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{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}). @xref{Conditions, ,Break conditions}.
2921 For remote targets, you can restrict the number of hardware
2922 breakpoints @value{GDBN} will use, see @ref{set remote
2923 hardware-breakpoint-limit}.
2927 @item thbreak @var{args}
2928 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2929 are the same as for the @code{hbreak} command and the breakpoint is set in
2930 the same way. However, like the @code{tbreak} command,
2931 the breakpoint is automatically deleted after the
2932 first time your program stops there. Also, like the @code{hbreak}
2933 command, the breakpoint requires hardware support and some target hardware
2934 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2935 See also @ref{Conditions, ,Break conditions}.
2938 @cindex regular expression
2939 @cindex breakpoints in functions matching a regexp
2940 @cindex set breakpoints in many functions
2941 @item rbreak @var{regex}
2942 Set breakpoints on all functions matching the regular expression
2943 @var{regex}. This command sets an unconditional breakpoint on all
2944 matches, printing a list of all breakpoints it set. Once these
2945 breakpoints are set, they are treated just like the breakpoints set with
2946 the @code{break} command. You can delete them, disable them, or make
2947 them conditional the same way as any other breakpoint.
2949 The syntax of the regular expression is the standard one used with tools
2950 like @file{grep}. Note that this is different from the syntax used by
2951 shells, so for instance @code{foo*} matches all functions that include
2952 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2953 @code{.*} leading and trailing the regular expression you supply, so to
2954 match only functions that begin with @code{foo}, use @code{^foo}.
2956 @cindex non-member C@t{++} functions, set breakpoint in
2957 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2958 breakpoints on overloaded functions that are not members of any special
2961 @cindex set breakpoints on all functions
2962 The @code{rbreak} command can be used to set breakpoints in
2963 @strong{all} the functions in a program, like this:
2966 (@value{GDBP}) rbreak .
2969 @kindex info breakpoints
2970 @cindex @code{$_} and @code{info breakpoints}
2971 @item info breakpoints @r{[}@var{n}@r{]}
2972 @itemx info break @r{[}@var{n}@r{]}
2973 @itemx info watchpoints @r{[}@var{n}@r{]}
2974 Print a table of all breakpoints, watchpoints, and catchpoints set and
2975 not deleted. Optional argument @var{n} means print information only
2976 about the specified breakpoint (or watchpoint or catchpoint). For
2977 each breakpoint, following columns are printed:
2980 @item Breakpoint Numbers
2982 Breakpoint, watchpoint, or catchpoint.
2984 Whether the breakpoint is marked to be disabled or deleted when hit.
2985 @item Enabled or Disabled
2986 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2987 that are not enabled.
2989 Where the breakpoint is in your program, as a memory address. If the
2990 breakpoint is pending (see below for details) on a future load of a shared library, the address
2991 will be listed as @samp{<PENDING>}.
2993 Where the breakpoint is in the source for your program, as a file and
2994 line number. For a pending breakpoint, the original string passed to
2995 the breakpoint command will be listed as it cannot be resolved until
2996 the appropriate shared library is loaded in the future.
3000 If a breakpoint is conditional, @code{info break} shows the condition on
3001 the line following the affected breakpoint; breakpoint commands, if any,
3002 are listed after that. A pending breakpoint is allowed to have a condition
3003 specified for it. The condition is not parsed for validity until a shared
3004 library is loaded that allows the pending breakpoint to resolve to a
3008 @code{info break} with a breakpoint
3009 number @var{n} as argument lists only that breakpoint. The
3010 convenience variable @code{$_} and the default examining-address for
3011 the @code{x} command are set to the address of the last breakpoint
3012 listed (@pxref{Memory, ,Examining memory}).
3015 @code{info break} displays a count of the number of times the breakpoint
3016 has been hit. This is especially useful in conjunction with the
3017 @code{ignore} command. You can ignore a large number of breakpoint
3018 hits, look at the breakpoint info to see how many times the breakpoint
3019 was hit, and then run again, ignoring one less than that number. This
3020 will get you quickly to the last hit of that breakpoint.
3023 @value{GDBN} allows you to set any number of breakpoints at the same place in
3024 your program. There is nothing silly or meaningless about this. When
3025 the breakpoints are conditional, this is even useful
3026 (@pxref{Conditions, ,Break conditions}).
3028 @cindex pending breakpoints
3029 If a specified breakpoint location cannot be found, it may be due to the fact
3030 that the location is in a shared library that is yet to be loaded. In such
3031 a case, you may want @value{GDBN} to create a special breakpoint (known as
3032 a @dfn{pending breakpoint}) that
3033 attempts to resolve itself in the future when an appropriate shared library
3036 Pending breakpoints are useful to set at the start of your
3037 @value{GDBN} session for locations that you know will be dynamically loaded
3038 later by the program being debugged. When shared libraries are loaded,
3039 a check is made to see if the load resolves any pending breakpoint locations.
3040 If a pending breakpoint location gets resolved,
3041 a regular breakpoint is created and the original pending breakpoint is removed.
3043 @value{GDBN} provides some additional commands for controlling pending
3046 @kindex set breakpoint pending
3047 @kindex show breakpoint pending
3049 @item set breakpoint pending auto
3050 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3051 location, it queries you whether a pending breakpoint should be created.
3053 @item set breakpoint pending on
3054 This indicates that an unrecognized breakpoint location should automatically
3055 result in a pending breakpoint being created.
3057 @item set breakpoint pending off
3058 This indicates that pending breakpoints are not to be created. Any
3059 unrecognized breakpoint location results in an error. This setting does
3060 not affect any pending breakpoints previously created.
3062 @item show breakpoint pending
3063 Show the current behavior setting for creating pending breakpoints.
3066 @cindex operations allowed on pending breakpoints
3067 Normal breakpoint operations apply to pending breakpoints as well. You may
3068 specify a condition for a pending breakpoint and/or commands to run when the
3069 breakpoint is reached. You can also enable or disable
3070 the pending breakpoint. When you specify a condition for a pending breakpoint,
3071 the parsing of the condition will be deferred until the point where the
3072 pending breakpoint location is resolved. Disabling a pending breakpoint
3073 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
3074 shared library load. When a pending breakpoint is re-enabled,
3075 @value{GDBN} checks to see if the location is already resolved.
3076 This is done because any number of shared library loads could have
3077 occurred since the time the breakpoint was disabled and one or more
3078 of these loads could resolve the location.
3080 @cindex automatic hardware breakpoints
3081 For some targets, @value{GDBN} can automatically decide if hardware or
3082 software breakpoints should be used, depending on whether the
3083 breakpoint address is read-only or read-write. This applies to
3084 breakpoints set with the @code{break} command as well as to internal
3085 breakpoints set by commands like @code{next} and @code{finish}. For
3086 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3089 You can control this automatic behaviour with the following commands::
3091 @kindex set breakpoint auto-hw
3092 @kindex show breakpoint auto-hw
3094 @item set breakpoint auto-hw on
3095 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3096 will try to use the target memory map to decide if software or hardware
3097 breakpoint must be used.
3099 @item set breakpoint auto-hw off
3100 This indicates @value{GDBN} should not automatically select breakpoint
3101 type. If the target provides a memory map, @value{GDBN} will warn when
3102 trying to set software breakpoint at a read-only address.
3106 @cindex negative breakpoint numbers
3107 @cindex internal @value{GDBN} breakpoints
3108 @value{GDBN} itself sometimes sets breakpoints in your program for
3109 special purposes, such as proper handling of @code{longjmp} (in C
3110 programs). These internal breakpoints are assigned negative numbers,
3111 starting with @code{-1}; @samp{info breakpoints} does not display them.
3112 You can see these breakpoints with the @value{GDBN} maintenance command
3113 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3116 @node Set Watchpoints
3117 @subsection Setting watchpoints
3119 @cindex setting watchpoints
3120 You can use a watchpoint to stop execution whenever the value of an
3121 expression changes, without having to predict a particular place where
3122 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3123 The expression may be as simple as the value of a single variable, or
3124 as complex as many variables combined by operators. Examples include:
3128 A reference to the value of a single variable.
3131 An address cast to an appropriate data type. For example,
3132 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3133 address (assuming an @code{int} occupies 4 bytes).
3136 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3137 expression can use any operators valid in the program's native
3138 language (@pxref{Languages}).
3141 @cindex software watchpoints
3142 @cindex hardware watchpoints
3143 Depending on your system, watchpoints may be implemented in software or
3144 hardware. @value{GDBN} does software watchpointing by single-stepping your
3145 program and testing the variable's value each time, which is hundreds of
3146 times slower than normal execution. (But this may still be worth it, to
3147 catch errors where you have no clue what part of your program is the
3150 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
3151 x86-based targets, @value{GDBN} includes support for hardware
3152 watchpoints, which do not slow down the running of your program.
3156 @item watch @var{expr}
3157 Set a watchpoint for an expression. @value{GDBN} will break when the
3158 expression @var{expr} is written into by the program and its value
3159 changes. The simplest (and the most popular) use of this command is
3160 to watch the value of a single variable:
3163 (@value{GDBP}) watch foo
3167 @item rwatch @var{expr}
3168 Set a watchpoint that will break when the value of @var{expr} is read
3172 @item awatch @var{expr}
3173 Set a watchpoint that will break when @var{expr} is either read from
3174 or written into by the program.
3176 @kindex info watchpoints @r{[}@var{n}@r{]}
3177 @item info watchpoints
3178 This command prints a list of watchpoints, breakpoints, and catchpoints;
3179 it is the same as @code{info break} (@pxref{Set Breaks}).
3182 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3183 watchpoints execute very quickly, and the debugger reports a change in
3184 value at the exact instruction where the change occurs. If @value{GDBN}
3185 cannot set a hardware watchpoint, it sets a software watchpoint, which
3186 executes more slowly and reports the change in value at the next
3187 @emph{statement}, not the instruction, after the change occurs.
3189 @cindex use only software watchpoints
3190 You can force @value{GDBN} to use only software watchpoints with the
3191 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3192 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3193 the underlying system supports them. (Note that hardware-assisted
3194 watchpoints that were set @emph{before} setting
3195 @code{can-use-hw-watchpoints} to zero will still use the hardware
3196 mechanism of watching expression values.)
3199 @item set can-use-hw-watchpoints
3200 @kindex set can-use-hw-watchpoints
3201 Set whether or not to use hardware watchpoints.
3203 @item show can-use-hw-watchpoints
3204 @kindex show can-use-hw-watchpoints
3205 Show the current mode of using hardware watchpoints.
3208 For remote targets, you can restrict the number of hardware
3209 watchpoints @value{GDBN} will use, see @ref{set remote
3210 hardware-breakpoint-limit}.
3212 When you issue the @code{watch} command, @value{GDBN} reports
3215 Hardware watchpoint @var{num}: @var{expr}
3219 if it was able to set a hardware watchpoint.
3221 Currently, the @code{awatch} and @code{rwatch} commands can only set
3222 hardware watchpoints, because accesses to data that don't change the
3223 value of the watched expression cannot be detected without examining
3224 every instruction as it is being executed, and @value{GDBN} does not do
3225 that currently. If @value{GDBN} finds that it is unable to set a
3226 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3227 will print a message like this:
3230 Expression cannot be implemented with read/access watchpoint.
3233 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3234 data type of the watched expression is wider than what a hardware
3235 watchpoint on the target machine can handle. For example, some systems
3236 can only watch regions that are up to 4 bytes wide; on such systems you
3237 cannot set hardware watchpoints for an expression that yields a
3238 double-precision floating-point number (which is typically 8 bytes
3239 wide). As a work-around, it might be possible to break the large region
3240 into a series of smaller ones and watch them with separate watchpoints.
3242 If you set too many hardware watchpoints, @value{GDBN} might be unable
3243 to insert all of them when you resume the execution of your program.
3244 Since the precise number of active watchpoints is unknown until such
3245 time as the program is about to be resumed, @value{GDBN} might not be
3246 able to warn you about this when you set the watchpoints, and the
3247 warning will be printed only when the program is resumed:
3250 Hardware watchpoint @var{num}: Could not insert watchpoint
3254 If this happens, delete or disable some of the watchpoints.
3256 Watching complex expressions that reference many variables can also
3257 exhaust the resources available for hardware-assisted watchpoints.
3258 That's because @value{GDBN} needs to watch every variable in the
3259 expression with separately allocated resources.
3261 The SPARClite DSU will generate traps when a program accesses some data
3262 or instruction address that is assigned to the debug registers. For the
3263 data addresses, DSU facilitates the @code{watch} command. However the
3264 hardware breakpoint registers can only take two data watchpoints, and
3265 both watchpoints must be the same kind. For example, you can set two
3266 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3267 @strong{or} two with @code{awatch} commands, but you cannot set one
3268 watchpoint with one command and the other with a different command.
3269 @value{GDBN} will reject the command if you try to mix watchpoints.
3270 Delete or disable unused watchpoint commands before setting new ones.
3272 If you call a function interactively using @code{print} or @code{call},
3273 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3274 kind of breakpoint or the call completes.
3276 @value{GDBN} automatically deletes watchpoints that watch local
3277 (automatic) variables, or expressions that involve such variables, when
3278 they go out of scope, that is, when the execution leaves the block in
3279 which these variables were defined. In particular, when the program
3280 being debugged terminates, @emph{all} local variables go out of scope,
3281 and so only watchpoints that watch global variables remain set. If you
3282 rerun the program, you will need to set all such watchpoints again. One
3283 way of doing that would be to set a code breakpoint at the entry to the
3284 @code{main} function and when it breaks, set all the watchpoints.
3287 @cindex watchpoints and threads
3288 @cindex threads and watchpoints
3289 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3290 usefulness. With the current watchpoint implementation, @value{GDBN}
3291 can only watch the value of an expression @emph{in a single thread}. If
3292 you are confident that the expression can only change due to the current
3293 thread's activity (and if you are also confident that no other thread
3294 can become current), then you can use watchpoints as usual. However,
3295 @value{GDBN} may not notice when a non-current thread's activity changes
3298 @c FIXME: this is almost identical to the previous paragraph.
3299 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3300 have only limited usefulness. If @value{GDBN} creates a software
3301 watchpoint, it can only watch the value of an expression @emph{in a
3302 single thread}. If you are confident that the expression can only
3303 change due to the current thread's activity (and if you are also
3304 confident that no other thread can become current), then you can use
3305 software watchpoints as usual. However, @value{GDBN} may not notice
3306 when a non-current thread's activity changes the expression. (Hardware
3307 watchpoints, in contrast, watch an expression in all threads.)
3310 @xref{set remote hardware-watchpoint-limit}.
3312 @node Set Catchpoints
3313 @subsection Setting catchpoints
3314 @cindex catchpoints, setting
3315 @cindex exception handlers
3316 @cindex event handling
3318 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3319 kinds of program events, such as C@t{++} exceptions or the loading of a
3320 shared library. Use the @code{catch} command to set a catchpoint.
3324 @item catch @var{event}
3325 Stop when @var{event} occurs. @var{event} can be any of the following:
3328 @cindex stop on C@t{++} exceptions
3329 The throwing of a C@t{++} exception.
3332 The catching of a C@t{++} exception.
3335 @cindex Ada exception catching
3336 @cindex catch Ada exceptions
3337 An Ada exception being raised. If an exception name is specified
3338 at the end of the command (eg @code{catch exception Program_Error}),
3339 the debugger will stop only when this specific exception is raised.
3340 Otherwise, the debugger stops execution when any Ada exception is raised.
3342 @item exception unhandled
3343 An exception that was raised but is not handled by the program.
3346 A failed Ada assertion.
3349 @cindex break on fork/exec
3350 A call to @code{exec}. This is currently only available for HP-UX.
3353 A call to @code{fork}. This is currently only available for HP-UX.
3356 A call to @code{vfork}. This is currently only available for HP-UX.
3359 @itemx load @var{libname}
3360 @cindex break on load/unload of shared library
3361 The dynamic loading of any shared library, or the loading of the library
3362 @var{libname}. This is currently only available for HP-UX.
3365 @itemx unload @var{libname}
3366 The unloading of any dynamically loaded shared library, or the unloading
3367 of the library @var{libname}. This is currently only available for HP-UX.
3370 @item tcatch @var{event}
3371 Set a catchpoint that is enabled only for one stop. The catchpoint is
3372 automatically deleted after the first time the event is caught.
3376 Use the @code{info break} command to list the current catchpoints.
3378 There are currently some limitations to C@t{++} exception handling
3379 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3383 If you call a function interactively, @value{GDBN} normally returns
3384 control to you when the function has finished executing. If the call
3385 raises an exception, however, the call may bypass the mechanism that
3386 returns control to you and cause your program either to abort or to
3387 simply continue running until it hits a breakpoint, catches a signal
3388 that @value{GDBN} is listening for, or exits. This is the case even if
3389 you set a catchpoint for the exception; catchpoints on exceptions are
3390 disabled within interactive calls.
3393 You cannot raise an exception interactively.
3396 You cannot install an exception handler interactively.
3399 @cindex raise exceptions
3400 Sometimes @code{catch} is not the best way to debug exception handling:
3401 if you need to know exactly where an exception is raised, it is better to
3402 stop @emph{before} the exception handler is called, since that way you
3403 can see the stack before any unwinding takes place. If you set a
3404 breakpoint in an exception handler instead, it may not be easy to find
3405 out where the exception was raised.
3407 To stop just before an exception handler is called, you need some
3408 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3409 raised by calling a library function named @code{__raise_exception}
3410 which has the following ANSI C interface:
3413 /* @var{addr} is where the exception identifier is stored.
3414 @var{id} is the exception identifier. */
3415 void __raise_exception (void **addr, void *id);
3419 To make the debugger catch all exceptions before any stack
3420 unwinding takes place, set a breakpoint on @code{__raise_exception}
3421 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3423 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3424 that depends on the value of @var{id}, you can stop your program when
3425 a specific exception is raised. You can use multiple conditional
3426 breakpoints to stop your program when any of a number of exceptions are
3431 @subsection Deleting breakpoints
3433 @cindex clearing breakpoints, watchpoints, catchpoints
3434 @cindex deleting breakpoints, watchpoints, catchpoints
3435 It is often necessary to eliminate a breakpoint, watchpoint, or
3436 catchpoint once it has done its job and you no longer want your program
3437 to stop there. This is called @dfn{deleting} the breakpoint. A
3438 breakpoint that has been deleted no longer exists; it is forgotten.
3440 With the @code{clear} command you can delete breakpoints according to
3441 where they are in your program. With the @code{delete} command you can
3442 delete individual breakpoints, watchpoints, or catchpoints by specifying
3443 their breakpoint numbers.
3445 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3446 automatically ignores breakpoints on the first instruction to be executed
3447 when you continue execution without changing the execution address.
3452 Delete any breakpoints at the next instruction to be executed in the
3453 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3454 the innermost frame is selected, this is a good way to delete a
3455 breakpoint where your program just stopped.
3457 @item clear @var{function}
3458 @itemx clear @var{filename}:@var{function}
3459 Delete any breakpoints set at entry to the named @var{function}.
3461 @item clear @var{linenum}
3462 @itemx clear @var{filename}:@var{linenum}
3463 Delete any breakpoints set at or within the code of the specified
3464 @var{linenum} of the specified @var{filename}.
3466 @cindex delete breakpoints
3468 @kindex d @r{(@code{delete})}
3469 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3470 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3471 ranges specified as arguments. If no argument is specified, delete all
3472 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3473 confirm off}). You can abbreviate this command as @code{d}.
3477 @subsection Disabling breakpoints
3479 @cindex enable/disable a breakpoint
3480 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3481 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3482 it had been deleted, but remembers the information on the breakpoint so
3483 that you can @dfn{enable} it again later.
3485 You disable and enable breakpoints, watchpoints, and catchpoints with
3486 the @code{enable} and @code{disable} commands, optionally specifying one
3487 or more breakpoint numbers as arguments. Use @code{info break} or
3488 @code{info watch} to print a list of breakpoints, watchpoints, and
3489 catchpoints if you do not know which numbers to use.
3491 A breakpoint, watchpoint, or catchpoint can have any of four different
3492 states of enablement:
3496 Enabled. The breakpoint stops your program. A breakpoint set
3497 with the @code{break} command starts out in this state.
3499 Disabled. The breakpoint has no effect on your program.
3501 Enabled once. The breakpoint stops your program, but then becomes
3504 Enabled for deletion. The breakpoint stops your program, but
3505 immediately after it does so it is deleted permanently. A breakpoint
3506 set with the @code{tbreak} command starts out in this state.
3509 You can use the following commands to enable or disable breakpoints,
3510 watchpoints, and catchpoints:
3514 @kindex dis @r{(@code{disable})}
3515 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3516 Disable the specified breakpoints---or all breakpoints, if none are
3517 listed. A disabled breakpoint has no effect but is not forgotten. All
3518 options such as ignore-counts, conditions and commands are remembered in
3519 case the breakpoint is enabled again later. You may abbreviate
3520 @code{disable} as @code{dis}.
3523 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3524 Enable the specified breakpoints (or all defined breakpoints). They
3525 become effective once again in stopping your program.
3527 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3528 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3529 of these breakpoints immediately after stopping your program.
3531 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3532 Enable the specified breakpoints to work once, then die. @value{GDBN}
3533 deletes any of these breakpoints as soon as your program stops there.
3534 Breakpoints set by the @code{tbreak} command start out in this state.
3537 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3538 @c confusing: tbreak is also initially enabled.
3539 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3540 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3541 subsequently, they become disabled or enabled only when you use one of
3542 the commands above. (The command @code{until} can set and delete a
3543 breakpoint of its own, but it does not change the state of your other
3544 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3548 @subsection Break conditions
3549 @cindex conditional breakpoints
3550 @cindex breakpoint conditions
3552 @c FIXME what is scope of break condition expr? Context where wanted?
3553 @c in particular for a watchpoint?
3554 The simplest sort of breakpoint breaks every time your program reaches a
3555 specified place. You can also specify a @dfn{condition} for a
3556 breakpoint. A condition is just a Boolean expression in your
3557 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3558 a condition evaluates the expression each time your program reaches it,
3559 and your program stops only if the condition is @emph{true}.
3561 This is the converse of using assertions for program validation; in that
3562 situation, you want to stop when the assertion is violated---that is,
3563 when the condition is false. In C, if you want to test an assertion expressed
3564 by the condition @var{assert}, you should set the condition
3565 @samp{! @var{assert}} on the appropriate breakpoint.
3567 Conditions are also accepted for watchpoints; you may not need them,
3568 since a watchpoint is inspecting the value of an expression anyhow---but
3569 it might be simpler, say, to just set a watchpoint on a variable name,
3570 and specify a condition that tests whether the new value is an interesting
3573 Break conditions can have side effects, and may even call functions in
3574 your program. This can be useful, for example, to activate functions
3575 that log program progress, or to use your own print functions to
3576 format special data structures. The effects are completely predictable
3577 unless there is another enabled breakpoint at the same address. (In
3578 that case, @value{GDBN} might see the other breakpoint first and stop your
3579 program without checking the condition of this one.) Note that
3580 breakpoint commands are usually more convenient and flexible than break
3582 purpose of performing side effects when a breakpoint is reached
3583 (@pxref{Break Commands, ,Breakpoint command lists}).
3585 Break conditions can be specified when a breakpoint is set, by using
3586 @samp{if} in the arguments to the @code{break} command. @xref{Set
3587 Breaks, ,Setting breakpoints}. They can also be changed at any time
3588 with the @code{condition} command.
3590 You can also use the @code{if} keyword with the @code{watch} command.
3591 The @code{catch} command does not recognize the @code{if} keyword;
3592 @code{condition} is the only way to impose a further condition on a
3597 @item condition @var{bnum} @var{expression}
3598 Specify @var{expression} as the break condition for breakpoint,
3599 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3600 breakpoint @var{bnum} stops your program only if the value of
3601 @var{expression} is true (nonzero, in C). When you use
3602 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3603 syntactic correctness, and to determine whether symbols in it have
3604 referents in the context of your breakpoint. If @var{expression} uses
3605 symbols not referenced in the context of the breakpoint, @value{GDBN}
3606 prints an error message:
3609 No symbol "foo" in current context.
3614 not actually evaluate @var{expression} at the time the @code{condition}
3615 command (or a command that sets a breakpoint with a condition, like
3616 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3618 @item condition @var{bnum}
3619 Remove the condition from breakpoint number @var{bnum}. It becomes
3620 an ordinary unconditional breakpoint.
3623 @cindex ignore count (of breakpoint)
3624 A special case of a breakpoint condition is to stop only when the
3625 breakpoint has been reached a certain number of times. This is so
3626 useful that there is a special way to do it, using the @dfn{ignore
3627 count} of the breakpoint. Every breakpoint has an ignore count, which
3628 is an integer. Most of the time, the ignore count is zero, and
3629 therefore has no effect. But if your program reaches a breakpoint whose
3630 ignore count is positive, then instead of stopping, it just decrements
3631 the ignore count by one and continues. As a result, if the ignore count
3632 value is @var{n}, the breakpoint does not stop the next @var{n} times
3633 your program reaches it.
3637 @item ignore @var{bnum} @var{count}
3638 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3639 The next @var{count} times the breakpoint is reached, your program's
3640 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3643 To make the breakpoint stop the next time it is reached, specify
3646 When you use @code{continue} to resume execution of your program from a
3647 breakpoint, you can specify an ignore count directly as an argument to
3648 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3649 Stepping,,Continuing and stepping}.
3651 If a breakpoint has a positive ignore count and a condition, the
3652 condition is not checked. Once the ignore count reaches zero,
3653 @value{GDBN} resumes checking the condition.
3655 You could achieve the effect of the ignore count with a condition such
3656 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3657 is decremented each time. @xref{Convenience Vars, ,Convenience
3661 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3664 @node Break Commands
3665 @subsection Breakpoint command lists
3667 @cindex breakpoint commands
3668 You can give any breakpoint (or watchpoint or catchpoint) a series of
3669 commands to execute when your program stops due to that breakpoint. For
3670 example, you might want to print the values of certain expressions, or
3671 enable other breakpoints.
3675 @kindex end@r{ (breakpoint commands)}
3676 @item commands @r{[}@var{bnum}@r{]}
3677 @itemx @dots{} @var{command-list} @dots{}
3679 Specify a list of commands for breakpoint number @var{bnum}. The commands
3680 themselves appear on the following lines. Type a line containing just
3681 @code{end} to terminate the commands.
3683 To remove all commands from a breakpoint, type @code{commands} and
3684 follow it immediately with @code{end}; that is, give no commands.
3686 With no @var{bnum} argument, @code{commands} refers to the last
3687 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3688 recently encountered).
3691 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3692 disabled within a @var{command-list}.
3694 You can use breakpoint commands to start your program up again. Simply
3695 use the @code{continue} command, or @code{step}, or any other command
3696 that resumes execution.
3698 Any other commands in the command list, after a command that resumes
3699 execution, are ignored. This is because any time you resume execution
3700 (even with a simple @code{next} or @code{step}), you may encounter
3701 another breakpoint---which could have its own command list, leading to
3702 ambiguities about which list to execute.
3705 If the first command you specify in a command list is @code{silent}, the
3706 usual message about stopping at a breakpoint is not printed. This may
3707 be desirable for breakpoints that are to print a specific message and
3708 then continue. If none of the remaining commands print anything, you
3709 see no sign that the breakpoint was reached. @code{silent} is
3710 meaningful only at the beginning of a breakpoint command list.
3712 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3713 print precisely controlled output, and are often useful in silent
3714 breakpoints. @xref{Output, ,Commands for controlled output}.
3716 For example, here is how you could use breakpoint commands to print the
3717 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3723 printf "x is %d\n",x
3728 One application for breakpoint commands is to compensate for one bug so
3729 you can test for another. Put a breakpoint just after the erroneous line
3730 of code, give it a condition to detect the case in which something
3731 erroneous has been done, and give it commands to assign correct values
3732 to any variables that need them. End with the @code{continue} command
3733 so that your program does not stop, and start with the @code{silent}
3734 command so that no output is produced. Here is an example:
3745 @node Breakpoint Menus
3746 @subsection Breakpoint menus
3748 @cindex symbol overloading
3750 Some programming languages (notably C@t{++} and Objective-C) permit a
3751 single function name
3752 to be defined several times, for application in different contexts.
3753 This is called @dfn{overloading}. When a function name is overloaded,
3754 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3755 a breakpoint. If you realize this is a problem, you can use
3756 something like @samp{break @var{function}(@var{types})} to specify which
3757 particular version of the function you want. Otherwise, @value{GDBN} offers
3758 you a menu of numbered choices for different possible breakpoints, and
3759 waits for your selection with the prompt @samp{>}. The first two
3760 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3761 sets a breakpoint at each definition of @var{function}, and typing
3762 @kbd{0} aborts the @code{break} command without setting any new
3765 For example, the following session excerpt shows an attempt to set a
3766 breakpoint at the overloaded symbol @code{String::after}.
3767 We choose three particular definitions of that function name:
3769 @c FIXME! This is likely to change to show arg type lists, at least
3772 (@value{GDBP}) b String::after
3775 [2] file:String.cc; line number:867
3776 [3] file:String.cc; line number:860
3777 [4] file:String.cc; line number:875
3778 [5] file:String.cc; line number:853
3779 [6] file:String.cc; line number:846
3780 [7] file:String.cc; line number:735
3782 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3783 Breakpoint 2 at 0xb344: file String.cc, line 875.
3784 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3785 Multiple breakpoints were set.
3786 Use the "delete" command to delete unwanted
3792 @c @ifclear BARETARGET
3793 @node Error in Breakpoints
3794 @subsection ``Cannot insert breakpoints''
3796 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3798 Under some operating systems, breakpoints cannot be used in a program if
3799 any other process is running that program. In this situation,
3800 attempting to run or continue a program with a breakpoint causes
3801 @value{GDBN} to print an error message:
3804 Cannot insert breakpoints.
3805 The same program may be running in another process.
3808 When this happens, you have three ways to proceed:
3812 Remove or disable the breakpoints, then continue.
3815 Suspend @value{GDBN}, and copy the file containing your program to a new
3816 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3817 that @value{GDBN} should run your program under that name.
3818 Then start your program again.
3821 Relink your program so that the text segment is nonsharable, using the
3822 linker option @samp{-N}. The operating system limitation may not apply
3823 to nonsharable executables.
3827 A similar message can be printed if you request too many active
3828 hardware-assisted breakpoints and watchpoints:
3830 @c FIXME: the precise wording of this message may change; the relevant
3831 @c source change is not committed yet (Sep 3, 1999).
3833 Stopped; cannot insert breakpoints.
3834 You may have requested too many hardware breakpoints and watchpoints.
3838 This message is printed when you attempt to resume the program, since
3839 only then @value{GDBN} knows exactly how many hardware breakpoints and
3840 watchpoints it needs to insert.
3842 When this message is printed, you need to disable or remove some of the
3843 hardware-assisted breakpoints and watchpoints, and then continue.
3845 @node Breakpoint related warnings
3846 @subsection ``Breakpoint address adjusted...''
3847 @cindex breakpoint address adjusted
3849 Some processor architectures place constraints on the addresses at
3850 which breakpoints may be placed. For architectures thus constrained,
3851 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3852 with the constraints dictated by the architecture.
3854 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3855 a VLIW architecture in which a number of RISC-like instructions may be
3856 bundled together for parallel execution. The FR-V architecture
3857 constrains the location of a breakpoint instruction within such a
3858 bundle to the instruction with the lowest address. @value{GDBN}
3859 honors this constraint by adjusting a breakpoint's address to the
3860 first in the bundle.
3862 It is not uncommon for optimized code to have bundles which contain
3863 instructions from different source statements, thus it may happen that
3864 a breakpoint's address will be adjusted from one source statement to
3865 another. Since this adjustment may significantly alter @value{GDBN}'s
3866 breakpoint related behavior from what the user expects, a warning is
3867 printed when the breakpoint is first set and also when the breakpoint
3870 A warning like the one below is printed when setting a breakpoint
3871 that's been subject to address adjustment:
3874 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3877 Such warnings are printed both for user settable and @value{GDBN}'s
3878 internal breakpoints. If you see one of these warnings, you should
3879 verify that a breakpoint set at the adjusted address will have the
3880 desired affect. If not, the breakpoint in question may be removed and
3881 other breakpoints may be set which will have the desired behavior.
3882 E.g., it may be sufficient to place the breakpoint at a later
3883 instruction. A conditional breakpoint may also be useful in some
3884 cases to prevent the breakpoint from triggering too often.
3886 @value{GDBN} will also issue a warning when stopping at one of these
3887 adjusted breakpoints:
3890 warning: Breakpoint 1 address previously adjusted from 0x00010414
3894 When this warning is encountered, it may be too late to take remedial
3895 action except in cases where the breakpoint is hit earlier or more
3896 frequently than expected.
3898 @node Continuing and Stepping
3899 @section Continuing and stepping
3903 @cindex resuming execution
3904 @dfn{Continuing} means resuming program execution until your program
3905 completes normally. In contrast, @dfn{stepping} means executing just
3906 one more ``step'' of your program, where ``step'' may mean either one
3907 line of source code, or one machine instruction (depending on what
3908 particular command you use). Either when continuing or when stepping,
3909 your program may stop even sooner, due to a breakpoint or a signal. (If
3910 it stops due to a signal, you may want to use @code{handle}, or use
3911 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3915 @kindex c @r{(@code{continue})}
3916 @kindex fg @r{(resume foreground execution)}
3917 @item continue @r{[}@var{ignore-count}@r{]}
3918 @itemx c @r{[}@var{ignore-count}@r{]}
3919 @itemx fg @r{[}@var{ignore-count}@r{]}
3920 Resume program execution, at the address where your program last stopped;
3921 any breakpoints set at that address are bypassed. The optional argument
3922 @var{ignore-count} allows you to specify a further number of times to
3923 ignore a breakpoint at this location; its effect is like that of
3924 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3926 The argument @var{ignore-count} is meaningful only when your program
3927 stopped due to a breakpoint. At other times, the argument to
3928 @code{continue} is ignored.
3930 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3931 debugged program is deemed to be the foreground program) are provided
3932 purely for convenience, and have exactly the same behavior as
3936 To resume execution at a different place, you can use @code{return}
3937 (@pxref{Returning, ,Returning from a function}) to go back to the
3938 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3939 different address}) to go to an arbitrary location in your program.
3941 A typical technique for using stepping is to set a breakpoint
3942 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3943 beginning of the function or the section of your program where a problem
3944 is believed to lie, run your program until it stops at that breakpoint,
3945 and then step through the suspect area, examining the variables that are
3946 interesting, until you see the problem happen.
3950 @kindex s @r{(@code{step})}
3952 Continue running your program until control reaches a different source
3953 line, then stop it and return control to @value{GDBN}. This command is
3954 abbreviated @code{s}.
3957 @c "without debugging information" is imprecise; actually "without line
3958 @c numbers in the debugging information". (gcc -g1 has debugging info but
3959 @c not line numbers). But it seems complex to try to make that
3960 @c distinction here.
3961 @emph{Warning:} If you use the @code{step} command while control is
3962 within a function that was compiled without debugging information,
3963 execution proceeds until control reaches a function that does have
3964 debugging information. Likewise, it will not step into a function which
3965 is compiled without debugging information. To step through functions
3966 without debugging information, use the @code{stepi} command, described
3970 The @code{step} command only stops at the first instruction of a source
3971 line. This prevents the multiple stops that could otherwise occur in
3972 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3973 to stop if a function that has debugging information is called within
3974 the line. In other words, @code{step} @emph{steps inside} any functions
3975 called within the line.
3977 Also, the @code{step} command only enters a function if there is line
3978 number information for the function. Otherwise it acts like the
3979 @code{next} command. This avoids problems when using @code{cc -gl}
3980 on MIPS machines. Previously, @code{step} entered subroutines if there
3981 was any debugging information about the routine.
3983 @item step @var{count}
3984 Continue running as in @code{step}, but do so @var{count} times. If a
3985 breakpoint is reached, or a signal not related to stepping occurs before
3986 @var{count} steps, stepping stops right away.
3989 @kindex n @r{(@code{next})}
3990 @item next @r{[}@var{count}@r{]}
3991 Continue to the next source line in the current (innermost) stack frame.
3992 This is similar to @code{step}, but function calls that appear within
3993 the line of code are executed without stopping. Execution stops when
3994 control reaches a different line of code at the original stack level
3995 that was executing when you gave the @code{next} command. This command
3996 is abbreviated @code{n}.
3998 An argument @var{count} is a repeat count, as for @code{step}.
4001 @c FIX ME!! Do we delete this, or is there a way it fits in with
4002 @c the following paragraph? --- Vctoria
4004 @c @code{next} within a function that lacks debugging information acts like
4005 @c @code{step}, but any function calls appearing within the code of the
4006 @c function are executed without stopping.
4008 The @code{next} command only stops at the first instruction of a
4009 source line. This prevents multiple stops that could otherwise occur in
4010 @code{switch} statements, @code{for} loops, etc.
4012 @kindex set step-mode
4014 @cindex functions without line info, and stepping
4015 @cindex stepping into functions with no line info
4016 @itemx set step-mode on
4017 The @code{set step-mode on} command causes the @code{step} command to
4018 stop at the first instruction of a function which contains no debug line
4019 information rather than stepping over it.
4021 This is useful in cases where you may be interested in inspecting the
4022 machine instructions of a function which has no symbolic info and do not
4023 want @value{GDBN} to automatically skip over this function.
4025 @item set step-mode off
4026 Causes the @code{step} command to step over any functions which contains no
4027 debug information. This is the default.
4029 @item show step-mode
4030 Show whether @value{GDBN} will stop in or step over functions without
4031 source line debug information.
4035 Continue running until just after function in the selected stack frame
4036 returns. Print the returned value (if any).
4038 Contrast this with the @code{return} command (@pxref{Returning,
4039 ,Returning from a function}).
4042 @kindex u @r{(@code{until})}
4043 @cindex run until specified location
4046 Continue running until a source line past the current line, in the
4047 current stack frame, is reached. This command is used to avoid single
4048 stepping through a loop more than once. It is like the @code{next}
4049 command, except that when @code{until} encounters a jump, it
4050 automatically continues execution until the program counter is greater
4051 than the address of the jump.
4053 This means that when you reach the end of a loop after single stepping
4054 though it, @code{until} makes your program continue execution until it
4055 exits the loop. In contrast, a @code{next} command at the end of a loop
4056 simply steps back to the beginning of the loop, which forces you to step
4057 through the next iteration.
4059 @code{until} always stops your program if it attempts to exit the current
4062 @code{until} may produce somewhat counterintuitive results if the order
4063 of machine code does not match the order of the source lines. For
4064 example, in the following excerpt from a debugging session, the @code{f}
4065 (@code{frame}) command shows that execution is stopped at line
4066 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4070 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4072 (@value{GDBP}) until
4073 195 for ( ; argc > 0; NEXTARG) @{
4076 This happened because, for execution efficiency, the compiler had
4077 generated code for the loop closure test at the end, rather than the
4078 start, of the loop---even though the test in a C @code{for}-loop is
4079 written before the body of the loop. The @code{until} command appeared
4080 to step back to the beginning of the loop when it advanced to this
4081 expression; however, it has not really gone to an earlier
4082 statement---not in terms of the actual machine code.
4084 @code{until} with no argument works by means of single
4085 instruction stepping, and hence is slower than @code{until} with an
4088 @item until @var{location}
4089 @itemx u @var{location}
4090 Continue running your program until either the specified location is
4091 reached, or the current stack frame returns. @var{location} is any of
4092 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4093 ,Setting breakpoints}). This form of the command uses breakpoints, and
4094 hence is quicker than @code{until} without an argument. The specified
4095 location is actually reached only if it is in the current frame. This
4096 implies that @code{until} can be used to skip over recursive function
4097 invocations. For instance in the code below, if the current location is
4098 line @code{96}, issuing @code{until 99} will execute the program up to
4099 line @code{99} in the same invocation of factorial, i.e. after the inner
4100 invocations have returned.
4103 94 int factorial (int value)
4105 96 if (value > 1) @{
4106 97 value *= factorial (value - 1);
4113 @kindex advance @var{location}
4114 @itemx advance @var{location}
4115 Continue running the program up to the given @var{location}. An argument is
4116 required, which should be of the same form as arguments for the @code{break}
4117 command. Execution will also stop upon exit from the current stack
4118 frame. This command is similar to @code{until}, but @code{advance} will
4119 not skip over recursive function calls, and the target location doesn't
4120 have to be in the same frame as the current one.
4124 @kindex si @r{(@code{stepi})}
4126 @itemx stepi @var{arg}
4128 Execute one machine instruction, then stop and return to the debugger.
4130 It is often useful to do @samp{display/i $pc} when stepping by machine
4131 instructions. This makes @value{GDBN} automatically display the next
4132 instruction to be executed, each time your program stops. @xref{Auto
4133 Display,, Automatic display}.
4135 An argument is a repeat count, as in @code{step}.
4139 @kindex ni @r{(@code{nexti})}
4141 @itemx nexti @var{arg}
4143 Execute one machine instruction, but if it is a function call,
4144 proceed until the function returns.
4146 An argument is a repeat count, as in @code{next}.
4153 A signal is an asynchronous event that can happen in a program. The
4154 operating system defines the possible kinds of signals, and gives each
4155 kind a name and a number. For example, in Unix @code{SIGINT} is the
4156 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4157 @code{SIGSEGV} is the signal a program gets from referencing a place in
4158 memory far away from all the areas in use; @code{SIGALRM} occurs when
4159 the alarm clock timer goes off (which happens only if your program has
4160 requested an alarm).
4162 @cindex fatal signals
4163 Some signals, including @code{SIGALRM}, are a normal part of the
4164 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4165 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4166 program has not specified in advance some other way to handle the signal.
4167 @code{SIGINT} does not indicate an error in your program, but it is normally
4168 fatal so it can carry out the purpose of the interrupt: to kill the program.
4170 @value{GDBN} has the ability to detect any occurrence of a signal in your
4171 program. You can tell @value{GDBN} in advance what to do for each kind of
4174 @cindex handling signals
4175 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4176 @code{SIGALRM} be silently passed to your program
4177 (so as not to interfere with their role in the program's functioning)
4178 but to stop your program immediately whenever an error signal happens.
4179 You can change these settings with the @code{handle} command.
4182 @kindex info signals
4186 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4187 handle each one. You can use this to see the signal numbers of all
4188 the defined types of signals.
4190 @item info signals @var{sig}
4191 Similar, but print information only about the specified signal number.
4193 @code{info handle} is an alias for @code{info signals}.
4196 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4197 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4198 can be the number of a signal or its name (with or without the
4199 @samp{SIG} at the beginning); a list of signal numbers of the form
4200 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4201 known signals. Optional arguments @var{keywords}, described below,
4202 say what change to make.
4206 The keywords allowed by the @code{handle} command can be abbreviated.
4207 Their full names are:
4211 @value{GDBN} should not stop your program when this signal happens. It may
4212 still print a message telling you that the signal has come in.
4215 @value{GDBN} should stop your program when this signal happens. This implies
4216 the @code{print} keyword as well.
4219 @value{GDBN} should print a message when this signal happens.
4222 @value{GDBN} should not mention the occurrence of the signal at all. This
4223 implies the @code{nostop} keyword as well.
4227 @value{GDBN} should allow your program to see this signal; your program
4228 can handle the signal, or else it may terminate if the signal is fatal
4229 and not handled. @code{pass} and @code{noignore} are synonyms.
4233 @value{GDBN} should not allow your program to see this signal.
4234 @code{nopass} and @code{ignore} are synonyms.
4238 When a signal stops your program, the signal is not visible to the
4240 continue. Your program sees the signal then, if @code{pass} is in
4241 effect for the signal in question @emph{at that time}. In other words,
4242 after @value{GDBN} reports a signal, you can use the @code{handle}
4243 command with @code{pass} or @code{nopass} to control whether your
4244 program sees that signal when you continue.
4246 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4247 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4248 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4251 You can also use the @code{signal} command to prevent your program from
4252 seeing a signal, or cause it to see a signal it normally would not see,
4253 or to give it any signal at any time. For example, if your program stopped
4254 due to some sort of memory reference error, you might store correct
4255 values into the erroneous variables and continue, hoping to see more
4256 execution; but your program would probably terminate immediately as
4257 a result of the fatal signal once it saw the signal. To prevent this,
4258 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4262 @section Stopping and starting multi-thread programs
4264 When your program has multiple threads (@pxref{Threads,, Debugging
4265 programs with multiple threads}), you can choose whether to set
4266 breakpoints on all threads, or on a particular thread.
4269 @cindex breakpoints and threads
4270 @cindex thread breakpoints
4271 @kindex break @dots{} thread @var{threadno}
4272 @item break @var{linespec} thread @var{threadno}
4273 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4274 @var{linespec} specifies source lines; there are several ways of
4275 writing them, but the effect is always to specify some source line.
4277 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4278 to specify that you only want @value{GDBN} to stop the program when a
4279 particular thread reaches this breakpoint. @var{threadno} is one of the
4280 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4281 column of the @samp{info threads} display.
4283 If you do not specify @samp{thread @var{threadno}} when you set a
4284 breakpoint, the breakpoint applies to @emph{all} threads of your
4287 You can use the @code{thread} qualifier on conditional breakpoints as
4288 well; in this case, place @samp{thread @var{threadno}} before the
4289 breakpoint condition, like this:
4292 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4297 @cindex stopped threads
4298 @cindex threads, stopped
4299 Whenever your program stops under @value{GDBN} for any reason,
4300 @emph{all} threads of execution stop, not just the current thread. This
4301 allows you to examine the overall state of the program, including
4302 switching between threads, without worrying that things may change
4305 @cindex thread breakpoints and system calls
4306 @cindex system calls and thread breakpoints
4307 @cindex premature return from system calls
4308 There is an unfortunate side effect. If one thread stops for a
4309 breakpoint, or for some other reason, and another thread is blocked in a
4310 system call, then the system call may return prematurely. This is a
4311 consequence of the interaction between multiple threads and the signals
4312 that @value{GDBN} uses to implement breakpoints and other events that
4315 To handle this problem, your program should check the return value of
4316 each system call and react appropriately. This is good programming
4319 For example, do not write code like this:
4325 The call to @code{sleep} will return early if a different thread stops
4326 at a breakpoint or for some other reason.
4328 Instead, write this:
4333 unslept = sleep (unslept);
4336 A system call is allowed to return early, so the system is still
4337 conforming to its specification. But @value{GDBN} does cause your
4338 multi-threaded program to behave differently than it would without
4341 Also, @value{GDBN} uses internal breakpoints in the thread library to
4342 monitor certain events such as thread creation and thread destruction.
4343 When such an event happens, a system call in another thread may return
4344 prematurely, even though your program does not appear to stop.
4346 @cindex continuing threads
4347 @cindex threads, continuing
4348 Conversely, whenever you restart the program, @emph{all} threads start
4349 executing. @emph{This is true even when single-stepping} with commands
4350 like @code{step} or @code{next}.
4352 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4353 Since thread scheduling is up to your debugging target's operating
4354 system (not controlled by @value{GDBN}), other threads may
4355 execute more than one statement while the current thread completes a
4356 single step. Moreover, in general other threads stop in the middle of a
4357 statement, rather than at a clean statement boundary, when the program
4360 You might even find your program stopped in another thread after
4361 continuing or even single-stepping. This happens whenever some other
4362 thread runs into a breakpoint, a signal, or an exception before the
4363 first thread completes whatever you requested.
4365 On some OSes, you can lock the OS scheduler and thus allow only a single
4369 @item set scheduler-locking @var{mode}
4370 @cindex scheduler locking mode
4371 @cindex lock scheduler
4372 Set the scheduler locking mode. If it is @code{off}, then there is no
4373 locking and any thread may run at any time. If @code{on}, then only the
4374 current thread may run when the inferior is resumed. The @code{step}
4375 mode optimizes for single-stepping. It stops other threads from
4376 ``seizing the prompt'' by preempting the current thread while you are
4377 stepping. Other threads will only rarely (or never) get a chance to run
4378 when you step. They are more likely to run when you @samp{next} over a
4379 function call, and they are completely free to run when you use commands
4380 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4381 thread hits a breakpoint during its timeslice, they will never steal the
4382 @value{GDBN} prompt away from the thread that you are debugging.
4384 @item show scheduler-locking
4385 Display the current scheduler locking mode.
4390 @chapter Examining the Stack
4392 When your program has stopped, the first thing you need to know is where it
4393 stopped and how it got there.
4396 Each time your program performs a function call, information about the call
4398 That information includes the location of the call in your program,
4399 the arguments of the call,
4400 and the local variables of the function being called.
4401 The information is saved in a block of data called a @dfn{stack frame}.
4402 The stack frames are allocated in a region of memory called the @dfn{call
4405 When your program stops, the @value{GDBN} commands for examining the
4406 stack allow you to see all of this information.
4408 @cindex selected frame
4409 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4410 @value{GDBN} commands refer implicitly to the selected frame. In
4411 particular, whenever you ask @value{GDBN} for the value of a variable in
4412 your program, the value is found in the selected frame. There are
4413 special @value{GDBN} commands to select whichever frame you are
4414 interested in. @xref{Selection, ,Selecting a frame}.
4416 When your program stops, @value{GDBN} automatically selects the
4417 currently executing frame and describes it briefly, similar to the
4418 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4421 * Frames:: Stack frames
4422 * Backtrace:: Backtraces
4423 * Selection:: Selecting a frame
4424 * Frame Info:: Information on a frame
4429 @section Stack frames
4431 @cindex frame, definition
4433 The call stack is divided up into contiguous pieces called @dfn{stack
4434 frames}, or @dfn{frames} for short; each frame is the data associated
4435 with one call to one function. The frame contains the arguments given
4436 to the function, the function's local variables, and the address at
4437 which the function is executing.
4439 @cindex initial frame
4440 @cindex outermost frame
4441 @cindex innermost frame
4442 When your program is started, the stack has only one frame, that of the
4443 function @code{main}. This is called the @dfn{initial} frame or the
4444 @dfn{outermost} frame. Each time a function is called, a new frame is
4445 made. Each time a function returns, the frame for that function invocation
4446 is eliminated. If a function is recursive, there can be many frames for
4447 the same function. The frame for the function in which execution is
4448 actually occurring is called the @dfn{innermost} frame. This is the most
4449 recently created of all the stack frames that still exist.
4451 @cindex frame pointer
4452 Inside your program, stack frames are identified by their addresses. A
4453 stack frame consists of many bytes, each of which has its own address; each
4454 kind of computer has a convention for choosing one byte whose
4455 address serves as the address of the frame. Usually this address is kept
4456 in a register called the @dfn{frame pointer register}
4457 (@pxref{Registers, $fp}) while execution is going on in that frame.
4459 @cindex frame number
4460 @value{GDBN} assigns numbers to all existing stack frames, starting with
4461 zero for the innermost frame, one for the frame that called it,
4462 and so on upward. These numbers do not really exist in your program;
4463 they are assigned by @value{GDBN} to give you a way of designating stack
4464 frames in @value{GDBN} commands.
4466 @c The -fomit-frame-pointer below perennially causes hbox overflow
4467 @c underflow problems.
4468 @cindex frameless execution
4469 Some compilers provide a way to compile functions so that they operate
4470 without stack frames. (For example, the @value{NGCC} option
4472 @samp{-fomit-frame-pointer}
4474 generates functions without a frame.)
4475 This is occasionally done with heavily used library functions to save
4476 the frame setup time. @value{GDBN} has limited facilities for dealing
4477 with these function invocations. If the innermost function invocation
4478 has no stack frame, @value{GDBN} nevertheless regards it as though
4479 it had a separate frame, which is numbered zero as usual, allowing
4480 correct tracing of the function call chain. However, @value{GDBN} has
4481 no provision for frameless functions elsewhere in the stack.
4484 @kindex frame@r{, command}
4485 @cindex current stack frame
4486 @item frame @var{args}
4487 The @code{frame} command allows you to move from one stack frame to another,
4488 and to print the stack frame you select. @var{args} may be either the
4489 address of the frame or the stack frame number. Without an argument,
4490 @code{frame} prints the current stack frame.
4492 @kindex select-frame
4493 @cindex selecting frame silently
4495 The @code{select-frame} command allows you to move from one stack frame
4496 to another without printing the frame. This is the silent version of
4504 @cindex call stack traces
4505 A backtrace is a summary of how your program got where it is. It shows one
4506 line per frame, for many frames, starting with the currently executing
4507 frame (frame zero), followed by its caller (frame one), and on up the
4512 @kindex bt @r{(@code{backtrace})}
4515 Print a backtrace of the entire stack: one line per frame for all
4516 frames in the stack.
4518 You can stop the backtrace at any time by typing the system interrupt
4519 character, normally @kbd{Ctrl-c}.
4521 @item backtrace @var{n}
4523 Similar, but print only the innermost @var{n} frames.
4525 @item backtrace -@var{n}
4527 Similar, but print only the outermost @var{n} frames.
4529 @item backtrace full
4531 @itemx bt full @var{n}
4532 @itemx bt full -@var{n}
4533 Print the values of the local variables also. @var{n} specifies the
4534 number of frames to print, as described above.
4539 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4540 are additional aliases for @code{backtrace}.
4542 @cindex multiple threads, backtrace
4543 In a multi-threaded program, @value{GDBN} by default shows the
4544 backtrace only for the current thread. To display the backtrace for
4545 several or all of the threads, use the command @code{thread apply}
4546 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4547 apply all backtrace}, @value{GDBN} will display the backtrace for all
4548 the threads; this is handy when you debug a core dump of a
4549 multi-threaded program.
4551 Each line in the backtrace shows the frame number and the function name.
4552 The program counter value is also shown---unless you use @code{set
4553 print address off}. The backtrace also shows the source file name and
4554 line number, as well as the arguments to the function. The program
4555 counter value is omitted if it is at the beginning of the code for that
4558 Here is an example of a backtrace. It was made with the command
4559 @samp{bt 3}, so it shows the innermost three frames.
4563 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4565 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4566 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4568 (More stack frames follow...)
4573 The display for frame zero does not begin with a program counter
4574 value, indicating that your program has stopped at the beginning of the
4575 code for line @code{993} of @code{builtin.c}.
4577 @cindex value optimized out, in backtrace
4578 @cindex function call arguments, optimized out
4579 If your program was compiled with optimizations, some compilers will
4580 optimize away arguments passed to functions if those arguments are
4581 never used after the call. Such optimizations generate code that
4582 passes arguments through registers, but doesn't store those arguments
4583 in the stack frame. @value{GDBN} has no way of displaying such
4584 arguments in stack frames other than the innermost one. Here's what
4585 such a backtrace might look like:
4589 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4591 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4592 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4594 (More stack frames follow...)
4599 The values of arguments that were not saved in their stack frames are
4600 shown as @samp{<value optimized out>}.
4602 If you need to display the values of such optimized-out arguments,
4603 either deduce that from other variables whose values depend on the one
4604 you are interested in, or recompile without optimizations.
4606 @cindex backtrace beyond @code{main} function
4607 @cindex program entry point
4608 @cindex startup code, and backtrace
4609 Most programs have a standard user entry point---a place where system
4610 libraries and startup code transition into user code. For C this is
4611 @code{main}@footnote{
4612 Note that embedded programs (the so-called ``free-standing''
4613 environment) are not required to have a @code{main} function as the
4614 entry point. They could even have multiple entry points.}.
4615 When @value{GDBN} finds the entry function in a backtrace
4616 it will terminate the backtrace, to avoid tracing into highly
4617 system-specific (and generally uninteresting) code.
4619 If you need to examine the startup code, or limit the number of levels
4620 in a backtrace, you can change this behavior:
4623 @item set backtrace past-main
4624 @itemx set backtrace past-main on
4625 @kindex set backtrace
4626 Backtraces will continue past the user entry point.
4628 @item set backtrace past-main off
4629 Backtraces will stop when they encounter the user entry point. This is the
4632 @item show backtrace past-main
4633 @kindex show backtrace
4634 Display the current user entry point backtrace policy.
4636 @item set backtrace past-entry
4637 @itemx set backtrace past-entry on
4638 Backtraces will continue past the internal entry point of an application.
4639 This entry point is encoded by the linker when the application is built,
4640 and is likely before the user entry point @code{main} (or equivalent) is called.
4642 @item set backtrace past-entry off
4643 Backtraces will stop when they encounter the internal entry point of an
4644 application. This is the default.
4646 @item show backtrace past-entry
4647 Display the current internal entry point backtrace policy.
4649 @item set backtrace limit @var{n}
4650 @itemx set backtrace limit 0
4651 @cindex backtrace limit
4652 Limit the backtrace to @var{n} levels. A value of zero means
4655 @item show backtrace limit
4656 Display the current limit on backtrace levels.
4660 @section Selecting a frame
4662 Most commands for examining the stack and other data in your program work on
4663 whichever stack frame is selected at the moment. Here are the commands for
4664 selecting a stack frame; all of them finish by printing a brief description
4665 of the stack frame just selected.
4668 @kindex frame@r{, selecting}
4669 @kindex f @r{(@code{frame})}
4672 Select frame number @var{n}. Recall that frame zero is the innermost
4673 (currently executing) frame, frame one is the frame that called the
4674 innermost one, and so on. The highest-numbered frame is the one for
4677 @item frame @var{addr}
4679 Select the frame at address @var{addr}. This is useful mainly if the
4680 chaining of stack frames has been damaged by a bug, making it
4681 impossible for @value{GDBN} to assign numbers properly to all frames. In
4682 addition, this can be useful when your program has multiple stacks and
4683 switches between them.
4685 On the SPARC architecture, @code{frame} needs two addresses to
4686 select an arbitrary frame: a frame pointer and a stack pointer.
4688 On the MIPS and Alpha architecture, it needs two addresses: a stack
4689 pointer and a program counter.
4691 On the 29k architecture, it needs three addresses: a register stack
4692 pointer, a program counter, and a memory stack pointer.
4696 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4697 advances toward the outermost frame, to higher frame numbers, to frames
4698 that have existed longer. @var{n} defaults to one.
4701 @kindex do @r{(@code{down})}
4703 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4704 advances toward the innermost frame, to lower frame numbers, to frames
4705 that were created more recently. @var{n} defaults to one. You may
4706 abbreviate @code{down} as @code{do}.
4709 All of these commands end by printing two lines of output describing the
4710 frame. The first line shows the frame number, the function name, the
4711 arguments, and the source file and line number of execution in that
4712 frame. The second line shows the text of that source line.
4720 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4722 10 read_input_file (argv[i]);
4726 After such a printout, the @code{list} command with no arguments
4727 prints ten lines centered on the point of execution in the frame.
4728 You can also edit the program at the point of execution with your favorite
4729 editing program by typing @code{edit}.
4730 @xref{List, ,Printing source lines},
4734 @kindex down-silently
4736 @item up-silently @var{n}
4737 @itemx down-silently @var{n}
4738 These two commands are variants of @code{up} and @code{down},
4739 respectively; they differ in that they do their work silently, without
4740 causing display of the new frame. They are intended primarily for use
4741 in @value{GDBN} command scripts, where the output might be unnecessary and
4746 @section Information about a frame
4748 There are several other commands to print information about the selected
4754 When used without any argument, this command does not change which
4755 frame is selected, but prints a brief description of the currently
4756 selected stack frame. It can be abbreviated @code{f}. With an
4757 argument, this command is used to select a stack frame.
4758 @xref{Selection, ,Selecting a frame}.
4761 @kindex info f @r{(@code{info frame})}
4764 This command prints a verbose description of the selected stack frame,
4769 the address of the frame
4771 the address of the next frame down (called by this frame)
4773 the address of the next frame up (caller of this frame)
4775 the language in which the source code corresponding to this frame is written
4777 the address of the frame's arguments
4779 the address of the frame's local variables
4781 the program counter saved in it (the address of execution in the caller frame)
4783 which registers were saved in the frame
4786 @noindent The verbose description is useful when
4787 something has gone wrong that has made the stack format fail to fit
4788 the usual conventions.
4790 @item info frame @var{addr}
4791 @itemx info f @var{addr}
4792 Print a verbose description of the frame at address @var{addr}, without
4793 selecting that frame. The selected frame remains unchanged by this
4794 command. This requires the same kind of address (more than one for some
4795 architectures) that you specify in the @code{frame} command.
4796 @xref{Selection, ,Selecting a frame}.
4800 Print the arguments of the selected frame, each on a separate line.
4804 Print the local variables of the selected frame, each on a separate
4805 line. These are all variables (declared either static or automatic)
4806 accessible at the point of execution of the selected frame.
4809 @cindex catch exceptions, list active handlers
4810 @cindex exception handlers, how to list
4812 Print a list of all the exception handlers that are active in the
4813 current stack frame at the current point of execution. To see other
4814 exception handlers, visit the associated frame (using the @code{up},
4815 @code{down}, or @code{frame} commands); then type @code{info catch}.
4816 @xref{Set Catchpoints, , Setting catchpoints}.
4822 @chapter Examining Source Files
4824 @value{GDBN} can print parts of your program's source, since the debugging
4825 information recorded in the program tells @value{GDBN} what source files were
4826 used to build it. When your program stops, @value{GDBN} spontaneously prints
4827 the line where it stopped. Likewise, when you select a stack frame
4828 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4829 execution in that frame has stopped. You can print other portions of
4830 source files by explicit command.
4832 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4833 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4834 @value{GDBN} under @sc{gnu} Emacs}.
4837 * List:: Printing source lines
4838 * Edit:: Editing source files
4839 * Search:: Searching source files
4840 * Source Path:: Specifying source directories
4841 * Machine Code:: Source and machine code
4845 @section Printing source lines
4848 @kindex l @r{(@code{list})}
4849 To print lines from a source file, use the @code{list} command
4850 (abbreviated @code{l}). By default, ten lines are printed.
4851 There are several ways to specify what part of the file you want to print.
4853 Here are the forms of the @code{list} command most commonly used:
4856 @item list @var{linenum}
4857 Print lines centered around line number @var{linenum} in the
4858 current source file.
4860 @item list @var{function}
4861 Print lines centered around the beginning of function
4865 Print more lines. If the last lines printed were printed with a
4866 @code{list} command, this prints lines following the last lines
4867 printed; however, if the last line printed was a solitary line printed
4868 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4869 Stack}), this prints lines centered around that line.
4872 Print lines just before the lines last printed.
4875 @cindex @code{list}, how many lines to display
4876 By default, @value{GDBN} prints ten source lines with any of these forms of
4877 the @code{list} command. You can change this using @code{set listsize}:
4880 @kindex set listsize
4881 @item set listsize @var{count}
4882 Make the @code{list} command display @var{count} source lines (unless
4883 the @code{list} argument explicitly specifies some other number).
4885 @kindex show listsize
4887 Display the number of lines that @code{list} prints.
4890 Repeating a @code{list} command with @key{RET} discards the argument,
4891 so it is equivalent to typing just @code{list}. This is more useful
4892 than listing the same lines again. An exception is made for an
4893 argument of @samp{-}; that argument is preserved in repetition so that
4894 each repetition moves up in the source file.
4897 In general, the @code{list} command expects you to supply zero, one or two
4898 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4899 of writing them, but the effect is always to specify some source line.
4900 Here is a complete description of the possible arguments for @code{list}:
4903 @item list @var{linespec}
4904 Print lines centered around the line specified by @var{linespec}.
4906 @item list @var{first},@var{last}
4907 Print lines from @var{first} to @var{last}. Both arguments are
4910 @item list ,@var{last}
4911 Print lines ending with @var{last}.
4913 @item list @var{first},
4914 Print lines starting with @var{first}.
4917 Print lines just after the lines last printed.
4920 Print lines just before the lines last printed.
4923 As described in the preceding table.
4926 Here are the ways of specifying a single source line---all the
4931 Specifies line @var{number} of the current source file.
4932 When a @code{list} command has two linespecs, this refers to
4933 the same source file as the first linespec.
4936 Specifies the line @var{offset} lines after the last line printed.
4937 When used as the second linespec in a @code{list} command that has
4938 two, this specifies the line @var{offset} lines down from the
4942 Specifies the line @var{offset} lines before the last line printed.
4944 @item @var{filename}:@var{number}
4945 Specifies line @var{number} in the source file @var{filename}.
4947 @item @var{function}
4948 Specifies the line that begins the body of the function @var{function}.
4949 For example: in C, this is the line with the open brace.
4951 @item @var{filename}:@var{function}
4952 Specifies the line of the open-brace that begins the body of the
4953 function @var{function} in the file @var{filename}. You only need the
4954 file name with a function name to avoid ambiguity when there are
4955 identically named functions in different source files.
4957 @item *@var{address}
4958 Specifies the line containing the program address @var{address}.
4959 @var{address} may be any expression.
4963 @section Editing source files
4964 @cindex editing source files
4967 @kindex e @r{(@code{edit})}
4968 To edit the lines in a source file, use the @code{edit} command.
4969 The editing program of your choice
4970 is invoked with the current line set to
4971 the active line in the program.
4972 Alternatively, there are several ways to specify what part of the file you
4973 want to print if you want to see other parts of the program.
4975 Here are the forms of the @code{edit} command most commonly used:
4979 Edit the current source file at the active line number in the program.
4981 @item edit @var{number}
4982 Edit the current source file with @var{number} as the active line number.
4984 @item edit @var{function}
4985 Edit the file containing @var{function} at the beginning of its definition.
4987 @item edit @var{filename}:@var{number}
4988 Specifies line @var{number} in the source file @var{filename}.
4990 @item edit @var{filename}:@var{function}
4991 Specifies the line that begins the body of the
4992 function @var{function} in the file @var{filename}. You only need the
4993 file name with a function name to avoid ambiguity when there are
4994 identically named functions in different source files.
4996 @item edit *@var{address}
4997 Specifies the line containing the program address @var{address}.
4998 @var{address} may be any expression.
5001 @subsection Choosing your editor
5002 You can customize @value{GDBN} to use any editor you want
5004 The only restriction is that your editor (say @code{ex}), recognizes the
5005 following command-line syntax:
5007 ex +@var{number} file
5009 The optional numeric value +@var{number} specifies the number of the line in
5010 the file where to start editing.}.
5011 By default, it is @file{@value{EDITOR}}, but you can change this
5012 by setting the environment variable @code{EDITOR} before using
5013 @value{GDBN}. For example, to configure @value{GDBN} to use the
5014 @code{vi} editor, you could use these commands with the @code{sh} shell:
5020 or in the @code{csh} shell,
5022 setenv EDITOR /usr/bin/vi
5027 @section Searching source files
5028 @cindex searching source files
5030 There are two commands for searching through the current source file for a
5035 @kindex forward-search
5036 @item forward-search @var{regexp}
5037 @itemx search @var{regexp}
5038 The command @samp{forward-search @var{regexp}} checks each line,
5039 starting with the one following the last line listed, for a match for
5040 @var{regexp}. It lists the line that is found. You can use the
5041 synonym @samp{search @var{regexp}} or abbreviate the command name as
5044 @kindex reverse-search
5045 @item reverse-search @var{regexp}
5046 The command @samp{reverse-search @var{regexp}} checks each line, starting
5047 with the one before the last line listed and going backward, for a match
5048 for @var{regexp}. It lists the line that is found. You can abbreviate
5049 this command as @code{rev}.
5053 @section Specifying source directories
5056 @cindex directories for source files
5057 Executable programs sometimes do not record the directories of the source
5058 files from which they were compiled, just the names. Even when they do,
5059 the directories could be moved between the compilation and your debugging
5060 session. @value{GDBN} has a list of directories to search for source files;
5061 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5062 it tries all the directories in the list, in the order they are present
5063 in the list, until it finds a file with the desired name.
5065 For example, suppose an executable references the file
5066 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5067 @file{/mnt/cross}. The file is first looked up literally; if this
5068 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5069 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5070 message is printed. @value{GDBN} does not look up the parts of the
5071 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5072 Likewise, the subdirectories of the source path are not searched: if
5073 the source path is @file{/mnt/cross}, and the binary refers to
5074 @file{foo.c}, @value{GDBN} would not find it under
5075 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5077 Plain file names, relative file names with leading directories, file
5078 names containing dots, etc.@: are all treated as described above; for
5079 instance, if the source path is @file{/mnt/cross}, and the source file
5080 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5081 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5082 that---@file{/mnt/cross/foo.c}.
5084 Note that the executable search path is @emph{not} used to locate the
5087 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5088 any information it has cached about where source files are found and where
5089 each line is in the file.
5093 When you start @value{GDBN}, its source path includes only @samp{cdir}
5094 and @samp{cwd}, in that order.
5095 To add other directories, use the @code{directory} command.
5097 The search path is used to find both program source files and @value{GDBN}
5098 script files (read using the @samp{-command} option and @samp{source} command).
5100 In addition to the source path, @value{GDBN} provides a set of commands
5101 that manage a list of source path substitution rules. A @dfn{substitution
5102 rule} specifies how to rewrite source directories stored in the program's
5103 debug information in case the sources were moved to a different
5104 directory between compilation and debugging. A rule is made of
5105 two strings, the first specifying what needs to be rewritten in
5106 the path, and the second specifying how it should be rewritten.
5107 In @ref{set substitute-path}, we name these two parts @var{from} and
5108 @var{to} respectively. @value{GDBN} does a simple string replacement
5109 of @var{from} with @var{to} at the start of the directory part of the
5110 source file name, and uses that result instead of the original file
5111 name to look up the sources.
5113 Using the previous example, suppose the @file{foo-1.0} tree has been
5114 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5115 @value{GDBN} to replace @file{/usr/src} in all source path names with
5116 @file{/mnt/cross}. The first lookup will then be
5117 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5118 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5119 substitution rule, use the @code{set substitute-path} command
5120 (@pxref{set substitute-path}).
5122 To avoid unexpected substitution results, a rule is applied only if the
5123 @var{from} part of the directory name ends at a directory separator.
5124 For instance, a rule substituting @file{/usr/source} into
5125 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5126 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5127 is applied only at the beginning of the directory name, this rule will
5128 not be applied to @file{/root/usr/source/baz.c} either.
5130 In many cases, you can achieve the same result using the @code{directory}
5131 command. However, @code{set substitute-path} can be more efficient in
5132 the case where the sources are organized in a complex tree with multiple
5133 subdirectories. With the @code{directory} command, you need to add each
5134 subdirectory of your project. If you moved the entire tree while
5135 preserving its internal organization, then @code{set substitute-path}
5136 allows you to direct the debugger to all the sources with one single
5139 @code{set substitute-path} is also more than just a shortcut command.
5140 The source path is only used if the file at the original location no
5141 longer exists. On the other hand, @code{set substitute-path} modifies
5142 the debugger behavior to look at the rewritten location instead. So, if
5143 for any reason a source file that is not relevant to your executable is
5144 located at the original location, a substitution rule is the only
5145 method available to point @value{GDBN} at the new location.
5148 @item directory @var{dirname} @dots{}
5149 @item dir @var{dirname} @dots{}
5150 Add directory @var{dirname} to the front of the source path. Several
5151 directory names may be given to this command, separated by @samp{:}
5152 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5153 part of absolute file names) or
5154 whitespace. You may specify a directory that is already in the source
5155 path; this moves it forward, so @value{GDBN} searches it sooner.
5159 @vindex $cdir@r{, convenience variable}
5160 @vindex $cwd@r{, convenience variable}
5161 @cindex compilation directory
5162 @cindex current directory
5163 @cindex working directory
5164 @cindex directory, current
5165 @cindex directory, compilation
5166 You can use the string @samp{$cdir} to refer to the compilation
5167 directory (if one is recorded), and @samp{$cwd} to refer to the current
5168 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5169 tracks the current working directory as it changes during your @value{GDBN}
5170 session, while the latter is immediately expanded to the current
5171 directory at the time you add an entry to the source path.
5174 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5176 @c RET-repeat for @code{directory} is explicitly disabled, but since
5177 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5179 @item show directories
5180 @kindex show directories
5181 Print the source path: show which directories it contains.
5183 @anchor{set substitute-path}
5184 @item set substitute-path @var{from} @var{to}
5185 @kindex set substitute-path
5186 Define a source path substitution rule, and add it at the end of the
5187 current list of existing substitution rules. If a rule with the same
5188 @var{from} was already defined, then the old rule is also deleted.
5190 For example, if the file @file{/foo/bar/baz.c} was moved to
5191 @file{/mnt/cross/baz.c}, then the command
5194 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5198 will tell @value{GDBN} to replace @samp{/usr/src} with
5199 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5200 @file{baz.c} even though it was moved.
5202 In the case when more than one substitution rule have been defined,
5203 the rules are evaluated one by one in the order where they have been
5204 defined. The first one matching, if any, is selected to perform
5207 For instance, if we had entered the following commands:
5210 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5211 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5215 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5216 @file{/mnt/include/defs.h} by using the first rule. However, it would
5217 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5218 @file{/mnt/src/lib/foo.c}.
5221 @item unset substitute-path [path]
5222 @kindex unset substitute-path
5223 If a path is specified, search the current list of substitution rules
5224 for a rule that would rewrite that path. Delete that rule if found.
5225 A warning is emitted by the debugger if no rule could be found.
5227 If no path is specified, then all substitution rules are deleted.
5229 @item show substitute-path [path]
5230 @kindex show substitute-path
5231 If a path is specified, then print the source path substitution rule
5232 which would rewrite that path, if any.
5234 If no path is specified, then print all existing source path substitution
5239 If your source path is cluttered with directories that are no longer of
5240 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5241 versions of source. You can correct the situation as follows:
5245 Use @code{directory} with no argument to reset the source path to its default value.
5248 Use @code{directory} with suitable arguments to reinstall the
5249 directories you want in the source path. You can add all the
5250 directories in one command.
5254 @section Source and machine code
5255 @cindex source line and its code address
5257 You can use the command @code{info line} to map source lines to program
5258 addresses (and vice versa), and the command @code{disassemble} to display
5259 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5260 mode, the @code{info line} command causes the arrow to point to the
5261 line specified. Also, @code{info line} prints addresses in symbolic form as
5266 @item info line @var{linespec}
5267 Print the starting and ending addresses of the compiled code for
5268 source line @var{linespec}. You can specify source lines in any of
5269 the ways understood by the @code{list} command (@pxref{List, ,Printing
5273 For example, we can use @code{info line} to discover the location of
5274 the object code for the first line of function
5275 @code{m4_changequote}:
5277 @c FIXME: I think this example should also show the addresses in
5278 @c symbolic form, as they usually would be displayed.
5280 (@value{GDBP}) info line m4_changequote
5281 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5285 @cindex code address and its source line
5286 We can also inquire (using @code{*@var{addr}} as the form for
5287 @var{linespec}) what source line covers a particular address:
5289 (@value{GDBP}) info line *0x63ff
5290 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5293 @cindex @code{$_} and @code{info line}
5294 @cindex @code{x} command, default address
5295 @kindex x@r{(examine), and} info line
5296 After @code{info line}, the default address for the @code{x} command
5297 is changed to the starting address of the line, so that @samp{x/i} is
5298 sufficient to begin examining the machine code (@pxref{Memory,
5299 ,Examining memory}). Also, this address is saved as the value of the
5300 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5305 @cindex assembly instructions
5306 @cindex instructions, assembly
5307 @cindex machine instructions
5308 @cindex listing machine instructions
5310 This specialized command dumps a range of memory as machine
5311 instructions. The default memory range is the function surrounding the
5312 program counter of the selected frame. A single argument to this
5313 command is a program counter value; @value{GDBN} dumps the function
5314 surrounding this value. Two arguments specify a range of addresses
5315 (first inclusive, second exclusive) to dump.
5318 The following example shows the disassembly of a range of addresses of
5319 HP PA-RISC 2.0 code:
5322 (@value{GDBP}) disas 0x32c4 0x32e4
5323 Dump of assembler code from 0x32c4 to 0x32e4:
5324 0x32c4 <main+204>: addil 0,dp
5325 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5326 0x32cc <main+212>: ldil 0x3000,r31
5327 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5328 0x32d4 <main+220>: ldo 0(r31),rp
5329 0x32d8 <main+224>: addil -0x800,dp
5330 0x32dc <main+228>: ldo 0x588(r1),r26
5331 0x32e0 <main+232>: ldil 0x3000,r31
5332 End of assembler dump.
5335 Some architectures have more than one commonly-used set of instruction
5336 mnemonics or other syntax.
5338 For programs that were dynamically linked and use shared libraries,
5339 instructions that call functions or branch to locations in the shared
5340 libraries might show a seemingly bogus location---it's actually a
5341 location of the relocation table. On some architectures, @value{GDBN}
5342 might be able to resolve these to actual function names.
5345 @kindex set disassembly-flavor
5346 @cindex Intel disassembly flavor
5347 @cindex AT&T disassembly flavor
5348 @item set disassembly-flavor @var{instruction-set}
5349 Select the instruction set to use when disassembling the
5350 program via the @code{disassemble} or @code{x/i} commands.
