1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
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
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.1 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
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}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2010 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
168 * Formatting Documentation:: How to format and print @value{GDBN} documentation
169 * Installing GDB:: Installing GDB
170 * Maintenance Commands:: Maintenance Commands
171 * Remote Protocol:: GDB Remote Serial Protocol
172 * Agent Expressions:: The GDB Agent Expression Mechanism
173 * Target Descriptions:: How targets can describe themselves to
175 * Operating System Information:: Getting additional information from
177 * Trace File Format:: GDB trace file format
178 * Copying:: GNU General Public License says
179 how you can copy and share GDB
180 * GNU Free Documentation License:: The license for this documentation
189 @unnumbered Summary of @value{GDBN}
191 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
192 going on ``inside'' another program while it executes---or what another
193 program was doing at the moment it crashed.
195 @value{GDBN} can do four main kinds of things (plus other things in support of
196 these) to help you catch bugs in the act:
200 Start your program, specifying anything that might affect its behavior.
203 Make your program stop on specified conditions.
206 Examine what has happened, when your program has stopped.
209 Change things in your program, so you can experiment with correcting the
210 effects of one bug and go on to learn about another.
213 You can use @value{GDBN} to debug programs written in C and C@t{++}.
214 For more information, see @ref{Supported Languages,,Supported Languages}.
215 For more information, see @ref{C,,C and C++}.
218 Support for Modula-2 is partial. For information on Modula-2, see
219 @ref{Modula-2,,Modula-2}.
222 Debugging Pascal programs which use sets, subranges, file variables, or
223 nested functions does not currently work. @value{GDBN} does not support
224 entering expressions, printing values, or similar features using Pascal
228 @value{GDBN} can be used to debug programs written in Fortran, although
229 it may be necessary to refer to some variables with a trailing
232 @value{GDBN} can be used to debug programs written in Objective-C,
233 using either the Apple/NeXT or the GNU Objective-C runtime.
236 * Free Software:: Freely redistributable software
237 * Contributors:: Contributors to GDB
241 @unnumberedsec Free Software
243 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
244 General Public License
245 (GPL). The GPL gives you the freedom to copy or adapt a licensed
246 program---but every person getting a copy also gets with it the
247 freedom to modify that copy (which means that they must get access to
248 the source code), and the freedom to distribute further copies.
249 Typical software companies use copyrights to limit your freedoms; the
250 Free Software Foundation uses the GPL to preserve these freedoms.
252 Fundamentally, the General Public License is a license which says that
253 you have these freedoms and that you cannot take these freedoms away
256 @unnumberedsec Free Software Needs Free Documentation
258 The biggest deficiency in the free software community today is not in
259 the software---it is the lack of good free documentation that we can
260 include with the free software. Many of our most important
261 programs do not come with free reference manuals and free introductory
262 texts. Documentation is an essential part of any software package;
263 when an important free software package does not come with a free
264 manual and a free tutorial, that is a major gap. We have many such
267 Consider Perl, for instance. The tutorial manuals that people
268 normally use are non-free. How did this come about? Because the
269 authors of those manuals published them with restrictive terms---no
270 copying, no modification, source files not available---which exclude
271 them from the free software world.
273 That wasn't the first time this sort of thing happened, and it was far
274 from the last. Many times we have heard a GNU user eagerly describe a
275 manual that he is writing, his intended contribution to the community,
276 only to learn that he had ruined everything by signing a publication
277 contract to make it non-free.
279 Free documentation, like free software, is a matter of freedom, not
280 price. The problem with the non-free manual is not that publishers
281 charge a price for printed copies---that in itself is fine. (The Free
282 Software Foundation sells printed copies of manuals, too.) The
283 problem is the restrictions on the use of the manual. Free manuals
284 are available in source code form, and give you permission to copy and
285 modify. Non-free manuals do not allow this.
287 The criteria of freedom for a free manual are roughly the same as for
288 free software. Redistribution (including the normal kinds of
289 commercial redistribution) must be permitted, so that the manual can
290 accompany every copy of the program, both on-line and on paper.
292 Permission for modification of the technical content is crucial too.
293 When people modify the software, adding or changing features, if they
294 are conscientious they will change the manual too---so they can
295 provide accurate and clear documentation for the modified program. A
296 manual that leaves you no choice but to write a new manual to document
297 a changed version of the program is not really available to our
300 Some kinds of limits on the way modification is handled are
301 acceptable. For example, requirements to preserve the original
302 author's copyright notice, the distribution terms, or the list of
303 authors, are ok. It is also no problem to require modified versions
304 to include notice that they were modified. Even entire sections that
305 may not be deleted or changed are acceptable, as long as they deal
306 with nontechnical topics (like this one). These kinds of restrictions
307 are acceptable because they don't obstruct the community's normal use
310 However, it must be possible to modify all the @emph{technical}
311 content of the manual, and then distribute the result in all the usual
312 media, through all the usual channels. Otherwise, the restrictions
313 obstruct the use of the manual, it is not free, and we need another
314 manual to replace it.
316 Please spread the word about this issue. Our community continues to
317 lose manuals to proprietary publishing. If we spread the word that
318 free software needs free reference manuals and free tutorials, perhaps
319 the next person who wants to contribute by writing documentation will
320 realize, before it is too late, that only free manuals contribute to
321 the free software community.
323 If you are writing documentation, please insist on publishing it under
324 the GNU Free Documentation License or another free documentation
325 license. Remember that this decision requires your approval---you
326 don't have to let the publisher decide. Some commercial publishers
327 will use a free license if you insist, but they will not propose the
328 option; it is up to you to raise the issue and say firmly that this is
329 what you want. If the publisher you are dealing with refuses, please
330 try other publishers. If you're not sure whether a proposed license
331 is free, write to @email{licensing@@gnu.org}.
333 You can encourage commercial publishers to sell more free, copylefted
334 manuals and tutorials by buying them, and particularly by buying
335 copies from the publishers that paid for their writing or for major
336 improvements. Meanwhile, try to avoid buying non-free documentation
337 at all. Check the distribution terms of a manual before you buy it,
338 and insist that whoever seeks your business must respect your freedom.
339 Check the history of the book, and try to reward the publishers that
340 have paid or pay the authors to work on it.
342 The Free Software Foundation maintains a list of free documentation
343 published by other publishers, at
344 @url{http://www.fsf.org/doc/other-free-books.html}.
347 @unnumberedsec Contributors to @value{GDBN}
349 Richard Stallman was the original author of @value{GDBN}, and of many
350 other @sc{gnu} programs. Many others have contributed to its
351 development. This section attempts to credit major contributors. One
352 of the virtues of free software is that everyone is free to contribute
353 to it; with regret, we cannot actually acknowledge everyone here. The
354 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
355 blow-by-blow account.
357 Changes much prior to version 2.0 are lost in the mists of time.
360 @emph{Plea:} Additions to this section are particularly welcome. If you
361 or your friends (or enemies, to be evenhanded) have been unfairly
362 omitted from this list, we would like to add your names!
365 So that they may not regard their many labors as thankless, we
366 particularly thank those who shepherded @value{GDBN} through major
368 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
369 Jim Blandy (release 4.18);
370 Jason Molenda (release 4.17);
371 Stan Shebs (release 4.14);
372 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
373 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
374 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
375 Jim Kingdon (releases 3.5, 3.4, and 3.3);
376 and Randy Smith (releases 3.2, 3.1, and 3.0).
378 Richard Stallman, assisted at various times by Peter TerMaat, Chris
379 Hanson, and Richard Mlynarik, handled releases through 2.8.
381 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
382 in @value{GDBN}, with significant additional contributions from Per
383 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
384 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
385 much general update work leading to release 3.0).
387 @value{GDBN} uses the BFD subroutine library to examine multiple
388 object-file formats; BFD was a joint project of David V.
389 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
391 David Johnson wrote the original COFF support; Pace Willison did
392 the original support for encapsulated COFF.
394 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
396 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
397 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
399 Jean-Daniel Fekete contributed Sun 386i support.
400 Chris Hanson improved the HP9000 support.
401 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
402 David Johnson contributed Encore Umax support.
403 Jyrki Kuoppala contributed Altos 3068 support.
404 Jeff Law contributed HP PA and SOM support.
405 Keith Packard contributed NS32K support.
406 Doug Rabson contributed Acorn Risc Machine support.
407 Bob Rusk contributed Harris Nighthawk CX-UX support.
408 Chris Smith contributed Convex support (and Fortran debugging).
409 Jonathan Stone contributed Pyramid support.
410 Michael Tiemann contributed SPARC support.
411 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
412 Pace Willison contributed Intel 386 support.
413 Jay Vosburgh contributed Symmetry support.
414 Marko Mlinar contributed OpenRISC 1000 support.
416 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
418 Rich Schaefer and Peter Schauer helped with support of SunOS shared
421 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
422 about several machine instruction sets.
424 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
425 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
426 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
427 and RDI targets, respectively.
429 Brian Fox is the author of the readline libraries providing
430 command-line editing and command history.
432 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
433 Modula-2 support, and contributed the Languages chapter of this manual.
435 Fred Fish wrote most of the support for Unix System Vr4.
436 He also enhanced the command-completion support to cover C@t{++} overloaded
439 Hitachi America (now Renesas America), Ltd. sponsored the support for
440 H8/300, H8/500, and Super-H processors.
442 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
444 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
447 Toshiba sponsored the support for the TX39 Mips processor.
449 Matsushita sponsored the support for the MN10200 and MN10300 processors.
451 Fujitsu sponsored the support for SPARClite and FR30 processors.
453 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
456 Michael Snyder added support for tracepoints.
458 Stu Grossman wrote gdbserver.
460 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
461 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
463 The following people at the Hewlett-Packard Company contributed
464 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
465 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
466 compiler, and the Text User Interface (nee Terminal User Interface):
467 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
468 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
469 provided HP-specific information in this manual.
471 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
472 Robert Hoehne made significant contributions to the DJGPP port.
474 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
475 development since 1991. Cygnus engineers who have worked on @value{GDBN}
476 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
477 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
478 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
479 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
480 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
481 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
482 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
483 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
484 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
485 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
486 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
487 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
488 Zuhn have made contributions both large and small.
490 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
491 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
493 Jim Blandy added support for preprocessor macros, while working for Red
496 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
497 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
498 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
499 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
500 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
501 with the migration of old architectures to this new framework.
503 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
504 unwinder framework, this consisting of a fresh new design featuring
505 frame IDs, independent frame sniffers, and the sentinel frame. Mark
506 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
507 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
508 trad unwinders. The architecture-specific changes, each involving a
509 complete rewrite of the architecture's frame code, were carried out by
510 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
511 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
512 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
513 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
516 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
517 Tensilica, Inc.@: contributed support for Xtensa processors. Others
518 who have worked on the Xtensa port of @value{GDBN} in the past include
519 Steve Tjiang, John Newlin, and Scott Foehner.
521 Michael Eager and staff of Xilinx, Inc., contributed support for the
522 Xilinx MicroBlaze architecture.
525 @chapter A Sample @value{GDBN} Session
527 You can use this manual at your leisure to read all about @value{GDBN}.
528 However, a handful of commands are enough to get started using the
529 debugger. This chapter illustrates those commands.
532 In this sample session, we emphasize user input like this: @b{input},
533 to make it easier to pick out from the surrounding output.
536 @c FIXME: this example may not be appropriate for some configs, where
537 @c FIXME...primary interest is in remote use.
539 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
540 processor) exhibits the following bug: sometimes, when we change its
541 quote strings from the default, the commands used to capture one macro
542 definition within another stop working. In the following short @code{m4}
543 session, we define a macro @code{foo} which expands to @code{0000}; we
544 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
545 same thing. However, when we change the open quote string to
546 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
547 procedure fails to define a new synonym @code{baz}:
556 @b{define(bar,defn(`foo'))}
560 @b{changequote(<QUOTE>,<UNQUOTE>)}
562 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
565 m4: End of input: 0: fatal error: EOF in string
569 Let us use @value{GDBN} to try to see what is going on.
572 $ @b{@value{GDBP} m4}
573 @c FIXME: this falsifies the exact text played out, to permit smallbook
574 @c FIXME... format to come out better.
575 @value{GDBN} is free software and you are welcome to distribute copies
576 of it under certain conditions; type "show copying" to see
578 There is absolutely no warranty for @value{GDBN}; type "show warranty"
581 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
586 @value{GDBN} reads only enough symbol data to know where to find the
587 rest when needed; as a result, the first prompt comes up very quickly.
588 We now tell @value{GDBN} to use a narrower display width than usual, so
589 that examples fit in this manual.
592 (@value{GDBP}) @b{set width 70}
596 We need to see how the @code{m4} built-in @code{changequote} works.
597 Having looked at the source, we know the relevant subroutine is
598 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
599 @code{break} command.
602 (@value{GDBP}) @b{break m4_changequote}
603 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
607 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
608 control; as long as control does not reach the @code{m4_changequote}
609 subroutine, the program runs as usual:
612 (@value{GDBP}) @b{run}
613 Starting program: /work/Editorial/gdb/gnu/m4/m4
621 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
622 suspends execution of @code{m4}, displaying information about the
623 context where it stops.
626 @b{changequote(<QUOTE>,<UNQUOTE>)}
628 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
630 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
634 Now we use the command @code{n} (@code{next}) to advance execution to
635 the next line of the current function.
639 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
644 @code{set_quotes} looks like a promising subroutine. We can go into it
645 by using the command @code{s} (@code{step}) instead of @code{next}.
646 @code{step} goes to the next line to be executed in @emph{any}
647 subroutine, so it steps into @code{set_quotes}.
651 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
653 530 if (lquote != def_lquote)
657 The display that shows the subroutine where @code{m4} is now
658 suspended (and its arguments) is called a stack frame display. It
659 shows a summary of the stack. We can use the @code{backtrace}
660 command (which can also be spelled @code{bt}), to see where we are
661 in the stack as a whole: the @code{backtrace} command displays a
662 stack frame for each active subroutine.
665 (@value{GDBP}) @b{bt}
666 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
668 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
670 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
671 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
673 #4 0x79dc in expand_input () at macro.c:40
674 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
678 We step through a few more lines to see what happens. The first two
679 times, we can use @samp{s}; the next two times we use @code{n} to avoid
680 falling into the @code{xstrdup} subroutine.
684 0x3b5c 532 if (rquote != def_rquote)
686 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
687 def_lquote : xstrdup(lq);
689 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
692 538 len_lquote = strlen(rquote);
696 The last line displayed looks a little odd; we can examine the variables
697 @code{lquote} and @code{rquote} to see if they are in fact the new left
698 and right quotes we specified. We use the command @code{p}
699 (@code{print}) to see their values.
702 (@value{GDBP}) @b{p lquote}
703 $1 = 0x35d40 "<QUOTE>"
704 (@value{GDBP}) @b{p rquote}
705 $2 = 0x35d50 "<UNQUOTE>"
709 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
710 To look at some context, we can display ten lines of source
711 surrounding the current line with the @code{l} (@code{list}) command.
717 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
719 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
722 538 len_lquote = strlen(rquote);
723 539 len_rquote = strlen(lquote);
730 Let us step past the two lines that set @code{len_lquote} and
731 @code{len_rquote}, and then examine the values of those variables.
735 539 len_rquote = strlen(lquote);
738 (@value{GDBP}) @b{p len_lquote}
740 (@value{GDBP}) @b{p len_rquote}
745 That certainly looks wrong, assuming @code{len_lquote} and
746 @code{len_rquote} are meant to be the lengths of @code{lquote} and
747 @code{rquote} respectively. We can set them to better values using
748 the @code{p} command, since it can print the value of
749 any expression---and that expression can include subroutine calls and
753 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
755 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
760 Is that enough to fix the problem of using the new quotes with the
761 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
762 executing with the @code{c} (@code{continue}) command, and then try the
763 example that caused trouble initially:
769 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
776 Success! The new quotes now work just as well as the default ones. The
777 problem seems to have been just the two typos defining the wrong
778 lengths. We allow @code{m4} exit by giving it an EOF as input:
782 Program exited normally.
786 The message @samp{Program exited normally.} is from @value{GDBN}; it
787 indicates @code{m4} has finished executing. We can end our @value{GDBN}
788 session with the @value{GDBN} @code{quit} command.
791 (@value{GDBP}) @b{quit}
795 @chapter Getting In and Out of @value{GDBN}
797 This chapter discusses how to start @value{GDBN}, and how to get out of it.
801 type @samp{@value{GDBP}} to start @value{GDBN}.
803 type @kbd{quit} or @kbd{Ctrl-d} to exit.
807 * Invoking GDB:: How to start @value{GDBN}
808 * Quitting GDB:: How to quit @value{GDBN}
809 * Shell Commands:: How to use shell commands inside @value{GDBN}
810 * Logging Output:: How to log @value{GDBN}'s output to a file
814 @section Invoking @value{GDBN}
816 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
817 @value{GDBN} reads commands from the terminal until you tell it to exit.
819 You can also run @code{@value{GDBP}} with a variety of arguments and options,
820 to specify more of your debugging environment at the outset.
822 The command-line options described here are designed
823 to cover a variety of situations; in some environments, some of these
824 options may effectively be unavailable.
826 The most usual way to start @value{GDBN} is with one argument,
827 specifying an executable program:
830 @value{GDBP} @var{program}
834 You can also start with both an executable program and a core file
838 @value{GDBP} @var{program} @var{core}
841 You can, instead, specify a process ID as a second argument, if you want
842 to debug a running process:
845 @value{GDBP} @var{program} 1234
849 would attach @value{GDBN} to process @code{1234} (unless you also have a file
850 named @file{1234}; @value{GDBN} does check for a core file first).
852 Taking advantage of the second command-line argument requires a fairly
853 complete operating system; when you use @value{GDBN} as a remote
854 debugger attached to a bare board, there may not be any notion of
855 ``process'', and there is often no way to get a core dump. @value{GDBN}
856 will warn you if it is unable to attach or to read core dumps.
858 You can optionally have @code{@value{GDBP}} pass any arguments after the
859 executable file to the inferior using @code{--args}. This option stops
862 @value{GDBP} --args gcc -O2 -c foo.c
864 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
865 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
867 You can run @code{@value{GDBP}} without printing the front material, which describes
868 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
875 You can further control how @value{GDBN} starts up by using command-line
876 options. @value{GDBN} itself can remind you of the options available.
886 to display all available options and briefly describe their use
887 (@samp{@value{GDBP} -h} is a shorter equivalent).
889 All options and command line arguments you give are processed
890 in sequential order. The order makes a difference when the
891 @samp{-x} option is used.
895 * File Options:: Choosing files
896 * Mode Options:: Choosing modes
897 * Startup:: What @value{GDBN} does during startup
901 @subsection Choosing Files
903 When @value{GDBN} starts, it reads any arguments other than options as
904 specifying an executable file and core file (or process ID). This is
905 the same as if the arguments were specified by the @samp{-se} and
906 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
907 first argument that does not have an associated option flag as
908 equivalent to the @samp{-se} option followed by that argument; and the
909 second argument that does not have an associated option flag, if any, as
910 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
911 If the second argument begins with a decimal digit, @value{GDBN} will
912 first attempt to attach to it as a process, and if that fails, attempt
913 to open it as a corefile. If you have a corefile whose name begins with
914 a digit, you can prevent @value{GDBN} from treating it as a pid by
915 prefixing it with @file{./}, e.g.@: @file{./12345}.
917 If @value{GDBN} has not been configured to included core file support,
918 such as for most embedded targets, then it will complain about a second
919 argument and ignore it.
921 Many options have both long and short forms; both are shown in the
922 following list. @value{GDBN} also recognizes the long forms if you truncate
923 them, so long as enough of the option is present to be unambiguous.
924 (If you prefer, you can flag option arguments with @samp{--} rather
925 than @samp{-}, though we illustrate the more usual convention.)
927 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
928 @c way, both those who look for -foo and --foo in the index, will find
932 @item -symbols @var{file}
934 @cindex @code{--symbols}
936 Read symbol table from file @var{file}.
938 @item -exec @var{file}
940 @cindex @code{--exec}
942 Use file @var{file} as the executable file to execute when appropriate,
943 and for examining pure data in conjunction with a core dump.
947 Read symbol table from file @var{file} and use it as the executable
950 @item -core @var{file}
952 @cindex @code{--core}
954 Use file @var{file} as a core dump to examine.
956 @item -pid @var{number}
957 @itemx -p @var{number}
960 Connect to process ID @var{number}, as with the @code{attach} command.
962 @item -command @var{file}
964 @cindex @code{--command}
966 Execute commands from file @var{file}. The contents of this file is
967 evaluated exactly as the @code{source} command would.
968 @xref{Command Files,, Command files}.
970 @item -eval-command @var{command}
971 @itemx -ex @var{command}
972 @cindex @code{--eval-command}
974 Execute a single @value{GDBN} command.
976 This option may be used multiple times to call multiple commands. It may
977 also be interleaved with @samp{-command} as required.
980 @value{GDBP} -ex 'target sim' -ex 'load' \
981 -x setbreakpoints -ex 'run' a.out
984 @item -directory @var{directory}
985 @itemx -d @var{directory}
986 @cindex @code{--directory}
988 Add @var{directory} to the path to search for source and script files.
992 @cindex @code{--readnow}
994 Read each symbol file's entire symbol table immediately, rather than
995 the default, which is to read it incrementally as it is needed.
996 This makes startup slower, but makes future operations faster.
1001 @subsection Choosing Modes
1003 You can run @value{GDBN} in various alternative modes---for example, in
1004 batch mode or quiet mode.
1011 Do not execute commands found in any initialization files. Normally,
1012 @value{GDBN} executes the commands in these files after all the command
1013 options and arguments have been processed. @xref{Command Files,,Command
1019 @cindex @code{--quiet}
1020 @cindex @code{--silent}
1022 ``Quiet''. Do not print the introductory and copyright messages. These
1023 messages are also suppressed in batch mode.
1026 @cindex @code{--batch}
1027 Run in batch mode. Exit with status @code{0} after processing all the
1028 command files specified with @samp{-x} (and all commands from
1029 initialization files, if not inhibited with @samp{-n}). Exit with
1030 nonzero status if an error occurs in executing the @value{GDBN} commands
1031 in the command files. Batch mode also disables pagination;
1032 @pxref{Screen Size} and acts as if @kbd{set confirm off} were in
1033 effect (@pxref{Messages/Warnings}).
1035 Batch mode may be useful for running @value{GDBN} as a filter, for
1036 example to download and run a program on another computer; in order to
1037 make this more useful, the message
1040 Program exited normally.
1044 (which is ordinarily issued whenever a program running under
1045 @value{GDBN} control terminates) is not issued when running in batch
1049 @cindex @code{--batch-silent}
1050 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1051 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1052 unaffected). This is much quieter than @samp{-silent} and would be useless
1053 for an interactive session.
1055 This is particularly useful when using targets that give @samp{Loading section}
1056 messages, for example.
1058 Note that targets that give their output via @value{GDBN}, as opposed to
1059 writing directly to @code{stdout}, will also be made silent.
1061 @item -return-child-result
1062 @cindex @code{--return-child-result}
1063 The return code from @value{GDBN} will be the return code from the child
1064 process (the process being debugged), with the following exceptions:
1068 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1069 internal error. In this case the exit code is the same as it would have been
1070 without @samp{-return-child-result}.
1072 The user quits with an explicit value. E.g., @samp{quit 1}.
1074 The child process never runs, or is not allowed to terminate, in which case
1075 the exit code will be -1.
1078 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1079 when @value{GDBN} is being used as a remote program loader or simulator
1084 @cindex @code{--nowindows}
1086 ``No windows''. If @value{GDBN} comes with a graphical user interface
1087 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1088 interface. If no GUI is available, this option has no effect.
1092 @cindex @code{--windows}
1094 If @value{GDBN} includes a GUI, then this option requires it to be
1097 @item -cd @var{directory}
1099 Run @value{GDBN} using @var{directory} as its working directory,
1100 instead of the current directory.
1104 @cindex @code{--fullname}
1106 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1107 subprocess. It tells @value{GDBN} to output the full file name and line
1108 number in a standard, recognizable fashion each time a stack frame is
1109 displayed (which includes each time your program stops). This
1110 recognizable format looks like two @samp{\032} characters, followed by
1111 the file name, line number and character position separated by colons,
1112 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1113 @samp{\032} characters as a signal to display the source code for the
1117 @cindex @code{--epoch}
1118 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1119 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1120 routines so as to allow Epoch to display values of expressions in a
1123 @item -annotate @var{level}
1124 @cindex @code{--annotate}
1125 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1126 effect is identical to using @samp{set annotate @var{level}}
1127 (@pxref{Annotations}). The annotation @var{level} controls how much
1128 information @value{GDBN} prints together with its prompt, values of
1129 expressions, source lines, and other types of output. Level 0 is the
1130 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1131 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1132 that control @value{GDBN}, and level 2 has been deprecated.
1134 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1138 @cindex @code{--args}
1139 Change interpretation of command line so that arguments following the
1140 executable file are passed as command line arguments to the inferior.
1141 This option stops option processing.
1143 @item -baud @var{bps}
1145 @cindex @code{--baud}
1147 Set the line speed (baud rate or bits per second) of any serial
1148 interface used by @value{GDBN} for remote debugging.
1150 @item -l @var{timeout}
1152 Set the timeout (in seconds) of any communication used by @value{GDBN}
1153 for remote debugging.
1155 @item -tty @var{device}
1156 @itemx -t @var{device}
1157 @cindex @code{--tty}
1159 Run using @var{device} for your program's standard input and output.
1160 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1162 @c resolve the situation of these eventually
1164 @cindex @code{--tui}
1165 Activate the @dfn{Text User Interface} when starting. The Text User
1166 Interface manages several text windows on the terminal, showing
1167 source, assembly, registers and @value{GDBN} command outputs
1168 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1169 Text User Interface can be enabled by invoking the program
1170 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1171 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1174 @c @cindex @code{--xdb}
1175 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1176 @c For information, see the file @file{xdb_trans.html}, which is usually
1177 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1180 @item -interpreter @var{interp}
1181 @cindex @code{--interpreter}
1182 Use the interpreter @var{interp} for interface with the controlling
1183 program or device. This option is meant to be set by programs which
1184 communicate with @value{GDBN} using it as a back end.
1185 @xref{Interpreters, , Command Interpreters}.
1187 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1188 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1189 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1190 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1191 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1192 @sc{gdb/mi} interfaces are no longer supported.
1195 @cindex @code{--write}
1196 Open the executable and core files for both reading and writing. This
1197 is equivalent to the @samp{set write on} command inside @value{GDBN}
1201 @cindex @code{--statistics}
1202 This option causes @value{GDBN} to print statistics about time and
1203 memory usage after it completes each command and returns to the prompt.
1206 @cindex @code{--version}
1207 This option causes @value{GDBN} to print its version number and
1208 no-warranty blurb, and exit.
1213 @subsection What @value{GDBN} Does During Startup
1214 @cindex @value{GDBN} startup
1216 Here's the description of what @value{GDBN} does during session startup:
1220 Sets up the command interpreter as specified by the command line
1221 (@pxref{Mode Options, interpreter}).
1225 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1226 used when building @value{GDBN}; @pxref{System-wide configuration,
1227 ,System-wide configuration and settings}) and executes all the commands in
1231 Reads the init file (if any) in your home directory@footnote{On
1232 DOS/Windows systems, the home directory is the one pointed to by the
1233 @code{HOME} environment variable.} and executes all the commands in
1237 Processes command line options and operands.
1240 Reads and executes the commands from init file (if any) in the current
1241 working directory. This is only done if the current directory is
1242 different from your home directory. Thus, you can have more than one
1243 init file, one generic in your home directory, and another, specific
1244 to the program you are debugging, in the directory where you invoke
1248 Reads command files specified by the @samp{-x} option. @xref{Command
1249 Files}, for more details about @value{GDBN} command files.
1252 Reads the command history recorded in the @dfn{history file}.
1253 @xref{Command History}, for more details about the command history and the
1254 files where @value{GDBN} records it.
1257 Init files use the same syntax as @dfn{command files} (@pxref{Command
1258 Files}) and are processed by @value{GDBN} in the same way. The init
1259 file in your home directory can set options (such as @samp{set
1260 complaints}) that affect subsequent processing of command line options
1261 and operands. Init files are not executed if you use the @samp{-nx}
1262 option (@pxref{Mode Options, ,Choosing Modes}).
1264 To display the list of init files loaded by gdb at startup, you
1265 can use @kbd{gdb --help}.
1267 @cindex init file name
1268 @cindex @file{.gdbinit}
1269 @cindex @file{gdb.ini}
1270 The @value{GDBN} init files are normally called @file{.gdbinit}.
1271 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1272 the limitations of file names imposed by DOS filesystems. The Windows
1273 ports of @value{GDBN} use the standard name, but if they find a
1274 @file{gdb.ini} file, they warn you about that and suggest to rename
1275 the file to the standard name.
1279 @section Quitting @value{GDBN}
1280 @cindex exiting @value{GDBN}
1281 @cindex leaving @value{GDBN}
1284 @kindex quit @r{[}@var{expression}@r{]}
1285 @kindex q @r{(@code{quit})}
1286 @item quit @r{[}@var{expression}@r{]}
1288 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1289 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1290 do not supply @var{expression}, @value{GDBN} will terminate normally;
1291 otherwise it will terminate using the result of @var{expression} as the
1296 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1297 terminates the action of any @value{GDBN} command that is in progress and
1298 returns to @value{GDBN} command level. It is safe to type the interrupt
1299 character at any time because @value{GDBN} does not allow it to take effect
1300 until a time when it is safe.
1302 If you have been using @value{GDBN} to control an attached process or
1303 device, you can release it with the @code{detach} command
1304 (@pxref{Attach, ,Debugging an Already-running Process}).
1306 @node Shell Commands
1307 @section Shell Commands
1309 If you need to execute occasional shell commands during your
1310 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1311 just use the @code{shell} command.
1315 @cindex shell escape
1316 @item shell @var{command string}
1317 Invoke a standard shell to execute @var{command string}.
1318 If it exists, the environment variable @code{SHELL} determines which
1319 shell to run. Otherwise @value{GDBN} uses the default shell
1320 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1323 The utility @code{make} is often needed in development environments.
1324 You do not have to use the @code{shell} command for this purpose in
1329 @cindex calling make
1330 @item make @var{make-args}
1331 Execute the @code{make} program with the specified
1332 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1335 @node Logging Output
1336 @section Logging Output
1337 @cindex logging @value{GDBN} output
1338 @cindex save @value{GDBN} output to a file
1340 You may want to save the output of @value{GDBN} commands to a file.
1341 There are several commands to control @value{GDBN}'s logging.
1345 @item set logging on
1347 @item set logging off
1349 @cindex logging file name
1350 @item set logging file @var{file}
1351 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1352 @item set logging overwrite [on|off]
1353 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1354 you want @code{set logging on} to overwrite the logfile instead.
1355 @item set logging redirect [on|off]
1356 By default, @value{GDBN} output will go to both the terminal and the logfile.
1357 Set @code{redirect} if you want output to go only to the log file.
1358 @kindex show logging
1360 Show the current values of the logging settings.
1364 @chapter @value{GDBN} Commands
1366 You can abbreviate a @value{GDBN} command to the first few letters of the command
1367 name, if that abbreviation is unambiguous; and you can repeat certain
1368 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1369 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1370 show you the alternatives available, if there is more than one possibility).
1373 * Command Syntax:: How to give commands to @value{GDBN}
1374 * Completion:: Command completion
1375 * Help:: How to ask @value{GDBN} for help
1378 @node Command Syntax
1379 @section Command Syntax
1381 A @value{GDBN} command is a single line of input. There is no limit on
1382 how long it can be. It starts with a command name, which is followed by
1383 arguments whose meaning depends on the command name. For example, the
1384 command @code{step} accepts an argument which is the number of times to
1385 step, as in @samp{step 5}. You can also use the @code{step} command
1386 with no arguments. Some commands do not allow any arguments.
1388 @cindex abbreviation
1389 @value{GDBN} command names may always be truncated if that abbreviation is
1390 unambiguous. Other possible command abbreviations are listed in the
1391 documentation for individual commands. In some cases, even ambiguous
1392 abbreviations are allowed; for example, @code{s} is specially defined as
1393 equivalent to @code{step} even though there are other commands whose
1394 names start with @code{s}. You can test abbreviations by using them as
1395 arguments to the @code{help} command.
1397 @cindex repeating commands
1398 @kindex RET @r{(repeat last command)}
1399 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1400 repeat the previous command. Certain commands (for example, @code{run})
1401 will not repeat this way; these are commands whose unintentional
1402 repetition might cause trouble and which you are unlikely to want to
1403 repeat. User-defined commands can disable this feature; see
1404 @ref{Define, dont-repeat}.
1406 The @code{list} and @code{x} commands, when you repeat them with
1407 @key{RET}, construct new arguments rather than repeating
1408 exactly as typed. This permits easy scanning of source or memory.
1410 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1411 output, in a way similar to the common utility @code{more}
1412 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1413 @key{RET} too many in this situation, @value{GDBN} disables command
1414 repetition after any command that generates this sort of display.
1416 @kindex # @r{(a comment)}
1418 Any text from a @kbd{#} to the end of the line is a comment; it does
1419 nothing. This is useful mainly in command files (@pxref{Command
1420 Files,,Command Files}).
1422 @cindex repeating command sequences
1423 @kindex Ctrl-o @r{(operate-and-get-next)}
1424 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1425 commands. This command accepts the current line, like @key{RET}, and
1426 then fetches the next line relative to the current line from the history
1430 @section Command Completion
1433 @cindex word completion
1434 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1435 only one possibility; it can also show you what the valid possibilities
1436 are for the next word in a command, at any time. This works for @value{GDBN}
1437 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1439 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1440 of a word. If there is only one possibility, @value{GDBN} fills in the
1441 word, and waits for you to finish the command (or press @key{RET} to
1442 enter it). For example, if you type
1444 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1445 @c complete accuracy in these examples; space introduced for clarity.
1446 @c If texinfo enhancements make it unnecessary, it would be nice to
1447 @c replace " @key" by "@key" in the following...
1449 (@value{GDBP}) info bre @key{TAB}
1453 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1454 the only @code{info} subcommand beginning with @samp{bre}:
1457 (@value{GDBP}) info breakpoints
1461 You can either press @key{RET} at this point, to run the @code{info
1462 breakpoints} command, or backspace and enter something else, if
1463 @samp{breakpoints} does not look like the command you expected. (If you
1464 were sure you wanted @code{info breakpoints} in the first place, you
1465 might as well just type @key{RET} immediately after @samp{info bre},
1466 to exploit command abbreviations rather than command completion).
1468 If there is more than one possibility for the next word when you press
1469 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1470 characters and try again, or just press @key{TAB} a second time;
1471 @value{GDBN} displays all the possible completions for that word. For
1472 example, you might want to set a breakpoint on a subroutine whose name
1473 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1474 just sounds the bell. Typing @key{TAB} again displays all the
1475 function names in your program that begin with those characters, for
1479 (@value{GDBP}) b make_ @key{TAB}
1480 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1481 make_a_section_from_file make_environ
1482 make_abs_section make_function_type
1483 make_blockvector make_pointer_type
1484 make_cleanup make_reference_type
1485 make_command make_symbol_completion_list
1486 (@value{GDBP}) b make_
1490 After displaying the available possibilities, @value{GDBN} copies your
1491 partial input (@samp{b make_} in the example) so you can finish the
1494 If you just want to see the list of alternatives in the first place, you
1495 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1496 means @kbd{@key{META} ?}. You can type this either by holding down a
1497 key designated as the @key{META} shift on your keyboard (if there is
1498 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1500 @cindex quotes in commands
1501 @cindex completion of quoted strings
1502 Sometimes the string you need, while logically a ``word'', may contain
1503 parentheses or other characters that @value{GDBN} normally excludes from
1504 its notion of a word. To permit word completion to work in this
1505 situation, you may enclose words in @code{'} (single quote marks) in
1506 @value{GDBN} commands.
1508 The most likely situation where you might need this is in typing the
1509 name of a C@t{++} function. This is because C@t{++} allows function
1510 overloading (multiple definitions of the same function, distinguished
1511 by argument type). For example, when you want to set a breakpoint you
1512 may need to distinguish whether you mean the version of @code{name}
1513 that takes an @code{int} parameter, @code{name(int)}, or the version
1514 that takes a @code{float} parameter, @code{name(float)}. To use the
1515 word-completion facilities in this situation, type a single quote
1516 @code{'} at the beginning of the function name. This alerts
1517 @value{GDBN} that it may need to consider more information than usual
1518 when you press @key{TAB} or @kbd{M-?} to request word completion:
1521 (@value{GDBP}) b 'bubble( @kbd{M-?}
1522 bubble(double,double) bubble(int,int)
1523 (@value{GDBP}) b 'bubble(
1526 In some cases, @value{GDBN} can tell that completing a name requires using
1527 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1528 completing as much as it can) if you do not type the quote in the first
1532 (@value{GDBP}) b bub @key{TAB}
1533 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1534 (@value{GDBP}) b 'bubble(
1538 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1539 you have not yet started typing the argument list when you ask for
1540 completion on an overloaded symbol.
1542 For more information about overloaded functions, see @ref{C Plus Plus
1543 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1544 overload-resolution off} to disable overload resolution;
1545 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1547 @cindex completion of structure field names
1548 @cindex structure field name completion
1549 @cindex completion of union field names
1550 @cindex union field name completion
1551 When completing in an expression which looks up a field in a
1552 structure, @value{GDBN} also tries@footnote{The completer can be
1553 confused by certain kinds of invalid expressions. Also, it only
1554 examines the static type of the expression, not the dynamic type.} to
1555 limit completions to the field names available in the type of the
1559 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1560 magic to_delete to_fputs to_put to_rewind
1561 to_data to_flush to_isatty to_read to_write
1565 This is because the @code{gdb_stdout} is a variable of the type
1566 @code{struct ui_file} that is defined in @value{GDBN} sources as
1573 ui_file_flush_ftype *to_flush;
1574 ui_file_write_ftype *to_write;
1575 ui_file_fputs_ftype *to_fputs;
1576 ui_file_read_ftype *to_read;
1577 ui_file_delete_ftype *to_delete;
1578 ui_file_isatty_ftype *to_isatty;
1579 ui_file_rewind_ftype *to_rewind;
1580 ui_file_put_ftype *to_put;
1587 @section Getting Help
1588 @cindex online documentation
1591 You can always ask @value{GDBN} itself for information on its commands,
1592 using the command @code{help}.
1595 @kindex h @r{(@code{help})}
1598 You can use @code{help} (abbreviated @code{h}) with no arguments to
1599 display a short list of named classes of commands:
1603 List of classes of commands:
1605 aliases -- Aliases of other commands
1606 breakpoints -- Making program stop at certain points
1607 data -- Examining data
1608 files -- Specifying and examining files
1609 internals -- Maintenance commands
1610 obscure -- Obscure features
1611 running -- Running the program
1612 stack -- Examining the stack
1613 status -- Status inquiries
1614 support -- Support facilities
1615 tracepoints -- Tracing of program execution without
1616 stopping the program
1617 user-defined -- User-defined commands
1619 Type "help" followed by a class name for a list of
1620 commands in that class.
1621 Type "help" followed by command name for full
1623 Command name abbreviations are allowed if unambiguous.
1626 @c the above line break eliminates huge line overfull...
1628 @item help @var{class}
1629 Using one of the general help classes as an argument, you can get a
1630 list of the individual commands in that class. For example, here is the
1631 help display for the class @code{status}:
1634 (@value{GDBP}) help status
1639 @c Line break in "show" line falsifies real output, but needed
1640 @c to fit in smallbook page size.
1641 info -- Generic command for showing things
1642 about the program being debugged
1643 show -- Generic command for showing things
1646 Type "help" followed by command name for full
1648 Command name abbreviations are allowed if unambiguous.
1652 @item help @var{command}
1653 With a command name as @code{help} argument, @value{GDBN} displays a
1654 short paragraph on how to use that command.
1657 @item apropos @var{args}
1658 The @code{apropos} command searches through all of the @value{GDBN}
1659 commands, and their documentation, for the regular expression specified in
1660 @var{args}. It prints out all matches found. For example:
1671 set symbol-reloading -- Set dynamic symbol table reloading
1672 multiple times in one run
1673 show symbol-reloading -- Show dynamic symbol table reloading
1674 multiple times in one run
1679 @item complete @var{args}
1680 The @code{complete @var{args}} command lists all the possible completions
1681 for the beginning of a command. Use @var{args} to specify the beginning of the
1682 command you want completed. For example:
1688 @noindent results in:
1699 @noindent This is intended for use by @sc{gnu} Emacs.
1702 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1703 and @code{show} to inquire about the state of your program, or the state
1704 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1705 manual introduces each of them in the appropriate context. The listings
1706 under @code{info} and under @code{show} in the Index point to
1707 all the sub-commands. @xref{Index}.
1712 @kindex i @r{(@code{info})}
1714 This command (abbreviated @code{i}) is for describing the state of your
1715 program. For example, you can show the arguments passed to a function
1716 with @code{info args}, list the registers currently in use with @code{info
1717 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1718 You can get a complete list of the @code{info} sub-commands with
1719 @w{@code{help info}}.
1723 You can assign the result of an expression to an environment variable with
1724 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1725 @code{set prompt $}.
1729 In contrast to @code{info}, @code{show} is for describing the state of
1730 @value{GDBN} itself.
1731 You can change most of the things you can @code{show}, by using the
1732 related command @code{set}; for example, you can control what number
1733 system is used for displays with @code{set radix}, or simply inquire
1734 which is currently in use with @code{show radix}.
1737 To display all the settable parameters and their current
1738 values, you can use @code{show} with no arguments; you may also use
1739 @code{info set}. Both commands produce the same display.
1740 @c FIXME: "info set" violates the rule that "info" is for state of
1741 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1742 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1746 Here are three miscellaneous @code{show} subcommands, all of which are
1747 exceptional in lacking corresponding @code{set} commands:
1750 @kindex show version
1751 @cindex @value{GDBN} version number
1753 Show what version of @value{GDBN} is running. You should include this
1754 information in @value{GDBN} bug-reports. If multiple versions of
1755 @value{GDBN} are in use at your site, you may need to determine which
1756 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1757 commands are introduced, and old ones may wither away. Also, many
1758 system vendors ship variant versions of @value{GDBN}, and there are
1759 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1760 The version number is the same as the one announced when you start
1763 @kindex show copying
1764 @kindex info copying
1765 @cindex display @value{GDBN} copyright
1768 Display information about permission for copying @value{GDBN}.
1770 @kindex show warranty
1771 @kindex info warranty
1773 @itemx info warranty
1774 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1775 if your version of @value{GDBN} comes with one.
1780 @chapter Running Programs Under @value{GDBN}
1782 When you run a program under @value{GDBN}, you must first generate
1783 debugging information when you compile it.
1785 You may start @value{GDBN} with its arguments, if any, in an environment
1786 of your choice. If you are doing native debugging, you may redirect
1787 your program's input and output, debug an already running process, or
1788 kill a child process.
1791 * Compilation:: Compiling for debugging
1792 * Starting:: Starting your program
1793 * Arguments:: Your program's arguments
1794 * Environment:: Your program's environment
1796 * Working Directory:: Your program's working directory
1797 * Input/Output:: Your program's input and output
1798 * Attach:: Debugging an already-running process
1799 * Kill Process:: Killing the child process
1801 * Inferiors and Programs:: Debugging multiple inferiors and programs
1802 * Threads:: Debugging programs with multiple threads
1803 * Forks:: Debugging forks
1804 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1808 @section Compiling for Debugging
1810 In order to debug a program effectively, you need to generate
1811 debugging information when you compile it. This debugging information
1812 is stored in the object file; it describes the data type of each
1813 variable or function and the correspondence between source line numbers
1814 and addresses in the executable code.
1816 To request debugging information, specify the @samp{-g} option when you run
1819 Programs that are to be shipped to your customers are compiled with
1820 optimizations, using the @samp{-O} compiler option. However, some
1821 compilers are unable to handle the @samp{-g} and @samp{-O} options
1822 together. Using those compilers, you cannot generate optimized
1823 executables containing debugging information.
1825 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1826 without @samp{-O}, making it possible to debug optimized code. We
1827 recommend that you @emph{always} use @samp{-g} whenever you compile a
1828 program. You may think your program is correct, but there is no sense
1829 in pushing your luck. For more information, see @ref{Optimized Code}.
1831 Older versions of the @sc{gnu} C compiler permitted a variant option
1832 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1833 format; if your @sc{gnu} C compiler has this option, do not use it.
1835 @value{GDBN} knows about preprocessor macros and can show you their
1836 expansion (@pxref{Macros}). Most compilers do not include information
1837 about preprocessor macros in the debugging information if you specify
1838 the @option{-g} flag alone, because this information is rather large.
1839 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1840 provides macro information if you specify the options
1841 @option{-gdwarf-2} and @option{-g3}; the former option requests
1842 debugging information in the Dwarf 2 format, and the latter requests
1843 ``extra information''. In the future, we hope to find more compact
1844 ways to represent macro information, so that it can be included with
1849 @section Starting your Program
1855 @kindex r @r{(@code{run})}
1858 Use the @code{run} command to start your program under @value{GDBN}.
1859 You must first specify the program name (except on VxWorks) with an
1860 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1861 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1862 (@pxref{Files, ,Commands to Specify Files}).
1866 If you are running your program in an execution environment that
1867 supports processes, @code{run} creates an inferior process and makes
1868 that process run your program. In some environments without processes,
1869 @code{run} jumps to the start of your program. Other targets,
1870 like @samp{remote}, are always running. If you get an error
1871 message like this one:
1874 The "remote" target does not support "run".
1875 Try "help target" or "continue".
1879 then use @code{continue} to run your program. You may need @code{load}
1880 first (@pxref{load}).
1882 The execution of a program is affected by certain information it
1883 receives from its superior. @value{GDBN} provides ways to specify this
1884 information, which you must do @emph{before} starting your program. (You
1885 can change it after starting your program, but such changes only affect
1886 your program the next time you start it.) This information may be
1887 divided into four categories:
1890 @item The @emph{arguments.}
1891 Specify the arguments to give your program as the arguments of the
1892 @code{run} command. If a shell is available on your target, the shell
1893 is used to pass the arguments, so that you may use normal conventions
1894 (such as wildcard expansion or variable substitution) in describing
1896 In Unix systems, you can control which shell is used with the
1897 @code{SHELL} environment variable.
1898 @xref{Arguments, ,Your Program's Arguments}.
1900 @item The @emph{environment.}
1901 Your program normally inherits its environment from @value{GDBN}, but you can
1902 use the @value{GDBN} commands @code{set environment} and @code{unset
1903 environment} to change parts of the environment that affect
1904 your program. @xref{Environment, ,Your Program's Environment}.
1906 @item The @emph{working directory.}
1907 Your program inherits its working directory from @value{GDBN}. You can set
1908 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1909 @xref{Working Directory, ,Your Program's Working Directory}.
1911 @item The @emph{standard input and output.}
1912 Your program normally uses the same device for standard input and
1913 standard output as @value{GDBN} is using. You can redirect input and output
1914 in the @code{run} command line, or you can use the @code{tty} command to
1915 set a different device for your program.
1916 @xref{Input/Output, ,Your Program's Input and Output}.
1919 @emph{Warning:} While input and output redirection work, you cannot use
1920 pipes to pass the output of the program you are debugging to another
1921 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1925 When you issue the @code{run} command, your program begins to execute
1926 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1927 of how to arrange for your program to stop. Once your program has
1928 stopped, you may call functions in your program, using the @code{print}
1929 or @code{call} commands. @xref{Data, ,Examining Data}.
1931 If the modification time of your symbol file has changed since the last
1932 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1933 table, and reads it again. When it does this, @value{GDBN} tries to retain
1934 your current breakpoints.
1939 @cindex run to main procedure
1940 The name of the main procedure can vary from language to language.
1941 With C or C@t{++}, the main procedure name is always @code{main}, but
1942 other languages such as Ada do not require a specific name for their
1943 main procedure. The debugger provides a convenient way to start the
1944 execution of the program and to stop at the beginning of the main
1945 procedure, depending on the language used.
1947 The @samp{start} command does the equivalent of setting a temporary
1948 breakpoint at the beginning of the main procedure and then invoking
1949 the @samp{run} command.
1951 @cindex elaboration phase
1952 Some programs contain an @dfn{elaboration} phase where some startup code is
1953 executed before the main procedure is called. This depends on the
1954 languages used to write your program. In C@t{++}, for instance,
1955 constructors for static and global objects are executed before
1956 @code{main} is called. It is therefore possible that the debugger stops
1957 before reaching the main procedure. However, the temporary breakpoint
1958 will remain to halt execution.
1960 Specify the arguments to give to your program as arguments to the
1961 @samp{start} command. These arguments will be given verbatim to the
1962 underlying @samp{run} command. Note that the same arguments will be
1963 reused if no argument is provided during subsequent calls to
1964 @samp{start} or @samp{run}.
1966 It is sometimes necessary to debug the program during elaboration. In
1967 these cases, using the @code{start} command would stop the execution of
1968 your program too late, as the program would have already completed the
1969 elaboration phase. Under these circumstances, insert breakpoints in your
1970 elaboration code before running your program.
1972 @kindex set exec-wrapper
1973 @item set exec-wrapper @var{wrapper}
1974 @itemx show exec-wrapper
1975 @itemx unset exec-wrapper
1976 When @samp{exec-wrapper} is set, the specified wrapper is used to
1977 launch programs for debugging. @value{GDBN} starts your program
1978 with a shell command of the form @kbd{exec @var{wrapper}
1979 @var{program}}. Quoting is added to @var{program} and its
1980 arguments, but not to @var{wrapper}, so you should add quotes if
1981 appropriate for your shell. The wrapper runs until it executes
1982 your program, and then @value{GDBN} takes control.
1984 You can use any program that eventually calls @code{execve} with
1985 its arguments as a wrapper. Several standard Unix utilities do
1986 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1987 with @code{exec "$@@"} will also work.
1989 For example, you can use @code{env} to pass an environment variable to
1990 the debugged program, without setting the variable in your shell's
1994 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1998 This command is available when debugging locally on most targets, excluding
1999 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2001 @kindex set disable-randomization
2002 @item set disable-randomization
2003 @itemx set disable-randomization on
2004 This option (enabled by default in @value{GDBN}) will turn off the native
2005 randomization of the virtual address space of the started program. This option
2006 is useful for multiple debugging sessions to make the execution better
2007 reproducible and memory addresses reusable across debugging sessions.
2009 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2013 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2016 @item set disable-randomization off
2017 Leave the behavior of the started executable unchanged. Some bugs rear their
2018 ugly heads only when the program is loaded at certain addresses. If your bug
2019 disappears when you run the program under @value{GDBN}, that might be because
2020 @value{GDBN} by default disables the address randomization on platforms, such
2021 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2022 disable-randomization off} to try to reproduce such elusive bugs.
2024 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2025 It protects the programs against some kinds of security attacks. In these
2026 cases the attacker needs to know the exact location of a concrete executable
2027 code. Randomizing its location makes it impossible to inject jumps misusing
2028 a code at its expected addresses.
2030 Prelinking shared libraries provides a startup performance advantage but it
2031 makes addresses in these libraries predictable for privileged processes by
2032 having just unprivileged access at the target system. Reading the shared
2033 library binary gives enough information for assembling the malicious code
2034 misusing it. Still even a prelinked shared library can get loaded at a new
2035 random address just requiring the regular relocation process during the
2036 startup. Shared libraries not already prelinked are always loaded at
2037 a randomly chosen address.
2039 Position independent executables (PIE) contain position independent code
2040 similar to the shared libraries and therefore such executables get loaded at
2041 a randomly chosen address upon startup. PIE executables always load even
2042 already prelinked shared libraries at a random address. You can build such
2043 executable using @command{gcc -fPIE -pie}.
2045 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2046 (as long as the randomization is enabled).
2048 @item show disable-randomization
2049 Show the current setting of the explicit disable of the native randomization of
2050 the virtual address space of the started program.
2055 @section Your Program's Arguments
2057 @cindex arguments (to your program)
2058 The arguments to your program can be specified by the arguments of the
2060 They are passed to a shell, which expands wildcard characters and
2061 performs redirection of I/O, and thence to your program. Your
2062 @code{SHELL} environment variable (if it exists) specifies what shell
2063 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2064 the default shell (@file{/bin/sh} on Unix).
2066 On non-Unix systems, the program is usually invoked directly by
2067 @value{GDBN}, which emulates I/O redirection via the appropriate system
2068 calls, and the wildcard characters are expanded by the startup code of
2069 the program, not by the shell.
2071 @code{run} with no arguments uses the same arguments used by the previous
2072 @code{run}, or those set by the @code{set args} command.
2077 Specify the arguments to be used the next time your program is run. If
2078 @code{set args} has no arguments, @code{run} executes your program
2079 with no arguments. Once you have run your program with arguments,
2080 using @code{set args} before the next @code{run} is the only way to run
2081 it again without arguments.
2085 Show the arguments to give your program when it is started.
2089 @section Your Program's Environment
2091 @cindex environment (of your program)
2092 The @dfn{environment} consists of a set of environment variables and
2093 their values. Environment variables conventionally record such things as
2094 your user name, your home directory, your terminal type, and your search
2095 path for programs to run. Usually you set up environment variables with
2096 the shell and they are inherited by all the other programs you run. When
2097 debugging, it can be useful to try running your program with a modified
2098 environment without having to start @value{GDBN} over again.
2102 @item path @var{directory}
2103 Add @var{directory} to the front of the @code{PATH} environment variable
2104 (the search path for executables) that will be passed to your program.
2105 The value of @code{PATH} used by @value{GDBN} does not change.
2106 You may specify several directory names, separated by whitespace or by a
2107 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2108 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2109 is moved to the front, so it is searched sooner.
2111 You can use the string @samp{$cwd} to refer to whatever is the current
2112 working directory at the time @value{GDBN} searches the path. If you
2113 use @samp{.} instead, it refers to the directory where you executed the
2114 @code{path} command. @value{GDBN} replaces @samp{.} in the
2115 @var{directory} argument (with the current path) before adding
2116 @var{directory} to the search path.
2117 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2118 @c document that, since repeating it would be a no-op.
2122 Display the list of search paths for executables (the @code{PATH}
2123 environment variable).
2125 @kindex show environment
2126 @item show environment @r{[}@var{varname}@r{]}
2127 Print the value of environment variable @var{varname} to be given to
2128 your program when it starts. If you do not supply @var{varname},
2129 print the names and values of all environment variables to be given to
2130 your program. You can abbreviate @code{environment} as @code{env}.
2132 @kindex set environment
2133 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2134 Set environment variable @var{varname} to @var{value}. The value
2135 changes for your program only, not for @value{GDBN} itself. @var{value} may
2136 be any string; the values of environment variables are just strings, and
2137 any interpretation is supplied by your program itself. The @var{value}
2138 parameter is optional; if it is eliminated, the variable is set to a
2140 @c "any string" here does not include leading, trailing
2141 @c blanks. Gnu asks: does anyone care?
2143 For example, this command:
2150 tells the debugged program, when subsequently run, that its user is named
2151 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2152 are not actually required.)
2154 @kindex unset environment
2155 @item unset environment @var{varname}
2156 Remove variable @var{varname} from the environment to be passed to your
2157 program. This is different from @samp{set env @var{varname} =};
2158 @code{unset environment} removes the variable from the environment,
2159 rather than assigning it an empty value.
2162 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2164 by your @code{SHELL} environment variable if it exists (or
2165 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2166 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2167 @file{.bashrc} for BASH---any variables you set in that file affect
2168 your program. You may wish to move setting of environment variables to
2169 files that are only run when you sign on, such as @file{.login} or
2172 @node Working Directory
2173 @section Your Program's Working Directory
2175 @cindex working directory (of your program)
2176 Each time you start your program with @code{run}, it inherits its
2177 working directory from the current working directory of @value{GDBN}.
2178 The @value{GDBN} working directory is initially whatever it inherited
2179 from its parent process (typically the shell), but you can specify a new
2180 working directory in @value{GDBN} with the @code{cd} command.
2182 The @value{GDBN} working directory also serves as a default for the commands
2183 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2188 @cindex change working directory
2189 @item cd @var{directory}
2190 Set the @value{GDBN} working directory to @var{directory}.
2194 Print the @value{GDBN} working directory.
2197 It is generally impossible to find the current working directory of
2198 the process being debugged (since a program can change its directory
2199 during its run). If you work on a system where @value{GDBN} is
2200 configured with the @file{/proc} support, you can use the @code{info
2201 proc} command (@pxref{SVR4 Process Information}) to find out the
2202 current working directory of the debuggee.
2205 @section Your Program's Input and Output
2210 By default, the program you run under @value{GDBN} does input and output to
2211 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2212 to its own terminal modes to interact with you, but it records the terminal
2213 modes your program was using and switches back to them when you continue
2214 running your program.
2217 @kindex info terminal
2219 Displays information recorded by @value{GDBN} about the terminal modes your
2223 You can redirect your program's input and/or output using shell
2224 redirection with the @code{run} command. For example,
2231 starts your program, diverting its output to the file @file{outfile}.
2234 @cindex controlling terminal
2235 Another way to specify where your program should do input and output is
2236 with the @code{tty} command. This command accepts a file name as
2237 argument, and causes this file to be the default for future @code{run}
2238 commands. It also resets the controlling terminal for the child
2239 process, for future @code{run} commands. For example,
2246 directs that processes started with subsequent @code{run} commands
2247 default to do input and output on the terminal @file{/dev/ttyb} and have
2248 that as their controlling terminal.
2250 An explicit redirection in @code{run} overrides the @code{tty} command's
2251 effect on the input/output device, but not its effect on the controlling
2254 When you use the @code{tty} command or redirect input in the @code{run}
2255 command, only the input @emph{for your program} is affected. The input
2256 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2257 for @code{set inferior-tty}.
2259 @cindex inferior tty
2260 @cindex set inferior controlling terminal
2261 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2262 display the name of the terminal that will be used for future runs of your
2266 @item set inferior-tty /dev/ttyb
2267 @kindex set inferior-tty
2268 Set the tty for the program being debugged to /dev/ttyb.
2270 @item show inferior-tty
2271 @kindex show inferior-tty
2272 Show the current tty for the program being debugged.
2276 @section Debugging an Already-running Process
2281 @item attach @var{process-id}
2282 This command attaches to a running process---one that was started
2283 outside @value{GDBN}. (@code{info files} shows your active
2284 targets.) The command takes as argument a process ID. The usual way to
2285 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2286 or with the @samp{jobs -l} shell command.
2288 @code{attach} does not repeat if you press @key{RET} a second time after
2289 executing the command.
2292 To use @code{attach}, your program must be running in an environment
2293 which supports processes; for example, @code{attach} does not work for
2294 programs on bare-board targets that lack an operating system. You must
2295 also have permission to send the process a signal.
2297 When you use @code{attach}, the debugger finds the program running in
2298 the process first by looking in the current working directory, then (if
2299 the program is not found) by using the source file search path
2300 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2301 the @code{file} command to load the program. @xref{Files, ,Commands to
2304 The first thing @value{GDBN} does after arranging to debug the specified
2305 process is to stop it. You can examine and modify an attached process
2306 with all the @value{GDBN} commands that are ordinarily available when
2307 you start processes with @code{run}. You can insert breakpoints; you
2308 can step and continue; you can modify storage. If you would rather the
2309 process continue running, you may use the @code{continue} command after
2310 attaching @value{GDBN} to the process.
2315 When you have finished debugging the attached process, you can use the
2316 @code{detach} command to release it from @value{GDBN} control. Detaching
2317 the process continues its execution. After the @code{detach} command,
2318 that process and @value{GDBN} become completely independent once more, and you
2319 are ready to @code{attach} another process or start one with @code{run}.
2320 @code{detach} does not repeat if you press @key{RET} again after
2321 executing the command.
2324 If you exit @value{GDBN} while you have an attached process, you detach
2325 that process. If you use the @code{run} command, you kill that process.
2326 By default, @value{GDBN} asks for confirmation if you try to do either of these
2327 things; you can control whether or not you need to confirm by using the
2328 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2332 @section Killing the Child Process
2337 Kill the child process in which your program is running under @value{GDBN}.
2340 This command is useful if you wish to debug a core dump instead of a
2341 running process. @value{GDBN} ignores any core dump file while your program
2344 On some operating systems, a program cannot be executed outside @value{GDBN}
2345 while you have breakpoints set on it inside @value{GDBN}. You can use the
2346 @code{kill} command in this situation to permit running your program
2347 outside the debugger.
2349 The @code{kill} command is also useful if you wish to recompile and
2350 relink your program, since on many systems it is impossible to modify an
2351 executable file while it is running in a process. In this case, when you
2352 next type @code{run}, @value{GDBN} notices that the file has changed, and
2353 reads the symbol table again (while trying to preserve your current
2354 breakpoint settings).
2356 @node Inferiors and Programs
2357 @section Debugging Multiple Inferiors and Programs
2359 @value{GDBN} lets you run and debug multiple programs in a single
2360 session. In addition, @value{GDBN} on some systems may let you run
2361 several programs simultaneously (otherwise you have to exit from one
2362 before starting another). In the most general case, you can have
2363 multiple threads of execution in each of multiple processes, launched
2364 from multiple executables.
2367 @value{GDBN} represents the state of each program execution with an
2368 object called an @dfn{inferior}. An inferior typically corresponds to
2369 a process, but is more general and applies also to targets that do not
2370 have processes. Inferiors may be created before a process runs, and
2371 may be retained after a process exits. Inferiors have unique
2372 identifiers that are different from process ids. Usually each
2373 inferior will also have its own distinct address space, although some
2374 embedded targets may have several inferiors running in different parts
2375 of a single address space. Each inferior may in turn have multiple
2376 threads running in it.
2378 To find out what inferiors exist at any moment, use @w{@code{info
2382 @kindex info inferiors
2383 @item info inferiors
2384 Print a list of all inferiors currently being managed by @value{GDBN}.
2386 @value{GDBN} displays for each inferior (in this order):
2390 the inferior number assigned by @value{GDBN}
2393 the target system's inferior identifier
2396 the name of the executable the inferior is running.
2401 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2402 indicates the current inferior.
2406 @c end table here to get a little more width for example
2409 (@value{GDBP}) info inferiors
2410 Num Description Executable
2411 2 process 2307 hello
2412 * 1 process 3401 goodbye
2415 To switch focus between inferiors, use the @code{inferior} command:
2418 @kindex inferior @var{infno}
2419 @item inferior @var{infno}
2420 Make inferior number @var{infno} the current inferior. The argument
2421 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2422 in the first field of the @samp{info inferiors} display.
2426 You can get multiple executables into a debugging session via the
2427 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2428 systems @value{GDBN} can add inferiors to the debug session
2429 automatically by following calls to @code{fork} and @code{exec}. To
2430 remove inferiors from the debugging session use the
2431 @w{@code{remove-inferior}} command.
2434 @kindex add-inferior
2435 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2436 Adds @var{n} inferiors to be run using @var{executable} as the
2437 executable. @var{n} defaults to 1. If no executable is specified,
2438 the inferiors begins empty, with no program. You can still assign or
2439 change the program assigned to the inferior at any time by using the
2440 @code{file} command with the executable name as its argument.
2442 @kindex clone-inferior
2443 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2444 Adds @var{n} inferiors ready to execute the same program as inferior
2445 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2446 number of the current inferior. This is a convenient command when you
2447 want to run another instance of the inferior you are debugging.
2450 (@value{GDBP}) info inferiors
2451 Num Description Executable
2452 * 1 process 29964 helloworld
2453 (@value{GDBP}) clone-inferior
2456 (@value{GDBP}) info inferiors
2457 Num Description Executable
2459 * 1 process 29964 helloworld
2462 You can now simply switch focus to inferior 2 and run it.
2464 @kindex remove-inferior
2465 @item remove-inferior @var{infno}
2466 Removes the inferior @var{infno}. It is not possible to remove an
2467 inferior that is running with this command. For those, use the
2468 @code{kill} or @code{detach} command first.
2472 To quit debugging one of the running inferiors that is not the current
2473 inferior, you can either detach from it by using the @w{@code{detach
2474 inferior}} command (allowing it to run independently), or kill it
2475 using the @w{@code{kill inferior}} command:
2478 @kindex detach inferior @var{infno}
2479 @item detach inferior @var{infno}
2480 Detach from the inferior identified by @value{GDBN} inferior number
2481 @var{infno}, and remove it from the inferior list.
2483 @kindex kill inferior @var{infno}
2484 @item kill inferior @var{infno}
2485 Kill the inferior identified by @value{GDBN} inferior number
2486 @var{infno}, and remove it from the inferior list.
2489 After the successful completion of a command such as @code{detach},
2490 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2491 a normal process exit, the inferior is still valid and listed with
2492 @code{info inferiors}, ready to be restarted.
2495 To be notified when inferiors are started or exit under @value{GDBN}'s
2496 control use @w{@code{set print inferior-events}}:
2499 @kindex set print inferior-events
2500 @cindex print messages on inferior start and exit
2501 @item set print inferior-events
2502 @itemx set print inferior-events on
2503 @itemx set print inferior-events off
2504 The @code{set print inferior-events} command allows you to enable or
2505 disable printing of messages when @value{GDBN} notices that new
2506 inferiors have started or that inferiors have exited or have been
2507 detached. By default, these messages will not be printed.
2509 @kindex show print inferior-events
2510 @item show print inferior-events
2511 Show whether messages will be printed when @value{GDBN} detects that
2512 inferiors have started, exited or have been detached.
2515 Many commands will work the same with multiple programs as with a
2516 single program: e.g., @code{print myglobal} will simply display the
2517 value of @code{myglobal} in the current inferior.
2520 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2521 get more info about the relationship of inferiors, programs, address
2522 spaces in a debug session. You can do that with the @w{@code{maint
2523 info program-spaces}} command.
2526 @kindex maint info program-spaces
2527 @item maint info program-spaces
2528 Print a list of all program spaces currently being managed by
2531 @value{GDBN} displays for each program space (in this order):
2535 the program space number assigned by @value{GDBN}
2538 the name of the executable loaded into the program space, with e.g.,
2539 the @code{file} command.
2544 An asterisk @samp{*} preceding the @value{GDBN} program space number
2545 indicates the current program space.
2547 In addition, below each program space line, @value{GDBN} prints extra
2548 information that isn't suitable to display in tabular form. For
2549 example, the list of inferiors bound to the program space.
2552 (@value{GDBP}) maint info program-spaces
2555 Bound inferiors: ID 1 (process 21561)
2559 Here we can see that no inferior is running the program @code{hello},
2560 while @code{process 21561} is running the program @code{goodbye}. On
2561 some targets, it is possible that multiple inferiors are bound to the
2562 same program space. The most common example is that of debugging both
2563 the parent and child processes of a @code{vfork} call. For example,
2566 (@value{GDBP}) maint info program-spaces
2569 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2572 Here, both inferior 2 and inferior 1 are running in the same program
2573 space as a result of inferior 1 having executed a @code{vfork} call.
2577 @section Debugging Programs with Multiple Threads
2579 @cindex threads of execution
2580 @cindex multiple threads
2581 @cindex switching threads
2582 In some operating systems, such as HP-UX and Solaris, a single program
2583 may have more than one @dfn{thread} of execution. The precise semantics
2584 of threads differ from one operating system to another, but in general
2585 the threads of a single program are akin to multiple processes---except
2586 that they share one address space (that is, they can all examine and
2587 modify the same variables). On the other hand, each thread has its own
2588 registers and execution stack, and perhaps private memory.
2590 @value{GDBN} provides these facilities for debugging multi-thread
2594 @item automatic notification of new threads
2595 @item @samp{thread @var{threadno}}, a command to switch among threads
2596 @item @samp{info threads}, a command to inquire about existing threads
2597 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2598 a command to apply a command to a list of threads
2599 @item thread-specific breakpoints
2600 @item @samp{set print thread-events}, which controls printing of
2601 messages on thread start and exit.
2602 @item @samp{set libthread-db-search-path @var{path}}, which lets
2603 the user specify which @code{libthread_db} to use if the default choice
2604 isn't compatible with the program.
2608 @emph{Warning:} These facilities are not yet available on every
2609 @value{GDBN} configuration where the operating system supports threads.
2610 If your @value{GDBN} does not support threads, these commands have no
2611 effect. For example, a system without thread support shows no output
2612 from @samp{info threads}, and always rejects the @code{thread} command,
2616 (@value{GDBP}) info threads
2617 (@value{GDBP}) thread 1
2618 Thread ID 1 not known. Use the "info threads" command to
2619 see the IDs of currently known threads.
2621 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2622 @c doesn't support threads"?
2625 @cindex focus of debugging
2626 @cindex current thread
2627 The @value{GDBN} thread debugging facility allows you to observe all
2628 threads while your program runs---but whenever @value{GDBN} takes
2629 control, one thread in particular is always the focus of debugging.
2630 This thread is called the @dfn{current thread}. Debugging commands show
2631 program information from the perspective of the current thread.
2633 @cindex @code{New} @var{systag} message
2634 @cindex thread identifier (system)
2635 @c FIXME-implementors!! It would be more helpful if the [New...] message
2636 @c included GDB's numeric thread handle, so you could just go to that
2637 @c thread without first checking `info threads'.
2638 Whenever @value{GDBN} detects a new thread in your program, it displays
2639 the target system's identification for the thread with a message in the
2640 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2641 whose form varies depending on the particular system. For example, on
2642 @sc{gnu}/Linux, you might see
2645 [New Thread 46912507313328 (LWP 25582)]
2649 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2650 the @var{systag} is simply something like @samp{process 368}, with no
2653 @c FIXME!! (1) Does the [New...] message appear even for the very first
2654 @c thread of a program, or does it only appear for the
2655 @c second---i.e.@: when it becomes obvious we have a multithread
2657 @c (2) *Is* there necessarily a first thread always? Or do some
2658 @c multithread systems permit starting a program with multiple
2659 @c threads ab initio?
2661 @cindex thread number
2662 @cindex thread identifier (GDB)
2663 For debugging purposes, @value{GDBN} associates its own thread
2664 number---always a single integer---with each thread in your program.
2667 @kindex info threads
2669 Display a summary of all threads currently in your
2670 program. @value{GDBN} displays for each thread (in this order):
2674 the thread number assigned by @value{GDBN}
2677 the target system's thread identifier (@var{systag})
2680 the current stack frame summary for that thread
2684 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2685 indicates the current thread.
2689 @c end table here to get a little more width for example
2692 (@value{GDBP}) info threads
2693 3 process 35 thread 27 0x34e5 in sigpause ()
2694 2 process 35 thread 23 0x34e5 in sigpause ()
2695 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2701 @cindex debugging multithreaded programs (on HP-UX)
2702 @cindex thread identifier (GDB), on HP-UX
2703 For debugging purposes, @value{GDBN} associates its own thread
2704 number---a small integer assigned in thread-creation order---with each
2705 thread in your program.
2707 @cindex @code{New} @var{systag} message, on HP-UX
2708 @cindex thread identifier (system), on HP-UX
2709 @c FIXME-implementors!! It would be more helpful if the [New...] message
2710 @c included GDB's numeric thread handle, so you could just go to that
2711 @c thread without first checking `info threads'.
2712 Whenever @value{GDBN} detects a new thread in your program, it displays
2713 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2714 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2715 whose form varies depending on the particular system. For example, on
2719 [New thread 2 (system thread 26594)]
2723 when @value{GDBN} notices a new thread.
2726 @kindex info threads (HP-UX)
2728 Display a summary of all threads currently in your
2729 program. @value{GDBN} displays for each thread (in this order):
2732 @item the thread number assigned by @value{GDBN}
2734 @item the target system's thread identifier (@var{systag})
2736 @item the current stack frame summary for that thread
2740 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2741 indicates the current thread.
2745 @c end table here to get a little more width for example
2748 (@value{GDBP}) info threads
2749 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2751 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2752 from /usr/lib/libc.2
2753 1 system thread 27905 0x7b003498 in _brk () \@*
2754 from /usr/lib/libc.2
2757 On Solaris, you can display more information about user threads with a
2758 Solaris-specific command:
2761 @item maint info sol-threads
2762 @kindex maint info sol-threads
2763 @cindex thread info (Solaris)
2764 Display info on Solaris user threads.
2768 @kindex thread @var{threadno}
2769 @item thread @var{threadno}
2770 Make thread number @var{threadno} the current thread. The command
2771 argument @var{threadno} is the internal @value{GDBN} thread number, as
2772 shown in the first field of the @samp{info threads} display.
2773 @value{GDBN} responds by displaying the system identifier of the thread
2774 you selected, and its current stack frame summary:
2777 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2778 (@value{GDBP}) thread 2
2779 [Switching to process 35 thread 23]
2780 0x34e5 in sigpause ()
2784 As with the @samp{[New @dots{}]} message, the form of the text after
2785 @samp{Switching to} depends on your system's conventions for identifying
2788 @kindex thread apply
2789 @cindex apply command to several threads
2790 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2791 The @code{thread apply} command allows you to apply the named
2792 @var{command} to one or more threads. Specify the numbers of the
2793 threads that you want affected with the command argument
2794 @var{threadno}. It can be a single thread number, one of the numbers
2795 shown in the first field of the @samp{info threads} display; or it
2796 could be a range of thread numbers, as in @code{2-4}. To apply a
2797 command to all threads, type @kbd{thread apply all @var{command}}.
2799 @kindex set print thread-events
2800 @cindex print messages on thread start and exit
2801 @item set print thread-events
2802 @itemx set print thread-events on
2803 @itemx set print thread-events off
2804 The @code{set print thread-events} command allows you to enable or
2805 disable printing of messages when @value{GDBN} notices that new threads have
2806 started or that threads have exited. By default, these messages will
2807 be printed if detection of these events is supported by the target.
2808 Note that these messages cannot be disabled on all targets.
2810 @kindex show print thread-events
2811 @item show print thread-events
2812 Show whether messages will be printed when @value{GDBN} detects that threads
2813 have started and exited.
2816 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2817 more information about how @value{GDBN} behaves when you stop and start
2818 programs with multiple threads.
2820 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2821 watchpoints in programs with multiple threads.
2824 @kindex set libthread-db-search-path
2825 @cindex search path for @code{libthread_db}
2826 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2827 If this variable is set, @var{path} is a colon-separated list of
2828 directories @value{GDBN} will use to search for @code{libthread_db}.
2829 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2832 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2833 @code{libthread_db} library to obtain information about threads in the
2834 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2835 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2836 with default system shared library directories, and finally the directory
2837 from which @code{libpthread} was loaded in the inferior process.
2839 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2840 @value{GDBN} attempts to initialize it with the current inferior process.
2841 If this initialization fails (which could happen because of a version
2842 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2843 will unload @code{libthread_db}, and continue with the next directory.
2844 If none of @code{libthread_db} libraries initialize successfully,
2845 @value{GDBN} will issue a warning and thread debugging will be disabled.
2847 Setting @code{libthread-db-search-path} is currently implemented
2848 only on some platforms.
2850 @kindex show libthread-db-search-path
2851 @item show libthread-db-search-path
2852 Display current libthread_db search path.
2856 @section Debugging Forks
2858 @cindex fork, debugging programs which call
2859 @cindex multiple processes
2860 @cindex processes, multiple
2861 On most systems, @value{GDBN} has no special support for debugging
2862 programs which create additional processes using the @code{fork}
2863 function. When a program forks, @value{GDBN} will continue to debug the
2864 parent process and the child process will run unimpeded. If you have
2865 set a breakpoint in any code which the child then executes, the child
2866 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2867 will cause it to terminate.
2869 However, if you want to debug the child process there is a workaround
2870 which isn't too painful. Put a call to @code{sleep} in the code which
2871 the child process executes after the fork. It may be useful to sleep
2872 only if a certain environment variable is set, or a certain file exists,
2873 so that the delay need not occur when you don't want to run @value{GDBN}
2874 on the child. While the child is sleeping, use the @code{ps} program to
2875 get its process ID. Then tell @value{GDBN} (a new invocation of
2876 @value{GDBN} if you are also debugging the parent process) to attach to
2877 the child process (@pxref{Attach}). From that point on you can debug
2878 the child process just like any other process which you attached to.
2880 On some systems, @value{GDBN} provides support for debugging programs that
2881 create additional processes using the @code{fork} or @code{vfork} functions.
2882 Currently, the only platforms with this feature are HP-UX (11.x and later
2883 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2885 By default, when a program forks, @value{GDBN} will continue to debug
2886 the parent process and the child process will run unimpeded.
2888 If you want to follow the child process instead of the parent process,
2889 use the command @w{@code{set follow-fork-mode}}.
2892 @kindex set follow-fork-mode
2893 @item set follow-fork-mode @var{mode}
2894 Set the debugger response to a program call of @code{fork} or
2895 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2896 process. The @var{mode} argument can be:
2900 The original process is debugged after a fork. The child process runs
2901 unimpeded. This is the default.
2904 The new process is debugged after a fork. The parent process runs
2909 @kindex show follow-fork-mode
2910 @item show follow-fork-mode
2911 Display the current debugger response to a @code{fork} or @code{vfork} call.
2914 @cindex debugging multiple processes
2915 On Linux, if you want to debug both the parent and child processes, use the
2916 command @w{@code{set detach-on-fork}}.
2919 @kindex set detach-on-fork
2920 @item set detach-on-fork @var{mode}
2921 Tells gdb whether to detach one of the processes after a fork, or
2922 retain debugger control over them both.
2926 The child process (or parent process, depending on the value of
2927 @code{follow-fork-mode}) will be detached and allowed to run
2928 independently. This is the default.
2931 Both processes will be held under the control of @value{GDBN}.
2932 One process (child or parent, depending on the value of
2933 @code{follow-fork-mode}) is debugged as usual, while the other
2938 @kindex show detach-on-fork
2939 @item show detach-on-fork
2940 Show whether detach-on-fork mode is on/off.
2943 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2944 will retain control of all forked processes (including nested forks).
2945 You can list the forked processes under the control of @value{GDBN} by
2946 using the @w{@code{info inferiors}} command, and switch from one fork
2947 to another by using the @code{inferior} command (@pxref{Inferiors and
2948 Programs, ,Debugging Multiple Inferiors and Programs}).
2950 To quit debugging one of the forked processes, you can either detach
2951 from it by using the @w{@code{detach inferior}} command (allowing it
2952 to run independently), or kill it using the @w{@code{kill inferior}}
2953 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2956 If you ask to debug a child process and a @code{vfork} is followed by an
2957 @code{exec}, @value{GDBN} executes the new target up to the first
2958 breakpoint in the new target. If you have a breakpoint set on
2959 @code{main} in your original program, the breakpoint will also be set on
2960 the child process's @code{main}.
2962 On some systems, when a child process is spawned by @code{vfork}, you
2963 cannot debug the child or parent until an @code{exec} call completes.
2965 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2966 call executes, the new target restarts. To restart the parent
2967 process, use the @code{file} command with the parent executable name
2968 as its argument. By default, after an @code{exec} call executes,
2969 @value{GDBN} discards the symbols of the previous executable image.
2970 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2974 @kindex set follow-exec-mode
2975 @item set follow-exec-mode @var{mode}
2977 Set debugger response to a program call of @code{exec}. An
2978 @code{exec} call replaces the program image of a process.
2980 @code{follow-exec-mode} can be:
2984 @value{GDBN} creates a new inferior and rebinds the process to this
2985 new inferior. The program the process was running before the
2986 @code{exec} call can be restarted afterwards by restarting the
2992 (@value{GDBP}) info inferiors
2994 Id Description Executable
2997 process 12020 is executing new program: prog2
2998 Program exited normally.
2999 (@value{GDBP}) info inferiors
3000 Id Description Executable
3006 @value{GDBN} keeps the process bound to the same inferior. The new
3007 executable image replaces the previous executable loaded in the
3008 inferior. Restarting the inferior after the @code{exec} call, with
3009 e.g., the @code{run} command, restarts the executable the process was
3010 running after the @code{exec} call. This is the default mode.
3015 (@value{GDBP}) info inferiors
3016 Id Description Executable
3019 process 12020 is executing new program: prog2
3020 Program exited normally.
3021 (@value{GDBP}) info inferiors
3022 Id Description Executable
3029 You can use the @code{catch} command to make @value{GDBN} stop whenever
3030 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3031 Catchpoints, ,Setting Catchpoints}.
3033 @node Checkpoint/Restart
3034 @section Setting a @emph{Bookmark} to Return to Later
3039 @cindex snapshot of a process
3040 @cindex rewind program state
3042 On certain operating systems@footnote{Currently, only
3043 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3044 program's state, called a @dfn{checkpoint}, and come back to it
3047 Returning to a checkpoint effectively undoes everything that has
3048 happened in the program since the @code{checkpoint} was saved. This
3049 includes changes in memory, registers, and even (within some limits)
3050 system state. Effectively, it is like going back in time to the
3051 moment when the checkpoint was saved.
3053 Thus, if you're stepping thru a program and you think you're
3054 getting close to the point where things go wrong, you can save
3055 a checkpoint. Then, if you accidentally go too far and miss
3056 the critical statement, instead of having to restart your program
3057 from the beginning, you can just go back to the checkpoint and
3058 start again from there.
3060 This can be especially useful if it takes a lot of time or
3061 steps to reach the point where you think the bug occurs.
3063 To use the @code{checkpoint}/@code{restart} method of debugging:
3068 Save a snapshot of the debugged program's current execution state.
3069 The @code{checkpoint} command takes no arguments, but each checkpoint
3070 is assigned a small integer id, similar to a breakpoint id.
3072 @kindex info checkpoints
3073 @item info checkpoints
3074 List the checkpoints that have been saved in the current debugging
3075 session. For each checkpoint, the following information will be
3082 @item Source line, or label
3085 @kindex restart @var{checkpoint-id}
3086 @item restart @var{checkpoint-id}
3087 Restore the program state that was saved as checkpoint number
3088 @var{checkpoint-id}. All program variables, registers, stack frames
3089 etc.@: will be returned to the values that they had when the checkpoint
3090 was saved. In essence, gdb will ``wind back the clock'' to the point
3091 in time when the checkpoint was saved.
3093 Note that breakpoints, @value{GDBN} variables, command history etc.
3094 are not affected by restoring a checkpoint. In general, a checkpoint
3095 only restores things that reside in the program being debugged, not in
3098 @kindex delete checkpoint @var{checkpoint-id}
3099 @item delete checkpoint @var{checkpoint-id}
3100 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3104 Returning to a previously saved checkpoint will restore the user state
3105 of the program being debugged, plus a significant subset of the system
3106 (OS) state, including file pointers. It won't ``un-write'' data from
3107 a file, but it will rewind the file pointer to the previous location,
3108 so that the previously written data can be overwritten. For files
3109 opened in read mode, the pointer will also be restored so that the
3110 previously read data can be read again.
3112 Of course, characters that have been sent to a printer (or other
3113 external device) cannot be ``snatched back'', and characters received
3114 from eg.@: a serial device can be removed from internal program buffers,
3115 but they cannot be ``pushed back'' into the serial pipeline, ready to
3116 be received again. Similarly, the actual contents of files that have
3117 been changed cannot be restored (at this time).
3119 However, within those constraints, you actually can ``rewind'' your
3120 program to a previously saved point in time, and begin debugging it
3121 again --- and you can change the course of events so as to debug a
3122 different execution path this time.
3124 @cindex checkpoints and process id
3125 Finally, there is one bit of internal program state that will be
3126 different when you return to a checkpoint --- the program's process
3127 id. Each checkpoint will have a unique process id (or @var{pid}),
3128 and each will be different from the program's original @var{pid}.
3129 If your program has saved a local copy of its process id, this could
3130 potentially pose a problem.
3132 @subsection A Non-obvious Benefit of Using Checkpoints
3134 On some systems such as @sc{gnu}/Linux, address space randomization
3135 is performed on new processes for security reasons. This makes it
3136 difficult or impossible to set a breakpoint, or watchpoint, on an
3137 absolute address if you have to restart the program, since the
3138 absolute location of a symbol will change from one execution to the
3141 A checkpoint, however, is an @emph{identical} copy of a process.
3142 Therefore if you create a checkpoint at (eg.@:) the start of main,
3143 and simply return to that checkpoint instead of restarting the
3144 process, you can avoid the effects of address randomization and
3145 your symbols will all stay in the same place.
3148 @chapter Stopping and Continuing
3150 The principal purposes of using a debugger are so that you can stop your
3151 program before it terminates; or so that, if your program runs into
3152 trouble, you can investigate and find out why.
3154 Inside @value{GDBN}, your program may stop for any of several reasons,
3155 such as a signal, a breakpoint, or reaching a new line after a
3156 @value{GDBN} command such as @code{step}. You may then examine and
3157 change variables, set new breakpoints or remove old ones, and then
3158 continue execution. Usually, the messages shown by @value{GDBN} provide
3159 ample explanation of the status of your program---but you can also
3160 explicitly request this information at any time.
3163 @kindex info program
3165 Display information about the status of your program: whether it is
3166 running or not, what process it is, and why it stopped.
3170 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3171 * Continuing and Stepping:: Resuming execution
3173 * Thread Stops:: Stopping and starting multi-thread programs
3177 @section Breakpoints, Watchpoints, and Catchpoints
3180 A @dfn{breakpoint} makes your program stop whenever a certain point in
3181 the program is reached. For each breakpoint, you can add conditions to
3182 control in finer detail whether your program stops. You can set
3183 breakpoints with the @code{break} command and its variants (@pxref{Set
3184 Breaks, ,Setting Breakpoints}), to specify the place where your program
3185 should stop by line number, function name or exact address in the
3188 On some systems, you can set breakpoints in shared libraries before
3189 the executable is run. There is a minor limitation on HP-UX systems:
3190 you must wait until the executable is run in order to set breakpoints
3191 in shared library routines that are not called directly by the program
3192 (for example, routines that are arguments in a @code{pthread_create}
3196 @cindex data breakpoints
3197 @cindex memory tracing
3198 @cindex breakpoint on memory address
3199 @cindex breakpoint on variable modification
3200 A @dfn{watchpoint} is a special breakpoint that stops your program
3201 when the value of an expression changes. The expression may be a value
3202 of a variable, or it could involve values of one or more variables
3203 combined by operators, such as @samp{a + b}. This is sometimes called
3204 @dfn{data breakpoints}. You must use a different command to set
3205 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3206 from that, you can manage a watchpoint like any other breakpoint: you
3207 enable, disable, and delete both breakpoints and watchpoints using the
3210 You can arrange to have values from your program displayed automatically
3211 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3215 @cindex breakpoint on events
3216 A @dfn{catchpoint} is another special breakpoint that stops your program
3217 when a certain kind of event occurs, such as the throwing of a C@t{++}
3218 exception or the loading of a library. As with watchpoints, you use a
3219 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3220 Catchpoints}), but aside from that, you can manage a catchpoint like any
3221 other breakpoint. (To stop when your program receives a signal, use the
3222 @code{handle} command; see @ref{Signals, ,Signals}.)
3224 @cindex breakpoint numbers
3225 @cindex numbers for breakpoints
3226 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3227 catchpoint when you create it; these numbers are successive integers
3228 starting with one. In many of the commands for controlling various
3229 features of breakpoints you use the breakpoint number to say which
3230 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3231 @dfn{disabled}; if disabled, it has no effect on your program until you
3234 @cindex breakpoint ranges
3235 @cindex ranges of breakpoints
3236 Some @value{GDBN} commands accept a range of breakpoints on which to
3237 operate. A breakpoint range is either a single breakpoint number, like
3238 @samp{5}, or two such numbers, in increasing order, separated by a
3239 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3240 all breakpoints in that range are operated on.
3243 * Set Breaks:: Setting breakpoints
3244 * Set Watchpoints:: Setting watchpoints
3245 * Set Catchpoints:: Setting catchpoints
3246 * Delete Breaks:: Deleting breakpoints
3247 * Disabling:: Disabling breakpoints
3248 * Conditions:: Break conditions
3249 * Break Commands:: Breakpoint command lists
3250 * Save Breakpoints:: How to save breakpoints in a file
3251 * Error in Breakpoints:: ``Cannot insert breakpoints''
3252 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3256 @subsection Setting Breakpoints
3258 @c FIXME LMB what does GDB do if no code on line of breakpt?
3259 @c consider in particular declaration with/without initialization.
3261 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3264 @kindex b @r{(@code{break})}
3265 @vindex $bpnum@r{, convenience variable}
3266 @cindex latest breakpoint
3267 Breakpoints are set with the @code{break} command (abbreviated
3268 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3269 number of the breakpoint you've set most recently; see @ref{Convenience
3270 Vars,, Convenience Variables}, for a discussion of what you can do with
3271 convenience variables.
3274 @item break @var{location}
3275 Set a breakpoint at the given @var{location}, which can specify a
3276 function name, a line number, or an address of an instruction.
3277 (@xref{Specify Location}, for a list of all the possible ways to
3278 specify a @var{location}.) The breakpoint will stop your program just
3279 before it executes any of the code in the specified @var{location}.
3281 When using source languages that permit overloading of symbols, such as
3282 C@t{++}, a function name may refer to more than one possible place to break.
3283 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3286 It is also possible to insert a breakpoint that will stop the program
3287 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3288 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3291 When called without any arguments, @code{break} sets a breakpoint at
3292 the next instruction to be executed in the selected stack frame
3293 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3294 innermost, this makes your program stop as soon as control
3295 returns to that frame. This is similar to the effect of a
3296 @code{finish} command in the frame inside the selected frame---except
3297 that @code{finish} does not leave an active breakpoint. If you use
3298 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3299 the next time it reaches the current location; this may be useful
3302 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3303 least one instruction has been executed. If it did not do this, you
3304 would be unable to proceed past a breakpoint without first disabling the
3305 breakpoint. This rule applies whether or not the breakpoint already
3306 existed when your program stopped.
3308 @item break @dots{} if @var{cond}
3309 Set a breakpoint with condition @var{cond}; evaluate the expression
3310 @var{cond} each time the breakpoint is reached, and stop only if the
3311 value is nonzero---that is, if @var{cond} evaluates as true.
3312 @samp{@dots{}} stands for one of the possible arguments described
3313 above (or no argument) specifying where to break. @xref{Conditions,
3314 ,Break Conditions}, for more information on breakpoint conditions.
3317 @item tbreak @var{args}
3318 Set a breakpoint enabled only for one stop. @var{args} are the
3319 same as for the @code{break} command, and the breakpoint is set in the same
3320 way, but the breakpoint is automatically deleted after the first time your
3321 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3324 @cindex hardware breakpoints
3325 @item hbreak @var{args}
3326 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3327 @code{break} command and the breakpoint is set in the same way, but the
3328 breakpoint requires hardware support and some target hardware may not
3329 have this support. The main purpose of this is EPROM/ROM code
3330 debugging, so you can set a breakpoint at an instruction without
3331 changing the instruction. This can be used with the new trap-generation
3332 provided by SPARClite DSU and most x86-based targets. These targets
3333 will generate traps when a program accesses some data or instruction
3334 address that is assigned to the debug registers. However the hardware
3335 breakpoint registers can take a limited number of breakpoints. For
3336 example, on the DSU, only two data breakpoints can be set at a time, and
3337 @value{GDBN} will reject this command if more than two are used. Delete
3338 or disable unused hardware breakpoints before setting new ones
3339 (@pxref{Disabling, ,Disabling Breakpoints}).
3340 @xref{Conditions, ,Break Conditions}.
3341 For remote targets, you can restrict the number of hardware
3342 breakpoints @value{GDBN} will use, see @ref{set remote
3343 hardware-breakpoint-limit}.
3346 @item thbreak @var{args}
3347 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3348 are the same as for the @code{hbreak} command and the breakpoint is set in
3349 the same way. However, like the @code{tbreak} command,
3350 the breakpoint is automatically deleted after the
3351 first time your program stops there. Also, like the @code{hbreak}
3352 command, the breakpoint requires hardware support and some target hardware
3353 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3354 See also @ref{Conditions, ,Break Conditions}.
3357 @cindex regular expression
3358 @cindex breakpoints in functions matching a regexp
3359 @cindex set breakpoints in many functions
3360 @item rbreak @var{regex}
3361 Set breakpoints on all functions matching the regular expression
3362 @var{regex}. This command sets an unconditional breakpoint on all
3363 matches, printing a list of all breakpoints it set. Once these
3364 breakpoints are set, they are treated just like the breakpoints set with
3365 the @code{break} command. You can delete them, disable them, or make
3366 them conditional the same way as any other breakpoint.
3368 The syntax of the regular expression is the standard one used with tools
3369 like @file{grep}. Note that this is different from the syntax used by
3370 shells, so for instance @code{foo*} matches all functions that include
3371 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3372 @code{.*} leading and trailing the regular expression you supply, so to
3373 match only functions that begin with @code{foo}, use @code{^foo}.
3375 @cindex non-member C@t{++} functions, set breakpoint in
3376 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3377 breakpoints on overloaded functions that are not members of any special
3380 @cindex set breakpoints on all functions
3381 The @code{rbreak} command can be used to set breakpoints in
3382 @strong{all} the functions in a program, like this:
3385 (@value{GDBP}) rbreak .
3388 @kindex info breakpoints
3389 @cindex @code{$_} and @code{info breakpoints}
3390 @item info breakpoints @r{[}@var{n}@r{]}
3391 @itemx info break @r{[}@var{n}@r{]}
3392 Print a table of all breakpoints, watchpoints, and catchpoints set and
3393 not deleted. Optional argument @var{n} means print information only
3394 about the specified breakpoint (or watchpoint or catchpoint). For
3395 each breakpoint, following columns are printed:
3398 @item Breakpoint Numbers
3400 Breakpoint, watchpoint, or catchpoint.
3402 Whether the breakpoint is marked to be disabled or deleted when hit.
3403 @item Enabled or Disabled
3404 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3405 that are not enabled.
3407 Where the breakpoint is in your program, as a memory address. For a
3408 pending breakpoint whose address is not yet known, this field will
3409 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3410 library that has the symbol or line referred by breakpoint is loaded.
3411 See below for details. A breakpoint with several locations will
3412 have @samp{<MULTIPLE>} in this field---see below for details.
3414 Where the breakpoint is in the source for your program, as a file and
3415 line number. For a pending breakpoint, the original string passed to
3416 the breakpoint command will be listed as it cannot be resolved until
3417 the appropriate shared library is loaded in the future.
3421 If a breakpoint is conditional, @code{info break} shows the condition on
3422 the line following the affected breakpoint; breakpoint commands, if any,
3423 are listed after that. A pending breakpoint is allowed to have a condition
3424 specified for it. The condition is not parsed for validity until a shared
3425 library is loaded that allows the pending breakpoint to resolve to a
3429 @code{info break} with a breakpoint
3430 number @var{n} as argument lists only that breakpoint. The
3431 convenience variable @code{$_} and the default examining-address for
3432 the @code{x} command are set to the address of the last breakpoint
3433 listed (@pxref{Memory, ,Examining Memory}).
3436 @code{info break} displays a count of the number of times the breakpoint
3437 has been hit. This is especially useful in conjunction with the
3438 @code{ignore} command. You can ignore a large number of breakpoint
3439 hits, look at the breakpoint info to see how many times the breakpoint
3440 was hit, and then run again, ignoring one less than that number. This
3441 will get you quickly to the last hit of that breakpoint.
3444 @value{GDBN} allows you to set any number of breakpoints at the same place in
3445 your program. There is nothing silly or meaningless about this. When
3446 the breakpoints are conditional, this is even useful
3447 (@pxref{Conditions, ,Break Conditions}).
3449 @cindex multiple locations, breakpoints
3450 @cindex breakpoints, multiple locations
3451 It is possible that a breakpoint corresponds to several locations
3452 in your program. Examples of this situation are:
3456 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3457 instances of the function body, used in different cases.
3460 For a C@t{++} template function, a given line in the function can
3461 correspond to any number of instantiations.
3464 For an inlined function, a given source line can correspond to
3465 several places where that function is inlined.
3468 In all those cases, @value{GDBN} will insert a breakpoint at all
3469 the relevant locations@footnote{
3470 As of this writing, multiple-location breakpoints work only if there's
3471 line number information for all the locations. This means that they
3472 will generally not work in system libraries, unless you have debug
3473 info with line numbers for them.}.
3475 A breakpoint with multiple locations is displayed in the breakpoint
3476 table using several rows---one header row, followed by one row for
3477 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3478 address column. The rows for individual locations contain the actual
3479 addresses for locations, and show the functions to which those
3480 locations belong. The number column for a location is of the form
3481 @var{breakpoint-number}.@var{location-number}.
3486 Num Type Disp Enb Address What
3487 1 breakpoint keep y <MULTIPLE>
3489 breakpoint already hit 1 time
3490 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3491 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3494 Each location can be individually enabled or disabled by passing
3495 @var{breakpoint-number}.@var{location-number} as argument to the
3496 @code{enable} and @code{disable} commands. Note that you cannot
3497 delete the individual locations from the list, you can only delete the
3498 entire list of locations that belong to their parent breakpoint (with
3499 the @kbd{delete @var{num}} command, where @var{num} is the number of
3500 the parent breakpoint, 1 in the above example). Disabling or enabling
3501 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3502 that belong to that breakpoint.
3504 @cindex pending breakpoints
3505 It's quite common to have a breakpoint inside a shared library.
3506 Shared libraries can be loaded and unloaded explicitly,
3507 and possibly repeatedly, as the program is executed. To support
3508 this use case, @value{GDBN} updates breakpoint locations whenever
3509 any shared library is loaded or unloaded. Typically, you would
3510 set a breakpoint in a shared library at the beginning of your
3511 debugging session, when the library is not loaded, and when the
3512 symbols from the library are not available. When you try to set
3513 breakpoint, @value{GDBN} will ask you if you want to set
3514 a so called @dfn{pending breakpoint}---breakpoint whose address
3515 is not yet resolved.
3517 After the program is run, whenever a new shared library is loaded,
3518 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3519 shared library contains the symbol or line referred to by some
3520 pending breakpoint, that breakpoint is resolved and becomes an
3521 ordinary breakpoint. When a library is unloaded, all breakpoints
3522 that refer to its symbols or source lines become pending again.
3524 This logic works for breakpoints with multiple locations, too. For
3525 example, if you have a breakpoint in a C@t{++} template function, and
3526 a newly loaded shared library has an instantiation of that template,
3527 a new location is added to the list of locations for the breakpoint.
3529 Except for having unresolved address, pending breakpoints do not
3530 differ from regular breakpoints. You can set conditions or commands,
3531 enable and disable them and perform other breakpoint operations.
3533 @value{GDBN} provides some additional commands for controlling what
3534 happens when the @samp{break} command cannot resolve breakpoint
3535 address specification to an address:
3537 @kindex set breakpoint pending
3538 @kindex show breakpoint pending
3540 @item set breakpoint pending auto
3541 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3542 location, it queries you whether a pending breakpoint should be created.
3544 @item set breakpoint pending on
3545 This indicates that an unrecognized breakpoint location should automatically
3546 result in a pending breakpoint being created.
3548 @item set breakpoint pending off
3549 This indicates that pending breakpoints are not to be created. Any
3550 unrecognized breakpoint location results in an error. This setting does
3551 not affect any pending breakpoints previously created.
3553 @item show breakpoint pending
3554 Show the current behavior setting for creating pending breakpoints.
3557 The settings above only affect the @code{break} command and its
3558 variants. Once breakpoint is set, it will be automatically updated
3559 as shared libraries are loaded and unloaded.
3561 @cindex automatic hardware breakpoints
3562 For some targets, @value{GDBN} can automatically decide if hardware or
3563 software breakpoints should be used, depending on whether the
3564 breakpoint address is read-only or read-write. This applies to
3565 breakpoints set with the @code{break} command as well as to internal
3566 breakpoints set by commands like @code{next} and @code{finish}. For
3567 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3570 You can control this automatic behaviour with the following commands::
3572 @kindex set breakpoint auto-hw
3573 @kindex show breakpoint auto-hw
3575 @item set breakpoint auto-hw on
3576 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3577 will try to use the target memory map to decide if software or hardware
3578 breakpoint must be used.
3580 @item set breakpoint auto-hw off
3581 This indicates @value{GDBN} should not automatically select breakpoint
3582 type. If the target provides a memory map, @value{GDBN} will warn when
3583 trying to set software breakpoint at a read-only address.
3586 @value{GDBN} normally implements breakpoints by replacing the program code
3587 at the breakpoint address with a special instruction, which, when
3588 executed, given control to the debugger. By default, the program
3589 code is so modified only when the program is resumed. As soon as
3590 the program stops, @value{GDBN} restores the original instructions. This
3591 behaviour guards against leaving breakpoints inserted in the
3592 target should gdb abrubptly disconnect. However, with slow remote
3593 targets, inserting and removing breakpoint can reduce the performance.
3594 This behavior can be controlled with the following commands::
3596 @kindex set breakpoint always-inserted
3597 @kindex show breakpoint always-inserted
3599 @item set breakpoint always-inserted off
3600 All breakpoints, including newly added by the user, are inserted in
3601 the target only when the target is resumed. All breakpoints are
3602 removed from the target when it stops.
3604 @item set breakpoint always-inserted on
3605 Causes all breakpoints to be inserted in the target at all times. If
3606 the user adds a new breakpoint, or changes an existing breakpoint, the
3607 breakpoints in the target are updated immediately. A breakpoint is
3608 removed from the target only when breakpoint itself is removed.
3610 @cindex non-stop mode, and @code{breakpoint always-inserted}
3611 @item set breakpoint always-inserted auto
3612 This is the default mode. If @value{GDBN} is controlling the inferior
3613 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3614 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3615 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3616 @code{breakpoint always-inserted} mode is off.
3619 @cindex negative breakpoint numbers
3620 @cindex internal @value{GDBN} breakpoints
3621 @value{GDBN} itself sometimes sets breakpoints in your program for
3622 special purposes, such as proper handling of @code{longjmp} (in C
3623 programs). These internal breakpoints are assigned negative numbers,
3624 starting with @code{-1}; @samp{info breakpoints} does not display them.
3625 You can see these breakpoints with the @value{GDBN} maintenance command
3626 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3629 @node Set Watchpoints
3630 @subsection Setting Watchpoints
3632 @cindex setting watchpoints
3633 You can use a watchpoint to stop execution whenever the value of an
3634 expression changes, without having to predict a particular place where
3635 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3636 The expression may be as simple as the value of a single variable, or
3637 as complex as many variables combined by operators. Examples include:
3641 A reference to the value of a single variable.
3644 An address cast to an appropriate data type. For example,
3645 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3646 address (assuming an @code{int} occupies 4 bytes).
3649 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3650 expression can use any operators valid in the program's native
3651 language (@pxref{Languages}).
3654 You can set a watchpoint on an expression even if the expression can
3655 not be evaluated yet. For instance, you can set a watchpoint on
3656 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3657 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3658 the expression produces a valid value. If the expression becomes
3659 valid in some other way than changing a variable (e.g.@: if the memory
3660 pointed to by @samp{*global_ptr} becomes readable as the result of a
3661 @code{malloc} call), @value{GDBN} may not stop until the next time
3662 the expression changes.
3664 @cindex software watchpoints
3665 @cindex hardware watchpoints
3666 Depending on your system, watchpoints may be implemented in software or
3667 hardware. @value{GDBN} does software watchpointing by single-stepping your
3668 program and testing the variable's value each time, which is hundreds of
3669 times slower than normal execution. (But this may still be worth it, to
3670 catch errors where you have no clue what part of your program is the
3673 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3674 x86-based targets, @value{GDBN} includes support for hardware
3675 watchpoints, which do not slow down the running of your program.
3679 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3680 Set a watchpoint for an expression. @value{GDBN} will break when the
3681 expression @var{expr} is written into by the program and its value
3682 changes. The simplest (and the most popular) use of this command is
3683 to watch the value of a single variable:
3686 (@value{GDBP}) watch foo
3689 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3690 clause, @value{GDBN} breaks only when the thread identified by
3691 @var{threadnum} changes the value of @var{expr}. If any other threads
3692 change the value of @var{expr}, @value{GDBN} will not break. Note
3693 that watchpoints restricted to a single thread in this way only work
3694 with Hardware Watchpoints.
3697 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3698 Set a watchpoint that will break when the value of @var{expr} is read
3702 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3703 Set a watchpoint that will break when @var{expr} is either read from
3704 or written into by the program.
3706 @kindex info watchpoints @r{[}@var{n}@r{]}
3707 @item info watchpoints
3708 This command prints a list of watchpoints, using the same format as
3709 @code{info break} (@pxref{Set Breaks}).
3712 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3713 watchpoints execute very quickly, and the debugger reports a change in
3714 value at the exact instruction where the change occurs. If @value{GDBN}
3715 cannot set a hardware watchpoint, it sets a software watchpoint, which
3716 executes more slowly and reports the change in value at the next
3717 @emph{statement}, not the instruction, after the change occurs.
3719 @cindex use only software watchpoints
3720 You can force @value{GDBN} to use only software watchpoints with the
3721 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3722 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3723 the underlying system supports them. (Note that hardware-assisted
3724 watchpoints that were set @emph{before} setting
3725 @code{can-use-hw-watchpoints} to zero will still use the hardware
3726 mechanism of watching expression values.)
3729 @item set can-use-hw-watchpoints
3730 @kindex set can-use-hw-watchpoints
3731 Set whether or not to use hardware watchpoints.
3733 @item show can-use-hw-watchpoints
3734 @kindex show can-use-hw-watchpoints
3735 Show the current mode of using hardware watchpoints.
3738 For remote targets, you can restrict the number of hardware
3739 watchpoints @value{GDBN} will use, see @ref{set remote
3740 hardware-breakpoint-limit}.
3742 When you issue the @code{watch} command, @value{GDBN} reports
3745 Hardware watchpoint @var{num}: @var{expr}
3749 if it was able to set a hardware watchpoint.
3751 Currently, the @code{awatch} and @code{rwatch} commands can only set
3752 hardware watchpoints, because accesses to data that don't change the
3753 value of the watched expression cannot be detected without examining
3754 every instruction as it is being executed, and @value{GDBN} does not do
3755 that currently. If @value{GDBN} finds that it is unable to set a
3756 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3757 will print a message like this:
3760 Expression cannot be implemented with read/access watchpoint.
3763 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3764 data type of the watched expression is wider than what a hardware
3765 watchpoint on the target machine can handle. For example, some systems
3766 can only watch regions that are up to 4 bytes wide; on such systems you
3767 cannot set hardware watchpoints for an expression that yields a
3768 double-precision floating-point number (which is typically 8 bytes
3769 wide). As a work-around, it might be possible to break the large region
3770 into a series of smaller ones and watch them with separate watchpoints.
3772 If you set too many hardware watchpoints, @value{GDBN} might be unable
3773 to insert all of them when you resume the execution of your program.
3774 Since the precise number of active watchpoints is unknown until such
3775 time as the program is about to be resumed, @value{GDBN} might not be
3776 able to warn you about this when you set the watchpoints, and the
3777 warning will be printed only when the program is resumed:
3780 Hardware watchpoint @var{num}: Could not insert watchpoint
3784 If this happens, delete or disable some of the watchpoints.
3786 Watching complex expressions that reference many variables can also
3787 exhaust the resources available for hardware-assisted watchpoints.
3788 That's because @value{GDBN} needs to watch every variable in the
3789 expression with separately allocated resources.
3791 If you call a function interactively using @code{print} or @code{call},
3792 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3793 kind of breakpoint or the call completes.
3795 @value{GDBN} automatically deletes watchpoints that watch local
3796 (automatic) variables, or expressions that involve such variables, when
3797 they go out of scope, that is, when the execution leaves the block in
3798 which these variables were defined. In particular, when the program
3799 being debugged terminates, @emph{all} local variables go out of scope,
3800 and so only watchpoints that watch global variables remain set. If you
3801 rerun the program, you will need to set all such watchpoints again. One
3802 way of doing that would be to set a code breakpoint at the entry to the
3803 @code{main} function and when it breaks, set all the watchpoints.
3805 @cindex watchpoints and threads
3806 @cindex threads and watchpoints
3807 In multi-threaded programs, watchpoints will detect changes to the
3808 watched expression from every thread.
3811 @emph{Warning:} In multi-threaded programs, software watchpoints
3812 have only limited usefulness. If @value{GDBN} creates a software
3813 watchpoint, it can only watch the value of an expression @emph{in a
3814 single thread}. If you are confident that the expression can only
3815 change due to the current thread's activity (and if you are also
3816 confident that no other thread can become current), then you can use
3817 software watchpoints as usual. However, @value{GDBN} may not notice
3818 when a non-current thread's activity changes the expression. (Hardware
3819 watchpoints, in contrast, watch an expression in all threads.)
3822 @xref{set remote hardware-watchpoint-limit}.
3824 @node Set Catchpoints
3825 @subsection Setting Catchpoints
3826 @cindex catchpoints, setting
3827 @cindex exception handlers
3828 @cindex event handling
3830 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3831 kinds of program events, such as C@t{++} exceptions or the loading of a
3832 shared library. Use the @code{catch} command to set a catchpoint.
3836 @item catch @var{event}
3837 Stop when @var{event} occurs. @var{event} can be any of the following:
3840 @cindex stop on C@t{++} exceptions
3841 The throwing of a C@t{++} exception.
3844 The catching of a C@t{++} exception.
3847 @cindex Ada exception catching
3848 @cindex catch Ada exceptions
3849 An Ada exception being raised. If an exception name is specified
3850 at the end of the command (eg @code{catch exception Program_Error}),
3851 the debugger will stop only when this specific exception is raised.
3852 Otherwise, the debugger stops execution when any Ada exception is raised.
3854 When inserting an exception catchpoint on a user-defined exception whose
3855 name is identical to one of the exceptions defined by the language, the
3856 fully qualified name must be used as the exception name. Otherwise,
3857 @value{GDBN} will assume that it should stop on the pre-defined exception
3858 rather than the user-defined one. For instance, assuming an exception
3859 called @code{Constraint_Error} is defined in package @code{Pck}, then
3860 the command to use to catch such exceptions is @kbd{catch exception
3861 Pck.Constraint_Error}.
3863 @item exception unhandled
3864 An exception that was raised but is not handled by the program.
3867 A failed Ada assertion.
3870 @cindex break on fork/exec
3871 A call to @code{exec}. This is currently only available for HP-UX
3875 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3876 @cindex break on a system call.
3877 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3878 syscall is a mechanism for application programs to request a service
3879 from the operating system (OS) or one of the OS system services.
3880 @value{GDBN} can catch some or all of the syscalls issued by the
3881 debuggee, and show the related information for each syscall. If no
3882 argument is specified, calls to and returns from all system calls
3885 @var{name} can be any system call name that is valid for the
3886 underlying OS. Just what syscalls are valid depends on the OS. On
3887 GNU and Unix systems, you can find the full list of valid syscall
3888 names on @file{/usr/include/asm/unistd.h}.
3890 @c For MS-Windows, the syscall names and the corresponding numbers
3891 @c can be found, e.g., on this URL:
3892 @c http://www.metasploit.com/users/opcode/syscalls.html
3893 @c but we don't support Windows syscalls yet.
3895 Normally, @value{GDBN} knows in advance which syscalls are valid for
3896 each OS, so you can use the @value{GDBN} command-line completion
3897 facilities (@pxref{Completion,, command completion}) to list the
3900 You may also specify the system call numerically. A syscall's
3901 number is the value passed to the OS's syscall dispatcher to
3902 identify the requested service. When you specify the syscall by its
3903 name, @value{GDBN} uses its database of syscalls to convert the name
3904 into the corresponding numeric code, but using the number directly
3905 may be useful if @value{GDBN}'s database does not have the complete
3906 list of syscalls on your system (e.g., because @value{GDBN} lags
3907 behind the OS upgrades).
3909 The example below illustrates how this command works if you don't provide
3913 (@value{GDBP}) catch syscall
3914 Catchpoint 1 (syscall)
3916 Starting program: /tmp/catch-syscall
3918 Catchpoint 1 (call to syscall 'close'), \
3919 0xffffe424 in __kernel_vsyscall ()
3923 Catchpoint 1 (returned from syscall 'close'), \
3924 0xffffe424 in __kernel_vsyscall ()
3928 Here is an example of catching a system call by name:
3931 (@value{GDBP}) catch syscall chroot
3932 Catchpoint 1 (syscall 'chroot' [61])
3934 Starting program: /tmp/catch-syscall
3936 Catchpoint 1 (call to syscall 'chroot'), \
3937 0xffffe424 in __kernel_vsyscall ()
3941 Catchpoint 1 (returned from syscall 'chroot'), \
3942 0xffffe424 in __kernel_vsyscall ()
3946 An example of specifying a system call numerically. In the case
3947 below, the syscall number has a corresponding entry in the XML
3948 file, so @value{GDBN} finds its name and prints it:
3951 (@value{GDBP}) catch syscall 252
3952 Catchpoint 1 (syscall(s) 'exit_group')
3954 Starting program: /tmp/catch-syscall
3956 Catchpoint 1 (call to syscall 'exit_group'), \
3957 0xffffe424 in __kernel_vsyscall ()
3961 Program exited normally.
3965 However, there can be situations when there is no corresponding name
3966 in XML file for that syscall number. In this case, @value{GDBN} prints
3967 a warning message saying that it was not able to find the syscall name,
3968 but the catchpoint will be set anyway. See the example below:
3971 (@value{GDBP}) catch syscall 764
3972 warning: The number '764' does not represent a known syscall.
3973 Catchpoint 2 (syscall 764)
3977 If you configure @value{GDBN} using the @samp{--without-expat} option,
3978 it will not be able to display syscall names. Also, if your
3979 architecture does not have an XML file describing its system calls,
3980 you will not be able to see the syscall names. It is important to
3981 notice that these two features are used for accessing the syscall
3982 name database. In either case, you will see a warning like this:
3985 (@value{GDBP}) catch syscall
3986 warning: Could not open "syscalls/i386-linux.xml"
3987 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
3988 GDB will not be able to display syscall names.
3989 Catchpoint 1 (syscall)
3993 Of course, the file name will change depending on your architecture and system.
3995 Still using the example above, you can also try to catch a syscall by its
3996 number. In this case, you would see something like:
3999 (@value{GDBP}) catch syscall 252
4000 Catchpoint 1 (syscall(s) 252)
4003 Again, in this case @value{GDBN} would not be able to display syscall's names.
4006 A call to @code{fork}. This is currently only available for HP-UX
4010 A call to @code{vfork}. This is currently only available for HP-UX
4015 @item tcatch @var{event}
4016 Set a catchpoint that is enabled only for one stop. The catchpoint is
4017 automatically deleted after the first time the event is caught.
4021 Use the @code{info break} command to list the current catchpoints.
4023 There are currently some limitations to C@t{++} exception handling
4024 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4028 If you call a function interactively, @value{GDBN} normally returns
4029 control to you when the function has finished executing. If the call
4030 raises an exception, however, the call may bypass the mechanism that
4031 returns control to you and cause your program either to abort or to
4032 simply continue running until it hits a breakpoint, catches a signal
4033 that @value{GDBN} is listening for, or exits. This is the case even if
4034 you set a catchpoint for the exception; catchpoints on exceptions are
4035 disabled within interactive calls.
4038 You cannot raise an exception interactively.
4041 You cannot install an exception handler interactively.
4044 @cindex raise exceptions
4045 Sometimes @code{catch} is not the best way to debug exception handling:
4046 if you need to know exactly where an exception is raised, it is better to
4047 stop @emph{before} the exception handler is called, since that way you
4048 can see the stack before any unwinding takes place. If you set a
4049 breakpoint in an exception handler instead, it may not be easy to find
4050 out where the exception was raised.
4052 To stop just before an exception handler is called, you need some
4053 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4054 raised by calling a library function named @code{__raise_exception}
4055 which has the following ANSI C interface:
4058 /* @var{addr} is where the exception identifier is stored.
4059 @var{id} is the exception identifier. */
4060 void __raise_exception (void **addr, void *id);
4064 To make the debugger catch all exceptions before any stack
4065 unwinding takes place, set a breakpoint on @code{__raise_exception}
4066 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4068 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4069 that depends on the value of @var{id}, you can stop your program when
4070 a specific exception is raised. You can use multiple conditional
4071 breakpoints to stop your program when any of a number of exceptions are
4076 @subsection Deleting Breakpoints
4078 @cindex clearing breakpoints, watchpoints, catchpoints
4079 @cindex deleting breakpoints, watchpoints, catchpoints
4080 It is often necessary to eliminate a breakpoint, watchpoint, or
4081 catchpoint once it has done its job and you no longer want your program
4082 to stop there. This is called @dfn{deleting} the breakpoint. A
4083 breakpoint that has been deleted no longer exists; it is forgotten.
4085 With the @code{clear} command you can delete breakpoints according to
4086 where they are in your program. With the @code{delete} command you can
4087 delete individual breakpoints, watchpoints, or catchpoints by specifying
4088 their breakpoint numbers.
4090 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4091 automatically ignores breakpoints on the first instruction to be executed
4092 when you continue execution without changing the execution address.
4097 Delete any breakpoints at the next instruction to be executed in the
4098 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4099 the innermost frame is selected, this is a good way to delete a
4100 breakpoint where your program just stopped.
4102 @item clear @var{location}
4103 Delete any breakpoints set at the specified @var{location}.
4104 @xref{Specify Location}, for the various forms of @var{location}; the
4105 most useful ones are listed below:
4108 @item clear @var{function}
4109 @itemx clear @var{filename}:@var{function}
4110 Delete any breakpoints set at entry to the named @var{function}.
4112 @item clear @var{linenum}
4113 @itemx clear @var{filename}:@var{linenum}
4114 Delete any breakpoints set at or within the code of the specified
4115 @var{linenum} of the specified @var{filename}.
4118 @cindex delete breakpoints
4120 @kindex d @r{(@code{delete})}
4121 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4122 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4123 ranges specified as arguments. If no argument is specified, delete all
4124 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4125 confirm off}). You can abbreviate this command as @code{d}.
4129 @subsection Disabling Breakpoints
4131 @cindex enable/disable a breakpoint
4132 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4133 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4134 it had been deleted, but remembers the information on the breakpoint so
4135 that you can @dfn{enable} it again later.
4137 You disable and enable breakpoints, watchpoints, and catchpoints with
4138 the @code{enable} and @code{disable} commands, optionally specifying
4139 one or more breakpoint numbers as arguments. Use @code{info break} to
4140 print a list of all breakpoints, watchpoints, and catchpoints if you
4141 do not know which numbers to use.
4143 Disabling and enabling a breakpoint that has multiple locations
4144 affects all of its locations.
4146 A breakpoint, watchpoint, or catchpoint can have any of four different
4147 states of enablement:
4151 Enabled. The breakpoint stops your program. A breakpoint set
4152 with the @code{break} command starts out in this state.
4154 Disabled. The breakpoint has no effect on your program.
4156 Enabled once. The breakpoint stops your program, but then becomes
4159 Enabled for deletion. The breakpoint stops your program, but
4160 immediately after it does so it is deleted permanently. A breakpoint
4161 set with the @code{tbreak} command starts out in this state.
4164 You can use the following commands to enable or disable breakpoints,
4165 watchpoints, and catchpoints:
4169 @kindex dis @r{(@code{disable})}
4170 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4171 Disable the specified breakpoints---or all breakpoints, if none are
4172 listed. A disabled breakpoint has no effect but is not forgotten. All
4173 options such as ignore-counts, conditions and commands are remembered in
4174 case the breakpoint is enabled again later. You may abbreviate
4175 @code{disable} as @code{dis}.
4178 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4179 Enable the specified breakpoints (or all defined breakpoints). They
4180 become effective once again in stopping your program.
4182 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4183 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4184 of these breakpoints immediately after stopping your program.
4186 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4187 Enable the specified breakpoints to work once, then die. @value{GDBN}
4188 deletes any of these breakpoints as soon as your program stops there.
4189 Breakpoints set by the @code{tbreak} command start out in this state.
4192 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4193 @c confusing: tbreak is also initially enabled.
4194 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4195 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4196 subsequently, they become disabled or enabled only when you use one of
4197 the commands above. (The command @code{until} can set and delete a
4198 breakpoint of its own, but it does not change the state of your other
4199 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4203 @subsection Break Conditions
4204 @cindex conditional breakpoints
4205 @cindex breakpoint conditions
4207 @c FIXME what is scope of break condition expr? Context where wanted?
4208 @c in particular for a watchpoint?
4209 The simplest sort of breakpoint breaks every time your program reaches a
4210 specified place. You can also specify a @dfn{condition} for a
4211 breakpoint. A condition is just a Boolean expression in your
4212 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4213 a condition evaluates the expression each time your program reaches it,
4214 and your program stops only if the condition is @emph{true}.
