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 * TUI:: @value{GDBN} Text User Interface
148 * Interpreters:: Command Interpreters
149 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
150 * Annotations:: @value{GDBN}'s annotation interface.
151 * GDB/MI:: @value{GDBN}'s Machine Interface.
153 * GDB Bugs:: Reporting bugs in @value{GDBN}
154 * Formatting Documentation:: How to format and print @value{GDBN} documentation
156 * Command Line Editing:: Command Line Editing
157 * Using History Interactively:: Using History Interactively
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 gdb --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 The @value{GDBN} init files are normally called @file{.gdbinit}.
1244 On some configurations of @value{GDBN}, the init file is known by a
1245 different name (these are typically environments where a specialized
1246 form of @value{GDBN} may need to coexist with other forms, hence a
1247 different name for the specialized version's init file). These are the
1248 environments with special init file names:
1251 @cindex @file{gdb.ini}
1253 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1254 the limitations of file names imposed by DOS filesystems. The Windows
1255 ports of @value{GDBN} use the standard name, but if they find a
1256 @file{gdb.ini} file, they warn you about that and suggest to rename
1257 the file to the standard name.
1259 @cindex @file{.vxgdbinit}
1261 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1263 @cindex @file{.os68gdbinit}
1265 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1267 @cindex @file{.esgdbinit}
1269 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1272 CISCO 68k: @file{.cisco-gdbinit}
1277 @section Quitting @value{GDBN}
1278 @cindex exiting @value{GDBN}
1279 @cindex leaving @value{GDBN}
1282 @kindex quit @r{[}@var{expression}@r{]}
1283 @kindex q @r{(@code{quit})}
1284 @item quit @r{[}@var{expression}@r{]}
1286 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1287 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1288 do not supply @var{expression}, @value{GDBN} will terminate normally;
1289 otherwise it will terminate using the result of @var{expression} as the
1294 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1295 terminates the action of any @value{GDBN} command that is in progress and
1296 returns to @value{GDBN} command level. It is safe to type the interrupt
1297 character at any time because @value{GDBN} does not allow it to take effect
1298 until a time when it is safe.
1300 If you have been using @value{GDBN} to control an attached process or
1301 device, you can release it with the @code{detach} command
1302 (@pxref{Attach, ,Debugging an already-running process}).
1304 @node Shell Commands
1305 @section Shell commands
1307 If you need to execute occasional shell commands during your
1308 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1309 just use the @code{shell} command.
1313 @cindex shell escape
1314 @item shell @var{command string}
1315 Invoke a standard shell to execute @var{command string}.
1316 If it exists, the environment variable @code{SHELL} determines which
1317 shell to run. Otherwise @value{GDBN} uses the default shell
1318 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1321 The utility @code{make} is often needed in development environments.
1322 You do not have to use the @code{shell} command for this purpose in
1327 @cindex calling make
1328 @item make @var{make-args}
1329 Execute the @code{make} program with the specified
1330 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1333 @node Logging output
1334 @section Logging output
1335 @cindex logging @value{GDBN} output
1336 @cindex save @value{GDBN} output to a file
1338 You may want to save the output of @value{GDBN} commands to a file.
1339 There are several commands to control @value{GDBN}'s logging.
1343 @item set logging on
1345 @item set logging off
1347 @cindex logging file name
1348 @item set logging file @var{file}
1349 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1350 @item set logging overwrite [on|off]
1351 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1352 you want @code{set logging on} to overwrite the logfile instead.
1353 @item set logging redirect [on|off]
1354 By default, @value{GDBN} output will go to both the terminal and the logfile.
1355 Set @code{redirect} if you want output to go only to the log file.
1356 @kindex show logging
1358 Show the current values of the logging settings.
1362 @chapter @value{GDBN} Commands
1364 You can abbreviate a @value{GDBN} command to the first few letters of the command
1365 name, if that abbreviation is unambiguous; and you can repeat certain
1366 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1367 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1368 show you the alternatives available, if there is more than one possibility).
1371 * Command Syntax:: How to give commands to @value{GDBN}
1372 * Completion:: Command completion
1373 * Help:: How to ask @value{GDBN} for help
1376 @node Command Syntax
1377 @section Command syntax
1379 A @value{GDBN} command is a single line of input. There is no limit on
1380 how long it can be. It starts with a command name, which is followed by
1381 arguments whose meaning depends on the command name. For example, the
1382 command @code{step} accepts an argument which is the number of times to
1383 step, as in @samp{step 5}. You can also use the @code{step} command
1384 with no arguments. Some commands do not allow any arguments.
1386 @cindex abbreviation
1387 @value{GDBN} command names may always be truncated if that abbreviation is
1388 unambiguous. Other possible command abbreviations are listed in the
1389 documentation for individual commands. In some cases, even ambiguous
1390 abbreviations are allowed; for example, @code{s} is specially defined as
1391 equivalent to @code{step} even though there are other commands whose
1392 names start with @code{s}. You can test abbreviations by using them as
1393 arguments to the @code{help} command.
1395 @cindex repeating commands
1396 @kindex RET @r{(repeat last command)}
1397 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1398 repeat the previous command. Certain commands (for example, @code{run})
1399 will not repeat this way; these are commands whose unintentional
1400 repetition might cause trouble and which you are unlikely to want to
1401 repeat. User-defined commands can disable this feature; see
1402 @ref{Define, dont-repeat}.
1404 The @code{list} and @code{x} commands, when you repeat them with
1405 @key{RET}, construct new arguments rather than repeating
1406 exactly as typed. This permits easy scanning of source or memory.
1408 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1409 output, in a way similar to the common utility @code{more}
1410 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1411 @key{RET} too many in this situation, @value{GDBN} disables command
1412 repetition after any command that generates this sort of display.
1414 @kindex # @r{(a comment)}
1416 Any text from a @kbd{#} to the end of the line is a comment; it does
1417 nothing. This is useful mainly in command files (@pxref{Command
1418 Files,,Command files}).
1420 @cindex repeating command sequences
1421 @kindex Ctrl-o @r{(operate-and-get-next)}
1422 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1423 commands. This command accepts the current line, like @key{RET}, and
1424 then fetches the next line relative to the current line from the history
1428 @section Command completion
1431 @cindex word completion
1432 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1433 only one possibility; it can also show you what the valid possibilities
1434 are for the next word in a command, at any time. This works for @value{GDBN}
1435 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1437 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1438 of a word. If there is only one possibility, @value{GDBN} fills in the
1439 word, and waits for you to finish the command (or press @key{RET} to
1440 enter it). For example, if you type
1442 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1443 @c complete accuracy in these examples; space introduced for clarity.
1444 @c If texinfo enhancements make it unnecessary, it would be nice to
1445 @c replace " @key" by "@key" in the following...
1447 (@value{GDBP}) info bre @key{TAB}
1451 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1452 the only @code{info} subcommand beginning with @samp{bre}:
1455 (@value{GDBP}) info breakpoints
1459 You can either press @key{RET} at this point, to run the @code{info
1460 breakpoints} command, or backspace and enter something else, if
1461 @samp{breakpoints} does not look like the command you expected. (If you
1462 were sure you wanted @code{info breakpoints} in the first place, you
1463 might as well just type @key{RET} immediately after @samp{info bre},
1464 to exploit command abbreviations rather than command completion).
1466 If there is more than one possibility for the next word when you press
1467 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1468 characters and try again, or just press @key{TAB} a second time;
1469 @value{GDBN} displays all the possible completions for that word. For
1470 example, you might want to set a breakpoint on a subroutine whose name
1471 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1472 just sounds the bell. Typing @key{TAB} again displays all the
1473 function names in your program that begin with those characters, for
1477 (@value{GDBP}) b make_ @key{TAB}
1478 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1479 make_a_section_from_file make_environ
1480 make_abs_section make_function_type
1481 make_blockvector make_pointer_type
1482 make_cleanup make_reference_type
1483 make_command make_symbol_completion_list
1484 (@value{GDBP}) b make_
1488 After displaying the available possibilities, @value{GDBN} copies your
1489 partial input (@samp{b make_} in the example) so you can finish the
1492 If you just want to see the list of alternatives in the first place, you
1493 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1494 means @kbd{@key{META} ?}. You can type this either by holding down a
1495 key designated as the @key{META} shift on your keyboard (if there is
1496 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1498 @cindex quotes in commands
1499 @cindex completion of quoted strings
1500 Sometimes the string you need, while logically a ``word'', may contain
1501 parentheses or other characters that @value{GDBN} normally excludes from
1502 its notion of a word. To permit word completion to work in this
1503 situation, you may enclose words in @code{'} (single quote marks) in
1504 @value{GDBN} commands.
1506 The most likely situation where you might need this is in typing the
1507 name of a C@t{++} function. This is because C@t{++} allows function
1508 overloading (multiple definitions of the same function, distinguished
1509 by argument type). For example, when you want to set a breakpoint you
1510 may need to distinguish whether you mean the version of @code{name}
1511 that takes an @code{int} parameter, @code{name(int)}, or the version
1512 that takes a @code{float} parameter, @code{name(float)}. To use the
1513 word-completion facilities in this situation, type a single quote
1514 @code{'} at the beginning of the function name. This alerts
1515 @value{GDBN} that it may need to consider more information than usual
1516 when you press @key{TAB} or @kbd{M-?} to request word completion:
1519 (@value{GDBP}) b 'bubble( @kbd{M-?}
1520 bubble(double,double) bubble(int,int)
1521 (@value{GDBP}) b 'bubble(
1524 In some cases, @value{GDBN} can tell that completing a name requires using
1525 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1526 completing as much as it can) if you do not type the quote in the first
1530 (@value{GDBP}) b bub @key{TAB}
1531 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1532 (@value{GDBP}) b 'bubble(
1536 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1537 you have not yet started typing the argument list when you ask for
1538 completion on an overloaded symbol.
1540 For more information about overloaded functions, see @ref{C plus plus
1541 expressions, ,C@t{++} expressions}. You can use the command @code{set
1542 overload-resolution off} to disable overload resolution;
1543 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1547 @section Getting help
1548 @cindex online documentation
1551 You can always ask @value{GDBN} itself for information on its commands,
1552 using the command @code{help}.
1555 @kindex h @r{(@code{help})}
1558 You can use @code{help} (abbreviated @code{h}) with no arguments to
1559 display a short list of named classes of commands:
1563 List of classes of commands:
1565 aliases -- Aliases of other commands
1566 breakpoints -- Making program stop at certain points
1567 data -- Examining data
1568 files -- Specifying and examining files
1569 internals -- Maintenance commands
1570 obscure -- Obscure features
1571 running -- Running the program
1572 stack -- Examining the stack
1573 status -- Status inquiries
1574 support -- Support facilities
1575 tracepoints -- Tracing of program execution without@*
1576 stopping the program
1577 user-defined -- User-defined commands
1579 Type "help" followed by a class name for a list of
1580 commands in that class.
1581 Type "help" followed by command name for full
1583 Command name abbreviations are allowed if unambiguous.
1586 @c the above line break eliminates huge line overfull...
1588 @item help @var{class}
1589 Using one of the general help classes as an argument, you can get a
1590 list of the individual commands in that class. For example, here is the
1591 help display for the class @code{status}:
1594 (@value{GDBP}) help status
1599 @c Line break in "show" line falsifies real output, but needed
1600 @c to fit in smallbook page size.
1601 info -- Generic command for showing things
1602 about the program being debugged
1603 show -- Generic command for showing things
1606 Type "help" followed by command name for full
1608 Command name abbreviations are allowed if unambiguous.
1612 @item help @var{command}
1613 With a command name as @code{help} argument, @value{GDBN} displays a
1614 short paragraph on how to use that command.
1617 @item apropos @var{args}
1618 The @code{apropos} command searches through all of the @value{GDBN}
1619 commands, and their documentation, for the regular expression specified in
1620 @var{args}. It prints out all matches found. For example:
1631 set symbol-reloading -- Set dynamic symbol table reloading
1632 multiple times in one run
1633 show symbol-reloading -- Show dynamic symbol table reloading
1634 multiple times in one run
1639 @item complete @var{args}
1640 The @code{complete @var{args}} command lists all the possible completions
1641 for the beginning of a command. Use @var{args} to specify the beginning of the
1642 command you want completed. For example:
1648 @noindent results in:
1659 @noindent This is intended for use by @sc{gnu} Emacs.
1662 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1663 and @code{show} to inquire about the state of your program, or the state
1664 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1665 manual introduces each of them in the appropriate context. The listings
1666 under @code{info} and under @code{show} in the Index point to
1667 all the sub-commands. @xref{Index}.
1672 @kindex i @r{(@code{info})}
1674 This command (abbreviated @code{i}) is for describing the state of your
1675 program. For example, you can list the arguments given to your program
1676 with @code{info args}, list the registers currently in use with @code{info
1677 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1678 You can get a complete list of the @code{info} sub-commands with
1679 @w{@code{help info}}.
1683 You can assign the result of an expression to an environment variable with
1684 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1685 @code{set prompt $}.
1689 In contrast to @code{info}, @code{show} is for describing the state of
1690 @value{GDBN} itself.
1691 You can change most of the things you can @code{show}, by using the
1692 related command @code{set}; for example, you can control what number
1693 system is used for displays with @code{set radix}, or simply inquire
1694 which is currently in use with @code{show radix}.
1697 To display all the settable parameters and their current
1698 values, you can use @code{show} with no arguments; you may also use
1699 @code{info set}. Both commands produce the same display.
1700 @c FIXME: "info set" violates the rule that "info" is for state of
1701 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1702 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1706 Here are three miscellaneous @code{show} subcommands, all of which are
1707 exceptional in lacking corresponding @code{set} commands:
1710 @kindex show version
1711 @cindex @value{GDBN} version number
1713 Show what version of @value{GDBN} is running. You should include this
1714 information in @value{GDBN} bug-reports. If multiple versions of
1715 @value{GDBN} are in use at your site, you may need to determine which
1716 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1717 commands are introduced, and old ones may wither away. Also, many
1718 system vendors ship variant versions of @value{GDBN}, and there are
1719 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1720 The version number is the same as the one announced when you start
1723 @kindex show copying
1724 @kindex info copying
1725 @cindex display @value{GDBN} copyright
1728 Display information about permission for copying @value{GDBN}.
1730 @kindex show warranty
1731 @kindex info warranty
1733 @itemx info warranty
1734 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1735 if your version of @value{GDBN} comes with one.
1740 @chapter Running Programs Under @value{GDBN}
1742 When you run a program under @value{GDBN}, you must first generate
1743 debugging information when you compile it.
1745 You may start @value{GDBN} with its arguments, if any, in an environment
1746 of your choice. If you are doing native debugging, you may redirect
1747 your program's input and output, debug an already running process, or
1748 kill a child process.
1751 * Compilation:: Compiling for debugging
1752 * Starting:: Starting your program
1753 * Arguments:: Your program's arguments
1754 * Environment:: Your program's environment
1756 * Working Directory:: Your program's working directory
1757 * Input/Output:: Your program's input and output
1758 * Attach:: Debugging an already-running process
1759 * Kill Process:: Killing the child process
1761 * Threads:: Debugging programs with multiple threads
1762 * Processes:: Debugging programs with multiple processes
1763 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1767 @section Compiling for debugging
1769 In order to debug a program effectively, you need to generate
1770 debugging information when you compile it. This debugging information
1771 is stored in the object file; it describes the data type of each
1772 variable or function and the correspondence between source line numbers
1773 and addresses in the executable code.
1775 To request debugging information, specify the @samp{-g} option when you run
1778 Programs that are to be shipped to your customers are compiled with
1779 optimizations, using the @samp{-O} compiler option. However, many
1780 compilers are unable to handle the @samp{-g} and @samp{-O} options
1781 together. Using those compilers, you cannot generate optimized
1782 executables containing debugging information.
1784 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1785 without @samp{-O}, making it possible to debug optimized code. We
1786 recommend that you @emph{always} use @samp{-g} whenever you compile a
1787 program. You may think your program is correct, but there is no sense
1788 in pushing your luck.
1790 @cindex optimized code, debugging
1791 @cindex debugging optimized code
1792 When you debug a program compiled with @samp{-g -O}, remember that the
1793 optimizer is rearranging your code; the debugger shows you what is
1794 really there. Do not be too surprised when the execution path does not
1795 exactly match your source file! An extreme example: if you define a
1796 variable, but never use it, @value{GDBN} never sees that
1797 variable---because the compiler optimizes it out of existence.
1799 Some things do not work as well with @samp{-g -O} as with just
1800 @samp{-g}, particularly on machines with instruction scheduling. If in
1801 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1802 please report it to us as a bug (including a test case!).
1803 @xref{Variables}, for more information about debugging optimized code.
1805 Older versions of the @sc{gnu} C compiler permitted a variant option
1806 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1807 format; if your @sc{gnu} C compiler has this option, do not use it.
1809 @value{GDBN} knows about preprocessor macros and can show you their
1810 expansion (@pxref{Macros}). Most compilers do not include information
1811 about preprocessor macros in the debugging information if you specify
1812 the @option{-g} flag alone, because this information is rather large.
1813 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1814 provides macro information if you specify the options
1815 @option{-gdwarf-2} and @option{-g3}; the former option requests
1816 debugging information in the Dwarf 2 format, and the latter requests
1817 ``extra information''. In the future, we hope to find more compact
1818 ways to represent macro information, so that it can be included with
1823 @section Starting your program
1829 @kindex r @r{(@code{run})}
1832 Use the @code{run} command to start your program under @value{GDBN}.
1833 You must first specify the program name (except on VxWorks) with an
1834 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1835 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1836 (@pxref{Files, ,Commands to specify files}).
1840 If you are running your program in an execution environment that
1841 supports processes, @code{run} creates an inferior process and makes
1842 that process run your program. (In environments without processes,
1843 @code{run} jumps to the start of your program.)
1845 The execution of a program is affected by certain information it
1846 receives from its superior. @value{GDBN} provides ways to specify this
1847 information, which you must do @emph{before} starting your program. (You
1848 can change it after starting your program, but such changes only affect
1849 your program the next time you start it.) This information may be
1850 divided into four categories:
1853 @item The @emph{arguments.}
1854 Specify the arguments to give your program as the arguments of the
1855 @code{run} command. If a shell is available on your target, the shell
1856 is used to pass the arguments, so that you may use normal conventions
1857 (such as wildcard expansion or variable substitution) in describing
1859 In Unix systems, you can control which shell is used with the
1860 @code{SHELL} environment variable.
1861 @xref{Arguments, ,Your program's arguments}.
1863 @item The @emph{environment.}
1864 Your program normally inherits its environment from @value{GDBN}, but you can
1865 use the @value{GDBN} commands @code{set environment} and @code{unset
1866 environment} to change parts of the environment that affect
1867 your program. @xref{Environment, ,Your program's environment}.
1869 @item The @emph{working directory.}
1870 Your program inherits its working directory from @value{GDBN}. You can set
1871 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1872 @xref{Working Directory, ,Your program's working directory}.
1874 @item The @emph{standard input and output.}
1875 Your program normally uses the same device for standard input and
1876 standard output as @value{GDBN} is using. You can redirect input and output
1877 in the @code{run} command line, or you can use the @code{tty} command to
1878 set a different device for your program.
1879 @xref{Input/Output, ,Your program's input and output}.
1882 @emph{Warning:} While input and output redirection work, you cannot use
1883 pipes to pass the output of the program you are debugging to another
1884 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1888 When you issue the @code{run} command, your program begins to execute
1889 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1890 of how to arrange for your program to stop. Once your program has
1891 stopped, you may call functions in your program, using the @code{print}
1892 or @code{call} commands. @xref{Data, ,Examining Data}.
1894 If the modification time of your symbol file has changed since the last
1895 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1896 table, and reads it again. When it does this, @value{GDBN} tries to retain
1897 your current breakpoints.
1902 @cindex run to main procedure
1903 The name of the main procedure can vary from language to language.
1904 With C or C@t{++}, the main procedure name is always @code{main}, but
1905 other languages such as Ada do not require a specific name for their
1906 main procedure. The debugger provides a convenient way to start the
1907 execution of the program and to stop at the beginning of the main
1908 procedure, depending on the language used.
1910 The @samp{start} command does the equivalent of setting a temporary
1911 breakpoint at the beginning of the main procedure and then invoking
1912 the @samp{run} command.
1914 @cindex elaboration phase
1915 Some programs contain an @dfn{elaboration} phase where some startup code is
1916 executed before the main procedure is called. This depends on the
1917 languages used to write your program. In C@t{++}, for instance,
1918 constructors for static and global objects are executed before
1919 @code{main} is called. It is therefore possible that the debugger stops
1920 before reaching the main procedure. However, the temporary breakpoint
1921 will remain to halt execution.
1923 Specify the arguments to give to your program as arguments to the
1924 @samp{start} command. These arguments will be given verbatim to the
1925 underlying @samp{run} command. Note that the same arguments will be
1926 reused if no argument is provided during subsequent calls to
1927 @samp{start} or @samp{run}.
1929 It is sometimes necessary to debug the program during elaboration. In
1930 these cases, using the @code{start} command would stop the execution of
1931 your program too late, as the program would have already completed the
1932 elaboration phase. Under these circumstances, insert breakpoints in your
1933 elaboration code before running your program.
1937 @section Your program's arguments
1939 @cindex arguments (to your program)
1940 The arguments to your program can be specified by the arguments of the
1942 They are passed to a shell, which expands wildcard characters and
1943 performs redirection of I/O, and thence to your program. Your
1944 @code{SHELL} environment variable (if it exists) specifies what shell
1945 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1946 the default shell (@file{/bin/sh} on Unix).
1948 On non-Unix systems, the program is usually invoked directly by
1949 @value{GDBN}, which emulates I/O redirection via the appropriate system
1950 calls, and the wildcard characters are expanded by the startup code of
1951 the program, not by the shell.
1953 @code{run} with no arguments uses the same arguments used by the previous
1954 @code{run}, or those set by the @code{set args} command.
1959 Specify the arguments to be used the next time your program is run. If
1960 @code{set args} has no arguments, @code{run} executes your program
1961 with no arguments. Once you have run your program with arguments,
1962 using @code{set args} before the next @code{run} is the only way to run
1963 it again without arguments.
1967 Show the arguments to give your program when it is started.
1971 @section Your program's environment
1973 @cindex environment (of your program)
1974 The @dfn{environment} consists of a set of environment variables and
1975 their values. Environment variables conventionally record such things as
1976 your user name, your home directory, your terminal type, and your search
1977 path for programs to run. Usually you set up environment variables with
1978 the shell and they are inherited by all the other programs you run. When
1979 debugging, it can be useful to try running your program with a modified
1980 environment without having to start @value{GDBN} over again.
1984 @item path @var{directory}
1985 Add @var{directory} to the front of the @code{PATH} environment variable
1986 (the search path for executables) that will be passed to your program.
1987 The value of @code{PATH} used by @value{GDBN} does not change.
1988 You may specify several directory names, separated by whitespace or by a
1989 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1990 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1991 is moved to the front, so it is searched sooner.
1993 You can use the string @samp{$cwd} to refer to whatever is the current
1994 working directory at the time @value{GDBN} searches the path. If you
1995 use @samp{.} instead, it refers to the directory where you executed the
1996 @code{path} command. @value{GDBN} replaces @samp{.} in the
1997 @var{directory} argument (with the current path) before adding
1998 @var{directory} to the search path.
1999 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2000 @c document that, since repeating it would be a no-op.
2004 Display the list of search paths for executables (the @code{PATH}
2005 environment variable).
2007 @kindex show environment
2008 @item show environment @r{[}@var{varname}@r{]}
2009 Print the value of environment variable @var{varname} to be given to
2010 your program when it starts. If you do not supply @var{varname},
2011 print the names and values of all environment variables to be given to
2012 your program. You can abbreviate @code{environment} as @code{env}.
2014 @kindex set environment
2015 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2016 Set environment variable @var{varname} to @var{value}. The value
2017 changes for your program only, not for @value{GDBN} itself. @var{value} may
2018 be any string; the values of environment variables are just strings, and
2019 any interpretation is supplied by your program itself. The @var{value}
2020 parameter is optional; if it is eliminated, the variable is set to a
2022 @c "any string" here does not include leading, trailing
2023 @c blanks. Gnu asks: does anyone care?
2025 For example, this command:
2032 tells the debugged program, when subsequently run, that its user is named
2033 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2034 are not actually required.)
2036 @kindex unset environment
2037 @item unset environment @var{varname}
2038 Remove variable @var{varname} from the environment to be passed to your
2039 program. This is different from @samp{set env @var{varname} =};
2040 @code{unset environment} removes the variable from the environment,
2041 rather than assigning it an empty value.
2044 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2046 by your @code{SHELL} environment variable if it exists (or
2047 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2048 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2049 @file{.bashrc} for BASH---any variables you set in that file affect
2050 your program. You may wish to move setting of environment variables to
2051 files that are only run when you sign on, such as @file{.login} or
2054 @node Working Directory
2055 @section Your program's working directory
2057 @cindex working directory (of your program)
2058 Each time you start your program with @code{run}, it inherits its
2059 working directory from the current working directory of @value{GDBN}.
2060 The @value{GDBN} working directory is initially whatever it inherited
2061 from its parent process (typically the shell), but you can specify a new
2062 working directory in @value{GDBN} with the @code{cd} command.
2064 The @value{GDBN} working directory also serves as a default for the commands
2065 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2070 @cindex change working directory
2071 @item cd @var{directory}
2072 Set the @value{GDBN} working directory to @var{directory}.
2076 Print the @value{GDBN} working directory.
2079 It is generally impossible to find the current working directory of
2080 the process being debugged (since a program can change its directory
2081 during its run). If you work on a system where @value{GDBN} is
2082 configured with the @file{/proc} support, you can use the @code{info
2083 proc} command (@pxref{SVR4 Process Information}) to find out the
2084 current working directory of the debuggee.
2087 @section Your program's input and output
2092 By default, the program you run under @value{GDBN} does input and output to
2093 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2094 to its own terminal modes to interact with you, but it records the terminal
2095 modes your program was using and switches back to them when you continue
2096 running your program.
2099 @kindex info terminal
2101 Displays information recorded by @value{GDBN} about the terminal modes your
2105 You can redirect your program's input and/or output using shell
2106 redirection with the @code{run} command. For example,
2113 starts your program, diverting its output to the file @file{outfile}.
2116 @cindex controlling terminal
2117 Another way to specify where your program should do input and output is
2118 with the @code{tty} command. This command accepts a file name as
2119 argument, and causes this file to be the default for future @code{run}
2120 commands. It also resets the controlling terminal for the child
2121 process, for future @code{run} commands. For example,
2128 directs that processes started with subsequent @code{run} commands
2129 default to do input and output on the terminal @file{/dev/ttyb} and have
2130 that as their controlling terminal.
2132 An explicit redirection in @code{run} overrides the @code{tty} command's
2133 effect on the input/output device, but not its effect on the controlling
2136 When you use the @code{tty} command or redirect input in the @code{run}
2137 command, only the input @emph{for your program} is affected. The input
2138 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2139 for @code{set inferior-tty}.
2141 @cindex inferior tty
2142 @cindex set inferior controlling terminal
2143 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2144 display the name of the terminal that will be used for future runs of your
2148 @item set inferior-tty /dev/ttyb
2149 @kindex set inferior-tty
2150 Set the tty for the program being debugged to /dev/ttyb.
2152 @item show inferior-tty
2153 @kindex show inferior-tty
2154 Show the current tty for the program being debugged.
2158 @section Debugging an already-running process
2163 @item attach @var{process-id}
2164 This command attaches to a running process---one that was started
2165 outside @value{GDBN}. (@code{info files} shows your active
2166 targets.) The command takes as argument a process ID. The usual way to
2167 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2168 or with the @samp{jobs -l} shell command.
2170 @code{attach} does not repeat if you press @key{RET} a second time after
2171 executing the command.
2174 To use @code{attach}, your program must be running in an environment
2175 which supports processes; for example, @code{attach} does not work for
2176 programs on bare-board targets that lack an operating system. You must
2177 also have permission to send the process a signal.
2179 When you use @code{attach}, the debugger finds the program running in
2180 the process first by looking in the current working directory, then (if
2181 the program is not found) by using the source file search path
2182 (@pxref{Source Path, ,Specifying source directories}). You can also use
2183 the @code{file} command to load the program. @xref{Files, ,Commands to
2186 The first thing @value{GDBN} does after arranging to debug the specified
2187 process is to stop it. You can examine and modify an attached process
2188 with all the @value{GDBN} commands that are ordinarily available when
2189 you start processes with @code{run}. You can insert breakpoints; you
2190 can step and continue; you can modify storage. If you would rather the
2191 process continue running, you may use the @code{continue} command after
2192 attaching @value{GDBN} to the process.
2197 When you have finished debugging the attached process, you can use the
2198 @code{detach} command to release it from @value{GDBN} control. Detaching
2199 the process continues its execution. After the @code{detach} command,
2200 that process and @value{GDBN} become completely independent once more, and you
2201 are ready to @code{attach} another process or start one with @code{run}.
2202 @code{detach} does not repeat if you press @key{RET} again after
2203 executing the command.
2206 If you exit @value{GDBN} or use the @code{run} command while you have an
2207 attached process, you kill that process. By default, @value{GDBN} asks
2208 for confirmation if you try to do either of these things; you can
2209 control whether or not you need to confirm by using the @code{set
2210 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2214 @section Killing the child process
2219 Kill the child process in which your program is running under @value{GDBN}.
2222 This command is useful if you wish to debug a core dump instead of a
2223 running process. @value{GDBN} ignores any core dump file while your program
2226 On some operating systems, a program cannot be executed outside @value{GDBN}
2227 while you have breakpoints set on it inside @value{GDBN}. You can use the
2228 @code{kill} command in this situation to permit running your program
2229 outside the debugger.
2231 The @code{kill} command is also useful if you wish to recompile and
2232 relink your program, since on many systems it is impossible to modify an
2233 executable file while it is running in a process. In this case, when you
2234 next type @code{run}, @value{GDBN} notices that the file has changed, and
2235 reads the symbol table again (while trying to preserve your current
2236 breakpoint settings).
2239 @section Debugging programs with multiple threads
2241 @cindex threads of execution
2242 @cindex multiple threads
2243 @cindex switching threads
2244 In some operating systems, such as HP-UX and Solaris, a single program
2245 may have more than one @dfn{thread} of execution. The precise semantics
2246 of threads differ from one operating system to another, but in general
2247 the threads of a single program are akin to multiple processes---except
2248 that they share one address space (that is, they can all examine and
2249 modify the same variables). On the other hand, each thread has its own
2250 registers and execution stack, and perhaps private memory.
2252 @value{GDBN} provides these facilities for debugging multi-thread
2256 @item automatic notification of new threads
2257 @item @samp{thread @var{threadno}}, a command to switch among threads
2258 @item @samp{info threads}, a command to inquire about existing threads
2259 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2260 a command to apply a command to a list of threads
2261 @item thread-specific breakpoints
2265 @emph{Warning:} These facilities are not yet available on every
2266 @value{GDBN} configuration where the operating system supports threads.
2267 If your @value{GDBN} does not support threads, these commands have no
2268 effect. For example, a system without thread support shows no output
2269 from @samp{info threads}, and always rejects the @code{thread} command,
2273 (@value{GDBP}) info threads
2274 (@value{GDBP}) thread 1
2275 Thread ID 1 not known. Use the "info threads" command to
2276 see the IDs of currently known threads.
2278 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2279 @c doesn't support threads"?
2282 @cindex focus of debugging
2283 @cindex current thread
2284 The @value{GDBN} thread debugging facility allows you to observe all
2285 threads while your program runs---but whenever @value{GDBN} takes
2286 control, one thread in particular is always the focus of debugging.
2287 This thread is called the @dfn{current thread}. Debugging commands show
2288 program information from the perspective of the current thread.
2290 @cindex @code{New} @var{systag} message
2291 @cindex thread identifier (system)
2292 @c FIXME-implementors!! It would be more helpful if the [New...] message
2293 @c included GDB's numeric thread handle, so you could just go to that
2294 @c thread without first checking `info threads'.
2295 Whenever @value{GDBN} detects a new thread in your program, it displays
2296 the target system's identification for the thread with a message in the
2297 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2298 whose form varies depending on the particular system. For example, on
2299 LynxOS, you might see
2302 [New process 35 thread 27]
2306 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2307 the @var{systag} is simply something like @samp{process 368}, with no
2310 @c FIXME!! (1) Does the [New...] message appear even for the very first
2311 @c thread of a program, or does it only appear for the
2312 @c second---i.e.@: when it becomes obvious we have a multithread
2314 @c (2) *Is* there necessarily a first thread always? Or do some
2315 @c multithread systems permit starting a program with multiple
2316 @c threads ab initio?
2318 @cindex thread number
2319 @cindex thread identifier (GDB)
2320 For debugging purposes, @value{GDBN} associates its own thread
2321 number---always a single integer---with each thread in your program.
2324 @kindex info threads
2326 Display a summary of all threads currently in your
2327 program. @value{GDBN} displays for each thread (in this order):
2331 the thread number assigned by @value{GDBN}
2334 the target system's thread identifier (@var{systag})
2337 the current stack frame summary for that thread
2341 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2342 indicates the current thread.
2346 @c end table here to get a little more width for example
2349 (@value{GDBP}) info threads
2350 3 process 35 thread 27 0x34e5 in sigpause ()
2351 2 process 35 thread 23 0x34e5 in sigpause ()
2352 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2358 @cindex debugging multithreaded programs (on HP-UX)
2359 @cindex thread identifier (GDB), on HP-UX
2360 For debugging purposes, @value{GDBN} associates its own thread
2361 number---a small integer assigned in thread-creation order---with each
2362 thread in your program.
2364 @cindex @code{New} @var{systag} message, on HP-UX
2365 @cindex thread identifier (system), on HP-UX
2366 @c FIXME-implementors!! It would be more helpful if the [New...] message
2367 @c included GDB's numeric thread handle, so you could just go to that
2368 @c thread without first checking `info threads'.
2369 Whenever @value{GDBN} detects a new thread in your program, it displays
2370 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2371 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2372 whose form varies depending on the particular system. For example, on
2376 [New thread 2 (system thread 26594)]
2380 when @value{GDBN} notices a new thread.
2383 @kindex info threads (HP-UX)
2385 Display a summary of all threads currently in your
2386 program. @value{GDBN} displays for each thread (in this order):
2389 @item the thread number assigned by @value{GDBN}
2391 @item the target system's thread identifier (@var{systag})
2393 @item the current stack frame summary for that thread
2397 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2398 indicates the current thread.
2402 @c end table here to get a little more width for example
2405 (@value{GDBP}) info threads
2406 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2408 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2409 from /usr/lib/libc.2
2410 1 system thread 27905 0x7b003498 in _brk () \@*
2411 from /usr/lib/libc.2
2414 On Solaris, you can display more information about user threads with a
2415 Solaris-specific command:
2418 @item maint info sol-threads
2419 @kindex maint info sol-threads
2420 @cindex thread info (Solaris)
2421 Display info on Solaris user threads.
2425 @kindex thread @var{threadno}
2426 @item thread @var{threadno}
2427 Make thread number @var{threadno} the current thread. The command
2428 argument @var{threadno} is the internal @value{GDBN} thread number, as
2429 shown in the first field of the @samp{info threads} display.
2430 @value{GDBN} responds by displaying the system identifier of the thread
2431 you selected, and its current stack frame summary:
2434 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2435 (@value{GDBP}) thread 2
2436 [Switching to process 35 thread 23]
2437 0x34e5 in sigpause ()
2441 As with the @samp{[New @dots{}]} message, the form of the text after
2442 @samp{Switching to} depends on your system's conventions for identifying
2445 @kindex thread apply
2446 @cindex apply command to several threads
2447 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2448 The @code{thread apply} command allows you to apply the named
2449 @var{command} to one or more threads. Specify the numbers of the
2450 threads that you want affected with the command argument
2451 @var{threadno}. It can be a single thread number, one of the numbers
2452 shown in the first field of the @samp{info threads} display; or it
2453 could be a range of thread numbers, as in @code{2-4}. To apply a
2454 command to all threads, type @kbd{thread apply all @var{command}}.
2457 @cindex automatic thread selection
2458 @cindex switching threads automatically
2459 @cindex threads, automatic switching
2460 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2461 signal, it automatically selects the thread where that breakpoint or
2462 signal happened. @value{GDBN} alerts you to the context switch with a
2463 message of the form @samp{[Switching to @var{systag}]} to identify the
2466 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2467 more information about how @value{GDBN} behaves when you stop and start
2468 programs with multiple threads.
2470 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2471 watchpoints in programs with multiple threads.
2474 @section Debugging programs with multiple processes
2476 @cindex fork, debugging programs which call
2477 @cindex multiple processes
2478 @cindex processes, multiple
2479 On most systems, @value{GDBN} has no special support for debugging
2480 programs which create additional processes using the @code{fork}
2481 function. When a program forks, @value{GDBN} will continue to debug the
2482 parent process and the child process will run unimpeded. If you have
2483 set a breakpoint in any code which the child then executes, the child
2484 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2485 will cause it to terminate.
2487 However, if you want to debug the child process there is a workaround
2488 which isn't too painful. Put a call to @code{sleep} in the code which
2489 the child process executes after the fork. It may be useful to sleep
2490 only if a certain environment variable is set, or a certain file exists,
2491 so that the delay need not occur when you don't want to run @value{GDBN}
2492 on the child. While the child is sleeping, use the @code{ps} program to
2493 get its process ID. Then tell @value{GDBN} (a new invocation of
2494 @value{GDBN} if you are also debugging the parent process) to attach to
2495 the child process (@pxref{Attach}). From that point on you can debug
2496 the child process just like any other process which you attached to.
2498 On some systems, @value{GDBN} provides support for debugging programs that
2499 create additional processes using the @code{fork} or @code{vfork} functions.
2500 Currently, the only platforms with this feature are HP-UX (11.x and later
2501 only?) and GNU/Linux (kernel version 2.5.60 and later).
2503 By default, when a program forks, @value{GDBN} will continue to debug
2504 the parent process and the child process will run unimpeded.
2506 If you want to follow the child process instead of the parent process,
2507 use the command @w{@code{set follow-fork-mode}}.
2510 @kindex set follow-fork-mode
2511 @item set follow-fork-mode @var{mode}
2512 Set the debugger response to a program call of @code{fork} or
2513 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2514 process. The @var{mode} argument can be:
2518 The original process is debugged after a fork. The child process runs
2519 unimpeded. This is the default.
2522 The new process is debugged after a fork. The parent process runs
2527 @kindex show follow-fork-mode
2528 @item show follow-fork-mode
2529 Display the current debugger response to a @code{fork} or @code{vfork} call.
2532 @cindex debugging multiple processes
2533 On Linux, if you want to debug both the parent and child processes, use the
2534 command @w{@code{set detach-on-fork}}.
2537 @kindex set detach-on-fork
2538 @item set detach-on-fork @var{mode}
2539 Tells gdb whether to detach one of the processes after a fork, or
2540 retain debugger control over them both.
2544 The child process (or parent process, depending on the value of
2545 @code{follow-fork-mode}) will be detached and allowed to run
2546 independently. This is the default.
2549 Both processes will be held under the control of @value{GDBN}.
2550 One process (child or parent, depending on the value of
2551 @code{follow-fork-mode}) is debugged as usual, while the other
2556 @kindex show detach-on-follow
2557 @item show detach-on-follow
2558 Show whether detach-on-follow mode is on/off.
2561 If you choose to set @var{detach-on-follow} mode off, then
2562 @value{GDBN} will retain control of all forked processes (including
2563 nested forks). You can list the forked processes under the control of
2564 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2565 from one fork to another by using the @w{@code{fork}} command.
2570 Print a list of all forked processes under the control of @value{GDBN}.
2571 The listing will include a fork id, a process id, and the current
2572 position (program counter) of the process.
2575 @kindex fork @var{fork-id}
2576 @item fork @var{fork-id}
2577 Make fork number @var{fork-id} the current process. The argument
2578 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2579 as shown in the first field of the @samp{info forks} display.
2583 To quit debugging one of the forked processes, you can either detach
2584 from it by using the @w{@code{detach fork}} command (allowing it to
2585 run independently), or delete (and kill) it using the
2586 @w{@code{delete fork}} command.
2589 @kindex detach fork @var{fork-id}
2590 @item detach fork @var{fork-id}
2591 Detach from the process identified by @value{GDBN} fork number
2592 @var{fork-id}, and remove it from the fork list. The process will be
2593 allowed to run independently.
2595 @kindex delete fork @var{fork-id}
2596 @item delete fork @var{fork-id}
2597 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2598 and remove it from the fork list.
2602 If you ask to debug a child process and a @code{vfork} is followed by an
2603 @code{exec}, @value{GDBN} executes the new target up to the first
2604 breakpoint in the new target. If you have a breakpoint set on
2605 @code{main} in your original program, the breakpoint will also be set on
2606 the child process's @code{main}.
2608 When a child process is spawned by @code{vfork}, you cannot debug the
2609 child or parent until an @code{exec} call completes.
2611 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2612 call executes, the new target restarts. To restart the parent process,
2613 use the @code{file} command with the parent executable name as its
2616 You can use the @code{catch} command to make @value{GDBN} stop whenever
2617 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2618 Catchpoints, ,Setting catchpoints}.
2620 @node Checkpoint/Restart
2621 @section Setting a @emph{bookmark} to return to later
2626 @cindex snapshot of a process
2627 @cindex rewind program state
2629 On certain operating systems@footnote{Currently, only
2630 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2631 program's state, called a @dfn{checkpoint}, and come back to it
2634 Returning to a checkpoint effectively undoes everything that has
2635 happened in the program since the @code{checkpoint} was saved. This
2636 includes changes in memory, registers, and even (within some limits)
2637 system state. Effectively, it is like going back in time to the
2638 moment when the checkpoint was saved.
2640 Thus, if you're stepping thru a program and you think you're
2641 getting close to the point where things go wrong, you can save
2642 a checkpoint. Then, if you accidentally go too far and miss
2643 the critical statement, instead of having to restart your program
2644 from the beginning, you can just go back to the checkpoint and
2645 start again from there.
2647 This can be especially useful if it takes a lot of time or
2648 steps to reach the point where you think the bug occurs.
2650 To use the @code{checkpoint}/@code{restart} method of debugging:
2655 Save a snapshot of the debugged program's current execution state.
2656 The @code{checkpoint} command takes no arguments, but each checkpoint
2657 is assigned a small integer id, similar to a breakpoint id.
2659 @kindex info checkpoints
2660 @item info checkpoints
2661 List the checkpoints that have been saved in the current debugging
2662 session. For each checkpoint, the following information will be
2669 @item Source line, or label
2672 @kindex restart @var{checkpoint-id}
2673 @item restart @var{checkpoint-id}
2674 Restore the program state that was saved as checkpoint number
2675 @var{checkpoint-id}. All program variables, registers, stack frames
2676 etc.@: will be returned to the values that they had when the checkpoint
2677 was saved. In essence, gdb will ``wind back the clock'' to the point
2678 in time when the checkpoint was saved.
2680 Note that breakpoints, @value{GDBN} variables, command history etc.
2681 are not affected by restoring a checkpoint. In general, a checkpoint
2682 only restores things that reside in the program being debugged, not in
2685 @kindex delete checkpoint @var{checkpoint-id}
2686 @item delete checkpoint @var{checkpoint-id}
2687 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2691 Returning to a previously saved checkpoint will restore the user state
2692 of the program being debugged, plus a significant subset of the system
2693 (OS) state, including file pointers. It won't ``un-write'' data from
2694 a file, but it will rewind the file pointer to the previous location,
2695 so that the previously written data can be overwritten. For files
2696 opened in read mode, the pointer will also be restored so that the
2697 previously read data can be read again.
2699 Of course, characters that have been sent to a printer (or other
2700 external device) cannot be ``snatched back'', and characters received
2701 from eg.@: a serial device can be removed from internal program buffers,
2702 but they cannot be ``pushed back'' into the serial pipeline, ready to
2703 be received again. Similarly, the actual contents of files that have
2704 been changed cannot be restored (at this time).
2706 However, within those constraints, you actually can ``rewind'' your
2707 program to a previously saved point in time, and begin debugging it
2708 again --- and you can change the course of events so as to debug a
2709 different execution path this time.
2711 @cindex checkpoints and process id
2712 Finally, there is one bit of internal program state that will be
2713 different when you return to a checkpoint --- the program's process
2714 id. Each checkpoint will have a unique process id (or @var{pid}),
2715 and each will be different from the program's original @var{pid}.
2716 If your program has saved a local copy of its process id, this could
2717 potentially pose a problem.
2719 @subsection A non-obvious benefit of using checkpoints
2721 On some systems such as @sc{gnu}/Linux, address space randomization
2722 is performed on new processes for security reasons. This makes it
2723 difficult or impossible to set a breakpoint, or watchpoint, on an
2724 absolute address if you have to restart the program, since the
2725 absolute location of a symbol will change from one execution to the
2728 A checkpoint, however, is an @emph{identical} copy of a process.
2729 Therefore if you create a checkpoint at (eg.@:) the start of main,
2730 and simply return to that checkpoint instead of restarting the
2731 process, you can avoid the effects of address randomization and
2732 your symbols will all stay in the same place.
2735 @chapter Stopping and Continuing
2737 The principal purposes of using a debugger are so that you can stop your
2738 program before it terminates; or so that, if your program runs into
2739 trouble, you can investigate and find out why.
2741 Inside @value{GDBN}, your program may stop for any of several reasons,
2742 such as a signal, a breakpoint, or reaching a new line after a
2743 @value{GDBN} command such as @code{step}. You may then examine and
2744 change variables, set new breakpoints or remove old ones, and then
2745 continue execution. Usually, the messages shown by @value{GDBN} provide
2746 ample explanation of the status of your program---but you can also
2747 explicitly request this information at any time.
2750 @kindex info program
2752 Display information about the status of your program: whether it is
2753 running or not, what process it is, and why it stopped.
2757 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2758 * Continuing and Stepping:: Resuming execution
2760 * Thread Stops:: Stopping and starting multi-thread programs
2764 @section Breakpoints, watchpoints, and catchpoints
2767 A @dfn{breakpoint} makes your program stop whenever a certain point in
2768 the program is reached. For each breakpoint, you can add conditions to
2769 control in finer detail whether your program stops. You can set
2770 breakpoints with the @code{break} command and its variants (@pxref{Set
2771 Breaks, ,Setting breakpoints}), to specify the place where your program
2772 should stop by line number, function name or exact address in the
2775 On some systems, you can set breakpoints in shared libraries before
2776 the executable is run. There is a minor limitation on HP-UX systems:
2777 you must wait until the executable is run in order to set breakpoints
2778 in shared library routines that are not called directly by the program
2779 (for example, routines that are arguments in a @code{pthread_create}
2783 @cindex data breakpoints
2784 @cindex memory tracing
2785 @cindex breakpoint on memory address
2786 @cindex breakpoint on variable modification
2787 A @dfn{watchpoint} is a special breakpoint that stops your program
2788 when the value of an expression changes. The expression may be a value
2789 of a variable, or it could involve values of one or more variables
2790 combined by operators, such as @samp{a + b}. This is sometimes called
2791 @dfn{data breakpoints}. You must use a different command to set
2792 watchpoints (@pxref{Set Watchpoints, ,Setting watchpoints}), but aside
2793 from that, you can manage a watchpoint like any other breakpoint: you
2794 enable, disable, and delete both breakpoints and watchpoints using the
2797 You can arrange to have values from your program displayed automatically
2798 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2802 @cindex breakpoint on events
2803 A @dfn{catchpoint} is another special breakpoint that stops your program
2804 when a certain kind of event occurs, such as the throwing of a C@t{++}
2805 exception or the loading of a library. As with watchpoints, you use a
2806 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2807 catchpoints}), but aside from that, you can manage a catchpoint like any
2808 other breakpoint. (To stop when your program receives a signal, use the
2809 @code{handle} command; see @ref{Signals, ,Signals}.)
2811 @cindex breakpoint numbers
2812 @cindex numbers for breakpoints
2813 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2814 catchpoint when you create it; these numbers are successive integers
2815 starting with one. In many of the commands for controlling various
2816 features of breakpoints you use the breakpoint number to say which
2817 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2818 @dfn{disabled}; if disabled, it has no effect on your program until you
2821 @cindex breakpoint ranges
2822 @cindex ranges of breakpoints
2823 Some @value{GDBN} commands accept a range of breakpoints on which to
2824 operate. A breakpoint range is either a single breakpoint number, like
2825 @samp{5}, or two such numbers, in increasing order, separated by a
2826 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2827 all breakpoint in that range are operated on.
2830 * Set Breaks:: Setting breakpoints
2831 * Set Watchpoints:: Setting watchpoints
2832 * Set Catchpoints:: Setting catchpoints
2833 * Delete Breaks:: Deleting breakpoints
2834 * Disabling:: Disabling breakpoints
2835 * Conditions:: Break conditions
2836 * Break Commands:: Breakpoint command lists
2837 * Breakpoint Menus:: Breakpoint menus
2838 * Error in Breakpoints:: ``Cannot insert breakpoints''
2839 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2843 @subsection Setting breakpoints
2845 @c FIXME LMB what does GDB do if no code on line of breakpt?
2846 @c consider in particular declaration with/without initialization.
2848 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2851 @kindex b @r{(@code{break})}
2852 @vindex $bpnum@r{, convenience variable}
2853 @cindex latest breakpoint
2854 Breakpoints are set with the @code{break} command (abbreviated
2855 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2856 number of the breakpoint you've set most recently; see @ref{Convenience
2857 Vars,, Convenience variables}, for a discussion of what you can do with
2858 convenience variables.
2860 You have several ways to say where the breakpoint should go.
2863 @item break @var{function}
2864 Set a breakpoint at entry to function @var{function}.
2865 When using source languages that permit overloading of symbols, such as
2866 C@t{++}, @var{function} may refer to more than one possible place to break.
2867 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2869 @item break +@var{offset}
2870 @itemx break -@var{offset}
2871 Set a breakpoint some number of lines forward or back from the position
2872 at which execution stopped in the currently selected @dfn{stack frame}.
2873 (@xref{Frames, ,Frames}, for a description of stack frames.)
2875 @item break @var{linenum}
2876 Set a breakpoint at line @var{linenum} in the current source file.
2877 The current source file is the last file whose source text was printed.
2878 The breakpoint will stop your program just before it executes any of the
2881 @item break @var{filename}:@var{linenum}
2882 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2884 @item break @var{filename}:@var{function}
2885 Set a breakpoint at entry to function @var{function} found in file
2886 @var{filename}. Specifying a file name as well as a function name is
2887 superfluous except when multiple files contain similarly named
2890 @item break *@var{address}
2891 Set a breakpoint at address @var{address}. You can use this to set
2892 breakpoints in parts of your program which do not have debugging
2893 information or source files.
2896 When called without any arguments, @code{break} sets a breakpoint at
2897 the next instruction to be executed in the selected stack frame
2898 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2899 innermost, this makes your program stop as soon as control
2900 returns to that frame. This is similar to the effect of a
2901 @code{finish} command in the frame inside the selected frame---except
2902 that @code{finish} does not leave an active breakpoint. If you use
2903 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2904 the next time it reaches the current location; this may be useful
2907 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2908 least one instruction has been executed. If it did not do this, you
2909 would be unable to proceed past a breakpoint without first disabling the
2910 breakpoint. This rule applies whether or not the breakpoint already
2911 existed when your program stopped.
2913 @item break @dots{} if @var{cond}
2914 Set a breakpoint with condition @var{cond}; evaluate the expression
2915 @var{cond} each time the breakpoint is reached, and stop only if the
2916 value is nonzero---that is, if @var{cond} evaluates as true.
2917 @samp{@dots{}} stands for one of the possible arguments described
2918 above (or no argument) specifying where to break. @xref{Conditions,
2919 ,Break conditions}, for more information on breakpoint conditions.
2922 @item tbreak @var{args}
2923 Set a breakpoint enabled only for one stop. @var{args} are the
2924 same as for the @code{break} command, and the breakpoint is set in the same
2925 way, but the breakpoint is automatically deleted after the first time your
2926 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2929 @cindex hardware breakpoints
2930 @item hbreak @var{args}
2931 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2932 @code{break} command and the breakpoint is set in the same way, but the
2933 breakpoint requires hardware support and some target hardware may not
2934 have this support. The main purpose of this is EPROM/ROM code
2935 debugging, so you can set a breakpoint at an instruction without
2936 changing the instruction. This can be used with the new trap-generation
2937 provided by SPARClite DSU and most x86-based targets. These targets
2938 will generate traps when a program accesses some data or instruction
2939 address that is assigned to the debug registers. However the hardware
2940 breakpoint registers can take a limited number of breakpoints. For
2941 example, on the DSU, only two data breakpoints can be set at a time, and
2942 @value{GDBN} will reject this command if more than two are used. Delete
2943 or disable unused hardware breakpoints before setting new ones
2944 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2945 For remote targets, you can restrict the number of hardware
2946 breakpoints @value{GDBN} will use, see @ref{set remote
2947 hardware-breakpoint-limit}.
2951 @item thbreak @var{args}
2952 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2953 are the same as for the @code{hbreak} command and the breakpoint is set in
2954 the same way. However, like the @code{tbreak} command,
2955 the breakpoint is automatically deleted after the
2956 first time your program stops there. Also, like the @code{hbreak}
2957 command, the breakpoint requires hardware support and some target hardware
2958 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2959 See also @ref{Conditions, ,Break conditions}.
2962 @cindex regular expression
2963 @cindex breakpoints in functions matching a regexp
2964 @cindex set breakpoints in many functions
2965 @item rbreak @var{regex}
2966 Set breakpoints on all functions matching the regular expression
2967 @var{regex}. This command sets an unconditional breakpoint on all
2968 matches, printing a list of all breakpoints it set. Once these
2969 breakpoints are set, they are treated just like the breakpoints set with
2970 the @code{break} command. You can delete them, disable them, or make
2971 them conditional the same way as any other breakpoint.
2973 The syntax of the regular expression is the standard one used with tools
2974 like @file{grep}. Note that this is different from the syntax used by
2975 shells, so for instance @code{foo*} matches all functions that include
2976 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2977 @code{.*} leading and trailing the regular expression you supply, so to
2978 match only functions that begin with @code{foo}, use @code{^foo}.
2980 @cindex non-member C@t{++} functions, set breakpoint in
2981 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2982 breakpoints on overloaded functions that are not members of any special
2985 @cindex set breakpoints on all functions
2986 The @code{rbreak} command can be used to set breakpoints in
2987 @strong{all} the functions in a program, like this:
2990 (@value{GDBP}) rbreak .
2993 @kindex info breakpoints
2994 @cindex @code{$_} and @code{info breakpoints}
2995 @item info breakpoints @r{[}@var{n}@r{]}
2996 @itemx info break @r{[}@var{n}@r{]}
2997 @itemx info watchpoints @r{[}@var{n}@r{]}
2998 Print a table of all breakpoints, watchpoints, and catchpoints set and
2999 not deleted. Optional argument @var{n} means print information only
3000 about the specified breakpoint (or watchpoint or catchpoint). For
3001 each breakpoint, following columns are printed:
3004 @item Breakpoint Numbers
3006 Breakpoint, watchpoint, or catchpoint.
3008 Whether the breakpoint is marked to be disabled or deleted when hit.
3009 @item Enabled or Disabled
3010 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3011 that are not enabled.
3013 Where the breakpoint is in your program, as a memory address. If the
3014 breakpoint is pending (see below for details) on a future load of a shared library, the address
3015 will be listed as @samp{<PENDING>}.
3017 Where the breakpoint is in the source for your program, as a file and
3018 line number. For a pending breakpoint, the original string passed to
3019 the breakpoint command will be listed as it cannot be resolved until
3020 the appropriate shared library is loaded in the future.
3024 If a breakpoint is conditional, @code{info break} shows the condition on
3025 the line following the affected breakpoint; breakpoint commands, if any,
3026 are listed after that. A pending breakpoint is allowed to have a condition
3027 specified for it. The condition is not parsed for validity until a shared
3028 library is loaded that allows the pending breakpoint to resolve to a
3032 @code{info break} with a breakpoint
3033 number @var{n} as argument lists only that breakpoint. The
3034 convenience variable @code{$_} and the default examining-address for
3035 the @code{x} command are set to the address of the last breakpoint
3036 listed (@pxref{Memory, ,Examining memory}).
3039 @code{info break} displays a count of the number of times the breakpoint
3040 has been hit. This is especially useful in conjunction with the
3041 @code{ignore} command. You can ignore a large number of breakpoint
3042 hits, look at the breakpoint info to see how many times the breakpoint
3043 was hit, and then run again, ignoring one less than that number. This
3044 will get you quickly to the last hit of that breakpoint.
3047 @value{GDBN} allows you to set any number of breakpoints at the same place in
3048 your program. There is nothing silly or meaningless about this. When
3049 the breakpoints are conditional, this is even useful
3050 (@pxref{Conditions, ,Break conditions}).
3052 @cindex pending breakpoints
3053 If a specified breakpoint location cannot be found, it may be due to the fact
3054 that the location is in a shared library that is yet to be loaded. In such
3055 a case, you may want @value{GDBN} to create a special breakpoint (known as
3056 a @dfn{pending breakpoint}) that
3057 attempts to resolve itself in the future when an appropriate shared library
3060 Pending breakpoints are useful to set at the start of your
3061 @value{GDBN} session for locations that you know will be dynamically loaded
3062 later by the program being debugged. When shared libraries are loaded,
3063 a check is made to see if the load resolves any pending breakpoint locations.
3064 If a pending breakpoint location gets resolved,
3065 a regular breakpoint is created and the original pending breakpoint is removed.
3067 @value{GDBN} provides some additional commands for controlling pending
3070 @kindex set breakpoint pending
3071 @kindex show breakpoint pending
3073 @item set breakpoint pending auto
3074 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3075 location, it queries you whether a pending breakpoint should be created.
3077 @item set breakpoint pending on
3078 This indicates that an unrecognized breakpoint location should automatically
3079 result in a pending breakpoint being created.
3081 @item set breakpoint pending off
3082 This indicates that pending breakpoints are not to be created. Any
3083 unrecognized breakpoint location results in an error. This setting does
3084 not affect any pending breakpoints previously created.
3086 @item show breakpoint pending
3087 Show the current behavior setting for creating pending breakpoints.
3090 @cindex operations allowed on pending breakpoints
3091 Normal breakpoint operations apply to pending breakpoints as well. You may
3092 specify a condition for a pending breakpoint and/or commands to run when the
3093 breakpoint is reached. You can also enable or disable
3094 the pending breakpoint. When you specify a condition for a pending breakpoint,
3095 the parsing of the condition will be deferred until the point where the
3096 pending breakpoint location is resolved. Disabling a pending breakpoint
3097 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
3098 shared library load. When a pending breakpoint is re-enabled,
3099 @value{GDBN} checks to see if the location is already resolved.
3100 This is done because any number of shared library loads could have
3101 occurred since the time the breakpoint was disabled and one or more
3102 of these loads could resolve the location.
3104 @cindex automatic hardware breakpoints
3105 For some targets, @value{GDBN} can automatically decide if hardware or
3106 software breakpoints should be used, depending on whether the
3107 breakpoint address is read-only or read-write. This applies to
3108 breakpoints set with the @code{break} command as well as to internal
3109 breakpoints set by commands like @code{next} and @code{finish}. For
3110 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3113 You can control this automatic behaviour with the following commands::
3115 @kindex set breakpoint auto-hw
3116 @kindex show breakpoint auto-hw
3118 @item set breakpoint auto-hw on
3119 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3120 will try to use the target memory map to decide if software or hardware
3121 breakpoint must be used.
3123 @item set breakpoint auto-hw off
3124 This indicates @value{GDBN} should not automatically select breakpoint
3125 type. If the target provides a memory map, @value{GDBN} will warn when
3126 trying to set software breakpoint at a read-only address.
3130 @cindex negative breakpoint numbers
3131 @cindex internal @value{GDBN} breakpoints
3132 @value{GDBN} itself sometimes sets breakpoints in your program for
3133 special purposes, such as proper handling of @code{longjmp} (in C
3134 programs). These internal breakpoints are assigned negative numbers,
3135 starting with @code{-1}; @samp{info breakpoints} does not display them.
3136 You can see these breakpoints with the @value{GDBN} maintenance command
3137 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3140 @node Set Watchpoints
3141 @subsection Setting watchpoints
3143 @cindex setting watchpoints
3144 You can use a watchpoint to stop execution whenever the value of an
3145 expression changes, without having to predict a particular place where
3146 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3147 The expression may be as simple as the value of a single variable, or
3148 as complex as many variables combined by operators. Examples include:
3152 A reference to the value of a single variable.
3155 An address cast to an appropriate data type. For example,
3156 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3157 address (assuming an @code{int} occupies 4 bytes).
3160 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3161 expression can use any operators valid in the program's native
3162 language (@pxref{Languages}).
3165 @cindex software watchpoints
3166 @cindex hardware watchpoints
3167 Depending on your system, watchpoints may be implemented in software or
3168 hardware. @value{GDBN} does software watchpointing by single-stepping your
3169 program and testing the variable's value each time, which is hundreds of
3170 times slower than normal execution. (But this may still be worth it, to
3171 catch errors where you have no clue what part of your program is the
3174 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
3175 x86-based targets, @value{GDBN} includes support for hardware
3176 watchpoints, which do not slow down the running of your program.
3180 @item watch @var{expr}
3181 Set a watchpoint for an expression. @value{GDBN} will break when the
3182 expression @var{expr} is written into by the program and its value
3183 changes. The simplest (and the most popular) use of this command is
3184 to watch the value of a single variable:
3187 (@value{GDBP}) watch foo
3191 @item rwatch @var{expr}
3192 Set a watchpoint that will break when the value of @var{expr} is read
3196 @item awatch @var{expr}
3197 Set a watchpoint that will break when @var{expr} is either read from
3198 or written into by the program.
3200 @kindex info watchpoints @r{[}@var{n}@r{]}
3201 @item info watchpoints
3202 This command prints a list of watchpoints, breakpoints, and catchpoints;
3203 it is the same as @code{info break} (@pxref{Set Breaks}).
3206 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3207 watchpoints execute very quickly, and the debugger reports a change in
3208 value at the exact instruction where the change occurs. If @value{GDBN}
3209 cannot set a hardware watchpoint, it sets a software watchpoint, which
3210 executes more slowly and reports the change in value at the next
3211 @emph{statement}, not the instruction, after the change occurs.
3213 @cindex use only software watchpoints
3214 You can force @value{GDBN} to use only software watchpoints with the
3215 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3216 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3217 the underlying system supports them. (Note that hardware-assisted
3218 watchpoints that were set @emph{before} setting
3219 @code{can-use-hw-watchpoints} to zero will still use the hardware
3220 mechanism of watching expression values.)
3223 @item set can-use-hw-watchpoints
3224 @kindex set can-use-hw-watchpoints
3225 Set whether or not to use hardware watchpoints.
3227 @item show can-use-hw-watchpoints
3228 @kindex show can-use-hw-watchpoints
3229 Show the current mode of using hardware watchpoints.
3232 For remote targets, you can restrict the number of hardware
3233 watchpoints @value{GDBN} will use, see @ref{set remote
3234 hardware-breakpoint-limit}.
3236 When you issue the @code{watch} command, @value{GDBN} reports
3239 Hardware watchpoint @var{num}: @var{expr}
3243 if it was able to set a hardware watchpoint.
3245 Currently, the @code{awatch} and @code{rwatch} commands can only set
3246 hardware watchpoints, because accesses to data that don't change the
3247 value of the watched expression cannot be detected without examining
3248 every instruction as it is being executed, and @value{GDBN} does not do
3249 that currently. If @value{GDBN} finds that it is unable to set a
3250 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3251 will print a message like this:
3254 Expression cannot be implemented with read/access watchpoint.
3257 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3258 data type of the watched expression is wider than what a hardware
3259 watchpoint on the target machine can handle. For example, some systems
3260 can only watch regions that are up to 4 bytes wide; on such systems you
3261 cannot set hardware watchpoints for an expression that yields a
3262 double-precision floating-point number (which is typically 8 bytes
3263 wide). As a work-around, it might be possible to break the large region
3264 into a series of smaller ones and watch them with separate watchpoints.
3266 If you set too many hardware watchpoints, @value{GDBN} might be unable
3267 to insert all of them when you resume the execution of your program.
3268 Since the precise number of active watchpoints is unknown until such
3269 time as the program is about to be resumed, @value{GDBN} might not be
3270 able to warn you about this when you set the watchpoints, and the
3271 warning will be printed only when the program is resumed:
3274 Hardware watchpoint @var{num}: Could not insert watchpoint
3278 If this happens, delete or disable some of the watchpoints.
3280 Watching complex expressions that reference many variables can also
3281 exhaust the resources available for hardware-assisted watchpoints.
3282 That's because @value{GDBN} needs to watch every variable in the
3283 expression with separately allocated resources.
3285 The SPARClite DSU will generate traps when a program accesses some data
3286 or instruction address that is assigned to the debug registers. For the
3287 data addresses, DSU facilitates the @code{watch} command. However the
3288 hardware breakpoint registers can only take two data watchpoints, and
3289 both watchpoints must be the same kind. For example, you can set two
3290 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3291 @strong{or} two with @code{awatch} commands, but you cannot set one
3292 watchpoint with one command and the other with a different command.
3293 @value{GDBN} will reject the command if you try to mix watchpoints.
3294 Delete or disable unused watchpoint commands before setting new ones.
3296 If you call a function interactively using @code{print} or @code{call},
3297 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3298 kind of breakpoint or the call completes.
3300 @value{GDBN} automatically deletes watchpoints that watch local
3301 (automatic) variables, or expressions that involve such variables, when
3302 they go out of scope, that is, when the execution leaves the block in
3303 which these variables were defined. In particular, when the program
3304 being debugged terminates, @emph{all} local variables go out of scope,
3305 and so only watchpoints that watch global variables remain set. If you
3306 rerun the program, you will need to set all such watchpoints again. One
3307 way of doing that would be to set a code breakpoint at the entry to the
3308 @code{main} function and when it breaks, set all the watchpoints.
3311 @cindex watchpoints and threads
3312 @cindex threads and watchpoints
3313 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3314 usefulness. With the current watchpoint implementation, @value{GDBN}
3315 can only watch the value of an expression @emph{in a single thread}. If
3316 you are confident that the expression can only change due to the current
3317 thread's activity (and if you are also confident that no other thread
3318 can become current), then you can use watchpoints as usual. However,
3319 @value{GDBN} may not notice when a non-current thread's activity changes
3322 @c FIXME: this is almost identical to the previous paragraph.
3323 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3324 have only limited usefulness. If @value{GDBN} creates a software
3325 watchpoint, it can only watch the value of an expression @emph{in a
3326 single thread}. If you are confident that the expression can only
3327 change due to the current thread's activity (and if you are also
3328 confident that no other thread can become current), then you can use
3329 software watchpoints as usual. However, @value{GDBN} may not notice
3330 when a non-current thread's activity changes the expression. (Hardware
3331 watchpoints, in contrast, watch an expression in all threads.)
3334 @xref{set remote hardware-watchpoint-limit}.
3336 @node Set Catchpoints
3337 @subsection Setting catchpoints
3338 @cindex catchpoints, setting
3339 @cindex exception handlers
3340 @cindex event handling
3342 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3343 kinds of program events, such as C@t{++} exceptions or the loading of a
3344 shared library. Use the @code{catch} command to set a catchpoint.
3348 @item catch @var{event}
3349 Stop when @var{event} occurs. @var{event} can be any of the following:
3352 @cindex stop on C@t{++} exceptions
3353 The throwing of a C@t{++} exception.
3356 The catching of a C@t{++} exception.
3359 @cindex Ada exception catching
3360 @cindex catch Ada exceptions
3361 An Ada exception being raised. If an exception name is specified
3362 at the end of the command (eg @code{catch exception Program_Error}),
3363 the debugger will stop only when this specific exception is raised.
3364 Otherwise, the debugger stops execution when any Ada exception is raised.
3366 @item exception unhandled
3367 An exception that was raised but is not handled by the program.
3370 A failed Ada assertion.
3373 @cindex break on fork/exec
3374 A call to @code{exec}. This is currently only available for HP-UX.
3377 A call to @code{fork}. This is currently only available for HP-UX.
3380 A call to @code{vfork}. This is currently only available for HP-UX.
3383 @itemx load @var{libname}
3384 @cindex break on load/unload of shared library
3385 The dynamic loading of any shared library, or the loading of the library
3386 @var{libname}. This is currently only available for HP-UX.
3389 @itemx unload @var{libname}
3390 The unloading of any dynamically loaded shared library, or the unloading
3391 of the library @var{libname}. This is currently only available for HP-UX.
3394 @item tcatch @var{event}
3395 Set a catchpoint that is enabled only for one stop. The catchpoint is
3396 automatically deleted after the first time the event is caught.
3400 Use the @code{info break} command to list the current catchpoints.
3402 There are currently some limitations to C@t{++} exception handling
3403 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3407 If you call a function interactively, @value{GDBN} normally returns
3408 control to you when the function has finished executing. If the call
3409 raises an exception, however, the call may bypass the mechanism that
3410 returns control to you and cause your program either to abort or to
3411 simply continue running until it hits a breakpoint, catches a signal
3412 that @value{GDBN} is listening for, or exits. This is the case even if
3413 you set a catchpoint for the exception; catchpoints on exceptions are
3414 disabled within interactive calls.
3417 You cannot raise an exception interactively.
3420 You cannot install an exception handler interactively.
3423 @cindex raise exceptions
3424 Sometimes @code{catch} is not the best way to debug exception handling:
3425 if you need to know exactly where an exception is raised, it is better to
3426 stop @emph{before} the exception handler is called, since that way you
3427 can see the stack before any unwinding takes place. If you set a
3428 breakpoint in an exception handler instead, it may not be easy to find
3429 out where the exception was raised.
3431 To stop just before an exception handler is called, you need some
3432 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3433 raised by calling a library function named @code{__raise_exception}
3434 which has the following ANSI C interface:
3437 /* @var{addr} is where the exception identifier is stored.
3438 @var{id} is the exception identifier. */
3439 void __raise_exception (void **addr, void *id);
3443 To make the debugger catch all exceptions before any stack
3444 unwinding takes place, set a breakpoint on @code{__raise_exception}
3445 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3447 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3448 that depends on the value of @var{id}, you can stop your program when
3449 a specific exception is raised. You can use multiple conditional
3450 breakpoints to stop your program when any of a number of exceptions are
3455 @subsection Deleting breakpoints
3457 @cindex clearing breakpoints, watchpoints, catchpoints
3458 @cindex deleting breakpoints, watchpoints, catchpoints
3459 It is often necessary to eliminate a breakpoint, watchpoint, or
3460 catchpoint once it has done its job and you no longer want your program
3461 to stop there. This is called @dfn{deleting} the breakpoint. A
3462 breakpoint that has been deleted no longer exists; it is forgotten.
3464 With the @code{clear} command you can delete breakpoints according to
3465 where they are in your program. With the @code{delete} command you can
3466 delete individual breakpoints, watchpoints, or catchpoints by specifying
3467 their breakpoint numbers.
3469 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3470 automatically ignores breakpoints on the first instruction to be executed
3471 when you continue execution without changing the execution address.
3476 Delete any breakpoints at the next instruction to be executed in the
3477 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3478 the innermost frame is selected, this is a good way to delete a
3479 breakpoint where your program just stopped.
3481 @item clear @var{function}
3482 @itemx clear @var{filename}:@var{function}
3483 Delete any breakpoints set at entry to the named @var{function}.
3485 @item clear @var{linenum}
3486 @itemx clear @var{filename}:@var{linenum}
3487 Delete any breakpoints set at or within the code of the specified
3488 @var{linenum} of the specified @var{filename}.
3490 @cindex delete breakpoints
3492 @kindex d @r{(@code{delete})}
3493 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3494 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3495 ranges specified as arguments. If no argument is specified, delete all
3496 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3497 confirm off}). You can abbreviate this command as @code{d}.
3501 @subsection Disabling breakpoints
3503 @cindex enable/disable a breakpoint
3504 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3505 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3506 it had been deleted, but remembers the information on the breakpoint so
3507 that you can @dfn{enable} it again later.
3509 You disable and enable breakpoints, watchpoints, and catchpoints with
3510 the @code{enable} and @code{disable} commands, optionally specifying one
3511 or more breakpoint numbers as arguments. Use @code{info break} or
3512 @code{info watch} to print a list of breakpoints, watchpoints, and
3513 catchpoints if you do not know which numbers to use.
3515 A breakpoint, watchpoint, or catchpoint can have any of four different
3516 states of enablement:
3520 Enabled. The breakpoint stops your program. A breakpoint set
3521 with the @code{break} command starts out in this state.
3523 Disabled. The breakpoint has no effect on your program.
3525 Enabled once. The breakpoint stops your program, but then becomes
3528 Enabled for deletion. The breakpoint stops your program, but
3529 immediately after it does so it is deleted permanently. A breakpoint
3530 set with the @code{tbreak} command starts out in this state.
3533 You can use the following commands to enable or disable breakpoints,
3534 watchpoints, and catchpoints:
3538 @kindex dis @r{(@code{disable})}
3539 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3540 Disable the specified breakpoints---or all breakpoints, if none are
3541 listed. A disabled breakpoint has no effect but is not forgotten. All
3542 options such as ignore-counts, conditions and commands are remembered in
3543 case the breakpoint is enabled again later. You may abbreviate
3544 @code{disable} as @code{dis}.
3547 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3548 Enable the specified breakpoints (or all defined breakpoints). They
3549 become effective once again in stopping your program.
3551 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3552 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3553 of these breakpoints immediately after stopping your program.
3555 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3556 Enable the specified breakpoints to work once, then die. @value{GDBN}
3557 deletes any of these breakpoints as soon as your program stops there.
3558 Breakpoints set by the @code{tbreak} command start out in this state.
3561 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3562 @c confusing: tbreak is also initially enabled.
3563 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3564 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3565 subsequently, they become disabled or enabled only when you use one of
3566 the commands above. (The command @code{until} can set and delete a
3567 breakpoint of its own, but it does not change the state of your other
3568 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3572 @subsection Break conditions
3573 @cindex conditional breakpoints
3574 @cindex breakpoint conditions
3576 @c FIXME what is scope of break condition expr? Context where wanted?
3577 @c in particular for a watchpoint?
3578 The simplest sort of breakpoint breaks every time your program reaches a
3579 specified place. You can also specify a @dfn{condition} for a
3580 breakpoint. A condition is just a Boolean expression in your
3581 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3582 a condition evaluates the expression each time your program reaches it,
3583 and your program stops only if the condition is @emph{true}.
3585 This is the converse of using assertions for program validation; in that
3586 situation, you want to stop when the assertion is violated---that is,
3587 when the condition is false. In C, if you want to test an assertion expressed
3588 by the condition @var{assert}, you should set the condition
3589 @samp{! @var{assert}} on the appropriate breakpoint.
3591 Conditions are also accepted for watchpoints; you may not need them,
3592 since a watchpoint is inspecting the value of an expression anyhow---but
3593 it might be simpler, say, to just set a watchpoint on a variable name,
3594 and specify a condition that tests whether the new value is an interesting
3597 Break conditions can have side effects, and may even call functions in
3598 your program. This can be useful, for example, to activate functions
3599 that log program progress, or to use your own print functions to
3600 format special data structures. The effects are completely predictable
3601 unless there is another enabled breakpoint at the same address. (In
3602 that case, @value{GDBN} might see the other breakpoint first and stop your
3603 program without checking the condition of this one.) Note that
3604 breakpoint commands are usually more convenient and flexible than break
3606 purpose of performing side effects when a breakpoint is reached
3607 (@pxref{Break Commands, ,Breakpoint command lists}).
3609 Break conditions can be specified when a breakpoint is set, by using
3610 @samp{if} in the arguments to the @code{break} command. @xref{Set
3611 Breaks, ,Setting breakpoints}. They can also be changed at any time
3612 with the @code{condition} command.
3614 You can also use the @code{if} keyword with the @code{watch} command.
3615 The @code{catch} command does not recognize the @code{if} keyword;
3616 @code{condition} is the only way to impose a further condition on a
3621 @item condition @var{bnum} @var{expression}
3622 Specify @var{expression} as the break condition for breakpoint,
3623 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3624 breakpoint @var{bnum} stops your program only if the value of
3625 @var{expression} is true (nonzero, in C). When you use
3626 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3627 syntactic correctness, and to determine whether symbols in it have
3628 referents in the context of your breakpoint. If @var{expression} uses
3629 symbols not referenced in the context of the breakpoint, @value{GDBN}
3630 prints an error message:
3633 No symbol "foo" in current context.
3638 not actually evaluate @var{expression} at the time the @code{condition}
3639 command (or a command that sets a breakpoint with a condition, like
3640 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3642 @item condition @var{bnum}
3643 Remove the condition from breakpoint number @var{bnum}. It becomes
3644 an ordinary unconditional breakpoint.
3647 @cindex ignore count (of breakpoint)
3648 A special case of a breakpoint condition is to stop only when the
3649 breakpoint has been reached a certain number of times. This is so
3650 useful that there is a special way to do it, using the @dfn{ignore
3651 count} of the breakpoint. Every breakpoint has an ignore count, which
3652 is an integer. Most of the time, the ignore count is zero, and
3653 therefore has no effect. But if your program reaches a breakpoint whose
3654 ignore count is positive, then instead of stopping, it just decrements
3655 the ignore count by one and continues. As a result, if the ignore count
3656 value is @var{n}, the breakpoint does not stop the next @var{n} times
3657 your program reaches it.
3661 @item ignore @var{bnum} @var{count}
3662 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3663 The next @var{count} times the breakpoint is reached, your program's
3664 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3667 To make the breakpoint stop the next time it is reached, specify
3670 When you use @code{continue} to resume execution of your program from a
3671 breakpoint, you can specify an ignore count directly as an argument to
3672 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3673 Stepping,,Continuing and stepping}.
3675 If a breakpoint has a positive ignore count and a condition, the
3676 condition is not checked. Once the ignore count reaches zero,
3677 @value{GDBN} resumes checking the condition.
3679 You could achieve the effect of the ignore count with a condition such
3680 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3681 is decremented each time. @xref{Convenience Vars, ,Convenience
3685 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3688 @node Break Commands
3689 @subsection Breakpoint command lists
3691 @cindex breakpoint commands
3692 You can give any breakpoint (or watchpoint or catchpoint) a series of
3693 commands to execute when your program stops due to that breakpoint. For
3694 example, you might want to print the values of certain expressions, or
3695 enable other breakpoints.
3699 @kindex end@r{ (breakpoint commands)}
3700 @item commands @r{[}@var{bnum}@r{]}
3701 @itemx @dots{} @var{command-list} @dots{}
3703 Specify a list of commands for breakpoint number @var{bnum}. The commands
3704 themselves appear on the following lines. Type a line containing just
3705 @code{end} to terminate the commands.
3707 To remove all commands from a breakpoint, type @code{commands} and
3708 follow it immediately with @code{end}; that is, give no commands.
3710 With no @var{bnum} argument, @code{commands} refers to the last
3711 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3712 recently encountered).
3715 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3716 disabled within a @var{command-list}.
3718 You can use breakpoint commands to start your program up again. Simply
3719 use the @code{continue} command, or @code{step}, or any other command
3720 that resumes execution.
3722 Any other commands in the command list, after a command that resumes
3723 execution, are ignored. This is because any time you resume execution
3724 (even with a simple @code{next} or @code{step}), you may encounter
3725 another breakpoint---which could have its own command list, leading to
3726 ambiguities about which list to execute.
3729 If the first command you specify in a command list is @code{silent}, the
3730 usual message about stopping at a breakpoint is not printed. This may
3731 be desirable for breakpoints that are to print a specific message and
3732 then continue. If none of the remaining commands print anything, you
3733 see no sign that the breakpoint was reached. @code{silent} is
3734 meaningful only at the beginning of a breakpoint command list.
3736 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3737 print precisely controlled output, and are often useful in silent
3738 breakpoints. @xref{Output, ,Commands for controlled output}.
3740 For example, here is how you could use breakpoint commands to print the
3741 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3747 printf "x is %d\n",x
3752 One application for breakpoint commands is to compensate for one bug so
3753 you can test for another. Put a breakpoint just after the erroneous line
3754 of code, give it a condition to detect the case in which something
3755 erroneous has been done, and give it commands to assign correct values
3756 to any variables that need them. End with the @code{continue} command
3757 so that your program does not stop, and start with the @code{silent}
3758 command so that no output is produced. Here is an example:
3769 @node Breakpoint Menus
3770 @subsection Breakpoint menus
3772 @cindex symbol overloading
3774 Some programming languages (notably C@t{++} and Objective-C) permit a
3775 single function name
3776 to be defined several times, for application in different contexts.
3777 This is called @dfn{overloading}. When a function name is overloaded,
3778 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3779 a breakpoint. If you realize this is a problem, you can use
3780 something like @samp{break @var{function}(@var{types})} to specify which
3781 particular version of the function you want. Otherwise, @value{GDBN} offers
3782 you a menu of numbered choices for different possible breakpoints, and
3783 waits for your selection with the prompt @samp{>}. The first two
3784 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3785 sets a breakpoint at each definition of @var{function}, and typing
3786 @kbd{0} aborts the @code{break} command without setting any new
3789 For example, the following session excerpt shows an attempt to set a
3790 breakpoint at the overloaded symbol @code{String::after}.
3791 We choose three particular definitions of that function name:
3793 @c FIXME! This is likely to change to show arg type lists, at least
3796 (@value{GDBP}) b String::after
3799 [2] file:String.cc; line number:867
3800 [3] file:String.cc; line number:860
3801 [4] file:String.cc; line number:875
3802 [5] file:String.cc; line number:853
3803 [6] file:String.cc; line number:846
3804 [7] file:String.cc; line number:735
3806 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3807 Breakpoint 2 at 0xb344: file String.cc, line 875.
3808 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3809 Multiple breakpoints were set.
3810 Use the "delete" command to delete unwanted
3816 @c @ifclear BARETARGET
3817 @node Error in Breakpoints
3818 @subsection ``Cannot insert breakpoints''
3820 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3822 Under some operating systems, breakpoints cannot be used in a program if
3823 any other process is running that program. In this situation,
3824 attempting to run or continue a program with a breakpoint causes
3825 @value{GDBN} to print an error message:
3828 Cannot insert breakpoints.
3829 The same program may be running in another process.
3832 When this happens, you have three ways to proceed:
3836 Remove or disable the breakpoints, then continue.
3839 Suspend @value{GDBN}, and copy the file containing your program to a new
3840 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3841 that @value{GDBN} should run your program under that name.