5352 Currently this command is only defined for the Intel x86 family. You
5353 can set @var{instruction-set} to either @code{intel} or @code{att}.
5354 The default is @code{att}, the AT&T flavor used by default by Unix
5355 assemblers for x86-based targets.
5357 @kindex show disassembly-flavor
5358 @item show disassembly-flavor
5359 Show the current setting of the disassembly flavor.
5364 @chapter Examining Data
5366 @cindex printing data
5367 @cindex examining data
5370 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5371 @c document because it is nonstandard... Under Epoch it displays in a
5372 @c different window or something like that.
5373 The usual way to examine data in your program is with the @code{print}
5374 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5375 evaluates and prints the value of an expression of the language your
5376 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5377 Different Languages}).
5380 @item print @var{expr}
5381 @itemx print /@var{f} @var{expr}
5382 @var{expr} is an expression (in the source language). By default the
5383 value of @var{expr} is printed in a format appropriate to its data type;
5384 you can choose a different format by specifying @samp{/@var{f}}, where
5385 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5389 @itemx print /@var{f}
5390 @cindex reprint the last value
5391 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5392 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
5393 conveniently inspect the same value in an alternative format.
5396 A more low-level way of examining data is with the @code{x} command.
5397 It examines data in memory at a specified address and prints it in a
5398 specified format. @xref{Memory, ,Examining memory}.
5400 If you are interested in information about types, or about how the
5401 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5402 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5406 * Expressions:: Expressions
5407 * Variables:: Program variables
5408 * Arrays:: Artificial arrays
5409 * Output Formats:: Output formats
5410 * Memory:: Examining memory
5411 * Auto Display:: Automatic display
5412 * Print Settings:: Print settings
5413 * Value History:: Value history
5414 * Convenience Vars:: Convenience variables
5415 * Registers:: Registers
5416 * Floating Point Hardware:: Floating point hardware
5417 * Vector Unit:: Vector Unit
5418 * OS Information:: Auxiliary data provided by operating system
5419 * Memory Region Attributes:: Memory region attributes
5420 * Dump/Restore Files:: Copy between memory and a file
5421 * Core File Generation:: Cause a program dump its core
5422 * Character Sets:: Debugging programs that use a different
5423 character set than GDB does
5424 * Caching Remote Data:: Data caching for remote targets
5428 @section Expressions
5431 @code{print} and many other @value{GDBN} commands accept an expression and
5432 compute its value. Any kind of constant, variable or operator defined
5433 by the programming language you are using is valid in an expression in
5434 @value{GDBN}. This includes conditional expressions, function calls,
5435 casts, and string constants. It also includes preprocessor macros, if
5436 you compiled your program to include this information; see
5439 @cindex arrays in expressions
5440 @value{GDBN} supports array constants in expressions input by
5441 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5442 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5443 memory that is @code{malloc}ed in the target program.
5445 Because C is so widespread, most of the expressions shown in examples in
5446 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5447 Languages}, for information on how to use expressions in other
5450 In this section, we discuss operators that you can use in @value{GDBN}
5451 expressions regardless of your programming language.
5453 @cindex casts, in expressions
5454 Casts are supported in all languages, not just in C, because it is so
5455 useful to cast a number into a pointer in order to examine a structure
5456 at that address in memory.
5457 @c FIXME: casts supported---Mod2 true?
5459 @value{GDBN} supports these operators, in addition to those common
5460 to programming languages:
5464 @samp{@@} is a binary operator for treating parts of memory as arrays.
5465 @xref{Arrays, ,Artificial arrays}, for more information.
5468 @samp{::} allows you to specify a variable in terms of the file or
5469 function where it is defined. @xref{Variables, ,Program variables}.
5471 @cindex @{@var{type}@}
5472 @cindex type casting memory
5473 @cindex memory, viewing as typed object
5474 @cindex casts, to view memory
5475 @item @{@var{type}@} @var{addr}
5476 Refers to an object of type @var{type} stored at address @var{addr} in
5477 memory. @var{addr} may be any expression whose value is an integer or
5478 pointer (but parentheses are required around binary operators, just as in
5479 a cast). This construct is allowed regardless of what kind of data is
5480 normally supposed to reside at @var{addr}.
5484 @section Program variables
5486 The most common kind of expression to use is the name of a variable
5489 Variables in expressions are understood in the selected stack frame
5490 (@pxref{Selection, ,Selecting a frame}); they must be either:
5494 global (or file-static)
5501 visible according to the scope rules of the
5502 programming language from the point of execution in that frame
5505 @noindent This means that in the function
5520 you can examine and use the variable @code{a} whenever your program is
5521 executing within the function @code{foo}, but you can only use or
5522 examine the variable @code{b} while your program is executing inside
5523 the block where @code{b} is declared.
5525 @cindex variable name conflict
5526 There is an exception: you can refer to a variable or function whose
5527 scope is a single source file even if the current execution point is not
5528 in this file. But it is possible to have more than one such variable or
5529 function with the same name (in different source files). If that
5530 happens, referring to that name has unpredictable effects. If you wish,
5531 you can specify a static variable in a particular function or file,
5532 using the colon-colon (@code{::}) notation:
5534 @cindex colon-colon, context for variables/functions
5536 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5537 @cindex @code{::}, context for variables/functions
5540 @var{file}::@var{variable}
5541 @var{function}::@var{variable}
5545 Here @var{file} or @var{function} is the name of the context for the
5546 static @var{variable}. In the case of file names, you can use quotes to
5547 make sure @value{GDBN} parses the file name as a single word---for example,
5548 to print a global value of @code{x} defined in @file{f2.c}:
5551 (@value{GDBP}) p 'f2.c'::x
5554 @cindex C@t{++} scope resolution
5555 This use of @samp{::} is very rarely in conflict with the very similar
5556 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5557 scope resolution operator in @value{GDBN} expressions.
5558 @c FIXME: Um, so what happens in one of those rare cases where it's in
5561 @cindex wrong values
5562 @cindex variable values, wrong
5563 @cindex function entry/exit, wrong values of variables
5564 @cindex optimized code, wrong values of variables
5566 @emph{Warning:} Occasionally, a local variable may appear to have the
5567 wrong value at certain points in a function---just after entry to a new
5568 scope, and just before exit.
5570 You may see this problem when you are stepping by machine instructions.
5571 This is because, on most machines, it takes more than one instruction to
5572 set up a stack frame (including local variable definitions); if you are
5573 stepping by machine instructions, variables may appear to have the wrong
5574 values until the stack frame is completely built. On exit, it usually
5575 also takes more than one machine instruction to destroy a stack frame;
5576 after you begin stepping through that group of instructions, local
5577 variable definitions may be gone.
5579 This may also happen when the compiler does significant optimizations.
5580 To be sure of always seeing accurate values, turn off all optimization
5583 @cindex ``No symbol "foo" in current context''
5584 Another possible effect of compiler optimizations is to optimize
5585 unused variables out of existence, or assign variables to registers (as
5586 opposed to memory addresses). Depending on the support for such cases
5587 offered by the debug info format used by the compiler, @value{GDBN}
5588 might not be able to display values for such local variables. If that
5589 happens, @value{GDBN} will print a message like this:
5592 No symbol "foo" in current context.
5595 To solve such problems, either recompile without optimizations, or use a
5596 different debug info format, if the compiler supports several such
5597 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5598 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5599 produces debug info in a format that is superior to formats such as
5600 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5601 an effective form for debug info. @xref{Debugging Options,,Options
5602 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5603 Compiler Collection (GCC)}.
5604 @xref{C, , Debugging C++}, for more information about debug info formats
5605 that are best suited to C@t{++} programs.
5607 If you ask to print an object whose contents are unknown to
5608 @value{GDBN}, e.g., because its data type is not completely specified
5609 by the debug information, @value{GDBN} will say @samp{<incomplete
5610 type>}. @xref{Symbols, incomplete type}, for more about this.
5612 Strings are identified as arrays of @code{char} values without specified
5613 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5614 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5615 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5616 defines literal string type @code{"char"} as @code{char} without a sign.
5621 signed char var1[] = "A";
5624 You get during debugging
5629 $2 = @{65 'A', 0 '\0'@}
5633 @section Artificial arrays
5635 @cindex artificial array
5637 @kindex @@@r{, referencing memory as an array}
5638 It is often useful to print out several successive objects of the
5639 same type in memory; a section of an array, or an array of
5640 dynamically determined size for which only a pointer exists in the
5643 You can do this by referring to a contiguous span of memory as an
5644 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5645 operand of @samp{@@} should be the first element of the desired array
5646 and be an individual object. The right operand should be the desired length
5647 of the array. The result is an array value whose elements are all of
5648 the type of the left argument. The first element is actually the left
5649 argument; the second element comes from bytes of memory immediately
5650 following those that hold the first element, and so on. Here is an
5651 example. If a program says
5654 int *array = (int *) malloc (len * sizeof (int));
5658 you can print the contents of @code{array} with
5664 The left operand of @samp{@@} must reside in memory. Array values made
5665 with @samp{@@} in this way behave just like other arrays in terms of
5666 subscripting, and are coerced to pointers when used in expressions.
5667 Artificial arrays most often appear in expressions via the value history
5668 (@pxref{Value History, ,Value history}), after printing one out.
5670 Another way to create an artificial array is to use a cast.
5671 This re-interprets a value as if it were an array.
5672 The value need not be in memory:
5674 (@value{GDBP}) p/x (short[2])0x12345678
5675 $1 = @{0x1234, 0x5678@}
5678 As a convenience, if you leave the array length out (as in
5679 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5680 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5682 (@value{GDBP}) p/x (short[])0x12345678
5683 $2 = @{0x1234, 0x5678@}
5686 Sometimes the artificial array mechanism is not quite enough; in
5687 moderately complex data structures, the elements of interest may not
5688 actually be adjacent---for example, if you are interested in the values
5689 of pointers in an array. One useful work-around in this situation is
5690 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5691 variables}) as a counter in an expression that prints the first
5692 interesting value, and then repeat that expression via @key{RET}. For
5693 instance, suppose you have an array @code{dtab} of pointers to
5694 structures, and you are interested in the values of a field @code{fv}
5695 in each structure. Here is an example of what you might type:
5705 @node Output Formats
5706 @section Output formats
5708 @cindex formatted output
5709 @cindex output formats
5710 By default, @value{GDBN} prints a value according to its data type. Sometimes
5711 this is not what you want. For example, you might want to print a number
5712 in hex, or a pointer in decimal. Or you might want to view data in memory
5713 at a certain address as a character string or as an instruction. To do
5714 these things, specify an @dfn{output format} when you print a value.
5716 The simplest use of output formats is to say how to print a value
5717 already computed. This is done by starting the arguments of the
5718 @code{print} command with a slash and a format letter. The format
5719 letters supported are:
5723 Regard the bits of the value as an integer, and print the integer in
5727 Print as integer in signed decimal.
5730 Print as integer in unsigned decimal.
5733 Print as integer in octal.
5736 Print as integer in binary. The letter @samp{t} stands for ``two''.
5737 @footnote{@samp{b} cannot be used because these format letters are also
5738 used with the @code{x} command, where @samp{b} stands for ``byte'';
5739 see @ref{Memory,,Examining memory}.}
5742 @cindex unknown address, locating
5743 @cindex locate address
5744 Print as an address, both absolute in hexadecimal and as an offset from
5745 the nearest preceding symbol. You can use this format used to discover
5746 where (in what function) an unknown address is located:
5749 (@value{GDBP}) p/a 0x54320
5750 $3 = 0x54320 <_initialize_vx+396>
5754 The command @code{info symbol 0x54320} yields similar results.
5755 @xref{Symbols, info symbol}.
5758 Regard as an integer and print it as a character constant. This
5759 prints both the numerical value and its character representation. The
5760 character representation is replaced with the octal escape @samp{\nnn}
5761 for characters outside the 7-bit @sc{ascii} range.
5764 Regard the bits of the value as a floating point number and print
5765 using typical floating point syntax.
5768 For example, to print the program counter in hex (@pxref{Registers}), type
5775 Note that no space is required before the slash; this is because command
5776 names in @value{GDBN} cannot contain a slash.
5778 To reprint the last value in the value history with a different format,
5779 you can use the @code{print} command with just a format and no
5780 expression. For example, @samp{p/x} reprints the last value in hex.
5783 @section Examining memory
5785 You can use the command @code{x} (for ``examine'') to examine memory in
5786 any of several formats, independently of your program's data types.
5788 @cindex examining memory
5790 @kindex x @r{(examine memory)}
5791 @item x/@var{nfu} @var{addr}
5794 Use the @code{x} command to examine memory.
5797 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5798 much memory to display and how to format it; @var{addr} is an
5799 expression giving the address where you want to start displaying memory.
5800 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5801 Several commands set convenient defaults for @var{addr}.
5804 @item @var{n}, the repeat count
5805 The repeat count is a decimal integer; the default is 1. It specifies
5806 how much memory (counting by units @var{u}) to display.
5807 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5810 @item @var{f}, the display format
5811 The display format is one of the formats used by @code{print}
5812 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5813 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5814 @samp{i} (for machine instructions). The default is @samp{x}
5815 (hexadecimal) initially. The default changes each time you use either
5816 @code{x} or @code{print}.
5818 @item @var{u}, the unit size
5819 The unit size is any of
5825 Halfwords (two bytes).
5827 Words (four bytes). This is the initial default.
5829 Giant words (eight bytes).
5832 Each time you specify a unit size with @code{x}, that size becomes the
5833 default unit the next time you use @code{x}. (For the @samp{s} and
5834 @samp{i} formats, the unit size is ignored and is normally not written.)
5836 @item @var{addr}, starting display address
5837 @var{addr} is the address where you want @value{GDBN} to begin displaying
5838 memory. The expression need not have a pointer value (though it may);
5839 it is always interpreted as an integer address of a byte of memory.
5840 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5841 @var{addr} is usually just after the last address examined---but several
5842 other commands also set the default address: @code{info breakpoints} (to
5843 the address of the last breakpoint listed), @code{info line} (to the
5844 starting address of a line), and @code{print} (if you use it to display
5845 a value from memory).
5848 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5849 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5850 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5851 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5852 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5854 Since the letters indicating unit sizes are all distinct from the
5855 letters specifying output formats, you do not have to remember whether
5856 unit size or format comes first; either order works. The output
5857 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5858 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5860 Even though the unit size @var{u} is ignored for the formats @samp{s}
5861 and @samp{i}, you might still want to use a count @var{n}; for example,
5862 @samp{3i} specifies that you want to see three machine instructions,
5863 including any operands. The command @code{disassemble} gives an
5864 alternative way of inspecting machine instructions; see @ref{Machine
5865 Code,,Source and machine code}.
5867 All the defaults for the arguments to @code{x} are designed to make it
5868 easy to continue scanning memory with minimal specifications each time
5869 you use @code{x}. For example, after you have inspected three machine
5870 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5871 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5872 the repeat count @var{n} is used again; the other arguments default as
5873 for successive uses of @code{x}.
5875 @cindex @code{$_}, @code{$__}, and value history
5876 The addresses and contents printed by the @code{x} command are not saved
5877 in the value history because there is often too much of them and they
5878 would get in the way. Instead, @value{GDBN} makes these values available for
5879 subsequent use in expressions as values of the convenience variables
5880 @code{$_} and @code{$__}. After an @code{x} command, the last address
5881 examined is available for use in expressions in the convenience variable
5882 @code{$_}. The contents of that address, as examined, are available in
5883 the convenience variable @code{$__}.
5885 If the @code{x} command has a repeat count, the address and contents saved
5886 are from the last memory unit printed; this is not the same as the last
5887 address printed if several units were printed on the last line of output.
5889 @cindex remote memory comparison
5890 @cindex verify remote memory image
5891 When you are debugging a program running on a remote target machine
5892 (@pxref{Remote}), you may wish to verify the program's image in the
5893 remote machine's memory against the executable file you downloaded to
5894 the target. The @code{compare-sections} command is provided for such
5898 @kindex compare-sections
5899 @item compare-sections @r{[}@var{section-name}@r{]}
5900 Compare the data of a loadable section @var{section-name} in the
5901 executable file of the program being debugged with the same section in
5902 the remote machine's memory, and report any mismatches. With no
5903 arguments, compares all loadable sections. This command's
5904 availability depends on the target's support for the @code{"qCRC"}
5909 @section Automatic display
5910 @cindex automatic display
5911 @cindex display of expressions
5913 If you find that you want to print the value of an expression frequently
5914 (to see how it changes), you might want to add it to the @dfn{automatic
5915 display list} so that @value{GDBN} prints its value each time your program stops.
5916 Each expression added to the list is given a number to identify it;
5917 to remove an expression from the list, you specify that number.
5918 The automatic display looks like this:
5922 3: bar[5] = (struct hack *) 0x3804
5926 This display shows item numbers, expressions and their current values. As with
5927 displays you request manually using @code{x} or @code{print}, you can
5928 specify the output format you prefer; in fact, @code{display} decides
5929 whether to use @code{print} or @code{x} depending on how elaborate your
5930 format specification is---it uses @code{x} if you specify a unit size,
5931 or one of the two formats (@samp{i} and @samp{s}) that are only
5932 supported by @code{x}; otherwise it uses @code{print}.
5936 @item display @var{expr}
5937 Add the expression @var{expr} to the list of expressions to display
5938 each time your program stops. @xref{Expressions, ,Expressions}.
5940 @code{display} does not repeat if you press @key{RET} again after using it.
5942 @item display/@var{fmt} @var{expr}
5943 For @var{fmt} specifying only a display format and not a size or
5944 count, add the expression @var{expr} to the auto-display list but
5945 arrange to display it each time in the specified format @var{fmt}.
5946 @xref{Output Formats,,Output formats}.
5948 @item display/@var{fmt} @var{addr}
5949 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5950 number of units, add the expression @var{addr} as a memory address to
5951 be examined each time your program stops. Examining means in effect
5952 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5955 For example, @samp{display/i $pc} can be helpful, to see the machine
5956 instruction about to be executed each time execution stops (@samp{$pc}
5957 is a common name for the program counter; @pxref{Registers, ,Registers}).
5960 @kindex delete display
5962 @item undisplay @var{dnums}@dots{}
5963 @itemx delete display @var{dnums}@dots{}
5964 Remove item numbers @var{dnums} from the list of expressions to display.
5966 @code{undisplay} does not repeat if you press @key{RET} after using it.
5967 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5969 @kindex disable display
5970 @item disable display @var{dnums}@dots{}
5971 Disable the display of item numbers @var{dnums}. A disabled display
5972 item is not printed automatically, but is not forgotten. It may be
5973 enabled again later.
5975 @kindex enable display
5976 @item enable display @var{dnums}@dots{}
5977 Enable display of item numbers @var{dnums}. It becomes effective once
5978 again in auto display of its expression, until you specify otherwise.
5981 Display the current values of the expressions on the list, just as is
5982 done when your program stops.
5984 @kindex info display
5986 Print the list of expressions previously set up to display
5987 automatically, each one with its item number, but without showing the
5988 values. This includes disabled expressions, which are marked as such.
5989 It also includes expressions which would not be displayed right now
5990 because they refer to automatic variables not currently available.
5993 @cindex display disabled out of scope
5994 If a display expression refers to local variables, then it does not make
5995 sense outside the lexical context for which it was set up. Such an
5996 expression is disabled when execution enters a context where one of its
5997 variables is not defined. For example, if you give the command
5998 @code{display last_char} while inside a function with an argument
5999 @code{last_char}, @value{GDBN} displays this argument while your program
6000 continues to stop inside that function. When it stops elsewhere---where
6001 there is no variable @code{last_char}---the display is disabled
6002 automatically. The next time your program stops where @code{last_char}
6003 is meaningful, you can enable the display expression once again.
6005 @node Print Settings
6006 @section Print settings
6008 @cindex format options
6009 @cindex print settings
6010 @value{GDBN} provides the following ways to control how arrays, structures,
6011 and symbols are printed.
6014 These settings are useful for debugging programs in any language:
6018 @item set print address
6019 @itemx set print address on
6020 @cindex print/don't print memory addresses
6021 @value{GDBN} prints memory addresses showing the location of stack
6022 traces, structure values, pointer values, breakpoints, and so forth,
6023 even when it also displays the contents of those addresses. The default
6024 is @code{on}. For example, this is what a stack frame display looks like with
6025 @code{set print address on}:
6030 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6032 530 if (lquote != def_lquote)
6036 @item set print address off
6037 Do not print addresses when displaying their contents. For example,
6038 this is the same stack frame displayed with @code{set print address off}:
6042 (@value{GDBP}) set print addr off
6044 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6045 530 if (lquote != def_lquote)
6049 You can use @samp{set print address off} to eliminate all machine
6050 dependent displays from the @value{GDBN} interface. For example, with
6051 @code{print address off}, you should get the same text for backtraces on
6052 all machines---whether or not they involve pointer arguments.
6055 @item show print address
6056 Show whether or not addresses are to be printed.
6059 When @value{GDBN} prints a symbolic address, it normally prints the
6060 closest earlier symbol plus an offset. If that symbol does not uniquely
6061 identify the address (for example, it is a name whose scope is a single
6062 source file), you may need to clarify. One way to do this is with
6063 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6064 you can set @value{GDBN} to print the source file and line number when
6065 it prints a symbolic address:
6068 @item set print symbol-filename on
6069 @cindex source file and line of a symbol
6070 @cindex symbol, source file and line
6071 Tell @value{GDBN} to print the source file name and line number of a
6072 symbol in the symbolic form of an address.
6074 @item set print symbol-filename off
6075 Do not print source file name and line number of a symbol. This is the
6078 @item show print symbol-filename
6079 Show whether or not @value{GDBN} will print the source file name and
6080 line number of a symbol in the symbolic form of an address.
6083 Another situation where it is helpful to show symbol filenames and line
6084 numbers is when disassembling code; @value{GDBN} shows you the line
6085 number and source file that corresponds to each instruction.
6087 Also, you may wish to see the symbolic form only if the address being
6088 printed is reasonably close to the closest earlier symbol:
6091 @item set print max-symbolic-offset @var{max-offset}
6092 @cindex maximum value for offset of closest symbol
6093 Tell @value{GDBN} to only display the symbolic form of an address if the
6094 offset between the closest earlier symbol and the address is less than
6095 @var{max-offset}. The default is 0, which tells @value{GDBN}
6096 to always print the symbolic form of an address if any symbol precedes it.
6098 @item show print max-symbolic-offset
6099 Ask how large the maximum offset is that @value{GDBN} prints in a
6103 @cindex wild pointer, interpreting
6104 @cindex pointer, finding referent
6105 If you have a pointer and you are not sure where it points, try
6106 @samp{set print symbol-filename on}. Then you can determine the name
6107 and source file location of the variable where it points, using
6108 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6109 For example, here @value{GDBN} shows that a variable @code{ptt} points
6110 at another variable @code{t}, defined in @file{hi2.c}:
6113 (@value{GDBP}) set print symbol-filename on
6114 (@value{GDBP}) p/a ptt
6115 $4 = 0xe008 <t in hi2.c>
6119 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6120 does not show the symbol name and filename of the referent, even with
6121 the appropriate @code{set print} options turned on.
6124 Other settings control how different kinds of objects are printed:
6127 @item set print array
6128 @itemx set print array on
6129 @cindex pretty print arrays
6130 Pretty print arrays. This format is more convenient to read,
6131 but uses more space. The default is off.
6133 @item set print array off
6134 Return to compressed format for arrays.
6136 @item show print array
6137 Show whether compressed or pretty format is selected for displaying
6140 @cindex print array indexes
6141 @item set print array-indexes
6142 @itemx set print array-indexes on
6143 Print the index of each element when displaying arrays. May be more
6144 convenient to locate a given element in the array or quickly find the
6145 index of a given element in that printed array. The default is off.
6147 @item set print array-indexes off
6148 Stop printing element indexes when displaying arrays.
6150 @item show print array-indexes
6151 Show whether the index of each element is printed when displaying
6154 @item set print elements @var{number-of-elements}
6155 @cindex number of array elements to print
6156 @cindex limit on number of printed array elements
6157 Set a limit on how many elements of an array @value{GDBN} will print.
6158 If @value{GDBN} is printing a large array, it stops printing after it has
6159 printed the number of elements set by the @code{set print elements} command.
6160 This limit also applies to the display of strings.
6161 When @value{GDBN} starts, this limit is set to 200.
6162 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6164 @item show print elements
6165 Display the number of elements of a large array that @value{GDBN} will print.
6166 If the number is 0, then the printing is unlimited.
6168 @item set print repeats
6169 @cindex repeated array elements
6170 Set the threshold for suppressing display of repeated array
6171 elements. When the number of consecutive identical elements of an
6172 array exceeds the threshold, @value{GDBN} prints the string
6173 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6174 identical repetitions, instead of displaying the identical elements
6175 themselves. Setting the threshold to zero will cause all elements to
6176 be individually printed. The default threshold is 10.
6178 @item show print repeats
6179 Display the current threshold for printing repeated identical
6182 @item set print null-stop
6183 @cindex @sc{null} elements in arrays
6184 Cause @value{GDBN} to stop printing the characters of an array when the first
6185 @sc{null} is encountered. This is useful when large arrays actually
6186 contain only short strings.
6189 @item show print null-stop
6190 Show whether @value{GDBN} stops printing an array on the first
6191 @sc{null} character.
6193 @item set print pretty on
6194 @cindex print structures in indented form
6195 @cindex indentation in structure display
6196 Cause @value{GDBN} to print structures in an indented format with one member
6197 per line, like this:
6212 @item set print pretty off
6213 Cause @value{GDBN} to print structures in a compact format, like this:
6217 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6218 meat = 0x54 "Pork"@}
6223 This is the default format.
6225 @item show print pretty
6226 Show which format @value{GDBN} is using to print structures.
6228 @item set print sevenbit-strings on
6229 @cindex eight-bit characters in strings
6230 @cindex octal escapes in strings
6231 Print using only seven-bit characters; if this option is set,
6232 @value{GDBN} displays any eight-bit characters (in strings or
6233 character values) using the notation @code{\}@var{nnn}. This setting is
6234 best if you are working in English (@sc{ascii}) and you use the
6235 high-order bit of characters as a marker or ``meta'' bit.
6237 @item set print sevenbit-strings off
6238 Print full eight-bit characters. This allows the use of more
6239 international character sets, and is the default.
6241 @item show print sevenbit-strings
6242 Show whether or not @value{GDBN} is printing only seven-bit characters.
6244 @item set print union on
6245 @cindex unions in structures, printing
6246 Tell @value{GDBN} to print unions which are contained in structures
6247 and other unions. This is the default setting.
6249 @item set print union off
6250 Tell @value{GDBN} not to print unions which are contained in
6251 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6254 @item show print union
6255 Ask @value{GDBN} whether or not it will print unions which are contained in
6256 structures and other unions.
6258 For example, given the declarations
6261 typedef enum @{Tree, Bug@} Species;
6262 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6263 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6274 struct thing foo = @{Tree, @{Acorn@}@};
6278 with @code{set print union on} in effect @samp{p foo} would print
6281 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6285 and with @code{set print union off} in effect it would print
6288 $1 = @{it = Tree, form = @{...@}@}
6292 @code{set print union} affects programs written in C-like languages
6298 These settings are of interest when debugging C@t{++} programs:
6301 @cindex demangling C@t{++} names
6302 @item set print demangle
6303 @itemx set print demangle on
6304 Print C@t{++} names in their source form rather than in the encoded
6305 (``mangled'') form passed to the assembler and linker for type-safe
6306 linkage. The default is on.
6308 @item show print demangle
6309 Show whether C@t{++} names are printed in mangled or demangled form.
6311 @item set print asm-demangle
6312 @itemx set print asm-demangle on
6313 Print C@t{++} names in their source form rather than their mangled form, even
6314 in assembler code printouts such as instruction disassemblies.
6317 @item show print asm-demangle
6318 Show whether C@t{++} names in assembly listings are printed in mangled
6321 @cindex C@t{++} symbol decoding style
6322 @cindex symbol decoding style, C@t{++}
6323 @kindex set demangle-style
6324 @item set demangle-style @var{style}
6325 Choose among several encoding schemes used by different compilers to
6326 represent C@t{++} names. The choices for @var{style} are currently:
6330 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6333 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6334 This is the default.
6337 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6340 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6343 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6344 @strong{Warning:} this setting alone is not sufficient to allow
6345 debugging @code{cfront}-generated executables. @value{GDBN} would
6346 require further enhancement to permit that.
6349 If you omit @var{style}, you will see a list of possible formats.
6351 @item show demangle-style
6352 Display the encoding style currently in use for decoding C@t{++} symbols.
6354 @item set print object
6355 @itemx set print object on
6356 @cindex derived type of an object, printing
6357 @cindex display derived types
6358 When displaying a pointer to an object, identify the @emph{actual}
6359 (derived) type of the object rather than the @emph{declared} type, using
6360 the virtual function table.
6362 @item set print object off
6363 Display only the declared type of objects, without reference to the
6364 virtual function table. This is the default setting.
6366 @item show print object
6367 Show whether actual, or declared, object types are displayed.
6369 @item set print static-members
6370 @itemx set print static-members on
6371 @cindex static members of C@t{++} objects
6372 Print static members when displaying a C@t{++} object. The default is on.
6374 @item set print static-members off
6375 Do not print static members when displaying a C@t{++} object.
6377 @item show print static-members
6378 Show whether C@t{++} static members are printed or not.
6380 @item set print pascal_static-members
6381 @itemx set print pascal_static-members on
6382 @cindex static members of Pascal objects
6383 @cindex Pascal objects, static members display
6384 Print static members when displaying a Pascal object. The default is on.
6386 @item set print pascal_static-members off
6387 Do not print static members when displaying a Pascal object.
6389 @item show print pascal_static-members
6390 Show whether Pascal static members are printed or not.
6392 @c These don't work with HP ANSI C++ yet.
6393 @item set print vtbl
6394 @itemx set print vtbl on
6395 @cindex pretty print C@t{++} virtual function tables
6396 @cindex virtual functions (C@t{++}) display
6397 @cindex VTBL display
6398 Pretty print C@t{++} virtual function tables. The default is off.
6399 (The @code{vtbl} commands do not work on programs compiled with the HP
6400 ANSI C@t{++} compiler (@code{aCC}).)
6402 @item set print vtbl off
6403 Do not pretty print C@t{++} virtual function tables.
6405 @item show print vtbl
6406 Show whether C@t{++} virtual function tables are pretty printed, or not.
6410 @section Value history
6412 @cindex value history
6413 @cindex history of values printed by @value{GDBN}
6414 Values printed by the @code{print} command are saved in the @value{GDBN}
6415 @dfn{value history}. This allows you to refer to them in other expressions.
6416 Values are kept until the symbol table is re-read or discarded
6417 (for example with the @code{file} or @code{symbol-file} commands).
6418 When the symbol table changes, the value history is discarded,
6419 since the values may contain pointers back to the types defined in the
6424 @cindex history number
6425 The values printed are given @dfn{history numbers} by which you can
6426 refer to them. These are successive integers starting with one.
6427 @code{print} shows you the history number assigned to a value by
6428 printing @samp{$@var{num} = } before the value; here @var{num} is the
6431 To refer to any previous value, use @samp{$} followed by the value's
6432 history number. The way @code{print} labels its output is designed to
6433 remind you of this. Just @code{$} refers to the most recent value in
6434 the history, and @code{$$} refers to the value before that.
6435 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6436 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6437 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6439 For example, suppose you have just printed a pointer to a structure and
6440 want to see the contents of the structure. It suffices to type
6446 If you have a chain of structures where the component @code{next} points
6447 to the next one, you can print the contents of the next one with this:
6454 You can print successive links in the chain by repeating this
6455 command---which you can do by just typing @key{RET}.
6457 Note that the history records values, not expressions. If the value of
6458 @code{x} is 4 and you type these commands:
6466 then the value recorded in the value history by the @code{print} command
6467 remains 4 even though the value of @code{x} has changed.
6472 Print the last ten values in the value history, with their item numbers.
6473 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6474 values} does not change the history.
6476 @item show values @var{n}
6477 Print ten history values centered on history item number @var{n}.
6480 Print ten history values just after the values last printed. If no more
6481 values are available, @code{show values +} produces no display.
6484 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6485 same effect as @samp{show values +}.
6487 @node Convenience Vars
6488 @section Convenience variables
6490 @cindex convenience variables
6491 @cindex user-defined variables
6492 @value{GDBN} provides @dfn{convenience variables} that you can use within
6493 @value{GDBN} to hold on to a value and refer to it later. These variables
6494 exist entirely within @value{GDBN}; they are not part of your program, and
6495 setting a convenience variable has no direct effect on further execution
6496 of your program. That is why you can use them freely.
6498 Convenience variables are prefixed with @samp{$}. Any name preceded by
6499 @samp{$} can be used for a convenience variable, unless it is one of
6500 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6501 (Value history references, in contrast, are @emph{numbers} preceded
6502 by @samp{$}. @xref{Value History, ,Value history}.)
6504 You can save a value in a convenience variable with an assignment
6505 expression, just as you would set a variable in your program.
6509 set $foo = *object_ptr
6513 would save in @code{$foo} the value contained in the object pointed to by
6516 Using a convenience variable for the first time creates it, but its
6517 value is @code{void} until you assign a new value. You can alter the
6518 value with another assignment at any time.
6520 Convenience variables have no fixed types. You can assign a convenience
6521 variable any type of value, including structures and arrays, even if
6522 that variable already has a value of a different type. The convenience
6523 variable, when used as an expression, has the type of its current value.
6526 @kindex show convenience
6527 @cindex show all user variables
6528 @item show convenience
6529 Print a list of convenience variables used so far, and their values.
6530 Abbreviated @code{show conv}.
6532 @kindex init-if-undefined
6533 @cindex convenience variables, initializing
6534 @item init-if-undefined $@var{variable} = @var{expression}
6535 Set a convenience variable if it has not already been set. This is useful
6536 for user-defined commands that keep some state. It is similar, in concept,
6537 to using local static variables with initializers in C (except that
6538 convenience variables are global). It can also be used to allow users to
6539 override default values used in a command script.
6541 If the variable is already defined then the expression is not evaluated so
6542 any side-effects do not occur.
6545 One of the ways to use a convenience variable is as a counter to be
6546 incremented or a pointer to be advanced. For example, to print
6547 a field from successive elements of an array of structures:
6551 print bar[$i++]->contents
6555 Repeat that command by typing @key{RET}.
6557 Some convenience variables are created automatically by @value{GDBN} and given
6558 values likely to be useful.
6561 @vindex $_@r{, convenience variable}
6563 The variable @code{$_} is automatically set by the @code{x} command to
6564 the last address examined (@pxref{Memory, ,Examining memory}). Other
6565 commands which provide a default address for @code{x} to examine also
6566 set @code{$_} to that address; these commands include @code{info line}
6567 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6568 except when set by the @code{x} command, in which case it is a pointer
6569 to the type of @code{$__}.
6571 @vindex $__@r{, convenience variable}
6573 The variable @code{$__} is automatically set by the @code{x} command
6574 to the value found in the last address examined. Its type is chosen
6575 to match the format in which the data was printed.
6578 @vindex $_exitcode@r{, convenience variable}
6579 The variable @code{$_exitcode} is automatically set to the exit code when
6580 the program being debugged terminates.
6583 On HP-UX systems, if you refer to a function or variable name that
6584 begins with a dollar sign, @value{GDBN} searches for a user or system
6585 name first, before it searches for a convenience variable.
6591 You can refer to machine register contents, in expressions, as variables
6592 with names starting with @samp{$}. The names of registers are different
6593 for each machine; use @code{info registers} to see the names used on
6597 @kindex info registers
6598 @item info registers
6599 Print the names and values of all registers except floating-point
6600 and vector registers (in the selected stack frame).
6602 @kindex info all-registers
6603 @cindex floating point registers
6604 @item info all-registers
6605 Print the names and values of all registers, including floating-point
6606 and vector registers (in the selected stack frame).
6608 @item info registers @var{regname} @dots{}
6609 Print the @dfn{relativized} value of each specified register @var{regname}.
6610 As discussed in detail below, register values are normally relative to
6611 the selected stack frame. @var{regname} may be any register name valid on
6612 the machine you are using, with or without the initial @samp{$}.
6615 @cindex stack pointer register
6616 @cindex program counter register
6617 @cindex process status register
6618 @cindex frame pointer register
6619 @cindex standard registers
6620 @value{GDBN} has four ``standard'' register names that are available (in
6621 expressions) on most machines---whenever they do not conflict with an
6622 architecture's canonical mnemonics for registers. The register names
6623 @code{$pc} and @code{$sp} are used for the program counter register and
6624 the stack pointer. @code{$fp} is used for a register that contains a
6625 pointer to the current stack frame, and @code{$ps} is used for a
6626 register that contains the processor status. For example,
6627 you could print the program counter in hex with
6634 or print the instruction to be executed next with
6641 or add four to the stack pointer@footnote{This is a way of removing
6642 one word from the stack, on machines where stacks grow downward in
6643 memory (most machines, nowadays). This assumes that the innermost
6644 stack frame is selected; setting @code{$sp} is not allowed when other
6645 stack frames are selected. To pop entire frames off the stack,
6646 regardless of machine architecture, use @code{return};
6647 see @ref{Returning, ,Returning from a function}.} with
6653 Whenever possible, these four standard register names are available on
6654 your machine even though the machine has different canonical mnemonics,
6655 so long as there is no conflict. The @code{info registers} command
6656 shows the canonical names. For example, on the SPARC, @code{info
6657 registers} displays the processor status register as @code{$psr} but you
6658 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6659 is an alias for the @sc{eflags} register.
6661 @value{GDBN} always considers the contents of an ordinary register as an
6662 integer when the register is examined in this way. Some machines have
6663 special registers which can hold nothing but floating point; these
6664 registers are considered to have floating point values. There is no way
6665 to refer to the contents of an ordinary register as floating point value
6666 (although you can @emph{print} it as a floating point value with
6667 @samp{print/f $@var{regname}}).
6669 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6670 means that the data format in which the register contents are saved by
6671 the operating system is not the same one that your program normally
6672 sees. For example, the registers of the 68881 floating point
6673 coprocessor are always saved in ``extended'' (raw) format, but all C
6674 programs expect to work with ``double'' (virtual) format. In such
6675 cases, @value{GDBN} normally works with the virtual format only (the format
6676 that makes sense for your program), but the @code{info registers} command
6677 prints the data in both formats.
6679 @cindex SSE registers (x86)
6680 @cindex MMX registers (x86)
6681 Some machines have special registers whose contents can be interpreted
6682 in several different ways. For example, modern x86-based machines
6683 have SSE and MMX registers that can hold several values packed
6684 together in several different formats. @value{GDBN} refers to such
6685 registers in @code{struct} notation:
6688 (@value{GDBP}) print $xmm1
6690 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6691 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6692 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6693 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6694 v4_int32 = @{0, 20657912, 11, 13@},
6695 v2_int64 = @{88725056443645952, 55834574859@},
6696 uint128 = 0x0000000d0000000b013b36f800000000
6701 To set values of such registers, you need to tell @value{GDBN} which
6702 view of the register you wish to change, as if you were assigning
6703 value to a @code{struct} member:
6706 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6709 Normally, register values are relative to the selected stack frame
6710 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6711 value that the register would contain if all stack frames farther in
6712 were exited and their saved registers restored. In order to see the
6713 true contents of hardware registers, you must select the innermost
6714 frame (with @samp{frame 0}).
6716 However, @value{GDBN} must deduce where registers are saved, from the machine
6717 code generated by your compiler. If some registers are not saved, or if
6718 @value{GDBN} is unable to locate the saved registers, the selected stack
6719 frame makes no difference.
6721 @node Floating Point Hardware
6722 @section Floating point hardware
6723 @cindex floating point
6725 Depending on the configuration, @value{GDBN} may be able to give
6726 you more information about the status of the floating point hardware.
6731 Display hardware-dependent information about the floating
6732 point unit. The exact contents and layout vary depending on the
6733 floating point chip. Currently, @samp{info float} is supported on
6734 the ARM and x86 machines.
6738 @section Vector Unit
6741 Depending on the configuration, @value{GDBN} may be able to give you
6742 more information about the status of the vector unit.
6747 Display information about the vector unit. The exact contents and
6748 layout vary depending on the hardware.
6751 @node OS Information
6752 @section Operating system auxiliary information
6753 @cindex OS information
6755 @value{GDBN} provides interfaces to useful OS facilities that can help
6756 you debug your program.
6758 @cindex @code{ptrace} system call
6759 @cindex @code{struct user} contents
6760 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6761 machines), it interfaces with the inferior via the @code{ptrace}
6762 system call. The operating system creates a special sata structure,
6763 called @code{struct user}, for this interface. You can use the
6764 command @code{info udot} to display the contents of this data
6770 Display the contents of the @code{struct user} maintained by the OS
6771 kernel for the program being debugged. @value{GDBN} displays the
6772 contents of @code{struct user} as a list of hex numbers, similar to
6773 the @code{examine} command.
6776 @cindex auxiliary vector
6777 @cindex vector, auxiliary
6778 Some operating systems supply an @dfn{auxiliary vector} to programs at
6779 startup. This is akin to the arguments and environment that you
6780 specify for a program, but contains a system-dependent variety of
6781 binary values that tell system libraries important details about the
6782 hardware, operating system, and process. Each value's purpose is
6783 identified by an integer tag; the meanings are well-known but system-specific.
6784 Depending on the configuration and operating system facilities,
6785 @value{GDBN} may be able to show you this information. For remote
6786 targets, this functionality may further depend on the remote stub's
6787 support of the @samp{qXfer:auxv:read} packet, see
6788 @ref{qXfer auxiliary vector read}.
6793 Display the auxiliary vector of the inferior, which can be either a
6794 live process or a core dump file. @value{GDBN} prints each tag value
6795 numerically, and also shows names and text descriptions for recognized
6796 tags. Some values in the vector are numbers, some bit masks, and some
6797 pointers to strings or other data. @value{GDBN} displays each value in the
6798 most appropriate form for a recognized tag, and in hexadecimal for
6799 an unrecognized tag.
6803 @node Memory Region Attributes
6804 @section Memory region attributes
6805 @cindex memory region attributes
6807 @dfn{Memory region attributes} allow you to describe special handling
6808 required by regions of your target's memory. @value{GDBN} uses
6809 attributes to determine whether to allow certain types of memory
6810 accesses; whether to use specific width accesses; and whether to cache
6811 target memory. By default the description of memory regions is
6812 fetched from the target (if the current target supports this), but the
6813 user can override the fetched regions.
6815 Defined memory regions can be individually enabled and disabled. When a
6816 memory region is disabled, @value{GDBN} uses the default attributes when
6817 accessing memory in that region. Similarly, if no memory regions have
6818 been defined, @value{GDBN} uses the default attributes when accessing
6821 When a memory region is defined, it is given a number to identify it;
6822 to enable, disable, or remove a memory region, you specify that number.
6826 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6827 Define a memory region bounded by @var{lower} and @var{upper} with
6828 attributes @var{attributes}@dots{}, and add it to the list of regions
6829 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6830 case: it is treated as the target's maximum memory address.
6831 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6834 Discard any user changes to the memory regions and use target-supplied
6835 regions, if available, or no regions if the target does not support.
6838 @item delete mem @var{nums}@dots{}
6839 Remove memory regions @var{nums}@dots{} from the list of regions
6840 monitored by @value{GDBN}.
6843 @item disable mem @var{nums}@dots{}
6844 Disable monitoring of memory regions @var{nums}@dots{}.
6845 A disabled memory region is not forgotten.
6846 It may be enabled again later.
6849 @item enable mem @var{nums}@dots{}
6850 Enable monitoring of memory regions @var{nums}@dots{}.
6854 Print a table of all defined memory regions, with the following columns
6858 @item Memory Region Number
6859 @item Enabled or Disabled.
6860 Enabled memory regions are marked with @samp{y}.
6861 Disabled memory regions are marked with @samp{n}.
6864 The address defining the inclusive lower bound of the memory region.
6867 The address defining the exclusive upper bound of the memory region.
6870 The list of attributes set for this memory region.
6875 @subsection Attributes
6877 @subsubsection Memory Access Mode
6878 The access mode attributes set whether @value{GDBN} may make read or
6879 write accesses to a memory region.
6881 While these attributes prevent @value{GDBN} from performing invalid
6882 memory accesses, they do nothing to prevent the target system, I/O DMA,
6883 etc.@: from accessing memory.
6887 Memory is read only.
6889 Memory is write only.
6891 Memory is read/write. This is the default.
6894 @subsubsection Memory Access Size
6895 The access size attribute tells @value{GDBN} to use specific sized
6896 accesses in the memory region. Often memory mapped device registers
6897 require specific sized accesses. If no access size attribute is
6898 specified, @value{GDBN} may use accesses of any size.
6902 Use 8 bit memory accesses.
6904 Use 16 bit memory accesses.
6906 Use 32 bit memory accesses.
6908 Use 64 bit memory accesses.
6911 @c @subsubsection Hardware/Software Breakpoints
6912 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6913 @c will use hardware or software breakpoints for the internal breakpoints
6914 @c used by the step, next, finish, until, etc. commands.
6918 @c Always use hardware breakpoints
6919 @c @item swbreak (default)
6922 @subsubsection Data Cache
6923 The data cache attributes set whether @value{GDBN} will cache target
6924 memory. While this generally improves performance by reducing debug
6925 protocol overhead, it can lead to incorrect results because @value{GDBN}
6926 does not know about volatile variables or memory mapped device
6931 Enable @value{GDBN} to cache target memory.
6933 Disable @value{GDBN} from caching target memory. This is the default.
6936 @subsection Memory Access Checking
6937 @value{GDBN} can be instructed to refuse accesses to memory that is
6938 not explicitly described. This can be useful if accessing such
6939 regions has undesired effects for a specific target, or to provide
6940 better error checking. The following commands control this behaviour.
6943 @kindex set mem inaccessible-by-default
6944 @item set mem inaccessible-by-default [on|off]
6945 If @code{on} is specified, make @value{GDBN} treat memory not
6946 explicitly described by the memory ranges as non-existent and refuse accesses
6947 to such memory. The checks are only performed if there's at least one
6948 memory range defined. If @code{off} is specified, make @value{GDBN}
6949 treat the memory not explicitly described by the memory ranges as RAM.
6950 The default value is @code{off}.
6951 @kindex show mem inaccessible-by-default
6952 @item show mem inaccessible-by-default
6953 Show the current handling of accesses to unknown memory.
6957 @c @subsubsection Memory Write Verification
6958 @c The memory write verification attributes set whether @value{GDBN}
6959 @c will re-reads data after each write to verify the write was successful.
6963 @c @item noverify (default)
6966 @node Dump/Restore Files
6967 @section Copy between memory and a file
6968 @cindex dump/restore files
6969 @cindex append data to a file
6970 @cindex dump data to a file
6971 @cindex restore data from a file
6973 You can use the commands @code{dump}, @code{append}, and
6974 @code{restore} to copy data between target memory and a file. The
6975 @code{dump} and @code{append} commands write data to a file, and the
6976 @code{restore} command reads data from a file back into the inferior's
6977 memory. Files may be in binary, Motorola S-record, Intel hex, or
6978 Tektronix Hex format; however, @value{GDBN} can only append to binary
6984 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6985 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6986 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6987 or the value of @var{expr}, to @var{filename} in the given format.
6989 The @var{format} parameter may be any one of:
6996 Motorola S-record format.
6998 Tektronix Hex format.
7001 @value{GDBN} uses the same definitions of these formats as the
7002 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7003 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7007 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7008 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7009 Append the contents of memory from @var{start_addr} to @var{end_addr},
7010 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7011 (@value{GDBN} can only append data to files in raw binary form.)
7014 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7015 Restore the contents of file @var{filename} into memory. The
7016 @code{restore} command can automatically recognize any known @sc{bfd}
7017 file format, except for raw binary. To restore a raw binary file you
7018 must specify the optional keyword @code{binary} after the filename.
7020 If @var{bias} is non-zero, its value will be added to the addresses
7021 contained in the file. Binary files always start at address zero, so
7022 they will be restored at address @var{bias}. Other bfd files have
7023 a built-in location; they will be restored at offset @var{bias}
7026 If @var{start} and/or @var{end} are non-zero, then only data between
7027 file offset @var{start} and file offset @var{end} will be restored.
7028 These offsets are relative to the addresses in the file, before
7029 the @var{bias} argument is applied.
7033 @node Core File Generation
7034 @section How to Produce a Core File from Your Program
7035 @cindex dump core from inferior
7037 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7038 image of a running process and its process status (register values
7039 etc.). Its primary use is post-mortem debugging of a program that
7040 crashed while it ran outside a debugger. A program that crashes
7041 automatically produces a core file, unless this feature is disabled by
7042 the user. @xref{Files}, for information on invoking @value{GDBN} in
7043 the post-mortem debugging mode.
7045 Occasionally, you may wish to produce a core file of the program you
7046 are debugging in order to preserve a snapshot of its state.
7047 @value{GDBN} has a special command for that.
7051 @kindex generate-core-file
7052 @item generate-core-file [@var{file}]
7053 @itemx gcore [@var{file}]
7054 Produce a core dump of the inferior process. The optional argument
7055 @var{file} specifies the file name where to put the core dump. If not
7056 specified, the file name defaults to @file{core.@var{pid}}, where
7057 @var{pid} is the inferior process ID.
7059 Note that this command is implemented only for some systems (as of
7060 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7063 @node Character Sets
7064 @section Character Sets
7065 @cindex character sets
7067 @cindex translating between character sets
7068 @cindex host character set
7069 @cindex target character set
7071 If the program you are debugging uses a different character set to
7072 represent characters and strings than the one @value{GDBN} uses itself,
7073 @value{GDBN} can automatically translate between the character sets for
7074 you. The character set @value{GDBN} uses we call the @dfn{host
7075 character set}; the one the inferior program uses we call the
7076 @dfn{target character set}.
7078 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7079 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7080 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
7081 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7082 then the host character set is Latin-1, and the target character set is
7083 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7084 target-charset EBCDIC-US}, then @value{GDBN} translates between
7085 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7086 character and string literals in expressions.
7088 @value{GDBN} has no way to automatically recognize which character set
7089 the inferior program uses; you must tell it, using the @code{set
7090 target-charset} command, described below.
7092 Here are the commands for controlling @value{GDBN}'s character set
7096 @item set target-charset @var{charset}
7097 @kindex set target-charset
7098 Set the current target character set to @var{charset}. We list the
7099 character set names @value{GDBN} recognizes below, but if you type
7100 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7101 list the target character sets it supports.
7105 @item set host-charset @var{charset}
7106 @kindex set host-charset
7107 Set the current host character set to @var{charset}.
7109 By default, @value{GDBN} uses a host character set appropriate to the
7110 system it is running on; you can override that default using the
7111 @code{set host-charset} command.
7113 @value{GDBN} can only use certain character sets as its host character
7114 set. We list the character set names @value{GDBN} recognizes below, and
7115 indicate which can be host character sets, but if you type
7116 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7117 list the host character sets it supports.
7119 @item set charset @var{charset}
7121 Set the current host and target character sets to @var{charset}. As
7122 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7123 @value{GDBN} will list the name of the character sets that can be used
7124 for both host and target.
7128 @kindex show charset
7129 Show the names of the current host and target charsets.
7131 @itemx show host-charset
7132 @kindex show host-charset
7133 Show the name of the current host charset.
7135 @itemx show target-charset
7136 @kindex show target-charset
7137 Show the name of the current target charset.
7141 @value{GDBN} currently includes support for the following character
7147 @cindex ASCII character set
7148 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7152 @cindex ISO 8859-1 character set
7153 @cindex ISO Latin 1 character set
7154 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7155 characters needed for French, German, and Spanish. @value{GDBN} can use
7156 this as its host character set.
7160 @cindex EBCDIC character set
7161 @cindex IBM1047 character set
7162 Variants of the @sc{ebcdic} character set, used on some of IBM's
7163 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7164 @value{GDBN} cannot use these as its host character set.
7168 Note that these are all single-byte character sets. More work inside
7169 @value{GDBN} is needed to support multi-byte or variable-width character
7170 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7172 Here is an example of @value{GDBN}'s character set support in action.
7173 Assume that the following source code has been placed in the file
7174 @file{charset-test.c}:
7180 = @{72, 101, 108, 108, 111, 44, 32, 119,
7181 111, 114, 108, 100, 33, 10, 0@};
7182 char ibm1047_hello[]
7183 = @{200, 133, 147, 147, 150, 107, 64, 166,
7184 150, 153, 147, 132, 90, 37, 0@};
7188 printf ("Hello, world!\n");
7192 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7193 containing the string @samp{Hello, world!} followed by a newline,
7194 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7196 We compile the program, and invoke the debugger on it:
7199 $ gcc -g charset-test.c -o charset-test
7200 $ gdb -nw charset-test
7201 GNU gdb 2001-12-19-cvs
7202 Copyright 2001 Free Software Foundation, Inc.
7207 We can use the @code{show charset} command to see what character sets
7208 @value{GDBN} is currently using to interpret and display characters and
7212 (@value{GDBP}) show charset
7213 The current host and target character set is `ISO-8859-1'.
7217 For the sake of printing this manual, let's use @sc{ascii} as our
7218 initial character set:
7220 (@value{GDBP}) set charset ASCII
7221 (@value{GDBP}) show charset
7222 The current host and target character set is `ASCII'.
7226 Let's assume that @sc{ascii} is indeed the correct character set for our
7227 host system --- in other words, let's assume that if @value{GDBN} prints
7228 characters using the @sc{ascii} character set, our terminal will display
7229 them properly. Since our current target character set is also
7230 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7233 (@value{GDBP}) print ascii_hello
7234 $1 = 0x401698 "Hello, world!\n"
7235 (@value{GDBP}) print ascii_hello[0]
7240 @value{GDBN} uses the target character set for character and string
7241 literals you use in expressions:
7244 (@value{GDBP}) print '+'
7249 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7252 @value{GDBN} relies on the user to tell it which character set the
7253 target program uses. If we print @code{ibm1047_hello} while our target
7254 character set is still @sc{ascii}, we get jibberish:
7257 (@value{GDBP}) print ibm1047_hello
7258 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7259 (@value{GDBP}) print ibm1047_hello[0]
7264 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7265 @value{GDBN} tells us the character sets it supports:
7268 (@value{GDBP}) set target-charset
7269 ASCII EBCDIC-US IBM1047 ISO-8859-1
7270 (@value{GDBP}) set target-charset
7273 We can select @sc{ibm1047} as our target character set, and examine the
7274 program's strings again. Now the @sc{ascii} string is wrong, but
7275 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7276 target character set, @sc{ibm1047}, to the host character set,
7277 @sc{ascii}, and they display correctly:
7280 (@value{GDBP}) set target-charset IBM1047
7281 (@value{GDBP}) show charset
7282 The current host character set is `ASCII'.
7283 The current target character set is `IBM1047'.
7284 (@value{GDBP}) print ascii_hello
7285 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7286 (@value{GDBP}) print ascii_hello[0]
7288 (@value{GDBP}) print ibm1047_hello
7289 $8 = 0x4016a8 "Hello, world!\n"
7290 (@value{GDBP}) print ibm1047_hello[0]
7295 As above, @value{GDBN} uses the target character set for character and
7296 string literals you use in expressions:
7299 (@value{GDBP}) print '+'
7304 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7307 @node Caching Remote Data
7308 @section Caching Data of Remote Targets
7309 @cindex caching data of remote targets
7311 @value{GDBN} can cache data exchanged between the debugger and a
7312 remote target (@pxref{Remote}). Such caching generally improves
7313 performance, because it reduces the overhead of the remote protocol by
7314 bundling memory reads and writes into large chunks. Unfortunately,
7315 @value{GDBN} does not currently know anything about volatile
7316 registers, and thus data caching will produce incorrect results when
7317 volatile registers are in use.
7320 @kindex set remotecache
7321 @item set remotecache on
7322 @itemx set remotecache off
7323 Set caching state for remote targets. When @code{ON}, use data
7324 caching. By default, this option is @code{OFF}.
7326 @kindex show remotecache
7327 @item show remotecache
7328 Show the current state of data caching for remote targets.
7332 Print the information about the data cache performance. The
7333 information displayed includes: the dcache width and depth; and for
7334 each cache line, how many times it was referenced, and its data and
7335 state (dirty, bad, ok, etc.). This command is useful for debugging
7336 the data cache operation.
7341 @chapter C Preprocessor Macros
7343 Some languages, such as C and C@t{++}, provide a way to define and invoke
7344 ``preprocessor macros'' which expand into strings of tokens.
7345 @value{GDBN} can evaluate expressions containing macro invocations, show
7346 the result of macro expansion, and show a macro's definition, including
7347 where it was defined.
7349 You may need to compile your program specially to provide @value{GDBN}
7350 with information about preprocessor macros. Most compilers do not
7351 include macros in their debugging information, even when you compile
7352 with the @option{-g} flag. @xref{Compilation}.
7354 A program may define a macro at one point, remove that definition later,
7355 and then provide a different definition after that. Thus, at different
7356 points in the program, a macro may have different definitions, or have
7357 no definition at all. If there is a current stack frame, @value{GDBN}
7358 uses the macros in scope at that frame's source code line. Otherwise,
7359 @value{GDBN} uses the macros in scope at the current listing location;
7362 At the moment, @value{GDBN} does not support the @code{##}
7363 token-splicing operator, the @code{#} stringification operator, or
7364 variable-arity macros.
7366 Whenever @value{GDBN} evaluates an expression, it always expands any
7367 macro invocations present in the expression. @value{GDBN} also provides
7368 the following commands for working with macros explicitly.
7372 @kindex macro expand
7373 @cindex macro expansion, showing the results of preprocessor
7374 @cindex preprocessor macro expansion, showing the results of
7375 @cindex expanding preprocessor macros
7376 @item macro expand @var{expression}
7377 @itemx macro exp @var{expression}
7378 Show the results of expanding all preprocessor macro invocations in
7379 @var{expression}. Since @value{GDBN} simply expands macros, but does
7380 not parse the result, @var{expression} need not be a valid expression;
7381 it can be any string of tokens.
7384 @item macro expand-once @var{expression}
7385 @itemx macro exp1 @var{expression}
7386 @cindex expand macro once
7387 @i{(This command is not yet implemented.)} Show the results of
7388 expanding those preprocessor macro invocations that appear explicitly in
7389 @var{expression}. Macro invocations appearing in that expansion are
7390 left unchanged. This command allows you to see the effect of a
7391 particular macro more clearly, without being confused by further
7392 expansions. Since @value{GDBN} simply expands macros, but does not
7393 parse the result, @var{expression} need not be a valid expression; it
7394 can be any string of tokens.
7397 @cindex macro definition, showing
7398 @cindex definition, showing a macro's
7399 @item info macro @var{macro}
7400 Show the definition of the macro named @var{macro}, and describe the
7401 source location where that definition was established.
7403 @kindex macro define
7404 @cindex user-defined macros
7405 @cindex defining macros interactively
7406 @cindex macros, user-defined
7407 @item macro define @var{macro} @var{replacement-list}
7408 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7409 @i{(This command is not yet implemented.)} Introduce a definition for a
7410 preprocessor macro named @var{macro}, invocations of which are replaced
7411 by the tokens given in @var{replacement-list}. The first form of this
7412 command defines an ``object-like'' macro, which takes no arguments; the
7413 second form defines a ``function-like'' macro, which takes the arguments
7414 given in @var{arglist}.
7416 A definition introduced by this command is in scope in every expression
7417 evaluated in @value{GDBN}, until it is removed with the @command{macro
7418 undef} command, described below. The definition overrides all
7419 definitions for @var{macro} present in the program being debugged, as
7420 well as any previous user-supplied definition.
7423 @item macro undef @var{macro}
7424 @i{(This command is not yet implemented.)} Remove any user-supplied
7425 definition for the macro named @var{macro}. This command only affects
7426 definitions provided with the @command{macro define} command, described
7427 above; it cannot remove definitions present in the program being
7432 @i{(This command is not yet implemented.)} List all the macros
7433 defined using the @code{macro define} command.
7436 @cindex macros, example of debugging with
7437 Here is a transcript showing the above commands in action. First, we
7438 show our source files:
7446 #define ADD(x) (M + x)
7451 printf ("Hello, world!\n");
7453 printf ("We're so creative.\n");
7455 printf ("Goodbye, world!\n");
7462 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7463 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7464 compiler includes information about preprocessor macros in the debugging
7468 $ gcc -gdwarf-2 -g3 sample.c -o sample
7472 Now, we start @value{GDBN} on our sample program:
7476 GNU gdb 2002-05-06-cvs
7477 Copyright 2002 Free Software Foundation, Inc.
7478 GDB is free software, @dots{}
7482 We can expand macros and examine their definitions, even when the
7483 program is not running. @value{GDBN} uses the current listing position
7484 to decide which macro definitions are in scope:
7487 (@value{GDBP}) list main
7490 5 #define ADD(x) (M + x)
7495 10 printf ("Hello, world!\n");
7497 12 printf ("We're so creative.\n");
7498 (@value{GDBP}) info macro ADD
7499 Defined at /home/jimb/gdb/macros/play/sample.c:5
7500 #define ADD(x) (M + x)
7501 (@value{GDBP}) info macro Q
7502 Defined at /home/jimb/gdb/macros/play/sample.h:1
7503 included at /home/jimb/gdb/macros/play/sample.c:2
7505 (@value{GDBP}) macro expand ADD(1)
7506 expands to: (42 + 1)
7507 (@value{GDBP}) macro expand-once ADD(1)
7508 expands to: once (M + 1)
7512 In the example above, note that @command{macro expand-once} expands only
7513 the macro invocation explicit in the original text --- the invocation of
7514 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7515 which was introduced by @code{ADD}.
7517 Once the program is running, @value{GDBN} uses the macro definitions in
7518 force at the source line of the current stack frame:
7521 (@value{GDBP}) break main
7522 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7524 Starting program: /home/jimb/gdb/macros/play/sample
7526 Breakpoint 1, main () at sample.c:10
7527 10 printf ("Hello, world!\n");
7531 At line 10, the definition of the macro @code{N} at line 9 is in force:
7534 (@value{GDBP}) info macro N
7535 Defined at /home/jimb/gdb/macros/play/sample.c:9
7537 (@value{GDBP}) macro expand N Q M
7539 (@value{GDBP}) print N Q M
7544 As we step over directives that remove @code{N}'s definition, and then
7545 give it a new definition, @value{GDBN} finds the definition (or lack
7546 thereof) in force at each point:
7551 12 printf ("We're so creative.\n");
7552 (@value{GDBP}) info macro N
7553 The symbol `N' has no definition as a C/C++ preprocessor macro
7554 at /home/jimb/gdb/macros/play/sample.c:12
7557 14 printf ("Goodbye, world!\n");
7558 (@value{GDBP}) info macro N
7559 Defined at /home/jimb/gdb/macros/play/sample.c:13
7561 (@value{GDBP}) macro expand N Q M
7562 expands to: 1729 < 42
7563 (@value{GDBP}) print N Q M
7570 @chapter Tracepoints
7571 @c This chapter is based on the documentation written by Michael
7572 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7575 In some applications, it is not feasible for the debugger to interrupt
7576 the program's execution long enough for the developer to learn
7577 anything helpful about its behavior. If the program's correctness
7578 depends on its real-time behavior, delays introduced by a debugger
7579 might cause the program to change its behavior drastically, or perhaps
7580 fail, even when the code itself is correct. It is useful to be able
7581 to observe the program's behavior without interrupting it.
7583 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7584 specify locations in the program, called @dfn{tracepoints}, and
7585 arbitrary expressions to evaluate when those tracepoints are reached.
7586 Later, using the @code{tfind} command, you can examine the values
7587 those expressions had when the program hit the tracepoints. The
7588 expressions may also denote objects in memory---structures or arrays,
7589 for example---whose values @value{GDBN} should record; while visiting
7590 a particular tracepoint, you may inspect those objects as if they were
7591 in memory at that moment. However, because @value{GDBN} records these
7592 values without interacting with you, it can do so quickly and
7593 unobtrusively, hopefully not disturbing the program's behavior.
7595 The tracepoint facility is currently available only for remote
7596 targets. @xref{Targets}. In addition, your remote target must know
7597 how to collect trace data. This functionality is implemented in the
7598 remote stub; however, none of the stubs distributed with @value{GDBN}
7599 support tracepoints as of this writing. The format of the remote
7600 packets used to implement tracepoints are described in @ref{Tracepoint
7603 This chapter describes the tracepoint commands and features.
7607 * Analyze Collected Data::
7608 * Tracepoint Variables::
7611 @node Set Tracepoints
7612 @section Commands to Set Tracepoints
7614 Before running such a @dfn{trace experiment}, an arbitrary number of
7615 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7616 tracepoint has a number assigned to it by @value{GDBN}. Like with
7617 breakpoints, tracepoint numbers are successive integers starting from
7618 one. Many of the commands associated with tracepoints take the
7619 tracepoint number as their argument, to identify which tracepoint to
7622 For each tracepoint, you can specify, in advance, some arbitrary set
7623 of data that you want the target to collect in the trace buffer when
7624 it hits that tracepoint. The collected data can include registers,
7625 local variables, or global data. Later, you can use @value{GDBN}
7626 commands to examine the values these data had at the time the
7629 This section describes commands to set tracepoints and associated
7630 conditions and actions.
7633 * Create and Delete Tracepoints::
7634 * Enable and Disable Tracepoints::
7635 * Tracepoint Passcounts::
7636 * Tracepoint Actions::
7637 * Listing Tracepoints::
7638 * Starting and Stopping Trace Experiment::
7641 @node Create and Delete Tracepoints
7642 @subsection Create and Delete Tracepoints
7645 @cindex set tracepoint
7648 The @code{trace} command is very similar to the @code{break} command.
7649 Its argument can be a source line, a function name, or an address in
7650 the target program. @xref{Set Breaks}. The @code{trace} command
7651 defines a tracepoint, which is a point in the target program where the
7652 debugger will briefly stop, collect some data, and then allow the
7653 program to continue. Setting a tracepoint or changing its commands
7654 doesn't take effect until the next @code{tstart} command; thus, you
7655 cannot change the tracepoint attributes once a trace experiment is
7658 Here are some examples of using the @code{trace} command:
7661 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7663 (@value{GDBP}) @b{trace +2} // 2 lines forward
7665 (@value{GDBP}) @b{trace my_function} // first source line of function
7667 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7669 (@value{GDBP}) @b{trace *0x2117c4} // an address
7673 You can abbreviate @code{trace} as @code{tr}.
7676 @cindex last tracepoint number
7677 @cindex recent tracepoint number
7678 @cindex tracepoint number
7679 The convenience variable @code{$tpnum} records the tracepoint number
7680 of the most recently set tracepoint.
7682 @kindex delete tracepoint
7683 @cindex tracepoint deletion
7684 @item delete tracepoint @r{[}@var{num}@r{]}
7685 Permanently delete one or more tracepoints. With no argument, the
7686 default is to delete all tracepoints.
7691 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7693 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7697 You can abbreviate this command as @code{del tr}.
7700 @node Enable and Disable Tracepoints
7701 @subsection Enable and Disable Tracepoints
7704 @kindex disable tracepoint
7705 @item disable tracepoint @r{[}@var{num}@r{]}
7706 Disable tracepoint @var{num}, or all tracepoints if no argument
7707 @var{num} is given. A disabled tracepoint will have no effect during
7708 the next trace experiment, but it is not forgotten. You can re-enable
7709 a disabled tracepoint using the @code{enable tracepoint} command.
7711 @kindex enable tracepoint
7712 @item enable tracepoint @r{[}@var{num}@r{]}
7713 Enable tracepoint @var{num}, or all tracepoints. The enabled
7714 tracepoints will become effective the next time a trace experiment is
7718 @node Tracepoint Passcounts
7719 @subsection Tracepoint Passcounts
7723 @cindex tracepoint pass count
7724 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7725 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7726 automatically stop a trace experiment. If a tracepoint's passcount is
7727 @var{n}, then the trace experiment will be automatically stopped on
7728 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7729 @var{num} is not specified, the @code{passcount} command sets the
7730 passcount of the most recently defined tracepoint. If no passcount is
7731 given, the trace experiment will run until stopped explicitly by the
7737 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7738 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7740 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7741 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7742 (@value{GDBP}) @b{trace foo}
7743 (@value{GDBP}) @b{pass 3}
7744 (@value{GDBP}) @b{trace bar}
7745 (@value{GDBP}) @b{pass 2}
7746 (@value{GDBP}) @b{trace baz}
7747 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7748 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7749 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7750 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7754 @node Tracepoint Actions
7755 @subsection Tracepoint Action Lists
7759 @cindex tracepoint actions
7760 @item actions @r{[}@var{num}@r{]}
7761 This command will prompt for a list of actions to be taken when the
7762 tracepoint is hit. If the tracepoint number @var{num} is not
7763 specified, this command sets the actions for the one that was most
7764 recently defined (so that you can define a tracepoint and then say
7765 @code{actions} without bothering about its number). You specify the
7766 actions themselves on the following lines, one action at a time, and
7767 terminate the actions list with a line containing just @code{end}. So
7768 far, the only defined actions are @code{collect} and
7769 @code{while-stepping}.
7771 @cindex remove actions from a tracepoint
7772 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7773 and follow it immediately with @samp{end}.
7776 (@value{GDBP}) @b{collect @var{data}} // collect some data
7778 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7780 (@value{GDBP}) @b{end} // signals the end of actions.
7783 In the following example, the action list begins with @code{collect}
7784 commands indicating the things to be collected when the tracepoint is
7785 hit. Then, in order to single-step and collect additional data
7786 following the tracepoint, a @code{while-stepping} command is used,
7787 followed by the list of things to be collected while stepping. The
7788 @code{while-stepping} command is terminated by its own separate
7789 @code{end} command. Lastly, the action list is terminated by an
7793 (@value{GDBP}) @b{trace foo}
7794 (@value{GDBP}) @b{actions}
7795 Enter actions for tracepoint 1, one per line:
7804 @kindex collect @r{(tracepoints)}
7805 @item collect @var{expr1}, @var{expr2}, @dots{}
7806 Collect values of the given expressions when the tracepoint is hit.
7807 This command accepts a comma-separated list of any valid expressions.
7808 In addition to global, static, or local variables, the following
7809 special arguments are supported:
7813 collect all registers
7816 collect all function arguments
7819 collect all local variables.
7822 You can give several consecutive @code{collect} commands, each one
7823 with a single argument, or one @code{collect} command with several
7824 arguments separated by commas: the effect is the same.
7826 The command @code{info scope} (@pxref{Symbols, info scope}) is
7827 particularly useful for figuring out what data to collect.
7829 @kindex while-stepping @r{(tracepoints)}
7830 @item while-stepping @var{n}
7831 Perform @var{n} single-step traces after the tracepoint, collecting
7832 new data at each step. The @code{while-stepping} command is
7833 followed by the list of what to collect while stepping (followed by
7834 its own @code{end} command):
7838 > collect $regs, myglobal
7844 You may abbreviate @code{while-stepping} as @code{ws} or
7848 @node Listing Tracepoints
7849 @subsection Listing Tracepoints
7852 @kindex info tracepoints
7854 @cindex information about tracepoints
7855 @item info tracepoints @r{[}@var{num}@r{]}
7856 Display information about the tracepoint @var{num}. If you don't specify
7857 a tracepoint number, displays information about all the tracepoints
7858 defined so far. For each tracepoint, the following information is
7865 whether it is enabled or disabled
7869 its passcount as given by the @code{passcount @var{n}} command
7871 its step count as given by the @code{while-stepping @var{n}} command
7873 where in the source files is the tracepoint set
7875 its action list as given by the @code{actions} command
7879 (@value{GDBP}) @b{info trace}
7880 Num Enb Address PassC StepC What
7881 1 y 0x002117c4 0 0 <gdb_asm>
7882 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7883 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7888 This command can be abbreviated @code{info tp}.
7891 @node Starting and Stopping Trace Experiment
7892 @subsection Starting and Stopping Trace Experiment
7896 @cindex start a new trace experiment
7897 @cindex collected data discarded
7899 This command takes no arguments. It starts the trace experiment, and
7900 begins collecting data. This has the side effect of discarding all
7901 the data collected in the trace buffer during the previous trace
7905 @cindex stop a running trace experiment
7907 This command takes no arguments. It ends the trace experiment, and
7908 stops collecting data.
7910 @strong{Note}: a trace experiment and data collection may stop
7911 automatically if any tracepoint's passcount is reached
7912 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7915 @cindex status of trace data collection
7916 @cindex trace experiment, status of
7918 This command displays the status of the current trace data
7922 Here is an example of the commands we described so far:
7925 (@value{GDBP}) @b{trace gdb_c_test}
7926 (@value{GDBP}) @b{actions}
7927 Enter actions for tracepoint #1, one per line.
7928 > collect $regs,$locals,$args
7933 (@value{GDBP}) @b{tstart}
7934 [time passes @dots{}]
7935 (@value{GDBP}) @b{tstop}
7939 @node Analyze Collected Data
7940 @section Using the collected data
7942 After the tracepoint experiment ends, you use @value{GDBN} commands
7943 for examining the trace data. The basic idea is that each tracepoint
7944 collects a trace @dfn{snapshot} every time it is hit and another
7945 snapshot every time it single-steps. All these snapshots are
7946 consecutively numbered from zero and go into a buffer, and you can
7947 examine them later. The way you examine them is to @dfn{focus} on a
7948 specific trace snapshot. When the remote stub is focused on a trace
7949 snapshot, it will respond to all @value{GDBN} requests for memory and
7950 registers by reading from the buffer which belongs to that snapshot,
7951 rather than from @emph{real} memory or registers of the program being
7952 debugged. This means that @strong{all} @value{GDBN} commands
7953 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7954 behave as if we were currently debugging the program state as it was
7955 when the tracepoint occurred. Any requests for data that are not in
7956 the buffer will fail.
7959 * tfind:: How to select a trace snapshot
7960 * tdump:: How to display all data for a snapshot
7961 * save-tracepoints:: How to save tracepoints for a future run
7965 @subsection @code{tfind @var{n}}
7968 @cindex select trace snapshot
7969 @cindex find trace snapshot
7970 The basic command for selecting a trace snapshot from the buffer is
7971 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7972 counting from zero. If no argument @var{n} is given, the next
7973 snapshot is selected.
7975 Here are the various forms of using the @code{tfind} command.
7979 Find the first snapshot in the buffer. This is a synonym for
7980 @code{tfind 0} (since 0 is the number of the first snapshot).
7983 Stop debugging trace snapshots, resume @emph{live} debugging.
7986 Same as @samp{tfind none}.
7989 No argument means find the next trace snapshot.
7992 Find the previous trace snapshot before the current one. This permits
7993 retracing earlier steps.
7995 @item tfind tracepoint @var{num}
7996 Find the next snapshot associated with tracepoint @var{num}. Search
7997 proceeds forward from the last examined trace snapshot. If no
7998 argument @var{num} is given, it means find the next snapshot collected
7999 for the same tracepoint as the current snapshot.
8001 @item tfind pc @var{addr}
8002 Find the next snapshot associated with the value @var{addr} of the
8003 program counter. Search proceeds forward from the last examined trace
8004 snapshot. If no argument @var{addr} is given, it means find the next
8005 snapshot with the same value of PC as the current snapshot.
8007 @item tfind outside @var{addr1}, @var{addr2}
8008 Find the next snapshot whose PC is outside the given range of
8011 @item tfind range @var{addr1}, @var{addr2}
8012 Find the next snapshot whose PC is between @var{addr1} and
8013 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8015 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8016 Find the next snapshot associated with the source line @var{n}. If
8017 the optional argument @var{file} is given, refer to line @var{n} in
8018 that source file. Search proceeds forward from the last examined
8019 trace snapshot. If no argument @var{n} is given, it means find the
8020 next line other than the one currently being examined; thus saying
8021 @code{tfind line} repeatedly can appear to have the same effect as
8022 stepping from line to line in a @emph{live} debugging session.
8025 The default arguments for the @code{tfind} commands are specifically
8026 designed to make it easy to scan through the trace buffer. For
8027 instance, @code{tfind} with no argument selects the next trace
8028 snapshot, and @code{tfind -} with no argument selects the previous
8029 trace snapshot. So, by giving one @code{tfind} command, and then
8030 simply hitting @key{RET} repeatedly you can examine all the trace
8031 snapshots in order. Or, by saying @code{tfind -} and then hitting
8032 @key{RET} repeatedly you can examine the snapshots in reverse order.