4216 This is the converse of using assertions for program validation; in that
4217 situation, you want to stop when the assertion is violated---that is,
4218 when the condition is false. In C, if you want to test an assertion expressed
4219 by the condition @var{assert}, you should set the condition
4220 @samp{! @var{assert}} on the appropriate breakpoint.
4222 Conditions are also accepted for watchpoints; you may not need them,
4223 since a watchpoint is inspecting the value of an expression anyhow---but
4224 it might be simpler, say, to just set a watchpoint on a variable name,
4225 and specify a condition that tests whether the new value is an interesting
4228 Break conditions can have side effects, and may even call functions in
4229 your program. This can be useful, for example, to activate functions
4230 that log program progress, or to use your own print functions to
4231 format special data structures. The effects are completely predictable
4232 unless there is another enabled breakpoint at the same address. (In
4233 that case, @value{GDBN} might see the other breakpoint first and stop your
4234 program without checking the condition of this one.) Note that
4235 breakpoint commands are usually more convenient and flexible than break
4237 purpose of performing side effects when a breakpoint is reached
4238 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4240 Break conditions can be specified when a breakpoint is set, by using
4241 @samp{if} in the arguments to the @code{break} command. @xref{Set
4242 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4243 with the @code{condition} command.
4245 You can also use the @code{if} keyword with the @code{watch} command.
4246 The @code{catch} command does not recognize the @code{if} keyword;
4247 @code{condition} is the only way to impose a further condition on a
4252 @item condition @var{bnum} @var{expression}
4253 Specify @var{expression} as the break condition for breakpoint,
4254 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4255 breakpoint @var{bnum} stops your program only if the value of
4256 @var{expression} is true (nonzero, in C). When you use
4257 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4258 syntactic correctness, and to determine whether symbols in it have
4259 referents in the context of your breakpoint. If @var{expression} uses
4260 symbols not referenced in the context of the breakpoint, @value{GDBN}
4261 prints an error message:
4264 No symbol "foo" in current context.
4269 not actually evaluate @var{expression} at the time the @code{condition}
4270 command (or a command that sets a breakpoint with a condition, like
4271 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4273 @item condition @var{bnum}
4274 Remove the condition from breakpoint number @var{bnum}. It becomes
4275 an ordinary unconditional breakpoint.
4278 @cindex ignore count (of breakpoint)
4279 A special case of a breakpoint condition is to stop only when the
4280 breakpoint has been reached a certain number of times. This is so
4281 useful that there is a special way to do it, using the @dfn{ignore
4282 count} of the breakpoint. Every breakpoint has an ignore count, which
4283 is an integer. Most of the time, the ignore count is zero, and
4284 therefore has no effect. But if your program reaches a breakpoint whose
4285 ignore count is positive, then instead of stopping, it just decrements
4286 the ignore count by one and continues. As a result, if the ignore count
4287 value is @var{n}, the breakpoint does not stop the next @var{n} times
4288 your program reaches it.
4292 @item ignore @var{bnum} @var{count}
4293 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4294 The next @var{count} times the breakpoint is reached, your program's
4295 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4298 To make the breakpoint stop the next time it is reached, specify
4301 When you use @code{continue} to resume execution of your program from a
4302 breakpoint, you can specify an ignore count directly as an argument to
4303 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4304 Stepping,,Continuing and Stepping}.
4306 If a breakpoint has a positive ignore count and a condition, the
4307 condition is not checked. Once the ignore count reaches zero,
4308 @value{GDBN} resumes checking the condition.
4310 You could achieve the effect of the ignore count with a condition such
4311 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4312 is decremented each time. @xref{Convenience Vars, ,Convenience
4316 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4319 @node Break Commands
4320 @subsection Breakpoint Command Lists
4322 @cindex breakpoint commands
4323 You can give any breakpoint (or watchpoint or catchpoint) a series of
4324 commands to execute when your program stops due to that breakpoint. For
4325 example, you might want to print the values of certain expressions, or
4326 enable other breakpoints.
4330 @kindex end@r{ (breakpoint commands)}
4331 @item commands @r{[}@var{range}@dots{}@r{]}
4332 @itemx @dots{} @var{command-list} @dots{}
4334 Specify a list of commands for the given breakpoints. The commands
4335 themselves appear on the following lines. Type a line containing just
4336 @code{end} to terminate the commands.
4338 To remove all commands from a breakpoint, type @code{commands} and
4339 follow it immediately with @code{end}; that is, give no commands.
4341 With no argument, @code{commands} refers to the last breakpoint,
4342 watchpoint, or catchpoint set (not to the breakpoint most recently
4343 encountered). If the most recent breakpoints were set with a single
4344 command, then the @code{commands} will apply to all the breakpoints
4345 set by that command. This applies to breakpoints set by
4346 @code{rbreak}, and also applies when a single @code{break} command
4347 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4351 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4352 disabled within a @var{command-list}.
4354 You can use breakpoint commands to start your program up again. Simply
4355 use the @code{continue} command, or @code{step}, or any other command
4356 that resumes execution.
4358 Any other commands in the command list, after a command that resumes
4359 execution, are ignored. This is because any time you resume execution
4360 (even with a simple @code{next} or @code{step}), you may encounter
4361 another breakpoint---which could have its own command list, leading to
4362 ambiguities about which list to execute.
4365 If the first command you specify in a command list is @code{silent}, the
4366 usual message about stopping at a breakpoint is not printed. This may
4367 be desirable for breakpoints that are to print a specific message and
4368 then continue. If none of the remaining commands print anything, you
4369 see no sign that the breakpoint was reached. @code{silent} is
4370 meaningful only at the beginning of a breakpoint command list.
4372 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4373 print precisely controlled output, and are often useful in silent
4374 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4376 For example, here is how you could use breakpoint commands to print the
4377 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4383 printf "x is %d\n",x
4388 One application for breakpoint commands is to compensate for one bug so
4389 you can test for another. Put a breakpoint just after the erroneous line
4390 of code, give it a condition to detect the case in which something
4391 erroneous has been done, and give it commands to assign correct values
4392 to any variables that need them. End with the @code{continue} command
4393 so that your program does not stop, and start with the @code{silent}
4394 command so that no output is produced. Here is an example:
4405 @node Save Breakpoints
4406 @subsection How to save breakpoints to a file
4408 To save breakpoint definitions to a file use the @w{@code{save
4409 breakpoints}} command.
4412 @kindex save breakpoints
4413 @cindex save breakpoints to a file for future sessions
4414 @item save breakpoints [@var{filename}]
4415 This command saves all current breakpoint definitions together with
4416 their commands and ignore counts, into a file @file{@var{filename}}
4417 suitable for use in a later debugging session. This includes all
4418 types of breakpoints (breakpoints, watchpoints, catchpoints,
4419 tracepoints). To read the saved breakpoint definitions, use the
4420 @code{source} command (@pxref{Command Files}). Note that watchpoints
4421 with expressions involving local variables may fail to be recreated
4422 because it may not be possible to access the context where the
4423 watchpoint is valid anymore. Because the saved breakpoint definitions
4424 are simply a sequence of @value{GDBN} commands that recreate the
4425 breakpoints, you can edit the file in your favorite editing program,
4426 and remove the breakpoint definitions you're not interested in, or
4427 that can no longer be recreated.
4430 @c @ifclear BARETARGET
4431 @node Error in Breakpoints
4432 @subsection ``Cannot insert breakpoints''
4434 If you request too many active hardware-assisted breakpoints and
4435 watchpoints, you will see this error message:
4437 @c FIXME: the precise wording of this message may change; the relevant
4438 @c source change is not committed yet (Sep 3, 1999).
4440 Stopped; cannot insert breakpoints.
4441 You may have requested too many hardware breakpoints and watchpoints.
4445 This message is printed when you attempt to resume the program, since
4446 only then @value{GDBN} knows exactly how many hardware breakpoints and
4447 watchpoints it needs to insert.
4449 When this message is printed, you need to disable or remove some of the
4450 hardware-assisted breakpoints and watchpoints, and then continue.
4452 @node Breakpoint-related Warnings
4453 @subsection ``Breakpoint address adjusted...''
4454 @cindex breakpoint address adjusted
4456 Some processor architectures place constraints on the addresses at
4457 which breakpoints may be placed. For architectures thus constrained,
4458 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4459 with the constraints dictated by the architecture.
4461 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4462 a VLIW architecture in which a number of RISC-like instructions may be
4463 bundled together for parallel execution. The FR-V architecture
4464 constrains the location of a breakpoint instruction within such a
4465 bundle to the instruction with the lowest address. @value{GDBN}
4466 honors this constraint by adjusting a breakpoint's address to the
4467 first in the bundle.
4469 It is not uncommon for optimized code to have bundles which contain
4470 instructions from different source statements, thus it may happen that
4471 a breakpoint's address will be adjusted from one source statement to
4472 another. Since this adjustment may significantly alter @value{GDBN}'s
4473 breakpoint related behavior from what the user expects, a warning is
4474 printed when the breakpoint is first set and also when the breakpoint
4477 A warning like the one below is printed when setting a breakpoint
4478 that's been subject to address adjustment:
4481 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4484 Such warnings are printed both for user settable and @value{GDBN}'s
4485 internal breakpoints. If you see one of these warnings, you should
4486 verify that a breakpoint set at the adjusted address will have the
4487 desired affect. If not, the breakpoint in question may be removed and
4488 other breakpoints may be set which will have the desired behavior.
4489 E.g., it may be sufficient to place the breakpoint at a later
4490 instruction. A conditional breakpoint may also be useful in some
4491 cases to prevent the breakpoint from triggering too often.
4493 @value{GDBN} will also issue a warning when stopping at one of these
4494 adjusted breakpoints:
4497 warning: Breakpoint 1 address previously adjusted from 0x00010414
4501 When this warning is encountered, it may be too late to take remedial
4502 action except in cases where the breakpoint is hit earlier or more
4503 frequently than expected.
4505 @node Continuing and Stepping
4506 @section Continuing and Stepping
4510 @cindex resuming execution
4511 @dfn{Continuing} means resuming program execution until your program
4512 completes normally. In contrast, @dfn{stepping} means executing just
4513 one more ``step'' of your program, where ``step'' may mean either one
4514 line of source code, or one machine instruction (depending on what
4515 particular command you use). Either when continuing or when stepping,
4516 your program may stop even sooner, due to a breakpoint or a signal. (If
4517 it stops due to a signal, you may want to use @code{handle}, or use
4518 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4522 @kindex c @r{(@code{continue})}
4523 @kindex fg @r{(resume foreground execution)}
4524 @item continue @r{[}@var{ignore-count}@r{]}
4525 @itemx c @r{[}@var{ignore-count}@r{]}
4526 @itemx fg @r{[}@var{ignore-count}@r{]}
4527 Resume program execution, at the address where your program last stopped;
4528 any breakpoints set at that address are bypassed. The optional argument
4529 @var{ignore-count} allows you to specify a further number of times to
4530 ignore a breakpoint at this location; its effect is like that of
4531 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4533 The argument @var{ignore-count} is meaningful only when your program
4534 stopped due to a breakpoint. At other times, the argument to
4535 @code{continue} is ignored.
4537 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4538 debugged program is deemed to be the foreground program) are provided
4539 purely for convenience, and have exactly the same behavior as
4543 To resume execution at a different place, you can use @code{return}
4544 (@pxref{Returning, ,Returning from a Function}) to go back to the
4545 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4546 Different Address}) to go to an arbitrary location in your program.
4548 A typical technique for using stepping is to set a breakpoint
4549 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4550 beginning of the function or the section of your program where a problem
4551 is believed to lie, run your program until it stops at that breakpoint,
4552 and then step through the suspect area, examining the variables that are
4553 interesting, until you see the problem happen.
4557 @kindex s @r{(@code{step})}
4559 Continue running your program until control reaches a different source
4560 line, then stop it and return control to @value{GDBN}. This command is
4561 abbreviated @code{s}.
4564 @c "without debugging information" is imprecise; actually "without line
4565 @c numbers in the debugging information". (gcc -g1 has debugging info but
4566 @c not line numbers). But it seems complex to try to make that
4567 @c distinction here.
4568 @emph{Warning:} If you use the @code{step} command while control is
4569 within a function that was compiled without debugging information,
4570 execution proceeds until control reaches a function that does have
4571 debugging information. Likewise, it will not step into a function which
4572 is compiled without debugging information. To step through functions
4573 without debugging information, use the @code{stepi} command, described
4577 The @code{step} command only stops at the first instruction of a source
4578 line. This prevents the multiple stops that could otherwise occur in
4579 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4580 to stop if a function that has debugging information is called within
4581 the line. In other words, @code{step} @emph{steps inside} any functions
4582 called within the line.
4584 Also, the @code{step} command only enters a function if there is line
4585 number information for the function. Otherwise it acts like the
4586 @code{next} command. This avoids problems when using @code{cc -gl}
4587 on MIPS machines. Previously, @code{step} entered subroutines if there
4588 was any debugging information about the routine.
4590 @item step @var{count}
4591 Continue running as in @code{step}, but do so @var{count} times. If a
4592 breakpoint is reached, or a signal not related to stepping occurs before
4593 @var{count} steps, stepping stops right away.
4596 @kindex n @r{(@code{next})}
4597 @item next @r{[}@var{count}@r{]}
4598 Continue to the next source line in the current (innermost) stack frame.
4599 This is similar to @code{step}, but function calls that appear within
4600 the line of code are executed without stopping. Execution stops when
4601 control reaches a different line of code at the original stack level
4602 that was executing when you gave the @code{next} command. This command
4603 is abbreviated @code{n}.
4605 An argument @var{count} is a repeat count, as for @code{step}.
4608 @c FIX ME!! Do we delete this, or is there a way it fits in with
4609 @c the following paragraph? --- Vctoria
4611 @c @code{next} within a function that lacks debugging information acts like
4612 @c @code{step}, but any function calls appearing within the code of the
4613 @c function are executed without stopping.
4615 The @code{next} command only stops at the first instruction of a
4616 source line. This prevents multiple stops that could otherwise occur in
4617 @code{switch} statements, @code{for} loops, etc.
4619 @kindex set step-mode
4621 @cindex functions without line info, and stepping
4622 @cindex stepping into functions with no line info
4623 @itemx set step-mode on
4624 The @code{set step-mode on} command causes the @code{step} command to
4625 stop at the first instruction of a function which contains no debug line
4626 information rather than stepping over it.
4628 This is useful in cases where you may be interested in inspecting the
4629 machine instructions of a function which has no symbolic info and do not
4630 want @value{GDBN} to automatically skip over this function.
4632 @item set step-mode off
4633 Causes the @code{step} command to step over any functions which contains no
4634 debug information. This is the default.
4636 @item show step-mode
4637 Show whether @value{GDBN} will stop in or step over functions without
4638 source line debug information.
4641 @kindex fin @r{(@code{finish})}
4643 Continue running until just after function in the selected stack frame
4644 returns. Print the returned value (if any). This command can be
4645 abbreviated as @code{fin}.
4647 Contrast this with the @code{return} command (@pxref{Returning,
4648 ,Returning from a Function}).
4651 @kindex u @r{(@code{until})}
4652 @cindex run until specified location
4655 Continue running until a source line past the current line, in the
4656 current stack frame, is reached. This command is used to avoid single
4657 stepping through a loop more than once. It is like the @code{next}
4658 command, except that when @code{until} encounters a jump, it
4659 automatically continues execution until the program counter is greater
4660 than the address of the jump.
4662 This means that when you reach the end of a loop after single stepping
4663 though it, @code{until} makes your program continue execution until it
4664 exits the loop. In contrast, a @code{next} command at the end of a loop
4665 simply steps back to the beginning of the loop, which forces you to step
4666 through the next iteration.
4668 @code{until} always stops your program if it attempts to exit the current
4671 @code{until} may produce somewhat counterintuitive results if the order
4672 of machine code does not match the order of the source lines. For
4673 example, in the following excerpt from a debugging session, the @code{f}
4674 (@code{frame}) command shows that execution is stopped at line
4675 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4679 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4681 (@value{GDBP}) until
4682 195 for ( ; argc > 0; NEXTARG) @{
4685 This happened because, for execution efficiency, the compiler had
4686 generated code for the loop closure test at the end, rather than the
4687 start, of the loop---even though the test in a C @code{for}-loop is
4688 written before the body of the loop. The @code{until} command appeared
4689 to step back to the beginning of the loop when it advanced to this
4690 expression; however, it has not really gone to an earlier
4691 statement---not in terms of the actual machine code.
4693 @code{until} with no argument works by means of single
4694 instruction stepping, and hence is slower than @code{until} with an
4697 @item until @var{location}
4698 @itemx u @var{location}
4699 Continue running your program until either the specified location is
4700 reached, or the current stack frame returns. @var{location} is any of
4701 the forms described in @ref{Specify Location}.
4702 This form of the command uses temporary breakpoints, and
4703 hence is quicker than @code{until} without an argument. The specified
4704 location is actually reached only if it is in the current frame. This
4705 implies that @code{until} can be used to skip over recursive function
4706 invocations. For instance in the code below, if the current location is
4707 line @code{96}, issuing @code{until 99} will execute the program up to
4708 line @code{99} in the same invocation of factorial, i.e., after the inner
4709 invocations have returned.
4712 94 int factorial (int value)
4714 96 if (value > 1) @{
4715 97 value *= factorial (value - 1);
4722 @kindex advance @var{location}
4723 @itemx advance @var{location}
4724 Continue running the program up to the given @var{location}. An argument is
4725 required, which should be of one of the forms described in
4726 @ref{Specify Location}.
4727 Execution will also stop upon exit from the current stack
4728 frame. This command is similar to @code{until}, but @code{advance} will
4729 not skip over recursive function calls, and the target location doesn't
4730 have to be in the same frame as the current one.
4734 @kindex si @r{(@code{stepi})}
4736 @itemx stepi @var{arg}
4738 Execute one machine instruction, then stop and return to the debugger.
4740 It is often useful to do @samp{display/i $pc} when stepping by machine
4741 instructions. This makes @value{GDBN} automatically display the next
4742 instruction to be executed, each time your program stops. @xref{Auto
4743 Display,, Automatic Display}.
4745 An argument is a repeat count, as in @code{step}.
4749 @kindex ni @r{(@code{nexti})}
4751 @itemx nexti @var{arg}
4753 Execute one machine instruction, but if it is a function call,
4754 proceed until the function returns.
4756 An argument is a repeat count, as in @code{next}.
4763 A signal is an asynchronous event that can happen in a program. The
4764 operating system defines the possible kinds of signals, and gives each
4765 kind a name and a number. For example, in Unix @code{SIGINT} is the
4766 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4767 @code{SIGSEGV} is the signal a program gets from referencing a place in
4768 memory far away from all the areas in use; @code{SIGALRM} occurs when
4769 the alarm clock timer goes off (which happens only if your program has
4770 requested an alarm).
4772 @cindex fatal signals
4773 Some signals, including @code{SIGALRM}, are a normal part of the
4774 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4775 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4776 program has not specified in advance some other way to handle the signal.
4777 @code{SIGINT} does not indicate an error in your program, but it is normally
4778 fatal so it can carry out the purpose of the interrupt: to kill the program.
4780 @value{GDBN} has the ability to detect any occurrence of a signal in your
4781 program. You can tell @value{GDBN} in advance what to do for each kind of
4784 @cindex handling signals
4785 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4786 @code{SIGALRM} be silently passed to your program
4787 (so as not to interfere with their role in the program's functioning)
4788 but to stop your program immediately whenever an error signal happens.
4789 You can change these settings with the @code{handle} command.
4792 @kindex info signals
4796 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4797 handle each one. You can use this to see the signal numbers of all
4798 the defined types of signals.
4800 @item info signals @var{sig}
4801 Similar, but print information only about the specified signal number.
4803 @code{info handle} is an alias for @code{info signals}.
4806 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4807 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4808 can be the number of a signal or its name (with or without the
4809 @samp{SIG} at the beginning); a list of signal numbers of the form
4810 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4811 known signals. Optional arguments @var{keywords}, described below,
4812 say what change to make.
4816 The keywords allowed by the @code{handle} command can be abbreviated.
4817 Their full names are:
4821 @value{GDBN} should not stop your program when this signal happens. It may
4822 still print a message telling you that the signal has come in.
4825 @value{GDBN} should stop your program when this signal happens. This implies
4826 the @code{print} keyword as well.
4829 @value{GDBN} should print a message when this signal happens.
4832 @value{GDBN} should not mention the occurrence of the signal at all. This
4833 implies the @code{nostop} keyword as well.
4837 @value{GDBN} should allow your program to see this signal; your program
4838 can handle the signal, or else it may terminate if the signal is fatal
4839 and not handled. @code{pass} and @code{noignore} are synonyms.
4843 @value{GDBN} should not allow your program to see this signal.
4844 @code{nopass} and @code{ignore} are synonyms.
4848 When a signal stops your program, the signal is not visible to the
4850 continue. Your program sees the signal then, if @code{pass} is in
4851 effect for the signal in question @emph{at that time}. In other words,
4852 after @value{GDBN} reports a signal, you can use the @code{handle}
4853 command with @code{pass} or @code{nopass} to control whether your
4854 program sees that signal when you continue.
4856 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4857 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4858 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4861 You can also use the @code{signal} command to prevent your program from
4862 seeing a signal, or cause it to see a signal it normally would not see,
4863 or to give it any signal at any time. For example, if your program stopped
4864 due to some sort of memory reference error, you might store correct
4865 values into the erroneous variables and continue, hoping to see more
4866 execution; but your program would probably terminate immediately as
4867 a result of the fatal signal once it saw the signal. To prevent this,
4868 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4871 @cindex extra signal information
4872 @anchor{extra signal information}
4874 On some targets, @value{GDBN} can inspect extra signal information
4875 associated with the intercepted signal, before it is actually
4876 delivered to the program being debugged. This information is exported
4877 by the convenience variable @code{$_siginfo}, and consists of data
4878 that is passed by the kernel to the signal handler at the time of the
4879 receipt of a signal. The data type of the information itself is
4880 target dependent. You can see the data type using the @code{ptype
4881 $_siginfo} command. On Unix systems, it typically corresponds to the
4882 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4885 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4886 referenced address that raised a segmentation fault.
4890 (@value{GDBP}) continue
4891 Program received signal SIGSEGV, Segmentation fault.
4892 0x0000000000400766 in main ()
4894 (@value{GDBP}) ptype $_siginfo
4901 struct @{...@} _kill;
4902 struct @{...@} _timer;
4904 struct @{...@} _sigchld;
4905 struct @{...@} _sigfault;
4906 struct @{...@} _sigpoll;
4909 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4913 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4914 $1 = (void *) 0x7ffff7ff7000
4918 Depending on target support, @code{$_siginfo} may also be writable.
4921 @section Stopping and Starting Multi-thread Programs
4923 @cindex stopped threads
4924 @cindex threads, stopped
4926 @cindex continuing threads
4927 @cindex threads, continuing
4929 @value{GDBN} supports debugging programs with multiple threads
4930 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4931 are two modes of controlling execution of your program within the
4932 debugger. In the default mode, referred to as @dfn{all-stop mode},
4933 when any thread in your program stops (for example, at a breakpoint
4934 or while being stepped), all other threads in the program are also stopped by
4935 @value{GDBN}. On some targets, @value{GDBN} also supports
4936 @dfn{non-stop mode}, in which other threads can continue to run freely while
4937 you examine the stopped thread in the debugger.
4940 * All-Stop Mode:: All threads stop when GDB takes control
4941 * Non-Stop Mode:: Other threads continue to execute
4942 * Background Execution:: Running your program asynchronously
4943 * Thread-Specific Breakpoints:: Controlling breakpoints
4944 * Interrupted System Calls:: GDB may interfere with system calls
4948 @subsection All-Stop Mode
4950 @cindex all-stop mode
4952 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4953 @emph{all} threads of execution stop, not just the current thread. This
4954 allows you to examine the overall state of the program, including
4955 switching between threads, without worrying that things may change
4958 Conversely, whenever you restart the program, @emph{all} threads start
4959 executing. @emph{This is true even when single-stepping} with commands
4960 like @code{step} or @code{next}.
4962 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4963 Since thread scheduling is up to your debugging target's operating
4964 system (not controlled by @value{GDBN}), other threads may
4965 execute more than one statement while the current thread completes a
4966 single step. Moreover, in general other threads stop in the middle of a
4967 statement, rather than at a clean statement boundary, when the program
4970 You might even find your program stopped in another thread after
4971 continuing or even single-stepping. This happens whenever some other
4972 thread runs into a breakpoint, a signal, or an exception before the
4973 first thread completes whatever you requested.
4975 @cindex automatic thread selection
4976 @cindex switching threads automatically
4977 @cindex threads, automatic switching
4978 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4979 signal, it automatically selects the thread where that breakpoint or
4980 signal happened. @value{GDBN} alerts you to the context switch with a
4981 message such as @samp{[Switching to Thread @var{n}]} to identify the
4984 On some OSes, you can modify @value{GDBN}'s default behavior by
4985 locking the OS scheduler to allow only a single thread to run.
4988 @item set scheduler-locking @var{mode}
4989 @cindex scheduler locking mode
4990 @cindex lock scheduler
4991 Set the scheduler locking mode. If it is @code{off}, then there is no
4992 locking and any thread may run at any time. If @code{on}, then only the
4993 current thread may run when the inferior is resumed. The @code{step}
4994 mode optimizes for single-stepping; it prevents other threads
4995 from preempting the current thread while you are stepping, so that
4996 the focus of debugging does not change unexpectedly.
4997 Other threads only rarely (or never) get a chance to run
4998 when you step. They are more likely to run when you @samp{next} over a
4999 function call, and they are completely free to run when you use commands
5000 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5001 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5002 the current thread away from the thread that you are debugging.
5004 @item show scheduler-locking
5005 Display the current scheduler locking mode.
5008 @cindex resume threads of multiple processes simultaneously
5009 By default, when you issue one of the execution commands such as
5010 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5011 threads of the current inferior to run. For example, if @value{GDBN}
5012 is attached to two inferiors, each with two threads, the
5013 @code{continue} command resumes only the two threads of the current
5014 inferior. This is useful, for example, when you debug a program that
5015 forks and you want to hold the parent stopped (so that, for instance,
5016 it doesn't run to exit), while you debug the child. In other
5017 situations, you may not be interested in inspecting the current state
5018 of any of the processes @value{GDBN} is attached to, and you may want
5019 to resume them all until some breakpoint is hit. In the latter case,
5020 you can instruct @value{GDBN} to allow all threads of all the
5021 inferiors to run with the @w{@code{set schedule-multiple}} command.
5024 @kindex set schedule-multiple
5025 @item set schedule-multiple
5026 Set the mode for allowing threads of multiple processes to be resumed
5027 when an execution command is issued. When @code{on}, all threads of
5028 all processes are allowed to run. When @code{off}, only the threads
5029 of the current process are resumed. The default is @code{off}. The
5030 @code{scheduler-locking} mode takes precedence when set to @code{on},
5031 or while you are stepping and set to @code{step}.
5033 @item show schedule-multiple
5034 Display the current mode for resuming the execution of threads of
5039 @subsection Non-Stop Mode
5041 @cindex non-stop mode
5043 @c This section is really only a place-holder, and needs to be expanded
5044 @c with more details.
5046 For some multi-threaded targets, @value{GDBN} supports an optional
5047 mode of operation in which you can examine stopped program threads in
5048 the debugger while other threads continue to execute freely. This
5049 minimizes intrusion when debugging live systems, such as programs
5050 where some threads have real-time constraints or must continue to
5051 respond to external events. This is referred to as @dfn{non-stop} mode.
5053 In non-stop mode, when a thread stops to report a debugging event,
5054 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5055 threads as well, in contrast to the all-stop mode behavior. Additionally,
5056 execution commands such as @code{continue} and @code{step} apply by default
5057 only to the current thread in non-stop mode, rather than all threads as
5058 in all-stop mode. This allows you to control threads explicitly in
5059 ways that are not possible in all-stop mode --- for example, stepping
5060 one thread while allowing others to run freely, stepping
5061 one thread while holding all others stopped, or stepping several threads
5062 independently and simultaneously.
5064 To enter non-stop mode, use this sequence of commands before you run
5065 or attach to your program:
5068 # Enable the async interface.
5071 # If using the CLI, pagination breaks non-stop.
5074 # Finally, turn it on!
5078 You can use these commands to manipulate the non-stop mode setting:
5081 @kindex set non-stop
5082 @item set non-stop on
5083 Enable selection of non-stop mode.
5084 @item set non-stop off
5085 Disable selection of non-stop mode.
5086 @kindex show non-stop
5088 Show the current non-stop enablement setting.
5091 Note these commands only reflect whether non-stop mode is enabled,
5092 not whether the currently-executing program is being run in non-stop mode.
5093 In particular, the @code{set non-stop} preference is only consulted when
5094 @value{GDBN} starts or connects to the target program, and it is generally
5095 not possible to switch modes once debugging has started. Furthermore,
5096 since not all targets support non-stop mode, even when you have enabled
5097 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5100 In non-stop mode, all execution commands apply only to the current thread
5101 by default. That is, @code{continue} only continues one thread.
5102 To continue all threads, issue @code{continue -a} or @code{c -a}.
5104 You can use @value{GDBN}'s background execution commands
5105 (@pxref{Background Execution}) to run some threads in the background
5106 while you continue to examine or step others from @value{GDBN}.
5107 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5108 always executed asynchronously in non-stop mode.
5110 Suspending execution is done with the @code{interrupt} command when
5111 running in the background, or @kbd{Ctrl-c} during foreground execution.
5112 In all-stop mode, this stops the whole process;
5113 but in non-stop mode the interrupt applies only to the current thread.
5114 To stop the whole program, use @code{interrupt -a}.
5116 Other execution commands do not currently support the @code{-a} option.
5118 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5119 that thread current, as it does in all-stop mode. This is because the
5120 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5121 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5122 changed to a different thread just as you entered a command to operate on the
5123 previously current thread.
5125 @node Background Execution
5126 @subsection Background Execution
5128 @cindex foreground execution
5129 @cindex background execution
5130 @cindex asynchronous execution
5131 @cindex execution, foreground, background and asynchronous
5133 @value{GDBN}'s execution commands have two variants: the normal
5134 foreground (synchronous) behavior, and a background
5135 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5136 the program to report that some thread has stopped before prompting for
5137 another command. In background execution, @value{GDBN} immediately gives
5138 a command prompt so that you can issue other commands while your program runs.
5140 You need to explicitly enable asynchronous mode before you can use
5141 background execution commands. You can use these commands to
5142 manipulate the asynchronous mode setting:
5145 @kindex set target-async
5146 @item set target-async on
5147 Enable asynchronous mode.
5148 @item set target-async off
5149 Disable asynchronous mode.
5150 @kindex show target-async
5151 @item show target-async
5152 Show the current target-async setting.
5155 If the target doesn't support async mode, @value{GDBN} issues an error
5156 message if you attempt to use the background execution commands.
5158 To specify background execution, add a @code{&} to the command. For example,
5159 the background form of the @code{continue} command is @code{continue&}, or
5160 just @code{c&}. The execution commands that accept background execution
5166 @xref{Starting, , Starting your Program}.
5170 @xref{Attach, , Debugging an Already-running Process}.
5174 @xref{Continuing and Stepping, step}.
5178 @xref{Continuing and Stepping, stepi}.
5182 @xref{Continuing and Stepping, next}.
5186 @xref{Continuing and Stepping, nexti}.
5190 @xref{Continuing and Stepping, continue}.
5194 @xref{Continuing and Stepping, finish}.
5198 @xref{Continuing and Stepping, until}.
5202 Background execution is especially useful in conjunction with non-stop
5203 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5204 However, you can also use these commands in the normal all-stop mode with
5205 the restriction that you cannot issue another execution command until the
5206 previous one finishes. Examples of commands that are valid in all-stop
5207 mode while the program is running include @code{help} and @code{info break}.
5209 You can interrupt your program while it is running in the background by
5210 using the @code{interrupt} command.
5217 Suspend execution of the running program. In all-stop mode,
5218 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5219 only the current thread. To stop the whole program in non-stop mode,
5220 use @code{interrupt -a}.
5223 @node Thread-Specific Breakpoints
5224 @subsection Thread-Specific Breakpoints
5226 When your program has multiple threads (@pxref{Threads,, Debugging
5227 Programs with Multiple Threads}), you can choose whether to set
5228 breakpoints on all threads, or on a particular thread.
5231 @cindex breakpoints and threads
5232 @cindex thread breakpoints
5233 @kindex break @dots{} thread @var{threadno}
5234 @item break @var{linespec} thread @var{threadno}
5235 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5236 @var{linespec} specifies source lines; there are several ways of
5237 writing them (@pxref{Specify Location}), but the effect is always to
5238 specify some source line.
5240 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5241 to specify that you only want @value{GDBN} to stop the program when a
5242 particular thread reaches this breakpoint. @var{threadno} is one of the
5243 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5244 column of the @samp{info threads} display.
5246 If you do not specify @samp{thread @var{threadno}} when you set a
5247 breakpoint, the breakpoint applies to @emph{all} threads of your
5250 You can use the @code{thread} qualifier on conditional breakpoints as
5251 well; in this case, place @samp{thread @var{threadno}} before or
5252 after the breakpoint condition, like this:
5255 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5260 @node Interrupted System Calls
5261 @subsection Interrupted System Calls
5263 @cindex thread breakpoints and system calls
5264 @cindex system calls and thread breakpoints
5265 @cindex premature return from system calls
5266 There is an unfortunate side effect when using @value{GDBN} to debug
5267 multi-threaded programs. If one thread stops for a
5268 breakpoint, or for some other reason, and another thread is blocked in a
5269 system call, then the system call may return prematurely. This is a
5270 consequence of the interaction between multiple threads and the signals
5271 that @value{GDBN} uses to implement breakpoints and other events that
5274 To handle this problem, your program should check the return value of
5275 each system call and react appropriately. This is good programming
5278 For example, do not write code like this:
5284 The call to @code{sleep} will return early if a different thread stops
5285 at a breakpoint or for some other reason.
5287 Instead, write this:
5292 unslept = sleep (unslept);
5295 A system call is allowed to return early, so the system is still
5296 conforming to its specification. But @value{GDBN} does cause your
5297 multi-threaded program to behave differently than it would without
5300 Also, @value{GDBN} uses internal breakpoints in the thread library to
5301 monitor certain events such as thread creation and thread destruction.
5302 When such an event happens, a system call in another thread may return
5303 prematurely, even though your program does not appear to stop.
5306 @node Reverse Execution
5307 @chapter Running programs backward
5308 @cindex reverse execution
5309 @cindex running programs backward
5311 When you are debugging a program, it is not unusual to realize that
5312 you have gone too far, and some event of interest has already happened.
5313 If the target environment supports it, @value{GDBN} can allow you to
5314 ``rewind'' the program by running it backward.
5316 A target environment that supports reverse execution should be able
5317 to ``undo'' the changes in machine state that have taken place as the
5318 program was executing normally. Variables, registers etc.@: should
5319 revert to their previous values. Obviously this requires a great
5320 deal of sophistication on the part of the target environment; not
5321 all target environments can support reverse execution.
5323 When a program is executed in reverse, the instructions that
5324 have most recently been executed are ``un-executed'', in reverse
5325 order. The program counter runs backward, following the previous
5326 thread of execution in reverse. As each instruction is ``un-executed'',
5327 the values of memory and/or registers that were changed by that
5328 instruction are reverted to their previous states. After executing
5329 a piece of source code in reverse, all side effects of that code
5330 should be ``undone'', and all variables should be returned to their
5331 prior values@footnote{
5332 Note that some side effects are easier to undo than others. For instance,
5333 memory and registers are relatively easy, but device I/O is hard. Some
5334 targets may be able undo things like device I/O, and some may not.
5336 The contract between @value{GDBN} and the reverse executing target
5337 requires only that the target do something reasonable when
5338 @value{GDBN} tells it to execute backwards, and then report the
5339 results back to @value{GDBN}. Whatever the target reports back to
5340 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5341 assumes that the memory and registers that the target reports are in a
5342 consistant state, but @value{GDBN} accepts whatever it is given.
5345 If you are debugging in a target environment that supports
5346 reverse execution, @value{GDBN} provides the following commands.
5349 @kindex reverse-continue
5350 @kindex rc @r{(@code{reverse-continue})}
5351 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5352 @itemx rc @r{[}@var{ignore-count}@r{]}
5353 Beginning at the point where your program last stopped, start executing
5354 in reverse. Reverse execution will stop for breakpoints and synchronous
5355 exceptions (signals), just like normal execution. Behavior of
5356 asynchronous signals depends on the target environment.
5358 @kindex reverse-step
5359 @kindex rs @r{(@code{step})}
5360 @item reverse-step @r{[}@var{count}@r{]}
5361 Run the program backward until control reaches the start of a
5362 different source line; then stop it, and return control to @value{GDBN}.
5364 Like the @code{step} command, @code{reverse-step} will only stop
5365 at the beginning of a source line. It ``un-executes'' the previously
5366 executed source line. If the previous source line included calls to
5367 debuggable functions, @code{reverse-step} will step (backward) into
5368 the called function, stopping at the beginning of the @emph{last}
5369 statement in the called function (typically a return statement).
5371 Also, as with the @code{step} command, if non-debuggable functions are
5372 called, @code{reverse-step} will run thru them backward without stopping.
5374 @kindex reverse-stepi
5375 @kindex rsi @r{(@code{reverse-stepi})}
5376 @item reverse-stepi @r{[}@var{count}@r{]}
5377 Reverse-execute one machine instruction. Note that the instruction
5378 to be reverse-executed is @emph{not} the one pointed to by the program
5379 counter, but the instruction executed prior to that one. For instance,
5380 if the last instruction was a jump, @code{reverse-stepi} will take you
5381 back from the destination of the jump to the jump instruction itself.
5383 @kindex reverse-next
5384 @kindex rn @r{(@code{reverse-next})}
5385 @item reverse-next @r{[}@var{count}@r{]}
5386 Run backward to the beginning of the previous line executed in
5387 the current (innermost) stack frame. If the line contains function
5388 calls, they will be ``un-executed'' without stopping. Starting from
5389 the first line of a function, @code{reverse-next} will take you back
5390 to the caller of that function, @emph{before} the function was called,
5391 just as the normal @code{next} command would take you from the last
5392 line of a function back to its return to its caller
5393 @footnote{Unless the code is too heavily optimized.}.
5395 @kindex reverse-nexti
5396 @kindex rni @r{(@code{reverse-nexti})}
5397 @item reverse-nexti @r{[}@var{count}@r{]}
5398 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5399 in reverse, except that called functions are ``un-executed'' atomically.
5400 That is, if the previously executed instruction was a return from
5401 another function, @code{reverse-nexti} will continue to execute
5402 in reverse until the call to that function (from the current stack
5405 @kindex reverse-finish
5406 @item reverse-finish
5407 Just as the @code{finish} command takes you to the point where the
5408 current function returns, @code{reverse-finish} takes you to the point
5409 where it was called. Instead of ending up at the end of the current
5410 function invocation, you end up at the beginning.
5412 @kindex set exec-direction
5413 @item set exec-direction
5414 Set the direction of target execution.
5415 @itemx set exec-direction reverse
5416 @cindex execute forward or backward in time
5417 @value{GDBN} will perform all execution commands in reverse, until the
5418 exec-direction mode is changed to ``forward''. Affected commands include
5419 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5420 command cannot be used in reverse mode.
5421 @item set exec-direction forward
5422 @value{GDBN} will perform all execution commands in the normal fashion.
5423 This is the default.
5427 @node Process Record and Replay
5428 @chapter Recording Inferior's Execution and Replaying It
5429 @cindex process record and replay
5430 @cindex recording inferior's execution and replaying it
5432 On some platforms, @value{GDBN} provides a special @dfn{process record
5433 and replay} target that can record a log of the process execution, and
5434 replay it later with both forward and reverse execution commands.
5437 When this target is in use, if the execution log includes the record
5438 for the next instruction, @value{GDBN} will debug in @dfn{replay
5439 mode}. In the replay mode, the inferior does not really execute code
5440 instructions. Instead, all the events that normally happen during
5441 code execution are taken from the execution log. While code is not
5442 really executed in replay mode, the values of registers (including the
5443 program counter register) and the memory of the inferior are still
5444 changed as they normally would. Their contents are taken from the
5448 If the record for the next instruction is not in the execution log,
5449 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5450 inferior executes normally, and @value{GDBN} records the execution log
5453 The process record and replay target supports reverse execution
5454 (@pxref{Reverse Execution}), even if the platform on which the
5455 inferior runs does not. However, the reverse execution is limited in
5456 this case by the range of the instructions recorded in the execution
5457 log. In other words, reverse execution on platforms that don't
5458 support it directly can only be done in the replay mode.
5460 When debugging in the reverse direction, @value{GDBN} will work in
5461 replay mode as long as the execution log includes the record for the
5462 previous instruction; otherwise, it will work in record mode, if the
5463 platform supports reverse execution, or stop if not.
5465 For architecture environments that support process record and replay,
5466 @value{GDBN} provides the following commands:
5469 @kindex target record
5473 This command starts the process record and replay target. The process
5474 record and replay target can only debug a process that is already
5475 running. Therefore, you need first to start the process with the
5476 @kbd{run} or @kbd{start} commands, and then start the recording with
5477 the @kbd{target record} command.
5479 Both @code{record} and @code{rec} are aliases of @code{target record}.
5481 @cindex displaced stepping, and process record and replay
5482 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5483 will be automatically disabled when process record and replay target
5484 is started. That's because the process record and replay target
5485 doesn't support displaced stepping.
5487 @cindex non-stop mode, and process record and replay
5488 @cindex asynchronous execution, and process record and replay
5489 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5490 the asynchronous execution mode (@pxref{Background Execution}), the
5491 process record and replay target cannot be started because it doesn't
5492 support these two modes.
5497 Stop the process record and replay target. When process record and
5498 replay target stops, the entire execution log will be deleted and the
5499 inferior will either be terminated, or will remain in its final state.
5501 When you stop the process record and replay target in record mode (at
5502 the end of the execution log), the inferior will be stopped at the
5503 next instruction that would have been recorded. In other words, if
5504 you record for a while and then stop recording, the inferior process
5505 will be left in the same state as if the recording never happened.
5507 On the other hand, if the process record and replay target is stopped
5508 while in replay mode (that is, not at the end of the execution log,
5509 but at some earlier point), the inferior process will become ``live''
5510 at that earlier state, and it will then be possible to continue the
5511 usual ``live'' debugging of the process from that state.
5513 When the inferior process exits, or @value{GDBN} detaches from it,
5514 process record and replay target will automatically stop itself.
5516 @kindex set record insn-number-max
5517 @item set record insn-number-max @var{limit}
5518 Set the limit of instructions to be recorded. Default value is 200000.
5520 If @var{limit} is a positive number, then @value{GDBN} will start
5521 deleting instructions from the log once the number of the record
5522 instructions becomes greater than @var{limit}. For every new recorded
5523 instruction, @value{GDBN} will delete the earliest recorded
5524 instruction to keep the number of recorded instructions at the limit.
5525 (Since deleting recorded instructions loses information, @value{GDBN}
5526 lets you control what happens when the limit is reached, by means of
5527 the @code{stop-at-limit} option, described below.)
5529 If @var{limit} is zero, @value{GDBN} will never delete recorded
5530 instructions from the execution log. The number of recorded
5531 instructions is unlimited in this case.
5533 @kindex show record insn-number-max
5534 @item show record insn-number-max
5535 Show the limit of instructions to be recorded.
5537 @kindex set record stop-at-limit
5538 @item set record stop-at-limit
5539 Control the behavior when the number of recorded instructions reaches
5540 the limit. If ON (the default), @value{GDBN} will stop when the limit
5541 is reached for the first time and ask you whether you want to stop the
5542 inferior or continue running it and recording the execution log. If
5543 you decide to continue recording, each new recorded instruction will
5544 cause the oldest one to be deleted.
5546 If this option is OFF, @value{GDBN} will automatically delete the
5547 oldest record to make room for each new one, without asking.
5549 @kindex show record stop-at-limit
5550 @item show record stop-at-limit
5551 Show the current setting of @code{stop-at-limit}.
5555 Show various statistics about the state of process record and its
5556 in-memory execution log buffer, including:
5560 Whether in record mode or replay mode.
5562 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5564 Highest recorded instruction number.
5566 Current instruction about to be replayed (if in replay mode).
5568 Number of instructions contained in the execution log.
5570 Maximum number of instructions that may be contained in the execution log.
5573 @kindex record delete
5576 When record target runs in replay mode (``in the past''), delete the
5577 subsequent execution log and begin to record a new execution log starting
5578 from the current address. This means you will abandon the previously
5579 recorded ``future'' and begin recording a new ``future''.
5584 @chapter Examining the Stack
5586 When your program has stopped, the first thing you need to know is where it
5587 stopped and how it got there.
5590 Each time your program performs a function call, information about the call
5592 That information includes the location of the call in your program,
5593 the arguments of the call,
5594 and the local variables of the function being called.
5595 The information is saved in a block of data called a @dfn{stack frame}.
5596 The stack frames are allocated in a region of memory called the @dfn{call
5599 When your program stops, the @value{GDBN} commands for examining the
5600 stack allow you to see all of this information.
5602 @cindex selected frame
5603 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5604 @value{GDBN} commands refer implicitly to the selected frame. In
5605 particular, whenever you ask @value{GDBN} for the value of a variable in
5606 your program, the value is found in the selected frame. There are
5607 special @value{GDBN} commands to select whichever frame you are
5608 interested in. @xref{Selection, ,Selecting a Frame}.
5610 When your program stops, @value{GDBN} automatically selects the
5611 currently executing frame and describes it briefly, similar to the
5612 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5615 * Frames:: Stack frames
5616 * Backtrace:: Backtraces
5617 * Selection:: Selecting a frame
5618 * Frame Info:: Information on a frame
5623 @section Stack Frames
5625 @cindex frame, definition
5627 The call stack is divided up into contiguous pieces called @dfn{stack
5628 frames}, or @dfn{frames} for short; each frame is the data associated
5629 with one call to one function. The frame contains the arguments given
5630 to the function, the function's local variables, and the address at
5631 which the function is executing.
5633 @cindex initial frame
5634 @cindex outermost frame
5635 @cindex innermost frame
5636 When your program is started, the stack has only one frame, that of the
5637 function @code{main}. This is called the @dfn{initial} frame or the
5638 @dfn{outermost} frame. Each time a function is called, a new frame is
5639 made. Each time a function returns, the frame for that function invocation
5640 is eliminated. If a function is recursive, there can be many frames for
5641 the same function. The frame for the function in which execution is
5642 actually occurring is called the @dfn{innermost} frame. This is the most
5643 recently created of all the stack frames that still exist.
5645 @cindex frame pointer
5646 Inside your program, stack frames are identified by their addresses. A
5647 stack frame consists of many bytes, each of which has its own address; each
5648 kind of computer has a convention for choosing one byte whose
5649 address serves as the address of the frame. Usually this address is kept
5650 in a register called the @dfn{frame pointer register}
5651 (@pxref{Registers, $fp}) while execution is going on in that frame.
5653 @cindex frame number
5654 @value{GDBN} assigns numbers to all existing stack frames, starting with
5655 zero for the innermost frame, one for the frame that called it,
5656 and so on upward. These numbers do not really exist in your program;
5657 they are assigned by @value{GDBN} to give you a way of designating stack
5658 frames in @value{GDBN} commands.
5660 @c The -fomit-frame-pointer below perennially causes hbox overflow
5661 @c underflow problems.
5662 @cindex frameless execution
5663 Some compilers provide a way to compile functions so that they operate
5664 without stack frames. (For example, the @value{NGCC} option
5666 @samp{-fomit-frame-pointer}
5668 generates functions without a frame.)
5669 This is occasionally done with heavily used library functions to save
5670 the frame setup time. @value{GDBN} has limited facilities for dealing
5671 with these function invocations. If the innermost function invocation
5672 has no stack frame, @value{GDBN} nevertheless regards it as though
5673 it had a separate frame, which is numbered zero as usual, allowing
5674 correct tracing of the function call chain. However, @value{GDBN} has
5675 no provision for frameless functions elsewhere in the stack.
5678 @kindex frame@r{, command}
5679 @cindex current stack frame
5680 @item frame @var{args}
5681 The @code{frame} command allows you to move from one stack frame to another,
5682 and to print the stack frame you select. @var{args} may be either the
5683 address of the frame or the stack frame number. Without an argument,
5684 @code{frame} prints the current stack frame.
5686 @kindex select-frame
5687 @cindex selecting frame silently
5689 The @code{select-frame} command allows you to move from one stack frame
5690 to another without printing the frame. This is the silent version of
5698 @cindex call stack traces
5699 A backtrace is a summary of how your program got where it is. It shows one
5700 line per frame, for many frames, starting with the currently executing
5701 frame (frame zero), followed by its caller (frame one), and on up the
5706 @kindex bt @r{(@code{backtrace})}
5709 Print a backtrace of the entire stack: one line per frame for all
5710 frames in the stack.
5712 You can stop the backtrace at any time by typing the system interrupt
5713 character, normally @kbd{Ctrl-c}.
5715 @item backtrace @var{n}
5717 Similar, but print only the innermost @var{n} frames.
5719 @item backtrace -@var{n}
5721 Similar, but print only the outermost @var{n} frames.
5723 @item backtrace full
5725 @itemx bt full @var{n}
5726 @itemx bt full -@var{n}
5727 Print the values of the local variables also. @var{n} specifies the
5728 number of frames to print, as described above.
5733 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5734 are additional aliases for @code{backtrace}.
5736 @cindex multiple threads, backtrace
5737 In a multi-threaded program, @value{GDBN} by default shows the
5738 backtrace only for the current thread. To display the backtrace for
5739 several or all of the threads, use the command @code{thread apply}
5740 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5741 apply all backtrace}, @value{GDBN} will display the backtrace for all
5742 the threads; this is handy when you debug a core dump of a
5743 multi-threaded program.
5745 Each line in the backtrace shows the frame number and the function name.
5746 The program counter value is also shown---unless you use @code{set
5747 print address off}. The backtrace also shows the source file name and
5748 line number, as well as the arguments to the function. The program
5749 counter value is omitted if it is at the beginning of the code for that
5752 Here is an example of a backtrace. It was made with the command
5753 @samp{bt 3}, so it shows the innermost three frames.
5757 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5759 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5760 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5762 (More stack frames follow...)
5767 The display for frame zero does not begin with a program counter
5768 value, indicating that your program has stopped at the beginning of the
5769 code for line @code{993} of @code{builtin.c}.
5772 The value of parameter @code{data} in frame 1 has been replaced by
5773 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5774 only if it is a scalar (integer, pointer, enumeration, etc). See command
5775 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5776 on how to configure the way function parameter values are printed.
5778 @cindex value optimized out, in backtrace
5779 @cindex function call arguments, optimized out
5780 If your program was compiled with optimizations, some compilers will
5781 optimize away arguments passed to functions if those arguments are
5782 never used after the call. Such optimizations generate code that
5783 passes arguments through registers, but doesn't store those arguments
5784 in the stack frame. @value{GDBN} has no way of displaying such
5785 arguments in stack frames other than the innermost one. Here's what
5786 such a backtrace might look like:
5790 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5792 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5793 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5795 (More stack frames follow...)
5800 The values of arguments that were not saved in their stack frames are
5801 shown as @samp{<value optimized out>}.
5803 If you need to display the values of such optimized-out arguments,
5804 either deduce that from other variables whose values depend on the one
5805 you are interested in, or recompile without optimizations.
5807 @cindex backtrace beyond @code{main} function
5808 @cindex program entry point
5809 @cindex startup code, and backtrace
5810 Most programs have a standard user entry point---a place where system
5811 libraries and startup code transition into user code. For C this is
5812 @code{main}@footnote{
5813 Note that embedded programs (the so-called ``free-standing''
5814 environment) are not required to have a @code{main} function as the
5815 entry point. They could even have multiple entry points.}.
5816 When @value{GDBN} finds the entry function in a backtrace
5817 it will terminate the backtrace, to avoid tracing into highly
5818 system-specific (and generally uninteresting) code.
5820 If you need to examine the startup code, or limit the number of levels
5821 in a backtrace, you can change this behavior:
5824 @item set backtrace past-main
5825 @itemx set backtrace past-main on
5826 @kindex set backtrace
5827 Backtraces will continue past the user entry point.
5829 @item set backtrace past-main off
5830 Backtraces will stop when they encounter the user entry point. This is the
5833 @item show backtrace past-main
5834 @kindex show backtrace
5835 Display the current user entry point backtrace policy.
5837 @item set backtrace past-entry
5838 @itemx set backtrace past-entry on
5839 Backtraces will continue past the internal entry point of an application.
5840 This entry point is encoded by the linker when the application is built,
5841 and is likely before the user entry point @code{main} (or equivalent) is called.
5843 @item set backtrace past-entry off
5844 Backtraces will stop when they encounter the internal entry point of an
5845 application. This is the default.
5847 @item show backtrace past-entry
5848 Display the current internal entry point backtrace policy.
5850 @item set backtrace limit @var{n}
5851 @itemx set backtrace limit 0
5852 @cindex backtrace limit
5853 Limit the backtrace to @var{n} levels. A value of zero means
5856 @item show backtrace limit
5857 Display the current limit on backtrace levels.
5861 @section Selecting a Frame
5863 Most commands for examining the stack and other data in your program work on
5864 whichever stack frame is selected at the moment. Here are the commands for
5865 selecting a stack frame; all of them finish by printing a brief description
5866 of the stack frame just selected.
5869 @kindex frame@r{, selecting}
5870 @kindex f @r{(@code{frame})}
5873 Select frame number @var{n}. Recall that frame zero is the innermost
5874 (currently executing) frame, frame one is the frame that called the
5875 innermost one, and so on. The highest-numbered frame is the one for
5878 @item frame @var{addr}
5880 Select the frame at address @var{addr}. This is useful mainly if the
5881 chaining of stack frames has been damaged by a bug, making it
5882 impossible for @value{GDBN} to assign numbers properly to all frames. In
5883 addition, this can be useful when your program has multiple stacks and
5884 switches between them.
5886 On the SPARC architecture, @code{frame} needs two addresses to
5887 select an arbitrary frame: a frame pointer and a stack pointer.
5889 On the MIPS and Alpha architecture, it needs two addresses: a stack
5890 pointer and a program counter.
5892 On the 29k architecture, it needs three addresses: a register stack
5893 pointer, a program counter, and a memory stack pointer.
5897 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5898 advances toward the outermost frame, to higher frame numbers, to frames
5899 that have existed longer. @var{n} defaults to one.
5902 @kindex do @r{(@code{down})}
5904 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5905 advances toward the innermost frame, to lower frame numbers, to frames
5906 that were created more recently. @var{n} defaults to one. You may
5907 abbreviate @code{down} as @code{do}.
5910 All of these commands end by printing two lines of output describing the
5911 frame. The first line shows the frame number, the function name, the
5912 arguments, and the source file and line number of execution in that
5913 frame. The second line shows the text of that source line.
5921 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5923 10 read_input_file (argv[i]);
5927 After such a printout, the @code{list} command with no arguments
5928 prints ten lines centered on the point of execution in the frame.
5929 You can also edit the program at the point of execution with your favorite
5930 editing program by typing @code{edit}.
5931 @xref{List, ,Printing Source Lines},
5935 @kindex down-silently
5937 @item up-silently @var{n}
5938 @itemx down-silently @var{n}
5939 These two commands are variants of @code{up} and @code{down},
5940 respectively; they differ in that they do their work silently, without
5941 causing display of the new frame. They are intended primarily for use
5942 in @value{GDBN} command scripts, where the output might be unnecessary and
5947 @section Information About a Frame
5949 There are several other commands to print information about the selected
5955 When used without any argument, this command does not change which
5956 frame is selected, but prints a brief description of the currently
5957 selected stack frame. It can be abbreviated @code{f}. With an
5958 argument, this command is used to select a stack frame.
5959 @xref{Selection, ,Selecting a Frame}.
5962 @kindex info f @r{(@code{info frame})}
5965 This command prints a verbose description of the selected stack frame,
5970 the address of the frame
5972 the address of the next frame down (called by this frame)
5974 the address of the next frame up (caller of this frame)
5976 the language in which the source code corresponding to this frame is written
5978 the address of the frame's arguments
5980 the address of the frame's local variables
5982 the program counter saved in it (the address of execution in the caller frame)
5984 which registers were saved in the frame
5987 @noindent The verbose description is useful when
5988 something has gone wrong that has made the stack format fail to fit
5989 the usual conventions.
5991 @item info frame @var{addr}
5992 @itemx info f @var{addr}
5993 Print a verbose description of the frame at address @var{addr}, without
5994 selecting that frame. The selected frame remains unchanged by this
5995 command. This requires the same kind of address (more than one for some
5996 architectures) that you specify in the @code{frame} command.
5997 @xref{Selection, ,Selecting a Frame}.
6001 Print the arguments of the selected frame, each on a separate line.
6005 Print the local variables of the selected frame, each on a separate
6006 line. These are all variables (declared either static or automatic)
6007 accessible at the point of execution of the selected frame.
6010 @cindex catch exceptions, list active handlers
6011 @cindex exception handlers, how to list
6013 Print a list of all the exception handlers that are active in the
6014 current stack frame at the current point of execution. To see other
6015 exception handlers, visit the associated frame (using the @code{up},
6016 @code{down}, or @code{frame} commands); then type @code{info catch}.
6017 @xref{Set Catchpoints, , Setting Catchpoints}.
6023 @chapter Examining Source Files
6025 @value{GDBN} can print parts of your program's source, since the debugging
6026 information recorded in the program tells @value{GDBN} what source files were
6027 used to build it. When your program stops, @value{GDBN} spontaneously prints
6028 the line where it stopped. Likewise, when you select a stack frame
6029 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6030 execution in that frame has stopped. You can print other portions of
6031 source files by explicit command.
6033 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6034 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6035 @value{GDBN} under @sc{gnu} Emacs}.
6038 * List:: Printing source lines
6039 * Specify Location:: How to specify code locations
6040 * Edit:: Editing source files
6041 * Search:: Searching source files
6042 * Source Path:: Specifying source directories
6043 * Machine Code:: Source and machine code
6047 @section Printing Source Lines
6050 @kindex l @r{(@code{list})}
6051 To print lines from a source file, use the @code{list} command
6052 (abbreviated @code{l}). By default, ten lines are printed.
6053 There are several ways to specify what part of the file you want to
6054 print; see @ref{Specify Location}, for the full list.
6056 Here are the forms of the @code{list} command most commonly used:
6059 @item list @var{linenum}
6060 Print lines centered around line number @var{linenum} in the
6061 current source file.
6063 @item list @var{function}
6064 Print lines centered around the beginning of function
6068 Print more lines. If the last lines printed were printed with a
6069 @code{list} command, this prints lines following the last lines
6070 printed; however, if the last line printed was a solitary line printed
6071 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6072 Stack}), this prints lines centered around that line.
6075 Print lines just before the lines last printed.
6078 @cindex @code{list}, how many lines to display
6079 By default, @value{GDBN} prints ten source lines with any of these forms of
6080 the @code{list} command. You can change this using @code{set listsize}:
6083 @kindex set listsize
6084 @item set listsize @var{count}
6085 Make the @code{list} command display @var{count} source lines (unless
6086 the @code{list} argument explicitly specifies some other number).
6088 @kindex show listsize
6090 Display the number of lines that @code{list} prints.
6093 Repeating a @code{list} command with @key{RET} discards the argument,
6094 so it is equivalent to typing just @code{list}. This is more useful
6095 than listing the same lines again. An exception is made for an
6096 argument of @samp{-}; that argument is preserved in repetition so that
6097 each repetition moves up in the source file.
6099 In general, the @code{list} command expects you to supply zero, one or two
6100 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6101 of writing them (@pxref{Specify Location}), but the effect is always
6102 to specify some source line.
6104 Here is a complete description of the possible arguments for @code{list}:
6107 @item list @var{linespec}
6108 Print lines centered around the line specified by @var{linespec}.
6110 @item list @var{first},@var{last}
6111 Print lines from @var{first} to @var{last}. Both arguments are
6112 linespecs. When a @code{list} command has two linespecs, and the
6113 source file of the second linespec is omitted, this refers to
6114 the same source file as the first linespec.
6116 @item list ,@var{last}
6117 Print lines ending with @var{last}.
6119 @item list @var{first},
6120 Print lines starting with @var{first}.
6123 Print lines just after the lines last printed.
6126 Print lines just before the lines last printed.
6129 As described in the preceding table.
6132 @node Specify Location
6133 @section Specifying a Location
6134 @cindex specifying location
6137 Several @value{GDBN} commands accept arguments that specify a location
6138 of your program's code. Since @value{GDBN} is a source-level
6139 debugger, a location usually specifies some line in the source code;
6140 for that reason, locations are also known as @dfn{linespecs}.
6142 Here are all the different ways of specifying a code location that
6143 @value{GDBN} understands:
6147 Specifies the line number @var{linenum} of the current source file.
6150 @itemx +@var{offset}
6151 Specifies the line @var{offset} lines before or after the @dfn{current
6152 line}. For the @code{list} command, the current line is the last one
6153 printed; for the breakpoint commands, this is the line at which
6154 execution stopped in the currently selected @dfn{stack frame}
6155 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6156 used as the second of the two linespecs in a @code{list} command,
6157 this specifies the line @var{offset} lines up or down from the first
6160 @item @var{filename}:@var{linenum}
6161 Specifies the line @var{linenum} in the source file @var{filename}.
6163 @item @var{function}
6164 Specifies the line that begins the body of the function @var{function}.
6165 For example, in C, this is the line with the open brace.
6167 @item @var{filename}:@var{function}
6168 Specifies the line that begins the body of the function @var{function}
6169 in the file @var{filename}. You only need the file name with a
6170 function name to avoid ambiguity when there are identically named
6171 functions in different source files.
6173 @item *@var{address}
6174 Specifies the program address @var{address}. For line-oriented
6175 commands, such as @code{list} and @code{edit}, this specifies a source
6176 line that contains @var{address}. For @code{break} and other
6177 breakpoint oriented commands, this can be used to set breakpoints in
6178 parts of your program which do not have debugging information or
6181 Here @var{address} may be any expression valid in the current working
6182 language (@pxref{Languages, working language}) that specifies a code
6183 address. In addition, as a convenience, @value{GDBN} extends the
6184 semantics of expressions used in locations to cover the situations
6185 that frequently happen during debugging. Here are the various forms
6189 @item @var{expression}
6190 Any expression valid in the current working language.
6192 @item @var{funcaddr}
6193 An address of a function or procedure derived from its name. In C,
6194 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6195 simply the function's name @var{function} (and actually a special case
6196 of a valid expression). In Pascal and Modula-2, this is
6197 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6198 (although the Pascal form also works).
6200 This form specifies the address of the function's first instruction,
6201 before the stack frame and arguments have been set up.
6203 @item '@var{filename}'::@var{funcaddr}
6204 Like @var{funcaddr} above, but also specifies the name of the source
6205 file explicitly. This is useful if the name of the function does not
6206 specify the function unambiguously, e.g., if there are several
6207 functions with identical names in different source files.
6214 @section Editing Source Files
6215 @cindex editing source files
6218 @kindex e @r{(@code{edit})}
6219 To edit the lines in a source file, use the @code{edit} command.
6220 The editing program of your choice
6221 is invoked with the current line set to
6222 the active line in the program.
6223 Alternatively, there are several ways to specify what part of the file you
6224 want to print if you want to see other parts of the program:
6227 @item edit @var{location}
6228 Edit the source file specified by @code{location}. Editing starts at
6229 that @var{location}, e.g., at the specified source line of the
6230 specified file. @xref{Specify Location}, for all the possible forms
6231 of the @var{location} argument; here are the forms of the @code{edit}
6232 command most commonly used:
6235 @item edit @var{number}
6236 Edit the current source file with @var{number} as the active line number.
6238 @item edit @var{function}
6239 Edit the file containing @var{function} at the beginning of its definition.
6244 @subsection Choosing your Editor
6245 You can customize @value{GDBN} to use any editor you want
6247 The only restriction is that your editor (say @code{ex}), recognizes the
6248 following command-line syntax:
6250 ex +@var{number} file
6252 The optional numeric value +@var{number} specifies the number of the line in
6253 the file where to start editing.}.
6254 By default, it is @file{@value{EDITOR}}, but you can change this
6255 by setting the environment variable @code{EDITOR} before using
6256 @value{GDBN}. For example, to configure @value{GDBN} to use the
6257 @code{vi} editor, you could use these commands with the @code{sh} shell:
6263 or in the @code{csh} shell,
6265 setenv EDITOR /usr/bin/vi
6270 @section Searching Source Files
6271 @cindex searching source files
6273 There are two commands for searching through the current source file for a
6278 @kindex forward-search
6279 @item forward-search @var{regexp}
6280 @itemx search @var{regexp}
6281 The command @samp{forward-search @var{regexp}} checks each line,
6282 starting with the one following the last line listed, for a match for
6283 @var{regexp}. It lists the line that is found. You can use the
6284 synonym @samp{search @var{regexp}} or abbreviate the command name as
6287 @kindex reverse-search
6288 @item reverse-search @var{regexp}
6289 The command @samp{reverse-search @var{regexp}} checks each line, starting
6290 with the one before the last line listed and going backward, for a match
6291 for @var{regexp}. It lists the line that is found. You can abbreviate
6292 this command as @code{rev}.
6296 @section Specifying Source Directories
6299 @cindex directories for source files
6300 Executable programs sometimes do not record the directories of the source
6301 files from which they were compiled, just the names. Even when they do,
6302 the directories could be moved between the compilation and your debugging
6303 session. @value{GDBN} has a list of directories to search for source files;
6304 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6305 it tries all the directories in the list, in the order they are present
6306 in the list, until it finds a file with the desired name.
6308 For example, suppose an executable references the file
6309 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6310 @file{/mnt/cross}. The file is first looked up literally; if this
6311 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6312 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6313 message is printed. @value{GDBN} does not look up the parts of the
6314 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6315 Likewise, the subdirectories of the source path are not searched: if
6316 the source path is @file{/mnt/cross}, and the binary refers to
6317 @file{foo.c}, @value{GDBN} would not find it under
6318 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6320 Plain file names, relative file names with leading directories, file
6321 names containing dots, etc.@: are all treated as described above; for
6322 instance, if the source path is @file{/mnt/cross}, and the source file
6323 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6324 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6325 that---@file{/mnt/cross/foo.c}.
6327 Note that the executable search path is @emph{not} used to locate the
6330 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6331 any information it has cached about where source files are found and where
6332 each line is in the file.
6336 When you start @value{GDBN}, its source path includes only @samp{cdir}
6337 and @samp{cwd}, in that order.
6338 To add other directories, use the @code{directory} command.
6340 The search path is used to find both program source files and @value{GDBN}
6341 script files (read using the @samp{-command} option and @samp{source} command).
6343 In addition to the source path, @value{GDBN} provides a set of commands
6344 that manage a list of source path substitution rules. A @dfn{substitution
6345 rule} specifies how to rewrite source directories stored in the program's
6346 debug information in case the sources were moved to a different
6347 directory between compilation and debugging. A rule is made of
6348 two strings, the first specifying what needs to be rewritten in
6349 the path, and the second specifying how it should be rewritten.
6350 In @ref{set substitute-path}, we name these two parts @var{from} and
6351 @var{to} respectively. @value{GDBN} does a simple string replacement
6352 of @var{from} with @var{to} at the start of the directory part of the
6353 source file name, and uses that result instead of the original file
6354 name to look up the sources.
6356 Using the previous example, suppose the @file{foo-1.0} tree has been
6357 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6358 @value{GDBN} to replace @file{/usr/src} in all source path names with
6359 @file{/mnt/cross}. The first lookup will then be
6360 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6361 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6362 substitution rule, use the @code{set substitute-path} command
6363 (@pxref{set substitute-path}).
6365 To avoid unexpected substitution results, a rule is applied only if the
6366 @var{from} part of the directory name ends at a directory separator.
6367 For instance, a rule substituting @file{/usr/source} into
6368 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6369 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6370 is applied only at the beginning of the directory name, this rule will
6371 not be applied to @file{/root/usr/source/baz.c} either.
6373 In many cases, you can achieve the same result using the @code{directory}
6374 command. However, @code{set substitute-path} can be more efficient in
6375 the case where the sources are organized in a complex tree with multiple
6376 subdirectories. With the @code{directory} command, you need to add each
6377 subdirectory of your project. If you moved the entire tree while
6378 preserving its internal organization, then @code{set substitute-path}
6379 allows you to direct the debugger to all the sources with one single
6382 @code{set substitute-path} is also more than just a shortcut command.
6383 The source path is only used if the file at the original location no
6384 longer exists. On the other hand, @code{set substitute-path} modifies
6385 the debugger behavior to look at the rewritten location instead. So, if
6386 for any reason a source file that is not relevant to your executable is
6387 located at the original location, a substitution rule is the only
6388 method available to point @value{GDBN} at the new location.
6390 @cindex @samp{--with-relocated-sources}
6391 @cindex default source path substitution
6392 You can configure a default source path substitution rule by
6393 configuring @value{GDBN} with the
6394 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6395 should be the name of a directory under @value{GDBN}'s configured
6396 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6397 directory names in debug information under @var{dir} will be adjusted
6398 automatically if the installed @value{GDBN} is moved to a new
6399 location. This is useful if @value{GDBN}, libraries or executables
6400 with debug information and corresponding source code are being moved
6404 @item directory @var{dirname} @dots{}
6405 @item dir @var{dirname} @dots{}
6406 Add directory @var{dirname} to the front of the source path. Several
6407 directory names may be given to this command, separated by @samp{:}
6408 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6409 part of absolute file names) or
6410 whitespace. You may specify a directory that is already in the source
6411 path; this moves it forward, so @value{GDBN} searches it sooner.
6415 @vindex $cdir@r{, convenience variable}
6416 @vindex $cwd@r{, convenience variable}
6417 @cindex compilation directory
6418 @cindex current directory
6419 @cindex working directory
6420 @cindex directory, current
6421 @cindex directory, compilation
6422 You can use the string @samp{$cdir} to refer to the compilation
6423 directory (if one is recorded), and @samp{$cwd} to refer to the current
6424 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6425 tracks the current working directory as it changes during your @value{GDBN}
6426 session, while the latter is immediately expanded to the current
6427 directory at the time you add an entry to the source path.
6430 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6432 @c RET-repeat for @code{directory} is explicitly disabled, but since
6433 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6435 @item show directories
6436 @kindex show directories
6437 Print the source path: show which directories it contains.
6439 @anchor{set substitute-path}
6440 @item set substitute-path @var{from} @var{to}
6441 @kindex set substitute-path
6442 Define a source path substitution rule, and add it at the end of the
6443 current list of existing substitution rules. If a rule with the same
6444 @var{from} was already defined, then the old rule is also deleted.
6446 For example, if the file @file{/foo/bar/baz.c} was moved to
6447 @file{/mnt/cross/baz.c}, then the command
6450 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6454 will tell @value{GDBN} to replace @samp{/usr/src} with
6455 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6456 @file{baz.c} even though it was moved.
6458 In the case when more than one substitution rule have been defined,
6459 the rules are evaluated one by one in the order where they have been
6460 defined. The first one matching, if any, is selected to perform
6463 For instance, if we had entered the following commands:
6466 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6467 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6471 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6472 @file{/mnt/include/defs.h} by using the first rule. However, it would
6473 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6474 @file{/mnt/src/lib/foo.c}.
6477 @item unset substitute-path [path]
6478 @kindex unset substitute-path
6479 If a path is specified, search the current list of substitution rules
6480 for a rule that would rewrite that path. Delete that rule if found.
6481 A warning is emitted by the debugger if no rule could be found.
6483 If no path is specified, then all substitution rules are deleted.
6485 @item show substitute-path [path]
6486 @kindex show substitute-path
6487 If a path is specified, then print the source path substitution rule
6488 which would rewrite that path, if any.
6490 If no path is specified, then print all existing source path substitution
6495 If your source path is cluttered with directories that are no longer of
6496 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6497 versions of source. You can correct the situation as follows:
6501 Use @code{directory} with no argument to reset the source path to its default value.
6504 Use @code{directory} with suitable arguments to reinstall the
6505 directories you want in the source path. You can add all the
6506 directories in one command.
6510 @section Source and Machine Code
6511 @cindex source line and its code address
6513 You can use the command @code{info line} to map source lines to program
6514 addresses (and vice versa), and the command @code{disassemble} to display
6515 a range of addresses as machine instructions. You can use the command
6516 @code{set disassemble-next-line} to set whether to disassemble next
6517 source line when execution stops. When run under @sc{gnu} Emacs
6518 mode, the @code{info line} command causes the arrow to point to the
6519 line specified. Also, @code{info line} prints addresses in symbolic form as
6524 @item info line @var{linespec}
6525 Print the starting and ending addresses of the compiled code for
6526 source line @var{linespec}. You can specify source lines in any of
6527 the ways documented in @ref{Specify Location}.
6530 For example, we can use @code{info line} to discover the location of
6531 the object code for the first line of function
6532 @code{m4_changequote}:
6534 @c FIXME: I think this example should also show the addresses in
6535 @c symbolic form, as they usually would be displayed.
6537 (@value{GDBP}) info line m4_changequote
6538 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6542 @cindex code address and its source line
6543 We can also inquire (using @code{*@var{addr}} as the form for
6544 @var{linespec}) what source line covers a particular address:
6546 (@value{GDBP}) info line *0x63ff
6547 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6550 @cindex @code{$_} and @code{info line}
6551 @cindex @code{x} command, default address
6552 @kindex x@r{(examine), and} info line
6553 After @code{info line}, the default address for the @code{x} command
6554 is changed to the starting address of the line, so that @samp{x/i} is
6555 sufficient to begin examining the machine code (@pxref{Memory,
6556 ,Examining Memory}). Also, this address is saved as the value of the
6557 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6562 @cindex assembly instructions
6563 @cindex instructions, assembly
6564 @cindex machine instructions
6565 @cindex listing machine instructions
6567 @itemx disassemble /m
6568 @itemx disassemble /r
6569 This specialized command dumps a range of memory as machine
6570 instructions. It can also print mixed source+disassembly by specifying
6571 the @code{/m} modifier and print the raw instructions in hex as well as
6572 in symbolic form by specifying the @code{/r}.
6573 The default memory range is the function surrounding the
6574 program counter of the selected frame. A single argument to this
6575 command is a program counter value; @value{GDBN} dumps the function
6576 surrounding this value. When two arguments are given, they should
6577 be separated by a comma, possibly surrounded by whitespace. The
6578 arguments specify a range of addresses (first inclusive, second exclusive)
6579 to dump. In that case, the name of the function is also printed (since
6580 there could be several functions in the given range).
6582 The argument(s) can be any expression yielding a numeric value, such as
6583 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6585 If the range of memory being disassembled contains current program counter,
6586 the instruction at that location is shown with a @code{=>} marker.
6589 The following example shows the disassembly of a range of addresses of
6590 HP PA-RISC 2.0 code:
6593 (@value{GDBP}) disas 0x32c4, 0x32e4
6594 Dump of assembler code from 0x32c4 to 0x32e4:
6595 0x32c4 <main+204>: addil 0,dp
6596 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6597 0x32cc <main+212>: ldil 0x3000,r31
6598 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6599 0x32d4 <main+220>: ldo 0(r31),rp
6600 0x32d8 <main+224>: addil -0x800,dp
6601 0x32dc <main+228>: ldo 0x588(r1),r26
6602 0x32e0 <main+232>: ldil 0x3000,r31
6603 End of assembler dump.
6606 Here is an example showing mixed source+assembly for Intel x86, when the
6607 program is stopped just after function prologue:
6610 (@value{GDBP}) disas /m main
6611 Dump of assembler code for function main:
6613 0x08048330 <+0>: push %ebp
6614 0x08048331 <+1>: mov %esp,%ebp
6615 0x08048333 <+3>: sub $0x8,%esp
6616 0x08048336 <+6>: and $0xfffffff0,%esp
6617 0x08048339 <+9>: sub $0x10,%esp
6619 6 printf ("Hello.\n");
6620 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6621 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6625 0x08048348 <+24>: mov $0x0,%eax
6626 0x0804834d <+29>: leave
6627 0x0804834e <+30>: ret
6629 End of assembler dump.
6632 Some architectures have more than one commonly-used set of instruction
6633 mnemonics or other syntax.
6635 For programs that were dynamically linked and use shared libraries,
6636 instructions that call functions or branch to locations in the shared
6637 libraries might show a seemingly bogus location---it's actually a
6638 location of the relocation table. On some architectures, @value{GDBN}
6639 might be able to resolve these to actual function names.
6642 @kindex set disassembly-flavor
6643 @cindex Intel disassembly flavor
6644 @cindex AT&T disassembly flavor
6645 @item set disassembly-flavor @var{instruction-set}
6646 Select the instruction set to use when disassembling the
6647 program via the @code{disassemble} or @code{x/i} commands.
6649 Currently this command is only defined for the Intel x86 family. You
6650 can set @var{instruction-set} to either @code{intel} or @code{att}.
6651 The default is @code{att}, the AT&T flavor used by default by Unix
6652 assemblers for x86-based targets.
6654 @kindex show disassembly-flavor
6655 @item show disassembly-flavor
6656 Show the current setting of the disassembly flavor.
6660 @kindex set disassemble-next-line
6661 @kindex show disassemble-next-line
6662 @item set disassemble-next-line
6663 @itemx show disassemble-next-line
6664 Control whether or not @value{GDBN} will disassemble the next source
6665 line or instruction when execution stops. If ON, @value{GDBN} will
6666 display disassembly of the next source line when execution of the
6667 program being debugged stops. This is @emph{in addition} to
6668 displaying the source line itself, which @value{GDBN} always does if
6669 possible. If the next source line cannot be displayed for some reason
6670 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6671 info in the debug info), @value{GDBN} will display disassembly of the
6672 next @emph{instruction} instead of showing the next source line. If
6673 AUTO, @value{GDBN} will display disassembly of next instruction only
6674 if the source line cannot be displayed. This setting causes
6675 @value{GDBN} to display some feedback when you step through a function
6676 with no line info or whose source file is unavailable. The default is
6677 OFF, which means never display the disassembly of the next line or
6683 @chapter Examining Data
6685 @cindex printing data
6686 @cindex examining data
6689 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6690 @c document because it is nonstandard... Under Epoch it displays in a
6691 @c different window or something like that.
6692 The usual way to examine data in your program is with the @code{print}
6693 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6694 evaluates and prints the value of an expression of the language your
6695 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6696 Different Languages}). It may also print the expression using a
6697 Python-based pretty-printer (@pxref{Pretty Printing}).
6700 @item print @var{expr}
6701 @itemx print /@var{f} @var{expr}
6702 @var{expr} is an expression (in the source language). By default the
6703 value of @var{expr} is printed in a format appropriate to its data type;
6704 you can choose a different format by specifying @samp{/@var{f}}, where
6705 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6709 @itemx print /@var{f}
6710 @cindex reprint the last value
6711 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6712 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6713 conveniently inspect the same value in an alternative format.
6716 A more low-level way of examining data is with the @code{x} command.
6717 It examines data in memory at a specified address and prints it in a
6718 specified format. @xref{Memory, ,Examining Memory}.
6720 If you are interested in information about types, or about how the
6721 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6722 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6726 * Expressions:: Expressions
6727 * Ambiguous Expressions:: Ambiguous Expressions
6728 * Variables:: Program variables
6729 * Arrays:: Artificial arrays
6730 * Output Formats:: Output formats
6731 * Memory:: Examining memory
6732 * Auto Display:: Automatic display
6733 * Print Settings:: Print settings
6734 * Value History:: Value history
6735 * Convenience Vars:: Convenience variables
6736 * Registers:: Registers
6737 * Floating Point Hardware:: Floating point hardware
6738 * Vector Unit:: Vector Unit
6739 * OS Information:: Auxiliary data provided by operating system
6740 * Memory Region Attributes:: Memory region attributes
6741 * Dump/Restore Files:: Copy between memory and a file
6742 * Core File Generation:: Cause a program dump its core
6743 * Character Sets:: Debugging programs that use a different
6744 character set than GDB does
6745 * Caching Remote Data:: Data caching for remote targets
6746 * Searching Memory:: Searching memory for a sequence of bytes
6750 @section Expressions
6753 @code{print} and many other @value{GDBN} commands accept an expression and
6754 compute its value. Any kind of constant, variable or operator defined
6755 by the programming language you are using is valid in an expression in
6756 @value{GDBN}. This includes conditional expressions, function calls,
6757 casts, and string constants. It also includes preprocessor macros, if
6758 you compiled your program to include this information; see
6761 @cindex arrays in expressions
6762 @value{GDBN} supports array constants in expressions input by
6763 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6764 you can use the command @code{print @{1, 2, 3@}} to create an array
6765 of three integers. If you pass an array to a function or assign it
6766 to a program variable, @value{GDBN} copies the array to memory that
6767 is @code{malloc}ed in the target program.
6769 Because C is so widespread, most of the expressions shown in examples in
6770 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6771 Languages}, for information on how to use expressions in other
6774 In this section, we discuss operators that you can use in @value{GDBN}
6775 expressions regardless of your programming language.
6777 @cindex casts, in expressions
6778 Casts are supported in all languages, not just in C, because it is so
6779 useful to cast a number into a pointer in order to examine a structure
6780 at that address in memory.
6781 @c FIXME: casts supported---Mod2 true?
6783 @value{GDBN} supports these operators, in addition to those common
6784 to programming languages:
6788 @samp{@@} is a binary operator for treating parts of memory as arrays.
6789 @xref{Arrays, ,Artificial Arrays}, for more information.
6792 @samp{::} allows you to specify a variable in terms of the file or
6793 function where it is defined. @xref{Variables, ,Program Variables}.
6795 @cindex @{@var{type}@}
6796 @cindex type casting memory
6797 @cindex memory, viewing as typed object
6798 @cindex casts, to view memory
6799 @item @{@var{type}@} @var{addr}
6800 Refers to an object of type @var{type} stored at address @var{addr} in
6801 memory. @var{addr} may be any expression whose value is an integer or
6802 pointer (but parentheses are required around binary operators, just as in
6803 a cast). This construct is allowed regardless of what kind of data is
6804 normally supposed to reside at @var{addr}.
6807 @node Ambiguous Expressions
6808 @section Ambiguous Expressions
6809 @cindex ambiguous expressions
6811 Expressions can sometimes contain some ambiguous elements. For instance,
6812 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6813 a single function name to be defined several times, for application in
6814 different contexts. This is called @dfn{overloading}. Another example
6815 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6816 templates and is typically instantiated several times, resulting in
6817 the same function name being defined in different contexts.
6819 In some cases and depending on the language, it is possible to adjust
6820 the expression to remove the ambiguity. For instance in C@t{++}, you
6821 can specify the signature of the function you want to break on, as in
6822 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6823 qualified name of your function often makes the expression unambiguous
6826 When an ambiguity that needs to be resolved is detected, the debugger
6827 has the capability to display a menu of numbered choices for each
6828 possibility, and then waits for the selection with the prompt @samp{>}.
6829 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6830 aborts the current command. If the command in which the expression was
6831 used allows more than one choice to be selected, the next option in the
6832 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6835 For example, the following session excerpt shows an attempt to set a
6836 breakpoint at the overloaded symbol @code{String::after}.
6837 We choose three particular definitions of that function name:
6839 @c FIXME! This is likely to change to show arg type lists, at least
6842 (@value{GDBP}) b String::after
6845 [2] file:String.cc; line number:867
6846 [3] file:String.cc; line number:860
6847 [4] file:String.cc; line number:875
6848 [5] file:String.cc; line number:853
6849 [6] file:String.cc; line number:846
6850 [7] file:String.cc; line number:735
6852 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6853 Breakpoint 2 at 0xb344: file String.cc, line 875.
6854 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6855 Multiple breakpoints were set.
6856 Use the "delete" command to delete unwanted
6863 @kindex set multiple-symbols
6864 @item set multiple-symbols @var{mode}
6865 @cindex multiple-symbols menu
6867 This option allows you to adjust the debugger behavior when an expression
6870 By default, @var{mode} is set to @code{all}. If the command with which
6871 the expression is used allows more than one choice, then @value{GDBN}
6872 automatically selects all possible choices. For instance, inserting
6873 a breakpoint on a function using an ambiguous name results in a breakpoint
6874 inserted on each possible match. However, if a unique choice must be made,
6875 then @value{GDBN} uses the menu to help you disambiguate the expression.
6876 For instance, printing the address of an overloaded function will result
6877 in the use of the menu.
6879 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6880 when an ambiguity is detected.
6882 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6883 an error due to the ambiguity and the command is aborted.
6885 @kindex show multiple-symbols
6886 @item show multiple-symbols
6887 Show the current value of the @code{multiple-symbols} setting.
6891 @section Program Variables
6893 The most common kind of expression to use is the name of a variable
6896 Variables in expressions are understood in the selected stack frame
6897 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6901 global (or file-static)
6908 visible according to the scope rules of the
6909 programming language from the point of execution in that frame
6912 @noindent This means that in the function
6927 you can examine and use the variable @code{a} whenever your program is
6928 executing within the function @code{foo}, but you can only use or
6929 examine the variable @code{b} while your program is executing inside
6930 the block where @code{b} is declared.
6932 @cindex variable name conflict
6933 There is an exception: you can refer to a variable or function whose
6934 scope is a single source file even if the current execution point is not
6935 in this file. But it is possible to have more than one such variable or
6936 function with the same name (in different source files). If that
6937 happens, referring to that name has unpredictable effects. If you wish,
6938 you can specify a static variable in a particular function or file,
6939 using the colon-colon (@code{::}) notation:
6941 @cindex colon-colon, context for variables/functions
6943 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6944 @cindex @code{::}, context for variables/functions
6947 @var{file}::@var{variable}
6948 @var{function}::@var{variable}
6952 Here @var{file} or @var{function} is the name of the context for the
6953 static @var{variable}. In the case of file names, you can use quotes to
6954 make sure @value{GDBN} parses the file name as a single word---for example,
6955 to print a global value of @code{x} defined in @file{f2.c}:
6958 (@value{GDBP}) p 'f2.c'::x
6961 @cindex C@t{++} scope resolution
6962 This use of @samp{::} is very rarely in conflict with the very similar
6963 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6964 scope resolution operator in @value{GDBN} expressions.
6965 @c FIXME: Um, so what happens in one of those rare cases where it's in
6968 @cindex wrong values
6969 @cindex variable values, wrong
6970 @cindex function entry/exit, wrong values of variables
6971 @cindex optimized code, wrong values of variables
6973 @emph{Warning:} Occasionally, a local variable may appear to have the
6974 wrong value at certain points in a function---just after entry to a new
6975 scope, and just before exit.
6977 You may see this problem when you are stepping by machine instructions.
6978 This is because, on most machines, it takes more than one instruction to
6979 set up a stack frame (including local variable definitions); if you are
6980 stepping by machine instructions, variables may appear to have the wrong
6981 values until the stack frame is completely built. On exit, it usually
6982 also takes more than one machine instruction to destroy a stack frame;
6983 after you begin stepping through that group of instructions, local
6984 variable definitions may be gone.
6986 This may also happen when the compiler does significant optimizations.
6987 To be sure of always seeing accurate values, turn off all optimization
6990 @cindex ``No symbol "foo" in current context''
6991 Another possible effect of compiler optimizations is to optimize
6992 unused variables out of existence, or assign variables to registers (as
6993 opposed to memory addresses). Depending on the support for such cases
6994 offered by the debug info format used by the compiler, @value{GDBN}
6995 might not be able to display values for such local variables. If that
6996 happens, @value{GDBN} will print a message like this:
6999 No symbol "foo" in current context.
7002 To solve such problems, either recompile without optimizations, or use a
7003 different debug info format, if the compiler supports several such
7004 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7005 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7006 produces debug info in a format that is superior to formats such as
7007 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7008 an effective form for debug info. @xref{Debugging Options,,Options
7009 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7010 Compiler Collection (GCC)}.
7011 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7012 that are best suited to C@t{++} programs.
7014 If you ask to print an object whose contents are unknown to
7015 @value{GDBN}, e.g., because its data type is not completely specified
7016 by the debug information, @value{GDBN} will say @samp{<incomplete
7017 type>}. @xref{Symbols, incomplete type}, for more about this.
7019 Strings are identified as arrays of @code{char} values without specified
7020 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7021 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7022 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7023 defines literal string type @code{"char"} as @code{char} without a sign.
7028 signed char var1[] = "A";
7031 You get during debugging
7036 $2 = @{65 'A', 0 '\0'@}
7040 @section Artificial Arrays
7042 @cindex artificial array
7044 @kindex @@@r{, referencing memory as an array}
7045 It is often useful to print out several successive objects of the
7046 same type in memory; a section of an array, or an array of
7047 dynamically determined size for which only a pointer exists in the
7050 You can do this by referring to a contiguous span of memory as an
7051 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7052 operand of @samp{@@} should be the first element of the desired array
7053 and be an individual object. The right operand should be the desired length
7054 of the array. The result is an array value whose elements are all of
7055 the type of the left argument. The first element is actually the left
7056 argument; the second element comes from bytes of memory immediately
7057 following those that hold the first element, and so on. Here is an
7058 example. If a program says
7061 int *array = (int *) malloc (len * sizeof (int));
7065 you can print the contents of @code{array} with
7071 The left operand of @samp{@@} must reside in memory. Array values made
7072 with @samp{@@} in this way behave just like other arrays in terms of
7073 subscripting, and are coerced to pointers when used in expressions.
7074 Artificial arrays most often appear in expressions via the value history
7075 (@pxref{Value History, ,Value History}), after printing one out.
7077 Another way to create an artificial array is to use a cast.
7078 This re-interprets a value as if it were an array.
7079 The value need not be in memory:
7081 (@value{GDBP}) p/x (short[2])0x12345678
7082 $1 = @{0x1234, 0x5678@}
7085 As a convenience, if you leave the array length out (as in
7086 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7087 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7089 (@value{GDBP}) p/x (short[])0x12345678
7090 $2 = @{0x1234, 0x5678@}
7093 Sometimes the artificial array mechanism is not quite enough; in
7094 moderately complex data structures, the elements of interest may not
7095 actually be adjacent---for example, if you are interested in the values
7096 of pointers in an array. One useful work-around in this situation is
7097 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7098 Variables}) as a counter in an expression that prints the first
7099 interesting value, and then repeat that expression via @key{RET}. For
7100 instance, suppose you have an array @code{dtab} of pointers to
7101 structures, and you are interested in the values of a field @code{fv}
7102 in each structure. Here is an example of what you might type:
7112 @node Output Formats
7113 @section Output Formats
7115 @cindex formatted output
7116 @cindex output formats
7117 By default, @value{GDBN} prints a value according to its data type. Sometimes
7118 this is not what you want. For example, you might want to print a number
7119 in hex, or a pointer in decimal. Or you might want to view data in memory
7120 at a certain address as a character string or as an instruction. To do
7121 these things, specify an @dfn{output format} when you print a value.
7123 The simplest use of output formats is to say how to print a value
7124 already computed. This is done by starting the arguments of the
7125 @code{print} command with a slash and a format letter. The format
7126 letters supported are:
7130 Regard the bits of the value as an integer, and print the integer in
7134 Print as integer in signed decimal.
7137 Print as integer in unsigned decimal.
7140 Print as integer in octal.
7143 Print as integer in binary. The letter @samp{t} stands for ``two''.
7144 @footnote{@samp{b} cannot be used because these format letters are also
7145 used with the @code{x} command, where @samp{b} stands for ``byte'';
7146 see @ref{Memory,,Examining Memory}.}
7149 @cindex unknown address, locating
7150 @cindex locate address
7151 Print as an address, both absolute in hexadecimal and as an offset from
7152 the nearest preceding symbol. You can use this format used to discover
7153 where (in what function) an unknown address is located:
7156 (@value{GDBP}) p/a 0x54320
7157 $3 = 0x54320 <_initialize_vx+396>
7161 The command @code{info symbol 0x54320} yields similar results.
7162 @xref{Symbols, info symbol}.
7165 Regard as an integer and print it as a character constant. This
7166 prints both the numerical value and its character representation. The
7167 character representation is replaced with the octal escape @samp{\nnn}
7168 for characters outside the 7-bit @sc{ascii} range.
7170 Without this format, @value{GDBN} displays @code{char},
7171 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7172 constants. Single-byte members of vectors are displayed as integer
7176 Regard the bits of the value as a floating point number and print
7177 using typical floating point syntax.
7180 @cindex printing strings
7181 @cindex printing byte arrays
7182 Regard as a string, if possible. With this format, pointers to single-byte
7183 data are displayed as null-terminated strings and arrays of single-byte data
7184 are displayed as fixed-length strings. Other values are displayed in their
7187 Without this format, @value{GDBN} displays pointers to and arrays of
7188 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7189 strings. Single-byte members of a vector are displayed as an integer
7193 @cindex raw printing
7194 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7195 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7196 Printing}). This typically results in a higher-level display of the
7197 value's contents. The @samp{r} format bypasses any Python
7198 pretty-printer which might exist.
7201 For example, to print the program counter in hex (@pxref{Registers}), type
7208 Note that no space is required before the slash; this is because command
7209 names in @value{GDBN} cannot contain a slash.
7211 To reprint the last value in the value history with a different format,
7212 you can use the @code{print} command with just a format and no
7213 expression. For example, @samp{p/x} reprints the last value in hex.
7216 @section Examining Memory
7218 You can use the command @code{x} (for ``examine'') to examine memory in
7219 any of several formats, independently of your program's data types.
7221 @cindex examining memory
7223 @kindex x @r{(examine memory)}
7224 @item x/@var{nfu} @var{addr}
7227 Use the @code{x} command to examine memory.
7230 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7231 much memory to display and how to format it; @var{addr} is an
7232 expression giving the address where you want to start displaying memory.
7233 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7234 Several commands set convenient defaults for @var{addr}.
7237 @item @var{n}, the repeat count
7238 The repeat count is a decimal integer; the default is 1. It specifies
7239 how much memory (counting by units @var{u}) to display.
7240 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7243 @item @var{f}, the display format
7244 The display format is one of the formats used by @code{print}
7245 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7246 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7247 The default is @samp{x} (hexadecimal) initially. The default changes
7248 each time you use either @code{x} or @code{print}.
7250 @item @var{u}, the unit size
7251 The unit size is any of
7257 Halfwords (two bytes).
7259 Words (four bytes). This is the initial default.
7261 Giant words (eight bytes).
7264 Each time you specify a unit size with @code{x}, that size becomes the
7265 default unit the next time you use @code{x}. For the @samp{i} format,
7266 the unit size is ignored and is normally not written. For the @samp{s} format,
7267 the unit size defaults to @samp{b}, unless it is explicitly given.
7268 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7269 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7270 Note that the results depend on the programming language of the
7271 current compilation unit. If the language is C, the @samp{s}
7272 modifier will use the UTF-16 encoding while @samp{w} will use
7273 UTF-32. The encoding is set by the programming language and cannot
7276 @item @var{addr}, starting display address
7277 @var{addr} is the address where you want @value{GDBN} to begin displaying
7278 memory. The expression need not have a pointer value (though it may);
7279 it is always interpreted as an integer address of a byte of memory.
7280 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7281 @var{addr} is usually just after the last address examined---but several
7282 other commands also set the default address: @code{info breakpoints} (to
7283 the address of the last breakpoint listed), @code{info line} (to the
7284 starting address of a line), and @code{print} (if you use it to display
7285 a value from memory).
7288 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7289 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7290 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7291 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7292 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7294 Since the letters indicating unit sizes are all distinct from the
7295 letters specifying output formats, you do not have to remember whether
7296 unit size or format comes first; either order works. The output
7297 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7298 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7300 Even though the unit size @var{u} is ignored for the formats @samp{s}
7301 and @samp{i}, you might still want to use a count @var{n}; for example,
7302 @samp{3i} specifies that you want to see three machine instructions,
7303 including any operands. For convenience, especially when used with
7304 the @code{display} command, the @samp{i} format also prints branch delay
7305 slot instructions, if any, beyond the count specified, which immediately
7306 follow the last instruction that is within the count. The command
7307 @code{disassemble} gives an alternative way of inspecting machine
7308 instructions; see @ref{Machine Code,,Source and Machine Code}.
7310 All the defaults for the arguments to @code{x} are designed to make it
7311 easy to continue scanning memory with minimal specifications each time
7312 you use @code{x}. For example, after you have inspected three machine
7313 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7314 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7315 the repeat count @var{n} is used again; the other arguments default as
7316 for successive uses of @code{x}.
7318 When examining machine instructions, the instruction at current program
7319 counter is shown with a @code{=>} marker. For example:
7322 (@value{GDBP}) x/5i $pc-6
7323 0x804837f <main+11>: mov %esp,%ebp
7324 0x8048381 <main+13>: push %ecx
7325 0x8048382 <main+14>: sub $0x4,%esp
7326 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7327 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7330 @cindex @code{$_}, @code{$__}, and value history
7331 The addresses and contents printed by the @code{x} command are not saved
7332 in the value history because there is often too much of them and they
7333 would get in the way. Instead, @value{GDBN} makes these values available for
7334 subsequent use in expressions as values of the convenience variables
7335 @code{$_} and @code{$__}. After an @code{x} command, the last address
7336 examined is available for use in expressions in the convenience variable
7337 @code{$_}. The contents of that address, as examined, are available in
7338 the convenience variable @code{$__}.
7340 If the @code{x} command has a repeat count, the address and contents saved
7341 are from the last memory unit printed; this is not the same as the last
7342 address printed if several units were printed on the last line of output.
7344 @cindex remote memory comparison
7345 @cindex verify remote memory image
7346 When you are debugging a program running on a remote target machine
7347 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7348 remote machine's memory against the executable file you downloaded to
7349 the target. The @code{compare-sections} command is provided for such
7353 @kindex compare-sections
7354 @item compare-sections @r{[}@var{section-name}@r{]}
7355 Compare the data of a loadable section @var{section-name} in the
7356 executable file of the program being debugged with the same section in
7357 the remote machine's memory, and report any mismatches. With no
7358 arguments, compares all loadable sections. This command's
7359 availability depends on the target's support for the @code{"qCRC"}
7364 @section Automatic Display
7365 @cindex automatic display
7366 @cindex display of expressions
7368 If you find that you want to print the value of an expression frequently
7369 (to see how it changes), you might want to add it to the @dfn{automatic
7370 display list} so that @value{GDBN} prints its value each time your program stops.
7371 Each expression added to the list is given a number to identify it;
7372 to remove an expression from the list, you specify that number.
7373 The automatic display looks like this:
7377 3: bar[5] = (struct hack *) 0x3804
7381 This display shows item numbers, expressions and their current values. As with
7382 displays you request manually using @code{x} or @code{print}, you can
7383 specify the output format you prefer; in fact, @code{display} decides
7384 whether to use @code{print} or @code{x} depending your format
7385 specification---it uses @code{x} if you specify either the @samp{i}
7386 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7390 @item display @var{expr}
7391 Add the expression @var{expr} to the list of expressions to display
7392 each time your program stops. @xref{Expressions, ,Expressions}.
7394 @code{display} does not repeat if you press @key{RET} again after using it.
7396 @item display/@var{fmt} @var{expr}
7397 For @var{fmt} specifying only a display format and not a size or
7398 count, add the expression @var{expr} to the auto-display list but
7399 arrange to display it each time in the specified format @var{fmt}.
7400 @xref{Output Formats,,Output Formats}.
7402 @item display/@var{fmt} @var{addr}
7403 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7404 number of units, add the expression @var{addr} as a memory address to
7405 be examined each time your program stops. Examining means in effect
7406 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7409 For example, @samp{display/i $pc} can be helpful, to see the machine
7410 instruction about to be executed each time execution stops (@samp{$pc}
7411 is a common name for the program counter; @pxref{Registers, ,Registers}).
7414 @kindex delete display
7416 @item undisplay @var{dnums}@dots{}
7417 @itemx delete display @var{dnums}@dots{}
7418 Remove item numbers @var{dnums} from the list of expressions to display.
7420 @code{undisplay} does not repeat if you press @key{RET} after using it.
7421 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7423 @kindex disable display
7424 @item disable display @var{dnums}@dots{}
7425 Disable the display of item numbers @var{dnums}. A disabled display
7426 item is not printed automatically, but is not forgotten. It may be
7427 enabled again later.
7429 @kindex enable display
7430 @item enable display @var{dnums}@dots{}
7431 Enable display of item numbers @var{dnums}. It becomes effective once
7432 again in auto display of its expression, until you specify otherwise.
7435 Display the current values of the expressions on the list, just as is
7436 done when your program stops.
7438 @kindex info display
7440 Print the list of expressions previously set up to display
7441 automatically, each one with its item number, but without showing the
7442 values. This includes disabled expressions, which are marked as such.
7443 It also includes expressions which would not be displayed right now
7444 because they refer to automatic variables not currently available.
7447 @cindex display disabled out of scope
7448 If a display expression refers to local variables, then it does not make
7449 sense outside the lexical context for which it was set up. Such an
7450 expression is disabled when execution enters a context where one of its
7451 variables is not defined. For example, if you give the command
7452 @code{display last_char} while inside a function with an argument
7453 @code{last_char}, @value{GDBN} displays this argument while your program
7454 continues to stop inside that function. When it stops elsewhere---where
7455 there is no variable @code{last_char}---the display is disabled
7456 automatically. The next time your program stops where @code{last_char}
7457 is meaningful, you can enable the display expression once again.
7459 @node Print Settings
7460 @section Print Settings
7462 @cindex format options
7463 @cindex print settings
7464 @value{GDBN} provides the following ways to control how arrays, structures,
7465 and symbols are printed.
7468 These settings are useful for debugging programs in any language:
7472 @item set print address
7473 @itemx set print address on
7474 @cindex print/don't print memory addresses
7475 @value{GDBN} prints memory addresses showing the location of stack
7476 traces, structure values, pointer values, breakpoints, and so forth,
7477 even when it also displays the contents of those addresses. The default
7478 is @code{on}. For example, this is what a stack frame display looks like with
7479 @code{set print address on}:
7484 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7486 530 if (lquote != def_lquote)
7490 @item set print address off
7491 Do not print addresses when displaying their contents. For example,
7492 this is the same stack frame displayed with @code{set print address off}:
7496 (@value{GDBP}) set print addr off
7498 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7499 530 if (lquote != def_lquote)
7503 You can use @samp{set print address off} to eliminate all machine
7504 dependent displays from the @value{GDBN} interface. For example, with
7505 @code{print address off}, you should get the same text for backtraces on
7506 all machines---whether or not they involve pointer arguments.
7509 @item show print address
7510 Show whether or not addresses are to be printed.
7513 When @value{GDBN} prints a symbolic address, it normally prints the
7514 closest earlier symbol plus an offset. If that symbol does not uniquely
7515 identify the address (for example, it is a name whose scope is a single
7516 source file), you may need to clarify. One way to do this is with
7517 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7518 you can set @value{GDBN} to print the source file and line number when
7519 it prints a symbolic address:
7522 @item set print symbol-filename on
7523 @cindex source file and line of a symbol
7524 @cindex symbol, source file and line
7525 Tell @value{GDBN} to print the source file name and line number of a
7526 symbol in the symbolic form of an address.
7528 @item set print symbol-filename off
7529 Do not print source file name and line number of a symbol. This is the
7532 @item show print symbol-filename
7533 Show whether or not @value{GDBN} will print the source file name and
7534 line number of a symbol in the symbolic form of an address.
7537 Another situation where it is helpful to show symbol filenames and line
7538 numbers is when disassembling code; @value{GDBN} shows you the line
7539 number and source file that corresponds to each instruction.
7541 Also, you may wish to see the symbolic form only if the address being
7542 printed is reasonably close to the closest earlier symbol:
7545 @item set print max-symbolic-offset @var{max-offset}
7546 @cindex maximum value for offset of closest symbol
7547 Tell @value{GDBN} to only display the symbolic form of an address if the
7548 offset between the closest earlier symbol and the address is less than
7549 @var{max-offset}. The default is 0, which tells @value{GDBN}
7550 to always print the symbolic form of an address if any symbol precedes it.
7552 @item show print max-symbolic-offset
7553 Ask how large the maximum offset is that @value{GDBN} prints in a
7557 @cindex wild pointer, interpreting
7558 @cindex pointer, finding referent
7559 If you have a pointer and you are not sure where it points, try
7560 @samp{set print symbol-filename on}. Then you can determine the name
7561 and source file location of the variable where it points, using
7562 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7563 For example, here @value{GDBN} shows that a variable @code{ptt} points
7564 at another variable @code{t}, defined in @file{hi2.c}:
7567 (@value{GDBP}) set print symbol-filename on
7568 (@value{GDBP}) p/a ptt
7569 $4 = 0xe008 <t in hi2.c>
7573 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7574 does not show the symbol name and filename of the referent, even with
7575 the appropriate @code{set print} options turned on.
7578 Other settings control how different kinds of objects are printed:
7581 @item set print array
7582 @itemx set print array on
7583 @cindex pretty print arrays
7584 Pretty print arrays. This format is more convenient to read,
7585 but uses more space. The default is off.
7587 @item set print array off
7588 Return to compressed format for arrays.
7590 @item show print array
7591 Show whether compressed or pretty format is selected for displaying
7594 @cindex print array indexes
7595 @item set print array-indexes
7596 @itemx set print array-indexes on
7597 Print the index of each element when displaying arrays. May be more
7598 convenient to locate a given element in the array or quickly find the
7599 index of a given element in that printed array. The default is off.
7601 @item set print array-indexes off
7602 Stop printing element indexes when displaying arrays.
7604 @item show print array-indexes
7605 Show whether the index of each element is printed when displaying
7608 @item set print elements @var{number-of-elements}
7609 @cindex number of array elements to print
7610 @cindex limit on number of printed array elements
7611 Set a limit on how many elements of an array @value{GDBN} will print.
7612 If @value{GDBN} is printing a large array, it stops printing after it has
7613 printed the number of elements set by the @code{set print elements} command.
7614 This limit also applies to the display of strings.
7615 When @value{GDBN} starts, this limit is set to 200.
7616 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7618 @item show print elements
7619 Display the number of elements of a large array that @value{GDBN} will print.
7620 If the number is 0, then the printing is unlimited.
7622 @item set print frame-arguments @var{value}
7623 @kindex set print frame-arguments
7624 @cindex printing frame argument values
7625 @cindex print all frame argument values
7626 @cindex print frame argument values for scalars only
7627 @cindex do not print frame argument values
7628 This command allows to control how the values of arguments are printed
7629 when the debugger prints a frame (@pxref{Frames}). The possible
7634 The values of all arguments are printed.
7637 Print the value of an argument only if it is a scalar. The value of more
7638 complex arguments such as arrays, structures, unions, etc, is replaced
7639 by @code{@dots{}}. This is the default. Here is an example where
7640 only scalar arguments are shown:
7643 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7648 None of the argument values are printed. Instead, the value of each argument
7649 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7652 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7657 By default, only scalar arguments are printed. This command can be used
7658 to configure the debugger to print the value of all arguments, regardless
7659 of their type. However, it is often advantageous to not print the value
7660 of more complex parameters. For instance, it reduces the amount of
7661 information printed in each frame, making the backtrace more readable.
7662 Also, it improves performance when displaying Ada frames, because
7663 the computation of large arguments can sometimes be CPU-intensive,
7664 especially in large applications. Setting @code{print frame-arguments}
7665 to @code{scalars} (the default) or @code{none} avoids this computation,
7666 thus speeding up the display of each Ada frame.
7668 @item show print frame-arguments
7669 Show how the value of arguments should be displayed when printing a frame.
7671 @item set print repeats
7672 @cindex repeated array elements
7673 Set the threshold for suppressing display of repeated array
7674 elements. When the number of consecutive identical elements of an
7675 array exceeds the threshold, @value{GDBN} prints the string
7676 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7677 identical repetitions, instead of displaying the identical elements
7678 themselves. Setting the threshold to zero will cause all elements to
7679 be individually printed. The default threshold is 10.
7681 @item show print repeats
7682 Display the current threshold for printing repeated identical
7685 @item set print null-stop
7686 @cindex @sc{null} elements in arrays
7687 Cause @value{GDBN} to stop printing the characters of an array when the first
7688 @sc{null} is encountered. This is useful when large arrays actually
7689 contain only short strings.
7692 @item show print null-stop
7693 Show whether @value{GDBN} stops printing an array on the first
7694 @sc{null} character.
7696 @item set print pretty on
7697 @cindex print structures in indented form
7698 @cindex indentation in structure display
7699 Cause @value{GDBN} to print structures in an indented format with one member
7700 per line, like this:
7715 @item set print pretty off
7716 Cause @value{GDBN} to print structures in a compact format, like this:
7720 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7721 meat = 0x54 "Pork"@}
7726 This is the default format.
7728 @item show print pretty
7729 Show which format @value{GDBN} is using to print structures.
7731 @item set print sevenbit-strings on
7732 @cindex eight-bit characters in strings
7733 @cindex octal escapes in strings
7734 Print using only seven-bit characters; if this option is set,
7735 @value{GDBN} displays any eight-bit characters (in strings or
7736 character values) using the notation @code{\}@var{nnn}. This setting is
7737 best if you are working in English (@sc{ascii}) and you use the
7738 high-order bit of characters as a marker or ``meta'' bit.
7740 @item set print sevenbit-strings off
7741 Print full eight-bit characters. This allows the use of more
7742 international character sets, and is the default.
7744 @item show print sevenbit-strings
7745 Show whether or not @value{GDBN} is printing only seven-bit characters.
7747 @item set print union on
7748 @cindex unions in structures, printing
7749 Tell @value{GDBN} to print unions which are contained in structures
7750 and other unions. This is the default setting.
7752 @item set print union off
7753 Tell @value{GDBN} not to print unions which are contained in
7754 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7757 @item show print union
7758 Ask @value{GDBN} whether or not it will print unions which are contained in
7759 structures and other unions.
7761 For example, given the declarations
7764 typedef enum @{Tree, Bug@} Species;
7765 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7766 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7777 struct thing foo = @{Tree, @{Acorn@}@};
7781 with @code{set print union on} in effect @samp{p foo} would print
7784 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7788 and with @code{set print union off} in effect it would print
7791 $1 = @{it = Tree, form = @{...@}@}
7795 @code{set print union} affects programs written in C-like languages
7801 These settings are of interest when debugging C@t{++} programs:
7804 @cindex demangling C@t{++} names
7805 @item set print demangle
7806 @itemx set print demangle on
7807 Print C@t{++} names in their source form rather than in the encoded
7808 (``mangled'') form passed to the assembler and linker for type-safe
7809 linkage. The default is on.
7811 @item show print demangle
7812 Show whether C@t{++} names are printed in mangled or demangled form.
7814 @item set print asm-demangle
7815 @itemx set print asm-demangle on
7816 Print C@t{++} names in their source form rather than their mangled form, even
7817 in assembler code printouts such as instruction disassemblies.
7820 @item show print asm-demangle
7821 Show whether C@t{++} names in assembly listings are printed in mangled
7824 @cindex C@t{++} symbol decoding style
7825 @cindex symbol decoding style, C@t{++}
7826 @kindex set demangle-style
7827 @item set demangle-style @var{style}
7828 Choose among several encoding schemes used by different compilers to
7829 represent C@t{++} names. The choices for @var{style} are currently:
7833 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7836 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7837 This is the default.
7840 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7843 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7846 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7847 @strong{Warning:} this setting alone is not sufficient to allow
7848 debugging @code{cfront}-generated executables. @value{GDBN} would
7849 require further enhancement to permit that.
7852 If you omit @var{style}, you will see a list of possible formats.
7854 @item show demangle-style
7855 Display the encoding style currently in use for decoding C@t{++} symbols.
7857 @item set print object
7858 @itemx set print object on
7859 @cindex derived type of an object, printing
7860 @cindex display derived types
7861 When displaying a pointer to an object, identify the @emph{actual}
7862 (derived) type of the object rather than the @emph{declared} type, using
7863 the virtual function table.
7865 @item set print object off
7866 Display only the declared type of objects, without reference to the
7867 virtual function table. This is the default setting.
7869 @item show print object
7870 Show whether actual, or declared, object types are displayed.
7872 @item set print static-members
7873 @itemx set print static-members on
7874 @cindex static members of C@t{++} objects
7875 Print static members when displaying a C@t{++} object. The default is on.
7877 @item set print static-members off
7878 Do not print static members when displaying a C@t{++} object.
7880 @item show print static-members
7881 Show whether C@t{++} static members are printed or not.
7883 @item set print pascal_static-members
7884 @itemx set print pascal_static-members on
7885 @cindex static members of Pascal objects
7886 @cindex Pascal objects, static members display
7887 Print static members when displaying a Pascal object. The default is on.
7889 @item set print pascal_static-members off
7890 Do not print static members when displaying a Pascal object.
7892 @item show print pascal_static-members
7893 Show whether Pascal static members are printed or not.
7895 @c These don't work with HP ANSI C++ yet.
7896 @item set print vtbl
7897 @itemx set print vtbl on
7898 @cindex pretty print C@t{++} virtual function tables
7899 @cindex virtual functions (C@t{++}) display
7900 @cindex VTBL display
7901 Pretty print C@t{++} virtual function tables. The default is off.
7902 (The @code{vtbl} commands do not work on programs compiled with the HP
7903 ANSI C@t{++} compiler (@code{aCC}).)
7905 @item set print vtbl off
7906 Do not pretty print C@t{++} virtual function tables.
7908 @item show print vtbl
7909 Show whether C@t{++} virtual function tables are pretty printed, or not.
7913 @section Value History
7915 @cindex value history
7916 @cindex history of values printed by @value{GDBN}
7917 Values printed by the @code{print} command are saved in the @value{GDBN}
7918 @dfn{value history}. This allows you to refer to them in other expressions.
7919 Values are kept until the symbol table is re-read or discarded
7920 (for example with the @code{file} or @code{symbol-file} commands).
7921 When the symbol table changes, the value history is discarded,
7922 since the values may contain pointers back to the types defined in the
7927 @cindex history number
7928 The values printed are given @dfn{history numbers} by which you can
7929 refer to them. These are successive integers starting with one.
7930 @code{print} shows you the history number assigned to a value by
7931 printing @samp{$@var{num} = } before the value; here @var{num} is the
7934 To refer to any previous value, use @samp{$} followed by the value's
7935 history number. The way @code{print} labels its output is designed to
7936 remind you of this. Just @code{$} refers to the most recent value in
7937 the history, and @code{$$} refers to the value before that.
7938 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7939 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7940 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7942 For example, suppose you have just printed a pointer to a structure and
7943 want to see the contents of the structure. It suffices to type
7949 If you have a chain of structures where the component @code{next} points
7950 to the next one, you can print the contents of the next one with this:
7957 You can print successive links in the chain by repeating this
7958 command---which you can do by just typing @key{RET}.
7960 Note that the history records values, not expressions. If the value of
7961 @code{x} is 4 and you type these commands:
7969 then the value recorded in the value history by the @code{print} command
7970 remains 4 even though the value of @code{x} has changed.
7975 Print the last ten values in the value history, with their item numbers.
7976 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7977 values} does not change the history.
7979 @item show values @var{n}
7980 Print ten history values centered on history item number @var{n}.
7983 Print ten history values just after the values last printed. If no more
7984 values are available, @code{show values +} produces no display.
7987 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7988 same effect as @samp{show values +}.
7990 @node Convenience Vars
7991 @section Convenience Variables
7993 @cindex convenience variables
7994 @cindex user-defined variables
7995 @value{GDBN} provides @dfn{convenience variables} that you can use within
7996 @value{GDBN} to hold on to a value and refer to it later. These variables
7997 exist entirely within @value{GDBN}; they are not part of your program, and
7998 setting a convenience variable has no direct effect on further execution
7999 of your program. That is why you can use them freely.
8001 Convenience variables are prefixed with @samp{$}. Any name preceded by
8002 @samp{$} can be used for a convenience variable, unless it is one of
8003 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8004 (Value history references, in contrast, are @emph{numbers} preceded
8005 by @samp{$}. @xref{Value History, ,Value History}.)
8007 You can save a value in a convenience variable with an assignment
8008 expression, just as you would set a variable in your program.
8012 set $foo = *object_ptr
8016 would save in @code{$foo} the value contained in the object pointed to by
8019 Using a convenience variable for the first time creates it, but its
8020 value is @code{void} until you assign a new value. You can alter the
8021 value with another assignment at any time.
8023 Convenience variables have no fixed types. You can assign a convenience
8024 variable any type of value, including structures and arrays, even if
8025 that variable already has a value of a different type. The convenience
8026 variable, when used as an expression, has the type of its current value.
8029 @kindex show convenience
8030 @cindex show all user variables
8031 @item show convenience
8032 Print a list of convenience variables used so far, and their values.
8033 Abbreviated @code{show conv}.
8035 @kindex init-if-undefined
8036 @cindex convenience variables, initializing
8037 @item init-if-undefined $@var{variable} = @var{expression}
8038 Set a convenience variable if it has not already been set. This is useful
8039 for user-defined commands that keep some state. It is similar, in concept,
8040 to using local static variables with initializers in C (except that
8041 convenience variables are global). It can also be used to allow users to
8042 override default values used in a command script.
8044 If the variable is already defined then the expression is not evaluated so
8045 any side-effects do not occur.
8048 One of the ways to use a convenience variable is as a counter to be
8049 incremented or a pointer to be advanced. For example, to print
8050 a field from successive elements of an array of structures:
8054 print bar[$i++]->contents
8058 Repeat that command by typing @key{RET}.
8060 Some convenience variables are created automatically by @value{GDBN} and given
8061 values likely to be useful.
8064 @vindex $_@r{, convenience variable}
8066 The variable @code{$_} is automatically set by the @code{x} command to
8067 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8068 commands which provide a default address for @code{x} to examine also
8069 set @code{$_} to that address; these commands include @code{info line}
8070 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8071 except when set by the @code{x} command, in which case it is a pointer
8072 to the type of @code{$__}.
8074 @vindex $__@r{, convenience variable}
8076 The variable @code{$__} is automatically set by the @code{x} command
8077 to the value found in the last address examined. Its type is chosen
8078 to match the format in which the data was printed.
8081 @vindex $_exitcode@r{, convenience variable}
8082 The variable @code{$_exitcode} is automatically set to the exit code when
8083 the program being debugged terminates.
8086 @vindex $_siginfo@r{, convenience variable}
8087 The variable @code{$_siginfo} contains extra signal information
8088 (@pxref{extra signal information}). Note that @code{$_siginfo}
8089 could be empty, if the application has not yet received any signals.
8090 For example, it will be empty before you execute the @code{run} command.
8093 @vindex $_tlb@r{, convenience variable}
8094 The variable @code{$_tlb} is automatically set when debugging
8095 applications running on MS-Windows in native mode or connected to
8096 gdbserver that supports the @code{qGetTIBAddr} request.
8097 @xref{General Query Packets}.
8098 This variable contains the address of the thread information block.
8102 On HP-UX systems, if you refer to a function or variable name that
8103 begins with a dollar sign, @value{GDBN} searches for a user or system
8104 name first, before it searches for a convenience variable.
8106 @cindex convenience functions
8107 @value{GDBN} also supplies some @dfn{convenience functions}. These
8108 have a syntax similar to convenience variables. A convenience
8109 function can be used in an expression just like an ordinary function;
8110 however, a convenience function is implemented internally to
8115 @kindex help function
8116 @cindex show all convenience functions
8117 Print a list of all convenience functions.
8124 You can refer to machine register contents, in expressions, as variables
8125 with names starting with @samp{$}. The names of registers are different
8126 for each machine; use @code{info registers} to see the names used on
8130 @kindex info registers
8131 @item info registers
8132 Print the names and values of all registers except floating-point
8133 and vector registers (in the selected stack frame).
8135 @kindex info all-registers
8136 @cindex floating point registers
8137 @item info all-registers
8138 Print the names and values of all registers, including floating-point
8139 and vector registers (in the selected stack frame).
8141 @item info registers @var{regname} @dots{}
8142 Print the @dfn{relativized} value of each specified register @var{regname}.
8143 As discussed in detail below, register values are normally relative to
8144 the selected stack frame. @var{regname} may be any register name valid on
8145 the machine you are using, with or without the initial @samp{$}.
