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 * Error in Breakpoints:: ``Cannot insert breakpoints''
3251 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3255 @subsection Setting Breakpoints
3257 @c FIXME LMB what does GDB do if no code on line of breakpt?
3258 @c consider in particular declaration with/without initialization.
3260 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3263 @kindex b @r{(@code{break})}
3264 @vindex $bpnum@r{, convenience variable}
3265 @cindex latest breakpoint
3266 Breakpoints are set with the @code{break} command (abbreviated
3267 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3268 number of the breakpoint you've set most recently; see @ref{Convenience
3269 Vars,, Convenience Variables}, for a discussion of what you can do with
3270 convenience variables.
3273 @item break @var{location}
3274 Set a breakpoint at the given @var{location}, which can specify a
3275 function name, a line number, or an address of an instruction.
3276 (@xref{Specify Location}, for a list of all the possible ways to
3277 specify a @var{location}.) The breakpoint will stop your program just
3278 before it executes any of the code in the specified @var{location}.
3280 When using source languages that permit overloading of symbols, such as
3281 C@t{++}, a function name may refer to more than one possible place to break.
3282 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3285 It is also possible to insert a breakpoint that will stop the program
3286 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3287 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3290 When called without any arguments, @code{break} sets a breakpoint at
3291 the next instruction to be executed in the selected stack frame
3292 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3293 innermost, this makes your program stop as soon as control
3294 returns to that frame. This is similar to the effect of a
3295 @code{finish} command in the frame inside the selected frame---except
3296 that @code{finish} does not leave an active breakpoint. If you use
3297 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3298 the next time it reaches the current location; this may be useful
3301 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3302 least one instruction has been executed. If it did not do this, you
3303 would be unable to proceed past a breakpoint without first disabling the
3304 breakpoint. This rule applies whether or not the breakpoint already
3305 existed when your program stopped.
3307 @item break @dots{} if @var{cond}
3308 Set a breakpoint with condition @var{cond}; evaluate the expression
3309 @var{cond} each time the breakpoint is reached, and stop only if the
3310 value is nonzero---that is, if @var{cond} evaluates as true.
3311 @samp{@dots{}} stands for one of the possible arguments described
3312 above (or no argument) specifying where to break. @xref{Conditions,
3313 ,Break Conditions}, for more information on breakpoint conditions.
3316 @item tbreak @var{args}
3317 Set a breakpoint enabled only for one stop. @var{args} are the
3318 same as for the @code{break} command, and the breakpoint is set in the same
3319 way, but the breakpoint is automatically deleted after the first time your
3320 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3323 @cindex hardware breakpoints
3324 @item hbreak @var{args}
3325 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3326 @code{break} command and the breakpoint is set in the same way, but the
3327 breakpoint requires hardware support and some target hardware may not
3328 have this support. The main purpose of this is EPROM/ROM code
3329 debugging, so you can set a breakpoint at an instruction without
3330 changing the instruction. This can be used with the new trap-generation
3331 provided by SPARClite DSU and most x86-based targets. These targets
3332 will generate traps when a program accesses some data or instruction
3333 address that is assigned to the debug registers. However the hardware
3334 breakpoint registers can take a limited number of breakpoints. For
3335 example, on the DSU, only two data breakpoints can be set at a time, and
3336 @value{GDBN} will reject this command if more than two are used. Delete
3337 or disable unused hardware breakpoints before setting new ones
3338 (@pxref{Disabling, ,Disabling Breakpoints}).
3339 @xref{Conditions, ,Break Conditions}.
3340 For remote targets, you can restrict the number of hardware
3341 breakpoints @value{GDBN} will use, see @ref{set remote
3342 hardware-breakpoint-limit}.
3345 @item thbreak @var{args}
3346 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3347 are the same as for the @code{hbreak} command and the breakpoint is set in
3348 the same way. However, like the @code{tbreak} command,
3349 the breakpoint is automatically deleted after the
3350 first time your program stops there. Also, like the @code{hbreak}
3351 command, the breakpoint requires hardware support and some target hardware
3352 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3353 See also @ref{Conditions, ,Break Conditions}.
3356 @cindex regular expression
3357 @cindex breakpoints in functions matching a regexp
3358 @cindex set breakpoints in many functions
3359 @item rbreak @var{regex}
3360 Set breakpoints on all functions matching the regular expression
3361 @var{regex}. This command sets an unconditional breakpoint on all
3362 matches, printing a list of all breakpoints it set. Once these
3363 breakpoints are set, they are treated just like the breakpoints set with
3364 the @code{break} command. You can delete them, disable them, or make
3365 them conditional the same way as any other breakpoint.
3367 The syntax of the regular expression is the standard one used with tools
3368 like @file{grep}. Note that this is different from the syntax used by
3369 shells, so for instance @code{foo*} matches all functions that include
3370 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3371 @code{.*} leading and trailing the regular expression you supply, so to
3372 match only functions that begin with @code{foo}, use @code{^foo}.
3374 @cindex non-member C@t{++} functions, set breakpoint in
3375 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3376 breakpoints on overloaded functions that are not members of any special
3379 @cindex set breakpoints on all functions
3380 The @code{rbreak} command can be used to set breakpoints in
3381 @strong{all} the functions in a program, like this:
3384 (@value{GDBP}) rbreak .
3387 @kindex info breakpoints
3388 @cindex @code{$_} and @code{info breakpoints}
3389 @item info breakpoints @r{[}@var{n}@r{]}
3390 @itemx info break @r{[}@var{n}@r{]}
3391 @itemx info watchpoints @r{[}@var{n}@r{]}
3392 Print a table of all breakpoints, watchpoints, and catchpoints set and
3393 not deleted. Optional argument @var{n} means print information only
3394 about the specified breakpoint (or watchpoint or catchpoint). For
3395 each breakpoint, following columns are printed:
3398 @item Breakpoint Numbers
3400 Breakpoint, watchpoint, or catchpoint.
3402 Whether the breakpoint is marked to be disabled or deleted when hit.
3403 @item Enabled or Disabled
3404 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3405 that are not enabled.
3407 Where the breakpoint is in your program, as a memory address. For a
3408 pending breakpoint whose address is not yet known, this field will
3409 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3410 library that has the symbol or line referred by breakpoint is loaded.
3411 See below for details. A breakpoint with several locations will
3412 have @samp{<MULTIPLE>} in this field---see below for details.
3414 Where the breakpoint is in the source for your program, as a file and
3415 line number. For a pending breakpoint, the original string passed to
3416 the breakpoint command will be listed as it cannot be resolved until
3417 the appropriate shared library is loaded in the future.
3421 If a breakpoint is conditional, @code{info break} shows the condition on
3422 the line following the affected breakpoint; breakpoint commands, if any,
3423 are listed after that. A pending breakpoint is allowed to have a condition
3424 specified for it. The condition is not parsed for validity until a shared
3425 library is loaded that allows the pending breakpoint to resolve to a
3429 @code{info break} with a breakpoint
3430 number @var{n} as argument lists only that breakpoint. The
3431 convenience variable @code{$_} 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, breakpoints, and catchpoints;
3709 it is the same as @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 one
4139 or more breakpoint numbers as arguments. Use @code{info break} or
4140 @code{info watch} to print a list of breakpoints, watchpoints, and
4141 catchpoints if you 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 breakpoints set with @code{break} that have
4350 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4351 disabled within a @var{command-list}.
4353 You can use breakpoint commands to start your program up again. Simply
4354 use the @code{continue} command, or @code{step}, or any other command
4355 that resumes execution.
4357 Any other commands in the command list, after a command that resumes
4358 execution, are ignored. This is because any time you resume execution
4359 (even with a simple @code{next} or @code{step}), you may encounter
4360 another breakpoint---which could have its own command list, leading to
4361 ambiguities about which list to execute.
4364 If the first command you specify in a command list is @code{silent}, the
4365 usual message about stopping at a breakpoint is not printed. This may
4366 be desirable for breakpoints that are to print a specific message and
4367 then continue. If none of the remaining commands print anything, you
4368 see no sign that the breakpoint was reached. @code{silent} is
4369 meaningful only at the beginning of a breakpoint command list.
4371 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4372 print precisely controlled output, and are often useful in silent
4373 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4375 For example, here is how you could use breakpoint commands to print the
4376 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4382 printf "x is %d\n",x
4387 One application for breakpoint commands is to compensate for one bug so
4388 you can test for another. Put a breakpoint just after the erroneous line
4389 of code, give it a condition to detect the case in which something
4390 erroneous has been done, and give it commands to assign correct values
4391 to any variables that need them. End with the @code{continue} command
4392 so that your program does not stop, and start with the @code{silent}
4393 command so that no output is produced. Here is an example:
4404 @c @ifclear BARETARGET
4405 @node Error in Breakpoints
4406 @subsection ``Cannot insert breakpoints''
4408 If you request too many active hardware-assisted breakpoints and
4409 watchpoints, you will see this error message:
4411 @c FIXME: the precise wording of this message may change; the relevant
4412 @c source change is not committed yet (Sep 3, 1999).
4414 Stopped; cannot insert breakpoints.
4415 You may have requested too many hardware breakpoints and watchpoints.
4419 This message is printed when you attempt to resume the program, since
4420 only then @value{GDBN} knows exactly how many hardware breakpoints and
4421 watchpoints it needs to insert.
4423 When this message is printed, you need to disable or remove some of the
4424 hardware-assisted breakpoints and watchpoints, and then continue.
4426 @node Breakpoint-related Warnings
4427 @subsection ``Breakpoint address adjusted...''
4428 @cindex breakpoint address adjusted
4430 Some processor architectures place constraints on the addresses at
4431 which breakpoints may be placed. For architectures thus constrained,
4432 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4433 with the constraints dictated by the architecture.
4435 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4436 a VLIW architecture in which a number of RISC-like instructions may be
4437 bundled together for parallel execution. The FR-V architecture
4438 constrains the location of a breakpoint instruction within such a
4439 bundle to the instruction with the lowest address. @value{GDBN}
4440 honors this constraint by adjusting a breakpoint's address to the
4441 first in the bundle.
4443 It is not uncommon for optimized code to have bundles which contain
4444 instructions from different source statements, thus it may happen that
4445 a breakpoint's address will be adjusted from one source statement to
4446 another. Since this adjustment may significantly alter @value{GDBN}'s
4447 breakpoint related behavior from what the user expects, a warning is
4448 printed when the breakpoint is first set and also when the breakpoint
4451 A warning like the one below is printed when setting a breakpoint
4452 that's been subject to address adjustment:
4455 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4458 Such warnings are printed both for user settable and @value{GDBN}'s
4459 internal breakpoints. If you see one of these warnings, you should
4460 verify that a breakpoint set at the adjusted address will have the
4461 desired affect. If not, the breakpoint in question may be removed and
4462 other breakpoints may be set which will have the desired behavior.
4463 E.g., it may be sufficient to place the breakpoint at a later
4464 instruction. A conditional breakpoint may also be useful in some
4465 cases to prevent the breakpoint from triggering too often.
4467 @value{GDBN} will also issue a warning when stopping at one of these
4468 adjusted breakpoints:
4471 warning: Breakpoint 1 address previously adjusted from 0x00010414
4475 When this warning is encountered, it may be too late to take remedial
4476 action except in cases where the breakpoint is hit earlier or more
4477 frequently than expected.
4479 @node Continuing and Stepping
4480 @section Continuing and Stepping
4484 @cindex resuming execution
4485 @dfn{Continuing} means resuming program execution until your program
4486 completes normally. In contrast, @dfn{stepping} means executing just
4487 one more ``step'' of your program, where ``step'' may mean either one
4488 line of source code, or one machine instruction (depending on what
4489 particular command you use). Either when continuing or when stepping,
4490 your program may stop even sooner, due to a breakpoint or a signal. (If
4491 it stops due to a signal, you may want to use @code{handle}, or use
4492 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4496 @kindex c @r{(@code{continue})}
4497 @kindex fg @r{(resume foreground execution)}
4498 @item continue @r{[}@var{ignore-count}@r{]}
4499 @itemx c @r{[}@var{ignore-count}@r{]}
4500 @itemx fg @r{[}@var{ignore-count}@r{]}
4501 Resume program execution, at the address where your program last stopped;
4502 any breakpoints set at that address are bypassed. The optional argument
4503 @var{ignore-count} allows you to specify a further number of times to
4504 ignore a breakpoint at this location; its effect is like that of
4505 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4507 The argument @var{ignore-count} is meaningful only when your program
4508 stopped due to a breakpoint. At other times, the argument to
4509 @code{continue} is ignored.
4511 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4512 debugged program is deemed to be the foreground program) are provided
4513 purely for convenience, and have exactly the same behavior as
4517 To resume execution at a different place, you can use @code{return}
4518 (@pxref{Returning, ,Returning from a Function}) to go back to the
4519 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4520 Different Address}) to go to an arbitrary location in your program.
4522 A typical technique for using stepping is to set a breakpoint
4523 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4524 beginning of the function or the section of your program where a problem
4525 is believed to lie, run your program until it stops at that breakpoint,
4526 and then step through the suspect area, examining the variables that are
4527 interesting, until you see the problem happen.
4531 @kindex s @r{(@code{step})}
4533 Continue running your program until control reaches a different source
4534 line, then stop it and return control to @value{GDBN}. This command is
4535 abbreviated @code{s}.
4538 @c "without debugging information" is imprecise; actually "without line
4539 @c numbers in the debugging information". (gcc -g1 has debugging info but
4540 @c not line numbers). But it seems complex to try to make that
4541 @c distinction here.
4542 @emph{Warning:} If you use the @code{step} command while control is
4543 within a function that was compiled without debugging information,
4544 execution proceeds until control reaches a function that does have
4545 debugging information. Likewise, it will not step into a function which
4546 is compiled without debugging information. To step through functions
4547 without debugging information, use the @code{stepi} command, described
4551 The @code{step} command only stops at the first instruction of a source
4552 line. This prevents the multiple stops that could otherwise occur in
4553 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4554 to stop if a function that has debugging information is called within
4555 the line. In other words, @code{step} @emph{steps inside} any functions
4556 called within the line.
4558 Also, the @code{step} command only enters a function if there is line
4559 number information for the function. Otherwise it acts like the
4560 @code{next} command. This avoids problems when using @code{cc -gl}
4561 on MIPS machines. Previously, @code{step} entered subroutines if there
4562 was any debugging information about the routine.
4564 @item step @var{count}
4565 Continue running as in @code{step}, but do so @var{count} times. If a
4566 breakpoint is reached, or a signal not related to stepping occurs before
4567 @var{count} steps, stepping stops right away.
4570 @kindex n @r{(@code{next})}
4571 @item next @r{[}@var{count}@r{]}
4572 Continue to the next source line in the current (innermost) stack frame.
4573 This is similar to @code{step}, but function calls that appear within
4574 the line of code are executed without stopping. Execution stops when
4575 control reaches a different line of code at the original stack level
4576 that was executing when you gave the @code{next} command. This command
4577 is abbreviated @code{n}.
4579 An argument @var{count} is a repeat count, as for @code{step}.
4582 @c FIX ME!! Do we delete this, or is there a way it fits in with
4583 @c the following paragraph? --- Vctoria
4585 @c @code{next} within a function that lacks debugging information acts like
4586 @c @code{step}, but any function calls appearing within the code of the
4587 @c function are executed without stopping.
4589 The @code{next} command only stops at the first instruction of a
4590 source line. This prevents multiple stops that could otherwise occur in
4591 @code{switch} statements, @code{for} loops, etc.
4593 @kindex set step-mode
4595 @cindex functions without line info, and stepping
4596 @cindex stepping into functions with no line info
4597 @itemx set step-mode on
4598 The @code{set step-mode on} command causes the @code{step} command to
4599 stop at the first instruction of a function which contains no debug line
4600 information rather than stepping over it.
4602 This is useful in cases where you may be interested in inspecting the
4603 machine instructions of a function which has no symbolic info and do not
4604 want @value{GDBN} to automatically skip over this function.
4606 @item set step-mode off
4607 Causes the @code{step} command to step over any functions which contains no
4608 debug information. This is the default.
4610 @item show step-mode
4611 Show whether @value{GDBN} will stop in or step over functions without
4612 source line debug information.
4615 @kindex fin @r{(@code{finish})}
4617 Continue running until just after function in the selected stack frame
4618 returns. Print the returned value (if any). This command can be
4619 abbreviated as @code{fin}.
4621 Contrast this with the @code{return} command (@pxref{Returning,
4622 ,Returning from a Function}).
4625 @kindex u @r{(@code{until})}
4626 @cindex run until specified location
4629 Continue running until a source line past the current line, in the
4630 current stack frame, is reached. This command is used to avoid single
4631 stepping through a loop more than once. It is like the @code{next}
4632 command, except that when @code{until} encounters a jump, it
4633 automatically continues execution until the program counter is greater
4634 than the address of the jump.
4636 This means that when you reach the end of a loop after single stepping
4637 though it, @code{until} makes your program continue execution until it
4638 exits the loop. In contrast, a @code{next} command at the end of a loop
4639 simply steps back to the beginning of the loop, which forces you to step
4640 through the next iteration.
4642 @code{until} always stops your program if it attempts to exit the current
4645 @code{until} may produce somewhat counterintuitive results if the order
4646 of machine code does not match the order of the source lines. For
4647 example, in the following excerpt from a debugging session, the @code{f}
4648 (@code{frame}) command shows that execution is stopped at line
4649 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4653 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4655 (@value{GDBP}) until
4656 195 for ( ; argc > 0; NEXTARG) @{
4659 This happened because, for execution efficiency, the compiler had
4660 generated code for the loop closure test at the end, rather than the
4661 start, of the loop---even though the test in a C @code{for}-loop is
4662 written before the body of the loop. The @code{until} command appeared
4663 to step back to the beginning of the loop when it advanced to this
4664 expression; however, it has not really gone to an earlier
4665 statement---not in terms of the actual machine code.
4667 @code{until} with no argument works by means of single
4668 instruction stepping, and hence is slower than @code{until} with an
4671 @item until @var{location}
4672 @itemx u @var{location}
4673 Continue running your program until either the specified location is
4674 reached, or the current stack frame returns. @var{location} is any of
4675 the forms described in @ref{Specify Location}.
4676 This form of the command uses temporary breakpoints, and
4677 hence is quicker than @code{until} without an argument. The specified
4678 location is actually reached only if it is in the current frame. This
4679 implies that @code{until} can be used to skip over recursive function
4680 invocations. For instance in the code below, if the current location is
4681 line @code{96}, issuing @code{until 99} will execute the program up to
4682 line @code{99} in the same invocation of factorial, i.e., after the inner
4683 invocations have returned.
4686 94 int factorial (int value)
4688 96 if (value > 1) @{
4689 97 value *= factorial (value - 1);
4696 @kindex advance @var{location}
4697 @itemx advance @var{location}
4698 Continue running the program up to the given @var{location}. An argument is
4699 required, which should be of one of the forms described in
4700 @ref{Specify Location}.
4701 Execution will also stop upon exit from the current stack
4702 frame. This command is similar to @code{until}, but @code{advance} will
4703 not skip over recursive function calls, and the target location doesn't
4704 have to be in the same frame as the current one.
4708 @kindex si @r{(@code{stepi})}
4710 @itemx stepi @var{arg}
4712 Execute one machine instruction, then stop and return to the debugger.
4714 It is often useful to do @samp{display/i $pc} when stepping by machine
4715 instructions. This makes @value{GDBN} automatically display the next
4716 instruction to be executed, each time your program stops. @xref{Auto
4717 Display,, Automatic Display}.
4719 An argument is a repeat count, as in @code{step}.
4723 @kindex ni @r{(@code{nexti})}
4725 @itemx nexti @var{arg}
4727 Execute one machine instruction, but if it is a function call,
4728 proceed until the function returns.
4730 An argument is a repeat count, as in @code{next}.
4737 A signal is an asynchronous event that can happen in a program. The
4738 operating system defines the possible kinds of signals, and gives each
4739 kind a name and a number. For example, in Unix @code{SIGINT} is the
4740 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4741 @code{SIGSEGV} is the signal a program gets from referencing a place in
4742 memory far away from all the areas in use; @code{SIGALRM} occurs when
4743 the alarm clock timer goes off (which happens only if your program has
4744 requested an alarm).
4746 @cindex fatal signals
4747 Some signals, including @code{SIGALRM}, are a normal part of the
4748 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4749 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4750 program has not specified in advance some other way to handle the signal.
4751 @code{SIGINT} does not indicate an error in your program, but it is normally
4752 fatal so it can carry out the purpose of the interrupt: to kill the program.
4754 @value{GDBN} has the ability to detect any occurrence of a signal in your
4755 program. You can tell @value{GDBN} in advance what to do for each kind of
4758 @cindex handling signals
4759 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4760 @code{SIGALRM} be silently passed to your program
4761 (so as not to interfere with their role in the program's functioning)
4762 but to stop your program immediately whenever an error signal happens.
4763 You can change these settings with the @code{handle} command.
4766 @kindex info signals
4770 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4771 handle each one. You can use this to see the signal numbers of all
4772 the defined types of signals.
4774 @item info signals @var{sig}
4775 Similar, but print information only about the specified signal number.
4777 @code{info handle} is an alias for @code{info signals}.
4780 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4781 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4782 can be the number of a signal or its name (with or without the
4783 @samp{SIG} at the beginning); a list of signal numbers of the form
4784 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4785 known signals. Optional arguments @var{keywords}, described below,
4786 say what change to make.
4790 The keywords allowed by the @code{handle} command can be abbreviated.
4791 Their full names are:
4795 @value{GDBN} should not stop your program when this signal happens. It may
4796 still print a message telling you that the signal has come in.
4799 @value{GDBN} should stop your program when this signal happens. This implies
4800 the @code{print} keyword as well.
4803 @value{GDBN} should print a message when this signal happens.
4806 @value{GDBN} should not mention the occurrence of the signal at all. This
4807 implies the @code{nostop} keyword as well.
4811 @value{GDBN} should allow your program to see this signal; your program
4812 can handle the signal, or else it may terminate if the signal is fatal
4813 and not handled. @code{pass} and @code{noignore} are synonyms.
4817 @value{GDBN} should not allow your program to see this signal.
4818 @code{nopass} and @code{ignore} are synonyms.
4822 When a signal stops your program, the signal is not visible to the
4824 continue. Your program sees the signal then, if @code{pass} is in
4825 effect for the signal in question @emph{at that time}. In other words,
4826 after @value{GDBN} reports a signal, you can use the @code{handle}
4827 command with @code{pass} or @code{nopass} to control whether your
4828 program sees that signal when you continue.
4830 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4831 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4832 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4835 You can also use the @code{signal} command to prevent your program from
4836 seeing a signal, or cause it to see a signal it normally would not see,
4837 or to give it any signal at any time. For example, if your program stopped
4838 due to some sort of memory reference error, you might store correct
4839 values into the erroneous variables and continue, hoping to see more
4840 execution; but your program would probably terminate immediately as
4841 a result of the fatal signal once it saw the signal. To prevent this,
4842 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4845 @cindex extra signal information
4846 @anchor{extra signal information}
4848 On some targets, @value{GDBN} can inspect extra signal information
4849 associated with the intercepted signal, before it is actually
4850 delivered to the program being debugged. This information is exported
4851 by the convenience variable @code{$_siginfo}, and consists of data
4852 that is passed by the kernel to the signal handler at the time of the
4853 receipt of a signal. The data type of the information itself is
4854 target dependent. You can see the data type using the @code{ptype
4855 $_siginfo} command. On Unix systems, it typically corresponds to the
4856 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4859 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4860 referenced address that raised a segmentation fault.
4864 (@value{GDBP}) continue
4865 Program received signal SIGSEGV, Segmentation fault.
4866 0x0000000000400766 in main ()
4868 (@value{GDBP}) ptype $_siginfo
4875 struct @{...@} _kill;
4876 struct @{...@} _timer;
4878 struct @{...@} _sigchld;
4879 struct @{...@} _sigfault;
4880 struct @{...@} _sigpoll;
4883 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4887 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4888 $1 = (void *) 0x7ffff7ff7000
4892 Depending on target support, @code{$_siginfo} may also be writable.
4895 @section Stopping and Starting Multi-thread Programs
4897 @cindex stopped threads
4898 @cindex threads, stopped
4900 @cindex continuing threads
4901 @cindex threads, continuing
4903 @value{GDBN} supports debugging programs with multiple threads
4904 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4905 are two modes of controlling execution of your program within the
4906 debugger. In the default mode, referred to as @dfn{all-stop mode},
4907 when any thread in your program stops (for example, at a breakpoint
4908 or while being stepped), all other threads in the program are also stopped by
4909 @value{GDBN}. On some targets, @value{GDBN} also supports
4910 @dfn{non-stop mode}, in which other threads can continue to run freely while
4911 you examine the stopped thread in the debugger.
4914 * All-Stop Mode:: All threads stop when GDB takes control
4915 * Non-Stop Mode:: Other threads continue to execute
4916 * Background Execution:: Running your program asynchronously
4917 * Thread-Specific Breakpoints:: Controlling breakpoints
4918 * Interrupted System Calls:: GDB may interfere with system calls
4922 @subsection All-Stop Mode
4924 @cindex all-stop mode
4926 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4927 @emph{all} threads of execution stop, not just the current thread. This
4928 allows you to examine the overall state of the program, including
4929 switching between threads, without worrying that things may change
4932 Conversely, whenever you restart the program, @emph{all} threads start
4933 executing. @emph{This is true even when single-stepping} with commands
4934 like @code{step} or @code{next}.
4936 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4937 Since thread scheduling is up to your debugging target's operating
4938 system (not controlled by @value{GDBN}), other threads may
4939 execute more than one statement while the current thread completes a
4940 single step. Moreover, in general other threads stop in the middle of a
4941 statement, rather than at a clean statement boundary, when the program
4944 You might even find your program stopped in another thread after
4945 continuing or even single-stepping. This happens whenever some other
4946 thread runs into a breakpoint, a signal, or an exception before the
4947 first thread completes whatever you requested.
4949 @cindex automatic thread selection
4950 @cindex switching threads automatically
4951 @cindex threads, automatic switching
4952 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4953 signal, it automatically selects the thread where that breakpoint or
4954 signal happened. @value{GDBN} alerts you to the context switch with a
4955 message such as @samp{[Switching to Thread @var{n}]} to identify the
4958 On some OSes, you can modify @value{GDBN}'s default behavior by
4959 locking the OS scheduler to allow only a single thread to run.
4962 @item set scheduler-locking @var{mode}
4963 @cindex scheduler locking mode
4964 @cindex lock scheduler
4965 Set the scheduler locking mode. If it is @code{off}, then there is no
4966 locking and any thread may run at any time. If @code{on}, then only the
4967 current thread may run when the inferior is resumed. The @code{step}
4968 mode optimizes for single-stepping; it prevents other threads
4969 from preempting the current thread while you are stepping, so that
4970 the focus of debugging does not change unexpectedly.
4971 Other threads only rarely (or never) get a chance to run
4972 when you step. They are more likely to run when you @samp{next} over a
4973 function call, and they are completely free to run when you use commands
4974 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4975 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4976 the current thread away from the thread that you are debugging.
4978 @item show scheduler-locking
4979 Display the current scheduler locking mode.
4982 @cindex resume threads of multiple processes simultaneously
4983 By default, when you issue one of the execution commands such as
4984 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
4985 threads of the current inferior to run. For example, if @value{GDBN}
4986 is attached to two inferiors, each with two threads, the
4987 @code{continue} command resumes only the two threads of the current
4988 inferior. This is useful, for example, when you debug a program that
4989 forks and you want to hold the parent stopped (so that, for instance,
4990 it doesn't run to exit), while you debug the child. In other
4991 situations, you may not be interested in inspecting the current state
4992 of any of the processes @value{GDBN} is attached to, and you may want
4993 to resume them all until some breakpoint is hit. In the latter case,
4994 you can instruct @value{GDBN} to allow all threads of all the
4995 inferiors to run with the @w{@code{set schedule-multiple}} command.