8033 The @code{tfind line} command with no argument selects the snapshot
8034 for the next source line executed. The @code{tfind pc} command with
8035 no argument selects the next snapshot with the same program counter
8036 (PC) as the current frame. The @code{tfind tracepoint} command with
8037 no argument selects the next trace snapshot collected by the same
8038 tracepoint as the current one.
8040 In addition to letting you scan through the trace buffer manually,
8041 these commands make it easy to construct @value{GDBN} scripts that
8042 scan through the trace buffer and print out whatever collected data
8043 you are interested in. Thus, if we want to examine the PC, FP, and SP
8044 registers from each trace frame in the buffer, we can say this:
8047 (@value{GDBP}) @b{tfind start}
8048 (@value{GDBP}) @b{while ($trace_frame != -1)}
8049 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8050 $trace_frame, $pc, $sp, $fp
8054 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8055 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8056 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8057 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8058 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8059 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8060 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8061 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8062 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8063 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8064 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8067 Or, if we want to examine the variable @code{X} at each source line in
8071 (@value{GDBP}) @b{tfind start}
8072 (@value{GDBP}) @b{while ($trace_frame != -1)}
8073 > printf "Frame %d, X == %d\n", $trace_frame, X
8083 @subsection @code{tdump}
8085 @cindex dump all data collected at tracepoint
8086 @cindex tracepoint data, display
8088 This command takes no arguments. It prints all the data collected at
8089 the current trace snapshot.
8092 (@value{GDBP}) @b{trace 444}
8093 (@value{GDBP}) @b{actions}
8094 Enter actions for tracepoint #2, one per line:
8095 > collect $regs, $locals, $args, gdb_long_test
8098 (@value{GDBP}) @b{tstart}
8100 (@value{GDBP}) @b{tfind line 444}
8101 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8103 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8105 (@value{GDBP}) @b{tdump}
8106 Data collected at tracepoint 2, trace frame 1:
8107 d0 0xc4aa0085 -995491707
8111 d4 0x71aea3d 119204413
8116 a1 0x3000668 50333288
8119 a4 0x3000698 50333336
8121 fp 0x30bf3c 0x30bf3c
8122 sp 0x30bf34 0x30bf34
8124 pc 0x20b2c8 0x20b2c8
8128 p = 0x20e5b4 "gdb-test"
8135 gdb_long_test = 17 '\021'
8140 @node save-tracepoints
8141 @subsection @code{save-tracepoints @var{filename}}
8142 @kindex save-tracepoints
8143 @cindex save tracepoints for future sessions
8145 This command saves all current tracepoint definitions together with
8146 their actions and passcounts, into a file @file{@var{filename}}
8147 suitable for use in a later debugging session. To read the saved
8148 tracepoint definitions, use the @code{source} command (@pxref{Command
8151 @node Tracepoint Variables
8152 @section Convenience Variables for Tracepoints
8153 @cindex tracepoint variables
8154 @cindex convenience variables for tracepoints
8157 @vindex $trace_frame
8158 @item (int) $trace_frame
8159 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8160 snapshot is selected.
8163 @item (int) $tracepoint
8164 The tracepoint for the current trace snapshot.
8167 @item (int) $trace_line
8168 The line number for the current trace snapshot.
8171 @item (char []) $trace_file
8172 The source file for the current trace snapshot.
8175 @item (char []) $trace_func
8176 The name of the function containing @code{$tracepoint}.
8179 Note: @code{$trace_file} is not suitable for use in @code{printf},
8180 use @code{output} instead.
8182 Here's a simple example of using these convenience variables for
8183 stepping through all the trace snapshots and printing some of their
8187 (@value{GDBP}) @b{tfind start}
8189 (@value{GDBP}) @b{while $trace_frame != -1}
8190 > output $trace_file
8191 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8197 @chapter Debugging Programs That Use Overlays
8200 If your program is too large to fit completely in your target system's
8201 memory, you can sometimes use @dfn{overlays} to work around this
8202 problem. @value{GDBN} provides some support for debugging programs that
8206 * How Overlays Work:: A general explanation of overlays.
8207 * Overlay Commands:: Managing overlays in @value{GDBN}.
8208 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8209 mapped by asking the inferior.
8210 * Overlay Sample Program:: A sample program using overlays.
8213 @node How Overlays Work
8214 @section How Overlays Work
8215 @cindex mapped overlays
8216 @cindex unmapped overlays
8217 @cindex load address, overlay's
8218 @cindex mapped address
8219 @cindex overlay area
8221 Suppose you have a computer whose instruction address space is only 64
8222 kilobytes long, but which has much more memory which can be accessed by
8223 other means: special instructions, segment registers, or memory
8224 management hardware, for example. Suppose further that you want to
8225 adapt a program which is larger than 64 kilobytes to run on this system.
8227 One solution is to identify modules of your program which are relatively
8228 independent, and need not call each other directly; call these modules
8229 @dfn{overlays}. Separate the overlays from the main program, and place
8230 their machine code in the larger memory. Place your main program in
8231 instruction memory, but leave at least enough space there to hold the
8232 largest overlay as well.
8234 Now, to call a function located in an overlay, you must first copy that
8235 overlay's machine code from the large memory into the space set aside
8236 for it in the instruction memory, and then jump to its entry point
8239 @c NB: In the below the mapped area's size is greater or equal to the
8240 @c size of all overlays. This is intentional to remind the developer
8241 @c that overlays don't necessarily need to be the same size.
8245 Data Instruction Larger
8246 Address Space Address Space Address Space
8247 +-----------+ +-----------+ +-----------+
8249 +-----------+ +-----------+ +-----------+<-- overlay 1
8250 | program | | main | .----| overlay 1 | load address
8251 | variables | | program | | +-----------+
8252 | and heap | | | | | |
8253 +-----------+ | | | +-----------+<-- overlay 2
8254 | | +-----------+ | | | load address
8255 +-----------+ | | | .-| overlay 2 |
8257 mapped --->+-----------+ | | +-----------+
8259 | overlay | <-' | | |
8260 | area | <---' +-----------+<-- overlay 3
8261 | | <---. | | load address
8262 +-----------+ `--| overlay 3 |
8269 @anchor{A code overlay}A code overlay
8273 The diagram (@pxref{A code overlay}) shows a system with separate data
8274 and instruction address spaces. To map an overlay, the program copies
8275 its code from the larger address space to the instruction address space.
8276 Since the overlays shown here all use the same mapped address, only one
8277 may be mapped at a time. For a system with a single address space for
8278 data and instructions, the diagram would be similar, except that the
8279 program variables and heap would share an address space with the main
8280 program and the overlay area.
8282 An overlay loaded into instruction memory and ready for use is called a
8283 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8284 instruction memory. An overlay not present (or only partially present)
8285 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8286 is its address in the larger memory. The mapped address is also called
8287 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8288 called the @dfn{load memory address}, or @dfn{LMA}.
8290 Unfortunately, overlays are not a completely transparent way to adapt a
8291 program to limited instruction memory. They introduce a new set of
8292 global constraints you must keep in mind as you design your program:
8297 Before calling or returning to a function in an overlay, your program
8298 must make sure that overlay is actually mapped. Otherwise, the call or
8299 return will transfer control to the right address, but in the wrong
8300 overlay, and your program will probably crash.
8303 If the process of mapping an overlay is expensive on your system, you
8304 will need to choose your overlays carefully to minimize their effect on
8305 your program's performance.
8308 The executable file you load onto your system must contain each
8309 overlay's instructions, appearing at the overlay's load address, not its
8310 mapped address. However, each overlay's instructions must be relocated
8311 and its symbols defined as if the overlay were at its mapped address.
8312 You can use GNU linker scripts to specify different load and relocation
8313 addresses for pieces of your program; see @ref{Overlay Description,,,
8314 ld.info, Using ld: the GNU linker}.
8317 The procedure for loading executable files onto your system must be able
8318 to load their contents into the larger address space as well as the
8319 instruction and data spaces.
8323 The overlay system described above is rather simple, and could be
8324 improved in many ways:
8329 If your system has suitable bank switch registers or memory management
8330 hardware, you could use those facilities to make an overlay's load area
8331 contents simply appear at their mapped address in instruction space.
8332 This would probably be faster than copying the overlay to its mapped
8333 area in the usual way.
8336 If your overlays are small enough, you could set aside more than one
8337 overlay area, and have more than one overlay mapped at a time.
8340 You can use overlays to manage data, as well as instructions. In
8341 general, data overlays are even less transparent to your design than
8342 code overlays: whereas code overlays only require care when you call or
8343 return to functions, data overlays require care every time you access
8344 the data. Also, if you change the contents of a data overlay, you
8345 must copy its contents back out to its load address before you can copy a
8346 different data overlay into the same mapped area.
8351 @node Overlay Commands
8352 @section Overlay Commands
8354 To use @value{GDBN}'s overlay support, each overlay in your program must
8355 correspond to a separate section of the executable file. The section's
8356 virtual memory address and load memory address must be the overlay's
8357 mapped and load addresses. Identifying overlays with sections allows
8358 @value{GDBN} to determine the appropriate address of a function or
8359 variable, depending on whether the overlay is mapped or not.
8361 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8362 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8367 Disable @value{GDBN}'s overlay support. When overlay support is
8368 disabled, @value{GDBN} assumes that all functions and variables are
8369 always present at their mapped addresses. By default, @value{GDBN}'s
8370 overlay support is disabled.
8372 @item overlay manual
8373 @cindex manual overlay debugging
8374 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8375 relies on you to tell it which overlays are mapped, and which are not,
8376 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8377 commands described below.
8379 @item overlay map-overlay @var{overlay}
8380 @itemx overlay map @var{overlay}
8381 @cindex map an overlay
8382 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8383 be the name of the object file section containing the overlay. When an
8384 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8385 functions and variables at their mapped addresses. @value{GDBN} assumes
8386 that any other overlays whose mapped ranges overlap that of
8387 @var{overlay} are now unmapped.
8389 @item overlay unmap-overlay @var{overlay}
8390 @itemx overlay unmap @var{overlay}
8391 @cindex unmap an overlay
8392 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8393 must be the name of the object file section containing the overlay.
8394 When an overlay is unmapped, @value{GDBN} assumes it can find the
8395 overlay's functions and variables at their load addresses.
8398 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8399 consults a data structure the overlay manager maintains in the inferior
8400 to see which overlays are mapped. For details, see @ref{Automatic
8403 @item overlay load-target
8405 @cindex reloading the overlay table
8406 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8407 re-reads the table @value{GDBN} automatically each time the inferior
8408 stops, so this command should only be necessary if you have changed the
8409 overlay mapping yourself using @value{GDBN}. This command is only
8410 useful when using automatic overlay debugging.
8412 @item overlay list-overlays
8414 @cindex listing mapped overlays
8415 Display a list of the overlays currently mapped, along with their mapped
8416 addresses, load addresses, and sizes.
8420 Normally, when @value{GDBN} prints a code address, it includes the name
8421 of the function the address falls in:
8424 (@value{GDBP}) print main
8425 $3 = @{int ()@} 0x11a0 <main>
8428 When overlay debugging is enabled, @value{GDBN} recognizes code in
8429 unmapped overlays, and prints the names of unmapped functions with
8430 asterisks around them. For example, if @code{foo} is a function in an
8431 unmapped overlay, @value{GDBN} prints it this way:
8434 (@value{GDBP}) overlay list
8435 No sections are mapped.
8436 (@value{GDBP}) print foo
8437 $5 = @{int (int)@} 0x100000 <*foo*>
8440 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8444 (@value{GDBP}) overlay list
8445 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8446 mapped at 0x1016 - 0x104a
8447 (@value{GDBP}) print foo
8448 $6 = @{int (int)@} 0x1016 <foo>
8451 When overlay debugging is enabled, @value{GDBN} can find the correct
8452 address for functions and variables in an overlay, whether or not the
8453 overlay is mapped. This allows most @value{GDBN} commands, like
8454 @code{break} and @code{disassemble}, to work normally, even on unmapped
8455 code. However, @value{GDBN}'s breakpoint support has some limitations:
8459 @cindex breakpoints in overlays
8460 @cindex overlays, setting breakpoints in
8461 You can set breakpoints in functions in unmapped overlays, as long as
8462 @value{GDBN} can write to the overlay at its load address.
8464 @value{GDBN} can not set hardware or simulator-based breakpoints in
8465 unmapped overlays. However, if you set a breakpoint at the end of your
8466 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8467 you are using manual overlay management), @value{GDBN} will re-set its
8468 breakpoints properly.
8472 @node Automatic Overlay Debugging
8473 @section Automatic Overlay Debugging
8474 @cindex automatic overlay debugging
8476 @value{GDBN} can automatically track which overlays are mapped and which
8477 are not, given some simple co-operation from the overlay manager in the
8478 inferior. If you enable automatic overlay debugging with the
8479 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8480 looks in the inferior's memory for certain variables describing the
8481 current state of the overlays.
8483 Here are the variables your overlay manager must define to support
8484 @value{GDBN}'s automatic overlay debugging:
8488 @item @code{_ovly_table}:
8489 This variable must be an array of the following structures:
8494 /* The overlay's mapped address. */
8497 /* The size of the overlay, in bytes. */
8500 /* The overlay's load address. */
8503 /* Non-zero if the overlay is currently mapped;
8505 unsigned long mapped;
8509 @item @code{_novlys}:
8510 This variable must be a four-byte signed integer, holding the total
8511 number of elements in @code{_ovly_table}.
8515 To decide whether a particular overlay is mapped or not, @value{GDBN}
8516 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8517 @code{lma} members equal the VMA and LMA of the overlay's section in the
8518 executable file. When @value{GDBN} finds a matching entry, it consults
8519 the entry's @code{mapped} member to determine whether the overlay is
8522 In addition, your overlay manager may define a function called
8523 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8524 will silently set a breakpoint there. If the overlay manager then
8525 calls this function whenever it has changed the overlay table, this
8526 will enable @value{GDBN} to accurately keep track of which overlays
8527 are in program memory, and update any breakpoints that may be set
8528 in overlays. This will allow breakpoints to work even if the
8529 overlays are kept in ROM or other non-writable memory while they
8530 are not being executed.
8532 @node Overlay Sample Program
8533 @section Overlay Sample Program
8534 @cindex overlay example program
8536 When linking a program which uses overlays, you must place the overlays
8537 at their load addresses, while relocating them to run at their mapped
8538 addresses. To do this, you must write a linker script (@pxref{Overlay
8539 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8540 since linker scripts are specific to a particular host system, target
8541 architecture, and target memory layout, this manual cannot provide
8542 portable sample code demonstrating @value{GDBN}'s overlay support.
8544 However, the @value{GDBN} source distribution does contain an overlaid
8545 program, with linker scripts for a few systems, as part of its test
8546 suite. The program consists of the following files from
8547 @file{gdb/testsuite/gdb.base}:
8551 The main program file.
8553 A simple overlay manager, used by @file{overlays.c}.
8558 Overlay modules, loaded and used by @file{overlays.c}.
8561 Linker scripts for linking the test program on the @code{d10v-elf}
8562 and @code{m32r-elf} targets.
8565 You can build the test program using the @code{d10v-elf} GCC
8566 cross-compiler like this:
8569 $ d10v-elf-gcc -g -c overlays.c
8570 $ d10v-elf-gcc -g -c ovlymgr.c
8571 $ d10v-elf-gcc -g -c foo.c
8572 $ d10v-elf-gcc -g -c bar.c
8573 $ d10v-elf-gcc -g -c baz.c
8574 $ d10v-elf-gcc -g -c grbx.c
8575 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8576 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8579 The build process is identical for any other architecture, except that
8580 you must substitute the appropriate compiler and linker script for the
8581 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8585 @chapter Using @value{GDBN} with Different Languages
8588 Although programming languages generally have common aspects, they are
8589 rarely expressed in the same manner. For instance, in ANSI C,
8590 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8591 Modula-2, it is accomplished by @code{p^}. Values can also be
8592 represented (and displayed) differently. Hex numbers in C appear as
8593 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8595 @cindex working language
8596 Language-specific information is built into @value{GDBN} for some languages,
8597 allowing you to express operations like the above in your program's
8598 native language, and allowing @value{GDBN} to output values in a manner
8599 consistent with the syntax of your program's native language. The
8600 language you use to build expressions is called the @dfn{working
8604 * Setting:: Switching between source languages
8605 * Show:: Displaying the language
8606 * Checks:: Type and range checks
8607 * Supported languages:: Supported languages
8608 * Unsupported languages:: Unsupported languages
8612 @section Switching between source languages
8614 There are two ways to control the working language---either have @value{GDBN}
8615 set it automatically, or select it manually yourself. You can use the
8616 @code{set language} command for either purpose. On startup, @value{GDBN}
8617 defaults to setting the language automatically. The working language is
8618 used to determine how expressions you type are interpreted, how values
8621 In addition to the working language, every source file that
8622 @value{GDBN} knows about has its own working language. For some object
8623 file formats, the compiler might indicate which language a particular
8624 source file is in. However, most of the time @value{GDBN} infers the
8625 language from the name of the file. The language of a source file
8626 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8627 show each frame appropriately for its own language. There is no way to
8628 set the language of a source file from within @value{GDBN}, but you can
8629 set the language associated with a filename extension. @xref{Show, ,
8630 Displaying the language}.
8632 This is most commonly a problem when you use a program, such
8633 as @code{cfront} or @code{f2c}, that generates C but is written in
8634 another language. In that case, make the
8635 program use @code{#line} directives in its C output; that way
8636 @value{GDBN} will know the correct language of the source code of the original
8637 program, and will display that source code, not the generated C code.
8640 * Filenames:: Filename extensions and languages.
8641 * Manually:: Setting the working language manually
8642 * Automatically:: Having @value{GDBN} infer the source language
8646 @subsection List of filename extensions and languages
8648 If a source file name ends in one of the following extensions, then
8649 @value{GDBN} infers that its language is the one indicated.
8670 Objective-C source file
8677 Modula-2 source file
8681 Assembler source file. This actually behaves almost like C, but
8682 @value{GDBN} does not skip over function prologues when stepping.
8685 In addition, you may set the language associated with a filename
8686 extension. @xref{Show, , Displaying the language}.
8689 @subsection Setting the working language
8691 If you allow @value{GDBN} to set the language automatically,
8692 expressions are interpreted the same way in your debugging session and
8695 @kindex set language
8696 If you wish, you may set the language manually. To do this, issue the
8697 command @samp{set language @var{lang}}, where @var{lang} is the name of
8699 @code{c} or @code{modula-2}.
8700 For a list of the supported languages, type @samp{set language}.
8702 Setting the language manually prevents @value{GDBN} from updating the working
8703 language automatically. This can lead to confusion if you try
8704 to debug a program when the working language is not the same as the
8705 source language, when an expression is acceptable to both
8706 languages---but means different things. For instance, if the current
8707 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8715 might not have the effect you intended. In C, this means to add
8716 @code{b} and @code{c} and place the result in @code{a}. The result
8717 printed would be the value of @code{a}. In Modula-2, this means to compare
8718 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8721 @subsection Having @value{GDBN} infer the source language
8723 To have @value{GDBN} set the working language automatically, use
8724 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8725 then infers the working language. That is, when your program stops in a
8726 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8727 working language to the language recorded for the function in that
8728 frame. If the language for a frame is unknown (that is, if the function
8729 or block corresponding to the frame was defined in a source file that
8730 does not have a recognized extension), the current working language is
8731 not changed, and @value{GDBN} issues a warning.
8733 This may not seem necessary for most programs, which are written
8734 entirely in one source language. However, program modules and libraries
8735 written in one source language can be used by a main program written in
8736 a different source language. Using @samp{set language auto} in this
8737 case frees you from having to set the working language manually.
8740 @section Displaying the language
8742 The following commands help you find out which language is the
8743 working language, and also what language source files were written in.
8747 @kindex show language
8748 Display the current working language. This is the
8749 language you can use with commands such as @code{print} to
8750 build and compute expressions that may involve variables in your program.
8753 @kindex info frame@r{, show the source language}
8754 Display the source language for this frame. This language becomes the
8755 working language if you use an identifier from this frame.
8756 @xref{Frame Info, ,Information about a frame}, to identify the other
8757 information listed here.
8760 @kindex info source@r{, show the source language}
8761 Display the source language of this source file.
8762 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8763 information listed here.
8766 In unusual circumstances, you may have source files with extensions
8767 not in the standard list. You can then set the extension associated
8768 with a language explicitly:
8771 @item set extension-language @var{ext} @var{language}
8772 @kindex set extension-language
8773 Tell @value{GDBN} that source files with extension @var{ext} are to be
8774 assumed as written in the source language @var{language}.
8776 @item info extensions
8777 @kindex info extensions
8778 List all the filename extensions and the associated languages.
8782 @section Type and range checking
8785 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8786 checking are included, but they do not yet have any effect. This
8787 section documents the intended facilities.
8789 @c FIXME remove warning when type/range code added
8791 Some languages are designed to guard you against making seemingly common
8792 errors through a series of compile- and run-time checks. These include
8793 checking the type of arguments to functions and operators, and making
8794 sure mathematical overflows are caught at run time. Checks such as
8795 these help to ensure a program's correctness once it has been compiled
8796 by eliminating type mismatches, and providing active checks for range
8797 errors when your program is running.
8799 @value{GDBN} can check for conditions like the above if you wish.
8800 Although @value{GDBN} does not check the statements in your program,
8801 it can check expressions entered directly into @value{GDBN} for
8802 evaluation via the @code{print} command, for example. As with the
8803 working language, @value{GDBN} can also decide whether or not to check
8804 automatically based on your program's source language.
8805 @xref{Supported languages, ,Supported languages}, for the default
8806 settings of supported languages.
8809 * Type Checking:: An overview of type checking
8810 * Range Checking:: An overview of range checking
8813 @cindex type checking
8814 @cindex checks, type
8816 @subsection An overview of type checking
8818 Some languages, such as Modula-2, are strongly typed, meaning that the
8819 arguments to operators and functions have to be of the correct type,
8820 otherwise an error occurs. These checks prevent type mismatch
8821 errors from ever causing any run-time problems. For example,
8829 The second example fails because the @code{CARDINAL} 1 is not
8830 type-compatible with the @code{REAL} 2.3.
8832 For the expressions you use in @value{GDBN} commands, you can tell the
8833 @value{GDBN} type checker to skip checking;
8834 to treat any mismatches as errors and abandon the expression;
8835 or to only issue warnings when type mismatches occur,
8836 but evaluate the expression anyway. When you choose the last of
8837 these, @value{GDBN} evaluates expressions like the second example above, but
8838 also issues a warning.
8840 Even if you turn type checking off, there may be other reasons
8841 related to type that prevent @value{GDBN} from evaluating an expression.
8842 For instance, @value{GDBN} does not know how to add an @code{int} and
8843 a @code{struct foo}. These particular type errors have nothing to do
8844 with the language in use, and usually arise from expressions, such as
8845 the one described above, which make little sense to evaluate anyway.
8847 Each language defines to what degree it is strict about type. For
8848 instance, both Modula-2 and C require the arguments to arithmetical
8849 operators to be numbers. In C, enumerated types and pointers can be
8850 represented as numbers, so that they are valid arguments to mathematical
8851 operators. @xref{Supported languages, ,Supported languages}, for further
8852 details on specific languages.
8854 @value{GDBN} provides some additional commands for controlling the type checker:
8856 @kindex set check type
8857 @kindex show check type
8859 @item set check type auto
8860 Set type checking on or off based on the current working language.
8861 @xref{Supported languages, ,Supported languages}, for the default settings for
8864 @item set check type on
8865 @itemx set check type off
8866 Set type checking on or off, overriding the default setting for the
8867 current working language. Issue a warning if the setting does not
8868 match the language default. If any type mismatches occur in
8869 evaluating an expression while type checking is on, @value{GDBN} prints a
8870 message and aborts evaluation of the expression.
8872 @item set check type warn
8873 Cause the type checker to issue warnings, but to always attempt to
8874 evaluate the expression. Evaluating the expression may still
8875 be impossible for other reasons. For example, @value{GDBN} cannot add
8876 numbers and structures.
8879 Show the current setting of the type checker, and whether or not @value{GDBN}
8880 is setting it automatically.
8883 @cindex range checking
8884 @cindex checks, range
8885 @node Range Checking
8886 @subsection An overview of range checking
8888 In some languages (such as Modula-2), it is an error to exceed the
8889 bounds of a type; this is enforced with run-time checks. Such range
8890 checking is meant to ensure program correctness by making sure
8891 computations do not overflow, or indices on an array element access do
8892 not exceed the bounds of the array.
8894 For expressions you use in @value{GDBN} commands, you can tell
8895 @value{GDBN} to treat range errors in one of three ways: ignore them,
8896 always treat them as errors and abandon the expression, or issue
8897 warnings but evaluate the expression anyway.
8899 A range error can result from numerical overflow, from exceeding an
8900 array index bound, or when you type a constant that is not a member
8901 of any type. Some languages, however, do not treat overflows as an
8902 error. In many implementations of C, mathematical overflow causes the
8903 result to ``wrap around'' to lower values---for example, if @var{m} is
8904 the largest integer value, and @var{s} is the smallest, then
8907 @var{m} + 1 @result{} @var{s}
8910 This, too, is specific to individual languages, and in some cases
8911 specific to individual compilers or machines. @xref{Supported languages, ,
8912 Supported languages}, for further details on specific languages.
8914 @value{GDBN} provides some additional commands for controlling the range checker:
8916 @kindex set check range
8917 @kindex show check range
8919 @item set check range auto
8920 Set range checking on or off based on the current working language.
8921 @xref{Supported languages, ,Supported languages}, for the default settings for
8924 @item set check range on
8925 @itemx set check range off
8926 Set range checking on or off, overriding the default setting for the
8927 current working language. A warning is issued if the setting does not
8928 match the language default. If a range error occurs and range checking is on,
8929 then a message is printed and evaluation of the expression is aborted.
8931 @item set check range warn
8932 Output messages when the @value{GDBN} range checker detects a range error,
8933 but attempt to evaluate the expression anyway. Evaluating the
8934 expression may still be impossible for other reasons, such as accessing
8935 memory that the process does not own (a typical example from many Unix
8939 Show the current setting of the range checker, and whether or not it is
8940 being set automatically by @value{GDBN}.
8943 @node Supported languages
8944 @section Supported languages
8946 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8947 assembly, Modula-2, and Ada.
8948 @c This is false ...
8949 Some @value{GDBN} features may be used in expressions regardless of the
8950 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8951 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8952 ,Expressions}) can be used with the constructs of any supported
8955 The following sections detail to what degree each source language is
8956 supported by @value{GDBN}. These sections are not meant to be language
8957 tutorials or references, but serve only as a reference guide to what the
8958 @value{GDBN} expression parser accepts, and what input and output
8959 formats should look like for different languages. There are many good
8960 books written on each of these languages; please look to these for a
8961 language reference or tutorial.
8965 * Objective-C:: Objective-C
8968 * Modula-2:: Modula-2
8973 @subsection C and C@t{++}
8975 @cindex C and C@t{++}
8976 @cindex expressions in C or C@t{++}
8978 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8979 to both languages. Whenever this is the case, we discuss those languages
8983 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8984 @cindex @sc{gnu} C@t{++}
8985 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8986 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8987 effectively, you must compile your C@t{++} programs with a supported
8988 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8989 compiler (@code{aCC}).
8991 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8992 format; if it doesn't work on your system, try the stabs+ debugging
8993 format. You can select those formats explicitly with the @code{g++}
8994 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8995 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
8996 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
8999 * C Operators:: C and C@t{++} operators
9000 * C Constants:: C and C@t{++} constants
9001 * C plus plus expressions:: C@t{++} expressions
9002 * C Defaults:: Default settings for C and C@t{++}
9003 * C Checks:: C and C@t{++} type and range checks
9004 * Debugging C:: @value{GDBN} and C
9005 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
9009 @subsubsection C and C@t{++} operators
9011 @cindex C and C@t{++} operators
9013 Operators must be defined on values of specific types. For instance,
9014 @code{+} is defined on numbers, but not on structures. Operators are
9015 often defined on groups of types.
9017 For the purposes of C and C@t{++}, the following definitions hold:
9022 @emph{Integral types} include @code{int} with any of its storage-class
9023 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9026 @emph{Floating-point types} include @code{float}, @code{double}, and
9027 @code{long double} (if supported by the target platform).
9030 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9033 @emph{Scalar types} include all of the above.
9038 The following operators are supported. They are listed here
9039 in order of increasing precedence:
9043 The comma or sequencing operator. Expressions in a comma-separated list
9044 are evaluated from left to right, with the result of the entire
9045 expression being the last expression evaluated.
9048 Assignment. The value of an assignment expression is the value
9049 assigned. Defined on scalar types.
9052 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9053 and translated to @w{@code{@var{a} = @var{a op b}}}.
9054 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9055 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9056 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9059 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9060 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9064 Logical @sc{or}. Defined on integral types.
9067 Logical @sc{and}. Defined on integral types.
9070 Bitwise @sc{or}. Defined on integral types.
9073 Bitwise exclusive-@sc{or}. Defined on integral types.
9076 Bitwise @sc{and}. Defined on integral types.
9079 Equality and inequality. Defined on scalar types. The value of these
9080 expressions is 0 for false and non-zero for true.
9082 @item <@r{, }>@r{, }<=@r{, }>=
9083 Less than, greater than, less than or equal, greater than or equal.
9084 Defined on scalar types. The value of these expressions is 0 for false
9085 and non-zero for true.
9088 left shift, and right shift. Defined on integral types.
9091 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9094 Addition and subtraction. Defined on integral types, floating-point types and
9097 @item *@r{, }/@r{, }%
9098 Multiplication, division, and modulus. Multiplication and division are
9099 defined on integral and floating-point types. Modulus is defined on
9103 Increment and decrement. When appearing before a variable, the
9104 operation is performed before the variable is used in an expression;
9105 when appearing after it, the variable's value is used before the
9106 operation takes place.
9109 Pointer dereferencing. Defined on pointer types. Same precedence as
9113 Address operator. Defined on variables. Same precedence as @code{++}.
9115 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9116 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9117 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
9118 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9122 Negative. Defined on integral and floating-point types. Same
9123 precedence as @code{++}.
9126 Logical negation. Defined on integral types. Same precedence as
9130 Bitwise complement operator. Defined on integral types. Same precedence as
9135 Structure member, and pointer-to-structure member. For convenience,
9136 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9137 pointer based on the stored type information.
9138 Defined on @code{struct} and @code{union} data.
9141 Dereferences of pointers to members.
9144 Array indexing. @code{@var{a}[@var{i}]} is defined as
9145 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9148 Function parameter list. Same precedence as @code{->}.
9151 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9152 and @code{class} types.
9155 Doubled colons also represent the @value{GDBN} scope operator
9156 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9160 If an operator is redefined in the user code, @value{GDBN} usually
9161 attempts to invoke the redefined version instead of using the operator's
9165 @subsubsection C and C@t{++} constants
9167 @cindex C and C@t{++} constants
9169 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9174 Integer constants are a sequence of digits. Octal constants are
9175 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9176 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9177 @samp{l}, specifying that the constant should be treated as a
9181 Floating point constants are a sequence of digits, followed by a decimal
9182 point, followed by a sequence of digits, and optionally followed by an
9183 exponent. An exponent is of the form:
9184 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9185 sequence of digits. The @samp{+} is optional for positive exponents.
9186 A floating-point constant may also end with a letter @samp{f} or
9187 @samp{F}, specifying that the constant should be treated as being of
9188 the @code{float} (as opposed to the default @code{double}) type; or with
9189 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9193 Enumerated constants consist of enumerated identifiers, or their
9194 integral equivalents.
9197 Character constants are a single character surrounded by single quotes
9198 (@code{'}), or a number---the ordinal value of the corresponding character
9199 (usually its @sc{ascii} value). Within quotes, the single character may
9200 be represented by a letter or by @dfn{escape sequences}, which are of
9201 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9202 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9203 @samp{@var{x}} is a predefined special character---for example,
9204 @samp{\n} for newline.
9207 String constants are a sequence of character constants surrounded by
9208 double quotes (@code{"}). Any valid character constant (as described
9209 above) may appear. Double quotes within the string must be preceded by
9210 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9214 Pointer constants are an integral value. You can also write pointers
9215 to constants using the C operator @samp{&}.
9218 Array constants are comma-separated lists surrounded by braces @samp{@{}
9219 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9220 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9221 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9224 @node C plus plus expressions
9225 @subsubsection C@t{++} expressions
9227 @cindex expressions in C@t{++}
9228 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9230 @cindex debugging C@t{++} programs
9231 @cindex C@t{++} compilers
9232 @cindex debug formats and C@t{++}
9233 @cindex @value{NGCC} and C@t{++}
9235 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9236 proper compiler and the proper debug format. Currently, @value{GDBN}
9237 works best when debugging C@t{++} code that is compiled with
9238 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9239 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9240 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9241 stabs+ as their default debug format, so you usually don't need to
9242 specify a debug format explicitly. Other compilers and/or debug formats
9243 are likely to work badly or not at all when using @value{GDBN} to debug
9249 @cindex member functions
9251 Member function calls are allowed; you can use expressions like
9254 count = aml->GetOriginal(x, y)
9257 @vindex this@r{, inside C@t{++} member functions}
9258 @cindex namespace in C@t{++}
9260 While a member function is active (in the selected stack frame), your
9261 expressions have the same namespace available as the member function;
9262 that is, @value{GDBN} allows implicit references to the class instance
9263 pointer @code{this} following the same rules as C@t{++}.
9265 @cindex call overloaded functions
9266 @cindex overloaded functions, calling
9267 @cindex type conversions in C@t{++}
9269 You can call overloaded functions; @value{GDBN} resolves the function
9270 call to the right definition, with some restrictions. @value{GDBN} does not
9271 perform overload resolution involving user-defined type conversions,
9272 calls to constructors, or instantiations of templates that do not exist
9273 in the program. It also cannot handle ellipsis argument lists or
9276 It does perform integral conversions and promotions, floating-point
9277 promotions, arithmetic conversions, pointer conversions, conversions of
9278 class objects to base classes, and standard conversions such as those of
9279 functions or arrays to pointers; it requires an exact match on the
9280 number of function arguments.
9282 Overload resolution is always performed, unless you have specified
9283 @code{set overload-resolution off}. @xref{Debugging C plus plus,
9284 ,@value{GDBN} features for C@t{++}}.
9286 You must specify @code{set overload-resolution off} in order to use an
9287 explicit function signature to call an overloaded function, as in
9289 p 'foo(char,int)'('x', 13)
9292 The @value{GDBN} command-completion facility can simplify this;
9293 see @ref{Completion, ,Command completion}.
9295 @cindex reference declarations
9297 @value{GDBN} understands variables declared as C@t{++} references; you can use
9298 them in expressions just as you do in C@t{++} source---they are automatically
9301 In the parameter list shown when @value{GDBN} displays a frame, the values of
9302 reference variables are not displayed (unlike other variables); this
9303 avoids clutter, since references are often used for large structures.
9304 The @emph{address} of a reference variable is always shown, unless
9305 you have specified @samp{set print address off}.
9308 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9309 expressions can use it just as expressions in your program do. Since
9310 one scope may be defined in another, you can use @code{::} repeatedly if
9311 necessary, for example in an expression like
9312 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9313 resolving name scope by reference to source files, in both C and C@t{++}
9314 debugging (@pxref{Variables, ,Program variables}).
9317 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9318 calling virtual functions correctly, printing out virtual bases of
9319 objects, calling functions in a base subobject, casting objects, and
9320 invoking user-defined operators.
9323 @subsubsection C and C@t{++} defaults
9325 @cindex C and C@t{++} defaults
9327 If you allow @value{GDBN} to set type and range checking automatically, they
9328 both default to @code{off} whenever the working language changes to
9329 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9330 selects the working language.
9332 If you allow @value{GDBN} to set the language automatically, it
9333 recognizes source files whose names end with @file{.c}, @file{.C}, or
9334 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9335 these files, it sets the working language to C or C@t{++}.
9336 @xref{Automatically, ,Having @value{GDBN} infer the source language},
9337 for further details.
9339 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9340 @c unimplemented. If (b) changes, it might make sense to let this node
9341 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9344 @subsubsection C and C@t{++} type and range checks
9346 @cindex C and C@t{++} checks
9348 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9349 is not used. However, if you turn type checking on, @value{GDBN}
9350 considers two variables type equivalent if:
9354 The two variables are structured and have the same structure, union, or
9358 The two variables have the same type name, or types that have been
9359 declared equivalent through @code{typedef}.
9362 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9365 The two @code{struct}, @code{union}, or @code{enum} variables are
9366 declared in the same declaration. (Note: this may not be true for all C
9371 Range checking, if turned on, is done on mathematical operations. Array
9372 indices are not checked, since they are often used to index a pointer
9373 that is not itself an array.
9376 @subsubsection @value{GDBN} and C
9378 The @code{set print union} and @code{show print union} commands apply to
9379 the @code{union} type. When set to @samp{on}, any @code{union} that is
9380 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9381 appears as @samp{@{...@}}.
9383 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9384 with pointers and a memory allocation function. @xref{Expressions,
9387 @node Debugging C plus plus
9388 @subsubsection @value{GDBN} features for C@t{++}
9390 @cindex commands for C@t{++}
9392 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9393 designed specifically for use with C@t{++}. Here is a summary:
9396 @cindex break in overloaded functions
9397 @item @r{breakpoint menus}
9398 When you want a breakpoint in a function whose name is overloaded,
9399 @value{GDBN} breakpoint menus help you specify which function definition
9400 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
9402 @cindex overloading in C@t{++}
9403 @item rbreak @var{regex}
9404 Setting breakpoints using regular expressions is helpful for setting
9405 breakpoints on overloaded functions that are not members of any special
9407 @xref{Set Breaks, ,Setting breakpoints}.
9409 @cindex C@t{++} exception handling
9412 Debug C@t{++} exception handling using these commands. @xref{Set
9413 Catchpoints, , Setting catchpoints}.
9416 @item ptype @var{typename}
9417 Print inheritance relationships as well as other information for type
9419 @xref{Symbols, ,Examining the Symbol Table}.
9421 @cindex C@t{++} symbol display
9422 @item set print demangle
9423 @itemx show print demangle
9424 @itemx set print asm-demangle
9425 @itemx show print asm-demangle
9426 Control whether C@t{++} symbols display in their source form, both when
9427 displaying code as C@t{++} source and when displaying disassemblies.
9428 @xref{Print Settings, ,Print settings}.
9430 @item set print object
9431 @itemx show print object
9432 Choose whether to print derived (actual) or declared types of objects.
9433 @xref{Print Settings, ,Print settings}.
9435 @item set print vtbl
9436 @itemx show print vtbl
9437 Control the format for printing virtual function tables.
9438 @xref{Print Settings, ,Print settings}.
9439 (The @code{vtbl} commands do not work on programs compiled with the HP
9440 ANSI C@t{++} compiler (@code{aCC}).)
9442 @kindex set overload-resolution
9443 @cindex overloaded functions, overload resolution
9444 @item set overload-resolution on
9445 Enable overload resolution for C@t{++} expression evaluation. The default
9446 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9447 and searches for a function whose signature matches the argument types,
9448 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
9449 expressions}, for details). If it cannot find a match, it emits a
9452 @item set overload-resolution off
9453 Disable overload resolution for C@t{++} expression evaluation. For
9454 overloaded functions that are not class member functions, @value{GDBN}
9455 chooses the first function of the specified name that it finds in the
9456 symbol table, whether or not its arguments are of the correct type. For
9457 overloaded functions that are class member functions, @value{GDBN}
9458 searches for a function whose signature @emph{exactly} matches the
9461 @kindex show overload-resolution
9462 @item show overload-resolution
9463 Show the current setting of overload resolution.
9465 @item @r{Overloaded symbol names}
9466 You can specify a particular definition of an overloaded symbol, using
9467 the same notation that is used to declare such symbols in C@t{++}: type
9468 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9469 also use the @value{GDBN} command-line word completion facilities to list the
9470 available choices, or to finish the type list for you.
9471 @xref{Completion,, Command completion}, for details on how to do this.
9475 @subsection Objective-C
9478 This section provides information about some commands and command
9479 options that are useful for debugging Objective-C code. See also
9480 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9481 few more commands specific to Objective-C support.
9484 * Method Names in Commands::
9485 * The Print Command with Objective-C::
9488 @node Method Names in Commands
9489 @subsubsection Method Names in Commands
9491 The following commands have been extended to accept Objective-C method
9492 names as line specifications:
9494 @kindex clear@r{, and Objective-C}
9495 @kindex break@r{, and Objective-C}
9496 @kindex info line@r{, and Objective-C}
9497 @kindex jump@r{, and Objective-C}
9498 @kindex list@r{, and Objective-C}
9502 @item @code{info line}
9507 A fully qualified Objective-C method name is specified as
9510 -[@var{Class} @var{methodName}]
9513 where the minus sign is used to indicate an instance method and a
9514 plus sign (not shown) is used to indicate a class method. The class
9515 name @var{Class} and method name @var{methodName} are enclosed in
9516 brackets, similar to the way messages are specified in Objective-C
9517 source code. For example, to set a breakpoint at the @code{create}
9518 instance method of class @code{Fruit} in the program currently being
9522 break -[Fruit create]
9525 To list ten program lines around the @code{initialize} class method,
9529 list +[NSText initialize]
9532 In the current version of @value{GDBN}, the plus or minus sign is
9533 required. In future versions of @value{GDBN}, the plus or minus
9534 sign will be optional, but you can use it to narrow the search. It
9535 is also possible to specify just a method name:
9541 You must specify the complete method name, including any colons. If
9542 your program's source files contain more than one @code{create} method,
9543 you'll be presented with a numbered list of classes that implement that
9544 method. Indicate your choice by number, or type @samp{0} to exit if
9547 As another example, to clear a breakpoint established at the
9548 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9551 clear -[NSWindow makeKeyAndOrderFront:]
9554 @node The Print Command with Objective-C
9555 @subsubsection The Print Command With Objective-C
9556 @cindex Objective-C, print objects
9557 @kindex print-object
9558 @kindex po @r{(@code{print-object})}
9560 The print command has also been extended to accept methods. For example:
9563 print -[@var{object} hash]
9566 @cindex print an Objective-C object description
9567 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9569 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9570 and print the result. Also, an additional command has been added,
9571 @code{print-object} or @code{po} for short, which is meant to print
9572 the description of an object. However, this command may only work
9573 with certain Objective-C libraries that have a particular hook
9574 function, @code{_NSPrintForDebugger}, defined.
9578 @cindex Fortran-specific support in @value{GDBN}
9580 @value{GDBN} can be used to debug programs written in Fortran, but it
9581 currently supports only the features of Fortran 77 language.
9583 @cindex trailing underscore, in Fortran symbols
9584 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9585 among them) append an underscore to the names of variables and
9586 functions. When you debug programs compiled by those compilers, you
9587 will need to refer to variables and functions with a trailing
9591 * Fortran Operators:: Fortran operators and expressions
9592 * Fortran Defaults:: Default settings for Fortran
9593 * Special Fortran commands:: Special @value{GDBN} commands for Fortran
9596 @node Fortran Operators
9597 @subsubsection Fortran operators and expressions
9599 @cindex Fortran operators and expressions
9601 Operators must be defined on values of specific types. For instance,
9602 @code{+} is defined on numbers, but not on characters or other non-
9603 arithmetic types. Operators are often defined on groups of types.
9607 The exponentiation operator. It raises the first operand to the power
9611 The range operator. Normally used in the form of array(low:high) to
9612 represent a section of array.
9615 @node Fortran Defaults
9616 @subsubsection Fortran Defaults
9618 @cindex Fortran Defaults
9620 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9621 default uses case-insensitive matches for Fortran symbols. You can
9622 change that with the @samp{set case-insensitive} command, see
9623 @ref{Symbols}, for the details.
9625 @node Special Fortran commands
9626 @subsubsection Special Fortran commands
9628 @cindex Special Fortran commands
9630 @value{GDBN} had some commands to support Fortran specific feature,
9631 such as common block displaying.
9634 @cindex @code{COMMON} blocks, Fortran
9636 @item info common @r{[}@var{common-name}@r{]}
9637 This command prints the values contained in the Fortran @code{COMMON}
9638 block whose name is @var{common-name}. With no argument, the names of
9639 all @code{COMMON} blocks visible at the current program location are
9646 @cindex Pascal support in @value{GDBN}, limitations
9647 Debugging Pascal programs which use sets, subranges, file variables, or
9648 nested functions does not currently work. @value{GDBN} does not support
9649 entering expressions, printing values, or similar features using Pascal
9652 The Pascal-specific command @code{set print pascal_static-members}
9653 controls whether static members of Pascal objects are displayed.
9654 @xref{Print Settings, pascal_static-members}.
9657 @subsection Modula-2
9659 @cindex Modula-2, @value{GDBN} support
9661 The extensions made to @value{GDBN} to support Modula-2 only support
9662 output from the @sc{gnu} Modula-2 compiler (which is currently being
9663 developed). Other Modula-2 compilers are not currently supported, and
9664 attempting to debug executables produced by them is most likely
9665 to give an error as @value{GDBN} reads in the executable's symbol
9668 @cindex expressions in Modula-2
9670 * M2 Operators:: Built-in operators
9671 * Built-In Func/Proc:: Built-in functions and procedures
9672 * M2 Constants:: Modula-2 constants
9673 * M2 Types:: Modula-2 types
9674 * M2 Defaults:: Default settings for Modula-2
9675 * Deviations:: Deviations from standard Modula-2
9676 * M2 Checks:: Modula-2 type and range checks
9677 * M2 Scope:: The scope operators @code{::} and @code{.}
9678 * GDB/M2:: @value{GDBN} and Modula-2
9682 @subsubsection Operators
9683 @cindex Modula-2 operators
9685 Operators must be defined on values of specific types. For instance,
9686 @code{+} is defined on numbers, but not on structures. Operators are
9687 often defined on groups of types. For the purposes of Modula-2, the
9688 following definitions hold:
9693 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9697 @emph{Character types} consist of @code{CHAR} and its subranges.
9700 @emph{Floating-point types} consist of @code{REAL}.
9703 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9707 @emph{Scalar types} consist of all of the above.
9710 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9713 @emph{Boolean types} consist of @code{BOOLEAN}.
9717 The following operators are supported, and appear in order of
9718 increasing precedence:
9722 Function argument or array index separator.
9725 Assignment. The value of @var{var} @code{:=} @var{value} is
9729 Less than, greater than on integral, floating-point, or enumerated
9733 Less than or equal to, greater than or equal to
9734 on integral, floating-point and enumerated types, or set inclusion on
9735 set types. Same precedence as @code{<}.
9737 @item =@r{, }<>@r{, }#
9738 Equality and two ways of expressing inequality, valid on scalar types.
9739 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9740 available for inequality, since @code{#} conflicts with the script
9744 Set membership. Defined on set types and the types of their members.
9745 Same precedence as @code{<}.
9748 Boolean disjunction. Defined on boolean types.
9751 Boolean conjunction. Defined on boolean types.
9754 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9757 Addition and subtraction on integral and floating-point types, or union
9758 and difference on set types.
9761 Multiplication on integral and floating-point types, or set intersection
9765 Division on floating-point types, or symmetric set difference on set
9766 types. Same precedence as @code{*}.
9769 Integer division and remainder. Defined on integral types. Same
9770 precedence as @code{*}.
9773 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9776 Pointer dereferencing. Defined on pointer types.
9779 Boolean negation. Defined on boolean types. Same precedence as
9783 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9784 precedence as @code{^}.
9787 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9790 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9794 @value{GDBN} and Modula-2 scope operators.
9798 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9799 treats the use of the operator @code{IN}, or the use of operators
9800 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9801 @code{<=}, and @code{>=} on sets as an error.
9805 @node Built-In Func/Proc
9806 @subsubsection Built-in functions and procedures
9807 @cindex Modula-2 built-ins
9809 Modula-2 also makes available several built-in procedures and functions.
9810 In describing these, the following metavariables are used:
9815 represents an @code{ARRAY} variable.
9818 represents a @code{CHAR} constant or variable.
9821 represents a variable or constant of integral type.
9824 represents an identifier that belongs to a set. Generally used in the
9825 same function with the metavariable @var{s}. The type of @var{s} should
9826 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9829 represents a variable or constant of integral or floating-point type.
9832 represents a variable or constant of floating-point type.
9838 represents a variable.
9841 represents a variable or constant of one of many types. See the
9842 explanation of the function for details.
9845 All Modula-2 built-in procedures also return a result, described below.
9849 Returns the absolute value of @var{n}.
9852 If @var{c} is a lower case letter, it returns its upper case
9853 equivalent, otherwise it returns its argument.
9856 Returns the character whose ordinal value is @var{i}.
9859 Decrements the value in the variable @var{v} by one. Returns the new value.
9861 @item DEC(@var{v},@var{i})
9862 Decrements the value in the variable @var{v} by @var{i}. Returns the
9865 @item EXCL(@var{m},@var{s})
9866 Removes the element @var{m} from the set @var{s}. Returns the new
9869 @item FLOAT(@var{i})
9870 Returns the floating point equivalent of the integer @var{i}.
9873 Returns the index of the last member of @var{a}.
9876 Increments the value in the variable @var{v} by one. Returns the new value.
9878 @item INC(@var{v},@var{i})
9879 Increments the value in the variable @var{v} by @var{i}. Returns the
9882 @item INCL(@var{m},@var{s})
9883 Adds the element @var{m} to the set @var{s} if it is not already
9884 there. Returns the new set.
9887 Returns the maximum value of the type @var{t}.
9890 Returns the minimum value of the type @var{t}.
9893 Returns boolean TRUE if @var{i} is an odd number.
9896 Returns the ordinal value of its argument. For example, the ordinal
9897 value of a character is its @sc{ascii} value (on machines supporting the
9898 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9899 integral, character and enumerated types.
9902 Returns the size of its argument. @var{x} can be a variable or a type.
9904 @item TRUNC(@var{r})
9905 Returns the integral part of @var{r}.
9907 @item VAL(@var{t},@var{i})
9908 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9912 @emph{Warning:} Sets and their operations are not yet supported, so
9913 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9917 @cindex Modula-2 constants
9919 @subsubsection Constants
9921 @value{GDBN} allows you to express the constants of Modula-2 in the following
9927 Integer constants are simply a sequence of digits. When used in an
9928 expression, a constant is interpreted to be type-compatible with the
9929 rest of the expression. Hexadecimal integers are specified by a
9930 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9933 Floating point constants appear as a sequence of digits, followed by a
9934 decimal point and another sequence of digits. An optional exponent can
9935 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9936 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9937 digits of the floating point constant must be valid decimal (base 10)
9941 Character constants consist of a single character enclosed by a pair of
9942 like quotes, either single (@code{'}) or double (@code{"}). They may
9943 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9944 followed by a @samp{C}.
9947 String constants consist of a sequence of characters enclosed by a
9948 pair of like quotes, either single (@code{'}) or double (@code{"}).
9949 Escape sequences in the style of C are also allowed. @xref{C
9950 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9954 Enumerated constants consist of an enumerated identifier.
9957 Boolean constants consist of the identifiers @code{TRUE} and
9961 Pointer constants consist of integral values only.
9964 Set constants are not yet supported.
9968 @subsubsection Modula-2 Types
9969 @cindex Modula-2 types
9971 Currently @value{GDBN} can print the following data types in Modula-2
9972 syntax: array types, record types, set types, pointer types, procedure
9973 types, enumerated types, subrange types and base types. You can also
9974 print the contents of variables declared using these type.
9975 This section gives a number of simple source code examples together with
9976 sample @value{GDBN} sessions.
9978 The first example contains the following section of code:
9987 and you can request @value{GDBN} to interrogate the type and value of
9988 @code{r} and @code{s}.
9991 (@value{GDBP}) print s
9993 (@value{GDBP}) ptype s
9995 (@value{GDBP}) print r
9997 (@value{GDBP}) ptype r
10002 Likewise if your source code declares @code{s} as:
10006 s: SET ['A'..'Z'] ;
10010 then you may query the type of @code{s} by:
10013 (@value{GDBP}) ptype s
10014 type = SET ['A'..'Z']
10018 Note that at present you cannot interactively manipulate set
10019 expressions using the debugger.
10021 The following example shows how you might declare an array in Modula-2
10022 and how you can interact with @value{GDBN} to print its type and contents:
10026 s: ARRAY [-10..10] OF CHAR ;
10030 (@value{GDBP}) ptype s
10031 ARRAY [-10..10] OF CHAR
10034 Note that the array handling is not yet complete and although the type
10035 is printed correctly, expression handling still assumes that all
10036 arrays have a lower bound of zero and not @code{-10} as in the example
10037 above. Unbounded arrays are also not yet recognized in @value{GDBN}.
10039 Here are some more type related Modula-2 examples:
10043 colour = (blue, red, yellow, green) ;
10044 t = [blue..yellow] ;
10052 The @value{GDBN} interaction shows how you can query the data type
10053 and value of a variable.
10056 (@value{GDBP}) print s
10058 (@value{GDBP}) ptype t
10059 type = [blue..yellow]
10063 In this example a Modula-2 array is declared and its contents
10064 displayed. Observe that the contents are written in the same way as
10065 their @code{C} counterparts.
10069 s: ARRAY [1..5] OF CARDINAL ;
10075 (@value{GDBP}) print s
10076 $1 = @{1, 0, 0, 0, 0@}
10077 (@value{GDBP}) ptype s
10078 type = ARRAY [1..5] OF CARDINAL
10081 The Modula-2 language interface to @value{GDBN} also understands
10082 pointer types as shown in this example:
10086 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10093 and you can request that @value{GDBN} describes the type of @code{s}.
10096 (@value{GDBP}) ptype s
10097 type = POINTER TO ARRAY [1..5] OF CARDINAL
10100 @value{GDBN} handles compound types as we can see in this example.
10101 Here we combine array types, record types, pointer types and subrange
10112 myarray = ARRAY myrange OF CARDINAL ;
10113 myrange = [-2..2] ;
10115 s: POINTER TO ARRAY myrange OF foo ;
10119 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10123 (@value{GDBP}) ptype s
10124 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10127 f3 : ARRAY [-2..2] OF CARDINAL;
10132 @subsubsection Modula-2 defaults
10133 @cindex Modula-2 defaults
10135 If type and range checking are set automatically by @value{GDBN}, they
10136 both default to @code{on} whenever the working language changes to
10137 Modula-2. This happens regardless of whether you or @value{GDBN}
10138 selected the working language.
10140 If you allow @value{GDBN} to set the language automatically, then entering
10141 code compiled from a file whose name ends with @file{.mod} sets the
10142 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
10143 the language automatically}, for further details.
10146 @subsubsection Deviations from standard Modula-2
10147 @cindex Modula-2, deviations from
10149 A few changes have been made to make Modula-2 programs easier to debug.
10150 This is done primarily via loosening its type strictness:
10154 Unlike in standard Modula-2, pointer constants can be formed by
10155 integers. This allows you to modify pointer variables during
10156 debugging. (In standard Modula-2, the actual address contained in a
10157 pointer variable is hidden from you; it can only be modified
10158 through direct assignment to another pointer variable or expression that
10159 returned a pointer.)
10162 C escape sequences can be used in strings and characters to represent
10163 non-printable characters. @value{GDBN} prints out strings with these
10164 escape sequences embedded. Single non-printable characters are
10165 printed using the @samp{CHR(@var{nnn})} format.
10168 The assignment operator (@code{:=}) returns the value of its right-hand
10172 All built-in procedures both modify @emph{and} return their argument.
10176 @subsubsection Modula-2 type and range checks
10177 @cindex Modula-2 checks
10180 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10183 @c FIXME remove warning when type/range checks added
10185 @value{GDBN} considers two Modula-2 variables type equivalent if:
10189 They are of types that have been declared equivalent via a @code{TYPE
10190 @var{t1} = @var{t2}} statement
10193 They have been declared on the same line. (Note: This is true of the
10194 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10197 As long as type checking is enabled, any attempt to combine variables
10198 whose types are not equivalent is an error.
10200 Range checking is done on all mathematical operations, assignment, array
10201 index bounds, and all built-in functions and procedures.
10204 @subsubsection The scope operators @code{::} and @code{.}
10206 @cindex @code{.}, Modula-2 scope operator
10207 @cindex colon, doubled as scope operator
10209 @vindex colon-colon@r{, in Modula-2}
10210 @c Info cannot handle :: but TeX can.
10213 @vindex ::@r{, in Modula-2}
10216 There are a few subtle differences between the Modula-2 scope operator
10217 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10222 @var{module} . @var{id}
10223 @var{scope} :: @var{id}
10227 where @var{scope} is the name of a module or a procedure,
10228 @var{module} the name of a module, and @var{id} is any declared
10229 identifier within your program, except another module.
10231 Using the @code{::} operator makes @value{GDBN} search the scope
10232 specified by @var{scope} for the identifier @var{id}. If it is not
10233 found in the specified scope, then @value{GDBN} searches all scopes
10234 enclosing the one specified by @var{scope}.
10236 Using the @code{.} operator makes @value{GDBN} search the current scope for
10237 the identifier specified by @var{id} that was imported from the
10238 definition module specified by @var{module}. With this operator, it is
10239 an error if the identifier @var{id} was not imported from definition
10240 module @var{module}, or if @var{id} is not an identifier in
10244 @subsubsection @value{GDBN} and Modula-2
10246 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10247 Five subcommands of @code{set print} and @code{show print} apply
10248 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10249 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10250 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10251 analogue in Modula-2.
10253 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10254 with any language, is not useful with Modula-2. Its
10255 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10256 created in Modula-2 as they can in C or C@t{++}. However, because an
10257 address can be specified by an integral constant, the construct
10258 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10260 @cindex @code{#} in Modula-2
10261 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10262 interpreted as the beginning of a comment. Use @code{<>} instead.
10268 The extensions made to @value{GDBN} for Ada only support
10269 output from the @sc{gnu} Ada (GNAT) compiler.
10270 Other Ada compilers are not currently supported, and
10271 attempting to debug executables produced by them is most likely
10275 @cindex expressions in Ada
10277 * Ada Mode Intro:: General remarks on the Ada syntax
10278 and semantics supported by Ada mode
10280 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10281 * Additions to Ada:: Extensions of the Ada expression syntax.
10282 * Stopping Before Main Program:: Debugging the program during elaboration.
10283 * Ada Glitches:: Known peculiarities of Ada mode.
10286 @node Ada Mode Intro
10287 @subsubsection Introduction
10288 @cindex Ada mode, general
10290 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10291 syntax, with some extensions.
10292 The philosophy behind the design of this subset is
10296 That @value{GDBN} should provide basic literals and access to operations for
10297 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10298 leaving more sophisticated computations to subprograms written into the
10299 program (which therefore may be called from @value{GDBN}).
10302 That type safety and strict adherence to Ada language restrictions
10303 are not particularly important to the @value{GDBN} user.
10306 That brevity is important to the @value{GDBN} user.
10309 Thus, for brevity, the debugger acts as if there were
10310 implicit @code{with} and @code{use} clauses in effect for all user-written
10311 packages, making it unnecessary to fully qualify most names with
10312 their packages, regardless of context. Where this causes ambiguity,
10313 @value{GDBN} asks the user's intent.
10315 The debugger will start in Ada mode if it detects an Ada main program.
10316 As for other languages, it will enter Ada mode when stopped in a program that
10317 was translated from an Ada source file.
10319 While in Ada mode, you may use `@t{--}' for comments. This is useful
10320 mostly for documenting command files. The standard @value{GDBN} comment
10321 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10322 middle (to allow based literals).
10324 The debugger supports limited overloading. Given a subprogram call in which
10325 the function symbol has multiple definitions, it will use the number of
10326 actual parameters and some information about their types to attempt to narrow
10327 the set of definitions. It also makes very limited use of context, preferring
10328 procedures to functions in the context of the @code{call} command, and
10329 functions to procedures elsewhere.
10331 @node Omissions from Ada
10332 @subsubsection Omissions from Ada
10333 @cindex Ada, omissions from
10335 Here are the notable omissions from the subset:
10339 Only a subset of the attributes are supported:
10343 @t{'First}, @t{'Last}, and @t{'Length}
10344 on array objects (not on types and subtypes).
10347 @t{'Min} and @t{'Max}.
10350 @t{'Pos} and @t{'Val}.
10356 @t{'Range} on array objects (not subtypes), but only as the right
10357 operand of the membership (@code{in}) operator.
10360 @t{'Access}, @t{'Unchecked_Access}, and
10361 @t{'Unrestricted_Access} (a GNAT extension).
10369 @code{Characters.Latin_1} are not available and
10370 concatenation is not implemented. Thus, escape characters in strings are
10371 not currently available.
10374 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10375 equality of representations. They will generally work correctly
10376 for strings and arrays whose elements have integer or enumeration types.
10377 They may not work correctly for arrays whose element
10378 types have user-defined equality, for arrays of real values
10379 (in particular, IEEE-conformant floating point, because of negative
10380 zeroes and NaNs), and for arrays whose elements contain unused bits with
10381 indeterminate values.
10384 The other component-by-component array operations (@code{and}, @code{or},
10385 @code{xor}, @code{not}, and relational tests other than equality)
10386 are not implemented.
10389 @cindex array aggregates (Ada)
10390 @cindex record aggregates (Ada)
10391 @cindex aggregates (Ada)
10392 There is limited support for array and record aggregates. They are
10393 permitted only on the right sides of assignments, as in these examples:
10396 set An_Array := (1, 2, 3, 4, 5, 6)
10397 set An_Array := (1, others => 0)
10398 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10399 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10400 set A_Record := (1, "Peter", True);
10401 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10405 discriminant's value by assigning an aggregate has an
10406 undefined effect if that discriminant is used within the record.
10407 However, you can first modify discriminants by directly assigning to
10408 them (which normally would not be allowed in Ada), and then performing an
10409 aggregate assignment. For example, given a variable @code{A_Rec}
10410 declared to have a type such as:
10413 type Rec (Len : Small_Integer := 0) is record
10415 Vals : IntArray (1 .. Len);
10419 you can assign a value with a different size of @code{Vals} with two
10424 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10427 As this example also illustrates, @value{GDBN} is very loose about the usual
10428 rules concerning aggregates. You may leave out some of the
10429 components of an array or record aggregate (such as the @code{Len}
10430 component in the assignment to @code{A_Rec} above); they will retain their
10431 original values upon assignment. You may freely use dynamic values as
10432 indices in component associations. You may even use overlapping or
10433 redundant component associations, although which component values are
10434 assigned in such cases is not defined.
10437 Calls to dispatching subprograms are not implemented.
10440 The overloading algorithm is much more limited (i.e., less selective)
10441 than that of real Ada. It makes only limited use of the context in
10442 which a subexpression appears to resolve its meaning, and it is much
10443 looser in its rules for allowing type matches. As a result, some
10444 function calls will be ambiguous, and the user will be asked to choose
10445 the proper resolution.
10448 The @code{new} operator is not implemented.
10451 Entry calls are not implemented.
10454 Aside from printing, arithmetic operations on the native VAX floating-point
10455 formats are not supported.
10458 It is not possible to slice a packed array.
10461 @node Additions to Ada
10462 @subsubsection Additions to Ada
10463 @cindex Ada, deviations from
10465 As it does for other languages, @value{GDBN} makes certain generic
10466 extensions to Ada (@pxref{Expressions}):
10470 If the expression @var{E} is a variable residing in memory (typically
10471 a local variable or array element) and @var{N} is a positive integer,
10472 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10473 @var{N}-1 adjacent variables following it in memory as an array. In
10474 Ada, this operator is generally not necessary, since its prime use is
10475 in displaying parts of an array, and slicing will usually do this in
10476 Ada. However, there are occasional uses when debugging programs in
10477 which certain debugging information has been optimized away.
10480 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10481 appears in function or file @var{B}.'' When @var{B} is a file name,
10482 you must typically surround it in single quotes.
10485 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10486 @var{type} that appears at address @var{addr}.''
10489 A name starting with @samp{$} is a convenience variable
10490 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10493 In addition, @value{GDBN} provides a few other shortcuts and outright
10494 additions specific to Ada:
10498 The assignment statement is allowed as an expression, returning
10499 its right-hand operand as its value. Thus, you may enter
10503 print A(tmp := y + 1)
10507 The semicolon is allowed as an ``operator,'' returning as its value
10508 the value of its right-hand operand.
10509 This allows, for example,
10510 complex conditional breaks:
10514 condition 1 (report(i); k += 1; A(k) > 100)
10518 Rather than use catenation and symbolic character names to introduce special
10519 characters into strings, one may instead use a special bracket notation,
10520 which is also used to print strings. A sequence of characters of the form
10521 @samp{["@var{XX}"]} within a string or character literal denotes the
10522 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10523 sequence of characters @samp{["""]} also denotes a single quotation mark
10524 in strings. For example,
10526 "One line.["0a"]Next line.["0a"]"
10529 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10533 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10534 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10542 When printing arrays, @value{GDBN} uses positional notation when the
10543 array has a lower bound of 1, and uses a modified named notation otherwise.
10544 For example, a one-dimensional array of three integers with a lower bound
10545 of 3 might print as
10552 That is, in contrast to valid Ada, only the first component has a @code{=>}
10556 You may abbreviate attributes in expressions with any unique,
10557 multi-character subsequence of
10558 their names (an exact match gets preference).
10559 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10560 in place of @t{a'length}.
10563 @cindex quoting Ada internal identifiers
10564 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10565 to lower case. The GNAT compiler uses upper-case characters for
10566 some of its internal identifiers, which are normally of no interest to users.
10567 For the rare occasions when you actually have to look at them,
10568 enclose them in angle brackets to avoid the lower-case mapping.
10571 @value{GDBP} print <JMPBUF_SAVE>[0]
10575 Printing an object of class-wide type or dereferencing an
10576 access-to-class-wide value will display all the components of the object's
10577 specific type (as indicated by its run-time tag). Likewise, component
10578 selection on such a value will operate on the specific type of the
10583 @node Stopping Before Main Program
10584 @subsubsection Stopping at the Very Beginning
10586 @cindex breakpointing Ada elaboration code
10587 It is sometimes necessary to debug the program during elaboration, and
10588 before reaching the main procedure.
10589 As defined in the Ada Reference
10590 Manual, the elaboration code is invoked from a procedure called
10591 @code{adainit}. To run your program up to the beginning of
10592 elaboration, simply use the following two commands:
10593 @code{tbreak adainit} and @code{run}.
10596 @subsubsection Known Peculiarities of Ada Mode
10597 @cindex Ada, problems
10599 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10600 we know of several problems with and limitations of Ada mode in
10602 some of which will be fixed with planned future releases of the debugger
10603 and the GNU Ada compiler.
10607 Currently, the debugger
10608 has insufficient information to determine whether certain pointers represent
10609 pointers to objects or the objects themselves.
10610 Thus, the user may have to tack an extra @code{.all} after an expression
10611 to get it printed properly.
10614 Static constants that the compiler chooses not to materialize as objects in
10615 storage are invisible to the debugger.
10618 Named parameter associations in function argument lists are ignored (the
10619 argument lists are treated as positional).
10622 Many useful library packages are currently invisible to the debugger.
10625 Fixed-point arithmetic, conversions, input, and output is carried out using
10626 floating-point arithmetic, and may give results that only approximate those on
10630 The type of the @t{'Address} attribute may not be @code{System.Address}.
10633 The GNAT compiler never generates the prefix @code{Standard} for any of
10634 the standard symbols defined by the Ada language. @value{GDBN} knows about
10635 this: it will strip the prefix from names when you use it, and will never
10636 look for a name you have so qualified among local symbols, nor match against
10637 symbols in other packages or subprograms. If you have
10638 defined entities anywhere in your program other than parameters and
10639 local variables whose simple names match names in @code{Standard},
10640 GNAT's lack of qualification here can cause confusion. When this happens,
10641 you can usually resolve the confusion
10642 by qualifying the problematic names with package
10643 @code{Standard} explicitly.
10646 @node Unsupported languages
10647 @section Unsupported languages
10649 @cindex unsupported languages
10650 @cindex minimal language
10651 In addition to the other fully-supported programming languages,
10652 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10653 It does not represent a real programming language, but provides a set
10654 of capabilities close to what the C or assembly languages provide.
10655 This should allow most simple operations to be performed while debugging
10656 an application that uses a language currently not supported by @value{GDBN}.
10658 If the language is set to @code{auto}, @value{GDBN} will automatically
10659 select this language if the current frame corresponds to an unsupported
10663 @chapter Examining the Symbol Table
10665 The commands described in this chapter allow you to inquire about the
10666 symbols (names of variables, functions and types) defined in your
10667 program. This information is inherent in the text of your program and
10668 does not change as your program executes. @value{GDBN} finds it in your
10669 program's symbol table, in the file indicated when you started @value{GDBN}
10670 (@pxref{File Options, ,Choosing files}), or by one of the
10671 file-management commands (@pxref{Files, ,Commands to specify files}).
10673 @cindex symbol names
10674 @cindex names of symbols
10675 @cindex quoting names
10676 Occasionally, you may need to refer to symbols that contain unusual
10677 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10678 most frequent case is in referring to static variables in other
10679 source files (@pxref{Variables,,Program variables}). File names
10680 are recorded in object files as debugging symbols, but @value{GDBN} would
10681 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10682 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10683 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10690 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10693 @cindex case-insensitive symbol names
10694 @cindex case sensitivity in symbol names
10695 @kindex set case-sensitive
10696 @item set case-sensitive on
10697 @itemx set case-sensitive off
10698 @itemx set case-sensitive auto
10699 Normally, when @value{GDBN} looks up symbols, it matches their names
10700 with case sensitivity determined by the current source language.
10701 Occasionally, you may wish to control that. The command @code{set
10702 case-sensitive} lets you do that by specifying @code{on} for
10703 case-sensitive matches or @code{off} for case-insensitive ones. If
10704 you specify @code{auto}, case sensitivity is reset to the default
10705 suitable for the source language. The default is case-sensitive
10706 matches for all languages except for Fortran, for which the default is
10707 case-insensitive matches.
10709 @kindex show case-sensitive
10710 @item show case-sensitive
10711 This command shows the current setting of case sensitivity for symbols
10714 @kindex info address
10715 @cindex address of a symbol
10716 @item info address @var{symbol}
10717 Describe where the data for @var{symbol} is stored. For a register
10718 variable, this says which register it is kept in. For a non-register
10719 local variable, this prints the stack-frame offset at which the variable
10722 Note the contrast with @samp{print &@var{symbol}}, which does not work
10723 at all for a register variable, and for a stack local variable prints
10724 the exact address of the current instantiation of the variable.
10726 @kindex info symbol
10727 @cindex symbol from address
10728 @cindex closest symbol and offset for an address
10729 @item info symbol @var{addr}
10730 Print the name of a symbol which is stored at the address @var{addr}.
10731 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10732 nearest symbol and an offset from it:
10735 (@value{GDBP}) info symbol 0x54320
10736 _initialize_vx + 396 in section .text
10740 This is the opposite of the @code{info address} command. You can use
10741 it to find out the name of a variable or a function given its address.
10744 @item whatis [@var{arg}]
10745 Print the data type of @var{arg}, which can be either an expression or
10746 a data type. With no argument, print the data type of @code{$}, the
10747 last value in the value history. If @var{arg} is an expression, it is
10748 not actually evaluated, and any side-effecting operations (such as
10749 assignments or function calls) inside it do not take place. If
10750 @var{arg} is a type name, it may be the name of a type or typedef, or
10751 for C code it may have the form @samp{class @var{class-name}},
10752 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10753 @samp{enum @var{enum-tag}}.
10754 @xref{Expressions, ,Expressions}.
10757 @item ptype [@var{arg}]
10758 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10759 detailed description of the type, instead of just the name of the type.
10760 @xref{Expressions, ,Expressions}.
10762 For example, for this variable declaration:
10765 struct complex @{double real; double imag;@} v;
10769 the two commands give this output:
10773 (@value{GDBP}) whatis v
10774 type = struct complex
10775 (@value{GDBP}) ptype v
10776 type = struct complex @{
10784 As with @code{whatis}, using @code{ptype} without an argument refers to
10785 the type of @code{$}, the last value in the value history.
10787 @cindex incomplete type
10788 Sometimes, programs use opaque data types or incomplete specifications
10789 of complex data structure. If the debug information included in the
10790 program does not allow @value{GDBN} to display a full declaration of
10791 the data type, it will say @samp{<incomplete type>}. For example,
10792 given these declarations:
10796 struct foo *fooptr;
10800 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10803 (@value{GDBP}) ptype foo
10804 $1 = <incomplete type>
10808 ``Incomplete type'' is C terminology for data types that are not
10809 completely specified.
10812 @item info types @var{regexp}
10814 Print a brief description of all types whose names match the regular
10815 expression @var{regexp} (or all types in your program, if you supply
10816 no argument). Each complete typename is matched as though it were a
10817 complete line; thus, @samp{i type value} gives information on all
10818 types in your program whose names include the string @code{value}, but
10819 @samp{i type ^value$} gives information only on types whose complete
10820 name is @code{value}.
10822 This command differs from @code{ptype} in two ways: first, like
10823 @code{whatis}, it does not print a detailed description; second, it
10824 lists all source files where a type is defined.
10827 @cindex local variables
10828 @item info scope @var{location}
10829 List all the variables local to a particular scope. This command
10830 accepts a @var{location} argument---a function name, a source line, or
10831 an address preceded by a @samp{*}, and prints all the variables local
10832 to the scope defined by that location. For example:
10835 (@value{GDBP}) @b{info scope command_line_handler}
10836 Scope for command_line_handler:
10837 Symbol rl is an argument at stack/frame offset 8, length 4.
10838 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10839 Symbol linelength is in static storage at address 0x150a1c, length 4.
10840 Symbol p is a local variable in register $esi, length 4.
10841 Symbol p1 is a local variable in register $ebx, length 4.
10842 Symbol nline is a local variable in register $edx, length 4.
10843 Symbol repeat is a local variable at frame offset -8, length 4.
10847 This command is especially useful for determining what data to collect
10848 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10851 @kindex info source
10853 Show information about the current source file---that is, the source file for
10854 the function containing the current point of execution:
10857 the name of the source file, and the directory containing it,
10859 the directory it was compiled in,
10861 its length, in lines,
10863 which programming language it is written in,
10865 whether the executable includes debugging information for that file, and
10866 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10868 whether the debugging information includes information about
10869 preprocessor macros.
10873 @kindex info sources
10875 Print the names of all source files in your program for which there is
10876 debugging information, organized into two lists: files whose symbols
10877 have already been read, and files whose symbols will be read when needed.
10879 @kindex info functions
10880 @item info functions
10881 Print the names and data types of all defined functions.
10883 @item info functions @var{regexp}
10884 Print the names and data types of all defined functions
10885 whose names contain a match for regular expression @var{regexp}.
10886 Thus, @samp{info fun step} finds all functions whose names
10887 include @code{step}; @samp{info fun ^step} finds those whose names
10888 start with @code{step}. If a function name contains characters
10889 that conflict with the regular expression language (e.g.@:
10890 @samp{operator*()}), they may be quoted with a backslash.
10892 @kindex info variables
10893 @item info variables
10894 Print the names and data types of all variables that are declared
10895 outside of functions (i.e.@: excluding local variables).
10897 @item info variables @var{regexp}
10898 Print the names and data types of all variables (except for local
10899 variables) whose names contain a match for regular expression
10902 @kindex info classes
10903 @cindex Objective-C, classes and selectors
10905 @itemx info classes @var{regexp}
10906 Display all Objective-C classes in your program, or
10907 (with the @var{regexp} argument) all those matching a particular regular
10910 @kindex info selectors
10911 @item info selectors
10912 @itemx info selectors @var{regexp}
10913 Display all Objective-C selectors in your program, or
10914 (with the @var{regexp} argument) all those matching a particular regular
10918 This was never implemented.
10919 @kindex info methods
10921 @itemx info methods @var{regexp}
10922 The @code{info methods} command permits the user to examine all defined
10923 methods within C@t{++} program, or (with the @var{regexp} argument) a
10924 specific set of methods found in the various C@t{++} classes. Many
10925 C@t{++} classes provide a large number of methods. Thus, the output
10926 from the @code{ptype} command can be overwhelming and hard to use. The
10927 @code{info-methods} command filters the methods, printing only those
10928 which match the regular-expression @var{regexp}.
10931 @cindex reloading symbols
10932 Some systems allow individual object files that make up your program to
10933 be replaced without stopping and restarting your program. For example,
10934 in VxWorks you can simply recompile a defective object file and keep on
10935 running. If you are running on one of these systems, you can allow
10936 @value{GDBN} to reload the symbols for automatically relinked modules:
10939 @kindex set symbol-reloading
10940 @item set symbol-reloading on
10941 Replace symbol definitions for the corresponding source file when an
10942 object file with a particular name is seen again.
