value in hex.
5784 @section Examining Memory
5786 You can use the command @code{x} (for ``examine'') to examine memory in
5787 any of several formats, independently of your program's data types.
5789 @cindex examining memory
5791 @kindex x @r{(examine memory)}
5792 @item x/@var{nfu} @var{addr}
5795 Use the @code{x} command to examine memory.
5798 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5799 much memory to display and how to format it; @var{addr} is an
5800 expression giving the address where you want to start displaying memory.
5801 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5802 Several commands set convenient defaults for @var{addr}.
5805 @item @var{n}, the repeat count
5806 The repeat count is a decimal integer; the default is 1. It specifies
5807 how much memory (counting by units @var{u}) to display.
5808 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5811 @item @var{f}, the display format
5812 The display format is one of the formats used by @code{print}
5813 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5814 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5815 @samp{i} (for machine instructions). The default is @samp{x}
5816 (hexadecimal) initially. The default changes each time you use either
5817 @code{x} or @code{print}.
5819 @item @var{u}, the unit size
5820 The unit size is any of
5826 Halfwords (two bytes).
5828 Words (four bytes). This is the initial default.
5830 Giant words (eight bytes).
5833 Each time you specify a unit size with @code{x}, that size becomes the
5834 default unit the next time you use @code{x}. (For the @samp{s} and
5835 @samp{i} formats, the unit size is ignored and is normally not written.)
5837 @item @var{addr}, starting display address
5838 @var{addr} is the address where you want @value{GDBN} to begin displaying
5839 memory. The expression need not have a pointer value (though it may);
5840 it is always interpreted as an integer address of a byte of memory.
5841 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5842 @var{addr} is usually just after the last address examined---but several
5843 other commands also set the default address: @code{info breakpoints} (to
5844 the address of the last breakpoint listed), @code{info line} (to the
5845 starting address of a line), and @code{print} (if you use it to display
5846 a value from memory).
5849 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5850 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5851 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5852 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5853 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5855 Since the letters indicating unit sizes are all distinct from the
5856 letters specifying output formats, you do not have to remember whether
5857 unit size or format comes first; either order works. The output
5858 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5859 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5861 Even though the unit size @var{u} is ignored for the formats @samp{s}
5862 and @samp{i}, you might still want to use a count @var{n}; for example,
5863 @samp{3i} specifies that you want to see three machine instructions,
5864 including any operands. The command @code{disassemble} gives an
5865 alternative way of inspecting machine instructions; see @ref{Machine
5866 Code,,Source and Machine Code}.
5868 All the defaults for the arguments to @code{x} are designed to make it
5869 easy to continue scanning memory with minimal specifications each time
5870 you use @code{x}. For example, after you have inspected three machine
5871 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5872 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5873 the repeat count @var{n} is used again; the other arguments default as
5874 for successive uses of @code{x}.
5876 @cindex @code{$_}, @code{$__}, and value history
5877 The addresses and contents printed by the @code{x} command are not saved
5878 in the value history because there is often too much of them and they
5879 would get in the way. Instead, @value{GDBN} makes these values available for
5880 subsequent use in expressions as values of the convenience variables
5881 @code{$_} and @code{$__}. After an @code{x} command, the last address
5882 examined is available for use in expressions in the convenience variable
5883 @code{$_}. The contents of that address, as examined, are available in
5884 the convenience variable @code{$__}.
5886 If the @code{x} command has a repeat count, the address and contents saved
5887 are from the last memory unit printed; this is not the same as the last
5888 address printed if several units were printed on the last line of output.
5890 @cindex remote memory comparison
5891 @cindex verify remote memory image
5892 When you are debugging a program running on a remote target machine
5893 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
5894 remote machine's memory against the executable file you downloaded to
5895 the target. The @code{compare-sections} command is provided for such
5899 @kindex compare-sections
5900 @item compare-sections @r{[}@var{section-name}@r{]}
5901 Compare the data of a loadable section @var{section-name} in the
5902 executable file of the program being debugged with the same section in
5903 the remote machine's memory, and report any mismatches. With no
5904 arguments, compares all loadable sections. This command's
5905 availability depends on the target's support for the @code{"qCRC"}
5910 @section Automatic Display
5911 @cindex automatic display
5912 @cindex display of expressions
5914 If you find that you want to print the value of an expression frequently
5915 (to see how it changes), you might want to add it to the @dfn{automatic
5916 display list} so that @value{GDBN} prints its value each time your program stops.
5917 Each expression added to the list is given a number to identify it;
5918 to remove an expression from the list, you specify that number.
5919 The automatic display looks like this:
5923 3: bar[5] = (struct hack *) 0x3804
5927 This display shows item numbers, expressions and their current values. As with
5928 displays you request manually using @code{x} or @code{print}, you can
5929 specify the output format you prefer; in fact, @code{display} decides
5930 whether to use @code{print} or @code{x} depending on how elaborate your
5931 format specification is---it uses @code{x} if you specify a unit size,
5932 or one of the two formats (@samp{i} and @samp{s}) that are only
5933 supported by @code{x}; otherwise it uses @code{print}.
5937 @item display @var{expr}
5938 Add the expression @var{expr} to the list of expressions to display
5939 each time your program stops. @xref{Expressions, ,Expressions}.
5941 @code{display} does not repeat if you press @key{RET} again after using it.
5943 @item display/@var{fmt} @var{expr}
5944 For @var{fmt} specifying only a display format and not a size or
5945 count, add the expression @var{expr} to the auto-display list but
5946 arrange to display it each time in the specified format @var{fmt}.
5947 @xref{Output Formats,,Output Formats}.
5949 @item display/@var{fmt} @var{addr}
5950 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5951 number of units, add the expression @var{addr} as a memory address to
5952 be examined each time your program stops. Examining means in effect
5953 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
5956 For example, @samp{display/i $pc} can be helpful, to see the machine
5957 instruction about to be executed each time execution stops (@samp{$pc}
5958 is a common name for the program counter; @pxref{Registers, ,Registers}).
5961 @kindex delete display
5963 @item undisplay @var{dnums}@dots{}
5964 @itemx delete display @var{dnums}@dots{}
5965 Remove item numbers @var{dnums} from the list of expressions to display.
5967 @code{undisplay} does not repeat if you press @key{RET} after using it.
5968 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5970 @kindex disable display
5971 @item disable display @var{dnums}@dots{}
5972 Disable the display of item numbers @var{dnums}. A disabled display
5973 item is not printed automatically, but is not forgotten. It may be
5974 enabled again later.
5976 @kindex enable display
5977 @item enable display @var{dnums}@dots{}
5978 Enable display of item numbers @var{dnums}. It becomes effective once
5979 again in auto display of its expression, until you specify otherwise.
5982 Display the current values of the expressions on the list, just as is
5983 done when your program stops.
5985 @kindex info display
5987 Print the list of expressions previously set up to display
5988 automatically, each one with its item number, but without showing the
5989 values. This includes disabled expressions, which are marked as such.
5990 It also includes expressions which would not be displayed right now
5991 because they refer to automatic variables not currently available.
5994 @cindex display disabled out of scope
5995 If a display expression refers to local variables, then it does not make
5996 sense outside the lexical context for which it was set up. Such an
5997 expression is disabled when execution enters a context where one of its
5998 variables is not defined. For example, if you give the command
5999 @code{display last_char} while inside a function with an argument
6000 @code{last_char}, @value{GDBN} displays this argument while your program
6001 continues to stop inside that function. When it stops elsewhere---where
6002 there is no variable @code{last_char}---the display is disabled
6003 automatically. The next time your program stops where @code{last_char}
6004 is meaningful, you can enable the display expression once again.
6006 @node Print Settings
6007 @section Print Settings
6009 @cindex format options
6010 @cindex print settings
6011 @value{GDBN} provides the following ways to control how arrays, structures,
6012 and symbols are printed.
6015 These settings are useful for debugging programs in any language:
6019 @item set print address
6020 @itemx set print address on
6021 @cindex print/don't print memory addresses
6022 @value{GDBN} prints memory addresses showing the location of stack
6023 traces, structure values, pointer values, breakpoints, and so forth,
6024 even when it also displays the contents of those addresses. The default
6025 is @code{on}. For example, this is what a stack frame display looks like with
6026 @code{set print address on}:
6031 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6033 530 if (lquote != def_lquote)
6037 @item set print address off
6038 Do not print addresses when displaying their contents. For example,
6039 this is the same stack frame displayed with @code{set print address off}:
6043 (@value{GDBP}) set print addr off
6045 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6046 530 if (lquote != def_lquote)
6050 You can use @samp{set print address off} to eliminate all machine
6051 dependent displays from the @value{GDBN} interface. For example, with
6052 @code{print address off}, you should get the same text for backtraces on
6053 all machines---whether or not they involve pointer arguments.
6056 @item show print address
6057 Show whether or not addresses are to be printed.
6060 When @value{GDBN} prints a symbolic address, it normally prints the
6061 closest earlier symbol plus an offset. If that symbol does not uniquely
6062 identify the address (for example, it is a name whose scope is a single
6063 source file), you may need to clarify. One way to do this is with
6064 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6065 you can set @value{GDBN} to print the source file and line number when
6066 it prints a symbolic address:
6069 @item set print symbol-filename on
6070 @cindex source file and line of a symbol
6071 @cindex symbol, source file and line
6072 Tell @value{GDBN} to print the source file name and line number of a
6073 symbol in the symbolic form of an address.
6075 @item set print symbol-filename off
6076 Do not print source file name and line number of a symbol. This is the
6079 @item show print symbol-filename
6080 Show whether or not @value{GDBN} will print the source file name and
6081 line number of a symbol in the symbolic form of an address.
6084 Another situation where it is helpful to show symbol filenames and line
6085 numbers is when disassembling code; @value{GDBN} shows you the line
6086 number and source file that corresponds to each instruction.
6088 Also, you may wish to see the symbolic form only if the address being
6089 printed is reasonably close to the closest earlier symbol:
6092 @item set print max-symbolic-offset @var{max-offset}
6093 @cindex maximum value for offset of closest symbol
6094 Tell @value{GDBN} to only display the symbolic form of an address if the
6095 offset between the closest earlier symbol and the address is less than
6096 @var{max-offset}. The default is 0, which tells @value{GDBN}
6097 to always print the symbolic form of an address if any symbol precedes it.
6099 @item show print max-symbolic-offset
6100 Ask how large the maximum offset is that @value{GDBN} prints in a
6104 @cindex wild pointer, interpreting
6105 @cindex pointer, finding referent
6106 If you have a pointer and you are not sure where it points, try
6107 @samp{set print symbol-filename on}. Then you can determine the name
6108 and source file location of the variable where it points, using
6109 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6110 For example, here @value{GDBN} shows that a variable @code{ptt} points
6111 at another variable @code{t}, defined in @file{hi2.c}:
6114 (@value{GDBP}) set print symbol-filename on
6115 (@value{GDBP}) p/a ptt
6116 $4 = 0xe008 <t in hi2.c>
6120 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6121 does not show the symbol name and filename of the referent, even with
6122 the appropriate @code{set print} options turned on.
6125 Other settings control how different kinds of objects are printed:
6128 @item set print array
6129 @itemx set print array on
6130 @cindex pretty print arrays
6131 Pretty print arrays. This format is more convenient to read,
6132 but uses more space. The default is off.
6134 @item set print array off
6135 Return to compressed format for arrays.
6137 @item show print array
6138 Show whether compressed or pretty format is selected for displaying
6141 @cindex print array indexes
6142 @item set print array-indexes
6143 @itemx set print array-indexes on
6144 Print the index of each element when displaying arrays. May be more
6145 convenient to locate a given element in the array or quickly find the
6146 index of a given element in that printed array. The default is off.
6148 @item set print array-indexes off
6149 Stop printing element indexes when displaying arrays.
6151 @item show print array-indexes
6152 Show whether the index of each element is printed when displaying
6155 @item set print elements @var{number-of-elements}
6156 @cindex number of array elements to print
6157 @cindex limit on number of printed array elements
6158 Set a limit on how many elements of an array @value{GDBN} will print.
6159 If @value{GDBN} is printing a large array, it stops printing after it has
6160 printed the number of elements set by the @code{set print elements} command.
6161 This limit also applies to the display of strings.
6162 When @value{GDBN} starts, this limit is set to 200.
6163 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6165 @item show print elements
6166 Display the number of elements of a large array that @value{GDBN} will print.
6167 If the number is 0, then the printing is unlimited.
6169 @item set print repeats
6170 @cindex repeated array elements
6171 Set the threshold for suppressing display of repeated array
6172 elements. When the number of consecutive identical elements of an
6173 array exceeds the threshold, @value{GDBN} prints the string
6174 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6175 identical repetitions, instead of displaying the identical elements
6176 themselves. Setting the threshold to zero will cause all elements to
6177 be individually printed. The default threshold is 10.
6179 @item show print repeats
6180 Display the current threshold for printing repeated identical
6183 @item set print null-stop
6184 @cindex @sc{null} elements in arrays
6185 Cause @value{GDBN} to stop printing the characters of an array when the first
6186 @sc{null} is encountered. This is useful when large arrays actually
6187 contain only short strings.
6190 @item show print null-stop
6191 Show whether @value{GDBN} stops printing an array on the first
6192 @sc{null} character.
6194 @item set print pretty on
6195 @cindex print structures in indented form
6196 @cindex indentation in structure display
6197 Cause @value{GDBN} to print structures in an indented format with one member
6198 per line, like this:
6213 @item set print pretty off
6214 Cause @value{GDBN} to print structures in a compact format, like this:
6218 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6219 meat = 0x54 "Pork"@}
6224 This is the default format.
6226 @item show print pretty
6227 Show which format @value{GDBN} is using to print structures.
6229 @item set print sevenbit-strings on
6230 @cindex eight-bit characters in strings
6231 @cindex octal escapes in strings
6232 Print using only seven-bit characters; if this option is set,
6233 @value{GDBN} displays any eight-bit characters (in strings or
6234 character values) using the notation @code{\}@var{nnn}. This setting is
6235 best if you are working in English (@sc{ascii}) and you use the
6236 high-order bit of characters as a marker or ``meta'' bit.
6238 @item set print sevenbit-strings off
6239 Print full eight-bit characters. This allows the use of more
6240 international character sets, and is the default.
6242 @item show print sevenbit-strings
6243 Show whether or not @value{GDBN} is printing only seven-bit characters.
6245 @item set print union on
6246 @cindex unions in structures, printing
6247 Tell @value{GDBN} to print unions which are contained in structures
6248 and other unions. This is the default setting.
6250 @item set print union off
6251 Tell @value{GDBN} not to print unions which are contained in
6252 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6255 @item show print union
6256 Ask @value{GDBN} whether or not it will print unions which are contained in
6257 structures and other unions.
6259 For example, given the declarations
6262 typedef enum @{Tree, Bug@} Species;
6263 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6264 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6275 struct thing foo = @{Tree, @{Acorn@}@};
6279 with @code{set print union on} in effect @samp{p foo} would print
6282 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6286 and with @code{set print union off} in effect it would print
6289 $1 = @{it = Tree, form = @{...@}@}
6293 @code{set print union} affects programs written in C-like languages
6299 These settings are of interest when debugging C@t{++} programs:
6302 @cindex demangling C@t{++} names
6303 @item set print demangle
6304 @itemx set print demangle on
6305 Print C@t{++} names in their source form rather than in the encoded
6306 (``mangled'') form passed to the assembler and linker for type-safe
6307 linkage. The default is on.
6309 @item show print demangle
6310 Show whether C@t{++} names are printed in mangled or demangled form.
6312 @item set print asm-demangle
6313 @itemx set print asm-demangle on
6314 Print C@t{++} names in their source form rather than their mangled form, even
6315 in assembler code printouts such as instruction disassemblies.
6318 @item show print asm-demangle
6319 Show whether C@t{++} names in assembly listings are printed in mangled
6322 @cindex C@t{++} symbol decoding style
6323 @cindex symbol decoding style, C@t{++}
6324 @kindex set demangle-style
6325 @item set demangle-style @var{style}
6326 Choose among several encoding schemes used by different compilers to
6327 represent C@t{++} names. The choices for @var{style} are currently:
6331 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6334 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6335 This is the default.
6338 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6341 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6344 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6345 @strong{Warning:} this setting alone is not sufficient to allow
6346 debugging @code{cfront}-generated executables. @value{GDBN} would
6347 require further enhancement to permit that.
6350 If you omit @var{style}, you will see a list of possible formats.
6352 @item show demangle-style
6353 Display the encoding style currently in use for decoding C@t{++} symbols.
6355 @item set print object
6356 @itemx set print object on
6357 @cindex derived type of an object, printing
6358 @cindex display derived types
6359 When displaying a pointer to an object, identify the @emph{actual}
6360 (derived) type of the object rather than the @emph{declared} type, using
6361 the virtual function table.
6363 @item set print object off
6364 Display only the declared type of objects, without reference to the
6365 virtual function table. This is the default setting.
6367 @item show print object
6368 Show whether actual, or declared, object types are displayed.
6370 @item set print static-members
6371 @itemx set print static-members on
6372 @cindex static members of C@t{++} objects
6373 Print static members when displaying a C@t{++} object. The default is on.
6375 @item set print static-members off
6376 Do not print static members when displaying a C@t{++} object.
6378 @item show print static-members
6379 Show whether C@t{++} static members are printed or not.
6381 @item set print pascal_static-members
6382 @itemx set print pascal_static-members on
6383 @cindex static members of Pascal objects
6384 @cindex Pascal objects, static members display
6385 Print static members when displaying a Pascal object. The default is on.
6387 @item set print pascal_static-members off
6388 Do not print static members when displaying a Pascal object.
6390 @item show print pascal_static-members
6391 Show whether Pascal static members are printed or not.
6393 @c These don't work with HP ANSI C++ yet.
6394 @item set print vtbl
6395 @itemx set print vtbl on
6396 @cindex pretty print C@t{++} virtual function tables
6397 @cindex virtual functions (C@t{++}) display
6398 @cindex VTBL display
6399 Pretty print C@t{++} virtual function tables. The default is off.
6400 (The @code{vtbl} commands do not work on programs compiled with the HP
6401 ANSI C@t{++} compiler (@code{aCC}).)
6403 @item set print vtbl off
6404 Do not pretty print C@t{++} virtual function tables.
6406 @item show print vtbl
6407 Show whether C@t{++} virtual function tables are pretty printed, or not.
6411 @section Value History
6413 @cindex value history
6414 @cindex history of values printed by @value{GDBN}
6415 Values printed by the @code{print} command are saved in the @value{GDBN}
6416 @dfn{value history}. This allows you to refer to them in other expressions.
6417 Values are kept until the symbol table is re-read or discarded
6418 (for example with the @code{file} or @code{symbol-file} commands).
6419 When the symbol table changes, the value history is discarded,
6420 since the values may contain pointers back to the types defined in the
6425 @cindex history number
6426 The values printed are given @dfn{history numbers} by which you can
6427 refer to them. These are successive integers starting with one.
6428 @code{print} shows you the history number assigned to a value by
6429 printing @samp{$@var{num} = } before the value; here @var{num} is the
6432 To refer to any previous value, use @samp{$} followed by the value's
6433 history number. The way @code{print} labels its output is designed to
6434 remind you of this. Just @code{$} refers to the most recent value in
6435 the history, and @code{$$} refers to the value before that.
6436 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6437 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6438 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6440 For example, suppose you have just printed a pointer to a structure and
6441 want to see the contents of the structure. It suffices to type
6447 If you have a chain of structures where the component @code{next} points
6448 to the next one, you can print the contents of the next one with this:
6455 You can print successive links in the chain by repeating this
6456 command---which you can do by just typing @key{RET}.
6458 Note that the history records values, not expressions. If the value of
6459 @code{x} is 4 and you type these commands:
6467 then the value recorded in the value history by the @code{print} command
6468 remains 4 even though the value of @code{x} has changed.
6473 Print the last ten values in the value history, with their item numbers.
6474 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6475 values} does not change the history.
6477 @item show values @var{n}
6478 Print ten history values centered on history item number @var{n}.
6481 Print ten history values just after the values last printed. If no more
6482 values are available, @code{show values +} produces no display.
6485 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6486 same effect as @samp{show values +}.
6488 @node Convenience Vars
6489 @section Convenience Variables
6491 @cindex convenience variables
6492 @cindex user-defined variables
6493 @value{GDBN} provides @dfn{convenience variables} that you can use within
6494 @value{GDBN} to hold on to a value and refer to it later. These variables
6495 exist entirely within @value{GDBN}; they are not part of your program, and
6496 setting a convenience variable has no direct effect on further execution
6497 of your program. That is why you can use them freely.
6499 Convenience variables are prefixed with @samp{$}. Any name preceded by
6500 @samp{$} can be used for a convenience variable, unless it is one of
6501 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6502 (Value history references, in contrast, are @emph{numbers} preceded
6503 by @samp{$}. @xref{Value History, ,Value History}.)
6505 You can save a value in a convenience variable with an assignment
6506 expression, just as you would set a variable in your program.
6510 set $foo = *object_ptr
6514 would save in @code{$foo} the value contained in the object pointed to by
6517 Using a convenience variable for the first time creates it, but its
6518 value is @code{void} until you assign a new value. You can alter the
6519 value with another assignment at any time.
6521 Convenience variables have no fixed types. You can assign a convenience
6522 variable any type of value, including structures and arrays, even if
6523 that variable already has a value of a different type. The convenience
6524 variable, when used as an expression, has the type of its current value.
6527 @kindex show convenience
6528 @cindex show all user variables
6529 @item show convenience
6530 Print a list of convenience variables used so far, and their values.
6531 Abbreviated @code{show conv}.
6533 @kindex init-if-undefined
6534 @cindex convenience variables, initializing
6535 @item init-if-undefined $@var{variable} = @var{expression}
6536 Set a convenience variable if it has not already been set. This is useful
6537 for user-defined commands that keep some state. It is similar, in concept,
6538 to using local static variables with initializers in C (except that
6539 convenience variables are global). It can also be used to allow users to
6540 override default values used in a command script.
6542 If the variable is already defined then the expression is not evaluated so
6543 any side-effects do not occur.
6546 One of the ways to use a convenience variable is as a counter to be
6547 incremented or a pointer to be advanced. For example, to print
6548 a field from successive elements of an array of structures:
6552 print bar[$i++]->contents
6556 Repeat that command by typing @key{RET}.
6558 Some convenience variables are created automatically by @value{GDBN} and given
6559 values likely to be useful.
6562 @vindex $_@r{, convenience variable}
6564 The variable @code{$_} is automatically set by the @code{x} command to
6565 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6566 commands which provide a default address for @code{x} to examine also
6567 set @code{$_} to that address; these commands include @code{info line}
6568 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6569 except when set by the @code{x} command, in which case it is a pointer
6570 to the type of @code{$__}.
6572 @vindex $__@r{, convenience variable}
6574 The variable @code{$__} is automatically set by the @code{x} command
6575 to the value found in the last address examined. Its type is chosen
6576 to match the format in which the data was printed.
6579 @vindex $_exitcode@r{, convenience variable}
6580 The variable @code{$_exitcode} is automatically set to the exit code when
6581 the program being debugged terminates.
6584 On HP-UX systems, if you refer to a function or variable name that
6585 begins with a dollar sign, @value{GDBN} searches for a user or system
6586 name first, before it searches for a convenience variable.
6592 You can refer to machine register contents, in expressions, as variables
6593 with names starting with @samp{$}. The names of registers are different
6594 for each machine; use @code{info registers} to see the names used on
6598 @kindex info registers
6599 @item info registers
6600 Print the names and values of all registers except floating-point
6601 and vector registers (in the selected stack frame).
6603 @kindex info all-registers
6604 @cindex floating point registers
6605 @item info all-registers
6606 Print the names and values of all registers, including floating-point
6607 and vector registers (in the selected stack frame).
6609 @item info registers @var{regname} @dots{}
6610 Print the @dfn{relativized} value of each specified register @var{regname}.
6611 As discussed in detail below, register values are normally relative to
6612 the selected stack frame. @var{regname} may be any register name valid on
6613 the machine you are using, with or without the initial @samp{$}.
6616 @cindex stack pointer register
6617 @cindex program counter register
6618 @cindex process status register
6619 @cindex frame pointer register
6620 @cindex standard registers
6621 @value{GDBN} has four ``standard'' register names that are available (in
6622 expressions) on most machines---whenever they do not conflict with an
6623 architecture's canonical mnemonics for registers. The register names
6624 @code{$pc} and @code{$sp} are used for the program counter register and
6625 the stack pointer. @code{$fp} is used for a register that contains a
6626 pointer to the current stack frame, and @code{$ps} is used for a
6627 register that contains the processor status. For example,
6628 you could print the program counter in hex with
6635 or print the instruction to be executed next with
6642 or add four to the stack pointer@footnote{This is a way of removing
6643 one word from the stack, on machines where stacks grow downward in
6644 memory (most machines, nowadays). This assumes that the innermost
6645 stack frame is selected; setting @code{$sp} is not allowed when other
6646 stack frames are selected. To pop entire frames off the stack,
6647 regardless of machine architecture, use @code{return};
6648 see @ref{Returning, ,Returning from a Function}.} with
6654 Whenever possible, these four standard register names are available on
6655 your machine even though the machine has different canonical mnemonics,
6656 so long as there is no conflict. The @code{info registers} command
6657 shows the canonical names. For example, on the SPARC, @code{info
6658 registers} displays the processor status register as @code{$psr} but you
6659 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6660 is an alias for the @sc{eflags} register.
6662 @value{GDBN} always considers the contents of an ordinary register as an
6663 integer when the register is examined in this way. Some machines have
6664 special registers which can hold nothing but floating point; these
6665 registers are considered to have floating point values. There is no way
6666 to refer to the contents of an ordinary register as floating point value
6667 (although you can @emph{print} it as a floating point value with
6668 @samp{print/f $@var{regname}}).
6670 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6671 means that the data format in which the register contents are saved by
6672 the operating system is not the same one that your program normally
6673 sees. For example, the registers of the 68881 floating point
6674 coprocessor are always saved in ``extended'' (raw) format, but all C
6675 programs expect to work with ``double'' (virtual) format. In such
6676 cases, @value{GDBN} normally works with the virtual format only (the format
6677 that makes sense for your program), but the @code{info registers} command
6678 prints the data in both formats.
6680 @cindex SSE registers (x86)
6681 @cindex MMX registers (x86)
6682 Some machines have special registers whose contents can be interpreted
6683 in several different ways. For example, modern x86-based machines
6684 have SSE and MMX registers that can hold several values packed
6685 together in several different formats. @value{GDBN} refers to such
6686 registers in @code{struct} notation:
6689 (@value{GDBP}) print $xmm1
6691 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6692 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6693 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6694 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6695 v4_int32 = @{0, 20657912, 11, 13@},
6696 v2_int64 = @{88725056443645952, 55834574859@},
6697 uint128 = 0x0000000d0000000b013b36f800000000
6702 To set values of such registers, you need to tell @value{GDBN} which
6703 view of the register you wish to change, as if you were assigning
6704 value to a @code{struct} member:
6707 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6710 Normally, register values are relative to the selected stack frame
6711 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
6712 value that the register would contain if all stack frames farther in
6713 were exited and their saved registers restored. In order to see the
6714 true contents of hardware registers, you must select the innermost
6715 frame (with @samp{frame 0}).
6717 However, @value{GDBN} must deduce where registers are saved, from the machine
6718 code generated by your compiler. If some registers are not saved, or if
6719 @value{GDBN} is unable to locate the saved registers, the selected stack
6720 frame makes no difference.
6722 @node Floating Point Hardware
6723 @section Floating Point Hardware
6724 @cindex floating point
6726 Depending on the configuration, @value{GDBN} may be able to give
6727 you more information about the status of the floating point hardware.
6732 Display hardware-dependent information about the floating
6733 point unit. The exact contents and layout vary depending on the
6734 floating point chip. Currently, @samp{info float} is supported on
6735 the ARM and x86 machines.
6739 @section Vector Unit
6742 Depending on the configuration, @value{GDBN} may be able to give you
6743 more information about the status of the vector unit.
6748 Display information about the vector unit. The exact contents and
6749 layout vary depending on the hardware.
6752 @node OS Information
6753 @section Operating System Auxiliary Information
6754 @cindex OS information
6756 @value{GDBN} provides interfaces to useful OS facilities that can help
6757 you debug your program.
6759 @cindex @code{ptrace} system call
6760 @cindex @code{struct user} contents
6761 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6762 machines), it interfaces with the inferior via the @code{ptrace}
6763 system call. The operating system creates a special sata structure,
6764 called @code{struct user}, for this interface. You can use the
6765 command @code{info udot} to display the contents of this data
6771 Display the contents of the @code{struct user} maintained by the OS
6772 kernel for the program being debugged. @value{GDBN} displays the
6773 contents of @code{struct user} as a list of hex numbers, similar to
6774 the @code{examine} command.
6777 @cindex auxiliary vector
6778 @cindex vector, auxiliary
6779 Some operating systems supply an @dfn{auxiliary vector} to programs at
6780 startup. This is akin to the arguments and environment that you
6781 specify for a program, but contains a system-dependent variety of
6782 binary values that tell system libraries important details about the
6783 hardware, operating system, and process. Each value's purpose is
6784 identified by an integer tag; the meanings are well-known but system-specific.
6785 Depending on the configuration and operating system facilities,
6786 @value{GDBN} may be able to show you this information. For remote
6787 targets, this functionality may further depend on the remote stub's
6788 support of the @samp{qXfer:auxv:read} packet, see
6789 @ref{qXfer auxiliary vector read}.
6794 Display the auxiliary vector of the inferior, which can be either a
6795 live process or a core dump file. @value{GDBN} prints each tag value
6796 numerically, and also shows names and text descriptions for recognized
6797 tags. Some values in the vector are numbers, some bit masks, and some
6798 pointers to strings or other data. @value{GDBN} displays each value in the
6799 most appropriate form for a recognized tag, and in hexadecimal for
6800 an unrecognized tag.
6804 @node Memory Region Attributes
6805 @section Memory Region Attributes
6806 @cindex memory region attributes
6808 @dfn{Memory region attributes} allow you to describe special handling
6809 required by regions of your target's memory. @value{GDBN} uses
6810 attributes to determine whether to allow certain types of memory
6811 accesses; whether to use specific width accesses; and whether to cache
6812 target memory. By default the description of memory regions is
6813 fetched from the target (if the current target supports this), but the
6814 user can override the fetched regions.
6816 Defined memory regions can be individually enabled and disabled. When a
6817 memory region is disabled, @value{GDBN} uses the default attributes when
6818 accessing memory in that region. Similarly, if no memory regions have
6819 been defined, @value{GDBN} uses the default attributes when accessing
6822 When a memory region is defined, it is given a number to identify it;
6823 to enable, disable, or remove a memory region, you specify that number.
6827 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6828 Define a memory region bounded by @var{lower} and @var{upper} with
6829 attributes @var{attributes}@dots{}, and add it to the list of regions
6830 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6831 case: it is treated as the target's maximum memory address.
6832 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6835 Discard any user changes to the memory regions and use target-supplied
6836 regions, if available, or no regions if the target does not support.
6839 @item delete mem @var{nums}@dots{}
6840 Remove memory regions @var{nums}@dots{} from the list of regions
6841 monitored by @value{GDBN}.
6844 @item disable mem @var{nums}@dots{}
6845 Disable monitoring of memory regions @var{nums}@dots{}.
6846 A disabled memory region is not forgotten.
6847 It may be enabled again later.
6850 @item enable mem @var{nums}@dots{}
6851 Enable monitoring of memory regions @var{nums}@dots{}.
6855 Print a table of all defined memory regions, with the following columns
6859 @item Memory Region Number
6860 @item Enabled or Disabled.
6861 Enabled memory regions are marked with @samp{y}.
6862 Disabled memory regions are marked with @samp{n}.
6865 The address defining the inclusive lower bound of the memory region.
6868 The address defining the exclusive upper bound of the memory region.
6871 The list of attributes set for this memory region.
6876 @subsection Attributes
6878 @subsubsection Memory Access Mode
6879 The access mode attributes set whether @value{GDBN} may make read or
6880 write accesses to a memory region.
6882 While these attributes prevent @value{GDBN} from performing invalid
6883 memory accesses, they do nothing to prevent the target system, I/O DMA,
6884 etc.@: from accessing memory.
6888 Memory is read only.
6890 Memory is write only.
6892 Memory is read/write. This is the default.
6895 @subsubsection Memory Access Size
6896 The access size attribute tells @value{GDBN} to use specific sized
6897 accesses in the memory region. Often memory mapped device registers
6898 require specific sized accesses. If no access size attribute is
6899 specified, @value{GDBN} may use accesses of any size.
6903 Use 8 bit memory accesses.
6905 Use 16 bit memory accesses.
6907 Use 32 bit memory accesses.
6909 Use 64 bit memory accesses.
6912 @c @subsubsection Hardware/Software Breakpoints
6913 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6914 @c will use hardware or software breakpoints for the internal breakpoints
6915 @c used by the step, next, finish, until, etc. commands.
6919 @c Always use hardware breakpoints
6920 @c @item swbreak (default)
6923 @subsubsection Data Cache
6924 The data cache attributes set whether @value{GDBN} will cache target
6925 memory. While this generally improves performance by reducing debug
6926 protocol overhead, it can lead to incorrect results because @value{GDBN}
6927 does not know about volatile variables or memory mapped device
6932 Enable @value{GDBN} to cache target memory.
6934 Disable @value{GDBN} from caching target memory. This is the default.
6937 @subsection Memory Access Checking
6938 @value{GDBN} can be instructed to refuse accesses to memory that is
6939 not explicitly described. This can be useful if accessing such
6940 regions has undesired effects for a specific target, or to provide
6941 better error checking. The following commands control this behaviour.
6944 @kindex set mem inaccessible-by-default
6945 @item set mem inaccessible-by-default [on|off]
6946 If @code{on} is specified, make @value{GDBN} treat memory not
6947 explicitly described by the memory ranges as non-existent and refuse accesses
6948 to such memory. The checks are only performed if there's at least one
6949 memory range defined. If @code{off} is specified, make @value{GDBN}
6950 treat the memory not explicitly described by the memory ranges as RAM.
6951 The default value is @code{off}.
6952 @kindex show mem inaccessible-by-default
6953 @item show mem inaccessible-by-default
6954 Show the current handling of accesses to unknown memory.
6958 @c @subsubsection Memory Write Verification
6959 @c The memory write verification attributes set whether @value{GDBN}
6960 @c will re-reads data after each write to verify the write was successful.
6964 @c @item noverify (default)
6967 @node Dump/Restore Files
6968 @section Copy Between Memory and a File
6969 @cindex dump/restore files
6970 @cindex append data to a file
6971 @cindex dump data to a file
6972 @cindex restore data from a file
6974 You can use the commands @code{dump}, @code{append}, and
6975 @code{restore} to copy data between target memory and a file. The
6976 @code{dump} and @code{append} commands write data to a file, and the
6977 @code{restore} command reads data from a file back into the inferior's
6978 memory. Files may be in binary, Motorola S-record, Intel hex, or
6979 Tektronix Hex format; however, @value{GDBN} can only append to binary
6985 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6986 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6987 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6988 or the value of @var{expr}, to @var{filename} in the given format.
6990 The @var{format} parameter may be any one of:
6997 Motorola S-record format.
6999 Tektronix Hex format.
7002 @value{GDBN} uses the same definitions of these formats as the
7003 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7004 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7008 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7009 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7010 Append the contents of memory from @var{start_addr} to @var{end_addr},
7011 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7012 (@value{GDBN} can only append data to files in raw binary form.)
7015 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7016 Restore the contents of file @var{filename} into memory. The
7017 @code{restore} command can automatically recognize any known @sc{bfd}
7018 file format, except for raw binary. To restore a raw binary file you
7019 must specify the optional keyword @code{binary} after the filename.
7021 If @var{bias} is non-zero, its value will be added to the addresses
7022 contained in the file. Binary files always start at address zero, so
7023 they will be restored at address @var{bias}. Other bfd files have
7024 a built-in location; they will be restored at offset @var{bias}
7027 If @var{start} and/or @var{end} are non-zero, then only data between
7028 file offset @var{start} and file offset @var{end} will be restored.
7029 These offsets are relative to the addresses in the file, before
7030 the @var{bias} argument is applied.
7034 @node Core File Generation
7035 @section How to Produce a Core File from Your Program
7036 @cindex dump core from inferior
7038 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7039 image of a running process and its process status (register values
7040 etc.). Its primary use is post-mortem debugging of a program that
7041 crashed while it ran outside a debugger. A program that crashes
7042 automatically produces a core file, unless this feature is disabled by
7043 the user. @xref{Files}, for information on invoking @value{GDBN} in
7044 the post-mortem debugging mode.
7046 Occasionally, you may wish to produce a core file of the program you
7047 are debugging in order to preserve a snapshot of its state.
7048 @value{GDBN} has a special command for that.
7052 @kindex generate-core-file
7053 @item generate-core-file [@var{file}]
7054 @itemx gcore [@var{file}]
7055 Produce a core dump of the inferior process. The optional argument
7056 @var{file} specifies the file name where to put the core dump. If not
7057 specified, the file name defaults to @file{core.@var{pid}}, where
7058 @var{pid} is the inferior process ID.
7060 Note that this command is implemented only for some systems (as of
7061 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7064 @node Character Sets
7065 @section Character Sets
7066 @cindex character sets
7068 @cindex translating between character sets
7069 @cindex host character set
7070 @cindex target character set
7072 If the program you are debugging uses a different character set to
7073 represent characters and strings than the one @value{GDBN} uses itself,
7074 @value{GDBN} can automatically translate between the character sets for
7075 you. The character set @value{GDBN} uses we call the @dfn{host
7076 character set}; the one the inferior program uses we call the
7077 @dfn{target character set}.
7079 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7080 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7081 remote protocol (@pxref{Remote Debugging}) to debug a program
7082 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7083 then the host character set is Latin-1, and the target character set is
7084 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7085 target-charset EBCDIC-US}, then @value{GDBN} translates between
7086 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7087 character and string literals in expressions.
7089 @value{GDBN} has no way to automatically recognize which character set
7090 the inferior program uses; you must tell it, using the @code{set
7091 target-charset} command, described below.
7093 Here are the commands for controlling @value{GDBN}'s character set
7097 @item set target-charset @var{charset}
7098 @kindex set target-charset
7099 Set the current target character set to @var{charset}. We list the
7100 character set names @value{GDBN} recognizes below, but if you type
7101 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7102 list the target character sets it supports.
7106 @item set host-charset @var{charset}
7107 @kindex set host-charset
7108 Set the current host character set to @var{charset}.
7110 By default, @value{GDBN} uses a host character set appropriate to the
7111 system it is running on; you can override that default using the
7112 @code{set host-charset} command.
7114 @value{GDBN} can only use certain character sets as its host character
7115 set. We list the character set names @value{GDBN} recognizes below, and
7116 indicate which can be host character sets, but if you type
7117 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7118 list the host character sets it supports.
7120 @item set charset @var{charset}
7122 Set the current host and target character sets to @var{charset}. As
7123 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7124 @value{GDBN} will list the name of the character sets that can be used
7125 for both host and target.
7129 @kindex show charset
7130 Show the names of the current host and target charsets.
7132 @itemx show host-charset
7133 @kindex show host-charset
7134 Show the name of the current host charset.
7136 @itemx show target-charset
7137 @kindex show target-charset
7138 Show the name of the current target charset.
7142 @value{GDBN} currently includes support for the following character
7148 @cindex ASCII character set
7149 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7153 @cindex ISO 8859-1 character set
7154 @cindex ISO Latin 1 character set
7155 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7156 characters needed for French, German, and Spanish. @value{GDBN} can use
7157 this as its host character set.
7161 @cindex EBCDIC character set
7162 @cindex IBM1047 character set
7163 Variants of the @sc{ebcdic} character set, used on some of IBM's
7164 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7165 @value{GDBN} cannot use these as its host character set.
7169 Note that these are all single-byte character sets. More work inside
7170 @value{GDBN} is needed to support multi-byte or variable-width character
7171 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7173 Here is an example of @value{GDBN}'s character set support in action.
7174 Assume that the following source code has been placed in the file
7175 @file{charset-test.c}:
7181 = @{72, 101, 108, 108, 111, 44, 32, 119,
7182 111, 114, 108, 100, 33, 10, 0@};
7183 char ibm1047_hello[]
7184 = @{200, 133, 147, 147, 150, 107, 64, 166,
7185 150, 153, 147, 132, 90, 37, 0@};
7189 printf ("Hello, world!\n");
7193 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7194 containing the string @samp{Hello, world!} followed by a newline,
7195 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7197 We compile the program, and invoke the debugger on it:
7200 $ gcc -g charset-test.c -o charset-test
7201 $ gdb -nw charset-test
7202 GNU gdb 2001-12-19-cvs
7203 Copyright 2001 Free Software Foundation, Inc.
7208 We can use the @code{show charset} command to see what character sets
7209 @value{GDBN} is currently using to interpret and display characters and
7213 (@value{GDBP}) show charset
7214 The current host and target character set is `ISO-8859-1'.
7218 For the sake of printing this manual, let's use @sc{ascii} as our
7219 initial character set:
7221 (@value{GDBP}) set charset ASCII
7222 (@value{GDBP}) show charset
7223 The current host and target character set is `ASCII'.
7227 Let's assume that @sc{ascii} is indeed the correct character set for our
7228 host system --- in other words, let's assume that if @value{GDBN} prints
7229 characters using the @sc{ascii} character set, our terminal will display
7230 them properly. Since our current target character set is also
7231 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7234 (@value{GDBP}) print ascii_hello
7235 $1 = 0x401698 "Hello, world!\n"
7236 (@value{GDBP}) print ascii_hello[0]
7241 @value{GDBN} uses the target character set for character and string
7242 literals you use in expressions:
7245 (@value{GDBP}) print '+'
7250 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7253 @value{GDBN} relies on the user to tell it which character set the
7254 target program uses. If we print @code{ibm1047_hello} while our target
7255 character set is still @sc{ascii}, we get jibberish:
7258 (@value{GDBP}) print ibm1047_hello
7259 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7260 (@value{GDBP}) print ibm1047_hello[0]
7265 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7266 @value{GDBN} tells us the character sets it supports:
7269 (@value{GDBP}) set target-charset
7270 ASCII EBCDIC-US IBM1047 ISO-8859-1
7271 (@value{GDBP}) set target-charset
7274 We can select @sc{ibm1047} as our target character set, and examine the
7275 program's strings again. Now the @sc{ascii} string is wrong, but
7276 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7277 target character set, @sc{ibm1047}, to the host character set,
7278 @sc{ascii}, and they display correctly:
7281 (@value{GDBP}) set target-charset IBM1047
7282 (@value{GDBP}) show charset
7283 The current host character set is `ASCII'.
7284 The current target character set is `IBM1047'.
7285 (@value{GDBP}) print ascii_hello
7286 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7287 (@value{GDBP}) print ascii_hello[0]
7289 (@value{GDBP}) print ibm1047_hello
7290 $8 = 0x4016a8 "Hello, world!\n"
7291 (@value{GDBP}) print ibm1047_hello[0]
7296 As above, @value{GDBN} uses the target character set for character and
7297 string literals you use in expressions:
7300 (@value{GDBP}) print '+'
7305 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7308 @node Caching Remote Data
7309 @section Caching Data of Remote Targets
7310 @cindex caching data of remote targets
7312 @value{GDBN} can cache data exchanged between the debugger and a
7313 remote target (@pxref{Remote Debugging}). Such caching generally improves
7314 performance, because it reduces the overhead of the remote protocol by
7315 bundling memory reads and writes into large chunks. Unfortunately,
7316 @value{GDBN} does not currently know anything about volatile
7317 registers, and thus data caching will produce incorrect results when
7318 volatile registers are in use.
7321 @kindex set remotecache
7322 @item set remotecache on
7323 @itemx set remotecache off
7324 Set caching state for remote targets. When @code{ON}, use data
7325 caching. By default, this option is @code{OFF}.
7327 @kindex show remotecache
7328 @item show remotecache
7329 Show the current state of data caching for remote targets.
7333 Print the information about the data cache performance. The
7334 information displayed includes: the dcache width and depth; and for
7335 each cache line, how many times it was referenced, and its data and
7336 state (dirty, bad, ok, etc.). This command is useful for debugging
7337 the data cache operation.
7342 @chapter C Preprocessor Macros
7344 Some languages, such as C and C@t{++}, provide a way to define and invoke
7345 ``preprocessor macros'' which expand into strings of tokens.
7346 @value{GDBN} can evaluate expressions containing macro invocations, show
7347 the result of macro expansion, and show a macro's definition, including
7348 where it was defined.
7350 You may need to compile your program specially to provide @value{GDBN}
7351 with information about preprocessor macros. Most compilers do not
7352 include macros in their debugging information, even when you compile
7353 with the @option{-g} flag. @xref{Compilation}.
7355 A program may define a macro at one point, remove that definition later,
7356 and then provide a different definition after that. Thus, at different
7357 points in the program, a macro may have different definitions, or have
7358 no definition at all. If there is a current stack frame, @value{GDBN}
7359 uses the macros in scope at that frame's source code line. Otherwise,
7360 @value{GDBN} uses the macros in scope at the current listing location;
7363 At the moment, @value{GDBN} does not support the @code{##}
7364 token-splicing operator, the @code{#} stringification operator, or
7365 variable-arity macros.
7367 Whenever @value{GDBN} evaluates an expression, it always expands any
7368 macro invocations present in the expression. @value{GDBN} also provides
7369 the following commands for working with macros explicitly.
7373 @kindex macro expand
7374 @cindex macro expansion, showing the results of preprocessor
7375 @cindex preprocessor macro expansion, showing the results of
7376 @cindex expanding preprocessor macros
7377 @item macro expand @var{expression}
7378 @itemx macro exp @var{expression}
7379 Show the results of expanding all preprocessor macro invocations in
7380 @var{expression}. Since @value{GDBN} simply expands macros, but does
7381 not parse the result, @var{expression} need not be a valid expression;
7382 it can be any string of tokens.
7385 @item macro expand-once @var{expression}
7386 @itemx macro exp1 @var{expression}
7387 @cindex expand macro once
7388 @i{(This command is not yet implemented.)} Show the results of
7389 expanding those preprocessor macro invocations that appear explicitly in
7390 @var{expression}. Macro invocations appearing in that expansion are
7391 left unchanged. This command allows you to see the effect of a
7392 particular macro more clearly, without being confused by further
7393 expansions. Since @value{GDBN} simply expands macros, but does not
7394 parse the result, @var{expression} need not be a valid expression; it
7395 can be any string of tokens.
7398 @cindex macro definition, showing
7399 @cindex definition, showing a macro's
7400 @item info macro @var{macro}
7401 Show the definition of the macro named @var{macro}, and describe the
7402 source location where that definition was established.
7404 @kindex macro define
7405 @cindex user-defined macros
7406 @cindex defining macros interactively
7407 @cindex macros, user-defined
7408 @item macro define @var{macro} @var{replacement-list}
7409 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7410 @i{(This command is not yet implemented.)} Introduce a definition for a
7411 preprocessor macro named @var{macro}, invocations of which are replaced
7412 by the tokens given in @var{replacement-list}. The first form of this
7413 command defines an ``object-like'' macro, which takes no arguments; the
7414 second form defines a ``function-like'' macro, which takes the arguments
7415 given in @var{arglist}.
7417 A definition introduced by this command is in scope in every expression
7418 evaluated in @value{GDBN}, until it is removed with the @command{macro
7419 undef} command, described below. The definition overrides all
7420 definitions for @var{macro} present in the program being debugged, as
7421 well as any previous user-supplied definition.
7424 @item macro undef @var{macro}
7425 @i{(This command is not yet implemented.)} Remove any user-supplied
7426 definition for the macro named @var{macro}. This command only affects
7427 definitions provided with the @command{macro define} command, described
7428 above; it cannot remove definitions present in the program being
7433 @i{(This command is not yet implemented.)} List all the macros
7434 defined using the @code{macro define} command.
7437 @cindex macros, example of debugging with
7438 Here is a transcript showing the above commands in action. First, we
7439 show our source files:
7447 #define ADD(x) (M + x)
7452 printf ("Hello, world!\n");
7454 printf ("We're so creative.\n");
7456 printf ("Goodbye, world!\n");
7463 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7464 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7465 compiler includes information about preprocessor macros in the debugging
7469 $ gcc -gdwarf-2 -g3 sample.c -o sample
7473 Now, we start @value{GDBN} on our sample program:
7477 GNU gdb 2002-05-06-cvs
7478 Copyright 2002 Free Software Foundation, Inc.
7479 GDB is free software, @dots{}
7483 We can expand macros and examine their definitions, even when the
7484 program is not running. @value{GDBN} uses the current listing position
7485 to decide which macro definitions are in scope:
7488 (@value{GDBP}) list main
7491 5 #define ADD(x) (M + x)
7496 10 printf ("Hello, world!\n");
7498 12 printf ("We're so creative.\n");
7499 (@value{GDBP}) info macro ADD
7500 Defined at /home/jimb/gdb/macros/play/sample.c:5
7501 #define ADD(x) (M + x)
7502 (@value{GDBP}) info macro Q
7503 Defined at /home/jimb/gdb/macros/play/sample.h:1
7504 included at /home/jimb/gdb/macros/play/sample.c:2
7506 (@value{GDBP}) macro expand ADD(1)
7507 expands to: (42 + 1)
7508 (@value{GDBP}) macro expand-once ADD(1)
7509 expands to: once (M + 1)
7513 In the example above, note that @command{macro expand-once} expands only
7514 the macro invocation explicit in the original text --- the invocation of
7515 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7516 which was introduced by @code{ADD}.
7518 Once the program is running, @value{GDBN} uses the macro definitions in
7519 force at the source line of the current stack frame:
7522 (@value{GDBP}) break main
7523 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7525 Starting program: /home/jimb/gdb/macros/play/sample
7527 Breakpoint 1, main () at sample.c:10
7528 10 printf ("Hello, world!\n");
7532 At line 10, the definition of the macro @code{N} at line 9 is in force:
7535 (@value{GDBP}) info macro N
7536 Defined at /home/jimb/gdb/macros/play/sample.c:9
7538 (@value{GDBP}) macro expand N Q M
7540 (@value{GDBP}) print N Q M
7545 As we step over directives that remove @code{N}'s definition, and then
7546 give it a new definition, @value{GDBN} finds the definition (or lack
7547 thereof) in force at each point:
7552 12 printf ("We're so creative.\n");
7553 (@value{GDBP}) info macro N
7554 The symbol `N' has no definition as a C/C++ preprocessor macro
7555 at /home/jimb/gdb/macros/play/sample.c:12
7558 14 printf ("Goodbye, world!\n");
7559 (@value{GDBP}) info macro N
7560 Defined at /home/jimb/gdb/macros/play/sample.c:13
7562 (@value{GDBP}) macro expand N Q M
7563 expands to: 1729 < 42
7564 (@value{GDBP}) print N Q M
7571 @chapter Tracepoints
7572 @c This chapter is based on the documentation written by Michael
7573 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7576 In some applications, it is not feasible for the debugger to interrupt
7577 the program's execution long enough for the developer to learn
7578 anything helpful about its behavior. If the program's correctness
7579 depends on its real-time behavior, delays introduced by a debugger
7580 might cause the program to change its behavior drastically, or perhaps
7581 fail, even when the code itself is correct. It is useful to be able
7582 to observe the program's behavior without interrupting it.
7584 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7585 specify locations in the program, called @dfn{tracepoints}, and
7586 arbitrary expressions to evaluate when those tracepoints are reached.
7587 Later, using the @code{tfind} command, you can examine the values
7588 those expressions had when the program hit the tracepoints. The
7589 expressions may also denote objects in memory---structures or arrays,
7590 for example---whose values @value{GDBN} should record; while visiting
7591 a particular tracepoint, you may inspect those objects as if they were
7592 in memory at that moment. However, because @value{GDBN} records these
7593 values without interacting with you, it can do so quickly and
7594 unobtrusively, hopefully not disturbing the program's behavior.
7596 The tracepoint facility is currently available only for remote
7597 targets. @xref{Targets}. In addition, your remote target must know
7598 how to collect trace data. This functionality is implemented in the
7599 remote stub; however, none of the stubs distributed with @value{GDBN}
7600 support tracepoints as of this writing. The format of the remote
7601 packets used to implement tracepoints are described in @ref{Tracepoint
7604 This chapter describes the tracepoint commands and features.
7608 * Analyze Collected Data::
7609 * Tracepoint Variables::
7612 @node Set Tracepoints
7613 @section Commands to Set Tracepoints
7615 Before running such a @dfn{trace experiment}, an arbitrary number of
7616 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7617 tracepoint has a number assigned to it by @value{GDBN}. Like with
7618 breakpoints, tracepoint numbers are successive integers starting from
7619 one. Many of the commands associated with tracepoints take the
7620 tracepoint number as their argument, to identify which tracepoint to
7623 For each tracepoint, you can specify, in advance, some arbitrary set
7624 of data that you want the target to collect in the trace buffer when
7625 it hits that tracepoint. The collected data can include registers,
7626 local variables, or global data. Later, you can use @value{GDBN}
7627 commands to examine the values these data had at the time the
7630 This section describes commands to set tracepoints and associated
7631 conditions and actions.
7634 * Create and Delete Tracepoints::
7635 * Enable and Disable Tracepoints::
7636 * Tracepoint Passcounts::
7637 * Tracepoint Actions::
7638 * Listing Tracepoints::
7639 * Starting and Stopping Trace Experiments::
7642 @node Create and Delete Tracepoints
7643 @subsection Create and Delete Tracepoints
7646 @cindex set tracepoint
7649 The @code{trace} command is very similar to the @code{break} command.
7650 Its argument can be a source line, a function name, or an address in
7651 the target program. @xref{Set Breaks}. The @code{trace} command
7652 defines a tracepoint, which is a point in the target program where the
7653 debugger will briefly stop, collect some data, and then allow the
7654 program to continue. Setting a tracepoint or changing its commands
7655 doesn't take effect until the next @code{tstart} command; thus, you
7656 cannot change the tracepoint attributes once a trace experiment is
7659 Here are some examples of using the @code{trace} command:
7662 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7664 (@value{GDBP}) @b{trace +2} // 2 lines forward
7666 (@value{GDBP}) @b{trace my_function} // first source line of function
7668 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7670 (@value{GDBP}) @b{trace *0x2117c4} // an address
7674 You can abbreviate @code{trace} as @code{tr}.
7677 @cindex last tracepoint number
7678 @cindex recent tracepoint number
7679 @cindex tracepoint number
7680 The convenience variable @code{$tpnum} records the tracepoint number
7681 of the most recently set tracepoint.
7683 @kindex delete tracepoint
7684 @cindex tracepoint deletion
7685 @item delete tracepoint @r{[}@var{num}@r{]}
7686 Permanently delete one or more tracepoints. With no argument, the
7687 default is to delete all tracepoints.
7692 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7694 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7698 You can abbreviate this command as @code{del tr}.
7701 @node Enable and Disable Tracepoints
7702 @subsection Enable and Disable Tracepoints
7705 @kindex disable tracepoint
7706 @item disable tracepoint @r{[}@var{num}@r{]}
7707 Disable tracepoint @var{num}, or all tracepoints if no argument
7708 @var{num} is given. A disabled tracepoint will have no effect during
7709 the next trace experiment, but it is not forgotten. You can re-enable
7710 a disabled tracepoint using the @code{enable tracepoint} command.
7712 @kindex enable tracepoint
7713 @item enable tracepoint @r{[}@var{num}@r{]}
7714 Enable tracepoint @var{num}, or all tracepoints. The enabled
7715 tracepoints will become effective the next time a trace experiment is
7719 @node Tracepoint Passcounts
7720 @subsection Tracepoint Passcounts
7724 @cindex tracepoint pass count
7725 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7726 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7727 automatically stop a trace experiment. If a tracepoint's passcount is
7728 @var{n}, then the trace experiment will be automatically stopped on
7729 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7730 @var{num} is not specified, the @code{passcount} command sets the
7731 passcount of the most recently defined tracepoint. If no passcount is
7732 given, the trace experiment will run until stopped explicitly by the
7738 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7739 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7741 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7742 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7743 (@value{GDBP}) @b{trace foo}
7744 (@value{GDBP}) @b{pass 3}
7745 (@value{GDBP}) @b{trace bar}
7746 (@value{GDBP}) @b{pass 2}
7747 (@value{GDBP}) @b{trace baz}
7748 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7749 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7750 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7751 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7755 @node Tracepoint Actions
7756 @subsection Tracepoint Action Lists
7760 @cindex tracepoint actions
7761 @item actions @r{[}@var{num}@r{]}
7762 This command will prompt for a list of actions to be taken when the
7763 tracepoint is hit. If the tracepoint number @var{num} is not
7764 specified, this command sets the actions for the one that was most
7765 recently defined (so that you can define a tracepoint and then say
7766 @code{actions} without bothering about its number). You specify the
7767 actions themselves on the following lines, one action at a time, and
7768 terminate the actions list with a line containing just @code{end}. So
7769 far, the only defined actions are @code{collect} and
7770 @code{while-stepping}.
7772 @cindex remove actions from a tracepoint
7773 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7774 and follow it immediately with @samp{end}.
7777 (@value{GDBP}) @b{collect @var{data}} // collect some data
7779 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7781 (@value{GDBP}) @b{end} // signals the end of actions.
7784 In the following example, the action list begins with @code{collect}
7785 commands indicating the things to be collected when the tracepoint is
7786 hit. Then, in order to single-step and collect additional data
7787 following the tracepoint, a @code{while-stepping} command is used,
7788 followed by the list of things to be collected while stepping. The
7789 @code{while-stepping} command is terminated by its own separate
7790 @code{end} command. Lastly, the action list is terminated by an
7794 (@value{GDBP}) @b{trace foo}
7795 (@value{GDBP}) @b{actions}
7796 Enter actions for tracepoint 1, one per line:
7805 @kindex collect @r{(tracepoints)}
7806 @item collect @var{expr1}, @var{expr2}, @dots{}
7807 Collect values of the given expressions when the tracepoint is hit.
7808 This command accepts a comma-separated list of any valid expressions.
7809 In addition to global, static, or local variables, the following
7810 special arguments are supported:
7814 collect all registers
7817 collect all function arguments
7820 collect all local variables.
7823 You can give several consecutive @code{collect} commands, each one
7824 with a single argument, or one @code{collect} command with several
7825 arguments separated by commas: the effect is the same.
7827 The command @code{info scope} (@pxref{Symbols, info scope}) is
7828 particularly useful for figuring out what data to collect.
7830 @kindex while-stepping @r{(tracepoints)}
7831 @item while-stepping @var{n}
7832 Perform @var{n} single-step traces after the tracepoint, collecting
7833 new data at each step. The @code{while-stepping} command is
7834 followed by the list of what to collect while stepping (followed by
7835 its own @code{end} command):
7839 > collect $regs, myglobal
7845 You may abbreviate @code{while-stepping} as @code{ws} or
7849 @node Listing Tracepoints
7850 @subsection Listing Tracepoints
7853 @kindex info tracepoints
7855 @cindex information about tracepoints
7856 @item info tracepoints @r{[}@var{num}@r{]}
7857 Display information about the tracepoint @var{num}. If you don't specify
7858 a tracepoint number, displays information about all the tracepoints
7859 defined so far. For each tracepoint, the following information is
7866 whether it is enabled or disabled
7870 its passcount as given by the @code{passcount @var{n}} command
7872 its step count as given by the @code{while-stepping @var{n}} command
7874 where in the source files is the tracepoint set
7876 its action list as given by the @code{actions} command
7880 (@value{GDBP}) @b{info trace}
7881 Num Enb Address PassC StepC What
7882 1 y 0x002117c4 0 0 <gdb_asm>
7883 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7884 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7889 This command can be abbreviated @code{info tp}.
7892 @node Starting and Stopping Trace Experiments
7893 @subsection Starting and Stopping Trace Experiments
7897 @cindex start a new trace experiment
7898 @cindex collected data discarded
7900 This command takes no arguments. It starts the trace experiment, and
7901 begins collecting data. This has the side effect of discarding all
7902 the data collected in the trace buffer during the previous trace
7906 @cindex stop a running trace experiment
7908 This command takes no arguments. It ends the trace experiment, and
7909 stops collecting data.
7911 @strong{Note}: a trace experiment and data collection may stop
7912 automatically if any tracepoint's passcount is reached
7913 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7916 @cindex status of trace data collection
7917 @cindex trace experiment, status of
7919 This command displays the status of the current trace data
7923 Here is an example of the commands we described so far:
7926 (@value{GDBP}) @b{trace gdb_c_test}
7927 (@value{GDBP}) @b{actions}
7928 Enter actions for tracepoint #1, one per line.
7929 > collect $regs,$locals,$args
7934 (@value{GDBP}) @b{tstart}
7935 [time passes @dots{}]
7936 (@value{GDBP}) @b{tstop}
7940 @node Analyze Collected Data
7941 @section Using the Collected Data
7943 After the tracepoint experiment ends, you use @value{GDBN} commands
7944 for examining the trace data. The basic idea is that each tracepoint
7945 collects a trace @dfn{snapshot} every time it is hit and another
7946 snapshot every time it single-steps. All these snapshots are
7947 consecutively numbered from zero and go into a buffer, and you can
7948 examine them later. The way you examine them is to @dfn{focus} on a
7949 specific trace snapshot. When the remote stub is focused on a trace
7950 snapshot, it will respond to all @value{GDBN} requests for memory and
7951 registers by reading from the buffer which belongs to that snapshot,
7952 rather than from @emph{real} memory or registers of the program being
7953 debugged. This means that @strong{all} @value{GDBN} commands
7954 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7955 behave as if we were currently debugging the program state as it was
7956 when the tracepoint occurred. Any requests for data that are not in
7957 the buffer will fail.
7960 * tfind:: How to select a trace snapshot
7961 * tdump:: How to display all data for a snapshot
7962 * save-tracepoints:: How to save tracepoints for a future run
7966 @subsection @code{tfind @var{n}}
7969 @cindex select trace snapshot
7970 @cindex find trace snapshot
7971 The basic command for selecting a trace snapshot from the buffer is
7972 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7973 counting from zero. If no argument @var{n} is given, the next
7974 snapshot is selected.
7976 Here are the various forms of using the @code{tfind} command.
7980 Find the first snapshot in the buffer. This is a synonym for
7981 @code{tfind 0} (since 0 is the number of the first snapshot).
7984 Stop debugging trace snapshots, resume @emph{live} debugging.
7987 Same as @samp{tfind none}.
7990 No argument means find the next trace snapshot.
7993 Find the previous trace snapshot before the current one. This permits
7994 retracing earlier steps.
7996 @item tfind tracepoint @var{num}
7997 Find the next snapshot associated with tracepoint @var{num}. Search
7998 proceeds forward from the last examined trace snapshot. If no
7999 argument @var{num} is given, it means find the next snapshot collected
8000 for the same tracepoint as the current snapshot.
8002 @item tfind pc @var{addr}
8003 Find the next snapshot associated with the value @var{addr} of the
8004 program counter. Search proceeds forward from the last examined trace
8005 snapshot. If no argument @var{addr} is given, it means find the next
8006 snapshot with the same value of PC as the current snapshot.
8008 @item tfind outside @var{addr1}, @var{addr2}
8009 Find the next snapshot whose PC is outside the given range of
8012 @item tfind range @var{addr1}, @var{addr2}
8013 Find the next snapshot whose PC is between @var{addr1} and
8014 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8016 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8017 Find the next snapshot associated with the source line @var{n}. If
8018 the optional argument @var{file} is given, refer to line @var{n} in
8019 that source file. Search proceeds forward from the last examined
8020 trace snapshot. If no argument @var{n} is given, it means find the
8021 next line other than the one currently being examined; thus saying
8022 @code{tfind line} repeatedly can appear to have the same effect as
8023 stepping from line to line in a @emph{live} debugging session.
8026 The default arguments for the @code{tfind} commands are specifically
8027 designed to make it easy to scan through the trace buffer. For
8028 instance, @code{tfind} with no argument selects the next trace
8029 snapshot, and @code{tfind -} with no argument selects the previous
8030 trace snapshot. So, by giving one @code{tfind} command, and then
8031 simply hitting @key{RET} repeatedly you can examine all the trace
8032 snapshots in order. Or, by saying @code{tfind -} and then hitting
8033 @key{RET} repeatedly you can examine the snapshots in reverse order.
8034 The @code{tfind line} command with no argument selects the snapshot
8035 for the next source line executed. The @code{tfind pc} command with
8036 no argument selects the next snapshot with the same program counter
8037 (PC) as the current frame. The @code{tfind tracepoint} command with
8038 no argument selects the next trace snapshot collected by the same
8039 tracepoint as the current one.