3842 Then start your program again.
3845 Relink your program so that the text segment is nonsharable, using the
3846 linker option @samp{-N}. The operating system limitation may not apply
3847 to nonsharable executables.
3851 A similar message can be printed if you request too many active
3852 hardware-assisted breakpoints and watchpoints:
3854 @c FIXME: the precise wording of this message may change; the relevant
3855 @c source change is not committed yet (Sep 3, 1999).
3857 Stopped; cannot insert breakpoints.
3858 You may have requested too many hardware breakpoints and watchpoints.
3862 This message is printed when you attempt to resume the program, since
3863 only then @value{GDBN} knows exactly how many hardware breakpoints and
3864 watchpoints it needs to insert.
3866 When this message is printed, you need to disable or remove some of the
3867 hardware-assisted breakpoints and watchpoints, and then continue.
3869 @node Breakpoint related warnings
3870 @subsection ``Breakpoint address adjusted...''
3871 @cindex breakpoint address adjusted
3873 Some processor architectures place constraints on the addresses at
3874 which breakpoints may be placed. For architectures thus constrained,
3875 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3876 with the constraints dictated by the architecture.
3878 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3879 a VLIW architecture in which a number of RISC-like instructions may be
3880 bundled together for parallel execution. The FR-V architecture
3881 constrains the location of a breakpoint instruction within such a
3882 bundle to the instruction with the lowest address. @value{GDBN}
3883 honors this constraint by adjusting a breakpoint's address to the
3884 first in the bundle.
3886 It is not uncommon for optimized code to have bundles which contain
3887 instructions from different source statements, thus it may happen that
3888 a breakpoint's address will be adjusted from one source statement to
3889 another. Since this adjustment may significantly alter @value{GDBN}'s
3890 breakpoint related behavior from what the user expects, a warning is
3891 printed when the breakpoint is first set and also when the breakpoint
3894 A warning like the one below is printed when setting a breakpoint
3895 that's been subject to address adjustment:
3898 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3901 Such warnings are printed both for user settable and @value{GDBN}'s
3902 internal breakpoints. If you see one of these warnings, you should
3903 verify that a breakpoint set at the adjusted address will have the
3904 desired affect. If not, the breakpoint in question may be removed and
3905 other breakpoints may be set which will have the desired behavior.
3906 E.g., it may be sufficient to place the breakpoint at a later
3907 instruction. A conditional breakpoint may also be useful in some
3908 cases to prevent the breakpoint from triggering too often.
3910 @value{GDBN} will also issue a warning when stopping at one of these
3911 adjusted breakpoints:
3914 warning: Breakpoint 1 address previously adjusted from 0x00010414
3918 When this warning is encountered, it may be too late to take remedial
3919 action except in cases where the breakpoint is hit earlier or more
3920 frequently than expected.
3922 @node Continuing and Stepping
3923 @section Continuing and stepping
3927 @cindex resuming execution
3928 @dfn{Continuing} means resuming program execution until your program
3929 completes normally. In contrast, @dfn{stepping} means executing just
3930 one more ``step'' of your program, where ``step'' may mean either one
3931 line of source code, or one machine instruction (depending on what
3932 particular command you use). Either when continuing or when stepping,
3933 your program may stop even sooner, due to a breakpoint or a signal. (If
3934 it stops due to a signal, you may want to use @code{handle}, or use
3935 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3939 @kindex c @r{(@code{continue})}
3940 @kindex fg @r{(resume foreground execution)}
3941 @item continue @r{[}@var{ignore-count}@r{]}
3942 @itemx c @r{[}@var{ignore-count}@r{]}
3943 @itemx fg @r{[}@var{ignore-count}@r{]}
3944 Resume program execution, at the address where your program last stopped;
3945 any breakpoints set at that address are bypassed. The optional argument
3946 @var{ignore-count} allows you to specify a further number of times to
3947 ignore a breakpoint at this location; its effect is like that of
3948 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3950 The argument @var{ignore-count} is meaningful only when your program
3951 stopped due to a breakpoint. At other times, the argument to
3952 @code{continue} is ignored.
3954 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3955 debugged program is deemed to be the foreground program) are provided
3956 purely for convenience, and have exactly the same behavior as
3960 To resume execution at a different place, you can use @code{return}
3961 (@pxref{Returning, ,Returning from a function}) to go back to the
3962 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3963 different address}) to go to an arbitrary location in your program.
3965 A typical technique for using stepping is to set a breakpoint
3966 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3967 beginning of the function or the section of your program where a problem
3968 is believed to lie, run your program until it stops at that breakpoint,
3969 and then step through the suspect area, examining the variables that are
3970 interesting, until you see the problem happen.
3974 @kindex s @r{(@code{step})}
3976 Continue running your program until control reaches a different source
3977 line, then stop it and return control to @value{GDBN}. This command is
3978 abbreviated @code{s}.
3981 @c "without debugging information" is imprecise; actually "without line
3982 @c numbers in the debugging information". (gcc -g1 has debugging info but
3983 @c not line numbers). But it seems complex to try to make that
3984 @c distinction here.
3985 @emph{Warning:} If you use the @code{step} command while control is
3986 within a function that was compiled without debugging information,
3987 execution proceeds until control reaches a function that does have
3988 debugging information. Likewise, it will not step into a function which
3989 is compiled without debugging information. To step through functions
3990 without debugging information, use the @code{stepi} command, described
3994 The @code{step} command only stops at the first instruction of a source
3995 line. This prevents the multiple stops that could otherwise occur in
3996 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3997 to stop if a function that has debugging information is called within
3998 the line. In other words, @code{step} @emph{steps inside} any functions
3999 called within the line.
4001 Also, the @code{step} command only enters a function if there is line
4002 number information for the function. Otherwise it acts like the
4003 @code{next} command. This avoids problems when using @code{cc -gl}
4004 on MIPS machines. Previously, @code{step} entered subroutines if there
4005 was any debugging information about the routine.
4007 @item step @var{count}
4008 Continue running as in @code{step}, but do so @var{count} times. If a
4009 breakpoint is reached, or a signal not related to stepping occurs before
4010 @var{count} steps, stepping stops right away.
4013 @kindex n @r{(@code{next})}
4014 @item next @r{[}@var{count}@r{]}
4015 Continue to the next source line in the current (innermost) stack frame.
4016 This is similar to @code{step}, but function calls that appear within
4017 the line of code are executed without stopping. Execution stops when
4018 control reaches a different line of code at the original stack level
4019 that was executing when you gave the @code{next} command. This command
4020 is abbreviated @code{n}.
4022 An argument @var{count} is a repeat count, as for @code{step}.
4025 @c FIX ME!! Do we delete this, or is there a way it fits in with
4026 @c the following paragraph? --- Vctoria
4028 @c @code{next} within a function that lacks debugging information acts like
4029 @c @code{step}, but any function calls appearing within the code of the
4030 @c function are executed without stopping.
4032 The @code{next} command only stops at the first instruction of a
4033 source line. This prevents multiple stops that could otherwise occur in
4034 @code{switch} statements, @code{for} loops, etc.
4036 @kindex set step-mode
4038 @cindex functions without line info, and stepping
4039 @cindex stepping into functions with no line info
4040 @itemx set step-mode on
4041 The @code{set step-mode on} command causes the @code{step} command to
4042 stop at the first instruction of a function which contains no debug line
4043 information rather than stepping over it.
4045 This is useful in cases where you may be interested in inspecting the
4046 machine instructions of a function which has no symbolic info and do not
4047 want @value{GDBN} to automatically skip over this function.
4049 @item set step-mode off
4050 Causes the @code{step} command to step over any functions which contains no
4051 debug information. This is the default.
4053 @item show step-mode
4054 Show whether @value{GDBN} will stop in or step over functions without
4055 source line debug information.
4059 Continue running until just after function in the selected stack frame
4060 returns. Print the returned value (if any).
4062 Contrast this with the @code{return} command (@pxref{Returning,
4063 ,Returning from a function}).
4066 @kindex u @r{(@code{until})}
4067 @cindex run until specified location
4070 Continue running until a source line past the current line, in the
4071 current stack frame, is reached. This command is used to avoid single
4072 stepping through a loop more than once. It is like the @code{next}
4073 command, except that when @code{until} encounters a jump, it
4074 automatically continues execution until the program counter is greater
4075 than the address of the jump.
4077 This means that when you reach the end of a loop after single stepping
4078 though it, @code{until} makes your program continue execution until it
4079 exits the loop. In contrast, a @code{next} command at the end of a loop
4080 simply steps back to the beginning of the loop, which forces you to step
4081 through the next iteration.
4083 @code{until} always stops your program if it attempts to exit the current
4086 @code{until} may produce somewhat counterintuitive results if the order
4087 of machine code does not match the order of the source lines. For
4088 example, in the following excerpt from a debugging session, the @code{f}
4089 (@code{frame}) command shows that execution is stopped at line
4090 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4094 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4096 (@value{GDBP}) until
4097 195 for ( ; argc > 0; NEXTARG) @{
4100 This happened because, for execution efficiency, the compiler had
4101 generated code for the loop closure test at the end, rather than the
4102 start, of the loop---even though the test in a C @code{for}-loop is
4103 written before the body of the loop. The @code{until} command appeared
4104 to step back to the beginning of the loop when it advanced to this
4105 expression; however, it has not really gone to an earlier
4106 statement---not in terms of the actual machine code.
4108 @code{until} with no argument works by means of single
4109 instruction stepping, and hence is slower than @code{until} with an
4112 @item until @var{location}
4113 @itemx u @var{location}
4114 Continue running your program until either the specified location is
4115 reached, or the current stack frame returns. @var{location} is any of
4116 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4117 ,Setting breakpoints}). This form of the command uses breakpoints, and
4118 hence is quicker than @code{until} without an argument. The specified
4119 location is actually reached only if it is in the current frame. This
4120 implies that @code{until} can be used to skip over recursive function
4121 invocations. For instance in the code below, if the current location is
4122 line @code{96}, issuing @code{until 99} will execute the program up to
4123 line @code{99} in the same invocation of factorial, i.e. after the inner
4124 invocations have returned.
4127 94 int factorial (int value)
4129 96 if (value > 1) @{
4130 97 value *= factorial (value - 1);
4137 @kindex advance @var{location}
4138 @itemx advance @var{location}
4139 Continue running the program up to the given @var{location}. An argument is
4140 required, which should be of the same form as arguments for the @code{break}
4141 command. Execution will also stop upon exit from the current stack
4142 frame. This command is similar to @code{until}, but @code{advance} will
4143 not skip over recursive function calls, and the target location doesn't
4144 have to be in the same frame as the current one.
4148 @kindex si @r{(@code{stepi})}
4150 @itemx stepi @var{arg}
4152 Execute one machine instruction, then stop and return to the debugger.
4154 It is often useful to do @samp{display/i $pc} when stepping by machine
4155 instructions. This makes @value{GDBN} automatically display the next
4156 instruction to be executed, each time your program stops. @xref{Auto
4157 Display,, Automatic display}.
4159 An argument is a repeat count, as in @code{step}.
4163 @kindex ni @r{(@code{nexti})}
4165 @itemx nexti @var{arg}
4167 Execute one machine instruction, but if it is a function call,
4168 proceed until the function returns.
4170 An argument is a repeat count, as in @code{next}.
4177 A signal is an asynchronous event that can happen in a program. The
4178 operating system defines the possible kinds of signals, and gives each
4179 kind a name and a number. For example, in Unix @code{SIGINT} is the
4180 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4181 @code{SIGSEGV} is the signal a program gets from referencing a place in
4182 memory far away from all the areas in use; @code{SIGALRM} occurs when
4183 the alarm clock timer goes off (which happens only if your program has
4184 requested an alarm).
4186 @cindex fatal signals
4187 Some signals, including @code{SIGALRM}, are a normal part of the
4188 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4189 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4190 program has not specified in advance some other way to handle the signal.
4191 @code{SIGINT} does not indicate an error in your program, but it is normally
4192 fatal so it can carry out the purpose of the interrupt: to kill the program.
4194 @value{GDBN} has the ability to detect any occurrence of a signal in your
4195 program. You can tell @value{GDBN} in advance what to do for each kind of
4198 @cindex handling signals
4199 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4200 @code{SIGALRM} be silently passed to your program
4201 (so as not to interfere with their role in the program's functioning)
4202 but to stop your program immediately whenever an error signal happens.
4203 You can change these settings with the @code{handle} command.
4206 @kindex info signals
4210 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4211 handle each one. You can use this to see the signal numbers of all
4212 the defined types of signals.
4214 @item info signals @var{sig}
4215 Similar, but print information only about the specified signal number.
4217 @code{info handle} is an alias for @code{info signals}.
4220 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4221 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4222 can be the number of a signal or its name (with or without the
4223 @samp{SIG} at the beginning); a list of signal numbers of the form
4224 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4225 known signals. Optional arguments @var{keywords}, described below,
4226 say what change to make.
4230 The keywords allowed by the @code{handle} command can be abbreviated.
4231 Their full names are:
4235 @value{GDBN} should not stop your program when this signal happens. It may
4236 still print a message telling you that the signal has come in.
4239 @value{GDBN} should stop your program when this signal happens. This implies
4240 the @code{print} keyword as well.
4243 @value{GDBN} should print a message when this signal happens.
4246 @value{GDBN} should not mention the occurrence of the signal at all. This
4247 implies the @code{nostop} keyword as well.
4251 @value{GDBN} should allow your program to see this signal; your program
4252 can handle the signal, or else it may terminate if the signal is fatal
4253 and not handled. @code{pass} and @code{noignore} are synonyms.
4257 @value{GDBN} should not allow your program to see this signal.
4258 @code{nopass} and @code{ignore} are synonyms.
4262 When a signal stops your program, the signal is not visible to the
4264 continue. Your program sees the signal then, if @code{pass} is in
4265 effect for the signal in question @emph{at that time}. In other words,
4266 after @value{GDBN} reports a signal, you can use the @code{handle}
4267 command with @code{pass} or @code{nopass} to control whether your
4268 program sees that signal when you continue.
4270 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4271 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4272 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4275 You can also use the @code{signal} command to prevent your program from
4276 seeing a signal, or cause it to see a signal it normally would not see,
4277 or to give it any signal at any time. For example, if your program stopped
4278 due to some sort of memory reference error, you might store correct
4279 values into the erroneous variables and continue, hoping to see more
4280 execution; but your program would probably terminate immediately as
4281 a result of the fatal signal once it saw the signal. To prevent this,
4282 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4286 @section Stopping and starting multi-thread programs
4288 When your program has multiple threads (@pxref{Threads,, Debugging
4289 programs with multiple threads}), you can choose whether to set
4290 breakpoints on all threads, or on a particular thread.
4293 @cindex breakpoints and threads
4294 @cindex thread breakpoints
4295 @kindex break @dots{} thread @var{threadno}
4296 @item break @var{linespec} thread @var{threadno}
4297 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4298 @var{linespec} specifies source lines; there are several ways of
4299 writing them, but the effect is always to specify some source line.
4301 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4302 to specify that you only want @value{GDBN} to stop the program when a
4303 particular thread reaches this breakpoint. @var{threadno} is one of the
4304 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4305 column of the @samp{info threads} display.
4307 If you do not specify @samp{thread @var{threadno}} when you set a
4308 breakpoint, the breakpoint applies to @emph{all} threads of your
4311 You can use the @code{thread} qualifier on conditional breakpoints as
4312 well; in this case, place @samp{thread @var{threadno}} before the
4313 breakpoint condition, like this:
4316 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4321 @cindex stopped threads
4322 @cindex threads, stopped
4323 Whenever your program stops under @value{GDBN} for any reason,
4324 @emph{all} threads of execution stop, not just the current thread. This
4325 allows you to examine the overall state of the program, including
4326 switching between threads, without worrying that things may change
4329 @cindex thread breakpoints and system calls
4330 @cindex system calls and thread breakpoints
4331 @cindex premature return from system calls
4332 There is an unfortunate side effect. If one thread stops for a
4333 breakpoint, or for some other reason, and another thread is blocked in a
4334 system call, then the system call may return prematurely. This is a
4335 consequence of the interaction between multiple threads and the signals
4336 that @value{GDBN} uses to implement breakpoints and other events that
4339 To handle this problem, your program should check the return value of
4340 each system call and react appropriately. This is good programming
4343 For example, do not write code like this:
4349 The call to @code{sleep} will return early if a different thread stops
4350 at a breakpoint or for some other reason.
4352 Instead, write this:
4357 unslept = sleep (unslept);
4360 A system call is allowed to return early, so the system is still
4361 conforming to its specification. But @value{GDBN} does cause your
4362 multi-threaded program to behave differently than it would without
4365 Also, @value{GDBN} uses internal breakpoints in the thread library to
4366 monitor certain events such as thread creation and thread destruction.
4367 When such an event happens, a system call in another thread may return
4368 prematurely, even though your program does not appear to stop.
4370 @cindex continuing threads
4371 @cindex threads, continuing
4372 Conversely, whenever you restart the program, @emph{all} threads start
4373 executing. @emph{This is true even when single-stepping} with commands
4374 like @code{step} or @code{next}.
4376 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4377 Since thread scheduling is up to your debugging target's operating
4378 system (not controlled by @value{GDBN}), other threads may
4379 execute more than one statement while the current thread completes a
4380 single step. Moreover, in general other threads stop in the middle of a
4381 statement, rather than at a clean statement boundary, when the program
4384 You might even find your program stopped in another thread after
4385 continuing or even single-stepping. This happens whenever some other
4386 thread runs into a breakpoint, a signal, or an exception before the
4387 first thread completes whatever you requested.
4389 On some OSes, you can lock the OS scheduler and thus allow only a single
4393 @item set scheduler-locking @var{mode}
4394 @cindex scheduler locking mode
4395 @cindex lock scheduler
4396 Set the scheduler locking mode. If it is @code{off}, then there is no
4397 locking and any thread may run at any time. If @code{on}, then only the
4398 current thread may run when the inferior is resumed. The @code{step}
4399 mode optimizes for single-stepping. It stops other threads from
4400 ``seizing the prompt'' by preempting the current thread while you are
4401 stepping. Other threads will only rarely (or never) get a chance to run
4402 when you step. They are more likely to run when you @samp{next} over a
4403 function call, and they are completely free to run when you use commands
4404 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4405 thread hits a breakpoint during its timeslice, they will never steal the
4406 @value{GDBN} prompt away from the thread that you are debugging.
4408 @item show scheduler-locking
4409 Display the current scheduler locking mode.
4414 @chapter Examining the Stack
4416 When your program has stopped, the first thing you need to know is where it
4417 stopped and how it got there.
4420 Each time your program performs a function call, information about the call
4422 That information includes the location of the call in your program,
4423 the arguments of the call,
4424 and the local variables of the function being called.
4425 The information is saved in a block of data called a @dfn{stack frame}.
4426 The stack frames are allocated in a region of memory called the @dfn{call
4429 When your program stops, the @value{GDBN} commands for examining the
4430 stack allow you to see all of this information.
4432 @cindex selected frame
4433 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4434 @value{GDBN} commands refer implicitly to the selected frame. In
4435 particular, whenever you ask @value{GDBN} for the value of a variable in
4436 your program, the value is found in the selected frame. There are
4437 special @value{GDBN} commands to select whichever frame you are
4438 interested in. @xref{Selection, ,Selecting a frame}.
4440 When your program stops, @value{GDBN} automatically selects the
4441 currently executing frame and describes it briefly, similar to the
4442 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4445 * Frames:: Stack frames
4446 * Backtrace:: Backtraces
4447 * Selection:: Selecting a frame
4448 * Frame Info:: Information on a frame
4453 @section Stack frames
4455 @cindex frame, definition
4457 The call stack is divided up into contiguous pieces called @dfn{stack
4458 frames}, or @dfn{frames} for short; each frame is the data associated
4459 with one call to one function. The frame contains the arguments given
4460 to the function, the function's local variables, and the address at
4461 which the function is executing.
4463 @cindex initial frame
4464 @cindex outermost frame
4465 @cindex innermost frame
4466 When your program is started, the stack has only one frame, that of the
4467 function @code{main}. This is called the @dfn{initial} frame or the
4468 @dfn{outermost} frame. Each time a function is called, a new frame is
4469 made. Each time a function returns, the frame for that function invocation
4470 is eliminated. If a function is recursive, there can be many frames for
4471 the same function. The frame for the function in which execution is
4472 actually occurring is called the @dfn{innermost} frame. This is the most
4473 recently created of all the stack frames that still exist.
4475 @cindex frame pointer
4476 Inside your program, stack frames are identified by their addresses. A
4477 stack frame consists of many bytes, each of which has its own address; each
4478 kind of computer has a convention for choosing one byte whose
4479 address serves as the address of the frame. Usually this address is kept
4480 in a register called the @dfn{frame pointer register}
4481 (@pxref{Registers, $fp}) while execution is going on in that frame.
4483 @cindex frame number
4484 @value{GDBN} assigns numbers to all existing stack frames, starting with
4485 zero for the innermost frame, one for the frame that called it,
4486 and so on upward. These numbers do not really exist in your program;
4487 they are assigned by @value{GDBN} to give you a way of designating stack
4488 frames in @value{GDBN} commands.
4490 @c The -fomit-frame-pointer below perennially causes hbox overflow
4491 @c underflow problems.
4492 @cindex frameless execution
4493 Some compilers provide a way to compile functions so that they operate
4494 without stack frames. (For example, the @value{NGCC} option
4496 @samp{-fomit-frame-pointer}
4498 generates functions without a frame.)
4499 This is occasionally done with heavily used library functions to save
4500 the frame setup time. @value{GDBN} has limited facilities for dealing
4501 with these function invocations. If the innermost function invocation
4502 has no stack frame, @value{GDBN} nevertheless regards it as though
4503 it had a separate frame, which is numbered zero as usual, allowing
4504 correct tracing of the function call chain. However, @value{GDBN} has
4505 no provision for frameless functions elsewhere in the stack.
4508 @kindex frame@r{, command}
4509 @cindex current stack frame
4510 @item frame @var{args}
4511 The @code{frame} command allows you to move from one stack frame to another,
4512 and to print the stack frame you select. @var{args} may be either the
4513 address of the frame or the stack frame number. Without an argument,
4514 @code{frame} prints the current stack frame.
4516 @kindex select-frame
4517 @cindex selecting frame silently
4519 The @code{select-frame} command allows you to move from one stack frame
4520 to another without printing the frame. This is the silent version of
4528 @cindex call stack traces
4529 A backtrace is a summary of how your program got where it is. It shows one
4530 line per frame, for many frames, starting with the currently executing
4531 frame (frame zero), followed by its caller (frame one), and on up the
4536 @kindex bt @r{(@code{backtrace})}
4539 Print a backtrace of the entire stack: one line per frame for all
4540 frames in the stack.
4542 You can stop the backtrace at any time by typing the system interrupt
4543 character, normally @kbd{Ctrl-c}.
4545 @item backtrace @var{n}
4547 Similar, but print only the innermost @var{n} frames.
4549 @item backtrace -@var{n}
4551 Similar, but print only the outermost @var{n} frames.
4553 @item backtrace full
4555 @itemx bt full @var{n}
4556 @itemx bt full -@var{n}
4557 Print the values of the local variables also. @var{n} specifies the
4558 number of frames to print, as described above.
4563 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4564 are additional aliases for @code{backtrace}.
4566 @cindex multiple threads, backtrace
4567 In a multi-threaded program, @value{GDBN} by default shows the
4568 backtrace only for the current thread. To display the backtrace for
4569 several or all of the threads, use the command @code{thread apply}
4570 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4571 apply all backtrace}, @value{GDBN} will display the backtrace for all
4572 the threads; this is handy when you debug a core dump of a
4573 multi-threaded program.
4575 Each line in the backtrace shows the frame number and the function name.
4576 The program counter value is also shown---unless you use @code{set
4577 print address off}. The backtrace also shows the source file name and
4578 line number, as well as the arguments to the function. The program
4579 counter value is omitted if it is at the beginning of the code for that
4582 Here is an example of a backtrace. It was made with the command
4583 @samp{bt 3}, so it shows the innermost three frames.
4587 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4589 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4590 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4592 (More stack frames follow...)
4597 The display for frame zero does not begin with a program counter
4598 value, indicating that your program has stopped at the beginning of the
4599 code for line @code{993} of @code{builtin.c}.
4601 @cindex value optimized out, in backtrace
4602 @cindex function call arguments, optimized out
4603 If your program was compiled with optimizations, some compilers will
4604 optimize away arguments passed to functions if those arguments are
4605 never used after the call. Such optimizations generate code that
4606 passes arguments through registers, but doesn't store those arguments
4607 in the stack frame. @value{GDBN} has no way of displaying such
4608 arguments in stack frames other than the innermost one. Here's what
4609 such a backtrace might look like:
4613 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4615 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4616 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4618 (More stack frames follow...)
4623 The values of arguments that were not saved in their stack frames are
4624 shown as @samp{<value optimized out>}.
4626 If you need to display the values of such optimized-out arguments,
4627 either deduce that from other variables whose values depend on the one
4628 you are interested in, or recompile without optimizations.
4630 @cindex backtrace beyond @code{main} function
4631 @cindex program entry point
4632 @cindex startup code, and backtrace
4633 Most programs have a standard user entry point---a place where system
4634 libraries and startup code transition into user code. For C this is
4635 @code{main}@footnote{
4636 Note that embedded programs (the so-called ``free-standing''
4637 environment) are not required to have a @code{main} function as the
4638 entry point. They could even have multiple entry points.}.
4639 When @value{GDBN} finds the entry function in a backtrace
4640 it will terminate the backtrace, to avoid tracing into highly
4641 system-specific (and generally uninteresting) code.
4643 If you need to examine the startup code, or limit the number of levels
4644 in a backtrace, you can change this behavior:
4647 @item set backtrace past-main
4648 @itemx set backtrace past-main on
4649 @kindex set backtrace
4650 Backtraces will continue past the user entry point.
4652 @item set backtrace past-main off
4653 Backtraces will stop when they encounter the user entry point. This is the
4656 @item show backtrace past-main
4657 @kindex show backtrace
4658 Display the current user entry point backtrace policy.
4660 @item set backtrace past-entry
4661 @itemx set backtrace past-entry on
4662 Backtraces will continue past the internal entry point of an application.
4663 This entry point is encoded by the linker when the application is built,
4664 and is likely before the user entry point @code{main} (or equivalent) is called.
4666 @item set backtrace past-entry off
4667 Backtraces will stop when they encounter the internal entry point of an
4668 application. This is the default.
4670 @item show backtrace past-entry
4671 Display the current internal entry point backtrace policy.
4673 @item set backtrace limit @var{n}
4674 @itemx set backtrace limit 0
4675 @cindex backtrace limit
4676 Limit the backtrace to @var{n} levels. A value of zero means
4679 @item show backtrace limit
4680 Display the current limit on backtrace levels.
4684 @section Selecting a frame
4686 Most commands for examining the stack and other data in your program work on
4687 whichever stack frame is selected at the moment. Here are the commands for
4688 selecting a stack frame; all of them finish by printing a brief description
4689 of the stack frame just selected.
4692 @kindex frame@r{, selecting}
4693 @kindex f @r{(@code{frame})}
4696 Select frame number @var{n}. Recall that frame zero is the innermost
4697 (currently executing) frame, frame one is the frame that called the
4698 innermost one, and so on. The highest-numbered frame is the one for
4701 @item frame @var{addr}
4703 Select the frame at address @var{addr}. This is useful mainly if the
4704 chaining of stack frames has been damaged by a bug, making it
4705 impossible for @value{GDBN} to assign numbers properly to all frames. In
4706 addition, this can be useful when your program has multiple stacks and
4707 switches between them.
4709 On the SPARC architecture, @code{frame} needs two addresses to
4710 select an arbitrary frame: a frame pointer and a stack pointer.
4712 On the MIPS and Alpha architecture, it needs two addresses: a stack
4713 pointer and a program counter.
4715 On the 29k architecture, it needs three addresses: a register stack
4716 pointer, a program counter, and a memory stack pointer.
4720 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4721 advances toward the outermost frame, to higher frame numbers, to frames
4722 that have existed longer. @var{n} defaults to one.
4725 @kindex do @r{(@code{down})}
4727 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4728 advances toward the innermost frame, to lower frame numbers, to frames
4729 that were created more recently. @var{n} defaults to one. You may
4730 abbreviate @code{down} as @code{do}.
4733 All of these commands end by printing two lines of output describing the
4734 frame. The first line shows the frame number, the function name, the
4735 arguments, and the source file and line number of execution in that
4736 frame. The second line shows the text of that source line.
4744 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4746 10 read_input_file (argv[i]);
4750 After such a printout, the @code{list} command with no arguments
4751 prints ten lines centered on the point of execution in the frame.
4752 You can also edit the program at the point of execution with your favorite
4753 editing program by typing @code{edit}.
4754 @xref{List, ,Printing source lines},
4758 @kindex down-silently
4760 @item up-silently @var{n}
4761 @itemx down-silently @var{n}
4762 These two commands are variants of @code{up} and @code{down},
4763 respectively; they differ in that they do their work silently, without
4764 causing display of the new frame. They are intended primarily for use
4765 in @value{GDBN} command scripts, where the output might be unnecessary and
4770 @section Information about a frame
4772 There are several other commands to print information about the selected
4778 When used without any argument, this command does not change which
4779 frame is selected, but prints a brief description of the currently
4780 selected stack frame. It can be abbreviated @code{f}. With an
4781 argument, this command is used to select a stack frame.
4782 @xref{Selection, ,Selecting a frame}.
4785 @kindex info f @r{(@code{info frame})}
4788 This command prints a verbose description of the selected stack frame,
4793 the address of the frame
4795 the address of the next frame down (called by this frame)
4797 the address of the next frame up (caller of this frame)
4799 the language in which the source code corresponding to this frame is written
4801 the address of the frame's arguments
4803 the address of the frame's local variables
4805 the program counter saved in it (the address of execution in the caller frame)
4807 which registers were saved in the frame
4810 @noindent The verbose description is useful when
4811 something has gone wrong that has made the stack format fail to fit
4812 the usual conventions.
4814 @item info frame @var{addr}
4815 @itemx info f @var{addr}
4816 Print a verbose description of the frame at address @var{addr}, without
4817 selecting that frame. The selected frame remains unchanged by this
4818 command. This requires the same kind of address (more than one for some
4819 architectures) that you specify in the @code{frame} command.
4820 @xref{Selection, ,Selecting a frame}.
4824 Print the arguments of the selected frame, each on a separate line.
4828 Print the local variables of the selected frame, each on a separate
4829 line. These are all variables (declared either static or automatic)
4830 accessible at the point of execution of the selected frame.
4833 @cindex catch exceptions, list active handlers
4834 @cindex exception handlers, how to list
4836 Print a list of all the exception handlers that are active in the
4837 current stack frame at the current point of execution. To see other
4838 exception handlers, visit the associated frame (using the @code{up},
4839 @code{down}, or @code{frame} commands); then type @code{info catch}.
4840 @xref{Set Catchpoints, , Setting catchpoints}.
4846 @chapter Examining Source Files
4848 @value{GDBN} can print parts of your program's source, since the debugging
4849 information recorded in the program tells @value{GDBN} what source files were
4850 used to build it. When your program stops, @value{GDBN} spontaneously prints
4851 the line where it stopped. Likewise, when you select a stack frame
4852 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4853 execution in that frame has stopped. You can print other portions of
4854 source files by explicit command.
4856 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4857 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4858 @value{GDBN} under @sc{gnu} Emacs}.
4861 * List:: Printing source lines
4862 * Edit:: Editing source files
4863 * Search:: Searching source files
4864 * Source Path:: Specifying source directories
4865 * Machine Code:: Source and machine code
4869 @section Printing source lines
4872 @kindex l @r{(@code{list})}
4873 To print lines from a source file, use the @code{list} command
4874 (abbreviated @code{l}). By default, ten lines are printed.
4875 There are several ways to specify what part of the file you want to print.
4877 Here are the forms of the @code{list} command most commonly used:
4880 @item list @var{linenum}
4881 Print lines centered around line number @var{linenum} in the
4882 current source file.
4884 @item list @var{function}
4885 Print lines centered around the beginning of function
4889 Print more lines. If the last lines printed were printed with a
4890 @code{list} command, this prints lines following the last lines
4891 printed; however, if the last line printed was a solitary line printed
4892 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4893 Stack}), this prints lines centered around that line.
4896 Print lines just before the lines last printed.
4899 @cindex @code{list}, how many lines to display
4900 By default, @value{GDBN} prints ten source lines with any of these forms of
4901 the @code{list} command. You can change this using @code{set listsize}:
4904 @kindex set listsize
4905 @item set listsize @var{count}
4906 Make the @code{list} command display @var{count} source lines (unless
4907 the @code{list} argument explicitly specifies some other number).
4909 @kindex show listsize
4911 Display the number of lines that @code{list} prints.
4914 Repeating a @code{list} command with @key{RET} discards the argument,
4915 so it is equivalent to typing just @code{list}. This is more useful
4916 than listing the same lines again. An exception is made for an
4917 argument of @samp{-}; that argument is preserved in repetition so that
4918 each repetition moves up in the source file.
4921 In general, the @code{list} command expects you to supply zero, one or two
4922 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4923 of writing them, but the effect is always to specify some source line.
4924 Here is a complete description of the possible arguments for @code{list}:
4927 @item list @var{linespec}
4928 Print lines centered around the line specified by @var{linespec}.
4930 @item list @var{first},@var{last}
4931 Print lines from @var{first} to @var{last}. Both arguments are
4934 @item list ,@var{last}
4935 Print lines ending with @var{last}.
4937 @item list @var{first},
4938 Print lines starting with @var{first}.
4941 Print lines just after the lines last printed.
4944 Print lines just before the lines last printed.
4947 As described in the preceding table.
4950 Here are the ways of specifying a single source line---all the
4955 Specifies line @var{number} of the current source file.
4956 When a @code{list} command has two linespecs, this refers to
4957 the same source file as the first linespec.
4960 Specifies the line @var{offset} lines after the last line printed.
4961 When used as the second linespec in a @code{list} command that has
4962 two, this specifies the line @var{offset} lines down from the
4966 Specifies the line @var{offset} lines before the last line printed.
4968 @item @var{filename}:@var{number}
4969 Specifies line @var{number} in the source file @var{filename}.
4971 @item @var{function}
4972 Specifies the line that begins the body of the function @var{function}.
4973 For example: in C, this is the line with the open brace.
4975 @item @var{filename}:@var{function}
4976 Specifies the line of the open-brace that begins the body of the
4977 function @var{function} in the file @var{filename}. You only need the
4978 file name with a function name to avoid ambiguity when there are
4979 identically named functions in different source files.
4981 @item *@var{address}
4982 Specifies the line containing the program address @var{address}.
4983 @var{address} may be any expression.
4987 @section Editing source files
4988 @cindex editing source files
4991 @kindex e @r{(@code{edit})}
4992 To edit the lines in a source file, use the @code{edit} command.
4993 The editing program of your choice
4994 is invoked with the current line set to
4995 the active line in the program.
4996 Alternatively, there are several ways to specify what part of the file you
4997 want to print if you want to see other parts of the program.
4999 Here are the forms of the @code{edit} command most commonly used:
5003 Edit the current source file at the active line number in the program.
5005 @item edit @var{number}
5006 Edit the current source file with @var{number} as the active line number.
5008 @item edit @var{function}
5009 Edit the file containing @var{function} at the beginning of its definition.
5011 @item edit @var{filename}:@var{number}
5012 Specifies line @var{number} in the source file @var{filename}.
5014 @item edit @var{filename}:@var{function}
5015 Specifies the line that begins the body of the
5016 function @var{function} in the file @var{filename}. You only need the
5017 file name with a function name to avoid ambiguity when there are
5018 identically named functions in different source files.
5020 @item edit *@var{address}
5021 Specifies the line containing the program address @var{address}.
5022 @var{address} may be any expression.
5025 @subsection Choosing your editor
5026 You can customize @value{GDBN} to use any editor you want
5028 The only restriction is that your editor (say @code{ex}), recognizes the
5029 following command-line syntax:
5031 ex +@var{number} file
5033 The optional numeric value +@var{number} specifies the number of the line in
5034 the file where to start editing.}.
5035 By default, it is @file{@value{EDITOR}}, but you can change this
5036 by setting the environment variable @code{EDITOR} before using
5037 @value{GDBN}. For example, to configure @value{GDBN} to use the
5038 @code{vi} editor, you could use these commands with the @code{sh} shell:
5044 or in the @code{csh} shell,
5046 setenv EDITOR /usr/bin/vi
5051 @section Searching source files
5052 @cindex searching source files
5054 There are two commands for searching through the current source file for a
5059 @kindex forward-search
5060 @item forward-search @var{regexp}
5061 @itemx search @var{regexp}
5062 The command @samp{forward-search @var{regexp}} checks each line,
5063 starting with the one following the last line listed, for a match for
5064 @var{regexp}. It lists the line that is found. You can use the
5065 synonym @samp{search @var{regexp}} or abbreviate the command name as
5068 @kindex reverse-search
5069 @item reverse-search @var{regexp}
5070 The command @samp{reverse-search @var{regexp}} checks each line, starting
5071 with the one before the last line listed and going backward, for a match
5072 for @var{regexp}. It lists the line that is found. You can abbreviate
5073 this command as @code{rev}.
5077 @section Specifying source directories
5080 @cindex directories for source files
5081 Executable programs sometimes do not record the directories of the source
5082 files from which they were compiled, just the names. Even when they do,
5083 the directories could be moved between the compilation and your debugging
5084 session. @value{GDBN} has a list of directories to search for source files;
5085 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5086 it tries all the directories in the list, in the order they are present
5087 in the list, until it finds a file with the desired name.
5089 For example, suppose an executable references the file
5090 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5091 @file{/mnt/cross}. The file is first looked up literally; if this
5092 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5093 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5094 message is printed. @value{GDBN} does not look up the parts of the
5095 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5096 Likewise, the subdirectories of the source path are not searched: if
5097 the source path is @file{/mnt/cross}, and the binary refers to
5098 @file{foo.c}, @value{GDBN} would not find it under
5099 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5101 Plain file names, relative file names with leading directories, file
5102 names containing dots, etc.@: are all treated as described above; for
5103 instance, if the source path is @file{/mnt/cross}, and the source file
5104 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5105 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5106 that---@file{/mnt/cross/foo.c}.
5108 Note that the executable search path is @emph{not} used to locate the
5111 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5112 any information it has cached about where source files are found and where
5113 each line is in the file.
5117 When you start @value{GDBN}, its source path includes only @samp{cdir}
5118 and @samp{cwd}, in that order.
5119 To add other directories, use the @code{directory} command.
5121 The search path is used to find both program source files and @value{GDBN}
5122 script files (read using the @samp{-command} option and @samp{source} command).
5124 In addition to the source path, @value{GDBN} provides a set of commands
5125 that manage a list of source path substitution rules. A @dfn{substitution
5126 rule} specifies how to rewrite source directories stored in the program's
5127 debug information in case the sources were moved to a different
5128 directory between compilation and debugging. A rule is made of
5129 two strings, the first specifying what needs to be rewritten in
5130 the path, and the second specifying how it should be rewritten.
5131 In @ref{set substitute-path}, we name these two parts @var{from} and
5132 @var{to} respectively. @value{GDBN} does a simple string replacement
5133 of @var{from} with @var{to} at the start of the directory part of the
5134 source file name, and uses that result instead of the original file
5135 name to look up the sources.
5137 Using the previous example, suppose the @file{foo-1.0} tree has been
5138 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5139 GDB to replace @file{/usr/src} in all source path names with
5140 @file{/mnt/cross}. The first lookup will then be
5141 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5142 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5143 substitution rule, use the @code{set substitute-path} command
5144 (@pxref{set substitute-path}).
5146 To avoid unexpected substitution results, a rule is applied only if the
5147 @var{from} part of the directory name ends at a directory separator.
5148 For instance, a rule substituting @file{/usr/source} into
5149 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5150 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5151 is applied only at the beginning of the directory name, this rule will
5152 not be applied to @file{/root/usr/source/baz.c} either.
5154 In many cases, you can achieve the same result using the @code{directory}
5155 command. However, @code{set substitute-path} can be more efficient in
5156 the case where the sources are organized in a complex tree with multiple
5157 subdirectories. With the @code{directory} command, you need to add each
5158 subdirectory of your project. If you moved the entire tree while
5159 preserving its internal organization, then @code{set substitute-path}
5160 allows you to direct the debugger to all the sources with one single
5163 @code{set substitute-path} is also more than just a shortcut command.
5164 The source path is only used if the file at the original location no
5165 longer exists. On the other hand, @code{set substitute-path} modifies
5166 the debugger behavior to look at the rewritten location instead. So, if
5167 for any reason a source file that is not relevant to your executable is
5168 located at the original location, a substitution rule is the only
5169 method available to point GDB at the new location.
5172 @item directory @var{dirname} @dots{}
5173 @item dir @var{dirname} @dots{}
5174 Add directory @var{dirname} to the front of the source path. Several
5175 directory names may be given to this command, separated by @samp{:}
5176 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5177 part of absolute file names) or
5178 whitespace. You may specify a directory that is already in the source
5179 path; this moves it forward, so @value{GDBN} searches it sooner.
5183 @vindex $cdir@r{, convenience variable}
5184 @vindex $cwd@r{, convenience variable}
5185 @cindex compilation directory
5186 @cindex current directory
5187 @cindex working directory
5188 @cindex directory, current
5189 @cindex directory, compilation
5190 You can use the string @samp{$cdir} to refer to the compilation
5191 directory (if one is recorded), and @samp{$cwd} to refer to the current
5192 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5193 tracks the current working directory as it changes during your @value{GDBN}
5194 session, while the latter is immediately expanded to the current
5195 directory at the time you add an entry to the source path.
5198 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5200 @c RET-repeat for @code{directory} is explicitly disabled, but since
5201 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5203 @item show directories
5204 @kindex show directories
5205 Print the source path: show which directories it contains.
5207 @anchor{set substitute-path}
5208 @item set substitute-path @var{from} @var{to}
5209 @kindex set substitute-path
5210 Define a source path substitution rule, and add it at the end of the
5211 current list of existing substitution rules. If a rule with the same
5212 @var{from} was already defined, then the old rule is also deleted.
5214 For example, if the file @file{/foo/bar/baz.c} was moved to
5215 @file{/mnt/cross/baz.c}, then the command
5218 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5222 will tell @value{GDBN} to replace @samp{/usr/src} with
5223 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5224 @file{baz.c} even though it was moved.
5226 In the case when more than one substitution rule have been defined,
5227 the rules are evaluated one by one in the order where they have been
5228 defined. The first one matching, if any, is selected to perform
5231 For instance, if we had entered the following commands:
5234 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5235 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5239 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5240 @file{/mnt/include/defs.h} by using the first rule. However, it would
5241 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5242 @file{/mnt/src/lib/foo.c}.
5245 @item unset substitute-path [path]
5246 @kindex unset substitute-path
5247 If a path is specified, search the current list of substitution rules
5248 for a rule that would rewrite that path. Delete that rule if found.
5249 A warning is emitted by the debugger if no rule could be found.
5251 If no path is specified, then all substitution rules are deleted.
5253 @item show substitute-path [path]
5254 @kindex show substitute-path
5255 If a path is specified, then print the source path substitution rule
5256 which would rewrite that path, if any.
5258 If no path is specified, then print all existing source path substitution
5263 If your source path is cluttered with directories that are no longer of
5264 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5265 versions of source. You can correct the situation as follows:
5269 Use @code{directory} with no argument to reset the source path to its default value.
5272 Use @code{directory} with suitable arguments to reinstall the
5273 directories you want in the source path. You can add all the
5274 directories in one command.
5278 @section Source and machine code
5279 @cindex source line and its code address
5281 You can use the command @code{info line} to map source lines to program
5282 addresses (and vice versa), and the command @code{disassemble} to display
5283 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5284 mode, the @code{info line} command causes the arrow to point to the
5285 line specified. Also, @code{info line} prints addresses in symbolic form as
5290 @item info line @var{linespec}
5291 Print the starting and ending addresses of the compiled code for
5292 source line @var{linespec}. You can specify source lines in any of
5293 the ways understood by the @code{list} command (@pxref{List, ,Printing
5297 For example, we can use @code{info line} to discover the location of
5298 the object code for the first line of function
5299 @code{m4_changequote}:
5301 @c FIXME: I think this example should also show the addresses in
5302 @c symbolic form, as they usually would be displayed.
5304 (@value{GDBP}) info line m4_changequote
5305 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5309 @cindex code address and its source line
5310 We can also inquire (using @code{*@var{addr}} as the form for
5311 @var{linespec}) what source line covers a particular address:
5313 (@value{GDBP}) info line *0x63ff
5314 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5317 @cindex @code{$_} and @code{info line}
5318 @cindex @code{x} command, default address
5319 @kindex x@r{(examine), and} info line
5320 After @code{info line}, the default address for the @code{x} command
5321 is changed to the starting address of the line, so that @samp{x/i} is
5322 sufficient to begin examining the machine code (@pxref{Memory,
5323 ,Examining memory}). Also, this address is saved as the value of the
5324 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5329 @cindex assembly instructions
5330 @cindex instructions, assembly
5331 @cindex machine instructions
5332 @cindex listing machine instructions
5334 This specialized command dumps a range of memory as machine
5335 instructions. The default memory range is the function surrounding the
5336 program counter of the selected frame. A single argument to this
5337 command is a program counter value; @value{GDBN} dumps the function
5338 surrounding this value. Two arguments specify a range of addresses
5339 (first inclusive, second exclusive) to dump.
5342 The following example shows the disassembly of a range of addresses of
5343 HP PA-RISC 2.0 code:
5346 (@value{GDBP}) disas 0x32c4 0x32e4
5347 Dump of assembler code from 0x32c4 to 0x32e4:
5348 0x32c4 <main+204>: addil 0,dp
5349 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5350 0x32cc <main+212>: ldil 0x3000,r31
5351 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5352 0x32d4 <main+220>: ldo 0(r31),rp
5353 0x32d8 <main+224>: addil -0x800,dp
5354 0x32dc <main+228>: ldo 0x588(r1),r26
5355 0x32e0 <main+232>: ldil 0x3000,r31
5356 End of assembler dump.
5359 Some architectures have more than one commonly-used set of instruction
5360 mnemonics or other syntax.
5362 For programs that were dynamically linked and use shared libraries,
5363 instructions that call functions or branch to locations in the shared
5364 libraries might show a seemingly bogus location---it's actually a
5365 location of the relocation table. On some architectures, @value{GDBN}
5366 might be able to resolve these to actual function names.
5369 @kindex set disassembly-flavor
5370 @cindex Intel disassembly flavor
5371 @cindex AT&T disassembly flavor
5372 @item set disassembly-flavor @var{instruction-set}
5373 Select the instruction set to use when disassembling the
5374 program via the @code{disassemble} or @code{x/i} commands.
5376 Currently this command is only defined for the Intel x86 family. You
5377 can set @var{instruction-set} to either @code{intel} or @code{att}.
5378 The default is @code{att}, the AT&T flavor used by default by Unix
5379 assemblers for x86-based targets.
5381 @kindex show disassembly-flavor
5382 @item show disassembly-flavor
5383 Show the current setting of the disassembly flavor.
5388 @chapter Examining Data
5390 @cindex printing data
5391 @cindex examining data
5394 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5395 @c document because it is nonstandard... Under Epoch it displays in a
5396 @c different window or something like that.
5397 The usual way to examine data in your program is with the @code{print}
5398 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5399 evaluates and prints the value of an expression of the language your
5400 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5401 Different Languages}).
5404 @item print @var{expr}
5405 @itemx print /@var{f} @var{expr}
5406 @var{expr} is an expression (in the source language). By default the
5407 value of @var{expr} is printed in a format appropriate to its data type;
5408 you can choose a different format by specifying @samp{/@var{f}}, where
5409 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5413 @itemx print /@var{f}
5414 @cindex reprint the last value
5415 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5416 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
5417 conveniently inspect the same value in an alternative format.
5420 A more low-level way of examining data is with the @code{x} command.
5421 It examines data in memory at a specified address and prints it in a
5422 specified format. @xref{Memory, ,Examining memory}.
5424 If you are interested in information about types, or about how the
5425 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5426 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5430 * Expressions:: Expressions
5431 * Variables:: Program variables
5432 * Arrays:: Artificial arrays
5433 * Output Formats:: Output formats
5434 * Memory:: Examining memory
5435 * Auto Display:: Automatic display
5436 * Print Settings:: Print settings
5437 * Value History:: Value history
5438 * Convenience Vars:: Convenience variables
5439 * Registers:: Registers
5440 * Floating Point Hardware:: Floating point hardware
5441 * Vector Unit:: Vector Unit
5442 * OS Information:: Auxiliary data provided by operating system
5443 * Memory Region Attributes:: Memory region attributes
5444 * Dump/Restore Files:: Copy between memory and a file
5445 * Core File Generation:: Cause a program dump its core
5446 * Character Sets:: Debugging programs that use a different
5447 character set than GDB does
5448 * Caching Remote Data:: Data caching for remote targets
5452 @section Expressions
5455 @code{print} and many other @value{GDBN} commands accept an expression and
5456 compute its value. Any kind of constant, variable or operator defined
5457 by the programming language you are using is valid in an expression in
5458 @value{GDBN}. This includes conditional expressions, function calls,
5459 casts, and string constants. It also includes preprocessor macros, if
5460 you compiled your program to include this information; see
5463 @cindex arrays in expressions
5464 @value{GDBN} supports array constants in expressions input by
5465 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5466 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5467 memory that is @code{malloc}ed in the target program.
5469 Because C is so widespread, most of the expressions shown in examples in
5470 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5471 Languages}, for information on how to use expressions in other
5474 In this section, we discuss operators that you can use in @value{GDBN}
5475 expressions regardless of your programming language.
5477 @cindex casts, in expressions
5478 Casts are supported in all languages, not just in C, because it is so
5479 useful to cast a number into a pointer in order to examine a structure
5480 at that address in memory.
5481 @c FIXME: casts supported---Mod2 true?
5483 @value{GDBN} supports these operators, in addition to those common
5484 to programming languages:
5488 @samp{@@} is a binary operator for treating parts of memory as arrays.
5489 @xref{Arrays, ,Artificial arrays}, for more information.
5492 @samp{::} allows you to specify a variable in terms of the file or
5493 function where it is defined. @xref{Variables, ,Program variables}.
5495 @cindex @{@var{type}@}
5496 @cindex type casting memory
5497 @cindex memory, viewing as typed object
5498 @cindex casts, to view memory
5499 @item @{@var{type}@} @var{addr}
5500 Refers to an object of type @var{type} stored at address @var{addr} in
5501 memory. @var{addr} may be any expression whose value is an integer or
5502 pointer (but parentheses are required around binary operators, just as in
5503 a cast). This construct is allowed regardless of what kind of data is
5504 normally supposed to reside at @var{addr}.
5508 @section Program variables
5510 The most common kind of expression to use is the name of a variable
5513 Variables in expressions are understood in the selected stack frame
5514 (@pxref{Selection, ,Selecting a frame}); they must be either:
5518 global (or file-static)
5525 visible according to the scope rules of the
5526 programming language from the point of execution in that frame
5529 @noindent This means that in the function
5544 you can examine and use the variable @code{a} whenever your program is
5545 executing within the function @code{foo}, but you can only use or
5546 examine the variable @code{b} while your program is executing inside
5547 the block where @code{b} is declared.
5549 @cindex variable name conflict
5550 There is an exception: you can refer to a variable or function whose
5551 scope is a single source file even if the current execution point is not
5552 in this file. But it is possible to have more than one such variable or
5553 function with the same name (in different source files). If that
5554 happens, referring to that name has unpredictable effects. If you wish,
5555 you can specify a static variable in a particular function or file,
5556 using the colon-colon (@code{::}) notation:
5558 @cindex colon-colon, context for variables/functions
5560 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5561 @cindex @code{::}, context for variables/functions
5564 @var{file}::@var{variable}
5565 @var{function}::@var{variable}
5569 Here @var{file} or @var{function} is the name of the context for the
5570 static @var{variable}. In the case of file names, you can use quotes to
5571 make sure @value{GDBN} parses the file name as a single word---for example,
5572 to print a global value of @code{x} defined in @file{f2.c}:
5575 (@value{GDBP}) p 'f2.c'::x
5578 @cindex C@t{++} scope resolution
5579 This use of @samp{::} is very rarely in conflict with the very similar
5580 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5581 scope resolution operator in @value{GDBN} expressions.
5582 @c FIXME: Um, so what happens in one of those rare cases where it's in
5585 @cindex wrong values
5586 @cindex variable values, wrong
5587 @cindex function entry/exit, wrong values of variables
5588 @cindex optimized code, wrong values of variables
5590 @emph{Warning:} Occasionally, a local variable may appear to have the
5591 wrong value at certain points in a function---just after entry to a new
5592 scope, and just before exit.
5594 You may see this problem when you are stepping by machine instructions.
5595 This is because, on most machines, it takes more than one instruction to
5596 set up a stack frame (including local variable definitions); if you are
5597 stepping by machine instructions, variables may appear to have the wrong
5598 values until the stack frame is completely built. On exit, it usually
5599 also takes more than one machine instruction to destroy a stack frame;
5600 after you begin stepping through that group of instructions, local
5601 variable definitions may be gone.
5603 This may also happen when the compiler does significant optimizations.
5604 To be sure of always seeing accurate values, turn off all optimization
5607 @cindex ``No symbol "foo" in current context''
5608 Another possible effect of compiler optimizations is to optimize
5609 unused variables out of existence, or assign variables to registers (as
5610 opposed to memory addresses). Depending on the support for such cases
5611 offered by the debug info format used by the compiler, @value{GDBN}
5612 might not be able to display values for such local variables. If that
5613 happens, @value{GDBN} will print a message like this:
5616 No symbol "foo" in current context.
5619 To solve such problems, either recompile without optimizations, or use a
5620 different debug info format, if the compiler supports several such
5621 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5622 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5623 produces debug info in a format that is superior to formats such as
5624 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5625 an effective form for debug info. @xref{Debugging Options,,Options
5626 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5627 @xref{C, , Debugging C++}, for more info about debug info formats
5628 that are best suited to C@t{++} programs.
5630 If you ask to print an object whose contents are unknown to
5631 @value{GDBN}, e.g., because its data type is not completely specified
5632 by the debug information, @value{GDBN} will say @samp{<incomplete
5633 type>}. @xref{Symbols, incomplete type}, for more about this.
5635 Strings are identified as arrays of @code{char} values without specified
5636 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5637 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5638 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5639 defines literal string type @code{"char"} as @code{char} without a sign.
5644 signed char var1[] = "A";
5647 You get during debugging
5652 $2 = @{65 'A', 0 '\0'@}
5656 @section Artificial arrays
5658 @cindex artificial array
5660 @kindex @@@r{, referencing memory as an array}
5661 It is often useful to print out several successive objects of the
5662 same type in memory; a section of an array, or an array of
5663 dynamically determined size for which only a pointer exists in the
5666 You can do this by referring to a contiguous span of memory as an
5667 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5668 operand of @samp{@@} should be the first element of the desired array
5669 and be an individual object. The right operand should be the desired length
5670 of the array. The result is an array value whose elements are all of
5671 the type of the left argument. The first element is actually the left
5672 argument; the second element comes from bytes of memory immediately
5673 following those that hold the first element, and so on. Here is an
5674 example. If a program says
5677 int *array = (int *) malloc (len * sizeof (int));
5681 you can print the contents of @code{array} with
5687 The left operand of @samp{@@} must reside in memory. Array values made
5688 with @samp{@@} in this way behave just like other arrays in terms of
5689 subscripting, and are coerced to pointers when used in expressions.
5690 Artificial arrays most often appear in expressions via the value history
5691 (@pxref{Value History, ,Value history}), after printing one out.
5693 Another way to create an artificial array is to use a cast.
5694 This re-interprets a value as if it were an array.
5695 The value need not be in memory:
5697 (@value{GDBP}) p/x (short[2])0x12345678
5698 $1 = @{0x1234, 0x5678@}
5701 As a convenience, if you leave the array length out (as in
5702 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5703 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5705 (@value{GDBP}) p/x (short[])0x12345678
5706 $2 = @{0x1234, 0x5678@}
5709 Sometimes the artificial array mechanism is not quite enough; in
5710 moderately complex data structures, the elements of interest may not
5711 actually be adjacent---for example, if you are interested in the values
5712 of pointers in an array. One useful work-around in this situation is
5713 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5714 variables}) as a counter in an expression that prints the first
5715 interesting value, and then repeat that expression via @key{RET}. For
5716 instance, suppose you have an array @code{dtab} of pointers to
5717 structures, and you are interested in the values of a field @code{fv}
5718 in each structure. Here is an example of what you might type:
5728 @node Output Formats
5729 @section Output formats
5731 @cindex formatted output
5732 @cindex output formats
5733 By default, @value{GDBN} prints a value according to its data type. Sometimes
5734 this is not what you want. For example, you might want to print a number
5735 in hex, or a pointer in decimal. Or you might want to view data in memory
5736 at a certain address as a character string or as an instruction. To do
5737 these things, specify an @dfn{output format} when you print a value.
5739 The simplest use of output formats is to say how to print a value
5740 already computed. This is done by starting the arguments of the
5741 @code{print} command with a slash and a format letter. The format
5742 letters supported are:
5746 Regard the bits of the value as an integer, and print the integer in
5750 Print as integer in signed decimal.
5753 Print as integer in unsigned decimal.
5756 Print as integer in octal.
5759 Print as integer in binary. The letter @samp{t} stands for ``two''.
5760 @footnote{@samp{b} cannot be used because these format letters are also
5761 used with the @code{x} command, where @samp{b} stands for ``byte'';
5762 see @ref{Memory,,Examining memory}.}
5765 @cindex unknown address, locating
5766 @cindex locate address
5767 Print as an address, both absolute in hexadecimal and as an offset from
5768 the nearest preceding symbol. You can use this format used to discover
5769 where (in what function) an unknown address is located:
5772 (@value{GDBP}) p/a 0x54320
5773 $3 = 0x54320 <_initialize_vx+396>
5777 The command @code{info symbol 0x54320} yields similar results.
5778 @xref{Symbols, info symbol}.
5781 Regard as an integer and print it as a character constant. This
5782 prints both the numerical value and its character representation. The
5783 character representation is replaced with the octal escape @samp{\nnn}
5784 for characters outside the 7-bit @sc{ascii} range.
5787 Regard the bits of the value as a floating point number and print
5788 using typical floating point syntax.
5791 For example, to print the program counter in hex (@pxref{Registers}), type
5798 Note that no space is required before the slash; this is because command
5799 names in @value{GDBN} cannot contain a slash.
5801 To reprint the last value in the value history with a different format,
5802 you can use the @code{print} command with just a format and no
5803 expression. For example, @samp{p/x} reprints the last value in hex.
5806 @section Examining memory
5808 You can use the command @code{x} (for ``examine'') to examine memory in
5809 any of several formats, independently of your program's data types.
5811 @cindex examining memory
5813 @kindex x @r{(examine memory)}
5814 @item x/@var{nfu} @var{addr}
5817 Use the @code{x} command to examine memory.
5820 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5821 much memory to display and how to format it; @var{addr} is an
5822 expression giving the address where you want to start displaying memory.
5823 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5824 Several commands set convenient defaults for @var{addr}.
5827 @item @var{n}, the repeat count
5828 The repeat count is a decimal integer; the default is 1. It specifies
5829 how much memory (counting by units @var{u}) to display.
5830 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5833 @item @var{f}, the display format
5834 The display format is one of the formats used by @code{print}
5835 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5836 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5837 @samp{i} (for machine instructions). The default is @samp{x}
5838 (hexadecimal) initially. The default changes each time you use either
5839 @code{x} or @code{print}.
5841 @item @var{u}, the unit size
5842 The unit size is any of
5848 Halfwords (two bytes).
5850 Words (four bytes). This is the initial default.
5852 Giant words (eight bytes).
5855 Each time you specify a unit size with @code{x}, that size becomes the
5856 default unit the next time you use @code{x}. (For the @samp{s} and
5857 @samp{i} formats, the unit size is ignored and is normally not written.)
5859 @item @var{addr}, starting display address
5860 @var{addr} is the address where you want @value{GDBN} to begin displaying
5861 memory. The expression need not have a pointer value (though it may);
5862 it is always interpreted as an integer address of a byte of memory.
5863 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5864 @var{addr} is usually just after the last address examined---but several
5865 other commands also set the default address: @code{info breakpoints} (to
5866 the address of the last breakpoint listed), @code{info line} (to the
5867 starting address of a line), and @code{print} (if you use it to display
5868 a value from memory).
5871 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5872 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5873 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5874 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5875 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5877 Since the letters indicating unit sizes are all distinct from the
5878 letters specifying output formats, you do not have to remember whether
5879 unit size or format comes first; either order works. The output
5880 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5881 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5883 Even though the unit size @var{u} is ignored for the formats @samp{s}
5884 and @samp{i}, you might still want to use a count @var{n}; for example,
5885 @samp{3i} specifies that you want to see three machine instructions,
5886 including any operands. The command @code{disassemble} gives an
5887 alternative way of inspecting machine instructions; see @ref{Machine
5888 Code,,Source and machine code}.
5890 All the defaults for the arguments to @code{x} are designed to make it
5891 easy to continue scanning memory with minimal specifications each time
5892 you use @code{x}. For example, after you have inspected three machine
5893 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5894 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5895 the repeat count @var{n} is used again; the other arguments default as
5896 for successive uses of @code{x}.
5898 @cindex @code{$_}, @code{$__}, and value history
5899 The addresses and contents printed by the @code{x} command are not saved
5900 in the value history because there is often too much of them and they
5901 would get in the way. Instead, @value{GDBN} makes these values available for
5902 subsequent use in expressions as values of the convenience variables
5903 @code{$_} and @code{$__}. After an @code{x} command, the last address
5904 examined is available for use in expressions in the convenience variable
5905 @code{$_}. The contents of that address, as examined, are available in
5906 the convenience variable @code{$__}.
5908 If the @code{x} command has a repeat count, the address and contents saved
5909 are from the last memory unit printed; this is not the same as the last
5910 address printed if several units were printed on the last line of output.
5912 @cindex remote memory comparison
5913 @cindex verify remote memory image
5914 When you are debugging a program running on a remote target machine
5915 (@pxref{Remote}), you may wish to verify the program's image in the
5916 remote machine's memory against the executable file you downloaded to
5917 the target. The @code{compare-sections} command is provided for such
5921 @kindex compare-sections
5922 @item compare-sections @r{[}@var{section-name}@r{]}
5923 Compare the data of a loadable section @var{section-name} in the
5924 executable file of the program being debugged with the same section in
5925 the remote machine's memory, and report any mismatches. With no
5926 arguments, compares all loadable sections. This command's
5927 availability depends on the target's support for the @code{"qCRC"}
5932 @section Automatic display
5933 @cindex automatic display
5934 @cindex display of expressions
5936 If you find that you want to print the value of an expression frequently
5937 (to see how it changes), you might want to add it to the @dfn{automatic
5938 display list} so that @value{GDBN} prints its value each time your program stops.
5939 Each expression added to the list is given a number to identify it;
5940 to remove an expression from the list, you specify that number.
5941 The automatic display looks like this:
5945 3: bar[5] = (struct hack *) 0x3804
5949 This display shows item numbers, expressions and their current values. As with
5950 displays you request manually using @code{x} or @code{print}, you can
5951 specify the output format you prefer; in fact, @code{display} decides
5952 whether to use @code{print} or @code{x} depending on how elaborate your
5953 format specification is---it uses @code{x} if you specify a unit size,
5954 or one of the two formats (@samp{i} and @samp{s}) that are only
5955 supported by @code{x}; otherwise it uses @code{print}.
5959 @item display @var{expr}
5960 Add the expression @var{expr} to the list of expressions to display
5961 each time your program stops. @xref{Expressions, ,Expressions}.
5963 @code{display} does not repeat if you press @key{RET} again after using it.
5965 @item display/@var{fmt} @var{expr}
5966 For @var{fmt} specifying only a display format and not a size or
5967 count, add the expression @var{expr} to the auto-display list but
5968 arrange to display it each time in the specified format @var{fmt}.
5969 @xref{Output Formats,,Output formats}.
5971 @item display/@var{fmt} @var{addr}
5972 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5973 number of units, add the expression @var{addr} as a memory address to
5974 be examined each time your program stops. Examining means in effect
5975 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5978 For example, @samp{display/i $pc} can be helpful, to see the machine
5979 instruction about to be executed each time execution stops (@samp{$pc}
5980 is a common name for the program counter; @pxref{Registers, ,Registers}).
5983 @kindex delete display
5985 @item undisplay @var{dnums}@dots{}
5986 @itemx delete display @var{dnums}@dots{}
5987 Remove item numbers @var{dnums} from the list of expressions to display.
5989 @code{undisplay} does not repeat if you press @key{RET} after using it.
5990 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5992 @kindex disable display
5993 @item disable display @var{dnums}@dots{}
5994 Disable the display of item numbers @var{dnums}. A disabled display
5995 item is not printed automatically, but is not forgotten. It may be
5996 enabled again later.
5998 @kindex enable display
5999 @item enable display @var{dnums}@dots{}
6000 Enable display of item numbers @var{dnums}. It becomes effective once
6001 again in auto display of its expression, until you specify otherwise.
6004 Display the current values of the expressions on the list, just as is
6005 done when your program stops.
6007 @kindex info display
6009 Print the list of expressions previously set up to display
6010 automatically, each one with its item number, but without showing the
6011 values. This includes disabled expressions, which are marked as such.
6012 It also includes expressions which would not be displayed right now
6013 because they refer to automatic variables not currently available.
6016 @cindex display disabled out of scope
6017 If a display expression refers to local variables, then it does not make
6018 sense outside the lexical context for which it was set up. Such an
6019 expression is disabled when execution enters a context where one of its
6020 variables is not defined. For example, if you give the command
6021 @code{display last_char} while inside a function with an argument
6022 @code{last_char}, @value{GDBN} displays this argument while your program
6023 continues to stop inside that function. When it stops elsewhere---where
6024 there is no variable @code{last_char}---the display is disabled
6025 automatically. The next time your program stops where @code{last_char}
6026 is meaningful, you can enable the display expression once again.
6028 @node Print Settings
6029 @section Print settings
6031 @cindex format options
6032 @cindex print settings
6033 @value{GDBN} provides the following ways to control how arrays, structures,
6034 and symbols are printed.
6037 These settings are useful for debugging programs in any language:
6041 @item set print address
6042 @itemx set print address on
6043 @cindex print/don't print memory addresses
6044 @value{GDBN} prints memory addresses showing the location of stack
6045 traces, structure values, pointer values, breakpoints, and so forth,
6046 even when it also displays the contents of those addresses. The default
6047 is @code{on}. For example, this is what a stack frame display looks like with
6048 @code{set print address on}:
6053 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6055 530 if (lquote != def_lquote)
6059 @item set print address off
6060 Do not print addresses when displaying their contents. For example,
6061 this is the same stack frame displayed with @code{set print address off}:
6065 (@value{GDBP}) set print addr off
6067 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6068 530 if (lquote != def_lquote)
6072 You can use @samp{set print address off} to eliminate all machine
6073 dependent displays from the @value{GDBN} interface. For example, with
6074 @code{print address off}, you should get the same text for backtraces on
6075 all machines---whether or not they involve pointer arguments.
6078 @item show print address
6079 Show whether or not addresses are to be printed.
6082 When @value{GDBN} prints a symbolic address, it normally prints the
6083 closest earlier symbol plus an offset. If that symbol does not uniquely
6084 identify the address (for example, it is a name whose scope is a single
6085 source file), you may need to clarify. One way to do this is with
6086 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6087 you can set @value{GDBN} to print the source file and line number when
6088 it prints a symbolic address:
6091 @item set print symbol-filename on
6092 @cindex source file and line of a symbol
6093 @cindex symbol, source file and line
6094 Tell @value{GDBN} to print the source file name and line number of a
6095 symbol in the symbolic form of an address.
6097 @item set print symbol-filename off
6098 Do not print source file name and line number of a symbol. This is the
6101 @item show print symbol-filename
6102 Show whether or not @value{GDBN} will print the source file name and
6103 line number of a symbol in the symbolic form of an address.
6106 Another situation where it is helpful to show symbol filenames and line
6107 numbers is when disassembling code; @value{GDBN} shows you the line
6108 number and source file that corresponds to each instruction.
6110 Also, you may wish to see the symbolic form only if the address being
6111 printed is reasonably close to the closest earlier symbol:
6114 @item set print max-symbolic-offset @var{max-offset}
6115 @cindex maximum value for offset of closest symbol
6116 Tell @value{GDBN} to only display the symbolic form of an address if the
6117 offset between the closest earlier symbol and the address is less than
6118 @var{max-offset}. The default is 0, which tells @value{GDBN}
6119 to always print the symbolic form of an address if any symbol precedes it.
6121 @item show print max-symbolic-offset
6122 Ask how large the maximum offset is that @value{GDBN} prints in a
6126 @cindex wild pointer, interpreting
6127 @cindex pointer, finding referent
6128 If you have a pointer and you are not sure where it points, try
6129 @samp{set print symbol-filename on}. Then you can determine the name
6130 and source file location of the variable where it points, using
6131 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6132 For example, here @value{GDBN} shows that a variable @code{ptt} points
6133 at another variable @code{t}, defined in @file{hi2.c}:
6136 (@value{GDBP}) set print symbol-filename on
6137 (@value{GDBP}) p/a ptt
6138 $4 = 0xe008 <t in hi2.c>
6142 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6143 does not show the symbol name and filename of the referent, even with
6144 the appropriate @code{set print} options turned on.
6147 Other settings control how different kinds of objects are printed:
6150 @item set print array
6151 @itemx set print array on
6152 @cindex pretty print arrays
6153 Pretty print arrays. This format is more convenient to read,
6154 but uses more space. The default is off.
6156 @item set print array off
6157 Return to compressed format for arrays.
6159 @item show print array
6160 Show whether compressed or pretty format is selected for displaying
6163 @cindex print array indexes
6164 @item set print array-indexes
6165 @itemx set print array-indexes on
6166 Print the index of each element when displaying arrays. May be more
6167 convenient to locate a given element in the array or quickly find the
6168 index of a given element in that printed array. The default is off.
6170 @item set print array-indexes off
6171 Stop printing element indexes when displaying arrays.
6173 @item show print array-indexes
6174 Show whether the index of each element is printed when displaying
6177 @item set print elements @var{number-of-elements}
6178 @cindex number of array elements to print
6179 @cindex limit on number of printed array elements
6180 Set a limit on how many elements of an array @value{GDBN} will print.
6181 If @value{GDBN} is printing a large array, it stops printing after it has
6182 printed the number of elements set by the @code{set print elements} command.
6183 This limit also applies to the display of strings.
6184 When @value{GDBN} starts, this limit is set to 200.
6185 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6187 @item show print elements
6188 Display the number of elements of a large array that @value{GDBN} will print.
6189 If the number is 0, then the printing is unlimited.
6191 @item set print repeats
6192 @cindex repeated array elements
6193 Set the threshold for suppressing display of repeated array
6194 elements. When the number of consecutive identical elements of an
6195 array exceeds the threshold, @value{GDBN} prints the string
6196 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6197 identical repetitions, instead of displaying the identical elements
6198 themselves. Setting the threshold to zero will cause all elements to
6199 be individually printed. The default threshold is 10.
6201 @item show print repeats
6202 Display the current threshold for printing repeated identical
6205 @item set print null-stop
6206 @cindex @sc{null} elements in arrays
6207 Cause @value{GDBN} to stop printing the characters of an array when the first
6208 @sc{null} is encountered. This is useful when large arrays actually
6209 contain only short strings.
6212 @item show print null-stop
6213 Show whether @value{GDBN} stops printing an array on the first
6214 @sc{null} character.
6216 @item set print pretty on
6217 @cindex print structures in indented form
6218 @cindex indentation in structure display
6219 Cause @value{GDBN} to print structures in an indented format with one member
6220 per line, like this:
6235 @item set print pretty off
6236 Cause @value{GDBN} to print structures in a compact format, like this:
6240 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6241 meat = 0x54 "Pork"@}
6246 This is the default format.
6248 @item show print pretty
6249 Show which format @value{GDBN} is using to print structures.
6251 @item set print sevenbit-strings on
6252 @cindex eight-bit characters in strings
6253 @cindex octal escapes in strings
6254 Print using only seven-bit characters; if this option is set,
6255 @value{GDBN} displays any eight-bit characters (in strings or
6256 character values) using the notation @code{\}@var{nnn}. This setting is
6257 best if you are working in English (@sc{ascii}) and you use the
6258 high-order bit of characters as a marker or ``meta'' bit.
6260 @item set print sevenbit-strings off
6261 Print full eight-bit characters. This allows the use of more
6262 international character sets, and is the default.
6264 @item show print sevenbit-strings
6265 Show whether or not @value{GDBN} is printing only seven-bit characters.
6267 @item set print union on
6268 @cindex unions in structures, printing
6269 Tell @value{GDBN} to print unions which are contained in structures
6270 and other unions. This is the default setting.
6272 @item set print union off
6273 Tell @value{GDBN} not to print unions which are contained in
6274 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6277 @item show print union
6278 Ask @value{GDBN} whether or not it will print unions which are contained in
6279 structures and other unions.
6281 For example, given the declarations
6284 typedef enum @{Tree, Bug@} Species;
6285 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6286 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6297 struct thing foo = @{Tree, @{Acorn@}@};
6301 with @code{set print union on} in effect @samp{p foo} would print
6304 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6308 and with @code{set print union off} in effect it would print
6311 $1 = @{it = Tree, form = @{...@}@}
6315 @code{set print union} affects programs written in C-like languages
6321 These settings are of interest when debugging C@t{++} programs:
6324 @cindex demangling C@t{++} names
6325 @item set print demangle
6326 @itemx set print demangle on
6327 Print C@t{++} names in their source form rather than in the encoded
6328 (``mangled'') form passed to the assembler and linker for type-safe
6329 linkage. The default is on.
6331 @item show print demangle
6332 Show whether C@t{++} names are printed in mangled or demangled form.
6334 @item set print asm-demangle
6335 @itemx set print asm-demangle on
6336 Print C@t{++} names in their source form rather than their mangled form, even
6337 in assembler code printouts such as instruction disassemblies.
6340 @item show print asm-demangle
6341 Show whether C@t{++} names in assembly listings are printed in mangled
6344 @cindex C@t{++} symbol decoding style
6345 @cindex symbol decoding style, C@t{++}
6346 @kindex set demangle-style
6347 @item set demangle-style @var{style}
6348 Choose among several encoding schemes used by different compilers to
6349 represent C@t{++} names. The choices for @var{style} are currently:
6353 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6356 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6357 This is the default.
6360 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6363 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6366 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6367 @strong{Warning:} this setting alone is not sufficient to allow
6368 debugging @code{cfront}-generated executables. @value{GDBN} would
6369 require further enhancement to permit that.
6372 If you omit @var{style}, you will see a list of possible formats.
6374 @item show demangle-style
6375 Display the encoding style currently in use for decoding C@t{++} symbols.
6377 @item set print object
6378 @itemx set print object on
6379 @cindex derived type of an object, printing
6380 @cindex display derived types
6381 When displaying a pointer to an object, identify the @emph{actual}
6382 (derived) type of the object rather than the @emph{declared} type, using
6383 the virtual function table.
6385 @item set print object off
6386 Display only the declared type of objects, without reference to the
6387 virtual function table. This is the default setting.
6389 @item show print object
6390 Show whether actual, or declared, object types are displayed.
6392 @item set print static-members
6393 @itemx set print static-members on
6394 @cindex static members of C@t{++} objects
6395 Print static members when displaying a C@t{++} object. The default is on.
6397 @item set print static-members off
6398 Do not print static members when displaying a C@t{++} object.
6400 @item show print static-members
6401 Show whether C@t{++} static members are printed or not.
6403 @item set print pascal_static-members
6404 @itemx set print pascal_static-members on
6405 @cindex static members of Pascal objects
6406 @cindex Pascal objects, static members display
6407 Print static members when displaying a Pascal object. The default is on.
6409 @item set print pascal_static-members off
6410 Do not print static members when displaying a Pascal object.
6412 @item show print pascal_static-members
6413 Show whether Pascal static members are printed or not.
6415 @c These don't work with HP ANSI C++ yet.
6416 @item set print vtbl
6417 @itemx set print vtbl on
6418 @cindex pretty print C@t{++} virtual function tables
6419 @cindex virtual functions (C@t{++}) display
6420 @cindex VTBL display
6421 Pretty print C@t{++} virtual function tables. The default is off.
6422 (The @code{vtbl} commands do not work on programs compiled with the HP
6423 ANSI C@t{++} compiler (@code{aCC}).)
6425 @item set print vtbl off
6426 Do not pretty print C@t{++} virtual function tables.
6428 @item show print vtbl
6429 Show whether C@t{++} virtual function tables are pretty printed, or not.
6433 @section Value history
6435 @cindex value history
6436 @cindex history of values printed by @value{GDBN}
6437 Values printed by the @code{print} command are saved in the @value{GDBN}
6438 @dfn{value history}. This allows you to refer to them in other expressions.
6439 Values are kept until the symbol table is re-read or discarded
6440 (for example with the @code{file} or @code{symbol-file} commands).
6441 When the symbol table changes, the value history is discarded,
6442 since the values may contain pointers back to the types defined in the
6447 @cindex history number
6448 The values printed are given @dfn{history numbers} by which you can
6449 refer to them. These are successive integers starting with one.
6450 @code{print} shows you the history number assigned to a value by
6451 printing @samp{$@var{num} = } before the value; here @var{num} is the
6454 To refer to any previous value, use @samp{$} followed by the value's
6455 history number. The way @code{print} labels its output is designed to
6456 remind you of this. Just @code{$} refers to the most recent value in
6457 the history, and @code{$$} refers to the value before that.
6458 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6459 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6460 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6462 For example, suppose you have just printed a pointer to a structure and
6463 want to see the contents of the structure. It suffices to type
6469 If you have a chain of structures where the component @code{next} points
6470 to the next one, you can print the contents of the next one with this:
6477 You can print successive links in the chain by repeating this
6478 command---which you can do by just typing @key{RET}.
6480 Note that the history records values, not expressions. If the value of
6481 @code{x} is 4 and you type these commands:
6489 then the value recorded in the value history by the @code{print} command
6490 remains 4 even though the value of @code{x} has changed.
6495 Print the last ten values in the value history, with their item numbers.
6496 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6497 values} does not change the history.
6499 @item show values @var{n}
6500 Print ten history values centered on history item number @var{n}.
6503 Print ten history values just after the values last printed. If no more
6504 values are available, @code{show values +} produces no display.
6507 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6508 same effect as @samp{show values +}.
6510 @node Convenience Vars
6511 @section Convenience variables
6513 @cindex convenience variables
6514 @cindex user-defined variables
6515 @value{GDBN} provides @dfn{convenience variables} that you can use within
6516 @value{GDBN} to hold on to a value and refer to it later. These variables
6517 exist entirely within @value{GDBN}; they are not part of your program, and
6518 setting a convenience variable has no direct effect on further execution
6519 of your program. That is why you can use them freely.
6521 Convenience variables are prefixed with @samp{$}. Any name preceded by
6522 @samp{$} can be used for a convenience variable, unless it is one of
6523 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6524 (Value history references, in contrast, are @emph{numbers} preceded
6525 by @samp{$}. @xref{Value History, ,Value history}.)
6527 You can save a value in a convenience variable with an assignment
6528 expression, just as you would set a variable in your program.
6532 set $foo = *object_ptr
6536 would save in @code{$foo} the value contained in the object pointed to by
6539 Using a convenience variable for the first time creates it, but its
6540 value is @code{void} until you assign a new value. You can alter the
6541 value with another assignment at any time.
6543 Convenience variables have no fixed types. You can assign a convenience
6544 variable any type of value, including structures and arrays, even if
6545 that variable already has a value of a different type. The convenience
6546 variable, when used as an expression, has the type of its current value.
6549 @kindex show convenience
6550 @cindex show all user variables
6551 @item show convenience
6552 Print a list of convenience variables used so far, and their values.
6553 Abbreviated @code{show conv}.
6555 @kindex init-if-undefined
6556 @cindex convenience variables, initializing
6557 @item init-if-undefined $@var{variable} = @var{expression}
6558 Set a convenience variable if it has not already been set. This is useful
6559 for user-defined commands that keep some state. It is similar, in concept,
6560 to using local static variables with initializers in C (except that
6561 convenience variables are global). It can also be used to allow users to
6562 override default values used in a command script.
6564 If the variable is already defined then the expression is not evaluated so
6565 any side-effects do not occur.
6568 One of the ways to use a convenience variable is as a counter to be
6569 incremented or a pointer to be advanced. For example, to print
6570 a field from successive elements of an array of structures:
6574 print bar[$i++]->contents
6578 Repeat that command by typing @key{RET}.
6580 Some convenience variables are created automatically by @value{GDBN} and given
6581 values likely to be useful.
6584 @vindex $_@r{, convenience variable}
6586 The variable @code{$_} is automatically set by the @code{x} command to
6587 the last address examined (@pxref{Memory, ,Examining memory}). Other
6588 commands which provide a default address for @code{x} to examine also
6589 set @code{$_} to that address; these commands include @code{info line}
6590 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6591 except when set by the @code{x} command, in which case it is a pointer
6592 to the type of @code{$__}.
6594 @vindex $__@r{, convenience variable}
6596 The variable @code{$__} is automatically set by the @code{x} command
6597 to the value found in the last address examined. Its type is chosen
6598 to match the format in which the data was printed.
6601 @vindex $_exitcode@r{, convenience variable}
6602 The variable @code{$_exitcode} is automatically set to the exit code when
6603 the program being debugged terminates.
6606 On HP-UX systems, if you refer to a function or variable name that
6607 begins with a dollar sign, @value{GDBN} searches for a user or system
6608 name first, before it searches for a convenience variable.
6614 You can refer to machine register contents, in expressions, as variables
6615 with names starting with @samp{$}. The names of registers are different
6616 for each machine; use @code{info registers} to see the names used on
6620 @kindex info registers
6621 @item info registers
6622 Print the names and values of all registers except floating-point
6623 and vector registers (in the selected stack frame).