10944 @item set symbol-reloading off
10945 Do not replace symbol definitions when encountering object files of the
10946 same name more than once. This is the default state; if you are not
10947 running on a system that permits automatic relinking of modules, you
10948 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10949 may discard symbols when linking large programs, that may contain
10950 several modules (from different directories or libraries) with the same
10953 @kindex show symbol-reloading
10954 @item show symbol-reloading
10955 Show the current @code{on} or @code{off} setting.
10958 @cindex opaque data types
10959 @kindex set opaque-type-resolution
10960 @item set opaque-type-resolution on
10961 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10962 declared as a pointer to a @code{struct}, @code{class}, or
10963 @code{union}---for example, @code{struct MyType *}---that is used in one
10964 source file although the full declaration of @code{struct MyType} is in
10965 another source file. The default is on.
10967 A change in the setting of this subcommand will not take effect until
10968 the next time symbols for a file are loaded.
10970 @item set opaque-type-resolution off
10971 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10972 is printed as follows:
10974 @{<no data fields>@}
10977 @kindex show opaque-type-resolution
10978 @item show opaque-type-resolution
10979 Show whether opaque types are resolved or not.
10981 @kindex maint print symbols
10982 @cindex symbol dump
10983 @kindex maint print psymbols
10984 @cindex partial symbol dump
10985 @item maint print symbols @var{filename}
10986 @itemx maint print psymbols @var{filename}
10987 @itemx maint print msymbols @var{filename}
10988 Write a dump of debugging symbol data into the file @var{filename}.
10989 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10990 symbols with debugging data are included. If you use @samp{maint print
10991 symbols}, @value{GDBN} includes all the symbols for which it has already
10992 collected full details: that is, @var{filename} reflects symbols for
10993 only those files whose symbols @value{GDBN} has read. You can use the
10994 command @code{info sources} to find out which files these are. If you
10995 use @samp{maint print psymbols} instead, the dump shows information about
10996 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10997 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10998 @samp{maint print msymbols} dumps just the minimal symbol information
10999 required for each object file from which @value{GDBN} has read some symbols.
11000 @xref{Files, ,Commands to specify files}, for a discussion of how
11001 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11003 @kindex maint info symtabs
11004 @kindex maint info psymtabs
11005 @cindex listing @value{GDBN}'s internal symbol tables
11006 @cindex symbol tables, listing @value{GDBN}'s internal
11007 @cindex full symbol tables, listing @value{GDBN}'s internal
11008 @cindex partial symbol tables, listing @value{GDBN}'s internal
11009 @item maint info symtabs @r{[} @var{regexp} @r{]}
11010 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11012 List the @code{struct symtab} or @code{struct partial_symtab}
11013 structures whose names match @var{regexp}. If @var{regexp} is not
11014 given, list them all. The output includes expressions which you can
11015 copy into a @value{GDBN} debugging this one to examine a particular
11016 structure in more detail. For example:
11019 (@value{GDBP}) maint info psymtabs dwarf2read
11020 @{ objfile /home/gnu/build/gdb/gdb
11021 ((struct objfile *) 0x82e69d0)
11022 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11023 ((struct partial_symtab *) 0x8474b10)
11026 text addresses 0x814d3c8 -- 0x8158074
11027 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11028 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11029 dependencies (none)
11032 (@value{GDBP}) maint info symtabs
11036 We see that there is one partial symbol table whose filename contains
11037 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11038 and we see that @value{GDBN} has not read in any symtabs yet at all.
11039 If we set a breakpoint on a function, that will cause @value{GDBN} to
11040 read the symtab for the compilation unit containing that function:
11043 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11044 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11046 (@value{GDBP}) maint info symtabs
11047 @{ objfile /home/gnu/build/gdb/gdb
11048 ((struct objfile *) 0x82e69d0)
11049 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11050 ((struct symtab *) 0x86c1f38)
11053 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11054 debugformat DWARF 2
11063 @chapter Altering Execution
11065 Once you think you have found an error in your program, you might want to
11066 find out for certain whether correcting the apparent error would lead to
11067 correct results in the rest of the run. You can find the answer by
11068 experiment, using the @value{GDBN} features for altering execution of the
11071 For example, you can store new values into variables or memory
11072 locations, give your program a signal, restart it at a different
11073 address, or even return prematurely from a function.
11076 * Assignment:: Assignment to variables
11077 * Jumping:: Continuing at a different address
11078 * Signaling:: Giving your program a signal
11079 * Returning:: Returning from a function
11080 * Calling:: Calling your program's functions
11081 * Patching:: Patching your program
11085 @section Assignment to variables
11088 @cindex setting variables
11089 To alter the value of a variable, evaluate an assignment expression.
11090 @xref{Expressions, ,Expressions}. For example,
11097 stores the value 4 into the variable @code{x}, and then prints the
11098 value of the assignment expression (which is 4).
11099 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11100 information on operators in supported languages.
11102 @kindex set variable
11103 @cindex variables, setting
11104 If you are not interested in seeing the value of the assignment, use the
11105 @code{set} command instead of the @code{print} command. @code{set} is
11106 really the same as @code{print} except that the expression's value is
11107 not printed and is not put in the value history (@pxref{Value History,
11108 ,Value history}). The expression is evaluated only for its effects.
11110 If the beginning of the argument string of the @code{set} command
11111 appears identical to a @code{set} subcommand, use the @code{set
11112 variable} command instead of just @code{set}. This command is identical
11113 to @code{set} except for its lack of subcommands. For example, if your
11114 program has a variable @code{width}, you get an error if you try to set
11115 a new value with just @samp{set width=13}, because @value{GDBN} has the
11116 command @code{set width}:
11119 (@value{GDBP}) whatis width
11121 (@value{GDBP}) p width
11123 (@value{GDBP}) set width=47
11124 Invalid syntax in expression.
11128 The invalid expression, of course, is @samp{=47}. In
11129 order to actually set the program's variable @code{width}, use
11132 (@value{GDBP}) set var width=47
11135 Because the @code{set} command has many subcommands that can conflict
11136 with the names of program variables, it is a good idea to use the
11137 @code{set variable} command instead of just @code{set}. For example, if
11138 your program has a variable @code{g}, you run into problems if you try
11139 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11140 the command @code{set gnutarget}, abbreviated @code{set g}:
11144 (@value{GDBP}) whatis g
11148 (@value{GDBP}) set g=4
11152 The program being debugged has been started already.
11153 Start it from the beginning? (y or n) y
11154 Starting program: /home/smith/cc_progs/a.out
11155 "/home/smith/cc_progs/a.out": can't open to read symbols:
11156 Invalid bfd target.
11157 (@value{GDBP}) show g
11158 The current BFD target is "=4".
11163 The program variable @code{g} did not change, and you silently set the
11164 @code{gnutarget} to an invalid value. In order to set the variable
11168 (@value{GDBP}) set var g=4
11171 @value{GDBN} allows more implicit conversions in assignments than C; you can
11172 freely store an integer value into a pointer variable or vice versa,
11173 and you can convert any structure to any other structure that is the
11174 same length or shorter.
11175 @comment FIXME: how do structs align/pad in these conversions?
11176 @comment /doc@cygnus.com 18dec1990
11178 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11179 construct to generate a value of specified type at a specified address
11180 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11181 to memory location @code{0x83040} as an integer (which implies a certain size
11182 and representation in memory), and
11185 set @{int@}0x83040 = 4
11189 stores the value 4 into that memory location.
11192 @section Continuing at a different address
11194 Ordinarily, when you continue your program, you do so at the place where
11195 it stopped, with the @code{continue} command. You can instead continue at
11196 an address of your own choosing, with the following commands:
11200 @item jump @var{linespec}
11201 Resume execution at line @var{linespec}. Execution stops again
11202 immediately if there is a breakpoint there. @xref{List, ,Printing
11203 source lines}, for a description of the different forms of
11204 @var{linespec}. It is common practice to use the @code{tbreak} command
11205 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11208 The @code{jump} command does not change the current stack frame, or
11209 the stack pointer, or the contents of any memory location or any
11210 register other than the program counter. If line @var{linespec} is in
11211 a different function from the one currently executing, the results may
11212 be bizarre if the two functions expect different patterns of arguments or
11213 of local variables. For this reason, the @code{jump} command requests
11214 confirmation if the specified line is not in the function currently
11215 executing. However, even bizarre results are predictable if you are
11216 well acquainted with the machine-language code of your program.
11218 @item jump *@var{address}
11219 Resume execution at the instruction at address @var{address}.
11222 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11223 On many systems, you can get much the same effect as the @code{jump}
11224 command by storing a new value into the register @code{$pc}. The
11225 difference is that this does not start your program running; it only
11226 changes the address of where it @emph{will} run when you continue. For
11234 makes the next @code{continue} command or stepping command execute at
11235 address @code{0x485}, rather than at the address where your program stopped.
11236 @xref{Continuing and Stepping, ,Continuing and stepping}.
11238 The most common occasion to use the @code{jump} command is to back
11239 up---perhaps with more breakpoints set---over a portion of a program
11240 that has already executed, in order to examine its execution in more
11245 @section Giving your program a signal
11246 @cindex deliver a signal to a program
11250 @item signal @var{signal}
11251 Resume execution where your program stopped, but immediately give it the
11252 signal @var{signal}. @var{signal} can be the name or the number of a
11253 signal. For example, on many systems @code{signal 2} and @code{signal
11254 SIGINT} are both ways of sending an interrupt signal.
11256 Alternatively, if @var{signal} is zero, continue execution without
11257 giving a signal. This is useful when your program stopped on account of
11258 a signal and would ordinary see the signal when resumed with the
11259 @code{continue} command; @samp{signal 0} causes it to resume without a
11262 @code{signal} does not repeat when you press @key{RET} a second time
11263 after executing the command.
11267 Invoking the @code{signal} command is not the same as invoking the
11268 @code{kill} utility from the shell. Sending a signal with @code{kill}
11269 causes @value{GDBN} to decide what to do with the signal depending on
11270 the signal handling tables (@pxref{Signals}). The @code{signal} command
11271 passes the signal directly to your program.
11275 @section Returning from a function
11278 @cindex returning from a function
11281 @itemx return @var{expression}
11282 You can cancel execution of a function call with the @code{return}
11283 command. If you give an
11284 @var{expression} argument, its value is used as the function's return
11288 When you use @code{return}, @value{GDBN} discards the selected stack frame
11289 (and all frames within it). You can think of this as making the
11290 discarded frame return prematurely. If you wish to specify a value to
11291 be returned, give that value as the argument to @code{return}.
11293 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11294 frame}), and any other frames inside of it, leaving its caller as the
11295 innermost remaining frame. That frame becomes selected. The
11296 specified value is stored in the registers used for returning values
11299 The @code{return} command does not resume execution; it leaves the
11300 program stopped in the state that would exist if the function had just
11301 returned. In contrast, the @code{finish} command (@pxref{Continuing
11302 and Stepping, ,Continuing and stepping}) resumes execution until the
11303 selected stack frame returns naturally.
11306 @section Calling program functions
11309 @cindex calling functions
11310 @cindex inferior functions, calling
11311 @item print @var{expr}
11312 Evaluate the expression @var{expr} and display the resulting value.
11313 @var{expr} may include calls to functions in the program being
11317 @item call @var{expr}
11318 Evaluate the expression @var{expr} without displaying @code{void}
11321 You can use this variant of the @code{print} command if you want to
11322 execute a function from your program that does not return anything
11323 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11324 with @code{void} returned values that @value{GDBN} will otherwise
11325 print. If the result is not void, it is printed and saved in the
11329 It is possible for the function you call via the @code{print} or
11330 @code{call} command to generate a signal (e.g., if there's a bug in
11331 the function, or if you passed it incorrect arguments). What happens
11332 in that case is controlled by the @code{set unwindonsignal} command.
11335 @item set unwindonsignal
11336 @kindex set unwindonsignal
11337 @cindex unwind stack in called functions
11338 @cindex call dummy stack unwinding
11339 Set unwinding of the stack if a signal is received while in a function
11340 that @value{GDBN} called in the program being debugged. If set to on,
11341 @value{GDBN} unwinds the stack it created for the call and restores
11342 the context to what it was before the call. If set to off (the
11343 default), @value{GDBN} stops in the frame where the signal was
11346 @item show unwindonsignal
11347 @kindex show unwindonsignal
11348 Show the current setting of stack unwinding in the functions called by
11352 @cindex weak alias functions
11353 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11354 for another function. In such case, @value{GDBN} might not pick up
11355 the type information, including the types of the function arguments,
11356 which causes @value{GDBN} to call the inferior function incorrectly.
11357 As a result, the called function will function erroneously and may
11358 even crash. A solution to that is to use the name of the aliased
11362 @section Patching programs
11364 @cindex patching binaries
11365 @cindex writing into executables
11366 @cindex writing into corefiles
11368 By default, @value{GDBN} opens the file containing your program's
11369 executable code (or the corefile) read-only. This prevents accidental
11370 alterations to machine code; but it also prevents you from intentionally
11371 patching your program's binary.
11373 If you'd like to be able to patch the binary, you can specify that
11374 explicitly with the @code{set write} command. For example, you might
11375 want to turn on internal debugging flags, or even to make emergency
11381 @itemx set write off
11382 If you specify @samp{set write on}, @value{GDBN} opens executable and
11383 core files for both reading and writing; if you specify @samp{set write
11384 off} (the default), @value{GDBN} opens them read-only.
11386 If you have already loaded a file, you must load it again (using the
11387 @code{exec-file} or @code{core-file} command) after changing @code{set
11388 write}, for your new setting to take effect.
11392 Display whether executable files and core files are opened for writing
11393 as well as reading.
11397 @chapter @value{GDBN} Files
11399 @value{GDBN} needs to know the file name of the program to be debugged,
11400 both in order to read its symbol table and in order to start your
11401 program. To debug a core dump of a previous run, you must also tell
11402 @value{GDBN} the name of the core dump file.
11405 * Files:: Commands to specify files
11406 * Separate Debug Files:: Debugging information in separate files
11407 * Symbol Errors:: Errors reading symbol files
11411 @section Commands to specify files
11413 @cindex symbol table
11414 @cindex core dump file
11416 You may want to specify executable and core dump file names. The usual
11417 way to do this is at start-up time, using the arguments to
11418 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11419 Out of @value{GDBN}}).
11421 Occasionally it is necessary to change to a different file during a
11422 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11423 specify a file you want to use. Or you are debugging a remote target
11424 via @code{gdbserver} (@pxref{Server, file, Using the gdbserver
11425 program}). In these situations the @value{GDBN} commands to specify
11426 new files are useful.
11429 @cindex executable file
11431 @item file @var{filename}
11432 Use @var{filename} as the program to be debugged. It is read for its
11433 symbols and for the contents of pure memory. It is also the program
11434 executed when you use the @code{run} command. If you do not specify a
11435 directory and the file is not found in the @value{GDBN} working directory,
11436 @value{GDBN} uses the environment variable @code{PATH} as a list of
11437 directories to search, just as the shell does when looking for a program
11438 to run. You can change the value of this variable, for both @value{GDBN}
11439 and your program, using the @code{path} command.
11441 @cindex unlinked object files
11442 @cindex patching object files
11443 You can load unlinked object @file{.o} files into @value{GDBN} using
11444 the @code{file} command. You will not be able to ``run'' an object
11445 file, but you can disassemble functions and inspect variables. Also,
11446 if the underlying BFD functionality supports it, you could use
11447 @kbd{gdb -write} to patch object files using this technique. Note
11448 that @value{GDBN} can neither interpret nor modify relocations in this
11449 case, so branches and some initialized variables will appear to go to
11450 the wrong place. But this feature is still handy from time to time.
11453 @code{file} with no argument makes @value{GDBN} discard any information it
11454 has on both executable file and the symbol table.
11457 @item exec-file @r{[} @var{filename} @r{]}
11458 Specify that the program to be run (but not the symbol table) is found
11459 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11460 if necessary to locate your program. Omitting @var{filename} means to
11461 discard information on the executable file.
11463 @kindex symbol-file
11464 @item symbol-file @r{[} @var{filename} @r{]}
11465 Read symbol table information from file @var{filename}. @code{PATH} is
11466 searched when necessary. Use the @code{file} command to get both symbol
11467 table and program to run from the same file.
11469 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11470 program's symbol table.
11472 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11473 some breakpoints and auto-display expressions. This is because they may
11474 contain pointers to the internal data recording symbols and data types,
11475 which are part of the old symbol table data being discarded inside
11478 @code{symbol-file} does not repeat if you press @key{RET} again after
11481 When @value{GDBN} is configured for a particular environment, it
11482 understands debugging information in whatever format is the standard
11483 generated for that environment; you may use either a @sc{gnu} compiler, or
11484 other compilers that adhere to the local conventions.
11485 Best results are usually obtained from @sc{gnu} compilers; for example,
11486 using @code{@value{NGCC}} you can generate debugging information for
11489 For most kinds of object files, with the exception of old SVR3 systems
11490 using COFF, the @code{symbol-file} command does not normally read the
11491 symbol table in full right away. Instead, it scans the symbol table
11492 quickly to find which source files and which symbols are present. The
11493 details are read later, one source file at a time, as they are needed.
11495 The purpose of this two-stage reading strategy is to make @value{GDBN}
11496 start up faster. For the most part, it is invisible except for
11497 occasional pauses while the symbol table details for a particular source
11498 file are being read. (The @code{set verbose} command can turn these
11499 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11500 warnings and messages}.)
11502 We have not implemented the two-stage strategy for COFF yet. When the
11503 symbol table is stored in COFF format, @code{symbol-file} reads the
11504 symbol table data in full right away. Note that ``stabs-in-COFF''
11505 still does the two-stage strategy, since the debug info is actually
11509 @cindex reading symbols immediately
11510 @cindex symbols, reading immediately
11511 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11512 @itemx file @var{filename} @r{[} -readnow @r{]}
11513 You can override the @value{GDBN} two-stage strategy for reading symbol
11514 tables by using the @samp{-readnow} option with any of the commands that
11515 load symbol table information, if you want to be sure @value{GDBN} has the
11516 entire symbol table available.
11518 @c FIXME: for now no mention of directories, since this seems to be in
11519 @c flux. 13mar1992 status is that in theory GDB would look either in
11520 @c current dir or in same dir as myprog; but issues like competing
11521 @c GDB's, or clutter in system dirs, mean that in practice right now
11522 @c only current dir is used. FFish says maybe a special GDB hierarchy
11523 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11527 @item core-file @r{[}@var{filename}@r{]}
11529 Specify the whereabouts of a core dump file to be used as the ``contents
11530 of memory''. Traditionally, core files contain only some parts of the
11531 address space of the process that generated them; @value{GDBN} can access the
11532 executable file itself for other parts.
11534 @code{core-file} with no argument specifies that no core file is
11537 Note that the core file is ignored when your program is actually running
11538 under @value{GDBN}. So, if you have been running your program and you
11539 wish to debug a core file instead, you must kill the subprocess in which
11540 the program is running. To do this, use the @code{kill} command
11541 (@pxref{Kill Process, ,Killing the child process}).
11543 @kindex add-symbol-file
11544 @cindex dynamic linking
11545 @item add-symbol-file @var{filename} @var{address}
11546 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11547 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11548 The @code{add-symbol-file} command reads additional symbol table
11549 information from the file @var{filename}. You would use this command
11550 when @var{filename} has been dynamically loaded (by some other means)
11551 into the program that is running. @var{address} should be the memory
11552 address at which the file has been loaded; @value{GDBN} cannot figure
11553 this out for itself. You can additionally specify an arbitrary number
11554 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11555 section name and base address for that section. You can specify any
11556 @var{address} as an expression.
11558 The symbol table of the file @var{filename} is added to the symbol table
11559 originally read with the @code{symbol-file} command. You can use the
11560 @code{add-symbol-file} command any number of times; the new symbol data
11561 thus read keeps adding to the old. To discard all old symbol data
11562 instead, use the @code{symbol-file} command without any arguments.
11564 @cindex relocatable object files, reading symbols from
11565 @cindex object files, relocatable, reading symbols from
11566 @cindex reading symbols from relocatable object files
11567 @cindex symbols, reading from relocatable object files
11568 @cindex @file{.o} files, reading symbols from
11569 Although @var{filename} is typically a shared library file, an
11570 executable file, or some other object file which has been fully
11571 relocated for loading into a process, you can also load symbolic
11572 information from relocatable @file{.o} files, as long as:
11576 the file's symbolic information refers only to linker symbols defined in
11577 that file, not to symbols defined by other object files,
11579 every section the file's symbolic information refers to has actually
11580 been loaded into the inferior, as it appears in the file, and
11582 you can determine the address at which every section was loaded, and
11583 provide these to the @code{add-symbol-file} command.
11587 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11588 relocatable files into an already running program; such systems
11589 typically make the requirements above easy to meet. However, it's
11590 important to recognize that many native systems use complex link
11591 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11592 assembly, for example) that make the requirements difficult to meet. In
11593 general, one cannot assume that using @code{add-symbol-file} to read a
11594 relocatable object file's symbolic information will have the same effect
11595 as linking the relocatable object file into the program in the normal
11598 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11600 @kindex add-symbol-file-from-memory
11601 @cindex @code{syscall DSO}
11602 @cindex load symbols from memory
11603 @item add-symbol-file-from-memory @var{address}
11604 Load symbols from the given @var{address} in a dynamically loaded
11605 object file whose image is mapped directly into the inferior's memory.
11606 For example, the Linux kernel maps a @code{syscall DSO} into each
11607 process's address space; this DSO provides kernel-specific code for
11608 some system calls. The argument can be any expression whose
11609 evaluation yields the address of the file's shared object file header.
11610 For this command to work, you must have used @code{symbol-file} or
11611 @code{exec-file} commands in advance.
11613 @kindex add-shared-symbol-files
11615 @item add-shared-symbol-files @var{library-file}
11616 @itemx assf @var{library-file}
11617 The @code{add-shared-symbol-files} command can currently be used only
11618 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11619 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11620 @value{GDBN} automatically looks for shared libraries, however if
11621 @value{GDBN} does not find yours, you can invoke
11622 @code{add-shared-symbol-files}. It takes one argument: the shared
11623 library's file name. @code{assf} is a shorthand alias for
11624 @code{add-shared-symbol-files}.
11627 @item section @var{section} @var{addr}
11628 The @code{section} command changes the base address of the named
11629 @var{section} of the exec file to @var{addr}. This can be used if the
11630 exec file does not contain section addresses, (such as in the
11631 @code{a.out} format), or when the addresses specified in the file
11632 itself are wrong. Each section must be changed separately. The
11633 @code{info files} command, described below, lists all the sections and
11637 @kindex info target
11640 @code{info files} and @code{info target} are synonymous; both print the
11641 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11642 including the names of the executable and core dump files currently in
11643 use by @value{GDBN}, and the files from which symbols were loaded. The
11644 command @code{help target} lists all possible targets rather than
11647 @kindex maint info sections
11648 @item maint info sections
11649 Another command that can give you extra information about program sections
11650 is @code{maint info sections}. In addition to the section information
11651 displayed by @code{info files}, this command displays the flags and file
11652 offset of each section in the executable and core dump files. In addition,
11653 @code{maint info sections} provides the following command options (which
11654 may be arbitrarily combined):
11658 Display sections for all loaded object files, including shared libraries.
11659 @item @var{sections}
11660 Display info only for named @var{sections}.
11661 @item @var{section-flags}
11662 Display info only for sections for which @var{section-flags} are true.
11663 The section flags that @value{GDBN} currently knows about are:
11666 Section will have space allocated in the process when loaded.
11667 Set for all sections except those containing debug information.
11669 Section will be loaded from the file into the child process memory.
11670 Set for pre-initialized code and data, clear for @code{.bss} sections.
11672 Section needs to be relocated before loading.
11674 Section cannot be modified by the child process.
11676 Section contains executable code only.
11678 Section contains data only (no executable code).
11680 Section will reside in ROM.
11682 Section contains data for constructor/destructor lists.
11684 Section is not empty.
11686 An instruction to the linker to not output the section.
11687 @item COFF_SHARED_LIBRARY
11688 A notification to the linker that the section contains
11689 COFF shared library information.
11691 Section contains common symbols.
11694 @kindex set trust-readonly-sections
11695 @cindex read-only sections
11696 @item set trust-readonly-sections on
11697 Tell @value{GDBN} that readonly sections in your object file
11698 really are read-only (i.e.@: that their contents will not change).
11699 In that case, @value{GDBN} can fetch values from these sections
11700 out of the object file, rather than from the target program.
11701 For some targets (notably embedded ones), this can be a significant
11702 enhancement to debugging performance.
11704 The default is off.
11706 @item set trust-readonly-sections off
11707 Tell @value{GDBN} not to trust readonly sections. This means that
11708 the contents of the section might change while the program is running,
11709 and must therefore be fetched from the target when needed.
11711 @item show trust-readonly-sections
11712 Show the current setting of trusting readonly sections.
11715 All file-specifying commands allow both absolute and relative file names
11716 as arguments. @value{GDBN} always converts the file name to an absolute file
11717 name and remembers it that way.
11719 @cindex shared libraries
11720 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11721 and IBM RS/6000 AIX shared libraries.
11723 @value{GDBN} automatically loads symbol definitions from shared libraries
11724 when you use the @code{run} command, or when you examine a core file.
11725 (Before you issue the @code{run} command, @value{GDBN} does not understand
11726 references to a function in a shared library, however---unless you are
11727 debugging a core file).
11729 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11730 automatically loads the symbols at the time of the @code{shl_load} call.
11732 @c FIXME: some @value{GDBN} release may permit some refs to undef
11733 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11734 @c FIXME...lib; check this from time to time when updating manual
11736 There are times, however, when you may wish to not automatically load
11737 symbol definitions from shared libraries, such as when they are
11738 particularly large or there are many of them.
11740 To control the automatic loading of shared library symbols, use the
11744 @kindex set auto-solib-add
11745 @item set auto-solib-add @var{mode}
11746 If @var{mode} is @code{on}, symbols from all shared object libraries
11747 will be loaded automatically when the inferior begins execution, you
11748 attach to an independently started inferior, or when the dynamic linker
11749 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11750 is @code{off}, symbols must be loaded manually, using the
11751 @code{sharedlibrary} command. The default value is @code{on}.
11753 @cindex memory used for symbol tables
11754 If your program uses lots of shared libraries with debug info that
11755 takes large amounts of memory, you can decrease the @value{GDBN}
11756 memory footprint by preventing it from automatically loading the
11757 symbols from shared libraries. To that end, type @kbd{set
11758 auto-solib-add off} before running the inferior, then load each
11759 library whose debug symbols you do need with @kbd{sharedlibrary
11760 @var{regexp}}, where @var{regexp} is a regular expression that matches
11761 the libraries whose symbols you want to be loaded.
11763 @kindex show auto-solib-add
11764 @item show auto-solib-add
11765 Display the current autoloading mode.
11768 @cindex load shared library
11769 To explicitly load shared library symbols, use the @code{sharedlibrary}
11773 @kindex info sharedlibrary
11776 @itemx info sharedlibrary
11777 Print the names of the shared libraries which are currently loaded.
11779 @kindex sharedlibrary
11781 @item sharedlibrary @var{regex}
11782 @itemx share @var{regex}
11783 Load shared object library symbols for files matching a
11784 Unix regular expression.
11785 As with files loaded automatically, it only loads shared libraries
11786 required by your program for a core file or after typing @code{run}. If
11787 @var{regex} is omitted all shared libraries required by your program are
11790 @item nosharedlibrary
11791 @kindex nosharedlibrary
11792 @cindex unload symbols from shared libraries
11793 Unload all shared object library symbols. This discards all symbols
11794 that have been loaded from all shared libraries. Symbols from shared
11795 libraries that were loaded by explicit user requests are not
11799 Sometimes you may wish that @value{GDBN} stops and gives you control
11800 when any of shared library events happen. Use the @code{set
11801 stop-on-solib-events} command for this:
11804 @item set stop-on-solib-events
11805 @kindex set stop-on-solib-events
11806 This command controls whether @value{GDBN} should give you control
11807 when the dynamic linker notifies it about some shared library event.
11808 The most common event of interest is loading or unloading of a new
11811 @item show stop-on-solib-events
11812 @kindex show stop-on-solib-events
11813 Show whether @value{GDBN} stops and gives you control when shared
11814 library events happen.
11817 Shared libraries are also supported in many cross or remote debugging
11818 configurations. A copy of the target's libraries need to be present on the
11819 host system; they need to be the same as the target libraries, although the
11820 copies on the target can be stripped as long as the copies on the host are
11823 @cindex where to look for shared libraries
11824 For remote debugging, you need to tell @value{GDBN} where the target
11825 libraries are, so that it can load the correct copies---otherwise, it
11826 may try to load the host's libraries. @value{GDBN} has two variables
11827 to specify the search directories for target libraries.
11830 @cindex prefix for shared library file names
11831 @cindex system root, alternate
11832 @kindex set solib-absolute-prefix
11833 @kindex set sysroot
11834 @item set sysroot @var{path}
11835 Use @var{path} as the system root for the program being debugged. Any
11836 absolute shared library paths will be prefixed with @var{path}; many
11837 runtime loaders store the absolute paths to the shared library in the
11838 target program's memory. If you use @code{set sysroot} to find shared
11839 libraries, they need to be laid out in the same way that they are on
11840 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
11843 The @code{set solib-absolute-prefix} command is an alias for @code{set
11846 @cindex default system root
11847 @cindex @samp{--with-sysroot}
11848 You can set the default system root by using the configure-time
11849 @samp{--with-sysroot} option. If the system root is inside
11850 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
11851 @samp{--exec-prefix}), then the default system root will be updated
11852 automatically if the installed @value{GDBN} is moved to a new
11855 @kindex show sysroot
11857 Display the current shared library prefix.
11859 @kindex set solib-search-path
11860 @item set solib-search-path @var{path}
11861 If this variable is set, @var{path} is a colon-separated list of
11862 directories to search for shared libraries. @samp{solib-search-path}
11863 is used after @samp{sysroot} fails to locate the library, or if the
11864 path to the library is relative instead of absolute. If you want to
11865 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
11866 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
11867 finding your host's libraries. @samp{sysroot} is preferred; setting
11868 it to a nonexistent directory may interfere with automatic loading
11869 of shared library symbols.
11871 @kindex show solib-search-path
11872 @item show solib-search-path
11873 Display the current shared library search path.
11877 @node Separate Debug Files
11878 @section Debugging Information in Separate Files
11879 @cindex separate debugging information files
11880 @cindex debugging information in separate files
11881 @cindex @file{.debug} subdirectories
11882 @cindex debugging information directory, global
11883 @cindex global debugging information directory
11885 @value{GDBN} allows you to put a program's debugging information in a
11886 file separate from the executable itself, in a way that allows
11887 @value{GDBN} to find and load the debugging information automatically.
11888 Since debugging information can be very large --- sometimes larger
11889 than the executable code itself --- some systems distribute debugging
11890 information for their executables in separate files, which users can
11891 install only when they need to debug a problem.
11893 If an executable's debugging information has been extracted to a
11894 separate file, the executable should contain a @dfn{debug link} giving
11895 the name of the debugging information file (with no directory
11896 components), and a checksum of its contents. (The exact form of a
11897 debug link is described below.) If the full name of the directory
11898 containing the executable is @var{execdir}, and the executable has a
11899 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11900 will automatically search for the debugging information file in three
11905 the directory containing the executable file (that is, it will look
11906 for a file named @file{@var{execdir}/@var{debugfile}},
11908 a subdirectory of that directory named @file{.debug} (that is, the
11909 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11911 a subdirectory of the global debug file directory that includes the
11912 executable's full path, and the name from the link (that is, the file
11913 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11914 @var{globaldebugdir} is the global debug file directory, and
11915 @var{execdir} has been turned into a relative path).
11918 @value{GDBN} checks under each of these names for a debugging
11919 information file whose checksum matches that given in the link, and
11920 reads the debugging information from the first one it finds.
11922 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11923 which has a link containing the name @file{ls.debug}, and the global
11924 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11925 for debug information in @file{/usr/bin/ls.debug},
11926 @file{/usr/bin/.debug/ls.debug}, and
11927 @file{/usr/lib/debug/usr/bin/ls.debug}.
11929 You can set the global debugging info directory's name, and view the
11930 name @value{GDBN} is currently using.
11934 @kindex set debug-file-directory
11935 @item set debug-file-directory @var{directory}
11936 Set the directory which @value{GDBN} searches for separate debugging
11937 information files to @var{directory}.
11939 @kindex show debug-file-directory
11940 @item show debug-file-directory
11941 Show the directory @value{GDBN} searches for separate debugging
11946 @cindex @code{.gnu_debuglink} sections
11947 @cindex debug links
11948 A debug link is a special section of the executable file named
11949 @code{.gnu_debuglink}. The section must contain:
11953 A filename, with any leading directory components removed, followed by
11956 zero to three bytes of padding, as needed to reach the next four-byte
11957 boundary within the section, and
11959 a four-byte CRC checksum, stored in the same endianness used for the
11960 executable file itself. The checksum is computed on the debugging
11961 information file's full contents by the function given below, passing
11962 zero as the @var{crc} argument.
11965 Any executable file format can carry a debug link, as long as it can
11966 contain a section named @code{.gnu_debuglink} with the contents
11969 The debugging information file itself should be an ordinary
11970 executable, containing a full set of linker symbols, sections, and
11971 debugging information. The sections of the debugging information file
11972 should have the same names, addresses and sizes as the original file,
11973 but they need not contain any data --- much like a @code{.bss} section
11974 in an ordinary executable.
11976 As of December 2002, there is no standard GNU utility to produce
11977 separated executable / debugging information file pairs. Ulrich
11978 Drepper's @file{elfutils} package, starting with version 0.53,
11979 contains a version of the @code{strip} command such that the command
11980 @kbd{strip foo -f foo.debug} removes the debugging information from
11981 the executable file @file{foo}, places it in the file
11982 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11984 Since there are many different ways to compute CRC's (different
11985 polynomials, reversals, byte ordering, etc.), the simplest way to
11986 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11987 complete code for a function that computes it:
11989 @kindex gnu_debuglink_crc32
11992 gnu_debuglink_crc32 (unsigned long crc,
11993 unsigned char *buf, size_t len)
11995 static const unsigned long crc32_table[256] =
11997 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11998 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11999 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12000 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12001 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12002 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12003 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12004 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12005 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12006 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12007 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12008 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12009 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12010 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12011 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12012 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12013 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12014 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12015 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12016 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12017 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12018 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12019 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12020 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12021 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12022 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12023 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12024 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12025 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12026 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12027 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12028 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12029 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12030 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12031 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12032 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12033 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12034 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12035 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12036 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12037 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12038 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12039 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12040 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12041 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12042 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12043 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12044 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12045 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12046 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12047 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12050 unsigned char *end;
12052 crc = ~crc & 0xffffffff;
12053 for (end = buf + len; buf < end; ++buf)
12054 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12055 return ~crc & 0xffffffff;
12060 @node Symbol Errors
12061 @section Errors reading symbol files
12063 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12064 such as symbol types it does not recognize, or known bugs in compiler
12065 output. By default, @value{GDBN} does not notify you of such problems, since
12066 they are relatively common and primarily of interest to people
12067 debugging compilers. If you are interested in seeing information
12068 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12069 only one message about each such type of problem, no matter how many
12070 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12071 to see how many times the problems occur, with the @code{set
12072 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
12075 The messages currently printed, and their meanings, include:
12078 @item inner block not inside outer block in @var{symbol}
12080 The symbol information shows where symbol scopes begin and end
12081 (such as at the start of a function or a block of statements). This
12082 error indicates that an inner scope block is not fully contained
12083 in its outer scope blocks.
12085 @value{GDBN} circumvents the problem by treating the inner block as if it had
12086 the same scope as the outer block. In the error message, @var{symbol}
12087 may be shown as ``@code{(don't know)}'' if the outer block is not a
12090 @item block at @var{address} out of order
12092 The symbol information for symbol scope blocks should occur in
12093 order of increasing addresses. This error indicates that it does not
12096 @value{GDBN} does not circumvent this problem, and has trouble
12097 locating symbols in the source file whose symbols it is reading. (You
12098 can often determine what source file is affected by specifying
12099 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
12102 @item bad block start address patched
12104 The symbol information for a symbol scope block has a start address
12105 smaller than the address of the preceding source line. This is known
12106 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12108 @value{GDBN} circumvents the problem by treating the symbol scope block as
12109 starting on the previous source line.
12111 @item bad string table offset in symbol @var{n}
12114 Symbol number @var{n} contains a pointer into the string table which is
12115 larger than the size of the string table.
12117 @value{GDBN} circumvents the problem by considering the symbol to have the
12118 name @code{foo}, which may cause other problems if many symbols end up
12121 @item unknown symbol type @code{0x@var{nn}}
12123 The symbol information contains new data types that @value{GDBN} does
12124 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12125 uncomprehended information, in hexadecimal.
12127 @value{GDBN} circumvents the error by ignoring this symbol information.
12128 This usually allows you to debug your program, though certain symbols
12129 are not accessible. If you encounter such a problem and feel like
12130 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12131 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12132 and examine @code{*bufp} to see the symbol.
12134 @item stub type has NULL name
12136 @value{GDBN} could not find the full definition for a struct or class.
12138 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12139 The symbol information for a C@t{++} member function is missing some
12140 information that recent versions of the compiler should have output for
12143 @item info mismatch between compiler and debugger
12145 @value{GDBN} could not parse a type specification output by the compiler.
12150 @chapter Specifying a Debugging Target
12152 @cindex debugging target
12153 A @dfn{target} is the execution environment occupied by your program.
12155 Often, @value{GDBN} runs in the same host environment as your program;
12156 in that case, the debugging target is specified as a side effect when
12157 you use the @code{file} or @code{core} commands. When you need more
12158 flexibility---for example, running @value{GDBN} on a physically separate
12159 host, or controlling a standalone system over a serial port or a
12160 realtime system over a TCP/IP connection---you can use the @code{target}
12161 command to specify one of the target types configured for @value{GDBN}
12162 (@pxref{Target Commands, ,Commands for managing targets}).
12164 @cindex target architecture
12165 It is possible to build @value{GDBN} for several different @dfn{target
12166 architectures}. When @value{GDBN} is built like that, you can choose
12167 one of the available architectures with the @kbd{set architecture}
12171 @kindex set architecture
12172 @kindex show architecture
12173 @item set architecture @var{arch}
12174 This command sets the current target architecture to @var{arch}. The
12175 value of @var{arch} can be @code{"auto"}, in addition to one of the
12176 supported architectures.
12178 @item show architecture
12179 Show the current target architecture.
12181 @item set processor
12183 @kindex set processor
12184 @kindex show processor
12185 These are alias commands for, respectively, @code{set architecture}
12186 and @code{show architecture}.
12190 * Active Targets:: Active targets
12191 * Target Commands:: Commands for managing targets
12192 * Byte Order:: Choosing target byte order
12193 * Remote:: Remote debugging
12197 @node Active Targets
12198 @section Active targets
12200 @cindex stacking targets
12201 @cindex active targets
12202 @cindex multiple targets
12204 There are three classes of targets: processes, core files, and
12205 executable files. @value{GDBN} can work concurrently on up to three
12206 active targets, one in each class. This allows you to (for example)
12207 start a process and inspect its activity without abandoning your work on
12210 For example, if you execute @samp{gdb a.out}, then the executable file
12211 @code{a.out} is the only active target. If you designate a core file as
12212 well---presumably from a prior run that crashed and coredumped---then
12213 @value{GDBN} has two active targets and uses them in tandem, looking
12214 first in the corefile target, then in the executable file, to satisfy
12215 requests for memory addresses. (Typically, these two classes of target
12216 are complementary, since core files contain only a program's
12217 read-write memory---variables and so on---plus machine status, while
12218 executable files contain only the program text and initialized data.)
12220 When you type @code{run}, your executable file becomes an active process
12221 target as well. When a process target is active, all @value{GDBN}
12222 commands requesting memory addresses refer to that target; addresses in
12223 an active core file or executable file target are obscured while the
12224 process target is active.
12226 Use the @code{core-file} and @code{exec-file} commands to select a new
12227 core file or executable target (@pxref{Files, ,Commands to specify
12228 files}). To specify as a target a process that is already running, use
12229 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
12232 @node Target Commands
12233 @section Commands for managing targets
12236 @item target @var{type} @var{parameters}
12237 Connects the @value{GDBN} host environment to a target machine or
12238 process. A target is typically a protocol for talking to debugging
12239 facilities. You use the argument @var{type} to specify the type or
12240 protocol of the target machine.
12242 Further @var{parameters} are interpreted by the target protocol, but
12243 typically include things like device names or host names to connect
12244 with, process numbers, and baud rates.
12246 The @code{target} command does not repeat if you press @key{RET} again
12247 after executing the command.
12249 @kindex help target
12251 Displays the names of all targets available. To display targets
12252 currently selected, use either @code{info target} or @code{info files}
12253 (@pxref{Files, ,Commands to specify files}).
12255 @item help target @var{name}
12256 Describe a particular target, including any parameters necessary to
12259 @kindex set gnutarget
12260 @item set gnutarget @var{args}
12261 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12262 knows whether it is reading an @dfn{executable},
12263 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12264 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12265 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12268 @emph{Warning:} To specify a file format with @code{set gnutarget},
12269 you must know the actual BFD name.
12273 @xref{Files, , Commands to specify files}.
12275 @kindex show gnutarget
12276 @item show gnutarget
12277 Use the @code{show gnutarget} command to display what file format
12278 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12279 @value{GDBN} will determine the file format for each file automatically,
12280 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12283 @cindex common targets
12284 Here are some common targets (available, or not, depending on the GDB
12289 @item target exec @var{program}
12290 @cindex executable file target
12291 An executable file. @samp{target exec @var{program}} is the same as
12292 @samp{exec-file @var{program}}.
12294 @item target core @var{filename}
12295 @cindex core dump file target
12296 A core dump file. @samp{target core @var{filename}} is the same as
12297 @samp{core-file @var{filename}}.
12299 @item target remote @var{medium}
12300 @cindex remote target
12301 A remote system connected to @value{GDBN} via a serial line or network
12302 connection. This command tells @value{GDBN} to use its own remote
12303 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12305 For example, if you have a board connected to @file{/dev/ttya} on the
12306 machine running @value{GDBN}, you could say:
12309 target remote /dev/ttya
12312 @code{target remote} supports the @code{load} command. This is only
12313 useful if you have some other way of getting the stub to the target
12314 system, and you can put it somewhere in memory where it won't get
12315 clobbered by the download.
12318 @cindex built-in simulator target
12319 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12327 works; however, you cannot assume that a specific memory map, device
12328 drivers, or even basic I/O is available, although some simulators do
12329 provide these. For info about any processor-specific simulator details,
12330 see the appropriate section in @ref{Embedded Processors, ,Embedded
12335 Some configurations may include these targets as well:
12339 @item target nrom @var{dev}
12340 @cindex NetROM ROM emulator target
12341 NetROM ROM emulator. This target only supports downloading.
12345 Different targets are available on different configurations of @value{GDBN};
12346 your configuration may have more or fewer targets.
12348 Many remote targets require you to download the executable's code once
12349 you've successfully established a connection. You may wish to control
12350 various aspects of this process.
12355 @kindex set hash@r{, for remote monitors}
12356 @cindex hash mark while downloading
12357 This command controls whether a hash mark @samp{#} is displayed while
12358 downloading a file to the remote monitor. If on, a hash mark is
12359 displayed after each S-record is successfully downloaded to the
12363 @kindex show hash@r{, for remote monitors}
12364 Show the current status of displaying the hash mark.
12366 @item set debug monitor
12367 @kindex set debug monitor
12368 @cindex display remote monitor communications
12369 Enable or disable display of communications messages between
12370 @value{GDBN} and the remote monitor.
12372 @item show debug monitor
12373 @kindex show debug monitor
12374 Show the current status of displaying communications between
12375 @value{GDBN} and the remote monitor.
12380 @kindex load @var{filename}
12381 @item load @var{filename}
12382 Depending on what remote debugging facilities are configured into
12383 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12384 is meant to make @var{filename} (an executable) available for debugging
12385 on the remote system---by downloading, or dynamic linking, for example.
12386 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12387 the @code{add-symbol-file} command.
12389 If your @value{GDBN} does not have a @code{load} command, attempting to
12390 execute it gets the error message ``@code{You can't do that when your
12391 target is @dots{}}''
12393 The file is loaded at whatever address is specified in the executable.
12394 For some object file formats, you can specify the load address when you
12395 link the program; for other formats, like a.out, the object file format
12396 specifies a fixed address.
12397 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12399 Depending on the remote side capabilities, @value{GDBN} may be able to
12400 load programs into flash memory.
12402 @code{load} does not repeat if you press @key{RET} again after using it.
12406 @section Choosing target byte order
12408 @cindex choosing target byte order
12409 @cindex target byte order
12411 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12412 offer the ability to run either big-endian or little-endian byte
12413 orders. Usually the executable or symbol will include a bit to
12414 designate the endian-ness, and you will not need to worry about
12415 which to use. However, you may still find it useful to adjust
12416 @value{GDBN}'s idea of processor endian-ness manually.
12420 @item set endian big
12421 Instruct @value{GDBN} to assume the target is big-endian.
12423 @item set endian little
12424 Instruct @value{GDBN} to assume the target is little-endian.
12426 @item set endian auto
12427 Instruct @value{GDBN} to use the byte order associated with the
12431 Display @value{GDBN}'s current idea of the target byte order.
12435 Note that these commands merely adjust interpretation of symbolic
12436 data on the host, and that they have absolutely no effect on the
12440 @section Remote debugging
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.
12459 Once you've connected to the remote target, @value{GDBN} allows you to
12460 send arbitrary commands to the remote monitor:
12463 @item remote @var{command}
12464 @kindex remote@r{, a command}
12465 @cindex send command to remote monitor
12466 Send an arbitrary @var{command} string to the remote monitor.
12470 @node Remote Debugging
12471 @chapter Debugging remote programs
12474 * Connecting:: Connecting to a remote target
12475 * Server:: Using the gdbserver program
12476 * Remote configuration:: Remote configuration
12477 * remote stub:: Implementing a remote stub
12481 @section Connecting to a remote target
12483 On the @value{GDBN} host machine, you will need an unstripped copy of
12484 your program, since @value{GDBN} needs symbol and debugging information.
12485 Start up @value{GDBN} as usual, using the name of the local copy of your
12486 program as the first argument.
12488 @cindex @code{target remote}
12489 @value{GDBN} can communicate with the target over a serial line, or
12490 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12491 each case, @value{GDBN} uses the same protocol for debugging your
12492 program; only the medium carrying the debugging packets varies. The
12493 @code{target remote} command establishes a connection to the target.
12494 Its arguments indicate which medium to use:
12498 @item target remote @var{serial-device}
12499 @cindex serial line, @code{target remote}
12500 Use @var{serial-device} to communicate with the target. For example,
12501 to use a serial line connected to the device named @file{/dev/ttyb}:
12504 target remote /dev/ttyb
12507 If you're using a serial line, you may want to give @value{GDBN} the
12508 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12509 (@pxref{Remote configuration, set remotebaud}) before the
12510 @code{target} command.
12512 @item target remote @code{@var{host}:@var{port}}
12513 @itemx target remote @code{tcp:@var{host}:@var{port}}
12514 @cindex @acronym{TCP} port, @code{target remote}
12515 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12516 The @var{host} may be either a host name or a numeric @acronym{IP}
12517 address; @var{port} must be a decimal number. The @var{host} could be
12518 the target machine itself, if it is directly connected to the net, or
12519 it might be a terminal server which in turn has a serial line to the
12522 For example, to connect to port 2828 on a terminal server named
12526 target remote manyfarms:2828
12529 If your remote target is actually running on the same machine as your
12530 debugger session (e.g.@: a simulator for your target running on the
12531 same host), you can omit the hostname. For example, to connect to
12532 port 1234 on your local machine:
12535 target remote :1234
12539 Note that the colon is still required here.
12541 @item target remote @code{udp:@var{host}:@var{port}}
12542 @cindex @acronym{UDP} port, @code{target remote}
12543 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12544 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12547 target remote udp:manyfarms:2828
12550 When using a @acronym{UDP} connection for remote debugging, you should
12551 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12552 can silently drop packets on busy or unreliable networks, which will
12553 cause havoc with your debugging session.
12555 @item target remote | @var{command}
12556 @cindex pipe, @code{target remote} to
12557 Run @var{command} in the background and communicate with it using a
12558 pipe. The @var{command} is a shell command, to be parsed and expanded
12559 by the system's command shell, @code{/bin/sh}; it should expect remote
12560 protocol packets on its standard input, and send replies on its
12561 standard output. You could use this to run a stand-alone simulator
12562 that speaks the remote debugging protocol, to make net connections
12563 using programs like @code{ssh}, or for other similar tricks.
12565 If @var{command} closes its standard output (perhaps by exiting),
12566 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12567 program has already exited, this will have no effect.)
12571 Once the connection has been established, you can use all the usual
12572 commands to examine and change data and to step and continue the
12575 @cindex interrupting remote programs
12576 @cindex remote programs, interrupting
12577 Whenever @value{GDBN} is waiting for the remote program, if you type the
12578 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12579 program. This may or may not succeed, depending in part on the hardware
12580 and the serial drivers the remote system uses. If you type the
12581 interrupt character once again, @value{GDBN} displays this prompt:
12584 Interrupted while waiting for the program.
12585 Give up (and stop debugging it)? (y or n)
12588 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12589 (If you decide you want to try again later, you can use @samp{target
12590 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12591 goes back to waiting.
12594 @kindex detach (remote)
12596 When you have finished debugging the remote program, you can use the
12597 @code{detach} command to release it from @value{GDBN} control.
12598 Detaching from the target normally resumes its execution, but the results
12599 will depend on your particular remote stub. After the @code{detach}
12600 command, @value{GDBN} is free to connect to another target.
12604 The @code{disconnect} command behaves like @code{detach}, except that
12605 the target is generally not resumed. It will wait for @value{GDBN}
12606 (this instance or another one) to connect and continue debugging. After
12607 the @code{disconnect} command, @value{GDBN} is again free to connect to
12610 @cindex send command to remote monitor
12611 @cindex extend @value{GDBN} for remote targets
12612 @cindex add new commands for external monitor
12614 @item monitor @var{cmd}
12615 This command allows you to send arbitrary commands directly to the
12616 remote monitor. Since @value{GDBN} doesn't care about the commands it
12617 sends like this, this command is the way to extend @value{GDBN}---you
12618 can add new commands that only the external monitor will understand
12623 @section Using the @code{gdbserver} program
12626 @cindex remote connection without stubs
12627 @code{gdbserver} is a control program for Unix-like systems, which
12628 allows you to connect your program with a remote @value{GDBN} via
12629 @code{target remote}---but without linking in the usual debugging stub.
12631 @code{gdbserver} is not a complete replacement for the debugging stubs,
12632 because it requires essentially the same operating-system facilities
12633 that @value{GDBN} itself does. In fact, a system that can run
12634 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12635 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12636 because it is a much smaller program than @value{GDBN} itself. It is
12637 also easier to port than all of @value{GDBN}, so you may be able to get
12638 started more quickly on a new system by using @code{gdbserver}.
12639 Finally, if you develop code for real-time systems, you may find that
12640 the tradeoffs involved in real-time operation make it more convenient to
12641 do as much development work as possible on another system, for example
12642 by cross-compiling. You can use @code{gdbserver} to make a similar
12643 choice for debugging.
12645 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12646 or a TCP connection, using the standard @value{GDBN} remote serial
12650 @item On the target machine,
12651 you need to have a copy of the program you want to debug.
12652 @code{gdbserver} does not need your program's symbol table, so you can
12653 strip the program if necessary to save space. @value{GDBN} on the host
12654 system does all the symbol handling.
12656 To use the server, you must tell it how to communicate with @value{GDBN};
12657 the name of your program; and the arguments for your program. The usual
12661 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12664 @var{comm} is either a device name (to use a serial line) or a TCP
12665 hostname and portnumber. For example, to debug Emacs with the argument
12666 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12670 target> gdbserver /dev/com1 emacs foo.txt
12673 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12676 To use a TCP connection instead of a serial line:
12679 target> gdbserver host:2345 emacs foo.txt
12682 The only difference from the previous example is the first argument,
12683 specifying that you are communicating with the host @value{GDBN} via
12684 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12685 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12686 (Currently, the @samp{host} part is ignored.) You can choose any number
12687 you want for the port number as long as it does not conflict with any
12688 TCP ports already in use on the target system (for example, @code{23} is
12689 reserved for @code{telnet}).@footnote{If you choose a port number that
12690 conflicts with another service, @code{gdbserver} prints an error message
12691 and exits.} You must use the same port number with the host @value{GDBN}
12692 @code{target remote} command.
12694 On some targets, @code{gdbserver} can also attach to running programs.
12695 This is accomplished via the @code{--attach} argument. The syntax is:
12698 target> gdbserver @var{comm} --attach @var{pid}
12701 @var{pid} is the process ID of a currently running process. It isn't necessary
12702 to point @code{gdbserver} at a binary for the running process.
12705 @cindex attach to a program by name
12706 You can debug processes by name instead of process ID if your target has the
12707 @code{pidof} utility:
12710 target> gdbserver @var{comm} --attach `pidof @var{program}`
12713 In case more than one copy of @var{program} is running, or @var{program}
12714 has multiple threads, most versions of @code{pidof} support the
12715 @code{-s} option to only return the first process ID.
12717 @item On the host machine,
12718 first make sure you have the necessary symbol files. Load symbols for
12719 your application using the @code{file} command before you connect. Use
12720 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
12721 was compiled with the correct sysroot using @code{--with-system-root}).
12723 The symbol file and target libraries must exactly match the executable
12724 and libraries on the target, with one exception: the files on the host
12725 system should not be stripped, even if the files on the target system
12726 are. Mismatched or missing files will lead to confusing results
12727 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
12728 files may also prevent @code{gdbserver} from debugging multi-threaded
12731 Connect to your target (@pxref{Connecting,,Connecting to a remote target}).
12732 For TCP connections, you must start up @code{gdbserver} prior to using
12733 the @code{target remote} command. Otherwise you may get an error whose
12734 text depends on the host system, but which usually looks something like
12735 @samp{Connection refused}. You don't need to use the @code{load}
12736 command in @value{GDBN} when using @code{gdbserver}, since the program is
12737 already on the target.
12741 @subsection Monitor commands for @code{gdbserver}
12742 @cindex monitor commands, for @code{gdbserver}
12744 During a @value{GDBN} session using @code{gdbserver}, you can use the
12745 @code{monitor} command to send special requests to @code{gdbserver}.
12746 Here are the available commands; they are only of interest when
12747 debugging @value{GDBN} or @code{gdbserver}.
12751 List the available monitor commands.
12753 @item monitor set debug 0
12754 @itemx monitor set debug 1
12755 Disable or enable general debugging messages.
12757 @item monitor set remote-debug 0
12758 @itemx monitor set remote-debug 1
12759 Disable or enable specific debugging messages associated with the remote
12760 protocol (@pxref{Remote Protocol}).
12764 @node Remote configuration
12765 @section Remote configuration
12768 @kindex show remote
12769 This section documents the configuration options available when
12770 debugging remote programs. For the options related to the File I/O
12771 extensions of the remote protocol, see @ref{system,
12772 system-call-allowed}.
12775 @item set remoteaddresssize @var{bits}
12776 @cindex address size for remote targets
12777 @cindex bits in remote address
12778 Set the maximum size of address in a memory packet to the specified
12779 number of bits. @value{GDBN} will mask off the address bits above
12780 that number, when it passes addresses to the remote target. The
12781 default value is the number of bits in the target's address.
12783 @item show remoteaddresssize
12784 Show the current value of remote address size in bits.
12786 @item set remotebaud @var{n}
12787 @cindex baud rate for remote targets
12788 Set the baud rate for the remote serial I/O to @var{n} baud. The
12789 value is used to set the speed of the serial port used for debugging
12792 @item show remotebaud
12793 Show the current speed of the remote connection.
12795 @item set remotebreak
12796 @cindex interrupt remote programs
12797 @cindex BREAK signal instead of Ctrl-C
12798 @anchor{set remotebreak}
12799 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12800 when you type @kbd{Ctrl-c} to interrupt the program running
12801 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12802 character instead. The default is off, since most remote systems
12803 expect to see @samp{Ctrl-C} as the interrupt signal.
12805 @item show remotebreak
12806 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12807 interrupt the remote program.
12809 @item set remotedevice @var{device}
12810 @cindex serial port name
12811 Set the name of the serial port through which to communicate to the
12812 remote target to @var{device}. This is the device used by
12813 @value{GDBN} to open the serial communications line to the remote
12814 target. There's no default, so you must set a valid port name for the
12815 remote serial communications to work. (Some varieties of the
12816 @code{target} command accept the port name as part of their
12819 @item show remotedevice
12820 Show the current name of the serial port.
12822 @item set remotelogbase @var{base}
12823 Set the base (a.k.a.@: radix) of logging serial protocol
12824 communications to @var{base}. Supported values of @var{base} are:
12825 @code{ascii}, @code{octal}, and @code{hex}. The default is
12828 @item show remotelogbase
12829 Show the current setting of the radix for logging remote serial
12832 @item set remotelogfile @var{file}
12833 @cindex record serial communications on file
12834 Record remote serial communications on the named @var{file}. The
12835 default is not to record at all.
12837 @item show remotelogfile.
12838 Show the current setting of the file name on which to record the
12839 serial communications.
12841 @item set remotetimeout @var{num}
12842 @cindex timeout for serial communications
12843 @cindex remote timeout
12844 Set the timeout limit to wait for the remote target to respond to
12845 @var{num} seconds. The default is 2 seconds.
12847 @item show remotetimeout
12848 Show the current number of seconds to wait for the remote target
12851 @cindex limit hardware breakpoints and watchpoints
12852 @cindex remote target, limit break- and watchpoints
12853 @anchor{set remote hardware-watchpoint-limit}
12854 @anchor{set remote hardware-breakpoint-limit}
12855 @item set remote hardware-watchpoint-limit @var{limit}
12856 @itemx set remote hardware-breakpoint-limit @var{limit}
12857 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12858 watchpoints. A limit of -1, the default, is treated as unlimited.
12861 @cindex remote packets, enabling and disabling
12862 The @value{GDBN} remote protocol autodetects the packets supported by
12863 your debugging stub. If you need to override the autodetection, you
12864 can use these commands to enable or disable individual packets. Each
12865 packet can be set to @samp{on} (the remote target supports this
12866 packet), @samp{off} (the remote target does not support this packet),
12867 or @samp{auto} (detect remote target support for this packet). They
12868 all default to @samp{auto}. For more information about each packet,
12869 see @ref{Remote Protocol}.
12871 During normal use, you should not have to use any of these commands.
12872 If you do, that may be a bug in your remote debugging stub, or a bug
12873 in @value{GDBN}. You may want to report the problem to the
12874 @value{GDBN} developers.
12876 The available settings are:
12878 @multitable @columnfractions 0.3 0.2 0.35
12881 @tab Related Features
12883 @item @code{fetch-register-packet}
12885 @tab @code{info registers}
12887 @item @code{set-register-packet}
12891 @item @code{binary-download-packet}
12893 @tab @code{load}, @code{set}
12895 @item @code{read-aux-vector-packet}
12896 @tab @code{qXfer:auxv:read}
12897 @tab @code{info auxv}
12899 @item @code{symbol-lookup-packet}
12900 @tab @code{qSymbol}
12901 @tab Detecting multiple threads
12903 @item @code{verbose-resume-packet}
12905 @tab Stepping or resuming multiple threads
12907 @item @code{software-breakpoint-packet}
12911 @item @code{hardware-breakpoint-packet}
12915 @item @code{write-watchpoint-packet}
12919 @item @code{read-watchpoint-packet}
12923 @item @code{access-watchpoint-packet}
12927 @item @code{get-thread-local-storage-address-packet}
12928 @tab @code{qGetTLSAddr}
12929 @tab Displaying @code{__thread} variables
12931 @item @code{supported-packets}
12932 @tab @code{qSupported}
12933 @tab Remote communications parameters
12935 @item @code{pass-signals-packet}
12936 @tab @code{QPassSignals}
12937 @tab @code{handle @var{signal}}
12942 @section Implementing a remote stub
12944 @cindex debugging stub, example
12945 @cindex remote stub, example
12946 @cindex stub example, remote debugging
12947 The stub files provided with @value{GDBN} implement the target side of the
12948 communication protocol, and the @value{GDBN} side is implemented in the
12949 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12950 these subroutines to communicate, and ignore the details. (If you're
12951 implementing your own stub file, you can still ignore the details: start
12952 with one of the existing stub files. @file{sparc-stub.c} is the best
12953 organized, and therefore the easiest to read.)
12955 @cindex remote serial debugging, overview
12956 To debug a program running on another machine (the debugging
12957 @dfn{target} machine), you must first arrange for all the usual
12958 prerequisites for the program to run by itself. For example, for a C
12963 A startup routine to set up the C runtime environment; these usually
12964 have a name like @file{crt0}. The startup routine may be supplied by
12965 your hardware supplier, or you may have to write your own.
12968 A C subroutine library to support your program's
12969 subroutine calls, notably managing input and output.
12972 A way of getting your program to the other machine---for example, a
12973 download program. These are often supplied by the hardware
12974 manufacturer, but you may have to write your own from hardware
12978 The next step is to arrange for your program to use a serial port to
12979 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12980 machine). In general terms, the scheme looks like this:
12984 @value{GDBN} already understands how to use this protocol; when everything
12985 else is set up, you can simply use the @samp{target remote} command
12986 (@pxref{Targets,,Specifying a Debugging Target}).
12988 @item On the target,
12989 you must link with your program a few special-purpose subroutines that
12990 implement the @value{GDBN} remote serial protocol. The file containing these
12991 subroutines is called a @dfn{debugging stub}.
12993 On certain remote targets, you can use an auxiliary program
12994 @code{gdbserver} instead of linking a stub into your program.
12995 @xref{Server,,Using the @code{gdbserver} program}, for details.
12998 The debugging stub is specific to the architecture of the remote
12999 machine; for example, use @file{sparc-stub.c} to debug programs on
13002 @cindex remote serial stub list
13003 These working remote stubs are distributed with @value{GDBN}:
13008 @cindex @file{i386-stub.c}
13011 For Intel 386 and compatible architectures.
13014 @cindex @file{m68k-stub.c}
13015 @cindex Motorola 680x0
13017 For Motorola 680x0 architectures.
13020 @cindex @file{sh-stub.c}
13023 For Renesas SH architectures.
13026 @cindex @file{sparc-stub.c}
13028 For @sc{sparc} architectures.
13030 @item sparcl-stub.c
13031 @cindex @file{sparcl-stub.c}
13034 For Fujitsu @sc{sparclite} architectures.
13038 The @file{README} file in the @value{GDBN} distribution may list other
13039 recently added stubs.
13042 * Stub Contents:: What the stub can do for you
13043 * Bootstrapping:: What you must do for the stub
13044 * Debug Session:: Putting it all together
13047 @node Stub Contents
13048 @subsection What the stub can do for you
13050 @cindex remote serial stub
13051 The debugging stub for your architecture supplies these three
13055 @item set_debug_traps
13056 @findex set_debug_traps
13057 @cindex remote serial stub, initialization
13058 This routine arranges for @code{handle_exception} to run when your
13059 program stops. You must call this subroutine explicitly near the
13060 beginning of your program.
13062 @item handle_exception
13063 @findex handle_exception
13064 @cindex remote serial stub, main routine
13065 This is the central workhorse, but your program never calls it
13066 explicitly---the setup code arranges for @code{handle_exception} to
13067 run when a trap is triggered.
13069 @code{handle_exception} takes control when your program stops during
13070 execution (for example, on a breakpoint), and mediates communications
13071 with @value{GDBN} on the host machine. This is where the communications
13072 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13073 representative on the target machine. It begins by sending summary
13074 information on the state of your program, then continues to execute,
13075 retrieving and transmitting any information @value{GDBN} needs, until you
13076 execute a @value{GDBN} command that makes your program resume; at that point,
13077 @code{handle_exception} returns control to your own code on the target
13081 @cindex @code{breakpoint} subroutine, remote
13082 Use this auxiliary subroutine to make your program contain a
13083 breakpoint. Depending on the particular situation, this may be the only
13084 way for @value{GDBN} to get control. For instance, if your target
13085 machine has some sort of interrupt button, you won't need to call this;
13086 pressing the interrupt button transfers control to
13087 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13088 simply receiving characters on the serial port may also trigger a trap;
13089 again, in that situation, you don't need to call @code{breakpoint} from
13090 your own program---simply running @samp{target remote} from the host
13091 @value{GDBN} session gets control.
13093 Call @code{breakpoint} if none of these is true, or if you simply want
13094 to make certain your program stops at a predetermined point for the
13095 start of your debugging session.
13098 @node Bootstrapping
13099 @subsection What you must do for the stub
13101 @cindex remote stub, support routines
13102 The debugging stubs that come with @value{GDBN} are set up for a particular
13103 chip architecture, but they have no information about the rest of your
13104 debugging target machine.
13106 First of all you need to tell the stub how to communicate with the
13110 @item int getDebugChar()
13111 @findex getDebugChar
13112 Write this subroutine to read a single character from the serial port.
13113 It may be identical to @code{getchar} for your target system; a
13114 different name is used to allow you to distinguish the two if you wish.
13116 @item void putDebugChar(int)
13117 @findex putDebugChar
13118 Write this subroutine to write a single character to the serial port.
13119 It may be identical to @code{putchar} for your target system; a
13120 different name is used to allow you to distinguish the two if you wish.
13123 @cindex control C, and remote debugging
13124 @cindex interrupting remote targets
13125 If you want @value{GDBN} to be able to stop your program while it is
13126 running, you need to use an interrupt-driven serial driver, and arrange
13127 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13128 character). That is the character which @value{GDBN} uses to tell the
13129 remote system to stop.
13131 Getting the debugging target to return the proper status to @value{GDBN}
13132 probably requires changes to the standard stub; one quick and dirty way
13133 is to just execute a breakpoint instruction (the ``dirty'' part is that
13134 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13136 Other routines you need to supply are:
13139 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13140 @findex exceptionHandler
13141 Write this function to install @var{exception_address} in the exception
13142 handling tables. You need to do this because the stub does not have any
13143 way of knowing what the exception handling tables on your target system
13144 are like (for example, the processor's table might be in @sc{rom},
13145 containing entries which point to a table in @sc{ram}).
13146 @var{exception_number} is the exception number which should be changed;
13147 its meaning is architecture-dependent (for example, different numbers
13148 might represent divide by zero, misaligned access, etc). When this
13149 exception occurs, control should be transferred directly to
13150 @var{exception_address}, and the processor state (stack, registers,
13151 and so on) should be just as it is when a processor exception occurs. So if
13152 you want to use a jump instruction to reach @var{exception_address}, it
13153 should be a simple jump, not a jump to subroutine.
13155 For the 386, @var{exception_address} should be installed as an interrupt
13156 gate so that interrupts are masked while the handler runs. The gate
13157 should be at privilege level 0 (the most privileged level). The
13158 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13159 help from @code{exceptionHandler}.
13161 @item void flush_i_cache()
13162 @findex flush_i_cache
13163 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13164 instruction cache, if any, on your target machine. If there is no
13165 instruction cache, this subroutine may be a no-op.
13167 On target machines that have instruction caches, @value{GDBN} requires this
13168 function to make certain that the state of your program is stable.
13172 You must also make sure this library routine is available:
13175 @item void *memset(void *, int, int)
13177 This is the standard library function @code{memset} that sets an area of
13178 memory to a known value. If you have one of the free versions of
13179 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13180 either obtain it from your hardware manufacturer, or write your own.
13183 If you do not use the GNU C compiler, you may need other standard
13184 library subroutines as well; this varies from one stub to another,
13185 but in general the stubs are likely to use any of the common library
13186 subroutines which @code{@value{NGCC}} generates as inline code.
13189 @node Debug Session
13190 @subsection Putting it all together
13192 @cindex remote serial debugging summary
13193 In summary, when your program is ready to debug, you must follow these
13198 Make sure you have defined the supporting low-level routines
13199 (@pxref{Bootstrapping,,What you must do for the stub}):
13201 @code{getDebugChar}, @code{putDebugChar},
13202 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13206 Insert these lines near the top of your program:
13214 For the 680x0 stub only, you need to provide a variable called
13215 @code{exceptionHook}. Normally you just use:
13218 void (*exceptionHook)() = 0;
13222 but if before calling @code{set_debug_traps}, you set it to point to a
13223 function in your program, that function is called when
13224 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13225 error). The function indicated by @code{exceptionHook} is called with
13226 one parameter: an @code{int} which is the exception number.
13229 Compile and link together: your program, the @value{GDBN} debugging stub for
13230 your target architecture, and the supporting subroutines.
13233 Make sure you have a serial connection between your target machine and
13234 the @value{GDBN} host, and identify the serial port on the host.
13237 @c The "remote" target now provides a `load' command, so we should
13238 @c document that. FIXME.
13239 Download your program to your target machine (or get it there by
13240 whatever means the manufacturer provides), and start it.
13243 Start @value{GDBN} on the host, and connect to the target
13244 (@pxref{Connecting,,Connecting to a remote target}).
13248 @node Configurations
13249 @chapter Configuration-Specific Information
13251 While nearly all @value{GDBN} commands are available for all native and
13252 cross versions of the debugger, there are some exceptions. This chapter
13253 describes things that are only available in certain configurations.
13255 There are three major categories of configurations: native
13256 configurations, where the host and target are the same, embedded
13257 operating system configurations, which are usually the same for several
13258 different processor architectures, and bare embedded processors, which
13259 are quite different from each other.
13264 * Embedded Processors::
13271 This section describes details specific to particular native
13276 * BSD libkvm Interface:: Debugging BSD kernel memory images
13277 * SVR4 Process Information:: SVR4 process information
13278 * DJGPP Native:: Features specific to the DJGPP port
13279 * Cygwin Native:: Features specific to the Cygwin port
13280 * Hurd Native:: Features specific to @sc{gnu} Hurd
13281 * Neutrino:: Features specific to QNX Neutrino
13287 On HP-UX systems, if you refer to a function or variable name that
13288 begins with a dollar sign, @value{GDBN} searches for a user or system
13289 name first, before it searches for a convenience variable.
13292 @node BSD libkvm Interface
13293 @subsection BSD libkvm Interface
13296 @cindex kernel memory image
13297 @cindex kernel crash dump
13299 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13300 interface that provides a uniform interface for accessing kernel virtual
13301 memory images, including live systems and crash dumps. @value{GDBN}
13302 uses this interface to allow you to debug live kernels and kernel crash
13303 dumps on many native BSD configurations. This is implemented as a
13304 special @code{kvm} debugging target. For debugging a live system, load
13305 the currently running kernel into @value{GDBN} and connect to the
13309 (@value{GDBP}) @b{target kvm}
13312 For debugging crash dumps, provide the file name of the crash dump as an
13316 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13319 Once connected to the @code{kvm} target, the following commands are
13325 Set current context from the @dfn{Process Control Block} (PCB) address.
13328 Set current context from proc address. This command isn't available on
13329 modern FreeBSD systems.
13332 @node SVR4 Process Information
13333 @subsection SVR4 process information
13335 @cindex examine process image
13336 @cindex process info via @file{/proc}
13338 Many versions of SVR4 and compatible systems provide a facility called
13339 @samp{/proc} that can be used to examine the image of a running
13340 process using file-system subroutines. If @value{GDBN} is configured
13341 for an operating system with this facility, the command @code{info
13342 proc} is available to report information about the process running
13343 your program, or about any process running on your system. @code{info
13344 proc} works only on SVR4 systems that include the @code{procfs} code.
13345 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13346 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13352 @itemx info proc @var{process-id}
13353 Summarize available information about any running process. If a
13354 process ID is specified by @var{process-id}, display information about
13355 that process; otherwise display information about the program being
13356 debugged. The summary includes the debugged process ID, the command
13357 line used to invoke it, its current working directory, and its
13358 executable file's absolute file name.
13360 On some systems, @var{process-id} can be of the form
13361 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13362 within a process. If the optional @var{pid} part is missing, it means
13363 a thread from the process being debugged (the leading @samp{/} still
13364 needs to be present, or else @value{GDBN} will interpret the number as
13365 a process ID rather than a thread ID).
13367 @item info proc mappings
13368 @cindex memory address space mappings
13369 Report the memory address space ranges accessible in the program, with
13370 information on whether the process has read, write, or execute access
13371 rights to each range. On @sc{gnu}/Linux systems, each memory range
13372 includes the object file which is mapped to that range, instead of the
13373 memory access rights to that range.
13375 @item info proc stat
13376 @itemx info proc status
13377 @cindex process detailed status information
13378 These subcommands are specific to @sc{gnu}/Linux systems. They show
13379 the process-related information, including the user ID and group ID;
13380 how many threads are there in the process; its virtual memory usage;
13381 the signals that are pending, blocked, and ignored; its TTY; its
13382 consumption of system and user time; its stack size; its @samp{nice}
13383 value; etc. For more information, see the @samp{proc} man page
13384 (type @kbd{man 5 proc} from your shell prompt).
13386 @item info proc all
13387 Show all the information about the process described under all of the
13388 above @code{info proc} subcommands.
13391 @comment These sub-options of 'info proc' were not included when
13392 @comment procfs.c was re-written. Keep their descriptions around
13393 @comment against the day when someone finds the time to put them back in.
13394 @kindex info proc times
13395 @item info proc times
13396 Starting time, user CPU time, and system CPU time for your program and
13399 @kindex info proc id
13401 Report on the process IDs related to your program: its own process ID,
13402 the ID of its parent, the process group ID, and the session ID.
13405 @item set procfs-trace
13406 @kindex set procfs-trace
13407 @cindex @code{procfs} API calls
13408 This command enables and disables tracing of @code{procfs} API calls.
13410 @item show procfs-trace
13411 @kindex show procfs-trace
13412 Show the current state of @code{procfs} API call tracing.
13414 @item set procfs-file @var{file}
13415 @kindex set procfs-file
13416 Tell @value{GDBN} to write @code{procfs} API trace to the named
13417 @var{file}. @value{GDBN} appends the trace info to the previous
13418 contents of the file. The default is to display the trace on the
13421 @item show procfs-file
13422 @kindex show procfs-file
13423 Show the file to which @code{procfs} API trace is written.
13425 @item proc-trace-entry
13426 @itemx proc-trace-exit
13427 @itemx proc-untrace-entry
13428 @itemx proc-untrace-exit
13429 @kindex proc-trace-entry
13430 @kindex proc-trace-exit
13431 @kindex proc-untrace-entry
13432 @kindex proc-untrace-exit
13433 These commands enable and disable tracing of entries into and exits
13434 from the @code{syscall} interface.
13437 @kindex info pidlist
13438 @cindex process list, QNX Neutrino
13439 For QNX Neutrino only, this command displays the list of all the
13440 processes and all the threads within each process.
13443 @kindex info meminfo
13444 @cindex mapinfo list, QNX Neutrino
13445 For QNX Neutrino only, this command displays the list of all mapinfos.
13449 @subsection Features for Debugging @sc{djgpp} Programs
13450 @cindex @sc{djgpp} debugging
13451 @cindex native @sc{djgpp} debugging
13452 @cindex MS-DOS-specific commands
13455 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13456 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13457 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13458 top of real-mode DOS systems and their emulations.
13460 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13461 defines a few commands specific to the @sc{djgpp} port. This
13462 subsection describes those commands.
13467 This is a prefix of @sc{djgpp}-specific commands which print
13468 information about the target system and important OS structures.
13471 @cindex MS-DOS system info
13472 @cindex free memory information (MS-DOS)
13473 @item info dos sysinfo
13474 This command displays assorted information about the underlying
13475 platform: the CPU type and features, the OS version and flavor, the
13476 DPMI version, and the available conventional and DPMI memory.
13481 @cindex segment descriptor tables
13482 @cindex descriptor tables display
13484 @itemx info dos ldt
13485 @itemx info dos idt
13486 These 3 commands display entries from, respectively, Global, Local,
13487 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13488 tables are data structures which store a descriptor for each segment
13489 that is currently in use. The segment's selector is an index into a
13490 descriptor table; the table entry for that index holds the
13491 descriptor's base address and limit, and its attributes and access
13494 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13495 segment (used for both data and the stack), and a DOS segment (which
13496 allows access to DOS/BIOS data structures and absolute addresses in
13497 conventional memory). However, the DPMI host will usually define
13498 additional segments in order to support the DPMI environment.