4998 @kindex set schedule-multiple
4999 @item set schedule-multiple
5000 Set the mode for allowing threads of multiple processes to be resumed
5001 when an execution command is issued. When @code{on}, all threads of
5002 all processes are allowed to run. When @code{off}, only the threads
5003 of the current process are resumed. The default is @code{off}. The
5004 @code{scheduler-locking} mode takes precedence when set to @code{on},
5005 or while you are stepping and set to @code{step}.
5007 @item show schedule-multiple
5008 Display the current mode for resuming the execution of threads of
5013 @subsection Non-Stop Mode
5015 @cindex non-stop mode
5017 @c This section is really only a place-holder, and needs to be expanded
5018 @c with more details.
5020 For some multi-threaded targets, @value{GDBN} supports an optional
5021 mode of operation in which you can examine stopped program threads in
5022 the debugger while other threads continue to execute freely. This
5023 minimizes intrusion when debugging live systems, such as programs
5024 where some threads have real-time constraints or must continue to
5025 respond to external events. This is referred to as @dfn{non-stop} mode.
5027 In non-stop mode, when a thread stops to report a debugging event,
5028 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5029 threads as well, in contrast to the all-stop mode behavior. Additionally,
5030 execution commands such as @code{continue} and @code{step} apply by default
5031 only to the current thread in non-stop mode, rather than all threads as
5032 in all-stop mode. This allows you to control threads explicitly in
5033 ways that are not possible in all-stop mode --- for example, stepping
5034 one thread while allowing others to run freely, stepping
5035 one thread while holding all others stopped, or stepping several threads
5036 independently and simultaneously.
5038 To enter non-stop mode, use this sequence of commands before you run
5039 or attach to your program:
5042 # Enable the async interface.
5045 # If using the CLI, pagination breaks non-stop.
5048 # Finally, turn it on!
5052 You can use these commands to manipulate the non-stop mode setting:
5055 @kindex set non-stop
5056 @item set non-stop on
5057 Enable selection of non-stop mode.
5058 @item set non-stop off
5059 Disable selection of non-stop mode.
5060 @kindex show non-stop
5062 Show the current non-stop enablement setting.
5065 Note these commands only reflect whether non-stop mode is enabled,
5066 not whether the currently-executing program is being run in non-stop mode.
5067 In particular, the @code{set non-stop} preference is only consulted when
5068 @value{GDBN} starts or connects to the target program, and it is generally
5069 not possible to switch modes once debugging has started. Furthermore,
5070 since not all targets support non-stop mode, even when you have enabled
5071 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5074 In non-stop mode, all execution commands apply only to the current thread
5075 by default. That is, @code{continue} only continues one thread.
5076 To continue all threads, issue @code{continue -a} or @code{c -a}.
5078 You can use @value{GDBN}'s background execution commands
5079 (@pxref{Background Execution}) to run some threads in the background
5080 while you continue to examine or step others from @value{GDBN}.
5081 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5082 always executed asynchronously in non-stop mode.
5084 Suspending execution is done with the @code{interrupt} command when
5085 running in the background, or @kbd{Ctrl-c} during foreground execution.
5086 In all-stop mode, this stops the whole process;
5087 but in non-stop mode the interrupt applies only to the current thread.
5088 To stop the whole program, use @code{interrupt -a}.
5090 Other execution commands do not currently support the @code{-a} option.
5092 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5093 that thread current, as it does in all-stop mode. This is because the
5094 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5095 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5096 changed to a different thread just as you entered a command to operate on the
5097 previously current thread.
5099 @node Background Execution
5100 @subsection Background Execution
5102 @cindex foreground execution
5103 @cindex background execution
5104 @cindex asynchronous execution
5105 @cindex execution, foreground, background and asynchronous
5107 @value{GDBN}'s execution commands have two variants: the normal
5108 foreground (synchronous) behavior, and a background
5109 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5110 the program to report that some thread has stopped before prompting for
5111 another command. In background execution, @value{GDBN} immediately gives
5112 a command prompt so that you can issue other commands while your program runs.
5114 You need to explicitly enable asynchronous mode before you can use
5115 background execution commands. You can use these commands to
5116 manipulate the asynchronous mode setting:
5119 @kindex set target-async
5120 @item set target-async on
5121 Enable asynchronous mode.
5122 @item set target-async off
5123 Disable asynchronous mode.
5124 @kindex show target-async
5125 @item show target-async
5126 Show the current target-async setting.
5129 If the target doesn't support async mode, @value{GDBN} issues an error
5130 message if you attempt to use the background execution commands.
5132 To specify background execution, add a @code{&} to the command. For example,
5133 the background form of the @code{continue} command is @code{continue&}, or
5134 just @code{c&}. The execution commands that accept background execution
5140 @xref{Starting, , Starting your Program}.
5144 @xref{Attach, , Debugging an Already-running Process}.
5148 @xref{Continuing and Stepping, step}.
5152 @xref{Continuing and Stepping, stepi}.
5156 @xref{Continuing and Stepping, next}.
5160 @xref{Continuing and Stepping, nexti}.
5164 @xref{Continuing and Stepping, continue}.
5168 @xref{Continuing and Stepping, finish}.
5172 @xref{Continuing and Stepping, until}.
5176 Background execution is especially useful in conjunction with non-stop
5177 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5178 However, you can also use these commands in the normal all-stop mode with
5179 the restriction that you cannot issue another execution command until the
5180 previous one finishes. Examples of commands that are valid in all-stop
5181 mode while the program is running include @code{help} and @code{info break}.
5183 You can interrupt your program while it is running in the background by
5184 using the @code{interrupt} command.
5191 Suspend execution of the running program. In all-stop mode,
5192 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5193 only the current thread. To stop the whole program in non-stop mode,
5194 use @code{interrupt -a}.
5197 @node Thread-Specific Breakpoints
5198 @subsection Thread-Specific Breakpoints
5200 When your program has multiple threads (@pxref{Threads,, Debugging
5201 Programs with Multiple Threads}), you can choose whether to set
5202 breakpoints on all threads, or on a particular thread.
5205 @cindex breakpoints and threads
5206 @cindex thread breakpoints
5207 @kindex break @dots{} thread @var{threadno}
5208 @item break @var{linespec} thread @var{threadno}
5209 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5210 @var{linespec} specifies source lines; there are several ways of
5211 writing them (@pxref{Specify Location}), but the effect is always to
5212 specify some source line.
5214 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5215 to specify that you only want @value{GDBN} to stop the program when a
5216 particular thread reaches this breakpoint. @var{threadno} is one of the
5217 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5218 column of the @samp{info threads} display.
5220 If you do not specify @samp{thread @var{threadno}} when you set a
5221 breakpoint, the breakpoint applies to @emph{all} threads of your
5224 You can use the @code{thread} qualifier on conditional breakpoints as
5225 well; in this case, place @samp{thread @var{threadno}} before or
5226 after the breakpoint condition, like this:
5229 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5234 @node Interrupted System Calls
5235 @subsection Interrupted System Calls
5237 @cindex thread breakpoints and system calls
5238 @cindex system calls and thread breakpoints
5239 @cindex premature return from system calls
5240 There is an unfortunate side effect when using @value{GDBN} to debug
5241 multi-threaded programs. If one thread stops for a
5242 breakpoint, or for some other reason, and another thread is blocked in a
5243 system call, then the system call may return prematurely. This is a
5244 consequence of the interaction between multiple threads and the signals
5245 that @value{GDBN} uses to implement breakpoints and other events that
5248 To handle this problem, your program should check the return value of
5249 each system call and react appropriately. This is good programming
5252 For example, do not write code like this:
5258 The call to @code{sleep} will return early if a different thread stops
5259 at a breakpoint or for some other reason.
5261 Instead, write this:
5266 unslept = sleep (unslept);
5269 A system call is allowed to return early, so the system is still
5270 conforming to its specification. But @value{GDBN} does cause your
5271 multi-threaded program to behave differently than it would without
5274 Also, @value{GDBN} uses internal breakpoints in the thread library to
5275 monitor certain events such as thread creation and thread destruction.
5276 When such an event happens, a system call in another thread may return
5277 prematurely, even though your program does not appear to stop.
5280 @node Reverse Execution
5281 @chapter Running programs backward
5282 @cindex reverse execution
5283 @cindex running programs backward
5285 When you are debugging a program, it is not unusual to realize that
5286 you have gone too far, and some event of interest has already happened.
5287 If the target environment supports it, @value{GDBN} can allow you to
5288 ``rewind'' the program by running it backward.
5290 A target environment that supports reverse execution should be able
5291 to ``undo'' the changes in machine state that have taken place as the
5292 program was executing normally. Variables, registers etc.@: should
5293 revert to their previous values. Obviously this requires a great
5294 deal of sophistication on the part of the target environment; not
5295 all target environments can support reverse execution.
5297 When a program is executed in reverse, the instructions that
5298 have most recently been executed are ``un-executed'', in reverse
5299 order. The program counter runs backward, following the previous
5300 thread of execution in reverse. As each instruction is ``un-executed'',
5301 the values of memory and/or registers that were changed by that
5302 instruction are reverted to their previous states. After executing
5303 a piece of source code in reverse, all side effects of that code
5304 should be ``undone'', and all variables should be returned to their
5305 prior values@footnote{
5306 Note that some side effects are easier to undo than others. For instance,
5307 memory and registers are relatively easy, but device I/O is hard. Some
5308 targets may be able undo things like device I/O, and some may not.
5310 The contract between @value{GDBN} and the reverse executing target
5311 requires only that the target do something reasonable when
5312 @value{GDBN} tells it to execute backwards, and then report the
5313 results back to @value{GDBN}. Whatever the target reports back to
5314 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5315 assumes that the memory and registers that the target reports are in a
5316 consistant state, but @value{GDBN} accepts whatever it is given.
5319 If you are debugging in a target environment that supports
5320 reverse execution, @value{GDBN} provides the following commands.
5323 @kindex reverse-continue
5324 @kindex rc @r{(@code{reverse-continue})}
5325 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5326 @itemx rc @r{[}@var{ignore-count}@r{]}
5327 Beginning at the point where your program last stopped, start executing
5328 in reverse. Reverse execution will stop for breakpoints and synchronous
5329 exceptions (signals), just like normal execution. Behavior of
5330 asynchronous signals depends on the target environment.
5332 @kindex reverse-step
5333 @kindex rs @r{(@code{step})}
5334 @item reverse-step @r{[}@var{count}@r{]}
5335 Run the program backward until control reaches the start of a
5336 different source line; then stop it, and return control to @value{GDBN}.
5338 Like the @code{step} command, @code{reverse-step} will only stop
5339 at the beginning of a source line. It ``un-executes'' the previously
5340 executed source line. If the previous source line included calls to
5341 debuggable functions, @code{reverse-step} will step (backward) into
5342 the called function, stopping at the beginning of the @emph{last}
5343 statement in the called function (typically a return statement).
5345 Also, as with the @code{step} command, if non-debuggable functions are
5346 called, @code{reverse-step} will run thru them backward without stopping.
5348 @kindex reverse-stepi
5349 @kindex rsi @r{(@code{reverse-stepi})}
5350 @item reverse-stepi @r{[}@var{count}@r{]}
5351 Reverse-execute one machine instruction. Note that the instruction
5352 to be reverse-executed is @emph{not} the one pointed to by the program
5353 counter, but the instruction executed prior to that one. For instance,
5354 if the last instruction was a jump, @code{reverse-stepi} will take you
5355 back from the destination of the jump to the jump instruction itself.
5357 @kindex reverse-next
5358 @kindex rn @r{(@code{reverse-next})}
5359 @item reverse-next @r{[}@var{count}@r{]}
5360 Run backward to the beginning of the previous line executed in
5361 the current (innermost) stack frame. If the line contains function
5362 calls, they will be ``un-executed'' without stopping. Starting from
5363 the first line of a function, @code{reverse-next} will take you back
5364 to the caller of that function, @emph{before} the function was called,
5365 just as the normal @code{next} command would take you from the last
5366 line of a function back to its return to its caller
5367 @footnote{Unless the code is too heavily optimized.}.
5369 @kindex reverse-nexti
5370 @kindex rni @r{(@code{reverse-nexti})}
5371 @item reverse-nexti @r{[}@var{count}@r{]}
5372 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5373 in reverse, except that called functions are ``un-executed'' atomically.
5374 That is, if the previously executed instruction was a return from
5375 another function, @code{reverse-nexti} will continue to execute
5376 in reverse until the call to that function (from the current stack
5379 @kindex reverse-finish
5380 @item reverse-finish
5381 Just as the @code{finish} command takes you to the point where the
5382 current function returns, @code{reverse-finish} takes you to the point
5383 where it was called. Instead of ending up at the end of the current
5384 function invocation, you end up at the beginning.
5386 @kindex set exec-direction
5387 @item set exec-direction
5388 Set the direction of target execution.
5389 @itemx set exec-direction reverse
5390 @cindex execute forward or backward in time
5391 @value{GDBN} will perform all execution commands in reverse, until the
5392 exec-direction mode is changed to ``forward''. Affected commands include
5393 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5394 command cannot be used in reverse mode.
5395 @item set exec-direction forward
5396 @value{GDBN} will perform all execution commands in the normal fashion.
5397 This is the default.
5401 @node Process Record and Replay
5402 @chapter Recording Inferior's Execution and Replaying It
5403 @cindex process record and replay
5404 @cindex recording inferior's execution and replaying it
5406 On some platforms, @value{GDBN} provides a special @dfn{process record
5407 and replay} target that can record a log of the process execution, and
5408 replay it later with both forward and reverse execution commands.
5411 When this target is in use, if the execution log includes the record
5412 for the next instruction, @value{GDBN} will debug in @dfn{replay
5413 mode}. In the replay mode, the inferior does not really execute code
5414 instructions. Instead, all the events that normally happen during
5415 code execution are taken from the execution log. While code is not
5416 really executed in replay mode, the values of registers (including the
5417 program counter register) and the memory of the inferior are still
5418 changed as they normally would. Their contents are taken from the
5422 If the record for the next instruction is not in the execution log,
5423 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5424 inferior executes normally, and @value{GDBN} records the execution log
5427 The process record and replay target supports reverse execution
5428 (@pxref{Reverse Execution}), even if the platform on which the
5429 inferior runs does not. However, the reverse execution is limited in
5430 this case by the range of the instructions recorded in the execution
5431 log. In other words, reverse execution on platforms that don't
5432 support it directly can only be done in the replay mode.
5434 When debugging in the reverse direction, @value{GDBN} will work in
5435 replay mode as long as the execution log includes the record for the
5436 previous instruction; otherwise, it will work in record mode, if the
5437 platform supports reverse execution, or stop if not.
5439 For architecture environments that support process record and replay,
5440 @value{GDBN} provides the following commands:
5443 @kindex target record
5447 This command starts the process record and replay target. The process
5448 record and replay target can only debug a process that is already
5449 running. Therefore, you need first to start the process with the
5450 @kbd{run} or @kbd{start} commands, and then start the recording with
5451 the @kbd{target record} command.
5453 Both @code{record} and @code{rec} are aliases of @code{target record}.
5455 @cindex displaced stepping, and process record and replay
5456 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5457 will be automatically disabled when process record and replay target
5458 is started. That's because the process record and replay target
5459 doesn't support displaced stepping.
5461 @cindex non-stop mode, and process record and replay
5462 @cindex asynchronous execution, and process record and replay
5463 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5464 the asynchronous execution mode (@pxref{Background Execution}), the
5465 process record and replay target cannot be started because it doesn't
5466 support these two modes.
5471 Stop the process record and replay target. When process record and
5472 replay target stops, the entire execution log will be deleted and the
5473 inferior will either be terminated, or will remain in its final state.
5475 When you stop the process record and replay target in record mode (at
5476 the end of the execution log), the inferior will be stopped at the
5477 next instruction that would have been recorded. In other words, if
5478 you record for a while and then stop recording, the inferior process
5479 will be left in the same state as if the recording never happened.
5481 On the other hand, if the process record and replay target is stopped
5482 while in replay mode (that is, not at the end of the execution log,
5483 but at some earlier point), the inferior process will become ``live''
5484 at that earlier state, and it will then be possible to continue the
5485 usual ``live'' debugging of the process from that state.
5487 When the inferior process exits, or @value{GDBN} detaches from it,
5488 process record and replay target will automatically stop itself.
5490 @kindex set record insn-number-max
5491 @item set record insn-number-max @var{limit}
5492 Set the limit of instructions to be recorded. Default value is 200000.
5494 If @var{limit} is a positive number, then @value{GDBN} will start
5495 deleting instructions from the log once the number of the record
5496 instructions becomes greater than @var{limit}. For every new recorded
5497 instruction, @value{GDBN} will delete the earliest recorded
5498 instruction to keep the number of recorded instructions at the limit.
5499 (Since deleting recorded instructions loses information, @value{GDBN}
5500 lets you control what happens when the limit is reached, by means of
5501 the @code{stop-at-limit} option, described below.)
5503 If @var{limit} is zero, @value{GDBN} will never delete recorded
5504 instructions from the execution log. The number of recorded
5505 instructions is unlimited in this case.
5507 @kindex show record insn-number-max
5508 @item show record insn-number-max
5509 Show the limit of instructions to be recorded.
5511 @kindex set record stop-at-limit
5512 @item set record stop-at-limit
5513 Control the behavior when the number of recorded instructions reaches
5514 the limit. If ON (the default), @value{GDBN} will stop when the limit
5515 is reached for the first time and ask you whether you want to stop the
5516 inferior or continue running it and recording the execution log. If
5517 you decide to continue recording, each new recorded instruction will
5518 cause the oldest one to be deleted.
5520 If this option is OFF, @value{GDBN} will automatically delete the
5521 oldest record to make room for each new one, without asking.
5523 @kindex show record stop-at-limit
5524 @item show record stop-at-limit
5525 Show the current setting of @code{stop-at-limit}.
5529 Show various statistics about the state of process record and its
5530 in-memory execution log buffer, including:
5534 Whether in record mode or replay mode.
5536 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5538 Highest recorded instruction number.
5540 Current instruction about to be replayed (if in replay mode).
5542 Number of instructions contained in the execution log.
5544 Maximum number of instructions that may be contained in the execution log.
5547 @kindex record delete
5550 When record target runs in replay mode (``in the past''), delete the
5551 subsequent execution log and begin to record a new execution log starting
5552 from the current address. This means you will abandon the previously
5553 recorded ``future'' and begin recording a new ``future''.
5558 @chapter Examining the Stack
5560 When your program has stopped, the first thing you need to know is where it
5561 stopped and how it got there.
5564 Each time your program performs a function call, information about the call
5566 That information includes the location of the call in your program,
5567 the arguments of the call,
5568 and the local variables of the function being called.
5569 The information is saved in a block of data called a @dfn{stack frame}.
5570 The stack frames are allocated in a region of memory called the @dfn{call
5573 When your program stops, the @value{GDBN} commands for examining the
5574 stack allow you to see all of this information.
5576 @cindex selected frame
5577 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5578 @value{GDBN} commands refer implicitly to the selected frame. In
5579 particular, whenever you ask @value{GDBN} for the value of a variable in
5580 your program, the value is found in the selected frame. There are
5581 special @value{GDBN} commands to select whichever frame you are
5582 interested in. @xref{Selection, ,Selecting a Frame}.
5584 When your program stops, @value{GDBN} automatically selects the
5585 currently executing frame and describes it briefly, similar to the
5586 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5589 * Frames:: Stack frames
5590 * Backtrace:: Backtraces
5591 * Selection:: Selecting a frame
5592 * Frame Info:: Information on a frame
5597 @section Stack Frames
5599 @cindex frame, definition
5601 The call stack is divided up into contiguous pieces called @dfn{stack
5602 frames}, or @dfn{frames} for short; each frame is the data associated
5603 with one call to one function. The frame contains the arguments given
5604 to the function, the function's local variables, and the address at
5605 which the function is executing.
5607 @cindex initial frame
5608 @cindex outermost frame
5609 @cindex innermost frame
5610 When your program is started, the stack has only one frame, that of the
5611 function @code{main}. This is called the @dfn{initial} frame or the
5612 @dfn{outermost} frame. Each time a function is called, a new frame is
5613 made. Each time a function returns, the frame for that function invocation
5614 is eliminated. If a function is recursive, there can be many frames for
5615 the same function. The frame for the function in which execution is
5616 actually occurring is called the @dfn{innermost} frame. This is the most
5617 recently created of all the stack frames that still exist.
5619 @cindex frame pointer
5620 Inside your program, stack frames are identified by their addresses. A
5621 stack frame consists of many bytes, each of which has its own address; each
5622 kind of computer has a convention for choosing one byte whose
5623 address serves as the address of the frame. Usually this address is kept
5624 in a register called the @dfn{frame pointer register}
5625 (@pxref{Registers, $fp}) while execution is going on in that frame.
5627 @cindex frame number
5628 @value{GDBN} assigns numbers to all existing stack frames, starting with
5629 zero for the innermost frame, one for the frame that called it,
5630 and so on upward. These numbers do not really exist in your program;
5631 they are assigned by @value{GDBN} to give you a way of designating stack
5632 frames in @value{GDBN} commands.
5634 @c The -fomit-frame-pointer below perennially causes hbox overflow
5635 @c underflow problems.
5636 @cindex frameless execution
5637 Some compilers provide a way to compile functions so that they operate
5638 without stack frames. (For example, the @value{NGCC} option
5640 @samp{-fomit-frame-pointer}
5642 generates functions without a frame.)
5643 This is occasionally done with heavily used library functions to save
5644 the frame setup time. @value{GDBN} has limited facilities for dealing
5645 with these function invocations. If the innermost function invocation
5646 has no stack frame, @value{GDBN} nevertheless regards it as though
5647 it had a separate frame, which is numbered zero as usual, allowing
5648 correct tracing of the function call chain. However, @value{GDBN} has
5649 no provision for frameless functions elsewhere in the stack.
5652 @kindex frame@r{, command}
5653 @cindex current stack frame
5654 @item frame @var{args}
5655 The @code{frame} command allows you to move from one stack frame to another,
5656 and to print the stack frame you select. @var{args} may be either the
5657 address of the frame or the stack frame number. Without an argument,
5658 @code{frame} prints the current stack frame.
5660 @kindex select-frame
5661 @cindex selecting frame silently
5663 The @code{select-frame} command allows you to move from one stack frame
5664 to another without printing the frame. This is the silent version of
5672 @cindex call stack traces
5673 A backtrace is a summary of how your program got where it is. It shows one
5674 line per frame, for many frames, starting with the currently executing
5675 frame (frame zero), followed by its caller (frame one), and on up the
5680 @kindex bt @r{(@code{backtrace})}
5683 Print a backtrace of the entire stack: one line per frame for all
5684 frames in the stack.
5686 You can stop the backtrace at any time by typing the system interrupt
5687 character, normally @kbd{Ctrl-c}.
5689 @item backtrace @var{n}
5691 Similar, but print only the innermost @var{n} frames.
5693 @item backtrace -@var{n}
5695 Similar, but print only the outermost @var{n} frames.
5697 @item backtrace full
5699 @itemx bt full @var{n}
5700 @itemx bt full -@var{n}
5701 Print the values of the local variables also. @var{n} specifies the
5702 number of frames to print, as described above.
5707 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5708 are additional aliases for @code{backtrace}.
5710 @cindex multiple threads, backtrace
5711 In a multi-threaded program, @value{GDBN} by default shows the
5712 backtrace only for the current thread. To display the backtrace for
5713 several or all of the threads, use the command @code{thread apply}
5714 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5715 apply all backtrace}, @value{GDBN} will display the backtrace for all
5716 the threads; this is handy when you debug a core dump of a
5717 multi-threaded program.
5719 Each line in the backtrace shows the frame number and the function name.
5720 The program counter value is also shown---unless you use @code{set
5721 print address off}. The backtrace also shows the source file name and
5722 line number, as well as the arguments to the function. The program
5723 counter value is omitted if it is at the beginning of the code for that
5726 Here is an example of a backtrace. It was made with the command
5727 @samp{bt 3}, so it shows the innermost three frames.
5731 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5733 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5734 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5736 (More stack frames follow...)
5741 The display for frame zero does not begin with a program counter
5742 value, indicating that your program has stopped at the beginning of the
5743 code for line @code{993} of @code{builtin.c}.
5746 The value of parameter @code{data} in frame 1 has been replaced by
5747 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5748 only if it is a scalar (integer, pointer, enumeration, etc). See command
5749 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5750 on how to configure the way function parameter values are printed.
5752 @cindex value optimized out, in backtrace
5753 @cindex function call arguments, optimized out
5754 If your program was compiled with optimizations, some compilers will
5755 optimize away arguments passed to functions if those arguments are
5756 never used after the call. Such optimizations generate code that
5757 passes arguments through registers, but doesn't store those arguments
5758 in the stack frame. @value{GDBN} has no way of displaying such
5759 arguments in stack frames other than the innermost one. Here's what
5760 such a backtrace might look like:
5764 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5766 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5767 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5769 (More stack frames follow...)
5774 The values of arguments that were not saved in their stack frames are
5775 shown as @samp{<value optimized out>}.
5777 If you need to display the values of such optimized-out arguments,
5778 either deduce that from other variables whose values depend on the one
5779 you are interested in, or recompile without optimizations.
5781 @cindex backtrace beyond @code{main} function
5782 @cindex program entry point
5783 @cindex startup code, and backtrace
5784 Most programs have a standard user entry point---a place where system
5785 libraries and startup code transition into user code. For C this is
5786 @code{main}@footnote{
5787 Note that embedded programs (the so-called ``free-standing''
5788 environment) are not required to have a @code{main} function as the
5789 entry point. They could even have multiple entry points.}.
5790 When @value{GDBN} finds the entry function in a backtrace
5791 it will terminate the backtrace, to avoid tracing into highly
5792 system-specific (and generally uninteresting) code.
5794 If you need to examine the startup code, or limit the number of levels
5795 in a backtrace, you can change this behavior:
5798 @item set backtrace past-main
5799 @itemx set backtrace past-main on
5800 @kindex set backtrace
5801 Backtraces will continue past the user entry point.
5803 @item set backtrace past-main off
5804 Backtraces will stop when they encounter the user entry point. This is the
5807 @item show backtrace past-main
5808 @kindex show backtrace
5809 Display the current user entry point backtrace policy.
5811 @item set backtrace past-entry
5812 @itemx set backtrace past-entry on
5813 Backtraces will continue past the internal entry point of an application.
5814 This entry point is encoded by the linker when the application is built,
5815 and is likely before the user entry point @code{main} (or equivalent) is called.
5817 @item set backtrace past-entry off
5818 Backtraces will stop when they encounter the internal entry point of an
5819 application. This is the default.
5821 @item show backtrace past-entry
5822 Display the current internal entry point backtrace policy.
5824 @item set backtrace limit @var{n}
5825 @itemx set backtrace limit 0
5826 @cindex backtrace limit
5827 Limit the backtrace to @var{n} levels. A value of zero means
5830 @item show backtrace limit
5831 Display the current limit on backtrace levels.
5835 @section Selecting a Frame
5837 Most commands for examining the stack and other data in your program work on
5838 whichever stack frame is selected at the moment. Here are the commands for
5839 selecting a stack frame; all of them finish by printing a brief description
5840 of the stack frame just selected.