8041 In addition to letting you scan through the trace buffer manually,
8042 these commands make it easy to construct @value{GDBN} scripts that
8043 scan through the trace buffer and print out whatever collected data
8044 you are interested in. Thus, if we want to examine the PC, FP, and SP
8045 registers from each trace frame in the buffer, we can say this:
8048 (@value{GDBP}) @b{tfind start}
8049 (@value{GDBP}) @b{while ($trace_frame != -1)}
8050 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8051 $trace_frame, $pc, $sp, $fp
8055 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8056 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8057 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8058 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8059 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8060 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8061 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8062 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8063 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8064 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8065 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8068 Or, if we want to examine the variable @code{X} at each source line in
8072 (@value{GDBP}) @b{tfind start}
8073 (@value{GDBP}) @b{while ($trace_frame != -1)}
8074 > printf "Frame %d, X == %d\n", $trace_frame, X
8084 @subsection @code{tdump}
8086 @cindex dump all data collected at tracepoint
8087 @cindex tracepoint data, display
8089 This command takes no arguments. It prints all the data collected at
8090 the current trace snapshot.
8093 (@value{GDBP}) @b{trace 444}
8094 (@value{GDBP}) @b{actions}
8095 Enter actions for tracepoint #2, one per line:
8096 > collect $regs, $locals, $args, gdb_long_test
8099 (@value{GDBP}) @b{tstart}
8101 (@value{GDBP}) @b{tfind line 444}
8102 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8104 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8106 (@value{GDBP}) @b{tdump}
8107 Data collected at tracepoint 2, trace frame 1:
8108 d0 0xc4aa0085 -995491707
8112 d4 0x71aea3d 119204413
8117 a1 0x3000668 50333288
8120 a4 0x3000698 50333336
8122 fp 0x30bf3c 0x30bf3c
8123 sp 0x30bf34 0x30bf34
8125 pc 0x20b2c8 0x20b2c8
8129 p = 0x20e5b4 "gdb-test"
8136 gdb_long_test = 17 '\021'
8141 @node save-tracepoints
8142 @subsection @code{save-tracepoints @var{filename}}
8143 @kindex save-tracepoints
8144 @cindex save tracepoints for future sessions
8146 This command saves all current tracepoint definitions together with
8147 their actions and passcounts, into a file @file{@var{filename}}
8148 suitable for use in a later debugging session. To read the saved
8149 tracepoint definitions, use the @code{source} command (@pxref{Command
8152 @node Tracepoint Variables
8153 @section Convenience Variables for Tracepoints
8154 @cindex tracepoint variables
8155 @cindex convenience variables for tracepoints
8158 @vindex $trace_frame
8159 @item (int) $trace_frame
8160 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8161 snapshot is selected.
8164 @item (int) $tracepoint
8165 The tracepoint for the current trace snapshot.
8168 @item (int) $trace_line
8169 The line number for the current trace snapshot.
8172 @item (char []) $trace_file
8173 The source file for the current trace snapshot.
8176 @item (char []) $trace_func
8177 The name of the function containing @code{$tracepoint}.
8180 Note: @code{$trace_file} is not suitable for use in @code{printf},
8181 use @code{output} instead.
8183 Here's a simple example of using these convenience variables for
8184 stepping through all the trace snapshots and printing some of their
8188 (@value{GDBP}) @b{tfind start}
8190 (@value{GDBP}) @b{while $trace_frame != -1}
8191 > output $trace_file
8192 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8198 @chapter Debugging Programs That Use Overlays
8201 If your program is too large to fit completely in your target system's
8202 memory, you can sometimes use @dfn{overlays} to work around this
8203 problem. @value{GDBN} provides some support for debugging programs that
8207 * How Overlays Work:: A general explanation of overlays.
8208 * Overlay Commands:: Managing overlays in @value{GDBN}.
8209 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8210 mapped by asking the inferior.
8211 * Overlay Sample Program:: A sample program using overlays.
8214 @node How Overlays Work
8215 @section How Overlays Work
8216 @cindex mapped overlays
8217 @cindex unmapped overlays
8218 @cindex load address, overlay's
8219 @cindex mapped address
8220 @cindex overlay area
8222 Suppose you have a computer whose instruction address space is only 64
8223 kilobytes long, but which has much more memory which can be accessed by
8224 other means: special instructions, segment registers, or memory
8225 management hardware, for example. Suppose further that you want to
8226 adapt a program which is larger than 64 kilobytes to run on this system.
8228 One solution is to identify modules of your program which are relatively
8229 independent, and need not call each other directly; call these modules
8230 @dfn{overlays}. Separate the overlays from the main program, and place
8231 their machine code in the larger memory. Place your main program in
8232 instruction memory, but leave at least enough space there to hold the
8233 largest overlay as well.
8235 Now, to call a function located in an overlay, you must first copy that
8236 overlay's machine code from the large memory into the space set aside
8237 for it in the instruction memory, and then jump to its entry point
8240 @c NB: In the below the mapped area's size is greater or equal to the
8241 @c size of all overlays. This is intentional to remind the developer
8242 @c that overlays don't necessarily need to be the same size.
8246 Data Instruction Larger
8247 Address Space Address Space Address Space
8248 +-----------+ +-----------+ +-----------+
8250 +-----------+ +-----------+ +-----------+<-- overlay 1
8251 | program | | main | .----| overlay 1 | load address
8252 | variables | | program | | +-----------+
8253 | and heap | | | | | |
8254 +-----------+ | | | +-----------+<-- overlay 2
8255 | | +-----------+ | | | load address
8256 +-----------+ | | | .-| overlay 2 |
8258 mapped --->+-----------+ | | +-----------+
8260 | overlay | <-' | | |
8261 | area | <---' +-----------+<-- overlay 3
8262 | | <---. | | load address
8263 +-----------+ `--| overlay 3 |
8270 @anchor{A code overlay}A code overlay
8274 The diagram (@pxref{A code overlay}) shows a system with separate data
8275 and instruction address spaces. To map an overlay, the program copies
8276 its code from the larger address space to the instruction address space.
8277 Since the overlays shown here all use the same mapped address, only one
8278 may be mapped at a time. For a system with a single address space for
8279 data and instructions, the diagram would be similar, except that the
8280 program variables and heap would share an address space with the main
8281 program and the overlay area.
8283 An overlay loaded into instruction memory and ready for use is called a
8284 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8285 instruction memory. An overlay not present (or only partially present)
8286 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8287 is its address in the larger memory. The mapped address is also called
8288 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8289 called the @dfn{load memory address}, or @dfn{LMA}.
8291 Unfortunately, overlays are not a completely transparent way to adapt a
8292 program to limited instruction memory. They introduce a new set of
8293 global constraints you must keep in mind as you design your program:
8298 Before calling or returning to a function in an overlay, your program
8299 must make sure that overlay is actually mapped. Otherwise, the call or
8300 return will transfer control to the right address, but in the wrong
8301 overlay, and your program will probably crash.
8304 If the process of mapping an overlay is expensive on your system, you
8305 will need to choose your overlays carefully to minimize their effect on
8306 your program's performance.
8309 The executable file you load onto your system must contain each
8310 overlay's instructions, appearing at the overlay's load address, not its
8311 mapped address. However, each overlay's instructions must be relocated
8312 and its symbols defined as if the overlay were at its mapped address.
8313 You can use GNU linker scripts to specify different load and relocation
8314 addresses for pieces of your program; see @ref{Overlay Description,,,
8315 ld.info, Using ld: the GNU linker}.
8318 The procedure for loading executable files onto your system must be able
8319 to load their contents into the larger address space as well as the
8320 instruction and data spaces.
8324 The overlay system described above is rather simple, and could be
8325 improved in many ways:
8330 If your system has suitable bank switch registers or memory management
8331 hardware, you could use those facilities to make an overlay's load area
8332 contents simply appear at their mapped address in instruction space.
8333 This would probably be faster than copying the overlay to its mapped
8334 area in the usual way.
8337 If your overlays are small enough, you could set aside more than one
8338 overlay area, and have more than one overlay mapped at a time.
8341 You can use overlays to manage data, as well as instructions. In
8342 general, data overlays are even less transparent to your design than
8343 code overlays: whereas code overlays only require care when you call or
8344 return to functions, data overlays require care every time you access
8345 the data. Also, if you change the contents of a data overlay, you
8346 must copy its contents back out to its load address before you can copy a
8347 different data overlay into the same mapped area.
8352 @node Overlay Commands
8353 @section Overlay Commands
8355 To use @value{GDBN}'s overlay support, each overlay in your program must
8356 correspond to a separate section of the executable file. The section's
8357 virtual memory address and load memory address must be the overlay's
8358 mapped and load addresses. Identifying overlays with sections allows
8359 @value{GDBN} to determine the appropriate address of a function or
8360 variable, depending on whether the overlay is mapped or not.
8362 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8363 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8368 Disable @value{GDBN}'s overlay support. When overlay support is
8369 disabled, @value{GDBN} assumes that all functions and variables are
8370 always present at their mapped addresses. By default, @value{GDBN}'s
8371 overlay support is disabled.
8373 @item overlay manual
8374 @cindex manual overlay debugging
8375 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8376 relies on you to tell it which overlays are mapped, and which are not,
8377 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8378 commands described below.
8380 @item overlay map-overlay @var{overlay}
8381 @itemx overlay map @var{overlay}
8382 @cindex map an overlay
8383 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8384 be the name of the object file section containing the overlay. When an
8385 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8386 functions and variables at their mapped addresses. @value{GDBN} assumes
8387 that any other overlays whose mapped ranges overlap that of
8388 @var{overlay} are now unmapped.
8390 @item overlay unmap-overlay @var{overlay}
8391 @itemx overlay unmap @var{overlay}
8392 @cindex unmap an overlay
8393 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8394 must be the name of the object file section containing the overlay.
8395 When an overlay is unmapped, @value{GDBN} assumes it can find the
8396 overlay's functions and variables at their load addresses.
8399 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8400 consults a data structure the overlay manager maintains in the inferior
8401 to see which overlays are mapped. For details, see @ref{Automatic
8404 @item overlay load-target
8406 @cindex reloading the overlay table
8407 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8408 re-reads the table @value{GDBN} automatically each time the inferior
8409 stops, so this command should only be necessary if you have changed the
8410 overlay mapping yourself using @value{GDBN}. This command is only
8411 useful when using automatic overlay debugging.
8413 @item overlay list-overlays
8415 @cindex listing mapped overlays
8416 Display a list of the overlays currently mapped, along with their mapped
8417 addresses, load addresses, and sizes.
8421 Normally, when @value{GDBN} prints a code address, it includes the name
8422 of the function the address falls in:
8425 (@value{GDBP}) print main
8426 $3 = @{int ()@} 0x11a0 <main>
8429 When overlay debugging is enabled, @value{GDBN} recognizes code in
8430 unmapped overlays, and prints the names of unmapped functions with
8431 asterisks around them. For example, if @code{foo} is a function in an
8432 unmapped overlay, @value{GDBN} prints it this way:
8435 (@value{GDBP}) overlay list
8436 No sections are mapped.
8437 (@value{GDBP}) print foo
8438 $5 = @{int (int)@} 0x100000 <*foo*>
8441 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8445 (@value{GDBP}) overlay list
8446 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8447 mapped at 0x1016 - 0x104a
8448 (@value{GDBP}) print foo
8449 $6 = @{int (int)@} 0x1016 <foo>
8452 When overlay debugging is enabled, @value{GDBN} can find the correct
8453 address for functions and variables in an overlay, whether or not the
8454 overlay is mapped. This allows most @value{GDBN} commands, like
8455 @code{break} and @code{disassemble}, to work normally, even on unmapped
8456 code. However, @value{GDBN}'s breakpoint support has some limitations:
8460 @cindex breakpoints in overlays
8461 @cindex overlays, setting breakpoints in
8462 You can set breakpoints in functions in unmapped overlays, as long as
8463 @value{GDBN} can write to the overlay at its load address.
8465 @value{GDBN} can not set hardware or simulator-based breakpoints in
8466 unmapped overlays. However, if you set a breakpoint at the end of your
8467 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8468 you are using manual overlay management), @value{GDBN} will re-set its
8469 breakpoints properly.
8473 @node Automatic Overlay Debugging
8474 @section Automatic Overlay Debugging
8475 @cindex automatic overlay debugging
8477 @value{GDBN} can automatically track which overlays are mapped and which
8478 are not, given some simple co-operation from the overlay manager in the
8479 inferior. If you enable automatic overlay debugging with the
8480 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8481 looks in the inferior's memory for certain variables describing the
8482 current state of the overlays.
8484 Here are the variables your overlay manager must define to support
8485 @value{GDBN}'s automatic overlay debugging:
8489 @item @code{_ovly_table}:
8490 This variable must be an array of the following structures:
8495 /* The overlay's mapped address. */
8498 /* The size of the overlay, in bytes. */
8501 /* The overlay's load address. */
8504 /* Non-zero if the overlay is currently mapped;
8506 unsigned long mapped;
8510 @item @code{_novlys}:
8511 This variable must be a four-byte signed integer, holding the total
8512 number of elements in @code{_ovly_table}.
8516 To decide whether a particular overlay is mapped or not, @value{GDBN}
8517 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8518 @code{lma} members equal the VMA and LMA of the overlay's section in the
8519 executable file. When @value{GDBN} finds a matching entry, it consults
8520 the entry's @code{mapped} member to determine whether the overlay is
8523 In addition, your overlay manager may define a function called
8524 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8525 will silently set a breakpoint there. If the overlay manager then
8526 calls this function whenever it has changed the overlay table, this
8527 will enable @value{GDBN} to accurately keep track of which overlays
8528 are in program memory, and update any breakpoints that may be set
8529 in overlays. This will allow breakpoints to work even if the
8530 overlays are kept in ROM or other non-writable memory while they
8531 are not being executed.
8533 @node Overlay Sample Program
8534 @section Overlay Sample Program
8535 @cindex overlay example program
8537 When linking a program which uses overlays, you must place the overlays
8538 at their load addresses, while relocating them to run at their mapped
8539 addresses. To do this, you must write a linker script (@pxref{Overlay
8540 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8541 since linker scripts are specific to a particular host system, target
8542 architecture, and target memory layout, this manual cannot provide
8543 portable sample code demonstrating @value{GDBN}'s overlay support.
8545 However, the @value{GDBN} source distribution does contain an overlaid
8546 program, with linker scripts for a few systems, as part of its test
8547 suite. The program consists of the following files from
8548 @file{gdb/testsuite/gdb.base}:
8552 The main program file.
8554 A simple overlay manager, used by @file{overlays.c}.
8559 Overlay modules, loaded and used by @file{overlays.c}.
8562 Linker scripts for linking the test program on the @code{d10v-elf}
8563 and @code{m32r-elf} targets.
8566 You can build the test program using the @code{d10v-elf} GCC
8567 cross-compiler like this:
8570 $ d10v-elf-gcc -g -c overlays.c
8571 $ d10v-elf-gcc -g -c ovlymgr.c
8572 $ d10v-elf-gcc -g -c foo.c
8573 $ d10v-elf-gcc -g -c bar.c
8574 $ d10v-elf-gcc -g -c baz.c
8575 $ d10v-elf-gcc -g -c grbx.c
8576 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8577 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8580 The build process is identical for any other architecture, except that
8581 you must substitute the appropriate compiler and linker script for the
8582 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8586 @chapter Using @value{GDBN} with Different Languages
8589 Although programming languages generally have common aspects, they are
8590 rarely expressed in the same manner. For instance, in ANSI C,
8591 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8592 Modula-2, it is accomplished by @code{p^}. Values can also be
8593 represented (and displayed) differently. Hex numbers in C appear as
8594 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8596 @cindex working language
8597 Language-specific information is built into @value{GDBN} for some languages,
8598 allowing you to express operations like the above in your program's
8599 native language, and allowing @value{GDBN} to output values in a manner
8600 consistent with the syntax of your program's native language. The
8601 language you use to build expressions is called the @dfn{working
8605 * Setting:: Switching between source languages
8606 * Show:: Displaying the language
8607 * Checks:: Type and range checks
8608 * Supported Languages:: Supported languages
8609 * Unsupported Languages:: Unsupported languages
8613 @section Switching Between Source Languages
8615 There are two ways to control the working language---either have @value{GDBN}
8616 set it automatically, or select it manually yourself. You can use the
8617 @code{set language} command for either purpose. On startup, @value{GDBN}
8618 defaults to setting the language automatically. The working language is
8619 used to determine how expressions you type are interpreted, how values
8622 In addition to the working language, every source file that
8623 @value{GDBN} knows about has its own working language. For some object
8624 file formats, the compiler might indicate which language a particular
8625 source file is in. However, most of the time @value{GDBN} infers the
8626 language from the name of the file. The language of a source file
8627 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8628 show each frame appropriately for its own language. There is no way to
8629 set the language of a source file from within @value{GDBN}, but you can
8630 set the language associated with a filename extension. @xref{Show, ,
8631 Displaying the Language}.
8633 This is most commonly a problem when you use a program, such
8634 as @code{cfront} or @code{f2c}, that generates C but is written in
8635 another language. In that case, make the
8636 program use @code{#line} directives in its C output; that way
8637 @value{GDBN} will know the correct language of the source code of the original
8638 program, and will display that source code, not the generated C code.
8641 * Filenames:: Filename extensions and languages.
8642 * Manually:: Setting the working language manually
8643 * Automatically:: Having @value{GDBN} infer the source language
8647 @subsection List of Filename Extensions and Languages
8649 If a source file name ends in one of the following extensions, then
8650 @value{GDBN} infers that its language is the one indicated.
8671 Objective-C source file
8678 Modula-2 source file
8682 Assembler source file. This actually behaves almost like C, but
8683 @value{GDBN} does not skip over function prologues when stepping.
8686 In addition, you may set the language associated with a filename
8687 extension. @xref{Show, , Displaying the Language}.
8690 @subsection Setting the Working Language
8692 If you allow @value{GDBN} to set the language automatically,
8693 expressions are interpreted the same way in your debugging session and
8696 @kindex set language
8697 If you wish, you may set the language manually. To do this, issue the
8698 command @samp{set language @var{lang}}, where @var{lang} is the name of
8700 @code{c} or @code{modula-2}.
8701 For a list of the supported languages, type @samp{set language}.
8703 Setting the language manually prevents @value{GDBN} from updating the working
8704 language automatically. This can lead to confusion if you try
8705 to debug a program when the working language is not the same as the
8706 source language, when an expression is acceptable to both
8707 languages---but means different things. For instance, if the current
8708 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8716 might not have the effect you intended. In C, this means to add
8717 @code{b} and @code{c} and place the result in @code{a}. The result
8718 printed would be the value of @code{a}. In Modula-2, this means to compare
8719 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8722 @subsection Having @value{GDBN} Infer the Source Language
8724 To have @value{GDBN} set the working language automatically, use
8725 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8726 then infers the working language. That is, when your program stops in a
8727 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8728 working language to the language recorded for the function in that
8729 frame. If the language for a frame is unknown (that is, if the function
8730 or block corresponding to the frame was defined in a source file that
8731 does not have a recognized extension), the current working language is
8732 not changed, and @value{GDBN} issues a warning.
8734 This may not seem necessary for most programs, which are written
8735 entirely in one source language. However, program modules and libraries
8736 written in one source language can be used by a main program written in
8737 a different source language. Using @samp{set language auto} in this
8738 case frees you from having to set the working language manually.
8741 @section Displaying the Language
8743 The following commands help you find out which language is the
8744 working language, and also what language source files were written in.
8748 @kindex show language
8749 Display the current working language. This is the
8750 language you can use with commands such as @code{print} to
8751 build and compute expressions that may involve variables in your program.
8754 @kindex info frame@r{, show the source language}
8755 Display the source language for this frame. This language becomes the
8756 working language if you use an identifier from this frame.
8757 @xref{Frame Info, ,Information about a Frame}, to identify the other
8758 information listed here.
8761 @kindex info source@r{, show the source language}
8762 Display the source language of this source file.
8763 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8764 information listed here.
8767 In unusual circumstances, you may have source files with extensions
8768 not in the standard list. You can then set the extension associated
8769 with a language explicitly:
8772 @item set extension-language @var{ext} @var{language}
8773 @kindex set extension-language
8774 Tell @value{GDBN} that source files with extension @var{ext} are to be
8775 assumed as written in the source language @var{language}.
8777 @item info extensions
8778 @kindex info extensions
8779 List all the filename extensions and the associated languages.
8783 @section Type and Range Checking
8786 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8787 checking are included, but they do not yet have any effect. This
8788 section documents the intended facilities.
8790 @c FIXME remove warning when type/range code added
8792 Some languages are designed to guard you against making seemingly common
8793 errors through a series of compile- and run-time checks. These include
8794 checking the type of arguments to functions and operators, and making
8795 sure mathematical overflows are caught at run time. Checks such as
8796 these help to ensure a program's correctness once it has been compiled
8797 by eliminating type mismatches, and providing active checks for range
8798 errors when your program is running.
8800 @value{GDBN} can check for conditions like the above if you wish.
8801 Although @value{GDBN} does not check the statements in your program,
8802 it can check expressions entered directly into @value{GDBN} for
8803 evaluation via the @code{print} command, for example. As with the
8804 working language, @value{GDBN} can also decide whether or not to check
8805 automatically based on your program's source language.
8806 @xref{Supported Languages, ,Supported Languages}, for the default
8807 settings of supported languages.
8810 * Type Checking:: An overview of type checking
8811 * Range Checking:: An overview of range checking
8814 @cindex type checking
8815 @cindex checks, type
8817 @subsection An Overview of Type Checking
8819 Some languages, such as Modula-2, are strongly typed, meaning that the
8820 arguments to operators and functions have to be of the correct type,
8821 otherwise an error occurs. These checks prevent type mismatch
8822 errors from ever causing any run-time problems. For example,
8830 The second example fails because the @code{CARDINAL} 1 is not
8831 type-compatible with the @code{REAL} 2.3.
8833 For the expressions you use in @value{GDBN} commands, you can tell the
8834 @value{GDBN} type checker to skip checking;
8835 to treat any mismatches as errors and abandon the expression;
8836 or to only issue warnings when type mismatches occur,
8837 but evaluate the expression anyway. When you choose the last of
8838 these, @value{GDBN} evaluates expressions like the second example above, but
8839 also issues a warning.
8841 Even if you turn type checking off, there may be other reasons
8842 related to type that prevent @value{GDBN} from evaluating an expression.
8843 For instance, @value{GDBN} does not know how to add an @code{int} and
8844 a @code{struct foo}. These particular type errors have nothing to do
8845 with the language in use, and usually arise from expressions, such as
8846 the one described above, which make little sense to evaluate anyway.
8848 Each language defines to what degree it is strict about type. For
8849 instance, both Modula-2 and C require the arguments to arithmetical
8850 operators to be numbers. In C, enumerated types and pointers can be
8851 represented as numbers, so that they are valid arguments to mathematical
8852 operators. @xref{Supported Languages, ,Supported Languages}, for further
8853 details on specific languages.
8855 @value{GDBN} provides some additional commands for controlling the type checker:
8857 @kindex set check type
8858 @kindex show check type
8860 @item set check type auto
8861 Set type checking on or off based on the current working language.
8862 @xref{Supported Languages, ,Supported Languages}, for the default settings for
8865 @item set check type on
8866 @itemx set check type off
8867 Set type checking on or off, overriding the default setting for the
8868 current working language. Issue a warning if the setting does not
8869 match the language default. If any type mismatches occur in
8870 evaluating an expression while type checking is on, @value{GDBN} prints a
8871 message and aborts evaluation of the expression.
8873 @item set check type warn
8874 Cause the type checker to issue warnings, but to always attempt to
8875 evaluate the expression. Evaluating the expression may still
8876 be impossible for other reasons. For example, @value{GDBN} cannot add
8877 numbers and structures.
8880 Show the current setting of the type checker, and whether or not @value{GDBN}
8881 is setting it automatically.
8884 @cindex range checking
8885 @cindex checks, range
8886 @node Range Checking
8887 @subsection An Overview of Range Checking
8889 In some languages (such as Modula-2), it is an error to exceed the
8890 bounds of a type; this is enforced with run-time checks. Such range
8891 checking is meant to ensure program correctness by making sure
8892 computations do not overflow, or indices on an array element access do
8893 not exceed the bounds of the array.
8895 For expressions you use in @value{GDBN} commands, you can tell
8896 @value{GDBN} to treat range errors in one of three ways: ignore them,
8897 always treat them as errors and abandon the expression, or issue
8898 warnings but evaluate the expression anyway.
8900 A range error can result from numerical overflow, from exceeding an
8901 array index bound, or when you type a constant that is not a member
8902 of any type. Some languages, however, do not treat overflows as an
8903 error. In many implementations of C, mathematical overflow causes the
8904 result to ``wrap around'' to lower values---for example, if @var{m} is
8905 the largest integer value, and @var{s} is the smallest, then
8908 @var{m} + 1 @result{} @var{s}
8911 This, too, is specific to individual languages, and in some cases
8912 specific to individual compilers or machines. @xref{Supported Languages, ,
8913 Supported Languages}, for further details on specific languages.
8915 @value{GDBN} provides some additional commands for controlling the range checker:
8917 @kindex set check range
8918 @kindex show check range
8920 @item set check range auto
8921 Set range checking on or off based on the current working language.
8922 @xref{Supported Languages, ,Supported Languages}, for the default settings for
8925 @item set check range on
8926 @itemx set check range off
8927 Set range checking on or off, overriding the default setting for the
8928 current working language. A warning is issued if the setting does not
8929 match the language default. If a range error occurs and range checking is on,
8930 then a message is printed and evaluation of the expression is aborted.
8932 @item set check range warn
8933 Output messages when the @value{GDBN} range checker detects a range error,
8934 but attempt to evaluate the expression anyway. Evaluating the
8935 expression may still be impossible for other reasons, such as accessing
8936 memory that the process does not own (a typical example from many Unix
8940 Show the current setting of the range checker, and whether or not it is
8941 being set automatically by @value{GDBN}.
8944 @node Supported Languages
8945 @section Supported Languages
8947 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8948 assembly, Modula-2, and Ada.
8949 @c This is false ...
8950 Some @value{GDBN} features may be used in expressions regardless of the
8951 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8952 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8953 ,Expressions}) can be used with the constructs of any supported
8956 The following sections detail to what degree each source language is
8957 supported by @value{GDBN}. These sections are not meant to be language
8958 tutorials or references, but serve only as a reference guide to what the
8959 @value{GDBN} expression parser accepts, and what input and output
8960 formats should look like for different languages. There are many good
8961 books written on each of these languages; please look to these for a
8962 language reference or tutorial.
8966 * Objective-C:: Objective-C
8969 * Modula-2:: Modula-2
8974 @subsection C and C@t{++}
8976 @cindex C and C@t{++}
8977 @cindex expressions in C or C@t{++}
8979 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8980 to both languages. Whenever this is the case, we discuss those languages
8984 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8985 @cindex @sc{gnu} C@t{++}
8986 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8987 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8988 effectively, you must compile your C@t{++} programs with a supported
8989 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8990 compiler (@code{aCC}).
8992 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8993 format; if it doesn't work on your system, try the stabs+ debugging
8994 format. You can select those formats explicitly with the @code{g++}
8995 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8996 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
8997 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9000 * C Operators:: C and C@t{++} operators
9001 * C Constants:: C and C@t{++} constants
9002 * C Plus Plus Expressions:: C@t{++} expressions
9003 * C Defaults:: Default settings for C and C@t{++}
9004 * C Checks:: C and C@t{++} type and range checks
9005 * Debugging C:: @value{GDBN} and C
9006 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9010 @subsubsection C and C@t{++} Operators
9012 @cindex C and C@t{++} operators
9014 Operators must be defined on values of specific types. For instance,
9015 @code{+} is defined on numbers, but not on structures. Operators are
9016 often defined on groups of types.
9018 For the purposes of C and C@t{++}, the following definitions hold:
9023 @emph{Integral types} include @code{int} with any of its storage-class
9024 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9027 @emph{Floating-point types} include @code{float}, @code{double}, and
9028 @code{long double} (if supported by the target platform).
9031 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9034 @emph{Scalar types} include all of the above.
9039 The following operators are supported. They are listed here
9040 in order of increasing precedence:
9044 The comma or sequencing operator. Expressions in a comma-separated list
9045 are evaluated from left to right, with the result of the entire
9046 expression being the last expression evaluated.
9049 Assignment. The value of an assignment expression is the value
9050 assigned. Defined on scalar types.
9053 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9054 and translated to @w{@code{@var{a} = @var{a op b}}}.
9055 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9056 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9057 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9060 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9061 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9065 Logical @sc{or}. Defined on integral types.
9068 Logical @sc{and}. Defined on integral types.
9071 Bitwise @sc{or}. Defined on integral types.
9074 Bitwise exclusive-@sc{or}. Defined on integral types.
9077 Bitwise @sc{and}. Defined on integral types.
9080 Equality and inequality. Defined on scalar types. The value of these
9081 expressions is 0 for false and non-zero for true.
9083 @item <@r{, }>@r{, }<=@r{, }>=
9084 Less than, greater than, less than or equal, greater than or equal.
9085 Defined on scalar types. The value of these expressions is 0 for false
9086 and non-zero for true.
9089 left shift, and right shift. Defined on integral types.
9092 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9095 Addition and subtraction. Defined on integral types, floating-point types and
9098 @item *@r{, }/@r{, }%
9099 Multiplication, division, and modulus. Multiplication and division are
9100 defined on integral and floating-point types. Modulus is defined on
9104 Increment and decrement. When appearing before a variable, the
9105 operation is performed before the variable is used in an expression;
9106 when appearing after it, the variable's value is used before the
9107 operation takes place.
9110 Pointer dereferencing. Defined on pointer types. Same precedence as
9114 Address operator. Defined on variables. Same precedence as @code{++}.
9116 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9117 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9118 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
9119 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9123 Negative. Defined on integral and floating-point types. Same
9124 precedence as @code{++}.
9127 Logical negation. Defined on integral types. Same precedence as
9131 Bitwise complement operator. Defined on integral types. Same precedence as
9136 Structure member, and pointer-to-structure member. For convenience,
9137 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9138 pointer based on the stored type information.
9139 Defined on @code{struct} and @code{union} data.
9142 Dereferences of pointers to members.
9145 Array indexing. @code{@var{a}[@var{i}]} is defined as
9146 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9149 Function parameter list. Same precedence as @code{->}.
9152 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9153 and @code{class} types.
9156 Doubled colons also represent the @value{GDBN} scope operator
9157 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9161 If an operator is redefined in the user code, @value{GDBN} usually
9162 attempts to invoke the redefined version instead of using the operator's
9166 @subsubsection C and C@t{++} Constants
9168 @cindex C and C@t{++} constants
9170 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9175 Integer constants are a sequence of digits. Octal constants are
9176 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9177 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9178 @samp{l}, specifying that the constant should be treated as a
9182 Floating point constants are a sequence of digits, followed by a decimal
9183 point, followed by a sequence of digits, and optionally followed by an
9184 exponent. An exponent is of the form:
9185 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9186 sequence of digits. The @samp{+} is optional for positive exponents.
9187 A floating-point constant may also end with a letter @samp{f} or
9188 @samp{F}, specifying that the constant should be treated as being of
9189 the @code{float} (as opposed to the default @code{double}) type; or with
9190 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9194 Enumerated constants consist of enumerated identifiers, or their
9195 integral equivalents.
9198 Character constants are a single character surrounded by single quotes
9199 (@code{'}), or a number---the ordinal value of the corresponding character
9200 (usually its @sc{ascii} value). Within quotes, the single character may
9201 be represented by a letter or by @dfn{escape sequences}, which are of
9202 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9203 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9204 @samp{@var{x}} is a predefined special character---for example,
9205 @samp{\n} for newline.
9208 String constants are a sequence of character constants surrounded by
9209 double quotes (@code{"}). Any valid character constant (as described
9210 above) may appear. Double quotes within the string must be preceded by
9211 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9215 Pointer constants are an integral value. You can also write pointers
9216 to constants using the C operator @samp{&}.
9219 Array constants are comma-separated lists surrounded by braces @samp{@{}
9220 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9221 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9222 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9225 @node C Plus Plus Expressions
9226 @subsubsection C@t{++} Expressions
9228 @cindex expressions in C@t{++}
9229 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9231 @cindex debugging C@t{++} programs
9232 @cindex C@t{++} compilers
9233 @cindex debug formats and C@t{++}
9234 @cindex @value{NGCC} and C@t{++}
9236 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9237 proper compiler and the proper debug format. Currently, @value{GDBN}
9238 works best when debugging C@t{++} code that is compiled with
9239 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9240 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9241 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9242 stabs+ as their default debug format, so you usually don't need to
9243 specify a debug format explicitly. Other compilers and/or debug formats
9244 are likely to work badly or not at all when using @value{GDBN} to debug
9250 @cindex member functions
9252 Member function calls are allowed; you can use expressions like
9255 count = aml->GetOriginal(x, y)
9258 @vindex this@r{, inside C@t{++} member functions}
9259 @cindex namespace in C@t{++}
9261 While a member function is active (in the selected stack frame), your
9262 expressions have the same namespace available as the member function;
9263 that is, @value{GDBN} allows implicit references to the class instance
9264 pointer @code{this} following the same rules as C@t{++}.
9266 @cindex call overloaded functions
9267 @cindex overloaded functions, calling
9268 @cindex type conversions in C@t{++}
9270 You can call overloaded functions; @value{GDBN} resolves the function
9271 call to the right definition, with some restrictions. @value{GDBN} does not
9272 perform overload resolution involving user-defined type conversions,
9273 calls to constructors, or instantiations of templates that do not exist
9274 in the program. It also cannot handle ellipsis argument lists or
9277 It does perform integral conversions and promotions, floating-point
9278 promotions, arithmetic conversions, pointer conversions, conversions of
9279 class objects to base classes, and standard conversions such as those of
9280 functions or arrays to pointers; it requires an exact match on the
9281 number of function arguments.
9283 Overload resolution is always performed, unless you have specified
9284 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9285 ,@value{GDBN} Features for C@t{++}}.
9287 You must specify @code{set overload-resolution off} in order to use an
9288 explicit function signature to call an overloaded function, as in
9290 p 'foo(char,int)'('x', 13)
9293 The @value{GDBN} command-completion facility can simplify this;
9294 see @ref{Completion, ,Command Completion}.
9296 @cindex reference declarations
9298 @value{GDBN} understands variables declared as C@t{++} references; you can use
9299 them in expressions just as you do in C@t{++} source---they are automatically
9302 In the parameter list shown when @value{GDBN} displays a frame, the values of
9303 reference variables are not displayed (unlike other variables); this
9304 avoids clutter, since references are often used for large structures.
9305 The @emph{address} of a reference variable is always shown, unless
9306 you have specified @samp{set print address off}.
9309 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9310 expressions can use it just as expressions in your program do. Since
9311 one scope may be defined in another, you can use @code{::} repeatedly if
9312 necessary, for example in an expression like
9313 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9314 resolving name scope by reference to source files, in both C and C@t{++}
9315 debugging (@pxref{Variables, ,Program Variables}).
9318 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9319 calling virtual functions correctly, printing out virtual bases of
9320 objects, calling functions in a base subobject, casting objects, and
9321 invoking user-defined operators.
9324 @subsubsection C and C@t{++} Defaults
9326 @cindex C and C@t{++} defaults
9328 If you allow @value{GDBN} to set type and range checking automatically, they
9329 both default to @code{off} whenever the working language changes to
9330 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9331 selects the working language.
9333 If you allow @value{GDBN} to set the language automatically, it
9334 recognizes source files whose names end with @file{.c}, @file{.C}, or
9335 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9336 these files, it sets the working language to C or C@t{++}.
9337 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9338 for further details.
9340 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9341 @c unimplemented. If (b) changes, it might make sense to let this node
9342 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9345 @subsubsection C and C@t{++} Type and Range Checks
9347 @cindex C and C@t{++} checks
9349 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9350 is not used. However, if you turn type checking on, @value{GDBN}
9351 considers two variables type equivalent if:
9355 The two variables are structured and have the same structure, union, or
9359 The two variables have the same type name, or types that have been
9360 declared equivalent through @code{typedef}.
9363 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9366 The two @code{struct}, @code{union}, or @code{enum} variables are
9367 declared in the same declaration. (Note: this may not be true for all C
9372 Range checking, if turned on, is done on mathematical operations. Array
9373 indices are not checked, since they are often used to index a pointer
9374 that is not itself an array.
9377 @subsubsection @value{GDBN} and C
9379 The @code{set print union} and @code{show print union} commands apply to
9380 the @code{union} type. When set to @samp{on}, any @code{union} that is
9381 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9382 appears as @samp{@{...@}}.
9384 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9385 with pointers and a memory allocation function. @xref{Expressions,
9388 @node Debugging C Plus Plus
9389 @subsubsection @value{GDBN} Features for C@t{++}
9391 @cindex commands for C@t{++}
9393 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9394 designed specifically for use with C@t{++}. Here is a summary:
9397 @cindex break in overloaded functions
9398 @item @r{breakpoint menus}
9399 When you want a breakpoint in a function whose name is overloaded,
9400 @value{GDBN} breakpoint menus help you specify which function definition
9401 you want. @xref{Breakpoint Menus,,Breakpoint Menus}.
9403 @cindex overloading in C@t{++}
9404 @item rbreak @var{regex}
9405 Setting breakpoints using regular expressions is helpful for setting
9406 breakpoints on overloaded functions that are not members of any special
9408 @xref{Set Breaks, ,Setting Breakpoints}.
9410 @cindex C@t{++} exception handling
9413 Debug C@t{++} exception handling using these commands. @xref{Set
9414 Catchpoints, , Setting Catchpoints}.
9417 @item ptype @var{typename}
9418 Print inheritance relationships as well as other information for type
9420 @xref{Symbols, ,Examining the Symbol Table}.
9422 @cindex C@t{++} symbol display
9423 @item set print demangle
9424 @itemx show print demangle
9425 @itemx set print asm-demangle
9426 @itemx show print asm-demangle
9427 Control whether C@t{++} symbols display in their source form, both when
9428 displaying code as C@t{++} source and when displaying disassemblies.
9429 @xref{Print Settings, ,Print Settings}.
9431 @item set print object
9432 @itemx show print object
9433 Choose whether to print derived (actual) or declared types of objects.
9434 @xref{Print Settings, ,Print Settings}.
9436 @item set print vtbl
9437 @itemx show print vtbl
9438 Control the format for printing virtual function tables.
9439 @xref{Print Settings, ,Print Settings}.
9440 (The @code{vtbl} commands do not work on programs compiled with the HP
9441 ANSI C@t{++} compiler (@code{aCC}).)
9443 @kindex set overload-resolution
9444 @cindex overloaded functions, overload resolution
9445 @item set overload-resolution on
9446 Enable overload resolution for C@t{++} expression evaluation. The default
9447 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9448 and searches for a function whose signature matches the argument types,
9449 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9450 Expressions, ,C@t{++} Expressions}, for details).
9451 If it cannot find a match, it emits a message.
9453 @item set overload-resolution off
9454 Disable overload resolution for C@t{++} expression evaluation. For
9455 overloaded functions that are not class member functions, @value{GDBN}
9456 chooses the first function of the specified name that it finds in the
9457 symbol table, whether or not its arguments are of the correct type. For
9458 overloaded functions that are class member functions, @value{GDBN}
9459 searches for a function whose signature @emph{exactly} matches the
9462 @kindex show overload-resolution
9463 @item show overload-resolution
9464 Show the current setting of overload resolution.
9466 @item @r{Overloaded symbol names}
9467 You can specify a particular definition of an overloaded symbol, using
9468 the same notation that is used to declare such symbols in C@t{++}: type
9469 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9470 also use the @value{GDBN} command-line word completion facilities to list the
9471 available choices, or to finish the type list for you.
9472 @xref{Completion,, Command Completion}, for details on how to do this.
9476 @subsection Objective-C
9479 This section provides information about some commands and command
9480 options that are useful for debugging Objective-C code. See also
9481 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9482 few more commands specific to Objective-C support.
9485 * Method Names in Commands::
9486 * The Print Command with Objective-C::
9489 @node Method Names in Commands
9490 @subsubsection Method Names in Commands
9492 The following commands have been extended to accept Objective-C method
9493 names as line specifications:
9495 @kindex clear@r{, and Objective-C}
9496 @kindex break@r{, and Objective-C}
9497 @kindex info line@r{, and Objective-C}
9498 @kindex jump@r{, and Objective-C}
9499 @kindex list@r{, and Objective-C}
9503 @item @code{info line}
9508 A fully qualified Objective-C method name is specified as
9511 -[@var{Class} @var{methodName}]
9514 where the minus sign is used to indicate an instance method and a
9515 plus sign (not shown) is used to indicate a class method. The class
9516 name @var{Class} and method name @var{methodName} are enclosed in
9517 brackets, similar to the way messages are specified in Objective-C
9518 source code. For example, to set a breakpoint at the @code{create}
9519 instance method of class @code{Fruit} in the program currently being
9523 break -[Fruit create]
9526 To list ten program lines around the @code{initialize} class method,
9530 list +[NSText initialize]
9533 In the current version of @value{GDBN}, the plus or minus sign is
9534 required. In future versions of @value{GDBN}, the plus or minus
9535 sign will be optional, but you can use it to narrow the search. It
9536 is also possible to specify just a method name:
9542 You must specify the complete method name, including any colons. If
9543 your program's source files contain more than one @code{create} method,
9544 you'll be presented with a numbered list of classes that implement that
9545 method. Indicate your choice by number, or type @samp{0} to exit if
9548 As another example, to clear a breakpoint established at the
9549 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9552 clear -[NSWindow makeKeyAndOrderFront:]
9555 @node The Print Command with Objective-C
9556 @subsubsection The Print Command With Objective-C
9557 @cindex Objective-C, print objects
9558 @kindex print-object
9559 @kindex po @r{(@code{print-object})}
9561 The print command has also been extended to accept methods. For example:
9564 print -[@var{object} hash]
9567 @cindex print an Objective-C object description
9568 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9570 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9571 and print the result. Also, an additional command has been added,
9572 @code{print-object} or @code{po} for short, which is meant to print
9573 the description of an object. However, this command may only work
9574 with certain Objective-C libraries that have a particular hook
9575 function, @code{_NSPrintForDebugger}, defined.
9579 @cindex Fortran-specific support in @value{GDBN}
9581 @value{GDBN} can be used to debug programs written in Fortran, but it
9582 currently supports only the features of Fortran 77 language.
9584 @cindex trailing underscore, in Fortran symbols
9585 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9586 among them) append an underscore to the names of variables and
9587 functions. When you debug programs compiled by those compilers, you
9588 will need to refer to variables and functions with a trailing
9592 * Fortran Operators:: Fortran operators and expressions
9593 * Fortran Defaults:: Default settings for Fortran
9594 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
9597 @node Fortran Operators
9598 @subsubsection Fortran Operators and Expressions
9600 @cindex Fortran operators and expressions
9602 Operators must be defined on values of specific types. For instance,
9603 @code{+} is defined on numbers, but not on characters or other non-
9604 arithmetic types. Operators are often defined on groups of types.
9608 The exponentiation operator. It raises the first operand to the power
9612 The range operator. Normally used in the form of array(low:high) to
9613 represent a section of array.
9616 @node Fortran Defaults
9617 @subsubsection Fortran Defaults
9619 @cindex Fortran Defaults
9621 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9622 default uses case-insensitive matches for Fortran symbols. You can
9623 change that with the @samp{set case-insensitive} command, see
9624 @ref{Symbols}, for the details.
9626 @node Special Fortran Commands
9627 @subsubsection Special Fortran Commands
9629 @cindex Special Fortran commands
9631 @value{GDBN} has some commands to support Fortran-specific features,
9632 such as displaying common blocks.
9635 @cindex @code{COMMON} blocks, Fortran
9637 @item info common @r{[}@var{common-name}@r{]}
9638 This command prints the values contained in the Fortran @code{COMMON}
9639 block whose name is @var{common-name}. With no argument, the names of
9640 all @code{COMMON} blocks visible at the current program location are
9647 @cindex Pascal support in @value{GDBN}, limitations
9648 Debugging Pascal programs which use sets, subranges, file variables, or
9649 nested functions does not currently work. @value{GDBN} does not support
9650 entering expressions, printing values, or similar features using Pascal
9653 The Pascal-specific command @code{set print pascal_static-members}
9654 controls whether static members of Pascal objects are displayed.
9655 @xref{Print Settings, pascal_static-members}.
9658 @subsection Modula-2
9660 @cindex Modula-2, @value{GDBN} support
9662 The extensions made to @value{GDBN} to support Modula-2 only support
9663 output from the @sc{gnu} Modula-2 compiler (which is currently being
9664 developed). Other Modula-2 compilers are not currently supported, and
9665 attempting to debug executables produced by them is most likely
9666 to give an error as @value{GDBN} reads in the executable's symbol
9669 @cindex expressions in Modula-2
9671 * M2 Operators:: Built-in operators
9672 * Built-In Func/Proc:: Built-in functions and procedures
9673 * M2 Constants:: Modula-2 constants
9674 * M2 Types:: Modula-2 types
9675 * M2 Defaults:: Default settings for Modula-2
9676 * Deviations:: Deviations from standard Modula-2
9677 * M2 Checks:: Modula-2 type and range checks
9678 * M2 Scope:: The scope operators @code{::} and @code{.}
9679 * GDB/M2:: @value{GDBN} and Modula-2
9683 @subsubsection Operators
9684 @cindex Modula-2 operators
9686 Operators must be defined on values of specific types. For instance,
9687 @code{+} is defined on numbers, but not on structures. Operators are
9688 often defined on groups of types. For the purposes of Modula-2, the
9689 following definitions hold:
9694 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9698 @emph{Character types} consist of @code{CHAR} and its subranges.
9701 @emph{Floating-point types} consist of @code{REAL}.
9704 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9708 @emph{Scalar types} consist of all of the above.
9711 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9714 @emph{Boolean types} consist of @code{BOOLEAN}.
9718 The following operators are supported, and appear in order of
9719 increasing precedence:
9723 Function argument or array index separator.
9726 Assignment. The value of @var{var} @code{:=} @var{value} is
9730 Less than, greater than on integral, floating-point, or enumerated
9734 Less than or equal to, greater than or equal to
9735 on integral, floating-point and enumerated types, or set inclusion on
9736 set types. Same precedence as @code{<}.
9738 @item =@r{, }<>@r{, }#
9739 Equality and two ways of expressing inequality, valid on scalar types.
9740 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9741 available for inequality, since @code{#} conflicts with the script
9745 Set membership. Defined on set types and the types of their members.
9746 Same precedence as @code{<}.
9749 Boolean disjunction. Defined on boolean types.
9752 Boolean conjunction. Defined on boolean types.
9755 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9758 Addition and subtraction on integral and floating-point types, or union
9759 and difference on set types.
9762 Multiplication on integral and floating-point types, or set intersection
9766 Division on floating-point types, or symmetric set difference on set
9767 types. Same precedence as @code{*}.
9770 Integer division and remainder. Defined on integral types. Same
9771 precedence as @code{*}.
9774 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9777 Pointer dereferencing. Defined on pointer types.
9780 Boolean negation. Defined on boolean types. Same precedence as
9784 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9785 precedence as @code{^}.
9788 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9791 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9795 @value{GDBN} and Modula-2 scope operators.
9799 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9800 treats the use of the operator @code{IN}, or the use of operators
9801 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9802 @code{<=}, and @code{>=} on sets as an error.
9806 @node Built-In Func/Proc
9807 @subsubsection Built-in Functions and Procedures
9808 @cindex Modula-2 built-ins
9810 Modula-2 also makes available several built-in procedures and functions.
9811 In describing these, the following metavariables are used:
9816 represents an @code{ARRAY} variable.
9819 represents a @code{CHAR} constant or variable.
9822 represents a variable or constant of integral type.
9825 represents an identifier that belongs to a set. Generally used in the
9826 same function with the metavariable @var{s}. The type of @var{s} should
9827 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9830 represents a variable or constant of integral or floating-point type.
9833 represents a variable or constant of floating-point type.
9839 represents a variable.
9842 represents a variable or constant of one of many types. See the
9843 explanation of the function for details.
9846 All Modula-2 built-in procedures also return a result, described below.
9850 Returns the absolute value of @var{n}.
9853 If @var{c} is a lower case letter, it returns its upper case
9854 equivalent, otherwise it returns its argument.
9857 Returns the character whose ordinal value is @var{i}.
9860 Decrements the value in the variable @var{v} by one. Returns the new value.
9862 @item DEC(@var{v},@var{i})
9863 Decrements the value in the variable @var{v} by @var{i}. Returns the
9866 @item EXCL(@var{m},@var{s})
9867 Removes the element @var{m} from the set @var{s}. Returns the new
9870 @item FLOAT(@var{i})
9871 Returns the floating point equivalent of the integer @var{i}.
9874 Returns the index of the last member of @var{a}.
9877 Increments the value in the variable @var{v} by one. Returns the new value.
9879 @item INC(@var{v},@var{i})
9880 Increments the value in the variable @var{v} by @var{i}. Returns the
9883 @item INCL(@var{m},@var{s})
9884 Adds the element @var{m} to the set @var{s} if it is not already
9885 there. Returns the new set.
9888 Returns the maximum value of the type @var{t}.
9891 Returns the minimum value of the type @var{t}.
9894 Returns boolean TRUE if @var{i} is an odd number.
9897 Returns the ordinal value of its argument. For example, the ordinal
9898 value of a character is its @sc{ascii} value (on machines supporting the
9899 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9900 integral, character and enumerated types.
9903 Returns the size of its argument. @var{x} can be a variable or a type.
9905 @item TRUNC(@var{r})
9906 Returns the integral part of @var{r}.
9908 @item VAL(@var{t},@var{i})
9909 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9913 @emph{Warning:} Sets and their operations are not yet supported, so
9914 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9918 @cindex Modula-2 constants
9920 @subsubsection Constants
9922 @value{GDBN} allows you to express the constants of Modula-2 in the following
9928 Integer constants are simply a sequence of digits. When used in an
9929 expression, a constant is interpreted to be type-compatible with the
9930 rest of the expression. Hexadecimal integers are specified by a
9931 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9934 Floating point constants appear as a sequence of digits, followed by a
9935 decimal point and another sequence of digits. An optional exponent can
9936 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9937 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9938 digits of the floating point constant must be valid decimal (base 10)
9942 Character constants consist of a single character enclosed by a pair of
9943 like quotes, either single (@code{'}) or double (@code{"}). They may
9944 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9945 followed by a @samp{C}.
9948 String constants consist of a sequence of characters enclosed by a
9949 pair of like quotes, either single (@code{'}) or double (@code{"}).
9950 Escape sequences in the style of C are also allowed. @xref{C
9951 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
9955 Enumerated constants consist of an enumerated identifier.
9958 Boolean constants consist of the identifiers @code{TRUE} and
9962 Pointer constants consist of integral values only.
9965 Set constants are not yet supported.
9969 @subsubsection Modula-2 Types
9970 @cindex Modula-2 types
9972 Currently @value{GDBN} can print the following data types in Modula-2
9973 syntax: array types, record types, set types, pointer types, procedure
9974 types, enumerated types, subrange types and base types. You can also
9975 print the contents of variables declared using these type.
9976 This section gives a number of simple source code examples together with
9977 sample @value{GDBN} sessions.
9979 The first example contains the following section of code:
9988 and you can request @value{GDBN} to interrogate the type and value of
9989 @code{r} and @code{s}.
9992 (@value{GDBP}) print s
9994 (@value{GDBP}) ptype s
9996 (@value{GDBP}) print r
9998 (@value{GDBP}) ptype r
10003 Likewise if your source code declares @code{s} as:
10007 s: SET ['A'..'Z'] ;
10011 then you may query the type of @code{s} by:
10014 (@value{GDBP}) ptype s
10015 type = SET ['A'..'Z']
10019 Note that at present you cannot interactively manipulate set
10020 expressions using the debugger.
10022 The following example shows how you might declare an array in Modula-2
10023 and how you can interact with @value{GDBN} to print its type and contents:
10027 s: ARRAY [-10..10] OF CHAR ;
10031 (@value{GDBP}) ptype s
10032 ARRAY [-10..10] OF CHAR
10035 Note that the array handling is not yet complete and although the type
10036 is printed correctly, expression handling still assumes that all
10037 arrays have a lower bound of zero and not @code{-10} as in the example
10038 above. Unbounded arrays are also not yet recognized in @value{GDBN}.
10040 Here are some more type related Modula-2 examples:
10044 colour = (blue, red, yellow, green) ;
10045 t = [blue..yellow] ;
10053 The @value{GDBN} interaction shows how you can query the data type
10054 and value of a variable.
10057 (@value{GDBP}) print s
10059 (@value{GDBP}) ptype t
10060 type = [blue..yellow]
10064 In this example a Modula-2 array is declared and its contents
10065 displayed. Observe that the contents are written in the same way as
10066 their @code{C} counterparts.
10070 s: ARRAY [1..5] OF CARDINAL ;
10076 (@value{GDBP}) print s
10077 $1 = @{1, 0, 0, 0, 0@}
10078 (@value{GDBP}) ptype s
10079 type = ARRAY [1..5] OF CARDINAL
10082 The Modula-2 language interface to @value{GDBN} also understands
10083 pointer types as shown in this example:
10087 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10094 and you can request that @value{GDBN} describes the type of @code{s}.
10097 (@value{GDBP}) ptype s
10098 type = POINTER TO ARRAY [1..5] OF CARDINAL
10101 @value{GDBN} handles compound types as we can see in this example.
10102 Here we combine array types, record types, pointer types and subrange
10113 myarray = ARRAY myrange OF CARDINAL ;
10114 myrange = [-2..2] ;
10116 s: POINTER TO ARRAY myrange OF foo ;
10120 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10124 (@value{GDBP}) ptype s
10125 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10128 f3 : ARRAY [-2..2] OF CARDINAL;
10133 @subsubsection Modula-2 Defaults
10134 @cindex Modula-2 defaults
10136 If type and range checking are set automatically by @value{GDBN}, they
10137 both default to @code{on} whenever the working language changes to
10138 Modula-2. This happens regardless of whether you or @value{GDBN}
10139 selected the working language.
10141 If you allow @value{GDBN} to set the language automatically, then entering
10142 code compiled from a file whose name ends with @file{.mod} sets the
10143 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10144 Infer the Source Language}, for further details.
10147 @subsubsection Deviations from Standard Modula-2
10148 @cindex Modula-2, deviations from
10150 A few changes have been made to make Modula-2 programs easier to debug.
10151 This is done primarily via loosening its type strictness:
10155 Unlike in standard Modula-2, pointer constants can be formed by
10156 integers. This allows you to modify pointer variables during
10157 debugging. (In standard Modula-2, the actual address contained in a
10158 pointer variable is hidden from you; it can only be modified
10159 through direct assignment to another pointer variable or expression that
10160 returned a pointer.)
10163 C escape sequences can be used in strings and characters to represent
10164 non-printable characters. @value{GDBN} prints out strings with these
10165 escape sequences embedded. Single non-printable characters are
10166 printed using the @samp{CHR(@var{nnn})} format.
10169 The assignment operator (@code{:=}) returns the value of its right-hand
10173 All built-in procedures both modify @emph{and} return their argument.
10177 @subsubsection Modula-2 Type and Range Checks
10178 @cindex Modula-2 checks
10181 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10184 @c FIXME remove warning when type/range checks added
10186 @value{GDBN} considers two Modula-2 variables type equivalent if:
10190 They are of types that have been declared equivalent via a @code{TYPE
10191 @var{t1} = @var{t2}} statement
10194 They have been declared on the same line. (Note: This is true of the
10195 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10198 As long as type checking is enabled, any attempt to combine variables
10199 whose types are not equivalent is an error.
10201 Range checking is done on all mathematical operations, assignment, array
10202 index bounds, and all built-in functions and procedures.
10205 @subsubsection The Scope Operators @code{::} and @code{.}
10207 @cindex @code{.}, Modula-2 scope operator
10208 @cindex colon, doubled as scope operator
10210 @vindex colon-colon@r{, in Modula-2}
10211 @c Info cannot handle :: but TeX can.
10214 @vindex ::@r{, in Modula-2}
10217 There are a few subtle differences between the Modula-2 scope operator
10218 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10223 @var{module} . @var{id}
10224 @var{scope} :: @var{id}
10228 where @var{scope} is the name of a module or a procedure,
10229 @var{module} the name of a module, and @var{id} is any declared
10230 identifier within your program, except another module.
10232 Using the @code{::} operator makes @value{GDBN} search the scope
10233 specified by @var{scope} for the identifier @var{id}. If it is not
10234 found in the specified scope, then @value{GDBN} searches all scopes
10235 enclosing the one specified by @var{scope}.
10237 Using the @code{.} operator makes @value{GDBN} search the current scope for
10238 the identifier specified by @var{id} that was imported from the
10239 definition module specified by @var{module}. With this operator, it is
10240 an error if the identifier @var{id} was not imported from definition
10241 module @var{module}, or if @var{id} is not an identifier in
10245 @subsubsection @value{GDBN} and Modula-2
10247 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10248 Five subcommands of @code{set print} and @code{show print} apply
10249 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10250 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10251 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10252 analogue in Modula-2.
10254 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10255 with any language, is not useful with Modula-2. Its
10256 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10257 created in Modula-2 as they can in C or C@t{++}. However, because an
10258 address can be specified by an integral constant, the construct
10259 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10261 @cindex @code{#} in Modula-2
10262 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10263 interpreted as the beginning of a comment. Use @code{<>} instead.
10269 The extensions made to @value{GDBN} for Ada only support
10270 output from the @sc{gnu} Ada (GNAT) compiler.
10271 Other Ada compilers are not currently supported, and
10272 attempting to debug executables produced by them is most likely
10276 @cindex expressions in Ada
10278 * Ada Mode Intro:: General remarks on the Ada syntax
10279 and semantics supported by Ada mode
10281 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10282 * Additions to Ada:: Extensions of the Ada expression syntax.
10283 * Stopping Before Main Program:: Debugging the program during elaboration.
10284 * Ada Glitches:: Known peculiarities of Ada mode.
10287 @node Ada Mode Intro
10288 @subsubsection Introduction
10289 @cindex Ada mode, general
10291 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10292 syntax, with some extensions.
10293 The philosophy behind the design of this subset is
10297 That @value{GDBN} should provide basic literals and access to operations for
10298 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10299 leaving more sophisticated computations to subprograms written into the
10300 program (which therefore may be called from @value{GDBN}).
10303 That type safety and strict adherence to Ada language restrictions
10304 are not particularly important to the @value{GDBN} user.
10307 That brevity is important to the @value{GDBN} user.
10310 Thus, for brevity, the debugger acts as if there were
10311 implicit @code{with} and @code{use} clauses in effect for all user-written
10312 packages, making it unnecessary to fully qualify most names with
10313 their packages, regardless of context. Where this causes ambiguity,
10314 @value{GDBN} asks the user's intent.
10316 The debugger will start in Ada mode if it detects an Ada main program.
10317 As for other languages, it will enter Ada mode when stopped in a program that
10318 was translated from an Ada source file.
10320 While in Ada mode, you may use `@t{--}' for comments. This is useful
10321 mostly for documenting command files. The standard @value{GDBN} comment
10322 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10323 middle (to allow based literals).
10325 The debugger supports limited overloading. Given a subprogram call in which
10326 the function symbol has multiple definitions, it will use the number of
10327 actual parameters and some information about their types to attempt to narrow
10328 the set of definitions. It also makes very limited use of context, preferring
10329 procedures to functions in the context of the @code{call} command, and
10330 functions to procedures elsewhere.
10332 @node Omissions from Ada
10333 @subsubsection Omissions from Ada
10334 @cindex Ada, omissions from
10336 Here are the notable omissions from the subset:
10340 Only a subset of the attributes are supported:
10344 @t{'First}, @t{'Last}, and @t{'Length}
10345 on array objects (not on types and subtypes).
10348 @t{'Min} and @t{'Max}.
10351 @t{'Pos} and @t{'Val}.
10357 @t{'Range} on array objects (not subtypes), but only as the right
10358 operand of the membership (@code{in}) operator.
10361 @t{'Access}, @t{'Unchecked_Access}, and
10362 @t{'Unrestricted_Access} (a GNAT extension).
10370 @code{Characters.Latin_1} are not available and
10371 concatenation is not implemented. Thus, escape characters in strings are
10372 not currently available.
10375 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10376 equality of representations. They will generally work correctly
10377 for strings and arrays whose elements have integer or enumeration types.
10378 They may not work correctly for arrays whose element
10379 types have user-defined equality, for arrays of real values
10380 (in particular, IEEE-conformant floating point, because of negative
10381 zeroes and NaNs), and for arrays whose elements contain unused bits with
10382 indeterminate values.
10385 The other component-by-component array operations (@code{and}, @code{or},
10386 @code{xor}, @code{not}, and relational tests other than equality)
10387 are not implemented.
10390 @cindex array aggregates (Ada)
10391 @cindex record aggregates (Ada)
10392 @cindex aggregates (Ada)
10393 There is limited support for array and record aggregates. They are
10394 permitted only on the right sides of assignments, as in these examples:
10397 set An_Array := (1, 2, 3, 4, 5, 6)
10398 set An_Array := (1, others => 0)
10399 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10400 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10401 set A_Record := (1, "Peter", True);
10402 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10406 discriminant's value by assigning an aggregate has an
10407 undefined effect if that discriminant is used within the record.
10408 However, you can first modify discriminants by directly assigning to
10409 them (which normally would not be allowed in Ada), and then performing an
10410 aggregate assignment. For example, given a variable @code{A_Rec}
10411 declared to have a type such as:
10414 type Rec (Len : Small_Integer := 0) is record
10416 Vals : IntArray (1 .. Len);
10420 you can assign a value with a different size of @code{Vals} with two
10425 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10428 As this example also illustrates, @value{GDBN} is very loose about the usual
10429 rules concerning aggregates. You may leave out some of the
10430 components of an array or record aggregate (such as the @code{Len}
10431 component in the assignment to @code{A_Rec} above); they will retain their
10432 original values upon assignment. You may freely use dynamic values as
10433 indices in component associations. You may even use overlapping or
10434 redundant component associations, although which component values are
10435 assigned in such cases is not defined.
10438 Calls to dispatching subprograms are not implemented.
10441 The overloading algorithm is much more limited (i.e., less selective)
10442 than that of real Ada. It makes only limited use of the context in
10443 which a subexpression appears to resolve its meaning, and it is much
10444 looser in its rules for allowing type matches. As a result, some
10445 function calls will be ambiguous, and the user will be asked to choose
10446 the proper resolution.
10449 The @code{new} operator is not implemented.
10452 Entry calls are not implemented.
10455 Aside from printing, arithmetic operations on the native VAX floating-point
10456 formats are not supported.
10459 It is not possible to slice a packed array.
10462 @node Additions to Ada
10463 @subsubsection Additions to Ada
10464 @cindex Ada, deviations from
10466 As it does for other languages, @value{GDBN} makes certain generic
10467 extensions to Ada (@pxref{Expressions}):
10471 If the expression @var{E} is a variable residing in memory (typically
10472 a local variable or array element) and @var{N} is a positive integer,
10473 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10474 @var{N}-1 adjacent variables following it in memory as an array. In
10475 Ada, this operator is generally not necessary, since its prime use is
10476 in displaying parts of an array, and slicing will usually do this in
10477 Ada. However, there are occasional uses when debugging programs in
10478 which certain debugging information has been optimized away.
10481 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10482 appears in function or file @var{B}.'' When @var{B} is a file name,
10483 you must typically surround it in single quotes.
10486 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10487 @var{type} that appears at address @var{addr}.''
10490 A name starting with @samp{$} is a convenience variable
10491 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10494 In addition, @value{GDBN} provides a few other shortcuts and outright
10495 additions specific to Ada:
10499 The assignment statement is allowed as an expression, returning
10500 its right-hand operand as its value. Thus, you may enter
10504 print A(tmp := y + 1)
10508 The semicolon is allowed as an ``operator,'' returning as its value
10509 the value of its right-hand operand.
10510 This allows, for example,
10511 complex conditional breaks:
10515 condition 1 (report(i); k += 1; A(k) > 100)
10519 Rather than use catenation and symbolic character names to introduce special
10520 characters into strings, one may instead use a special bracket notation,
10521 which is also used to print strings. A sequence of characters of the form
10522 @samp{["@var{XX}"]} within a string or character literal denotes the
10523 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10524 sequence of characters @samp{["""]} also denotes a single quotation mark
10525 in strings. For example,
10527 "One line.["0a"]Next line.["0a"]"
10530 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10534 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10535 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10543 When printing arrays, @value{GDBN} uses positional notation when the
10544 array has a lower bound of 1, and uses a modified named notation otherwise.