13500 @cindex garbled pointers
13501 These commands allow to display entries from the descriptor tables.
13502 Without an argument, all entries from the specified table are
13503 displayed. An argument, which should be an integer expression, means
13504 display a single entry whose index is given by the argument. For
13505 example, here's a convenient way to display information about the
13506 debugged program's data segment:
13509 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13510 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13514 This comes in handy when you want to see whether a pointer is outside
13515 the data segment's limit (i.e.@: @dfn{garbled}).
13517 @cindex page tables display (MS-DOS)
13519 @itemx info dos pte
13520 These two commands display entries from, respectively, the Page
13521 Directory and the Page Tables. Page Directories and Page Tables are
13522 data structures which control how virtual memory addresses are mapped
13523 into physical addresses. A Page Table includes an entry for every
13524 page of memory that is mapped into the program's address space; there
13525 may be several Page Tables, each one holding up to 4096 entries. A
13526 Page Directory has up to 4096 entries, one each for every Page Table
13527 that is currently in use.
13529 Without an argument, @kbd{info dos pde} displays the entire Page
13530 Directory, and @kbd{info dos pte} displays all the entries in all of
13531 the Page Tables. An argument, an integer expression, given to the
13532 @kbd{info dos pde} command means display only that entry from the Page
13533 Directory table. An argument given to the @kbd{info dos pte} command
13534 means display entries from a single Page Table, the one pointed to by
13535 the specified entry in the Page Directory.
13537 @cindex direct memory access (DMA) on MS-DOS
13538 These commands are useful when your program uses @dfn{DMA} (Direct
13539 Memory Access), which needs physical addresses to program the DMA
13542 These commands are supported only with some DPMI servers.
13544 @cindex physical address from linear address
13545 @item info dos address-pte @var{addr}
13546 This command displays the Page Table entry for a specified linear
13547 address. The argument @var{addr} is a linear address which should
13548 already have the appropriate segment's base address added to it,
13549 because this command accepts addresses which may belong to @emph{any}
13550 segment. For example, here's how to display the Page Table entry for
13551 the page where a variable @code{i} is stored:
13554 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13555 @exdent @code{Page Table entry for address 0x11a00d30:}
13556 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13560 This says that @code{i} is stored at offset @code{0xd30} from the page
13561 whose physical base address is @code{0x02698000}, and shows all the
13562 attributes of that page.
13564 Note that you must cast the addresses of variables to a @code{char *},
13565 since otherwise the value of @code{__djgpp_base_address}, the base
13566 address of all variables and functions in a @sc{djgpp} program, will
13567 be added using the rules of C pointer arithmetics: if @code{i} is
13568 declared an @code{int}, @value{GDBN} will add 4 times the value of
13569 @code{__djgpp_base_address} to the address of @code{i}.
13571 Here's another example, it displays the Page Table entry for the
13575 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13576 @exdent @code{Page Table entry for address 0x29110:}
13577 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13581 (The @code{+ 3} offset is because the transfer buffer's address is the
13582 3rd member of the @code{_go32_info_block} structure.) The output
13583 clearly shows that this DPMI server maps the addresses in conventional
13584 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13585 linear (@code{0x29110}) addresses are identical.
13587 This command is supported only with some DPMI servers.
13590 @cindex DOS serial data link, remote debugging
13591 In addition to native debugging, the DJGPP port supports remote
13592 debugging via a serial data link. The following commands are specific
13593 to remote serial debugging in the DJGPP port of @value{GDBN}.
13596 @kindex set com1base
13597 @kindex set com1irq
13598 @kindex set com2base
13599 @kindex set com2irq
13600 @kindex set com3base
13601 @kindex set com3irq
13602 @kindex set com4base
13603 @kindex set com4irq
13604 @item set com1base @var{addr}
13605 This command sets the base I/O port address of the @file{COM1} serial
13608 @item set com1irq @var{irq}
13609 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13610 for the @file{COM1} serial port.
13612 There are similar commands @samp{set com2base}, @samp{set com3irq},
13613 etc.@: for setting the port address and the @code{IRQ} lines for the
13616 @kindex show com1base
13617 @kindex show com1irq
13618 @kindex show com2base
13619 @kindex show com2irq
13620 @kindex show com3base
13621 @kindex show com3irq
13622 @kindex show com4base
13623 @kindex show com4irq
13624 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13625 display the current settings of the base address and the @code{IRQ}
13626 lines used by the COM ports.
13629 @kindex info serial
13630 @cindex DOS serial port status
13631 This command prints the status of the 4 DOS serial ports. For each
13632 port, it prints whether it's active or not, its I/O base address and
13633 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13634 counts of various errors encountered so far.
13638 @node Cygwin Native
13639 @subsection Features for Debugging MS Windows PE executables
13640 @cindex MS Windows debugging
13641 @cindex native Cygwin debugging
13642 @cindex Cygwin-specific commands
13644 @value{GDBN} supports native debugging of MS Windows programs, including
13645 DLLs with and without symbolic debugging information. There are various
13646 additional Cygwin-specific commands, described in this subsection. The
13647 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
13648 that have no debugging symbols.
13654 This is a prefix of MS Windows specific commands which print
13655 information about the target system and important OS structures.
13657 @item info w32 selector
13658 This command displays information returned by
13659 the Win32 API @code{GetThreadSelectorEntry} function.
13660 It takes an optional argument that is evaluated to
13661 a long value to give the information about this given selector.
13662 Without argument, this command displays information
13663 about the six segment registers.
13667 This is a Cygwin specific alias of info shared.
13669 @kindex dll-symbols
13671 This command loads symbols from a dll similarly to
13672 add-sym command but without the need to specify a base address.
13674 @kindex set cygwin-exceptions
13675 @cindex debugging the Cygwin DLL
13676 @cindex Cygwin DLL, debugging
13677 @item set cygwin-exceptions @var{mode}
13678 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13679 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13680 @value{GDBN} will delay recognition of exceptions, and may ignore some
13681 exceptions which seem to be caused by internal Cygwin DLL
13682 ``bookkeeping''. This option is meant primarily for debugging the
13683 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13684 @value{GDBN} users with false @code{SIGSEGV} signals.
13686 @kindex show cygwin-exceptions
13687 @item show cygwin-exceptions
13688 Displays whether @value{GDBN} will break on exceptions that happen
13689 inside the Cygwin DLL itself.
13691 @kindex set new-console
13692 @item set new-console @var{mode}
13693 If @var{mode} is @code{on} the debuggee will
13694 be started in a new console on next start.
13695 If @var{mode} is @code{off}i, the debuggee will
13696 be started in the same console as the debugger.
13698 @kindex show new-console
13699 @item show new-console
13700 Displays whether a new console is used
13701 when the debuggee is started.
13703 @kindex set new-group
13704 @item set new-group @var{mode}
13705 This boolean value controls whether the debuggee should
13706 start a new group or stay in the same group as the debugger.
13707 This affects the way the Windows OS handles
13710 @kindex show new-group
13711 @item show new-group
13712 Displays current value of new-group boolean.
13714 @kindex set debugevents
13715 @item set debugevents
13716 This boolean value adds debug output concerning kernel events related
13717 to the debuggee seen by the debugger. This includes events that
13718 signal thread and process creation and exit, DLL loading and
13719 unloading, console interrupts, and debugging messages produced by the
13720 Windows @code{OutputDebugString} API call.
13722 @kindex set debugexec
13723 @item set debugexec
13724 This boolean value adds debug output concerning execute events
13725 (such as resume thread) seen by the debugger.
13727 @kindex set debugexceptions
13728 @item set debugexceptions
13729 This boolean value adds debug output concerning exceptions in the
13730 debuggee seen by the debugger.
13732 @kindex set debugmemory
13733 @item set debugmemory
13734 This boolean value adds debug output concerning debuggee memory reads
13735 and writes by the debugger.
13739 This boolean values specifies whether the debuggee is called
13740 via a shell or directly (default value is on).
13744 Displays if the debuggee will be started with a shell.
13749 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13752 @node Non-debug DLL symbols
13753 @subsubsection Support for DLLs without debugging symbols
13754 @cindex DLLs with no debugging symbols
13755 @cindex Minimal symbols and DLLs
13757 Very often on windows, some of the DLLs that your program relies on do
13758 not include symbolic debugging information (for example,
13759 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13760 symbols in a DLL, it relies on the minimal amount of symbolic
13761 information contained in the DLL's export table. This subsubsection
13762 describes working with such symbols, known internally to @value{GDBN} as
13763 ``minimal symbols''.
13765 Note that before the debugged program has started execution, no DLLs
13766 will have been loaded. The easiest way around this problem is simply to
13767 start the program --- either by setting a breakpoint or letting the
13768 program run once to completion. It is also possible to force
13769 @value{GDBN} to load a particular DLL before starting the executable ---
13770 see the shared library information in @ref{Files}, or the
13771 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
13772 explicitly loading symbols from a DLL with no debugging information will
13773 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13774 which may adversely affect symbol lookup performance.
13776 @subsubsection DLL name prefixes
13778 In keeping with the naming conventions used by the Microsoft debugging
13779 tools, DLL export symbols are made available with a prefix based on the
13780 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13781 also entered into the symbol table, so @code{CreateFileA} is often
13782 sufficient. In some cases there will be name clashes within a program
13783 (particularly if the executable itself includes full debugging symbols)
13784 necessitating the use of the fully qualified name when referring to the
13785 contents of the DLL. Use single-quotes around the name to avoid the
13786 exclamation mark (``!'') being interpreted as a language operator.
13788 Note that the internal name of the DLL may be all upper-case, even
13789 though the file name of the DLL is lower-case, or vice-versa. Since
13790 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13791 some confusion. If in doubt, try the @code{info functions} and
13792 @code{info variables} commands or even @code{maint print msymbols}
13793 (@pxref{Symbols}). Here's an example:
13796 (@value{GDBP}) info function CreateFileA
13797 All functions matching regular expression "CreateFileA":
13799 Non-debugging symbols:
13800 0x77e885f4 CreateFileA
13801 0x77e885f4 KERNEL32!CreateFileA
13805 (@value{GDBP}) info function !
13806 All functions matching regular expression "!":
13808 Non-debugging symbols:
13809 0x6100114c cygwin1!__assert
13810 0x61004034 cygwin1!_dll_crt0@@0
13811 0x61004240 cygwin1!dll_crt0(per_process *)
13815 @subsubsection Working with minimal symbols
13817 Symbols extracted from a DLL's export table do not contain very much
13818 type information. All that @value{GDBN} can do is guess whether a symbol
13819 refers to a function or variable depending on the linker section that
13820 contains the symbol. Also note that the actual contents of the memory
13821 contained in a DLL are not available unless the program is running. This
13822 means that you cannot examine the contents of a variable or disassemble
13823 a function within a DLL without a running program.
13825 Variables are generally treated as pointers and dereferenced
13826 automatically. For this reason, it is often necessary to prefix a
13827 variable name with the address-of operator (``&'') and provide explicit
13828 type information in the command. Here's an example of the type of
13832 (@value{GDBP}) print 'cygwin1!__argv'
13837 (@value{GDBP}) x 'cygwin1!__argv'
13838 0x10021610: "\230y\""
13841 And two possible solutions:
13844 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13845 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13849 (@value{GDBP}) x/2x &'cygwin1!__argv'
13850 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13851 (@value{GDBP}) x/x 0x10021608
13852 0x10021608: 0x0022fd98
13853 (@value{GDBP}) x/s 0x0022fd98
13854 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13857 Setting a break point within a DLL is possible even before the program
13858 starts execution. However, under these circumstances, @value{GDBN} can't
13859 examine the initial instructions of the function in order to skip the
13860 function's frame set-up code. You can work around this by using ``*&''
13861 to set the breakpoint at a raw memory address:
13864 (@value{GDBP}) break *&'python22!PyOS_Readline'
13865 Breakpoint 1 at 0x1e04eff0
13868 The author of these extensions is not entirely convinced that setting a
13869 break point within a shared DLL like @file{kernel32.dll} is completely
13873 @subsection Commands specific to @sc{gnu} Hurd systems
13874 @cindex @sc{gnu} Hurd debugging
13876 This subsection describes @value{GDBN} commands specific to the
13877 @sc{gnu} Hurd native debugging.
13882 @kindex set signals@r{, Hurd command}
13883 @kindex set sigs@r{, Hurd command}
13884 This command toggles the state of inferior signal interception by
13885 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13886 affected by this command. @code{sigs} is a shorthand alias for
13891 @kindex show signals@r{, Hurd command}
13892 @kindex show sigs@r{, Hurd command}
13893 Show the current state of intercepting inferior's signals.
13895 @item set signal-thread
13896 @itemx set sigthread
13897 @kindex set signal-thread
13898 @kindex set sigthread
13899 This command tells @value{GDBN} which thread is the @code{libc} signal
13900 thread. That thread is run when a signal is delivered to a running
13901 process. @code{set sigthread} is the shorthand alias of @code{set
13904 @item show signal-thread
13905 @itemx show sigthread
13906 @kindex show signal-thread
13907 @kindex show sigthread
13908 These two commands show which thread will run when the inferior is
13909 delivered a signal.
13912 @kindex set stopped@r{, Hurd command}
13913 This commands tells @value{GDBN} that the inferior process is stopped,
13914 as with the @code{SIGSTOP} signal. The stopped process can be
13915 continued by delivering a signal to it.
13918 @kindex show stopped@r{, Hurd command}
13919 This command shows whether @value{GDBN} thinks the debuggee is
13922 @item set exceptions
13923 @kindex set exceptions@r{, Hurd command}
13924 Use this command to turn off trapping of exceptions in the inferior.
13925 When exception trapping is off, neither breakpoints nor
13926 single-stepping will work. To restore the default, set exception
13929 @item show exceptions
13930 @kindex show exceptions@r{, Hurd command}
13931 Show the current state of trapping exceptions in the inferior.
13933 @item set task pause
13934 @kindex set task@r{, Hurd commands}
13935 @cindex task attributes (@sc{gnu} Hurd)
13936 @cindex pause current task (@sc{gnu} Hurd)
13937 This command toggles task suspension when @value{GDBN} has control.
13938 Setting it to on takes effect immediately, and the task is suspended
13939 whenever @value{GDBN} gets control. Setting it to off will take
13940 effect the next time the inferior is continued. If this option is set
13941 to off, you can use @code{set thread default pause on} or @code{set
13942 thread pause on} (see below) to pause individual threads.
13944 @item show task pause
13945 @kindex show task@r{, Hurd commands}
13946 Show the current state of task suspension.
13948 @item set task detach-suspend-count
13949 @cindex task suspend count
13950 @cindex detach from task, @sc{gnu} Hurd
13951 This command sets the suspend count the task will be left with when
13952 @value{GDBN} detaches from it.
13954 @item show task detach-suspend-count
13955 Show the suspend count the task will be left with when detaching.
13957 @item set task exception-port
13958 @itemx set task excp
13959 @cindex task exception port, @sc{gnu} Hurd
13960 This command sets the task exception port to which @value{GDBN} will
13961 forward exceptions. The argument should be the value of the @dfn{send
13962 rights} of the task. @code{set task excp} is a shorthand alias.
13964 @item set noninvasive
13965 @cindex noninvasive task options
13966 This command switches @value{GDBN} to a mode that is the least
13967 invasive as far as interfering with the inferior is concerned. This
13968 is the same as using @code{set task pause}, @code{set exceptions}, and
13969 @code{set signals} to values opposite to the defaults.
13971 @item info send-rights
13972 @itemx info receive-rights
13973 @itemx info port-rights
13974 @itemx info port-sets
13975 @itemx info dead-names
13978 @cindex send rights, @sc{gnu} Hurd
13979 @cindex receive rights, @sc{gnu} Hurd
13980 @cindex port rights, @sc{gnu} Hurd
13981 @cindex port sets, @sc{gnu} Hurd
13982 @cindex dead names, @sc{gnu} Hurd
13983 These commands display information about, respectively, send rights,
13984 receive rights, port rights, port sets, and dead names of a task.
13985 There are also shorthand aliases: @code{info ports} for @code{info
13986 port-rights} and @code{info psets} for @code{info port-sets}.
13988 @item set thread pause
13989 @kindex set thread@r{, Hurd command}
13990 @cindex thread properties, @sc{gnu} Hurd
13991 @cindex pause current thread (@sc{gnu} Hurd)
13992 This command toggles current thread suspension when @value{GDBN} has
13993 control. Setting it to on takes effect immediately, and the current
13994 thread is suspended whenever @value{GDBN} gets control. Setting it to
13995 off will take effect the next time the inferior is continued.
13996 Normally, this command has no effect, since when @value{GDBN} has
13997 control, the whole task is suspended. However, if you used @code{set
13998 task pause off} (see above), this command comes in handy to suspend
13999 only the current thread.
14001 @item show thread pause
14002 @kindex show thread@r{, Hurd command}
14003 This command shows the state of current thread suspension.
14005 @item set thread run
14006 This command sets whether the current thread is allowed to run.
14008 @item show thread run
14009 Show whether the current thread is allowed to run.
14011 @item set thread detach-suspend-count
14012 @cindex thread suspend count, @sc{gnu} Hurd
14013 @cindex detach from thread, @sc{gnu} Hurd
14014 This command sets the suspend count @value{GDBN} will leave on a
14015 thread when detaching. This number is relative to the suspend count
14016 found by @value{GDBN} when it notices the thread; use @code{set thread
14017 takeover-suspend-count} to force it to an absolute value.
14019 @item show thread detach-suspend-count
14020 Show the suspend count @value{GDBN} will leave on the thread when
14023 @item set thread exception-port
14024 @itemx set thread excp
14025 Set the thread exception port to which to forward exceptions. This
14026 overrides the port set by @code{set task exception-port} (see above).
14027 @code{set thread excp} is the shorthand alias.
14029 @item set thread takeover-suspend-count
14030 Normally, @value{GDBN}'s thread suspend counts are relative to the
14031 value @value{GDBN} finds when it notices each thread. This command
14032 changes the suspend counts to be absolute instead.
14034 @item set thread default
14035 @itemx show thread default
14036 @cindex thread default settings, @sc{gnu} Hurd
14037 Each of the above @code{set thread} commands has a @code{set thread
14038 default} counterpart (e.g., @code{set thread default pause}, @code{set
14039 thread default exception-port}, etc.). The @code{thread default}
14040 variety of commands sets the default thread properties for all
14041 threads; you can then change the properties of individual threads with
14042 the non-default commands.
14047 @subsection QNX Neutrino
14048 @cindex QNX Neutrino
14050 @value{GDBN} provides the following commands specific to the QNX
14054 @item set debug nto-debug
14055 @kindex set debug nto-debug
14056 When set to on, enables debugging messages specific to the QNX
14059 @item show debug nto-debug
14060 @kindex show debug nto-debug
14061 Show the current state of QNX Neutrino messages.
14066 @section Embedded Operating Systems
14068 This section describes configurations involving the debugging of
14069 embedded operating systems that are available for several different
14073 * VxWorks:: Using @value{GDBN} with VxWorks
14076 @value{GDBN} includes the ability to debug programs running on
14077 various real-time operating systems.
14080 @subsection Using @value{GDBN} with VxWorks
14086 @kindex target vxworks
14087 @item target vxworks @var{machinename}
14088 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14089 is the target system's machine name or IP address.
14093 On VxWorks, @code{load} links @var{filename} dynamically on the
14094 current target system as well as adding its symbols in @value{GDBN}.
14096 @value{GDBN} enables developers to spawn and debug tasks running on networked
14097 VxWorks targets from a Unix host. Already-running tasks spawned from
14098 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14099 both the Unix host and on the VxWorks target. The program
14100 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14101 installed with the name @code{vxgdb}, to distinguish it from a
14102 @value{GDBN} for debugging programs on the host itself.)
14105 @item VxWorks-timeout @var{args}
14106 @kindex vxworks-timeout
14107 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14108 This option is set by the user, and @var{args} represents the number of
14109 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14110 your VxWorks target is a slow software simulator or is on the far side
14111 of a thin network line.
14114 The following information on connecting to VxWorks was current when
14115 this manual was produced; newer releases of VxWorks may use revised
14118 @findex INCLUDE_RDB
14119 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14120 to include the remote debugging interface routines in the VxWorks
14121 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14122 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14123 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14124 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14125 information on configuring and remaking VxWorks, see the manufacturer's
14127 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14129 Once you have included @file{rdb.a} in your VxWorks system image and set
14130 your Unix execution search path to find @value{GDBN}, you are ready to
14131 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14132 @code{vxgdb}, depending on your installation).
14134 @value{GDBN} comes up showing the prompt:
14141 * VxWorks Connection:: Connecting to VxWorks
14142 * VxWorks Download:: VxWorks download
14143 * VxWorks Attach:: Running tasks
14146 @node VxWorks Connection
14147 @subsubsection Connecting to VxWorks
14149 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14150 network. To connect to a target whose host name is ``@code{tt}'', type:
14153 (vxgdb) target vxworks tt
14157 @value{GDBN} displays messages like these:
14160 Attaching remote machine across net...
14165 @value{GDBN} then attempts to read the symbol tables of any object modules
14166 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14167 these files by searching the directories listed in the command search
14168 path (@pxref{Environment, ,Your program's environment}); if it fails
14169 to find an object file, it displays a message such as:
14172 prog.o: No such file or directory.
14175 When this happens, add the appropriate directory to the search path with
14176 the @value{GDBN} command @code{path}, and execute the @code{target}
14179 @node VxWorks Download
14180 @subsubsection VxWorks download
14182 @cindex download to VxWorks
14183 If you have connected to the VxWorks target and you want to debug an
14184 object that has not yet been loaded, you can use the @value{GDBN}
14185 @code{load} command to download a file from Unix to VxWorks
14186 incrementally. The object file given as an argument to the @code{load}
14187 command is actually opened twice: first by the VxWorks target in order
14188 to download the code, then by @value{GDBN} in order to read the symbol
14189 table. This can lead to problems if the current working directories on
14190 the two systems differ. If both systems have NFS mounted the same
14191 filesystems, you can avoid these problems by using absolute paths.
14192 Otherwise, it is simplest to set the working directory on both systems
14193 to the directory in which the object file resides, and then to reference
14194 the file by its name, without any path. For instance, a program
14195 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14196 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14197 program, type this on VxWorks:
14200 -> cd "@var{vxpath}/vw/demo/rdb"
14204 Then, in @value{GDBN}, type:
14207 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14208 (vxgdb) load prog.o
14211 @value{GDBN} displays a response similar to this:
14214 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14217 You can also use the @code{load} command to reload an object module
14218 after editing and recompiling the corresponding source file. Note that
14219 this makes @value{GDBN} delete all currently-defined breakpoints,
14220 auto-displays, and convenience variables, and to clear the value
14221 history. (This is necessary in order to preserve the integrity of
14222 debugger's data structures that reference the target system's symbol
14225 @node VxWorks Attach
14226 @subsubsection Running tasks
14228 @cindex running VxWorks tasks
14229 You can also attach to an existing task using the @code{attach} command as
14233 (vxgdb) attach @var{task}
14237 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14238 or suspended when you attach to it. Running tasks are suspended at
14239 the time of attachment.
14241 @node Embedded Processors
14242 @section Embedded Processors
14244 This section goes into details specific to particular embedded
14247 @cindex send command to simulator
14248 Whenever a specific embedded processor has a simulator, @value{GDBN}
14249 allows to send an arbitrary command to the simulator.
14252 @item sim @var{command}
14253 @kindex sim@r{, a command}
14254 Send an arbitrary @var{command} string to the simulator. Consult the
14255 documentation for the specific simulator in use for information about
14256 acceptable commands.
14262 * H8/300:: Renesas H8/300
14263 * H8/500:: Renesas H8/500
14264 * M32R/D:: Renesas M32R/D
14265 * M68K:: Motorola M68K
14266 * MIPS Embedded:: MIPS Embedded
14267 * OpenRISC 1000:: OpenRisc 1000
14268 * PA:: HP PA Embedded
14269 * PowerPC:: PowerPC
14271 * Sparclet:: Tsqware Sparclet
14272 * Sparclite:: Fujitsu Sparclite
14273 * Z8000:: Zilog Z8000
14276 * Super-H:: Renesas Super-H
14277 * WinCE:: Windows CE child processes
14286 @item target rdi @var{dev}
14287 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14288 use this target to communicate with both boards running the Angel
14289 monitor, or with the EmbeddedICE JTAG debug device.
14292 @item target rdp @var{dev}
14297 @value{GDBN} provides the following ARM-specific commands:
14300 @item set arm disassembler
14302 This commands selects from a list of disassembly styles. The
14303 @code{"std"} style is the standard style.
14305 @item show arm disassembler
14307 Show the current disassembly style.
14309 @item set arm apcs32
14310 @cindex ARM 32-bit mode
14311 This command toggles ARM operation mode between 32-bit and 26-bit.
14313 @item show arm apcs32
14314 Display the current usage of the ARM 32-bit mode.
14316 @item set arm fpu @var{fputype}
14317 This command sets the ARM floating-point unit (FPU) type. The
14318 argument @var{fputype} can be one of these:
14322 Determine the FPU type by querying the OS ABI.
14324 Software FPU, with mixed-endian doubles on little-endian ARM
14327 GCC-compiled FPA co-processor.
14329 Software FPU with pure-endian doubles.
14335 Show the current type of the FPU.
14338 This command forces @value{GDBN} to use the specified ABI.
14341 Show the currently used ABI.
14343 @item set debug arm
14344 Toggle whether to display ARM-specific debugging messages from the ARM
14345 target support subsystem.
14347 @item show debug arm
14348 Show whether ARM-specific debugging messages are enabled.
14351 The following commands are available when an ARM target is debugged
14352 using the RDI interface:
14355 @item rdilogfile @r{[}@var{file}@r{]}
14357 @cindex ADP (Angel Debugger Protocol) logging
14358 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14359 With an argument, sets the log file to the specified @var{file}. With
14360 no argument, show the current log file name. The default log file is
14363 @item rdilogenable @r{[}@var{arg}@r{]}
14364 @kindex rdilogenable
14365 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14366 enables logging, with an argument 0 or @code{"no"} disables it. With
14367 no arguments displays the current setting. When logging is enabled,
14368 ADP packets exchanged between @value{GDBN} and the RDI target device
14369 are logged to a file.
14371 @item set rdiromatzero
14372 @kindex set rdiromatzero
14373 @cindex ROM at zero address, RDI
14374 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14375 vector catching is disabled, so that zero address can be used. If off
14376 (the default), vector catching is enabled. For this command to take
14377 effect, it needs to be invoked prior to the @code{target rdi} command.
14379 @item show rdiromatzero
14380 @kindex show rdiromatzero
14381 Show the current setting of ROM at zero address.
14383 @item set rdiheartbeat
14384 @kindex set rdiheartbeat
14385 @cindex RDI heartbeat
14386 Enable or disable RDI heartbeat packets. It is not recommended to
14387 turn on this option, since it confuses ARM and EPI JTAG interface, as
14388 well as the Angel monitor.
14390 @item show rdiheartbeat
14391 @kindex show rdiheartbeat
14392 Show the setting of RDI heartbeat packets.
14397 @subsection Renesas H8/300
14401 @kindex target hms@r{, with H8/300}
14402 @item target hms @var{dev}
14403 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
14404 Use special commands @code{device} and @code{speed} to control the serial
14405 line and the communications speed used.
14407 @kindex target e7000@r{, with H8/300}
14408 @item target e7000 @var{dev}
14409 E7000 emulator for Renesas H8 and SH.
14411 @kindex target sh3@r{, with H8/300}
14412 @kindex target sh3e@r{, with H8/300}
14413 @item target sh3 @var{dev}
14414 @itemx target sh3e @var{dev}
14415 Renesas SH-3 and SH-3E target systems.
14419 @cindex download to H8/300 or H8/500
14420 @cindex H8/300 or H8/500 download
14421 @cindex download to Renesas SH
14422 @cindex Renesas SH download
14423 When you select remote debugging to a Renesas SH, H8/300, or H8/500
14424 board, the @code{load} command downloads your program to the Renesas
14425 board and also opens it as the current executable target for
14426 @value{GDBN} on your host (like the @code{file} command).
14428 @value{GDBN} needs to know these things to talk to your
14429 Renesas SH, H8/300, or H8/500:
14433 that you want to use @samp{target hms}, the remote debugging interface
14434 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
14435 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
14436 the default when @value{GDBN} is configured specifically for the Renesas SH,
14437 H8/300, or H8/500.)
14440 what serial device connects your host to your Renesas board (the first
14441 serial device available on your host is the default).
14444 what speed to use over the serial device.
14448 * Renesas Boards:: Connecting to Renesas boards.
14449 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
14450 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
14453 @node Renesas Boards
14454 @subsubsection Connecting to Renesas boards
14456 @c only for Unix hosts
14458 @cindex serial device, Renesas micros
14459 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
14460 need to explicitly set the serial device. The default @var{port} is the
14461 first available port on your host. This is only necessary on Unix
14462 hosts, where it is typically something like @file{/dev/ttya}.
14465 @cindex serial line speed, Renesas micros
14466 @code{@value{GDBN}} has another special command to set the communications
14467 speed: @samp{speed @var{bps}}. This command also is only used from Unix
14468 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
14469 the DOS @code{mode} command (for instance,
14470 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
14472 The @samp{device} and @samp{speed} commands are available only when you
14473 use a Unix host to debug your Renesas microprocessor programs. If you
14475 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
14476 called @code{asynctsr} to communicate with the development board
14477 through a PC serial port. You must also use the DOS @code{mode} command
14478 to set up the serial port on the DOS side.
14480 The following sample session illustrates the steps needed to start a
14481 program under @value{GDBN} control on an H8/300. The example uses a
14482 sample H8/300 program called @file{t.x}. The procedure is the same for
14483 the Renesas SH and the H8/500.
14485 First hook up your development board. In this example, we use a
14486 board attached to serial port @code{COM2}; if you use a different serial
14487 port, substitute its name in the argument of the @code{mode} command.
14488 When you call @code{asynctsr}, the auxiliary comms program used by the
14489 debugger, you give it just the numeric part of the serial port's name;
14490 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
14494 C:\H8300\TEST> asynctsr 2
14495 C:\H8300\TEST> mode com2:9600,n,8,1,p
14497 Resident portion of MODE loaded
14499 COM2: 9600, n, 8, 1, p
14504 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
14505 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
14506 disable it, or even boot without it, to use @code{asynctsr} to control
14507 your development board.
14510 @kindex target hms@r{, and serial protocol}
14511 Now that serial communications are set up, and the development board is
14512 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
14513 the name of your program as the argument. @code{@value{GDBN}} prompts
14514 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
14515 commands to begin your debugging session: @samp{target hms} to specify
14516 cross-debugging to the Renesas board, and the @code{load} command to
14517 download your program to the board. @code{load} displays the names of
14518 the program's sections, and a @samp{*} for each 2K of data downloaded.
14519 (If you want to refresh @value{GDBN} data on symbols or on the
14520 executable file without downloading, use the @value{GDBN} commands
14521 @code{file} or @code{symbol-file}. These commands, and @code{load}
14522 itself, are described in @ref{Files,,Commands to specify files}.)
14525 (eg-C:\H8300\TEST) @value{GDBP} t.x
14526 @value{GDBN} is free software and you are welcome to distribute copies
14527 of it under certain conditions; type "show copying" to see
14529 There is absolutely no warranty for @value{GDBN}; type "show warranty"
14531 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
14532 (@value{GDBP}) target hms
14533 Connected to remote H8/300 HMS system.
14534 (@value{GDBP}) load t.x
14535 .text : 0x8000 .. 0xabde ***********
14536 .data : 0xabde .. 0xad30 *
14537 .stack : 0xf000 .. 0xf014 *
14540 At this point, you're ready to run or debug your program. From here on,
14541 you can use all the usual @value{GDBN} commands. The @code{break} command
14542 sets breakpoints; the @code{run} command starts your program;
14543 @code{print} or @code{x} display data; the @code{continue} command
14544 resumes execution after stopping at a breakpoint. You can use the
14545 @code{help} command at any time to find out more about @value{GDBN} commands.
14547 Remember, however, that @emph{operating system} facilities aren't
14548 available on your development board; for example, if your program hangs,
14549 you can't send an interrupt---but you can press the @sc{reset} switch!
14551 Use the @sc{reset} button on the development board
14554 to interrupt your program (don't use @kbd{Ctrl-c} on the DOS host---it has
14555 no way to pass an interrupt signal to the development board); and
14558 to return to the @value{GDBN} command prompt after your program finishes
14559 normally. The communications protocol provides no other way for @value{GDBN}
14560 to detect program completion.
14563 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
14564 development board as a ``normal exit'' of your program.
14567 @subsubsection Using the E7000 in-circuit emulator
14569 @kindex target e7000@r{, with Renesas ICE}
14570 You can use the E7000 in-circuit emulator to develop code for either the
14571 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
14572 e7000} command to connect @value{GDBN} to your E7000:
14575 @item target e7000 @var{port} @var{speed}
14576 Use this form if your E7000 is connected to a serial port. The
14577 @var{port} argument identifies what serial port to use (for example,
14578 @samp{com2}). The third argument is the line speed in bits per second
14579 (for example, @samp{9600}).
14581 @item target e7000 @var{hostname}
14582 If your E7000 is installed as a host on a TCP/IP network, you can just
14583 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
14586 The following special commands are available when debugging with the
14590 @item e7000 @var{command}
14592 @cindex send command to E7000 monitor
14593 This sends the specified @var{command} to the E7000 monitor.
14595 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
14596 @kindex ftplogin@r{, E7000}
14597 This command records information for subsequent interface with the
14598 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
14599 named @var{machine} using specified @var{username} and @var{password},
14600 and then chdir to the named directory @var{dir}.
14602 @item ftpload @var{file}
14603 @kindex ftpload@r{, E7000}
14604 This command uses credentials recorded by @code{ftplogin} to fetch and
14605 load the named @var{file} from the E7000 monitor.
14608 @kindex drain@r{, E7000}
14609 This command drains any pending text buffers stored on the E7000.
14611 @item set usehardbreakpoints
14612 @itemx show usehardbreakpoints
14613 @kindex set usehardbreakpoints@r{, E7000}
14614 @kindex show usehardbreakpoints@r{, E7000}
14615 @cindex hardware breakpoints, and E7000
14616 These commands set and show the use of hardware breakpoints for all
14617 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
14618 more information about using hardware breakpoints selectively.
14621 @node Renesas Special
14622 @subsubsection Special @value{GDBN} commands for Renesas micros
14624 Some @value{GDBN} commands are available only for the H8/300:
14628 @kindex set machine
14629 @kindex show machine
14630 @item set machine h8300
14631 @itemx set machine h8300h
14632 Condition @value{GDBN} for one of the two variants of the H8/300
14633 architecture with @samp{set machine}. You can use @samp{show machine}
14634 to check which variant is currently in effect.
14643 @kindex set memory @var{mod}
14644 @cindex memory models, H8/500
14645 @item set memory @var{mod}
14647 Specify which H8/500 memory model (@var{mod}) you are using with
14648 @samp{set memory}; check which memory model is in effect with @samp{show
14649 memory}. The accepted values for @var{mod} are @code{small},
14650 @code{big}, @code{medium}, and @code{compact}.
14655 @subsection Renesas M32R/D and M32R/SDI
14658 @kindex target m32r
14659 @item target m32r @var{dev}
14660 Renesas M32R/D ROM monitor.
14662 @kindex target m32rsdi
14663 @item target m32rsdi @var{dev}
14664 Renesas M32R SDI server, connected via parallel port to the board.
14667 The following @value{GDBN} commands are specific to the M32R monitor:
14670 @item set download-path @var{path}
14671 @kindex set download-path
14672 @cindex find downloadable @sc{srec} files (M32R)
14673 Set the default path for finding downloadable @sc{srec} files.
14675 @item show download-path
14676 @kindex show download-path
14677 Show the default path for downloadable @sc{srec} files.
14679 @item set board-address @var{addr}
14680 @kindex set board-address
14681 @cindex M32-EVA target board address
14682 Set the IP address for the M32R-EVA target board.
14684 @item show board-address
14685 @kindex show board-address
14686 Show the current IP address of the target board.
14688 @item set server-address @var{addr}
14689 @kindex set server-address
14690 @cindex download server address (M32R)
14691 Set the IP address for the download server, which is the @value{GDBN}'s
14694 @item show server-address
14695 @kindex show server-address
14696 Display the IP address of the download server.
14698 @item upload @r{[}@var{file}@r{]}
14699 @kindex upload@r{, M32R}
14700 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14701 upload capability. If no @var{file} argument is given, the current
14702 executable file is uploaded.
14704 @item tload @r{[}@var{file}@r{]}
14705 @kindex tload@r{, M32R}
14706 Test the @code{upload} command.
14709 The following commands are available for M32R/SDI:
14714 @cindex reset SDI connection, M32R
14715 This command resets the SDI connection.
14719 This command shows the SDI connection status.
14722 @kindex debug_chaos
14723 @cindex M32R/Chaos debugging
14724 Instructs the remote that M32R/Chaos debugging is to be used.
14726 @item use_debug_dma
14727 @kindex use_debug_dma
14728 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14731 @kindex use_mon_code
14732 Instructs the remote to use the MON_CODE method of accessing memory.
14735 @kindex use_ib_break
14736 Instructs the remote to set breakpoints by IB break.
14738 @item use_dbt_break
14739 @kindex use_dbt_break
14740 Instructs the remote to set breakpoints by DBT.
14746 The Motorola m68k configuration includes ColdFire support, and
14747 target command for the following ROM monitors.
14751 @kindex target abug
14752 @item target abug @var{dev}
14753 ABug ROM monitor for M68K.
14755 @kindex target cpu32bug
14756 @item target cpu32bug @var{dev}
14757 CPU32BUG monitor, running on a CPU32 (M68K) board.
14759 @kindex target dbug
14760 @item target dbug @var{dev}
14761 dBUG ROM monitor for Motorola ColdFire.
14764 @item target est @var{dev}
14765 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14767 @kindex target rom68k
14768 @item target rom68k @var{dev}
14769 ROM 68K monitor, running on an M68K IDP board.
14775 @kindex target rombug
14776 @item target rombug @var{dev}
14777 ROMBUG ROM monitor for OS/9000.
14781 @node MIPS Embedded
14782 @subsection MIPS Embedded
14784 @cindex MIPS boards
14785 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14786 MIPS board attached to a serial line. This is available when
14787 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14790 Use these @value{GDBN} commands to specify the connection to your target board:
14793 @item target mips @var{port}
14794 @kindex target mips @var{port}
14795 To run a program on the board, start up @code{@value{GDBP}} with the
14796 name of your program as the argument. To connect to the board, use the
14797 command @samp{target mips @var{port}}, where @var{port} is the name of
14798 the serial port connected to the board. If the program has not already
14799 been downloaded to the board, you may use the @code{load} command to
14800 download it. You can then use all the usual @value{GDBN} commands.
14802 For example, this sequence connects to the target board through a serial
14803 port, and loads and runs a program called @var{prog} through the
14807 host$ @value{GDBP} @var{prog}
14808 @value{GDBN} is free software and @dots{}
14809 (@value{GDBP}) target mips /dev/ttyb
14810 (@value{GDBP}) load @var{prog}
14814 @item target mips @var{hostname}:@var{portnumber}
14815 On some @value{GDBN} host configurations, you can specify a TCP
14816 connection (for instance, to a serial line managed by a terminal
14817 concentrator) instead of a serial port, using the syntax
14818 @samp{@var{hostname}:@var{portnumber}}.
14820 @item target pmon @var{port}
14821 @kindex target pmon @var{port}
14824 @item target ddb @var{port}
14825 @kindex target ddb @var{port}
14826 NEC's DDB variant of PMON for Vr4300.
14828 @item target lsi @var{port}
14829 @kindex target lsi @var{port}
14830 LSI variant of PMON.
14832 @kindex target r3900
14833 @item target r3900 @var{dev}
14834 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14836 @kindex target array
14837 @item target array @var{dev}
14838 Array Tech LSI33K RAID controller board.
14844 @value{GDBN} also supports these special commands for MIPS targets:
14847 @item set mipsfpu double
14848 @itemx set mipsfpu single
14849 @itemx set mipsfpu none
14850 @itemx set mipsfpu auto
14851 @itemx show mipsfpu
14852 @kindex set mipsfpu
14853 @kindex show mipsfpu
14854 @cindex MIPS remote floating point
14855 @cindex floating point, MIPS remote
14856 If your target board does not support the MIPS floating point
14857 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14858 need this, you may wish to put the command in your @value{GDBN} init
14859 file). This tells @value{GDBN} how to find the return value of
14860 functions which return floating point values. It also allows
14861 @value{GDBN} to avoid saving the floating point registers when calling
14862 functions on the board. If you are using a floating point coprocessor
14863 with only single precision floating point support, as on the @sc{r4650}
14864 processor, use the command @samp{set mipsfpu single}. The default
14865 double precision floating point coprocessor may be selected using
14866 @samp{set mipsfpu double}.
14868 In previous versions the only choices were double precision or no
14869 floating point, so @samp{set mipsfpu on} will select double precision
14870 and @samp{set mipsfpu off} will select no floating point.
14872 As usual, you can inquire about the @code{mipsfpu} variable with
14873 @samp{show mipsfpu}.
14875 @item set timeout @var{seconds}
14876 @itemx set retransmit-timeout @var{seconds}
14877 @itemx show timeout
14878 @itemx show retransmit-timeout
14879 @cindex @code{timeout}, MIPS protocol
14880 @cindex @code{retransmit-timeout}, MIPS protocol
14881 @kindex set timeout
14882 @kindex show timeout
14883 @kindex set retransmit-timeout
14884 @kindex show retransmit-timeout
14885 You can control the timeout used while waiting for a packet, in the MIPS
14886 remote protocol, with the @code{set timeout @var{seconds}} command. The
14887 default is 5 seconds. Similarly, you can control the timeout used while
14888 waiting for an acknowledgement of a packet with the @code{set
14889 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14890 You can inspect both values with @code{show timeout} and @code{show
14891 retransmit-timeout}. (These commands are @emph{only} available when
14892 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14894 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14895 is waiting for your program to stop. In that case, @value{GDBN} waits
14896 forever because it has no way of knowing how long the program is going
14897 to run before stopping.
14899 @item set syn-garbage-limit @var{num}
14900 @kindex set syn-garbage-limit@r{, MIPS remote}
14901 @cindex synchronize with remote MIPS target
14902 Limit the maximum number of characters @value{GDBN} should ignore when
14903 it tries to synchronize with the remote target. The default is 10
14904 characters. Setting the limit to -1 means there's no limit.
14906 @item show syn-garbage-limit
14907 @kindex show syn-garbage-limit@r{, MIPS remote}
14908 Show the current limit on the number of characters to ignore when
14909 trying to synchronize with the remote system.
14911 @item set monitor-prompt @var{prompt}
14912 @kindex set monitor-prompt@r{, MIPS remote}
14913 @cindex remote monitor prompt
14914 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14915 remote monitor. The default depends on the target:
14925 @item show monitor-prompt
14926 @kindex show monitor-prompt@r{, MIPS remote}
14927 Show the current strings @value{GDBN} expects as the prompt from the
14930 @item set monitor-warnings
14931 @kindex set monitor-warnings@r{, MIPS remote}
14932 Enable or disable monitor warnings about hardware breakpoints. This
14933 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14934 display warning messages whose codes are returned by the @code{lsi}
14935 PMON monitor for breakpoint commands.
14937 @item show monitor-warnings
14938 @kindex show monitor-warnings@r{, MIPS remote}
14939 Show the current setting of printing monitor warnings.
14941 @item pmon @var{command}
14942 @kindex pmon@r{, MIPS remote}
14943 @cindex send PMON command
14944 This command allows sending an arbitrary @var{command} string to the
14945 monitor. The monitor must be in debug mode for this to work.
14948 @node OpenRISC 1000
14949 @subsection OpenRISC 1000
14950 @cindex OpenRISC 1000
14952 @cindex or1k boards
14953 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14954 about platform and commands.
14958 @kindex target jtag
14959 @item target jtag jtag://@var{host}:@var{port}
14961 Connects to remote JTAG server.
14962 JTAG remote server can be either an or1ksim or JTAG server,
14963 connected via parallel port to the board.
14965 Example: @code{target jtag jtag://localhost:9999}
14968 @item or1ksim @var{command}
14969 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14970 Simulator, proprietary commands can be executed.
14972 @kindex info or1k spr
14973 @item info or1k spr
14974 Displays spr groups.
14976 @item info or1k spr @var{group}
14977 @itemx info or1k spr @var{groupno}
14978 Displays register names in selected group.
14980 @item info or1k spr @var{group} @var{register}
14981 @itemx info or1k spr @var{register}
14982 @itemx info or1k spr @var{groupno} @var{registerno}
14983 @itemx info or1k spr @var{registerno}
14984 Shows information about specified spr register.
14987 @item spr @var{group} @var{register} @var{value}
14988 @itemx spr @var{register @var{value}}
14989 @itemx spr @var{groupno} @var{registerno @var{value}}
14990 @itemx spr @var{registerno @var{value}}
14991 Writes @var{value} to specified spr register.
14994 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14995 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14996 program execution and is thus much faster. Hardware breakpoints/watchpoint
14997 triggers can be set using:
15000 Load effective address/data
15002 Store effective address/data
15004 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15009 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15010 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15012 @code{htrace} commands:
15013 @cindex OpenRISC 1000 htrace
15016 @item hwatch @var{conditional}
15017 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15018 or Data. For example:
15020 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15022 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15026 Display information about current HW trace configuration.
15028 @item htrace trigger @var{conditional}
15029 Set starting criteria for HW trace.
15031 @item htrace qualifier @var{conditional}
15032 Set acquisition qualifier for HW trace.
15034 @item htrace stop @var{conditional}
15035 Set HW trace stopping criteria.
15037 @item htrace record [@var{data}]*
15038 Selects the data to be recorded, when qualifier is met and HW trace was
15041 @item htrace enable
15042 @itemx htrace disable
15043 Enables/disables the HW trace.
15045 @item htrace rewind [@var{filename}]
15046 Clears currently recorded trace data.
15048 If filename is specified, new trace file is made and any newly collected data
15049 will be written there.
15051 @item htrace print [@var{start} [@var{len}]]
15052 Prints trace buffer, using current record configuration.
15054 @item htrace mode continuous
15055 Set continuous trace mode.
15057 @item htrace mode suspend
15058 Set suspend trace mode.
15063 @subsection PowerPC
15066 @kindex target dink32
15067 @item target dink32 @var{dev}
15068 DINK32 ROM monitor.
15070 @kindex target ppcbug
15071 @item target ppcbug @var{dev}
15072 @kindex target ppcbug1
15073 @item target ppcbug1 @var{dev}
15074 PPCBUG ROM monitor for PowerPC.
15077 @item target sds @var{dev}
15078 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15081 @cindex SDS protocol
15082 The following commands specific to the SDS protocol are supported
15086 @item set sdstimeout @var{nsec}
15087 @kindex set sdstimeout
15088 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15089 default is 2 seconds.
15091 @item show sdstimeout
15092 @kindex show sdstimeout
15093 Show the current value of the SDS timeout.
15095 @item sds @var{command}
15096 @kindex sds@r{, a command}
15097 Send the specified @var{command} string to the SDS monitor.
15102 @subsection HP PA Embedded
15106 @kindex target op50n
15107 @item target op50n @var{dev}
15108 OP50N monitor, running on an OKI HPPA board.
15110 @kindex target w89k
15111 @item target w89k @var{dev}
15112 W89K monitor, running on a Winbond HPPA board.
15117 @subsection Renesas SH
15121 @kindex target hms@r{, with Renesas SH}
15122 @item target hms @var{dev}
15123 A Renesas SH board attached via serial line to your host. Use special
15124 commands @code{device} and @code{speed} to control the serial line and
15125 the communications speed used.
15127 @kindex target e7000@r{, with Renesas SH}
15128 @item target e7000 @var{dev}
15129 E7000 emulator for Renesas SH.
15131 @kindex target sh3@r{, with SH}
15132 @kindex target sh3e@r{, with SH}
15133 @item target sh3 @var{dev}
15134 @item target sh3e @var{dev}
15135 Renesas SH-3 and SH-3E target systems.
15140 @subsection Tsqware Sparclet
15144 @value{GDBN} enables developers to debug tasks running on
15145 Sparclet targets from a Unix host.
15146 @value{GDBN} uses code that runs on
15147 both the Unix host and on the Sparclet target. The program
15148 @code{@value{GDBP}} is installed and executed on the Unix host.
15151 @item remotetimeout @var{args}
15152 @kindex remotetimeout
15153 @value{GDBN} supports the option @code{remotetimeout}.
15154 This option is set by the user, and @var{args} represents the number of
15155 seconds @value{GDBN} waits for responses.
15158 @cindex compiling, on Sparclet
15159 When compiling for debugging, include the options @samp{-g} to get debug
15160 information and @samp{-Ttext} to relocate the program to where you wish to
15161 load it on the target. You may also want to add the options @samp{-n} or
15162 @samp{-N} in order to reduce the size of the sections. Example:
15165 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15168 You can use @code{objdump} to verify that the addresses are what you intended:
15171 sparclet-aout-objdump --headers --syms prog
15174 @cindex running, on Sparclet
15176 your Unix execution search path to find @value{GDBN}, you are ready to
15177 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15178 (or @code{sparclet-aout-gdb}, depending on your installation).
15180 @value{GDBN} comes up showing the prompt:
15187 * Sparclet File:: Setting the file to debug
15188 * Sparclet Connection:: Connecting to Sparclet
15189 * Sparclet Download:: Sparclet download
15190 * Sparclet Execution:: Running and debugging
15193 @node Sparclet File
15194 @subsubsection Setting file to debug
15196 The @value{GDBN} command @code{file} lets you choose with program to debug.
15199 (gdbslet) file prog
15203 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15204 @value{GDBN} locates
15205 the file by searching the directories listed in the command search
15207 If the file was compiled with debug information (option @samp{-g}), source
15208 files will be searched as well.
15209 @value{GDBN} locates
15210 the source files by searching the directories listed in the directory search
15211 path (@pxref{Environment, ,Your program's environment}).
15213 to find a file, it displays a message such as:
15216 prog: No such file or directory.
15219 When this happens, add the appropriate directories to the search paths with
15220 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15221 @code{target} command again.
15223 @node Sparclet Connection
15224 @subsubsection Connecting to Sparclet
15226 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15227 To connect to a target on serial port ``@code{ttya}'', type:
15230 (gdbslet) target sparclet /dev/ttya
15231 Remote target sparclet connected to /dev/ttya
15232 main () at ../prog.c:3
15236 @value{GDBN} displays messages like these:
15242 @node Sparclet Download
15243 @subsubsection Sparclet download
15245 @cindex download to Sparclet
15246 Once connected to the Sparclet target,
15247 you can use the @value{GDBN}
15248 @code{load} command to download the file from the host to the target.
15249 The file name and load offset should be given as arguments to the @code{load}
15251 Since the file format is aout, the program must be loaded to the starting
15252 address. You can use @code{objdump} to find out what this value is. The load
15253 offset is an offset which is added to the VMA (virtual memory address)
15254 of each of the file's sections.
15255 For instance, if the program
15256 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15257 and bss at 0x12010170, in @value{GDBN}, type:
15260 (gdbslet) load prog 0x12010000
15261 Loading section .text, size 0xdb0 vma 0x12010000
15264 If the code is loaded at a different address then what the program was linked
15265 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15266 to tell @value{GDBN} where to map the symbol table.
15268 @node Sparclet Execution
15269 @subsubsection Running and debugging
15271 @cindex running and debugging Sparclet programs
15272 You can now begin debugging the task using @value{GDBN}'s execution control
15273 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15274 manual for the list of commands.
15278 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15280 Starting program: prog
15281 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15282 3 char *symarg = 0;
15284 4 char *execarg = "hello!";
15289 @subsection Fujitsu Sparclite
15293 @kindex target sparclite
15294 @item target sparclite @var{dev}
15295 Fujitsu sparclite boards, used only for the purpose of loading.
15296 You must use an additional command to debug the program.
15297 For example: target remote @var{dev} using @value{GDBN} standard
15303 @subsection Zilog Z8000
15306 @cindex simulator, Z8000
15307 @cindex Zilog Z8000 simulator
15309 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15312 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15313 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15314 segmented variant). The simulator recognizes which architecture is
15315 appropriate by inspecting the object code.
15318 @item target sim @var{args}
15320 @kindex target sim@r{, with Z8000}
15321 Debug programs on a simulated CPU. If the simulator supports setup
15322 options, specify them via @var{args}.
15326 After specifying this target, you can debug programs for the simulated
15327 CPU in the same style as programs for your host computer; use the
15328 @code{file} command to load a new program image, the @code{run} command
15329 to run your program, and so on.
15331 As well as making available all the usual machine registers
15332 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15333 additional items of information as specially named registers:
15338 Counts clock-ticks in the simulator.
15341 Counts instructions run in the simulator.
15344 Execution time in 60ths of a second.
15348 You can refer to these values in @value{GDBN} expressions with the usual
15349 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15350 conditional breakpoint that suspends only after at least 5000
15351 simulated clock ticks.
15354 @subsection Atmel AVR
15357 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15358 following AVR-specific commands:
15361 @item info io_registers
15362 @kindex info io_registers@r{, AVR}
15363 @cindex I/O registers (Atmel AVR)
15364 This command displays information about the AVR I/O registers. For
15365 each register, @value{GDBN} prints its number and value.
15372 When configured for debugging CRIS, @value{GDBN} provides the
15373 following CRIS-specific commands:
15376 @item set cris-version @var{ver}
15377 @cindex CRIS version
15378 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15379 The CRIS version affects register names and sizes. This command is useful in
15380 case autodetection of the CRIS version fails.
15382 @item show cris-version
15383 Show the current CRIS version.
15385 @item set cris-dwarf2-cfi
15386 @cindex DWARF-2 CFI and CRIS
15387 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15388 Change to @samp{off} when using @code{gcc-cris} whose version is below
15391 @item show cris-dwarf2-cfi
15392 Show the current state of using DWARF-2 CFI.
15394 @item set cris-mode @var{mode}
15396 Set the current CRIS mode to @var{mode}. It should only be changed when
15397 debugging in guru mode, in which case it should be set to
15398 @samp{guru} (the default is @samp{normal}).
15400 @item show cris-mode
15401 Show the current CRIS mode.
15405 @subsection Renesas Super-H
15408 For the Renesas Super-H processor, @value{GDBN} provides these
15413 @kindex regs@r{, Super-H}
15414 Show the values of all Super-H registers.
15418 @subsection Windows CE
15421 The following commands are available for Windows CE:
15424 @item set remotedirectory @var{dir}
15425 @kindex set remotedirectory
15426 Tell @value{GDBN} to upload files from the named directory @var{dir}.
15427 The default is @file{/gdb}, i.e.@: the root directory on the current
15430 @item show remotedirectory
15431 @kindex show remotedirectory
15432 Show the current value of the upload directory.
15434 @item set remoteupload @var{method}
15435 @kindex set remoteupload
15436 Set the method used to upload files to remote device. Valid values
15437 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
15438 The default is @samp{newer}.
15440 @item show remoteupload
15441 @kindex show remoteupload
15442 Show the current setting of the upload method.
15444 @item set remoteaddhost
15445 @kindex set remoteaddhost
15446 Tell @value{GDBN} whether to add this host to the remote stub's
15447 arguments when you debug over a network.
15449 @item show remoteaddhost
15450 @kindex show remoteaddhost
15451 Show whether to add this host to remote stub's arguments when
15452 debugging over a network.
15456 @node Architectures
15457 @section Architectures
15459 This section describes characteristics of architectures that affect
15460 all uses of @value{GDBN} with the architecture, both native and cross.
15467 * HPPA:: HP PA architecture
15471 @subsection x86 Architecture-specific issues.
15474 @item set struct-convention @var{mode}
15475 @kindex set struct-convention
15476 @cindex struct return convention
15477 @cindex struct/union returned in registers
15478 Set the convention used by the inferior to return @code{struct}s and
15479 @code{union}s from functions to @var{mode}. Possible values of
15480 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15481 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15482 are returned on the stack, while @code{"reg"} means that a
15483 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15484 be returned in a register.
15486 @item show struct-convention
15487 @kindex show struct-convention
15488 Show the current setting of the convention to return @code{struct}s
15497 @kindex set rstack_high_address
15498 @cindex AMD 29K register stack
15499 @cindex register stack, AMD29K
15500 @item set rstack_high_address @var{address}
15501 On AMD 29000 family processors, registers are saved in a separate
15502 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15503 extent of this stack. Normally, @value{GDBN} just assumes that the
15504 stack is ``large enough''. This may result in @value{GDBN} referencing
15505 memory locations that do not exist. If necessary, you can get around
15506 this problem by specifying the ending address of the register stack with
15507 the @code{set rstack_high_address} command. The argument should be an
15508 address, which you probably want to precede with @samp{0x} to specify in
15511 @kindex show rstack_high_address
15512 @item show rstack_high_address
15513 Display the current limit of the register stack, on AMD 29000 family
15521 See the following section.
15526 @cindex stack on Alpha
15527 @cindex stack on MIPS
15528 @cindex Alpha stack
15530 Alpha- and MIPS-based computers use an unusual stack frame, which
15531 sometimes requires @value{GDBN} to search backward in the object code to
15532 find the beginning of a function.
15534 @cindex response time, MIPS debugging
15535 To improve response time (especially for embedded applications, where
15536 @value{GDBN} may be restricted to a slow serial line for this search)
15537 you may want to limit the size of this search, using one of these
15541 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15542 @item set heuristic-fence-post @var{limit}
15543 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15544 search for the beginning of a function. A value of @var{0} (the
15545 default) means there is no limit. However, except for @var{0}, the
15546 larger the limit the more bytes @code{heuristic-fence-post} must search
15547 and therefore the longer it takes to run. You should only need to use
15548 this command when debugging a stripped executable.
15550 @item show heuristic-fence-post
15551 Display the current limit.
15555 These commands are available @emph{only} when @value{GDBN} is configured
15556 for debugging programs on Alpha or MIPS processors.
15558 Several MIPS-specific commands are available when debugging MIPS
15562 @item set mips saved-gpreg-size @var{size}
15563 @kindex set mips saved-gpreg-size
15564 @cindex MIPS GP register size on stack
15565 Set the size of MIPS general-purpose registers saved on the stack.
15566 The argument @var{size} can be one of the following:
15570 32-bit GP registers
15572 64-bit GP registers
15574 Use the target's default setting or autodetect the saved size from the
15575 information contained in the executable. This is the default
15578 @item show mips saved-gpreg-size
15579 @kindex show mips saved-gpreg-size
15580 Show the current size of MIPS GP registers on the stack.
15582 @item set mips stack-arg-size @var{size}
15583 @kindex set mips stack-arg-size
15584 @cindex MIPS stack space for arguments
15585 Set the amount of stack space reserved for arguments to functions.
15586 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
15589 @item set mips abi @var{arg}
15590 @kindex set mips abi
15591 @cindex set ABI for MIPS
15592 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15593 values of @var{arg} are:
15597 The default ABI associated with the current binary (this is the
15608 @item show mips abi
15609 @kindex show mips abi
15610 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15613 @itemx show mipsfpu
15614 @xref{MIPS Embedded, set mipsfpu}.
15616 @item set mips mask-address @var{arg}
15617 @kindex set mips mask-address
15618 @cindex MIPS addresses, masking
15619 This command determines whether the most-significant 32 bits of 64-bit
15620 MIPS addresses are masked off. The argument @var{arg} can be
15621 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15622 setting, which lets @value{GDBN} determine the correct value.
15624 @item show mips mask-address
15625 @kindex show mips mask-address
15626 Show whether the upper 32 bits of MIPS addresses are masked off or
15629 @item set remote-mips64-transfers-32bit-regs
15630 @kindex set remote-mips64-transfers-32bit-regs
15631 This command controls compatibility with 64-bit MIPS targets that
15632 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15633 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15634 and 64 bits for other registers, set this option to @samp{on}.
15636 @item show remote-mips64-transfers-32bit-regs
15637 @kindex show remote-mips64-transfers-32bit-regs
15638 Show the current setting of compatibility with older MIPS 64 targets.
15640 @item set debug mips
15641 @kindex set debug mips
15642 This command turns on and off debugging messages for the MIPS-specific
15643 target code in @value{GDBN}.
15645 @item show debug mips
15646 @kindex show debug mips
15647 Show the current setting of MIPS debugging messages.
15653 @cindex HPPA support
15655 When @value{GDBN} is debugging the HP PA architecture, it provides the
15656 following special commands:
15659 @item set debug hppa
15660 @kindex set debug hppa
15661 This command determines whether HPPA architecture specific debugging
15662 messages are to be displayed.
15664 @item show debug hppa
15665 Show whether HPPA debugging messages are displayed.
15667 @item maint print unwind @var{address}
15668 @kindex maint print unwind@r{, HPPA}
15669 This command displays the contents of the unwind table entry at the
15670 given @var{address}.
15675 @node Controlling GDB
15676 @chapter Controlling @value{GDBN}
15678 You can alter the way @value{GDBN} interacts with you by using the
15679 @code{set} command. For commands controlling how @value{GDBN} displays
15680 data, see @ref{Print Settings, ,Print settings}. Other settings are
15685 * Editing:: Command editing
15686 * Command History:: Command history
15687 * Screen Size:: Screen size
15688 * Numbers:: Numbers
15689 * ABI:: Configuring the current ABI
15690 * Messages/Warnings:: Optional warnings and messages
15691 * Debugging Output:: Optional messages about internal happenings
15699 @value{GDBN} indicates its readiness to read a command by printing a string
15700 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15701 can change the prompt string with the @code{set prompt} command. For
15702 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15703 the prompt in one of the @value{GDBN} sessions so that you can always tell
15704 which one you are talking to.
15706 @emph{Note:} @code{set prompt} does not add a space for you after the
15707 prompt you set. This allows you to set a prompt which ends in a space
15708 or a prompt that does not.
15712 @item set prompt @var{newprompt}
15713 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15715 @kindex show prompt
15717 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15721 @section Command editing
15723 @cindex command line editing
15725 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15726 @sc{gnu} library provides consistent behavior for programs which provide a
15727 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15728 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15729 substitution, and a storage and recall of command history across
15730 debugging sessions.
15732 You may control the behavior of command line editing in @value{GDBN} with the
15733 command @code{set}.
15736 @kindex set editing
15739 @itemx set editing on
15740 Enable command line editing (enabled by default).
15742 @item set editing off
15743 Disable command line editing.
15745 @kindex show editing
15747 Show whether command line editing is enabled.
15750 @xref{Command Line Editing}, for more details about the Readline
15751 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15752 encouraged to read that chapter.
15754 @node Command History
15755 @section Command history
15756 @cindex command history
15758 @value{GDBN} can keep track of the commands you type during your
15759 debugging sessions, so that you can be certain of precisely what
15760 happened. Use these commands to manage the @value{GDBN} command
15763 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15764 package, to provide the history facility. @xref{Using History
15765 Interactively}, for the detailed description of the History library.
15767 To issue a command to @value{GDBN} without affecting certain aspects of
15768 the state which is seen by users, prefix it with @samp{server }. This
15769 means that this command will not affect the command history, nor will it
15770 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15771 pressed on a line by itself.
15773 @cindex @code{server}, command prefix
15774 The server prefix does not affect the recording of values into the value
15775 history; to print a value without recording it into the value history,
15776 use the @code{output} command instead of the @code{print} command.
15778 Here is the description of @value{GDBN} commands related to command
15782 @cindex history substitution
15783 @cindex history file
15784 @kindex set history filename
15785 @cindex @env{GDBHISTFILE}, environment variable
15786 @item set history filename @var{fname}
15787 Set the name of the @value{GDBN} command history file to @var{fname}.
15788 This is the file where @value{GDBN} reads an initial command history
15789 list, and where it writes the command history from this session when it
15790 exits. You can access this list through history expansion or through
15791 the history command editing characters listed below. This file defaults
15792 to the value of the environment variable @code{GDBHISTFILE}, or to
15793 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15796 @cindex save command history
15797 @kindex set history save
15798 @item set history save
15799 @itemx set history save on
15800 Record command history in a file, whose name may be specified with the
15801 @code{set history filename} command. By default, this option is disabled.
15803 @item set history save off
15804 Stop recording command history in a file.
15806 @cindex history size
15807 @kindex set history size
15808 @cindex @env{HISTSIZE}, environment variable
15809 @item set history size @var{size}
15810 Set the number of commands which @value{GDBN} keeps in its history list.
15811 This defaults to the value of the environment variable
15812 @code{HISTSIZE}, or to 256 if this variable is not set.
15815 History expansion assigns special meaning to the character @kbd{!}.
15816 @xref{Event Designators}, for more details.
15818 @cindex history expansion, turn on/off
15819 Since @kbd{!} is also the logical not operator in C, history expansion
15820 is off by default. If you decide to enable history expansion with the
15821 @code{set history expansion on} command, you may sometimes need to
15822 follow @kbd{!} (when it is used as logical not, in an expression) with
15823 a space or a tab to prevent it from being expanded. The readline
15824 history facilities do not attempt substitution on the strings
15825 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15827 The commands to control history expansion are:
15830 @item set history expansion on
15831 @itemx set history expansion
15832 @kindex set history expansion
15833 Enable history expansion. History expansion is off by default.
15835 @item set history expansion off
15836 Disable history expansion.
15839 @kindex show history
15841 @itemx show history filename
15842 @itemx show history save
15843 @itemx show history size
15844 @itemx show history expansion
15845 These commands display the state of the @value{GDBN} history parameters.
15846 @code{show history} by itself displays all four states.
15851 @kindex show commands
15852 @cindex show last commands
15853 @cindex display command history
15854 @item show commands
15855 Display the last ten commands in the command history.
15857 @item show commands @var{n}
15858 Print ten commands centered on command number @var{n}.
15860 @item show commands +
15861 Print ten commands just after the commands last printed.
15865 @section Screen size
15866 @cindex size of screen
15867 @cindex pauses in output
15869 Certain commands to @value{GDBN} may produce large amounts of
15870 information output to the screen. To help you read all of it,
15871 @value{GDBN} pauses and asks you for input at the end of each page of
15872 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15873 to discard the remaining output. Also, the screen width setting
15874 determines when to wrap lines of output. Depending on what is being
15875 printed, @value{GDBN} tries to break the line at a readable place,
15876 rather than simply letting it overflow onto the following line.
15878 Normally @value{GDBN} knows the size of the screen from the terminal
15879 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15880 together with the value of the @code{TERM} environment variable and the
15881 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15882 you can override it with the @code{set height} and @code{set
15889 @kindex show height
15890 @item set height @var{lpp}
15892 @itemx set width @var{cpl}
15894 These @code{set} commands specify a screen height of @var{lpp} lines and
15895 a screen width of @var{cpl} characters. The associated @code{show}
15896 commands display the current settings.
15898 If you specify a height of zero lines, @value{GDBN} does not pause during
15899 output no matter how long the output is. This is useful if output is to a
15900 file or to an editor buffer.
15902 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15903 from wrapping its output.
15905 @item set pagination on
15906 @itemx set pagination off
15907 @kindex set pagination
15908 Turn the output pagination on or off; the default is on. Turning
15909 pagination off is the alternative to @code{set height 0}.
15911 @item show pagination
15912 @kindex show pagination
15913 Show the current pagination mode.
15918 @cindex number representation
15919 @cindex entering numbers
15921 You can always enter numbers in octal, decimal, or hexadecimal in
15922 @value{GDBN} by the usual conventions: octal numbers begin with
15923 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15924 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15925 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15926 10; likewise, the default display for numbers---when no particular
15927 format is specified---is base 10. You can change the default base for
15928 both input and output with the commands described below.
15931 @kindex set input-radix
15932 @item set input-radix @var{base}
15933 Set the default base for numeric input. Supported choices
15934 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15935 specified either unambiguously or using the current input radix; for
15939 set input-radix 012
15940 set input-radix 10.
15941 set input-radix 0xa
15945 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15946 leaves the input radix unchanged, no matter what it was, since
15947 @samp{10}, being without any leading or trailing signs of its base, is
15948 interpreted in the current radix. Thus, if the current radix is 16,
15949 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15952 @kindex set output-radix
15953 @item set output-radix @var{base}
15954 Set the default base for numeric display. Supported choices
15955 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15956 specified either unambiguously or using the current input radix.
15958 @kindex show input-radix
15959 @item show input-radix
15960 Display the current default base for numeric input.
15962 @kindex show output-radix
15963 @item show output-radix
15964 Display the current default base for numeric display.
15966 @item set radix @r{[}@var{base}@r{]}
15970 These commands set and show the default base for both input and output
15971 of numbers. @code{set radix} sets the radix of input and output to
15972 the same base; without an argument, it resets the radix back to its
15973 default value of 10.
15978 @section Configuring the current ABI
15980 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15981 application automatically. However, sometimes you need to override its
15982 conclusions. Use these commands to manage @value{GDBN}'s view of the
15989 One @value{GDBN} configuration can debug binaries for multiple operating
15990 system targets, either via remote debugging or native emulation.
15991 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15992 but you can override its conclusion using the @code{set osabi} command.
15993 One example where this is useful is in debugging of binaries which use
15994 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15995 not have the same identifying marks that the standard C library for your
16000 Show the OS ABI currently in use.
16003 With no argument, show the list of registered available OS ABI's.
16005 @item set osabi @var{abi}
16006 Set the current OS ABI to @var{abi}.
16009 @cindex float promotion
16011 Generally, the way that an argument of type @code{float} is passed to a
16012 function depends on whether the function is prototyped. For a prototyped
16013 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16014 according to the architecture's convention for @code{float}. For unprototyped
16015 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16016 @code{double} and then passed.
16018 Unfortunately, some forms of debug information do not reliably indicate whether
16019 a function is prototyped. If @value{GDBN} calls a function that is not marked
16020 as prototyped, it consults @kbd{set coerce-float-to-double}.
16023 @kindex set coerce-float-to-double
16024 @item set coerce-float-to-double
16025 @itemx set coerce-float-to-double on
16026 Arguments of type @code{float} will be promoted to @code{double} when passed
16027 to an unprototyped function. This is the default setting.
16029 @item set coerce-float-to-double off
16030 Arguments of type @code{float} will be passed directly to unprototyped
16033 @kindex show coerce-float-to-double
16034 @item show coerce-float-to-double
16035 Show the current setting of promoting @code{float} to @code{double}.
16039 @kindex show cp-abi
16040 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16041 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16042 used to build your application. @value{GDBN} only fully supports
16043 programs with a single C@t{++} ABI; if your program contains code using
16044 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16045 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16046 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16047 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16048 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16049 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16054 Show the C@t{++} ABI currently in use.
16057 With no argument, show the list of supported C@t{++} ABI's.
16059 @item set cp-abi @var{abi}
16060 @itemx set cp-abi auto
16061 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16064 @node Messages/Warnings
16065 @section Optional warnings and messages
16067 @cindex verbose operation
16068 @cindex optional warnings
16069 By default, @value{GDBN} is silent about its inner workings. If you are
16070 running on a slow machine, you may want to use the @code{set verbose}
16071 command. This makes @value{GDBN} tell you when it does a lengthy
16072 internal operation, so you will not think it has crashed.
16074 Currently, the messages controlled by @code{set verbose} are those
16075 which announce that the symbol table for a source file is being read;
16076 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
16079 @kindex set verbose
16080 @item set verbose on
16081 Enables @value{GDBN} output of certain informational messages.
16083 @item set verbose off
16084 Disables @value{GDBN} output of certain informational messages.
16086 @kindex show verbose
16088 Displays whether @code{set verbose} is on or off.
16091 By default, if @value{GDBN} encounters bugs in the symbol table of an
16092 object file, it is silent; but if you are debugging a compiler, you may
16093 find this information useful (@pxref{Symbol Errors, ,Errors reading
16098 @kindex set complaints
16099 @item set complaints @var{limit}
16100 Permits @value{GDBN} to output @var{limit} complaints about each type of
16101 unusual symbols before becoming silent about the problem. Set
16102 @var{limit} to zero to suppress all complaints; set it to a large number
16103 to prevent complaints from being suppressed.
16105 @kindex show complaints
16106 @item show complaints
16107 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16111 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16112 lot of stupid questions to confirm certain commands. For example, if
16113 you try to run a program which is already running:
16117 The program being debugged has been started already.
16118 Start it from the beginning? (y or n)
16121 If you are willing to unflinchingly face the consequences of your own
16122 commands, you can disable this ``feature'':
16126 @kindex set confirm
16128 @cindex confirmation
16129 @cindex stupid questions
16130 @item set confirm off
16131 Disables confirmation requests.
16133 @item set confirm on
16134 Enables confirmation requests (the default).
16136 @kindex show confirm
16138 Displays state of confirmation requests.
16142 @cindex command tracing
16143 If you need to debug user-defined commands or sourced files you may find it
16144 useful to enable @dfn{command tracing}. In this mode each command will be
16145 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16146 quantity denoting the call depth of each command.
16149 @kindex set trace-commands
16150 @cindex command scripts, debugging
16151 @item set trace-commands on
16152 Enable command tracing.
16153 @item set trace-commands off
16154 Disable command tracing.
16155 @item show trace-commands
16156 Display the current state of command tracing.
16159 @node Debugging Output
16160 @section Optional messages about internal happenings
16161 @cindex optional debugging messages
16163 @value{GDBN} has commands that enable optional debugging messages from
16164 various @value{GDBN} subsystems; normally these commands are of
16165 interest to @value{GDBN} maintainers, or when reporting a bug. This
16166 section documents those commands.
16169 @kindex set exec-done-display
16170 @item set exec-done-display
16171 Turns on or off the notification of asynchronous commands'
16172 completion. When on, @value{GDBN} will print a message when an
16173 asynchronous command finishes its execution. The default is off.
16174 @kindex show exec-done-display
16175 @item show exec-done-display
16176 Displays the current setting of asynchronous command completion
16179 @cindex gdbarch debugging info
16180 @cindex architecture debugging info
16181 @item set debug arch
16182 Turns on or off display of gdbarch debugging info. The default is off
16184 @item show debug arch
16185 Displays the current state of displaying gdbarch debugging info.
16186 @item set debug aix-thread
16187 @cindex AIX threads
16188 Display debugging messages about inner workings of the AIX thread
16190 @item show debug aix-thread
16191 Show the current state of AIX thread debugging info display.
16192 @item set debug event
16193 @cindex event debugging info
16194 Turns on or off display of @value{GDBN} event debugging info. The
16196 @item show debug event
16197 Displays the current state of displaying @value{GDBN} event debugging
16199 @item set debug expression
16200 @cindex expression debugging info
16201 Turns on or off display of debugging info about @value{GDBN}
16202 expression parsing. The default is off.
16203 @item show debug expression
16204 Displays the current state of displaying debugging info about
16205 @value{GDBN} expression parsing.
16206 @item set debug frame
16207 @cindex frame debugging info
16208 Turns on or off display of @value{GDBN} frame debugging info. The
16210 @item show debug frame
16211 Displays the current state of displaying @value{GDBN} frame debugging
16213 @item set debug infrun
16214 @cindex inferior debugging info
16215 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16216 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16217 for implementing operations such as single-stepping the inferior.
16218 @item show debug infrun
16219 Displays the current state of @value{GDBN} inferior debugging.
16220 @item set debug lin-lwp
16221 @cindex @sc{gnu}/Linux LWP debug messages
16222 @cindex Linux lightweight processes
16223 Turns on or off debugging messages from the Linux LWP debug support.
16224 @item show debug lin-lwp
16225 Show the current state of Linux LWP debugging messages.
16226 @item set debug observer
16227 @cindex observer debugging info
16228 Turns on or off display of @value{GDBN} observer debugging. This
16229 includes info such as the notification of observable events.
16230 @item show debug observer
16231 Displays the current state of observer debugging.
16232 @item set debug overload
16233 @cindex C@t{++} overload debugging info
16234 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16235 info. This includes info such as ranking of functions, etc. The default
16237 @item show debug overload
16238 Displays the current state of displaying @value{GDBN} C@t{++} overload
16240 @cindex packets, reporting on stdout
16241 @cindex serial connections, debugging
16242 @cindex debug remote protocol
16243 @cindex remote protocol debugging
16244 @cindex display remote packets
16245 @item set debug remote
16246 Turns on or off display of reports on all packets sent back and forth across
16247 the serial line to the remote machine. The info is printed on the
16248 @value{GDBN} standard output stream. The default is off.