8148 @cindex stack pointer register
8149 @cindex program counter register
8150 @cindex process status register
8151 @cindex frame pointer register
8152 @cindex standard registers
8153 @value{GDBN} has four ``standard'' register names that are available (in
8154 expressions) on most machines---whenever they do not conflict with an
8155 architecture's canonical mnemonics for registers. The register names
8156 @code{$pc} and @code{$sp} are used for the program counter register and
8157 the stack pointer. @code{$fp} is used for a register that contains a
8158 pointer to the current stack frame, and @code{$ps} is used for a
8159 register that contains the processor status. For example,
8160 you could print the program counter in hex with
8167 or print the instruction to be executed next with
8174 or add four to the stack pointer@footnote{This is a way of removing
8175 one word from the stack, on machines where stacks grow downward in
8176 memory (most machines, nowadays). This assumes that the innermost
8177 stack frame is selected; setting @code{$sp} is not allowed when other
8178 stack frames are selected. To pop entire frames off the stack,
8179 regardless of machine architecture, use @code{return};
8180 see @ref{Returning, ,Returning from a Function}.} with
8186 Whenever possible, these four standard register names are available on
8187 your machine even though the machine has different canonical mnemonics,
8188 so long as there is no conflict. The @code{info registers} command
8189 shows the canonical names. For example, on the SPARC, @code{info
8190 registers} displays the processor status register as @code{$psr} but you
8191 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8192 is an alias for the @sc{eflags} register.
8194 @value{GDBN} always considers the contents of an ordinary register as an
8195 integer when the register is examined in this way. Some machines have
8196 special registers which can hold nothing but floating point; these
8197 registers are considered to have floating point values. There is no way
8198 to refer to the contents of an ordinary register as floating point value
8199 (although you can @emph{print} it as a floating point value with
8200 @samp{print/f $@var{regname}}).
8202 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8203 means that the data format in which the register contents are saved by
8204 the operating system is not the same one that your program normally
8205 sees. For example, the registers of the 68881 floating point
8206 coprocessor are always saved in ``extended'' (raw) format, but all C
8207 programs expect to work with ``double'' (virtual) format. In such
8208 cases, @value{GDBN} normally works with the virtual format only (the format
8209 that makes sense for your program), but the @code{info registers} command
8210 prints the data in both formats.
8212 @cindex SSE registers (x86)
8213 @cindex MMX registers (x86)
8214 Some machines have special registers whose contents can be interpreted
8215 in several different ways. For example, modern x86-based machines
8216 have SSE and MMX registers that can hold several values packed
8217 together in several different formats. @value{GDBN} refers to such
8218 registers in @code{struct} notation:
8221 (@value{GDBP}) print $xmm1
8223 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8224 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8225 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8226 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8227 v4_int32 = @{0, 20657912, 11, 13@},
8228 v2_int64 = @{88725056443645952, 55834574859@},
8229 uint128 = 0x0000000d0000000b013b36f800000000
8234 To set values of such registers, you need to tell @value{GDBN} which
8235 view of the register you wish to change, as if you were assigning
8236 value to a @code{struct} member:
8239 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8242 Normally, register values are relative to the selected stack frame
8243 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8244 value that the register would contain if all stack frames farther in
8245 were exited and their saved registers restored. In order to see the
8246 true contents of hardware registers, you must select the innermost
8247 frame (with @samp{frame 0}).
8249 However, @value{GDBN} must deduce where registers are saved, from the machine
8250 code generated by your compiler. If some registers are not saved, or if
8251 @value{GDBN} is unable to locate the saved registers, the selected stack
8252 frame makes no difference.
8254 @node Floating Point Hardware
8255 @section Floating Point Hardware
8256 @cindex floating point
8258 Depending on the configuration, @value{GDBN} may be able to give
8259 you more information about the status of the floating point hardware.
8264 Display hardware-dependent information about the floating
8265 point unit. The exact contents and layout vary depending on the
8266 floating point chip. Currently, @samp{info float} is supported on
8267 the ARM and x86 machines.
8271 @section Vector Unit
8274 Depending on the configuration, @value{GDBN} may be able to give you
8275 more information about the status of the vector unit.
8280 Display information about the vector unit. The exact contents and
8281 layout vary depending on the hardware.
8284 @node OS Information
8285 @section Operating System Auxiliary Information
8286 @cindex OS information
8288 @value{GDBN} provides interfaces to useful OS facilities that can help
8289 you debug your program.
8291 @cindex @code{ptrace} system call
8292 @cindex @code{struct user} contents
8293 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8294 machines), it interfaces with the inferior via the @code{ptrace}
8295 system call. The operating system creates a special sata structure,
8296 called @code{struct user}, for this interface. You can use the
8297 command @code{info udot} to display the contents of this data
8303 Display the contents of the @code{struct user} maintained by the OS
8304 kernel for the program being debugged. @value{GDBN} displays the
8305 contents of @code{struct user} as a list of hex numbers, similar to
8306 the @code{examine} command.
8309 @cindex auxiliary vector
8310 @cindex vector, auxiliary
8311 Some operating systems supply an @dfn{auxiliary vector} to programs at
8312 startup. This is akin to the arguments and environment that you
8313 specify for a program, but contains a system-dependent variety of
8314 binary values that tell system libraries important details about the
8315 hardware, operating system, and process. Each value's purpose is
8316 identified by an integer tag; the meanings are well-known but system-specific.
8317 Depending on the configuration and operating system facilities,
8318 @value{GDBN} may be able to show you this information. For remote
8319 targets, this functionality may further depend on the remote stub's
8320 support of the @samp{qXfer:auxv:read} packet, see
8321 @ref{qXfer auxiliary vector read}.
8326 Display the auxiliary vector of the inferior, which can be either a
8327 live process or a core dump file. @value{GDBN} prints each tag value
8328 numerically, and also shows names and text descriptions for recognized
8329 tags. Some values in the vector are numbers, some bit masks, and some
8330 pointers to strings or other data. @value{GDBN} displays each value in the
8331 most appropriate form for a recognized tag, and in hexadecimal for
8332 an unrecognized tag.
8335 On some targets, @value{GDBN} can access operating-system-specific information
8336 and display it to user, without interpretation. For remote targets,
8337 this functionality depends on the remote stub's support of the
8338 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8341 @kindex info os processes
8342 @item info os processes
8343 Display the list of processes on the target. For each process,
8344 @value{GDBN} prints the process identifier, the name of the user, and
8345 the command corresponding to the process.
8348 @node Memory Region Attributes
8349 @section Memory Region Attributes
8350 @cindex memory region attributes
8352 @dfn{Memory region attributes} allow you to describe special handling
8353 required by regions of your target's memory. @value{GDBN} uses
8354 attributes to determine whether to allow certain types of memory
8355 accesses; whether to use specific width accesses; and whether to cache
8356 target memory. By default the description of memory regions is
8357 fetched from the target (if the current target supports this), but the
8358 user can override the fetched regions.
8360 Defined memory regions can be individually enabled and disabled. When a
8361 memory region is disabled, @value{GDBN} uses the default attributes when
8362 accessing memory in that region. Similarly, if no memory regions have
8363 been defined, @value{GDBN} uses the default attributes when accessing
8366 When a memory region is defined, it is given a number to identify it;
8367 to enable, disable, or remove a memory region, you specify that number.
8371 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8372 Define a memory region bounded by @var{lower} and @var{upper} with
8373 attributes @var{attributes}@dots{}, and add it to the list of regions
8374 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8375 case: it is treated as the target's maximum memory address.
8376 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8379 Discard any user changes to the memory regions and use target-supplied
8380 regions, if available, or no regions if the target does not support.
8383 @item delete mem @var{nums}@dots{}
8384 Remove memory regions @var{nums}@dots{} from the list of regions
8385 monitored by @value{GDBN}.
8388 @item disable mem @var{nums}@dots{}
8389 Disable monitoring of memory regions @var{nums}@dots{}.
8390 A disabled memory region is not forgotten.
8391 It may be enabled again later.
8394 @item enable mem @var{nums}@dots{}
8395 Enable monitoring of memory regions @var{nums}@dots{}.
8399 Print a table of all defined memory regions, with the following columns
8403 @item Memory Region Number
8404 @item Enabled or Disabled.
8405 Enabled memory regions are marked with @samp{y}.
8406 Disabled memory regions are marked with @samp{n}.
8409 The address defining the inclusive lower bound of the memory region.
8412 The address defining the exclusive upper bound of the memory region.
8415 The list of attributes set for this memory region.
8420 @subsection Attributes
8422 @subsubsection Memory Access Mode
8423 The access mode attributes set whether @value{GDBN} may make read or
8424 write accesses to a memory region.
8426 While these attributes prevent @value{GDBN} from performing invalid
8427 memory accesses, they do nothing to prevent the target system, I/O DMA,
8428 etc.@: from accessing memory.
8432 Memory is read only.
8434 Memory is write only.
8436 Memory is read/write. This is the default.
8439 @subsubsection Memory Access Size
8440 The access size attribute tells @value{GDBN} to use specific sized
8441 accesses in the memory region. Often memory mapped device registers
8442 require specific sized accesses. If no access size attribute is
8443 specified, @value{GDBN} may use accesses of any size.
8447 Use 8 bit memory accesses.
8449 Use 16 bit memory accesses.
8451 Use 32 bit memory accesses.
8453 Use 64 bit memory accesses.
8456 @c @subsubsection Hardware/Software Breakpoints
8457 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8458 @c will use hardware or software breakpoints for the internal breakpoints
8459 @c used by the step, next, finish, until, etc. commands.
8463 @c Always use hardware breakpoints
8464 @c @item swbreak (default)
8467 @subsubsection Data Cache
8468 The data cache attributes set whether @value{GDBN} will cache target
8469 memory. While this generally improves performance by reducing debug
8470 protocol overhead, it can lead to incorrect results because @value{GDBN}
8471 does not know about volatile variables or memory mapped device
8476 Enable @value{GDBN} to cache target memory.
8478 Disable @value{GDBN} from caching target memory. This is the default.
8481 @subsection Memory Access Checking
8482 @value{GDBN} can be instructed to refuse accesses to memory that is
8483 not explicitly described. This can be useful if accessing such
8484 regions has undesired effects for a specific target, or to provide
8485 better error checking. The following commands control this behaviour.
8488 @kindex set mem inaccessible-by-default
8489 @item set mem inaccessible-by-default [on|off]
8490 If @code{on} is specified, make @value{GDBN} treat memory not
8491 explicitly described by the memory ranges as non-existent and refuse accesses
8492 to such memory. The checks are only performed if there's at least one
8493 memory range defined. If @code{off} is specified, make @value{GDBN}
8494 treat the memory not explicitly described by the memory ranges as RAM.
8495 The default value is @code{on}.
8496 @kindex show mem inaccessible-by-default
8497 @item show mem inaccessible-by-default
8498 Show the current handling of accesses to unknown memory.
8502 @c @subsubsection Memory Write Verification
8503 @c The memory write verification attributes set whether @value{GDBN}
8504 @c will re-reads data after each write to verify the write was successful.
8508 @c @item noverify (default)
8511 @node Dump/Restore Files
8512 @section Copy Between Memory and a File
8513 @cindex dump/restore files
8514 @cindex append data to a file
8515 @cindex dump data to a file
8516 @cindex restore data from a file
8518 You can use the commands @code{dump}, @code{append}, and
8519 @code{restore} to copy data between target memory and a file. The
8520 @code{dump} and @code{append} commands write data to a file, and the
8521 @code{restore} command reads data from a file back into the inferior's
8522 memory. Files may be in binary, Motorola S-record, Intel hex, or
8523 Tektronix Hex format; however, @value{GDBN} can only append to binary
8529 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8530 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8531 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8532 or the value of @var{expr}, to @var{filename} in the given format.
8534 The @var{format} parameter may be any one of:
8541 Motorola S-record format.
8543 Tektronix Hex format.
8546 @value{GDBN} uses the same definitions of these formats as the
8547 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8548 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8552 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8553 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8554 Append the contents of memory from @var{start_addr} to @var{end_addr},
8555 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8556 (@value{GDBN} can only append data to files in raw binary form.)
8559 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8560 Restore the contents of file @var{filename} into memory. The
8561 @code{restore} command can automatically recognize any known @sc{bfd}
8562 file format, except for raw binary. To restore a raw binary file you
8563 must specify the optional keyword @code{binary} after the filename.
8565 If @var{bias} is non-zero, its value will be added to the addresses
8566 contained in the file. Binary files always start at address zero, so
8567 they will be restored at address @var{bias}. Other bfd files have
8568 a built-in location; they will be restored at offset @var{bias}
8571 If @var{start} and/or @var{end} are non-zero, then only data between
8572 file offset @var{start} and file offset @var{end} will be restored.
8573 These offsets are relative to the addresses in the file, before
8574 the @var{bias} argument is applied.
8578 @node Core File Generation
8579 @section How to Produce a Core File from Your Program
8580 @cindex dump core from inferior
8582 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8583 image of a running process and its process status (register values
8584 etc.). Its primary use is post-mortem debugging of a program that
8585 crashed while it ran outside a debugger. A program that crashes
8586 automatically produces a core file, unless this feature is disabled by
8587 the user. @xref{Files}, for information on invoking @value{GDBN} in
8588 the post-mortem debugging mode.
8590 Occasionally, you may wish to produce a core file of the program you
8591 are debugging in order to preserve a snapshot of its state.
8592 @value{GDBN} has a special command for that.
8596 @kindex generate-core-file
8597 @item generate-core-file [@var{file}]
8598 @itemx gcore [@var{file}]
8599 Produce a core dump of the inferior process. The optional argument
8600 @var{file} specifies the file name where to put the core dump. If not
8601 specified, the file name defaults to @file{core.@var{pid}}, where
8602 @var{pid} is the inferior process ID.
8604 Note that this command is implemented only for some systems (as of
8605 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8608 @node Character Sets
8609 @section Character Sets
8610 @cindex character sets
8612 @cindex translating between character sets
8613 @cindex host character set
8614 @cindex target character set
8616 If the program you are debugging uses a different character set to
8617 represent characters and strings than the one @value{GDBN} uses itself,
8618 @value{GDBN} can automatically translate between the character sets for
8619 you. The character set @value{GDBN} uses we call the @dfn{host
8620 character set}; the one the inferior program uses we call the
8621 @dfn{target character set}.
8623 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8624 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8625 remote protocol (@pxref{Remote Debugging}) to debug a program
8626 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8627 then the host character set is Latin-1, and the target character set is
8628 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8629 target-charset EBCDIC-US}, then @value{GDBN} translates between
8630 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8631 character and string literals in expressions.
8633 @value{GDBN} has no way to automatically recognize which character set
8634 the inferior program uses; you must tell it, using the @code{set
8635 target-charset} command, described below.
8637 Here are the commands for controlling @value{GDBN}'s character set
8641 @item set target-charset @var{charset}
8642 @kindex set target-charset
8643 Set the current target character set to @var{charset}. To display the
8644 list of supported target character sets, type
8645 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8647 @item set host-charset @var{charset}
8648 @kindex set host-charset
8649 Set the current host character set to @var{charset}.
8651 By default, @value{GDBN} uses a host character set appropriate to the
8652 system it is running on; you can override that default using the
8653 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8654 automatically determine the appropriate host character set. In this
8655 case, @value{GDBN} uses @samp{UTF-8}.
8657 @value{GDBN} can only use certain character sets as its host character
8658 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8659 @value{GDBN} will list the host character sets it supports.
8661 @item set charset @var{charset}
8663 Set the current host and target character sets to @var{charset}. As
8664 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8665 @value{GDBN} will list the names of the character sets that can be used
8666 for both host and target.
8669 @kindex show charset
8670 Show the names of the current host and target character sets.
8672 @item show host-charset
8673 @kindex show host-charset
8674 Show the name of the current host character set.
8676 @item show target-charset
8677 @kindex show target-charset
8678 Show the name of the current target character set.
8680 @item set target-wide-charset @var{charset}
8681 @kindex set target-wide-charset
8682 Set the current target's wide character set to @var{charset}. This is
8683 the character set used by the target's @code{wchar_t} type. To
8684 display the list of supported wide character sets, type
8685 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8687 @item show target-wide-charset
8688 @kindex show target-wide-charset
8689 Show the name of the current target's wide character set.
8692 Here is an example of @value{GDBN}'s character set support in action.
8693 Assume that the following source code has been placed in the file
8694 @file{charset-test.c}:
8700 = @{72, 101, 108, 108, 111, 44, 32, 119,
8701 111, 114, 108, 100, 33, 10, 0@};
8702 char ibm1047_hello[]
8703 = @{200, 133, 147, 147, 150, 107, 64, 166,
8704 150, 153, 147, 132, 90, 37, 0@};
8708 printf ("Hello, world!\n");
8712 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8713 containing the string @samp{Hello, world!} followed by a newline,
8714 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8716 We compile the program, and invoke the debugger on it:
8719 $ gcc -g charset-test.c -o charset-test
8720 $ gdb -nw charset-test
8721 GNU gdb 2001-12-19-cvs
8722 Copyright 2001 Free Software Foundation, Inc.
8727 We can use the @code{show charset} command to see what character sets
8728 @value{GDBN} is currently using to interpret and display characters and
8732 (@value{GDBP}) show charset
8733 The current host and target character set is `ISO-8859-1'.
8737 For the sake of printing this manual, let's use @sc{ascii} as our
8738 initial character set:
8740 (@value{GDBP}) set charset ASCII
8741 (@value{GDBP}) show charset
8742 The current host and target character set is `ASCII'.
8746 Let's assume that @sc{ascii} is indeed the correct character set for our
8747 host system --- in other words, let's assume that if @value{GDBN} prints
8748 characters using the @sc{ascii} character set, our terminal will display
8749 them properly. Since our current target character set is also
8750 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8753 (@value{GDBP}) print ascii_hello
8754 $1 = 0x401698 "Hello, world!\n"
8755 (@value{GDBP}) print ascii_hello[0]
8760 @value{GDBN} uses the target character set for character and string
8761 literals you use in expressions:
8764 (@value{GDBP}) print '+'
8769 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8772 @value{GDBN} relies on the user to tell it which character set the
8773 target program uses. If we print @code{ibm1047_hello} while our target
8774 character set is still @sc{ascii}, we get jibberish:
8777 (@value{GDBP}) print ibm1047_hello
8778 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8779 (@value{GDBP}) print ibm1047_hello[0]
8784 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8785 @value{GDBN} tells us the character sets it supports:
8788 (@value{GDBP}) set target-charset
8789 ASCII EBCDIC-US IBM1047 ISO-8859-1
8790 (@value{GDBP}) set target-charset
8793 We can select @sc{ibm1047} as our target character set, and examine the
8794 program's strings again. Now the @sc{ascii} string is wrong, but
8795 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8796 target character set, @sc{ibm1047}, to the host character set,
8797 @sc{ascii}, and they display correctly:
8800 (@value{GDBP}) set target-charset IBM1047
8801 (@value{GDBP}) show charset
8802 The current host character set is `ASCII'.
8803 The current target character set is `IBM1047'.
8804 (@value{GDBP}) print ascii_hello
8805 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8806 (@value{GDBP}) print ascii_hello[0]
8808 (@value{GDBP}) print ibm1047_hello
8809 $8 = 0x4016a8 "Hello, world!\n"
8810 (@value{GDBP}) print ibm1047_hello[0]
8815 As above, @value{GDBN} uses the target character set for character and
8816 string literals you use in expressions:
8819 (@value{GDBP}) print '+'
8824 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8827 @node Caching Remote Data
8828 @section Caching Data of Remote Targets
8829 @cindex caching data of remote targets
8831 @value{GDBN} caches data exchanged between the debugger and a
8832 remote target (@pxref{Remote Debugging}). Such caching generally improves
8833 performance, because it reduces the overhead of the remote protocol by
8834 bundling memory reads and writes into large chunks. Unfortunately, simply
8835 caching everything would lead to incorrect results, since @value{GDBN}
8836 does not necessarily know anything about volatile values, memory-mapped I/O
8837 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
8838 memory can be changed @emph{while} a gdb command is executing.
8839 Therefore, by default, @value{GDBN} only caches data
8840 known to be on the stack@footnote{In non-stop mode, it is moderately
8841 rare for a running thread to modify the stack of a stopped thread
8842 in a way that would interfere with a backtrace, and caching of
8843 stack reads provides a significant speed up of remote backtraces.}.
8844 Other regions of memory can be explicitly marked as
8845 cacheable; see @pxref{Memory Region Attributes}.
8848 @kindex set remotecache
8849 @item set remotecache on
8850 @itemx set remotecache off
8851 This option no longer does anything; it exists for compatibility
8854 @kindex show remotecache
8855 @item show remotecache
8856 Show the current state of the obsolete remotecache flag.
8858 @kindex set stack-cache
8859 @item set stack-cache on
8860 @itemx set stack-cache off
8861 Enable or disable caching of stack accesses. When @code{ON}, use
8862 caching. By default, this option is @code{ON}.
8864 @kindex show stack-cache
8865 @item show stack-cache
8866 Show the current state of data caching for memory accesses.
8869 @item info dcache @r{[}line@r{]}
8870 Print the information about the data cache performance. The
8871 information displayed includes the dcache width and depth, and for
8872 each cache line, its number, address, and how many times it was
8873 referenced. This command is useful for debugging the data cache
8876 If a line number is specified, the contents of that line will be
8880 @node Searching Memory
8881 @section Search Memory
8882 @cindex searching memory
8884 Memory can be searched for a particular sequence of bytes with the
8885 @code{find} command.
8889 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8890 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8891 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8892 etc. The search begins at address @var{start_addr} and continues for either
8893 @var{len} bytes or through to @var{end_addr} inclusive.
8896 @var{s} and @var{n} are optional parameters.
8897 They may be specified in either order, apart or together.
8900 @item @var{s}, search query size
8901 The size of each search query value.
8907 halfwords (two bytes)
8911 giant words (eight bytes)
8914 All values are interpreted in the current language.
8915 This means, for example, that if the current source language is C/C@t{++}
8916 then searching for the string ``hello'' includes the trailing '\0'.
8918 If the value size is not specified, it is taken from the
8919 value's type in the current language.
8920 This is useful when one wants to specify the search
8921 pattern as a mixture of types.
8922 Note that this means, for example, that in the case of C-like languages
8923 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8924 which is typically four bytes.
8926 @item @var{n}, maximum number of finds
8927 The maximum number of matches to print. The default is to print all finds.
8930 You can use strings as search values. Quote them with double-quotes
8932 The string value is copied into the search pattern byte by byte,
8933 regardless of the endianness of the target and the size specification.
8935 The address of each match found is printed as well as a count of the
8936 number of matches found.
8938 The address of the last value found is stored in convenience variable
8940 A count of the number of matches is stored in @samp{$numfound}.
8942 For example, if stopped at the @code{printf} in this function:
8948 static char hello[] = "hello-hello";
8949 static struct @{ char c; short s; int i; @}
8950 __attribute__ ((packed)) mixed
8951 = @{ 'c', 0x1234, 0x87654321 @};
8952 printf ("%s\n", hello);
8957 you get during debugging:
8960 (gdb) find &hello[0], +sizeof(hello), "hello"
8961 0x804956d <hello.1620+6>
8963 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8964 0x8049567 <hello.1620>
8965 0x804956d <hello.1620+6>
8967 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8968 0x8049567 <hello.1620>
8970 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8971 0x8049560 <mixed.1625>
8973 (gdb) print $numfound
8976 $2 = (void *) 0x8049560
8979 @node Optimized Code
8980 @chapter Debugging Optimized Code
8981 @cindex optimized code, debugging
8982 @cindex debugging optimized code
8984 Almost all compilers support optimization. With optimization
8985 disabled, the compiler generates assembly code that corresponds
8986 directly to your source code, in a simplistic way. As the compiler
8987 applies more powerful optimizations, the generated assembly code
8988 diverges from your original source code. With help from debugging
8989 information generated by the compiler, @value{GDBN} can map from
8990 the running program back to constructs from your original source.
8992 @value{GDBN} is more accurate with optimization disabled. If you
8993 can recompile without optimization, it is easier to follow the
8994 progress of your program during debugging. But, there are many cases
8995 where you may need to debug an optimized version.
8997 When you debug a program compiled with @samp{-g -O}, remember that the
8998 optimizer has rearranged your code; the debugger shows you what is
8999 really there. Do not be too surprised when the execution path does not
9000 exactly match your source file! An extreme example: if you define a
9001 variable, but never use it, @value{GDBN} never sees that
9002 variable---because the compiler optimizes it out of existence.
9004 Some things do not work as well with @samp{-g -O} as with just
9005 @samp{-g}, particularly on machines with instruction scheduling. If in
9006 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9007 please report it to us as a bug (including a test case!).
9008 @xref{Variables}, for more information about debugging optimized code.
9011 * Inline Functions:: How @value{GDBN} presents inlining
9014 @node Inline Functions
9015 @section Inline Functions
9016 @cindex inline functions, debugging
9018 @dfn{Inlining} is an optimization that inserts a copy of the function
9019 body directly at each call site, instead of jumping to a shared
9020 routine. @value{GDBN} displays inlined functions just like
9021 non-inlined functions. They appear in backtraces. You can view their
9022 arguments and local variables, step into them with @code{step}, skip
9023 them with @code{next}, and escape from them with @code{finish}.
9024 You can check whether a function was inlined by using the
9025 @code{info frame} command.
9027 For @value{GDBN} to support inlined functions, the compiler must
9028 record information about inlining in the debug information ---
9029 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9030 other compilers do also. @value{GDBN} only supports inlined functions
9031 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9032 do not emit two required attributes (@samp{DW_AT_call_file} and
9033 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9034 function calls with earlier versions of @value{NGCC}. It instead
9035 displays the arguments and local variables of inlined functions as
9036 local variables in the caller.
9038 The body of an inlined function is directly included at its call site;
9039 unlike a non-inlined function, there are no instructions devoted to
9040 the call. @value{GDBN} still pretends that the call site and the
9041 start of the inlined function are different instructions. Stepping to
9042 the call site shows the call site, and then stepping again shows
9043 the first line of the inlined function, even though no additional
9044 instructions are executed.
9046 This makes source-level debugging much clearer; you can see both the
9047 context of the call and then the effect of the call. Only stepping by
9048 a single instruction using @code{stepi} or @code{nexti} does not do
9049 this; single instruction steps always show the inlined body.
9051 There are some ways that @value{GDBN} does not pretend that inlined
9052 function calls are the same as normal calls:
9056 You cannot set breakpoints on inlined functions. @value{GDBN}
9057 either reports that there is no symbol with that name, or else sets the
9058 breakpoint only on non-inlined copies of the function. This limitation
9059 will be removed in a future version of @value{GDBN}; until then,
9060 set a breakpoint by line number on the first line of the inlined
9064 Setting breakpoints at the call site of an inlined function may not
9065 work, because the call site does not contain any code. @value{GDBN}
9066 may incorrectly move the breakpoint to the next line of the enclosing
9067 function, after the call. This limitation will be removed in a future
9068 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9069 or inside the inlined function instead.
9072 @value{GDBN} cannot locate the return value of inlined calls after
9073 using the @code{finish} command. This is a limitation of compiler-generated
9074 debugging information; after @code{finish}, you can step to the next line
9075 and print a variable where your program stored the return value.
9081 @chapter C Preprocessor Macros
9083 Some languages, such as C and C@t{++}, provide a way to define and invoke
9084 ``preprocessor macros'' which expand into strings of tokens.
9085 @value{GDBN} can evaluate expressions containing macro invocations, show
9086 the result of macro expansion, and show a macro's definition, including
9087 where it was defined.
9089 You may need to compile your program specially to provide @value{GDBN}
9090 with information about preprocessor macros. Most compilers do not
9091 include macros in their debugging information, even when you compile
9092 with the @option{-g} flag. @xref{Compilation}.
9094 A program may define a macro at one point, remove that definition later,
9095 and then provide a different definition after that. Thus, at different
9096 points in the program, a macro may have different definitions, or have
9097 no definition at all. If there is a current stack frame, @value{GDBN}
9098 uses the macros in scope at that frame's source code line. Otherwise,
9099 @value{GDBN} uses the macros in scope at the current listing location;
9102 Whenever @value{GDBN} evaluates an expression, it always expands any
9103 macro invocations present in the expression. @value{GDBN} also provides
9104 the following commands for working with macros explicitly.
9108 @kindex macro expand
9109 @cindex macro expansion, showing the results of preprocessor
9110 @cindex preprocessor macro expansion, showing the results of
9111 @cindex expanding preprocessor macros
9112 @item macro expand @var{expression}
9113 @itemx macro exp @var{expression}
9114 Show the results of expanding all preprocessor macro invocations in
9115 @var{expression}. Since @value{GDBN} simply expands macros, but does
9116 not parse the result, @var{expression} need not be a valid expression;
9117 it can be any string of tokens.
9120 @item macro expand-once @var{expression}
9121 @itemx macro exp1 @var{expression}
9122 @cindex expand macro once
9123 @i{(This command is not yet implemented.)} Show the results of
9124 expanding those preprocessor macro invocations that appear explicitly in
9125 @var{expression}. Macro invocations appearing in that expansion are
9126 left unchanged. This command allows you to see the effect of a
9127 particular macro more clearly, without being confused by further
9128 expansions. Since @value{GDBN} simply expands macros, but does not
9129 parse the result, @var{expression} need not be a valid expression; it
9130 can be any string of tokens.
9133 @cindex macro definition, showing
9134 @cindex definition, showing a macro's
9135 @item info macro @var{macro}
9136 Show the definition of the macro named @var{macro}, and describe the
9137 source location or compiler command-line where that definition was established.
9139 @kindex macro define
9140 @cindex user-defined macros
9141 @cindex defining macros interactively
9142 @cindex macros, user-defined
9143 @item macro define @var{macro} @var{replacement-list}
9144 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9145 Introduce a definition for a preprocessor macro named @var{macro},
9146 invocations of which are replaced by the tokens given in
9147 @var{replacement-list}. The first form of this command defines an
9148 ``object-like'' macro, which takes no arguments; the second form
9149 defines a ``function-like'' macro, which takes the arguments given in
9152 A definition introduced by this command is in scope in every
9153 expression evaluated in @value{GDBN}, until it is removed with the
9154 @code{macro undef} command, described below. The definition overrides
9155 all definitions for @var{macro} present in the program being debugged,
9156 as well as any previous user-supplied definition.
9159 @item macro undef @var{macro}
9160 Remove any user-supplied definition for the macro named @var{macro}.
9161 This command only affects definitions provided with the @code{macro
9162 define} command, described above; it cannot remove definitions present
9163 in the program being debugged.
9167 List all the macros defined using the @code{macro define} command.
9170 @cindex macros, example of debugging with
9171 Here is a transcript showing the above commands in action. First, we
9172 show our source files:
9180 #define ADD(x) (M + x)
9185 printf ("Hello, world!\n");
9187 printf ("We're so creative.\n");
9189 printf ("Goodbye, world!\n");
9196 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9197 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9198 compiler includes information about preprocessor macros in the debugging
9202 $ gcc -gdwarf-2 -g3 sample.c -o sample
9206 Now, we start @value{GDBN} on our sample program:
9210 GNU gdb 2002-05-06-cvs
9211 Copyright 2002 Free Software Foundation, Inc.
9212 GDB is free software, @dots{}
9216 We can expand macros and examine their definitions, even when the
9217 program is not running. @value{GDBN} uses the current listing position
9218 to decide which macro definitions are in scope:
9221 (@value{GDBP}) list main
9224 5 #define ADD(x) (M + x)
9229 10 printf ("Hello, world!\n");
9231 12 printf ("We're so creative.\n");
9232 (@value{GDBP}) info macro ADD
9233 Defined at /home/jimb/gdb/macros/play/sample.c:5
9234 #define ADD(x) (M + x)
9235 (@value{GDBP}) info macro Q
9236 Defined at /home/jimb/gdb/macros/play/sample.h:1
9237 included at /home/jimb/gdb/macros/play/sample.c:2
9239 (@value{GDBP}) macro expand ADD(1)
9240 expands to: (42 + 1)
9241 (@value{GDBP}) macro expand-once ADD(1)
9242 expands to: once (M + 1)
9246 In the example above, note that @code{macro expand-once} expands only
9247 the macro invocation explicit in the original text --- the invocation of
9248 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9249 which was introduced by @code{ADD}.
9251 Once the program is running, @value{GDBN} uses the macro definitions in
9252 force at the source line of the current stack frame:
9255 (@value{GDBP}) break main
9256 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9258 Starting program: /home/jimb/gdb/macros/play/sample
9260 Breakpoint 1, main () at sample.c:10
9261 10 printf ("Hello, world!\n");
9265 At line 10, the definition of the macro @code{N} at line 9 is in force:
9268 (@value{GDBP}) info macro N
9269 Defined at /home/jimb/gdb/macros/play/sample.c:9
9271 (@value{GDBP}) macro expand N Q M
9273 (@value{GDBP}) print N Q M
9278 As we step over directives that remove @code{N}'s definition, and then
9279 give it a new definition, @value{GDBN} finds the definition (or lack
9280 thereof) in force at each point:
9285 12 printf ("We're so creative.\n");
9286 (@value{GDBP}) info macro N
9287 The symbol `N' has no definition as a C/C++ preprocessor macro
9288 at /home/jimb/gdb/macros/play/sample.c:12
9291 14 printf ("Goodbye, world!\n");
9292 (@value{GDBP}) info macro N
9293 Defined at /home/jimb/gdb/macros/play/sample.c:13
9295 (@value{GDBP}) macro expand N Q M
9296 expands to: 1729 < 42
9297 (@value{GDBP}) print N Q M
9302 In addition to source files, macros can be defined on the compilation command
9303 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9304 such a way, @value{GDBN} displays the location of their definition as line zero
9305 of the source file submitted to the compiler.
9308 (@value{GDBP}) info macro __STDC__
9309 Defined at /home/jimb/gdb/macros/play/sample.c:0
9316 @chapter Tracepoints
9317 @c This chapter is based on the documentation written by Michael
9318 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9321 In some applications, it is not feasible for the debugger to interrupt
9322 the program's execution long enough for the developer to learn
9323 anything helpful about its behavior. If the program's correctness
9324 depends on its real-time behavior, delays introduced by a debugger
9325 might cause the program to change its behavior drastically, or perhaps
9326 fail, even when the code itself is correct. It is useful to be able
9327 to observe the program's behavior without interrupting it.
9329 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9330 specify locations in the program, called @dfn{tracepoints}, and
9331 arbitrary expressions to evaluate when those tracepoints are reached.
9332 Later, using the @code{tfind} command, you can examine the values
9333 those expressions had when the program hit the tracepoints. The
9334 expressions may also denote objects in memory---structures or arrays,
9335 for example---whose values @value{GDBN} should record; while visiting
9336 a particular tracepoint, you may inspect those objects as if they were
9337 in memory at that moment. However, because @value{GDBN} records these
9338 values without interacting with you, it can do so quickly and
9339 unobtrusively, hopefully not disturbing the program's behavior.
9341 The tracepoint facility is currently available only for remote
9342 targets. @xref{Targets}. In addition, your remote target must know
9343 how to collect trace data. This functionality is implemented in the
9344 remote stub; however, none of the stubs distributed with @value{GDBN}
9345 support tracepoints as of this writing. The format of the remote
9346 packets used to implement tracepoints are described in @ref{Tracepoint
9349 It is also possible to get trace data from a file, in a manner reminiscent
9350 of corefiles; you specify the filename, and use @code{tfind} to search
9351 through the file. @xref{Trace Files}, for more details.
9353 This chapter describes the tracepoint commands and features.
9357 * Analyze Collected Data::
9358 * Tracepoint Variables::
9362 @node Set Tracepoints
9363 @section Commands to Set Tracepoints
9365 Before running such a @dfn{trace experiment}, an arbitrary number of
9366 tracepoints can be set. A tracepoint is actually a special type of
9367 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9368 standard breakpoint commands. For instance, as with breakpoints,
9369 tracepoint numbers are successive integers starting from one, and many
9370 of the commands associated with tracepoints take the tracepoint number
9371 as their argument, to identify which tracepoint to work on.
9373 For each tracepoint, you can specify, in advance, some arbitrary set
9374 of data that you want the target to collect in the trace buffer when
9375 it hits that tracepoint. The collected data can include registers,
9376 local variables, or global data. Later, you can use @value{GDBN}
9377 commands to examine the values these data had at the time the
9380 Tracepoints do not support every breakpoint feature. Ignore counts on
9381 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9382 commands when they are hit. Tracepoints may not be thread-specific
9385 @cindex fast tracepoints
9386 Some targets may support @dfn{fast tracepoints}, which are inserted in
9387 a different way (such as with a jump instead of a trap), that is
9388 faster but possibly restricted in where they may be installed.
9390 This section describes commands to set tracepoints and associated
9391 conditions and actions.
9394 * Create and Delete Tracepoints::
9395 * Enable and Disable Tracepoints::
9396 * Tracepoint Passcounts::
9397 * Tracepoint Conditions::
9398 * Trace State Variables::
9399 * Tracepoint Actions::
9400 * Listing Tracepoints::
9401 * Starting and Stopping Trace Experiments::
9402 * Tracepoint Restrictions::
9405 @node Create and Delete Tracepoints
9406 @subsection Create and Delete Tracepoints
9409 @cindex set tracepoint
9411 @item trace @var{location}
9412 The @code{trace} command is very similar to the @code{break} command.
9413 Its argument @var{location} can be a source line, a function name, or
9414 an address in the target program. @xref{Specify Location}. The
9415 @code{trace} command defines a tracepoint, which is a point in the
9416 target program where the debugger will briefly stop, collect some
9417 data, and then allow the program to continue. Setting a tracepoint or
9418 changing its actions doesn't take effect until the next @code{tstart}
9419 command, and once a trace experiment is running, further changes will
9420 not have any effect until the next trace experiment starts.
9422 Here are some examples of using the @code{trace} command:
9425 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9427 (@value{GDBP}) @b{trace +2} // 2 lines forward
9429 (@value{GDBP}) @b{trace my_function} // first source line of function
9431 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9433 (@value{GDBP}) @b{trace *0x2117c4} // an address
9437 You can abbreviate @code{trace} as @code{tr}.
9439 @item trace @var{location} if @var{cond}
9440 Set a tracepoint with condition @var{cond}; evaluate the expression
9441 @var{cond} each time the tracepoint is reached, and collect data only
9442 if the value is nonzero---that is, if @var{cond} evaluates as true.
9443 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9444 information on tracepoint conditions.
9446 @item ftrace @var{location} [ if @var{cond} ]
9447 @cindex set fast tracepoint
9449 The @code{ftrace} command sets a fast tracepoint. For targets that
9450 support them, fast tracepoints will use a more efficient but possibly
9451 less general technique to trigger data collection, such as a jump
9452 instruction instead of a trap, or some sort of hardware support. It
9453 may not be possible to create a fast tracepoint at the desired
9454 location, in which case the command will exit with an explanatory
9457 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9461 @cindex last tracepoint number
9462 @cindex recent tracepoint number
9463 @cindex tracepoint number
9464 The convenience variable @code{$tpnum} records the tracepoint number
9465 of the most recently set tracepoint.
9467 @kindex delete tracepoint
9468 @cindex tracepoint deletion
9469 @item delete tracepoint @r{[}@var{num}@r{]}
9470 Permanently delete one or more tracepoints. With no argument, the
9471 default is to delete all tracepoints. Note that the regular
9472 @code{delete} command can remove tracepoints also.
9477 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9479 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9483 You can abbreviate this command as @code{del tr}.
9486 @node Enable and Disable Tracepoints
9487 @subsection Enable and Disable Tracepoints
9489 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9492 @kindex disable tracepoint
9493 @item disable tracepoint @r{[}@var{num}@r{]}
9494 Disable tracepoint @var{num}, or all tracepoints if no argument
9495 @var{num} is given. A disabled tracepoint will have no effect during
9496 the next trace experiment, but it is not forgotten. You can re-enable
9497 a disabled tracepoint using the @code{enable tracepoint} command.
9499 @kindex enable tracepoint
9500 @item enable tracepoint @r{[}@var{num}@r{]}
9501 Enable tracepoint @var{num}, or all tracepoints. The enabled
9502 tracepoints will become effective the next time a trace experiment is
9506 @node Tracepoint Passcounts
9507 @subsection Tracepoint Passcounts
9511 @cindex tracepoint pass count
9512 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9513 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9514 automatically stop a trace experiment. If a tracepoint's passcount is
9515 @var{n}, then the trace experiment will be automatically stopped on
9516 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9517 @var{num} is not specified, the @code{passcount} command sets the
9518 passcount of the most recently defined tracepoint. If no passcount is
9519 given, the trace experiment will run until stopped explicitly by the
9525 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9526 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9528 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9529 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9530 (@value{GDBP}) @b{trace foo}
9531 (@value{GDBP}) @b{pass 3}
9532 (@value{GDBP}) @b{trace bar}
9533 (@value{GDBP}) @b{pass 2}
9534 (@value{GDBP}) @b{trace baz}
9535 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9536 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9537 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9538 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9542 @node Tracepoint Conditions
9543 @subsection Tracepoint Conditions
9544 @cindex conditional tracepoints
9545 @cindex tracepoint conditions
9547 The simplest sort of tracepoint collects data every time your program
9548 reaches a specified place. You can also specify a @dfn{condition} for
9549 a tracepoint. A condition is just a Boolean expression in your
9550 programming language (@pxref{Expressions, ,Expressions}). A
9551 tracepoint with a condition evaluates the expression each time your
9552 program reaches it, and data collection happens only if the condition
9555 Tracepoint conditions can be specified when a tracepoint is set, by
9556 using @samp{if} in the arguments to the @code{trace} command.
9557 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9558 also be set or changed at any time with the @code{condition} command,
9559 just as with breakpoints.
9561 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9562 the conditional expression itself. Instead, @value{GDBN} encodes the
9563 expression into an agent expression (@pxref{Agent Expressions}
9564 suitable for execution on the target, independently of @value{GDBN}.
9565 Global variables become raw memory locations, locals become stack
9566 accesses, and so forth.
9568 For instance, suppose you have a function that is usually called
9569 frequently, but should not be called after an error has occurred. You
9570 could use the following tracepoint command to collect data about calls
9571 of that function that happen while the error code is propagating
9572 through the program; an unconditional tracepoint could end up
9573 collecting thousands of useless trace frames that you would have to
9577 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9580 @node Trace State Variables
9581 @subsection Trace State Variables
9582 @cindex trace state variables
9584 A @dfn{trace state variable} is a special type of variable that is
9585 created and managed by target-side code. The syntax is the same as
9586 that for GDB's convenience variables (a string prefixed with ``$''),
9587 but they are stored on the target. They must be created explicitly,
9588 using a @code{tvariable} command. They are always 64-bit signed
9591 Trace state variables are remembered by @value{GDBN}, and downloaded
9592 to the target along with tracepoint information when the trace
9593 experiment starts. There are no intrinsic limits on the number of
9594 trace state variables, beyond memory limitations of the target.
9596 @cindex convenience variables, and trace state variables
9597 Although trace state variables are managed by the target, you can use
9598 them in print commands and expressions as if they were convenience
9599 variables; @value{GDBN} will get the current value from the target
9600 while the trace experiment is running. Trace state variables share
9601 the same namespace as other ``$'' variables, which means that you
9602 cannot have trace state variables with names like @code{$23} or
9603 @code{$pc}, nor can you have a trace state variable and a convenience
9604 variable with the same name.
9608 @item tvariable $@var{name} [ = @var{expression} ]
9610 The @code{tvariable} command creates a new trace state variable named
9611 @code{$@var{name}}, and optionally gives it an initial value of
9612 @var{expression}. @var{expression} is evaluated when this command is
9613 entered; the result will be converted to an integer if possible,
9614 otherwise @value{GDBN} will report an error. A subsequent
9615 @code{tvariable} command specifying the same name does not create a
9616 variable, but instead assigns the supplied initial value to the
9617 existing variable of that name, overwriting any previous initial
9618 value. The default initial value is 0.
9620 @item info tvariables
9621 @kindex info tvariables
9622 List all the trace state variables along with their initial values.
9623 Their current values may also be displayed, if the trace experiment is
9626 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9627 @kindex delete tvariable
9628 Delete the given trace state variables, or all of them if no arguments
9633 @node Tracepoint Actions
9634 @subsection Tracepoint Action Lists
9638 @cindex tracepoint actions
9639 @item actions @r{[}@var{num}@r{]}
9640 This command will prompt for a list of actions to be taken when the
9641 tracepoint is hit. If the tracepoint number @var{num} is not
9642 specified, this command sets the actions for the one that was most
9643 recently defined (so that you can define a tracepoint and then say
9644 @code{actions} without bothering about its number). You specify the
9645 actions themselves on the following lines, one action at a time, and
9646 terminate the actions list with a line containing just @code{end}. So
9647 far, the only defined actions are @code{collect}, @code{teval}, and
9648 @code{while-stepping}.
9650 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9651 Commands, ,Breakpoint Command Lists}), except that only the defined
9652 actions are allowed; any other @value{GDBN} command is rejected.
9654 @cindex remove actions from a tracepoint
9655 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9656 and follow it immediately with @samp{end}.
9659 (@value{GDBP}) @b{collect @var{data}} // collect some data
9661 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9663 (@value{GDBP}) @b{end} // signals the end of actions.
9666 In the following example, the action list begins with @code{collect}
9667 commands indicating the things to be collected when the tracepoint is
9668 hit. Then, in order to single-step and collect additional data
9669 following the tracepoint, a @code{while-stepping} command is used,
9670 followed by the list of things to be collected after each step in a
9671 sequence of single steps. The @code{while-stepping} command is
9672 terminated by its own separate @code{end} command. Lastly, the action
9673 list is terminated by an @code{end} command.
9676 (@value{GDBP}) @b{trace foo}
9677 (@value{GDBP}) @b{actions}
9678 Enter actions for tracepoint 1, one per line:
9682 > collect $pc, arr[i]
9687 @kindex collect @r{(tracepoints)}
9688 @item collect @var{expr1}, @var{expr2}, @dots{}
9689 Collect values of the given expressions when the tracepoint is hit.
9690 This command accepts a comma-separated list of any valid expressions.
9691 In addition to global, static, or local variables, the following
9692 special arguments are supported:
9696 collect all registers
9699 collect all function arguments
9702 collect all local variables.
9705 You can give several consecutive @code{collect} commands, each one
9706 with a single argument, or one @code{collect} command with several
9707 arguments separated by commas; the effect is the same.
9709 The command @code{info scope} (@pxref{Symbols, info scope}) is
9710 particularly useful for figuring out what data to collect.
9712 @kindex teval @r{(tracepoints)}
9713 @item teval @var{expr1}, @var{expr2}, @dots{}
9714 Evaluate the given expressions when the tracepoint is hit. This
9715 command accepts a comma-separated list of expressions. The results
9716 are discarded, so this is mainly useful for assigning values to trace
9717 state variables (@pxref{Trace State Variables}) without adding those
9718 values to the trace buffer, as would be the case if the @code{collect}
9721 @kindex while-stepping @r{(tracepoints)}
9722 @item while-stepping @var{n}
9723 Perform @var{n} single-step instruction traces after the tracepoint,
9724 collecting new data after each step. The @code{while-stepping}
9725 command is followed by the list of what to collect while stepping
9726 (followed by its own @code{end} command):
9730 > collect $regs, myglobal
9736 Note that @code{$pc} is not automatically collected by
9737 @code{while-stepping}; you need to explicitly collect that register if
9738 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
9741 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
9742 @kindex set default-collect
9743 @cindex default collection action
9744 This variable is a list of expressions to collect at each tracepoint
9745 hit. It is effectively an additional @code{collect} action prepended
9746 to every tracepoint action list. The expressions are parsed
9747 individually for each tracepoint, so for instance a variable named
9748 @code{xyz} may be interpreted as a global for one tracepoint, and a
9749 local for another, as appropriate to the tracepoint's location.
9751 @item show default-collect
9752 @kindex show default-collect
9753 Show the list of expressions that are collected by default at each
9758 @node Listing Tracepoints
9759 @subsection Listing Tracepoints
9762 @kindex info tracepoints
9764 @cindex information about tracepoints
9765 @item info tracepoints @r{[}@var{num}@r{]}
9766 Display information about the tracepoint @var{num}. If you don't
9767 specify a tracepoint number, displays information about all the
9768 tracepoints defined so far. The format is similar to that used for
9769 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9770 command, simply restricting itself to tracepoints.
9772 A tracepoint's listing may include additional information specific to
9777 its passcount as given by the @code{passcount @var{n}} command
9781 (@value{GDBP}) @b{info trace}
9782 Num Type Disp Enb Address What
9783 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9785 collect globfoo, $regs
9794 This command can be abbreviated @code{info tp}.
9797 @node Starting and Stopping Trace Experiments
9798 @subsection Starting and Stopping Trace Experiments
9802 @cindex start a new trace experiment
9803 @cindex collected data discarded
9805 This command takes no arguments. It starts the trace experiment, and
9806 begins collecting data. This has the side effect of discarding all
9807 the data collected in the trace buffer during the previous trace
9811 @cindex stop a running trace experiment
9813 This command takes no arguments. It ends the trace experiment, and
9814 stops collecting data.
9816 @strong{Note}: a trace experiment and data collection may stop
9817 automatically if any tracepoint's passcount is reached
9818 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9821 @cindex status of trace data collection
9822 @cindex trace experiment, status of
9824 This command displays the status of the current trace data
9828 Here is an example of the commands we described so far:
9831 (@value{GDBP}) @b{trace gdb_c_test}
9832 (@value{GDBP}) @b{actions}
9833 Enter actions for tracepoint #1, one per line.
9834 > collect $regs,$locals,$args
9839 (@value{GDBP}) @b{tstart}
9840 [time passes @dots{}]
9841 (@value{GDBP}) @b{tstop}
9844 @cindex disconnected tracing
9845 You can choose to continue running the trace experiment even if
9846 @value{GDBN} disconnects from the target, voluntarily or
9847 involuntarily. For commands such as @code{detach}, the debugger will
9848 ask what you want to do with the trace. But for unexpected
9849 terminations (@value{GDBN} crash, network outage), it would be
9850 unfortunate to lose hard-won trace data, so the variable
9851 @code{disconnected-tracing} lets you decide whether the trace should
9852 continue running without @value{GDBN}.
9855 @item set disconnected-tracing on
9856 @itemx set disconnected-tracing off
9857 @kindex set disconnected-tracing
9858 Choose whether a tracing run should continue to run if @value{GDBN}
9859 has disconnected from the target. Note that @code{detach} or
9860 @code{quit} will ask you directly what to do about a running trace no
9861 matter what this variable's setting, so the variable is mainly useful
9862 for handling unexpected situations, such as loss of the network.
9864 @item show disconnected-tracing
9865 @kindex show disconnected-tracing
9866 Show the current choice for disconnected tracing.
9870 When you reconnect to the target, the trace experiment may or may not
9871 still be running; it might have filled the trace buffer in the
9872 meantime, or stopped for one of the other reasons. If it is running,
9873 it will continue after reconnection.
9875 Upon reconnection, the target will upload information about the
9876 tracepoints in effect. @value{GDBN} will then compare that
9877 information to the set of tracepoints currently defined, and attempt
9878 to match them up, allowing for the possibility that the numbers may
9879 have changed due to creation and deletion in the meantime. If one of
9880 the target's tracepoints does not match any in @value{GDBN}, the
9881 debugger will create a new tracepoint, so that you have a number with
9882 which to specify that tracepoint. This matching-up process is
9883 necessarily heuristic, and it may result in useless tracepoints being
9884 created; you may simply delete them if they are of no use.
9886 @cindex circular trace buffer
9887 If your target agent supports a @dfn{circular trace buffer}, then you
9888 can run a trace experiment indefinitely without filling the trace
9889 buffer; when space runs out, the agent deletes already-collected trace
9890 frames, oldest first, until there is enough room to continue
9891 collecting. This is especially useful if your tracepoints are being
9892 hit too often, and your trace gets terminated prematurely because the
9893 buffer is full. To ask for a circular trace buffer, simply set
9894 @samp{circular_trace_buffer} to on. You can set this at any time,
9895 including during tracing; if the agent can do it, it will change
9896 buffer handling on the fly, otherwise it will not take effect until
9900 @item set circular-trace-buffer on
9901 @itemx set circular-trace-buffer off
9902 @kindex set circular-trace-buffer
9903 Choose whether a tracing run should use a linear or circular buffer
9904 for trace data. A linear buffer will not lose any trace data, but may
9905 fill up prematurely, while a circular buffer will discard old trace
9906 data, but it will have always room for the latest tracepoint hits.
9908 @item show circular-trace-buffer
9909 @kindex show circular-trace-buffer
9910 Show the current choice for the trace buffer. Note that this may not
9911 match the agent's current buffer handling, nor is it guaranteed to
9912 match the setting that might have been in effect during a past run,
9913 for instance if you are looking at frames from a trace file.
9917 @node Tracepoint Restrictions
9918 @subsection Tracepoint Restrictions
9920 @cindex tracepoint restrictions
9921 There are a number of restrictions on the use of tracepoints. As
9922 described above, tracepoint data gathering occurs on the target
9923 without interaction from @value{GDBN}. Thus the full capabilities of
9924 the debugger are not available during data gathering, and then at data
9925 examination time, you will be limited by only having what was
9926 collected. The following items describe some common problems, but it
9927 is not exhaustive, and you may run into additional difficulties not
9933 Tracepoint expressions are intended to gather objects (lvalues). Thus
9934 the full flexibility of GDB's expression evaluator is not available.
9935 You cannot call functions, cast objects to aggregate types, access
9936 convenience variables or modify values (except by assignment to trace
9937 state variables). Some language features may implicitly call
9938 functions (for instance Objective-C fields with accessors), and therefore
9939 cannot be collected either.
9942 Collection of local variables, either individually or in bulk with
9943 @code{$locals} or @code{$args}, during @code{while-stepping} may
9944 behave erratically. The stepping action may enter a new scope (for
9945 instance by stepping into a function), or the location of the variable
9946 may change (for instance it is loaded into a register). The
9947 tracepoint data recorded uses the location information for the
9948 variables that is correct for the tracepoint location. When the
9949 tracepoint is created, it is not possible, in general, to determine
9950 where the steps of a @code{while-stepping} sequence will advance the
9951 program---particularly if a conditional branch is stepped.
9954 Collection of an incompletely-initialized or partially-destroyed object
9955 may result in something that @value{GDBN} cannot display, or displays
9956 in a misleading way.
9959 When @value{GDBN} displays a pointer to character it automatically
9960 dereferences the pointer to also display characters of the string
9961 being pointed to. However, collecting the pointer during tracing does
9962 not automatically collect the string. You need to explicitly
9963 dereference the pointer and provide size information if you want to
9964 collect not only the pointer, but the memory pointed to. For example,
9965 @code{*ptr@@50} can be used to collect the 50 element array pointed to
9969 It is not possible to collect a complete stack backtrace at a
9970 tracepoint. Instead, you may collect the registers and a few hundred
9971 bytes from the stack pointer with something like @code{*$esp@@300}
9972 (adjust to use the name of the actual stack pointer register on your
9973 target architecture, and the amount of stack you wish to capture).
9974 Then the @code{backtrace} command will show a partial backtrace when
9975 using a trace frame. The number of stack frames that can be examined
9976 depends on the sizes of the frames in the collected stack. Note that
9977 if you ask for a block so large that it goes past the bottom of the
9978 stack, the target agent may report an error trying to read from an
9982 If you do not collect registers at a tracepoint, @value{GDBN} can
9983 infer that the value of @code{$pc} must be the same as the address of
9984 the tracepoint and use that when you are looking at a trace frame
9985 for that tracepoint. However, this cannot work if the tracepoint has
9986 multiple locations (for instance if it was set in a function that was
9987 inlined), or if it has a @code{while-stepping} loop. In those cases
9988 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
9993 @node Analyze Collected Data
9994 @section Using the Collected Data
9996 After the tracepoint experiment ends, you use @value{GDBN} commands
9997 for examining the trace data. The basic idea is that each tracepoint
9998 collects a trace @dfn{snapshot} every time it is hit and another
9999 snapshot every time it single-steps. All these snapshots are
10000 consecutively numbered from zero and go into a buffer, and you can
10001 examine them later. The way you examine them is to @dfn{focus} on a
10002 specific trace snapshot. When the remote stub is focused on a trace
10003 snapshot, it will respond to all @value{GDBN} requests for memory and
10004 registers by reading from the buffer which belongs to that snapshot,
10005 rather than from @emph{real} memory or registers of the program being
10006 debugged. This means that @strong{all} @value{GDBN} commands
10007 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10008 behave as if we were currently debugging the program state as it was
10009 when the tracepoint occurred. Any requests for data that are not in
10010 the buffer will fail.
10013 * tfind:: How to select a trace snapshot
10014 * tdump:: How to display all data for a snapshot
10015 * save tracepoints:: How to save tracepoints for a future run
10019 @subsection @code{tfind @var{n}}
10022 @cindex select trace snapshot
10023 @cindex find trace snapshot
10024 The basic command for selecting a trace snapshot from the buffer is
10025 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10026 counting from zero. If no argument @var{n} is given, the next
10027 snapshot is selected.
10029 Here are the various forms of using the @code{tfind} command.
10033 Find the first snapshot in the buffer. This is a synonym for
10034 @code{tfind 0} (since 0 is the number of the first snapshot).
10037 Stop debugging trace snapshots, resume @emph{live} debugging.
10040 Same as @samp{tfind none}.
10043 No argument means find the next trace snapshot.
10046 Find the previous trace snapshot before the current one. This permits
10047 retracing earlier steps.
10049 @item tfind tracepoint @var{num}
10050 Find the next snapshot associated with tracepoint @var{num}. Search
10051 proceeds forward from the last examined trace snapshot. If no
10052 argument @var{num} is given, it means find the next snapshot collected
10053 for the same tracepoint as the current snapshot.
10055 @item tfind pc @var{addr}
10056 Find the next snapshot associated with the value @var{addr} of the
10057 program counter. Search proceeds forward from the last examined trace
10058 snapshot. If no argument @var{addr} is given, it means find the next
10059 snapshot with the same value of PC as the current snapshot.
10061 @item tfind outside @var{addr1}, @var{addr2}
10062 Find the next snapshot whose PC is outside the given range of
10063 addresses (exclusive).
10065 @item tfind range @var{addr1}, @var{addr2}
10066 Find the next snapshot whose PC is between @var{addr1} and
10067 @var{addr2} (inclusive).
10069 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10070 Find the next snapshot associated with the source line @var{n}. If
10071 the optional argument @var{file} is given, refer to line @var{n} in
10072 that source file. Search proceeds forward from the last examined
10073 trace snapshot. If no argument @var{n} is given, it means find the
10074 next line other than the one currently being examined; thus saying
10075 @code{tfind line} repeatedly can appear to have the same effect as
10076 stepping from line to line in a @emph{live} debugging session.
10079 The default arguments for the @code{tfind} commands are specifically
10080 designed to make it easy to scan through the trace buffer. For
10081 instance, @code{tfind} with no argument selects the next trace
10082 snapshot, and @code{tfind -} with no argument selects the previous
10083 trace snapshot. So, by giving one @code{tfind} command, and then
10084 simply hitting @key{RET} repeatedly you can examine all the trace
10085 snapshots in order. Or, by saying @code{tfind -} and then hitting
10086 @key{RET} repeatedly you can examine the snapshots in reverse order.
10087 The @code{tfind line} command with no argument selects the snapshot
10088 for the next source line executed. The @code{tfind pc} command with
10089 no argument selects the next snapshot with the same program counter
10090 (PC) as the current frame. The @code{tfind tracepoint} command with
10091 no argument selects the next trace snapshot collected by the same
10092 tracepoint as the current one.
10094 In addition to letting you scan through the trace buffer manually,
10095 these commands make it easy to construct @value{GDBN} scripts that
10096 scan through the trace buffer and print out whatever collected data
10097 you are interested in. Thus, if we want to examine the PC, FP, and SP
10098 registers from each trace frame in the buffer, we can say this:
10101 (@value{GDBP}) @b{tfind start}
10102 (@value{GDBP}) @b{while ($trace_frame != -1)}
10103 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10104 $trace_frame, $pc, $sp, $fp
10108 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10109 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10110 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10111 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10112 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10113 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10114 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10115 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10116 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10117 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10118 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10121 Or, if we want to examine the variable @code{X} at each source line in
10125 (@value{GDBP}) @b{tfind start}
10126 (@value{GDBP}) @b{while ($trace_frame != -1)}
10127 > printf "Frame %d, X == %d\n", $trace_frame, X
10137 @subsection @code{tdump}
10139 @cindex dump all data collected at tracepoint
10140 @cindex tracepoint data, display
10142 This command takes no arguments. It prints all the data collected at
10143 the current trace snapshot.
10146 (@value{GDBP}) @b{trace 444}
10147 (@value{GDBP}) @b{actions}
10148 Enter actions for tracepoint #2, one per line:
10149 > collect $regs, $locals, $args, gdb_long_test
10152 (@value{GDBP}) @b{tstart}
10154 (@value{GDBP}) @b{tfind line 444}
10155 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10157 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10159 (@value{GDBP}) @b{tdump}
10160 Data collected at tracepoint 2, trace frame 1:
10161 d0 0xc4aa0085 -995491707
10165 d4 0x71aea3d 119204413
10168 d7 0x380035 3670069
10169 a0 0x19e24a 1696330
10170 a1 0x3000668 50333288
10172 a3 0x322000 3284992
10173 a4 0x3000698 50333336
10174 a5 0x1ad3cc 1758156
10175 fp 0x30bf3c 0x30bf3c
10176 sp 0x30bf34 0x30bf34
10178 pc 0x20b2c8 0x20b2c8
10182 p = 0x20e5b4 "gdb-test"
10189 gdb_long_test = 17 '\021'
10194 @code{tdump} works by scanning the tracepoint's current collection
10195 actions and printing the value of each expression listed. So
10196 @code{tdump} can fail, if after a run, you change the tracepoint's
10197 actions to mention variables that were not collected during the run.
10199 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10200 uses the collected value of @code{$pc} to distinguish between trace
10201 frames that were collected at the tracepoint hit, and frames that were
10202 collected while stepping. This allows it to correctly choose whether
10203 to display the basic list of collections, or the collections from the
10204 body of the while-stepping loop. However, if @code{$pc} was not collected,
10205 then @code{tdump} will always attempt to dump using the basic collection
10206 list, and may fail if a while-stepping frame does not include all the
10207 same data that is collected at the tracepoint hit.
10208 @c This is getting pretty arcane, example would be good.
10210 @node save tracepoints
10211 @subsection @code{save tracepoints @var{filename}}
10212 @kindex save tracepoints
10213 @kindex save-tracepoints
10214 @cindex save tracepoints for future sessions
10216 This command saves all current tracepoint definitions together with
10217 their actions and passcounts, into a file @file{@var{filename}}
10218 suitable for use in a later debugging session. To read the saved
10219 tracepoint definitions, use the @code{source} command (@pxref{Command
10220 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10221 alias for @w{@code{save tracepoints}}
10223 @node Tracepoint Variables
10224 @section Convenience Variables for Tracepoints
10225 @cindex tracepoint variables
10226 @cindex convenience variables for tracepoints
10229 @vindex $trace_frame
10230 @item (int) $trace_frame
10231 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10232 snapshot is selected.
10234 @vindex $tracepoint
10235 @item (int) $tracepoint
10236 The tracepoint for the current trace snapshot.
10238 @vindex $trace_line
10239 @item (int) $trace_line
10240 The line number for the current trace snapshot.
10242 @vindex $trace_file
10243 @item (char []) $trace_file
10244 The source file for the current trace snapshot.
10246 @vindex $trace_func
10247 @item (char []) $trace_func
10248 The name of the function containing @code{$tracepoint}.
10251 Note: @code{$trace_file} is not suitable for use in @code{printf},
10252 use @code{output} instead.
10254 Here's a simple example of using these convenience variables for
10255 stepping through all the trace snapshots and printing some of their
10256 data. Note that these are not the same as trace state variables,
10257 which are managed by the target.
10260 (@value{GDBP}) @b{tfind start}
10262 (@value{GDBP}) @b{while $trace_frame != -1}
10263 > output $trace_file
10264 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10270 @section Using Trace Files
10271 @cindex trace files
10273 In some situations, the target running a trace experiment may no
10274 longer be available; perhaps it crashed, or the hardware was needed
10275 for a different activity. To handle these cases, you can arrange to
10276 dump the trace data into a file, and later use that file as a source
10277 of trace data, via the @code{target tfile} command.
10282 @item tsave [ -r ] @var{filename}
10283 Save the trace data to @var{filename}. By default, this command
10284 assumes that @var{filename} refers to the host filesystem, so if
10285 necessary @value{GDBN} will copy raw trace data up from the target and
10286 then save it. If the target supports it, you can also supply the
10287 optional argument @code{-r} (``remote'') to direct the target to save
10288 the data directly into @var{filename} in its own filesystem, which may be
10289 more efficient if the trace buffer is very large. (Note, however, that
10290 @code{target tfile} can only read from files accessible to the host.)
10292 @kindex target tfile
10294 @item target tfile @var{filename}
10295 Use the file named @var{filename} as a source of trace data. Commands
10296 that examine data work as they do with a live target, but it is not
10297 possible to run any new trace experiments. @code{tstatus} will report
10298 the state of the trace run at the moment the data was saved, as well
10299 as the current trace frame you are examining. @var{filename} must be
10300 on a filesystem accessible to the host.
10305 @chapter Debugging Programs That Use Overlays
10308 If your program is too large to fit completely in your target system's
10309 memory, you can sometimes use @dfn{overlays} to work around this
10310 problem. @value{GDBN} provides some support for debugging programs that
10314 * How Overlays Work:: A general explanation of overlays.
10315 * Overlay Commands:: Managing overlays in @value{GDBN}.
10316 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10317 mapped by asking the inferior.
10318 * Overlay Sample Program:: A sample program using overlays.
10321 @node How Overlays Work
10322 @section How Overlays Work
10323 @cindex mapped overlays
10324 @cindex unmapped overlays
10325 @cindex load address, overlay's
10326 @cindex mapped address
10327 @cindex overlay area
10329 Suppose you have a computer whose instruction address space is only 64
10330 kilobytes long, but which has much more memory which can be accessed by
10331 other means: special instructions, segment registers, or memory
10332 management hardware, for example. Suppose further that you want to
10333 adapt a program which is larger than 64 kilobytes to run on this system.
10335 One solution is to identify modules of your program which are relatively
10336 independent, and need not call each other directly; call these modules
10337 @dfn{overlays}. Separate the overlays from the main program, and place
10338 their machine code in the larger memory. Place your main program in
10339 instruction memory, but leave at least enough space there to hold the
10340 largest overlay as well.
10342 Now, to call a function located in an overlay, you must first copy that
10343 overlay's machine code from the large memory into the space set aside
10344 for it in the instruction memory, and then jump to its entry point
10347 @c NB: In the below the mapped area's size is greater or equal to the
10348 @c size of all overlays. This is intentional to remind the developer
10349 @c that overlays don't necessarily need to be the same size.
10353 Data Instruction Larger
10354 Address Space Address Space Address Space
10355 +-----------+ +-----------+ +-----------+
10357 +-----------+ +-----------+ +-----------+<-- overlay 1
10358 | program | | main | .----| overlay 1 | load address
10359 | variables | | program | | +-----------+
10360 | and heap | | | | | |
10361 +-----------+ | | | +-----------+<-- overlay 2
10362 | | +-----------+ | | | load address
10363 +-----------+ | | | .-| overlay 2 |
10365 mapped --->+-----------+ | | +-----------+
10366 address | | | | | |
10367 | overlay | <-' | | |
10368 | area | <---' +-----------+<-- overlay 3
10369 | | <---. | | load address
10370 +-----------+ `--| overlay 3 |
10377 @anchor{A code overlay}A code overlay
10381 The diagram (@pxref{A code overlay}) shows a system with separate data
10382 and instruction address spaces. To map an overlay, the program copies
10383 its code from the larger address space to the instruction address space.
10384 Since the overlays shown here all use the same mapped address, only one
10385 may be mapped at a time. For a system with a single address space for
10386 data and instructions, the diagram would be similar, except that the
10387 program variables and heap would share an address space with the main
10388 program and the overlay area.
10390 An overlay loaded into instruction memory and ready for use is called a
10391 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10392 instruction memory. An overlay not present (or only partially present)
10393 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10394 is its address in the larger memory. The mapped address is also called
10395 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10396 called the @dfn{load memory address}, or @dfn{LMA}.
10398 Unfortunately, overlays are not a completely transparent way to adapt a
10399 program to limited instruction memory. They introduce a new set of
10400 global constraints you must keep in mind as you design your program:
10405 Before calling or returning to a function in an overlay, your program
10406 must make sure that overlay is actually mapped. Otherwise, the call or
10407 return will transfer control to the right address, but in the wrong
10408 overlay, and your program will probably crash.
10411 If the process of mapping an overlay is expensive on your system, you
10412 will need to choose your overlays carefully to minimize their effect on
10413 your program's performance.
10416 The executable file you load onto your system must contain each
10417 overlay's instructions, appearing at the overlay's load address, not its
10418 mapped address. However, each overlay's instructions must be relocated
10419 and its symbols defined as if the overlay were at its mapped address.
10420 You can use GNU linker scripts to specify different load and relocation
10421 addresses for pieces of your program; see @ref{Overlay Description,,,
10422 ld.info, Using ld: the GNU linker}.
10425 The procedure for loading executable files onto your system must be able
10426 to load their contents into the larger address space as well as the
10427 instruction and data spaces.
10431 The overlay system described above is rather simple, and could be
10432 improved in many ways:
10437 If your system has suitable bank switch registers or memory management
10438 hardware, you could use those facilities to make an overlay's load area
10439 contents simply appear at their mapped address in instruction space.
10440 This would probably be faster than copying the overlay to its mapped
10441 area in the usual way.
10444 If your overlays are small enough, you could set aside more than one
10445 overlay area, and have more than one overlay mapped at a time.
10448 You can use overlays to manage data, as well as instructions. In
10449 general, data overlays are even less transparent to your design than
10450 code overlays: whereas code overlays only require care when you call or
10451 return to functions, data overlays require care every time you access
10452 the data. Also, if you change the contents of a data overlay, you
10453 must copy its contents back out to its load address before you can copy a
10454 different data overlay into the same mapped area.
10459 @node Overlay Commands
10460 @section Overlay Commands
10462 To use @value{GDBN}'s overlay support, each overlay in your program must
10463 correspond to a separate section of the executable file. The section's
10464 virtual memory address and load memory address must be the overlay's
10465 mapped and load addresses. Identifying overlays with sections allows
10466 @value{GDBN} to determine the appropriate address of a function or
10467 variable, depending on whether the overlay is mapped or not.
10469 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10470 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10475 Disable @value{GDBN}'s overlay support. When overlay support is
10476 disabled, @value{GDBN} assumes that all functions and variables are
10477 always present at their mapped addresses. By default, @value{GDBN}'s
10478 overlay support is disabled.
10480 @item overlay manual
10481 @cindex manual overlay debugging
10482 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10483 relies on you to tell it which overlays are mapped, and which are not,
10484 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10485 commands described below.
10487 @item overlay map-overlay @var{overlay}
10488 @itemx overlay map @var{overlay}
10489 @cindex map an overlay
10490 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10491 be the name of the object file section containing the overlay. When an
10492 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10493 functions and variables at their mapped addresses. @value{GDBN} assumes
10494 that any other overlays whose mapped ranges overlap that of
10495 @var{overlay} are now unmapped.
10497 @item overlay unmap-overlay @var{overlay}
10498 @itemx overlay unmap @var{overlay}
10499 @cindex unmap an overlay
10500 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10501 must be the name of the object file section containing the overlay.
10502 When an overlay is unmapped, @value{GDBN} assumes it can find the
10503 overlay's functions and variables at their load addresses.
10506 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10507 consults a data structure the overlay manager maintains in the inferior
10508 to see which overlays are mapped. For details, see @ref{Automatic
10509 Overlay Debugging}.
10511 @item overlay load-target
10512 @itemx overlay load
10513 @cindex reloading the overlay table
10514 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10515 re-reads the table @value{GDBN} automatically each time the inferior
10516 stops, so this command should only be necessary if you have changed the
10517 overlay mapping yourself using @value{GDBN}. This command is only
10518 useful when using automatic overlay debugging.
10520 @item overlay list-overlays
10521 @itemx overlay list
10522 @cindex listing mapped overlays
10523 Display a list of the overlays currently mapped, along with their mapped
10524 addresses, load addresses, and sizes.
10528 Normally, when @value{GDBN} prints a code address, it includes the name
10529 of the function the address falls in:
10532 (@value{GDBP}) print main
10533 $3 = @{int ()@} 0x11a0 <main>
10536 When overlay debugging is enabled, @value{GDBN} recognizes code in
10537 unmapped overlays, and prints the names of unmapped functions with
10538 asterisks around them. For example, if @code{foo} is a function in an
10539 unmapped overlay, @value{GDBN} prints it this way:
10542 (@value{GDBP}) overlay list
10543 No sections are mapped.
10544 (@value{GDBP}) print foo
10545 $5 = @{int (int)@} 0x100000 <*foo*>
10548 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10552 (@value{GDBP}) overlay list
10553 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10554 mapped at 0x1016 - 0x104a
10555 (@value{GDBP}) print foo
10556 $6 = @{int (int)@} 0x1016 <foo>
10559 When overlay debugging is enabled, @value{GDBN} can find the correct
10560 address for functions and variables in an overlay, whether or not the
10561 overlay is mapped. This allows most @value{GDBN} commands, like
10562 @code{break} and @code{disassemble}, to work normally, even on unmapped
10563 code. However, @value{GDBN}'s breakpoint support has some limitations:
10567 @cindex breakpoints in overlays
10568 @cindex overlays, setting breakpoints in
10569 You can set breakpoints in functions in unmapped overlays, as long as
10570 @value{GDBN} can write to the overlay at its load address.
10572 @value{GDBN} can not set hardware or simulator-based breakpoints in
10573 unmapped overlays. However, if you set a breakpoint at the end of your
10574 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10575 you are using manual overlay management), @value{GDBN} will re-set its
10576 breakpoints properly.
10580 @node Automatic Overlay Debugging
10581 @section Automatic Overlay Debugging
10582 @cindex automatic overlay debugging
10584 @value{GDBN} can automatically track which overlays are mapped and which
10585 are not, given some simple co-operation from the overlay manager in the
10586 inferior. If you enable automatic overlay debugging with the
10587 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10588 looks in the inferior's memory for certain variables describing the
10589 current state of the overlays.
10591 Here are the variables your overlay manager must define to support
10592 @value{GDBN}'s automatic overlay debugging:
10596 @item @code{_ovly_table}:
10597 This variable must be an array of the following structures:
10602 /* The overlay's mapped address. */
10605 /* The size of the overlay, in bytes. */
10606 unsigned long size;
10608 /* The overlay's load address. */
10611 /* Non-zero if the overlay is currently mapped;
10613 unsigned long mapped;
10617 @item @code{_novlys}:
10618 This variable must be a four-byte signed integer, holding the total
10619 number of elements in @code{_ovly_table}.
10623 To decide whether a particular overlay is mapped or not, @value{GDBN}
10624 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10625 @code{lma} members equal the VMA and LMA of the overlay's section in the
10626 executable file. When @value{GDBN} finds a matching entry, it consults
10627 the entry's @code{mapped} member to determine whether the overlay is
10630 In addition, your overlay manager may define a function called
10631 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10632 will silently set a breakpoint there. If the overlay manager then
10633 calls this function whenever it has changed the overlay table, this
10634 will enable @value{GDBN} to accurately keep track of which overlays
10635 are in program memory, and update any breakpoints that may be set
10636 in overlays. This will allow breakpoints to work even if the
10637 overlays are kept in ROM or other non-writable memory while they
10638 are not being executed.
10640 @node Overlay Sample Program
10641 @section Overlay Sample Program
10642 @cindex overlay example program
10644 When linking a program which uses overlays, you must place the overlays
10645 at their load addresses, while relocating them to run at their mapped
10646 addresses. To do this, you must write a linker script (@pxref{Overlay
10647 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10648 since linker scripts are specific to a particular host system, target
10649 architecture, and target memory layout, this manual cannot provide
10650 portable sample code demonstrating @value{GDBN}'s overlay support.
10652 However, the @value{GDBN} source distribution does contain an overlaid
10653 program, with linker scripts for a few systems, as part of its test
10654 suite. The program consists of the following files from
10655 @file{gdb/testsuite/gdb.base}:
10659 The main program file.
10661 A simple overlay manager, used by @file{overlays.c}.
10666 Overlay modules, loaded and used by @file{overlays.c}.
10669 Linker scripts for linking the test program on the @code{d10v-elf}
10670 and @code{m32r-elf} targets.
10673 You can build the test program using the @code{d10v-elf} GCC
10674 cross-compiler like this:
10677 $ d10v-elf-gcc -g -c overlays.c
10678 $ d10v-elf-gcc -g -c ovlymgr.c
10679 $ d10v-elf-gcc -g -c foo.c
10680 $ d10v-elf-gcc -g -c bar.c
10681 $ d10v-elf-gcc -g -c baz.c
10682 $ d10v-elf-gcc -g -c grbx.c
10683 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10684 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10687 The build process is identical for any other architecture, except that
10688 you must substitute the appropriate compiler and linker script for the
10689 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10693 @chapter Using @value{GDBN} with Different Languages
10696 Although programming languages generally have common aspects, they are
10697 rarely expressed in the same manner. For instance, in ANSI C,
10698 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10699 Modula-2, it is accomplished by @code{p^}. Values can also be
10700 represented (and displayed) differently. Hex numbers in C appear as
10701 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10703 @cindex working language
10704 Language-specific information is built into @value{GDBN} for some languages,
10705 allowing you to express operations like the above in your program's
10706 native language, and allowing @value{GDBN} to output values in a manner
10707 consistent with the syntax of your program's native language. The
10708 language you use to build expressions is called the @dfn{working
10712 * Setting:: Switching between source languages
10713 * Show:: Displaying the language
10714 * Checks:: Type and range checks
10715 * Supported Languages:: Supported languages
10716 * Unsupported Languages:: Unsupported languages
10720 @section Switching Between Source Languages
10722 There are two ways to control the working language---either have @value{GDBN}
10723 set it automatically, or select it manually yourself. You can use the
10724 @code{set language} command for either purpose. On startup, @value{GDBN}
10725 defaults to setting the language automatically. The working language is
10726 used to determine how expressions you type are interpreted, how values
10729 In addition to the working language, every source file that
10730 @value{GDBN} knows about has its own working language. For some object
10731 file formats, the compiler might indicate which language a particular
10732 source file is in. However, most of the time @value{GDBN} infers the
10733 language from the name of the file. The language of a source file
10734 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10735 show each frame appropriately for its own language. There is no way to
10736 set the language of a source file from within @value{GDBN}, but you can
10737 set the language associated with a filename extension. @xref{Show, ,
10738 Displaying the Language}.
10740 This is most commonly a problem when you use a program, such
10741 as @code{cfront} or @code{f2c}, that generates C but is written in
10742 another language. In that case, make the
10743 program use @code{#line} directives in its C output; that way
10744 @value{GDBN} will know the correct language of the source code of the original
10745 program, and will display that source code, not the generated C code.
10748 * Filenames:: Filename extensions and languages.
10749 * Manually:: Setting the working language manually
10750 * Automatically:: Having @value{GDBN} infer the source language
10754 @subsection List of Filename Extensions and Languages
10756 If a source file name ends in one of the following extensions, then
10757 @value{GDBN} infers that its language is the one indicated.
10775 C@t{++} source file
10778 Objective-C source file
10782 Fortran source file
10785 Modula-2 source file
10789 Assembler source file. This actually behaves almost like C, but
10790 @value{GDBN} does not skip over function prologues when stepping.
10793 In addition, you may set the language associated with a filename
10794 extension. @xref{Show, , Displaying the Language}.
10797 @subsection Setting the Working Language
10799 If you allow @value{GDBN} to set the language automatically,
10800 expressions are interpreted the same way in your debugging session and
10803 @kindex set language
10804 If you wish, you may set the language manually. To do this, issue the
10805 command @samp{set language @var{lang}}, where @var{lang} is the name of
10806 a language, such as
10807 @code{c} or @code{modula-2}.
10808 For a list of the supported languages, type @samp{set language}.
10810 Setting the language manually prevents @value{GDBN} from updating the working
10811 language automatically. This can lead to confusion if you try
10812 to debug a program when the working language is not the same as the
10813 source language, when an expression is acceptable to both
10814 languages---but means different things. For instance, if the current
10815 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10823 might not have the effect you intended. In C, this means to add
10824 @code{b} and @code{c} and place the result in @code{a}. The result
10825 printed would be the value of @code{a}. In Modula-2, this means to compare
10826 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10828 @node Automatically
10829 @subsection Having @value{GDBN} Infer the Source Language
10831 To have @value{GDBN} set the working language automatically, use
10832 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10833 then infers the working language. That is, when your program stops in a
10834 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10835 working language to the language recorded for the function in that
10836 frame. If the language for a frame is unknown (that is, if the function
10837 or block corresponding to the frame was defined in a source file that
10838 does not have a recognized extension), the current working language is
10839 not changed, and @value{GDBN} issues a warning.
10841 This may not seem necessary for most programs, which are written
10842 entirely in one source language. However, program modules and libraries
10843 written in one source language can be used by a main program written in
10844 a different source language. Using @samp{set language auto} in this
10845 case frees you from having to set the working language manually.
10848 @section Displaying the Language
10850 The following commands help you find out which language is the
10851 working language, and also what language source files were written in.
10854 @item show language
10855 @kindex show language
10856 Display the current working language. This is the
10857 language you can use with commands such as @code{print} to
10858 build and compute expressions that may involve variables in your program.
10861 @kindex info frame@r{, show the source language}
10862 Display the source language for this frame. This language becomes the
10863 working language if you use an identifier from this frame.
10864 @xref{Frame Info, ,Information about a Frame}, to identify the other
10865 information listed here.
10868 @kindex info source@r{, show the source language}
10869 Display the source language of this source file.
10870 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
10871 information listed here.
10874 In unusual circumstances, you may have source files with extensions
10875 not in the standard list. You can then set the extension associated
10876 with a language explicitly:
10879 @item set extension-language @var{ext} @var{language}
10880 @kindex set extension-language
10881 Tell @value{GDBN} that source files with extension @var{ext} are to be
10882 assumed as written in the source language @var{language}.
10884 @item info extensions
10885 @kindex info extensions
10886 List all the filename extensions and the associated languages.
10890 @section Type and Range Checking
10893 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
10894 checking are included, but they do not yet have any effect. This
10895 section documents the intended facilities.
10897 @c FIXME remove warning when type/range code added
10899 Some languages are designed to guard you against making seemingly common
10900 errors through a series of compile- and run-time checks. These include
10901 checking the type of arguments to functions and operators, and making
10902 sure mathematical overflows are caught at run time. Checks such as
10903 these help to ensure a program's correctness once it has been compiled
10904 by eliminating type mismatches, and providing active checks for range
10905 errors when your program is running.
10907 @value{GDBN} can check for conditions like the above if you wish.
10908 Although @value{GDBN} does not check the statements in your program,
10909 it can check expressions entered directly into @value{GDBN} for
10910 evaluation via the @code{print} command, for example. As with the
10911 working language, @value{GDBN} can also decide whether or not to check
10912 automatically based on your program's source language.
10913 @xref{Supported Languages, ,Supported Languages}, for the default
10914 settings of supported languages.
10917 * Type Checking:: An overview of type checking
10918 * Range Checking:: An overview of range checking
10921 @cindex type checking
10922 @cindex checks, type
10923 @node Type Checking
10924 @subsection An Overview of Type Checking
10926 Some languages, such as Modula-2, are strongly typed, meaning that the
10927 arguments to operators and functions have to be of the correct type,
10928 otherwise an error occurs. These checks prevent type mismatch
10929 errors from ever causing any run-time problems. For example,
10937 The second example fails because the @code{CARDINAL} 1 is not
10938 type-compatible with the @code{REAL} 2.3.
10940 For the expressions you use in @value{GDBN} commands, you can tell the
10941 @value{GDBN} type checker to skip checking;
10942 to treat any mismatches as errors and abandon the expression;
10943 or to only issue warnings when type mismatches occur,
10944 but evaluate the expression anyway. When you choose the last of
10945 these, @value{GDBN} evaluates expressions like the second example above, but
10946 also issues a warning.
10948 Even if you turn type checking off, there may be other reasons
10949 related to type that prevent @value{GDBN} from evaluating an expression.
10950 For instance, @value{GDBN} does not know how to add an @code{int} and
10951 a @code{struct foo}. These particular type errors have nothing to do
10952 with the language in use, and usually arise from expressions, such as
10953 the one described above, which make little sense to evaluate anyway.
10955 Each language defines to what degree it is strict about type. For
10956 instance, both Modula-2 and C require the arguments to arithmetical
10957 operators to be numbers. In C, enumerated types and pointers can be
10958 represented as numbers, so that they are valid arguments to mathematical
10959 operators. @xref{Supported Languages, ,Supported Languages}, for further
10960 details on specific languages.
10962 @value{GDBN} provides some additional commands for controlling the type checker:
10964 @kindex set check type
10965 @kindex show check type
10967 @item set check type auto
10968 Set type checking on or off based on the current working language.
10969 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10972 @item set check type on
10973 @itemx set check type off
10974 Set type checking on or off, overriding the default setting for the
10975 current working language. Issue a warning if the setting does not
10976 match the language default. If any type mismatches occur in
10977 evaluating an expression while type checking is on, @value{GDBN} prints a
10978 message and aborts evaluation of the expression.
10980 @item set check type warn
10981 Cause the type checker to issue warnings, but to always attempt to
10982 evaluate the expression. Evaluating the expression may still
10983 be impossible for other reasons. For example, @value{GDBN} cannot add
10984 numbers and structures.
10987 Show the current setting of the type checker, and whether or not @value{GDBN}
10988 is setting it automatically.
10991 @cindex range checking
10992 @cindex checks, range
10993 @node Range Checking
10994 @subsection An Overview of Range Checking
10996 In some languages (such as Modula-2), it is an error to exceed the
10997 bounds of a type; this is enforced with run-time checks. Such range
10998 checking is meant to ensure program correctness by making sure
10999 computations do not overflow, or indices on an array element access do
11000 not exceed the bounds of the array.
11002 For expressions you use in @value{GDBN} commands, you can tell
11003 @value{GDBN} to treat range errors in one of three ways: ignore them,
11004 always treat them as errors and abandon the expression, or issue
11005 warnings but evaluate the expression anyway.
11007 A range error can result from numerical overflow, from exceeding an
11008 array index bound, or when you type a constant that is not a member
11009 of any type. Some languages, however, do not treat overflows as an
11010 error. In many implementations of C, mathematical overflow causes the
11011 result to ``wrap around'' to lower values---for example, if @var{m} is
11012 the largest integer value, and @var{s} is the smallest, then
11015 @var{m} + 1 @result{} @var{s}
11018 This, too, is specific to individual languages, and in some cases
11019 specific to individual compilers or machines. @xref{Supported Languages, ,
11020 Supported Languages}, for further details on specific languages.
11022 @value{GDBN} provides some additional commands for controlling the range checker:
11024 @kindex set check range
11025 @kindex show check range
11027 @item set check range auto
11028 Set range checking on or off based on the current working language.
11029 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11032 @item set check range on
11033 @itemx set check range off
11034 Set range checking on or off, overriding the default setting for the
11035 current working language. A warning is issued if the setting does not
11036 match the language default. If a range error occurs and range checking is on,
11037 then a message is printed and evaluation of the expression is aborted.
11039 @item set check range warn
11040 Output messages when the @value{GDBN} range checker detects a range error,
11041 but attempt to evaluate the expression anyway. Evaluating the
11042 expression may still be impossible for other reasons, such as accessing
11043 memory that the process does not own (a typical example from many Unix
11047 Show the current setting of the range checker, and whether or not it is
11048 being set automatically by @value{GDBN}.
11051 @node Supported Languages
11052 @section Supported Languages
11054 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
11055 assembly, Modula-2, and Ada.
11056 @c This is false ...
11057 Some @value{GDBN} features may be used in expressions regardless of the
11058 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11059 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11060 ,Expressions}) can be used with the constructs of any supported
11063 The following sections detail to what degree each source language is
11064 supported by @value{GDBN}. These sections are not meant to be language
11065 tutorials or references, but serve only as a reference guide to what the
11066 @value{GDBN} expression parser accepts, and what input and output
11067 formats should look like for different languages. There are many good
11068 books written on each of these languages; please look to these for a
11069 language reference or tutorial.
11072 * C:: C and C@t{++}
11073 * Objective-C:: Objective-C
11074 * Fortran:: Fortran
11076 * Modula-2:: Modula-2
11081 @subsection C and C@t{++}
11083 @cindex C and C@t{++}
11084 @cindex expressions in C or C@t{++}
11086 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11087 to both languages. Whenever this is the case, we discuss those languages
11091 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11092 @cindex @sc{gnu} C@t{++}
11093 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11094 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11095 effectively, you must compile your C@t{++} programs with a supported
11096 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11097 compiler (@code{aCC}).
11099 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11100 format; if it doesn't work on your system, try the stabs+ debugging
11101 format. You can select those formats explicitly with the @code{g++}
11102 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11103 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11104 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11107 * C Operators:: C and C@t{++} operators
11108 * C Constants:: C and C@t{++} constants
11109 * C Plus Plus Expressions:: C@t{++} expressions
11110 * C Defaults:: Default settings for C and C@t{++}
11111 * C Checks:: C and C@t{++} type and range checks
11112 * Debugging C:: @value{GDBN} and C
11113 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11114 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11118 @subsubsection C and C@t{++} Operators
11120 @cindex C and C@t{++} operators
11122 Operators must be defined on values of specific types. For instance,
11123 @code{+} is defined on numbers, but not on structures. Operators are
11124 often defined on groups of types.
11126 For the purposes of C and C@t{++}, the following definitions hold:
11131 @emph{Integral types} include @code{int} with any of its storage-class
11132 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11135 @emph{Floating-point types} include @code{float}, @code{double}, and
11136 @code{long double} (if supported by the target platform).
11139 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11142 @emph{Scalar types} include all of the above.
11147 The following operators are supported. They are listed here
11148 in order of increasing precedence:
11152 The comma or sequencing operator. Expressions in a comma-separated list
11153 are evaluated from left to right, with the result of the entire
11154 expression being the last expression evaluated.
11157 Assignment. The value of an assignment expression is the value
11158 assigned. Defined on scalar types.
11161 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11162 and translated to @w{@code{@var{a} = @var{a op b}}}.
11163 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11164 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11165 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11168 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11169 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11173 Logical @sc{or}. Defined on integral types.
11176 Logical @sc{and}. Defined on integral types.
11179 Bitwise @sc{or}. Defined on integral types.
11182 Bitwise exclusive-@sc{or}. Defined on integral types.
11185 Bitwise @sc{and}. Defined on integral types.
11188 Equality and inequality. Defined on scalar types. The value of these
11189 expressions is 0 for false and non-zero for true.
11191 @item <@r{, }>@r{, }<=@r{, }>=
11192 Less than, greater than, less than or equal, greater than or equal.
11193 Defined on scalar types. The value of these expressions is 0 for false
11194 and non-zero for true.
11197 left shift, and right shift. Defined on integral types.
11200 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11203 Addition and subtraction. Defined on integral types, floating-point types and
11206 @item *@r{, }/@r{, }%
11207 Multiplication, division, and modulus. Multiplication and division are
11208 defined on integral and floating-point types. Modulus is defined on
11212 Increment and decrement. When appearing before a variable, the
11213 operation is performed before the variable is used in an expression;
11214 when appearing after it, the variable's value is used before the
11215 operation takes place.
11218 Pointer dereferencing. Defined on pointer types. Same precedence as
11222 Address operator. Defined on variables. Same precedence as @code{++}.
11224 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11225 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11226 to examine the address
11227 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11231 Negative. Defined on integral and floating-point types. Same
11232 precedence as @code{++}.
11235 Logical negation. Defined on integral types. Same precedence as
11239 Bitwise complement operator. Defined on integral types. Same precedence as
11244 Structure member, and pointer-to-structure member. For convenience,
11245 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11246 pointer based on the stored type information.
11247 Defined on @code{struct} and @code{union} data.
11250 Dereferences of pointers to members.
11253 Array indexing. @code{@var{a}[@var{i}]} is defined as
11254 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11257 Function parameter list. Same precedence as @code{->}.
11260 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11261 and @code{class} types.
11264 Doubled colons also represent the @value{GDBN} scope operator
11265 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11269 If an operator is redefined in the user code, @value{GDBN} usually
11270 attempts to invoke the redefined version instead of using the operator's
11271 predefined meaning.
11274 @subsubsection C and C@t{++} Constants
11276 @cindex C and C@t{++} constants
11278 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11283 Integer constants are a sequence of digits. Octal constants are
11284 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11285 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11286 @samp{l}, specifying that the constant should be treated as a
11290 Floating point constants are a sequence of digits, followed by a decimal
11291 point, followed by a sequence of digits, and optionally followed by an
11292 exponent. An exponent is of the form:
11293 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11294 sequence of digits. The @samp{+} is optional for positive exponents.
11295 A floating-point constant may also end with a letter @samp{f} or
11296 @samp{F}, specifying that the constant should be treated as being of
11297 the @code{float} (as opposed to the default @code{double}) type; or with
11298 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11302 Enumerated constants consist of enumerated identifiers, or their
11303 integral equivalents.
11306 Character constants are a single character surrounded by single quotes
11307 (@code{'}), or a number---the ordinal value of the corresponding character
11308 (usually its @sc{ascii} value). Within quotes, the single character may
11309 be represented by a letter or by @dfn{escape sequences}, which are of
11310 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11311 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11312 @samp{@var{x}} is a predefined special character---for example,
11313 @samp{\n} for newline.
11316 String constants are a sequence of character constants surrounded by
11317 double quotes (@code{"}). Any valid character constant (as described
11318 above) may appear. Double quotes within the string must be preceded by
11319 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11323 Pointer constants are an integral value. You can also write pointers
11324 to constants using the C operator @samp{&}.
11327 Array constants are comma-separated lists surrounded by braces @samp{@{}
11328 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11329 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11330 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11333 @node C Plus Plus Expressions
11334 @subsubsection C@t{++} Expressions
11336 @cindex expressions in C@t{++}
11337 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11339 @cindex debugging C@t{++} programs
11340 @cindex C@t{++} compilers
11341 @cindex debug formats and C@t{++}
11342 @cindex @value{NGCC} and C@t{++}
11344 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11345 proper compiler and the proper debug format. Currently, @value{GDBN}
11346 works best when debugging C@t{++} code that is compiled with
11347 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11348 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11349 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11350 stabs+ as their default debug format, so you usually don't need to
11351 specify a debug format explicitly. Other compilers and/or debug formats
11352 are likely to work badly or not at all when using @value{GDBN} to debug
11358 @cindex member functions
11360 Member function calls are allowed; you can use expressions like
11363 count = aml->GetOriginal(x, y)
11366 @vindex this@r{, inside C@t{++} member functions}
11367 @cindex namespace in C@t{++}
11369 While a member function is active (in the selected stack frame), your
11370 expressions have the same namespace available as the member function;
11371 that is, @value{GDBN} allows implicit references to the class instance
11372 pointer @code{this} following the same rules as C@t{++}.
11374 @cindex call overloaded functions
11375 @cindex overloaded functions, calling
11376 @cindex type conversions in C@t{++}
11378 You can call overloaded functions; @value{GDBN} resolves the function
11379 call to the right definition, with some restrictions. @value{GDBN} does not
11380 perform overload resolution involving user-defined type conversions,
11381 calls to constructors, or instantiations of templates that do not exist
11382 in the program. It also cannot handle ellipsis argument lists or
11385 It does perform integral conversions and promotions, floating-point
11386 promotions, arithmetic conversions, pointer conversions, conversions of
11387 class objects to base classes, and standard conversions such as those of
11388 functions or arrays to pointers; it requires an exact match on the
11389 number of function arguments.
11391 Overload resolution is always performed, unless you have specified
11392 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11393 ,@value{GDBN} Features for C@t{++}}.
11395 You must specify @code{set overload-resolution off} in order to use an
11396 explicit function signature to call an overloaded function, as in
11398 p 'foo(char,int)'('x', 13)
11401 The @value{GDBN} command-completion facility can simplify this;
11402 see @ref{Completion, ,Command Completion}.
11404 @cindex reference declarations
11406 @value{GDBN} understands variables declared as C@t{++} references; you can use
11407 them in expressions just as you do in C@t{++} source---they are automatically
11410 In the parameter list shown when @value{GDBN} displays a frame, the values of
11411 reference variables are not displayed (unlike other variables); this
11412 avoids clutter, since references are often used for large structures.
11413 The @emph{address} of a reference variable is always shown, unless
11414 you have specified @samp{set print address off}.
11417 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11418 expressions can use it just as expressions in your program do. Since
11419 one scope may be defined in another, you can use @code{::} repeatedly if
11420 necessary, for example in an expression like
11421 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11422 resolving name scope by reference to source files, in both C and C@t{++}
11423 debugging (@pxref{Variables, ,Program Variables}).
11426 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11427 calling virtual functions correctly, printing out virtual bases of
11428 objects, calling functions in a base subobject, casting objects, and
11429 invoking user-defined operators.
11432 @subsubsection C and C@t{++} Defaults
11434 @cindex C and C@t{++} defaults
11436 If you allow @value{GDBN} to set type and range checking automatically, they
11437 both default to @code{off} whenever the working language changes to
11438 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11439 selects the working language.
11441 If you allow @value{GDBN} to set the language automatically, it
11442 recognizes source files whose names end with @file{.c}, @file{.C}, or
11443 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11444 these files, it sets the working language to C or C@t{++}.
11445 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11446 for further details.
11448 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11449 @c unimplemented. If (b) changes, it might make sense to let this node
11450 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11453 @subsubsection C and C@t{++} Type and Range Checks
11455 @cindex C and C@t{++} checks
11457 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11458 is not used. However, if you turn type checking on, @value{GDBN}
11459 considers two variables type equivalent if:
11463 The two variables are structured and have the same structure, union, or
11467 The two variables have the same type name, or types that have been
11468 declared equivalent through @code{typedef}.
11471 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11474 The two @code{struct}, @code{union}, or @code{enum} variables are
11475 declared in the same declaration. (Note: this may not be true for all C
11480 Range checking, if turned on, is done on mathematical operations. Array
11481 indices are not checked, since they are often used to index a pointer
11482 that is not itself an array.
11485 @subsubsection @value{GDBN} and C
11487 The @code{set print union} and @code{show print union} commands apply to
11488 the @code{union} type. When set to @samp{on}, any @code{union} that is
11489 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11490 appears as @samp{@{...@}}.
11492 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11493 with pointers and a memory allocation function. @xref{Expressions,
11496 @node Debugging C Plus Plus
11497 @subsubsection @value{GDBN} Features for C@t{++}
11499 @cindex commands for C@t{++}
11501 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11502 designed specifically for use with C@t{++}. Here is a summary:
11505 @cindex break in overloaded functions
11506 @item @r{breakpoint menus}
11507 When you want a breakpoint in a function whose name is overloaded,
11508 @value{GDBN} has the capability to display a menu of possible breakpoint
11509 locations to help you specify which function definition you want.
11510 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11512 @cindex overloading in C@t{++}
11513 @item rbreak @var{regex}
11514 Setting breakpoints using regular expressions is helpful for setting
11515 breakpoints on overloaded functions that are not members of any special
11517 @xref{Set Breaks, ,Setting Breakpoints}.
11519 @cindex C@t{++} exception handling
11522 Debug C@t{++} exception handling using these commands. @xref{Set
11523 Catchpoints, , Setting Catchpoints}.
11525 @cindex inheritance
11526 @item ptype @var{typename}
11527 Print inheritance relationships as well as other information for type
11529 @xref{Symbols, ,Examining the Symbol Table}.
11531 @cindex C@t{++} symbol display
11532 @item set print demangle
11533 @itemx show print demangle
11534 @itemx set print asm-demangle
11535 @itemx show print asm-demangle
11536 Control whether C@t{++} symbols display in their source form, both when
11537 displaying code as C@t{++} source and when displaying disassemblies.
11538 @xref{Print Settings, ,Print Settings}.
11540 @item set print object
11541 @itemx show print object
11542 Choose whether to print derived (actual) or declared types of objects.
11543 @xref{Print Settings, ,Print Settings}.
11545 @item set print vtbl
11546 @itemx show print vtbl
11547 Control the format for printing virtual function tables.
11548 @xref{Print Settings, ,Print Settings}.
11549 (The @code{vtbl} commands do not work on programs compiled with the HP
11550 ANSI C@t{++} compiler (@code{aCC}).)
11552 @kindex set overload-resolution
11553 @cindex overloaded functions, overload resolution
11554 @item set overload-resolution on
11555 Enable overload resolution for C@t{++} expression evaluation. The default
11556 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11557 and searches for a function whose signature matches the argument types,
11558 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11559 Expressions, ,C@t{++} Expressions}, for details).
11560 If it cannot find a match, it emits a message.
11562 @item set overload-resolution off
11563 Disable overload resolution for C@t{++} expression evaluation. For
11564 overloaded functions that are not class member functions, @value{GDBN}
11565 chooses the first function of the specified name that it finds in the
11566 symbol table, whether or not its arguments are of the correct type. For
11567 overloaded functions that are class member functions, @value{GDBN}
11568 searches for a function whose signature @emph{exactly} matches the
11571 @kindex show overload-resolution
11572 @item show overload-resolution
11573 Show the current setting of overload resolution.
11575 @item @r{Overloaded symbol names}
11576 You can specify a particular definition of an overloaded symbol, using
11577 the same notation that is used to declare such symbols in C@t{++}: type
11578 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11579 also use the @value{GDBN} command-line word completion facilities to list the
11580 available choices, or to finish the type list for you.
11581 @xref{Completion,, Command Completion}, for details on how to do this.
11584 @node Decimal Floating Point
11585 @subsubsection Decimal Floating Point format
11586 @cindex decimal floating point format
11588 @value{GDBN} can examine, set and perform computations with numbers in
11589 decimal floating point format, which in the C language correspond to the
11590 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11591 specified by the extension to support decimal floating-point arithmetic.
11593 There are two encodings in use, depending on the architecture: BID (Binary
11594 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11595 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11598 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11599 to manipulate decimal floating point numbers, it is not possible to convert
11600 (using a cast, for example) integers wider than 32-bit to decimal float.
11602 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11603 point computations, error checking in decimal float operations ignores
11604 underflow, overflow and divide by zero exceptions.
11606 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11607 to inspect @code{_Decimal128} values stored in floating point registers.
11608 See @ref{PowerPC,,PowerPC} for more details.
11611 @subsection Objective-C
11613 @cindex Objective-C
11614 This section provides information about some commands and command
11615 options that are useful for debugging Objective-C code. See also
11616 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11617 few more commands specific to Objective-C support.
11620 * Method Names in Commands::
11621 * The Print Command with Objective-C::
11624 @node Method Names in Commands
11625 @subsubsection Method Names in Commands
11627 The following commands have been extended to accept Objective-C method
11628 names as line specifications:
11630 @kindex clear@r{, and Objective-C}
11631 @kindex break@r{, and Objective-C}
11632 @kindex info line@r{, and Objective-C}
11633 @kindex jump@r{, and Objective-C}
11634 @kindex list@r{, and Objective-C}
11638 @item @code{info line}
11643 A fully qualified Objective-C method name is specified as
11646 -[@var{Class} @var{methodName}]
11649 where the minus sign is used to indicate an instance method and a
11650 plus sign (not shown) is used to indicate a class method. The class
11651 name @var{Class} and method name @var{methodName} are enclosed in
11652 brackets, similar to the way messages are specified in Objective-C
11653 source code. For example, to set a breakpoint at the @code{create}
11654 instance method of class @code{Fruit} in the program currently being
11658 break -[Fruit create]
11661 To list ten program lines around the @code{initialize} class method,
11665 list +[NSText initialize]
11668 In the current version of @value{GDBN}, the plus or minus sign is
11669 required. In future versions of @value{GDBN}, the plus or minus
11670 sign will be optional, but you can use it to narrow the search. It
11671 is also possible to specify just a method name:
11677 You must specify the complete method name, including any colons. If
11678 your program's source files contain more than one @code{create} method,
11679 you'll be presented with a numbered list of classes that implement that
11680 method. Indicate your choice by number, or type @samp{0} to exit if
11683 As another example, to clear a breakpoint established at the
11684 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11687 clear -[NSWindow makeKeyAndOrderFront:]
11690 @node The Print Command with Objective-C
11691 @subsubsection The Print Command With Objective-C
11692 @cindex Objective-C, print objects
11693 @kindex print-object
11694 @kindex po @r{(@code{print-object})}
11696 The print command has also been extended to accept methods. For example:
11699 print -[@var{object} hash]
11702 @cindex print an Objective-C object description
11703 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11705 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11706 and print the result. Also, an additional command has been added,
11707 @code{print-object} or @code{po} for short, which is meant to print
11708 the description of an object. However, this command may only work
11709 with certain Objective-C libraries that have a particular hook
11710 function, @code{_NSPrintForDebugger}, defined.
11713 @subsection Fortran
11714 @cindex Fortran-specific support in @value{GDBN}
11716 @value{GDBN} can be used to debug programs written in Fortran, but it
11717 currently supports only the features of Fortran 77 language.
11719 @cindex trailing underscore, in Fortran symbols
11720 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11721 among them) append an underscore to the names of variables and
11722 functions. When you debug programs compiled by those compilers, you
11723 will need to refer to variables and functions with a trailing
11727 * Fortran Operators:: Fortran operators and expressions
11728 * Fortran Defaults:: Default settings for Fortran
11729 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11732 @node Fortran Operators
11733 @subsubsection Fortran Operators and Expressions
11735 @cindex Fortran operators and expressions
11737 Operators must be defined on values of specific types. For instance,
11738 @code{+} is defined on numbers, but not on characters or other non-
11739 arithmetic types. Operators are often defined on groups of types.
11743 The exponentiation operator. It raises the first operand to the power
11747 The range operator. Normally used in the form of array(low:high) to
11748 represent a section of array.
11751 The access component operator. Normally used to access elements in derived
11752 types. Also suitable for unions. As unions aren't part of regular Fortran,
11753 this can only happen when accessing a register that uses a gdbarch-defined
11757 @node Fortran Defaults
11758 @subsubsection Fortran Defaults
11760 @cindex Fortran Defaults
11762 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11763 default uses case-insensitive matches for Fortran symbols. You can
11764 change that with the @samp{set case-insensitive} command, see
11765 @ref{Symbols}, for the details.
11767 @node Special Fortran Commands
11768 @subsubsection Special Fortran Commands
11770 @cindex Special Fortran commands
11772 @value{GDBN} has some commands to support Fortran-specific features,
11773 such as displaying common blocks.
11776 @cindex @code{COMMON} blocks, Fortran
11777 @kindex info common
11778 @item info common @r{[}@var{common-name}@r{]}
11779 This command prints the values contained in the Fortran @code{COMMON}
11780 block whose name is @var{common-name}. With no argument, the names of
11781 all @code{COMMON} blocks visible at the current program location are
11788 @cindex Pascal support in @value{GDBN}, limitations
11789 Debugging Pascal programs which use sets, subranges, file variables, or
11790 nested functions does not currently work. @value{GDBN} does not support
11791 entering expressions, printing values, or similar features using Pascal
11794 The Pascal-specific command @code{set print pascal_static-members}
11795 controls whether static members of Pascal objects are displayed.
11796 @xref{Print Settings, pascal_static-members}.
11799 @subsection Modula-2
11801 @cindex Modula-2, @value{GDBN} support
11803 The extensions made to @value{GDBN} to support Modula-2 only support
11804 output from the @sc{gnu} Modula-2 compiler (which is currently being
11805 developed). Other Modula-2 compilers are not currently supported, and
11806 attempting to debug executables produced by them is most likely
11807 to give an error as @value{GDBN} reads in the executable's symbol
11810 @cindex expressions in Modula-2
11812 * M2 Operators:: Built-in operators
11813 * Built-In Func/Proc:: Built-in functions and procedures
11814 * M2 Constants:: Modula-2 constants
11815 * M2 Types:: Modula-2 types
11816 * M2 Defaults:: Default settings for Modula-2
11817 * Deviations:: Deviations from standard Modula-2
11818 * M2 Checks:: Modula-2 type and range checks
11819 * M2 Scope:: The scope operators @code{::} and @code{.}
11820 * GDB/M2:: @value{GDBN} and Modula-2
11824 @subsubsection Operators
11825 @cindex Modula-2 operators
11827 Operators must be defined on values of specific types. For instance,
11828 @code{+} is defined on numbers, but not on structures. Operators are
11829 often defined on groups of types. For the purposes of Modula-2, the
11830 following definitions hold:
11835 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
11839 @emph{Character types} consist of @code{CHAR} and its subranges.
11842 @emph{Floating-point types} consist of @code{REAL}.
11845 @emph{Pointer types} consist of anything declared as @code{POINTER TO
11849 @emph{Scalar types} consist of all of the above.
11852 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
11855 @emph{Boolean types} consist of @code{BOOLEAN}.
11859 The following operators are supported, and appear in order of
11860 increasing precedence:
11864 Function argument or array index separator.
11867 Assignment. The value of @var{var} @code{:=} @var{value} is
11871 Less than, greater than on integral, floating-point, or enumerated
11875 Less than or equal to, greater than or equal to
11876 on integral, floating-point and enumerated types, or set inclusion on
11877 set types. Same precedence as @code{<}.
11879 @item =@r{, }<>@r{, }#
11880 Equality and two ways of expressing inequality, valid on scalar types.
11881 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
11882 available for inequality, since @code{#} conflicts with the script
11886 Set membership. Defined on set types and the types of their members.
11887 Same precedence as @code{<}.
11890 Boolean disjunction. Defined on boolean types.
11893 Boolean conjunction. Defined on boolean types.
11896 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11899 Addition and subtraction on integral and floating-point types, or union
11900 and difference on set types.
11903 Multiplication on integral and floating-point types, or set intersection
11907 Division on floating-point types, or symmetric set difference on set
11908 types. Same precedence as @code{*}.
11911 Integer division and remainder. Defined on integral types. Same
11912 precedence as @code{*}.
11915 Negative. Defined on @code{INTEGER} and @code{REAL} data.
11918 Pointer dereferencing. Defined on pointer types.
11921 Boolean negation. Defined on boolean types. Same precedence as
11925 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
11926 precedence as @code{^}.
11929 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
11932 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
11936 @value{GDBN} and Modula-2 scope operators.
11940 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
11941 treats the use of the operator @code{IN}, or the use of operators
11942 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
11943 @code{<=}, and @code{>=} on sets as an error.
11947 @node Built-In Func/Proc
11948 @subsubsection Built-in Functions and Procedures
11949 @cindex Modula-2 built-ins
11951 Modula-2 also makes available several built-in procedures and functions.
11952 In describing these, the following metavariables are used:
11957 represents an @code{ARRAY} variable.
11960 represents a @code{CHAR} constant or variable.
11963 represents a variable or constant of integral type.
11966 represents an identifier that belongs to a set. Generally used in the
11967 same function with the metavariable @var{s}. The type of @var{s} should
11968 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
11971 represents a variable or constant of integral or floating-point type.
11974 represents a variable or constant of floating-point type.
11980 represents a variable.
11983 represents a variable or constant of one of many types. See the
11984 explanation of the function for details.
11987 All Modula-2 built-in procedures also return a result, described below.
11991 Returns the absolute value of @var{n}.
11994 If @var{c} is a lower case letter, it returns its upper case
11995 equivalent, otherwise it returns its argument.
11998 Returns the character whose ordinal value is @var{i}.
12001 Decrements the value in the variable @var{v} by one. Returns the new value.
12003 @item DEC(@var{v},@var{i})
12004 Decrements the value in the variable @var{v} by @var{i}. Returns the
12007 @item EXCL(@var{m},@var{s})
12008 Removes the element @var{m} from the set @var{s}. Returns the new
12011 @item FLOAT(@var{i})
12012 Returns the floating point equivalent of the integer @var{i}.
12014 @item HIGH(@var{a})
12015 Returns the index of the last member of @var{a}.
12018 Increments the value in the variable @var{v} by one. Returns the new value.
12020 @item INC(@var{v},@var{i})
12021 Increments the value in the variable @var{v} by @var{i}. Returns the
12024 @item INCL(@var{m},@var{s})
12025 Adds the element @var{m} to the set @var{s} if it is not already
12026 there. Returns the new set.
12029 Returns the maximum value of the type @var{t}.
12032 Returns the minimum value of the type @var{t}.
12035 Returns boolean TRUE if @var{i} is an odd number.
12038 Returns the ordinal value of its argument. For example, the ordinal
12039 value of a character is its @sc{ascii} value (on machines supporting the
12040 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12041 integral, character and enumerated types.
12043 @item SIZE(@var{x})
12044 Returns the size of its argument. @var{x} can be a variable or a type.
12046 @item TRUNC(@var{r})
12047 Returns the integral part of @var{r}.
12049 @item TSIZE(@var{x})
12050 Returns the size of its argument. @var{x} can be a variable or a type.
12052 @item VAL(@var{t},@var{i})
12053 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12057 @emph{Warning:} Sets and their operations are not yet supported, so
12058 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12062 @cindex Modula-2 constants
12064 @subsubsection Constants
12066 @value{GDBN} allows you to express the constants of Modula-2 in the following
12072 Integer constants are simply a sequence of digits. When used in an
12073 expression, a constant is interpreted to be type-compatible with the
12074 rest of the expression. Hexadecimal integers are specified by a
12075 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12078 Floating point constants appear as a sequence of digits, followed by a
12079 decimal point and another sequence of digits. An optional exponent can
12080 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12081 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12082 digits of the floating point constant must be valid decimal (base 10)
12086 Character constants consist of a single character enclosed by a pair of
12087 like quotes, either single (@code{'}) or double (@code{"}). They may
12088 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12089 followed by a @samp{C}.
12092 String constants consist of a sequence of characters enclosed by a
12093 pair of like quotes, either single (@code{'}) or double (@code{"}).
12094 Escape sequences in the style of C are also allowed. @xref{C
12095 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12099 Enumerated constants consist of an enumerated identifier.
12102 Boolean constants consist of the identifiers @code{TRUE} and
12106 Pointer constants consist of integral values only.
12109 Set constants are not yet supported.
12113 @subsubsection Modula-2 Types
12114 @cindex Modula-2 types
12116 Currently @value{GDBN} can print the following data types in Modula-2
12117 syntax: array types, record types, set types, pointer types, procedure
12118 types, enumerated types, subrange types and base types. You can also
12119 print the contents of variables declared using these type.
12120 This section gives a number of simple source code examples together with
12121 sample @value{GDBN} sessions.
12123 The first example contains the following section of code:
12132 and you can request @value{GDBN} to interrogate the type and value of
12133 @code{r} and @code{s}.
12136 (@value{GDBP}) print s
12138 (@value{GDBP}) ptype s
12140 (@value{GDBP}) print r
12142 (@value{GDBP}) ptype r
12147 Likewise if your source code declares @code{s} as:
12151 s: SET ['A'..'Z'] ;
12155 then you may query the type of @code{s} by:
12158 (@value{GDBP}) ptype s
12159 type = SET ['A'..'Z']
12163 Note that at present you cannot interactively manipulate set
12164 expressions using the debugger.
12166 The following example shows how you might declare an array in Modula-2
12167 and how you can interact with @value{GDBN} to print its type and contents:
12171 s: ARRAY [-10..10] OF CHAR ;
12175 (@value{GDBP}) ptype s
12176 ARRAY [-10..10] OF CHAR
12179 Note that the array handling is not yet complete and although the type
12180 is printed correctly, expression handling still assumes that all
12181 arrays have a lower bound of zero and not @code{-10} as in the example
12184 Here are some more type related Modula-2 examples:
12188 colour = (blue, red, yellow, green) ;
12189 t = [blue..yellow] ;
12197 The @value{GDBN} interaction shows how you can query the data type
12198 and value of a variable.
12201 (@value{GDBP}) print s
12203 (@value{GDBP}) ptype t
12204 type = [blue..yellow]
12208 In this example a Modula-2 array is declared and its contents
12209 displayed. Observe that the contents are written in the same way as
12210 their @code{C} counterparts.
12214 s: ARRAY [1..5] OF CARDINAL ;
12220 (@value{GDBP}) print s
12221 $1 = @{1, 0, 0, 0, 0@}
12222 (@value{GDBP}) ptype s
12223 type = ARRAY [1..5] OF CARDINAL
12226 The Modula-2 language interface to @value{GDBN} also understands
12227 pointer types as shown in this example:
12231 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12238 and you can request that @value{GDBN} describes the type of @code{s}.
12241 (@value{GDBP}) ptype s
12242 type = POINTER TO ARRAY [1..5] OF CARDINAL
12245 @value{GDBN} handles compound types as we can see in this example.
12246 Here we combine array types, record types, pointer types and subrange
12257 myarray = ARRAY myrange OF CARDINAL ;
12258 myrange = [-2..2] ;
12260 s: POINTER TO ARRAY myrange OF foo ;
12264 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12268 (@value{GDBP}) ptype s
12269 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12272 f3 : ARRAY [-2..2] OF CARDINAL;
12277 @subsubsection Modula-2 Defaults
12278 @cindex Modula-2 defaults
12280 If type and range checking are set automatically by @value{GDBN}, they
12281 both default to @code{on} whenever the working language changes to
12282 Modula-2. This happens regardless of whether you or @value{GDBN}
12283 selected the working language.
12285 If you allow @value{GDBN} to set the language automatically, then entering
12286 code compiled from a file whose name ends with @file{.mod} sets the
12287 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12288 Infer the Source Language}, for further details.
12291 @subsubsection Deviations from Standard Modula-2
12292 @cindex Modula-2, deviations from
12294 A few changes have been made to make Modula-2 programs easier to debug.
12295 This is done primarily via loosening its type strictness:
12299 Unlike in standard Modula-2, pointer constants can be formed by
12300 integers. This allows you to modify pointer variables during
12301 debugging. (In standard Modula-2, the actual address contained in a
12302 pointer variable is hidden from you; it can only be modified
12303 through direct assignment to another pointer variable or expression that
12304 returned a pointer.)
12307 C escape sequences can be used in strings and characters to represent
12308 non-printable characters. @value{GDBN} prints out strings with these
12309 escape sequences embedded. Single non-printable characters are
12310 printed using the @samp{CHR(@var{nnn})} format.
12313 The assignment operator (@code{:=}) returns the value of its right-hand
12317 All built-in procedures both modify @emph{and} return their argument.
12321 @subsubsection Modula-2 Type and Range Checks
12322 @cindex Modula-2 checks
12325 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12328 @c FIXME remove warning when type/range checks added
12330 @value{GDBN} considers two Modula-2 variables type equivalent if:
12334 They are of types that have been declared equivalent via a @code{TYPE
12335 @var{t1} = @var{t2}} statement
12338 They have been declared on the same line. (Note: This is true of the
12339 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12342 As long as type checking is enabled, any attempt to combine variables
12343 whose types are not equivalent is an error.
12345 Range checking is done on all mathematical operations, assignment, array
12346 index bounds, and all built-in functions and procedures.
12349 @subsubsection The Scope Operators @code{::} and @code{.}
12351 @cindex @code{.}, Modula-2 scope operator
12352 @cindex colon, doubled as scope operator
12354 @vindex colon-colon@r{, in Modula-2}
12355 @c Info cannot handle :: but TeX can.
12358 @vindex ::@r{, in Modula-2}
12361 There are a few subtle differences between the Modula-2 scope operator
12362 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12367 @var{module} . @var{id}
12368 @var{scope} :: @var{id}
12372 where @var{scope} is the name of a module or a procedure,
12373 @var{module} the name of a module, and @var{id} is any declared
12374 identifier within your program, except another module.
12376 Using the @code{::} operator makes @value{GDBN} search the scope
12377 specified by @var{scope} for the identifier @var{id}. If it is not
12378 found in the specified scope, then @value{GDBN} searches all scopes
12379 enclosing the one specified by @var{scope}.
12381 Using the @code{.} operator makes @value{GDBN} search the current scope for
12382 the identifier specified by @var{id} that was imported from the
12383 definition module specified by @var{module}. With this operator, it is
12384 an error if the identifier @var{id} was not imported from definition
12385 module @var{module}, or if @var{id} is not an identifier in
12389 @subsubsection @value{GDBN} and Modula-2
12391 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12392 Five subcommands of @code{set print} and @code{show print} apply
12393 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12394 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12395 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12396 analogue in Modula-2.
12398 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12399 with any language, is not useful with Modula-2. Its
12400 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12401 created in Modula-2 as they can in C or C@t{++}. However, because an
12402 address can be specified by an integral constant, the construct
12403 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12405 @cindex @code{#} in Modula-2
12406 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12407 interpreted as the beginning of a comment. Use @code{<>} instead.