10545 For example, a one-dimensional array of three integers with a lower bound
10546 of 3 might print as
10553 That is, in contrast to valid Ada, only the first component has a @code{=>}
10557 You may abbreviate attributes in expressions with any unique,
10558 multi-character subsequence of
10559 their names (an exact match gets preference).
10560 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10561 in place of @t{a'length}.
10564 @cindex quoting Ada internal identifiers
10565 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10566 to lower case. The GNAT compiler uses upper-case characters for
10567 some of its internal identifiers, which are normally of no interest to users.
10568 For the rare occasions when you actually have to look at them,
10569 enclose them in angle brackets to avoid the lower-case mapping.
10572 @value{GDBP} print <JMPBUF_SAVE>[0]
10576 Printing an object of class-wide type or dereferencing an
10577 access-to-class-wide value will display all the components of the object's
10578 specific type (as indicated by its run-time tag). Likewise, component
10579 selection on such a value will operate on the specific type of the
10584 @node Stopping Before Main Program
10585 @subsubsection Stopping at the Very Beginning
10587 @cindex breakpointing Ada elaboration code
10588 It is sometimes necessary to debug the program during elaboration, and
10589 before reaching the main procedure.
10590 As defined in the Ada Reference
10591 Manual, the elaboration code is invoked from a procedure called
10592 @code{adainit}. To run your program up to the beginning of
10593 elaboration, simply use the following two commands:
10594 @code{tbreak adainit} and @code{run}.
10597 @subsubsection Known Peculiarities of Ada Mode
10598 @cindex Ada, problems
10600 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10601 we know of several problems with and limitations of Ada mode in
10603 some of which will be fixed with planned future releases of the debugger
10604 and the GNU Ada compiler.
10608 Currently, the debugger
10609 has insufficient information to determine whether certain pointers represent
10610 pointers to objects or the objects themselves.
10611 Thus, the user may have to tack an extra @code{.all} after an expression
10612 to get it printed properly.
10615 Static constants that the compiler chooses not to materialize as objects in
10616 storage are invisible to the debugger.
10619 Named parameter associations in function argument lists are ignored (the
10620 argument lists are treated as positional).
10623 Many useful library packages are currently invisible to the debugger.
10626 Fixed-point arithmetic, conversions, input, and output is carried out using
10627 floating-point arithmetic, and may give results that only approximate those on
10631 The type of the @t{'Address} attribute may not be @code{System.Address}.
10634 The GNAT compiler never generates the prefix @code{Standard} for any of
10635 the standard symbols defined by the Ada language. @value{GDBN} knows about
10636 this: it will strip the prefix from names when you use it, and will never
10637 look for a name you have so qualified among local symbols, nor match against
10638 symbols in other packages or subprograms. If you have
10639 defined entities anywhere in your program other than parameters and
10640 local variables whose simple names match names in @code{Standard},
10641 GNAT's lack of qualification here can cause confusion. When this happens,
10642 you can usually resolve the confusion
10643 by qualifying the problematic names with package
10644 @code{Standard} explicitly.
10647 @node Unsupported Languages
10648 @section Unsupported Languages
10650 @cindex unsupported languages
10651 @cindex minimal language
10652 In addition to the other fully-supported programming languages,
10653 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10654 It does not represent a real programming language, but provides a set
10655 of capabilities close to what the C or assembly languages provide.
10656 This should allow most simple operations to be performed while debugging
10657 an application that uses a language currently not supported by @value{GDBN}.
10659 If the language is set to @code{auto}, @value{GDBN} will automatically
10660 select this language if the current frame corresponds to an unsupported
10664 @chapter Examining the Symbol Table
10666 The commands described in this chapter allow you to inquire about the
10667 symbols (names of variables, functions and types) defined in your
10668 program. This information is inherent in the text of your program and
10669 does not change as your program executes. @value{GDBN} finds it in your
10670 program's symbol table, in the file indicated when you started @value{GDBN}
10671 (@pxref{File Options, ,Choosing Files}), or by one of the
10672 file-management commands (@pxref{Files, ,Commands to Specify Files}).
10674 @cindex symbol names
10675 @cindex names of symbols
10676 @cindex quoting names
10677 Occasionally, you may need to refer to symbols that contain unusual
10678 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10679 most frequent case is in referring to static variables in other
10680 source files (@pxref{Variables,,Program Variables}). File names
10681 are recorded in object files as debugging symbols, but @value{GDBN} would
10682 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10683 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10684 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10691 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10694 @cindex case-insensitive symbol names
10695 @cindex case sensitivity in symbol names
10696 @kindex set case-sensitive
10697 @item set case-sensitive on
10698 @itemx set case-sensitive off
10699 @itemx set case-sensitive auto
10700 Normally, when @value{GDBN} looks up symbols, it matches their names
10701 with case sensitivity determined by the current source language.
10702 Occasionally, you may wish to control that. The command @code{set
10703 case-sensitive} lets you do that by specifying @code{on} for
10704 case-sensitive matches or @code{off} for case-insensitive ones. If
10705 you specify @code{auto}, case sensitivity is reset to the default
10706 suitable for the source language. The default is case-sensitive
10707 matches for all languages except for Fortran, for which the default is
10708 case-insensitive matches.
10710 @kindex show case-sensitive
10711 @item show case-sensitive
10712 This command shows the current setting of case sensitivity for symbols
10715 @kindex info address
10716 @cindex address of a symbol
10717 @item info address @var{symbol}
10718 Describe where the data for @var{symbol} is stored. For a register
10719 variable, this says which register it is kept in. For a non-register
10720 local variable, this prints the stack-frame offset at which the variable
10723 Note the contrast with @samp{print &@var{symbol}}, which does not work
10724 at all for a register variable, and for a stack local variable prints
10725 the exact address of the current instantiation of the variable.
10727 @kindex info symbol
10728 @cindex symbol from address
10729 @cindex closest symbol and offset for an address
10730 @item info symbol @var{addr}
10731 Print the name of a symbol which is stored at the address @var{addr}.
10732 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10733 nearest symbol and an offset from it:
10736 (@value{GDBP}) info symbol 0x54320
10737 _initialize_vx + 396 in section .text
10741 This is the opposite of the @code{info address} command. You can use
10742 it to find out the name of a variable or a function given its address.
10745 @item whatis [@var{arg}]
10746 Print the data type of @var{arg}, which can be either an expression or
10747 a data type. With no argument, print the data type of @code{$}, the
10748 last value in the value history. If @var{arg} is an expression, it is
10749 not actually evaluated, and any side-effecting operations (such as
10750 assignments or function calls) inside it do not take place. If
10751 @var{arg} is a type name, it may be the name of a type or typedef, or
10752 for C code it may have the form @samp{class @var{class-name}},
10753 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10754 @samp{enum @var{enum-tag}}.
10755 @xref{Expressions, ,Expressions}.
10758 @item ptype [@var{arg}]
10759 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10760 detailed description of the type, instead of just the name of the type.
10761 @xref{Expressions, ,Expressions}.
10763 For example, for this variable declaration:
10766 struct complex @{double real; double imag;@} v;
10770 the two commands give this output:
10774 (@value{GDBP}) whatis v
10775 type = struct complex
10776 (@value{GDBP}) ptype v
10777 type = struct complex @{
10785 As with @code{whatis}, using @code{ptype} without an argument refers to
10786 the type of @code{$}, the last value in the value history.
10788 @cindex incomplete type
10789 Sometimes, programs use opaque data types or incomplete specifications
10790 of complex data structure. If the debug information included in the
10791 program does not allow @value{GDBN} to display a full declaration of
10792 the data type, it will say @samp{<incomplete type>}. For example,
10793 given these declarations:
10797 struct foo *fooptr;
10801 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10804 (@value{GDBP}) ptype foo
10805 $1 = <incomplete type>
10809 ``Incomplete type'' is C terminology for data types that are not
10810 completely specified.
10813 @item info types @var{regexp}
10815 Print a brief description of all types whose names match the regular
10816 expression @var{regexp} (or all types in your program, if you supply
10817 no argument). Each complete typename is matched as though it were a
10818 complete line; thus, @samp{i type value} gives information on all
10819 types in your program whose names include the string @code{value}, but
10820 @samp{i type ^value$} gives information only on types whose complete
10821 name is @code{value}.
10823 This command differs from @code{ptype} in two ways: first, like
10824 @code{whatis}, it does not print a detailed description; second, it
10825 lists all source files where a type is defined.
10828 @cindex local variables
10829 @item info scope @var{location}
10830 List all the variables local to a particular scope. This command
10831 accepts a @var{location} argument---a function name, a source line, or
10832 an address preceded by a @samp{*}, and prints all the variables local
10833 to the scope defined by that location. For example:
10836 (@value{GDBP}) @b{info scope command_line_handler}
10837 Scope for command_line_handler:
10838 Symbol rl is an argument at stack/frame offset 8, length 4.
10839 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10840 Symbol linelength is in static storage at address 0x150a1c, length 4.
10841 Symbol p is a local variable in register $esi, length 4.
10842 Symbol p1 is a local variable in register $ebx, length 4.
10843 Symbol nline is a local variable in register $edx, length 4.
10844 Symbol repeat is a local variable at frame offset -8, length 4.
10848 This command is especially useful for determining what data to collect
10849 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10852 @kindex info source
10854 Show information about the current source file---that is, the source file for
10855 the function containing the current point of execution:
10858 the name of the source file, and the directory containing it,
10860 the directory it was compiled in,
10862 its length, in lines,
10864 which programming language it is written in,
10866 whether the executable includes debugging information for that file, and
10867 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10869 whether the debugging information includes information about
10870 preprocessor macros.
10874 @kindex info sources
10876 Print the names of all source files in your program for which there is
10877 debugging information, organized into two lists: files whose symbols
10878 have already been read, and files whose symbols will be read when needed.
10880 @kindex info functions
10881 @item info functions
10882 Print the names and data types of all defined functions.
10884 @item info functions @var{regexp}
10885 Print the names and data types of all defined functions
10886 whose names contain a match for regular expression @var{regexp}.
10887 Thus, @samp{info fun step} finds all functions whose names
10888 include @code{step}; @samp{info fun ^step} finds those whose names
10889 start with @code{step}. If a function name contains characters
10890 that conflict with the regular expression language (e.g.@:
10891 @samp{operator*()}), they may be quoted with a backslash.
10893 @kindex info variables
10894 @item info variables
10895 Print the names and data types of all variables that are declared
10896 outside of functions (i.e.@: excluding local variables).
10898 @item info variables @var{regexp}
10899 Print the names and data types of all variables (except for local
10900 variables) whose names contain a match for regular expression
10903 @kindex info classes
10904 @cindex Objective-C, classes and selectors
10906 @itemx info classes @var{regexp}
10907 Display all Objective-C classes in your program, or
10908 (with the @var{regexp} argument) all those matching a particular regular
10911 @kindex info selectors
10912 @item info selectors
10913 @itemx info selectors @var{regexp}
10914 Display all Objective-C selectors in your program, or
10915 (with the @var{regexp} argument) all those matching a particular regular
10919 This was never implemented.
10920 @kindex info methods
10922 @itemx info methods @var{regexp}
10923 The @code{info methods} command permits the user to examine all defined
10924 methods within C@t{++} program, or (with the @var{regexp} argument) a
10925 specific set of methods found in the various C@t{++} classes. Many
10926 C@t{++} classes provide a large number of methods. Thus, the output
10927 from the @code{ptype} command can be overwhelming and hard to use. The
10928 @code{info-methods} command filters the methods, printing only those
10929 which match the regular-expression @var{regexp}.
10932 @cindex reloading symbols
10933 Some systems allow individual object files that make up your program to
10934 be replaced without stopping and restarting your program. For example,
10935 in VxWorks you can simply recompile a defective object file and keep on
10936 running. If you are running on one of these systems, you can allow
10937 @value{GDBN} to reload the symbols for automatically relinked modules:
10940 @kindex set symbol-reloading
10941 @item set symbol-reloading on
10942 Replace symbol definitions for the corresponding source file when an
10943 object file with a particular name is seen again.
10945 @item set symbol-reloading off
10946 Do not replace symbol definitions when encountering object files of the
10947 same name more than once. This is the default state; if you are not
10948 running on a system that permits automatic relinking of modules, you
10949 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10950 may discard symbols when linking large programs, that may contain
10951 several modules (from different directories or libraries) with the same
10954 @kindex show symbol-reloading
10955 @item show symbol-reloading
10956 Show the current @code{on} or @code{off} setting.
10959 @cindex opaque data types
10960 @kindex set opaque-type-resolution
10961 @item set opaque-type-resolution on
10962 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10963 declared as a pointer to a @code{struct}, @code{class}, or
10964 @code{union}---for example, @code{struct MyType *}---that is used in one
10965 source file although the full declaration of @code{struct MyType} is in
10966 another source file. The default is on.
10968 A change in the setting of this subcommand will not take effect until
10969 the next time symbols for a file are loaded.
10971 @item set opaque-type-resolution off
10972 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10973 is printed as follows:
10975 @{<no data fields>@}
10978 @kindex show opaque-type-resolution
10979 @item show opaque-type-resolution
10980 Show whether opaque types are resolved or not.
10982 @kindex maint print symbols
10983 @cindex symbol dump
10984 @kindex maint print psymbols
10985 @cindex partial symbol dump
10986 @item maint print symbols @var{filename}
10987 @itemx maint print psymbols @var{filename}
10988 @itemx maint print msymbols @var{filename}
10989 Write a dump of debugging symbol data into the file @var{filename}.
10990 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10991 symbols with debugging data are included. If you use @samp{maint print
10992 symbols}, @value{GDBN} includes all the symbols for which it has already
10993 collected full details: that is, @var{filename} reflects symbols for
10994 only those files whose symbols @value{GDBN} has read. You can use the
10995 command @code{info sources} to find out which files these are. If you
10996 use @samp{maint print psymbols} instead, the dump shows information about
10997 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10998 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10999 @samp{maint print msymbols} dumps just the minimal symbol information
11000 required for each object file from which @value{GDBN} has read some symbols.
11001 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11002 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11004 @kindex maint info symtabs
11005 @kindex maint info psymtabs
11006 @cindex listing @value{GDBN}'s internal symbol tables
11007 @cindex symbol tables, listing @value{GDBN}'s internal
11008 @cindex full symbol tables, listing @value{GDBN}'s internal
11009 @cindex partial symbol tables, listing @value{GDBN}'s internal
11010 @item maint info symtabs @r{[} @var{regexp} @r{]}
11011 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11013 List the @code{struct symtab} or @code{struct partial_symtab}
11014 structures whose names match @var{regexp}. If @var{regexp} is not
11015 given, list them all. The output includes expressions which you can
11016 copy into a @value{GDBN} debugging this one to examine a particular
11017 structure in more detail. For example:
11020 (@value{GDBP}) maint info psymtabs dwarf2read
11021 @{ objfile /home/gnu/build/gdb/gdb
11022 ((struct objfile *) 0x82e69d0)
11023 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11024 ((struct partial_symtab *) 0x8474b10)
11027 text addresses 0x814d3c8 -- 0x8158074
11028 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11029 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11030 dependencies (none)
11033 (@value{GDBP}) maint info symtabs
11037 We see that there is one partial symbol table whose filename contains
11038 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11039 and we see that @value{GDBN} has not read in any symtabs yet at all.
11040 If we set a breakpoint on a function, that will cause @value{GDBN} to
11041 read the symtab for the compilation unit containing that function:
11044 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11045 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11047 (@value{GDBP}) maint info symtabs
11048 @{ objfile /home/gnu/build/gdb/gdb
11049 ((struct objfile *) 0x82e69d0)
11050 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11051 ((struct symtab *) 0x86c1f38)
11054 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11055 debugformat DWARF 2
11064 @chapter Altering Execution
11066 Once you think you have found an error in your program, you might want to
11067 find out for certain whether correcting the apparent error would lead to
11068 correct results in the rest of the run. You can find the answer by
11069 experiment, using the @value{GDBN} features for altering execution of the
11072 For example, you can store new values into variables or memory
11073 locations, give your program a signal, restart it at a different
11074 address, or even return prematurely from a function.
11077 * Assignment:: Assignment to variables
11078 * Jumping:: Continuing at a different address
11079 * Signaling:: Giving your program a signal
11080 * Returning:: Returning from a function
11081 * Calling:: Calling your program's functions
11082 * Patching:: Patching your program
11086 @section Assignment to Variables
11089 @cindex setting variables
11090 To alter the value of a variable, evaluate an assignment expression.
11091 @xref{Expressions, ,Expressions}. For example,
11098 stores the value 4 into the variable @code{x}, and then prints the
11099 value of the assignment expression (which is 4).
11100 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11101 information on operators in supported languages.
11103 @kindex set variable
11104 @cindex variables, setting
11105 If you are not interested in seeing the value of the assignment, use the
11106 @code{set} command instead of the @code{print} command. @code{set} is
11107 really the same as @code{print} except that the expression's value is
11108 not printed and is not put in the value history (@pxref{Value History,
11109 ,Value History}). The expression is evaluated only for its effects.
11111 If the beginning of the argument string of the @code{set} command
11112 appears identical to a @code{set} subcommand, use the @code{set
11113 variable} command instead of just @code{set}. This command is identical
11114 to @code{set} except for its lack of subcommands. For example, if your
11115 program has a variable @code{width}, you get an error if you try to set
11116 a new value with just @samp{set width=13}, because @value{GDBN} has the
11117 command @code{set width}:
11120 (@value{GDBP}) whatis width
11122 (@value{GDBP}) p width
11124 (@value{GDBP}) set width=47
11125 Invalid syntax in expression.
11129 The invalid expression, of course, is @samp{=47}. In
11130 order to actually set the program's variable @code{width}, use
11133 (@value{GDBP}) set var width=47
11136 Because the @code{set} command has many subcommands that can conflict
11137 with the names of program variables, it is a good idea to use the
11138 @code{set variable} command instead of just @code{set}. For example, if
11139 your program has a variable @code{g}, you run into problems if you try
11140 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11141 the command @code{set gnutarget}, abbreviated @code{set g}:
11145 (@value{GDBP}) whatis g
11149 (@value{GDBP}) set g=4
11153 The program being debugged has been started already.
11154 Start it from the beginning? (y or n) y
11155 Starting program: /home/smith/cc_progs/a.out
11156 "/home/smith/cc_progs/a.out": can't open to read symbols:
11157 Invalid bfd target.
11158 (@value{GDBP}) show g
11159 The current BFD target is "=4".
11164 The program variable @code{g} did not change, and you silently set the
11165 @code{gnutarget} to an invalid value. In order to set the variable
11169 (@value{GDBP}) set var g=4
11172 @value{GDBN} allows more implicit conversions in assignments than C; you can
11173 freely store an integer value into a pointer variable or vice versa,
11174 and you can convert any structure to any other structure that is the
11175 same length or shorter.
11176 @comment FIXME: how do structs align/pad in these conversions?
11177 @comment /doc@cygnus.com 18dec1990
11179 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11180 construct to generate a value of specified type at a specified address
11181 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11182 to memory location @code{0x83040} as an integer (which implies a certain size
11183 and representation in memory), and
11186 set @{int@}0x83040 = 4
11190 stores the value 4 into that memory location.
11193 @section Continuing at a Different Address
11195 Ordinarily, when you continue your program, you do so at the place where
11196 it stopped, with the @code{continue} command. You can instead continue at
11197 an address of your own choosing, with the following commands:
11201 @item jump @var{linespec}
11202 Resume execution at line @var{linespec}. Execution stops again
11203 immediately if there is a breakpoint there. @xref{List, ,Printing
11204 Source Lines}, for a description of the different forms of
11205 @var{linespec}. It is common practice to use the @code{tbreak} command
11206 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11209 The @code{jump} command does not change the current stack frame, or
11210 the stack pointer, or the contents of any memory location or any
11211 register other than the program counter. If line @var{linespec} is in
11212 a different function from the one currently executing, the results may
11213 be bizarre if the two functions expect different patterns of arguments or
11214 of local variables. For this reason, the @code{jump} command requests
11215 confirmation if the specified line is not in the function currently
11216 executing. However, even bizarre results are predictable if you are
11217 well acquainted with the machine-language code of your program.
11219 @item jump *@var{address}
11220 Resume execution at the instruction at address @var{address}.
11223 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11224 On many systems, you can get much the same effect as the @code{jump}
11225 command by storing a new value into the register @code{$pc}. The
11226 difference is that this does not start your program running; it only
11227 changes the address of where it @emph{will} run when you continue. For
11235 makes the next @code{continue} command or stepping command execute at
11236 address @code{0x485}, rather than at the address where your program stopped.
11237 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11239 The most common occasion to use the @code{jump} command is to back
11240 up---perhaps with more breakpoints set---over a portion of a program
11241 that has already executed, in order to examine its execution in more
11246 @section Giving your Program a Signal
11247 @cindex deliver a signal to a program
11251 @item signal @var{signal}
11252 Resume execution where your program stopped, but immediately give it the
11253 signal @var{signal}. @var{signal} can be the name or the number of a
11254 signal. For example, on many systems @code{signal 2} and @code{signal
11255 SIGINT} are both ways of sending an interrupt signal.
11257 Alternatively, if @var{signal} is zero, continue execution without
11258 giving a signal. This is useful when your program stopped on account of
11259 a signal and would ordinary see the signal when resumed with the
11260 @code{continue} command; @samp{signal 0} causes it to resume without a
11263 @code{signal} does not repeat when you press @key{RET} a second time
11264 after executing the command.
11268 Invoking the @code{signal} command is not the same as invoking the
11269 @code{kill} utility from the shell. Sending a signal with @code{kill}
11270 causes @value{GDBN} to decide what to do with the signal depending on
11271 the signal handling tables (@pxref{Signals}). The @code{signal} command
11272 passes the signal directly to your program.
11276 @section Returning from a Function
11279 @cindex returning from a function
11282 @itemx return @var{expression}
11283 You can cancel execution of a function call with the @code{return}
11284 command. If you give an
11285 @var{expression} argument, its value is used as the function's return
11289 When you use @code{return}, @value{GDBN} discards the selected stack frame
11290 (and all frames within it). You can think of this as making the
11291 discarded frame return prematurely. If you wish to specify a value to
11292 be returned, give that value as the argument to @code{return}.
11294 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11295 Frame}), and any other frames inside of it, leaving its caller as the
11296 innermost remaining frame. That frame becomes selected. The
11297 specified value is stored in the registers used for returning values
11300 The @code{return} command does not resume execution; it leaves the
11301 program stopped in the state that would exist if the function had just
11302 returned. In contrast, the @code{finish} command (@pxref{Continuing
11303 and Stepping, ,Continuing and Stepping}) resumes execution until the
11304 selected stack frame returns naturally.
11307 @section Calling Program Functions
11310 @cindex calling functions
11311 @cindex inferior functions, calling
11312 @item print @var{expr}
11313 Evaluate the expression @var{expr} and display the resulting value.
11314 @var{expr} may include calls to functions in the program being
11318 @item call @var{expr}
11319 Evaluate the expression @var{expr} without displaying @code{void}
11322 You can use this variant of the @code{print} command if you want to
11323 execute a function from your program that does not return anything
11324 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11325 with @code{void} returned values that @value{GDBN} will otherwise
11326 print. If the result is not void, it is printed and saved in the
11330 It is possible for the function you call via the @code{print} or
11331 @code{call} command to generate a signal (e.g., if there's a bug in
11332 the function, or if you passed it incorrect arguments). What happens
11333 in that case is controlled by the @code{set unwindonsignal} command.
11336 @item set unwindonsignal
11337 @kindex set unwindonsignal
11338 @cindex unwind stack in called functions
11339 @cindex call dummy stack unwinding
11340 Set unwinding of the stack if a signal is received while in a function
11341 that @value{GDBN} called in the program being debugged. If set to on,
11342 @value{GDBN} unwinds the stack it created for the call and restores
11343 the context to what it was before the call. If set to off (the
11344 default), @value{GDBN} stops in the frame where the signal was
11347 @item show unwindonsignal
11348 @kindex show unwindonsignal
11349 Show the current setting of stack unwinding in the functions called by
11353 @cindex weak alias functions
11354 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11355 for another function. In such case, @value{GDBN} might not pick up
11356 the type information, including the types of the function arguments,
11357 which causes @value{GDBN} to call the inferior function incorrectly.
11358 As a result, the called function will function erroneously and may
11359 even crash. A solution to that is to use the name of the aliased
11363 @section Patching Programs
11365 @cindex patching binaries
11366 @cindex writing into executables
11367 @cindex writing into corefiles
11369 By default, @value{GDBN} opens the file containing your program's
11370 executable code (or the corefile) read-only. This prevents accidental
11371 alterations to machine code; but it also prevents you from intentionally
11372 patching your program's binary.
11374 If you'd like to be able to patch the binary, you can specify that
11375 explicitly with the @code{set write} command. For example, you might
11376 want to turn on internal debugging flags, or even to make emergency
11382 @itemx set write off
11383 If you specify @samp{set write on}, @value{GDBN} opens executable and
11384 core files for both reading and writing; if you specify @samp{set write
11385 off} (the default), @value{GDBN} opens them read-only.
11387 If you have already loaded a file, you must load it again (using the
11388 @code{exec-file} or @code{core-file} command) after changing @code{set
11389 write}, for your new setting to take effect.
11393 Display whether executable files and core files are opened for writing
11394 as well as reading.
11398 @chapter @value{GDBN} Files
11400 @value{GDBN} needs to know the file name of the program to be debugged,
11401 both in order to read its symbol table and in order to start your
11402 program. To debug a core dump of a previous run, you must also tell
11403 @value{GDBN} the name of the core dump file.
11406 * Files:: Commands to specify files
11407 * Separate Debug Files:: Debugging information in separate files
11408 * Symbol Errors:: Errors reading symbol files
11412 @section Commands to Specify Files
11414 @cindex symbol table
11415 @cindex core dump file
11417 You may want to specify executable and core dump file names. The usual
11418 way to do this is at start-up time, using the arguments to
11419 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11420 Out of @value{GDBN}}).
11422 Occasionally it is necessary to change to a different file during a
11423 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11424 specify a file you want to use. Or you are debugging a remote target
11425 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11426 Program}). In these situations the @value{GDBN} commands to specify
11427 new files are useful.
11430 @cindex executable file
11432 @item file @var{filename}
11433 Use @var{filename} as the program to be debugged. It is read for its
11434 symbols and for the contents of pure memory. It is also the program
11435 executed when you use the @code{run} command. If you do not specify a
11436 directory and the file is not found in the @value{GDBN} working directory,
11437 @value{GDBN} uses the environment variable @code{PATH} as a list of
11438 directories to search, just as the shell does when looking for a program
11439 to run. You can change the value of this variable, for both @value{GDBN}
11440 and your program, using the @code{path} command.
11442 @cindex unlinked object files
11443 @cindex patching object files
11444 You can load unlinked object @file{.o} files into @value{GDBN} using
11445 the @code{file} command. You will not be able to ``run'' an object
11446 file, but you can disassemble functions and inspect variables. Also,
11447 if the underlying BFD functionality supports it, you could use
11448 @kbd{gdb -write} to patch object files using this technique. Note
11449 that @value{GDBN} can neither interpret nor modify relocations in this
11450 case, so branches and some initialized variables will appear to go to
11451 the wrong place. But this feature is still handy from time to time.
11454 @code{file} with no argument makes @value{GDBN} discard any information it
11455 has on both executable file and the symbol table.
11458 @item exec-file @r{[} @var{filename} @r{]}
11459 Specify that the program to be run (but not the symbol table) is found
11460 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11461 if necessary to locate your program. Omitting @var{filename} means to
11462 discard information on the executable file.
11464 @kindex symbol-file
11465 @item symbol-file @r{[} @var{filename} @r{]}
11466 Read symbol table information from file @var{filename}. @code{PATH} is
11467 searched when necessary. Use the @code{file} command to get both symbol
11468 table and program to run from the same file.
11470 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11471 program's symbol table.
11473 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11474 some breakpoints and auto-display expressions. This is because they may
11475 contain pointers to the internal data recording symbols and data types,
11476 which are part of the old symbol table data being discarded inside
11479 @code{symbol-file} does not repeat if you press @key{RET} again after
11482 When @value{GDBN} is configured for a particular environment, it
11483 understands debugging information in whatever format is the standard
11484 generated for that environment; you may use either a @sc{gnu} compiler, or
11485 other compilers that adhere to the local conventions.
11486 Best results are usually obtained from @sc{gnu} compilers; for example,
11487 using @code{@value{NGCC}} you can generate debugging information for
11490 For most kinds of object files, with the exception of old SVR3 systems
11491 using COFF, the @code{symbol-file} command does not normally read the
11492 symbol table in full right away. Instead, it scans the symbol table
11493 quickly to find which source files and which symbols are present. The
11494 details are read later, one source file at a time, as they are needed.
11496 The purpose of this two-stage reading strategy is to make @value{GDBN}
11497 start up faster. For the most part, it is invisible except for
11498 occasional pauses while the symbol table details for a particular source
11499 file are being read. (The @code{set verbose} command can turn these
11500 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11501 Warnings and Messages}.)
11503 We have not implemented the two-stage strategy for COFF yet. When the
11504 symbol table is stored in COFF format, @code{symbol-file} reads the
11505 symbol table data in full right away. Note that ``stabs-in-COFF''
11506 still does the two-stage strategy, since the debug info is actually
11510 @cindex reading symbols immediately
11511 @cindex symbols, reading immediately
11512 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11513 @itemx file @var{filename} @r{[} -readnow @r{]}
11514 You can override the @value{GDBN} two-stage strategy for reading symbol
11515 tables by using the @samp{-readnow} option with any of the commands that
11516 load symbol table information, if you want to be sure @value{GDBN} has the
11517 entire symbol table available.
11519 @c FIXME: for now no mention of directories, since this seems to be in
11520 @c flux. 13mar1992 status is that in theory GDB would look either in
11521 @c current dir or in same dir as myprog; but issues like competing
11522 @c GDB's, or clutter in system dirs, mean that in practice right now
11523 @c only current dir is used. FFish says maybe a special GDB hierarchy
11524 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11528 @item core-file @r{[}@var{filename}@r{]}
11530 Specify the whereabouts of a core dump file to be used as the ``contents
11531 of memory''. Traditionally, core files contain only some parts of the
11532 address space of the process that generated them; @value{GDBN} can access the
11533 executable file itself for other parts.
11535 @code{core-file} with no argument specifies that no core file is
11538 Note that the core file is ignored when your program is actually running
11539 under @value{GDBN}. So, if you have been running your program and you
11540 wish to debug a core file instead, you must kill the subprocess in which
11541 the program is running. To do this, use the @code{kill} command
11542 (@pxref{Kill Process, ,Killing the Child Process}).
11544 @kindex add-symbol-file
11545 @cindex dynamic linking
11546 @item add-symbol-file @var{filename} @var{address}
11547 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11548 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11549 The @code{add-symbol-file} command reads additional symbol table
11550 information from the file @var{filename}. You would use this command
11551 when @var{filename} has been dynamically loaded (by some other means)
11552 into the program that is running. @var{address} should be the memory
11553 address at which the file has been loaded; @value{GDBN} cannot figure
11554 this out for itself. You can additionally specify an arbitrary number
11555 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11556 section name and base address for that section. You can specify any
11557 @var{address} as an expression.
11559 The symbol table of the file @var{filename} is added to the symbol table
11560 originally read with the @code{symbol-file} command. You can use the
11561 @code{add-symbol-file} command any number of times; the new symbol data
11562 thus read keeps adding to the old. To discard all old symbol data
11563 instead, use the @code{symbol-file} command without any arguments.
11565 @cindex relocatable object files, reading symbols from
11566 @cindex object files, relocatable, reading symbols from
11567 @cindex reading symbols from relocatable object files
11568 @cindex symbols, reading from relocatable object files
11569 @cindex @file{.o} files, reading symbols from
11570 Although @var{filename} is typically a shared library file, an
11571 executable file, or some other object file which has been fully
11572 relocated for loading into a process, you can also load symbolic
11573 information from relocatable @file{.o} files, as long as:
11577 the file's symbolic information refers only to linker symbols defined in
11578 that file, not to symbols defined by other object files,
11580 every section the file's symbolic information refers to has actually
11581 been loaded into the inferior, as it appears in the file, and
11583 you can determine the address at which every section was loaded, and
11584 provide these to the @code{add-symbol-file} command.
11588 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11589 relocatable files into an already running program; such systems
11590 typically make the requirements above easy to meet. However, it's
11591 important to recognize that many native systems use complex link
11592 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11593 assembly, for example) that make the requirements difficult to meet. In
11594 general, one cannot assume that using @code{add-symbol-file} to read a
11595 relocatable object file's symbolic information will have the same effect
11596 as linking the relocatable object file into the program in the normal
11599 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11601 @kindex add-symbol-file-from-memory
11602 @cindex @code{syscall DSO}
11603 @cindex load symbols from memory
11604 @item add-symbol-file-from-memory @var{address}
11605 Load symbols from the given @var{address} in a dynamically loaded
11606 object file whose image is mapped directly into the inferior's memory.
11607 For example, the Linux kernel maps a @code{syscall DSO} into each
11608 process's address space; this DSO provides kernel-specific code for
11609 some system calls. The argument can be any expression whose
11610 evaluation yields the address of the file's shared object file header.
11611 For this command to work, you must have used @code{symbol-file} or
11612 @code{exec-file} commands in advance.
11614 @kindex add-shared-symbol-files
11616 @item add-shared-symbol-files @var{library-file}
11617 @itemx assf @var{library-file}
11618 The @code{add-shared-symbol-files} command can currently be used only
11619 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11620 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11621 @value{GDBN} automatically looks for shared libraries, however if
11622 @value{GDBN} does not find yours, you can invoke
11623 @code{add-shared-symbol-files}. It takes one argument: the shared
11624 library's file name. @code{assf} is a shorthand alias for
11625 @code{add-shared-symbol-files}.
11628 @item section @var{section} @var{addr}
11629 The @code{section} command changes the base address of the named
11630 @var{section} of the exec file to @var{addr}. This can be used if the
11631 exec file does not contain section addresses, (such as in the
11632 @code{a.out} format), or when the addresses specified in the file
11633 itself are wrong. Each section must be changed separately. The
11634 @code{info files} command, described below, lists all the sections and
11638 @kindex info target
11641 @code{info files} and @code{info target} are synonymous; both print the
11642 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11643 including the names of the executable and core dump files currently in
11644 use by @value{GDBN}, and the files from which symbols were loaded. The
11645 command @code{help target} lists all possible targets rather than
11648 @kindex maint info sections
11649 @item maint info sections
11650 Another command that can give you extra information about program sections
11651 is @code{maint info sections}. In addition to the section information
11652 displayed by @code{info files}, this command displays the flags and file
11653 offset of each section in the executable and core dump files. In addition,
11654 @code{maint info sections} provides the following command options (which
11655 may be arbitrarily combined):
11659 Display sections for all loaded object files, including shared libraries.
11660 @item @var{sections}
11661 Display info only for named @var{sections}.
11662 @item @var{section-flags}
11663 Display info only for sections for which @var{section-flags} are true.
11664 The section flags that @value{GDBN} currently knows about are:
11667 Section will have space allocated in the process when loaded.
11668 Set for all sections except those containing debug information.
11670 Section will be loaded from the file into the child process memory.
11671 Set for pre-initialized code and data, clear for @code{.bss} sections.
11673 Section needs to be relocated before loading.
11675 Section cannot be modified by the child process.
11677 Section contains executable code only.
11679 Section contains data only (no executable code).
11681 Section will reside in ROM.
11683 Section contains data for constructor/destructor lists.
11685 Section is not empty.
11687 An instruction to the linker to not output the section.
11688 @item COFF_SHARED_LIBRARY
11689 A notification to the linker that the section contains
11690 COFF shared library information.
11692 Section contains common symbols.
11695 @kindex set trust-readonly-sections
11696 @cindex read-only sections
11697 @item set trust-readonly-sections on
11698 Tell @value{GDBN} that readonly sections in your object file
11699 really are read-only (i.e.@: that their contents will not change).
11700 In that case, @value{GDBN} can fetch values from these sections
11701 out of the object file, rather than from the target program.
11702 For some targets (notably embedded ones), this can be a significant
11703 enhancement to debugging performance.
11705 The default is off.
11707 @item set trust-readonly-sections off
11708 Tell @value{GDBN} not to trust readonly sections. This means that
11709 the contents of the section might change while the program is running,
11710 and must therefore be fetched from the target when needed.
11712 @item show trust-readonly-sections
11713 Show the current setting of trusting readonly sections.
11716 All file-specifying commands allow both absolute and relative file names
11717 as arguments. @value{GDBN} always converts the file name to an absolute file
11718 name and remembers it that way.
11720 @cindex shared libraries
11721 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11722 and IBM RS/6000 AIX shared libraries.
11724 @value{GDBN} automatically loads symbol definitions from shared libraries
11725 when you use the @code{run} command, or when you examine a core file.
11726 (Before you issue the @code{run} command, @value{GDBN} does not understand
11727 references to a function in a shared library, however---unless you are
11728 debugging a core file).
11730 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11731 automatically loads the symbols at the time of the @code{shl_load} call.
11733 @c FIXME: some @value{GDBN} release may permit some refs to undef
11734 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11735 @c FIXME...lib; check this from time to time when updating manual
11737 There are times, however, when you may wish to not automatically load
11738 symbol definitions from shared libraries, such as when they are
11739 particularly large or there are many of them.
11741 To control the automatic loading of shared library symbols, use the
11745 @kindex set auto-solib-add
11746 @item set auto-solib-add @var{mode}
11747 If @var{mode} is @code{on}, symbols from all shared object libraries
11748 will be loaded automatically when the inferior begins execution, you
11749 attach to an independently started inferior, or when the dynamic linker
11750 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11751 is @code{off}, symbols must be loaded manually, using the
11752 @code{sharedlibrary} command. The default value is @code{on}.
11754 @cindex memory used for symbol tables
11755 If your program uses lots of shared libraries with debug info that
11756 takes large amounts of memory, you can decrease the @value{GDBN}
11757 memory footprint by preventing it from automatically loading the
11758 symbols from shared libraries. To that end, type @kbd{set
11759 auto-solib-add off} before running the inferior, then load each
11760 library whose debug symbols you do need with @kbd{sharedlibrary
11761 @var{regexp}}, where @var{regexp} is a regular expression that matches
11762 the libraries whose symbols you want to be loaded.
11764 @kindex show auto-solib-add
11765 @item show auto-solib-add
11766 Display the current autoloading mode.
11769 @cindex load shared library
11770 To explicitly load shared library symbols, use the @code{sharedlibrary}
11774 @kindex info sharedlibrary
11777 @itemx info sharedlibrary
11778 Print the names of the shared libraries which are currently loaded.
11780 @kindex sharedlibrary
11782 @item sharedlibrary @var{regex}
11783 @itemx share @var{regex}
11784 Load shared object library symbols for files matching a
11785 Unix regular expression.
11786 As with files loaded automatically, it only loads shared libraries
11787 required by your program for a core file or after typing @code{run}. If
11788 @var{regex} is omitted all shared libraries required by your program are
11791 @item nosharedlibrary
11792 @kindex nosharedlibrary
11793 @cindex unload symbols from shared libraries
11794 Unload all shared object library symbols. This discards all symbols
11795 that have been loaded from all shared libraries. Symbols from shared
11796 libraries that were loaded by explicit user requests are not
11800 Sometimes you may wish that @value{GDBN} stops and gives you control
11801 when any of shared library events happen. Use the @code{set
11802 stop-on-solib-events} command for this:
11805 @item set stop-on-solib-events
11806 @kindex set stop-on-solib-events
11807 This command controls whether @value{GDBN} should give you control
11808 when the dynamic linker notifies it about some shared library event.
11809 The most common event of interest is loading or unloading of a new
11812 @item show stop-on-solib-events
11813 @kindex show stop-on-solib-events
11814 Show whether @value{GDBN} stops and gives you control when shared
11815 library events happen.
11818 Shared libraries are also supported in many cross or remote debugging
11819 configurations. A copy of the target's libraries need to be present on the
11820 host system; they need to be the same as the target libraries, although the
11821 copies on the target can be stripped as long as the copies on the host are
11824 @cindex where to look for shared libraries
11825 For remote debugging, you need to tell @value{GDBN} where the target
11826 libraries are, so that it can load the correct copies---otherwise, it
11827 may try to load the host's libraries. @value{GDBN} has two variables
11828 to specify the search directories for target libraries.
11831 @cindex prefix for shared library file names
11832 @cindex system root, alternate
11833 @kindex set solib-absolute-prefix
11834 @kindex set sysroot
11835 @item set sysroot @var{path}
11836 Use @var{path} as the system root for the program being debugged. Any
11837 absolute shared library paths will be prefixed with @var{path}; many
11838 runtime loaders store the absolute paths to the shared library in the
11839 target program's memory. If you use @code{set sysroot} to find shared
11840 libraries, they need to be laid out in the same way that they are on
11841 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
11844 The @code{set solib-absolute-prefix} command is an alias for @code{set
11847 @cindex default system root
11848 @cindex @samp{--with-sysroot}
11849 You can set the default system root by using the configure-time
11850 @samp{--with-sysroot} option. If the system root is inside
11851 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
11852 @samp{--exec-prefix}), then the default system root will be updated
11853 automatically if the installed @value{GDBN} is moved to a new
11856 @kindex show sysroot
11858 Display the current shared library prefix.
11860 @kindex set solib-search-path
11861 @item set solib-search-path @var{path}
11862 If this variable is set, @var{path} is a colon-separated list of
11863 directories to search for shared libraries. @samp{solib-search-path}
11864 is used after @samp{sysroot} fails to locate the library, or if the
11865 path to the library is relative instead of absolute. If you want to
11866 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
11867 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
11868 finding your host's libraries. @samp{sysroot} is preferred; setting
11869 it to a nonexistent directory may interfere with automatic loading
11870 of shared library symbols.
11872 @kindex show solib-search-path
11873 @item show solib-search-path
11874 Display the current shared library search path.
11878 @node Separate Debug Files
11879 @section Debugging Information in Separate Files
11880 @cindex separate debugging information files
11881 @cindex debugging information in separate files
11882 @cindex @file{.debug} subdirectories
11883 @cindex debugging information directory, global
11884 @cindex global debugging information directory
11886 @value{GDBN} allows you to put a program's debugging information in a
11887 file separate from the executable itself, in a way that allows
11888 @value{GDBN} to find and load the debugging information automatically.
11889 Since debugging information can be very large --- sometimes larger
11890 than the executable code itself --- some systems distribute debugging
11891 information for their executables in separate files, which users can
11892 install only when they need to debug a problem.
11894 If an executable's debugging information has been extracted to a
11895 separate file, the executable should contain a @dfn{debug link} giving
11896 the name of the debugging information file (with no directory
11897 components), and a checksum of its contents. (The exact form of a
11898 debug link is described below.) If the full name of the directory
11899 containing the executable is @var{execdir}, and the executable has a
11900 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11901 will automatically search for the debugging information file in three
11906 the directory containing the executable file (that is, it will look
11907 for a file named @file{@var{execdir}/@var{debugfile}},
11909 a subdirectory of that directory named @file{.debug} (that is, the
11910 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11912 a subdirectory of the global debug file directory that includes the
11913 executable's full path, and the name from the link (that is, the file
11914 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11915 @var{globaldebugdir} is the global debug file directory, and
11916 @var{execdir} has been turned into a relative path).
11919 @value{GDBN} checks under each of these names for a debugging
11920 information file whose checksum matches that given in the link, and
11921 reads the debugging information from the first one it finds.
11923 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11924 which has a link containing the name @file{ls.debug}, and the global
11925 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11926 for debug information in @file{/usr/bin/ls.debug},
11927 @file{/usr/bin/.debug/ls.debug}, and
11928 @file{/usr/lib/debug/usr/bin/ls.debug}.
11930 You can set the global debugging info directory's name, and view the
11931 name @value{GDBN} is currently using.
11935 @kindex set debug-file-directory
11936 @item set debug-file-directory @var{directory}
11937 Set the directory which @value{GDBN} searches for separate debugging
11938 information files to @var{directory}.
11940 @kindex show debug-file-directory
11941 @item show debug-file-directory
11942 Show the directory @value{GDBN} searches for separate debugging
11947 @cindex @code{.gnu_debuglink} sections
11948 @cindex debug links
11949 A debug link is a special section of the executable file named
11950 @code{.gnu_debuglink}. The section must contain:
11954 A filename, with any leading directory components removed, followed by
11957 zero to three bytes of padding, as needed to reach the next four-byte
11958 boundary within the section, and
11960 a four-byte CRC checksum, stored in the same endianness used for the
11961 executable file itself. The checksum is computed on the debugging
11962 information file's full contents by the function given below, passing
11963 zero as the @var{crc} argument.
11966 Any executable file format can carry a debug link, as long as it can
11967 contain a section named @code{.gnu_debuglink} with the contents
11970 The debugging information file itself should be an ordinary
11971 executable, containing a full set of linker symbols, sections, and
11972 debugging information. The sections of the debugging information file
11973 should have the same names, addresses and sizes as the original file,
11974 but they need not contain any data --- much like a @code{.bss} section
11975 in an ordinary executable.
11977 As of December 2002, there is no standard GNU utility to produce
11978 separated executable / debugging information file pairs. Ulrich
11979 Drepper's @file{elfutils} package, starting with version 0.53,
11980 contains a version of the @code{strip} command such that the command
11981 @kbd{strip foo -f foo.debug} removes the debugging information from
11982 the executable file @file{foo}, places it in the file
11983 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11985 Since there are many different ways to compute CRC's (different
11986 polynomials, reversals, byte ordering, etc.), the simplest way to
11987 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11988 complete code for a function that computes it:
11990 @kindex gnu_debuglink_crc32
11993 gnu_debuglink_crc32 (unsigned long crc,
11994 unsigned char *buf, size_t len)
11996 static const unsigned long crc32_table[256] =
11998 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11999 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12000 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12001 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12002 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12003 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12004 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12005 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12006 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12007 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12008 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12009 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12010 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12011 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12012 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12013 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12014 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12015 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12016 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12017 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12018 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12019 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12020 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12021 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12022 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12023 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12024 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12025 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12026 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12027 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12028 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12029 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12030 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12031 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12032 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12033 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12034 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12035 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12036 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12037 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12038 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12039 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12040 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12041 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12042 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12043 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12044 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12045 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12046 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12047 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12048 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12051 unsigned char *end;
12053 crc = ~crc & 0xffffffff;
12054 for (end = buf + len; buf < end; ++buf)
12055 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12056 return ~crc & 0xffffffff;
12061 @node Symbol Errors
12062 @section Errors Reading Symbol Files
12064 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12065 such as symbol types it does not recognize, or known bugs in compiler
12066 output. By default, @value{GDBN} does not notify you of such problems, since
12067 they are relatively common and primarily of interest to people
12068 debugging compilers. If you are interested in seeing information
12069 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12070 only one message about each such type of problem, no matter how many
12071 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12072 to see how many times the problems occur, with the @code{set
12073 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12076 The messages currently printed, and their meanings, include:
12079 @item inner block not inside outer block in @var{symbol}
12081 The symbol information shows where symbol scopes begin and end
12082 (such as at the start of a function or a block of statements). This
12083 error indicates that an inner scope block is not fully contained
12084 in its outer scope blocks.
12086 @value{GDBN} circumvents the problem by treating the inner block as if it had
12087 the same scope as the outer block. In the error message, @var{symbol}
12088 may be shown as ``@code{(don't know)}'' if the outer block is not a
12091 @item block at @var{address} out of order
12093 The symbol information for symbol scope blocks should occur in
12094 order of increasing addresses. This error indicates that it does not
12097 @value{GDBN} does not circumvent this problem, and has trouble
12098 locating symbols in the source file whose symbols it is reading. (You
12099 can often determine what source file is affected by specifying
12100 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12103 @item bad block start address patched
12105 The symbol information for a symbol scope block has a start address
12106 smaller than the address of the preceding source line. This is known
12107 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12109 @value{GDBN} circumvents the problem by treating the symbol scope block as
12110 starting on the previous source line.
12112 @item bad string table offset in symbol @var{n}
12115 Symbol number @var{n} contains a pointer into the string table which is
12116 larger than the size of the string table.
12118 @value{GDBN} circumvents the problem by considering the symbol to have the
12119 name @code{foo}, which may cause other problems if many symbols end up
12122 @item unknown symbol type @code{0x@var{nn}}
12124 The symbol information contains new data types that @value{GDBN} does
12125 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12126 uncomprehended information, in hexadecimal.
12128 @value{GDBN} circumvents the error by ignoring this symbol information.
12129 This usually allows you to debug your program, though certain symbols
12130 are not accessible. If you encounter such a problem and feel like
12131 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12132 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12133 and examine @code{*bufp} to see the symbol.
12135 @item stub type has NULL name
12137 @value{GDBN} could not find the full definition for a struct or class.
12139 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12140 The symbol information for a C@t{++} member function is missing some
12141 information that recent versions of the compiler should have output for
12144 @item info mismatch between compiler and debugger
12146 @value{GDBN} could not parse a type specification output by the compiler.
12151 @chapter Specifying a Debugging Target
12153 @cindex debugging target
12154 A @dfn{target} is the execution environment occupied by your program.
12156 Often, @value{GDBN} runs in the same host environment as your program;
12157 in that case, the debugging target is specified as a side effect when
12158 you use the @code{file} or @code{core} commands. When you need more
12159 flexibility---for example, running @value{GDBN} on a physically separate
12160 host, or controlling a standalone system over a serial port or a
12161 realtime system over a TCP/IP connection---you can use the @code{target}
12162 command to specify one of the target types configured for @value{GDBN}
12163 (@pxref{Target Commands, ,Commands for Managing Targets}).
12165 @cindex target architecture
12166 It is possible to build @value{GDBN} for several different @dfn{target
12167 architectures}. When @value{GDBN} is built like that, you can choose
12168 one of the available architectures with the @kbd{set architecture}
12172 @kindex set architecture
12173 @kindex show architecture
12174 @item set architecture @var{arch}
12175 This command sets the current target architecture to @var{arch}. The
12176 value of @var{arch} can be @code{"auto"}, in addition to one of the
12177 supported architectures.
12179 @item show architecture
12180 Show the current target architecture.
12182 @item set processor
12184 @kindex set processor
12185 @kindex show processor
12186 These are alias commands for, respectively, @code{set architecture}
12187 and @code{show architecture}.
12191 * Active Targets:: Active targets
12192 * Target Commands:: Commands for managing targets
12193 * Byte Order:: Choosing target byte order
12196 @node Active Targets
12197 @section Active Targets
12199 @cindex stacking targets
12200 @cindex active targets
12201 @cindex multiple targets
12203 There are three classes of targets: processes, core files, and
12204 executable files. @value{GDBN} can work concurrently on up to three
12205 active targets, one in each class. This allows you to (for example)
12206 start a process and inspect its activity without abandoning your work on
12209 For example, if you execute @samp{gdb a.out}, then the executable file
12210 @code{a.out} is the only active target. If you designate a core file as
12211 well---presumably from a prior run that crashed and coredumped---then
12212 @value{GDBN} has two active targets and uses them in tandem, looking
12213 first in the corefile target, then in the executable file, to satisfy
12214 requests for memory addresses. (Typically, these two classes of target
12215 are complementary, since core files contain only a program's
12216 read-write memory---variables and so on---plus machine status, while
12217 executable files contain only the program text and initialized data.)
12219 When you type @code{run}, your executable file becomes an active process
12220 target as well. When a process target is active, all @value{GDBN}
12221 commands requesting memory addresses refer to that target; addresses in
12222 an active core file or executable file target are obscured while the
12223 process target is active.
12225 Use the @code{core-file} and @code{exec-file} commands to select a new
12226 core file or executable target (@pxref{Files, ,Commands to Specify
12227 Files}). To specify as a target a process that is already running, use
12228 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12231 @node Target Commands
12232 @section Commands for Managing Targets
12235 @item target @var{type} @var{parameters}
12236 Connects the @value{GDBN} host environment to a target machine or
12237 process. A target is typically a protocol for talking to debugging
12238 facilities. You use the argument @var{type} to specify the type or
12239 protocol of the target machine.
12241 Further @var{parameters} are interpreted by the target protocol, but
12242 typically include things like device names or host names to connect
12243 with, process numbers, and baud rates.
12245 The @code{target} command does not repeat if you press @key{RET} again
12246 after executing the command.
12248 @kindex help target
12250 Displays the names of all targets available. To display targets
12251 currently selected, use either @code{info target} or @code{info files}
12252 (@pxref{Files, ,Commands to Specify Files}).
12254 @item help target @var{name}
12255 Describe a particular target, including any parameters necessary to
12258 @kindex set gnutarget
12259 @item set gnutarget @var{args}
12260 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12261 knows whether it is reading an @dfn{executable},
12262 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12263 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12264 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12267 @emph{Warning:} To specify a file format with @code{set gnutarget},
12268 you must know the actual BFD name.
12272 @xref{Files, , Commands to Specify Files}.
12274 @kindex show gnutarget
12275 @item show gnutarget
12276 Use the @code{show gnutarget} command to display what file format
12277 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12278 @value{GDBN} will determine the file format for each file automatically,
12279 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12282 @cindex common targets
12283 Here are some common targets (available, or not, depending on the GDB
12288 @item target exec @var{program}
12289 @cindex executable file target
12290 An executable file. @samp{target exec @var{program}} is the same as
12291 @samp{exec-file @var{program}}.
12293 @item target core @var{filename}
12294 @cindex core dump file target
12295 A core dump file. @samp{target core @var{filename}} is the same as
12296 @samp{core-file @var{filename}}.
12298 @item target remote @var{medium}
12299 @cindex remote target
12300 A remote system connected to @value{GDBN} via a serial line or network
12301 connection. This command tells @value{GDBN} to use its own remote
12302 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12304 For example, if you have a board connected to @file{/dev/ttya} on the
12305 machine running @value{GDBN}, you could say:
12308 target remote /dev/ttya
12311 @code{target remote} supports the @code{load} command. This is only
12312 useful if you have some other way of getting the stub to the target
12313 system, and you can put it somewhere in memory where it won't get
12314 clobbered by the download.
12317 @cindex built-in simulator target
12318 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12326 works; however, you cannot assume that a specific memory map, device
12327 drivers, or even basic I/O is available, although some simulators do
12328 provide these. For info about any processor-specific simulator details,
12329 see the appropriate section in @ref{Embedded Processors, ,Embedded
12334 Some configurations may include these targets as well:
12338 @item target nrom @var{dev}
12339 @cindex NetROM ROM emulator target
12340 NetROM ROM emulator. This target only supports downloading.
12344 Different targets are available on different configurations of @value{GDBN};
12345 your configuration may have more or fewer targets.
12347 Many remote targets require you to download the executable's code once
12348 you've successfully established a connection. You may wish to control
12349 various aspects of this process.
12354 @kindex set hash@r{, for remote monitors}
12355 @cindex hash mark while downloading
12356 This command controls whether a hash mark @samp{#} is displayed while
12357 downloading a file to the remote monitor. If on, a hash mark is
12358 displayed after each S-record is successfully downloaded to the
12362 @kindex show hash@r{, for remote monitors}
12363 Show the current status of displaying the hash mark.
12365 @item set debug monitor
12366 @kindex set debug monitor
12367 @cindex display remote monitor communications
12368 Enable or disable display of communications messages between
12369 @value{GDBN} and the remote monitor.
12371 @item show debug monitor
12372 @kindex show debug monitor
12373 Show the current status of displaying communications between
12374 @value{GDBN} and the remote monitor.
12379 @kindex load @var{filename}
12380 @item load @var{filename}
12381 Depending on what remote debugging facilities are configured into
12382 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12383 is meant to make @var{filename} (an executable) available for debugging
12384 on the remote system---by downloading, or dynamic linking, for example.
12385 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12386 the @code{add-symbol-file} command.
12388 If your @value{GDBN} does not have a @code{load} command, attempting to
12389 execute it gets the error message ``@code{You can't do that when your
12390 target is @dots{}}''
12392 The file is loaded at whatever address is specified in the executable.
12393 For some object file formats, you can specify the load address when you
12394 link the program; for other formats, like a.out, the object file format
12395 specifies a fixed address.
12396 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12398 Depending on the remote side capabilities, @value{GDBN} may be able to
12399 load programs into flash memory.
12401 @code{load} does not repeat if you press @key{RET} again after using it.
12405 @section Choosing Target Byte Order
12407 @cindex choosing target byte order
12408 @cindex target byte order
12410 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12411 offer the ability to run either big-endian or little-endian byte
12412 orders. Usually the executable or symbol will include a bit to
12413 designate the endian-ness, and you will not need to worry about
12414 which to use. However, you may still find it useful to adjust
12415 @value{GDBN}'s idea of processor endian-ness manually.
12419 @item set endian big
12420 Instruct @value{GDBN} to assume the target is big-endian.
12422 @item set endian little
12423 Instruct @value{GDBN} to assume the target is little-endian.
12425 @item set endian auto
12426 Instruct @value{GDBN} to use the byte order associated with the
12430 Display @value{GDBN}'s current idea of the target byte order.
12434 Note that these commands merely adjust interpretation of symbolic
12435 data on the host, and that they have absolutely no effect on the
12439 @node Remote Debugging
12440 @chapter Debugging Remote Programs
12441 @cindex remote debugging
12443 If you are trying to debug a program running on a machine that cannot run
12444 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12445 For example, you might use remote debugging on an operating system kernel,
12446 or on a small system which does not have a general purpose operating system
12447 powerful enough to run a full-featured debugger.
12449 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12450 to make this work with particular debugging targets. In addition,
12451 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12452 but not specific to any particular target system) which you can use if you
12453 write the remote stubs---the code that runs on the remote system to
12454 communicate with @value{GDBN}.
12456 Other remote targets may be available in your
12457 configuration of @value{GDBN}; use @code{help target} to list them.
12460 * Connecting:: Connecting to a remote target
12461 * Server:: Using the gdbserver program
12462 * Remote Configuration:: Remote configuration
12463 * Remote Stub:: Implementing a remote stub
12467 @section Connecting to a Remote Target
12469 On the @value{GDBN} host machine, you will need an unstripped copy of
12470 your program, since @value{GDBN} needs symbol and debugging information.
12471 Start up @value{GDBN} as usual, using the name of the local copy of your
12472 program as the first argument.
12474 @cindex @code{target remote}
12475 @value{GDBN} can communicate with the target over a serial line, or
12476 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12477 each case, @value{GDBN} uses the same protocol for debugging your
12478 program; only the medium carrying the debugging packets varies. The
12479 @code{target remote} command establishes a connection to the target.
12480 Its arguments indicate which medium to use:
12484 @item target remote @var{serial-device}
12485 @cindex serial line, @code{target remote}
12486 Use @var{serial-device} to communicate with the target. For example,
12487 to use a serial line connected to the device named @file{/dev/ttyb}:
12490 target remote /dev/ttyb
12493 If you're using a serial line, you may want to give @value{GDBN} the
12494 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12495 (@pxref{Remote Configuration, set remotebaud}) before the
12496 @code{target} command.
12498 @item target remote @code{@var{host}:@var{port}}
12499 @itemx target remote @code{tcp:@var{host}:@var{port}}
12500 @cindex @acronym{TCP} port, @code{target remote}
12501 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12502 The @var{host} may be either a host name or a numeric @acronym{IP}
12503 address; @var{port} must be a decimal number. The @var{host} could be
12504 the target machine itself, if it is directly connected to the net, or
12505 it might be a terminal server which in turn has a serial line to the
12508 For example, to connect to port 2828 on a terminal server named
12512 target remote manyfarms:2828
12515 If your remote target is actually running on the same machine as your
12516 debugger session (e.g.@: a simulator for your target running on the
12517 same host), you can omit the hostname. For example, to connect to
12518 port 1234 on your local machine:
12521 target remote :1234
12525 Note that the colon is still required here.
12527 @item target remote @code{udp:@var{host}:@var{port}}
12528 @cindex @acronym{UDP} port, @code{target remote}
12529 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12530 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12533 target remote udp:manyfarms:2828
12536 When using a @acronym{UDP} connection for remote debugging, you should
12537 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12538 can silently drop packets on busy or unreliable networks, which will
12539 cause havoc with your debugging session.
12541 @item target remote | @var{command}
12542 @cindex pipe, @code{target remote} to
12543 Run @var{command} in the background and communicate with it using a
12544 pipe. The @var{command} is a shell command, to be parsed and expanded
12545 by the system's command shell, @code{/bin/sh}; it should expect remote
12546 protocol packets on its standard input, and send replies on its
12547 standard output. You could use this to run a stand-alone simulator
12548 that speaks the remote debugging protocol, to make net connections
12549 using programs like @code{ssh}, or for other similar tricks.
12551 If @var{command} closes its standard output (perhaps by exiting),
12552 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12553 program has already exited, this will have no effect.)
12557 Once the connection has been established, you can use all the usual
12558 commands to examine and change data and to step and continue the
12561 @cindex interrupting remote programs
12562 @cindex remote programs, interrupting
12563 Whenever @value{GDBN} is waiting for the remote program, if you type the
12564 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12565 program. This may or may not succeed, depending in part on the hardware
12566 and the serial drivers the remote system uses. If you type the
12567 interrupt character once again, @value{GDBN} displays this prompt:
12570 Interrupted while waiting for the program.
12571 Give up (and stop debugging it)? (y or n)
12574 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12575 (If you decide you want to try again later, you can use @samp{target
12576 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12577 goes back to waiting.
12580 @kindex detach (remote)
12582 When you have finished debugging the remote program, you can use the
12583 @code{detach} command to release it from @value{GDBN} control.
12584 Detaching from the target normally resumes its execution, but the results
12585 will depend on your particular remote stub. After the @code{detach}
12586 command, @value{GDBN} is free to connect to another target.
12590 The @code{disconnect} command behaves like @code{detach}, except that
12591 the target is generally not resumed. It will wait for @value{GDBN}
12592 (this instance or another one) to connect and continue debugging. After
12593 the @code{disconnect} command, @value{GDBN} is again free to connect to
12596 @cindex send command to remote monitor
12597 @cindex extend @value{GDBN} for remote targets
12598 @cindex add new commands for external monitor
12600 @item monitor @var{cmd}
12601 This command allows you to send arbitrary commands directly to the
12602 remote monitor. Since @value{GDBN} doesn't care about the commands it
12603 sends like this, this command is the way to extend @value{GDBN}---you
12604 can add new commands that only the external monitor will understand
12609 @section Using the @code{gdbserver} Program
12612 @cindex remote connection without stubs
12613 @code{gdbserver} is a control program for Unix-like systems, which
12614 allows you to connect your program with a remote @value{GDBN} via
12615 @code{target remote}---but without linking in the usual debugging stub.
12617 @code{gdbserver} is not a complete replacement for the debugging stubs,
12618 because it requires essentially the same operating-system facilities
12619 that @value{GDBN} itself does. In fact, a system that can run
12620 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12621 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12622 because it is a much smaller program than @value{GDBN} itself. It is
12623 also easier to port than all of @value{GDBN}, so you may be able to get
12624 started more quickly on a new system by using @code{gdbserver}.
12625 Finally, if you develop code for real-time systems, you may find that
12626 the tradeoffs involved in real-time operation make it more convenient to
12627 do as much development work as possible on another system, for example
12628 by cross-compiling. You can use @code{gdbserver} to make a similar
12629 choice for debugging.
12631 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12632 or a TCP connection, using the standard @value{GDBN} remote serial
12636 @item On the target machine,
12637 you need to have a copy of the program you want to debug.
12638 @code{gdbserver} does not need your program's symbol table, so you can
12639 strip the program if necessary to save space. @value{GDBN} on the host
12640 system does all the symbol handling.
12642 To use the server, you must tell it how to communicate with @value{GDBN};
12643 the name of your program; and the arguments for your program. The usual
12647 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12650 @var{comm} is either a device name (to use a serial line) or a TCP
12651 hostname and portnumber. For example, to debug Emacs with the argument
12652 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12656 target> gdbserver /dev/com1 emacs foo.txt
12659 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12662 To use a TCP connection instead of a serial line:
12665 target> gdbserver host:2345 emacs foo.txt
12668 The only difference from the previous example is the first argument,
12669 specifying that you are communicating with the host @value{GDBN} via
12670 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12671 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12672 (Currently, the @samp{host} part is ignored.) You can choose any number
12673 you want for the port number as long as it does not conflict with any
12674 TCP ports already in use on the target system (for example, @code{23} is
12675 reserved for @code{telnet}).@footnote{If you choose a port number that
12676 conflicts with another service, @code{gdbserver} prints an error message
12677 and exits.} You must use the same port number with the host @value{GDBN}
12678 @code{target remote} command.