6625 @kindex info all-registers
6626 @cindex floating point registers
6627 @item info all-registers
6628 Print the names and values of all registers, including floating-point
6629 and vector registers (in the selected stack frame).
6631 @item info registers @var{regname} @dots{}
6632 Print the @dfn{relativized} value of each specified register @var{regname}.
6633 As discussed in detail below, register values are normally relative to
6634 the selected stack frame. @var{regname} may be any register name valid on
6635 the machine you are using, with or without the initial @samp{$}.
6638 @cindex stack pointer register
6639 @cindex program counter register
6640 @cindex process status register
6641 @cindex frame pointer register
6642 @cindex standard registers
6643 @value{GDBN} has four ``standard'' register names that are available (in
6644 expressions) on most machines---whenever they do not conflict with an
6645 architecture's canonical mnemonics for registers. The register names
6646 @code{$pc} and @code{$sp} are used for the program counter register and
6647 the stack pointer. @code{$fp} is used for a register that contains a
6648 pointer to the current stack frame, and @code{$ps} is used for a
6649 register that contains the processor status. For example,
6650 you could print the program counter in hex with
6657 or print the instruction to be executed next with
6664 or add four to the stack pointer@footnote{This is a way of removing
6665 one word from the stack, on machines where stacks grow downward in
6666 memory (most machines, nowadays). This assumes that the innermost
6667 stack frame is selected; setting @code{$sp} is not allowed when other
6668 stack frames are selected. To pop entire frames off the stack,
6669 regardless of machine architecture, use @code{return};
6670 see @ref{Returning, ,Returning from a function}.} with
6676 Whenever possible, these four standard register names are available on
6677 your machine even though the machine has different canonical mnemonics,
6678 so long as there is no conflict. The @code{info registers} command
6679 shows the canonical names. For example, on the SPARC, @code{info
6680 registers} displays the processor status register as @code{$psr} but you
6681 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6682 is an alias for the @sc{eflags} register.
6684 @value{GDBN} always considers the contents of an ordinary register as an
6685 integer when the register is examined in this way. Some machines have
6686 special registers which can hold nothing but floating point; these
6687 registers are considered to have floating point values. There is no way
6688 to refer to the contents of an ordinary register as floating point value
6689 (although you can @emph{print} it as a floating point value with
6690 @samp{print/f $@var{regname}}).
6692 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6693 means that the data format in which the register contents are saved by
6694 the operating system is not the same one that your program normally
6695 sees. For example, the registers of the 68881 floating point
6696 coprocessor are always saved in ``extended'' (raw) format, but all C
6697 programs expect to work with ``double'' (virtual) format. In such
6698 cases, @value{GDBN} normally works with the virtual format only (the format
6699 that makes sense for your program), but the @code{info registers} command
6700 prints the data in both formats.
6702 @cindex SSE registers (x86)
6703 @cindex MMX registers (x86)
6704 Some machines have special registers whose contents can be interpreted
6705 in several different ways. For example, modern x86-based machines
6706 have SSE and MMX registers that can hold several values packed
6707 together in several different formats. @value{GDBN} refers to such
6708 registers in @code{struct} notation:
6711 (@value{GDBP}) print $xmm1
6713 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6714 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6715 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6716 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6717 v4_int32 = @{0, 20657912, 11, 13@},
6718 v2_int64 = @{88725056443645952, 55834574859@},
6719 uint128 = 0x0000000d0000000b013b36f800000000
6724 To set values of such registers, you need to tell @value{GDBN} which
6725 view of the register you wish to change, as if you were assigning
6726 value to a @code{struct} member:
6729 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6732 Normally, register values are relative to the selected stack frame
6733 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6734 value that the register would contain if all stack frames farther in
6735 were exited and their saved registers restored. In order to see the
6736 true contents of hardware registers, you must select the innermost
6737 frame (with @samp{frame 0}).
6739 However, @value{GDBN} must deduce where registers are saved, from the machine
6740 code generated by your compiler. If some registers are not saved, or if
6741 @value{GDBN} is unable to locate the saved registers, the selected stack
6742 frame makes no difference.
6744 @node Floating Point Hardware
6745 @section Floating point hardware
6746 @cindex floating point
6748 Depending on the configuration, @value{GDBN} may be able to give
6749 you more information about the status of the floating point hardware.
6754 Display hardware-dependent information about the floating
6755 point unit. The exact contents and layout vary depending on the
6756 floating point chip. Currently, @samp{info float} is supported on
6757 the ARM and x86 machines.
6761 @section Vector Unit
6764 Depending on the configuration, @value{GDBN} may be able to give you
6765 more information about the status of the vector unit.
6770 Display information about the vector unit. The exact contents and
6771 layout vary depending on the hardware.
6774 @node OS Information
6775 @section Operating system auxiliary information
6776 @cindex OS information
6778 @value{GDBN} provides interfaces to useful OS facilities that can help
6779 you debug your program.
6781 @cindex @code{ptrace} system call
6782 @cindex @code{struct user} contents
6783 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6784 machines), it interfaces with the inferior via the @code{ptrace}
6785 system call. The operating system creates a special sata structure,
6786 called @code{struct user}, for this interface. You can use the
6787 command @code{info udot} to display the contents of this data
6793 Display the contents of the @code{struct user} maintained by the OS
6794 kernel for the program being debugged. @value{GDBN} displays the
6795 contents of @code{struct user} as a list of hex numbers, similar to
6796 the @code{examine} command.
6799 @cindex auxiliary vector
6800 @cindex vector, auxiliary
6801 Some operating systems supply an @dfn{auxiliary vector} to programs at
6802 startup. This is akin to the arguments and environment that you
6803 specify for a program, but contains a system-dependent variety of
6804 binary values that tell system libraries important details about the
6805 hardware, operating system, and process. Each value's purpose is
6806 identified by an integer tag; the meanings are well-known but system-specific.
6807 Depending on the configuration and operating system facilities,
6808 @value{GDBN} may be able to show you this information. For remote
6809 targets, this functionality may further depend on the remote stub's
6810 support of the @samp{qXfer:auxv:read} packet, see
6811 @ref{qXfer auxiliary vector read}.
6816 Display the auxiliary vector of the inferior, which can be either a
6817 live process or a core dump file. @value{GDBN} prints each tag value
6818 numerically, and also shows names and text descriptions for recognized
6819 tags. Some values in the vector are numbers, some bit masks, and some
6820 pointers to strings or other data. @value{GDBN} displays each value in the
6821 most appropriate form for a recognized tag, and in hexadecimal for
6822 an unrecognized tag.
6826 @node Memory Region Attributes
6827 @section Memory region attributes
6828 @cindex memory region attributes
6830 @dfn{Memory region attributes} allow you to describe special handling
6831 required by regions of your target's memory. @value{GDBN} uses
6832 attributes to determine whether to allow certain types of memory
6833 accesses; whether to use specific width accesses; and whether to cache
6834 target memory. By default the description of memory regions is
6835 fetched from the target (if the current target supports this), but the
6836 user can override the fetched regions.
6838 Defined memory regions can be individually enabled and disabled. When a
6839 memory region is disabled, @value{GDBN} uses the default attributes when
6840 accessing memory in that region. Similarly, if no memory regions have
6841 been defined, @value{GDBN} uses the default attributes when accessing
6844 When a memory region is defined, it is given a number to identify it;
6845 to enable, disable, or remove a memory region, you specify that number.
6849 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6850 Define a memory region bounded by @var{lower} and @var{upper} with
6851 attributes @var{attributes}@dots{}, and add it to the list of regions
6852 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6853 case: it is treated as the target's maximum memory address.
6854 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6857 Discard any user changes to the memory regions and use target-supplied
6858 regions, if available, or no regions if the target does not support.
6861 @item delete mem @var{nums}@dots{}
6862 Remove memory regions @var{nums}@dots{} from the list of regions
6863 monitored by @value{GDBN}.
6866 @item disable mem @var{nums}@dots{}
6867 Disable monitoring of memory regions @var{nums}@dots{}.
6868 A disabled memory region is not forgotten.
6869 It may be enabled again later.
6872 @item enable mem @var{nums}@dots{}
6873 Enable monitoring of memory regions @var{nums}@dots{}.
6877 Print a table of all defined memory regions, with the following columns
6881 @item Memory Region Number
6882 @item Enabled or Disabled.
6883 Enabled memory regions are marked with @samp{y}.
6884 Disabled memory regions are marked with @samp{n}.
6887 The address defining the inclusive lower bound of the memory region.
6890 The address defining the exclusive upper bound of the memory region.
6893 The list of attributes set for this memory region.
6898 @subsection Attributes
6900 @subsubsection Memory Access Mode
6901 The access mode attributes set whether @value{GDBN} may make read or
6902 write accesses to a memory region.
6904 While these attributes prevent @value{GDBN} from performing invalid
6905 memory accesses, they do nothing to prevent the target system, I/O DMA,
6906 etc.@: from accessing memory.
6910 Memory is read only.
6912 Memory is write only.
6914 Memory is read/write. This is the default.
6917 @subsubsection Memory Access Size
6918 The access size attribute tells @value{GDBN} to use specific sized
6919 accesses in the memory region. Often memory mapped device registers
6920 require specific sized accesses. If no access size attribute is
6921 specified, @value{GDBN} may use accesses of any size.
6925 Use 8 bit memory accesses.
6927 Use 16 bit memory accesses.
6929 Use 32 bit memory accesses.
6931 Use 64 bit memory accesses.
6934 @c @subsubsection Hardware/Software Breakpoints
6935 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6936 @c will use hardware or software breakpoints for the internal breakpoints
6937 @c used by the step, next, finish, until, etc. commands.
6941 @c Always use hardware breakpoints
6942 @c @item swbreak (default)
6945 @subsubsection Data Cache
6946 The data cache attributes set whether @value{GDBN} will cache target
6947 memory. While this generally improves performance by reducing debug
6948 protocol overhead, it can lead to incorrect results because @value{GDBN}
6949 does not know about volatile variables or memory mapped device
6954 Enable @value{GDBN} to cache target memory.
6956 Disable @value{GDBN} from caching target memory. This is the default.
6959 @subsection Memory Access Checking
6960 @value{GDBN} can be instructed to refuse accesses to memory that is
6961 not explicitly described. This can be useful if accessing such
6962 regions has undesired effects for a specific target, or to provide
6963 better error checking. The following commands control this behaviour.
6966 @kindex set mem inaccessible-by-default
6967 @item set mem inaccessible-by-default [on|off]
6968 If @code{on} is specified, make @value{GDBN} treat memory not
6969 explicitly described by the memory ranges as non-existent and refuse accesses
6970 to such memory. The checks are only performed if there's at least one
6971 memory range defined. If @code{off} is specified, make @value{GDBN}
6972 treat the memory not explicitly described by the memory ranges as RAM.
6973 The default value is @code{off}.
6974 @kindex show mem inaccessible-by-default
6975 @item show mem inaccessible-by-default
6976 Show the current handling of accesses to unknown memory.
6980 @c @subsubsection Memory Write Verification
6981 @c The memory write verification attributes set whether @value{GDBN}
6982 @c will re-reads data after each write to verify the write was successful.
6986 @c @item noverify (default)
6989 @node Dump/Restore Files
6990 @section Copy between memory and a file
6991 @cindex dump/restore files
6992 @cindex append data to a file
6993 @cindex dump data to a file
6994 @cindex restore data from a file
6996 You can use the commands @code{dump}, @code{append}, and
6997 @code{restore} to copy data between target memory and a file. The
6998 @code{dump} and @code{append} commands write data to a file, and the
6999 @code{restore} command reads data from a file back into the inferior's
7000 memory. Files may be in binary, Motorola S-record, Intel hex, or
7001 Tektronix Hex format; however, @value{GDBN} can only append to binary
7007 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7008 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7009 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7010 or the value of @var{expr}, to @var{filename} in the given format.
7012 The @var{format} parameter may be any one of:
7019 Motorola S-record format.
7021 Tektronix Hex format.
7024 @value{GDBN} uses the same definitions of these formats as the
7025 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7026 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7030 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7031 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7032 Append the contents of memory from @var{start_addr} to @var{end_addr},
7033 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7034 (@value{GDBN} can only append data to files in raw binary form.)
7037 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7038 Restore the contents of file @var{filename} into memory. The
7039 @code{restore} command can automatically recognize any known @sc{bfd}
7040 file format, except for raw binary. To restore a raw binary file you
7041 must specify the optional keyword @code{binary} after the filename.
7043 If @var{bias} is non-zero, its value will be added to the addresses
7044 contained in the file. Binary files always start at address zero, so
7045 they will be restored at address @var{bias}. Other bfd files have
7046 a built-in location; they will be restored at offset @var{bias}
7049 If @var{start} and/or @var{end} are non-zero, then only data between
7050 file offset @var{start} and file offset @var{end} will be restored.
7051 These offsets are relative to the addresses in the file, before
7052 the @var{bias} argument is applied.
7056 @node Core File Generation
7057 @section How to Produce a Core File from Your Program
7058 @cindex dump core from inferior
7060 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7061 image of a running process and its process status (register values
7062 etc.). Its primary use is post-mortem debugging of a program that
7063 crashed while it ran outside a debugger. A program that crashes
7064 automatically produces a core file, unless this feature is disabled by
7065 the user. @xref{Files}, for information on invoking @value{GDBN} in
7066 the post-mortem debugging mode.
7068 Occasionally, you may wish to produce a core file of the program you
7069 are debugging in order to preserve a snapshot of its state.
7070 @value{GDBN} has a special command for that.
7074 @kindex generate-core-file
7075 @item generate-core-file [@var{file}]
7076 @itemx gcore [@var{file}]
7077 Produce a core dump of the inferior process. The optional argument
7078 @var{file} specifies the file name where to put the core dump. If not
7079 specified, the file name defaults to @file{core.@var{pid}}, where
7080 @var{pid} is the inferior process ID.
7082 Note that this command is implemented only for some systems (as of
7083 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7086 @node Character Sets
7087 @section Character Sets
7088 @cindex character sets
7090 @cindex translating between character sets
7091 @cindex host character set
7092 @cindex target character set
7094 If the program you are debugging uses a different character set to
7095 represent characters and strings than the one @value{GDBN} uses itself,
7096 @value{GDBN} can automatically translate between the character sets for
7097 you. The character set @value{GDBN} uses we call the @dfn{host
7098 character set}; the one the inferior program uses we call the
7099 @dfn{target character set}.
7101 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7102 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7103 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
7104 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7105 then the host character set is Latin-1, and the target character set is
7106 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7107 target-charset EBCDIC-US}, then @value{GDBN} translates between
7108 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7109 character and string literals in expressions.
7111 @value{GDBN} has no way to automatically recognize which character set
7112 the inferior program uses; you must tell it, using the @code{set
7113 target-charset} command, described below.
7115 Here are the commands for controlling @value{GDBN}'s character set
7119 @item set target-charset @var{charset}
7120 @kindex set target-charset
7121 Set the current target character set to @var{charset}. We list the
7122 character set names @value{GDBN} recognizes below, but if you type
7123 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7124 list the target character sets it supports.
7128 @item set host-charset @var{charset}
7129 @kindex set host-charset
7130 Set the current host character set to @var{charset}.
7132 By default, @value{GDBN} uses a host character set appropriate to the
7133 system it is running on; you can override that default using the
7134 @code{set host-charset} command.
7136 @value{GDBN} can only use certain character sets as its host character
7137 set. We list the character set names @value{GDBN} recognizes below, and
7138 indicate which can be host character sets, but if you type
7139 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7140 list the host character sets it supports.
7142 @item set charset @var{charset}
7144 Set the current host and target character sets to @var{charset}. As
7145 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7146 @value{GDBN} will list the name of the character sets that can be used
7147 for both host and target.
7151 @kindex show charset
7152 Show the names of the current host and target charsets.
7154 @itemx show host-charset
7155 @kindex show host-charset
7156 Show the name of the current host charset.
7158 @itemx show target-charset
7159 @kindex show target-charset
7160 Show the name of the current target charset.
7164 @value{GDBN} currently includes support for the following character
7170 @cindex ASCII character set
7171 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7175 @cindex ISO 8859-1 character set
7176 @cindex ISO Latin 1 character set
7177 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7178 characters needed for French, German, and Spanish. @value{GDBN} can use
7179 this as its host character set.
7183 @cindex EBCDIC character set
7184 @cindex IBM1047 character set
7185 Variants of the @sc{ebcdic} character set, used on some of IBM's
7186 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7187 @value{GDBN} cannot use these as its host character set.
7191 Note that these are all single-byte character sets. More work inside
7192 GDB is needed to support multi-byte or variable-width character
7193 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7195 Here is an example of @value{GDBN}'s character set support in action.
7196 Assume that the following source code has been placed in the file
7197 @file{charset-test.c}:
7203 = @{72, 101, 108, 108, 111, 44, 32, 119,
7204 111, 114, 108, 100, 33, 10, 0@};
7205 char ibm1047_hello[]
7206 = @{200, 133, 147, 147, 150, 107, 64, 166,
7207 150, 153, 147, 132, 90, 37, 0@};
7211 printf ("Hello, world!\n");
7215 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7216 containing the string @samp{Hello, world!} followed by a newline,
7217 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7219 We compile the program, and invoke the debugger on it:
7222 $ gcc -g charset-test.c -o charset-test
7223 $ gdb -nw charset-test
7224 GNU gdb 2001-12-19-cvs
7225 Copyright 2001 Free Software Foundation, Inc.
7230 We can use the @code{show charset} command to see what character sets
7231 @value{GDBN} is currently using to interpret and display characters and
7235 (@value{GDBP}) show charset
7236 The current host and target character set is `ISO-8859-1'.
7240 For the sake of printing this manual, let's use @sc{ascii} as our
7241 initial character set:
7243 (@value{GDBP}) set charset ASCII
7244 (@value{GDBP}) show charset
7245 The current host and target character set is `ASCII'.
7249 Let's assume that @sc{ascii} is indeed the correct character set for our
7250 host system --- in other words, let's assume that if @value{GDBN} prints
7251 characters using the @sc{ascii} character set, our terminal will display
7252 them properly. Since our current target character set is also
7253 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7256 (@value{GDBP}) print ascii_hello
7257 $1 = 0x401698 "Hello, world!\n"
7258 (@value{GDBP}) print ascii_hello[0]
7263 @value{GDBN} uses the target character set for character and string
7264 literals you use in expressions:
7267 (@value{GDBP}) print '+'
7272 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7275 @value{GDBN} relies on the user to tell it which character set the
7276 target program uses. If we print @code{ibm1047_hello} while our target
7277 character set is still @sc{ascii}, we get jibberish:
7280 (@value{GDBP}) print ibm1047_hello
7281 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7282 (@value{GDBP}) print ibm1047_hello[0]
7287 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7288 @value{GDBN} tells us the character sets it supports:
7291 (@value{GDBP}) set target-charset
7292 ASCII EBCDIC-US IBM1047 ISO-8859-1
7293 (@value{GDBP}) set target-charset
7296 We can select @sc{ibm1047} as our target character set, and examine the
7297 program's strings again. Now the @sc{ascii} string is wrong, but
7298 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7299 target character set, @sc{ibm1047}, to the host character set,
7300 @sc{ascii}, and they display correctly:
7303 (@value{GDBP}) set target-charset IBM1047
7304 (@value{GDBP}) show charset
7305 The current host character set is `ASCII'.
7306 The current target character set is `IBM1047'.
7307 (@value{GDBP}) print ascii_hello
7308 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7309 (@value{GDBP}) print ascii_hello[0]
7311 (@value{GDBP}) print ibm1047_hello
7312 $8 = 0x4016a8 "Hello, world!\n"
7313 (@value{GDBP}) print ibm1047_hello[0]
7318 As above, @value{GDBN} uses the target character set for character and
7319 string literals you use in expressions:
7322 (@value{GDBP}) print '+'
7327 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7330 @node Caching Remote Data
7331 @section Caching Data of Remote Targets
7332 @cindex caching data of remote targets
7334 @value{GDBN} can cache data exchanged between the debugger and a
7335 remote target (@pxref{Remote}). Such caching generally improves
7336 performance, because it reduces the overhead of the remote protocol by
7337 bundling memory reads and writes into large chunks. Unfortunately,
7338 @value{GDBN} does not currently know anything about volatile
7339 registers, and thus data caching will produce incorrect results when
7340 volatile registers are in use.
7343 @kindex set remotecache
7344 @item set remotecache on
7345 @itemx set remotecache off
7346 Set caching state for remote targets. When @code{ON}, use data
7347 caching. By default, this option is @code{OFF}.
7349 @kindex show remotecache
7350 @item show remotecache
7351 Show the current state of data caching for remote targets.
7355 Print the information about the data cache performance. The
7356 information displayed includes: the dcache width and depth; and for
7357 each cache line, how many times it was referenced, and its data and
7358 state (dirty, bad, ok, etc.). This command is useful for debugging
7359 the data cache operation.
7364 @chapter C Preprocessor Macros
7366 Some languages, such as C and C@t{++}, provide a way to define and invoke
7367 ``preprocessor macros'' which expand into strings of tokens.
7368 @value{GDBN} can evaluate expressions containing macro invocations, show
7369 the result of macro expansion, and show a macro's definition, including
7370 where it was defined.
7372 You may need to compile your program specially to provide @value{GDBN}
7373 with information about preprocessor macros. Most compilers do not
7374 include macros in their debugging information, even when you compile
7375 with the @option{-g} flag. @xref{Compilation}.
7377 A program may define a macro at one point, remove that definition later,
7378 and then provide a different definition after that. Thus, at different
7379 points in the program, a macro may have different definitions, or have
7380 no definition at all. If there is a current stack frame, @value{GDBN}
7381 uses the macros in scope at that frame's source code line. Otherwise,
7382 @value{GDBN} uses the macros in scope at the current listing location;
7385 At the moment, @value{GDBN} does not support the @code{##}
7386 token-splicing operator, the @code{#} stringification operator, or
7387 variable-arity macros.
7389 Whenever @value{GDBN} evaluates an expression, it always expands any
7390 macro invocations present in the expression. @value{GDBN} also provides
7391 the following commands for working with macros explicitly.
7395 @kindex macro expand
7396 @cindex macro expansion, showing the results of preprocessor
7397 @cindex preprocessor macro expansion, showing the results of
7398 @cindex expanding preprocessor macros
7399 @item macro expand @var{expression}
7400 @itemx macro exp @var{expression}
7401 Show the results of expanding all preprocessor macro invocations in
7402 @var{expression}. Since @value{GDBN} simply expands macros, but does
7403 not parse the result, @var{expression} need not be a valid expression;
7404 it can be any string of tokens.
7407 @item macro expand-once @var{expression}
7408 @itemx macro exp1 @var{expression}
7409 @cindex expand macro once
7410 @i{(This command is not yet implemented.)} Show the results of
7411 expanding those preprocessor macro invocations that appear explicitly in
7412 @var{expression}. Macro invocations appearing in that expansion are
7413 left unchanged. This command allows you to see the effect of a
7414 particular macro more clearly, without being confused by further
7415 expansions. Since @value{GDBN} simply expands macros, but does not
7416 parse the result, @var{expression} need not be a valid expression; it
7417 can be any string of tokens.
7420 @cindex macro definition, showing
7421 @cindex definition, showing a macro's
7422 @item info macro @var{macro}
7423 Show the definition of the macro named @var{macro}, and describe the
7424 source location where that definition was established.
7426 @kindex macro define
7427 @cindex user-defined macros
7428 @cindex defining macros interactively
7429 @cindex macros, user-defined
7430 @item macro define @var{macro} @var{replacement-list}
7431 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7432 @i{(This command is not yet implemented.)} Introduce a definition for a
7433 preprocessor macro named @var{macro}, invocations of which are replaced
7434 by the tokens given in @var{replacement-list}. The first form of this
7435 command defines an ``object-like'' macro, which takes no arguments; the
7436 second form defines a ``function-like'' macro, which takes the arguments
7437 given in @var{arglist}.
7439 A definition introduced by this command is in scope in every expression
7440 evaluated in @value{GDBN}, until it is removed with the @command{macro
7441 undef} command, described below. The definition overrides all
7442 definitions for @var{macro} present in the program being debugged, as
7443 well as any previous user-supplied definition.
7446 @item macro undef @var{macro}
7447 @i{(This command is not yet implemented.)} Remove any user-supplied
7448 definition for the macro named @var{macro}. This command only affects
7449 definitions provided with the @command{macro define} command, described
7450 above; it cannot remove definitions present in the program being
7455 @i{(This command is not yet implemented.)} List all the macros
7456 defined using the @code{macro define} command.
7459 @cindex macros, example of debugging with
7460 Here is a transcript showing the above commands in action. First, we
7461 show our source files:
7469 #define ADD(x) (M + x)
7474 printf ("Hello, world!\n");
7476 printf ("We're so creative.\n");
7478 printf ("Goodbye, world!\n");
7485 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7486 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7487 compiler includes information about preprocessor macros in the debugging
7491 $ gcc -gdwarf-2 -g3 sample.c -o sample
7495 Now, we start @value{GDBN} on our sample program:
7499 GNU gdb 2002-05-06-cvs
7500 Copyright 2002 Free Software Foundation, Inc.
7501 GDB is free software, @dots{}
7505 We can expand macros and examine their definitions, even when the
7506 program is not running. @value{GDBN} uses the current listing position
7507 to decide which macro definitions are in scope:
7510 (@value{GDBP}) list main
7513 5 #define ADD(x) (M + x)
7518 10 printf ("Hello, world!\n");
7520 12 printf ("We're so creative.\n");
7521 (@value{GDBP}) info macro ADD
7522 Defined at /home/jimb/gdb/macros/play/sample.c:5
7523 #define ADD(x) (M + x)
7524 (@value{GDBP}) info macro Q
7525 Defined at /home/jimb/gdb/macros/play/sample.h:1
7526 included at /home/jimb/gdb/macros/play/sample.c:2
7528 (@value{GDBP}) macro expand ADD(1)
7529 expands to: (42 + 1)
7530 (@value{GDBP}) macro expand-once ADD(1)
7531 expands to: once (M + 1)
7535 In the example above, note that @command{macro expand-once} expands only
7536 the macro invocation explicit in the original text --- the invocation of
7537 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7538 which was introduced by @code{ADD}.
7540 Once the program is running, GDB uses the macro definitions in force at
7541 the source line of the current stack frame:
7544 (@value{GDBP}) break main
7545 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7547 Starting program: /home/jimb/gdb/macros/play/sample
7549 Breakpoint 1, main () at sample.c:10
7550 10 printf ("Hello, world!\n");
7554 At line 10, the definition of the macro @code{N} at line 9 is in force:
7557 (@value{GDBP}) info macro N
7558 Defined at /home/jimb/gdb/macros/play/sample.c:9
7560 (@value{GDBP}) macro expand N Q M
7562 (@value{GDBP}) print N Q M
7567 As we step over directives that remove @code{N}'s definition, and then
7568 give it a new definition, @value{GDBN} finds the definition (or lack
7569 thereof) in force at each point:
7574 12 printf ("We're so creative.\n");
7575 (@value{GDBP}) info macro N
7576 The symbol `N' has no definition as a C/C++ preprocessor macro
7577 at /home/jimb/gdb/macros/play/sample.c:12
7580 14 printf ("Goodbye, world!\n");
7581 (@value{GDBP}) info macro N
7582 Defined at /home/jimb/gdb/macros/play/sample.c:13
7584 (@value{GDBP}) macro expand N Q M
7585 expands to: 1729 < 42
7586 (@value{GDBP}) print N Q M
7593 @chapter Tracepoints
7594 @c This chapter is based on the documentation written by Michael
7595 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7598 In some applications, it is not feasible for the debugger to interrupt
7599 the program's execution long enough for the developer to learn
7600 anything helpful about its behavior. If the program's correctness
7601 depends on its real-time behavior, delays introduced by a debugger
7602 might cause the program to change its behavior drastically, or perhaps
7603 fail, even when the code itself is correct. It is useful to be able
7604 to observe the program's behavior without interrupting it.
7606 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7607 specify locations in the program, called @dfn{tracepoints}, and
7608 arbitrary expressions to evaluate when those tracepoints are reached.
7609 Later, using the @code{tfind} command, you can examine the values
7610 those expressions had when the program hit the tracepoints. The
7611 expressions may also denote objects in memory---structures or arrays,
7612 for example---whose values @value{GDBN} should record; while visiting
7613 a particular tracepoint, you may inspect those objects as if they were
7614 in memory at that moment. However, because @value{GDBN} records these
7615 values without interacting with you, it can do so quickly and
7616 unobtrusively, hopefully not disturbing the program's behavior.
7618 The tracepoint facility is currently available only for remote
7619 targets. @xref{Targets}. In addition, your remote target must know
7620 how to collect trace data. This functionality is implemented in the
7621 remote stub; however, none of the stubs distributed with @value{GDBN}
7622 support tracepoints as of this writing. The format of the remote
7623 packets used to implement tracepoints are described in @ref{Tracepoint
7626 This chapter describes the tracepoint commands and features.
7630 * Analyze Collected Data::
7631 * Tracepoint Variables::
7634 @node Set Tracepoints
7635 @section Commands to Set Tracepoints
7637 Before running such a @dfn{trace experiment}, an arbitrary number of
7638 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7639 tracepoint has a number assigned to it by @value{GDBN}. Like with
7640 breakpoints, tracepoint numbers are successive integers starting from
7641 one. Many of the commands associated with tracepoints take the
7642 tracepoint number as their argument, to identify which tracepoint to
7645 For each tracepoint, you can specify, in advance, some arbitrary set
7646 of data that you want the target to collect in the trace buffer when
7647 it hits that tracepoint. The collected data can include registers,
7648 local variables, or global data. Later, you can use @value{GDBN}
7649 commands to examine the values these data had at the time the
7652 This section describes commands to set tracepoints and associated
7653 conditions and actions.
7656 * Create and Delete Tracepoints::
7657 * Enable and Disable Tracepoints::
7658 * Tracepoint Passcounts::
7659 * Tracepoint Actions::
7660 * Listing Tracepoints::
7661 * Starting and Stopping Trace Experiment::
7664 @node Create and Delete Tracepoints
7665 @subsection Create and Delete Tracepoints
7668 @cindex set tracepoint
7671 The @code{trace} command is very similar to the @code{break} command.
7672 Its argument can be a source line, a function name, or an address in
7673 the target program. @xref{Set Breaks}. The @code{trace} command
7674 defines a tracepoint, which is a point in the target program where the
7675 debugger will briefly stop, collect some data, and then allow the
7676 program to continue. Setting a tracepoint or changing its commands
7677 doesn't take effect until the next @code{tstart} command; thus, you
7678 cannot change the tracepoint attributes once a trace experiment is
7681 Here are some examples of using the @code{trace} command:
7684 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7686 (@value{GDBP}) @b{trace +2} // 2 lines forward
7688 (@value{GDBP}) @b{trace my_function} // first source line of function
7690 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7692 (@value{GDBP}) @b{trace *0x2117c4} // an address
7696 You can abbreviate @code{trace} as @code{tr}.
7699 @cindex last tracepoint number
7700 @cindex recent tracepoint number
7701 @cindex tracepoint number
7702 The convenience variable @code{$tpnum} records the tracepoint number
7703 of the most recently set tracepoint.
7705 @kindex delete tracepoint
7706 @cindex tracepoint deletion
7707 @item delete tracepoint @r{[}@var{num}@r{]}
7708 Permanently delete one or more tracepoints. With no argument, the
7709 default is to delete all tracepoints.
7714 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7716 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7720 You can abbreviate this command as @code{del tr}.
7723 @node Enable and Disable Tracepoints
7724 @subsection Enable and Disable Tracepoints
7727 @kindex disable tracepoint
7728 @item disable tracepoint @r{[}@var{num}@r{]}
7729 Disable tracepoint @var{num}, or all tracepoints if no argument
7730 @var{num} is given. A disabled tracepoint will have no effect during
7731 the next trace experiment, but it is not forgotten. You can re-enable
7732 a disabled tracepoint using the @code{enable tracepoint} command.
7734 @kindex enable tracepoint
7735 @item enable tracepoint @r{[}@var{num}@r{]}
7736 Enable tracepoint @var{num}, or all tracepoints. The enabled
7737 tracepoints will become effective the next time a trace experiment is
7741 @node Tracepoint Passcounts
7742 @subsection Tracepoint Passcounts
7746 @cindex tracepoint pass count
7747 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7748 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7749 automatically stop a trace experiment. If a tracepoint's passcount is
7750 @var{n}, then the trace experiment will be automatically stopped on
7751 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7752 @var{num} is not specified, the @code{passcount} command sets the
7753 passcount of the most recently defined tracepoint. If no passcount is
7754 given, the trace experiment will run until stopped explicitly by the
7760 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7761 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7763 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7764 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7765 (@value{GDBP}) @b{trace foo}
7766 (@value{GDBP}) @b{pass 3}
7767 (@value{GDBP}) @b{trace bar}
7768 (@value{GDBP}) @b{pass 2}
7769 (@value{GDBP}) @b{trace baz}
7770 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7771 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7772 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7773 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7777 @node Tracepoint Actions
7778 @subsection Tracepoint Action Lists
7782 @cindex tracepoint actions
7783 @item actions @r{[}@var{num}@r{]}
7784 This command will prompt for a list of actions to be taken when the
7785 tracepoint is hit. If the tracepoint number @var{num} is not
7786 specified, this command sets the actions for the one that was most
7787 recently defined (so that you can define a tracepoint and then say
7788 @code{actions} without bothering about its number). You specify the
7789 actions themselves on the following lines, one action at a time, and
7790 terminate the actions list with a line containing just @code{end}. So
7791 far, the only defined actions are @code{collect} and
7792 @code{while-stepping}.
7794 @cindex remove actions from a tracepoint
7795 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7796 and follow it immediately with @samp{end}.
7799 (@value{GDBP}) @b{collect @var{data}} // collect some data
7801 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7803 (@value{GDBP}) @b{end} // signals the end of actions.
7806 In the following example, the action list begins with @code{collect}
7807 commands indicating the things to be collected when the tracepoint is
7808 hit. Then, in order to single-step and collect additional data
7809 following the tracepoint, a @code{while-stepping} command is used,
7810 followed by the list of things to be collected while stepping. The
7811 @code{while-stepping} command is terminated by its own separate
7812 @code{end} command. Lastly, the action list is terminated by an
7816 (@value{GDBP}) @b{trace foo}
7817 (@value{GDBP}) @b{actions}
7818 Enter actions for tracepoint 1, one per line:
7827 @kindex collect @r{(tracepoints)}
7828 @item collect @var{expr1}, @var{expr2}, @dots{}
7829 Collect values of the given expressions when the tracepoint is hit.
7830 This command accepts a comma-separated list of any valid expressions.
7831 In addition to global, static, or local variables, the following
7832 special arguments are supported:
7836 collect all registers
7839 collect all function arguments
7842 collect all local variables.
7845 You can give several consecutive @code{collect} commands, each one
7846 with a single argument, or one @code{collect} command with several
7847 arguments separated by commas: the effect is the same.
7849 The command @code{info scope} (@pxref{Symbols, info scope}) is
7850 particularly useful for figuring out what data to collect.
7852 @kindex while-stepping @r{(tracepoints)}
7853 @item while-stepping @var{n}
7854 Perform @var{n} single-step traces after the tracepoint, collecting
7855 new data at each step. The @code{while-stepping} command is
7856 followed by the list of what to collect while stepping (followed by
7857 its own @code{end} command):
7861 > collect $regs, myglobal
7867 You may abbreviate @code{while-stepping} as @code{ws} or
7871 @node Listing Tracepoints
7872 @subsection Listing Tracepoints
7875 @kindex info tracepoints
7877 @cindex information about tracepoints
7878 @item info tracepoints @r{[}@var{num}@r{]}
7879 Display information about the tracepoint @var{num}. If you don't specify
7880 a tracepoint number, displays information about all the tracepoints
7881 defined so far. For each tracepoint, the following information is
7888 whether it is enabled or disabled
7892 its passcount as given by the @code{passcount @var{n}} command
7894 its step count as given by the @code{while-stepping @var{n}} command
7896 where in the source files is the tracepoint set
7898 its action list as given by the @code{actions} command
7902 (@value{GDBP}) @b{info trace}
7903 Num Enb Address PassC StepC What
7904 1 y 0x002117c4 0 0 <gdb_asm>
7905 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7906 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7911 This command can be abbreviated @code{info tp}.
7914 @node Starting and Stopping Trace Experiment
7915 @subsection Starting and Stopping Trace Experiment
7919 @cindex start a new trace experiment
7920 @cindex collected data discarded
7922 This command takes no arguments. It starts the trace experiment, and
7923 begins collecting data. This has the side effect of discarding all
7924 the data collected in the trace buffer during the previous trace
7928 @cindex stop a running trace experiment
7930 This command takes no arguments. It ends the trace experiment, and
7931 stops collecting data.
7933 @strong{Note}: a trace experiment and data collection may stop
7934 automatically if any tracepoint's passcount is reached
7935 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7938 @cindex status of trace data collection
7939 @cindex trace experiment, status of
7941 This command displays the status of the current trace data
7945 Here is an example of the commands we described so far:
7948 (@value{GDBP}) @b{trace gdb_c_test}
7949 (@value{GDBP}) @b{actions}
7950 Enter actions for tracepoint #1, one per line.
7951 > collect $regs,$locals,$args
7956 (@value{GDBP}) @b{tstart}
7957 [time passes @dots{}]
7958 (@value{GDBP}) @b{tstop}
7962 @node Analyze Collected Data
7963 @section Using the collected data
7965 After the tracepoint experiment ends, you use @value{GDBN} commands
7966 for examining the trace data. The basic idea is that each tracepoint
7967 collects a trace @dfn{snapshot} every time it is hit and another
7968 snapshot every time it single-steps. All these snapshots are
7969 consecutively numbered from zero and go into a buffer, and you can
7970 examine them later. The way you examine them is to @dfn{focus} on a
7971 specific trace snapshot. When the remote stub is focused on a trace
7972 snapshot, it will respond to all @value{GDBN} requests for memory and
7973 registers by reading from the buffer which belongs to that snapshot,
7974 rather than from @emph{real} memory or registers of the program being
7975 debugged. This means that @strong{all} @value{GDBN} commands
7976 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7977 behave as if we were currently debugging the program state as it was
7978 when the tracepoint occurred. Any requests for data that are not in
7979 the buffer will fail.
7982 * tfind:: How to select a trace snapshot
7983 * tdump:: How to display all data for a snapshot
7984 * save-tracepoints:: How to save tracepoints for a future run
7988 @subsection @code{tfind @var{n}}
7991 @cindex select trace snapshot
7992 @cindex find trace snapshot
7993 The basic command for selecting a trace snapshot from the buffer is
7994 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7995 counting from zero. If no argument @var{n} is given, the next
7996 snapshot is selected.
7998 Here are the various forms of using the @code{tfind} command.
8002 Find the first snapshot in the buffer. This is a synonym for
8003 @code{tfind 0} (since 0 is the number of the first snapshot).
8006 Stop debugging trace snapshots, resume @emph{live} debugging.
8009 Same as @samp{tfind none}.
8012 No argument means find the next trace snapshot.
8015 Find the previous trace snapshot before the current one. This permits
8016 retracing earlier steps.
8018 @item tfind tracepoint @var{num}
8019 Find the next snapshot associated with tracepoint @var{num}. Search
8020 proceeds forward from the last examined trace snapshot. If no
8021 argument @var{num} is given, it means find the next snapshot collected
8022 for the same tracepoint as the current snapshot.
8024 @item tfind pc @var{addr}
8025 Find the next snapshot associated with the value @var{addr} of the
8026 program counter. Search proceeds forward from the last examined trace
8027 snapshot. If no argument @var{addr} is given, it means find the next
8028 snapshot with the same value of PC as the current snapshot.
8030 @item tfind outside @var{addr1}, @var{addr2}
8031 Find the next snapshot whose PC is outside the given range of
8034 @item tfind range @var{addr1}, @var{addr2}
8035 Find the next snapshot whose PC is between @var{addr1} and
8036 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8038 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8039 Find the next snapshot associated with the source line @var{n}. If
8040 the optional argument @var{file} is given, refer to line @var{n} in
8041 that source file. Search proceeds forward from the last examined
8042 trace snapshot. If no argument @var{n} is given, it means find the
8043 next line other than the one currently being examined; thus saying
8044 @code{tfind line} repeatedly can appear to have the same effect as
8045 stepping from line to line in a @emph{live} debugging session.
8048 The default arguments for the @code{tfind} commands are specifically
8049 designed to make it easy to scan through the trace buffer. For
8050 instance, @code{tfind} with no argument selects the next trace
8051 snapshot, and @code{tfind -} with no argument selects the previous
8052 trace snapshot. So, by giving one @code{tfind} command, and then
8053 simply hitting @key{RET} repeatedly you can examine all the trace
8054 snapshots in order. Or, by saying @code{tfind -} and then hitting
8055 @key{RET} repeatedly you can examine the snapshots in reverse order.
8056 The @code{tfind line} command with no argument selects the snapshot
8057 for the next source line executed. The @code{tfind pc} command with
8058 no argument selects the next snapshot with the same program counter
8059 (PC) as the current frame. The @code{tfind tracepoint} command with
8060 no argument selects the next trace snapshot collected by the same
8061 tracepoint as the current one.
8063 In addition to letting you scan through the trace buffer manually,
8064 these commands make it easy to construct @value{GDBN} scripts that
8065 scan through the trace buffer and print out whatever collected data
8066 you are interested in. Thus, if we want to examine the PC, FP, and SP
8067 registers from each trace frame in the buffer, we can say this:
8070 (@value{GDBP}) @b{tfind start}
8071 (@value{GDBP}) @b{while ($trace_frame != -1)}
8072 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8073 $trace_frame, $pc, $sp, $fp
8077 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8078 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8079 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8080 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8081 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8082 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8083 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8084 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8085 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8086 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8087 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8090 Or, if we want to examine the variable @code{X} at each source line in
8094 (@value{GDBP}) @b{tfind start}
8095 (@value{GDBP}) @b{while ($trace_frame != -1)}
8096 > printf "Frame %d, X == %d\n", $trace_frame, X
8106 @subsection @code{tdump}
8108 @cindex dump all data collected at tracepoint
8109 @cindex tracepoint data, display
8111 This command takes no arguments. It prints all the data collected at
8112 the current trace snapshot.
8115 (@value{GDBP}) @b{trace 444}
8116 (@value{GDBP}) @b{actions}
8117 Enter actions for tracepoint #2, one per line:
8118 > collect $regs, $locals, $args, gdb_long_test
8121 (@value{GDBP}) @b{tstart}
8123 (@value{GDBP}) @b{tfind line 444}
8124 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8126 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8128 (@value{GDBP}) @b{tdump}
8129 Data collected at tracepoint 2, trace frame 1:
8130 d0 0xc4aa0085 -995491707
8134 d4 0x71aea3d 119204413
8139 a1 0x3000668 50333288
8142 a4 0x3000698 50333336
8144 fp 0x30bf3c 0x30bf3c
8145 sp 0x30bf34 0x30bf34
8147 pc 0x20b2c8 0x20b2c8
8151 p = 0x20e5b4 "gdb-test"
8158 gdb_long_test = 17 '\021'
8163 @node save-tracepoints
8164 @subsection @code{save-tracepoints @var{filename}}
8165 @kindex save-tracepoints
8166 @cindex save tracepoints for future sessions
8168 This command saves all current tracepoint definitions together with
8169 their actions and passcounts, into a file @file{@var{filename}}
8170 suitable for use in a later debugging session. To read the saved
8171 tracepoint definitions, use the @code{source} command (@pxref{Command
8174 @node Tracepoint Variables
8175 @section Convenience Variables for Tracepoints
8176 @cindex tracepoint variables
8177 @cindex convenience variables for tracepoints
8180 @vindex $trace_frame
8181 @item (int) $trace_frame
8182 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8183 snapshot is selected.
8186 @item (int) $tracepoint
8187 The tracepoint for the current trace snapshot.
8190 @item (int) $trace_line
8191 The line number for the current trace snapshot.
8194 @item (char []) $trace_file
8195 The source file for the current trace snapshot.
8198 @item (char []) $trace_func
8199 The name of the function containing @code{$tracepoint}.
8202 Note: @code{$trace_file} is not suitable for use in @code{printf},
8203 use @code{output} instead.
8205 Here's a simple example of using these convenience variables for
8206 stepping through all the trace snapshots and printing some of their
8210 (@value{GDBP}) @b{tfind start}
8212 (@value{GDBP}) @b{while $trace_frame != -1}
8213 > output $trace_file
8214 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8220 @chapter Debugging Programs That Use Overlays
8223 If your program is too large to fit completely in your target system's
8224 memory, you can sometimes use @dfn{overlays} to work around this
8225 problem. @value{GDBN} provides some support for debugging programs that
8229 * How Overlays Work:: A general explanation of overlays.
8230 * Overlay Commands:: Managing overlays in @value{GDBN}.
8231 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8232 mapped by asking the inferior.
8233 * Overlay Sample Program:: A sample program using overlays.
8236 @node How Overlays Work
8237 @section How Overlays Work
8238 @cindex mapped overlays
8239 @cindex unmapped overlays
8240 @cindex load address, overlay's
8241 @cindex mapped address
8242 @cindex overlay area
8244 Suppose you have a computer whose instruction address space is only 64
8245 kilobytes long, but which has much more memory which can be accessed by
8246 other means: special instructions, segment registers, or memory
8247 management hardware, for example. Suppose further that you want to
8248 adapt a program which is larger than 64 kilobytes to run on this system.
8250 One solution is to identify modules of your program which are relatively
8251 independent, and need not call each other directly; call these modules
8252 @dfn{overlays}. Separate the overlays from the main program, and place
8253 their machine code in the larger memory. Place your main program in
8254 instruction memory, but leave at least enough space there to hold the
8255 largest overlay as well.
8257 Now, to call a function located in an overlay, you must first copy that
8258 overlay's machine code from the large memory into the space set aside
8259 for it in the instruction memory, and then jump to its entry point
8262 @c NB: In the below the mapped area's size is greater or equal to the
8263 @c size of all overlays. This is intentional to remind the developer
8264 @c that overlays don't necessarily need to be the same size.
8268 Data Instruction Larger
8269 Address Space Address Space Address Space
8270 +-----------+ +-----------+ +-----------+
8272 +-----------+ +-----------+ +-----------+<-- overlay 1
8273 | program | | main | .----| overlay 1 | load address
8274 | variables | | program | | +-----------+
8275 | and heap | | | | | |
8276 +-----------+ | | | +-----------+<-- overlay 2
8277 | | +-----------+ | | | load address
8278 +-----------+ | | | .-| overlay 2 |
8280 mapped --->+-----------+ | | +-----------+
8282 | overlay | <-' | | |
8283 | area | <---' +-----------+<-- overlay 3
8284 | | <---. | | load address
8285 +-----------+ `--| overlay 3 |
8292 @anchor{A code overlay}A code overlay
8296 The diagram (@pxref{A code overlay}) shows a system with separate data
8297 and instruction address spaces. To map an overlay, the program copies
8298 its code from the larger address space to the instruction address space.
8299 Since the overlays shown here all use the same mapped address, only one
8300 may be mapped at a time. For a system with a single address space for
8301 data and instructions, the diagram would be similar, except that the
8302 program variables and heap would share an address space with the main
8303 program and the overlay area.
8305 An overlay loaded into instruction memory and ready for use is called a
8306 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8307 instruction memory. An overlay not present (or only partially present)
8308 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8309 is its address in the larger memory. The mapped address is also called
8310 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8311 called the @dfn{load memory address}, or @dfn{LMA}.
8313 Unfortunately, overlays are not a completely transparent way to adapt a
8314 program to limited instruction memory. They introduce a new set of
8315 global constraints you must keep in mind as you design your program:
8320 Before calling or returning to a function in an overlay, your program
8321 must make sure that overlay is actually mapped. Otherwise, the call or
8322 return will transfer control to the right address, but in the wrong
8323 overlay, and your program will probably crash.
8326 If the process of mapping an overlay is expensive on your system, you
8327 will need to choose your overlays carefully to minimize their effect on
8328 your program's performance.
8331 The executable file you load onto your system must contain each
8332 overlay's instructions, appearing at the overlay's load address, not its
8333 mapped address. However, each overlay's instructions must be relocated
8334 and its symbols defined as if the overlay were at its mapped address.
8335 You can use GNU linker scripts to specify different load and relocation
8336 addresses for pieces of your program; see @ref{Overlay Description,,,
8337 ld.info, Using ld: the GNU linker}.
8340 The procedure for loading executable files onto your system must be able
8341 to load their contents into the larger address space as well as the
8342 instruction and data spaces.
8346 The overlay system described above is rather simple, and could be
8347 improved in many ways:
8352 If your system has suitable bank switch registers or memory management
8353 hardware, you could use those facilities to make an overlay's load area
8354 contents simply appear at their mapped address in instruction space.
8355 This would probably be faster than copying the overlay to its mapped
8356 area in the usual way.
8359 If your overlays are small enough, you could set aside more than one
8360 overlay area, and have more than one overlay mapped at a time.
8363 You can use overlays to manage data, as well as instructions. In
8364 general, data overlays are even less transparent to your design than
8365 code overlays: whereas code overlays only require care when you call or
8366 return to functions, data overlays require care every time you access
8367 the data. Also, if you change the contents of a data overlay, you
8368 must copy its contents back out to its load address before you can copy a
8369 different data overlay into the same mapped area.
8374 @node Overlay Commands
8375 @section Overlay Commands
8377 To use @value{GDBN}'s overlay support, each overlay in your program must
8378 correspond to a separate section of the executable file. The section's
8379 virtual memory address and load memory address must be the overlay's
8380 mapped and load addresses. Identifying overlays with sections allows
8381 @value{GDBN} to determine the appropriate address of a function or
8382 variable, depending on whether the overlay is mapped or not.
8384 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8385 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8390 Disable @value{GDBN}'s overlay support. When overlay support is
8391 disabled, @value{GDBN} assumes that all functions and variables are
8392 always present at their mapped addresses. By default, @value{GDBN}'s
8393 overlay support is disabled.
8395 @item overlay manual
8396 @cindex manual overlay debugging
8397 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8398 relies on you to tell it which overlays are mapped, and which are not,
8399 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8400 commands described below.
8402 @item overlay map-overlay @var{overlay}
8403 @itemx overlay map @var{overlay}
8404 @cindex map an overlay
8405 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8406 be the name of the object file section containing the overlay. When an
8407 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8408 functions and variables at their mapped addresses. @value{GDBN} assumes
8409 that any other overlays whose mapped ranges overlap that of
8410 @var{overlay} are now unmapped.
8412 @item overlay unmap-overlay @var{overlay}
8413 @itemx overlay unmap @var{overlay}
8414 @cindex unmap an overlay
8415 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8416 must be the name of the object file section containing the overlay.
8417 When an overlay is unmapped, @value{GDBN} assumes it can find the
8418 overlay's functions and variables at their load addresses.
8421 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8422 consults a data structure the overlay manager maintains in the inferior
8423 to see which overlays are mapped. For details, see @ref{Automatic
8426 @item overlay load-target
8428 @cindex reloading the overlay table
8429 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8430 re-reads the table @value{GDBN} automatically each time the inferior
8431 stops, so this command should only be necessary if you have changed the
8432 overlay mapping yourself using @value{GDBN}. This command is only
8433 useful when using automatic overlay debugging.
8435 @item overlay list-overlays
8437 @cindex listing mapped overlays
8438 Display a list of the overlays currently mapped, along with their mapped
8439 addresses, load addresses, and sizes.
8443 Normally, when @value{GDBN} prints a code address, it includes the name
8444 of the function the address falls in:
8447 (@value{GDBP}) print main
8448 $3 = @{int ()@} 0x11a0 <main>
8451 When overlay debugging is enabled, @value{GDBN} recognizes code in
8452 unmapped overlays, and prints the names of unmapped functions with
8453 asterisks around them. For example, if @code{foo} is a function in an
8454 unmapped overlay, @value{GDBN} prints it this way:
8457 (@value{GDBP}) overlay list
8458 No sections are mapped.
8459 (@value{GDBP}) print foo
8460 $5 = @{int (int)@} 0x100000 <*foo*>
8463 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8467 (@value{GDBP}) overlay list
8468 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8469 mapped at 0x1016 - 0x104a
8470 (@value{GDBP}) print foo
8471 $6 = @{int (int)@} 0x1016 <foo>
8474 When overlay debugging is enabled, @value{GDBN} can find the correct
8475 address for functions and variables in an overlay, whether or not the
8476 overlay is mapped. This allows most @value{GDBN} commands, like
8477 @code{break} and @code{disassemble}, to work normally, even on unmapped
8478 code. However, @value{GDBN}'s breakpoint support has some limitations:
8482 @cindex breakpoints in overlays
8483 @cindex overlays, setting breakpoints in
8484 You can set breakpoints in functions in unmapped overlays, as long as
8485 @value{GDBN} can write to the overlay at its load address.
8487 @value{GDBN} can not set hardware or simulator-based breakpoints in
8488 unmapped overlays. However, if you set a breakpoint at the end of your
8489 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8490 you are using manual overlay management), @value{GDBN} will re-set its
8491 breakpoints properly.
8495 @node Automatic Overlay Debugging
8496 @section Automatic Overlay Debugging
8497 @cindex automatic overlay debugging
8499 @value{GDBN} can automatically track which overlays are mapped and which
8500 are not, given some simple co-operation from the overlay manager in the
8501 inferior. If you enable automatic overlay debugging with the
8502 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8503 looks in the inferior's memory for certain variables describing the
8504 current state of the overlays.
8506 Here are the variables your overlay manager must define to support
8507 @value{GDBN}'s automatic overlay debugging:
8511 @item @code{_ovly_table}:
8512 This variable must be an array of the following structures:
8517 /* The overlay's mapped address. */
8520 /* The size of the overlay, in bytes. */
8523 /* The overlay's load address. */
8526 /* Non-zero if the overlay is currently mapped;
8528 unsigned long mapped;
8532 @item @code{_novlys}:
8533 This variable must be a four-byte signed integer, holding the total
8534 number of elements in @code{_ovly_table}.
8538 To decide whether a particular overlay is mapped or not, @value{GDBN}
8539 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8540 @code{lma} members equal the VMA and LMA of the overlay's section in the
8541 executable file. When @value{GDBN} finds a matching entry, it consults
8542 the entry's @code{mapped} member to determine whether the overlay is
8545 In addition, your overlay manager may define a function called
8546 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8547 will silently set a breakpoint there. If the overlay manager then
8548 calls this function whenever it has changed the overlay table, this
8549 will enable @value{GDBN} to accurately keep track of which overlays
8550 are in program memory, and update any breakpoints that may be set
8551 in overlays. This will allow breakpoints to work even if the
8552 overlays are kept in ROM or other non-writable memory while they
8553 are not being executed.
8555 @node Overlay Sample Program
8556 @section Overlay Sample Program
8557 @cindex overlay example program
8559 When linking a program which uses overlays, you must place the overlays
8560 at their load addresses, while relocating them to run at their mapped
8561 addresses. To do this, you must write a linker script (@pxref{Overlay
8562 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8563 since linker scripts are specific to a particular host system, target
8564 architecture, and target memory layout, this manual cannot provide
8565 portable sample code demonstrating @value{GDBN}'s overlay support.
8567 However, the @value{GDBN} source distribution does contain an overlaid
8568 program, with linker scripts for a few systems, as part of its test
8569 suite. The program consists of the following files from
8570 @file{gdb/testsuite/gdb.base}:
8574 The main program file.
8576 A simple overlay manager, used by @file{overlays.c}.
8581 Overlay modules, loaded and used by @file{overlays.c}.
8584 Linker scripts for linking the test program on the @code{d10v-elf}
8585 and @code{m32r-elf} targets.
8588 You can build the test program using the @code{d10v-elf} GCC
8589 cross-compiler like this:
8592 $ d10v-elf-gcc -g -c overlays.c
8593 $ d10v-elf-gcc -g -c ovlymgr.c
8594 $ d10v-elf-gcc -g -c foo.c
8595 $ d10v-elf-gcc -g -c bar.c
8596 $ d10v-elf-gcc -g -c baz.c
8597 $ d10v-elf-gcc -g -c grbx.c
8598 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8599 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8602 The build process is identical for any other architecture, except that
8603 you must substitute the appropriate compiler and linker script for the
8604 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8608 @chapter Using @value{GDBN} with Different Languages
8611 Although programming languages generally have common aspects, they are
8612 rarely expressed in the same manner. For instance, in ANSI C,
8613 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8614 Modula-2, it is accomplished by @code{p^}. Values can also be
8615 represented (and displayed) differently. Hex numbers in C appear as
8616 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8618 @cindex working language
8619 Language-specific information is built into @value{GDBN} for some languages,
8620 allowing you to express operations like the above in your program's
8621 native language, and allowing @value{GDBN} to output values in a manner
8622 consistent with the syntax of your program's native language. The
8623 language you use to build expressions is called the @dfn{working
8627 * Setting:: Switching between source languages
8628 * Show:: Displaying the language
8629 * Checks:: Type and range checks
8630 * Supported languages:: Supported languages
8631 * Unsupported languages:: Unsupported languages
8635 @section Switching between source languages
8637 There are two ways to control the working language---either have @value{GDBN}
8638 set it automatically, or select it manually yourself. You can use the
8639 @code{set language} command for either purpose. On startup, @value{GDBN}
8640 defaults to setting the language automatically. The working language is
8641 used to determine how expressions you type are interpreted, how values
8644 In addition to the working language, every source file that
8645 @value{GDBN} knows about has its own working language. For some object
8646 file formats, the compiler might indicate which language a particular
8647 source file is in. However, most of the time @value{GDBN} infers the
8648 language from the name of the file. The language of a source file
8649 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8650 show each frame appropriately for its own language. There is no way to
8651 set the language of a source file from within @value{GDBN}, but you can
8652 set the language associated with a filename extension. @xref{Show, ,
8653 Displaying the language}.
8655 This is most commonly a problem when you use a program, such
8656 as @code{cfront} or @code{f2c}, that generates C but is written in
8657 another language. In that case, make the
8658 program use @code{#line} directives in its C output; that way
8659 @value{GDBN} will know the correct language of the source code of the original
8660 program, and will display that source code, not the generated C code.
8663 * Filenames:: Filename extensions and languages.
8664 * Manually:: Setting the working language manually
8665 * Automatically:: Having @value{GDBN} infer the source language
8669 @subsection List of filename extensions and languages
8671 If a source file name ends in one of the following extensions, then
8672 @value{GDBN} infers that its language is the one indicated.
8693 Objective-C source file
8700 Modula-2 source file
8704 Assembler source file. This actually behaves almost like C, but
8705 @value{GDBN} does not skip over function prologues when stepping.
8708 In addition, you may set the language associated with a filename
8709 extension. @xref{Show, , Displaying the language}.
8712 @subsection Setting the working language
8714 If you allow @value{GDBN} to set the language automatically,
8715 expressions are interpreted the same way in your debugging session and
8718 @kindex set language
8719 If you wish, you may set the language manually. To do this, issue the
8720 command @samp{set language @var{lang}}, where @var{lang} is the name of
8722 @code{c} or @code{modula-2}.
8723 For a list of the supported languages, type @samp{set language}.
8725 Setting the language manually prevents @value{GDBN} from updating the working
8726 language automatically. This can lead to confusion if you try
8727 to debug a program when the working language is not the same as the
8728 source language, when an expression is acceptable to both
8729 languages---but means different things. For instance, if the current
8730 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8738 might not have the effect you intended. In C, this means to add
8739 @code{b} and @code{c} and place the result in @code{a}. The result
8740 printed would be the value of @code{a}. In Modula-2, this means to compare
8741 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8744 @subsection Having @value{GDBN} infer the source language
8746 To have @value{GDBN} set the working language automatically, use
8747 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8748 then infers the working language. That is, when your program stops in a
8749 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8750 working language to the language recorded for the function in that
8751 frame. If the language for a frame is unknown (that is, if the function
8752 or block corresponding to the frame was defined in a source file that
8753 does not have a recognized extension), the current working language is
8754 not changed, and @value{GDBN} issues a warning.
8756 This may not seem necessary for most programs, which are written
8757 entirely in one source language. However, program modules and libraries
8758 written in one source language can be used by a main program written in
8759 a different source language. Using @samp{set language auto} in this
8760 case frees you from having to set the working language manually.
8763 @section Displaying the language
8765 The following commands help you find out which language is the
8766 working language, and also what language source files were written in.
8770 @kindex show language
8771 Display the current working language. This is the
8772 language you can use with commands such as @code{print} to
8773 build and compute expressions that may involve variables in your program.
8776 @kindex info frame@r{, show the source language}
8777 Display the source language for this frame. This language becomes the
8778 working language if you use an identifier from this frame.
8779 @xref{Frame Info, ,Information about a frame}, to identify the other
8780 information listed here.
8783 @kindex info source@r{, show the source language}
8784 Display the source language of this source file.
8785 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8786 information listed here.
8789 In unusual circumstances, you may have source files with extensions
8790 not in the standard list. You can then set the extension associated
8791 with a language explicitly:
8794 @item set extension-language @var{ext} @var{language}
8795 @kindex set extension-language
8796 Tell @value{GDBN} that source files with extension @var{ext} are to be
8797 assumed as written in the source language @var{language}.
8799 @item info extensions
8800 @kindex info extensions
8801 List all the filename extensions and the associated languages.
8805 @section Type and range checking
8808 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8809 checking are included, but they do not yet have any effect. This
8810 section documents the intended facilities.
8812 @c FIXME remove warning when type/range code added
8814 Some languages are designed to guard you against making seemingly common
8815 errors through a series of compile- and run-time checks. These include
8816 checking the type of arguments to functions and operators, and making
8817 sure mathematical overflows are caught at run time. Checks such as
8818 these help to ensure a program's correctness once it has been compiled
8819 by eliminating type mismatches, and providing active checks for range
8820 errors when your program is running.
8822 @value{GDBN} can check for conditions like the above if you wish.
8823 Although @value{GDBN} does not check the statements in your program,
8824 it can check expressions entered directly into @value{GDBN} for
8825 evaluation via the @code{print} command, for example. As with the
8826 working language, @value{GDBN} can also decide whether or not to check
8827 automatically based on your program's source language.
8828 @xref{Supported languages, ,Supported languages}, for the default
8829 settings of supported languages.
8832 * Type Checking:: An overview of type checking
8833 * Range Checking:: An overview of range checking
8836 @cindex type checking
8837 @cindex checks, type
8839 @subsection An overview of type checking
8841 Some languages, such as Modula-2, are strongly typed, meaning that the
8842 arguments to operators and functions have to be of the correct type,
8843 otherwise an error occurs. These checks prevent type mismatch
8844 errors from ever causing any run-time problems. For example,
8852 The second example fails because the @code{CARDINAL} 1 is not
8853 type-compatible with the @code{REAL} 2.3.
8855 For the expressions you use in @value{GDBN} commands, you can tell the
8856 @value{GDBN} type checker to skip checking;
8857 to treat any mismatches as errors and abandon the expression;
8858 or to only issue warnings when type mismatches occur,
8859 but evaluate the expression anyway. When you choose the last of
8860 these, @value{GDBN} evaluates expressions like the second example above, but
8861 also issues a warning.
8863 Even if you turn type checking off, there may be other reasons
8864 related to type that prevent @value{GDBN} from evaluating an expression.
8865 For instance, @value{GDBN} does not know how to add an @code{int} and
8866 a @code{struct foo}. These particular type errors have nothing to do
8867 with the language in use, and usually arise from expressions, such as
8868 the one described above, which make little sense to evaluate anyway.
8870 Each language defines to what degree it is strict about type. For
8871 instance, both Modula-2 and C require the arguments to arithmetical
8872 operators to be numbers. In C, enumerated types and pointers can be
8873 represented as numbers, so that they are valid arguments to mathematical
8874 operators. @xref{Supported languages, ,Supported languages}, for further
8875 details on specific languages.
8877 @value{GDBN} provides some additional commands for controlling the type checker:
8879 @kindex set check type
8880 @kindex show check type
8882 @item set check type auto
8883 Set type checking on or off based on the current working language.
8884 @xref{Supported languages, ,Supported languages}, for the default settings for
8887 @item set check type on
8888 @itemx set check type off
8889 Set type checking on or off, overriding the default setting for the
8890 current working language. Issue a warning if the setting does not
8891 match the language default. If any type mismatches occur in
8892 evaluating an expression while type checking is on, @value{GDBN} prints a
8893 message and aborts evaluation of the expression.
8895 @item set check type warn
8896 Cause the type checker to issue warnings, but to always attempt to
8897 evaluate the expression. Evaluating the expression may still
8898 be impossible for other reasons. For example, @value{GDBN} cannot add
8899 numbers and structures.
8902 Show the current setting of the type checker, and whether or not @value{GDBN}
8903 is setting it automatically.
8906 @cindex range checking
8907 @cindex checks, range
8908 @node Range Checking
8909 @subsection An overview of range checking
8911 In some languages (such as Modula-2), it is an error to exceed the
8912 bounds of a type; this is enforced with run-time checks. Such range
8913 checking is meant to ensure program correctness by making sure
8914 computations do not overflow, or indices on an array element access do
8915 not exceed the bounds of the array.
8917 For expressions you use in @value{GDBN} commands, you can tell
8918 @value{GDBN} to treat range errors in one of three ways: ignore them,
8919 always treat them as errors and abandon the expression, or issue
8920 warnings but evaluate the expression anyway.
8922 A range error can result from numerical overflow, from exceeding an
8923 array index bound, or when you type a constant that is not a member
8924 of any type. Some languages, however, do not treat overflows as an
8925 error. In many implementations of C, mathematical overflow causes the
8926 result to ``wrap around'' to lower values---for example, if @var{m} is
8927 the largest integer value, and @var{s} is the smallest, then
8930 @var{m} + 1 @result{} @var{s}
8933 This, too, is specific to individual languages, and in some cases
8934 specific to individual compilers or machines. @xref{Supported languages, ,
8935 Supported languages}, for further details on specific languages.
8937 @value{GDBN} provides some additional commands for controlling the range checker:
8939 @kindex set check range
8940 @kindex show check range
8942 @item set check range auto
8943 Set range checking on or off based on the current working language.
8944 @xref{Supported languages, ,Supported languages}, for the default settings for
8947 @item set check range on
8948 @itemx set check range off
8949 Set range checking on or off, overriding the default setting for the
8950 current working language. A warning is issued if the setting does not
8951 match the language default. If a range error occurs and range checking is on,
8952 then a message is printed and evaluation of the expression is aborted.
8954 @item set check range warn
8955 Output messages when the @value{GDBN} range checker detects a range error,
8956 but attempt to evaluate the expression anyway. Evaluating the
8957 expression may still be impossible for other reasons, such as accessing
8958 memory that the process does not own (a typical example from many Unix
8962 Show the current setting of the range checker, and whether or not it is
8963 being set automatically by @value{GDBN}.
8966 @node Supported languages
8967 @section Supported languages
8969 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8970 assembly, Modula-2, and Ada.
8971 @c This is false ...
8972 Some @value{GDBN} features may be used in expressions regardless of the
8973 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8974 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8975 ,Expressions}) can be used with the constructs of any supported
8978 The following sections detail to what degree each source language is
8979 supported by @value{GDBN}. These sections are not meant to be language
8980 tutorials or references, but serve only as a reference guide to what the
8981 @value{GDBN} expression parser accepts, and what input and output
8982 formats should look like for different languages. There are many good
8983 books written on each of these languages; please look to these for a
8984 language reference or tutorial.
8988 * Objective-C:: Objective-C
8991 * Modula-2:: Modula-2
8996 @subsection C and C@t{++}
8998 @cindex C and C@t{++}
8999 @cindex expressions in C or C@t{++}
9001 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9002 to both languages. Whenever this is the case, we discuss those languages
9006 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9007 @cindex @sc{gnu} C@t{++}
9008 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9009 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9010 effectively, you must compile your C@t{++} programs with a supported
9011 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9012 compiler (@code{aCC}).
9014 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9015 format; if it doesn't work on your system, try the stabs+ debugging
9016 format. You can select those formats explicitly with the @code{g++}
9017 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9018 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
9019 CC, gcc.info, Using @sc{gnu} CC}.
9022 * C Operators:: C and C@t{++} operators
9023 * C Constants:: C and C@t{++} constants
9024 * C plus plus expressions:: C@t{++} expressions
9025 * C Defaults:: Default settings for C and C@t{++}
9026 * C Checks:: C and C@t{++} type and range checks
9027 * Debugging C:: @value{GDBN} and C
9028 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
9032 @subsubsection C and C@t{++} operators
9034 @cindex C and C@t{++} operators
9036 Operators must be defined on values of specific types. For instance,
9037 @code{+} is defined on numbers, but not on structures. Operators are
9038 often defined on groups of types.
9040 For the purposes of C and C@t{++}, the following definitions hold:
9045 @emph{Integral types} include @code{int} with any of its storage-class
9046 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9049 @emph{Floating-point types} include @code{float}, @code{double}, and
9050 @code{long double} (if supported by the target platform).
9053 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9056 @emph{Scalar types} include all of the above.
9061 The following operators are supported. They are listed here
9062 in order of increasing precedence:
9066 The comma or sequencing operator. Expressions in a comma-separated list
9067 are evaluated from left to right, with the result of the entire
9068 expression being the last expression evaluated.
9071 Assignment. The value of an assignment expression is the value
9072 assigned. Defined on scalar types.
9075 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9076 and translated to @w{@code{@var{a} = @var{a op b}}}.
9077 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9078 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9079 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9082 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9083 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9087 Logical @sc{or}. Defined on integral types.
9090 Logical @sc{and}. Defined on integral types.
9093 Bitwise @sc{or}. Defined on integral types.
9096 Bitwise exclusive-@sc{or}. Defined on integral types.
9099 Bitwise @sc{and}. Defined on integral types.
9102 Equality and inequality. Defined on scalar types. The value of these
9103 expressions is 0 for false and non-zero for true.
9105 @item <@r{, }>@r{, }<=@r{, }>=
9106 Less than, greater than, less than or equal, greater than or equal.
9107 Defined on scalar types. The value of these expressions is 0 for false
9108 and non-zero for true.
9111 left shift, and right shift. Defined on integral types.
9114 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9117 Addition and subtraction. Defined on integral types, floating-point types and
9120 @item *@r{, }/@r{, }%
9121 Multiplication, division, and modulus. Multiplication and division are
9122 defined on integral and floating-point types. Modulus is defined on
9126 Increment and decrement. When appearing before a variable, the
9127 operation is performed before the variable is used in an expression;
9128 when appearing after it, the variable's value is used before the
9129 operation takes place.
9132 Pointer dereferencing. Defined on pointer types. Same precedence as
9136 Address operator. Defined on variables. Same precedence as @code{++}.
9138 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9139 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9140 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
9141 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9145 Negative. Defined on integral and floating-point types. Same
9146 precedence as @code{++}.
9149 Logical negation. Defined on integral types. Same precedence as
9153 Bitwise complement operator. Defined on integral types. Same precedence as
9158 Structure member, and pointer-to-structure member. For convenience,
9159 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9160 pointer based on the stored type information.
9161 Defined on @code{struct} and @code{union} data.
9164 Dereferences of pointers to members.
9167 Array indexing. @code{@var{a}[@var{i}]} is defined as
9168 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9171 Function parameter list. Same precedence as @code{->}.
9174 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9175 and @code{class} types.
9178 Doubled colons also represent the @value{GDBN} scope operator
9179 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9183 If an operator is redefined in the user code, @value{GDBN} usually
9184 attempts to invoke the redefined version instead of using the operator's
9192 @subsubsection C and C@t{++} constants
9194 @cindex C and C@t{++} constants
9196 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9201 Integer constants are a sequence of digits. Octal constants are
9202 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9203 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9204 @samp{l}, specifying that the constant should be treated as a
9208 Floating point constants are a sequence of digits, followed by a decimal
9209 point, followed by a sequence of digits, and optionally followed by an
9210 exponent. An exponent is of the form:
9211 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9212 sequence of digits. The @samp{+} is optional for positive exponents.
9213 A floating-point constant may also end with a letter @samp{f} or
9214 @samp{F}, specifying that the constant should be treated as being of
9215 the @code{float} (as opposed to the default @code{double}) type; or with
9216 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9220 Enumerated constants consist of enumerated identifiers, or their
9221 integral equivalents.
9224 Character constants are a single character surrounded by single quotes
9225 (@code{'}), or a number---the ordinal value of the corresponding character
9226 (usually its @sc{ascii} value). Within quotes, the single character may
9227 be represented by a letter or by @dfn{escape sequences}, which are of
9228 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9229 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9230 @samp{@var{x}} is a predefined special character---for example,
9231 @samp{\n} for newline.
9234 String constants are a sequence of character constants surrounded by
9235 double quotes (@code{"}). Any valid character constant (as described
9236 above) may appear. Double quotes within the string must be preceded by
9237 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9241 Pointer constants are an integral value. You can also write pointers
9242 to constants using the C operator @samp{&}.
9245 Array constants are comma-separated lists surrounded by braces @samp{@{}
9246 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9247 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9248 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9252 * C plus plus expressions::
9259 @node C plus plus expressions
9260 @subsubsection C@t{++} expressions
9262 @cindex expressions in C@t{++}
9263 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9265 @cindex debugging C@t{++} programs
9266 @cindex C@t{++} compilers
9267 @cindex debug formats and C@t{++}
9268 @cindex @value{NGCC} and C@t{++}
9270 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9271 proper compiler and the proper debug format. Currently, @value{GDBN}
9272 works best when debugging C@t{++} code that is compiled with
9273 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9274 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9275 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9276 stabs+ as their default debug format, so you usually don't need to
9277 specify a debug format explicitly. Other compilers and/or debug formats
9278 are likely to work badly or not at all when using @value{GDBN} to debug
9284 @cindex member functions
9286 Member function calls are allowed; you can use expressions like
9289 count = aml->GetOriginal(x, y)
9292 @vindex this@r{, inside C@t{++} member functions}
9293 @cindex namespace in C@t{++}
9295 While a member function is active (in the selected stack frame), your
9296 expressions have the same namespace available as the member function;
9297 that is, @value{GDBN} allows implicit references to the class instance
9298 pointer @code{this} following the same rules as C@t{++}.
9300 @cindex call overloaded functions
9301 @cindex overloaded functions, calling
9302 @cindex type conversions in C@t{++}
9304 You can call overloaded functions; @value{GDBN} resolves the function
9305 call to the right definition, with some restrictions. @value{GDBN} does not
9306 perform overload resolution involving user-defined type conversions,
9307 calls to constructors, or instantiations of templates that do not exist
9308 in the program. It also cannot handle ellipsis argument lists or
9311 It does perform integral conversions and promotions, floating-point
9312 promotions, arithmetic conversions, pointer conversions, conversions of
9313 class objects to base classes, and standard conversions such as those of
9314 functions or arrays to pointers; it requires an exact match on the
9315 number of function arguments.
9317 Overload resolution is always performed, unless you have specified
9318 @code{set overload-resolution off}. @xref{Debugging C plus plus,
9319 ,@value{GDBN} features for C@t{++}}.
9321 You must specify @code{set overload-resolution off} in order to use an
9322 explicit function signature to call an overloaded function, as in
9324 p 'foo(char,int)'('x', 13)
9327 The @value{GDBN} command-completion facility can simplify this;
9328 see @ref{Completion, ,Command completion}.
9330 @cindex reference declarations
9332 @value{GDBN} understands variables declared as C@t{++} references; you can use
9333 them in expressions just as you do in C@t{++} source---they are automatically
9336 In the parameter list shown when @value{GDBN} displays a frame, the values of
9337 reference variables are not displayed (unlike other variables); this
9338 avoids clutter, since references are often used for large structures.
9339 The @emph{address} of a reference variable is always shown, unless
9340 you have specified @samp{set print address off}.
9343 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9344 expressions can use it just as expressions in your program do. Since
9345 one scope may be defined in another, you can use @code{::} repeatedly if
9346 necessary, for example in an expression like
9347 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9348 resolving name scope by reference to source files, in both C and C@t{++}
9349 debugging (@pxref{Variables, ,Program variables}).
9352 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9353 calling virtual functions correctly, printing out virtual bases of
9354 objects, calling functions in a base subobject, casting objects, and
9355 invoking user-defined operators.
9358 @subsubsection C and C@t{++} defaults
9360 @cindex C and C@t{++} defaults
9362 If you allow @value{GDBN} to set type and range checking automatically, they
9363 both default to @code{off} whenever the working language changes to
9364 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9365 selects the working language.
9367 If you allow @value{GDBN} to set the language automatically, it
9368 recognizes source files whose names end with @file{.c}, @file{.C}, or
9369 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9370 these files, it sets the working language to C or C@t{++}.
9371 @xref{Automatically, ,Having @value{GDBN} infer the source language},
9372 for further details.
9374 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9375 @c unimplemented. If (b) changes, it might make sense to let this node
9376 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9379 @subsubsection C and C@t{++} type and range checks
9381 @cindex C and C@t{++} checks
9383 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9384 is not used. However, if you turn type checking on, @value{GDBN}
9385 considers two variables type equivalent if:
9389 The two variables are structured and have the same structure, union, or
9393 The two variables have the same type name, or types that have been
9394 declared equivalent through @code{typedef}.
9397 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9400 The two @code{struct}, @code{union}, or @code{enum} variables are
9401 declared in the same declaration. (Note: this may not be true for all C
9406 Range checking, if turned on, is done on mathematical operations. Array
9407 indices are not checked, since they are often used to index a pointer
9408 that is not itself an array.
9411 @subsubsection @value{GDBN} and C
9413 The @code{set print union} and @code{show print union} commands apply to
9414 the @code{union} type. When set to @samp{on}, any @code{union} that is
9415 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9416 appears as @samp{@{...@}}.
9418 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9419 with pointers and a memory allocation function. @xref{Expressions,
9423 * Debugging C plus plus::
9426 @node Debugging C plus plus
9427 @subsubsection @value{GDBN} features for C@t{++}
9429 @cindex commands for C@t{++}
9431 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9432 designed specifically for use with C@t{++}. Here is a summary:
9435 @cindex break in overloaded functions
9436 @item @r{breakpoint menus}
9437 When you want a breakpoint in a function whose name is overloaded,
9438 @value{GDBN} breakpoint menus help you specify which function definition
9439 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
9441 @cindex overloading in C@t{++}
9442 @item rbreak @var{regex}
9443 Setting breakpoints using regular expressions is helpful for setting
9444 breakpoints on overloaded functions that are not members of any special
9446 @xref{Set Breaks, ,Setting breakpoints}.
9448 @cindex C@t{++} exception handling
9451 Debug C@t{++} exception handling using these commands. @xref{Set
9452 Catchpoints, , Setting catchpoints}.
9455 @item ptype @var{typename}
9456 Print inheritance relationships as well as other information for type
9458 @xref{Symbols, ,Examining the Symbol Table}.
9460 @cindex C@t{++} symbol display
9461 @item set print demangle
9462 @itemx show print demangle
9463 @itemx set print asm-demangle
9464 @itemx show print asm-demangle
9465 Control whether C@t{++} symbols display in their source form, both when
9466 displaying code as C@t{++} source and when displaying disassemblies.
9467 @xref{Print Settings, ,Print settings}.
9469 @item set print object
9470 @itemx show print object
9471 Choose whether to print derived (actual) or declared types of objects.
9472 @xref{Print Settings, ,Print settings}.
9474 @item set print vtbl
9475 @itemx show print vtbl
9476 Control the format for printing virtual function tables.
9477 @xref{Print Settings, ,Print settings}.
9478 (The @code{vtbl} commands do not work on programs compiled with the HP
9479 ANSI C@t{++} compiler (@code{aCC}).)
9481 @kindex set overload-resolution
9482 @cindex overloaded functions, overload resolution
9483 @item set overload-resolution on
9484 Enable overload resolution for C@t{++} expression evaluation. The default
9485 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9486 and searches for a function whose signature matches the argument types,
9487 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
9488 expressions}, for details). If it cannot find a match, it emits a
9491 @item set overload-resolution off
9492 Disable overload resolution for C@t{++} expression evaluation. For
9493 overloaded functions that are not class member functions, @value{GDBN}
9494 chooses the first function of the specified name that it finds in the
9495 symbol table, whether or not its arguments are of the correct type. For
9496 overloaded functions that are class member functions, @value{GDBN}
9497 searches for a function whose signature @emph{exactly} matches the
9500 @kindex show overload-resolution
9501 @item show overload-resolution
9502 Show the current setting of overload resolution.
9504 @item @r{Overloaded symbol names}
9505 You can specify a particular definition of an overloaded symbol, using
9506 the same notation that is used to declare such symbols in C@t{++}: type
9507 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9508 also use the @value{GDBN} command-line word completion facilities to list the
9509 available choices, or to finish the type list for you.
9510 @xref{Completion,, Command completion}, for details on how to do this.
9514 @subsection Objective-C
9517 This section provides information about some commands and command
9518 options that are useful for debugging Objective-C code. See also
9519 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9520 few more commands specific to Objective-C support.
9523 * Method Names in Commands::
9524 * The Print Command with Objective-C::
9527 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
9528 @subsubsection Method Names in Commands
9530 The following commands have been extended to accept Objective-C method
9531 names as line specifications:
9533 @kindex clear@r{, and Objective-C}
9534 @kindex break@r{, and Objective-C}
9535 @kindex info line@r{, and Objective-C}
9536 @kindex jump@r{, and Objective-C}
9537 @kindex list@r{, and Objective-C}
9541 @item @code{info line}
9546 A fully qualified Objective-C method name is specified as
9549 -[@var{Class} @var{methodName}]
9552 where the minus sign is used to indicate an instance method and a
9553 plus sign (not shown) is used to indicate a class method. The class
9554 name @var{Class} and method name @var{methodName} are enclosed in
9555 brackets, similar to the way messages are specified in Objective-C
9556 source code. For example, to set a breakpoint at the @code{create}
9557 instance method of class @code{Fruit} in the program currently being
9561 break -[Fruit create]
9564 To list ten program lines around the @code{initialize} class method,
9568 list +[NSText initialize]
9571 In the current version of @value{GDBN}, the plus or minus sign is
9572 required. In future versions of @value{GDBN}, the plus or minus
9573 sign will be optional, but you can use it to narrow the search. It
9574 is also possible to specify just a method name:
9580 You must specify the complete method name, including any colons. If
9581 your program's source files contain more than one @code{create} method,
9582 you'll be presented with a numbered list of classes that implement that
9583 method. Indicate your choice by number, or type @samp{0} to exit if
9586 As another example, to clear a breakpoint established at the
9587 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9590 clear -[NSWindow makeKeyAndOrderFront:]
9593 @node The Print Command with Objective-C
9594 @subsubsection The Print Command With Objective-C
9595 @cindex Objective-C, print objects
9596 @kindex print-object
9597 @kindex po @r{(@code{print-object})}
9599 The print command has also been extended to accept methods. For example:
9602 print -[@var{object} hash]
9605 @cindex print an Objective-C object description
9606 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9608 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9609 and print the result. Also, an additional command has been added,
9610 @code{print-object} or @code{po} for short, which is meant to print
9611 the description of an object. However, this command may only work
9612 with certain Objective-C libraries that have a particular hook
9613 function, @code{_NSPrintForDebugger}, defined.