16249 @item show debug remote
16250 Displays the state of display of remote packets.
16251 @item set debug serial
16252 Turns on or off display of @value{GDBN} serial debugging info. The
16254 @item show debug serial
16255 Displays the current state of displaying @value{GDBN} serial debugging
16257 @item set debug solib-frv
16258 @cindex FR-V shared-library debugging
16259 Turns on or off debugging messages for FR-V shared-library code.
16260 @item show debug solib-frv
16261 Display the current state of FR-V shared-library code debugging
16263 @item set debug target
16264 @cindex target debugging info
16265 Turns on or off display of @value{GDBN} target debugging info. This info
16266 includes what is going on at the target level of GDB, as it happens. The
16267 default is 0. Set it to 1 to track events, and to 2 to also track the
16268 value of large memory transfers. Changes to this flag do not take effect
16269 until the next time you connect to a target or use the @code{run} command.
16270 @item show debug target
16271 Displays the current state of displaying @value{GDBN} target debugging
16273 @item set debugvarobj
16274 @cindex variable object debugging info
16275 Turns on or off display of @value{GDBN} variable object debugging
16276 info. The default is off.
16277 @item show debugvarobj
16278 Displays the current state of displaying @value{GDBN} variable object
16280 @item set debug xml
16281 @cindex XML parser debugging
16282 Turns on or off debugging messages for built-in XML parsers.
16283 @item show debug xml
16284 Displays the current state of XML debugging messages.
16288 @chapter Canned Sequences of Commands
16290 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16291 command lists}), @value{GDBN} provides two ways to store sequences of
16292 commands for execution as a unit: user-defined commands and command
16296 * Define:: How to define your own commands
16297 * Hooks:: Hooks for user-defined commands
16298 * Command Files:: How to write scripts of commands to be stored in a file
16299 * Output:: Commands for controlled output
16303 @section User-defined commands
16305 @cindex user-defined command
16306 @cindex arguments, to user-defined commands
16307 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16308 which you assign a new name as a command. This is done with the
16309 @code{define} command. User commands may accept up to 10 arguments
16310 separated by whitespace. Arguments are accessed within the user command
16311 via @code{$arg0@dots{}$arg9}. A trivial example:
16315 print $arg0 + $arg1 + $arg2
16320 To execute the command use:
16327 This defines the command @code{adder}, which prints the sum of
16328 its three arguments. Note the arguments are text substitutions, so they may
16329 reference variables, use complex expressions, or even perform inferior
16332 @cindex argument count in user-defined commands
16333 @cindex how many arguments (user-defined commands)
16334 In addition, @code{$argc} may be used to find out how many arguments have
16335 been passed. This expands to a number in the range 0@dots{}10.
16340 print $arg0 + $arg1
16343 print $arg0 + $arg1 + $arg2
16351 @item define @var{commandname}
16352 Define a command named @var{commandname}. If there is already a command
16353 by that name, you are asked to confirm that you want to redefine it.
16355 The definition of the command is made up of other @value{GDBN} command lines,
16356 which are given following the @code{define} command. The end of these
16357 commands is marked by a line containing @code{end}.
16360 @kindex end@r{ (user-defined commands)}
16361 @item document @var{commandname}
16362 Document the user-defined command @var{commandname}, so that it can be
16363 accessed by @code{help}. The command @var{commandname} must already be
16364 defined. This command reads lines of documentation just as @code{define}
16365 reads the lines of the command definition, ending with @code{end}.
16366 After the @code{document} command is finished, @code{help} on command
16367 @var{commandname} displays the documentation you have written.
16369 You may use the @code{document} command again to change the
16370 documentation of a command. Redefining the command with @code{define}
16371 does not change the documentation.
16373 @kindex dont-repeat
16374 @cindex don't repeat command
16376 Used inside a user-defined command, this tells @value{GDBN} that this
16377 command should not be repeated when the user hits @key{RET}
16378 (@pxref{Command Syntax, repeat last command}).
16380 @kindex help user-defined
16381 @item help user-defined
16382 List all user-defined commands, with the first line of the documentation
16387 @itemx show user @var{commandname}
16388 Display the @value{GDBN} commands used to define @var{commandname} (but
16389 not its documentation). If no @var{commandname} is given, display the
16390 definitions for all user-defined commands.
16392 @cindex infinite recursion in user-defined commands
16393 @kindex show max-user-call-depth
16394 @kindex set max-user-call-depth
16395 @item show max-user-call-depth
16396 @itemx set max-user-call-depth
16397 The value of @code{max-user-call-depth} controls how many recursion
16398 levels are allowed in user-defined commands before @value{GDBN} suspects an
16399 infinite recursion and aborts the command.
16402 In addition to the above commands, user-defined commands frequently
16403 use control flow commands, described in @ref{Command Files}.
16405 When user-defined commands are executed, the
16406 commands of the definition are not printed. An error in any command
16407 stops execution of the user-defined command.
16409 If used interactively, commands that would ask for confirmation proceed
16410 without asking when used inside a user-defined command. Many @value{GDBN}
16411 commands that normally print messages to say what they are doing omit the
16412 messages when used in a user-defined command.
16415 @section User-defined command hooks
16416 @cindex command hooks
16417 @cindex hooks, for commands
16418 @cindex hooks, pre-command
16421 You may define @dfn{hooks}, which are a special kind of user-defined
16422 command. Whenever you run the command @samp{foo}, if the user-defined
16423 command @samp{hook-foo} exists, it is executed (with no arguments)
16424 before that command.
16426 @cindex hooks, post-command
16428 A hook may also be defined which is run after the command you executed.
16429 Whenever you run the command @samp{foo}, if the user-defined command
16430 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16431 that command. Post-execution hooks may exist simultaneously with
16432 pre-execution hooks, for the same command.
16434 It is valid for a hook to call the command which it hooks. If this
16435 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16437 @c It would be nice if hookpost could be passed a parameter indicating
16438 @c if the command it hooks executed properly or not. FIXME!
16440 @kindex stop@r{, a pseudo-command}
16441 In addition, a pseudo-command, @samp{stop} exists. Defining
16442 (@samp{hook-stop}) makes the associated commands execute every time
16443 execution stops in your program: before breakpoint commands are run,
16444 displays are printed, or the stack frame is printed.
16446 For example, to ignore @code{SIGALRM} signals while
16447 single-stepping, but treat them normally during normal execution,
16452 handle SIGALRM nopass
16456 handle SIGALRM pass
16459 define hook-continue
16460 handle SIGALRM pass
16464 As a further example, to hook at the beginning and end of the @code{echo}
16465 command, and to add extra text to the beginning and end of the message,
16473 define hookpost-echo
16477 (@value{GDBP}) echo Hello World
16478 <<<---Hello World--->>>
16483 You can define a hook for any single-word command in @value{GDBN}, but
16484 not for command aliases; you should define a hook for the basic command
16485 name, e.g.@: @code{backtrace} rather than @code{bt}.
16486 @c FIXME! So how does Joe User discover whether a command is an alias
16488 If an error occurs during the execution of your hook, execution of
16489 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16490 (before the command that you actually typed had a chance to run).
16492 If you try to define a hook which does not match any known command, you
16493 get a warning from the @code{define} command.
16495 @node Command Files
16496 @section Command files
16498 @cindex command files
16499 @cindex scripting commands
16500 A command file for @value{GDBN} is a text file made of lines that are
16501 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16502 also be included. An empty line in a command file does nothing; it
16503 does not mean to repeat the last command, as it would from the
16506 You can request the execution of a command file with the @code{source}
16511 @cindex execute commands from a file
16512 @item source [@code{-v}] @var{filename}
16513 Execute the command file @var{filename}.
16516 The lines in a command file are generally executed sequentially,
16517 unless the order of execution is changed by one of the
16518 @emph{flow-control commands} described below. The commands are not
16519 printed as they are executed. An error in any command terminates
16520 execution of the command file and control is returned to the console.
16522 @value{GDBN} searches for @var{filename} in the current directory and then
16523 on the search path (specified with the @samp{directory} command).
16525 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16526 each command as it is executed. The option must be given before
16527 @var{filename}, and is interpreted as part of the filename anywhere else.
16529 Commands that would ask for confirmation if used interactively proceed
16530 without asking when used in a command file. Many @value{GDBN} commands that
16531 normally print messages to say what they are doing omit the messages
16532 when called from command files.
16534 @value{GDBN} also accepts command input from standard input. In this
16535 mode, normal output goes to standard output and error output goes to
16536 standard error. Errors in a command file supplied on standard input do
16537 not terminate execution of the command file---execution continues with
16541 gdb < cmds > log 2>&1
16544 (The syntax above will vary depending on the shell used.) This example
16545 will execute commands from the file @file{cmds}. All output and errors
16546 would be directed to @file{log}.
16548 Since commands stored on command files tend to be more general than
16549 commands typed interactively, they frequently need to deal with
16550 complicated situations, such as different or unexpected values of
16551 variables and symbols, changes in how the program being debugged is
16552 built, etc. @value{GDBN} provides a set of flow-control commands to
16553 deal with these complexities. Using these commands, you can write
16554 complex scripts that loop over data structures, execute commands
16555 conditionally, etc.
16562 This command allows to include in your script conditionally executed
16563 commands. The @code{if} command takes a single argument, which is an
16564 expression to evaluate. It is followed by a series of commands that
16565 are executed only if the expression is true (its value is nonzero).
16566 There can then optionally be an @code{else} line, followed by a series
16567 of commands that are only executed if the expression was false. The
16568 end of the list is marked by a line containing @code{end}.
16572 This command allows to write loops. Its syntax is similar to
16573 @code{if}: the command takes a single argument, which is an expression
16574 to evaluate, and must be followed by the commands to execute, one per
16575 line, terminated by an @code{end}. These commands are called the
16576 @dfn{body} of the loop. The commands in the body of @code{while} are
16577 executed repeatedly as long as the expression evaluates to true.
16581 This command exits the @code{while} loop in whose body it is included.
16582 Execution of the script continues after that @code{while}s @code{end}
16585 @kindex loop_continue
16586 @item loop_continue
16587 This command skips the execution of the rest of the body of commands
16588 in the @code{while} loop in whose body it is included. Execution
16589 branches to the beginning of the @code{while} loop, where it evaluates
16590 the controlling expression.
16592 @kindex end@r{ (if/else/while commands)}
16594 Terminate the block of commands that are the body of @code{if},
16595 @code{else}, or @code{while} flow-control commands.
16600 @section Commands for controlled output
16602 During the execution of a command file or a user-defined command, normal
16603 @value{GDBN} output is suppressed; the only output that appears is what is
16604 explicitly printed by the commands in the definition. This section
16605 describes three commands useful for generating exactly the output you
16610 @item echo @var{text}
16611 @c I do not consider backslash-space a standard C escape sequence
16612 @c because it is not in ANSI.
16613 Print @var{text}. Nonprinting characters can be included in
16614 @var{text} using C escape sequences, such as @samp{\n} to print a
16615 newline. @strong{No newline is printed unless you specify one.}
16616 In addition to the standard C escape sequences, a backslash followed
16617 by a space stands for a space. This is useful for displaying a
16618 string with spaces at the beginning or the end, since leading and
16619 trailing spaces are otherwise trimmed from all arguments.
16620 To print @samp{@w{ }and foo =@w{ }}, use the command
16621 @samp{echo \@w{ }and foo = \@w{ }}.
16623 A backslash at the end of @var{text} can be used, as in C, to continue
16624 the command onto subsequent lines. For example,
16627 echo This is some text\n\
16628 which is continued\n\
16629 onto several lines.\n
16632 produces the same output as
16635 echo This is some text\n
16636 echo which is continued\n
16637 echo onto several lines.\n
16641 @item output @var{expression}
16642 Print the value of @var{expression} and nothing but that value: no
16643 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16644 value history either. @xref{Expressions, ,Expressions}, for more information
16647 @item output/@var{fmt} @var{expression}
16648 Print the value of @var{expression} in format @var{fmt}. You can use
16649 the same formats as for @code{print}. @xref{Output Formats,,Output
16650 formats}, for more information.
16653 @item printf @var{string}, @var{expressions}@dots{}
16654 Print the values of the @var{expressions} under the control of
16655 @var{string}. The @var{expressions} are separated by commas and may be
16656 either numbers or pointers. Their values are printed as specified by
16657 @var{string}, exactly as if your program were to execute the C
16659 @c FIXME: the above implies that at least all ANSI C formats are
16660 @c supported, but it isn't true: %E and %G don't work (or so it seems).
16661 @c Either this is a bug, or the manual should document what formats are
16665 printf (@var{string}, @var{expressions}@dots{});
16668 For example, you can print two values in hex like this:
16671 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16674 The only backslash-escape sequences that you can use in the format
16675 string are the simple ones that consist of backslash followed by a
16680 @chapter Command Interpreters
16681 @cindex command interpreters
16683 @value{GDBN} supports multiple command interpreters, and some command
16684 infrastructure to allow users or user interface writers to switch
16685 between interpreters or run commands in other interpreters.
16687 @value{GDBN} currently supports two command interpreters, the console
16688 interpreter (sometimes called the command-line interpreter or @sc{cli})
16689 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16690 describes both of these interfaces in great detail.
16692 By default, @value{GDBN} will start with the console interpreter.
16693 However, the user may choose to start @value{GDBN} with another
16694 interpreter by specifying the @option{-i} or @option{--interpreter}
16695 startup options. Defined interpreters include:
16699 @cindex console interpreter
16700 The traditional console or command-line interpreter. This is the most often
16701 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16702 @value{GDBN} will use this interpreter.
16705 @cindex mi interpreter
16706 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16707 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16708 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16712 @cindex mi2 interpreter
16713 The current @sc{gdb/mi} interface.
16716 @cindex mi1 interpreter
16717 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16721 @cindex invoke another interpreter
16722 The interpreter being used by @value{GDBN} may not be dynamically
16723 switched at runtime. Although possible, this could lead to a very
16724 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16725 enters the command "interpreter-set console" in a console view,
16726 @value{GDBN} would switch to using the console interpreter, rendering
16727 the IDE inoperable!
16729 @kindex interpreter-exec
16730 Although you may only choose a single interpreter at startup, you may execute
16731 commands in any interpreter from the current interpreter using the appropriate
16732 command. If you are running the console interpreter, simply use the
16733 @code{interpreter-exec} command:
16736 interpreter-exec mi "-data-list-register-names"
16739 @sc{gdb/mi} has a similar command, although it is only available in versions of
16740 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16743 @chapter @value{GDBN} Text User Interface
16745 @cindex Text User Interface
16748 * TUI Overview:: TUI overview
16749 * TUI Keys:: TUI key bindings
16750 * TUI Single Key Mode:: TUI single key mode
16751 * TUI Commands:: TUI specific commands
16752 * TUI Configuration:: TUI configuration variables
16755 The @value{GDBN} Text User Interface, TUI in short, is a terminal
16756 interface which uses the @code{curses} library to show the source
16757 file, the assembly output, the program registers and @value{GDBN}
16758 commands in separate text windows.
16760 The TUI is enabled by invoking @value{GDBN} using either
16762 @samp{gdbtui} or @samp{gdb -tui}.
16765 @section TUI overview
16767 The TUI has two display modes that can be switched while
16772 A curses (or TUI) mode in which it displays several text
16773 windows on the terminal.
16776 A standard mode which corresponds to the @value{GDBN} configured without
16780 In the TUI mode, @value{GDBN} can display several text window
16785 This window is the @value{GDBN} command window with the @value{GDBN}
16786 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
16787 managed using readline but through the TUI. The @emph{command}
16788 window is always visible.
16791 The source window shows the source file of the program. The current
16792 line as well as active breakpoints are displayed in this window.
16795 The assembly window shows the disassembly output of the program.
16798 This window shows the processor registers. It detects when
16799 a register is changed and when this is the case, registers that have
16800 changed are highlighted.
16804 The source and assembly windows show the current program position
16805 by highlighting the current line and marking them with the @samp{>} marker.
16806 Breakpoints are also indicated with two markers. A first one
16807 indicates the breakpoint type:
16811 Breakpoint which was hit at least once.
16814 Breakpoint which was never hit.
16817 Hardware breakpoint which was hit at least once.
16820 Hardware breakpoint which was never hit.
16824 The second marker indicates whether the breakpoint is enabled or not:
16828 Breakpoint is enabled.
16831 Breakpoint is disabled.
16835 The source, assembly and register windows are attached to the thread
16836 and the frame position. They are updated when the current thread
16837 changes, when the frame changes or when the program counter changes.
16838 These three windows are arranged by the TUI according to several
16839 layouts. The layout defines which of these three windows are visible.
16840 The following layouts are available:
16850 source and assembly
16853 source and registers
16856 assembly and registers
16860 On top of the command window a status line gives various information
16861 concerning the current process begin debugged. The status line is
16862 updated when the information it shows changes. The following fields
16867 Indicates the current gdb target
16868 (@pxref{Targets, ,Specifying a Debugging Target}).
16871 Gives information about the current process or thread number.
16872 When no process is being debugged, this field is set to @code{No process}.
16875 Gives the current function name for the selected frame.
16876 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16877 When there is no symbol corresponding to the current program counter
16878 the string @code{??} is displayed.
16881 Indicates the current line number for the selected frame.
16882 When the current line number is not known the string @code{??} is displayed.
16885 Indicates the current program counter address.
16890 @section TUI Key Bindings
16891 @cindex TUI key bindings
16893 The TUI installs several key bindings in the readline keymaps
16894 (@pxref{Command Line Editing}).
16895 They allow to leave or enter in the TUI mode or they operate
16896 directly on the TUI layout and windows. The TUI also provides
16897 a @emph{SingleKey} keymap which binds several keys directly to
16898 @value{GDBN} commands. The following key bindings
16899 are installed for both TUI mode and the @value{GDBN} standard mode.
16908 Enter or leave the TUI mode. When the TUI mode is left,
16909 the curses window management is left and @value{GDBN} operates using
16910 its standard mode writing on the terminal directly. When the TUI
16911 mode is entered, the control is given back to the curses windows.
16912 The screen is then refreshed.
16916 Use a TUI layout with only one window. The layout will
16917 either be @samp{source} or @samp{assembly}. When the TUI mode
16918 is not active, it will switch to the TUI mode.
16920 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16924 Use a TUI layout with at least two windows. When the current
16925 layout shows already two windows, a next layout with two windows is used.
16926 When a new layout is chosen, one window will always be common to the
16927 previous layout and the new one.
16929 Think of it as the Emacs @kbd{C-x 2} binding.
16933 Change the active window. The TUI associates several key bindings
16934 (like scrolling and arrow keys) to the active window. This command
16935 gives the focus to the next TUI window.
16937 Think of it as the Emacs @kbd{C-x o} binding.
16941 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16942 (@pxref{TUI Single Key Mode}).
16946 The following key bindings are handled only by the TUI mode:
16951 Scroll the active window one page up.
16955 Scroll the active window one page down.
16959 Scroll the active window one line up.
16963 Scroll the active window one line down.
16967 Scroll the active window one column left.
16971 Scroll the active window one column right.
16975 Refresh the screen.
16979 In the TUI mode, the arrow keys are used by the active window
16980 for scrolling. This means they are available for readline when the
16981 active window is the command window. When the command window
16982 does not have the focus, it is necessary to use other readline
16983 key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b} and @kbd{C-f}.
16985 @node TUI Single Key Mode
16986 @section TUI Single Key Mode
16987 @cindex TUI single key mode
16989 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16990 key binding in the readline keymaps to connect single keys to
16994 @kindex c @r{(SingleKey TUI key)}
16998 @kindex d @r{(SingleKey TUI key)}
17002 @kindex f @r{(SingleKey TUI key)}
17006 @kindex n @r{(SingleKey TUI key)}
17010 @kindex q @r{(SingleKey TUI key)}
17012 exit the @emph{SingleKey} mode.
17014 @kindex r @r{(SingleKey TUI key)}
17018 @kindex s @r{(SingleKey TUI key)}
17022 @kindex u @r{(SingleKey TUI key)}
17026 @kindex v @r{(SingleKey TUI key)}
17030 @kindex w @r{(SingleKey TUI key)}
17036 Other keys temporarily switch to the @value{GDBN} command prompt.
17037 The key that was pressed is inserted in the editing buffer so that
17038 it is possible to type most @value{GDBN} commands without interaction
17039 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
17040 @emph{SingleKey} mode is restored. The only way to permanently leave
17041 this mode is by typing @kbd{q} or @kbd{C-x s}.
17045 @section TUI specific commands
17046 @cindex TUI commands
17048 The TUI has specific commands to control the text windows.
17049 These commands are always available, that is they do not depend on
17050 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
17051 is in the standard mode, using these commands will automatically switch
17057 List and give the size of all displayed windows.
17061 Display the next layout.
17064 Display the previous layout.
17067 Display the source window only.
17070 Display the assembly window only.
17073 Display the source and assembly window.
17076 Display the register window together with the source or assembly window.
17078 @item focus next | prev | src | asm | regs | split
17080 Set the focus to the named window.
17081 This command allows to change the active window so that scrolling keys
17082 can be affected to another window.
17086 Refresh the screen. This is similar to typing @kbd{C-L}.
17088 @item tui reg float
17090 Show the floating point registers in the register window.
17092 @item tui reg general
17093 Show the general registers in the register window.
17096 Show the next register group. The list of register groups as well as
17097 their order is target specific. The predefined register groups are the
17098 following: @code{general}, @code{float}, @code{system}, @code{vector},
17099 @code{all}, @code{save}, @code{restore}.
17101 @item tui reg system
17102 Show the system registers in the register window.
17106 Update the source window and the current execution point.
17108 @item winheight @var{name} +@var{count}
17109 @itemx winheight @var{name} -@var{count}
17111 Change the height of the window @var{name} by @var{count}
17112 lines. Positive counts increase the height, while negative counts
17116 @kindex tabset @var{nchars}
17117 Set the width of tab stops to be @var{nchars} characters.
17121 @node TUI Configuration
17122 @section TUI configuration variables
17123 @cindex TUI configuration variables
17125 The TUI has several configuration variables that control the
17126 appearance of windows on the terminal.
17129 @item set tui border-kind @var{kind}
17130 @kindex set tui border-kind
17131 Select the border appearance for the source, assembly and register windows.
17132 The possible values are the following:
17135 Use a space character to draw the border.
17138 Use ascii characters + - and | to draw the border.
17141 Use the Alternate Character Set to draw the border. The border is
17142 drawn using character line graphics if the terminal supports them.
17146 @item set tui active-border-mode @var{mode}
17147 @kindex set tui active-border-mode
17148 Select the attributes to display the border of the active window.
17149 The possible values are @code{normal}, @code{standout}, @code{reverse},
17150 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
17152 @item set tui border-mode @var{mode}
17153 @kindex set tui border-mode
17154 Select the attributes to display the border of other windows.
17155 The @var{mode} can be one of the following:
17158 Use normal attributes to display the border.
17164 Use reverse video mode.
17167 Use half bright mode.
17169 @item half-standout
17170 Use half bright and standout mode.
17173 Use extra bright or bold mode.
17175 @item bold-standout
17176 Use extra bright or bold and standout mode.
17183 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17186 @cindex @sc{gnu} Emacs
17187 A special interface allows you to use @sc{gnu} Emacs to view (and
17188 edit) the source files for the program you are debugging with
17191 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17192 executable file you want to debug as an argument. This command starts
17193 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17194 created Emacs buffer.
17195 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17197 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
17202 All ``terminal'' input and output goes through the Emacs buffer.
17205 This applies both to @value{GDBN} commands and their output, and to the input
17206 and output done by the program you are debugging.
17208 This is useful because it means that you can copy the text of previous
17209 commands and input them again; you can even use parts of the output
17212 All the facilities of Emacs' Shell mode are available for interacting
17213 with your program. In particular, you can send signals the usual
17214 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17219 @value{GDBN} displays source code through Emacs.
17222 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17223 source file for that frame and puts an arrow (@samp{=>}) at the
17224 left margin of the current line. Emacs uses a separate buffer for
17225 source display, and splits the screen to show both your @value{GDBN} session
17228 Explicit @value{GDBN} @code{list} or search commands still produce output as
17229 usual, but you probably have no reason to use them from Emacs.
17231 If you specify an absolute file name when prompted for the @kbd{M-x
17232 gdb} argument, then Emacs sets your current working directory to where
17233 your program resides. If you only specify the file name, then Emacs
17234 sets your current working directory to to the directory associated
17235 with the previous buffer. In this case, @value{GDBN} may find your
17236 program by searching your environment's @code{PATH} variable, but on
17237 some operating systems it might not find the source. So, although the
17238 @value{GDBN} input and output session proceeds normally, the auxiliary
17239 buffer does not display the current source and line of execution.
17241 The initial working directory of @value{GDBN} is printed on the top
17242 line of the @value{GDBN} I/O buffer and this serves as a default for
17243 the commands that specify files for @value{GDBN} to operate
17244 on. @xref{Files, ,Commands to specify files}.
17246 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17247 need to call @value{GDBN} by a different name (for example, if you
17248 keep several configurations around, with different names) you can
17249 customize the Emacs variable @code{gud-gdb-command-name} to run the
17252 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
17253 addition to the standard Shell mode commands:
17257 Describe the features of Emacs' @value{GDBN} Mode.
17260 Execute to another source line, like the @value{GDBN} @code{step} command; also
17261 update the display window to show the current file and location.
17264 Execute to next source line in this function, skipping all function
17265 calls, like the @value{GDBN} @code{next} command. Then update the display window
17266 to show the current file and location.
17269 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17270 display window accordingly.
17273 Execute until exit from the selected stack frame, like the @value{GDBN}
17274 @code{finish} command.
17277 Continue execution of your program, like the @value{GDBN} @code{continue}
17281 Go up the number of frames indicated by the numeric argument
17282 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17283 like the @value{GDBN} @code{up} command.
17286 Go down the number of frames indicated by the numeric argument, like the
17287 @value{GDBN} @code{down} command.
17290 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17291 tells @value{GDBN} to set a breakpoint on the source line point is on.
17293 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
17294 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
17295 point to any frame in the stack and type @key{RET} to make it become the
17296 current frame and display the associated source in the source buffer.
17297 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
17300 If you accidentally delete the source-display buffer, an easy way to get
17301 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17302 request a frame display; when you run under Emacs, this recreates
17303 the source buffer if necessary to show you the context of the current
17306 The source files displayed in Emacs are in ordinary Emacs buffers
17307 which are visiting the source files in the usual way. You can edit
17308 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17309 communicates with Emacs in terms of line numbers. If you add or
17310 delete lines from the text, the line numbers that @value{GDBN} knows cease
17311 to correspond properly with the code.
17313 The description given here is for GNU Emacs version 21.3 and a more
17314 detailed description of its interaction with @value{GDBN} is given in
17315 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
17317 @c The following dropped because Epoch is nonstandard. Reactivate
17318 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17320 @kindex Emacs Epoch environment
17324 Version 18 of @sc{gnu} Emacs has a built-in window system
17325 called the @code{epoch}
17326 environment. Users of this environment can use a new command,
17327 @code{inspect} which performs identically to @code{print} except that
17328 each value is printed in its own window.
17333 @chapter The @sc{gdb/mi} Interface
17335 @unnumberedsec Function and Purpose
17337 @cindex @sc{gdb/mi}, its purpose
17338 @sc{gdb/mi} is a line based machine oriented text interface to
17339 @value{GDBN} and is activated by specifying using the
17340 @option{--interpreter} command line option (@pxref{Mode Options}). It
17341 is specifically intended to support the development of systems which
17342 use the debugger as just one small component of a larger system.
17344 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17345 in the form of a reference manual.
17347 Note that @sc{gdb/mi} is still under construction, so some of the
17348 features described below are incomplete and subject to change
17349 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17351 @unnumberedsec Notation and Terminology
17353 @cindex notational conventions, for @sc{gdb/mi}
17354 This chapter uses the following notation:
17358 @code{|} separates two alternatives.
17361 @code{[ @var{something} ]} indicates that @var{something} is optional:
17362 it may or may not be given.
17365 @code{( @var{group} )*} means that @var{group} inside the parentheses
17366 may repeat zero or more times.
17369 @code{( @var{group} )+} means that @var{group} inside the parentheses
17370 may repeat one or more times.
17373 @code{"@var{string}"} means a literal @var{string}.
17377 @heading Dependencies
17381 * GDB/MI Command Syntax::
17382 * GDB/MI Compatibility with CLI::
17383 * GDB/MI Development and Front Ends::
17384 * GDB/MI Output Records::
17385 * GDB/MI Simple Examples::
17386 * GDB/MI Command Description Format::
17387 * GDB/MI Breakpoint Commands::
17388 * GDB/MI Program Context::
17389 * GDB/MI Thread Commands::
17390 * GDB/MI Program Execution::
17391 * GDB/MI Stack Manipulation::
17392 * GDB/MI Variable Objects::
17393 * GDB/MI Data Manipulation::
17394 * GDB/MI Tracepoint Commands::
17395 * GDB/MI Symbol Query::
17396 * GDB/MI File Commands::
17398 * GDB/MI Kod Commands::
17399 * GDB/MI Memory Overlay Commands::
17400 * GDB/MI Signal Handling Commands::
17402 * GDB/MI Target Manipulation::
17403 * GDB/MI Miscellaneous Commands::
17406 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17407 @node GDB/MI Command Syntax
17408 @section @sc{gdb/mi} Command Syntax
17411 * GDB/MI Input Syntax::
17412 * GDB/MI Output Syntax::
17415 @node GDB/MI Input Syntax
17416 @subsection @sc{gdb/mi} Input Syntax
17418 @cindex input syntax for @sc{gdb/mi}
17419 @cindex @sc{gdb/mi}, input syntax
17421 @item @var{command} @expansion{}
17422 @code{@var{cli-command} | @var{mi-command}}
17424 @item @var{cli-command} @expansion{}
17425 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17426 @var{cli-command} is any existing @value{GDBN} CLI command.
17428 @item @var{mi-command} @expansion{}
17429 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17430 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17432 @item @var{token} @expansion{}
17433 "any sequence of digits"
17435 @item @var{option} @expansion{}
17436 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17438 @item @var{parameter} @expansion{}
17439 @code{@var{non-blank-sequence} | @var{c-string}}
17441 @item @var{operation} @expansion{}
17442 @emph{any of the operations described in this chapter}
17444 @item @var{non-blank-sequence} @expansion{}
17445 @emph{anything, provided it doesn't contain special characters such as
17446 "-", @var{nl}, """ and of course " "}
17448 @item @var{c-string} @expansion{}
17449 @code{""" @var{seven-bit-iso-c-string-content} """}
17451 @item @var{nl} @expansion{}
17460 The CLI commands are still handled by the @sc{mi} interpreter; their
17461 output is described below.
17464 The @code{@var{token}}, when present, is passed back when the command
17468 Some @sc{mi} commands accept optional arguments as part of the parameter
17469 list. Each option is identified by a leading @samp{-} (dash) and may be
17470 followed by an optional argument parameter. Options occur first in the
17471 parameter list and can be delimited from normal parameters using
17472 @samp{--} (this is useful when some parameters begin with a dash).
17479 We want easy access to the existing CLI syntax (for debugging).
17482 We want it to be easy to spot a @sc{mi} operation.
17485 @node GDB/MI Output Syntax
17486 @subsection @sc{gdb/mi} Output Syntax
17488 @cindex output syntax of @sc{gdb/mi}
17489 @cindex @sc{gdb/mi}, output syntax
17490 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17491 followed, optionally, by a single result record. This result record
17492 is for the most recent command. The sequence of output records is
17493 terminated by @samp{(gdb)}.
17495 If an input command was prefixed with a @code{@var{token}} then the
17496 corresponding output for that command will also be prefixed by that same
17500 @item @var{output} @expansion{}
17501 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17503 @item @var{result-record} @expansion{}
17504 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17506 @item @var{out-of-band-record} @expansion{}
17507 @code{@var{async-record} | @var{stream-record}}
17509 @item @var{async-record} @expansion{}
17510 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17512 @item @var{exec-async-output} @expansion{}
17513 @code{[ @var{token} ] "*" @var{async-output}}
17515 @item @var{status-async-output} @expansion{}
17516 @code{[ @var{token} ] "+" @var{async-output}}
17518 @item @var{notify-async-output} @expansion{}
17519 @code{[ @var{token} ] "=" @var{async-output}}
17521 @item @var{async-output} @expansion{}
17522 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17524 @item @var{result-class} @expansion{}
17525 @code{"done" | "running" | "connected" | "error" | "exit"}
17527 @item @var{async-class} @expansion{}
17528 @code{"stopped" | @var{others}} (where @var{others} will be added
17529 depending on the needs---this is still in development).
17531 @item @var{result} @expansion{}
17532 @code{ @var{variable} "=" @var{value}}
17534 @item @var{variable} @expansion{}
17535 @code{ @var{string} }
17537 @item @var{value} @expansion{}
17538 @code{ @var{const} | @var{tuple} | @var{list} }
17540 @item @var{const} @expansion{}
17541 @code{@var{c-string}}
17543 @item @var{tuple} @expansion{}
17544 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17546 @item @var{list} @expansion{}
17547 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17548 @var{result} ( "," @var{result} )* "]" }
17550 @item @var{stream-record} @expansion{}
17551 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17553 @item @var{console-stream-output} @expansion{}
17554 @code{"~" @var{c-string}}
17556 @item @var{target-stream-output} @expansion{}
17557 @code{"@@" @var{c-string}}
17559 @item @var{log-stream-output} @expansion{}
17560 @code{"&" @var{c-string}}
17562 @item @var{nl} @expansion{}
17565 @item @var{token} @expansion{}
17566 @emph{any sequence of digits}.
17574 All output sequences end in a single line containing a period.
17577 The @code{@var{token}} is from the corresponding request. If an execution
17578 command is interrupted by the @samp{-exec-interrupt} command, the
17579 @var{token} associated with the @samp{*stopped} message is the one of the
17580 original execution command, not the one of the interrupt command.
17583 @cindex status output in @sc{gdb/mi}
17584 @var{status-async-output} contains on-going status information about the
17585 progress of a slow operation. It can be discarded. All status output is
17586 prefixed by @samp{+}.
17589 @cindex async output in @sc{gdb/mi}
17590 @var{exec-async-output} contains asynchronous state change on the target
17591 (stopped, started, disappeared). All async output is prefixed by
17595 @cindex notify output in @sc{gdb/mi}
17596 @var{notify-async-output} contains supplementary information that the
17597 client should handle (e.g., a new breakpoint information). All notify
17598 output is prefixed by @samp{=}.
17601 @cindex console output in @sc{gdb/mi}
17602 @var{console-stream-output} is output that should be displayed as is in the
17603 console. It is the textual response to a CLI command. All the console
17604 output is prefixed by @samp{~}.
17607 @cindex target output in @sc{gdb/mi}
17608 @var{target-stream-output} is the output produced by the target program.
17609 All the target output is prefixed by @samp{@@}.
17612 @cindex log output in @sc{gdb/mi}
17613 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17614 instance messages that should be displayed as part of an error log. All
17615 the log output is prefixed by @samp{&}.
17618 @cindex list output in @sc{gdb/mi}
17619 New @sc{gdb/mi} commands should only output @var{lists} containing
17625 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17626 details about the various output records.
17628 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17629 @node GDB/MI Compatibility with CLI
17630 @section @sc{gdb/mi} Compatibility with CLI
17632 @cindex compatibility, @sc{gdb/mi} and CLI
17633 @cindex @sc{gdb/mi}, compatibility with CLI
17635 For the developers convenience CLI commands can be entered directly,
17636 but there may be some unexpected behaviour. For example, commands
17637 that query the user will behave as if the user replied yes, breakpoint
17638 command lists are not executed and some CLI commands, such as
17639 @code{if}, @code{when} and @code{define}, prompt for further input with
17640 @samp{>}, which is not valid MI output.
17642 This feature may be removed at some stage in the future and it is
17643 recommended that front ends use the @code{-interpreter-exec} command
17644 (@pxref{-interpreter-exec}).
17646 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17647 @node GDB/MI Development and Front Ends
17648 @section @sc{gdb/mi} Development and Front Ends
17649 @cindex @sc{gdb/mi} development
17651 The application which takes the MI output and presents the state of the
17652 program being debugged to the user is called a @dfn{front end}.
17654 Although @sc{gdb/mi} is still incomplete, it is currently being used
17655 by a variety of front ends to @value{GDBN}. This makes it difficult
17656 to introduce new functionality without breaking existing usage. This
17657 section tries to minimize the problems by describing how the protocol
17660 Some changes in MI need not break a carefully designed front end, and
17661 for these the MI version will remain unchanged. The following is a
17662 list of changes that may occur within one level, so front ends should
17663 parse MI output in a way that can handle them:
17667 New MI commands may be added.
17670 New fields may be added to the output of any MI command.
17673 The range of values for fields with specified values, e.g.,
17674 @code{in_scope} (@pxref{-var-update}) may be extended.
17676 @c The format of field's content e.g type prefix, may change so parse it
17677 @c at your own risk. Yes, in general?
17679 @c The order of fields may change? Shouldn't really matter but it might
17680 @c resolve inconsistencies.
17683 If the changes are likely to break front ends, the MI version level
17684 will be increased by one. This will allow the front end to parse the
17685 output according to the MI version. Apart from mi0, new versions of
17686 @value{GDBN} will not support old versions of MI and it will be the
17687 responsibility of the front end to work with the new one.
17689 @c Starting with mi3, add a new command -mi-version that prints the MI
17692 The best way to avoid unexpected changes in MI that might break your front
17693 end is to make your project known to @value{GDBN} developers and
17694 follow development on @email{gdb@@sourceware.org} and
17695 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17696 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17697 Group, which has the aim of creating a more general MI protocol
17698 called Debugger Machine Interface (DMI) that will become a standard
17699 for all debuggers, not just @value{GDBN}.
17700 @cindex mailing lists
17702 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17703 @node GDB/MI Output Records
17704 @section @sc{gdb/mi} Output Records
17707 * GDB/MI Result Records::
17708 * GDB/MI Stream Records::
17709 * GDB/MI Out-of-band Records::
17712 @node GDB/MI Result Records
17713 @subsection @sc{gdb/mi} Result Records
17715 @cindex result records in @sc{gdb/mi}
17716 @cindex @sc{gdb/mi}, result records
17717 In addition to a number of out-of-band notifications, the response to a
17718 @sc{gdb/mi} command includes one of the following result indications:
17722 @item "^done" [ "," @var{results} ]
17723 The synchronous operation was successful, @code{@var{results}} are the return
17728 @c Is this one correct? Should it be an out-of-band notification?
17729 The asynchronous operation was successfully started. The target is
17734 @value{GDBN} has connected to a remote target.
17736 @item "^error" "," @var{c-string}
17738 The operation failed. The @code{@var{c-string}} contains the corresponding
17743 @value{GDBN} has terminated.
17747 @node GDB/MI Stream Records
17748 @subsection @sc{gdb/mi} Stream Records
17750 @cindex @sc{gdb/mi}, stream records
17751 @cindex stream records in @sc{gdb/mi}
17752 @value{GDBN} internally maintains a number of output streams: the console, the
17753 target, and the log. The output intended for each of these streams is
17754 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17756 Each stream record begins with a unique @dfn{prefix character} which
17757 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17758 Syntax}). In addition to the prefix, each stream record contains a
17759 @code{@var{string-output}}. This is either raw text (with an implicit new
17760 line) or a quoted C string (which does not contain an implicit newline).
17763 @item "~" @var{string-output}
17764 The console output stream contains text that should be displayed in the
17765 CLI console window. It contains the textual responses to CLI commands.
17767 @item "@@" @var{string-output}
17768 The target output stream contains any textual output from the running
17769 target. This is only present when GDB's event loop is truly
17770 asynchronous, which is currently only the case for remote targets.
17772 @item "&" @var{string-output}
17773 The log stream contains debugging messages being produced by @value{GDBN}'s
17777 @node GDB/MI Out-of-band Records
17778 @subsection @sc{gdb/mi} Out-of-band Records
17780 @cindex out-of-band records in @sc{gdb/mi}
17781 @cindex @sc{gdb/mi}, out-of-band records
17782 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17783 additional changes that have occurred. Those changes can either be a
17784 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17785 target activity (e.g., target stopped).
17787 The following is a preliminary list of possible out-of-band records.
17788 In particular, the @var{exec-async-output} records.
17791 @item *stopped,reason="@var{reason}"
17794 @var{reason} can be one of the following:
17797 @item breakpoint-hit
17798 A breakpoint was reached.
17799 @item watchpoint-trigger
17800 A watchpoint was triggered.
17801 @item read-watchpoint-trigger
17802 A read watchpoint was triggered.
17803 @item access-watchpoint-trigger
17804 An access watchpoint was triggered.
17805 @item function-finished
17806 An -exec-finish or similar CLI command was accomplished.
17807 @item location-reached
17808 An -exec-until or similar CLI command was accomplished.
17809 @item watchpoint-scope
17810 A watchpoint has gone out of scope.
17811 @item end-stepping-range
17812 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17813 similar CLI command was accomplished.
17814 @item exited-signalled
17815 The inferior exited because of a signal.
17817 The inferior exited.
17818 @item exited-normally
17819 The inferior exited normally.
17820 @item signal-received
17821 A signal was received by the inferior.
17825 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17826 @node GDB/MI Simple Examples
17827 @section Simple Examples of @sc{gdb/mi} Interaction
17828 @cindex @sc{gdb/mi}, simple examples
17830 This subsection presents several simple examples of interaction using
17831 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17832 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17833 the output received from @sc{gdb/mi}.
17835 Note the line breaks shown in the examples are here only for
17836 readability, they don't appear in the real output.
17838 @subheading Setting a breakpoint
17840 Setting a breakpoint generates synchronous output which contains detailed
17841 information of the breakpoint.
17844 -> -break-insert main
17845 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17846 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17847 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17851 @subheading Program Execution
17853 Program execution generates asynchronous records and MI gives the
17854 reason that execution stopped.
17860 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17861 frame=@{addr="0x08048564",func="main",
17862 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17863 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17868 <- *stopped,reason="exited-normally"
17872 @subheading Quitting @value{GDBN}
17874 Quitting @value{GDBN} just prints the result class @samp{^exit}.
17882 @subheading A Bad Command
17884 Here's what happens if you pass a non-existent command:
17888 <- ^error,msg="Undefined MI command: rubbish"
17893 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17894 @node GDB/MI Command Description Format
17895 @section @sc{gdb/mi} Command Description Format
17897 The remaining sections describe blocks of commands. Each block of
17898 commands is laid out in a fashion similar to this section.
17900 @subheading Motivation
17902 The motivation for this collection of commands.
17904 @subheading Introduction
17906 A brief introduction to this collection of commands as a whole.
17908 @subheading Commands
17910 For each command in the block, the following is described:
17912 @subsubheading Synopsis
17915 -command @var{args}@dots{}
17918 @subsubheading Result
17920 @subsubheading @value{GDBN} Command
17922 The corresponding @value{GDBN} CLI command(s), if any.
17924 @subsubheading Example
17926 Example(s) formatted for readability. Some of the described commands have
17927 not been implemented yet and these are labeled N.A.@: (not available).
17930 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17931 @node GDB/MI Breakpoint Commands
17932 @section @sc{gdb/mi} Breakpoint Commands
17934 @cindex breakpoint commands for @sc{gdb/mi}
17935 @cindex @sc{gdb/mi}, breakpoint commands
17936 This section documents @sc{gdb/mi} commands for manipulating
17939 @subheading The @code{-break-after} Command
17940 @findex -break-after
17942 @subsubheading Synopsis
17945 -break-after @var{number} @var{count}
17948 The breakpoint number @var{number} is not in effect until it has been
17949 hit @var{count} times. To see how this is reflected in the output of
17950 the @samp{-break-list} command, see the description of the
17951 @samp{-break-list} command below.
17953 @subsubheading @value{GDBN} Command
17955 The corresponding @value{GDBN} command is @samp{ignore}.
17957 @subsubheading Example
17962 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17963 fullname="/home/foo/hello.c",line="5",times="0"@}
17970 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17971 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17972 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17973 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17974 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17975 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17976 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17977 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17978 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17979 line="5",times="0",ignore="3"@}]@}
17984 @subheading The @code{-break-catch} Command
17985 @findex -break-catch
17987 @subheading The @code{-break-commands} Command
17988 @findex -break-commands
17992 @subheading The @code{-break-condition} Command
17993 @findex -break-condition
17995 @subsubheading Synopsis
17998 -break-condition @var{number} @var{expr}
18001 Breakpoint @var{number} will stop the program only if the condition in
18002 @var{expr} is true. The condition becomes part of the
18003 @samp{-break-list} output (see the description of the @samp{-break-list}
18006 @subsubheading @value{GDBN} Command
18008 The corresponding @value{GDBN} command is @samp{condition}.
18010 @subsubheading Example
18014 -break-condition 1 1
18018 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18019 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18020 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18021 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18022 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18023 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18024 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18025 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18026 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18027 line="5",cond="1",times="0",ignore="3"@}]@}
18031 @subheading The @code{-break-delete} Command
18032 @findex -break-delete
18034 @subsubheading Synopsis
18037 -break-delete ( @var{breakpoint} )+
18040 Delete the breakpoint(s) whose number(s) are specified in the argument
18041 list. This is obviously reflected in the breakpoint list.
18043 @subsubheading @value{GDBN} command
18045 The corresponding @value{GDBN} command is @samp{delete}.
18047 @subsubheading Example
18055 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18056 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18057 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18058 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18059 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18060 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18061 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18066 @subheading The @code{-break-disable} Command
18067 @findex -break-disable
18069 @subsubheading Synopsis
18072 -break-disable ( @var{breakpoint} )+
18075 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18076 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18078 @subsubheading @value{GDBN} Command
18080 The corresponding @value{GDBN} command is @samp{disable}.
18082 @subsubheading Example
18090 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18091 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18092 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18093 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18094 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18095 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18096 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18097 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18098 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18099 line="5",times="0"@}]@}
18103 @subheading The @code{-break-enable} Command
18104 @findex -break-enable
18106 @subsubheading Synopsis
18109 -break-enable ( @var{breakpoint} )+
18112 Enable (previously disabled) @var{breakpoint}(s).
18114 @subsubheading @value{GDBN} Command
18116 The corresponding @value{GDBN} command is @samp{enable}.
18118 @subsubheading Example
18126 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18127 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18128 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18129 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18130 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18131 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18132 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18133 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18134 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18135 line="5",times="0"@}]@}
18139 @subheading The @code{-break-info} Command
18140 @findex -break-info
18142 @subsubheading Synopsis
18145 -break-info @var{breakpoint}
18149 Get information about a single breakpoint.
18151 @subsubheading @value{GDBN} command
18153 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18155 @subsubheading Example
18158 @subheading The @code{-break-insert} Command
18159 @findex -break-insert
18161 @subsubheading Synopsis
18164 -break-insert [ -t ] [ -h ] [ -r ]
18165 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18166 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
18170 If specified, @var{line}, can be one of:
18177 @item filename:linenum
18178 @item filename:function
18182 The possible optional parameters of this command are:
18186 Insert a temporary breakpoint.
18188 Insert a hardware breakpoint.
18189 @item -c @var{condition}
18190 Make the breakpoint conditional on @var{condition}.
18191 @item -i @var{ignore-count}
18192 Initialize the @var{ignore-count}.
18194 Insert a regular breakpoint in all the functions whose names match the
18195 given regular expression. Other flags are not applicable to regular
18199 @subsubheading Result
18201 The result is in the form:
18204 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18205 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18206 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18207 times="@var{times}"@}
18211 where @var{number} is the @value{GDBN} number for this breakpoint,
18212 @var{funcname} is the name of the function where the breakpoint was
18213 inserted, @var{filename} is the name of the source file which contains
18214 this function, @var{lineno} is the source line number within that file
18215 and @var{times} the number of times that the breakpoint has been hit
18216 (always 0 for -break-insert but may be greater for -break-info or -break-list
18217 which use the same output).
18219 Note: this format is open to change.
18220 @c An out-of-band breakpoint instead of part of the result?
18222 @subsubheading @value{GDBN} Command
18224 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18225 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18227 @subsubheading Example
18232 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18233 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18235 -break-insert -t foo
18236 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18237 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18240 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18241 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18242 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18243 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18244 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18245 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18246 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18247 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18248 addr="0x0001072c", func="main",file="recursive2.c",
18249 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18250 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18251 addr="0x00010774",func="foo",file="recursive2.c",
18252 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18254 -break-insert -r foo.*
18255 ~int foo(int, int);
18256 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18257 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18261 @subheading The @code{-break-list} Command
18262 @findex -break-list
18264 @subsubheading Synopsis
18270 Displays the list of inserted breakpoints, showing the following fields:
18274 number of the breakpoint
18276 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18278 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18281 is the breakpoint enabled or no: @samp{y} or @samp{n}
18283 memory location at which the breakpoint is set
18285 logical location of the breakpoint, expressed by function name, file
18288 number of times the breakpoint has been hit
18291 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18292 @code{body} field is an empty list.
18294 @subsubheading @value{GDBN} Command
18296 The corresponding @value{GDBN} command is @samp{info break}.
18298 @subsubheading Example
18303 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18304 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18305 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18306 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18307 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18308 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18309 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18310 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18311 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18312 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18313 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18314 line="13",times="0"@}]@}
18318 Here's an example of the result when there are no breakpoints:
18323 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18324 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18325 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18326 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18327 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18328 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18329 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18334 @subheading The @code{-break-watch} Command
18335 @findex -break-watch
18337 @subsubheading Synopsis
18340 -break-watch [ -a | -r ]
18343 Create a watchpoint. With the @samp{-a} option it will create an
18344 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18345 read from or on a write to the memory location. With the @samp{-r}
18346 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18347 trigger only when the memory location is accessed for reading. Without
18348 either of the options, the watchpoint created is a regular watchpoint,
18349 i.e., it will trigger when the memory location is accessed for writing.
18350 @xref{Set Watchpoints, , Setting watchpoints}.
18352 Note that @samp{-break-list} will report a single list of watchpoints and
18353 breakpoints inserted.
18355 @subsubheading @value{GDBN} Command
18357 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18360 @subsubheading Example
18362 Setting a watchpoint on a variable in the @code{main} function:
18367 ^done,wpt=@{number="2",exp="x"@}
18372 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18373 value=@{old="-268439212",new="55"@},
18374 frame=@{func="main",args=[],file="recursive2.c",
18375 fullname="/home/foo/bar/recursive2.c",line="5"@}
18379 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18380 the program execution twice: first for the variable changing value, then
18381 for the watchpoint going out of scope.
18386 ^done,wpt=@{number="5",exp="C"@}
18391 *stopped,reason="watchpoint-trigger",
18392 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18393 frame=@{func="callee4",args=[],
18394 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18395 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18400 *stopped,reason="watchpoint-scope",wpnum="5",
18401 frame=@{func="callee3",args=[@{name="strarg",
18402 value="0x11940 \"A string argument.\""@}],
18403 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18404 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18408 Listing breakpoints and watchpoints, at different points in the program
18409 execution. Note that once the watchpoint goes out of scope, it is
18415 ^done,wpt=@{number="2",exp="C"@}
18418 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18419 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18420 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18421 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18422 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18423 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18424 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18425 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18426 addr="0x00010734",func="callee4",
18427 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18428 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18429 bkpt=@{number="2",type="watchpoint",disp="keep",
18430 enabled="y",addr="",what="C",times="0"@}]@}
18435 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18436 value=@{old="-276895068",new="3"@},
18437 frame=@{func="callee4",args=[],
18438 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18439 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18442 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18443 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18444 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18445 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18446 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18447 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18448 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18449 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18450 addr="0x00010734",func="callee4",
18451 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18452 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18453 bkpt=@{number="2",type="watchpoint",disp="keep",
18454 enabled="y",addr="",what="C",times="-5"@}]@}
18458 ^done,reason="watchpoint-scope",wpnum="2",
18459 frame=@{func="callee3",args=[@{name="strarg",
18460 value="0x11940 \"A string argument.\""@}],
18461 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18462 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18465 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18466 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18467 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18468 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18469 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18470 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18471 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18472 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18473 addr="0x00010734",func="callee4",
18474 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18475 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18480 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18481 @node GDB/MI Program Context
18482 @section @sc{gdb/mi} Program Context
18484 @subheading The @code{-exec-arguments} Command
18485 @findex -exec-arguments
18488 @subsubheading Synopsis
18491 -exec-arguments @var{args}
18494 Set the inferior program arguments, to be used in the next
18497 @subsubheading @value{GDBN} Command
18499 The corresponding @value{GDBN} command is @samp{set args}.
18501 @subsubheading Example
18504 Don't have one around.
18507 @subheading The @code{-exec-show-arguments} Command
18508 @findex -exec-show-arguments
18510 @subsubheading Synopsis
18513 -exec-show-arguments
18516 Print the arguments of the program.
18518 @subsubheading @value{GDBN} Command
18520 The corresponding @value{GDBN} command is @samp{show args}.
18522 @subsubheading Example
18526 @subheading The @code{-environment-cd} Command
18527 @findex -environment-cd
18529 @subsubheading Synopsis
18532 -environment-cd @var{pathdir}
18535 Set @value{GDBN}'s working directory.
18537 @subsubheading @value{GDBN} Command
18539 The corresponding @value{GDBN} command is @samp{cd}.
18541 @subsubheading Example
18545 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18551 @subheading The @code{-environment-directory} Command
18552 @findex -environment-directory
18554 @subsubheading Synopsis
18557 -environment-directory [ -r ] [ @var{pathdir} ]+
18560 Add directories @var{pathdir} to beginning of search path for source files.
18561 If the @samp{-r} option is used, the search path is reset to the default
18562 search path. If directories @var{pathdir} are supplied in addition to the
18563 @samp{-r} option, the search path is first reset and then addition
18565 Multiple directories may be specified, separated by blanks. Specifying
18566 multiple directories in a single command
18567 results in the directories added to the beginning of the
18568 search path in the same order they were presented in the command.
18569 If blanks are needed as
18570 part of a directory name, double-quotes should be used around
18571 the name. In the command output, the path will show up separated
18572 by the system directory-separator character. The directory-separator
18573 character must not be used
18574 in any directory name.
18575 If no directories are specified, the current search path is displayed.
18577 @subsubheading @value{GDBN} Command
18579 The corresponding @value{GDBN} command is @samp{dir}.
18581 @subsubheading Example
18585 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18586 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18588 -environment-directory ""
18589 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18591 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18592 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18594 -environment-directory -r
18595 ^done,source-path="$cdir:$cwd"
18600 @subheading The @code{-environment-path} Command
18601 @findex -environment-path
18603 @subsubheading Synopsis
18606 -environment-path [ -r ] [ @var{pathdir} ]+
18609 Add directories @var{pathdir} to beginning of search path for object files.
18610 If the @samp{-r} option is used, the search path is reset to the original
18611 search path that existed at gdb start-up. If directories @var{pathdir} are
18612 supplied in addition to the
18613 @samp{-r} option, the search path is first reset and then addition
18615 Multiple directories may be specified, separated by blanks. Specifying
18616 multiple directories in a single command
18617 results in the directories added to the beginning of the
18618 search path in the same order they were presented in the command.
18619 If blanks are needed as
18620 part of a directory name, double-quotes should be used around
18621 the name. In the command output, the path will show up separated
18622 by the system directory-separator character. The directory-separator
18623 character must not be used
18624 in any directory name.
18625 If no directories are specified, the current path is displayed.
18628 @subsubheading @value{GDBN} Command
18630 The corresponding @value{GDBN} command is @samp{path}.
18632 @subsubheading Example
18637 ^done,path="/usr/bin"
18639 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18640 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18642 -environment-path -r /usr/local/bin
18643 ^done,path="/usr/local/bin:/usr/bin"
18648 @subheading The @code{-environment-pwd} Command
18649 @findex -environment-pwd
18651 @subsubheading Synopsis
18657 Show the current working directory.
18659 @subsubheading @value{GDBN} command
18661 The corresponding @value{GDBN} command is @samp{pwd}.
18663 @subsubheading Example
18668 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18672 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18673 @node GDB/MI Thread Commands
18674 @section @sc{gdb/mi} Thread Commands
18677 @subheading The @code{-thread-info} Command
18678 @findex -thread-info
18680 @subsubheading Synopsis
18686 @subsubheading @value{GDBN} command
18690 @subsubheading Example
18694 @subheading The @code{-thread-list-all-threads} Command
18695 @findex -thread-list-all-threads
18697 @subsubheading Synopsis
18700 -thread-list-all-threads
18703 @subsubheading @value{GDBN} Command
18705 The equivalent @value{GDBN} command is @samp{info threads}.
18707 @subsubheading Example
18711 @subheading The @code{-thread-list-ids} Command
18712 @findex -thread-list-ids
18714 @subsubheading Synopsis
18720 Produces a list of the currently known @value{GDBN} thread ids. At the
18721 end of the list it also prints the total number of such threads.
18723 @subsubheading @value{GDBN} Command
18725 Part of @samp{info threads} supplies the same information.
18727 @subsubheading Example
18729 No threads present, besides the main process:
18734 ^done,thread-ids=@{@},number-of-threads="0"
18744 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18745 number-of-threads="3"
18750 @subheading The @code{-thread-select} Command
18751 @findex -thread-select
18753 @subsubheading Synopsis
18756 -thread-select @var{threadnum}
18759 Make @var{threadnum} the current thread. It prints the number of the new
18760 current thread, and the topmost frame for that thread.
18762 @subsubheading @value{GDBN} Command
18764 The corresponding @value{GDBN} command is @samp{thread}.
18766 @subsubheading Example
18773 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18774 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18778 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18779 number-of-threads="3"
18782 ^done,new-thread-id="3",
18783 frame=@{level="0",func="vprintf",
18784 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18785 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18789 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18790 @node GDB/MI Program Execution
18791 @section @sc{gdb/mi} Program Execution
18793 These are the asynchronous commands which generate the out-of-band
18794 record @samp{*stopped}. Currently @value{GDBN} only really executes
18795 asynchronously with remote targets and this interaction is mimicked in
18798 @subheading The @code{-exec-continue} Command
18799 @findex -exec-continue
18801 @subsubheading Synopsis
18807 Resumes the execution of the inferior program until a breakpoint is
18808 encountered, or until the inferior exits.
18810 @subsubheading @value{GDBN} Command
18812 The corresponding @value{GDBN} corresponding is @samp{continue}.
18814 @subsubheading Example
18821 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18822 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18827 @subheading The @code{-exec-finish} Command
18828 @findex -exec-finish
18830 @subsubheading Synopsis
18836 Resumes the execution of the inferior program until the current
18837 function is exited. Displays the results returned by the function.
18839 @subsubheading @value{GDBN} Command
18841 The corresponding @value{GDBN} command is @samp{finish}.
18843 @subsubheading Example
18845 Function returning @code{void}.
18852 *stopped,reason="function-finished",frame=@{func="main",args=[],
18853 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18857 Function returning other than @code{void}. The name of the internal
18858 @value{GDBN} variable storing the result is printed, together with the
18865 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18866 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18867 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18868 gdb-result-var="$1",return-value="0"
18873 @subheading The @code{-exec-interrupt} Command
18874 @findex -exec-interrupt
18876 @subsubheading Synopsis
18882 Interrupts the background execution of the target. Note how the token
18883 associated with the stop message is the one for the execution command
18884 that has been interrupted. The token for the interrupt itself only
18885 appears in the @samp{^done} output. If the user is trying to
18886 interrupt a non-running program, an error message will be printed.
18888 @subsubheading @value{GDBN} Command
18890 The corresponding @value{GDBN} command is @samp{interrupt}.
18892 @subsubheading Example
18903 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18904 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18905 fullname="/home/foo/bar/try.c",line="13"@}
18910 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18915 @subheading The @code{-exec-next} Command
18918 @subsubheading Synopsis
18924 Resumes execution of the inferior program, stopping when the beginning
18925 of the next source line is reached.
18927 @subsubheading @value{GDBN} Command
18929 The corresponding @value{GDBN} command is @samp{next}.
18931 @subsubheading Example
18937 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18942 @subheading The @code{-exec-next-instruction} Command
18943 @findex -exec-next-instruction
18945 @subsubheading Synopsis
18948 -exec-next-instruction
18951 Executes one machine instruction. If the instruction is a function
18952 call, continues until the function returns. If the program stops at an
18953 instruction in the middle of a source line, the address will be
18956 @subsubheading @value{GDBN} Command
18958 The corresponding @value{GDBN} command is @samp{nexti}.
18960 @subsubheading Example
18964 -exec-next-instruction
18968 *stopped,reason="end-stepping-range",
18969 addr="0x000100d4",line="5",file="hello.c"
18974 @subheading The @code{-exec-return} Command
18975 @findex -exec-return
18977 @subsubheading Synopsis
18983 Makes current function return immediately. Doesn't execute the inferior.
18984 Displays the new current frame.
18986 @subsubheading @value{GDBN} Command
18988 The corresponding @value{GDBN} command is @samp{return}.
18990 @subsubheading Example
18994 200-break-insert callee4
18995 200^done,bkpt=@{number="1",addr="0x00010734",
18996 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19001 000*stopped,reason="breakpoint-hit",bkptno="1",
19002 frame=@{func="callee4",args=[],
19003 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19004 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19010 111^done,frame=@{level="0",func="callee3",
19011 args=[@{name="strarg",
19012 value="0x11940 \"A string argument.\""@}],
19013 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19014 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19019 @subheading The @code{-exec-run} Command
19022 @subsubheading Synopsis
19028 Starts execution of the inferior from the beginning. The inferior
19029 executes until either a breakpoint is encountered or the program
19030 exits. In the latter case the output will include an exit code, if
19031 the program has exited exceptionally.
19033 @subsubheading @value{GDBN} Command
19035 The corresponding @value{GDBN} command is @samp{run}.
19037 @subsubheading Examples
19042 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19047 *stopped,reason="breakpoint-hit",bkptno="1",
19048 frame=@{func="main",args=[],file="recursive2.c",
19049 fullname="/home/foo/bar/recursive2.c",line="4"@}
19054 Program exited normally:
19062 *stopped,reason="exited-normally"
19067 Program exited exceptionally:
19075 *stopped,reason="exited",exit-code="01"
19079 Another way the program can terminate is if it receives a signal such as
19080 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19084 *stopped,reason="exited-signalled",signal-name="SIGINT",
19085 signal-meaning="Interrupt"
19089 @c @subheading -exec-signal
19092 @subheading The @code{-exec-step} Command
19095 @subsubheading Synopsis
19101 Resumes execution of the inferior program, stopping when the beginning
19102 of the next source line is reached, if the next source line is not a
19103 function call. If it is, stop at the first instruction of the called
19106 @subsubheading @value{GDBN} Command
19108 The corresponding @value{GDBN} command is @samp{step}.
19110 @subsubheading Example
19112 Stepping into a function:
19118 *stopped,reason="end-stepping-range",
19119 frame=@{func="foo",args=[@{name="a",value="10"@},
19120 @{name="b",value="0"@}],file="recursive2.c",
19121 fullname="/home/foo/bar/recursive2.c",line="11"@}
19131 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19136 @subheading The @code{-exec-step-instruction} Command
19137 @findex -exec-step-instruction
19139 @subsubheading Synopsis
19142 -exec-step-instruction
19145 Resumes the inferior which executes one machine instruction. The
19146 output, once @value{GDBN} has stopped, will vary depending on whether
19147 we have stopped in the middle of a source line or not. In the former
19148 case, the address at which the program stopped will be printed as
19151 @subsubheading @value{GDBN} Command
19153 The corresponding @value{GDBN} command is @samp{stepi}.
19155 @subsubheading Example
19159 -exec-step-instruction
19163 *stopped,reason="end-stepping-range",
19164 frame=@{func="foo",args=[],file="try.c",
19165 fullname="/home/foo/bar/try.c",line="10"@}
19167 -exec-step-instruction
19171 *stopped,reason="end-stepping-range",
19172 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19173 fullname="/home/foo/bar/try.c",line="10"@}
19178 @subheading The @code{-exec-until} Command
19179 @findex -exec-until
19181 @subsubheading Synopsis
19184 -exec-until [ @var{location} ]
19187 Executes the inferior until the @var{location} specified in the
19188 argument is reached. If there is no argument, the inferior executes
19189 until a source line greater than the current one is reached. The
19190 reason for stopping in this case will be @samp{location-reached}.
19192 @subsubheading @value{GDBN} Command
19194 The corresponding @value{GDBN} command is @samp{until}.
19196 @subsubheading Example
19200 -exec-until recursive2.c:6
19204 *stopped,reason="location-reached",frame=@{func="main",args=[],
19205 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19210 @subheading -file-clear
19211 Is this going away????
19214 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19215 @node GDB/MI Stack Manipulation
19216 @section @sc{gdb/mi} Stack Manipulation Commands
19219 @subheading The @code{-stack-info-frame} Command
19220 @findex -stack-info-frame
19222 @subsubheading Synopsis
19228 Get info on the selected frame.
19230 @subsubheading @value{GDBN} Command
19232 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19233 (without arguments).
19235 @subsubheading Example
19240 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19241 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19242 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19246 @subheading The @code{-stack-info-depth} Command
19247 @findex -stack-info-depth
19249 @subsubheading Synopsis
19252 -stack-info-depth [ @var{max-depth} ]
19255 Return the depth of the stack. If the integer argument @var{max-depth}
19256 is specified, do not count beyond @var{max-depth} frames.
19258 @subsubheading @value{GDBN} Command
19260 There's no equivalent @value{GDBN} command.
19262 @subsubheading Example
19264 For a stack with frame levels 0 through 11:
19271 -stack-info-depth 4
19274 -stack-info-depth 12
19277 -stack-info-depth 11
19280 -stack-info-depth 13
19285 @subheading The @code{-stack-list-arguments} Command
19286 @findex -stack-list-arguments
19288 @subsubheading Synopsis
19291 -stack-list-arguments @var{show-values}
19292 [ @var{low-frame} @var{high-frame} ]
19295 Display a list of the arguments for the frames between @var{low-frame}
19296 and @var{high-frame} (inclusive). If @var{low-frame} and
19297 @var{high-frame} are not provided, list the arguments for the whole
19298 call stack. If the two arguments are equal, show the single frame
19299 at the corresponding level. It is an error if @var{low-frame} is
19300 larger than the actual number of frames. On the other hand,
19301 @var{high-frame} may be larger than the actual number of frames, in
19302 which case only existing frames will be returned.
19304 The @var{show-values} argument must have a value of 0 or 1. A value of
19305 0 means that only the names of the arguments are listed, a value of 1
19306 means that both names and values of the arguments are printed.
19308 @subsubheading @value{GDBN} Command
19310 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19311 @samp{gdb_get_args} command which partially overlaps with the
19312 functionality of @samp{-stack-list-arguments}.
19314 @subsubheading Example
19321 frame=@{level="0",addr="0x00010734",func="callee4",
19322 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19323 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19324 frame=@{level="1",addr="0x0001076c",func="callee3",
19325 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19326 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19327 frame=@{level="2",addr="0x0001078c",func="callee2",
19328 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19329 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19330 frame=@{level="3",addr="0x000107b4",func="callee1",
19331 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19332 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19333 frame=@{level="4",addr="0x000107e0",func="main",
19334 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19335 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19337 -stack-list-arguments 0
19340 frame=@{level="0",args=[]@},
19341 frame=@{level="1",args=[name="strarg"]@},
19342 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19343 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19344 frame=@{level="4",args=[]@}]
19346 -stack-list-arguments 1
19349 frame=@{level="0",args=[]@},
19351 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19352 frame=@{level="2",args=[
19353 @{name="intarg",value="2"@},
19354 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19355 @{frame=@{level="3",args=[
19356 @{name="intarg",value="2"@},
19357 @{name="strarg",value="0x11940 \"A string argument.\""@},
19358 @{name="fltarg",value="3.5"@}]@},
19359 frame=@{level="4",args=[]@}]
19361 -stack-list-arguments 0 2 2
19362 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19364 -stack-list-arguments 1 2 2
19365 ^done,stack-args=[frame=@{level="2",
19366 args=[@{name="intarg",value="2"@},
19367 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19371 @c @subheading -stack-list-exception-handlers
19374 @subheading The @code{-stack-list-frames} Command
19375 @findex -stack-list-frames
19377 @subsubheading Synopsis
19380 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19383 List the frames currently on the stack. For each frame it displays the
19388 The frame number, 0 being the topmost frame, i.e., the innermost function.
19390 The @code{$pc} value for that frame.
19394 File name of the source file where the function lives.
19396 Line number corresponding to the @code{$pc}.
19399 If invoked without arguments, this command prints a backtrace for the
19400 whole stack. If given two integer arguments, it shows the frames whose
19401 levels are between the two arguments (inclusive). If the two arguments
19402 are equal, it shows the single frame at the corresponding level. It is
19403 an error if @var{low-frame} is larger than the actual number of
19404 frames. On the other hand, @var{high-frame} may be larger than the
19405 actual number of frames, in which case only existing frames will be returned.
19407 @subsubheading @value{GDBN} Command
19409 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19411 @subsubheading Example
19413 Full stack backtrace:
19419 [frame=@{level="0",addr="0x0001076c",func="foo",
19420 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19421 frame=@{level="1",addr="0x000107a4",func="foo",
19422 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19423 frame=@{level="2",addr="0x000107a4",func="foo",
19424 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19425 frame=@{level="3",addr="0x000107a4",func="foo",
19426 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19427 frame=@{level="4",addr="0x000107a4",func="foo",
19428 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19429 frame=@{level="5",addr="0x000107a4",func="foo",
19430 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19431 frame=@{level="6",addr="0x000107a4",func="foo",
19432 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19433 frame=@{level="7",addr="0x000107a4",func="foo",
19434 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19435 frame=@{level="8",addr="0x000107a4",func="foo",
19436 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19437 frame=@{level="9",addr="0x000107a4",func="foo",
19438 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19439 frame=@{level="10",addr="0x000107a4",func="foo",
19440 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19441 frame=@{level="11",addr="0x00010738",func="main",
19442 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19446 Show frames between @var{low_frame} and @var{high_frame}:
19450 -stack-list-frames 3 5
19452 [frame=@{level="3",addr="0x000107a4",func="foo",
19453 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19454 frame=@{level="4",addr="0x000107a4",func="foo",
19455 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19456 frame=@{level="5",addr="0x000107a4",func="foo",
19457 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19461 Show a single frame:
19465 -stack-list-frames 3 3
19467 [frame=@{level="3",addr="0x000107a4",func="foo",
19468 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19473 @subheading The @code{-stack-list-locals} Command
19474 @findex -stack-list-locals
19476 @subsubheading Synopsis
19479 -stack-list-locals @var{print-values}
19482 Display the local variable names for the selected frame. If
19483 @var{print-values} is 0 or @code{--no-values}, print only the names of
19484 the variables; if it is 1 or @code{--all-values}, print also their
19485 values; and if it is 2 or @code{--simple-values}, print the name,
19486 type and value for simple data types and the name and type for arrays,
19487 structures and unions. In this last case, a frontend can immediately
19488 display the value of simple data types and create variable objects for
19489 other data types when the user wishes to explore their values in
19492 @subsubheading @value{GDBN} Command
19494 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19496 @subsubheading Example
19500 -stack-list-locals 0
19501 ^done,locals=[name="A",name="B",name="C"]
19503 -stack-list-locals --all-values
19504 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19505 @{name="C",value="@{1, 2, 3@}"@}]
19506 -stack-list-locals --simple-values
19507 ^done,locals=[@{name="A",type="int",value="1"@},
19508 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19513 @subheading The @code{-stack-select-frame} Command
19514 @findex -stack-select-frame
19516 @subsubheading Synopsis
19519 -stack-select-frame @var{framenum}
19522 Change the selected frame. Select a different frame @var{framenum} on
19525 @subsubheading @value{GDBN} Command
19527 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19528 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19530 @subsubheading Example
19534 -stack-select-frame 2
19539 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19540 @node GDB/MI Variable Objects
19541 @section @sc{gdb/mi} Variable Objects
19545 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19547 For the implementation of a variable debugger window (locals, watched
19548 expressions, etc.), we are proposing the adaptation of the existing code
19549 used by @code{Insight}.
19551 The two main reasons for that are:
19555 It has been proven in practice (it is already on its second generation).
19558 It will shorten development time (needless to say how important it is
19562 The original interface was designed to be used by Tcl code, so it was
19563 slightly changed so it could be used through @sc{gdb/mi}. This section
19564 describes the @sc{gdb/mi} operations that will be available and gives some
19565 hints about their use.
19567 @emph{Note}: In addition to the set of operations described here, we
19568 expect the @sc{gui} implementation of a variable window to require, at
19569 least, the following operations:
19572 @item @code{-gdb-show} @code{output-radix}
19573 @item @code{-stack-list-arguments}
19574 @item @code{-stack-list-locals}
19575 @item @code{-stack-select-frame}
19580 @subheading Introduction to Variable Objects
19582 @cindex variable objects in @sc{gdb/mi}
19584 Variable objects are "object-oriented" MI interface for examining and
19585 changing values of expressions. Unlike some other MI interfaces that
19586 work with expressions, variable objects are specifically designed for
19587 simple and efficient presentation in the frontend. A variable object
19588 is identified by string name. When a variable object is created, the
19589 frontend specifies the expression for that variable object. The
19590 expression can be a simple variable, or it can be an arbitrary complex
19591 expression, and can even involve CPU registers. After creating a
19592 variable object, the frontend can invoke other variable object
19593 operations---for example to obtain or change the value of a variable
19594 object, or to change display format.
19596 Variable objects have hierarchical tree structure. Any variable object
19597 that corresponds to a composite type, such as structure in C, has
19598 a number of child variable objects, for example corresponding to each
19599 element of a structure. A child variable object can itself have
19600 children, recursively. Recursion ends when we reach
19601 leaf variable objects, which always have built-in types.
19603 For a leaf variable object it is possible to obtain its value as a
19604 string, or set the value from a string. String value can be also
19605 obtained for a non-leaf variable object, but it's generally a string
19606 that only indicates the type of the object, and does not list its
19607 contents. Assignment to a non-leaf variable object is not allowed.
19609 A frontend does not need to read the values of all variable objects each time
19610 the program stops. Instead, MI provides an update command that lists all
19611 variable objects whose values has changed since the last update
19612 operation. This considerably reduces the amount of data that must
19613 be transferred to the frontend.
19615 The following is the complete set of @sc{gdb/mi} operations defined to
19616 access this functionality:
19618 @multitable @columnfractions .4 .6
19619 @item @strong{Operation}
19620 @tab @strong{Description}
19622 @item @code{-var-create}
19623 @tab create a variable object
19624 @item @code{-var-delete}
19625 @tab delete the variable object and/or its children
19626 @item @code{-var-set-format}
19627 @tab set the display format of this variable
19628 @item @code{-var-show-format}
19629 @tab show the display format of this variable
19630 @item @code{-var-info-num-children}
19631 @tab tells how many children this object has
19632 @item @code{-var-list-children}
19633 @tab return a list of the object's children
19634 @item @code{-var-info-type}
19635 @tab show the type of this variable object
19636 @item @code{-var-info-expression}
19637 @tab print what this variable object represents
19638 @item @code{-var-show-attributes}
19639 @tab is this variable editable? does it exist here?
19640 @item @code{-var-evaluate-expression}
19641 @tab get the value of this variable
19642 @item @code{-var-assign}
19643 @tab set the value of this variable
19644 @item @code{-var-update}
19645 @tab update the variable and its children
19648 In the next subsection we describe each operation in detail and suggest
19649 how it can be used.
19651 @subheading Description And Use of Operations on Variable Objects
19653 @subheading The @code{-var-create} Command
19654 @findex -var-create
19656 @subsubheading Synopsis
19659 -var-create @{@var{name} | "-"@}
19660 @{@var{frame-addr} | "*"@} @var{expression}
19663 This operation creates a variable object, which allows the monitoring of
19664 a variable, the result of an expression, a memory cell or a CPU
19667 The @var{name} parameter is the string by which the object can be
19668 referenced. It must be unique. If @samp{-} is specified, the varobj
19669 system will generate a string ``varNNNNNN'' automatically. It will be
19670 unique provided that one does not specify @var{name} on that format.
19671 The command fails if a duplicate name is found.
19673 The frame under which the expression should be evaluated can be
19674 specified by @var{frame-addr}. A @samp{*} indicates that the current
19675 frame should be used.
19677 @var{expression} is any expression valid on the current language set (must not
19678 begin with a @samp{*}), or one of the following:
19682 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19685 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19688 @samp{$@var{regname}} --- a CPU register name
19691 @subsubheading Result
19693 This operation returns the name, number of children and the type of the
19694 object created. Type is returned as a string as the ones generated by
19695 the @value{GDBN} CLI:
19698 name="@var{name}",numchild="N",type="@var{type}"
19702 @subheading The @code{-var-delete} Command
19703 @findex -var-delete
19705 @subsubheading Synopsis
19708 -var-delete [ -c ] @var{name}
19711 Deletes a previously created variable object and all of its children.
19712 With the @samp{-c} option, just deletes the children.
19714 Returns an error if the object @var{name} is not found.
19717 @subheading The @code{-var-set-format} Command
19718 @findex -var-set-format
19720 @subsubheading Synopsis
19723 -var-set-format @var{name} @var{format-spec}
19726 Sets the output format for the value of the object @var{name} to be
19729 The syntax for the @var{format-spec} is as follows:
19732 @var{format-spec} @expansion{}
19733 @{binary | decimal | hexadecimal | octal | natural@}
19736 The natural format is the default format choosen automatically
19737 based on the variable type (like decimal for an @code{int}, hex
19738 for pointers, etc.).