12680 On some targets, @code{gdbserver} can also attach to running programs.
12681 This is accomplished via the @code{--attach} argument. The syntax is:
12684 target> gdbserver @var{comm} --attach @var{pid}
12687 @var{pid} is the process ID of a currently running process. It isn't necessary
12688 to point @code{gdbserver} at a binary for the running process.
12691 @cindex attach to a program by name
12692 You can debug processes by name instead of process ID if your target has the
12693 @code{pidof} utility:
12696 target> gdbserver @var{comm} --attach `pidof @var{program}`
12699 In case more than one copy of @var{program} is running, or @var{program}
12700 has multiple threads, most versions of @code{pidof} support the
12701 @code{-s} option to only return the first process ID.
12703 @item On the host machine,
12704 first make sure you have the necessary symbol files. Load symbols for
12705 your application using the @code{file} command before you connect. Use
12706 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
12707 was compiled with the correct sysroot using @code{--with-system-root}).
12709 The symbol file and target libraries must exactly match the executable
12710 and libraries on the target, with one exception: the files on the host
12711 system should not be stripped, even if the files on the target system
12712 are. Mismatched or missing files will lead to confusing results
12713 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
12714 files may also prevent @code{gdbserver} from debugging multi-threaded
12717 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
12718 For TCP connections, you must start up @code{gdbserver} prior to using
12719 the @code{target remote} command. Otherwise you may get an error whose
12720 text depends on the host system, but which usually looks something like
12721 @samp{Connection refused}. You don't need to use the @code{load}
12722 command in @value{GDBN} when using @code{gdbserver}, since the program is
12723 already on the target.
12727 @subsection Monitor Commands for @code{gdbserver}
12728 @cindex monitor commands, for @code{gdbserver}
12730 During a @value{GDBN} session using @code{gdbserver}, you can use the
12731 @code{monitor} command to send special requests to @code{gdbserver}.
12732 Here are the available commands; they are only of interest when
12733 debugging @value{GDBN} or @code{gdbserver}.
12737 List the available monitor commands.
12739 @item monitor set debug 0
12740 @itemx monitor set debug 1
12741 Disable or enable general debugging messages.
12743 @item monitor set remote-debug 0
12744 @itemx monitor set remote-debug 1
12745 Disable or enable specific debugging messages associated with the remote
12746 protocol (@pxref{Remote Protocol}).
12750 @node Remote Configuration
12751 @section Remote Configuration
12754 @kindex show remote
12755 This section documents the configuration options available when
12756 debugging remote programs. For the options related to the File I/O
12757 extensions of the remote protocol, see @ref{system,
12758 system-call-allowed}.
12761 @item set remoteaddresssize @var{bits}
12762 @cindex address size for remote targets
12763 @cindex bits in remote address
12764 Set the maximum size of address in a memory packet to the specified
12765 number of bits. @value{GDBN} will mask off the address bits above
12766 that number, when it passes addresses to the remote target. The
12767 default value is the number of bits in the target's address.
12769 @item show remoteaddresssize
12770 Show the current value of remote address size in bits.
12772 @item set remotebaud @var{n}
12773 @cindex baud rate for remote targets
12774 Set the baud rate for the remote serial I/O to @var{n} baud. The
12775 value is used to set the speed of the serial port used for debugging
12778 @item show remotebaud
12779 Show the current speed of the remote connection.
12781 @item set remotebreak
12782 @cindex interrupt remote programs
12783 @cindex BREAK signal instead of Ctrl-C
12784 @anchor{set remotebreak}
12785 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12786 when you type @kbd{Ctrl-c} to interrupt the program running
12787 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12788 character instead. The default is off, since most remote systems
12789 expect to see @samp{Ctrl-C} as the interrupt signal.
12791 @item show remotebreak
12792 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12793 interrupt the remote program.
12795 @item set remoteflow on
12796 @itemx set remoteflow off
12797 @kindex set remoteflow
12798 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
12799 on the serial port used to communicate to the remote target.
12801 @item show remoteflow
12802 @kindex show remoteflow
12803 Show the current setting of hardware flow control.
12805 @item set remotelogbase @var{base}
12806 Set the base (a.k.a.@: radix) of logging serial protocol
12807 communications to @var{base}. Supported values of @var{base} are:
12808 @code{ascii}, @code{octal}, and @code{hex}. The default is
12811 @item show remotelogbase
12812 Show the current setting of the radix for logging remote serial
12815 @item set remotelogfile @var{file}
12816 @cindex record serial communications on file
12817 Record remote serial communications on the named @var{file}. The
12818 default is not to record at all.
12820 @item show remotelogfile.
12821 Show the current setting of the file name on which to record the
12822 serial communications.
12824 @item set remotetimeout @var{num}
12825 @cindex timeout for serial communications
12826 @cindex remote timeout
12827 Set the timeout limit to wait for the remote target to respond to
12828 @var{num} seconds. The default is 2 seconds.
12830 @item show remotetimeout
12831 Show the current number of seconds to wait for the remote target
12834 @cindex limit hardware breakpoints and watchpoints
12835 @cindex remote target, limit break- and watchpoints
12836 @anchor{set remote hardware-watchpoint-limit}
12837 @anchor{set remote hardware-breakpoint-limit}
12838 @item set remote hardware-watchpoint-limit @var{limit}
12839 @itemx set remote hardware-breakpoint-limit @var{limit}
12840 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12841 watchpoints. A limit of -1, the default, is treated as unlimited.
12844 @cindex remote packets, enabling and disabling
12845 The @value{GDBN} remote protocol autodetects the packets supported by
12846 your debugging stub. If you need to override the autodetection, you
12847 can use these commands to enable or disable individual packets. Each
12848 packet can be set to @samp{on} (the remote target supports this
12849 packet), @samp{off} (the remote target does not support this packet),
12850 or @samp{auto} (detect remote target support for this packet). They
12851 all default to @samp{auto}. For more information about each packet,
12852 see @ref{Remote Protocol}.
12854 During normal use, you should not have to use any of these commands.
12855 If you do, that may be a bug in your remote debugging stub, or a bug
12856 in @value{GDBN}. You may want to report the problem to the
12857 @value{GDBN} developers.
12859 The available settings are:
12861 @multitable @columnfractions 0.3 0.2 0.35
12864 @tab Related Features
12866 @item @code{fetch-register-packet}
12868 @tab @code{info registers}
12870 @item @code{set-register-packet}
12874 @item @code{binary-download-packet}
12876 @tab @code{load}, @code{set}
12878 @item @code{read-aux-vector-packet}
12879 @tab @code{qXfer:auxv:read}
12880 @tab @code{info auxv}
12882 @item @code{symbol-lookup-packet}
12883 @tab @code{qSymbol}
12884 @tab Detecting multiple threads
12886 @item @code{verbose-resume-packet}
12888 @tab Stepping or resuming multiple threads
12890 @item @code{software-breakpoint-packet}
12894 @item @code{hardware-breakpoint-packet}
12898 @item @code{write-watchpoint-packet}
12902 @item @code{read-watchpoint-packet}
12906 @item @code{access-watchpoint-packet}
12910 @item @code{get-thread-local-storage-address-packet}
12911 @tab @code{qGetTLSAddr}
12912 @tab Displaying @code{__thread} variables
12914 @item @code{supported-packets}
12915 @tab @code{qSupported}
12916 @tab Remote communications parameters
12918 @item @code{pass-signals-packet}
12919 @tab @code{QPassSignals}
12920 @tab @code{handle @var{signal}}
12925 @section Implementing a Remote Stub
12927 @cindex debugging stub, example
12928 @cindex remote stub, example
12929 @cindex stub example, remote debugging
12930 The stub files provided with @value{GDBN} implement the target side of the
12931 communication protocol, and the @value{GDBN} side is implemented in the
12932 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12933 these subroutines to communicate, and ignore the details. (If you're
12934 implementing your own stub file, you can still ignore the details: start
12935 with one of the existing stub files. @file{sparc-stub.c} is the best
12936 organized, and therefore the easiest to read.)
12938 @cindex remote serial debugging, overview
12939 To debug a program running on another machine (the debugging
12940 @dfn{target} machine), you must first arrange for all the usual
12941 prerequisites for the program to run by itself. For example, for a C
12946 A startup routine to set up the C runtime environment; these usually
12947 have a name like @file{crt0}. The startup routine may be supplied by
12948 your hardware supplier, or you may have to write your own.
12951 A C subroutine library to support your program's
12952 subroutine calls, notably managing input and output.
12955 A way of getting your program to the other machine---for example, a
12956 download program. These are often supplied by the hardware
12957 manufacturer, but you may have to write your own from hardware
12961 The next step is to arrange for your program to use a serial port to
12962 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12963 machine). In general terms, the scheme looks like this:
12967 @value{GDBN} already understands how to use this protocol; when everything
12968 else is set up, you can simply use the @samp{target remote} command
12969 (@pxref{Targets,,Specifying a Debugging Target}).
12971 @item On the target,
12972 you must link with your program a few special-purpose subroutines that
12973 implement the @value{GDBN} remote serial protocol. The file containing these
12974 subroutines is called a @dfn{debugging stub}.
12976 On certain remote targets, you can use an auxiliary program
12977 @code{gdbserver} instead of linking a stub into your program.
12978 @xref{Server,,Using the @code{gdbserver} Program}, for details.
12981 The debugging stub is specific to the architecture of the remote
12982 machine; for example, use @file{sparc-stub.c} to debug programs on
12985 @cindex remote serial stub list
12986 These working remote stubs are distributed with @value{GDBN}:
12991 @cindex @file{i386-stub.c}
12994 For Intel 386 and compatible architectures.
12997 @cindex @file{m68k-stub.c}
12998 @cindex Motorola 680x0
13000 For Motorola 680x0 architectures.
13003 @cindex @file{sh-stub.c}
13006 For Renesas SH architectures.
13009 @cindex @file{sparc-stub.c}
13011 For @sc{sparc} architectures.
13013 @item sparcl-stub.c
13014 @cindex @file{sparcl-stub.c}
13017 For Fujitsu @sc{sparclite} architectures.
13021 The @file{README} file in the @value{GDBN} distribution may list other
13022 recently added stubs.
13025 * Stub Contents:: What the stub can do for you
13026 * Bootstrapping:: What you must do for the stub
13027 * Debug Session:: Putting it all together
13030 @node Stub Contents
13031 @subsection What the Stub Can Do for You
13033 @cindex remote serial stub
13034 The debugging stub for your architecture supplies these three
13038 @item set_debug_traps
13039 @findex set_debug_traps
13040 @cindex remote serial stub, initialization
13041 This routine arranges for @code{handle_exception} to run when your
13042 program stops. You must call this subroutine explicitly near the
13043 beginning of your program.
13045 @item handle_exception
13046 @findex handle_exception
13047 @cindex remote serial stub, main routine
13048 This is the central workhorse, but your program never calls it
13049 explicitly---the setup code arranges for @code{handle_exception} to
13050 run when a trap is triggered.
13052 @code{handle_exception} takes control when your program stops during
13053 execution (for example, on a breakpoint), and mediates communications
13054 with @value{GDBN} on the host machine. This is where the communications
13055 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13056 representative on the target machine. It begins by sending summary
13057 information on the state of your program, then continues to execute,
13058 retrieving and transmitting any information @value{GDBN} needs, until you
13059 execute a @value{GDBN} command that makes your program resume; at that point,
13060 @code{handle_exception} returns control to your own code on the target
13064 @cindex @code{breakpoint} subroutine, remote
13065 Use this auxiliary subroutine to make your program contain a
13066 breakpoint. Depending on the particular situation, this may be the only
13067 way for @value{GDBN} to get control. For instance, if your target
13068 machine has some sort of interrupt button, you won't need to call this;
13069 pressing the interrupt button transfers control to
13070 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13071 simply receiving characters on the serial port may also trigger a trap;
13072 again, in that situation, you don't need to call @code{breakpoint} from
13073 your own program---simply running @samp{target remote} from the host
13074 @value{GDBN} session gets control.
13076 Call @code{breakpoint} if none of these is true, or if you simply want
13077 to make certain your program stops at a predetermined point for the
13078 start of your debugging session.
13081 @node Bootstrapping
13082 @subsection What You Must Do for the Stub
13084 @cindex remote stub, support routines
13085 The debugging stubs that come with @value{GDBN} are set up for a particular
13086 chip architecture, but they have no information about the rest of your
13087 debugging target machine.
13089 First of all you need to tell the stub how to communicate with the
13093 @item int getDebugChar()
13094 @findex getDebugChar
13095 Write this subroutine to read a single character from the serial port.
13096 It may be identical to @code{getchar} for your target system; a
13097 different name is used to allow you to distinguish the two if you wish.
13099 @item void putDebugChar(int)
13100 @findex putDebugChar
13101 Write this subroutine to write a single character to the serial port.
13102 It may be identical to @code{putchar} for your target system; a
13103 different name is used to allow you to distinguish the two if you wish.
13106 @cindex control C, and remote debugging
13107 @cindex interrupting remote targets
13108 If you want @value{GDBN} to be able to stop your program while it is
13109 running, you need to use an interrupt-driven serial driver, and arrange
13110 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13111 character). That is the character which @value{GDBN} uses to tell the
13112 remote system to stop.
13114 Getting the debugging target to return the proper status to @value{GDBN}
13115 probably requires changes to the standard stub; one quick and dirty way
13116 is to just execute a breakpoint instruction (the ``dirty'' part is that
13117 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13119 Other routines you need to supply are:
13122 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13123 @findex exceptionHandler
13124 Write this function to install @var{exception_address} in the exception
13125 handling tables. You need to do this because the stub does not have any
13126 way of knowing what the exception handling tables on your target system
13127 are like (for example, the processor's table might be in @sc{rom},
13128 containing entries which point to a table in @sc{ram}).
13129 @var{exception_number} is the exception number which should be changed;
13130 its meaning is architecture-dependent (for example, different numbers
13131 might represent divide by zero, misaligned access, etc). When this
13132 exception occurs, control should be transferred directly to
13133 @var{exception_address}, and the processor state (stack, registers,
13134 and so on) should be just as it is when a processor exception occurs. So if
13135 you want to use a jump instruction to reach @var{exception_address}, it
13136 should be a simple jump, not a jump to subroutine.
13138 For the 386, @var{exception_address} should be installed as an interrupt
13139 gate so that interrupts are masked while the handler runs. The gate
13140 should be at privilege level 0 (the most privileged level). The
13141 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13142 help from @code{exceptionHandler}.
13144 @item void flush_i_cache()
13145 @findex flush_i_cache
13146 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13147 instruction cache, if any, on your target machine. If there is no
13148 instruction cache, this subroutine may be a no-op.
13150 On target machines that have instruction caches, @value{GDBN} requires this
13151 function to make certain that the state of your program is stable.
13155 You must also make sure this library routine is available:
13158 @item void *memset(void *, int, int)
13160 This is the standard library function @code{memset} that sets an area of
13161 memory to a known value. If you have one of the free versions of
13162 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13163 either obtain it from your hardware manufacturer, or write your own.
13166 If you do not use the GNU C compiler, you may need other standard
13167 library subroutines as well; this varies from one stub to another,
13168 but in general the stubs are likely to use any of the common library
13169 subroutines which @code{@value{NGCC}} generates as inline code.
13172 @node Debug Session
13173 @subsection Putting it All Together
13175 @cindex remote serial debugging summary
13176 In summary, when your program is ready to debug, you must follow these
13181 Make sure you have defined the supporting low-level routines
13182 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13184 @code{getDebugChar}, @code{putDebugChar},
13185 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13189 Insert these lines near the top of your program:
13197 For the 680x0 stub only, you need to provide a variable called
13198 @code{exceptionHook}. Normally you just use:
13201 void (*exceptionHook)() = 0;
13205 but if before calling @code{set_debug_traps}, you set it to point to a
13206 function in your program, that function is called when
13207 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13208 error). The function indicated by @code{exceptionHook} is called with
13209 one parameter: an @code{int} which is the exception number.
13212 Compile and link together: your program, the @value{GDBN} debugging stub for
13213 your target architecture, and the supporting subroutines.
13216 Make sure you have a serial connection between your target machine and
13217 the @value{GDBN} host, and identify the serial port on the host.
13220 @c The "remote" target now provides a `load' command, so we should
13221 @c document that. FIXME.
13222 Download your program to your target machine (or get it there by
13223 whatever means the manufacturer provides), and start it.
13226 Start @value{GDBN} on the host, and connect to the target
13227 (@pxref{Connecting,,Connecting to a Remote Target}).
13231 @node Configurations
13232 @chapter Configuration-Specific Information
13234 While nearly all @value{GDBN} commands are available for all native and
13235 cross versions of the debugger, there are some exceptions. This chapter
13236 describes things that are only available in certain configurations.
13238 There are three major categories of configurations: native
13239 configurations, where the host and target are the same, embedded
13240 operating system configurations, which are usually the same for several
13241 different processor architectures, and bare embedded processors, which
13242 are quite different from each other.
13247 * Embedded Processors::
13254 This section describes details specific to particular native
13259 * BSD libkvm Interface:: Debugging BSD kernel memory images
13260 * SVR4 Process Information:: SVR4 process information
13261 * DJGPP Native:: Features specific to the DJGPP port
13262 * Cygwin Native:: Features specific to the Cygwin port
13263 * Hurd Native:: Features specific to @sc{gnu} Hurd
13264 * Neutrino:: Features specific to QNX Neutrino
13270 On HP-UX systems, if you refer to a function or variable name that
13271 begins with a dollar sign, @value{GDBN} searches for a user or system
13272 name first, before it searches for a convenience variable.
13275 @node BSD libkvm Interface
13276 @subsection BSD libkvm Interface
13279 @cindex kernel memory image
13280 @cindex kernel crash dump
13282 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13283 interface that provides a uniform interface for accessing kernel virtual
13284 memory images, including live systems and crash dumps. @value{GDBN}
13285 uses this interface to allow you to debug live kernels and kernel crash
13286 dumps on many native BSD configurations. This is implemented as a
13287 special @code{kvm} debugging target. For debugging a live system, load
13288 the currently running kernel into @value{GDBN} and connect to the
13292 (@value{GDBP}) @b{target kvm}
13295 For debugging crash dumps, provide the file name of the crash dump as an
13299 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13302 Once connected to the @code{kvm} target, the following commands are
13308 Set current context from the @dfn{Process Control Block} (PCB) address.
13311 Set current context from proc address. This command isn't available on
13312 modern FreeBSD systems.
13315 @node SVR4 Process Information
13316 @subsection SVR4 Process Information
13318 @cindex examine process image
13319 @cindex process info via @file{/proc}
13321 Many versions of SVR4 and compatible systems provide a facility called
13322 @samp{/proc} that can be used to examine the image of a running
13323 process using file-system subroutines. If @value{GDBN} is configured
13324 for an operating system with this facility, the command @code{info
13325 proc} is available to report information about the process running
13326 your program, or about any process running on your system. @code{info
13327 proc} works only on SVR4 systems that include the @code{procfs} code.
13328 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13329 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13335 @itemx info proc @var{process-id}
13336 Summarize available information about any running process. If a
13337 process ID is specified by @var{process-id}, display information about
13338 that process; otherwise display information about the program being
13339 debugged. The summary includes the debugged process ID, the command
13340 line used to invoke it, its current working directory, and its
13341 executable file's absolute file name.
13343 On some systems, @var{process-id} can be of the form
13344 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13345 within a process. If the optional @var{pid} part is missing, it means
13346 a thread from the process being debugged (the leading @samp{/} still
13347 needs to be present, or else @value{GDBN} will interpret the number as
13348 a process ID rather than a thread ID).
13350 @item info proc mappings
13351 @cindex memory address space mappings
13352 Report the memory address space ranges accessible in the program, with
13353 information on whether the process has read, write, or execute access
13354 rights to each range. On @sc{gnu}/Linux systems, each memory range
13355 includes the object file which is mapped to that range, instead of the
13356 memory access rights to that range.
13358 @item info proc stat
13359 @itemx info proc status
13360 @cindex process detailed status information
13361 These subcommands are specific to @sc{gnu}/Linux systems. They show
13362 the process-related information, including the user ID and group ID;
13363 how many threads are there in the process; its virtual memory usage;
13364 the signals that are pending, blocked, and ignored; its TTY; its
13365 consumption of system and user time; its stack size; its @samp{nice}
13366 value; etc. For more information, see the @samp{proc} man page
13367 (type @kbd{man 5 proc} from your shell prompt).
13369 @item info proc all
13370 Show all the information about the process described under all of the
13371 above @code{info proc} subcommands.
13374 @comment These sub-options of 'info proc' were not included when
13375 @comment procfs.c was re-written. Keep their descriptions around
13376 @comment against the day when someone finds the time to put them back in.
13377 @kindex info proc times
13378 @item info proc times
13379 Starting time, user CPU time, and system CPU time for your program and
13382 @kindex info proc id
13384 Report on the process IDs related to your program: its own process ID,
13385 the ID of its parent, the process group ID, and the session ID.
13388 @item set procfs-trace
13389 @kindex set procfs-trace
13390 @cindex @code{procfs} API calls
13391 This command enables and disables tracing of @code{procfs} API calls.
13393 @item show procfs-trace
13394 @kindex show procfs-trace
13395 Show the current state of @code{procfs} API call tracing.
13397 @item set procfs-file @var{file}
13398 @kindex set procfs-file
13399 Tell @value{GDBN} to write @code{procfs} API trace to the named
13400 @var{file}. @value{GDBN} appends the trace info to the previous
13401 contents of the file. The default is to display the trace on the
13404 @item show procfs-file
13405 @kindex show procfs-file
13406 Show the file to which @code{procfs} API trace is written.
13408 @item proc-trace-entry
13409 @itemx proc-trace-exit
13410 @itemx proc-untrace-entry
13411 @itemx proc-untrace-exit
13412 @kindex proc-trace-entry
13413 @kindex proc-trace-exit
13414 @kindex proc-untrace-entry
13415 @kindex proc-untrace-exit
13416 These commands enable and disable tracing of entries into and exits
13417 from the @code{syscall} interface.
13420 @kindex info pidlist
13421 @cindex process list, QNX Neutrino
13422 For QNX Neutrino only, this command displays the list of all the
13423 processes and all the threads within each process.
13426 @kindex info meminfo
13427 @cindex mapinfo list, QNX Neutrino
13428 For QNX Neutrino only, this command displays the list of all mapinfos.
13432 @subsection Features for Debugging @sc{djgpp} Programs
13433 @cindex @sc{djgpp} debugging
13434 @cindex native @sc{djgpp} debugging
13435 @cindex MS-DOS-specific commands
13438 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13439 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13440 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13441 top of real-mode DOS systems and their emulations.
13443 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13444 defines a few commands specific to the @sc{djgpp} port. This
13445 subsection describes those commands.
13450 This is a prefix of @sc{djgpp}-specific commands which print
13451 information about the target system and important OS structures.
13454 @cindex MS-DOS system info
13455 @cindex free memory information (MS-DOS)
13456 @item info dos sysinfo
13457 This command displays assorted information about the underlying
13458 platform: the CPU type and features, the OS version and flavor, the
13459 DPMI version, and the available conventional and DPMI memory.
13464 @cindex segment descriptor tables
13465 @cindex descriptor tables display
13467 @itemx info dos ldt
13468 @itemx info dos idt
13469 These 3 commands display entries from, respectively, Global, Local,
13470 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13471 tables are data structures which store a descriptor for each segment
13472 that is currently in use. The segment's selector is an index into a
13473 descriptor table; the table entry for that index holds the
13474 descriptor's base address and limit, and its attributes and access
13477 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13478 segment (used for both data and the stack), and a DOS segment (which
13479 allows access to DOS/BIOS data structures and absolute addresses in
13480 conventional memory). However, the DPMI host will usually define
13481 additional segments in order to support the DPMI environment.
13483 @cindex garbled pointers
13484 These commands allow to display entries from the descriptor tables.
13485 Without an argument, all entries from the specified table are
13486 displayed. An argument, which should be an integer expression, means
13487 display a single entry whose index is given by the argument. For
13488 example, here's a convenient way to display information about the
13489 debugged program's data segment:
13492 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13493 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13497 This comes in handy when you want to see whether a pointer is outside
13498 the data segment's limit (i.e.@: @dfn{garbled}).
13500 @cindex page tables display (MS-DOS)
13502 @itemx info dos pte
13503 These two commands display entries from, respectively, the Page
13504 Directory and the Page Tables. Page Directories and Page Tables are
13505 data structures which control how virtual memory addresses are mapped
13506 into physical addresses. A Page Table includes an entry for every
13507 page of memory that is mapped into the program's address space; there
13508 may be several Page Tables, each one holding up to 4096 entries. A
13509 Page Directory has up to 4096 entries, one each for every Page Table
13510 that is currently in use.
13512 Without an argument, @kbd{info dos pde} displays the entire Page
13513 Directory, and @kbd{info dos pte} displays all the entries in all of
13514 the Page Tables. An argument, an integer expression, given to the
13515 @kbd{info dos pde} command means display only that entry from the Page
13516 Directory table. An argument given to the @kbd{info dos pte} command
13517 means display entries from a single Page Table, the one pointed to by
13518 the specified entry in the Page Directory.
13520 @cindex direct memory access (DMA) on MS-DOS
13521 These commands are useful when your program uses @dfn{DMA} (Direct
13522 Memory Access), which needs physical addresses to program the DMA
13525 These commands are supported only with some DPMI servers.
13527 @cindex physical address from linear address
13528 @item info dos address-pte @var{addr}
13529 This command displays the Page Table entry for a specified linear
13530 address. The argument @var{addr} is a linear address which should
13531 already have the appropriate segment's base address added to it,
13532 because this command accepts addresses which may belong to @emph{any}
13533 segment. For example, here's how to display the Page Table entry for
13534 the page where a variable @code{i} is stored:
13537 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13538 @exdent @code{Page Table entry for address 0x11a00d30:}
13539 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13543 This says that @code{i} is stored at offset @code{0xd30} from the page
13544 whose physical base address is @code{0x02698000}, and shows all the
13545 attributes of that page.
13547 Note that you must cast the addresses of variables to a @code{char *},
13548 since otherwise the value of @code{__djgpp_base_address}, the base
13549 address of all variables and functions in a @sc{djgpp} program, will
13550 be added using the rules of C pointer arithmetics: if @code{i} is
13551 declared an @code{int}, @value{GDBN} will add 4 times the value of
13552 @code{__djgpp_base_address} to the address of @code{i}.
13554 Here's another example, it displays the Page Table entry for the
13558 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13559 @exdent @code{Page Table entry for address 0x29110:}
13560 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13564 (The @code{+ 3} offset is because the transfer buffer's address is the
13565 3rd member of the @code{_go32_info_block} structure.) The output
13566 clearly shows that this DPMI server maps the addresses in conventional
13567 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13568 linear (@code{0x29110}) addresses are identical.
13570 This command is supported only with some DPMI servers.
13573 @cindex DOS serial data link, remote debugging
13574 In addition to native debugging, the DJGPP port supports remote
13575 debugging via a serial data link. The following commands are specific
13576 to remote serial debugging in the DJGPP port of @value{GDBN}.
13579 @kindex set com1base
13580 @kindex set com1irq
13581 @kindex set com2base
13582 @kindex set com2irq
13583 @kindex set com3base
13584 @kindex set com3irq
13585 @kindex set com4base
13586 @kindex set com4irq
13587 @item set com1base @var{addr}
13588 This command sets the base I/O port address of the @file{COM1} serial
13591 @item set com1irq @var{irq}
13592 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13593 for the @file{COM1} serial port.
13595 There are similar commands @samp{set com2base}, @samp{set com3irq},
13596 etc.@: for setting the port address and the @code{IRQ} lines for the
13599 @kindex show com1base
13600 @kindex show com1irq
13601 @kindex show com2base
13602 @kindex show com2irq
13603 @kindex show com3base
13604 @kindex show com3irq
13605 @kindex show com4base
13606 @kindex show com4irq
13607 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13608 display the current settings of the base address and the @code{IRQ}
13609 lines used by the COM ports.
13612 @kindex info serial
13613 @cindex DOS serial port status
13614 This command prints the status of the 4 DOS serial ports. For each
13615 port, it prints whether it's active or not, its I/O base address and
13616 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13617 counts of various errors encountered so far.
13621 @node Cygwin Native
13622 @subsection Features for Debugging MS Windows PE Executables
13623 @cindex MS Windows debugging
13624 @cindex native Cygwin debugging
13625 @cindex Cygwin-specific commands
13627 @value{GDBN} supports native debugging of MS Windows programs, including
13628 DLLs with and without symbolic debugging information. There are various
13629 additional Cygwin-specific commands, described in this section.
13630 Working with DLLs that have no debugging symbols is described in
13631 @ref{Non-debug DLL Symbols}.
13636 This is a prefix of MS Windows-specific commands which print
13637 information about the target system and important OS structures.
13639 @item info w32 selector
13640 This command displays information returned by
13641 the Win32 API @code{GetThreadSelectorEntry} function.
13642 It takes an optional argument that is evaluated to
13643 a long value to give the information about this given selector.
13644 Without argument, this command displays information
13645 about the six segment registers.
13649 This is a Cygwin-specific alias of @code{info shared}.
13651 @kindex dll-symbols
13653 This command loads symbols from a dll similarly to
13654 add-sym command but without the need to specify a base address.
13656 @kindex set cygwin-exceptions
13657 @cindex debugging the Cygwin DLL
13658 @cindex Cygwin DLL, debugging
13659 @item set cygwin-exceptions @var{mode}
13660 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13661 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13662 @value{GDBN} will delay recognition of exceptions, and may ignore some
13663 exceptions which seem to be caused by internal Cygwin DLL
13664 ``bookkeeping''. This option is meant primarily for debugging the
13665 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13666 @value{GDBN} users with false @code{SIGSEGV} signals.
13668 @kindex show cygwin-exceptions
13669 @item show cygwin-exceptions
13670 Displays whether @value{GDBN} will break on exceptions that happen
13671 inside the Cygwin DLL itself.
13673 @kindex set new-console
13674 @item set new-console @var{mode}
13675 If @var{mode} is @code{on} the debuggee will
13676 be started in a new console on next start.
13677 If @var{mode} is @code{off}i, the debuggee will
13678 be started in the same console as the debugger.
13680 @kindex show new-console
13681 @item show new-console
13682 Displays whether a new console is used
13683 when the debuggee is started.
13685 @kindex set new-group
13686 @item set new-group @var{mode}
13687 This boolean value controls whether the debuggee should
13688 start a new group or stay in the same group as the debugger.
13689 This affects the way the Windows OS handles
13692 @kindex show new-group
13693 @item show new-group
13694 Displays current value of new-group boolean.
13696 @kindex set debugevents
13697 @item set debugevents
13698 This boolean value adds debug output concerning kernel events related
13699 to the debuggee seen by the debugger. This includes events that
13700 signal thread and process creation and exit, DLL loading and
13701 unloading, console interrupts, and debugging messages produced by the
13702 Windows @code{OutputDebugString} API call.
13704 @kindex set debugexec
13705 @item set debugexec
13706 This boolean value adds debug output concerning execute events
13707 (such as resume thread) seen by the debugger.
13709 @kindex set debugexceptions
13710 @item set debugexceptions
13711 This boolean value adds debug output concerning exceptions in the
13712 debuggee seen by the debugger.
13714 @kindex set debugmemory
13715 @item set debugmemory
13716 This boolean value adds debug output concerning debuggee memory reads
13717 and writes by the debugger.
13721 This boolean values specifies whether the debuggee is called
13722 via a shell or directly (default value is on).
13726 Displays if the debuggee will be started with a shell.
13731 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
13734 @node Non-debug DLL Symbols
13735 @subsubsection Support for DLLs without Debugging Symbols
13736 @cindex DLLs with no debugging symbols
13737 @cindex Minimal symbols and DLLs
13739 Very often on windows, some of the DLLs that your program relies on do
13740 not include symbolic debugging information (for example,
13741 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13742 symbols in a DLL, it relies on the minimal amount of symbolic
13743 information contained in the DLL's export table. This section
13744 describes working with such symbols, known internally to @value{GDBN} as
13745 ``minimal symbols''.
13747 Note that before the debugged program has started execution, no DLLs
13748 will have been loaded. The easiest way around this problem is simply to
13749 start the program --- either by setting a breakpoint or letting the
13750 program run once to completion. It is also possible to force
13751 @value{GDBN} to load a particular DLL before starting the executable ---
13752 see the shared library information in @ref{Files}, or the
13753 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
13754 explicitly loading symbols from a DLL with no debugging information will
13755 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13756 which may adversely affect symbol lookup performance.
13758 @subsubsection DLL Name Prefixes
13760 In keeping with the naming conventions used by the Microsoft debugging
13761 tools, DLL export symbols are made available with a prefix based on the
13762 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13763 also entered into the symbol table, so @code{CreateFileA} is often
13764 sufficient. In some cases there will be name clashes within a program
13765 (particularly if the executable itself includes full debugging symbols)
13766 necessitating the use of the fully qualified name when referring to the
13767 contents of the DLL. Use single-quotes around the name to avoid the
13768 exclamation mark (``!'') being interpreted as a language operator.
13770 Note that the internal name of the DLL may be all upper-case, even
13771 though the file name of the DLL is lower-case, or vice-versa. Since
13772 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13773 some confusion. If in doubt, try the @code{info functions} and
13774 @code{info variables} commands or even @code{maint print msymbols}
13775 (@pxref{Symbols}). Here's an example:
13778 (@value{GDBP}) info function CreateFileA
13779 All functions matching regular expression "CreateFileA":
13781 Non-debugging symbols:
13782 0x77e885f4 CreateFileA
13783 0x77e885f4 KERNEL32!CreateFileA
13787 (@value{GDBP}) info function !
13788 All functions matching regular expression "!":
13790 Non-debugging symbols:
13791 0x6100114c cygwin1!__assert
13792 0x61004034 cygwin1!_dll_crt0@@0
13793 0x61004240 cygwin1!dll_crt0(per_process *)
13797 @subsubsection Working with Minimal Symbols
13799 Symbols extracted from a DLL's export table do not contain very much
13800 type information. All that @value{GDBN} can do is guess whether a symbol
13801 refers to a function or variable depending on the linker section that
13802 contains the symbol. Also note that the actual contents of the memory
13803 contained in a DLL are not available unless the program is running. This
13804 means that you cannot examine the contents of a variable or disassemble
13805 a function within a DLL without a running program.
13807 Variables are generally treated as pointers and dereferenced
13808 automatically. For this reason, it is often necessary to prefix a
13809 variable name with the address-of operator (``&'') and provide explicit
13810 type information in the command. Here's an example of the type of
13814 (@value{GDBP}) print 'cygwin1!__argv'
13819 (@value{GDBP}) x 'cygwin1!__argv'
13820 0x10021610: "\230y\""
13823 And two possible solutions:
13826 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13827 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13831 (@value{GDBP}) x/2x &'cygwin1!__argv'
13832 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13833 (@value{GDBP}) x/x 0x10021608
13834 0x10021608: 0x0022fd98
13835 (@value{GDBP}) x/s 0x0022fd98
13836 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13839 Setting a break point within a DLL is possible even before the program
13840 starts execution. However, under these circumstances, @value{GDBN} can't
13841 examine the initial instructions of the function in order to skip the
13842 function's frame set-up code. You can work around this by using ``*&''
13843 to set the breakpoint at a raw memory address:
13846 (@value{GDBP}) break *&'python22!PyOS_Readline'
13847 Breakpoint 1 at 0x1e04eff0
13850 The author of these extensions is not entirely convinced that setting a
13851 break point within a shared DLL like @file{kernel32.dll} is completely
13855 @subsection Commands Specific to @sc{gnu} Hurd Systems
13856 @cindex @sc{gnu} Hurd debugging
13858 This subsection describes @value{GDBN} commands specific to the
13859 @sc{gnu} Hurd native debugging.
13864 @kindex set signals@r{, Hurd command}
13865 @kindex set sigs@r{, Hurd command}
13866 This command toggles the state of inferior signal interception by
13867 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13868 affected by this command. @code{sigs} is a shorthand alias for
13873 @kindex show signals@r{, Hurd command}
13874 @kindex show sigs@r{, Hurd command}
13875 Show the current state of intercepting inferior's signals.
13877 @item set signal-thread
13878 @itemx set sigthread
13879 @kindex set signal-thread
13880 @kindex set sigthread
13881 This command tells @value{GDBN} which thread is the @code{libc} signal
13882 thread. That thread is run when a signal is delivered to a running
13883 process. @code{set sigthread} is the shorthand alias of @code{set
13886 @item show signal-thread
13887 @itemx show sigthread
13888 @kindex show signal-thread
13889 @kindex show sigthread
13890 These two commands show which thread will run when the inferior is
13891 delivered a signal.
13894 @kindex set stopped@r{, Hurd command}
13895 This commands tells @value{GDBN} that the inferior process is stopped,
13896 as with the @code{SIGSTOP} signal. The stopped process can be
13897 continued by delivering a signal to it.
13900 @kindex show stopped@r{, Hurd command}
13901 This command shows whether @value{GDBN} thinks the debuggee is
13904 @item set exceptions
13905 @kindex set exceptions@r{, Hurd command}
13906 Use this command to turn off trapping of exceptions in the inferior.
13907 When exception trapping is off, neither breakpoints nor
13908 single-stepping will work. To restore the default, set exception
13911 @item show exceptions
13912 @kindex show exceptions@r{, Hurd command}
13913 Show the current state of trapping exceptions in the inferior.
13915 @item set task pause
13916 @kindex set task@r{, Hurd commands}
13917 @cindex task attributes (@sc{gnu} Hurd)
13918 @cindex pause current task (@sc{gnu} Hurd)
13919 This command toggles task suspension when @value{GDBN} has control.
13920 Setting it to on takes effect immediately, and the task is suspended
13921 whenever @value{GDBN} gets control. Setting it to off will take
13922 effect the next time the inferior is continued. If this option is set
13923 to off, you can use @code{set thread default pause on} or @code{set
13924 thread pause on} (see below) to pause individual threads.
13926 @item show task pause
13927 @kindex show task@r{, Hurd commands}
13928 Show the current state of task suspension.
13930 @item set task detach-suspend-count
13931 @cindex task suspend count
13932 @cindex detach from task, @sc{gnu} Hurd
13933 This command sets the suspend count the task will be left with when
13934 @value{GDBN} detaches from it.
13936 @item show task detach-suspend-count
13937 Show the suspend count the task will be left with when detaching.
13939 @item set task exception-port
13940 @itemx set task excp
13941 @cindex task exception port, @sc{gnu} Hurd
13942 This command sets the task exception port to which @value{GDBN} will
13943 forward exceptions. The argument should be the value of the @dfn{send
13944 rights} of the task. @code{set task excp} is a shorthand alias.
13946 @item set noninvasive
13947 @cindex noninvasive task options
13948 This command switches @value{GDBN} to a mode that is the least
13949 invasive as far as interfering with the inferior is concerned. This
13950 is the same as using @code{set task pause}, @code{set exceptions}, and
13951 @code{set signals} to values opposite to the defaults.
13953 @item info send-rights
13954 @itemx info receive-rights
13955 @itemx info port-rights
13956 @itemx info port-sets
13957 @itemx info dead-names
13960 @cindex send rights, @sc{gnu} Hurd
13961 @cindex receive rights, @sc{gnu} Hurd
13962 @cindex port rights, @sc{gnu} Hurd
13963 @cindex port sets, @sc{gnu} Hurd
13964 @cindex dead names, @sc{gnu} Hurd
13965 These commands display information about, respectively, send rights,
13966 receive rights, port rights, port sets, and dead names of a task.
13967 There are also shorthand aliases: @code{info ports} for @code{info
13968 port-rights} and @code{info psets} for @code{info port-sets}.
13970 @item set thread pause
13971 @kindex set thread@r{, Hurd command}
13972 @cindex thread properties, @sc{gnu} Hurd
13973 @cindex pause current thread (@sc{gnu} Hurd)
13974 This command toggles current thread suspension when @value{GDBN} has
13975 control. Setting it to on takes effect immediately, and the current
13976 thread is suspended whenever @value{GDBN} gets control. Setting it to
13977 off will take effect the next time the inferior is continued.
13978 Normally, this command has no effect, since when @value{GDBN} has
13979 control, the whole task is suspended. However, if you used @code{set
13980 task pause off} (see above), this command comes in handy to suspend
13981 only the current thread.
13983 @item show thread pause
13984 @kindex show thread@r{, Hurd command}
13985 This command shows the state of current thread suspension.
13987 @item set thread run
13988 This command sets whether the current thread is allowed to run.
13990 @item show thread run
13991 Show whether the current thread is allowed to run.
13993 @item set thread detach-suspend-count
13994 @cindex thread suspend count, @sc{gnu} Hurd
13995 @cindex detach from thread, @sc{gnu} Hurd
13996 This command sets the suspend count @value{GDBN} will leave on a
13997 thread when detaching. This number is relative to the suspend count
13998 found by @value{GDBN} when it notices the thread; use @code{set thread
13999 takeover-suspend-count} to force it to an absolute value.
14001 @item show thread detach-suspend-count
14002 Show the suspend count @value{GDBN} will leave on the thread when
14005 @item set thread exception-port
14006 @itemx set thread excp
14007 Set the thread exception port to which to forward exceptions. This
14008 overrides the port set by @code{set task exception-port} (see above).
14009 @code{set thread excp} is the shorthand alias.
14011 @item set thread takeover-suspend-count
14012 Normally, @value{GDBN}'s thread suspend counts are relative to the
14013 value @value{GDBN} finds when it notices each thread. This command
14014 changes the suspend counts to be absolute instead.
14016 @item set thread default
14017 @itemx show thread default
14018 @cindex thread default settings, @sc{gnu} Hurd
14019 Each of the above @code{set thread} commands has a @code{set thread
14020 default} counterpart (e.g., @code{set thread default pause}, @code{set
14021 thread default exception-port}, etc.). The @code{thread default}
14022 variety of commands sets the default thread properties for all
14023 threads; you can then change the properties of individual threads with
14024 the non-default commands.
14029 @subsection QNX Neutrino
14030 @cindex QNX Neutrino
14032 @value{GDBN} provides the following commands specific to the QNX
14036 @item set debug nto-debug
14037 @kindex set debug nto-debug
14038 When set to on, enables debugging messages specific to the QNX
14041 @item show debug nto-debug
14042 @kindex show debug nto-debug
14043 Show the current state of QNX Neutrino messages.
14048 @section Embedded Operating Systems
14050 This section describes configurations involving the debugging of
14051 embedded operating systems that are available for several different
14055 * VxWorks:: Using @value{GDBN} with VxWorks
14058 @value{GDBN} includes the ability to debug programs running on
14059 various real-time operating systems.
14062 @subsection Using @value{GDBN} with VxWorks
14068 @kindex target vxworks
14069 @item target vxworks @var{machinename}
14070 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14071 is the target system's machine name or IP address.
14075 On VxWorks, @code{load} links @var{filename} dynamically on the
14076 current target system as well as adding its symbols in @value{GDBN}.
14078 @value{GDBN} enables developers to spawn and debug tasks running on networked
14079 VxWorks targets from a Unix host. Already-running tasks spawned from
14080 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14081 both the Unix host and on the VxWorks target. The program
14082 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14083 installed with the name @code{vxgdb}, to distinguish it from a
14084 @value{GDBN} for debugging programs on the host itself.)
14087 @item VxWorks-timeout @var{args}
14088 @kindex vxworks-timeout
14089 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14090 This option is set by the user, and @var{args} represents the number of
14091 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14092 your VxWorks target is a slow software simulator or is on the far side
14093 of a thin network line.
14096 The following information on connecting to VxWorks was current when
14097 this manual was produced; newer releases of VxWorks may use revised
14100 @findex INCLUDE_RDB
14101 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14102 to include the remote debugging interface routines in the VxWorks
14103 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14104 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14105 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14106 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14107 information on configuring and remaking VxWorks, see the manufacturer's
14109 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14111 Once you have included @file{rdb.a} in your VxWorks system image and set
14112 your Unix execution search path to find @value{GDBN}, you are ready to
14113 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14114 @code{vxgdb}, depending on your installation).
14116 @value{GDBN} comes up showing the prompt:
14123 * VxWorks Connection:: Connecting to VxWorks
14124 * VxWorks Download:: VxWorks download
14125 * VxWorks Attach:: Running tasks
14128 @node VxWorks Connection
14129 @subsubsection Connecting to VxWorks
14131 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14132 network. To connect to a target whose host name is ``@code{tt}'', type:
14135 (vxgdb) target vxworks tt
14139 @value{GDBN} displays messages like these:
14142 Attaching remote machine across net...
14147 @value{GDBN} then attempts to read the symbol tables of any object modules
14148 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14149 these files by searching the directories listed in the command search
14150 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14151 to find an object file, it displays a message such as:
14154 prog.o: No such file or directory.
14157 When this happens, add the appropriate directory to the search path with
14158 the @value{GDBN} command @code{path}, and execute the @code{target}
14161 @node VxWorks Download
14162 @subsubsection VxWorks Download
14164 @cindex download to VxWorks
14165 If you have connected to the VxWorks target and you want to debug an
14166 object that has not yet been loaded, you can use the @value{GDBN}
14167 @code{load} command to download a file from Unix to VxWorks
14168 incrementally. The object file given as an argument to the @code{load}
14169 command is actually opened twice: first by the VxWorks target in order
14170 to download the code, then by @value{GDBN} in order to read the symbol
14171 table. This can lead to problems if the current working directories on
14172 the two systems differ. If both systems have NFS mounted the same
14173 filesystems, you can avoid these problems by using absolute paths.
14174 Otherwise, it is simplest to set the working directory on both systems
14175 to the directory in which the object file resides, and then to reference
14176 the file by its name, without any path. For instance, a program
14177 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14178 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14179 program, type this on VxWorks:
14182 -> cd "@var{vxpath}/vw/demo/rdb"
14186 Then, in @value{GDBN}, type:
14189 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14190 (vxgdb) load prog.o
14193 @value{GDBN} displays a response similar to this:
14196 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14199 You can also use the @code{load} command to reload an object module
14200 after editing and recompiling the corresponding source file. Note that
14201 this makes @value{GDBN} delete all currently-defined breakpoints,
14202 auto-displays, and convenience variables, and to clear the value
14203 history. (This is necessary in order to preserve the integrity of
14204 debugger's data structures that reference the target system's symbol
14207 @node VxWorks Attach
14208 @subsubsection Running Tasks
14210 @cindex running VxWorks tasks
14211 You can also attach to an existing task using the @code{attach} command as
14215 (vxgdb) attach @var{task}
14219 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14220 or suspended when you attach to it. Running tasks are suspended at
14221 the time of attachment.
14223 @node Embedded Processors
14224 @section Embedded Processors
14226 This section goes into details specific to particular embedded
14229 @cindex send command to simulator
14230 Whenever a specific embedded processor has a simulator, @value{GDBN}
14231 allows to send an arbitrary command to the simulator.
14234 @item sim @var{command}
14235 @kindex sim@r{, a command}
14236 Send an arbitrary @var{command} string to the simulator. Consult the
14237 documentation for the specific simulator in use for information about
14238 acceptable commands.
14244 * M32R/D:: Renesas M32R/D
14245 * M68K:: Motorola M68K
14246 * MIPS Embedded:: MIPS Embedded
14247 * OpenRISC 1000:: OpenRisc 1000
14248 * PA:: HP PA Embedded
14249 * PowerPC:: PowerPC
14250 * Sparclet:: Tsqware Sparclet
14251 * Sparclite:: Fujitsu Sparclite
14252 * Z8000:: Zilog Z8000
14255 * Super-H:: Renesas Super-H
14264 @item target rdi @var{dev}
14265 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14266 use this target to communicate with both boards running the Angel
14267 monitor, or with the EmbeddedICE JTAG debug device.
14270 @item target rdp @var{dev}
14275 @value{GDBN} provides the following ARM-specific commands:
14278 @item set arm disassembler
14280 This commands selects from a list of disassembly styles. The
14281 @code{"std"} style is the standard style.
14283 @item show arm disassembler
14285 Show the current disassembly style.
14287 @item set arm apcs32
14288 @cindex ARM 32-bit mode
14289 This command toggles ARM operation mode between 32-bit and 26-bit.
14291 @item show arm apcs32
14292 Display the current usage of the ARM 32-bit mode.
14294 @item set arm fpu @var{fputype}
14295 This command sets the ARM floating-point unit (FPU) type. The
14296 argument @var{fputype} can be one of these:
14300 Determine the FPU type by querying the OS ABI.
14302 Software FPU, with mixed-endian doubles on little-endian ARM
14305 GCC-compiled FPA co-processor.
14307 Software FPU with pure-endian doubles.
14313 Show the current type of the FPU.
14316 This command forces @value{GDBN} to use the specified ABI.
14319 Show the currently used ABI.
14321 @item set debug arm
14322 Toggle whether to display ARM-specific debugging messages from the ARM
14323 target support subsystem.
14325 @item show debug arm
14326 Show whether ARM-specific debugging messages are enabled.
14329 The following commands are available when an ARM target is debugged
14330 using the RDI interface:
14333 @item rdilogfile @r{[}@var{file}@r{]}
14335 @cindex ADP (Angel Debugger Protocol) logging
14336 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14337 With an argument, sets the log file to the specified @var{file}. With
14338 no argument, show the current log file name. The default log file is
14341 @item rdilogenable @r{[}@var{arg}@r{]}
14342 @kindex rdilogenable
14343 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14344 enables logging, with an argument 0 or @code{"no"} disables it. With
14345 no arguments displays the current setting. When logging is enabled,
14346 ADP packets exchanged between @value{GDBN} and the RDI target device
14347 are logged to a file.
14349 @item set rdiromatzero
14350 @kindex set rdiromatzero
14351 @cindex ROM at zero address, RDI
14352 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14353 vector catching is disabled, so that zero address can be used. If off
14354 (the default), vector catching is enabled. For this command to take
14355 effect, it needs to be invoked prior to the @code{target rdi} command.
14357 @item show rdiromatzero
14358 @kindex show rdiromatzero
14359 Show the current setting of ROM at zero address.
14361 @item set rdiheartbeat
14362 @kindex set rdiheartbeat
14363 @cindex RDI heartbeat
14364 Enable or disable RDI heartbeat packets. It is not recommended to
14365 turn on this option, since it confuses ARM and EPI JTAG interface, as
14366 well as the Angel monitor.
14368 @item show rdiheartbeat
14369 @kindex show rdiheartbeat
14370 Show the setting of RDI heartbeat packets.
14375 @subsection Renesas M32R/D and M32R/SDI
14378 @kindex target m32r
14379 @item target m32r @var{dev}
14380 Renesas M32R/D ROM monitor.
14382 @kindex target m32rsdi
14383 @item target m32rsdi @var{dev}
14384 Renesas M32R SDI server, connected via parallel port to the board.
14387 The following @value{GDBN} commands are specific to the M32R monitor:
14390 @item set download-path @var{path}
14391 @kindex set download-path
14392 @cindex find downloadable @sc{srec} files (M32R)
14393 Set the default path for finding downloadable @sc{srec} files.
14395 @item show download-path
14396 @kindex show download-path
14397 Show the default path for downloadable @sc{srec} files.
14399 @item set board-address @var{addr}
14400 @kindex set board-address
14401 @cindex M32-EVA target board address
14402 Set the IP address for the M32R-EVA target board.
14404 @item show board-address
14405 @kindex show board-address
14406 Show the current IP address of the target board.
14408 @item set server-address @var{addr}
14409 @kindex set server-address
14410 @cindex download server address (M32R)
14411 Set the IP address for the download server, which is the @value{GDBN}'s
14414 @item show server-address
14415 @kindex show server-address
14416 Display the IP address of the download server.
14418 @item upload @r{[}@var{file}@r{]}
14419 @kindex upload@r{, M32R}
14420 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14421 upload capability. If no @var{file} argument is given, the current
14422 executable file is uploaded.
14424 @item tload @r{[}@var{file}@r{]}
14425 @kindex tload@r{, M32R}
14426 Test the @code{upload} command.
14429 The following commands are available for M32R/SDI:
14434 @cindex reset SDI connection, M32R
14435 This command resets the SDI connection.
14439 This command shows the SDI connection status.
14442 @kindex debug_chaos
14443 @cindex M32R/Chaos debugging
14444 Instructs the remote that M32R/Chaos debugging is to be used.
14446 @item use_debug_dma
14447 @kindex use_debug_dma
14448 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14451 @kindex use_mon_code
14452 Instructs the remote to use the MON_CODE method of accessing memory.
14455 @kindex use_ib_break
14456 Instructs the remote to set breakpoints by IB break.
14458 @item use_dbt_break
14459 @kindex use_dbt_break
14460 Instructs the remote to set breakpoints by DBT.
14466 The Motorola m68k configuration includes ColdFire support, and a
14467 target command for the following ROM monitor.
14471 @kindex target dbug
14472 @item target dbug @var{dev}
14473 dBUG ROM monitor for Motorola ColdFire.
14477 @node MIPS Embedded
14478 @subsection MIPS Embedded
14480 @cindex MIPS boards
14481 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14482 MIPS board attached to a serial line. This is available when
14483 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14486 Use these @value{GDBN} commands to specify the connection to your target board:
14489 @item target mips @var{port}
14490 @kindex target mips @var{port}
14491 To run a program on the board, start up @code{@value{GDBP}} with the
14492 name of your program as the argument. To connect to the board, use the
14493 command @samp{target mips @var{port}}, where @var{port} is the name of
14494 the serial port connected to the board. If the program has not already
14495 been downloaded to the board, you may use the @code{load} command to
14496 download it. You can then use all the usual @value{GDBN} commands.
14498 For example, this sequence connects to the target board through a serial
14499 port, and loads and runs a program called @var{prog} through the
14503 host$ @value{GDBP} @var{prog}
14504 @value{GDBN} is free software and @dots{}
14505 (@value{GDBP}) target mips /dev/ttyb
14506 (@value{GDBP}) load @var{prog}
14510 @item target mips @var{hostname}:@var{portnumber}
14511 On some @value{GDBN} host configurations, you can specify a TCP
14512 connection (for instance, to a serial line managed by a terminal
14513 concentrator) instead of a serial port, using the syntax
14514 @samp{@var{hostname}:@var{portnumber}}.
14516 @item target pmon @var{port}
14517 @kindex target pmon @var{port}
14520 @item target ddb @var{port}
14521 @kindex target ddb @var{port}
14522 NEC's DDB variant of PMON for Vr4300.
14524 @item target lsi @var{port}
14525 @kindex target lsi @var{port}
14526 LSI variant of PMON.
14528 @kindex target r3900
14529 @item target r3900 @var{dev}
14530 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14532 @kindex target array
14533 @item target array @var{dev}
14534 Array Tech LSI33K RAID controller board.
14540 @value{GDBN} also supports these special commands for MIPS targets:
14543 @item set mipsfpu double
14544 @itemx set mipsfpu single
14545 @itemx set mipsfpu none
14546 @itemx set mipsfpu auto
14547 @itemx show mipsfpu
14548 @kindex set mipsfpu
14549 @kindex show mipsfpu
14550 @cindex MIPS remote floating point
14551 @cindex floating point, MIPS remote
14552 If your target board does not support the MIPS floating point
14553 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14554 need this, you may wish to put the command in your @value{GDBN} init
14555 file). This tells @value{GDBN} how to find the return value of
14556 functions which return floating point values. It also allows
14557 @value{GDBN} to avoid saving the floating point registers when calling
14558 functions on the board. If you are using a floating point coprocessor
14559 with only single precision floating point support, as on the @sc{r4650}
14560 processor, use the command @samp{set mipsfpu single}. The default
14561 double precision floating point coprocessor may be selected using
14562 @samp{set mipsfpu double}.
14564 In previous versions the only choices were double precision or no
14565 floating point, so @samp{set mipsfpu on} will select double precision
14566 and @samp{set mipsfpu off} will select no floating point.
14568 As usual, you can inquire about the @code{mipsfpu} variable with
14569 @samp{show mipsfpu}.
14571 @item set timeout @var{seconds}
14572 @itemx set retransmit-timeout @var{seconds}
14573 @itemx show timeout
14574 @itemx show retransmit-timeout
14575 @cindex @code{timeout}, MIPS protocol
14576 @cindex @code{retransmit-timeout}, MIPS protocol
14577 @kindex set timeout
14578 @kindex show timeout
14579 @kindex set retransmit-timeout
14580 @kindex show retransmit-timeout
14581 You can control the timeout used while waiting for a packet, in the MIPS
14582 remote protocol, with the @code{set timeout @var{seconds}} command. The
14583 default is 5 seconds. Similarly, you can control the timeout used while
14584 waiting for an acknowledgement of a packet with the @code{set
14585 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14586 You can inspect both values with @code{show timeout} and @code{show
14587 retransmit-timeout}. (These commands are @emph{only} available when
14588 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14590 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14591 is waiting for your program to stop. In that case, @value{GDBN} waits
14592 forever because it has no way of knowing how long the program is going
14593 to run before stopping.
14595 @item set syn-garbage-limit @var{num}
14596 @kindex set syn-garbage-limit@r{, MIPS remote}
14597 @cindex synchronize with remote MIPS target
14598 Limit the maximum number of characters @value{GDBN} should ignore when
14599 it tries to synchronize with the remote target. The default is 10
14600 characters. Setting the limit to -1 means there's no limit.
14602 @item show syn-garbage-limit
14603 @kindex show syn-garbage-limit@r{, MIPS remote}
14604 Show the current limit on the number of characters to ignore when
14605 trying to synchronize with the remote system.
14607 @item set monitor-prompt @var{prompt}
14608 @kindex set monitor-prompt@r{, MIPS remote}
14609 @cindex remote monitor prompt
14610 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14611 remote monitor. The default depends on the target:
14621 @item show monitor-prompt
14622 @kindex show monitor-prompt@r{, MIPS remote}
14623 Show the current strings @value{GDBN} expects as the prompt from the
14626 @item set monitor-warnings
14627 @kindex set monitor-warnings@r{, MIPS remote}
14628 Enable or disable monitor warnings about hardware breakpoints. This
14629 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14630 display warning messages whose codes are returned by the @code{lsi}
14631 PMON monitor for breakpoint commands.
14633 @item show monitor-warnings
14634 @kindex show monitor-warnings@r{, MIPS remote}
14635 Show the current setting of printing monitor warnings.
14637 @item pmon @var{command}
14638 @kindex pmon@r{, MIPS remote}
14639 @cindex send PMON command
14640 This command allows sending an arbitrary @var{command} string to the
14641 monitor. The monitor must be in debug mode for this to work.
14644 @node OpenRISC 1000
14645 @subsection OpenRISC 1000
14646 @cindex OpenRISC 1000
14648 @cindex or1k boards
14649 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14650 about platform and commands.
14654 @kindex target jtag
14655 @item target jtag jtag://@var{host}:@var{port}
14657 Connects to remote JTAG server.
14658 JTAG remote server can be either an or1ksim or JTAG server,
14659 connected via parallel port to the board.
14661 Example: @code{target jtag jtag://localhost:9999}
14664 @item or1ksim @var{command}
14665 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14666 Simulator, proprietary commands can be executed.
14668 @kindex info or1k spr
14669 @item info or1k spr
14670 Displays spr groups.
14672 @item info or1k spr @var{group}
14673 @itemx info or1k spr @var{groupno}
14674 Displays register names in selected group.
14676 @item info or1k spr @var{group} @var{register}
14677 @itemx info or1k spr @var{register}
14678 @itemx info or1k spr @var{groupno} @var{registerno}
14679 @itemx info or1k spr @var{registerno}
14680 Shows information about specified spr register.
14683 @item spr @var{group} @var{register} @var{value}
14684 @itemx spr @var{register @var{value}}
14685 @itemx spr @var{groupno} @var{registerno @var{value}}
14686 @itemx spr @var{registerno @var{value}}
14687 Writes @var{value} to specified spr register.
14690 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14691 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14692 program execution and is thus much faster. Hardware breakpoints/watchpoint
14693 triggers can be set using:
14696 Load effective address/data
14698 Store effective address/data
14700 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14705 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14706 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14708 @code{htrace} commands:
14709 @cindex OpenRISC 1000 htrace
14712 @item hwatch @var{conditional}
14713 Set hardware watchpoint on combination of Load/Store Effective Address(es)
14714 or Data. For example:
14716 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14718 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14722 Display information about current HW trace configuration.
14724 @item htrace trigger @var{conditional}
14725 Set starting criteria for HW trace.
14727 @item htrace qualifier @var{conditional}
14728 Set acquisition qualifier for HW trace.
14730 @item htrace stop @var{conditional}
14731 Set HW trace stopping criteria.
14733 @item htrace record [@var{data}]*
14734 Selects the data to be recorded, when qualifier is met and HW trace was
14737 @item htrace enable
14738 @itemx htrace disable
14739 Enables/disables the HW trace.
14741 @item htrace rewind [@var{filename}]
14742 Clears currently recorded trace data.
14744 If filename is specified, new trace file is made and any newly collected data
14745 will be written there.
14747 @item htrace print [@var{start} [@var{len}]]
14748 Prints trace buffer, using current record configuration.
14750 @item htrace mode continuous
14751 Set continuous trace mode.
14753 @item htrace mode suspend
14754 Set suspend trace mode.
14759 @subsection PowerPC
14762 @kindex target dink32
14763 @item target dink32 @var{dev}
14764 DINK32 ROM monitor.
14766 @kindex target ppcbug
14767 @item target ppcbug @var{dev}
14768 @kindex target ppcbug1
14769 @item target ppcbug1 @var{dev}
14770 PPCBUG ROM monitor for PowerPC.
14773 @item target sds @var{dev}
14774 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14777 @cindex SDS protocol
14778 The following commands specific to the SDS protocol are supported
14782 @item set sdstimeout @var{nsec}
14783 @kindex set sdstimeout
14784 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14785 default is 2 seconds.
14787 @item show sdstimeout
14788 @kindex show sdstimeout
14789 Show the current value of the SDS timeout.
14791 @item sds @var{command}
14792 @kindex sds@r{, a command}
14793 Send the specified @var{command} string to the SDS monitor.
14798 @subsection HP PA Embedded
14802 @kindex target op50n
14803 @item target op50n @var{dev}
14804 OP50N monitor, running on an OKI HPPA board.
14806 @kindex target w89k
14807 @item target w89k @var{dev}
14808 W89K monitor, running on a Winbond HPPA board.
14813 @subsection Tsqware Sparclet
14817 @value{GDBN} enables developers to debug tasks running on
14818 Sparclet targets from a Unix host.
14819 @value{GDBN} uses code that runs on
14820 both the Unix host and on the Sparclet target. The program
14821 @code{@value{GDBP}} is installed and executed on the Unix host.
14824 @item remotetimeout @var{args}
14825 @kindex remotetimeout
14826 @value{GDBN} supports the option @code{remotetimeout}.
14827 This option is set by the user, and @var{args} represents the number of
14828 seconds @value{GDBN} waits for responses.
14831 @cindex compiling, on Sparclet
14832 When compiling for debugging, include the options @samp{-g} to get debug
14833 information and @samp{-Ttext} to relocate the program to where you wish to
14834 load it on the target. You may also want to add the options @samp{-n} or
14835 @samp{-N} in order to reduce the size of the sections. Example:
14838 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14841 You can use @code{objdump} to verify that the addresses are what you intended:
14844 sparclet-aout-objdump --headers --syms prog
14847 @cindex running, on Sparclet
14849 your Unix execution search path to find @value{GDBN}, you are ready to
14850 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14851 (or @code{sparclet-aout-gdb}, depending on your installation).
14853 @value{GDBN} comes up showing the prompt:
14860 * Sparclet File:: Setting the file to debug
14861 * Sparclet Connection:: Connecting to Sparclet
14862 * Sparclet Download:: Sparclet download
14863 * Sparclet Execution:: Running and debugging
14866 @node Sparclet File
14867 @subsubsection Setting File to Debug
14869 The @value{GDBN} command @code{file} lets you choose with program to debug.
14872 (gdbslet) file prog
14876 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14877 @value{GDBN} locates
14878 the file by searching the directories listed in the command search
14880 If the file was compiled with debug information (option @samp{-g}), source
14881 files will be searched as well.
14882 @value{GDBN} locates
14883 the source files by searching the directories listed in the directory search
14884 path (@pxref{Environment, ,Your Program's Environment}).
14886 to find a file, it displays a message such as:
14889 prog: No such file or directory.
14892 When this happens, add the appropriate directories to the search paths with
14893 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14894 @code{target} command again.