9617 @cindex Fortran-specific support in @value{GDBN}
9619 @value{GDBN} can be used to debug programs written in Fortran, but it
9620 currently supports only the features of Fortran 77 language.
9622 @cindex trailing underscore, in Fortran symbols
9623 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9624 among them) append an underscore to the names of variables and
9625 functions. When you debug programs compiled by those compilers, you
9626 will need to refer to variables and functions with a trailing
9630 * Fortran Operators:: Fortran operators and expressions
9631 * Fortran Defaults:: Default settings for Fortran
9632 * Special Fortran commands:: Special @value{GDBN} commands for Fortran
9635 @node Fortran Operators
9636 @subsubsection Fortran operators and expressions
9638 @cindex Fortran operators and expressions
9640 Operators must be defined on values of specific types. For instance,
9641 @code{+} is defined on numbers, but not on characters or other non-
9642 arithmetic types. Operators are often defined on groups of types.
9646 The exponentiation operator. It raises the first operand to the power
9650 The range operator. Normally used in the form of array(low:high) to
9651 represent a section of array.
9654 @node Fortran Defaults
9655 @subsubsection Fortran Defaults
9657 @cindex Fortran Defaults
9659 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9660 default uses case-insensitive matches for Fortran symbols. You can
9661 change that with the @samp{set case-insensitive} command, see
9662 @ref{Symbols}, for the details.
9664 @node Special Fortran commands
9665 @subsubsection Special Fortran commands
9667 @cindex Special Fortran commands
9669 @value{GDBN} had some commands to support Fortran specific feature,
9670 such as common block displaying.
9673 @cindex @code{COMMON} blocks, Fortran
9675 @item info common @r{[}@var{common-name}@r{]}
9676 This command prints the values contained in the Fortran @code{COMMON}
9677 block whose name is @var{common-name}. With no argument, the names of
9678 all @code{COMMON} blocks visible at current program location are
9685 @cindex Pascal support in @value{GDBN}, limitations
9686 Debugging Pascal programs which use sets, subranges, file variables, or
9687 nested functions does not currently work. @value{GDBN} does not support
9688 entering expressions, printing values, or similar features using Pascal
9691 The Pascal-specific command @code{set print pascal_static-members}
9692 controls whether static members of Pascal objects are displayed.
9693 @xref{Print Settings, pascal_static-members}.
9696 @subsection Modula-2
9698 @cindex Modula-2, @value{GDBN} support
9700 The extensions made to @value{GDBN} to support Modula-2 only support
9701 output from the @sc{gnu} Modula-2 compiler (which is currently being
9702 developed). Other Modula-2 compilers are not currently supported, and
9703 attempting to debug executables produced by them is most likely
9704 to give an error as @value{GDBN} reads in the executable's symbol
9707 @cindex expressions in Modula-2
9709 * M2 Operators:: Built-in operators
9710 * Built-In Func/Proc:: Built-in functions and procedures
9711 * M2 Constants:: Modula-2 constants
9712 * M2 Types:: Modula-2 types
9713 * M2 Defaults:: Default settings for Modula-2
9714 * Deviations:: Deviations from standard Modula-2
9715 * M2 Checks:: Modula-2 type and range checks
9716 * M2 Scope:: The scope operators @code{::} and @code{.}
9717 * GDB/M2:: @value{GDBN} and Modula-2
9721 @subsubsection Operators
9722 @cindex Modula-2 operators
9724 Operators must be defined on values of specific types. For instance,
9725 @code{+} is defined on numbers, but not on structures. Operators are
9726 often defined on groups of types. For the purposes of Modula-2, the
9727 following definitions hold:
9732 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9736 @emph{Character types} consist of @code{CHAR} and its subranges.
9739 @emph{Floating-point types} consist of @code{REAL}.
9742 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9746 @emph{Scalar types} consist of all of the above.
9749 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9752 @emph{Boolean types} consist of @code{BOOLEAN}.
9756 The following operators are supported, and appear in order of
9757 increasing precedence:
9761 Function argument or array index separator.
9764 Assignment. The value of @var{var} @code{:=} @var{value} is
9768 Less than, greater than on integral, floating-point, or enumerated
9772 Less than or equal to, greater than or equal to
9773 on integral, floating-point and enumerated types, or set inclusion on
9774 set types. Same precedence as @code{<}.
9776 @item =@r{, }<>@r{, }#
9777 Equality and two ways of expressing inequality, valid on scalar types.
9778 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9779 available for inequality, since @code{#} conflicts with the script
9783 Set membership. Defined on set types and the types of their members.
9784 Same precedence as @code{<}.
9787 Boolean disjunction. Defined on boolean types.
9790 Boolean conjunction. Defined on boolean types.
9793 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9796 Addition and subtraction on integral and floating-point types, or union
9797 and difference on set types.
9800 Multiplication on integral and floating-point types, or set intersection
9804 Division on floating-point types, or symmetric set difference on set
9805 types. Same precedence as @code{*}.
9808 Integer division and remainder. Defined on integral types. Same
9809 precedence as @code{*}.
9812 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9815 Pointer dereferencing. Defined on pointer types.
9818 Boolean negation. Defined on boolean types. Same precedence as
9822 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9823 precedence as @code{^}.
9826 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9829 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9833 @value{GDBN} and Modula-2 scope operators.
9837 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9838 treats the use of the operator @code{IN}, or the use of operators
9839 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9840 @code{<=}, and @code{>=} on sets as an error.
9844 @node Built-In Func/Proc
9845 @subsubsection Built-in functions and procedures
9846 @cindex Modula-2 built-ins
9848 Modula-2 also makes available several built-in procedures and functions.
9849 In describing these, the following metavariables are used:
9854 represents an @code{ARRAY} variable.
9857 represents a @code{CHAR} constant or variable.
9860 represents a variable or constant of integral type.
9863 represents an identifier that belongs to a set. Generally used in the
9864 same function with the metavariable @var{s}. The type of @var{s} should
9865 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9868 represents a variable or constant of integral or floating-point type.
9871 represents a variable or constant of floating-point type.
9877 represents a variable.
9880 represents a variable or constant of one of many types. See the
9881 explanation of the function for details.
9884 All Modula-2 built-in procedures also return a result, described below.
9888 Returns the absolute value of @var{n}.
9891 If @var{c} is a lower case letter, it returns its upper case
9892 equivalent, otherwise it returns its argument.
9895 Returns the character whose ordinal value is @var{i}.
9898 Decrements the value in the variable @var{v} by one. Returns the new value.
9900 @item DEC(@var{v},@var{i})
9901 Decrements the value in the variable @var{v} by @var{i}. Returns the
9904 @item EXCL(@var{m},@var{s})
9905 Removes the element @var{m} from the set @var{s}. Returns the new
9908 @item FLOAT(@var{i})
9909 Returns the floating point equivalent of the integer @var{i}.
9912 Returns the index of the last member of @var{a}.
9915 Increments the value in the variable @var{v} by one. Returns the new value.
9917 @item INC(@var{v},@var{i})
9918 Increments the value in the variable @var{v} by @var{i}. Returns the
9921 @item INCL(@var{m},@var{s})
9922 Adds the element @var{m} to the set @var{s} if it is not already
9923 there. Returns the new set.
9926 Returns the maximum value of the type @var{t}.
9929 Returns the minimum value of the type @var{t}.
9932 Returns boolean TRUE if @var{i} is an odd number.
9935 Returns the ordinal value of its argument. For example, the ordinal
9936 value of a character is its @sc{ascii} value (on machines supporting the
9937 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9938 integral, character and enumerated types.
9941 Returns the size of its argument. @var{x} can be a variable or a type.
9943 @item TRUNC(@var{r})
9944 Returns the integral part of @var{r}.
9946 @item VAL(@var{t},@var{i})
9947 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9951 @emph{Warning:} Sets and their operations are not yet supported, so
9952 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9956 @cindex Modula-2 constants
9958 @subsubsection Constants
9960 @value{GDBN} allows you to express the constants of Modula-2 in the following
9966 Integer constants are simply a sequence of digits. When used in an
9967 expression, a constant is interpreted to be type-compatible with the
9968 rest of the expression. Hexadecimal integers are specified by a
9969 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9972 Floating point constants appear as a sequence of digits, followed by a
9973 decimal point and another sequence of digits. An optional exponent can
9974 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9975 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9976 digits of the floating point constant must be valid decimal (base 10)
9980 Character constants consist of a single character enclosed by a pair of
9981 like quotes, either single (@code{'}) or double (@code{"}). They may
9982 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9983 followed by a @samp{C}.
9986 String constants consist of a sequence of characters enclosed by a
9987 pair of like quotes, either single (@code{'}) or double (@code{"}).
9988 Escape sequences in the style of C are also allowed. @xref{C
9989 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9993 Enumerated constants consist of an enumerated identifier.
9996 Boolean constants consist of the identifiers @code{TRUE} and
10000 Pointer constants consist of integral values only.
10003 Set constants are not yet supported.
10007 @subsubsection Modula-2 Types
10008 @cindex Modula-2 types
10010 Currently @value{GDBN} can print the following data types in Modula-2
10011 syntax: array types, record types, set types, pointer types, procedure
10012 types, enumerated types, subrange types and base types. You can also
10013 print the contents of variables declared using these type.
10014 This section gives a number of simple source code examples together with
10015 sample @value{GDBN} sessions.
10017 The first example contains the following section of code:
10026 and you can request @value{GDBN} to interrogate the type and value of
10027 @code{r} and @code{s}.
10030 (@value{GDBP}) print s
10032 (@value{GDBP}) ptype s
10034 (@value{GDBP}) print r
10036 (@value{GDBP}) ptype r
10041 Likewise if your source code declares @code{s} as:
10045 s: SET ['A'..'Z'] ;
10049 then you may query the type of @code{s} by:
10052 (@value{GDBP}) ptype s
10053 type = SET ['A'..'Z']
10057 Note that at present you cannot interactively manipulate set
10058 expressions using the debugger.
10060 The following example shows how you might declare an array in Modula-2
10061 and how you can interact with @value{GDBN} to print its type and contents:
10065 s: ARRAY [-10..10] OF CHAR ;
10069 (@value{GDBP}) ptype s
10070 ARRAY [-10..10] OF CHAR
10073 Note that the array handling is not yet complete and although the type
10074 is printed correctly, expression handling still assumes that all
10075 arrays have a lower bound of zero and not @code{-10} as in the example
10076 above. Unbounded arrays are also not yet recognized in @value{GDBN}.
10078 Here are some more type related Modula-2 examples:
10082 colour = (blue, red, yellow, green) ;
10083 t = [blue..yellow] ;
10091 The @value{GDBN} interaction shows how you can query the data type
10092 and value of a variable.
10095 (@value{GDBP}) print s
10097 (@value{GDBP}) ptype t
10098 type = [blue..yellow]
10102 In this example a Modula-2 array is declared and its contents
10103 displayed. Observe that the contents are written in the same way as
10104 their @code{C} counterparts.
10108 s: ARRAY [1..5] OF CARDINAL ;
10114 (@value{GDBP}) print s
10115 $1 = @{1, 0, 0, 0, 0@}
10116 (@value{GDBP}) ptype s
10117 type = ARRAY [1..5] OF CARDINAL
10120 The Modula-2 language interface to @value{GDBN} also understands
10121 pointer types as shown in this example:
10125 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10132 and you can request that @value{GDBN} describes the type of @code{s}.
10135 (@value{GDBP}) ptype s
10136 type = POINTER TO ARRAY [1..5] OF CARDINAL
10139 @value{GDBN} handles compound types as we can see in this example.
10140 Here we combine array types, record types, pointer types and subrange
10151 myarray = ARRAY myrange OF CARDINAL ;
10152 myrange = [-2..2] ;
10154 s: POINTER TO ARRAY myrange OF foo ;
10158 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10162 (@value{GDBP}) ptype s
10163 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10166 f3 : ARRAY [-2..2] OF CARDINAL;
10171 @subsubsection Modula-2 defaults
10172 @cindex Modula-2 defaults
10174 If type and range checking are set automatically by @value{GDBN}, they
10175 both default to @code{on} whenever the working language changes to
10176 Modula-2. This happens regardless of whether you or @value{GDBN}
10177 selected the working language.
10179 If you allow @value{GDBN} to set the language automatically, then entering
10180 code compiled from a file whose name ends with @file{.mod} sets the
10181 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
10182 the language automatically}, for further details.
10185 @subsubsection Deviations from standard Modula-2
10186 @cindex Modula-2, deviations from
10188 A few changes have been made to make Modula-2 programs easier to debug.
10189 This is done primarily via loosening its type strictness:
10193 Unlike in standard Modula-2, pointer constants can be formed by
10194 integers. This allows you to modify pointer variables during
10195 debugging. (In standard Modula-2, the actual address contained in a
10196 pointer variable is hidden from you; it can only be modified
10197 through direct assignment to another pointer variable or expression that
10198 returned a pointer.)
10201 C escape sequences can be used in strings and characters to represent
10202 non-printable characters. @value{GDBN} prints out strings with these
10203 escape sequences embedded. Single non-printable characters are
10204 printed using the @samp{CHR(@var{nnn})} format.
10207 The assignment operator (@code{:=}) returns the value of its right-hand
10211 All built-in procedures both modify @emph{and} return their argument.
10215 @subsubsection Modula-2 type and range checks
10216 @cindex Modula-2 checks
10219 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10222 @c FIXME remove warning when type/range checks added
10224 @value{GDBN} considers two Modula-2 variables type equivalent if:
10228 They are of types that have been declared equivalent via a @code{TYPE
10229 @var{t1} = @var{t2}} statement
10232 They have been declared on the same line. (Note: This is true of the
10233 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10236 As long as type checking is enabled, any attempt to combine variables
10237 whose types are not equivalent is an error.
10239 Range checking is done on all mathematical operations, assignment, array
10240 index bounds, and all built-in functions and procedures.
10243 @subsubsection The scope operators @code{::} and @code{.}
10245 @cindex @code{.}, Modula-2 scope operator
10246 @cindex colon, doubled as scope operator
10248 @vindex colon-colon@r{, in Modula-2}
10249 @c Info cannot handle :: but TeX can.
10252 @vindex ::@r{, in Modula-2}
10255 There are a few subtle differences between the Modula-2 scope operator
10256 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10261 @var{module} . @var{id}
10262 @var{scope} :: @var{id}
10266 where @var{scope} is the name of a module or a procedure,
10267 @var{module} the name of a module, and @var{id} is any declared
10268 identifier within your program, except another module.
10270 Using the @code{::} operator makes @value{GDBN} search the scope
10271 specified by @var{scope} for the identifier @var{id}. If it is not
10272 found in the specified scope, then @value{GDBN} searches all scopes
10273 enclosing the one specified by @var{scope}.
10275 Using the @code{.} operator makes @value{GDBN} search the current scope for
10276 the identifier specified by @var{id} that was imported from the
10277 definition module specified by @var{module}. With this operator, it is
10278 an error if the identifier @var{id} was not imported from definition
10279 module @var{module}, or if @var{id} is not an identifier in
10283 @subsubsection @value{GDBN} and Modula-2
10285 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10286 Five subcommands of @code{set print} and @code{show print} apply
10287 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10288 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10289 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10290 analogue in Modula-2.
10292 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10293 with any language, is not useful with Modula-2. Its
10294 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10295 created in Modula-2 as they can in C or C@t{++}. However, because an
10296 address can be specified by an integral constant, the construct
10297 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10299 @cindex @code{#} in Modula-2
10300 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10301 interpreted as the beginning of a comment. Use @code{<>} instead.
10307 The extensions made to @value{GDBN} for Ada only support
10308 output from the @sc{gnu} Ada (GNAT) compiler.
10309 Other Ada compilers are not currently supported, and
10310 attempting to debug executables produced by them is most likely
10314 @cindex expressions in Ada
10316 * Ada Mode Intro:: General remarks on the Ada syntax
10317 and semantics supported by Ada mode
10319 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10320 * Additions to Ada:: Extensions of the Ada expression syntax.
10321 * Stopping Before Main Program:: Debugging the program during elaboration.
10322 * Ada Glitches:: Known peculiarities of Ada mode.
10325 @node Ada Mode Intro
10326 @subsubsection Introduction
10327 @cindex Ada mode, general
10329 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10330 syntax, with some extensions.
10331 The philosophy behind the design of this subset is
10335 That @value{GDBN} should provide basic literals and access to operations for
10336 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10337 leaving more sophisticated computations to subprograms written into the
10338 program (which therefore may be called from @value{GDBN}).
10341 That type safety and strict adherence to Ada language restrictions
10342 are not particularly important to the @value{GDBN} user.
10345 That brevity is important to the @value{GDBN} user.
10348 Thus, for brevity, the debugger acts as if there were
10349 implicit @code{with} and @code{use} clauses in effect for all user-written
10350 packages, making it unnecessary to fully qualify most names with
10351 their packages, regardless of context. Where this causes ambiguity,
10352 @value{GDBN} asks the user's intent.
10354 The debugger will start in Ada mode if it detects an Ada main program.
10355 As for other languages, it will enter Ada mode when stopped in a program that
10356 was translated from an Ada source file.
10358 While in Ada mode, you may use `@t{--}' for comments. This is useful
10359 mostly for documenting command files. The standard @value{GDBN} comment
10360 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10361 middle (to allow based literals).
10363 The debugger supports limited overloading. Given a subprogram call in which
10364 the function symbol has multiple definitions, it will use the number of
10365 actual parameters and some information about their types to attempt to narrow
10366 the set of definitions. It also makes very limited use of context, preferring
10367 procedures to functions in the context of the @code{call} command, and
10368 functions to procedures elsewhere.
10370 @node Omissions from Ada
10371 @subsubsection Omissions from Ada
10372 @cindex Ada, omissions from
10374 Here are the notable omissions from the subset:
10378 Only a subset of the attributes are supported:
10382 @t{'First}, @t{'Last}, and @t{'Length}
10383 on array objects (not on types and subtypes).
10386 @t{'Min} and @t{'Max}.
10389 @t{'Pos} and @t{'Val}.
10395 @t{'Range} on array objects (not subtypes), but only as the right
10396 operand of the membership (@code{in}) operator.
10399 @t{'Access}, @t{'Unchecked_Access}, and
10400 @t{'Unrestricted_Access} (a GNAT extension).
10408 @code{Characters.Latin_1} are not available and
10409 concatenation is not implemented. Thus, escape characters in strings are
10410 not currently available.
10413 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10414 equality of representations. They will generally work correctly
10415 for strings and arrays whose elements have integer or enumeration types.
10416 They may not work correctly for arrays whose element
10417 types have user-defined equality, for arrays of real values
10418 (in particular, IEEE-conformant floating point, because of negative
10419 zeroes and NaNs), and for arrays whose elements contain unused bits with
10420 indeterminate values.
10423 The other component-by-component array operations (@code{and}, @code{or},
10424 @code{xor}, @code{not}, and relational tests other than equality)
10425 are not implemented.
10428 @cindex array aggregates (Ada)
10429 @cindex record aggregates (Ada)
10430 @cindex aggregates (Ada)
10431 There is limited support for array and record aggregates. They are
10432 permitted only on the right sides of assignments, as in these examples:
10435 set An_Array := (1, 2, 3, 4, 5, 6)
10436 set An_Array := (1, others => 0)
10437 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10438 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10439 set A_Record := (1, "Peter", True);
10440 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10444 discriminant's value by assigning an aggregate has an
10445 undefined effect if that discriminant is used within the record.
10446 However, you can first modify discriminants by directly assigning to
10447 them (which normally would not be allowed in Ada), and then performing an
10448 aggregate assignment. For example, given a variable @code{A_Rec}
10449 declared to have a type such as:
10452 type Rec (Len : Small_Integer := 0) is record
10454 Vals : IntArray (1 .. Len);
10458 you can assign a value with a different size of @code{Vals} with two
10463 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10466 As this example also illustrates, @value{GDBN} is very loose about the usual
10467 rules concerning aggregates. You may leave out some of the
10468 components of an array or record aggregate (such as the @code{Len}
10469 component in the assignment to @code{A_Rec} above); they will retain their
10470 original values upon assignment. You may freely use dynamic values as
10471 indices in component associations. You may even use overlapping or
10472 redundant component associations, although which component values are
10473 assigned in such cases is not defined.
10476 Calls to dispatching subprograms are not implemented.
10479 The overloading algorithm is much more limited (i.e., less selective)
10480 than that of real Ada. It makes only limited use of the context in which a subexpression
10481 appears to resolve its meaning, and it is much looser in its rules for allowing
10482 type matches. As a result, some function calls will be ambiguous, and the user
10483 will be asked to choose the proper resolution.
10486 The @code{new} operator is not implemented.
10489 Entry calls are not implemented.
10492 Aside from printing, arithmetic operations on the native VAX floating-point
10493 formats are not supported.
10496 It is not possible to slice a packed array.
10499 @node Additions to Ada
10500 @subsubsection Additions to Ada
10501 @cindex Ada, deviations from
10503 As it does for other languages, @value{GDBN} makes certain generic
10504 extensions to Ada (@pxref{Expressions}):
10508 If the expression @var{E} is a variable residing in memory
10509 (typically a local variable or array element) and @var{N} is
10510 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
10511 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
10512 In Ada, this operator is generally not necessary, since its prime use
10513 is in displaying parts of an array, and slicing will usually do this in Ada.
10514 However, there are occasional uses when debugging programs
10515 in which certain debugging information has been optimized away.
10518 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
10519 in function or file @var{B}.'' When @var{B} is a file name, you must typically
10520 surround it in single quotes.
10523 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10524 @var{type} that appears at address @var{addr}.''
10527 A name starting with @samp{$} is a convenience variable
10528 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10531 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
10536 The assignment statement is allowed as an expression, returning
10537 its right-hand operand as its value. Thus, you may enter
10541 print A(tmp := y + 1)
10545 The semicolon is allowed as an ``operator,'' returning as its value
10546 the value of its right-hand operand.
10547 This allows, for example,
10548 complex conditional breaks:
10552 condition 1 (report(i); k += 1; A(k) > 100)
10556 Rather than use catenation and symbolic character names to introduce special
10557 characters into strings, one may instead use a special bracket notation,
10558 which is also used to print strings. A sequence of characters of the form
10559 @samp{["@var{XX}"]} within a string or character literal denotes the
10560 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10561 sequence of characters @samp{["""]} also denotes a single quotation mark
10562 in strings. For example,
10564 "One line.["0a"]Next line.["0a"]"
10567 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
10571 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10572 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10580 When printing arrays, @value{GDBN} uses positional notation when the
10581 array has a lower bound of 1, and uses a modified named notation otherwise.
10582 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
10589 That is, in contrast to valid Ada, only the first component has a @code{=>}
10593 You may abbreviate attributes in expressions with any unique,
10594 multi-character subsequence of
10595 their names (an exact match gets preference).
10596 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10597 in place of @t{a'length}.
10600 @cindex quoting Ada internal identifiers
10601 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10602 to lower case. The GNAT compiler uses upper-case characters for
10603 some of its internal identifiers, which are normally of no interest to users.
10604 For the rare occasions when you actually have to look at them,
10605 enclose them in angle brackets to avoid the lower-case mapping.
10608 @value{GDBP} print <JMPBUF_SAVE>[0]
10612 Printing an object of class-wide type or dereferencing an
10613 access-to-class-wide value will display all the components of the object's
10614 specific type (as indicated by its run-time tag). Likewise, component
10615 selection on such a value will operate on the specific type of the
10620 @node Stopping Before Main Program
10621 @subsubsection Stopping at the Very Beginning
10623 @cindex breakpointing Ada elaboration code
10624 It is sometimes necessary to debug the program during elaboration, and
10625 before reaching the main procedure.
10626 As defined in the Ada Reference
10627 Manual, the elaboration code is invoked from a procedure called
10628 @code{adainit}. To run your program up to the beginning of
10629 elaboration, simply use the following two commands:
10630 @code{tbreak adainit} and @code{run}.
10633 @subsubsection Known Peculiarities of Ada Mode
10634 @cindex Ada, problems
10636 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10637 we know of several problems with and limitations of Ada mode in
10639 some of which will be fixed with planned future releases of the debugger
10640 and the GNU Ada compiler.
10644 Currently, the debugger
10645 has insufficient information to determine whether certain pointers represent
10646 pointers to objects or the objects themselves.
10647 Thus, the user may have to tack an extra @code{.all} after an expression
10648 to get it printed properly.
10651 Static constants that the compiler chooses not to materialize as objects in
10652 storage are invisible to the debugger.
10655 Named parameter associations in function argument lists are ignored (the
10656 argument lists are treated as positional).
10659 Many useful library packages are currently invisible to the debugger.
10662 Fixed-point arithmetic, conversions, input, and output is carried out using
10663 floating-point arithmetic, and may give results that only approximate those on
10667 The type of the @t{'Address} attribute may not be @code{System.Address}.
10670 The GNAT compiler never generates the prefix @code{Standard} for any of
10671 the standard symbols defined by the Ada language. @value{GDBN} knows about
10672 this: it will strip the prefix from names when you use it, and will never
10673 look for a name you have so qualified among local symbols, nor match against
10674 symbols in other packages or subprograms. If you have
10675 defined entities anywhere in your program other than parameters and
10676 local variables whose simple names match names in @code{Standard},
10677 GNAT's lack of qualification here can cause confusion. When this happens,
10678 you can usually resolve the confusion
10679 by qualifying the problematic names with package
10680 @code{Standard} explicitly.
10683 @node Unsupported languages
10684 @section Unsupported languages
10686 @cindex unsupported languages
10687 @cindex minimal language
10688 In addition to the other fully-supported programming languages,
10689 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10690 It does not represent a real programming language, but provides a set
10691 of capabilities close to what the C or assembly languages provide.
10692 This should allow most simple operations to be performed while debugging
10693 an application that uses a language currently not supported by @value{GDBN}.
10695 If the language is set to @code{auto}, @value{GDBN} will automatically
10696 select this language if the current frame corresponds to an unsupported
10700 @chapter Examining the Symbol Table
10702 The commands described in this chapter allow you to inquire about the
10703 symbols (names of variables, functions and types) defined in your
10704 program. This information is inherent in the text of your program and
10705 does not change as your program executes. @value{GDBN} finds it in your
10706 program's symbol table, in the file indicated when you started @value{GDBN}
10707 (@pxref{File Options, ,Choosing files}), or by one of the
10708 file-management commands (@pxref{Files, ,Commands to specify files}).
10710 @cindex symbol names
10711 @cindex names of symbols
10712 @cindex quoting names
10713 Occasionally, you may need to refer to symbols that contain unusual
10714 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10715 most frequent case is in referring to static variables in other
10716 source files (@pxref{Variables,,Program variables}). File names
10717 are recorded in object files as debugging symbols, but @value{GDBN} would
10718 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10719 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10720 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10727 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10730 @cindex case-insensitive symbol names
10731 @cindex case sensitivity in symbol names
10732 @kindex set case-sensitive
10733 @item set case-sensitive on
10734 @itemx set case-sensitive off
10735 @itemx set case-sensitive auto
10736 Normally, when @value{GDBN} looks up symbols, it matches their names
10737 with case sensitivity determined by the current source language.
10738 Occasionally, you may wish to control that. The command @code{set
10739 case-sensitive} lets you do that by specifying @code{on} for
10740 case-sensitive matches or @code{off} for case-insensitive ones. If
10741 you specify @code{auto}, case sensitivity is reset to the default
10742 suitable for the source language. The default is case-sensitive
10743 matches for all languages except for Fortran, for which the default is
10744 case-insensitive matches.
10746 @kindex show case-sensitive
10747 @item show case-sensitive
10748 This command shows the current setting of case sensitivity for symbols
10751 @kindex info address
10752 @cindex address of a symbol
10753 @item info address @var{symbol}
10754 Describe where the data for @var{symbol} is stored. For a register
10755 variable, this says which register it is kept in. For a non-register
10756 local variable, this prints the stack-frame offset at which the variable
10759 Note the contrast with @samp{print &@var{symbol}}, which does not work
10760 at all for a register variable, and for a stack local variable prints
10761 the exact address of the current instantiation of the variable.
10763 @kindex info symbol
10764 @cindex symbol from address
10765 @cindex closest symbol and offset for an address
10766 @item info symbol @var{addr}
10767 Print the name of a symbol which is stored at the address @var{addr}.
10768 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10769 nearest symbol and an offset from it:
10772 (@value{GDBP}) info symbol 0x54320
10773 _initialize_vx + 396 in section .text
10777 This is the opposite of the @code{info address} command. You can use
10778 it to find out the name of a variable or a function given its address.
10781 @item whatis [@var{arg}]
10782 Print the data type of @var{arg}, which can be either an expression or
10783 a data type. With no argument, print the data type of @code{$}, the
10784 last value in the value history. If @var{arg} is an expression, it is
10785 not actually evaluated, and any side-effecting operations (such as
10786 assignments or function calls) inside it do not take place. If
10787 @var{arg} is a type name, it may be the name of a type or typedef, or
10788 for C code it may have the form @samp{class @var{class-name}},
10789 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10790 @samp{enum @var{enum-tag}}.
10791 @xref{Expressions, ,Expressions}.
10794 @item ptype [@var{arg}]
10795 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10796 detailed description of the type, instead of just the name of the type.
10797 @xref{Expressions, ,Expressions}.
10799 For example, for this variable declaration:
10802 struct complex @{double real; double imag;@} v;
10806 the two commands give this output:
10810 (@value{GDBP}) whatis v
10811 type = struct complex
10812 (@value{GDBP}) ptype v
10813 type = struct complex @{
10821 As with @code{whatis}, using @code{ptype} without an argument refers to
10822 the type of @code{$}, the last value in the value history.
10824 @cindex incomplete type
10825 Sometimes, programs use opaque data types or incomplete specifications
10826 of complex data structure. If the debug information included in the
10827 program does not allow @value{GDBN} to display a full declaration of
10828 the data type, it will say @samp{<incomplete type>}. For example,
10829 given these declarations:
10833 struct foo *fooptr;
10837 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10840 (@value{GDBP}) ptype foo
10841 $1 = <incomplete type>
10845 ``Incomplete type'' is C terminology for data types that are not
10846 completely specified.
10849 @item info types @var{regexp}
10851 Print a brief description of all types whose names match the regular
10852 expression @var{regexp} (or all types in your program, if you supply
10853 no argument). Each complete typename is matched as though it were a
10854 complete line; thus, @samp{i type value} gives information on all
10855 types in your program whose names include the string @code{value}, but
10856 @samp{i type ^value$} gives information only on types whose complete
10857 name is @code{value}.
10859 This command differs from @code{ptype} in two ways: first, like
10860 @code{whatis}, it does not print a detailed description; second, it
10861 lists all source files where a type is defined.
10864 @cindex local variables
10865 @item info scope @var{location}
10866 List all the variables local to a particular scope. This command
10867 accepts a @var{location} argument---a function name, a source line, or
10868 an address preceded by a @samp{*}, and prints all the variables local
10869 to the scope defined by that location. For example:
10872 (@value{GDBP}) @b{info scope command_line_handler}
10873 Scope for command_line_handler:
10874 Symbol rl is an argument at stack/frame offset 8, length 4.
10875 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10876 Symbol linelength is in static storage at address 0x150a1c, length 4.
10877 Symbol p is a local variable in register $esi, length 4.
10878 Symbol p1 is a local variable in register $ebx, length 4.
10879 Symbol nline is a local variable in register $edx, length 4.
10880 Symbol repeat is a local variable at frame offset -8, length 4.
10884 This command is especially useful for determining what data to collect
10885 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10888 @kindex info source
10890 Show information about the current source file---that is, the source file for
10891 the function containing the current point of execution:
10894 the name of the source file, and the directory containing it,
10896 the directory it was compiled in,
10898 its length, in lines,
10900 which programming language it is written in,
10902 whether the executable includes debugging information for that file, and
10903 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10905 whether the debugging information includes information about
10906 preprocessor macros.
10910 @kindex info sources
10912 Print the names of all source files in your program for which there is
10913 debugging information, organized into two lists: files whose symbols
10914 have already been read, and files whose symbols will be read when needed.
10916 @kindex info functions
10917 @item info functions
10918 Print the names and data types of all defined functions.
10920 @item info functions @var{regexp}
10921 Print the names and data types of all defined functions
10922 whose names contain a match for regular expression @var{regexp}.
10923 Thus, @samp{info fun step} finds all functions whose names
10924 include @code{step}; @samp{info fun ^step} finds those whose names
10925 start with @code{step}. If a function name contains characters
10926 that conflict with the regular expression language (e.g.@:
10927 @samp{operator*()}), they may be quoted with a backslash.
10929 @kindex info variables
10930 @item info variables
10931 Print the names and data types of all variables that are declared
10932 outside of functions (i.e.@: excluding local variables).
10934 @item info variables @var{regexp}
10935 Print the names and data types of all variables (except for local
10936 variables) whose names contain a match for regular expression
10939 @kindex info classes
10940 @cindex Objective-C, classes and selectors
10942 @itemx info classes @var{regexp}
10943 Display all Objective-C classes in your program, or
10944 (with the @var{regexp} argument) all those matching a particular regular
10947 @kindex info selectors
10948 @item info selectors
10949 @itemx info selectors @var{regexp}
10950 Display all Objective-C selectors in your program, or
10951 (with the @var{regexp} argument) all those matching a particular regular
10955 This was never implemented.
10956 @kindex info methods
10958 @itemx info methods @var{regexp}
10959 The @code{info methods} command permits the user to examine all defined
10960 methods within C@t{++} program, or (with the @var{regexp} argument) a
10961 specific set of methods found in the various C@t{++} classes. Many
10962 C@t{++} classes provide a large number of methods. Thus, the output
10963 from the @code{ptype} command can be overwhelming and hard to use. The
10964 @code{info-methods} command filters the methods, printing only those
10965 which match the regular-expression @var{regexp}.
10968 @cindex reloading symbols
10969 Some systems allow individual object files that make up your program to
10970 be replaced without stopping and restarting your program. For example,
10971 in VxWorks you can simply recompile a defective object file and keep on
10972 running. If you are running on one of these systems, you can allow
10973 @value{GDBN} to reload the symbols for automatically relinked modules:
10976 @kindex set symbol-reloading
10977 @item set symbol-reloading on
10978 Replace symbol definitions for the corresponding source file when an
10979 object file with a particular name is seen again.
10981 @item set symbol-reloading off
10982 Do not replace symbol definitions when encountering object files of the
10983 same name more than once. This is the default state; if you are not
10984 running on a system that permits automatic relinking of modules, you
10985 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10986 may discard symbols when linking large programs, that may contain
10987 several modules (from different directories or libraries) with the same
10990 @kindex show symbol-reloading
10991 @item show symbol-reloading
10992 Show the current @code{on} or @code{off} setting.
10995 @cindex opaque data types
10996 @kindex set opaque-type-resolution
10997 @item set opaque-type-resolution on
10998 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10999 declared as a pointer to a @code{struct}, @code{class}, or
11000 @code{union}---for example, @code{struct MyType *}---that is used in one
11001 source file although the full declaration of @code{struct MyType} is in
11002 another source file. The default is on.
11004 A change in the setting of this subcommand will not take effect until
11005 the next time symbols for a file are loaded.
11007 @item set opaque-type-resolution off
11008 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11009 is printed as follows:
11011 @{<no data fields>@}
11014 @kindex show opaque-type-resolution
11015 @item show opaque-type-resolution
11016 Show whether opaque types are resolved or not.
11018 @kindex maint print symbols
11019 @cindex symbol dump
11020 @kindex maint print psymbols
11021 @cindex partial symbol dump
11022 @item maint print symbols @var{filename}
11023 @itemx maint print psymbols @var{filename}
11024 @itemx maint print msymbols @var{filename}
11025 Write a dump of debugging symbol data into the file @var{filename}.
11026 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11027 symbols with debugging data are included. If you use @samp{maint print
11028 symbols}, @value{GDBN} includes all the symbols for which it has already
11029 collected full details: that is, @var{filename} reflects symbols for
11030 only those files whose symbols @value{GDBN} has read. You can use the
11031 command @code{info sources} to find out which files these are. If you
11032 use @samp{maint print psymbols} instead, the dump shows information about
11033 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11034 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11035 @samp{maint print msymbols} dumps just the minimal symbol information
11036 required for each object file from which @value{GDBN} has read some symbols.
11037 @xref{Files, ,Commands to specify files}, for a discussion of how
11038 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11040 @kindex maint info symtabs
11041 @kindex maint info psymtabs
11042 @cindex listing @value{GDBN}'s internal symbol tables
11043 @cindex symbol tables, listing @value{GDBN}'s internal
11044 @cindex full symbol tables, listing @value{GDBN}'s internal
11045 @cindex partial symbol tables, listing @value{GDBN}'s internal
11046 @item maint info symtabs @r{[} @var{regexp} @r{]}
11047 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11049 List the @code{struct symtab} or @code{struct partial_symtab}
11050 structures whose names match @var{regexp}. If @var{regexp} is not
11051 given, list them all. The output includes expressions which you can
11052 copy into a @value{GDBN} debugging this one to examine a particular
11053 structure in more detail. For example:
11056 (@value{GDBP}) maint info psymtabs dwarf2read
11057 @{ objfile /home/gnu/build/gdb/gdb
11058 ((struct objfile *) 0x82e69d0)
11059 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11060 ((struct partial_symtab *) 0x8474b10)
11063 text addresses 0x814d3c8 -- 0x8158074
11064 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11065 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11066 dependencies (none)
11069 (@value{GDBP}) maint info symtabs
11073 We see that there is one partial symbol table whose filename contains
11074 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11075 and we see that @value{GDBN} has not read in any symtabs yet at all.
11076 If we set a breakpoint on a function, that will cause @value{GDBN} to
11077 read the symtab for the compilation unit containing that function:
11080 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11081 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11083 (@value{GDBP}) maint info symtabs
11084 @{ objfile /home/gnu/build/gdb/gdb
11085 ((struct objfile *) 0x82e69d0)
11086 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11087 ((struct symtab *) 0x86c1f38)
11090 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11091 debugformat DWARF 2
11100 @chapter Altering Execution
11102 Once you think you have found an error in your program, you might want to
11103 find out for certain whether correcting the apparent error would lead to
11104 correct results in the rest of the run. You can find the answer by
11105 experiment, using the @value{GDBN} features for altering execution of the
11108 For example, you can store new values into variables or memory
11109 locations, give your program a signal, restart it at a different
11110 address, or even return prematurely from a function.
11113 * Assignment:: Assignment to variables
11114 * Jumping:: Continuing at a different address
11115 * Signaling:: Giving your program a signal
11116 * Returning:: Returning from a function
11117 * Calling:: Calling your program's functions
11118 * Patching:: Patching your program
11122 @section Assignment to variables
11125 @cindex setting variables
11126 To alter the value of a variable, evaluate an assignment expression.
11127 @xref{Expressions, ,Expressions}. For example,
11134 stores the value 4 into the variable @code{x}, and then prints the
11135 value of the assignment expression (which is 4).
11136 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11137 information on operators in supported languages.
11139 @kindex set variable
11140 @cindex variables, setting
11141 If you are not interested in seeing the value of the assignment, use the
11142 @code{set} command instead of the @code{print} command. @code{set} is
11143 really the same as @code{print} except that the expression's value is
11144 not printed and is not put in the value history (@pxref{Value History,
11145 ,Value history}). The expression is evaluated only for its effects.
11147 If the beginning of the argument string of the @code{set} command
11148 appears identical to a @code{set} subcommand, use the @code{set
11149 variable} command instead of just @code{set}. This command is identical
11150 to @code{set} except for its lack of subcommands. For example, if your
11151 program has a variable @code{width}, you get an error if you try to set
11152 a new value with just @samp{set width=13}, because @value{GDBN} has the
11153 command @code{set width}:
11156 (@value{GDBP}) whatis width
11158 (@value{GDBP}) p width
11160 (@value{GDBP}) set width=47
11161 Invalid syntax in expression.
11165 The invalid expression, of course, is @samp{=47}. In
11166 order to actually set the program's variable @code{width}, use
11169 (@value{GDBP}) set var width=47
11172 Because the @code{set} command has many subcommands that can conflict
11173 with the names of program variables, it is a good idea to use the
11174 @code{set variable} command instead of just @code{set}. For example, if
11175 your program has a variable @code{g}, you run into problems if you try
11176 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11177 the command @code{set gnutarget}, abbreviated @code{set g}:
11181 (@value{GDBP}) whatis g
11185 (@value{GDBP}) set g=4
11189 The program being debugged has been started already.
11190 Start it from the beginning? (y or n) y
11191 Starting program: /home/smith/cc_progs/a.out
11192 "/home/smith/cc_progs/a.out": can't open to read symbols:
11193 Invalid bfd target.
11194 (@value{GDBP}) show g
11195 The current BFD target is "=4".
11200 The program variable @code{g} did not change, and you silently set the
11201 @code{gnutarget} to an invalid value. In order to set the variable
11205 (@value{GDBP}) set var g=4
11208 @value{GDBN} allows more implicit conversions in assignments than C; you can
11209 freely store an integer value into a pointer variable or vice versa,
11210 and you can convert any structure to any other structure that is the
11211 same length or shorter.
11212 @comment FIXME: how do structs align/pad in these conversions?
11213 @comment /doc@cygnus.com 18dec1990
11215 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11216 construct to generate a value of specified type at a specified address
11217 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11218 to memory location @code{0x83040} as an integer (which implies a certain size
11219 and representation in memory), and
11222 set @{int@}0x83040 = 4
11226 stores the value 4 into that memory location.
11229 @section Continuing at a different address
11231 Ordinarily, when you continue your program, you do so at the place where
11232 it stopped, with the @code{continue} command. You can instead continue at
11233 an address of your own choosing, with the following commands:
11237 @item jump @var{linespec}
11238 Resume execution at line @var{linespec}. Execution stops again
11239 immediately if there is a breakpoint there. @xref{List, ,Printing
11240 source lines}, for a description of the different forms of
11241 @var{linespec}. It is common practice to use the @code{tbreak} command
11242 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11245 The @code{jump} command does not change the current stack frame, or
11246 the stack pointer, or the contents of any memory location or any
11247 register other than the program counter. If line @var{linespec} is in
11248 a different function from the one currently executing, the results may
11249 be bizarre if the two functions expect different patterns of arguments or
11250 of local variables. For this reason, the @code{jump} command requests
11251 confirmation if the specified line is not in the function currently
11252 executing. However, even bizarre results are predictable if you are
11253 well acquainted with the machine-language code of your program.
11255 @item jump *@var{address}
11256 Resume execution at the instruction at address @var{address}.
11259 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11260 On many systems, you can get much the same effect as the @code{jump}
11261 command by storing a new value into the register @code{$pc}. The
11262 difference is that this does not start your program running; it only
11263 changes the address of where it @emph{will} run when you continue. For
11271 makes the next @code{continue} command or stepping command execute at
11272 address @code{0x485}, rather than at the address where your program stopped.
11273 @xref{Continuing and Stepping, ,Continuing and stepping}.
11275 The most common occasion to use the @code{jump} command is to back
11276 up---perhaps with more breakpoints set---over a portion of a program
11277 that has already executed, in order to examine its execution in more
11282 @section Giving your program a signal
11283 @cindex deliver a signal to a program
11287 @item signal @var{signal}
11288 Resume execution where your program stopped, but immediately give it the
11289 signal @var{signal}. @var{signal} can be the name or the number of a
11290 signal. For example, on many systems @code{signal 2} and @code{signal
11291 SIGINT} are both ways of sending an interrupt signal.
11293 Alternatively, if @var{signal} is zero, continue execution without
11294 giving a signal. This is useful when your program stopped on account of
11295 a signal and would ordinary see the signal when resumed with the
11296 @code{continue} command; @samp{signal 0} causes it to resume without a
11299 @code{signal} does not repeat when you press @key{RET} a second time
11300 after executing the command.
11304 Invoking the @code{signal} command is not the same as invoking the
11305 @code{kill} utility from the shell. Sending a signal with @code{kill}
11306 causes @value{GDBN} to decide what to do with the signal depending on
11307 the signal handling tables (@pxref{Signals}). The @code{signal} command
11308 passes the signal directly to your program.
11312 @section Returning from a function
11315 @cindex returning from a function
11318 @itemx return @var{expression}
11319 You can cancel execution of a function call with the @code{return}
11320 command. If you give an
11321 @var{expression} argument, its value is used as the function's return
11325 When you use @code{return}, @value{GDBN} discards the selected stack frame
11326 (and all frames within it). You can think of this as making the
11327 discarded frame return prematurely. If you wish to specify a value to
11328 be returned, give that value as the argument to @code{return}.
11330 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11331 frame}), and any other frames inside of it, leaving its caller as the
11332 innermost remaining frame. That frame becomes selected. The
11333 specified value is stored in the registers used for returning values
11336 The @code{return} command does not resume execution; it leaves the
11337 program stopped in the state that would exist if the function had just
11338 returned. In contrast, the @code{finish} command (@pxref{Continuing
11339 and Stepping, ,Continuing and stepping}) resumes execution until the
11340 selected stack frame returns naturally.
11343 @section Calling program functions
11346 @cindex calling functions
11347 @cindex inferior functions, calling
11348 @item print @var{expr}
11349 Evaluate the expression @var{expr} and display the resulting value.
11350 @var{expr} may include calls to functions in the program being
11354 @item call @var{expr}
11355 Evaluate the expression @var{expr} without displaying @code{void}
11358 You can use this variant of the @code{print} command if you want to
11359 execute a function from your program that does not return anything
11360 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11361 with @code{void} returned values that @value{GDBN} will otherwise
11362 print. If the result is not void, it is printed and saved in the
11366 It is possible for the function you call via the @code{print} or
11367 @code{call} command to generate a signal (e.g., if there's a bug in
11368 the function, or if you passed it incorrect arguments). What happens
11369 in that case is controlled by the @code{set unwindonsignal} command.
11372 @item set unwindonsignal
11373 @kindex set unwindonsignal
11374 @cindex unwind stack in called functions
11375 @cindex call dummy stack unwinding
11376 Set unwinding of the stack if a signal is received while in a function
11377 that @value{GDBN} called in the program being debugged. If set to on,
11378 @value{GDBN} unwinds the stack it created for the call and restores
11379 the context to what it was before the call. If set to off (the
11380 default), @value{GDBN} stops in the frame where the signal was
11383 @item show unwindonsignal
11384 @kindex show unwindonsignal
11385 Show the current setting of stack unwinding in the functions called by
11389 @cindex weak alias functions
11390 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11391 for another function. In such case, @value{GDBN} might not pick up
11392 the type information, including the types of the function arguments,
11393 which causes @value{GDBN} to call the inferior function incorrectly.
11394 As a result, the called function will function erroneously and may
11395 even crash. A solution to that is to use the name of the aliased
11399 @section Patching programs
11401 @cindex patching binaries
11402 @cindex writing into executables
11403 @cindex writing into corefiles
11405 By default, @value{GDBN} opens the file containing your program's
11406 executable code (or the corefile) read-only. This prevents accidental
11407 alterations to machine code; but it also prevents you from intentionally
11408 patching your program's binary.
11410 If you'd like to be able to patch the binary, you can specify that
11411 explicitly with the @code{set write} command. For example, you might
11412 want to turn on internal debugging flags, or even to make emergency
11418 @itemx set write off
11419 If you specify @samp{set write on}, @value{GDBN} opens executable and
11420 core files for both reading and writing; if you specify @samp{set write
11421 off} (the default), @value{GDBN} opens them read-only.
11423 If you have already loaded a file, you must load it again (using the
11424 @code{exec-file} or @code{core-file} command) after changing @code{set
11425 write}, for your new setting to take effect.
11429 Display whether executable files and core files are opened for writing
11430 as well as reading.
11434 @chapter @value{GDBN} Files
11436 @value{GDBN} needs to know the file name of the program to be debugged,
11437 both in order to read its symbol table and in order to start your
11438 program. To debug a core dump of a previous run, you must also tell
11439 @value{GDBN} the name of the core dump file.
11442 * Files:: Commands to specify files
11443 * Separate Debug Files:: Debugging information in separate files
11444 * Symbol Errors:: Errors reading symbol files
11448 @section Commands to specify files
11450 @cindex symbol table
11451 @cindex core dump file
11453 You may want to specify executable and core dump file names. The usual
11454 way to do this is at start-up time, using the arguments to
11455 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11456 Out of @value{GDBN}}).
11458 Occasionally it is necessary to change to a different file during a
11459 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11460 specify a file you want to use. Or you are debugging a remote target
11461 via @code{gdbserver} (@pxref{Server, file}). In these situations the
11462 @value{GDBN} commands to specify new files are useful.
11465 @cindex executable file
11467 @item file @var{filename}
11468 Use @var{filename} as the program to be debugged. It is read for its
11469 symbols and for the contents of pure memory. It is also the program
11470 executed when you use the @code{run} command. If you do not specify a
11471 directory and the file is not found in the @value{GDBN} working directory,
11472 @value{GDBN} uses the environment variable @code{PATH} as a list of
11473 directories to search, just as the shell does when looking for a program
11474 to run. You can change the value of this variable, for both @value{GDBN}
11475 and your program, using the @code{path} command.
11477 @cindex unlinked object files
11478 @cindex patching object files
11479 You can load unlinked object @file{.o} files into @value{GDBN} using
11480 the @code{file} command. You will not be able to ``run'' an object
11481 file, but you can disassemble functions and inspect variables. Also,
11482 if the underlying BFD functionality supports it, you could use
11483 @kbd{gdb -write} to patch object files using this technique. Note
11484 that @value{GDBN} can neither interpret nor modify relocations in this
11485 case, so branches and some initialized variables will appear to go to
11486 the wrong place. But this feature is still handy from time to time.
11489 @code{file} with no argument makes @value{GDBN} discard any information it
11490 has on both executable file and the symbol table.
11493 @item exec-file @r{[} @var{filename} @r{]}
11494 Specify that the program to be run (but not the symbol table) is found
11495 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11496 if necessary to locate your program. Omitting @var{filename} means to
11497 discard information on the executable file.
11499 @kindex symbol-file
11500 @item symbol-file @r{[} @var{filename} @r{]}
11501 Read symbol table information from file @var{filename}. @code{PATH} is
11502 searched when necessary. Use the @code{file} command to get both symbol
11503 table and program to run from the same file.
11505 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11506 program's symbol table.
11508 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11509 some breakpoints and auto-display expressions. This is because they may
11510 contain pointers to the internal data recording symbols and data types,
11511 which are part of the old symbol table data being discarded inside
11514 @code{symbol-file} does not repeat if you press @key{RET} again after
11517 When @value{GDBN} is configured for a particular environment, it
11518 understands debugging information in whatever format is the standard
11519 generated for that environment; you may use either a @sc{gnu} compiler, or
11520 other compilers that adhere to the local conventions.
11521 Best results are usually obtained from @sc{gnu} compilers; for example,
11522 using @code{@value{NGCC}} you can generate debugging information for
11525 For most kinds of object files, with the exception of old SVR3 systems
11526 using COFF, the @code{symbol-file} command does not normally read the
11527 symbol table in full right away. Instead, it scans the symbol table
11528 quickly to find which source files and which symbols are present. The
11529 details are read later, one source file at a time, as they are needed.
11531 The purpose of this two-stage reading strategy is to make @value{GDBN}
11532 start up faster. For the most part, it is invisible except for
11533 occasional pauses while the symbol table details for a particular source
11534 file are being read. (The @code{set verbose} command can turn these
11535 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11536 warnings and messages}.)
11538 We have not implemented the two-stage strategy for COFF yet. When the
11539 symbol table is stored in COFF format, @code{symbol-file} reads the
11540 symbol table data in full right away. Note that ``stabs-in-COFF''
11541 still does the two-stage strategy, since the debug info is actually
11545 @cindex reading symbols immediately
11546 @cindex symbols, reading immediately
11547 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11548 @itemx file @var{filename} @r{[} -readnow @r{]}
11549 You can override the @value{GDBN} two-stage strategy for reading symbol
11550 tables by using the @samp{-readnow} option with any of the commands that
11551 load symbol table information, if you want to be sure @value{GDBN} has the
11552 entire symbol table available.
11554 @c FIXME: for now no mention of directories, since this seems to be in
11555 @c flux. 13mar1992 status is that in theory GDB would look either in
11556 @c current dir or in same dir as myprog; but issues like competing
11557 @c GDB's, or clutter in system dirs, mean that in practice right now
11558 @c only current dir is used. FFish says maybe a special GDB hierarchy
11559 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11563 @item core-file @r{[}@var{filename}@r{]}
11565 Specify the whereabouts of a core dump file to be used as the ``contents
11566 of memory''. Traditionally, core files contain only some parts of the
11567 address space of the process that generated them; @value{GDBN} can access the
11568 executable file itself for other parts.
11570 @code{core-file} with no argument specifies that no core file is
11573 Note that the core file is ignored when your program is actually running
11574 under @value{GDBN}. So, if you have been running your program and you
11575 wish to debug a core file instead, you must kill the subprocess in which
11576 the program is running. To do this, use the @code{kill} command
11577 (@pxref{Kill Process, ,Killing the child process}).
11579 @kindex add-symbol-file
11580 @cindex dynamic linking
11581 @item add-symbol-file @var{filename} @var{address}
11582 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11583 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11584 The @code{add-symbol-file} command reads additional symbol table
11585 information from the file @var{filename}. You would use this command
11586 when @var{filename} has been dynamically loaded (by some other means)
11587 into the program that is running. @var{address} should be the memory
11588 address at which the file has been loaded; @value{GDBN} cannot figure
11589 this out for itself. You can additionally specify an arbitrary number
11590 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11591 section name and base address for that section. You can specify any
11592 @var{address} as an expression.
11594 The symbol table of the file @var{filename} is added to the symbol table
11595 originally read with the @code{symbol-file} command. You can use the
11596 @code{add-symbol-file} command any number of times; the new symbol data
11597 thus read keeps adding to the old. To discard all old symbol data
11598 instead, use the @code{symbol-file} command without any arguments.
11600 @cindex relocatable object files, reading symbols from
11601 @cindex object files, relocatable, reading symbols from
11602 @cindex reading symbols from relocatable object files
11603 @cindex symbols, reading from relocatable object files
11604 @cindex @file{.o} files, reading symbols from
11605 Although @var{filename} is typically a shared library file, an
11606 executable file, or some other object file which has been fully
11607 relocated for loading into a process, you can also load symbolic
11608 information from relocatable @file{.o} files, as long as:
11612 the file's symbolic information refers only to linker symbols defined in
11613 that file, not to symbols defined by other object files,
11615 every section the file's symbolic information refers to has actually
11616 been loaded into the inferior, as it appears in the file, and
11618 you can determine the address at which every section was loaded, and
11619 provide these to the @code{add-symbol-file} command.
11623 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11624 relocatable files into an already running program; such systems
11625 typically make the requirements above easy to meet. However, it's
11626 important to recognize that many native systems use complex link
11627 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11628 assembly, for example) that make the requirements difficult to meet. In
11629 general, one cannot assume that using @code{add-symbol-file} to read a
11630 relocatable object file's symbolic information will have the same effect
11631 as linking the relocatable object file into the program in the normal
11634 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11636 @kindex add-symbol-file-from-memory
11637 @cindex @code{syscall DSO}
11638 @cindex load symbols from memory
11639 @item add-symbol-file-from-memory @var{address}
11640 Load symbols from the given @var{address} in a dynamically loaded
11641 object file whose image is mapped directly into the inferior's memory.
11642 For example, the Linux kernel maps a @code{syscall DSO} into each
11643 process's address space; this DSO provides kernel-specific code for
11644 some system calls. The argument can be any expression whose
11645 evaluation yields the address of the file's shared object file header.
11646 For this command to work, you must have used @code{symbol-file} or
11647 @code{exec-file} commands in advance.
11649 @kindex add-shared-symbol-files
11651 @item add-shared-symbol-files @var{library-file}
11652 @itemx assf @var{library-file}
11653 The @code{add-shared-symbol-files} command can currently be used only
11654 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11655 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11656 @value{GDBN} automatically looks for shared libraries, however if
11657 @value{GDBN} does not find yours, you can invoke
11658 @code{add-shared-symbol-files}. It takes one argument: the shared
11659 library's file name. @code{assf} is a shorthand alias for
11660 @code{add-shared-symbol-files}.
11663 @item section @var{section} @var{addr}
11664 The @code{section} command changes the base address of the named
11665 @var{section} of the exec file to @var{addr}. This can be used if the
11666 exec file does not contain section addresses, (such as in the
11667 @code{a.out} format), or when the addresses specified in the file
11668 itself are wrong. Each section must be changed separately. The
11669 @code{info files} command, described below, lists all the sections and
11673 @kindex info target
11676 @code{info files} and @code{info target} are synonymous; both print the
11677 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11678 including the names of the executable and core dump files currently in
11679 use by @value{GDBN}, and the files from which symbols were loaded. The
11680 command @code{help target} lists all possible targets rather than
11683 @kindex maint info sections
11684 @item maint info sections
11685 Another command that can give you extra information about program sections
11686 is @code{maint info sections}. In addition to the section information
11687 displayed by @code{info files}, this command displays the flags and file
11688 offset of each section in the executable and core dump files. In addition,
11689 @code{maint info sections} provides the following command options (which
11690 may be arbitrarily combined):
11694 Display sections for all loaded object files, including shared libraries.
11695 @item @var{sections}
11696 Display info only for named @var{sections}.
11697 @item @var{section-flags}
11698 Display info only for sections for which @var{section-flags} are true.
11699 The section flags that @value{GDBN} currently knows about are:
11702 Section will have space allocated in the process when loaded.
11703 Set for all sections except those containing debug information.
11705 Section will be loaded from the file into the child process memory.
11706 Set for pre-initialized code and data, clear for @code{.bss} sections.
11708 Section needs to be relocated before loading.
11710 Section cannot be modified by the child process.
11712 Section contains executable code only.
11714 Section contains data only (no executable code).
11716 Section will reside in ROM.
11718 Section contains data for constructor/destructor lists.
11720 Section is not empty.
11722 An instruction to the linker to not output the section.
11723 @item COFF_SHARED_LIBRARY
11724 A notification to the linker that the section contains
11725 COFF shared library information.
11727 Section contains common symbols.
11730 @kindex set trust-readonly-sections
11731 @cindex read-only sections
11732 @item set trust-readonly-sections on
11733 Tell @value{GDBN} that readonly sections in your object file
11734 really are read-only (i.e.@: that their contents will not change).
11735 In that case, @value{GDBN} can fetch values from these sections
11736 out of the object file, rather than from the target program.
11737 For some targets (notably embedded ones), this can be a significant
11738 enhancement to debugging performance.
11740 The default is off.
11742 @item set trust-readonly-sections off
11743 Tell @value{GDBN} not to trust readonly sections. This means that
11744 the contents of the section might change while the program is running,
11745 and must therefore be fetched from the target when needed.
11747 @item show trust-readonly-sections
11748 Show the current setting of trusting readonly sections.
11751 All file-specifying commands allow both absolute and relative file names
11752 as arguments. @value{GDBN} always converts the file name to an absolute file
11753 name and remembers it that way.
11755 @cindex shared libraries
11756 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11757 and IBM RS/6000 AIX shared libraries.
11759 @value{GDBN} automatically loads symbol definitions from shared libraries
11760 when you use the @code{run} command, or when you examine a core file.
11761 (Before you issue the @code{run} command, @value{GDBN} does not understand
11762 references to a function in a shared library, however---unless you are
11763 debugging a core file).
11765 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11766 automatically loads the symbols at the time of the @code{shl_load} call.
11768 @c FIXME: some @value{GDBN} release may permit some refs to undef
11769 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11770 @c FIXME...lib; check this from time to time when updating manual
11772 There are times, however, when you may wish to not automatically load
11773 symbol definitions from shared libraries, such as when they are
11774 particularly large or there are many of them.
11776 To control the automatic loading of shared library symbols, use the
11780 @kindex set auto-solib-add
11781 @item set auto-solib-add @var{mode}
11782 If @var{mode} is @code{on}, symbols from all shared object libraries
11783 will be loaded automatically when the inferior begins execution, you
11784 attach to an independently started inferior, or when the dynamic linker
11785 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11786 is @code{off}, symbols must be loaded manually, using the
11787 @code{sharedlibrary} command. The default value is @code{on}.
11789 @cindex memory used for symbol tables
11790 If your program uses lots of shared libraries with debug info that
11791 takes large amounts of memory, you can decrease the @value{GDBN}
11792 memory footprint by preventing it from automatically loading the
11793 symbols from shared libraries. To that end, type @kbd{set
11794 auto-solib-add off} before running the inferior, then load each
11795 library whose debug symbols you do need with @kbd{sharedlibrary
11796 @var{regexp}}, where @var{regexp} is a regular expression that matches
11797 the libraries whose symbols you want to be loaded.
11799 @kindex show auto-solib-add
11800 @item show auto-solib-add
11801 Display the current autoloading mode.
11804 @cindex load shared library
11805 To explicitly load shared library symbols, use the @code{sharedlibrary}
11809 @kindex info sharedlibrary
11812 @itemx info sharedlibrary
11813 Print the names of the shared libraries which are currently loaded.
11815 @kindex sharedlibrary
11817 @item sharedlibrary @var{regex}
11818 @itemx share @var{regex}
11819 Load shared object library symbols for files matching a
11820 Unix regular expression.
11821 As with files loaded automatically, it only loads shared libraries
11822 required by your program for a core file or after typing @code{run}. If
11823 @var{regex} is omitted all shared libraries required by your program are
11826 @item nosharedlibrary
11827 @kindex nosharedlibrary
11828 @cindex unload symbols from shared libraries
11829 Unload all shared object library symbols. This discards all symbols
11830 that have been loaded from all shared libraries. Symbols from shared
11831 libraries that were loaded by explicit user requests are not
11835 Sometimes you may wish that @value{GDBN} stops and gives you control
11836 when any of shared library events happen. Use the @code{set
11837 stop-on-solib-events} command for this:
11840 @item set stop-on-solib-events
11841 @kindex set stop-on-solib-events
11842 This command controls whether @value{GDBN} should give you control
11843 when the dynamic linker notifies it about some shared library event.
11844 The most common event of interest is loading or unloading of a new
11847 @item show stop-on-solib-events
11848 @kindex show stop-on-solib-events
11849 Show whether @value{GDBN} stops and gives you control when shared
11850 library events happen.
11853 Shared libraries are also supported in many cross or remote debugging
11854 configurations. A copy of the target's libraries need to be present on the
11855 host system; they need to be the same as the target libraries, although the
11856 copies on the target can be stripped as long as the copies on the host are
11859 @cindex where to look for shared libraries
11860 For remote debugging, you need to tell @value{GDBN} where the target
11861 libraries are, so that it can load the correct copies---otherwise, it
11862 may try to load the host's libraries. @value{GDBN} has two variables
11863 to specify the search directories for target libraries.
11866 @cindex prefix for shared library file names
11867 @cindex system root, alternate
11868 @kindex set solib-absolute-prefix
11869 @kindex set sysroot
11870 @item set sysroot @var{path}
11871 Use @var{path} as the system root for the program being debugged. Any
11872 absolute shared library paths will be prefixed with @var{path}; many
11873 runtime loaders store the absolute paths to the shared library in the
11874 target program's memory. If you use @code{set sysroot} to find shared
11875 libraries, they need to be laid out in the same way that they are on
11876 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
11879 The @code{set solib-absolute-prefix} command is an alias for @code{set
11882 @cindex default system root
11883 @cindex @samp{--with-sysroot}
11884 You can set the default system root by using the configure-time
11885 @samp{--with-sysroot} option. If the system root is inside
11886 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
11887 @samp{--exec-prefix}), then the default system root will be updated
11888 automatically if the installed @value{GDBN} is moved to a new
11891 @kindex show sysroot
11893 Display the current shared library prefix.
11895 @kindex set solib-search-path
11896 @item set solib-search-path @var{path}
11897 If this variable is set, @var{path} is a colon-separated list of
11898 directories to search for shared libraries. @samp{solib-search-path}
11899 is used after @samp{sysroot} fails to locate the library, or if the
11900 path to the library is relative instead of absolute. If you want to
11901 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
11902 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
11903 finding your host's libraries. @samp{sysroot} is preferred; setting
11904 it to a nonexistent directory may interfere with automatic loading
11905 of shared library symbols.
11907 @kindex show solib-search-path
11908 @item show solib-search-path
11909 Display the current shared library search path.
11913 @node Separate Debug Files
11914 @section Debugging Information in Separate Files
11915 @cindex separate debugging information files
11916 @cindex debugging information in separate files
11917 @cindex @file{.debug} subdirectories
11918 @cindex debugging information directory, global
11919 @cindex global debugging information directory
11921 @value{GDBN} allows you to put a program's debugging information in a
11922 file separate from the executable itself, in a way that allows
11923 @value{GDBN} to find and load the debugging information automatically.
11924 Since debugging information can be very large --- sometimes larger
11925 than the executable code itself --- some systems distribute debugging
11926 information for their executables in separate files, which users can
11927 install only when they need to debug a problem.
11929 If an executable's debugging information has been extracted to a
11930 separate file, the executable should contain a @dfn{debug link} giving
11931 the name of the debugging information file (with no directory
11932 components), and a checksum of its contents. (The exact form of a
11933 debug link is described below.) If the full name of the directory
11934 containing the executable is @var{execdir}, and the executable has a
11935 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11936 will automatically search for the debugging information file in three
11941 the directory containing the executable file (that is, it will look
11942 for a file named @file{@var{execdir}/@var{debugfile}},
11944 a subdirectory of that directory named @file{.debug} (that is, the
11945 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11947 a subdirectory of the global debug file directory that includes the
11948 executable's full path, and the name from the link (that is, the file
11949 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11950 @var{globaldebugdir} is the global debug file directory, and
11951 @var{execdir} has been turned into a relative path).
11954 @value{GDBN} checks under each of these names for a debugging
11955 information file whose checksum matches that given in the link, and
11956 reads the debugging information from the first one it finds.
11958 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11959 which has a link containing the name @file{ls.debug}, and the global
11960 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11961 for debug information in @file{/usr/bin/ls.debug},
11962 @file{/usr/bin/.debug/ls.debug}, and
11963 @file{/usr/lib/debug/usr/bin/ls.debug}.
11965 You can set the global debugging info directory's name, and view the
11966 name @value{GDBN} is currently using.
11970 @kindex set debug-file-directory
11971 @item set debug-file-directory @var{directory}
11972 Set the directory which @value{GDBN} searches for separate debugging
11973 information files to @var{directory}.
11975 @kindex show debug-file-directory
11976 @item show debug-file-directory
11977 Show the directory @value{GDBN} searches for separate debugging
11982 @cindex @code{.gnu_debuglink} sections
11983 @cindex debug links
11984 A debug link is a special section of the executable file named
11985 @code{.gnu_debuglink}. The section must contain:
11989 A filename, with any leading directory components removed, followed by
11992 zero to three bytes of padding, as needed to reach the next four-byte
11993 boundary within the section, and
11995 a four-byte CRC checksum, stored in the same endianness used for the
11996 executable file itself. The checksum is computed on the debugging
11997 information file's full contents by the function given below, passing
11998 zero as the @var{crc} argument.
12001 Any executable file format can carry a debug link, as long as it can
12002 contain a section named @code{.gnu_debuglink} with the contents
12005 The debugging information file itself should be an ordinary
12006 executable, containing a full set of linker symbols, sections, and
12007 debugging information. The sections of the debugging information file
12008 should have the same names, addresses and sizes as the original file,
12009 but they need not contain any data --- much like a @code{.bss} section
12010 in an ordinary executable.
12012 As of December 2002, there is no standard GNU utility to produce
12013 separated executable / debugging information file pairs. Ulrich
12014 Drepper's @file{elfutils} package, starting with version 0.53,
12015 contains a version of the @code{strip} command such that the command
12016 @kbd{strip foo -f foo.debug} removes the debugging information from
12017 the executable file @file{foo}, places it in the file
12018 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
12020 Since there are many different ways to compute CRC's (different
12021 polynomials, reversals, byte ordering, etc.), the simplest way to
12022 describe the CRC used in @code{.gnu_debuglink} sections is to give the
12023 complete code for a function that computes it:
12025 @kindex gnu_debuglink_crc32
12028 gnu_debuglink_crc32 (unsigned long crc,
12029 unsigned char *buf, size_t len)
12031 static const unsigned long crc32_table[256] =
12033 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12034 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12035 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12036 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12037 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12038 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12039 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12040 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12041 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12042 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12043 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12044 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12045 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12046 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12047 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12048 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12049 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12050 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12051 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12052 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12053 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12054 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12055 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12056 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12057 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12058 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12059 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12060 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12061 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12062 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12063 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12064 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12065 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12066 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12067 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12068 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12069 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12070 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12071 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12072 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12073 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12074 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12075 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12076 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12077 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12078 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12079 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12080 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12081 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12082 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12083 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12086 unsigned char *end;
12088 crc = ~crc & 0xffffffff;
12089 for (end = buf + len; buf < end; ++buf)
12090 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12091 return ~crc & 0xffffffff;
12096 @node Symbol Errors
12097 @section Errors reading symbol files
12099 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12100 such as symbol types it does not recognize, or known bugs in compiler
12101 output. By default, @value{GDBN} does not notify you of such problems, since
12102 they are relatively common and primarily of interest to people
12103 debugging compilers. If you are interested in seeing information
12104 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12105 only one message about each such type of problem, no matter how many
12106 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12107 to see how many times the problems occur, with the @code{set
12108 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
12111 The messages currently printed, and their meanings, include:
12114 @item inner block not inside outer block in @var{symbol}
12116 The symbol information shows where symbol scopes begin and end
12117 (such as at the start of a function or a block of statements). This
12118 error indicates that an inner scope block is not fully contained
12119 in its outer scope blocks.
12121 @value{GDBN} circumvents the problem by treating the inner block as if it had
12122 the same scope as the outer block. In the error message, @var{symbol}
12123 may be shown as ``@code{(don't know)}'' if the outer block is not a
12126 @item block at @var{address} out of order
12128 The symbol information for symbol scope blocks should occur in
12129 order of increasing addresses. This error indicates that it does not
12132 @value{GDBN} does not circumvent this problem, and has trouble
12133 locating symbols in the source file whose symbols it is reading. (You
12134 can often determine what source file is affected by specifying
12135 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
12138 @item bad block start address patched
12140 The symbol information for a symbol scope block has a start address
12141 smaller than the address of the preceding source line. This is known
12142 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12144 @value{GDBN} circumvents the problem by treating the symbol scope block as
12145 starting on the previous source line.
12147 @item bad string table offset in symbol @var{n}
12150 Symbol number @var{n} contains a pointer into the string table which is
12151 larger than the size of the string table.
12153 @value{GDBN} circumvents the problem by considering the symbol to have the
12154 name @code{foo}, which may cause other problems if many symbols end up
12157 @item unknown symbol type @code{0x@var{nn}}
12159 The symbol information contains new data types that @value{GDBN} does
12160 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12161 uncomprehended information, in hexadecimal.
12163 @value{GDBN} circumvents the error by ignoring this symbol information.
12164 This usually allows you to debug your program, though certain symbols
12165 are not accessible. If you encounter such a problem and feel like
12166 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12167 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12168 and examine @code{*bufp} to see the symbol.
12170 @item stub type has NULL name
12172 @value{GDBN} could not find the full definition for a struct or class.
12174 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12175 The symbol information for a C@t{++} member function is missing some
12176 information that recent versions of the compiler should have output for
12179 @item info mismatch between compiler and debugger
12181 @value{GDBN} could not parse a type specification output by the compiler.
12186 @chapter Specifying a Debugging Target
12188 @cindex debugging target
12189 A @dfn{target} is the execution environment occupied by your program.
12191 Often, @value{GDBN} runs in the same host environment as your program;
12192 in that case, the debugging target is specified as a side effect when
12193 you use the @code{file} or @code{core} commands. When you need more
12194 flexibility---for example, running @value{GDBN} on a physically separate
12195 host, or controlling a standalone system over a serial port or a
12196 realtime system over a TCP/IP connection---you can use the @code{target}
12197 command to specify one of the target types configured for @value{GDBN}
12198 (@pxref{Target Commands, ,Commands for managing targets}).
12200 @cindex target architecture
12201 It is possible to build @value{GDBN} for several different @dfn{target
12202 architectures}. When @value{GDBN} is built like that, you can choose
12203 one of the available architectures with the @kbd{set architecture}
12207 @kindex set architecture
12208 @kindex show architecture
12209 @item set architecture @var{arch}
12210 This command sets the current target architecture to @var{arch}. The
12211 value of @var{arch} can be @code{"auto"}, in addition to one of the
12212 supported architectures.
12214 @item show architecture
12215 Show the current target architecture.
12217 @item set processor
12219 @kindex set processor
12220 @kindex show processor
12221 These are alias commands for, respectively, @code{set architecture}
12222 and @code{show architecture}.
12226 * Active Targets:: Active targets
12227 * Target Commands:: Commands for managing targets
12228 * Byte Order:: Choosing target byte order
12229 * Remote:: Remote debugging
12233 @node Active Targets
12234 @section Active targets
12236 @cindex stacking targets
12237 @cindex active targets
12238 @cindex multiple targets
12240 There are three classes of targets: processes, core files, and
12241 executable files. @value{GDBN} can work concurrently on up to three
12242 active targets, one in each class. This allows you to (for example)
12243 start a process and inspect its activity without abandoning your work on
12246 For example, if you execute @samp{gdb a.out}, then the executable file
12247 @code{a.out} is the only active target. If you designate a core file as
12248 well---presumably from a prior run that crashed and coredumped---then
12249 @value{GDBN} has two active targets and uses them in tandem, looking
12250 first in the corefile target, then in the executable file, to satisfy
12251 requests for memory addresses. (Typically, these two classes of target
12252 are complementary, since core files contain only a program's
12253 read-write memory---variables and so on---plus machine status, while
12254 executable files contain only the program text and initialized data.)
12256 When you type @code{run}, your executable file becomes an active process
12257 target as well. When a process target is active, all @value{GDBN}
12258 commands requesting memory addresses refer to that target; addresses in
12259 an active core file or executable file target are obscured while the
12260 process target is active.
12262 Use the @code{core-file} and @code{exec-file} commands to select a new
12263 core file or executable target (@pxref{Files, ,Commands to specify
12264 files}). To specify as a target a process that is already running, use
12265 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
12268 @node Target Commands
12269 @section Commands for managing targets
12272 @item target @var{type} @var{parameters}
12273 Connects the @value{GDBN} host environment to a target machine or
12274 process. A target is typically a protocol for talking to debugging
12275 facilities. You use the argument @var{type} to specify the type or
12276 protocol of the target machine.
12278 Further @var{parameters} are interpreted by the target protocol, but
12279 typically include things like device names or host names to connect
12280 with, process numbers, and baud rates.
12282 The @code{target} command does not repeat if you press @key{RET} again
12283 after executing the command.
12285 @kindex help target
12287 Displays the names of all targets available. To display targets
12288 currently selected, use either @code{info target} or @code{info files}
12289 (@pxref{Files, ,Commands to specify files}).
12291 @item help target @var{name}
12292 Describe a particular target, including any parameters necessary to
12295 @kindex set gnutarget
12296 @item set gnutarget @var{args}
12297 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12298 knows whether it is reading an @dfn{executable},
12299 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12300 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12301 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12304 @emph{Warning:} To specify a file format with @code{set gnutarget},
12305 you must know the actual BFD name.
12309 @xref{Files, , Commands to specify files}.
12311 @kindex show gnutarget
12312 @item show gnutarget
12313 Use the @code{show gnutarget} command to display what file format
12314 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12315 @value{GDBN} will determine the file format for each file automatically,
12316 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12319 @cindex common targets
12320 Here are some common targets (available, or not, depending on the GDB
12325 @item target exec @var{program}
12326 @cindex executable file target
12327 An executable file. @samp{target exec @var{program}} is the same as
12328 @samp{exec-file @var{program}}.
12330 @item target core @var{filename}
12331 @cindex core dump file target
12332 A core dump file. @samp{target core @var{filename}} is the same as
12333 @samp{core-file @var{filename}}.
12335 @item target remote @var{medium}
12336 @cindex remote target
12337 A remote system connected to @value{GDBN} via a serial line or network
12338 connection. This command tells @value{GDBN} to use its own remote
12339 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12341 For example, if you have a board connected to @file{/dev/ttya} on the
12342 machine running @value{GDBN}, you could say:
12345 target remote /dev/ttya
12348 @code{target remote} supports the @code{load} command. This is only
12349 useful if you have some other way of getting the stub to the target
12350 system, and you can put it somewhere in memory where it won't get
12351 clobbered by the download.
12354 @cindex built-in simulator target
12355 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12363 works; however, you cannot assume that a specific memory map, device
12364 drivers, or even basic I/O is available, although some simulators do
12365 provide these. For info about any processor-specific simulator details,
12366 see the appropriate section in @ref{Embedded Processors, ,Embedded
12371 Some configurations may include these targets as well:
12375 @item target nrom @var{dev}
12376 @cindex NetROM ROM emulator target
12377 NetROM ROM emulator. This target only supports downloading.
12381 Different targets are available on different configurations of @value{GDBN};
12382 your configuration may have more or fewer targets.
12384 Many remote targets require you to download the executable's code once
12385 you've successfully established a connection. You may wish to control
12386 various aspects of this process.
12391 @kindex set hash@r{, for remote monitors}
12392 @cindex hash mark while downloading
12393 This command controls whether a hash mark @samp{#} is displayed while
12394 downloading a file to the remote monitor. If on, a hash mark is
12395 displayed after each S-record is successfully downloaded to the
12399 @kindex show hash@r{, for remote monitors}
12400 Show the current status of displaying the hash mark.
12402 @item set debug monitor
12403 @kindex set debug monitor
12404 @cindex display remote monitor communications
12405 Enable or disable display of communications messages between
12406 @value{GDBN} and the remote monitor.
12408 @item show debug monitor
12409 @kindex show debug monitor
12410 Show the current status of displaying communications between
12411 @value{GDBN} and the remote monitor.
12416 @kindex load @var{filename}
12417 @item load @var{filename}
12418 Depending on what remote debugging facilities are configured into
12419 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12420 is meant to make @var{filename} (an executable) available for debugging
12421 on the remote system---by downloading, or dynamic linking, for example.
12422 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12423 the @code{add-symbol-file} command.
12425 If your @value{GDBN} does not have a @code{load} command, attempting to
12426 execute it gets the error message ``@code{You can't do that when your
12427 target is @dots{}}''
12429 The file is loaded at whatever address is specified in the executable.
12430 For some object file formats, you can specify the load address when you
12431 link the program; for other formats, like a.out, the object file format
12432 specifies a fixed address.
12433 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12435 Depending on the remote side capabilities, @value{GDBN} may be able to
12436 load programs into flash memory.
12438 @code{load} does not repeat if you press @key{RET} again after using it.
12442 @section Choosing target byte order
12444 @cindex choosing target byte order
12445 @cindex target byte order
12447 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12448 offer the ability to run either big-endian or little-endian byte
12449 orders. Usually the executable or symbol will include a bit to
12450 designate the endian-ness, and you will not need to worry about
12451 which to use. However, you may still find it useful to adjust
12452 @value{GDBN}'s idea of processor endian-ness manually.
12456 @item set endian big
12457 Instruct @value{GDBN} to assume the target is big-endian.
12459 @item set endian little
12460 Instruct @value{GDBN} to assume the target is little-endian.
12462 @item set endian auto
12463 Instruct @value{GDBN} to use the byte order associated with the
12467 Display @value{GDBN}'s current idea of the target byte order.
12471 Note that these commands merely adjust interpretation of symbolic
12472 data on the host, and that they have absolutely no effect on the
12476 @section Remote debugging
12477 @cindex remote debugging
12479 If you are trying to debug a program running on a machine that cannot run
12480 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12481 For example, you might use remote debugging on an operating system kernel,
12482 or on a small system which does not have a general purpose operating system
12483 powerful enough to run a full-featured debugger.
12485 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12486 to make this work with particular debugging targets. In addition,
12487 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12488 but not specific to any particular target system) which you can use if you
12489 write the remote stubs---the code that runs on the remote system to
12490 communicate with @value{GDBN}.
12492 Other remote targets may be available in your
12493 configuration of @value{GDBN}; use @code{help target} to list them.
12495 Once you've connected to the remote target, @value{GDBN} allows you to
12496 send arbitrary commands to the remote monitor:
12499 @item remote @var{command}
12500 @kindex remote@r{, a command}
12501 @cindex send command to remote monitor
12502 Send an arbitrary @var{command} string to the remote monitor.
12506 @node Remote Debugging
12507 @chapter Debugging remote programs
12510 * Connecting:: Connecting to a remote target
12511 * Server:: Using the gdbserver program
12512 * Remote configuration:: Remote configuration
12513 * remote stub:: Implementing a remote stub
12517 @section Connecting to a remote target
12519 On the @value{GDBN} host machine, you will need an unstripped copy of
12520 your program, since @value{GDBN} needs symbol and debugging information.
12521 Start up @value{GDBN} as usual, using the name of the local copy of your
12522 program as the first argument.
12524 @cindex @code{target remote}
12525 @value{GDBN} can communicate with the target over a serial line, or
12526 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12527 each case, @value{GDBN} uses the same protocol for debugging your
12528 program; only the medium carrying the debugging packets varies. The
12529 @code{target remote} command establishes a connection to the target.