5843 @kindex frame@r{, selecting}
5844 @kindex f @r{(@code{frame})}
5847 Select frame number @var{n}. Recall that frame zero is the innermost
5848 (currently executing) frame, frame one is the frame that called the
5849 innermost one, and so on. The highest-numbered frame is the one for
5852 @item frame @var{addr}
5854 Select the frame at address @var{addr}. This is useful mainly if the
5855 chaining of stack frames has been damaged by a bug, making it
5856 impossible for @value{GDBN} to assign numbers properly to all frames. In
5857 addition, this can be useful when your program has multiple stacks and
5858 switches between them.
5860 On the SPARC architecture, @code{frame} needs two addresses to
5861 select an arbitrary frame: a frame pointer and a stack pointer.
5863 On the MIPS and Alpha architecture, it needs two addresses: a stack
5864 pointer and a program counter.
5866 On the 29k architecture, it needs three addresses: a register stack
5867 pointer, a program counter, and a memory stack pointer.
5871 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5872 advances toward the outermost frame, to higher frame numbers, to frames
5873 that have existed longer. @var{n} defaults to one.
5876 @kindex do @r{(@code{down})}
5878 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5879 advances toward the innermost frame, to lower frame numbers, to frames
5880 that were created more recently. @var{n} defaults to one. You may
5881 abbreviate @code{down} as @code{do}.
5884 All of these commands end by printing two lines of output describing the
5885 frame. The first line shows the frame number, the function name, the
5886 arguments, and the source file and line number of execution in that
5887 frame. The second line shows the text of that source line.
5895 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5897 10 read_input_file (argv[i]);
5901 After such a printout, the @code{list} command with no arguments
5902 prints ten lines centered on the point of execution in the frame.
5903 You can also edit the program at the point of execution with your favorite
5904 editing program by typing @code{edit}.
5905 @xref{List, ,Printing Source Lines},
5909 @kindex down-silently
5911 @item up-silently @var{n}
5912 @itemx down-silently @var{n}
5913 These two commands are variants of @code{up} and @code{down},
5914 respectively; they differ in that they do their work silently, without
5915 causing display of the new frame. They are intended primarily for use
5916 in @value{GDBN} command scripts, where the output might be unnecessary and
5921 @section Information About a Frame
5923 There are several other commands to print information about the selected
5929 When used without any argument, this command does not change which
5930 frame is selected, but prints a brief description of the currently
5931 selected stack frame. It can be abbreviated @code{f}. With an
5932 argument, this command is used to select a stack frame.
5933 @xref{Selection, ,Selecting a Frame}.
5936 @kindex info f @r{(@code{info frame})}
5939 This command prints a verbose description of the selected stack frame,
5944 the address of the frame
5946 the address of the next frame down (called by this frame)
5948 the address of the next frame up (caller of this frame)
5950 the language in which the source code corresponding to this frame is written
5952 the address of the frame's arguments
5954 the address of the frame's local variables
5956 the program counter saved in it (the address of execution in the caller frame)
5958 which registers were saved in the frame
5961 @noindent The verbose description is useful when
5962 something has gone wrong that has made the stack format fail to fit
5963 the usual conventions.
5965 @item info frame @var{addr}
5966 @itemx info f @var{addr}
5967 Print a verbose description of the frame at address @var{addr}, without
5968 selecting that frame. The selected frame remains unchanged by this
5969 command. This requires the same kind of address (more than one for some
5970 architectures) that you specify in the @code{frame} command.
5971 @xref{Selection, ,Selecting a Frame}.
5975 Print the arguments of the selected frame, each on a separate line.
5979 Print the local variables of the selected frame, each on a separate
5980 line. These are all variables (declared either static or automatic)
5981 accessible at the point of execution of the selected frame.
5984 @cindex catch exceptions, list active handlers
5985 @cindex exception handlers, how to list
5987 Print a list of all the exception handlers that are active in the
5988 current stack frame at the current point of execution. To see other
5989 exception handlers, visit the associated frame (using the @code{up},
5990 @code{down}, or @code{frame} commands); then type @code{info catch}.
5991 @xref{Set Catchpoints, , Setting Catchpoints}.
5997 @chapter Examining Source Files
5999 @value{GDBN} can print parts of your program's source, since the debugging
6000 information recorded in the program tells @value{GDBN} what source files were
6001 used to build it. When your program stops, @value{GDBN} spontaneously prints
6002 the line where it stopped. Likewise, when you select a stack frame
6003 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6004 execution in that frame has stopped. You can print other portions of
6005 source files by explicit command.
6007 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6008 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6009 @value{GDBN} under @sc{gnu} Emacs}.
6012 * List:: Printing source lines
6013 * Specify Location:: How to specify code locations
6014 * Edit:: Editing source files
6015 * Search:: Searching source files
6016 * Source Path:: Specifying source directories
6017 * Machine Code:: Source and machine code
6021 @section Printing Source Lines
6024 @kindex l @r{(@code{list})}
6025 To print lines from a source file, use the @code{list} command
6026 (abbreviated @code{l}). By default, ten lines are printed.
6027 There are several ways to specify what part of the file you want to
6028 print; see @ref{Specify Location}, for the full list.
6030 Here are the forms of the @code{list} command most commonly used:
6033 @item list @var{linenum}
6034 Print lines centered around line number @var{linenum} in the
6035 current source file.
6037 @item list @var{function}
6038 Print lines centered around the beginning of function
6042 Print more lines. If the last lines printed were printed with a
6043 @code{list} command, this prints lines following the last lines
6044 printed; however, if the last line printed was a solitary line printed
6045 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6046 Stack}), this prints lines centered around that line.
6049 Print lines just before the lines last printed.
6052 @cindex @code{list}, how many lines to display
6053 By default, @value{GDBN} prints ten source lines with any of these forms of
6054 the @code{list} command. You can change this using @code{set listsize}:
6057 @kindex set listsize
6058 @item set listsize @var{count}
6059 Make the @code{list} command display @var{count} source lines (unless
6060 the @code{list} argument explicitly specifies some other number).
6062 @kindex show listsize
6064 Display the number of lines that @code{list} prints.
6067 Repeating a @code{list} command with @key{RET} discards the argument,
6068 so it is equivalent to typing just @code{list}. This is more useful
6069 than listing the same lines again. An exception is made for an
6070 argument of @samp{-}; that argument is preserved in repetition so that
6071 each repetition moves up in the source file.
6073 In general, the @code{list} command expects you to supply zero, one or two
6074 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6075 of writing them (@pxref{Specify Location}), but the effect is always
6076 to specify some source line.
6078 Here is a complete description of the possible arguments for @code{list}:
6081 @item list @var{linespec}
6082 Print lines centered around the line specified by @var{linespec}.
6084 @item list @var{first},@var{last}
6085 Print lines from @var{first} to @var{last}. Both arguments are
6086 linespecs. When a @code{list} command has two linespecs, and the
6087 source file of the second linespec is omitted, this refers to
6088 the same source file as the first linespec.
6090 @item list ,@var{last}
6091 Print lines ending with @var{last}.
6093 @item list @var{first},
6094 Print lines starting with @var{first}.
6097 Print lines just after the lines last printed.
6100 Print lines just before the lines last printed.
6103 As described in the preceding table.
6106 @node Specify Location
6107 @section Specifying a Location
6108 @cindex specifying location
6111 Several @value{GDBN} commands accept arguments that specify a location
6112 of your program's code. Since @value{GDBN} is a source-level
6113 debugger, a location usually specifies some line in the source code;
6114 for that reason, locations are also known as @dfn{linespecs}.
6116 Here are all the different ways of specifying a code location that
6117 @value{GDBN} understands:
6121 Specifies the line number @var{linenum} of the current source file.
6124 @itemx +@var{offset}
6125 Specifies the line @var{offset} lines before or after the @dfn{current
6126 line}. For the @code{list} command, the current line is the last one
6127 printed; for the breakpoint commands, this is the line at which
6128 execution stopped in the currently selected @dfn{stack frame}
6129 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6130 used as the second of the two linespecs in a @code{list} command,
6131 this specifies the line @var{offset} lines up or down from the first
6134 @item @var{filename}:@var{linenum}
6135 Specifies the line @var{linenum} in the source file @var{filename}.
6137 @item @var{function}
6138 Specifies the line that begins the body of the function @var{function}.
6139 For example, in C, this is the line with the open brace.
6141 @item @var{filename}:@var{function}
6142 Specifies the line that begins the body of the function @var{function}
6143 in the file @var{filename}. You only need the file name with a
6144 function name to avoid ambiguity when there are identically named
6145 functions in different source files.
6147 @item *@var{address}
6148 Specifies the program address @var{address}. For line-oriented
6149 commands, such as @code{list} and @code{edit}, this specifies a source
6150 line that contains @var{address}. For @code{break} and other
6151 breakpoint oriented commands, this can be used to set breakpoints in
6152 parts of your program which do not have debugging information or
6155 Here @var{address} may be any expression valid in the current working
6156 language (@pxref{Languages, working language}) that specifies a code
6157 address. In addition, as a convenience, @value{GDBN} extends the
6158 semantics of expressions used in locations to cover the situations
6159 that frequently happen during debugging. Here are the various forms
6163 @item @var{expression}
6164 Any expression valid in the current working language.
6166 @item @var{funcaddr}
6167 An address of a function or procedure derived from its name. In C,
6168 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6169 simply the function's name @var{function} (and actually a special case
6170 of a valid expression). In Pascal and Modula-2, this is
6171 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6172 (although the Pascal form also works).
6174 This form specifies the address of the function's first instruction,
6175 before the stack frame and arguments have been set up.
6177 @item '@var{filename}'::@var{funcaddr}
6178 Like @var{funcaddr} above, but also specifies the name of the source
6179 file explicitly. This is useful if the name of the function does not
6180 specify the function unambiguously, e.g., if there are several
6181 functions with identical names in different source files.
6188 @section Editing Source Files
6189 @cindex editing source files
6192 @kindex e @r{(@code{edit})}
6193 To edit the lines in a source file, use the @code{edit} command.
6194 The editing program of your choice
6195 is invoked with the current line set to
6196 the active line in the program.
6197 Alternatively, there are several ways to specify what part of the file you
6198 want to print if you want to see other parts of the program:
6201 @item edit @var{location}
6202 Edit the source file specified by @code{location}. Editing starts at
6203 that @var{location}, e.g., at the specified source line of the
6204 specified file. @xref{Specify Location}, for all the possible forms
6205 of the @var{location} argument; here are the forms of the @code{edit}
6206 command most commonly used:
6209 @item edit @var{number}
6210 Edit the current source file with @var{number} as the active line number.
6212 @item edit @var{function}
6213 Edit the file containing @var{function} at the beginning of its definition.
6218 @subsection Choosing your Editor
6219 You can customize @value{GDBN} to use any editor you want
6221 The only restriction is that your editor (say @code{ex}), recognizes the
6222 following command-line syntax:
6224 ex +@var{number} file
6226 The optional numeric value +@var{number} specifies the number of the line in
6227 the file where to start editing.}.
6228 By default, it is @file{@value{EDITOR}}, but you can change this
6229 by setting the environment variable @code{EDITOR} before using
6230 @value{GDBN}. For example, to configure @value{GDBN} to use the
6231 @code{vi} editor, you could use these commands with the @code{sh} shell:
6237 or in the @code{csh} shell,
6239 setenv EDITOR /usr/bin/vi
6244 @section Searching Source Files
6245 @cindex searching source files
6247 There are two commands for searching through the current source file for a
6252 @kindex forward-search
6253 @item forward-search @var{regexp}
6254 @itemx search @var{regexp}
6255 The command @samp{forward-search @var{regexp}} checks each line,
6256 starting with the one following the last line listed, for a match for
6257 @var{regexp}. It lists the line that is found. You can use the
6258 synonym @samp{search @var{regexp}} or abbreviate the command name as
6261 @kindex reverse-search
6262 @item reverse-search @var{regexp}
6263 The command @samp{reverse-search @var{regexp}} checks each line, starting
6264 with the one before the last line listed and going backward, for a match
6265 for @var{regexp}. It lists the line that is found. You can abbreviate
6266 this command as @code{rev}.
6270 @section Specifying Source Directories
6273 @cindex directories for source files
6274 Executable programs sometimes do not record the directories of the source
6275 files from which they were compiled, just the names. Even when they do,
6276 the directories could be moved between the compilation and your debugging
6277 session. @value{GDBN} has a list of directories to search for source files;
6278 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6279 it tries all the directories in the list, in the order they are present
6280 in the list, until it finds a file with the desired name.
6282 For example, suppose an executable references the file
6283 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6284 @file{/mnt/cross}. The file is first looked up literally; if this
6285 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6286 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6287 message is printed. @value{GDBN} does not look up the parts of the
6288 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6289 Likewise, the subdirectories of the source path are not searched: if
6290 the source path is @file{/mnt/cross}, and the binary refers to
6291 @file{foo.c}, @value{GDBN} would not find it under
6292 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6294 Plain file names, relative file names with leading directories, file
6295 names containing dots, etc.@: are all treated as described above; for
6296 instance, if the source path is @file{/mnt/cross}, and the source file
6297 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6298 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6299 that---@file{/mnt/cross/foo.c}.
6301 Note that the executable search path is @emph{not} used to locate the
6304 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6305 any information it has cached about where source files are found and where
6306 each line is in the file.
6310 When you start @value{GDBN}, its source path includes only @samp{cdir}
6311 and @samp{cwd}, in that order.
6312 To add other directories, use the @code{directory} command.
6314 The search path is used to find both program source files and @value{GDBN}
6315 script files (read using the @samp{-command} option and @samp{source} command).
6317 In addition to the source path, @value{GDBN} provides a set of commands
6318 that manage a list of source path substitution rules. A @dfn{substitution
6319 rule} specifies how to rewrite source directories stored in the program's
6320 debug information in case the sources were moved to a different
6321 directory between compilation and debugging. A rule is made of
6322 two strings, the first specifying what needs to be rewritten in
6323 the path, and the second specifying how it should be rewritten.
6324 In @ref{set substitute-path}, we name these two parts @var{from} and
6325 @var{to} respectively. @value{GDBN} does a simple string replacement
6326 of @var{from} with @var{to} at the start of the directory part of the
6327 source file name, and uses that result instead of the original file
6328 name to look up the sources.
6330 Using the previous example, suppose the @file{foo-1.0} tree has been
6331 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6332 @value{GDBN} to replace @file{/usr/src} in all source path names with
6333 @file{/mnt/cross}. The first lookup will then be
6334 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6335 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6336 substitution rule, use the @code{set substitute-path} command
6337 (@pxref{set substitute-path}).
6339 To avoid unexpected substitution results, a rule is applied only if the
6340 @var{from} part of the directory name ends at a directory separator.
6341 For instance, a rule substituting @file{/usr/source} into
6342 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6343 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6344 is applied only at the beginning of the directory name, this rule will
6345 not be applied to @file{/root/usr/source/baz.c} either.
6347 In many cases, you can achieve the same result using the @code{directory}
6348 command. However, @code{set substitute-path} can be more efficient in
6349 the case where the sources are organized in a complex tree with multiple
6350 subdirectories. With the @code{directory} command, you need to add each
6351 subdirectory of your project. If you moved the entire tree while
6352 preserving its internal organization, then @code{set substitute-path}
6353 allows you to direct the debugger to all the sources with one single
6356 @code{set substitute-path} is also more than just a shortcut command.
6357 The source path is only used if the file at the original location no
6358 longer exists. On the other hand, @code{set substitute-path} modifies
6359 the debugger behavior to look at the rewritten location instead. So, if
6360 for any reason a source file that is not relevant to your executable is
6361 located at the original location, a substitution rule is the only
6362 method available to point @value{GDBN} at the new location.
6364 @cindex @samp{--with-relocated-sources}
6365 @cindex default source path substitution
6366 You can configure a default source path substitution rule by
6367 configuring @value{GDBN} with the
6368 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6369 should be the name of a directory under @value{GDBN}'s configured
6370 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6371 directory names in debug information under @var{dir} will be adjusted
6372 automatically if the installed @value{GDBN} is moved to a new
6373 location. This is useful if @value{GDBN}, libraries or executables
6374 with debug information and corresponding source code are being moved
6378 @item directory @var{dirname} @dots{}
6379 @item dir @var{dirname} @dots{}
6380 Add directory @var{dirname} to the front of the source path. Several
6381 directory names may be given to this command, separated by @samp{:}
6382 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6383 part of absolute file names) or
6384 whitespace. You may specify a directory that is already in the source
6385 path; this moves it forward, so @value{GDBN} searches it sooner.
6389 @vindex $cdir@r{, convenience variable}
6390 @vindex $cwd@r{, convenience variable}
6391 @cindex compilation directory
6392 @cindex current directory
6393 @cindex working directory
6394 @cindex directory, current
6395 @cindex directory, compilation
6396 You can use the string @samp{$cdir} to refer to the compilation
6397 directory (if one is recorded), and @samp{$cwd} to refer to the current
6398 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6399 tracks the current working directory as it changes during your @value{GDBN}
6400 session, while the latter is immediately expanded to the current
6401 directory at the time you add an entry to the source path.
6404 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6406 @c RET-repeat for @code{directory} is explicitly disabled, but since
6407 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6409 @item show directories
6410 @kindex show directories
6411 Print the source path: show which directories it contains.
6413 @anchor{set substitute-path}
6414 @item set substitute-path @var{from} @var{to}
6415 @kindex set substitute-path
6416 Define a source path substitution rule, and add it at the end of the
6417 current list of existing substitution rules. If a rule with the same
6418 @var{from} was already defined, then the old rule is also deleted.
6420 For example, if the file @file{/foo/bar/baz.c} was moved to
6421 @file{/mnt/cross/baz.c}, then the command
6424 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6428 will tell @value{GDBN} to replace @samp{/usr/src} with
6429 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6430 @file{baz.c} even though it was moved.
6432 In the case when more than one substitution rule have been defined,
6433 the rules are evaluated one by one in the order where they have been
6434 defined. The first one matching, if any, is selected to perform
6437 For instance, if we had entered the following commands:
6440 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6441 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6445 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6446 @file{/mnt/include/defs.h} by using the first rule. However, it would
6447 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6448 @file{/mnt/src/lib/foo.c}.
6451 @item unset substitute-path [path]
6452 @kindex unset substitute-path
6453 If a path is specified, search the current list of substitution rules
6454 for a rule that would rewrite that path. Delete that rule if found.
6455 A warning is emitted by the debugger if no rule could be found.
6457 If no path is specified, then all substitution rules are deleted.
6459 @item show substitute-path [path]
6460 @kindex show substitute-path
6461 If a path is specified, then print the source path substitution rule
6462 which would rewrite that path, if any.
6464 If no path is specified, then print all existing source path substitution
6469 If your source path is cluttered with directories that are no longer of
6470 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6471 versions of source. You can correct the situation as follows:
6475 Use @code{directory} with no argument to reset the source path to its default value.
6478 Use @code{directory} with suitable arguments to reinstall the
6479 directories you want in the source path. You can add all the
6480 directories in one command.
6484 @section Source and Machine Code
6485 @cindex source line and its code address
6487 You can use the command @code{info line} to map source lines to program
6488 addresses (and vice versa), and the command @code{disassemble} to display
6489 a range of addresses as machine instructions. You can use the command
6490 @code{set disassemble-next-line} to set whether to disassemble next
6491 source line when execution stops. When run under @sc{gnu} Emacs
6492 mode, the @code{info line} command causes the arrow to point to the
6493 line specified. Also, @code{info line} prints addresses in symbolic form as
6498 @item info line @var{linespec}
6499 Print the starting and ending addresses of the compiled code for
6500 source line @var{linespec}. You can specify source lines in any of
6501 the ways documented in @ref{Specify Location}.
6504 For example, we can use @code{info line} to discover the location of
6505 the object code for the first line of function
6506 @code{m4_changequote}:
6508 @c FIXME: I think this example should also show the addresses in
6509 @c symbolic form, as they usually would be displayed.
6511 (@value{GDBP}) info line m4_changequote
6512 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6516 @cindex code address and its source line
6517 We can also inquire (using @code{*@var{addr}} as the form for
6518 @var{linespec}) what source line covers a particular address:
6520 (@value{GDBP}) info line *0x63ff
6521 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6524 @cindex @code{$_} and @code{info line}
6525 @cindex @code{x} command, default address
6526 @kindex x@r{(examine), and} info line
6527 After @code{info line}, the default address for the @code{x} command
6528 is changed to the starting address of the line, so that @samp{x/i} is
6529 sufficient to begin examining the machine code (@pxref{Memory,
6530 ,Examining Memory}). Also, this address is saved as the value of the
6531 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6536 @cindex assembly instructions
6537 @cindex instructions, assembly
6538 @cindex machine instructions
6539 @cindex listing machine instructions
6541 @itemx disassemble /m
6542 @itemx disassemble /r
6543 This specialized command dumps a range of memory as machine
6544 instructions. It can also print mixed source+disassembly by specifying
6545 the @code{/m} modifier and print the raw instructions in hex as well as
6546 in symbolic form by specifying the @code{/r}.
6547 The default memory range is the function surrounding the
6548 program counter of the selected frame. A single argument to this
6549 command is a program counter value; @value{GDBN} dumps the function
6550 surrounding this value. When two arguments are given, they should
6551 be separated by a comma, possibly surrounded by whitespace. The
6552 arguments specify a range of addresses (first inclusive, second exclusive)
6553 to dump. In that case, the name of the function is also printed (since
6554 there could be several functions in the given range).
6556 The argument(s) can be any expression yielding a numeric value, such as
6557 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6559 If the range of memory being disassembled contains current program counter,
6560 the instruction at that location is shown with a @code{=>} marker.
6563 The following example shows the disassembly of a range of addresses of
6564 HP PA-RISC 2.0 code:
6567 (@value{GDBP}) disas 0x32c4, 0x32e4
6568 Dump of assembler code from 0x32c4 to 0x32e4:
6569 0x32c4 <main+204>: addil 0,dp
6570 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6571 0x32cc <main+212>: ldil 0x3000,r31
6572 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6573 0x32d4 <main+220>: ldo 0(r31),rp
6574 0x32d8 <main+224>: addil -0x800,dp
6575 0x32dc <main+228>: ldo 0x588(r1),r26
6576 0x32e0 <main+232>: ldil 0x3000,r31
6577 End of assembler dump.
6580 Here is an example showing mixed source+assembly for Intel x86, when the
6581 program is stopped just after function prologue:
6584 (@value{GDBP}) disas /m main
6585 Dump of assembler code for function main:
6587 0x08048330 <+0>: push %ebp
6588 0x08048331 <+1>: mov %esp,%ebp
6589 0x08048333 <+3>: sub $0x8,%esp
6590 0x08048336 <+6>: and $0xfffffff0,%esp
6591 0x08048339 <+9>: sub $0x10,%esp
6593 6 printf ("Hello.\n");
6594 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6595 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6599 0x08048348 <+24>: mov $0x0,%eax
6600 0x0804834d <+29>: leave
6601 0x0804834e <+30>: ret
6603 End of assembler dump.
6606 Some architectures have more than one commonly-used set of instruction
6607 mnemonics or other syntax.
6609 For programs that were dynamically linked and use shared libraries,
6610 instructions that call functions or branch to locations in the shared
6611 libraries might show a seemingly bogus location---it's actually a
6612 location of the relocation table. On some architectures, @value{GDBN}
6613 might be able to resolve these to actual function names.
6616 @kindex set disassembly-flavor
6617 @cindex Intel disassembly flavor
6618 @cindex AT&T disassembly flavor
6619 @item set disassembly-flavor @var{instruction-set}
6620 Select the instruction set to use when disassembling the
6621 program via the @code{disassemble} or @code{x/i} commands.
6623 Currently this command is only defined for the Intel x86 family. You
6624 can set @var{instruction-set} to either @code{intel} or @code{att}.
6625 The default is @code{att}, the AT&T flavor used by default by Unix
6626 assemblers for x86-based targets.
6628 @kindex show disassembly-flavor
6629 @item show disassembly-flavor
6630 Show the current setting of the disassembly flavor.
6634 @kindex set disassemble-next-line
6635 @kindex show disassemble-next-line
6636 @item set disassemble-next-line
6637 @itemx show disassemble-next-line
6638 Control whether or not @value{GDBN} will disassemble the next source
6639 line or instruction when execution stops. If ON, @value{GDBN} will
6640 display disassembly of the next source line when execution of the
6641 program being debugged stops. This is @emph{in addition} to
6642 displaying the source line itself, which @value{GDBN} always does if
6643 possible. If the next source line cannot be displayed for some reason
6644 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6645 info in the debug info), @value{GDBN} will display disassembly of the
6646 next @emph{instruction} instead of showing the next source line. If
6647 AUTO, @value{GDBN} will display disassembly of next instruction only
6648 if the source line cannot be displayed. This setting causes
6649 @value{GDBN} to display some feedback when you step through a function
6650 with no line info or whose source file is unavailable. The default is
6651 OFF, which means never display the disassembly of the next line or
6657 @chapter Examining Data
6659 @cindex printing data
6660 @cindex examining data
6663 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6664 @c document because it is nonstandard... Under Epoch it displays in a
6665 @c different window or something like that.
6666 The usual way to examine data in your program is with the @code{print}
6667 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6668 evaluates and prints the value of an expression of the language your
6669 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6670 Different Languages}). It may also print the expression using a
6671 Python-based pretty-printer (@pxref{Pretty Printing}).
6674 @item print @var{expr}
6675 @itemx print /@var{f} @var{expr}
6676 @var{expr} is an expression (in the source language). By default the
6677 value of @var{expr} is printed in a format appropriate to its data type;
6678 you can choose a different format by specifying @samp{/@var{f}}, where
6679 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6683 @itemx print /@var{f}
6684 @cindex reprint the last value
6685 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6686 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6687 conveniently inspect the same value in an alternative format.
6690 A more low-level way of examining data is with the @code{x} command.
6691 It examines data in memory at a specified address and prints it in a
6692 specified format. @xref{Memory, ,Examining Memory}.
6694 If you are interested in information about types, or about how the
6695 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6696 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6700 * Expressions:: Expressions
6701 * Ambiguous Expressions:: Ambiguous Expressions
6702 * Variables:: Program variables
6703 * Arrays:: Artificial arrays
6704 * Output Formats:: Output formats
6705 * Memory:: Examining memory
6706 * Auto Display:: Automatic display
6707 * Print Settings:: Print settings
6708 * Value History:: Value history
6709 * Convenience Vars:: Convenience variables
6710 * Registers:: Registers
6711 * Floating Point Hardware:: Floating point hardware
6712 * Vector Unit:: Vector Unit
6713 * OS Information:: Auxiliary data provided by operating system
6714 * Memory Region Attributes:: Memory region attributes
6715 * Dump/Restore Files:: Copy between memory and a file
6716 * Core File Generation:: Cause a program dump its core
6717 * Character Sets:: Debugging programs that use a different
6718 character set than GDB does
6719 * Caching Remote Data:: Data caching for remote targets
6720 * Searching Memory:: Searching memory for a sequence of bytes
6724 @section Expressions
6727 @code{print} and many other @value{GDBN} commands accept an expression and
6728 compute its value. Any kind of constant, variable or operator defined
6729 by the programming language you are using is valid in an expression in
6730 @value{GDBN}. This includes conditional expressions, function calls,
6731 casts, and string constants. It also includes preprocessor macros, if
6732 you compiled your program to include this information; see
6735 @cindex arrays in expressions
6736 @value{GDBN} supports array constants in expressions input by
6737 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6738 you can use the command @code{print @{1, 2, 3@}} to create an array
6739 of three integers. If you pass an array to a function or assign it
6740 to a program variable, @value{GDBN} copies the array to memory that
6741 is @code{malloc}ed in the target program.