14896 @node Sparclet Connection
14897 @subsubsection Connecting to Sparclet
14899 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14900 To connect to a target on serial port ``@code{ttya}'', type:
14903 (gdbslet) target sparclet /dev/ttya
14904 Remote target sparclet connected to /dev/ttya
14905 main () at ../prog.c:3
14909 @value{GDBN} displays messages like these:
14915 @node Sparclet Download
14916 @subsubsection Sparclet Download
14918 @cindex download to Sparclet
14919 Once connected to the Sparclet target,
14920 you can use the @value{GDBN}
14921 @code{load} command to download the file from the host to the target.
14922 The file name and load offset should be given as arguments to the @code{load}
14924 Since the file format is aout, the program must be loaded to the starting
14925 address. You can use @code{objdump} to find out what this value is. The load
14926 offset is an offset which is added to the VMA (virtual memory address)
14927 of each of the file's sections.
14928 For instance, if the program
14929 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14930 and bss at 0x12010170, in @value{GDBN}, type:
14933 (gdbslet) load prog 0x12010000
14934 Loading section .text, size 0xdb0 vma 0x12010000
14937 If the code is loaded at a different address then what the program was linked
14938 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14939 to tell @value{GDBN} where to map the symbol table.
14941 @node Sparclet Execution
14942 @subsubsection Running and Debugging
14944 @cindex running and debugging Sparclet programs
14945 You can now begin debugging the task using @value{GDBN}'s execution control
14946 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14947 manual for the list of commands.
14951 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14953 Starting program: prog
14954 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14955 3 char *symarg = 0;
14957 4 char *execarg = "hello!";
14962 @subsection Fujitsu Sparclite
14966 @kindex target sparclite
14967 @item target sparclite @var{dev}
14968 Fujitsu sparclite boards, used only for the purpose of loading.
14969 You must use an additional command to debug the program.
14970 For example: target remote @var{dev} using @value{GDBN} standard
14976 @subsection Zilog Z8000
14979 @cindex simulator, Z8000
14980 @cindex Zilog Z8000 simulator
14982 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14985 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14986 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14987 segmented variant). The simulator recognizes which architecture is
14988 appropriate by inspecting the object code.
14991 @item target sim @var{args}
14993 @kindex target sim@r{, with Z8000}
14994 Debug programs on a simulated CPU. If the simulator supports setup
14995 options, specify them via @var{args}.
14999 After specifying this target, you can debug programs for the simulated
15000 CPU in the same style as programs for your host computer; use the
15001 @code{file} command to load a new program image, the @code{run} command
15002 to run your program, and so on.
15004 As well as making available all the usual machine registers
15005 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15006 additional items of information as specially named registers:
15011 Counts clock-ticks in the simulator.
15014 Counts instructions run in the simulator.
15017 Execution time in 60ths of a second.
15021 You can refer to these values in @value{GDBN} expressions with the usual
15022 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15023 conditional breakpoint that suspends only after at least 5000
15024 simulated clock ticks.
15027 @subsection Atmel AVR
15030 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15031 following AVR-specific commands:
15034 @item info io_registers
15035 @kindex info io_registers@r{, AVR}
15036 @cindex I/O registers (Atmel AVR)
15037 This command displays information about the AVR I/O registers. For
15038 each register, @value{GDBN} prints its number and value.
15045 When configured for debugging CRIS, @value{GDBN} provides the
15046 following CRIS-specific commands:
15049 @item set cris-version @var{ver}
15050 @cindex CRIS version
15051 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15052 The CRIS version affects register names and sizes. This command is useful in
15053 case autodetection of the CRIS version fails.
15055 @item show cris-version
15056 Show the current CRIS version.
15058 @item set cris-dwarf2-cfi
15059 @cindex DWARF-2 CFI and CRIS
15060 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15061 Change to @samp{off} when using @code{gcc-cris} whose version is below
15064 @item show cris-dwarf2-cfi
15065 Show the current state of using DWARF-2 CFI.
15067 @item set cris-mode @var{mode}
15069 Set the current CRIS mode to @var{mode}. It should only be changed when
15070 debugging in guru mode, in which case it should be set to
15071 @samp{guru} (the default is @samp{normal}).
15073 @item show cris-mode
15074 Show the current CRIS mode.
15078 @subsection Renesas Super-H
15081 For the Renesas Super-H processor, @value{GDBN} provides these
15086 @kindex regs@r{, Super-H}
15087 Show the values of all Super-H registers.
15091 @node Architectures
15092 @section Architectures
15094 This section describes characteristics of architectures that affect
15095 all uses of @value{GDBN} with the architecture, both native and cross.
15102 * HPPA:: HP PA architecture
15106 @subsection x86 Architecture-specific Issues
15109 @item set struct-convention @var{mode}
15110 @kindex set struct-convention
15111 @cindex struct return convention
15112 @cindex struct/union returned in registers
15113 Set the convention used by the inferior to return @code{struct}s and
15114 @code{union}s from functions to @var{mode}. Possible values of
15115 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15116 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15117 are returned on the stack, while @code{"reg"} means that a
15118 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15119 be returned in a register.
15121 @item show struct-convention
15122 @kindex show struct-convention
15123 Show the current setting of the convention to return @code{struct}s
15132 @kindex set rstack_high_address
15133 @cindex AMD 29K register stack
15134 @cindex register stack, AMD29K
15135 @item set rstack_high_address @var{address}
15136 On AMD 29000 family processors, registers are saved in a separate
15137 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15138 extent of this stack. Normally, @value{GDBN} just assumes that the
15139 stack is ``large enough''. This may result in @value{GDBN} referencing
15140 memory locations that do not exist. If necessary, you can get around
15141 this problem by specifying the ending address of the register stack with
15142 the @code{set rstack_high_address} command. The argument should be an
15143 address, which you probably want to precede with @samp{0x} to specify in
15146 @kindex show rstack_high_address
15147 @item show rstack_high_address
15148 Display the current limit of the register stack, on AMD 29000 family
15156 See the following section.
15161 @cindex stack on Alpha
15162 @cindex stack on MIPS
15163 @cindex Alpha stack
15165 Alpha- and MIPS-based computers use an unusual stack frame, which
15166 sometimes requires @value{GDBN} to search backward in the object code to
15167 find the beginning of a function.
15169 @cindex response time, MIPS debugging
15170 To improve response time (especially for embedded applications, where
15171 @value{GDBN} may be restricted to a slow serial line for this search)
15172 you may want to limit the size of this search, using one of these
15176 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15177 @item set heuristic-fence-post @var{limit}
15178 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15179 search for the beginning of a function. A value of @var{0} (the
15180 default) means there is no limit. However, except for @var{0}, the
15181 larger the limit the more bytes @code{heuristic-fence-post} must search
15182 and therefore the longer it takes to run. You should only need to use
15183 this command when debugging a stripped executable.
15185 @item show heuristic-fence-post
15186 Display the current limit.
15190 These commands are available @emph{only} when @value{GDBN} is configured
15191 for debugging programs on Alpha or MIPS processors.
15193 Several MIPS-specific commands are available when debugging MIPS
15197 @item set mips abi @var{arg}
15198 @kindex set mips abi
15199 @cindex set ABI for MIPS
15200 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15201 values of @var{arg} are:
15205 The default ABI associated with the current binary (this is the
15216 @item show mips abi
15217 @kindex show mips abi
15218 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15221 @itemx show mipsfpu
15222 @xref{MIPS Embedded, set mipsfpu}.
15224 @item set mips mask-address @var{arg}
15225 @kindex set mips mask-address
15226 @cindex MIPS addresses, masking
15227 This command determines whether the most-significant 32 bits of 64-bit
15228 MIPS addresses are masked off. The argument @var{arg} can be
15229 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15230 setting, which lets @value{GDBN} determine the correct value.
15232 @item show mips mask-address
15233 @kindex show mips mask-address
15234 Show whether the upper 32 bits of MIPS addresses are masked off or
15237 @item set remote-mips64-transfers-32bit-regs
15238 @kindex set remote-mips64-transfers-32bit-regs
15239 This command controls compatibility with 64-bit MIPS targets that
15240 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15241 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15242 and 64 bits for other registers, set this option to @samp{on}.
15244 @item show remote-mips64-transfers-32bit-regs
15245 @kindex show remote-mips64-transfers-32bit-regs
15246 Show the current setting of compatibility with older MIPS 64 targets.
15248 @item set debug mips
15249 @kindex set debug mips
15250 This command turns on and off debugging messages for the MIPS-specific
15251 target code in @value{GDBN}.
15253 @item show debug mips
15254 @kindex show debug mips
15255 Show the current setting of MIPS debugging messages.
15261 @cindex HPPA support
15263 When @value{GDBN} is debugging the HP PA architecture, it provides the
15264 following special commands:
15267 @item set debug hppa
15268 @kindex set debug hppa
15269 This command determines whether HPPA architecture-specific debugging
15270 messages are to be displayed.
15272 @item show debug hppa
15273 Show whether HPPA debugging messages are displayed.
15275 @item maint print unwind @var{address}
15276 @kindex maint print unwind@r{, HPPA}
15277 This command displays the contents of the unwind table entry at the
15278 given @var{address}.
15283 @node Controlling GDB
15284 @chapter Controlling @value{GDBN}
15286 You can alter the way @value{GDBN} interacts with you by using the
15287 @code{set} command. For commands controlling how @value{GDBN} displays
15288 data, see @ref{Print Settings, ,Print Settings}. Other settings are
15293 * Editing:: Command editing
15294 * Command History:: Command history
15295 * Screen Size:: Screen size
15296 * Numbers:: Numbers
15297 * ABI:: Configuring the current ABI
15298 * Messages/Warnings:: Optional warnings and messages
15299 * Debugging Output:: Optional messages about internal happenings
15307 @value{GDBN} indicates its readiness to read a command by printing a string
15308 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15309 can change the prompt string with the @code{set prompt} command. For
15310 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15311 the prompt in one of the @value{GDBN} sessions so that you can always tell
15312 which one you are talking to.
15314 @emph{Note:} @code{set prompt} does not add a space for you after the
15315 prompt you set. This allows you to set a prompt which ends in a space
15316 or a prompt that does not.
15320 @item set prompt @var{newprompt}
15321 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15323 @kindex show prompt
15325 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15329 @section Command Editing
15331 @cindex command line editing
15333 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15334 @sc{gnu} library provides consistent behavior for programs which provide a
15335 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15336 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15337 substitution, and a storage and recall of command history across
15338 debugging sessions.
15340 You may control the behavior of command line editing in @value{GDBN} with the
15341 command @code{set}.
15344 @kindex set editing
15347 @itemx set editing on
15348 Enable command line editing (enabled by default).
15350 @item set editing off
15351 Disable command line editing.
15353 @kindex show editing
15355 Show whether command line editing is enabled.
15358 @xref{Command Line Editing}, for more details about the Readline
15359 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15360 encouraged to read that chapter.
15362 @node Command History
15363 @section Command History
15364 @cindex command history
15366 @value{GDBN} can keep track of the commands you type during your
15367 debugging sessions, so that you can be certain of precisely what
15368 happened. Use these commands to manage the @value{GDBN} command
15371 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15372 package, to provide the history facility. @xref{Using History
15373 Interactively}, for the detailed description of the History library.
15375 To issue a command to @value{GDBN} without affecting certain aspects of
15376 the state which is seen by users, prefix it with @samp{server }. This
15377 means that this command will not affect the command history, nor will it
15378 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15379 pressed on a line by itself.
15381 @cindex @code{server}, command prefix
15382 The server prefix does not affect the recording of values into the value
15383 history; to print a value without recording it into the value history,
15384 use the @code{output} command instead of the @code{print} command.
15386 Here is the description of @value{GDBN} commands related to command
15390 @cindex history substitution
15391 @cindex history file
15392 @kindex set history filename
15393 @cindex @env{GDBHISTFILE}, environment variable
15394 @item set history filename @var{fname}
15395 Set the name of the @value{GDBN} command history file to @var{fname}.
15396 This is the file where @value{GDBN} reads an initial command history
15397 list, and where it writes the command history from this session when it
15398 exits. You can access this list through history expansion or through
15399 the history command editing characters listed below. This file defaults
15400 to the value of the environment variable @code{GDBHISTFILE}, or to
15401 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15404 @cindex save command history
15405 @kindex set history save
15406 @item set history save
15407 @itemx set history save on
15408 Record command history in a file, whose name may be specified with the
15409 @code{set history filename} command. By default, this option is disabled.
15411 @item set history save off
15412 Stop recording command history in a file.
15414 @cindex history size
15415 @kindex set history size
15416 @cindex @env{HISTSIZE}, environment variable
15417 @item set history size @var{size}
15418 Set the number of commands which @value{GDBN} keeps in its history list.
15419 This defaults to the value of the environment variable
15420 @code{HISTSIZE}, or to 256 if this variable is not set.
15423 History expansion assigns special meaning to the character @kbd{!}.
15424 @xref{Event Designators}, for more details.
15426 @cindex history expansion, turn on/off
15427 Since @kbd{!} is also the logical not operator in C, history expansion
15428 is off by default. If you decide to enable history expansion with the
15429 @code{set history expansion on} command, you may sometimes need to
15430 follow @kbd{!} (when it is used as logical not, in an expression) with
15431 a space or a tab to prevent it from being expanded. The readline
15432 history facilities do not attempt substitution on the strings
15433 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15435 The commands to control history expansion are:
15438 @item set history expansion on
15439 @itemx set history expansion
15440 @kindex set history expansion
15441 Enable history expansion. History expansion is off by default.
15443 @item set history expansion off
15444 Disable history expansion.
15447 @kindex show history
15449 @itemx show history filename
15450 @itemx show history save
15451 @itemx show history size
15452 @itemx show history expansion
15453 These commands display the state of the @value{GDBN} history parameters.
15454 @code{show history} by itself displays all four states.
15459 @kindex show commands
15460 @cindex show last commands
15461 @cindex display command history
15462 @item show commands
15463 Display the last ten commands in the command history.
15465 @item show commands @var{n}
15466 Print ten commands centered on command number @var{n}.
15468 @item show commands +
15469 Print ten commands just after the commands last printed.
15473 @section Screen Size
15474 @cindex size of screen
15475 @cindex pauses in output
15477 Certain commands to @value{GDBN} may produce large amounts of
15478 information output to the screen. To help you read all of it,
15479 @value{GDBN} pauses and asks you for input at the end of each page of
15480 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15481 to discard the remaining output. Also, the screen width setting
15482 determines when to wrap lines of output. Depending on what is being
15483 printed, @value{GDBN} tries to break the line at a readable place,
15484 rather than simply letting it overflow onto the following line.
15486 Normally @value{GDBN} knows the size of the screen from the terminal
15487 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15488 together with the value of the @code{TERM} environment variable and the
15489 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15490 you can override it with the @code{set height} and @code{set
15497 @kindex show height
15498 @item set height @var{lpp}
15500 @itemx set width @var{cpl}
15502 These @code{set} commands specify a screen height of @var{lpp} lines and
15503 a screen width of @var{cpl} characters. The associated @code{show}
15504 commands display the current settings.
15506 If you specify a height of zero lines, @value{GDBN} does not pause during
15507 output no matter how long the output is. This is useful if output is to a
15508 file or to an editor buffer.
15510 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15511 from wrapping its output.
15513 @item set pagination on
15514 @itemx set pagination off
15515 @kindex set pagination
15516 Turn the output pagination on or off; the default is on. Turning
15517 pagination off is the alternative to @code{set height 0}.
15519 @item show pagination
15520 @kindex show pagination
15521 Show the current pagination mode.
15526 @cindex number representation
15527 @cindex entering numbers
15529 You can always enter numbers in octal, decimal, or hexadecimal in
15530 @value{GDBN} by the usual conventions: octal numbers begin with
15531 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15532 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15533 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15534 10; likewise, the default display for numbers---when no particular
15535 format is specified---is base 10. You can change the default base for
15536 both input and output with the commands described below.
15539 @kindex set input-radix
15540 @item set input-radix @var{base}
15541 Set the default base for numeric input. Supported choices
15542 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15543 specified either unambiguously or using the current input radix; for
15547 set input-radix 012
15548 set input-radix 10.
15549 set input-radix 0xa
15553 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15554 leaves the input radix unchanged, no matter what it was, since
15555 @samp{10}, being without any leading or trailing signs of its base, is
15556 interpreted in the current radix. Thus, if the current radix is 16,
15557 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15560 @kindex set output-radix
15561 @item set output-radix @var{base}
15562 Set the default base for numeric display. Supported choices
15563 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15564 specified either unambiguously or using the current input radix.
15566 @kindex show input-radix
15567 @item show input-radix
15568 Display the current default base for numeric input.
15570 @kindex show output-radix
15571 @item show output-radix
15572 Display the current default base for numeric display.
15574 @item set radix @r{[}@var{base}@r{]}
15578 These commands set and show the default base for both input and output
15579 of numbers. @code{set radix} sets the radix of input and output to
15580 the same base; without an argument, it resets the radix back to its
15581 default value of 10.
15586 @section Configuring the Current ABI
15588 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15589 application automatically. However, sometimes you need to override its
15590 conclusions. Use these commands to manage @value{GDBN}'s view of the
15597 One @value{GDBN} configuration can debug binaries for multiple operating
15598 system targets, either via remote debugging or native emulation.
15599 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15600 but you can override its conclusion using the @code{set osabi} command.
15601 One example where this is useful is in debugging of binaries which use
15602 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15603 not have the same identifying marks that the standard C library for your
15608 Show the OS ABI currently in use.
15611 With no argument, show the list of registered available OS ABI's.
15613 @item set osabi @var{abi}
15614 Set the current OS ABI to @var{abi}.
15617 @cindex float promotion
15619 Generally, the way that an argument of type @code{float} is passed to a
15620 function depends on whether the function is prototyped. For a prototyped
15621 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15622 according to the architecture's convention for @code{float}. For unprototyped
15623 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15624 @code{double} and then passed.
15626 Unfortunately, some forms of debug information do not reliably indicate whether
15627 a function is prototyped. If @value{GDBN} calls a function that is not marked
15628 as prototyped, it consults @kbd{set coerce-float-to-double}.
15631 @kindex set coerce-float-to-double
15632 @item set coerce-float-to-double
15633 @itemx set coerce-float-to-double on
15634 Arguments of type @code{float} will be promoted to @code{double} when passed
15635 to an unprototyped function. This is the default setting.
15637 @item set coerce-float-to-double off
15638 Arguments of type @code{float} will be passed directly to unprototyped
15641 @kindex show coerce-float-to-double
15642 @item show coerce-float-to-double
15643 Show the current setting of promoting @code{float} to @code{double}.
15647 @kindex show cp-abi
15648 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15649 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15650 used to build your application. @value{GDBN} only fully supports
15651 programs with a single C@t{++} ABI; if your program contains code using
15652 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15653 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15654 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15655 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15656 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15657 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15662 Show the C@t{++} ABI currently in use.
15665 With no argument, show the list of supported C@t{++} ABI's.
15667 @item set cp-abi @var{abi}
15668 @itemx set cp-abi auto
15669 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15672 @node Messages/Warnings
15673 @section Optional Warnings and Messages
15675 @cindex verbose operation
15676 @cindex optional warnings
15677 By default, @value{GDBN} is silent about its inner workings. If you are
15678 running on a slow machine, you may want to use the @code{set verbose}
15679 command. This makes @value{GDBN} tell you when it does a lengthy
15680 internal operation, so you will not think it has crashed.
15682 Currently, the messages controlled by @code{set verbose} are those
15683 which announce that the symbol table for a source file is being read;
15684 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
15687 @kindex set verbose
15688 @item set verbose on
15689 Enables @value{GDBN} output of certain informational messages.
15691 @item set verbose off
15692 Disables @value{GDBN} output of certain informational messages.
15694 @kindex show verbose
15696 Displays whether @code{set verbose} is on or off.
15699 By default, if @value{GDBN} encounters bugs in the symbol table of an
15700 object file, it is silent; but if you are debugging a compiler, you may
15701 find this information useful (@pxref{Symbol Errors, ,Errors Reading
15706 @kindex set complaints
15707 @item set complaints @var{limit}
15708 Permits @value{GDBN} to output @var{limit} complaints about each type of
15709 unusual symbols before becoming silent about the problem. Set
15710 @var{limit} to zero to suppress all complaints; set it to a large number
15711 to prevent complaints from being suppressed.
15713 @kindex show complaints
15714 @item show complaints
15715 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15719 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15720 lot of stupid questions to confirm certain commands. For example, if
15721 you try to run a program which is already running:
15725 The program being debugged has been started already.
15726 Start it from the beginning? (y or n)
15729 If you are willing to unflinchingly face the consequences of your own
15730 commands, you can disable this ``feature'':
15734 @kindex set confirm
15736 @cindex confirmation
15737 @cindex stupid questions
15738 @item set confirm off
15739 Disables confirmation requests.
15741 @item set confirm on
15742 Enables confirmation requests (the default).
15744 @kindex show confirm
15746 Displays state of confirmation requests.
15750 @cindex command tracing
15751 If you need to debug user-defined commands or sourced files you may find it
15752 useful to enable @dfn{command tracing}. In this mode each command will be
15753 printed as it is executed, prefixed with one or more @samp{+} symbols, the
15754 quantity denoting the call depth of each command.
15757 @kindex set trace-commands
15758 @cindex command scripts, debugging
15759 @item set trace-commands on
15760 Enable command tracing.
15761 @item set trace-commands off
15762 Disable command tracing.
15763 @item show trace-commands
15764 Display the current state of command tracing.
15767 @node Debugging Output
15768 @section Optional Messages about Internal Happenings
15769 @cindex optional debugging messages
15771 @value{GDBN} has commands that enable optional debugging messages from
15772 various @value{GDBN} subsystems; normally these commands are of
15773 interest to @value{GDBN} maintainers, or when reporting a bug. This
15774 section documents those commands.
15777 @kindex set exec-done-display
15778 @item set exec-done-display
15779 Turns on or off the notification of asynchronous commands'
15780 completion. When on, @value{GDBN} will print a message when an
15781 asynchronous command finishes its execution. The default is off.
15782 @kindex show exec-done-display
15783 @item show exec-done-display
15784 Displays the current setting of asynchronous command completion
15787 @cindex gdbarch debugging info
15788 @cindex architecture debugging info
15789 @item set debug arch
15790 Turns on or off display of gdbarch debugging info. The default is off
15792 @item show debug arch
15793 Displays the current state of displaying gdbarch debugging info.
15794 @item set debug aix-thread
15795 @cindex AIX threads
15796 Display debugging messages about inner workings of the AIX thread
15798 @item show debug aix-thread
15799 Show the current state of AIX thread debugging info display.
15800 @item set debug event
15801 @cindex event debugging info
15802 Turns on or off display of @value{GDBN} event debugging info. The
15804 @item show debug event
15805 Displays the current state of displaying @value{GDBN} event debugging
15807 @item set debug expression
15808 @cindex expression debugging info
15809 Turns on or off display of debugging info about @value{GDBN}
15810 expression parsing. The default is off.
15811 @item show debug expression
15812 Displays the current state of displaying debugging info about
15813 @value{GDBN} expression parsing.
15814 @item set debug frame
15815 @cindex frame debugging info
15816 Turns on or off display of @value{GDBN} frame debugging info. The
15818 @item show debug frame
15819 Displays the current state of displaying @value{GDBN} frame debugging
15821 @item set debug infrun
15822 @cindex inferior debugging info
15823 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15824 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15825 for implementing operations such as single-stepping the inferior.
15826 @item show debug infrun
15827 Displays the current state of @value{GDBN} inferior debugging.
15828 @item set debug lin-lwp
15829 @cindex @sc{gnu}/Linux LWP debug messages
15830 @cindex Linux lightweight processes
15831 Turns on or off debugging messages from the Linux LWP debug support.
15832 @item show debug lin-lwp
15833 Show the current state of Linux LWP debugging messages.
15834 @item set debug observer
15835 @cindex observer debugging info
15836 Turns on or off display of @value{GDBN} observer debugging. This
15837 includes info such as the notification of observable events.
15838 @item show debug observer
15839 Displays the current state of observer debugging.
15840 @item set debug overload
15841 @cindex C@t{++} overload debugging info
15842 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15843 info. This includes info such as ranking of functions, etc. The default
15845 @item show debug overload
15846 Displays the current state of displaying @value{GDBN} C@t{++} overload
15848 @cindex packets, reporting on stdout
15849 @cindex serial connections, debugging
15850 @cindex debug remote protocol
15851 @cindex remote protocol debugging
15852 @cindex display remote packets
15853 @item set debug remote
15854 Turns on or off display of reports on all packets sent back and forth across
15855 the serial line to the remote machine. The info is printed on the
15856 @value{GDBN} standard output stream. The default is off.
15857 @item show debug remote
15858 Displays the state of display of remote packets.
15859 @item set debug serial
15860 Turns on or off display of @value{GDBN} serial debugging info. The
15862 @item show debug serial
15863 Displays the current state of displaying @value{GDBN} serial debugging
15865 @item set debug solib-frv
15866 @cindex FR-V shared-library debugging
15867 Turns on or off debugging messages for FR-V shared-library code.
15868 @item show debug solib-frv
15869 Display the current state of FR-V shared-library code debugging
15871 @item set debug target
15872 @cindex target debugging info
15873 Turns on or off display of @value{GDBN} target debugging info. This info
15874 includes what is going on at the target level of GDB, as it happens. The
15875 default is 0. Set it to 1 to track events, and to 2 to also track the
15876 value of large memory transfers. Changes to this flag do not take effect
15877 until the next time you connect to a target or use the @code{run} command.
15878 @item show debug target
15879 Displays the current state of displaying @value{GDBN} target debugging
15881 @item set debugvarobj
15882 @cindex variable object debugging info
15883 Turns on or off display of @value{GDBN} variable object debugging
15884 info. The default is off.
15885 @item show debugvarobj
15886 Displays the current state of displaying @value{GDBN} variable object
15888 @item set debug xml
15889 @cindex XML parser debugging
15890 Turns on or off debugging messages for built-in XML parsers.
15891 @item show debug xml
15892 Displays the current state of XML debugging messages.
15896 @chapter Canned Sequences of Commands
15898 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15899 Command Lists}), @value{GDBN} provides two ways to store sequences of
15900 commands for execution as a unit: user-defined commands and command
15904 * Define:: How to define your own commands
15905 * Hooks:: Hooks for user-defined commands
15906 * Command Files:: How to write scripts of commands to be stored in a file
15907 * Output:: Commands for controlled output
15911 @section User-defined Commands
15913 @cindex user-defined command
15914 @cindex arguments, to user-defined commands
15915 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15916 which you assign a new name as a command. This is done with the
15917 @code{define} command. User commands may accept up to 10 arguments
15918 separated by whitespace. Arguments are accessed within the user command
15919 via @code{$arg0@dots{}$arg9}. A trivial example:
15923 print $arg0 + $arg1 + $arg2
15928 To execute the command use:
15935 This defines the command @code{adder}, which prints the sum of
15936 its three arguments. Note the arguments are text substitutions, so they may
15937 reference variables, use complex expressions, or even perform inferior
15940 @cindex argument count in user-defined commands
15941 @cindex how many arguments (user-defined commands)
15942 In addition, @code{$argc} may be used to find out how many arguments have
15943 been passed. This expands to a number in the range 0@dots{}10.
15948 print $arg0 + $arg1
15951 print $arg0 + $arg1 + $arg2
15959 @item define @var{commandname}
15960 Define a command named @var{commandname}. If there is already a command
15961 by that name, you are asked to confirm that you want to redefine it.
15963 The definition of the command is made up of other @value{GDBN} command lines,
15964 which are given following the @code{define} command. The end of these
15965 commands is marked by a line containing @code{end}.
15968 @kindex end@r{ (user-defined commands)}
15969 @item document @var{commandname}
15970 Document the user-defined command @var{commandname}, so that it can be
15971 accessed by @code{help}. The command @var{commandname} must already be
15972 defined. This command reads lines of documentation just as @code{define}
15973 reads the lines of the command definition, ending with @code{end}.
15974 After the @code{document} command is finished, @code{help} on command
15975 @var{commandname} displays the documentation you have written.
15977 You may use the @code{document} command again to change the
15978 documentation of a command. Redefining the command with @code{define}
15979 does not change the documentation.
15981 @kindex dont-repeat
15982 @cindex don't repeat command
15984 Used inside a user-defined command, this tells @value{GDBN} that this
15985 command should not be repeated when the user hits @key{RET}
15986 (@pxref{Command Syntax, repeat last command}).
15988 @kindex help user-defined
15989 @item help user-defined
15990 List all user-defined commands, with the first line of the documentation
15995 @itemx show user @var{commandname}
15996 Display the @value{GDBN} commands used to define @var{commandname} (but
15997 not its documentation). If no @var{commandname} is given, display the
15998 definitions for all user-defined commands.
16000 @cindex infinite recursion in user-defined commands
16001 @kindex show max-user-call-depth
16002 @kindex set max-user-call-depth
16003 @item show max-user-call-depth
16004 @itemx set max-user-call-depth
16005 The value of @code{max-user-call-depth} controls how many recursion
16006 levels are allowed in user-defined commands before @value{GDBN} suspects an
16007 infinite recursion and aborts the command.
16010 In addition to the above commands, user-defined commands frequently
16011 use control flow commands, described in @ref{Command Files}.
16013 When user-defined commands are executed, the
16014 commands of the definition are not printed. An error in any command
16015 stops execution of the user-defined command.
16017 If used interactively, commands that would ask for confirmation proceed
16018 without asking when used inside a user-defined command. Many @value{GDBN}
16019 commands that normally print messages to say what they are doing omit the
16020 messages when used in a user-defined command.
16023 @section User-defined Command Hooks
16024 @cindex command hooks
16025 @cindex hooks, for commands
16026 @cindex hooks, pre-command
16029 You may define @dfn{hooks}, which are a special kind of user-defined
16030 command. Whenever you run the command @samp{foo}, if the user-defined
16031 command @samp{hook-foo} exists, it is executed (with no arguments)
16032 before that command.
16034 @cindex hooks, post-command
16036 A hook may also be defined which is run after the command you executed.
16037 Whenever you run the command @samp{foo}, if the user-defined command
16038 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16039 that command. Post-execution hooks may exist simultaneously with
16040 pre-execution hooks, for the same command.
16042 It is valid for a hook to call the command which it hooks. If this
16043 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16045 @c It would be nice if hookpost could be passed a parameter indicating
16046 @c if the command it hooks executed properly or not. FIXME!
16048 @kindex stop@r{, a pseudo-command}
16049 In addition, a pseudo-command, @samp{stop} exists. Defining
16050 (@samp{hook-stop}) makes the associated commands execute every time
16051 execution stops in your program: before breakpoint commands are run,
16052 displays are printed, or the stack frame is printed.
16054 For example, to ignore @code{SIGALRM} signals while
16055 single-stepping, but treat them normally during normal execution,
16060 handle SIGALRM nopass
16064 handle SIGALRM pass
16067 define hook-continue
16068 handle SIGALRM pass
16072 As a further example, to hook at the beginning and end of the @code{echo}
16073 command, and to add extra text to the beginning and end of the message,
16081 define hookpost-echo
16085 (@value{GDBP}) echo Hello World
16086 <<<---Hello World--->>>
16091 You can define a hook for any single-word command in @value{GDBN}, but
16092 not for command aliases; you should define a hook for the basic command
16093 name, e.g.@: @code{backtrace} rather than @code{bt}.
16094 @c FIXME! So how does Joe User discover whether a command is an alias
16096 If an error occurs during the execution of your hook, execution of
16097 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16098 (before the command that you actually typed had a chance to run).
16100 If you try to define a hook which does not match any known command, you
16101 get a warning from the @code{define} command.
16103 @node Command Files
16104 @section Command Files
16106 @cindex command files
16107 @cindex scripting commands
16108 A command file for @value{GDBN} is a text file made of lines that are
16109 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16110 also be included. An empty line in a command file does nothing; it
16111 does not mean to repeat the last command, as it would from the
16114 You can request the execution of a command file with the @code{source}
16119 @cindex execute commands from a file
16120 @item source [@code{-v}] @var{filename}
16121 Execute the command file @var{filename}.
16124 The lines in a command file are generally executed sequentially,
16125 unless the order of execution is changed by one of the
16126 @emph{flow-control commands} described below. The commands are not
16127 printed as they are executed. An error in any command terminates
16128 execution of the command file and control is returned to the console.
16130 @value{GDBN} searches for @var{filename} in the current directory and then
16131 on the search path (specified with the @samp{directory} command).
16133 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16134 each command as it is executed. The option must be given before
16135 @var{filename}, and is interpreted as part of the filename anywhere else.
16137 Commands that would ask for confirmation if used interactively proceed
16138 without asking when used in a command file. Many @value{GDBN} commands that
16139 normally print messages to say what they are doing omit the messages
16140 when called from command files.
16142 @value{GDBN} also accepts command input from standard input. In this
16143 mode, normal output goes to standard output and error output goes to
16144 standard error. Errors in a command file supplied on standard input do
16145 not terminate execution of the command file---execution continues with
16149 gdb < cmds > log 2>&1
16152 (The syntax above will vary depending on the shell used.) This example
16153 will execute commands from the file @file{cmds}. All output and errors
16154 would be directed to @file{log}.
16156 Since commands stored on command files tend to be more general than
16157 commands typed interactively, they frequently need to deal with
16158 complicated situations, such as different or unexpected values of
16159 variables and symbols, changes in how the program being debugged is
16160 built, etc. @value{GDBN} provides a set of flow-control commands to
16161 deal with these complexities. Using these commands, you can write
16162 complex scripts that loop over data structures, execute commands
16163 conditionally, etc.
16170 This command allows to include in your script conditionally executed
16171 commands. The @code{if} command takes a single argument, which is an
16172 expression to evaluate. It is followed by a series of commands that
16173 are executed only if the expression is true (its value is nonzero).
16174 There can then optionally be an @code{else} line, followed by a series
16175 of commands that are only executed if the expression was false. The
16176 end of the list is marked by a line containing @code{end}.
16180 This command allows to write loops. Its syntax is similar to
16181 @code{if}: the command takes a single argument, which is an expression
16182 to evaluate, and must be followed by the commands to execute, one per
16183 line, terminated by an @code{end}. These commands are called the
16184 @dfn{body} of the loop. The commands in the body of @code{while} are
16185 executed repeatedly as long as the expression evaluates to true.
16189 This command exits the @code{while} loop in whose body it is included.
16190 Execution of the script continues after that @code{while}s @code{end}
16193 @kindex loop_continue
16194 @item loop_continue
16195 This command skips the execution of the rest of the body of commands
16196 in the @code{while} loop in whose body it is included. Execution
16197 branches to the beginning of the @code{while} loop, where it evaluates
16198 the controlling expression.
16200 @kindex end@r{ (if/else/while commands)}
16202 Terminate the block of commands that are the body of @code{if},
16203 @code{else}, or @code{while} flow-control commands.
16208 @section Commands for Controlled Output
16210 During the execution of a command file or a user-defined command, normal
16211 @value{GDBN} output is suppressed; the only output that appears is what is
16212 explicitly printed by the commands in the definition. This section
16213 describes three commands useful for generating exactly the output you
16218 @item echo @var{text}
16219 @c I do not consider backslash-space a standard C escape sequence
16220 @c because it is not in ANSI.
16221 Print @var{text}. Nonprinting characters can be included in
16222 @var{text} using C escape sequences, such as @samp{\n} to print a
16223 newline. @strong{No newline is printed unless you specify one.}
16224 In addition to the standard C escape sequences, a backslash followed
16225 by a space stands for a space. This is useful for displaying a
16226 string with spaces at the beginning or the end, since leading and
16227 trailing spaces are otherwise trimmed from all arguments.
16228 To print @samp{@w{ }and foo =@w{ }}, use the command
16229 @samp{echo \@w{ }and foo = \@w{ }}.
16231 A backslash at the end of @var{text} can be used, as in C, to continue
16232 the command onto subsequent lines. For example,
16235 echo This is some text\n\
16236 which is continued\n\
16237 onto several lines.\n
16240 produces the same output as
16243 echo This is some text\n
16244 echo which is continued\n
16245 echo onto several lines.\n
16249 @item output @var{expression}
16250 Print the value of @var{expression} and nothing but that value: no
16251 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16252 value history either. @xref{Expressions, ,Expressions}, for more information
16255 @item output/@var{fmt} @var{expression}
16256 Print the value of @var{expression} in format @var{fmt}. You can use
16257 the same formats as for @code{print}. @xref{Output Formats,,Output
16258 Formats}, for more information.
16261 @item printf @var{string}, @var{expressions}@dots{}
16262 Print the values of the @var{expressions} under the control of
16263 @var{string}. The @var{expressions} are separated by commas and may be
16264 either numbers or pointers. Their values are printed as specified by
16265 @var{string}, exactly as if your program were to execute the C
16267 @c FIXME: the above implies that at least all ANSI C formats are
16268 @c supported, but it isn't true: %E and %G don't work (or so it seems).
16269 @c Either this is a bug, or the manual should document what formats are
16273 printf (@var{string}, @var{expressions}@dots{});
16276 For example, you can print two values in hex like this:
16279 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16282 The only backslash-escape sequences that you can use in the format
16283 string are the simple ones that consist of backslash followed by a
16288 @chapter Command Interpreters
16289 @cindex command interpreters
16291 @value{GDBN} supports multiple command interpreters, and some command
16292 infrastructure to allow users or user interface writers to switch
16293 between interpreters or run commands in other interpreters.
16295 @value{GDBN} currently supports two command interpreters, the console
16296 interpreter (sometimes called the command-line interpreter or @sc{cli})
16297 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16298 describes both of these interfaces in great detail.
16300 By default, @value{GDBN} will start with the console interpreter.
16301 However, the user may choose to start @value{GDBN} with another
16302 interpreter by specifying the @option{-i} or @option{--interpreter}
16303 startup options. Defined interpreters include:
16307 @cindex console interpreter
16308 The traditional console or command-line interpreter. This is the most often
16309 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16310 @value{GDBN} will use this interpreter.
16313 @cindex mi interpreter
16314 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16315 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16316 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16320 @cindex mi2 interpreter
16321 The current @sc{gdb/mi} interface.
16324 @cindex mi1 interpreter
16325 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16329 @cindex invoke another interpreter
16330 The interpreter being used by @value{GDBN} may not be dynamically
16331 switched at runtime. Although possible, this could lead to a very
16332 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16333 enters the command "interpreter-set console" in a console view,
16334 @value{GDBN} would switch to using the console interpreter, rendering
16335 the IDE inoperable!
16337 @kindex interpreter-exec
16338 Although you may only choose a single interpreter at startup, you may execute
16339 commands in any interpreter from the current interpreter using the appropriate
16340 command. If you are running the console interpreter, simply use the
16341 @code{interpreter-exec} command:
16344 interpreter-exec mi "-data-list-register-names"
16347 @sc{gdb/mi} has a similar command, although it is only available in versions of
16348 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16351 @chapter @value{GDBN} Text User Interface
16353 @cindex Text User Interface
16356 * TUI Overview:: TUI overview
16357 * TUI Keys:: TUI key bindings
16358 * TUI Single Key Mode:: TUI single key mode
16359 * TUI Commands:: TUI-specific commands
16360 * TUI Configuration:: TUI configuration variables
16363 The @value{GDBN} Text User Interface (TUI) is a terminal
16364 interface which uses the @code{curses} library to show the source
16365 file, the assembly output, the program registers and @value{GDBN}
16366 commands in separate text windows. The TUI mode is supported only
16367 on platforms where a suitable version of the @code{curses} library
16370 @pindex @value{GDBTUI}
16371 The TUI mode is enabled by default when you invoke @value{GDBN} as
16372 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
16373 You can also switch in and out of TUI mode while @value{GDBN} runs by
16374 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
16375 @xref{TUI Keys, ,TUI Key Bindings}.
16378 @section TUI Overview
16380 In TUI mode, @value{GDBN} can display several text windows:
16384 This window is the @value{GDBN} command window with the @value{GDBN}
16385 prompt and the @value{GDBN} output. The @value{GDBN} input is still
16386 managed using readline.
16389 The source window shows the source file of the program. The current
16390 line and active breakpoints are displayed in this window.
16393 The assembly window shows the disassembly output of the program.
16396 This window shows the processor registers. Registers are highlighted
16397 when their values change.
16400 The source and assembly windows show the current program position
16401 by highlighting the current line and marking it with a @samp{>} marker.
16402 Breakpoints are indicated with two markers. The first marker
16403 indicates the breakpoint type:
16407 Breakpoint which was hit at least once.
16410 Breakpoint which was never hit.
16413 Hardware breakpoint which was hit at least once.
16416 Hardware breakpoint which was never hit.
16419 The second marker indicates whether the breakpoint is enabled or not:
16423 Breakpoint is enabled.
16426 Breakpoint is disabled.
16429 The source, assembly and register windows are updated when the current
16430 thread changes, when the frame changes, or when the program counter
16433 These windows are not all visible at the same time. The command
16434 window is always visible. The others can be arranged in several
16445 source and assembly,
16448 source and registers, or
16451 assembly and registers.
16454 A status line above the command window shows the following information:
16458 Indicates the current @value{GDBN} target.
16459 (@pxref{Targets, ,Specifying a Debugging Target}).
16462 Gives the current process or thread number.
16463 When no process is being debugged, this field is set to @code{No process}.
16466 Gives the current function name for the selected frame.
16467 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16468 When there is no symbol corresponding to the current program counter,
16469 the string @code{??} is displayed.
16472 Indicates the current line number for the selected frame.
16473 When the current line number is not known, the string @code{??} is displayed.
16476 Indicates the current program counter address.
16480 @section TUI Key Bindings
16481 @cindex TUI key bindings
16483 The TUI installs several key bindings in the readline keymaps
16484 (@pxref{Command Line Editing}). The following key bindings
16485 are installed for both TUI mode and the @value{GDBN} standard mode.
16494 Enter or leave the TUI mode. When leaving the TUI mode,
16495 the curses window management stops and @value{GDBN} operates using
16496 its standard mode, writing on the terminal directly. When reentering
16497 the TUI mode, control is given back to the curses windows.
16498 The screen is then refreshed.
16502 Use a TUI layout with only one window. The layout will
16503 either be @samp{source} or @samp{assembly}. When the TUI mode
16504 is not active, it will switch to the TUI mode.
16506 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16510 Use a TUI layout with at least two windows. When the current
16511 layout already has two windows, the next layout with two windows is used.
16512 When a new layout is chosen, one window will always be common to the
16513 previous layout and the new one.
16515 Think of it as the Emacs @kbd{C-x 2} binding.
16519 Change the active window. The TUI associates several key bindings
16520 (like scrolling and arrow keys) with the active window. This command
16521 gives the focus to the next TUI window.
16523 Think of it as the Emacs @kbd{C-x o} binding.
16527 Switch in and out of the TUI SingleKey mode that binds single
16528 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
16531 The following key bindings only work in the TUI mode:
16536 Scroll the active window one page up.
16540 Scroll the active window one page down.
16544 Scroll the active window one line up.
16548 Scroll the active window one line down.
16552 Scroll the active window one column left.
16556 Scroll the active window one column right.
16560 Refresh the screen.
16563 Because the arrow keys scroll the active window in the TUI mode, they
16564 are not available for their normal use by readline unless the command
16565 window has the focus. When another window is active, you must use
16566 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
16567 and @kbd{C-f} to control the command window.
16569 @node TUI Single Key Mode
16570 @section TUI Single Key Mode
16571 @cindex TUI single key mode
16573 The TUI also provides a @dfn{SingleKey} mode, which binds several
16574 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
16575 switch into this mode, where the following key bindings are used:
16578 @kindex c @r{(SingleKey TUI key)}
16582 @kindex d @r{(SingleKey TUI key)}
16586 @kindex f @r{(SingleKey TUI key)}
16590 @kindex n @r{(SingleKey TUI key)}
16594 @kindex q @r{(SingleKey TUI key)}
16596 exit the SingleKey mode.
16598 @kindex r @r{(SingleKey TUI key)}
16602 @kindex s @r{(SingleKey TUI key)}
16606 @kindex u @r{(SingleKey TUI key)}
16610 @kindex v @r{(SingleKey TUI key)}
16614 @kindex w @r{(SingleKey TUI key)}
16619 Other keys temporarily switch to the @value{GDBN} command prompt.
16620 The key that was pressed is inserted in the editing buffer so that
16621 it is possible to type most @value{GDBN} commands without interaction
16622 with the TUI SingleKey mode. Once the command is entered the TUI
16623 SingleKey mode is restored. The only way to permanently leave
16624 this mode is by typing @kbd{q} or @kbd{C-x s}.
16628 @section TUI-specific Commands
16629 @cindex TUI commands
16631 The TUI has specific commands to control the text windows.
16632 These commands are always available, even when @value{GDBN} is not in
16633 the TUI mode. When @value{GDBN} is in the standard mode, most
16634 of these commands will automatically switch to the TUI mode.
16639 List and give the size of all displayed windows.
16643 Display the next layout.
16646 Display the previous layout.
16649 Display the source window only.
16652 Display the assembly window only.
16655 Display the source and assembly window.
16658 Display the register window together with the source or assembly window.
16662 Make the next window active for scrolling.
16665 Make the previous window active for scrolling.
16668 Make the source window active for scrolling.
16671 Make the assembly window active for scrolling.
16674 Make the register window active for scrolling.
16677 Make the command window active for scrolling.
16681 Refresh the screen. This is similar to typing @kbd{C-L}.
16683 @item tui reg float
16685 Show the floating point registers in the register window.
16687 @item tui reg general
16688 Show the general registers in the register window.
16691 Show the next register group. The list of register groups as well as
16692 their order is target specific. The predefined register groups are the
16693 following: @code{general}, @code{float}, @code{system}, @code{vector},
16694 @code{all}, @code{save}, @code{restore}.
16696 @item tui reg system
16697 Show the system registers in the register window.
16701 Update the source window and the current execution point.
16703 @item winheight @var{name} +@var{count}
16704 @itemx winheight @var{name} -@var{count}
16706 Change the height of the window @var{name} by @var{count}
16707 lines. Positive counts increase the height, while negative counts
16710 @item tabset @var{nchars}
16712 Set the width of tab stops to be @var{nchars} characters.
16715 @node TUI Configuration
16716 @section TUI Configuration Variables
16717 @cindex TUI configuration variables
16719 Several configuration variables control the appearance of TUI windows.
16722 @item set tui border-kind @var{kind}
16723 @kindex set tui border-kind
16724 Select the border appearance for the source, assembly and register windows.
16725 The possible values are the following:
16728 Use a space character to draw the border.
16731 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
16734 Use the Alternate Character Set to draw the border. The border is
16735 drawn using character line graphics if the terminal supports them.
16738 @item set tui border-mode @var{mode}
16739 @kindex set tui border-mode
16740 @itemx set tui active-border-mode @var{mode}
16741 @kindex set tui active-border-mode
16742 Select the display attributes for the borders of the inactive windows
16743 or the active window. The @var{mode} can be one of the following:
16746 Use normal attributes to display the border.
16752 Use reverse video mode.
16755 Use half bright mode.
16757 @item half-standout
16758 Use half bright and standout mode.
16761 Use extra bright or bold mode.
16763 @item bold-standout
16764 Use extra bright or bold and standout mode.
16769 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16772 @cindex @sc{gnu} Emacs
16773 A special interface allows you to use @sc{gnu} Emacs to view (and
16774 edit) the source files for the program you are debugging with
16777 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16778 executable file you want to debug as an argument. This command starts
16779 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16780 created Emacs buffer.
16781 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16783 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16788 All ``terminal'' input and output goes through the Emacs buffer.
16791 This applies both to @value{GDBN} commands and their output, and to the input
16792 and output done by the program you are debugging.
16794 This is useful because it means that you can copy the text of previous
16795 commands and input them again; you can even use parts of the output
16798 All the facilities of Emacs' Shell mode are available for interacting
16799 with your program. In particular, you can send signals the usual
16800 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16805 @value{GDBN} displays source code through Emacs.
16808 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16809 source file for that frame and puts an arrow (@samp{=>}) at the
16810 left margin of the current line. Emacs uses a separate buffer for
16811 source display, and splits the screen to show both your @value{GDBN} session
16814 Explicit @value{GDBN} @code{list} or search commands still produce output as
16815 usual, but you probably have no reason to use them from Emacs.
16817 If you specify an absolute file name when prompted for the @kbd{M-x
16818 gdb} argument, then Emacs sets your current working directory to where
16819 your program resides. If you only specify the file name, then Emacs
16820 sets your current working directory to to the directory associated
16821 with the previous buffer. In this case, @value{GDBN} may find your
16822 program by searching your environment's @code{PATH} variable, but on
16823 some operating systems it might not find the source. So, although the
16824 @value{GDBN} input and output session proceeds normally, the auxiliary
16825 buffer does not display the current source and line of execution.
16827 The initial working directory of @value{GDBN} is printed on the top
16828 line of the @value{GDBN} I/O buffer and this serves as a default for
16829 the commands that specify files for @value{GDBN} to operate
16830 on. @xref{Files, ,Commands to Specify Files}.
16832 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16833 need to call @value{GDBN} by a different name (for example, if you
16834 keep several configurations around, with different names) you can
16835 customize the Emacs variable @code{gud-gdb-command-name} to run the
16838 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16839 addition to the standard Shell mode commands:
16843 Describe the features of Emacs' @value{GDBN} Mode.
16846 Execute to another source line, like the @value{GDBN} @code{step} command; also
16847 update the display window to show the current file and location.
16850 Execute to next source line in this function, skipping all function
16851 calls, like the @value{GDBN} @code{next} command. Then update the display window
16852 to show the current file and location.
16855 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16856 display window accordingly.
16859 Execute until exit from the selected stack frame, like the @value{GDBN}
16860 @code{finish} command.
16863 Continue execution of your program, like the @value{GDBN} @code{continue}
16867 Go up the number of frames indicated by the numeric argument
16868 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16869 like the @value{GDBN} @code{up} command.
16872 Go down the number of frames indicated by the numeric argument, like the
16873 @value{GDBN} @code{down} command.
16876 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
16877 tells @value{GDBN} to set a breakpoint on the source line point is on.
16879 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16880 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16881 point to any frame in the stack and type @key{RET} to make it become the
16882 current frame and display the associated source in the source buffer.
16883 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16886 If you accidentally delete the source-display buffer, an easy way to get
16887 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16888 request a frame display; when you run under Emacs, this recreates
16889 the source buffer if necessary to show you the context of the current
16892 The source files displayed in Emacs are in ordinary Emacs buffers
16893 which are visiting the source files in the usual way. You can edit
16894 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16895 communicates with Emacs in terms of line numbers. If you add or
16896 delete lines from the text, the line numbers that @value{GDBN} knows cease
16897 to correspond properly with the code.
16899 The description given here is for GNU Emacs version 21.3 and a more
16900 detailed description of its interaction with @value{GDBN} is given in
16901 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16903 @c The following dropped because Epoch is nonstandard. Reactivate
16904 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16906 @kindex Emacs Epoch environment
16910 Version 18 of @sc{gnu} Emacs has a built-in window system
16911 called the @code{epoch}
16912 environment. Users of this environment can use a new command,
16913 @code{inspect} which performs identically to @code{print} except that
16914 each value is printed in its own window.
16919 @chapter The @sc{gdb/mi} Interface
16921 @unnumberedsec Function and Purpose
16923 @cindex @sc{gdb/mi}, its purpose
16924 @sc{gdb/mi} is a line based machine oriented text interface to
16925 @value{GDBN} and is activated by specifying using the
16926 @option{--interpreter} command line option (@pxref{Mode Options}). It
16927 is specifically intended to support the development of systems which
16928 use the debugger as just one small component of a larger system.
16930 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16931 in the form of a reference manual.
16933 Note that @sc{gdb/mi} is still under construction, so some of the
16934 features described below are incomplete and subject to change
16935 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
16937 @unnumberedsec Notation and Terminology
16939 @cindex notational conventions, for @sc{gdb/mi}
16940 This chapter uses the following notation:
16944 @code{|} separates two alternatives.
16947 @code{[ @var{something} ]} indicates that @var{something} is optional:
16948 it may or may not be given.
16951 @code{( @var{group} )*} means that @var{group} inside the parentheses
16952 may repeat zero or more times.
16955 @code{( @var{group} )+} means that @var{group} inside the parentheses
16956 may repeat one or more times.
16959 @code{"@var{string}"} means a literal @var{string}.
16963 @heading Dependencies
16967 * GDB/MI Command Syntax::
16968 * GDB/MI Compatibility with CLI::
16969 * GDB/MI Development and Front Ends::
16970 * GDB/MI Output Records::
16971 * GDB/MI Simple Examples::
16972 * GDB/MI Command Description Format::
16973 * GDB/MI Breakpoint Commands::
16974 * GDB/MI Program Context::
16975 * GDB/MI Thread Commands::
16976 * GDB/MI Program Execution::
16977 * GDB/MI Stack Manipulation::
16978 * GDB/MI Variable Objects::
16979 * GDB/MI Data Manipulation::
16980 * GDB/MI Tracepoint Commands::
16981 * GDB/MI Symbol Query::
16982 * GDB/MI File Commands::
16984 * GDB/MI Kod Commands::
16985 * GDB/MI Memory Overlay Commands::
16986 * GDB/MI Signal Handling Commands::
16988 * GDB/MI Target Manipulation::
16989 * GDB/MI Miscellaneous Commands::
16992 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16993 @node GDB/MI Command Syntax
16994 @section @sc{gdb/mi} Command Syntax
16997 * GDB/MI Input Syntax::
16998 * GDB/MI Output Syntax::
17001 @node GDB/MI Input Syntax
17002 @subsection @sc{gdb/mi} Input Syntax
17004 @cindex input syntax for @sc{gdb/mi}
17005 @cindex @sc{gdb/mi}, input syntax
17007 @item @var{command} @expansion{}
17008 @code{@var{cli-command} | @var{mi-command}}
17010 @item @var{cli-command} @expansion{}
17011 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17012 @var{cli-command} is any existing @value{GDBN} CLI command.
17014 @item @var{mi-command} @expansion{}
17015 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17016 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17018 @item @var{token} @expansion{}
17019 "any sequence of digits"
17021 @item @var{option} @expansion{}
17022 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17024 @item @var{parameter} @expansion{}
17025 @code{@var{non-blank-sequence} | @var{c-string}}
17027 @item @var{operation} @expansion{}
17028 @emph{any of the operations described in this chapter}
17030 @item @var{non-blank-sequence} @expansion{}
17031 @emph{anything, provided it doesn't contain special characters such as
17032 "-", @var{nl}, """ and of course " "}
17034 @item @var{c-string} @expansion{}
17035 @code{""" @var{seven-bit-iso-c-string-content} """}
17037 @item @var{nl} @expansion{}
17046 The CLI commands are still handled by the @sc{mi} interpreter; their
17047 output is described below.
17050 The @code{@var{token}}, when present, is passed back when the command
17054 Some @sc{mi} commands accept optional arguments as part of the parameter
17055 list. Each option is identified by a leading @samp{-} (dash) and may be
17056 followed by an optional argument parameter. Options occur first in the
17057 parameter list and can be delimited from normal parameters using
17058 @samp{--} (this is useful when some parameters begin with a dash).
17065 We want easy access to the existing CLI syntax (for debugging).
17068 We want it to be easy to spot a @sc{mi} operation.
17071 @node GDB/MI Output Syntax
17072 @subsection @sc{gdb/mi} Output Syntax
17074 @cindex output syntax of @sc{gdb/mi}
17075 @cindex @sc{gdb/mi}, output syntax
17076 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17077 followed, optionally, by a single result record. This result record
17078 is for the most recent command. The sequence of output records is
17079 terminated by @samp{(gdb)}.
17081 If an input command was prefixed with a @code{@var{token}} then the
17082 corresponding output for that command will also be prefixed by that same
17086 @item @var{output} @expansion{}
17087 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17089 @item @var{result-record} @expansion{}
17090 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17092 @item @var{out-of-band-record} @expansion{}
17093 @code{@var{async-record} | @var{stream-record}}
17095 @item @var{async-record} @expansion{}
17096 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17098 @item @var{exec-async-output} @expansion{}
17099 @code{[ @var{token} ] "*" @var{async-output}}
17101 @item @var{status-async-output} @expansion{}
17102 @code{[ @var{token} ] "+" @var{async-output}}
17104 @item @var{notify-async-output} @expansion{}
17105 @code{[ @var{token} ] "=" @var{async-output}}
17107 @item @var{async-output} @expansion{}
17108 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17110 @item @var{result-class} @expansion{}
17111 @code{"done" | "running" | "connected" | "error" | "exit"}
17113 @item @var{async-class} @expansion{}
17114 @code{"stopped" | @var{others}} (where @var{others} will be added
17115 depending on the needs---this is still in development).
17117 @item @var{result} @expansion{}
17118 @code{ @var{variable} "=" @var{value}}
17120 @item @var{variable} @expansion{}
17121 @code{ @var{string} }
17123 @item @var{value} @expansion{}
17124 @code{ @var{const} | @var{tuple} | @var{list} }
17126 @item @var{const} @expansion{}
17127 @code{@var{c-string}}
17129 @item @var{tuple} @expansion{}
17130 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17132 @item @var{list} @expansion{}
17133 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17134 @var{result} ( "," @var{result} )* "]" }
17136 @item @var{stream-record} @expansion{}
17137 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17139 @item @var{console-stream-output} @expansion{}
17140 @code{"~" @var{c-string}}
17142 @item @var{target-stream-output} @expansion{}
17143 @code{"@@" @var{c-string}}
17145 @item @var{log-stream-output} @expansion{}
17146 @code{"&" @var{c-string}}
17148 @item @var{nl} @expansion{}
17151 @item @var{token} @expansion{}
17152 @emph{any sequence of digits}.
17160 All output sequences end in a single line containing a period.
17163 The @code{@var{token}} is from the corresponding request. If an execution
17164 command is interrupted by the @samp{-exec-interrupt} command, the
17165 @var{token} associated with the @samp{*stopped} message is the one of the
17166 original execution command, not the one of the interrupt command.
17169 @cindex status output in @sc{gdb/mi}
17170 @var{status-async-output} contains on-going status information about the
17171 progress of a slow operation. It can be discarded. All status output is
17172 prefixed by @samp{+}.
17175 @cindex async output in @sc{gdb/mi}
17176 @var{exec-async-output} contains asynchronous state change on the target
17177 (stopped, started, disappeared). All async output is prefixed by
17181 @cindex notify output in @sc{gdb/mi}
17182 @var{notify-async-output} contains supplementary information that the
17183 client should handle (e.g., a new breakpoint information). All notify
17184 output is prefixed by @samp{=}.
17187 @cindex console output in @sc{gdb/mi}
17188 @var{console-stream-output} is output that should be displayed as is in the
17189 console. It is the textual response to a CLI command. All the console
17190 output is prefixed by @samp{~}.
17193 @cindex target output in @sc{gdb/mi}
17194 @var{target-stream-output} is the output produced by the target program.
17195 All the target output is prefixed by @samp{@@}.
17198 @cindex log output in @sc{gdb/mi}
17199 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17200 instance messages that should be displayed as part of an error log. All
17201 the log output is prefixed by @samp{&}.
17204 @cindex list output in @sc{gdb/mi}
17205 New @sc{gdb/mi} commands should only output @var{lists} containing
17211 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17212 details about the various output records.
17214 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17215 @node GDB/MI Compatibility with CLI
17216 @section @sc{gdb/mi} Compatibility with CLI
17218 @cindex compatibility, @sc{gdb/mi} and CLI
17219 @cindex @sc{gdb/mi}, compatibility with CLI
17221 For the developers convenience CLI commands can be entered directly,
17222 but there may be some unexpected behaviour. For example, commands
17223 that query the user will behave as if the user replied yes, breakpoint
17224 command lists are not executed and some CLI commands, such as
17225 @code{if}, @code{when} and @code{define}, prompt for further input with
17226 @samp{>}, which is not valid MI output.
17228 This feature may be removed at some stage in the future and it is
17229 recommended that front ends use the @code{-interpreter-exec} command
17230 (@pxref{-interpreter-exec}).
17232 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17233 @node GDB/MI Development and Front Ends
17234 @section @sc{gdb/mi} Development and Front Ends
17235 @cindex @sc{gdb/mi} development
17237 The application which takes the MI output and presents the state of the
17238 program being debugged to the user is called a @dfn{front end}.
17240 Although @sc{gdb/mi} is still incomplete, it is currently being used
17241 by a variety of front ends to @value{GDBN}. This makes it difficult
17242 to introduce new functionality without breaking existing usage. This
17243 section tries to minimize the problems by describing how the protocol
17246 Some changes in MI need not break a carefully designed front end, and
17247 for these the MI version will remain unchanged. The following is a
17248 list of changes that may occur within one level, so front ends should
17249 parse MI output in a way that can handle them:
17253 New MI commands may be added.
17256 New fields may be added to the output of any MI command.
17259 The range of values for fields with specified values, e.g.,
17260 @code{in_scope} (@pxref{-var-update-fields}) may be extended.
17262 @c The format of field's content e.g type prefix, may change so parse it
17263 @c at your own risk. Yes, in general?
17265 @c The order of fields may change? Shouldn't really matter but it might
17266 @c resolve inconsistencies.
17269 If the changes are likely to break front ends, the MI version level
17270 will be increased by one. This will allow the front end to parse the
17271 output according to the MI version. Apart from mi0, new versions of
17272 @value{GDBN} will not support old versions of MI and it will be the
17273 responsibility of the front end to work with the new one.
17275 @c Starting with mi3, add a new command -mi-version that prints the MI
17278 The best way to avoid unexpected changes in MI that might break your front
17279 end is to make your project known to @value{GDBN} developers and
17280 follow development on @email{gdb@@sourceware.org} and
17281 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17282 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17283 Group, which has the aim of creating a more general MI protocol
17284 called Debugger Machine Interface (DMI) that will become a standard
17285 for all debuggers, not just @value{GDBN}.
17286 @cindex mailing lists
17288 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17289 @node GDB/MI Output Records
17290 @section @sc{gdb/mi} Output Records
17293 * GDB/MI Result Records::
17294 * GDB/MI Stream Records::
17295 * GDB/MI Out-of-band Records::
17298 @node GDB/MI Result Records
17299 @subsection @sc{gdb/mi} Result Records
17301 @cindex result records in @sc{gdb/mi}
17302 @cindex @sc{gdb/mi}, result records
17303 In addition to a number of out-of-band notifications, the response to a
17304 @sc{gdb/mi} command includes one of the following result indications:
17308 @item "^done" [ "," @var{results} ]
17309 The synchronous operation was successful, @code{@var{results}} are the return
17314 @c Is this one correct? Should it be an out-of-band notification?
17315 The asynchronous operation was successfully started. The target is
17320 @value{GDBN} has connected to a remote target.
17322 @item "^error" "," @var{c-string}
17324 The operation failed. The @code{@var{c-string}} contains the corresponding
17329 @value{GDBN} has terminated.
17333 @node GDB/MI Stream Records
17334 @subsection @sc{gdb/mi} Stream Records
17336 @cindex @sc{gdb/mi}, stream records
17337 @cindex stream records in @sc{gdb/mi}
17338 @value{GDBN} internally maintains a number of output streams: the console, the
17339 target, and the log. The output intended for each of these streams is
17340 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17342 Each stream record begins with a unique @dfn{prefix character} which
17343 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17344 Syntax}). In addition to the prefix, each stream record contains a
17345 @code{@var{string-output}}. This is either raw text (with an implicit new
17346 line) or a quoted C string (which does not contain an implicit newline).
17349 @item "~" @var{string-output}
17350 The console output stream contains text that should be displayed in the
17351 CLI console window. It contains the textual responses to CLI commands.
17353 @item "@@" @var{string-output}
17354 The target output stream contains any textual output from the running
17355 target. This is only present when GDB's event loop is truly
17356 asynchronous, which is currently only the case for remote targets.
17358 @item "&" @var{string-output}
17359 The log stream contains debugging messages being produced by @value{GDBN}'s
17363 @node GDB/MI Out-of-band Records
17364 @subsection @sc{gdb/mi} Out-of-band Records
17366 @cindex out-of-band records in @sc{gdb/mi}
17367 @cindex @sc{gdb/mi}, out-of-band records
17368 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17369 additional changes that have occurred. Those changes can either be a
17370 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17371 target activity (e.g., target stopped).