12530 Its arguments indicate which medium to use:
12534 @item target remote @var{serial-device}
12535 @cindex serial line, @code{target remote}
12536 Use @var{serial-device} to communicate with the target. For example,
12537 to use a serial line connected to the device named @file{/dev/ttyb}:
12540 target remote /dev/ttyb
12543 If you're using a serial line, you may want to give @value{GDBN} the
12544 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12545 (@pxref{Remote configuration, set remotebaud}) before the
12546 @code{target} command.
12548 @item target remote @code{@var{host}:@var{port}}
12549 @itemx target remote @code{tcp:@var{host}:@var{port}}
12550 @cindex @acronym{TCP} port, @code{target remote}
12551 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12552 The @var{host} may be either a host name or a numeric @acronym{IP}
12553 address; @var{port} must be a decimal number. The @var{host} could be
12554 the target machine itself, if it is directly connected to the net, or
12555 it might be a terminal server which in turn has a serial line to the
12558 For example, to connect to port 2828 on a terminal server named
12562 target remote manyfarms:2828
12565 If your remote target is actually running on the same machine as your
12566 debugger session (e.g.@: a simulator for your target running on the
12567 same host), you can omit the hostname. For example, to connect to
12568 port 1234 on your local machine:
12571 target remote :1234
12575 Note that the colon is still required here.
12577 @item target remote @code{udp:@var{host}:@var{port}}
12578 @cindex @acronym{UDP} port, @code{target remote}
12579 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12580 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12583 target remote udp:manyfarms:2828
12586 When using a @acronym{UDP} connection for remote debugging, you should
12587 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12588 can silently drop packets on busy or unreliable networks, which will
12589 cause havoc with your debugging session.
12591 @item target remote | @var{command}
12592 @cindex pipe, @code{target remote} to
12593 Run @var{command} in the background and communicate with it using a
12594 pipe. The @var{command} is a shell command, to be parsed and expanded
12595 by the system's command shell, @code{/bin/sh}; it should expect remote
12596 protocol packets on its standard input, and send replies on its
12597 standard output. You could use this to run a stand-alone simulator
12598 that speaks the remote debugging protocol, to make net connections
12599 using programs like @code{ssh}, or for other similar tricks.
12601 If @var{command} closes its standard output (perhaps by exiting),
12602 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12603 program has already exited, this will have no effect.)
12607 Once the connection has been established, you can use all the usual
12608 commands to examine and change data and to step and continue the
12611 @cindex interrupting remote programs
12612 @cindex remote programs, interrupting
12613 Whenever @value{GDBN} is waiting for the remote program, if you type the
12614 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12615 program. This may or may not succeed, depending in part on the hardware
12616 and the serial drivers the remote system uses. If you type the
12617 interrupt character once again, @value{GDBN} displays this prompt:
12620 Interrupted while waiting for the program.
12621 Give up (and stop debugging it)? (y or n)
12624 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12625 (If you decide you want to try again later, you can use @samp{target
12626 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12627 goes back to waiting.
12630 @kindex detach (remote)
12632 When you have finished debugging the remote program, you can use the
12633 @code{detach} command to release it from @value{GDBN} control.
12634 Detaching from the target normally resumes its execution, but the results
12635 will depend on your particular remote stub. After the @code{detach}
12636 command, @value{GDBN} is free to connect to another target.
12640 The @code{disconnect} command behaves like @code{detach}, except that
12641 the target is generally not resumed. It will wait for @value{GDBN}
12642 (this instance or another one) to connect and continue debugging. After
12643 the @code{disconnect} command, @value{GDBN} is again free to connect to
12646 @cindex send command to remote monitor
12647 @cindex extend @value{GDBN} for remote targets
12648 @cindex add new commands for external monitor
12650 @item monitor @var{cmd}
12651 This command allows you to send arbitrary commands directly to the
12652 remote monitor. Since @value{GDBN} doesn't care about the commands it
12653 sends like this, this command is the way to extend @value{GDBN}---you
12654 can add new commands that only the external monitor will understand
12659 @section Using the @code{gdbserver} program
12662 @cindex remote connection without stubs
12663 @code{gdbserver} is a control program for Unix-like systems, which
12664 allows you to connect your program with a remote @value{GDBN} via
12665 @code{target remote}---but without linking in the usual debugging stub.
12667 @code{gdbserver} is not a complete replacement for the debugging stubs,
12668 because it requires essentially the same operating-system facilities
12669 that @value{GDBN} itself does. In fact, a system that can run
12670 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12671 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12672 because it is a much smaller program than @value{GDBN} itself. It is
12673 also easier to port than all of @value{GDBN}, so you may be able to get
12674 started more quickly on a new system by using @code{gdbserver}.
12675 Finally, if you develop code for real-time systems, you may find that
12676 the tradeoffs involved in real-time operation make it more convenient to
12677 do as much development work as possible on another system, for example
12678 by cross-compiling. You can use @code{gdbserver} to make a similar
12679 choice for debugging.
12681 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12682 or a TCP connection, using the standard @value{GDBN} remote serial
12686 @item On the target machine,
12687 you need to have a copy of the program you want to debug.
12688 @code{gdbserver} does not need your program's symbol table, so you can
12689 strip the program if necessary to save space. @value{GDBN} on the host
12690 system does all the symbol handling.
12692 To use the server, you must tell it how to communicate with @value{GDBN};
12693 the name of your program; and the arguments for your program. The usual
12697 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12700 @var{comm} is either a device name (to use a serial line) or a TCP
12701 hostname and portnumber. For example, to debug Emacs with the argument
12702 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12706 target> gdbserver /dev/com1 emacs foo.txt
12709 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12712 To use a TCP connection instead of a serial line:
12715 target> gdbserver host:2345 emacs foo.txt
12718 The only difference from the previous example is the first argument,
12719 specifying that you are communicating with the host @value{GDBN} via
12720 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12721 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12722 (Currently, the @samp{host} part is ignored.) You can choose any number
12723 you want for the port number as long as it does not conflict with any
12724 TCP ports already in use on the target system (for example, @code{23} is
12725 reserved for @code{telnet}).@footnote{If you choose a port number that
12726 conflicts with another service, @code{gdbserver} prints an error message
12727 and exits.} You must use the same port number with the host @value{GDBN}
12728 @code{target remote} command.
12730 On some targets, @code{gdbserver} can also attach to running programs.
12731 This is accomplished via the @code{--attach} argument. The syntax is:
12734 target> gdbserver @var{comm} --attach @var{pid}
12737 @var{pid} is the process ID of a currently running process. It isn't necessary
12738 to point @code{gdbserver} at a binary for the running process.
12741 @cindex attach to a program by name
12742 You can debug processes by name instead of process ID if your target has the
12743 @code{pidof} utility:
12746 target> gdbserver @var{comm} --attach `pidof @var{program}`
12749 In case more than one copy of @var{program} is running, or @var{program}
12750 has multiple threads, most versions of @code{pidof} support the
12751 @code{-s} option to only return the first process ID.
12753 @item On the host machine,
12754 first make sure you have the necessary symbol files. Load symbols for
12755 your application using the @code{file} command before you connect. Use
12756 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
12757 was compiled with the correct sysroot using @code{--with-system-root}).
12759 The symbol file and target libraries must exactly match the executable
12760 and libraries on the target, with one exception: the files on the host
12761 system should not be stripped, even if the files on the target system
12762 are. Mismatched or missing files will lead to confusing results
12763 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
12764 files may also prevent @code{gdbserver} from debugging multi-threaded
12767 Connect to your target (@pxref{Connecting,,Connecting to a remote target}).
12768 For TCP connections, you must start up @code{gdbserver} prior to using
12769 the @code{target remote} command. Otherwise you may get an error whose
12770 text depends on the host system, but which usually looks something like
12771 @samp{Connection refused}. You don't need to use the @code{load}
12772 command in @value{GDBN} when using @code{gdbserver}, since the program is
12773 already on the target.
12777 @node Remote configuration
12778 @section Remote configuration
12781 @kindex show remote
12782 This section documents the configuration options available when
12783 debugging remote programs. For the options related to the File I/O
12784 extensions of the remote protocol, see @ref{system,
12785 system-call-allowed}.
12788 @item set remoteaddresssize @var{bits}
12789 @cindex address size for remote targets
12790 @cindex bits in remote address
12791 Set the maximum size of address in a memory packet to the specified
12792 number of bits. @value{GDBN} will mask off the address bits above
12793 that number, when it passes addresses to the remote target. The
12794 default value is the number of bits in the target's address.
12796 @item show remoteaddresssize
12797 Show the current value of remote address size in bits.
12799 @item set remotebaud @var{n}
12800 @cindex baud rate for remote targets
12801 Set the baud rate for the remote serial I/O to @var{n} baud. The
12802 value is used to set the speed of the serial port used for debugging
12805 @item show remotebaud
12806 Show the current speed of the remote connection.
12808 @item set remotebreak
12809 @cindex interrupt remote programs
12810 @cindex BREAK signal instead of Ctrl-C
12811 @anchor{set remotebreak}
12812 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12813 when you type @kbd{Ctrl-c} to interrupt the program running
12814 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12815 character instead. The default is off, since most remote systems
12816 expect to see @samp{Ctrl-C} as the interrupt signal.
12818 @item show remotebreak
12819 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12820 interrupt the remote program.
12822 @item set remotedevice @var{device}
12823 @cindex serial port name
12824 Set the name of the serial port through which to communicate to the
12825 remote target to @var{device}. This is the device used by
12826 @value{GDBN} to open the serial communications line to the remote
12827 target. There's no default, so you must set a valid port name for the
12828 remote serial communications to work. (Some varieties of the
12829 @code{target} command accept the port name as part of their
12832 @item show remotedevice
12833 Show the current name of the serial port.
12835 @item set remotelogbase @var{base}
12836 Set the base (a.k.a.@: radix) of logging serial protocol
12837 communications to @var{base}. Supported values of @var{base} are:
12838 @code{ascii}, @code{octal}, and @code{hex}. The default is
12841 @item show remotelogbase
12842 Show the current setting of the radix for logging remote serial
12845 @item set remotelogfile @var{file}
12846 @cindex record serial communications on file
12847 Record remote serial communications on the named @var{file}. The
12848 default is not to record at all.
12850 @item show remotelogfile.
12851 Show the current setting of the file name on which to record the
12852 serial communications.
12854 @item set remotetimeout @var{num}
12855 @cindex timeout for serial communications
12856 @cindex remote timeout
12857 Set the timeout limit to wait for the remote target to respond to
12858 @var{num} seconds. The default is 2 seconds.
12860 @item show remotetimeout
12861 Show the current number of seconds to wait for the remote target
12864 @cindex limit hardware breakpoints and watchpoints
12865 @cindex remote target, limit break- and watchpoints
12866 @anchor{set remote hardware-watchpoint-limit}
12867 @anchor{set remote hardware-breakpoint-limit}
12868 @item set remote hardware-watchpoint-limit @var{limit}
12869 @itemx set remote hardware-breakpoint-limit @var{limit}
12870 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12871 watchpoints. A limit of -1, the default, is treated as unlimited.
12874 @cindex remote packets, enabling and disabling
12875 The @value{GDBN} remote protocol autodetects the packets supported by
12876 your debugging stub. If you need to override the autodetection, you
12877 can use these commands to enable or disable individual packets. Each
12878 packet can be set to @samp{on} (the remote target supports this
12879 packet), @samp{off} (the remote target does not support this packet),
12880 or @samp{auto} (detect remote target support for this packet). They
12881 all default to @samp{auto}. For more information about each packet,
12882 see @ref{Remote Protocol}.
12884 During normal use, you should not have to use any of these commands.
12885 If you do, that may be a bug in your remote debugging stub, or a bug
12886 in @value{GDBN}. You may want to report the problem to the
12887 @value{GDBN} developers.
12889 The available settings are:
12891 @multitable @columnfractions 0.3 0.2 0.35
12894 @tab Related Features
12896 @item @code{fetch-register-packet}
12898 @tab @code{info registers}
12900 @item @code{set-register-packet}
12904 @item @code{binary-download-packet}
12906 @tab @code{load}, @code{set}
12908 @item @code{read-aux-vector-packet}
12909 @tab @code{qXfer:auxv:read}
12910 @tab @code{info auxv}
12912 @item @code{symbol-lookup-packet}
12913 @tab @code{qSymbol}
12914 @tab Detecting multiple threads
12916 @item @code{verbose-resume-packet}
12918 @tab Stepping or resuming multiple threads
12920 @item @code{software-breakpoint-packet}
12924 @item @code{hardware-breakpoint-packet}
12928 @item @code{write-watchpoint-packet}
12932 @item @code{read-watchpoint-packet}
12936 @item @code{access-watchpoint-packet}
12940 @item @code{get-thread-local-storage-address-packet}
12941 @tab @code{qGetTLSAddr}
12942 @tab Displaying @code{__thread} variables
12944 @item @code{supported-packets}
12945 @tab @code{qSupported}
12946 @tab Remote communications parameters
12948 @item @code{pass-signals-packet}
12949 @tab @code{QPassSignals}
12950 @tab @code{handle @var{signal}}
12955 @section Implementing a remote stub
12957 @cindex debugging stub, example
12958 @cindex remote stub, example
12959 @cindex stub example, remote debugging
12960 The stub files provided with @value{GDBN} implement the target side of the
12961 communication protocol, and the @value{GDBN} side is implemented in the
12962 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12963 these subroutines to communicate, and ignore the details. (If you're
12964 implementing your own stub file, you can still ignore the details: start
12965 with one of the existing stub files. @file{sparc-stub.c} is the best
12966 organized, and therefore the easiest to read.)
12968 @cindex remote serial debugging, overview
12969 To debug a program running on another machine (the debugging
12970 @dfn{target} machine), you must first arrange for all the usual
12971 prerequisites for the program to run by itself. For example, for a C
12976 A startup routine to set up the C runtime environment; these usually
12977 have a name like @file{crt0}. The startup routine may be supplied by
12978 your hardware supplier, or you may have to write your own.
12981 A C subroutine library to support your program's
12982 subroutine calls, notably managing input and output.
12985 A way of getting your program to the other machine---for example, a
12986 download program. These are often supplied by the hardware
12987 manufacturer, but you may have to write your own from hardware
12991 The next step is to arrange for your program to use a serial port to
12992 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12993 machine). In general terms, the scheme looks like this:
12997 @value{GDBN} already understands how to use this protocol; when everything
12998 else is set up, you can simply use the @samp{target remote} command
12999 (@pxref{Targets,,Specifying a Debugging Target}).
13001 @item On the target,
13002 you must link with your program a few special-purpose subroutines that
13003 implement the @value{GDBN} remote serial protocol. The file containing these
13004 subroutines is called a @dfn{debugging stub}.
13006 On certain remote targets, you can use an auxiliary program
13007 @code{gdbserver} instead of linking a stub into your program.
13008 @xref{Server,,Using the @code{gdbserver} program}, for details.
13011 The debugging stub is specific to the architecture of the remote
13012 machine; for example, use @file{sparc-stub.c} to debug programs on
13015 @cindex remote serial stub list
13016 These working remote stubs are distributed with @value{GDBN}:
13021 @cindex @file{i386-stub.c}
13024 For Intel 386 and compatible architectures.
13027 @cindex @file{m68k-stub.c}
13028 @cindex Motorola 680x0
13030 For Motorola 680x0 architectures.
13033 @cindex @file{sh-stub.c}
13036 For Renesas SH architectures.
13039 @cindex @file{sparc-stub.c}
13041 For @sc{sparc} architectures.
13043 @item sparcl-stub.c
13044 @cindex @file{sparcl-stub.c}
13047 For Fujitsu @sc{sparclite} architectures.
13051 The @file{README} file in the @value{GDBN} distribution may list other
13052 recently added stubs.
13055 * Stub Contents:: What the stub can do for you
13056 * Bootstrapping:: What you must do for the stub
13057 * Debug Session:: Putting it all together
13060 @node Stub Contents
13061 @subsection What the stub can do for you
13063 @cindex remote serial stub
13064 The debugging stub for your architecture supplies these three
13068 @item set_debug_traps
13069 @findex set_debug_traps
13070 @cindex remote serial stub, initialization
13071 This routine arranges for @code{handle_exception} to run when your
13072 program stops. You must call this subroutine explicitly near the
13073 beginning of your program.
13075 @item handle_exception
13076 @findex handle_exception
13077 @cindex remote serial stub, main routine
13078 This is the central workhorse, but your program never calls it
13079 explicitly---the setup code arranges for @code{handle_exception} to
13080 run when a trap is triggered.
13082 @code{handle_exception} takes control when your program stops during
13083 execution (for example, on a breakpoint), and mediates communications
13084 with @value{GDBN} on the host machine. This is where the communications
13085 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13086 representative on the target machine. It begins by sending summary
13087 information on the state of your program, then continues to execute,
13088 retrieving and transmitting any information @value{GDBN} needs, until you
13089 execute a @value{GDBN} command that makes your program resume; at that point,
13090 @code{handle_exception} returns control to your own code on the target
13094 @cindex @code{breakpoint} subroutine, remote
13095 Use this auxiliary subroutine to make your program contain a
13096 breakpoint. Depending on the particular situation, this may be the only
13097 way for @value{GDBN} to get control. For instance, if your target
13098 machine has some sort of interrupt button, you won't need to call this;
13099 pressing the interrupt button transfers control to
13100 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13101 simply receiving characters on the serial port may also trigger a trap;
13102 again, in that situation, you don't need to call @code{breakpoint} from
13103 your own program---simply running @samp{target remote} from the host
13104 @value{GDBN} session gets control.
13106 Call @code{breakpoint} if none of these is true, or if you simply want
13107 to make certain your program stops at a predetermined point for the
13108 start of your debugging session.
13111 @node Bootstrapping
13112 @subsection What you must do for the stub
13114 @cindex remote stub, support routines
13115 The debugging stubs that come with @value{GDBN} are set up for a particular
13116 chip architecture, but they have no information about the rest of your
13117 debugging target machine.
13119 First of all you need to tell the stub how to communicate with the
13123 @item int getDebugChar()
13124 @findex getDebugChar
13125 Write this subroutine to read a single character from the serial port.
13126 It may be identical to @code{getchar} for your target system; a
13127 different name is used to allow you to distinguish the two if you wish.
13129 @item void putDebugChar(int)
13130 @findex putDebugChar
13131 Write this subroutine to write a single character to the serial port.
13132 It may be identical to @code{putchar} for your target system; a
13133 different name is used to allow you to distinguish the two if you wish.
13136 @cindex control C, and remote debugging
13137 @cindex interrupting remote targets
13138 If you want @value{GDBN} to be able to stop your program while it is
13139 running, you need to use an interrupt-driven serial driver, and arrange
13140 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13141 character). That is the character which @value{GDBN} uses to tell the
13142 remote system to stop.
13144 Getting the debugging target to return the proper status to @value{GDBN}
13145 probably requires changes to the standard stub; one quick and dirty way
13146 is to just execute a breakpoint instruction (the ``dirty'' part is that
13147 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13149 Other routines you need to supply are:
13152 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13153 @findex exceptionHandler
13154 Write this function to install @var{exception_address} in the exception
13155 handling tables. You need to do this because the stub does not have any
13156 way of knowing what the exception handling tables on your target system
13157 are like (for example, the processor's table might be in @sc{rom},
13158 containing entries which point to a table in @sc{ram}).
13159 @var{exception_number} is the exception number which should be changed;
13160 its meaning is architecture-dependent (for example, different numbers
13161 might represent divide by zero, misaligned access, etc). When this
13162 exception occurs, control should be transferred directly to
13163 @var{exception_address}, and the processor state (stack, registers,
13164 and so on) should be just as it is when a processor exception occurs. So if
13165 you want to use a jump instruction to reach @var{exception_address}, it
13166 should be a simple jump, not a jump to subroutine.
13168 For the 386, @var{exception_address} should be installed as an interrupt
13169 gate so that interrupts are masked while the handler runs. The gate
13170 should be at privilege level 0 (the most privileged level). The
13171 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13172 help from @code{exceptionHandler}.
13174 @item void flush_i_cache()
13175 @findex flush_i_cache
13176 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13177 instruction cache, if any, on your target machine. If there is no
13178 instruction cache, this subroutine may be a no-op.
13180 On target machines that have instruction caches, @value{GDBN} requires this
13181 function to make certain that the state of your program is stable.
13185 You must also make sure this library routine is available:
13188 @item void *memset(void *, int, int)
13190 This is the standard library function @code{memset} that sets an area of
13191 memory to a known value. If you have one of the free versions of
13192 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13193 either obtain it from your hardware manufacturer, or write your own.
13196 If you do not use the GNU C compiler, you may need other standard
13197 library subroutines as well; this varies from one stub to another,
13198 but in general the stubs are likely to use any of the common library
13199 subroutines which @code{@value{NGCC}} generates as inline code.
13202 @node Debug Session
13203 @subsection Putting it all together
13205 @cindex remote serial debugging summary
13206 In summary, when your program is ready to debug, you must follow these
13211 Make sure you have defined the supporting low-level routines
13212 (@pxref{Bootstrapping,,What you must do for the stub}):
13214 @code{getDebugChar}, @code{putDebugChar},
13215 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13219 Insert these lines near the top of your program:
13227 For the 680x0 stub only, you need to provide a variable called
13228 @code{exceptionHook}. Normally you just use:
13231 void (*exceptionHook)() = 0;
13235 but if before calling @code{set_debug_traps}, you set it to point to a
13236 function in your program, that function is called when
13237 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13238 error). The function indicated by @code{exceptionHook} is called with
13239 one parameter: an @code{int} which is the exception number.
13242 Compile and link together: your program, the @value{GDBN} debugging stub for
13243 your target architecture, and the supporting subroutines.
13246 Make sure you have a serial connection between your target machine and
13247 the @value{GDBN} host, and identify the serial port on the host.
13250 @c The "remote" target now provides a `load' command, so we should
13251 @c document that. FIXME.
13252 Download your program to your target machine (or get it there by
13253 whatever means the manufacturer provides), and start it.
13256 Start @value{GDBN} on the host, and connect to the target
13257 (@pxref{Connecting,,Connecting to a remote target}).
13261 @node Configurations
13262 @chapter Configuration-Specific Information
13264 While nearly all @value{GDBN} commands are available for all native and
13265 cross versions of the debugger, there are some exceptions. This chapter
13266 describes things that are only available in certain configurations.
13268 There are three major categories of configurations: native
13269 configurations, where the host and target are the same, embedded
13270 operating system configurations, which are usually the same for several
13271 different processor architectures, and bare embedded processors, which
13272 are quite different from each other.
13277 * Embedded Processors::
13284 This section describes details specific to particular native
13289 * BSD libkvm Interface:: Debugging BSD kernel memory images
13290 * SVR4 Process Information:: SVR4 process information
13291 * DJGPP Native:: Features specific to the DJGPP port
13292 * Cygwin Native:: Features specific to the Cygwin port
13293 * Hurd Native:: Features specific to @sc{gnu} Hurd
13294 * Neutrino:: Features specific to QNX Neutrino
13300 On HP-UX systems, if you refer to a function or variable name that
13301 begins with a dollar sign, @value{GDBN} searches for a user or system
13302 name first, before it searches for a convenience variable.
13305 @node BSD libkvm Interface
13306 @subsection BSD libkvm Interface
13309 @cindex kernel memory image
13310 @cindex kernel crash dump
13312 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13313 interface that provides a uniform interface for accessing kernel virtual
13314 memory images, including live systems and crash dumps. @value{GDBN}
13315 uses this interface to allow you to debug live kernels and kernel crash
13316 dumps on many native BSD configurations. This is implemented as a
13317 special @code{kvm} debugging target. For debugging a live system, load
13318 the currently running kernel into @value{GDBN} and connect to the
13322 (@value{GDBP}) @b{target kvm}
13325 For debugging crash dumps, provide the file name of the crash dump as an
13329 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13332 Once connected to the @code{kvm} target, the following commands are
13338 Set current context from the @dfn{Process Control Block} (PCB) address.
13341 Set current context from proc address. This command isn't available on
13342 modern FreeBSD systems.
13345 @node SVR4 Process Information
13346 @subsection SVR4 process information
13348 @cindex examine process image
13349 @cindex process info via @file{/proc}
13351 Many versions of SVR4 and compatible systems provide a facility called
13352 @samp{/proc} that can be used to examine the image of a running
13353 process using file-system subroutines. If @value{GDBN} is configured
13354 for an operating system with this facility, the command @code{info
13355 proc} is available to report information about the process running
13356 your program, or about any process running on your system. @code{info
13357 proc} works only on SVR4 systems that include the @code{procfs} code.
13358 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13359 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13365 @itemx info proc @var{process-id}
13366 Summarize available information about any running process. If a
13367 process ID is specified by @var{process-id}, display information about
13368 that process; otherwise display information about the program being
13369 debugged. The summary includes the debugged process ID, the command
13370 line used to invoke it, its current working directory, and its
13371 executable file's absolute file name.
13373 On some systems, @var{process-id} can be of the form
13374 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13375 within a process. If the optional @var{pid} part is missing, it means
13376 a thread from the process being debugged (the leading @samp{/} still
13377 needs to be present, or else @value{GDBN} will interpret the number as
13378 a process ID rather than a thread ID).
13380 @item info proc mappings
13381 @cindex memory address space mappings
13382 Report the memory address space ranges accessible in the program, with
13383 information on whether the process has read, write, or execute access
13384 rights to each range. On @sc{gnu}/Linux systems, each memory range
13385 includes the object file which is mapped to that range, instead of the
13386 memory access rights to that range.
13388 @item info proc stat
13389 @itemx info proc status
13390 @cindex process detailed status information
13391 These subcommands are specific to @sc{gnu}/Linux systems. They show
13392 the process-related information, including the user ID and group ID;
13393 how many threads are there in the process; its virtual memory usage;
13394 the signals that are pending, blocked, and ignored; its TTY; its
13395 consumption of system and user time; its stack size; its @samp{nice}
13396 value; etc. For more information, see the @samp{proc} man page
13397 (type @kbd{man 5 proc} from your shell prompt).
13399 @item info proc all
13400 Show all the information about the process described under all of the
13401 above @code{info proc} subcommands.
13404 @comment These sub-options of 'info proc' were not included when
13405 @comment procfs.c was re-written. Keep their descriptions around
13406 @comment against the day when someone finds the time to put them back in.
13407 @kindex info proc times
13408 @item info proc times
13409 Starting time, user CPU time, and system CPU time for your program and
13412 @kindex info proc id
13414 Report on the process IDs related to your program: its own process ID,
13415 the ID of its parent, the process group ID, and the session ID.
13418 @item set procfs-trace
13419 @kindex set procfs-trace
13420 @cindex @code{procfs} API calls
13421 This command enables and disables tracing of @code{procfs} API calls.
13423 @item show procfs-trace
13424 @kindex show procfs-trace
13425 Show the current state of @code{procfs} API call tracing.
13427 @item set procfs-file @var{file}
13428 @kindex set procfs-file
13429 Tell @value{GDBN} to write @code{procfs} API trace to the named
13430 @var{file}. @value{GDBN} appends the trace info to the previous
13431 contents of the file. The default is to display the trace on the
13434 @item show procfs-file
13435 @kindex show procfs-file
13436 Show the file to which @code{procfs} API trace is written.
13438 @item proc-trace-entry
13439 @itemx proc-trace-exit
13440 @itemx proc-untrace-entry
13441 @itemx proc-untrace-exit
13442 @kindex proc-trace-entry
13443 @kindex proc-trace-exit
13444 @kindex proc-untrace-entry
13445 @kindex proc-untrace-exit
13446 These commands enable and disable tracing of entries into and exits
13447 from the @code{syscall} interface.
13450 @kindex info pidlist
13451 @cindex process list, QNX Neutrino
13452 For QNX Neutrino only, this command displays the list of all the
13453 processes and all the threads within each process.
13456 @kindex info meminfo
13457 @cindex mapinfo list, QNX Neutrino
13458 For QNX Neutrino only, this command displays the list of all mapinfos.
13462 @subsection Features for Debugging @sc{djgpp} Programs
13463 @cindex @sc{djgpp} debugging
13464 @cindex native @sc{djgpp} debugging
13465 @cindex MS-DOS-specific commands
13468 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13469 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13470 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13471 top of real-mode DOS systems and their emulations.
13473 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13474 defines a few commands specific to the @sc{djgpp} port. This
13475 subsection describes those commands.
13480 This is a prefix of @sc{djgpp}-specific commands which print
13481 information about the target system and important OS structures.
13484 @cindex MS-DOS system info
13485 @cindex free memory information (MS-DOS)
13486 @item info dos sysinfo
13487 This command displays assorted information about the underlying
13488 platform: the CPU type and features, the OS version and flavor, the
13489 DPMI version, and the available conventional and DPMI memory.
13494 @cindex segment descriptor tables
13495 @cindex descriptor tables display
13497 @itemx info dos ldt
13498 @itemx info dos idt
13499 These 3 commands display entries from, respectively, Global, Local,
13500 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13501 tables are data structures which store a descriptor for each segment
13502 that is currently in use. The segment's selector is an index into a
13503 descriptor table; the table entry for that index holds the
13504 descriptor's base address and limit, and its attributes and access
13507 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13508 segment (used for both data and the stack), and a DOS segment (which
13509 allows access to DOS/BIOS data structures and absolute addresses in
13510 conventional memory). However, the DPMI host will usually define
13511 additional segments in order to support the DPMI environment.
13513 @cindex garbled pointers
13514 These commands allow to display entries from the descriptor tables.
13515 Without an argument, all entries from the specified table are
13516 displayed. An argument, which should be an integer expression, means
13517 display a single entry whose index is given by the argument. For
13518 example, here's a convenient way to display information about the
13519 debugged program's data segment:
13522 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13523 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13527 This comes in handy when you want to see whether a pointer is outside
13528 the data segment's limit (i.e.@: @dfn{garbled}).
13530 @cindex page tables display (MS-DOS)
13532 @itemx info dos pte
13533 These two commands display entries from, respectively, the Page
13534 Directory and the Page Tables. Page Directories and Page Tables are
13535 data structures which control how virtual memory addresses are mapped
13536 into physical addresses. A Page Table includes an entry for every
13537 page of memory that is mapped into the program's address space; there
13538 may be several Page Tables, each one holding up to 4096 entries. A
13539 Page Directory has up to 4096 entries, one each for every Page Table
13540 that is currently in use.
13542 Without an argument, @kbd{info dos pde} displays the entire Page
13543 Directory, and @kbd{info dos pte} displays all the entries in all of
13544 the Page Tables. An argument, an integer expression, given to the
13545 @kbd{info dos pde} command means display only that entry from the Page
13546 Directory table. An argument given to the @kbd{info dos pte} command
13547 means display entries from a single Page Table, the one pointed to by
13548 the specified entry in the Page Directory.
13550 @cindex direct memory access (DMA) on MS-DOS
13551 These commands are useful when your program uses @dfn{DMA} (Direct
13552 Memory Access), which needs physical addresses to program the DMA
13555 These commands are supported only with some DPMI servers.
13557 @cindex physical address from linear address
13558 @item info dos address-pte @var{addr}
13559 This command displays the Page Table entry for a specified linear
13560 address. The argument @var{addr} is a linear address which should
13561 already have the appropriate segment's base address added to it,
13562 because this command accepts addresses which may belong to @emph{any}
13563 segment. For example, here's how to display the Page Table entry for
13564 the page where a variable @code{i} is stored:
13567 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13568 @exdent @code{Page Table entry for address 0x11a00d30:}
13569 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13573 This says that @code{i} is stored at offset @code{0xd30} from the page
13574 whose physical base address is @code{0x02698000}, and shows all the
13575 attributes of that page.
13577 Note that you must cast the addresses of variables to a @code{char *},
13578 since otherwise the value of @code{__djgpp_base_address}, the base
13579 address of all variables and functions in a @sc{djgpp} program, will
13580 be added using the rules of C pointer arithmetics: if @code{i} is
13581 declared an @code{int}, @value{GDBN} will add 4 times the value of
13582 @code{__djgpp_base_address} to the address of @code{i}.
13584 Here's another example, it displays the Page Table entry for the
13588 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13589 @exdent @code{Page Table entry for address 0x29110:}
13590 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13594 (The @code{+ 3} offset is because the transfer buffer's address is the
13595 3rd member of the @code{_go32_info_block} structure.) The output
13596 clearly shows that this DPMI server maps the addresses in conventional
13597 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13598 linear (@code{0x29110}) addresses are identical.
13600 This command is supported only with some DPMI servers.
13603 @cindex DOS serial data link, remote debugging
13604 In addition to native debugging, the DJGPP port supports remote
13605 debugging via a serial data link. The following commands are specific
13606 to remote serial debugging in the DJGPP port of @value{GDBN}.
13609 @kindex set com1base
13610 @kindex set com1irq
13611 @kindex set com2base
13612 @kindex set com2irq
13613 @kindex set com3base
13614 @kindex set com3irq
13615 @kindex set com4base
13616 @kindex set com4irq
13617 @item set com1base @var{addr}
13618 This command sets the base I/O port address of the @file{COM1} serial
13621 @item set com1irq @var{irq}
13622 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13623 for the @file{COM1} serial port.
13625 There are similar commands @samp{set com2base}, @samp{set com3irq},
13626 etc.@: for setting the port address and the @code{IRQ} lines for the
13629 @kindex show com1base
13630 @kindex show com1irq
13631 @kindex show com2base
13632 @kindex show com2irq
13633 @kindex show com3base
13634 @kindex show com3irq
13635 @kindex show com4base
13636 @kindex show com4irq
13637 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13638 display the current settings of the base address and the @code{IRQ}
13639 lines used by the COM ports.
13642 @kindex info serial
13643 @cindex DOS serial port status
13644 This command prints the status of the 4 DOS serial ports. For each
13645 port, it prints whether it's active or not, its I/O base address and
13646 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13647 counts of various errors encountered so far.
13651 @node Cygwin Native
13652 @subsection Features for Debugging MS Windows PE executables
13653 @cindex MS Windows debugging
13654 @cindex native Cygwin debugging
13655 @cindex Cygwin-specific commands
13657 @value{GDBN} supports native debugging of MS Windows programs, including
13658 DLLs with and without symbolic debugging information. There are various
13659 additional Cygwin-specific commands, described in this subsection. The
13660 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
13661 that have no debugging symbols.
13667 This is a prefix of MS Windows specific commands which print
13668 information about the target system and important OS structures.
13670 @item info w32 selector
13671 This command displays information returned by
13672 the Win32 API @code{GetThreadSelectorEntry} function.
13673 It takes an optional argument that is evaluated to
13674 a long value to give the information about this given selector.
13675 Without argument, this command displays information
13676 about the six segment registers.
13680 This is a Cygwin specific alias of info shared.
13682 @kindex dll-symbols
13684 This command loads symbols from a dll similarly to
13685 add-sym command but without the need to specify a base address.
13687 @kindex set cygwin-exceptions
13688 @cindex debugging the Cygwin DLL
13689 @cindex Cygwin DLL, debugging
13690 @item set cygwin-exceptions @var{mode}
13691 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13692 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13693 @value{GDBN} will delay recognition of exceptions, and may ignore some
13694 exceptions which seem to be caused by internal Cygwin DLL
13695 ``bookkeeping''. This option is meant primarily for debugging the
13696 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13697 @value{GDBN} users with false @code{SIGSEGV} signals.
13699 @kindex show cygwin-exceptions
13700 @item show cygwin-exceptions
13701 Displays whether @value{GDBN} will break on exceptions that happen
13702 inside the Cygwin DLL itself.
13704 @kindex set new-console
13705 @item set new-console @var{mode}
13706 If @var{mode} is @code{on} the debuggee will
13707 be started in a new console on next start.
13708 If @var{mode} is @code{off}i, the debuggee will
13709 be started in the same console as the debugger.
13711 @kindex show new-console
13712 @item show new-console
13713 Displays whether a new console is used
13714 when the debuggee is started.
13716 @kindex set new-group
13717 @item set new-group @var{mode}
13718 This boolean value controls whether the debuggee should
13719 start a new group or stay in the same group as the debugger.
13720 This affects the way the Windows OS handles
13723 @kindex show new-group
13724 @item show new-group
13725 Displays current value of new-group boolean.
13727 @kindex set debugevents
13728 @item set debugevents
13729 This boolean value adds debug output concerning kernel events related
13730 to the debuggee seen by the debugger. This includes events that
13731 signal thread and process creation and exit, DLL loading and
13732 unloading, console interrupts, and debugging messages produced by the
13733 Windows @code{OutputDebugString} API call.
13735 @kindex set debugexec
13736 @item set debugexec
13737 This boolean value adds debug output concerning execute events
13738 (such as resume thread) seen by the debugger.
13740 @kindex set debugexceptions
13741 @item set debugexceptions
13742 This boolean value adds debug output concerning exceptions in the
13743 debuggee seen by the debugger.
13745 @kindex set debugmemory
13746 @item set debugmemory
13747 This boolean value adds debug output concerning debuggee memory reads
13748 and writes by the debugger.
13752 This boolean values specifies whether the debuggee is called
13753 via a shell or directly (default value is on).
13757 Displays if the debuggee will be started with a shell.
13762 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13765 @node Non-debug DLL symbols
13766 @subsubsection Support for DLLs without debugging symbols
13767 @cindex DLLs with no debugging symbols
13768 @cindex Minimal symbols and DLLs
13770 Very often on windows, some of the DLLs that your program relies on do
13771 not include symbolic debugging information (for example,
13772 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13773 symbols in a DLL, it relies on the minimal amount of symbolic
13774 information contained in the DLL's export table. This subsubsection
13775 describes working with such symbols, known internally to @value{GDBN} as
13776 ``minimal symbols''.
13778 Note that before the debugged program has started execution, no DLLs
13779 will have been loaded. The easiest way around this problem is simply to
13780 start the program --- either by setting a breakpoint or letting the
13781 program run once to completion. It is also possible to force
13782 @value{GDBN} to load a particular DLL before starting the executable ---
13783 see the shared library information in @pxref{Files} or the
13784 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13785 explicitly loading symbols from a DLL with no debugging information will
13786 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13787 which may adversely affect symbol lookup performance.
13789 @subsubsection DLL name prefixes
13791 In keeping with the naming conventions used by the Microsoft debugging
13792 tools, DLL export symbols are made available with a prefix based on the
13793 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13794 also entered into the symbol table, so @code{CreateFileA} is often
13795 sufficient. In some cases there will be name clashes within a program
13796 (particularly if the executable itself includes full debugging symbols)
13797 necessitating the use of the fully qualified name when referring to the
13798 contents of the DLL. Use single-quotes around the name to avoid the
13799 exclamation mark (``!'') being interpreted as a language operator.
13801 Note that the internal name of the DLL may be all upper-case, even
13802 though the file name of the DLL is lower-case, or vice-versa. Since
13803 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13804 some confusion. If in doubt, try the @code{info functions} and
13805 @code{info variables} commands or even @code{maint print msymbols} (see
13806 @pxref{Symbols}). Here's an example:
13809 (@value{GDBP}) info function CreateFileA
13810 All functions matching regular expression "CreateFileA":
13812 Non-debugging symbols:
13813 0x77e885f4 CreateFileA
13814 0x77e885f4 KERNEL32!CreateFileA
13818 (@value{GDBP}) info function !
13819 All functions matching regular expression "!":
13821 Non-debugging symbols:
13822 0x6100114c cygwin1!__assert
13823 0x61004034 cygwin1!_dll_crt0@@0
13824 0x61004240 cygwin1!dll_crt0(per_process *)
13828 @subsubsection Working with minimal symbols
13830 Symbols extracted from a DLL's export table do not contain very much
13831 type information. All that @value{GDBN} can do is guess whether a symbol
13832 refers to a function or variable depending on the linker section that
13833 contains the symbol. Also note that the actual contents of the memory
13834 contained in a DLL are not available unless the program is running. This
13835 means that you cannot examine the contents of a variable or disassemble
13836 a function within a DLL without a running program.
13838 Variables are generally treated as pointers and dereferenced
13839 automatically. For this reason, it is often necessary to prefix a
13840 variable name with the address-of operator (``&'') and provide explicit
13841 type information in the command. Here's an example of the type of
13845 (@value{GDBP}) print 'cygwin1!__argv'
13850 (@value{GDBP}) x 'cygwin1!__argv'
13851 0x10021610: "\230y\""
13854 And two possible solutions:
13857 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13858 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13862 (@value{GDBP}) x/2x &'cygwin1!__argv'
13863 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13864 (@value{GDBP}) x/x 0x10021608
13865 0x10021608: 0x0022fd98
13866 (@value{GDBP}) x/s 0x0022fd98
13867 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13870 Setting a break point within a DLL is possible even before the program
13871 starts execution. However, under these circumstances, @value{GDBN} can't
13872 examine the initial instructions of the function in order to skip the
13873 function's frame set-up code. You can work around this by using ``*&''
13874 to set the breakpoint at a raw memory address:
13877 (@value{GDBP}) break *&'python22!PyOS_Readline'
13878 Breakpoint 1 at 0x1e04eff0
13881 The author of these extensions is not entirely convinced that setting a
13882 break point within a shared DLL like @file{kernel32.dll} is completely
13886 @subsection Commands specific to @sc{gnu} Hurd systems
13887 @cindex @sc{gnu} Hurd debugging
13889 This subsection describes @value{GDBN} commands specific to the
13890 @sc{gnu} Hurd native debugging.
13895 @kindex set signals@r{, Hurd command}
13896 @kindex set sigs@r{, Hurd command}
13897 This command toggles the state of inferior signal interception by
13898 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13899 affected by this command. @code{sigs} is a shorthand alias for
13904 @kindex show signals@r{, Hurd command}
13905 @kindex show sigs@r{, Hurd command}
13906 Show the current state of intercepting inferior's signals.
13908 @item set signal-thread
13909 @itemx set sigthread
13910 @kindex set signal-thread
13911 @kindex set sigthread
13912 This command tells @value{GDBN} which thread is the @code{libc} signal
13913 thread. That thread is run when a signal is delivered to a running
13914 process. @code{set sigthread} is the shorthand alias of @code{set
13917 @item show signal-thread
13918 @itemx show sigthread
13919 @kindex show signal-thread
13920 @kindex show sigthread
13921 These two commands show which thread will run when the inferior is
13922 delivered a signal.
13925 @kindex set stopped@r{, Hurd command}
13926 This commands tells @value{GDBN} that the inferior process is stopped,
13927 as with the @code{SIGSTOP} signal. The stopped process can be
13928 continued by delivering a signal to it.
13931 @kindex show stopped@r{, Hurd command}
13932 This command shows whether @value{GDBN} thinks the debuggee is
13935 @item set exceptions
13936 @kindex set exceptions@r{, Hurd command}
13937 Use this command to turn off trapping of exceptions in the inferior.
13938 When exception trapping is off, neither breakpoints nor
13939 single-stepping will work. To restore the default, set exception
13942 @item show exceptions
13943 @kindex show exceptions@r{, Hurd command}
13944 Show the current state of trapping exceptions in the inferior.
13946 @item set task pause
13947 @kindex set task@r{, Hurd commands}
13948 @cindex task attributes (@sc{gnu} Hurd)
13949 @cindex pause current task (@sc{gnu} Hurd)
13950 This command toggles task suspension when @value{GDBN} has control.
13951 Setting it to on takes effect immediately, and the task is suspended
13952 whenever @value{GDBN} gets control. Setting it to off will take
13953 effect the next time the inferior is continued. If this option is set
13954 to off, you can use @code{set thread default pause on} or @code{set
13955 thread pause on} (see below) to pause individual threads.
13957 @item show task pause
13958 @kindex show task@r{, Hurd commands}
13959 Show the current state of task suspension.
13961 @item set task detach-suspend-count
13962 @cindex task suspend count
13963 @cindex detach from task, @sc{gnu} Hurd
13964 This command sets the suspend count the task will be left with when
13965 @value{GDBN} detaches from it.
13967 @item show task detach-suspend-count
13968 Show the suspend count the task will be left with when detaching.
13970 @item set task exception-port
13971 @itemx set task excp
13972 @cindex task exception port, @sc{gnu} Hurd
13973 This command sets the task exception port to which @value{GDBN} will
13974 forward exceptions. The argument should be the value of the @dfn{send
13975 rights} of the task. @code{set task excp} is a shorthand alias.
13977 @item set noninvasive
13978 @cindex noninvasive task options
13979 This command switches @value{GDBN} to a mode that is the least
13980 invasive as far as interfering with the inferior is concerned. This
13981 is the same as using @code{set task pause}, @code{set exceptions}, and
13982 @code{set signals} to values opposite to the defaults.
13984 @item info send-rights
13985 @itemx info receive-rights
13986 @itemx info port-rights
13987 @itemx info port-sets
13988 @itemx info dead-names
13991 @cindex send rights, @sc{gnu} Hurd
13992 @cindex receive rights, @sc{gnu} Hurd
13993 @cindex port rights, @sc{gnu} Hurd
13994 @cindex port sets, @sc{gnu} Hurd
13995 @cindex dead names, @sc{gnu} Hurd
13996 These commands display information about, respectively, send rights,
13997 receive rights, port rights, port sets, and dead names of a task.
13998 There are also shorthand aliases: @code{info ports} for @code{info
13999 port-rights} and @code{info psets} for @code{info port-sets}.
14001 @item set thread pause
14002 @kindex set thread@r{, Hurd command}
14003 @cindex thread properties, @sc{gnu} Hurd
14004 @cindex pause current thread (@sc{gnu} Hurd)
14005 This command toggles current thread suspension when @value{GDBN} has
14006 control. Setting it to on takes effect immediately, and the current
14007 thread is suspended whenever @value{GDBN} gets control. Setting it to
14008 off will take effect the next time the inferior is continued.
14009 Normally, this command has no effect, since when @value{GDBN} has
14010 control, the whole task is suspended. However, if you used @code{set
14011 task pause off} (see above), this command comes in handy to suspend
14012 only the current thread.
14014 @item show thread pause
14015 @kindex show thread@r{, Hurd command}
14016 This command shows the state of current thread suspension.
14018 @item set thread run
14019 This command sets whether the current thread is allowed to run.
14021 @item show thread run
14022 Show whether the current thread is allowed to run.
14024 @item set thread detach-suspend-count
14025 @cindex thread suspend count, @sc{gnu} Hurd
14026 @cindex detach from thread, @sc{gnu} Hurd
14027 This command sets the suspend count @value{GDBN} will leave on a
14028 thread when detaching. This number is relative to the suspend count
14029 found by @value{GDBN} when it notices the thread; use @code{set thread
14030 takeover-suspend-count} to force it to an absolute value.
14032 @item show thread detach-suspend-count
14033 Show the suspend count @value{GDBN} will leave on the thread when
14036 @item set thread exception-port
14037 @itemx set thread excp
14038 Set the thread exception port to which to forward exceptions. This
14039 overrides the port set by @code{set task exception-port} (see above).
14040 @code{set thread excp} is the shorthand alias.
14042 @item set thread takeover-suspend-count
14043 Normally, @value{GDBN}'s thread suspend counts are relative to the
14044 value @value{GDBN} finds when it notices each thread. This command
14045 changes the suspend counts to be absolute instead.
14047 @item set thread default
14048 @itemx show thread default
14049 @cindex thread default settings, @sc{gnu} Hurd
14050 Each of the above @code{set thread} commands has a @code{set thread
14051 default} counterpart (e.g., @code{set thread default pause}, @code{set
14052 thread default exception-port}, etc.). The @code{thread default}
14053 variety of commands sets the default thread properties for all
14054 threads; you can then change the properties of individual threads with
14055 the non-default commands.
14060 @subsection QNX Neutrino
14061 @cindex QNX Neutrino
14063 @value{GDBN} provides the following commands specific to the QNX
14067 @item set debug nto-debug
14068 @kindex set debug nto-debug
14069 When set to on, enables debugging messages specific to the QNX
14072 @item show debug nto-debug
14073 @kindex show debug nto-debug
14074 Show the current state of QNX Neutrino messages.
14079 @section Embedded Operating Systems
14081 This section describes configurations involving the debugging of
14082 embedded operating systems that are available for several different
14086 * VxWorks:: Using @value{GDBN} with VxWorks
14089 @value{GDBN} includes the ability to debug programs running on
14090 various real-time operating systems.
14093 @subsection Using @value{GDBN} with VxWorks
14099 @kindex target vxworks
14100 @item target vxworks @var{machinename}
14101 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14102 is the target system's machine name or IP address.
14106 On VxWorks, @code{load} links @var{filename} dynamically on the
14107 current target system as well as adding its symbols in @value{GDBN}.
14109 @value{GDBN} enables developers to spawn and debug tasks running on networked
14110 VxWorks targets from a Unix host. Already-running tasks spawned from
14111 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14112 both the Unix host and on the VxWorks target. The program
14113 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14114 installed with the name @code{vxgdb}, to distinguish it from a
14115 @value{GDBN} for debugging programs on the host itself.)
14118 @item VxWorks-timeout @var{args}
14119 @kindex vxworks-timeout
14120 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14121 This option is set by the user, and @var{args} represents the number of
14122 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14123 your VxWorks target is a slow software simulator or is on the far side
14124 of a thin network line.
14127 The following information on connecting to VxWorks was current when
14128 this manual was produced; newer releases of VxWorks may use revised
14131 @findex INCLUDE_RDB
14132 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14133 to include the remote debugging interface routines in the VxWorks
14134 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14135 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14136 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14137 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14138 information on configuring and remaking VxWorks, see the manufacturer's
14140 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14142 Once you have included @file{rdb.a} in your VxWorks system image and set
14143 your Unix execution search path to find @value{GDBN}, you are ready to
14144 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14145 @code{vxgdb}, depending on your installation).
14147 @value{GDBN} comes up showing the prompt:
14154 * VxWorks Connection:: Connecting to VxWorks
14155 * VxWorks Download:: VxWorks download
14156 * VxWorks Attach:: Running tasks
14159 @node VxWorks Connection
14160 @subsubsection Connecting to VxWorks
14162 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14163 network. To connect to a target whose host name is ``@code{tt}'', type:
14166 (vxgdb) target vxworks tt
14170 @value{GDBN} displays messages like these:
14173 Attaching remote machine across net...
14178 @value{GDBN} then attempts to read the symbol tables of any object modules
14179 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14180 these files by searching the directories listed in the command search
14181 path (@pxref{Environment, ,Your program's environment}); if it fails
14182 to find an object file, it displays a message such as:
14185 prog.o: No such file or directory.
14188 When this happens, add the appropriate directory to the search path with
14189 the @value{GDBN} command @code{path}, and execute the @code{target}
14192 @node VxWorks Download
14193 @subsubsection VxWorks download
14195 @cindex download to VxWorks
14196 If you have connected to the VxWorks target and you want to debug an
14197 object that has not yet been loaded, you can use the @value{GDBN}
14198 @code{load} command to download a file from Unix to VxWorks
14199 incrementally. The object file given as an argument to the @code{load}
14200 command is actually opened twice: first by the VxWorks target in order
14201 to download the code, then by @value{GDBN} in order to read the symbol
14202 table. This can lead to problems if the current working directories on
14203 the two systems differ. If both systems have NFS mounted the same
14204 filesystems, you can avoid these problems by using absolute paths.
14205 Otherwise, it is simplest to set the working directory on both systems
14206 to the directory in which the object file resides, and then to reference
14207 the file by its name, without any path. For instance, a program
14208 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14209 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14210 program, type this on VxWorks:
14213 -> cd "@var{vxpath}/vw/demo/rdb"
14217 Then, in @value{GDBN}, type:
14220 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14221 (vxgdb) load prog.o
14224 @value{GDBN} displays a response similar to this:
14227 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14230 You can also use the @code{load} command to reload an object module
14231 after editing and recompiling the corresponding source file. Note that
14232 this makes @value{GDBN} delete all currently-defined breakpoints,
14233 auto-displays, and convenience variables, and to clear the value
14234 history. (This is necessary in order to preserve the integrity of
14235 debugger's data structures that reference the target system's symbol
14238 @node VxWorks Attach
14239 @subsubsection Running tasks
14241 @cindex running VxWorks tasks
14242 You can also attach to an existing task using the @code{attach} command as
14246 (vxgdb) attach @var{task}
14250 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14251 or suspended when you attach to it. Running tasks are suspended at
14252 the time of attachment.
14254 @node Embedded Processors
14255 @section Embedded Processors
14257 This section goes into details specific to particular embedded
14260 @cindex send command to simulator
14261 Whenever a specific embedded processor has a simulator, @value{GDBN}
14262 allows to send an arbitrary command to the simulator.
14265 @item sim @var{command}
14266 @kindex sim@r{, a command}
14267 Send an arbitrary @var{command} string to the simulator. Consult the
14268 documentation for the specific simulator in use for information about
14269 acceptable commands.
14275 * H8/300:: Renesas H8/300
14276 * H8/500:: Renesas H8/500
14277 * M32R/D:: Renesas M32R/D
14278 * M68K:: Motorola M68K
14279 * MIPS Embedded:: MIPS Embedded
14280 * OpenRISC 1000:: OpenRisc 1000
14281 * PA:: HP PA Embedded
14284 * Sparclet:: Tsqware Sparclet
14285 * Sparclite:: Fujitsu Sparclite
14286 * ST2000:: Tandem ST2000
14287 * Z8000:: Zilog Z8000
14290 * Super-H:: Renesas Super-H
14291 * WinCE:: Windows CE child processes
14300 @item target rdi @var{dev}
14301 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14302 use this target to communicate with both boards running the Angel
14303 monitor, or with the EmbeddedICE JTAG debug device.
14306 @item target rdp @var{dev}
14311 @value{GDBN} provides the following ARM-specific commands:
14314 @item set arm disassembler
14316 This commands selects from a list of disassembly styles. The
14317 @code{"std"} style is the standard style.
14319 @item show arm disassembler
14321 Show the current disassembly style.
14323 @item set arm apcs32
14324 @cindex ARM 32-bit mode
14325 This command toggles ARM operation mode between 32-bit and 26-bit.
14327 @item show arm apcs32
14328 Display the current usage of the ARM 32-bit mode.
14330 @item set arm fpu @var{fputype}
14331 This command sets the ARM floating-point unit (FPU) type. The
14332 argument @var{fputype} can be one of these:
14336 Determine the FPU type by querying the OS ABI.
14338 Software FPU, with mixed-endian doubles on little-endian ARM
14341 GCC-compiled FPA co-processor.
14343 Software FPU with pure-endian doubles.
14349 Show the current type of the FPU.
14352 This command forces @value{GDBN} to use the specified ABI.
14355 Show the currently used ABI.
14357 @item set debug arm
14358 Toggle whether to display ARM-specific debugging messages from the ARM
14359 target support subsystem.
14361 @item show debug arm
14362 Show whether ARM-specific debugging messages are enabled.
14365 The following commands are available when an ARM target is debugged
14366 using the RDI interface:
14369 @item rdilogfile @r{[}@var{file}@r{]}
14371 @cindex ADP (Angel Debugger Protocol) logging
14372 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14373 With an argument, sets the log file to the specified @var{file}. With
14374 no argument, show the current log file name. The default log file is
14377 @item rdilogenable @r{[}@var{arg}@r{]}
14378 @kindex rdilogenable
14379 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14380 enables logging, with an argument 0 or @code{"no"} disables it. With
14381 no arguments displays the current setting. When logging is enabled,
14382 ADP packets exchanged between @value{GDBN} and the RDI target device
14383 are logged to a file.
14385 @item set rdiromatzero
14386 @kindex set rdiromatzero
14387 @cindex ROM at zero address, RDI
14388 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14389 vector catching is disabled, so that zero address can be used. If off
14390 (the default), vector catching is enabled. For this command to take
14391 effect, it needs to be invoked prior to the @code{target rdi} command.
14393 @item show rdiromatzero
14394 @kindex show rdiromatzero
14395 Show the current setting of ROM at zero address.
14397 @item set rdiheartbeat
14398 @kindex set rdiheartbeat
14399 @cindex RDI heartbeat
14400 Enable or disable RDI heartbeat packets. It is not recommended to
14401 turn on this option, since it confuses ARM and EPI JTAG interface, as
14402 well as the Angel monitor.
14404 @item show rdiheartbeat
14405 @kindex show rdiheartbeat
14406 Show the setting of RDI heartbeat packets.
14411 @subsection Renesas H8/300
14415 @kindex target hms@r{, with H8/300}
14416 @item target hms @var{dev}
14417 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
14418 Use special commands @code{device} and @code{speed} to control the serial
14419 line and the communications speed used.
14421 @kindex target e7000@r{, with H8/300}
14422 @item target e7000 @var{dev}
14423 E7000 emulator for Renesas H8 and SH.
14425 @kindex target sh3@r{, with H8/300}
14426 @kindex target sh3e@r{, with H8/300}
14427 @item target sh3 @var{dev}
14428 @itemx target sh3e @var{dev}
14429 Renesas SH-3 and SH-3E target systems.
14433 @cindex download to H8/300 or H8/500
14434 @cindex H8/300 or H8/500 download
14435 @cindex download to Renesas SH
14436 @cindex Renesas SH download
14437 When you select remote debugging to a Renesas SH, H8/300, or H8/500
14438 board, the @code{load} command downloads your program to the Renesas
14439 board and also opens it as the current executable target for
14440 @value{GDBN} on your host (like the @code{file} command).
14442 @value{GDBN} needs to know these things to talk to your
14443 Renesas SH, H8/300, or H8/500:
14447 that you want to use @samp{target hms}, the remote debugging interface
14448 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
14449 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
14450 the default when @value{GDBN} is configured specifically for the Renesas SH,
14451 H8/300, or H8/500.)
14454 what serial device connects your host to your Renesas board (the first
14455 serial device available on your host is the default).
14458 what speed to use over the serial device.
14462 * Renesas Boards:: Connecting to Renesas boards.
14463 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
14464 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
14467 @node Renesas Boards
14468 @subsubsection Connecting to Renesas boards
14470 @c only for Unix hosts
14472 @cindex serial device, Renesas micros
14473 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
14474 need to explicitly set the serial device. The default @var{port} is the
14475 first available port on your host. This is only necessary on Unix
14476 hosts, where it is typically something like @file{/dev/ttya}.
14479 @cindex serial line speed, Renesas micros
14480 @code{@value{GDBN}} has another special command to set the communications
14481 speed: @samp{speed @var{bps}}. This command also is only used from Unix
14482 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
14483 the DOS @code{mode} command (for instance,
14484 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
14486 The @samp{device} and @samp{speed} commands are available only when you
14487 use a Unix host to debug your Renesas microprocessor programs. If you
14489 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
14490 called @code{asynctsr} to communicate with the development board
14491 through a PC serial port. You must also use the DOS @code{mode} command
14492 to set up the serial port on the DOS side.
14494 The following sample session illustrates the steps needed to start a
14495 program under @value{GDBN} control on an H8/300. The example uses a
14496 sample H8/300 program called @file{t.x}. The procedure is the same for
14497 the Renesas SH and the H8/500.
14499 First hook up your development board. In this example, we use a
14500 board attached to serial port @code{COM2}; if you use a different serial
14501 port, substitute its name in the argument of the @code{mode} command.
14502 When you call @code{asynctsr}, the auxiliary comms program used by the
14503 debugger, you give it just the numeric part of the serial port's name;
14504 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
14508 C:\H8300\TEST> asynctsr 2
14509 C:\H8300\TEST> mode com2:9600,n,8,1,p
14511 Resident portion of MODE loaded
14513 COM2: 9600, n, 8, 1, p
14518 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
14519 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
14520 disable it, or even boot without it, to use @code{asynctsr} to control
14521 your development board.
14524 @kindex target hms@r{, and serial protocol}
14525 Now that serial communications are set up, and the development board is
14526 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
14527 the name of your program as the argument. @code{@value{GDBN}} prompts
14528 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
14529 commands to begin your debugging session: @samp{target hms} to specify
14530 cross-debugging to the Renesas board, and the @code{load} command to
14531 download your program to the board. @code{load} displays the names of
14532 the program's sections, and a @samp{*} for each 2K of data downloaded.
14533 (If you want to refresh @value{GDBN} data on symbols or on the
14534 executable file without downloading, use the @value{GDBN} commands
14535 @code{file} or @code{symbol-file}. These commands, and @code{load}
14536 itself, are described in @ref{Files,,Commands to specify files}.)
14539 (eg-C:\H8300\TEST) @value{GDBP} t.x
14540 @value{GDBN} is free software and you are welcome to distribute copies
14541 of it under certain conditions; type "show copying" to see
14543 There is absolutely no warranty for @value{GDBN}; type "show warranty"
14545 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
14546 (@value{GDBP}) target hms
14547 Connected to remote H8/300 HMS system.
14548 (@value{GDBP}) load t.x
14549 .text : 0x8000 .. 0xabde ***********
14550 .data : 0xabde .. 0xad30 *
14551 .stack : 0xf000 .. 0xf014 *
14554 At this point, you're ready to run or debug your program. From here on,
14555 you can use all the usual @value{GDBN} commands. The @code{break} command
14556 sets breakpoints; the @code{run} command starts your program;
14557 @code{print} or @code{x} display data; the @code{continue} command
14558 resumes execution after stopping at a breakpoint. You can use the
14559 @code{help} command at any time to find out more about @value{GDBN} commands.
14561 Remember, however, that @emph{operating system} facilities aren't
14562 available on your development board; for example, if your program hangs,
14563 you can't send an interrupt---but you can press the @sc{reset} switch!
14565 Use the @sc{reset} button on the development board
14568 to interrupt your program (don't use @kbd{Ctrl-c} on the DOS host---it has
14569 no way to pass an interrupt signal to the development board); and
14572 to return to the @value{GDBN} command prompt after your program finishes
14573 normally. The communications protocol provides no other way for @value{GDBN}
14574 to detect program completion.
14577 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
14578 development board as a ``normal exit'' of your program.
14581 @subsubsection Using the E7000 in-circuit emulator
14583 @kindex target e7000@r{, with Renesas ICE}
14584 You can use the E7000 in-circuit emulator to develop code for either the
14585 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
14586 e7000} command to connect @value{GDBN} to your E7000:
14589 @item target e7000 @var{port} @var{speed}
14590 Use this form if your E7000 is connected to a serial port. The
14591 @var{port} argument identifies what serial port to use (for example,
14592 @samp{com2}). The third argument is the line speed in bits per second
14593 (for example, @samp{9600}).
14595 @item target e7000 @var{hostname}
14596 If your E7000 is installed as a host on a TCP/IP network, you can just
14597 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
14600 The following special commands are available when debugging with the
14604 @item e7000 @var{command}
14606 @cindex send command to E7000 monitor
14607 This sends the specified @var{command} to the E7000 monitor.
14609 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
14610 @kindex ftplogin@r{, E7000}
14611 This command records information for subsequent interface with the
14612 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
14613 named @var{machine} using specified @var{username} and @var{password},
14614 and then chdir to the named directory @var{dir}.
14616 @item ftpload @var{file}
14617 @kindex ftpload@r{, E7000}
14618 This command uses credentials recorded by @code{ftplogin} to fetch and
14619 load the named @var{file} from the E7000 monitor.
14622 @kindex drain@r{, E7000}
14623 This command drains any pending text buffers stored on the E7000.
14625 @item set usehardbreakpoints
14626 @itemx show usehardbreakpoints
14627 @kindex set usehardbreakpoints@r{, E7000}
14628 @kindex show usehardbreakpoints@r{, E7000}
14629 @cindex hardware breakpoints, and E7000
14630 These commands set and show the use of hardware breakpoints for all
14631 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
14632 more information about using hardware breakpoints selectively.
14635 @node Renesas Special
14636 @subsubsection Special @value{GDBN} commands for Renesas micros
14638 Some @value{GDBN} commands are available only for the H8/300:
14642 @kindex set machine
14643 @kindex show machine
14644 @item set machine h8300
14645 @itemx set machine h8300h
14646 Condition @value{GDBN} for one of the two variants of the H8/300
14647 architecture with @samp{set machine}. You can use @samp{show machine}
14648 to check which variant is currently in effect.
14657 @kindex set memory @var{mod}
14658 @cindex memory models, H8/500
14659 @item set memory @var{mod}
14661 Specify which H8/500 memory model (@var{mod}) you are using with
14662 @samp{set memory}; check which memory model is in effect with @samp{show
14663 memory}. The accepted values for @var{mod} are @code{small},
14664 @code{big}, @code{medium}, and @code{compact}.
14669 @subsection Renesas M32R/D and M32R/SDI
14672 @kindex target m32r
14673 @item target m32r @var{dev}
14674 Renesas M32R/D ROM monitor.
14676 @kindex target m32rsdi
14677 @item target m32rsdi @var{dev}
14678 Renesas M32R SDI server, connected via parallel port to the board.
14681 The following @value{GDBN} commands are specific to the M32R monitor:
14684 @item set download-path @var{path}
14685 @kindex set download-path
14686 @cindex find downloadable @sc{srec} files (M32R)
14687 Set the default path for finding downloadable @sc{srec} files.
14689 @item show download-path
14690 @kindex show download-path
14691 Show the default path for downloadable @sc{srec} files.
14693 @item set board-address @var{addr}
14694 @kindex set board-address
14695 @cindex M32-EVA target board address
14696 Set the IP address for the M32R-EVA target board.
14698 @item show board-address
14699 @kindex show board-address
14700 Show the current IP address of the target board.
14702 @item set server-address @var{addr}
14703 @kindex set server-address
14704 @cindex download server address (M32R)
14705 Set the IP address for the download server, which is the @value{GDBN}'s
14708 @item show server-address
14709 @kindex show server-address
14710 Display the IP address of the download server.
14712 @item upload @r{[}@var{file}@r{]}
14713 @kindex upload@r{, M32R}
14714 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14715 upload capability. If no @var{file} argument is given, the current
14716 executable file is uploaded.
14718 @item tload @r{[}@var{file}@r{]}
14719 @kindex tload@r{, M32R}
14720 Test the @code{upload} command.
14723 The following commands are available for M32R/SDI:
14728 @cindex reset SDI connection, M32R
14729 This command resets the SDI connection.
14733 This command shows the SDI connection status.
14736 @kindex debug_chaos
14737 @cindex M32R/Chaos debugging
14738 Instructs the remote that M32R/Chaos debugging is to be used.
14740 @item use_debug_dma
14741 @kindex use_debug_dma
14742 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14745 @kindex use_mon_code
14746 Instructs the remote to use the MON_CODE method of accessing memory.
14749 @kindex use_ib_break
14750 Instructs the remote to set breakpoints by IB break.
14752 @item use_dbt_break
14753 @kindex use_dbt_break
14754 Instructs the remote to set breakpoints by DBT.
14760 The Motorola m68k configuration includes ColdFire support, and
14761 target command for the following ROM monitors.
14765 @kindex target abug
14766 @item target abug @var{dev}
14767 ABug ROM monitor for M68K.
14769 @kindex target cpu32bug
14770 @item target cpu32bug @var{dev}
14771 CPU32BUG monitor, running on a CPU32 (M68K) board.
14773 @kindex target dbug
14774 @item target dbug @var{dev}
14775 dBUG ROM monitor for Motorola ColdFire.
14778 @item target est @var{dev}
14779 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14781 @kindex target rom68k
14782 @item target rom68k @var{dev}
14783 ROM 68K monitor, running on an M68K IDP board.
14789 @kindex target rombug
14790 @item target rombug @var{dev}
14791 ROMBUG ROM monitor for OS/9000.
14795 @node MIPS Embedded
14796 @subsection MIPS Embedded
14798 @cindex MIPS boards
14799 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14800 MIPS board attached to a serial line. This is available when
14801 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14804 Use these @value{GDBN} commands to specify the connection to your target board:
14807 @item target mips @var{port}
14808 @kindex target mips @var{port}
14809 To run a program on the board, start up @code{@value{GDBP}} with the
14810 name of your program as the argument. To connect to the board, use the
14811 command @samp{target mips @var{port}}, where @var{port} is the name of
14812 the serial port connected to the board. If the program has not already
14813 been downloaded to the board, you may use the @code{load} command to
14814 download it. You can then use all the usual @value{GDBN} commands.
14816 For example, this sequence connects to the target board through a serial
14817 port, and loads and runs a program called @var{prog} through the
14821 host$ @value{GDBP} @var{prog}
14822 @value{GDBN} is free software and @dots{}
14823 (@value{GDBP}) target mips /dev/ttyb
14824 (@value{GDBP}) load @var{prog}
14828 @item target mips @var{hostname}:@var{portnumber}
14829 On some @value{GDBN} host configurations, you can specify a TCP
14830 connection (for instance, to a serial line managed by a terminal
14831 concentrator) instead of a serial port, using the syntax
14832 @samp{@var{hostname}:@var{portnumber}}.
14834 @item target pmon @var{port}
14835 @kindex target pmon @var{port}
14838 @item target ddb @var{port}
14839 @kindex target ddb @var{port}
14840 NEC's DDB variant of PMON for Vr4300.
14842 @item target lsi @var{port}
14843 @kindex target lsi @var{port}
14844 LSI variant of PMON.
14846 @kindex target r3900
14847 @item target r3900 @var{dev}
14848 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14850 @kindex target array
14851 @item target array @var{dev}
14852 Array Tech LSI33K RAID controller board.
14858 @value{GDBN} also supports these special commands for MIPS targets:
14861 @item set mipsfpu double
14862 @itemx set mipsfpu single
14863 @itemx set mipsfpu none
14864 @itemx set mipsfpu auto
14865 @itemx show mipsfpu
14866 @kindex set mipsfpu
14867 @kindex show mipsfpu
14868 @cindex MIPS remote floating point
14869 @cindex floating point, MIPS remote
14870 If your target board does not support the MIPS floating point
14871 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14872 need this, you may wish to put the command in your @value{GDBN} init
14873 file). This tells @value{GDBN} how to find the return value of
14874 functions which return floating point values. It also allows
14875 @value{GDBN} to avoid saving the floating point registers when calling
14876 functions on the board. If you are using a floating point coprocessor
14877 with only single precision floating point support, as on the @sc{r4650}
14878 processor, use the command @samp{set mipsfpu single}. The default
14879 double precision floating point coprocessor may be selected using
14880 @samp{set mipsfpu double}.
14882 In previous versions the only choices were double precision or no
14883 floating point, so @samp{set mipsfpu on} will select double precision
14884 and @samp{set mipsfpu off} will select no floating point.
14886 As usual, you can inquire about the @code{mipsfpu} variable with
14887 @samp{show mipsfpu}.
14889 @item set timeout @var{seconds}
14890 @itemx set retransmit-timeout @var{seconds}
14891 @itemx show timeout
14892 @itemx show retransmit-timeout
14893 @cindex @code{timeout}, MIPS protocol
14894 @cindex @code{retransmit-timeout}, MIPS protocol
14895 @kindex set timeout
14896 @kindex show timeout
14897 @kindex set retransmit-timeout
14898 @kindex show retransmit-timeout
14899 You can control the timeout used while waiting for a packet, in the MIPS
14900 remote protocol, with the @code{set timeout @var{seconds}} command. The
14901 default is 5 seconds. Similarly, you can control the timeout used while
14902 waiting for an acknowledgement of a packet with the @code{set
14903 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14904 You can inspect both values with @code{show timeout} and @code{show
14905 retransmit-timeout}. (These commands are @emph{only} available when
14906 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14908 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14909 is waiting for your program to stop. In that case, @value{GDBN} waits
14910 forever because it has no way of knowing how long the program is going
14911 to run before stopping.
14913 @item set syn-garbage-limit @var{num}
14914 @kindex set syn-garbage-limit@r{, MIPS remote}
14915 @cindex synchronize with remote MIPS target
14916 Limit the maximum number of characters @value{GDBN} should ignore when
14917 it tries to synchronize with the remote target. The default is 10
14918 characters. Setting the limit to -1 means there's no limit.
14920 @item show syn-garbage-limit
14921 @kindex show syn-garbage-limit@r{, MIPS remote}
14922 Show the current limit on the number of characters to ignore when
14923 trying to synchronize with the remote system.
14925 @item set monitor-prompt @var{prompt}
14926 @kindex set monitor-prompt@r{, MIPS remote}
14927 @cindex remote monitor prompt
14928 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14929 remote monitor. The default depends on the target:
14939 @item show monitor-prompt
14940 @kindex show monitor-prompt@r{, MIPS remote}
14941 Show the current strings @value{GDBN} expects as the prompt from the
14944 @item set monitor-warnings
14945 @kindex set monitor-warnings@r{, MIPS remote}
14946 Enable or disable monitor warnings about hardware breakpoints. This
14947 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14948 display warning messages whose codes are returned by the @code{lsi}
14949 PMON monitor for breakpoint commands.
14951 @item show monitor-warnings
14952 @kindex show monitor-warnings@r{, MIPS remote}
14953 Show the current setting of printing monitor warnings.
14955 @item pmon @var{command}
14956 @kindex pmon@r{, MIPS remote}
14957 @cindex send PMON command
14958 This command allows sending an arbitrary @var{command} string to the
14959 monitor. The monitor must be in debug mode for this to work.
14962 @node OpenRISC 1000
14963 @subsection OpenRISC 1000
14964 @cindex OpenRISC 1000
14966 @cindex or1k boards
14967 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14968 about platform and commands.
14972 @kindex target jtag
14973 @item target jtag jtag://@var{host}:@var{port}
14975 Connects to remote JTAG server.
14976 JTAG remote server can be either an or1ksim or JTAG server,
14977 connected via parallel port to the board.
14979 Example: @code{target jtag jtag://localhost:9999}
14982 @item or1ksim @var{command}
14983 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14984 Simulator, proprietary commands can be executed.
14986 @kindex info or1k spr
14987 @item info or1k spr
14988 Displays spr groups.
14990 @item info or1k spr @var{group}
14991 @itemx info or1k spr @var{groupno}
14992 Displays register names in selected group.
14994 @item info or1k spr @var{group} @var{register}
14995 @itemx info or1k spr @var{register}
14996 @itemx info or1k spr @var{groupno} @var{registerno}
14997 @itemx info or1k spr @var{registerno}
14998 Shows information about specified spr register.
15001 @item spr @var{group} @var{register} @var{value}
15002 @itemx spr @var{register @var{value}}
15003 @itemx spr @var{groupno} @var{registerno @var{value}}
15004 @itemx spr @var{registerno @var{value}}
15005 Writes @var{value} to specified spr register.
15008 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15009 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15010 program execution and is thus much faster. Hardware breakpoints/watchpoint
15011 triggers can be set using:
15014 Load effective address/data
15016 Store effective address/data
15018 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15023 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15024 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15026 @code{htrace} commands:
15027 @cindex OpenRISC 1000 htrace
15030 @item hwatch @var{conditional}
15031 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15032 or Data. For example:
15034 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15036 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15040 Display information about current HW trace configuration.
15042 @item htrace trigger @var{conditional}
15043 Set starting criteria for HW trace.
15045 @item htrace qualifier @var{conditional}
15046 Set acquisition qualifier for HW trace.
15048 @item htrace stop @var{conditional}
15049 Set HW trace stopping criteria.
15051 @item htrace record [@var{data}]*
15052 Selects the data to be recorded, when qualifier is met and HW trace was
15055 @item htrace enable
15056 @itemx htrace disable
15057 Enables/disables the HW trace.
15059 @item htrace rewind [@var{filename}]
15060 Clears currently recorded trace data.
15062 If filename is specified, new trace file is made and any newly collected data
15063 will be written there.
15065 @item htrace print [@var{start} [@var{len}]]
15066 Prints trace buffer, using current record configuration.
15068 @item htrace mode continuous
15069 Set continuous trace mode.
15071 @item htrace mode suspend
15072 Set suspend trace mode.
15077 @subsection PowerPC
15080 @kindex target dink32
15081 @item target dink32 @var{dev}
15082 DINK32 ROM monitor.
15084 @kindex target ppcbug
15085 @item target ppcbug @var{dev}
15086 @kindex target ppcbug1
15087 @item target ppcbug1 @var{dev}
15088 PPCBUG ROM monitor for PowerPC.
15091 @item target sds @var{dev}
15092 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15095 @cindex SDS protocol
15096 The following commands specify to the SDS protocol are supported
15100 @item set sdstimeout @var{nsec}
15101 @kindex set sdstimeout
15102 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15103 default is 2 seconds.
15105 @item show sdstimeout
15106 @kindex show sdstimeout
15107 Show the current value of the SDS timeout.
15109 @item sds @var{command}
15110 @kindex sds@r{, a command}
15111 Send the specified @var{command} string to the SDS monitor.
15116 @subsection HP PA Embedded
15120 @kindex target op50n
15121 @item target op50n @var{dev}
15122 OP50N monitor, running on an OKI HPPA board.
15124 @kindex target w89k
15125 @item target w89k @var{dev}
15126 W89K monitor, running on a Winbond HPPA board.
15131 @subsection Renesas SH
15135 @kindex target hms@r{, with Renesas SH}
15136 @item target hms @var{dev}
15137 A Renesas SH board attached via serial line to your host. Use special
15138 commands @code{device} and @code{speed} to control the serial line and
15139 the communications speed used.
15141 @kindex target e7000@r{, with Renesas SH}
15142 @item target e7000 @var{dev}
15143 E7000 emulator for Renesas SH.
15145 @kindex target sh3@r{, with SH}
15146 @kindex target sh3e@r{, with SH}
15147 @item target sh3 @var{dev}
15148 @item target sh3e @var{dev}
15149 Renesas SH-3 and SH-3E target systems.
15154 @subsection Tsqware Sparclet
15158 @value{GDBN} enables developers to debug tasks running on
15159 Sparclet targets from a Unix host.
15160 @value{GDBN} uses code that runs on
15161 both the Unix host and on the Sparclet target. The program
15162 @code{@value{GDBP}} is installed and executed on the Unix host.
15165 @item remotetimeout @var{args}
15166 @kindex remotetimeout
15167 @value{GDBN} supports the option @code{remotetimeout}.
15168 This option is set by the user, and @var{args} represents the number of
15169 seconds @value{GDBN} waits for responses.
15172 @cindex compiling, on Sparclet
15173 When compiling for debugging, include the options @samp{-g} to get debug
15174 information and @samp{-Ttext} to relocate the program to where you wish to
15175 load it on the target. You may also want to add the options @samp{-n} or
15176 @samp{-N} in order to reduce the size of the sections. Example:
15179 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15182 You can use @code{objdump} to verify that the addresses are what you intended:
15185 sparclet-aout-objdump --headers --syms prog
15188 @cindex running, on Sparclet
15190 your Unix execution search path to find @value{GDBN}, you are ready to
15191 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15192 (or @code{sparclet-aout-gdb}, depending on your installation).
15194 @value{GDBN} comes up showing the prompt:
15201 * Sparclet File:: Setting the file to debug
15202 * Sparclet Connection:: Connecting to Sparclet
15203 * Sparclet Download:: Sparclet download
15204 * Sparclet Execution:: Running and debugging
15207 @node Sparclet File
15208 @subsubsection Setting file to debug
15210 The @value{GDBN} command @code{file} lets you choose with program to debug.
15213 (gdbslet) file prog
15217 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15218 @value{GDBN} locates
15219 the file by searching the directories listed in the command search
15221 If the file was compiled with debug information (option "-g"), source
15222 files will be searched as well.
15223 @value{GDBN} locates
15224 the source files by searching the directories listed in the directory search
15225 path (@pxref{Environment, ,Your program's environment}).
15227 to find a file, it displays a message such as:
15230 prog: No such file or directory.
15233 When this happens, add the appropriate directories to the search paths with
15234 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15235 @code{target} command again.
15237 @node Sparclet Connection
15238 @subsubsection Connecting to Sparclet
15240 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15241 To connect to a target on serial port ``@code{ttya}'', type:
15244 (gdbslet) target sparclet /dev/ttya
15245 Remote target sparclet connected to /dev/ttya
15246 main () at ../prog.c:3
15250 @value{GDBN} displays messages like these:
15256 @node Sparclet Download
15257 @subsubsection Sparclet download
15259 @cindex download to Sparclet
15260 Once connected to the Sparclet target,
15261 you can use the @value{GDBN}
15262 @code{load} command to download the file from the host to the target.
15263 The file name and load offset should be given as arguments to the @code{load}
15265 Since the file format is aout, the program must be loaded to the starting
15266 address. You can use @code{objdump} to find out what this value is. The load
15267 offset is an offset which is added to the VMA (virtual memory address)
15268 of each of the file's sections.
15269 For instance, if the program
15270 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15271 and bss at 0x12010170, in @value{GDBN}, type:
15274 (gdbslet) load prog 0x12010000
15275 Loading section .text, size 0xdb0 vma 0x12010000
15278 If the code is loaded at a different address then what the program was linked
15279 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15280 to tell @value{GDBN} where to map the symbol table.
15282 @node Sparclet Execution
15283 @subsubsection Running and debugging
15285 @cindex running and debugging Sparclet programs
15286 You can now begin debugging the task using @value{GDBN}'s execution control
15287 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15288 manual for the list of commands.
15292 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15294 Starting program: prog
15295 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15296 3 char *symarg = 0;
15298 4 char *execarg = "hello!";
15303 @subsection Fujitsu Sparclite
15307 @kindex target sparclite
15308 @item target sparclite @var{dev}
15309 Fujitsu sparclite boards, used only for the purpose of loading.
15310 You must use an additional command to debug the program.
15311 For example: target remote @var{dev} using @value{GDBN} standard
15317 @subsection Tandem ST2000
15319 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
15322 To connect your ST2000 to the host system, see the manufacturer's
15323 manual. Once the ST2000 is physically attached, you can run:
15326 target st2000 @var{dev} @var{speed}
15330 to establish it as your debugging environment. @var{dev} is normally
15331 the name of a serial device, such as @file{/dev/ttya}, connected to the
15332 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
15333 connection (for example, to a serial line attached via a terminal
15334 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
15336 The @code{load} and @code{attach} commands are @emph{not} defined for
15337 this target; you must load your program into the ST2000 as you normally
15338 would for standalone operation. @value{GDBN} reads debugging information
15339 (such as symbols) from a separate, debugging version of the program
15340 available on your host computer.
15341 @c FIXME!! This is terribly vague; what little content is here is
15342 @c basically hearsay.
15344 @cindex ST2000 auxiliary commands
15345 These auxiliary @value{GDBN} commands are available to help you with the ST2000
15349 @item st2000 @var{command}
15350 @kindex st2000 @var{cmd}
15351 @cindex STDBUG commands (ST2000)
15352 @cindex commands to STDBUG (ST2000)
15353 Send a @var{command} to the STDBUG monitor. See the manufacturer's
15354 manual for available commands.