19740 For a variable with children, the format is set only on the
19741 variable itself, and the children are not affected.
19743 @subheading The @code{-var-show-format} Command
19744 @findex -var-show-format
19746 @subsubheading Synopsis
19749 -var-show-format @var{name}
19752 Returns the format used to display the value of the object @var{name}.
19755 @var{format} @expansion{}
19760 @subheading The @code{-var-info-num-children} Command
19761 @findex -var-info-num-children
19763 @subsubheading Synopsis
19766 -var-info-num-children @var{name}
19769 Returns the number of children of a variable object @var{name}:
19776 @subheading The @code{-var-list-children} Command
19777 @findex -var-list-children
19779 @subsubheading Synopsis
19782 -var-list-children [@var{print-values}] @var{name}
19784 @anchor{-var-list-children}
19786 Return a list of the children of the specified variable object and
19787 create variable objects for them, if they do not already exist. With
19788 a single argument or if @var{print-values} has a value for of 0 or
19789 @code{--no-values}, print only the names of the variables; if
19790 @var{print-values} is 1 or @code{--all-values}, also print their
19791 values; and if it is 2 or @code{--simple-values} print the name and
19792 value for simple data types and just the name for arrays, structures
19795 @subsubheading Example
19799 -var-list-children n
19800 ^done,numchild=@var{n},children=[@{name=@var{name},
19801 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19803 -var-list-children --all-values n
19804 ^done,numchild=@var{n},children=[@{name=@var{name},
19805 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19809 @subheading The @code{-var-info-type} Command
19810 @findex -var-info-type
19812 @subsubheading Synopsis
19815 -var-info-type @var{name}
19818 Returns the type of the specified variable @var{name}. The type is
19819 returned as a string in the same format as it is output by the
19823 type=@var{typename}
19827 @subheading The @code{-var-info-expression} Command
19828 @findex -var-info-expression
19830 @subsubheading Synopsis
19833 -var-info-expression @var{name}
19836 Returns what is represented by the variable object @var{name}:
19839 lang=@var{lang-spec},exp=@var{expression}
19843 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
19845 @subheading The @code{-var-show-attributes} Command
19846 @findex -var-show-attributes
19848 @subsubheading Synopsis
19851 -var-show-attributes @var{name}
19854 List attributes of the specified variable object @var{name}:
19857 status=@var{attr} [ ( ,@var{attr} )* ]
19861 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19863 @subheading The @code{-var-evaluate-expression} Command
19864 @findex -var-evaluate-expression
19866 @subsubheading Synopsis
19869 -var-evaluate-expression @var{name}
19872 Evaluates the expression that is represented by the specified variable
19873 object and returns its value as a string. The format of the
19874 string can be changed using the @code{-var-set-format} command.
19880 Note that one must invoke @code{-var-list-children} for a variable
19881 before the value of a child variable can be evaluated.
19883 @subheading The @code{-var-assign} Command
19884 @findex -var-assign
19886 @subsubheading Synopsis
19889 -var-assign @var{name} @var{expression}
19892 Assigns the value of @var{expression} to the variable object specified
19893 by @var{name}. The object must be @samp{editable}. If the variable's
19894 value is altered by the assign, the variable will show up in any
19895 subsequent @code{-var-update} list.
19897 @subsubheading Example
19905 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19909 @subheading The @code{-var-update} Command
19910 @findex -var-update
19912 @subsubheading Synopsis
19915 -var-update [@var{print-values}] @{@var{name} | "*"@}
19918 Reevaluate the expressions corresponding to the variable object
19919 @var{name} and all its direct and indirect children, and return the
19920 list of variable objects whose values have changed; @var{name} must
19921 be a root variable object. Here, ``changed'' means that the result of
19922 @code{-var-evaluate-expression} before and after the
19923 @code{-var-update} is different. If @samp{*} is used as the variable
19924 object names, all existing variable objects are updated. The option
19925 @var{print-values} determines whether both names and values, or just
19926 names are printed. The possible values of this options are the same
19927 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
19928 recommended to use the @samp{--all-values} option, to reduce the
19929 number of MI commands needed on each program stop.
19932 @subsubheading Example
19939 -var-update --all-values var1
19940 ^done,changelist=[@{name="var1",value="3",in_scope="true",
19941 type_changed="false"@}]
19945 @anchor{-var-update}
19946 The field in_scope may take three values:
19950 The variable object's current value is valid.
19953 The variable object does not currently hold a valid value but it may
19954 hold one in the future if its associated expression comes back into
19958 The variable object no longer holds a valid value.
19959 This can occur when the executable file being debugged has changed,
19960 either through recompilation or by using the @value{GDBN} @code{file}
19961 command. The front end should normally choose to delete these variable
19965 In the future new values may be added to this list so the front should
19966 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
19968 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19969 @node GDB/MI Data Manipulation
19970 @section @sc{gdb/mi} Data Manipulation
19972 @cindex data manipulation, in @sc{gdb/mi}
19973 @cindex @sc{gdb/mi}, data manipulation
19974 This section describes the @sc{gdb/mi} commands that manipulate data:
19975 examine memory and registers, evaluate expressions, etc.
19977 @c REMOVED FROM THE INTERFACE.
19978 @c @subheading -data-assign
19979 @c Change the value of a program variable. Plenty of side effects.
19980 @c @subsubheading GDB command
19982 @c @subsubheading Example
19985 @subheading The @code{-data-disassemble} Command
19986 @findex -data-disassemble
19988 @subsubheading Synopsis
19992 [ -s @var{start-addr} -e @var{end-addr} ]
19993 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20001 @item @var{start-addr}
20002 is the beginning address (or @code{$pc})
20003 @item @var{end-addr}
20005 @item @var{filename}
20006 is the name of the file to disassemble
20007 @item @var{linenum}
20008 is the line number to disassemble around
20010 is the number of disassembly lines to be produced. If it is -1,
20011 the whole function will be disassembled, in case no @var{end-addr} is
20012 specified. If @var{end-addr} is specified as a non-zero value, and
20013 @var{lines} is lower than the number of disassembly lines between
20014 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20015 displayed; if @var{lines} is higher than the number of lines between
20016 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20019 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20023 @subsubheading Result
20025 The output for each instruction is composed of four fields:
20034 Note that whatever included in the instruction field, is not manipulated
20035 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20037 @subsubheading @value{GDBN} Command
20039 There's no direct mapping from this command to the CLI.
20041 @subsubheading Example
20043 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20047 -data-disassemble -s $pc -e "$pc + 20" -- 0
20050 @{address="0x000107c0",func-name="main",offset="4",
20051 inst="mov 2, %o0"@},
20052 @{address="0x000107c4",func-name="main",offset="8",
20053 inst="sethi %hi(0x11800), %o2"@},
20054 @{address="0x000107c8",func-name="main",offset="12",
20055 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20056 @{address="0x000107cc",func-name="main",offset="16",
20057 inst="sethi %hi(0x11800), %o2"@},
20058 @{address="0x000107d0",func-name="main",offset="20",
20059 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20063 Disassemble the whole @code{main} function. Line 32 is part of
20067 -data-disassemble -f basics.c -l 32 -- 0
20069 @{address="0x000107bc",func-name="main",offset="0",
20070 inst="save %sp, -112, %sp"@},
20071 @{address="0x000107c0",func-name="main",offset="4",
20072 inst="mov 2, %o0"@},
20073 @{address="0x000107c4",func-name="main",offset="8",
20074 inst="sethi %hi(0x11800), %o2"@},
20076 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20077 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20081 Disassemble 3 instructions from the start of @code{main}:
20085 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20087 @{address="0x000107bc",func-name="main",offset="0",
20088 inst="save %sp, -112, %sp"@},
20089 @{address="0x000107c0",func-name="main",offset="4",
20090 inst="mov 2, %o0"@},
20091 @{address="0x000107c4",func-name="main",offset="8",
20092 inst="sethi %hi(0x11800), %o2"@}]
20096 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20100 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20102 src_and_asm_line=@{line="31",
20103 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20104 testsuite/gdb.mi/basics.c",line_asm_insn=[
20105 @{address="0x000107bc",func-name="main",offset="0",
20106 inst="save %sp, -112, %sp"@}]@},
20107 src_and_asm_line=@{line="32",
20108 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20109 testsuite/gdb.mi/basics.c",line_asm_insn=[
20110 @{address="0x000107c0",func-name="main",offset="4",
20111 inst="mov 2, %o0"@},
20112 @{address="0x000107c4",func-name="main",offset="8",
20113 inst="sethi %hi(0x11800), %o2"@}]@}]
20118 @subheading The @code{-data-evaluate-expression} Command
20119 @findex -data-evaluate-expression
20121 @subsubheading Synopsis
20124 -data-evaluate-expression @var{expr}
20127 Evaluate @var{expr} as an expression. The expression could contain an
20128 inferior function call. The function call will execute synchronously.
20129 If the expression contains spaces, it must be enclosed in double quotes.
20131 @subsubheading @value{GDBN} Command
20133 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20134 @samp{call}. In @code{gdbtk} only, there's a corresponding
20135 @samp{gdb_eval} command.
20137 @subsubheading Example
20139 In the following example, the numbers that precede the commands are the
20140 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20141 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20145 211-data-evaluate-expression A
20148 311-data-evaluate-expression &A
20149 311^done,value="0xefffeb7c"
20151 411-data-evaluate-expression A+3
20154 511-data-evaluate-expression "A + 3"
20160 @subheading The @code{-data-list-changed-registers} Command
20161 @findex -data-list-changed-registers
20163 @subsubheading Synopsis
20166 -data-list-changed-registers
20169 Display a list of the registers that have changed.
20171 @subsubheading @value{GDBN} Command
20173 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20174 has the corresponding command @samp{gdb_changed_register_list}.
20176 @subsubheading Example
20178 On a PPC MBX board:
20186 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20187 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20189 -data-list-changed-registers
20190 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20191 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20192 "24","25","26","27","28","30","31","64","65","66","67","69"]
20197 @subheading The @code{-data-list-register-names} Command
20198 @findex -data-list-register-names
20200 @subsubheading Synopsis
20203 -data-list-register-names [ ( @var{regno} )+ ]
20206 Show a list of register names for the current target. If no arguments
20207 are given, it shows a list of the names of all the registers. If
20208 integer numbers are given as arguments, it will print a list of the
20209 names of the registers corresponding to the arguments. To ensure
20210 consistency between a register name and its number, the output list may
20211 include empty register names.
20213 @subsubheading @value{GDBN} Command
20215 @value{GDBN} does not have a command which corresponds to
20216 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20217 corresponding command @samp{gdb_regnames}.
20219 @subsubheading Example
20221 For the PPC MBX board:
20224 -data-list-register-names
20225 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20226 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20227 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20228 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20229 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20230 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20231 "", "pc","ps","cr","lr","ctr","xer"]
20233 -data-list-register-names 1 2 3
20234 ^done,register-names=["r1","r2","r3"]
20238 @subheading The @code{-data-list-register-values} Command
20239 @findex -data-list-register-values
20241 @subsubheading Synopsis
20244 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20247 Display the registers' contents. @var{fmt} is the format according to
20248 which the registers' contents are to be returned, followed by an optional
20249 list of numbers specifying the registers to display. A missing list of
20250 numbers indicates that the contents of all the registers must be returned.
20252 Allowed formats for @var{fmt} are:
20269 @subsubheading @value{GDBN} Command
20271 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20272 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20274 @subsubheading Example
20276 For a PPC MBX board (note: line breaks are for readability only, they
20277 don't appear in the actual output):
20281 -data-list-register-values r 64 65
20282 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20283 @{number="65",value="0x00029002"@}]
20285 -data-list-register-values x
20286 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20287 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20288 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20289 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20290 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20291 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20292 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20293 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20294 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20295 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20296 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20297 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20298 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20299 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20300 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20301 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20302 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20303 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20304 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20305 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20306 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20307 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20308 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20309 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20310 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20311 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20312 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20313 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20314 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20315 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20316 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20317 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20318 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20319 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20320 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20321 @{number="69",value="0x20002b03"@}]
20326 @subheading The @code{-data-read-memory} Command
20327 @findex -data-read-memory
20329 @subsubheading Synopsis
20332 -data-read-memory [ -o @var{byte-offset} ]
20333 @var{address} @var{word-format} @var{word-size}
20334 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20341 @item @var{address}
20342 An expression specifying the address of the first memory word to be
20343 read. Complex expressions containing embedded white space should be
20344 quoted using the C convention.
20346 @item @var{word-format}
20347 The format to be used to print the memory words. The notation is the
20348 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20351 @item @var{word-size}
20352 The size of each memory word in bytes.
20354 @item @var{nr-rows}
20355 The number of rows in the output table.
20357 @item @var{nr-cols}
20358 The number of columns in the output table.
20361 If present, indicates that each row should include an @sc{ascii} dump. The
20362 value of @var{aschar} is used as a padding character when a byte is not a
20363 member of the printable @sc{ascii} character set (printable @sc{ascii}
20364 characters are those whose code is between 32 and 126, inclusively).
20366 @item @var{byte-offset}
20367 An offset to add to the @var{address} before fetching memory.
20370 This command displays memory contents as a table of @var{nr-rows} by
20371 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20372 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20373 (returned as @samp{total-bytes}). Should less than the requested number
20374 of bytes be returned by the target, the missing words are identified
20375 using @samp{N/A}. The number of bytes read from the target is returned
20376 in @samp{nr-bytes} and the starting address used to read memory in
20379 The address of the next/previous row or page is available in
20380 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20383 @subsubheading @value{GDBN} Command
20385 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20386 @samp{gdb_get_mem} memory read command.
20388 @subsubheading Example
20390 Read six bytes of memory starting at @code{bytes+6} but then offset by
20391 @code{-6} bytes. Format as three rows of two columns. One byte per
20392 word. Display each word in hex.
20396 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20397 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20398 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20399 prev-page="0x0000138a",memory=[
20400 @{addr="0x00001390",data=["0x00","0x01"]@},
20401 @{addr="0x00001392",data=["0x02","0x03"]@},
20402 @{addr="0x00001394",data=["0x04","0x05"]@}]
20406 Read two bytes of memory starting at address @code{shorts + 64} and
20407 display as a single word formatted in decimal.
20411 5-data-read-memory shorts+64 d 2 1 1
20412 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20413 next-row="0x00001512",prev-row="0x0000150e",
20414 next-page="0x00001512",prev-page="0x0000150e",memory=[
20415 @{addr="0x00001510",data=["128"]@}]
20419 Read thirty two bytes of memory starting at @code{bytes+16} and format
20420 as eight rows of four columns. Include a string encoding with @samp{x}
20421 used as the non-printable character.
20425 4-data-read-memory bytes+16 x 1 8 4 x
20426 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20427 next-row="0x000013c0",prev-row="0x0000139c",
20428 next-page="0x000013c0",prev-page="0x00001380",memory=[
20429 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20430 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20431 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20432 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20433 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20434 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20435 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20436 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20440 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20441 @node GDB/MI Tracepoint Commands
20442 @section @sc{gdb/mi} Tracepoint Commands
20444 The tracepoint commands are not yet implemented.
20446 @c @subheading -trace-actions
20448 @c @subheading -trace-delete
20450 @c @subheading -trace-disable
20452 @c @subheading -trace-dump
20454 @c @subheading -trace-enable
20456 @c @subheading -trace-exists
20458 @c @subheading -trace-find
20460 @c @subheading -trace-frame-number
20462 @c @subheading -trace-info
20464 @c @subheading -trace-insert
20466 @c @subheading -trace-list
20468 @c @subheading -trace-pass-count
20470 @c @subheading -trace-save
20472 @c @subheading -trace-start
20474 @c @subheading -trace-stop
20477 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20478 @node GDB/MI Symbol Query
20479 @section @sc{gdb/mi} Symbol Query Commands
20482 @subheading The @code{-symbol-info-address} Command
20483 @findex -symbol-info-address
20485 @subsubheading Synopsis
20488 -symbol-info-address @var{symbol}
20491 Describe where @var{symbol} is stored.
20493 @subsubheading @value{GDBN} Command
20495 The corresponding @value{GDBN} command is @samp{info address}.
20497 @subsubheading Example
20501 @subheading The @code{-symbol-info-file} Command
20502 @findex -symbol-info-file
20504 @subsubheading Synopsis
20510 Show the file for the symbol.
20512 @subsubheading @value{GDBN} Command
20514 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20515 @samp{gdb_find_file}.
20517 @subsubheading Example
20521 @subheading The @code{-symbol-info-function} Command
20522 @findex -symbol-info-function
20524 @subsubheading Synopsis
20527 -symbol-info-function
20530 Show which function the symbol lives in.
20532 @subsubheading @value{GDBN} Command
20534 @samp{gdb_get_function} in @code{gdbtk}.
20536 @subsubheading Example
20540 @subheading The @code{-symbol-info-line} Command
20541 @findex -symbol-info-line
20543 @subsubheading Synopsis
20549 Show the core addresses of the code for a source line.
20551 @subsubheading @value{GDBN} Command
20553 The corresponding @value{GDBN} command is @samp{info line}.
20554 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20556 @subsubheading Example
20560 @subheading The @code{-symbol-info-symbol} Command
20561 @findex -symbol-info-symbol
20563 @subsubheading Synopsis
20566 -symbol-info-symbol @var{addr}
20569 Describe what symbol is at location @var{addr}.
20571 @subsubheading @value{GDBN} Command
20573 The corresponding @value{GDBN} command is @samp{info symbol}.
20575 @subsubheading Example
20579 @subheading The @code{-symbol-list-functions} Command
20580 @findex -symbol-list-functions
20582 @subsubheading Synopsis
20585 -symbol-list-functions
20588 List the functions in the executable.
20590 @subsubheading @value{GDBN} Command
20592 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20593 @samp{gdb_search} in @code{gdbtk}.
20595 @subsubheading Example
20599 @subheading The @code{-symbol-list-lines} Command
20600 @findex -symbol-list-lines
20602 @subsubheading Synopsis
20605 -symbol-list-lines @var{filename}
20608 Print the list of lines that contain code and their associated program
20609 addresses for the given source filename. The entries are sorted in
20610 ascending PC order.
20612 @subsubheading @value{GDBN} Command
20614 There is no corresponding @value{GDBN} command.
20616 @subsubheading Example
20619 -symbol-list-lines basics.c
20620 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20625 @subheading The @code{-symbol-list-types} Command
20626 @findex -symbol-list-types
20628 @subsubheading Synopsis
20634 List all the type names.
20636 @subsubheading @value{GDBN} Command
20638 The corresponding commands are @samp{info types} in @value{GDBN},
20639 @samp{gdb_search} in @code{gdbtk}.
20641 @subsubheading Example
20645 @subheading The @code{-symbol-list-variables} Command
20646 @findex -symbol-list-variables
20648 @subsubheading Synopsis
20651 -symbol-list-variables
20654 List all the global and static variable names.
20656 @subsubheading @value{GDBN} Command
20658 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20660 @subsubheading Example
20664 @subheading The @code{-symbol-locate} Command
20665 @findex -symbol-locate
20667 @subsubheading Synopsis
20673 @subsubheading @value{GDBN} Command
20675 @samp{gdb_loc} in @code{gdbtk}.
20677 @subsubheading Example
20681 @subheading The @code{-symbol-type} Command
20682 @findex -symbol-type
20684 @subsubheading Synopsis
20687 -symbol-type @var{variable}
20690 Show type of @var{variable}.
20692 @subsubheading @value{GDBN} Command
20694 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20695 @samp{gdb_obj_variable}.
20697 @subsubheading Example
20701 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20702 @node GDB/MI File Commands
20703 @section @sc{gdb/mi} File Commands
20705 This section describes the GDB/MI commands to specify executable file names
20706 and to read in and obtain symbol table information.
20708 @subheading The @code{-file-exec-and-symbols} Command
20709 @findex -file-exec-and-symbols
20711 @subsubheading Synopsis
20714 -file-exec-and-symbols @var{file}
20717 Specify the executable file to be debugged. This file is the one from
20718 which the symbol table is also read. If no file is specified, the
20719 command clears the executable and symbol information. If breakpoints
20720 are set when using this command with no arguments, @value{GDBN} will produce
20721 error messages. Otherwise, no output is produced, except a completion
20724 @subsubheading @value{GDBN} Command
20726 The corresponding @value{GDBN} command is @samp{file}.
20728 @subsubheading Example
20732 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20738 @subheading The @code{-file-exec-file} Command
20739 @findex -file-exec-file
20741 @subsubheading Synopsis
20744 -file-exec-file @var{file}
20747 Specify the executable file to be debugged. Unlike
20748 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20749 from this file. If used without argument, @value{GDBN} clears the information
20750 about the executable file. No output is produced, except a completion
20753 @subsubheading @value{GDBN} Command
20755 The corresponding @value{GDBN} command is @samp{exec-file}.
20757 @subsubheading Example
20761 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20767 @subheading The @code{-file-list-exec-sections} Command
20768 @findex -file-list-exec-sections
20770 @subsubheading Synopsis
20773 -file-list-exec-sections
20776 List the sections of the current executable file.
20778 @subsubheading @value{GDBN} Command
20780 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20781 information as this command. @code{gdbtk} has a corresponding command
20782 @samp{gdb_load_info}.
20784 @subsubheading Example
20788 @subheading The @code{-file-list-exec-source-file} Command
20789 @findex -file-list-exec-source-file
20791 @subsubheading Synopsis
20794 -file-list-exec-source-file
20797 List the line number, the current source file, and the absolute path
20798 to the current source file for the current executable.
20800 @subsubheading @value{GDBN} Command
20802 The @value{GDBN} equivalent is @samp{info source}
20804 @subsubheading Example
20808 123-file-list-exec-source-file
20809 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20814 @subheading The @code{-file-list-exec-source-files} Command
20815 @findex -file-list-exec-source-files
20817 @subsubheading Synopsis
20820 -file-list-exec-source-files
20823 List the source files for the current executable.
20825 It will always output the filename, but only when @value{GDBN} can find
20826 the absolute file name of a source file, will it output the fullname.
20828 @subsubheading @value{GDBN} Command
20830 The @value{GDBN} equivalent is @samp{info sources}.
20831 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20833 @subsubheading Example
20836 -file-list-exec-source-files
20838 @{file=foo.c,fullname=/home/foo.c@},
20839 @{file=/home/bar.c,fullname=/home/bar.c@},
20840 @{file=gdb_could_not_find_fullpath.c@}]
20844 @subheading The @code{-file-list-shared-libraries} Command
20845 @findex -file-list-shared-libraries
20847 @subsubheading Synopsis
20850 -file-list-shared-libraries
20853 List the shared libraries in the program.
20855 @subsubheading @value{GDBN} Command
20857 The corresponding @value{GDBN} command is @samp{info shared}.
20859 @subsubheading Example
20863 @subheading The @code{-file-list-symbol-files} Command
20864 @findex -file-list-symbol-files
20866 @subsubheading Synopsis
20869 -file-list-symbol-files
20874 @subsubheading @value{GDBN} Command
20876 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20878 @subsubheading Example
20882 @subheading The @code{-file-symbol-file} Command
20883 @findex -file-symbol-file
20885 @subsubheading Synopsis
20888 -file-symbol-file @var{file}
20891 Read symbol table info from the specified @var{file} argument. When
20892 used without arguments, clears @value{GDBN}'s symbol table info. No output is
20893 produced, except for a completion notification.
20895 @subsubheading @value{GDBN} Command
20897 The corresponding @value{GDBN} command is @samp{symbol-file}.
20899 @subsubheading Example
20903 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20909 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20910 @node GDB/MI Memory Overlay Commands
20911 @section @sc{gdb/mi} Memory Overlay Commands
20913 The memory overlay commands are not implemented.
20915 @c @subheading -overlay-auto
20917 @c @subheading -overlay-list-mapping-state
20919 @c @subheading -overlay-list-overlays
20921 @c @subheading -overlay-map
20923 @c @subheading -overlay-off
20925 @c @subheading -overlay-on
20927 @c @subheading -overlay-unmap
20929 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20930 @node GDB/MI Signal Handling Commands
20931 @section @sc{gdb/mi} Signal Handling Commands
20933 Signal handling commands are not implemented.
20935 @c @subheading -signal-handle
20937 @c @subheading -signal-list-handle-actions
20939 @c @subheading -signal-list-signal-types
20943 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20944 @node GDB/MI Target Manipulation
20945 @section @sc{gdb/mi} Target Manipulation Commands
20948 @subheading The @code{-target-attach} Command
20949 @findex -target-attach
20951 @subsubheading Synopsis
20954 -target-attach @var{pid} | @var{file}
20957 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
20959 @subsubheading @value{GDBN} command
20961 The corresponding @value{GDBN} command is @samp{attach}.
20963 @subsubheading Example
20967 @subheading The @code{-target-compare-sections} Command
20968 @findex -target-compare-sections
20970 @subsubheading Synopsis
20973 -target-compare-sections [ @var{section} ]
20976 Compare data of section @var{section} on target to the exec file.
20977 Without the argument, all sections are compared.
20979 @subsubheading @value{GDBN} Command
20981 The @value{GDBN} equivalent is @samp{compare-sections}.
20983 @subsubheading Example
20987 @subheading The @code{-target-detach} Command
20988 @findex -target-detach
20990 @subsubheading Synopsis
20996 Detach from the remote target which normally resumes its execution.
20999 @subsubheading @value{GDBN} command
21001 The corresponding @value{GDBN} command is @samp{detach}.
21003 @subsubheading Example
21013 @subheading The @code{-target-disconnect} Command
21014 @findex -target-disconnect
21016 @subsubheading Synopsis
21022 Disconnect from the remote target. There's no output and the target is
21023 generally not resumed.
21025 @subsubheading @value{GDBN} command
21027 The corresponding @value{GDBN} command is @samp{disconnect}.
21029 @subsubheading Example
21039 @subheading The @code{-target-download} Command
21040 @findex -target-download
21042 @subsubheading Synopsis
21048 Loads the executable onto the remote target.
21049 It prints out an update message every half second, which includes the fields:
21053 The name of the section.
21055 The size of what has been sent so far for that section.
21057 The size of the section.
21059 The total size of what was sent so far (the current and the previous sections).
21061 The size of the overall executable to download.
21065 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21066 @sc{gdb/mi} Output Syntax}).
21068 In addition, it prints the name and size of the sections, as they are
21069 downloaded. These messages include the following fields:
21073 The name of the section.
21075 The size of the section.
21077 The size of the overall executable to download.
21081 At the end, a summary is printed.
21083 @subsubheading @value{GDBN} Command
21085 The corresponding @value{GDBN} command is @samp{load}.
21087 @subsubheading Example
21089 Note: each status message appears on a single line. Here the messages
21090 have been broken down so that they can fit onto a page.
21095 +download,@{section=".text",section-size="6668",total-size="9880"@}
21096 +download,@{section=".text",section-sent="512",section-size="6668",
21097 total-sent="512",total-size="9880"@}
21098 +download,@{section=".text",section-sent="1024",section-size="6668",
21099 total-sent="1024",total-size="9880"@}
21100 +download,@{section=".text",section-sent="1536",section-size="6668",
21101 total-sent="1536",total-size="9880"@}
21102 +download,@{section=".text",section-sent="2048",section-size="6668",
21103 total-sent="2048",total-size="9880"@}
21104 +download,@{section=".text",section-sent="2560",section-size="6668",
21105 total-sent="2560",total-size="9880"@}
21106 +download,@{section=".text",section-sent="3072",section-size="6668",
21107 total-sent="3072",total-size="9880"@}
21108 +download,@{section=".text",section-sent="3584",section-size="6668",
21109 total-sent="3584",total-size="9880"@}
21110 +download,@{section=".text",section-sent="4096",section-size="6668",
21111 total-sent="4096",total-size="9880"@}
21112 +download,@{section=".text",section-sent="4608",section-size="6668",
21113 total-sent="4608",total-size="9880"@}
21114 +download,@{section=".text",section-sent="5120",section-size="6668",
21115 total-sent="5120",total-size="9880"@}
21116 +download,@{section=".text",section-sent="5632",section-size="6668",
21117 total-sent="5632",total-size="9880"@}
21118 +download,@{section=".text",section-sent="6144",section-size="6668",
21119 total-sent="6144",total-size="9880"@}
21120 +download,@{section=".text",section-sent="6656",section-size="6668",
21121 total-sent="6656",total-size="9880"@}
21122 +download,@{section=".init",section-size="28",total-size="9880"@}
21123 +download,@{section=".fini",section-size="28",total-size="9880"@}
21124 +download,@{section=".data",section-size="3156",total-size="9880"@}
21125 +download,@{section=".data",section-sent="512",section-size="3156",
21126 total-sent="7236",total-size="9880"@}
21127 +download,@{section=".data",section-sent="1024",section-size="3156",
21128 total-sent="7748",total-size="9880"@}
21129 +download,@{section=".data",section-sent="1536",section-size="3156",
21130 total-sent="8260",total-size="9880"@}
21131 +download,@{section=".data",section-sent="2048",section-size="3156",
21132 total-sent="8772",total-size="9880"@}
21133 +download,@{section=".data",section-sent="2560",section-size="3156",
21134 total-sent="9284",total-size="9880"@}
21135 +download,@{section=".data",section-sent="3072",section-size="3156",
21136 total-sent="9796",total-size="9880"@}
21137 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21143 @subheading The @code{-target-exec-status} Command
21144 @findex -target-exec-status
21146 @subsubheading Synopsis
21149 -target-exec-status
21152 Provide information on the state of the target (whether it is running or
21153 not, for instance).
21155 @subsubheading @value{GDBN} Command
21157 There's no equivalent @value{GDBN} command.
21159 @subsubheading Example
21163 @subheading The @code{-target-list-available-targets} Command
21164 @findex -target-list-available-targets
21166 @subsubheading Synopsis
21169 -target-list-available-targets
21172 List the possible targets to connect to.
21174 @subsubheading @value{GDBN} Command
21176 The corresponding @value{GDBN} command is @samp{help target}.
21178 @subsubheading Example
21182 @subheading The @code{-target-list-current-targets} Command
21183 @findex -target-list-current-targets
21185 @subsubheading Synopsis
21188 -target-list-current-targets
21191 Describe the current target.
21193 @subsubheading @value{GDBN} Command
21195 The corresponding information is printed by @samp{info file} (among
21198 @subsubheading Example
21202 @subheading The @code{-target-list-parameters} Command
21203 @findex -target-list-parameters
21205 @subsubheading Synopsis
21208 -target-list-parameters
21213 @subsubheading @value{GDBN} Command
21217 @subsubheading Example
21221 @subheading The @code{-target-select} Command
21222 @findex -target-select
21224 @subsubheading Synopsis
21227 -target-select @var{type} @var{parameters @dots{}}
21230 Connect @value{GDBN} to the remote target. This command takes two args:
21234 The type of target, for instance @samp{async}, @samp{remote}, etc.
21235 @item @var{parameters}
21236 Device names, host names and the like. @xref{Target Commands, ,
21237 Commands for managing targets}, for more details.
21240 The output is a connection notification, followed by the address at
21241 which the target program is, in the following form:
21244 ^connected,addr="@var{address}",func="@var{function name}",
21245 args=[@var{arg list}]
21248 @subsubheading @value{GDBN} Command
21250 The corresponding @value{GDBN} command is @samp{target}.
21252 @subsubheading Example
21256 -target-select async /dev/ttya
21257 ^connected,addr="0xfe00a300",func="??",args=[]
21261 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21262 @node GDB/MI Miscellaneous Commands
21263 @section Miscellaneous @sc{gdb/mi} Commands
21265 @c @subheading -gdb-complete
21267 @subheading The @code{-gdb-exit} Command
21270 @subsubheading Synopsis
21276 Exit @value{GDBN} immediately.
21278 @subsubheading @value{GDBN} Command
21280 Approximately corresponds to @samp{quit}.
21282 @subsubheading Example
21291 @subheading The @code{-exec-abort} Command
21292 @findex -exec-abort
21294 @subsubheading Synopsis
21300 Kill the inferior running program.
21302 @subsubheading @value{GDBN} Command
21304 The corresponding @value{GDBN} command is @samp{kill}.
21306 @subsubheading Example
21310 @subheading The @code{-gdb-set} Command
21313 @subsubheading Synopsis
21319 Set an internal @value{GDBN} variable.
21320 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21322 @subsubheading @value{GDBN} Command
21324 The corresponding @value{GDBN} command is @samp{set}.
21326 @subsubheading Example
21336 @subheading The @code{-gdb-show} Command
21339 @subsubheading Synopsis
21345 Show the current value of a @value{GDBN} variable.
21347 @subsubheading @value{GDBN} command
21349 The corresponding @value{GDBN} command is @samp{show}.
21351 @subsubheading Example
21360 @c @subheading -gdb-source
21363 @subheading The @code{-gdb-version} Command
21364 @findex -gdb-version
21366 @subsubheading Synopsis
21372 Show version information for @value{GDBN}. Used mostly in testing.
21374 @subsubheading @value{GDBN} Command
21376 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21377 default shows this information when you start an interactive session.
21379 @subsubheading Example
21381 @c This example modifies the actual output from GDB to avoid overfull
21387 ~Copyright 2000 Free Software Foundation, Inc.
21388 ~GDB is free software, covered by the GNU General Public License, and
21389 ~you are welcome to change it and/or distribute copies of it under
21390 ~ certain conditions.
21391 ~Type "show copying" to see the conditions.
21392 ~There is absolutely no warranty for GDB. Type "show warranty" for
21394 ~This GDB was configured as
21395 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21400 @subheading The @code{-interpreter-exec} Command
21401 @findex -interpreter-exec
21403 @subheading Synopsis
21406 -interpreter-exec @var{interpreter} @var{command}
21408 @anchor{-interpreter-exec}
21410 Execute the specified @var{command} in the given @var{interpreter}.
21412 @subheading @value{GDBN} Command
21414 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21416 @subheading Example
21420 -interpreter-exec console "break main"
21421 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21422 &"During symbol reading, bad structure-type format.\n"
21423 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21428 @subheading The @code{-inferior-tty-set} Command
21429 @findex -inferior-tty-set
21431 @subheading Synopsis
21434 -inferior-tty-set /dev/pts/1
21437 Set terminal for future runs of the program being debugged.
21439 @subheading @value{GDBN} Command
21441 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21443 @subheading Example
21447 -inferior-tty-set /dev/pts/1
21452 @subheading The @code{-inferior-tty-show} Command
21453 @findex -inferior-tty-show
21455 @subheading Synopsis
21461 Show terminal for future runs of program being debugged.
21463 @subheading @value{GDBN} Command
21465 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21467 @subheading Example
21471 -inferior-tty-set /dev/pts/1
21475 ^done,inferior_tty_terminal="/dev/pts/1"
21479 @subheading The @code{-enable-timings} Command
21480 @findex -enable-timings
21482 @subheading Synopsis
21485 -enable-timings [yes | no]
21488 Toggle the printing of the wallclock, user and system times for an MI
21489 command as a field in its output. This command is to help frontend
21490 developers optimize the performance of their code. No argument is
21491 equivalent to @samp{yes}.
21493 @subheading @value{GDBN} Command
21497 @subheading Example
21505 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21506 addr="0x080484ed",func="main",file="myprog.c",
21507 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
21508 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
21516 *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
21517 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
21518 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
21519 fullname="/home/nickrob/myprog.c",line="73"@}
21524 @chapter @value{GDBN} Annotations
21526 This chapter describes annotations in @value{GDBN}. Annotations were
21527 designed to interface @value{GDBN} to graphical user interfaces or other
21528 similar programs which want to interact with @value{GDBN} at a
21529 relatively high level.
21531 The annotation mechanism has largely been superseded by @sc{gdb/mi}
21535 This is Edition @value{EDITION}, @value{DATE}.
21539 * Annotations Overview:: What annotations are; the general syntax.
21540 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21541 * Errors:: Annotations for error messages.
21542 * Invalidation:: Some annotations describe things now invalid.
21543 * Annotations for Running::
21544 Whether the program is running, how it stopped, etc.
21545 * Source Annotations:: Annotations describing source code.
21548 @node Annotations Overview
21549 @section What is an Annotation?
21550 @cindex annotations
21552 Annotations start with a newline character, two @samp{control-z}
21553 characters, and the name of the annotation. If there is no additional
21554 information associated with this annotation, the name of the annotation
21555 is followed immediately by a newline. If there is additional
21556 information, the name of the annotation is followed by a space, the
21557 additional information, and a newline. The additional information
21558 cannot contain newline characters.
21560 Any output not beginning with a newline and two @samp{control-z}
21561 characters denotes literal output from @value{GDBN}. Currently there is
21562 no need for @value{GDBN} to output a newline followed by two
21563 @samp{control-z} characters, but if there was such a need, the
21564 annotations could be extended with an @samp{escape} annotation which
21565 means those three characters as output.
21567 The annotation @var{level}, which is specified using the
21568 @option{--annotate} command line option (@pxref{Mode Options}), controls
21569 how much information @value{GDBN} prints together with its prompt,
21570 values of expressions, source lines, and other types of output. Level 0
21571 is for no annotations, level 1 is for use when @value{GDBN} is run as a
21572 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21573 for programs that control @value{GDBN}, and level 2 annotations have
21574 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21575 Interface, annotate, GDB's Obsolete Annotations}).
21578 @kindex set annotate
21579 @item set annotate @var{level}
21580 The @value{GDBN} command @code{set annotate} sets the level of
21581 annotations to the specified @var{level}.
21583 @item show annotate
21584 @kindex show annotate
21585 Show the current annotation level.
21588 This chapter describes level 3 annotations.
21590 A simple example of starting up @value{GDBN} with annotations is:
21593 $ @kbd{gdb --annotate=3}
21595 Copyright 2003 Free Software Foundation, Inc.
21596 GDB is free software, covered by the GNU General Public License,
21597 and you are welcome to change it and/or distribute copies of it
21598 under certain conditions.
21599 Type "show copying" to see the conditions.
21600 There is absolutely no warranty for GDB. Type "show warranty"
21602 This GDB was configured as "i386-pc-linux-gnu"
21613 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21614 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21615 denotes a @samp{control-z} character) are annotations; the rest is
21616 output from @value{GDBN}.
21619 @section Annotation for @value{GDBN} Input
21621 @cindex annotations for prompts
21622 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21623 to know when to send output, when the output from a given command is
21626 Different kinds of input each have a different @dfn{input type}. Each
21627 input type has three annotations: a @code{pre-} annotation, which
21628 denotes the beginning of any prompt which is being output, a plain
21629 annotation, which denotes the end of the prompt, and then a @code{post-}
21630 annotation which denotes the end of any echo which may (or may not) be
21631 associated with the input. For example, the @code{prompt} input type
21632 features the following annotations:
21640 The input types are
21643 @findex pre-prompt annotation
21644 @findex prompt annotation
21645 @findex post-prompt annotation
21647 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21649 @findex pre-commands annotation
21650 @findex commands annotation
21651 @findex post-commands annotation
21653 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21654 command. The annotations are repeated for each command which is input.
21656 @findex pre-overload-choice annotation
21657 @findex overload-choice annotation
21658 @findex post-overload-choice annotation
21659 @item overload-choice
21660 When @value{GDBN} wants the user to select between various overloaded functions.
21662 @findex pre-query annotation
21663 @findex query annotation
21664 @findex post-query annotation
21666 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21668 @findex pre-prompt-for-continue annotation
21669 @findex prompt-for-continue annotation
21670 @findex post-prompt-for-continue annotation
21671 @item prompt-for-continue
21672 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21673 expect this to work well; instead use @code{set height 0} to disable
21674 prompting. This is because the counting of lines is buggy in the
21675 presence of annotations.
21680 @cindex annotations for errors, warnings and interrupts
21682 @findex quit annotation
21687 This annotation occurs right before @value{GDBN} responds to an interrupt.
21689 @findex error annotation
21694 This annotation occurs right before @value{GDBN} responds to an error.
21696 Quit and error annotations indicate that any annotations which @value{GDBN} was
21697 in the middle of may end abruptly. For example, if a
21698 @code{value-history-begin} annotation is followed by a @code{error}, one
21699 cannot expect to receive the matching @code{value-history-end}. One
21700 cannot expect not to receive it either, however; an error annotation
21701 does not necessarily mean that @value{GDBN} is immediately returning all the way
21704 @findex error-begin annotation
21705 A quit or error annotation may be preceded by
21711 Any output between that and the quit or error annotation is the error
21714 Warning messages are not yet annotated.
21715 @c If we want to change that, need to fix warning(), type_error(),
21716 @c range_error(), and possibly other places.
21719 @section Invalidation Notices
21721 @cindex annotations for invalidation messages
21722 The following annotations say that certain pieces of state may have
21726 @findex frames-invalid annotation
21727 @item ^Z^Zframes-invalid
21729 The frames (for example, output from the @code{backtrace} command) may
21732 @findex breakpoints-invalid annotation
21733 @item ^Z^Zbreakpoints-invalid
21735 The breakpoints may have changed. For example, the user just added or
21736 deleted a breakpoint.
21739 @node Annotations for Running
21740 @section Running the Program
21741 @cindex annotations for running programs
21743 @findex starting annotation
21744 @findex stopping annotation
21745 When the program starts executing due to a @value{GDBN} command such as
21746 @code{step} or @code{continue},
21752 is output. When the program stops,
21758 is output. Before the @code{stopped} annotation, a variety of
21759 annotations describe how the program stopped.
21762 @findex exited annotation
21763 @item ^Z^Zexited @var{exit-status}
21764 The program exited, and @var{exit-status} is the exit status (zero for
21765 successful exit, otherwise nonzero).
21767 @findex signalled annotation
21768 @findex signal-name annotation
21769 @findex signal-name-end annotation
21770 @findex signal-string annotation
21771 @findex signal-string-end annotation
21772 @item ^Z^Zsignalled
21773 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21774 annotation continues:
21780 ^Z^Zsignal-name-end
21784 ^Z^Zsignal-string-end
21789 where @var{name} is the name of the signal, such as @code{SIGILL} or
21790 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21791 as @code{Illegal Instruction} or @code{Segmentation fault}.
21792 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21793 user's benefit and have no particular format.
21795 @findex signal annotation
21797 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21798 just saying that the program received the signal, not that it was
21799 terminated with it.
21801 @findex breakpoint annotation
21802 @item ^Z^Zbreakpoint @var{number}
21803 The program hit breakpoint number @var{number}.
21805 @findex watchpoint annotation
21806 @item ^Z^Zwatchpoint @var{number}
21807 The program hit watchpoint number @var{number}.
21810 @node Source Annotations
21811 @section Displaying Source
21812 @cindex annotations for source display
21814 @findex source annotation
21815 The following annotation is used instead of displaying source code:
21818 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21821 where @var{filename} is an absolute file name indicating which source
21822 file, @var{line} is the line number within that file (where 1 is the
21823 first line in the file), @var{character} is the character position
21824 within the file (where 0 is the first character in the file) (for most
21825 debug formats this will necessarily point to the beginning of a line),
21826 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21827 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21828 @var{addr} is the address in the target program associated with the
21829 source which is being displayed. @var{addr} is in the form @samp{0x}
21830 followed by one or more lowercase hex digits (note that this does not
21831 depend on the language).
21834 @chapter Reporting Bugs in @value{GDBN}
21835 @cindex bugs in @value{GDBN}
21836 @cindex reporting bugs in @value{GDBN}
21838 Your bug reports play an essential role in making @value{GDBN} reliable.
21840 Reporting a bug may help you by bringing a solution to your problem, or it
21841 may not. But in any case the principal function of a bug report is to help
21842 the entire community by making the next version of @value{GDBN} work better. Bug
21843 reports are your contribution to the maintenance of @value{GDBN}.
21845 In order for a bug report to serve its purpose, you must include the
21846 information that enables us to fix the bug.
21849 * Bug Criteria:: Have you found a bug?
21850 * Bug Reporting:: How to report bugs
21854 @section Have you found a bug?
21855 @cindex bug criteria
21857 If you are not sure whether you have found a bug, here are some guidelines:
21860 @cindex fatal signal
21861 @cindex debugger crash
21862 @cindex crash of debugger
21864 If the debugger gets a fatal signal, for any input whatever, that is a
21865 @value{GDBN} bug. Reliable debuggers never crash.
21867 @cindex error on valid input
21869 If @value{GDBN} produces an error message for valid input, that is a
21870 bug. (Note that if you're cross debugging, the problem may also be
21871 somewhere in the connection to the target.)
21873 @cindex invalid input
21875 If @value{GDBN} does not produce an error message for invalid input,
21876 that is a bug. However, you should note that your idea of
21877 ``invalid input'' might be our idea of ``an extension'' or ``support
21878 for traditional practice''.
21881 If you are an experienced user of debugging tools, your suggestions
21882 for improvement of @value{GDBN} are welcome in any case.
21885 @node Bug Reporting
21886 @section How to report bugs
21887 @cindex bug reports
21888 @cindex @value{GDBN} bugs, reporting
21890 A number of companies and individuals offer support for @sc{gnu} products.
21891 If you obtained @value{GDBN} from a support organization, we recommend you
21892 contact that organization first.
21894 You can find contact information for many support companies and
21895 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21897 @c should add a web page ref...
21899 In any event, we also recommend that you submit bug reports for
21900 @value{GDBN}. The preferred method is to submit them directly using
21901 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21902 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21905 @strong{Do not send bug reports to @samp{info-gdb}, or to
21906 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21907 not want to receive bug reports. Those that do have arranged to receive
21910 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21911 serves as a repeater. The mailing list and the newsgroup carry exactly
21912 the same messages. Often people think of posting bug reports to the
21913 newsgroup instead of mailing them. This appears to work, but it has one
21914 problem which can be crucial: a newsgroup posting often lacks a mail
21915 path back to the sender. Thus, if we need to ask for more information,
21916 we may be unable to reach you. For this reason, it is better to send
21917 bug reports to the mailing list.
21919 The fundamental principle of reporting bugs usefully is this:
21920 @strong{report all the facts}. If you are not sure whether to state a
21921 fact or leave it out, state it!
21923 Often people omit facts because they think they know what causes the
21924 problem and assume that some details do not matter. Thus, you might
21925 assume that the name of the variable you use in an example does not matter.
21926 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21927 stray memory reference which happens to fetch from the location where that
21928 name is stored in memory; perhaps, if the name were different, the contents
21929 of that location would fool the debugger into doing the right thing despite
21930 the bug. Play it safe and give a specific, complete example. That is the
21931 easiest thing for you to do, and the most helpful.
21933 Keep in mind that the purpose of a bug report is to enable us to fix the
21934 bug. It may be that the bug has been reported previously, but neither
21935 you nor we can know that unless your bug report is complete and
21938 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21939 bell?'' Those bug reports are useless, and we urge everyone to
21940 @emph{refuse to respond to them} except to chide the sender to report
21943 To enable us to fix the bug, you should include all these things:
21947 The version of @value{GDBN}. @value{GDBN} announces it if you start
21948 with no arguments; you can also print it at any time using @code{show
21951 Without this, we will not know whether there is any point in looking for
21952 the bug in the current version of @value{GDBN}.
21955 The type of machine you are using, and the operating system name and
21959 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21960 ``@value{GCC}--2.8.1''.
21963 What compiler (and its version) was used to compile the program you are
21964 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21965 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
21966 to get this information; for other compilers, see the documentation for
21970 The command arguments you gave the compiler to compile your example and
21971 observe the bug. For example, did you use @samp{-O}? To guarantee
21972 you will not omit something important, list them all. A copy of the
21973 Makefile (or the output from make) is sufficient.
21975 If we were to try to guess the arguments, we would probably guess wrong
21976 and then we might not encounter the bug.
21979 A complete input script, and all necessary source files, that will
21983 A description of what behavior you observe that you believe is
21984 incorrect. For example, ``It gets a fatal signal.''
21986 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21987 will certainly notice it. But if the bug is incorrect output, we might
21988 not notice unless it is glaringly wrong. You might as well not give us
21989 a chance to make a mistake.
21991 Even if the problem you experience is a fatal signal, you should still
21992 say so explicitly. Suppose something strange is going on, such as, your
21993 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21994 the C library on your system. (This has happened!) Your copy might
21995 crash and ours would not. If you told us to expect a crash, then when
21996 ours fails to crash, we would know that the bug was not happening for
21997 us. If you had not told us to expect a crash, then we would not be able
21998 to draw any conclusion from our observations.
22001 @cindex recording a session script
22002 To collect all this information, you can use a session recording program
22003 such as @command{script}, which is available on many Unix systems.
22004 Just run your @value{GDBN} session inside @command{script} and then
22005 include the @file{typescript} file with your bug report.
22007 Another way to record a @value{GDBN} session is to run @value{GDBN}
22008 inside Emacs and then save the entire buffer to a file.
22011 If you wish to suggest changes to the @value{GDBN} source, send us context
22012 diffs. If you even discuss something in the @value{GDBN} source, refer to
22013 it by context, not by line number.
22015 The line numbers in our development sources will not match those in your
22016 sources. Your line numbers would convey no useful information to us.
22020 Here are some things that are not necessary:
22024 A description of the envelope of the bug.
22026 Often people who encounter a bug spend a lot of time investigating
22027 which changes to the input file will make the bug go away and which
22028 changes will not affect it.
22030 This is often time consuming and not very useful, because the way we
22031 will find the bug is by running a single example under the debugger
22032 with breakpoints, not by pure deduction from a series of examples.
22033 We recommend that you save your time for something else.
22035 Of course, if you can find a simpler example to report @emph{instead}
22036 of the original one, that is a convenience for us. Errors in the
22037 output will be easier to spot, running under the debugger will take
22038 less time, and so on.
22040 However, simplification is not vital; if you do not want to do this,
22041 report the bug anyway and send us the entire test case you used.
22044 A patch for the bug.
22046 A patch for the bug does help us if it is a good one. But do not omit
22047 the necessary information, such as the test case, on the assumption that
22048 a patch is all we need. We might see problems with your patch and decide
22049 to fix the problem another way, or we might not understand it at all.
22051 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22052 construct an example that will make the program follow a certain path
22053 through the code. If you do not send us the example, we will not be able
22054 to construct one, so we will not be able to verify that the bug is fixed.
22056 And if we cannot understand what bug you are trying to fix, or why your
22057 patch should be an improvement, we will not install it. A test case will
22058 help us to understand.
22061 A guess about what the bug is or what it depends on.
22063 Such guesses are usually wrong. Even we cannot guess right about such
22064 things without first using the debugger to find the facts.
22067 @c The readline documentation is distributed with the readline code
22068 @c and consists of the two following files:
22070 @c inc-hist.texinfo
22071 @c Use -I with makeinfo to point to the appropriate directory,
22072 @c environment var TEXINPUTS with TeX.
22073 @include rluser.texi
22074 @include inc-hist.texinfo
22077 @node Formatting Documentation
22078 @appendix Formatting Documentation
22080 @cindex @value{GDBN} reference card
22081 @cindex reference card
22082 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22083 for printing with PostScript or Ghostscript, in the @file{gdb}
22084 subdirectory of the main source directory@footnote{In
22085 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22086 release.}. If you can use PostScript or Ghostscript with your printer,
22087 you can print the reference card immediately with @file{refcard.ps}.
22089 The release also includes the source for the reference card. You
22090 can format it, using @TeX{}, by typing:
22096 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22097 mode on US ``letter'' size paper;
22098 that is, on a sheet 11 inches wide by 8.5 inches
22099 high. You will need to specify this form of printing as an option to
22100 your @sc{dvi} output program.
22102 @cindex documentation
22104 All the documentation for @value{GDBN} comes as part of the machine-readable
22105 distribution. The documentation is written in Texinfo format, which is
22106 a documentation system that uses a single source file to produce both
22107 on-line information and a printed manual. You can use one of the Info
22108 formatting commands to create the on-line version of the documentation
22109 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22111 @value{GDBN} includes an already formatted copy of the on-line Info
22112 version of this manual in the @file{gdb} subdirectory. The main Info
22113 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22114 subordinate files matching @samp{gdb.info*} in the same directory. If
22115 necessary, you can print out these files, or read them with any editor;
22116 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22117 Emacs or the standalone @code{info} program, available as part of the
22118 @sc{gnu} Texinfo distribution.
22120 If you want to format these Info files yourself, you need one of the
22121 Info formatting programs, such as @code{texinfo-format-buffer} or
22124 If you have @code{makeinfo} installed, and are in the top level
22125 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22126 version @value{GDBVN}), you can make the Info file by typing:
22133 If you want to typeset and print copies of this manual, you need @TeX{},
22134 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22135 Texinfo definitions file.
22137 @TeX{} is a typesetting program; it does not print files directly, but
22138 produces output files called @sc{dvi} files. To print a typeset
22139 document, you need a program to print @sc{dvi} files. If your system
22140 has @TeX{} installed, chances are it has such a program. The precise
22141 command to use depends on your system; @kbd{lpr -d} is common; another
22142 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22143 require a file name without any extension or a @samp{.dvi} extension.
22145 @TeX{} also requires a macro definitions file called
22146 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22147 written in Texinfo format. On its own, @TeX{} cannot either read or
22148 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22149 and is located in the @file{gdb-@var{version-number}/texinfo}
22152 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22153 typeset and print this manual. First switch to the @file{gdb}
22154 subdirectory of the main source directory (for example, to
22155 @file{gdb-@value{GDBVN}/gdb}) and type:
22161 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22163 @node Installing GDB
22164 @appendix Installing @value{GDBN}
22165 @cindex installation
22168 * Requirements:: Requirements for building @value{GDBN}
22169 * Running Configure:: Invoking the @value{GDBN} @code{configure} script
22170 * Separate Objdir:: Compiling @value{GDBN} in another directory
22171 * Config Names:: Specifying names for hosts and targets
22172 * Configure Options:: Summary of options for configure
22176 @section Requirements for building @value{GDBN}
22177 @cindex building @value{GDBN}, requirements for
22179 Building @value{GDBN} requires various tools and packages to be available.
22180 Other packages will be used only if they are found.
22182 @heading Tools/packages necessary for building @value{GDBN}
22184 @item ISO C90 compiler
22185 @value{GDBN} is written in ISO C90. It should be buildable with any
22186 working C90 compiler, e.g.@: GCC.
22190 @heading Tools/packages optional for building @value{GDBN}
22194 @value{GDBN} can use the Expat XML parsing library. This library may be
22195 included with your operating system distribution; if it is not, you
22196 can get the latest version from @url{http://expat.sourceforge.net}.
22197 The @code{configure} script will search for this library in several
22198 standard locations; if it is installed in an unusual path, you can
22199 use the @option{--with-libexpat-prefix} option to specify its location.
22201 Expat is used for remote protocol memory maps (@pxref{Memory map format})
22202 and for target descriptions (@pxref{Target Descriptions}).
22206 @node Running Configure
22207 @section Invoking the @value{GDBN} @code{configure} script
22208 @cindex configuring @value{GDBN}
22209 @value{GDBN} comes with a @code{configure} script that automates the process
22210 of preparing @value{GDBN} for installation; you can then use @code{make} to
22211 build the @code{gdb} program.
22213 @c irrelevant in info file; it's as current as the code it lives with.
22214 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22215 look at the @file{README} file in the sources; we may have improved the
22216 installation procedures since publishing this manual.}
22219 The @value{GDBN} distribution includes all the source code you need for
22220 @value{GDBN} in a single directory, whose name is usually composed by
22221 appending the version number to @samp{gdb}.
22223 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22224 @file{gdb-@value{GDBVN}} directory. That directory contains:
22227 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22228 script for configuring @value{GDBN} and all its supporting libraries
22230 @item gdb-@value{GDBVN}/gdb
22231 the source specific to @value{GDBN} itself
22233 @item gdb-@value{GDBVN}/bfd
22234 source for the Binary File Descriptor library
22236 @item gdb-@value{GDBVN}/include
22237 @sc{gnu} include files
22239 @item gdb-@value{GDBVN}/libiberty
22240 source for the @samp{-liberty} free software library
22242 @item gdb-@value{GDBVN}/opcodes
22243 source for the library of opcode tables and disassemblers
22245 @item gdb-@value{GDBVN}/readline
22246 source for the @sc{gnu} command-line interface
22248 @item gdb-@value{GDBVN}/glob
22249 source for the @sc{gnu} filename pattern-matching subroutine
22251 @item gdb-@value{GDBVN}/mmalloc
22252 source for the @sc{gnu} memory-mapped malloc package
22255 The simplest way to configure and build @value{GDBN} is to run @code{configure}
22256 from the @file{gdb-@var{version-number}} source directory, which in
22257 this example is the @file{gdb-@value{GDBVN}} directory.
22259 First switch to the @file{gdb-@var{version-number}} source directory
22260 if you are not already in it; then run @code{configure}. Pass the
22261 identifier for the platform on which @value{GDBN} will run as an
22267 cd gdb-@value{GDBVN}
22268 ./configure @var{host}
22273 where @var{host} is an identifier such as @samp{sun4} or
22274 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22275 (You can often leave off @var{host}; @code{configure} tries to guess the
22276 correct value by examining your system.)
22278 Running @samp{configure @var{host}} and then running @code{make} builds the
22279 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22280 libraries, then @code{gdb} itself. The configured source files, and the
22281 binaries, are left in the corresponding source directories.
22284 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22285 system does not recognize this automatically when you run a different
22286 shell, you may need to run @code{sh} on it explicitly:
22289 sh configure @var{host}
22292 If you run @code{configure} from a directory that contains source
22293 directories for multiple libraries or programs, such as the
22294 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
22295 creates configuration files for every directory level underneath (unless
22296 you tell it not to, with the @samp{--norecursion} option).
22298 You should run the @code{configure} script from the top directory in the
22299 source tree, the @file{gdb-@var{version-number}} directory. If you run
22300 @code{configure} from one of the subdirectories, you will configure only
22301 that subdirectory. That is usually not what you want. In particular,
22302 if you run the first @code{configure} from the @file{gdb} subdirectory
22303 of the @file{gdb-@var{version-number}} directory, you will omit the
22304 configuration of @file{bfd}, @file{readline}, and other sibling
22305 directories of the @file{gdb} subdirectory. This leads to build errors
22306 about missing include files such as @file{bfd/bfd.h}.
22308 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22309 However, you should make sure that the shell on your path (named by
22310 the @samp{SHELL} environment variable) is publicly readable. Remember
22311 that @value{GDBN} uses the shell to start your program---some systems refuse to
22312 let @value{GDBN} debug child processes whose programs are not readable.
22314 @node Separate Objdir
22315 @section Compiling @value{GDBN} in another directory
22317 If you want to run @value{GDBN} versions for several host or target machines,
22318 you need a different @code{gdb} compiled for each combination of
22319 host and target. @code{configure} is designed to make this easy by
22320 allowing you to generate each configuration in a separate subdirectory,
22321 rather than in the source directory. If your @code{make} program
22322 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22323 @code{make} in each of these directories builds the @code{gdb}
22324 program specified there.
22326 To build @code{gdb} in a separate directory, run @code{configure}
22327 with the @samp{--srcdir} option to specify where to find the source.
22328 (You also need to specify a path to find @code{configure}
22329 itself from your working directory. If the path to @code{configure}
22330 would be the same as the argument to @samp{--srcdir}, you can leave out
22331 the @samp{--srcdir} option; it is assumed.)
22333 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22334 separate directory for a Sun 4 like this:
22338 cd gdb-@value{GDBVN}
22341 ../gdb-@value{GDBVN}/configure sun4
22346 When @code{configure} builds a configuration using a remote source
22347 directory, it creates a tree for the binaries with the same structure
22348 (and using the same names) as the tree under the source directory. In
22349 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22350 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22351 @file{gdb-sun4/gdb}.
22353 Make sure that your path to the @file{configure} script has just one
22354 instance of @file{gdb} in it. If your path to @file{configure} looks
22355 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22356 one subdirectory of @value{GDBN}, not the whole package. This leads to
22357 build errors about missing include files such as @file{bfd/bfd.h}.
22359 One popular reason to build several @value{GDBN} configurations in separate
22360 directories is to configure @value{GDBN} for cross-compiling (where
22361 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22362 programs that run on another machine---the @dfn{target}).
22363 You specify a cross-debugging target by
22364 giving the @samp{--target=@var{target}} option to @code{configure}.
22366 When you run @code{make} to build a program or library, you must run
22367 it in a configured directory---whatever directory you were in when you
22368 called @code{configure} (or one of its subdirectories).
22370 The @code{Makefile} that @code{configure} generates in each source
22371 directory also runs recursively. If you type @code{make} in a source
22372 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22373 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22374 will build all the required libraries, and then build GDB.
22376 When you have multiple hosts or targets configured in separate
22377 directories, you can run @code{make} on them in parallel (for example,
22378 if they are NFS-mounted on each of the hosts); they will not interfere
22382 @section Specifying names for hosts and targets
22384 The specifications used for hosts and targets in the @code{configure}
22385 script are based on a three-part naming scheme, but some short predefined
22386 aliases are also supported. The full naming scheme encodes three pieces
22387 of information in the following pattern:
22390 @var{architecture}-@var{vendor}-@var{os}
22393 For example, you can use the alias @code{sun4} as a @var{host} argument,
22394 or as the value for @var{target} in a @code{--target=@var{target}}
22395 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22397 The @code{configure} script accompanying @value{GDBN} does not provide
22398 any query facility to list all supported host and target names or
22399 aliases. @code{configure} calls the Bourne shell script
22400 @code{config.sub} to map abbreviations to full names; you can read the
22401 script, if you wish, or you can use it to test your guesses on
22402 abbreviations---for example:
22405 % sh config.sub i386-linux
22407 % sh config.sub alpha-linux
22408 alpha-unknown-linux-gnu
22409 % sh config.sub hp9k700
22411 % sh config.sub sun4
22412 sparc-sun-sunos4.1.1
22413 % sh config.sub sun3
22414 m68k-sun-sunos4.1.1
22415 % sh config.sub i986v
22416 Invalid configuration `i986v': machine `i986v' not recognized
22420 @code{config.sub} is also distributed in the @value{GDBN} source
22421 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22423 @node Configure Options
22424 @section @code{configure} options
22426 Here is a summary of the @code{configure} options and arguments that
22427 are most often useful for building @value{GDBN}. @code{configure} also has
22428 several other options not listed here. @inforef{What Configure
22429 Does,,configure.info}, for a full explanation of @code{configure}.
22432 configure @r{[}--help@r{]}
22433 @r{[}--prefix=@var{dir}@r{]}
22434 @r{[}--exec-prefix=@var{dir}@r{]}
22435 @r{[}--srcdir=@var{dirname}@r{]}
22436 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22437 @r{[}--target=@var{target}@r{]}
22442 You may introduce options with a single @samp{-} rather than
22443 @samp{--} if you prefer; but you may abbreviate option names if you use
22448 Display a quick summary of how to invoke @code{configure}.
22450 @item --prefix=@var{dir}
22451 Configure the source to install programs and files under directory
22454 @item --exec-prefix=@var{dir}
22455 Configure the source to install programs under directory
22458 @c avoid splitting the warning from the explanation:
22460 @item --srcdir=@var{dirname}
22461 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22462 @code{make} that implements the @code{VPATH} feature.}@*
22463 Use this option to make configurations in directories separate from the
22464 @value{GDBN} source directories. Among other things, you can use this to
22465 build (or maintain) several configurations simultaneously, in separate
22466 directories. @code{configure} writes configuration specific files in
22467 the current directory, but arranges for them to use the source in the
22468 directory @var{dirname}. @code{configure} creates directories under
22469 the working directory in parallel to the source directories below
22472 @item --norecursion
22473 Configure only the directory level where @code{configure} is executed; do not
22474 propagate configuration to subdirectories.
22476 @item --target=@var{target}
22477 Configure @value{GDBN} for cross-debugging programs running on the specified
22478 @var{target}. Without this option, @value{GDBN} is configured to debug
22479 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22481 There is no convenient way to generate a list of all available targets.
22483 @item @var{host} @dots{}
22484 Configure @value{GDBN} to run on the specified @var{host}.
22486 There is no convenient way to generate a list of all available hosts.
22489 There are many other options available as well, but they are generally
22490 needed for special purposes only.
22492 @node Maintenance Commands
22493 @appendix Maintenance Commands
22494 @cindex maintenance commands
22495 @cindex internal commands
22497 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22498 includes a number of commands intended for @value{GDBN} developers,
22499 that are not documented elsewhere in this manual. These commands are
22500 provided here for reference. (For commands that turn on debugging
22501 messages, see @ref{Debugging Output}.)
22504 @kindex maint agent
22505 @item maint agent @var{expression}
22506 Translate the given @var{expression} into remote agent bytecodes.
22507 This command is useful for debugging the Agent Expression mechanism
22508 (@pxref{Agent Expressions}).
22510 @kindex maint info breakpoints
22511 @item @anchor{maint info breakpoints}maint info breakpoints
22512 Using the same format as @samp{info breakpoints}, display both the
22513 breakpoints you've set explicitly, and those @value{GDBN} is using for
22514 internal purposes. Internal breakpoints are shown with negative
22515 breakpoint numbers. The type column identifies what kind of breakpoint
22520 Normal, explicitly set breakpoint.
22523 Normal, explicitly set watchpoint.
22526 Internal breakpoint, used to handle correctly stepping through
22527 @code{longjmp} calls.
22529 @item longjmp resume
22530 Internal breakpoint at the target of a @code{longjmp}.
22533 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22536 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22539 Shared library events.
22543 @kindex maint check-symtabs
22544 @item maint check-symtabs
22545 Check the consistency of psymtabs and symtabs.
22547 @kindex maint cplus first_component
22548 @item maint cplus first_component @var{name}
22549 Print the first C@t{++} class/namespace component of @var{name}.
22551 @kindex maint cplus namespace
22552 @item maint cplus namespace
22553 Print the list of possible C@t{++} namespaces.
22555 @kindex maint demangle
22556 @item maint demangle @var{name}
22557 Demangle a C@t{++} or Objective-C mangled @var{name}.
22559 @kindex maint deprecate
22560 @kindex maint undeprecate
22561 @cindex deprecated commands
22562 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22563 @itemx maint undeprecate @var{command}
22564 Deprecate or undeprecate the named @var{command}. Deprecated commands
22565 cause @value{GDBN} to issue a warning when you use them. The optional
22566 argument @var{replacement} says which newer command should be used in
22567 favor of the deprecated one; if it is given, @value{GDBN} will mention
22568 the replacement as part of the warning.
22570 @kindex maint dump-me
22571 @item maint dump-me
22572 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22573 Cause a fatal signal in the debugger and force it to dump its core.
22574 This is supported only on systems which support aborting a program
22575 with the @code{SIGQUIT} signal.
22577 @kindex maint internal-error
22578 @kindex maint internal-warning
22579 @item maint internal-error @r{[}@var{message-text}@r{]}
22580 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22581 Cause @value{GDBN} to call the internal function @code{internal_error}
22582 or @code{internal_warning} and hence behave as though an internal error
22583 or internal warning has been detected. In addition to reporting the
22584 internal problem, these functions give the user the opportunity to
22585 either quit @value{GDBN} or create a core file of the current
22586 @value{GDBN} session.
22588 These commands take an optional parameter @var{message-text} that is
22589 used as the text of the error or warning message.
22591 Here's an example of using @code{internal-error}:
22594 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22595 @dots{}/maint.c:121: internal-error: testing, 1, 2
22596 A problem internal to GDB has been detected. Further
22597 debugging may prove unreliable.
22598 Quit this debugging session? (y or n) @kbd{n}
22599 Create a core file? (y or n) @kbd{n}
22603 @kindex maint packet
22604 @item maint packet @var{text}
22605 If @value{GDBN} is talking to an inferior via the serial protocol,
22606 then this command sends the string @var{text} to the inferior, and
22607 displays the response packet. @value{GDBN} supplies the initial
22608 @samp{$} character, the terminating @samp{#} character, and the
22611 @kindex maint print architecture
22612 @item maint print architecture @r{[}@var{file}@r{]}
22613 Print the entire architecture configuration. The optional argument
22614 @var{file} names the file where the output goes.
22616 @kindex maint print dummy-frames
22617 @item maint print dummy-frames
22618 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22621 (@value{GDBP}) @kbd{b add}
22623 (@value{GDBP}) @kbd{print add(2,3)}
22624 Breakpoint 2, add (a=2, b=3) at @dots{}
22626 The program being debugged stopped while in a function called from GDB.
22628 (@value{GDBP}) @kbd{maint print dummy-frames}
22629 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22630 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22631 call_lo=0x01014000 call_hi=0x01014001
22635 Takes an optional file parameter.
22637 @kindex maint print registers
22638 @kindex maint print raw-registers
22639 @kindex maint print cooked-registers
22640 @kindex maint print register-groups
22641 @item maint print registers @r{[}@var{file}@r{]}
22642 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22643 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22644 @itemx maint print register-groups @r{[}@var{file}@r{]}
22645 Print @value{GDBN}'s internal register data structures.
22647 The command @code{maint print raw-registers} includes the contents of
22648 the raw register cache; the command @code{maint print cooked-registers}
22649 includes the (cooked) value of all registers; and the command
22650 @code{maint print register-groups} includes the groups that each
22651 register is a member of. @xref{Registers,, Registers, gdbint,
22652 @value{GDBN} Internals}.
22654 These commands take an optional parameter, a file name to which to
22655 write the information.
22657 @kindex maint print reggroups
22658 @item maint print reggroups @r{[}@var{file}@r{]}
22659 Print @value{GDBN}'s internal register group data structures. The
22660 optional argument @var{file} tells to what file to write the
22663 The register groups info looks like this:
22666 (@value{GDBP}) @kbd{maint print reggroups}
22679 This command forces @value{GDBN} to flush its internal register cache.
22681 @kindex maint print objfiles
22682 @cindex info for known object files
22683 @item maint print objfiles
22684 Print a dump of all known object files. For each object file, this
22685 command prints its name, address in memory, and all of its psymtabs
22688 @kindex maint print statistics
22689 @cindex bcache statistics
22690 @item maint print statistics
22691 This command prints, for each object file in the program, various data
22692 about that object file followed by the byte cache (@dfn{bcache})
22693 statistics for the object file. The objfile data includes the number
22694 of minimal, partial, full, and stabs symbols, the number of types
22695 defined by the objfile, the number of as yet unexpanded psym tables,
22696 the number of line tables and string tables, and the amount of memory
22697 used by the various tables. The bcache statistics include the counts,
22698 sizes, and counts of duplicates of all and unique objects, max,
22699 average, and median entry size, total memory used and its overhead and
22700 savings, and various measures of the hash table size and chain
22703 @kindex maint print target-stack
22704 @cindex target stack description
22705 @item maint print target-stack
22706 A @dfn{target} is an interface between the debugger and a particular
22707 kind of file or process. Targets can be stacked in @dfn{strata},
22708 so that more than one target can potentially respond to a request.
22709 In particular, memory accesses will walk down the stack of targets
22710 until they find a target that is interested in handling that particular
22713 This command prints a short description of each layer that was pushed on
22714 the @dfn{target stack}, starting from the top layer down to the bottom one.
22716 @kindex maint print type
22717 @cindex type chain of a data type
22718 @item maint print type @var{expr}
22719 Print the type chain for a type specified by @var{expr}. The argument
22720 can be either a type name or a symbol. If it is a symbol, the type of
22721 that symbol is described. The type chain produced by this command is
22722 a recursive definition of the data type as stored in @value{GDBN}'s
22723 data structures, including its flags and contained types.
22725 @kindex maint set dwarf2 max-cache-age
22726 @kindex maint show dwarf2 max-cache-age
22727 @item maint set dwarf2 max-cache-age
22728 @itemx maint show dwarf2 max-cache-age
22729 Control the DWARF 2 compilation unit cache.
22731 @cindex DWARF 2 compilation units cache
22732 In object files with inter-compilation-unit references, such as those
22733 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22734 reader needs to frequently refer to previously read compilation units.
22735 This setting controls how long a compilation unit will remain in the
22736 cache if it is not referenced. A higher limit means that cached
22737 compilation units will be stored in memory longer, and more total
22738 memory will be used. Setting it to zero disables caching, which will
22739 slow down @value{GDBN} startup, but reduce memory consumption.
22741 @kindex maint set profile
22742 @kindex maint show profile
22743 @cindex profiling GDB
22744 @item maint set profile
22745 @itemx maint show profile
22746 Control profiling of @value{GDBN}.
22748 Profiling will be disabled until you use the @samp{maint set profile}
22749 command to enable it. When you enable profiling, the system will begin
22750 collecting timing and execution count data; when you disable profiling or
22751 exit @value{GDBN}, the results will be written to a log file. Remember that
22752 if you use profiling, @value{GDBN} will overwrite the profiling log file
22753 (often called @file{gmon.out}). If you have a record of important profiling
22754 data in a @file{gmon.out} file, be sure to move it to a safe location.
22756 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
22757 compiled with the @samp{-pg} compiler option.
22759 @kindex maint show-debug-regs
22760 @cindex x86 hardware debug registers
22761 @item maint show-debug-regs
22762 Control whether to show variables that mirror the x86 hardware debug
22763 registers. Use @code{ON} to enable, @code{OFF} to disable. If
22764 enabled, the debug registers values are shown when @value{GDBN} inserts or
22765 removes a hardware breakpoint or watchpoint, and when the inferior
22766 triggers a hardware-assisted breakpoint or watchpoint.
22768 @kindex maint space
22769 @cindex memory used by commands
22771 Control whether to display memory usage for each command. If set to a
22772 nonzero value, @value{GDBN} will display how much memory each command
22773 took, following the command's own output. This can also be requested
22774 by invoking @value{GDBN} with the @option{--statistics} command-line
22775 switch (@pxref{Mode Options}).
22778 @cindex time of command execution
22780 Control whether to display the execution time for each command. If
22781 set to a nonzero value, @value{GDBN} will display how much time it
22782 took to execute each command, following the command's own output.
22783 This can also be requested by invoking @value{GDBN} with the
22784 @option{--statistics} command-line switch (@pxref{Mode Options}).
22786 @kindex maint translate-address
22787 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22788 Find the symbol stored at the location specified by the address
22789 @var{addr} and an optional section name @var{section}. If found,
22790 @value{GDBN} prints the name of the closest symbol and an offset from
22791 the symbol's location to the specified address. This is similar to
22792 the @code{info address} command (@pxref{Symbols}), except that this
22793 command also allows to find symbols in other sections.
22797 The following command is useful for non-interactive invocations of
22798 @value{GDBN}, such as in the test suite.
22801 @item set watchdog @var{nsec}
22802 @kindex set watchdog
22803 @cindex watchdog timer
22804 @cindex timeout for commands
22805 Set the maximum number of seconds @value{GDBN} will wait for the
22806 target operation to finish. If this time expires, @value{GDBN}
22807 reports and error and the command is aborted.
22809 @item show watchdog
22810 Show the current setting of the target wait timeout.
22813 @node Remote Protocol
22814 @appendix @value{GDBN} Remote Serial Protocol
22819 * Stop Reply Packets::
22820 * General Query Packets::
22821 * Register Packet Format::
22822 * Tracepoint Packets::
22825 * File-I/O remote protocol extension::
22826 * Memory map format::
22832 There may be occasions when you need to know something about the
22833 protocol---for example, if there is only one serial port to your target
22834 machine, you might want your program to do something special if it
22835 recognizes a packet meant for @value{GDBN}.
22837 In the examples below, @samp{->} and @samp{<-} are used to indicate
22838 transmitted and received data respectfully.
22840 @cindex protocol, @value{GDBN} remote serial
22841 @cindex serial protocol, @value{GDBN} remote
22842 @cindex remote serial protocol
22843 All @value{GDBN} commands and responses (other than acknowledgments) are
22844 sent as a @var{packet}. A @var{packet} is introduced with the character
22845 @samp{$}, the actual @var{packet-data}, and the terminating character
22846 @samp{#} followed by a two-digit @var{checksum}:
22849 @code{$}@var{packet-data}@code{#}@var{checksum}
22853 @cindex checksum, for @value{GDBN} remote
22855 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22856 characters between the leading @samp{$} and the trailing @samp{#} (an
22857 eight bit unsigned checksum).