17373 The following is a preliminary list of possible out-of-band records.
17374 In particular, the @var{exec-async-output} records.
17377 @item *stopped,reason="@var{reason}"
17380 @var{reason} can be one of the following:
17383 @item breakpoint-hit
17384 A breakpoint was reached.
17385 @item watchpoint-trigger
17386 A watchpoint was triggered.
17387 @item read-watchpoint-trigger
17388 A read watchpoint was triggered.
17389 @item access-watchpoint-trigger
17390 An access watchpoint was triggered.
17391 @item function-finished
17392 An -exec-finish or similar CLI command was accomplished.
17393 @item location-reached
17394 An -exec-until or similar CLI command was accomplished.
17395 @item watchpoint-scope
17396 A watchpoint has gone out of scope.
17397 @item end-stepping-range
17398 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17399 similar CLI command was accomplished.
17400 @item exited-signalled
17401 The inferior exited because of a signal.
17403 The inferior exited.
17404 @item exited-normally
17405 The inferior exited normally.
17406 @item signal-received
17407 A signal was received by the inferior.
17411 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17412 @node GDB/MI Simple Examples
17413 @section Simple Examples of @sc{gdb/mi} Interaction
17414 @cindex @sc{gdb/mi}, simple examples
17416 This subsection presents several simple examples of interaction using
17417 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17418 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17419 the output received from @sc{gdb/mi}.
17421 Note the line breaks shown in the examples are here only for
17422 readability, they don't appear in the real output.
17424 @subheading Setting a Breakpoint
17426 Setting a breakpoint generates synchronous output which contains detailed
17427 information of the breakpoint.
17430 -> -break-insert main
17431 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17432 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17433 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17437 @subheading Program Execution
17439 Program execution generates asynchronous records and MI gives the
17440 reason that execution stopped.
17446 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17447 frame=@{addr="0x08048564",func="main",
17448 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17449 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17454 <- *stopped,reason="exited-normally"
17458 @subheading Quitting @value{GDBN}
17460 Quitting @value{GDBN} just prints the result class @samp{^exit}.
17468 @subheading A Bad Command
17470 Here's what happens if you pass a non-existent command:
17474 <- ^error,msg="Undefined MI command: rubbish"
17479 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17480 @node GDB/MI Command Description Format
17481 @section @sc{gdb/mi} Command Description Format
17483 The remaining sections describe blocks of commands. Each block of
17484 commands is laid out in a fashion similar to this section.
17486 @subheading Motivation
17488 The motivation for this collection of commands.
17490 @subheading Introduction
17492 A brief introduction to this collection of commands as a whole.
17494 @subheading Commands
17496 For each command in the block, the following is described:
17498 @subsubheading Synopsis
17501 -command @var{args}@dots{}
17504 @subsubheading Result
17506 @subsubheading @value{GDBN} Command
17508 The corresponding @value{GDBN} CLI command(s), if any.
17510 @subsubheading Example
17512 Example(s) formatted for readability. Some of the described commands have
17513 not been implemented yet and these are labeled N.A.@: (not available).
17516 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17517 @node GDB/MI Breakpoint Commands
17518 @section @sc{gdb/mi} Breakpoint Commands
17520 @cindex breakpoint commands for @sc{gdb/mi}
17521 @cindex @sc{gdb/mi}, breakpoint commands
17522 This section documents @sc{gdb/mi} commands for manipulating
17525 @subheading The @code{-break-after} Command
17526 @findex -break-after
17528 @subsubheading Synopsis
17531 -break-after @var{number} @var{count}
17534 The breakpoint number @var{number} is not in effect until it has been
17535 hit @var{count} times. To see how this is reflected in the output of
17536 the @samp{-break-list} command, see the description of the
17537 @samp{-break-list} command below.
17539 @subsubheading @value{GDBN} Command
17541 The corresponding @value{GDBN} command is @samp{ignore}.
17543 @subsubheading Example
17548 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17549 fullname="/home/foo/hello.c",line="5",times="0"@}
17556 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17557 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17558 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17559 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17560 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17561 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17562 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17563 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17564 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17565 line="5",times="0",ignore="3"@}]@}
17570 @subheading The @code{-break-catch} Command
17571 @findex -break-catch
17573 @subheading The @code{-break-commands} Command
17574 @findex -break-commands
17578 @subheading The @code{-break-condition} Command
17579 @findex -break-condition
17581 @subsubheading Synopsis
17584 -break-condition @var{number} @var{expr}
17587 Breakpoint @var{number} will stop the program only if the condition in
17588 @var{expr} is true. The condition becomes part of the
17589 @samp{-break-list} output (see the description of the @samp{-break-list}
17592 @subsubheading @value{GDBN} Command
17594 The corresponding @value{GDBN} command is @samp{condition}.
17596 @subsubheading Example
17600 -break-condition 1 1
17604 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17605 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17606 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17607 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17608 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17609 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17610 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17611 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17612 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17613 line="5",cond="1",times="0",ignore="3"@}]@}
17617 @subheading The @code{-break-delete} Command
17618 @findex -break-delete
17620 @subsubheading Synopsis
17623 -break-delete ( @var{breakpoint} )+
17626 Delete the breakpoint(s) whose number(s) are specified in the argument
17627 list. This is obviously reflected in the breakpoint list.
17629 @subsubheading @value{GDBN} Command
17631 The corresponding @value{GDBN} command is @samp{delete}.
17633 @subsubheading Example
17641 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17642 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17643 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17644 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17645 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17646 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17647 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17652 @subheading The @code{-break-disable} Command
17653 @findex -break-disable
17655 @subsubheading Synopsis
17658 -break-disable ( @var{breakpoint} )+
17661 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17662 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17664 @subsubheading @value{GDBN} Command
17666 The corresponding @value{GDBN} command is @samp{disable}.
17668 @subsubheading Example
17676 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17677 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17678 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17679 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17680 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17681 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17682 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17683 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17684 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17685 line="5",times="0"@}]@}
17689 @subheading The @code{-break-enable} Command
17690 @findex -break-enable
17692 @subsubheading Synopsis
17695 -break-enable ( @var{breakpoint} )+
17698 Enable (previously disabled) @var{breakpoint}(s).
17700 @subsubheading @value{GDBN} Command
17702 The corresponding @value{GDBN} command is @samp{enable}.
17704 @subsubheading Example
17712 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17713 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17714 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17715 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17716 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17717 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17718 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17719 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17720 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17721 line="5",times="0"@}]@}
17725 @subheading The @code{-break-info} Command
17726 @findex -break-info
17728 @subsubheading Synopsis
17731 -break-info @var{breakpoint}
17735 Get information about a single breakpoint.
17737 @subsubheading @value{GDBN} Command
17739 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17741 @subsubheading Example
17744 @subheading The @code{-break-insert} Command
17745 @findex -break-insert
17747 @subsubheading Synopsis
17750 -break-insert [ -t ] [ -h ] [ -r ]
17751 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17752 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17756 If specified, @var{line}, can be one of:
17763 @item filename:linenum
17764 @item filename:function
17768 The possible optional parameters of this command are:
17772 Insert a temporary breakpoint.
17774 Insert a hardware breakpoint.
17775 @item -c @var{condition}
17776 Make the breakpoint conditional on @var{condition}.
17777 @item -i @var{ignore-count}
17778 Initialize the @var{ignore-count}.
17780 Insert a regular breakpoint in all the functions whose names match the
17781 given regular expression. Other flags are not applicable to regular
17785 @subsubheading Result
17787 The result is in the form:
17790 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
17791 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
17792 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
17793 times="@var{times}"@}
17797 where @var{number} is the @value{GDBN} number for this breakpoint,
17798 @var{funcname} is the name of the function where the breakpoint was
17799 inserted, @var{filename} is the name of the source file which contains
17800 this function, @var{lineno} is the source line number within that file
17801 and @var{times} the number of times that the breakpoint has been hit
17802 (always 0 for -break-insert but may be greater for -break-info or -break-list
17803 which use the same output).
17805 Note: this format is open to change.
17806 @c An out-of-band breakpoint instead of part of the result?
17808 @subsubheading @value{GDBN} Command
17810 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17811 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17813 @subsubheading Example
17818 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
17819 fullname="/home/foo/recursive2.c,line="4",times="0"@}
17821 -break-insert -t foo
17822 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
17823 fullname="/home/foo/recursive2.c,line="11",times="0"@}
17826 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17827 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17828 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17829 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17830 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17831 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17832 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17833 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17834 addr="0x0001072c", func="main",file="recursive2.c",
17835 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
17836 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17837 addr="0x00010774",func="foo",file="recursive2.c",
17838 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
17840 -break-insert -r foo.*
17841 ~int foo(int, int);
17842 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
17843 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
17847 @subheading The @code{-break-list} Command
17848 @findex -break-list
17850 @subsubheading Synopsis
17856 Displays the list of inserted breakpoints, showing the following fields:
17860 number of the breakpoint
17862 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17864 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17867 is the breakpoint enabled or no: @samp{y} or @samp{n}
17869 memory location at which the breakpoint is set
17871 logical location of the breakpoint, expressed by function name, file
17874 number of times the breakpoint has been hit
17877 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17878 @code{body} field is an empty list.
17880 @subsubheading @value{GDBN} Command
17882 The corresponding @value{GDBN} command is @samp{info break}.
17884 @subsubheading Example
17889 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17890 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17891 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17892 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17893 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17894 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17895 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17896 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17897 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17898 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17899 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
17900 line="13",times="0"@}]@}
17904 Here's an example of the result when there are no breakpoints:
17909 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17910 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17911 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17912 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17913 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17914 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17915 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17920 @subheading The @code{-break-watch} Command
17921 @findex -break-watch
17923 @subsubheading Synopsis
17926 -break-watch [ -a | -r ]
17929 Create a watchpoint. With the @samp{-a} option it will create an
17930 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
17931 read from or on a write to the memory location. With the @samp{-r}
17932 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
17933 trigger only when the memory location is accessed for reading. Without
17934 either of the options, the watchpoint created is a regular watchpoint,
17935 i.e., it will trigger when the memory location is accessed for writing.
17936 @xref{Set Watchpoints, , Setting Watchpoints}.
17938 Note that @samp{-break-list} will report a single list of watchpoints and
17939 breakpoints inserted.
17941 @subsubheading @value{GDBN} Command
17943 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17946 @subsubheading Example
17948 Setting a watchpoint on a variable in the @code{main} function:
17953 ^done,wpt=@{number="2",exp="x"@}
17958 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17959 value=@{old="-268439212",new="55"@},
17960 frame=@{func="main",args=[],file="recursive2.c",
17961 fullname="/home/foo/bar/recursive2.c",line="5"@}
17965 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17966 the program execution twice: first for the variable changing value, then
17967 for the watchpoint going out of scope.
17972 ^done,wpt=@{number="5",exp="C"@}
17977 *stopped,reason="watchpoint-trigger",
17978 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17979 frame=@{func="callee4",args=[],
17980 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17981 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17986 *stopped,reason="watchpoint-scope",wpnum="5",
17987 frame=@{func="callee3",args=[@{name="strarg",
17988 value="0x11940 \"A string argument.\""@}],
17989 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17990 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17994 Listing breakpoints and watchpoints, at different points in the program
17995 execution. Note that once the watchpoint goes out of scope, it is
18001 ^done,wpt=@{number="2",exp="C"@}
18004 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18005 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18006 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18007 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18008 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18009 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18010 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18011 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18012 addr="0x00010734",func="callee4",
18013 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18014 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18015 bkpt=@{number="2",type="watchpoint",disp="keep",
18016 enabled="y",addr="",what="C",times="0"@}]@}
18021 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18022 value=@{old="-276895068",new="3"@},
18023 frame=@{func="callee4",args=[],
18024 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18025 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18028 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18029 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18030 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18031 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18032 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18033 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18034 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18035 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18036 addr="0x00010734",func="callee4",
18037 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18038 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18039 bkpt=@{number="2",type="watchpoint",disp="keep",
18040 enabled="y",addr="",what="C",times="-5"@}]@}
18044 ^done,reason="watchpoint-scope",wpnum="2",
18045 frame=@{func="callee3",args=[@{name="strarg",
18046 value="0x11940 \"A string argument.\""@}],
18047 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18048 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18051 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18052 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18053 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18054 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18055 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18056 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18057 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18058 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18059 addr="0x00010734",func="callee4",
18060 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18061 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18066 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18067 @node GDB/MI Program Context
18068 @section @sc{gdb/mi} Program Context
18070 @subheading The @code{-exec-arguments} Command
18071 @findex -exec-arguments
18074 @subsubheading Synopsis
18077 -exec-arguments @var{args}
18080 Set the inferior program arguments, to be used in the next
18083 @subsubheading @value{GDBN} Command
18085 The corresponding @value{GDBN} command is @samp{set args}.
18087 @subsubheading Example
18090 Don't have one around.
18093 @subheading The @code{-exec-show-arguments} Command
18094 @findex -exec-show-arguments
18096 @subsubheading Synopsis
18099 -exec-show-arguments
18102 Print the arguments of the program.
18104 @subsubheading @value{GDBN} Command
18106 The corresponding @value{GDBN} command is @samp{show args}.
18108 @subsubheading Example
18112 @subheading The @code{-environment-cd} Command
18113 @findex -environment-cd
18115 @subsubheading Synopsis
18118 -environment-cd @var{pathdir}
18121 Set @value{GDBN}'s working directory.
18123 @subsubheading @value{GDBN} Command
18125 The corresponding @value{GDBN} command is @samp{cd}.
18127 @subsubheading Example
18131 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18137 @subheading The @code{-environment-directory} Command
18138 @findex -environment-directory
18140 @subsubheading Synopsis
18143 -environment-directory [ -r ] [ @var{pathdir} ]+
18146 Add directories @var{pathdir} to beginning of search path for source files.
18147 If the @samp{-r} option is used, the search path is reset to the default
18148 search path. If directories @var{pathdir} are supplied in addition to the
18149 @samp{-r} option, the search path is first reset and then addition
18151 Multiple directories may be specified, separated by blanks. Specifying
18152 multiple directories in a single command
18153 results in the directories added to the beginning of the
18154 search path in the same order they were presented in the command.
18155 If blanks are needed as
18156 part of a directory name, double-quotes should be used around
18157 the name. In the command output, the path will show up separated
18158 by the system directory-separator character. The directory-separator
18159 character must not be used
18160 in any directory name.
18161 If no directories are specified, the current search path is displayed.
18163 @subsubheading @value{GDBN} Command
18165 The corresponding @value{GDBN} command is @samp{dir}.
18167 @subsubheading Example
18171 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18172 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18174 -environment-directory ""
18175 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18177 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18178 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18180 -environment-directory -r
18181 ^done,source-path="$cdir:$cwd"
18186 @subheading The @code{-environment-path} Command
18187 @findex -environment-path
18189 @subsubheading Synopsis
18192 -environment-path [ -r ] [ @var{pathdir} ]+
18195 Add directories @var{pathdir} to beginning of search path for object files.
18196 If the @samp{-r} option is used, the search path is reset to the original
18197 search path that existed at gdb start-up. If directories @var{pathdir} are
18198 supplied in addition to the
18199 @samp{-r} option, the search path is first reset and then addition
18201 Multiple directories may be specified, separated by blanks. Specifying
18202 multiple directories in a single command
18203 results in the directories added to the beginning of the
18204 search path in the same order they were presented in the command.
18205 If blanks are needed as
18206 part of a directory name, double-quotes should be used around
18207 the name. In the command output, the path will show up separated
18208 by the system directory-separator character. The directory-separator
18209 character must not be used
18210 in any directory name.
18211 If no directories are specified, the current path is displayed.
18214 @subsubheading @value{GDBN} Command
18216 The corresponding @value{GDBN} command is @samp{path}.
18218 @subsubheading Example
18223 ^done,path="/usr/bin"
18225 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18226 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18228 -environment-path -r /usr/local/bin
18229 ^done,path="/usr/local/bin:/usr/bin"
18234 @subheading The @code{-environment-pwd} Command
18235 @findex -environment-pwd
18237 @subsubheading Synopsis
18243 Show the current working directory.
18245 @subsubheading @value{GDBN} Command
18247 The corresponding @value{GDBN} command is @samp{pwd}.
18249 @subsubheading Example
18254 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18258 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18259 @node GDB/MI Thread Commands
18260 @section @sc{gdb/mi} Thread Commands
18263 @subheading The @code{-thread-info} Command
18264 @findex -thread-info
18266 @subsubheading Synopsis
18272 @subsubheading @value{GDBN} Command
18276 @subsubheading Example
18280 @subheading The @code{-thread-list-all-threads} Command
18281 @findex -thread-list-all-threads
18283 @subsubheading Synopsis
18286 -thread-list-all-threads
18289 @subsubheading @value{GDBN} Command
18291 The equivalent @value{GDBN} command is @samp{info threads}.
18293 @subsubheading Example
18297 @subheading The @code{-thread-list-ids} Command
18298 @findex -thread-list-ids
18300 @subsubheading Synopsis
18306 Produces a list of the currently known @value{GDBN} thread ids. At the
18307 end of the list it also prints the total number of such threads.
18309 @subsubheading @value{GDBN} Command
18311 Part of @samp{info threads} supplies the same information.
18313 @subsubheading Example
18315 No threads present, besides the main process:
18320 ^done,thread-ids=@{@},number-of-threads="0"
18330 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18331 number-of-threads="3"
18336 @subheading The @code{-thread-select} Command
18337 @findex -thread-select
18339 @subsubheading Synopsis
18342 -thread-select @var{threadnum}
18345 Make @var{threadnum} the current thread. It prints the number of the new
18346 current thread, and the topmost frame for that thread.
18348 @subsubheading @value{GDBN} Command
18350 The corresponding @value{GDBN} command is @samp{thread}.
18352 @subsubheading Example
18359 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18360 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18364 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18365 number-of-threads="3"
18368 ^done,new-thread-id="3",
18369 frame=@{level="0",func="vprintf",
18370 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18371 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18375 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18376 @node GDB/MI Program Execution
18377 @section @sc{gdb/mi} Program Execution
18379 These are the asynchronous commands which generate the out-of-band
18380 record @samp{*stopped}. Currently @value{GDBN} only really executes
18381 asynchronously with remote targets and this interaction is mimicked in
18384 @subheading The @code{-exec-continue} Command
18385 @findex -exec-continue
18387 @subsubheading Synopsis
18393 Resumes the execution of the inferior program until a breakpoint is
18394 encountered, or until the inferior exits.
18396 @subsubheading @value{GDBN} Command
18398 The corresponding @value{GDBN} corresponding is @samp{continue}.
18400 @subsubheading Example
18407 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18408 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18413 @subheading The @code{-exec-finish} Command
18414 @findex -exec-finish
18416 @subsubheading Synopsis
18422 Resumes the execution of the inferior program until the current
18423 function is exited. Displays the results returned by the function.
18425 @subsubheading @value{GDBN} Command
18427 The corresponding @value{GDBN} command is @samp{finish}.
18429 @subsubheading Example
18431 Function returning @code{void}.
18438 *stopped,reason="function-finished",frame=@{func="main",args=[],
18439 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18443 Function returning other than @code{void}. The name of the internal
18444 @value{GDBN} variable storing the result is printed, together with the
18451 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18452 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18453 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18454 gdb-result-var="$1",return-value="0"
18459 @subheading The @code{-exec-interrupt} Command
18460 @findex -exec-interrupt
18462 @subsubheading Synopsis
18468 Interrupts the background execution of the target. Note how the token
18469 associated with the stop message is the one for the execution command
18470 that has been interrupted. The token for the interrupt itself only
18471 appears in the @samp{^done} output. If the user is trying to
18472 interrupt a non-running program, an error message will be printed.
18474 @subsubheading @value{GDBN} Command
18476 The corresponding @value{GDBN} command is @samp{interrupt}.
18478 @subsubheading Example
18489 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18490 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18491 fullname="/home/foo/bar/try.c",line="13"@}
18496 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18501 @subheading The @code{-exec-next} Command
18504 @subsubheading Synopsis
18510 Resumes execution of the inferior program, stopping when the beginning
18511 of the next source line is reached.
18513 @subsubheading @value{GDBN} Command
18515 The corresponding @value{GDBN} command is @samp{next}.
18517 @subsubheading Example
18523 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18528 @subheading The @code{-exec-next-instruction} Command
18529 @findex -exec-next-instruction
18531 @subsubheading Synopsis
18534 -exec-next-instruction
18537 Executes one machine instruction. If the instruction is a function
18538 call, continues until the function returns. If the program stops at an
18539 instruction in the middle of a source line, the address will be
18542 @subsubheading @value{GDBN} Command
18544 The corresponding @value{GDBN} command is @samp{nexti}.
18546 @subsubheading Example
18550 -exec-next-instruction
18554 *stopped,reason="end-stepping-range",
18555 addr="0x000100d4",line="5",file="hello.c"
18560 @subheading The @code{-exec-return} Command
18561 @findex -exec-return
18563 @subsubheading Synopsis
18569 Makes current function return immediately. Doesn't execute the inferior.
18570 Displays the new current frame.
18572 @subsubheading @value{GDBN} Command
18574 The corresponding @value{GDBN} command is @samp{return}.
18576 @subsubheading Example
18580 200-break-insert callee4
18581 200^done,bkpt=@{number="1",addr="0x00010734",
18582 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18587 000*stopped,reason="breakpoint-hit",bkptno="1",
18588 frame=@{func="callee4",args=[],
18589 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18590 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18596 111^done,frame=@{level="0",func="callee3",
18597 args=[@{name="strarg",
18598 value="0x11940 \"A string argument.\""@}],
18599 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18600 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18605 @subheading The @code{-exec-run} Command
18608 @subsubheading Synopsis
18614 Starts execution of the inferior from the beginning. The inferior
18615 executes until either a breakpoint is encountered or the program
18616 exits. In the latter case the output will include an exit code, if
18617 the program has exited exceptionally.
18619 @subsubheading @value{GDBN} Command
18621 The corresponding @value{GDBN} command is @samp{run}.
18623 @subsubheading Examples
18628 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18633 *stopped,reason="breakpoint-hit",bkptno="1",
18634 frame=@{func="main",args=[],file="recursive2.c",
18635 fullname="/home/foo/bar/recursive2.c",line="4"@}
18640 Program exited normally:
18648 *stopped,reason="exited-normally"
18653 Program exited exceptionally:
18661 *stopped,reason="exited",exit-code="01"
18665 Another way the program can terminate is if it receives a signal such as
18666 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18670 *stopped,reason="exited-signalled",signal-name="SIGINT",
18671 signal-meaning="Interrupt"
18675 @c @subheading -exec-signal
18678 @subheading The @code{-exec-step} Command
18681 @subsubheading Synopsis
18687 Resumes execution of the inferior program, stopping when the beginning
18688 of the next source line is reached, if the next source line is not a
18689 function call. If it is, stop at the first instruction of the called
18692 @subsubheading @value{GDBN} Command
18694 The corresponding @value{GDBN} command is @samp{step}.
18696 @subsubheading Example
18698 Stepping into a function:
18704 *stopped,reason="end-stepping-range",
18705 frame=@{func="foo",args=[@{name="a",value="10"@},
18706 @{name="b",value="0"@}],file="recursive2.c",
18707 fullname="/home/foo/bar/recursive2.c",line="11"@}
18717 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18722 @subheading The @code{-exec-step-instruction} Command
18723 @findex -exec-step-instruction
18725 @subsubheading Synopsis
18728 -exec-step-instruction
18731 Resumes the inferior which executes one machine instruction. The
18732 output, once @value{GDBN} has stopped, will vary depending on whether
18733 we have stopped in the middle of a source line or not. In the former
18734 case, the address at which the program stopped will be printed as
18737 @subsubheading @value{GDBN} Command
18739 The corresponding @value{GDBN} command is @samp{stepi}.
18741 @subsubheading Example
18745 -exec-step-instruction
18749 *stopped,reason="end-stepping-range",
18750 frame=@{func="foo",args=[],file="try.c",
18751 fullname="/home/foo/bar/try.c",line="10"@}
18753 -exec-step-instruction
18757 *stopped,reason="end-stepping-range",
18758 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
18759 fullname="/home/foo/bar/try.c",line="10"@}
18764 @subheading The @code{-exec-until} Command
18765 @findex -exec-until
18767 @subsubheading Synopsis
18770 -exec-until [ @var{location} ]
18773 Executes the inferior until the @var{location} specified in the
18774 argument is reached. If there is no argument, the inferior executes
18775 until a source line greater than the current one is reached. The
18776 reason for stopping in this case will be @samp{location-reached}.
18778 @subsubheading @value{GDBN} Command
18780 The corresponding @value{GDBN} command is @samp{until}.
18782 @subsubheading Example
18786 -exec-until recursive2.c:6
18790 *stopped,reason="location-reached",frame=@{func="main",args=[],
18791 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
18796 @subheading -file-clear
18797 Is this going away????
18800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18801 @node GDB/MI Stack Manipulation
18802 @section @sc{gdb/mi} Stack Manipulation Commands
18805 @subheading The @code{-stack-info-frame} Command
18806 @findex -stack-info-frame
18808 @subsubheading Synopsis
18814 Get info on the selected frame.
18816 @subsubheading @value{GDBN} Command
18818 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
18819 (without arguments).
18821 @subsubheading Example
18826 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
18827 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18828 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
18832 @subheading The @code{-stack-info-depth} Command
18833 @findex -stack-info-depth
18835 @subsubheading Synopsis
18838 -stack-info-depth [ @var{max-depth} ]
18841 Return the depth of the stack. If the integer argument @var{max-depth}
18842 is specified, do not count beyond @var{max-depth} frames.
18844 @subsubheading @value{GDBN} Command
18846 There's no equivalent @value{GDBN} command.
18848 @subsubheading Example
18850 For a stack with frame levels 0 through 11:
18857 -stack-info-depth 4
18860 -stack-info-depth 12
18863 -stack-info-depth 11
18866 -stack-info-depth 13
18871 @subheading The @code{-stack-list-arguments} Command
18872 @findex -stack-list-arguments
18874 @subsubheading Synopsis
18877 -stack-list-arguments @var{show-values}
18878 [ @var{low-frame} @var{high-frame} ]
18881 Display a list of the arguments for the frames between @var{low-frame}
18882 and @var{high-frame} (inclusive). If @var{low-frame} and
18883 @var{high-frame} are not provided, list the arguments for the whole
18884 call stack. If the two arguments are equal, show the single frame
18885 at the corresponding level. It is an error if @var{low-frame} is
18886 larger than the actual number of frames. On the other hand,
18887 @var{high-frame} may be larger than the actual number of frames, in
18888 which case only existing frames will be returned.
18890 The @var{show-values} argument must have a value of 0 or 1. A value of
18891 0 means that only the names of the arguments are listed, a value of 1
18892 means that both names and values of the arguments are printed.
18894 @subsubheading @value{GDBN} Command
18896 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
18897 @samp{gdb_get_args} command which partially overlaps with the
18898 functionality of @samp{-stack-list-arguments}.
18900 @subsubheading Example
18907 frame=@{level="0",addr="0x00010734",func="callee4",
18908 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18909 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
18910 frame=@{level="1",addr="0x0001076c",func="callee3",
18911 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18912 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
18913 frame=@{level="2",addr="0x0001078c",func="callee2",
18914 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18915 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
18916 frame=@{level="3",addr="0x000107b4",func="callee1",
18917 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18918 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
18919 frame=@{level="4",addr="0x000107e0",func="main",
18920 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18921 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
18923 -stack-list-arguments 0
18926 frame=@{level="0",args=[]@},
18927 frame=@{level="1",args=[name="strarg"]@},
18928 frame=@{level="2",args=[name="intarg",name="strarg"]@},
18929 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
18930 frame=@{level="4",args=[]@}]
18932 -stack-list-arguments 1
18935 frame=@{level="0",args=[]@},
18937 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
18938 frame=@{level="2",args=[
18939 @{name="intarg",value="2"@},
18940 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
18941 @{frame=@{level="3",args=[
18942 @{name="intarg",value="2"@},
18943 @{name="strarg",value="0x11940 \"A string argument.\""@},
18944 @{name="fltarg",value="3.5"@}]@},
18945 frame=@{level="4",args=[]@}]
18947 -stack-list-arguments 0 2 2
18948 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
18950 -stack-list-arguments 1 2 2
18951 ^done,stack-args=[frame=@{level="2",
18952 args=[@{name="intarg",value="2"@},
18953 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
18957 @c @subheading -stack-list-exception-handlers
18960 @subheading The @code{-stack-list-frames} Command
18961 @findex -stack-list-frames
18963 @subsubheading Synopsis
18966 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
18969 List the frames currently on the stack. For each frame it displays the
18974 The frame number, 0 being the topmost frame, i.e., the innermost function.
18976 The @code{$pc} value for that frame.
18980 File name of the source file where the function lives.
18982 Line number corresponding to the @code{$pc}.
18985 If invoked without arguments, this command prints a backtrace for the
18986 whole stack. If given two integer arguments, it shows the frames whose
18987 levels are between the two arguments (inclusive). If the two arguments
18988 are equal, it shows the single frame at the corresponding level. It is
18989 an error if @var{low-frame} is larger than the actual number of
18990 frames. On the other hand, @var{high-frame} may be larger than the
18991 actual number of frames, in which case only existing frames will be returned.
18993 @subsubheading @value{GDBN} Command
18995 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
18997 @subsubheading Example
18999 Full stack backtrace:
19005 [frame=@{level="0",addr="0x0001076c",func="foo",
19006 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19007 frame=@{level="1",addr="0x000107a4",func="foo",
19008 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19009 frame=@{level="2",addr="0x000107a4",func="foo",
19010 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19011 frame=@{level="3",addr="0x000107a4",func="foo",
19012 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19013 frame=@{level="4",addr="0x000107a4",func="foo",
19014 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19015 frame=@{level="5",addr="0x000107a4",func="foo",
19016 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19017 frame=@{level="6",addr="0x000107a4",func="foo",
19018 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19019 frame=@{level="7",addr="0x000107a4",func="foo",
19020 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19021 frame=@{level="8",addr="0x000107a4",func="foo",
19022 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19023 frame=@{level="9",addr="0x000107a4",func="foo",
19024 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19025 frame=@{level="10",addr="0x000107a4",func="foo",
19026 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19027 frame=@{level="11",addr="0x00010738",func="main",
19028 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19032 Show frames between @var{low_frame} and @var{high_frame}:
19036 -stack-list-frames 3 5
19038 [frame=@{level="3",addr="0x000107a4",func="foo",
19039 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19040 frame=@{level="4",addr="0x000107a4",func="foo",
19041 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19042 frame=@{level="5",addr="0x000107a4",func="foo",
19043 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19047 Show a single frame:
19051 -stack-list-frames 3 3
19053 [frame=@{level="3",addr="0x000107a4",func="foo",
19054 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19059 @subheading The @code{-stack-list-locals} Command
19060 @findex -stack-list-locals
19062 @subsubheading Synopsis
19065 -stack-list-locals @var{print-values}
19068 Display the local variable names for the selected frame. If
19069 @var{print-values} is 0 or @code{--no-values}, print only the names of
19070 the variables; if it is 1 or @code{--all-values}, print also their
19071 values; and if it is 2 or @code{--simple-values}, print the name,
19072 type and value for simple data types and the name and type for arrays,
19073 structures and unions. In this last case, a frontend can immediately
19074 display the value of simple data types and create variable objects for
19075 other data types when the user wishes to explore their values in
19078 @subsubheading @value{GDBN} Command
19080 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19082 @subsubheading Example
19086 -stack-list-locals 0
19087 ^done,locals=[name="A",name="B",name="C"]
19089 -stack-list-locals --all-values
19090 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19091 @{name="C",value="@{1, 2, 3@}"@}]
19092 -stack-list-locals --simple-values
19093 ^done,locals=[@{name="A",type="int",value="1"@},
19094 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19099 @subheading The @code{-stack-select-frame} Command
19100 @findex -stack-select-frame
19102 @subsubheading Synopsis
19105 -stack-select-frame @var{framenum}
19108 Change the selected frame. Select a different frame @var{framenum} on
19111 @subsubheading @value{GDBN} Command
19113 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19114 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19116 @subsubheading Example
19120 -stack-select-frame 2
19125 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19126 @node GDB/MI Variable Objects
19127 @section @sc{gdb/mi} Variable Objects
19131 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19133 For the implementation of a variable debugger window (locals, watched
19134 expressions, etc.), we are proposing the adaptation of the existing code
19135 used by @code{Insight}.
19137 The two main reasons for that are:
19141 It has been proven in practice (it is already on its second generation).
19144 It will shorten development time (needless to say how important it is
19148 The original interface was designed to be used by Tcl code, so it was
19149 slightly changed so it could be used through @sc{gdb/mi}. This section
19150 describes the @sc{gdb/mi} operations that will be available and gives some
19151 hints about their use.
19153 @emph{Note}: In addition to the set of operations described here, we
19154 expect the @sc{gui} implementation of a variable window to require, at
19155 least, the following operations:
19158 @item @code{-gdb-show} @code{output-radix}
19159 @item @code{-stack-list-arguments}
19160 @item @code{-stack-list-locals}
19161 @item @code{-stack-select-frame}
19166 @subheading Introduction to Variable Objects
19168 @cindex variable objects in @sc{gdb/mi}
19170 Variable objects are "object-oriented" MI interface for examining and
19171 changing values of expressions. Unlike some other MI interfaces that
19172 work with expressions, variable objects are specifically designed for
19173 simple and efficient presentation in the frontend. A variable object
19174 is identified by string name. When a variable object is created, the
19175 frontend specifies the expression for that variable object. The
19176 expression can be a simple variable, or it can be an arbitrary complex
19177 expression, and can even involve CPU registers. After creating a
19178 variable object, the frontend can invoke other variable object
19179 operations---for example to obtain or change the value of a variable
19180 object, or to change display format.
19182 Variable objects have hierarchical tree structure. Any variable object
19183 that corresponds to a composite type, such as structure in C, has
19184 a number of child variable objects, for example corresponding to each
19185 element of a structure. A child variable object can itself have
19186 children, recursively. Recursion ends when we reach
19187 leaf variable objects, which always have built-in types. Child variable
19188 objects are created only by explicit request, so if a frontend
19189 is not interested in the children of a particular variable object, no
19190 child will be created.
19192 For a leaf variable object it is possible to obtain its value as a
19193 string, or set the value from a string. String value can be also
19194 obtained for a non-leaf variable object, but it's generally a string
19195 that only indicates the type of the object, and does not list its
19196 contents. Assignment to a non-leaf variable object is not allowed.
19198 A frontend does not need to read the values of all variable objects each time
19199 the program stops. Instead, MI provides an update command that lists all
19200 variable objects whose values has changed since the last update
19201 operation. This considerably reduces the amount of data that must
19202 be transferred to the frontend. As noted above, children variable
19203 objects are created on demand, and only leaf variable objects have a
19204 real value. As result, gdb will read target memory only for leaf
19205 variables that frontend has created.
19207 The automatic update is not always desirable. For example, a frontend
19208 might want to keep a value of some expression for future reference,
19209 and never update it. For another example, fetching memory is
19210 relatively slow for embedded targets, so a frontend might want
19211 to disable automatic update for the variables that are either not
19212 visible on the screen, or ``closed''. This is possible using so
19213 called ``frozen variable objects''. Such variable objects are never
19214 implicitly updated.
19216 The following is the complete set of @sc{gdb/mi} operations defined to
19217 access this functionality:
19219 @multitable @columnfractions .4 .6
19220 @item @strong{Operation}
19221 @tab @strong{Description}
19223 @item @code{-var-create}
19224 @tab create a variable object
19225 @item @code{-var-delete}
19226 @tab delete the variable object and/or its children
19227 @item @code{-var-set-format}
19228 @tab set the display format of this variable
19229 @item @code{-var-show-format}
19230 @tab show the display format of this variable
19231 @item @code{-var-info-num-children}
19232 @tab tells how many children this object has
19233 @item @code{-var-list-children}
19234 @tab return a list of the object's children
19235 @item @code{-var-info-type}
19236 @tab show the type of this variable object
19237 @item @code{-var-info-expression}
19238 @tab print what this variable object represents
19239 @item @code{-var-show-attributes}
19240 @tab is this variable editable? does it exist here?
19241 @item @code{-var-evaluate-expression}
19242 @tab get the value of this variable
19243 @item @code{-var-assign}
19244 @tab set the value of this variable
19245 @item @code{-var-update}
19246 @tab update the variable and its children
19247 @item @code{-var-set-frozen}
19248 @tab set frozeness attribute
19251 In the next subsection we describe each operation in detail and suggest
19252 how it can be used.
19254 @subheading Description And Use of Operations on Variable Objects
19256 @subheading The @code{-var-create} Command
19257 @findex -var-create
19259 @subsubheading Synopsis
19262 -var-create @{@var{name} | "-"@}
19263 @{@var{frame-addr} | "*"@} @var{expression}
19266 This operation creates a variable object, which allows the monitoring of
19267 a variable, the result of an expression, a memory cell or a CPU
19270 The @var{name} parameter is the string by which the object can be
19271 referenced. It must be unique. If @samp{-} is specified, the varobj
19272 system will generate a string ``varNNNNNN'' automatically. It will be
19273 unique provided that one does not specify @var{name} on that format.
19274 The command fails if a duplicate name is found.
19276 The frame under which the expression should be evaluated can be
19277 specified by @var{frame-addr}. A @samp{*} indicates that the current
19278 frame should be used.
19280 @var{expression} is any expression valid on the current language set (must not
19281 begin with a @samp{*}), or one of the following:
19285 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19288 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19291 @samp{$@var{regname}} --- a CPU register name
19294 @subsubheading Result
19296 This operation returns the name, number of children and the type of the
19297 object created. Type is returned as a string as the ones generated by
19298 the @value{GDBN} CLI:
19301 name="@var{name}",numchild="N",type="@var{type}"
19305 @subheading The @code{-var-delete} Command
19306 @findex -var-delete
19308 @subsubheading Synopsis
19311 -var-delete [ -c ] @var{name}
19314 Deletes a previously created variable object and all of its children.
19315 With the @samp{-c} option, just deletes the children.
19317 Returns an error if the object @var{name} is not found.
19320 @subheading The @code{-var-set-format} Command
19321 @findex -var-set-format
19323 @subsubheading Synopsis
19326 -var-set-format @var{name} @var{format-spec}
19329 Sets the output format for the value of the object @var{name} to be
19332 The syntax for the @var{format-spec} is as follows:
19335 @var{format-spec} @expansion{}
19336 @{binary | decimal | hexadecimal | octal | natural@}
19339 The natural format is the default format choosen automatically
19340 based on the variable type (like decimal for an @code{int}, hex
19341 for pointers, etc.).
19343 For a variable with children, the format is set only on the
19344 variable itself, and the children are not affected.
19346 @subheading The @code{-var-show-format} Command
19347 @findex -var-show-format
19349 @subsubheading Synopsis
19352 -var-show-format @var{name}
19355 Returns the format used to display the value of the object @var{name}.
19358 @var{format} @expansion{}
19363 @subheading The @code{-var-info-num-children} Command
19364 @findex -var-info-num-children
19366 @subsubheading Synopsis
19369 -var-info-num-children @var{name}
19372 Returns the number of children of a variable object @var{name}:
19379 @subheading The @code{-var-list-children} Command
19380 @findex -var-list-children
19382 @subsubheading Synopsis
19385 -var-list-children [@var{print-values}] @var{name}
19387 @anchor{-var-list-children}
19389 Return a list of the children of the specified variable object and
19390 create variable objects for them, if they do not already exist. With
19391 a single argument or if @var{print-values} has a value for of 0 or
19392 @code{--no-values}, print only the names of the variables; if
19393 @var{print-values} is 1 or @code{--all-values}, also print their
19394 values; and if it is 2 or @code{--simple-values} print the name and
19395 value for simple data types and just the name for arrays, structures
19398 @subsubheading Example
19402 -var-list-children n
19403 ^done,numchild=@var{n},children=[@{name=@var{name},
19404 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19406 -var-list-children --all-values n
19407 ^done,numchild=@var{n},children=[@{name=@var{name},
19408 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19412 @subheading The @code{-var-info-type} Command
19413 @findex -var-info-type
19415 @subsubheading Synopsis
19418 -var-info-type @var{name}
19421 Returns the type of the specified variable @var{name}. The type is
19422 returned as a string in the same format as it is output by the
19426 type=@var{typename}
19430 @subheading The @code{-var-info-expression} Command
19431 @findex -var-info-expression
19433 @subsubheading Synopsis
19436 -var-info-expression @var{name}
19439 Returns what is represented by the variable object @var{name}:
19442 lang=@var{lang-spec},exp=@var{expression}
19446 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
19448 @subheading The @code{-var-show-attributes} Command
19449 @findex -var-show-attributes
19451 @subsubheading Synopsis
19454 -var-show-attributes @var{name}
19457 List attributes of the specified variable object @var{name}:
19460 status=@var{attr} [ ( ,@var{attr} )* ]
19464 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19466 @subheading The @code{-var-evaluate-expression} Command
19467 @findex -var-evaluate-expression
19469 @subsubheading Synopsis
19472 -var-evaluate-expression @var{name}
19475 Evaluates the expression that is represented by the specified variable
19476 object and returns its value as a string. The format of the
19477 string can be changed using the @code{-var-set-format} command.
19483 Note that one must invoke @code{-var-list-children} for a variable
19484 before the value of a child variable can be evaluated.
19486 @subheading The @code{-var-assign} Command
19487 @findex -var-assign
19489 @subsubheading Synopsis
19492 -var-assign @var{name} @var{expression}
19495 Assigns the value of @var{expression} to the variable object specified
19496 by @var{name}. The object must be @samp{editable}. If the variable's
19497 value is altered by the assign, the variable will show up in any
19498 subsequent @code{-var-update} list.
19500 @subsubheading Example
19508 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19512 @subheading The @code{-var-update} Command
19513 @findex -var-update
19514 @anchor{-var-update}
19516 @subsubheading Synopsis
19519 -var-update [@var{print-values}] @{@var{name} | "*"@}
19522 Reevaluate the expressions corresponding to the variable object
19523 @var{name} and all its direct and indirect children, and return the
19524 list of variable objects whose values have changed; @var{name} must
19525 be a root variable object. Here, ``changed'' means that the result of
19526 @code{-var-evaluate-expression} before and after the
19527 @code{-var-update} is different. If @samp{*} is used as the variable
19528 object names, all existing variable objects are updated. The option
19529 @var{print-values} determines whether both names and values, or just
19530 names are printed. The possible values of this options are the same
19531 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
19532 recommended to use the @samp{--all-values} option, to reduce the
19533 number of MI commands needed on each program stop.
19536 @subsubheading Example
19543 -var-update --all-values var1
19544 ^done,changelist=[@{name="var1",value="3",in_scope="true",
19545 type_changed="false"@}]
19549 @anchor{-var-update-fields}
19550 The field in_scope may take three values:
19554 The variable object's current value is valid.
19557 The variable object does not currently hold a valid value but it may
19558 hold one in the future if its associated expression comes back into
19562 The variable object no longer holds a valid value.
19563 This can occur when the executable file being debugged has changed,
19564 either through recompilation or by using the @value{GDBN} @code{file}
19565 command. The front end should normally choose to delete these variable
19569 In the future new values may be added to this list so the front should
19570 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
19572 @subheading The @code{-var-set-frozen} Command
19573 @findex -var-set-frozen
19575 @subsubheading Synopsis
19578 -var-set-frozen @var{name} @samp{flag}
19581 Set the frozeness flag on the variable object @var{name}. The
19582 @var{flag} parameter should be either @samp{1} to make the variable
19583 frozen or @samp{0} to make it unfozen. If a variable object is
19584 frozen, then neither itself, nor any of its children, are
19585 implicitly updated by @code{-var-update} (@pxref{-var-update}) of
19586 a parent variable or by @code{-var-update *}. Only
19587 @code{-var-update} of the variable itself will update its value and
19588 values of its children. After a variable object is unfrozen, it is
19589 implicitly updated by all subsequent @code{-var-update} operations.
19590 Unfreezing a variable does not update it, only subsequent
19591 @code{-var-update} does.
19593 @subsubheading Example
19597 -var-set-frozen V 1
19603 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19604 @node GDB/MI Data Manipulation
19605 @section @sc{gdb/mi} Data Manipulation
19607 @cindex data manipulation, in @sc{gdb/mi}
19608 @cindex @sc{gdb/mi}, data manipulation
19609 This section describes the @sc{gdb/mi} commands that manipulate data:
19610 examine memory and registers, evaluate expressions, etc.
19612 @c REMOVED FROM THE INTERFACE.
19613 @c @subheading -data-assign
19614 @c Change the value of a program variable. Plenty of side effects.
19615 @c @subsubheading GDB Command
19617 @c @subsubheading Example
19620 @subheading The @code{-data-disassemble} Command
19621 @findex -data-disassemble
19623 @subsubheading Synopsis
19627 [ -s @var{start-addr} -e @var{end-addr} ]
19628 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
19636 @item @var{start-addr}
19637 is the beginning address (or @code{$pc})
19638 @item @var{end-addr}
19640 @item @var{filename}
19641 is the name of the file to disassemble
19642 @item @var{linenum}
19643 is the line number to disassemble around
19645 is the number of disassembly lines to be produced. If it is -1,
19646 the whole function will be disassembled, in case no @var{end-addr} is
19647 specified. If @var{end-addr} is specified as a non-zero value, and
19648 @var{lines} is lower than the number of disassembly lines between
19649 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
19650 displayed; if @var{lines} is higher than the number of lines between
19651 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
19654 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
19658 @subsubheading Result
19660 The output for each instruction is composed of four fields:
19669 Note that whatever included in the instruction field, is not manipulated
19670 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
19672 @subsubheading @value{GDBN} Command
19674 There's no direct mapping from this command to the CLI.
19676 @subsubheading Example
19678 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
19682 -data-disassemble -s $pc -e "$pc + 20" -- 0
19685 @{address="0x000107c0",func-name="main",offset="4",
19686 inst="mov 2, %o0"@},
19687 @{address="0x000107c4",func-name="main",offset="8",
19688 inst="sethi %hi(0x11800), %o2"@},
19689 @{address="0x000107c8",func-name="main",offset="12",
19690 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
19691 @{address="0x000107cc",func-name="main",offset="16",
19692 inst="sethi %hi(0x11800), %o2"@},
19693 @{address="0x000107d0",func-name="main",offset="20",
19694 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
19698 Disassemble the whole @code{main} function. Line 32 is part of
19702 -data-disassemble -f basics.c -l 32 -- 0
19704 @{address="0x000107bc",func-name="main",offset="0",
19705 inst="save %sp, -112, %sp"@},
19706 @{address="0x000107c0",func-name="main",offset="4",
19707 inst="mov 2, %o0"@},
19708 @{address="0x000107c4",func-name="main",offset="8",
19709 inst="sethi %hi(0x11800), %o2"@},
19711 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
19712 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
19716 Disassemble 3 instructions from the start of @code{main}:
19720 -data-disassemble -f basics.c -l 32 -n 3 -- 0
19722 @{address="0x000107bc",func-name="main",offset="0",
19723 inst="save %sp, -112, %sp"@},
19724 @{address="0x000107c0",func-name="main",offset="4",
19725 inst="mov 2, %o0"@},
19726 @{address="0x000107c4",func-name="main",offset="8",
19727 inst="sethi %hi(0x11800), %o2"@}]
19731 Disassemble 3 instructions from the start of @code{main} in mixed mode:
19735 -data-disassemble -f basics.c -l 32 -n 3 -- 1
19737 src_and_asm_line=@{line="31",
19738 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
19739 testsuite/gdb.mi/basics.c",line_asm_insn=[
19740 @{address="0x000107bc",func-name="main",offset="0",
19741 inst="save %sp, -112, %sp"@}]@},
19742 src_and_asm_line=@{line="32",
19743 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
19744 testsuite/gdb.mi/basics.c",line_asm_insn=[
19745 @{address="0x000107c0",func-name="main",offset="4",
19746 inst="mov 2, %o0"@},
19747 @{address="0x000107c4",func-name="main",offset="8",
19748 inst="sethi %hi(0x11800), %o2"@}]@}]
19753 @subheading The @code{-data-evaluate-expression} Command
19754 @findex -data-evaluate-expression
19756 @subsubheading Synopsis
19759 -data-evaluate-expression @var{expr}
19762 Evaluate @var{expr} as an expression. The expression could contain an
19763 inferior function call. The function call will execute synchronously.
19764 If the expression contains spaces, it must be enclosed in double quotes.
19766 @subsubheading @value{GDBN} Command
19768 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
19769 @samp{call}. In @code{gdbtk} only, there's a corresponding
19770 @samp{gdb_eval} command.
19772 @subsubheading Example
19774 In the following example, the numbers that precede the commands are the
19775 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
19776 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
19780 211-data-evaluate-expression A
19783 311-data-evaluate-expression &A
19784 311^done,value="0xefffeb7c"
19786 411-data-evaluate-expression A+3
19789 511-data-evaluate-expression "A + 3"
19795 @subheading The @code{-data-list-changed-registers} Command
19796 @findex -data-list-changed-registers
19798 @subsubheading Synopsis
19801 -data-list-changed-registers
19804 Display a list of the registers that have changed.
19806 @subsubheading @value{GDBN} Command
19808 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
19809 has the corresponding command @samp{gdb_changed_register_list}.
19811 @subsubheading Example
19813 On a PPC MBX board:
19821 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
19822 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
19824 -data-list-changed-registers
19825 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
19826 "10","11","13","14","15","16","17","18","19","20","21","22","23",
19827 "24","25","26","27","28","30","31","64","65","66","67","69"]
19832 @subheading The @code{-data-list-register-names} Command
19833 @findex -data-list-register-names
19835 @subsubheading Synopsis
19838 -data-list-register-names [ ( @var{regno} )+ ]
19841 Show a list of register names for the current target. If no arguments
19842 are given, it shows a list of the names of all the registers. If
19843 integer numbers are given as arguments, it will print a list of the
19844 names of the registers corresponding to the arguments. To ensure
19845 consistency between a register name and its number, the output list may
19846 include empty register names.
19848 @subsubheading @value{GDBN} Command
19850 @value{GDBN} does not have a command which corresponds to
19851 @samp{-data-list-register-names}. In @code{gdbtk} there is a
19852 corresponding command @samp{gdb_regnames}.
19854 @subsubheading Example
19856 For the PPC MBX board:
19859 -data-list-register-names
19860 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
19861 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
19862 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
19863 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
19864 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
19865 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
19866 "", "pc","ps","cr","lr","ctr","xer"]
19868 -data-list-register-names 1 2 3
19869 ^done,register-names=["r1","r2","r3"]
19873 @subheading The @code{-data-list-register-values} Command
19874 @findex -data-list-register-values
19876 @subsubheading Synopsis
19879 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
19882 Display the registers' contents. @var{fmt} is the format according to
19883 which the registers' contents are to be returned, followed by an optional
19884 list of numbers specifying the registers to display. A missing list of
19885 numbers indicates that the contents of all the registers must be returned.
19887 Allowed formats for @var{fmt} are:
19904 @subsubheading @value{GDBN} Command
19906 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
19907 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
19909 @subsubheading Example
19911 For a PPC MBX board (note: line breaks are for readability only, they
19912 don't appear in the actual output):
19916 -data-list-register-values r 64 65
19917 ^done,register-values=[@{number="64",value="0xfe00a300"@},
19918 @{number="65",value="0x00029002"@}]
19920 -data-list-register-values x
19921 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
19922 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
19923 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
19924 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
19925 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
19926 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
19927 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
19928 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
19929 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
19930 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
19931 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
19932 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
19933 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
19934 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
19935 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
19936 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
19937 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
19938 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
19939 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
19940 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
19941 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
19942 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
19943 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
19944 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
19945 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
19946 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
19947 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
19948 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
19949 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
19950 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
19951 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
19952 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
19953 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
19954 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
19955 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
19956 @{number="69",value="0x20002b03"@}]
19961 @subheading The @code{-data-read-memory} Command
19962 @findex -data-read-memory
19964 @subsubheading Synopsis
19967 -data-read-memory [ -o @var{byte-offset} ]
19968 @var{address} @var{word-format} @var{word-size}
19969 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
19976 @item @var{address}
19977 An expression specifying the address of the first memory word to be
19978 read. Complex expressions containing embedded white space should be
19979 quoted using the C convention.
19981 @item @var{word-format}
19982 The format to be used to print the memory words. The notation is the
19983 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
19986 @item @var{word-size}
19987 The size of each memory word in bytes.
19989 @item @var{nr-rows}
19990 The number of rows in the output table.
19992 @item @var{nr-cols}
19993 The number of columns in the output table.
19996 If present, indicates that each row should include an @sc{ascii} dump. The
19997 value of @var{aschar} is used as a padding character when a byte is not a
19998 member of the printable @sc{ascii} character set (printable @sc{ascii}
19999 characters are those whose code is between 32 and 126, inclusively).
20001 @item @var{byte-offset}
20002 An offset to add to the @var{address} before fetching memory.
20005 This command displays memory contents as a table of @var{nr-rows} by
20006 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20007 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20008 (returned as @samp{total-bytes}). Should less than the requested number
20009 of bytes be returned by the target, the missing words are identified
20010 using @samp{N/A}. The number of bytes read from the target is returned
20011 in @samp{nr-bytes} and the starting address used to read memory in
20014 The address of the next/previous row or page is available in
20015 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20018 @subsubheading @value{GDBN} Command
20020 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20021 @samp{gdb_get_mem} memory read command.
20023 @subsubheading Example
20025 Read six bytes of memory starting at @code{bytes+6} but then offset by
20026 @code{-6} bytes. Format as three rows of two columns. One byte per
20027 word. Display each word in hex.
20031 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20032 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20033 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20034 prev-page="0x0000138a",memory=[
20035 @{addr="0x00001390",data=["0x00","0x01"]@},
20036 @{addr="0x00001392",data=["0x02","0x03"]@},
20037 @{addr="0x00001394",data=["0x04","0x05"]@}]
20041 Read two bytes of memory starting at address @code{shorts + 64} and
20042 display as a single word formatted in decimal.
20046 5-data-read-memory shorts+64 d 2 1 1
20047 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20048 next-row="0x00001512",prev-row="0x0000150e",
20049 next-page="0x00001512",prev-page="0x0000150e",memory=[
20050 @{addr="0x00001510",data=["128"]@}]
20054 Read thirty two bytes of memory starting at @code{bytes+16} and format
20055 as eight rows of four columns. Include a string encoding with @samp{x}
20056 used as the non-printable character.
20060 4-data-read-memory bytes+16 x 1 8 4 x
20061 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20062 next-row="0x000013c0",prev-row="0x0000139c",
20063 next-page="0x000013c0",prev-page="0x00001380",memory=[
20064 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20065 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20066 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20067 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20068 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20069 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20070 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20071 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20075 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20076 @node GDB/MI Tracepoint Commands
20077 @section @sc{gdb/mi} Tracepoint Commands
20079 The tracepoint commands are not yet implemented.
20081 @c @subheading -trace-actions
20083 @c @subheading -trace-delete
20085 @c @subheading -trace-disable
20087 @c @subheading -trace-dump
20089 @c @subheading -trace-enable
20091 @c @subheading -trace-exists
20093 @c @subheading -trace-find
20095 @c @subheading -trace-frame-number
20097 @c @subheading -trace-info
20099 @c @subheading -trace-insert
20101 @c @subheading -trace-list
20103 @c @subheading -trace-pass-count
20105 @c @subheading -trace-save
20107 @c @subheading -trace-start
20109 @c @subheading -trace-stop
20112 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20113 @node GDB/MI Symbol Query
20114 @section @sc{gdb/mi} Symbol Query Commands
20117 @subheading The @code{-symbol-info-address} Command
20118 @findex -symbol-info-address
20120 @subsubheading Synopsis
20123 -symbol-info-address @var{symbol}
20126 Describe where @var{symbol} is stored.
20128 @subsubheading @value{GDBN} Command
20130 The corresponding @value{GDBN} command is @samp{info address}.
20132 @subsubheading Example
20136 @subheading The @code{-symbol-info-file} Command
20137 @findex -symbol-info-file
20139 @subsubheading Synopsis
20145 Show the file for the symbol.
20147 @subsubheading @value{GDBN} Command
20149 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20150 @samp{gdb_find_file}.
20152 @subsubheading Example
20156 @subheading The @code{-symbol-info-function} Command
20157 @findex -symbol-info-function
20159 @subsubheading Synopsis
20162 -symbol-info-function
20165 Show which function the symbol lives in.
20167 @subsubheading @value{GDBN} Command
20169 @samp{gdb_get_function} in @code{gdbtk}.
20171 @subsubheading Example
20175 @subheading The @code{-symbol-info-line} Command
20176 @findex -symbol-info-line
20178 @subsubheading Synopsis
20184 Show the core addresses of the code for a source line.
20186 @subsubheading @value{GDBN} Command
20188 The corresponding @value{GDBN} command is @samp{info line}.
20189 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20191 @subsubheading Example
20195 @subheading The @code{-symbol-info-symbol} Command
20196 @findex -symbol-info-symbol
20198 @subsubheading Synopsis
20201 -symbol-info-symbol @var{addr}
20204 Describe what symbol is at location @var{addr}.
20206 @subsubheading @value{GDBN} Command
20208 The corresponding @value{GDBN} command is @samp{info symbol}.
20210 @subsubheading Example
20214 @subheading The @code{-symbol-list-functions} Command
20215 @findex -symbol-list-functions
20217 @subsubheading Synopsis
20220 -symbol-list-functions
20223 List the functions in the executable.
20225 @subsubheading @value{GDBN} Command
20227 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20228 @samp{gdb_search} in @code{gdbtk}.
20230 @subsubheading Example
20234 @subheading The @code{-symbol-list-lines} Command
20235 @findex -symbol-list-lines
20237 @subsubheading Synopsis
20240 -symbol-list-lines @var{filename}
20243 Print the list of lines that contain code and their associated program
20244 addresses for the given source filename. The entries are sorted in
20245 ascending PC order.
20247 @subsubheading @value{GDBN} Command
20249 There is no corresponding @value{GDBN} command.
20251 @subsubheading Example
20254 -symbol-list-lines basics.c
20255 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20260 @subheading The @code{-symbol-list-types} Command
20261 @findex -symbol-list-types
20263 @subsubheading Synopsis
20269 List all the type names.
20271 @subsubheading @value{GDBN} Command
20273 The corresponding commands are @samp{info types} in @value{GDBN},
20274 @samp{gdb_search} in @code{gdbtk}.
20276 @subsubheading Example
20280 @subheading The @code{-symbol-list-variables} Command
20281 @findex -symbol-list-variables
20283 @subsubheading Synopsis
20286 -symbol-list-variables
20289 List all the global and static variable names.
20291 @subsubheading @value{GDBN} Command
20293 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20295 @subsubheading Example
20299 @subheading The @code{-symbol-locate} Command
20300 @findex -symbol-locate
20302 @subsubheading Synopsis
20308 @subsubheading @value{GDBN} Command
20310 @samp{gdb_loc} in @code{gdbtk}.
20312 @subsubheading Example
20316 @subheading The @code{-symbol-type} Command
20317 @findex -symbol-type
20319 @subsubheading Synopsis
20322 -symbol-type @var{variable}
20325 Show type of @var{variable}.
20327 @subsubheading @value{GDBN} Command
20329 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20330 @samp{gdb_obj_variable}.
20332 @subsubheading Example
20336 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20337 @node GDB/MI File Commands
20338 @section @sc{gdb/mi} File Commands
20340 This section describes the GDB/MI commands to specify executable file names
20341 and to read in and obtain symbol table information.
20343 @subheading The @code{-file-exec-and-symbols} Command
20344 @findex -file-exec-and-symbols
20346 @subsubheading Synopsis
20349 -file-exec-and-symbols @var{file}
20352 Specify the executable file to be debugged. This file is the one from
20353 which the symbol table is also read. If no file is specified, the
20354 command clears the executable and symbol information. If breakpoints
20355 are set when using this command with no arguments, @value{GDBN} will produce
20356 error messages. Otherwise, no output is produced, except a completion
20359 @subsubheading @value{GDBN} Command
20361 The corresponding @value{GDBN} command is @samp{file}.
20363 @subsubheading Example
20367 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20373 @subheading The @code{-file-exec-file} Command
20374 @findex -file-exec-file
20376 @subsubheading Synopsis
20379 -file-exec-file @var{file}
20382 Specify the executable file to be debugged. Unlike
20383 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20384 from this file. If used without argument, @value{GDBN} clears the information
20385 about the executable file. No output is produced, except a completion
20388 @subsubheading @value{GDBN} Command
20390 The corresponding @value{GDBN} command is @samp{exec-file}.
20392 @subsubheading Example
20396 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20402 @subheading The @code{-file-list-exec-sections} Command
20403 @findex -file-list-exec-sections
20405 @subsubheading Synopsis
20408 -file-list-exec-sections
20411 List the sections of the current executable file.
20413 @subsubheading @value{GDBN} Command
20415 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20416 information as this command. @code{gdbtk} has a corresponding command
20417 @samp{gdb_load_info}.
20419 @subsubheading Example
20423 @subheading The @code{-file-list-exec-source-file} Command
20424 @findex -file-list-exec-source-file
20426 @subsubheading Synopsis
20429 -file-list-exec-source-file
20432 List the line number, the current source file, and the absolute path
20433 to the current source file for the current executable.
20435 @subsubheading @value{GDBN} Command
20437 The @value{GDBN} equivalent is @samp{info source}
20439 @subsubheading Example
20443 123-file-list-exec-source-file
20444 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20449 @subheading The @code{-file-list-exec-source-files} Command
20450 @findex -file-list-exec-source-files
20452 @subsubheading Synopsis
20455 -file-list-exec-source-files
20458 List the source files for the current executable.
20460 It will always output the filename, but only when @value{GDBN} can find
20461 the absolute file name of a source file, will it output the fullname.
20463 @subsubheading @value{GDBN} Command
20465 The @value{GDBN} equivalent is @samp{info sources}.
20466 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20468 @subsubheading Example
20471 -file-list-exec-source-files
20473 @{file=foo.c,fullname=/home/foo.c@},
20474 @{file=/home/bar.c,fullname=/home/bar.c@},
20475 @{file=gdb_could_not_find_fullpath.c@}]
20479 @subheading The @code{-file-list-shared-libraries} Command
20480 @findex -file-list-shared-libraries
20482 @subsubheading Synopsis
20485 -file-list-shared-libraries
20488 List the shared libraries in the program.
20490 @subsubheading @value{GDBN} Command
20492 The corresponding @value{GDBN} command is @samp{info shared}.
20494 @subsubheading Example
20498 @subheading The @code{-file-list-symbol-files} Command
20499 @findex -file-list-symbol-files
20501 @subsubheading Synopsis
20504 -file-list-symbol-files
20509 @subsubheading @value{GDBN} Command
20511 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20513 @subsubheading Example
20517 @subheading The @code{-file-symbol-file} Command
20518 @findex -file-symbol-file
20520 @subsubheading Synopsis
20523 -file-symbol-file @var{file}
20526 Read symbol table info from the specified @var{file} argument. When
20527 used without arguments, clears @value{GDBN}'s symbol table info. No output is
20528 produced, except for a completion notification.
20530 @subsubheading @value{GDBN} Command
20532 The corresponding @value{GDBN} command is @samp{symbol-file}.
20534 @subsubheading Example
20538 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20544 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20545 @node GDB/MI Memory Overlay Commands
20546 @section @sc{gdb/mi} Memory Overlay Commands
20548 The memory overlay commands are not implemented.
20550 @c @subheading -overlay-auto
20552 @c @subheading -overlay-list-mapping-state
20554 @c @subheading -overlay-list-overlays
20556 @c @subheading -overlay-map
20558 @c @subheading -overlay-off
20560 @c @subheading -overlay-on
20562 @c @subheading -overlay-unmap
20564 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20565 @node GDB/MI Signal Handling Commands
20566 @section @sc{gdb/mi} Signal Handling Commands
20568 Signal handling commands are not implemented.
20570 @c @subheading -signal-handle
20572 @c @subheading -signal-list-handle-actions
20574 @c @subheading -signal-list-signal-types
20578 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20579 @node GDB/MI Target Manipulation
20580 @section @sc{gdb/mi} Target Manipulation Commands
20583 @subheading The @code{-target-attach} Command
20584 @findex -target-attach
20586 @subsubheading Synopsis
20589 -target-attach @var{pid} | @var{file}
20592 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
20594 @subsubheading @value{GDBN} Command
20596 The corresponding @value{GDBN} command is @samp{attach}.
20598 @subsubheading Example
20602 @subheading The @code{-target-compare-sections} Command
20603 @findex -target-compare-sections
20605 @subsubheading Synopsis
20608 -target-compare-sections [ @var{section} ]
20611 Compare data of section @var{section} on target to the exec file.
20612 Without the argument, all sections are compared.
20614 @subsubheading @value{GDBN} Command
20616 The @value{GDBN} equivalent is @samp{compare-sections}.
20618 @subsubheading Example
20622 @subheading The @code{-target-detach} Command
20623 @findex -target-detach
20625 @subsubheading Synopsis
20631 Detach from the remote target which normally resumes its execution.
20634 @subsubheading @value{GDBN} Command
20636 The corresponding @value{GDBN} command is @samp{detach}.
20638 @subsubheading Example
20648 @subheading The @code{-target-disconnect} Command
20649 @findex -target-disconnect
20651 @subsubheading Synopsis
20657 Disconnect from the remote target. There's no output and the target is
20658 generally not resumed.