15357 @cindex connect (to STDBUG)
15358 Connect the controlling terminal to the STDBUG command monitor. When
15359 you are done interacting with STDBUG, typing either of two character
15360 sequences gets you back to the @value{GDBN} command prompt:
15361 @kbd{@key{RET} ~ .} (Return, followed by tilde and period) or
15362 @kbd{@key{RET} ~ Ctrl-d} (Return, followed by tilde and control-D).
15366 @subsection Zilog Z8000
15369 @cindex simulator, Z8000
15370 @cindex Zilog Z8000 simulator
15372 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15375 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15376 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15377 segmented variant). The simulator recognizes which architecture is
15378 appropriate by inspecting the object code.
15381 @item target sim @var{args}
15383 @kindex target sim@r{, with Z8000}
15384 Debug programs on a simulated CPU. If the simulator supports setup
15385 options, specify them via @var{args}.
15389 After specifying this target, you can debug programs for the simulated
15390 CPU in the same style as programs for your host computer; use the
15391 @code{file} command to load a new program image, the @code{run} command
15392 to run your program, and so on.
15394 As well as making available all the usual machine registers
15395 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15396 additional items of information as specially named registers:
15401 Counts clock-ticks in the simulator.
15404 Counts instructions run in the simulator.
15407 Execution time in 60ths of a second.
15411 You can refer to these values in @value{GDBN} expressions with the usual
15412 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15413 conditional breakpoint that suspends only after at least 5000
15414 simulated clock ticks.
15417 @subsection Atmel AVR
15420 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15421 following AVR-specific commands:
15424 @item info io_registers
15425 @kindex info io_registers@r{, AVR}
15426 @cindex I/O registers (Atmel AVR)
15427 This command displays information about the AVR I/O registers. For
15428 each register, @value{GDBN} prints its number and value.
15435 When configured for debugging CRIS, @value{GDBN} provides the
15436 following CRIS-specific commands:
15439 @item set cris-version @var{ver}
15440 @cindex CRIS version
15441 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15442 The CRIS version affects register names and sizes. This command is useful in
15443 case autodetection of the CRIS version fails.
15445 @item show cris-version
15446 Show the current CRIS version.
15448 @item set cris-dwarf2-cfi
15449 @cindex DWARF-2 CFI and CRIS
15450 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15451 Change to @samp{off} when using @code{gcc-cris} whose version is below
15454 @item show cris-dwarf2-cfi
15455 Show the current state of using DWARF-2 CFI.
15457 @item set cris-mode @var{mode}
15459 Set the current CRIS mode to @var{mode}. It should only be changed when
15460 debugging in guru mode, in which case it should be set to
15461 @samp{guru} (the default is @samp{normal}).
15463 @item show cris-mode
15464 Show the current CRIS mode.
15468 @subsection Renesas Super-H
15471 For the Renesas Super-H processor, @value{GDBN} provides these
15476 @kindex regs@r{, Super-H}
15477 Show the values of all Super-H registers.
15481 @subsection Windows CE
15484 The following commands are available for Windows CE:
15487 @item set remotedirectory @var{dir}
15488 @kindex set remotedirectory
15489 Tell @value{GDBN} to upload files from the named directory @var{dir}.
15490 The default is @file{/gdb}, i.e.@: the root directory on the current
15493 @item show remotedirectory
15494 @kindex show remotedirectory
15495 Show the current value of the upload directory.
15497 @item set remoteupload @var{method}
15498 @kindex set remoteupload
15499 Set the method used to upload files to remote device. Valid values
15500 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
15501 The default is @samp{newer}.
15503 @item show remoteupload
15504 @kindex show remoteupload
15505 Show the current setting of the upload method.
15507 @item set remoteaddhost
15508 @kindex set remoteaddhost
15509 Tell @value{GDBN} whether to add this host to the remote stub's
15510 arguments when you debug over a network.
15512 @item show remoteaddhost
15513 @kindex show remoteaddhost
15514 Show whether to add this host to remote stub's arguments when
15515 debugging over a network.
15519 @node Architectures
15520 @section Architectures
15522 This section describes characteristics of architectures that affect
15523 all uses of @value{GDBN} with the architecture, both native and cross.
15530 * HPPA:: HP PA architecture
15534 @subsection x86 Architecture-specific issues.
15537 @item set struct-convention @var{mode}
15538 @kindex set struct-convention
15539 @cindex struct return convention
15540 @cindex struct/union returned in registers
15541 Set the convention used by the inferior to return @code{struct}s and
15542 @code{union}s from functions to @var{mode}. Possible values of
15543 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15544 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15545 are returned on the stack, while @code{"reg"} means that a
15546 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15547 be returned in a register.
15549 @item show struct-convention
15550 @kindex show struct-convention
15551 Show the current setting of the convention to return @code{struct}s
15560 @kindex set rstack_high_address
15561 @cindex AMD 29K register stack
15562 @cindex register stack, AMD29K
15563 @item set rstack_high_address @var{address}
15564 On AMD 29000 family processors, registers are saved in a separate
15565 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15566 extent of this stack. Normally, @value{GDBN} just assumes that the
15567 stack is ``large enough''. This may result in @value{GDBN} referencing
15568 memory locations that do not exist. If necessary, you can get around
15569 this problem by specifying the ending address of the register stack with
15570 the @code{set rstack_high_address} command. The argument should be an
15571 address, which you probably want to precede with @samp{0x} to specify in
15574 @kindex show rstack_high_address
15575 @item show rstack_high_address
15576 Display the current limit of the register stack, on AMD 29000 family
15584 See the following section.
15589 @cindex stack on Alpha
15590 @cindex stack on MIPS
15591 @cindex Alpha stack
15593 Alpha- and MIPS-based computers use an unusual stack frame, which
15594 sometimes requires @value{GDBN} to search backward in the object code to
15595 find the beginning of a function.
15597 @cindex response time, MIPS debugging
15598 To improve response time (especially for embedded applications, where
15599 @value{GDBN} may be restricted to a slow serial line for this search)
15600 you may want to limit the size of this search, using one of these
15604 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15605 @item set heuristic-fence-post @var{limit}
15606 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15607 search for the beginning of a function. A value of @var{0} (the
15608 default) means there is no limit. However, except for @var{0}, the
15609 larger the limit the more bytes @code{heuristic-fence-post} must search
15610 and therefore the longer it takes to run. You should only need to use
15611 this command when debugging a stripped executable.
15613 @item show heuristic-fence-post
15614 Display the current limit.
15618 These commands are available @emph{only} when @value{GDBN} is configured
15619 for debugging programs on Alpha or MIPS processors.
15621 Several MIPS-specific commands are available when debugging MIPS
15625 @item set mips saved-gpreg-size @var{size}
15626 @kindex set mips saved-gpreg-size
15627 @cindex MIPS GP register size on stack
15628 Set the size of MIPS general-purpose registers saved on the stack.
15629 The argument @var{size} can be one of the following:
15633 32-bit GP registers
15635 64-bit GP registers
15637 Use the target's default setting or autodetect the saved size from the
15638 information contained in the executable. This is the default
15641 @item show mips saved-gpreg-size
15642 @kindex show mips saved-gpreg-size
15643 Show the current size of MIPS GP registers on the stack.
15645 @item set mips stack-arg-size @var{size}
15646 @kindex set mips stack-arg-size
15647 @cindex MIPS stack space for arguments
15648 Set the amount of stack space reserved for arguments to functions.
15649 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
15652 @item set mips abi @var{arg}
15653 @kindex set mips abi
15654 @cindex set ABI for MIPS
15655 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15656 values of @var{arg} are:
15660 The default ABI associated with the current binary (this is the
15671 @item show mips abi
15672 @kindex show mips abi
15673 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15676 @itemx show mipsfpu
15677 @xref{MIPS Embedded, set mipsfpu}.
15679 @item set mips mask-address @var{arg}
15680 @kindex set mips mask-address
15681 @cindex MIPS addresses, masking
15682 This command determines whether the most-significant 32 bits of 64-bit
15683 MIPS addresses are masked off. The argument @var{arg} can be
15684 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15685 setting, which lets @value{GDBN} determine the correct value.
15687 @item show mips mask-address
15688 @kindex show mips mask-address
15689 Show whether the upper 32 bits of MIPS addresses are masked off or
15692 @item set remote-mips64-transfers-32bit-regs
15693 @kindex set remote-mips64-transfers-32bit-regs
15694 This command controls compatibility with 64-bit MIPS targets that
15695 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15696 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15697 and 64 bits for other registers, set this option to @samp{on}.
15699 @item show remote-mips64-transfers-32bit-regs
15700 @kindex show remote-mips64-transfers-32bit-regs
15701 Show the current setting of compatibility with older MIPS 64 targets.
15703 @item set debug mips
15704 @kindex set debug mips
15705 This command turns on and off debugging messages for the MIPS-specific
15706 target code in @value{GDBN}.
15708 @item show debug mips
15709 @kindex show debug mips
15710 Show the current setting of MIPS debugging messages.
15716 @cindex HPPA support
15718 When @value{GDBN} is debugging the HP PA architecture, it provides the
15719 following special commands:
15722 @item set debug hppa
15723 @kindex set debug hppa
15724 This command determines whether HPPA architecture specific debugging
15725 messages are to be displayed.
15727 @item show debug hppa
15728 Show whether HPPA debugging messages are displayed.
15730 @item maint print unwind @var{address}
15731 @kindex maint print unwind@r{, HPPA}
15732 This command displays the contents of the unwind table entry at the
15733 given @var{address}.
15738 @node Controlling GDB
15739 @chapter Controlling @value{GDBN}
15741 You can alter the way @value{GDBN} interacts with you by using the
15742 @code{set} command. For commands controlling how @value{GDBN} displays
15743 data, see @ref{Print Settings, ,Print settings}. Other settings are
15748 * Editing:: Command editing
15749 * Command History:: Command history
15750 * Screen Size:: Screen size
15751 * Numbers:: Numbers
15752 * ABI:: Configuring the current ABI
15753 * Messages/Warnings:: Optional warnings and messages
15754 * Debugging Output:: Optional messages about internal happenings
15762 @value{GDBN} indicates its readiness to read a command by printing a string
15763 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15764 can change the prompt string with the @code{set prompt} command. For
15765 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15766 the prompt in one of the @value{GDBN} sessions so that you can always tell
15767 which one you are talking to.
15769 @emph{Note:} @code{set prompt} does not add a space for you after the
15770 prompt you set. This allows you to set a prompt which ends in a space
15771 or a prompt that does not.
15775 @item set prompt @var{newprompt}
15776 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15778 @kindex show prompt
15780 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15784 @section Command editing
15786 @cindex command line editing
15788 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15789 @sc{gnu} library provides consistent behavior for programs which provide a
15790 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15791 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15792 substitution, and a storage and recall of command history across
15793 debugging sessions.
15795 You may control the behavior of command line editing in @value{GDBN} with the
15796 command @code{set}.
15799 @kindex set editing
15802 @itemx set editing on
15803 Enable command line editing (enabled by default).
15805 @item set editing off
15806 Disable command line editing.
15808 @kindex show editing
15810 Show whether command line editing is enabled.
15813 @xref{Command Line Editing}, for more details about the Readline
15814 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15815 encouraged to read that chapter.
15817 @node Command History
15818 @section Command history
15819 @cindex command history
15821 @value{GDBN} can keep track of the commands you type during your
15822 debugging sessions, so that you can be certain of precisely what
15823 happened. Use these commands to manage the @value{GDBN} command
15826 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15827 package, to provide the history facility. @xref{Using History
15828 Interactively}, for the detailed description of the History library.
15830 To issue a command to @value{GDBN} without affecting certain aspects of
15831 the state which is seen by users, prefix it with @samp{server }. This
15832 means that this command will not affect the command history, nor will it
15833 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15834 pressed on a line by itself.
15836 @cindex @code{server}, command prefix
15837 The server prefix does not affect the recording of values into the value
15838 history; to print a value without recording it into the value history,
15839 use the @code{output} command instead of the @code{print} command.
15841 Here is the description of @value{GDBN} commands related to command
15845 @cindex history substitution
15846 @cindex history file
15847 @kindex set history filename
15848 @cindex @env{GDBHISTFILE}, environment variable
15849 @item set history filename @var{fname}
15850 Set the name of the @value{GDBN} command history file to @var{fname}.
15851 This is the file where @value{GDBN} reads an initial command history
15852 list, and where it writes the command history from this session when it
15853 exits. You can access this list through history expansion or through
15854 the history command editing characters listed below. This file defaults
15855 to the value of the environment variable @code{GDBHISTFILE}, or to
15856 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15859 @cindex save command history
15860 @kindex set history save
15861 @item set history save
15862 @itemx set history save on
15863 Record command history in a file, whose name may be specified with the
15864 @code{set history filename} command. By default, this option is disabled.
15866 @item set history save off
15867 Stop recording command history in a file.
15869 @cindex history size
15870 @kindex set history size
15871 @cindex @env{HISTSIZE}, environment variable
15872 @item set history size @var{size}
15873 Set the number of commands which @value{GDBN} keeps in its history list.
15874 This defaults to the value of the environment variable
15875 @code{HISTSIZE}, or to 256 if this variable is not set.
15878 History expansion assigns special meaning to the character @kbd{!}.
15879 @xref{Event Designators}, for more details.
15881 @cindex history expansion, turn on/off
15882 Since @kbd{!} is also the logical not operator in C, history expansion
15883 is off by default. If you decide to enable history expansion with the
15884 @code{set history expansion on} command, you may sometimes need to
15885 follow @kbd{!} (when it is used as logical not, in an expression) with
15886 a space or a tab to prevent it from being expanded. The readline
15887 history facilities do not attempt substitution on the strings
15888 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15890 The commands to control history expansion are:
15893 @item set history expansion on
15894 @itemx set history expansion
15895 @kindex set history expansion
15896 Enable history expansion. History expansion is off by default.
15898 @item set history expansion off
15899 Disable history expansion.
15902 @kindex show history
15904 @itemx show history filename
15905 @itemx show history save
15906 @itemx show history size
15907 @itemx show history expansion
15908 These commands display the state of the @value{GDBN} history parameters.
15909 @code{show history} by itself displays all four states.
15914 @kindex show commands
15915 @cindex show last commands
15916 @cindex display command history
15917 @item show commands
15918 Display the last ten commands in the command history.
15920 @item show commands @var{n}
15921 Print ten commands centered on command number @var{n}.
15923 @item show commands +
15924 Print ten commands just after the commands last printed.
15928 @section Screen size
15929 @cindex size of screen
15930 @cindex pauses in output
15932 Certain commands to @value{GDBN} may produce large amounts of
15933 information output to the screen. To help you read all of it,
15934 @value{GDBN} pauses and asks you for input at the end of each page of
15935 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15936 to discard the remaining output. Also, the screen width setting
15937 determines when to wrap lines of output. Depending on what is being
15938 printed, @value{GDBN} tries to break the line at a readable place,
15939 rather than simply letting it overflow onto the following line.
15941 Normally @value{GDBN} knows the size of the screen from the terminal
15942 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15943 together with the value of the @code{TERM} environment variable and the
15944 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15945 you can override it with the @code{set height} and @code{set
15952 @kindex show height
15953 @item set height @var{lpp}
15955 @itemx set width @var{cpl}
15957 These @code{set} commands specify a screen height of @var{lpp} lines and
15958 a screen width of @var{cpl} characters. The associated @code{show}
15959 commands display the current settings.
15961 If you specify a height of zero lines, @value{GDBN} does not pause during
15962 output no matter how long the output is. This is useful if output is to a
15963 file or to an editor buffer.
15965 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15966 from wrapping its output.
15968 @item set pagination on
15969 @itemx set pagination off
15970 @kindex set pagination
15971 Turn the output pagination on or off; the default is on. Turning
15972 pagination off is the alternative to @code{set height 0}.
15974 @item show pagination
15975 @kindex show pagination
15976 Show the current pagination mode.
15981 @cindex number representation
15982 @cindex entering numbers
15984 You can always enter numbers in octal, decimal, or hexadecimal in
15985 @value{GDBN} by the usual conventions: octal numbers begin with
15986 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15987 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15988 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15989 10; likewise, the default display for numbers---when no particular
15990 format is specified---is base 10. You can change the default base for
15991 both input and output with the commands described below.
15994 @kindex set input-radix
15995 @item set input-radix @var{base}
15996 Set the default base for numeric input. Supported choices
15997 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15998 specified either unambiguously or using the current input radix; for
16002 set input-radix 012
16003 set input-radix 10.
16004 set input-radix 0xa
16008 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
16009 leaves the input radix unchanged, no matter what it was, since
16010 @samp{10}, being without any leading or trailing signs of its base, is
16011 interpreted in the current radix. Thus, if the current radix is 16,
16012 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
16015 @kindex set output-radix
16016 @item set output-radix @var{base}
16017 Set the default base for numeric display. Supported choices
16018 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16019 specified either unambiguously or using the current input radix.
16021 @kindex show input-radix
16022 @item show input-radix
16023 Display the current default base for numeric input.
16025 @kindex show output-radix
16026 @item show output-radix
16027 Display the current default base for numeric display.
16029 @item set radix @r{[}@var{base}@r{]}
16033 These commands set and show the default base for both input and output
16034 of numbers. @code{set radix} sets the radix of input and output to
16035 the same base; without an argument, it resets the radix back to its
16036 default value of 10.
16041 @section Configuring the current ABI
16043 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
16044 application automatically. However, sometimes you need to override its
16045 conclusions. Use these commands to manage @value{GDBN}'s view of the
16052 One @value{GDBN} configuration can debug binaries for multiple operating
16053 system targets, either via remote debugging or native emulation.
16054 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
16055 but you can override its conclusion using the @code{set osabi} command.
16056 One example where this is useful is in debugging of binaries which use
16057 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16058 not have the same identifying marks that the standard C library for your
16063 Show the OS ABI currently in use.
16066 With no argument, show the list of registered available OS ABI's.
16068 @item set osabi @var{abi}
16069 Set the current OS ABI to @var{abi}.
16072 @cindex float promotion
16074 Generally, the way that an argument of type @code{float} is passed to a
16075 function depends on whether the function is prototyped. For a prototyped
16076 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16077 according to the architecture's convention for @code{float}. For unprototyped
16078 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16079 @code{double} and then passed.
16081 Unfortunately, some forms of debug information do not reliably indicate whether
16082 a function is prototyped. If @value{GDBN} calls a function that is not marked
16083 as prototyped, it consults @kbd{set coerce-float-to-double}.
16086 @kindex set coerce-float-to-double
16087 @item set coerce-float-to-double
16088 @itemx set coerce-float-to-double on
16089 Arguments of type @code{float} will be promoted to @code{double} when passed
16090 to an unprototyped function. This is the default setting.
16092 @item set coerce-float-to-double off
16093 Arguments of type @code{float} will be passed directly to unprototyped
16096 @kindex show coerce-float-to-double
16097 @item show coerce-float-to-double
16098 Show the current setting of promoting @code{float} to @code{double}.
16102 @kindex show cp-abi
16103 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16104 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16105 used to build your application. @value{GDBN} only fully supports
16106 programs with a single C@t{++} ABI; if your program contains code using
16107 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16108 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16109 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16110 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16111 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16112 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16117 Show the C@t{++} ABI currently in use.
16120 With no argument, show the list of supported C@t{++} ABI's.
16122 @item set cp-abi @var{abi}
16123 @itemx set cp-abi auto
16124 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16127 @node Messages/Warnings
16128 @section Optional warnings and messages
16130 @cindex verbose operation
16131 @cindex optional warnings
16132 By default, @value{GDBN} is silent about its inner workings. If you are
16133 running on a slow machine, you may want to use the @code{set verbose}
16134 command. This makes @value{GDBN} tell you when it does a lengthy
16135 internal operation, so you will not think it has crashed.
16137 Currently, the messages controlled by @code{set verbose} are those
16138 which announce that the symbol table for a source file is being read;
16139 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
16142 @kindex set verbose
16143 @item set verbose on
16144 Enables @value{GDBN} output of certain informational messages.
16146 @item set verbose off
16147 Disables @value{GDBN} output of certain informational messages.
16149 @kindex show verbose
16151 Displays whether @code{set verbose} is on or off.
16154 By default, if @value{GDBN} encounters bugs in the symbol table of an
16155 object file, it is silent; but if you are debugging a compiler, you may
16156 find this information useful (@pxref{Symbol Errors, ,Errors reading
16161 @kindex set complaints
16162 @item set complaints @var{limit}
16163 Permits @value{GDBN} to output @var{limit} complaints about each type of
16164 unusual symbols before becoming silent about the problem. Set
16165 @var{limit} to zero to suppress all complaints; set it to a large number
16166 to prevent complaints from being suppressed.
16168 @kindex show complaints
16169 @item show complaints
16170 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16174 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16175 lot of stupid questions to confirm certain commands. For example, if
16176 you try to run a program which is already running:
16180 The program being debugged has been started already.
16181 Start it from the beginning? (y or n)
16184 If you are willing to unflinchingly face the consequences of your own
16185 commands, you can disable this ``feature'':
16189 @kindex set confirm
16191 @cindex confirmation
16192 @cindex stupid questions
16193 @item set confirm off
16194 Disables confirmation requests.
16196 @item set confirm on
16197 Enables confirmation requests (the default).
16199 @kindex show confirm
16201 Displays state of confirmation requests.
16205 @cindex command tracing
16206 If you need to debug user-defined commands or sourced files you may find it
16207 useful to enable @dfn{command tracing}. In this mode each command will be
16208 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16209 quantity denoting the call depth of each command.
16212 @kindex set trace-commands
16213 @cindex command scripts, debugging
16214 @item set trace-commands on
16215 Enable command tracing.
16216 @item set trace-commands off
16217 Disable command tracing.
16218 @item show trace-commands
16219 Display the current state of command tracing.
16222 @node Debugging Output
16223 @section Optional messages about internal happenings
16224 @cindex optional debugging messages
16226 @value{GDBN} has commands that enable optional debugging messages from
16227 various @value{GDBN} subsystems; normally these commands are of
16228 interest to @value{GDBN} maintainers, or when reporting a bug. This
16229 section documents those commands.
16232 @kindex set exec-done-display
16233 @item set exec-done-display
16234 Turns on or off the notification of asynchronous commands'
16235 completion. When on, @value{GDBN} will print a message when an
16236 asynchronous command finishes its execution. The default is off.
16237 @kindex show exec-done-display
16238 @item show exec-done-display
16239 Displays the current setting of asynchronous command completion
16242 @cindex gdbarch debugging info
16243 @cindex architecture debugging info
16244 @item set debug arch
16245 Turns on or off display of gdbarch debugging info. The default is off
16247 @item show debug arch
16248 Displays the current state of displaying gdbarch debugging info.
16249 @item set debug aix-thread
16250 @cindex AIX threads
16251 Display debugging messages about inner workings of the AIX thread
16253 @item show debug aix-thread
16254 Show the current state of AIX thread debugging info display.
16255 @item set debug event
16256 @cindex event debugging info
16257 Turns on or off display of @value{GDBN} event debugging info. The
16259 @item show debug event
16260 Displays the current state of displaying @value{GDBN} event debugging
16262 @item set debug expression
16263 @cindex expression debugging info
16264 Turns on or off display of debugging info about @value{GDBN}
16265 expression parsing. The default is off.
16266 @item show debug expression
16267 Displays the current state of displaying debugging info about
16268 @value{GDBN} expression parsing.
16269 @item set debug frame
16270 @cindex frame debugging info
16271 Turns on or off display of @value{GDBN} frame debugging info. The
16273 @item show debug frame
16274 Displays the current state of displaying @value{GDBN} frame debugging
16276 @item set debug infrun
16277 @cindex inferior debugging info
16278 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16279 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16280 for implementing operations such as single-stepping the inferior.
16281 @item show debug infrun
16282 Displays the current state of @value{GDBN} inferior debugging.
16283 @item set debug lin-lwp
16284 @cindex @sc{gnu}/Linux LWP debug messages
16285 @cindex Linux lightweight processes
16286 Turns on or off debugging messages from the Linux LWP debug support.
16287 @item show debug lin-lwp
16288 Show the current state of Linux LWP debugging messages.
16289 @item set debug observer
16290 @cindex observer debugging info
16291 Turns on or off display of @value{GDBN} observer debugging. This
16292 includes info such as the notification of observable events.
16293 @item show debug observer
16294 Displays the current state of observer debugging.
16295 @item set debug overload
16296 @cindex C@t{++} overload debugging info
16297 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16298 info. This includes info such as ranking of functions, etc. The default
16300 @item show debug overload
16301 Displays the current state of displaying @value{GDBN} C@t{++} overload
16303 @cindex packets, reporting on stdout
16304 @cindex serial connections, debugging
16305 @cindex debug remote protocol
16306 @cindex remote protocol debugging
16307 @cindex display remote packets
16308 @item set debug remote
16309 Turns on or off display of reports on all packets sent back and forth across
16310 the serial line to the remote machine. The info is printed on the
16311 @value{GDBN} standard output stream. The default is off.
16312 @item show debug remote
16313 Displays the state of display of remote packets.
16314 @item set debug serial
16315 Turns on or off display of @value{GDBN} serial debugging info. The
16317 @item show debug serial
16318 Displays the current state of displaying @value{GDBN} serial debugging
16320 @item set debug solib-frv
16321 @cindex FR-V shared-library debugging
16322 Turns on or off debugging messages for FR-V shared-library code.
16323 @item show debug solib-frv
16324 Display the current state of FR-V shared-library code debugging
16326 @item set debug target
16327 @cindex target debugging info
16328 Turns on or off display of @value{GDBN} target debugging info. This info
16329 includes what is going on at the target level of GDB, as it happens. The
16330 default is 0. Set it to 1 to track events, and to 2 to also track the
16331 value of large memory transfers. Changes to this flag do not take effect
16332 until the next time you connect to a target or use the @code{run} command.
16333 @item show debug target
16334 Displays the current state of displaying @value{GDBN} target debugging
16336 @item set debugvarobj
16337 @cindex variable object debugging info
16338 Turns on or off display of @value{GDBN} variable object debugging
16339 info. The default is off.
16340 @item show debugvarobj
16341 Displays the current state of displaying @value{GDBN} variable object
16343 @item set debug xml
16344 @cindex XML parser debugging
16345 Turns on or off debugging messages for built-in XML parsers.
16346 @item show debug xml
16347 Displays the current state of XML debugging messages.
16351 @chapter Canned Sequences of Commands
16353 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16354 command lists}), @value{GDBN} provides two ways to store sequences of
16355 commands for execution as a unit: user-defined commands and command
16359 * Define:: How to define your own commands
16360 * Hooks:: Hooks for user-defined commands
16361 * Command Files:: How to write scripts of commands to be stored in a file
16362 * Output:: Commands for controlled output
16366 @section User-defined commands
16368 @cindex user-defined command
16369 @cindex arguments, to user-defined commands
16370 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16371 which you assign a new name as a command. This is done with the
16372 @code{define} command. User commands may accept up to 10 arguments
16373 separated by whitespace. Arguments are accessed within the user command
16374 via @code{$arg0@dots{}$arg9}. A trivial example:
16378 print $arg0 + $arg1 + $arg2
16383 To execute the command use:
16390 This defines the command @code{adder}, which prints the sum of
16391 its three arguments. Note the arguments are text substitutions, so they may
16392 reference variables, use complex expressions, or even perform inferior
16395 @cindex argument count in user-defined commands
16396 @cindex how many arguments (user-defined commands)
16397 In addition, @code{$argc} may be used to find out how many arguments have
16398 been passed. This expands to a number in the range 0@dots{}10.
16403 print $arg0 + $arg1
16406 print $arg0 + $arg1 + $arg2
16414 @item define @var{commandname}
16415 Define a command named @var{commandname}. If there is already a command
16416 by that name, you are asked to confirm that you want to redefine it.
16418 The definition of the command is made up of other @value{GDBN} command lines,
16419 which are given following the @code{define} command. The end of these
16420 commands is marked by a line containing @code{end}.
16423 @kindex end@r{ (user-defined commands)}
16424 @item document @var{commandname}
16425 Document the user-defined command @var{commandname}, so that it can be
16426 accessed by @code{help}. The command @var{commandname} must already be
16427 defined. This command reads lines of documentation just as @code{define}
16428 reads the lines of the command definition, ending with @code{end}.
16429 After the @code{document} command is finished, @code{help} on command
16430 @var{commandname} displays the documentation you have written.
16432 You may use the @code{document} command again to change the
16433 documentation of a command. Redefining the command with @code{define}
16434 does not change the documentation.
16436 @kindex dont-repeat
16437 @cindex don't repeat command
16439 Used inside a user-defined command, this tells @value{GDBN} that this
16440 command should not be repeated when the user hits @key{RET}
16441 (@pxref{Command Syntax, repeat last command}).
16443 @kindex help user-defined
16444 @item help user-defined
16445 List all user-defined commands, with the first line of the documentation
16450 @itemx show user @var{commandname}
16451 Display the @value{GDBN} commands used to define @var{commandname} (but
16452 not its documentation). If no @var{commandname} is given, display the
16453 definitions for all user-defined commands.
16455 @cindex infinite recursion in user-defined commands
16456 @kindex show max-user-call-depth
16457 @kindex set max-user-call-depth
16458 @item show max-user-call-depth
16459 @itemx set max-user-call-depth
16460 The value of @code{max-user-call-depth} controls how many recursion
16461 levels are allowed in user-defined commands before GDB suspects an
16462 infinite recursion and aborts the command.
16465 In addition to the above commands, user-defined commands frequently
16466 use control flow commands, described in @ref{Command Files}.
16468 When user-defined commands are executed, the
16469 commands of the definition are not printed. An error in any command
16470 stops execution of the user-defined command.
16472 If used interactively, commands that would ask for confirmation proceed
16473 without asking when used inside a user-defined command. Many @value{GDBN}
16474 commands that normally print messages to say what they are doing omit the
16475 messages when used in a user-defined command.
16478 @section User-defined command hooks
16479 @cindex command hooks
16480 @cindex hooks, for commands
16481 @cindex hooks, pre-command
16484 You may define @dfn{hooks}, which are a special kind of user-defined
16485 command. Whenever you run the command @samp{foo}, if the user-defined
16486 command @samp{hook-foo} exists, it is executed (with no arguments)
16487 before that command.
16489 @cindex hooks, post-command
16491 A hook may also be defined which is run after the command you executed.
16492 Whenever you run the command @samp{foo}, if the user-defined command
16493 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16494 that command. Post-execution hooks may exist simultaneously with
16495 pre-execution hooks, for the same command.
16497 It is valid for a hook to call the command which it hooks. If this
16498 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16500 @c It would be nice if hookpost could be passed a parameter indicating
16501 @c if the command it hooks executed properly or not. FIXME!
16503 @kindex stop@r{, a pseudo-command}
16504 In addition, a pseudo-command, @samp{stop} exists. Defining
16505 (@samp{hook-stop}) makes the associated commands execute every time
16506 execution stops in your program: before breakpoint commands are run,
16507 displays are printed, or the stack frame is printed.
16509 For example, to ignore @code{SIGALRM} signals while
16510 single-stepping, but treat them normally during normal execution,
16515 handle SIGALRM nopass
16519 handle SIGALRM pass
16522 define hook-continue
16523 handle SIGALRM pass
16527 As a further example, to hook at the beginning and end of the @code{echo}
16528 command, and to add extra text to the beginning and end of the message,
16536 define hookpost-echo
16540 (@value{GDBP}) echo Hello World
16541 <<<---Hello World--->>>
16546 You can define a hook for any single-word command in @value{GDBN}, but
16547 not for command aliases; you should define a hook for the basic command
16548 name, e.g.@: @code{backtrace} rather than @code{bt}.
16549 @c FIXME! So how does Joe User discover whether a command is an alias
16551 If an error occurs during the execution of your hook, execution of
16552 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16553 (before the command that you actually typed had a chance to run).
16555 If you try to define a hook which does not match any known command, you
16556 get a warning from the @code{define} command.
16558 @node Command Files
16559 @section Command files
16561 @cindex command files
16562 @cindex scripting commands
16563 A command file for @value{GDBN} is a text file made of lines that are
16564 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16565 also be included. An empty line in a command file does nothing; it
16566 does not mean to repeat the last command, as it would from the
16569 You can request the execution of a command file with the @code{source}
16574 @cindex execute commands from a file
16575 @item source [@code{-v}] @var{filename}
16576 Execute the command file @var{filename}.
16579 The lines in a command file are generally executed sequentially,
16580 unless the order of execution is changed by one of the
16581 @emph{flow-control commands} described below. The commands are not
16582 printed as they are executed. An error in any command terminates
16583 execution of the command file and control is returned to the console.
16585 @value{GDBN} searches for @var{filename} in the current directory and then
16586 on the search path (specified with the @samp{directory} command).
16588 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16589 each command as it is executed. The option must be given before
16590 @var{filename}, and is interpreted as part of the filename anywhere else.
16592 Commands that would ask for confirmation if used interactively proceed
16593 without asking when used in a command file. Many @value{GDBN} commands that
16594 normally print messages to say what they are doing omit the messages
16595 when called from command files.
16597 @value{GDBN} also accepts command input from standard input. In this
16598 mode, normal output goes to standard output and error output goes to
16599 standard error. Errors in a command file supplied on standard input do
16600 not terminate execution of the command file---execution continues with
16604 gdb < cmds > log 2>&1
16607 (The syntax above will vary depending on the shell used.) This example
16608 will execute commands from the file @file{cmds}. All output and errors
16609 would be directed to @file{log}.
16611 Since commands stored on command files tend to be more general than
16612 commands typed interactively, they frequently need to deal with
16613 complicated situations, such as different or unexpected values of
16614 variables and symbols, changes in how the program being debugged is
16615 built, etc. @value{GDBN} provides a set of flow-control commands to
16616 deal with these complexities. Using these commands, you can write
16617 complex scripts that loop over data structures, execute commands
16618 conditionally, etc.
16625 This command allows to include in your script conditionally executed
16626 commands. The @code{if} command takes a single argument, which is an
16627 expression to evaluate. It is followed by a series of commands that
16628 are executed only if the expression is true (its value is nonzero).
16629 There can then optionally be an @code{else} line, followed by a series
16630 of commands that are only executed if the expression was false. The
16631 end of the list is marked by a line containing @code{end}.
16635 This command allows to write loops. Its syntax is similar to
16636 @code{if}: the command takes a single argument, which is an expression
16637 to evaluate, and must be followed by the commands to execute, one per
16638 line, terminated by an @code{end}. These commands are called the
16639 @dfn{body} of the loop. The commands in the body of @code{while} are
16640 executed repeatedly as long as the expression evaluates to true.
16644 This command exits the @code{while} loop in whose body it is included.
16645 Execution of the script continues after that @code{while}s @code{end}
16648 @kindex loop_continue
16649 @item loop_continue
16650 This command skips the execution of the rest of the body of commands
16651 in the @code{while} loop in whose body it is included. Execution
16652 branches to the beginning of the @code{while} loop, where it evaluates
16653 the controlling expression.
16655 @kindex end@r{ (if/else/while commands)}
16657 Terminate the block of commands that are the body of @code{if},
16658 @code{else}, or @code{while} flow-control commands.
16663 @section Commands for controlled output
16665 During the execution of a command file or a user-defined command, normal
16666 @value{GDBN} output is suppressed; the only output that appears is what is
16667 explicitly printed by the commands in the definition. This section
16668 describes three commands useful for generating exactly the output you
16673 @item echo @var{text}
16674 @c I do not consider backslash-space a standard C escape sequence
16675 @c because it is not in ANSI.
16676 Print @var{text}. Nonprinting characters can be included in
16677 @var{text} using C escape sequences, such as @samp{\n} to print a
16678 newline. @strong{No newline is printed unless you specify one.}
16679 In addition to the standard C escape sequences, a backslash followed
16680 by a space stands for a space. This is useful for displaying a
16681 string with spaces at the beginning or the end, since leading and
16682 trailing spaces are otherwise trimmed from all arguments.
16683 To print @samp{@w{ }and foo =@w{ }}, use the command
16684 @samp{echo \@w{ }and foo = \@w{ }}.
16686 A backslash at the end of @var{text} can be used, as in C, to continue
16687 the command onto subsequent lines. For example,
16690 echo This is some text\n\
16691 which is continued\n\
16692 onto several lines.\n
16695 produces the same output as
16698 echo This is some text\n
16699 echo which is continued\n
16700 echo onto several lines.\n
16704 @item output @var{expression}
16705 Print the value of @var{expression} and nothing but that value: no
16706 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16707 value history either. @xref{Expressions, ,Expressions}, for more information
16710 @item output/@var{fmt} @var{expression}
16711 Print the value of @var{expression} in format @var{fmt}. You can use
16712 the same formats as for @code{print}. @xref{Output Formats,,Output
16713 formats}, for more information.
16716 @item printf @var{string}, @var{expressions}@dots{}
16717 Print the values of the @var{expressions} under the control of
16718 @var{string}. The @var{expressions} are separated by commas and may be
16719 either numbers or pointers. Their values are printed as specified by
16720 @var{string}, exactly as if your program were to execute the C
16722 @c FIXME: the above implies that at least all ANSI C formats are
16723 @c supported, but it isn't true: %E and %G don't work (or so it seems).
16724 @c Either this is a bug, or the manual should document what formats are
16728 printf (@var{string}, @var{expressions}@dots{});
16731 For example, you can print two values in hex like this:
16734 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16737 The only backslash-escape sequences that you can use in the format
16738 string are the simple ones that consist of backslash followed by a
16743 @chapter Command Interpreters
16744 @cindex command interpreters
16746 @value{GDBN} supports multiple command interpreters, and some command
16747 infrastructure to allow users or user interface writers to switch
16748 between interpreters or run commands in other interpreters.
16750 @value{GDBN} currently supports two command interpreters, the console
16751 interpreter (sometimes called the command-line interpreter or @sc{cli})
16752 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16753 describes both of these interfaces in great detail.
16755 By default, @value{GDBN} will start with the console interpreter.
16756 However, the user may choose to start @value{GDBN} with another
16757 interpreter by specifying the @option{-i} or @option{--interpreter}
16758 startup options. Defined interpreters include:
16762 @cindex console interpreter
16763 The traditional console or command-line interpreter. This is the most often
16764 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16765 @value{GDBN} will use this interpreter.
16768 @cindex mi interpreter
16769 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16770 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16771 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16775 @cindex mi2 interpreter
16776 The current @sc{gdb/mi} interface.
16779 @cindex mi1 interpreter
16780 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16784 @cindex invoke another interpreter
16785 The interpreter being used by @value{GDBN} may not be dynamically
16786 switched at runtime. Although possible, this could lead to a very
16787 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16788 enters the command "interpreter-set console" in a console view,
16789 @value{GDBN} would switch to using the console interpreter, rendering
16790 the IDE inoperable!
16792 @kindex interpreter-exec
16793 Although you may only choose a single interpreter at startup, you may execute
16794 commands in any interpreter from the current interpreter using the appropriate
16795 command. If you are running the console interpreter, simply use the
16796 @code{interpreter-exec} command:
16799 interpreter-exec mi "-data-list-register-names"
16802 @sc{gdb/mi} has a similar command, although it is only available in versions of
16803 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16806 @chapter @value{GDBN} Text User Interface
16808 @cindex Text User Interface
16811 * TUI Overview:: TUI overview
16812 * TUI Keys:: TUI key bindings
16813 * TUI Single Key Mode:: TUI single key mode
16814 * TUI Commands:: TUI specific commands
16815 * TUI Configuration:: TUI configuration variables
16818 The @value{GDBN} Text User Interface, TUI in short, is a terminal
16819 interface which uses the @code{curses} library to show the source
16820 file, the assembly output, the program registers and @value{GDBN}
16821 commands in separate text windows.
16823 The TUI is enabled by invoking @value{GDBN} using either
16825 @samp{gdbtui} or @samp{gdb -tui}.
16828 @section TUI overview
16830 The TUI has two display modes that can be switched while
16835 A curses (or TUI) mode in which it displays several text
16836 windows on the terminal.
16839 A standard mode which corresponds to the @value{GDBN} configured without
16843 In the TUI mode, @value{GDBN} can display several text window
16848 This window is the @value{GDBN} command window with the @value{GDBN}
16849 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
16850 managed using readline but through the TUI. The @emph{command}
16851 window is always visible.
16854 The source window shows the source file of the program. The current
16855 line as well as active breakpoints are displayed in this window.
16858 The assembly window shows the disassembly output of the program.
16861 This window shows the processor registers. It detects when
16862 a register is changed and when this is the case, registers that have
16863 changed are highlighted.
16867 The source and assembly windows show the current program position
16868 by highlighting the current line and marking them with the @samp{>} marker.
16869 Breakpoints are also indicated with two markers. A first one
16870 indicates the breakpoint type:
16874 Breakpoint which was hit at least once.
16877 Breakpoint which was never hit.
16880 Hardware breakpoint which was hit at least once.
16883 Hardware breakpoint which was never hit.
16887 The second marker indicates whether the breakpoint is enabled or not:
16891 Breakpoint is enabled.
16894 Breakpoint is disabled.
16898 The source, assembly and register windows are attached to the thread
16899 and the frame position. They are updated when the current thread
16900 changes, when the frame changes or when the program counter changes.
16901 These three windows are arranged by the TUI according to several
16902 layouts. The layout defines which of these three windows are visible.
16903 The following layouts are available:
16913 source and assembly
16916 source and registers
16919 assembly and registers
16923 On top of the command window a status line gives various information
16924 concerning the current process begin debugged. The status line is
16925 updated when the information it shows changes. The following fields
16930 Indicates the current gdb target
16931 (@pxref{Targets, ,Specifying a Debugging Target}).
16934 Gives information about the current process or thread number.
16935 When no process is being debugged, this field is set to @code{No process}.
16938 Gives the current function name for the selected frame.
16939 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16940 When there is no symbol corresponding to the current program counter
16941 the string @code{??} is displayed.
16944 Indicates the current line number for the selected frame.
16945 When the current line number is not known the string @code{??} is displayed.
16948 Indicates the current program counter address.
16953 @section TUI Key Bindings
16954 @cindex TUI key bindings
16956 The TUI installs several key bindings in the readline keymaps
16957 (@pxref{Command Line Editing}).
16958 They allow to leave or enter in the TUI mode or they operate
16959 directly on the TUI layout and windows. The TUI also provides
16960 a @emph{SingleKey} keymap which binds several keys directly to
16961 @value{GDBN} commands. The following key bindings
16962 are installed for both TUI mode and the @value{GDBN} standard mode.
16971 Enter or leave the TUI mode. When the TUI mode is left,
16972 the curses window management is left and @value{GDBN} operates using
16973 its standard mode writing on the terminal directly. When the TUI
16974 mode is entered, the control is given back to the curses windows.
16975 The screen is then refreshed.
16979 Use a TUI layout with only one window. The layout will
16980 either be @samp{source} or @samp{assembly}. When the TUI mode
16981 is not active, it will switch to the TUI mode.
16983 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16987 Use a TUI layout with at least two windows. When the current
16988 layout shows already two windows, a next layout with two windows is used.
16989 When a new layout is chosen, one window will always be common to the
16990 previous layout and the new one.
16992 Think of it as the Emacs @kbd{C-x 2} binding.
16996 Change the active window. The TUI associates several key bindings
16997 (like scrolling and arrow keys) to the active window. This command
16998 gives the focus to the next TUI window.
17000 Think of it as the Emacs @kbd{C-x o} binding.
17004 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
17005 (@pxref{TUI Single Key Mode}).
17009 The following key bindings are handled only by the TUI mode:
17014 Scroll the active window one page up.
17018 Scroll the active window one page down.
17022 Scroll the active window one line up.
17026 Scroll the active window one line down.
17030 Scroll the active window one column left.
17034 Scroll the active window one column right.
17038 Refresh the screen.
17042 In the TUI mode, the arrow keys are used by the active window
17043 for scrolling. This means they are available for readline when the
17044 active window is the command window. When the command window
17045 does not have the focus, it is necessary to use other readline
17046 key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b} and @kbd{C-f}.
17048 @node TUI Single Key Mode
17049 @section TUI Single Key Mode
17050 @cindex TUI single key mode
17052 The TUI provides a @emph{SingleKey} mode in which it installs a particular
17053 key binding in the readline keymaps to connect single keys to
17057 @kindex c @r{(SingleKey TUI key)}
17061 @kindex d @r{(SingleKey TUI key)}
17065 @kindex f @r{(SingleKey TUI key)}
17069 @kindex n @r{(SingleKey TUI key)}
17073 @kindex q @r{(SingleKey TUI key)}
17075 exit the @emph{SingleKey} mode.
17077 @kindex r @r{(SingleKey TUI key)}
17081 @kindex s @r{(SingleKey TUI key)}
17085 @kindex u @r{(SingleKey TUI key)}
17089 @kindex v @r{(SingleKey TUI key)}
17093 @kindex w @r{(SingleKey TUI key)}
17099 Other keys temporarily switch to the @value{GDBN} command prompt.
17100 The key that was pressed is inserted in the editing buffer so that
17101 it is possible to type most @value{GDBN} commands without interaction
17102 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
17103 @emph{SingleKey} mode is restored. The only way to permanently leave
17104 this mode is by typing @kbd{q} or @kbd{C-x s}.
17108 @section TUI specific commands
17109 @cindex TUI commands
17111 The TUI has specific commands to control the text windows.
17112 These commands are always available, that is they do not depend on
17113 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
17114 is in the standard mode, using these commands will automatically switch
17120 List and give the size of all displayed windows.
17124 Display the next layout.
17127 Display the previous layout.
17130 Display the source window only.
17133 Display the assembly window only.
17136 Display the source and assembly window.
17139 Display the register window together with the source or assembly window.
17141 @item focus next | prev | src | asm | regs | split
17143 Set the focus to the named window.
17144 This command allows to change the active window so that scrolling keys
17145 can be affected to another window.
17149 Refresh the screen. This is similar to typing @kbd{C-L}.
17151 @item tui reg float
17153 Show the floating point registers in the register window.
17155 @item tui reg general
17156 Show the general registers in the register window.
17159 Show the next register group. The list of register groups as well as
17160 their order is target specific. The predefined register groups are the
17161 following: @code{general}, @code{float}, @code{system}, @code{vector},
17162 @code{all}, @code{save}, @code{restore}.
17164 @item tui reg system
17165 Show the system registers in the register window.
17169 Update the source window and the current execution point.
17171 @item winheight @var{name} +@var{count}
17172 @itemx winheight @var{name} -@var{count}
17174 Change the height of the window @var{name} by @var{count}
17175 lines. Positive counts increase the height, while negative counts
17179 @kindex tabset @var{nchars}
17180 Set the width of tab stops to be @var{nchars} characters.
17184 @node TUI Configuration
17185 @section TUI configuration variables
17186 @cindex TUI configuration variables
17188 The TUI has several configuration variables that control the
17189 appearance of windows on the terminal.
17192 @item set tui border-kind @var{kind}
17193 @kindex set tui border-kind
17194 Select the border appearance for the source, assembly and register windows.
17195 The possible values are the following:
17198 Use a space character to draw the border.
17201 Use ascii characters + - and | to draw the border.
17204 Use the Alternate Character Set to draw the border. The border is
17205 drawn using character line graphics if the terminal supports them.
17209 @item set tui active-border-mode @var{mode}
17210 @kindex set tui active-border-mode
17211 Select the attributes to display the border of the active window.
17212 The possible values are @code{normal}, @code{standout}, @code{reverse},
17213 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
17215 @item set tui border-mode @var{mode}
17216 @kindex set tui border-mode
17217 Select the attributes to display the border of other windows.
17218 The @var{mode} can be one of the following:
17221 Use normal attributes to display the border.
17227 Use reverse video mode.
17230 Use half bright mode.
17232 @item half-standout
17233 Use half bright and standout mode.
17236 Use extra bright or bold mode.
17238 @item bold-standout
17239 Use extra bright or bold and standout mode.
17246 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17249 @cindex @sc{gnu} Emacs
17250 A special interface allows you to use @sc{gnu} Emacs to view (and
17251 edit) the source files for the program you are debugging with
17254 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17255 executable file you want to debug as an argument. This command starts
17256 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17257 created Emacs buffer.
17258 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17260 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
17265 All ``terminal'' input and output goes through the Emacs buffer.
17268 This applies both to @value{GDBN} commands and their output, and to the input
17269 and output done by the program you are debugging.
17271 This is useful because it means that you can copy the text of previous
17272 commands and input them again; you can even use parts of the output
17275 All the facilities of Emacs' Shell mode are available for interacting
17276 with your program. In particular, you can send signals the usual
17277 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17282 @value{GDBN} displays source code through Emacs.
17285 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17286 source file for that frame and puts an arrow (@samp{=>}) at the
17287 left margin of the current line. Emacs uses a separate buffer for
17288 source display, and splits the screen to show both your @value{GDBN} session
17291 Explicit @value{GDBN} @code{list} or search commands still produce output as
17292 usual, but you probably have no reason to use them from Emacs.
17294 If you specify an absolute file name when prompted for the @kbd{M-x
17295 gdb} argument, then Emacs sets your current working directory to where
17296 your program resides. If you only specify the file name, then Emacs
17297 sets your current working directory to to the directory associated
17298 with the previous buffer. In this case, @value{GDBN} may find your
17299 program by searching your environment's @code{PATH} variable, but on
17300 some operating systems it might not find the source. So, although the
17301 @value{GDBN} input and output session proceeds normally, the auxiliary
17302 buffer does not display the current source and line of execution.
17304 The initial working directory of @value{GDBN} is printed on the top
17305 line of the @value{GDBN} I/O buffer and this serves as a default for
17306 the commands that specify files for @value{GDBN} to operate
17307 on. @xref{Files, ,Commands to specify files}.
17309 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17310 need to call @value{GDBN} by a different name (for example, if you
17311 keep several configurations around, with different names) you can
17312 customize the Emacs variable @code{gud-gdb-command-name} to run the
17315 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
17316 addition to the standard Shell mode commands:
17320 Describe the features of Emacs' @value{GDBN} Mode.
17323 Execute to another source line, like the @value{GDBN} @code{step} command; also
17324 update the display window to show the current file and location.
17327 Execute to next source line in this function, skipping all function
17328 calls, like the @value{GDBN} @code{next} command. Then update the display window
17329 to show the current file and location.
17332 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17333 display window accordingly.
17336 Execute until exit from the selected stack frame, like the @value{GDBN}
17337 @code{finish} command.
17340 Continue execution of your program, like the @value{GDBN} @code{continue}
17344 Go up the number of frames indicated by the numeric argument
17345 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17346 like the @value{GDBN} @code{up} command.
17349 Go down the number of frames indicated by the numeric argument, like the
17350 @value{GDBN} @code{down} command.
17353 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17354 tells @value{GDBN} to set a breakpoint on the source line point is on.
17356 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
17357 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
17358 point to any frame in the stack and type @key{RET} to make it become the
17359 current frame and display the associated source in the source buffer.
17360 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
17363 If you accidentally delete the source-display buffer, an easy way to get
17364 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17365 request a frame display; when you run under Emacs, this recreates
17366 the source buffer if necessary to show you the context of the current
17369 The source files displayed in Emacs are in ordinary Emacs buffers
17370 which are visiting the source files in the usual way. You can edit
17371 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17372 communicates with Emacs in terms of line numbers. If you add or
17373 delete lines from the text, the line numbers that @value{GDBN} knows cease
17374 to correspond properly with the code.
17376 The description given here is for GNU Emacs version 21.3 and a more
17377 detailed description of its interaction with @value{GDBN} is given in
17378 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
17380 @c The following dropped because Epoch is nonstandard. Reactivate
17381 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17383 @kindex Emacs Epoch environment
17387 Version 18 of @sc{gnu} Emacs has a built-in window system
17388 called the @code{epoch}
17389 environment. Users of this environment can use a new command,
17390 @code{inspect} which performs identically to @code{print} except that
17391 each value is printed in its own window.
17396 @chapter The @sc{gdb/mi} Interface
17398 @unnumberedsec Function and Purpose
17400 @cindex @sc{gdb/mi}, its purpose
17401 @sc{gdb/mi} is a line based machine oriented text interface to
17402 @value{GDBN} and is activated by specifying using the
17403 @option{--interpreter} command line option (@pxref{Mode Options}). It
17404 is specifically intended to support the development of systems which
17405 use the debugger as just one small component of a larger system.
17407 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17408 in the form of a reference manual.
17410 Note that @sc{gdb/mi} is still under construction, so some of the
17411 features described below are incomplete and subject to change
17412 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17414 @unnumberedsec Notation and Terminology
17416 @cindex notational conventions, for @sc{gdb/mi}
17417 This chapter uses the following notation:
17421 @code{|} separates two alternatives.
17424 @code{[ @var{something} ]} indicates that @var{something} is optional:
17425 it may or may not be given.
17428 @code{( @var{group} )*} means that @var{group} inside the parentheses
17429 may repeat zero or more times.
17432 @code{( @var{group} )+} means that @var{group} inside the parentheses
17433 may repeat one or more times.
17436 @code{"@var{string}"} means a literal @var{string}.
17440 @heading Dependencies
17444 * GDB/MI Command Syntax::
17445 * GDB/MI Compatibility with CLI::
17446 * GDB/MI Development and Front Ends::
17447 * GDB/MI Output Records::
17448 * GDB/MI Simple Examples::
17449 * GDB/MI Command Description Format::
17450 * GDB/MI Breakpoint Commands::
17451 * GDB/MI Program Context::
17452 * GDB/MI Thread Commands::
17453 * GDB/MI Program Execution::
17454 * GDB/MI Stack Manipulation::
17455 * GDB/MI Variable Objects::
17456 * GDB/MI Data Manipulation::
17457 * GDB/MI Tracepoint Commands::
17458 * GDB/MI Symbol Query::
17459 * GDB/MI File Commands::
17461 * GDB/MI Kod Commands::
17462 * GDB/MI Memory Overlay Commands::
17463 * GDB/MI Signal Handling Commands::
17465 * GDB/MI Target Manipulation::
17466 * GDB/MI Miscellaneous Commands::
17469 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17470 @node GDB/MI Command Syntax
17471 @section @sc{gdb/mi} Command Syntax
17474 * GDB/MI Input Syntax::
17475 * GDB/MI Output Syntax::
17478 @node GDB/MI Input Syntax
17479 @subsection @sc{gdb/mi} Input Syntax
17481 @cindex input syntax for @sc{gdb/mi}
17482 @cindex @sc{gdb/mi}, input syntax
17484 @item @var{command} @expansion{}
17485 @code{@var{cli-command} | @var{mi-command}}
17487 @item @var{cli-command} @expansion{}
17488 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17489 @var{cli-command} is any existing @value{GDBN} CLI command.
17491 @item @var{mi-command} @expansion{}
17492 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17493 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17495 @item @var{token} @expansion{}
17496 "any sequence of digits"
17498 @item @var{option} @expansion{}
17499 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17501 @item @var{parameter} @expansion{}
17502 @code{@var{non-blank-sequence} | @var{c-string}}
17504 @item @var{operation} @expansion{}
17505 @emph{any of the operations described in this chapter}
17507 @item @var{non-blank-sequence} @expansion{}
17508 @emph{anything, provided it doesn't contain special characters such as
17509 "-", @var{nl}, """ and of course " "}
17511 @item @var{c-string} @expansion{}
17512 @code{""" @var{seven-bit-iso-c-string-content} """}
17514 @item @var{nl} @expansion{}
17523 The CLI commands are still handled by the @sc{mi} interpreter; their
17524 output is described below.
17527 The @code{@var{token}}, when present, is passed back when the command
17531 Some @sc{mi} commands accept optional arguments as part of the parameter
17532 list. Each option is identified by a leading @samp{-} (dash) and may be
17533 followed by an optional argument parameter. Options occur first in the
17534 parameter list and can be delimited from normal parameters using
17535 @samp{--} (this is useful when some parameters begin with a dash).
17542 We want easy access to the existing CLI syntax (for debugging).
17545 We want it to be easy to spot a @sc{mi} operation.
17548 @node GDB/MI Output Syntax
17549 @subsection @sc{gdb/mi} Output Syntax
17551 @cindex output syntax of @sc{gdb/mi}
17552 @cindex @sc{gdb/mi}, output syntax
17553 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17554 followed, optionally, by a single result record. This result record
17555 is for the most recent command. The sequence of output records is
17556 terminated by @samp{(gdb)}.
17558 If an input command was prefixed with a @code{@var{token}} then the
17559 corresponding output for that command will also be prefixed by that same
17563 @item @var{output} @expansion{}
17564 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17566 @item @var{result-record} @expansion{}
17567 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17569 @item @var{out-of-band-record} @expansion{}
17570 @code{@var{async-record} | @var{stream-record}}
17572 @item @var{async-record} @expansion{}
17573 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17575 @item @var{exec-async-output} @expansion{}
17576 @code{[ @var{token} ] "*" @var{async-output}}
17578 @item @var{status-async-output} @expansion{}
17579 @code{[ @var{token} ] "+" @var{async-output}}
17581 @item @var{notify-async-output} @expansion{}
17582 @code{[ @var{token} ] "=" @var{async-output}}
17584 @item @var{async-output} @expansion{}
17585 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17587 @item @var{result-class} @expansion{}
17588 @code{"done" | "running" | "connected" | "error" | "exit"}
17590 @item @var{async-class} @expansion{}
17591 @code{"stopped" | @var{others}} (where @var{others} will be added
17592 depending on the needs---this is still in development).
17594 @item @var{result} @expansion{}
17595 @code{ @var{variable} "=" @var{value}}
17597 @item @var{variable} @expansion{}
17598 @code{ @var{string} }
17600 @item @var{value} @expansion{}
17601 @code{ @var{const} | @var{tuple} | @var{list} }
17603 @item @var{const} @expansion{}
17604 @code{@var{c-string}}
17606 @item @var{tuple} @expansion{}
17607 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17609 @item @var{list} @expansion{}
17610 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17611 @var{result} ( "," @var{result} )* "]" }
17613 @item @var{stream-record} @expansion{}
17614 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17616 @item @var{console-stream-output} @expansion{}
17617 @code{"~" @var{c-string}}
17619 @item @var{target-stream-output} @expansion{}
17620 @code{"@@" @var{c-string}}
17622 @item @var{log-stream-output} @expansion{}
17623 @code{"&" @var{c-string}}
17625 @item @var{nl} @expansion{}
17628 @item @var{token} @expansion{}
17629 @emph{any sequence of digits}.
17637 All output sequences end in a single line containing a period.
17640 The @code{@var{token}} is from the corresponding request. If an execution
17641 command is interrupted by the @samp{-exec-interrupt} command, the
17642 @var{token} associated with the @samp{*stopped} message is the one of the
17643 original execution command, not the one of the interrupt command.
17646 @cindex status output in @sc{gdb/mi}
17647 @var{status-async-output} contains on-going status information about the
17648 progress of a slow operation. It can be discarded. All status output is
17649 prefixed by @samp{+}.
17652 @cindex async output in @sc{gdb/mi}
17653 @var{exec-async-output} contains asynchronous state change on the target
17654 (stopped, started, disappeared). All async output is prefixed by
17658 @cindex notify output in @sc{gdb/mi}
17659 @var{notify-async-output} contains supplementary information that the
17660 client should handle (e.g., a new breakpoint information). All notify
17661 output is prefixed by @samp{=}.
17664 @cindex console output in @sc{gdb/mi}
17665 @var{console-stream-output} is output that should be displayed as is in the
17666 console. It is the textual response to a CLI command. All the console
17667 output is prefixed by @samp{~}.
17670 @cindex target output in @sc{gdb/mi}
17671 @var{target-stream-output} is the output produced by the target program.
17672 All the target output is prefixed by @samp{@@}.
17675 @cindex log output in @sc{gdb/mi}
17676 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17677 instance messages that should be displayed as part of an error log. All
17678 the log output is prefixed by @samp{&}.
17681 @cindex list output in @sc{gdb/mi}
17682 New @sc{gdb/mi} commands should only output @var{lists} containing
17688 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17689 details about the various output records.
17691 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17692 @node GDB/MI Compatibility with CLI
17693 @section @sc{gdb/mi} Compatibility with CLI
17695 @cindex compatibility, @sc{gdb/mi} and CLI
17696 @cindex @sc{gdb/mi}, compatibility with CLI
17698 For the developers convenience CLI commands can be entered directly,
17699 but there may be some unexpected behaviour. For example, commands
17700 that query the user will behave as if the user replied yes, breakpoint
17701 command lists are not executed and some CLI commands, such as
17702 @code{if}, @code{when} and @code{define}, prompt for further input with
17703 @samp{>}, which is not valid MI output.
17705 This feature may be removed at some stage in the future and it is
17706 recommended that front ends use the @code{-interpreter-exec} command
17707 (@pxref{-interpreter-exec}).
17709 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17710 @node GDB/MI Development and Front Ends
17711 @section @sc{gdb/mi} Development and Front Ends
17712 @cindex @sc{gdb/mi} development
17714 The application which takes the MI output and presents the state of the
17715 program being debugged to the user is called a @dfn{front end}.
17717 Although @sc{gdb/mi} is still incomplete, it is currently being used
17718 by a variety of front ends to @value{GDBN}. This makes it difficult
17719 to introduce new functionality without breaking existing usage. This
17720 section tries to minimize the problems by describing how the protocol
17723 Some changes in MI need not break a carefully designed front end, and
17724 for these the MI version will remain unchanged. The following is a
17725 list of changes that may occur within one level, so front ends should
17726 parse MI output in a way that can handle them:
17730 New MI commands may be added.
17733 New fields may be added to the output of any MI command.
17735 @c The format of field's content e.g type prefix, may change so parse it
17736 @c at your own risk. Yes, in general?
17738 @c The order of fields may change? Shouldn't really matter but it might
17739 @c resolve inconsistencies.
17742 If the changes are likely to break front ends, the MI version level
17743 will be increased by one. This will allow the front end to parse the
17744 output according to the MI version. Apart from mi0, new versions of
17745 @value{GDBN} will not support old versions of MI and it will be the
17746 responsibility of the front end to work with the new one.
17748 @c Starting with mi3, add a new command -mi-version that prints the MI
17751 The best way to avoid unexpected changes in MI that might break your front
17752 end is to make your project known to @value{GDBN} developers and
17753 follow development on @email{gdb@@sourceware.org} and
17754 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17755 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17756 Group, which has the aim of creating a more general MI protocol
17757 called Debugger Machine Interface (DMI) that will become a standard
17758 for all debuggers, not just @value{GDBN}.
17759 @cindex mailing lists
17761 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17762 @node GDB/MI Output Records
17763 @section @sc{gdb/mi} Output Records
17766 * GDB/MI Result Records::
17767 * GDB/MI Stream Records::
17768 * GDB/MI Out-of-band Records::
17771 @node GDB/MI Result Records
17772 @subsection @sc{gdb/mi} Result Records
17774 @cindex result records in @sc{gdb/mi}
17775 @cindex @sc{gdb/mi}, result records
17776 In addition to a number of out-of-band notifications, the response to a
17777 @sc{gdb/mi} command includes one of the following result indications:
17781 @item "^done" [ "," @var{results} ]
17782 The synchronous operation was successful, @code{@var{results}} are the return
17787 @c Is this one correct? Should it be an out-of-band notification?
17788 The asynchronous operation was successfully started. The target is
17793 GDB has connected to a remote target.
17795 @item "^error" "," @var{c-string}
17797 The operation failed. The @code{@var{c-string}} contains the corresponding
17802 GDB has terminated.
17806 @node GDB/MI Stream Records
17807 @subsection @sc{gdb/mi} Stream Records
17809 @cindex @sc{gdb/mi}, stream records
17810 @cindex stream records in @sc{gdb/mi}
17811 @value{GDBN} internally maintains a number of output streams: the console, the
17812 target, and the log. The output intended for each of these streams is
17813 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17815 Each stream record begins with a unique @dfn{prefix character} which
17816 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17817 Syntax}). In addition to the prefix, each stream record contains a
17818 @code{@var{string-output}}. This is either raw text (with an implicit new
17819 line) or a quoted C string (which does not contain an implicit newline).
17822 @item "~" @var{string-output}
17823 The console output stream contains text that should be displayed in the
17824 CLI console window. It contains the textual responses to CLI commands.
17826 @item "@@" @var{string-output}
17827 The target output stream contains any textual output from the running
17828 target. This is only present when GDB's event loop is truly
17829 asynchronous, which is currently only the case for remote targets.
17831 @item "&" @var{string-output}
17832 The log stream contains debugging messages being produced by @value{GDBN}'s
17836 @node GDB/MI Out-of-band Records
17837 @subsection @sc{gdb/mi} Out-of-band Records
17839 @cindex out-of-band records in @sc{gdb/mi}
17840 @cindex @sc{gdb/mi}, out-of-band records
17841 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17842 additional changes that have occurred. Those changes can either be a
17843 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17844 target activity (e.g., target stopped).
17846 The following is a preliminary list of possible out-of-band records.
17847 In particular, the @var{exec-async-output} records.
17850 @item *stopped,reason="@var{reason}"
17853 @var{reason} can be one of the following:
17856 @item breakpoint-hit
17857 A breakpoint was reached.
17858 @item watchpoint-trigger
17859 A watchpoint was triggered.
17860 @item read-watchpoint-trigger
17861 A read watchpoint was triggered.
17862 @item access-watchpoint-trigger
17863 An access watchpoint was triggered.
17864 @item function-finished
17865 An -exec-finish or similar CLI command was accomplished.
17866 @item location-reached
17867 An -exec-until or similar CLI command was accomplished.
17868 @item watchpoint-scope
17869 A watchpoint has gone out of scope.
17870 @item end-stepping-range
17871 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17872 similar CLI command was accomplished.
17873 @item exited-signalled
17874 The inferior exited because of a signal.
17876 The inferior exited.
17877 @item exited-normally
17878 The inferior exited normally.
17879 @item signal-received
17880 A signal was received by the inferior.
17884 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17885 @node GDB/MI Simple Examples
17886 @section Simple Examples of @sc{gdb/mi} Interaction
17887 @cindex @sc{gdb/mi}, simple examples
17889 This subsection presents several simple examples of interaction using
17890 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17891 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17892 the output received from @sc{gdb/mi}.
17894 Note the line breaks shown in the examples are here only for
17895 readability, they don't appear in the real output.
17897 @subheading Setting a breakpoint
17899 Setting a breakpoint generates synchronous output which contains detailed
17900 information of the breakpoint.
17903 -> -break-insert main
17904 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17905 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17906 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17910 @subheading Program Execution
17912 Program execution generates asynchronous records and MI gives the
17913 reason that execution stopped.
17919 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17920 frame=@{addr="0x08048564",func="main",
17921 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17922 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17927 <- *stopped,reason="exited-normally"
17931 @subheading Quitting GDB
17933 Quitting GDB just prints the result class @samp{^exit}.
17941 @subheading A Bad Command
17943 Here's what happens if you pass a non-existent command:
17947 <- ^error,msg="Undefined MI command: rubbish"
17952 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17953 @node GDB/MI Command Description Format
17954 @section @sc{gdb/mi} Command Description Format
17956 The remaining sections describe blocks of commands. Each block of
17957 commands is laid out in a fashion similar to this section.
17959 @subheading Motivation
17961 The motivation for this collection of commands.
17963 @subheading Introduction
17965 A brief introduction to this collection of commands as a whole.
17967 @subheading Commands
17969 For each command in the block, the following is described:
17971 @subsubheading Synopsis
17974 -command @var{args}@dots{}
17977 @subsubheading Result
17979 @subsubheading @value{GDBN} Command
17981 The corresponding @value{GDBN} CLI command(s), if any.
17983 @subsubheading Example
17985 Example(s) formatted for readability. Some of the described commands have
17986 not been implemented yet and these are labeled N.A.@: (not available).
17989 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17990 @node GDB/MI Breakpoint Commands
17991 @section @sc{gdb/mi} Breakpoint Commands
17993 @cindex breakpoint commands for @sc{gdb/mi}
17994 @cindex @sc{gdb/mi}, breakpoint commands
17995 This section documents @sc{gdb/mi} commands for manipulating
17998 @subheading The @code{-break-after} Command
17999 @findex -break-after
18001 @subsubheading Synopsis
18004 -break-after @var{number} @var{count}
18007 The breakpoint number @var{number} is not in effect until it has been
18008 hit @var{count} times. To see how this is reflected in the output of
18009 the @samp{-break-list} command, see the description of the
18010 @samp{-break-list} command below.
18012 @subsubheading @value{GDBN} Command
18014 The corresponding @value{GDBN} command is @samp{ignore}.
18016 @subsubheading Example
18021 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
18022 fullname="/home/foo/hello.c",line="5",times="0"@}
18029 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18030 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18031 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18032 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18033 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18034 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18035 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18036 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18037 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18038 line="5",times="0",ignore="3"@}]@}
18043 @subheading The @code{-break-catch} Command
18044 @findex -break-catch
18046 @subheading The @code{-break-commands} Command
18047 @findex -break-commands
18051 @subheading The @code{-break-condition} Command
18052 @findex -break-condition
18054 @subsubheading Synopsis
18057 -break-condition @var{number} @var{expr}
18060 Breakpoint @var{number} will stop the program only if the condition in
18061 @var{expr} is true. The condition becomes part of the
18062 @samp{-break-list} output (see the description of the @samp{-break-list}
18065 @subsubheading @value{GDBN} Command
18067 The corresponding @value{GDBN} command is @samp{condition}.
18069 @subsubheading Example
18073 -break-condition 1 1
18077 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18078 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18079 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18080 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18081 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18082 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18083 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18084 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18085 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18086 line="5",cond="1",times="0",ignore="3"@}]@}
18090 @subheading The @code{-break-delete} Command
18091 @findex -break-delete
18093 @subsubheading Synopsis
18096 -break-delete ( @var{breakpoint} )+
18099 Delete the breakpoint(s) whose number(s) are specified in the argument
18100 list. This is obviously reflected in the breakpoint list.
18102 @subsubheading @value{GDBN} command
18104 The corresponding @value{GDBN} command is @samp{delete}.
18106 @subsubheading Example
18114 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18115 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18116 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18117 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18118 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18119 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18120 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18125 @subheading The @code{-break-disable} Command
18126 @findex -break-disable
18128 @subsubheading Synopsis
18131 -break-disable ( @var{breakpoint} )+
18134 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18135 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18137 @subsubheading @value{GDBN} Command
18139 The corresponding @value{GDBN} command is @samp{disable}.
18141 @subsubheading Example
18149 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18150 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18151 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18152 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18153 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18154 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18155 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18156 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18157 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18158 line="5",times="0"@}]@}
18162 @subheading The @code{-break-enable} Command
18163 @findex -break-enable
18165 @subsubheading Synopsis
18168 -break-enable ( @var{breakpoint} )+
18171 Enable (previously disabled) @var{breakpoint}(s).
18173 @subsubheading @value{GDBN} Command
18175 The corresponding @value{GDBN} command is @samp{enable}.
18177 @subsubheading Example
18185 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18186 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18187 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18188 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18189 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18190 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18191 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18192 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18193 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18194 line="5",times="0"@}]@}
18198 @subheading The @code{-break-info} Command
18199 @findex -break-info
18201 @subsubheading Synopsis
18204 -break-info @var{breakpoint}
18208 Get information about a single breakpoint.
18210 @subsubheading @value{GDBN} command
18212 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18214 @subsubheading Example
18217 @subheading The @code{-break-insert} Command
18218 @findex -break-insert
18220 @subsubheading Synopsis
18223 -break-insert [ -t ] [ -h ] [ -r ]
18224 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18225 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
18229 If specified, @var{line}, can be one of:
18236 @item filename:linenum
18237 @item filename:function
18241 The possible optional parameters of this command are:
18245 Insert a temporary breakpoint.
18247 Insert a hardware breakpoint.
18248 @item -c @var{condition}
18249 Make the breakpoint conditional on @var{condition}.
18250 @item -i @var{ignore-count}
18251 Initialize the @var{ignore-count}.
18253 Insert a regular breakpoint in all the functions whose names match the
18254 given regular expression. Other flags are not applicable to regular
18258 @subsubheading Result
18260 The result is in the form:
18263 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18264 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18265 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18266 times="@var{times}"@}
18270 where @var{number} is the @value{GDBN} number for this breakpoint,
18271 @var{funcname} is the name of the function where the breakpoint was
18272 inserted, @var{filename} is the name of the source file which contains
18273 this function, @var{lineno} is the source line number within that file
18274 and @var{times} the number of times that the breakpoint has been hit
18275 (always 0 for -break-insert but may be greater for -break-info or -break-list
18276 which use the same output).
18278 Note: this format is open to change.
18279 @c An out-of-band breakpoint instead of part of the result?
18281 @subsubheading @value{GDBN} Command
18283 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18284 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18286 @subsubheading Example
18291 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18292 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18294 -break-insert -t foo
18295 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18296 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18299 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18300 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18301 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18302 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18303 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18304 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18305 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18306 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18307 addr="0x0001072c", func="main",file="recursive2.c",
18308 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18309 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18310 addr="0x00010774",func="foo",file="recursive2.c",
18311 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18313 -break-insert -r foo.*
18314 ~int foo(int, int);
18315 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18316 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18320 @subheading The @code{-break-list} Command
18321 @findex -break-list
18323 @subsubheading Synopsis
18329 Displays the list of inserted breakpoints, showing the following fields:
18333 number of the breakpoint
18335 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18337 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18340 is the breakpoint enabled or no: @samp{y} or @samp{n}
18342 memory location at which the breakpoint is set
18344 logical location of the breakpoint, expressed by function name, file
18347 number of times the breakpoint has been hit
18350 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18351 @code{body} field is an empty list.
18353 @subsubheading @value{GDBN} Command
18355 The corresponding @value{GDBN} command is @samp{info break}.
18357 @subsubheading Example
18362 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18363 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18364 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18365 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18366 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18367 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18368 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18369 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18370 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18371 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18372 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18373 line="13",times="0"@}]@}
18377 Here's an example of the result when there are no breakpoints:
18382 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18383 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18384 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18385 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18386 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18387 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18388 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18393 @subheading The @code{-break-watch} Command
18394 @findex -break-watch
18396 @subsubheading Synopsis
18399 -break-watch [ -a | -r ]
18402 Create a watchpoint. With the @samp{-a} option it will create an
18403 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18404 read from or on a write to the memory location. With the @samp{-r}
18405 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18406 trigger only when the memory location is accessed for reading. Without
18407 either of the options, the watchpoint created is a regular watchpoint,
18408 i.e., it will trigger when the memory location is accessed for writing.
18409 @xref{Set Watchpoints, , Setting watchpoints}.
18411 Note that @samp{-break-list} will report a single list of watchpoints and
18412 breakpoints inserted.
18414 @subsubheading @value{GDBN} Command
18416 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18419 @subsubheading Example
18421 Setting a watchpoint on a variable in the @code{main} function:
18426 ^done,wpt=@{number="2",exp="x"@}
18430 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18431 value=@{old="-268439212",new="55"@},
18432 frame=@{func="main",args=[],file="recursive2.c",
18433 fullname="/home/foo/bar/recursive2.c",line="5"@}
18437 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18438 the program execution twice: first for the variable changing value, then
18439 for the watchpoint going out of scope.
18444 ^done,wpt=@{number="5",exp="C"@}
18448 ^done,reason="watchpoint-trigger",
18449 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18450 frame=@{func="callee4",args=[],
18451 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18452 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18456 ^done,reason="watchpoint-scope",wpnum="5",
18457 frame=@{func="callee3",args=[@{name="strarg",
18458 value="0x11940 \"A string argument.\""@}],
18459 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18460 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18464 Listing breakpoints and watchpoints, at different points in the program
18465 execution. Note that once the watchpoint goes out of scope, it is
18471 ^done,wpt=@{number="2",exp="C"@}
18474 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18475 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18476 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18477 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18478 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18479 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18480 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18481 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18482 addr="0x00010734",func="callee4",
18483 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18484 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18485 bkpt=@{number="2",type="watchpoint",disp="keep",
18486 enabled="y",addr="",what="C",times="0"@}]@}
18490 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18491 value=@{old="-276895068",new="3"@},
18492 frame=@{func="callee4",args=[],
18493 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18494 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18497 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18498 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18499 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18500 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18501 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18502 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18503 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18504 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18505 addr="0x00010734",func="callee4",
18506 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18507 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18508 bkpt=@{number="2",type="watchpoint",disp="keep",
18509 enabled="y",addr="",what="C",times="-5"@}]@}
18513 ^done,reason="watchpoint-scope",wpnum="2",
18514 frame=@{func="callee3",args=[@{name="strarg",
18515 value="0x11940 \"A string argument.\""@}],
18516 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18517 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18520 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18521 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18522 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18523 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18524 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18525 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18526 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18527 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18528 addr="0x00010734",func="callee4",
18529 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18530 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18535 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18536 @node GDB/MI Program Context
18537 @section @sc{gdb/mi} Program Context
18539 @subheading The @code{-exec-arguments} Command
18540 @findex -exec-arguments
18543 @subsubheading Synopsis
18546 -exec-arguments @var{args}
18549 Set the inferior program arguments, to be used in the next
18552 @subsubheading @value{GDBN} Command
18554 The corresponding @value{GDBN} command is @samp{set args}.
18556 @subsubheading Example
18559 Don't have one around.
18562 @subheading The @code{-exec-show-arguments} Command
18563 @findex -exec-show-arguments
18565 @subsubheading Synopsis
18568 -exec-show-arguments
18571 Print the arguments of the program.
18573 @subsubheading @value{GDBN} Command
18575 The corresponding @value{GDBN} command is @samp{show args}.
18577 @subsubheading Example
18581 @subheading The @code{-environment-cd} Command
18582 @findex -environment-cd
18584 @subsubheading Synopsis
18587 -environment-cd @var{pathdir}
18590 Set @value{GDBN}'s working directory.
18592 @subsubheading @value{GDBN} Command
18594 The corresponding @value{GDBN} command is @samp{cd}.
18596 @subsubheading Example
18600 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18606 @subheading The @code{-environment-directory} Command
18607 @findex -environment-directory
18609 @subsubheading Synopsis
18612 -environment-directory [ -r ] [ @var{pathdir} ]+
18615 Add directories @var{pathdir} to beginning of search path for source files.
18616 If the @samp{-r} option is used, the search path is reset to the default
18617 search path. If directories @var{pathdir} are supplied in addition to the
18618 @samp{-r} option, the search path is first reset and then addition
18620 Multiple directories may be specified, separated by blanks. Specifying
18621 multiple directories in a single command
18622 results in the directories added to the beginning of the
18623 search path in the same order they were presented in the command.
18624 If blanks are needed as
18625 part of a directory name, double-quotes should be used around
18626 the name. In the command output, the path will show up separated
18627 by the system directory-separator character. The directory-separator
18628 character must not be used
18629 in any directory name.
18630 If no directories are specified, the current search path is displayed.
18632 @subsubheading @value{GDBN} Command
18634 The corresponding @value{GDBN} command is @samp{dir}.
18636 @subsubheading Example
18640 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18641 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18643 -environment-directory ""
18644 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18646 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18647 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18649 -environment-directory -r
18650 ^done,source-path="$cdir:$cwd"
18655 @subheading The @code{-environment-path} Command
18656 @findex -environment-path
18658 @subsubheading Synopsis
18661 -environment-path [ -r ] [ @var{pathdir} ]+
18664 Add directories @var{pathdir} to beginning of search path for object files.
18665 If the @samp{-r} option is used, the search path is reset to the original
18666 search path that existed at gdb start-up. If directories @var{pathdir} are
18667 supplied in addition to the
18668 @samp{-r} option, the search path is first reset and then addition
18670 Multiple directories may be specified, separated by blanks. Specifying
18671 multiple directories in a single command
18672 results in the directories added to the beginning of the
18673 search path in the same order they were presented in the command.
18674 If blanks are needed as
18675 part of a directory name, double-quotes should be used around
18676 the name. In the command output, the path will show up separated
18677 by the system directory-separator character. The directory-separator
18678 character must not be used
18679 in any directory name.
18680 If no directories are specified, the current path is displayed.
18683 @subsubheading @value{GDBN} Command
18685 The corresponding @value{GDBN} command is @samp{path}.
18687 @subsubheading Example
18692 ^done,path="/usr/bin"
18694 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18695 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18697 -environment-path -r /usr/local/bin
18698 ^done,path="/usr/local/bin:/usr/bin"
18703 @subheading The @code{-environment-pwd} Command
18704 @findex -environment-pwd
18706 @subsubheading Synopsis
18712 Show the current working directory.
18714 @subsubheading @value{GDBN} command
18716 The corresponding @value{GDBN} command is @samp{pwd}.
18718 @subsubheading Example
18723 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18727 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18728 @node GDB/MI Thread Commands
18729 @section @sc{gdb/mi} Thread Commands
18732 @subheading The @code{-thread-info} Command
18733 @findex -thread-info
18735 @subsubheading Synopsis
18741 @subsubheading @value{GDBN} command
18745 @subsubheading Example
18749 @subheading The @code{-thread-list-all-threads} Command
18750 @findex -thread-list-all-threads
18752 @subsubheading Synopsis
18755 -thread-list-all-threads
18758 @subsubheading @value{GDBN} Command
18760 The equivalent @value{GDBN} command is @samp{info threads}.
18762 @subsubheading Example
18766 @subheading The @code{-thread-list-ids} Command
18767 @findex -thread-list-ids
18769 @subsubheading Synopsis
18775 Produces a list of the currently known @value{GDBN} thread ids. At the
18776 end of the list it also prints the total number of such threads.
18778 @subsubheading @value{GDBN} Command
18780 Part of @samp{info threads} supplies the same information.
18782 @subsubheading Example
18784 No threads present, besides the main process:
18789 ^done,thread-ids=@{@},number-of-threads="0"
18799 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18800 number-of-threads="3"
18805 @subheading The @code{-thread-select} Command
18806 @findex -thread-select
18808 @subsubheading Synopsis
18811 -thread-select @var{threadnum}
18814 Make @var{threadnum} the current thread. It prints the number of the new
18815 current thread, and the topmost frame for that thread.
18817 @subsubheading @value{GDBN} Command
18819 The corresponding @value{GDBN} command is @samp{thread}.
18821 @subsubheading Example
18828 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18829 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18833 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18834 number-of-threads="3"
18837 ^done,new-thread-id="3",
18838 frame=@{level="0",func="vprintf",
18839 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18840 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18844 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18845 @node GDB/MI Program Execution
18846 @section @sc{gdb/mi} Program Execution
18848 These are the asynchronous commands which generate the out-of-band
18849 record @samp{*stopped}. Currently GDB only really executes
18850 asynchronously with remote targets and this interaction is mimicked in
18853 @subheading The @code{-exec-continue} Command
18854 @findex -exec-continue
18856 @subsubheading Synopsis
18862 Resumes the execution of the inferior program until a breakpoint is
18863 encountered, or until the inferior exits.