12413 The extensions made to @value{GDBN} for Ada only support
12414 output from the @sc{gnu} Ada (GNAT) compiler.
12415 Other Ada compilers are not currently supported, and
12416 attempting to debug executables produced by them is most likely
12420 @cindex expressions in Ada
12422 * Ada Mode Intro:: General remarks on the Ada syntax
12423 and semantics supported by Ada mode
12425 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12426 * Additions to Ada:: Extensions of the Ada expression syntax.
12427 * Stopping Before Main Program:: Debugging the program during elaboration.
12428 * Ada Tasks:: Listing and setting breakpoints in tasks.
12429 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12430 * Ada Glitches:: Known peculiarities of Ada mode.
12433 @node Ada Mode Intro
12434 @subsubsection Introduction
12435 @cindex Ada mode, general
12437 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12438 syntax, with some extensions.
12439 The philosophy behind the design of this subset is
12443 That @value{GDBN} should provide basic literals and access to operations for
12444 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12445 leaving more sophisticated computations to subprograms written into the
12446 program (which therefore may be called from @value{GDBN}).
12449 That type safety and strict adherence to Ada language restrictions
12450 are not particularly important to the @value{GDBN} user.
12453 That brevity is important to the @value{GDBN} user.
12456 Thus, for brevity, the debugger acts as if all names declared in
12457 user-written packages are directly visible, even if they are not visible
12458 according to Ada rules, thus making it unnecessary to fully qualify most
12459 names with their packages, regardless of context. Where this causes
12460 ambiguity, @value{GDBN} asks the user's intent.
12462 The debugger will start in Ada mode if it detects an Ada main program.
12463 As for other languages, it will enter Ada mode when stopped in a program that
12464 was translated from an Ada source file.
12466 While in Ada mode, you may use `@t{--}' for comments. This is useful
12467 mostly for documenting command files. The standard @value{GDBN} comment
12468 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12469 middle (to allow based literals).
12471 The debugger supports limited overloading. Given a subprogram call in which
12472 the function symbol has multiple definitions, it will use the number of
12473 actual parameters and some information about their types to attempt to narrow
12474 the set of definitions. It also makes very limited use of context, preferring
12475 procedures to functions in the context of the @code{call} command, and
12476 functions to procedures elsewhere.
12478 @node Omissions from Ada
12479 @subsubsection Omissions from Ada
12480 @cindex Ada, omissions from
12482 Here are the notable omissions from the subset:
12486 Only a subset of the attributes are supported:
12490 @t{'First}, @t{'Last}, and @t{'Length}
12491 on array objects (not on types and subtypes).
12494 @t{'Min} and @t{'Max}.
12497 @t{'Pos} and @t{'Val}.
12503 @t{'Range} on array objects (not subtypes), but only as the right
12504 operand of the membership (@code{in}) operator.
12507 @t{'Access}, @t{'Unchecked_Access}, and
12508 @t{'Unrestricted_Access} (a GNAT extension).
12516 @code{Characters.Latin_1} are not available and
12517 concatenation is not implemented. Thus, escape characters in strings are
12518 not currently available.
12521 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12522 equality of representations. They will generally work correctly
12523 for strings and arrays whose elements have integer or enumeration types.
12524 They may not work correctly for arrays whose element
12525 types have user-defined equality, for arrays of real values
12526 (in particular, IEEE-conformant floating point, because of negative
12527 zeroes and NaNs), and for arrays whose elements contain unused bits with
12528 indeterminate values.
12531 The other component-by-component array operations (@code{and}, @code{or},
12532 @code{xor}, @code{not}, and relational tests other than equality)
12533 are not implemented.
12536 @cindex array aggregates (Ada)
12537 @cindex record aggregates (Ada)
12538 @cindex aggregates (Ada)
12539 There is limited support for array and record aggregates. They are
12540 permitted only on the right sides of assignments, as in these examples:
12543 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12544 (@value{GDBP}) set An_Array := (1, others => 0)
12545 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12546 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12547 (@value{GDBP}) set A_Record := (1, "Peter", True);
12548 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12552 discriminant's value by assigning an aggregate has an
12553 undefined effect if that discriminant is used within the record.
12554 However, you can first modify discriminants by directly assigning to
12555 them (which normally would not be allowed in Ada), and then performing an
12556 aggregate assignment. For example, given a variable @code{A_Rec}
12557 declared to have a type such as:
12560 type Rec (Len : Small_Integer := 0) is record
12562 Vals : IntArray (1 .. Len);
12566 you can assign a value with a different size of @code{Vals} with two
12570 (@value{GDBP}) set A_Rec.Len := 4
12571 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12574 As this example also illustrates, @value{GDBN} is very loose about the usual
12575 rules concerning aggregates. You may leave out some of the
12576 components of an array or record aggregate (such as the @code{Len}
12577 component in the assignment to @code{A_Rec} above); they will retain their
12578 original values upon assignment. You may freely use dynamic values as
12579 indices in component associations. You may even use overlapping or
12580 redundant component associations, although which component values are
12581 assigned in such cases is not defined.
12584 Calls to dispatching subprograms are not implemented.
12587 The overloading algorithm is much more limited (i.e., less selective)
12588 than that of real Ada. It makes only limited use of the context in
12589 which a subexpression appears to resolve its meaning, and it is much
12590 looser in its rules for allowing type matches. As a result, some
12591 function calls will be ambiguous, and the user will be asked to choose
12592 the proper resolution.
12595 The @code{new} operator is not implemented.
12598 Entry calls are not implemented.
12601 Aside from printing, arithmetic operations on the native VAX floating-point
12602 formats are not supported.
12605 It is not possible to slice a packed array.
12608 The names @code{True} and @code{False}, when not part of a qualified name,
12609 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12611 Should your program
12612 redefine these names in a package or procedure (at best a dubious practice),
12613 you will have to use fully qualified names to access their new definitions.
12616 @node Additions to Ada
12617 @subsubsection Additions to Ada
12618 @cindex Ada, deviations from
12620 As it does for other languages, @value{GDBN} makes certain generic
12621 extensions to Ada (@pxref{Expressions}):
12625 If the expression @var{E} is a variable residing in memory (typically
12626 a local variable or array element) and @var{N} is a positive integer,
12627 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12628 @var{N}-1 adjacent variables following it in memory as an array. In
12629 Ada, this operator is generally not necessary, since its prime use is
12630 in displaying parts of an array, and slicing will usually do this in
12631 Ada. However, there are occasional uses when debugging programs in
12632 which certain debugging information has been optimized away.
12635 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12636 appears in function or file @var{B}.'' When @var{B} is a file name,
12637 you must typically surround it in single quotes.
12640 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12641 @var{type} that appears at address @var{addr}.''
12644 A name starting with @samp{$} is a convenience variable
12645 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12648 In addition, @value{GDBN} provides a few other shortcuts and outright
12649 additions specific to Ada:
12653 The assignment statement is allowed as an expression, returning
12654 its right-hand operand as its value. Thus, you may enter
12657 (@value{GDBP}) set x := y + 3
12658 (@value{GDBP}) print A(tmp := y + 1)
12662 The semicolon is allowed as an ``operator,'' returning as its value
12663 the value of its right-hand operand.
12664 This allows, for example,
12665 complex conditional breaks:
12668 (@value{GDBP}) break f
12669 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12673 Rather than use catenation and symbolic character names to introduce special
12674 characters into strings, one may instead use a special bracket notation,
12675 which is also used to print strings. A sequence of characters of the form
12676 @samp{["@var{XX}"]} within a string or character literal denotes the
12677 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12678 sequence of characters @samp{["""]} also denotes a single quotation mark
12679 in strings. For example,
12681 "One line.["0a"]Next line.["0a"]"
12684 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12688 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12689 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12693 (@value{GDBP}) print 'max(x, y)
12697 When printing arrays, @value{GDBN} uses positional notation when the
12698 array has a lower bound of 1, and uses a modified named notation otherwise.
12699 For example, a one-dimensional array of three integers with a lower bound
12700 of 3 might print as
12707 That is, in contrast to valid Ada, only the first component has a @code{=>}
12711 You may abbreviate attributes in expressions with any unique,
12712 multi-character subsequence of
12713 their names (an exact match gets preference).
12714 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12715 in place of @t{a'length}.
12718 @cindex quoting Ada internal identifiers
12719 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12720 to lower case. The GNAT compiler uses upper-case characters for
12721 some of its internal identifiers, which are normally of no interest to users.
12722 For the rare occasions when you actually have to look at them,
12723 enclose them in angle brackets to avoid the lower-case mapping.
12726 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12730 Printing an object of class-wide type or dereferencing an
12731 access-to-class-wide value will display all the components of the object's
12732 specific type (as indicated by its run-time tag). Likewise, component
12733 selection on such a value will operate on the specific type of the
12738 @node Stopping Before Main Program
12739 @subsubsection Stopping at the Very Beginning
12741 @cindex breakpointing Ada elaboration code
12742 It is sometimes necessary to debug the program during elaboration, and
12743 before reaching the main procedure.
12744 As defined in the Ada Reference
12745 Manual, the elaboration code is invoked from a procedure called
12746 @code{adainit}. To run your program up to the beginning of
12747 elaboration, simply use the following two commands:
12748 @code{tbreak adainit} and @code{run}.
12751 @subsubsection Extensions for Ada Tasks
12752 @cindex Ada, tasking
12754 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12755 @value{GDBN} provides the following task-related commands:
12760 This command shows a list of current Ada tasks, as in the following example:
12767 (@value{GDBP}) info tasks
12768 ID TID P-ID Pri State Name
12769 1 8088000 0 15 Child Activation Wait main_task
12770 2 80a4000 1 15 Accept Statement b
12771 3 809a800 1 15 Child Activation Wait a
12772 * 4 80ae800 3 15 Runnable c
12777 In this listing, the asterisk before the last task indicates it to be the
12778 task currently being inspected.
12782 Represents @value{GDBN}'s internal task number.
12788 The parent's task ID (@value{GDBN}'s internal task number).
12791 The base priority of the task.
12794 Current state of the task.
12798 The task has been created but has not been activated. It cannot be
12802 The task is not blocked for any reason known to Ada. (It may be waiting
12803 for a mutex, though.) It is conceptually "executing" in normal mode.
12806 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12807 that were waiting on terminate alternatives have been awakened and have
12808 terminated themselves.
12810 @item Child Activation Wait
12811 The task is waiting for created tasks to complete activation.
12813 @item Accept Statement
12814 The task is waiting on an accept or selective wait statement.
12816 @item Waiting on entry call
12817 The task is waiting on an entry call.
12819 @item Async Select Wait
12820 The task is waiting to start the abortable part of an asynchronous
12824 The task is waiting on a select statement with only a delay
12827 @item Child Termination Wait
12828 The task is sleeping having completed a master within itself, and is
12829 waiting for the tasks dependent on that master to become terminated or
12830 waiting on a terminate Phase.
12832 @item Wait Child in Term Alt
12833 The task is sleeping waiting for tasks on terminate alternatives to
12834 finish terminating.
12836 @item Accepting RV with @var{taskno}
12837 The task is accepting a rendez-vous with the task @var{taskno}.
12841 Name of the task in the program.
12845 @kindex info task @var{taskno}
12846 @item info task @var{taskno}
12847 This command shows detailled informations on the specified task, as in
12848 the following example:
12853 (@value{GDBP}) info tasks
12854 ID TID P-ID Pri State Name
12855 1 8077880 0 15 Child Activation Wait main_task
12856 * 2 807c468 1 15 Runnable task_1
12857 (@value{GDBP}) info task 2
12858 Ada Task: 0x807c468
12861 Parent: 1 (main_task)
12867 @kindex task@r{ (Ada)}
12868 @cindex current Ada task ID
12869 This command prints the ID of the current task.
12875 (@value{GDBP}) info tasks
12876 ID TID P-ID Pri State Name
12877 1 8077870 0 15 Child Activation Wait main_task
12878 * 2 807c458 1 15 Runnable t
12879 (@value{GDBP}) task
12880 [Current task is 2]
12883 @item task @var{taskno}
12884 @cindex Ada task switching
12885 This command is like the @code{thread @var{threadno}}
12886 command (@pxref{Threads}). It switches the context of debugging
12887 from the current task to the given task.
12893 (@value{GDBP}) info tasks
12894 ID TID P-ID Pri State Name
12895 1 8077870 0 15 Child Activation Wait main_task
12896 * 2 807c458 1 15 Runnable t
12897 (@value{GDBP}) task 1
12898 [Switching to task 1]
12899 #0 0x8067726 in pthread_cond_wait ()
12901 #0 0x8067726 in pthread_cond_wait ()
12902 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
12903 #2 0x805cb63 in system.task_primitives.operations.sleep ()
12904 #3 0x806153e in system.tasking.stages.activate_tasks ()
12905 #4 0x804aacc in un () at un.adb:5
12908 @item break @var{linespec} task @var{taskno}
12909 @itemx break @var{linespec} task @var{taskno} if @dots{}
12910 @cindex breakpoints and tasks, in Ada
12911 @cindex task breakpoints, in Ada
12912 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
12913 These commands are like the @code{break @dots{} thread @dots{}}
12914 command (@pxref{Thread Stops}).
12915 @var{linespec} specifies source lines, as described
12916 in @ref{Specify Location}.
12918 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
12919 to specify that you only want @value{GDBN} to stop the program when a
12920 particular Ada task reaches this breakpoint. @var{taskno} is one of the
12921 numeric task identifiers assigned by @value{GDBN}, shown in the first
12922 column of the @samp{info tasks} display.
12924 If you do not specify @samp{task @var{taskno}} when you set a
12925 breakpoint, the breakpoint applies to @emph{all} tasks of your
12928 You can use the @code{task} qualifier on conditional breakpoints as
12929 well; in this case, place @samp{task @var{taskno}} before the
12930 breakpoint condition (before the @code{if}).
12938 (@value{GDBP}) info tasks
12939 ID TID P-ID Pri State Name
12940 1 140022020 0 15 Child Activation Wait main_task
12941 2 140045060 1 15 Accept/Select Wait t2
12942 3 140044840 1 15 Runnable t1
12943 * 4 140056040 1 15 Runnable t3
12944 (@value{GDBP}) b 15 task 2
12945 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
12946 (@value{GDBP}) cont
12951 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
12953 (@value{GDBP}) info tasks
12954 ID TID P-ID Pri State Name
12955 1 140022020 0 15 Child Activation Wait main_task
12956 * 2 140045060 1 15 Runnable t2
12957 3 140044840 1 15 Runnable t1
12958 4 140056040 1 15 Delay Sleep t3
12962 @node Ada Tasks and Core Files
12963 @subsubsection Tasking Support when Debugging Core Files
12964 @cindex Ada tasking and core file debugging
12966 When inspecting a core file, as opposed to debugging a live program,
12967 tasking support may be limited or even unavailable, depending on
12968 the platform being used.
12969 For instance, on x86-linux, the list of tasks is available, but task
12970 switching is not supported. On Tru64, however, task switching will work
12973 On certain platforms, including Tru64, the debugger needs to perform some
12974 memory writes in order to provide Ada tasking support. When inspecting
12975 a core file, this means that the core file must be opened with read-write
12976 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
12977 Under these circumstances, you should make a backup copy of the core
12978 file before inspecting it with @value{GDBN}.
12981 @subsubsection Known Peculiarities of Ada Mode
12982 @cindex Ada, problems
12984 Besides the omissions listed previously (@pxref{Omissions from Ada}),
12985 we know of several problems with and limitations of Ada mode in
12987 some of which will be fixed with planned future releases of the debugger
12988 and the GNU Ada compiler.
12992 Currently, the debugger
12993 has insufficient information to determine whether certain pointers represent
12994 pointers to objects or the objects themselves.
12995 Thus, the user may have to tack an extra @code{.all} after an expression
12996 to get it printed properly.
12999 Static constants that the compiler chooses not to materialize as objects in
13000 storage are invisible to the debugger.
13003 Named parameter associations in function argument lists are ignored (the
13004 argument lists are treated as positional).
13007 Many useful library packages are currently invisible to the debugger.
13010 Fixed-point arithmetic, conversions, input, and output is carried out using
13011 floating-point arithmetic, and may give results that only approximate those on
13015 The GNAT compiler never generates the prefix @code{Standard} for any of
13016 the standard symbols defined by the Ada language. @value{GDBN} knows about
13017 this: it will strip the prefix from names when you use it, and will never
13018 look for a name you have so qualified among local symbols, nor match against
13019 symbols in other packages or subprograms. If you have
13020 defined entities anywhere in your program other than parameters and
13021 local variables whose simple names match names in @code{Standard},
13022 GNAT's lack of qualification here can cause confusion. When this happens,
13023 you can usually resolve the confusion
13024 by qualifying the problematic names with package
13025 @code{Standard} explicitly.
13028 Older versions of the compiler sometimes generate erroneous debugging
13029 information, resulting in the debugger incorrectly printing the value
13030 of affected entities. In some cases, the debugger is able to work
13031 around an issue automatically. In other cases, the debugger is able
13032 to work around the issue, but the work-around has to be specifically
13035 @kindex set ada trust-PAD-over-XVS
13036 @kindex show ada trust-PAD-over-XVS
13039 @item set ada trust-PAD-over-XVS on
13040 Configure GDB to strictly follow the GNAT encoding when computing the
13041 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13042 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13043 a complete description of the encoding used by the GNAT compiler).
13044 This is the default.
13046 @item set ada trust-PAD-over-XVS off
13047 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13048 sometimes prints the wrong value for certain entities, changing @code{ada
13049 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13050 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13051 @code{off}, but this incurs a slight performance penalty, so it is
13052 recommended to leave this setting to @code{on} unless necessary.
13056 @node Unsupported Languages
13057 @section Unsupported Languages
13059 @cindex unsupported languages
13060 @cindex minimal language
13061 In addition to the other fully-supported programming languages,
13062 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13063 It does not represent a real programming language, but provides a set
13064 of capabilities close to what the C or assembly languages provide.
13065 This should allow most simple operations to be performed while debugging
13066 an application that uses a language currently not supported by @value{GDBN}.
13068 If the language is set to @code{auto}, @value{GDBN} will automatically
13069 select this language if the current frame corresponds to an unsupported
13073 @chapter Examining the Symbol Table
13075 The commands described in this chapter allow you to inquire about the
13076 symbols (names of variables, functions and types) defined in your
13077 program. This information is inherent in the text of your program and
13078 does not change as your program executes. @value{GDBN} finds it in your
13079 program's symbol table, in the file indicated when you started @value{GDBN}
13080 (@pxref{File Options, ,Choosing Files}), or by one of the
13081 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13083 @cindex symbol names
13084 @cindex names of symbols
13085 @cindex quoting names
13086 Occasionally, you may need to refer to symbols that contain unusual
13087 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13088 most frequent case is in referring to static variables in other
13089 source files (@pxref{Variables,,Program Variables}). File names
13090 are recorded in object files as debugging symbols, but @value{GDBN} would
13091 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13092 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13093 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13100 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13103 @cindex case-insensitive symbol names
13104 @cindex case sensitivity in symbol names
13105 @kindex set case-sensitive
13106 @item set case-sensitive on
13107 @itemx set case-sensitive off
13108 @itemx set case-sensitive auto
13109 Normally, when @value{GDBN} looks up symbols, it matches their names
13110 with case sensitivity determined by the current source language.
13111 Occasionally, you may wish to control that. The command @code{set
13112 case-sensitive} lets you do that by specifying @code{on} for
13113 case-sensitive matches or @code{off} for case-insensitive ones. If
13114 you specify @code{auto}, case sensitivity is reset to the default
13115 suitable for the source language. The default is case-sensitive
13116 matches for all languages except for Fortran, for which the default is
13117 case-insensitive matches.
13119 @kindex show case-sensitive
13120 @item show case-sensitive
13121 This command shows the current setting of case sensitivity for symbols
13124 @kindex info address
13125 @cindex address of a symbol
13126 @item info address @var{symbol}
13127 Describe where the data for @var{symbol} is stored. For a register
13128 variable, this says which register it is kept in. For a non-register
13129 local variable, this prints the stack-frame offset at which the variable
13132 Note the contrast with @samp{print &@var{symbol}}, which does not work
13133 at all for a register variable, and for a stack local variable prints
13134 the exact address of the current instantiation of the variable.
13136 @kindex info symbol
13137 @cindex symbol from address
13138 @cindex closest symbol and offset for an address
13139 @item info symbol @var{addr}
13140 Print the name of a symbol which is stored at the address @var{addr}.
13141 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13142 nearest symbol and an offset from it:
13145 (@value{GDBP}) info symbol 0x54320
13146 _initialize_vx + 396 in section .text
13150 This is the opposite of the @code{info address} command. You can use
13151 it to find out the name of a variable or a function given its address.
13153 For dynamically linked executables, the name of executable or shared
13154 library containing the symbol is also printed:
13157 (@value{GDBP}) info symbol 0x400225
13158 _start + 5 in section .text of /tmp/a.out
13159 (@value{GDBP}) info symbol 0x2aaaac2811cf
13160 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13164 @item whatis [@var{arg}]
13165 Print the data type of @var{arg}, which can be either an expression or
13166 a data type. With no argument, print the data type of @code{$}, the
13167 last value in the value history. If @var{arg} is an expression, it is
13168 not actually evaluated, and any side-effecting operations (such as
13169 assignments or function calls) inside it do not take place. If
13170 @var{arg} is a type name, it may be the name of a type or typedef, or
13171 for C code it may have the form @samp{class @var{class-name}},
13172 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13173 @samp{enum @var{enum-tag}}.
13174 @xref{Expressions, ,Expressions}.
13177 @item ptype [@var{arg}]
13178 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13179 detailed description of the type, instead of just the name of the type.
13180 @xref{Expressions, ,Expressions}.
13182 For example, for this variable declaration:
13185 struct complex @{double real; double imag;@} v;
13189 the two commands give this output:
13193 (@value{GDBP}) whatis v
13194 type = struct complex
13195 (@value{GDBP}) ptype v
13196 type = struct complex @{
13204 As with @code{whatis}, using @code{ptype} without an argument refers to
13205 the type of @code{$}, the last value in the value history.
13207 @cindex incomplete type
13208 Sometimes, programs use opaque data types or incomplete specifications
13209 of complex data structure. If the debug information included in the
13210 program does not allow @value{GDBN} to display a full declaration of
13211 the data type, it will say @samp{<incomplete type>}. For example,
13212 given these declarations:
13216 struct foo *fooptr;
13220 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13223 (@value{GDBP}) ptype foo
13224 $1 = <incomplete type>
13228 ``Incomplete type'' is C terminology for data types that are not
13229 completely specified.
13232 @item info types @var{regexp}
13234 Print a brief description of all types whose names match the regular
13235 expression @var{regexp} (or all types in your program, if you supply
13236 no argument). Each complete typename is matched as though it were a
13237 complete line; thus, @samp{i type value} gives information on all
13238 types in your program whose names include the string @code{value}, but
13239 @samp{i type ^value$} gives information only on types whose complete
13240 name is @code{value}.
13242 This command differs from @code{ptype} in two ways: first, like
13243 @code{whatis}, it does not print a detailed description; second, it
13244 lists all source files where a type is defined.
13247 @cindex local variables
13248 @item info scope @var{location}
13249 List all the variables local to a particular scope. This command
13250 accepts a @var{location} argument---a function name, a source line, or
13251 an address preceded by a @samp{*}, and prints all the variables local
13252 to the scope defined by that location. (@xref{Specify Location}, for
13253 details about supported forms of @var{location}.) For example:
13256 (@value{GDBP}) @b{info scope command_line_handler}
13257 Scope for command_line_handler:
13258 Symbol rl is an argument at stack/frame offset 8, length 4.
13259 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13260 Symbol linelength is in static storage at address 0x150a1c, length 4.
13261 Symbol p is a local variable in register $esi, length 4.
13262 Symbol p1 is a local variable in register $ebx, length 4.
13263 Symbol nline is a local variable in register $edx, length 4.
13264 Symbol repeat is a local variable at frame offset -8, length 4.
13268 This command is especially useful for determining what data to collect
13269 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13272 @kindex info source
13274 Show information about the current source file---that is, the source file for
13275 the function containing the current point of execution:
13278 the name of the source file, and the directory containing it,
13280 the directory it was compiled in,
13282 its length, in lines,
13284 which programming language it is written in,
13286 whether the executable includes debugging information for that file, and
13287 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13289 whether the debugging information includes information about
13290 preprocessor macros.
13294 @kindex info sources
13296 Print the names of all source files in your program for which there is
13297 debugging information, organized into two lists: files whose symbols
13298 have already been read, and files whose symbols will be read when needed.
13300 @kindex info functions
13301 @item info functions
13302 Print the names and data types of all defined functions.
13304 @item info functions @var{regexp}
13305 Print the names and data types of all defined functions
13306 whose names contain a match for regular expression @var{regexp}.
13307 Thus, @samp{info fun step} finds all functions whose names
13308 include @code{step}; @samp{info fun ^step} finds those whose names
13309 start with @code{step}. If a function name contains characters
13310 that conflict with the regular expression language (e.g.@:
13311 @samp{operator*()}), they may be quoted with a backslash.
13313 @kindex info variables
13314 @item info variables
13315 Print the names and data types of all variables that are defined
13316 outside of functions (i.e.@: excluding local variables).
13318 @item info variables @var{regexp}
13319 Print the names and data types of all variables (except for local
13320 variables) whose names contain a match for regular expression
13323 @kindex info classes
13324 @cindex Objective-C, classes and selectors
13326 @itemx info classes @var{regexp}
13327 Display all Objective-C classes in your program, or
13328 (with the @var{regexp} argument) all those matching a particular regular
13331 @kindex info selectors
13332 @item info selectors
13333 @itemx info selectors @var{regexp}
13334 Display all Objective-C selectors in your program, or
13335 (with the @var{regexp} argument) all those matching a particular regular
13339 This was never implemented.
13340 @kindex info methods
13342 @itemx info methods @var{regexp}
13343 The @code{info methods} command permits the user to examine all defined
13344 methods within C@t{++} program, or (with the @var{regexp} argument) a
13345 specific set of methods found in the various C@t{++} classes. Many
13346 C@t{++} classes provide a large number of methods. Thus, the output
13347 from the @code{ptype} command can be overwhelming and hard to use. The
13348 @code{info-methods} command filters the methods, printing only those
13349 which match the regular-expression @var{regexp}.
13352 @cindex reloading symbols
13353 Some systems allow individual object files that make up your program to
13354 be replaced without stopping and restarting your program. For example,
13355 in VxWorks you can simply recompile a defective object file and keep on
13356 running. If you are running on one of these systems, you can allow
13357 @value{GDBN} to reload the symbols for automatically relinked modules:
13360 @kindex set symbol-reloading
13361 @item set symbol-reloading on
13362 Replace symbol definitions for the corresponding source file when an
13363 object file with a particular name is seen again.
13365 @item set symbol-reloading off
13366 Do not replace symbol definitions when encountering object files of the
13367 same name more than once. This is the default state; if you are not
13368 running on a system that permits automatic relinking of modules, you
13369 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13370 may discard symbols when linking large programs, that may contain
13371 several modules (from different directories or libraries) with the same
13374 @kindex show symbol-reloading
13375 @item show symbol-reloading
13376 Show the current @code{on} or @code{off} setting.
13379 @cindex opaque data types
13380 @kindex set opaque-type-resolution
13381 @item set opaque-type-resolution on
13382 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13383 declared as a pointer to a @code{struct}, @code{class}, or
13384 @code{union}---for example, @code{struct MyType *}---that is used in one
13385 source file although the full declaration of @code{struct MyType} is in
13386 another source file. The default is on.
13388 A change in the setting of this subcommand will not take effect until
13389 the next time symbols for a file are loaded.
13391 @item set opaque-type-resolution off
13392 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13393 is printed as follows:
13395 @{<no data fields>@}
13398 @kindex show opaque-type-resolution
13399 @item show opaque-type-resolution
13400 Show whether opaque types are resolved or not.
13402 @kindex maint print symbols
13403 @cindex symbol dump
13404 @kindex maint print psymbols
13405 @cindex partial symbol dump
13406 @item maint print symbols @var{filename}
13407 @itemx maint print psymbols @var{filename}
13408 @itemx maint print msymbols @var{filename}
13409 Write a dump of debugging symbol data into the file @var{filename}.
13410 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13411 symbols with debugging data are included. If you use @samp{maint print
13412 symbols}, @value{GDBN} includes all the symbols for which it has already
13413 collected full details: that is, @var{filename} reflects symbols for
13414 only those files whose symbols @value{GDBN} has read. You can use the
13415 command @code{info sources} to find out which files these are. If you
13416 use @samp{maint print psymbols} instead, the dump shows information about
13417 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13418 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13419 @samp{maint print msymbols} dumps just the minimal symbol information
13420 required for each object file from which @value{GDBN} has read some symbols.
13421 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13422 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13424 @kindex maint info symtabs
13425 @kindex maint info psymtabs
13426 @cindex listing @value{GDBN}'s internal symbol tables
13427 @cindex symbol tables, listing @value{GDBN}'s internal
13428 @cindex full symbol tables, listing @value{GDBN}'s internal
13429 @cindex partial symbol tables, listing @value{GDBN}'s internal
13430 @item maint info symtabs @r{[} @var{regexp} @r{]}
13431 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13433 List the @code{struct symtab} or @code{struct partial_symtab}
13434 structures whose names match @var{regexp}. If @var{regexp} is not
13435 given, list them all. The output includes expressions which you can
13436 copy into a @value{GDBN} debugging this one to examine a particular
13437 structure in more detail. For example:
13440 (@value{GDBP}) maint info psymtabs dwarf2read
13441 @{ objfile /home/gnu/build/gdb/gdb
13442 ((struct objfile *) 0x82e69d0)
13443 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13444 ((struct partial_symtab *) 0x8474b10)
13447 text addresses 0x814d3c8 -- 0x8158074
13448 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13449 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13450 dependencies (none)
13453 (@value{GDBP}) maint info symtabs
13457 We see that there is one partial symbol table whose filename contains
13458 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13459 and we see that @value{GDBN} has not read in any symtabs yet at all.
13460 If we set a breakpoint on a function, that will cause @value{GDBN} to
13461 read the symtab for the compilation unit containing that function:
13464 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13465 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13467 (@value{GDBP}) maint info symtabs
13468 @{ objfile /home/gnu/build/gdb/gdb
13469 ((struct objfile *) 0x82e69d0)
13470 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13471 ((struct symtab *) 0x86c1f38)
13474 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13475 linetable ((struct linetable *) 0x8370fa0)
13476 debugformat DWARF 2
13485 @chapter Altering Execution
13487 Once you think you have found an error in your program, you might want to
13488 find out for certain whether correcting the apparent error would lead to
13489 correct results in the rest of the run. You can find the answer by
13490 experiment, using the @value{GDBN} features for altering execution of the
13493 For example, you can store new values into variables or memory
13494 locations, give your program a signal, restart it at a different
13495 address, or even return prematurely from a function.
13498 * Assignment:: Assignment to variables
13499 * Jumping:: Continuing at a different address
13500 * Signaling:: Giving your program a signal
13501 * Returning:: Returning from a function
13502 * Calling:: Calling your program's functions
13503 * Patching:: Patching your program
13507 @section Assignment to Variables
13510 @cindex setting variables
13511 To alter the value of a variable, evaluate an assignment expression.
13512 @xref{Expressions, ,Expressions}. For example,
13519 stores the value 4 into the variable @code{x}, and then prints the
13520 value of the assignment expression (which is 4).
13521 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13522 information on operators in supported languages.
13524 @kindex set variable
13525 @cindex variables, setting
13526 If you are not interested in seeing the value of the assignment, use the
13527 @code{set} command instead of the @code{print} command. @code{set} is
13528 really the same as @code{print} except that the expression's value is
13529 not printed and is not put in the value history (@pxref{Value History,
13530 ,Value History}). The expression is evaluated only for its effects.
13532 If the beginning of the argument string of the @code{set} command
13533 appears identical to a @code{set} subcommand, use the @code{set
13534 variable} command instead of just @code{set}. This command is identical
13535 to @code{set} except for its lack of subcommands. For example, if your
13536 program has a variable @code{width}, you get an error if you try to set
13537 a new value with just @samp{set width=13}, because @value{GDBN} has the
13538 command @code{set width}:
13541 (@value{GDBP}) whatis width
13543 (@value{GDBP}) p width
13545 (@value{GDBP}) set width=47
13546 Invalid syntax in expression.
13550 The invalid expression, of course, is @samp{=47}. In
13551 order to actually set the program's variable @code{width}, use
13554 (@value{GDBP}) set var width=47
13557 Because the @code{set} command has many subcommands that can conflict
13558 with the names of program variables, it is a good idea to use the
13559 @code{set variable} command instead of just @code{set}. For example, if
13560 your program has a variable @code{g}, you run into problems if you try
13561 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13562 the command @code{set gnutarget}, abbreviated @code{set g}:
13566 (@value{GDBP}) whatis g
13570 (@value{GDBP}) set g=4
13574 The program being debugged has been started already.
13575 Start it from the beginning? (y or n) y
13576 Starting program: /home/smith/cc_progs/a.out
13577 "/home/smith/cc_progs/a.out": can't open to read symbols:
13578 Invalid bfd target.
13579 (@value{GDBP}) show g
13580 The current BFD target is "=4".
13585 The program variable @code{g} did not change, and you silently set the
13586 @code{gnutarget} to an invalid value. In order to set the variable
13590 (@value{GDBP}) set var g=4
13593 @value{GDBN} allows more implicit conversions in assignments than C; you can
13594 freely store an integer value into a pointer variable or vice versa,
13595 and you can convert any structure to any other structure that is the
13596 same length or shorter.
13597 @comment FIXME: how do structs align/pad in these conversions?
13598 @comment /doc@cygnus.com 18dec1990
13600 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13601 construct to generate a value of specified type at a specified address
13602 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13603 to memory location @code{0x83040} as an integer (which implies a certain size
13604 and representation in memory), and
13607 set @{int@}0x83040 = 4
13611 stores the value 4 into that memory location.
13614 @section Continuing at a Different Address
13616 Ordinarily, when you continue your program, you do so at the place where
13617 it stopped, with the @code{continue} command. You can instead continue at
13618 an address of your own choosing, with the following commands:
13622 @item jump @var{linespec}
13623 @itemx jump @var{location}
13624 Resume execution at line @var{linespec} or at address given by
13625 @var{location}. Execution stops again immediately if there is a
13626 breakpoint there. @xref{Specify Location}, for a description of the
13627 different forms of @var{linespec} and @var{location}. It is common
13628 practice to use the @code{tbreak} command in conjunction with
13629 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13631 The @code{jump} command does not change the current stack frame, or
13632 the stack pointer, or the contents of any memory location or any
13633 register other than the program counter. If line @var{linespec} is in
13634 a different function from the one currently executing, the results may
13635 be bizarre if the two functions expect different patterns of arguments or
13636 of local variables. For this reason, the @code{jump} command requests
13637 confirmation if the specified line is not in the function currently
13638 executing. However, even bizarre results are predictable if you are
13639 well acquainted with the machine-language code of your program.
13642 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13643 On many systems, you can get much the same effect as the @code{jump}
13644 command by storing a new value into the register @code{$pc}. The
13645 difference is that this does not start your program running; it only
13646 changes the address of where it @emph{will} run when you continue. For
13654 makes the next @code{continue} command or stepping command execute at
13655 address @code{0x485}, rather than at the address where your program stopped.
13656 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13658 The most common occasion to use the @code{jump} command is to back
13659 up---perhaps with more breakpoints set---over a portion of a program
13660 that has already executed, in order to examine its execution in more
13665 @section Giving your Program a Signal
13666 @cindex deliver a signal to a program
13670 @item signal @var{signal}
13671 Resume execution where your program stopped, but immediately give it the
13672 signal @var{signal}. @var{signal} can be the name or the number of a
13673 signal. For example, on many systems @code{signal 2} and @code{signal
13674 SIGINT} are both ways of sending an interrupt signal.
13676 Alternatively, if @var{signal} is zero, continue execution without
13677 giving a signal. This is useful when your program stopped on account of
13678 a signal and would ordinary see the signal when resumed with the
13679 @code{continue} command; @samp{signal 0} causes it to resume without a
13682 @code{signal} does not repeat when you press @key{RET} a second time
13683 after executing the command.
13687 Invoking the @code{signal} command is not the same as invoking the
13688 @code{kill} utility from the shell. Sending a signal with @code{kill}
13689 causes @value{GDBN} to decide what to do with the signal depending on
13690 the signal handling tables (@pxref{Signals}). The @code{signal} command
13691 passes the signal directly to your program.
13695 @section Returning from a Function
13698 @cindex returning from a function
13701 @itemx return @var{expression}
13702 You can cancel execution of a function call with the @code{return}
13703 command. If you give an
13704 @var{expression} argument, its value is used as the function's return
13708 When you use @code{return}, @value{GDBN} discards the selected stack frame
13709 (and all frames within it). You can think of this as making the
13710 discarded frame return prematurely. If you wish to specify a value to
13711 be returned, give that value as the argument to @code{return}.
13713 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13714 Frame}), and any other frames inside of it, leaving its caller as the
13715 innermost remaining frame. That frame becomes selected. The
13716 specified value is stored in the registers used for returning values
13719 The @code{return} command does not resume execution; it leaves the
13720 program stopped in the state that would exist if the function had just
13721 returned. In contrast, the @code{finish} command (@pxref{Continuing
13722 and Stepping, ,Continuing and Stepping}) resumes execution until the
13723 selected stack frame returns naturally.
13725 @value{GDBN} needs to know how the @var{expression} argument should be set for
13726 the inferior. The concrete registers assignment depends on the OS ABI and the
13727 type being returned by the selected stack frame. For example it is common for
13728 OS ABI to return floating point values in FPU registers while integer values in
13729 CPU registers. Still some ABIs return even floating point values in CPU
13730 registers. Larger integer widths (such as @code{long long int}) also have
13731 specific placement rules. @value{GDBN} already knows the OS ABI from its
13732 current target so it needs to find out also the type being returned to make the
13733 assignment into the right register(s).
13735 Normally, the selected stack frame has debug info. @value{GDBN} will always
13736 use the debug info instead of the implicit type of @var{expression} when the
13737 debug info is available. For example, if you type @kbd{return -1}, and the
13738 function in the current stack frame is declared to return a @code{long long
13739 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13740 into a @code{long long int}:
13743 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13745 (@value{GDBP}) return -1
13746 Make func return now? (y or n) y
13747 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13748 43 printf ("result=%lld\n", func ());
13752 However, if the selected stack frame does not have a debug info, e.g., if the
13753 function was compiled without debug info, @value{GDBN} has to find out the type
13754 to return from user. Specifying a different type by mistake may set the value
13755 in different inferior registers than the caller code expects. For example,
13756 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13757 of a @code{long long int} result for a debug info less function (on 32-bit
13758 architectures). Therefore the user is required to specify the return type by
13759 an appropriate cast explicitly:
13762 Breakpoint 2, 0x0040050b in func ()
13763 (@value{GDBP}) return -1
13764 Return value type not available for selected stack frame.
13765 Please use an explicit cast of the value to return.
13766 (@value{GDBP}) return (long long int) -1
13767 Make selected stack frame return now? (y or n) y
13768 #0 0x00400526 in main ()
13773 @section Calling Program Functions
13776 @cindex calling functions
13777 @cindex inferior functions, calling
13778 @item print @var{expr}
13779 Evaluate the expression @var{expr} and display the resulting value.
13780 @var{expr} may include calls to functions in the program being
13784 @item call @var{expr}
13785 Evaluate the expression @var{expr} without displaying @code{void}
13788 You can use this variant of the @code{print} command if you want to
13789 execute a function from your program that does not return anything
13790 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13791 with @code{void} returned values that @value{GDBN} will otherwise
13792 print. If the result is not void, it is printed and saved in the
13796 It is possible for the function you call via the @code{print} or
13797 @code{call} command to generate a signal (e.g., if there's a bug in
13798 the function, or if you passed it incorrect arguments). What happens
13799 in that case is controlled by the @code{set unwindonsignal} command.
13801 Similarly, with a C@t{++} program it is possible for the function you
13802 call via the @code{print} or @code{call} command to generate an
13803 exception that is not handled due to the constraints of the dummy
13804 frame. In this case, any exception that is raised in the frame, but has
13805 an out-of-frame exception handler will not be found. GDB builds a
13806 dummy-frame for the inferior function call, and the unwinder cannot
13807 seek for exception handlers outside of this dummy-frame. What happens
13808 in that case is controlled by the
13809 @code{set unwind-on-terminating-exception} command.
13812 @item set unwindonsignal
13813 @kindex set unwindonsignal
13814 @cindex unwind stack in called functions
13815 @cindex call dummy stack unwinding
13816 Set unwinding of the stack if a signal is received while in a function
13817 that @value{GDBN} called in the program being debugged. If set to on,
13818 @value{GDBN} unwinds the stack it created for the call and restores
13819 the context to what it was before the call. If set to off (the
13820 default), @value{GDBN} stops in the frame where the signal was
13823 @item show unwindonsignal
13824 @kindex show unwindonsignal
13825 Show the current setting of stack unwinding in the functions called by
13828 @item set unwind-on-terminating-exception
13829 @kindex set unwind-on-terminating-exception
13830 @cindex unwind stack in called functions with unhandled exceptions
13831 @cindex call dummy stack unwinding on unhandled exception.
13832 Set unwinding of the stack if a C@t{++} exception is raised, but left
13833 unhandled while in a function that @value{GDBN} called in the program being
13834 debugged. If set to on (the default), @value{GDBN} unwinds the stack
13835 it created for the call and restores the context to what it was before
13836 the call. If set to off, @value{GDBN} the exception is delivered to
13837 the default C@t{++} exception handler and the inferior terminated.
13839 @item show unwind-on-terminating-exception
13840 @kindex show unwind-on-terminating-exception
13841 Show the current setting of stack unwinding in the functions called by
13846 @cindex weak alias functions
13847 Sometimes, a function you wish to call is actually a @dfn{weak alias}
13848 for another function. In such case, @value{GDBN} might not pick up
13849 the type information, including the types of the function arguments,
13850 which causes @value{GDBN} to call the inferior function incorrectly.
13851 As a result, the called function will function erroneously and may
13852 even crash. A solution to that is to use the name of the aliased
13856 @section Patching Programs
13858 @cindex patching binaries
13859 @cindex writing into executables
13860 @cindex writing into corefiles
13862 By default, @value{GDBN} opens the file containing your program's
13863 executable code (or the corefile) read-only. This prevents accidental
13864 alterations to machine code; but it also prevents you from intentionally
13865 patching your program's binary.
13867 If you'd like to be able to patch the binary, you can specify that
13868 explicitly with the @code{set write} command. For example, you might
13869 want to turn on internal debugging flags, or even to make emergency
13875 @itemx set write off
13876 If you specify @samp{set write on}, @value{GDBN} opens executable and
13877 core files for both reading and writing; if you specify @kbd{set write
13878 off} (the default), @value{GDBN} opens them read-only.
13880 If you have already loaded a file, you must load it again (using the
13881 @code{exec-file} or @code{core-file} command) after changing @code{set
13882 write}, for your new setting to take effect.
13886 Display whether executable files and core files are opened for writing
13887 as well as reading.
13891 @chapter @value{GDBN} Files
13893 @value{GDBN} needs to know the file name of the program to be debugged,
13894 both in order to read its symbol table and in order to start your
13895 program. To debug a core dump of a previous run, you must also tell
13896 @value{GDBN} the name of the core dump file.
13899 * Files:: Commands to specify files
13900 * Separate Debug Files:: Debugging information in separate files
13901 * Symbol Errors:: Errors reading symbol files
13902 * Data Files:: GDB data files
13906 @section Commands to Specify Files
13908 @cindex symbol table
13909 @cindex core dump file
13911 You may want to specify executable and core dump file names. The usual
13912 way to do this is at start-up time, using the arguments to
13913 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
13914 Out of @value{GDBN}}).
13916 Occasionally it is necessary to change to a different file during a
13917 @value{GDBN} session. Or you may run @value{GDBN} and forget to
13918 specify a file you want to use. Or you are debugging a remote target
13919 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
13920 Program}). In these situations the @value{GDBN} commands to specify
13921 new files are useful.
13924 @cindex executable file
13926 @item file @var{filename}
13927 Use @var{filename} as the program to be debugged. It is read for its
13928 symbols and for the contents of pure memory. It is also the program
13929 executed when you use the @code{run} command. If you do not specify a
13930 directory and the file is not found in the @value{GDBN} working directory,
13931 @value{GDBN} uses the environment variable @code{PATH} as a list of
13932 directories to search, just as the shell does when looking for a program
13933 to run. You can change the value of this variable, for both @value{GDBN}
13934 and your program, using the @code{path} command.
13936 @cindex unlinked object files
13937 @cindex patching object files
13938 You can load unlinked object @file{.o} files into @value{GDBN} using
13939 the @code{file} command. You will not be able to ``run'' an object
13940 file, but you can disassemble functions and inspect variables. Also,
13941 if the underlying BFD functionality supports it, you could use
13942 @kbd{gdb -write} to patch object files using this technique. Note
13943 that @value{GDBN} can neither interpret nor modify relocations in this
13944 case, so branches and some initialized variables will appear to go to
13945 the wrong place. But this feature is still handy from time to time.
13948 @code{file} with no argument makes @value{GDBN} discard any information it
13949 has on both executable file and the symbol table.
13952 @item exec-file @r{[} @var{filename} @r{]}
13953 Specify that the program to be run (but not the symbol table) is found
13954 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
13955 if necessary to locate your program. Omitting @var{filename} means to
13956 discard information on the executable file.
13958 @kindex symbol-file
13959 @item symbol-file @r{[} @var{filename} @r{]}
13960 Read symbol table information from file @var{filename}. @code{PATH} is
13961 searched when necessary. Use the @code{file} command to get both symbol
13962 table and program to run from the same file.
13964 @code{symbol-file} with no argument clears out @value{GDBN} information on your
13965 program's symbol table.
13967 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
13968 some breakpoints and auto-display expressions. This is because they may
13969 contain pointers to the internal data recording symbols and data types,
13970 which are part of the old symbol table data being discarded inside
13973 @code{symbol-file} does not repeat if you press @key{RET} again after
13976 When @value{GDBN} is configured for a particular environment, it
13977 understands debugging information in whatever format is the standard
13978 generated for that environment; you may use either a @sc{gnu} compiler, or
13979 other compilers that adhere to the local conventions.
13980 Best results are usually obtained from @sc{gnu} compilers; for example,
13981 using @code{@value{NGCC}} you can generate debugging information for
13984 For most kinds of object files, with the exception of old SVR3 systems
13985 using COFF, the @code{symbol-file} command does not normally read the
13986 symbol table in full right away. Instead, it scans the symbol table
13987 quickly to find which source files and which symbols are present. The
13988 details are read later, one source file at a time, as they are needed.
13990 The purpose of this two-stage reading strategy is to make @value{GDBN}
13991 start up faster. For the most part, it is invisible except for
13992 occasional pauses while the symbol table details for a particular source
13993 file are being read. (The @code{set verbose} command can turn these
13994 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
13995 Warnings and Messages}.)
13997 We have not implemented the two-stage strategy for COFF yet. When the
13998 symbol table is stored in COFF format, @code{symbol-file} reads the
13999 symbol table data in full right away. Note that ``stabs-in-COFF''
14000 still does the two-stage strategy, since the debug info is actually
14004 @cindex reading symbols immediately
14005 @cindex symbols, reading immediately
14006 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14007 @itemx file @r{[} -readnow @r{]} @var{filename}
14008 You can override the @value{GDBN} two-stage strategy for reading symbol
14009 tables by using the @samp{-readnow} option with any of the commands that
14010 load symbol table information, if you want to be sure @value{GDBN} has the
14011 entire symbol table available.
14013 @c FIXME: for now no mention of directories, since this seems to be in
14014 @c flux. 13mar1992 status is that in theory GDB would look either in
14015 @c current dir or in same dir as myprog; but issues like competing
14016 @c GDB's, or clutter in system dirs, mean that in practice right now
14017 @c only current dir is used. FFish says maybe a special GDB hierarchy
14018 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14022 @item core-file @r{[}@var{filename}@r{]}
14024 Specify the whereabouts of a core dump file to be used as the ``contents
14025 of memory''. Traditionally, core files contain only some parts of the
14026 address space of the process that generated them; @value{GDBN} can access the
14027 executable file itself for other parts.
14029 @code{core-file} with no argument specifies that no core file is
14032 Note that the core file is ignored when your program is actually running
14033 under @value{GDBN}. So, if you have been running your program and you
14034 wish to debug a core file instead, you must kill the subprocess in which
14035 the program is running. To do this, use the @code{kill} command
14036 (@pxref{Kill Process, ,Killing the Child Process}).
14038 @kindex add-symbol-file
14039 @cindex dynamic linking
14040 @item add-symbol-file @var{filename} @var{address}
14041 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14042 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14043 The @code{add-symbol-file} command reads additional symbol table
14044 information from the file @var{filename}. You would use this command
14045 when @var{filename} has been dynamically loaded (by some other means)
14046 into the program that is running. @var{address} should be the memory
14047 address at which the file has been loaded; @value{GDBN} cannot figure
14048 this out for itself. You can additionally specify an arbitrary number
14049 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14050 section name and base address for that section. You can specify any
14051 @var{address} as an expression.
14053 The symbol table of the file @var{filename} is added to the symbol table
14054 originally read with the @code{symbol-file} command. You can use the
14055 @code{add-symbol-file} command any number of times; the new symbol data
14056 thus read keeps adding to the old. To discard all old symbol data
14057 instead, use the @code{symbol-file} command without any arguments.
14059 @cindex relocatable object files, reading symbols from
14060 @cindex object files, relocatable, reading symbols from
14061 @cindex reading symbols from relocatable object files
14062 @cindex symbols, reading from relocatable object files
14063 @cindex @file{.o} files, reading symbols from
14064 Although @var{filename} is typically a shared library file, an
14065 executable file, or some other object file which has been fully
14066 relocated for loading into a process, you can also load symbolic
14067 information from relocatable @file{.o} files, as long as:
14071 the file's symbolic information refers only to linker symbols defined in
14072 that file, not to symbols defined by other object files,
14074 every section the file's symbolic information refers to has actually
14075 been loaded into the inferior, as it appears in the file, and
14077 you can determine the address at which every section was loaded, and
14078 provide these to the @code{add-symbol-file} command.
14082 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14083 relocatable files into an already running program; such systems
14084 typically make the requirements above easy to meet. However, it's
14085 important to recognize that many native systems use complex link
14086 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14087 assembly, for example) that make the requirements difficult to meet. In
14088 general, one cannot assume that using @code{add-symbol-file} to read a
14089 relocatable object file's symbolic information will have the same effect
14090 as linking the relocatable object file into the program in the normal
14093 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14095 @kindex add-symbol-file-from-memory
14096 @cindex @code{syscall DSO}
14097 @cindex load symbols from memory
14098 @item add-symbol-file-from-memory @var{address}
14099 Load symbols from the given @var{address} in a dynamically loaded
14100 object file whose image is mapped directly into the inferior's memory.
14101 For example, the Linux kernel maps a @code{syscall DSO} into each
14102 process's address space; this DSO provides kernel-specific code for
14103 some system calls. The argument can be any expression whose
14104 evaluation yields the address of the file's shared object file header.
14105 For this command to work, you must have used @code{symbol-file} or
14106 @code{exec-file} commands in advance.
14108 @kindex add-shared-symbol-files
14110 @item add-shared-symbol-files @var{library-file}
14111 @itemx assf @var{library-file}
14112 The @code{add-shared-symbol-files} command can currently be used only
14113 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14114 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14115 @value{GDBN} automatically looks for shared libraries, however if
14116 @value{GDBN} does not find yours, you can invoke
14117 @code{add-shared-symbol-files}. It takes one argument: the shared
14118 library's file name. @code{assf} is a shorthand alias for
14119 @code{add-shared-symbol-files}.
14122 @item section @var{section} @var{addr}
14123 The @code{section} command changes the base address of the named
14124 @var{section} of the exec file to @var{addr}. This can be used if the
14125 exec file does not contain section addresses, (such as in the
14126 @code{a.out} format), or when the addresses specified in the file
14127 itself are wrong. Each section must be changed separately. The
14128 @code{info files} command, described below, lists all the sections and
14132 @kindex info target
14135 @code{info files} and @code{info target} are synonymous; both print the
14136 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14137 including the names of the executable and core dump files currently in
14138 use by @value{GDBN}, and the files from which symbols were loaded. The
14139 command @code{help target} lists all possible targets rather than
14142 @kindex maint info sections
14143 @item maint info sections
14144 Another command that can give you extra information about program sections
14145 is @code{maint info sections}. In addition to the section information
14146 displayed by @code{info files}, this command displays the flags and file
14147 offset of each section in the executable and core dump files. In addition,
14148 @code{maint info sections} provides the following command options (which
14149 may be arbitrarily combined):
14153 Display sections for all loaded object files, including shared libraries.
14154 @item @var{sections}
14155 Display info only for named @var{sections}.
14156 @item @var{section-flags}
14157 Display info only for sections for which @var{section-flags} are true.
14158 The section flags that @value{GDBN} currently knows about are:
14161 Section will have space allocated in the process when loaded.
14162 Set for all sections except those containing debug information.
14164 Section will be loaded from the file into the child process memory.
14165 Set for pre-initialized code and data, clear for @code{.bss} sections.
14167 Section needs to be relocated before loading.
14169 Section cannot be modified by the child process.
14171 Section contains executable code only.
14173 Section contains data only (no executable code).
14175 Section will reside in ROM.
14177 Section contains data for constructor/destructor lists.
14179 Section is not empty.
14181 An instruction to the linker to not output the section.
14182 @item COFF_SHARED_LIBRARY
14183 A notification to the linker that the section contains
14184 COFF shared library information.
14186 Section contains common symbols.
14189 @kindex set trust-readonly-sections
14190 @cindex read-only sections
14191 @item set trust-readonly-sections on
14192 Tell @value{GDBN} that readonly sections in your object file
14193 really are read-only (i.e.@: that their contents will not change).
14194 In that case, @value{GDBN} can fetch values from these sections
14195 out of the object file, rather than from the target program.
14196 For some targets (notably embedded ones), this can be a significant
14197 enhancement to debugging performance.
14199 The default is off.
14201 @item set trust-readonly-sections off
14202 Tell @value{GDBN} not to trust readonly sections. This means that
14203 the contents of the section might change while the program is running,
14204 and must therefore be fetched from the target when needed.
14206 @item show trust-readonly-sections
14207 Show the current setting of trusting readonly sections.
14210 All file-specifying commands allow both absolute and relative file names
14211 as arguments. @value{GDBN} always converts the file name to an absolute file
14212 name and remembers it that way.
14214 @cindex shared libraries
14215 @anchor{Shared Libraries}
14216 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14217 and IBM RS/6000 AIX shared libraries.
14219 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14220 shared libraries. @xref{Expat}.
14222 @value{GDBN} automatically loads symbol definitions from shared libraries
14223 when you use the @code{run} command, or when you examine a core file.
14224 (Before you issue the @code{run} command, @value{GDBN} does not understand
14225 references to a function in a shared library, however---unless you are
14226 debugging a core file).
14228 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14229 automatically loads the symbols at the time of the @code{shl_load} call.
14231 @c FIXME: some @value{GDBN} release may permit some refs to undef
14232 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14233 @c FIXME...lib; check this from time to time when updating manual
14235 There are times, however, when you may wish to not automatically load
14236 symbol definitions from shared libraries, such as when they are
14237 particularly large or there are many of them.
14239 To control the automatic loading of shared library symbols, use the
14243 @kindex set auto-solib-add
14244 @item set auto-solib-add @var{mode}
14245 If @var{mode} is @code{on}, symbols from all shared object libraries
14246 will be loaded automatically when the inferior begins execution, you
14247 attach to an independently started inferior, or when the dynamic linker
14248 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14249 is @code{off}, symbols must be loaded manually, using the
14250 @code{sharedlibrary} command. The default value is @code{on}.
14252 @cindex memory used for symbol tables
14253 If your program uses lots of shared libraries with debug info that
14254 takes large amounts of memory, you can decrease the @value{GDBN}
14255 memory footprint by preventing it from automatically loading the
14256 symbols from shared libraries. To that end, type @kbd{set
14257 auto-solib-add off} before running the inferior, then load each
14258 library whose debug symbols you do need with @kbd{sharedlibrary
14259 @var{regexp}}, where @var{regexp} is a regular expression that matches
14260 the libraries whose symbols you want to be loaded.
14262 @kindex show auto-solib-add
14263 @item show auto-solib-add
14264 Display the current autoloading mode.
14267 @cindex load shared library
14268 To explicitly load shared library symbols, use the @code{sharedlibrary}
14272 @kindex info sharedlibrary
14274 @item info share @var{regex}
14275 @itemx info sharedlibrary @var{regex}
14276 Print the names of the shared libraries which are currently loaded
14277 that match @var{regex}. If @var{regex} is omitted then print
14278 all shared libraries that are loaded.
14280 @kindex sharedlibrary
14282 @item sharedlibrary @var{regex}
14283 @itemx share @var{regex}
14284 Load shared object library symbols for files matching a
14285 Unix regular expression.
14286 As with files loaded automatically, it only loads shared libraries
14287 required by your program for a core file or after typing @code{run}. If
14288 @var{regex} is omitted all shared libraries required by your program are
14291 @item nosharedlibrary
14292 @kindex nosharedlibrary
14293 @cindex unload symbols from shared libraries
14294 Unload all shared object library symbols. This discards all symbols
14295 that have been loaded from all shared libraries. Symbols from shared
14296 libraries that were loaded by explicit user requests are not
14300 Sometimes you may wish that @value{GDBN} stops and gives you control
14301 when any of shared library events happen. Use the @code{set
14302 stop-on-solib-events} command for this:
14305 @item set stop-on-solib-events
14306 @kindex set stop-on-solib-events
14307 This command controls whether @value{GDBN} should give you control
14308 when the dynamic linker notifies it about some shared library event.
14309 The most common event of interest is loading or unloading of a new
14312 @item show stop-on-solib-events
14313 @kindex show stop-on-solib-events
14314 Show whether @value{GDBN} stops and gives you control when shared
14315 library events happen.
14318 Shared libraries are also supported in many cross or remote debugging
14319 configurations. @value{GDBN} needs to have access to the target's libraries;
14320 this can be accomplished either by providing copies of the libraries
14321 on the host system, or by asking @value{GDBN} to automatically retrieve the
14322 libraries from the target. If copies of the target libraries are
14323 provided, they need to be the same as the target libraries, although the
14324 copies on the target can be stripped as long as the copies on the host are
14327 @cindex where to look for shared libraries
14328 For remote debugging, you need to tell @value{GDBN} where the target
14329 libraries are, so that it can load the correct copies---otherwise, it
14330 may try to load the host's libraries. @value{GDBN} has two variables
14331 to specify the search directories for target libraries.
14334 @cindex prefix for shared library file names
14335 @cindex system root, alternate
14336 @kindex set solib-absolute-prefix
14337 @kindex set sysroot
14338 @item set sysroot @var{path}
14339 Use @var{path} as the system root for the program being debugged. Any
14340 absolute shared library paths will be prefixed with @var{path}; many
14341 runtime loaders store the absolute paths to the shared library in the
14342 target program's memory. If you use @code{set sysroot} to find shared
14343 libraries, they need to be laid out in the same way that they are on
14344 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14347 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14348 retrieve the target libraries from the remote system. This is only
14349 supported when using a remote target that supports the @code{remote get}
14350 command (@pxref{File Transfer,,Sending files to a remote system}).
14351 The part of @var{path} following the initial @file{remote:}
14352 (if present) is used as system root prefix on the remote file system.
14353 @footnote{If you want to specify a local system root using a directory
14354 that happens to be named @file{remote:}, you need to use some equivalent
14355 variant of the name like @file{./remote:}.}
14357 The @code{set solib-absolute-prefix} command is an alias for @code{set
14360 @cindex default system root
14361 @cindex @samp{--with-sysroot}
14362 You can set the default system root by using the configure-time
14363 @samp{--with-sysroot} option. If the system root is inside
14364 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14365 @samp{--exec-prefix}), then the default system root will be updated
14366 automatically if the installed @value{GDBN} is moved to a new
14369 @kindex show sysroot
14371 Display the current shared library prefix.
14373 @kindex set solib-search-path
14374 @item set solib-search-path @var{path}
14375 If this variable is set, @var{path} is a colon-separated list of
14376 directories to search for shared libraries. @samp{solib-search-path}
14377 is used after @samp{sysroot} fails to locate the library, or if the
14378 path to the library is relative instead of absolute. If you want to
14379 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14380 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14381 finding your host's libraries. @samp{sysroot} is preferred; setting
14382 it to a nonexistent directory may interfere with automatic loading
14383 of shared library symbols.
14385 @kindex show solib-search-path
14386 @item show solib-search-path
14387 Display the current shared library search path.
14391 @node Separate Debug Files
14392 @section Debugging Information in Separate Files
14393 @cindex separate debugging information files
14394 @cindex debugging information in separate files
14395 @cindex @file{.debug} subdirectories
14396 @cindex debugging information directory, global
14397 @cindex global debugging information directory
14398 @cindex build ID, and separate debugging files
14399 @cindex @file{.build-id} directory
14401 @value{GDBN} allows you to put a program's debugging information in a
14402 file separate from the executable itself, in a way that allows
14403 @value{GDBN} to find and load the debugging information automatically.
14404 Since debugging information can be very large---sometimes larger
14405 than the executable code itself---some systems distribute debugging
14406 information for their executables in separate files, which users can
14407 install only when they need to debug a problem.
14409 @value{GDBN} supports two ways of specifying the separate debug info
14414 The executable contains a @dfn{debug link} that specifies the name of
14415 the separate debug info file. The separate debug file's name is
14416 usually @file{@var{executable}.debug}, where @var{executable} is the
14417 name of the corresponding executable file without leading directories
14418 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14419 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14420 checksum for the debug file, which @value{GDBN} uses to validate that
14421 the executable and the debug file came from the same build.
14424 The executable contains a @dfn{build ID}, a unique bit string that is
14425 also present in the corresponding debug info file. (This is supported
14426 only on some operating systems, notably those which use the ELF format
14427 for binary files and the @sc{gnu} Binutils.) For more details about
14428 this feature, see the description of the @option{--build-id}
14429 command-line option in @ref{Options, , Command Line Options, ld.info,
14430 The GNU Linker}. The debug info file's name is not specified
14431 explicitly by the build ID, but can be computed from the build ID, see
14435 Depending on the way the debug info file is specified, @value{GDBN}
14436 uses two different methods of looking for the debug file:
14440 For the ``debug link'' method, @value{GDBN} looks up the named file in
14441 the directory of the executable file, then in a subdirectory of that
14442 directory named @file{.debug}, and finally under the global debug
14443 directory, in a subdirectory whose name is identical to the leading
14444 directories of the executable's absolute file name.
14447 For the ``build ID'' method, @value{GDBN} looks in the
14448 @file{.build-id} subdirectory of the global debug directory for a file
14449 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14450 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14451 are the rest of the bit string. (Real build ID strings are 32 or more
14452 hex characters, not 10.)
14455 So, for example, suppose you ask @value{GDBN} to debug
14456 @file{/usr/bin/ls}, which has a debug link that specifies the
14457 file @file{ls.debug}, and a build ID whose value in hex is
14458 @code{abcdef1234}. If the global debug directory is
14459 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14460 debug information files, in the indicated order:
14464 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14466 @file{/usr/bin/ls.debug}
14468 @file{/usr/bin/.debug/ls.debug}
14470 @file{/usr/lib/debug/usr/bin/ls.debug}.
14473 You can set the global debugging info directory's name, and view the
14474 name @value{GDBN} is currently using.
14478 @kindex set debug-file-directory
14479 @item set debug-file-directory @var{directories}
14480 Set the directories which @value{GDBN} searches for separate debugging
14481 information files to @var{directory}. Multiple directory components can be set
14482 concatenating them by a directory separator.
14484 @kindex show debug-file-directory
14485 @item show debug-file-directory
14486 Show the directories @value{GDBN} searches for separate debugging
14491 @cindex @code{.gnu_debuglink} sections
14492 @cindex debug link sections
14493 A debug link is a special section of the executable file named
14494 @code{.gnu_debuglink}. The section must contain:
14498 A filename, with any leading directory components removed, followed by
14501 zero to three bytes of padding, as needed to reach the next four-byte
14502 boundary within the section, and
14504 a four-byte CRC checksum, stored in the same endianness used for the
14505 executable file itself. The checksum is computed on the debugging
14506 information file's full contents by the function given below, passing
14507 zero as the @var{crc} argument.
14510 Any executable file format can carry a debug link, as long as it can
14511 contain a section named @code{.gnu_debuglink} with the contents
14514 @cindex @code{.note.gnu.build-id} sections
14515 @cindex build ID sections
14516 The build ID is a special section in the executable file (and in other
14517 ELF binary files that @value{GDBN} may consider). This section is
14518 often named @code{.note.gnu.build-id}, but that name is not mandatory.
14519 It contains unique identification for the built files---the ID remains
14520 the same across multiple builds of the same build tree. The default
14521 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
14522 content for the build ID string. The same section with an identical
14523 value is present in the original built binary with symbols, in its
14524 stripped variant, and in the separate debugging information file.
14526 The debugging information file itself should be an ordinary
14527 executable, containing a full set of linker symbols, sections, and
14528 debugging information. The sections of the debugging information file
14529 should have the same names, addresses, and sizes as the original file,
14530 but they need not contain any data---much like a @code{.bss} section
14531 in an ordinary executable.
14533 The @sc{gnu} binary utilities (Binutils) package includes the
14534 @samp{objcopy} utility that can produce
14535 the separated executable / debugging information file pairs using the
14536 following commands:
14539 @kbd{objcopy --only-keep-debug foo foo.debug}
14544 These commands remove the debugging
14545 information from the executable file @file{foo} and place it in the file
14546 @file{foo.debug}. You can use the first, second or both methods to link the
14551 The debug link method needs the following additional command to also leave
14552 behind a debug link in @file{foo}:
14555 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
14558 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
14559 a version of the @code{strip} command such that the command @kbd{strip foo -f
14560 foo.debug} has the same functionality as the two @code{objcopy} commands and
14561 the @code{ln -s} command above, together.
14564 Build ID gets embedded into the main executable using @code{ld --build-id} or
14565 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
14566 compatibility fixes for debug files separation are present in @sc{gnu} binary
14567 utilities (Binutils) package since version 2.18.
14572 @cindex CRC algorithm definition
14573 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
14574 IEEE 802.3 using the polynomial:
14576 @c TexInfo requires naked braces for multi-digit exponents for Tex
14577 @c output, but this causes HTML output to barf. HTML has to be set using
14578 @c raw commands. So we end up having to specify this equation in 2
14583 <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
14584 + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
14590 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
14591 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
14595 The function is computed byte at a time, taking the least
14596 significant bit of each byte first. The initial pattern
14597 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
14598 the final result is inverted to ensure trailing zeros also affect the
14601 @emph{Note:} This is the same CRC polynomial as used in handling the
14602 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
14603 , @value{GDBN} Remote Serial Protocol}). However in the
14604 case of the Remote Serial Protocol, the CRC is computed @emph{most}
14605 significant bit first, and the result is not inverted, so trailing
14606 zeros have no effect on the CRC value.
14608 To complete the description, we show below the code of the function
14609 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14610 initially supplied @code{crc} argument means that an initial call to
14611 this function passing in zero will start computing the CRC using
14614 @kindex gnu_debuglink_crc32
14617 gnu_debuglink_crc32 (unsigned long crc,
14618 unsigned char *buf, size_t len)
14620 static const unsigned long crc32_table[256] =
14622 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14623 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14624 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14625 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14626 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14627 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14628 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14629 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14630 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14631 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14632 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14633 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14634 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14635 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14636 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14637 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14638 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14639 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14640 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14641 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14642 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14643 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14644 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14645 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14646 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14647 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14648 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14649 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14650 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14651 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14652 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14653 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14654 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14655 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14656 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14657 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14658 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14659 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14660 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14661 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14662 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14663 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14664 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14665 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14666 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14667 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14668 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14669 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14670 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14671 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14672 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14675 unsigned char *end;
14677 crc = ~crc & 0xffffffff;
14678 for (end = buf + len; buf < end; ++buf)
14679 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14680 return ~crc & 0xffffffff;
14685 This computation does not apply to the ``build ID'' method.
14688 @node Symbol Errors
14689 @section Errors Reading Symbol Files
14691 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14692 such as symbol types it does not recognize, or known bugs in compiler
14693 output. By default, @value{GDBN} does not notify you of such problems, since
14694 they are relatively common and primarily of interest to people
14695 debugging compilers. If you are interested in seeing information
14696 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14697 only one message about each such type of problem, no matter how many
14698 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14699 to see how many times the problems occur, with the @code{set
14700 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14703 The messages currently printed, and their meanings, include:
14706 @item inner block not inside outer block in @var{symbol}
14708 The symbol information shows where symbol scopes begin and end
14709 (such as at the start of a function or a block of statements). This
14710 error indicates that an inner scope block is not fully contained
14711 in its outer scope blocks.
14713 @value{GDBN} circumvents the problem by treating the inner block as if it had
14714 the same scope as the outer block. In the error message, @var{symbol}
14715 may be shown as ``@code{(don't know)}'' if the outer block is not a
14718 @item block at @var{address} out of order
14720 The symbol information for symbol scope blocks should occur in
14721 order of increasing addresses. This error indicates that it does not
14724 @value{GDBN} does not circumvent this problem, and has trouble
14725 locating symbols in the source file whose symbols it is reading. (You
14726 can often determine what source file is affected by specifying
14727 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
14730 @item bad block start address patched
14732 The symbol information for a symbol scope block has a start address
14733 smaller than the address of the preceding source line. This is known
14734 to occur in the SunOS 4.1.1 (and earlier) C compiler.
14736 @value{GDBN} circumvents the problem by treating the symbol scope block as
14737 starting on the previous source line.
14739 @item bad string table offset in symbol @var{n}
14742 Symbol number @var{n} contains a pointer into the string table which is
14743 larger than the size of the string table.
14745 @value{GDBN} circumvents the problem by considering the symbol to have the
14746 name @code{foo}, which may cause other problems if many symbols end up
14749 @item unknown symbol type @code{0x@var{nn}}
14751 The symbol information contains new data types that @value{GDBN} does
14752 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
14753 uncomprehended information, in hexadecimal.
14755 @value{GDBN} circumvents the error by ignoring this symbol information.
14756 This usually allows you to debug your program, though certain symbols
14757 are not accessible. If you encounter such a problem and feel like
14758 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
14759 on @code{complain}, then go up to the function @code{read_dbx_symtab}
14760 and examine @code{*bufp} to see the symbol.
14762 @item stub type has NULL name
14764 @value{GDBN} could not find the full definition for a struct or class.
14766 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
14767 The symbol information for a C@t{++} member function is missing some
14768 information that recent versions of the compiler should have output for
14771 @item info mismatch between compiler and debugger
14773 @value{GDBN} could not parse a type specification output by the compiler.
14778 @section GDB Data Files
14780 @cindex prefix for data files
14781 @value{GDBN} will sometimes read an auxiliary data file. These files
14782 are kept in a directory known as the @dfn{data directory}.
14784 You can set the data directory's name, and view the name @value{GDBN}
14785 is currently using.
14788 @kindex set data-directory
14789 @item set data-directory @var{directory}
14790 Set the directory which @value{GDBN} searches for auxiliary data files
14791 to @var{directory}.
14793 @kindex show data-directory
14794 @item show data-directory
14795 Show the directory @value{GDBN} searches for auxiliary data files.
14798 @cindex default data directory
14799 @cindex @samp{--with-gdb-datadir}
14800 You can set the default data directory by using the configure-time
14801 @samp{--with-gdb-datadir} option. If the data directory is inside
14802 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14803 @samp{--exec-prefix}), then the default data directory will be updated
14804 automatically if the installed @value{GDBN} is moved to a new
14808 @chapter Specifying a Debugging Target
14810 @cindex debugging target
14811 A @dfn{target} is the execution environment occupied by your program.
14813 Often, @value{GDBN} runs in the same host environment as your program;
14814 in that case, the debugging target is specified as a side effect when
14815 you use the @code{file} or @code{core} commands. When you need more
14816 flexibility---for example, running @value{GDBN} on a physically separate
14817 host, or controlling a standalone system over a serial port or a
14818 realtime system over a TCP/IP connection---you can use the @code{target}
14819 command to specify one of the target types configured for @value{GDBN}
14820 (@pxref{Target Commands, ,Commands for Managing Targets}).
14822 @cindex target architecture
14823 It is possible to build @value{GDBN} for several different @dfn{target
14824 architectures}. When @value{GDBN} is built like that, you can choose
14825 one of the available architectures with the @kbd{set architecture}
14829 @kindex set architecture
14830 @kindex show architecture
14831 @item set architecture @var{arch}
14832 This command sets the current target architecture to @var{arch}. The
14833 value of @var{arch} can be @code{"auto"}, in addition to one of the
14834 supported architectures.
14836 @item show architecture
14837 Show the current target architecture.
14839 @item set processor
14841 @kindex set processor
14842 @kindex show processor
14843 These are alias commands for, respectively, @code{set architecture}
14844 and @code{show architecture}.
14848 * Active Targets:: Active targets
14849 * Target Commands:: Commands for managing targets
14850 * Byte Order:: Choosing target byte order
14853 @node Active Targets
14854 @section Active Targets
14856 @cindex stacking targets
14857 @cindex active targets
14858 @cindex multiple targets
14860 There are three classes of targets: processes, core files, and
14861 executable files. @value{GDBN} can work concurrently on up to three
14862 active targets, one in each class. This allows you to (for example)
14863 start a process and inspect its activity without abandoning your work on
14866 For example, if you execute @samp{gdb a.out}, then the executable file
14867 @code{a.out} is the only active target. If you designate a core file as
14868 well---presumably from a prior run that crashed and coredumped---then
14869 @value{GDBN} has two active targets and uses them in tandem, looking
14870 first in the corefile target, then in the executable file, to satisfy
14871 requests for memory addresses. (Typically, these two classes of target
14872 are complementary, since core files contain only a program's
14873 read-write memory---variables and so on---plus machine status, while
14874 executable files contain only the program text and initialized data.)
14876 When you type @code{run}, your executable file becomes an active process
14877 target as well. When a process target is active, all @value{GDBN}
14878 commands requesting memory addresses refer to that target; addresses in
14879 an active core file or executable file target are obscured while the
14880 process target is active.
14882 Use the @code{core-file} and @code{exec-file} commands to select a new
14883 core file or executable target (@pxref{Files, ,Commands to Specify
14884 Files}). To specify as a target a process that is already running, use
14885 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
14888 @node Target Commands
14889 @section Commands for Managing Targets
14892 @item target @var{type} @var{parameters}
14893 Connects the @value{GDBN} host environment to a target machine or
14894 process. A target is typically a protocol for talking to debugging
14895 facilities. You use the argument @var{type} to specify the type or
14896 protocol of the target machine.
14898 Further @var{parameters} are interpreted by the target protocol, but
14899 typically include things like device names or host names to connect
14900 with, process numbers, and baud rates.
14902 The @code{target} command does not repeat if you press @key{RET} again
14903 after executing the command.
14905 @kindex help target
14907 Displays the names of all targets available. To display targets
14908 currently selected, use either @code{info target} or @code{info files}
14909 (@pxref{Files, ,Commands to Specify Files}).
14911 @item help target @var{name}
14912 Describe a particular target, including any parameters necessary to
14915 @kindex set gnutarget
14916 @item set gnutarget @var{args}
14917 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
14918 knows whether it is reading an @dfn{executable},
14919 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
14920 with the @code{set gnutarget} command. Unlike most @code{target} commands,
14921 with @code{gnutarget} the @code{target} refers to a program, not a machine.
14924 @emph{Warning:} To specify a file format with @code{set gnutarget},
14925 you must know the actual BFD name.
14929 @xref{Files, , Commands to Specify Files}.
14931 @kindex show gnutarget
14932 @item show gnutarget
14933 Use the @code{show gnutarget} command to display what file format
14934 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
14935 @value{GDBN} will determine the file format for each file automatically,
14936 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
14939 @cindex common targets
14940 Here are some common targets (available, or not, depending on the GDB
14945 @item target exec @var{program}
14946 @cindex executable file target
14947 An executable file. @samp{target exec @var{program}} is the same as
14948 @samp{exec-file @var{program}}.
14950 @item target core @var{filename}
14951 @cindex core dump file target
14952 A core dump file. @samp{target core @var{filename}} is the same as
14953 @samp{core-file @var{filename}}.
14955 @item target remote @var{medium}
14956 @cindex remote target
14957 A remote system connected to @value{GDBN} via a serial line or network
14958 connection. This command tells @value{GDBN} to use its own remote
14959 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
14961 For example, if you have a board connected to @file{/dev/ttya} on the
14962 machine running @value{GDBN}, you could say:
14965 target remote /dev/ttya
14968 @code{target remote} supports the @code{load} command. This is only
14969 useful if you have some other way of getting the stub to the target
14970 system, and you can put it somewhere in memory where it won't get
14971 clobbered by the download.
14973 @item target sim @r{[}@var{simargs}@r{]} @dots{}
14974 @cindex built-in simulator target
14975 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
14983 works; however, you cannot assume that a specific memory map, device
14984 drivers, or even basic I/O is available, although some simulators do
14985 provide these. For info about any processor-specific simulator details,
14986 see the appropriate section in @ref{Embedded Processors, ,Embedded
14991 Some configurations may include these targets as well:
14995 @item target nrom @var{dev}
14996 @cindex NetROM ROM emulator target
14997 NetROM ROM emulator. This target only supports downloading.
15001 Different targets are available on different configurations of @value{GDBN};
15002 your configuration may have more or fewer targets.
15004 Many remote targets require you to download the executable's code once
15005 you've successfully established a connection. You may wish to control
15006 various aspects of this process.
15011 @kindex set hash@r{, for remote monitors}
15012 @cindex hash mark while downloading
15013 This command controls whether a hash mark @samp{#} is displayed while
15014 downloading a file to the remote monitor. If on, a hash mark is
15015 displayed after each S-record is successfully downloaded to the
15019 @kindex show hash@r{, for remote monitors}
15020 Show the current status of displaying the hash mark.
15022 @item set debug monitor
15023 @kindex set debug monitor
15024 @cindex display remote monitor communications
15025 Enable or disable display of communications messages between
15026 @value{GDBN} and the remote monitor.
15028 @item show debug monitor
15029 @kindex show debug monitor
15030 Show the current status of displaying communications between
15031 @value{GDBN} and the remote monitor.
15036 @kindex load @var{filename}
15037 @item load @var{filename}
15039 Depending on what remote debugging facilities are configured into
15040 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15041 is meant to make @var{filename} (an executable) available for debugging
15042 on the remote system---by downloading, or dynamic linking, for example.
15043 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15044 the @code{add-symbol-file} command.
15046 If your @value{GDBN} does not have a @code{load} command, attempting to
15047 execute it gets the error message ``@code{You can't do that when your
15048 target is @dots{}}''
15050 The file is loaded at whatever address is specified in the executable.
15051 For some object file formats, you can specify the load address when you
15052 link the program; for other formats, like a.out, the object file format
15053 specifies a fixed address.
15054 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15056 Depending on the remote side capabilities, @value{GDBN} may be able to
15057 load programs into flash memory.
15059 @code{load} does not repeat if you press @key{RET} again after using it.
15063 @section Choosing Target Byte Order
15065 @cindex choosing target byte order
15066 @cindex target byte order
15068 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15069 offer the ability to run either big-endian or little-endian byte
15070 orders. Usually the executable or symbol will include a bit to
15071 designate the endian-ness, and you will not need to worry about
15072 which to use. However, you may still find it useful to adjust
15073 @value{GDBN}'s idea of processor endian-ness manually.
15077 @item set endian big
15078 Instruct @value{GDBN} to assume the target is big-endian.
15080 @item set endian little
15081 Instruct @value{GDBN} to assume the target is little-endian.
15083 @item set endian auto
15084 Instruct @value{GDBN} to use the byte order associated with the
15088 Display @value{GDBN}'s current idea of the target byte order.
15092 Note that these commands merely adjust interpretation of symbolic
15093 data on the host, and that they have absolutely no effect on the
15097 @node Remote Debugging
15098 @chapter Debugging Remote Programs
15099 @cindex remote debugging
15101 If you are trying to debug a program running on a machine that cannot run
15102 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15103 For example, you might use remote debugging on an operating system kernel,
15104 or on a small system which does not have a general purpose operating system
15105 powerful enough to run a full-featured debugger.
15107 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15108 to make this work with particular debugging targets. In addition,
15109 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15110 but not specific to any particular target system) which you can use if you
15111 write the remote stubs---the code that runs on the remote system to
15112 communicate with @value{GDBN}.
15114 Other remote targets may be available in your
15115 configuration of @value{GDBN}; use @code{help target} to list them.
15118 * Connecting:: Connecting to a remote target
15119 * File Transfer:: Sending files to a remote system
15120 * Server:: Using the gdbserver program
15121 * Remote Configuration:: Remote configuration
15122 * Remote Stub:: Implementing a remote stub
15126 @section Connecting to a Remote Target
15128 On the @value{GDBN} host machine, you will need an unstripped copy of
15129 your program, since @value{GDBN} needs symbol and debugging information.
15130 Start up @value{GDBN} as usual, using the name of the local copy of your
15131 program as the first argument.
15133 @cindex @code{target remote}
15134 @value{GDBN} can communicate with the target over a serial line, or
15135 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15136 each case, @value{GDBN} uses the same protocol for debugging your
15137 program; only the medium carrying the debugging packets varies. The
15138 @code{target remote} command establishes a connection to the target.
15139 Its arguments indicate which medium to use:
15143 @item target remote @var{serial-device}
15144 @cindex serial line, @code{target remote}
15145 Use @var{serial-device} to communicate with the target. For example,
15146 to use a serial line connected to the device named @file{/dev/ttyb}:
15149 target remote /dev/ttyb
15152 If you're using a serial line, you may want to give @value{GDBN} the
15153 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15154 (@pxref{Remote Configuration, set remotebaud}) before the
15155 @code{target} command.
15157 @item target remote @code{@var{host}:@var{port}}
15158 @itemx target remote @code{tcp:@var{host}:@var{port}}
15159 @cindex @acronym{TCP} port, @code{target remote}
15160 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15161 The @var{host} may be either a host name or a numeric @acronym{IP}
15162 address; @var{port} must be a decimal number. The @var{host} could be
15163 the target machine itself, if it is directly connected to the net, or
15164 it might be a terminal server which in turn has a serial line to the
15167 For example, to connect to port 2828 on a terminal server named
15171 target remote manyfarms:2828
15174 If your remote target is actually running on the same machine as your
15175 debugger session (e.g.@: a simulator for your target running on the
15176 same host), you can omit the hostname. For example, to connect to
15177 port 1234 on your local machine:
15180 target remote :1234
15184 Note that the colon is still required here.
15186 @item target remote @code{udp:@var{host}:@var{port}}
15187 @cindex @acronym{UDP} port, @code{target remote}
15188 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15189 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15192 target remote udp:manyfarms:2828
15195 When using a @acronym{UDP} connection for remote debugging, you should
15196 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15197 can silently drop packets on busy or unreliable networks, which will
15198 cause havoc with your debugging session.
15200 @item target remote | @var{command}
15201 @cindex pipe, @code{target remote} to
15202 Run @var{command} in the background and communicate with it using a
15203 pipe. The @var{command} is a shell command, to be parsed and expanded
15204 by the system's command shell, @code{/bin/sh}; it should expect remote
15205 protocol packets on its standard input, and send replies on its
15206 standard output. You could use this to run a stand-alone simulator
15207 that speaks the remote debugging protocol, to make net connections
15208 using programs like @code{ssh}, or for other similar tricks.
15210 If @var{command} closes its standard output (perhaps by exiting),
15211 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15212 program has already exited, this will have no effect.)
15216 Once the connection has been established, you can use all the usual
15217 commands to examine and change data. The remote program is already
15218 running; you can use @kbd{step} and @kbd{continue}, and you do not
15219 need to use @kbd{run}.
15221 @cindex interrupting remote programs
15222 @cindex remote programs, interrupting
15223 Whenever @value{GDBN} is waiting for the remote program, if you type the
15224 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15225 program. This may or may not succeed, depending in part on the hardware
15226 and the serial drivers the remote system uses. If you type the
15227 interrupt character once again, @value{GDBN} displays this prompt:
15230 Interrupted while waiting for the program.
15231 Give up (and stop debugging it)? (y or n)
15234 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15235 (If you decide you want to try again later, you can use @samp{target
15236 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15237 goes back to waiting.
15240 @kindex detach (remote)
15242 When you have finished debugging the remote program, you can use the
15243 @code{detach} command to release it from @value{GDBN} control.
15244 Detaching from the target normally resumes its execution, but the results
15245 will depend on your particular remote stub. After the @code{detach}
15246 command, @value{GDBN} is free to connect to another target.
15250 The @code{disconnect} command behaves like @code{detach}, except that
15251 the target is generally not resumed. It will wait for @value{GDBN}
15252 (this instance or another one) to connect and continue debugging. After
15253 the @code{disconnect} command, @value{GDBN} is again free to connect to
15256 @cindex send command to remote monitor
15257 @cindex extend @value{GDBN} for remote targets
15258 @cindex add new commands for external monitor
15260 @item monitor @var{cmd}
15261 This command allows you to send arbitrary commands directly to the
15262 remote monitor. Since @value{GDBN} doesn't care about the commands it
15263 sends like this, this command is the way to extend @value{GDBN}---you
15264 can add new commands that only the external monitor will understand
15268 @node File Transfer
15269 @section Sending files to a remote system
15270 @cindex remote target, file transfer
15271 @cindex file transfer
15272 @cindex sending files to remote systems
15274 Some remote targets offer the ability to transfer files over the same
15275 connection used to communicate with @value{GDBN}. This is convenient
15276 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15277 running @code{gdbserver} over a network interface. For other targets,
15278 e.g.@: embedded devices with only a single serial port, this may be
15279 the only way to upload or download files.
15281 Not all remote targets support these commands.
15285 @item remote put @var{hostfile} @var{targetfile}
15286 Copy file @var{hostfile} from the host system (the machine running
15287 @value{GDBN}) to @var{targetfile} on the target system.
15290 @item remote get @var{targetfile} @var{hostfile}
15291 Copy file @var{targetfile} from the target system to @var{hostfile}
15292 on the host system.
15294 @kindex remote delete
15295 @item remote delete @var{targetfile}
15296 Delete @var{targetfile} from the target system.
15301 @section Using the @code{gdbserver} Program
15304 @cindex remote connection without stubs
15305 @code{gdbserver} is a control program for Unix-like systems, which
15306 allows you to connect your program with a remote @value{GDBN} via
15307 @code{target remote}---but without linking in the usual debugging stub.
15309 @code{gdbserver} is not a complete replacement for the debugging stubs,
15310 because it requires essentially the same operating-system facilities
15311 that @value{GDBN} itself does. In fact, a system that can run
15312 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15313 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15314 because it is a much smaller program than @value{GDBN} itself. It is
15315 also easier to port than all of @value{GDBN}, so you may be able to get
15316 started more quickly on a new system by using @code{gdbserver}.
15317 Finally, if you develop code for real-time systems, you may find that
15318 the tradeoffs involved in real-time operation make it more convenient to
15319 do as much development work as possible on another system, for example
15320 by cross-compiling. You can use @code{gdbserver} to make a similar
15321 choice for debugging.
15323 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15324 or a TCP connection, using the standard @value{GDBN} remote serial
15328 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15329 Do not run @code{gdbserver} connected to any public network; a
15330 @value{GDBN} connection to @code{gdbserver} provides access to the
15331 target system with the same privileges as the user running
15335 @subsection Running @code{gdbserver}
15336 @cindex arguments, to @code{gdbserver}
15338 Run @code{gdbserver} on the target system. You need a copy of the
15339 program you want to debug, including any libraries it requires.
15340 @code{gdbserver} does not need your program's symbol table, so you can
15341 strip the program if necessary to save space. @value{GDBN} on the host
15342 system does all the symbol handling.
15344 To use the server, you must tell it how to communicate with @value{GDBN};
15345 the name of your program; and the arguments for your program. The usual
15349 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15352 @var{comm} is either a device name (to use a serial line) or a TCP
15353 hostname and portnumber. For example, to debug Emacs with the argument
15354 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15358 target> gdbserver /dev/com1 emacs foo.txt
15361 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15364 To use a TCP connection instead of a serial line:
15367 target> gdbserver host:2345 emacs foo.txt
15370 The only difference from the previous example is the first argument,
15371 specifying that you are communicating with the host @value{GDBN} via
15372 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15373 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15374 (Currently, the @samp{host} part is ignored.) You can choose any number
15375 you want for the port number as long as it does not conflict with any
15376 TCP ports already in use on the target system (for example, @code{23} is
15377 reserved for @code{telnet}).@footnote{If you choose a port number that
15378 conflicts with another service, @code{gdbserver} prints an error message
15379 and exits.} You must use the same port number with the host @value{GDBN}
15380 @code{target remote} command.
15382 @subsubsection Attaching to a Running Program
15384 On some targets, @code{gdbserver} can also attach to running programs.
15385 This is accomplished via the @code{--attach} argument. The syntax is:
15388 target> gdbserver --attach @var{comm} @var{pid}
15391 @var{pid} is the process ID of a currently running process. It isn't necessary
15392 to point @code{gdbserver} at a binary for the running process.
15395 @cindex attach to a program by name
15396 You can debug processes by name instead of process ID if your target has the
15397 @code{pidof} utility:
15400 target> gdbserver --attach @var{comm} `pidof @var{program}`
15403 In case more than one copy of @var{program} is running, or @var{program}
15404 has multiple threads, most versions of @code{pidof} support the
15405 @code{-s} option to only return the first process ID.
15407 @subsubsection Multi-Process Mode for @code{gdbserver}
15408 @cindex gdbserver, multiple processes
15409 @cindex multiple processes with gdbserver
15411 When you connect to @code{gdbserver} using @code{target remote},
15412 @code{gdbserver} debugs the specified program only once. When the
15413 program exits, or you detach from it, @value{GDBN} closes the connection
15414 and @code{gdbserver} exits.
15416 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15417 enters multi-process mode. When the debugged program exits, or you
15418 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15419 though no program is running. The @code{run} and @code{attach}
15420 commands instruct @code{gdbserver} to run or attach to a new program.
15421 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15422 remote exec-file}) to select the program to run. Command line
15423 arguments are supported, except for wildcard expansion and I/O
15424 redirection (@pxref{Arguments}).
15426 To start @code{gdbserver} without supplying an initial command to run
15427 or process ID to attach, use the @option{--multi} command line option.
15428 Then you can connect using @kbd{target extended-remote} and start
15429 the program you want to debug.
15431 @code{gdbserver} does not automatically exit in multi-process mode.
15432 You can terminate it by using @code{monitor exit}
15433 (@pxref{Monitor Commands for gdbserver}).
15435 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15437 The @option{--debug} option tells @code{gdbserver} to display extra
15438 status information about the debugging process. The
15439 @option{--remote-debug} option tells @code{gdbserver} to display
15440 remote protocol debug output. These options are intended for
15441 @code{gdbserver} development and for bug reports to the developers.
15443 The @option{--wrapper} option specifies a wrapper to launch programs
15444 for debugging. The option should be followed by the name of the
15445 wrapper, then any command-line arguments to pass to the wrapper, then
15446 @kbd{--} indicating the end of the wrapper arguments.
15448 @code{gdbserver} runs the specified wrapper program with a combined
15449 command line including the wrapper arguments, then the name of the
15450 program to debug, then any arguments to the program. The wrapper
15451 runs until it executes your program, and then @value{GDBN} gains control.
15453 You can use any program that eventually calls @code{execve} with
15454 its arguments as a wrapper. Several standard Unix utilities do
15455 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15456 with @code{exec "$@@"} will also work.
15458 For example, you can use @code{env} to pass an environment variable to
15459 the debugged program, without setting the variable in @code{gdbserver}'s
15463 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15466 @subsection Connecting to @code{gdbserver}
15468 Run @value{GDBN} on the host system.
15470 First make sure you have the necessary symbol files. Load symbols for
15471 your application using the @code{file} command before you connect. Use
15472 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15473 was compiled with the correct sysroot using @code{--with-sysroot}).
15475 The symbol file and target libraries must exactly match the executable
15476 and libraries on the target, with one exception: the files on the host
15477 system should not be stripped, even if the files on the target system
15478 are. Mismatched or missing files will lead to confusing results
15479 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15480 files may also prevent @code{gdbserver} from debugging multi-threaded
15483 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15484 For TCP connections, you must start up @code{gdbserver} prior to using
15485 the @code{target remote} command. Otherwise you may get an error whose
15486 text depends on the host system, but which usually looks something like
15487 @samp{Connection refused}. Don't use the @code{load}
15488 command in @value{GDBN} when using @code{gdbserver}, since the program is
15489 already on the target.
15491 @subsection Monitor Commands for @code{gdbserver}
15492 @cindex monitor commands, for @code{gdbserver}
15493 @anchor{Monitor Commands for gdbserver}
15495 During a @value{GDBN} session using @code{gdbserver}, you can use the
15496 @code{monitor} command to send special requests to @code{gdbserver}.
15497 Here are the available commands.
15501 List the available monitor commands.
15503 @item monitor set debug 0
15504 @itemx monitor set debug 1
15505 Disable or enable general debugging messages.
15507 @item monitor set remote-debug 0
15508 @itemx monitor set remote-debug 1
15509 Disable or enable specific debugging messages associated with the remote
15510 protocol (@pxref{Remote Protocol}).
15512 @item monitor set libthread-db-search-path [PATH]
15513 @cindex gdbserver, search path for @code{libthread_db}
15514 When this command is issued, @var{path} is a colon-separated list of
15515 directories to search for @code{libthread_db} (@pxref{Threads,,set
15516 libthread-db-search-path}). If you omit @var{path},
15517 @samp{libthread-db-search-path} will be reset to an empty list.
15520 Tell gdbserver to exit immediately. This command should be followed by
15521 @code{disconnect} to close the debugging session. @code{gdbserver} will
15522 detach from any attached processes and kill any processes it created.
15523 Use @code{monitor exit} to terminate @code{gdbserver} at the end
15524 of a multi-process mode debug session.
15528 @node Remote Configuration
15529 @section Remote Configuration
15532 @kindex show remote
15533 This section documents the configuration options available when
15534 debugging remote programs. For the options related to the File I/O
15535 extensions of the remote protocol, see @ref{system,
15536 system-call-allowed}.
15539 @item set remoteaddresssize @var{bits}
15540 @cindex address size for remote targets
15541 @cindex bits in remote address
15542 Set the maximum size of address in a memory packet to the specified
15543 number of bits. @value{GDBN} will mask off the address bits above
15544 that number, when it passes addresses to the remote target. The
15545 default value is the number of bits in the target's address.
15547 @item show remoteaddresssize
15548 Show the current value of remote address size in bits.
15550 @item set remotebaud @var{n}
15551 @cindex baud rate for remote targets
15552 Set the baud rate for the remote serial I/O to @var{n} baud. The
15553 value is used to set the speed of the serial port used for debugging
15556 @item show remotebaud
15557 Show the current speed of the remote connection.
15559 @item set remotebreak
15560 @cindex interrupt remote programs
15561 @cindex BREAK signal instead of Ctrl-C
15562 @anchor{set remotebreak}
15563 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
15564 when you type @kbd{Ctrl-c} to interrupt the program running
15565 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
15566 character instead. The default is off, since most remote systems
15567 expect to see @samp{Ctrl-C} as the interrupt signal.
15569 @item show remotebreak
15570 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
15571 interrupt the remote program.
15573 @item set remoteflow on
15574 @itemx set remoteflow off
15575 @kindex set remoteflow
15576 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
15577 on the serial port used to communicate to the remote target.
15579 @item show remoteflow
15580 @kindex show remoteflow
15581 Show the current setting of hardware flow control.
15583 @item set remotelogbase @var{base}
15584 Set the base (a.k.a.@: radix) of logging serial protocol
15585 communications to @var{base}. Supported values of @var{base} are:
15586 @code{ascii}, @code{octal}, and @code{hex}. The default is
15589 @item show remotelogbase
15590 Show the current setting of the radix for logging remote serial
15593 @item set remotelogfile @var{file}
15594 @cindex record serial communications on file
15595 Record remote serial communications on the named @var{file}. The
15596 default is not to record at all.
15598 @item show remotelogfile.
15599 Show the current setting of the file name on which to record the
15600 serial communications.
15602 @item set remotetimeout @var{num}
15603 @cindex timeout for serial communications
15604 @cindex remote timeout
15605 Set the timeout limit to wait for the remote target to respond to
15606 @var{num} seconds. The default is 2 seconds.
15608 @item show remotetimeout
15609 Show the current number of seconds to wait for the remote target
15612 @cindex limit hardware breakpoints and watchpoints
15613 @cindex remote target, limit break- and watchpoints
15614 @anchor{set remote hardware-watchpoint-limit}
15615 @anchor{set remote hardware-breakpoint-limit}
15616 @item set remote hardware-watchpoint-limit @var{limit}
15617 @itemx set remote hardware-breakpoint-limit @var{limit}
15618 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15619 watchpoints. A limit of -1, the default, is treated as unlimited.
15621 @item set remote exec-file @var{filename}
15622 @itemx show remote exec-file
15623 @anchor{set remote exec-file}
15624 @cindex executable file, for remote target
15625 Select the file used for @code{run} with @code{target
15626 extended-remote}. This should be set to a filename valid on the
15627 target system. If it is not set, the target will use a default
15628 filename (e.g.@: the last program run).
15630 @item set remote interrupt-sequence
15631 @cindex interrupt remote programs
15632 @cindex select Ctrl-C, BREAK or BREAK-g
15633 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
15634 @samp{BREAK-g} as the
15635 sequence to the remote target in order to interrupt the execution.
15636 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
15637 is high level of serial line for some certain time.
15638 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
15639 It is @code{BREAK} signal followed by character @code{g}.
15641 @item show interrupt-sequence
15642 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
15643 is sent by @value{GDBN} to interrupt the remote program.
15644 @code{BREAK-g} is BREAK signal followed by @code{g} and
15645 also known as Magic SysRq g.
15647 @item set remote interrupt-on-connect
15648 @cindex send interrupt-sequence on start
15649 Specify whether interrupt-sequence is sent to remote target when
15650 @value{GDBN} connects to it. This is mostly needed when you debug
15651 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
15652 which is known as Magic SysRq g in order to connect @value{GDBN}.
15654 @item show interrupt-on-connect
15655 Show whether interrupt-sequence is sent
15656 to remote target when @value{GDBN} connects to it.
15660 @item set tcp auto-retry on
15661 @cindex auto-retry, for remote TCP target
15662 Enable auto-retry for remote TCP connections. This is useful if the remote
15663 debugging agent is launched in parallel with @value{GDBN}; there is a race
15664 condition because the agent may not become ready to accept the connection
15665 before @value{GDBN} attempts to connect. When auto-retry is
15666 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
15667 to establish the connection using the timeout specified by
15668 @code{set tcp connect-timeout}.
15670 @item set tcp auto-retry off
15671 Do not auto-retry failed TCP connections.
15673 @item show tcp auto-retry
15674 Show the current auto-retry setting.
15676 @item set tcp connect-timeout @var{seconds}
15677 @cindex connection timeout, for remote TCP target
15678 @cindex timeout, for remote target connection
15679 Set the timeout for establishing a TCP connection to the remote target to
15680 @var{seconds}. The timeout affects both polling to retry failed connections
15681 (enabled by @code{set tcp auto-retry on}) and waiting for connections
15682 that are merely slow to complete, and represents an approximate cumulative
15685 @item show tcp connect-timeout
15686 Show the current connection timeout setting.
15689 @cindex remote packets, enabling and disabling
15690 The @value{GDBN} remote protocol autodetects the packets supported by
15691 your debugging stub. If you need to override the autodetection, you
15692 can use these commands to enable or disable individual packets. Each
15693 packet can be set to @samp{on} (the remote target supports this
15694 packet), @samp{off} (the remote target does not support this packet),
15695 or @samp{auto} (detect remote target support for this packet). They
15696 all default to @samp{auto}. For more information about each packet,
15697 see @ref{Remote Protocol}.
15699 During normal use, you should not have to use any of these commands.
15700 If you do, that may be a bug in your remote debugging stub, or a bug
15701 in @value{GDBN}. You may want to report the problem to the
15702 @value{GDBN} developers.
15704 For each packet @var{name}, the command to enable or disable the
15705 packet is @code{set remote @var{name}-packet}. The available settings
15708 @multitable @columnfractions 0.28 0.32 0.25
15711 @tab Related Features
15713 @item @code{fetch-register}
15715 @tab @code{info registers}
15717 @item @code{set-register}
15721 @item @code{binary-download}
15723 @tab @code{load}, @code{set}
15725 @item @code{read-aux-vector}
15726 @tab @code{qXfer:auxv:read}
15727 @tab @code{info auxv}
15729 @item @code{symbol-lookup}
15730 @tab @code{qSymbol}
15731 @tab Detecting multiple threads
15733 @item @code{attach}
15734 @tab @code{vAttach}
15737 @item @code{verbose-resume}
15739 @tab Stepping or resuming multiple threads
15745 @item @code{software-breakpoint}
15749 @item @code{hardware-breakpoint}
15753 @item @code{write-watchpoint}
15757 @item @code{read-watchpoint}
15761 @item @code{access-watchpoint}
15765 @item @code{target-features}
15766 @tab @code{qXfer:features:read}
15767 @tab @code{set architecture}
15769 @item @code{library-info}
15770 @tab @code{qXfer:libraries:read}
15771 @tab @code{info sharedlibrary}
15773 @item @code{memory-map}
15774 @tab @code{qXfer:memory-map:read}
15775 @tab @code{info mem}
15777 @item @code{read-spu-object}
15778 @tab @code{qXfer:spu:read}
15779 @tab @code{info spu}
15781 @item @code{write-spu-object}
15782 @tab @code{qXfer:spu:write}
15783 @tab @code{info spu}
15785 @item @code{read-siginfo-object}
15786 @tab @code{qXfer:siginfo:read}
15787 @tab @code{print $_siginfo}
15789 @item @code{write-siginfo-object}
15790 @tab @code{qXfer:siginfo:write}
15791 @tab @code{set $_siginfo}
15793 @item @code{threads}
15794 @tab @code{qXfer:threads:read}
15795 @tab @code{info threads}
15797 @item @code{get-thread-local-@*storage-address}
15798 @tab @code{qGetTLSAddr}
15799 @tab Displaying @code{__thread} variables
15801 @item @code{get-thread-information-block-address}
15802 @tab @code{qGetTIBAddr}
15803 @tab Display MS-Windows Thread Information Block.
15805 @item @code{search-memory}
15806 @tab @code{qSearch:memory}
15809 @item @code{supported-packets}
15810 @tab @code{qSupported}
15811 @tab Remote communications parameters
15813 @item @code{pass-signals}
15814 @tab @code{QPassSignals}
15815 @tab @code{handle @var{signal}}
15817 @item @code{hostio-close-packet}
15818 @tab @code{vFile:close}
15819 @tab @code{remote get}, @code{remote put}
15821 @item @code{hostio-open-packet}
15822 @tab @code{vFile:open}
15823 @tab @code{remote get}, @code{remote put}
15825 @item @code{hostio-pread-packet}
15826 @tab @code{vFile:pread}
15827 @tab @code{remote get}, @code{remote put}
15829 @item @code{hostio-pwrite-packet}
15830 @tab @code{vFile:pwrite}
15831 @tab @code{remote get}, @code{remote put}
15833 @item @code{hostio-unlink-packet}
15834 @tab @code{vFile:unlink}
15835 @tab @code{remote delete}
15837 @item @code{noack-packet}
15838 @tab @code{QStartNoAckMode}
15839 @tab Packet acknowledgment
15841 @item @code{osdata}
15842 @tab @code{qXfer:osdata:read}
15843 @tab @code{info os}
15845 @item @code{query-attached}
15846 @tab @code{qAttached}
15847 @tab Querying remote process attach state.
15851 @section Implementing a Remote Stub
15853 @cindex debugging stub, example
15854 @cindex remote stub, example
15855 @cindex stub example, remote debugging
15856 The stub files provided with @value{GDBN} implement the target side of the
15857 communication protocol, and the @value{GDBN} side is implemented in the
15858 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
15859 these subroutines to communicate, and ignore the details. (If you're
15860 implementing your own stub file, you can still ignore the details: start
15861 with one of the existing stub files. @file{sparc-stub.c} is the best
15862 organized, and therefore the easiest to read.)
15864 @cindex remote serial debugging, overview
15865 To debug a program running on another machine (the debugging
15866 @dfn{target} machine), you must first arrange for all the usual
15867 prerequisites for the program to run by itself. For example, for a C
15872 A startup routine to set up the C runtime environment; these usually
15873 have a name like @file{crt0}. The startup routine may be supplied by
15874 your hardware supplier, or you may have to write your own.
15877 A C subroutine library to support your program's
15878 subroutine calls, notably managing input and output.
15881 A way of getting your program to the other machine---for example, a
15882 download program. These are often supplied by the hardware
15883 manufacturer, but you may have to write your own from hardware
15887 The next step is to arrange for your program to use a serial port to
15888 communicate with the machine where @value{GDBN} is running (the @dfn{host}
15889 machine). In general terms, the scheme looks like this:
15893 @value{GDBN} already understands how to use this protocol; when everything
15894 else is set up, you can simply use the @samp{target remote} command
15895 (@pxref{Targets,,Specifying a Debugging Target}).
15897 @item On the target,
15898 you must link with your program a few special-purpose subroutines that
15899 implement the @value{GDBN} remote serial protocol. The file containing these
15900 subroutines is called a @dfn{debugging stub}.
15902 On certain remote targets, you can use an auxiliary program
15903 @code{gdbserver} instead of linking a stub into your program.
15904 @xref{Server,,Using the @code{gdbserver} Program}, for details.
15907 The debugging stub is specific to the architecture of the remote
15908 machine; for example, use @file{sparc-stub.c} to debug programs on
15911 @cindex remote serial stub list
15912 These working remote stubs are distributed with @value{GDBN}:
15917 @cindex @file{i386-stub.c}
15920 For Intel 386 and compatible architectures.
15923 @cindex @file{m68k-stub.c}
15924 @cindex Motorola 680x0
15926 For Motorola 680x0 architectures.
15929 @cindex @file{sh-stub.c}
15932 For Renesas SH architectures.
15935 @cindex @file{sparc-stub.c}
15937 For @sc{sparc} architectures.
15939 @item sparcl-stub.c
15940 @cindex @file{sparcl-stub.c}
15943 For Fujitsu @sc{sparclite} architectures.
15947 The @file{README} file in the @value{GDBN} distribution may list other
15948 recently added stubs.
15951 * Stub Contents:: What the stub can do for you
15952 * Bootstrapping:: What you must do for the stub
15953 * Debug Session:: Putting it all together
15956 @node Stub Contents
15957 @subsection What the Stub Can Do for You
15959 @cindex remote serial stub
15960 The debugging stub for your architecture supplies these three
15964 @item set_debug_traps
15965 @findex set_debug_traps
15966 @cindex remote serial stub, initialization
15967 This routine arranges for @code{handle_exception} to run when your
15968 program stops. You must call this subroutine explicitly near the
15969 beginning of your program.
15971 @item handle_exception
15972 @findex handle_exception
15973 @cindex remote serial stub, main routine
15974 This is the central workhorse, but your program never calls it
15975 explicitly---the setup code arranges for @code{handle_exception} to
15976 run when a trap is triggered.
15978 @code{handle_exception} takes control when your program stops during
15979 execution (for example, on a breakpoint), and mediates communications
15980 with @value{GDBN} on the host machine. This is where the communications
15981 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
15982 representative on the target machine. It begins by sending summary
15983 information on the state of your program, then continues to execute,
15984 retrieving and transmitting any information @value{GDBN} needs, until you
15985 execute a @value{GDBN} command that makes your program resume; at that point,
15986 @code{handle_exception} returns control to your own code on the target
15990 @cindex @code{breakpoint} subroutine, remote
15991 Use this auxiliary subroutine to make your program contain a
15992 breakpoint. Depending on the particular situation, this may be the only
15993 way for @value{GDBN} to get control. For instance, if your target
15994 machine has some sort of interrupt button, you won't need to call this;
15995 pressing the interrupt button transfers control to
15996 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
15997 simply receiving characters on the serial port may also trigger a trap;
15998 again, in that situation, you don't need to call @code{breakpoint} from
15999 your own program---simply running @samp{target remote} from the host
16000 @value{GDBN} session gets control.
16002 Call @code{breakpoint} if none of these is true, or if you simply want
16003 to make certain your program stops at a predetermined point for the
16004 start of your debugging session.
16007 @node Bootstrapping
16008 @subsection What You Must Do for the Stub
16010 @cindex remote stub, support routines
16011 The debugging stubs that come with @value{GDBN} are set up for a particular
16012 chip architecture, but they have no information about the rest of your
16013 debugging target machine.
16015 First of all you need to tell the stub how to communicate with the
16019 @item int getDebugChar()
16020 @findex getDebugChar
16021 Write this subroutine to read a single character from the serial port.
16022 It may be identical to @code{getchar} for your target system; a
16023 different name is used to allow you to distinguish the two if you wish.
16025 @item void putDebugChar(int)
16026 @findex putDebugChar
16027 Write this subroutine to write a single character to the serial port.
16028 It may be identical to @code{putchar} for your target system; a
16029 different name is used to allow you to distinguish the two if you wish.
16032 @cindex control C, and remote debugging
16033 @cindex interrupting remote targets
16034 If you want @value{GDBN} to be able to stop your program while it is
16035 running, you need to use an interrupt-driven serial driver, and arrange
16036 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16037 character). That is the character which @value{GDBN} uses to tell the
16038 remote system to stop.
16040 Getting the debugging target to return the proper status to @value{GDBN}
16041 probably requires changes to the standard stub; one quick and dirty way
16042 is to just execute a breakpoint instruction (the ``dirty'' part is that
16043 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16045 Other routines you need to supply are:
16048 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16049 @findex exceptionHandler
16050 Write this function to install @var{exception_address} in the exception
16051 handling tables. You need to do this because the stub does not have any
16052 way of knowing what the exception handling tables on your target system
16053 are like (for example, the processor's table might be in @sc{rom},
16054 containing entries which point to a table in @sc{ram}).
16055 @var{exception_number} is the exception number which should be changed;
16056 its meaning is architecture-dependent (for example, different numbers
16057 might represent divide by zero, misaligned access, etc). When this
16058 exception occurs, control should be transferred directly to
16059 @var{exception_address}, and the processor state (stack, registers,
16060 and so on) should be just as it is when a processor exception occurs. So if
16061 you want to use a jump instruction to reach @var{exception_address}, it
16062 should be a simple jump, not a jump to subroutine.
16064 For the 386, @var{exception_address} should be installed as an interrupt
16065 gate so that interrupts are masked while the handler runs. The gate
16066 should be at privilege level 0 (the most privileged level). The
16067 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16068 help from @code{exceptionHandler}.
16070 @item void flush_i_cache()
16071 @findex flush_i_cache
16072 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16073 instruction cache, if any, on your target machine. If there is no
16074 instruction cache, this subroutine may be a no-op.
16076 On target machines that have instruction caches, @value{GDBN} requires this
16077 function to make certain that the state of your program is stable.
16081 You must also make sure this library routine is available:
16084 @item void *memset(void *, int, int)
16086 This is the standard library function @code{memset} that sets an area of
16087 memory to a known value. If you have one of the free versions of
16088 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16089 either obtain it from your hardware manufacturer, or write your own.
16092 If you do not use the GNU C compiler, you may need other standard
16093 library subroutines as well; this varies from one stub to another,
16094 but in general the stubs are likely to use any of the common library
16095 subroutines which @code{@value{NGCC}} generates as inline code.
16098 @node Debug Session
16099 @subsection Putting it All Together
16101 @cindex remote serial debugging summary
16102 In summary, when your program is ready to debug, you must follow these
16107 Make sure you have defined the supporting low-level routines
16108 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16110 @code{getDebugChar}, @code{putDebugChar},
16111 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16115 Insert these lines near the top of your program:
16123 For the 680x0 stub only, you need to provide a variable called
16124 @code{exceptionHook}. Normally you just use:
16127 void (*exceptionHook)() = 0;
16131 but if before calling @code{set_debug_traps}, you set it to point to a
16132 function in your program, that function is called when
16133 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16134 error). The function indicated by @code{exceptionHook} is called with
16135 one parameter: an @code{int} which is the exception number.
16138 Compile and link together: your program, the @value{GDBN} debugging stub for
16139 your target architecture, and the supporting subroutines.
16142 Make sure you have a serial connection between your target machine and
16143 the @value{GDBN} host, and identify the serial port on the host.
16146 @c The "remote" target now provides a `load' command, so we should
16147 @c document that. FIXME.
16148 Download your program to your target machine (or get it there by
16149 whatever means the manufacturer provides), and start it.
16152 Start @value{GDBN} on the host, and connect to the target
16153 (@pxref{Connecting,,Connecting to a Remote Target}).
16157 @node Configurations
16158 @chapter Configuration-Specific Information
16160 While nearly all @value{GDBN} commands are available for all native and
16161 cross versions of the debugger, there are some exceptions. This chapter
16162 describes things that are only available in certain configurations.
16164 There are three major categories of configurations: native
16165 configurations, where the host and target are the same, embedded
16166 operating system configurations, which are usually the same for several
16167 different processor architectures, and bare embedded processors, which
16168 are quite different from each other.
16173 * Embedded Processors::
16180 This section describes details specific to particular native
16185 * BSD libkvm Interface:: Debugging BSD kernel memory images
16186 * SVR4 Process Information:: SVR4 process information
16187 * DJGPP Native:: Features specific to the DJGPP port
16188 * Cygwin Native:: Features specific to the Cygwin port
16189 * Hurd Native:: Features specific to @sc{gnu} Hurd
16190 * Neutrino:: Features specific to QNX Neutrino
16191 * Darwin:: Features specific to Darwin
16197 On HP-UX systems, if you refer to a function or variable name that
16198 begins with a dollar sign, @value{GDBN} searches for a user or system
16199 name first, before it searches for a convenience variable.
16202 @node BSD libkvm Interface
16203 @subsection BSD libkvm Interface
16206 @cindex kernel memory image
16207 @cindex kernel crash dump
16209 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16210 interface that provides a uniform interface for accessing kernel virtual
16211 memory images, including live systems and crash dumps. @value{GDBN}
16212 uses this interface to allow you to debug live kernels and kernel crash
16213 dumps on many native BSD configurations. This is implemented as a
16214 special @code{kvm} debugging target. For debugging a live system, load
16215 the currently running kernel into @value{GDBN} and connect to the
16219 (@value{GDBP}) @b{target kvm}
16222 For debugging crash dumps, provide the file name of the crash dump as an
16226 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16229 Once connected to the @code{kvm} target, the following commands are
16235 Set current context from the @dfn{Process Control Block} (PCB) address.
16238 Set current context from proc address. This command isn't available on
16239 modern FreeBSD systems.
16242 @node SVR4 Process Information
16243 @subsection SVR4 Process Information
16245 @cindex examine process image
16246 @cindex process info via @file{/proc}
16248 Many versions of SVR4 and compatible systems provide a facility called
16249 @samp{/proc} that can be used to examine the image of a running
16250 process using file-system subroutines. If @value{GDBN} is configured
16251 for an operating system with this facility, the command @code{info
16252 proc} is available to report information about the process running
16253 your program, or about any process running on your system. @code{info
16254 proc} works only on SVR4 systems that include the @code{procfs} code.
16255 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16256 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16262 @itemx info proc @var{process-id}
16263 Summarize available information about any running process. If a
16264 process ID is specified by @var{process-id}, display information about
16265 that process; otherwise display information about the program being
16266 debugged. The summary includes the debugged process ID, the command
16267 line used to invoke it, its current working directory, and its
16268 executable file's absolute file name.
16270 On some systems, @var{process-id} can be of the form
16271 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16272 within a process. If the optional @var{pid} part is missing, it means
16273 a thread from the process being debugged (the leading @samp{/} still
16274 needs to be present, or else @value{GDBN} will interpret the number as
16275 a process ID rather than a thread ID).
16277 @item info proc mappings
16278 @cindex memory address space mappings
16279 Report the memory address space ranges accessible in the program, with
16280 information on whether the process has read, write, or execute access
16281 rights to each range. On @sc{gnu}/Linux systems, each memory range
16282 includes the object file which is mapped to that range, instead of the
16283 memory access rights to that range.
16285 @item info proc stat
16286 @itemx info proc status
16287 @cindex process detailed status information
16288 These subcommands are specific to @sc{gnu}/Linux systems. They show
16289 the process-related information, including the user ID and group ID;
16290 how many threads are there in the process; its virtual memory usage;
16291 the signals that are pending, blocked, and ignored; its TTY; its
16292 consumption of system and user time; its stack size; its @samp{nice}
16293 value; etc. For more information, see the @samp{proc} man page
16294 (type @kbd{man 5 proc} from your shell prompt).
16296 @item info proc all
16297 Show all the information about the process described under all of the
16298 above @code{info proc} subcommands.
16301 @comment These sub-options of 'info proc' were not included when
16302 @comment procfs.c was re-written. Keep their descriptions around
16303 @comment against the day when someone finds the time to put them back in.
16304 @kindex info proc times
16305 @item info proc times
16306 Starting time, user CPU time, and system CPU time for your program and
16309 @kindex info proc id
16311 Report on the process IDs related to your program: its own process ID,
16312 the ID of its parent, the process group ID, and the session ID.
16315 @item set procfs-trace
16316 @kindex set procfs-trace
16317 @cindex @code{procfs} API calls
16318 This command enables and disables tracing of @code{procfs} API calls.
16320 @item show procfs-trace
16321 @kindex show procfs-trace
16322 Show the current state of @code{procfs} API call tracing.
16324 @item set procfs-file @var{file}
16325 @kindex set procfs-file
16326 Tell @value{GDBN} to write @code{procfs} API trace to the named
16327 @var{file}. @value{GDBN} appends the trace info to the previous
16328 contents of the file. The default is to display the trace on the
16331 @item show procfs-file
16332 @kindex show procfs-file
16333 Show the file to which @code{procfs} API trace is written.
16335 @item proc-trace-entry
16336 @itemx proc-trace-exit
16337 @itemx proc-untrace-entry
16338 @itemx proc-untrace-exit
16339 @kindex proc-trace-entry
16340 @kindex proc-trace-exit
16341 @kindex proc-untrace-entry
16342 @kindex proc-untrace-exit
16343 These commands enable and disable tracing of entries into and exits
16344 from the @code{syscall} interface.
16347 @kindex info pidlist
16348 @cindex process list, QNX Neutrino
16349 For QNX Neutrino only, this command displays the list of all the
16350 processes and all the threads within each process.
16353 @kindex info meminfo
16354 @cindex mapinfo list, QNX Neutrino
16355 For QNX Neutrino only, this command displays the list of all mapinfos.
16359 @subsection Features for Debugging @sc{djgpp} Programs
16360 @cindex @sc{djgpp} debugging
16361 @cindex native @sc{djgpp} debugging
16362 @cindex MS-DOS-specific commands
16365 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16366 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16367 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
16368 top of real-mode DOS systems and their emulations.
16370 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
16371 defines a few commands specific to the @sc{djgpp} port. This
16372 subsection describes those commands.
16377 This is a prefix of @sc{djgpp}-specific commands which print
16378 information about the target system and important OS structures.
16381 @cindex MS-DOS system info
16382 @cindex free memory information (MS-DOS)
16383 @item info dos sysinfo
16384 This command displays assorted information about the underlying
16385 platform: the CPU type and features, the OS version and flavor, the
16386 DPMI version, and the available conventional and DPMI memory.
16391 @cindex segment descriptor tables
16392 @cindex descriptor tables display
16394 @itemx info dos ldt
16395 @itemx info dos idt
16396 These 3 commands display entries from, respectively, Global, Local,
16397 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
16398 tables are data structures which store a descriptor for each segment
16399 that is currently in use. The segment's selector is an index into a
16400 descriptor table; the table entry for that index holds the
16401 descriptor's base address and limit, and its attributes and access
16404 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
16405 segment (used for both data and the stack), and a DOS segment (which
16406 allows access to DOS/BIOS data structures and absolute addresses in
16407 conventional memory). However, the DPMI host will usually define
16408 additional segments in order to support the DPMI environment.