20660 @subsubheading @value{GDBN} Command
20662 The corresponding @value{GDBN} command is @samp{disconnect}.
20664 @subsubheading Example
20674 @subheading The @code{-target-download} Command
20675 @findex -target-download
20677 @subsubheading Synopsis
20683 Loads the executable onto the remote target.
20684 It prints out an update message every half second, which includes the fields:
20688 The name of the section.
20690 The size of what has been sent so far for that section.
20692 The size of the section.
20694 The total size of what was sent so far (the current and the previous sections).
20696 The size of the overall executable to download.
20700 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
20701 @sc{gdb/mi} Output Syntax}).
20703 In addition, it prints the name and size of the sections, as they are
20704 downloaded. These messages include the following fields:
20708 The name of the section.
20710 The size of the section.
20712 The size of the overall executable to download.
20716 At the end, a summary is printed.
20718 @subsubheading @value{GDBN} Command
20720 The corresponding @value{GDBN} command is @samp{load}.
20722 @subsubheading Example
20724 Note: each status message appears on a single line. Here the messages
20725 have been broken down so that they can fit onto a page.
20730 +download,@{section=".text",section-size="6668",total-size="9880"@}
20731 +download,@{section=".text",section-sent="512",section-size="6668",
20732 total-sent="512",total-size="9880"@}
20733 +download,@{section=".text",section-sent="1024",section-size="6668",
20734 total-sent="1024",total-size="9880"@}
20735 +download,@{section=".text",section-sent="1536",section-size="6668",
20736 total-sent="1536",total-size="9880"@}
20737 +download,@{section=".text",section-sent="2048",section-size="6668",
20738 total-sent="2048",total-size="9880"@}
20739 +download,@{section=".text",section-sent="2560",section-size="6668",
20740 total-sent="2560",total-size="9880"@}
20741 +download,@{section=".text",section-sent="3072",section-size="6668",
20742 total-sent="3072",total-size="9880"@}
20743 +download,@{section=".text",section-sent="3584",section-size="6668",
20744 total-sent="3584",total-size="9880"@}
20745 +download,@{section=".text",section-sent="4096",section-size="6668",
20746 total-sent="4096",total-size="9880"@}
20747 +download,@{section=".text",section-sent="4608",section-size="6668",
20748 total-sent="4608",total-size="9880"@}
20749 +download,@{section=".text",section-sent="5120",section-size="6668",
20750 total-sent="5120",total-size="9880"@}
20751 +download,@{section=".text",section-sent="5632",section-size="6668",
20752 total-sent="5632",total-size="9880"@}
20753 +download,@{section=".text",section-sent="6144",section-size="6668",
20754 total-sent="6144",total-size="9880"@}
20755 +download,@{section=".text",section-sent="6656",section-size="6668",
20756 total-sent="6656",total-size="9880"@}
20757 +download,@{section=".init",section-size="28",total-size="9880"@}
20758 +download,@{section=".fini",section-size="28",total-size="9880"@}
20759 +download,@{section=".data",section-size="3156",total-size="9880"@}
20760 +download,@{section=".data",section-sent="512",section-size="3156",
20761 total-sent="7236",total-size="9880"@}
20762 +download,@{section=".data",section-sent="1024",section-size="3156",
20763 total-sent="7748",total-size="9880"@}
20764 +download,@{section=".data",section-sent="1536",section-size="3156",
20765 total-sent="8260",total-size="9880"@}
20766 +download,@{section=".data",section-sent="2048",section-size="3156",
20767 total-sent="8772",total-size="9880"@}
20768 +download,@{section=".data",section-sent="2560",section-size="3156",
20769 total-sent="9284",total-size="9880"@}
20770 +download,@{section=".data",section-sent="3072",section-size="3156",
20771 total-sent="9796",total-size="9880"@}
20772 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
20778 @subheading The @code{-target-exec-status} Command
20779 @findex -target-exec-status
20781 @subsubheading Synopsis
20784 -target-exec-status
20787 Provide information on the state of the target (whether it is running or
20788 not, for instance).
20790 @subsubheading @value{GDBN} Command
20792 There's no equivalent @value{GDBN} command.
20794 @subsubheading Example
20798 @subheading The @code{-target-list-available-targets} Command
20799 @findex -target-list-available-targets
20801 @subsubheading Synopsis
20804 -target-list-available-targets
20807 List the possible targets to connect to.
20809 @subsubheading @value{GDBN} Command
20811 The corresponding @value{GDBN} command is @samp{help target}.
20813 @subsubheading Example
20817 @subheading The @code{-target-list-current-targets} Command
20818 @findex -target-list-current-targets
20820 @subsubheading Synopsis
20823 -target-list-current-targets
20826 Describe the current target.
20828 @subsubheading @value{GDBN} Command
20830 The corresponding information is printed by @samp{info file} (among
20833 @subsubheading Example
20837 @subheading The @code{-target-list-parameters} Command
20838 @findex -target-list-parameters
20840 @subsubheading Synopsis
20843 -target-list-parameters
20848 @subsubheading @value{GDBN} Command
20852 @subsubheading Example
20856 @subheading The @code{-target-select} Command
20857 @findex -target-select
20859 @subsubheading Synopsis
20862 -target-select @var{type} @var{parameters @dots{}}
20865 Connect @value{GDBN} to the remote target. This command takes two args:
20869 The type of target, for instance @samp{async}, @samp{remote}, etc.
20870 @item @var{parameters}
20871 Device names, host names and the like. @xref{Target Commands, ,
20872 Commands for Managing Targets}, for more details.
20875 The output is a connection notification, followed by the address at
20876 which the target program is, in the following form:
20879 ^connected,addr="@var{address}",func="@var{function name}",
20880 args=[@var{arg list}]
20883 @subsubheading @value{GDBN} Command
20885 The corresponding @value{GDBN} command is @samp{target}.
20887 @subsubheading Example
20891 -target-select async /dev/ttya
20892 ^connected,addr="0xfe00a300",func="??",args=[]
20896 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20897 @node GDB/MI Miscellaneous Commands
20898 @section Miscellaneous @sc{gdb/mi} Commands
20900 @c @subheading -gdb-complete
20902 @subheading The @code{-gdb-exit} Command
20905 @subsubheading Synopsis
20911 Exit @value{GDBN} immediately.
20913 @subsubheading @value{GDBN} Command
20915 Approximately corresponds to @samp{quit}.
20917 @subsubheading Example
20926 @subheading The @code{-exec-abort} Command
20927 @findex -exec-abort
20929 @subsubheading Synopsis
20935 Kill the inferior running program.
20937 @subsubheading @value{GDBN} Command
20939 The corresponding @value{GDBN} command is @samp{kill}.
20941 @subsubheading Example
20945 @subheading The @code{-gdb-set} Command
20948 @subsubheading Synopsis
20954 Set an internal @value{GDBN} variable.
20955 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
20957 @subsubheading @value{GDBN} Command
20959 The corresponding @value{GDBN} command is @samp{set}.
20961 @subsubheading Example
20971 @subheading The @code{-gdb-show} Command
20974 @subsubheading Synopsis
20980 Show the current value of a @value{GDBN} variable.
20982 @subsubheading @value{GDBN} Command
20984 The corresponding @value{GDBN} command is @samp{show}.
20986 @subsubheading Example
20995 @c @subheading -gdb-source
20998 @subheading The @code{-gdb-version} Command
20999 @findex -gdb-version
21001 @subsubheading Synopsis
21007 Show version information for @value{GDBN}. Used mostly in testing.
21009 @subsubheading @value{GDBN} Command
21011 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21012 default shows this information when you start an interactive session.
21014 @subsubheading Example
21016 @c This example modifies the actual output from GDB to avoid overfull
21022 ~Copyright 2000 Free Software Foundation, Inc.
21023 ~GDB is free software, covered by the GNU General Public License, and
21024 ~you are welcome to change it and/or distribute copies of it under
21025 ~ certain conditions.
21026 ~Type "show copying" to see the conditions.
21027 ~There is absolutely no warranty for GDB. Type "show warranty" for
21029 ~This GDB was configured as
21030 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21035 @subheading The @code{-interpreter-exec} Command
21036 @findex -interpreter-exec
21038 @subheading Synopsis
21041 -interpreter-exec @var{interpreter} @var{command}
21043 @anchor{-interpreter-exec}
21045 Execute the specified @var{command} in the given @var{interpreter}.
21047 @subheading @value{GDBN} Command
21049 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21051 @subheading Example
21055 -interpreter-exec console "break main"
21056 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21057 &"During symbol reading, bad structure-type format.\n"
21058 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21063 @subheading The @code{-inferior-tty-set} Command
21064 @findex -inferior-tty-set
21066 @subheading Synopsis
21069 -inferior-tty-set /dev/pts/1
21072 Set terminal for future runs of the program being debugged.
21074 @subheading @value{GDBN} Command
21076 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21078 @subheading Example
21082 -inferior-tty-set /dev/pts/1
21087 @subheading The @code{-inferior-tty-show} Command
21088 @findex -inferior-tty-show
21090 @subheading Synopsis
21096 Show terminal for future runs of program being debugged.
21098 @subheading @value{GDBN} Command
21100 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21102 @subheading Example
21106 -inferior-tty-set /dev/pts/1
21110 ^done,inferior_tty_terminal="/dev/pts/1"
21114 @subheading The @code{-enable-timings} Command
21115 @findex -enable-timings
21117 @subheading Synopsis
21120 -enable-timings [yes | no]
21123 Toggle the printing of the wallclock, user and system times for an MI
21124 command as a field in its output. This command is to help frontend
21125 developers optimize the performance of their code. No argument is
21126 equivalent to @samp{yes}.
21128 @subheading @value{GDBN} Command
21132 @subheading Example
21140 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21141 addr="0x080484ed",func="main",file="myprog.c",
21142 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
21143 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
21151 *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
21152 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
21153 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
21154 fullname="/home/nickrob/myprog.c",line="73"@}
21159 @chapter @value{GDBN} Annotations
21161 This chapter describes annotations in @value{GDBN}. Annotations were
21162 designed to interface @value{GDBN} to graphical user interfaces or other
21163 similar programs which want to interact with @value{GDBN} at a
21164 relatively high level.
21166 The annotation mechanism has largely been superseded by @sc{gdb/mi}
21170 This is Edition @value{EDITION}, @value{DATE}.
21174 * Annotations Overview:: What annotations are; the general syntax.
21175 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21176 * Errors:: Annotations for error messages.
21177 * Invalidation:: Some annotations describe things now invalid.
21178 * Annotations for Running::
21179 Whether the program is running, how it stopped, etc.
21180 * Source Annotations:: Annotations describing source code.
21183 @node Annotations Overview
21184 @section What is an Annotation?
21185 @cindex annotations
21187 Annotations start with a newline character, two @samp{control-z}
21188 characters, and the name of the annotation. If there is no additional
21189 information associated with this annotation, the name of the annotation
21190 is followed immediately by a newline. If there is additional
21191 information, the name of the annotation is followed by a space, the
21192 additional information, and a newline. The additional information
21193 cannot contain newline characters.
21195 Any output not beginning with a newline and two @samp{control-z}
21196 characters denotes literal output from @value{GDBN}. Currently there is
21197 no need for @value{GDBN} to output a newline followed by two
21198 @samp{control-z} characters, but if there was such a need, the
21199 annotations could be extended with an @samp{escape} annotation which
21200 means those three characters as output.
21202 The annotation @var{level}, which is specified using the
21203 @option{--annotate} command line option (@pxref{Mode Options}), controls
21204 how much information @value{GDBN} prints together with its prompt,
21205 values of expressions, source lines, and other types of output. Level 0
21206 is for no annotations, level 1 is for use when @value{GDBN} is run as a
21207 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21208 for programs that control @value{GDBN}, and level 2 annotations have
21209 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21210 Interface, annotate, GDB's Obsolete Annotations}).
21213 @kindex set annotate
21214 @item set annotate @var{level}
21215 The @value{GDBN} command @code{set annotate} sets the level of
21216 annotations to the specified @var{level}.
21218 @item show annotate
21219 @kindex show annotate
21220 Show the current annotation level.
21223 This chapter describes level 3 annotations.
21225 A simple example of starting up @value{GDBN} with annotations is:
21228 $ @kbd{gdb --annotate=3}
21230 Copyright 2003 Free Software Foundation, Inc.
21231 GDB is free software, covered by the GNU General Public License,
21232 and you are welcome to change it and/or distribute copies of it
21233 under certain conditions.
21234 Type "show copying" to see the conditions.
21235 There is absolutely no warranty for GDB. Type "show warranty"
21237 This GDB was configured as "i386-pc-linux-gnu"
21248 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21249 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21250 denotes a @samp{control-z} character) are annotations; the rest is
21251 output from @value{GDBN}.
21254 @section Annotation for @value{GDBN} Input
21256 @cindex annotations for prompts
21257 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21258 to know when to send output, when the output from a given command is
21261 Different kinds of input each have a different @dfn{input type}. Each
21262 input type has three annotations: a @code{pre-} annotation, which
21263 denotes the beginning of any prompt which is being output, a plain
21264 annotation, which denotes the end of the prompt, and then a @code{post-}
21265 annotation which denotes the end of any echo which may (or may not) be
21266 associated with the input. For example, the @code{prompt} input type
21267 features the following annotations:
21275 The input types are
21278 @findex pre-prompt annotation
21279 @findex prompt annotation
21280 @findex post-prompt annotation
21282 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21284 @findex pre-commands annotation
21285 @findex commands annotation
21286 @findex post-commands annotation
21288 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21289 command. The annotations are repeated for each command which is input.
21291 @findex pre-overload-choice annotation
21292 @findex overload-choice annotation
21293 @findex post-overload-choice annotation
21294 @item overload-choice
21295 When @value{GDBN} wants the user to select between various overloaded functions.
21297 @findex pre-query annotation
21298 @findex query annotation
21299 @findex post-query annotation
21301 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21303 @findex pre-prompt-for-continue annotation
21304 @findex prompt-for-continue annotation
21305 @findex post-prompt-for-continue annotation
21306 @item prompt-for-continue
21307 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21308 expect this to work well; instead use @code{set height 0} to disable
21309 prompting. This is because the counting of lines is buggy in the
21310 presence of annotations.
21315 @cindex annotations for errors, warnings and interrupts
21317 @findex quit annotation
21322 This annotation occurs right before @value{GDBN} responds to an interrupt.
21324 @findex error annotation
21329 This annotation occurs right before @value{GDBN} responds to an error.
21331 Quit and error annotations indicate that any annotations which @value{GDBN} was
21332 in the middle of may end abruptly. For example, if a
21333 @code{value-history-begin} annotation is followed by a @code{error}, one
21334 cannot expect to receive the matching @code{value-history-end}. One
21335 cannot expect not to receive it either, however; an error annotation
21336 does not necessarily mean that @value{GDBN} is immediately returning all the way
21339 @findex error-begin annotation
21340 A quit or error annotation may be preceded by
21346 Any output between that and the quit or error annotation is the error
21349 Warning messages are not yet annotated.
21350 @c If we want to change that, need to fix warning(), type_error(),
21351 @c range_error(), and possibly other places.
21354 @section Invalidation Notices
21356 @cindex annotations for invalidation messages
21357 The following annotations say that certain pieces of state may have
21361 @findex frames-invalid annotation
21362 @item ^Z^Zframes-invalid
21364 The frames (for example, output from the @code{backtrace} command) may
21367 @findex breakpoints-invalid annotation
21368 @item ^Z^Zbreakpoints-invalid
21370 The breakpoints may have changed. For example, the user just added or
21371 deleted a breakpoint.
21374 @node Annotations for Running
21375 @section Running the Program
21376 @cindex annotations for running programs
21378 @findex starting annotation
21379 @findex stopping annotation
21380 When the program starts executing due to a @value{GDBN} command such as
21381 @code{step} or @code{continue},
21387 is output. When the program stops,
21393 is output. Before the @code{stopped} annotation, a variety of
21394 annotations describe how the program stopped.
21397 @findex exited annotation
21398 @item ^Z^Zexited @var{exit-status}
21399 The program exited, and @var{exit-status} is the exit status (zero for
21400 successful exit, otherwise nonzero).
21402 @findex signalled annotation
21403 @findex signal-name annotation
21404 @findex signal-name-end annotation
21405 @findex signal-string annotation
21406 @findex signal-string-end annotation
21407 @item ^Z^Zsignalled
21408 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21409 annotation continues:
21415 ^Z^Zsignal-name-end
21419 ^Z^Zsignal-string-end
21424 where @var{name} is the name of the signal, such as @code{SIGILL} or
21425 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21426 as @code{Illegal Instruction} or @code{Segmentation fault}.
21427 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21428 user's benefit and have no particular format.
21430 @findex signal annotation
21432 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21433 just saying that the program received the signal, not that it was
21434 terminated with it.
21436 @findex breakpoint annotation
21437 @item ^Z^Zbreakpoint @var{number}
21438 The program hit breakpoint number @var{number}.
21440 @findex watchpoint annotation
21441 @item ^Z^Zwatchpoint @var{number}
21442 The program hit watchpoint number @var{number}.
21445 @node Source Annotations
21446 @section Displaying Source
21447 @cindex annotations for source display
21449 @findex source annotation
21450 The following annotation is used instead of displaying source code:
21453 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21456 where @var{filename} is an absolute file name indicating which source
21457 file, @var{line} is the line number within that file (where 1 is the
21458 first line in the file), @var{character} is the character position
21459 within the file (where 0 is the first character in the file) (for most
21460 debug formats this will necessarily point to the beginning of a line),
21461 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21462 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21463 @var{addr} is the address in the target program associated with the
21464 source which is being displayed. @var{addr} is in the form @samp{0x}
21465 followed by one or more lowercase hex digits (note that this does not
21466 depend on the language).
21469 @chapter Reporting Bugs in @value{GDBN}
21470 @cindex bugs in @value{GDBN}
21471 @cindex reporting bugs in @value{GDBN}
21473 Your bug reports play an essential role in making @value{GDBN} reliable.
21475 Reporting a bug may help you by bringing a solution to your problem, or it
21476 may not. But in any case the principal function of a bug report is to help
21477 the entire community by making the next version of @value{GDBN} work better. Bug
21478 reports are your contribution to the maintenance of @value{GDBN}.
21480 In order for a bug report to serve its purpose, you must include the
21481 information that enables us to fix the bug.
21484 * Bug Criteria:: Have you found a bug?
21485 * Bug Reporting:: How to report bugs
21489 @section Have You Found a Bug?
21490 @cindex bug criteria
21492 If you are not sure whether you have found a bug, here are some guidelines:
21495 @cindex fatal signal
21496 @cindex debugger crash
21497 @cindex crash of debugger
21499 If the debugger gets a fatal signal, for any input whatever, that is a
21500 @value{GDBN} bug. Reliable debuggers never crash.
21502 @cindex error on valid input
21504 If @value{GDBN} produces an error message for valid input, that is a
21505 bug. (Note that if you're cross debugging, the problem may also be
21506 somewhere in the connection to the target.)
21508 @cindex invalid input
21510 If @value{GDBN} does not produce an error message for invalid input,
21511 that is a bug. However, you should note that your idea of
21512 ``invalid input'' might be our idea of ``an extension'' or ``support
21513 for traditional practice''.
21516 If you are an experienced user of debugging tools, your suggestions
21517 for improvement of @value{GDBN} are welcome in any case.
21520 @node Bug Reporting
21521 @section How to Report Bugs
21522 @cindex bug reports
21523 @cindex @value{GDBN} bugs, reporting
21525 A number of companies and individuals offer support for @sc{gnu} products.
21526 If you obtained @value{GDBN} from a support organization, we recommend you
21527 contact that organization first.
21529 You can find contact information for many support companies and
21530 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21532 @c should add a web page ref...
21534 In any event, we also recommend that you submit bug reports for
21535 @value{GDBN}. The preferred method is to submit them directly using
21536 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21537 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21540 @strong{Do not send bug reports to @samp{info-gdb}, or to
21541 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21542 not want to receive bug reports. Those that do have arranged to receive
21545 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21546 serves as a repeater. The mailing list and the newsgroup carry exactly
21547 the same messages. Often people think of posting bug reports to the
21548 newsgroup instead of mailing them. This appears to work, but it has one
21549 problem which can be crucial: a newsgroup posting often lacks a mail
21550 path back to the sender. Thus, if we need to ask for more information,
21551 we may be unable to reach you. For this reason, it is better to send
21552 bug reports to the mailing list.
21554 The fundamental principle of reporting bugs usefully is this:
21555 @strong{report all the facts}. If you are not sure whether to state a
21556 fact or leave it out, state it!
21558 Often people omit facts because they think they know what causes the
21559 problem and assume that some details do not matter. Thus, you might
21560 assume that the name of the variable you use in an example does not matter.
21561 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21562 stray memory reference which happens to fetch from the location where that
21563 name is stored in memory; perhaps, if the name were different, the contents
21564 of that location would fool the debugger into doing the right thing despite
21565 the bug. Play it safe and give a specific, complete example. That is the
21566 easiest thing for you to do, and the most helpful.
21568 Keep in mind that the purpose of a bug report is to enable us to fix the
21569 bug. It may be that the bug has been reported previously, but neither
21570 you nor we can know that unless your bug report is complete and
21573 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21574 bell?'' Those bug reports are useless, and we urge everyone to
21575 @emph{refuse to respond to them} except to chide the sender to report
21578 To enable us to fix the bug, you should include all these things:
21582 The version of @value{GDBN}. @value{GDBN} announces it if you start
21583 with no arguments; you can also print it at any time using @code{show
21586 Without this, we will not know whether there is any point in looking for
21587 the bug in the current version of @value{GDBN}.
21590 The type of machine you are using, and the operating system name and
21594 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21595 ``@value{GCC}--2.8.1''.
21598 What compiler (and its version) was used to compile the program you are
21599 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21600 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
21601 to get this information; for other compilers, see the documentation for
21605 The command arguments you gave the compiler to compile your example and
21606 observe the bug. For example, did you use @samp{-O}? To guarantee
21607 you will not omit something important, list them all. A copy of the
21608 Makefile (or the output from make) is sufficient.
21610 If we were to try to guess the arguments, we would probably guess wrong
21611 and then we might not encounter the bug.
21614 A complete input script, and all necessary source files, that will
21618 A description of what behavior you observe that you believe is
21619 incorrect. For example, ``It gets a fatal signal.''
21621 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21622 will certainly notice it. But if the bug is incorrect output, we might
21623 not notice unless it is glaringly wrong. You might as well not give us
21624 a chance to make a mistake.
21626 Even if the problem you experience is a fatal signal, you should still
21627 say so explicitly. Suppose something strange is going on, such as, your
21628 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21629 the C library on your system. (This has happened!) Your copy might
21630 crash and ours would not. If you told us to expect a crash, then when
21631 ours fails to crash, we would know that the bug was not happening for
21632 us. If you had not told us to expect a crash, then we would not be able
21633 to draw any conclusion from our observations.
21636 @cindex recording a session script
21637 To collect all this information, you can use a session recording program
21638 such as @command{script}, which is available on many Unix systems.
21639 Just run your @value{GDBN} session inside @command{script} and then
21640 include the @file{typescript} file with your bug report.
21642 Another way to record a @value{GDBN} session is to run @value{GDBN}
21643 inside Emacs and then save the entire buffer to a file.
21646 If you wish to suggest changes to the @value{GDBN} source, send us context
21647 diffs. If you even discuss something in the @value{GDBN} source, refer to
21648 it by context, not by line number.
21650 The line numbers in our development sources will not match those in your
21651 sources. Your line numbers would convey no useful information to us.
21655 Here are some things that are not necessary:
21659 A description of the envelope of the bug.
21661 Often people who encounter a bug spend a lot of time investigating
21662 which changes to the input file will make the bug go away and which
21663 changes will not affect it.
21665 This is often time consuming and not very useful, because the way we
21666 will find the bug is by running a single example under the debugger
21667 with breakpoints, not by pure deduction from a series of examples.
21668 We recommend that you save your time for something else.
21670 Of course, if you can find a simpler example to report @emph{instead}
21671 of the original one, that is a convenience for us. Errors in the
21672 output will be easier to spot, running under the debugger will take
21673 less time, and so on.
21675 However, simplification is not vital; if you do not want to do this,
21676 report the bug anyway and send us the entire test case you used.
21679 A patch for the bug.
21681 A patch for the bug does help us if it is a good one. But do not omit
21682 the necessary information, such as the test case, on the assumption that
21683 a patch is all we need. We might see problems with your patch and decide
21684 to fix the problem another way, or we might not understand it at all.
21686 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21687 construct an example that will make the program follow a certain path
21688 through the code. If you do not send us the example, we will not be able
21689 to construct one, so we will not be able to verify that the bug is fixed.
21691 And if we cannot understand what bug you are trying to fix, or why your
21692 patch should be an improvement, we will not install it. A test case will
21693 help us to understand.
21696 A guess about what the bug is or what it depends on.
21698 Such guesses are usually wrong. Even we cannot guess right about such
21699 things without first using the debugger to find the facts.
21702 @c The readline documentation is distributed with the readline code
21703 @c and consists of the two following files:
21705 @c inc-hist.texinfo
21706 @c Use -I with makeinfo to point to the appropriate directory,
21707 @c environment var TEXINPUTS with TeX.
21708 @include rluser.texi
21709 @include inc-hist.texinfo
21712 @node Formatting Documentation
21713 @appendix Formatting Documentation
21715 @cindex @value{GDBN} reference card
21716 @cindex reference card
21717 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21718 for printing with PostScript or Ghostscript, in the @file{gdb}
21719 subdirectory of the main source directory@footnote{In
21720 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21721 release.}. If you can use PostScript or Ghostscript with your printer,
21722 you can print the reference card immediately with @file{refcard.ps}.
21724 The release also includes the source for the reference card. You
21725 can format it, using @TeX{}, by typing:
21731 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21732 mode on US ``letter'' size paper;
21733 that is, on a sheet 11 inches wide by 8.5 inches
21734 high. You will need to specify this form of printing as an option to
21735 your @sc{dvi} output program.
21737 @cindex documentation
21739 All the documentation for @value{GDBN} comes as part of the machine-readable
21740 distribution. The documentation is written in Texinfo format, which is
21741 a documentation system that uses a single source file to produce both
21742 on-line information and a printed manual. You can use one of the Info
21743 formatting commands to create the on-line version of the documentation
21744 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21746 @value{GDBN} includes an already formatted copy of the on-line Info
21747 version of this manual in the @file{gdb} subdirectory. The main Info
21748 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21749 subordinate files matching @samp{gdb.info*} in the same directory. If
21750 necessary, you can print out these files, or read them with any editor;
21751 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21752 Emacs or the standalone @code{info} program, available as part of the
21753 @sc{gnu} Texinfo distribution.
21755 If you want to format these Info files yourself, you need one of the
21756 Info formatting programs, such as @code{texinfo-format-buffer} or
21759 If you have @code{makeinfo} installed, and are in the top level
21760 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21761 version @value{GDBVN}), you can make the Info file by typing:
21768 If you want to typeset and print copies of this manual, you need @TeX{},
21769 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21770 Texinfo definitions file.
21772 @TeX{} is a typesetting program; it does not print files directly, but
21773 produces output files called @sc{dvi} files. To print a typeset
21774 document, you need a program to print @sc{dvi} files. If your system
21775 has @TeX{} installed, chances are it has such a program. The precise
21776 command to use depends on your system; @kbd{lpr -d} is common; another
21777 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21778 require a file name without any extension or a @samp{.dvi} extension.
21780 @TeX{} also requires a macro definitions file called
21781 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21782 written in Texinfo format. On its own, @TeX{} cannot either read or
21783 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21784 and is located in the @file{gdb-@var{version-number}/texinfo}
21787 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21788 typeset and print this manual. First switch to the @file{gdb}
21789 subdirectory of the main source directory (for example, to
21790 @file{gdb-@value{GDBVN}/gdb}) and type:
21796 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21798 @node Installing GDB
21799 @appendix Installing @value{GDBN}
21800 @cindex installation
21803 * Requirements:: Requirements for building @value{GDBN}
21804 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
21805 * Separate Objdir:: Compiling @value{GDBN} in another directory
21806 * Config Names:: Specifying names for hosts and targets
21807 * Configure Options:: Summary of options for configure
21811 @section Requirements for Building @value{GDBN}
21812 @cindex building @value{GDBN}, requirements for
21814 Building @value{GDBN} requires various tools and packages to be available.
21815 Other packages will be used only if they are found.
21817 @heading Tools/Packages Necessary for Building @value{GDBN}
21819 @item ISO C90 compiler
21820 @value{GDBN} is written in ISO C90. It should be buildable with any
21821 working C90 compiler, e.g.@: GCC.
21825 @heading Tools/Packages Optional for Building @value{GDBN}
21829 @value{GDBN} can use the Expat XML parsing library. This library may be
21830 included with your operating system distribution; if it is not, you
21831 can get the latest version from @url{http://expat.sourceforge.net}.
21832 The @file{configure} script will search for this library in several
21833 standard locations; if it is installed in an unusual path, you can
21834 use the @option{--with-libexpat-prefix} option to specify its location.
21836 Expat is used for remote protocol memory maps (@pxref{Memory Map Format})
21837 and for target descriptions (@pxref{Target Descriptions}).
21841 @node Running Configure
21842 @section Invoking the @value{GDBN} @file{configure} Script
21843 @cindex configuring @value{GDBN}
21844 @value{GDBN} comes with a @file{configure} script that automates the process
21845 of preparing @value{GDBN} for installation; you can then use @code{make} to
21846 build the @code{gdb} program.
21848 @c irrelevant in info file; it's as current as the code it lives with.
21849 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21850 look at the @file{README} file in the sources; we may have improved the
21851 installation procedures since publishing this manual.}
21854 The @value{GDBN} distribution includes all the source code you need for
21855 @value{GDBN} in a single directory, whose name is usually composed by
21856 appending the version number to @samp{gdb}.
21858 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21859 @file{gdb-@value{GDBVN}} directory. That directory contains:
21862 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21863 script for configuring @value{GDBN} and all its supporting libraries
21865 @item gdb-@value{GDBVN}/gdb
21866 the source specific to @value{GDBN} itself
21868 @item gdb-@value{GDBVN}/bfd
21869 source for the Binary File Descriptor library
21871 @item gdb-@value{GDBVN}/include
21872 @sc{gnu} include files
21874 @item gdb-@value{GDBVN}/libiberty
21875 source for the @samp{-liberty} free software library
21877 @item gdb-@value{GDBVN}/opcodes
21878 source for the library of opcode tables and disassemblers
21880 @item gdb-@value{GDBVN}/readline
21881 source for the @sc{gnu} command-line interface
21883 @item gdb-@value{GDBVN}/glob
21884 source for the @sc{gnu} filename pattern-matching subroutine
21886 @item gdb-@value{GDBVN}/mmalloc
21887 source for the @sc{gnu} memory-mapped malloc package
21890 The simplest way to configure and build @value{GDBN} is to run @file{configure}
21891 from the @file{gdb-@var{version-number}} source directory, which in
21892 this example is the @file{gdb-@value{GDBVN}} directory.
21894 First switch to the @file{gdb-@var{version-number}} source directory
21895 if you are not already in it; then run @file{configure}. Pass the
21896 identifier for the platform on which @value{GDBN} will run as an
21902 cd gdb-@value{GDBVN}
21903 ./configure @var{host}
21908 where @var{host} is an identifier such as @samp{sun4} or
21909 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21910 (You can often leave off @var{host}; @file{configure} tries to guess the
21911 correct value by examining your system.)
21913 Running @samp{configure @var{host}} and then running @code{make} builds the
21914 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21915 libraries, then @code{gdb} itself. The configured source files, and the
21916 binaries, are left in the corresponding source directories.
21919 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21920 system does not recognize this automatically when you run a different
21921 shell, you may need to run @code{sh} on it explicitly:
21924 sh configure @var{host}
21927 If you run @file{configure} from a directory that contains source
21928 directories for multiple libraries or programs, such as the
21929 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
21931 creates configuration files for every directory level underneath (unless
21932 you tell it not to, with the @samp{--norecursion} option).
21934 You should run the @file{configure} script from the top directory in the
21935 source tree, the @file{gdb-@var{version-number}} directory. If you run
21936 @file{configure} from one of the subdirectories, you will configure only
21937 that subdirectory. That is usually not what you want. In particular,
21938 if you run the first @file{configure} from the @file{gdb} subdirectory
21939 of the @file{gdb-@var{version-number}} directory, you will omit the
21940 configuration of @file{bfd}, @file{readline}, and other sibling
21941 directories of the @file{gdb} subdirectory. This leads to build errors
21942 about missing include files such as @file{bfd/bfd.h}.
21944 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21945 However, you should make sure that the shell on your path (named by
21946 the @samp{SHELL} environment variable) is publicly readable. Remember
21947 that @value{GDBN} uses the shell to start your program---some systems refuse to
21948 let @value{GDBN} debug child processes whose programs are not readable.
21950 @node Separate Objdir
21951 @section Compiling @value{GDBN} in Another Directory
21953 If you want to run @value{GDBN} versions for several host or target machines,
21954 you need a different @code{gdb} compiled for each combination of
21955 host and target. @file{configure} is designed to make this easy by
21956 allowing you to generate each configuration in a separate subdirectory,
21957 rather than in the source directory. If your @code{make} program
21958 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21959 @code{make} in each of these directories builds the @code{gdb}
21960 program specified there.
21962 To build @code{gdb} in a separate directory, run @file{configure}
21963 with the @samp{--srcdir} option to specify where to find the source.
21964 (You also need to specify a path to find @file{configure}
21965 itself from your working directory. If the path to @file{configure}
21966 would be the same as the argument to @samp{--srcdir}, you can leave out
21967 the @samp{--srcdir} option; it is assumed.)
21969 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21970 separate directory for a Sun 4 like this:
21974 cd gdb-@value{GDBVN}
21977 ../gdb-@value{GDBVN}/configure sun4
21982 When @file{configure} builds a configuration using a remote source
21983 directory, it creates a tree for the binaries with the same structure
21984 (and using the same names) as the tree under the source directory. In
21985 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21986 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21987 @file{gdb-sun4/gdb}.
21989 Make sure that your path to the @file{configure} script has just one
21990 instance of @file{gdb} in it. If your path to @file{configure} looks
21991 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21992 one subdirectory of @value{GDBN}, not the whole package. This leads to
21993 build errors about missing include files such as @file{bfd/bfd.h}.
21995 One popular reason to build several @value{GDBN} configurations in separate
21996 directories is to configure @value{GDBN} for cross-compiling (where
21997 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21998 programs that run on another machine---the @dfn{target}).
21999 You specify a cross-debugging target by
22000 giving the @samp{--target=@var{target}} option to @file{configure}.
22002 When you run @code{make} to build a program or library, you must run
22003 it in a configured directory---whatever directory you were in when you
22004 called @file{configure} (or one of its subdirectories).
22006 The @code{Makefile} that @file{configure} generates in each source
22007 directory also runs recursively. If you type @code{make} in a source
22008 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22009 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22010 will build all the required libraries, and then build GDB.
22012 When you have multiple hosts or targets configured in separate
22013 directories, you can run @code{make} on them in parallel (for example,
22014 if they are NFS-mounted on each of the hosts); they will not interfere
22018 @section Specifying Names for Hosts and Targets
22020 The specifications used for hosts and targets in the @file{configure}
22021 script are based on a three-part naming scheme, but some short predefined
22022 aliases are also supported. The full naming scheme encodes three pieces
22023 of information in the following pattern:
22026 @var{architecture}-@var{vendor}-@var{os}
22029 For example, you can use the alias @code{sun4} as a @var{host} argument,
22030 or as the value for @var{target} in a @code{--target=@var{target}}
22031 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22033 The @file{configure} script accompanying @value{GDBN} does not provide
22034 any query facility to list all supported host and target names or
22035 aliases. @file{configure} calls the Bourne shell script
22036 @code{config.sub} to map abbreviations to full names; you can read the
22037 script, if you wish, or you can use it to test your guesses on
22038 abbreviations---for example:
22041 % sh config.sub i386-linux
22043 % sh config.sub alpha-linux
22044 alpha-unknown-linux-gnu
22045 % sh config.sub hp9k700
22047 % sh config.sub sun4
22048 sparc-sun-sunos4.1.1
22049 % sh config.sub sun3
22050 m68k-sun-sunos4.1.1
22051 % sh config.sub i986v
22052 Invalid configuration `i986v': machine `i986v' not recognized
22056 @code{config.sub} is also distributed in the @value{GDBN} source
22057 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22059 @node Configure Options
22060 @section @file{configure} Options
22062 Here is a summary of the @file{configure} options and arguments that
22063 are most often useful for building @value{GDBN}. @file{configure} also has
22064 several other options not listed here. @inforef{What Configure
22065 Does,,configure.info}, for a full explanation of @file{configure}.
22068 configure @r{[}--help@r{]}
22069 @r{[}--prefix=@var{dir}@r{]}
22070 @r{[}--exec-prefix=@var{dir}@r{]}
22071 @r{[}--srcdir=@var{dirname}@r{]}
22072 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22073 @r{[}--target=@var{target}@r{]}
22078 You may introduce options with a single @samp{-} rather than
22079 @samp{--} if you prefer; but you may abbreviate option names if you use
22084 Display a quick summary of how to invoke @file{configure}.
22086 @item --prefix=@var{dir}
22087 Configure the source to install programs and files under directory
22090 @item --exec-prefix=@var{dir}
22091 Configure the source to install programs under directory
22094 @c avoid splitting the warning from the explanation:
22096 @item --srcdir=@var{dirname}
22097 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22098 @code{make} that implements the @code{VPATH} feature.}@*
22099 Use this option to make configurations in directories separate from the
22100 @value{GDBN} source directories. Among other things, you can use this to
22101 build (or maintain) several configurations simultaneously, in separate
22102 directories. @file{configure} writes configuration-specific files in
22103 the current directory, but arranges for them to use the source in the
22104 directory @var{dirname}. @file{configure} creates directories under
22105 the working directory in parallel to the source directories below
22108 @item --norecursion
22109 Configure only the directory level where @file{configure} is executed; do not
22110 propagate configuration to subdirectories.
22112 @item --target=@var{target}
22113 Configure @value{GDBN} for cross-debugging programs running on the specified
22114 @var{target}. Without this option, @value{GDBN} is configured to debug
22115 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22117 There is no convenient way to generate a list of all available targets.
22119 @item @var{host} @dots{}
22120 Configure @value{GDBN} to run on the specified @var{host}.
22122 There is no convenient way to generate a list of all available hosts.
22125 There are many other options available as well, but they are generally
22126 needed for special purposes only.
22128 @node Maintenance Commands
22129 @appendix Maintenance Commands
22130 @cindex maintenance commands
22131 @cindex internal commands
22133 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22134 includes a number of commands intended for @value{GDBN} developers,
22135 that are not documented elsewhere in this manual. These commands are
22136 provided here for reference. (For commands that turn on debugging
22137 messages, see @ref{Debugging Output}.)
22140 @kindex maint agent
22141 @item maint agent @var{expression}
22142 Translate the given @var{expression} into remote agent bytecodes.
22143 This command is useful for debugging the Agent Expression mechanism
22144 (@pxref{Agent Expressions}).
22146 @kindex maint info breakpoints
22147 @item @anchor{maint info breakpoints}maint info breakpoints
22148 Using the same format as @samp{info breakpoints}, display both the
22149 breakpoints you've set explicitly, and those @value{GDBN} is using for
22150 internal purposes. Internal breakpoints are shown with negative
22151 breakpoint numbers. The type column identifies what kind of breakpoint
22156 Normal, explicitly set breakpoint.
22159 Normal, explicitly set watchpoint.
22162 Internal breakpoint, used to handle correctly stepping through
22163 @code{longjmp} calls.
22165 @item longjmp resume
22166 Internal breakpoint at the target of a @code{longjmp}.
22169 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22172 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22175 Shared library events.
22179 @kindex maint check-symtabs
22180 @item maint check-symtabs
22181 Check the consistency of psymtabs and symtabs.
22183 @kindex maint cplus first_component
22184 @item maint cplus first_component @var{name}
22185 Print the first C@t{++} class/namespace component of @var{name}.
22187 @kindex maint cplus namespace
22188 @item maint cplus namespace
22189 Print the list of possible C@t{++} namespaces.
22191 @kindex maint demangle
22192 @item maint demangle @var{name}
22193 Demangle a C@t{++} or Objective-C mangled @var{name}.
22195 @kindex maint deprecate
22196 @kindex maint undeprecate
22197 @cindex deprecated commands
22198 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22199 @itemx maint undeprecate @var{command}
22200 Deprecate or undeprecate the named @var{command}. Deprecated commands
22201 cause @value{GDBN} to issue a warning when you use them. The optional
22202 argument @var{replacement} says which newer command should be used in
22203 favor of the deprecated one; if it is given, @value{GDBN} will mention
22204 the replacement as part of the warning.
22206 @kindex maint dump-me
22207 @item maint dump-me
22208 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22209 Cause a fatal signal in the debugger and force it to dump its core.
22210 This is supported only on systems which support aborting a program
22211 with the @code{SIGQUIT} signal.
22213 @kindex maint internal-error
22214 @kindex maint internal-warning
22215 @item maint internal-error @r{[}@var{message-text}@r{]}
22216 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22217 Cause @value{GDBN} to call the internal function @code{internal_error}
22218 or @code{internal_warning} and hence behave as though an internal error
22219 or internal warning has been detected. In addition to reporting the
22220 internal problem, these functions give the user the opportunity to
22221 either quit @value{GDBN} or create a core file of the current
22222 @value{GDBN} session.
22224 These commands take an optional parameter @var{message-text} that is
22225 used as the text of the error or warning message.
22227 Here's an example of using @code{internal-error}:
22230 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22231 @dots{}/maint.c:121: internal-error: testing, 1, 2
22232 A problem internal to GDB has been detected. Further
22233 debugging may prove unreliable.
22234 Quit this debugging session? (y or n) @kbd{n}
22235 Create a core file? (y or n) @kbd{n}
22239 @kindex maint packet
22240 @item maint packet @var{text}
22241 If @value{GDBN} is talking to an inferior via the serial protocol,
22242 then this command sends the string @var{text} to the inferior, and
22243 displays the response packet. @value{GDBN} supplies the initial
22244 @samp{$} character, the terminating @samp{#} character, and the
22247 @kindex maint print architecture
22248 @item maint print architecture @r{[}@var{file}@r{]}
22249 Print the entire architecture configuration. The optional argument
22250 @var{file} names the file where the output goes.
22252 @kindex maint print dummy-frames
22253 @item maint print dummy-frames
22254 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22257 (@value{GDBP}) @kbd{b add}
22259 (@value{GDBP}) @kbd{print add(2,3)}
22260 Breakpoint 2, add (a=2, b=3) at @dots{}
22262 The program being debugged stopped while in a function called from GDB.
22264 (@value{GDBP}) @kbd{maint print dummy-frames}
22265 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22266 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22267 call_lo=0x01014000 call_hi=0x01014001
22271 Takes an optional file parameter.
22273 @kindex maint print registers
22274 @kindex maint print raw-registers
22275 @kindex maint print cooked-registers
22276 @kindex maint print register-groups
22277 @item maint print registers @r{[}@var{file}@r{]}
22278 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22279 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22280 @itemx maint print register-groups @r{[}@var{file}@r{]}
22281 Print @value{GDBN}'s internal register data structures.
22283 The command @code{maint print raw-registers} includes the contents of
22284 the raw register cache; the command @code{maint print cooked-registers}
22285 includes the (cooked) value of all registers; and the command
22286 @code{maint print register-groups} includes the groups that each
22287 register is a member of. @xref{Registers,, Registers, gdbint,
22288 @value{GDBN} Internals}.
22290 These commands take an optional parameter, a file name to which to
22291 write the information.
22293 @kindex maint print reggroups
22294 @item maint print reggroups @r{[}@var{file}@r{]}
22295 Print @value{GDBN}'s internal register group data structures. The
22296 optional argument @var{file} tells to what file to write the
22299 The register groups info looks like this:
22302 (@value{GDBP}) @kbd{maint print reggroups}
22315 This command forces @value{GDBN} to flush its internal register cache.
22317 @kindex maint print objfiles
22318 @cindex info for known object files
22319 @item maint print objfiles
22320 Print a dump of all known object files. For each object file, this
22321 command prints its name, address in memory, and all of its psymtabs
22324 @kindex maint print statistics
22325 @cindex bcache statistics
22326 @item maint print statistics
22327 This command prints, for each object file in the program, various data
22328 about that object file followed by the byte cache (@dfn{bcache})
22329 statistics for the object file. The objfile data includes the number
22330 of minimal, partial, full, and stabs symbols, the number of types
22331 defined by the objfile, the number of as yet unexpanded psym tables,
22332 the number of line tables and string tables, and the amount of memory
22333 used by the various tables. The bcache statistics include the counts,
22334 sizes, and counts of duplicates of all and unique objects, max,
22335 average, and median entry size, total memory used and its overhead and
22336 savings, and various measures of the hash table size and chain
22339 @kindex maint print target-stack
22340 @cindex target stack description
22341 @item maint print target-stack
22342 A @dfn{target} is an interface between the debugger and a particular
22343 kind of file or process. Targets can be stacked in @dfn{strata},
22344 so that more than one target can potentially respond to a request.
22345 In particular, memory accesses will walk down the stack of targets
22346 until they find a target that is interested in handling that particular
22349 This command prints a short description of each layer that was pushed on
22350 the @dfn{target stack}, starting from the top layer down to the bottom one.
22352 @kindex maint print type
22353 @cindex type chain of a data type
22354 @item maint print type @var{expr}
22355 Print the type chain for a type specified by @var{expr}. The argument
22356 can be either a type name or a symbol. If it is a symbol, the type of
22357 that symbol is described. The type chain produced by this command is
22358 a recursive definition of the data type as stored in @value{GDBN}'s
22359 data structures, including its flags and contained types.
22361 @kindex maint set dwarf2 max-cache-age
22362 @kindex maint show dwarf2 max-cache-age
22363 @item maint set dwarf2 max-cache-age
22364 @itemx maint show dwarf2 max-cache-age
22365 Control the DWARF 2 compilation unit cache.
22367 @cindex DWARF 2 compilation units cache
22368 In object files with inter-compilation-unit references, such as those
22369 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22370 reader needs to frequently refer to previously read compilation units.
22371 This setting controls how long a compilation unit will remain in the
22372 cache if it is not referenced. A higher limit means that cached
22373 compilation units will be stored in memory longer, and more total
22374 memory will be used. Setting it to zero disables caching, which will
22375 slow down @value{GDBN} startup, but reduce memory consumption.
22377 @kindex maint set profile
22378 @kindex maint show profile
22379 @cindex profiling GDB
22380 @item maint set profile
22381 @itemx maint show profile
22382 Control profiling of @value{GDBN}.
22384 Profiling will be disabled until you use the @samp{maint set profile}
22385 command to enable it. When you enable profiling, the system will begin
22386 collecting timing and execution count data; when you disable profiling or
22387 exit @value{GDBN}, the results will be written to a log file. Remember that
22388 if you use profiling, @value{GDBN} will overwrite the profiling log file
22389 (often called @file{gmon.out}). If you have a record of important profiling
22390 data in a @file{gmon.out} file, be sure to move it to a safe location.
22392 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
22393 compiled with the @samp{-pg} compiler option.
22395 @kindex maint show-debug-regs
22396 @cindex x86 hardware debug registers
22397 @item maint show-debug-regs
22398 Control whether to show variables that mirror the x86 hardware debug
22399 registers. Use @code{ON} to enable, @code{OFF} to disable. If
22400 enabled, the debug registers values are shown when @value{GDBN} inserts or
22401 removes a hardware breakpoint or watchpoint, and when the inferior
22402 triggers a hardware-assisted breakpoint or watchpoint.
22404 @kindex maint space
22405 @cindex memory used by commands
22407 Control whether to display memory usage for each command. If set to a
22408 nonzero value, @value{GDBN} will display how much memory each command
22409 took, following the command's own output. This can also be requested
22410 by invoking @value{GDBN} with the @option{--statistics} command-line
22411 switch (@pxref{Mode Options}).
22414 @cindex time of command execution
22416 Control whether to display the execution time for each command. If
22417 set to a nonzero value, @value{GDBN} will display how much time it
22418 took to execute each command, following the command's own output.
22419 This can also be requested by invoking @value{GDBN} with the
22420 @option{--statistics} command-line switch (@pxref{Mode Options}).
22422 @kindex maint translate-address
22423 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22424 Find the symbol stored at the location specified by the address
22425 @var{addr} and an optional section name @var{section}. If found,
22426 @value{GDBN} prints the name of the closest symbol and an offset from
22427 the symbol's location to the specified address. This is similar to
22428 the @code{info address} command (@pxref{Symbols}), except that this
22429 command also allows to find symbols in other sections.
22433 The following command is useful for non-interactive invocations of
22434 @value{GDBN}, such as in the test suite.
22437 @item set watchdog @var{nsec}
22438 @kindex set watchdog
22439 @cindex watchdog timer
22440 @cindex timeout for commands
22441 Set the maximum number of seconds @value{GDBN} will wait for the
22442 target operation to finish. If this time expires, @value{GDBN}
22443 reports and error and the command is aborted.
22445 @item show watchdog
22446 Show the current setting of the target wait timeout.
22449 @node Remote Protocol
22450 @appendix @value{GDBN} Remote Serial Protocol
22455 * Stop Reply Packets::
22456 * General Query Packets::
22457 * Register Packet Format::
22458 * Tracepoint Packets::
22461 * File-I/O Remote Protocol Extension::
22462 * Memory Map Format::
22468 There may be occasions when you need to know something about the
22469 protocol---for example, if there is only one serial port to your target
22470 machine, you might want your program to do something special if it
22471 recognizes a packet meant for @value{GDBN}.
22473 In the examples below, @samp{->} and @samp{<-} are used to indicate
22474 transmitted and received data respectfully.
22476 @cindex protocol, @value{GDBN} remote serial
22477 @cindex serial protocol, @value{GDBN} remote
22478 @cindex remote serial protocol
22479 All @value{GDBN} commands and responses (other than acknowledgments) are
22480 sent as a @var{packet}. A @var{packet} is introduced with the character
22481 @samp{$}, the actual @var{packet-data}, and the terminating character
22482 @samp{#} followed by a two-digit @var{checksum}:
22485 @code{$}@var{packet-data}@code{#}@var{checksum}
22489 @cindex checksum, for @value{GDBN} remote
22491 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22492 characters between the leading @samp{$} and the trailing @samp{#} (an
22493 eight bit unsigned checksum).
22495 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22496 specification also included an optional two-digit @var{sequence-id}:
22499 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22502 @cindex sequence-id, for @value{GDBN} remote
22504 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22505 has never output @var{sequence-id}s. Stubs that handle packets added
22506 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22508 @cindex acknowledgment, for @value{GDBN} remote
22509 When either the host or the target machine receives a packet, the first
22510 response expected is an acknowledgment: either @samp{+} (to indicate
22511 the package was received correctly) or @samp{-} (to request
22515 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22520 The host (@value{GDBN}) sends @var{command}s, and the target (the
22521 debugging stub incorporated in your program) sends a @var{response}. In
22522 the case of step and continue @var{command}s, the response is only sent
22523 when the operation has completed (the target has again stopped).
22525 @var{packet-data} consists of a sequence of characters with the
22526 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22529 @cindex remote protocol, field separator
22530 Fields within the packet should be separated using @samp{,} @samp{;} or
22531 @samp{:}. Except where otherwise noted all numbers are represented in
22532 @sc{hex} with leading zeros suppressed.
22534 Implementors should note that prior to @value{GDBN} 5.0, the character
22535 @samp{:} could not appear as the third character in a packet (as it
22536 would potentially conflict with the @var{sequence-id}).
22538 @cindex remote protocol, binary data
22539 @anchor{Binary Data}
22540 Binary data in most packets is encoded either as two hexadecimal
22541 digits per byte of binary data. This allowed the traditional remote
22542 protocol to work over connections which were only seven-bit clean.
22543 Some packets designed more recently assume an eight-bit clean
22544 connection, and use a more efficient encoding to send and receive
22547 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
22548 as an escape character. Any escaped byte is transmitted as the escape
22549 character followed by the original character XORed with @code{0x20}.
22550 For example, the byte @code{0x7d} would be transmitted as the two
22551 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
22552 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
22553 @samp{@}}) must always be escaped. Responses sent by the stub
22554 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
22555 is not interpreted as the start of a run-length encoded sequence
22558 Response @var{data} can be run-length encoded to save space. A @samp{*}
22559 means that the next character is an @sc{ascii} encoding giving a repeat count
22560 which stands for that many repetitions of the character preceding the
22561 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22562 where @code{n >=3} (which is where rle starts to win). The printable
22563 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22564 value greater than 126 should not be used.
22571 means the same as "0000".
22573 The error response returned for some packets includes a two character
22574 error number. That number is not well defined.
22576 @cindex empty response, for unsupported packets
22577 For any @var{command} not supported by the stub, an empty response
22578 (@samp{$#00}) should be returned. That way it is possible to extend the
22579 protocol. A newer @value{GDBN} can tell if a packet is supported based
22582 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22583 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22589 The following table provides a complete list of all currently defined
22590 @var{command}s and their corresponding response @var{data}.
22591 @xref{File-I/O Remote Protocol Extension}, for details about the File
22592 I/O extension of the remote protocol.
22594 Each packet's description has a template showing the packet's overall
22595 syntax, followed by an explanation of the packet's meaning. We
22596 include spaces in some of the templates for clarity; these are not
22597 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22598 separate its components. For example, a template like @samp{foo
22599 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22600 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22601 @var{baz}. @value{GDBN} does not transmit a space character between the
22602 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22605 Note that all packet forms beginning with an upper- or lower-case
22606 letter, other than those described here, are reserved for future use.
22608 Here are the packet descriptions.
22613 @cindex @samp{!} packet
22614 Enable extended mode. In extended mode, the remote server is made
22615 persistent. The @samp{R} packet is used to restart the program being
22621 The remote target both supports and has enabled extended mode.
22625 @cindex @samp{?} packet
22626 Indicate the reason the target halted. The reply is the same as for
22630 @xref{Stop Reply Packets}, for the reply specifications.
22632 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22633 @cindex @samp{A} packet
22634 Initialized @code{argv[]} array passed into program. @var{arglen}
22635 specifies the number of bytes in the hex encoded byte stream
22636 @var{arg}. See @code{gdbserver} for more details.
22641 The arguments were set.
22647 @cindex @samp{b} packet
22648 (Don't use this packet; its behavior is not well-defined.)
22649 Change the serial line speed to @var{baud}.
22651 JTC: @emph{When does the transport layer state change? When it's
22652 received, or after the ACK is transmitted. In either case, there are
22653 problems if the command or the acknowledgment packet is dropped.}
22655 Stan: @emph{If people really wanted to add something like this, and get
22656 it working for the first time, they ought to modify ser-unix.c to send
22657 some kind of out-of-band message to a specially-setup stub and have the
22658 switch happen "in between" packets, so that from remote protocol's point
22659 of view, nothing actually happened.}
22661 @item B @var{addr},@var{mode}
22662 @cindex @samp{B} packet
22663 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
22664 breakpoint at @var{addr}.
22666 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
22667 (@pxref{insert breakpoint or watchpoint packet}).
22669 @item c @r{[}@var{addr}@r{]}
22670 @cindex @samp{c} packet
22671 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
22672 resume at current address.
22675 @xref{Stop Reply Packets}, for the reply specifications.
22677 @item C @var{sig}@r{[};@var{addr}@r{]}
22678 @cindex @samp{C} packet
22679 Continue with signal @var{sig} (hex signal number). If
22680 @samp{;@var{addr}} is omitted, resume at same address.
22683 @xref{Stop Reply Packets}, for the reply specifications.
22686 @cindex @samp{d} packet
22689 Don't use this packet; instead, define a general set packet
22690 (@pxref{General Query Packets}).
22693 @cindex @samp{D} packet
22694 Detach @value{GDBN} from the remote system. Sent to the remote target
22695 before @value{GDBN} disconnects via the @code{detach} command.
22705 @item F @var{RC},@var{EE},@var{CF};@var{XX}
22706 @cindex @samp{F} packet
22707 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
22708 This is part of the File-I/O protocol extension. @xref{File-I/O
22709 Remote Protocol Extension}, for the specification.
22712 @anchor{read registers packet}
22713 @cindex @samp{g} packet
22714 Read general registers.
22718 @item @var{XX@dots{}}
22719 Each byte of register data is described by two hex digits. The bytes
22720 with the register are transmitted in target byte order. The size of
22721 each register and their position within the @samp{g} packet are
22722 determined by the @value{GDBN} internal macros
22723 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{REGISTER_NAME} macros. The
22724 specification of several standard @samp{g} packets is specified below.
22729 @item G @var{XX@dots{}}
22730 @cindex @samp{G} packet
22731 Write general registers. @xref{read registers packet}, for a
22732 description of the @var{XX@dots{}} data.
22742 @item H @var{c} @var{t}
22743 @cindex @samp{H} packet
22744 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22745 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22746 should be @samp{c} for step and continue operations, @samp{g} for other
22747 operations. The thread designator @var{t} may be @samp{-1}, meaning all
22748 the threads, a thread number, or @samp{0} which means pick any thread.
22759 @c 'H': How restrictive (or permissive) is the thread model. If a
22760 @c thread is selected and stopped, are other threads allowed
22761 @c to continue to execute? As I mentioned above, I think the
22762 @c semantics of each command when a thread is selected must be
22763 @c described. For example:
22765 @c 'g': If the stub supports threads and a specific thread is
22766 @c selected, returns the register block from that thread;
22767 @c otherwise returns current registers.
22769 @c 'G' If the stub supports threads and a specific thread is
22770 @c selected, sets the registers of the register block of
22771 @c that thread; otherwise sets current registers.
22773 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
22774 @anchor{cycle step packet}
22775 @cindex @samp{i} packet
22776 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
22777 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22778 step starting at that address.
22781 @cindex @samp{I} packet
22782 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
22786 @cindex @samp{k} packet
22789 FIXME: @emph{There is no description of how to operate when a specific
22790 thread context has been selected (i.e.@: does 'k' kill only that
22793 @item m @var{addr},@var{length}
22794 @cindex @samp{m} packet
22795 Read @var{length} bytes of memory starting at address @var{addr}.
22796 Note that @var{addr} may not be aligned to any particular boundary.
22798 The stub need not use any particular size or alignment when gathering
22799 data from memory for the response; even if @var{addr} is word-aligned
22800 and @var{length} is a multiple of the word size, the stub is free to
22801 use byte accesses, or not. For this reason, this packet may not be
22802 suitable for accessing memory-mapped I/O devices.
22803 @cindex alignment of remote memory accesses
22804 @cindex size of remote memory accesses
22805 @cindex memory, alignment and size of remote accesses
22809 @item @var{XX@dots{}}
22810 Memory contents; each byte is transmitted as a two-digit hexadecimal
22811 number. The reply may contain fewer bytes than requested if the
22812 server was able to read only part of the region of memory.
22817 @item M @var{addr},@var{length}:@var{XX@dots{}}
22818 @cindex @samp{M} packet
22819 Write @var{length} bytes of memory starting at address @var{addr}.
22820 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
22821 hexadecimal number.
22828 for an error (this includes the case where only part of the data was
22833 @cindex @samp{p} packet
22834 Read the value of register @var{n}; @var{n} is in hex.
22835 @xref{read registers packet}, for a description of how the returned
22836 register value is encoded.
22840 @item @var{XX@dots{}}
22841 the register's value
22845 Indicating an unrecognized @var{query}.
22848 @item P @var{n@dots{}}=@var{r@dots{}}
22849 @anchor{write register packet}
22850 @cindex @samp{P} packet
22851 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
22852 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
22853 digits for each byte in the register (target byte order).
22863 @item q @var{name} @var{params}@dots{}
22864 @itemx Q @var{name} @var{params}@dots{}
22865 @cindex @samp{q} packet
22866 @cindex @samp{Q} packet
22867 General query (@samp{q}) and set (@samp{Q}). These packets are
22868 described fully in @ref{General Query Packets}.
22871 @cindex @samp{r} packet
22872 Reset the entire system.
22874 Don't use this packet; use the @samp{R} packet instead.
22877 @cindex @samp{R} packet
22878 Restart the program being debugged. @var{XX}, while needed, is ignored.
22879 This packet is only available in extended mode.
22881 The @samp{R} packet has no reply.
22883 @item s @r{[}@var{addr}@r{]}
22884 @cindex @samp{s} packet
22885 Single step. @var{addr} is the address at which to resume. If
22886 @var{addr} is omitted, resume at same address.
22889 @xref{Stop Reply Packets}, for the reply specifications.
22891 @item S @var{sig}@r{[};@var{addr}@r{]}
22892 @anchor{step with signal packet}
22893 @cindex @samp{S} packet
22894 Step with signal. This is analogous to the @samp{C} packet, but
22895 requests a single-step, rather than a normal resumption of execution.
22898 @xref{Stop Reply Packets}, for the reply specifications.
22900 @item t @var{addr}:@var{PP},@var{MM}
22901 @cindex @samp{t} packet
22902 Search backwards starting at address @var{addr} for a match with pattern
22903 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22904 @var{addr} must be at least 3 digits.
22907 @cindex @samp{T} packet
22908 Find out if the thread XX is alive.
22913 thread is still alive
22919 Packets starting with @samp{v} are identified by a multi-letter name,
22920 up to the first @samp{;} or @samp{?} (or the end of the packet).
22922 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
22923 @cindex @samp{vCont} packet
22924 Resume the inferior, specifying different actions for each thread.
22925 If an action is specified with no @var{tid}, then it is applied to any
22926 threads that don't have a specific action specified; if no default action is
22927 specified then other threads should remain stopped. Specifying multiple
22928 default actions is an error; specifying no actions is also an error.
22929 Thread IDs are specified in hexadecimal. Currently supported actions are:
22935 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22939 Step with signal @var{sig}. @var{sig} should be two hex digits.
22942 The optional @var{addr} argument normally associated with these packets is
22943 not supported in @samp{vCont}.
22946 @xref{Stop Reply Packets}, for the reply specifications.
22949 @cindex @samp{vCont?} packet
22950 Request a list of actions supported by the @samp{vCont} packet.
22954 @item vCont@r{[};@var{action}@dots{}@r{]}
22955 The @samp{vCont} packet is supported. Each @var{action} is a supported
22956 command in the @samp{vCont} packet.
22958 The @samp{vCont} packet is not supported.
22961 @item vFlashErase:@var{addr},@var{length}
22962 @cindex @samp{vFlashErase} packet
22963 Direct the stub to erase @var{length} bytes of flash starting at
22964 @var{addr}. The region may enclose any number of flash blocks, but
22965 its start and end must fall on block boundaries, as indicated by the
22966 flash block size appearing in the memory map (@pxref{Memory Map
22967 Format}). @value{GDBN} groups flash memory programming operations
22968 together, and sends a @samp{vFlashDone} request after each group; the
22969 stub is allowed to delay erase operation until the @samp{vFlashDone}
22970 packet is received.
22980 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
22981 @cindex @samp{vFlashWrite} packet
22982 Direct the stub to write data to flash address @var{addr}. The data
22983 is passed in binary form using the same encoding as for the @samp{X}
22984 packet (@pxref{Binary Data}). The memory ranges specified by
22985 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
22986 not overlap, and must appear in order of increasing addresses
22987 (although @samp{vFlashErase} packets for higher addresses may already
22988 have been received; the ordering is guaranteed only between
22989 @samp{vFlashWrite} packets). If a packet writes to an address that was
22990 neither erased by a preceding @samp{vFlashErase} packet nor by some other
22991 target-specific method, the results are unpredictable.
22999 for vFlashWrite addressing non-flash memory
23005 @cindex @samp{vFlashDone} packet
23006 Indicate to the stub that flash programming operation is finished.
23007 The stub is permitted to delay or batch the effects of a group of
23008 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23009 @samp{vFlashDone} packet is received. The contents of the affected
23010 regions of flash memory are unpredictable until the @samp{vFlashDone}
23011 request is completed.