6743 Because C is so widespread, most of the expressions shown in examples in
6744 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6745 Languages}, for information on how to use expressions in other
6748 In this section, we discuss operators that you can use in @value{GDBN}
6749 expressions regardless of your programming language.
6751 @cindex casts, in expressions
6752 Casts are supported in all languages, not just in C, because it is so
6753 useful to cast a number into a pointer in order to examine a structure
6754 at that address in memory.
6755 @c FIXME: casts supported---Mod2 true?
6757 @value{GDBN} supports these operators, in addition to those common
6758 to programming languages:
6762 @samp{@@} is a binary operator for treating parts of memory as arrays.
6763 @xref{Arrays, ,Artificial Arrays}, for more information.
6766 @samp{::} allows you to specify a variable in terms of the file or
6767 function where it is defined. @xref{Variables, ,Program Variables}.
6769 @cindex @{@var{type}@}
6770 @cindex type casting memory
6771 @cindex memory, viewing as typed object
6772 @cindex casts, to view memory
6773 @item @{@var{type}@} @var{addr}
6774 Refers to an object of type @var{type} stored at address @var{addr} in
6775 memory. @var{addr} may be any expression whose value is an integer or
6776 pointer (but parentheses are required around binary operators, just as in
6777 a cast). This construct is allowed regardless of what kind of data is
6778 normally supposed to reside at @var{addr}.
6781 @node Ambiguous Expressions
6782 @section Ambiguous Expressions
6783 @cindex ambiguous expressions
6785 Expressions can sometimes contain some ambiguous elements. For instance,
6786 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6787 a single function name to be defined several times, for application in
6788 different contexts. This is called @dfn{overloading}. Another example
6789 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6790 templates and is typically instantiated several times, resulting in
6791 the same function name being defined in different contexts.
6793 In some cases and depending on the language, it is possible to adjust
6794 the expression to remove the ambiguity. For instance in C@t{++}, you
6795 can specify the signature of the function you want to break on, as in
6796 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6797 qualified name of your function often makes the expression unambiguous
6800 When an ambiguity that needs to be resolved is detected, the debugger
6801 has the capability to display a menu of numbered choices for each
6802 possibility, and then waits for the selection with the prompt @samp{>}.
6803 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6804 aborts the current command. If the command in which the expression was
6805 used allows more than one choice to be selected, the next option in the
6806 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6809 For example, the following session excerpt shows an attempt to set a
6810 breakpoint at the overloaded symbol @code{String::after}.
6811 We choose three particular definitions of that function name:
6813 @c FIXME! This is likely to change to show arg type lists, at least
6816 (@value{GDBP}) b String::after
6819 [2] file:String.cc; line number:867
6820 [3] file:String.cc; line number:860
6821 [4] file:String.cc; line number:875
6822 [5] file:String.cc; line number:853
6823 [6] file:String.cc; line number:846
6824 [7] file:String.cc; line number:735
6826 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6827 Breakpoint 2 at 0xb344: file String.cc, line 875.
6828 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6829 Multiple breakpoints were set.
6830 Use the "delete" command to delete unwanted
6837 @kindex set multiple-symbols
6838 @item set multiple-symbols @var{mode}
6839 @cindex multiple-symbols menu
6841 This option allows you to adjust the debugger behavior when an expression
6844 By default, @var{mode} is set to @code{all}. If the command with which
6845 the expression is used allows more than one choice, then @value{GDBN}
6846 automatically selects all possible choices. For instance, inserting
6847 a breakpoint on a function using an ambiguous name results in a breakpoint
6848 inserted on each possible match. However, if a unique choice must be made,
6849 then @value{GDBN} uses the menu to help you disambiguate the expression.
6850 For instance, printing the address of an overloaded function will result
6851 in the use of the menu.
6853 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6854 when an ambiguity is detected.
6856 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6857 an error due to the ambiguity and the command is aborted.
6859 @kindex show multiple-symbols
6860 @item show multiple-symbols
6861 Show the current value of the @code{multiple-symbols} setting.
6865 @section Program Variables
6867 The most common kind of expression to use is the name of a variable
6870 Variables in expressions are understood in the selected stack frame
6871 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6875 global (or file-static)
6882 visible according to the scope rules of the
6883 programming language from the point of execution in that frame
6886 @noindent This means that in the function
6901 you can examine and use the variable @code{a} whenever your program is
6902 executing within the function @code{foo}, but you can only use or
6903 examine the variable @code{b} while your program is executing inside
6904 the block where @code{b} is declared.
6906 @cindex variable name conflict
6907 There is an exception: you can refer to a variable or function whose
6908 scope is a single source file even if the current execution point is not
6909 in this file. But it is possible to have more than one such variable or
6910 function with the same name (in different source files). If that
6911 happens, referring to that name has unpredictable effects. If you wish,
6912 you can specify a static variable in a particular function or file,
6913 using the colon-colon (@code{::}) notation:
6915 @cindex colon-colon, context for variables/functions
6917 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6918 @cindex @code{::}, context for variables/functions
6921 @var{file}::@var{variable}
6922 @var{function}::@var{variable}
6926 Here @var{file} or @var{function} is the name of the context for the
6927 static @var{variable}. In the case of file names, you can use quotes to
6928 make sure @value{GDBN} parses the file name as a single word---for example,
6929 to print a global value of @code{x} defined in @file{f2.c}:
6932 (@value{GDBP}) p 'f2.c'::x
6935 @cindex C@t{++} scope resolution
6936 This use of @samp{::} is very rarely in conflict with the very similar
6937 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6938 scope resolution operator in @value{GDBN} expressions.
6939 @c FIXME: Um, so what happens in one of those rare cases where it's in
6942 @cindex wrong values
6943 @cindex variable values, wrong
6944 @cindex function entry/exit, wrong values of variables
6945 @cindex optimized code, wrong values of variables
6947 @emph{Warning:} Occasionally, a local variable may appear to have the
6948 wrong value at certain points in a function---just after entry to a new
6949 scope, and just before exit.
6951 You may see this problem when you are stepping by machine instructions.
6952 This is because, on most machines, it takes more than one instruction to
6953 set up a stack frame (including local variable definitions); if you are
6954 stepping by machine instructions, variables may appear to have the wrong
6955 values until the stack frame is completely built. On exit, it usually
6956 also takes more than one machine instruction to destroy a stack frame;
6957 after you begin stepping through that group of instructions, local
6958 variable definitions may be gone.
6960 This may also happen when the compiler does significant optimizations.
6961 To be sure of always seeing accurate values, turn off all optimization
6964 @cindex ``No symbol "foo" in current context''
6965 Another possible effect of compiler optimizations is to optimize
6966 unused variables out of existence, or assign variables to registers (as
6967 opposed to memory addresses). Depending on the support for such cases
6968 offered by the debug info format used by the compiler, @value{GDBN}
6969 might not be able to display values for such local variables. If that
6970 happens, @value{GDBN} will print a message like this:
6973 No symbol "foo" in current context.
6976 To solve such problems, either recompile without optimizations, or use a
6977 different debug info format, if the compiler supports several such
6978 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6979 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6980 produces debug info in a format that is superior to formats such as
6981 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6982 an effective form for debug info. @xref{Debugging Options,,Options
6983 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6984 Compiler Collection (GCC)}.
6985 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6986 that are best suited to C@t{++} programs.
6988 If you ask to print an object whose contents are unknown to
6989 @value{GDBN}, e.g., because its data type is not completely specified
6990 by the debug information, @value{GDBN} will say @samp{<incomplete
6991 type>}. @xref{Symbols, incomplete type}, for more about this.
6993 Strings are identified as arrays of @code{char} values without specified
6994 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6995 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6996 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6997 defines literal string type @code{"char"} as @code{char} without a sign.
7002 signed char var1[] = "A";
7005 You get during debugging
7010 $2 = @{65 'A', 0 '\0'@}
7014 @section Artificial Arrays
7016 @cindex artificial array
7018 @kindex @@@r{, referencing memory as an array}
7019 It is often useful to print out several successive objects of the
7020 same type in memory; a section of an array, or an array of
7021 dynamically determined size for which only a pointer exists in the
7024 You can do this by referring to a contiguous span of memory as an
7025 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7026 operand of @samp{@@} should be the first element of the desired array
7027 and be an individual object. The right operand should be the desired length
7028 of the array. The result is an array value whose elements are all of
7029 the type of the left argument. The first element is actually the left
7030 argument; the second element comes from bytes of memory immediately
7031 following those that hold the first element, and so on. Here is an
7032 example. If a program says
7035 int *array = (int *) malloc (len * sizeof (int));
7039 you can print the contents of @code{array} with
7045 The left operand of @samp{@@} must reside in memory. Array values made
7046 with @samp{@@} in this way behave just like other arrays in terms of
7047 subscripting, and are coerced to pointers when used in expressions.
7048 Artificial arrays most often appear in expressions via the value history
7049 (@pxref{Value History, ,Value History}), after printing one out.
7051 Another way to create an artificial array is to use a cast.
7052 This re-interprets a value as if it were an array.
7053 The value need not be in memory:
7055 (@value{GDBP}) p/x (short[2])0x12345678
7056 $1 = @{0x1234, 0x5678@}
7059 As a convenience, if you leave the array length out (as in
7060 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7061 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7063 (@value{GDBP}) p/x (short[])0x12345678
7064 $2 = @{0x1234, 0x5678@}
7067 Sometimes the artificial array mechanism is not quite enough; in
7068 moderately complex data structures, the elements of interest may not
7069 actually be adjacent---for example, if you are interested in the values
7070 of pointers in an array. One useful work-around in this situation is
7071 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7072 Variables}) as a counter in an expression that prints the first
7073 interesting value, and then repeat that expression via @key{RET}. For
7074 instance, suppose you have an array @code{dtab} of pointers to
7075 structures, and you are interested in the values of a field @code{fv}
7076 in each structure. Here is an example of what you might type:
7086 @node Output Formats
7087 @section Output Formats
7089 @cindex formatted output
7090 @cindex output formats
7091 By default, @value{GDBN} prints a value according to its data type. Sometimes
7092 this is not what you want. For example, you might want to print a number
7093 in hex, or a pointer in decimal. Or you might want to view data in memory
7094 at a certain address as a character string or as an instruction. To do
7095 these things, specify an @dfn{output format} when you print a value.
7097 The simplest use of output formats is to say how to print a value
7098 already computed. This is done by starting the arguments of the
7099 @code{print} command with a slash and a format letter. The format
7100 letters supported are:
7104 Regard the bits of the value as an integer, and print the integer in
7108 Print as integer in signed decimal.
7111 Print as integer in unsigned decimal.
7114 Print as integer in octal.
7117 Print as integer in binary. The letter @samp{t} stands for ``two''.
7118 @footnote{@samp{b} cannot be used because these format letters are also
7119 used with the @code{x} command, where @samp{b} stands for ``byte'';
7120 see @ref{Memory,,Examining Memory}.}
7123 @cindex unknown address, locating
7124 @cindex locate address
7125 Print as an address, both absolute in hexadecimal and as an offset from
7126 the nearest preceding symbol. You can use this format used to discover
7127 where (in what function) an unknown address is located:
7130 (@value{GDBP}) p/a 0x54320
7131 $3 = 0x54320 <_initialize_vx+396>
7135 The command @code{info symbol 0x54320} yields similar results.
7136 @xref{Symbols, info symbol}.
7139 Regard as an integer and print it as a character constant. This
7140 prints both the numerical value and its character representation. The
7141 character representation is replaced with the octal escape @samp{\nnn}
7142 for characters outside the 7-bit @sc{ascii} range.
7144 Without this format, @value{GDBN} displays @code{char},
7145 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7146 constants. Single-byte members of vectors are displayed as integer
7150 Regard the bits of the value as a floating point number and print
7151 using typical floating point syntax.
7154 @cindex printing strings
7155 @cindex printing byte arrays
7156 Regard as a string, if possible. With this format, pointers to single-byte
7157 data are displayed as null-terminated strings and arrays of single-byte data
7158 are displayed as fixed-length strings. Other values are displayed in their
7161 Without this format, @value{GDBN} displays pointers to and arrays of
7162 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7163 strings. Single-byte members of a vector are displayed as an integer
7167 @cindex raw printing
7168 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7169 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7170 Printing}). This typically results in a higher-level display of the
7171 value's contents. The @samp{r} format bypasses any Python
7172 pretty-printer which might exist.
7175 For example, to print the program counter in hex (@pxref{Registers}), type
7182 Note that no space is required before the slash; this is because command
7183 names in @value{GDBN} cannot contain a slash.
7185 To reprint the last value in the value history with a different format,
7186 you can use the @code{print} command with just a format and no
7187 expression. For example, @samp{p/x} reprints the last value in hex.
7190 @section Examining Memory
7192 You can use the command @code{x} (for ``examine'') to examine memory in
7193 any of several formats, independently of your program's data types.
7195 @cindex examining memory
7197 @kindex x @r{(examine memory)}
7198 @item x/@var{nfu} @var{addr}
7201 Use the @code{x} command to examine memory.
7204 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7205 much memory to display and how to format it; @var{addr} is an
7206 expression giving the address where you want to start displaying memory.
7207 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7208 Several commands set convenient defaults for @var{addr}.
7211 @item @var{n}, the repeat count
7212 The repeat count is a decimal integer; the default is 1. It specifies
7213 how much memory (counting by units @var{u}) to display.
7214 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7217 @item @var{f}, the display format
7218 The display format is one of the formats used by @code{print}
7219 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7220 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7221 The default is @samp{x} (hexadecimal) initially. The default changes
7222 each time you use either @code{x} or @code{print}.
7224 @item @var{u}, the unit size
7225 The unit size is any of
7231 Halfwords (two bytes).
7233 Words (four bytes). This is the initial default.
7235 Giant words (eight bytes).
7238 Each time you specify a unit size with @code{x}, that size becomes the
7239 default unit the next time you use @code{x}. (For the @samp{s} and
7240 @samp{i} formats, the unit size is ignored and is normally not written.)
7242 @item @var{addr}, starting display address
7243 @var{addr} is the address where you want @value{GDBN} to begin displaying
7244 memory. The expression need not have a pointer value (though it may);
7245 it is always interpreted as an integer address of a byte of memory.
7246 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7247 @var{addr} is usually just after the last address examined---but several
7248 other commands also set the default address: @code{info breakpoints} (to
7249 the address of the last breakpoint listed), @code{info line} (to the
7250 starting address of a line), and @code{print} (if you use it to display
7251 a value from memory).
7254 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7255 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7256 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7257 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7258 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7260 Since the letters indicating unit sizes are all distinct from the
7261 letters specifying output formats, you do not have to remember whether
7262 unit size or format comes first; either order works. The output
7263 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7264 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7266 Even though the unit size @var{u} is ignored for the formats @samp{s}
7267 and @samp{i}, you might still want to use a count @var{n}; for example,
7268 @samp{3i} specifies that you want to see three machine instructions,
7269 including any operands. For convenience, especially when used with
7270 the @code{display} command, the @samp{i} format also prints branch delay
7271 slot instructions, if any, beyond the count specified, which immediately
7272 follow the last instruction that is within the count. The command
7273 @code{disassemble} gives an alternative way of inspecting machine
7274 instructions; see @ref{Machine Code,,Source and Machine Code}.
7276 All the defaults for the arguments to @code{x} are designed to make it
7277 easy to continue scanning memory with minimal specifications each time
7278 you use @code{x}. For example, after you have inspected three machine
7279 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7280 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7281 the repeat count @var{n} is used again; the other arguments default as
7282 for successive uses of @code{x}.
7284 When examining machine instructions, the instruction at current program
7285 counter is shown with a @code{=>} marker. For example:
7288 (@value{GDBP}) x/5i $pc-6
7289 0x804837f <main+11>: mov %esp,%ebp
7290 0x8048381 <main+13>: push %ecx
7291 0x8048382 <main+14>: sub $0x4,%esp
7292 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7293 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7296 @cindex @code{$_}, @code{$__}, and value history
7297 The addresses and contents printed by the @code{x} command are not saved
7298 in the value history because there is often too much of them and they
7299 would get in the way. Instead, @value{GDBN} makes these values available for
7300 subsequent use in expressions as values of the convenience variables
7301 @code{$_} and @code{$__}. After an @code{x} command, the last address
7302 examined is available for use in expressions in the convenience variable
7303 @code{$_}. The contents of that address, as examined, are available in
7304 the convenience variable @code{$__}.
7306 If the @code{x} command has a repeat count, the address and contents saved
7307 are from the last memory unit printed; this is not the same as the last
7308 address printed if several units were printed on the last line of output.
7310 @cindex remote memory comparison
7311 @cindex verify remote memory image
7312 When you are debugging a program running on a remote target machine
7313 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7314 remote machine's memory against the executable file you downloaded to
7315 the target. The @code{compare-sections} command is provided for such
7319 @kindex compare-sections
7320 @item compare-sections @r{[}@var{section-name}@r{]}
7321 Compare the data of a loadable section @var{section-name} in the
7322 executable file of the program being debugged with the same section in
7323 the remote machine's memory, and report any mismatches. With no
7324 arguments, compares all loadable sections. This command's
7325 availability depends on the target's support for the @code{"qCRC"}
7330 @section Automatic Display
7331 @cindex automatic display
7332 @cindex display of expressions
7334 If you find that you want to print the value of an expression frequently
7335 (to see how it changes), you might want to add it to the @dfn{automatic
7336 display list} so that @value{GDBN} prints its value each time your program stops.
7337 Each expression added to the list is given a number to identify it;
7338 to remove an expression from the list, you specify that number.
7339 The automatic display looks like this:
7343 3: bar[5] = (struct hack *) 0x3804
7347 This display shows item numbers, expressions and their current values. As with
7348 displays you request manually using @code{x} or @code{print}, you can
7349 specify the output format you prefer; in fact, @code{display} decides
7350 whether to use @code{print} or @code{x} depending your format
7351 specification---it uses @code{x} if you specify either the @samp{i}
7352 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7356 @item display @var{expr}
7357 Add the expression @var{expr} to the list of expressions to display
7358 each time your program stops. @xref{Expressions, ,Expressions}.
7360 @code{display} does not repeat if you press @key{RET} again after using it.
7362 @item display/@var{fmt} @var{expr}
7363 For @var{fmt} specifying only a display format and not a size or
7364 count, add the expression @var{expr} to the auto-display list but
7365 arrange to display it each time in the specified format @var{fmt}.
7366 @xref{Output Formats,,Output Formats}.
7368 @item display/@var{fmt} @var{addr}
7369 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7370 number of units, add the expression @var{addr} as a memory address to
7371 be examined each time your program stops. Examining means in effect
7372 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7375 For example, @samp{display/i $pc} can be helpful, to see the machine
7376 instruction about to be executed each time execution stops (@samp{$pc}
7377 is a common name for the program counter; @pxref{Registers, ,Registers}).
7380 @kindex delete display
7382 @item undisplay @var{dnums}@dots{}
7383 @itemx delete display @var{dnums}@dots{}
7384 Remove item numbers @var{dnums} from the list of expressions to display.
7386 @code{undisplay} does not repeat if you press @key{RET} after using it.
7387 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7389 @kindex disable display
7390 @item disable display @var{dnums}@dots{}
7391 Disable the display of item numbers @var{dnums}. A disabled display
7392 item is not printed automatically, but is not forgotten. It may be
7393 enabled again later.
7395 @kindex enable display
7396 @item enable display @var{dnums}@dots{}
7397 Enable display of item numbers @var{dnums}. It becomes effective once
7398 again in auto display of its expression, until you specify otherwise.
7401 Display the current values of the expressions on the list, just as is
7402 done when your program stops.
7404 @kindex info display
7406 Print the list of expressions previously set up to display
7407 automatically, each one with its item number, but without showing the
7408 values. This includes disabled expressions, which are marked as such.
7409 It also includes expressions which would not be displayed right now
7410 because they refer to automatic variables not currently available.
7413 @cindex display disabled out of scope
7414 If a display expression refers to local variables, then it does not make
7415 sense outside the lexical context for which it was set up. Such an
7416 expression is disabled when execution enters a context where one of its
7417 variables is not defined. For example, if you give the command
7418 @code{display last_char} while inside a function with an argument
7419 @code{last_char}, @value{GDBN} displays this argument while your program
7420 continues to stop inside that function. When it stops elsewhere---where
7421 there is no variable @code{last_char}---the display is disabled
7422 automatically. The next time your program stops where @code{last_char}
7423 is meaningful, you can enable the display expression once again.
7425 @node Print Settings
7426 @section Print Settings
7428 @cindex format options
7429 @cindex print settings
7430 @value{GDBN} provides the following ways to control how arrays, structures,
7431 and symbols are printed.
7434 These settings are useful for debugging programs in any language:
7438 @item set print address
7439 @itemx set print address on
7440 @cindex print/don't print memory addresses
7441 @value{GDBN} prints memory addresses showing the location of stack
7442 traces, structure values, pointer values, breakpoints, and so forth,
7443 even when it also displays the contents of those addresses. The default
7444 is @code{on}. For example, this is what a stack frame display looks like with
7445 @code{set print address on}:
7450 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7452 530 if (lquote != def_lquote)
7456 @item set print address off
7457 Do not print addresses when displaying their contents. For example,
7458 this is the same stack frame displayed with @code{set print address off}:
7462 (@value{GDBP}) set print addr off
7464 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7465 530 if (lquote != def_lquote)
7469 You can use @samp{set print address off} to eliminate all machine
7470 dependent displays from the @value{GDBN} interface. For example, with
7471 @code{print address off}, you should get the same text for backtraces on
7472 all machines---whether or not they involve pointer arguments.
7475 @item show print address
7476 Show whether or not addresses are to be printed.
7479 When @value{GDBN} prints a symbolic address, it normally prints the
7480 closest earlier symbol plus an offset. If that symbol does not uniquely
7481 identify the address (for example, it is a name whose scope is a single
7482 source file), you may need to clarify. One way to do this is with
7483 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7484 you can set @value{GDBN} to print the source file and line number when
7485 it prints a symbolic address:
7488 @item set print symbol-filename on
7489 @cindex source file and line of a symbol
7490 @cindex symbol, source file and line
7491 Tell @value{GDBN} to print the source file name and line number of a
7492 symbol in the symbolic form of an address.
7494 @item set print symbol-filename off
7495 Do not print source file name and line number of a symbol. This is the
7498 @item show print symbol-filename
7499 Show whether or not @value{GDBN} will print the source file name and
7500 line number of a symbol in the symbolic form of an address.
7503 Another situation where it is helpful to show symbol filenames and line
7504 numbers is when disassembling code; @value{GDBN} shows you the line
7505 number and source file that corresponds to each instruction.
7507 Also, you may wish to see the symbolic form only if the address being
7508 printed is reasonably close to the closest earlier symbol:
7511 @item set print max-symbolic-offset @var{max-offset}
7512 @cindex maximum value for offset of closest symbol
7513 Tell @value{GDBN} to only display the symbolic form of an address if the
7514 offset between the closest earlier symbol and the address is less than
7515 @var{max-offset}. The default is 0, which tells @value{GDBN}
7516 to always print the symbolic form of an address if any symbol precedes it.
7518 @item show print max-symbolic-offset
7519 Ask how large the maximum offset is that @value{GDBN} prints in a
7523 @cindex wild pointer, interpreting
7524 @cindex pointer, finding referent
7525 If you have a pointer and you are not sure where it points, try
7526 @samp{set print symbol-filename on}. Then you can determine the name
7527 and source file location of the variable where it points, using
7528 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7529 For example, here @value{GDBN} shows that a variable @code{ptt} points
7530 at another variable @code{t}, defined in @file{hi2.c}:
7533 (@value{GDBP}) set print symbol-filename on
7534 (@value{GDBP}) p/a ptt
7535 $4 = 0xe008 <t in hi2.c>
7539 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7540 does not show the symbol name and filename of the referent, even with
7541 the appropriate @code{set print} options turned on.
7544 Other settings control how different kinds of objects are printed:
7547 @item set print array
7548 @itemx set print array on
7549 @cindex pretty print arrays
7550 Pretty print arrays. This format is more convenient to read,
7551 but uses more space. The default is off.
7553 @item set print array off
7554 Return to compressed format for arrays.
7556 @item show print array
7557 Show whether compressed or pretty format is selected for displaying
7560 @cindex print array indexes
7561 @item set print array-indexes
7562 @itemx set print array-indexes on
7563 Print the index of each element when displaying arrays. May be more
7564 convenient to locate a given element in the array or quickly find the
7565 index of a given element in that printed array. The default is off.
7567 @item set print array-indexes off
7568 Stop printing element indexes when displaying arrays.
7570 @item show print array-indexes
7571 Show whether the index of each element is printed when displaying
7574 @item set print elements @var{number-of-elements}
7575 @cindex number of array elements to print
7576 @cindex limit on number of printed array elements
7577 Set a limit on how many elements of an array @value{GDBN} will print.
7578 If @value{GDBN} is printing a large array, it stops printing after it has
7579 printed the number of elements set by the @code{set print elements} command.
7580 This limit also applies to the display of strings.
7581 When @value{GDBN} starts, this limit is set to 200.
7582 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7584 @item show print elements
7585 Display the number of elements of a large array that @value{GDBN} will print.
7586 If the number is 0, then the printing is unlimited.
7588 @item set print frame-arguments @var{value}
7589 @kindex set print frame-arguments
7590 @cindex printing frame argument values
7591 @cindex print all frame argument values
7592 @cindex print frame argument values for scalars only
7593 @cindex do not print frame argument values
7594 This command allows to control how the values of arguments are printed
7595 when the debugger prints a frame (@pxref{Frames}). The possible
7600 The values of all arguments are printed.
7603 Print the value of an argument only if it is a scalar. The value of more
7604 complex arguments such as arrays, structures, unions, etc, is replaced
7605 by @code{@dots{}}. This is the default. Here is an example where
7606 only scalar arguments are shown:
7609 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7614 None of the argument values are printed. Instead, the value of each argument
7615 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7618 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7623 By default, only scalar arguments are printed. This command can be used
7624 to configure the debugger to print the value of all arguments, regardless
7625 of their type. However, it is often advantageous to not print the value
7626 of more complex parameters. For instance, it reduces the amount of
7627 information printed in each frame, making the backtrace more readable.
7628 Also, it improves performance when displaying Ada frames, because
7629 the computation of large arguments can sometimes be CPU-intensive,
7630 especially in large applications. Setting @code{print frame-arguments}
7631 to @code{scalars} (the default) or @code{none} avoids this computation,
7632 thus speeding up the display of each Ada frame.
7634 @item show print frame-arguments
7635 Show how the value of arguments should be displayed when printing a frame.
7637 @item set print repeats
7638 @cindex repeated array elements
7639 Set the threshold for suppressing display of repeated array
7640 elements. When the number of consecutive identical elements of an
7641 array exceeds the threshold, @value{GDBN} prints the string
7642 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7643 identical repetitions, instead of displaying the identical elements
7644 themselves. Setting the threshold to zero will cause all elements to
7645 be individually printed. The default threshold is 10.
7647 @item show print repeats
7648 Display the current threshold for printing repeated identical
7651 @item set print null-stop
7652 @cindex @sc{null} elements in arrays
7653 Cause @value{GDBN} to stop printing the characters of an array when the first
7654 @sc{null} is encountered. This is useful when large arrays actually
7655 contain only short strings.