16410 @cindex garbled pointers
16411 These commands allow to display entries from the descriptor tables.
16412 Without an argument, all entries from the specified table are
16413 displayed. An argument, which should be an integer expression, means
16414 display a single entry whose index is given by the argument. For
16415 example, here's a convenient way to display information about the
16416 debugged program's data segment:
16419 @exdent @code{(@value{GDBP}) info dos ldt $ds}
16420 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
16424 This comes in handy when you want to see whether a pointer is outside
16425 the data segment's limit (i.e.@: @dfn{garbled}).
16427 @cindex page tables display (MS-DOS)
16429 @itemx info dos pte
16430 These two commands display entries from, respectively, the Page
16431 Directory and the Page Tables. Page Directories and Page Tables are
16432 data structures which control how virtual memory addresses are mapped
16433 into physical addresses. A Page Table includes an entry for every
16434 page of memory that is mapped into the program's address space; there
16435 may be several Page Tables, each one holding up to 4096 entries. A
16436 Page Directory has up to 4096 entries, one each for every Page Table
16437 that is currently in use.
16439 Without an argument, @kbd{info dos pde} displays the entire Page
16440 Directory, and @kbd{info dos pte} displays all the entries in all of
16441 the Page Tables. An argument, an integer expression, given to the
16442 @kbd{info dos pde} command means display only that entry from the Page
16443 Directory table. An argument given to the @kbd{info dos pte} command
16444 means display entries from a single Page Table, the one pointed to by
16445 the specified entry in the Page Directory.
16447 @cindex direct memory access (DMA) on MS-DOS
16448 These commands are useful when your program uses @dfn{DMA} (Direct
16449 Memory Access), which needs physical addresses to program the DMA
16452 These commands are supported only with some DPMI servers.
16454 @cindex physical address from linear address
16455 @item info dos address-pte @var{addr}
16456 This command displays the Page Table entry for a specified linear
16457 address. The argument @var{addr} is a linear address which should
16458 already have the appropriate segment's base address added to it,
16459 because this command accepts addresses which may belong to @emph{any}
16460 segment. For example, here's how to display the Page Table entry for
16461 the page where a variable @code{i} is stored:
16464 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
16465 @exdent @code{Page Table entry for address 0x11a00d30:}
16466 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
16470 This says that @code{i} is stored at offset @code{0xd30} from the page
16471 whose physical base address is @code{0x02698000}, and shows all the
16472 attributes of that page.
16474 Note that you must cast the addresses of variables to a @code{char *},
16475 since otherwise the value of @code{__djgpp_base_address}, the base
16476 address of all variables and functions in a @sc{djgpp} program, will
16477 be added using the rules of C pointer arithmetics: if @code{i} is
16478 declared an @code{int}, @value{GDBN} will add 4 times the value of
16479 @code{__djgpp_base_address} to the address of @code{i}.
16481 Here's another example, it displays the Page Table entry for the
16485 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
16486 @exdent @code{Page Table entry for address 0x29110:}
16487 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
16491 (The @code{+ 3} offset is because the transfer buffer's address is the
16492 3rd member of the @code{_go32_info_block} structure.) The output
16493 clearly shows that this DPMI server maps the addresses in conventional
16494 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
16495 linear (@code{0x29110}) addresses are identical.
16497 This command is supported only with some DPMI servers.
16500 @cindex DOS serial data link, remote debugging
16501 In addition to native debugging, the DJGPP port supports remote
16502 debugging via a serial data link. The following commands are specific
16503 to remote serial debugging in the DJGPP port of @value{GDBN}.
16506 @kindex set com1base
16507 @kindex set com1irq
16508 @kindex set com2base
16509 @kindex set com2irq
16510 @kindex set com3base
16511 @kindex set com3irq
16512 @kindex set com4base
16513 @kindex set com4irq
16514 @item set com1base @var{addr}
16515 This command sets the base I/O port address of the @file{COM1} serial
16518 @item set com1irq @var{irq}
16519 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
16520 for the @file{COM1} serial port.
16522 There are similar commands @samp{set com2base}, @samp{set com3irq},
16523 etc.@: for setting the port address and the @code{IRQ} lines for the
16526 @kindex show com1base
16527 @kindex show com1irq
16528 @kindex show com2base
16529 @kindex show com2irq
16530 @kindex show com3base
16531 @kindex show com3irq
16532 @kindex show com4base
16533 @kindex show com4irq
16534 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
16535 display the current settings of the base address and the @code{IRQ}
16536 lines used by the COM ports.
16539 @kindex info serial
16540 @cindex DOS serial port status
16541 This command prints the status of the 4 DOS serial ports. For each
16542 port, it prints whether it's active or not, its I/O base address and
16543 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
16544 counts of various errors encountered so far.
16548 @node Cygwin Native
16549 @subsection Features for Debugging MS Windows PE Executables
16550 @cindex MS Windows debugging
16551 @cindex native Cygwin debugging
16552 @cindex Cygwin-specific commands
16554 @value{GDBN} supports native debugging of MS Windows programs, including
16555 DLLs with and without symbolic debugging information.
16557 @cindex Ctrl-BREAK, MS-Windows
16558 @cindex interrupt debuggee on MS-Windows
16559 MS-Windows programs that call @code{SetConsoleMode} to switch off the
16560 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
16561 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
16562 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
16563 sequence, which can be used to interrupt the debuggee even if it
16566 There are various additional Cygwin-specific commands, described in
16567 this section. Working with DLLs that have no debugging symbols is
16568 described in @ref{Non-debug DLL Symbols}.
16573 This is a prefix of MS Windows-specific commands which print
16574 information about the target system and important OS structures.
16576 @item info w32 selector
16577 This command displays information returned by
16578 the Win32 API @code{GetThreadSelectorEntry} function.
16579 It takes an optional argument that is evaluated to
16580 a long value to give the information about this given selector.
16581 Without argument, this command displays information
16582 about the six segment registers.
16584 @item info w32 thread-information-block
16585 This command displays thread specific information stored in the
16586 Thread Information Block (readable on the X86 CPU family using @code{$fs}
16587 selector for 32-bit programs and @code{$gs} for 64-bit programs).
16591 This is a Cygwin-specific alias of @code{info shared}.
16593 @kindex dll-symbols
16595 This command loads symbols from a dll similarly to
16596 add-sym command but without the need to specify a base address.
16598 @kindex set cygwin-exceptions
16599 @cindex debugging the Cygwin DLL
16600 @cindex Cygwin DLL, debugging
16601 @item set cygwin-exceptions @var{mode}
16602 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
16603 happen inside the Cygwin DLL. If @var{mode} is @code{off},
16604 @value{GDBN} will delay recognition of exceptions, and may ignore some
16605 exceptions which seem to be caused by internal Cygwin DLL
16606 ``bookkeeping''. This option is meant primarily for debugging the
16607 Cygwin DLL itself; the default value is @code{off} to avoid annoying
16608 @value{GDBN} users with false @code{SIGSEGV} signals.
16610 @kindex show cygwin-exceptions
16611 @item show cygwin-exceptions
16612 Displays whether @value{GDBN} will break on exceptions that happen
16613 inside the Cygwin DLL itself.
16615 @kindex set new-console
16616 @item set new-console @var{mode}
16617 If @var{mode} is @code{on} the debuggee will
16618 be started in a new console on next start.
16619 If @var{mode} is @code{off}, the debuggee will
16620 be started in the same console as the debugger.
16622 @kindex show new-console
16623 @item show new-console
16624 Displays whether a new console is used
16625 when the debuggee is started.
16627 @kindex set new-group
16628 @item set new-group @var{mode}
16629 This boolean value controls whether the debuggee should
16630 start a new group or stay in the same group as the debugger.
16631 This affects the way the Windows OS handles
16634 @kindex show new-group
16635 @item show new-group
16636 Displays current value of new-group boolean.
16638 @kindex set debugevents
16639 @item set debugevents
16640 This boolean value adds debug output concerning kernel events related
16641 to the debuggee seen by the debugger. This includes events that
16642 signal thread and process creation and exit, DLL loading and
16643 unloading, console interrupts, and debugging messages produced by the
16644 Windows @code{OutputDebugString} API call.
16646 @kindex set debugexec
16647 @item set debugexec
16648 This boolean value adds debug output concerning execute events
16649 (such as resume thread) seen by the debugger.
16651 @kindex set debugexceptions
16652 @item set debugexceptions
16653 This boolean value adds debug output concerning exceptions in the
16654 debuggee seen by the debugger.
16656 @kindex set debugmemory
16657 @item set debugmemory
16658 This boolean value adds debug output concerning debuggee memory reads
16659 and writes by the debugger.
16663 This boolean values specifies whether the debuggee is called
16664 via a shell or directly (default value is on).
16668 Displays if the debuggee will be started with a shell.
16673 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
16676 @node Non-debug DLL Symbols
16677 @subsubsection Support for DLLs without Debugging Symbols
16678 @cindex DLLs with no debugging symbols
16679 @cindex Minimal symbols and DLLs
16681 Very often on windows, some of the DLLs that your program relies on do
16682 not include symbolic debugging information (for example,
16683 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
16684 symbols in a DLL, it relies on the minimal amount of symbolic
16685 information contained in the DLL's export table. This section
16686 describes working with such symbols, known internally to @value{GDBN} as
16687 ``minimal symbols''.
16689 Note that before the debugged program has started execution, no DLLs
16690 will have been loaded. The easiest way around this problem is simply to
16691 start the program --- either by setting a breakpoint or letting the
16692 program run once to completion. It is also possible to force
16693 @value{GDBN} to load a particular DLL before starting the executable ---
16694 see the shared library information in @ref{Files}, or the
16695 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
16696 explicitly loading symbols from a DLL with no debugging information will
16697 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
16698 which may adversely affect symbol lookup performance.
16700 @subsubsection DLL Name Prefixes
16702 In keeping with the naming conventions used by the Microsoft debugging
16703 tools, DLL export symbols are made available with a prefix based on the
16704 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
16705 also entered into the symbol table, so @code{CreateFileA} is often
16706 sufficient. In some cases there will be name clashes within a program
16707 (particularly if the executable itself includes full debugging symbols)
16708 necessitating the use of the fully qualified name when referring to the
16709 contents of the DLL. Use single-quotes around the name to avoid the
16710 exclamation mark (``!'') being interpreted as a language operator.
16712 Note that the internal name of the DLL may be all upper-case, even
16713 though the file name of the DLL is lower-case, or vice-versa. Since
16714 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
16715 some confusion. If in doubt, try the @code{info functions} and
16716 @code{info variables} commands or even @code{maint print msymbols}
16717 (@pxref{Symbols}). Here's an example:
16720 (@value{GDBP}) info function CreateFileA
16721 All functions matching regular expression "CreateFileA":
16723 Non-debugging symbols:
16724 0x77e885f4 CreateFileA
16725 0x77e885f4 KERNEL32!CreateFileA
16729 (@value{GDBP}) info function !
16730 All functions matching regular expression "!":
16732 Non-debugging symbols:
16733 0x6100114c cygwin1!__assert
16734 0x61004034 cygwin1!_dll_crt0@@0
16735 0x61004240 cygwin1!dll_crt0(per_process *)
16739 @subsubsection Working with Minimal Symbols
16741 Symbols extracted from a DLL's export table do not contain very much
16742 type information. All that @value{GDBN} can do is guess whether a symbol
16743 refers to a function or variable depending on the linker section that
16744 contains the symbol. Also note that the actual contents of the memory
16745 contained in a DLL are not available unless the program is running. This
16746 means that you cannot examine the contents of a variable or disassemble
16747 a function within a DLL without a running program.
16749 Variables are generally treated as pointers and dereferenced
16750 automatically. For this reason, it is often necessary to prefix a
16751 variable name with the address-of operator (``&'') and provide explicit
16752 type information in the command. Here's an example of the type of
16756 (@value{GDBP}) print 'cygwin1!__argv'
16761 (@value{GDBP}) x 'cygwin1!__argv'
16762 0x10021610: "\230y\""
16765 And two possible solutions:
16768 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
16769 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
16773 (@value{GDBP}) x/2x &'cygwin1!__argv'
16774 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
16775 (@value{GDBP}) x/x 0x10021608
16776 0x10021608: 0x0022fd98
16777 (@value{GDBP}) x/s 0x0022fd98
16778 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
16781 Setting a break point within a DLL is possible even before the program
16782 starts execution. However, under these circumstances, @value{GDBN} can't
16783 examine the initial instructions of the function in order to skip the
16784 function's frame set-up code. You can work around this by using ``*&''
16785 to set the breakpoint at a raw memory address:
16788 (@value{GDBP}) break *&'python22!PyOS_Readline'
16789 Breakpoint 1 at 0x1e04eff0
16792 The author of these extensions is not entirely convinced that setting a
16793 break point within a shared DLL like @file{kernel32.dll} is completely
16797 @subsection Commands Specific to @sc{gnu} Hurd Systems
16798 @cindex @sc{gnu} Hurd debugging
16800 This subsection describes @value{GDBN} commands specific to the
16801 @sc{gnu} Hurd native debugging.
16806 @kindex set signals@r{, Hurd command}
16807 @kindex set sigs@r{, Hurd command}
16808 This command toggles the state of inferior signal interception by
16809 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
16810 affected by this command. @code{sigs} is a shorthand alias for
16815 @kindex show signals@r{, Hurd command}
16816 @kindex show sigs@r{, Hurd command}
16817 Show the current state of intercepting inferior's signals.
16819 @item set signal-thread
16820 @itemx set sigthread
16821 @kindex set signal-thread
16822 @kindex set sigthread
16823 This command tells @value{GDBN} which thread is the @code{libc} signal
16824 thread. That thread is run when a signal is delivered to a running
16825 process. @code{set sigthread} is the shorthand alias of @code{set
16828 @item show signal-thread
16829 @itemx show sigthread
16830 @kindex show signal-thread
16831 @kindex show sigthread
16832 These two commands show which thread will run when the inferior is
16833 delivered a signal.
16836 @kindex set stopped@r{, Hurd command}
16837 This commands tells @value{GDBN} that the inferior process is stopped,
16838 as with the @code{SIGSTOP} signal. The stopped process can be
16839 continued by delivering a signal to it.
16842 @kindex show stopped@r{, Hurd command}
16843 This command shows whether @value{GDBN} thinks the debuggee is
16846 @item set exceptions
16847 @kindex set exceptions@r{, Hurd command}
16848 Use this command to turn off trapping of exceptions in the inferior.
16849 When exception trapping is off, neither breakpoints nor
16850 single-stepping will work. To restore the default, set exception
16853 @item show exceptions
16854 @kindex show exceptions@r{, Hurd command}
16855 Show the current state of trapping exceptions in the inferior.
16857 @item set task pause
16858 @kindex set task@r{, Hurd commands}
16859 @cindex task attributes (@sc{gnu} Hurd)
16860 @cindex pause current task (@sc{gnu} Hurd)
16861 This command toggles task suspension when @value{GDBN} has control.
16862 Setting it to on takes effect immediately, and the task is suspended
16863 whenever @value{GDBN} gets control. Setting it to off will take
16864 effect the next time the inferior is continued. If this option is set
16865 to off, you can use @code{set thread default pause on} or @code{set
16866 thread pause on} (see below) to pause individual threads.
16868 @item show task pause
16869 @kindex show task@r{, Hurd commands}
16870 Show the current state of task suspension.
16872 @item set task detach-suspend-count
16873 @cindex task suspend count
16874 @cindex detach from task, @sc{gnu} Hurd
16875 This command sets the suspend count the task will be left with when
16876 @value{GDBN} detaches from it.
16878 @item show task detach-suspend-count
16879 Show the suspend count the task will be left with when detaching.
16881 @item set task exception-port
16882 @itemx set task excp
16883 @cindex task exception port, @sc{gnu} Hurd
16884 This command sets the task exception port to which @value{GDBN} will
16885 forward exceptions. The argument should be the value of the @dfn{send
16886 rights} of the task. @code{set task excp} is a shorthand alias.
16888 @item set noninvasive
16889 @cindex noninvasive task options
16890 This command switches @value{GDBN} to a mode that is the least
16891 invasive as far as interfering with the inferior is concerned. This
16892 is the same as using @code{set task pause}, @code{set exceptions}, and
16893 @code{set signals} to values opposite to the defaults.
16895 @item info send-rights
16896 @itemx info receive-rights
16897 @itemx info port-rights
16898 @itemx info port-sets
16899 @itemx info dead-names
16902 @cindex send rights, @sc{gnu} Hurd
16903 @cindex receive rights, @sc{gnu} Hurd
16904 @cindex port rights, @sc{gnu} Hurd
16905 @cindex port sets, @sc{gnu} Hurd
16906 @cindex dead names, @sc{gnu} Hurd
16907 These commands display information about, respectively, send rights,
16908 receive rights, port rights, port sets, and dead names of a task.
16909 There are also shorthand aliases: @code{info ports} for @code{info
16910 port-rights} and @code{info psets} for @code{info port-sets}.
16912 @item set thread pause
16913 @kindex set thread@r{, Hurd command}
16914 @cindex thread properties, @sc{gnu} Hurd
16915 @cindex pause current thread (@sc{gnu} Hurd)
16916 This command toggles current thread suspension when @value{GDBN} has
16917 control. Setting it to on takes effect immediately, and the current
16918 thread is suspended whenever @value{GDBN} gets control. Setting it to
16919 off will take effect the next time the inferior is continued.
16920 Normally, this command has no effect, since when @value{GDBN} has
16921 control, the whole task is suspended. However, if you used @code{set
16922 task pause off} (see above), this command comes in handy to suspend
16923 only the current thread.
16925 @item show thread pause
16926 @kindex show thread@r{, Hurd command}
16927 This command shows the state of current thread suspension.
16929 @item set thread run
16930 This command sets whether the current thread is allowed to run.
16932 @item show thread run
16933 Show whether the current thread is allowed to run.
16935 @item set thread detach-suspend-count
16936 @cindex thread suspend count, @sc{gnu} Hurd
16937 @cindex detach from thread, @sc{gnu} Hurd
16938 This command sets the suspend count @value{GDBN} will leave on a
16939 thread when detaching. This number is relative to the suspend count
16940 found by @value{GDBN} when it notices the thread; use @code{set thread
16941 takeover-suspend-count} to force it to an absolute value.
16943 @item show thread detach-suspend-count
16944 Show the suspend count @value{GDBN} will leave on the thread when
16947 @item set thread exception-port
16948 @itemx set thread excp
16949 Set the thread exception port to which to forward exceptions. This
16950 overrides the port set by @code{set task exception-port} (see above).
16951 @code{set thread excp} is the shorthand alias.
16953 @item set thread takeover-suspend-count
16954 Normally, @value{GDBN}'s thread suspend counts are relative to the
16955 value @value{GDBN} finds when it notices each thread. This command
16956 changes the suspend counts to be absolute instead.
16958 @item set thread default
16959 @itemx show thread default
16960 @cindex thread default settings, @sc{gnu} Hurd
16961 Each of the above @code{set thread} commands has a @code{set thread
16962 default} counterpart (e.g., @code{set thread default pause}, @code{set
16963 thread default exception-port}, etc.). The @code{thread default}
16964 variety of commands sets the default thread properties for all
16965 threads; you can then change the properties of individual threads with
16966 the non-default commands.
16971 @subsection QNX Neutrino
16972 @cindex QNX Neutrino
16974 @value{GDBN} provides the following commands specific to the QNX
16978 @item set debug nto-debug
16979 @kindex set debug nto-debug
16980 When set to on, enables debugging messages specific to the QNX
16983 @item show debug nto-debug
16984 @kindex show debug nto-debug
16985 Show the current state of QNX Neutrino messages.
16992 @value{GDBN} provides the following commands specific to the Darwin target:
16995 @item set debug darwin @var{num}
16996 @kindex set debug darwin
16997 When set to a non zero value, enables debugging messages specific to
16998 the Darwin support. Higher values produce more verbose output.
17000 @item show debug darwin
17001 @kindex show debug darwin
17002 Show the current state of Darwin messages.
17004 @item set debug mach-o @var{num}
17005 @kindex set debug mach-o
17006 When set to a non zero value, enables debugging messages while
17007 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17008 file format used on Darwin for object and executable files.) Higher
17009 values produce more verbose output. This is a command to diagnose
17010 problems internal to @value{GDBN} and should not be needed in normal
17013 @item show debug mach-o
17014 @kindex show debug mach-o
17015 Show the current state of Mach-O file messages.
17017 @item set mach-exceptions on
17018 @itemx set mach-exceptions off
17019 @kindex set mach-exceptions
17020 On Darwin, faults are first reported as a Mach exception and are then
17021 mapped to a Posix signal. Use this command to turn on trapping of
17022 Mach exceptions in the inferior. This might be sometimes useful to
17023 better understand the cause of a fault. The default is off.
17025 @item show mach-exceptions
17026 @kindex show mach-exceptions
17027 Show the current state of exceptions trapping.
17032 @section Embedded Operating Systems
17034 This section describes configurations involving the debugging of
17035 embedded operating systems that are available for several different
17039 * VxWorks:: Using @value{GDBN} with VxWorks
17042 @value{GDBN} includes the ability to debug programs running on
17043 various real-time operating systems.
17046 @subsection Using @value{GDBN} with VxWorks
17052 @kindex target vxworks
17053 @item target vxworks @var{machinename}
17054 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17055 is the target system's machine name or IP address.
17059 On VxWorks, @code{load} links @var{filename} dynamically on the
17060 current target system as well as adding its symbols in @value{GDBN}.
17062 @value{GDBN} enables developers to spawn and debug tasks running on networked
17063 VxWorks targets from a Unix host. Already-running tasks spawned from
17064 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17065 both the Unix host and on the VxWorks target. The program
17066 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17067 installed with the name @code{vxgdb}, to distinguish it from a
17068 @value{GDBN} for debugging programs on the host itself.)
17071 @item VxWorks-timeout @var{args}
17072 @kindex vxworks-timeout
17073 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17074 This option is set by the user, and @var{args} represents the number of
17075 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17076 your VxWorks target is a slow software simulator or is on the far side
17077 of a thin network line.
17080 The following information on connecting to VxWorks was current when
17081 this manual was produced; newer releases of VxWorks may use revised
17084 @findex INCLUDE_RDB
17085 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17086 to include the remote debugging interface routines in the VxWorks
17087 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17088 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17089 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17090 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17091 information on configuring and remaking VxWorks, see the manufacturer's
17093 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17095 Once you have included @file{rdb.a} in your VxWorks system image and set
17096 your Unix execution search path to find @value{GDBN}, you are ready to
17097 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17098 @code{vxgdb}, depending on your installation).
17100 @value{GDBN} comes up showing the prompt:
17107 * VxWorks Connection:: Connecting to VxWorks
17108 * VxWorks Download:: VxWorks download
17109 * VxWorks Attach:: Running tasks
17112 @node VxWorks Connection
17113 @subsubsection Connecting to VxWorks
17115 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17116 network. To connect to a target whose host name is ``@code{tt}'', type:
17119 (vxgdb) target vxworks tt
17123 @value{GDBN} displays messages like these:
17126 Attaching remote machine across net...
17131 @value{GDBN} then attempts to read the symbol tables of any object modules
17132 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17133 these files by searching the directories listed in the command search
17134 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17135 to find an object file, it displays a message such as:
17138 prog.o: No such file or directory.
17141 When this happens, add the appropriate directory to the search path with
17142 the @value{GDBN} command @code{path}, and execute the @code{target}
17145 @node VxWorks Download
17146 @subsubsection VxWorks Download
17148 @cindex download to VxWorks
17149 If you have connected to the VxWorks target and you want to debug an
17150 object that has not yet been loaded, you can use the @value{GDBN}
17151 @code{load} command to download a file from Unix to VxWorks
17152 incrementally. The object file given as an argument to the @code{load}
17153 command is actually opened twice: first by the VxWorks target in order
17154 to download the code, then by @value{GDBN} in order to read the symbol
17155 table. This can lead to problems if the current working directories on
17156 the two systems differ. If both systems have NFS mounted the same
17157 filesystems, you can avoid these problems by using absolute paths.
17158 Otherwise, it is simplest to set the working directory on both systems
17159 to the directory in which the object file resides, and then to reference
17160 the file by its name, without any path. For instance, a program
17161 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17162 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17163 program, type this on VxWorks:
17166 -> cd "@var{vxpath}/vw/demo/rdb"
17170 Then, in @value{GDBN}, type:
17173 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17174 (vxgdb) load prog.o
17177 @value{GDBN} displays a response similar to this:
17180 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17183 You can also use the @code{load} command to reload an object module
17184 after editing and recompiling the corresponding source file. Note that
17185 this makes @value{GDBN} delete all currently-defined breakpoints,
17186 auto-displays, and convenience variables, and to clear the value
17187 history. (This is necessary in order to preserve the integrity of
17188 debugger's data structures that reference the target system's symbol
17191 @node VxWorks Attach
17192 @subsubsection Running Tasks
17194 @cindex running VxWorks tasks
17195 You can also attach to an existing task using the @code{attach} command as
17199 (vxgdb) attach @var{task}
17203 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17204 or suspended when you attach to it. Running tasks are suspended at
17205 the time of attachment.
17207 @node Embedded Processors
17208 @section Embedded Processors
17210 This section goes into details specific to particular embedded
17213 @cindex send command to simulator
17214 Whenever a specific embedded processor has a simulator, @value{GDBN}
17215 allows to send an arbitrary command to the simulator.
17218 @item sim @var{command}
17219 @kindex sim@r{, a command}
17220 Send an arbitrary @var{command} string to the simulator. Consult the
17221 documentation for the specific simulator in use for information about
17222 acceptable commands.
17228 * M32R/D:: Renesas M32R/D
17229 * M68K:: Motorola M68K
17230 * MicroBlaze:: Xilinx MicroBlaze
17231 * MIPS Embedded:: MIPS Embedded
17232 * OpenRISC 1000:: OpenRisc 1000
17233 * PA:: HP PA Embedded
17234 * PowerPC Embedded:: PowerPC Embedded
17235 * Sparclet:: Tsqware Sparclet
17236 * Sparclite:: Fujitsu Sparclite
17237 * Z8000:: Zilog Z8000
17240 * Super-H:: Renesas Super-H
17249 @item target rdi @var{dev}
17250 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17251 use this target to communicate with both boards running the Angel
17252 monitor, or with the EmbeddedICE JTAG debug device.
17255 @item target rdp @var{dev}
17260 @value{GDBN} provides the following ARM-specific commands:
17263 @item set arm disassembler
17265 This commands selects from a list of disassembly styles. The
17266 @code{"std"} style is the standard style.
17268 @item show arm disassembler
17270 Show the current disassembly style.
17272 @item set arm apcs32
17273 @cindex ARM 32-bit mode
17274 This command toggles ARM operation mode between 32-bit and 26-bit.
17276 @item show arm apcs32
17277 Display the current usage of the ARM 32-bit mode.
17279 @item set arm fpu @var{fputype}
17280 This command sets the ARM floating-point unit (FPU) type. The
17281 argument @var{fputype} can be one of these:
17285 Determine the FPU type by querying the OS ABI.
17287 Software FPU, with mixed-endian doubles on little-endian ARM
17290 GCC-compiled FPA co-processor.
17292 Software FPU with pure-endian doubles.
17298 Show the current type of the FPU.
17301 This command forces @value{GDBN} to use the specified ABI.
17304 Show the currently used ABI.
17306 @item set arm fallback-mode (arm|thumb|auto)
17307 @value{GDBN} uses the symbol table, when available, to determine
17308 whether instructions are ARM or Thumb. This command controls
17309 @value{GDBN}'s default behavior when the symbol table is not
17310 available. The default is @samp{auto}, which causes @value{GDBN} to
17311 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17314 @item show arm fallback-mode
17315 Show the current fallback instruction mode.
17317 @item set arm force-mode (arm|thumb|auto)
17318 This command overrides use of the symbol table to determine whether
17319 instructions are ARM or Thumb. The default is @samp{auto}, which
17320 causes @value{GDBN} to use the symbol table and then the setting
17321 of @samp{set arm fallback-mode}.
17323 @item show arm force-mode
17324 Show the current forced instruction mode.
17326 @item set debug arm
17327 Toggle whether to display ARM-specific debugging messages from the ARM
17328 target support subsystem.
17330 @item show debug arm
17331 Show whether ARM-specific debugging messages are enabled.
17334 The following commands are available when an ARM target is debugged
17335 using the RDI interface:
17338 @item rdilogfile @r{[}@var{file}@r{]}
17340 @cindex ADP (Angel Debugger Protocol) logging
17341 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17342 With an argument, sets the log file to the specified @var{file}. With
17343 no argument, show the current log file name. The default log file is
17346 @item rdilogenable @r{[}@var{arg}@r{]}
17347 @kindex rdilogenable
17348 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17349 enables logging, with an argument 0 or @code{"no"} disables it. With
17350 no arguments displays the current setting. When logging is enabled,
17351 ADP packets exchanged between @value{GDBN} and the RDI target device
17352 are logged to a file.
17354 @item set rdiromatzero
17355 @kindex set rdiromatzero
17356 @cindex ROM at zero address, RDI
17357 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17358 vector catching is disabled, so that zero address can be used. If off
17359 (the default), vector catching is enabled. For this command to take
17360 effect, it needs to be invoked prior to the @code{target rdi} command.
17362 @item show rdiromatzero
17363 @kindex show rdiromatzero
17364 Show the current setting of ROM at zero address.
17366 @item set rdiheartbeat
17367 @kindex set rdiheartbeat
17368 @cindex RDI heartbeat
17369 Enable or disable RDI heartbeat packets. It is not recommended to
17370 turn on this option, since it confuses ARM and EPI JTAG interface, as
17371 well as the Angel monitor.
17373 @item show rdiheartbeat
17374 @kindex show rdiheartbeat
17375 Show the setting of RDI heartbeat packets.
17379 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17380 The @value{GDBN} ARM simulator accepts the following optional arguments.
17383 @item --swi-support=@var{type}
17384 Tell the simulator which SWI interfaces to support.
17385 @var{type} may be a comma separated list of the following values.
17386 The default value is @code{all}.
17399 @subsection Renesas M32R/D and M32R/SDI
17402 @kindex target m32r
17403 @item target m32r @var{dev}
17404 Renesas M32R/D ROM monitor.
17406 @kindex target m32rsdi
17407 @item target m32rsdi @var{dev}
17408 Renesas M32R SDI server, connected via parallel port to the board.
17411 The following @value{GDBN} commands are specific to the M32R monitor:
17414 @item set download-path @var{path}
17415 @kindex set download-path
17416 @cindex find downloadable @sc{srec} files (M32R)
17417 Set the default path for finding downloadable @sc{srec} files.
17419 @item show download-path
17420 @kindex show download-path
17421 Show the default path for downloadable @sc{srec} files.
17423 @item set board-address @var{addr}
17424 @kindex set board-address
17425 @cindex M32-EVA target board address
17426 Set the IP address for the M32R-EVA target board.
17428 @item show board-address
17429 @kindex show board-address
17430 Show the current IP address of the target board.
17432 @item set server-address @var{addr}
17433 @kindex set server-address
17434 @cindex download server address (M32R)
17435 Set the IP address for the download server, which is the @value{GDBN}'s
17438 @item show server-address
17439 @kindex show server-address
17440 Display the IP address of the download server.
17442 @item upload @r{[}@var{file}@r{]}
17443 @kindex upload@r{, M32R}
17444 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
17445 upload capability. If no @var{file} argument is given, the current
17446 executable file is uploaded.
17448 @item tload @r{[}@var{file}@r{]}
17449 @kindex tload@r{, M32R}
17450 Test the @code{upload} command.
17453 The following commands are available for M32R/SDI:
17458 @cindex reset SDI connection, M32R
17459 This command resets the SDI connection.
17463 This command shows the SDI connection status.
17466 @kindex debug_chaos
17467 @cindex M32R/Chaos debugging
17468 Instructs the remote that M32R/Chaos debugging is to be used.
17470 @item use_debug_dma
17471 @kindex use_debug_dma
17472 Instructs the remote to use the DEBUG_DMA method of accessing memory.
17475 @kindex use_mon_code
17476 Instructs the remote to use the MON_CODE method of accessing memory.
17479 @kindex use_ib_break
17480 Instructs the remote to set breakpoints by IB break.
17482 @item use_dbt_break
17483 @kindex use_dbt_break
17484 Instructs the remote to set breakpoints by DBT.
17490 The Motorola m68k configuration includes ColdFire support, and a
17491 target command for the following ROM monitor.
17495 @kindex target dbug
17496 @item target dbug @var{dev}
17497 dBUG ROM monitor for Motorola ColdFire.
17502 @subsection MicroBlaze
17503 @cindex Xilinx MicroBlaze
17504 @cindex XMD, Xilinx Microprocessor Debugger
17506 The MicroBlaze is a soft-core processor supported on various Xilinx
17507 FPGAs, such as Spartan or Virtex series. Boards with these processors
17508 usually have JTAG ports which connect to a host system running the Xilinx
17509 Embedded Development Kit (EDK) or Software Development Kit (SDK).
17510 This host system is used to download the configuration bitstream to
17511 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
17512 communicates with the target board using the JTAG interface and
17513 presents a @code{gdbserver} interface to the board. By default
17514 @code{xmd} uses port @code{1234}. (While it is possible to change
17515 this default port, it requires the use of undocumented @code{xmd}
17516 commands. Contact Xilinx support if you need to do this.)
17518 Use these GDB commands to connect to the MicroBlaze target processor.
17521 @item target remote :1234
17522 Use this command to connect to the target if you are running @value{GDBN}
17523 on the same system as @code{xmd}.
17525 @item target remote @var{xmd-host}:1234
17526 Use this command to connect to the target if it is connected to @code{xmd}
17527 running on a different system named @var{xmd-host}.
17530 Use this command to download a program to the MicroBlaze target.
17532 @item set debug microblaze @var{n}
17533 Enable MicroBlaze-specific debugging messages if non-zero.
17535 @item show debug microblaze @var{n}
17536 Show MicroBlaze-specific debugging level.
17539 @node MIPS Embedded
17540 @subsection MIPS Embedded
17542 @cindex MIPS boards
17543 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
17544 MIPS board attached to a serial line. This is available when
17545 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
17548 Use these @value{GDBN} commands to specify the connection to your target board:
17551 @item target mips @var{port}
17552 @kindex target mips @var{port}
17553 To run a program on the board, start up @code{@value{GDBP}} with the
17554 name of your program as the argument. To connect to the board, use the
17555 command @samp{target mips @var{port}}, where @var{port} is the name of
17556 the serial port connected to the board. If the program has not already
17557 been downloaded to the board, you may use the @code{load} command to
17558 download it. You can then use all the usual @value{GDBN} commands.
17560 For example, this sequence connects to the target board through a serial
17561 port, and loads and runs a program called @var{prog} through the
17565 host$ @value{GDBP} @var{prog}
17566 @value{GDBN} is free software and @dots{}
17567 (@value{GDBP}) target mips /dev/ttyb
17568 (@value{GDBP}) load @var{prog}
17572 @item target mips @var{hostname}:@var{portnumber}
17573 On some @value{GDBN} host configurations, you can specify a TCP
17574 connection (for instance, to a serial line managed by a terminal
17575 concentrator) instead of a serial port, using the syntax
17576 @samp{@var{hostname}:@var{portnumber}}.
17578 @item target pmon @var{port}
17579 @kindex target pmon @var{port}
17582 @item target ddb @var{port}
17583 @kindex target ddb @var{port}
17584 NEC's DDB variant of PMON for Vr4300.
17586 @item target lsi @var{port}
17587 @kindex target lsi @var{port}
17588 LSI variant of PMON.
17590 @kindex target r3900
17591 @item target r3900 @var{dev}
17592 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
17594 @kindex target array
17595 @item target array @var{dev}
17596 Array Tech LSI33K RAID controller board.
17602 @value{GDBN} also supports these special commands for MIPS targets:
17605 @item set mipsfpu double
17606 @itemx set mipsfpu single
17607 @itemx set mipsfpu none
17608 @itemx set mipsfpu auto
17609 @itemx show mipsfpu
17610 @kindex set mipsfpu
17611 @kindex show mipsfpu
17612 @cindex MIPS remote floating point
17613 @cindex floating point, MIPS remote
17614 If your target board does not support the MIPS floating point
17615 coprocessor, you should use the command @samp{set mipsfpu none} (if you
17616 need this, you may wish to put the command in your @value{GDBN} init
17617 file). This tells @value{GDBN} how to find the return value of
17618 functions which return floating point values. It also allows
17619 @value{GDBN} to avoid saving the floating point registers when calling
17620 functions on the board. If you are using a floating point coprocessor
17621 with only single precision floating point support, as on the @sc{r4650}
17622 processor, use the command @samp{set mipsfpu single}. The default
17623 double precision floating point coprocessor may be selected using
17624 @samp{set mipsfpu double}.
17626 In previous versions the only choices were double precision or no
17627 floating point, so @samp{set mipsfpu on} will select double precision
17628 and @samp{set mipsfpu off} will select no floating point.
17630 As usual, you can inquire about the @code{mipsfpu} variable with
17631 @samp{show mipsfpu}.
17633 @item set timeout @var{seconds}
17634 @itemx set retransmit-timeout @var{seconds}
17635 @itemx show timeout
17636 @itemx show retransmit-timeout
17637 @cindex @code{timeout}, MIPS protocol
17638 @cindex @code{retransmit-timeout}, MIPS protocol
17639 @kindex set timeout
17640 @kindex show timeout
17641 @kindex set retransmit-timeout
17642 @kindex show retransmit-timeout
17643 You can control the timeout used while waiting for a packet, in the MIPS
17644 remote protocol, with the @code{set timeout @var{seconds}} command. The
17645 default is 5 seconds. Similarly, you can control the timeout used while
17646 waiting for an acknowledgment of a packet with the @code{set
17647 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
17648 You can inspect both values with @code{show timeout} and @code{show
17649 retransmit-timeout}. (These commands are @emph{only} available when
17650 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
17652 The timeout set by @code{set timeout} does not apply when @value{GDBN}
17653 is waiting for your program to stop. In that case, @value{GDBN} waits
17654 forever because it has no way of knowing how long the program is going
17655 to run before stopping.
17657 @item set syn-garbage-limit @var{num}
17658 @kindex set syn-garbage-limit@r{, MIPS remote}
17659 @cindex synchronize with remote MIPS target
17660 Limit the maximum number of characters @value{GDBN} should ignore when
17661 it tries to synchronize with the remote target. The default is 10
17662 characters. Setting the limit to -1 means there's no limit.
17664 @item show syn-garbage-limit
17665 @kindex show syn-garbage-limit@r{, MIPS remote}
17666 Show the current limit on the number of characters to ignore when
17667 trying to synchronize with the remote system.
17669 @item set monitor-prompt @var{prompt}
17670 @kindex set monitor-prompt@r{, MIPS remote}
17671 @cindex remote monitor prompt
17672 Tell @value{GDBN} to expect the specified @var{prompt} string from the
17673 remote monitor. The default depends on the target:
17683 @item show monitor-prompt
17684 @kindex show monitor-prompt@r{, MIPS remote}
17685 Show the current strings @value{GDBN} expects as the prompt from the
17688 @item set monitor-warnings
17689 @kindex set monitor-warnings@r{, MIPS remote}
17690 Enable or disable monitor warnings about hardware breakpoints. This
17691 has effect only for the @code{lsi} target. When on, @value{GDBN} will
17692 display warning messages whose codes are returned by the @code{lsi}
17693 PMON monitor for breakpoint commands.
17695 @item show monitor-warnings
17696 @kindex show monitor-warnings@r{, MIPS remote}
17697 Show the current setting of printing monitor warnings.
17699 @item pmon @var{command}
17700 @kindex pmon@r{, MIPS remote}
17701 @cindex send PMON command
17702 This command allows sending an arbitrary @var{command} string to the
17703 monitor. The monitor must be in debug mode for this to work.
17706 @node OpenRISC 1000
17707 @subsection OpenRISC 1000
17708 @cindex OpenRISC 1000
17710 @cindex or1k boards
17711 See OR1k Architecture document (@uref{www.opencores.org}) for more information
17712 about platform and commands.
17716 @kindex target jtag
17717 @item target jtag jtag://@var{host}:@var{port}
17719 Connects to remote JTAG server.
17720 JTAG remote server can be either an or1ksim or JTAG server,
17721 connected via parallel port to the board.
17723 Example: @code{target jtag jtag://localhost:9999}
17726 @item or1ksim @var{command}
17727 If connected to @code{or1ksim} OpenRISC 1000 Architectural
17728 Simulator, proprietary commands can be executed.
17730 @kindex info or1k spr
17731 @item info or1k spr
17732 Displays spr groups.
17734 @item info or1k spr @var{group}
17735 @itemx info or1k spr @var{groupno}
17736 Displays register names in selected group.
17738 @item info or1k spr @var{group} @var{register}
17739 @itemx info or1k spr @var{register}
17740 @itemx info or1k spr @var{groupno} @var{registerno}
17741 @itemx info or1k spr @var{registerno}
17742 Shows information about specified spr register.
17745 @item spr @var{group} @var{register} @var{value}
17746 @itemx spr @var{register @var{value}}
17747 @itemx spr @var{groupno} @var{registerno @var{value}}
17748 @itemx spr @var{registerno @var{value}}
17749 Writes @var{value} to specified spr register.
17752 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
17753 It is very similar to @value{GDBN} trace, except it does not interfere with normal
17754 program execution and is thus much faster. Hardware breakpoints/watchpoint
17755 triggers can be set using:
17758 Load effective address/data
17760 Store effective address/data
17762 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
17767 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
17768 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
17770 @code{htrace} commands:
17771 @cindex OpenRISC 1000 htrace
17774 @item hwatch @var{conditional}
17775 Set hardware watchpoint on combination of Load/Store Effective Address(es)
17776 or Data. For example:
17778 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17780 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17784 Display information about current HW trace configuration.
17786 @item htrace trigger @var{conditional}
17787 Set starting criteria for HW trace.
17789 @item htrace qualifier @var{conditional}
17790 Set acquisition qualifier for HW trace.
17792 @item htrace stop @var{conditional}
17793 Set HW trace stopping criteria.
17795 @item htrace record [@var{data}]*
17796 Selects the data to be recorded, when qualifier is met and HW trace was
17799 @item htrace enable
17800 @itemx htrace disable
17801 Enables/disables the HW trace.
17803 @item htrace rewind [@var{filename}]
17804 Clears currently recorded trace data.
17806 If filename is specified, new trace file is made and any newly collected data
17807 will be written there.
17809 @item htrace print [@var{start} [@var{len}]]
17810 Prints trace buffer, using current record configuration.
17812 @item htrace mode continuous
17813 Set continuous trace mode.
17815 @item htrace mode suspend
17816 Set suspend trace mode.
17820 @node PowerPC Embedded
17821 @subsection PowerPC Embedded
17823 @value{GDBN} provides the following PowerPC-specific commands:
17826 @kindex set powerpc
17827 @item set powerpc soft-float
17828 @itemx show powerpc soft-float
17829 Force @value{GDBN} to use (or not use) a software floating point calling
17830 convention. By default, @value{GDBN} selects the calling convention based
17831 on the selected architecture and the provided executable file.
17833 @item set powerpc vector-abi
17834 @itemx show powerpc vector-abi
17835 Force @value{GDBN} to use the specified calling convention for vector
17836 arguments and return values. The valid options are @samp{auto};
17837 @samp{generic}, to avoid vector registers even if they are present;
17838 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
17839 registers. By default, @value{GDBN} selects the calling convention
17840 based on the selected architecture and the provided executable file.
17842 @kindex target dink32
17843 @item target dink32 @var{dev}
17844 DINK32 ROM monitor.
17846 @kindex target ppcbug
17847 @item target ppcbug @var{dev}
17848 @kindex target ppcbug1
17849 @item target ppcbug1 @var{dev}
17850 PPCBUG ROM monitor for PowerPC.
17853 @item target sds @var{dev}
17854 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
17857 @cindex SDS protocol
17858 The following commands specific to the SDS protocol are supported
17862 @item set sdstimeout @var{nsec}
17863 @kindex set sdstimeout
17864 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
17865 default is 2 seconds.
17867 @item show sdstimeout
17868 @kindex show sdstimeout
17869 Show the current value of the SDS timeout.
17871 @item sds @var{command}
17872 @kindex sds@r{, a command}
17873 Send the specified @var{command} string to the SDS monitor.
17878 @subsection HP PA Embedded
17882 @kindex target op50n
17883 @item target op50n @var{dev}
17884 OP50N monitor, running on an OKI HPPA board.
17886 @kindex target w89k
17887 @item target w89k @var{dev}
17888 W89K monitor, running on a Winbond HPPA board.
17893 @subsection Tsqware Sparclet
17897 @value{GDBN} enables developers to debug tasks running on
17898 Sparclet targets from a Unix host.
17899 @value{GDBN} uses code that runs on
17900 both the Unix host and on the Sparclet target. The program
17901 @code{@value{GDBP}} is installed and executed on the Unix host.
17904 @item remotetimeout @var{args}
17905 @kindex remotetimeout
17906 @value{GDBN} supports the option @code{remotetimeout}.
17907 This option is set by the user, and @var{args} represents the number of
17908 seconds @value{GDBN} waits for responses.
17911 @cindex compiling, on Sparclet
17912 When compiling for debugging, include the options @samp{-g} to get debug
17913 information and @samp{-Ttext} to relocate the program to where you wish to
17914 load it on the target. You may also want to add the options @samp{-n} or
17915 @samp{-N} in order to reduce the size of the sections. Example:
17918 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
17921 You can use @code{objdump} to verify that the addresses are what you intended:
17924 sparclet-aout-objdump --headers --syms prog
17927 @cindex running, on Sparclet
17929 your Unix execution search path to find @value{GDBN}, you are ready to
17930 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
17931 (or @code{sparclet-aout-gdb}, depending on your installation).
17933 @value{GDBN} comes up showing the prompt:
17940 * Sparclet File:: Setting the file to debug
17941 * Sparclet Connection:: Connecting to Sparclet
17942 * Sparclet Download:: Sparclet download
17943 * Sparclet Execution:: Running and debugging
17946 @node Sparclet File
17947 @subsubsection Setting File to Debug
17949 The @value{GDBN} command @code{file} lets you choose with program to debug.
17952 (gdbslet) file prog
17956 @value{GDBN} then attempts to read the symbol table of @file{prog}.
17957 @value{GDBN} locates
17958 the file by searching the directories listed in the command search
17960 If the file was compiled with debug information (option @samp{-g}), source
17961 files will be searched as well.
17962 @value{GDBN} locates
17963 the source files by searching the directories listed in the directory search
17964 path (@pxref{Environment, ,Your Program's Environment}).
17966 to find a file, it displays a message such as:
17969 prog: No such file or directory.
17972 When this happens, add the appropriate directories to the search paths with
17973 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
17974 @code{target} command again.
17976 @node Sparclet Connection
17977 @subsubsection Connecting to Sparclet
17979 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
17980 To connect to a target on serial port ``@code{ttya}'', type:
17983 (gdbslet) target sparclet /dev/ttya
17984 Remote target sparclet connected to /dev/ttya
17985 main () at ../prog.c:3
17989 @value{GDBN} displays messages like these:
17995 @node Sparclet Download
17996 @subsubsection Sparclet Download
17998 @cindex download to Sparclet
17999 Once connected to the Sparclet target,
18000 you can use the @value{GDBN}
18001 @code{load} command to download the file from the host to the target.
18002 The file name and load offset should be given as arguments to the @code{load}
18004 Since the file format is aout, the program must be loaded to the starting
18005 address. You can use @code{objdump} to find out what this value is. The load
18006 offset is an offset which is added to the VMA (virtual memory address)
18007 of each of the file's sections.
18008 For instance, if the program
18009 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18010 and bss at 0x12010170, in @value{GDBN}, type:
18013 (gdbslet) load prog 0x12010000
18014 Loading section .text, size 0xdb0 vma 0x12010000
18017 If the code is loaded at a different address then what the program was linked
18018 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18019 to tell @value{GDBN} where to map the symbol table.
18021 @node Sparclet Execution
18022 @subsubsection Running and Debugging
18024 @cindex running and debugging Sparclet programs
18025 You can now begin debugging the task using @value{GDBN}'s execution control
18026 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18027 manual for the list of commands.
18031 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18033 Starting program: prog
18034 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18035 3 char *symarg = 0;
18037 4 char *execarg = "hello!";
18042 @subsection Fujitsu Sparclite
18046 @kindex target sparclite
18047 @item target sparclite @var{dev}
18048 Fujitsu sparclite boards, used only for the purpose of loading.
18049 You must use an additional command to debug the program.
18050 For example: target remote @var{dev} using @value{GDBN} standard
18056 @subsection Zilog Z8000
18059 @cindex simulator, Z8000
18060 @cindex Zilog Z8000 simulator
18062 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18065 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18066 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18067 segmented variant). The simulator recognizes which architecture is
18068 appropriate by inspecting the object code.
18071 @item target sim @var{args}
18073 @kindex target sim@r{, with Z8000}
18074 Debug programs on a simulated CPU. If the simulator supports setup
18075 options, specify them via @var{args}.
18079 After specifying this target, you can debug programs for the simulated
18080 CPU in the same style as programs for your host computer; use the
18081 @code{file} command to load a new program image, the @code{run} command
18082 to run your program, and so on.
18084 As well as making available all the usual machine registers
18085 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18086 additional items of information as specially named registers:
18091 Counts clock-ticks in the simulator.
18094 Counts instructions run in the simulator.
18097 Execution time in 60ths of a second.
18101 You can refer to these values in @value{GDBN} expressions with the usual
18102 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18103 conditional breakpoint that suspends only after at least 5000
18104 simulated clock ticks.
18107 @subsection Atmel AVR
18110 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18111 following AVR-specific commands:
18114 @item info io_registers
18115 @kindex info io_registers@r{, AVR}
18116 @cindex I/O registers (Atmel AVR)
18117 This command displays information about the AVR I/O registers. For
18118 each register, @value{GDBN} prints its number and value.
18125 When configured for debugging CRIS, @value{GDBN} provides the
18126 following CRIS-specific commands:
18129 @item set cris-version @var{ver}
18130 @cindex CRIS version
18131 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18132 The CRIS version affects register names and sizes. This command is useful in
18133 case autodetection of the CRIS version fails.
18135 @item show cris-version
18136 Show the current CRIS version.
18138 @item set cris-dwarf2-cfi
18139 @cindex DWARF-2 CFI and CRIS
18140 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18141 Change to @samp{off} when using @code{gcc-cris} whose version is below
18144 @item show cris-dwarf2-cfi
18145 Show the current state of using DWARF-2 CFI.
18147 @item set cris-mode @var{mode}
18149 Set the current CRIS mode to @var{mode}. It should only be changed when
18150 debugging in guru mode, in which case it should be set to
18151 @samp{guru} (the default is @samp{normal}).
18153 @item show cris-mode
18154 Show the current CRIS mode.
18158 @subsection Renesas Super-H
18161 For the Renesas Super-H processor, @value{GDBN} provides these
18166 @kindex regs@r{, Super-H}
18167 Show the values of all Super-H registers.
18169 @item set sh calling-convention @var{convention}
18170 @kindex set sh calling-convention
18171 Set the calling-convention used when calling functions from @value{GDBN}.
18172 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18173 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18174 convention. If the DWARF-2 information of the called function specifies
18175 that the function follows the Renesas calling convention, the function
18176 is called using the Renesas calling convention. If the calling convention
18177 is set to @samp{renesas}, the Renesas calling convention is always used,
18178 regardless of the DWARF-2 information. This can be used to override the
18179 default of @samp{gcc} if debug information is missing, or the compiler
18180 does not emit the DWARF-2 calling convention entry for a function.
18182 @item show sh calling-convention
18183 @kindex show sh calling-convention
18184 Show the current calling convention setting.
18189 @node Architectures
18190 @section Architectures
18192 This section describes characteristics of architectures that affect
18193 all uses of @value{GDBN} with the architecture, both native and cross.
18200 * HPPA:: HP PA architecture
18201 * SPU:: Cell Broadband Engine SPU architecture
18206 @subsection x86 Architecture-specific Issues
18209 @item set struct-convention @var{mode}
18210 @kindex set struct-convention
18211 @cindex struct return convention
18212 @cindex struct/union returned in registers
18213 Set the convention used by the inferior to return @code{struct}s and
18214 @code{union}s from functions to @var{mode}. Possible values of
18215 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18216 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18217 are returned on the stack, while @code{"reg"} means that a
18218 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18219 be returned in a register.
18221 @item show struct-convention
18222 @kindex show struct-convention
18223 Show the current setting of the convention to return @code{struct}s
18232 @kindex set rstack_high_address
18233 @cindex AMD 29K register stack
18234 @cindex register stack, AMD29K
18235 @item set rstack_high_address @var{address}
18236 On AMD 29000 family processors, registers are saved in a separate
18237 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18238 extent of this stack. Normally, @value{GDBN} just assumes that the
18239 stack is ``large enough''. This may result in @value{GDBN} referencing
18240 memory locations that do not exist. If necessary, you can get around
18241 this problem by specifying the ending address of the register stack with
18242 the @code{set rstack_high_address} command. The argument should be an
18243 address, which you probably want to precede with @samp{0x} to specify in
18246 @kindex show rstack_high_address
18247 @item show rstack_high_address
18248 Display the current limit of the register stack, on AMD 29000 family
18256 See the following section.
18261 @cindex stack on Alpha
18262 @cindex stack on MIPS
18263 @cindex Alpha stack
18265 Alpha- and MIPS-based computers use an unusual stack frame, which
18266 sometimes requires @value{GDBN} to search backward in the object code to
18267 find the beginning of a function.
18269 @cindex response time, MIPS debugging
18270 To improve response time (especially for embedded applications, where
18271 @value{GDBN} may be restricted to a slow serial line for this search)
18272 you may want to limit the size of this search, using one of these
18276 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18277 @item set heuristic-fence-post @var{limit}
18278 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18279 search for the beginning of a function. A value of @var{0} (the
18280 default) means there is no limit. However, except for @var{0}, the
18281 larger the limit the more bytes @code{heuristic-fence-post} must search
18282 and therefore the longer it takes to run. You should only need to use
18283 this command when debugging a stripped executable.
18285 @item show heuristic-fence-post
18286 Display the current limit.
18290 These commands are available @emph{only} when @value{GDBN} is configured
18291 for debugging programs on Alpha or MIPS processors.
18293 Several MIPS-specific commands are available when debugging MIPS
18297 @item set mips abi @var{arg}
18298 @kindex set mips abi
18299 @cindex set ABI for MIPS
18300 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18301 values of @var{arg} are:
18305 The default ABI associated with the current binary (this is the
18316 @item show mips abi
18317 @kindex show mips abi
18318 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18321 @itemx show mipsfpu
18322 @xref{MIPS Embedded, set mipsfpu}.
18324 @item set mips mask-address @var{arg}
18325 @kindex set mips mask-address
18326 @cindex MIPS addresses, masking
18327 This command determines whether the most-significant 32 bits of 64-bit
18328 MIPS addresses are masked off. The argument @var{arg} can be
18329 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18330 setting, which lets @value{GDBN} determine the correct value.
18332 @item show mips mask-address
18333 @kindex show mips mask-address
18334 Show whether the upper 32 bits of MIPS addresses are masked off or
18337 @item set remote-mips64-transfers-32bit-regs
18338 @kindex set remote-mips64-transfers-32bit-regs
18339 This command controls compatibility with 64-bit MIPS targets that
18340 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18341 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18342 and 64 bits for other registers, set this option to @samp{on}.
18344 @item show remote-mips64-transfers-32bit-regs
18345 @kindex show remote-mips64-transfers-32bit-regs
18346 Show the current setting of compatibility with older MIPS 64 targets.
18348 @item set debug mips
18349 @kindex set debug mips
18350 This command turns on and off debugging messages for the MIPS-specific
18351 target code in @value{GDBN}.
18353 @item show debug mips
18354 @kindex show debug mips
18355 Show the current setting of MIPS debugging messages.
18361 @cindex HPPA support
18363 When @value{GDBN} is debugging the HP PA architecture, it provides the
18364 following special commands:
18367 @item set debug hppa
18368 @kindex set debug hppa
18369 This command determines whether HPPA architecture-specific debugging
18370 messages are to be displayed.
18372 @item show debug hppa
18373 Show whether HPPA debugging messages are displayed.
18375 @item maint print unwind @var{address}
18376 @kindex maint print unwind@r{, HPPA}
18377 This command displays the contents of the unwind table entry at the
18378 given @var{address}.
18384 @subsection Cell Broadband Engine SPU architecture
18385 @cindex Cell Broadband Engine
18388 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
18389 it provides the following special commands:
18392 @item info spu event
18394 Display SPU event facility status. Shows current event mask
18395 and pending event status.
18397 @item info spu signal
18398 Display SPU signal notification facility status. Shows pending
18399 signal-control word and signal notification mode of both signal
18400 notification channels.
18402 @item info spu mailbox
18403 Display SPU mailbox facility status. Shows all pending entries,
18404 in order of processing, in each of the SPU Write Outbound,
18405 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
18408 Display MFC DMA status. Shows all pending commands in the MFC
18409 DMA queue. For each entry, opcode, tag, class IDs, effective
18410 and local store addresses and transfer size are shown.
18412 @item info spu proxydma
18413 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
18414 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
18415 and local store addresses and transfer size are shown.
18419 When @value{GDBN} is debugging a combined PowerPC/SPU application
18420 on the Cell Broadband Engine, it provides in addition the following
18424 @item set spu stop-on-load @var{arg}
18426 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
18427 will give control to the user when a new SPE thread enters its @code{main}
18428 function. The default is @code{off}.
18430 @item show spu stop-on-load
18432 Show whether to stop for new SPE threads.
18434 @item set spu auto-flush-cache @var{arg}
18435 Set whether to automatically flush the software-managed cache. When set to
18436 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
18437 cache to be flushed whenever SPE execution stops. This provides a consistent
18438 view of PowerPC memory that is accessed via the cache. If an application
18439 does not use the software-managed cache, this option has no effect.
18441 @item show spu auto-flush-cache
18442 Show whether to automatically flush the software-managed cache.
18447 @subsection PowerPC
18448 @cindex PowerPC architecture
18450 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
18451 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
18452 numbers stored in the floating point registers. These values must be stored
18453 in two consecutive registers, always starting at an even register like
18454 @code{f0} or @code{f2}.
18456 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
18457 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
18458 @code{f2} and @code{f3} for @code{$dl1} and so on.
18460 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
18461 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
18464 @node Controlling GDB
18465 @chapter Controlling @value{GDBN}
18467 You can alter the way @value{GDBN} interacts with you by using the
18468 @code{set} command. For commands controlling how @value{GDBN} displays
18469 data, see @ref{Print Settings, ,Print Settings}. Other settings are
18474 * Editing:: Command editing
18475 * Command History:: Command history
18476 * Screen Size:: Screen size
18477 * Numbers:: Numbers
18478 * ABI:: Configuring the current ABI
18479 * Messages/Warnings:: Optional warnings and messages
18480 * Debugging Output:: Optional messages about internal happenings
18481 * Other Misc Settings:: Other Miscellaneous Settings
18489 @value{GDBN} indicates its readiness to read a command by printing a string
18490 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
18491 can change the prompt string with the @code{set prompt} command. For
18492 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
18493 the prompt in one of the @value{GDBN} sessions so that you can always tell
18494 which one you are talking to.
18496 @emph{Note:} @code{set prompt} does not add a space for you after the
18497 prompt you set. This allows you to set a prompt which ends in a space
18498 or a prompt that does not.
18502 @item set prompt @var{newprompt}
18503 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
18505 @kindex show prompt
18507 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
18511 @section Command Editing
18513 @cindex command line editing
18515 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
18516 @sc{gnu} library provides consistent behavior for programs which provide a
18517 command line interface to the user. Advantages are @sc{gnu} Emacs-style
18518 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
18519 substitution, and a storage and recall of command history across
18520 debugging sessions.
18522 You may control the behavior of command line editing in @value{GDBN} with the
18523 command @code{set}.
18526 @kindex set editing
18529 @itemx set editing on
18530 Enable command line editing (enabled by default).
18532 @item set editing off
18533 Disable command line editing.
18535 @kindex show editing
18537 Show whether command line editing is enabled.
18540 @xref{Command Line Editing}, for more details about the Readline
18541 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
18542 encouraged to read that chapter.
18544 @node Command History
18545 @section Command History
18546 @cindex command history
18548 @value{GDBN} can keep track of the commands you type during your
18549 debugging sessions, so that you can be certain of precisely what
18550 happened. Use these commands to manage the @value{GDBN} command
18553 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
18554 package, to provide the history facility. @xref{Using History
18555 Interactively}, for the detailed description of the History library.
18557 To issue a command to @value{GDBN} without affecting certain aspects of
18558 the state which is seen by users, prefix it with @samp{server }
18559 (@pxref{Server Prefix}). This
18560 means that this command will not affect the command history, nor will it
18561 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18562 pressed on a line by itself.
18564 @cindex @code{server}, command prefix
18565 The server prefix does not affect the recording of values into the value
18566 history; to print a value without recording it into the value history,
18567 use the @code{output} command instead of the @code{print} command.
18569 Here is the description of @value{GDBN} commands related to command
18573 @cindex history substitution
18574 @cindex history file
18575 @kindex set history filename
18576 @cindex @env{GDBHISTFILE}, environment variable
18577 @item set history filename @var{fname}
18578 Set the name of the @value{GDBN} command history file to @var{fname}.
18579 This is the file where @value{GDBN} reads an initial command history
18580 list, and where it writes the command history from this session when it
18581 exits. You can access this list through history expansion or through
18582 the history command editing characters listed below. This file defaults
18583 to the value of the environment variable @code{GDBHISTFILE}, or to
18584 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
18587 @cindex save command history
18588 @kindex set history save
18589 @item set history save
18590 @itemx set history save on
18591 Record command history in a file, whose name may be specified with the
18592 @code{set history filename} command. By default, this option is disabled.
18594 @item set history save off
18595 Stop recording command history in a file.
18597 @cindex history size
18598 @kindex set history size
18599 @cindex @env{HISTSIZE}, environment variable
18600 @item set history size @var{size}
18601 Set the number of commands which @value{GDBN} keeps in its history list.
18602 This defaults to the value of the environment variable
18603 @code{HISTSIZE}, or to 256 if this variable is not set.
18606 History expansion assigns special meaning to the character @kbd{!}.
18607 @xref{Event Designators}, for more details.
18609 @cindex history expansion, turn on/off
18610 Since @kbd{!} is also the logical not operator in C, history expansion
18611 is off by default. If you decide to enable history expansion with the
18612 @code{set history expansion on} command, you may sometimes need to
18613 follow @kbd{!} (when it is used as logical not, in an expression) with
18614 a space or a tab to prevent it from being expanded. The readline
18615 history facilities do not attempt substitution on the strings
18616 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
18618 The commands to control history expansion are:
18621 @item set history expansion on
18622 @itemx set history expansion
18623 @kindex set history expansion
18624 Enable history expansion. History expansion is off by default.
18626 @item set history expansion off
18627 Disable history expansion.
18630 @kindex show history
18632 @itemx show history filename
18633 @itemx show history save
18634 @itemx show history size
18635 @itemx show history expansion
18636 These commands display the state of the @value{GDBN} history parameters.
18637 @code{show history} by itself displays all four states.
18642 @kindex show commands
18643 @cindex show last commands
18644 @cindex display command history
18645 @item show commands
18646 Display the last ten commands in the command history.
18648 @item show commands @var{n}
18649 Print ten commands centered on command number @var{n}.
18651 @item show commands +
18652 Print ten commands just after the commands last printed.
18656 @section Screen Size
18657 @cindex size of screen
18658 @cindex pauses in output
18660 Certain commands to @value{GDBN} may produce large amounts of
18661 information output to the screen. To help you read all of it,
18662 @value{GDBN} pauses and asks you for input at the end of each page of
18663 output. Type @key{RET} when you want to continue the output, or @kbd{q}
18664 to discard the remaining output. Also, the screen width setting
18665 determines when to wrap lines of output. Depending on what is being
18666 printed, @value{GDBN} tries to break the line at a readable place,
18667 rather than simply letting it overflow onto the following line.
18669 Normally @value{GDBN} knows the size of the screen from the terminal
18670 driver software. For example, on Unix @value{GDBN} uses the termcap data base
18671 together with the value of the @code{TERM} environment variable and the
18672 @code{stty rows} and @code{stty cols} settings. If this is not correct,
18673 you can override it with the @code{set height} and @code{set
18680 @kindex show height
18681 @item set height @var{lpp}
18683 @itemx set width @var{cpl}
18685 These @code{set} commands specify a screen height of @var{lpp} lines and
18686 a screen width of @var{cpl} characters. The associated @code{show}
18687 commands display the current settings.
18689 If you specify a height of zero lines, @value{GDBN} does not pause during
18690 output no matter how long the output is. This is useful if output is to a
18691 file or to an editor buffer.
18693 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
18694 from wrapping its output.
18696 @item set pagination on
18697 @itemx set pagination off
18698 @kindex set pagination
18699 Turn the output pagination on or off; the default is on. Turning
18700 pagination off is the alternative to @code{set height 0}. Note that
18701 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
18702 Options, -batch}) also automatically disables pagination.
18704 @item show pagination
18705 @kindex show pagination
18706 Show the current pagination mode.
18711 @cindex number representation
18712 @cindex entering numbers
18714 You can always enter numbers in octal, decimal, or hexadecimal in
18715 @value{GDBN} by the usual conventions: octal numbers begin with
18716 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
18717 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
18718 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
18719 10; likewise, the default display for numbers---when no particular
18720 format is specified---is base 10. You can change the default base for
18721 both input and output with the commands described below.
18724 @kindex set input-radix
18725 @item set input-radix @var{base}
18726 Set the default base for numeric input. Supported choices
18727 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18728 specified either unambiguously or using the current input radix; for
18732 set input-radix 012
18733 set input-radix 10.
18734 set input-radix 0xa
18738 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
18739 leaves the input radix unchanged, no matter what it was, since
18740 @samp{10}, being without any leading or trailing signs of its base, is
18741 interpreted in the current radix. Thus, if the current radix is 16,
18742 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
18745 @kindex set output-radix
18746 @item set output-radix @var{base}
18747 Set the default base for numeric display. Supported choices
18748 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18749 specified either unambiguously or using the current input radix.
18751 @kindex show input-radix
18752 @item show input-radix
18753 Display the current default base for numeric input.
18755 @kindex show output-radix
18756 @item show output-radix
18757 Display the current default base for numeric display.
18759 @item set radix @r{[}@var{base}@r{]}
18763 These commands set and show the default base for both input and output
18764 of numbers. @code{set radix} sets the radix of input and output to
18765 the same base; without an argument, it resets the radix back to its
18766 default value of 10.
18771 @section Configuring the Current ABI
18773 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
18774 application automatically. However, sometimes you need to override its
18775 conclusions. Use these commands to manage @value{GDBN}'s view of the
18782 One @value{GDBN} configuration can debug binaries for multiple operating
18783 system targets, either via remote debugging or native emulation.
18784 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
18785 but you can override its conclusion using the @code{set osabi} command.
18786 One example where this is useful is in debugging of binaries which use
18787 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
18788 not have the same identifying marks that the standard C library for your
18793 Show the OS ABI currently in use.
18796 With no argument, show the list of registered available OS ABI's.
18798 @item set osabi @var{abi}
18799 Set the current OS ABI to @var{abi}.
18802 @cindex float promotion
18804 Generally, the way that an argument of type @code{float} is passed to a
18805 function depends on whether the function is prototyped. For a prototyped
18806 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
18807 according to the architecture's convention for @code{float}. For unprototyped
18808 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
18809 @code{double} and then passed.
18811 Unfortunately, some forms of debug information do not reliably indicate whether
18812 a function is prototyped. If @value{GDBN} calls a function that is not marked
18813 as prototyped, it consults @kbd{set coerce-float-to-double}.
18816 @kindex set coerce-float-to-double
18817 @item set coerce-float-to-double
18818 @itemx set coerce-float-to-double on
18819 Arguments of type @code{float} will be promoted to @code{double} when passed
18820 to an unprototyped function. This is the default setting.
18822 @item set coerce-float-to-double off
18823 Arguments of type @code{float} will be passed directly to unprototyped
18826 @kindex show coerce-float-to-double
18827 @item show coerce-float-to-double
18828 Show the current setting of promoting @code{float} to @code{double}.
18832 @kindex show cp-abi
18833 @value{GDBN} needs to know the ABI used for your program's C@t{++}
18834 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
18835 used to build your application. @value{GDBN} only fully supports
18836 programs with a single C@t{++} ABI; if your program contains code using
18837 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
18838 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
18839 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
18840 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
18841 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
18842 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
18847 Show the C@t{++} ABI currently in use.
18850 With no argument, show the list of supported C@t{++} ABI's.
18852 @item set cp-abi @var{abi}
18853 @itemx set cp-abi auto
18854 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
18857 @node Messages/Warnings
18858 @section Optional Warnings and Messages
18860 @cindex verbose operation
18861 @cindex optional warnings
18862 By default, @value{GDBN} is silent about its inner workings. If you are
18863 running on a slow machine, you may want to use the @code{set verbose}
18864 command. This makes @value{GDBN} tell you when it does a lengthy
18865 internal operation, so you will not think it has crashed.
18867 Currently, the messages controlled by @code{set verbose} are those
18868 which announce that the symbol table for a source file is being read;
18869 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
18872 @kindex set verbose
18873 @item set verbose on
18874 Enables @value{GDBN} output of certain informational messages.
18876 @item set verbose off
18877 Disables @value{GDBN} output of certain informational messages.
18879 @kindex show verbose
18881 Displays whether @code{set verbose} is on or off.
18884 By default, if @value{GDBN} encounters bugs in the symbol table of an
18885 object file, it is silent; but if you are debugging a compiler, you may
18886 find this information useful (@pxref{Symbol Errors, ,Errors Reading
18891 @kindex set complaints
18892 @item set complaints @var{limit}
18893 Permits @value{GDBN} to output @var{limit} complaints about each type of
18894 unusual symbols before becoming silent about the problem. Set
18895 @var{limit} to zero to suppress all complaints; set it to a large number
18896 to prevent complaints from being suppressed.
18898 @kindex show complaints
18899 @item show complaints
18900 Displays how many symbol complaints @value{GDBN} is permitted to produce.
18904 @anchor{confirmation requests}
18905 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
18906 lot of stupid questions to confirm certain commands. For example, if
18907 you try to run a program which is already running:
18911 The program being debugged has been started already.
18912 Start it from the beginning? (y or n)
18915 If you are willing to unflinchingly face the consequences of your own
18916 commands, you can disable this ``feature'':
18920 @kindex set confirm
18922 @cindex confirmation
18923 @cindex stupid questions
18924 @item set confirm off
18925 Disables confirmation requests. Note that running @value{GDBN} with
18926 the @option{--batch} option (@pxref{Mode Options, -batch}) also
18927 automatically disables confirmation requests.
18929 @item set confirm on
18930 Enables confirmation requests (the default).
18932 @kindex show confirm
18934 Displays state of confirmation requests.
18938 @cindex command tracing
18939 If you need to debug user-defined commands or sourced files you may find it
18940 useful to enable @dfn{command tracing}. In this mode each command will be
18941 printed as it is executed, prefixed with one or more @samp{+} symbols, the
18942 quantity denoting the call depth of each command.
18945 @kindex set trace-commands
18946 @cindex command scripts, debugging
18947 @item set trace-commands on
18948 Enable command tracing.
18949 @item set trace-commands off
18950 Disable command tracing.
18951 @item show trace-commands
18952 Display the current state of command tracing.
18955 @node Debugging Output
18956 @section Optional Messages about Internal Happenings
18957 @cindex optional debugging messages
18959 @value{GDBN} has commands that enable optional debugging messages from
18960 various @value{GDBN} subsystems; normally these commands are of
18961 interest to @value{GDBN} maintainers, or when reporting a bug. This
18962 section documents those commands.
18965 @kindex set exec-done-display
18966 @item set exec-done-display
18967 Turns on or off the notification of asynchronous commands'
18968 completion. When on, @value{GDBN} will print a message when an
18969 asynchronous command finishes its execution. The default is off.
18970 @kindex show exec-done-display
18971 @item show exec-done-display
18972 Displays the current setting of asynchronous command completion
18975 @cindex gdbarch debugging info
18976 @cindex architecture debugging info
18977 @item set debug arch
18978 Turns on or off display of gdbarch debugging info. The default is off
18980 @item show debug arch
18981 Displays the current state of displaying gdbarch debugging info.
18982 @item set debug aix-thread
18983 @cindex AIX threads
18984 Display debugging messages about inner workings of the AIX thread
18986 @item show debug aix-thread
18987 Show the current state of AIX thread debugging info display.
18988 @item set debug dwarf2-die
18989 @cindex DWARF2 DIEs
18990 Dump DWARF2 DIEs after they are read in.
18991 The value is the number of nesting levels to print.
18992 A value of zero turns off the display.
18993 @item show debug dwarf2-die
18994 Show the current state of DWARF2 DIE debugging.
18995 @item set debug displaced
18996 @cindex displaced stepping debugging info
18997 Turns on or off display of @value{GDBN} debugging info for the
18998 displaced stepping support. The default is off.
18999 @item show debug displaced
19000 Displays the current state of displaying @value{GDBN} debugging info
19001 related to displaced stepping.
19002 @item set debug event
19003 @cindex event debugging info
19004 Turns on or off display of @value{GDBN} event debugging info. The
19006 @item show debug event
19007 Displays the current state of displaying @value{GDBN} event debugging
19009 @item set debug expression
19010 @cindex expression debugging info
19011 Turns on or off display of debugging info about @value{GDBN}
19012 expression parsing. The default is off.
19013 @item show debug expression
19014 Displays the current state of displaying debugging info about
19015 @value{GDBN} expression parsing.
19016 @item set debug frame
19017 @cindex frame debugging info
19018 Turns on or off display of @value{GDBN} frame debugging info. The
19020 @item show debug frame
19021 Displays the current state of displaying @value{GDBN} frame debugging
19023 @item set debug gnu-nat
19024 @cindex @sc{gnu}/Hurd debug messages
19025 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19026 @item show debug gnu-nat
19027 Show the current state of @sc{gnu}/Hurd debugging messages.
19028 @item set debug infrun
19029 @cindex inferior debugging info
19030 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19031 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19032 for implementing operations such as single-stepping the inferior.
19033 @item show debug infrun
19034 Displays the current state of @value{GDBN} inferior debugging.
19035 @item set debug lin-lwp
19036 @cindex @sc{gnu}/Linux LWP debug messages
19037 @cindex Linux lightweight processes
19038 Turns on or off debugging messages from the Linux LWP debug support.
19039 @item show debug lin-lwp
19040 Show the current state of Linux LWP debugging messages.
19041 @item set debug lin-lwp-async
19042 @cindex @sc{gnu}/Linux LWP async debug messages
19043 @cindex Linux lightweight processes
19044 Turns on or off debugging messages from the Linux LWP async debug support.
19045 @item show debug lin-lwp-async
19046 Show the current state of Linux LWP async debugging messages.
19047 @item set debug observer
19048 @cindex observer debugging info
19049 Turns on or off display of @value{GDBN} observer debugging. This
19050 includes info such as the notification of observable events.
19051 @item show debug observer
19052 Displays the current state of observer debugging.
19053 @item set debug overload
19054 @cindex C@t{++} overload debugging info
19055 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19056 info. This includes info such as ranking of functions, etc. The default
19058 @item show debug overload
19059 Displays the current state of displaying @value{GDBN} C@t{++} overload
19061 @cindex expression parser, debugging info
19062 @cindex debug expression parser
19063 @item set debug parser
19064 Turns on or off the display of expression parser debugging output.
19065 Internally, this sets the @code{yydebug} variable in the expression
19066 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19067 details. The default is off.
19068 @item show debug parser
19069 Show the current state of expression parser debugging.
19070 @cindex packets, reporting on stdout
19071 @cindex serial connections, debugging
19072 @cindex debug remote protocol
19073 @cindex remote protocol debugging
19074 @cindex display remote packets
19075 @item set debug remote
19076 Turns on or off display of reports on all packets sent back and forth across
19077 the serial line to the remote machine. The info is printed on the
19078 @value{GDBN} standard output stream. The default is off.
19079 @item show debug remote
19080 Displays the state of display of remote packets.
19081 @item set debug serial
19082 Turns on or off display of @value{GDBN} serial debugging info. The
19084 @item show debug serial
19085 Displays the current state of displaying @value{GDBN} serial debugging
19087 @item set debug solib-frv
19088 @cindex FR-V shared-library debugging
19089 Turns on or off debugging messages for FR-V shared-library code.
19090 @item show debug solib-frv
19091 Display the current state of FR-V shared-library code debugging
19093 @item set debug target
19094 @cindex target debugging info
19095 Turns on or off display of @value{GDBN} target debugging info. This info
19096 includes what is going on at the target level of GDB, as it happens. The
19097 default is 0. Set it to 1 to track events, and to 2 to also track the
19098 value of large memory transfers. Changes to this flag do not take effect
19099 until the next time you connect to a target or use the @code{run} command.
19100 @item show debug target
19101 Displays the current state of displaying @value{GDBN} target debugging
19103 @item set debug timestamp
19104 @cindex timestampping debugging info
19105 Turns on or off display of timestamps with @value{GDBN} debugging info.
19106 When enabled, seconds and microseconds are displayed before each debugging
19108 @item show debug timestamp
19109 Displays the current state of displaying timestamps with @value{GDBN}
19111 @item set debugvarobj
19112 @cindex variable object debugging info
19113 Turns on or off display of @value{GDBN} variable object debugging
19114 info. The default is off.
19115 @item show debugvarobj
19116 Displays the current state of displaying @value{GDBN} variable object
19118 @item set debug xml
19119 @cindex XML parser debugging
19120 Turns on or off debugging messages for built-in XML parsers.
19121 @item show debug xml
19122 Displays the current state of XML debugging messages.
19125 @node Other Misc Settings
19126 @section Other Miscellaneous Settings
19127 @cindex miscellaneous settings
19130 @kindex set interactive-mode
19131 @item set interactive-mode
19132 If @code{on}, forces @value{GDBN} to operate interactively.
19133 If @code{off}, forces @value{GDBN} to operate non-interactively,
19134 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19135 based on whether the debugger was started in a terminal or not.
19137 In the vast majority of cases, the debugger should be able to guess
19138 correctly which mode should be used. But this setting can be useful
19139 in certain specific cases, such as running a MinGW @value{GDBN}
19140 inside a cygwin window.
19142 @kindex show interactive-mode
19143 @item show interactive-mode
19144 Displays whether the debugger is operating in interactive mode or not.
19147 @node Extending GDB
19148 @chapter Extending @value{GDBN}
19149 @cindex extending GDB
19151 @value{GDBN} provides two mechanisms for extension. The first is based
19152 on composition of @value{GDBN} commands, and the second is based on the
19153 Python scripting language.
19155 To facilitate the use of these extensions, @value{GDBN} is capable
19156 of evaluating the contents of a file. When doing so, @value{GDBN}
19157 can recognize which scripting language is being used by looking at
19158 the filename extension. Files with an unrecognized filename extension
19159 are always treated as a @value{GDBN} Command Files.
19160 @xref{Command Files,, Command files}.
19162 You can control how @value{GDBN} evaluates these files with the following
19166 @kindex set script-extension
19167 @kindex show script-extension
19168 @item set script-extension off
19169 All scripts are always evaluated as @value{GDBN} Command Files.
19171 @item set script-extension soft
19172 The debugger determines the scripting language based on filename
19173 extension. If this scripting language is supported, @value{GDBN}
19174 evaluates the script using that language. Otherwise, it evaluates
19175 the file as a @value{GDBN} Command File.
19177 @item set script-extension strict
19178 The debugger determines the scripting language based on filename
19179 extension, and evaluates the script using that language. If the
19180 language is not supported, then the evaluation fails.
19182 @item show script-extension
19183 Display the current value of the @code{script-extension} option.
19188 * Sequences:: Canned Sequences of Commands
19189 * Python:: Scripting @value{GDBN} using Python
19193 @section Canned Sequences of Commands
19195 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19196 Command Lists}), @value{GDBN} provides two ways to store sequences of
19197 commands for execution as a unit: user-defined commands and command
19201 * Define:: How to define your own commands
19202 * Hooks:: Hooks for user-defined commands
19203 * Command Files:: How to write scripts of commands to be stored in a file
19204 * Output:: Commands for controlled output
19208 @subsection User-defined Commands
19210 @cindex user-defined command
19211 @cindex arguments, to user-defined commands
19212 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19213 which you assign a new name as a command. This is done with the
19214 @code{define} command. User commands may accept up to 10 arguments
19215 separated by whitespace. Arguments are accessed within the user command
19216 via @code{$arg0@dots{}$arg9}. A trivial example:
19220 print $arg0 + $arg1 + $arg2
19225 To execute the command use:
19232 This defines the command @code{adder}, which prints the sum of
19233 its three arguments. Note the arguments are text substitutions, so they may
19234 reference variables, use complex expressions, or even perform inferior
19237 @cindex argument count in user-defined commands
19238 @cindex how many arguments (user-defined commands)
19239 In addition, @code{$argc} may be used to find out how many arguments have
19240 been passed. This expands to a number in the range 0@dots{}10.
19245 print $arg0 + $arg1
19248 print $arg0 + $arg1 + $arg2
19256 @item define @var{commandname}
19257 Define a command named @var{commandname}. If there is already a command
19258 by that name, you are asked to confirm that you want to redefine it.
19259 @var{commandname} may be a bare command name consisting of letters,
19260 numbers, dashes, and underscores. It may also start with any predefined
19261 prefix command. For example, @samp{define target my-target} creates
19262 a user-defined @samp{target my-target} command.
19264 The definition of the command is made up of other @value{GDBN} command lines,
19265 which are given following the @code{define} command. The end of these
19266 commands is marked by a line containing @code{end}.
19269 @kindex end@r{ (user-defined commands)}
19270 @item document @var{commandname}
19271 Document the user-defined command @var{commandname}, so that it can be
19272 accessed by @code{help}. The command @var{commandname} must already be
19273 defined. This command reads lines of documentation just as @code{define}
19274 reads the lines of the command definition, ending with @code{end}.
19275 After the @code{document} command is finished, @code{help} on command
19276 @var{commandname} displays the documentation you have written.
19278 You may use the @code{document} command again to change the
19279 documentation of a command. Redefining the command with @code{define}
19280 does not change the documentation.
19282 @kindex dont-repeat
19283 @cindex don't repeat command
19285 Used inside a user-defined command, this tells @value{GDBN} that this
19286 command should not be repeated when the user hits @key{RET}
19287 (@pxref{Command Syntax, repeat last command}).
19289 @kindex help user-defined
19290 @item help user-defined
19291 List all user-defined commands, with the first line of the documentation
19296 @itemx show user @var{commandname}
19297 Display the @value{GDBN} commands used to define @var{commandname} (but
19298 not its documentation). If no @var{commandname} is given, display the
19299 definitions for all user-defined commands.
19301 @cindex infinite recursion in user-defined commands
19302 @kindex show max-user-call-depth
19303 @kindex set max-user-call-depth
19304 @item show max-user-call-depth
19305 @itemx set max-user-call-depth
19306 The value of @code{max-user-call-depth} controls how many recursion
19307 levels are allowed in user-defined commands before @value{GDBN} suspects an
19308 infinite recursion and aborts the command.
19311 In addition to the above commands, user-defined commands frequently
19312 use control flow commands, described in @ref{Command Files}.
19314 When user-defined commands are executed, the
19315 commands of the definition are not printed. An error in any command
19316 stops execution of the user-defined command.
19318 If used interactively, commands that would ask for confirmation proceed
19319 without asking when used inside a user-defined command. Many @value{GDBN}
19320 commands that normally print messages to say what they are doing omit the
19321 messages when used in a user-defined command.
19324 @subsection User-defined Command Hooks
19325 @cindex command hooks
19326 @cindex hooks, for commands
19327 @cindex hooks, pre-command
19330 You may define @dfn{hooks}, which are a special kind of user-defined
19331 command. Whenever you run the command @samp{foo}, if the user-defined
19332 command @samp{hook-foo} exists, it is executed (with no arguments)
19333 before that command.
19335 @cindex hooks, post-command
19337 A hook may also be defined which is run after the command you executed.
19338 Whenever you run the command @samp{foo}, if the user-defined command
19339 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19340 that command. Post-execution hooks may exist simultaneously with
19341 pre-execution hooks, for the same command.
19343 It is valid for a hook to call the command which it hooks. If this
19344 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19346 @c It would be nice if hookpost could be passed a parameter indicating
19347 @c if the command it hooks executed properly or not. FIXME!
19349 @kindex stop@r{, a pseudo-command}
19350 In addition, a pseudo-command, @samp{stop} exists. Defining
19351 (@samp{hook-stop}) makes the associated commands execute every time
19352 execution stops in your program: before breakpoint commands are run,
19353 displays are printed, or the stack frame is printed.
19355 For example, to ignore @code{SIGALRM} signals while
19356 single-stepping, but treat them normally during normal execution,
19361 handle SIGALRM nopass
19365 handle SIGALRM pass
19368 define hook-continue
19369 handle SIGALRM pass
19373 As a further example, to hook at the beginning and end of the @code{echo}
19374 command, and to add extra text to the beginning and end of the message,
19382 define hookpost-echo
19386 (@value{GDBP}) echo Hello World
19387 <<<---Hello World--->>>
19392 You can define a hook for any single-word command in @value{GDBN}, but
19393 not for command aliases; you should define a hook for the basic command
19394 name, e.g.@: @code{backtrace} rather than @code{bt}.
19395 @c FIXME! So how does Joe User discover whether a command is an alias
19397 You can hook a multi-word command by adding @code{hook-} or
19398 @code{hookpost-} to the last word of the command, e.g.@:
19399 @samp{define target hook-remote} to add a hook to @samp{target remote}.
19401 If an error occurs during the execution of your hook, execution of
19402 @value{GDBN} commands stops and @value{GDBN} issues a prompt
19403 (before the command that you actually typed had a chance to run).
19405 If you try to define a hook which does not match any known command, you
19406 get a warning from the @code{define} command.
19408 @node Command Files
19409 @subsection Command Files
19411 @cindex command files
19412 @cindex scripting commands
19413 A command file for @value{GDBN} is a text file made of lines that are
19414 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
19415 also be included. An empty line in a command file does nothing; it
19416 does not mean to repeat the last command, as it would from the
19419 You can request the execution of a command file with the @code{source}
19420 command. Note that the @code{source} command is also used to evaluate
19421 scripts that are not Command Files. The exact behavior can be configured
19422 using the @code{script-extension} setting.
19423 @xref{Extending GDB,, Extending GDB}.
19427 @cindex execute commands from a file
19428 @item source [-s] [-v] @var{filename}
19429 Execute the command file @var{filename}.
19432 The lines in a command file are generally executed sequentially,
19433 unless the order of execution is changed by one of the
19434 @emph{flow-control commands} described below. The commands are not
19435 printed as they are executed. An error in any command terminates
19436 execution of the command file and control is returned to the console.
19438 @value{GDBN} first searches for @var{filename} in the current directory.
19439 If the file is not found there, and @var{filename} does not specify a
19440 directory, then @value{GDBN} also looks for the file on the source search path
19441 (specified with the @samp{directory} command);
19442 except that @file{$cdir} is not searched because the compilation directory
19443 is not relevant to scripts.
19445 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
19446 on the search path even if @var{filename} specifies a directory.
19447 The search is done by appending @var{filename} to each element of the
19448 search path. So, for example, if @var{filename} is @file{mylib/myscript}
19449 and the search path contains @file{/home/user} then @value{GDBN} will
19450 look for the script @file{/home/user/mylib/myscript}.
19451 The search is also done if @var{filename} is an absolute path.
19452 For example, if @var{filename} is @file{/tmp/myscript} and
19453 the search path contains @file{/home/user} then @value{GDBN} will
19454 look for the script @file{/home/user/tmp/myscript}.
19455 For DOS-like systems, if @var{filename} contains a drive specification,
19456 it is stripped before concatenation. For example, if @var{filename} is
19457 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
19458 will look for the script @file{c:/tmp/myscript}.
19460 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
19461 each command as it is executed. The option must be given before
19462 @var{filename}, and is interpreted as part of the filename anywhere else.
19464 Commands that would ask for confirmation if used interactively proceed
19465 without asking when used in a command file. Many @value{GDBN} commands that
19466 normally print messages to say what they are doing omit the messages
19467 when called from command files.
19469 @value{GDBN} also accepts command input from standard input. In this
19470 mode, normal output goes to standard output and error output goes to
19471 standard error. Errors in a command file supplied on standard input do
19472 not terminate execution of the command file---execution continues with
19476 gdb < cmds > log 2>&1
19479 (The syntax above will vary depending on the shell used.) This example
19480 will execute commands from the file @file{cmds}. All output and errors
19481 would be directed to @file{log}.
19483 Since commands stored on command files tend to be more general than
19484 commands typed interactively, they frequently need to deal with
19485 complicated situations, such as different or unexpected values of
19486 variables and symbols, changes in how the program being debugged is
19487 built, etc. @value{GDBN} provides a set of flow-control commands to
19488 deal with these complexities. Using these commands, you can write
19489 complex scripts that loop over data structures, execute commands
19490 conditionally, etc.
19497 This command allows to include in your script conditionally executed
19498 commands. The @code{if} command takes a single argument, which is an
19499 expression to evaluate. It is followed by a series of commands that
19500 are executed only if the expression is true (its value is nonzero).
19501 There can then optionally be an @code{else} line, followed by a series
19502 of commands that are only executed if the expression was false. The
19503 end of the list is marked by a line containing @code{end}.
19507 This command allows to write loops. Its syntax is similar to
19508 @code{if}: the command takes a single argument, which is an expression
19509 to evaluate, and must be followed by the commands to execute, one per
19510 line, terminated by an @code{end}. These commands are called the
19511 @dfn{body} of the loop. The commands in the body of @code{while} are
19512 executed repeatedly as long as the expression evaluates to true.
19516 This command exits the @code{while} loop in whose body it is included.
19517 Execution of the script continues after that @code{while}s @code{end}
19520 @kindex loop_continue
19521 @item loop_continue
19522 This command skips the execution of the rest of the body of commands
19523 in the @code{while} loop in whose body it is included. Execution
19524 branches to the beginning of the @code{while} loop, where it evaluates
19525 the controlling expression.
19527 @kindex end@r{ (if/else/while commands)}
19529 Terminate the block of commands that are the body of @code{if},
19530 @code{else}, or @code{while} flow-control commands.
19535 @subsection Commands for Controlled Output
19537 During the execution of a command file or a user-defined command, normal
19538 @value{GDBN} output is suppressed; the only output that appears is what is
19539 explicitly printed by the commands in the definition. This section
19540 describes three commands useful for generating exactly the output you
19545 @item echo @var{text}
19546 @c I do not consider backslash-space a standard C escape sequence
19547 @c because it is not in ANSI.
19548 Print @var{text}. Nonprinting characters can be included in
19549 @var{text} using C escape sequences, such as @samp{\n} to print a
19550 newline. @strong{No newline is printed unless you specify one.}
19551 In addition to the standard C escape sequences, a backslash followed
19552 by a space stands for a space. This is useful for displaying a
19553 string with spaces at the beginning or the end, since leading and
19554 trailing spaces are otherwise trimmed from all arguments.
19555 To print @samp{@w{ }and foo =@w{ }}, use the command
19556 @samp{echo \@w{ }and foo = \@w{ }}.
19558 A backslash at the end of @var{text} can be used, as in C, to continue
19559 the command onto subsequent lines. For example,
19562 echo This is some text\n\
19563 which is continued\n\
19564 onto several lines.\n
19567 produces the same output as
19570 echo This is some text\n
19571 echo which is continued\n
19572 echo onto several lines.\n
19576 @item output @var{expression}
19577 Print the value of @var{expression} and nothing but that value: no
19578 newlines, no @samp{$@var{nn} = }. The value is not entered in the
19579 value history either. @xref{Expressions, ,Expressions}, for more information
19582 @item output/@var{fmt} @var{expression}
19583 Print the value of @var{expression} in format @var{fmt}. You can use
19584 the same formats as for @code{print}. @xref{Output Formats,,Output
19585 Formats}, for more information.
19588 @item printf @var{template}, @var{expressions}@dots{}
19589 Print the values of one or more @var{expressions} under the control of
19590 the string @var{template}. To print several values, make
19591 @var{expressions} be a comma-separated list of individual expressions,
19592 which may be either numbers or pointers. Their values are printed as
19593 specified by @var{template}, exactly as a C program would do by
19594 executing the code below:
19597 printf (@var{template}, @var{expressions}@dots{});
19600 As in @code{C} @code{printf}, ordinary characters in @var{template}
19601 are printed verbatim, while @dfn{conversion specification} introduced
19602 by the @samp{%} character cause subsequent @var{expressions} to be
19603 evaluated, their values converted and formatted according to type and
19604 style information encoded in the conversion specifications, and then
19607 For example, you can print two values in hex like this:
19610 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
19613 @code{printf} supports all the standard @code{C} conversion
19614 specifications, including the flags and modifiers between the @samp{%}
19615 character and the conversion letter, with the following exceptions:
19619 The argument-ordering modifiers, such as @samp{2$}, are not supported.
19622 The modifier @samp{*} is not supported for specifying precision or
19626 The @samp{'} flag (for separation of digits into groups according to
19627 @code{LC_NUMERIC'}) is not supported.
19630 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
19634 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
19637 The conversion letters @samp{a} and @samp{A} are not supported.
19641 Note that the @samp{ll} type modifier is supported only if the
19642 underlying @code{C} implementation used to build @value{GDBN} supports
19643 the @code{long long int} type, and the @samp{L} type modifier is
19644 supported only if @code{long double} type is available.
19646 As in @code{C}, @code{printf} supports simple backslash-escape
19647 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
19648 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
19649 single character. Octal and hexadecimal escape sequences are not
19652 Additionally, @code{printf} supports conversion specifications for DFP
19653 (@dfn{Decimal Floating Point}) types using the following length modifiers
19654 together with a floating point specifier.
19659 @samp{H} for printing @code{Decimal32} types.
19662 @samp{D} for printing @code{Decimal64} types.
19665 @samp{DD} for printing @code{Decimal128} types.
19668 If the underlying @code{C} implementation used to build @value{GDBN} has
19669 support for the three length modifiers for DFP types, other modifiers
19670 such as width and precision will also be available for @value{GDBN} to use.
19672 In case there is no such @code{C} support, no additional modifiers will be
19673 available and the value will be printed in the standard way.
19675 Here's an example of printing DFP types using the above conversion letters:
19677 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
19683 @section Scripting @value{GDBN} using Python
19684 @cindex python scripting
19685 @cindex scripting with python
19687 You can script @value{GDBN} using the @uref{http://www.python.org/,
19688 Python programming language}. This feature is available only if
19689 @value{GDBN} was configured using @option{--with-python}.
19692 * Python Commands:: Accessing Python from @value{GDBN}.
19693 * Python API:: Accessing @value{GDBN} from Python.
19696 @node Python Commands
19697 @subsection Python Commands
19698 @cindex python commands
19699 @cindex commands to access python
19701 @value{GDBN} provides one command for accessing the Python interpreter,
19702 and one related setting:
19706 @item python @r{[}@var{code}@r{]}
19707 The @code{python} command can be used to evaluate Python code.
19709 If given an argument, the @code{python} command will evaluate the
19710 argument as a Python command. For example:
19713 (@value{GDBP}) python print 23
19717 If you do not provide an argument to @code{python}, it will act as a
19718 multi-line command, like @code{define}. In this case, the Python
19719 script is made up of subsequent command lines, given after the
19720 @code{python} command. This command list is terminated using a line
19721 containing @code{end}. For example:
19724 (@value{GDBP}) python
19726 End with a line saying just "end".
19732 @kindex maint set python print-stack
19733 @item maint set python print-stack
19734 By default, @value{GDBN} will print a stack trace when an error occurs
19735 in a Python script. This can be controlled using @code{maint set
19736 python print-stack}: if @code{on}, the default, then Python stack
19737 printing is enabled; if @code{off}, then Python stack printing is
19741 It is also possible to execute a Python script from the @value{GDBN}
19745 @item source @file{script-name}
19746 The script name must end with @samp{.py} and @value{GDBN} must be configured
19747 to recognize the script language based on filename extension using
19748 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
19750 @item python execfile ("script-name")
19751 This method is based on the @code{execfile} Python built-in function,
19752 and thus is always available.
19756 @subsection Python API
19758 @cindex programming in python
19760 @cindex python stdout
19761 @cindex python pagination
19762 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
19763 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
19764 A Python program which outputs to one of these streams may have its
19765 output interrupted by the user (@pxref{Screen Size}). In this
19766 situation, a Python @code{KeyboardInterrupt} exception is thrown.
19769 * Basic Python:: Basic Python Functions.
19770 * Exception Handling::
19771 * Auto-loading:: Automatically loading Python code.
19772 * Values From Inferior::
19773 * Types In Python:: Python representation of types.
19774 * Pretty Printing:: Pretty-printing values.
19775 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
19776 * Commands In Python:: Implementing new commands in Python.
19777 * Functions In Python:: Writing new convenience functions.
19778 * Progspaces In Python:: Program spaces.
19779 * Objfiles In Python:: Object files.
19780 * Frames In Python:: Accessing inferior stack frames from Python.
19781 * Blocks In Python:: Accessing frame blocks from Python.
19782 * Symbols In Python:: Python representation of symbols.
19783 * Symbol Tables In Python:: Python representation of symbol tables.
19784 * Lazy Strings In Python:: Python representation of lazy strings.
19785 * Breakpoints In Python:: Manipulating breakpoints using Python.
19789 @subsubsection Basic Python
19791 @cindex python functions
19792 @cindex python module
19794 @value{GDBN} introduces a new Python module, named @code{gdb}. All
19795 methods and classes added by @value{GDBN} are placed in this module.
19796 @value{GDBN} automatically @code{import}s the @code{gdb} module for
19797 use in all scripts evaluated by the @code{python} command.
19799 @findex gdb.execute
19800 @defun execute command [from_tty]
19801 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
19802 If a GDB exception happens while @var{command} runs, it is
19803 translated as described in @ref{Exception Handling,,Exception Handling}.
19804 If no exceptions occur, this function returns @code{None}.
19806 @var{from_tty} specifies whether @value{GDBN} ought to consider this
19807 command as having originated from the user invoking it interactively.
19808 It must be a boolean value. If omitted, it defaults to @code{False}.
19811 @findex gdb.breakpoints
19813 Return a sequence holding all of @value{GDBN}'s breakpoints.
19814 @xref{Breakpoints In Python}, for more information.
19817 @findex gdb.parameter
19818 @defun parameter parameter
19819 Return the value of a @value{GDBN} parameter. @var{parameter} is a
19820 string naming the parameter to look up; @var{parameter} may contain
19821 spaces if the parameter has a multi-part name. For example,
19822 @samp{print object} is a valid parameter name.
19824 If the named parameter does not exist, this function throws a
19825 @code{RuntimeError}. Otherwise, the parameter's value is converted to
19826 a Python value of the appropriate type, and returned.
19829 @findex gdb.history
19830 @defun history number
19831 Return a value from @value{GDBN}'s value history (@pxref{Value
19832 History}). @var{number} indicates which history element to return.
19833 If @var{number} is negative, then @value{GDBN} will take its absolute value
19834 and count backward from the last element (i.e., the most recent element) to
19835 find the value to return. If @var{number} is zero, then @value{GDBN} will
19836 return the most recent element. If the element specified by @var{number}
19837 doesn't exist in the value history, a @code{RuntimeError} exception will be
19840 If no exception is raised, the return value is always an instance of
19841 @code{gdb.Value} (@pxref{Values From Inferior}).
19844 @findex gdb.parse_and_eval
19845 @defun parse_and_eval expression
19846 Parse @var{expression} as an expression in the current language,
19847 evaluate it, and return the result as a @code{gdb.Value}.
19848 @var{expression} must be a string.
19850 This function can be useful when implementing a new command
19851 (@pxref{Commands In Python}), as it provides a way to parse the
19852 command's argument as an expression. It is also useful simply to
19853 compute values, for example, it is the only way to get the value of a
19854 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
19858 @defun write string
19859 Print a string to @value{GDBN}'s paginated standard output stream.
19860 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
19861 call this function.
19866 Flush @value{GDBN}'s paginated standard output stream. Flushing
19867 @code{sys.stdout} or @code{sys.stderr} will automatically call this
19871 @findex gdb.target_charset
19872 @defun target_charset
19873 Return the name of the current target character set (@pxref{Character
19874 Sets}). This differs from @code{gdb.parameter('target-charset')} in
19875 that @samp{auto} is never returned.
19878 @findex gdb.target_wide_charset
19879 @defun target_wide_charset
19880 Return the name of the current target wide character set
19881 (@pxref{Character Sets}). This differs from
19882 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
19886 @node Exception Handling
19887 @subsubsection Exception Handling
19888 @cindex python exceptions
19889 @cindex exceptions, python
19891 When executing the @code{python} command, Python exceptions
19892 uncaught within the Python code are translated to calls to
19893 @value{GDBN} error-reporting mechanism. If the command that called
19894 @code{python} does not handle the error, @value{GDBN} will
19895 terminate it and print an error message containing the Python
19896 exception name, the associated value, and the Python call stack
19897 backtrace at the point where the exception was raised. Example:
19900 (@value{GDBP}) python print foo
19901 Traceback (most recent call last):
19902 File "<string>", line 1, in <module>
19903 NameError: name 'foo' is not defined
19906 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
19907 code are converted to Python @code{RuntimeError} exceptions. User
19908 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
19909 prompt) is translated to a Python @code{KeyboardInterrupt}
19910 exception. If you catch these exceptions in your Python code, your
19911 exception handler will see @code{RuntimeError} or
19912 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
19913 message as its value, and the Python call stack backtrace at the
19914 Python statement closest to where the @value{GDBN} error occured as the
19918 @subsubsection Auto-loading
19919 @cindex auto-loading, Python
19921 When a new object file is read (for example, due to the @code{file}
19922 command, or because the inferior has loaded a shared library),
19923 @value{GDBN} will look for a file named @file{@var{objfile}-gdb.py},
19924 where @var{objfile} is the object file's real name, formed by ensuring
19925 that the file name is absolute, following all symlinks, and resolving
19926 @code{.} and @code{..} components. If this file exists and is
19927 readable, @value{GDBN} will evaluate it as a Python script.
19929 If this file does not exist, and if the parameter
19930 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
19931 then @value{GDBN} will use for its each separated directory component
19932 @code{component} the file named @file{@code{component}/@var{real-name}}, where
19933 @var{real-name} is the object file's real name, as described above.
19935 Finally, if this file does not exist, then @value{GDBN} will look for
19936 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
19937 @var{data-directory} is @value{GDBN}'s data directory (available via
19938 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
19939 is the object file's real name, as described above.
19941 When reading an auto-loaded file, @value{GDBN} sets the ``current
19942 objfile''. This is available via the @code{gdb.current_objfile}
19943 function (@pxref{Objfiles In Python}). This can be useful for
19944 registering objfile-specific pretty-printers.
19946 The auto-loading feature is useful for supplying application-specific
19947 debugging commands and scripts. You can enable or disable this
19948 feature, and view its current state.
19951 @kindex maint set python auto-load
19952 @item maint set python auto-load [yes|no]
19953 Enable or disable the Python auto-loading feature.
19955 @kindex maint show python auto-load
19956 @item maint show python auto-load
19957 Show whether Python auto-loading is enabled or disabled.
19960 @value{GDBN} does not track which files it has already auto-loaded.
19961 So, your @samp{-gdb.py} file should take care to ensure that it may be
19962 evaluated multiple times without error.
19964 @node Values From Inferior
19965 @subsubsection Values From Inferior
19966 @cindex values from inferior, with Python
19967 @cindex python, working with values from inferior
19969 @cindex @code{gdb.Value}
19970 @value{GDBN} provides values it obtains from the inferior program in
19971 an object of type @code{gdb.Value}. @value{GDBN} uses this object
19972 for its internal bookkeeping of the inferior's values, and for
19973 fetching values when necessary.
19975 Inferior values that are simple scalars can be used directly in
19976 Python expressions that are valid for the value's data type. Here's
19977 an example for an integer or floating-point value @code{some_val}:
19984 As result of this, @code{bar} will also be a @code{gdb.Value} object
19985 whose values are of the same type as those of @code{some_val}.
19987 Inferior values that are structures or instances of some class can
19988 be accessed using the Python @dfn{dictionary syntax}. For example, if
19989 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
19990 can access its @code{foo} element with:
19993 bar = some_val['foo']
19996 Again, @code{bar} will also be a @code{gdb.Value} object.
19998 The following attributes are provided:
20001 @defivar Value address
20002 If this object is addressable, this read-only attribute holds a
20003 @code{gdb.Value} object representing the address. Otherwise,
20004 this attribute holds @code{None}.
20007 @cindex optimized out value in Python
20008 @defivar Value is_optimized_out
20009 This read-only boolean attribute is true if the compiler optimized out
20010 this value, thus it is not available for fetching from the inferior.
20013 @defivar Value type
20014 The type of this @code{gdb.Value}. The value of this attribute is a
20015 @code{gdb.Type} object.
20019 The following methods are provided:
20022 @defmethod Value cast type
20023 Return a new instance of @code{gdb.Value} that is the result of
20024 casting this instance to the type described by @var{type}, which must
20025 be a @code{gdb.Type} object. If the cast cannot be performed for some
20026 reason, this method throws an exception.
20029 @defmethod Value dereference
20030 For pointer data types, this method returns a new @code{gdb.Value} object
20031 whose contents is the object pointed to by the pointer. For example, if
20032 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20039 then you can use the corresponding @code{gdb.Value} to access what
20040 @code{foo} points to like this:
20043 bar = foo.dereference ()
20046 The result @code{bar} will be a @code{gdb.Value} object holding the
20047 value pointed to by @code{foo}.
20050 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20051 If this @code{gdb.Value} represents a string, then this method
20052 converts the contents to a Python string. Otherwise, this method will
20053 throw an exception.
20055 Strings are recognized in a language-specific way; whether a given
20056 @code{gdb.Value} represents a string is determined by the current
20059 For C-like languages, a value is a string if it is a pointer to or an
20060 array of characters or ints. The string is assumed to be terminated
20061 by a zero of the appropriate width. However if the optional length
20062 argument is given, the string will be converted to that given length,
20063 ignoring any embedded zeros that the string may contain.
20065 If the optional @var{encoding} argument is given, it must be a string
20066 naming the encoding of the string in the @code{gdb.Value}, such as
20067 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20068 the same encodings as the corresponding argument to Python's
20069 @code{string.decode} method, and the Python codec machinery will be used
20070 to convert the string. If @var{encoding} is not given, or if
20071 @var{encoding} is the empty string, then either the @code{target-charset}
20072 (@pxref{Character Sets}) will be used, or a language-specific encoding
20073 will be used, if the current language is able to supply one.
20075 The optional @var{errors} argument is the same as the corresponding
20076 argument to Python's @code{string.decode} method.
20078 If the optional @var{length} argument is given, the string will be
20079 fetched and converted to the given length.
20082 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20083 If this @code{gdb.Value} represents a string, then this method
20084 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20085 In Python}). Otherwise, this method will throw an exception.
20087 If the optional @var{encoding} argument is given, it must be a string
20088 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20089 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20090 @var{encoding} argument is an encoding that @value{GDBN} does
20091 recognize, @value{GDBN} will raise an error.
20093 When a lazy string is printed, the @value{GDBN} encoding machinery is
20094 used to convert the string during printing. If the optional
20095 @var{encoding} argument is not provided, or is an empty string,
20096 @value{GDBN} will automatically select the encoding most suitable for
20097 the string type. For further information on encoding in @value{GDBN}
20098 please see @ref{Character Sets}.
20100 If the optional @var{length} argument is given, the string will be
20101 fetched and encoded to the length of characters specified. If
20102 the @var{length} argument is not provided, the string will be fetched
20103 and encoded until a null of appropriate width is found.
20107 @node Types In Python
20108 @subsubsection Types In Python
20109 @cindex types in Python
20110 @cindex Python, working with types
20113 @value{GDBN} represents types from the inferior using the class
20116 The following type-related functions are available in the @code{gdb}
20119 @findex gdb.lookup_type
20120 @defun lookup_type name [block]
20121 This function looks up a type by name. @var{name} is the name of the
20122 type to look up. It must be a string.
20124 If @var{block} is given, then @var{name} is looked up in that scope.
20125 Otherwise, it is searched for globally.
20127 Ordinarily, this function will return an instance of @code{gdb.Type}.
20128 If the named type cannot be found, it will throw an exception.
20131 An instance of @code{Type} has the following attributes:
20135 The type code for this type. The type code will be one of the
20136 @code{TYPE_CODE_} constants defined below.
20139 @defivar Type sizeof
20140 The size of this type, in target @code{char} units. Usually, a
20141 target's @code{char} type will be an 8-bit byte. However, on some
20142 unusual platforms, this type may have a different size.
20146 The tag name for this type. The tag name is the name after
20147 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20148 languages have this concept. If this type has no tag name, then
20149 @code{None} is returned.
20153 The following methods are provided:
20156 @defmethod Type fields
20157 For structure and union types, this method returns the fields. Range
20158 types have two fields, the minimum and maximum values. Enum types
20159 have one field per enum constant. Function and method types have one
20160 field per parameter. The base types of C@t{++} classes are also
20161 represented as fields. If the type has no fields, or does not fit
20162 into one of these categories, an empty sequence will be returned.
20164 Each field is an object, with some pre-defined attributes:
20167 This attribute is not available for @code{static} fields (as in
20168 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20169 position of the field.
20172 The name of the field, or @code{None} for anonymous fields.
20175 This is @code{True} if the field is artificial, usually meaning that
20176 it was provided by the compiler and not the user. This attribute is
20177 always provided, and is @code{False} if the field is not artificial.
20179 @item is_base_class
20180 This is @code{True} if the field represents a base class of a C@t{++}
20181 structure. This attribute is always provided, and is @code{False}
20182 if the field is not a base class of the type that is the argument of
20183 @code{fields}, or if that type was not a C@t{++} class.
20186 If the field is packed, or is a bitfield, then this will have a
20187 non-zero value, which is the size of the field in bits. Otherwise,
20188 this will be zero; in this case the field's size is given by its type.
20191 The type of the field. This is usually an instance of @code{Type},
20192 but it can be @code{None} in some situations.
20196 @defmethod Type const
20197 Return a new @code{gdb.Type} object which represents a
20198 @code{const}-qualified variant of this type.
20201 @defmethod Type volatile
20202 Return a new @code{gdb.Type} object which represents a
20203 @code{volatile}-qualified variant of this type.
20206 @defmethod Type unqualified
20207 Return a new @code{gdb.Type} object which represents an unqualified
20208 variant of this type. That is, the result is neither @code{const} nor
20212 @defmethod Type range
20213 Return a Python @code{Tuple} object that contains two elements: the
20214 low bound of the argument type and the high bound of that type. If
20215 the type does not have a range, @value{GDBN} will raise a
20216 @code{RuntimeError} exception.
20219 @defmethod Type reference
20220 Return a new @code{gdb.Type} object which represents a reference to this
20224 @defmethod Type pointer
20225 Return a new @code{gdb.Type} object which represents a pointer to this
20229 @defmethod Type strip_typedefs
20230 Return a new @code{gdb.Type} that represents the real type,
20231 after removing all layers of typedefs.
20234 @defmethod Type target
20235 Return a new @code{gdb.Type} object which represents the target type
20238 For a pointer type, the target type is the type of the pointed-to
20239 object. For an array type (meaning C-like arrays), the target type is
20240 the type of the elements of the array. For a function or method type,
20241 the target type is the type of the return value. For a complex type,
20242 the target type is the type of the elements. For a typedef, the
20243 target type is the aliased type.
20245 If the type does not have a target, this method will throw an
20249 @defmethod Type template_argument n [block]
20250 If this @code{gdb.Type} is an instantiation of a template, this will
20251 return a new @code{gdb.Type} which represents the type of the
20252 @var{n}th template argument.
20254 If this @code{gdb.Type} is not a template type, this will throw an
20255 exception. Ordinarily, only C@t{++} code will have template types.
20257 If @var{block} is given, then @var{name} is looked up in that scope.
20258 Otherwise, it is searched for globally.
20263 Each type has a code, which indicates what category this type falls
20264 into. The available type categories are represented by constants
20265 defined in the @code{gdb} module:
20268 @findex TYPE_CODE_PTR
20269 @findex gdb.TYPE_CODE_PTR
20270 @item TYPE_CODE_PTR
20271 The type is a pointer.
20273 @findex TYPE_CODE_ARRAY
20274 @findex gdb.TYPE_CODE_ARRAY
20275 @item TYPE_CODE_ARRAY
20276 The type is an array.
20278 @findex TYPE_CODE_STRUCT
20279 @findex gdb.TYPE_CODE_STRUCT
20280 @item TYPE_CODE_STRUCT
20281 The type is a structure.
20283 @findex TYPE_CODE_UNION
20284 @findex gdb.TYPE_CODE_UNION
20285 @item TYPE_CODE_UNION
20286 The type is a union.
20288 @findex TYPE_CODE_ENUM
20289 @findex gdb.TYPE_CODE_ENUM
20290 @item TYPE_CODE_ENUM
20291 The type is an enum.
20293 @findex TYPE_CODE_FLAGS
20294 @findex gdb.TYPE_CODE_FLAGS
20295 @item TYPE_CODE_FLAGS
20296 A bit flags type, used for things such as status registers.
20298 @findex TYPE_CODE_FUNC
20299 @findex gdb.TYPE_CODE_FUNC
20300 @item TYPE_CODE_FUNC
20301 The type is a function.
20303 @findex TYPE_CODE_INT
20304 @findex gdb.TYPE_CODE_INT
20305 @item TYPE_CODE_INT
20306 The type is an integer type.
20308 @findex TYPE_CODE_FLT
20309 @findex gdb.TYPE_CODE_FLT
20310 @item TYPE_CODE_FLT
20311 A floating point type.
20313 @findex TYPE_CODE_VOID
20314 @findex gdb.TYPE_CODE_VOID
20315 @item TYPE_CODE_VOID
20316 The special type @code{void}.
20318 @findex TYPE_CODE_SET
20319 @findex gdb.TYPE_CODE_SET
20320 @item TYPE_CODE_SET
20323 @findex TYPE_CODE_RANGE
20324 @findex gdb.TYPE_CODE_RANGE
20325 @item TYPE_CODE_RANGE
20326 A range type, that is, an integer type with bounds.
20328 @findex TYPE_CODE_STRING
20329 @findex gdb.TYPE_CODE_STRING
20330 @item TYPE_CODE_STRING
20331 A string type. Note that this is only used for certain languages with
20332 language-defined string types; C strings are not represented this way.
20334 @findex TYPE_CODE_BITSTRING
20335 @findex gdb.TYPE_CODE_BITSTRING
20336 @item TYPE_CODE_BITSTRING
20339 @findex TYPE_CODE_ERROR
20340 @findex gdb.TYPE_CODE_ERROR
20341 @item TYPE_CODE_ERROR
20342 An unknown or erroneous type.
20344 @findex TYPE_CODE_METHOD
20345 @findex gdb.TYPE_CODE_METHOD
20346 @item TYPE_CODE_METHOD
20347 A method type, as found in C@t{++} or Java.
20349 @findex TYPE_CODE_METHODPTR
20350 @findex gdb.TYPE_CODE_METHODPTR
20351 @item TYPE_CODE_METHODPTR
20352 A pointer-to-member-function.
20354 @findex TYPE_CODE_MEMBERPTR
20355 @findex gdb.TYPE_CODE_MEMBERPTR
20356 @item TYPE_CODE_MEMBERPTR
20357 A pointer-to-member.
20359 @findex TYPE_CODE_REF
20360 @findex gdb.TYPE_CODE_REF
20361 @item TYPE_CODE_REF
20364 @findex TYPE_CODE_CHAR
20365 @findex gdb.TYPE_CODE_CHAR
20366 @item TYPE_CODE_CHAR
20369 @findex TYPE_CODE_BOOL
20370 @findex gdb.TYPE_CODE_BOOL
20371 @item TYPE_CODE_BOOL
20374 @findex TYPE_CODE_COMPLEX
20375 @findex gdb.TYPE_CODE_COMPLEX
20376 @item TYPE_CODE_COMPLEX
20377 A complex float type.
20379 @findex TYPE_CODE_TYPEDEF
20380 @findex gdb.TYPE_CODE_TYPEDEF
20381 @item TYPE_CODE_TYPEDEF
20382 A typedef to some other type.
20384 @findex TYPE_CODE_NAMESPACE
20385 @findex gdb.TYPE_CODE_NAMESPACE
20386 @item TYPE_CODE_NAMESPACE
20387 A C@t{++} namespace.
20389 @findex TYPE_CODE_DECFLOAT
20390 @findex gdb.TYPE_CODE_DECFLOAT
20391 @item TYPE_CODE_DECFLOAT
20392 A decimal floating point type.
20394 @findex TYPE_CODE_INTERNAL_FUNCTION
20395 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
20396 @item TYPE_CODE_INTERNAL_FUNCTION
20397 A function internal to @value{GDBN}. This is the type used to represent
20398 convenience functions.
20401 @node Pretty Printing
20402 @subsubsection Pretty Printing
20404 @value{GDBN} provides a mechanism to allow pretty-printing of values
20405 using Python code. The pretty-printer API allows application-specific
20406 code to greatly simplify the display of complex objects. This
20407 mechanism works for both MI and the CLI.
20409 For example, here is how a C@t{++} @code{std::string} looks without a
20413 (@value{GDBP}) print s
20415 static npos = 4294967295,
20417 <std::allocator<char>> = @{
20418 <__gnu_cxx::new_allocator<char>> = @{<No data fields>@}, <No data fields>@},
20419 members of std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider:
20420 _M_p = 0x804a014 "abcd"
20425 After a pretty-printer for @code{std::string} has been installed, only
20426 the contents are printed:
20429 (@value{GDBP}) print s
20433 A pretty-printer is just an object that holds a value and implements a
20434 specific interface, defined here.
20436 @defop Operation {pretty printer} children (self)
20437 @value{GDBN} will call this method on a pretty-printer to compute the
20438 children of the pretty-printer's value.
20440 This method must return an object conforming to the Python iterator
20441 protocol. Each item returned by the iterator must be a tuple holding
20442 two elements. The first element is the ``name'' of the child; the
20443 second element is the child's value. The value can be any Python
20444 object which is convertible to a @value{GDBN} value.
20446 This method is optional. If it does not exist, @value{GDBN} will act
20447 as though the value has no children.
20450 @defop Operation {pretty printer} display_hint (self)
20451 The CLI may call this method and use its result to change the
20452 formatting of a value. The result will also be supplied to an MI
20453 consumer as a @samp{displayhint} attribute of the variable being
20456 This method is optional. If it does exist, this method must return a
20459 Some display hints are predefined by @value{GDBN}:
20463 Indicate that the object being printed is ``array-like''. The CLI
20464 uses this to respect parameters such as @code{set print elements} and
20465 @code{set print array}.
20468 Indicate that the object being printed is ``map-like'', and that the
20469 children of this value can be assumed to alternate between keys and
20473 Indicate that the object being printed is ``string-like''. If the
20474 printer's @code{to_string} method returns a Python string of some
20475 kind, then @value{GDBN} will call its internal language-specific
20476 string-printing function to format the string. For the CLI this means
20477 adding quotation marks, possibly escaping some characters, respecting
20478 @code{set print elements}, and the like.
20482 @defop Operation {pretty printer} to_string (self)
20483 @value{GDBN} will call this method to display the string
20484 representation of the value passed to the object's constructor.
20486 When printing from the CLI, if the @code{to_string} method exists,
20487 then @value{GDBN} will prepend its result to the values returned by
20488 @code{children}. Exactly how this formatting is done is dependent on
20489 the display hint, and may change as more hints are added. Also,
20490 depending on the print settings (@pxref{Print Settings}), the CLI may
20491 print just the result of @code{to_string} in a stack trace, omitting
20492 the result of @code{children}.
20494 If this method returns a string, it is printed verbatim.
20496 Otherwise, if this method returns an instance of @code{gdb.Value},
20497 then @value{GDBN} prints this value. This may result in a call to
20498 another pretty-printer.