23013 @item X @var{addr},@var{length}:@var{XX@dots{}}
23015 @cindex @samp{X} packet
23016 Write data to memory, where the data is transmitted in binary.
23017 @var{addr} is address, @var{length} is number of bytes,
23018 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23028 @item z @var{type},@var{addr},@var{length}
23029 @itemx Z @var{type},@var{addr},@var{length}
23030 @anchor{insert breakpoint or watchpoint packet}
23031 @cindex @samp{z} packet
23032 @cindex @samp{Z} packets
23033 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23034 watchpoint starting at address @var{address} and covering the next
23035 @var{length} bytes.
23037 Each breakpoint and watchpoint packet @var{type} is documented
23040 @emph{Implementation notes: A remote target shall return an empty string
23041 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23042 remote target shall support either both or neither of a given
23043 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23044 avoid potential problems with duplicate packets, the operations should
23045 be implemented in an idempotent way.}
23047 @item z0,@var{addr},@var{length}
23048 @itemx Z0,@var{addr},@var{length}
23049 @cindex @samp{z0} packet
23050 @cindex @samp{Z0} packet
23051 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23052 @var{addr} of size @var{length}.
23054 A memory breakpoint is implemented by replacing the instruction at
23055 @var{addr} with a software breakpoint or trap instruction. The
23056 @var{length} is used by targets that indicates the size of the
23057 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23058 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23060 @emph{Implementation note: It is possible for a target to copy or move
23061 code that contains memory breakpoints (e.g., when implementing
23062 overlays). The behavior of this packet, in the presence of such a
23063 target, is not defined.}
23075 @item z1,@var{addr},@var{length}
23076 @itemx Z1,@var{addr},@var{length}
23077 @cindex @samp{z1} packet
23078 @cindex @samp{Z1} packet
23079 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23080 address @var{addr} of size @var{length}.
23082 A hardware breakpoint is implemented using a mechanism that is not
23083 dependant on being able to modify the target's memory.
23085 @emph{Implementation note: A hardware breakpoint is not affected by code
23098 @item z2,@var{addr},@var{length}
23099 @itemx Z2,@var{addr},@var{length}
23100 @cindex @samp{z2} packet
23101 @cindex @samp{Z2} packet
23102 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23114 @item z3,@var{addr},@var{length}
23115 @itemx Z3,@var{addr},@var{length}
23116 @cindex @samp{z3} packet
23117 @cindex @samp{Z3} packet
23118 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23130 @item z4,@var{addr},@var{length}
23131 @itemx Z4,@var{addr},@var{length}
23132 @cindex @samp{z4} packet
23133 @cindex @samp{Z4} packet
23134 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23148 @node Stop Reply Packets
23149 @section Stop Reply Packets
23150 @cindex stop reply packets
23152 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23153 receive any of the below as a reply. In the case of the @samp{C},
23154 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23155 when the target halts. In the below the exact meaning of @dfn{signal
23156 number} is defined by the header @file{include/gdb/signals.h} in the
23157 @value{GDBN} source code.
23159 As in the description of request packets, we include spaces in the
23160 reply templates for clarity; these are not part of the reply packet's
23161 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23167 The program received signal number @var{AA} (a two-digit hexadecimal
23168 number). This is equivalent to a @samp{T} response with no
23169 @var{n}:@var{r} pairs.
23171 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23172 @cindex @samp{T} packet reply
23173 The program received signal number @var{AA} (a two-digit hexadecimal
23174 number). This is equivalent to an @samp{S} response, except that the
23175 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23176 and other information directly in the stop reply packet, reducing
23177 round-trip latency. Single-step and breakpoint traps are reported
23178 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23181 If @var{n} is a hexadecimal number, it is a register number, and the
23182 corresponding @var{r} gives that register's value. @var{r} is a
23183 series of bytes in target byte order, with each byte given by a
23184 two-digit hex number.
23186 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23189 If @var{n} is @samp{watch}, @samp{rwatch}, or @samp{awatch}, then the
23190 packet indicates a watchpoint hit, and @var{r} is the data address, in
23193 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23194 and go on to the next; this allows us to extend the protocol in the
23199 The process exited, and @var{AA} is the exit status. This is only
23200 applicable to certain targets.
23203 The process terminated with signal @var{AA}.
23205 @item O @var{XX}@dots{}
23206 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23207 written as the program's console output. This can happen at any time
23208 while the program is running and the debugger should continue to wait
23209 for @samp{W}, @samp{T}, etc.
23211 @item F @var{call-id},@var{parameter}@dots{}
23212 @var{call-id} is the identifier which says which host system call should
23213 be called. This is just the name of the function. Translation into the
23214 correct system call is only applicable as it's defined in @value{GDBN}.
23215 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
23218 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23219 this very system call.
23221 The target replies with this packet when it expects @value{GDBN} to
23222 call a host system call on behalf of the target. @value{GDBN} replies
23223 with an appropriate @samp{F} packet and keeps up waiting for the next
23224 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23225 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
23226 Protocol Extension}, for more details.
23230 @node General Query Packets
23231 @section General Query Packets
23232 @cindex remote query requests
23234 Packets starting with @samp{q} are @dfn{general query packets};
23235 packets starting with @samp{Q} are @dfn{general set packets}. General
23236 query and set packets are a semi-unified form for retrieving and
23237 sending information to and from the stub.
23239 The initial letter of a query or set packet is followed by a name
23240 indicating what sort of thing the packet applies to. For example,
23241 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23242 definitions with the stub. These packet names follow some
23247 The name must not contain commas, colons or semicolons.
23249 Most @value{GDBN} query and set packets have a leading upper case
23252 The names of custom vendor packets should use a company prefix, in
23253 lower case, followed by a period. For example, packets designed at
23254 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23255 foos) or @samp{Qacme.bar} (for setting bars).
23258 The name of a query or set packet should be separated from any
23259 parameters by a @samp{:}; the parameters themselves should be
23260 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23261 full packet name, and check for a separator or the end of the packet,
23262 in case two packet names share a common prefix. New packets should not begin
23263 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23264 packets predate these conventions, and have arguments without any terminator
23265 for the packet name; we suspect they are in widespread use in places that
23266 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23267 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23270 Like the descriptions of the other packets, each description here
23271 has a template showing the packet's overall syntax, followed by an
23272 explanation of the packet's meaning. We include spaces in some of the
23273 templates for clarity; these are not part of the packet's syntax. No
23274 @value{GDBN} packet uses spaces to separate its components.
23276 Here are the currently defined query and set packets:
23281 @cindex current thread, remote request
23282 @cindex @samp{qC} packet
23283 Return the current thread id.
23288 Where @var{pid} is an unsigned hexadecimal process id.
23289 @item @r{(anything else)}
23290 Any other reply implies the old pid.
23293 @item qCRC:@var{addr},@var{length}
23294 @cindex CRC of memory block, remote request
23295 @cindex @samp{qCRC} packet
23296 Compute the CRC checksum of a block of memory.
23300 An error (such as memory fault)
23301 @item C @var{crc32}
23302 The specified memory region's checksum is @var{crc32}.
23306 @itemx qsThreadInfo
23307 @cindex list active threads, remote request
23308 @cindex @samp{qfThreadInfo} packet
23309 @cindex @samp{qsThreadInfo} packet
23310 Obtain a list of all active thread ids from the target (OS). Since there
23311 may be too many active threads to fit into one reply packet, this query
23312 works iteratively: it may require more than one query/reply sequence to
23313 obtain the entire list of threads. The first query of the sequence will
23314 be the @samp{qfThreadInfo} query; subsequent queries in the
23315 sequence will be the @samp{qsThreadInfo} query.
23317 NOTE: This packet replaces the @samp{qL} query (see below).
23323 @item m @var{id},@var{id}@dots{}
23324 a comma-separated list of thread ids
23326 (lower case letter @samp{L}) denotes end of list.
23329 In response to each query, the target will reply with a list of one or
23330 more thread ids, in big-endian unsigned hex, separated by commas.
23331 @value{GDBN} will respond to each reply with a request for more thread
23332 ids (using the @samp{qs} form of the query), until the target responds
23333 with @samp{l} (lower-case el, for @dfn{last}).
23335 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23336 @cindex get thread-local storage address, remote request
23337 @cindex @samp{qGetTLSAddr} packet
23338 Fetch the address associated with thread local storage specified
23339 by @var{thread-id}, @var{offset}, and @var{lm}.
23341 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23342 thread for which to fetch the TLS address.
23344 @var{offset} is the (big endian, hex encoded) offset associated with the
23345 thread local variable. (This offset is obtained from the debug
23346 information associated with the variable.)
23348 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
23349 the load module associated with the thread local storage. For example,
23350 a @sc{gnu}/Linux system will pass the link map address of the shared
23351 object associated with the thread local storage under consideration.
23352 Other operating environments may choose to represent the load module
23353 differently, so the precise meaning of this parameter will vary.
23357 @item @var{XX}@dots{}
23358 Hex encoded (big endian) bytes representing the address of the thread
23359 local storage requested.
23362 An error occurred. @var{nn} are hex digits.
23365 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
23368 @item qL @var{startflag} @var{threadcount} @var{nextthread}
23369 Obtain thread information from RTOS. Where: @var{startflag} (one hex
23370 digit) is one to indicate the first query and zero to indicate a
23371 subsequent query; @var{threadcount} (two hex digits) is the maximum
23372 number of threads the response packet can contain; and @var{nextthread}
23373 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
23374 returned in the response as @var{argthread}.
23376 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
23380 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
23381 Where: @var{count} (two hex digits) is the number of threads being
23382 returned; @var{done} (one hex digit) is zero to indicate more threads
23383 and one indicates no further threads; @var{argthreadid} (eight hex
23384 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
23385 is a sequence of thread IDs from the target. @var{threadid} (eight hex
23386 digits). See @code{remote.c:parse_threadlist_response()}.
23390 @cindex section offsets, remote request
23391 @cindex @samp{qOffsets} packet
23392 Get section offsets that the target used when re-locating the downloaded
23393 image. @emph{Note: while a @code{Bss} offset is included in the
23394 response, @value{GDBN} ignores this and instead applies the @code{Data}
23395 offset to the @code{Bss} section.}
23399 @item Text=@var{xxx};Data=@var{yyy};Bss=@var{zzz}
23402 @item qP @var{mode} @var{threadid}
23403 @cindex thread information, remote request
23404 @cindex @samp{qP} packet
23405 Returns information on @var{threadid}. Where: @var{mode} is a hex
23406 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
23408 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
23411 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
23413 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
23414 @cindex pass signals to inferior, remote request
23415 @cindex @samp{QPassSignals} packet
23416 @anchor{QPassSignals}
23417 Each listed @var{signal} should be passed directly to the inferior process.
23418 Signals are numbered identically to continue packets and stop replies
23419 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
23420 strictly greater than the previous item. These signals do not need to stop
23421 the inferior, or be reported to @value{GDBN}. All other signals should be
23422 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
23423 combine; any earlier @samp{QPassSignals} list is completely replaced by the
23424 new list. This packet improves performance when using @samp{handle
23425 @var{signal} nostop noprint pass}.
23430 The request succeeded.
23433 An error occurred. @var{nn} are hex digits.
23436 An empty reply indicates that @samp{QPassSignals} is not supported by
23440 Use of this packet is controlled by the @code{set remote pass-signals}
23441 command (@pxref{Remote Configuration, set remote pass-signals}).
23442 This packet is not probed by default; the remote stub must request it,
23443 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23445 @item qRcmd,@var{command}
23446 @cindex execute remote command, remote request
23447 @cindex @samp{qRcmd} packet
23448 @var{command} (hex encoded) is passed to the local interpreter for
23449 execution. Invalid commands should be reported using the output
23450 string. Before the final result packet, the target may also respond
23451 with a number of intermediate @samp{O@var{output}} console output
23452 packets. @emph{Implementors should note that providing access to a
23453 stubs's interpreter may have security implications}.
23458 A command response with no output.
23460 A command response with the hex encoded output string @var{OUTPUT}.
23462 Indicate a badly formed request.
23464 An empty reply indicates that @samp{qRcmd} is not recognized.
23467 (Note that the @code{qRcmd} packet's name is separated from the
23468 command by a @samp{,}, not a @samp{:}, contrary to the naming
23469 conventions above. Please don't use this packet as a model for new
23472 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
23473 @cindex supported packets, remote query
23474 @cindex features of the remote protocol
23475 @cindex @samp{qSupported} packet
23476 @anchor{qSupported}
23477 Tell the remote stub about features supported by @value{GDBN}, and
23478 query the stub for features it supports. This packet allows
23479 @value{GDBN} and the remote stub to take advantage of each others'
23480 features. @samp{qSupported} also consolidates multiple feature probes
23481 at startup, to improve @value{GDBN} performance---a single larger
23482 packet performs better than multiple smaller probe packets on
23483 high-latency links. Some features may enable behavior which must not
23484 be on by default, e.g.@: because it would confuse older clients or
23485 stubs. Other features may describe packets which could be
23486 automatically probed for, but are not. These features must be
23487 reported before @value{GDBN} will use them. This ``default
23488 unsupported'' behavior is not appropriate for all packets, but it
23489 helps to keep the initial connection time under control with new
23490 versions of @value{GDBN} which support increasing numbers of packets.
23494 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
23495 The stub supports or does not support each returned @var{stubfeature},
23496 depending on the form of each @var{stubfeature} (see below for the
23499 An empty reply indicates that @samp{qSupported} is not recognized,
23500 or that no features needed to be reported to @value{GDBN}.
23503 The allowed forms for each feature (either a @var{gdbfeature} in the
23504 @samp{qSupported} packet, or a @var{stubfeature} in the response)
23508 @item @var{name}=@var{value}
23509 The remote protocol feature @var{name} is supported, and associated
23510 with the specified @var{value}. The format of @var{value} depends
23511 on the feature, but it must not include a semicolon.
23513 The remote protocol feature @var{name} is supported, and does not
23514 need an associated value.
23516 The remote protocol feature @var{name} is not supported.
23518 The remote protocol feature @var{name} may be supported, and
23519 @value{GDBN} should auto-detect support in some other way when it is
23520 needed. This form will not be used for @var{gdbfeature} notifications,
23521 but may be used for @var{stubfeature} responses.
23524 Whenever the stub receives a @samp{qSupported} request, the
23525 supplied set of @value{GDBN} features should override any previous
23526 request. This allows @value{GDBN} to put the stub in a known
23527 state, even if the stub had previously been communicating with
23528 a different version of @value{GDBN}.
23530 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
23531 are defined yet. Stubs should ignore any unknown values for
23532 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
23533 packet supports receiving packets of unlimited length (earlier
23534 versions of @value{GDBN} may reject overly long responses). Values
23535 for @var{gdbfeature} may be defined in the future to let the stub take
23536 advantage of new features in @value{GDBN}, e.g.@: incompatible
23537 improvements in the remote protocol---support for unlimited length
23538 responses would be a @var{gdbfeature} example, if it were not implied by
23539 the @samp{qSupported} query. The stub's reply should be independent
23540 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
23541 describes all the features it supports, and then the stub replies with
23542 all the features it supports.
23544 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
23545 responses, as long as each response uses one of the standard forms.
23547 Some features are flags. A stub which supports a flag feature
23548 should respond with a @samp{+} form response. Other features
23549 require values, and the stub should respond with an @samp{=}
23552 Each feature has a default value, which @value{GDBN} will use if
23553 @samp{qSupported} is not available or if the feature is not mentioned
23554 in the @samp{qSupported} response. The default values are fixed; a
23555 stub is free to omit any feature responses that match the defaults.
23557 Not all features can be probed, but for those which can, the probing
23558 mechanism is useful: in some cases, a stub's internal
23559 architecture may not allow the protocol layer to know some information
23560 about the underlying target in advance. This is especially common in
23561 stubs which may be configured for multiple targets.
23563 These are the currently defined stub features and their properties:
23565 @multitable @columnfractions 0.25 0.2 0.2 0.2
23566 @c NOTE: The first row should be @headitem, but we do not yet require
23567 @c a new enough version of Texinfo (4.7) to use @headitem.
23569 @tab Value Required
23573 @item @samp{PacketSize}
23578 @item @samp{qXfer:auxv:read}
23583 @item @samp{qXfer:features:read}
23588 @item @samp{qXfer:memory-map:read}
23593 @item @samp{QPassSignals}
23600 These are the currently defined stub features, in more detail:
23603 @cindex packet size, remote protocol
23604 @item PacketSize=@var{bytes}
23605 The remote stub can accept packets up to at least @var{bytes} in
23606 length. @value{GDBN} will send packets up to this size for bulk
23607 transfers, and will never send larger packets. This is a limit on the
23608 data characters in the packet, including the frame and checksum.
23609 There is no trailing NUL byte in a remote protocol packet; if the stub
23610 stores packets in a NUL-terminated format, it should allow an extra
23611 byte in its buffer for the NUL. If this stub feature is not supported,
23612 @value{GDBN} guesses based on the size of the @samp{g} packet response.
23614 @item qXfer:auxv:read
23615 The remote stub understands the @samp{qXfer:auxv:read} packet
23616 (@pxref{qXfer auxiliary vector read}).
23618 @item qXfer:features:read
23619 The remote stub understands the @samp{qXfer:features:read} packet
23620 (@pxref{qXfer target description read}).
23622 @item qXfer:memory-map:read
23623 The remote stub understands the @samp{qXfer:memory-map:read} packet
23624 (@pxref{qXfer memory map read}).
23627 The remote stub understands the @samp{QPassSignals} packet
23628 (@pxref{QPassSignals}).
23633 @cindex symbol lookup, remote request
23634 @cindex @samp{qSymbol} packet
23635 Notify the target that @value{GDBN} is prepared to serve symbol lookup
23636 requests. Accept requests from the target for the values of symbols.
23641 The target does not need to look up any (more) symbols.
23642 @item qSymbol:@var{sym_name}
23643 The target requests the value of symbol @var{sym_name} (hex encoded).
23644 @value{GDBN} may provide the value by using the
23645 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
23649 @item qSymbol:@var{sym_value}:@var{sym_name}
23650 Set the value of @var{sym_name} to @var{sym_value}.
23652 @var{sym_name} (hex encoded) is the name of a symbol whose value the
23653 target has previously requested.
23655 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
23656 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
23662 The target does not need to look up any (more) symbols.
23663 @item qSymbol:@var{sym_name}
23664 The target requests the value of a new symbol @var{sym_name} (hex
23665 encoded). @value{GDBN} will continue to supply the values of symbols
23666 (if available), until the target ceases to request them.
23671 @xref{Tracepoint Packets}.
23673 @item qThreadExtraInfo,@var{id}
23674 @cindex thread attributes info, remote request
23675 @cindex @samp{qThreadExtraInfo} packet
23676 Obtain a printable string description of a thread's attributes from
23677 the target OS. @var{id} is a thread-id in big-endian hex. This
23678 string may contain anything that the target OS thinks is interesting
23679 for @value{GDBN} to tell the user about the thread. The string is
23680 displayed in @value{GDBN}'s @code{info threads} display. Some
23681 examples of possible thread extra info strings are @samp{Runnable}, or
23682 @samp{Blocked on Mutex}.
23686 @item @var{XX}@dots{}
23687 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
23688 comprising the printable string containing the extra information about
23689 the thread's attributes.
23692 (Note that the @code{qThreadExtraInfo} packet's name is separated from
23693 the command by a @samp{,}, not a @samp{:}, contrary to the naming
23694 conventions above. Please don't use this packet as a model for new
23702 @xref{Tracepoint Packets}.
23704 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
23705 @cindex read special object, remote request
23706 @cindex @samp{qXfer} packet
23707 @anchor{qXfer read}
23708 Read uninterpreted bytes from the target's special data area
23709 identified by the keyword @var{object}. Request @var{length} bytes
23710 starting at @var{offset} bytes into the data. The content and
23711 encoding of @var{annex} is specific to the object; it can supply
23712 additional details about what data to access.
23714 Here are the specific requests of this form defined so far. All
23715 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
23716 formats, listed below.
23719 @item qXfer:auxv:read::@var{offset},@var{length}
23720 @anchor{qXfer auxiliary vector read}
23721 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
23722 auxiliary vector}. Note @var{annex} must be empty.
23724 This packet is not probed by default; the remote stub must request it,
23725 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23727 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
23728 @anchor{qXfer target description read}
23729 Access the @dfn{target description}. @xref{Target Descriptions}. The
23730 annex specifies which XML document to access. The main description is
23731 always loaded from the @samp{target.xml} annex.
23733 This packet is not probed by default; the remote stub must request it,
23734 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23736 @item qXfer:memory-map:read::@var{offset},@var{length}
23737 @anchor{qXfer memory map read}
23738 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
23739 annex part of the generic @samp{qXfer} packet must be empty
23740 (@pxref{qXfer read}).
23742 This packet is not probed by default; the remote stub must request it,
23743 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23749 Data @var{data} (@pxref{Binary Data}) has been read from the
23750 target. There may be more data at a higher address (although
23751 it is permitted to return @samp{m} even for the last valid
23752 block of data, as long as at least one byte of data was read).
23753 @var{data} may have fewer bytes than the @var{length} in the
23757 Data @var{data} (@pxref{Binary Data}) has been read from the target.
23758 There is no more data to be read. @var{data} may have fewer bytes
23759 than the @var{length} in the request.
23762 The @var{offset} in the request is at the end of the data.
23763 There is no more data to be read.
23766 The request was malformed, or @var{annex} was invalid.
23769 The offset was invalid, or there was an error encountered reading the data.
23770 @var{nn} is a hex-encoded @code{errno} value.
23773 An empty reply indicates the @var{object} string was not recognized by
23774 the stub, or that the object does not support reading.
23777 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
23778 @cindex write data into object, remote request
23779 Write uninterpreted bytes into the target's special data area
23780 identified by the keyword @var{object}, starting at @var{offset} bytes
23781 into the data. @samp{@var{data}@dots{}} is the binary-encoded data
23782 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
23783 is specific to the object; it can supply additional details about what data
23786 No requests of this form are presently in use. This specification
23787 serves as a placeholder to document the common format that new
23788 specific request specifications ought to use.
23793 @var{nn} (hex encoded) is the number of bytes written.
23794 This may be fewer bytes than supplied in the request.
23797 The request was malformed, or @var{annex} was invalid.
23800 The offset was invalid, or there was an error encountered writing the data.
23801 @var{nn} is a hex-encoded @code{errno} value.
23804 An empty reply indicates the @var{object} string was not
23805 recognized by the stub, or that the object does not support writing.
23808 @item qXfer:@var{object}:@var{operation}:@dots{}
23809 Requests of this form may be added in the future. When a stub does
23810 not recognize the @var{object} keyword, or its support for
23811 @var{object} does not recognize the @var{operation} keyword, the stub
23812 must respond with an empty packet.
23816 @node Register Packet Format
23817 @section Register Packet Format
23819 The following @code{g}/@code{G} packets have previously been defined.
23820 In the below, some thirty-two bit registers are transferred as
23821 sixty-four bits. Those registers should be zero/sign extended (which?)
23822 to fill the space allocated. Register bytes are transferred in target
23823 byte order. The two nibbles within a register byte are transferred
23824 most-significant - least-significant.
23830 All registers are transferred as thirty-two bit quantities in the order:
23831 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
23832 registers; fsr; fir; fp.
23836 All registers are transferred as sixty-four bit quantities (including
23837 thirty-two bit registers such as @code{sr}). The ordering is the same
23842 @node Tracepoint Packets
23843 @section Tracepoint Packets
23844 @cindex tracepoint packets
23845 @cindex packets, tracepoint
23847 Here we describe the packets @value{GDBN} uses to implement
23848 tracepoints (@pxref{Tracepoints}).
23852 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
23853 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
23854 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
23855 the tracepoint is disabled. @var{step} is the tracepoint's step
23856 count, and @var{pass} is its pass count. If the trailing @samp{-} is
23857 present, further @samp{QTDP} packets will follow to specify this
23858 tracepoint's actions.
23863 The packet was understood and carried out.
23865 The packet was not recognized.
23868 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
23869 Define actions to be taken when a tracepoint is hit. @var{n} and
23870 @var{addr} must be the same as in the initial @samp{QTDP} packet for
23871 this tracepoint. This packet may only be sent immediately after
23872 another @samp{QTDP} packet that ended with a @samp{-}. If the
23873 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
23874 specifying more actions for this tracepoint.
23876 In the series of action packets for a given tracepoint, at most one
23877 can have an @samp{S} before its first @var{action}. If such a packet
23878 is sent, it and the following packets define ``while-stepping''
23879 actions. Any prior packets define ordinary actions --- that is, those
23880 taken when the tracepoint is first hit. If no action packet has an
23881 @samp{S}, then all the packets in the series specify ordinary
23882 tracepoint actions.
23884 The @samp{@var{action}@dots{}} portion of the packet is a series of
23885 actions, concatenated without separators. Each action has one of the
23891 Collect the registers whose bits are set in @var{mask}. @var{mask} is
23892 a hexadecimal number whose @var{i}'th bit is set if register number
23893 @var{i} should be collected. (The least significant bit is numbered
23894 zero.) Note that @var{mask} may be any number of digits long; it may
23895 not fit in a 32-bit word.
23897 @item M @var{basereg},@var{offset},@var{len}
23898 Collect @var{len} bytes of memory starting at the address in register
23899 number @var{basereg}, plus @var{offset}. If @var{basereg} is
23900 @samp{-1}, then the range has a fixed address: @var{offset} is the
23901 address of the lowest byte to collect. The @var{basereg},
23902 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
23903 values (the @samp{-1} value for @var{basereg} is a special case).
23905 @item X @var{len},@var{expr}
23906 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
23907 it directs. @var{expr} is an agent expression, as described in
23908 @ref{Agent Expressions}. Each byte of the expression is encoded as a
23909 two-digit hex number in the packet; @var{len} is the number of bytes
23910 in the expression (and thus one-half the number of hex digits in the
23915 Any number of actions may be packed together in a single @samp{QTDP}
23916 packet, as long as the packet does not exceed the maximum packet
23917 length (400 bytes, for many stubs). There may be only one @samp{R}
23918 action per tracepoint, and it must precede any @samp{M} or @samp{X}
23919 actions. Any registers referred to by @samp{M} and @samp{X} actions
23920 must be collected by a preceding @samp{R} action. (The
23921 ``while-stepping'' actions are treated as if they were attached to a
23922 separate tracepoint, as far as these restrictions are concerned.)
23927 The packet was understood and carried out.
23929 The packet was not recognized.
23932 @item QTFrame:@var{n}
23933 Select the @var{n}'th tracepoint frame from the buffer, and use the
23934 register and memory contents recorded there to answer subsequent
23935 request packets from @value{GDBN}.
23937 A successful reply from the stub indicates that the stub has found the
23938 requested frame. The response is a series of parts, concatenated
23939 without separators, describing the frame we selected. Each part has
23940 one of the following forms:
23944 The selected frame is number @var{n} in the trace frame buffer;
23945 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
23946 was no frame matching the criteria in the request packet.
23949 The selected trace frame records a hit of tracepoint number @var{t};
23950 @var{t} is a hexadecimal number.
23954 @item QTFrame:pc:@var{addr}
23955 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23956 currently selected frame whose PC is @var{addr};
23957 @var{addr} is a hexadecimal number.
23959 @item QTFrame:tdp:@var{t}
23960 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23961 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
23962 is a hexadecimal number.
23964 @item QTFrame:range:@var{start}:@var{end}
23965 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23966 currently selected frame whose PC is between @var{start} (inclusive)
23967 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
23970 @item QTFrame:outside:@var{start}:@var{end}
23971 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
23972 frame @emph{outside} the given range of addresses.
23975 Begin the tracepoint experiment. Begin collecting data from tracepoint
23976 hits in the trace frame buffer.
23979 End the tracepoint experiment. Stop collecting trace frames.
23982 Clear the table of tracepoints, and empty the trace frame buffer.
23984 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
23985 Establish the given ranges of memory as ``transparent''. The stub
23986 will answer requests for these ranges from memory's current contents,
23987 if they were not collected as part of the tracepoint hit.
23989 @value{GDBN} uses this to mark read-only regions of memory, like those
23990 containing program code. Since these areas never change, they should
23991 still have the same contents they did when the tracepoint was hit, so
23992 there's no reason for the stub to refuse to provide their contents.
23995 Ask the stub if there is a trace experiment running right now.
24000 There is no trace experiment running.
24002 There is a trace experiment running.
24009 @section Interrupts
24010 @cindex interrupts (remote protocol)
24012 When a program on the remote target is running, @value{GDBN} may
24013 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24014 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24015 setting (@pxref{set remotebreak}).
24017 The precise meaning of @code{BREAK} is defined by the transport
24018 mechanism and may, in fact, be undefined. @value{GDBN} does
24019 not currently define a @code{BREAK} mechanism for any of the network
24022 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24023 transport mechanisms. It is represented by sending the single byte
24024 @code{0x03} without any of the usual packet overhead described in
24025 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24026 transmitted as part of a packet, it is considered to be packet data
24027 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24028 (@pxref{X packet}), used for binary downloads, may include an unescaped
24029 @code{0x03} as part of its packet.
24031 Stubs are not required to recognize these interrupt mechanisms and the
24032 precise meaning associated with receipt of the interrupt is
24033 implementation defined. If the stub is successful at interrupting the
24034 running program, it is expected that it will send one of the Stop
24035 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24036 of successfully stopping the program. Interrupts received while the
24037 program is stopped will be discarded.
24042 Example sequence of a target being re-started. Notice how the restart
24043 does not get any direct output:
24048 @emph{target restarts}
24051 <- @code{T001:1234123412341234}
24055 Example sequence of a target being stepped by a single instruction:
24058 -> @code{G1445@dots{}}
24063 <- @code{T001:1234123412341234}
24067 <- @code{1455@dots{}}
24071 @node File-I/O Remote Protocol Extension
24072 @section File-I/O Remote Protocol Extension
24073 @cindex File-I/O remote protocol extension
24076 * File-I/O Overview::
24077 * Protocol Basics::
24078 * The F Request Packet::
24079 * The F Reply Packet::
24080 * The Ctrl-C Message::
24082 * List of Supported Calls::
24083 * Protocol-specific Representation of Datatypes::
24085 * File-I/O Examples::
24088 @node File-I/O Overview
24089 @subsection File-I/O Overview
24090 @cindex file-i/o overview
24092 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24093 target to use the host's file system and console I/O to perform various
24094 system calls. System calls on the target system are translated into a
24095 remote protocol packet to the host system, which then performs the needed
24096 actions and returns a response packet to the target system.
24097 This simulates file system operations even on targets that lack file systems.
24099 The protocol is defined to be independent of both the host and target systems.
24100 It uses its own internal representation of datatypes and values. Both
24101 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24102 translating the system-dependent value representations into the internal
24103 protocol representations when data is transmitted.
24105 The communication is synchronous. A system call is possible only when
24106 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24107 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24108 the target is stopped to allow deterministic access to the target's
24109 memory. Therefore File-I/O is not interruptible by target signals. On
24110 the other hand, it is possible to interrupt File-I/O by a user interrupt
24111 (@samp{Ctrl-C}) within @value{GDBN}.
24113 The target's request to perform a host system call does not finish
24114 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24115 after finishing the system call, the target returns to continuing the
24116 previous activity (continue, step). No additional continue or step
24117 request from @value{GDBN} is required.
24120 (@value{GDBP}) continue
24121 <- target requests 'system call X'
24122 target is stopped, @value{GDBN} executes system call
24123 -> @value{GDBN} returns result
24124 ... target continues, @value{GDBN} returns to wait for the target
24125 <- target hits breakpoint and sends a Txx packet
24128 The protocol only supports I/O on the console and to regular files on
24129 the host file system. Character or block special devices, pipes,
24130 named pipes, sockets or any other communication method on the host
24131 system are not supported by this protocol.
24133 @node Protocol Basics
24134 @subsection Protocol Basics
24135 @cindex protocol basics, file-i/o
24137 The File-I/O protocol uses the @code{F} packet as the request as well
24138 as reply packet. Since a File-I/O system call can only occur when
24139 @value{GDBN} is waiting for a response from the continuing or stepping target,
24140 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24141 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24142 This @code{F} packet contains all information needed to allow @value{GDBN}
24143 to call the appropriate host system call:
24147 A unique identifier for the requested system call.
24150 All parameters to the system call. Pointers are given as addresses
24151 in the target memory address space. Pointers to strings are given as
24152 pointer/length pair. Numerical values are given as they are.
24153 Numerical control flags are given in a protocol-specific representation.
24157 At this point, @value{GDBN} has to perform the following actions.
24161 If the parameters include pointer values to data needed as input to a
24162 system call, @value{GDBN} requests this data from the target with a
24163 standard @code{m} packet request. This additional communication has to be
24164 expected by the target implementation and is handled as any other @code{m}
24168 @value{GDBN} translates all value from protocol representation to host
24169 representation as needed. Datatypes are coerced into the host types.
24172 @value{GDBN} calls the system call.
24175 It then coerces datatypes back to protocol representation.
24178 If the system call is expected to return data in buffer space specified
24179 by pointer parameters to the call, the data is transmitted to the
24180 target using a @code{M} or @code{X} packet. This packet has to be expected
24181 by the target implementation and is handled as any other @code{M} or @code{X}
24186 Eventually @value{GDBN} replies with another @code{F} packet which contains all
24187 necessary information for the target to continue. This at least contains
24194 @code{errno}, if has been changed by the system call.
24201 After having done the needed type and value coercion, the target continues
24202 the latest continue or step action.
24204 @node The F Request Packet
24205 @subsection The @code{F} Request Packet
24206 @cindex file-i/o request packet
24207 @cindex @code{F} request packet
24209 The @code{F} request packet has the following format:
24212 @item F@var{call-id},@var{parameter@dots{}}
24214 @var{call-id} is the identifier to indicate the host system call to be called.
24215 This is just the name of the function.
24217 @var{parameter@dots{}} are the parameters to the system call.
24218 Parameters are hexadecimal integer values, either the actual values in case
24219 of scalar datatypes, pointers to target buffer space in case of compound
24220 datatypes and unspecified memory areas, or pointer/length pairs in case
24221 of string parameters. These are appended to the @var{call-id} as a
24222 comma-delimited list. All values are transmitted in ASCII
24223 string representation, pointer/length pairs separated by a slash.
24229 @node The F Reply Packet
24230 @subsection The @code{F} Reply Packet
24231 @cindex file-i/o reply packet
24232 @cindex @code{F} reply packet
24234 The @code{F} reply packet has the following format:
24238 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific
24241 @var{retcode} is the return code of the system call as hexadecimal value.
24243 @var{errno} is the @code{errno} set by the call, in protocol-specific
24245 This parameter can be omitted if the call was successful.
24247 @var{Ctrl-C flag} is only sent if the user requested a break. In this
24248 case, @var{errno} must be sent as well, even if the call was successful.
24249 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
24256 or, if the call was interrupted before the host call has been performed:
24263 assuming 4 is the protocol-specific representation of @code{EINTR}.
24268 @node The Ctrl-C Message
24269 @subsection The @samp{Ctrl-C} Message
24270 @cindex ctrl-c message, in file-i/o protocol
24272 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
24273 reply packet (@pxref{The F Reply Packet}),
24274 the target should behave as if it had
24275 gotten a break message. The meaning for the target is ``system call
24276 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
24277 (as with a break message) and return to @value{GDBN} with a @code{T02}
24280 It's important for the target to know in which
24281 state the system call was interrupted. There are two possible cases:
24285 The system call hasn't been performed on the host yet.
24288 The system call on the host has been finished.
24292 These two states can be distinguished by the target by the value of the
24293 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
24294 call hasn't been performed. This is equivalent to the @code{EINTR} handling
24295 on POSIX systems. In any other case, the target may presume that the
24296 system call has been finished --- successfully or not --- and should behave
24297 as if the break message arrived right after the system call.
24299 @value{GDBN} must behave reliably. If the system call has not been called
24300 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
24301 @code{errno} in the packet. If the system call on the host has been finished
24302 before the user requests a break, the full action must be finished by
24303 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
24304 The @code{F} packet may only be sent when either nothing has happened
24305 or the full action has been completed.
24308 @subsection Console I/O
24309 @cindex console i/o as part of file-i/o
24311 By default and if not explicitly closed by the target system, the file
24312 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
24313 on the @value{GDBN} console is handled as any other file output operation
24314 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
24315 by @value{GDBN} so that after the target read request from file descriptor
24316 0 all following typing is buffered until either one of the following
24321 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
24323 system call is treated as finished.
24326 The user presses @key{RET}. This is treated as end of input with a trailing
24330 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
24331 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
24335 If the user has typed more characters than fit in the buffer given to
24336 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
24337 either another @code{read(0, @dots{})} is requested by the target, or debugging
24338 is stopped at the user's request.
24341 @node List of Supported Calls
24342 @subsection List of Supported Calls
24343 @cindex list of supported file-i/o calls
24360 @unnumberedsubsubsec open
24361 @cindex open, file-i/o system call
24366 int open(const char *pathname, int flags);
24367 int open(const char *pathname, int flags, mode_t mode);
24371 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
24374 @var{flags} is the bitwise @code{OR} of the following values:
24378 If the file does not exist it will be created. The host
24379 rules apply as far as file ownership and time stamps
24383 When used with @code{O_CREAT}, if the file already exists it is
24384 an error and open() fails.
24387 If the file already exists and the open mode allows
24388 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
24389 truncated to zero length.
24392 The file is opened in append mode.
24395 The file is opened for reading only.
24398 The file is opened for writing only.
24401 The file is opened for reading and writing.
24405 Other bits are silently ignored.
24409 @var{mode} is the bitwise @code{OR} of the following values:
24413 User has read permission.
24416 User has write permission.
24419 Group has read permission.
24422 Group has write permission.
24425 Others have read permission.
24428 Others have write permission.
24432 Other bits are silently ignored.
24435 @item Return value:
24436 @code{open} returns the new file descriptor or -1 if an error
24443 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
24446 @var{pathname} refers to a directory.
24449 The requested access is not allowed.
24452 @var{pathname} was too long.
24455 A directory component in @var{pathname} does not exist.
24458 @var{pathname} refers to a device, pipe, named pipe or socket.
24461 @var{pathname} refers to a file on a read-only filesystem and
24462 write access was requested.
24465 @var{pathname} is an invalid pointer value.
24468 No space on device to create the file.
24471 The process already has the maximum number of files open.
24474 The limit on the total number of files open on the system
24478 The call was interrupted by the user.
24484 @unnumberedsubsubsec close
24485 @cindex close, file-i/o system call
24494 @samp{Fclose,@var{fd}}
24496 @item Return value:
24497 @code{close} returns zero on success, or -1 if an error occurred.
24503 @var{fd} isn't a valid open file descriptor.
24506 The call was interrupted by the user.
24512 @unnumberedsubsubsec read
24513 @cindex read, file-i/o system call
24518 int read(int fd, void *buf, unsigned int count);
24522 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
24524 @item Return value:
24525 On success, the number of bytes read is returned.
24526 Zero indicates end of file. If count is zero, read
24527 returns zero as well. On error, -1 is returned.
24533 @var{fd} is not a valid file descriptor or is not open for
24537 @var{bufptr} is an invalid pointer value.
24540 The call was interrupted by the user.
24546 @unnumberedsubsubsec write
24547 @cindex write, file-i/o system call
24552 int write(int fd, const void *buf, unsigned int count);
24556 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
24558 @item Return value:
24559 On success, the number of bytes written are returned.
24560 Zero indicates nothing was written. On error, -1
24567 @var{fd} is not a valid file descriptor or is not open for
24571 @var{bufptr} is an invalid pointer value.
24574 An attempt was made to write a file that exceeds the
24575 host-specific maximum file size allowed.
24578 No space on device to write the data.
24581 The call was interrupted by the user.
24587 @unnumberedsubsubsec lseek
24588 @cindex lseek, file-i/o system call
24593 long lseek (int fd, long offset, int flag);
24597 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
24599 @var{flag} is one of:
24603 The offset is set to @var{offset} bytes.
24606 The offset is set to its current location plus @var{offset}
24610 The offset is set to the size of the file plus @var{offset}
24614 @item Return value:
24615 On success, the resulting unsigned offset in bytes from
24616 the beginning of the file is returned. Otherwise, a
24617 value of -1 is returned.
24623 @var{fd} is not a valid open file descriptor.
24626 @var{fd} is associated with the @value{GDBN} console.
24629 @var{flag} is not a proper value.
24632 The call was interrupted by the user.
24638 @unnumberedsubsubsec rename
24639 @cindex rename, file-i/o system call
24644 int rename(const char *oldpath, const char *newpath);
24648 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
24650 @item Return value:
24651 On success, zero is returned. On error, -1 is returned.
24657 @var{newpath} is an existing directory, but @var{oldpath} is not a
24661 @var{newpath} is a non-empty directory.
24664 @var{oldpath} or @var{newpath} is a directory that is in use by some
24668 An attempt was made to make a directory a subdirectory
24672 A component used as a directory in @var{oldpath} or new
24673 path is not a directory. Or @var{oldpath} is a directory
24674 and @var{newpath} exists but is not a directory.
24677 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
24680 No access to the file or the path of the file.
24684 @var{oldpath} or @var{newpath} was too long.
24687 A directory component in @var{oldpath} or @var{newpath} does not exist.
24690 The file is on a read-only filesystem.
24693 The device containing the file has no room for the new
24697 The call was interrupted by the user.
24703 @unnumberedsubsubsec unlink
24704 @cindex unlink, file-i/o system call
24709 int unlink(const char *pathname);
24713 @samp{Funlink,@var{pathnameptr}/@var{len}}
24715 @item Return value:
24716 On success, zero is returned. On error, -1 is returned.
24722 No access to the file or the path of the file.
24725 The system does not allow unlinking of directories.
24728 The file @var{pathname} cannot be unlinked because it's
24729 being used by another process.
24732 @var{pathnameptr} is an invalid pointer value.
24735 @var{pathname} was too long.
24738 A directory component in @var{pathname} does not exist.
24741 A component of the path is not a directory.
24744 The file is on a read-only filesystem.
24747 The call was interrupted by the user.
24753 @unnumberedsubsubsec stat/fstat
24754 @cindex fstat, file-i/o system call
24755 @cindex stat, file-i/o system call
24760 int stat(const char *pathname, struct stat *buf);
24761 int fstat(int fd, struct stat *buf);
24765 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
24766 @samp{Ffstat,@var{fd},@var{bufptr}}
24768 @item Return value:
24769 On success, zero is returned. On error, -1 is returned.
24775 @var{fd} is not a valid open file.
24778 A directory component in @var{pathname} does not exist or the
24779 path is an empty string.
24782 A component of the path is not a directory.
24785 @var{pathnameptr} is an invalid pointer value.
24788 No access to the file or the path of the file.
24791 @var{pathname} was too long.
24794 The call was interrupted by the user.
24800 @unnumberedsubsubsec gettimeofday
24801 @cindex gettimeofday, file-i/o system call
24806 int gettimeofday(struct timeval *tv, void *tz);
24810 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
24812 @item Return value:
24813 On success, 0 is returned, -1 otherwise.
24819 @var{tz} is a non-NULL pointer.
24822 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
24828 @unnumberedsubsubsec isatty
24829 @cindex isatty, file-i/o system call
24834 int isatty(int fd);
24838 @samp{Fisatty,@var{fd}}
24840 @item Return value:
24841 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
24847 The call was interrupted by the user.
24852 Note that the @code{isatty} call is treated as a special case: it returns
24853 1 to the target if the file descriptor is attached
24854 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
24855 would require implementing @code{ioctl} and would be more complex than
24860 @unnumberedsubsubsec system
24861 @cindex system, file-i/o system call
24866 int system(const char *command);
24870 @samp{Fsystem,@var{commandptr}/@var{len}}
24872 @item Return value:
24873 If @var{len} is zero, the return value indicates whether a shell is
24874 available. A zero return value indicates a shell is not available.
24875 For non-zero @var{len}, the value returned is -1 on error and the
24876 return status of the command otherwise. Only the exit status of the
24877 command is returned, which is extracted from the host's @code{system}
24878 return value by calling @code{WEXITSTATUS(retval)}. In case
24879 @file{/bin/sh} could not be executed, 127 is returned.
24885 The call was interrupted by the user.
24890 @value{GDBN} takes over the full task of calling the necessary host calls
24891 to perform the @code{system} call. The return value of @code{system} on
24892 the host is simplified before it's returned
24893 to the target. Any termination signal information from the child process
24894 is discarded, and the return value consists
24895 entirely of the exit status of the called command.
24897 Due to security concerns, the @code{system} call is by default refused
24898 by @value{GDBN}. The user has to allow this call explicitly with the
24899 @code{set remote system-call-allowed 1} command.
24902 @item set remote system-call-allowed
24903 @kindex set remote system-call-allowed
24904 Control whether to allow the @code{system} calls in the File I/O
24905 protocol for the remote target. The default is zero (disabled).
24907 @item show remote system-call-allowed
24908 @kindex show remote system-call-allowed
24909 Show whether the @code{system} calls are allowed in the File I/O
24913 @node Protocol-specific Representation of Datatypes
24914 @subsection Protocol-specific Representation of Datatypes
24915 @cindex protocol-specific representation of datatypes, in file-i/o protocol
24918 * Integral Datatypes::
24920 * Memory Transfer::
24925 @node Integral Datatypes
24926 @unnumberedsubsubsec Integral Datatypes
24927 @cindex integral datatypes, in file-i/o protocol
24929 The integral datatypes used in the system calls are @code{int},
24930 @code{unsigned int}, @code{long}, @code{unsigned long},
24931 @code{mode_t}, and @code{time_t}.
24933 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
24934 implemented as 32 bit values in this protocol.
24936 @code{long} and @code{unsigned long} are implemented as 64 bit types.
24938 @xref{Limits}, for corresponding MIN and MAX values (similar to those
24939 in @file{limits.h}) to allow range checking on host and target.
24941 @code{time_t} datatypes are defined as seconds since the Epoch.
24943 All integral datatypes transferred as part of a memory read or write of a
24944 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
24947 @node Pointer Values
24948 @unnumberedsubsubsec Pointer Values
24949 @cindex pointer values, in file-i/o protocol
24951 Pointers to target data are transmitted as they are. An exception
24952 is made for pointers to buffers for which the length isn't
24953 transmitted as part of the function call, namely strings. Strings
24954 are transmitted as a pointer/length pair, both as hex values, e.g.@:
24961 which is a pointer to data of length 18 bytes at position 0x1aaf.
24962 The length is defined as the full string length in bytes, including
24963 the trailing null byte. For example, the string @code{"hello world"}
24964 at address 0x123456 is transmitted as
24970 @node Memory Transfer
24971 @unnumberedsubsubsec Memory Transfer
24972 @cindex memory transfer, in file-i/o protocol
24974 Structured data which is transferred using a memory read or write (for
24975 example, a @code{struct stat}) is expected to be in a protocol-specific format
24976 with all scalar multibyte datatypes being big endian. Translation to
24977 this representation needs to be done both by the target before the @code{F}
24978 packet is sent, and by @value{GDBN} before
24979 it transfers memory to the target. Transferred pointers to structured
24980 data should point to the already-coerced data at any time.
24984 @unnumberedsubsubsec struct stat
24985 @cindex struct stat, in file-i/o protocol
24987 The buffer of type @code{struct stat} used by the target and @value{GDBN}
24988 is defined as follows:
24992 unsigned int st_dev; /* device */
24993 unsigned int st_ino; /* inode */
24994 mode_t st_mode; /* protection */
24995 unsigned int st_nlink; /* number of hard links */
24996 unsigned int st_uid; /* user ID of owner */
24997 unsigned int st_gid; /* group ID of owner */
24998 unsigned int st_rdev; /* device type (if inode device) */
24999 unsigned long st_size; /* total size, in bytes */
25000 unsigned long st_blksize; /* blocksize for filesystem I/O */
25001 unsigned long st_blocks; /* number of blocks allocated */
25002 time_t st_atime; /* time of last access */
25003 time_t st_mtime; /* time of last modification */
25004 time_t st_ctime; /* time of last change */
25008 The integral datatypes conform to the definitions given in the
25009 appropriate section (see @ref{Integral Datatypes}, for details) so this
25010 structure is of size 64 bytes.
25012 The values of several fields have a restricted meaning and/or
25018 A value of 0 represents a file, 1 the console.
25021 No valid meaning for the target. Transmitted unchanged.
25024 Valid mode bits are described in @ref{Constants}. Any other
25025 bits have currently no meaning for the target.
25030 No valid meaning for the target. Transmitted unchanged.
25035 These values have a host and file system dependent
25036 accuracy. Especially on Windows hosts, the file system may not
25037 support exact timing values.
25040 The target gets a @code{struct stat} of the above representation and is
25041 responsible for coercing it to the target representation before
25044 Note that due to size differences between the host, target, and protocol
25045 representations of @code{struct stat} members, these members could eventually
25046 get truncated on the target.
25048 @node struct timeval
25049 @unnumberedsubsubsec struct timeval
25050 @cindex struct timeval, in file-i/o protocol
25052 The buffer of type @code{struct timeval} used by the File-I/O protocol
25053 is defined as follows:
25057 time_t tv_sec; /* second */
25058 long tv_usec; /* microsecond */
25062 The integral datatypes conform to the definitions given in the
25063 appropriate section (see @ref{Integral Datatypes}, for details) so this
25064 structure is of size 8 bytes.
25067 @subsection Constants
25068 @cindex constants, in file-i/o protocol
25070 The following values are used for the constants inside of the
25071 protocol. @value{GDBN} and target are responsible for translating these
25072 values before and after the call as needed.
25083 @unnumberedsubsubsec Open Flags
25084 @cindex open flags, in file-i/o protocol
25086 All values are given in hexadecimal representation.
25098 @node mode_t Values
25099 @unnumberedsubsubsec mode_t Values
25100 @cindex mode_t values, in file-i/o protocol
25102 All values are given in octal representation.
25119 @unnumberedsubsubsec Errno Values
25120 @cindex errno values, in file-i/o protocol
25122 All values are given in decimal representation.
25147 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25148 any error value not in the list of supported error numbers.
25151 @unnumberedsubsubsec Lseek Flags
25152 @cindex lseek flags, in file-i/o protocol
25161 @unnumberedsubsubsec Limits
25162 @cindex limits, in file-i/o protocol
25164 All values are given in decimal representation.
25167 INT_MIN -2147483648
25169 UINT_MAX 4294967295
25170 LONG_MIN -9223372036854775808
25171 LONG_MAX 9223372036854775807
25172 ULONG_MAX 18446744073709551615
25175 @node File-I/O Examples
25176 @subsection File-I/O Examples
25177 @cindex file-i/o examples
25179 Example sequence of a write call, file descriptor 3, buffer is at target
25180 address 0x1234, 6 bytes should be written:
25183 <- @code{Fwrite,3,1234,6}
25184 @emph{request memory read from target}
25187 @emph{return "6 bytes written"}
25191 Example sequence of a read call, file descriptor 3, buffer is at target
25192 address 0x1234, 6 bytes should be read:
25195 <- @code{Fread,3,1234,6}
25196 @emph{request memory write to target}
25197 -> @code{X1234,6:XXXXXX}
25198 @emph{return "6 bytes read"}
25202 Example sequence of a read call, call fails on the host due to invalid
25203 file descriptor (@code{EBADF}):
25206 <- @code{Fread,3,1234,6}
25210 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
25214 <- @code{Fread,3,1234,6}
25219 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
25223 <- @code{Fread,3,1234,6}
25224 -> @code{X1234,6:XXXXXX}
25228 @node Memory Map Format
25229 @section Memory Map Format
25230 @cindex memory map format
25232 To be able to write into flash memory, @value{GDBN} needs to obtain a
25233 memory map from the target. This section describes the format of the
25236 The memory map is obtained using the @samp{qXfer:memory-map:read}
25237 (@pxref{qXfer memory map read}) packet and is an XML document that
25238 lists memory regions. The top-level structure of the document is shown below:
25241 <?xml version="1.0"?>
25242 <!DOCTYPE memory-map
25243 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
25244 "http://sourceware.org/gdb/gdb-memory-map.dtd">
25250 Each region can be either:
25255 A region of RAM starting at @var{addr} and extending for @var{length}
25259 <memory type="ram" start="@var{addr}" length="@var{length}"/>
25264 A region of read-only memory:
25267 <memory type="rom" start="@var{addr}" length="@var{length}"/>
25272 A region of flash memory, with erasure blocks @var{blocksize}
25276 <memory type="flash" start="@var{addr}" length="@var{length}">
25277 <property name="blocksize">@var{blocksize}</property>
25283 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
25284 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
25285 packets to write to addresses in such ranges.
25287 The formal DTD for memory map format is given below:
25290 <!-- ................................................... -->
25291 <!-- Memory Map XML DTD ................................ -->
25292 <!-- File: memory-map.dtd .............................. -->
25293 <!-- .................................... .............. -->
25294 <!-- memory-map.dtd -->
25295 <!-- memory-map: Root element with versioning -->
25296 <!ELEMENT memory-map (memory | property)>
25297 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
25298 <!ELEMENT memory (property)>
25299 <!-- memory: Specifies a memory region,
25300 and its type, or device. -->
25301 <!ATTLIST memory type CDATA #REQUIRED
25302 start CDATA #REQUIRED
25303 length CDATA #REQUIRED
25304 device CDATA #IMPLIED>
25305 <!-- property: Generic attribute tag -->
25306 <!ELEMENT property (#PCDATA | property)*>
25307 <!ATTLIST property name CDATA #REQUIRED>
25310 @include agentexpr.texi
25312 @node Target Descriptions
25313 @appendix Target Descriptions
25314 @cindex target descriptions
25316 @strong{Warning:} target descriptions are still under active development,
25317 and the contents and format may change between @value{GDBN} releases.
25318 The format is expected to stabilize in the future.
25320 One of the challenges of using @value{GDBN} to debug embedded systems
25321 is that there are so many minor variants of each processor
25322 architecture in use. It is common practice for vendors to start with
25323 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
25324 and then make changes to adapt it to a particular market niche. Some
25325 architectures have hundreds of variants, available from dozens of
25326 vendors. This leads to a number of problems:
25330 With so many different customized processors, it is difficult for
25331 the @value{GDBN} maintainers to keep up with the changes.
25333 Since individual variants may have short lifetimes or limited
25334 audiences, it may not be worthwhile to carry information about every
25335 variant in the @value{GDBN} source tree.
25337 When @value{GDBN} does support the architecture of the embedded system
25338 at hand, the task of finding the correct architecture name to give the
25339 @command{set architecture} command can be error-prone.
25342 To address these problems, the @value{GDBN} remote protocol allows a
25343 target system to not only identify itself to @value{GDBN}, but to
25344 actually describe its own features. This lets @value{GDBN} support
25345 processor variants it has never seen before --- to the extent that the
25346 descriptions are accurate, and that @value{GDBN} understands them.
25348 @value{GDBN} must be compiled with Expat support to support XML target
25349 descriptions. @xref{Expat}.
25352 * Retrieving Descriptions:: How descriptions are fetched from a target.
25353 * Target Description Format:: The contents of a target description.
25354 * Predefined Target Types:: Standard types available for target
25356 * Standard Target Features:: Features @value{GDBN} knows about.
25359 @node Retrieving Descriptions
25360 @section Retrieving Descriptions
25362 Target descriptions can be read from the target automatically, or
25363 specified by the user manually. The default behavior is to read the
25364 description from the target. @value{GDBN} retrieves it via the remote
25365 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
25366 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
25367 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
25368 XML document, of the form described in @ref{Target Description
25371 Alternatively, you can specify a file to read for the target description.
25372 If a file is set, the target will not be queried. The commands to
25373 specify a file are:
25376 @cindex set tdesc filename
25377 @item set tdesc filename @var{path}
25378 Read the target description from @var{path}.
25380 @cindex unset tdesc filename
25381 @item unset tdesc filename
25382 Do not read the XML target description from a file. @value{GDBN}
25383 will use the description supplied by the current target.
25385 @cindex show tdesc filename
25386 @item show tdesc filename
25387 Show the filename to read for a target description, if any.
25391 @node Target Description Format
25392 @section Target Description Format
25393 @cindex target descriptions, XML format
25395 A target description annex is an @uref{http://www.w3.org/XML/, XML}
25396 document which complies with the Document Type Definition provided in
25397 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
25398 means you can use generally available tools like @command{xmllint} to
25399 check that your feature descriptions are well-formed and valid.
25400 However, to help people unfamiliar with XML write descriptions for
25401 their targets, we also describe the grammar here.
25403 Target descriptions can identify the architecture of the remote target
25404 and (for some architectures) provide information about custom register
25405 sets. @value{GDBN} can use this information to autoconfigure for your
25406 target, or to warn you if you connect to an unsupported target.
25408 Here is a simple target description:
25412 <architecture>i386:x86-64</architecture>
25417 This minimal description only says that the target uses
25418 the x86-64 architecture.
25420 A target description has the following overall form, with [ ] marking
25421 optional elements and @dots{} marking repeatable elements. The elements
25422 are explained further below.
25425 <?xml version="1.0"?>
25426 <!DOCTYPE target SYSTEM "gdb-target.dtd">
25428 @r{[}@var{architecture}@r{]}
25429 @r{[}@var{feature}@dots{}@r{]}
25434 The description is generally insensitive to whitespace and line
25435 breaks, under the usual common-sense rules. The XML version
25436 declaration and document type declaration can generally be omitted
25437 (@value{GDBN} does not require them), but specifying them may be
25438 useful for XML validation tools.
25440 @subsection Inclusion
25441 @cindex target descriptions, inclusion
25444 @cindex <xi:include>
25447 It can sometimes be valuable to split a target description up into
25448 several different annexes, either for organizational purposes, or to
25449 share files between different possible target descriptions. You can
25450 divide a description into multiple files by replacing any element of
25451 the target description with an inclusion directive of the form:
25454 <xi:include href="@var{document}"/>
25458 When @value{GDBN} encounters an element of this form, it will retrieve
25459 the named XML @var{document}, and replace the inclusion directive with
25460 the contents of that document. If the current description was read
25461 using @samp{qXfer}, then so will be the included document;
25462 @var{document} will be interpreted as the name of an annex. If the
25463 current description was read from a file, @value{GDBN} will look for
25464 @var{document} as a file in the same directory where it found the
25465 original description.
25467 @subsection Architecture
25468 @cindex <architecture>
25470 An @samp{<architecture>} element has this form:
25473 <architecture>@var{arch}</architecture>
25476 @var{arch} is an architecture name from the same selection
25477 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
25478 Debugging Target}).
25480 @subsection Features
25483 Each @samp{<feature>} describes some logical portion of the target
25484 system. Features are currently used to describe available CPU
25485 registers and the types of their contents. A @samp{<feature>} element
25489 <feature name="@var{name}">
25490 @r{[}@var{type}@dots{}@r{]}
25496 Each feature's name should be unique within the description. The name
25497 of a feature does not matter unless @value{GDBN} has some special
25498 knowledge of the contents of that feature; if it does, the feature
25499 should have its standard name. @xref{Standard Target Features}.
25503 Any register's value is a collection of bits which @value{GDBN} must
25504 interpret. The default interpretation is a two's complement integer,
25505 but other types can be requested by name in the register description.
25506 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
25507 Target Types}), and the description can define additional composite types.
25509 Each type element must have an @samp{id} attribute, which gives
25510 a unique (within the containing @samp{<feature>}) name to the type.
25511 Types must be defined before they are used.
25514 Some targets offer vector registers, which can be treated as arrays
25515 of scalar elements. These types are written as @samp{<vector>} elements,
25516 specifying the array element type, @var{type}, and the number of elements,
25520 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
25524 If a register's value is usefully viewed in multiple ways, define it
25525 with a union type containing the useful representations. The
25526 @samp{<union>} element contains one or more @samp{<field>} elements,
25527 each of which has a @var{name} and a @var{type}:
25530 <union id="@var{id}">
25531 <field name="@var{name}" type="@var{type}"/>
25536 @subsection Registers
25539 Each register is represented as an element with this form:
25542 <reg name="@var{name}"
25543 bitsize="@var{size}"
25544 @r{[}regnum="@var{num}"@r{]}
25545 @r{[}save-restore="@var{save-restore}"@r{]}
25546 @r{[}type="@var{type}"@r{]}
25547 @r{[}group="@var{group}"@r{]}/>
25551 The components are as follows:
25556 The register's name; it must be unique within the target description.
25559 The register's size, in bits.
25562 The register's number. If omitted, a register's number is one greater
25563 than that of the previous register (either in the current feature or in
25564 a preceeding feature); the first register in the target description
25565 defaults to zero. This register number is used to read or write
25566 the register; e.g.@: it is used in the remote @code{p} and @code{P}
25567 packets, and registers appear in the @code{g} and @code{G} packets
25568 in order of increasing register number.
25571 Whether the register should be preserved across inferior function
25572 calls; this must be either @code{yes} or @code{no}. The default is
25573 @code{yes}, which is appropriate for most registers except for
25574 some system control registers; this is not related to the target's
25578 The type of the register. @var{type} may be a predefined type, a type
25579 defined in the current feature, or one of the special types @code{int}
25580 and @code{float}. @code{int} is an integer type of the correct size
25581 for @var{bitsize}, and @code{float} is a floating point type (in the
25582 architecture's normal floating point format) of the correct size for
25583 @var{bitsize}. The default is @code{int}.
25586 The register group to which this register belongs. @var{group} must
25587 be either @code{general}, @code{float}, or @code{vector}. If no
25588 @var{group} is specified, @value{GDBN} will not display the register
25589 in @code{info registers}.
25593 @node Predefined Target Types
25594 @section Predefined Target Types
25595 @cindex target descriptions, predefined types
25597 Type definitions in the self-description can build up composite types
25598 from basic building blocks, but can not define fundamental types. Instead,
25599 standard identifiers are provided by @value{GDBN} for the fundamental
25600 types. The currently supported types are:
25608 Signed integer types holding the specified number of bits.
25614 Unsigned integer types holding the specified number of bits.
25618 Pointers to unspecified code and data. The program counter and
25619 any dedicated return address register may be marked as code
25620 pointers; printing a code pointer converts it into a symbolic
25621 address. The stack pointer and any dedicated address registers
25622 may be marked as data pointers.
25625 Single precision IEEE floating point.
25628 Double precision IEEE floating point.
25631 The 12-byte extended precision format used by ARM FPA registers.
25635 @node Standard Target Features
25636 @section Standard Target Features
25637 @cindex target descriptions, standard features
25639 A target description must contain either no registers or all the
25640 target's registers. If the description contains no registers, then
25641 @value{GDBN} will assume a default register layout, selected based on
25642 the architecture. If the description contains any registers, the
25643 default layout will not be used; the standard registers must be
25644 described in the target description, in such a way that @value{GDBN}
25645 can recognize them.
25647 This is accomplished by giving specific names to feature elements
25648 which contain standard registers. @value{GDBN} will look for features
25649 with those names and verify that they contain the expected registers;
25650 if any known feature is missing required registers, or if any required
25651 feature is missing, @value{GDBN} will reject the target
25652 description. You can add additional registers to any of the
25653 standard features --- @value{GDBN} will display them just as if
25654 they were added to an unrecognized feature.
25656 This section lists the known features and their expected contents.
25657 Sample XML documents for these features are included in the
25658 @value{GDBN} source tree, in the directory @file{gdb/features}.
25660 Names recognized by @value{GDBN} should include the name of the
25661 company or organization which selected the name, and the overall
25662 architecture to which the feature applies; so e.g.@: the feature
25663 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
25665 The names of registers are not case sensitive for the purpose
25666 of recognizing standard features, but @value{GDBN} will only display
25667 registers using the capitalization used in the description.
25669 @subsection ARM Features
25670 @cindex target descriptions, ARM features
25672 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
25673 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
25674 @samp{lr}, @samp{pc}, and @samp{cpsr}.
25676 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
25677 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
25679 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
25680 it should contain at least registers @samp{wR0} through @samp{wR15} and
25681 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
25682 @samp{wCSSF}, and @samp{wCASF} registers are optional.
25696 % I think something like @colophon should be in texinfo. In the
25698 \long\def\colophon{\hbox to0pt{}\vfill
25699 \centerline{The body of this manual is set in}
25700 \centerline{\fontname\tenrm,}
25701 \centerline{with headings in {\bf\fontname\tenbf}}
25702 \centerline{and examples in {\tt\fontname\tentt}.}
25703 \centerline{{\it\fontname\tenit\/},}
25704 \centerline{{\bf\fontname\tenbf}, and}
25705 \centerline{{\sl\fontname\tensl\/}}
25706 \centerline{are used for emphasis.}\vfill}
25708 % Blame: doc@cygnus.com, 1991.