7658 @item show print null-stop
7659 Show whether @value{GDBN} stops printing an array on the first
7660 @sc{null} character.
7662 @item set print pretty on
7663 @cindex print structures in indented form
7664 @cindex indentation in structure display
7665 Cause @value{GDBN} to print structures in an indented format with one member
7666 per line, like this:
7681 @item set print pretty off
7682 Cause @value{GDBN} to print structures in a compact format, like this:
7686 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7687 meat = 0x54 "Pork"@}
7692 This is the default format.
7694 @item show print pretty
7695 Show which format @value{GDBN} is using to print structures.
7697 @item set print sevenbit-strings on
7698 @cindex eight-bit characters in strings
7699 @cindex octal escapes in strings
7700 Print using only seven-bit characters; if this option is set,
7701 @value{GDBN} displays any eight-bit characters (in strings or
7702 character values) using the notation @code{\}@var{nnn}. This setting is
7703 best if you are working in English (@sc{ascii}) and you use the
7704 high-order bit of characters as a marker or ``meta'' bit.
7706 @item set print sevenbit-strings off
7707 Print full eight-bit characters. This allows the use of more
7708 international character sets, and is the default.
7710 @item show print sevenbit-strings
7711 Show whether or not @value{GDBN} is printing only seven-bit characters.
7713 @item set print union on
7714 @cindex unions in structures, printing
7715 Tell @value{GDBN} to print unions which are contained in structures
7716 and other unions. This is the default setting.
7718 @item set print union off
7719 Tell @value{GDBN} not to print unions which are contained in
7720 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7723 @item show print union
7724 Ask @value{GDBN} whether or not it will print unions which are contained in
7725 structures and other unions.
7727 For example, given the declarations
7730 typedef enum @{Tree, Bug@} Species;
7731 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7732 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7743 struct thing foo = @{Tree, @{Acorn@}@};
7747 with @code{set print union on} in effect @samp{p foo} would print
7750 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7754 and with @code{set print union off} in effect it would print
7757 $1 = @{it = Tree, form = @{...@}@}
7761 @code{set print union} affects programs written in C-like languages
7767 These settings are of interest when debugging C@t{++} programs:
7770 @cindex demangling C@t{++} names
7771 @item set print demangle
7772 @itemx set print demangle on
7773 Print C@t{++} names in their source form rather than in the encoded
7774 (``mangled'') form passed to the assembler and linker for type-safe
7775 linkage. The default is on.
7777 @item show print demangle
7778 Show whether C@t{++} names are printed in mangled or demangled form.
7780 @item set print asm-demangle
7781 @itemx set print asm-demangle on
7782 Print C@t{++} names in their source form rather than their mangled form, even
7783 in assembler code printouts such as instruction disassemblies.
7786 @item show print asm-demangle
7787 Show whether C@t{++} names in assembly listings are printed in mangled
7790 @cindex C@t{++} symbol decoding style
7791 @cindex symbol decoding style, C@t{++}
7792 @kindex set demangle-style
7793 @item set demangle-style @var{style}
7794 Choose among several encoding schemes used by different compilers to
7795 represent C@t{++} names. The choices for @var{style} are currently:
7799 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7802 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7803 This is the default.
7806 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7809 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7812 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7813 @strong{Warning:} this setting alone is not sufficient to allow
7814 debugging @code{cfront}-generated executables. @value{GDBN} would
7815 require further enhancement to permit that.
7818 If you omit @var{style}, you will see a list of possible formats.
7820 @item show demangle-style
7821 Display the encoding style currently in use for decoding C@t{++} symbols.
7823 @item set print object
7824 @itemx set print object on
7825 @cindex derived type of an object, printing
7826 @cindex display derived types
7827 When displaying a pointer to an object, identify the @emph{actual}
7828 (derived) type of the object rather than the @emph{declared} type, using
7829 the virtual function table.
7831 @item set print object off
7832 Display only the declared type of objects, without reference to the
7833 virtual function table. This is the default setting.
7835 @item show print object
7836 Show whether actual, or declared, object types are displayed.
7838 @item set print static-members
7839 @itemx set print static-members on
7840 @cindex static members of C@t{++} objects
7841 Print static members when displaying a C@t{++} object. The default is on.
7843 @item set print static-members off
7844 Do not print static members when displaying a C@t{++} object.
7846 @item show print static-members
7847 Show whether C@t{++} static members are printed or not.
7849 @item set print pascal_static-members
7850 @itemx set print pascal_static-members on
7851 @cindex static members of Pascal objects
7852 @cindex Pascal objects, static members display
7853 Print static members when displaying a Pascal object. The default is on.
7855 @item set print pascal_static-members off
7856 Do not print static members when displaying a Pascal object.
7858 @item show print pascal_static-members
7859 Show whether Pascal static members are printed or not.
7861 @c These don't work with HP ANSI C++ yet.
7862 @item set print vtbl
7863 @itemx set print vtbl on
7864 @cindex pretty print C@t{++} virtual function tables
7865 @cindex virtual functions (C@t{++}) display
7866 @cindex VTBL display
7867 Pretty print C@t{++} virtual function tables. The default is off.
7868 (The @code{vtbl} commands do not work on programs compiled with the HP
7869 ANSI C@t{++} compiler (@code{aCC}).)
7871 @item set print vtbl off
7872 Do not pretty print C@t{++} virtual function tables.
7874 @item show print vtbl
7875 Show whether C@t{++} virtual function tables are pretty printed, or not.
7879 @section Value History
7881 @cindex value history
7882 @cindex history of values printed by @value{GDBN}
7883 Values printed by the @code{print} command are saved in the @value{GDBN}
7884 @dfn{value history}. This allows you to refer to them in other expressions.
7885 Values are kept until the symbol table is re-read or discarded
7886 (for example with the @code{file} or @code{symbol-file} commands).
7887 When the symbol table changes, the value history is discarded,
7888 since the values may contain pointers back to the types defined in the
7893 @cindex history number
7894 The values printed are given @dfn{history numbers} by which you can
7895 refer to them. These are successive integers starting with one.
7896 @code{print} shows you the history number assigned to a value by
7897 printing @samp{$@var{num} = } before the value; here @var{num} is the
7900 To refer to any previous value, use @samp{$} followed by the value's
7901 history number. The way @code{print} labels its output is designed to
7902 remind you of this. Just @code{$} refers to the most recent value in
7903 the history, and @code{$$} refers to the value before that.
7904 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7905 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7906 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7908 For example, suppose you have just printed a pointer to a structure and
7909 want to see the contents of the structure. It suffices to type
7915 If you have a chain of structures where the component @code{next} points
7916 to the next one, you can print the contents of the next one with this:
7923 You can print successive links in the chain by repeating this
7924 command---which you can do by just typing @key{RET}.
7926 Note that the history records values, not expressions. If the value of
7927 @code{x} is 4 and you type these commands:
7935 then the value recorded in the value history by the @code{print} command
7936 remains 4 even though the value of @code{x} has changed.
7941 Print the last ten values in the value history, with their item numbers.
7942 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7943 values} does not change the history.
7945 @item show values @var{n}
7946 Print ten history values centered on history item number @var{n}.
7949 Print ten history values just after the values last printed. If no more
7950 values are available, @code{show values +} produces no display.
7953 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7954 same effect as @samp{show values +}.
7956 @node Convenience Vars
7957 @section Convenience Variables
7959 @cindex convenience variables
7960 @cindex user-defined variables
7961 @value{GDBN} provides @dfn{convenience variables} that you can use within
7962 @value{GDBN} to hold on to a value and refer to it later. These variables
7963 exist entirely within @value{GDBN}; they are not part of your program, and
7964 setting a convenience variable has no direct effect on further execution
7965 of your program. That is why you can use them freely.
7967 Convenience variables are prefixed with @samp{$}. Any name preceded by
7968 @samp{$} can be used for a convenience variable, unless it is one of
7969 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7970 (Value history references, in contrast, are @emph{numbers} preceded
7971 by @samp{$}. @xref{Value History, ,Value History}.)
7973 You can save a value in a convenience variable with an assignment
7974 expression, just as you would set a variable in your program.
7978 set $foo = *object_ptr
7982 would save in @code{$foo} the value contained in the object pointed to by
7985 Using a convenience variable for the first time creates it, but its
7986 value is @code{void} until you assign a new value. You can alter the
7987 value with another assignment at any time.
7989 Convenience variables have no fixed types. You can assign a convenience
7990 variable any type of value, including structures and arrays, even if
7991 that variable already has a value of a different type. The convenience
7992 variable, when used as an expression, has the type of its current value.
7995 @kindex show convenience
7996 @cindex show all user variables
7997 @item show convenience
7998 Print a list of convenience variables used so far, and their values.
7999 Abbreviated @code{show conv}.
8001 @kindex init-if-undefined
8002 @cindex convenience variables, initializing
8003 @item init-if-undefined $@var{variable} = @var{expression}
8004 Set a convenience variable if it has not already been set. This is useful
8005 for user-defined commands that keep some state. It is similar, in concept,
8006 to using local static variables with initializers in C (except that
8007 convenience variables are global). It can also be used to allow users to
8008 override default values used in a command script.
8010 If the variable is already defined then the expression is not evaluated so
8011 any side-effects do not occur.
8014 One of the ways to use a convenience variable is as a counter to be
8015 incremented or a pointer to be advanced. For example, to print
8016 a field from successive elements of an array of structures:
8020 print bar[$i++]->contents
8024 Repeat that command by typing @key{RET}.
8026 Some convenience variables are created automatically by @value{GDBN} and given
8027 values likely to be useful.
8030 @vindex $_@r{, convenience variable}
8032 The variable @code{$_} is automatically set by the @code{x} command to
8033 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8034 commands which provide a default address for @code{x} to examine also
8035 set @code{$_} to that address; these commands include @code{info line}
8036 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8037 except when set by the @code{x} command, in which case it is a pointer
8038 to the type of @code{$__}.
8040 @vindex $__@r{, convenience variable}
8042 The variable @code{$__} is automatically set by the @code{x} command
8043 to the value found in the last address examined. Its type is chosen
8044 to match the format in which the data was printed.
8047 @vindex $_exitcode@r{, convenience variable}
8048 The variable @code{$_exitcode} is automatically set to the exit code when
8049 the program being debugged terminates.
8052 @vindex $_siginfo@r{, convenience variable}
8053 The variable @code{$_siginfo} contains extra signal information
8054 (@pxref{extra signal information}). Note that @code{$_siginfo}
8055 could be empty, if the application has not yet received any signals.
8056 For example, it will be empty before you execute the @code{run} command.
8059 On HP-UX systems, if you refer to a function or variable name that
8060 begins with a dollar sign, @value{GDBN} searches for a user or system
8061 name first, before it searches for a convenience variable.
8063 @cindex convenience functions
8064 @value{GDBN} also supplies some @dfn{convenience functions}. These
8065 have a syntax similar to convenience variables. A convenience
8066 function can be used in an expression just like an ordinary function;
8067 however, a convenience function is implemented internally to
8072 @kindex help function
8073 @cindex show all convenience functions
8074 Print a list of all convenience functions.
8081 You can refer to machine register contents, in expressions, as variables
8082 with names starting with @samp{$}. The names of registers are different
8083 for each machine; use @code{info registers} to see the names used on
8087 @kindex info registers
8088 @item info registers
8089 Print the names and values of all registers except floating-point
8090 and vector registers (in the selected stack frame).
8092 @kindex info all-registers
8093 @cindex floating point registers
8094 @item info all-registers
8095 Print the names and values of all registers, including floating-point
8096 and vector registers (in the selected stack frame).
8098 @item info registers @var{regname} @dots{}
8099 Print the @dfn{relativized} value of each specified register @var{regname}.
8100 As discussed in detail below, register values are normally relative to
8101 the selected stack frame. @var{regname} may be any register name valid on
8102 the machine you are using, with or without the initial @samp{$}.
8105 @cindex stack pointer register
8106 @cindex program counter register
8107 @cindex process status register
8108 @cindex frame pointer register
8109 @cindex standard registers
8110 @value{GDBN} has four ``standard'' register names that are available (in
8111 expressions) on most machines---whenever they do not conflict with an
8112 architecture's canonical mnemonics for registers. The register names
8113 @code{$pc} and @code{$sp} are used for the program counter register and
8114 the stack pointer. @code{$fp} is used for a register that contains a
8115 pointer to the current stack frame, and @code{$ps} is used for a
8116 register that contains the processor status. For example,
8117 you could print the program counter in hex with
8124 or print the instruction to be executed next with
8131 or add four to the stack pointer@footnote{This is a way of removing
8132 one word from the stack, on machines where stacks grow downward in
8133 memory (most machines, nowadays). This assumes that the innermost
8134 stack frame is selected; setting @code{$sp} is not allowed when other
8135 stack frames are selected. To pop entire frames off the stack,
8136 regardless of machine architecture, use @code{return};
8137 see @ref{Returning, ,Returning from a Function}.} with
8143 Whenever possible, these four standard register names are available on
8144 your machine even though the machine has different canonical mnemonics,
8145 so long as there is no conflict. The @code{info registers} command
8146 shows the canonical names. For example, on the SPARC, @code{info
8147 registers} displays the processor status register as @code{$psr} but you
8148 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8149 is an alias for the @sc{eflags} register.
8151 @value{GDBN} always considers the contents of an ordinary register as an
8152 integer when the register is examined in this way. Some machines have
8153 special registers which can hold nothing but floating point; these
8154 registers are considered to have floating point values. There is no way
8155 to refer to the contents of an ordinary register as floating point value
8156 (although you can @emph{print} it as a floating point value with
8157 @samp{print/f $@var{regname}}).
8159 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8160 means that the data format in which the register contents are saved by
8161 the operating system is not the same one that your program normally
8162 sees. For example, the registers of the 68881 floating point
8163 coprocessor are always saved in ``extended'' (raw) format, but all C
8164 programs expect to work with ``double'' (virtual) format. In such
8165 cases, @value{GDBN} normally works with the virtual format only (the format
8166 that makes sense for your program), but the @code{info registers} command
8167 prints the data in both formats.
8169 @cindex SSE registers (x86)
8170 @cindex MMX registers (x86)
8171 Some machines have special registers whose contents can be interpreted
8172 in several different ways. For example, modern x86-based machines
8173 have SSE and MMX registers that can hold several values packed
8174 together in several different formats. @value{GDBN} refers to such
8175 registers in @code{struct} notation:
8178 (@value{GDBP}) print $xmm1
8180 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8181 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8182 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8183 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8184 v4_int32 = @{0, 20657912, 11, 13@},
8185 v2_int64 = @{88725056443645952, 55834574859@},
8186 uint128 = 0x0000000d0000000b013b36f800000000
8191 To set values of such registers, you need to tell @value{GDBN} which
8192 view of the register you wish to change, as if you were assigning
8193 value to a @code{struct} member:
8196 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8199 Normally, register values are relative to the selected stack frame
8200 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8201 value that the register would contain if all stack frames farther in
8202 were exited and their saved registers restored. In order to see the
8203 true contents of hardware registers, you must select the innermost
8204 frame (with @samp{frame 0}).
8206 However, @value{GDBN} must deduce where registers are saved, from the machine
8207 code generated by your compiler. If some registers are not saved, or if
8208 @value{GDBN} is unable to locate the saved registers, the selected stack
8209 frame makes no difference.
8211 @node Floating Point Hardware
8212 @section Floating Point Hardware
8213 @cindex floating point
8215 Depending on the configuration, @value{GDBN} may be able to give
8216 you more information about the status of the floating point hardware.
8221 Display hardware-dependent information about the floating
8222 point unit. The exact contents and layout vary depending on the
8223 floating point chip. Currently, @samp{info float} is supported on
8224 the ARM and x86 machines.
8228 @section Vector Unit
8231 Depending on the configuration, @value{GDBN} may be able to give you
8232 more information about the status of the vector unit.
8237 Display information about the vector unit. The exact contents and
8238 layout vary depending on the hardware.
8241 @node OS Information
8242 @section Operating System Auxiliary Information
8243 @cindex OS information
8245 @value{GDBN} provides interfaces to useful OS facilities that can help
8246 you debug your program.
8248 @cindex @code{ptrace} system call
8249 @cindex @code{struct user} contents
8250 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8251 machines), it interfaces with the inferior via the @code{ptrace}
8252 system call. The operating system creates a special sata structure,
8253 called @code{struct user}, for this interface. You can use the
8254 command @code{info udot} to display the contents of this data
8260 Display the contents of the @code{struct user} maintained by the OS
8261 kernel for the program being debugged. @value{GDBN} displays the
8262 contents of @code{struct user} as a list of hex numbers, similar to
8263 the @code{examine} command.
8266 @cindex auxiliary vector
8267 @cindex vector, auxiliary
8268 Some operating systems supply an @dfn{auxiliary vector} to programs at
8269 startup. This is akin to the arguments and environment that you
8270 specify for a program, but contains a system-dependent variety of
8271 binary values that tell system libraries important details about the
8272 hardware, operating system, and process. Each value's purpose is
8273 identified by an integer tag; the meanings are well-known but system-specific.
8274 Depending on the configuration and operating system facilities,
8275 @value{GDBN} may be able to show you this information. For remote
8276 targets, this functionality may further depend on the remote stub's
8277 support of the @samp{qXfer:auxv:read} packet, see
8278 @ref{qXfer auxiliary vector read}.
8283 Display the auxiliary vector of the inferior, which can be either a
8284 live process or a core dump file. @value{GDBN} prints each tag value
8285 numerically, and also shows names and text descriptions for recognized
8286 tags. Some values in the vector are numbers, some bit masks, and some
8287 pointers to strings or other data. @value{GDBN} displays each value in the
8288 most appropriate form for a recognized tag, and in hexadecimal for
8289 an unrecognized tag.
8292 On some targets, @value{GDBN} can access operating-system-specific information
8293 and display it to user, without interpretation. For remote targets,
8294 this functionality depends on the remote stub's support of the
8295 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8298 @kindex info os processes
8299 @item info os processes
8300 Display the list of processes on the target. For each process,
8301 @value{GDBN} prints the process identifier, the name of the user, and
8302 the command corresponding to the process.
8305 @node Memory Region Attributes
8306 @section Memory Region Attributes
8307 @cindex memory region attributes
8309 @dfn{Memory region attributes} allow you to describe special handling
8310 required by regions of your target's memory. @value{GDBN} uses
8311 attributes to determine whether to allow certain types of memory
8312 accesses; whether to use specific width accesses; and whether to cache
8313 target memory. By default the description of memory regions is
8314 fetched from the target (if the current target supports this), but the
8315 user can override the fetched regions.
8317 Defined memory regions can be individually enabled and disabled. When a
8318 memory region is disabled, @value{GDBN} uses the default attributes when
8319 accessing memory in that region. Similarly, if no memory regions have
8320 been defined, @value{GDBN} uses the default attributes when accessing
8323 When a memory region is defined, it is given a number to identify it;
8324 to enable, disable, or remove a memory region, you specify that number.
8328 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8329 Define a memory region bounded by @var{lower} and @var{upper} with
8330 attributes @var{attributes}@dots{}, and add it to the list of regions
8331 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8332 case: it is treated as the target's maximum memory address.
8333 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8336 Discard any user changes to the memory regions and use target-supplied
8337 regions, if available, or no regions if the target does not support.
8340 @item delete mem @var{nums}@dots{}
8341 Remove memory regions @var{nums}@dots{} from the list of regions
8342 monitored by @value{GDBN}.
8345 @item disable mem @var{nums}@dots{}
8346 Disable monitoring of memory regions @var{nums}@dots{}.
8347 A disabled memory region is not forgotten.
8348 It may be enabled again later.
8351 @item enable mem @var{nums}@dots{}
8352 Enable monitoring of memory regions @var{nums}@dots{}.
8356 Print a table of all defined memory regions, with the following columns
8360 @item Memory Region Number
8361 @item Enabled or Disabled.
8362 Enabled memory regions are marked with @samp{y}.
8363 Disabled memory regions are marked with @samp{n}.
8366 The address defining the inclusive lower bound of the memory region.
8369 The address defining the exclusive upper bound of the memory region.
8372 The list of attributes set for this memory region.
8377 @subsection Attributes
8379 @subsubsection Memory Access Mode
8380 The access mode attributes set whether @value{GDBN} may make read or
8381 write accesses to a memory region.
8383 While these attributes prevent @value{GDBN} from performing invalid
8384 memory accesses, they do nothing to prevent the target system, I/O DMA,
8385 etc.@: from accessing memory.
8389 Memory is read only.
8391 Memory is write only.
8393 Memory is read/write. This is the default.
8396 @subsubsection Memory Access Size
8397 The access size attribute tells @value{GDBN} to use specific sized
8398 accesses in the memory region. Often memory mapped device registers
8399 require specific sized accesses. If no access size attribute is
8400 specified, @value{GDBN} may use accesses of any size.
8404 Use 8 bit memory accesses.
8406 Use 16 bit memory accesses.
8408 Use 32 bit memory accesses.
8410 Use 64 bit memory accesses.
8413 @c @subsubsection Hardware/Software Breakpoints
8414 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8415 @c will use hardware or software breakpoints for the internal breakpoints
8416 @c used by the step, next, finish, until, etc. commands.
8420 @c Always use hardware breakpoints
8421 @c @item swbreak (default)
8424 @subsubsection Data Cache
8425 The data cache attributes set whether @value{GDBN} will cache target
8426 memory. While this generally improves performance by reducing debug
8427 protocol overhead, it can lead to incorrect results because @value{GDBN}
8428 does not know about volatile variables or memory mapped device
8433 Enable @value{GDBN} to cache target memory.
8435 Disable @value{GDBN} from caching target memory. This is the default.
8438 @subsection Memory Access Checking
8439 @value{GDBN} can be instructed to refuse accesses to memory that is
8440 not explicitly described. This can be useful if accessing such
8441 regions has undesired effects for a specific target, or to provide
8442 better error checking. The following commands control this behaviour.
8445 @kindex set mem inaccessible-by-default
8446 @item set mem inaccessible-by-default [on|off]
8447 If @code{on} is specified, make @value{GDBN} treat memory not
8448 explicitly described by the memory ranges as non-existent and refuse accesses
8449 to such memory. The checks are only performed if there's at least one
8450 memory range defined. If @code{off} is specified, make @value{GDBN}
8451 treat the memory not explicitly described by the memory ranges as RAM.
8452 The default value is @code{on}.
8453 @kindex show mem inaccessible-by-default
8454 @item show mem inaccessible-by-default
8455 Show the current handling of accesses to unknown memory.
8459 @c @subsubsection Memory Write Verification
8460 @c The memory write verification attributes set whether @value{GDBN}
8461 @c will re-reads data after each write to verify the write was successful.
8465 @c @item noverify (default)
8468 @node Dump/Restore Files
8469 @section Copy Between Memory and a File
8470 @cindex dump/restore files
8471 @cindex append data to a file
8472 @cindex dump data to a file
8473 @cindex restore data from a file
8475 You can use the commands @code{dump}, @code{append}, and
8476 @code{restore} to copy data between target memory and a file. The
8477 @code{dump} and @code{append} commands write data to a file, and the
8478 @code{restore} command reads data from a file back into the inferior's
8479 memory. Files may be in binary, Motorola S-record, Intel hex, or
8480 Tektronix Hex format; however, @value{GDBN} can only append to binary
8486 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8487 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8488 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8489 or the value of @var{expr}, to @var{filename} in the given format.
8491 The @var{format} parameter may be any one of:
8498 Motorola S-record format.
8500 Tektronix Hex format.
8503 @value{GDBN} uses the same definitions of these formats as the
8504 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8505 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8509 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8510 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8511 Append the contents of memory from @var{start_addr} to @var{end_addr},
8512 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8513 (@value{GDBN} can only append data to files in raw binary form.)
8516 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8517 Restore the contents of file @var{filename} into memory. The
8518 @code{restore} command can automatically recognize any known @sc{bfd}
8519 file format, except for raw binary. To restore a raw binary file you
8520 must specify the optional keyword @code{binary} after the filename.
8522 If @var{bias} is non-zero, its value will be added to the addresses
8523 contained in the file. Binary files always start at address zero, so
8524 they will be restored at address @var{bias}. Other bfd files have
8525 a built-in location; they will be restored at offset @var{bias}
8528 If @var{start} and/or @var{end} are non-zero, then only data between
8529 file offset @var{start} and file offset @var{end} will be restored.
8530 These offsets are relative to the addresses in the file, before
8531 the @var{bias} argument is applied.
8535 @node Core File Generation
8536 @section How to Produce a Core File from Your Program
8537 @cindex dump core from inferior
8539 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8540 image of a running process and its process status (register values
8541 etc.). Its primary use is post-mortem debugging of a program that
8542 crashed while it ran outside a debugger. A program that crashes
8543 automatically produces a core file, unless this feature is disabled by
8544 the user. @xref{Files}, for information on invoking @value{GDBN} in
8545 the post-mortem debugging mode.
8547 Occasionally, you may wish to produce a core file of the program you
8548 are debugging in order to preserve a snapshot of its state.
8549 @value{GDBN} has a special command for that.
8553 @kindex generate-core-file
8554 @item generate-core-file [@var{file}]
8555 @itemx gcore [@var{file}]
8556 Produce a core dump of the inferior process. The optional argument
8557 @var{file} specifies the file name where to put the core dump. If not
8558 specified, the file name defaults to @file{core.@var{pid}}, where
8559 @var{pid} is the inferior process ID.
8561 Note that this command is implemented only for some systems (as of
8562 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8565 @node Character Sets
8566 @section Character Sets
8567 @cindex character sets
8569 @cindex translating between character sets
8570 @cindex host character set
8571 @cindex target character set
8573 If the program you are debugging uses a different character set to
8574 represent characters and strings than the one @value{GDBN} uses itself,
8575 @value{GDBN} can automatically translate between the character sets for
8576 you. The character set @value{GDBN} uses we call the @dfn{host
8577 character set}; the one the inferior program uses we call the
8578 @dfn{target character set}.
8580 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8581 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8582 remote protocol (@pxref{Remote Debugging}) to debug a program
8583 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8584 then the host character set is Latin-1, and the target character set is
8585 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8586 target-charset EBCDIC-US}, then @value{GDBN} translates between
8587 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8588 character and string literals in expressions.
8590 @value{GDBN} has no way to automatically recognize which character set
8591 the inferior program uses; you must tell it, using the @code{set
8592 target-charset} command, described below.
8594 Here are the commands for controlling @value{GDBN}'s character set
8598 @item set target-charset @var{charset}
8599 @kindex set target-charset
8600 Set the current target character set to @var{charset}. To display the
8601 list of supported target character sets, type
8602 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8604 @item set host-charset @var{charset}
8605 @kindex set host-charset
8606 Set the current host character set to @var{charset}.
8608 By default, @value{GDBN} uses a host character set appropriate to the
8609 system it is running on; you can override that default using the
8610 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8611 automatically determine the appropriate host character set. In this
8612 case, @value{GDBN} uses @samp{UTF-8}.
8614 @value{GDBN} can only use certain character sets as its host character
8615 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8616 @value{GDBN} will list the host character sets it supports.
8618 @item set charset @var{charset}
8620 Set the current host and target character sets to @var{charset}. As
8621 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8622 @value{GDBN} will list the names of the character sets that can be used
8623 for both host and target.