18865 @subsubheading @value{GDBN} Command
18867 The corresponding @value{GDBN} corresponding is @samp{continue}.
18869 @subsubheading Example
18876 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18877 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18882 @subheading The @code{-exec-finish} Command
18883 @findex -exec-finish
18885 @subsubheading Synopsis
18891 Resumes the execution of the inferior program until the current
18892 function is exited. Displays the results returned by the function.
18894 @subsubheading @value{GDBN} Command
18896 The corresponding @value{GDBN} command is @samp{finish}.
18898 @subsubheading Example
18900 Function returning @code{void}.
18907 *stopped,reason="function-finished",frame=@{func="main",args=[],
18908 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18912 Function returning other than @code{void}. The name of the internal
18913 @value{GDBN} variable storing the result is printed, together with the
18920 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18921 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18922 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18923 gdb-result-var="$1",return-value="0"
18928 @subheading The @code{-exec-interrupt} Command
18929 @findex -exec-interrupt
18931 @subsubheading Synopsis
18937 Interrupts the background execution of the target. Note how the token
18938 associated with the stop message is the one for the execution command
18939 that has been interrupted. The token for the interrupt itself only
18940 appears in the @samp{^done} output. If the user is trying to
18941 interrupt a non-running program, an error message will be printed.
18943 @subsubheading @value{GDBN} Command
18945 The corresponding @value{GDBN} command is @samp{interrupt}.
18947 @subsubheading Example
18958 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18959 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18960 fullname="/home/foo/bar/try.c",line="13"@}
18965 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18970 @subheading The @code{-exec-next} Command
18973 @subsubheading Synopsis
18979 Resumes execution of the inferior program, stopping when the beginning
18980 of the next source line is reached.
18982 @subsubheading @value{GDBN} Command
18984 The corresponding @value{GDBN} command is @samp{next}.
18986 @subsubheading Example
18992 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18997 @subheading The @code{-exec-next-instruction} Command
18998 @findex -exec-next-instruction
19000 @subsubheading Synopsis
19003 -exec-next-instruction
19006 Executes one machine instruction. If the instruction is a function
19007 call, continues until the function returns. If the program stops at an
19008 instruction in the middle of a source line, the address will be
19011 @subsubheading @value{GDBN} Command
19013 The corresponding @value{GDBN} command is @samp{nexti}.
19015 @subsubheading Example
19019 -exec-next-instruction
19023 *stopped,reason="end-stepping-range",
19024 addr="0x000100d4",line="5",file="hello.c"
19029 @subheading The @code{-exec-return} Command
19030 @findex -exec-return
19032 @subsubheading Synopsis
19038 Makes current function return immediately. Doesn't execute the inferior.
19039 Displays the new current frame.
19041 @subsubheading @value{GDBN} Command
19043 The corresponding @value{GDBN} command is @samp{return}.
19045 @subsubheading Example
19049 200-break-insert callee4
19050 200^done,bkpt=@{number="1",addr="0x00010734",
19051 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19056 000*stopped,reason="breakpoint-hit",bkptno="1",
19057 frame=@{func="callee4",args=[],
19058 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19059 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19065 111^done,frame=@{level="0",func="callee3",
19066 args=[@{name="strarg",
19067 value="0x11940 \"A string argument.\""@}],
19068 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19069 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19074 @subheading The @code{-exec-run} Command
19077 @subsubheading Synopsis
19083 Starts execution of the inferior from the beginning. The inferior
19084 executes until either a breakpoint is encountered or the program
19085 exits. In the latter case the output will include an exit code, if
19086 the program has exited exceptionally.
19088 @subsubheading @value{GDBN} Command
19090 The corresponding @value{GDBN} command is @samp{run}.
19092 @subsubheading Examples
19097 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19102 *stopped,reason="breakpoint-hit",bkptno="1",
19103 frame=@{func="main",args=[],file="recursive2.c",
19104 fullname="/home/foo/bar/recursive2.c",line="4"@}
19109 Program exited normally:
19117 *stopped,reason="exited-normally"
19122 Program exited exceptionally:
19130 *stopped,reason="exited",exit-code="01"
19134 Another way the program can terminate is if it receives a signal such as
19135 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19139 *stopped,reason="exited-signalled",signal-name="SIGINT",
19140 signal-meaning="Interrupt"
19144 @c @subheading -exec-signal
19147 @subheading The @code{-exec-step} Command
19150 @subsubheading Synopsis
19156 Resumes execution of the inferior program, stopping when the beginning
19157 of the next source line is reached, if the next source line is not a
19158 function call. If it is, stop at the first instruction of the called
19161 @subsubheading @value{GDBN} Command
19163 The corresponding @value{GDBN} command is @samp{step}.
19165 @subsubheading Example
19167 Stepping into a function:
19173 *stopped,reason="end-stepping-range",
19174 frame=@{func="foo",args=[@{name="a",value="10"@},
19175 @{name="b",value="0"@}],file="recursive2.c",
19176 fullname="/home/foo/bar/recursive2.c",line="11"@}
19186 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19191 @subheading The @code{-exec-step-instruction} Command
19192 @findex -exec-step-instruction
19194 @subsubheading Synopsis
19197 -exec-step-instruction
19200 Resumes the inferior which executes one machine instruction. The
19201 output, once @value{GDBN} has stopped, will vary depending on whether
19202 we have stopped in the middle of a source line or not. In the former
19203 case, the address at which the program stopped will be printed as
19206 @subsubheading @value{GDBN} Command
19208 The corresponding @value{GDBN} command is @samp{stepi}.
19210 @subsubheading Example
19214 -exec-step-instruction
19218 *stopped,reason="end-stepping-range",
19219 frame=@{func="foo",args=[],file="try.c",
19220 fullname="/home/foo/bar/try.c",line="10"@}
19222 -exec-step-instruction
19226 *stopped,reason="end-stepping-range",
19227 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19228 fullname="/home/foo/bar/try.c",line="10"@}
19233 @subheading The @code{-exec-until} Command
19234 @findex -exec-until
19236 @subsubheading Synopsis
19239 -exec-until [ @var{location} ]
19242 Executes the inferior until the @var{location} specified in the
19243 argument is reached. If there is no argument, the inferior executes
19244 until a source line greater than the current one is reached. The
19245 reason for stopping in this case will be @samp{location-reached}.
19247 @subsubheading @value{GDBN} Command
19249 The corresponding @value{GDBN} command is @samp{until}.
19251 @subsubheading Example
19255 -exec-until recursive2.c:6
19259 *stopped,reason="location-reached",frame=@{func="main",args=[],
19260 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19265 @subheading -file-clear
19266 Is this going away????
19269 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19270 @node GDB/MI Stack Manipulation
19271 @section @sc{gdb/mi} Stack Manipulation Commands
19274 @subheading The @code{-stack-info-frame} Command
19275 @findex -stack-info-frame
19277 @subsubheading Synopsis
19283 Get info on the selected frame.
19285 @subsubheading @value{GDBN} Command
19287 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19288 (without arguments).
19290 @subsubheading Example
19295 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19296 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19297 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19301 @subheading The @code{-stack-info-depth} Command
19302 @findex -stack-info-depth
19304 @subsubheading Synopsis
19307 -stack-info-depth [ @var{max-depth} ]
19310 Return the depth of the stack. If the integer argument @var{max-depth}
19311 is specified, do not count beyond @var{max-depth} frames.
19313 @subsubheading @value{GDBN} Command
19315 There's no equivalent @value{GDBN} command.
19317 @subsubheading Example
19319 For a stack with frame levels 0 through 11:
19326 -stack-info-depth 4
19329 -stack-info-depth 12
19332 -stack-info-depth 11
19335 -stack-info-depth 13
19340 @subheading The @code{-stack-list-arguments} Command
19341 @findex -stack-list-arguments
19343 @subsubheading Synopsis
19346 -stack-list-arguments @var{show-values}
19347 [ @var{low-frame} @var{high-frame} ]
19350 Display a list of the arguments for the frames between @var{low-frame}
19351 and @var{high-frame} (inclusive). If @var{low-frame} and
19352 @var{high-frame} are not provided, list the arguments for the whole
19353 call stack. If the two arguments are equal, show the single frame
19354 at the corresponding level. It is an error if @var{low-frame} is
19355 larger than the actual number of frames. On the other hand,
19356 @var{high-frame} may be larger than the actual number of frames, in
19357 which case only existing frames will be returned.
19359 The @var{show-values} argument must have a value of 0 or 1. A value of
19360 0 means that only the names of the arguments are listed, a value of 1
19361 means that both names and values of the arguments are printed.
19363 @subsubheading @value{GDBN} Command
19365 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19366 @samp{gdb_get_args} command which partially overlaps with the
19367 functionality of @samp{-stack-list-arguments}.
19369 @subsubheading Example
19376 frame=@{level="0",addr="0x00010734",func="callee4",
19377 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19378 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19379 frame=@{level="1",addr="0x0001076c",func="callee3",
19380 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19381 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19382 frame=@{level="2",addr="0x0001078c",func="callee2",
19383 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19384 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19385 frame=@{level="3",addr="0x000107b4",func="callee1",
19386 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19387 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19388 frame=@{level="4",addr="0x000107e0",func="main",
19389 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19390 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19392 -stack-list-arguments 0
19395 frame=@{level="0",args=[]@},
19396 frame=@{level="1",args=[name="strarg"]@},
19397 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19398 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19399 frame=@{level="4",args=[]@}]
19401 -stack-list-arguments 1
19404 frame=@{level="0",args=[]@},
19406 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19407 frame=@{level="2",args=[
19408 @{name="intarg",value="2"@},
19409 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19410 @{frame=@{level="3",args=[
19411 @{name="intarg",value="2"@},
19412 @{name="strarg",value="0x11940 \"A string argument.\""@},
19413 @{name="fltarg",value="3.5"@}]@},
19414 frame=@{level="4",args=[]@}]
19416 -stack-list-arguments 0 2 2
19417 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19419 -stack-list-arguments 1 2 2
19420 ^done,stack-args=[frame=@{level="2",
19421 args=[@{name="intarg",value="2"@},
19422 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19426 @c @subheading -stack-list-exception-handlers
19429 @subheading The @code{-stack-list-frames} Command
19430 @findex -stack-list-frames
19432 @subsubheading Synopsis
19435 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19438 List the frames currently on the stack. For each frame it displays the
19443 The frame number, 0 being the topmost frame, i.e., the innermost function.
19445 The @code{$pc} value for that frame.
19449 File name of the source file where the function lives.
19451 Line number corresponding to the @code{$pc}.
19454 If invoked without arguments, this command prints a backtrace for the
19455 whole stack. If given two integer arguments, it shows the frames whose
19456 levels are between the two arguments (inclusive). If the two arguments
19457 are equal, it shows the single frame at the corresponding level. It is
19458 an error if @var{low-frame} is larger than the actual number of
19459 frames. On the other hand, @var{high-frame} may be larger than the
19460 actual number of frames, in which case only existing frames will be returned.
19462 @subsubheading @value{GDBN} Command
19464 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19466 @subsubheading Example
19468 Full stack backtrace:
19474 [frame=@{level="0",addr="0x0001076c",func="foo",
19475 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19476 frame=@{level="1",addr="0x000107a4",func="foo",
19477 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19478 frame=@{level="2",addr="0x000107a4",func="foo",
19479 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19480 frame=@{level="3",addr="0x000107a4",func="foo",
19481 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19482 frame=@{level="4",addr="0x000107a4",func="foo",
19483 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19484 frame=@{level="5",addr="0x000107a4",func="foo",
19485 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19486 frame=@{level="6",addr="0x000107a4",func="foo",
19487 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19488 frame=@{level="7",addr="0x000107a4",func="foo",
19489 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19490 frame=@{level="8",addr="0x000107a4",func="foo",
19491 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19492 frame=@{level="9",addr="0x000107a4",func="foo",
19493 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19494 frame=@{level="10",addr="0x000107a4",func="foo",
19495 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19496 frame=@{level="11",addr="0x00010738",func="main",
19497 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19501 Show frames between @var{low_frame} and @var{high_frame}:
19505 -stack-list-frames 3 5
19507 [frame=@{level="3",addr="0x000107a4",func="foo",
19508 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19509 frame=@{level="4",addr="0x000107a4",func="foo",
19510 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19511 frame=@{level="5",addr="0x000107a4",func="foo",
19512 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19516 Show a single frame:
19520 -stack-list-frames 3 3
19522 [frame=@{level="3",addr="0x000107a4",func="foo",
19523 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19528 @subheading The @code{-stack-list-locals} Command
19529 @findex -stack-list-locals
19531 @subsubheading Synopsis
19534 -stack-list-locals @var{print-values}
19537 Display the local variable names for the selected frame. If
19538 @var{print-values} is 0 or @code{--no-values}, print only the names of
19539 the variables; if it is 1 or @code{--all-values}, print also their
19540 values; and if it is 2 or @code{--simple-values}, print the name,
19541 type and value for simple data types and the name and type for arrays,
19542 structures and unions. In this last case, a frontend can immediately
19543 display the value of simple data types and create variable objects for
19544 other data types when the user wishes to explore their values in
19547 @subsubheading @value{GDBN} Command
19549 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19551 @subsubheading Example
19555 -stack-list-locals 0
19556 ^done,locals=[name="A",name="B",name="C"]
19558 -stack-list-locals --all-values
19559 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19560 @{name="C",value="@{1, 2, 3@}"@}]
19561 -stack-list-locals --simple-values
19562 ^done,locals=[@{name="A",type="int",value="1"@},
19563 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19568 @subheading The @code{-stack-select-frame} Command
19569 @findex -stack-select-frame
19571 @subsubheading Synopsis
19574 -stack-select-frame @var{framenum}
19577 Change the selected frame. Select a different frame @var{framenum} on
19580 @subsubheading @value{GDBN} Command
19582 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19583 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19585 @subsubheading Example
19589 -stack-select-frame 2
19594 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19595 @node GDB/MI Variable Objects
19596 @section @sc{gdb/mi} Variable Objects
19600 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19602 For the implementation of a variable debugger window (locals, watched
19603 expressions, etc.), we are proposing the adaptation of the existing code
19604 used by @code{Insight}.
19606 The two main reasons for that are:
19610 It has been proven in practice (it is already on its second generation).
19613 It will shorten development time (needless to say how important it is
19617 The original interface was designed to be used by Tcl code, so it was
19618 slightly changed so it could be used through @sc{gdb/mi}. This section
19619 describes the @sc{gdb/mi} operations that will be available and gives some
19620 hints about their use.
19622 @emph{Note}: In addition to the set of operations described here, we
19623 expect the @sc{gui} implementation of a variable window to require, at
19624 least, the following operations:
19627 @item @code{-gdb-show} @code{output-radix}
19628 @item @code{-stack-list-arguments}
19629 @item @code{-stack-list-locals}
19630 @item @code{-stack-select-frame}
19635 @subheading Introduction to Variable Objects
19637 @cindex variable objects in @sc{gdb/mi}
19639 Variable objects are "object-oriented" MI interface for examining and
19640 changing values of expressions. Unlike some other MI interfaces that
19641 work with expressions, variable objects are specifically designed for
19642 simple and efficient presentation in the frontend. A variable object
19643 is identified by string name. When a variable object is created, the
19644 frontend specifies the expression for that variable object. The
19645 expression can be a simple variable, or it can be an arbitrary complex
19646 expression, and can even involve CPU registers. After creating a
19647 variable object, the frontend can invoke other variable object
19648 operations---for example to obtain or change the value of a variable
19649 object, or to change display format.
19651 Variable objects have hierarchical tree structure. Any variable object
19652 that corresponds to a composite type, such as structure in C, has
19653 a number of child variable objects, for example corresponding to each
19654 element of a structure. A child variable object can itself have
19655 children, recursively. Recursion ends when we reach
19656 leaf variable objects, which always have built-in types.
19658 For a leaf variable object it is possible to obtain its value as a
19659 string, or set the value from a string. String value can be also
19660 obtained for a non-leaf variable object, but it's generally a string
19661 that only indicates the type of the object, and does not list its
19662 contents. Assignment to a non-leaf variable object is not allowed.
19664 A frontend does not need to read the values of all variable objects each time
19665 the program stops. Instead, MI provides an update command that lists all
19666 variable objects whose values has changed since the last update
19667 operation. This considerably reduces the amount of data that must
19668 be transferred to the frontend.
19670 The following is the complete set of @sc{gdb/mi} operations defined to
19671 access this functionality:
19673 @multitable @columnfractions .4 .6
19674 @item @strong{Operation}
19675 @tab @strong{Description}
19677 @item @code{-var-create}
19678 @tab create a variable object
19679 @item @code{-var-delete}
19680 @tab delete the variable object and/or its children
19681 @item @code{-var-set-format}
19682 @tab set the display format of this variable
19683 @item @code{-var-show-format}
19684 @tab show the display format of this variable
19685 @item @code{-var-info-num-children}
19686 @tab tells how many children this object has
19687 @item @code{-var-list-children}
19688 @tab return a list of the object's children
19689 @item @code{-var-info-type}
19690 @tab show the type of this variable object
19691 @item @code{-var-info-expression}
19692 @tab print what this variable object represents
19693 @item @code{-var-show-attributes}
19694 @tab is this variable editable? does it exist here?
19695 @item @code{-var-evaluate-expression}
19696 @tab get the value of this variable
19697 @item @code{-var-assign}
19698 @tab set the value of this variable
19699 @item @code{-var-update}
19700 @tab update the variable and its children
19703 In the next subsection we describe each operation in detail and suggest
19704 how it can be used.
19706 @subheading Description And Use of Operations on Variable Objects
19708 @subheading The @code{-var-create} Command
19709 @findex -var-create
19711 @subsubheading Synopsis
19714 -var-create @{@var{name} | "-"@}
19715 @{@var{frame-addr} | "*"@} @var{expression}
19718 This operation creates a variable object, which allows the monitoring of
19719 a variable, the result of an expression, a memory cell or a CPU
19722 The @var{name} parameter is the string by which the object can be
19723 referenced. It must be unique. If @samp{-} is specified, the varobj
19724 system will generate a string ``varNNNNNN'' automatically. It will be
19725 unique provided that one does not specify @var{name} on that format.
19726 The command fails if a duplicate name is found.
19728 The frame under which the expression should be evaluated can be
19729 specified by @var{frame-addr}. A @samp{*} indicates that the current
19730 frame should be used.
19732 @var{expression} is any expression valid on the current language set (must not
19733 begin with a @samp{*}), or one of the following:
19737 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19740 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19743 @samp{$@var{regname}} --- a CPU register name
19746 @subsubheading Result
19748 This operation returns the name, number of children and the type of the
19749 object created. Type is returned as a string as the ones generated by
19750 the @value{GDBN} CLI:
19753 name="@var{name}",numchild="N",type="@var{type}"
19757 @subheading The @code{-var-delete} Command
19758 @findex -var-delete
19760 @subsubheading Synopsis
19763 -var-delete [ -c ] @var{name}
19766 Deletes a previously created variable object and all of its children.
19767 With the @samp{-c} option, just deletes the children.
19769 Returns an error if the object @var{name} is not found.
19772 @subheading The @code{-var-set-format} Command
19773 @findex -var-set-format
19775 @subsubheading Synopsis
19778 -var-set-format @var{name} @var{format-spec}
19781 Sets the output format for the value of the object @var{name} to be
19784 The syntax for the @var{format-spec} is as follows:
19787 @var{format-spec} @expansion{}
19788 @{binary | decimal | hexadecimal | octal | natural@}
19791 The natural format is the default format choosen automatically
19792 based on the variable type (like decimal for an @code{int}, hex
19793 for pointers, etc.).
19795 For a variable with children, the format is set only on the
19796 variable itself, and the children are not affected.
19798 @subheading The @code{-var-show-format} Command
19799 @findex -var-show-format
19801 @subsubheading Synopsis
19804 -var-show-format @var{name}
19807 Returns the format used to display the value of the object @var{name}.
19810 @var{format} @expansion{}
19815 @subheading The @code{-var-info-num-children} Command
19816 @findex -var-info-num-children
19818 @subsubheading Synopsis
19821 -var-info-num-children @var{name}
19824 Returns the number of children of a variable object @var{name}:
19831 @subheading The @code{-var-list-children} Command
19832 @findex -var-list-children
19834 @subsubheading Synopsis
19837 -var-list-children [@var{print-values}] @var{name}
19839 @anchor{-var-list-children}
19841 Return a list of the children of the specified variable object and
19842 create variable objects for them, if they do not already exist. With
19843 a single argument or if @var{print-values} has a value for of 0 or
19844 @code{--no-values}, print only the names of the variables; if
19845 @var{print-values} is 1 or @code{--all-values}, also print their
19846 values; and if it is 2 or @code{--simple-values} print the name and
19847 value for simple data types and just the name for arrays, structures
19850 @subsubheading Example
19854 -var-list-children n
19855 ^done,numchild=@var{n},children=[@{name=@var{name},
19856 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19858 -var-list-children --all-values n
19859 ^done,numchild=@var{n},children=[@{name=@var{name},
19860 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19864 @subheading The @code{-var-info-type} Command
19865 @findex -var-info-type
19867 @subsubheading Synopsis
19870 -var-info-type @var{name}
19873 Returns the type of the specified variable @var{name}. The type is
19874 returned as a string in the same format as it is output by the
19878 type=@var{typename}
19882 @subheading The @code{-var-info-expression} Command
19883 @findex -var-info-expression
19885 @subsubheading Synopsis
19888 -var-info-expression @var{name}
19891 Returns what is represented by the variable object @var{name}:
19894 lang=@var{lang-spec},exp=@var{expression}
19898 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
19900 @subheading The @code{-var-show-attributes} Command
19901 @findex -var-show-attributes
19903 @subsubheading Synopsis
19906 -var-show-attributes @var{name}
19909 List attributes of the specified variable object @var{name}:
19912 status=@var{attr} [ ( ,@var{attr} )* ]
19916 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19918 @subheading The @code{-var-evaluate-expression} Command
19919 @findex -var-evaluate-expression
19921 @subsubheading Synopsis
19924 -var-evaluate-expression @var{name}
19927 Evaluates the expression that is represented by the specified variable
19928 object and returns its value as a string. The format of the
19929 string can be changed using the @code{-var-set-format} command.
19935 Note that one must invoke @code{-var-list-children} for a variable
19936 before the value of a child variable can be evaluated.
19938 @subheading The @code{-var-assign} Command
19939 @findex -var-assign
19941 @subsubheading Synopsis
19944 -var-assign @var{name} @var{expression}
19947 Assigns the value of @var{expression} to the variable object specified
19948 by @var{name}. The object must be @samp{editable}. If the variable's
19949 value is altered by the assign, the variable will show up in any
19950 subsequent @code{-var-update} list.
19952 @subsubheading Example
19960 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19964 @subheading The @code{-var-update} Command
19965 @findex -var-update
19967 @subsubheading Synopsis
19970 -var-update [@var{print-values}] @{@var{name} | "*"@}
19973 Reevaluate the expressions corresponding to the variable object
19974 @var{name} and all its direct and indirect children, and return the
19975 list of variable objects whose values have changed. Here,
19976 ``changed'' means that the result of @code{-var-evaluate-expression} before
19977 and after the @code{-var-update} is different. If @samp{*} is used
19978 as the variable object names, all existing variable objects are
19979 updated. The option @var{print-values} determines whether both names
19980 and values, or just names are printed. The possible values of
19981 this options are the same as for @code{-var-list-children}
19982 (@pxref{-var-list-children}). It is recommended to use the
19983 @samp{--all-values} option, to reduce the number of MI commands needed
19984 on each program stop.
19987 @subsubheading Example
19994 -var-update --all-values var1
19995 ^done,changelist=[@{name="var1",value="3",in_scope="true",
19996 type_changed="false"@}]
20000 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20001 @node GDB/MI Data Manipulation
20002 @section @sc{gdb/mi} Data Manipulation
20004 @cindex data manipulation, in @sc{gdb/mi}
20005 @cindex @sc{gdb/mi}, data manipulation
20006 This section describes the @sc{gdb/mi} commands that manipulate data:
20007 examine memory and registers, evaluate expressions, etc.
20009 @c REMOVED FROM THE INTERFACE.
20010 @c @subheading -data-assign
20011 @c Change the value of a program variable. Plenty of side effects.
20012 @c @subsubheading GDB command
20014 @c @subsubheading Example
20017 @subheading The @code{-data-disassemble} Command
20018 @findex -data-disassemble
20020 @subsubheading Synopsis
20024 [ -s @var{start-addr} -e @var{end-addr} ]
20025 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20033 @item @var{start-addr}
20034 is the beginning address (or @code{$pc})
20035 @item @var{end-addr}
20037 @item @var{filename}
20038 is the name of the file to disassemble
20039 @item @var{linenum}
20040 is the line number to disassemble around
20042 is the number of disassembly lines to be produced. If it is -1,
20043 the whole function will be disassembled, in case no @var{end-addr} is
20044 specified. If @var{end-addr} is specified as a non-zero value, and
20045 @var{lines} is lower than the number of disassembly lines between
20046 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20047 displayed; if @var{lines} is higher than the number of lines between
20048 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20051 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20055 @subsubheading Result
20057 The output for each instruction is composed of four fields:
20066 Note that whatever included in the instruction field, is not manipulated
20067 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20069 @subsubheading @value{GDBN} Command
20071 There's no direct mapping from this command to the CLI.
20073 @subsubheading Example
20075 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20079 -data-disassemble -s $pc -e "$pc + 20" -- 0
20082 @{address="0x000107c0",func-name="main",offset="4",
20083 inst="mov 2, %o0"@},
20084 @{address="0x000107c4",func-name="main",offset="8",
20085 inst="sethi %hi(0x11800), %o2"@},
20086 @{address="0x000107c8",func-name="main",offset="12",
20087 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20088 @{address="0x000107cc",func-name="main",offset="16",
20089 inst="sethi %hi(0x11800), %o2"@},
20090 @{address="0x000107d0",func-name="main",offset="20",
20091 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20095 Disassemble the whole @code{main} function. Line 32 is part of
20099 -data-disassemble -f basics.c -l 32 -- 0
20101 @{address="0x000107bc",func-name="main",offset="0",
20102 inst="save %sp, -112, %sp"@},
20103 @{address="0x000107c0",func-name="main",offset="4",
20104 inst="mov 2, %o0"@},
20105 @{address="0x000107c4",func-name="main",offset="8",
20106 inst="sethi %hi(0x11800), %o2"@},
20108 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20109 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20113 Disassemble 3 instructions from the start of @code{main}:
20117 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20119 @{address="0x000107bc",func-name="main",offset="0",
20120 inst="save %sp, -112, %sp"@},
20121 @{address="0x000107c0",func-name="main",offset="4",
20122 inst="mov 2, %o0"@},
20123 @{address="0x000107c4",func-name="main",offset="8",
20124 inst="sethi %hi(0x11800), %o2"@}]
20128 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20132 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20134 src_and_asm_line=@{line="31",
20135 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20136 testsuite/gdb.mi/basics.c",line_asm_insn=[
20137 @{address="0x000107bc",func-name="main",offset="0",
20138 inst="save %sp, -112, %sp"@}]@},
20139 src_and_asm_line=@{line="32",
20140 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20141 testsuite/gdb.mi/basics.c",line_asm_insn=[
20142 @{address="0x000107c0",func-name="main",offset="4",
20143 inst="mov 2, %o0"@},
20144 @{address="0x000107c4",func-name="main",offset="8",
20145 inst="sethi %hi(0x11800), %o2"@}]@}]
20150 @subheading The @code{-data-evaluate-expression} Command
20151 @findex -data-evaluate-expression
20153 @subsubheading Synopsis
20156 -data-evaluate-expression @var{expr}
20159 Evaluate @var{expr} as an expression. The expression could contain an
20160 inferior function call. The function call will execute synchronously.
20161 If the expression contains spaces, it must be enclosed in double quotes.
20163 @subsubheading @value{GDBN} Command
20165 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20166 @samp{call}. In @code{gdbtk} only, there's a corresponding
20167 @samp{gdb_eval} command.
20169 @subsubheading Example
20171 In the following example, the numbers that precede the commands are the
20172 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20173 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20177 211-data-evaluate-expression A
20180 311-data-evaluate-expression &A
20181 311^done,value="0xefffeb7c"
20183 411-data-evaluate-expression A+3
20186 511-data-evaluate-expression "A + 3"
20192 @subheading The @code{-data-list-changed-registers} Command
20193 @findex -data-list-changed-registers
20195 @subsubheading Synopsis
20198 -data-list-changed-registers
20201 Display a list of the registers that have changed.
20203 @subsubheading @value{GDBN} Command
20205 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20206 has the corresponding command @samp{gdb_changed_register_list}.
20208 @subsubheading Example
20210 On a PPC MBX board:
20218 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20219 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20221 -data-list-changed-registers
20222 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20223 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20224 "24","25","26","27","28","30","31","64","65","66","67","69"]
20229 @subheading The @code{-data-list-register-names} Command
20230 @findex -data-list-register-names
20232 @subsubheading Synopsis
20235 -data-list-register-names [ ( @var{regno} )+ ]
20238 Show a list of register names for the current target. If no arguments
20239 are given, it shows a list of the names of all the registers. If
20240 integer numbers are given as arguments, it will print a list of the
20241 names of the registers corresponding to the arguments. To ensure
20242 consistency between a register name and its number, the output list may
20243 include empty register names.
20245 @subsubheading @value{GDBN} Command
20247 @value{GDBN} does not have a command which corresponds to
20248 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20249 corresponding command @samp{gdb_regnames}.
20251 @subsubheading Example
20253 For the PPC MBX board:
20256 -data-list-register-names
20257 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20258 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20259 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20260 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20261 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20262 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20263 "", "pc","ps","cr","lr","ctr","xer"]
20265 -data-list-register-names 1 2 3
20266 ^done,register-names=["r1","r2","r3"]
20270 @subheading The @code{-data-list-register-values} Command
20271 @findex -data-list-register-values
20273 @subsubheading Synopsis
20276 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20279 Display the registers' contents. @var{fmt} is the format according to
20280 which the registers' contents are to be returned, followed by an optional
20281 list of numbers specifying the registers to display. A missing list of
20282 numbers indicates that the contents of all the registers must be returned.
20284 Allowed formats for @var{fmt} are:
20301 @subsubheading @value{GDBN} Command
20303 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20304 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20306 @subsubheading Example
20308 For a PPC MBX board (note: line breaks are for readability only, they
20309 don't appear in the actual output):
20313 -data-list-register-values r 64 65
20314 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20315 @{number="65",value="0x00029002"@}]
20317 -data-list-register-values x
20318 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20319 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20320 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20321 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20322 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20323 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20324 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20325 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20326 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20327 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20328 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20329 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20330 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20331 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20332 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20333 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20334 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20335 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20336 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20337 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20338 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20339 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20340 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20341 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20342 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20343 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20344 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20345 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20346 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20347 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20348 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20349 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20350 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20351 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20352 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20353 @{number="69",value="0x20002b03"@}]
20358 @subheading The @code{-data-read-memory} Command
20359 @findex -data-read-memory
20361 @subsubheading Synopsis
20364 -data-read-memory [ -o @var{byte-offset} ]
20365 @var{address} @var{word-format} @var{word-size}
20366 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20373 @item @var{address}
20374 An expression specifying the address of the first memory word to be
20375 read. Complex expressions containing embedded white space should be
20376 quoted using the C convention.
20378 @item @var{word-format}
20379 The format to be used to print the memory words. The notation is the
20380 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20383 @item @var{word-size}
20384 The size of each memory word in bytes.
20386 @item @var{nr-rows}
20387 The number of rows in the output table.
20389 @item @var{nr-cols}
20390 The number of columns in the output table.
20393 If present, indicates that each row should include an @sc{ascii} dump. The
20394 value of @var{aschar} is used as a padding character when a byte is not a
20395 member of the printable @sc{ascii} character set (printable @sc{ascii}
20396 characters are those whose code is between 32 and 126, inclusively).
20398 @item @var{byte-offset}
20399 An offset to add to the @var{address} before fetching memory.
20402 This command displays memory contents as a table of @var{nr-rows} by
20403 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20404 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20405 (returned as @samp{total-bytes}). Should less than the requested number
20406 of bytes be returned by the target, the missing words are identified
20407 using @samp{N/A}. The number of bytes read from the target is returned
20408 in @samp{nr-bytes} and the starting address used to read memory in
20411 The address of the next/previous row or page is available in
20412 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20415 @subsubheading @value{GDBN} Command
20417 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20418 @samp{gdb_get_mem} memory read command.
20420 @subsubheading Example
20422 Read six bytes of memory starting at @code{bytes+6} but then offset by
20423 @code{-6} bytes. Format as three rows of two columns. One byte per
20424 word. Display each word in hex.
20428 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20429 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20430 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20431 prev-page="0x0000138a",memory=[
20432 @{addr="0x00001390",data=["0x00","0x01"]@},
20433 @{addr="0x00001392",data=["0x02","0x03"]@},
20434 @{addr="0x00001394",data=["0x04","0x05"]@}]
20438 Read two bytes of memory starting at address @code{shorts + 64} and
20439 display as a single word formatted in decimal.
20443 5-data-read-memory shorts+64 d 2 1 1
20444 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20445 next-row="0x00001512",prev-row="0x0000150e",
20446 next-page="0x00001512",prev-page="0x0000150e",memory=[
20447 @{addr="0x00001510",data=["128"]@}]
20451 Read thirty two bytes of memory starting at @code{bytes+16} and format
20452 as eight rows of four columns. Include a string encoding with @samp{x}
20453 used as the non-printable character.
20457 4-data-read-memory bytes+16 x 1 8 4 x
20458 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20459 next-row="0x000013c0",prev-row="0x0000139c",
20460 next-page="0x000013c0",prev-page="0x00001380",memory=[
20461 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20462 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20463 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20464 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20465 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20466 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20467 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20468 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20472 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20473 @node GDB/MI Tracepoint Commands
20474 @section @sc{gdb/mi} Tracepoint Commands
20476 The tracepoint commands are not yet implemented.
20478 @c @subheading -trace-actions
20480 @c @subheading -trace-delete
20482 @c @subheading -trace-disable
20484 @c @subheading -trace-dump
20486 @c @subheading -trace-enable
20488 @c @subheading -trace-exists
20490 @c @subheading -trace-find
20492 @c @subheading -trace-frame-number
20494 @c @subheading -trace-info
20496 @c @subheading -trace-insert
20498 @c @subheading -trace-list
20500 @c @subheading -trace-pass-count
20502 @c @subheading -trace-save
20504 @c @subheading -trace-start
20506 @c @subheading -trace-stop
20509 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20510 @node GDB/MI Symbol Query
20511 @section @sc{gdb/mi} Symbol Query Commands
20514 @subheading The @code{-symbol-info-address} Command
20515 @findex -symbol-info-address
20517 @subsubheading Synopsis
20520 -symbol-info-address @var{symbol}
20523 Describe where @var{symbol} is stored.
20525 @subsubheading @value{GDBN} Command
20527 The corresponding @value{GDBN} command is @samp{info address}.
20529 @subsubheading Example
20533 @subheading The @code{-symbol-info-file} Command
20534 @findex -symbol-info-file
20536 @subsubheading Synopsis
20542 Show the file for the symbol.
20544 @subsubheading @value{GDBN} Command
20546 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20547 @samp{gdb_find_file}.
20549 @subsubheading Example
20553 @subheading The @code{-symbol-info-function} Command
20554 @findex -symbol-info-function
20556 @subsubheading Synopsis
20559 -symbol-info-function
20562 Show which function the symbol lives in.
20564 @subsubheading @value{GDBN} Command
20566 @samp{gdb_get_function} in @code{gdbtk}.
20568 @subsubheading Example
20572 @subheading The @code{-symbol-info-line} Command
20573 @findex -symbol-info-line
20575 @subsubheading Synopsis
20581 Show the core addresses of the code for a source line.
20583 @subsubheading @value{GDBN} Command
20585 The corresponding @value{GDBN} command is @samp{info line}.
20586 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20588 @subsubheading Example
20592 @subheading The @code{-symbol-info-symbol} Command
20593 @findex -symbol-info-symbol
20595 @subsubheading Synopsis
20598 -symbol-info-symbol @var{addr}
20601 Describe what symbol is at location @var{addr}.
20603 @subsubheading @value{GDBN} Command
20605 The corresponding @value{GDBN} command is @samp{info symbol}.
20607 @subsubheading Example
20611 @subheading The @code{-symbol-list-functions} Command
20612 @findex -symbol-list-functions
20614 @subsubheading Synopsis
20617 -symbol-list-functions
20620 List the functions in the executable.
20622 @subsubheading @value{GDBN} Command
20624 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20625 @samp{gdb_search} in @code{gdbtk}.
20627 @subsubheading Example
20631 @subheading The @code{-symbol-list-lines} Command
20632 @findex -symbol-list-lines
20634 @subsubheading Synopsis
20637 -symbol-list-lines @var{filename}
20640 Print the list of lines that contain code and their associated program
20641 addresses for the given source filename. The entries are sorted in
20642 ascending PC order.
20644 @subsubheading @value{GDBN} Command
20646 There is no corresponding @value{GDBN} command.
20648 @subsubheading Example
20651 -symbol-list-lines basics.c
20652 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20657 @subheading The @code{-symbol-list-types} Command
20658 @findex -symbol-list-types
20660 @subsubheading Synopsis
20666 List all the type names.
20668 @subsubheading @value{GDBN} Command
20670 The corresponding commands are @samp{info types} in @value{GDBN},
20671 @samp{gdb_search} in @code{gdbtk}.
20673 @subsubheading Example
20677 @subheading The @code{-symbol-list-variables} Command
20678 @findex -symbol-list-variables
20680 @subsubheading Synopsis
20683 -symbol-list-variables
20686 List all the global and static variable names.
20688 @subsubheading @value{GDBN} Command
20690 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20692 @subsubheading Example
20696 @subheading The @code{-symbol-locate} Command
20697 @findex -symbol-locate
20699 @subsubheading Synopsis
20705 @subsubheading @value{GDBN} Command
20707 @samp{gdb_loc} in @code{gdbtk}.
20709 @subsubheading Example
20713 @subheading The @code{-symbol-type} Command
20714 @findex -symbol-type
20716 @subsubheading Synopsis
20719 -symbol-type @var{variable}
20722 Show type of @var{variable}.
20724 @subsubheading @value{GDBN} Command
20726 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20727 @samp{gdb_obj_variable}.
20729 @subsubheading Example
20733 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20734 @node GDB/MI File Commands
20735 @section @sc{gdb/mi} File Commands
20737 This section describes the GDB/MI commands to specify executable file names
20738 and to read in and obtain symbol table information.
20740 @subheading The @code{-file-exec-and-symbols} Command
20741 @findex -file-exec-and-symbols
20743 @subsubheading Synopsis
20746 -file-exec-and-symbols @var{file}
20749 Specify the executable file to be debugged. This file is the one from
20750 which the symbol table is also read. If no file is specified, the
20751 command clears the executable and symbol information. If breakpoints
20752 are set when using this command with no arguments, @value{GDBN} will produce
20753 error messages. Otherwise, no output is produced, except a completion
20756 @subsubheading @value{GDBN} Command
20758 The corresponding @value{GDBN} command is @samp{file}.
20760 @subsubheading Example
20764 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20770 @subheading The @code{-file-exec-file} Command
20771 @findex -file-exec-file
20773 @subsubheading Synopsis
20776 -file-exec-file @var{file}
20779 Specify the executable file to be debugged. Unlike
20780 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20781 from this file. If used without argument, @value{GDBN} clears the information
20782 about the executable file. No output is produced, except a completion
20785 @subsubheading @value{GDBN} Command
20787 The corresponding @value{GDBN} command is @samp{exec-file}.
20789 @subsubheading Example
20793 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20799 @subheading The @code{-file-list-exec-sections} Command
20800 @findex -file-list-exec-sections
20802 @subsubheading Synopsis
20805 -file-list-exec-sections
20808 List the sections of the current executable file.
20810 @subsubheading @value{GDBN} Command
20812 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20813 information as this command. @code{gdbtk} has a corresponding command
20814 @samp{gdb_load_info}.
20816 @subsubheading Example
20820 @subheading The @code{-file-list-exec-source-file} Command
20821 @findex -file-list-exec-source-file
20823 @subsubheading Synopsis
20826 -file-list-exec-source-file
20829 List the line number, the current source file, and the absolute path
20830 to the current source file for the current executable.
20832 @subsubheading @value{GDBN} Command
20834 The @value{GDBN} equivalent is @samp{info source}
20836 @subsubheading Example
20840 123-file-list-exec-source-file
20841 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20846 @subheading The @code{-file-list-exec-source-files} Command
20847 @findex -file-list-exec-source-files
20849 @subsubheading Synopsis
20852 -file-list-exec-source-files
20855 List the source files for the current executable.
20857 It will always output the filename, but only when GDB can find the absolute
20858 file name of a source file, will it output the fullname.
20860 @subsubheading @value{GDBN} Command
20862 The @value{GDBN} equivalent is @samp{info sources}.
20863 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20865 @subsubheading Example
20868 -file-list-exec-source-files
20870 @{file=foo.c,fullname=/home/foo.c@},
20871 @{file=/home/bar.c,fullname=/home/bar.c@},
20872 @{file=gdb_could_not_find_fullpath.c@}]
20876 @subheading The @code{-file-list-shared-libraries} Command
20877 @findex -file-list-shared-libraries
20879 @subsubheading Synopsis
20882 -file-list-shared-libraries
20885 List the shared libraries in the program.
20887 @subsubheading @value{GDBN} Command
20889 The corresponding @value{GDBN} command is @samp{info shared}.
20891 @subsubheading Example
20895 @subheading The @code{-file-list-symbol-files} Command
20896 @findex -file-list-symbol-files
20898 @subsubheading Synopsis
20901 -file-list-symbol-files
20906 @subsubheading @value{GDBN} Command
20908 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20910 @subsubheading Example
20914 @subheading The @code{-file-symbol-file} Command
20915 @findex -file-symbol-file
20917 @subsubheading Synopsis
20920 -file-symbol-file @var{file}
20923 Read symbol table info from the specified @var{file} argument. When
20924 used without arguments, clears @value{GDBN}'s symbol table info. No output is
20925 produced, except for a completion notification.
20927 @subsubheading @value{GDBN} Command
20929 The corresponding @value{GDBN} command is @samp{symbol-file}.
20931 @subsubheading Example
20935 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20941 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20942 @node GDB/MI Memory Overlay Commands
20943 @section @sc{gdb/mi} Memory Overlay Commands
20945 The memory overlay commands are not implemented.
20947 @c @subheading -overlay-auto
20949 @c @subheading -overlay-list-mapping-state
20951 @c @subheading -overlay-list-overlays
20953 @c @subheading -overlay-map
20955 @c @subheading -overlay-off
20957 @c @subheading -overlay-on
20959 @c @subheading -overlay-unmap
20961 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20962 @node GDB/MI Signal Handling Commands
20963 @section @sc{gdb/mi} Signal Handling Commands
20965 Signal handling commands are not implemented.
20967 @c @subheading -signal-handle
20969 @c @subheading -signal-list-handle-actions
20971 @c @subheading -signal-list-signal-types
20975 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20976 @node GDB/MI Target Manipulation
20977 @section @sc{gdb/mi} Target Manipulation Commands
20980 @subheading The @code{-target-attach} Command
20981 @findex -target-attach
20983 @subsubheading Synopsis
20986 -target-attach @var{pid} | @var{file}
20989 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
20991 @subsubheading @value{GDBN} command
20993 The corresponding @value{GDBN} command is @samp{attach}.
20995 @subsubheading Example
20999 @subheading The @code{-target-compare-sections} Command
21000 @findex -target-compare-sections
21002 @subsubheading Synopsis
21005 -target-compare-sections [ @var{section} ]
21008 Compare data of section @var{section} on target to the exec file.
21009 Without the argument, all sections are compared.
21011 @subsubheading @value{GDBN} Command
21013 The @value{GDBN} equivalent is @samp{compare-sections}.
21015 @subsubheading Example
21019 @subheading The @code{-target-detach} Command
21020 @findex -target-detach
21022 @subsubheading Synopsis
21028 Detach from the remote target which normally resumes its execution.
21031 @subsubheading @value{GDBN} command
21033 The corresponding @value{GDBN} command is @samp{detach}.
21035 @subsubheading Example
21045 @subheading The @code{-target-disconnect} Command
21046 @findex -target-disconnect
21048 @subsubheading Synopsis
21054 Disconnect from the remote target. There's no output and the target is
21055 generally not resumed.
21057 @subsubheading @value{GDBN} command
21059 The corresponding @value{GDBN} command is @samp{disconnect}.
21061 @subsubheading Example
21071 @subheading The @code{-target-download} Command
21072 @findex -target-download
21074 @subsubheading Synopsis
21080 Loads the executable onto the remote target.
21081 It prints out an update message every half second, which includes the fields:
21085 The name of the section.
21087 The size of what has been sent so far for that section.
21089 The size of the section.
21091 The total size of what was sent so far (the current and the previous sections).
21093 The size of the overall executable to download.
21097 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21098 @sc{gdb/mi} Output Syntax}).
21100 In addition, it prints the name and size of the sections, as they are
21101 downloaded. These messages include the following fields:
21105 The name of the section.
21107 The size of the section.
21109 The size of the overall executable to download.
21113 At the end, a summary is printed.
21115 @subsubheading @value{GDBN} Command
21117 The corresponding @value{GDBN} command is @samp{load}.
21119 @subsubheading Example
21121 Note: each status message appears on a single line. Here the messages
21122 have been broken down so that they can fit onto a page.
21127 +download,@{section=".text",section-size="6668",total-size="9880"@}
21128 +download,@{section=".text",section-sent="512",section-size="6668",
21129 total-sent="512",total-size="9880"@}
21130 +download,@{section=".text",section-sent="1024",section-size="6668",
21131 total-sent="1024",total-size="9880"@}
21132 +download,@{section=".text",section-sent="1536",section-size="6668",
21133 total-sent="1536",total-size="9880"@}
21134 +download,@{section=".text",section-sent="2048",section-size="6668",
21135 total-sent="2048",total-size="9880"@}
21136 +download,@{section=".text",section-sent="2560",section-size="6668",
21137 total-sent="2560",total-size="9880"@}
21138 +download,@{section=".text",section-sent="3072",section-size="6668",
21139 total-sent="3072",total-size="9880"@}
21140 +download,@{section=".text",section-sent="3584",section-size="6668",
21141 total-sent="3584",total-size="9880"@}
21142 +download,@{section=".text",section-sent="4096",section-size="6668",
21143 total-sent="4096",total-size="9880"@}
21144 +download,@{section=".text",section-sent="4608",section-size="6668",
21145 total-sent="4608",total-size="9880"@}
21146 +download,@{section=".text",section-sent="5120",section-size="6668",
21147 total-sent="5120",total-size="9880"@}
21148 +download,@{section=".text",section-sent="5632",section-size="6668",
21149 total-sent="5632",total-size="9880"@}
21150 +download,@{section=".text",section-sent="6144",section-size="6668",
21151 total-sent="6144",total-size="9880"@}
21152 +download,@{section=".text",section-sent="6656",section-size="6668",
21153 total-sent="6656",total-size="9880"@}
21154 +download,@{section=".init",section-size="28",total-size="9880"@}
21155 +download,@{section=".fini",section-size="28",total-size="9880"@}
21156 +download,@{section=".data",section-size="3156",total-size="9880"@}
21157 +download,@{section=".data",section-sent="512",section-size="3156",
21158 total-sent="7236",total-size="9880"@}
21159 +download,@{section=".data",section-sent="1024",section-size="3156",
21160 total-sent="7748",total-size="9880"@}
21161 +download,@{section=".data",section-sent="1536",section-size="3156",
21162 total-sent="8260",total-size="9880"@}
21163 +download,@{section=".data",section-sent="2048",section-size="3156",
21164 total-sent="8772",total-size="9880"@}
21165 +download,@{section=".data",section-sent="2560",section-size="3156",
21166 total-sent="9284",total-size="9880"@}
21167 +download,@{section=".data",section-sent="3072",section-size="3156",
21168 total-sent="9796",total-size="9880"@}
21169 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21175 @subheading The @code{-target-exec-status} Command
21176 @findex -target-exec-status
21178 @subsubheading Synopsis
21181 -target-exec-status
21184 Provide information on the state of the target (whether it is running or
21185 not, for instance).
21187 @subsubheading @value{GDBN} Command
21189 There's no equivalent @value{GDBN} command.
21191 @subsubheading Example
21195 @subheading The @code{-target-list-available-targets} Command
21196 @findex -target-list-available-targets
21198 @subsubheading Synopsis
21201 -target-list-available-targets
21204 List the possible targets to connect to.
21206 @subsubheading @value{GDBN} Command
21208 The corresponding @value{GDBN} command is @samp{help target}.
21210 @subsubheading Example
21214 @subheading The @code{-target-list-current-targets} Command
21215 @findex -target-list-current-targets
21217 @subsubheading Synopsis
21220 -target-list-current-targets
21223 Describe the current target.
21225 @subsubheading @value{GDBN} Command
21227 The corresponding information is printed by @samp{info file} (among
21230 @subsubheading Example
21234 @subheading The @code{-target-list-parameters} Command
21235 @findex -target-list-parameters
21237 @subsubheading Synopsis
21240 -target-list-parameters
21245 @subsubheading @value{GDBN} Command
21249 @subsubheading Example
21253 @subheading The @code{-target-select} Command
21254 @findex -target-select
21256 @subsubheading Synopsis
21259 -target-select @var{type} @var{parameters @dots{}}
21262 Connect @value{GDBN} to the remote target. This command takes two args:
21266 The type of target, for instance @samp{async}, @samp{remote}, etc.
21267 @item @var{parameters}
21268 Device names, host names and the like. @xref{Target Commands, ,
21269 Commands for managing targets}, for more details.
21272 The output is a connection notification, followed by the address at
21273 which the target program is, in the following form:
21276 ^connected,addr="@var{address}",func="@var{function name}",
21277 args=[@var{arg list}]
21280 @subsubheading @value{GDBN} Command
21282 The corresponding @value{GDBN} command is @samp{target}.
21284 @subsubheading Example
21288 -target-select async /dev/ttya
21289 ^connected,addr="0xfe00a300",func="??",args=[]
21293 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21294 @node GDB/MI Miscellaneous Commands
21295 @section Miscellaneous @sc{gdb/mi} Commands
21297 @c @subheading -gdb-complete
21299 @subheading The @code{-gdb-exit} Command
21302 @subsubheading Synopsis
21308 Exit @value{GDBN} immediately.
21310 @subsubheading @value{GDBN} Command
21312 Approximately corresponds to @samp{quit}.
21314 @subsubheading Example
21323 @subheading The @code{-exec-abort} Command
21324 @findex -exec-abort
21326 @subsubheading Synopsis
21332 Kill the inferior running program.
21334 @subsubheading @value{GDBN} Command
21336 The corresponding @value{GDBN} command is @samp{kill}.
21338 @subsubheading Example
21342 @subheading The @code{-gdb-set} Command
21345 @subsubheading Synopsis
21351 Set an internal @value{GDBN} variable.
21352 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21354 @subsubheading @value{GDBN} Command
21356 The corresponding @value{GDBN} command is @samp{set}.
21358 @subsubheading Example
21368 @subheading The @code{-gdb-show} Command
21371 @subsubheading Synopsis
21377 Show the current value of a @value{GDBN} variable.
21379 @subsubheading @value{GDBN} command
21381 The corresponding @value{GDBN} command is @samp{show}.
21383 @subsubheading Example
21392 @c @subheading -gdb-source
21395 @subheading The @code{-gdb-version} Command
21396 @findex -gdb-version
21398 @subsubheading Synopsis
21404 Show version information for @value{GDBN}. Used mostly in testing.
21406 @subsubheading @value{GDBN} Command
21408 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21409 default shows this information when you start an interactive session.
21411 @subsubheading Example
21413 @c This example modifies the actual output from GDB to avoid overfull
21419 ~Copyright 2000 Free Software Foundation, Inc.
21420 ~GDB is free software, covered by the GNU General Public License, and
21421 ~you are welcome to change it and/or distribute copies of it under
21422 ~ certain conditions.
21423 ~Type "show copying" to see the conditions.
21424 ~There is absolutely no warranty for GDB. Type "show warranty" for
21426 ~This GDB was configured as
21427 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21432 @subheading The @code{-interpreter-exec} Command
21433 @findex -interpreter-exec
21435 @subheading Synopsis
21438 -interpreter-exec @var{interpreter} @var{command}
21440 @anchor{-interpreter-exec}
21442 Execute the specified @var{command} in the given @var{interpreter}.
21444 @subheading @value{GDBN} Command
21446 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21448 @subheading Example
21452 -interpreter-exec console "break main"
21453 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21454 &"During symbol reading, bad structure-type format.\n"
21455 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21460 @subheading The @code{-inferior-tty-set} Command
21461 @findex -inferior-tty-set
21463 @subheading Synopsis
21466 -inferior-tty-set /dev/pts/1
21469 Set terminal for future runs of the program being debugged.
21471 @subheading @value{GDBN} Command
21473 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21475 @subheading Example
21479 -inferior-tty-set /dev/pts/1
21484 @subheading The @code{-inferior-tty-show} Command
21485 @findex -inferior-tty-show
21487 @subheading Synopsis
21493 Show terminal for future runs of program being debugged.
21495 @subheading @value{GDBN} Command
21497 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21499 @subheading Example
21503 -inferior-tty-set /dev/pts/1
21507 ^done,inferior_tty_terminal="/dev/pts/1"
21512 @chapter @value{GDBN} Annotations
21514 This chapter describes annotations in @value{GDBN}. Annotations were
21515 designed to interface @value{GDBN} to graphical user interfaces or other
21516 similar programs which want to interact with @value{GDBN} at a
21517 relatively high level.
21519 The annotation mechanism has largely been superseded by @sc{gdb/mi}
21523 This is Edition @value{EDITION}, @value{DATE}.
21527 * Annotations Overview:: What annotations are; the general syntax.
21528 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21529 * Errors:: Annotations for error messages.
21530 * Invalidation:: Some annotations describe things now invalid.
21531 * Annotations for Running::
21532 Whether the program is running, how it stopped, etc.
21533 * Source Annotations:: Annotations describing source code.
21536 @node Annotations Overview
21537 @section What is an Annotation?
21538 @cindex annotations
21540 Annotations start with a newline character, two @samp{control-z}
21541 characters, and the name of the annotation. If there is no additional
21542 information associated with this annotation, the name of the annotation
21543 is followed immediately by a newline. If there is additional
21544 information, the name of the annotation is followed by a space, the
21545 additional information, and a newline. The additional information
21546 cannot contain newline characters.
21548 Any output not beginning with a newline and two @samp{control-z}
21549 characters denotes literal output from @value{GDBN}. Currently there is
21550 no need for @value{GDBN} to output a newline followed by two
21551 @samp{control-z} characters, but if there was such a need, the
21552 annotations could be extended with an @samp{escape} annotation which
21553 means those three characters as output.
21555 The annotation @var{level}, which is specified using the
21556 @option{--annotate} command line option (@pxref{Mode Options}), controls
21557 how much information @value{GDBN} prints together with its prompt,
21558 values of expressions, source lines, and other types of output. Level 0
21559 is for no annotations, level 1 is for use when @value{GDBN} is run as a
21560 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21561 for programs that control @value{GDBN}, and level 2 annotations have
21562 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21563 Interface, annotate, GDB's Obsolete Annotations}).
21566 @kindex set annotate
21567 @item set annotate @var{level}
21568 The @value{GDBN} command @code{set annotate} sets the level of
21569 annotations to the specified @var{level}.
21571 @item show annotate
21572 @kindex show annotate
21573 Show the current annotation level.
21576 This chapter describes level 3 annotations.
21578 A simple example of starting up @value{GDBN} with annotations is:
21581 $ @kbd{gdb --annotate=3}
21583 Copyright 2003 Free Software Foundation, Inc.
21584 GDB is free software, covered by the GNU General Public License,
21585 and you are welcome to change it and/or distribute copies of it
21586 under certain conditions.
21587 Type "show copying" to see the conditions.
21588 There is absolutely no warranty for GDB. Type "show warranty"
21590 This GDB was configured as "i386-pc-linux-gnu"
21601 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21602 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21603 denotes a @samp{control-z} character) are annotations; the rest is
21604 output from @value{GDBN}.
21607 @section Annotation for @value{GDBN} Input
21609 @cindex annotations for prompts
21610 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21611 to know when to send output, when the output from a given command is
21614 Different kinds of input each have a different @dfn{input type}. Each
21615 input type has three annotations: a @code{pre-} annotation, which
21616 denotes the beginning of any prompt which is being output, a plain
21617 annotation, which denotes the end of the prompt, and then a @code{post-}
21618 annotation which denotes the end of any echo which may (or may not) be
21619 associated with the input. For example, the @code{prompt} input type
21620 features the following annotations:
21628 The input types are
21631 @findex pre-prompt annotation
21632 @findex prompt annotation
21633 @findex post-prompt annotation
21635 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21637 @findex pre-commands annotation
21638 @findex commands annotation
21639 @findex post-commands annotation
21641 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21642 command. The annotations are repeated for each command which is input.
21644 @findex pre-overload-choice annotation
21645 @findex overload-choice annotation
21646 @findex post-overload-choice annotation
21647 @item overload-choice
21648 When @value{GDBN} wants the user to select between various overloaded functions.
21650 @findex pre-query annotation
21651 @findex query annotation
21652 @findex post-query annotation
21654 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21656 @findex pre-prompt-for-continue annotation
21657 @findex prompt-for-continue annotation
21658 @findex post-prompt-for-continue annotation
21659 @item prompt-for-continue
21660 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21661 expect this to work well; instead use @code{set height 0} to disable
21662 prompting. This is because the counting of lines is buggy in the
21663 presence of annotations.
21668 @cindex annotations for errors, warnings and interrupts
21670 @findex quit annotation
21675 This annotation occurs right before @value{GDBN} responds to an interrupt.
21677 @findex error annotation
21682 This annotation occurs right before @value{GDBN} responds to an error.
21684 Quit and error annotations indicate that any annotations which @value{GDBN} was
21685 in the middle of may end abruptly. For example, if a
21686 @code{value-history-begin} annotation is followed by a @code{error}, one
21687 cannot expect to receive the matching @code{value-history-end}. One
21688 cannot expect not to receive it either, however; an error annotation
21689 does not necessarily mean that @value{GDBN} is immediately returning all the way
21692 @findex error-begin annotation
21693 A quit or error annotation may be preceded by
21699 Any output between that and the quit or error annotation is the error
21702 Warning messages are not yet annotated.
21703 @c If we want to change that, need to fix warning(), type_error(),
21704 @c range_error(), and possibly other places.
21707 @section Invalidation Notices
21709 @cindex annotations for invalidation messages
21710 The following annotations say that certain pieces of state may have
21714 @findex frames-invalid annotation
21715 @item ^Z^Zframes-invalid
21717 The frames (for example, output from the @code{backtrace} command) may
21720 @findex breakpoints-invalid annotation
21721 @item ^Z^Zbreakpoints-invalid
21723 The breakpoints may have changed. For example, the user just added or
21724 deleted a breakpoint.
21727 @node Annotations for Running
21728 @section Running the Program
21729 @cindex annotations for running programs
21731 @findex starting annotation
21732 @findex stopping annotation
21733 When the program starts executing due to a @value{GDBN} command such as
21734 @code{step} or @code{continue},
21740 is output. When the program stops,
21746 is output. Before the @code{stopped} annotation, a variety of
21747 annotations describe how the program stopped.
21750 @findex exited annotation
21751 @item ^Z^Zexited @var{exit-status}
21752 The program exited, and @var{exit-status} is the exit status (zero for
21753 successful exit, otherwise nonzero).
21755 @findex signalled annotation
21756 @findex signal-name annotation
21757 @findex signal-name-end annotation
21758 @findex signal-string annotation
21759 @findex signal-string-end annotation
21760 @item ^Z^Zsignalled
21761 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21762 annotation continues:
21768 ^Z^Zsignal-name-end
21772 ^Z^Zsignal-string-end
21777 where @var{name} is the name of the signal, such as @code{SIGILL} or
21778 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21779 as @code{Illegal Instruction} or @code{Segmentation fault}.
21780 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21781 user's benefit and have no particular format.
21783 @findex signal annotation
21785 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21786 just saying that the program received the signal, not that it was
21787 terminated with it.
21789 @findex breakpoint annotation
21790 @item ^Z^Zbreakpoint @var{number}
21791 The program hit breakpoint number @var{number}.
21793 @findex watchpoint annotation
21794 @item ^Z^Zwatchpoint @var{number}
21795 The program hit watchpoint number @var{number}.
21798 @node Source Annotations
21799 @section Displaying Source
21800 @cindex annotations for source display
21802 @findex source annotation
21803 The following annotation is used instead of displaying source code:
21806 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21809 where @var{filename} is an absolute file name indicating which source
21810 file, @var{line} is the line number within that file (where 1 is the
21811 first line in the file), @var{character} is the character position
21812 within the file (where 0 is the first character in the file) (for most
21813 debug formats this will necessarily point to the beginning of a line),
21814 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21815 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21816 @var{addr} is the address in the target program associated with the
21817 source which is being displayed. @var{addr} is in the form @samp{0x}
21818 followed by one or more lowercase hex digits (note that this does not
21819 depend on the language).
21822 @chapter Reporting Bugs in @value{GDBN}
21823 @cindex bugs in @value{GDBN}
21824 @cindex reporting bugs in @value{GDBN}
21826 Your bug reports play an essential role in making @value{GDBN} reliable.
21828 Reporting a bug may help you by bringing a solution to your problem, or it
21829 may not. But in any case the principal function of a bug report is to help
21830 the entire community by making the next version of @value{GDBN} work better. Bug
21831 reports are your contribution to the maintenance of @value{GDBN}.
21833 In order for a bug report to serve its purpose, you must include the
21834 information that enables us to fix the bug.
21837 * Bug Criteria:: Have you found a bug?
21838 * Bug Reporting:: How to report bugs
21842 @section Have you found a bug?
21843 @cindex bug criteria
21845 If you are not sure whether you have found a bug, here are some guidelines:
21848 @cindex fatal signal
21849 @cindex debugger crash
21850 @cindex crash of debugger
21852 If the debugger gets a fatal signal, for any input whatever, that is a
21853 @value{GDBN} bug. Reliable debuggers never crash.
21855 @cindex error on valid input
21857 If @value{GDBN} produces an error message for valid input, that is a
21858 bug. (Note that if you're cross debugging, the problem may also be
21859 somewhere in the connection to the target.)
21861 @cindex invalid input
21863 If @value{GDBN} does not produce an error message for invalid input,
21864 that is a bug. However, you should note that your idea of
21865 ``invalid input'' might be our idea of ``an extension'' or ``support
21866 for traditional practice''.
21869 If you are an experienced user of debugging tools, your suggestions
21870 for improvement of @value{GDBN} are welcome in any case.
21873 @node Bug Reporting
21874 @section How to report bugs
21875 @cindex bug reports
21876 @cindex @value{GDBN} bugs, reporting
21878 A number of companies and individuals offer support for @sc{gnu} products.
21879 If you obtained @value{GDBN} from a support organization, we recommend you
21880 contact that organization first.
21882 You can find contact information for many support companies and
21883 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21885 @c should add a web page ref...
21887 In any event, we also recommend that you submit bug reports for
21888 @value{GDBN}. The preferred method is to submit them directly using
21889 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21890 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21893 @strong{Do not send bug reports to @samp{info-gdb}, or to
21894 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21895 not want to receive bug reports. Those that do have arranged to receive
21898 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21899 serves as a repeater. The mailing list and the newsgroup carry exactly
21900 the same messages. Often people think of posting bug reports to the
21901 newsgroup instead of mailing them. This appears to work, but it has one
21902 problem which can be crucial: a newsgroup posting often lacks a mail
21903 path back to the sender. Thus, if we need to ask for more information,
21904 we may be unable to reach you. For this reason, it is better to send
21905 bug reports to the mailing list.
21907 The fundamental principle of reporting bugs usefully is this:
21908 @strong{report all the facts}. If you are not sure whether to state a
21909 fact or leave it out, state it!
21911 Often people omit facts because they think they know what causes the
21912 problem and assume that some details do not matter. Thus, you might
21913 assume that the name of the variable you use in an example does not matter.
21914 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21915 stray memory reference which happens to fetch from the location where that
21916 name is stored in memory; perhaps, if the name were different, the contents
21917 of that location would fool the debugger into doing the right thing despite
21918 the bug. Play it safe and give a specific, complete example. That is the
21919 easiest thing for you to do, and the most helpful.
21921 Keep in mind that the purpose of a bug report is to enable us to fix the
21922 bug. It may be that the bug has been reported previously, but neither
21923 you nor we can know that unless your bug report is complete and
21926 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21927 bell?'' Those bug reports are useless, and we urge everyone to
21928 @emph{refuse to respond to them} except to chide the sender to report
21931 To enable us to fix the bug, you should include all these things:
21935 The version of @value{GDBN}. @value{GDBN} announces it if you start
21936 with no arguments; you can also print it at any time using @code{show
21939 Without this, we will not know whether there is any point in looking for
21940 the bug in the current version of @value{GDBN}.
21943 The type of machine you are using, and the operating system name and
21947 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21948 ``@value{GCC}--2.8.1''.
21951 What compiler (and its version) was used to compile the program you are
21952 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21953 C Compiler''. For @value{NGCC}, you can say @kbd{gcc --version} to get this
21954 information; for other compilers, see the documentation for those
21958 The command arguments you gave the compiler to compile your example and
21959 observe the bug. For example, did you use @samp{-O}? To guarantee
21960 you will not omit something important, list them all. A copy of the
21961 Makefile (or the output from make) is sufficient.
21963 If we were to try to guess the arguments, we would probably guess wrong
21964 and then we might not encounter the bug.
21967 A complete input script, and all necessary source files, that will
21971 A description of what behavior you observe that you believe is
21972 incorrect. For example, ``It gets a fatal signal.''
21974 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21975 will certainly notice it. But if the bug is incorrect output, we might
21976 not notice unless it is glaringly wrong. You might as well not give us
21977 a chance to make a mistake.
21979 Even if the problem you experience is a fatal signal, you should still
21980 say so explicitly. Suppose something strange is going on, such as, your
21981 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21982 the C library on your system. (This has happened!) Your copy might
21983 crash and ours would not. If you told us to expect a crash, then when
21984 ours fails to crash, we would know that the bug was not happening for
21985 us. If you had not told us to expect a crash, then we would not be able
21986 to draw any conclusion from our observations.
21989 @cindex recording a session script
21990 To collect all this information, you can use a session recording program
21991 such as @command{script}, which is available on many Unix systems.
21992 Just run your @value{GDBN} session inside @command{script} and then
21993 include the @file{typescript} file with your bug report.
21995 Another way to record a @value{GDBN} session is to run @value{GDBN}
21996 inside Emacs and then save the entire buffer to a file.
21999 If you wish to suggest changes to the @value{GDBN} source, send us context
22000 diffs. If you even discuss something in the @value{GDBN} source, refer to
22001 it by context, not by line number.
22003 The line numbers in our development sources will not match those in your
22004 sources. Your line numbers would convey no useful information to us.
22008 Here are some things that are not necessary:
22012 A description of the envelope of the bug.
22014 Often people who encounter a bug spend a lot of time investigating
22015 which changes to the input file will make the bug go away and which
22016 changes will not affect it.
22018 This is often time consuming and not very useful, because the way we
22019 will find the bug is by running a single example under the debugger
22020 with breakpoints, not by pure deduction from a series of examples.
22021 We recommend that you save your time for something else.
22023 Of course, if you can find a simpler example to report @emph{instead}
22024 of the original one, that is a convenience for us. Errors in the
22025 output will be easier to spot, running under the debugger will take
22026 less time, and so on.
22028 However, simplification is not vital; if you do not want to do this,
22029 report the bug anyway and send us the entire test case you used.
22032 A patch for the bug.
22034 A patch for the bug does help us if it is a good one. But do not omit
22035 the necessary information, such as the test case, on the assumption that
22036 a patch is all we need. We might see problems with your patch and decide
22037 to fix the problem another way, or we might not understand it at all.
22039 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22040 construct an example that will make the program follow a certain path
22041 through the code. If you do not send us the example, we will not be able
22042 to construct one, so we will not be able to verify that the bug is fixed.
22044 And if we cannot understand what bug you are trying to fix, or why your
22045 patch should be an improvement, we will not install it. A test case will
22046 help us to understand.
22049 A guess about what the bug is or what it depends on.
22051 Such guesses are usually wrong. Even we cannot guess right about such
22052 things without first using the debugger to find the facts.
22055 @c The readline documentation is distributed with the readline code
22056 @c and consists of the two following files:
22058 @c inc-hist.texinfo
22059 @c Use -I with makeinfo to point to the appropriate directory,
22060 @c environment var TEXINPUTS with TeX.
22061 @include rluser.texi
22062 @include inc-hist.texinfo
22065 @node Formatting Documentation
22066 @appendix Formatting Documentation
22068 @cindex @value{GDBN} reference card
22069 @cindex reference card
22070 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22071 for printing with PostScript or Ghostscript, in the @file{gdb}
22072 subdirectory of the main source directory@footnote{In
22073 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22074 release.}. If you can use PostScript or Ghostscript with your printer,
22075 you can print the reference card immediately with @file{refcard.ps}.
22077 The release also includes the source for the reference card. You
22078 can format it, using @TeX{}, by typing:
22084 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22085 mode on US ``letter'' size paper;
22086 that is, on a sheet 11 inches wide by 8.5 inches
22087 high. You will need to specify this form of printing as an option to
22088 your @sc{dvi} output program.
22090 @cindex documentation
22092 All the documentation for @value{GDBN} comes as part of the machine-readable
22093 distribution. The documentation is written in Texinfo format, which is
22094 a documentation system that uses a single source file to produce both
22095 on-line information and a printed manual. You can use one of the Info
22096 formatting commands to create the on-line version of the documentation
22097 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22099 @value{GDBN} includes an already formatted copy of the on-line Info
22100 version of this manual in the @file{gdb} subdirectory. The main Info
22101 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22102 subordinate files matching @samp{gdb.info*} in the same directory. If
22103 necessary, you can print out these files, or read them with any editor;
22104 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22105 Emacs or the standalone @code{info} program, available as part of the
22106 @sc{gnu} Texinfo distribution.
22108 If you want to format these Info files yourself, you need one of the
22109 Info formatting programs, such as @code{texinfo-format-buffer} or
22112 If you have @code{makeinfo} installed, and are in the top level
22113 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22114 version @value{GDBVN}), you can make the Info file by typing:
22121 If you want to typeset and print copies of this manual, you need @TeX{},
22122 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22123 Texinfo definitions file.
22125 @TeX{} is a typesetting program; it does not print files directly, but
22126 produces output files called @sc{dvi} files. To print a typeset
22127 document, you need a program to print @sc{dvi} files. If your system
22128 has @TeX{} installed, chances are it has such a program. The precise
22129 command to use depends on your system; @kbd{lpr -d} is common; another
22130 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22131 require a file name without any extension or a @samp{.dvi} extension.
22133 @TeX{} also requires a macro definitions file called
22134 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22135 written in Texinfo format. On its own, @TeX{} cannot either read or
22136 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22137 and is located in the @file{gdb-@var{version-number}/texinfo}
22140 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22141 typeset and print this manual. First switch to the @file{gdb}
22142 subdirectory of the main source directory (for example, to
22143 @file{gdb-@value{GDBVN}/gdb}) and type:
22149 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22151 @node Installing GDB
22152 @appendix Installing @value{GDBN}
22153 @cindex installation
22156 * Requirements:: Requirements for building @value{GDBN}
22157 * Running Configure:: Invoking the @value{GDBN} @code{configure} script
22158 * Separate Objdir:: Compiling @value{GDBN} in another directory
22159 * Config Names:: Specifying names for hosts and targets
22160 * Configure Options:: Summary of options for configure
22164 @section Requirements for building @value{GDBN}
22165 @cindex building @value{GDBN}, requirements for
22167 Building @value{GDBN} requires various tools and packages to be available.
22168 Other packages will be used only if they are found.
22170 @heading Tools/packages necessary for building @value{GDBN}
22172 @item ISO C90 compiler
22173 @value{GDBN} is written in ISO C90. It should be buildable with any
22174 working C90 compiler, e.g.@: GCC.
22178 @heading Tools/packages optional for building @value{GDBN}
22181 @value{GDBN} can use the Expat XML parsing library. This library may be
22182 included with your operating system distribution; if it is not, you
22183 can get the latest version from @url{http://expat.sourceforge.net}.
22184 The @code{configure} script will search for this library in several
22185 standard locations; if it is installed in an unusual path, you can
22186 use the @option{--with-libexpat-prefix} option to specify its location.
22188 Expat is used currently only used to implement some remote-specific
22193 @node Running Configure
22194 @section Invoking the @value{GDBN} @code{configure} script
22195 @cindex configuring @value{GDBN}
22196 @value{GDBN} comes with a @code{configure} script that automates the process
22197 of preparing @value{GDBN} for installation; you can then use @code{make} to
22198 build the @code{gdb} program.
22200 @c irrelevant in info file; it's as current as the code it lives with.
22201 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22202 look at the @file{README} file in the sources; we may have improved the
22203 installation procedures since publishing this manual.}
22206 The @value{GDBN} distribution includes all the source code you need for
22207 @value{GDBN} in a single directory, whose name is usually composed by
22208 appending the version number to @samp{gdb}.
22210 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22211 @file{gdb-@value{GDBVN}} directory. That directory contains:
22214 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22215 script for configuring @value{GDBN} and all its supporting libraries
22217 @item gdb-@value{GDBVN}/gdb
22218 the source specific to @value{GDBN} itself
22220 @item gdb-@value{GDBVN}/bfd
22221 source for the Binary File Descriptor library
22223 @item gdb-@value{GDBVN}/include
22224 @sc{gnu} include files
22226 @item gdb-@value{GDBVN}/libiberty
22227 source for the @samp{-liberty} free software library
22229 @item gdb-@value{GDBVN}/opcodes
22230 source for the library of opcode tables and disassemblers
22232 @item gdb-@value{GDBVN}/readline
22233 source for the @sc{gnu} command-line interface
22235 @item gdb-@value{GDBVN}/glob
22236 source for the @sc{gnu} filename pattern-matching subroutine
22238 @item gdb-@value{GDBVN}/mmalloc
22239 source for the @sc{gnu} memory-mapped malloc package
22242 The simplest way to configure and build @value{GDBN} is to run @code{configure}
22243 from the @file{gdb-@var{version-number}} source directory, which in
22244 this example is the @file{gdb-@value{GDBVN}} directory.
22246 First switch to the @file{gdb-@var{version-number}} source directory
22247 if you are not already in it; then run @code{configure}. Pass the
22248 identifier for the platform on which @value{GDBN} will run as an
22254 cd gdb-@value{GDBVN}
22255 ./configure @var{host}
22260 where @var{host} is an identifier such as @samp{sun4} or
22261 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22262 (You can often leave off @var{host}; @code{configure} tries to guess the
22263 correct value by examining your system.)
22265 Running @samp{configure @var{host}} and then running @code{make} builds the
22266 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22267 libraries, then @code{gdb} itself. The configured source files, and the
22268 binaries, are left in the corresponding source directories.
22271 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22272 system does not recognize this automatically when you run a different
22273 shell, you may need to run @code{sh} on it explicitly:
22276 sh configure @var{host}
22279 If you run @code{configure} from a directory that contains source
22280 directories for multiple libraries or programs, such as the
22281 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
22282 creates configuration files for every directory level underneath (unless
22283 you tell it not to, with the @samp{--norecursion} option).
22285 You should run the @code{configure} script from the top directory in the
22286 source tree, the @file{gdb-@var{version-number}} directory. If you run
22287 @code{configure} from one of the subdirectories, you will configure only
22288 that subdirectory. That is usually not what you want. In particular,
22289 if you run the first @code{configure} from the @file{gdb} subdirectory
22290 of the @file{gdb-@var{version-number}} directory, you will omit the
22291 configuration of @file{bfd}, @file{readline}, and other sibling
22292 directories of the @file{gdb} subdirectory. This leads to build errors
22293 about missing include files such as @file{bfd/bfd.h}.
22295 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22296 However, you should make sure that the shell on your path (named by
22297 the @samp{SHELL} environment variable) is publicly readable. Remember
22298 that @value{GDBN} uses the shell to start your program---some systems refuse to
22299 let @value{GDBN} debug child processes whose programs are not readable.
22301 @node Separate Objdir
22302 @section Compiling @value{GDBN} in another directory
22304 If you want to run @value{GDBN} versions for several host or target machines,
22305 you need a different @code{gdb} compiled for each combination of
22306 host and target. @code{configure} is designed to make this easy by
22307 allowing you to generate each configuration in a separate subdirectory,
22308 rather than in the source directory. If your @code{make} program
22309 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22310 @code{make} in each of these directories builds the @code{gdb}
22311 program specified there.
22313 To build @code{gdb} in a separate directory, run @code{configure}
22314 with the @samp{--srcdir} option to specify where to find the source.
22315 (You also need to specify a path to find @code{configure}
22316 itself from your working directory. If the path to @code{configure}
22317 would be the same as the argument to @samp{--srcdir}, you can leave out
22318 the @samp{--srcdir} option; it is assumed.)
22320 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22321 separate directory for a Sun 4 like this:
22325 cd gdb-@value{GDBVN}
22328 ../gdb-@value{GDBVN}/configure sun4
22333 When @code{configure} builds a configuration using a remote source
22334 directory, it creates a tree for the binaries with the same structure
22335 (and using the same names) as the tree under the source directory. In
22336 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22337 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22338 @file{gdb-sun4/gdb}.
22340 Make sure that your path to the @file{configure} script has just one
22341 instance of @file{gdb} in it. If your path to @file{configure} looks
22342 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22343 one subdirectory of @value{GDBN}, not the whole package. This leads to
22344 build errors about missing include files such as @file{bfd/bfd.h}.
22346 One popular reason to build several @value{GDBN} configurations in separate
22347 directories is to configure @value{GDBN} for cross-compiling (where
22348 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22349 programs that run on another machine---the @dfn{target}).
22350 You specify a cross-debugging target by
22351 giving the @samp{--target=@var{target}} option to @code{configure}.
22353 When you run @code{make} to build a program or library, you must run
22354 it in a configured directory---whatever directory you were in when you
22355 called @code{configure} (or one of its subdirectories).
22357 The @code{Makefile} that @code{configure} generates in each source
22358 directory also runs recursively. If you type @code{make} in a source
22359 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22360 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22361 will build all the required libraries, and then build GDB.
22363 When you have multiple hosts or targets configured in separate
22364 directories, you can run @code{make} on them in parallel (for example,
22365 if they are NFS-mounted on each of the hosts); they will not interfere
22369 @section Specifying names for hosts and targets
22371 The specifications used for hosts and targets in the @code{configure}
22372 script are based on a three-part naming scheme, but some short predefined
22373 aliases are also supported. The full naming scheme encodes three pieces
22374 of information in the following pattern:
22377 @var{architecture}-@var{vendor}-@var{os}
22380 For example, you can use the alias @code{sun4} as a @var{host} argument,
22381 or as the value for @var{target} in a @code{--target=@var{target}}
22382 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22384 The @code{configure} script accompanying @value{GDBN} does not provide
22385 any query facility to list all supported host and target names or
22386 aliases. @code{configure} calls the Bourne shell script
22387 @code{config.sub} to map abbreviations to full names; you can read the
22388 script, if you wish, or you can use it to test your guesses on
22389 abbreviations---for example:
22392 % sh config.sub i386-linux
22394 % sh config.sub alpha-linux
22395 alpha-unknown-linux-gnu
22396 % sh config.sub hp9k700
22398 % sh config.sub sun4
22399 sparc-sun-sunos4.1.1
22400 % sh config.sub sun3
22401 m68k-sun-sunos4.1.1
22402 % sh config.sub i986v
22403 Invalid configuration `i986v': machine `i986v' not recognized
22407 @code{config.sub} is also distributed in the @value{GDBN} source
22408 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22410 @node Configure Options
22411 @section @code{configure} options
22413 Here is a summary of the @code{configure} options and arguments that
22414 are most often useful for building @value{GDBN}. @code{configure} also has
22415 several other options not listed here. @inforef{What Configure
22416 Does,,configure.info}, for a full explanation of @code{configure}.
22419 configure @r{[}--help@r{]}
22420 @r{[}--prefix=@var{dir}@r{]}
22421 @r{[}--exec-prefix=@var{dir}@r{]}
22422 @r{[}--srcdir=@var{dirname}@r{]}
22423 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22424 @r{[}--target=@var{target}@r{]}
22429 You may introduce options with a single @samp{-} rather than
22430 @samp{--} if you prefer; but you may abbreviate option names if you use
22435 Display a quick summary of how to invoke @code{configure}.
22437 @item --prefix=@var{dir}
22438 Configure the source to install programs and files under directory
22441 @item --exec-prefix=@var{dir}
22442 Configure the source to install programs under directory
22445 @c avoid splitting the warning from the explanation:
22447 @item --srcdir=@var{dirname}
22448 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22449 @code{make} that implements the @code{VPATH} feature.}@*
22450 Use this option to make configurations in directories separate from the
22451 @value{GDBN} source directories. Among other things, you can use this to
22452 build (or maintain) several configurations simultaneously, in separate
22453 directories. @code{configure} writes configuration specific files in
22454 the current directory, but arranges for them to use the source in the
22455 directory @var{dirname}. @code{configure} creates directories under
22456 the working directory in parallel to the source directories below
22459 @item --norecursion
22460 Configure only the directory level where @code{configure} is executed; do not
22461 propagate configuration to subdirectories.
22463 @item --target=@var{target}
22464 Configure @value{GDBN} for cross-debugging programs running on the specified
22465 @var{target}. Without this option, @value{GDBN} is configured to debug
22466 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22468 There is no convenient way to generate a list of all available targets.