20500 If instead the method returns a Python value which is convertible to a
20501 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
20502 the resulting value. Again, this may result in a call to another
20503 pretty-printer. Python scalars (integers, floats, and booleans) and
20504 strings are convertible to @code{gdb.Value}; other types are not.
20506 Finally, if this method returns @code{None} then no further operations
20507 are peformed in this method and nothing is printed.
20509 If the result is not one of these types, an exception is raised.
20512 @node Selecting Pretty-Printers
20513 @subsubsection Selecting Pretty-Printers
20515 The Python list @code{gdb.pretty_printers} contains an array of
20516 functions that have been registered via addition as a pretty-printer.
20517 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
20518 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
20521 A function on one of these lists is passed a single @code{gdb.Value}
20522 argument and should return a pretty-printer object conforming to the
20523 interface definition above (@pxref{Pretty Printing}). If a function
20524 cannot create a pretty-printer for the value, it should return
20527 @value{GDBN} first checks the @code{pretty_printers} attribute of each
20528 @code{gdb.Objfile} in the current program space and iteratively calls
20529 each function in the list for that @code{gdb.Objfile} until it receives
20530 a pretty-printer object.
20531 If no pretty-printer is found in the objfile lists, @value{GDBN} then
20532 searches the pretty-printer list of the current program space,
20533 calling each function until an object is returned.
20534 After these lists have been exhausted, it tries the global
20535 @code{gdb.pretty-printers} list, again calling each function until an
20536 object is returned.
20538 The order in which the objfiles are searched is not specified. For a
20539 given list, functions are always invoked from the head of the list,
20540 and iterated over sequentially until the end of the list, or a printer
20541 object is returned.
20543 Here is an example showing how a @code{std::string} printer might be
20547 class StdStringPrinter:
20548 "Print a std::string"
20550 def __init__ (self, val):
20553 def to_string (self):
20554 return self.val['_M_dataplus']['_M_p']
20556 def display_hint (self):
20560 And here is an example showing how a lookup function for the printer
20561 example above might be written.
20564 def str_lookup_function (val):
20566 lookup_tag = val.type.tag
20567 regex = re.compile ("^std::basic_string<char,.*>$")
20568 if lookup_tag == None:
20570 if regex.match (lookup_tag):
20571 return StdStringPrinter (val)
20576 The example lookup function extracts the value's type, and attempts to
20577 match it to a type that it can pretty-print. If it is a type the
20578 printer can pretty-print, it will return a printer object. If not, it
20579 returns @code{None}.
20581 We recommend that you put your core pretty-printers into a Python
20582 package. If your pretty-printers are for use with a library, we
20583 further recommend embedding a version number into the package name.
20584 This practice will enable @value{GDBN} to load multiple versions of
20585 your pretty-printers at the same time, because they will have
20588 You should write auto-loaded code (@pxref{Auto-loading}) such that it
20589 can be evaluated multiple times without changing its meaning. An
20590 ideal auto-load file will consist solely of @code{import}s of your
20591 printer modules, followed by a call to a register pretty-printers with
20592 the current objfile.
20594 Taken as a whole, this approach will scale nicely to multiple
20595 inferiors, each potentially using a different library version.
20596 Embedding a version number in the Python package name will ensure that
20597 @value{GDBN} is able to load both sets of printers simultaneously.
20598 Then, because the search for pretty-printers is done by objfile, and
20599 because your auto-loaded code took care to register your library's
20600 printers with a specific objfile, @value{GDBN} will find the correct
20601 printers for the specific version of the library used by each
20604 To continue the @code{std::string} example (@pxref{Pretty Printing}),
20605 this code might appear in @code{gdb.libstdcxx.v6}:
20608 def register_printers (objfile):
20609 objfile.pretty_printers.add (str_lookup_function)
20613 And then the corresponding contents of the auto-load file would be:
20616 import gdb.libstdcxx.v6
20617 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
20620 @node Commands In Python
20621 @subsubsection Commands In Python
20623 @cindex commands in python
20624 @cindex python commands
20625 You can implement new @value{GDBN} CLI commands in Python. A CLI
20626 command is implemented using an instance of the @code{gdb.Command}
20627 class, most commonly using a subclass.
20629 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
20630 The object initializer for @code{Command} registers the new command
20631 with @value{GDBN}. This initializer is normally invoked from the
20632 subclass' own @code{__init__} method.
20634 @var{name} is the name of the command. If @var{name} consists of
20635 multiple words, then the initial words are looked for as prefix
20636 commands. In this case, if one of the prefix commands does not exist,
20637 an exception is raised.
20639 There is no support for multi-line commands.
20641 @var{command_class} should be one of the @samp{COMMAND_} constants
20642 defined below. This argument tells @value{GDBN} how to categorize the
20643 new command in the help system.
20645 @var{completer_class} is an optional argument. If given, it should be
20646 one of the @samp{COMPLETE_} constants defined below. This argument
20647 tells @value{GDBN} how to perform completion for this command. If not
20648 given, @value{GDBN} will attempt to complete using the object's
20649 @code{complete} method (see below); if no such method is found, an
20650 error will occur when completion is attempted.
20652 @var{prefix} is an optional argument. If @code{True}, then the new
20653 command is a prefix command; sub-commands of this command may be
20656 The help text for the new command is taken from the Python
20657 documentation string for the command's class, if there is one. If no
20658 documentation string is provided, the default value ``This command is
20659 not documented.'' is used.
20662 @cindex don't repeat Python command
20663 @defmethod Command dont_repeat
20664 By default, a @value{GDBN} command is repeated when the user enters a
20665 blank line at the command prompt. A command can suppress this
20666 behavior by invoking the @code{dont_repeat} method. This is similar
20667 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
20670 @defmethod Command invoke argument from_tty
20671 This method is called by @value{GDBN} when this command is invoked.
20673 @var{argument} is a string. It is the argument to the command, after
20674 leading and trailing whitespace has been stripped.
20676 @var{from_tty} is a boolean argument. When true, this means that the
20677 command was entered by the user at the terminal; when false it means
20678 that the command came from elsewhere.
20680 If this method throws an exception, it is turned into a @value{GDBN}
20681 @code{error} call. Otherwise, the return value is ignored.
20684 @cindex completion of Python commands
20685 @defmethod Command complete text word
20686 This method is called by @value{GDBN} when the user attempts
20687 completion on this command. All forms of completion are handled by
20688 this method, that is, the @key{TAB} and @key{M-?} key bindings
20689 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
20692 The arguments @var{text} and @var{word} are both strings. @var{text}
20693 holds the complete command line up to the cursor's location.
20694 @var{word} holds the last word of the command line; this is computed
20695 using a word-breaking heuristic.
20697 The @code{complete} method can return several values:
20700 If the return value is a sequence, the contents of the sequence are
20701 used as the completions. It is up to @code{complete} to ensure that the
20702 contents actually do complete the word. A zero-length sequence is
20703 allowed, it means that there were no completions available. Only
20704 string elements of the sequence are used; other elements in the
20705 sequence are ignored.
20708 If the return value is one of the @samp{COMPLETE_} constants defined
20709 below, then the corresponding @value{GDBN}-internal completion
20710 function is invoked, and its result is used.
20713 All other results are treated as though there were no available
20718 When a new command is registered, it must be declared as a member of
20719 some general class of commands. This is used to classify top-level
20720 commands in the on-line help system; note that prefix commands are not
20721 listed under their own category but rather that of their top-level
20722 command. The available classifications are represented by constants
20723 defined in the @code{gdb} module:
20726 @findex COMMAND_NONE
20727 @findex gdb.COMMAND_NONE
20729 The command does not belong to any particular class. A command in
20730 this category will not be displayed in any of the help categories.
20732 @findex COMMAND_RUNNING
20733 @findex gdb.COMMAND_RUNNING
20734 @item COMMAND_RUNNING
20735 The command is related to running the inferior. For example,
20736 @code{start}, @code{step}, and @code{continue} are in this category.
20737 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
20738 commands in this category.
20740 @findex COMMAND_DATA
20741 @findex gdb.COMMAND_DATA
20743 The command is related to data or variables. For example,
20744 @code{call}, @code{find}, and @code{print} are in this category. Type
20745 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
20748 @findex COMMAND_STACK
20749 @findex gdb.COMMAND_STACK
20750 @item COMMAND_STACK
20751 The command has to do with manipulation of the stack. For example,
20752 @code{backtrace}, @code{frame}, and @code{return} are in this
20753 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
20754 list of commands in this category.
20756 @findex COMMAND_FILES
20757 @findex gdb.COMMAND_FILES
20758 @item COMMAND_FILES
20759 This class is used for file-related commands. For example,
20760 @code{file}, @code{list} and @code{section} are in this category.
20761 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
20762 commands in this category.
20764 @findex COMMAND_SUPPORT
20765 @findex gdb.COMMAND_SUPPORT
20766 @item COMMAND_SUPPORT
20767 This should be used for ``support facilities'', generally meaning
20768 things that are useful to the user when interacting with @value{GDBN},
20769 but not related to the state of the inferior. For example,
20770 @code{help}, @code{make}, and @code{shell} are in this category. Type
20771 @kbd{help support} at the @value{GDBN} prompt to see a list of
20772 commands in this category.
20774 @findex COMMAND_STATUS
20775 @findex gdb.COMMAND_STATUS
20776 @item COMMAND_STATUS
20777 The command is an @samp{info}-related command, that is, related to the
20778 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
20779 and @code{show} are in this category. Type @kbd{help status} at the
20780 @value{GDBN} prompt to see a list of commands in this category.
20782 @findex COMMAND_BREAKPOINTS
20783 @findex gdb.COMMAND_BREAKPOINTS
20784 @item COMMAND_BREAKPOINTS
20785 The command has to do with breakpoints. For example, @code{break},
20786 @code{clear}, and @code{delete} are in this category. Type @kbd{help
20787 breakpoints} at the @value{GDBN} prompt to see a list of commands in
20790 @findex COMMAND_TRACEPOINTS
20791 @findex gdb.COMMAND_TRACEPOINTS
20792 @item COMMAND_TRACEPOINTS
20793 The command has to do with tracepoints. For example, @code{trace},
20794 @code{actions}, and @code{tfind} are in this category. Type
20795 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
20796 commands in this category.
20798 @findex COMMAND_OBSCURE
20799 @findex gdb.COMMAND_OBSCURE
20800 @item COMMAND_OBSCURE
20801 The command is only used in unusual circumstances, or is not of
20802 general interest to users. For example, @code{checkpoint},
20803 @code{fork}, and @code{stop} are in this category. Type @kbd{help
20804 obscure} at the @value{GDBN} prompt to see a list of commands in this
20807 @findex COMMAND_MAINTENANCE
20808 @findex gdb.COMMAND_MAINTENANCE
20809 @item COMMAND_MAINTENANCE
20810 The command is only useful to @value{GDBN} maintainers. The
20811 @code{maintenance} and @code{flushregs} commands are in this category.
20812 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
20813 commands in this category.
20816 A new command can use a predefined completion function, either by
20817 specifying it via an argument at initialization, or by returning it
20818 from the @code{complete} method. These predefined completion
20819 constants are all defined in the @code{gdb} module:
20822 @findex COMPLETE_NONE
20823 @findex gdb.COMPLETE_NONE
20824 @item COMPLETE_NONE
20825 This constant means that no completion should be done.
20827 @findex COMPLETE_FILENAME
20828 @findex gdb.COMPLETE_FILENAME
20829 @item COMPLETE_FILENAME
20830 This constant means that filename completion should be performed.
20832 @findex COMPLETE_LOCATION
20833 @findex gdb.COMPLETE_LOCATION
20834 @item COMPLETE_LOCATION
20835 This constant means that location completion should be done.
20836 @xref{Specify Location}.
20838 @findex COMPLETE_COMMAND
20839 @findex gdb.COMPLETE_COMMAND
20840 @item COMPLETE_COMMAND
20841 This constant means that completion should examine @value{GDBN}
20844 @findex COMPLETE_SYMBOL
20845 @findex gdb.COMPLETE_SYMBOL
20846 @item COMPLETE_SYMBOL
20847 This constant means that completion should be done using symbol names
20851 The following code snippet shows how a trivial CLI command can be
20852 implemented in Python:
20855 class HelloWorld (gdb.Command):
20856 """Greet the whole world."""
20858 def __init__ (self):
20859 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20861 def invoke (self, arg, from_tty):
20862 print "Hello, World!"
20867 The last line instantiates the class, and is necessary to trigger the
20868 registration of the command with @value{GDBN}. Depending on how the
20869 Python code is read into @value{GDBN}, you may need to import the
20870 @code{gdb} module explicitly.
20872 @node Functions In Python
20873 @subsubsection Writing new convenience functions
20875 @cindex writing convenience functions
20876 @cindex convenience functions in python
20877 @cindex python convenience functions
20878 @tindex gdb.Function
20880 You can implement new convenience functions (@pxref{Convenience Vars})
20881 in Python. A convenience function is an instance of a subclass of the
20882 class @code{gdb.Function}.
20884 @defmethod Function __init__ name
20885 The initializer for @code{Function} registers the new function with
20886 @value{GDBN}. The argument @var{name} is the name of the function,
20887 a string. The function will be visible to the user as a convenience
20888 variable of type @code{internal function}, whose name is the same as
20889 the given @var{name}.
20891 The documentation for the new function is taken from the documentation
20892 string for the new class.
20895 @defmethod Function invoke @var{*args}
20896 When a convenience function is evaluated, its arguments are converted
20897 to instances of @code{gdb.Value}, and then the function's
20898 @code{invoke} method is called. Note that @value{GDBN} does not
20899 predetermine the arity of convenience functions. Instead, all
20900 available arguments are passed to @code{invoke}, following the
20901 standard Python calling convention. In particular, a convenience
20902 function can have default values for parameters without ill effect.
20904 The return value of this method is used as its value in the enclosing
20905 expression. If an ordinary Python value is returned, it is converted
20906 to a @code{gdb.Value} following the usual rules.
20909 The following code snippet shows how a trivial convenience function can
20910 be implemented in Python:
20913 class Greet (gdb.Function):
20914 """Return string to greet someone.
20915 Takes a name as argument."""
20917 def __init__ (self):
20918 super (Greet, self).__init__ ("greet")
20920 def invoke (self, name):
20921 return "Hello, %s!" % name.string ()
20926 The last line instantiates the class, and is necessary to trigger the
20927 registration of the function with @value{GDBN}. Depending on how the
20928 Python code is read into @value{GDBN}, you may need to import the
20929 @code{gdb} module explicitly.
20931 @node Progspaces In Python
20932 @subsubsection Program Spaces In Python
20934 @cindex progspaces in python
20935 @tindex gdb.Progspace
20937 A program space, or @dfn{progspace}, represents a symbolic view
20938 of an address space.
20939 It consists of all of the objfiles of the program.
20940 @xref{Objfiles In Python}.
20941 @xref{Inferiors and Programs, program spaces}, for more details
20942 about program spaces.
20944 The following progspace-related functions are available in the
20947 @findex gdb.current_progspace
20948 @defun current_progspace
20949 This function returns the program space of the currently selected inferior.
20950 @xref{Inferiors and Programs}.
20953 @findex gdb.progspaces
20955 Return a sequence of all the progspaces currently known to @value{GDBN}.
20958 Each progspace is represented by an instance of the @code{gdb.Progspace}
20961 @defivar Progspace filename
20962 The file name of the progspace as a string.
20965 @defivar Progspace pretty_printers
20966 The @code{pretty_printers} attribute is a list of functions. It is
20967 used to look up pretty-printers. A @code{Value} is passed to each
20968 function in order; if the function returns @code{None}, then the
20969 search continues. Otherwise, the return value should be an object
20970 which is used to format the value. @xref{Pretty Printing}, for more
20974 @node Objfiles In Python
20975 @subsubsection Objfiles In Python
20977 @cindex objfiles in python
20978 @tindex gdb.Objfile
20980 @value{GDBN} loads symbols for an inferior from various
20981 symbol-containing files (@pxref{Files}). These include the primary
20982 executable file, any shared libraries used by the inferior, and any
20983 separate debug info files (@pxref{Separate Debug Files}).
20984 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
20986 The following objfile-related functions are available in the
20989 @findex gdb.current_objfile
20990 @defun current_objfile
20991 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
20992 sets the ``current objfile'' to the corresponding objfile. This
20993 function returns the current objfile. If there is no current objfile,
20994 this function returns @code{None}.
20997 @findex gdb.objfiles
20999 Return a sequence of all the objfiles current known to @value{GDBN}.
21000 @xref{Objfiles In Python}.
21003 Each objfile is represented by an instance of the @code{gdb.Objfile}
21006 @defivar Objfile filename
21007 The file name of the objfile as a string.
21010 @defivar Objfile pretty_printers
21011 The @code{pretty_printers} attribute is a list of functions. It is
21012 used to look up pretty-printers. A @code{Value} is passed to each
21013 function in order; if the function returns @code{None}, then the
21014 search continues. Otherwise, the return value should be an object
21015 which is used to format the value. @xref{Pretty Printing}, for more
21019 @node Frames In Python
21020 @subsubsection Accessing inferior stack frames from Python.
21022 @cindex frames in python
21023 When the debugged program stops, @value{GDBN} is able to analyze its call
21024 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
21025 represents a frame in the stack. A @code{gdb.Frame} object is only valid
21026 while its corresponding frame exists in the inferior's stack. If you try
21027 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
21030 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
21034 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
21038 The following frame-related functions are available in the @code{gdb} module:
21040 @findex gdb.selected_frame
21041 @defun selected_frame
21042 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
21045 @defun frame_stop_reason_string reason
21046 Return a string explaining the reason why @value{GDBN} stopped unwinding
21047 frames, as expressed by the given @var{reason} code (an integer, see the
21048 @code{unwind_stop_reason} method further down in this section).
21051 A @code{gdb.Frame} object has the following methods:
21054 @defmethod Frame is_valid
21055 Returns true if the @code{gdb.Frame} object is valid, false if not.
21056 A frame object can become invalid if the frame it refers to doesn't
21057 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
21058 an exception if it is invalid at the time the method is called.
21061 @defmethod Frame name
21062 Returns the function name of the frame, or @code{None} if it can't be
21066 @defmethod Frame type
21067 Returns the type of the frame. The value can be one of
21068 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
21069 or @code{gdb.SENTINEL_FRAME}.
21072 @defmethod Frame unwind_stop_reason
21073 Return an integer representing the reason why it's not possible to find
21074 more frames toward the outermost frame. Use
21075 @code{gdb.frame_stop_reason_string} to convert the value returned by this
21076 function to a string.
21079 @defmethod Frame pc
21080 Returns the frame's resume address.
21083 @defmethod Frame block
21084 Return the frame's code block. @xref{Blocks In Python}.
21087 @defmethod Frame function
21088 Return the symbol for the function corresponding to this frame.
21089 @xref{Symbols In Python}.
21092 @defmethod Frame older
21093 Return the frame that called this frame.
21096 @defmethod Frame newer
21097 Return the frame called by this frame.
21100 @defmethod Frame find_sal
21101 Return the frame's symtab and line object.
21102 @xref{Symbol Tables In Python}.
21105 @defmethod Frame read_var variable @r{[}block@r{]}
21106 Return the value of @var{variable} in this frame. If the optional
21107 argument @var{block} is provided, search for the variable from that
21108 block; otherwise start at the frame's current block (which is
21109 determined by the frame's current program counter). @var{variable}
21110 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
21111 @code{gdb.Block} object.
21114 @defmethod Frame select
21115 Set this frame to be the selected frame. @xref{Stack, ,Examining the
21120 @node Blocks In Python
21121 @subsubsection Accessing frame blocks from Python.
21123 @cindex blocks in python
21126 Within each frame, @value{GDBN} maintains information on each block
21127 stored in that frame. These blocks are organized hierarchically, and
21128 are represented individually in Python as a @code{gdb.Block}.
21129 Please see @ref{Frames In Python}, for a more in-depth discussion on
21130 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
21131 detailed technical information on @value{GDBN}'s book-keeping of the
21134 The following block-related functions are available in the @code{gdb}
21137 @findex gdb.block_for_pc
21138 @defun block_for_pc pc
21139 Return the @code{gdb.Block} containing the given @var{pc} value. If the
21140 block cannot be found for the @var{pc} value specified, the function
21141 will return @code{None}.
21144 A @code{gdb.Block} object has the following attributes:
21147 @defivar Block start
21148 The start address of the block. This attribute is not writable.
21152 The end address of the block. This attribute is not writable.
21155 @defivar Block function
21156 The name of the block represented as a @code{gdb.Symbol}. If the
21157 block is not named, then this attribute holds @code{None}. This
21158 attribute is not writable.
21161 @defivar Block superblock
21162 The block containing this block. If this parent block does not exist,
21163 this attribute holds @code{None}. This attribute is not writable.
21167 @node Symbols In Python
21168 @subsubsection Python representation of Symbols.
21170 @cindex symbols in python
21173 @value{GDBN} represents every variable, function and type as an
21174 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
21175 Similarly, Python represents these symbols in @value{GDBN} with the
21176 @code{gdb.Symbol} object.
21178 The following symbol-related functions are available in the @code{gdb}
21181 @findex gdb.lookup_symbol
21182 @defun lookup_symbol name [block] [domain]
21183 This function searches for a symbol by name. The search scope can be
21184 restricted to the parameters defined in the optional domain and block
21187 @var{name} is the name of the symbol. It must be a string. The
21188 optional @var{block} argument restricts the search to symbols visible
21189 in that @var{block}. The @var{block} argument must be a
21190 @code{gdb.Block} object. The optional @var{domain} argument restricts
21191 the search to the domain type. The @var{domain} argument must be a
21192 domain constant defined in the @code{gdb} module and described later
21196 A @code{gdb.Symbol} object has the following attributes:
21199 @defivar Symbol symtab
21200 The symbol table in which the symbol appears. This attribute is
21201 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
21202 Python}. This attribute is not writable.
21205 @defivar Symbol name
21206 The name of the symbol as a string. This attribute is not writable.
21209 @defivar Symbol linkage_name
21210 The name of the symbol, as used by the linker (i.e., may be mangled).
21211 This attribute is not writable.
21214 @defivar Symbol print_name
21215 The name of the symbol in a form suitable for output. This is either
21216 @code{name} or @code{linkage_name}, depending on whether the user
21217 asked @value{GDBN} to display demangled or mangled names.
21220 @defivar Symbol addr_class
21221 The address class of the symbol. This classifies how to find the value
21222 of a symbol. Each address class is a constant defined in the
21223 @code{gdb} module and described later in this chapter.
21226 @defivar Symbol is_argument
21227 @code{True} if the symbol is an argument of a function.
21230 @defivar Symbol is_constant
21231 @code{True} if the symbol is a constant.
21234 @defivar Symbol is_function
21235 @code{True} if the symbol is a function or a method.
21238 @defivar Symbol is_variable
21239 @code{True} if the symbol is a variable.
21243 The available domain categories in @code{gdb.Symbol} are represented
21244 as constants in the @code{gdb} module:
21247 @findex SYMBOL_UNDEF_DOMAIN
21248 @findex gdb.SYMBOL_UNDEF_DOMAIN
21249 @item SYMBOL_UNDEF_DOMAIN
21250 This is used when a domain has not been discovered or none of the
21251 following domains apply. This usually indicates an error either
21252 in the symbol information or in @value{GDBN}'s handling of symbols.
21253 @findex SYMBOL_VAR_DOMAIN
21254 @findex gdb.SYMBOL_VAR_DOMAIN
21255 @item SYMBOL_VAR_DOMAIN
21256 This domain contains variables, function names, typedef names and enum
21258 @findex SYMBOL_STRUCT_DOMAIN
21259 @findex gdb.SYMBOL_STRUCT_DOMAIN
21260 @item SYMBOL_STRUCT_DOMAIN
21261 This domain holds struct, union and enum type names.
21262 @findex SYMBOL_LABEL_DOMAIN
21263 @findex gdb.SYMBOL_LABEL_DOMAIN
21264 @item SYMBOL_LABEL_DOMAIN
21265 This domain contains names of labels (for gotos).
21266 @findex SYMBOL_VARIABLES_DOMAIN
21267 @findex gdb.SYMBOL_VARIABLES_DOMAIN
21268 @item SYMBOL_VARIABLES_DOMAIN
21269 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
21270 contains everything minus functions and types.
21271 @findex SYMBOL_FUNCTIONS_DOMAIN
21272 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
21273 @item SYMBOL_FUNCTION_DOMAIN
21274 This domain contains all functions.
21275 @findex SYMBOL_TYPES_DOMAIN
21276 @findex gdb.SYMBOL_TYPES_DOMAIN
21277 @item SYMBOL_TYPES_DOMAIN
21278 This domain contains all types.
21281 The available address class categories in @code{gdb.Symbol} are represented
21282 as constants in the @code{gdb} module:
21285 @findex SYMBOL_LOC_UNDEF
21286 @findex gdb.SYMBOL_LOC_UNDEF
21287 @item SYMBOL_LOC_UNDEF
21288 If this is returned by address class, it indicates an error either in
21289 the symbol information or in @value{GDBN}'s handling of symbols.
21290 @findex SYMBOL_LOC_CONST
21291 @findex gdb.SYMBOL_LOC_CONST
21292 @item SYMBOL_LOC_CONST
21293 Value is constant int.
21294 @findex SYMBOL_LOC_STATIC
21295 @findex gdb.SYMBOL_LOC_STATIC
21296 @item SYMBOL_LOC_STATIC
21297 Value is at a fixed address.
21298 @findex SYMBOL_LOC_REGISTER
21299 @findex gdb.SYMBOL_LOC_REGISTER
21300 @item SYMBOL_LOC_REGISTER
21301 Value is in a register.
21302 @findex SYMBOL_LOC_ARG
21303 @findex gdb.SYMBOL_LOC_ARG
21304 @item SYMBOL_LOC_ARG
21305 Value is an argument. This value is at the offset stored within the
21306 symbol inside the frame's argument list.
21307 @findex SYMBOL_LOC_REF_ARG
21308 @findex gdb.SYMBOL_LOC_REF_ARG
21309 @item SYMBOL_LOC_REF_ARG
21310 Value address is stored in the frame's argument list. Just like
21311 @code{LOC_ARG} except that the value's address is stored at the
21312 offset, not the value itself.
21313 @findex SYMBOL_LOC_REGPARM_ADDR
21314 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
21315 @item SYMBOL_LOC_REGPARM_ADDR
21316 Value is a specified register. Just like @code{LOC_REGISTER} except
21317 the register holds the address of the argument instead of the argument
21319 @findex SYMBOL_LOC_LOCAL
21320 @findex gdb.SYMBOL_LOC_LOCAL
21321 @item SYMBOL_LOC_LOCAL
21322 Value is a local variable.
21323 @findex SYMBOL_LOC_TYPEDEF
21324 @findex gdb.SYMBOL_LOC_TYPEDEF
21325 @item SYMBOL_LOC_TYPEDEF
21326 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
21328 @findex SYMBOL_LOC_BLOCK
21329 @findex gdb.SYMBOL_LOC_BLOCK
21330 @item SYMBOL_LOC_BLOCK
21332 @findex SYMBOL_LOC_CONST_BYTES
21333 @findex gdb.SYMBOL_LOC_CONST_BYTES
21334 @item SYMBOL_LOC_CONST_BYTES
21335 Value is a byte-sequence.
21336 @findex SYMBOL_LOC_UNRESOLVED
21337 @findex gdb.SYMBOL_LOC_UNRESOLVED
21338 @item SYMBOL_LOC_UNRESOLVED
21339 Value is at a fixed address, but the address of the variable has to be
21340 determined from the minimal symbol table whenever the variable is
21342 @findex SYMBOL_LOC_OPTIMIZED_OUT
21343 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
21344 @item SYMBOL_LOC_OPTIMIZED_OUT
21345 The value does not actually exist in the program.
21346 @findex SYMBOL_LOC_COMPUTED
21347 @findex gdb.SYMBOL_LOC_COMPUTED
21348 @item SYMBOL_LOC_COMPUTED
21349 The value's address is a computed location.
21352 @node Symbol Tables In Python
21353 @subsubsection Symbol table representation in Python.
21355 @cindex symbol tables in python
21357 @tindex gdb.Symtab_and_line
21359 Access to symbol table data maintained by @value{GDBN} on the inferior
21360 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
21361 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
21362 from the @code{find_sal} method in @code{gdb.Frame} object.
21363 @xref{Frames In Python}.
21365 For more information on @value{GDBN}'s symbol table management, see
21366 @ref{Symbols, ,Examining the Symbol Table}, for more information.
21368 A @code{gdb.Symtab_and_line} object has the following attributes:
21371 @defivar Symtab_and_line symtab
21372 The symbol table object (@code{gdb.Symtab}) for this frame.
21373 This attribute is not writable.
21376 @defivar Symtab_and_line pc
21377 Indicates the current program counter address. This attribute is not
21381 @defivar Symtab_and_line line
21382 Indicates the current line number for this object. This
21383 attribute is not writable.
21387 A @code{gdb.Symtab} object has the following attributes:
21390 @defivar Symtab filename
21391 The symbol table's source filename. This attribute is not writable.
21394 @defivar Symtab objfile
21395 The symbol table's backing object file. @xref{Objfiles In Python}.
21396 This attribute is not writable.
21400 The following methods are provided:
21403 @defmethod Symtab fullname
21404 Return the symbol table's source absolute file name.
21408 @node Breakpoints In Python
21409 @subsubsection Manipulating breakpoints using Python
21411 @cindex breakpoints in python
21412 @tindex gdb.Breakpoint
21414 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
21417 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
21418 Create a new breakpoint. @var{spec} is a string naming the
21419 location of the breakpoint, or an expression that defines a
21420 watchpoint. The contents can be any location recognized by the
21421 @code{break} command, or in the case of a watchpoint, by the @code{watch}
21422 command. The optional @var{type} denotes the breakpoint to create
21423 from the types defined later in this chapter. This argument can be
21424 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
21425 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
21426 argument defines the class of watchpoint to create, if @var{type} is
21427 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
21428 provided, it is assumed to be a @var{WP_WRITE} class.
21431 The available watchpoint types represented by constants are defined in the
21436 @findex gdb.WP_READ
21438 Read only watchpoint.
21441 @findex gdb.WP_WRITE
21443 Write only watchpoint.
21446 @findex gdb.WP_ACCESS
21448 Read/Write watchpoint.
21451 @defmethod Breakpoint is_valid
21452 Return @code{True} if this @code{Breakpoint} object is valid,
21453 @code{False} otherwise. A @code{Breakpoint} object can become invalid
21454 if the user deletes the breakpoint. In this case, the object still
21455 exists, but the underlying breakpoint does not. In the cases of
21456 watchpoint scope, the watchpoint remains valid even if execution of the
21457 inferior leaves the scope of that watchpoint.
21460 @defivar Breakpoint enabled
21461 This attribute is @code{True} if the breakpoint is enabled, and
21462 @code{False} otherwise. This attribute is writable.
21465 @defivar Breakpoint silent
21466 This attribute is @code{True} if the breakpoint is silent, and
21467 @code{False} otherwise. This attribute is writable.
21469 Note that a breakpoint can also be silent if it has commands and the
21470 first command is @code{silent}. This is not reported by the
21471 @code{silent} attribute.
21474 @defivar Breakpoint thread
21475 If the breakpoint is thread-specific, this attribute holds the thread
21476 id. If the breakpoint is not thread-specific, this attribute is
21477 @code{None}. This attribute is writable.
21480 @defivar Breakpoint task
21481 If the breakpoint is Ada task-specific, this attribute holds the Ada task
21482 id. If the breakpoint is not task-specific (or the underlying
21483 language is not Ada), this attribute is @code{None}. This attribute
21487 @defivar Breakpoint ignore_count
21488 This attribute holds the ignore count for the breakpoint, an integer.
21489 This attribute is writable.
21492 @defivar Breakpoint number
21493 This attribute holds the breakpoint's number --- the identifier used by
21494 the user to manipulate the breakpoint. This attribute is not writable.
21497 @defivar Breakpoint type
21498 This attribute holds the breakpoint's type --- the identifier used to
21499 determine the actual breakpoint type or use-case. This attribute is not
21503 The available types are represented by constants defined in the @code{gdb}
21507 @findex BP_BREAKPOINT
21508 @findex gdb.BP_BREAKPOINT
21509 @item BP_BREAKPOINT
21510 Normal code breakpoint.
21512 @findex BP_WATCHPOINT
21513 @findex gdb.BP_WATCHPOINT
21514 @item BP_WATCHPOINT
21515 Watchpoint breakpoint.
21517 @findex BP_HARDWARE_WATCHPOINT
21518 @findex gdb.BP_HARDWARE_WATCHPOINT
21519 @item BP_HARDWARE_WATCHPOINT
21520 Hardware assisted watchpoint.
21522 @findex BP_READ_WATCHPOINT
21523 @findex gdb.BP_READ_WATCHPOINT
21524 @item BP_READ_WATCHPOINT
21525 Hardware assisted read watchpoint.
21527 @findex BP_ACCESS_WATCHPOINT
21528 @findex gdb.BP_ACCESS_WATCHPOINT
21529 @item BP_ACCESS_WATCHPOINT
21530 Hardware assisted access watchpoint.
21533 @defivar Breakpoint hit_count
21534 This attribute holds the hit count for the breakpoint, an integer.
21535 This attribute is writable, but currently it can only be set to zero.
21538 @defivar Breakpoint location
21539 This attribute holds the location of the breakpoint, as specified by
21540 the user. It is a string. If the breakpoint does not have a location
21541 (that is, it is a watchpoint) the attribute's value is @code{None}. This
21542 attribute is not writable.
21545 @defivar Breakpoint expression
21546 This attribute holds a breakpoint expression, as specified by
21547 the user. It is a string. If the breakpoint does not have an
21548 expression (the breakpoint is not a watchpoint) the attribute's value
21549 is @code{None}. This attribute is not writable.
21552 @defivar Breakpoint condition
21553 This attribute holds the condition of the breakpoint, as specified by
21554 the user. It is a string. If there is no condition, this attribute's
21555 value is @code{None}. This attribute is writable.
21558 @defivar Breakpoint commands
21559 This attribute holds the commands attached to the breakpoint. If
21560 there are commands, this attribute's value is a string holding all the
21561 commands, separated by newlines. If there are no commands, this
21562 attribute is @code{None}. This attribute is not writable.
21565 @node Lazy Strings In Python
21566 @subsubsection Python representation of lazy strings.
21568 @cindex lazy strings in python
21569 @tindex gdb.LazyString
21571 A @dfn{lazy string} is a string whose contents is not retrieved or
21572 encoded until it is needed.
21574 A @code{gdb.LazyString} is represented in @value{GDBN} as an
21575 @code{address} that points to a region of memory, an @code{encoding}
21576 that will be used to encode that region of memory, and a @code{length}
21577 to delimit the region of memory that represents the string. The
21578 difference between a @code{gdb.LazyString} and a string wrapped within
21579 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
21580 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
21581 retrieved and encoded during printing, while a @code{gdb.Value}
21582 wrapping a string is immediately retrieved and encoded on creation.
21584 A @code{gdb.LazyString} object has the following functions:
21586 @defmethod LazyString value
21587 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
21588 will point to the string in memory, but will lose all the delayed
21589 retrieval, encoding and handling that @value{GDBN} applies to a
21590 @code{gdb.LazyString}.
21593 @defivar LazyString address
21594 This attribute holds the address of the string. This attribute is not
21598 @defivar LazyString length
21599 This attribute holds the length of the string in characters. If the
21600 length is -1, then the string will be fetched and encoded up to the
21601 first null of appropriate width. This attribute is not writable.
21604 @defivar LazyString encoding
21605 This attribute holds the encoding that will be applied to the string
21606 when the string is printed by @value{GDBN}. If the encoding is not
21607 set, or contains an empty string, then @value{GDBN} will select the
21608 most appropriate encoding when the string is printed. This attribute
21612 @defivar LazyString type
21613 This attribute holds the type that is represented by the lazy string's
21614 type. For a lazy string this will always be a pointer type. To
21615 resolve this to the lazy string's character type, use the type's
21616 @code{target} method. @xref{Types In Python}. This attribute is not
21621 @chapter Command Interpreters
21622 @cindex command interpreters
21624 @value{GDBN} supports multiple command interpreters, and some command
21625 infrastructure to allow users or user interface writers to switch
21626 between interpreters or run commands in other interpreters.
21628 @value{GDBN} currently supports two command interpreters, the console
21629 interpreter (sometimes called the command-line interpreter or @sc{cli})
21630 and the machine interface interpreter (or @sc{gdb/mi}). This manual
21631 describes both of these interfaces in great detail.
21633 By default, @value{GDBN} will start with the console interpreter.
21634 However, the user may choose to start @value{GDBN} with another
21635 interpreter by specifying the @option{-i} or @option{--interpreter}
21636 startup options. Defined interpreters include:
21640 @cindex console interpreter
21641 The traditional console or command-line interpreter. This is the most often
21642 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
21643 @value{GDBN} will use this interpreter.
21646 @cindex mi interpreter
21647 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
21648 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
21649 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
21653 @cindex mi2 interpreter
21654 The current @sc{gdb/mi} interface.
21657 @cindex mi1 interpreter
21658 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
21662 @cindex invoke another interpreter
21663 The interpreter being used by @value{GDBN} may not be dynamically
21664 switched at runtime. Although possible, this could lead to a very
21665 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
21666 enters the command "interpreter-set console" in a console view,
21667 @value{GDBN} would switch to using the console interpreter, rendering
21668 the IDE inoperable!
21670 @kindex interpreter-exec
21671 Although you may only choose a single interpreter at startup, you may execute
21672 commands in any interpreter from the current interpreter using the appropriate
21673 command. If you are running the console interpreter, simply use the
21674 @code{interpreter-exec} command:
21677 interpreter-exec mi "-data-list-register-names"
21680 @sc{gdb/mi} has a similar command, although it is only available in versions of
21681 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
21684 @chapter @value{GDBN} Text User Interface
21686 @cindex Text User Interface
21689 * TUI Overview:: TUI overview
21690 * TUI Keys:: TUI key bindings
21691 * TUI Single Key Mode:: TUI single key mode
21692 * TUI Commands:: TUI-specific commands
21693 * TUI Configuration:: TUI configuration variables
21696 The @value{GDBN} Text User Interface (TUI) is a terminal
21697 interface which uses the @code{curses} library to show the source
21698 file, the assembly output, the program registers and @value{GDBN}
21699 commands in separate text windows. The TUI mode is supported only
21700 on platforms where a suitable version of the @code{curses} library
21703 @pindex @value{GDBTUI}
21704 The TUI mode is enabled by default when you invoke @value{GDBN} as
21705 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
21706 You can also switch in and out of TUI mode while @value{GDBN} runs by
21707 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
21708 @xref{TUI Keys, ,TUI Key Bindings}.
21711 @section TUI Overview
21713 In TUI mode, @value{GDBN} can display several text windows:
21717 This window is the @value{GDBN} command window with the @value{GDBN}
21718 prompt and the @value{GDBN} output. The @value{GDBN} input is still
21719 managed using readline.
21722 The source window shows the source file of the program. The current
21723 line and active breakpoints are displayed in this window.
21726 The assembly window shows the disassembly output of the program.
21729 This window shows the processor registers. Registers are highlighted
21730 when their values change.
21733 The source and assembly windows show the current program position
21734 by highlighting the current line and marking it with a @samp{>} marker.
21735 Breakpoints are indicated with two markers. The first marker
21736 indicates the breakpoint type:
21740 Breakpoint which was hit at least once.
21743 Breakpoint which was never hit.
21746 Hardware breakpoint which was hit at least once.
21749 Hardware breakpoint which was never hit.
21752 The second marker indicates whether the breakpoint is enabled or not:
21756 Breakpoint is enabled.
21759 Breakpoint is disabled.
21762 The source, assembly and register windows are updated when the current
21763 thread changes, when the frame changes, or when the program counter
21766 These windows are not all visible at the same time. The command
21767 window is always visible. The others can be arranged in several
21778 source and assembly,
21781 source and registers, or
21784 assembly and registers.
21787 A status line above the command window shows the following information:
21791 Indicates the current @value{GDBN} target.
21792 (@pxref{Targets, ,Specifying a Debugging Target}).
21795 Gives the current process or thread number.
21796 When no process is being debugged, this field is set to @code{No process}.
21799 Gives the current function name for the selected frame.
21800 The name is demangled if demangling is turned on (@pxref{Print Settings}).
21801 When there is no symbol corresponding to the current program counter,
21802 the string @code{??} is displayed.
21805 Indicates the current line number for the selected frame.
21806 When the current line number is not known, the string @code{??} is displayed.
21809 Indicates the current program counter address.
21813 @section TUI Key Bindings
21814 @cindex TUI key bindings
21816 The TUI installs several key bindings in the readline keymaps
21817 (@pxref{Command Line Editing}). The following key bindings
21818 are installed for both TUI mode and the @value{GDBN} standard mode.
21827 Enter or leave the TUI mode. When leaving the TUI mode,
21828 the curses window management stops and @value{GDBN} operates using
21829 its standard mode, writing on the terminal directly. When reentering
21830 the TUI mode, control is given back to the curses windows.
21831 The screen is then refreshed.
21835 Use a TUI layout with only one window. The layout will
21836 either be @samp{source} or @samp{assembly}. When the TUI mode
21837 is not active, it will switch to the TUI mode.
21839 Think of this key binding as the Emacs @kbd{C-x 1} binding.
21843 Use a TUI layout with at least two windows. When the current
21844 layout already has two windows, the next layout with two windows is used.
21845 When a new layout is chosen, one window will always be common to the
21846 previous layout and the new one.
21848 Think of it as the Emacs @kbd{C-x 2} binding.
21852 Change the active window. The TUI associates several key bindings
21853 (like scrolling and arrow keys) with the active window. This command
21854 gives the focus to the next TUI window.
21856 Think of it as the Emacs @kbd{C-x o} binding.
21860 Switch in and out of the TUI SingleKey mode that binds single
21861 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
21864 The following key bindings only work in the TUI mode:
21869 Scroll the active window one page up.
21873 Scroll the active window one page down.
21877 Scroll the active window one line up.
21881 Scroll the active window one line down.
21885 Scroll the active window one column left.
21889 Scroll the active window one column right.
21893 Refresh the screen.
21896 Because the arrow keys scroll the active window in the TUI mode, they
21897 are not available for their normal use by readline unless the command
21898 window has the focus. When another window is active, you must use
21899 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
21900 and @kbd{C-f} to control the command window.
21902 @node TUI Single Key Mode
21903 @section TUI Single Key Mode
21904 @cindex TUI single key mode
21906 The TUI also provides a @dfn{SingleKey} mode, which binds several
21907 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
21908 switch into this mode, where the following key bindings are used:
21911 @kindex c @r{(SingleKey TUI key)}
21915 @kindex d @r{(SingleKey TUI key)}
21919 @kindex f @r{(SingleKey TUI key)}
21923 @kindex n @r{(SingleKey TUI key)}
21927 @kindex q @r{(SingleKey TUI key)}
21929 exit the SingleKey mode.
21931 @kindex r @r{(SingleKey TUI key)}
21935 @kindex s @r{(SingleKey TUI key)}
21939 @kindex u @r{(SingleKey TUI key)}
21943 @kindex v @r{(SingleKey TUI key)}
21947 @kindex w @r{(SingleKey TUI key)}
21952 Other keys temporarily switch to the @value{GDBN} command prompt.
21953 The key that was pressed is inserted in the editing buffer so that
21954 it is possible to type most @value{GDBN} commands without interaction
21955 with the TUI SingleKey mode. Once the command is entered the TUI
21956 SingleKey mode is restored. The only way to permanently leave
21957 this mode is by typing @kbd{q} or @kbd{C-x s}.
21961 @section TUI-specific Commands
21962 @cindex TUI commands
21964 The TUI has specific commands to control the text windows.
21965 These commands are always available, even when @value{GDBN} is not in
21966 the TUI mode. When @value{GDBN} is in the standard mode, most
21967 of these commands will automatically switch to the TUI mode.
21969 Note that if @value{GDBN}'s @code{stdout} is not connected to a
21970 terminal, or @value{GDBN} has been started with the machine interface
21971 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
21972 these commands will fail with an error, because it would not be
21973 possible or desirable to enable curses window management.
21978 List and give the size of all displayed windows.
21982 Display the next layout.
21985 Display the previous layout.
21988 Display the source window only.
21991 Display the assembly window only.
21994 Display the source and assembly window.
21997 Display the register window together with the source or assembly window.
22001 Make the next window active for scrolling.
22004 Make the previous window active for scrolling.
22007 Make the source window active for scrolling.
22010 Make the assembly window active for scrolling.
22013 Make the register window active for scrolling.
22016 Make the command window active for scrolling.
22020 Refresh the screen. This is similar to typing @kbd{C-L}.
22022 @item tui reg float
22024 Show the floating point registers in the register window.
22026 @item tui reg general
22027 Show the general registers in the register window.
22030 Show the next register group. The list of register groups as well as
22031 their order is target specific. The predefined register groups are the
22032 following: @code{general}, @code{float}, @code{system}, @code{vector},
22033 @code{all}, @code{save}, @code{restore}.
22035 @item tui reg system
22036 Show the system registers in the register window.
22040 Update the source window and the current execution point.
22042 @item winheight @var{name} +@var{count}
22043 @itemx winheight @var{name} -@var{count}
22045 Change the height of the window @var{name} by @var{count}
22046 lines. Positive counts increase the height, while negative counts
22049 @item tabset @var{nchars}
22051 Set the width of tab stops to be @var{nchars} characters.
22054 @node TUI Configuration
22055 @section TUI Configuration Variables
22056 @cindex TUI configuration variables
22058 Several configuration variables control the appearance of TUI windows.
22061 @item set tui border-kind @var{kind}
22062 @kindex set tui border-kind
22063 Select the border appearance for the source, assembly and register windows.
22064 The possible values are the following:
22067 Use a space character to draw the border.
22070 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
22073 Use the Alternate Character Set to draw the border. The border is
22074 drawn using character line graphics if the terminal supports them.
22077 @item set tui border-mode @var{mode}
22078 @kindex set tui border-mode
22079 @itemx set tui active-border-mode @var{mode}
22080 @kindex set tui active-border-mode
22081 Select the display attributes for the borders of the inactive windows
22082 or the active window. The @var{mode} can be one of the following:
22085 Use normal attributes to display the border.
22091 Use reverse video mode.
22094 Use half bright mode.
22096 @item half-standout
22097 Use half bright and standout mode.
22100 Use extra bright or bold mode.
22102 @item bold-standout
22103 Use extra bright or bold and standout mode.
22108 @chapter Using @value{GDBN} under @sc{gnu} Emacs
22111 @cindex @sc{gnu} Emacs
22112 A special interface allows you to use @sc{gnu} Emacs to view (and
22113 edit) the source files for the program you are debugging with
22116 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
22117 executable file you want to debug as an argument. This command starts
22118 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
22119 created Emacs buffer.
22120 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
22122 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
22127 All ``terminal'' input and output goes through an Emacs buffer, called
22130 This applies both to @value{GDBN} commands and their output, and to the input
22131 and output done by the program you are debugging.
22133 This is useful because it means that you can copy the text of previous
22134 commands and input them again; you can even use parts of the output
22137 All the facilities of Emacs' Shell mode are available for interacting
22138 with your program. In particular, you can send signals the usual
22139 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
22143 @value{GDBN} displays source code through Emacs.
22145 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
22146 source file for that frame and puts an arrow (@samp{=>}) at the
22147 left margin of the current line. Emacs uses a separate buffer for
22148 source display, and splits the screen to show both your @value{GDBN} session
22151 Explicit @value{GDBN} @code{list} or search commands still produce output as
22152 usual, but you probably have no reason to use them from Emacs.
22155 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
22156 a graphical mode, enabled by default, which provides further buffers
22157 that can control the execution and describe the state of your program.
22158 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
22160 If you specify an absolute file name when prompted for the @kbd{M-x
22161 gdb} argument, then Emacs sets your current working directory to where
22162 your program resides. If you only specify the file name, then Emacs
22163 sets your current working directory to to the directory associated
22164 with the previous buffer. In this case, @value{GDBN} may find your
22165 program by searching your environment's @code{PATH} variable, but on
22166 some operating systems it might not find the source. So, although the
22167 @value{GDBN} input and output session proceeds normally, the auxiliary
22168 buffer does not display the current source and line of execution.
22170 The initial working directory of @value{GDBN} is printed on the top
22171 line of the GUD buffer and this serves as a default for the commands
22172 that specify files for @value{GDBN} to operate on. @xref{Files,
22173 ,Commands to Specify Files}.
22175 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
22176 need to call @value{GDBN} by a different name (for example, if you
22177 keep several configurations around, with different names) you can
22178 customize the Emacs variable @code{gud-gdb-command-name} to run the
22181 In the GUD buffer, you can use these special Emacs commands in
22182 addition to the standard Shell mode commands:
22186 Describe the features of Emacs' GUD Mode.
22189 Execute to another source line, like the @value{GDBN} @code{step} command; also
22190 update the display window to show the current file and location.
22193 Execute to next source line in this function, skipping all function
22194 calls, like the @value{GDBN} @code{next} command. Then update the display window
22195 to show the current file and location.
22198 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
22199 display window accordingly.
22202 Execute until exit from the selected stack frame, like the @value{GDBN}
22203 @code{finish} command.
22206 Continue execution of your program, like the @value{GDBN} @code{continue}
22210 Go up the number of frames indicated by the numeric argument
22211 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
22212 like the @value{GDBN} @code{up} command.
22215 Go down the number of frames indicated by the numeric argument, like the
22216 @value{GDBN} @code{down} command.
22219 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
22220 tells @value{GDBN} to set a breakpoint on the source line point is on.
22222 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
22223 separate frame which shows a backtrace when the GUD buffer is current.
22224 Move point to any frame in the stack and type @key{RET} to make it
22225 become the current frame and display the associated source in the
22226 source buffer. Alternatively, click @kbd{Mouse-2} to make the
22227 selected frame become the current one. In graphical mode, the
22228 speedbar displays watch expressions.
22230 If you accidentally delete the source-display buffer, an easy way to get
22231 it back is to type the command @code{f} in the @value{GDBN} buffer, to
22232 request a frame display; when you run under Emacs, this recreates
22233 the source buffer if necessary to show you the context of the current
22236 The source files displayed in Emacs are in ordinary Emacs buffers
22237 which are visiting the source files in the usual way. You can edit
22238 the files with these buffers if you wish; but keep in mind that @value{GDBN}
22239 communicates with Emacs in terms of line numbers. If you add or
22240 delete lines from the text, the line numbers that @value{GDBN} knows cease
22241 to correspond properly with the code.
22243 A more detailed description of Emacs' interaction with @value{GDBN} is
22244 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
22247 @c The following dropped because Epoch is nonstandard. Reactivate
22248 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
22250 @kindex Emacs Epoch environment
22254 Version 18 of @sc{gnu} Emacs has a built-in window system
22255 called the @code{epoch}
22256 environment. Users of this environment can use a new command,
22257 @code{inspect} which performs identically to @code{print} except that
22258 each value is printed in its own window.
22263 @chapter The @sc{gdb/mi} Interface
22265 @unnumberedsec Function and Purpose
22267 @cindex @sc{gdb/mi}, its purpose
22268 @sc{gdb/mi} is a line based machine oriented text interface to
22269 @value{GDBN} and is activated by specifying using the
22270 @option{--interpreter} command line option (@pxref{Mode Options}). It
22271 is specifically intended to support the development of systems which
22272 use the debugger as just one small component of a larger system.
22274 This chapter is a specification of the @sc{gdb/mi} interface. It is written
22275 in the form of a reference manual.
22277 Note that @sc{gdb/mi} is still under construction, so some of the
22278 features described below are incomplete and subject to change
22279 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
22281 @unnumberedsec Notation and Terminology
22283 @cindex notational conventions, for @sc{gdb/mi}
22284 This chapter uses the following notation:
22288 @code{|} separates two alternatives.
22291 @code{[ @var{something} ]} indicates that @var{something} is optional:
22292 it may or may not be given.
22295 @code{( @var{group} )*} means that @var{group} inside the parentheses
22296 may repeat zero or more times.
22299 @code{( @var{group} )+} means that @var{group} inside the parentheses
22300 may repeat one or more times.
22303 @code{"@var{string}"} means a literal @var{string}.
22307 @heading Dependencies
22311 * GDB/MI General Design::
22312 * GDB/MI Command Syntax::
22313 * GDB/MI Compatibility with CLI::
22314 * GDB/MI Development and Front Ends::
22315 * GDB/MI Output Records::
22316 * GDB/MI Simple Examples::
22317 * GDB/MI Command Description Format::
22318 * GDB/MI Breakpoint Commands::
22319 * GDB/MI Program Context::
22320 * GDB/MI Thread Commands::
22321 * GDB/MI Program Execution::
22322 * GDB/MI Stack Manipulation::
22323 * GDB/MI Variable Objects::
22324 * GDB/MI Data Manipulation::
22325 * GDB/MI Tracepoint Commands::
22326 * GDB/MI Symbol Query::
22327 * GDB/MI File Commands::
22329 * GDB/MI Kod Commands::
22330 * GDB/MI Memory Overlay Commands::
22331 * GDB/MI Signal Handling Commands::
22333 * GDB/MI Target Manipulation::
22334 * GDB/MI File Transfer Commands::
22335 * GDB/MI Miscellaneous Commands::
22338 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22339 @node GDB/MI General Design
22340 @section @sc{gdb/mi} General Design
22341 @cindex GDB/MI General Design
22343 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
22344 parts---commands sent to @value{GDBN}, responses to those commands
22345 and notifications. Each command results in exactly one response,
22346 indicating either successful completion of the command, or an error.
22347 For the commands that do not resume the target, the response contains the
22348 requested information. For the commands that resume the target, the
22349 response only indicates whether the target was successfully resumed.
22350 Notifications is the mechanism for reporting changes in the state of the
22351 target, or in @value{GDBN} state, that cannot conveniently be associated with
22352 a command and reported as part of that command response.
22354 The important examples of notifications are:
22358 Exec notifications. These are used to report changes in
22359 target state---when a target is resumed, or stopped. It would not
22360 be feasible to include this information in response of resuming
22361 commands, because one resume commands can result in multiple events in
22362 different threads. Also, quite some time may pass before any event
22363 happens in the target, while a frontend needs to know whether the resuming
22364 command itself was successfully executed.
22367 Console output, and status notifications. Console output
22368 notifications are used to report output of CLI commands, as well as
22369 diagnostics for other commands. Status notifications are used to
22370 report the progress of a long-running operation. Naturally, including
22371 this information in command response would mean no output is produced
22372 until the command is finished, which is undesirable.
22375 General notifications. Commands may have various side effects on
22376 the @value{GDBN} or target state beyond their official purpose. For example,
22377 a command may change the selected thread. Although such changes can
22378 be included in command response, using notification allows for more
22379 orthogonal frontend design.
22383 There's no guarantee that whenever an MI command reports an error,
22384 @value{GDBN} or the target are in any specific state, and especially,
22385 the state is not reverted to the state before the MI command was
22386 processed. Therefore, whenever an MI command results in an error,
22387 we recommend that the frontend refreshes all the information shown in
22388 the user interface.
22392 * Context management::
22393 * Asynchronous and non-stop modes::
22397 @node Context management
22398 @subsection Context management
22400 In most cases when @value{GDBN} accesses the target, this access is
22401 done in context of a specific thread and frame (@pxref{Frames}).
22402 Often, even when accessing global data, the target requires that a thread
22403 be specified. The CLI interface maintains the selected thread and frame,
22404 and supplies them to target on each command. This is convenient,
22405 because a command line user would not want to specify that information
22406 explicitly on each command, and because user interacts with
22407 @value{GDBN} via a single terminal, so no confusion is possible as
22408 to what thread and frame are the current ones.
22410 In the case of MI, the concept of selected thread and frame is less
22411 useful. First, a frontend can easily remember this information
22412 itself. Second, a graphical frontend can have more than one window,
22413 each one used for debugging a different thread, and the frontend might
22414 want to access additional threads for internal purposes. This
22415 increases the risk that by relying on implicitly selected thread, the
22416 frontend may be operating on a wrong one. Therefore, each MI command
22417 should explicitly specify which thread and frame to operate on. To
22418 make it possible, each MI command accepts the @samp{--thread} and
22419 @samp{--frame} options, the value to each is @value{GDBN} identifier
22420 for thread and frame to operate on.
22422 Usually, each top-level window in a frontend allows the user to select
22423 a thread and a frame, and remembers the user selection for further
22424 operations. However, in some cases @value{GDBN} may suggest that the
22425 current thread be changed. For example, when stopping on a breakpoint
22426 it is reasonable to switch to the thread where breakpoint is hit. For
22427 another example, if the user issues the CLI @samp{thread} command via
22428 the frontend, it is desirable to change the frontend's selected thread to the
22429 one specified by user. @value{GDBN} communicates the suggestion to
22430 change current thread using the @samp{=thread-selected} notification.
22431 No such notification is available for the selected frame at the moment.
22433 Note that historically, MI shares the selected thread with CLI, so
22434 frontends used the @code{-thread-select} to execute commands in the
22435 right context. However, getting this to work right is cumbersome. The
22436 simplest way is for frontend to emit @code{-thread-select} command
22437 before every command. This doubles the number of commands that need
22438 to be sent. The alternative approach is to suppress @code{-thread-select}
22439 if the selected thread in @value{GDBN} is supposed to be identical to the
22440 thread the frontend wants to operate on. However, getting this
22441 optimization right can be tricky. In particular, if the frontend
22442 sends several commands to @value{GDBN}, and one of the commands changes the
22443 selected thread, then the behaviour of subsequent commands will
22444 change. So, a frontend should either wait for response from such
22445 problematic commands, or explicitly add @code{-thread-select} for
22446 all subsequent commands. No frontend is known to do this exactly
22447 right, so it is suggested to just always pass the @samp{--thread} and
22448 @samp{--frame} options.
22450 @node Asynchronous and non-stop modes
22451 @subsection Asynchronous command execution and non-stop mode
22453 On some targets, @value{GDBN} is capable of processing MI commands
22454 even while the target is running. This is called @dfn{asynchronous
22455 command execution} (@pxref{Background Execution}). The frontend may
22456 specify a preferrence for asynchronous execution using the
22457 @code{-gdb-set target-async 1} command, which should be emitted before
22458 either running the executable or attaching to the target. After the
22459 frontend has started the executable or attached to the target, it can
22460 find if asynchronous execution is enabled using the
22461 @code{-list-target-features} command.
22463 Even if @value{GDBN} can accept a command while target is running,
22464 many commands that access the target do not work when the target is
22465 running. Therefore, asynchronous command execution is most useful
22466 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
22467 it is possible to examine the state of one thread, while other threads
22470 When a given thread is running, MI commands that try to access the
22471 target in the context of that thread may not work, or may work only on
22472 some targets. In particular, commands that try to operate on thread's
22473 stack will not work, on any target. Commands that read memory, or
22474 modify breakpoints, may work or not work, depending on the target. Note
22475 that even commands that operate on global state, such as @code{print},
22476 @code{set}, and breakpoint commands, still access the target in the
22477 context of a specific thread, so frontend should try to find a
22478 stopped thread and perform the operation on that thread (using the
22479 @samp{--thread} option).
22481 Which commands will work in the context of a running thread is
22482 highly target dependent. However, the two commands
22483 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
22484 to find the state of a thread, will always work.
22486 @node Thread groups
22487 @subsection Thread groups
22488 @value{GDBN} may be used to debug several processes at the same time.
22489 On some platfroms, @value{GDBN} may support debugging of several
22490 hardware systems, each one having several cores with several different
22491 processes running on each core. This section describes the MI
22492 mechanism to support such debugging scenarios.
22494 The key observation is that regardless of the structure of the
22495 target, MI can have a global list of threads, because most commands that
22496 accept the @samp{--thread} option do not need to know what process that
22497 thread belongs to. Therefore, it is not necessary to introduce
22498 neither additional @samp{--process} option, nor an notion of the
22499 current process in the MI interface. The only strictly new feature
22500 that is required is the ability to find how the threads are grouped
22503 To allow the user to discover such grouping, and to support arbitrary
22504 hierarchy of machines/cores/processes, MI introduces the concept of a
22505 @dfn{thread group}. Thread group is a collection of threads and other
22506 thread groups. A thread group always has a string identifier, a type,
22507 and may have additional attributes specific to the type. A new
22508 command, @code{-list-thread-groups}, returns the list of top-level
22509 thread groups, which correspond to processes that @value{GDBN} is
22510 debugging at the moment. By passing an identifier of a thread group
22511 to the @code{-list-thread-groups} command, it is possible to obtain
22512 the members of specific thread group.
22514 To allow the user to easily discover processes, and other objects, he
22515 wishes to debug, a concept of @dfn{available thread group} is
22516 introduced. Available thread group is an thread group that
22517 @value{GDBN} is not debugging, but that can be attached to, using the
22518 @code{-target-attach} command. The list of available top-level thread
22519 groups can be obtained using @samp{-list-thread-groups --available}.
22520 In general, the content of a thread group may be only retrieved only
22521 after attaching to that thread group.
22523 Thread groups are related to inferiors (@pxref{Inferiors and
22524 Programs}). Each inferior corresponds to a thread group of a special
22525 type @samp{process}, and some additional operations are permitted on
22526 such thread groups.
22528 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22529 @node GDB/MI Command Syntax
22530 @section @sc{gdb/mi} Command Syntax
22533 * GDB/MI Input Syntax::
22534 * GDB/MI Output Syntax::
22537 @node GDB/MI Input Syntax
22538 @subsection @sc{gdb/mi} Input Syntax
22540 @cindex input syntax for @sc{gdb/mi}
22541 @cindex @sc{gdb/mi}, input syntax
22543 @item @var{command} @expansion{}
22544 @code{@var{cli-command} | @var{mi-command}}
22546 @item @var{cli-command} @expansion{}
22547 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
22548 @var{cli-command} is any existing @value{GDBN} CLI command.
22550 @item @var{mi-command} @expansion{}
22551 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
22552 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
22554 @item @var{token} @expansion{}
22555 "any sequence of digits"
22557 @item @var{option} @expansion{}
22558 @code{"-" @var{parameter} [ " " @var{parameter} ]}
22560 @item @var{parameter} @expansion{}
22561 @code{@var{non-blank-sequence} | @var{c-string}}
22563 @item @var{operation} @expansion{}
22564 @emph{any of the operations described in this chapter}
22566 @item @var{non-blank-sequence} @expansion{}
22567 @emph{anything, provided it doesn't contain special characters such as
22568 "-", @var{nl}, """ and of course " "}
22570 @item @var{c-string} @expansion{}
22571 @code{""" @var{seven-bit-iso-c-string-content} """}
22573 @item @var{nl} @expansion{}
22582 The CLI commands are still handled by the @sc{mi} interpreter; their
22583 output is described below.
22586 The @code{@var{token}}, when present, is passed back when the command
22590 Some @sc{mi} commands accept optional arguments as part of the parameter
22591 list. Each option is identified by a leading @samp{-} (dash) and may be
22592 followed by an optional argument parameter. Options occur first in the
22593 parameter list and can be delimited from normal parameters using
22594 @samp{--} (this is useful when some parameters begin with a dash).
22601 We want easy access to the existing CLI syntax (for debugging).
22604 We want it to be easy to spot a @sc{mi} operation.
22607 @node GDB/MI Output Syntax
22608 @subsection @sc{gdb/mi} Output Syntax
22610 @cindex output syntax of @sc{gdb/mi}
22611 @cindex @sc{gdb/mi}, output syntax
22612 The output from @sc{gdb/mi} consists of zero or more out-of-band records
22613 followed, optionally, by a single result record. This result record
22614 is for the most recent command. The sequence of output records is
22615 terminated by @samp{(gdb)}.
22617 If an input command was prefixed with a @code{@var{token}} then the
22618 corresponding output for that command will also be prefixed by that same
22622 @item @var{output} @expansion{}
22623 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
22625 @item @var{result-record} @expansion{}
22626 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
22628 @item @var{out-of-band-record} @expansion{}
22629 @code{@var{async-record} | @var{stream-record}}
22631 @item @var{async-record} @expansion{}
22632 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
22634 @item @var{exec-async-output} @expansion{}
22635 @code{[ @var{token} ] "*" @var{async-output}}
22637 @item @var{status-async-output} @expansion{}
22638 @code{[ @var{token} ] "+" @var{async-output}}
22640 @item @var{notify-async-output} @expansion{}
22641 @code{[ @var{token} ] "=" @var{async-output}}
22643 @item @var{async-output} @expansion{}
22644 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
22646 @item @var{result-class} @expansion{}
22647 @code{"done" | "running" | "connected" | "error" | "exit"}
22649 @item @var{async-class} @expansion{}
22650 @code{"stopped" | @var{others}} (where @var{others} will be added
22651 depending on the needs---this is still in development).
22653 @item @var{result} @expansion{}
22654 @code{ @var{variable} "=" @var{value}}
22656 @item @var{variable} @expansion{}
22657 @code{ @var{string} }
22659 @item @var{value} @expansion{}
22660 @code{ @var{const} | @var{tuple} | @var{list} }
22662 @item @var{const} @expansion{}
22663 @code{@var{c-string}}
22665 @item @var{tuple} @expansion{}
22666 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
22668 @item @var{list} @expansion{}
22669 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
22670 @var{result} ( "," @var{result} )* "]" }
22672 @item @var{stream-record} @expansion{}
22673 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
22675 @item @var{console-stream-output} @expansion{}
22676 @code{"~" @var{c-string}}
22678 @item @var{target-stream-output} @expansion{}
22679 @code{"@@" @var{c-string}}
22681 @item @var{log-stream-output} @expansion{}
22682 @code{"&" @var{c-string}}
22684 @item @var{nl} @expansion{}
22687 @item @var{token} @expansion{}
22688 @emph{any sequence of digits}.
22696 All output sequences end in a single line containing a period.
22699 The @code{@var{token}} is from the corresponding request. Note that
22700 for all async output, while the token is allowed by the grammar and
22701 may be output by future versions of @value{GDBN} for select async
22702 output messages, it is generally omitted. Frontends should treat
22703 all async output as reporting general changes in the state of the
22704 target and there should be no need to associate async output to any
22708 @cindex status output in @sc{gdb/mi}
22709 @var{status-async-output} contains on-going status information about the
22710 progress of a slow operation. It can be discarded. All status output is
22711 prefixed by @samp{+}.
22714 @cindex async output in @sc{gdb/mi}
22715 @var{exec-async-output} contains asynchronous state change on the target
22716 (stopped, started, disappeared). All async output is prefixed by
22720 @cindex notify output in @sc{gdb/mi}
22721 @var{notify-async-output} contains supplementary information that the
22722 client should handle (e.g., a new breakpoint information). All notify
22723 output is prefixed by @samp{=}.
22726 @cindex console output in @sc{gdb/mi}
22727 @var{console-stream-output} is output that should be displayed as is in the
22728 console. It is the textual response to a CLI command. All the console
22729 output is prefixed by @samp{~}.
22732 @cindex target output in @sc{gdb/mi}
22733 @var{target-stream-output} is the output produced by the target program.
22734 All the target output is prefixed by @samp{@@}.
22737 @cindex log output in @sc{gdb/mi}
22738 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
22739 instance messages that should be displayed as part of an error log. All
22740 the log output is prefixed by @samp{&}.
22743 @cindex list output in @sc{gdb/mi}
22744 New @sc{gdb/mi} commands should only output @var{lists} containing
22750 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
22751 details about the various output records.
22753 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22754 @node GDB/MI Compatibility with CLI
22755 @section @sc{gdb/mi} Compatibility with CLI
22757 @cindex compatibility, @sc{gdb/mi} and CLI
22758 @cindex @sc{gdb/mi}, compatibility with CLI
22760 For the developers convenience CLI commands can be entered directly,
22761 but there may be some unexpected behaviour. For example, commands
22762 that query the user will behave as if the user replied yes, breakpoint
22763 command lists are not executed and some CLI commands, such as
22764 @code{if}, @code{when} and @code{define}, prompt for further input with
22765 @samp{>}, which is not valid MI output.
22767 This feature may be removed at some stage in the future and it is
22768 recommended that front ends use the @code{-interpreter-exec} command
22769 (@pxref{-interpreter-exec}).
22771 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22772 @node GDB/MI Development and Front Ends
22773 @section @sc{gdb/mi} Development and Front Ends
22774 @cindex @sc{gdb/mi} development
22776 The application which takes the MI output and presents the state of the
22777 program being debugged to the user is called a @dfn{front end}.
22779 Although @sc{gdb/mi} is still incomplete, it is currently being used
22780 by a variety of front ends to @value{GDBN}. This makes it difficult
22781 to introduce new functionality without breaking existing usage. This
22782 section tries to minimize the problems by describing how the protocol
22785 Some changes in MI need not break a carefully designed front end, and
22786 for these the MI version will remain unchanged. The following is a
22787 list of changes that may occur within one level, so front ends should
22788 parse MI output in a way that can handle them:
22792 New MI commands may be added.
22795 New fields may be added to the output of any MI command.
22798 The range of values for fields with specified values, e.g.,
22799 @code{in_scope} (@pxref{-var-update}) may be extended.
22801 @c The format of field's content e.g type prefix, may change so parse it
22802 @c at your own risk. Yes, in general?
22804 @c The order of fields may change? Shouldn't really matter but it might
22805 @c resolve inconsistencies.
22808 If the changes are likely to break front ends, the MI version level
22809 will be increased by one. This will allow the front end to parse the
22810 output according to the MI version. Apart from mi0, new versions of
22811 @value{GDBN} will not support old versions of MI and it will be the
22812 responsibility of the front end to work with the new one.
22814 @c Starting with mi3, add a new command -mi-version that prints the MI
22817 The best way to avoid unexpected changes in MI that might break your front
22818 end is to make your project known to @value{GDBN} developers and
22819 follow development on @email{gdb@@sourceware.org} and
22820 @email{gdb-patches@@sourceware.org}.
22821 @cindex mailing lists
22823 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22824 @node GDB/MI Output Records
22825 @section @sc{gdb/mi} Output Records
22828 * GDB/MI Result Records::
22829 * GDB/MI Stream Records::
22830 * GDB/MI Async Records::
22831 * GDB/MI Frame Information::
22832 * GDB/MI Thread Information::
22835 @node GDB/MI Result Records
22836 @subsection @sc{gdb/mi} Result Records
22838 @cindex result records in @sc{gdb/mi}
22839 @cindex @sc{gdb/mi}, result records
22840 In addition to a number of out-of-band notifications, the response to a
22841 @sc{gdb/mi} command includes one of the following result indications:
22845 @item "^done" [ "," @var{results} ]
22846 The synchronous operation was successful, @code{@var{results}} are the return
22851 This result record is equivalent to @samp{^done}. Historically, it
22852 was output instead of @samp{^done} if the command has resumed the
22853 target. This behaviour is maintained for backward compatibility, but
22854 all frontends should treat @samp{^done} and @samp{^running}
22855 identically and rely on the @samp{*running} output record to determine
22856 which threads are resumed.
22860 @value{GDBN} has connected to a remote target.
22862 @item "^error" "," @var{c-string}
22864 The operation failed. The @code{@var{c-string}} contains the corresponding
22869 @value{GDBN} has terminated.
22873 @node GDB/MI Stream Records
22874 @subsection @sc{gdb/mi} Stream Records
22876 @cindex @sc{gdb/mi}, stream records
22877 @cindex stream records in @sc{gdb/mi}
22878 @value{GDBN} internally maintains a number of output streams: the console, the
22879 target, and the log. The output intended for each of these streams is
22880 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
22882 Each stream record begins with a unique @dfn{prefix character} which
22883 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
22884 Syntax}). In addition to the prefix, each stream record contains a
22885 @code{@var{string-output}}. This is either raw text (with an implicit new
22886 line) or a quoted C string (which does not contain an implicit newline).
22889 @item "~" @var{string-output}
22890 The console output stream contains text that should be displayed in the
22891 CLI console window. It contains the textual responses to CLI commands.
22893 @item "@@" @var{string-output}
22894 The target output stream contains any textual output from the running
22895 target. This is only present when GDB's event loop is truly
22896 asynchronous, which is currently only the case for remote targets.
22898 @item "&" @var{string-output}
22899 The log stream contains debugging messages being produced by @value{GDBN}'s
22903 @node GDB/MI Async Records
22904 @subsection @sc{gdb/mi} Async Records
22906 @cindex async records in @sc{gdb/mi}
22907 @cindex @sc{gdb/mi}, async records
22908 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
22909 additional changes that have occurred. Those changes can either be a
22910 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
22911 target activity (e.g., target stopped).
22913 The following is the list of possible async records:
22917 @item *running,thread-id="@var{thread}"
22918 The target is now running. The @var{thread} field tells which
22919 specific thread is now running, and can be @samp{all} if all threads
22920 are running. The frontend should assume that no interaction with a
22921 running thread is possible after this notification is produced.
22922 The frontend should not assume that this notification is output
22923 only once for any command. @value{GDBN} may emit this notification
22924 several times, either for different threads, because it cannot resume
22925 all threads together, or even for a single thread, if the thread must
22926 be stepped though some code before letting it run freely.
22928 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
22929 The target has stopped. The @var{reason} field can have one of the
22933 @item breakpoint-hit
22934 A breakpoint was reached.
22935 @item watchpoint-trigger
22936 A watchpoint was triggered.
22937 @item read-watchpoint-trigger
22938 A read watchpoint was triggered.
22939 @item access-watchpoint-trigger
22940 An access watchpoint was triggered.
22941 @item function-finished
22942 An -exec-finish or similar CLI command was accomplished.
22943 @item location-reached
22944 An -exec-until or similar CLI command was accomplished.
22945 @item watchpoint-scope
22946 A watchpoint has gone out of scope.
22947 @item end-stepping-range
22948 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
22949 similar CLI command was accomplished.
22950 @item exited-signalled
22951 The inferior exited because of a signal.
22953 The inferior exited.
22954 @item exited-normally
22955 The inferior exited normally.
22956 @item signal-received
22957 A signal was received by the inferior.
22960 The @var{id} field identifies the thread that directly caused the stop
22961 -- for example by hitting a breakpoint. Depending on whether all-stop
22962 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
22963 stop all threads, or only the thread that directly triggered the stop.
22964 If all threads are stopped, the @var{stopped} field will have the
22965 value of @code{"all"}. Otherwise, the value of the @var{stopped}
22966 field will be a list of thread identifiers. Presently, this list will
22967 always include a single thread, but frontend should be prepared to see
22968 several threads in the list. The @var{core} field reports the
22969 processor core on which the stop event has happened. This field may be absent
22970 if such information is not available.
22972 @item =thread-group-added,id="@var{id}"
22973 @itemx =thread-group-removed,id="@var{id}"
22974 A thread group was either added or removed. The @var{id} field
22975 contains the @value{GDBN} identifier of the thread group. When a thread
22976 group is added, it generally might not be associated with a running
22977 process. When a thread group is removed, its id becomes invalid and
22978 cannot be used in any way.
22980 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
22981 A thread group became associated with a running program,
22982 either because the program was just started or the thread group
22983 was attached to a program. The @var{id} field contains the
22984 @value{GDBN} identifier of the thread group. The @var{pid} field
22985 contains process identifier, specific to the operating system.
22987 @itemx =thread-group-exited,id="@var{id}"
22988 A thread group is no longer associated with a running program,
22989 either because the program has exited, or because it was detached
22990 from. The @var{id} field contains the @value{GDBN} identifier of the
22993 @item =thread-created,id="@var{id}",group-id="@var{gid}"
22994 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
22995 A thread either was created, or has exited. The @var{id} field
22996 contains the @value{GDBN} identifier of the thread. The @var{gid}
22997 field identifies the thread group this thread belongs to.
22999 @item =thread-selected,id="@var{id}"
23000 Informs that the selected thread was changed as result of the last
23001 command. This notification is not emitted as result of @code{-thread-select}
23002 command but is emitted whenever an MI command that is not documented
23003 to change the selected thread actually changes it. In particular,
23004 invoking, directly or indirectly (via user-defined command), the CLI
23005 @code{thread} command, will generate this notification.
23007 We suggest that in response to this notification, front ends
23008 highlight the selected thread and cause subsequent commands to apply to
23011 @item =library-loaded,...
23012 Reports that a new library file was loaded by the program. This
23013 notification has 4 fields---@var{id}, @var{target-name},
23014 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
23015 opaque identifier of the library. For remote debugging case,
23016 @var{target-name} and @var{host-name} fields give the name of the
23017 library file on the target, and on the host respectively. For native
23018 debugging, both those fields have the same value. The
23019 @var{symbols-loaded} field reports if the debug symbols for this
23020 library are loaded. The @var{thread-group} field, if present,
23021 specifies the id of the thread group in whose context the library was loaded.
23022 If the field is absent, it means the library was loaded in the context
23023 of all present thread groups.
23025 @item =library-unloaded,...
23026 Reports that a library was unloaded by the program. This notification
23027 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
23028 the same meaning as for the @code{=library-loaded} notification.
23029 The @var{thread-group} field, if present, specifies the id of the
23030 thread group in whose context the library was unloaded. If the field is
23031 absent, it means the library was unloaded in the context of all present
23036 @node GDB/MI Frame Information
23037 @subsection @sc{gdb/mi} Frame Information
23039 Response from many MI commands includes an information about stack
23040 frame. This information is a tuple that may have the following
23045 The level of the stack frame. The innermost frame has the level of
23046 zero. This field is always present.
23049 The name of the function corresponding to the frame. This field may
23050 be absent if @value{GDBN} is unable to determine the function name.
23053 The code address for the frame. This field is always present.
23056 The name of the source files that correspond to the frame's code
23057 address. This field may be absent.
23060 The source line corresponding to the frames' code address. This field
23064 The name of the binary file (either executable or shared library) the
23065 corresponds to the frame's code address. This field may be absent.
23069 @node GDB/MI Thread Information
23070 @subsection @sc{gdb/mi} Thread Information
23072 Whenever @value{GDBN} has to report an information about a thread, it
23073 uses a tuple with the following fields:
23077 The numeric id assigned to the thread by @value{GDBN}. This field is
23081 Target-specific string identifying the thread. This field is always present.
23084 Additional information about the thread provided by the target.
23085 It is supposed to be human-readable and not interpreted by the
23086 frontend. This field is optional.
23089 Either @samp{stopped} or @samp{running}, depending on whether the
23090 thread is presently running. This field is always present.
23093 The value of this field is an integer number of the processor core the
23094 thread was last seen on. This field is optional.
23098 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23099 @node GDB/MI Simple Examples
23100 @section Simple Examples of @sc{gdb/mi} Interaction
23101 @cindex @sc{gdb/mi}, simple examples
23103 This subsection presents several simple examples of interaction using
23104 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
23105 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
23106 the output received from @sc{gdb/mi}.
23108 Note the line breaks shown in the examples are here only for
23109 readability, they don't appear in the real output.
23111 @subheading Setting a Breakpoint
23113 Setting a breakpoint generates synchronous output which contains detailed
23114 information of the breakpoint.
23117 -> -break-insert main
23118 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23119 enabled="y",addr="0x08048564",func="main",file="myprog.c",
23120 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
23124 @subheading Program Execution
23126 Program execution generates asynchronous records and MI gives the
23127 reason that execution stopped.
23133 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
23134 frame=@{addr="0x08048564",func="main",
23135 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
23136 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
23141 <- *stopped,reason="exited-normally"
23145 @subheading Quitting @value{GDBN}
23147 Quitting @value{GDBN} just prints the result class @samp{^exit}.
23155 Please note that @samp{^exit} is printed immediately, but it might
23156 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
23157 performs necessary cleanups, including killing programs being debugged
23158 or disconnecting from debug hardware, so the frontend should wait till
23159 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
23160 fails to exit in reasonable time.
23162 @subheading A Bad Command
23164 Here's what happens if you pass a non-existent command:
23168 <- ^error,msg="Undefined MI command: rubbish"
23173 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23174 @node GDB/MI Command Description Format
23175 @section @sc{gdb/mi} Command Description Format
23177 The remaining sections describe blocks of commands. Each block of
23178 commands is laid out in a fashion similar to this section.
23180 @subheading Motivation
23182 The motivation for this collection of commands.
23184 @subheading Introduction
23186 A brief introduction to this collection of commands as a whole.
23188 @subheading Commands
23190 For each command in the block, the following is described:
23192 @subsubheading Synopsis
23195 -command @var{args}@dots{}
23198 @subsubheading Result
23200 @subsubheading @value{GDBN} Command
23202 The corresponding @value{GDBN} CLI command(s), if any.
23204 @subsubheading Example
23206 Example(s) formatted for readability. Some of the described commands have
23207 not been implemented yet and these are labeled N.A.@: (not available).
23210 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23211 @node GDB/MI Breakpoint Commands
23212 @section @sc{gdb/mi} Breakpoint Commands
23214 @cindex breakpoint commands for @sc{gdb/mi}
23215 @cindex @sc{gdb/mi}, breakpoint commands
23216 This section documents @sc{gdb/mi} commands for manipulating
23219 @subheading The @code{-break-after} Command
23220 @findex -break-after
23222 @subsubheading Synopsis
23225 -break-after @var{number} @var{count}
23228 The breakpoint number @var{number} is not in effect until it has been
23229 hit @var{count} times. To see how this is reflected in the output of
23230 the @samp{-break-list} command, see the description of the
23231 @samp{-break-list} command below.
23233 @subsubheading @value{GDBN} Command
23235 The corresponding @value{GDBN} command is @samp{ignore}.
23237 @subsubheading Example
23242 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23243 enabled="y",addr="0x000100d0",func="main",file="hello.c",
23244 fullname="/home/foo/hello.c",line="5",times="0"@}
23251 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23252 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23253 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23254 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23255 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23256 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23257 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23258 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23259 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23260 line="5",times="0",ignore="3"@}]@}
23265 @subheading The @code{-break-catch} Command
23266 @findex -break-catch
23269 @subheading The @code{-break-commands} Command
23270 @findex -break-commands
23272 @subsubheading Synopsis
23275 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
23278 Specifies the CLI commands that should be executed when breakpoint
23279 @var{number} is hit. The parameters @var{command1} to @var{commandN}
23280 are the commands. If no command is specified, any previously-set
23281 commands are cleared. @xref{Break Commands}. Typical use of this
23282 functionality is tracing a program, that is, printing of values of
23283 some variables whenever breakpoint is hit and then continuing.
23285 @subsubheading @value{GDBN} Command
23287 The corresponding @value{GDBN} command is @samp{commands}.
23289 @subsubheading Example
23294 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23295 enabled="y",addr="0x000100d0",func="main",file="hello.c",
23296 fullname="/home/foo/hello.c",line="5",times="0"@}
23298 -break-commands 1 "print v" "continue"
23303 @subheading The @code{-break-condition} Command
23304 @findex -break-condition
23306 @subsubheading Synopsis
23309 -break-condition @var{number} @var{expr}
23312 Breakpoint @var{number} will stop the program only if the condition in
23313 @var{expr} is true. The condition becomes part of the
23314 @samp{-break-list} output (see the description of the @samp{-break-list}
23317 @subsubheading @value{GDBN} Command
23319 The corresponding @value{GDBN} command is @samp{condition}.
23321 @subsubheading Example
23325 -break-condition 1 1
23329 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23330 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23331 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23332 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23333 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23334 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23335 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23336 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23337 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23338 line="5",cond="1",times="0",ignore="3"@}]@}
23342 @subheading The @code{-break-delete} Command
23343 @findex -break-delete
23345 @subsubheading Synopsis
23348 -break-delete ( @var{breakpoint} )+
23351 Delete the breakpoint(s) whose number(s) are specified in the argument
23352 list. This is obviously reflected in the breakpoint list.
23354 @subsubheading @value{GDBN} Command
23356 The corresponding @value{GDBN} command is @samp{delete}.
23358 @subsubheading Example
23366 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23367 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23368 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23369 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23370 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23371 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23372 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23377 @subheading The @code{-break-disable} Command
23378 @findex -break-disable
23380 @subsubheading Synopsis
23383 -break-disable ( @var{breakpoint} )+
23386 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
23387 break list is now set to @samp{n} for the named @var{breakpoint}(s).
23389 @subsubheading @value{GDBN} Command
23391 The corresponding @value{GDBN} command is @samp{disable}.
23393 @subsubheading Example
23401 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23402 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23403 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23404 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23405 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23406 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23407 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23408 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
23409 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23410 line="5",times="0"@}]@}
23414 @subheading The @code{-break-enable} Command
23415 @findex -break-enable
23417 @subsubheading Synopsis
23420 -break-enable ( @var{breakpoint} )+
23423 Enable (previously disabled) @var{breakpoint}(s).
23425 @subsubheading @value{GDBN} Command
23427 The corresponding @value{GDBN} command is @samp{enable}.
23429 @subsubheading Example
23437 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23438 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23439 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23440 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23441 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23442 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23443 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23444 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23445 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23446 line="5",times="0"@}]@}
23450 @subheading The @code{-break-info} Command
23451 @findex -break-info
23453 @subsubheading Synopsis
23456 -break-info @var{breakpoint}
23460 Get information about a single breakpoint.
23462 @subsubheading @value{GDBN} Command
23464 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
23466 @subsubheading Example
23469 @subheading The @code{-break-insert} Command
23470 @findex -break-insert
23472 @subsubheading Synopsis
23475 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
23476 [ -c @var{condition} ] [ -i @var{ignore-count} ]
23477 [ -p @var{thread} ] [ @var{location} ]
23481 If specified, @var{location}, can be one of:
23488 @item filename:linenum
23489 @item filename:function
23493 The possible optional parameters of this command are:
23497 Insert a temporary breakpoint.
23499 Insert a hardware breakpoint.
23500 @item -c @var{condition}
23501 Make the breakpoint conditional on @var{condition}.
23502 @item -i @var{ignore-count}
23503 Initialize the @var{ignore-count}.
23505 If @var{location} cannot be parsed (for example if it
23506 refers to unknown files or functions), create a pending
23507 breakpoint. Without this flag, @value{GDBN} will report
23508 an error, and won't create a breakpoint, if @var{location}
23511 Create a disabled breakpoint.
23513 Create a tracepoint. @xref{Tracepoints}. When this parameter
23514 is used together with @samp{-h}, a fast tracepoint is created.
23517 @subsubheading Result
23519 The result is in the form:
23522 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
23523 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
23524 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
23525 times="@var{times}"@}
23529 where @var{number} is the @value{GDBN} number for this breakpoint,
23530 @var{funcname} is the name of the function where the breakpoint was
23531 inserted, @var{filename} is the name of the source file which contains
23532 this function, @var{lineno} is the source line number within that file
23533 and @var{times} the number of times that the breakpoint has been hit
23534 (always 0 for -break-insert but may be greater for -break-info or -break-list
23535 which use the same output).
23537 Note: this format is open to change.
23538 @c An out-of-band breakpoint instead of part of the result?
23540 @subsubheading @value{GDBN} Command
23542 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
23543 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
23545 @subsubheading Example
23550 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
23551 fullname="/home/foo/recursive2.c,line="4",times="0"@}
23553 -break-insert -t foo
23554 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
23555 fullname="/home/foo/recursive2.c,line="11",times="0"@}
23558 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23559 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23560 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23561 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23562 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23563 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23564 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23565 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23566 addr="0x0001072c", func="main",file="recursive2.c",
23567 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
23568 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
23569 addr="0x00010774",func="foo",file="recursive2.c",
23570 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
23572 -break-insert -r foo.*
23573 ~int foo(int, int);
23574 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
23575 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
23579 @subheading The @code{-break-list} Command
23580 @findex -break-list
23582 @subsubheading Synopsis
23588 Displays the list of inserted breakpoints, showing the following fields:
23592 number of the breakpoint
23594 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
23596 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
23599 is the breakpoint enabled or no: @samp{y} or @samp{n}
23601 memory location at which the breakpoint is set
23603 logical location of the breakpoint, expressed by function name, file
23606 number of times the breakpoint has been hit
23609 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
23610 @code{body} field is an empty list.
23612 @subsubheading @value{GDBN} Command
23614 The corresponding @value{GDBN} command is @samp{info break}.
23616 @subsubheading Example
23621 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23622 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23623 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23624 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23625 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23626 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23627 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23628 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23629 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
23630 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23631 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
23632 line="13",times="0"@}]@}
23636 Here's an example of the result when there are no breakpoints:
23641 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23642 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23643 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23644 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23645 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23646 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23647 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23652 @subheading The @code{-break-passcount} Command
23653 @findex -break-passcount
23655 @subsubheading Synopsis
23658 -break-passcount @var{tracepoint-number} @var{passcount}
23661 Set the passcount for tracepoint @var{tracepoint-number} to
23662 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
23663 is not a tracepoint, error is emitted. This corresponds to CLI
23664 command @samp{passcount}.
23666 @subheading The @code{-break-watch} Command
23667 @findex -break-watch
23669 @subsubheading Synopsis
23672 -break-watch [ -a | -r ]
23675 Create a watchpoint. With the @samp{-a} option it will create an
23676 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
23677 read from or on a write to the memory location. With the @samp{-r}
23678 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
23679 trigger only when the memory location is accessed for reading. Without
23680 either of the options, the watchpoint created is a regular watchpoint,
23681 i.e., it will trigger when the memory location is accessed for writing.
23682 @xref{Set Watchpoints, , Setting Watchpoints}.
23684 Note that @samp{-break-list} will report a single list of watchpoints and
23685 breakpoints inserted.
23687 @subsubheading @value{GDBN} Command
23689 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
23692 @subsubheading Example
23694 Setting a watchpoint on a variable in the @code{main} function:
23699 ^done,wpt=@{number="2",exp="x"@}
23704 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
23705 value=@{old="-268439212",new="55"@},
23706 frame=@{func="main",args=[],file="recursive2.c",
23707 fullname="/home/foo/bar/recursive2.c",line="5"@}
23711 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
23712 the program execution twice: first for the variable changing value, then
23713 for the watchpoint going out of scope.
23718 ^done,wpt=@{number="5",exp="C"@}
23723 *stopped,reason="watchpoint-trigger",
23724 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
23725 frame=@{func="callee4",args=[],
23726 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23727 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
23732 *stopped,reason="watchpoint-scope",wpnum="5",
23733 frame=@{func="callee3",args=[@{name="strarg",
23734 value="0x11940 \"A string argument.\""@}],
23735 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23736 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23740 Listing breakpoints and watchpoints, at different points in the program
23741 execution. Note that once the watchpoint goes out of scope, it is
23747 ^done,wpt=@{number="2",exp="C"@}
23750 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23751 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23752 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23753 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23754 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23755 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23756 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23757 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23758 addr="0x00010734",func="callee4",
23759 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23760 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
23761 bkpt=@{number="2",type="watchpoint",disp="keep",
23762 enabled="y",addr="",what="C",times="0"@}]@}
23767 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
23768 value=@{old="-276895068",new="3"@},
23769 frame=@{func="callee4",args=[],
23770 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23771 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
23774 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23775 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23776 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23777 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23778 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23779 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23780 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23781 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23782 addr="0x00010734",func="callee4",
23783 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23784 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
23785 bkpt=@{number="2",type="watchpoint",disp="keep",
23786 enabled="y",addr="",what="C",times="-5"@}]@}
23790 ^done,reason="watchpoint-scope",wpnum="2",
23791 frame=@{func="callee3",args=[@{name="strarg",
23792 value="0x11940 \"A string argument.\""@}],
23793 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23794 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23797 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23798 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23799 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23800 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23801 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23802 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23803 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23804 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23805 addr="0x00010734",func="callee4",
23806 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23807 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
23812 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23813 @node GDB/MI Program Context
23814 @section @sc{gdb/mi} Program Context
23816 @subheading The @code{-exec-arguments} Command
23817 @findex -exec-arguments
23820 @subsubheading Synopsis
23823 -exec-arguments @var{args}
23826 Set the inferior program arguments, to be used in the next
23829 @subsubheading @value{GDBN} Command
23831 The corresponding @value{GDBN} command is @samp{set args}.
23833 @subsubheading Example
23837 -exec-arguments -v word
23844 @subheading The @code{-exec-show-arguments} Command
23845 @findex -exec-show-arguments
23847 @subsubheading Synopsis
23850 -exec-show-arguments
23853 Print the arguments of the program.
23855 @subsubheading @value{GDBN} Command
23857 The corresponding @value{GDBN} command is @samp{show args}.
23859 @subsubheading Example
23864 @subheading The @code{-environment-cd} Command
23865 @findex -environment-cd
23867 @subsubheading Synopsis
23870 -environment-cd @var{pathdir}
23873 Set @value{GDBN}'s working directory.
23875 @subsubheading @value{GDBN} Command
23877 The corresponding @value{GDBN} command is @samp{cd}.
23879 @subsubheading Example
23883 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
23889 @subheading The @code{-environment-directory} Command
23890 @findex -environment-directory
23892 @subsubheading Synopsis
23895 -environment-directory [ -r ] [ @var{pathdir} ]+
23898 Add directories @var{pathdir} to beginning of search path for source files.
23899 If the @samp{-r} option is used, the search path is reset to the default
23900 search path. If directories @var{pathdir} are supplied in addition to the
23901 @samp{-r} option, the search path is first reset and then addition
23903 Multiple directories may be specified, separated by blanks. Specifying
23904 multiple directories in a single command
23905 results in the directories added to the beginning of the
23906 search path in the same order they were presented in the command.
23907 If blanks are needed as
23908 part of a directory name, double-quotes should be used around
23909 the name. In the command output, the path will show up separated
23910 by the system directory-separator character. The directory-separator
23911 character must not be used
23912 in any directory name.
23913 If no directories are specified, the current search path is displayed.
23915 @subsubheading @value{GDBN} Command
23917 The corresponding @value{GDBN} command is @samp{dir}.
23919 @subsubheading Example
23923 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
23924 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
23926 -environment-directory ""
23927 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
23929 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
23930 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
23932 -environment-directory -r
23933 ^done,source-path="$cdir:$cwd"
23938 @subheading The @code{-environment-path} Command
23939 @findex -environment-path
23941 @subsubheading Synopsis
23944 -environment-path [ -r ] [ @var{pathdir} ]+
23947 Add directories @var{pathdir} to beginning of search path for object files.
23948 If the @samp{-r} option is used, the search path is reset to the original
23949 search path that existed at gdb start-up. If directories @var{pathdir} are
23950 supplied in addition to the
23951 @samp{-r} option, the search path is first reset and then addition
23953 Multiple directories may be specified, separated by blanks. Specifying
23954 multiple directories in a single command
23955 results in the directories added to the beginning of the
23956 search path in the same order they were presented in the command.
23957 If blanks are needed as
23958 part of a directory name, double-quotes should be used around
23959 the name. In the command output, the path will show up separated
23960 by the system directory-separator character. The directory-separator
23961 character must not be used
23962 in any directory name.
23963 If no directories are specified, the current path is displayed.
23966 @subsubheading @value{GDBN} Command
23968 The corresponding @value{GDBN} command is @samp{path}.
23970 @subsubheading Example
23975 ^done,path="/usr/bin"
23977 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
23978 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
23980 -environment-path -r /usr/local/bin
23981 ^done,path="/usr/local/bin:/usr/bin"
23986 @subheading The @code{-environment-pwd} Command
23987 @findex -environment-pwd
23989 @subsubheading Synopsis
23995 Show the current working directory.
23997 @subsubheading @value{GDBN} Command
23999 The corresponding @value{GDBN} command is @samp{pwd}.
24001 @subsubheading Example
24006 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
24010 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24011 @node GDB/MI Thread Commands
24012 @section @sc{gdb/mi} Thread Commands
24015 @subheading The @code{-thread-info} Command
24016 @findex -thread-info
24018 @subsubheading Synopsis
24021 -thread-info [ @var{thread-id} ]
24024 Reports information about either a specific thread, if
24025 the @var{thread-id} parameter is present, or about all
24026 threads. When printing information about all threads,
24027 also reports the current thread.
24029 @subsubheading @value{GDBN} Command
24031 The @samp{info thread} command prints the same information
24034 @subsubheading Example
24039 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24040 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24041 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24042 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24043 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
24044 current-thread-id="1"
24048 The @samp{state} field may have the following values:
24052 The thread is stopped. Frame information is available for stopped
24056 The thread is running. There's no frame information for running
24061 @subheading The @code{-thread-list-ids} Command
24062 @findex -thread-list-ids
24064 @subsubheading Synopsis
24070 Produces a list of the currently known @value{GDBN} thread ids. At the
24071 end of the list it also prints the total number of such threads.
24073 This command is retained for historical reasons, the
24074 @code{-thread-info} command should be used instead.
24076 @subsubheading @value{GDBN} Command
24078 Part of @samp{info threads} supplies the same information.
24080 @subsubheading Example
24085 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
24086 current-thread-id="1",number-of-threads="3"
24091 @subheading The @code{-thread-select} Command
24092 @findex -thread-select
24094 @subsubheading Synopsis
24097 -thread-select @var{threadnum}
24100 Make @var{threadnum} the current thread. It prints the number of the new
24101 current thread, and the topmost frame for that thread.
24103 This command is deprecated in favor of explicitly using the
24104 @samp{--thread} option to each command.
24106 @subsubheading @value{GDBN} Command
24108 The corresponding @value{GDBN} command is @samp{thread}.
24110 @subsubheading Example
24117 *stopped,reason="end-stepping-range",thread-id="2",line="187",
24118 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
24122 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
24123 number-of-threads="3"
24126 ^done,new-thread-id="3",
24127 frame=@{level="0",func="vprintf",
24128 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
24129 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
24133 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24134 @node GDB/MI Program Execution
24135 @section @sc{gdb/mi} Program Execution
24137 These are the asynchronous commands which generate the out-of-band
24138 record @samp{*stopped}. Currently @value{GDBN} only really executes
24139 asynchronously with remote targets and this interaction is mimicked in
24142 @subheading The @code{-exec-continue} Command
24143 @findex -exec-continue
24145 @subsubheading Synopsis
24148 -exec-continue [--reverse] [--all|--thread-group N]
24151 Resumes the execution of the inferior program, which will continue
24152 to execute until it reaches a debugger stop event. If the
24153 @samp{--reverse} option is specified, execution resumes in reverse until
24154 it reaches a stop event. Stop events may include
24157 breakpoints or watchpoints
24159 signals or exceptions
24161 the end of the process (or its beginning under @samp{--reverse})
24163 the end or beginning of a replay log if one is being used.
24165 In all-stop mode (@pxref{All-Stop
24166 Mode}), may resume only one thread, or all threads, depending on the
24167 value of the @samp{scheduler-locking} variable. If @samp{--all} is
24168 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
24169 ignored in all-stop mode. If the @samp{--thread-group} options is
24170 specified, then all threads in that thread group are resumed.
24172 @subsubheading @value{GDBN} Command
24174 The corresponding @value{GDBN} corresponding is @samp{continue}.
24176 @subsubheading Example
24183 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
24184 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
24190 @subheading The @code{-exec-finish} Command
24191 @findex -exec-finish
24193 @subsubheading Synopsis
24196 -exec-finish [--reverse]
24199 Resumes the execution of the inferior program until the current
24200 function is exited. Displays the results returned by the function.
24201 If the @samp{--reverse} option is specified, resumes the reverse
24202 execution of the inferior program until the point where current
24203 function was called.
24205 @subsubheading @value{GDBN} Command
24207 The corresponding @value{GDBN} command is @samp{finish}.
24209 @subsubheading Example
24211 Function returning @code{void}.
24218 *stopped,reason="function-finished",frame=@{func="main",args=[],
24219 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
24223 Function returning other than @code{void}. The name of the internal
24224 @value{GDBN} variable storing the result is printed, together with the
24231 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
24232 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
24233 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24234 gdb-result-var="$1",return-value="0"
24239 @subheading The @code{-exec-interrupt} Command
24240 @findex -exec-interrupt
24242 @subsubheading Synopsis
24245 -exec-interrupt [--all|--thread-group N]
24248 Interrupts the background execution of the target. Note how the token
24249 associated with the stop message is the one for the execution command
24250 that has been interrupted. The token for the interrupt itself only
24251 appears in the @samp{^done} output. If the user is trying to
24252 interrupt a non-running program, an error message will be printed.
24254 Note that when asynchronous execution is enabled, this command is
24255 asynchronous just like other execution commands. That is, first the
24256 @samp{^done} response will be printed, and the target stop will be
24257 reported after that using the @samp{*stopped} notification.
24259 In non-stop mode, only the context thread is interrupted by default.
24260 All threads (in all inferiors) will be interrupted if the
24261 @samp{--all} option is specified. If the @samp{--thread-group}
24262 option is specified, all threads in that group will be interrupted.
24264 @subsubheading @value{GDBN} Command
24266 The corresponding @value{GDBN} command is @samp{interrupt}.
24268 @subsubheading Example
24279 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
24280 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
24281 fullname="/home/foo/bar/try.c",line="13"@}
24286 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
24290 @subheading The @code{-exec-jump} Command
24293 @subsubheading Synopsis
24296 -exec-jump @var{location}
24299 Resumes execution of the inferior program at the location specified by
24300 parameter. @xref{Specify Location}, for a description of the
24301 different forms of @var{location}.
24303 @subsubheading @value{GDBN} Command
24305 The corresponding @value{GDBN} command is @samp{jump}.
24307 @subsubheading Example
24310 -exec-jump foo.c:10
24311 *running,thread-id="all"
24316 @subheading The @code{-exec-next} Command
24319 @subsubheading Synopsis
24322 -exec-next [--reverse]
24325 Resumes execution of the inferior program, stopping when the beginning
24326 of the next source line is reached.
24328 If the @samp{--reverse} option is specified, resumes reverse execution
24329 of the inferior program, stopping at the beginning of the previous
24330 source line. If you issue this command on the first line of a
24331 function, it will take you back to the caller of that function, to the
24332 source line where the function was called.
24335 @subsubheading @value{GDBN} Command
24337 The corresponding @value{GDBN} command is @samp{next}.
24339 @subsubheading Example
24345 *stopped,reason="end-stepping-range",line="8",file="hello.c"
24350 @subheading The @code{-exec-next-instruction} Command
24351 @findex -exec-next-instruction
24353 @subsubheading Synopsis
24356 -exec-next-instruction [--reverse]
24359 Executes one machine instruction. If the instruction is a function
24360 call, continues until the function returns. If the program stops at an
24361 instruction in the middle of a source line, the address will be
24364 If the @samp{--reverse} option is specified, resumes reverse execution
24365 of the inferior program, stopping at the previous instruction. If the
24366 previously executed instruction was a return from another function,
24367 it will continue to execute in reverse until the call to that function
24368 (from the current stack frame) is reached.
24370 @subsubheading @value{GDBN} Command
24372 The corresponding @value{GDBN} command is @samp{nexti}.
24374 @subsubheading Example
24378 -exec-next-instruction
24382 *stopped,reason="end-stepping-range",
24383 addr="0x000100d4",line="5",file="hello.c"
24388 @subheading The @code{-exec-return} Command
24389 @findex -exec-return
24391 @subsubheading Synopsis
24397 Makes current function return immediately. Doesn't execute the inferior.
24398 Displays the new current frame.
24400 @subsubheading @value{GDBN} Command
24402 The corresponding @value{GDBN} command is @samp{return}.
24404 @subsubheading Example
24408 200-break-insert callee4
24409 200^done,bkpt=@{number="1",addr="0x00010734",
24410 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24415 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24416 frame=@{func="callee4",args=[],
24417 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24418 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24424 111^done,frame=@{level="0",func="callee3",
24425 args=[@{name="strarg",
24426 value="0x11940 \"A string argument.\""@}],
24427 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24428 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24433 @subheading The @code{-exec-run} Command
24436 @subsubheading Synopsis
24439 -exec-run [--all | --thread-group N]
24442 Starts execution of the inferior from the beginning. The inferior
24443 executes until either a breakpoint is encountered or the program
24444 exits. In the latter case the output will include an exit code, if
24445 the program has exited exceptionally.
24447 When no option is specified, the current inferior is started. If the
24448 @samp{--thread-group} option is specified, it should refer to a thread
24449 group of type @samp{process}, and that thread group will be started.
24450 If the @samp{--all} option is specified, then all inferiors will be started.
24452 @subsubheading @value{GDBN} Command
24454 The corresponding @value{GDBN} command is @samp{run}.
24456 @subsubheading Examples
24461 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
24466 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24467 frame=@{func="main",args=[],file="recursive2.c",
24468 fullname="/home/foo/bar/recursive2.c",line="4"@}
24473 Program exited normally:
24481 *stopped,reason="exited-normally"
24486 Program exited exceptionally:
24494 *stopped,reason="exited",exit-code="01"
24498 Another way the program can terminate is if it receives a signal such as
24499 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
24503 *stopped,reason="exited-signalled",signal-name="SIGINT",
24504 signal-meaning="Interrupt"
24508 @c @subheading -exec-signal
24511 @subheading The @code{-exec-step} Command
24514 @subsubheading Synopsis
24517 -exec-step [--reverse]
24520 Resumes execution of the inferior program, stopping when the beginning
24521 of the next source line is reached, if the next source line is not a
24522 function call. If it is, stop at the first instruction of the called
24523 function. If the @samp{--reverse} option is specified, resumes reverse
24524 execution of the inferior program, stopping at the beginning of the
24525 previously executed source line.
24527 @subsubheading @value{GDBN} Command
24529 The corresponding @value{GDBN} command is @samp{step}.
24531 @subsubheading Example
24533 Stepping into a function:
24539 *stopped,reason="end-stepping-range",
24540 frame=@{func="foo",args=[@{name="a",value="10"@},
24541 @{name="b",value="0"@}],file="recursive2.c",
24542 fullname="/home/foo/bar/recursive2.c",line="11"@}
24552 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
24557 @subheading The @code{-exec-step-instruction} Command
24558 @findex -exec-step-instruction
24560 @subsubheading Synopsis
24563 -exec-step-instruction [--reverse]
24566 Resumes the inferior which executes one machine instruction. If the
24567 @samp{--reverse} option is specified, resumes reverse execution of the
24568 inferior program, stopping at the previously executed instruction.
24569 The output, once @value{GDBN} has stopped, will vary depending on
24570 whether we have stopped in the middle of a source line or not. In the
24571 former case, the address at which the program stopped will be printed
24574 @subsubheading @value{GDBN} Command
24576 The corresponding @value{GDBN} command is @samp{stepi}.
24578 @subsubheading Example
24582 -exec-step-instruction
24586 *stopped,reason="end-stepping-range",
24587 frame=@{func="foo",args=[],file="try.c",
24588 fullname="/home/foo/bar/try.c",line="10"@}
24590 -exec-step-instruction
24594 *stopped,reason="end-stepping-range",
24595 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
24596 fullname="/home/foo/bar/try.c",line="10"@}
24601 @subheading The @code{-exec-until} Command
24602 @findex -exec-until
24604 @subsubheading Synopsis
24607 -exec-until [ @var{location} ]
24610 Executes the inferior until the @var{location} specified in the
24611 argument is reached. If there is no argument, the inferior executes
24612 until a source line greater than the current one is reached. The
24613 reason for stopping in this case will be @samp{location-reached}.
24615 @subsubheading @value{GDBN} Command
24617 The corresponding @value{GDBN} command is @samp{until}.
24619 @subsubheading Example
24623 -exec-until recursive2.c:6
24627 *stopped,reason="location-reached",frame=@{func="main",args=[],
24628 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
24633 @subheading -file-clear
24634 Is this going away????
24637 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24638 @node GDB/MI Stack Manipulation
24639 @section @sc{gdb/mi} Stack Manipulation Commands
24642 @subheading The @code{-stack-info-frame} Command
24643 @findex -stack-info-frame
24645 @subsubheading Synopsis
24651 Get info on the selected frame.
24653 @subsubheading @value{GDBN} Command
24655 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
24656 (without arguments).
24658 @subsubheading Example
24663 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
24664 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24665 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
24669 @subheading The @code{-stack-info-depth} Command
24670 @findex -stack-info-depth
24672 @subsubheading Synopsis
24675 -stack-info-depth [ @var{max-depth} ]
24678 Return the depth of the stack. If the integer argument @var{max-depth}
24679 is specified, do not count beyond @var{max-depth} frames.
24681 @subsubheading @value{GDBN} Command
24683 There's no equivalent @value{GDBN} command.
24685 @subsubheading Example
24687 For a stack with frame levels 0 through 11:
24694 -stack-info-depth 4
24697 -stack-info-depth 12
24700 -stack-info-depth 11
24703 -stack-info-depth 13
24708 @subheading The @code{-stack-list-arguments} Command
24709 @findex -stack-list-arguments
24711 @subsubheading Synopsis
24714 -stack-list-arguments @var{print-values}
24715 [ @var{low-frame} @var{high-frame} ]
24718 Display a list of the arguments for the frames between @var{low-frame}
24719 and @var{high-frame} (inclusive). If @var{low-frame} and
24720 @var{high-frame} are not provided, list the arguments for the whole
24721 call stack. If the two arguments are equal, show the single frame
24722 at the corresponding level. It is an error if @var{low-frame} is
24723 larger than the actual number of frames. On the other hand,
24724 @var{high-frame} may be larger than the actual number of frames, in
24725 which case only existing frames will be returned.
24727 If @var{print-values} is 0 or @code{--no-values}, print only the names of
24728 the variables; if it is 1 or @code{--all-values}, print also their
24729 values; and if it is 2 or @code{--simple-values}, print the name,
24730 type and value for simple data types, and the name and type for arrays,
24731 structures and unions.
24733 Use of this command to obtain arguments in a single frame is
24734 deprecated in favor of the @samp{-stack-list-variables} command.
24736 @subsubheading @value{GDBN} Command
24738 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
24739 @samp{gdb_get_args} command which partially overlaps with the
24740 functionality of @samp{-stack-list-arguments}.
24742 @subsubheading Example
24749 frame=@{level="0",addr="0x00010734",func="callee4",
24750 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24751 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
24752 frame=@{level="1",addr="0x0001076c",func="callee3",
24753 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24754 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
24755 frame=@{level="2",addr="0x0001078c",func="callee2",
24756 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24757 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
24758 frame=@{level="3",addr="0x000107b4",func="callee1",
24759 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24760 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
24761 frame=@{level="4",addr="0x000107e0",func="main",
24762 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24763 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
24765 -stack-list-arguments 0
24768 frame=@{level="0",args=[]@},
24769 frame=@{level="1",args=[name="strarg"]@},
24770 frame=@{level="2",args=[name="intarg",name="strarg"]@},
24771 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
24772 frame=@{level="4",args=[]@}]
24774 -stack-list-arguments 1
24777 frame=@{level="0",args=[]@},
24779 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
24780 frame=@{level="2",args=[
24781 @{name="intarg",value="2"@},
24782 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
24783 @{frame=@{level="3",args=[
24784 @{name="intarg",value="2"@},
24785 @{name="strarg",value="0x11940 \"A string argument.\""@},
24786 @{name="fltarg",value="3.5"@}]@},
24787 frame=@{level="4",args=[]@}]
24789 -stack-list-arguments 0 2 2
24790 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
24792 -stack-list-arguments 1 2 2
24793 ^done,stack-args=[frame=@{level="2",
24794 args=[@{name="intarg",value="2"@},
24795 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
24799 @c @subheading -stack-list-exception-handlers
24802 @subheading The @code{-stack-list-frames} Command
24803 @findex -stack-list-frames
24805 @subsubheading Synopsis
24808 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
24811 List the frames currently on the stack. For each frame it displays the
24816 The frame number, 0 being the topmost frame, i.e., the innermost function.
24818 The @code{$pc} value for that frame.
24822 File name of the source file where the function lives.
24824 Line number corresponding to the @code{$pc}.
24827 If invoked without arguments, this command prints a backtrace for the
24828 whole stack. If given two integer arguments, it shows the frames whose
24829 levels are between the two arguments (inclusive). If the two arguments
24830 are equal, it shows the single frame at the corresponding level. It is
24831 an error if @var{low-frame} is larger than the actual number of
24832 frames. On the other hand, @var{high-frame} may be larger than the
24833 actual number of frames, in which case only existing frames will be returned.
24835 @subsubheading @value{GDBN} Command
24837 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
24839 @subsubheading Example
24841 Full stack backtrace:
24847 [frame=@{level="0",addr="0x0001076c",func="foo",
24848 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
24849 frame=@{level="1",addr="0x000107a4",func="foo",
24850 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24851 frame=@{level="2",addr="0x000107a4",func="foo",
24852 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24853 frame=@{level="3",addr="0x000107a4",func="foo",
24854 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24855 frame=@{level="4",addr="0x000107a4",func="foo",
24856 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24857 frame=@{level="5",addr="0x000107a4",func="foo",
24858 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24859 frame=@{level="6",addr="0x000107a4",func="foo",
24860 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24861 frame=@{level="7",addr="0x000107a4",func="foo",
24862 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24863 frame=@{level="8",addr="0x000107a4",func="foo",
24864 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24865 frame=@{level="9",addr="0x000107a4",func="foo",
24866 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24867 frame=@{level="10",addr="0x000107a4",func="foo",
24868 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24869 frame=@{level="11",addr="0x00010738",func="main",
24870 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
24874 Show frames between @var{low_frame} and @var{high_frame}:
24878 -stack-list-frames 3 5
24880 [frame=@{level="3",addr="0x000107a4",func="foo",
24881 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24882 frame=@{level="4",addr="0x000107a4",func="foo",
24883 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24884 frame=@{level="5",addr="0x000107a4",func="foo",
24885 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
24889 Show a single frame:
24893 -stack-list-frames 3 3
24895 [frame=@{level="3",addr="0x000107a4",func="foo",
24896 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
24901 @subheading The @code{-stack-list-locals} Command
24902 @findex -stack-list-locals
24904 @subsubheading Synopsis
24907 -stack-list-locals @var{print-values}
24910 Display the local variable names for the selected frame. If
24911 @var{print-values} is 0 or @code{--no-values}, print only the names of
24912 the variables; if it is 1 or @code{--all-values}, print also their
24913 values; and if it is 2 or @code{--simple-values}, print the name,
24914 type and value for simple data types, and the name and type for arrays,
24915 structures and unions. In this last case, a frontend can immediately
24916 display the value of simple data types and create variable objects for
24917 other data types when the user wishes to explore their values in
24920 This command is deprecated in favor of the
24921 @samp{-stack-list-variables} command.
24923 @subsubheading @value{GDBN} Command
24925 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
24927 @subsubheading Example
24931 -stack-list-locals 0
24932 ^done,locals=[name="A",name="B",name="C"]
24934 -stack-list-locals --all-values
24935 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
24936 @{name="C",value="@{1, 2, 3@}"@}]
24937 -stack-list-locals --simple-values
24938 ^done,locals=[@{name="A",type="int",value="1"@},
24939 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
24943 @subheading The @code{-stack-list-variables} Command
24944 @findex -stack-list-variables
24946 @subsubheading Synopsis
24949 -stack-list-variables @var{print-values}
24952 Display the names of local variables and function arguments for the selected frame. If
24953 @var{print-values} is 0 or @code{--no-values}, print only the names of
24954 the variables; if it is 1 or @code{--all-values}, print also their
24955 values; and if it is 2 or @code{--simple-values}, print the name,
24956 type and value for simple data types, and the name and type for arrays,
24957 structures and unions.
24959 @subsubheading Example
24963 -stack-list-variables --thread 1 --frame 0 --all-values
24964 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
24969 @subheading The @code{-stack-select-frame} Command
24970 @findex -stack-select-frame
24972 @subsubheading Synopsis
24975 -stack-select-frame @var{framenum}
24978 Change the selected frame. Select a different frame @var{framenum} on
24981 This command in deprecated in favor of passing the @samp{--frame}
24982 option to every command.
24984 @subsubheading @value{GDBN} Command
24986 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
24987 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
24989 @subsubheading Example
24993 -stack-select-frame 2
24998 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24999 @node GDB/MI Variable Objects
25000 @section @sc{gdb/mi} Variable Objects
25004 @subheading Motivation for Variable Objects in @sc{gdb/mi}
25006 For the implementation of a variable debugger window (locals, watched
25007 expressions, etc.), we are proposing the adaptation of the existing code
25008 used by @code{Insight}.
25010 The two main reasons for that are:
25014 It has been proven in practice (it is already on its second generation).
25017 It will shorten development time (needless to say how important it is
25021 The original interface was designed to be used by Tcl code, so it was
25022 slightly changed so it could be used through @sc{gdb/mi}. This section
25023 describes the @sc{gdb/mi} operations that will be available and gives some
25024 hints about their use.
25026 @emph{Note}: In addition to the set of operations described here, we
25027 expect the @sc{gui} implementation of a variable window to require, at
25028 least, the following operations:
25031 @item @code{-gdb-show} @code{output-radix}
25032 @item @code{-stack-list-arguments}
25033 @item @code{-stack-list-locals}
25034 @item @code{-stack-select-frame}
25039 @subheading Introduction to Variable Objects
25041 @cindex variable objects in @sc{gdb/mi}
25043 Variable objects are "object-oriented" MI interface for examining and
25044 changing values of expressions. Unlike some other MI interfaces that
25045 work with expressions, variable objects are specifically designed for
25046 simple and efficient presentation in the frontend. A variable object
25047 is identified by string name. When a variable object is created, the
25048 frontend specifies the expression for that variable object. The
25049 expression can be a simple variable, or it can be an arbitrary complex
25050 expression, and can even involve CPU registers. After creating a
25051 variable object, the frontend can invoke other variable object
25052 operations---for example to obtain or change the value of a variable
25053 object, or to change display format.
25055 Variable objects have hierarchical tree structure. Any variable object
25056 that corresponds to a composite type, such as structure in C, has
25057 a number of child variable objects, for example corresponding to each
25058 element of a structure. A child variable object can itself have
25059 children, recursively. Recursion ends when we reach
25060 leaf variable objects, which always have built-in types. Child variable
25061 objects are created only by explicit request, so if a frontend
25062 is not interested in the children of a particular variable object, no
25063 child will be created.
25065 For a leaf variable object it is possible to obtain its value as a
25066 string, or set the value from a string. String value can be also
25067 obtained for a non-leaf variable object, but it's generally a string
25068 that only indicates the type of the object, and does not list its
25069 contents. Assignment to a non-leaf variable object is not allowed.
25071 A frontend does not need to read the values of all variable objects each time
25072 the program stops. Instead, MI provides an update command that lists all
25073 variable objects whose values has changed since the last update
25074 operation. This considerably reduces the amount of data that must
25075 be transferred to the frontend. As noted above, children variable
25076 objects are created on demand, and only leaf variable objects have a
25077 real value. As result, gdb will read target memory only for leaf
25078 variables that frontend has created.
25080 The automatic update is not always desirable. For example, a frontend
25081 might want to keep a value of some expression for future reference,
25082 and never update it. For another example, fetching memory is
25083 relatively slow for embedded targets, so a frontend might want
25084 to disable automatic update for the variables that are either not
25085 visible on the screen, or ``closed''. This is possible using so
25086 called ``frozen variable objects''. Such variable objects are never
25087 implicitly updated.
25089 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
25090 fixed variable object, the expression is parsed when the variable
25091 object is created, including associating identifiers to specific
25092 variables. The meaning of expression never changes. For a floating
25093 variable object the values of variables whose names appear in the
25094 expressions are re-evaluated every time in the context of the current
25095 frame. Consider this example:
25100 struct work_state state;
25107 If a fixed variable object for the @code{state} variable is created in
25108 this function, and we enter the recursive call, the the variable
25109 object will report the value of @code{state} in the top-level
25110 @code{do_work} invocation. On the other hand, a floating variable
25111 object will report the value of @code{state} in the current frame.
25113 If an expression specified when creating a fixed variable object
25114 refers to a local variable, the variable object becomes bound to the
25115 thread and frame in which the variable object is created. When such
25116 variable object is updated, @value{GDBN} makes sure that the
25117 thread/frame combination the variable object is bound to still exists,
25118 and re-evaluates the variable object in context of that thread/frame.
25120 The following is the complete set of @sc{gdb/mi} operations defined to
25121 access this functionality:
25123 @multitable @columnfractions .4 .6
25124 @item @strong{Operation}
25125 @tab @strong{Description}
25127 @item @code{-enable-pretty-printing}
25128 @tab enable Python-based pretty-printing
25129 @item @code{-var-create}
25130 @tab create a variable object
25131 @item @code{-var-delete}
25132 @tab delete the variable object and/or its children
25133 @item @code{-var-set-format}
25134 @tab set the display format of this variable
25135 @item @code{-var-show-format}
25136 @tab show the display format of this variable
25137 @item @code{-var-info-num-children}
25138 @tab tells how many children this object has
25139 @item @code{-var-list-children}
25140 @tab return a list of the object's children
25141 @item @code{-var-info-type}
25142 @tab show the type of this variable object
25143 @item @code{-var-info-expression}
25144 @tab print parent-relative expression that this variable object represents
25145 @item @code{-var-info-path-expression}
25146 @tab print full expression that this variable object represents
25147 @item @code{-var-show-attributes}
25148 @tab is this variable editable? does it exist here?