8626 @kindex show charset
8627 Show the names of the current host and target character sets.
8629 @item show host-charset
8630 @kindex show host-charset
8631 Show the name of the current host character set.
8633 @item show target-charset
8634 @kindex show target-charset
8635 Show the name of the current target character set.
8637 @item set target-wide-charset @var{charset}
8638 @kindex set target-wide-charset
8639 Set the current target's wide character set to @var{charset}. This is
8640 the character set used by the target's @code{wchar_t} type. To
8641 display the list of supported wide character sets, type
8642 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8644 @item show target-wide-charset
8645 @kindex show target-wide-charset
8646 Show the name of the current target's wide character set.
8649 Here is an example of @value{GDBN}'s character set support in action.
8650 Assume that the following source code has been placed in the file
8651 @file{charset-test.c}:
8657 = @{72, 101, 108, 108, 111, 44, 32, 119,
8658 111, 114, 108, 100, 33, 10, 0@};
8659 char ibm1047_hello[]
8660 = @{200, 133, 147, 147, 150, 107, 64, 166,
8661 150, 153, 147, 132, 90, 37, 0@};
8665 printf ("Hello, world!\n");
8669 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8670 containing the string @samp{Hello, world!} followed by a newline,
8671 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8673 We compile the program, and invoke the debugger on it:
8676 $ gcc -g charset-test.c -o charset-test
8677 $ gdb -nw charset-test
8678 GNU gdb 2001-12-19-cvs
8679 Copyright 2001 Free Software Foundation, Inc.
8684 We can use the @code{show charset} command to see what character sets
8685 @value{GDBN} is currently using to interpret and display characters and
8689 (@value{GDBP}) show charset
8690 The current host and target character set is `ISO-8859-1'.
8694 For the sake of printing this manual, let's use @sc{ascii} as our
8695 initial character set:
8697 (@value{GDBP}) set charset ASCII
8698 (@value{GDBP}) show charset
8699 The current host and target character set is `ASCII'.
8703 Let's assume that @sc{ascii} is indeed the correct character set for our
8704 host system --- in other words, let's assume that if @value{GDBN} prints
8705 characters using the @sc{ascii} character set, our terminal will display
8706 them properly. Since our current target character set is also
8707 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8710 (@value{GDBP}) print ascii_hello
8711 $1 = 0x401698 "Hello, world!\n"
8712 (@value{GDBP}) print ascii_hello[0]
8717 @value{GDBN} uses the target character set for character and string
8718 literals you use in expressions:
8721 (@value{GDBP}) print '+'
8726 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8729 @value{GDBN} relies on the user to tell it which character set the
8730 target program uses. If we print @code{ibm1047_hello} while our target
8731 character set is still @sc{ascii}, we get jibberish:
8734 (@value{GDBP}) print ibm1047_hello
8735 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8736 (@value{GDBP}) print ibm1047_hello[0]
8741 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8742 @value{GDBN} tells us the character sets it supports:
8745 (@value{GDBP}) set target-charset
8746 ASCII EBCDIC-US IBM1047 ISO-8859-1
8747 (@value{GDBP}) set target-charset
8750 We can select @sc{ibm1047} as our target character set, and examine the
8751 program's strings again. Now the @sc{ascii} string is wrong, but
8752 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8753 target character set, @sc{ibm1047}, to the host character set,
8754 @sc{ascii}, and they display correctly:
8757 (@value{GDBP}) set target-charset IBM1047
8758 (@value{GDBP}) show charset
8759 The current host character set is `ASCII'.
8760 The current target character set is `IBM1047'.
8761 (@value{GDBP}) print ascii_hello
8762 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8763 (@value{GDBP}) print ascii_hello[0]
8765 (@value{GDBP}) print ibm1047_hello
8766 $8 = 0x4016a8 "Hello, world!\n"
8767 (@value{GDBP}) print ibm1047_hello[0]
8772 As above, @value{GDBN} uses the target character set for character and
8773 string literals you use in expressions:
8776 (@value{GDBP}) print '+'
8781 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8784 @node Caching Remote Data
8785 @section Caching Data of Remote Targets
8786 @cindex caching data of remote targets
8788 @value{GDBN} caches data exchanged between the debugger and a
8789 remote target (@pxref{Remote Debugging}). Such caching generally improves
8790 performance, because it reduces the overhead of the remote protocol by
8791 bundling memory reads and writes into large chunks. Unfortunately, simply
8792 caching everything would lead to incorrect results, since @value{GDBN}
8793 does not necessarily know anything about volatile values, memory-mapped I/O
8794 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
8795 memory can be changed @emph{while} a gdb command is executing.
8796 Therefore, by default, @value{GDBN} only caches data
8797 known to be on the stack@footnote{In non-stop mode, it is moderately
8798 rare for a running thread to modify the stack of a stopped thread
8799 in a way that would interfere with a backtrace, and caching of
8800 stack reads provides a significant speed up of remote backtraces.}.
8801 Other regions of memory can be explicitly marked as
8802 cacheable; see @pxref{Memory Region Attributes}.
8805 @kindex set remotecache
8806 @item set remotecache on
8807 @itemx set remotecache off
8808 This option no longer does anything; it exists for compatibility
8811 @kindex show remotecache
8812 @item show remotecache
8813 Show the current state of the obsolete remotecache flag.
8815 @kindex set stack-cache
8816 @item set stack-cache on
8817 @itemx set stack-cache off
8818 Enable or disable caching of stack accesses. When @code{ON}, use
8819 caching. By default, this option is @code{ON}.
8821 @kindex show stack-cache
8822 @item show stack-cache
8823 Show the current state of data caching for memory accesses.
8826 @item info dcache @r{[}line@r{]}
8827 Print the information about the data cache performance. The
8828 information displayed includes the dcache width and depth, and for
8829 each cache line, its number, address, and how many times it was
8830 referenced. This command is useful for debugging the data cache
8833 If a line number is specified, the contents of that line will be
8837 @node Searching Memory
8838 @section Search Memory
8839 @cindex searching memory
8841 Memory can be searched for a particular sequence of bytes with the
8842 @code{find} command.
8846 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8847 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8848 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8849 etc. The search begins at address @var{start_addr} and continues for either
8850 @var{len} bytes or through to @var{end_addr} inclusive.
8853 @var{s} and @var{n} are optional parameters.
8854 They may be specified in either order, apart or together.
8857 @item @var{s}, search query size
8858 The size of each search query value.
8864 halfwords (two bytes)
8868 giant words (eight bytes)
8871 All values are interpreted in the current language.
8872 This means, for example, that if the current source language is C/C@t{++}
8873 then searching for the string ``hello'' includes the trailing '\0'.
8875 If the value size is not specified, it is taken from the
8876 value's type in the current language.
8877 This is useful when one wants to specify the search
8878 pattern as a mixture of types.
8879 Note that this means, for example, that in the case of C-like languages
8880 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8881 which is typically four bytes.
8883 @item @var{n}, maximum number of finds
8884 The maximum number of matches to print. The default is to print all finds.
8887 You can use strings as search values. Quote them with double-quotes
8889 The string value is copied into the search pattern byte by byte,
8890 regardless of the endianness of the target and the size specification.
8892 The address of each match found is printed as well as a count of the
8893 number of matches found.
8895 The address of the last value found is stored in convenience variable
8897 A count of the number of matches is stored in @samp{$numfound}.
8899 For example, if stopped at the @code{printf} in this function:
8905 static char hello[] = "hello-hello";
8906 static struct @{ char c; short s; int i; @}
8907 __attribute__ ((packed)) mixed
8908 = @{ 'c', 0x1234, 0x87654321 @};
8909 printf ("%s\n", hello);
8914 you get during debugging:
8917 (gdb) find &hello[0], +sizeof(hello), "hello"
8918 0x804956d <hello.1620+6>
8920 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8921 0x8049567 <hello.1620>
8922 0x804956d <hello.1620+6>
8924 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8925 0x8049567 <hello.1620>
8927 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8928 0x8049560 <mixed.1625>
8930 (gdb) print $numfound
8933 $2 = (void *) 0x8049560
8936 @node Optimized Code
8937 @chapter Debugging Optimized Code
8938 @cindex optimized code, debugging
8939 @cindex debugging optimized code
8941 Almost all compilers support optimization. With optimization
8942 disabled, the compiler generates assembly code that corresponds
8943 directly to your source code, in a simplistic way. As the compiler
8944 applies more powerful optimizations, the generated assembly code
8945 diverges from your original source code. With help from debugging
8946 information generated by the compiler, @value{GDBN} can map from
8947 the running program back to constructs from your original source.
8949 @value{GDBN} is more accurate with optimization disabled. If you
8950 can recompile without optimization, it is easier to follow the
8951 progress of your program during debugging. But, there are many cases
8952 where you may need to debug an optimized version.
8954 When you debug a program compiled with @samp{-g -O}, remember that the
8955 optimizer has rearranged your code; the debugger shows you what is
8956 really there. Do not be too surprised when the execution path does not
8957 exactly match your source file! An extreme example: if you define a
8958 variable, but never use it, @value{GDBN} never sees that
8959 variable---because the compiler optimizes it out of existence.
8961 Some things do not work as well with @samp{-g -O} as with just
8962 @samp{-g}, particularly on machines with instruction scheduling. If in
8963 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
8964 please report it to us as a bug (including a test case!).
8965 @xref{Variables}, for more information about debugging optimized code.
8968 * Inline Functions:: How @value{GDBN} presents inlining
8971 @node Inline Functions
8972 @section Inline Functions
8973 @cindex inline functions, debugging
8975 @dfn{Inlining} is an optimization that inserts a copy of the function
8976 body directly at each call site, instead of jumping to a shared
8977 routine. @value{GDBN} displays inlined functions just like
8978 non-inlined functions. They appear in backtraces. You can view their
8979 arguments and local variables, step into them with @code{step}, skip
8980 them with @code{next}, and escape from them with @code{finish}.
8981 You can check whether a function was inlined by using the
8982 @code{info frame} command.
8984 For @value{GDBN} to support inlined functions, the compiler must
8985 record information about inlining in the debug information ---
8986 @value{NGCC} using the @sc{dwarf 2} format does this, and several
8987 other compilers do also. @value{GDBN} only supports inlined functions
8988 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
8989 do not emit two required attributes (@samp{DW_AT_call_file} and
8990 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
8991 function calls with earlier versions of @value{NGCC}. It instead
8992 displays the arguments and local variables of inlined functions as
8993 local variables in the caller.
8995 The body of an inlined function is directly included at its call site;
8996 unlike a non-inlined function, there are no instructions devoted to
8997 the call. @value{GDBN} still pretends that the call site and the
8998 start of the inlined function are different instructions. Stepping to
8999 the call site shows the call site, and then stepping again shows
9000 the first line of the inlined function, even though no additional
9001 instructions are executed.
9003 This makes source-level debugging much clearer; you can see both the
9004 context of the call and then the effect of the call. Only stepping by
9005 a single instruction using @code{stepi} or @code{nexti} does not do
9006 this; single instruction steps always show the inlined body.
9008 There are some ways that @value{GDBN} does not pretend that inlined
9009 function calls are the same as normal calls:
9013 You cannot set breakpoints on inlined functions. @value{GDBN}
9014 either reports that there is no symbol with that name, or else sets the
9015 breakpoint only on non-inlined copies of the function. This limitation
9016 will be removed in a future version of @value{GDBN}; until then,
9017 set a breakpoint by line number on the first line of the inlined
9021 Setting breakpoints at the call site of an inlined function may not
9022 work, because the call site does not contain any code. @value{GDBN}
9023 may incorrectly move the breakpoint to the next line of the enclosing
9024 function, after the call. This limitation will be removed in a future
9025 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9026 or inside the inlined function instead.
9029 @value{GDBN} cannot locate the return value of inlined calls after
9030 using the @code{finish} command. This is a limitation of compiler-generated
9031 debugging information; after @code{finish}, you can step to the next line
9032 and print a variable where your program stored the return value.
9038 @chapter C Preprocessor Macros
9040 Some languages, such as C and C@t{++}, provide a way to define and invoke
9041 ``preprocessor macros'' which expand into strings of tokens.
9042 @value{GDBN} can evaluate expressions containing macro invocations, show
9043 the result of macro expansion, and show a macro's definition, including
9044 where it was defined.
9046 You may need to compile your program specially to provide @value{GDBN}
9047 with information about preprocessor macros. Most compilers do not
9048 include macros in their debugging information, even when you compile
9049 with the @option{-g} flag. @xref{Compilation}.
9051 A program may define a macro at one point, remove that definition later,
9052 and then provide a different definition after that. Thus, at different
9053 points in the program, a macro may have different definitions, or have
9054 no definition at all. If there is a current stack frame, @value{GDBN}
9055 uses the macros in scope at that frame's source code line. Otherwise,
9056 @value{GDBN} uses the macros in scope at the current listing location;
9059 Whenever @value{GDBN} evaluates an expression, it always expands any
9060 macro invocations present in the expression. @value{GDBN} also provides
9061 the following commands for working with macros explicitly.
9065 @kindex macro expand
9066 @cindex macro expansion, showing the results of preprocessor
9067 @cindex preprocessor macro expansion, showing the results of
9068 @cindex expanding preprocessor macros
9069 @item macro expand @var{expression}
9070 @itemx macro exp @var{expression}
9071 Show the results of expanding all preprocessor macro invocations in
9072 @var{expression}. Since @value{GDBN} simply expands macros, but does
9073 not parse the result, @var{expression} need not be a valid expression;
9074 it can be any string of tokens.
9077 @item macro expand-once @var{expression}
9078 @itemx macro exp1 @var{expression}
9079 @cindex expand macro once
9080 @i{(This command is not yet implemented.)} Show the results of
9081 expanding those preprocessor macro invocations that appear explicitly in
9082 @var{expression}. Macro invocations appearing in that expansion are
9083 left unchanged. This command allows you to see the effect of a
9084 particular macro more clearly, without being confused by further
9085 expansions. Since @value{GDBN} simply expands macros, but does not
9086 parse the result, @var{expression} need not be a valid expression; it
9087 can be any string of tokens.
9090 @cindex macro definition, showing
9091 @cindex definition, showing a macro's
9092 @item info macro @var{macro}
9093 Show the definition of the macro named @var{macro}, and describe the
9094 source location or compiler command-line where that definition was established.
9096 @kindex macro define
9097 @cindex user-defined macros
9098 @cindex defining macros interactively
9099 @cindex macros, user-defined
9100 @item macro define @var{macro} @var{replacement-list}
9101 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9102 Introduce a definition for a preprocessor macro named @var{macro},
9103 invocations of which are replaced by the tokens given in
9104 @var{replacement-list}. The first form of this command defines an
9105 ``object-like'' macro, which takes no arguments; the second form
9106 defines a ``function-like'' macro, which takes the arguments given in
9109 A definition introduced by this command is in scope in every
9110 expression evaluated in @value{GDBN}, until it is removed with the
9111 @code{macro undef} command, described below. The definition overrides
9112 all definitions for @var{macro} present in the program being debugged,
9113 as well as any previous user-supplied definition.
9116 @item macro undef @var{macro}
9117 Remove any user-supplied definition for the macro named @var{macro}.
9118 This command only affects definitions provided with the @code{macro
9119 define} command, described above; it cannot remove definitions present
9120 in the program being debugged.
9124 List all the macros defined using the @code{macro define} command.
9127 @cindex macros, example of debugging with
9128 Here is a transcript showing the above commands in action. First, we
9129 show our source files:
9137 #define ADD(x) (M + x)
9142 printf ("Hello, world!\n");
9144 printf ("We're so creative.\n");
9146 printf ("Goodbye, world!\n");
9153 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9154 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9155 compiler includes information about preprocessor macros in the debugging
9159 $ gcc -gdwarf-2 -g3 sample.c -o sample
9163 Now, we start @value{GDBN} on our sample program:
9167 GNU gdb 2002-05-06-cvs
9168 Copyright 2002 Free Software Foundation, Inc.
9169 GDB is free software, @dots{}
9173 We can expand macros and examine their definitions, even when the
9174 program is not running. @value{GDBN} uses the current listing position
9175 to decide which macro definitions are in scope:
9178 (@value{GDBP}) list main
9181 5 #define ADD(x) (M + x)
9186 10 printf ("Hello, world!\n");
9188 12 printf ("We're so creative.\n");
9189 (@value{GDBP}) info macro ADD
9190 Defined at /home/jimb/gdb/macros/play/sample.c:5
9191 #define ADD(x) (M + x)
9192 (@value{GDBP}) info macro Q
9193 Defined at /home/jimb/gdb/macros/play/sample.h:1
9194 included at /home/jimb/gdb/macros/play/sample.c:2
9196 (@value{GDBP}) macro expand ADD(1)
9197 expands to: (42 + 1)
9198 (@value{GDBP}) macro expand-once ADD(1)
9199 expands to: once (M + 1)
9203 In the example above, note that @code{macro expand-once} expands only
9204 the macro invocation explicit in the original text --- the invocation of
9205 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9206 which was introduced by @code{ADD}.
9208 Once the program is running, @value{GDBN} uses the macro definitions in
9209 force at the source line of the current stack frame:
9212 (@value{GDBP}) break main
9213 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9215 Starting program: /home/jimb/gdb/macros/play/sample
9217 Breakpoint 1, main () at sample.c:10
9218 10 printf ("Hello, world!\n");
9222 At line 10, the definition of the macro @code{N} at line 9 is in force:
9225 (@value{GDBP}) info macro N
9226 Defined at /home/jimb/gdb/macros/play/sample.c:9
9228 (@value{GDBP}) macro expand N Q M
9230 (@value{GDBP}) print N Q M
9235 As we step over directives that remove @code{N}'s definition, and then
9236 give it a new definition, @value{GDBN} finds the definition (or lack
9237 thereof) in force at each point:
9242 12 printf ("We're so creative.\n");
9243 (@value{GDBP}) info macro N
9244 The symbol `N' has no definition as a C/C++ preprocessor macro
9245 at /home/jimb/gdb/macros/play/sample.c:12
9248 14 printf ("Goodbye, world!\n");
9249 (@value{GDBP}) info macro N
9250 Defined at /home/jimb/gdb/macros/play/sample.c:13
9252 (@value{GDBP}) macro expand N Q M
9253 expands to: 1729 < 42
9254 (@value{GDBP}) print N Q M
9259 In addition to source files, macros can be defined on the compilation command
9260 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9261 such a way, @value{GDBN} displays the location of their definition as line zero
9262 of the source file submitted to the compiler.
9265 (@value{GDBP}) info macro __STDC__
9266 Defined at /home/jimb/gdb/macros/play/sample.c:0
9273 @chapter Tracepoints
9274 @c This chapter is based on the documentation written by Michael
9275 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9278 In some applications, it is not feasible for the debugger to interrupt
9279 the program's execution long enough for the developer to learn
9280 anything helpful about its behavior. If the program's correctness
9281 depends on its real-time behavior, delays introduced by a debugger
9282 might cause the program to change its behavior drastically, or perhaps
9283 fail, even when the code itself is correct. It is useful to be able
9284 to observe the program's behavior without interrupting it.
9286 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9287 specify locations in the program, called @dfn{tracepoints}, and
9288 arbitrary expressions to evaluate when those tracepoints are reached.
9289 Later, using the @code{tfind} command, you can examine the values
9290 those expressions had when the program hit the tracepoints. The
9291 expressions may also denote objects in memory---structures or arrays,
9292 for example---whose values @value{GDBN} should record; while visiting
9293 a particular tracepoint, you may inspect those objects as if they were
9294 in memory at that moment. However, because @value{GDBN} records these
9295 values without interacting with you, it can do so quickly and
9296 unobtrusively, hopefully not disturbing the program's behavior.
9298 The tracepoint facility is currently available only for remote
9299 targets. @xref{Targets}. In addition, your remote target must know
9300 how to collect trace data. This functionality is implemented in the
9301 remote stub; however, none of the stubs distributed with @value{GDBN}
9302 support tracepoints as of this writing. The format of the remote
9303 packets used to implement tracepoints are described in @ref{Tracepoint
9306 It is also possible to get trace data from a file, in a manner reminiscent
9307 of corefiles; you specify the filename, and use @code{tfind} to search
9308 through the file. @xref{Trace Files}, for more details.
9310 This chapter describes the tracepoint commands and features.
9314 * Analyze Collected Data::
9315 * Tracepoint Variables::
9319 @node Set Tracepoints
9320 @section Commands to Set Tracepoints
9322 Before running such a @dfn{trace experiment}, an arbitrary number of
9323 tracepoints can be set. A tracepoint is actually a special type of
9324 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9325 standard breakpoint commands. For instance, as with breakpoints,
9326 tracepoint numbers are successive integers starting from one, and many
9327 of the commands associated with tracepoints take the tracepoint number
9328 as their argument, to identify which tracepoint to work on.
9330 For each tracepoint, you can specify, in advance, some arbitrary set
9331 of data that you want the target to collect in the trace buffer when
9332 it hits that tracepoint. The collected data can include registers,
9333 local variables, or global data. Later, you can use @value{GDBN}
9334 commands to examine the values these data had at the time the
9337 Tracepoints do not support every breakpoint feature. Ignore counts on
9338 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9339 commands when they are hit. Tracepoints may not be thread-specific
9342 @cindex fast tracepoints
9343 Some targets may support @dfn{fast tracepoints}, which are inserted in
9344 a different way (such as with a jump instead of a trap), that is
9345 faster but possibly restricted in where they may be installed.
9347 This section describes commands to set tracepoints and associated
9348 conditions and actions.
9351 * Create and Delete Tracepoints::
9352 * Enable and Disable Tracepoints::
9353 * Tracepoint Passcounts::
9354 * Tracepoint Conditions::
9355 * Trace State Variables::
9356 * Tracepoint Actions::
9357 * Listing Tracepoints::
9358 * Starting and Stopping Trace Experiments::
9359 * Tracepoint Restrictions::
9362 @node Create and Delete Tracepoints
9363 @subsection Create and Delete Tracepoints
9366 @cindex set tracepoint
9368 @item trace @var{location}
9369 The @code{trace} command is very similar to the @code{break} command.
9370 Its argument @var{location} can be a source line, a function name, or
9371 an address in the target program. @xref{Specify Location}. The
9372 @code{trace} command defines a tracepoint, which is a point in the
9373 target program where the debugger will briefly stop, collect some
9374 data, and then allow the program to continue. Setting a tracepoint or
9375 changing its actions doesn't take effect until the next @code{tstart}
9376 command, and once a trace experiment is running, further changes will
9377 not have any effect until the next trace experiment starts.
9379 Here are some examples of using the @code{trace} command:
9382 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9384 (@value{GDBP}) @b{trace +2} // 2 lines forward
9386 (@value{GDBP}) @b{trace my_function} // first source line of function
9388 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9390 (@value{GDBP}) @b{trace *0x2117c4} // an address
9394 You can abbreviate @code{trace} as @code{tr}.
9396 @item trace @var{location} if @var{cond}
9397 Set a tracepoint with condition @var{cond}; evaluate the expression
9398 @var{cond} each time the tracepoint is reached, and collect data only
9399 if the value is nonzero---that is, if @var{cond} evaluates as true.
9400 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9401 information on tracepoint conditions.
9403 @item ftrace @var{location} [ if @var{cond} ]
9404 @cindex set fast tracepoint
9406 The @code{ftrace} command sets a fast tracepoint. For targets that
9407 support them, fast tracepoints will use a more efficient but possibly
9408 less general technique to trigger data collection, such as a jump
9409 instruction instead of a trap, or some sort of hardware support. It
9410 may not be possible to create a fast tracepoint at the desired
9411 location, in which case the command will exit with an explanatory
9414 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9418 @cindex last tracepoint number
9419 @cindex recent tracepoint number
9420 @cindex tracepoint number
9421 The convenience variable @code{$tpnum} records the tracepoint number
9422 of the most recently set tracepoint.
9424 @kindex delete tracepoint
9425 @cindex tracepoint deletion
9426 @item delete tracepoint @r{[}@var{num}@r{]}
9427 Permanently delete one or more tracepoints. With no argument, the
9428 default is to delete all tracepoints. Note that the regular
9429 @code{delete} command can remove tracepoints also.
9434 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9436 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9440 You can abbreviate this command as @code{del tr}.
9443 @node Enable and Disable Tracepoints
9444 @subsection Enable and Disable Tracepoints
9446 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9449 @kindex disable tracepoint
9450 @item disable tracepoint @r{[}@var{num}@r{]}
9451 Disable tracepoint @var{num}, or all tracepoints if no argument
9452 @var{num} is given. A disabled tracepoint will have no effect during
9453 the next trace experiment, but it is not forgotten. You can re-enable
9454 a disabled tracepoint using the @code{enable tracepoint} command.
9456 @kindex enable tracepoint
9457 @item enable tracepoint @r{[}@var{num}@r{]}
9458 Enable tracepoint @var{num}, or all tracepoints. The enabled
9459 tracepoints will become effective the next time a trace experiment is
9463 @node Tracepoint Passcounts
9464 @subsection Tracepoint Passcounts
9468 @cindex tracepoint pass count
9469 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9470 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9471 automatically stop a trace experiment. If a tracepoint's passcount is
9472 @var{n}, then the trace experiment will be automatically stopped on
9473 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9474 @var{num} is not specified, the @code{passcount} command sets the
9475 passcount of the most recently defined tracepoint. If no passcount is
9476 given, the trace experiment will run until stopped explicitly by the
9482 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9483 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9485 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9486 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9487 (@value{GDBP}) @b{trace foo}
9488 (@value{GDBP}) @b{pass 3}
9489 (@value{GDBP}) @b{trace bar}
9490 (@value{GDBP}) @b{pass 2}
9491 (@value{GDBP}) @b{trace baz}
9492 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9493 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9494 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9495 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9499 @node Tracepoint Conditions
9500 @subsection Tracepoint Conditions
9501 @cindex conditional tracepoints
9502 @cindex tracepoint conditions
9504 The simplest sort of tracepoint collects data every time your program
9505 reaches a specified place. You can also specify a @dfn{condition} for
9506 a tracepoint. A condition is just a Boolean expression in your
9507 programming language (@pxref{Expressions, ,Expressions}). A
9508 tracepoint with a condition evaluates the expression each time your
9509 program reaches it, and data collection happens only if the condition
9512 Tracepoint conditions can be specified when a tracepoint is set, by
9513 using @samp{if} in the arguments to the @code{trace} command.
9514 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9515 also be set or changed at any time with the @code{condition} command,
9516 just as with breakpoints.
9518 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9519 the conditional expression itself. Instead, @value{GDBN} encodes the
9520 expression into an agent expression (@pxref{Agent Expressions}
9521 suitable for execution on the target, independently of @value{GDBN}.
9522 Global variables become raw memory locations, locals become stack
9523 accesses, and so forth.
9525 For instance, suppose you have a function that is usually called
9526 frequently, but should not be called after an error has occurred. You
9527 could use the following tracepoint command to collect data about calls
9528 of that function that happen while the error code is propagating
9529 through the program; an unconditional tracepoint could end up
9530 collecting thousands of useless trace frames that you would have to
9534 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9537 @node Trace State Variables
9538 @subsection Trace State Variables
9539 @cindex trace state variables
9541 A @dfn{trace state variable} is a special type of variable that is
9542 created and managed by target-side code. The syntax is the same as
9543 that for GDB's convenience variables (a string prefixed with ``$''),
9544 but they are stored on the target. They must be created explicitly,
9545 using a @code{tvariable} command. They are always 64-bit signed
9548 Trace state variables are remembered by @value{GDBN}, and downloaded
9549 to the target along with tracepoint information when the trace
9550 experiment starts. There are no intrinsic limits on the number of
9551 trace state variables, beyond memory limitations of the target.