22859 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22860 specification also included an optional two-digit @var{sequence-id}:
22863 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22866 @cindex sequence-id, for @value{GDBN} remote
22868 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22869 has never output @var{sequence-id}s. Stubs that handle packets added
22870 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22872 @cindex acknowledgment, for @value{GDBN} remote
22873 When either the host or the target machine receives a packet, the first
22874 response expected is an acknowledgment: either @samp{+} (to indicate
22875 the package was received correctly) or @samp{-} (to request
22879 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22884 The host (@value{GDBN}) sends @var{command}s, and the target (the
22885 debugging stub incorporated in your program) sends a @var{response}. In
22886 the case of step and continue @var{command}s, the response is only sent
22887 when the operation has completed (the target has again stopped).
22889 @var{packet-data} consists of a sequence of characters with the
22890 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22893 @cindex remote protocol, field separator
22894 Fields within the packet should be separated using @samp{,} @samp{;} or
22895 @samp{:}. Except where otherwise noted all numbers are represented in
22896 @sc{hex} with leading zeros suppressed.
22898 Implementors should note that prior to @value{GDBN} 5.0, the character
22899 @samp{:} could not appear as the third character in a packet (as it
22900 would potentially conflict with the @var{sequence-id}).
22902 @cindex remote protocol, binary data
22903 @anchor{Binary Data}
22904 Binary data in most packets is encoded either as two hexadecimal
22905 digits per byte of binary data. This allowed the traditional remote
22906 protocol to work over connections which were only seven-bit clean.
22907 Some packets designed more recently assume an eight-bit clean
22908 connection, and use a more efficient encoding to send and receive
22911 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
22912 as an escape character. Any escaped byte is transmitted as the escape
22913 character followed by the original character XORed with @code{0x20}.
22914 For example, the byte @code{0x7d} would be transmitted as the two
22915 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
22916 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
22917 @samp{@}}) must always be escaped. Responses sent by the stub
22918 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
22919 is not interpreted as the start of a run-length encoded sequence
22922 Response @var{data} can be run-length encoded to save space. A @samp{*}
22923 means that the next character is an @sc{ascii} encoding giving a repeat count
22924 which stands for that many repetitions of the character preceding the
22925 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22926 where @code{n >=3} (which is where rle starts to win). The printable
22927 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22928 value greater than 126 should not be used.
22935 means the same as "0000".
22937 The error response returned for some packets includes a two character
22938 error number. That number is not well defined.
22940 @cindex empty response, for unsupported packets
22941 For any @var{command} not supported by the stub, an empty response
22942 (@samp{$#00}) should be returned. That way it is possible to extend the
22943 protocol. A newer @value{GDBN} can tell if a packet is supported based
22946 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22947 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22953 The following table provides a complete list of all currently defined
22954 @var{command}s and their corresponding response @var{data}.
22955 @xref{File-I/O remote protocol extension}, for details about the File
22956 I/O extension of the remote protocol.
22958 Each packet's description has a template showing the packet's overall
22959 syntax, followed by an explanation of the packet's meaning. We
22960 include spaces in some of the templates for clarity; these are not
22961 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22962 separate its components. For example, a template like @samp{foo
22963 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22964 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22965 @var{baz}. @value{GDBN} does not transmit a space character between the
22966 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22969 Note that all packet forms beginning with an upper- or lower-case
22970 letter, other than those described here, are reserved for future use.
22972 Here are the packet descriptions.
22977 @cindex @samp{!} packet
22978 Enable extended mode. In extended mode, the remote server is made
22979 persistent. The @samp{R} packet is used to restart the program being
22985 The remote target both supports and has enabled extended mode.
22989 @cindex @samp{?} packet
22990 Indicate the reason the target halted. The reply is the same as for
22994 @xref{Stop Reply Packets}, for the reply specifications.
22996 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22997 @cindex @samp{A} packet
22998 Initialized @code{argv[]} array passed into program. @var{arglen}
22999 specifies the number of bytes in the hex encoded byte stream
23000 @var{arg}. See @code{gdbserver} for more details.
23005 The arguments were set.
23011 @cindex @samp{b} packet
23012 (Don't use this packet; its behavior is not well-defined.)
23013 Change the serial line speed to @var{baud}.
23015 JTC: @emph{When does the transport layer state change? When it's
23016 received, or after the ACK is transmitted. In either case, there are
23017 problems if the command or the acknowledgment packet is dropped.}
23019 Stan: @emph{If people really wanted to add something like this, and get
23020 it working for the first time, they ought to modify ser-unix.c to send
23021 some kind of out-of-band message to a specially-setup stub and have the
23022 switch happen "in between" packets, so that from remote protocol's point
23023 of view, nothing actually happened.}
23025 @item B @var{addr},@var{mode}
23026 @cindex @samp{B} packet
23027 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23028 breakpoint at @var{addr}.
23030 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23031 (@pxref{insert breakpoint or watchpoint packet}).
23033 @item c @r{[}@var{addr}@r{]}
23034 @cindex @samp{c} packet
23035 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23036 resume at current address.
23039 @xref{Stop Reply Packets}, for the reply specifications.
23041 @item C @var{sig}@r{[};@var{addr}@r{]}
23042 @cindex @samp{C} packet
23043 Continue with signal @var{sig} (hex signal number). If
23044 @samp{;@var{addr}} is omitted, resume at same address.
23047 @xref{Stop Reply Packets}, for the reply specifications.
23050 @cindex @samp{d} packet
23053 Don't use this packet; instead, define a general set packet
23054 (@pxref{General Query Packets}).
23057 @cindex @samp{D} packet
23058 Detach @value{GDBN} from the remote system. Sent to the remote target
23059 before @value{GDBN} disconnects via the @code{detach} command.
23069 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23070 @cindex @samp{F} packet
23071 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23072 This is part of the File-I/O protocol extension. @xref{File-I/O
23073 remote protocol extension}, for the specification.
23076 @anchor{read registers packet}
23077 @cindex @samp{g} packet
23078 Read general registers.
23082 @item @var{XX@dots{}}
23083 Each byte of register data is described by two hex digits. The bytes
23084 with the register are transmitted in target byte order. The size of
23085 each register and their position within the @samp{g} packet are
23086 determined by the @value{GDBN} internal macros
23087 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{REGISTER_NAME} macros. The
23088 specification of several standard @samp{g} packets is specified below.
23093 @item G @var{XX@dots{}}
23094 @cindex @samp{G} packet
23095 Write general registers. @xref{read registers packet}, for a
23096 description of the @var{XX@dots{}} data.
23106 @item H @var{c} @var{t}
23107 @cindex @samp{H} packet
23108 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23109 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23110 should be @samp{c} for step and continue operations, @samp{g} for other
23111 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23112 the threads, a thread number, or @samp{0} which means pick any thread.
23123 @c 'H': How restrictive (or permissive) is the thread model. If a
23124 @c thread is selected and stopped, are other threads allowed
23125 @c to continue to execute? As I mentioned above, I think the
23126 @c semantics of each command when a thread is selected must be
23127 @c described. For example:
23129 @c 'g': If the stub supports threads and a specific thread is
23130 @c selected, returns the register block from that thread;
23131 @c otherwise returns current registers.
23133 @c 'G' If the stub supports threads and a specific thread is
23134 @c selected, sets the registers of the register block of
23135 @c that thread; otherwise sets current registers.
23137 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23138 @anchor{cycle step packet}
23139 @cindex @samp{i} packet
23140 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23141 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23142 step starting at that address.
23145 @cindex @samp{I} packet
23146 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23150 @cindex @samp{k} packet
23153 FIXME: @emph{There is no description of how to operate when a specific
23154 thread context has been selected (i.e.@: does 'k' kill only that
23157 @item m @var{addr},@var{length}
23158 @cindex @samp{m} packet
23159 Read @var{length} bytes of memory starting at address @var{addr}.
23160 Note that @var{addr} may not be aligned to any particular boundary.
23162 The stub need not use any particular size or alignment when gathering
23163 data from memory for the response; even if @var{addr} is word-aligned
23164 and @var{length} is a multiple of the word size, the stub is free to
23165 use byte accesses, or not. For this reason, this packet may not be
23166 suitable for accessing memory-mapped I/O devices.
23167 @cindex alignment of remote memory accesses
23168 @cindex size of remote memory accesses
23169 @cindex memory, alignment and size of remote accesses
23173 @item @var{XX@dots{}}
23174 Memory contents; each byte is transmitted as a two-digit hexadecimal
23175 number. The reply may contain fewer bytes than requested if the
23176 server was able to read only part of the region of memory.
23181 @item M @var{addr},@var{length}:@var{XX@dots{}}
23182 @cindex @samp{M} packet
23183 Write @var{length} bytes of memory starting at address @var{addr}.
23184 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23185 hexadecimal number.
23192 for an error (this includes the case where only part of the data was
23197 @cindex @samp{p} packet
23198 Read the value of register @var{n}; @var{n} is in hex.
23199 @xref{read registers packet}, for a description of how the returned
23200 register value is encoded.
23204 @item @var{XX@dots{}}
23205 the register's value
23209 Indicating an unrecognized @var{query}.
23212 @item P @var{n@dots{}}=@var{r@dots{}}
23213 @anchor{write register packet}
23214 @cindex @samp{P} packet
23215 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23216 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23217 digits for each byte in the register (target byte order).
23227 @item q @var{name} @var{params}@dots{}
23228 @itemx Q @var{name} @var{params}@dots{}
23229 @cindex @samp{q} packet
23230 @cindex @samp{Q} packet
23231 General query (@samp{q}) and set (@samp{Q}). These packets are
23232 described fully in @ref{General Query Packets}.
23235 @cindex @samp{r} packet
23236 Reset the entire system.
23238 Don't use this packet; use the @samp{R} packet instead.
23241 @cindex @samp{R} packet
23242 Restart the program being debugged. @var{XX}, while needed, is ignored.
23243 This packet is only available in extended mode.
23245 The @samp{R} packet has no reply.
23247 @item s @r{[}@var{addr}@r{]}
23248 @cindex @samp{s} packet
23249 Single step. @var{addr} is the address at which to resume. If
23250 @var{addr} is omitted, resume at same address.
23253 @xref{Stop Reply Packets}, for the reply specifications.
23255 @item S @var{sig}@r{[};@var{addr}@r{]}
23256 @anchor{step with signal packet}
23257 @cindex @samp{S} packet
23258 Step with signal. This is analogous to the @samp{C} packet, but
23259 requests a single-step, rather than a normal resumption of execution.
23262 @xref{Stop Reply Packets}, for the reply specifications.
23264 @item t @var{addr}:@var{PP},@var{MM}
23265 @cindex @samp{t} packet
23266 Search backwards starting at address @var{addr} for a match with pattern
23267 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23268 @var{addr} must be at least 3 digits.
23271 @cindex @samp{T} packet
23272 Find out if the thread XX is alive.
23277 thread is still alive
23283 Packets starting with @samp{v} are identified by a multi-letter name,
23284 up to the first @samp{;} or @samp{?} (or the end of the packet).
23286 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23287 @cindex @samp{vCont} packet
23288 Resume the inferior, specifying different actions for each thread.
23289 If an action is specified with no @var{tid}, then it is applied to any
23290 threads that don't have a specific action specified; if no default action is
23291 specified then other threads should remain stopped. Specifying multiple
23292 default actions is an error; specifying no actions is also an error.
23293 Thread IDs are specified in hexadecimal. Currently supported actions are:
23299 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23303 Step with signal @var{sig}. @var{sig} should be two hex digits.
23306 The optional @var{addr} argument normally associated with these packets is
23307 not supported in @samp{vCont}.
23310 @xref{Stop Reply Packets}, for the reply specifications.
23313 @cindex @samp{vCont?} packet
23314 Request a list of actions supported by the @samp{vCont} packet.
23318 @item vCont@r{[};@var{action}@dots{}@r{]}
23319 The @samp{vCont} packet is supported. Each @var{action} is a supported
23320 command in the @samp{vCont} packet.
23322 The @samp{vCont} packet is not supported.
23325 @item vFlashErase:@var{addr},@var{length}
23326 @cindex @samp{vFlashErase} packet
23327 Direct the stub to erase @var{length} bytes of flash starting at
23328 @var{addr}. The region may enclose any number of flash blocks, but
23329 its start and end must fall on block boundaries, as indicated by the
23330 flash block size appearing in the memory map (@pxref{Memory map
23331 format}). @value{GDBN} groups flash memory programming operations
23332 together, and sends a @samp{vFlashDone} request after each group; the
23333 stub is allowed to delay erase operation until the @samp{vFlashDone}
23334 packet is received.
23344 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23345 @cindex @samp{vFlashWrite} packet
23346 Direct the stub to write data to flash address @var{addr}. The data
23347 is passed in binary form using the same encoding as for the @samp{X}
23348 packet (@pxref{Binary Data}). The memory ranges specified by
23349 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23350 not overlap, and must appear in order of increasing addresses
23351 (although @samp{vFlashErase} packets for higher addresses may already
23352 have been received; the ordering is guaranteed only between
23353 @samp{vFlashWrite} packets). If a packet writes to an address that was
23354 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23355 target-specific method, the results are unpredictable.
23363 for vFlashWrite addressing non-flash memory
23369 @cindex @samp{vFlashDone} packet
23370 Indicate to the stub that flash programming operation is finished.
23371 The stub is permitted to delay or batch the effects of a group of
23372 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23373 @samp{vFlashDone} packet is received. The contents of the affected
23374 regions of flash memory are unpredictable until the @samp{vFlashDone}
23375 request is completed.
23377 @item X @var{addr},@var{length}:@var{XX@dots{}}
23379 @cindex @samp{X} packet
23380 Write data to memory, where the data is transmitted in binary.
23381 @var{addr} is address, @var{length} is number of bytes,
23382 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23392 @item z @var{type},@var{addr},@var{length}
23393 @itemx Z @var{type},@var{addr},@var{length}
23394 @anchor{insert breakpoint or watchpoint packet}
23395 @cindex @samp{z} packet
23396 @cindex @samp{Z} packets
23397 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23398 watchpoint starting at address @var{address} and covering the next
23399 @var{length} bytes.
23401 Each breakpoint and watchpoint packet @var{type} is documented
23404 @emph{Implementation notes: A remote target shall return an empty string
23405 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23406 remote target shall support either both or neither of a given
23407 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23408 avoid potential problems with duplicate packets, the operations should
23409 be implemented in an idempotent way.}
23411 @item z0,@var{addr},@var{length}
23412 @itemx Z0,@var{addr},@var{length}
23413 @cindex @samp{z0} packet
23414 @cindex @samp{Z0} packet
23415 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23416 @var{addr} of size @var{length}.
23418 A memory breakpoint is implemented by replacing the instruction at
23419 @var{addr} with a software breakpoint or trap instruction. The
23420 @var{length} is used by targets that indicates the size of the
23421 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23422 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23424 @emph{Implementation note: It is possible for a target to copy or move
23425 code that contains memory breakpoints (e.g., when implementing
23426 overlays). The behavior of this packet, in the presence of such a
23427 target, is not defined.}
23439 @item z1,@var{addr},@var{length}
23440 @itemx Z1,@var{addr},@var{length}
23441 @cindex @samp{z1} packet
23442 @cindex @samp{Z1} packet
23443 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23444 address @var{addr} of size @var{length}.
23446 A hardware breakpoint is implemented using a mechanism that is not
23447 dependant on being able to modify the target's memory.
23449 @emph{Implementation note: A hardware breakpoint is not affected by code
23462 @item z2,@var{addr},@var{length}
23463 @itemx Z2,@var{addr},@var{length}
23464 @cindex @samp{z2} packet
23465 @cindex @samp{Z2} packet
23466 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23478 @item z3,@var{addr},@var{length}
23479 @itemx Z3,@var{addr},@var{length}
23480 @cindex @samp{z3} packet
23481 @cindex @samp{Z3} packet
23482 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23494 @item z4,@var{addr},@var{length}
23495 @itemx Z4,@var{addr},@var{length}
23496 @cindex @samp{z4} packet
23497 @cindex @samp{Z4} packet
23498 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23512 @node Stop Reply Packets
23513 @section Stop Reply Packets
23514 @cindex stop reply packets
23516 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23517 receive any of the below as a reply. In the case of the @samp{C},
23518 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23519 when the target halts. In the below the exact meaning of @dfn{signal
23520 number} is defined by the header @file{include/gdb/signals.h} in the
23521 @value{GDBN} source code.
23523 As in the description of request packets, we include spaces in the
23524 reply templates for clarity; these are not part of the reply packet's
23525 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23531 The program received signal number @var{AA} (a two-digit hexadecimal
23532 number). This is equivalent to a @samp{T} response with no
23533 @var{n}:@var{r} pairs.
23535 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23536 @cindex @samp{T} packet reply
23537 The program received signal number @var{AA} (a two-digit hexadecimal
23538 number). This is equivalent to an @samp{S} response, except that the
23539 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23540 and other information directly in the stop reply packet, reducing
23541 round-trip latency. Single-step and breakpoint traps are reported
23542 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23545 If @var{n} is a hexadecimal number, it is a register number, and the
23546 corresponding @var{r} gives that register's value. @var{r} is a
23547 series of bytes in target byte order, with each byte given by a
23548 two-digit hex number.
23550 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23553 If @var{n} is @samp{watch}, @samp{rwatch}, or @samp{awatch}, then the
23554 packet indicates a watchpoint hit, and @var{r} is the data address, in
23557 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23558 and go on to the next; this allows us to extend the protocol in the
23563 The process exited, and @var{AA} is the exit status. This is only
23564 applicable to certain targets.
23567 The process terminated with signal @var{AA}.
23569 @item O @var{XX}@dots{}
23570 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23571 written as the program's console output. This can happen at any time
23572 while the program is running and the debugger should continue to wait
23573 for @samp{W}, @samp{T}, etc.
23575 @item F @var{call-id},@var{parameter}@dots{}
23576 @var{call-id} is the identifier which says which host system call should
23577 be called. This is just the name of the function. Translation into the
23578 correct system call is only applicable as it's defined in @value{GDBN}.
23579 @xref{File-I/O remote protocol extension}, for a list of implemented
23582 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23583 this very system call.
23585 The target replies with this packet when it expects @value{GDBN} to
23586 call a host system call on behalf of the target. @value{GDBN} replies
23587 with an appropriate @samp{F} packet and keeps up waiting for the next
23588 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23589 or @samp{s} action is expected to be continued. @xref{File-I/O remote
23590 protocol extension}, for more details.
23594 @node General Query Packets
23595 @section General Query Packets
23596 @cindex remote query requests
23598 Packets starting with @samp{q} are @dfn{general query packets};
23599 packets starting with @samp{Q} are @dfn{general set packets}. General
23600 query and set packets are a semi-unified form for retrieving and
23601 sending information to and from the stub.
23603 The initial letter of a query or set packet is followed by a name
23604 indicating what sort of thing the packet applies to. For example,
23605 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23606 definitions with the stub. These packet names follow some
23611 The name must not contain commas, colons or semicolons.
23613 Most @value{GDBN} query and set packets have a leading upper case
23616 The names of custom vendor packets should use a company prefix, in
23617 lower case, followed by a period. For example, packets designed at
23618 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23619 foos) or @samp{Qacme.bar} (for setting bars).
23622 The name of a query or set packet should be separated from any
23623 parameters by a @samp{:}; the parameters themselves should be
23624 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23625 full packet name, and check for a separator or the end of the packet,
23626 in case two packet names share a common prefix. New packets should not begin
23627 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23628 packets predate these conventions, and have arguments without any terminator
23629 for the packet name; we suspect they are in widespread use in places that
23630 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23631 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23634 Like the descriptions of the other packets, each description here
23635 has a template showing the packet's overall syntax, followed by an
23636 explanation of the packet's meaning. We include spaces in some of the
23637 templates for clarity; these are not part of the packet's syntax. No
23638 @value{GDBN} packet uses spaces to separate its components.
23640 Here are the currently defined query and set packets:
23645 @cindex current thread, remote request
23646 @cindex @samp{qC} packet
23647 Return the current thread id.
23652 Where @var{pid} is an unsigned hexadecimal process id.
23653 @item @r{(anything else)}
23654 Any other reply implies the old pid.
23657 @item qCRC:@var{addr},@var{length}
23658 @cindex CRC of memory block, remote request
23659 @cindex @samp{qCRC} packet
23660 Compute the CRC checksum of a block of memory.
23664 An error (such as memory fault)
23665 @item C @var{crc32}
23666 The specified memory region's checksum is @var{crc32}.
23670 @itemx qsThreadInfo
23671 @cindex list active threads, remote request
23672 @cindex @samp{qfThreadInfo} packet
23673 @cindex @samp{qsThreadInfo} packet
23674 Obtain a list of all active thread ids from the target (OS). Since there
23675 may be too many active threads to fit into one reply packet, this query
23676 works iteratively: it may require more than one query/reply sequence to
23677 obtain the entire list of threads. The first query of the sequence will
23678 be the @samp{qfThreadInfo} query; subsequent queries in the
23679 sequence will be the @samp{qsThreadInfo} query.
23681 NOTE: This packet replaces the @samp{qL} query (see below).
23687 @item m @var{id},@var{id}@dots{}
23688 a comma-separated list of thread ids
23690 (lower case letter @samp{L}) denotes end of list.
23693 In response to each query, the target will reply with a list of one or
23694 more thread ids, in big-endian unsigned hex, separated by commas.
23695 @value{GDBN} will respond to each reply with a request for more thread
23696 ids (using the @samp{qs} form of the query), until the target responds
23697 with @samp{l} (lower-case el, for @dfn{last}).
23699 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23700 @cindex get thread-local storage address, remote request
23701 @cindex @samp{qGetTLSAddr} packet
23702 Fetch the address associated with thread local storage specified
23703 by @var{thread-id}, @var{offset}, and @var{lm}.
23705 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23706 thread for which to fetch the TLS address.
23708 @var{offset} is the (big endian, hex encoded) offset associated with the
23709 thread local variable. (This offset is obtained from the debug
23710 information associated with the variable.)
23712 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
23713 the load module associated with the thread local storage. For example,
23714 a @sc{gnu}/Linux system will pass the link map address of the shared
23715 object associated with the thread local storage under consideration.
23716 Other operating environments may choose to represent the load module
23717 differently, so the precise meaning of this parameter will vary.
23721 @item @var{XX}@dots{}
23722 Hex encoded (big endian) bytes representing the address of the thread
23723 local storage requested.
23726 An error occurred. @var{nn} are hex digits.
23729 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
23732 @item qL @var{startflag} @var{threadcount} @var{nextthread}
23733 Obtain thread information from RTOS. Where: @var{startflag} (one hex
23734 digit) is one to indicate the first query and zero to indicate a
23735 subsequent query; @var{threadcount} (two hex digits) is the maximum
23736 number of threads the response packet can contain; and @var{nextthread}
23737 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
23738 returned in the response as @var{argthread}.
23740 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
23744 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
23745 Where: @var{count} (two hex digits) is the number of threads being
23746 returned; @var{done} (one hex digit) is zero to indicate more threads
23747 and one indicates no further threads; @var{argthreadid} (eight hex
23748 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
23749 is a sequence of thread IDs from the target. @var{threadid} (eight hex
23750 digits). See @code{remote.c:parse_threadlist_response()}.
23754 @cindex section offsets, remote request
23755 @cindex @samp{qOffsets} packet
23756 Get section offsets that the target used when re-locating the downloaded
23757 image. @emph{Note: while a @code{Bss} offset is included in the
23758 response, @value{GDBN} ignores this and instead applies the @code{Data}
23759 offset to the @code{Bss} section.}
23763 @item Text=@var{xxx};Data=@var{yyy};Bss=@var{zzz}
23766 @item qP @var{mode} @var{threadid}
23767 @cindex thread information, remote request
23768 @cindex @samp{qP} packet
23769 Returns information on @var{threadid}. Where: @var{mode} is a hex
23770 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
23772 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
23775 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
23777 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
23778 @cindex pass signals to inferior, remote request
23779 @cindex @samp{QPassSignals} packet
23780 @anchor{QPassSignals}
23781 Each listed @var{signal} should be passed directly to the inferior process.
23782 Signals are numbered identically to continue packets and stop replies
23783 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
23784 strictly greater than the previous item. These signals do not need to stop
23785 the inferior, or be reported to @value{GDBN}. All other signals should be
23786 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
23787 combine; any earlier @samp{QPassSignals} list is completely replaced by the
23788 new list. This packet improves performance when using @samp{handle
23789 @var{signal} nostop noprint pass}.
23794 The request succeeded.
23797 An error occurred. @var{nn} are hex digits.
23800 An empty reply indicates that @samp{QPassSignals} is not supported by
23804 Use of this packet is controlled by the @code{set remote pass-signals}
23805 command (@pxref{Remote configuration, set remote pass-signals}).
23806 This packet is not probed by default; the remote stub must request it,
23807 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23809 @item qRcmd,@var{command}
23810 @cindex execute remote command, remote request
23811 @cindex @samp{qRcmd} packet
23812 @var{command} (hex encoded) is passed to the local interpreter for
23813 execution. Invalid commands should be reported using the output
23814 string. Before the final result packet, the target may also respond
23815 with a number of intermediate @samp{O@var{output}} console output
23816 packets. @emph{Implementors should note that providing access to a
23817 stubs's interpreter may have security implications}.
23822 A command response with no output.
23824 A command response with the hex encoded output string @var{OUTPUT}.
23826 Indicate a badly formed request.
23828 An empty reply indicates that @samp{qRcmd} is not recognized.
23831 (Note that the @code{qRcmd} packet's name is separated from the
23832 command by a @samp{,}, not a @samp{:}, contrary to the naming
23833 conventions above. Please don't use this packet as a model for new
23836 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
23837 @cindex supported packets, remote query
23838 @cindex features of the remote protocol
23839 @cindex @samp{qSupported} packet
23840 @anchor{qSupported}
23841 Tell the remote stub about features supported by @value{GDBN}, and
23842 query the stub for features it supports. This packet allows
23843 @value{GDBN} and the remote stub to take advantage of each others'
23844 features. @samp{qSupported} also consolidates multiple feature probes
23845 at startup, to improve @value{GDBN} performance---a single larger
23846 packet performs better than multiple smaller probe packets on
23847 high-latency links. Some features may enable behavior which must not
23848 be on by default, e.g.@: because it would confuse older clients or
23849 stubs. Other features may describe packets which could be
23850 automatically probed for, but are not. These features must be
23851 reported before @value{GDBN} will use them. This ``default
23852 unsupported'' behavior is not appropriate for all packets, but it
23853 helps to keep the initial connection time under control with new
23854 versions of @value{GDBN} which support increasing numbers of packets.
23858 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
23859 The stub supports or does not support each returned @var{stubfeature},
23860 depending on the form of each @var{stubfeature} (see below for the
23863 An empty reply indicates that @samp{qSupported} is not recognized,
23864 or that no features needed to be reported to @value{GDBN}.
23867 The allowed forms for each feature (either a @var{gdbfeature} in the
23868 @samp{qSupported} packet, or a @var{stubfeature} in the response)
23872 @item @var{name}=@var{value}
23873 The remote protocol feature @var{name} is supported, and associated
23874 with the specified @var{value}. The format of @var{value} depends
23875 on the feature, but it must not include a semicolon.
23877 The remote protocol feature @var{name} is supported, and does not
23878 need an associated value.
23880 The remote protocol feature @var{name} is not supported.
23882 The remote protocol feature @var{name} may be supported, and
23883 @value{GDBN} should auto-detect support in some other way when it is
23884 needed. This form will not be used for @var{gdbfeature} notifications,
23885 but may be used for @var{stubfeature} responses.
23888 Whenever the stub receives a @samp{qSupported} request, the
23889 supplied set of @value{GDBN} features should override any previous
23890 request. This allows @value{GDBN} to put the stub in a known
23891 state, even if the stub had previously been communicating with
23892 a different version of @value{GDBN}.
23894 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
23895 are defined yet. Stubs should ignore any unknown values for
23896 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
23897 packet supports receiving packets of unlimited length (earlier
23898 versions of @value{GDBN} may reject overly long responses). Values
23899 for @var{gdbfeature} may be defined in the future to let the stub take
23900 advantage of new features in @value{GDBN}, e.g.@: incompatible
23901 improvements in the remote protocol---support for unlimited length
23902 responses would be a @var{gdbfeature} example, if it were not implied by
23903 the @samp{qSupported} query. The stub's reply should be independent
23904 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
23905 describes all the features it supports, and then the stub replies with
23906 all the features it supports.
23908 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
23909 responses, as long as each response uses one of the standard forms.
23911 Some features are flags. A stub which supports a flag feature
23912 should respond with a @samp{+} form response. Other features
23913 require values, and the stub should respond with an @samp{=}
23916 Each feature has a default value, which @value{GDBN} will use if
23917 @samp{qSupported} is not available or if the feature is not mentioned
23918 in the @samp{qSupported} response. The default values are fixed; a
23919 stub is free to omit any feature responses that match the defaults.
23921 Not all features can be probed, but for those which can, the probing
23922 mechanism is useful: in some cases, a stub's internal
23923 architecture may not allow the protocol layer to know some information
23924 about the underlying target in advance. This is especially common in
23925 stubs which may be configured for multiple targets.
23927 These are the currently defined stub features and their properties:
23929 @multitable @columnfractions 0.25 0.2 0.2 0.2
23930 @c NOTE: The first row should be @headitem, but we do not yet require
23931 @c a new enough version of Texinfo (4.7) to use @headitem.
23933 @tab Value Required
23937 @item @samp{PacketSize}
23942 @item @samp{qXfer:auxv:read}
23947 @item @samp{qXfer:features:read}
23952 @item @samp{qXfer:memory-map:read}
23957 @item @samp{QPassSignals}
23964 These are the currently defined stub features, in more detail:
23967 @cindex packet size, remote protocol
23968 @item PacketSize=@var{bytes}
23969 The remote stub can accept packets up to at least @var{bytes} in
23970 length. @value{GDBN} will send packets up to this size for bulk
23971 transfers, and will never send larger packets. This is a limit on the
23972 data characters in the packet, including the frame and checksum.
23973 There is no trailing NUL byte in a remote protocol packet; if the stub
23974 stores packets in a NUL-terminated format, it should allow an extra
23975 byte in its buffer for the NUL. If this stub feature is not supported,
23976 @value{GDBN} guesses based on the size of the @samp{g} packet response.
23978 @item qXfer:auxv:read
23979 The remote stub understands the @samp{qXfer:auxv:read} packet
23980 (@pxref{qXfer auxiliary vector read}).
23982 @item qXfer:features:read
23983 The remote stub understands the @samp{qXfer:features:read} packet
23984 (@pxref{qXfer target description read}).
23986 @item qXfer:memory-map:read
23987 The remote stub understands the @samp{qXfer:memory-map:read} packet
23988 (@pxref{qXfer memory map read}).
23991 The remote stub understands the @samp{QPassSignals} packet
23992 (@pxref{QPassSignals}).
23997 @cindex symbol lookup, remote request
23998 @cindex @samp{qSymbol} packet
23999 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24000 requests. Accept requests from the target for the values of symbols.
24005 The target does not need to look up any (more) symbols.
24006 @item qSymbol:@var{sym_name}
24007 The target requests the value of symbol @var{sym_name} (hex encoded).
24008 @value{GDBN} may provide the value by using the
24009 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24013 @item qSymbol:@var{sym_value}:@var{sym_name}
24014 Set the value of @var{sym_name} to @var{sym_value}.
24016 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24017 target has previously requested.
24019 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24020 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24026 The target does not need to look up any (more) symbols.
24027 @item qSymbol:@var{sym_name}
24028 The target requests the value of a new symbol @var{sym_name} (hex
24029 encoded). @value{GDBN} will continue to supply the values of symbols
24030 (if available), until the target ceases to request them.
24035 @xref{Tracepoint Packets}.
24037 @item qThreadExtraInfo,@var{id}
24038 @cindex thread attributes info, remote request
24039 @cindex @samp{qThreadExtraInfo} packet
24040 Obtain a printable string description of a thread's attributes from
24041 the target OS. @var{id} is a thread-id in big-endian hex. This
24042 string may contain anything that the target OS thinks is interesting
24043 for @value{GDBN} to tell the user about the thread. The string is
24044 displayed in @value{GDBN}'s @code{info threads} display. Some
24045 examples of possible thread extra info strings are @samp{Runnable}, or
24046 @samp{Blocked on Mutex}.
24050 @item @var{XX}@dots{}
24051 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
24052 comprising the printable string containing the extra information about
24053 the thread's attributes.
24056 (Note that the @code{qThreadExtraInfo} packet's name is separated from
24057 the command by a @samp{,}, not a @samp{:}, contrary to the naming
24058 conventions above. Please don't use this packet as a model for new
24066 @xref{Tracepoint Packets}.
24068 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
24069 @cindex read special object, remote request
24070 @cindex @samp{qXfer} packet
24071 @anchor{qXfer read}
24072 Read uninterpreted bytes from the target's special data area
24073 identified by the keyword @var{object}. Request @var{length} bytes
24074 starting at @var{offset} bytes into the data. The content and
24075 encoding of @var{annex} is specific to the object; it can supply
24076 additional details about what data to access.
24078 Here are the specific requests of this form defined so far. All
24079 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
24080 formats, listed below.
24083 @item qXfer:auxv:read::@var{offset},@var{length}
24084 @anchor{qXfer auxiliary vector read}
24085 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
24086 auxiliary vector}. Note @var{annex} must be empty.
24088 This packet is not probed by default; the remote stub must request it,
24089 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24091 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
24092 @anchor{qXfer target description read}
24093 Access the @dfn{target description}. @xref{Target Descriptions}. The
24094 annex specifies which XML document to access. The main description is
24095 always loaded from the @samp{target.xml} annex.
24097 This packet is not probed by default; the remote stub must request it,
24098 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24100 @item qXfer:memory-map:read::@var{offset},@var{length}
24101 @anchor{qXfer memory map read}
24102 Access the target's @dfn{memory-map}. @xref{Memory map format}. The
24103 annex part of the generic @samp{qXfer} packet must be empty
24104 (@pxref{qXfer read}).
24106 This packet is not probed by default; the remote stub must request it,
24107 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24113 Data @var{data} (@pxref{Binary Data}) has been read from the
24114 target. There may be more data at a higher address (although
24115 it is permitted to return @samp{m} even for the last valid
24116 block of data, as long as at least one byte of data was read).
24117 @var{data} may have fewer bytes than the @var{length} in the
24121 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24122 There is no more data to be read. @var{data} may have fewer bytes
24123 than the @var{length} in the request.
24126 The @var{offset} in the request is at the end of the data.
24127 There is no more data to be read.
24130 The request was malformed, or @var{annex} was invalid.
24133 The offset was invalid, or there was an error encountered reading the data.
24134 @var{nn} is a hex-encoded @code{errno} value.
24137 An empty reply indicates the @var{object} string was not recognized by
24138 the stub, or that the object does not support reading.
24141 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24142 @cindex write data into object, remote request
24143 Write uninterpreted bytes into the target's special data area
24144 identified by the keyword @var{object}, starting at @var{offset} bytes
24145 into the data. @samp{@var{data}@dots{}} is the binary-encoded data
24146 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24147 is specific to the object; it can supply additional details about what data
24150 No requests of this form are presently in use. This specification
24151 serves as a placeholder to document the common format that new
24152 specific request specifications ought to use.
24157 @var{nn} (hex encoded) is the number of bytes written.
24158 This may be fewer bytes than supplied in the request.
24161 The request was malformed, or @var{annex} was invalid.
24164 The offset was invalid, or there was an error encountered writing the data.
24165 @var{nn} is a hex-encoded @code{errno} value.
24168 An empty reply indicates the @var{object} string was not
24169 recognized by the stub, or that the object does not support writing.
24172 @item qXfer:@var{object}:@var{operation}:@dots{}
24173 Requests of this form may be added in the future. When a stub does
24174 not recognize the @var{object} keyword, or its support for
24175 @var{object} does not recognize the @var{operation} keyword, the stub
24176 must respond with an empty packet.
24180 @node Register Packet Format
24181 @section Register Packet Format
24183 The following @code{g}/@code{G} packets have previously been defined.
24184 In the below, some thirty-two bit registers are transferred as
24185 sixty-four bits. Those registers should be zero/sign extended (which?)
24186 to fill the space allocated. Register bytes are transferred in target
24187 byte order. The two nibbles within a register byte are transferred
24188 most-significant - least-significant.
24194 All registers are transferred as thirty-two bit quantities in the order:
24195 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24196 registers; fsr; fir; fp.
24200 All registers are transferred as sixty-four bit quantities (including
24201 thirty-two bit registers such as @code{sr}). The ordering is the same
24206 @node Tracepoint Packets
24207 @section Tracepoint Packets
24208 @cindex tracepoint packets
24209 @cindex packets, tracepoint
24211 Here we describe the packets @value{GDBN} uses to implement
24212 tracepoints (@pxref{Tracepoints}).
24216 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24217 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24218 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24219 the tracepoint is disabled. @var{step} is the tracepoint's step
24220 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24221 present, further @samp{QTDP} packets will follow to specify this
24222 tracepoint's actions.
24227 The packet was understood and carried out.
24229 The packet was not recognized.
24232 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24233 Define actions to be taken when a tracepoint is hit. @var{n} and
24234 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24235 this tracepoint. This packet may only be sent immediately after
24236 another @samp{QTDP} packet that ended with a @samp{-}. If the
24237 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24238 specifying more actions for this tracepoint.
24240 In the series of action packets for a given tracepoint, at most one
24241 can have an @samp{S} before its first @var{action}. If such a packet
24242 is sent, it and the following packets define ``while-stepping''
24243 actions. Any prior packets define ordinary actions --- that is, those
24244 taken when the tracepoint is first hit. If no action packet has an
24245 @samp{S}, then all the packets in the series specify ordinary
24246 tracepoint actions.
24248 The @samp{@var{action}@dots{}} portion of the packet is a series of
24249 actions, concatenated without separators. Each action has one of the
24255 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24256 a hexadecimal number whose @var{i}'th bit is set if register number
24257 @var{i} should be collected. (The least significant bit is numbered
24258 zero.) Note that @var{mask} may be any number of digits long; it may
24259 not fit in a 32-bit word.
24261 @item M @var{basereg},@var{offset},@var{len}
24262 Collect @var{len} bytes of memory starting at the address in register
24263 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24264 @samp{-1}, then the range has a fixed address: @var{offset} is the
24265 address of the lowest byte to collect. The @var{basereg},
24266 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24267 values (the @samp{-1} value for @var{basereg} is a special case).
24269 @item X @var{len},@var{expr}
24270 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24271 it directs. @var{expr} is an agent expression, as described in
24272 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24273 two-digit hex number in the packet; @var{len} is the number of bytes
24274 in the expression (and thus one-half the number of hex digits in the
24279 Any number of actions may be packed together in a single @samp{QTDP}
24280 packet, as long as the packet does not exceed the maximum packet
24281 length (400 bytes, for many stubs). There may be only one @samp{R}
24282 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24283 actions. Any registers referred to by @samp{M} and @samp{X} actions
24284 must be collected by a preceding @samp{R} action. (The
24285 ``while-stepping'' actions are treated as if they were attached to a
24286 separate tracepoint, as far as these restrictions are concerned.)
24291 The packet was understood and carried out.
24293 The packet was not recognized.
24296 @item QTFrame:@var{n}
24297 Select the @var{n}'th tracepoint frame from the buffer, and use the
24298 register and memory contents recorded there to answer subsequent
24299 request packets from @value{GDBN}.
24301 A successful reply from the stub indicates that the stub has found the
24302 requested frame. The response is a series of parts, concatenated
24303 without separators, describing the frame we selected. Each part has
24304 one of the following forms:
24308 The selected frame is number @var{n} in the trace frame buffer;
24309 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24310 was no frame matching the criteria in the request packet.
24313 The selected trace frame records a hit of tracepoint number @var{t};
24314 @var{t} is a hexadecimal number.
24318 @item QTFrame:pc:@var{addr}
24319 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24320 currently selected frame whose PC is @var{addr};
24321 @var{addr} is a hexadecimal number.
24323 @item QTFrame:tdp:@var{t}
24324 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24325 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24326 is a hexadecimal number.
24328 @item QTFrame:range:@var{start}:@var{end}
24329 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24330 currently selected frame whose PC is between @var{start} (inclusive)
24331 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24334 @item QTFrame:outside:@var{start}:@var{end}
24335 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24336 frame @emph{outside} the given range of addresses.
24339 Begin the tracepoint experiment. Begin collecting data from tracepoint
24340 hits in the trace frame buffer.
24343 End the tracepoint experiment. Stop collecting trace frames.
24346 Clear the table of tracepoints, and empty the trace frame buffer.
24348 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24349 Establish the given ranges of memory as ``transparent''. The stub
24350 will answer requests for these ranges from memory's current contents,
24351 if they were not collected as part of the tracepoint hit.
24353 @value{GDBN} uses this to mark read-only regions of memory, like those
24354 containing program code. Since these areas never change, they should
24355 still have the same contents they did when the tracepoint was hit, so
24356 there's no reason for the stub to refuse to provide their contents.
24359 Ask the stub if there is a trace experiment running right now.
24364 There is no trace experiment running.
24366 There is a trace experiment running.
24373 @section Interrupts
24374 @cindex interrupts (remote protocol)
24376 When a program on the remote target is running, @value{GDBN} may
24377 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24378 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24379 setting (@pxref{set remotebreak}).
24381 The precise meaning of @code{BREAK} is defined by the transport
24382 mechanism and may, in fact, be undefined. @value{GDBN} does
24383 not currently define a @code{BREAK} mechanism for any of the network
24386 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24387 transport mechanisms. It is represented by sending the single byte
24388 @code{0x03} without any of the usual packet overhead described in
24389 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24390 transmitted as part of a packet, it is considered to be packet data
24391 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24392 (@pxref{X packet}), used for binary downloads, may include an unescaped
24393 @code{0x03} as part of its packet.
24395 Stubs are not required to recognize these interrupt mechanisms and the
24396 precise meaning associated with receipt of the interrupt is
24397 implementation defined. If the stub is successful at interrupting the
24398 running program, it is expected that it will send one of the Stop
24399 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24400 of successfully stopping the program. Interrupts received while the
24401 program is stopped will be discarded.
24406 Example sequence of a target being re-started. Notice how the restart
24407 does not get any direct output:
24412 @emph{target restarts}
24415 <- @code{T001:1234123412341234}
24419 Example sequence of a target being stepped by a single instruction:
24422 -> @code{G1445@dots{}}
24427 <- @code{T001:1234123412341234}
24431 <- @code{1455@dots{}}
24435 @node File-I/O remote protocol extension
24436 @section File-I/O remote protocol extension
24437 @cindex File-I/O remote protocol extension
24440 * File-I/O Overview::
24441 * Protocol basics::
24442 * The F request packet::
24443 * The F reply packet::
24444 * The Ctrl-C message::
24446 * List of supported calls::
24447 * Protocol specific representation of datatypes::
24449 * File-I/O Examples::
24452 @node File-I/O Overview
24453 @subsection File-I/O Overview
24454 @cindex file-i/o overview
24456 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24457 target to use the host's file system and console I/O to perform various
24458 system calls. System calls on the target system are translated into a
24459 remote protocol packet to the host system, which then performs the needed
24460 actions and returns a response packet to the target system.
24461 This simulates file system operations even on targets that lack file systems.
24463 The protocol is defined to be independent of both the host and target systems.
24464 It uses its own internal representation of datatypes and values. Both
24465 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24466 translating the system-dependent value representations into the internal
24467 protocol representations when data is transmitted.
24469 The communication is synchronous. A system call is possible only when
24470 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24471 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24472 the target is stopped to allow deterministic access to the target's
24473 memory. Therefore File-I/O is not interruptible by target signals. On
24474 the other hand, it is possible to interrupt File-I/O by a user interrupt
24475 (@samp{Ctrl-C}) within @value{GDBN}.
24477 The target's request to perform a host system call does not finish
24478 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24479 after finishing the system call, the target returns to continuing the
24480 previous activity (continue, step). No additional continue or step
24481 request from @value{GDBN} is required.
24484 (@value{GDBP}) continue
24485 <- target requests 'system call X'
24486 target is stopped, @value{GDBN} executes system call
24487 -> @value{GDBN} returns result
24488 ... target continues, @value{GDBN} returns to wait for the target
24489 <- target hits breakpoint and sends a Txx packet
24492 The protocol only supports I/O on the console and to regular files on
24493 the host file system. Character or block special devices, pipes,
24494 named pipes, sockets or any other communication method on the host
24495 system are not supported by this protocol.
24497 @node Protocol basics
24498 @subsection Protocol basics
24499 @cindex protocol basics, file-i/o
24501 The File-I/O protocol uses the @code{F} packet as the request as well
24502 as reply packet. Since a File-I/O system call can only occur when
24503 @value{GDBN} is waiting for a response from the continuing or stepping target,
24504 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24505 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24506 This @code{F} packet contains all information needed to allow @value{GDBN}
24507 to call the appropriate host system call:
24511 A unique identifier for the requested system call.
24514 All parameters to the system call. Pointers are given as addresses
24515 in the target memory address space. Pointers to strings are given as
24516 pointer/length pair. Numerical values are given as they are.
24517 Numerical control flags are given in a protocol specific representation.
24521 At this point, @value{GDBN} has to perform the following actions.
24525 If the parameters include pointer values to data needed as input to a
24526 system call, @value{GDBN} requests this data from the target with a
24527 standard @code{m} packet request. This additional communication has to be
24528 expected by the target implementation and is handled as any other @code{m}
24532 @value{GDBN} translates all value from protocol representation to host
24533 representation as needed. Datatypes are coerced into the host types.
24536 @value{GDBN} calls the system call.
24539 It then coerces datatypes back to protocol representation.
24542 If the system call is expected to return data in buffer space specified
24543 by pointer parameters to the call, the data is transmitted to the
24544 target using a @code{M} or @code{X} packet. This packet has to be expected
24545 by the target implementation and is handled as any other @code{M} or @code{X}
24550 Eventually @value{GDBN} replies with another @code{F} packet which contains all
24551 necessary information for the target to continue. This at least contains
24558 @code{errno}, if has been changed by the system call.
24565 After having done the needed type and value coercion, the target continues
24566 the latest continue or step action.
24568 @node The F request packet
24569 @subsection The @code{F} request packet
24570 @cindex file-i/o request packet
24571 @cindex @code{F} request packet
24573 The @code{F} request packet has the following format:
24576 @item F@var{call-id},@var{parameter@dots{}}
24578 @var{call-id} is the identifier to indicate the host system call to be called.
24579 This is just the name of the function.
24581 @var{parameter@dots{}} are the parameters to the system call.
24582 Parameters are hexadecimal integer values, either the actual values in case
24583 of scalar datatypes, pointers to target buffer space in case of compound
24584 datatypes and unspecified memory areas, or pointer/length pairs in case
24585 of string parameters. These are appended to the @var{call-id} as a
24586 comma-delimited list. All values are transmitted in ASCII
24587 string representation, pointer/length pairs separated by a slash.
24593 @node The F reply packet
24594 @subsection The @code{F} reply packet
24595 @cindex file-i/o reply packet
24596 @cindex @code{F} reply packet
24598 The @code{F} reply packet has the following format:
24602 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call specific attachment}
24604 @var{retcode} is the return code of the system call as hexadecimal value.
24606 @var{errno} is the @code{errno} set by the call, in protocol specific representation.
24607 This parameter can be omitted if the call was successful.
24609 @var{Ctrl-C flag} is only sent if the user requested a break. In this
24610 case, @var{errno} must be sent as well, even if the call was successful.
24611 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
24618 or, if the call was interrupted before the host call has been performed:
24625 assuming 4 is the protocol specific representation of @code{EINTR}.
24630 @node The Ctrl-C message
24631 @subsection The @samp{Ctrl-C} message
24632 @cindex ctrl-c message, in file-i/o protocol
24634 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
24635 reply packet (@pxref{The F reply packet}),
24636 the target should behave as if it had
24637 gotten a break message. The meaning for the target is ``system call
24638 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
24639 (as with a break message) and return to @value{GDBN} with a @code{T02}
24642 It's important for the target to know in which
24643 state the system call was interrupted. There are two possible cases:
24647 The system call hasn't been performed on the host yet.
24650 The system call on the host has been finished.
24654 These two states can be distinguished by the target by the value of the
24655 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
24656 call hasn't been performed. This is equivalent to the @code{EINTR} handling
24657 on POSIX systems. In any other case, the target may presume that the
24658 system call has been finished --- successfully or not --- and should behave
24659 as if the break message arrived right after the system call.
24661 @value{GDBN} must behave reliably. If the system call has not been called
24662 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
24663 @code{errno} in the packet. If the system call on the host has been finished
24664 before the user requests a break, the full action must be finished by
24665 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
24666 The @code{F} packet may only be sent when either nothing has happened
24667 or the full action has been completed.
24670 @subsection Console I/O
24671 @cindex console i/o as part of file-i/o
24673 By default and if not explicitly closed by the target system, the file
24674 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
24675 on the @value{GDBN} console is handled as any other file output operation
24676 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
24677 by @value{GDBN} so that after the target read request from file descriptor
24678 0 all following typing is buffered until either one of the following
24683 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
24685 system call is treated as finished.
24688 The user presses @key{RET}. This is treated as end of input with a trailing
24692 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
24693 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
24697 If the user has typed more characters than fit in the buffer given to
24698 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
24699 either another @code{read(0, @dots{})} is requested by the target, or debugging
24700 is stopped at the user's request.
24703 @node List of supported calls
24704 @subsection List of supported calls
24705 @cindex list of supported file-i/o calls
24722 @unnumberedsubsubsec open
24723 @cindex open, file-i/o system call
24728 int open(const char *pathname, int flags);
24729 int open(const char *pathname, int flags, mode_t mode);
24733 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
24736 @var{flags} is the bitwise @code{OR} of the following values:
24740 If the file does not exist it will be created. The host
24741 rules apply as far as file ownership and time stamps
24745 When used with @code{O_CREAT}, if the file already exists it is
24746 an error and open() fails.
24749 If the file already exists and the open mode allows
24750 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
24751 truncated to zero length.
24754 The file is opened in append mode.
24757 The file is opened for reading only.
24760 The file is opened for writing only.
24763 The file is opened for reading and writing.
24767 Other bits are silently ignored.
24771 @var{mode} is the bitwise @code{OR} of the following values:
24775 User has read permission.
24778 User has write permission.
24781 Group has read permission.
24784 Group has write permission.
24787 Others have read permission.
24790 Others have write permission.
24794 Other bits are silently ignored.
24797 @item Return value:
24798 @code{open} returns the new file descriptor or -1 if an error
24805 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
24808 @var{pathname} refers to a directory.
24811 The requested access is not allowed.
24814 @var{pathname} was too long.
24817 A directory component in @var{pathname} does not exist.
24820 @var{pathname} refers to a device, pipe, named pipe or socket.
24823 @var{pathname} refers to a file on a read-only filesystem and
24824 write access was requested.
24827 @var{pathname} is an invalid pointer value.
24830 No space on device to create the file.
24833 The process already has the maximum number of files open.
24836 The limit on the total number of files open on the system
24840 The call was interrupted by the user.
24846 @unnumberedsubsubsec close
24847 @cindex close, file-i/o system call
24856 @samp{Fclose,@var{fd}}
24858 @item Return value:
24859 @code{close} returns zero on success, or -1 if an error occurred.
24865 @var{fd} isn't a valid open file descriptor.
24868 The call was interrupted by the user.
24874 @unnumberedsubsubsec read
24875 @cindex read, file-i/o system call
24880 int read(int fd, void *buf, unsigned int count);
24884 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
24886 @item Return value:
24887 On success, the number of bytes read is returned.
24888 Zero indicates end of file. If count is zero, read
24889 returns zero as well. On error, -1 is returned.
24895 @var{fd} is not a valid file descriptor or is not open for
24899 @var{bufptr} is an invalid pointer value.
24902 The call was interrupted by the user.
24908 @unnumberedsubsubsec write
24909 @cindex write, file-i/o system call
24914 int write(int fd, const void *buf, unsigned int count);
24918 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
24920 @item Return value:
24921 On success, the number of bytes written are returned.
24922 Zero indicates nothing was written. On error, -1
24929 @var{fd} is not a valid file descriptor or is not open for
24933 @var{bufptr} is an invalid pointer value.
24936 An attempt was made to write a file that exceeds the
24937 host specific maximum file size allowed.
24940 No space on device to write the data.
24943 The call was interrupted by the user.
24949 @unnumberedsubsubsec lseek
24950 @cindex lseek, file-i/o system call
24955 long lseek (int fd, long offset, int flag);
24959 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
24961 @var{flag} is one of:
24965 The offset is set to @var{offset} bytes.
24968 The offset is set to its current location plus @var{offset}
24972 The offset is set to the size of the file plus @var{offset}
24976 @item Return value:
24977 On success, the resulting unsigned offset in bytes from
24978 the beginning of the file is returned. Otherwise, a
24979 value of -1 is returned.
24985 @var{fd} is not a valid open file descriptor.
24988 @var{fd} is associated with the @value{GDBN} console.
24991 @var{flag} is not a proper value.
24994 The call was interrupted by the user.
25000 @unnumberedsubsubsec rename
25001 @cindex rename, file-i/o system call
25006 int rename(const char *oldpath, const char *newpath);
25010 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
25012 @item Return value:
25013 On success, zero is returned. On error, -1 is returned.
25019 @var{newpath} is an existing directory, but @var{oldpath} is not a
25023 @var{newpath} is a non-empty directory.
25026 @var{oldpath} or @var{newpath} is a directory that is in use by some
25030 An attempt was made to make a directory a subdirectory
25034 A component used as a directory in @var{oldpath} or new
25035 path is not a directory. Or @var{oldpath} is a directory
25036 and @var{newpath} exists but is not a directory.
25039 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
25042 No access to the file or the path of the file.
25046 @var{oldpath} or @var{newpath} was too long.
25049 A directory component in @var{oldpath} or @var{newpath} does not exist.
25052 The file is on a read-only filesystem.
25055 The device containing the file has no room for the new
25059 The call was interrupted by the user.
25065 @unnumberedsubsubsec unlink
25066 @cindex unlink, file-i/o system call
25071 int unlink(const char *pathname);
25075 @samp{Funlink,@var{pathnameptr}/@var{len}}
25077 @item Return value:
25078 On success, zero is returned. On error, -1 is returned.
25084 No access to the file or the path of the file.
25087 The system does not allow unlinking of directories.
25090 The file @var{pathname} cannot be unlinked because it's
25091 being used by another process.
25094 @var{pathnameptr} is an invalid pointer value.
25097 @var{pathname} was too long.
25100 A directory component in @var{pathname} does not exist.
25103 A component of the path is not a directory.
25106 The file is on a read-only filesystem.
25109 The call was interrupted by the user.
25115 @unnumberedsubsubsec stat/fstat
25116 @cindex fstat, file-i/o system call
25117 @cindex stat, file-i/o system call
25122 int stat(const char *pathname, struct stat *buf);
25123 int fstat(int fd, struct stat *buf);
25127 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25128 @samp{Ffstat,@var{fd},@var{bufptr}}
25130 @item Return value:
25131 On success, zero is returned. On error, -1 is returned.
25137 @var{fd} is not a valid open file.
25140 A directory component in @var{pathname} does not exist or the
25141 path is an empty string.
25144 A component of the path is not a directory.
25147 @var{pathnameptr} is an invalid pointer value.
25150 No access to the file or the path of the file.
25153 @var{pathname} was too long.
25156 The call was interrupted by the user.
25162 @unnumberedsubsubsec gettimeofday
25163 @cindex gettimeofday, file-i/o system call
25168 int gettimeofday(struct timeval *tv, void *tz);
25172 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25174 @item Return value:
25175 On success, 0 is returned, -1 otherwise.
25181 @var{tz} is a non-NULL pointer.
25184 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25190 @unnumberedsubsubsec isatty
25191 @cindex isatty, file-i/o system call
25196 int isatty(int fd);
25200 @samp{Fisatty,@var{fd}}
25202 @item Return value:
25203 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
25209 The call was interrupted by the user.
25214 Note that the @code{isatty} call is treated as a special case: it returns
25215 1 to the target if the file descriptor is attached
25216 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
25217 would require implementing @code{ioctl} and would be more complex than
25222 @unnumberedsubsubsec system
25223 @cindex system, file-i/o system call
25228 int system(const char *command);
25232 @samp{Fsystem,@var{commandptr}/@var{len}}
25234 @item Return value:
25235 If @var{len} is zero, the return value indicates whether a shell is
25236 available. A zero return value indicates a shell is not available.
25237 For non-zero @var{len}, the value returned is -1 on error and the
25238 return status of the command otherwise. Only the exit status of the
25239 command is returned, which is extracted from the host's @code{system}
25240 return value by calling @code{WEXITSTATUS(retval)}. In case
25241 @file{/bin/sh} could not be executed, 127 is returned.
25247 The call was interrupted by the user.
25252 @value{GDBN} takes over the full task of calling the necessary host calls
25253 to perform the @code{system} call. The return value of @code{system} on
25254 the host is simplified before it's returned
25255 to the target. Any termination signal information from the child process
25256 is discarded, and the return value consists
25257 entirely of the exit status of the called command.
25259 Due to security concerns, the @code{system} call is by default refused
25260 by @value{GDBN}. The user has to allow this call explicitly with the
25261 @code{set remote system-call-allowed 1} command.
25264 @item set remote system-call-allowed
25265 @kindex set remote system-call-allowed
25266 Control whether to allow the @code{system} calls in the File I/O
25267 protocol for the remote target. The default is zero (disabled).
25269 @item show remote system-call-allowed
25270 @kindex show remote system-call-allowed
25271 Show whether the @code{system} calls are allowed in the File I/O
25275 @node Protocol specific representation of datatypes
25276 @subsection Protocol specific representation of datatypes
25277 @cindex protocol specific representation of datatypes, in file-i/o protocol
25280 * Integral datatypes::
25282 * Memory transfer::
25287 @node Integral datatypes
25288 @unnumberedsubsubsec Integral datatypes
25289 @cindex integral datatypes, in file-i/o protocol
25291 The integral datatypes used in the system calls are @code{int},
25292 @code{unsigned int}, @code{long}, @code{unsigned long},
25293 @code{mode_t}, and @code{time_t}.
25295 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25296 implemented as 32 bit values in this protocol.
25298 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25300 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25301 in @file{limits.h}) to allow range checking on host and target.
25303 @code{time_t} datatypes are defined as seconds since the Epoch.
25305 All integral datatypes transferred as part of a memory read or write of a
25306 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25309 @node Pointer values
25310 @unnumberedsubsubsec Pointer values
25311 @cindex pointer values, in file-i/o protocol
25313 Pointers to target data are transmitted as they are. An exception
25314 is made for pointers to buffers for which the length isn't
25315 transmitted as part of the function call, namely strings. Strings
25316 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25323 which is a pointer to data of length 18 bytes at position 0x1aaf.
25324 The length is defined as the full string length in bytes, including
25325 the trailing null byte. For example, the string @code{"hello world"}
25326 at address 0x123456 is transmitted as
25332 @node Memory transfer
25333 @unnumberedsubsubsec Memory transfer
25334 @cindex memory transfer, in file-i/o protocol
25336 Structured data which is transferred using a memory read or write (for
25337 example, a @code{struct stat}) is expected to be in a protocol specific format
25338 with all scalar multibyte datatypes being big endian. Translation to
25339 this representation needs to be done both by the target before the @code{F}
25340 packet is sent, and by @value{GDBN} before
25341 it transfers memory to the target. Transferred pointers to structured
25342 data should point to the already-coerced data at any time.
25346 @unnumberedsubsubsec struct stat
25347 @cindex struct stat, in file-i/o protocol
25349 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25350 is defined as follows:
25354 unsigned int st_dev; /* device */
25355 unsigned int st_ino; /* inode */
25356 mode_t st_mode; /* protection */
25357 unsigned int st_nlink; /* number of hard links */
25358 unsigned int st_uid; /* user ID of owner */
25359 unsigned int st_gid; /* group ID of owner */
25360 unsigned int st_rdev; /* device type (if inode device) */
25361 unsigned long st_size; /* total size, in bytes */
25362 unsigned long st_blksize; /* blocksize for filesystem I/O */
25363 unsigned long st_blocks; /* number of blocks allocated */
25364 time_t st_atime; /* time of last access */
25365 time_t st_mtime; /* time of last modification */
25366 time_t st_ctime; /* time of last change */
25370 The integral datatypes conform to the definitions given in the
25371 appropriate section (see @ref{Integral datatypes}, for details) so this
25372 structure is of size 64 bytes.
25374 The values of several fields have a restricted meaning and/or
25380 A value of 0 represents a file, 1 the console.
25383 No valid meaning for the target. Transmitted unchanged.
25386 Valid mode bits are described in @ref{Constants}. Any other
25387 bits have currently no meaning for the target.
25392 No valid meaning for the target. Transmitted unchanged.
25397 These values have a host and file system dependent
25398 accuracy. Especially on Windows hosts, the file system may not
25399 support exact timing values.
25402 The target gets a @code{struct stat} of the above representation and is
25403 responsible for coercing it to the target representation before
25406 Note that due to size differences between the host, target, and protocol
25407 representations of @code{struct stat} members, these members could eventually
25408 get truncated on the target.
25410 @node struct timeval
25411 @unnumberedsubsubsec struct timeval
25412 @cindex struct timeval, in file-i/o protocol
25414 The buffer of type @code{struct timeval} used by the File-I/O protocol
25415 is defined as follows:
25419 time_t tv_sec; /* second */
25420 long tv_usec; /* microsecond */
25424 The integral datatypes conform to the definitions given in the
25425 appropriate section (see @ref{Integral datatypes}, for details) so this
25426 structure is of size 8 bytes.
25429 @subsection Constants
25430 @cindex constants, in file-i/o protocol
25432 The following values are used for the constants inside of the
25433 protocol. @value{GDBN} and target are responsible for translating these
25434 values before and after the call as needed.
25445 @unnumberedsubsubsec Open flags
25446 @cindex open flags, in file-i/o protocol
25448 All values are given in hexadecimal representation.
25460 @node mode_t values
25461 @unnumberedsubsubsec mode_t values
25462 @cindex mode_t values, in file-i/o protocol
25464 All values are given in octal representation.
25481 @unnumberedsubsubsec Errno values
25482 @cindex errno values, in file-i/o protocol
25484 All values are given in decimal representation.
25509 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25510 any error value not in the list of supported error numbers.
25513 @unnumberedsubsubsec Lseek flags
25514 @cindex lseek flags, in file-i/o protocol
25523 @unnumberedsubsubsec Limits
25524 @cindex limits, in file-i/o protocol
25526 All values are given in decimal representation.
25529 INT_MIN -2147483648
25531 UINT_MAX 4294967295
25532 LONG_MIN -9223372036854775808
25533 LONG_MAX 9223372036854775807
25534 ULONG_MAX 18446744073709551615
25537 @node File-I/O Examples
25538 @subsection File-I/O Examples
25539 @cindex file-i/o examples
25541 Example sequence of a write call, file descriptor 3, buffer is at target
25542 address 0x1234, 6 bytes should be written:
25545 <- @code{Fwrite,3,1234,6}
25546 @emph{request memory read from target}
25549 @emph{return "6 bytes written"}
25553 Example sequence of a read call, file descriptor 3, buffer is at target
25554 address 0x1234, 6 bytes should be read:
25557 <- @code{Fread,3,1234,6}
25558 @emph{request memory write to target}
25559 -> @code{X1234,6:XXXXXX}
25560 @emph{return "6 bytes read"}
25564 Example sequence of a read call, call fails on the host due to invalid
25565 file descriptor (@code{EBADF}):
25568 <- @code{Fread,3,1234,6}
25572 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
25576 <- @code{Fread,3,1234,6}
25581 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
25585 <- @code{Fread,3,1234,6}
25586 -> @code{X1234,6:XXXXXX}
25590 @node Memory map format
25591 @section Memory map format
25592 @cindex memory map format
25594 To be able to write into flash memory, @value{GDBN} needs to obtain a
25595 memory map from the target. This section describes the format of the
25598 The memory map is obtained using the @samp{qXfer:memory-map:read}
25599 (@pxref{qXfer memory map read}) packet and is an XML document that
25600 lists memory regions. The top-level structure of the document is shown below:
25603 <?xml version="1.0"?>
25604 <!DOCTYPE memory-map
25605 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
25606 "http://sourceware.org/gdb/gdb-memory-map.dtd">
25612 Each region can be either:
25617 A region of RAM starting at @var{addr} and extending for @var{length}
25621 <memory type="ram" start="@var{addr}" length="@var{length}"/>
25626 A region of read-only memory:
25629 <memory type="rom" start="@var{addr}" length="@var{length}"/>
25634 A region of flash memory, with erasure blocks @var{blocksize}
25638 <memory type="flash" start="@var{addr}" length="@var{length}">
25639 <property name="blocksize">@var{blocksize}</property>
25645 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
25646 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
25647 packets to write to addresses in such ranges.
25649 The formal DTD for memory map format is given below:
25652 <!-- ................................................... -->
25653 <!-- Memory Map XML DTD ................................ -->
25654 <!-- File: memory-map.dtd .............................. -->
25655 <!-- .................................... .............. -->
25656 <!-- memory-map.dtd -->
25657 <!-- memory-map: Root element with versioning -->
25658 <!ELEMENT memory-map (memory | property)>
25659 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
25660 <!ELEMENT memory (property)>
25661 <!-- memory: Specifies a memory region,
25662 and its type, or device. -->
25663 <!ATTLIST memory type CDATA #REQUIRED
25664 start CDATA #REQUIRED
25665 length CDATA #REQUIRED
25666 device CDATA #IMPLIED>
25667 <!-- property: Generic attribute tag -->
25668 <!ELEMENT property (#PCDATA | property)*>
25669 <!ATTLIST property name CDATA #REQUIRED>
25672 @include agentexpr.texi
25674 @node Target Descriptions
25675 @appendix Target Descriptions
25676 @cindex target descriptions
25678 @strong{Warning:} target descriptions are still under active development,
25679 and the contents and format may change between @value{GDBN} releases.
25680 The format is expected to stabilize in the future.
25682 One of the challenges of using @value{GDBN} to debug embedded systems
25683 is that there are so many minor variants of each processor
25684 architecture in use. It is common practice for vendors to start with
25685 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
25686 and then make changes to adapt it to a particular market niche. Some
25687 architectures have hundreds of variants, available from dozens of
25688 vendors. This leads to a number of problems:
25692 With so many different customized processors, it is difficult for
25693 the @value{GDBN} maintainers to keep up with the changes.
25695 Since individual variants may have short lifetimes or limited
25696 audiences, it may not be worthwhile to carry information about every
25697 variant in the @value{GDBN} source tree.
25699 When @value{GDBN} does support the architecture of the embedded system
25700 at hand, the task of finding the correct architecture name to give the
25701 @command{set architecture} command can be error-prone.
25704 To address these problems, the @value{GDBN} remote protocol allows a
25705 target system to not only identify itself to @value{GDBN}, but to
25706 actually describe its own features. This lets @value{GDBN} support
25707 processor variants it has never seen before --- to the extent that the
25708 descriptions are accurate, and that @value{GDBN} understands them.
25710 @value{GDBN} must be compiled with Expat support to support XML target
25711 descriptions. @xref{Expat}.
25714 * Retrieving Descriptions:: How descriptions are fetched from a target.
25715 * Target Description Format:: The contents of a target description.
25716 * Predefined Target Types:: Standard types available for target
25718 * Standard Target Features:: Features @value{GDBN} knows about.
25721 @node Retrieving Descriptions
25722 @section Retrieving Descriptions
25724 Target descriptions can be read from the target automatically, or
25725 specified by the user manually. The default behavior is to read the
25726 description from the target. @value{GDBN} retrieves it via the remote
25727 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
25728 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
25729 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
25730 XML document, of the form described in @ref{Target Description
25733 Alternatively, you can specify a file to read for the target description.
25734 If a file is set, the target will not be queried. The commands to
25735 specify a file are:
25738 @cindex set tdesc filename
25739 @item set tdesc filename @var{path}
25740 Read the target description from @var{path}.
25742 @cindex unset tdesc filename
25743 @item unset tdesc filename
25744 Do not read the XML target description from a file. @value{GDBN}
25745 will use the description supplied by the current target.
25747 @cindex show tdesc filename
25748 @item show tdesc filename
25749 Show the filename to read for a target description, if any.
25753 @node Target Description Format
25754 @section Target Description Format
25755 @cindex target descriptions, XML format
25757 A target description annex is an @uref{http://www.w3.org/XML/, XML}
25758 document which complies with the Document Type Definition provided in
25759 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
25760 means you can use generally available tools like @command{xmllint} to
25761 check that your feature descriptions are well-formed and valid.
25762 However, to help people unfamiliar with XML write descriptions for
25763 their targets, we also describe the grammar here.
25765 Target descriptions can identify the architecture of the remote target
25766 and (for some architectures) provide information about custom register
25767 sets. @value{GDBN} can use this information to autoconfigure for your
25768 target, or to warn you if you connect to an unsupported target.
25770 Here is a simple target description:
25774 <architecture>i386:x86-64</architecture>
25779 This minimal description only says that the target uses
25780 the x86-64 architecture.
25782 A target description has the following overall form, with [ ] marking
25783 optional elements and @dots{} marking repeatable elements. The elements
25784 are explained further below.
25787 <?xml version="1.0"?>
25788 <!DOCTYPE target SYSTEM "gdb-target.dtd">
25790 @r{[}@var{architecture}@r{]}
25791 @r{[}@var{feature}@dots{}@r{]}
25796 The description is generally insensitive to whitespace and line
25797 breaks, under the usual common-sense rules. The XML version
25798 declaration and document type declaration can generally be omitted
25799 (@value{GDBN} does not require them), but specifying them may be
25800 useful for XML validation tools.
25802 @subsection Inclusion
25803 @cindex target descriptions, inclusion
25806 @cindex <xi:include>
25809 It can sometimes be valuable to split a target description up into
25810 several different annexes, either for organizational purposes, or to
25811 share files between different possible target descriptions. You can
25812 divide a description into multiple files by replacing any element of
25813 the target description with an inclusion directive of the form:
25816 <xi:include href="@var{document}"/>
25820 When @value{GDBN} encounters an element of this form, it will retrieve
25821 the named XML @var{document}, and replace the inclusion directive with
25822 the contents of that document. If the current description was read
25823 using @samp{qXfer}, then so will be the included document;
25824 @var{document} will be interpreted as the name of an annex. If the
25825 current description was read from a file, @value{GDBN} will look for
25826 @var{document} as a file in the same directory where it found the
25827 original description.
25829 @subsection Architecture
25830 @cindex <architecture>
25832 An @samp{<architecture>} element has this form:
25835 <architecture>@var{arch}</architecture>
25838 @var{arch} is an architecture name from the same selection
25839 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
25840 Debugging Target}).
25842 @subsection Features
25845 Each @samp{<feature>} describes some logical portion of the target
25846 system. Features are currently used to describe available CPU
25847 registers and the types of their contents. A @samp{<feature>} element
25851 <feature name="@var{name}">
25852 @r{[}@var{type}@dots{}@r{]}
25858 Each feature's name should be unique within the description. The name
25859 of a feature does not matter unless @value{GDBN} has some special
25860 knowledge of the contents of that feature; if it does, the feature
25861 should have its standard name. @xref{Standard Target Features}.
25865 Any register's value is a collection of bits which @value{GDBN} must
25866 interpret. The default interpretation is a two's complement integer,
25867 but other types can be requested by name in the register description.
25868 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
25869 Target Types}), and the description can define additional composite types.
25871 Each type element must have an @samp{id} attribute, which gives
25872 a unique (within the containing @samp{<feature>}) name to the type.
25873 Types must be defined before they are used.
25876 Some targets offer vector registers, which can be treated as arrays
25877 of scalar elements. These types are written as @samp{<vector>} elements,
25878 specifying the array element type, @var{type}, and the number of elements,
25882 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
25886 If a register's value is usefully viewed in multiple ways, define it
25887 with a union type containing the useful representations. The
25888 @samp{<union>} element contains one or more @samp{<field>} elements,
25889 each of which has a @var{name} and a @var{type}:
25892 <union id="@var{id}">
25893 <field name="@var{name}" type="@var{type}"/>
25898 @subsection Registers
25901 Each register is represented as an element with this form:
25904 <reg name="@var{name}"
25905 bitsize="@var{size}"
25906 @r{[}regnum="@var{num}"@r{]}
25907 @r{[}save-restore="@var{save-restore}"@r{]}
25908 @r{[}type="@var{type}"@r{]}
25909 @r{[}group="@var{group}"@r{]}/>
25913 The components are as follows:
25918 The register's name; it must be unique within the target description.
25921 The register's size, in bits.
25924 The register's number. If omitted, a register's number is one greater
25925 than that of the previous register (either in the current feature or in
25926 a preceeding feature); the first register in the target description
25927 defaults to zero. This register number is used to read or write
25928 the register; e.g.@: it is used in the remote @code{p} and @code{P}
25929 packets, and registers appear in the @code{g} and @code{G} packets
25930 in order of increasing register number.
25933 Whether the register should be preserved across inferior function
25934 calls; this must be either @code{yes} or @code{no}. The default is
25935 @code{yes}, which is appropriate for most registers except for
25936 some system control registers; this is not related to the target's
25940 The type of the register. @var{type} may be a predefined type, a type
25941 defined in the current feature, or one of the special types @code{int}
25942 and @code{float}. @code{int} is an integer type of the correct size
25943 for @var{bitsize}, and @code{float} is a floating point type (in the
25944 architecture's normal floating point format) of the correct size for
25945 @var{bitsize}. The default is @code{int}.
25948 The register group to which this register belongs. @var{group} must
25949 be either @code{general}, @code{float}, or @code{vector}. If no
25950 @var{group} is specified, @value{GDBN} will not display the register
25951 in @code{info registers}.
25955 @node Predefined Target Types
25956 @section Predefined Target Types
25957 @cindex target descriptions, predefined types
25959 Type definitions in the self-description can build up composite types
25960 from basic building blocks, but can not define fundamental types. Instead,
25961 standard identifiers are provided by @value{GDBN} for the fundamental
25962 types. The currently supported types are:
25970 Signed integer types holding the specified number of bits.
25976 Unsigned integer types holding the specified number of bits.
25980 Pointers to unspecified code and data. The program counter and
25981 any dedicated return address register may be marked as code
25982 pointers; printing a code pointer converts it into a symbolic
25983 address. The stack pointer and any dedicated address registers
25984 may be marked as data pointers.
25987 The 12-byte extended precision format used by ARM FPA registers.
25991 @node Standard Target Features
25992 @section Standard Target Features
25993 @cindex target descriptions, standard features
25995 A target description must contain either no registers or all the
25996 target's registers. If the description contains no registers, then
25997 @value{GDBN} will assume a default register layout, selected based on
25998 the architecture. If the description contains any registers, the
25999 default layout will not be used; the standard registers must be
26000 described in the target description, in such a way that @value{GDBN}
26001 can recognize them.
26003 This is accomplished by giving specific names to feature elements
26004 which contain standard registers. @value{GDBN} will look for features
26005 with those names and verify that they contain the expected registers;
26006 if any known feature is missing required registers, or if any required
26007 feature is missing, @value{GDBN} will reject the target
26008 description. You can add additional registers to any of the
26009 standard features --- @value{GDBN} will display them just as if
26010 they were added to an unrecognized feature.
26012 This section lists the known features and their expected contents.
26013 Sample XML documents for these features are included in the
26014 @value{GDBN} source tree, in the directory @file{gdb/features}.
26016 Names recognized by @value{GDBN} should include the name of the
26017 company or organization which selected the name, and the overall
26018 architecture to which the feature applies; so e.g.@: the feature
26019 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
26021 The names of registers are not case sensitive for the purpose
26022 of recognizing standard features, but @value{GDBN} will only display
26023 registers using the capitalization used in the description.
26025 @subsection ARM Features
26026 @cindex target descriptions, ARM features
26028 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
26029 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
26030 @samp{lr}, @samp{pc}, and @samp{cpsr}.
26032 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
26033 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
26035 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
26036 it should contain at least registers @samp{wR0} through @samp{wR15} and
26037 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
26038 @samp{wCSSF}, and @samp{wCASF} registers are optional.
26052 % I think something like @colophon should be in texinfo. In the
26054 \long\def\colophon{\hbox to0pt{}\vfill
26055 \centerline{The body of this manual is set in}
26056 \centerline{\fontname\tenrm,}
26057 \centerline{with headings in {\bf\fontname\tenbf}}
26058 \centerline{and examples in {\tt\fontname\tentt}.}
26059 \centerline{{\it\fontname\tenit\/},}
26060 \centerline{{\bf\fontname\tenbf}, and}
26061 \centerline{{\sl\fontname\tensl\/}}
26062 \centerline{are used for emphasis.}\vfill}
26064 % Blame: doc@cygnus.com, 1991.