25149 @item @code{-var-evaluate-expression}
25150 @tab get the value of this variable
25151 @item @code{-var-assign}
25152 @tab set the value of this variable
25153 @item @code{-var-update}
25154 @tab update the variable and its children
25155 @item @code{-var-set-frozen}
25156 @tab set frozeness attribute
25157 @item @code{-var-set-update-range}
25158 @tab set range of children to display on update
25161 In the next subsection we describe each operation in detail and suggest
25162 how it can be used.
25164 @subheading Description And Use of Operations on Variable Objects
25166 @subheading The @code{-enable-pretty-printing} Command
25167 @findex -enable-pretty-printing
25170 -enable-pretty-printing
25173 @value{GDBN} allows Python-based visualizers to affect the output of the
25174 MI variable object commands. However, because there was no way to
25175 implement this in a fully backward-compatible way, a front end must
25176 request that this functionality be enabled.
25178 Once enabled, this feature cannot be disabled.
25180 Note that if Python support has not been compiled into @value{GDBN},
25181 this command will still succeed (and do nothing).
25183 This feature is currently (as of @value{GDBN} 7.0) experimental, and
25184 may work differently in future versions of @value{GDBN}.
25186 @subheading The @code{-var-create} Command
25187 @findex -var-create
25189 @subsubheading Synopsis
25192 -var-create @{@var{name} | "-"@}
25193 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
25196 This operation creates a variable object, which allows the monitoring of
25197 a variable, the result of an expression, a memory cell or a CPU
25200 The @var{name} parameter is the string by which the object can be
25201 referenced. It must be unique. If @samp{-} is specified, the varobj
25202 system will generate a string ``varNNNNNN'' automatically. It will be
25203 unique provided that one does not specify @var{name} of that format.
25204 The command fails if a duplicate name is found.
25206 The frame under which the expression should be evaluated can be
25207 specified by @var{frame-addr}. A @samp{*} indicates that the current
25208 frame should be used. A @samp{@@} indicates that a floating variable
25209 object must be created.
25211 @var{expression} is any expression valid on the current language set (must not
25212 begin with a @samp{*}), or one of the following:
25216 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
25219 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
25222 @samp{$@var{regname}} --- a CPU register name
25225 @cindex dynamic varobj
25226 A varobj's contents may be provided by a Python-based pretty-printer. In this
25227 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
25228 have slightly different semantics in some cases. If the
25229 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
25230 will never create a dynamic varobj. This ensures backward
25231 compatibility for existing clients.
25233 @subsubheading Result
25235 This operation returns attributes of the newly-created varobj. These
25240 The name of the varobj.
25243 The number of children of the varobj. This number is not necessarily
25244 reliable for a dynamic varobj. Instead, you must examine the
25245 @samp{has_more} attribute.
25248 The varobj's scalar value. For a varobj whose type is some sort of
25249 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
25250 will not be interesting.
25253 The varobj's type. This is a string representation of the type, as
25254 would be printed by the @value{GDBN} CLI.
25257 If a variable object is bound to a specific thread, then this is the
25258 thread's identifier.
25261 For a dynamic varobj, this indicates whether there appear to be any
25262 children available. For a non-dynamic varobj, this will be 0.
25265 This attribute will be present and have the value @samp{1} if the
25266 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
25267 then this attribute will not be present.
25270 A dynamic varobj can supply a display hint to the front end. The
25271 value comes directly from the Python pretty-printer object's
25272 @code{display_hint} method. @xref{Pretty Printing}.
25275 Typical output will look like this:
25278 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
25279 has_more="@var{has_more}"
25283 @subheading The @code{-var-delete} Command
25284 @findex -var-delete
25286 @subsubheading Synopsis
25289 -var-delete [ -c ] @var{name}
25292 Deletes a previously created variable object and all of its children.
25293 With the @samp{-c} option, just deletes the children.
25295 Returns an error if the object @var{name} is not found.
25298 @subheading The @code{-var-set-format} Command
25299 @findex -var-set-format
25301 @subsubheading Synopsis
25304 -var-set-format @var{name} @var{format-spec}
25307 Sets the output format for the value of the object @var{name} to be
25310 @anchor{-var-set-format}
25311 The syntax for the @var{format-spec} is as follows:
25314 @var{format-spec} @expansion{}
25315 @{binary | decimal | hexadecimal | octal | natural@}
25318 The natural format is the default format choosen automatically
25319 based on the variable type (like decimal for an @code{int}, hex
25320 for pointers, etc.).
25322 For a variable with children, the format is set only on the
25323 variable itself, and the children are not affected.
25325 @subheading The @code{-var-show-format} Command
25326 @findex -var-show-format
25328 @subsubheading Synopsis
25331 -var-show-format @var{name}
25334 Returns the format used to display the value of the object @var{name}.
25337 @var{format} @expansion{}
25342 @subheading The @code{-var-info-num-children} Command
25343 @findex -var-info-num-children
25345 @subsubheading Synopsis
25348 -var-info-num-children @var{name}
25351 Returns the number of children of a variable object @var{name}:
25357 Note that this number is not completely reliable for a dynamic varobj.
25358 It will return the current number of children, but more children may
25362 @subheading The @code{-var-list-children} Command
25363 @findex -var-list-children
25365 @subsubheading Synopsis
25368 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
25370 @anchor{-var-list-children}
25372 Return a list of the children of the specified variable object and
25373 create variable objects for them, if they do not already exist. With
25374 a single argument or if @var{print-values} has a value for of 0 or
25375 @code{--no-values}, print only the names of the variables; if
25376 @var{print-values} is 1 or @code{--all-values}, also print their
25377 values; and if it is 2 or @code{--simple-values} print the name and
25378 value for simple data types and just the name for arrays, structures
25381 @var{from} and @var{to}, if specified, indicate the range of children
25382 to report. If @var{from} or @var{to} is less than zero, the range is
25383 reset and all children will be reported. Otherwise, children starting
25384 at @var{from} (zero-based) and up to and excluding @var{to} will be
25387 If a child range is requested, it will only affect the current call to
25388 @code{-var-list-children}, but not future calls to @code{-var-update}.
25389 For this, you must instead use @code{-var-set-update-range}. The
25390 intent of this approach is to enable a front end to implement any
25391 update approach it likes; for example, scrolling a view may cause the
25392 front end to request more children with @code{-var-list-children}, and
25393 then the front end could call @code{-var-set-update-range} with a
25394 different range to ensure that future updates are restricted to just
25397 For each child the following results are returned:
25402 Name of the variable object created for this child.
25405 The expression to be shown to the user by the front end to designate this child.
25406 For example this may be the name of a structure member.
25408 For a dynamic varobj, this value cannot be used to form an
25409 expression. There is no way to do this at all with a dynamic varobj.
25411 For C/C@t{++} structures there are several pseudo children returned to
25412 designate access qualifiers. For these pseudo children @var{exp} is
25413 @samp{public}, @samp{private}, or @samp{protected}. In this case the
25414 type and value are not present.
25416 A dynamic varobj will not report the access qualifying
25417 pseudo-children, regardless of the language. This information is not
25418 available at all with a dynamic varobj.
25421 Number of children this child has. For a dynamic varobj, this will be
25425 The type of the child.
25428 If values were requested, this is the value.
25431 If this variable object is associated with a thread, this is the thread id.
25432 Otherwise this result is not present.
25435 If the variable object is frozen, this variable will be present with a value of 1.
25438 The result may have its own attributes:
25442 A dynamic varobj can supply a display hint to the front end. The
25443 value comes directly from the Python pretty-printer object's
25444 @code{display_hint} method. @xref{Pretty Printing}.
25447 This is an integer attribute which is nonzero if there are children
25448 remaining after the end of the selected range.
25451 @subsubheading Example
25455 -var-list-children n
25456 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25457 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
25459 -var-list-children --all-values n
25460 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25461 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
25465 @subheading The @code{-var-info-type} Command
25466 @findex -var-info-type
25468 @subsubheading Synopsis
25471 -var-info-type @var{name}
25474 Returns the type of the specified variable @var{name}. The type is
25475 returned as a string in the same format as it is output by the
25479 type=@var{typename}
25483 @subheading The @code{-var-info-expression} Command
25484 @findex -var-info-expression
25486 @subsubheading Synopsis
25489 -var-info-expression @var{name}
25492 Returns a string that is suitable for presenting this
25493 variable object in user interface. The string is generally
25494 not valid expression in the current language, and cannot be evaluated.
25496 For example, if @code{a} is an array, and variable object
25497 @code{A} was created for @code{a}, then we'll get this output:
25500 (gdb) -var-info-expression A.1
25501 ^done,lang="C",exp="1"
25505 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
25507 Note that the output of the @code{-var-list-children} command also
25508 includes those expressions, so the @code{-var-info-expression} command
25511 @subheading The @code{-var-info-path-expression} Command
25512 @findex -var-info-path-expression
25514 @subsubheading Synopsis
25517 -var-info-path-expression @var{name}
25520 Returns an expression that can be evaluated in the current
25521 context and will yield the same value that a variable object has.
25522 Compare this with the @code{-var-info-expression} command, which
25523 result can be used only for UI presentation. Typical use of
25524 the @code{-var-info-path-expression} command is creating a
25525 watchpoint from a variable object.
25527 This command is currently not valid for children of a dynamic varobj,
25528 and will give an error when invoked on one.
25530 For example, suppose @code{C} is a C@t{++} class, derived from class
25531 @code{Base}, and that the @code{Base} class has a member called
25532 @code{m_size}. Assume a variable @code{c} is has the type of
25533 @code{C} and a variable object @code{C} was created for variable
25534 @code{c}. Then, we'll get this output:
25536 (gdb) -var-info-path-expression C.Base.public.m_size
25537 ^done,path_expr=((Base)c).m_size)
25540 @subheading The @code{-var-show-attributes} Command
25541 @findex -var-show-attributes
25543 @subsubheading Synopsis
25546 -var-show-attributes @var{name}
25549 List attributes of the specified variable object @var{name}:
25552 status=@var{attr} [ ( ,@var{attr} )* ]
25556 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
25558 @subheading The @code{-var-evaluate-expression} Command
25559 @findex -var-evaluate-expression
25561 @subsubheading Synopsis
25564 -var-evaluate-expression [-f @var{format-spec}] @var{name}
25567 Evaluates the expression that is represented by the specified variable
25568 object and returns its value as a string. The format of the string
25569 can be specified with the @samp{-f} option. The possible values of
25570 this option are the same as for @code{-var-set-format}
25571 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
25572 the current display format will be used. The current display format
25573 can be changed using the @code{-var-set-format} command.
25579 Note that one must invoke @code{-var-list-children} for a variable
25580 before the value of a child variable can be evaluated.
25582 @subheading The @code{-var-assign} Command
25583 @findex -var-assign
25585 @subsubheading Synopsis
25588 -var-assign @var{name} @var{expression}
25591 Assigns the value of @var{expression} to the variable object specified
25592 by @var{name}. The object must be @samp{editable}. If the variable's
25593 value is altered by the assign, the variable will show up in any
25594 subsequent @code{-var-update} list.
25596 @subsubheading Example
25604 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
25608 @subheading The @code{-var-update} Command
25609 @findex -var-update
25611 @subsubheading Synopsis
25614 -var-update [@var{print-values}] @{@var{name} | "*"@}
25617 Reevaluate the expressions corresponding to the variable object
25618 @var{name} and all its direct and indirect children, and return the
25619 list of variable objects whose values have changed; @var{name} must
25620 be a root variable object. Here, ``changed'' means that the result of
25621 @code{-var-evaluate-expression} before and after the
25622 @code{-var-update} is different. If @samp{*} is used as the variable
25623 object names, all existing variable objects are updated, except
25624 for frozen ones (@pxref{-var-set-frozen}). The option
25625 @var{print-values} determines whether both names and values, or just
25626 names are printed. The possible values of this option are the same
25627 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
25628 recommended to use the @samp{--all-values} option, to reduce the
25629 number of MI commands needed on each program stop.
25631 With the @samp{*} parameter, if a variable object is bound to a
25632 currently running thread, it will not be updated, without any
25635 If @code{-var-set-update-range} was previously used on a varobj, then
25636 only the selected range of children will be reported.
25638 @code{-var-update} reports all the changed varobjs in a tuple named
25641 Each item in the change list is itself a tuple holding:
25645 The name of the varobj.
25648 If values were requested for this update, then this field will be
25649 present and will hold the value of the varobj.
25652 @anchor{-var-update}
25653 This field is a string which may take one of three values:
25657 The variable object's current value is valid.
25660 The variable object does not currently hold a valid value but it may
25661 hold one in the future if its associated expression comes back into
25665 The variable object no longer holds a valid value.
25666 This can occur when the executable file being debugged has changed,
25667 either through recompilation or by using the @value{GDBN} @code{file}
25668 command. The front end should normally choose to delete these variable
25672 In the future new values may be added to this list so the front should
25673 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
25676 This is only present if the varobj is still valid. If the type
25677 changed, then this will be the string @samp{true}; otherwise it will
25681 If the varobj's type changed, then this field will be present and will
25684 @item new_num_children
25685 For a dynamic varobj, if the number of children changed, or if the
25686 type changed, this will be the new number of children.
25688 The @samp{numchild} field in other varobj responses is generally not
25689 valid for a dynamic varobj -- it will show the number of children that
25690 @value{GDBN} knows about, but because dynamic varobjs lazily
25691 instantiate their children, this will not reflect the number of
25692 children which may be available.
25694 The @samp{new_num_children} attribute only reports changes to the
25695 number of children known by @value{GDBN}. This is the only way to
25696 detect whether an update has removed children (which necessarily can
25697 only happen at the end of the update range).
25700 The display hint, if any.
25703 This is an integer value, which will be 1 if there are more children
25704 available outside the varobj's update range.
25707 This attribute will be present and have the value @samp{1} if the
25708 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
25709 then this attribute will not be present.
25712 If new children were added to a dynamic varobj within the selected
25713 update range (as set by @code{-var-set-update-range}), then they will
25714 be listed in this attribute.
25717 @subsubheading Example
25724 -var-update --all-values var1
25725 ^done,changelist=[@{name="var1",value="3",in_scope="true",
25726 type_changed="false"@}]
25730 @subheading The @code{-var-set-frozen} Command
25731 @findex -var-set-frozen
25732 @anchor{-var-set-frozen}
25734 @subsubheading Synopsis
25737 -var-set-frozen @var{name} @var{flag}
25740 Set the frozenness flag on the variable object @var{name}. The
25741 @var{flag} parameter should be either @samp{1} to make the variable
25742 frozen or @samp{0} to make it unfrozen. If a variable object is
25743 frozen, then neither itself, nor any of its children, are
25744 implicitly updated by @code{-var-update} of
25745 a parent variable or by @code{-var-update *}. Only
25746 @code{-var-update} of the variable itself will update its value and
25747 values of its children. After a variable object is unfrozen, it is
25748 implicitly updated by all subsequent @code{-var-update} operations.
25749 Unfreezing a variable does not update it, only subsequent
25750 @code{-var-update} does.
25752 @subsubheading Example
25756 -var-set-frozen V 1
25761 @subheading The @code{-var-set-update-range} command
25762 @findex -var-set-update-range
25763 @anchor{-var-set-update-range}
25765 @subsubheading Synopsis
25768 -var-set-update-range @var{name} @var{from} @var{to}
25771 Set the range of children to be returned by future invocations of
25772 @code{-var-update}.
25774 @var{from} and @var{to} indicate the range of children to report. If
25775 @var{from} or @var{to} is less than zero, the range is reset and all
25776 children will be reported. Otherwise, children starting at @var{from}
25777 (zero-based) and up to and excluding @var{to} will be reported.
25779 @subsubheading Example
25783 -var-set-update-range V 1 2
25787 @subheading The @code{-var-set-visualizer} command
25788 @findex -var-set-visualizer
25789 @anchor{-var-set-visualizer}
25791 @subsubheading Synopsis
25794 -var-set-visualizer @var{name} @var{visualizer}
25797 Set a visualizer for the variable object @var{name}.
25799 @var{visualizer} is the visualizer to use. The special value
25800 @samp{None} means to disable any visualizer in use.
25802 If not @samp{None}, @var{visualizer} must be a Python expression.
25803 This expression must evaluate to a callable object which accepts a
25804 single argument. @value{GDBN} will call this object with the value of
25805 the varobj @var{name} as an argument (this is done so that the same
25806 Python pretty-printing code can be used for both the CLI and MI).
25807 When called, this object must return an object which conforms to the
25808 pretty-printing interface (@pxref{Pretty Printing}).
25810 The pre-defined function @code{gdb.default_visualizer} may be used to
25811 select a visualizer by following the built-in process
25812 (@pxref{Selecting Pretty-Printers}). This is done automatically when
25813 a varobj is created, and so ordinarily is not needed.
25815 This feature is only available if Python support is enabled. The MI
25816 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
25817 can be used to check this.
25819 @subsubheading Example
25821 Resetting the visualizer:
25825 -var-set-visualizer V None
25829 Reselecting the default (type-based) visualizer:
25833 -var-set-visualizer V gdb.default_visualizer
25837 Suppose @code{SomeClass} is a visualizer class. A lambda expression
25838 can be used to instantiate this class for a varobj:
25842 -var-set-visualizer V "lambda val: SomeClass()"
25846 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25847 @node GDB/MI Data Manipulation
25848 @section @sc{gdb/mi} Data Manipulation
25850 @cindex data manipulation, in @sc{gdb/mi}
25851 @cindex @sc{gdb/mi}, data manipulation
25852 This section describes the @sc{gdb/mi} commands that manipulate data:
25853 examine memory and registers, evaluate expressions, etc.
25855 @c REMOVED FROM THE INTERFACE.
25856 @c @subheading -data-assign
25857 @c Change the value of a program variable. Plenty of side effects.
25858 @c @subsubheading GDB Command
25860 @c @subsubheading Example
25863 @subheading The @code{-data-disassemble} Command
25864 @findex -data-disassemble
25866 @subsubheading Synopsis
25870 [ -s @var{start-addr} -e @var{end-addr} ]
25871 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
25879 @item @var{start-addr}
25880 is the beginning address (or @code{$pc})
25881 @item @var{end-addr}
25883 @item @var{filename}
25884 is the name of the file to disassemble
25885 @item @var{linenum}
25886 is the line number to disassemble around
25888 is the number of disassembly lines to be produced. If it is -1,
25889 the whole function will be disassembled, in case no @var{end-addr} is
25890 specified. If @var{end-addr} is specified as a non-zero value, and
25891 @var{lines} is lower than the number of disassembly lines between
25892 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
25893 displayed; if @var{lines} is higher than the number of lines between
25894 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
25897 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
25901 @subsubheading Result
25903 The output for each instruction is composed of four fields:
25912 Note that whatever included in the instruction field, is not manipulated
25913 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
25915 @subsubheading @value{GDBN} Command
25917 There's no direct mapping from this command to the CLI.
25919 @subsubheading Example
25921 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
25925 -data-disassemble -s $pc -e "$pc + 20" -- 0
25928 @{address="0x000107c0",func-name="main",offset="4",
25929 inst="mov 2, %o0"@},
25930 @{address="0x000107c4",func-name="main",offset="8",
25931 inst="sethi %hi(0x11800), %o2"@},
25932 @{address="0x000107c8",func-name="main",offset="12",
25933 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
25934 @{address="0x000107cc",func-name="main",offset="16",
25935 inst="sethi %hi(0x11800), %o2"@},
25936 @{address="0x000107d0",func-name="main",offset="20",
25937 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
25941 Disassemble the whole @code{main} function. Line 32 is part of
25945 -data-disassemble -f basics.c -l 32 -- 0
25947 @{address="0x000107bc",func-name="main",offset="0",
25948 inst="save %sp, -112, %sp"@},
25949 @{address="0x000107c0",func-name="main",offset="4",
25950 inst="mov 2, %o0"@},
25951 @{address="0x000107c4",func-name="main",offset="8",
25952 inst="sethi %hi(0x11800), %o2"@},
25954 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
25955 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
25959 Disassemble 3 instructions from the start of @code{main}:
25963 -data-disassemble -f basics.c -l 32 -n 3 -- 0
25965 @{address="0x000107bc",func-name="main",offset="0",
25966 inst="save %sp, -112, %sp"@},
25967 @{address="0x000107c0",func-name="main",offset="4",
25968 inst="mov 2, %o0"@},
25969 @{address="0x000107c4",func-name="main",offset="8",
25970 inst="sethi %hi(0x11800), %o2"@}]
25974 Disassemble 3 instructions from the start of @code{main} in mixed mode:
25978 -data-disassemble -f basics.c -l 32 -n 3 -- 1
25980 src_and_asm_line=@{line="31",
25981 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
25982 testsuite/gdb.mi/basics.c",line_asm_insn=[
25983 @{address="0x000107bc",func-name="main",offset="0",
25984 inst="save %sp, -112, %sp"@}]@},
25985 src_and_asm_line=@{line="32",
25986 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
25987 testsuite/gdb.mi/basics.c",line_asm_insn=[
25988 @{address="0x000107c0",func-name="main",offset="4",
25989 inst="mov 2, %o0"@},
25990 @{address="0x000107c4",func-name="main",offset="8",
25991 inst="sethi %hi(0x11800), %o2"@}]@}]
25996 @subheading The @code{-data-evaluate-expression} Command
25997 @findex -data-evaluate-expression
25999 @subsubheading Synopsis
26002 -data-evaluate-expression @var{expr}
26005 Evaluate @var{expr} as an expression. The expression could contain an
26006 inferior function call. The function call will execute synchronously.
26007 If the expression contains spaces, it must be enclosed in double quotes.
26009 @subsubheading @value{GDBN} Command
26011 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
26012 @samp{call}. In @code{gdbtk} only, there's a corresponding
26013 @samp{gdb_eval} command.
26015 @subsubheading Example
26017 In the following example, the numbers that precede the commands are the
26018 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
26019 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
26023 211-data-evaluate-expression A
26026 311-data-evaluate-expression &A
26027 311^done,value="0xefffeb7c"
26029 411-data-evaluate-expression A+3
26032 511-data-evaluate-expression "A + 3"
26038 @subheading The @code{-data-list-changed-registers} Command
26039 @findex -data-list-changed-registers
26041 @subsubheading Synopsis
26044 -data-list-changed-registers
26047 Display a list of the registers that have changed.
26049 @subsubheading @value{GDBN} Command
26051 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
26052 has the corresponding command @samp{gdb_changed_register_list}.
26054 @subsubheading Example
26056 On a PPC MBX board:
26064 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
26065 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
26068 -data-list-changed-registers
26069 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
26070 "10","11","13","14","15","16","17","18","19","20","21","22","23",
26071 "24","25","26","27","28","30","31","64","65","66","67","69"]
26076 @subheading The @code{-data-list-register-names} Command
26077 @findex -data-list-register-names
26079 @subsubheading Synopsis
26082 -data-list-register-names [ ( @var{regno} )+ ]
26085 Show a list of register names for the current target. If no arguments
26086 are given, it shows a list of the names of all the registers. If
26087 integer numbers are given as arguments, it will print a list of the
26088 names of the registers corresponding to the arguments. To ensure
26089 consistency between a register name and its number, the output list may
26090 include empty register names.
26092 @subsubheading @value{GDBN} Command
26094 @value{GDBN} does not have a command which corresponds to
26095 @samp{-data-list-register-names}. In @code{gdbtk} there is a
26096 corresponding command @samp{gdb_regnames}.
26098 @subsubheading Example
26100 For the PPC MBX board:
26103 -data-list-register-names
26104 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
26105 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
26106 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
26107 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
26108 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
26109 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
26110 "", "pc","ps","cr","lr","ctr","xer"]
26112 -data-list-register-names 1 2 3
26113 ^done,register-names=["r1","r2","r3"]
26117 @subheading The @code{-data-list-register-values} Command
26118 @findex -data-list-register-values
26120 @subsubheading Synopsis
26123 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
26126 Display the registers' contents. @var{fmt} is the format according to
26127 which the registers' contents are to be returned, followed by an optional
26128 list of numbers specifying the registers to display. A missing list of
26129 numbers indicates that the contents of all the registers must be returned.
26131 Allowed formats for @var{fmt} are:
26148 @subsubheading @value{GDBN} Command
26150 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
26151 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
26153 @subsubheading Example
26155 For a PPC MBX board (note: line breaks are for readability only, they
26156 don't appear in the actual output):
26160 -data-list-register-values r 64 65
26161 ^done,register-values=[@{number="64",value="0xfe00a300"@},
26162 @{number="65",value="0x00029002"@}]
26164 -data-list-register-values x
26165 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
26166 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
26167 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
26168 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
26169 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
26170 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
26171 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
26172 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
26173 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
26174 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
26175 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
26176 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
26177 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
26178 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
26179 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
26180 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
26181 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
26182 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
26183 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
26184 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
26185 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
26186 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
26187 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
26188 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
26189 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
26190 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
26191 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
26192 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
26193 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
26194 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
26195 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
26196 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
26197 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
26198 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
26199 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
26200 @{number="69",value="0x20002b03"@}]
26205 @subheading The @code{-data-read-memory} Command
26206 @findex -data-read-memory
26208 @subsubheading Synopsis
26211 -data-read-memory [ -o @var{byte-offset} ]
26212 @var{address} @var{word-format} @var{word-size}
26213 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
26220 @item @var{address}
26221 An expression specifying the address of the first memory word to be
26222 read. Complex expressions containing embedded white space should be
26223 quoted using the C convention.
26225 @item @var{word-format}
26226 The format to be used to print the memory words. The notation is the
26227 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
26230 @item @var{word-size}
26231 The size of each memory word in bytes.
26233 @item @var{nr-rows}
26234 The number of rows in the output table.
26236 @item @var{nr-cols}
26237 The number of columns in the output table.
26240 If present, indicates that each row should include an @sc{ascii} dump. The
26241 value of @var{aschar} is used as a padding character when a byte is not a
26242 member of the printable @sc{ascii} character set (printable @sc{ascii}
26243 characters are those whose code is between 32 and 126, inclusively).
26245 @item @var{byte-offset}
26246 An offset to add to the @var{address} before fetching memory.
26249 This command displays memory contents as a table of @var{nr-rows} by
26250 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
26251 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
26252 (returned as @samp{total-bytes}). Should less than the requested number
26253 of bytes be returned by the target, the missing words are identified
26254 using @samp{N/A}. The number of bytes read from the target is returned
26255 in @samp{nr-bytes} and the starting address used to read memory in
26258 The address of the next/previous row or page is available in
26259 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
26262 @subsubheading @value{GDBN} Command
26264 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
26265 @samp{gdb_get_mem} memory read command.
26267 @subsubheading Example
26269 Read six bytes of memory starting at @code{bytes+6} but then offset by
26270 @code{-6} bytes. Format as three rows of two columns. One byte per
26271 word. Display each word in hex.
26275 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
26276 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
26277 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
26278 prev-page="0x0000138a",memory=[
26279 @{addr="0x00001390",data=["0x00","0x01"]@},
26280 @{addr="0x00001392",data=["0x02","0x03"]@},
26281 @{addr="0x00001394",data=["0x04","0x05"]@}]
26285 Read two bytes of memory starting at address @code{shorts + 64} and
26286 display as a single word formatted in decimal.
26290 5-data-read-memory shorts+64 d 2 1 1
26291 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
26292 next-row="0x00001512",prev-row="0x0000150e",
26293 next-page="0x00001512",prev-page="0x0000150e",memory=[
26294 @{addr="0x00001510",data=["128"]@}]
26298 Read thirty two bytes of memory starting at @code{bytes+16} and format
26299 as eight rows of four columns. Include a string encoding with @samp{x}
26300 used as the non-printable character.
26304 4-data-read-memory bytes+16 x 1 8 4 x
26305 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
26306 next-row="0x000013c0",prev-row="0x0000139c",
26307 next-page="0x000013c0",prev-page="0x00001380",memory=[
26308 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
26309 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
26310 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
26311 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
26312 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
26313 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
26314 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
26315 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
26319 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26320 @node GDB/MI Tracepoint Commands
26321 @section @sc{gdb/mi} Tracepoint Commands
26323 The commands defined in this section implement MI support for
26324 tracepoints. For detailed introduction, see @ref{Tracepoints}.
26326 @subheading The @code{-trace-find} Command
26327 @findex -trace-find
26329 @subsubheading Synopsis
26332 -trace-find @var{mode} [@var{parameters}@dots{}]
26335 Find a trace frame using criteria defined by @var{mode} and
26336 @var{parameters}. The following table lists permissible
26337 modes and their parameters. For details of operation, see @ref{tfind}.
26342 No parameters are required. Stops examining trace frames.
26345 An integer is required as parameter. Selects tracepoint frame with
26348 @item tracepoint-number
26349 An integer is required as parameter. Finds next
26350 trace frame that corresponds to tracepoint with the specified number.
26353 An address is required as parameter. Finds
26354 next trace frame that corresponds to any tracepoint at the specified
26357 @item pc-inside-range
26358 Two addresses are required as parameters. Finds next trace
26359 frame that corresponds to a tracepoint at an address inside the
26360 specified range. Both bounds are considered to be inside the range.
26362 @item pc-outside-range
26363 Two addresses are required as parameters. Finds
26364 next trace frame that corresponds to a tracepoint at an address outside
26365 the specified range. Both bounds are considered to be inside the range.
26368 Line specification is required as parameter. @xref{Specify Location}.
26369 Finds next trace frame that corresponds to a tracepoint at
26370 the specified location.
26374 If @samp{none} was passed as @var{mode}, the response does not
26375 have fields. Otherwise, the response may have the following fields:
26379 This field has either @samp{0} or @samp{1} as the value, depending
26380 on whether a matching tracepoint was found.
26383 The index of the found traceframe. This field is present iff
26384 the @samp{found} field has value of @samp{1}.
26387 The index of the found tracepoint. This field is present iff
26388 the @samp{found} field has value of @samp{1}.
26391 The information about the frame corresponding to the found trace
26392 frame. This field is present only if a trace frame was found.
26393 @xref{GDB/MI Frame Information}, for description of this field.
26397 @subsubheading @value{GDBN} Command
26399 The corresponding @value{GDBN} command is @samp{tfind}.
26401 @subheading -trace-define-variable
26402 @findex -trace-define-variable
26404 @subsubheading Synopsis
26407 -trace-define-variable @var{name} [ @var{value} ]
26410 Create trace variable @var{name} if it does not exist. If
26411 @var{value} is specified, sets the initial value of the specified
26412 trace variable to that value. Note that the @var{name} should start
26413 with the @samp{$} character.
26415 @subsubheading @value{GDBN} Command
26417 The corresponding @value{GDBN} command is @samp{tvariable}.
26419 @subheading -trace-list-variables
26420 @findex -trace-list-variables
26422 @subsubheading Synopsis
26425 -trace-list-variables
26428 Return a table of all defined trace variables. Each element of the
26429 table has the following fields:
26433 The name of the trace variable. This field is always present.
26436 The initial value. This is a 64-bit signed integer. This
26437 field is always present.
26440 The value the trace variable has at the moment. This is a 64-bit
26441 signed integer. This field is absent iff current value is
26442 not defined, for example if the trace was never run, or is
26447 @subsubheading @value{GDBN} Command
26449 The corresponding @value{GDBN} command is @samp{tvariables}.
26451 @subsubheading Example
26455 -trace-list-variables
26456 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
26457 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
26458 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
26459 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
26460 body=[variable=@{name="$trace_timestamp",initial="0"@}
26461 variable=@{name="$foo",initial="10",current="15"@}]@}
26465 @subheading -trace-save
26466 @findex -trace-save
26468 @subsubheading Synopsis
26471 -trace-save [-r ] @var{filename}
26474 Saves the collected trace data to @var{filename}. Without the
26475 @samp{-r} option, the data is downloaded from the target and saved
26476 in a local file. With the @samp{-r} option the target is asked
26477 to perform the save.
26479 @subsubheading @value{GDBN} Command
26481 The corresponding @value{GDBN} command is @samp{tsave}.
26484 @subheading -trace-start
26485 @findex -trace-start
26487 @subsubheading Synopsis
26493 Starts a tracing experiments. The result of this command does not
26496 @subsubheading @value{GDBN} Command
26498 The corresponding @value{GDBN} command is @samp{tstart}.
26500 @subheading -trace-status
26501 @findex -trace-status
26503 @subsubheading Synopsis
26509 Obtains the status of a tracing experiment. The result may include
26510 the following fields:
26515 May have a value of either @samp{0}, when no tracing operations are
26516 supported, @samp{1}, when all tracing operations are supported, or
26517 @samp{file} when examining trace file. In the latter case, examining
26518 of trace frame is possible but new tracing experiement cannot be
26519 started. This field is always present.
26522 May have a value of either @samp{0} or @samp{1} depending on whether
26523 tracing experiement is in progress on target. This field is present
26524 if @samp{supported} field is not @samp{0}.
26527 Report the reason why the tracing was stopped last time. This field
26528 may be absent iff tracing was never stopped on target yet. The
26529 value of @samp{request} means the tracing was stopped as result of
26530 the @code{-trace-stop} command. The value of @samp{overflow} means
26531 the tracing buffer is full. The value of @samp{disconnection} means
26532 tracing was automatically stopped when @value{GDBN} has disconnected.
26533 The value of @samp{passcount} means tracing was stopped when a
26534 tracepoint was passed a maximal number of times for that tracepoint.
26535 This field is present if @samp{supported} field is not @samp{0}.
26537 @item stopping-tracepoint
26538 The number of tracepoint whose passcount as exceeded. This field is
26539 present iff the @samp{stop-reason} field has the value of
26543 @itemx frames-created
26544 The @samp{frames} field is a count of the total number of trace frames
26545 in the trace buffer, while @samp{frames-created} is the total created
26546 during the run, including ones that were discarded, such as when a
26547 circular trace buffer filled up. Both fields are optional.
26551 These fields tell the current size of the tracing buffer and the
26552 remaining space. These fields are optional.
26555 The value of the circular trace buffer flag. @code{1} means that the
26556 trace buffer is circular and old trace frames will be discarded if
26557 necessary to make room, @code{0} means that the trace buffer is linear
26561 The value of the disconnected tracing flag. @code{1} means that
26562 tracing will continue after @value{GDBN} disconnects, @code{0} means
26563 that the trace run will stop.
26567 @subsubheading @value{GDBN} Command
26569 The corresponding @value{GDBN} command is @samp{tstatus}.
26571 @subheading -trace-stop
26572 @findex -trace-stop
26574 @subsubheading Synopsis
26580 Stops a tracing experiment. The result of this command has the same
26581 fields as @code{-trace-status}, except that the @samp{supported} and
26582 @samp{running} fields are not output.
26584 @subsubheading @value{GDBN} Command
26586 The corresponding @value{GDBN} command is @samp{tstop}.
26589 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26590 @node GDB/MI Symbol Query
26591 @section @sc{gdb/mi} Symbol Query Commands
26595 @subheading The @code{-symbol-info-address} Command
26596 @findex -symbol-info-address
26598 @subsubheading Synopsis
26601 -symbol-info-address @var{symbol}
26604 Describe where @var{symbol} is stored.
26606 @subsubheading @value{GDBN} Command
26608 The corresponding @value{GDBN} command is @samp{info address}.
26610 @subsubheading Example
26614 @subheading The @code{-symbol-info-file} Command
26615 @findex -symbol-info-file
26617 @subsubheading Synopsis
26623 Show the file for the symbol.
26625 @subsubheading @value{GDBN} Command
26627 There's no equivalent @value{GDBN} command. @code{gdbtk} has
26628 @samp{gdb_find_file}.
26630 @subsubheading Example
26634 @subheading The @code{-symbol-info-function} Command
26635 @findex -symbol-info-function
26637 @subsubheading Synopsis
26640 -symbol-info-function
26643 Show which function the symbol lives in.
26645 @subsubheading @value{GDBN} Command
26647 @samp{gdb_get_function} in @code{gdbtk}.
26649 @subsubheading Example
26653 @subheading The @code{-symbol-info-line} Command
26654 @findex -symbol-info-line
26656 @subsubheading Synopsis
26662 Show the core addresses of the code for a source line.
26664 @subsubheading @value{GDBN} Command
26666 The corresponding @value{GDBN} command is @samp{info line}.
26667 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
26669 @subsubheading Example
26673 @subheading The @code{-symbol-info-symbol} Command
26674 @findex -symbol-info-symbol
26676 @subsubheading Synopsis
26679 -symbol-info-symbol @var{addr}
26682 Describe what symbol is at location @var{addr}.
26684 @subsubheading @value{GDBN} Command
26686 The corresponding @value{GDBN} command is @samp{info symbol}.
26688 @subsubheading Example
26692 @subheading The @code{-symbol-list-functions} Command
26693 @findex -symbol-list-functions
26695 @subsubheading Synopsis
26698 -symbol-list-functions
26701 List the functions in the executable.
26703 @subsubheading @value{GDBN} Command
26705 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
26706 @samp{gdb_search} in @code{gdbtk}.
26708 @subsubheading Example
26713 @subheading The @code{-symbol-list-lines} Command
26714 @findex -symbol-list-lines
26716 @subsubheading Synopsis
26719 -symbol-list-lines @var{filename}
26722 Print the list of lines that contain code and their associated program
26723 addresses for the given source filename. The entries are sorted in
26724 ascending PC order.
26726 @subsubheading @value{GDBN} Command
26728 There is no corresponding @value{GDBN} command.
26730 @subsubheading Example
26733 -symbol-list-lines basics.c
26734 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
26740 @subheading The @code{-symbol-list-types} Command
26741 @findex -symbol-list-types
26743 @subsubheading Synopsis
26749 List all the type names.
26751 @subsubheading @value{GDBN} Command
26753 The corresponding commands are @samp{info types} in @value{GDBN},
26754 @samp{gdb_search} in @code{gdbtk}.
26756 @subsubheading Example
26760 @subheading The @code{-symbol-list-variables} Command
26761 @findex -symbol-list-variables
26763 @subsubheading Synopsis
26766 -symbol-list-variables
26769 List all the global and static variable names.
26771 @subsubheading @value{GDBN} Command
26773 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
26775 @subsubheading Example
26779 @subheading The @code{-symbol-locate} Command
26780 @findex -symbol-locate
26782 @subsubheading Synopsis
26788 @subsubheading @value{GDBN} Command
26790 @samp{gdb_loc} in @code{gdbtk}.
26792 @subsubheading Example
26796 @subheading The @code{-symbol-type} Command
26797 @findex -symbol-type
26799 @subsubheading Synopsis
26802 -symbol-type @var{variable}
26805 Show type of @var{variable}.
26807 @subsubheading @value{GDBN} Command
26809 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
26810 @samp{gdb_obj_variable}.
26812 @subsubheading Example
26817 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26818 @node GDB/MI File Commands
26819 @section @sc{gdb/mi} File Commands
26821 This section describes the GDB/MI commands to specify executable file names
26822 and to read in and obtain symbol table information.
26824 @subheading The @code{-file-exec-and-symbols} Command
26825 @findex -file-exec-and-symbols
26827 @subsubheading Synopsis
26830 -file-exec-and-symbols @var{file}
26833 Specify the executable file to be debugged. This file is the one from
26834 which the symbol table is also read. If no file is specified, the
26835 command clears the executable and symbol information. If breakpoints
26836 are set when using this command with no arguments, @value{GDBN} will produce
26837 error messages. Otherwise, no output is produced, except a completion
26840 @subsubheading @value{GDBN} Command
26842 The corresponding @value{GDBN} command is @samp{file}.
26844 @subsubheading Example
26848 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26854 @subheading The @code{-file-exec-file} Command
26855 @findex -file-exec-file
26857 @subsubheading Synopsis
26860 -file-exec-file @var{file}
26863 Specify the executable file to be debugged. Unlike
26864 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
26865 from this file. If used without argument, @value{GDBN} clears the information
26866 about the executable file. No output is produced, except a completion
26869 @subsubheading @value{GDBN} Command
26871 The corresponding @value{GDBN} command is @samp{exec-file}.
26873 @subsubheading Example
26877 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26884 @subheading The @code{-file-list-exec-sections} Command
26885 @findex -file-list-exec-sections
26887 @subsubheading Synopsis
26890 -file-list-exec-sections
26893 List the sections of the current executable file.
26895 @subsubheading @value{GDBN} Command
26897 The @value{GDBN} command @samp{info file} shows, among the rest, the same
26898 information as this command. @code{gdbtk} has a corresponding command
26899 @samp{gdb_load_info}.
26901 @subsubheading Example
26906 @subheading The @code{-file-list-exec-source-file} Command
26907 @findex -file-list-exec-source-file
26909 @subsubheading Synopsis
26912 -file-list-exec-source-file
26915 List the line number, the current source file, and the absolute path
26916 to the current source file for the current executable. The macro
26917 information field has a value of @samp{1} or @samp{0} depending on
26918 whether or not the file includes preprocessor macro information.
26920 @subsubheading @value{GDBN} Command
26922 The @value{GDBN} equivalent is @samp{info source}
26924 @subsubheading Example
26928 123-file-list-exec-source-file
26929 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
26934 @subheading The @code{-file-list-exec-source-files} Command
26935 @findex -file-list-exec-source-files
26937 @subsubheading Synopsis
26940 -file-list-exec-source-files
26943 List the source files for the current executable.
26945 It will always output the filename, but only when @value{GDBN} can find
26946 the absolute file name of a source file, will it output the fullname.
26948 @subsubheading @value{GDBN} Command
26950 The @value{GDBN} equivalent is @samp{info sources}.
26951 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
26953 @subsubheading Example
26956 -file-list-exec-source-files
26958 @{file=foo.c,fullname=/home/foo.c@},
26959 @{file=/home/bar.c,fullname=/home/bar.c@},
26960 @{file=gdb_could_not_find_fullpath.c@}]
26965 @subheading The @code{-file-list-shared-libraries} Command
26966 @findex -file-list-shared-libraries
26968 @subsubheading Synopsis
26971 -file-list-shared-libraries
26974 List the shared libraries in the program.
26976 @subsubheading @value{GDBN} Command
26978 The corresponding @value{GDBN} command is @samp{info shared}.
26980 @subsubheading Example
26984 @subheading The @code{-file-list-symbol-files} Command
26985 @findex -file-list-symbol-files
26987 @subsubheading Synopsis
26990 -file-list-symbol-files
26995 @subsubheading @value{GDBN} Command
26997 The corresponding @value{GDBN} command is @samp{info file} (part of it).
26999 @subsubheading Example
27004 @subheading The @code{-file-symbol-file} Command
27005 @findex -file-symbol-file
27007 @subsubheading Synopsis
27010 -file-symbol-file @var{file}
27013 Read symbol table info from the specified @var{file} argument. When
27014 used without arguments, clears @value{GDBN}'s symbol table info. No output is
27015 produced, except for a completion notification.
27017 @subsubheading @value{GDBN} Command
27019 The corresponding @value{GDBN} command is @samp{symbol-file}.
27021 @subsubheading Example
27025 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27031 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27032 @node GDB/MI Memory Overlay Commands
27033 @section @sc{gdb/mi} Memory Overlay Commands
27035 The memory overlay commands are not implemented.
27037 @c @subheading -overlay-auto
27039 @c @subheading -overlay-list-mapping-state
27041 @c @subheading -overlay-list-overlays
27043 @c @subheading -overlay-map
27045 @c @subheading -overlay-off
27047 @c @subheading -overlay-on
27049 @c @subheading -overlay-unmap
27051 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27052 @node GDB/MI Signal Handling Commands
27053 @section @sc{gdb/mi} Signal Handling Commands
27055 Signal handling commands are not implemented.
27057 @c @subheading -signal-handle
27059 @c @subheading -signal-list-handle-actions
27061 @c @subheading -signal-list-signal-types
27065 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27066 @node GDB/MI Target Manipulation
27067 @section @sc{gdb/mi} Target Manipulation Commands
27070 @subheading The @code{-target-attach} Command
27071 @findex -target-attach
27073 @subsubheading Synopsis
27076 -target-attach @var{pid} | @var{gid} | @var{file}
27079 Attach to a process @var{pid} or a file @var{file} outside of
27080 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
27081 group, the id previously returned by
27082 @samp{-list-thread-groups --available} must be used.
27084 @subsubheading @value{GDBN} Command
27086 The corresponding @value{GDBN} command is @samp{attach}.
27088 @subsubheading Example
27092 =thread-created,id="1"
27093 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
27099 @subheading The @code{-target-compare-sections} Command
27100 @findex -target-compare-sections
27102 @subsubheading Synopsis
27105 -target-compare-sections [ @var{section} ]
27108 Compare data of section @var{section} on target to the exec file.
27109 Without the argument, all sections are compared.
27111 @subsubheading @value{GDBN} Command
27113 The @value{GDBN} equivalent is @samp{compare-sections}.
27115 @subsubheading Example
27120 @subheading The @code{-target-detach} Command
27121 @findex -target-detach
27123 @subsubheading Synopsis
27126 -target-detach [ @var{pid} | @var{gid} ]
27129 Detach from the remote target which normally resumes its execution.
27130 If either @var{pid} or @var{gid} is specified, detaches from either
27131 the specified process, or specified thread group. There's no output.
27133 @subsubheading @value{GDBN} Command
27135 The corresponding @value{GDBN} command is @samp{detach}.
27137 @subsubheading Example
27147 @subheading The @code{-target-disconnect} Command
27148 @findex -target-disconnect
27150 @subsubheading Synopsis
27156 Disconnect from the remote target. There's no output and the target is
27157 generally not resumed.
27159 @subsubheading @value{GDBN} Command
27161 The corresponding @value{GDBN} command is @samp{disconnect}.
27163 @subsubheading Example
27173 @subheading The @code{-target-download} Command
27174 @findex -target-download
27176 @subsubheading Synopsis
27182 Loads the executable onto the remote target.
27183 It prints out an update message every half second, which includes the fields:
27187 The name of the section.
27189 The size of what has been sent so far for that section.
27191 The size of the section.
27193 The total size of what was sent so far (the current and the previous sections).
27195 The size of the overall executable to download.
27199 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
27200 @sc{gdb/mi} Output Syntax}).
27202 In addition, it prints the name and size of the sections, as they are
27203 downloaded. These messages include the following fields:
27207 The name of the section.
27209 The size of the section.
27211 The size of the overall executable to download.
27215 At the end, a summary is printed.
27217 @subsubheading @value{GDBN} Command
27219 The corresponding @value{GDBN} command is @samp{load}.
27221 @subsubheading Example
27223 Note: each status message appears on a single line. Here the messages
27224 have been broken down so that they can fit onto a page.
27229 +download,@{section=".text",section-size="6668",total-size="9880"@}
27230 +download,@{section=".text",section-sent="512",section-size="6668",
27231 total-sent="512",total-size="9880"@}
27232 +download,@{section=".text",section-sent="1024",section-size="6668",
27233 total-sent="1024",total-size="9880"@}
27234 +download,@{section=".text",section-sent="1536",section-size="6668",
27235 total-sent="1536",total-size="9880"@}
27236 +download,@{section=".text",section-sent="2048",section-size="6668",
27237 total-sent="2048",total-size="9880"@}
27238 +download,@{section=".text",section-sent="2560",section-size="6668",
27239 total-sent="2560",total-size="9880"@}
27240 +download,@{section=".text",section-sent="3072",section-size="6668",
27241 total-sent="3072",total-size="9880"@}
27242 +download,@{section=".text",section-sent="3584",section-size="6668",
27243 total-sent="3584",total-size="9880"@}
27244 +download,@{section=".text",section-sent="4096",section-size="6668",
27245 total-sent="4096",total-size="9880"@}
27246 +download,@{section=".text",section-sent="4608",section-size="6668",
27247 total-sent="4608",total-size="9880"@}
27248 +download,@{section=".text",section-sent="5120",section-size="6668",
27249 total-sent="5120",total-size="9880"@}
27250 +download,@{section=".text",section-sent="5632",section-size="6668",
27251 total-sent="5632",total-size="9880"@}
27252 +download,@{section=".text",section-sent="6144",section-size="6668",
27253 total-sent="6144",total-size="9880"@}
27254 +download,@{section=".text",section-sent="6656",section-size="6668",
27255 total-sent="6656",total-size="9880"@}
27256 +download,@{section=".init",section-size="28",total-size="9880"@}
27257 +download,@{section=".fini",section-size="28",total-size="9880"@}
27258 +download,@{section=".data",section-size="3156",total-size="9880"@}
27259 +download,@{section=".data",section-sent="512",section-size="3156",
27260 total-sent="7236",total-size="9880"@}
27261 +download,@{section=".data",section-sent="1024",section-size="3156",
27262 total-sent="7748",total-size="9880"@}
27263 +download,@{section=".data",section-sent="1536",section-size="3156",
27264 total-sent="8260",total-size="9880"@}
27265 +download,@{section=".data",section-sent="2048",section-size="3156",
27266 total-sent="8772",total-size="9880"@}
27267 +download,@{section=".data",section-sent="2560",section-size="3156",
27268 total-sent="9284",total-size="9880"@}
27269 +download,@{section=".data",section-sent="3072",section-size="3156",
27270 total-sent="9796",total-size="9880"@}
27271 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
27278 @subheading The @code{-target-exec-status} Command
27279 @findex -target-exec-status
27281 @subsubheading Synopsis
27284 -target-exec-status
27287 Provide information on the state of the target (whether it is running or
27288 not, for instance).
27290 @subsubheading @value{GDBN} Command
27292 There's no equivalent @value{GDBN} command.
27294 @subsubheading Example
27298 @subheading The @code{-target-list-available-targets} Command
27299 @findex -target-list-available-targets
27301 @subsubheading Synopsis
27304 -target-list-available-targets
27307 List the possible targets to connect to.
27309 @subsubheading @value{GDBN} Command
27311 The corresponding @value{GDBN} command is @samp{help target}.
27313 @subsubheading Example
27317 @subheading The @code{-target-list-current-targets} Command
27318 @findex -target-list-current-targets
27320 @subsubheading Synopsis
27323 -target-list-current-targets
27326 Describe the current target.
27328 @subsubheading @value{GDBN} Command
27330 The corresponding information is printed by @samp{info file} (among
27333 @subsubheading Example
27337 @subheading The @code{-target-list-parameters} Command
27338 @findex -target-list-parameters
27340 @subsubheading Synopsis
27343 -target-list-parameters
27349 @subsubheading @value{GDBN} Command
27353 @subsubheading Example
27357 @subheading The @code{-target-select} Command
27358 @findex -target-select
27360 @subsubheading Synopsis
27363 -target-select @var{type} @var{parameters @dots{}}
27366 Connect @value{GDBN} to the remote target. This command takes two args:
27370 The type of target, for instance @samp{remote}, etc.
27371 @item @var{parameters}
27372 Device names, host names and the like. @xref{Target Commands, ,
27373 Commands for Managing Targets}, for more details.
27376 The output is a connection notification, followed by the address at
27377 which the target program is, in the following form:
27380 ^connected,addr="@var{address}",func="@var{function name}",
27381 args=[@var{arg list}]
27384 @subsubheading @value{GDBN} Command
27386 The corresponding @value{GDBN} command is @samp{target}.
27388 @subsubheading Example
27392 -target-select remote /dev/ttya
27393 ^connected,addr="0xfe00a300",func="??",args=[]
27397 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27398 @node GDB/MI File Transfer Commands
27399 @section @sc{gdb/mi} File Transfer Commands
27402 @subheading The @code{-target-file-put} Command
27403 @findex -target-file-put
27405 @subsubheading Synopsis
27408 -target-file-put @var{hostfile} @var{targetfile}
27411 Copy file @var{hostfile} from the host system (the machine running
27412 @value{GDBN}) to @var{targetfile} on the target system.
27414 @subsubheading @value{GDBN} Command
27416 The corresponding @value{GDBN} command is @samp{remote put}.
27418 @subsubheading Example
27422 -target-file-put localfile remotefile
27428 @subheading The @code{-target-file-get} Command
27429 @findex -target-file-get
27431 @subsubheading Synopsis
27434 -target-file-get @var{targetfile} @var{hostfile}
27437 Copy file @var{targetfile} from the target system to @var{hostfile}
27438 on the host system.
27440 @subsubheading @value{GDBN} Command
27442 The corresponding @value{GDBN} command is @samp{remote get}.
27444 @subsubheading Example
27448 -target-file-get remotefile localfile
27454 @subheading The @code{-target-file-delete} Command
27455 @findex -target-file-delete
27457 @subsubheading Synopsis
27460 -target-file-delete @var{targetfile}
27463 Delete @var{targetfile} from the target system.
27465 @subsubheading @value{GDBN} Command
27467 The corresponding @value{GDBN} command is @samp{remote delete}.
27469 @subsubheading Example
27473 -target-file-delete remotefile
27479 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27480 @node GDB/MI Miscellaneous Commands
27481 @section Miscellaneous @sc{gdb/mi} Commands
27483 @c @subheading -gdb-complete
27485 @subheading The @code{-gdb-exit} Command
27488 @subsubheading Synopsis
27494 Exit @value{GDBN} immediately.
27496 @subsubheading @value{GDBN} Command
27498 Approximately corresponds to @samp{quit}.
27500 @subsubheading Example
27510 @subheading The @code{-exec-abort} Command
27511 @findex -exec-abort
27513 @subsubheading Synopsis
27519 Kill the inferior running program.
27521 @subsubheading @value{GDBN} Command
27523 The corresponding @value{GDBN} command is @samp{kill}.
27525 @subsubheading Example
27530 @subheading The @code{-gdb-set} Command
27533 @subsubheading Synopsis
27539 Set an internal @value{GDBN} variable.
27540 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
27542 @subsubheading @value{GDBN} Command
27544 The corresponding @value{GDBN} command is @samp{set}.
27546 @subsubheading Example
27556 @subheading The @code{-gdb-show} Command
27559 @subsubheading Synopsis
27565 Show the current value of a @value{GDBN} variable.
27567 @subsubheading @value{GDBN} Command
27569 The corresponding @value{GDBN} command is @samp{show}.
27571 @subsubheading Example
27580 @c @subheading -gdb-source
27583 @subheading The @code{-gdb-version} Command
27584 @findex -gdb-version
27586 @subsubheading Synopsis
27592 Show version information for @value{GDBN}. Used mostly in testing.
27594 @subsubheading @value{GDBN} Command
27596 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
27597 default shows this information when you start an interactive session.
27599 @subsubheading Example
27601 @c This example modifies the actual output from GDB to avoid overfull
27607 ~Copyright 2000 Free Software Foundation, Inc.
27608 ~GDB is free software, covered by the GNU General Public License, and
27609 ~you are welcome to change it and/or distribute copies of it under
27610 ~ certain conditions.
27611 ~Type "show copying" to see the conditions.
27612 ~There is absolutely no warranty for GDB. Type "show warranty" for
27614 ~This GDB was configured as
27615 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
27620 @subheading The @code{-list-features} Command
27621 @findex -list-features
27623 Returns a list of particular features of the MI protocol that
27624 this version of gdb implements. A feature can be a command,
27625 or a new field in an output of some command, or even an
27626 important bugfix. While a frontend can sometimes detect presence
27627 of a feature at runtime, it is easier to perform detection at debugger
27630 The command returns a list of strings, with each string naming an
27631 available feature. Each returned string is just a name, it does not
27632 have any internal structure. The list of possible feature names
27638 (gdb) -list-features
27639 ^done,result=["feature1","feature2"]
27642 The current list of features is:
27645 @item frozen-varobjs
27646 Indicates presence of the @code{-var-set-frozen} command, as well
27647 as possible presense of the @code{frozen} field in the output
27648 of @code{-varobj-create}.
27649 @item pending-breakpoints
27650 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
27652 Indicates presence of Python scripting support, Python-based
27653 pretty-printing commands, and possible presence of the
27654 @samp{display_hint} field in the output of @code{-var-list-children}
27656 Indicates presence of the @code{-thread-info} command.
27660 @subheading The @code{-list-target-features} Command
27661 @findex -list-target-features
27663 Returns a list of particular features that are supported by the
27664 target. Those features affect the permitted MI commands, but
27665 unlike the features reported by the @code{-list-features} command, the
27666 features depend on which target GDB is using at the moment. Whenever
27667 a target can change, due to commands such as @code{-target-select},
27668 @code{-target-attach} or @code{-exec-run}, the list of target features
27669 may change, and the frontend should obtain it again.
27673 (gdb) -list-features
27674 ^done,result=["async"]
27677 The current list of features is:
27681 Indicates that the target is capable of asynchronous command
27682 execution, which means that @value{GDBN} will accept further commands
27683 while the target is running.
27687 @subheading The @code{-list-thread-groups} Command
27688 @findex -list-thread-groups
27690 @subheading Synopsis
27693 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
27696 Lists thread groups (@pxref{Thread groups}). When a single thread
27697 group is passed as the argument, lists the children of that group.
27698 When several thread group are passed, lists information about those
27699 thread groups. Without any parameters, lists information about all
27700 top-level thread groups.
27702 Normally, thread groups that are being debugged are reported.
27703 With the @samp{--available} option, @value{GDBN} reports thread groups
27704 available on the target.
27706 The output of this command may have either a @samp{threads} result or
27707 a @samp{groups} result. The @samp{thread} result has a list of tuples
27708 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
27709 Information}). The @samp{groups} result has a list of tuples as value,
27710 each tuple describing a thread group. If top-level groups are
27711 requested (that is, no parameter is passed), or when several groups
27712 are passed, the output always has a @samp{groups} result. The format
27713 of the @samp{group} result is described below.
27715 To reduce the number of roundtrips it's possible to list thread groups
27716 together with their children, by passing the @samp{--recurse} option
27717 and the recursion depth. Presently, only recursion depth of 1 is
27718 permitted. If this option is present, then every reported thread group
27719 will also include its children, either as @samp{group} or
27720 @samp{threads} field.
27722 In general, any combination of option and parameters is permitted, with
27723 the following caveats:
27727 When a single thread group is passed, the output will typically
27728 be the @samp{threads} result. Because threads may not contain
27729 anything, the @samp{recurse} option will be ignored.
27732 When the @samp{--available} option is passed, limited information may
27733 be available. In particular, the list of threads of a process might
27734 be inaccessible. Further, specifying specific thread groups might
27735 not give any performance advantage over listing all thread groups.
27736 The frontend should assume that @samp{-list-thread-groups --available}
27737 is always an expensive operation and cache the results.
27741 The @samp{groups} result is a list of tuples, where each tuple may
27742 have the following fields:
27746 Identifier of the thread group. This field is always present.
27747 The identifier is an opaque string; frontends should not try to
27748 convert it to an integer, even though it might look like one.
27751 The type of the thread group. At present, only @samp{process} is a
27755 The target-specific process identifier. This field is only present
27756 for thread groups of type @samp{process} and only if the process exists.
27759 The number of children this thread group has. This field may be
27760 absent for an available thread group.
27763 This field has a list of tuples as value, each tuple describing a
27764 thread. It may be present if the @samp{--recurse} option is
27765 specified, and it's actually possible to obtain the threads.
27768 This field is a list of integers, each identifying a core that one
27769 thread of the group is running on. This field may be absent if
27770 such information is not available.
27773 The name of the executable file that corresponds to this thread group.
27774 The field is only present for thread groups of type @samp{process},
27775 and only if there is a corresponding executable file.
27779 @subheading Example
27783 -list-thread-groups
27784 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
27785 -list-thread-groups 17
27786 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27787 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
27788 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27789 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
27790 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
27791 -list-thread-groups --available
27792 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
27793 -list-thread-groups --available --recurse 1
27794 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
27795 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
27796 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
27797 -list-thread-groups --available --recurse 1 17 18
27798 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
27799 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
27800 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
27804 @subheading The @code{-add-inferior} Command
27805 @findex -add-inferior
27807 @subheading Synopsis
27813 Creates a new inferior (@pxref{Inferiors and Programs}). The created
27814 inferior is not associated with any executable. Such association may
27815 be established with the @samp{-file-exec-and-symbols} command
27816 (@pxref{GDB/MI File Commands}). The command response has a single
27817 field, @samp{thread-group}, whose value is the identifier of the
27818 thread group corresponding to the new inferior.
27820 @subheading Example
27825 ^done,thread-group="i3"
27828 @subheading The @code{-interpreter-exec} Command
27829 @findex -interpreter-exec
27831 @subheading Synopsis
27834 -interpreter-exec @var{interpreter} @var{command}
27836 @anchor{-interpreter-exec}
27838 Execute the specified @var{command} in the given @var{interpreter}.
27840 @subheading @value{GDBN} Command
27842 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
27844 @subheading Example
27848 -interpreter-exec console "break main"
27849 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
27850 &"During symbol reading, bad structure-type format.\n"
27851 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
27856 @subheading The @code{-inferior-tty-set} Command
27857 @findex -inferior-tty-set
27859 @subheading Synopsis
27862 -inferior-tty-set /dev/pts/1
27865 Set terminal for future runs of the program being debugged.
27867 @subheading @value{GDBN} Command
27869 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
27871 @subheading Example
27875 -inferior-tty-set /dev/pts/1
27880 @subheading The @code{-inferior-tty-show} Command
27881 @findex -inferior-tty-show
27883 @subheading Synopsis
27889 Show terminal for future runs of program being debugged.
27891 @subheading @value{GDBN} Command
27893 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
27895 @subheading Example
27899 -inferior-tty-set /dev/pts/1
27903 ^done,inferior_tty_terminal="/dev/pts/1"
27907 @subheading The @code{-enable-timings} Command
27908 @findex -enable-timings
27910 @subheading Synopsis
27913 -enable-timings [yes | no]
27916 Toggle the printing of the wallclock, user and system times for an MI
27917 command as a field in its output. This command is to help frontend
27918 developers optimize the performance of their code. No argument is
27919 equivalent to @samp{yes}.
27921 @subheading @value{GDBN} Command
27925 @subheading Example
27933 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27934 addr="0x080484ed",func="main",file="myprog.c",
27935 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
27936 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
27944 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27945 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
27946 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
27947 fullname="/home/nickrob/myprog.c",line="73"@}
27952 @chapter @value{GDBN} Annotations
27954 This chapter describes annotations in @value{GDBN}. Annotations were
27955 designed to interface @value{GDBN} to graphical user interfaces or other
27956 similar programs which want to interact with @value{GDBN} at a
27957 relatively high level.
27959 The annotation mechanism has largely been superseded by @sc{gdb/mi}
27963 This is Edition @value{EDITION}, @value{DATE}.
27967 * Annotations Overview:: What annotations are; the general syntax.
27968 * Server Prefix:: Issuing a command without affecting user state.
27969 * Prompting:: Annotations marking @value{GDBN}'s need for input.
27970 * Errors:: Annotations for error messages.
27971 * Invalidation:: Some annotations describe things now invalid.
27972 * Annotations for Running::
27973 Whether the program is running, how it stopped, etc.
27974 * Source Annotations:: Annotations describing source code.
27977 @node Annotations Overview
27978 @section What is an Annotation?
27979 @cindex annotations
27981 Annotations start with a newline character, two @samp{control-z}
27982 characters, and the name of the annotation. If there is no additional
27983 information associated with this annotation, the name of the annotation
27984 is followed immediately by a newline. If there is additional
27985 information, the name of the annotation is followed by a space, the
27986 additional information, and a newline. The additional information
27987 cannot contain newline characters.
27989 Any output not beginning with a newline and two @samp{control-z}
27990 characters denotes literal output from @value{GDBN}. Currently there is
27991 no need for @value{GDBN} to output a newline followed by two
27992 @samp{control-z} characters, but if there was such a need, the
27993 annotations could be extended with an @samp{escape} annotation which
27994 means those three characters as output.
27996 The annotation @var{level}, which is specified using the
27997 @option{--annotate} command line option (@pxref{Mode Options}), controls
27998 how much information @value{GDBN} prints together with its prompt,
27999 values of expressions, source lines, and other types of output. Level 0
28000 is for no annotations, level 1 is for use when @value{GDBN} is run as a
28001 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
28002 for programs that control @value{GDBN}, and level 2 annotations have
28003 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
28004 Interface, annotate, GDB's Obsolete Annotations}).
28007 @kindex set annotate
28008 @item set annotate @var{level}
28009 The @value{GDBN} command @code{set annotate} sets the level of
28010 annotations to the specified @var{level}.
28012 @item show annotate
28013 @kindex show annotate
28014 Show the current annotation level.
28017 This chapter describes level 3 annotations.
28019 A simple example of starting up @value{GDBN} with annotations is:
28022 $ @kbd{gdb --annotate=3}
28024 Copyright 2003 Free Software Foundation, Inc.
28025 GDB is free software, covered by the GNU General Public License,
28026 and you are welcome to change it and/or distribute copies of it
28027 under certain conditions.
28028 Type "show copying" to see the conditions.
28029 There is absolutely no warranty for GDB. Type "show warranty"
28031 This GDB was configured as "i386-pc-linux-gnu"
28042 Here @samp{quit} is input to @value{GDBN}; the rest is output from
28043 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
28044 denotes a @samp{control-z} character) are annotations; the rest is
28045 output from @value{GDBN}.
28047 @node Server Prefix
28048 @section The Server Prefix
28049 @cindex server prefix
28051 If you prefix a command with @samp{server } then it will not affect
28052 the command history, nor will it affect @value{GDBN}'s notion of which
28053 command to repeat if @key{RET} is pressed on a line by itself. This
28054 means that commands can be run behind a user's back by a front-end in
28055 a transparent manner.
28057 The @code{server } prefix does not affect the recording of values into
28058 the value history; to print a value without recording it into the
28059 value history, use the @code{output} command instead of the
28060 @code{print} command.
28062 Using this prefix also disables confirmation requests
28063 (@pxref{confirmation requests}).
28066 @section Annotation for @value{GDBN} Input
28068 @cindex annotations for prompts
28069 When @value{GDBN} prompts for input, it annotates this fact so it is possible
28070 to know when to send output, when the output from a given command is
28073 Different kinds of input each have a different @dfn{input type}. Each
28074 input type has three annotations: a @code{pre-} annotation, which
28075 denotes the beginning of any prompt which is being output, a plain
28076 annotation, which denotes the end of the prompt, and then a @code{post-}
28077 annotation which denotes the end of any echo which may (or may not) be
28078 associated with the input. For example, the @code{prompt} input type
28079 features the following annotations:
28087 The input types are
28090 @findex pre-prompt annotation
28091 @findex prompt annotation
28092 @findex post-prompt annotation
28094 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
28096 @findex pre-commands annotation
28097 @findex commands annotation
28098 @findex post-commands annotation
28100 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
28101 command. The annotations are repeated for each command which is input.
28103 @findex pre-overload-choice annotation
28104 @findex overload-choice annotation
28105 @findex post-overload-choice annotation
28106 @item overload-choice
28107 When @value{GDBN} wants the user to select between various overloaded functions.
28109 @findex pre-query annotation
28110 @findex query annotation
28111 @findex post-query annotation
28113 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
28115 @findex pre-prompt-for-continue annotation
28116 @findex prompt-for-continue annotation
28117 @findex post-prompt-for-continue annotation
28118 @item prompt-for-continue
28119 When @value{GDBN} is asking the user to press return to continue. Note: Don't
28120 expect this to work well; instead use @code{set height 0} to disable
28121 prompting. This is because the counting of lines is buggy in the
28122 presence of annotations.
28127 @cindex annotations for errors, warnings and interrupts
28129 @findex quit annotation
28134 This annotation occurs right before @value{GDBN} responds to an interrupt.
28136 @findex error annotation
28141 This annotation occurs right before @value{GDBN} responds to an error.
28143 Quit and error annotations indicate that any annotations which @value{GDBN} was
28144 in the middle of may end abruptly. For example, if a
28145 @code{value-history-begin} annotation is followed by a @code{error}, one
28146 cannot expect to receive the matching @code{value-history-end}. One
28147 cannot expect not to receive it either, however; an error annotation
28148 does not necessarily mean that @value{GDBN} is immediately returning all the way
28151 @findex error-begin annotation
28152 A quit or error annotation may be preceded by
28158 Any output between that and the quit or error annotation is the error
28161 Warning messages are not yet annotated.
28162 @c If we want to change that, need to fix warning(), type_error(),
28163 @c range_error(), and possibly other places.
28166 @section Invalidation Notices
28168 @cindex annotations for invalidation messages
28169 The following annotations say that certain pieces of state may have
28173 @findex frames-invalid annotation
28174 @item ^Z^Zframes-invalid
28176 The frames (for example, output from the @code{backtrace} command) may
28179 @findex breakpoints-invalid annotation
28180 @item ^Z^Zbreakpoints-invalid
28182 The breakpoints may have changed. For example, the user just added or
28183 deleted a breakpoint.
28186 @node Annotations for Running
28187 @section Running the Program
28188 @cindex annotations for running programs
28190 @findex starting annotation
28191 @findex stopping annotation
28192 When the program starts executing due to a @value{GDBN} command such as
28193 @code{step} or @code{continue},
28199 is output. When the program stops,
28205 is output. Before the @code{stopped} annotation, a variety of
28206 annotations describe how the program stopped.
28209 @findex exited annotation
28210 @item ^Z^Zexited @var{exit-status}
28211 The program exited, and @var{exit-status} is the exit status (zero for
28212 successful exit, otherwise nonzero).
28214 @findex signalled annotation
28215 @findex signal-name annotation
28216 @findex signal-name-end annotation
28217 @findex signal-string annotation
28218 @findex signal-string-end annotation
28219 @item ^Z^Zsignalled
28220 The program exited with a signal. After the @code{^Z^Zsignalled}, the
28221 annotation continues:
28227 ^Z^Zsignal-name-end
28231 ^Z^Zsignal-string-end
28236 where @var{name} is the name of the signal, such as @code{SIGILL} or
28237 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
28238 as @code{Illegal Instruction} or @code{Segmentation fault}.
28239 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
28240 user's benefit and have no particular format.
28242 @findex signal annotation
28244 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
28245 just saying that the program received the signal, not that it was
28246 terminated with it.
28248 @findex breakpoint annotation
28249 @item ^Z^Zbreakpoint @var{number}
28250 The program hit breakpoint number @var{number}.
28252 @findex watchpoint annotation
28253 @item ^Z^Zwatchpoint @var{number}
28254 The program hit watchpoint number @var{number}.
28257 @node Source Annotations
28258 @section Displaying Source
28259 @cindex annotations for source display
28261 @findex source annotation
28262 The following annotation is used instead of displaying source code:
28265 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
28268 where @var{filename} is an absolute file name indicating which source
28269 file, @var{line} is the line number within that file (where 1 is the
28270 first line in the file), @var{character} is the character position
28271 within the file (where 0 is the first character in the file) (for most
28272 debug formats this will necessarily point to the beginning of a line),
28273 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
28274 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
28275 @var{addr} is the address in the target program associated with the
28276 source which is being displayed. @var{addr} is in the form @samp{0x}
28277 followed by one or more lowercase hex digits (note that this does not
28278 depend on the language).
28280 @node JIT Interface
28281 @chapter JIT Compilation Interface
28282 @cindex just-in-time compilation
28283 @cindex JIT compilation interface
28285 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
28286 interface. A JIT compiler is a program or library that generates native
28287 executable code at runtime and executes it, usually in order to achieve good
28288 performance while maintaining platform independence.
28290 Programs that use JIT compilation are normally difficult to debug because
28291 portions of their code are generated at runtime, instead of being loaded from
28292 object files, which is where @value{GDBN} normally finds the program's symbols
28293 and debug information. In order to debug programs that use JIT compilation,
28294 @value{GDBN} has an interface that allows the program to register in-memory
28295 symbol files with @value{GDBN} at runtime.
28297 If you are using @value{GDBN} to debug a program that uses this interface, then
28298 it should work transparently so long as you have not stripped the binary. If
28299 you are developing a JIT compiler, then the interface is documented in the rest
28300 of this chapter. At this time, the only known client of this interface is the
28303 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
28304 JIT compiler communicates with @value{GDBN} by writing data into a global
28305 variable and calling a fuction at a well-known symbol. When @value{GDBN}
28306 attaches, it reads a linked list of symbol files from the global variable to
28307 find existing code, and puts a breakpoint in the function so that it can find
28308 out about additional code.
28311 * Declarations:: Relevant C struct declarations
28312 * Registering Code:: Steps to register code
28313 * Unregistering Code:: Steps to unregister code
28317 @section JIT Declarations
28319 These are the relevant struct declarations that a C program should include to
28320 implement the interface:
28330 struct jit_code_entry
28332 struct jit_code_entry *next_entry;
28333 struct jit_code_entry *prev_entry;
28334 const char *symfile_addr;
28335 uint64_t symfile_size;
28338 struct jit_descriptor
28341 /* This type should be jit_actions_t, but we use uint32_t
28342 to be explicit about the bitwidth. */
28343 uint32_t action_flag;
28344 struct jit_code_entry *relevant_entry;
28345 struct jit_code_entry *first_entry;
28348 /* GDB puts a breakpoint in this function. */
28349 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
28351 /* Make sure to specify the version statically, because the
28352 debugger may check the version before we can set it. */
28353 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
28356 If the JIT is multi-threaded, then it is important that the JIT synchronize any
28357 modifications to this global data properly, which can easily be done by putting
28358 a global mutex around modifications to these structures.
28360 @node Registering Code
28361 @section Registering Code
28363 To register code with @value{GDBN}, the JIT should follow this protocol:
28367 Generate an object file in memory with symbols and other desired debug
28368 information. The file must include the virtual addresses of the sections.
28371 Create a code entry for the file, which gives the start and size of the symbol
28375 Add it to the linked list in the JIT descriptor.
28378 Point the relevant_entry field of the descriptor at the entry.
28381 Set @code{action_flag} to @code{JIT_REGISTER} and call
28382 @code{__jit_debug_register_code}.
28385 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
28386 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
28387 new code. However, the linked list must still be maintained in order to allow
28388 @value{GDBN} to attach to a running process and still find the symbol files.
28390 @node Unregistering Code
28391 @section Unregistering Code
28393 If code is freed, then the JIT should use the following protocol:
28397 Remove the code entry corresponding to the code from the linked list.
28400 Point the @code{relevant_entry} field of the descriptor at the code entry.
28403 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
28404 @code{__jit_debug_register_code}.
28407 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
28408 and the JIT will leak the memory used for the associated symbol files.
28411 @chapter Reporting Bugs in @value{GDBN}
28412 @cindex bugs in @value{GDBN}
28413 @cindex reporting bugs in @value{GDBN}
28415 Your bug reports play an essential role in making @value{GDBN} reliable.
28417 Reporting a bug may help you by bringing a solution to your problem, or it
28418 may not. But in any case the principal function of a bug report is to help
28419 the entire community by making the next version of @value{GDBN} work better. Bug
28420 reports are your contribution to the maintenance of @value{GDBN}.
28422 In order for a bug report to serve its purpose, you must include the
28423 information that enables us to fix the bug.
28426 * Bug Criteria:: Have you found a bug?
28427 * Bug Reporting:: How to report bugs
28431 @section Have You Found a Bug?
28432 @cindex bug criteria
28434 If you are not sure whether you have found a bug, here are some guidelines:
28437 @cindex fatal signal
28438 @cindex debugger crash
28439 @cindex crash of debugger
28441 If the debugger gets a fatal signal, for any input whatever, that is a
28442 @value{GDBN} bug. Reliable debuggers never crash.
28444 @cindex error on valid input
28446 If @value{GDBN} produces an error message for valid input, that is a
28447 bug. (Note that if you're cross debugging, the problem may also be
28448 somewhere in the connection to the target.)
28450 @cindex invalid input
28452 If @value{GDBN} does not produce an error message for invalid input,
28453 that is a bug. However, you should note that your idea of
28454 ``invalid input'' might be our idea of ``an extension'' or ``support
28455 for traditional practice''.
28458 If you are an experienced user of debugging tools, your suggestions
28459 for improvement of @value{GDBN} are welcome in any case.
28462 @node Bug Reporting
28463 @section How to Report Bugs
28464 @cindex bug reports
28465 @cindex @value{GDBN} bugs, reporting
28467 A number of companies and individuals offer support for @sc{gnu} products.
28468 If you obtained @value{GDBN} from a support organization, we recommend you
28469 contact that organization first.
28471 You can find contact information for many support companies and
28472 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
28474 @c should add a web page ref...
28477 @ifset BUGURL_DEFAULT
28478 In any event, we also recommend that you submit bug reports for
28479 @value{GDBN}. The preferred method is to submit them directly using
28480 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
28481 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
28484 @strong{Do not send bug reports to @samp{info-gdb}, or to
28485 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
28486 not want to receive bug reports. Those that do have arranged to receive
28489 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
28490 serves as a repeater. The mailing list and the newsgroup carry exactly
28491 the same messages. Often people think of posting bug reports to the
28492 newsgroup instead of mailing them. This appears to work, but it has one
28493 problem which can be crucial: a newsgroup posting often lacks a mail
28494 path back to the sender. Thus, if we need to ask for more information,
28495 we may be unable to reach you. For this reason, it is better to send
28496 bug reports to the mailing list.
28498 @ifclear BUGURL_DEFAULT
28499 In any event, we also recommend that you submit bug reports for
28500 @value{GDBN} to @value{BUGURL}.
28504 The fundamental principle of reporting bugs usefully is this:
28505 @strong{report all the facts}. If you are not sure whether to state a
28506 fact or leave it out, state it!
28508 Often people omit facts because they think they know what causes the
28509 problem and assume that some details do not matter. Thus, you might
28510 assume that the name of the variable you use in an example does not matter.
28511 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
28512 stray memory reference which happens to fetch from the location where that
28513 name is stored in memory; perhaps, if the name were different, the contents
28514 of that location would fool the debugger into doing the right thing despite
28515 the bug. Play it safe and give a specific, complete example. That is the
28516 easiest thing for you to do, and the most helpful.
28518 Keep in mind that the purpose of a bug report is to enable us to fix the
28519 bug. It may be that the bug has been reported previously, but neither
28520 you nor we can know that unless your bug report is complete and
28523 Sometimes people give a few sketchy facts and ask, ``Does this ring a
28524 bell?'' Those bug reports are useless, and we urge everyone to
28525 @emph{refuse to respond to them} except to chide the sender to report
28528 To enable us to fix the bug, you should include all these things:
28532 The version of @value{GDBN}. @value{GDBN} announces it if you start
28533 with no arguments; you can also print it at any time using @code{show
28536 Without this, we will not know whether there is any point in looking for
28537 the bug in the current version of @value{GDBN}.
28540 The type of machine you are using, and the operating system name and
28544 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
28545 ``@value{GCC}--2.8.1''.
28548 What compiler (and its version) was used to compile the program you are
28549 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
28550 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
28551 to get this information; for other compilers, see the documentation for
28555 The command arguments you gave the compiler to compile your example and
28556 observe the bug. For example, did you use @samp{-O}? To guarantee
28557 you will not omit something important, list them all. A copy of the
28558 Makefile (or the output from make) is sufficient.
28560 If we were to try to guess the arguments, we would probably guess wrong
28561 and then we might not encounter the bug.
28564 A complete input script, and all necessary source files, that will
28568 A description of what behavior you observe that you believe is
28569 incorrect. For example, ``It gets a fatal signal.''
28571 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
28572 will certainly notice it. But if the bug is incorrect output, we might
28573 not notice unless it is glaringly wrong. You might as well not give us
28574 a chance to make a mistake.
28576 Even if the problem you experience is a fatal signal, you should still
28577 say so explicitly. Suppose something strange is going on, such as, your
28578 copy of @value{GDBN} is out of synch, or you have encountered a bug in
28579 the C library on your system. (This has happened!) Your copy might
28580 crash and ours would not. If you told us to expect a crash, then when
28581 ours fails to crash, we would know that the bug was not happening for
28582 us. If you had not told us to expect a crash, then we would not be able
28583 to draw any conclusion from our observations.
28586 @cindex recording a session script
28587 To collect all this information, you can use a session recording program
28588 such as @command{script}, which is available on many Unix systems.
28589 Just run your @value{GDBN} session inside @command{script} and then
28590 include the @file{typescript} file with your bug report.
28592 Another way to record a @value{GDBN} session is to run @value{GDBN}
28593 inside Emacs and then save the entire buffer to a file.
28596 If you wish to suggest changes to the @value{GDBN} source, send us context
28597 diffs. If you even discuss something in the @value{GDBN} source, refer to
28598 it by context, not by line number.
28600 The line numbers in our development sources will not match those in your
28601 sources. Your line numbers would convey no useful information to us.
28605 Here are some things that are not necessary:
28609 A description of the envelope of the bug.
28611 Often people who encounter a bug spend a lot of time investigating
28612 which changes to the input file will make the bug go away and which
28613 changes will not affect it.
28615 This is often time consuming and not very useful, because the way we
28616 will find the bug is by running a single example under the debugger
28617 with breakpoints, not by pure deduction from a series of examples.
28618 We recommend that you save your time for something else.
28620 Of course, if you can find a simpler example to report @emph{instead}
28621 of the original one, that is a convenience for us. Errors in the
28622 output will be easier to spot, running under the debugger will take
28623 less time, and so on.
28625 However, simplification is not vital; if you do not want to do this,
28626 report the bug anyway and send us the entire test case you used.
28629 A patch for the bug.
28631 A patch for the bug does help us if it is a good one. But do not omit
28632 the necessary information, such as the test case, on the assumption that
28633 a patch is all we need. We might see problems with your patch and decide
28634 to fix the problem another way, or we might not understand it at all.
28636 Sometimes with a program as complicated as @value{GDBN} it is very hard to
28637 construct an example that will make the program follow a certain path
28638 through the code. If you do not send us the example, we will not be able
28639 to construct one, so we will not be able to verify that the bug is fixed.
28641 And if we cannot understand what bug you are trying to fix, or why your
28642 patch should be an improvement, we will not install it. A test case will
28643 help us to understand.
28646 A guess about what the bug is or what it depends on.
28648 Such guesses are usually wrong. Even we cannot guess right about such
28649 things without first using the debugger to find the facts.
28652 @c The readline documentation is distributed with the readline code
28653 @c and consists of the two following files:
28655 @c inc-hist.texinfo
28656 @c Use -I with makeinfo to point to the appropriate directory,
28657 @c environment var TEXINPUTS with TeX.
28658 @include rluser.texi
28659 @include inc-hist.texinfo
28662 @node Formatting Documentation
28663 @appendix Formatting Documentation
28665 @cindex @value{GDBN} reference card
28666 @cindex reference card
28667 The @value{GDBN} 4 release includes an already-formatted reference card, ready
28668 for printing with PostScript or Ghostscript, in the @file{gdb}
28669 subdirectory of the main source directory@footnote{In
28670 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
28671 release.}. If you can use PostScript or Ghostscript with your printer,
28672 you can print the reference card immediately with @file{refcard.ps}.
28674 The release also includes the source for the reference card. You
28675 can format it, using @TeX{}, by typing:
28681 The @value{GDBN} reference card is designed to print in @dfn{landscape}
28682 mode on US ``letter'' size paper;
28683 that is, on a sheet 11 inches wide by 8.5 inches
28684 high. You will need to specify this form of printing as an option to
28685 your @sc{dvi} output program.
28687 @cindex documentation
28689 All the documentation for @value{GDBN} comes as part of the machine-readable
28690 distribution. The documentation is written in Texinfo format, which is
28691 a documentation system that uses a single source file to produce both
28692 on-line information and a printed manual. You can use one of the Info
28693 formatting commands to create the on-line version of the documentation
28694 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
28696 @value{GDBN} includes an already formatted copy of the on-line Info
28697 version of this manual in the @file{gdb} subdirectory. The main Info
28698 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
28699 subordinate files matching @samp{gdb.info*} in the same directory. If
28700 necessary, you can print out these files, or read them with any editor;
28701 but they are easier to read using the @code{info} subsystem in @sc{gnu}
28702 Emacs or the standalone @code{info} program, available as part of the
28703 @sc{gnu} Texinfo distribution.
28705 If you want to format these Info files yourself, you need one of the
28706 Info formatting programs, such as @code{texinfo-format-buffer} or
28709 If you have @code{makeinfo} installed, and are in the top level
28710 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
28711 version @value{GDBVN}), you can make the Info file by typing:
28718 If you want to typeset and print copies of this manual, you need @TeX{},
28719 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
28720 Texinfo definitions file.
28722 @TeX{} is a typesetting program; it does not print files directly, but
28723 produces output files called @sc{dvi} files. To print a typeset
28724 document, you need a program to print @sc{dvi} files. If your system
28725 has @TeX{} installed, chances are it has such a program. The precise
28726 command to use depends on your system; @kbd{lpr -d} is common; another
28727 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
28728 require a file name without any extension or a @samp{.dvi} extension.
28730 @TeX{} also requires a macro definitions file called
28731 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
28732 written in Texinfo format. On its own, @TeX{} cannot either read or
28733 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
28734 and is located in the @file{gdb-@var{version-number}/texinfo}
28737 If you have @TeX{} and a @sc{dvi} printer program installed, you can
28738 typeset and print this manual. First switch to the @file{gdb}
28739 subdirectory of the main source directory (for example, to
28740 @file{gdb-@value{GDBVN}/gdb}) and type:
28746 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
28748 @node Installing GDB
28749 @appendix Installing @value{GDBN}
28750 @cindex installation
28753 * Requirements:: Requirements for building @value{GDBN}
28754 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
28755 * Separate Objdir:: Compiling @value{GDBN} in another directory
28756 * Config Names:: Specifying names for hosts and targets
28757 * Configure Options:: Summary of options for configure
28758 * System-wide configuration:: Having a system-wide init file
28762 @section Requirements for Building @value{GDBN}
28763 @cindex building @value{GDBN}, requirements for
28765 Building @value{GDBN} requires various tools and packages to be available.
28766 Other packages will be used only if they are found.
28768 @heading Tools/Packages Necessary for Building @value{GDBN}
28770 @item ISO C90 compiler
28771 @value{GDBN} is written in ISO C90. It should be buildable with any
28772 working C90 compiler, e.g.@: GCC.
28776 @heading Tools/Packages Optional for Building @value{GDBN}
28780 @value{GDBN} can use the Expat XML parsing library. This library may be
28781 included with your operating system distribution; if it is not, you
28782 can get the latest version from @url{http://expat.sourceforge.net}.
28783 The @file{configure} script will search for this library in several
28784 standard locations; if it is installed in an unusual path, you can
28785 use the @option{--with-libexpat-prefix} option to specify its location.
28791 Remote protocol memory maps (@pxref{Memory Map Format})
28793 Target descriptions (@pxref{Target Descriptions})
28795 Remote shared library lists (@pxref{Library List Format})
28797 MS-Windows shared libraries (@pxref{Shared Libraries})
28801 @cindex compressed debug sections
28802 @value{GDBN} will use the @samp{zlib} library, if available, to read
28803 compressed debug sections. Some linkers, such as GNU gold, are capable
28804 of producing binaries with compressed debug sections. If @value{GDBN}
28805 is compiled with @samp{zlib}, it will be able to read the debug
28806 information in such binaries.
28808 The @samp{zlib} library is likely included with your operating system
28809 distribution; if it is not, you can get the latest version from
28810 @url{http://zlib.net}.
28813 @value{GDBN}'s features related to character sets (@pxref{Character
28814 Sets}) require a functioning @code{iconv} implementation. If you are
28815 on a GNU system, then this is provided by the GNU C Library. Some
28816 other systems also provide a working @code{iconv}.
28818 On systems with @code{iconv}, you can install GNU Libiconv. If you
28819 have previously installed Libiconv, you can use the
28820 @option{--with-libiconv-prefix} option to configure.
28822 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
28823 arrange to build Libiconv if a directory named @file{libiconv} appears
28824 in the top-most source directory. If Libiconv is built this way, and
28825 if the operating system does not provide a suitable @code{iconv}
28826 implementation, then the just-built library will automatically be used
28827 by @value{GDBN}. One easy way to set this up is to download GNU
28828 Libiconv, unpack it, and then rename the directory holding the
28829 Libiconv source code to @samp{libiconv}.
28832 @node Running Configure
28833 @section Invoking the @value{GDBN} @file{configure} Script
28834 @cindex configuring @value{GDBN}
28835 @value{GDBN} comes with a @file{configure} script that automates the process
28836 of preparing @value{GDBN} for installation; you can then use @code{make} to
28837 build the @code{gdb} program.
28839 @c irrelevant in info file; it's as current as the code it lives with.
28840 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
28841 look at the @file{README} file in the sources; we may have improved the
28842 installation procedures since publishing this manual.}
28845 The @value{GDBN} distribution includes all the source code you need for
28846 @value{GDBN} in a single directory, whose name is usually composed by
28847 appending the version number to @samp{gdb}.
28849 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
28850 @file{gdb-@value{GDBVN}} directory. That directory contains:
28853 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
28854 script for configuring @value{GDBN} and all its supporting libraries
28856 @item gdb-@value{GDBVN}/gdb
28857 the source specific to @value{GDBN} itself
28859 @item gdb-@value{GDBVN}/bfd
28860 source for the Binary File Descriptor library
28862 @item gdb-@value{GDBVN}/include
28863 @sc{gnu} include files
28865 @item gdb-@value{GDBVN}/libiberty
28866 source for the @samp{-liberty} free software library
28868 @item gdb-@value{GDBVN}/opcodes
28869 source for the library of opcode tables and disassemblers
28871 @item gdb-@value{GDBVN}/readline
28872 source for the @sc{gnu} command-line interface
28874 @item gdb-@value{GDBVN}/glob
28875 source for the @sc{gnu} filename pattern-matching subroutine
28877 @item gdb-@value{GDBVN}/mmalloc
28878 source for the @sc{gnu} memory-mapped malloc package
28881 The simplest way to configure and build @value{GDBN} is to run @file{configure}
28882 from the @file{gdb-@var{version-number}} source directory, which in
28883 this example is the @file{gdb-@value{GDBVN}} directory.
28885 First switch to the @file{gdb-@var{version-number}} source directory
28886 if you are not already in it; then run @file{configure}. Pass the
28887 identifier for the platform on which @value{GDBN} will run as an
28893 cd gdb-@value{GDBVN}
28894 ./configure @var{host}
28899 where @var{host} is an identifier such as @samp{sun4} or
28900 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
28901 (You can often leave off @var{host}; @file{configure} tries to guess the
28902 correct value by examining your system.)
28904 Running @samp{configure @var{host}} and then running @code{make} builds the
28905 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
28906 libraries, then @code{gdb} itself. The configured source files, and the
28907 binaries, are left in the corresponding source directories.
28910 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
28911 system does not recognize this automatically when you run a different
28912 shell, you may need to run @code{sh} on it explicitly:
28915 sh configure @var{host}
28918 If you run @file{configure} from a directory that contains source
28919 directories for multiple libraries or programs, such as the
28920 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
28922 creates configuration files for every directory level underneath (unless
28923 you tell it not to, with the @samp{--norecursion} option).
28925 You should run the @file{configure} script from the top directory in the
28926 source tree, the @file{gdb-@var{version-number}} directory. If you run
28927 @file{configure} from one of the subdirectories, you will configure only
28928 that subdirectory. That is usually not what you want. In particular,
28929 if you run the first @file{configure} from the @file{gdb} subdirectory
28930 of the @file{gdb-@var{version-number}} directory, you will omit the
28931 configuration of @file{bfd}, @file{readline}, and other sibling
28932 directories of the @file{gdb} subdirectory. This leads to build errors
28933 about missing include files such as @file{bfd/bfd.h}.
28935 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
28936 However, you should make sure that the shell on your path (named by
28937 the @samp{SHELL} environment variable) is publicly readable. Remember
28938 that @value{GDBN} uses the shell to start your program---some systems refuse to
28939 let @value{GDBN} debug child processes whose programs are not readable.
28941 @node Separate Objdir
28942 @section Compiling @value{GDBN} in Another Directory
28944 If you want to run @value{GDBN} versions for several host or target machines,
28945 you need a different @code{gdb} compiled for each combination of
28946 host and target. @file{configure} is designed to make this easy by
28947 allowing you to generate each configuration in a separate subdirectory,
28948 rather than in the source directory. If your @code{make} program
28949 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
28950 @code{make} in each of these directories builds the @code{gdb}
28951 program specified there.
28953 To build @code{gdb} in a separate directory, run @file{configure}
28954 with the @samp{--srcdir} option to specify where to find the source.
28955 (You also need to specify a path to find @file{configure}
28956 itself from your working directory. If the path to @file{configure}
28957 would be the same as the argument to @samp{--srcdir}, you can leave out
28958 the @samp{--srcdir} option; it is assumed.)
28960 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
28961 separate directory for a Sun 4 like this:
28965 cd gdb-@value{GDBVN}
28968 ../gdb-@value{GDBVN}/configure sun4
28973 When @file{configure} builds a configuration using a remote source
28974 directory, it creates a tree for the binaries with the same structure
28975 (and using the same names) as the tree under the source directory. In
28976 the example, you'd find the Sun 4 library @file{libiberty.a} in the
28977 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
28978 @file{gdb-sun4/gdb}.
28980 Make sure that your path to the @file{configure} script has just one
28981 instance of @file{gdb} in it. If your path to @file{configure} looks
28982 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
28983 one subdirectory of @value{GDBN}, not the whole package. This leads to
28984 build errors about missing include files such as @file{bfd/bfd.h}.
28986 One popular reason to build several @value{GDBN} configurations in separate
28987 directories is to configure @value{GDBN} for cross-compiling (where
28988 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
28989 programs that run on another machine---the @dfn{target}).
28990 You specify a cross-debugging target by
28991 giving the @samp{--target=@var{target}} option to @file{configure}.
28993 When you run @code{make} to build a program or library, you must run
28994 it in a configured directory---whatever directory you were in when you
28995 called @file{configure} (or one of its subdirectories).
28997 The @code{Makefile} that @file{configure} generates in each source
28998 directory also runs recursively. If you type @code{make} in a source
28999 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
29000 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
29001 will build all the required libraries, and then build GDB.
29003 When you have multiple hosts or targets configured in separate
29004 directories, you can run @code{make} on them in parallel (for example,
29005 if they are NFS-mounted on each of the hosts); they will not interfere
29009 @section Specifying Names for Hosts and Targets
29011 The specifications used for hosts and targets in the @file{configure}
29012 script are based on a three-part naming scheme, but some short predefined
29013 aliases are also supported. The full naming scheme encodes three pieces
29014 of information in the following pattern:
29017 @var{architecture}-@var{vendor}-@var{os}
29020 For example, you can use the alias @code{sun4} as a @var{host} argument,
29021 or as the value for @var{target} in a @code{--target=@var{target}}
29022 option. The equivalent full name is @samp{sparc-sun-sunos4}.
29024 The @file{configure} script accompanying @value{GDBN} does not provide
29025 any query facility to list all supported host and target names or
29026 aliases. @file{configure} calls the Bourne shell script
29027 @code{config.sub} to map abbreviations to full names; you can read the
29028 script, if you wish, or you can use it to test your guesses on
29029 abbreviations---for example:
29032 % sh config.sub i386-linux
29034 % sh config.sub alpha-linux
29035 alpha-unknown-linux-gnu
29036 % sh config.sub hp9k700
29038 % sh config.sub sun4
29039 sparc-sun-sunos4.1.1
29040 % sh config.sub sun3
29041 m68k-sun-sunos4.1.1
29042 % sh config.sub i986v
29043 Invalid configuration `i986v': machine `i986v' not recognized
29047 @code{config.sub} is also distributed in the @value{GDBN} source
29048 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
29050 @node Configure Options
29051 @section @file{configure} Options
29053 Here is a summary of the @file{configure} options and arguments that
29054 are most often useful for building @value{GDBN}. @file{configure} also has
29055 several other options not listed here. @inforef{What Configure
29056 Does,,configure.info}, for a full explanation of @file{configure}.
29059 configure @r{[}--help@r{]}
29060 @r{[}--prefix=@var{dir}@r{]}
29061 @r{[}--exec-prefix=@var{dir}@r{]}
29062 @r{[}--srcdir=@var{dirname}@r{]}
29063 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
29064 @r{[}--target=@var{target}@r{]}
29069 You may introduce options with a single @samp{-} rather than
29070 @samp{--} if you prefer; but you may abbreviate option names if you use
29075 Display a quick summary of how to invoke @file{configure}.
29077 @item --prefix=@var{dir}
29078 Configure the source to install programs and files under directory
29081 @item --exec-prefix=@var{dir}
29082 Configure the source to install programs under directory
29085 @c avoid splitting the warning from the explanation:
29087 @item --srcdir=@var{dirname}
29088 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
29089 @code{make} that implements the @code{VPATH} feature.}@*
29090 Use this option to make configurations in directories separate from the
29091 @value{GDBN} source directories. Among other things, you can use this to
29092 build (or maintain) several configurations simultaneously, in separate
29093 directories. @file{configure} writes configuration-specific files in
29094 the current directory, but arranges for them to use the source in the
29095 directory @var{dirname}. @file{configure} creates directories under
29096 the working directory in parallel to the source directories below
29099 @item --norecursion
29100 Configure only the directory level where @file{configure} is executed; do not
29101 propagate configuration to subdirectories.
29103 @item --target=@var{target}
29104 Configure @value{GDBN} for cross-debugging programs running on the specified
29105 @var{target}. Without this option, @value{GDBN} is configured to debug
29106 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
29108 There is no convenient way to generate a list of all available targets.
29110 @item @var{host} @dots{}
29111 Configure @value{GDBN} to run on the specified @var{host}.
29113 There is no convenient way to generate a list of all available hosts.
29116 There are many other options available as well, but they are generally
29117 needed for special purposes only.
29119 @node System-wide configuration
29120 @section System-wide configuration and settings
29121 @cindex system-wide init file
29123 @value{GDBN} can be configured to have a system-wide init file;
29124 this file will be read and executed at startup (@pxref{Startup, , What
29125 @value{GDBN} does during startup}).
29127 Here is the corresponding configure option:
29130 @item --with-system-gdbinit=@var{file}
29131 Specify that the default location of the system-wide init file is
29135 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
29136 it may be subject to relocation. Two possible cases:
29140 If the default location of this init file contains @file{$prefix},
29141 it will be subject to relocation. Suppose that the configure options
29142 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
29143 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
29144 init file is looked for as @file{$install/etc/gdbinit} instead of
29145 @file{$prefix/etc/gdbinit}.
29148 By contrast, if the default location does not contain the prefix,
29149 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
29150 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
29151 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
29152 wherever @value{GDBN} is installed.
29155 @node Maintenance Commands
29156 @appendix Maintenance Commands
29157 @cindex maintenance commands
29158 @cindex internal commands
29160 In addition to commands intended for @value{GDBN} users, @value{GDBN}
29161 includes a number of commands intended for @value{GDBN} developers,
29162 that are not documented elsewhere in this manual. These commands are
29163 provided here for reference. (For commands that turn on debugging
29164 messages, see @ref{Debugging Output}.)
29167 @kindex maint agent
29168 @kindex maint agent-eval
29169 @item maint agent @var{expression}
29170 @itemx maint agent-eval @var{expression}
29171 Translate the given @var{expression} into remote agent bytecodes.
29172 This command is useful for debugging the Agent Expression mechanism
29173 (@pxref{Agent Expressions}). The @samp{agent} version produces an
29174 expression useful for data collection, such as by tracepoints, while
29175 @samp{maint agent-eval} produces an expression that evaluates directly
29176 to a result. For instance, a collection expression for @code{globa +
29177 globb} will include bytecodes to record four bytes of memory at each
29178 of the addresses of @code{globa} and @code{globb}, while discarding
29179 the result of the addition, while an evaluation expression will do the
29180 addition and return the sum.
29182 @kindex maint info breakpoints
29183 @item @anchor{maint info breakpoints}maint info breakpoints
29184 Using the same format as @samp{info breakpoints}, display both the
29185 breakpoints you've set explicitly, and those @value{GDBN} is using for
29186 internal purposes. Internal breakpoints are shown with negative
29187 breakpoint numbers. The type column identifies what kind of breakpoint
29192 Normal, explicitly set breakpoint.
29195 Normal, explicitly set watchpoint.
29198 Internal breakpoint, used to handle correctly stepping through
29199 @code{longjmp} calls.
29201 @item longjmp resume
29202 Internal breakpoint at the target of a @code{longjmp}.
29205 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
29208 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
29211 Shared library events.
29215 @kindex set displaced-stepping
29216 @kindex show displaced-stepping
29217 @cindex displaced stepping support
29218 @cindex out-of-line single-stepping
29219 @item set displaced-stepping
29220 @itemx show displaced-stepping
29221 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
29222 if the target supports it. Displaced stepping is a way to single-step
29223 over breakpoints without removing them from the inferior, by executing
29224 an out-of-line copy of the instruction that was originally at the
29225 breakpoint location. It is also known as out-of-line single-stepping.
29228 @item set displaced-stepping on
29229 If the target architecture supports it, @value{GDBN} will use
29230 displaced stepping to step over breakpoints.
29232 @item set displaced-stepping off
29233 @value{GDBN} will not use displaced stepping to step over breakpoints,
29234 even if such is supported by the target architecture.
29236 @cindex non-stop mode, and @samp{set displaced-stepping}
29237 @item set displaced-stepping auto
29238 This is the default mode. @value{GDBN} will use displaced stepping
29239 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
29240 architecture supports displaced stepping.
29243 @kindex maint check-symtabs
29244 @item maint check-symtabs
29245 Check the consistency of psymtabs and symtabs.
29247 @kindex maint cplus first_component
29248 @item maint cplus first_component @var{name}
29249 Print the first C@t{++} class/namespace component of @var{name}.
29251 @kindex maint cplus namespace
29252 @item maint cplus namespace
29253 Print the list of possible C@t{++} namespaces.
29255 @kindex maint demangle
29256 @item maint demangle @var{name}
29257 Demangle a C@t{++} or Objective-C mangled @var{name}.
29259 @kindex maint deprecate
29260 @kindex maint undeprecate
29261 @cindex deprecated commands
29262 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
29263 @itemx maint undeprecate @var{command}
29264 Deprecate or undeprecate the named @var{command}. Deprecated commands
29265 cause @value{GDBN} to issue a warning when you use them. The optional
29266 argument @var{replacement} says which newer command should be used in
29267 favor of the deprecated one; if it is given, @value{GDBN} will mention
29268 the replacement as part of the warning.
29270 @kindex maint dump-me
29271 @item maint dump-me
29272 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
29273 Cause a fatal signal in the debugger and force it to dump its core.
29274 This is supported only on systems which support aborting a program
29275 with the @code{SIGQUIT} signal.
29277 @kindex maint internal-error
29278 @kindex maint internal-warning
29279 @item maint internal-error @r{[}@var{message-text}@r{]}
29280 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
29281 Cause @value{GDBN} to call the internal function @code{internal_error}
29282 or @code{internal_warning} and hence behave as though an internal error
29283 or internal warning has been detected. In addition to reporting the
29284 internal problem, these functions give the user the opportunity to
29285 either quit @value{GDBN} or create a core file of the current
29286 @value{GDBN} session.
29288 These commands take an optional parameter @var{message-text} that is
29289 used as the text of the error or warning message.
29291 Here's an example of using @code{internal-error}:
29294 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
29295 @dots{}/maint.c:121: internal-error: testing, 1, 2
29296 A problem internal to GDB has been detected. Further
29297 debugging may prove unreliable.
29298 Quit this debugging session? (y or n) @kbd{n}
29299 Create a core file? (y or n) @kbd{n}
29303 @cindex @value{GDBN} internal error
29304 @cindex internal errors, control of @value{GDBN} behavior
29306 @kindex maint set internal-error
29307 @kindex maint show internal-error
29308 @kindex maint set internal-warning
29309 @kindex maint show internal-warning
29310 @item maint set internal-error @var{action} [ask|yes|no]
29311 @itemx maint show internal-error @var{action}
29312 @itemx maint set internal-warning @var{action} [ask|yes|no]
29313 @itemx maint show internal-warning @var{action}
29314 When @value{GDBN} reports an internal problem (error or warning) it
29315 gives the user the opportunity to both quit @value{GDBN} and create a
29316 core file of the current @value{GDBN} session. These commands let you
29317 override the default behaviour for each particular @var{action},
29318 described in the table below.
29322 You can specify that @value{GDBN} should always (yes) or never (no)
29323 quit. The default is to ask the user what to do.
29326 You can specify that @value{GDBN} should always (yes) or never (no)
29327 create a core file. The default is to ask the user what to do.
29330 @kindex maint packet
29331 @item maint packet @var{text}
29332 If @value{GDBN} is talking to an inferior via the serial protocol,
29333 then this command sends the string @var{text} to the inferior, and
29334 displays the response packet. @value{GDBN} supplies the initial
29335 @samp{$} character, the terminating @samp{#} character, and the
29338 @kindex maint print architecture
29339 @item maint print architecture @r{[}@var{file}@r{]}
29340 Print the entire architecture configuration. The optional argument
29341 @var{file} names the file where the output goes.
29343 @kindex maint print c-tdesc
29344 @item maint print c-tdesc
29345 Print the current target description (@pxref{Target Descriptions}) as
29346 a C source file. The created source file can be used in @value{GDBN}
29347 when an XML parser is not available to parse the description.
29349 @kindex maint print dummy-frames
29350 @item maint print dummy-frames
29351 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
29354 (@value{GDBP}) @kbd{b add}
29356 (@value{GDBP}) @kbd{print add(2,3)}
29357 Breakpoint 2, add (a=2, b=3) at @dots{}
29359 The program being debugged stopped while in a function called from GDB.
29361 (@value{GDBP}) @kbd{maint print dummy-frames}
29362 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
29363 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
29364 call_lo=0x01014000 call_hi=0x01014001
29368 Takes an optional file parameter.
29370 @kindex maint print registers
29371 @kindex maint print raw-registers
29372 @kindex maint print cooked-registers
29373 @kindex maint print register-groups
29374 @item maint print registers @r{[}@var{file}@r{]}
29375 @itemx maint print raw-registers @r{[}@var{file}@r{]}
29376 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
29377 @itemx maint print register-groups @r{[}@var{file}@r{]}
29378 Print @value{GDBN}'s internal register data structures.
29380 The command @code{maint print raw-registers} includes the contents of
29381 the raw register cache; the command @code{maint print cooked-registers}
29382 includes the (cooked) value of all registers, including registers which
29383 aren't available on the target nor visible to user; and the
29384 command @code{maint print register-groups} includes the groups that each
29385 register is a member of. @xref{Registers,, Registers, gdbint,
29386 @value{GDBN} Internals}.
29388 These commands take an optional parameter, a file name to which to
29389 write the information.
29391 @kindex maint print reggroups
29392 @item maint print reggroups @r{[}@var{file}@r{]}
29393 Print @value{GDBN}'s internal register group data structures. The
29394 optional argument @var{file} tells to what file to write the
29397 The register groups info looks like this:
29400 (@value{GDBP}) @kbd{maint print reggroups}
29413 This command forces @value{GDBN} to flush its internal register cache.
29415 @kindex maint print objfiles
29416 @cindex info for known object files
29417 @item maint print objfiles
29418 Print a dump of all known object files. For each object file, this
29419 command prints its name, address in memory, and all of its psymtabs
29422 @kindex maint print statistics
29423 @cindex bcache statistics
29424 @item maint print statistics
29425 This command prints, for each object file in the program, various data
29426 about that object file followed by the byte cache (@dfn{bcache})
29427 statistics for the object file. The objfile data includes the number
29428 of minimal, partial, full, and stabs symbols, the number of types
29429 defined by the objfile, the number of as yet unexpanded psym tables,
29430 the number of line tables and string tables, and the amount of memory
29431 used by the various tables. The bcache statistics include the counts,
29432 sizes, and counts of duplicates of all and unique objects, max,
29433 average, and median entry size, total memory used and its overhead and
29434 savings, and various measures of the hash table size and chain
29437 @kindex maint print target-stack
29438 @cindex target stack description
29439 @item maint print target-stack
29440 A @dfn{target} is an interface between the debugger and a particular
29441 kind of file or process. Targets can be stacked in @dfn{strata},
29442 so that more than one target can potentially respond to a request.
29443 In particular, memory accesses will walk down the stack of targets
29444 until they find a target that is interested in handling that particular
29447 This command prints a short description of each layer that was pushed on
29448 the @dfn{target stack}, starting from the top layer down to the bottom one.
29450 @kindex maint print type
29451 @cindex type chain of a data type
29452 @item maint print type @var{expr}
29453 Print the type chain for a type specified by @var{expr}. The argument
29454 can be either a type name or a symbol. If it is a symbol, the type of
29455 that symbol is described. The type chain produced by this command is
29456 a recursive definition of the data type as stored in @value{GDBN}'s
29457 data structures, including its flags and contained types.
29459 @kindex maint set dwarf2 max-cache-age
29460 @kindex maint show dwarf2 max-cache-age
29461 @item maint set dwarf2 max-cache-age
29462 @itemx maint show dwarf2 max-cache-age
29463 Control the DWARF 2 compilation unit cache.
29465 @cindex DWARF 2 compilation units cache
29466 In object files with inter-compilation-unit references, such as those
29467 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
29468 reader needs to frequently refer to previously read compilation units.
29469 This setting controls how long a compilation unit will remain in the
29470 cache if it is not referenced. A higher limit means that cached
29471 compilation units will be stored in memory longer, and more total
29472 memory will be used. Setting it to zero disables caching, which will
29473 slow down @value{GDBN} startup, but reduce memory consumption.
29475 @kindex maint set profile
29476 @kindex maint show profile
29477 @cindex profiling GDB
29478 @item maint set profile
29479 @itemx maint show profile
29480 Control profiling of @value{GDBN}.
29482 Profiling will be disabled until you use the @samp{maint set profile}
29483 command to enable it. When you enable profiling, the system will begin
29484 collecting timing and execution count data; when you disable profiling or
29485 exit @value{GDBN}, the results will be written to a log file. Remember that
29486 if you use profiling, @value{GDBN} will overwrite the profiling log file
29487 (often called @file{gmon.out}). If you have a record of important profiling
29488 data in a @file{gmon.out} file, be sure to move it to a safe location.
29490 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
29491 compiled with the @samp{-pg} compiler option.
29493 @kindex maint set show-debug-regs
29494 @kindex maint show show-debug-regs
29495 @cindex hardware debug registers
29496 @item maint set show-debug-regs
29497 @itemx maint show show-debug-regs
29498 Control whether to show variables that mirror the hardware debug
29499 registers. Use @code{ON} to enable, @code{OFF} to disable. If
29500 enabled, the debug registers values are shown when @value{GDBN} inserts or
29501 removes a hardware breakpoint or watchpoint, and when the inferior
29502 triggers a hardware-assisted breakpoint or watchpoint.
29504 @kindex maint set show-all-tib
29505 @kindex maint show show-all-tib
29506 @item maint set show-all-tib
29507 @itemx maint show show-all-tib
29508 Control whether to show all non zero areas within a 1k block starting
29509 at thread local base, when using the @samp{info w32 thread-information-block}
29512 @kindex maint space
29513 @cindex memory used by commands
29515 Control whether to display memory usage for each command. If set to a
29516 nonzero value, @value{GDBN} will display how much memory each command
29517 took, following the command's own output. This can also be requested
29518 by invoking @value{GDBN} with the @option{--statistics} command-line
29519 switch (@pxref{Mode Options}).
29522 @cindex time of command execution
29524 Control whether to display the execution time for each command. If
29525 set to a nonzero value, @value{GDBN} will display how much time it
29526 took to execute each command, following the command's own output.
29527 The time is not printed for the commands that run the target, since
29528 there's no mechanism currently to compute how much time was spend
29529 by @value{GDBN} and how much time was spend by the program been debugged.
29530 it's not possibly currently
29531 This can also be requested by invoking @value{GDBN} with the
29532 @option{--statistics} command-line switch (@pxref{Mode Options}).
29534 @kindex maint translate-address
29535 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
29536 Find the symbol stored at the location specified by the address
29537 @var{addr} and an optional section name @var{section}. If found,
29538 @value{GDBN} prints the name of the closest symbol and an offset from
29539 the symbol's location to the specified address. This is similar to
29540 the @code{info address} command (@pxref{Symbols}), except that this
29541 command also allows to find symbols in other sections.
29543 If section was not specified, the section in which the symbol was found
29544 is also printed. For dynamically linked executables, the name of
29545 executable or shared library containing the symbol is printed as well.
29549 The following command is useful for non-interactive invocations of
29550 @value{GDBN}, such as in the test suite.
29553 @item set watchdog @var{nsec}
29554 @kindex set watchdog
29555 @cindex watchdog timer
29556 @cindex timeout for commands
29557 Set the maximum number of seconds @value{GDBN} will wait for the
29558 target operation to finish. If this time expires, @value{GDBN}
29559 reports and error and the command is aborted.
29561 @item show watchdog
29562 Show the current setting of the target wait timeout.
29565 @node Remote Protocol
29566 @appendix @value{GDBN} Remote Serial Protocol
29571 * Stop Reply Packets::
29572 * General Query Packets::
29573 * Architecture-Specific Protocol Details::
29574 * Tracepoint Packets::
29575 * Host I/O Packets::
29577 * Notification Packets::
29578 * Remote Non-Stop::
29579 * Packet Acknowledgment::
29581 * File-I/O Remote Protocol Extension::
29582 * Library List Format::
29583 * Memory Map Format::
29584 * Thread List Format::
29590 There may be occasions when you need to know something about the
29591 protocol---for example, if there is only one serial port to your target
29592 machine, you might want your program to do something special if it
29593 recognizes a packet meant for @value{GDBN}.
29595 In the examples below, @samp{->} and @samp{<-} are used to indicate
29596 transmitted and received data, respectively.
29598 @cindex protocol, @value{GDBN} remote serial
29599 @cindex serial protocol, @value{GDBN} remote
29600 @cindex remote serial protocol
29601 All @value{GDBN} commands and responses (other than acknowledgments
29602 and notifications, see @ref{Notification Packets}) are sent as a
29603 @var{packet}. A @var{packet} is introduced with the character
29604 @samp{$}, the actual @var{packet-data}, and the terminating character
29605 @samp{#} followed by a two-digit @var{checksum}:
29608 @code{$}@var{packet-data}@code{#}@var{checksum}
29612 @cindex checksum, for @value{GDBN} remote
29614 The two-digit @var{checksum} is computed as the modulo 256 sum of all
29615 characters between the leading @samp{$} and the trailing @samp{#} (an
29616 eight bit unsigned checksum).
29618 Implementors should note that prior to @value{GDBN} 5.0 the protocol
29619 specification also included an optional two-digit @var{sequence-id}:
29622 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
29625 @cindex sequence-id, for @value{GDBN} remote
29627 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
29628 has never output @var{sequence-id}s. Stubs that handle packets added
29629 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
29631 When either the host or the target machine receives a packet, the first
29632 response expected is an acknowledgment: either @samp{+} (to indicate
29633 the package was received correctly) or @samp{-} (to request
29637 -> @code{$}@var{packet-data}@code{#}@var{checksum}
29642 The @samp{+}/@samp{-} acknowledgments can be disabled
29643 once a connection is established.
29644 @xref{Packet Acknowledgment}, for details.
29646 The host (@value{GDBN}) sends @var{command}s, and the target (the
29647 debugging stub incorporated in your program) sends a @var{response}. In
29648 the case of step and continue @var{command}s, the response is only sent
29649 when the operation has completed, and the target has again stopped all
29650 threads in all attached processes. This is the default all-stop mode
29651 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
29652 execution mode; see @ref{Remote Non-Stop}, for details.
29654 @var{packet-data} consists of a sequence of characters with the
29655 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
29658 @cindex remote protocol, field separator
29659 Fields within the packet should be separated using @samp{,} @samp{;} or
29660 @samp{:}. Except where otherwise noted all numbers are represented in
29661 @sc{hex} with leading zeros suppressed.
29663 Implementors should note that prior to @value{GDBN} 5.0, the character
29664 @samp{:} could not appear as the third character in a packet (as it
29665 would potentially conflict with the @var{sequence-id}).
29667 @cindex remote protocol, binary data
29668 @anchor{Binary Data}
29669 Binary data in most packets is encoded either as two hexadecimal
29670 digits per byte of binary data. This allowed the traditional remote
29671 protocol to work over connections which were only seven-bit clean.
29672 Some packets designed more recently assume an eight-bit clean
29673 connection, and use a more efficient encoding to send and receive
29676 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
29677 as an escape character. Any escaped byte is transmitted as the escape
29678 character followed by the original character XORed with @code{0x20}.
29679 For example, the byte @code{0x7d} would be transmitted as the two
29680 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
29681 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
29682 @samp{@}}) must always be escaped. Responses sent by the stub
29683 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
29684 is not interpreted as the start of a run-length encoded sequence
29687 Response @var{data} can be run-length encoded to save space.
29688 Run-length encoding replaces runs of identical characters with one
29689 instance of the repeated character, followed by a @samp{*} and a
29690 repeat count. The repeat count is itself sent encoded, to avoid
29691 binary characters in @var{data}: a value of @var{n} is sent as
29692 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
29693 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
29694 code 32) for a repeat count of 3. (This is because run-length
29695 encoding starts to win for counts 3 or more.) Thus, for example,
29696 @samp{0* } is a run-length encoding of ``0000'': the space character
29697 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
29700 The printable characters @samp{#} and @samp{$} or with a numeric value
29701 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
29702 seven repeats (@samp{$}) can be expanded using a repeat count of only
29703 five (@samp{"}). For example, @samp{00000000} can be encoded as
29706 The error response returned for some packets includes a two character
29707 error number. That number is not well defined.
29709 @cindex empty response, for unsupported packets
29710 For any @var{command} not supported by the stub, an empty response
29711 (@samp{$#00}) should be returned. That way it is possible to extend the
29712 protocol. A newer @value{GDBN} can tell if a packet is supported based
29715 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
29716 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
29722 The following table provides a complete list of all currently defined
29723 @var{command}s and their corresponding response @var{data}.
29724 @xref{File-I/O Remote Protocol Extension}, for details about the File
29725 I/O extension of the remote protocol.
29727 Each packet's description has a template showing the packet's overall
29728 syntax, followed by an explanation of the packet's meaning. We
29729 include spaces in some of the templates for clarity; these are not
29730 part of the packet's syntax. No @value{GDBN} packet uses spaces to
29731 separate its components. For example, a template like @samp{foo
29732 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
29733 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
29734 @var{baz}. @value{GDBN} does not transmit a space character between the
29735 @samp{foo} and the @var{bar}, or between the @var{bar} and the
29738 @cindex @var{thread-id}, in remote protocol
29739 @anchor{thread-id syntax}
29740 Several packets and replies include a @var{thread-id} field to identify
29741 a thread. Normally these are positive numbers with a target-specific
29742 interpretation, formatted as big-endian hex strings. A @var{thread-id}
29743 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
29746 In addition, the remote protocol supports a multiprocess feature in
29747 which the @var{thread-id} syntax is extended to optionally include both
29748 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
29749 The @var{pid} (process) and @var{tid} (thread) components each have the
29750 format described above: a positive number with target-specific
29751 interpretation formatted as a big-endian hex string, literal @samp{-1}
29752 to indicate all processes or threads (respectively), or @samp{0} to
29753 indicate an arbitrary process or thread. Specifying just a process, as
29754 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
29755 error to specify all processes but a specific thread, such as
29756 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
29757 for those packets and replies explicitly documented to include a process
29758 ID, rather than a @var{thread-id}.
29760 The multiprocess @var{thread-id} syntax extensions are only used if both
29761 @value{GDBN} and the stub report support for the @samp{multiprocess}
29762 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
29765 Note that all packet forms beginning with an upper- or lower-case
29766 letter, other than those described here, are reserved for future use.
29768 Here are the packet descriptions.
29773 @cindex @samp{!} packet
29774 @anchor{extended mode}
29775 Enable extended mode. In extended mode, the remote server is made
29776 persistent. The @samp{R} packet is used to restart the program being
29782 The remote target both supports and has enabled extended mode.
29786 @cindex @samp{?} packet
29787 Indicate the reason the target halted. The reply is the same as for
29788 step and continue. This packet has a special interpretation when the
29789 target is in non-stop mode; see @ref{Remote Non-Stop}.
29792 @xref{Stop Reply Packets}, for the reply specifications.
29794 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
29795 @cindex @samp{A} packet
29796 Initialized @code{argv[]} array passed into program. @var{arglen}
29797 specifies the number of bytes in the hex encoded byte stream
29798 @var{arg}. See @code{gdbserver} for more details.
29803 The arguments were set.
29809 @cindex @samp{b} packet
29810 (Don't use this packet; its behavior is not well-defined.)