9553 @cindex convenience variables, and trace state variables
9554 Although trace state variables are managed by the target, you can use
9555 them in print commands and expressions as if they were convenience
9556 variables; @value{GDBN} will get the current value from the target
9557 while the trace experiment is running. Trace state variables share
9558 the same namespace as other ``$'' variables, which means that you
9559 cannot have trace state variables with names like @code{$23} or
9560 @code{$pc}, nor can you have a trace state variable and a convenience
9561 variable with the same name.
9565 @item tvariable $@var{name} [ = @var{expression} ]
9567 The @code{tvariable} command creates a new trace state variable named
9568 @code{$@var{name}}, and optionally gives it an initial value of
9569 @var{expression}. @var{expression} is evaluated when this command is
9570 entered; the result will be converted to an integer if possible,
9571 otherwise @value{GDBN} will report an error. A subsequent
9572 @code{tvariable} command specifying the same name does not create a
9573 variable, but instead assigns the supplied initial value to the
9574 existing variable of that name, overwriting any previous initial
9575 value. The default initial value is 0.
9577 @item info tvariables
9578 @kindex info tvariables
9579 List all the trace state variables along with their initial values.
9580 Their current values may also be displayed, if the trace experiment is
9583 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9584 @kindex delete tvariable
9585 Delete the given trace state variables, or all of them if no arguments
9590 @node Tracepoint Actions
9591 @subsection Tracepoint Action Lists
9595 @cindex tracepoint actions
9596 @item actions @r{[}@var{num}@r{]}
9597 This command will prompt for a list of actions to be taken when the
9598 tracepoint is hit. If the tracepoint number @var{num} is not
9599 specified, this command sets the actions for the one that was most
9600 recently defined (so that you can define a tracepoint and then say
9601 @code{actions} without bothering about its number). You specify the
9602 actions themselves on the following lines, one action at a time, and
9603 terminate the actions list with a line containing just @code{end}. So
9604 far, the only defined actions are @code{collect}, @code{teval}, and
9605 @code{while-stepping}.
9607 @cindex remove actions from a tracepoint
9608 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9609 and follow it immediately with @samp{end}.
9612 (@value{GDBP}) @b{collect @var{data}} // collect some data
9614 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9616 (@value{GDBP}) @b{end} // signals the end of actions.
9619 In the following example, the action list begins with @code{collect}
9620 commands indicating the things to be collected when the tracepoint is
9621 hit. Then, in order to single-step and collect additional data
9622 following the tracepoint, a @code{while-stepping} command is used,
9623 followed by the list of things to be collected after each step in a
9624 sequence of single steps. The @code{while-stepping} command is
9625 terminated by its own separate @code{end} command. Lastly, the action
9626 list is terminated by an @code{end} command.
9629 (@value{GDBP}) @b{trace foo}
9630 (@value{GDBP}) @b{actions}
9631 Enter actions for tracepoint 1, one per line:
9640 @kindex collect @r{(tracepoints)}
9641 @item collect @var{expr1}, @var{expr2}, @dots{}
9642 Collect values of the given expressions when the tracepoint is hit.
9643 This command accepts a comma-separated list of any valid expressions.
9644 In addition to global, static, or local variables, the following
9645 special arguments are supported:
9649 collect all registers
9652 collect all function arguments
9655 collect all local variables.
9658 You can give several consecutive @code{collect} commands, each one
9659 with a single argument, or one @code{collect} command with several
9660 arguments separated by commas: the effect is the same.
9662 The command @code{info scope} (@pxref{Symbols, info scope}) is
9663 particularly useful for figuring out what data to collect.
9665 @kindex teval @r{(tracepoints)}
9666 @item teval @var{expr1}, @var{expr2}, @dots{}
9667 Evaluate the given expressions when the tracepoint is hit. This
9668 command accepts a comma-separated list of expressions. The results
9669 are discarded, so this is mainly useful for assigning values to trace
9670 state variables (@pxref{Trace State Variables}) without adding those
9671 values to the trace buffer, as would be the case if the @code{collect}
9674 @kindex while-stepping @r{(tracepoints)}
9675 @item while-stepping @var{n}
9676 Perform @var{n} single-step instruction traces after the tracepoint,
9677 collecting new data after each step. The @code{while-stepping}
9678 command is followed by the list of what to collect while stepping
9679 (followed by its own @code{end} command):
9683 > collect $regs, myglobal
9689 Note that @code{$pc} is not automatically collected by
9690 @code{while-stepping}; you need to explicitly collect that register if
9691 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
9694 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
9695 @kindex set default-collect
9696 @cindex default collection action
9697 This variable is a list of expressions to collect at each tracepoint
9698 hit. It is effectively an additional @code{collect} action prepended
9699 to every tracepoint action list. The expressions are parsed
9700 individually for each tracepoint, so for instance a variable named
9701 @code{xyz} may be interpreted as a global for one tracepoint, and a
9702 local for another, as appropriate to the tracepoint's location.
9704 @item show default-collect
9705 @kindex show default-collect
9706 Show the list of expressions that are collected by default at each
9711 @node Listing Tracepoints
9712 @subsection Listing Tracepoints
9715 @kindex info tracepoints
9717 @cindex information about tracepoints
9718 @item info tracepoints @r{[}@var{num}@r{]}
9719 Display information about the tracepoint @var{num}. If you don't
9720 specify a tracepoint number, displays information about all the
9721 tracepoints defined so far. The format is similar to that used for
9722 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9723 command, simply restricting itself to tracepoints.
9725 A tracepoint's listing may include additional information specific to
9730 its passcount as given by the @code{passcount @var{n}} command
9732 its step count as given by the @code{while-stepping @var{n}} command
9734 its action list as given by the @code{actions} command. The actions
9735 are prefixed with an @samp{A} so as to distinguish them from commands.
9739 (@value{GDBP}) @b{info trace}
9740 Num Type Disp Enb Address What
9741 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9745 A collect globfoo, $regs
9753 This command can be abbreviated @code{info tp}.
9756 @node Starting and Stopping Trace Experiments
9757 @subsection Starting and Stopping Trace Experiments
9761 @cindex start a new trace experiment
9762 @cindex collected data discarded
9764 This command takes no arguments. It starts the trace experiment, and
9765 begins collecting data. This has the side effect of discarding all
9766 the data collected in the trace buffer during the previous trace
9770 @cindex stop a running trace experiment
9772 This command takes no arguments. It ends the trace experiment, and
9773 stops collecting data.
9775 @strong{Note}: a trace experiment and data collection may stop
9776 automatically if any tracepoint's passcount is reached
9777 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9780 @cindex status of trace data collection
9781 @cindex trace experiment, status of
9783 This command displays the status of the current trace data
9787 Here is an example of the commands we described so far:
9790 (@value{GDBP}) @b{trace gdb_c_test}
9791 (@value{GDBP}) @b{actions}
9792 Enter actions for tracepoint #1, one per line.
9793 > collect $regs,$locals,$args
9798 (@value{GDBP}) @b{tstart}
9799 [time passes @dots{}]
9800 (@value{GDBP}) @b{tstop}
9803 @cindex disconnected tracing
9804 You can choose to continue running the trace experiment even if
9805 @value{GDBN} disconnects from the target, voluntarily or
9806 involuntarily. For commands such as @code{detach}, the debugger will
9807 ask what you want to do with the trace. But for unexpected
9808 terminations (@value{GDBN} crash, network outage), it would be
9809 unfortunate to lose hard-won trace data, so the variable
9810 @code{disconnected-tracing} lets you decide whether the trace should
9811 continue running without @value{GDBN}.
9814 @item set disconnected-tracing on
9815 @itemx set disconnected-tracing off
9816 @kindex set disconnected-tracing
9817 Choose whether a tracing run should continue to run if @value{GDBN}
9818 has disconnected from the target. Note that @code{detach} or
9819 @code{quit} will ask you directly what to do about a running trace no
9820 matter what this variable's setting, so the variable is mainly useful
9821 for handling unexpected situations, such as loss of the network.
9823 @item show disconnected-tracing
9824 @kindex show disconnected-tracing
9825 Show the current choice for disconnected tracing.
9829 When you reconnect to the target, the trace experiment may or may not
9830 still be running; it might have filled the trace buffer in the
9831 meantime, or stopped for one of the other reasons. If it is running,
9832 it will continue after reconnection.
9834 Upon reconnection, the target will upload information about the
9835 tracepoints in effect. @value{GDBN} will then compare that
9836 information to the set of tracepoints currently defined, and attempt
9837 to match them up, allowing for the possibility that the numbers may
9838 have changed due to creation and deletion in the meantime. If one of
9839 the target's tracepoints does not match any in @value{GDBN}, the
9840 debugger will create a new tracepoint, so that you have a number with
9841 which to specify that tracepoint. This matching-up process is
9842 necessarily heuristic, and it may result in useless tracepoints being
9843 created; you may simply delete them if they are of no use.
9845 @cindex circular trace buffer
9846 If your target agent supports a @dfn{circular trace buffer}, then you
9847 can run a trace experiment indefinitely without filling the trace
9848 buffer; when space runs out, the agent deletes already-collected trace
9849 frames, oldest first, until there is enough room to continue
9850 collecting. This is especially useful if your tracepoints are being
9851 hit too often, and your trace gets terminated prematurely because the
9852 buffer is full. To ask for a circular trace buffer, simply set
9853 @samp{circular_trace_buffer} to on. You can set this at any time,
9854 including during tracing; if the agent can do it, it will change
9855 buffer handling on the fly, otherwise it will not take effect until
9859 @item set circular-trace-buffer on
9860 @itemx set circular-trace-buffer off
9861 @kindex set circular-trace-buffer
9862 Choose whether a tracing run should use a linear or circular buffer
9863 for trace data. A linear buffer will not lose any trace data, but may
9864 fill up prematurely, while a circular buffer will discard old trace
9865 data, but it will have always room for the latest tracepoint hits.
9867 @item show circular-trace-buffer
9868 @kindex show circular-trace-buffer
9869 Show the current choice for the trace buffer. Note that this may not
9870 match the agent's current buffer handling, nor is it guaranteed to
9871 match the setting that might have been in effect during a past run,
9872 for instance if you are looking at frames from a trace file.
9876 @node Tracepoint Restrictions
9877 @subsection Tracepoint Restrictions
9879 @cindex tracepoint restrictions
9880 There are a number of restrictions on the use of tracepoints. As
9881 described above, tracepoint data gathering occurs on the target
9882 without interaction from @value{GDBN}. Thus the full capabilities of
9883 the debugger are not available during data gathering, and then at data
9884 examination time, you will be limited by only having what was
9885 collected. The following items describe some common problems, but it
9886 is not exhaustive, and you may run into additional difficulties not
9892 Tracepoint expressions are intended to gather objects (lvalues). Thus
9893 the full flexibility of GDB's expression evaluator is not available.
9894 You cannot call functions, cast objects to aggregate types, access
9895 convenience variables or modify values (except by assignment to trace
9896 state variables). Some language features may implicitly call
9897 functions (for instance Objective-C fields with accessors), and therefore
9898 cannot be collected either.
9901 Collection of local variables, either individually or in bulk with
9902 @code{$locals} or @code{$args}, during @code{while-stepping} may
9903 behave erratically. The stepping action may enter a new scope (for
9904 instance by stepping into a function), or the location of the variable
9905 may change (for instance it is loaded into a register). The
9906 tracepoint data recorded uses the location information for the
9907 variables that is correct for the tracepoint location. When the
9908 tracepoint is created, it is not possible, in general, to determine
9909 where the steps of a @code{while-stepping} sequence will advance the
9910 program---particularly if a conditional branch is stepped.
9913 Collection of an incompletely-initialized or partially-destroyed object
9914 may result in something that @value{GDBN} cannot display, or displays
9915 in a misleading way.
9918 When @value{GDBN} displays a pointer to character it automatically
9919 dereferences the pointer to also display characters of the string
9920 being pointed to. However, collecting the pointer during tracing does
9921 not automatically collect the string. You need to explicitly
9922 dereference the pointer and provide size information if you want to
9923 collect not only the pointer, but the memory pointed to. For example,
9924 @code{*ptr@@50} can be used to collect the 50 element array pointed to
9928 It is not possible to collect a complete stack backtrace at a
9929 tracepoint. Instead, you may collect the registers and a few hundred
9930 bytes from the stack pointer with something like @code{*$esp@@300}
9931 (adjust to use the name of the actual stack pointer register on your
9932 target architecture, and the amount of stack you wish to capture).
9933 Then the @code{backtrace} command will show a partial backtrace when
9934 using a trace frame. The number of stack frames that can be examined
9935 depends on the sizes of the frames in the collected stack. Note that
9936 if you ask for a block so large that it goes past the bottom of the
9937 stack, the target agent may report an error trying to read from an
9942 @node Analyze Collected Data
9943 @section Using the Collected Data
9945 After the tracepoint experiment ends, you use @value{GDBN} commands
9946 for examining the trace data. The basic idea is that each tracepoint
9947 collects a trace @dfn{snapshot} every time it is hit and another
9948 snapshot every time it single-steps. All these snapshots are
9949 consecutively numbered from zero and go into a buffer, and you can
9950 examine them later. The way you examine them is to @dfn{focus} on a
9951 specific trace snapshot. When the remote stub is focused on a trace
9952 snapshot, it will respond to all @value{GDBN} requests for memory and
9953 registers by reading from the buffer which belongs to that snapshot,
9954 rather than from @emph{real} memory or registers of the program being
9955 debugged. This means that @strong{all} @value{GDBN} commands
9956 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
9957 behave as if we were currently debugging the program state as it was
9958 when the tracepoint occurred. Any requests for data that are not in
9959 the buffer will fail.
9962 * tfind:: How to select a trace snapshot
9963 * tdump:: How to display all data for a snapshot
9964 * save-tracepoints:: How to save tracepoints for a future run
9968 @subsection @code{tfind @var{n}}
9971 @cindex select trace snapshot
9972 @cindex find trace snapshot
9973 The basic command for selecting a trace snapshot from the buffer is
9974 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
9975 counting from zero. If no argument @var{n} is given, the next
9976 snapshot is selected.
9978 Here are the various forms of using the @code{tfind} command.
9982 Find the first snapshot in the buffer. This is a synonym for
9983 @code{tfind 0} (since 0 is the number of the first snapshot).
9986 Stop debugging trace snapshots, resume @emph{live} debugging.
9989 Same as @samp{tfind none}.
9992 No argument means find the next trace snapshot.
9995 Find the previous trace snapshot before the current one. This permits
9996 retracing earlier steps.
9998 @item tfind tracepoint @var{num}
9999 Find the next snapshot associated with tracepoint @var{num}. Search
10000 proceeds forward from the last examined trace snapshot. If no
10001 argument @var{num} is given, it means find the next snapshot collected
10002 for the same tracepoint as the current snapshot.
10004 @item tfind pc @var{addr}
10005 Find the next snapshot associated with the value @var{addr} of the
10006 program counter. Search proceeds forward from the last examined trace
10007 snapshot. If no argument @var{addr} is given, it means find the next
10008 snapshot with the same value of PC as the current snapshot.
10010 @item tfind outside @var{addr1}, @var{addr2}
10011 Find the next snapshot whose PC is outside the given range of
10012 addresses (exclusive).
10014 @item tfind range @var{addr1}, @var{addr2}
10015 Find the next snapshot whose PC is between @var{addr1} and
10016 @var{addr2} (inclusive).
10018 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10019 Find the next snapshot associated with the source line @var{n}. If
10020 the optional argument @var{file} is given, refer to line @var{n} in
10021 that source file. Search proceeds forward from the last examined
10022 trace snapshot. If no argument @var{n} is given, it means find the
10023 next line other than the one currently being examined; thus saying
10024 @code{tfind line} repeatedly can appear to have the same effect as
10025 stepping from line to line in a @emph{live} debugging session.
10028 The default arguments for the @code{tfind} commands are specifically
10029 designed to make it easy to scan through the trace buffer. For
10030 instance, @code{tfind} with no argument selects the next trace
10031 snapshot, and @code{tfind -} with no argument selects the previous
10032 trace snapshot. So, by giving one @code{tfind} command, and then
10033 simply hitting @key{RET} repeatedly you can examine all the trace
10034 snapshots in order. Or, by saying @code{tfind -} and then hitting
10035 @key{RET} repeatedly you can examine the snapshots in reverse order.
10036 The @code{tfind line} command with no argument selects the snapshot
10037 for the next source line executed. The @code{tfind pc} command with
10038 no argument selects the next snapshot with the same program counter
10039 (PC) as the current frame. The @code{tfind tracepoint} command with
10040 no argument selects the next trace snapshot collected by the same
10041 tracepoint as the current one.
10043 In addition to letting you scan through the trace buffer manually,
10044 these commands make it easy to construct @value{GDBN} scripts that
10045 scan through the trace buffer and print out whatever collected data
10046 you are interested in. Thus, if we want to examine the PC, FP, and SP
10047 registers from each trace frame in the buffer, we can say this:
10050 (@value{GDBP}) @b{tfind start}
10051 (@value{GDBP}) @b{while ($trace_frame != -1)}
10052 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10053 $trace_frame, $pc, $sp, $fp
10057 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10058 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10059 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10060 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10061 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10062 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10063 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10064 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10065 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10066 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10067 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10070 Or, if we want to examine the variable @code{X} at each source line in
10074 (@value{GDBP}) @b{tfind start}
10075 (@value{GDBP}) @b{while ($trace_frame != -1)}
10076 > printf "Frame %d, X == %d\n", $trace_frame, X
10086 @subsection @code{tdump}
10088 @cindex dump all data collected at tracepoint
10089 @cindex tracepoint data, display
10091 This command takes no arguments. It prints all the data collected at
10092 the current trace snapshot.
10095 (@value{GDBP}) @b{trace 444}
10096 (@value{GDBP}) @b{actions}
10097 Enter actions for tracepoint #2, one per line:
10098 > collect $regs, $locals, $args, gdb_long_test
10101 (@value{GDBP}) @b{tstart}
10103 (@value{GDBP}) @b{tfind line 444}
10104 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10106 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10108 (@value{GDBP}) @b{tdump}
10109 Data collected at tracepoint 2, trace frame 1:
10110 d0 0xc4aa0085 -995491707
10114 d4 0x71aea3d 119204413
10117 d7 0x380035 3670069
10118 a0 0x19e24a 1696330
10119 a1 0x3000668 50333288
10121 a3 0x322000 3284992
10122 a4 0x3000698 50333336
10123 a5 0x1ad3cc 1758156
10124 fp 0x30bf3c 0x30bf3c
10125 sp 0x30bf34 0x30bf34
10127 pc 0x20b2c8 0x20b2c8
10131 p = 0x20e5b4 "gdb-test"
10138 gdb_long_test = 17 '\021'
10143 @node save-tracepoints
10144 @subsection @code{save-tracepoints @var{filename}}
10145 @kindex save-tracepoints
10146 @cindex save tracepoints for future sessions
10148 This command saves all current tracepoint definitions together with
10149 their actions and passcounts, into a file @file{@var{filename}}
10150 suitable for use in a later debugging session. To read the saved
10151 tracepoint definitions, use the @code{source} command (@pxref{Command
10154 @node Tracepoint Variables
10155 @section Convenience Variables for Tracepoints
10156 @cindex tracepoint variables
10157 @cindex convenience variables for tracepoints
10160 @vindex $trace_frame
10161 @item (int) $trace_frame
10162 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10163 snapshot is selected.
10165 @vindex $tracepoint
10166 @item (int) $tracepoint
10167 The tracepoint for the current trace snapshot.
10169 @vindex $trace_line
10170 @item (int) $trace_line
10171 The line number for the current trace snapshot.
10173 @vindex $trace_file
10174 @item (char []) $trace_file
10175 The source file for the current trace snapshot.
10177 @vindex $trace_func
10178 @item (char []) $trace_func
10179 The name of the function containing @code{$tracepoint}.
10182 Note: @code{$trace_file} is not suitable for use in @code{printf},
10183 use @code{output} instead.
10185 Here's a simple example of using these convenience variables for
10186 stepping through all the trace snapshots and printing some of their
10187 data. Note that these are not the same as trace state variables,
10188 which are managed by the target.
10191 (@value{GDBP}) @b{tfind start}
10193 (@value{GDBP}) @b{while $trace_frame != -1}
10194 > output $trace_file
10195 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10201 @section Using Trace Files
10202 @cindex trace files
10204 In some situations, the target running a trace experiment may no
10205 longer be available; perhaps it crashed, or the hardware was needed
10206 for a different activity. To handle these cases, you can arrange to
10207 dump the trace data into a file, and later use that file as a source
10208 of trace data, via the @code{target tfile} command.
10213 @item tsave [ -r ] @var{filename}
10214 Save the trace data to @var{filename}. By default, this command
10215 assumes that @var{filename} refers to the host filesystem, so if
10216 necessary @value{GDBN} will copy raw trace data up from the target and
10217 then save it. If the target supports it, you can also supply the
10218 optional argument @code{-r} (``remote'') to direct the target to save
10219 the data directly into @var{filename} in its own filesystem, which may be
10220 more efficient if the trace buffer is very large. (Note, however, that
10221 @code{target tfile} can only read from files accessible to the host.)
10223 @kindex target tfile
10225 @item target tfile @var{filename}
10226 Use the file named @var{filename} as a source of trace data. Commands
10227 that examine data work as they do with a live target, but it is not
10228 possible to run any new trace experiments. @code{tstatus} will report
10229 the state of the trace run at the moment the data was saved, as well
10230 as the current trace frame you are examining. @var{filename} must be
10231 on a filesystem accessible to the host.
10236 @chapter Debugging Programs That Use Overlays
10239 If your program is too large to fit completely in your target system's
10240 memory, you can sometimes use @dfn{overlays} to work around this
10241 problem. @value{GDBN} provides some support for debugging programs that
10245 * How Overlays Work:: A general explanation of overlays.
10246 * Overlay Commands:: Managing overlays in @value{GDBN}.
10247 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10248 mapped by asking the inferior.
10249 * Overlay Sample Program:: A sample program using overlays.
10252 @node How Overlays Work
10253 @section How Overlays Work
10254 @cindex mapped overlays
10255 @cindex unmapped overlays
10256 @cindex load address, overlay's
10257 @cindex mapped address
10258 @cindex overlay area
10260 Suppose you have a computer whose instruction address space is only 64
10261 kilobytes long, but which has much more memory which can be accessed by
10262 other means: special instructions, segment registers, or memory
10263 management hardware, for example. Suppose further that you want to
10264 adapt a program which is larger than 64 kilobytes to run on this system.
10266 One solution is to identify modules of your program which are relatively
10267 independent, and need not call each other directly; call these modules
10268 @dfn{overlays}. Separate the overlays from the main program, and place
10269 their machine code in the larger memory. Place your main program in
10270 instruction memory, but leave at least enough space there to hold the
10271 largest overlay as well.
10273 Now, to call a function located in an overlay, you must first copy that
10274 overlay's machine code from the large memory into the space set aside
10275 for it in the instruction memory, and then jump to its entry point
10278 @c NB: In the below the mapped area's size is greater or equal to the
10279 @c size of all overlays. This is intentional to remind the developer
10280 @c that overlays don't necessarily need to be the same size.
10284 Data Instruction Larger
10285 Address Space Address Space Address Space
10286 +-----------+ +-----------+ +-----------+
10288 +-----------+ +-----------+ +-----------+<-- overlay 1
10289 | program | | main | .----| overlay 1 | load address
10290 | variables | | program | | +-----------+
10291 | and heap | | | | | |
10292 +-----------+ | | | +-----------+<-- overlay 2
10293 | | +-----------+ | | | load address
10294 +-----------+ | | | .-| overlay 2 |
10296 mapped --->+-----------+ | | +-----------+
10297 address | | | | | |
10298 | overlay | <-' | | |
10299 | area | <---' +-----------+<-- overlay 3
10300 | | <---. | | load address
10301 +-----------+ `--| overlay 3 |
10308 @anchor{A code overlay}A code overlay
10312 The diagram (@pxref{A code overlay}) shows a system with separate data
10313 and instruction address spaces. To map an overlay, the program copies
10314 its code from the larger address space to the instruction address space.
10315 Since the overlays shown here all use the same mapped address, only one
10316 may be mapped at a time. For a system with a single address space for
10317 data and instructions, the diagram would be similar, except that the
10318 program variables and heap would share an address space with the main
10319 program and the overlay area.
10321 An overlay loaded into instruction memory and ready for use is called a
10322 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10323 instruction memory. An overlay not present (or only partially present)
10324 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10325 is its address in the larger memory. The mapped address is also called
10326 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10327 called the @dfn{load memory address}, or @dfn{LMA}.
10329 Unfortunately, overlays are not a completely transparent way to adapt a
10330 program to limited instruction memory. They introduce a new set of
10331 global constraints you must keep in mind as you design your program:
10336 Before calling or returning to a function in an overlay, your program
10337 must make sure that overlay is actually mapped. Otherwise, the call or
10338 return will transfer control to the right address, but in the wrong
10339 overlay, and your program will probably crash.
10342 If the process of mapping an overlay is expensive on your system, you
10343 will need to choose your overlays carefully to minimize their effect on
10344 your program's performance.
10347 The executable file you load onto your system must contain each
10348 overlay's instructions, appearing at the overlay's load address, not its
10349 mapped address. However, each overlay's instructions must be relocated
10350 and its symbols defined as if the overlay were at its mapped address.
10351 You can use GNU linker scripts to specify different load and relocation
10352 addresses for pieces of your program; see @ref{Overlay Description,,,
10353 ld.info, Using ld: the GNU linker}.
10356 The procedure for loading executable files onto your system must be able
10357 to load their contents into the larger address space as well as the
10358 instruction and data spaces.
10362 The overlay system described above is rather simple, and could be
10363 improved in many ways:
10368 If your system has suitable bank switch registers or memory management
10369 hardware, you could use those facilities to make an overlay's load area
10370 contents simply appear at their mapped address in instruction space.
10371 This would probably be faster than copying the overlay to its mapped
10372 area in the usual way.
10375 If your overlays are small enough, you could set aside more than one
10376 overlay area, and have more than one overlay mapped at a time.
10379 You can use overlays to manage data, as well as instructions. In
10380 general, data overlays are even less transparent to your design than
10381 code overlays: whereas code overlays only require care when you call or
10382 return to functions, data overlays require care every time you access
10383 the data. Also, if you change the contents of a data overlay, you
10384 must copy its contents back out to its load address before you can copy a
10385 different data overlay into the same mapped area.
10390 @node Overlay Commands
10391 @section Overlay Commands
10393 To use @value{GDBN}'s overlay support, each overlay in your program must
10394 correspond to a separate section of the executable file. The section's
10395 virtual memory address and load memory address must be the overlay's
10396 mapped and load addresses. Identifying overlays with sections allows
10397 @value{GDBN} to determine the appropriate address of a function or
10398 variable, depending on whether the overlay is mapped or not.
10400 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10401 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10406 Disable @value{GDBN}'s overlay support. When overlay support is
10407 disabled, @value{GDBN} assumes that all functions and variables are
10408 always present at their mapped addresses. By default, @value{GDBN}'s
10409 overlay support is disabled.
10411 @item overlay manual
10412 @cindex manual overlay debugging
10413 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10414 relies on you to tell it which overlays are mapped, and which are not,
10415 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10416 commands described below.
10418 @item overlay map-overlay @var{overlay}
10419 @itemx overlay map @var{overlay}
10420 @cindex map an overlay
10421 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10422 be the name of the object file section containing the overlay. When an
10423 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10424 functions and variables at their mapped addresses. @value{GDBN} assumes
10425 that any other overlays whose mapped ranges overlap that of
10426 @var{overlay} are now unmapped.