22470 @item @var{host} @dots{}
22471 Configure @value{GDBN} to run on the specified @var{host}.
22473 There is no convenient way to generate a list of all available hosts.
22476 There are many other options available as well, but they are generally
22477 needed for special purposes only.
22479 @node Maintenance Commands
22480 @appendix Maintenance Commands
22481 @cindex maintenance commands
22482 @cindex internal commands
22484 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22485 includes a number of commands intended for @value{GDBN} developers,
22486 that are not documented elsewhere in this manual. These commands are
22487 provided here for reference. (For commands that turn on debugging
22488 messages, see @ref{Debugging Output}.)
22491 @kindex maint agent
22492 @item maint agent @var{expression}
22493 Translate the given @var{expression} into remote agent bytecodes.
22494 This command is useful for debugging the Agent Expression mechanism
22495 (@pxref{Agent Expressions}).
22497 @kindex maint info breakpoints
22498 @item @anchor{maint info breakpoints}maint info breakpoints
22499 Using the same format as @samp{info breakpoints}, display both the
22500 breakpoints you've set explicitly, and those @value{GDBN} is using for
22501 internal purposes. Internal breakpoints are shown with negative
22502 breakpoint numbers. The type column identifies what kind of breakpoint
22507 Normal, explicitly set breakpoint.
22510 Normal, explicitly set watchpoint.
22513 Internal breakpoint, used to handle correctly stepping through
22514 @code{longjmp} calls.
22516 @item longjmp resume
22517 Internal breakpoint at the target of a @code{longjmp}.
22520 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22523 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22526 Shared library events.
22530 @kindex maint check-symtabs
22531 @item maint check-symtabs
22532 Check the consistency of psymtabs and symtabs.
22534 @kindex maint cplus first_component
22535 @item maint cplus first_component @var{name}
22536 Print the first C@t{++} class/namespace component of @var{name}.
22538 @kindex maint cplus namespace
22539 @item maint cplus namespace
22540 Print the list of possible C@t{++} namespaces.
22542 @kindex maint demangle
22543 @item maint demangle @var{name}
22544 Demangle a C@t{++} or Objective-C mangled @var{name}.
22546 @kindex maint deprecate
22547 @kindex maint undeprecate
22548 @cindex deprecated commands
22549 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22550 @itemx maint undeprecate @var{command}
22551 Deprecate or undeprecate the named @var{command}. Deprecated commands
22552 cause @value{GDBN} to issue a warning when you use them. The optional
22553 argument @var{replacement} says which newer command should be used in
22554 favor of the deprecated one; if it is given, @value{GDBN} will mention
22555 the replacement as part of the warning.
22557 @kindex maint dump-me
22558 @item maint dump-me
22559 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22560 Cause a fatal signal in the debugger and force it to dump its core.
22561 This is supported only on systems which support aborting a program
22562 with the @code{SIGQUIT} signal.
22564 @kindex maint internal-error
22565 @kindex maint internal-warning
22566 @item maint internal-error @r{[}@var{message-text}@r{]}
22567 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22568 Cause @value{GDBN} to call the internal function @code{internal_error}
22569 or @code{internal_warning} and hence behave as though an internal error
22570 or internal warning has been detected. In addition to reporting the
22571 internal problem, these functions give the user the opportunity to
22572 either quit @value{GDBN} or create a core file of the current
22573 @value{GDBN} session.
22575 These commands take an optional parameter @var{message-text} that is
22576 used as the text of the error or warning message.
22578 Here's an example of using @code{internal-error}:
22581 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22582 @dots{}/maint.c:121: internal-error: testing, 1, 2
22583 A problem internal to GDB has been detected. Further
22584 debugging may prove unreliable.
22585 Quit this debugging session? (y or n) @kbd{n}
22586 Create a core file? (y or n) @kbd{n}
22590 @kindex maint packet
22591 @item maint packet @var{text}
22592 If @value{GDBN} is talking to an inferior via the serial protocol,
22593 then this command sends the string @var{text} to the inferior, and
22594 displays the response packet. @value{GDBN} supplies the initial
22595 @samp{$} character, the terminating @samp{#} character, and the
22598 @kindex maint print architecture
22599 @item maint print architecture @r{[}@var{file}@r{]}
22600 Print the entire architecture configuration. The optional argument
22601 @var{file} names the file where the output goes.
22603 @kindex maint print dummy-frames
22604 @item maint print dummy-frames
22605 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22608 (@value{GDBP}) @kbd{b add}
22610 (@value{GDBP}) @kbd{print add(2,3)}
22611 Breakpoint 2, add (a=2, b=3) at @dots{}
22613 The program being debugged stopped while in a function called from GDB.
22615 (@value{GDBP}) @kbd{maint print dummy-frames}
22616 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22617 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22618 call_lo=0x01014000 call_hi=0x01014001
22622 Takes an optional file parameter.
22624 @kindex maint print registers
22625 @kindex maint print raw-registers
22626 @kindex maint print cooked-registers
22627 @kindex maint print register-groups
22628 @item maint print registers @r{[}@var{file}@r{]}
22629 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22630 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22631 @itemx maint print register-groups @r{[}@var{file}@r{]}
22632 Print @value{GDBN}'s internal register data structures.
22634 The command @code{maint print raw-registers} includes the contents of
22635 the raw register cache; the command @code{maint print cooked-registers}
22636 includes the (cooked) value of all registers; and the command
22637 @code{maint print register-groups} includes the groups that each
22638 register is a member of. @xref{Registers,, Registers, gdbint,
22639 @value{GDBN} Internals}.
22641 These commands take an optional parameter, a file name to which to
22642 write the information.
22644 @kindex maint print reggroups
22645 @item maint print reggroups @r{[}@var{file}@r{]}
22646 Print @value{GDBN}'s internal register group data structures. The
22647 optional argument @var{file} tells to what file to write the
22650 The register groups info looks like this:
22653 (@value{GDBP}) @kbd{maint print reggroups}
22666 This command forces @value{GDBN} to flush its internal register cache.
22668 @kindex maint print objfiles
22669 @cindex info for known object files
22670 @item maint print objfiles
22671 Print a dump of all known object files. For each object file, this
22672 command prints its name, address in memory, and all of its psymtabs
22675 @kindex maint print statistics
22676 @cindex bcache statistics
22677 @item maint print statistics
22678 This command prints, for each object file in the program, various data
22679 about that object file followed by the byte cache (@dfn{bcache})
22680 statistics for the object file. The objfile data includes the number
22681 of minimal, partial, full, and stabs symbols, the number of types
22682 defined by the objfile, the number of as yet unexpanded psym tables,
22683 the number of line tables and string tables, and the amount of memory
22684 used by the various tables. The bcache statistics include the counts,
22685 sizes, and counts of duplicates of all and unique objects, max,
22686 average, and median entry size, total memory used and its overhead and
22687 savings, and various measures of the hash table size and chain
22690 @kindex maint print target-stack
22691 @cindex target stack description
22692 @item maint print target-stack
22693 A @dfn{target} is an interface between the debugger and a particular
22694 kind of file or process. Targets can be stacked in @dfn{strata},
22695 so that more than one target can potentially respond to a request.
22696 In particular, memory accesses will walk down the stack of targets
22697 until they find a target that is interested in handling that particular
22700 This command prints a short description of each layer that was pushed on
22701 the @dfn{target stack}, starting from the top layer down to the bottom one.
22703 @kindex maint print type
22704 @cindex type chain of a data type
22705 @item maint print type @var{expr}
22706 Print the type chain for a type specified by @var{expr}. The argument
22707 can be either a type name or a symbol. If it is a symbol, the type of
22708 that symbol is described. The type chain produced by this command is
22709 a recursive definition of the data type as stored in @value{GDBN}'s
22710 data structures, including its flags and contained types.
22712 @kindex maint set dwarf2 max-cache-age
22713 @kindex maint show dwarf2 max-cache-age
22714 @item maint set dwarf2 max-cache-age
22715 @itemx maint show dwarf2 max-cache-age
22716 Control the DWARF 2 compilation unit cache.
22718 @cindex DWARF 2 compilation units cache
22719 In object files with inter-compilation-unit references, such as those
22720 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22721 reader needs to frequently refer to previously read compilation units.
22722 This setting controls how long a compilation unit will remain in the
22723 cache if it is not referenced. A higher limit means that cached
22724 compilation units will be stored in memory longer, and more total
22725 memory will be used. Setting it to zero disables caching, which will
22726 slow down @value{GDBN} startup, but reduce memory consumption.
22728 @kindex maint set profile
22729 @kindex maint show profile
22730 @cindex profiling GDB
22731 @item maint set profile
22732 @itemx maint show profile
22733 Control profiling of @value{GDBN}.
22735 Profiling will be disabled until you use the @samp{maint set profile}
22736 command to enable it. When you enable profiling, the system will begin
22737 collecting timing and execution count data; when you disable profiling or
22738 exit @value{GDBN}, the results will be written to a log file. Remember that
22739 if you use profiling, @value{GDBN} will overwrite the profiling log file
22740 (often called @file{gmon.out}). If you have a record of important profiling
22741 data in a @file{gmon.out} file, be sure to move it to a safe location.
22743 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
22744 compiled with the @samp{-pg} compiler option.
22746 @kindex maint show-debug-regs
22747 @cindex x86 hardware debug registers
22748 @item maint show-debug-regs
22749 Control whether to show variables that mirror the x86 hardware debug
22750 registers. Use @code{ON} to enable, @code{OFF} to disable. If
22751 enabled, the debug registers values are shown when GDB inserts or
22752 removes a hardware breakpoint or watchpoint, and when the inferior
22753 triggers a hardware-assisted breakpoint or watchpoint.
22755 @kindex maint space
22756 @cindex memory used by commands
22758 Control whether to display memory usage for each command. If set to a
22759 nonzero value, @value{GDBN} will display how much memory each command
22760 took, following the command's own output. This can also be requested
22761 by invoking @value{GDBN} with the @option{--statistics} command-line
22762 switch (@pxref{Mode Options}).
22765 @cindex time of command execution
22767 Control whether to display the execution time for each command. If
22768 set to a nonzero value, @value{GDBN} will display how much time it
22769 took to execute each command, following the command's own output.
22770 This can also be requested by invoking @value{GDBN} with the
22771 @option{--statistics} command-line switch (@pxref{Mode Options}).
22773 @kindex maint translate-address
22774 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22775 Find the symbol stored at the location specified by the address
22776 @var{addr} and an optional section name @var{section}. If found,
22777 @value{GDBN} prints the name of the closest symbol and an offset from
22778 the symbol's location to the specified address. This is similar to
22779 the @code{info address} command (@pxref{Symbols}), except that this
22780 command also allows to find symbols in other sections.
22784 The following command is useful for non-interactive invocations of
22785 @value{GDBN}, such as in the test suite.
22788 @item set watchdog @var{nsec}
22789 @kindex set watchdog
22790 @cindex watchdog timer
22791 @cindex timeout for commands
22792 Set the maximum number of seconds @value{GDBN} will wait for the
22793 target operation to finish. If this time expires, @value{GDBN}
22794 reports and error and the command is aborted.
22796 @item show watchdog
22797 Show the current setting of the target wait timeout.
22800 @node Remote Protocol
22801 @appendix @value{GDBN} Remote Serial Protocol
22806 * Stop Reply Packets::
22807 * General Query Packets::
22808 * Register Packet Format::
22809 * Tracepoint Packets::
22812 * File-I/O remote protocol extension::
22813 * Memory map format::
22819 There may be occasions when you need to know something about the
22820 protocol---for example, if there is only one serial port to your target
22821 machine, you might want your program to do something special if it
22822 recognizes a packet meant for @value{GDBN}.
22824 In the examples below, @samp{->} and @samp{<-} are used to indicate
22825 transmitted and received data respectfully.
22827 @cindex protocol, @value{GDBN} remote serial
22828 @cindex serial protocol, @value{GDBN} remote
22829 @cindex remote serial protocol
22830 All @value{GDBN} commands and responses (other than acknowledgments) are
22831 sent as a @var{packet}. A @var{packet} is introduced with the character
22832 @samp{$}, the actual @var{packet-data}, and the terminating character
22833 @samp{#} followed by a two-digit @var{checksum}:
22836 @code{$}@var{packet-data}@code{#}@var{checksum}
22840 @cindex checksum, for @value{GDBN} remote
22842 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22843 characters between the leading @samp{$} and the trailing @samp{#} (an
22844 eight bit unsigned checksum).
22846 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22847 specification also included an optional two-digit @var{sequence-id}:
22850 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22853 @cindex sequence-id, for @value{GDBN} remote
22855 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22856 has never output @var{sequence-id}s. Stubs that handle packets added
22857 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22859 @cindex acknowledgment, for @value{GDBN} remote
22860 When either the host or the target machine receives a packet, the first
22861 response expected is an acknowledgment: either @samp{+} (to indicate
22862 the package was received correctly) or @samp{-} (to request
22866 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22871 The host (@value{GDBN}) sends @var{command}s, and the target (the
22872 debugging stub incorporated in your program) sends a @var{response}. In
22873 the case of step and continue @var{command}s, the response is only sent
22874 when the operation has completed (the target has again stopped).
22876 @var{packet-data} consists of a sequence of characters with the
22877 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22880 @cindex remote protocol, field separator
22881 Fields within the packet should be separated using @samp{,} @samp{;} or
22882 @samp{:}. Except where otherwise noted all numbers are represented in
22883 @sc{hex} with leading zeros suppressed.
22885 Implementors should note that prior to @value{GDBN} 5.0, the character
22886 @samp{:} could not appear as the third character in a packet (as it
22887 would potentially conflict with the @var{sequence-id}).
22889 @cindex remote protocol, binary data
22890 @anchor{Binary Data}
22891 Binary data in most packets is encoded either as two hexadecimal
22892 digits per byte of binary data. This allowed the traditional remote
22893 protocol to work over connections which were only seven-bit clean.
22894 Some packets designed more recently assume an eight-bit clean
22895 connection, and use a more efficient encoding to send and receive
22898 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
22899 as an escape character. Any escaped byte is transmitted as the escape
22900 character followed by the original character XORed with @code{0x20}.
22901 For example, the byte @code{0x7d} would be transmitted as the two
22902 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
22903 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
22904 @samp{@}}) must always be escaped. Responses sent by the stub
22905 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
22906 is not interpreted as the start of a run-length encoded sequence
22909 Response @var{data} can be run-length encoded to save space. A @samp{*}
22910 means that the next character is an @sc{ascii} encoding giving a repeat count
22911 which stands for that many repetitions of the character preceding the
22912 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22913 where @code{n >=3} (which is where rle starts to win). The printable
22914 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22915 value greater than 126 should not be used.
22922 means the same as "0000".
22924 The error response returned for some packets includes a two character
22925 error number. That number is not well defined.
22927 @cindex empty response, for unsupported packets
22928 For any @var{command} not supported by the stub, an empty response
22929 (@samp{$#00}) should be returned. That way it is possible to extend the
22930 protocol. A newer @value{GDBN} can tell if a packet is supported based
22933 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22934 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22940 The following table provides a complete list of all currently defined
22941 @var{command}s and their corresponding response @var{data}.
22942 @xref{File-I/O remote protocol extension}, for details about the File
22943 I/O extension of the remote protocol.
22945 Each packet's description has a template showing the packet's overall
22946 syntax, followed by an explanation of the packet's meaning. We
22947 include spaces in some of the templates for clarity; these are not
22948 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22949 separate its components. For example, a template like @samp{foo
22950 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22951 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22952 @var{baz}. GDB does not transmit a space character between the
22953 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22956 Note that all packet forms beginning with an upper- or lower-case
22957 letter, other than those described here, are reserved for future use.
22959 Here are the packet descriptions.
22964 @cindex @samp{!} packet
22965 Enable extended mode. In extended mode, the remote server is made
22966 persistent. The @samp{R} packet is used to restart the program being
22972 The remote target both supports and has enabled extended mode.
22976 @cindex @samp{?} packet
22977 Indicate the reason the target halted. The reply is the same as for
22981 @xref{Stop Reply Packets}, for the reply specifications.
22983 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22984 @cindex @samp{A} packet
22985 Initialized @code{argv[]} array passed into program. @var{arglen}
22986 specifies the number of bytes in the hex encoded byte stream
22987 @var{arg}. See @code{gdbserver} for more details.
22992 The arguments were set.
22998 @cindex @samp{b} packet
22999 (Don't use this packet; its behavior is not well-defined.)
23000 Change the serial line speed to @var{baud}.
23002 JTC: @emph{When does the transport layer state change? When it's
23003 received, or after the ACK is transmitted. In either case, there are
23004 problems if the command or the acknowledgment packet is dropped.}
23006 Stan: @emph{If people really wanted to add something like this, and get
23007 it working for the first time, they ought to modify ser-unix.c to send
23008 some kind of out-of-band message to a specially-setup stub and have the
23009 switch happen "in between" packets, so that from remote protocol's point
23010 of view, nothing actually happened.}
23012 @item B @var{addr},@var{mode}
23013 @cindex @samp{B} packet
23014 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23015 breakpoint at @var{addr}.
23017 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23018 (@pxref{insert breakpoint or watchpoint packet}).
23020 @item c @r{[}@var{addr}@r{]}
23021 @cindex @samp{c} packet
23022 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23023 resume at current address.
23026 @xref{Stop Reply Packets}, for the reply specifications.
23028 @item C @var{sig}@r{[};@var{addr}@r{]}
23029 @cindex @samp{C} packet
23030 Continue with signal @var{sig} (hex signal number). If
23031 @samp{;@var{addr}} is omitted, resume at same address.
23034 @xref{Stop Reply Packets}, for the reply specifications.
23037 @cindex @samp{d} packet
23040 Don't use this packet; instead, define a general set packet
23041 (@pxref{General Query Packets}).
23044 @cindex @samp{D} packet
23045 Detach @value{GDBN} from the remote system. Sent to the remote target
23046 before @value{GDBN} disconnects via the @code{detach} command.
23056 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23057 @cindex @samp{F} packet
23058 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23059 This is part of the File-I/O protocol extension. @xref{File-I/O
23060 remote protocol extension}, for the specification.
23063 @anchor{read registers packet}
23064 @cindex @samp{g} packet
23065 Read general registers.
23069 @item @var{XX@dots{}}
23070 Each byte of register data is described by two hex digits. The bytes
23071 with the register are transmitted in target byte order. The size of
23072 each register and their position within the @samp{g} packet are
23073 determined by the @value{GDBN} internal macros
23074 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{REGISTER_NAME} macros. The
23075 specification of several standard @samp{g} packets is specified below.
23080 @item G @var{XX@dots{}}
23081 @cindex @samp{G} packet
23082 Write general registers. @xref{read registers packet}, for a
23083 description of the @var{XX@dots{}} data.
23093 @item H @var{c} @var{t}
23094 @cindex @samp{H} packet
23095 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23096 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23097 should be @samp{c} for step and continue operations, @samp{g} for other
23098 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23099 the threads, a thread number, or @samp{0} which means pick any thread.
23110 @c 'H': How restrictive (or permissive) is the thread model. If a
23111 @c thread is selected and stopped, are other threads allowed
23112 @c to continue to execute? As I mentioned above, I think the
23113 @c semantics of each command when a thread is selected must be
23114 @c described. For example:
23116 @c 'g': If the stub supports threads and a specific thread is
23117 @c selected, returns the register block from that thread;
23118 @c otherwise returns current registers.
23120 @c 'G' If the stub supports threads and a specific thread is
23121 @c selected, sets the registers of the register block of
23122 @c that thread; otherwise sets current registers.
23124 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23125 @anchor{cycle step packet}
23126 @cindex @samp{i} packet
23127 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23128 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23129 step starting at that address.
23132 @cindex @samp{I} packet
23133 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23137 @cindex @samp{k} packet
23140 FIXME: @emph{There is no description of how to operate when a specific
23141 thread context has been selected (i.e.@: does 'k' kill only that
23144 @item m @var{addr},@var{length}
23145 @cindex @samp{m} packet
23146 Read @var{length} bytes of memory starting at address @var{addr}.
23147 Note that @var{addr} may not be aligned to any particular boundary.
23149 The stub need not use any particular size or alignment when gathering
23150 data from memory for the response; even if @var{addr} is word-aligned
23151 and @var{length} is a multiple of the word size, the stub is free to
23152 use byte accesses, or not. For this reason, this packet may not be
23153 suitable for accessing memory-mapped I/O devices.
23154 @cindex alignment of remote memory accesses
23155 @cindex size of remote memory accesses
23156 @cindex memory, alignment and size of remote accesses
23160 @item @var{XX@dots{}}
23161 Memory contents; each byte is transmitted as a two-digit hexadecimal
23162 number. The reply may contain fewer bytes than requested if the
23163 server was able to read only part of the region of memory.
23168 @item M @var{addr},@var{length}:@var{XX@dots{}}
23169 @cindex @samp{M} packet
23170 Write @var{length} bytes of memory starting at address @var{addr}.
23171 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23172 hexadecimal number.
23179 for an error (this includes the case where only part of the data was
23184 @cindex @samp{p} packet
23185 Read the value of register @var{n}; @var{n} is in hex.
23186 @xref{read registers packet}, for a description of how the returned
23187 register value is encoded.
23191 @item @var{XX@dots{}}
23192 the register's value
23196 Indicating an unrecognized @var{query}.
23199 @item P @var{n@dots{}}=@var{r@dots{}}
23200 @anchor{write register packet}
23201 @cindex @samp{P} packet
23202 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23203 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23204 digits for each byte in the register (target byte order).
23214 @item q @var{name} @var{params}@dots{}
23215 @itemx Q @var{name} @var{params}@dots{}
23216 @cindex @samp{q} packet
23217 @cindex @samp{Q} packet
23218 General query (@samp{q}) and set (@samp{Q}). These packets are
23219 described fully in @ref{General Query Packets}.
23222 @cindex @samp{r} packet
23223 Reset the entire system.
23225 Don't use this packet; use the @samp{R} packet instead.
23228 @cindex @samp{R} packet
23229 Restart the program being debugged. @var{XX}, while needed, is ignored.
23230 This packet is only available in extended mode.
23232 The @samp{R} packet has no reply.
23234 @item s @r{[}@var{addr}@r{]}
23235 @cindex @samp{s} packet
23236 Single step. @var{addr} is the address at which to resume. If
23237 @var{addr} is omitted, resume at same address.
23240 @xref{Stop Reply Packets}, for the reply specifications.
23242 @item S @var{sig}@r{[};@var{addr}@r{]}
23243 @anchor{step with signal packet}
23244 @cindex @samp{S} packet
23245 Step with signal. This is analogous to the @samp{C} packet, but
23246 requests a single-step, rather than a normal resumption of execution.
23249 @xref{Stop Reply Packets}, for the reply specifications.
23251 @item t @var{addr}:@var{PP},@var{MM}
23252 @cindex @samp{t} packet
23253 Search backwards starting at address @var{addr} for a match with pattern
23254 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23255 @var{addr} must be at least 3 digits.
23258 @cindex @samp{T} packet
23259 Find out if the thread XX is alive.
23264 thread is still alive
23270 Packets starting with @samp{v} are identified by a multi-letter name,
23271 up to the first @samp{;} or @samp{?} (or the end of the packet).
23273 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23274 @cindex @samp{vCont} packet
23275 Resume the inferior, specifying different actions for each thread.
23276 If an action is specified with no @var{tid}, then it is applied to any
23277 threads that don't have a specific action specified; if no default action is
23278 specified then other threads should remain stopped. Specifying multiple
23279 default actions is an error; specifying no actions is also an error.
23280 Thread IDs are specified in hexadecimal. Currently supported actions are:
23286 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23290 Step with signal @var{sig}. @var{sig} should be two hex digits.
23293 The optional @var{addr} argument normally associated with these packets is
23294 not supported in @samp{vCont}.
23297 @xref{Stop Reply Packets}, for the reply specifications.
23300 @cindex @samp{vCont?} packet
23301 Request a list of actions supported by the @samp{vCont} packet.
23305 @item vCont@r{[};@var{action}@dots{}@r{]}
23306 The @samp{vCont} packet is supported. Each @var{action} is a supported
23307 command in the @samp{vCont} packet.
23309 The @samp{vCont} packet is not supported.
23312 @item vFlashErase:@var{addr},@var{length}
23313 @cindex @samp{vFlashErase} packet
23314 Direct the stub to erase @var{length} bytes of flash starting at
23315 @var{addr}. The region may enclose any number of flash blocks, but
23316 its start and end must fall on block boundaries, as indicated by the
23317 flash block size appearing in the memory map (@pxref{Memory map
23318 format}). @value{GDBN} groups flash memory programming operations
23319 together, and sends a @samp{vFlashDone} request after each group; the
23320 stub is allowed to delay erase operation until the @samp{vFlashDone}
23321 packet is received.
23331 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23332 @cindex @samp{vFlashWrite} packet
23333 Direct the stub to write data to flash address @var{addr}. The data
23334 is passed in binary form using the same encoding as for the @samp{X}
23335 packet (@pxref{Binary Data}). The memory ranges specified by
23336 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23337 not overlap, and must appear in order of increasing addresses
23338 (although @samp{vFlashErase} packets for higher addresses may already
23339 have been received; the ordering is guaranteed only between
23340 @samp{vFlashWrite} packets). If a packet writes to an address that was
23341 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23342 target-specific method, the results are unpredictable.
23350 for vFlashWrite addressing non-flash memory
23356 @cindex @samp{vFlashDone} packet
23357 Indicate to the stub that flash programming operation is finished.
23358 The stub is permitted to delay or batch the effects of a group of
23359 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23360 @samp{vFlashDone} packet is received. The contents of the affected
23361 regions of flash memory are unpredictable until the @samp{vFlashDone}
23362 request is completed.
23364 @item X @var{addr},@var{length}:@var{XX@dots{}}
23366 @cindex @samp{X} packet
23367 Write data to memory, where the data is transmitted in binary.
23368 @var{addr} is address, @var{length} is number of bytes,
23369 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23379 @item z @var{type},@var{addr},@var{length}
23380 @itemx Z @var{type},@var{addr},@var{length}
23381 @anchor{insert breakpoint or watchpoint packet}
23382 @cindex @samp{z} packet
23383 @cindex @samp{Z} packets
23384 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23385 watchpoint starting at address @var{address} and covering the next
23386 @var{length} bytes.
23388 Each breakpoint and watchpoint packet @var{type} is documented
23391 @emph{Implementation notes: A remote target shall return an empty string
23392 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23393 remote target shall support either both or neither of a given
23394 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23395 avoid potential problems with duplicate packets, the operations should
23396 be implemented in an idempotent way.}
23398 @item z0,@var{addr},@var{length}
23399 @itemx Z0,@var{addr},@var{length}
23400 @cindex @samp{z0} packet
23401 @cindex @samp{Z0} packet
23402 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23403 @var{addr} of size @var{length}.
23405 A memory breakpoint is implemented by replacing the instruction at
23406 @var{addr} with a software breakpoint or trap instruction. The
23407 @var{length} is used by targets that indicates the size of the
23408 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23409 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23411 @emph{Implementation note: It is possible for a target to copy or move
23412 code that contains memory breakpoints (e.g., when implementing
23413 overlays). The behavior of this packet, in the presence of such a
23414 target, is not defined.}
23426 @item z1,@var{addr},@var{length}
23427 @itemx Z1,@var{addr},@var{length}
23428 @cindex @samp{z1} packet
23429 @cindex @samp{Z1} packet
23430 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23431 address @var{addr} of size @var{length}.
23433 A hardware breakpoint is implemented using a mechanism that is not
23434 dependant on being able to modify the target's memory.
23436 @emph{Implementation note: A hardware breakpoint is not affected by code
23449 @item z2,@var{addr},@var{length}
23450 @itemx Z2,@var{addr},@var{length}
23451 @cindex @samp{z2} packet
23452 @cindex @samp{Z2} packet
23453 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23465 @item z3,@var{addr},@var{length}
23466 @itemx Z3,@var{addr},@var{length}
23467 @cindex @samp{z3} packet
23468 @cindex @samp{Z3} packet
23469 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23481 @item z4,@var{addr},@var{length}
23482 @itemx Z4,@var{addr},@var{length}
23483 @cindex @samp{z4} packet
23484 @cindex @samp{Z4} packet
23485 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23499 @node Stop Reply Packets
23500 @section Stop Reply Packets
23501 @cindex stop reply packets
23503 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23504 receive any of the below as a reply. In the case of the @samp{C},
23505 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23506 when the target halts. In the below the exact meaning of @dfn{signal
23507 number} is defined by the header @file{include/gdb/signals.h} in the
23508 @value{GDBN} source code.
23510 As in the description of request packets, we include spaces in the
23511 reply templates for clarity; these are not part of the reply packet's
23512 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23518 The program received signal number @var{AA} (a two-digit hexadecimal
23519 number). This is equivalent to a @samp{T} response with no
23520 @var{n}:@var{r} pairs.
23522 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23523 @cindex @samp{T} packet reply
23524 The program received signal number @var{AA} (a two-digit hexadecimal
23525 number). This is equivalent to an @samp{S} response, except that the
23526 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23527 and other information directly in the stop reply packet, reducing
23528 round-trip latency. Single-step and breakpoint traps are reported
23529 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23532 If @var{n} is a hexadecimal number, it is a register number, and the
23533 corresponding @var{r} gives that register's value. @var{r} is a
23534 series of bytes in target byte order, with each byte given by a
23535 two-digit hex number.
23537 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23540 If @var{n} is @samp{watch}, @samp{rwatch}, or @samp{awatch}, then the
23541 packet indicates a watchpoint hit, and @var{r} is the data address, in
23544 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23545 and go on to the next; this allows us to extend the protocol in the
23550 The process exited, and @var{AA} is the exit status. This is only
23551 applicable to certain targets.
23554 The process terminated with signal @var{AA}.
23556 @item O @var{XX}@dots{}
23557 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23558 written as the program's console output. This can happen at any time
23559 while the program is running and the debugger should continue to wait
23560 for @samp{W}, @samp{T}, etc.
23562 @item F @var{call-id},@var{parameter}@dots{}
23563 @var{call-id} is the identifier which says which host system call should
23564 be called. This is just the name of the function. Translation into the
23565 correct system call is only applicable as it's defined in @value{GDBN}.
23566 @xref{File-I/O remote protocol extension}, for a list of implemented
23569 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23570 this very system call.
23572 The target replies with this packet when it expects @value{GDBN} to
23573 call a host system call on behalf of the target. @value{GDBN} replies
23574 with an appropriate @samp{F} packet and keeps up waiting for the next
23575 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23576 or @samp{s} action is expected to be continued. @xref{File-I/O remote
23577 protocol extension}, for more details.
23581 @node General Query Packets
23582 @section General Query Packets
23583 @cindex remote query requests
23585 Packets starting with @samp{q} are @dfn{general query packets};
23586 packets starting with @samp{Q} are @dfn{general set packets}. General
23587 query and set packets are a semi-unified form for retrieving and
23588 sending information to and from the stub.
23590 The initial letter of a query or set packet is followed by a name
23591 indicating what sort of thing the packet applies to. For example,
23592 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23593 definitions with the stub. These packet names follow some
23598 The name must not contain commas, colons or semicolons.
23600 Most @value{GDBN} query and set packets have a leading upper case
23603 The names of custom vendor packets should use a company prefix, in
23604 lower case, followed by a period. For example, packets designed at
23605 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23606 foos) or @samp{Qacme.bar} (for setting bars).
23609 The name of a query or set packet should be separated from any
23610 parameters by a @samp{:}; the parameters themselves should be
23611 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23612 full packet name, and check for a separator or the end of the packet,
23613 in case two packet names share a common prefix. New packets should not begin
23614 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23615 packets predate these conventions, and have arguments without any terminator
23616 for the packet name; we suspect they are in widespread use in places that
23617 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23618 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23621 Like the descriptions of the other packets, each description here
23622 has a template showing the packet's overall syntax, followed by an
23623 explanation of the packet's meaning. We include spaces in some of the
23624 templates for clarity; these are not part of the packet's syntax. No
23625 @value{GDBN} packet uses spaces to separate its components.
23627 Here are the currently defined query and set packets:
23632 @cindex current thread, remote request
23633 @cindex @samp{qC} packet
23634 Return the current thread id.
23639 Where @var{pid} is an unsigned hexadecimal process id.
23640 @item @r{(anything else)}
23641 Any other reply implies the old pid.
23644 @item qCRC:@var{addr},@var{length}
23645 @cindex CRC of memory block, remote request
23646 @cindex @samp{qCRC} packet
23647 Compute the CRC checksum of a block of memory.
23651 An error (such as memory fault)
23652 @item C @var{crc32}
23653 The specified memory region's checksum is @var{crc32}.
23657 @itemx qsThreadInfo
23658 @cindex list active threads, remote request
23659 @cindex @samp{qfThreadInfo} packet
23660 @cindex @samp{qsThreadInfo} packet
23661 Obtain a list of all active thread ids from the target (OS). Since there
23662 may be too many active threads to fit into one reply packet, this query
23663 works iteratively: it may require more than one query/reply sequence to
23664 obtain the entire list of threads. The first query of the sequence will
23665 be the @samp{qfThreadInfo} query; subsequent queries in the
23666 sequence will be the @samp{qsThreadInfo} query.
23668 NOTE: This packet replaces the @samp{qL} query (see below).
23674 @item m @var{id},@var{id}@dots{}
23675 a comma-separated list of thread ids
23677 (lower case letter @samp{L}) denotes end of list.
23680 In response to each query, the target will reply with a list of one or
23681 more thread ids, in big-endian unsigned hex, separated by commas.
23682 @value{GDBN} will respond to each reply with a request for more thread
23683 ids (using the @samp{qs} form of the query), until the target responds
23684 with @samp{l} (lower-case el, for @dfn{last}).
23686 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23687 @cindex get thread-local storage address, remote request
23688 @cindex @samp{qGetTLSAddr} packet
23689 Fetch the address associated with thread local storage specified
23690 by @var{thread-id}, @var{offset}, and @var{lm}.
23692 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23693 thread for which to fetch the TLS address.
23695 @var{offset} is the (big endian, hex encoded) offset associated with the
23696 thread local variable. (This offset is obtained from the debug
23697 information associated with the variable.)
23699 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
23700 the load module associated with the thread local storage. For example,
23701 a @sc{gnu}/Linux system will pass the link map address of the shared
23702 object associated with the thread local storage under consideration.
23703 Other operating environments may choose to represent the load module
23704 differently, so the precise meaning of this parameter will vary.
23708 @item @var{XX}@dots{}
23709 Hex encoded (big endian) bytes representing the address of the thread
23710 local storage requested.
23713 An error occurred. @var{nn} are hex digits.
23716 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
23719 @item qL @var{startflag} @var{threadcount} @var{nextthread}
23720 Obtain thread information from RTOS. Where: @var{startflag} (one hex
23721 digit) is one to indicate the first query and zero to indicate a
23722 subsequent query; @var{threadcount} (two hex digits) is the maximum
23723 number of threads the response packet can contain; and @var{nextthread}
23724 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
23725 returned in the response as @var{argthread}.
23727 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
23731 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
23732 Where: @var{count} (two hex digits) is the number of threads being
23733 returned; @var{done} (one hex digit) is zero to indicate more threads
23734 and one indicates no further threads; @var{argthreadid} (eight hex
23735 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
23736 is a sequence of thread IDs from the target. @var{threadid} (eight hex
23737 digits). See @code{remote.c:parse_threadlist_response()}.
23741 @cindex section offsets, remote request
23742 @cindex @samp{qOffsets} packet
23743 Get section offsets that the target used when re-locating the downloaded
23744 image. @emph{Note: while a @code{Bss} offset is included in the
23745 response, @value{GDBN} ignores this and instead applies the @code{Data}
23746 offset to the @code{Bss} section.}
23750 @item Text=@var{xxx};Data=@var{yyy};Bss=@var{zzz}
23753 @item qP @var{mode} @var{threadid}
23754 @cindex thread information, remote request
23755 @cindex @samp{qP} packet
23756 Returns information on @var{threadid}. Where: @var{mode} is a hex
23757 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
23759 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
23762 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
23764 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
23765 @cindex pass signals to inferior, remote request
23766 @cindex @samp{QPassSignals} packet
23767 @anchor{QPassSignals}
23768 Each listed @var{signal} should be passed directly to the inferior process.
23769 Signals are numbered identically to continue packets and stop replies
23770 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
23771 strictly greater than the previous item. These signals do not need to stop
23772 the inferior, or be reported to @value{GDBN}. All other signals should be
23773 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
23774 combine; any earlier @samp{QPassSignals} list is completely replaced by the
23775 new list. This packet improves performance when using @samp{handle
23776 @var{signal} nostop noprint pass}.
23781 The request succeeded.
23784 An error occurred. @var{nn} are hex digits.
23787 An empty reply indicates that @samp{QPassSignals} is not supported by
23791 Use of this packet is controlled by the @code{set remote pass-signals}
23792 command (@pxref{Remote configuration, set remote pass-signals}).
23793 This packet is not probed by default; the remote stub must request it,
23794 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23796 @item qRcmd,@var{command}
23797 @cindex execute remote command, remote request
23798 @cindex @samp{qRcmd} packet
23799 @var{command} (hex encoded) is passed to the local interpreter for
23800 execution. Invalid commands should be reported using the output
23801 string. Before the final result packet, the target may also respond
23802 with a number of intermediate @samp{O@var{output}} console output
23803 packets. @emph{Implementors should note that providing access to a
23804 stubs's interpreter may have security implications}.
23809 A command response with no output.
23811 A command response with the hex encoded output string @var{OUTPUT}.
23813 Indicate a badly formed request.
23815 An empty reply indicates that @samp{qRcmd} is not recognized.
23818 (Note that the @code{qRcmd} packet's name is separated from the
23819 command by a @samp{,}, not a @samp{:}, contrary to the naming
23820 conventions above. Please don't use this packet as a model for new
23823 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
23824 @cindex supported packets, remote query
23825 @cindex features of the remote protocol
23826 @cindex @samp{qSupported} packet
23827 @anchor{qSupported}
23828 Tell the remote stub about features supported by @value{GDBN}, and
23829 query the stub for features it supports. This packet allows
23830 @value{GDBN} and the remote stub to take advantage of each others'
23831 features. @samp{qSupported} also consolidates multiple feature probes
23832 at startup, to improve @value{GDBN} performance---a single larger
23833 packet performs better than multiple smaller probe packets on
23834 high-latency links. Some features may enable behavior which must not
23835 be on by default, e.g.@: because it would confuse older clients or
23836 stubs. Other features may describe packets which could be
23837 automatically probed for, but are not. These features must be
23838 reported before @value{GDBN} will use them. This ``default
23839 unsupported'' behavior is not appropriate for all packets, but it
23840 helps to keep the initial connection time under control with new
23841 versions of @value{GDBN} which support increasing numbers of packets.
23845 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
23846 The stub supports or does not support each returned @var{stubfeature},
23847 depending on the form of each @var{stubfeature} (see below for the
23850 An empty reply indicates that @samp{qSupported} is not recognized,
23851 or that no features needed to be reported to @value{GDBN}.
23854 The allowed forms for each feature (either a @var{gdbfeature} in the
23855 @samp{qSupported} packet, or a @var{stubfeature} in the response)
23859 @item @var{name}=@var{value}
23860 The remote protocol feature @var{name} is supported, and associated
23861 with the specified @var{value}. The format of @var{value} depends
23862 on the feature, but it must not include a semicolon.
23864 The remote protocol feature @var{name} is supported, and does not
23865 need an associated value.
23867 The remote protocol feature @var{name} is not supported.
23869 The remote protocol feature @var{name} may be supported, and
23870 @value{GDBN} should auto-detect support in some other way when it is
23871 needed. This form will not be used for @var{gdbfeature} notifications,
23872 but may be used for @var{stubfeature} responses.
23875 Whenever the stub receives a @samp{qSupported} request, the
23876 supplied set of @value{GDBN} features should override any previous
23877 request. This allows @value{GDBN} to put the stub in a known
23878 state, even if the stub had previously been communicating with
23879 a different version of @value{GDBN}.
23881 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
23882 are defined yet. Stubs should ignore any unknown values for
23883 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
23884 packet supports receiving packets of unlimited length (earlier
23885 versions of @value{GDBN} may reject overly long responses). Values
23886 for @var{gdbfeature} may be defined in the future to let the stub take
23887 advantage of new features in @value{GDBN}, e.g.@: incompatible
23888 improvements in the remote protocol---support for unlimited length
23889 responses would be a @var{gdbfeature} example, if it were not implied by
23890 the @samp{qSupported} query. The stub's reply should be independent
23891 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
23892 describes all the features it supports, and then the stub replies with
23893 all the features it supports.
23895 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
23896 responses, as long as each response uses one of the standard forms.
23898 Some features are flags. A stub which supports a flag feature
23899 should respond with a @samp{+} form response. Other features
23900 require values, and the stub should respond with an @samp{=}
23903 Each feature has a default value, which @value{GDBN} will use if
23904 @samp{qSupported} is not available or if the feature is not mentioned
23905 in the @samp{qSupported} response. The default values are fixed; a
23906 stub is free to omit any feature responses that match the defaults.
23908 Not all features can be probed, but for those which can, the probing
23909 mechanism is useful: in some cases, a stub's internal
23910 architecture may not allow the protocol layer to know some information
23911 about the underlying target in advance. This is especially common in
23912 stubs which may be configured for multiple targets.
23914 These are the currently defined stub features and their properties:
23916 @multitable @columnfractions 0.25 0.2 0.2 0.2
23917 @c NOTE: The first row should be @headitem, but we do not yet require
23918 @c a new enough version of Texinfo (4.7) to use @headitem.
23920 @tab Value Required
23924 @item @samp{PacketSize}
23929 @item @samp{qXfer:auxv:read}
23934 @item @samp{qXfer:features:read}
23939 @item @samp{qXfer:memory-map:read}
23944 @item @samp{QPassSignals}
23951 These are the currently defined stub features, in more detail:
23954 @cindex packet size, remote protocol
23955 @item PacketSize=@var{bytes}
23956 The remote stub can accept packets up to at least @var{bytes} in
23957 length. @value{GDBN} will send packets up to this size for bulk
23958 transfers, and will never send larger packets. This is a limit on the
23959 data characters in the packet, including the frame and checksum.
23960 There is no trailing NUL byte in a remote protocol packet; if the stub
23961 stores packets in a NUL-terminated format, it should allow an extra
23962 byte in its buffer for the NUL. If this stub feature is not supported,
23963 @value{GDBN} guesses based on the size of the @samp{g} packet response.
23965 @item qXfer:auxv:read
23966 The remote stub understands the @samp{qXfer:auxv:read} packet
23967 (@pxref{qXfer auxiliary vector read}).
23969 @item qXfer:features:read
23970 The remote stub understands the @samp{qXfer:features:read} packet
23971 (@pxref{qXfer target description read}).
23973 @item qXfer:memory-map:read
23974 The remote stub understands the @samp{qXfer:memory-map:read} packet
23975 (@pxref{qXfer memory map read}).
23978 The remote stub understands the @samp{QPassSignals} packet
23979 (@pxref{QPassSignals}).
23984 @cindex symbol lookup, remote request
23985 @cindex @samp{qSymbol} packet
23986 Notify the target that @value{GDBN} is prepared to serve symbol lookup
23987 requests. Accept requests from the target for the values of symbols.
23992 The target does not need to look up any (more) symbols.
23993 @item qSymbol:@var{sym_name}
23994 The target requests the value of symbol @var{sym_name} (hex encoded).
23995 @value{GDBN} may provide the value by using the
23996 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24000 @item qSymbol:@var{sym_value}:@var{sym_name}
24001 Set the value of @var{sym_name} to @var{sym_value}.
24003 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24004 target has previously requested.
24006 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24007 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24013 The target does not need to look up any (more) symbols.
24014 @item qSymbol:@var{sym_name}
24015 The target requests the value of a new symbol @var{sym_name} (hex
24016 encoded). @value{GDBN} will continue to supply the values of symbols
24017 (if available), until the target ceases to request them.
24022 @xref{Tracepoint Packets}.
24024 @item qThreadExtraInfo,@var{id}
24025 @cindex thread attributes info, remote request
24026 @cindex @samp{qThreadExtraInfo} packet
24027 Obtain a printable string description of a thread's attributes from
24028 the target OS. @var{id} is a thread-id in big-endian hex. This
24029 string may contain anything that the target OS thinks is interesting
24030 for @value{GDBN} to tell the user about the thread. The string is
24031 displayed in @value{GDBN}'s @code{info threads} display. Some
24032 examples of possible thread extra info strings are @samp{Runnable}, or
24033 @samp{Blocked on Mutex}.
24037 @item @var{XX}@dots{}
24038 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
24039 comprising the printable string containing the extra information about
24040 the thread's attributes.
24043 (Note that the @code{qThreadExtraInfo} packet's name is separated from
24044 the command by a @samp{,}, not a @samp{:}, contrary to the naming
24045 conventions above. Please don't use this packet as a model for new
24053 @xref{Tracepoint Packets}.
24055 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
24056 @cindex read special object, remote request
24057 @cindex @samp{qXfer} packet
24058 @anchor{qXfer read}
24059 Read uninterpreted bytes from the target's special data area
24060 identified by the keyword @var{object}. Request @var{length} bytes
24061 starting at @var{offset} bytes into the data. The content and
24062 encoding of @var{annex} is specific to the object; it can supply
24063 additional details about what data to access.
24065 Here are the specific requests of this form defined so far. All
24066 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
24067 formats, listed below.
24070 @item qXfer:auxv:read::@var{offset},@var{length}
24071 @anchor{qXfer auxiliary vector read}
24072 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
24073 auxiliary vector}. Note @var{annex} must be empty.
24075 This packet is not probed by default; the remote stub must request it,
24076 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24078 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
24079 @anchor{qXfer target description read}
24080 Access the @dfn{target description}. @xref{Target Descriptions}. The
24081 annex specifies which XML document to access. The main description is
24082 always loaded from the @samp{target.xml} annex.
24084 This packet is not probed by default; the remote stub must request it,
24085 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24087 @item qXfer:memory-map:read::@var{offset},@var{length}
24088 @anchor{qXfer memory map read}
24089 Access the target's @dfn{memory-map}. @xref{Memory map format}. The
24090 annex part of the generic @samp{qXfer} packet must be empty
24091 (@pxref{qXfer read}).
24093 This packet is not probed by default; the remote stub must request it,
24094 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24100 Data @var{data} (@pxref{Binary Data}) has been read from the
24101 target. There may be more data at a higher address (although
24102 it is permitted to return @samp{m} even for the last valid
24103 block of data, as long as at least one byte of data was read).
24104 @var{data} may have fewer bytes than the @var{length} in the
24108 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24109 There is no more data to be read. @var{data} may have fewer bytes
24110 than the @var{length} in the request.
24113 The @var{offset} in the request is at the end of the data.
24114 There is no more data to be read.
24117 The request was malformed, or @var{annex} was invalid.
24120 The offset was invalid, or there was an error encountered reading the data.
24121 @var{nn} is a hex-encoded @code{errno} value.
24124 An empty reply indicates the @var{object} string was not recognized by
24125 the stub, or that the object does not support reading.
24128 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24129 @cindex write data into object, remote request
24130 Write uninterpreted bytes into the target's special data area
24131 identified by the keyword @var{object}, starting at @var{offset} bytes
24132 into the data. @samp{@var{data}@dots{}} is the binary-encoded data
24133 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24134 is specific to the object; it can supply additional details about what data
24137 No requests of this form are presently in use. This specification
24138 serves as a placeholder to document the common format that new
24139 specific request specifications ought to use.
24144 @var{nn} (hex encoded) is the number of bytes written.
24145 This may be fewer bytes than supplied in the request.
24148 The request was malformed, or @var{annex} was invalid.
24151 The offset was invalid, or there was an error encountered writing the data.
24152 @var{nn} is a hex-encoded @code{errno} value.
24155 An empty reply indicates the @var{object} string was not
24156 recognized by the stub, or that the object does not support writing.
24159 @item qXfer:@var{object}:@var{operation}:@dots{}
24160 Requests of this form may be added in the future. When a stub does
24161 not recognize the @var{object} keyword, or its support for
24162 @var{object} does not recognize the @var{operation} keyword, the stub
24163 must respond with an empty packet.
24167 @node Register Packet Format
24168 @section Register Packet Format
24170 The following @code{g}/@code{G} packets have previously been defined.
24171 In the below, some thirty-two bit registers are transferred as
24172 sixty-four bits. Those registers should be zero/sign extended (which?)
24173 to fill the space allocated. Register bytes are transferred in target
24174 byte order. The two nibbles within a register byte are transferred
24175 most-significant - least-significant.
24181 All registers are transferred as thirty-two bit quantities in the order:
24182 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24183 registers; fsr; fir; fp.
24187 All registers are transferred as sixty-four bit quantities (including
24188 thirty-two bit registers such as @code{sr}). The ordering is the same
24193 @node Tracepoint Packets
24194 @section Tracepoint Packets
24195 @cindex tracepoint packets
24196 @cindex packets, tracepoint
24198 Here we describe the packets @value{GDBN} uses to implement
24199 tracepoints (@pxref{Tracepoints}).
24203 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24204 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24205 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24206 the tracepoint is disabled. @var{step} is the tracepoint's step
24207 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24208 present, further @samp{QTDP} packets will follow to specify this
24209 tracepoint's actions.
24214 The packet was understood and carried out.
24216 The packet was not recognized.
24219 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24220 Define actions to be taken when a tracepoint is hit. @var{n} and
24221 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24222 this tracepoint. This packet may only be sent immediately after
24223 another @samp{QTDP} packet that ended with a @samp{-}. If the
24224 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24225 specifying more actions for this tracepoint.
24227 In the series of action packets for a given tracepoint, at most one
24228 can have an @samp{S} before its first @var{action}. If such a packet
24229 is sent, it and the following packets define ``while-stepping''
24230 actions. Any prior packets define ordinary actions --- that is, those
24231 taken when the tracepoint is first hit. If no action packet has an
24232 @samp{S}, then all the packets in the series specify ordinary
24233 tracepoint actions.
24235 The @samp{@var{action}@dots{}} portion of the packet is a series of
24236 actions, concatenated without separators. Each action has one of the
24242 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24243 a hexadecimal number whose @var{i}'th bit is set if register number
24244 @var{i} should be collected. (The least significant bit is numbered
24245 zero.) Note that @var{mask} may be any number of digits long; it may
24246 not fit in a 32-bit word.
24248 @item M @var{basereg},@var{offset},@var{len}
24249 Collect @var{len} bytes of memory starting at the address in register
24250 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24251 @samp{-1}, then the range has a fixed address: @var{offset} is the
24252 address of the lowest byte to collect. The @var{basereg},
24253 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24254 values (the @samp{-1} value for @var{basereg} is a special case).
24256 @item X @var{len},@var{expr}
24257 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24258 it directs. @var{expr} is an agent expression, as described in
24259 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24260 two-digit hex number in the packet; @var{len} is the number of bytes
24261 in the expression (and thus one-half the number of hex digits in the
24266 Any number of actions may be packed together in a single @samp{QTDP}
24267 packet, as long as the packet does not exceed the maximum packet
24268 length (400 bytes, for many stubs). There may be only one @samp{R}
24269 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24270 actions. Any registers referred to by @samp{M} and @samp{X} actions
24271 must be collected by a preceding @samp{R} action. (The
24272 ``while-stepping'' actions are treated as if they were attached to a
24273 separate tracepoint, as far as these restrictions are concerned.)
24278 The packet was understood and carried out.
24280 The packet was not recognized.
24283 @item QTFrame:@var{n}
24284 Select the @var{n}'th tracepoint frame from the buffer, and use the
24285 register and memory contents recorded there to answer subsequent
24286 request packets from @value{GDBN}.
24288 A successful reply from the stub indicates that the stub has found the
24289 requested frame. The response is a series of parts, concatenated
24290 without separators, describing the frame we selected. Each part has
24291 one of the following forms:
24295 The selected frame is number @var{n} in the trace frame buffer;
24296 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24297 was no frame matching the criteria in the request packet.
24300 The selected trace frame records a hit of tracepoint number @var{t};
24301 @var{t} is a hexadecimal number.
24305 @item QTFrame:pc:@var{addr}
24306 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24307 currently selected frame whose PC is @var{addr};
24308 @var{addr} is a hexadecimal number.
24310 @item QTFrame:tdp:@var{t}
24311 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24312 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24313 is a hexadecimal number.
24315 @item QTFrame:range:@var{start}:@var{end}
24316 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24317 currently selected frame whose PC is between @var{start} (inclusive)
24318 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24321 @item QTFrame:outside:@var{start}:@var{end}
24322 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24323 frame @emph{outside} the given range of addresses.
24326 Begin the tracepoint experiment. Begin collecting data from tracepoint
24327 hits in the trace frame buffer.
24330 End the tracepoint experiment. Stop collecting trace frames.
24333 Clear the table of tracepoints, and empty the trace frame buffer.
24335 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24336 Establish the given ranges of memory as ``transparent''. The stub
24337 will answer requests for these ranges from memory's current contents,
24338 if they were not collected as part of the tracepoint hit.
24340 @value{GDBN} uses this to mark read-only regions of memory, like those
24341 containing program code. Since these areas never change, they should
24342 still have the same contents they did when the tracepoint was hit, so
24343 there's no reason for the stub to refuse to provide their contents.
24346 Ask the stub if there is a trace experiment running right now.
24351 There is no trace experiment running.
24353 There is a trace experiment running.
24360 @section Interrupts
24361 @cindex interrupts (remote protocol)
24363 When a program on the remote target is running, @value{GDBN} may
24364 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24365 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24366 setting (@pxref{set remotebreak}).
24368 The precise meaning of @code{BREAK} is defined by the transport
24369 mechanism and may, in fact, be undefined. @value{GDBN} does
24370 not currently define a @code{BREAK} mechanism for any of the network
24373 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24374 transport mechanisms. It is represented by sending the single byte
24375 @code{0x03} without any of the usual packet overhead described in
24376 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24377 transmitted as part of a packet, it is considered to be packet data
24378 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24379 (@pxref{X packet}), used for binary downloads, may include an unescaped
24380 @code{0x03} as part of its packet.
24382 Stubs are not required to recognize these interrupt mechanisms and the
24383 precise meaning associated with receipt of the interrupt is
24384 implementation defined. If the stub is successful at interrupting the
24385 running program, it is expected that it will send one of the Stop
24386 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24387 of successfully stopping the program. Interrupts received while the
24388 program is stopped will be discarded.
24393 Example sequence of a target being re-started. Notice how the restart
24394 does not get any direct output:
24399 @emph{target restarts}
24402 <- @code{T001:1234123412341234}
24406 Example sequence of a target being stepped by a single instruction:
24409 -> @code{G1445@dots{}}
24414 <- @code{T001:1234123412341234}
24418 <- @code{1455@dots{}}
24422 @node File-I/O remote protocol extension
24423 @section File-I/O remote protocol extension
24424 @cindex File-I/O remote protocol extension
24427 * File-I/O Overview::
24428 * Protocol basics::
24429 * The F request packet::
24430 * The F reply packet::
24431 * The Ctrl-C message::
24433 * List of supported calls::
24434 * Protocol specific representation of datatypes::
24436 * File-I/O Examples::
24439 @node File-I/O Overview
24440 @subsection File-I/O Overview
24441 @cindex file-i/o overview
24443 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24444 target to use the host's file system and console I/O to perform various
24445 system calls. System calls on the target system are translated into a
24446 remote protocol packet to the host system, which then performs the needed
24447 actions and returns a response packet to the target system.
24448 This simulates file system operations even on targets that lack file systems.
24450 The protocol is defined to be independent of both the host and target systems.
24451 It uses its own internal representation of datatypes and values. Both
24452 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24453 translating the system-dependent value representations into the internal
24454 protocol representations when data is transmitted.
24456 The communication is synchronous. A system call is possible only when
24457 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24458 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24459 the target is stopped to allow deterministic access to the target's
24460 memory. Therefore File-I/O is not interruptible by target signals. On
24461 the other hand, it is possible to interrupt File-I/O by a user interrupt
24462 (@samp{Ctrl-C}) within @value{GDBN}.
24464 The target's request to perform a host system call does not finish
24465 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24466 after finishing the system call, the target returns to continuing the
24467 previous activity (continue, step). No additional continue or step
24468 request from @value{GDBN} is required.
24471 (@value{GDBP}) continue
24472 <- target requests 'system call X'
24473 target is stopped, @value{GDBN} executes system call
24474 -> GDB returns result
24475 ... target continues, GDB returns to wait for the target
24476 <- target hits breakpoint and sends a Txx packet
24479 The protocol only supports I/O on the console and to regular files on
24480 the host file system. Character or block special devices, pipes,
24481 named pipes, sockets or any other communication method on the host
24482 system are not supported by this protocol.
24484 @node Protocol basics
24485 @subsection Protocol basics
24486 @cindex protocol basics, file-i/o
24488 The File-I/O protocol uses the @code{F} packet as the request as well
24489 as reply packet. Since a File-I/O system call can only occur when
24490 @value{GDBN} is waiting for a response from the continuing or stepping target,
24491 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24492 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24493 This @code{F} packet contains all information needed to allow @value{GDBN}
24494 to call the appropriate host system call:
24498 A unique identifier for the requested system call.
24501 All parameters to the system call. Pointers are given as addresses
24502 in the target memory address space. Pointers to strings are given as
24503 pointer/length pair. Numerical values are given as they are.
24504 Numerical control flags are given in a protocol specific representation.
24508 At this point, @value{GDBN} has to perform the following actions.
24512 If the parameters include pointer values to data needed as input to a
24513 system call, @value{GDBN} requests this data from the target with a
24514 standard @code{m} packet request. This additional communication has to be
24515 expected by the target implementation and is handled as any other @code{m}
24519 @value{GDBN} translates all value from protocol representation to host
24520 representation as needed. Datatypes are coerced into the host types.
24523 @value{GDBN} calls the system call.
24526 It then coerces datatypes back to protocol representation.
24529 If the system call is expected to return data in buffer space specified
24530 by pointer parameters to the call, the data is transmitted to the
24531 target using a @code{M} or @code{X} packet. This packet has to be expected
24532 by the target implementation and is handled as any other @code{M} or @code{X}
24537 Eventually @value{GDBN} replies with another @code{F} packet which contains all
24538 necessary information for the target to continue. This at least contains
24545 @code{errno}, if has been changed by the system call.
24552 After having done the needed type and value coercion, the target continues
24553 the latest continue or step action.
24555 @node The F request packet
24556 @subsection The @code{F} request packet
24557 @cindex file-i/o request packet
24558 @cindex @code{F} request packet
24560 The @code{F} request packet has the following format:
24563 @item F@var{call-id},@var{parameter@dots{}}
24565 @var{call-id} is the identifier to indicate the host system call to be called.
24566 This is just the name of the function.
24568 @var{parameter@dots{}} are the parameters to the system call.
24569 Parameters are hexadecimal integer values, either the actual values in case
24570 of scalar datatypes, pointers to target buffer space in case of compound
24571 datatypes and unspecified memory areas, or pointer/length pairs in case
24572 of string parameters. These are appended to the @var{call-id} as a
24573 comma-delimited list. All values are transmitted in ASCII
24574 string representation, pointer/length pairs separated by a slash.
24580 @node The F reply packet
24581 @subsection The @code{F} reply packet
24582 @cindex file-i/o reply packet
24583 @cindex @code{F} reply packet
24585 The @code{F} reply packet has the following format:
24589 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call specific attachment}
24591 @var{retcode} is the return code of the system call as hexadecimal value.
24593 @var{errno} is the @code{errno} set by the call, in protocol specific representation.
24594 This parameter can be omitted if the call was successful.
24596 @var{Ctrl-C flag} is only sent if the user requested a break. In this
24597 case, @var{errno} must be sent as well, even if the call was successful.
24598 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
24605 or, if the call was interrupted before the host call has been performed:
24612 assuming 4 is the protocol specific representation of @code{EINTR}.
24617 @node The Ctrl-C message
24618 @subsection The @samp{Ctrl-C} message
24619 @cindex ctrl-c message, in file-i/o protocol
24621 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
24622 reply packet (@pxref{The F reply packet}),
24623 the target should behave as if it had
24624 gotten a break message. The meaning for the target is ``system call
24625 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
24626 (as with a break message) and return to @value{GDBN} with a @code{T02}
24629 It's important for the target to know in which
24630 state the system call was interrupted. There are two possible cases:
24634 The system call hasn't been performed on the host yet.
24637 The system call on the host has been finished.
24641 These two states can be distinguished by the target by the value of the
24642 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
24643 call hasn't been performed. This is equivalent to the @code{EINTR} handling
24644 on POSIX systems. In any other case, the target may presume that the
24645 system call has been finished --- successfully or not --- and should behave
24646 as if the break message arrived right after the system call.
24648 @value{GDBN} must behave reliably. If the system call has not been called
24649 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
24650 @code{errno} in the packet. If the system call on the host has been finished
24651 before the user requests a break, the full action must be finished by
24652 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
24653 The @code{F} packet may only be sent when either nothing has happened
24654 or the full action has been completed.
24657 @subsection Console I/O
24658 @cindex console i/o as part of file-i/o
24660 By default and if not explicitly closed by the target system, the file
24661 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
24662 on the @value{GDBN} console is handled as any other file output operation
24663 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
24664 by @value{GDBN} so that after the target read request from file descriptor
24665 0 all following typing is buffered until either one of the following
24670 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
24672 system call is treated as finished.
24675 The user presses @key{RET}. This is treated as end of input with a trailing
24679 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
24680 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
24684 If the user has typed more characters than fit in the buffer given to
24685 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
24686 either another @code{read(0, @dots{})} is requested by the target, or debugging
24687 is stopped at the user's request.
24690 @node List of supported calls
24691 @subsection List of supported calls
24692 @cindex list of supported file-i/o calls
24709 @unnumberedsubsubsec open
24710 @cindex open, file-i/o system call
24715 int open(const char *pathname, int flags);
24716 int open(const char *pathname, int flags, mode_t mode);
24720 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
24723 @var{flags} is the bitwise @code{OR} of the following values:
24727 If the file does not exist it will be created. The host
24728 rules apply as far as file ownership and time stamps
24732 When used with @code{O_CREAT}, if the file already exists it is
24733 an error and open() fails.
24736 If the file already exists and the open mode allows
24737 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
24738 truncated to zero length.
24741 The file is opened in append mode.
24744 The file is opened for reading only.
24747 The file is opened for writing only.
24750 The file is opened for reading and writing.
24754 Other bits are silently ignored.
24758 @var{mode} is the bitwise @code{OR} of the following values:
24762 User has read permission.
24765 User has write permission.
24768 Group has read permission.
24771 Group has write permission.
24774 Others have read permission.
24777 Others have write permission.
24781 Other bits are silently ignored.
24784 @item Return value:
24785 @code{open} returns the new file descriptor or -1 if an error
24792 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
24795 @var{pathname} refers to a directory.
24798 The requested access is not allowed.
24801 @var{pathname} was too long.
24804 A directory component in @var{pathname} does not exist.
24807 @var{pathname} refers to a device, pipe, named pipe or socket.
24810 @var{pathname} refers to a file on a read-only filesystem and
24811 write access was requested.
24814 @var{pathname} is an invalid pointer value.
24817 No space on device to create the file.
24820 The process already has the maximum number of files open.
24823 The limit on the total number of files open on the system
24827 The call was interrupted by the user.
24833 @unnumberedsubsubsec close
24834 @cindex close, file-i/o system call
24843 @samp{Fclose,@var{fd}}
24845 @item Return value:
24846 @code{close} returns zero on success, or -1 if an error occurred.
24852 @var{fd} isn't a valid open file descriptor.
24855 The call was interrupted by the user.
24861 @unnumberedsubsubsec read
24862 @cindex read, file-i/o system call
24867 int read(int fd, void *buf, unsigned int count);
24871 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
24873 @item Return value:
24874 On success, the number of bytes read is returned.
24875 Zero indicates end of file. If count is zero, read
24876 returns zero as well. On error, -1 is returned.
24882 @var{fd} is not a valid file descriptor or is not open for
24886 @var{bufptr} is an invalid pointer value.
24889 The call was interrupted by the user.
24895 @unnumberedsubsubsec write
24896 @cindex write, file-i/o system call
24901 int write(int fd, const void *buf, unsigned int count);
24905 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
24907 @item Return value:
24908 On success, the number of bytes written are returned.
24909 Zero indicates nothing was written. On error, -1
24916 @var{fd} is not a valid file descriptor or is not open for
24920 @var{bufptr} is an invalid pointer value.
24923 An attempt was made to write a file that exceeds the
24924 host specific maximum file size allowed.
24927 No space on device to write the data.
24930 The call was interrupted by the user.
24936 @unnumberedsubsubsec lseek
24937 @cindex lseek, file-i/o system call
24942 long lseek (int fd, long offset, int flag);
24946 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
24948 @var{flag} is one of:
24952 The offset is set to @var{offset} bytes.
24955 The offset is set to its current location plus @var{offset}
24959 The offset is set to the size of the file plus @var{offset}
24963 @item Return value:
24964 On success, the resulting unsigned offset in bytes from
24965 the beginning of the file is returned. Otherwise, a
24966 value of -1 is returned.
24972 @var{fd} is not a valid open file descriptor.
24975 @var{fd} is associated with the @value{GDBN} console.
24978 @var{flag} is not a proper value.
24981 The call was interrupted by the user.
24987 @unnumberedsubsubsec rename
24988 @cindex rename, file-i/o system call
24993 int rename(const char *oldpath, const char *newpath);
24997 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
24999 @item Return value:
25000 On success, zero is returned. On error, -1 is returned.
25006 @var{newpath} is an existing directory, but @var{oldpath} is not a
25010 @var{newpath} is a non-empty directory.
25013 @var{oldpath} or @var{newpath} is a directory that is in use by some
25017 An attempt was made to make a directory a subdirectory
25021 A component used as a directory in @var{oldpath} or new
25022 path is not a directory. Or @var{oldpath} is a directory
25023 and @var{newpath} exists but is not a directory.
25026 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
25029 No access to the file or the path of the file.
25033 @var{oldpath} or @var{newpath} was too long.
25036 A directory component in @var{oldpath} or @var{newpath} does not exist.
25039 The file is on a read-only filesystem.
25042 The device containing the file has no room for the new
25046 The call was interrupted by the user.
25052 @unnumberedsubsubsec unlink
25053 @cindex unlink, file-i/o system call
25058 int unlink(const char *pathname);
25062 @samp{Funlink,@var{pathnameptr}/@var{len}}
25064 @item Return value:
25065 On success, zero is returned. On error, -1 is returned.
25071 No access to the file or the path of the file.
25074 The system does not allow unlinking of directories.
25077 The file @var{pathname} cannot be unlinked because it's
25078 being used by another process.
25081 @var{pathnameptr} is an invalid pointer value.
25084 @var{pathname} was too long.
25087 A directory component in @var{pathname} does not exist.
25090 A component of the path is not a directory.
25093 The file is on a read-only filesystem.
25096 The call was interrupted by the user.
25102 @unnumberedsubsubsec stat/fstat
25103 @cindex fstat, file-i/o system call
25104 @cindex stat, file-i/o system call
25109 int stat(const char *pathname, struct stat *buf);
25110 int fstat(int fd, struct stat *buf);
25114 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25115 @samp{Ffstat,@var{fd},@var{bufptr}}
25117 @item Return value:
25118 On success, zero is returned. On error, -1 is returned.
25124 @var{fd} is not a valid open file.
25127 A directory component in @var{pathname} does not exist or the
25128 path is an empty string.
25131 A component of the path is not a directory.
25134 @var{pathnameptr} is an invalid pointer value.
25137 No access to the file or the path of the file.
25140 @var{pathname} was too long.
25143 The call was interrupted by the user.
25149 @unnumberedsubsubsec gettimeofday
25150 @cindex gettimeofday, file-i/o system call
25155 int gettimeofday(struct timeval *tv, void *tz);
25159 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25161 @item Return value:
25162 On success, 0 is returned, -1 otherwise.
25168 @var{tz} is a non-NULL pointer.
25171 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25177 @unnumberedsubsubsec isatty
25178 @cindex isatty, file-i/o system call
25183 int isatty(int fd);
25187 @samp{Fisatty,@var{fd}}
25189 @item Return value:
25190 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
25196 The call was interrupted by the user.
25201 Note that the @code{isatty} call is treated as a special case: it returns
25202 1 to the target if the file descriptor is attached
25203 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
25204 would require implementing @code{ioctl} and would be more complex than
25209 @unnumberedsubsubsec system
25210 @cindex system, file-i/o system call
25215 int system(const char *command);
25219 @samp{Fsystem,@var{commandptr}/@var{len}}
25221 @item Return value:
25222 If @var{len} is zero, the return value indicates whether a shell is
25223 available. A zero return value indicates a shell is not available.
25224 For non-zero @var{len}, the value returned is -1 on error and the
25225 return status of the command otherwise. Only the exit status of the
25226 command is returned, which is extracted from the host's @code{system}
25227 return value by calling @code{WEXITSTATUS(retval)}. In case
25228 @file{/bin/sh} could not be executed, 127 is returned.
25234 The call was interrupted by the user.
25239 @value{GDBN} takes over the full task of calling the necessary host calls
25240 to perform the @code{system} call. The return value of @code{system} on
25241 the host is simplified before it's returned
25242 to the target. Any termination signal information from the child process
25243 is discarded, and the return value consists
25244 entirely of the exit status of the called command.
25246 Due to security concerns, the @code{system} call is by default refused
25247 by @value{GDBN}. The user has to allow this call explicitly with the
25248 @code{set remote system-call-allowed 1} command.
25251 @item set remote system-call-allowed
25252 @kindex set remote system-call-allowed
25253 Control whether to allow the @code{system} calls in the File I/O
25254 protocol for the remote target. The default is zero (disabled).
25256 @item show remote system-call-allowed
25257 @kindex show remote system-call-allowed
25258 Show whether the @code{system} calls are allowed in the File I/O
25262 @node Protocol specific representation of datatypes
25263 @subsection Protocol specific representation of datatypes
25264 @cindex protocol specific representation of datatypes, in file-i/o protocol
25267 * Integral datatypes::
25269 * Memory transfer::
25274 @node Integral datatypes
25275 @unnumberedsubsubsec Integral datatypes
25276 @cindex integral datatypes, in file-i/o protocol
25278 The integral datatypes used in the system calls are @code{int},
25279 @code{unsigned int}, @code{long}, @code{unsigned long},
25280 @code{mode_t}, and @code{time_t}.
25282 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25283 implemented as 32 bit values in this protocol.
25285 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25287 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25288 in @file{limits.h}) to allow range checking on host and target.
25290 @code{time_t} datatypes are defined as seconds since the Epoch.
25292 All integral datatypes transferred as part of a memory read or write of a
25293 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25296 @node Pointer values
25297 @unnumberedsubsubsec Pointer values
25298 @cindex pointer values, in file-i/o protocol
25300 Pointers to target data are transmitted as they are. An exception
25301 is made for pointers to buffers for which the length isn't
25302 transmitted as part of the function call, namely strings. Strings
25303 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25310 which is a pointer to data of length 18 bytes at position 0x1aaf.
25311 The length is defined as the full string length in bytes, including
25312 the trailing null byte. For example, the string @code{"hello world"}
25313 at address 0x123456 is transmitted as
25319 @node Memory transfer
25320 @unnumberedsubsubsec Memory transfer
25321 @cindex memory transfer, in file-i/o protocol
25323 Structured data which is transferred using a memory read or write (for
25324 example, a @code{struct stat}) is expected to be in a protocol specific format
25325 with all scalar multibyte datatypes being big endian. Translation to
25326 this representation needs to be done both by the target before the @code{F}
25327 packet is sent, and by @value{GDBN} before
25328 it transfers memory to the target. Transferred pointers to structured
25329 data should point to the already-coerced data at any time.
25333 @unnumberedsubsubsec struct stat
25334 @cindex struct stat, in file-i/o protocol
25336 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25337 is defined as follows:
25341 unsigned int st_dev; /* device */
25342 unsigned int st_ino; /* inode */
25343 mode_t st_mode; /* protection */
25344 unsigned int st_nlink; /* number of hard links */
25345 unsigned int st_uid; /* user ID of owner */
25346 unsigned int st_gid; /* group ID of owner */
25347 unsigned int st_rdev; /* device type (if inode device) */
25348 unsigned long st_size; /* total size, in bytes */
25349 unsigned long st_blksize; /* blocksize for filesystem I/O */
25350 unsigned long st_blocks; /* number of blocks allocated */
25351 time_t st_atime; /* time of last access */
25352 time_t st_mtime; /* time of last modification */
25353 time_t st_ctime; /* time of last change */
25357 The integral datatypes conform to the definitions given in the
25358 appropriate section (see @ref{Integral datatypes}, for details) so this
25359 structure is of size 64 bytes.
25361 The values of several fields have a restricted meaning and/or
25367 A value of 0 represents a file, 1 the console.
25370 No valid meaning for the target. Transmitted unchanged.
25373 Valid mode bits are described in @ref{Constants}. Any other
25374 bits have currently no meaning for the target.
25379 No valid meaning for the target. Transmitted unchanged.
25384 These values have a host and file system dependent
25385 accuracy. Especially on Windows hosts, the file system may not
25386 support exact timing values.
25389 The target gets a @code{struct stat} of the above representation and is
25390 responsible for coercing it to the target representation before
25393 Note that due to size differences between the host, target, and protocol
25394 representations of @code{struct stat} members, these members could eventually
25395 get truncated on the target.
25397 @node struct timeval
25398 @unnumberedsubsubsec struct timeval
25399 @cindex struct timeval, in file-i/o protocol
25401 The buffer of type @code{struct timeval} used by the File-I/O protocol
25402 is defined as follows:
25406 time_t tv_sec; /* second */
25407 long tv_usec; /* microsecond */
25411 The integral datatypes conform to the definitions given in the
25412 appropriate section (see @ref{Integral datatypes}, for details) so this
25413 structure is of size 8 bytes.
25416 @subsection Constants
25417 @cindex constants, in file-i/o protocol
25419 The following values are used for the constants inside of the
25420 protocol. @value{GDBN} and target are responsible for translating these
25421 values before and after the call as needed.
25432 @unnumberedsubsubsec Open flags
25433 @cindex open flags, in file-i/o protocol
25435 All values are given in hexadecimal representation.
25447 @node mode_t values
25448 @unnumberedsubsubsec mode_t values
25449 @cindex mode_t values, in file-i/o protocol
25451 All values are given in octal representation.
25468 @unnumberedsubsubsec Errno values
25469 @cindex errno values, in file-i/o protocol
25471 All values are given in decimal representation.
25496 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25497 any error value not in the list of supported error numbers.
25500 @unnumberedsubsubsec Lseek flags
25501 @cindex lseek flags, in file-i/o protocol
25510 @unnumberedsubsubsec Limits
25511 @cindex limits, in file-i/o protocol
25513 All values are given in decimal representation.
25516 INT_MIN -2147483648
25518 UINT_MAX 4294967295
25519 LONG_MIN -9223372036854775808
25520 LONG_MAX 9223372036854775807
25521 ULONG_MAX 18446744073709551615
25524 @node File-I/O Examples
25525 @subsection File-I/O Examples
25526 @cindex file-i/o examples
25528 Example sequence of a write call, file descriptor 3, buffer is at target
25529 address 0x1234, 6 bytes should be written:
25532 <- @code{Fwrite,3,1234,6}
25533 @emph{request memory read from target}
25536 @emph{return "6 bytes written"}
25540 Example sequence of a read call, file descriptor 3, buffer is at target
25541 address 0x1234, 6 bytes should be read:
25544 <- @code{Fread,3,1234,6}
25545 @emph{request memory write to target}
25546 -> @code{X1234,6:XXXXXX}
25547 @emph{return "6 bytes read"}
25551 Example sequence of a read call, call fails on the host due to invalid
25552 file descriptor (@code{EBADF}):
25555 <- @code{Fread,3,1234,6}
25559 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
25563 <- @code{Fread,3,1234,6}
25568 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
25572 <- @code{Fread,3,1234,6}
25573 -> @code{X1234,6:XXXXXX}
25577 @node Memory map format
25578 @section Memory map format
25579 @cindex memory map format
25581 To be able to write into flash memory, @value{GDBN} needs to obtain a
25582 memory map from the target. This section describes the format of the
25585 The memory map is obtained using the @samp{qXfer:memory-map:read}
25586 (@pxref{qXfer memory map read}) packet and is an XML document that
25587 lists memory regions. The top-level structure of the document is shown below:
25590 <?xml version="1.0"?>
25591 <!DOCTYPE memory-map
25592 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
25593 "http://sourceware.org/gdb/gdb-memory-map.dtd">
25599 Each region can be either:
25604 A region of RAM starting at @var{addr} and extending for @var{length}
25608 <memory type="ram" start="@var{addr}" length="@var{length}"/>
25613 A region of read-only memory:
25616 <memory type="rom" start="@var{addr}" length="@var{length}"/>
25621 A region of flash memory, with erasure blocks @var{blocksize}
25625 <memory type="flash" start="@var{addr}" length="@var{length}">
25626 <property name="blocksize">@var{blocksize}</property>
25632 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
25633 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
25634 packets to write to addresses in such ranges.
25636 The formal DTD for memory map format is given below:
25639 <!-- ................................................... -->
25640 <!-- Memory Map XML DTD ................................ -->
25641 <!-- File: memory-map.dtd .............................. -->
25642 <!-- .................................... .............. -->
25643 <!-- memory-map.dtd -->
25644 <!-- memory-map: Root element with versioning -->
25645 <!ELEMENT memory-map (memory | property)>
25646 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
25647 <!ELEMENT memory (property)>
25648 <!-- memory: Specifies a memory region,
25649 and its type, or device. -->
25650 <!ATTLIST memory type CDATA #REQUIRED
25651 start CDATA #REQUIRED
25652 length CDATA #REQUIRED
25653 device CDATA #IMPLIED>
25654 <!-- property: Generic attribute tag -->
25655 <!ELEMENT property (#PCDATA | property)*>
25656 <!ATTLIST property name CDATA #REQUIRED>
25659 @include agentexpr.texi
25661 @node Target Descriptions
25662 @appendix Target Descriptions
25663 @cindex target descriptions
25665 @strong{Warning:} target descriptions are still under active development,
25666 and the contents and format may change between @value{GDBN} releases.
25667 The format is expected to stabilize in the future.
25669 One of the challenges of using @value{GDBN} to debug embedded systems
25670 is that there are so many minor variants of each processor
25671 architecture in use. It is common practice for vendors to start with
25672 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
25673 and then make changes to adapt it to a particular market niche. Some
25674 architectures have hundreds of variants, available from dozens of
25675 vendors. This leads to a number of problems:
25679 With so many different customized processors, it is difficult for
25680 the @value{GDBN} maintainers to keep up with the changes.
25682 Since individual variants may have short lifetimes or limited
25683 audiences, it may not be worthwhile to carry information about every
25684 variant in the @value{GDBN} source tree.
25686 When @value{GDBN} does support the architecture of the embedded system
25687 at hand, the task of finding the correct architecture name to give the
25688 @command{set architecture} command can be error-prone.
25691 To address these problems, the @value{GDBN} remote protocol allows a
25692 target system to not only identify itself to @value{GDBN}, but to
25693 actually describe its own features. This lets @value{GDBN} support
25694 processor variants it has never seen before --- to the extent that the
25695 descriptions are accurate, and that @value{GDBN} understands them.
25698 * Retrieving Descriptions:: How descriptions are fetched from a target.
25699 * Target Description Format:: The contents of a target description.
25702 @node Retrieving Descriptions
25703 @section Retrieving Descriptions
25705 Target descriptions can be read from the target automatically, or
25706 specified by the user manually. The default behavior is to read the
25707 description from the target. @value{GDBN} retrieves it via the remote
25708 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
25709 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
25710 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
25711 XML document, of the form described in @ref{Target Description
25714 Alternatively, you can specify a file to read for the target description.
25715 If a file is set, the target will not be queried. The commands to
25716 specify a file are:
25719 @cindex set tdesc filename
25720 @item set tdesc filename @var{path}
25721 Read the target description from @var{path}.
25723 @cindex unset tdesc filename
25724 @item unset tdesc filename
25725 Do not read the XML target description from a file. @value{GDBN}
25726 will use the description supplied by the current target.
25728 @cindex show tdesc filename
25729 @item show tdesc filename
25730 Show the filename to read for a target description, if any.
25734 @node Target Description Format
25735 @section Target Description Format
25736 @cindex target descriptions, XML format
25738 A target description annex is an @uref{http://www.w3.org/XML/, XML}
25739 document which complies with the Document Type Definition provided in
25740 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
25741 means you can use generally available tools like @command{xmllint} to
25742 check that your feature descriptions are well-formed and valid.
25743 However, to help people unfamiliar with XML write descriptions for
25744 their targets, we also describe the grammar here.
25746 At the moment, target descriptions can only provide minimal information
25747 about the architecture of the remote target. @value{GDBN} can use this
25748 information to autoconfigure, or to warn you if you connect to an
25749 unsupported target.
25751 Here is a simple target description:
25755 <architecture>i386:x86-64</architecture>
25760 This minimal description only says that the target uses
25761 the x86-64 architecture.
25763 A target description has the overall form:
25766 <?xml version="1.0"?>
25767 <!DOCTYPE target SYSTEM "gdb-target.dtd">
25769 <architecture>@var{arch name}</architecture>
25774 The description is generally insensitive to whitespace and line
25775 breaks, under the usual common-sense rules. The XML version
25776 declaration and document type declaration can generally be omitted
25777 (@value{GDBN} does not require them), but specifying them may be
25778 useful for XML validation tools.
25780 The content of the @samp{<architecture>} element is an architecture
25781 name, from the same selection accepted by @code{set architecture}
25782 (@pxref{Targets, ,Specifying a Debugging Target}).
25797 % I think something like @colophon should be in texinfo. In the
25799 \long\def\colophon{\hbox to0pt{}\vfill
25800 \centerline{The body of this manual is set in}
25801 \centerline{\fontname\tenrm,}
25802 \centerline{with headings in {\bf\fontname\tenbf}}
25803 \centerline{and examples in {\tt\fontname\tentt}.}
25804 \centerline{{\it\fontname\tenit\/},}
25805 \centerline{{\bf\fontname\tenbf}, and}
25806 \centerline{{\sl\fontname\tensl\/}}
25807 \centerline{are used for emphasis.}\vfill}
25809 % Blame: doc@cygnus.com, 1991.