29811 Change the serial line speed to @var{baud}.
29813 JTC: @emph{When does the transport layer state change? When it's
29814 received, or after the ACK is transmitted. In either case, there are
29815 problems if the command or the acknowledgment packet is dropped.}
29817 Stan: @emph{If people really wanted to add something like this, and get
29818 it working for the first time, they ought to modify ser-unix.c to send
29819 some kind of out-of-band message to a specially-setup stub and have the
29820 switch happen "in between" packets, so that from remote protocol's point
29821 of view, nothing actually happened.}
29823 @item B @var{addr},@var{mode}
29824 @cindex @samp{B} packet
29825 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
29826 breakpoint at @var{addr}.
29828 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
29829 (@pxref{insert breakpoint or watchpoint packet}).
29831 @cindex @samp{bc} packet
29834 Backward continue. Execute the target system in reverse. No parameter.
29835 @xref{Reverse Execution}, for more information.
29838 @xref{Stop Reply Packets}, for the reply specifications.
29840 @cindex @samp{bs} packet
29843 Backward single step. Execute one instruction in reverse. No parameter.
29844 @xref{Reverse Execution}, for more information.
29847 @xref{Stop Reply Packets}, for the reply specifications.
29849 @item c @r{[}@var{addr}@r{]}
29850 @cindex @samp{c} packet
29851 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
29852 resume at current address.
29855 @xref{Stop Reply Packets}, for the reply specifications.
29857 @item C @var{sig}@r{[};@var{addr}@r{]}
29858 @cindex @samp{C} packet
29859 Continue with signal @var{sig} (hex signal number). If
29860 @samp{;@var{addr}} is omitted, resume at same address.
29863 @xref{Stop Reply Packets}, for the reply specifications.
29866 @cindex @samp{d} packet
29869 Don't use this packet; instead, define a general set packet
29870 (@pxref{General Query Packets}).
29874 @cindex @samp{D} packet
29875 The first form of the packet is used to detach @value{GDBN} from the
29876 remote system. It is sent to the remote target
29877 before @value{GDBN} disconnects via the @code{detach} command.
29879 The second form, including a process ID, is used when multiprocess
29880 protocol extensions are enabled (@pxref{multiprocess extensions}), to
29881 detach only a specific process. The @var{pid} is specified as a
29882 big-endian hex string.
29892 @item F @var{RC},@var{EE},@var{CF};@var{XX}
29893 @cindex @samp{F} packet
29894 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
29895 This is part of the File-I/O protocol extension. @xref{File-I/O
29896 Remote Protocol Extension}, for the specification.
29899 @anchor{read registers packet}
29900 @cindex @samp{g} packet
29901 Read general registers.
29905 @item @var{XX@dots{}}
29906 Each byte of register data is described by two hex digits. The bytes
29907 with the register are transmitted in target byte order. The size of
29908 each register and their position within the @samp{g} packet are
29909 determined by the @value{GDBN} internal gdbarch functions
29910 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
29911 specification of several standard @samp{g} packets is specified below.
29916 @item G @var{XX@dots{}}
29917 @cindex @samp{G} packet
29918 Write general registers. @xref{read registers packet}, for a
29919 description of the @var{XX@dots{}} data.
29929 @item H @var{c} @var{thread-id}
29930 @cindex @samp{H} packet
29931 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
29932 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
29933 should be @samp{c} for step and continue operations, @samp{g} for other
29934 operations. The thread designator @var{thread-id} has the format and
29935 interpretation described in @ref{thread-id syntax}.
29946 @c 'H': How restrictive (or permissive) is the thread model. If a
29947 @c thread is selected and stopped, are other threads allowed
29948 @c to continue to execute? As I mentioned above, I think the
29949 @c semantics of each command when a thread is selected must be
29950 @c described. For example:
29952 @c 'g': If the stub supports threads and a specific thread is
29953 @c selected, returns the register block from that thread;
29954 @c otherwise returns current registers.
29956 @c 'G' If the stub supports threads and a specific thread is
29957 @c selected, sets the registers of the register block of
29958 @c that thread; otherwise sets current registers.
29960 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
29961 @anchor{cycle step packet}
29962 @cindex @samp{i} packet
29963 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
29964 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
29965 step starting at that address.
29968 @cindex @samp{I} packet
29969 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
29973 @cindex @samp{k} packet
29976 FIXME: @emph{There is no description of how to operate when a specific
29977 thread context has been selected (i.e.@: does 'k' kill only that
29980 @item m @var{addr},@var{length}
29981 @cindex @samp{m} packet
29982 Read @var{length} bytes of memory starting at address @var{addr}.
29983 Note that @var{addr} may not be aligned to any particular boundary.
29985 The stub need not use any particular size or alignment when gathering
29986 data from memory for the response; even if @var{addr} is word-aligned
29987 and @var{length} is a multiple of the word size, the stub is free to
29988 use byte accesses, or not. For this reason, this packet may not be
29989 suitable for accessing memory-mapped I/O devices.
29990 @cindex alignment of remote memory accesses
29991 @cindex size of remote memory accesses
29992 @cindex memory, alignment and size of remote accesses
29996 @item @var{XX@dots{}}
29997 Memory contents; each byte is transmitted as a two-digit hexadecimal
29998 number. The reply may contain fewer bytes than requested if the
29999 server was able to read only part of the region of memory.
30004 @item M @var{addr},@var{length}:@var{XX@dots{}}
30005 @cindex @samp{M} packet
30006 Write @var{length} bytes of memory starting at address @var{addr}.
30007 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
30008 hexadecimal number.
30015 for an error (this includes the case where only part of the data was
30020 @cindex @samp{p} packet
30021 Read the value of register @var{n}; @var{n} is in hex.
30022 @xref{read registers packet}, for a description of how the returned
30023 register value is encoded.
30027 @item @var{XX@dots{}}
30028 the register's value
30032 Indicating an unrecognized @var{query}.
30035 @item P @var{n@dots{}}=@var{r@dots{}}
30036 @anchor{write register packet}
30037 @cindex @samp{P} packet
30038 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
30039 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
30040 digits for each byte in the register (target byte order).
30050 @item q @var{name} @var{params}@dots{}
30051 @itemx Q @var{name} @var{params}@dots{}
30052 @cindex @samp{q} packet
30053 @cindex @samp{Q} packet
30054 General query (@samp{q}) and set (@samp{Q}). These packets are
30055 described fully in @ref{General Query Packets}.
30058 @cindex @samp{r} packet
30059 Reset the entire system.
30061 Don't use this packet; use the @samp{R} packet instead.
30064 @cindex @samp{R} packet
30065 Restart the program being debugged. @var{XX}, while needed, is ignored.
30066 This packet is only available in extended mode (@pxref{extended mode}).
30068 The @samp{R} packet has no reply.
30070 @item s @r{[}@var{addr}@r{]}
30071 @cindex @samp{s} packet
30072 Single step. @var{addr} is the address at which to resume. If
30073 @var{addr} is omitted, resume at same address.
30076 @xref{Stop Reply Packets}, for the reply specifications.
30078 @item S @var{sig}@r{[};@var{addr}@r{]}
30079 @anchor{step with signal packet}
30080 @cindex @samp{S} packet
30081 Step with signal. This is analogous to the @samp{C} packet, but
30082 requests a single-step, rather than a normal resumption of execution.
30085 @xref{Stop Reply Packets}, for the reply specifications.
30087 @item t @var{addr}:@var{PP},@var{MM}
30088 @cindex @samp{t} packet
30089 Search backwards starting at address @var{addr} for a match with pattern
30090 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
30091 @var{addr} must be at least 3 digits.
30093 @item T @var{thread-id}
30094 @cindex @samp{T} packet
30095 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
30100 thread is still alive
30106 Packets starting with @samp{v} are identified by a multi-letter name,
30107 up to the first @samp{;} or @samp{?} (or the end of the packet).
30109 @item vAttach;@var{pid}
30110 @cindex @samp{vAttach} packet
30111 Attach to a new process with the specified process ID @var{pid}.
30112 The process ID is a
30113 hexadecimal integer identifying the process. In all-stop mode, all
30114 threads in the attached process are stopped; in non-stop mode, it may be
30115 attached without being stopped if that is supported by the target.
30117 @c In non-stop mode, on a successful vAttach, the stub should set the
30118 @c current thread to a thread of the newly-attached process. After
30119 @c attaching, GDB queries for the attached process's thread ID with qC.
30120 @c Also note that, from a user perspective, whether or not the
30121 @c target is stopped on attach in non-stop mode depends on whether you
30122 @c use the foreground or background version of the attach command, not
30123 @c on what vAttach does; GDB does the right thing with respect to either
30124 @c stopping or restarting threads.
30126 This packet is only available in extended mode (@pxref{extended mode}).
30132 @item @r{Any stop packet}
30133 for success in all-stop mode (@pxref{Stop Reply Packets})
30135 for success in non-stop mode (@pxref{Remote Non-Stop})
30138 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
30139 @cindex @samp{vCont} packet
30140 Resume the inferior, specifying different actions for each thread.
30141 If an action is specified with no @var{thread-id}, then it is applied to any
30142 threads that don't have a specific action specified; if no default action is
30143 specified then other threads should remain stopped in all-stop mode and
30144 in their current state in non-stop mode.
30145 Specifying multiple
30146 default actions is an error; specifying no actions is also an error.
30147 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
30149 Currently supported actions are:
30155 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
30159 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
30164 The optional argument @var{addr} normally associated with the
30165 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
30166 not supported in @samp{vCont}.
30168 The @samp{t} action is only relevant in non-stop mode
30169 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
30170 A stop reply should be generated for any affected thread not already stopped.
30171 When a thread is stopped by means of a @samp{t} action,
30172 the corresponding stop reply should indicate that the thread has stopped with
30173 signal @samp{0}, regardless of whether the target uses some other signal
30174 as an implementation detail.
30177 @xref{Stop Reply Packets}, for the reply specifications.
30180 @cindex @samp{vCont?} packet
30181 Request a list of actions supported by the @samp{vCont} packet.
30185 @item vCont@r{[};@var{action}@dots{}@r{]}
30186 The @samp{vCont} packet is supported. Each @var{action} is a supported
30187 command in the @samp{vCont} packet.
30189 The @samp{vCont} packet is not supported.
30192 @item vFile:@var{operation}:@var{parameter}@dots{}
30193 @cindex @samp{vFile} packet
30194 Perform a file operation on the target system. For details,
30195 see @ref{Host I/O Packets}.
30197 @item vFlashErase:@var{addr},@var{length}
30198 @cindex @samp{vFlashErase} packet
30199 Direct the stub to erase @var{length} bytes of flash starting at
30200 @var{addr}. The region may enclose any number of flash blocks, but
30201 its start and end must fall on block boundaries, as indicated by the
30202 flash block size appearing in the memory map (@pxref{Memory Map
30203 Format}). @value{GDBN} groups flash memory programming operations
30204 together, and sends a @samp{vFlashDone} request after each group; the
30205 stub is allowed to delay erase operation until the @samp{vFlashDone}
30206 packet is received.
30208 The stub must support @samp{vCont} if it reports support for
30209 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
30210 this case @samp{vCont} actions can be specified to apply to all threads
30211 in a process by using the @samp{p@var{pid}.-1} form of the
30222 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
30223 @cindex @samp{vFlashWrite} packet
30224 Direct the stub to write data to flash address @var{addr}. The data
30225 is passed in binary form using the same encoding as for the @samp{X}
30226 packet (@pxref{Binary Data}). The memory ranges specified by
30227 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
30228 not overlap, and must appear in order of increasing addresses
30229 (although @samp{vFlashErase} packets for higher addresses may already
30230 have been received; the ordering is guaranteed only between
30231 @samp{vFlashWrite} packets). If a packet writes to an address that was
30232 neither erased by a preceding @samp{vFlashErase} packet nor by some other
30233 target-specific method, the results are unpredictable.
30241 for vFlashWrite addressing non-flash memory
30247 @cindex @samp{vFlashDone} packet
30248 Indicate to the stub that flash programming operation is finished.
30249 The stub is permitted to delay or batch the effects of a group of
30250 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
30251 @samp{vFlashDone} packet is received. The contents of the affected
30252 regions of flash memory are unpredictable until the @samp{vFlashDone}
30253 request is completed.
30255 @item vKill;@var{pid}
30256 @cindex @samp{vKill} packet
30257 Kill the process with the specified process ID. @var{pid} is a
30258 hexadecimal integer identifying the process. This packet is used in
30259 preference to @samp{k} when multiprocess protocol extensions are
30260 supported; see @ref{multiprocess extensions}.
30270 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
30271 @cindex @samp{vRun} packet
30272 Run the program @var{filename}, passing it each @var{argument} on its
30273 command line. The file and arguments are hex-encoded strings. If
30274 @var{filename} is an empty string, the stub may use a default program
30275 (e.g.@: the last program run). The program is created in the stopped
30278 @c FIXME: What about non-stop mode?
30280 This packet is only available in extended mode (@pxref{extended mode}).
30286 @item @r{Any stop packet}
30287 for success (@pxref{Stop Reply Packets})
30291 @anchor{vStopped packet}
30292 @cindex @samp{vStopped} packet
30294 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
30295 reply and prompt for the stub to report another one.
30299 @item @r{Any stop packet}
30300 if there is another unreported stop event (@pxref{Stop Reply Packets})
30302 if there are no unreported stop events
30305 @item X @var{addr},@var{length}:@var{XX@dots{}}
30307 @cindex @samp{X} packet
30308 Write data to memory, where the data is transmitted in binary.
30309 @var{addr} is address, @var{length} is number of bytes,
30310 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
30320 @item z @var{type},@var{addr},@var{kind}
30321 @itemx Z @var{type},@var{addr},@var{kind}
30322 @anchor{insert breakpoint or watchpoint packet}
30323 @cindex @samp{z} packet
30324 @cindex @samp{Z} packets
30325 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
30326 watchpoint starting at address @var{address} of kind @var{kind}.
30328 Each breakpoint and watchpoint packet @var{type} is documented
30331 @emph{Implementation notes: A remote target shall return an empty string
30332 for an unrecognized breakpoint or watchpoint packet @var{type}. A
30333 remote target shall support either both or neither of a given
30334 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
30335 avoid potential problems with duplicate packets, the operations should
30336 be implemented in an idempotent way.}
30338 @item z0,@var{addr},@var{kind}
30339 @itemx Z0,@var{addr},@var{kind}
30340 @cindex @samp{z0} packet
30341 @cindex @samp{Z0} packet
30342 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
30343 @var{addr} of type @var{kind}.
30345 A memory breakpoint is implemented by replacing the instruction at
30346 @var{addr} with a software breakpoint or trap instruction. The
30347 @var{kind} is target-specific and typically indicates the size of
30348 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
30349 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
30350 architectures have additional meanings for @var{kind};
30351 see @ref{Architecture-Specific Protocol Details}.
30353 @emph{Implementation note: It is possible for a target to copy or move
30354 code that contains memory breakpoints (e.g., when implementing
30355 overlays). The behavior of this packet, in the presence of such a
30356 target, is not defined.}
30368 @item z1,@var{addr},@var{kind}
30369 @itemx Z1,@var{addr},@var{kind}
30370 @cindex @samp{z1} packet
30371 @cindex @samp{Z1} packet
30372 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
30373 address @var{addr}.
30375 A hardware breakpoint is implemented using a mechanism that is not
30376 dependant on being able to modify the target's memory. @var{kind}
30377 has the same meaning as in @samp{Z0} packets.
30379 @emph{Implementation note: A hardware breakpoint is not affected by code
30392 @item z2,@var{addr},@var{kind}
30393 @itemx Z2,@var{addr},@var{kind}
30394 @cindex @samp{z2} packet
30395 @cindex @samp{Z2} packet
30396 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
30397 @var{kind} is interpreted as the number of bytes to watch.
30409 @item z3,@var{addr},@var{kind}
30410 @itemx Z3,@var{addr},@var{kind}
30411 @cindex @samp{z3} packet
30412 @cindex @samp{Z3} packet
30413 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
30414 @var{kind} is interpreted as the number of bytes to watch.
30426 @item z4,@var{addr},@var{kind}
30427 @itemx Z4,@var{addr},@var{kind}
30428 @cindex @samp{z4} packet
30429 @cindex @samp{Z4} packet
30430 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
30431 @var{kind} is interpreted as the number of bytes to watch.
30445 @node Stop Reply Packets
30446 @section Stop Reply Packets
30447 @cindex stop reply packets
30449 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
30450 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
30451 receive any of the below as a reply. Except for @samp{?}
30452 and @samp{vStopped}, that reply is only returned
30453 when the target halts. In the below the exact meaning of @dfn{signal
30454 number} is defined by the header @file{include/gdb/signals.h} in the
30455 @value{GDBN} source code.
30457 As in the description of request packets, we include spaces in the
30458 reply templates for clarity; these are not part of the reply packet's
30459 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
30465 The program received signal number @var{AA} (a two-digit hexadecimal
30466 number). This is equivalent to a @samp{T} response with no
30467 @var{n}:@var{r} pairs.
30469 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
30470 @cindex @samp{T} packet reply
30471 The program received signal number @var{AA} (a two-digit hexadecimal
30472 number). This is equivalent to an @samp{S} response, except that the
30473 @samp{@var{n}:@var{r}} pairs can carry values of important registers
30474 and other information directly in the stop reply packet, reducing
30475 round-trip latency. Single-step and breakpoint traps are reported
30476 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
30480 If @var{n} is a hexadecimal number, it is a register number, and the
30481 corresponding @var{r} gives that register's value. @var{r} is a
30482 series of bytes in target byte order, with each byte given by a
30483 two-digit hex number.
30486 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
30487 the stopped thread, as specified in @ref{thread-id syntax}.
30490 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
30491 the core on which the stop event was detected.
30494 If @var{n} is a recognized @dfn{stop reason}, it describes a more
30495 specific event that stopped the target. The currently defined stop
30496 reasons are listed below. @var{aa} should be @samp{05}, the trap
30497 signal. At most one stop reason should be present.
30500 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
30501 and go on to the next; this allows us to extend the protocol in the
30505 The currently defined stop reasons are:
30511 The packet indicates a watchpoint hit, and @var{r} is the data address, in
30514 @cindex shared library events, remote reply
30516 The packet indicates that the loaded libraries have changed.
30517 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
30518 list of loaded libraries. @var{r} is ignored.
30520 @cindex replay log events, remote reply
30522 The packet indicates that the target cannot continue replaying
30523 logged execution events, because it has reached the end (or the
30524 beginning when executing backward) of the log. The value of @var{r}
30525 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
30526 for more information.
30530 @itemx W @var{AA} ; process:@var{pid}
30531 The process exited, and @var{AA} is the exit status. This is only
30532 applicable to certain targets.
30534 The second form of the response, including the process ID of the exited
30535 process, can be used only when @value{GDBN} has reported support for
30536 multiprocess protocol extensions; see @ref{multiprocess extensions}.
30537 The @var{pid} is formatted as a big-endian hex string.
30540 @itemx X @var{AA} ; process:@var{pid}
30541 The process terminated with signal @var{AA}.
30543 The second form of the response, including the process ID of the
30544 terminated process, can be used only when @value{GDBN} has reported
30545 support for multiprocess protocol extensions; see @ref{multiprocess
30546 extensions}. The @var{pid} is formatted as a big-endian hex string.
30548 @item O @var{XX}@dots{}
30549 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
30550 written as the program's console output. This can happen at any time
30551 while the program is running and the debugger should continue to wait
30552 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
30554 @item F @var{call-id},@var{parameter}@dots{}
30555 @var{call-id} is the identifier which says which host system call should
30556 be called. This is just the name of the function. Translation into the
30557 correct system call is only applicable as it's defined in @value{GDBN}.
30558 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
30561 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
30562 this very system call.
30564 The target replies with this packet when it expects @value{GDBN} to
30565 call a host system call on behalf of the target. @value{GDBN} replies
30566 with an appropriate @samp{F} packet and keeps up waiting for the next
30567 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
30568 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
30569 Protocol Extension}, for more details.
30573 @node General Query Packets
30574 @section General Query Packets
30575 @cindex remote query requests
30577 Packets starting with @samp{q} are @dfn{general query packets};
30578 packets starting with @samp{Q} are @dfn{general set packets}. General
30579 query and set packets are a semi-unified form for retrieving and
30580 sending information to and from the stub.
30582 The initial letter of a query or set packet is followed by a name
30583 indicating what sort of thing the packet applies to. For example,
30584 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
30585 definitions with the stub. These packet names follow some
30590 The name must not contain commas, colons or semicolons.
30592 Most @value{GDBN} query and set packets have a leading upper case
30595 The names of custom vendor packets should use a company prefix, in
30596 lower case, followed by a period. For example, packets designed at
30597 the Acme Corporation might begin with @samp{qacme.foo} (for querying
30598 foos) or @samp{Qacme.bar} (for setting bars).
30601 The name of a query or set packet should be separated from any
30602 parameters by a @samp{:}; the parameters themselves should be
30603 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
30604 full packet name, and check for a separator or the end of the packet,
30605 in case two packet names share a common prefix. New packets should not begin
30606 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
30607 packets predate these conventions, and have arguments without any terminator
30608 for the packet name; we suspect they are in widespread use in places that
30609 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
30610 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
30613 Like the descriptions of the other packets, each description here
30614 has a template showing the packet's overall syntax, followed by an
30615 explanation of the packet's meaning. We include spaces in some of the
30616 templates for clarity; these are not part of the packet's syntax. No
30617 @value{GDBN} packet uses spaces to separate its components.
30619 Here are the currently defined query and set packets:
30624 @cindex current thread, remote request
30625 @cindex @samp{qC} packet
30626 Return the current thread ID.
30630 @item QC @var{thread-id}
30631 Where @var{thread-id} is a thread ID as documented in
30632 @ref{thread-id syntax}.
30633 @item @r{(anything else)}
30634 Any other reply implies the old thread ID.
30637 @item qCRC:@var{addr},@var{length}
30638 @cindex CRC of memory block, remote request
30639 @cindex @samp{qCRC} packet
30640 Compute the CRC checksum of a block of memory using CRC-32 defined in
30641 IEEE 802.3. The CRC is computed byte at a time, taking the most
30642 significant bit of each byte first. The initial pattern code
30643 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
30645 @emph{Note:} This is the same CRC used in validating separate debug
30646 files (@pxref{Separate Debug Files, , Debugging Information in Separate
30647 Files}). However the algorithm is slightly different. When validating
30648 separate debug files, the CRC is computed taking the @emph{least}
30649 significant bit of each byte first, and the final result is inverted to
30650 detect trailing zeros.
30655 An error (such as memory fault)
30656 @item C @var{crc32}
30657 The specified memory region's checksum is @var{crc32}.
30661 @itemx qsThreadInfo
30662 @cindex list active threads, remote request
30663 @cindex @samp{qfThreadInfo} packet
30664 @cindex @samp{qsThreadInfo} packet
30665 Obtain a list of all active thread IDs from the target (OS). Since there
30666 may be too many active threads to fit into one reply packet, this query
30667 works iteratively: it may require more than one query/reply sequence to
30668 obtain the entire list of threads. The first query of the sequence will
30669 be the @samp{qfThreadInfo} query; subsequent queries in the
30670 sequence will be the @samp{qsThreadInfo} query.
30672 NOTE: This packet replaces the @samp{qL} query (see below).
30676 @item m @var{thread-id}
30678 @item m @var{thread-id},@var{thread-id}@dots{}
30679 a comma-separated list of thread IDs
30681 (lower case letter @samp{L}) denotes end of list.
30684 In response to each query, the target will reply with a list of one or
30685 more thread IDs, separated by commas.
30686 @value{GDBN} will respond to each reply with a request for more thread
30687 ids (using the @samp{qs} form of the query), until the target responds
30688 with @samp{l} (lower-case el, for @dfn{last}).
30689 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
30692 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
30693 @cindex get thread-local storage address, remote request
30694 @cindex @samp{qGetTLSAddr} packet
30695 Fetch the address associated with thread local storage specified
30696 by @var{thread-id}, @var{offset}, and @var{lm}.
30698 @var{thread-id} is the thread ID associated with the
30699 thread for which to fetch the TLS address. @xref{thread-id syntax}.
30701 @var{offset} is the (big endian, hex encoded) offset associated with the
30702 thread local variable. (This offset is obtained from the debug
30703 information associated with the variable.)
30705 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
30706 the load module associated with the thread local storage. For example,
30707 a @sc{gnu}/Linux system will pass the link map address of the shared
30708 object associated with the thread local storage under consideration.
30709 Other operating environments may choose to represent the load module
30710 differently, so the precise meaning of this parameter will vary.
30714 @item @var{XX}@dots{}
30715 Hex encoded (big endian) bytes representing the address of the thread
30716 local storage requested.
30719 An error occurred. @var{nn} are hex digits.
30722 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
30725 @item qGetTIBAddr:@var{thread-id}
30726 @cindex get thread information block address
30727 @cindex @samp{qGetTIBAddr} packet
30728 Fetch address of the Windows OS specific Thread Information Block.
30730 @var{thread-id} is the thread ID associated with the thread.
30734 @item @var{XX}@dots{}
30735 Hex encoded (big endian) bytes representing the linear address of the
30736 thread information block.
30739 An error occured. This means that either the thread was not found, or the
30740 address could not be retrieved.
30743 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
30746 @item qL @var{startflag} @var{threadcount} @var{nextthread}
30747 Obtain thread information from RTOS. Where: @var{startflag} (one hex
30748 digit) is one to indicate the first query and zero to indicate a
30749 subsequent query; @var{threadcount} (two hex digits) is the maximum
30750 number of threads the response packet can contain; and @var{nextthread}
30751 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
30752 returned in the response as @var{argthread}.
30754 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
30758 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
30759 Where: @var{count} (two hex digits) is the number of threads being
30760 returned; @var{done} (one hex digit) is zero to indicate more threads
30761 and one indicates no further threads; @var{argthreadid} (eight hex
30762 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
30763 is a sequence of thread IDs from the target. @var{threadid} (eight hex
30764 digits). See @code{remote.c:parse_threadlist_response()}.
30768 @cindex section offsets, remote request
30769 @cindex @samp{qOffsets} packet
30770 Get section offsets that the target used when relocating the downloaded
30775 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
30776 Relocate the @code{Text} section by @var{xxx} from its original address.
30777 Relocate the @code{Data} section by @var{yyy} from its original address.
30778 If the object file format provides segment information (e.g.@: @sc{elf}
30779 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
30780 segments by the supplied offsets.
30782 @emph{Note: while a @code{Bss} offset may be included in the response,
30783 @value{GDBN} ignores this and instead applies the @code{Data} offset
30784 to the @code{Bss} section.}
30786 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
30787 Relocate the first segment of the object file, which conventionally
30788 contains program code, to a starting address of @var{xxx}. If
30789 @samp{DataSeg} is specified, relocate the second segment, which
30790 conventionally contains modifiable data, to a starting address of
30791 @var{yyy}. @value{GDBN} will report an error if the object file
30792 does not contain segment information, or does not contain at least
30793 as many segments as mentioned in the reply. Extra segments are
30794 kept at fixed offsets relative to the last relocated segment.
30797 @item qP @var{mode} @var{thread-id}
30798 @cindex thread information, remote request
30799 @cindex @samp{qP} packet
30800 Returns information on @var{thread-id}. Where: @var{mode} is a hex
30801 encoded 32 bit mode; @var{thread-id} is a thread ID
30802 (@pxref{thread-id syntax}).
30804 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
30807 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
30811 @cindex non-stop mode, remote request
30812 @cindex @samp{QNonStop} packet
30814 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
30815 @xref{Remote Non-Stop}, for more information.
30820 The request succeeded.
30823 An error occurred. @var{nn} are hex digits.
30826 An empty reply indicates that @samp{QNonStop} is not supported by
30830 This packet is not probed by default; the remote stub must request it,
30831 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30832 Use of this packet is controlled by the @code{set non-stop} command;
30833 @pxref{Non-Stop Mode}.
30835 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
30836 @cindex pass signals to inferior, remote request
30837 @cindex @samp{QPassSignals} packet
30838 @anchor{QPassSignals}
30839 Each listed @var{signal} should be passed directly to the inferior process.
30840 Signals are numbered identically to continue packets and stop replies
30841 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
30842 strictly greater than the previous item. These signals do not need to stop
30843 the inferior, or be reported to @value{GDBN}. All other signals should be
30844 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
30845 combine; any earlier @samp{QPassSignals} list is completely replaced by the
30846 new list. This packet improves performance when using @samp{handle
30847 @var{signal} nostop noprint pass}.
30852 The request succeeded.
30855 An error occurred. @var{nn} are hex digits.
30858 An empty reply indicates that @samp{QPassSignals} is not supported by
30862 Use of this packet is controlled by the @code{set remote pass-signals}
30863 command (@pxref{Remote Configuration, set remote pass-signals}).
30864 This packet is not probed by default; the remote stub must request it,
30865 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30867 @item qRcmd,@var{command}
30868 @cindex execute remote command, remote request
30869 @cindex @samp{qRcmd} packet
30870 @var{command} (hex encoded) is passed to the local interpreter for
30871 execution. Invalid commands should be reported using the output
30872 string. Before the final result packet, the target may also respond
30873 with a number of intermediate @samp{O@var{output}} console output
30874 packets. @emph{Implementors should note that providing access to a
30875 stubs's interpreter may have security implications}.
30880 A command response with no output.
30882 A command response with the hex encoded output string @var{OUTPUT}.
30884 Indicate a badly formed request.
30886 An empty reply indicates that @samp{qRcmd} is not recognized.
30889 (Note that the @code{qRcmd} packet's name is separated from the
30890 command by a @samp{,}, not a @samp{:}, contrary to the naming
30891 conventions above. Please don't use this packet as a model for new
30894 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
30895 @cindex searching memory, in remote debugging
30896 @cindex @samp{qSearch:memory} packet
30897 @anchor{qSearch memory}
30898 Search @var{length} bytes at @var{address} for @var{search-pattern}.
30899 @var{address} and @var{length} are encoded in hex.
30900 @var{search-pattern} is a sequence of bytes, hex encoded.
30905 The pattern was not found.
30907 The pattern was found at @var{address}.
30909 A badly formed request or an error was encountered while searching memory.
30911 An empty reply indicates that @samp{qSearch:memory} is not recognized.
30914 @item QStartNoAckMode
30915 @cindex @samp{QStartNoAckMode} packet
30916 @anchor{QStartNoAckMode}
30917 Request that the remote stub disable the normal @samp{+}/@samp{-}
30918 protocol acknowledgments (@pxref{Packet Acknowledgment}).
30923 The stub has switched to no-acknowledgment mode.
30924 @value{GDBN} acknowledges this reponse,
30925 but neither the stub nor @value{GDBN} shall send or expect further
30926 @samp{+}/@samp{-} acknowledgments in the current connection.
30928 An empty reply indicates that the stub does not support no-acknowledgment mode.
30931 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
30932 @cindex supported packets, remote query
30933 @cindex features of the remote protocol
30934 @cindex @samp{qSupported} packet
30935 @anchor{qSupported}
30936 Tell the remote stub about features supported by @value{GDBN}, and
30937 query the stub for features it supports. This packet allows
30938 @value{GDBN} and the remote stub to take advantage of each others'
30939 features. @samp{qSupported} also consolidates multiple feature probes
30940 at startup, to improve @value{GDBN} performance---a single larger
30941 packet performs better than multiple smaller probe packets on
30942 high-latency links. Some features may enable behavior which must not
30943 be on by default, e.g.@: because it would confuse older clients or
30944 stubs. Other features may describe packets which could be
30945 automatically probed for, but are not. These features must be
30946 reported before @value{GDBN} will use them. This ``default
30947 unsupported'' behavior is not appropriate for all packets, but it
30948 helps to keep the initial connection time under control with new
30949 versions of @value{GDBN} which support increasing numbers of packets.
30953 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
30954 The stub supports or does not support each returned @var{stubfeature},
30955 depending on the form of each @var{stubfeature} (see below for the
30958 An empty reply indicates that @samp{qSupported} is not recognized,
30959 or that no features needed to be reported to @value{GDBN}.
30962 The allowed forms for each feature (either a @var{gdbfeature} in the
30963 @samp{qSupported} packet, or a @var{stubfeature} in the response)
30967 @item @var{name}=@var{value}
30968 The remote protocol feature @var{name} is supported, and associated
30969 with the specified @var{value}. The format of @var{value} depends
30970 on the feature, but it must not include a semicolon.
30972 The remote protocol feature @var{name} is supported, and does not
30973 need an associated value.
30975 The remote protocol feature @var{name} is not supported.
30977 The remote protocol feature @var{name} may be supported, and
30978 @value{GDBN} should auto-detect support in some other way when it is
30979 needed. This form will not be used for @var{gdbfeature} notifications,
30980 but may be used for @var{stubfeature} responses.
30983 Whenever the stub receives a @samp{qSupported} request, the
30984 supplied set of @value{GDBN} features should override any previous
30985 request. This allows @value{GDBN} to put the stub in a known
30986 state, even if the stub had previously been communicating with
30987 a different version of @value{GDBN}.
30989 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
30994 This feature indicates whether @value{GDBN} supports multiprocess
30995 extensions to the remote protocol. @value{GDBN} does not use such
30996 extensions unless the stub also reports that it supports them by
30997 including @samp{multiprocess+} in its @samp{qSupported} reply.
30998 @xref{multiprocess extensions}, for details.
31001 This feature indicates that @value{GDBN} supports the XML target
31002 description. If the stub sees @samp{xmlRegisters=} with target
31003 specific strings separated by a comma, it will report register
31007 Stubs should ignore any unknown values for
31008 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
31009 packet supports receiving packets of unlimited length (earlier
31010 versions of @value{GDBN} may reject overly long responses). Additional values
31011 for @var{gdbfeature} may be defined in the future to let the stub take
31012 advantage of new features in @value{GDBN}, e.g.@: incompatible
31013 improvements in the remote protocol---the @samp{multiprocess} feature is
31014 an example of such a feature. The stub's reply should be independent
31015 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
31016 describes all the features it supports, and then the stub replies with
31017 all the features it supports.
31019 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
31020 responses, as long as each response uses one of the standard forms.
31022 Some features are flags. A stub which supports a flag feature
31023 should respond with a @samp{+} form response. Other features
31024 require values, and the stub should respond with an @samp{=}
31027 Each feature has a default value, which @value{GDBN} will use if
31028 @samp{qSupported} is not available or if the feature is not mentioned
31029 in the @samp{qSupported} response. The default values are fixed; a
31030 stub is free to omit any feature responses that match the defaults.
31032 Not all features can be probed, but for those which can, the probing
31033 mechanism is useful: in some cases, a stub's internal
31034 architecture may not allow the protocol layer to know some information
31035 about the underlying target in advance. This is especially common in
31036 stubs which may be configured for multiple targets.
31038 These are the currently defined stub features and their properties:
31040 @multitable @columnfractions 0.35 0.2 0.12 0.2
31041 @c NOTE: The first row should be @headitem, but we do not yet require
31042 @c a new enough version of Texinfo (4.7) to use @headitem.
31044 @tab Value Required
31048 @item @samp{PacketSize}
31053 @item @samp{qXfer:auxv:read}
31058 @item @samp{qXfer:features:read}
31063 @item @samp{qXfer:libraries:read}
31068 @item @samp{qXfer:memory-map:read}
31073 @item @samp{qXfer:spu:read}
31078 @item @samp{qXfer:spu:write}
31083 @item @samp{qXfer:siginfo:read}
31088 @item @samp{qXfer:siginfo:write}
31093 @item @samp{qXfer:threads:read}
31099 @item @samp{QNonStop}
31104 @item @samp{QPassSignals}
31109 @item @samp{QStartNoAckMode}
31114 @item @samp{multiprocess}
31119 @item @samp{ConditionalTracepoints}
31124 @item @samp{ReverseContinue}
31129 @item @samp{ReverseStep}
31134 @item @samp{TracepointSource}
31141 These are the currently defined stub features, in more detail:
31144 @cindex packet size, remote protocol
31145 @item PacketSize=@var{bytes}
31146 The remote stub can accept packets up to at least @var{bytes} in
31147 length. @value{GDBN} will send packets up to this size for bulk
31148 transfers, and will never send larger packets. This is a limit on the
31149 data characters in the packet, including the frame and checksum.
31150 There is no trailing NUL byte in a remote protocol packet; if the stub
31151 stores packets in a NUL-terminated format, it should allow an extra
31152 byte in its buffer for the NUL. If this stub feature is not supported,
31153 @value{GDBN} guesses based on the size of the @samp{g} packet response.
31155 @item qXfer:auxv:read
31156 The remote stub understands the @samp{qXfer:auxv:read} packet
31157 (@pxref{qXfer auxiliary vector read}).
31159 @item qXfer:features:read
31160 The remote stub understands the @samp{qXfer:features:read} packet
31161 (@pxref{qXfer target description read}).
31163 @item qXfer:libraries:read
31164 The remote stub understands the @samp{qXfer:libraries:read} packet
31165 (@pxref{qXfer library list read}).
31167 @item qXfer:memory-map:read
31168 The remote stub understands the @samp{qXfer:memory-map:read} packet
31169 (@pxref{qXfer memory map read}).
31171 @item qXfer:spu:read
31172 The remote stub understands the @samp{qXfer:spu:read} packet
31173 (@pxref{qXfer spu read}).
31175 @item qXfer:spu:write
31176 The remote stub understands the @samp{qXfer:spu:write} packet
31177 (@pxref{qXfer spu write}).
31179 @item qXfer:siginfo:read
31180 The remote stub understands the @samp{qXfer:siginfo:read} packet
31181 (@pxref{qXfer siginfo read}).
31183 @item qXfer:siginfo:write
31184 The remote stub understands the @samp{qXfer:siginfo:write} packet
31185 (@pxref{qXfer siginfo write}).
31187 @item qXfer:threads:read
31188 The remote stub understands the @samp{qXfer:threads:read} packet
31189 (@pxref{qXfer threads read}).
31192 The remote stub understands the @samp{QNonStop} packet
31193 (@pxref{QNonStop}).
31196 The remote stub understands the @samp{QPassSignals} packet
31197 (@pxref{QPassSignals}).
31199 @item QStartNoAckMode
31200 The remote stub understands the @samp{QStartNoAckMode} packet and
31201 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
31204 @anchor{multiprocess extensions}
31205 @cindex multiprocess extensions, in remote protocol
31206 The remote stub understands the multiprocess extensions to the remote
31207 protocol syntax. The multiprocess extensions affect the syntax of
31208 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
31209 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
31210 replies. Note that reporting this feature indicates support for the
31211 syntactic extensions only, not that the stub necessarily supports
31212 debugging of more than one process at a time. The stub must not use
31213 multiprocess extensions in packet replies unless @value{GDBN} has also
31214 indicated it supports them in its @samp{qSupported} request.
31216 @item qXfer:osdata:read
31217 The remote stub understands the @samp{qXfer:osdata:read} packet
31218 ((@pxref{qXfer osdata read}).
31220 @item ConditionalTracepoints
31221 The remote stub accepts and implements conditional expressions defined
31222 for tracepoints (@pxref{Tracepoint Conditions}).
31224 @item ReverseContinue
31225 The remote stub accepts and implements the reverse continue packet
31229 The remote stub accepts and implements the reverse step packet
31232 @item TracepointSource
31233 The remote stub understands the @samp{QTDPsrc} packet that supplies
31234 the source form of tracepoint definitions.
31239 @cindex symbol lookup, remote request
31240 @cindex @samp{qSymbol} packet
31241 Notify the target that @value{GDBN} is prepared to serve symbol lookup
31242 requests. Accept requests from the target for the values of symbols.
31247 The target does not need to look up any (more) symbols.
31248 @item qSymbol:@var{sym_name}
31249 The target requests the value of symbol @var{sym_name} (hex encoded).
31250 @value{GDBN} may provide the value by using the
31251 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
31255 @item qSymbol:@var{sym_value}:@var{sym_name}
31256 Set the value of @var{sym_name} to @var{sym_value}.
31258 @var{sym_name} (hex encoded) is the name of a symbol whose value the
31259 target has previously requested.
31261 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
31262 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
31268 The target does not need to look up any (more) symbols.
31269 @item qSymbol:@var{sym_name}
31270 The target requests the value of a new symbol @var{sym_name} (hex
31271 encoded). @value{GDBN} will continue to supply the values of symbols
31272 (if available), until the target ceases to request them.
31277 @item QTDisconnected
31284 @xref{Tracepoint Packets}.
31286 @item qThreadExtraInfo,@var{thread-id}
31287 @cindex thread attributes info, remote request
31288 @cindex @samp{qThreadExtraInfo} packet
31289 Obtain a printable string description of a thread's attributes from
31290 the target OS. @var{thread-id} is a thread ID;
31291 see @ref{thread-id syntax}. This
31292 string may contain anything that the target OS thinks is interesting
31293 for @value{GDBN} to tell the user about the thread. The string is
31294 displayed in @value{GDBN}'s @code{info threads} display. Some
31295 examples of possible thread extra info strings are @samp{Runnable}, or
31296 @samp{Blocked on Mutex}.
31300 @item @var{XX}@dots{}
31301 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
31302 comprising the printable string containing the extra information about
31303 the thread's attributes.
31306 (Note that the @code{qThreadExtraInfo} packet's name is separated from
31307 the command by a @samp{,}, not a @samp{:}, contrary to the naming
31308 conventions above. Please don't use this packet as a model for new
31320 @xref{Tracepoint Packets}.
31322 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
31323 @cindex read special object, remote request
31324 @cindex @samp{qXfer} packet
31325 @anchor{qXfer read}
31326 Read uninterpreted bytes from the target's special data area
31327 identified by the keyword @var{object}. Request @var{length} bytes
31328 starting at @var{offset} bytes into the data. The content and
31329 encoding of @var{annex} is specific to @var{object}; it can supply
31330 additional details about what data to access.
31332 Here are the specific requests of this form defined so far. All
31333 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
31334 formats, listed below.
31337 @item qXfer:auxv:read::@var{offset},@var{length}
31338 @anchor{qXfer auxiliary vector read}
31339 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
31340 auxiliary vector}. Note @var{annex} must be empty.
31342 This packet is not probed by default; the remote stub must request it,
31343 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31345 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
31346 @anchor{qXfer target description read}
31347 Access the @dfn{target description}. @xref{Target Descriptions}. The
31348 annex specifies which XML document to access. The main description is
31349 always loaded from the @samp{target.xml} annex.
31351 This packet is not probed by default; the remote stub must request it,
31352 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31354 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
31355 @anchor{qXfer library list read}
31356 Access the target's list of loaded libraries. @xref{Library List Format}.
31357 The annex part of the generic @samp{qXfer} packet must be empty
31358 (@pxref{qXfer read}).
31360 Targets which maintain a list of libraries in the program's memory do
31361 not need to implement this packet; it is designed for platforms where
31362 the operating system manages the list of loaded libraries.
31364 This packet is not probed by default; the remote stub must request it,
31365 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31367 @item qXfer:memory-map:read::@var{offset},@var{length}
31368 @anchor{qXfer memory map read}
31369 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
31370 annex part of the generic @samp{qXfer} packet must be empty
31371 (@pxref{qXfer read}).
31373 This packet is not probed by default; the remote stub must request it,
31374 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31376 @item qXfer:siginfo:read::@var{offset},@var{length}
31377 @anchor{qXfer siginfo read}
31378 Read contents of the extra signal information on the target
31379 system. The annex part of the generic @samp{qXfer} packet must be
31380 empty (@pxref{qXfer read}).
31382 This packet is not probed by default; the remote stub must request it,
31383 by supplying an appropriate @samp{qSupported} response
31384 (@pxref{qSupported}).
31386 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
31387 @anchor{qXfer spu read}
31388 Read contents of an @code{spufs} file on the target system. The
31389 annex specifies which file to read; it must be of the form
31390 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31391 in the target process, and @var{name} identifes the @code{spufs} file
31392 in that context to be accessed.
31394 This packet is not probed by default; the remote stub must request it,
31395 by supplying an appropriate @samp{qSupported} response
31396 (@pxref{qSupported}).
31398 @item qXfer:threads:read::@var{offset},@var{length}
31399 @anchor{qXfer threads read}
31400 Access the list of threads on target. @xref{Thread List Format}. The
31401 annex part of the generic @samp{qXfer} packet must be empty
31402 (@pxref{qXfer read}).
31404 This packet is not probed by default; the remote stub must request it,
31405 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31407 @item qXfer:osdata:read::@var{offset},@var{length}
31408 @anchor{qXfer osdata read}
31409 Access the target's @dfn{operating system information}.
31410 @xref{Operating System Information}.
31417 Data @var{data} (@pxref{Binary Data}) has been read from the
31418 target. There may be more data at a higher address (although
31419 it is permitted to return @samp{m} even for the last valid
31420 block of data, as long as at least one byte of data was read).
31421 @var{data} may have fewer bytes than the @var{length} in the
31425 Data @var{data} (@pxref{Binary Data}) has been read from the target.
31426 There is no more data to be read. @var{data} may have fewer bytes
31427 than the @var{length} in the request.
31430 The @var{offset} in the request is at the end of the data.
31431 There is no more data to be read.
31434 The request was malformed, or @var{annex} was invalid.
31437 The offset was invalid, or there was an error encountered reading the data.
31438 @var{nn} is a hex-encoded @code{errno} value.
31441 An empty reply indicates the @var{object} string was not recognized by
31442 the stub, or that the object does not support reading.
31445 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
31446 @cindex write data into object, remote request
31447 @anchor{qXfer write}
31448 Write uninterpreted bytes into the target's special data area
31449 identified by the keyword @var{object}, starting at @var{offset} bytes
31450 into the data. @var{data}@dots{} is the binary-encoded data
31451 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
31452 is specific to @var{object}; it can supply additional details about what data
31455 Here are the specific requests of this form defined so far. All
31456 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
31457 formats, listed below.
31460 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
31461 @anchor{qXfer siginfo write}
31462 Write @var{data} to the extra signal information on the target system.
31463 The annex part of the generic @samp{qXfer} packet must be
31464 empty (@pxref{qXfer write}).
31466 This packet is not probed by default; the remote stub must request it,
31467 by supplying an appropriate @samp{qSupported} response
31468 (@pxref{qSupported}).
31470 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
31471 @anchor{qXfer spu write}
31472 Write @var{data} to an @code{spufs} file on the target system. The
31473 annex specifies which file to write; it must be of the form
31474 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31475 in the target process, and @var{name} identifes the @code{spufs} file
31476 in that context to be accessed.
31478 This packet is not probed by default; the remote stub must request it,
31479 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31485 @var{nn} (hex encoded) is the number of bytes written.
31486 This may be fewer bytes than supplied in the request.
31489 The request was malformed, or @var{annex} was invalid.
31492 The offset was invalid, or there was an error encountered writing the data.
31493 @var{nn} is a hex-encoded @code{errno} value.
31496 An empty reply indicates the @var{object} string was not
31497 recognized by the stub, or that the object does not support writing.
31500 @item qXfer:@var{object}:@var{operation}:@dots{}
31501 Requests of this form may be added in the future. When a stub does
31502 not recognize the @var{object} keyword, or its support for
31503 @var{object} does not recognize the @var{operation} keyword, the stub
31504 must respond with an empty packet.
31506 @item qAttached:@var{pid}
31507 @cindex query attached, remote request
31508 @cindex @samp{qAttached} packet
31509 Return an indication of whether the remote server attached to an
31510 existing process or created a new process. When the multiprocess
31511 protocol extensions are supported (@pxref{multiprocess extensions}),
31512 @var{pid} is an integer in hexadecimal format identifying the target
31513 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
31514 the query packet will be simplified as @samp{qAttached}.
31516 This query is used, for example, to know whether the remote process
31517 should be detached or killed when a @value{GDBN} session is ended with
31518 the @code{quit} command.
31523 The remote server attached to an existing process.
31525 The remote server created a new process.
31527 A badly formed request or an error was encountered.
31532 @node Architecture-Specific Protocol Details
31533 @section Architecture-Specific Protocol Details
31535 This section describes how the remote protocol is applied to specific
31536 target architectures. Also see @ref{Standard Target Features}, for
31537 details of XML target descriptions for each architecture.
31541 @subsubsection Breakpoint Kinds
31543 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
31548 16-bit Thumb mode breakpoint.
31551 32-bit Thumb mode (Thumb-2) breakpoint.
31554 32-bit ARM mode breakpoint.
31560 @subsubsection Register Packet Format
31562 The following @code{g}/@code{G} packets have previously been defined.
31563 In the below, some thirty-two bit registers are transferred as
31564 sixty-four bits. Those registers should be zero/sign extended (which?)
31565 to fill the space allocated. Register bytes are transferred in target
31566 byte order. The two nibbles within a register byte are transferred
31567 most-significant - least-significant.
31573 All registers are transferred as thirty-two bit quantities in the order:
31574 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
31575 registers; fsr; fir; fp.
31579 All registers are transferred as sixty-four bit quantities (including
31580 thirty-two bit registers such as @code{sr}). The ordering is the same
31585 @node Tracepoint Packets
31586 @section Tracepoint Packets
31587 @cindex tracepoint packets
31588 @cindex packets, tracepoint
31590 Here we describe the packets @value{GDBN} uses to implement
31591 tracepoints (@pxref{Tracepoints}).
31595 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
31596 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
31597 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
31598 the tracepoint is disabled. @var{step} is the tracepoint's step
31599 count, and @var{pass} is its pass count. If an @samp{F} is present,
31600 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
31601 the number of bytes that the target should copy elsewhere to make room
31602 for the tracepoint. If an @samp{X} is present, it introduces a
31603 tracepoint condition, which consists of a hexadecimal length, followed
31604 by a comma and hex-encoded bytes, in a manner similar to action
31605 encodings as described below. If the trailing @samp{-} is present,
31606 further @samp{QTDP} packets will follow to specify this tracepoint's
31612 The packet was understood and carried out.
31614 The packet was not recognized.
31617 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
31618 Define actions to be taken when a tracepoint is hit. @var{n} and
31619 @var{addr} must be the same as in the initial @samp{QTDP} packet for
31620 this tracepoint. This packet may only be sent immediately after
31621 another @samp{QTDP} packet that ended with a @samp{-}. If the
31622 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
31623 specifying more actions for this tracepoint.
31625 In the series of action packets for a given tracepoint, at most one
31626 can have an @samp{S} before its first @var{action}. If such a packet
31627 is sent, it and the following packets define ``while-stepping''
31628 actions. Any prior packets define ordinary actions --- that is, those
31629 taken when the tracepoint is first hit. If no action packet has an
31630 @samp{S}, then all the packets in the series specify ordinary
31631 tracepoint actions.
31633 The @samp{@var{action}@dots{}} portion of the packet is a series of
31634 actions, concatenated without separators. Each action has one of the
31640 Collect the registers whose bits are set in @var{mask}. @var{mask} is
31641 a hexadecimal number whose @var{i}'th bit is set if register number
31642 @var{i} should be collected. (The least significant bit is numbered
31643 zero.) Note that @var{mask} may be any number of digits long; it may
31644 not fit in a 32-bit word.
31646 @item M @var{basereg},@var{offset},@var{len}
31647 Collect @var{len} bytes of memory starting at the address in register
31648 number @var{basereg}, plus @var{offset}. If @var{basereg} is
31649 @samp{-1}, then the range has a fixed address: @var{offset} is the
31650 address of the lowest byte to collect. The @var{basereg},
31651 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
31652 values (the @samp{-1} value for @var{basereg} is a special case).
31654 @item X @var{len},@var{expr}
31655 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
31656 it directs. @var{expr} is an agent expression, as described in
31657 @ref{Agent Expressions}. Each byte of the expression is encoded as a
31658 two-digit hex number in the packet; @var{len} is the number of bytes
31659 in the expression (and thus one-half the number of hex digits in the
31664 Any number of actions may be packed together in a single @samp{QTDP}
31665 packet, as long as the packet does not exceed the maximum packet
31666 length (400 bytes, for many stubs). There may be only one @samp{R}
31667 action per tracepoint, and it must precede any @samp{M} or @samp{X}
31668 actions. Any registers referred to by @samp{M} and @samp{X} actions
31669 must be collected by a preceding @samp{R} action. (The
31670 ``while-stepping'' actions are treated as if they were attached to a
31671 separate tracepoint, as far as these restrictions are concerned.)
31676 The packet was understood and carried out.
31678 The packet was not recognized.
31681 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
31682 @cindex @samp{QTDPsrc} packet
31683 Specify a source string of tracepoint @var{n} at address @var{addr}.
31684 This is useful to get accurate reproduction of the tracepoints
31685 originally downloaded at the beginning of the trace run. @var{type}
31686 is the name of the tracepoint part, such as @samp{cond} for the
31687 tracepoint's conditional expression (see below for a list of types), while
31688 @var{bytes} is the string, encoded in hexadecimal.
31690 @var{start} is the offset of the @var{bytes} within the overall source
31691 string, while @var{slen} is the total length of the source string.
31692 This is intended for handling source strings that are longer than will
31693 fit in a single packet.
31694 @c Add detailed example when this info is moved into a dedicated
31695 @c tracepoint descriptions section.
31697 The available string types are @samp{at} for the location,
31698 @samp{cond} for the conditional, and @samp{cmd} for an action command.
31699 @value{GDBN} sends a separate packet for each command in the action
31700 list, in the same order in which the commands are stored in the list.
31702 The target does not need to do anything with source strings except
31703 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
31706 Although this packet is optional, and @value{GDBN} will only send it
31707 if the target replies with @samp{TracepointSource} @xref{General
31708 Query Packets}, it makes both disconnected tracing and trace files
31709 much easier to use. Otherwise the user must be careful that the
31710 tracepoints in effect while looking at trace frames are identical to
31711 the ones in effect during the trace run; even a small discrepancy
31712 could cause @samp{tdump} not to work, or a particular trace frame not
31715 @item QTDV:@var{n}:@var{value}
31716 @cindex define trace state variable, remote request
31717 @cindex @samp{QTDV} packet
31718 Create a new trace state variable, number @var{n}, with an initial
31719 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
31720 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
31721 the option of not using this packet for initial values of zero; the
31722 target should simply create the trace state variables as they are
31723 mentioned in expressions.
31725 @item QTFrame:@var{n}
31726 Select the @var{n}'th tracepoint frame from the buffer, and use the
31727 register and memory contents recorded there to answer subsequent
31728 request packets from @value{GDBN}.
31730 A successful reply from the stub indicates that the stub has found the
31731 requested frame. The response is a series of parts, concatenated
31732 without separators, describing the frame we selected. Each part has
31733 one of the following forms:
31737 The selected frame is number @var{n} in the trace frame buffer;
31738 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
31739 was no frame matching the criteria in the request packet.
31742 The selected trace frame records a hit of tracepoint number @var{t};
31743 @var{t} is a hexadecimal number.
31747 @item QTFrame:pc:@var{addr}
31748 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31749 currently selected frame whose PC is @var{addr};
31750 @var{addr} is a hexadecimal number.
31752 @item QTFrame:tdp:@var{t}
31753 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31754 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
31755 is a hexadecimal number.
31757 @item QTFrame:range:@var{start}:@var{end}
31758 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31759 currently selected frame whose PC is between @var{start} (inclusive)
31760 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
31763 @item QTFrame:outside:@var{start}:@var{end}
31764 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
31765 frame @emph{outside} the given range of addresses (exclusive).
31768 Begin the tracepoint experiment. Begin collecting data from tracepoint
31769 hits in the trace frame buffer.
31772 End the tracepoint experiment. Stop collecting trace frames.
31775 Clear the table of tracepoints, and empty the trace frame buffer.
31777 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
31778 Establish the given ranges of memory as ``transparent''. The stub
31779 will answer requests for these ranges from memory's current contents,
31780 if they were not collected as part of the tracepoint hit.
31782 @value{GDBN} uses this to mark read-only regions of memory, like those
31783 containing program code. Since these areas never change, they should
31784 still have the same contents they did when the tracepoint was hit, so
31785 there's no reason for the stub to refuse to provide their contents.
31787 @item QTDisconnected:@var{value}
31788 Set the choice to what to do with the tracing run when @value{GDBN}
31789 disconnects from the target. A @var{value} of 1 directs the target to
31790 continue the tracing run, while 0 tells the target to stop tracing if
31791 @value{GDBN} is no longer in the picture.
31794 Ask the stub if there is a trace experiment running right now.
31796 The reply has the form:
31800 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
31801 @var{running} is a single digit @code{1} if the trace is presently
31802 running, or @code{0} if not. It is followed by semicolon-separated
31803 optional fields that an agent may use to report additional status.
31807 If the trace is not running, the agent may report any of several
31808 explanations as one of the optional fields:
31813 No trace has been run yet.
31816 The trace was stopped by a user-originated stop command.
31819 The trace stopped because the trace buffer filled up.
31821 @item tdisconnected:0
31822 The trace stopped because @value{GDBN} disconnected from the target.
31824 @item tpasscount:@var{tpnum}
31825 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
31827 @item terror:@var{text}:@var{tpnum}
31828 The trace stopped because tracepoint @var{tpnum} had an error. The
31829 string @var{text} is available to describe the nature of the error
31830 (for instance, a divide by zero in the condition expression).
31831 @var{text} is hex encoded.
31834 The trace stopped for some other reason.
31838 Additional optional fields supply statistical and other information.
31839 Although not required, they are extremely useful for users monitoring
31840 the progress of a trace run. If a trace has stopped, and these
31841 numbers are reported, they must reflect the state of the just-stopped
31846 @item tframes:@var{n}
31847 The number of trace frames in the buffer.
31849 @item tcreated:@var{n}
31850 The total number of trace frames created during the run. This may
31851 be larger than the trace frame count, if the buffer is circular.
31853 @item tsize:@var{n}
31854 The total size of the trace buffer, in bytes.
31856 @item tfree:@var{n}
31857 The number of bytes still unused in the buffer.
31859 @item circular:@var{n}
31860 The value of the circular trace buffer flag. @code{1} means that the
31861 trace buffer is circular and old trace frames will be discarded if
31862 necessary to make room, @code{0} means that the trace buffer is linear
31865 @item disconn:@var{n}
31866 The value of the disconnected tracing flag. @code{1} means that
31867 tracing will continue after @value{GDBN} disconnects, @code{0} means
31868 that the trace run will stop.
31872 @item qTV:@var{var}
31873 @cindex trace state variable value, remote request
31874 @cindex @samp{qTV} packet
31875 Ask the stub for the value of the trace state variable number @var{var}.
31880 The value of the variable is @var{value}. This will be the current
31881 value of the variable if the user is examining a running target, or a
31882 saved value if the variable was collected in the trace frame that the
31883 user is looking at. Note that multiple requests may result in
31884 different reply values, such as when requesting values while the
31885 program is running.
31888 The value of the variable is unknown. This would occur, for example,
31889 if the user is examining a trace frame in which the requested variable
31895 These packets request data about tracepoints that are being used by
31896 the target. @value{GDBN} sends @code{qTfP} to get the first piece
31897 of data, and multiple @code{qTsP} to get additional pieces. Replies
31898 to these packets generally take the form of the @code{QTDP} packets
31899 that define tracepoints. (FIXME add detailed syntax)
31903 These packets request data about trace state variables that are on the
31904 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
31905 and multiple @code{qTsV} to get additional variables. Replies to
31906 these packets follow the syntax of the @code{QTDV} packets that define
31907 trace state variables.
31909 @item QTSave:@var{filename}
31910 This packet directs the target to save trace data to the file name
31911 @var{filename} in the target's filesystem. @var{filename} is encoded
31912 as a hex string; the interpretation of the file name (relative vs
31913 absolute, wild cards, etc) is up to the target.
31915 @item qTBuffer:@var{offset},@var{len}
31916 Return up to @var{len} bytes of the current contents of trace buffer,
31917 starting at @var{offset}. The trace buffer is treated as if it were
31918 a contiguous collection of traceframes, as per the trace file format.
31919 The reply consists as many hex-encoded bytes as the target can deliver
31920 in a packet; it is not an error to return fewer than were asked for.
31921 A reply consisting of just @code{l} indicates that no bytes are
31924 @item QTBuffer:circular:@var{value}
31925 This packet directs the target to use a circular trace buffer if
31926 @var{value} is 1, or a linear buffer if the value is 0.
31930 @node Host I/O Packets
31931 @section Host I/O Packets
31932 @cindex Host I/O, remote protocol
31933 @cindex file transfer, remote protocol
31935 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
31936 operations on the far side of a remote link. For example, Host I/O is
31937 used to upload and download files to a remote target with its own
31938 filesystem. Host I/O uses the same constant values and data structure
31939 layout as the target-initiated File-I/O protocol. However, the
31940 Host I/O packets are structured differently. The target-initiated
31941 protocol relies on target memory to store parameters and buffers.
31942 Host I/O requests are initiated by @value{GDBN}, and the
31943 target's memory is not involved. @xref{File-I/O Remote Protocol
31944 Extension}, for more details on the target-initiated protocol.
31946 The Host I/O request packets all encode a single operation along with
31947 its arguments. They have this format:
31951 @item vFile:@var{operation}: @var{parameter}@dots{}
31952 @var{operation} is the name of the particular request; the target
31953 should compare the entire packet name up to the second colon when checking
31954 for a supported operation. The format of @var{parameter} depends on
31955 the operation. Numbers are always passed in hexadecimal. Negative
31956 numbers have an explicit minus sign (i.e.@: two's complement is not
31957 used). Strings (e.g.@: filenames) are encoded as a series of
31958 hexadecimal bytes. The last argument to a system call may be a
31959 buffer of escaped binary data (@pxref{Binary Data}).
31963 The valid responses to Host I/O packets are:
31967 @item F @var{result} [, @var{errno}] [; @var{attachment}]
31968 @var{result} is the integer value returned by this operation, usually
31969 non-negative for success and -1 for errors. If an error has occured,
31970 @var{errno} will be included in the result. @var{errno} will have a
31971 value defined by the File-I/O protocol (@pxref{Errno Values}). For
31972 operations which return data, @var{attachment} supplies the data as a
31973 binary buffer. Binary buffers in response packets are escaped in the
31974 normal way (@pxref{Binary Data}). See the individual packet
31975 documentation for the interpretation of @var{result} and
31979 An empty response indicates that this operation is not recognized.
31983 These are the supported Host I/O operations:
31986 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
31987 Open a file at @var{pathname} and return a file descriptor for it, or
31988 return -1 if an error occurs. @var{pathname} is a string,
31989 @var{flags} is an integer indicating a mask of open flags
31990 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
31991 of mode bits to use if the file is created (@pxref{mode_t Values}).
31992 @xref{open}, for details of the open flags and mode values.
31994 @item vFile:close: @var{fd}
31995 Close the open file corresponding to @var{fd} and return 0, or
31996 -1 if an error occurs.
31998 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
31999 Read data from the open file corresponding to @var{fd}. Up to
32000 @var{count} bytes will be read from the file, starting at @var{offset}
32001 relative to the start of the file. The target may read fewer bytes;
32002 common reasons include packet size limits and an end-of-file
32003 condition. The number of bytes read is returned. Zero should only be
32004 returned for a successful read at the end of the file, or if
32005 @var{count} was zero.
32007 The data read should be returned as a binary attachment on success.
32008 If zero bytes were read, the response should include an empty binary
32009 attachment (i.e.@: a trailing semicolon). The return value is the
32010 number of target bytes read; the binary attachment may be longer if
32011 some characters were escaped.
32013 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
32014 Write @var{data} (a binary buffer) to the open file corresponding
32015 to @var{fd}. Start the write at @var{offset} from the start of the
32016 file. Unlike many @code{write} system calls, there is no
32017 separate @var{count} argument; the length of @var{data} in the
32018 packet is used. @samp{vFile:write} returns the number of bytes written,
32019 which may be shorter than the length of @var{data}, or -1 if an
32022 @item vFile:unlink: @var{pathname}
32023 Delete the file at @var{pathname} on the target. Return 0,
32024 or -1 if an error occurs. @var{pathname} is a string.
32029 @section Interrupts
32030 @cindex interrupts (remote protocol)
32032 When a program on the remote target is running, @value{GDBN} may
32033 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
32034 a @code{BREAK} followed by @code{g},
32035 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
32037 The precise meaning of @code{BREAK} is defined by the transport
32038 mechanism and may, in fact, be undefined. @value{GDBN} does not
32039 currently define a @code{BREAK} mechanism for any of the network
32040 interfaces except for TCP, in which case @value{GDBN} sends the
32041 @code{telnet} BREAK sequence.
32043 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
32044 transport mechanisms. It is represented by sending the single byte
32045 @code{0x03} without any of the usual packet overhead described in
32046 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
32047 transmitted as part of a packet, it is considered to be packet data
32048 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
32049 (@pxref{X packet}), used for binary downloads, may include an unescaped
32050 @code{0x03} as part of its packet.
32052 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
32053 When Linux kernel receives this sequence from serial port,
32054 it stops execution and connects to gdb.
32056 Stubs are not required to recognize these interrupt mechanisms and the
32057 precise meaning associated with receipt of the interrupt is
32058 implementation defined. If the target supports debugging of multiple
32059 threads and/or processes, it should attempt to interrupt all
32060 currently-executing threads and processes.
32061 If the stub is successful at interrupting the
32062 running program, it should send one of the stop
32063 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
32064 of successfully stopping the program in all-stop mode, and a stop reply
32065 for each stopped thread in non-stop mode.
32066 Interrupts received while the
32067 program is stopped are discarded.
32069 @node Notification Packets
32070 @section Notification Packets
32071 @cindex notification packets
32072 @cindex packets, notification
32074 The @value{GDBN} remote serial protocol includes @dfn{notifications},
32075 packets that require no acknowledgment. Both the GDB and the stub
32076 may send notifications (although the only notifications defined at
32077 present are sent by the stub). Notifications carry information
32078 without incurring the round-trip latency of an acknowledgment, and so
32079 are useful for low-impact communications where occasional packet loss
32082 A notification packet has the form @samp{% @var{data} #
32083 @var{checksum}}, where @var{data} is the content of the notification,
32084 and @var{checksum} is a checksum of @var{data}, computed and formatted
32085 as for ordinary @value{GDBN} packets. A notification's @var{data}
32086 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
32087 receiving a notification, the recipient sends no @samp{+} or @samp{-}
32088 to acknowledge the notification's receipt or to report its corruption.
32090 Every notification's @var{data} begins with a name, which contains no
32091 colon characters, followed by a colon character.
32093 Recipients should silently ignore corrupted notifications and
32094 notifications they do not understand. Recipients should restart
32095 timeout periods on receipt of a well-formed notification, whether or
32096 not they understand it.
32098 Senders should only send the notifications described here when this
32099 protocol description specifies that they are permitted. In the
32100 future, we may extend the protocol to permit existing notifications in
32101 new contexts; this rule helps older senders avoid confusing newer
32104 (Older versions of @value{GDBN} ignore bytes received until they see
32105 the @samp{$} byte that begins an ordinary packet, so new stubs may
32106 transmit notifications without fear of confusing older clients. There
32107 are no notifications defined for @value{GDBN} to send at the moment, but we
32108 assume that most older stubs would ignore them, as well.)
32110 The following notification packets from the stub to @value{GDBN} are
32114 @item Stop: @var{reply}
32115 Report an asynchronous stop event in non-stop mode.
32116 The @var{reply} has the form of a stop reply, as
32117 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
32118 for information on how these notifications are acknowledged by
32122 @node Remote Non-Stop
32123 @section Remote Protocol Support for Non-Stop Mode
32125 @value{GDBN}'s remote protocol supports non-stop debugging of
32126 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
32127 supports non-stop mode, it should report that to @value{GDBN} by including
32128 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
32130 @value{GDBN} typically sends a @samp{QNonStop} packet only when
32131 establishing a new connection with the stub. Entering non-stop mode
32132 does not alter the state of any currently-running threads, but targets
32133 must stop all threads in any already-attached processes when entering
32134 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
32135 probe the target state after a mode change.
32137 In non-stop mode, when an attached process encounters an event that
32138 would otherwise be reported with a stop reply, it uses the
32139 asynchronous notification mechanism (@pxref{Notification Packets}) to
32140 inform @value{GDBN}. In contrast to all-stop mode, where all threads
32141 in all processes are stopped when a stop reply is sent, in non-stop
32142 mode only the thread reporting the stop event is stopped. That is,
32143 when reporting a @samp{S} or @samp{T} response to indicate completion
32144 of a step operation, hitting a breakpoint, or a fault, only the
32145 affected thread is stopped; any other still-running threads continue
32146 to run. When reporting a @samp{W} or @samp{X} response, all running
32147 threads belonging to other attached processes continue to run.
32149 Only one stop reply notification at a time may be pending; if
32150 additional stop events occur before @value{GDBN} has acknowledged the
32151 previous notification, they must be queued by the stub for later
32152 synchronous transmission in response to @samp{vStopped} packets from
32153 @value{GDBN}. Because the notification mechanism is unreliable,
32154 the stub is permitted to resend a stop reply notification
32155 if it believes @value{GDBN} may not have received it. @value{GDBN}
32156 ignores additional stop reply notifications received before it has
32157 finished processing a previous notification and the stub has completed
32158 sending any queued stop events.
32160 Otherwise, @value{GDBN} must be prepared to receive a stop reply
32161 notification at any time. Specifically, they may appear when
32162 @value{GDBN} is not otherwise reading input from the stub, or when
32163 @value{GDBN} is expecting to read a normal synchronous response or a
32164 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
32165 Notification packets are distinct from any other communication from
32166 the stub so there is no ambiguity.
32168 After receiving a stop reply notification, @value{GDBN} shall
32169 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
32170 as a regular, synchronous request to the stub. Such acknowledgment
32171 is not required to happen immediately, as @value{GDBN} is permitted to
32172 send other, unrelated packets to the stub first, which the stub should
32175 Upon receiving a @samp{vStopped} packet, if the stub has other queued
32176 stop events to report to @value{GDBN}, it shall respond by sending a
32177 normal stop reply response. @value{GDBN} shall then send another
32178 @samp{vStopped} packet to solicit further responses; again, it is
32179 permitted to send other, unrelated packets as well which the stub
32180 should process normally.
32182 If the stub receives a @samp{vStopped} packet and there are no
32183 additional stop events to report, the stub shall return an @samp{OK}
32184 response. At this point, if further stop events occur, the stub shall
32185 send a new stop reply notification, @value{GDBN} shall accept the
32186 notification, and the process shall be repeated.
32188 In non-stop mode, the target shall respond to the @samp{?} packet as
32189 follows. First, any incomplete stop reply notification/@samp{vStopped}
32190 sequence in progress is abandoned. The target must begin a new
32191 sequence reporting stop events for all stopped threads, whether or not
32192 it has previously reported those events to @value{GDBN}. The first
32193 stop reply is sent as a synchronous reply to the @samp{?} packet, and
32194 subsequent stop replies are sent as responses to @samp{vStopped} packets
32195 using the mechanism described above. The target must not send
32196 asynchronous stop reply notifications until the sequence is complete.
32197 If all threads are running when the target receives the @samp{?} packet,
32198 or if the target is not attached to any process, it shall respond
32201 @node Packet Acknowledgment
32202 @section Packet Acknowledgment
32204 @cindex acknowledgment, for @value{GDBN} remote
32205 @cindex packet acknowledgment, for @value{GDBN} remote
32206 By default, when either the host or the target machine receives a packet,
32207 the first response expected is an acknowledgment: either @samp{+} (to indicate
32208 the package was received correctly) or @samp{-} (to request retransmission).
32209 This mechanism allows the @value{GDBN} remote protocol to operate over
32210 unreliable transport mechanisms, such as a serial line.
32212 In cases where the transport mechanism is itself reliable (such as a pipe or
32213 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
32214 It may be desirable to disable them in that case to reduce communication
32215 overhead, or for other reasons. This can be accomplished by means of the
32216 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
32218 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
32219 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
32220 and response format still includes the normal checksum, as described in
32221 @ref{Overview}, but the checksum may be ignored by the receiver.
32223 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
32224 no-acknowledgment mode, it should report that to @value{GDBN}
32225 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
32226 @pxref{qSupported}.
32227 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
32228 disabled via the @code{set remote noack-packet off} command
32229 (@pxref{Remote Configuration}),
32230 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
32231 Only then may the stub actually turn off packet acknowledgments.
32232 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
32233 response, which can be safely ignored by the stub.
32235 Note that @code{set remote noack-packet} command only affects negotiation
32236 between @value{GDBN} and the stub when subsequent connections are made;
32237 it does not affect the protocol acknowledgment state for any current
32239 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
32240 new connection is established,
32241 there is also no protocol request to re-enable the acknowledgments
32242 for the current connection, once disabled.
32247 Example sequence of a target being re-started. Notice how the restart
32248 does not get any direct output:
32253 @emph{target restarts}
32256 <- @code{T001:1234123412341234}
32260 Example sequence of a target being stepped by a single instruction:
32263 -> @code{G1445@dots{}}
32268 <- @code{T001:1234123412341234}
32272 <- @code{1455@dots{}}
32276 @node File-I/O Remote Protocol Extension
32277 @section File-I/O Remote Protocol Extension
32278 @cindex File-I/O remote protocol extension
32281 * File-I/O Overview::
32282 * Protocol Basics::
32283 * The F Request Packet::
32284 * The F Reply Packet::
32285 * The Ctrl-C Message::
32287 * List of Supported Calls::
32288 * Protocol-specific Representation of Datatypes::
32290 * File-I/O Examples::
32293 @node File-I/O Overview
32294 @subsection File-I/O Overview
32295 @cindex file-i/o overview
32297 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
32298 target to use the host's file system and console I/O to perform various
32299 system calls. System calls on the target system are translated into a
32300 remote protocol packet to the host system, which then performs the needed
32301 actions and returns a response packet to the target system.
32302 This simulates file system operations even on targets that lack file systems.
32304 The protocol is defined to be independent of both the host and target systems.
32305 It uses its own internal representation of datatypes and values. Both
32306 @value{GDBN} and the target's @value{GDBN} stub are responsible for
32307 translating the system-dependent value representations into the internal
32308 protocol representations when data is transmitted.
32310 The communication is synchronous. A system call is possible only when
32311 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
32312 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
32313 the target is stopped to allow deterministic access to the target's
32314 memory. Therefore File-I/O is not interruptible by target signals. On
32315 the other hand, it is possible to interrupt File-I/O by a user interrupt
32316 (@samp{Ctrl-C}) within @value{GDBN}.
32318 The target's request to perform a host system call does not finish
32319 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
32320 after finishing the system call, the target returns to continuing the
32321 previous activity (continue, step). No additional continue or step
32322 request from @value{GDBN} is required.
32325 (@value{GDBP}) continue
32326 <- target requests 'system call X'
32327 target is stopped, @value{GDBN} executes system call
32328 -> @value{GDBN} returns result
32329 ... target continues, @value{GDBN} returns to wait for the target
32330 <- target hits breakpoint and sends a Txx packet
32333 The protocol only supports I/O on the console and to regular files on
32334 the host file system. Character or block special devices, pipes,
32335 named pipes, sockets or any other communication method on the host
32336 system are not supported by this protocol.
32338 File I/O is not supported in non-stop mode.
32340 @node Protocol Basics
32341 @subsection Protocol Basics
32342 @cindex protocol basics, file-i/o
32344 The File-I/O protocol uses the @code{F} packet as the request as well
32345 as reply packet. Since a File-I/O system call can only occur when
32346 @value{GDBN} is waiting for a response from the continuing or stepping target,
32347 the File-I/O request is a reply that @value{GDBN} has to expect as a result
32348 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
32349 This @code{F} packet contains all information needed to allow @value{GDBN}
32350 to call the appropriate host system call:
32354 A unique identifier for the requested system call.
32357 All parameters to the system call. Pointers are given as addresses
32358 in the target memory address space. Pointers to strings are given as
32359 pointer/length pair. Numerical values are given as they are.
32360 Numerical control flags are given in a protocol-specific representation.
32364 At this point, @value{GDBN} has to perform the following actions.
32368 If the parameters include pointer values to data needed as input to a
32369 system call, @value{GDBN} requests this data from the target with a
32370 standard @code{m} packet request. This additional communication has to be
32371 expected by the target implementation and is handled as any other @code{m}
32375 @value{GDBN} translates all value from protocol representation to host
32376 representation as needed. Datatypes are coerced into the host types.
32379 @value{GDBN} calls the system call.
32382 It then coerces datatypes back to protocol representation.
32385 If the system call is expected to return data in buffer space specified
32386 by pointer parameters to the call, the data is transmitted to the
32387 target using a @code{M} or @code{X} packet. This packet has to be expected
32388 by the target implementation and is handled as any other @code{M} or @code{X}
32393 Eventually @value{GDBN} replies with another @code{F} packet which contains all
32394 necessary information for the target to continue. This at least contains
32401 @code{errno}, if has been changed by the system call.
32408 After having done the needed type and value coercion, the target continues
32409 the latest continue or step action.
32411 @node The F Request Packet
32412 @subsection The @code{F} Request Packet
32413 @cindex file-i/o request packet
32414 @cindex @code{F} request packet
32416 The @code{F} request packet has the following format:
32419 @item F@var{call-id},@var{parameter@dots{}}
32421 @var{call-id} is the identifier to indicate the host system call to be called.
32422 This is just the name of the function.
32424 @var{parameter@dots{}} are the parameters to the system call.
32425 Parameters are hexadecimal integer values, either the actual values in case
32426 of scalar datatypes, pointers to target buffer space in case of compound
32427 datatypes and unspecified memory areas, or pointer/length pairs in case
32428 of string parameters. These are appended to the @var{call-id} as a
32429 comma-delimited list. All values are transmitted in ASCII
32430 string representation, pointer/length pairs separated by a slash.
32436 @node The F Reply Packet
32437 @subsection The @code{F} Reply Packet
32438 @cindex file-i/o reply packet
32439 @cindex @code{F} reply packet
32441 The @code{F} reply packet has the following format:
32445 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
32447 @var{retcode} is the return code of the system call as hexadecimal value.
32449 @var{errno} is the @code{errno} set by the call, in protocol-specific
32451 This parameter can be omitted if the call was successful.
32453 @var{Ctrl-C flag} is only sent if the user requested a break. In this
32454 case, @var{errno} must be sent as well, even if the call was successful.
32455 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
32462 or, if the call was interrupted before the host call has been performed:
32469 assuming 4 is the protocol-specific representation of @code{EINTR}.
32474 @node The Ctrl-C Message
32475 @subsection The @samp{Ctrl-C} Message
32476 @cindex ctrl-c message, in file-i/o protocol
32478 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
32479 reply packet (@pxref{The F Reply Packet}),
32480 the target should behave as if it had
32481 gotten a break message. The meaning for the target is ``system call
32482 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
32483 (as with a break message) and return to @value{GDBN} with a @code{T02}
32486 It's important for the target to know in which
32487 state the system call was interrupted. There are two possible cases:
32491 The system call hasn't been performed on the host yet.
32494 The system call on the host has been finished.
32498 These two states can be distinguished by the target by the value of the
32499 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
32500 call hasn't been performed. This is equivalent to the @code{EINTR} handling
32501 on POSIX systems. In any other case, the target may presume that the
32502 system call has been finished --- successfully or not --- and should behave
32503 as if the break message arrived right after the system call.
32505 @value{GDBN} must behave reliably. If the system call has not been called
32506 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
32507 @code{errno} in the packet. If the system call on the host has been finished
32508 before the user requests a break, the full action must be finished by
32509 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
32510 The @code{F} packet may only be sent when either nothing has happened
32511 or the full action has been completed.
32514 @subsection Console I/O
32515 @cindex console i/o as part of file-i/o
32517 By default and if not explicitly closed by the target system, the file
32518 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
32519 on the @value{GDBN} console is handled as any other file output operation
32520 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
32521 by @value{GDBN} so that after the target read request from file descriptor
32522 0 all following typing is buffered until either one of the following
32527 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
32529 system call is treated as finished.
32532 The user presses @key{RET}. This is treated as end of input with a trailing
32536 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
32537 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
32541 If the user has typed more characters than fit in the buffer given to
32542 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
32543 either another @code{read(0, @dots{})} is requested by the target, or debugging
32544 is stopped at the user's request.
32547 @node List of Supported Calls
32548 @subsection List of Supported Calls
32549 @cindex list of supported file-i/o calls
32566 @unnumberedsubsubsec open
32567 @cindex open, file-i/o system call
32572 int open(const char *pathname, int flags);
32573 int open(const char *pathname, int flags, mode_t mode);
32577 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
32580 @var{flags} is the bitwise @code{OR} of the following values:
32584 If the file does not exist it will be created. The host
32585 rules apply as far as file ownership and time stamps
32589 When used with @code{O_CREAT}, if the file already exists it is
32590 an error and open() fails.
32593 If the file already exists and the open mode allows
32594 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
32595 truncated to zero length.
32598 The file is opened in append mode.
32601 The file is opened for reading only.
32604 The file is opened for writing only.
32607 The file is opened for reading and writing.
32611 Other bits are silently ignored.
32615 @var{mode} is the bitwise @code{OR} of the following values:
32619 User has read permission.
32622 User has write permission.
32625 Group has read permission.
32628 Group has write permission.
32631 Others have read permission.
32634 Others have write permission.
32638 Other bits are silently ignored.
32641 @item Return value:
32642 @code{open} returns the new file descriptor or -1 if an error
32649 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
32652 @var{pathname} refers to a directory.
32655 The requested access is not allowed.
32658 @var{pathname} was too long.
32661 A directory component in @var{pathname} does not exist.
32664 @var{pathname} refers to a device, pipe, named pipe or socket.
32667 @var{pathname} refers to a file on a read-only filesystem and
32668 write access was requested.
32671 @var{pathname} is an invalid pointer value.
32674 No space on device to create the file.
32677 The process already has the maximum number of files open.
32680 The limit on the total number of files open on the system
32684 The call was interrupted by the user.
32690 @unnumberedsubsubsec close
32691 @cindex close, file-i/o system call
32700 @samp{Fclose,@var{fd}}
32702 @item Return value:
32703 @code{close} returns zero on success, or -1 if an error occurred.
32709 @var{fd} isn't a valid open file descriptor.
32712 The call was interrupted by the user.
32718 @unnumberedsubsubsec read
32719 @cindex read, file-i/o system call
32724 int read(int fd, void *buf, unsigned int count);
32728 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
32730 @item Return value:
32731 On success, the number of bytes read is returned.
32732 Zero indicates end of file. If count is zero, read
32733 returns zero as well. On error, -1 is returned.
32739 @var{fd} is not a valid file descriptor or is not open for
32743 @var{bufptr} is an invalid pointer value.
32746 The call was interrupted by the user.
32752 @unnumberedsubsubsec write
32753 @cindex write, file-i/o system call
32758 int write(int fd, const void *buf, unsigned int count);
32762 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
32764 @item Return value:
32765 On success, the number of bytes written are returned.
32766 Zero indicates nothing was written. On error, -1
32773 @var{fd} is not a valid file descriptor or is not open for
32777 @var{bufptr} is an invalid pointer value.
32780 An attempt was made to write a file that exceeds the
32781 host-specific maximum file size allowed.
32784 No space on device to write the data.
32787 The call was interrupted by the user.
32793 @unnumberedsubsubsec lseek
32794 @cindex lseek, file-i/o system call
32799 long lseek (int fd, long offset, int flag);
32803 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
32805 @var{flag} is one of:
32809 The offset is set to @var{offset} bytes.
32812 The offset is set to its current location plus @var{offset}
32816 The offset is set to the size of the file plus @var{offset}
32820 @item Return value:
32821 On success, the resulting unsigned offset in bytes from
32822 the beginning of the file is returned. Otherwise, a
32823 value of -1 is returned.
32829 @var{fd} is not a valid open file descriptor.
32832 @var{fd} is associated with the @value{GDBN} console.
32835 @var{flag} is not a proper value.
32838 The call was interrupted by the user.
32844 @unnumberedsubsubsec rename
32845 @cindex rename, file-i/o system call
32850 int rename(const char *oldpath, const char *newpath);
32854 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
32856 @item Return value:
32857 On success, zero is returned. On error, -1 is returned.
32863 @var{newpath} is an existing directory, but @var{oldpath} is not a
32867 @var{newpath} is a non-empty directory.
32870 @var{oldpath} or @var{newpath} is a directory that is in use by some
32874 An attempt was made to make a directory a subdirectory
32878 A component used as a directory in @var{oldpath} or new
32879 path is not a directory. Or @var{oldpath} is a directory
32880 and @var{newpath} exists but is not a directory.
32883 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
32886 No access to the file or the path of the file.
32890 @var{oldpath} or @var{newpath} was too long.
32893 A directory component in @var{oldpath} or @var{newpath} does not exist.
32896 The file is on a read-only filesystem.
32899 The device containing the file has no room for the new
32903 The call was interrupted by the user.
32909 @unnumberedsubsubsec unlink
32910 @cindex unlink, file-i/o system call
32915 int unlink(const char *pathname);
32919 @samp{Funlink,@var{pathnameptr}/@var{len}}
32921 @item Return value:
32922 On success, zero is returned. On error, -1 is returned.
32928 No access to the file or the path of the file.
32931 The system does not allow unlinking of directories.
32934 The file @var{pathname} cannot be unlinked because it's
32935 being used by another process.
32938 @var{pathnameptr} is an invalid pointer value.
32941 @var{pathname} was too long.
32944 A directory component in @var{pathname} does not exist.
32947 A component of the path is not a directory.
32950 The file is on a read-only filesystem.
32953 The call was interrupted by the user.
32959 @unnumberedsubsubsec stat/fstat
32960 @cindex fstat, file-i/o system call
32961 @cindex stat, file-i/o system call
32966 int stat(const char *pathname, struct stat *buf);
32967 int fstat(int fd, struct stat *buf);
32971 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
32972 @samp{Ffstat,@var{fd},@var{bufptr}}
32974 @item Return value:
32975 On success, zero is returned. On error, -1 is returned.
32981 @var{fd} is not a valid open file.
32984 A directory component in @var{pathname} does not exist or the
32985 path is an empty string.
32988 A component of the path is not a directory.
32991 @var{pathnameptr} is an invalid pointer value.
32994 No access to the file or the path of the file.
32997 @var{pathname} was too long.
33000 The call was interrupted by the user.
33006 @unnumberedsubsubsec gettimeofday
33007 @cindex gettimeofday, file-i/o system call
33012 int gettimeofday(struct timeval *tv, void *tz);
33016 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
33018 @item Return value:
33019 On success, 0 is returned, -1 otherwise.
33025 @var{tz} is a non-NULL pointer.
33028 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
33034 @unnumberedsubsubsec isatty
33035 @cindex isatty, file-i/o system call
33040 int isatty(int fd);
33044 @samp{Fisatty,@var{fd}}
33046 @item Return value:
33047 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
33053 The call was interrupted by the user.
33058 Note that the @code{isatty} call is treated as a special case: it returns
33059 1 to the target if the file descriptor is attached
33060 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
33061 would require implementing @code{ioctl} and would be more complex than
33066 @unnumberedsubsubsec system
33067 @cindex system, file-i/o system call
33072 int system(const char *command);
33076 @samp{Fsystem,@var{commandptr}/@var{len}}
33078 @item Return value:
33079 If @var{len} is zero, the return value indicates whether a shell is
33080 available. A zero return value indicates a shell is not available.
33081 For non-zero @var{len}, the value returned is -1 on error and the
33082 return status of the command otherwise. Only the exit status of the
33083 command is returned, which is extracted from the host's @code{system}
33084 return value by calling @code{WEXITSTATUS(retval)}. In case
33085 @file{/bin/sh} could not be executed, 127 is returned.
33091 The call was interrupted by the user.
33096 @value{GDBN} takes over the full task of calling the necessary host calls
33097 to perform the @code{system} call. The return value of @code{system} on
33098 the host is simplified before it's returned
33099 to the target. Any termination signal information from the child process
33100 is discarded, and the return value consists
33101 entirely of the exit status of the called command.
33103 Due to security concerns, the @code{system} call is by default refused
33104 by @value{GDBN}. The user has to allow this call explicitly with the
33105 @code{set remote system-call-allowed 1} command.
33108 @item set remote system-call-allowed
33109 @kindex set remote system-call-allowed
33110 Control whether to allow the @code{system} calls in the File I/O
33111 protocol for the remote target. The default is zero (disabled).
33113 @item show remote system-call-allowed
33114 @kindex show remote system-call-allowed
33115 Show whether the @code{system} calls are allowed in the File I/O
33119 @node Protocol-specific Representation of Datatypes
33120 @subsection Protocol-specific Representation of Datatypes
33121 @cindex protocol-specific representation of datatypes, in file-i/o protocol
33124 * Integral Datatypes::
33126 * Memory Transfer::
33131 @node Integral Datatypes
33132 @unnumberedsubsubsec Integral Datatypes
33133 @cindex integral datatypes, in file-i/o protocol
33135 The integral datatypes used in the system calls are @code{int},
33136 @code{unsigned int}, @code{long}, @code{unsigned long},
33137 @code{mode_t}, and @code{time_t}.
33139 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
33140 implemented as 32 bit values in this protocol.
33142 @code{long} and @code{unsigned long} are implemented as 64 bit types.
33144 @xref{Limits}, for corresponding MIN and MAX values (similar to those
33145 in @file{limits.h}) to allow range checking on host and target.
33147 @code{time_t} datatypes are defined as seconds since the Epoch.
33149 All integral datatypes transferred as part of a memory read or write of a
33150 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
33153 @node Pointer Values
33154 @unnumberedsubsubsec Pointer Values
33155 @cindex pointer values, in file-i/o protocol
33157 Pointers to target data are transmitted as they are. An exception
33158 is made for pointers to buffers for which the length isn't
33159 transmitted as part of the function call, namely strings. Strings
33160 are transmitted as a pointer/length pair, both as hex values, e.g.@:
33167 which is a pointer to data of length 18 bytes at position 0x1aaf.
33168 The length is defined as the full string length in bytes, including
33169 the trailing null byte. For example, the string @code{"hello world"}
33170 at address 0x123456 is transmitted as
33176 @node Memory Transfer
33177 @unnumberedsubsubsec Memory Transfer
33178 @cindex memory transfer, in file-i/o protocol
33180 Structured data which is transferred using a memory read or write (for
33181 example, a @code{struct stat}) is expected to be in a protocol-specific format
33182 with all scalar multibyte datatypes being big endian. Translation to
33183 this representation needs to be done both by the target before the @code{F}
33184 packet is sent, and by @value{GDBN} before
33185 it transfers memory to the target. Transferred pointers to structured
33186 data should point to the already-coerced data at any time.
33190 @unnumberedsubsubsec struct stat
33191 @cindex struct stat, in file-i/o protocol
33193 The buffer of type @code{struct stat} used by the target and @value{GDBN}
33194 is defined as follows:
33198 unsigned int st_dev; /* device */
33199 unsigned int st_ino; /* inode */
33200 mode_t st_mode; /* protection */
33201 unsigned int st_nlink; /* number of hard links */
33202 unsigned int st_uid; /* user ID of owner */
33203 unsigned int st_gid; /* group ID of owner */
33204 unsigned int st_rdev; /* device type (if inode device) */
33205 unsigned long st_size; /* total size, in bytes */
33206 unsigned long st_blksize; /* blocksize for filesystem I/O */
33207 unsigned long st_blocks; /* number of blocks allocated */
33208 time_t st_atime; /* time of last access */
33209 time_t st_mtime; /* time of last modification */
33210 time_t st_ctime; /* time of last change */
33214 The integral datatypes conform to the definitions given in the
33215 appropriate section (see @ref{Integral Datatypes}, for details) so this
33216 structure is of size 64 bytes.
33218 The values of several fields have a restricted meaning and/or
33224 A value of 0 represents a file, 1 the console.
33227 No valid meaning for the target. Transmitted unchanged.
33230 Valid mode bits are described in @ref{Constants}. Any other
33231 bits have currently no meaning for the target.
33236 No valid meaning for the target. Transmitted unchanged.
33241 These values have a host and file system dependent
33242 accuracy. Especially on Windows hosts, the file system may not
33243 support exact timing values.
33246 The target gets a @code{struct stat} of the above representation and is
33247 responsible for coercing it to the target representation before
33250 Note that due to size differences between the host, target, and protocol
33251 representations of @code{struct stat} members, these members could eventually
33252 get truncated on the target.
33254 @node struct timeval
33255 @unnumberedsubsubsec struct timeval
33256 @cindex struct timeval, in file-i/o protocol
33258 The buffer of type @code{struct timeval} used by the File-I/O protocol
33259 is defined as follows:
33263 time_t tv_sec; /* second */
33264 long tv_usec; /* microsecond */
33268 The integral datatypes conform to the definitions given in the
33269 appropriate section (see @ref{Integral Datatypes}, for details) so this
33270 structure is of size 8 bytes.
33273 @subsection Constants
33274 @cindex constants, in file-i/o protocol
33276 The following values are used for the constants inside of the
33277 protocol. @value{GDBN} and target are responsible for translating these
33278 values before and after the call as needed.
33289 @unnumberedsubsubsec Open Flags
33290 @cindex open flags, in file-i/o protocol
33292 All values are given in hexadecimal representation.
33304 @node mode_t Values
33305 @unnumberedsubsubsec mode_t Values
33306 @cindex mode_t values, in file-i/o protocol
33308 All values are given in octal representation.
33325 @unnumberedsubsubsec Errno Values
33326 @cindex errno values, in file-i/o protocol
33328 All values are given in decimal representation.
33353 @code{EUNKNOWN} is used as a fallback error value if a host system returns
33354 any error value not in the list of supported error numbers.
33357 @unnumberedsubsubsec Lseek Flags
33358 @cindex lseek flags, in file-i/o protocol
33367 @unnumberedsubsubsec Limits
33368 @cindex limits, in file-i/o protocol
33370 All values are given in decimal representation.
33373 INT_MIN -2147483648
33375 UINT_MAX 4294967295
33376 LONG_MIN -9223372036854775808
33377 LONG_MAX 9223372036854775807
33378 ULONG_MAX 18446744073709551615
33381 @node File-I/O Examples
33382 @subsection File-I/O Examples
33383 @cindex file-i/o examples
33385 Example sequence of a write call, file descriptor 3, buffer is at target
33386 address 0x1234, 6 bytes should be written:
33389 <- @code{Fwrite,3,1234,6}
33390 @emph{request memory read from target}
33393 @emph{return "6 bytes written"}
33397 Example sequence of a read call, file descriptor 3, buffer is at target
33398 address 0x1234, 6 bytes should be read:
33401 <- @code{Fread,3,1234,6}
33402 @emph{request memory write to target}
33403 -> @code{X1234,6:XXXXXX}
33404 @emph{return "6 bytes read"}
33408 Example sequence of a read call, call fails on the host due to invalid
33409 file descriptor (@code{EBADF}):
33412 <- @code{Fread,3,1234,6}
33416 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
33420 <- @code{Fread,3,1234,6}
33425 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
33429 <- @code{Fread,3,1234,6}
33430 -> @code{X1234,6:XXXXXX}
33434 @node Library List Format
33435 @section Library List Format
33436 @cindex library list format, remote protocol
33438 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
33439 same process as your application to manage libraries. In this case,
33440 @value{GDBN} can use the loader's symbol table and normal memory
33441 operations to maintain a list of shared libraries. On other
33442 platforms, the operating system manages loaded libraries.
33443 @value{GDBN} can not retrieve the list of currently loaded libraries
33444 through memory operations, so it uses the @samp{qXfer:libraries:read}
33445 packet (@pxref{qXfer library list read}) instead. The remote stub
33446 queries the target's operating system and reports which libraries
33449 The @samp{qXfer:libraries:read} packet returns an XML document which
33450 lists loaded libraries and their offsets. Each library has an
33451 associated name and one or more segment or section base addresses,
33452 which report where the library was loaded in memory.
33454 For the common case of libraries that are fully linked binaries, the
33455 library should have a list of segments. If the target supports
33456 dynamic linking of a relocatable object file, its library XML element
33457 should instead include a list of allocated sections. The segment or
33458 section bases are start addresses, not relocation offsets; they do not
33459 depend on the library's link-time base addresses.
33461 @value{GDBN} must be linked with the Expat library to support XML
33462 library lists. @xref{Expat}.
33464 A simple memory map, with one loaded library relocated by a single
33465 offset, looks like this:
33469 <library name="/lib/libc.so.6">
33470 <segment address="0x10000000"/>
33475 Another simple memory map, with one loaded library with three
33476 allocated sections (.text, .data, .bss), looks like this:
33480 <library name="sharedlib.o">
33481 <section address="0x10000000"/>
33482 <section address="0x20000000"/>
33483 <section address="0x30000000"/>
33488 The format of a library list is described by this DTD:
33491 <!-- library-list: Root element with versioning -->
33492 <!ELEMENT library-list (library)*>
33493 <!ATTLIST library-list version CDATA #FIXED "1.0">
33494 <!ELEMENT library (segment*, section*)>
33495 <!ATTLIST library name CDATA #REQUIRED>
33496 <!ELEMENT segment EMPTY>
33497 <!ATTLIST segment address CDATA #REQUIRED>
33498 <!ELEMENT section EMPTY>
33499 <!ATTLIST section address CDATA #REQUIRED>
33502 In addition, segments and section descriptors cannot be mixed within a
33503 single library element, and you must supply at least one segment or
33504 section for each library.
33506 @node Memory Map Format
33507 @section Memory Map Format
33508 @cindex memory map format
33510 To be able to write into flash memory, @value{GDBN} needs to obtain a
33511 memory map from the target. This section describes the format of the
33514 The memory map is obtained using the @samp{qXfer:memory-map:read}
33515 (@pxref{qXfer memory map read}) packet and is an XML document that
33516 lists memory regions.
33518 @value{GDBN} must be linked with the Expat library to support XML
33519 memory maps. @xref{Expat}.
33521 The top-level structure of the document is shown below:
33524 <?xml version="1.0"?>
33525 <!DOCTYPE memory-map
33526 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
33527 "http://sourceware.org/gdb/gdb-memory-map.dtd">
33533 Each region can be either:
33538 A region of RAM starting at @var{addr} and extending for @var{length}
33542 <memory type="ram" start="@var{addr}" length="@var{length}"/>
33547 A region of read-only memory:
33550 <memory type="rom" start="@var{addr}" length="@var{length}"/>
33555 A region of flash memory, with erasure blocks @var{blocksize}
33559 <memory type="flash" start="@var{addr}" length="@var{length}">
33560 <property name="blocksize">@var{blocksize}</property>
33566 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
33567 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
33568 packets to write to addresses in such ranges.
33570 The formal DTD for memory map format is given below:
33573 <!-- ................................................... -->
33574 <!-- Memory Map XML DTD ................................ -->
33575 <!-- File: memory-map.dtd .............................. -->
33576 <!-- .................................... .............. -->
33577 <!-- memory-map.dtd -->
33578 <!-- memory-map: Root element with versioning -->
33579 <!ELEMENT memory-map (memory | property)>
33580 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
33581 <!ELEMENT memory (property)>
33582 <!-- memory: Specifies a memory region,
33583 and its type, or device. -->
33584 <!ATTLIST memory type CDATA #REQUIRED
33585 start CDATA #REQUIRED
33586 length CDATA #REQUIRED
33587 device CDATA #IMPLIED>
33588 <!-- property: Generic attribute tag -->
33589 <!ELEMENT property (#PCDATA | property)*>
33590 <!ATTLIST property name CDATA #REQUIRED>
33593 @node Thread List Format
33594 @section Thread List Format
33595 @cindex thread list format
33597 To efficiently update the list of threads and their attributes,
33598 @value{GDBN} issues the @samp{qXfer:threads:read} packet
33599 (@pxref{qXfer threads read}) and obtains the XML document with
33600 the following structure:
33603 <?xml version="1.0"?>
33605 <thread id="id" core="0">
33606 ... description ...
33611 Each @samp{thread} element must have the @samp{id} attribute that
33612 identifies the thread (@pxref{thread-id syntax}). The
33613 @samp{core} attribute, if present, specifies which processor core
33614 the thread was last executing on. The content of the of @samp{thread}
33615 element is interpreted as human-readable auxilliary information.
33617 @include agentexpr.texi
33619 @node Trace File Format
33620 @appendix Trace File Format
33621 @cindex trace file format
33623 The trace file comes in three parts: a header, a textual description
33624 section, and a trace frame section with binary data.
33626 The header has the form @code{\x7fTRACE0\n}. The first byte is
33627 @code{0x7f} so as to indicate that the file contains binary data,
33628 while the @code{0} is a version number that may have different values
33631 The description section consists of multiple lines of @sc{ascii} text
33632 separated by newline characters (@code{0xa}). The lines may include a
33633 variety of optional descriptive or context-setting information, such
33634 as tracepoint definitions or register set size. @value{GDBN} will
33635 ignore any line that it does not recognize. An empty line marks the end
33638 @c FIXME add some specific types of data
33640 The trace frame section consists of a number of consecutive frames.
33641 Each frame begins with a two-byte tracepoint number, followed by a
33642 four-byte size giving the amount of data in the frame. The data in
33643 the frame consists of a number of blocks, each introduced by a
33644 character indicating its type (at least register, memory, and trace
33645 state variable). The data in this section is raw binary, not a
33646 hexadecimal or other encoding; its endianness matches the target's
33649 @c FIXME bi-arch may require endianness/arch info in description section
33652 @item R @var{bytes}
33653 Register block. The number and ordering of bytes matches that of a
33654 @code{g} packet in the remote protocol. Note that these are the
33655 actual bytes, in target order and @value{GDBN} register order, not a
33656 hexadecimal encoding.
33658 @item M @var{address} @var{length} @var{bytes}...
33659 Memory block. This is a contiguous block of memory, at the 8-byte
33660 address @var{address}, with a 2-byte length @var{length}, followed by
33661 @var{length} bytes.
33663 @item V @var{number} @var{value}
33664 Trace state variable block. This records the 8-byte signed value
33665 @var{value} of trace state variable numbered @var{number}.
33669 Future enhancements of the trace file format may include additional types
33672 @node Target Descriptions
33673 @appendix Target Descriptions
33674 @cindex target descriptions
33676 @strong{Warning:} target descriptions are still under active development,
33677 and the contents and format may change between @value{GDBN} releases.
33678 The format is expected to stabilize in the future.
33680 One of the challenges of using @value{GDBN} to debug embedded systems
33681 is that there are so many minor variants of each processor
33682 architecture in use. It is common practice for vendors to start with
33683 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
33684 and then make changes to adapt it to a particular market niche. Some
33685 architectures have hundreds of variants, available from dozens of
33686 vendors. This leads to a number of problems:
33690 With so many different customized processors, it is difficult for
33691 the @value{GDBN} maintainers to keep up with the changes.
33693 Since individual variants may have short lifetimes or limited
33694 audiences, it may not be worthwhile to carry information about every
33695 variant in the @value{GDBN} source tree.
33697 When @value{GDBN} does support the architecture of the embedded system
33698 at hand, the task of finding the correct architecture name to give the
33699 @command{set architecture} command can be error-prone.
33702 To address these problems, the @value{GDBN} remote protocol allows a
33703 target system to not only identify itself to @value{GDBN}, but to
33704 actually describe its own features. This lets @value{GDBN} support
33705 processor variants it has never seen before --- to the extent that the
33706 descriptions are accurate, and that @value{GDBN} understands them.
33708 @value{GDBN} must be linked with the Expat library to support XML
33709 target descriptions. @xref{Expat}.
33712 * Retrieving Descriptions:: How descriptions are fetched from a target.
33713 * Target Description Format:: The contents of a target description.
33714 * Predefined Target Types:: Standard types available for target
33716 * Standard Target Features:: Features @value{GDBN} knows about.
33719 @node Retrieving Descriptions
33720 @section Retrieving Descriptions
33722 Target descriptions can be read from the target automatically, or
33723 specified by the user manually. The default behavior is to read the
33724 description from the target. @value{GDBN} retrieves it via the remote
33725 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
33726 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
33727 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
33728 XML document, of the form described in @ref{Target Description
33731 Alternatively, you can specify a file to read for the target description.
33732 If a file is set, the target will not be queried. The commands to
33733 specify a file are:
33736 @cindex set tdesc filename
33737 @item set tdesc filename @var{path}
33738 Read the target description from @var{path}.
33740 @cindex unset tdesc filename
33741 @item unset tdesc filename
33742 Do not read the XML target description from a file. @value{GDBN}
33743 will use the description supplied by the current target.
33745 @cindex show tdesc filename
33746 @item show tdesc filename
33747 Show the filename to read for a target description, if any.
33751 @node Target Description Format
33752 @section Target Description Format
33753 @cindex target descriptions, XML format
33755 A target description annex is an @uref{http://www.w3.org/XML/, XML}
33756 document which complies with the Document Type Definition provided in
33757 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
33758 means you can use generally available tools like @command{xmllint} to
33759 check that your feature descriptions are well-formed and valid.
33760 However, to help people unfamiliar with XML write descriptions for
33761 their targets, we also describe the grammar here.
33763 Target descriptions can identify the architecture of the remote target
33764 and (for some architectures) provide information about custom register
33765 sets. They can also identify the OS ABI of the remote target.
33766 @value{GDBN} can use this information to autoconfigure for your
33767 target, or to warn you if you connect to an unsupported target.
33769 Here is a simple target description:
33772 <target version="1.0">
33773 <architecture>i386:x86-64</architecture>
33778 This minimal description only says that the target uses
33779 the x86-64 architecture.
33781 A target description has the following overall form, with [ ] marking
33782 optional elements and @dots{} marking repeatable elements. The elements
33783 are explained further below.
33786 <?xml version="1.0"?>
33787 <!DOCTYPE target SYSTEM "gdb-target.dtd">
33788 <target version="1.0">
33789 @r{[}@var{architecture}@r{]}
33790 @r{[}@var{osabi}@r{]}
33791 @r{[}@var{compatible}@r{]}
33792 @r{[}@var{feature}@dots{}@r{]}
33797 The description is generally insensitive to whitespace and line
33798 breaks, under the usual common-sense rules. The XML version
33799 declaration and document type declaration can generally be omitted
33800 (@value{GDBN} does not require them), but specifying them may be
33801 useful for XML validation tools. The @samp{version} attribute for
33802 @samp{<target>} may also be omitted, but we recommend
33803 including it; if future versions of @value{GDBN} use an incompatible
33804 revision of @file{gdb-target.dtd}, they will detect and report
33805 the version mismatch.
33807 @subsection Inclusion
33808 @cindex target descriptions, inclusion
33811 @cindex <xi:include>
33814 It can sometimes be valuable to split a target description up into
33815 several different annexes, either for organizational purposes, or to
33816 share files between different possible target descriptions. You can
33817 divide a description into multiple files by replacing any element of
33818 the target description with an inclusion directive of the form:
33821 <xi:include href="@var{document}"/>
33825 When @value{GDBN} encounters an element of this form, it will retrieve
33826 the named XML @var{document}, and replace the inclusion directive with
33827 the contents of that document. If the current description was read
33828 using @samp{qXfer}, then so will be the included document;
33829 @var{document} will be interpreted as the name of an annex. If the
33830 current description was read from a file, @value{GDBN} will look for
33831 @var{document} as a file in the same directory where it found the
33832 original description.
33834 @subsection Architecture
33835 @cindex <architecture>
33837 An @samp{<architecture>} element has this form:
33840 <architecture>@var{arch}</architecture>
33843 @var{arch} is one of the architectures from the set accepted by
33844 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
33847 @cindex @code{<osabi>}
33849 This optional field was introduced in @value{GDBN} version 7.0.
33850 Previous versions of @value{GDBN} ignore it.
33852 An @samp{<osabi>} element has this form:
33855 <osabi>@var{abi-name}</osabi>
33858 @var{abi-name} is an OS ABI name from the same selection accepted by
33859 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
33861 @subsection Compatible Architecture
33862 @cindex @code{<compatible>}
33864 This optional field was introduced in @value{GDBN} version 7.0.
33865 Previous versions of @value{GDBN} ignore it.
33867 A @samp{<compatible>} element has this form:
33870 <compatible>@var{arch}</compatible>
33873 @var{arch} is one of the architectures from the set accepted by
33874 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
33876 A @samp{<compatible>} element is used to specify that the target
33877 is able to run binaries in some other than the main target architecture
33878 given by the @samp{<architecture>} element. For example, on the
33879 Cell Broadband Engine, the main architecture is @code{powerpc:common}
33880 or @code{powerpc:common64}, but the system is able to run binaries
33881 in the @code{spu} architecture as well. The way to describe this
33882 capability with @samp{<compatible>} is as follows:
33885 <architecture>powerpc:common</architecture>
33886 <compatible>spu</compatible>
33889 @subsection Features
33892 Each @samp{<feature>} describes some logical portion of the target
33893 system. Features are currently used to describe available CPU
33894 registers and the types of their contents. A @samp{<feature>} element
33898 <feature name="@var{name}">
33899 @r{[}@var{type}@dots{}@r{]}
33905 Each feature's name should be unique within the description. The name
33906 of a feature does not matter unless @value{GDBN} has some special
33907 knowledge of the contents of that feature; if it does, the feature
33908 should have its standard name. @xref{Standard Target Features}.
33912 Any register's value is a collection of bits which @value{GDBN} must
33913 interpret. The default interpretation is a two's complement integer,
33914 but other types can be requested by name in the register description.
33915 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
33916 Target Types}), and the description can define additional composite types.
33918 Each type element must have an @samp{id} attribute, which gives
33919 a unique (within the containing @samp{<feature>}) name to the type.
33920 Types must be defined before they are used.
33923 Some targets offer vector registers, which can be treated as arrays
33924 of scalar elements. These types are written as @samp{<vector>} elements,
33925 specifying the array element type, @var{type}, and the number of elements,
33929 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
33933 If a register's value is usefully viewed in multiple ways, define it
33934 with a union type containing the useful representations. The
33935 @samp{<union>} element contains one or more @samp{<field>} elements,
33936 each of which has a @var{name} and a @var{type}:
33939 <union id="@var{id}">
33940 <field name="@var{name}" type="@var{type}"/>
33946 If a register's value is composed from several separate values, define
33947 it with a structure type. There are two forms of the @samp{<struct>}
33948 element; a @samp{<struct>} element must either contain only bitfields
33949 or contain no bitfields. If the structure contains only bitfields,
33950 its total size in bytes must be specified, each bitfield must have an
33951 explicit start and end, and bitfields are automatically assigned an
33952 integer type. The field's @var{start} should be less than or
33953 equal to its @var{end}, and zero represents the least significant bit.
33956 <struct id="@var{id}" size="@var{size}">
33957 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
33962 If the structure contains no bitfields, then each field has an
33963 explicit type, and no implicit padding is added.
33966 <struct id="@var{id}">
33967 <field name="@var{name}" type="@var{type}"/>
33973 If a register's value is a series of single-bit flags, define it with
33974 a flags type. The @samp{<flags>} element has an explicit @var{size}
33975 and contains one or more @samp{<field>} elements. Each field has a
33976 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
33980 <flags id="@var{id}" size="@var{size}">
33981 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
33986 @subsection Registers
33989 Each register is represented as an element with this form:
33992 <reg name="@var{name}"
33993 bitsize="@var{size}"
33994 @r{[}regnum="@var{num}"@r{]}
33995 @r{[}save-restore="@var{save-restore}"@r{]}
33996 @r{[}type="@var{type}"@r{]}
33997 @r{[}group="@var{group}"@r{]}/>
34001 The components are as follows:
34006 The register's name; it must be unique within the target description.
34009 The register's size, in bits.
34012 The register's number. If omitted, a register's number is one greater
34013 than that of the previous register (either in the current feature or in
34014 a preceeding feature); the first register in the target description
34015 defaults to zero. This register number is used to read or write
34016 the register; e.g.@: it is used in the remote @code{p} and @code{P}
34017 packets, and registers appear in the @code{g} and @code{G} packets
34018 in order of increasing register number.
34021 Whether the register should be preserved across inferior function
34022 calls; this must be either @code{yes} or @code{no}. The default is
34023 @code{yes}, which is appropriate for most registers except for
34024 some system control registers; this is not related to the target's
34028 The type of the register. @var{type} may be a predefined type, a type
34029 defined in the current feature, or one of the special types @code{int}
34030 and @code{float}. @code{int} is an integer type of the correct size
34031 for @var{bitsize}, and @code{float} is a floating point type (in the
34032 architecture's normal floating point format) of the correct size for
34033 @var{bitsize}. The default is @code{int}.
34036 The register group to which this register belongs. @var{group} must
34037 be either @code{general}, @code{float}, or @code{vector}. If no
34038 @var{group} is specified, @value{GDBN} will not display the register
34039 in @code{info registers}.
34043 @node Predefined Target Types
34044 @section Predefined Target Types
34045 @cindex target descriptions, predefined types
34047 Type definitions in the self-description can build up composite types
34048 from basic building blocks, but can not define fundamental types. Instead,
34049 standard identifiers are provided by @value{GDBN} for the fundamental
34050 types. The currently supported types are:
34059 Signed integer types holding the specified number of bits.
34066 Unsigned integer types holding the specified number of bits.
34070 Pointers to unspecified code and data. The program counter and
34071 any dedicated return address register may be marked as code
34072 pointers; printing a code pointer converts it into a symbolic
34073 address. The stack pointer and any dedicated address registers
34074 may be marked as data pointers.
34077 Single precision IEEE floating point.
34080 Double precision IEEE floating point.
34083 The 12-byte extended precision format used by ARM FPA registers.
34086 The 10-byte extended precision format used by x87 registers.
34089 32bit @sc{eflags} register used by x86.
34092 32bit @sc{mxcsr} register used by x86.
34096 @node Standard Target Features
34097 @section Standard Target Features
34098 @cindex target descriptions, standard features
34100 A target description must contain either no registers or all the
34101 target's registers. If the description contains no registers, then
34102 @value{GDBN} will assume a default register layout, selected based on
34103 the architecture. If the description contains any registers, the
34104 default layout will not be used; the standard registers must be
34105 described in the target description, in such a way that @value{GDBN}
34106 can recognize them.
34108 This is accomplished by giving specific names to feature elements
34109 which contain standard registers. @value{GDBN} will look for features
34110 with those names and verify that they contain the expected registers;
34111 if any known feature is missing required registers, or if any required
34112 feature is missing, @value{GDBN} will reject the target
34113 description. You can add additional registers to any of the
34114 standard features --- @value{GDBN} will display them just as if
34115 they were added to an unrecognized feature.
34117 This section lists the known features and their expected contents.
34118 Sample XML documents for these features are included in the
34119 @value{GDBN} source tree, in the directory @file{gdb/features}.
34121 Names recognized by @value{GDBN} should include the name of the
34122 company or organization which selected the name, and the overall
34123 architecture to which the feature applies; so e.g.@: the feature
34124 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
34126 The names of registers are not case sensitive for the purpose
34127 of recognizing standard features, but @value{GDBN} will only display
34128 registers using the capitalization used in the description.
34135 * PowerPC Features::
34140 @subsection ARM Features
34141 @cindex target descriptions, ARM features
34143 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
34144 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
34145 @samp{lr}, @samp{pc}, and @samp{cpsr}.
34147 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
34148 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
34150 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
34151 it should contain at least registers @samp{wR0} through @samp{wR15} and
34152 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
34153 @samp{wCSSF}, and @samp{wCASF} registers are optional.
34155 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
34156 should contain at least registers @samp{d0} through @samp{d15}. If
34157 they are present, @samp{d16} through @samp{d31} should also be included.
34158 @value{GDBN} will synthesize the single-precision registers from
34159 halves of the double-precision registers.
34161 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
34162 need to contain registers; it instructs @value{GDBN} to display the
34163 VFP double-precision registers as vectors and to synthesize the
34164 quad-precision registers from pairs of double-precision registers.
34165 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
34166 be present and include 32 double-precision registers.
34168 @node i386 Features
34169 @subsection i386 Features
34170 @cindex target descriptions, i386 features
34172 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
34173 targets. It should describe the following registers:
34177 @samp{eax} through @samp{edi} plus @samp{eip} for i386
34179 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
34181 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
34182 @samp{fs}, @samp{gs}
34184 @samp{st0} through @samp{st7}
34186 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
34187 @samp{foseg}, @samp{fooff} and @samp{fop}
34190 The register sets may be different, depending on the target.
34192 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
34193 describe registers:
34197 @samp{xmm0} through @samp{xmm7} for i386
34199 @samp{xmm0} through @samp{xmm15} for amd64
34204 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
34205 @samp{org.gnu.gdb.i386.sse} feature. It should
34206 describe the upper 128 bits of @sc{ymm} registers:
34210 @samp{ymm0h} through @samp{ymm7h} for i386
34212 @samp{ymm0h} through @samp{ymm15h} for amd64
34216 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
34217 describe a single register, @samp{orig_eax}.
34219 @node MIPS Features
34220 @subsection MIPS Features
34221 @cindex target descriptions, MIPS features
34223 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
34224 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
34225 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
34228 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
34229 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
34230 registers. They may be 32-bit or 64-bit depending on the target.
34232 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
34233 it may be optional in a future version of @value{GDBN}. It should
34234 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
34235 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
34237 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
34238 contain a single register, @samp{restart}, which is used by the
34239 Linux kernel to control restartable syscalls.
34241 @node M68K Features
34242 @subsection M68K Features
34243 @cindex target descriptions, M68K features
34246 @item @samp{org.gnu.gdb.m68k.core}
34247 @itemx @samp{org.gnu.gdb.coldfire.core}
34248 @itemx @samp{org.gnu.gdb.fido.core}
34249 One of those features must be always present.
34250 The feature that is present determines which flavor of m68k is
34251 used. The feature that is present should contain registers
34252 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
34253 @samp{sp}, @samp{ps} and @samp{pc}.
34255 @item @samp{org.gnu.gdb.coldfire.fp}
34256 This feature is optional. If present, it should contain registers
34257 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
34261 @node PowerPC Features
34262 @subsection PowerPC Features
34263 @cindex target descriptions, PowerPC features
34265 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
34266 targets. It should contain registers @samp{r0} through @samp{r31},
34267 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
34268 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
34270 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
34271 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
34273 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
34274 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
34277 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
34278 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
34279 will combine these registers with the floating point registers
34280 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
34281 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
34282 through @samp{vs63}, the set of vector registers for POWER7.
34284 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
34285 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
34286 @samp{spefscr}. SPE targets should provide 32-bit registers in
34287 @samp{org.gnu.gdb.power.core} and provide the upper halves in
34288 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
34289 these to present registers @samp{ev0} through @samp{ev31} to the
34292 @node Operating System Information
34293 @appendix Operating System Information
34294 @cindex operating system information
34300 Users of @value{GDBN} often wish to obtain information about the state of
34301 the operating system running on the target---for example the list of
34302 processes, or the list of open files. This section describes the
34303 mechanism that makes it possible. This mechanism is similar to the
34304 target features mechanism (@pxref{Target Descriptions}), but focuses
34305 on a different aspect of target.
34307 Operating system information is retrived from the target via the
34308 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
34309 read}). The object name in the request should be @samp{osdata}, and
34310 the @var{annex} identifies the data to be fetched.
34313 @appendixsection Process list
34314 @cindex operating system information, process list
34316 When requesting the process list, the @var{annex} field in the
34317 @samp{qXfer} request should be @samp{processes}. The returned data is
34318 an XML document. The formal syntax of this document is defined in
34319 @file{gdb/features/osdata.dtd}.
34321 An example document is:
34324 <?xml version="1.0"?>
34325 <!DOCTYPE target SYSTEM "osdata.dtd">
34326 <osdata type="processes">
34328 <column name="pid">1</column>
34329 <column name="user">root</column>
34330 <column name="command">/sbin/init</column>
34331 <column name="cores">1,2,3</column>
34336 Each item should include a column whose name is @samp{pid}. The value
34337 of that column should identify the process on the target. The
34338 @samp{user} and @samp{command} columns are optional, and will be
34339 displayed by @value{GDBN}. The @samp{cores} column, if present,
34340 should contain a comma-separated list of cores that this process
34341 is running on. Target may provide additional columns,
34342 which @value{GDBN} currently ignores.
34356 % I think something like @colophon should be in texinfo. In the
34358 \long\def\colophon{\hbox to0pt{}\vfill
34359 \centerline{The body of this manual is set in}
34360 \centerline{\fontname\tenrm,}
34361 \centerline{with headings in {\bf\fontname\tenbf}}
34362 \centerline{and examples in {\tt\fontname\tentt}.}
34363 \centerline{{\it\fontname\tenit\/},}
34364 \centerline{{\bf\fontname\tenbf}, and}
34365 \centerline{{\sl\fontname\tensl\/}}
34366 \centerline{are used for emphasis.}\vfill}
34368 % Blame: doc@cygnus.com, 1991.