10428 @item overlay unmap-overlay @var{overlay}
10429 @itemx overlay unmap @var{overlay}
10430 @cindex unmap an overlay
10431 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10432 must be the name of the object file section containing the overlay.
10433 When an overlay is unmapped, @value{GDBN} assumes it can find the
10434 overlay's functions and variables at their load addresses.
10437 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10438 consults a data structure the overlay manager maintains in the inferior
10439 to see which overlays are mapped. For details, see @ref{Automatic
10440 Overlay Debugging}.
10442 @item overlay load-target
10443 @itemx overlay load
10444 @cindex reloading the overlay table
10445 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10446 re-reads the table @value{GDBN} automatically each time the inferior
10447 stops, so this command should only be necessary if you have changed the
10448 overlay mapping yourself using @value{GDBN}. This command is only
10449 useful when using automatic overlay debugging.
10451 @item overlay list-overlays
10452 @itemx overlay list
10453 @cindex listing mapped overlays
10454 Display a list of the overlays currently mapped, along with their mapped
10455 addresses, load addresses, and sizes.
10459 Normally, when @value{GDBN} prints a code address, it includes the name
10460 of the function the address falls in:
10463 (@value{GDBP}) print main
10464 $3 = @{int ()@} 0x11a0 <main>
10467 When overlay debugging is enabled, @value{GDBN} recognizes code in
10468 unmapped overlays, and prints the names of unmapped functions with
10469 asterisks around them. For example, if @code{foo} is a function in an
10470 unmapped overlay, @value{GDBN} prints it this way:
10473 (@value{GDBP}) overlay list
10474 No sections are mapped.
10475 (@value{GDBP}) print foo
10476 $5 = @{int (int)@} 0x100000 <*foo*>
10479 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10483 (@value{GDBP}) overlay list
10484 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10485 mapped at 0x1016 - 0x104a
10486 (@value{GDBP}) print foo
10487 $6 = @{int (int)@} 0x1016 <foo>
10490 When overlay debugging is enabled, @value{GDBN} can find the correct
10491 address for functions and variables in an overlay, whether or not the
10492 overlay is mapped. This allows most @value{GDBN} commands, like
10493 @code{break} and @code{disassemble}, to work normally, even on unmapped
10494 code. However, @value{GDBN}'s breakpoint support has some limitations:
10498 @cindex breakpoints in overlays
10499 @cindex overlays, setting breakpoints in
10500 You can set breakpoints in functions in unmapped overlays, as long as
10501 @value{GDBN} can write to the overlay at its load address.
10503 @value{GDBN} can not set hardware or simulator-based breakpoints in
10504 unmapped overlays. However, if you set a breakpoint at the end of your
10505 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10506 you are using manual overlay management), @value{GDBN} will re-set its
10507 breakpoints properly.
10511 @node Automatic Overlay Debugging
10512 @section Automatic Overlay Debugging
10513 @cindex automatic overlay debugging
10515 @value{GDBN} can automatically track which overlays are mapped and which
10516 are not, given some simple co-operation from the overlay manager in the
10517 inferior. If you enable automatic overlay debugging with the
10518 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10519 looks in the inferior's memory for certain variables describing the
10520 current state of the overlays.
10522 Here are the variables your overlay manager must define to support
10523 @value{GDBN}'s automatic overlay debugging:
10527 @item @code{_ovly_table}:
10528 This variable must be an array of the following structures:
10533 /* The overlay's mapped address. */
10536 /* The size of the overlay, in bytes. */
10537 unsigned long size;
10539 /* The overlay's load address. */
10542 /* Non-zero if the overlay is currently mapped;
10544 unsigned long mapped;
10548 @item @code{_novlys}:
10549 This variable must be a four-byte signed integer, holding the total
10550 number of elements in @code{_ovly_table}.
10554 To decide whether a particular overlay is mapped or not, @value{GDBN}
10555 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10556 @code{lma} members equal the VMA and LMA of the overlay's section in the
10557 executable file. When @value{GDBN} finds a matching entry, it consults
10558 the entry's @code{mapped} member to determine whether the overlay is
10561 In addition, your overlay manager may define a function called
10562 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10563 will silently set a breakpoint there. If the overlay manager then
10564 calls this function whenever it has changed the overlay table, this
10565 will enable @value{GDBN} to accurately keep track of which overlays
10566 are in program memory, and update any breakpoints that may be set
10567 in overlays. This will allow breakpoints to work even if the
10568 overlays are kept in ROM or other non-writable memory while they
10569 are not being executed.
10571 @node Overlay Sample Program
10572 @section Overlay Sample Program
10573 @cindex overlay example program
10575 When linking a program which uses overlays, you must place the overlays
10576 at their load addresses, while relocating them to run at their mapped
10577 addresses. To do this, you must write a linker script (@pxref{Overlay
10578 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10579 since linker scripts are specific to a particular host system, target
10580 architecture, and target memory layout, this manual cannot provide
10581 portable sample code demonstrating @value{GDBN}'s overlay support.
10583 However, the @value{GDBN} source distribution does contain an overlaid
10584 program, with linker scripts for a few systems, as part of its test
10585 suite. The program consists of the following files from
10586 @file{gdb/testsuite/gdb.base}:
10590 The main program file.
10592 A simple overlay manager, used by @file{overlays.c}.
10597 Overlay modules, loaded and used by @file{overlays.c}.
10600 Linker scripts for linking the test program on the @code{d10v-elf}
10601 and @code{m32r-elf} targets.
10604 You can build the test program using the @code{d10v-elf} GCC
10605 cross-compiler like this:
10608 $ d10v-elf-gcc -g -c overlays.c
10609 $ d10v-elf-gcc -g -c ovlymgr.c
10610 $ d10v-elf-gcc -g -c foo.c
10611 $ d10v-elf-gcc -g -c bar.c
10612 $ d10v-elf-gcc -g -c baz.c
10613 $ d10v-elf-gcc -g -c grbx.c
10614 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10615 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10618 The build process is identical for any other architecture, except that
10619 you must substitute the appropriate compiler and linker script for the
10620 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10624 @chapter Using @value{GDBN} with Different Languages
10627 Although programming languages generally have common aspects, they are
10628 rarely expressed in the same manner. For instance, in ANSI C,
10629 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10630 Modula-2, it is accomplished by @code{p^}. Values can also be
10631 represented (and displayed) differently. Hex numbers in C appear as
10632 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10634 @cindex working language
10635 Language-specific information is built into @value{GDBN} for some languages,
10636 allowing you to express operations like the above in your program's
10637 native language, and allowing @value{GDBN} to output values in a manner
10638 consistent with the syntax of your program's native language. The
10639 language you use to build expressions is called the @dfn{working
10643 * Setting:: Switching between source languages
10644 * Show:: Displaying the language
10645 * Checks:: Type and range checks
10646 * Supported Languages:: Supported languages
10647 * Unsupported Languages:: Unsupported languages
10651 @section Switching Between Source Languages
10653 There are two ways to control the working language---either have @value{GDBN}
10654 set it automatically, or select it manually yourself. You can use the
10655 @code{set language} command for either purpose. On startup, @value{GDBN}
10656 defaults to setting the language automatically. The working language is
10657 used to determine how expressions you type are interpreted, how values
10660 In addition to the working language, every source file that
10661 @value{GDBN} knows about has its own working language. For some object
10662 file formats, the compiler might indicate which language a particular
10663 source file is in. However, most of the time @value{GDBN} infers the
10664 language from the name of the file. The language of a source file
10665 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10666 show each frame appropriately for its own language. There is no way to
10667 set the language of a source file from within @value{GDBN}, but you can
10668 set the language associated with a filename extension. @xref{Show, ,
10669 Displaying the Language}.
10671 This is most commonly a problem when you use a program, such
10672 as @code{cfront} or @code{f2c}, that generates C but is written in
10673 another language. In that case, make the
10674 program use @code{#line} directives in its C output; that way
10675 @value{GDBN} will know the correct language of the source code of the original
10676 program, and will display that source code, not the generated C code.
10679 * Filenames:: Filename extensions and languages.
10680 * Manually:: Setting the working language manually
10681 * Automatically:: Having @value{GDBN} infer the source language
10685 @subsection List of Filename Extensions and Languages
10687 If a source file name ends in one of the following extensions, then
10688 @value{GDBN} infers that its language is the one indicated.
10706 C@t{++} source file
10709 Objective-C source file
10713 Fortran source file
10716 Modula-2 source file
10720 Assembler source file. This actually behaves almost like C, but
10721 @value{GDBN} does not skip over function prologues when stepping.
10724 In addition, you may set the language associated with a filename
10725 extension. @xref{Show, , Displaying the Language}.
10728 @subsection Setting the Working Language
10730 If you allow @value{GDBN} to set the language automatically,
10731 expressions are interpreted the same way in your debugging session and
10734 @kindex set language
10735 If you wish, you may set the language manually. To do this, issue the
10736 command @samp{set language @var{lang}}, where @var{lang} is the name of
10737 a language, such as
10738 @code{c} or @code{modula-2}.
10739 For a list of the supported languages, type @samp{set language}.
10741 Setting the language manually prevents @value{GDBN} from updating the working
10742 language automatically. This can lead to confusion if you try
10743 to debug a program when the working language is not the same as the
10744 source language, when an expression is acceptable to both
10745 languages---but means different things. For instance, if the current
10746 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10754 might not have the effect you intended. In C, this means to add
10755 @code{b} and @code{c} and place the result in @code{a}. The result
10756 printed would be the value of @code{a}. In Modula-2, this means to compare
10757 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10759 @node Automatically
10760 @subsection Having @value{GDBN} Infer the Source Language
10762 To have @value{GDBN} set the working language automatically, use
10763 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10764 then infers the working language. That is, when your program stops in a
10765 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10766 working language to the language recorded for the function in that
10767 frame. If the language for a frame is unknown (that is, if the function
10768 or block corresponding to the frame was defined in a source file that
10769 does not have a recognized extension), the current working language is
10770 not changed, and @value{GDBN} issues a warning.
10772 This may not seem necessary for most programs, which are written
10773 entirely in one source language. However, program modules and libraries
10774 written in one source language can be used by a main program written in
10775 a different source language. Using @samp{set language auto} in this
10776 case frees you from having to set the working language manually.
10779 @section Displaying the Language
10781 The following commands help you find out which language is the
10782 working language, and also what language source files were written in.
10785 @item show language
10786 @kindex show language
10787 Display the current working language. This is the
10788 language you can use with commands such as @code{print} to
10789 build and compute expressions that may involve variables in your program.
10792 @kindex info frame@r{, show the source language}
10793 Display the source language for this frame. This language becomes the
10794 working language if you use an identifier from this frame.
10795 @xref{Frame Info, ,Information about a Frame}, to identify the other
10796 information listed here.
10799 @kindex info source@r{, show the source language}
10800 Display the source language of this source file.
10801 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
10802 information listed here.
10805 In unusual circumstances, you may have source files with extensions
10806 not in the standard list. You can then set the extension associated
10807 with a language explicitly:
10810 @item set extension-language @var{ext} @var{language}
10811 @kindex set extension-language
10812 Tell @value{GDBN} that source files with extension @var{ext} are to be
10813 assumed as written in the source language @var{language}.
10815 @item info extensions
10816 @kindex info extensions
10817 List all the filename extensions and the associated languages.
10821 @section Type and Range Checking
10824 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
10825 checking are included, but they do not yet have any effect. This
10826 section documents the intended facilities.
10828 @c FIXME remove warning when type/range code added
10830 Some languages are designed to guard you against making seemingly common
10831 errors through a series of compile- and run-time checks. These include
10832 checking the type of arguments to functions and operators, and making
10833 sure mathematical overflows are caught at run time. Checks such as
10834 these help to ensure a program's correctness once it has been compiled
10835 by eliminating type mismatches, and providing active checks for range
10836 errors when your program is running.
10838 @value{GDBN} can check for conditions like the above if you wish.
10839 Although @value{GDBN} does not check the statements in your program,
10840 it can check expressions entered directly into @value{GDBN} for
10841 evaluation via the @code{print} command, for example. As with the
10842 working language, @value{GDBN} can also decide whether or not to check
10843 automatically based on your program's source language.
10844 @xref{Supported Languages, ,Supported Languages}, for the default
10845 settings of supported languages.
10848 * Type Checking:: An overview of type checking
10849 * Range Checking:: An overview of range checking
10852 @cindex type checking
10853 @cindex checks, type
10854 @node Type Checking
10855 @subsection An Overview of Type Checking
10857 Some languages, such as Modula-2, are strongly typed, meaning that the
10858 arguments to operators and functions have to be of the correct type,
10859 otherwise an error occurs. These checks prevent type mismatch
10860 errors from ever causing any run-time problems. For example,
10868 The second example fails because the @code{CARDINAL} 1 is not
10869 type-compatible with the @code{REAL} 2.3.
10871 For the expressions you use in @value{GDBN} commands, you can tell the
10872 @value{GDBN} type checker to skip checking;
10873 to treat any mismatches as errors and abandon the expression;
10874 or to only issue warnings when type mismatches occur,
10875 but evaluate the expression anyway. When you choose the last of
10876 these, @value{GDBN} evaluates expressions like the second example above, but
10877 also issues a warning.
10879 Even if you turn type checking off, there may be other reasons
10880 related to type that prevent @value{GDBN} from evaluating an expression.
10881 For instance, @value{GDBN} does not know how to add an @code{int} and
10882 a @code{struct foo}. These particular type errors have nothing to do
10883 with the language in use, and usually arise from expressions, such as
10884 the one described above, which make little sense to evaluate anyway.
10886 Each language defines to what degree it is strict about type. For
10887 instance, both Modula-2 and C require the arguments to arithmetical
10888 operators to be numbers. In C, enumerated types and pointers can be
10889 represented as numbers, so that they are valid arguments to mathematical
10890 operators. @xref{Supported Languages, ,Supported Languages}, for further
10891 details on specific languages.
10893 @value{GDBN} provides some additional commands for controlling the type checker:
10895 @kindex set check type
10896 @kindex show check type
10898 @item set check type auto
10899 Set type checking on or off based on the current working language.
10900 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10903 @item set check type on
10904 @itemx set check type off
10905 Set type checking on or off, overriding the default setting for the
10906 current working language. Issue a warning if the setting does not
10907 match the language default. If any type mismatches occur in
10908 evaluating an expression while type checking is on, @value{GDBN} prints a
10909 message and aborts evaluation of the expression.
10911 @item set check type warn
10912 Cause the type checker to issue warnings, but to always attempt to
10913 evaluate the expression. Evaluating the expression may still
10914 be impossible for other reasons. For example, @value{GDBN} cannot add
10915 numbers and structures.
10918 Show the current setting of the type checker, and whether or not @value{GDBN}
10919 is setting it automatically.
10922 @cindex range checking
10923 @cindex checks, range
10924 @node Range Checking
10925 @subsection An Overview of Range Checking
10927 In some languages (such as Modula-2), it is an error to exceed the
10928 bounds of a type; this is enforced with run-time checks. Such range
10929 checking is meant to ensure program correctness by making sure
10930 computations do not overflow, or indices on an array element access do
10931 not exceed the bounds of the array.
10933 For expressions you use in @value{GDBN} commands, you can tell
10934 @value{GDBN} to treat range errors in one of three ways: ignore them,
10935 always treat them as errors and abandon the expression, or issue
10936 warnings but evaluate the expression anyway.
10938 A range error can result from numerical overflow, from exceeding an
10939 array index bound, or when you type a constant that is not a member
10940 of any type. Some languages, however, do not treat overflows as an
10941 error. In many implementations of C, mathematical overflow causes the
10942 result to ``wrap around'' to lower values---for example, if @var{m} is
10943 the largest integer value, and @var{s} is the smallest, then
10946 @var{m} + 1 @result{} @var{s}
10949 This, too, is specific to individual languages, and in some cases
10950 specific to individual compilers or machines. @xref{Supported Languages, ,
10951 Supported Languages}, for further details on specific languages.
10953 @value{GDBN} provides some additional commands for controlling the range checker:
10955 @kindex set check range
10956 @kindex show check range
10958 @item set check range auto
10959 Set range checking on or off based on the current working language.
10960 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10963 @item set check range on
10964 @itemx set check range off
10965 Set range checking on or off, overriding the default setting for the
10966 current working language. A warning is issued if the setting does not
10967 match the language default. If a range error occurs and range checking is on,
10968 then a message is printed and evaluation of the expression is aborted.
10970 @item set check range warn
10971 Output messages when the @value{GDBN} range checker detects a range error,
10972 but attempt to evaluate the expression anyway. Evaluating the
10973 expression may still be impossible for other reasons, such as accessing
10974 memory that the process does not own (a typical example from many Unix
10978 Show the current setting of the range checker, and whether or not it is
10979 being set automatically by @value{GDBN}.
10982 @node Supported Languages
10983 @section Supported Languages
10985 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
10986 assembly, Modula-2, and Ada.
10987 @c This is false ...
10988 Some @value{GDBN} features may be used in expressions regardless of the
10989 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
10990 and the @samp{@{type@}addr} construct (@pxref{Expressions,
10991 ,Expressions}) can be used with the constructs of any supported
10994 The following sections detail to what degree each source language is
10995 supported by @value{GDBN}. These sections are not meant to be language
10996 tutorials or references, but serve only as a reference guide to what the
10997 @value{GDBN} expression parser accepts, and what input and output
10998 formats should look like for different languages. There are many good
10999 books written on each of these languages; please look to these for a
11000 language reference or tutorial.
11003 * C:: C and C@t{++}
11004 * Objective-C:: Objective-C
11005 * Fortran:: Fortran
11007 * Modula-2:: Modula-2
11012 @subsection C and C@t{++}
11014 @cindex C and C@t{++}
11015 @cindex expressions in C or C@t{++}
11017 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11018 to both languages. Whenever this is the case, we discuss those languages
11022 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11023 @cindex @sc{gnu} C@t{++}
11024 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11025 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11026 effectively, you must compile your C@t{++} programs with a supported
11027 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11028 compiler (@code{aCC}).
11030 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11031 format; if it doesn't work on your system, try the stabs+ debugging
11032 format. You can select those formats explicitly with the @code{g++}
11033 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11034 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11035 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11038 * C Operators:: C and C@t{++} operators
11039 * C Constants:: C and C@t{++} constants
11040 * C Plus Plus Expressions:: C@t{++} expressions
11041 * C Defaults:: Default settings for C and C@t{++}
11042 * C Checks:: C and C@t{++} type and range checks
11043 * Debugging C:: @value{GDBN} and C
11044 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11045 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11049 @subsubsection C and C@t{++} Operators
11051 @cindex C and C@t{++} operators
11053 Operators must be defined on values of specific types. For instance,
11054 @code{+} is defined on numbers, but not on structures. Operators are
11055 often defined on groups of types.
11057 For the purposes of C and C@t{++}, the following definitions hold:
11062 @emph{Integral types} include @code{int} with any of its storage-class
11063 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11066 @emph{Floating-point types} include @code{float}, @code{double}, and
11067 @code{long double} (if supported by the target platform).
11070 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11073 @emph{Scalar types} include all of the above.
11078 The following operators are supported. They are listed here
11079 in order of increasing precedence:
11083 The comma or sequencing operator. Expressions in a comma-separated list
11084 are evaluated from left to right, with the result of the entire
11085 expression being the last expression evaluated.
11088 Assignment. The value of an assignment expression is the value
11089 assigned. Defined on scalar types.
11092 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11093 and translated to @w{@code{@var{a} = @var{a op b}}}.
11094 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11095 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11096 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11099 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11100 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11104 Logical @sc{or}. Defined on integral types.
11107 Logical @sc{and}. Defined on integral types.
11110 Bitwise @sc{or}. Defined on integral types.
11113 Bitwise exclusive-@sc{or}. Defined on integral types.
11116 Bitwise @sc{and}. Defined on integral types.
11119 Equality and inequality. Defined on scalar types. The value of these
11120 expressions is 0 for false and non-zero for true.
11122 @item <@r{, }>@r{, }<=@r{, }>=
11123 Less than, greater than, less than or equal, greater than or equal.
11124 Defined on scalar types. The value of these expressions is 0 for false
11125 and non-zero for true.
11128 left shift, and right shift. Defined on integral types.
11131 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11134 Addition and subtraction. Defined on integral types, floating-point types and
11137 @item *@r{, }/@r{, }%
11138 Multiplication, division, and modulus. Multiplication and division are
11139 defined on integral and floating-point types. Modulus is defined on
11143 Increment and decrement. When appearing before a variable, the
11144 operation is performed before the variable is used in an expression;
11145 when appearing after it, the variable's value is used before the
11146 operation takes place.
11149 Pointer dereferencing. Defined on pointer types. Same precedence as
11153 Address operator. Defined on variables. Same precedence as @code{++}.
11155 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11156 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11157 to examine the address
11158 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11162 Negative. Defined on integral and floating-point types. Same
11163 precedence as @code{++}.
11166 Logical negation. Defined on integral types. Same precedence as
11170 Bitwise complement operator. Defined on integral types. Same precedence as
11175 Structure member, and pointer-to-structure member. For convenience,
11176 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11177 pointer based on the stored type information.
11178 Defined on @code{struct} and @code{union} data.
11181 Dereferences of pointers to members.
11184 Array indexing. @code{@var{a}[@var{i}]} is defined as
11185 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11188 Function parameter list. Same precedence as @code{->}.
11191 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11192 and @code{class} types.
11195 Doubled colons also represent the @value{GDBN} scope operator
11196 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11200 If an operator is redefined in the user code, @value{GDBN} usually
11201 attempts to invoke the redefined version instead of using the operator's
11202 predefined meaning.
11205 @subsubsection C and C@t{++} Constants
11207 @cindex C and C@t{++} constants
11209 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11214 Integer constants are a sequence of digits. Octal constants are
11215 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11216 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11217 @samp{l}, specifying that the constant should be treated as a
11221 Floating point constants are a sequence of digits, followed by a decimal
11222 point, followed by a sequence of digits, and optionally followed by an
11223 exponent. An exponent is of the form:
11224 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11225 sequence of digits. The @samp{+} is optional for positive exponents.
11226 A floating-point constant may also end with a letter @samp{f} or
11227 @samp{F}, specifying that the constant should be treated as being of
11228 the @code{float} (as opposed to the default @code{double}) type; or with
11229 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11233 Enumerated constants consist of enumerated identifiers, or their
11234 integral equivalents.
11237 Character constants are a single character surrounded by single quotes
11238 (@code{'}), or a number---the ordinal value of the corresponding character
11239 (usually its @sc{ascii} value). Within quotes, the single character may
11240 be represented by a letter or by @dfn{escape sequences}, which are of
11241 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11242 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11243 @samp{@var{x}} is a predefined special character---for example,
11244 @samp{\n} for newline.
11247 String constants are a sequence of character constants surrounded by
11248 double quotes (@code{"}). Any valid character constant (as described
11249 above) may appear. Double quotes within the string must be preceded by
11250 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11254 Pointer constants are an integral value. You can also write pointers
11255 to constants using the C operator @samp{&}.
11258 Array constants are comma-separated lists surrounded by braces @samp{@{}
11259 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11260 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11261 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11264 @node C Plus Plus Expressions
11265 @subsubsection C@t{++} Expressions
11267 @cindex expressions in C@t{++}
11268 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11270 @cindex debugging C@t{++} programs
11271 @cindex C@t{++} compilers
11272 @cindex debug formats and C@t{++}
11273 @cindex @value{NGCC} and C@t{++}
11275 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11276 proper compiler and the proper debug format. Currently, @value{GDBN}
11277 works best when debugging C@t{++} code that is compiled with
11278 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11279 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11280 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11281 stabs+ as their default debug format, so you usually don't need to
11282 specify a debug format explicitly. Other compilers and/or debug formats
11283 are likely to work badly or not at all when using @value{GDBN} to debug
11289 @cindex member functions
11291 Member function calls are allowed; you can use expressions like
11294 count = aml->GetOriginal(x, y)
11297 @vindex this@r{, inside C@t{++} member functions}
11298 @cindex namespace in C@t{++}
11300 While a member function is active (in the selected stack frame), your
11301 expressions have the same namespace available as the member function;
11302 that is, @value{GDBN} allows implicit references to the class instance
11303 pointer @code{this} following the same rules as C@t{++}.
11305 @cindex call overloaded functions
11306 @cindex overloaded functions, calling
11307 @cindex type conversions in C@t{++}
11309 You can call overloaded functions; @value{GDBN} resolves the function
11310 call to the right definition, with some restrictions. @value{GDBN} does not
11311 perform overload resolution involving user-defined type conversions,
11312 calls to constructors, or instantiations of templates that do not exist
11313 in the program. It also cannot handle ellipsis argument lists or
11316 It does perform integral conversions and promotions, floating-point
11317 promotions, arithmetic conversions, pointer conversions, conversions of
11318 class objects to base classes, and standard conversions such as those of
11319 functions or arrays to pointers; it requires an exact match on the
11320 number of function arguments.
11322 Overload resolution is always performed, unless you have specified
11323 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11324 ,@value{GDBN} Features for C@t{++}}.
11326 You must specify @code{set overload-resolution off} in order to use an
11327 explicit function signature to call an overloaded function, as in
11329 p 'foo(char,int)'('x', 13)
11332 The @value{GDBN} command-completion facility can simplify this;
11333 see @ref{Completion, ,Command Completion}.
11335 @cindex reference declarations
11337 @value{GDBN} understands variables declared as C@t{++} references; you can use
11338 them in expressions just as you do in C@t{++} source---they are automatically
11341 In the parameter list shown when @value{GDBN} displays a frame, the values of
11342 reference variables are not displayed (unlike other variables); this
11343 avoids clutter, since references are often used for large structures.
11344 The @emph{address} of a reference variable is always shown, unless
11345 you have specified @samp{set print address off}.
11348 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11349 expressions can use it just as expressions in your program do. Since
11350 one scope may be defined in another, you can use @code{::} repeatedly if
11351 necessary, for example in an expression like
11352 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11353 resolving name scope by reference to source files, in both C and C@t{++}
11354 debugging (@pxref{Variables, ,Program Variables}).
11357 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11358 calling virtual functions correctly, printing out virtual bases of
11359 objects, calling functions in a base subobject, casting objects, and
11360 invoking user-defined operators.
11363 @subsubsection C and C@t{++} Defaults
11365 @cindex C and C@t{++} defaults
11367 If you allow @value{GDBN} to set type and range checking automatically, they
11368 both default to @code{off} whenever the working language changes to
11369 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11370 selects the working language.
11372 If you allow @value{GDBN} to set the language automatically, it
11373 recognizes source files whose names end with @file{.c}, @file{.C}, or
11374 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11375 these files, it sets the working language to C or C@t{++}.
11376 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11377 for further details.
11379 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11380 @c unimplemented. If (b) changes, it might make sense to let this node
11381 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11384 @subsubsection C and C@t{++} Type and Range Checks
11386 @cindex C and C@t{++} checks
11388 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11389 is not used. However, if you turn type checking on, @value{GDBN}
11390 considers two variables type equivalent if:
11394 The two variables are structured and have the same structure, union, or
11398 The two variables have the same type name, or types that have been
11399 declared equivalent through @code{typedef}.
11402 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11405 The two @code{struct}, @code{union}, or @code{enum} variables are
11406 declared in the same declaration. (Note: this may not be true for all C
11411 Range checking, if turned on, is done on mathematical operations. Array
11412 indices are not checked, since they are often used to index a pointer
11413 that is not itself an array.
11416 @subsubsection @value{GDBN} and C
11418 The @code{set print union} and @code{show print union} commands apply to
11419 the @code{union} type. When set to @samp{on}, any @code{union} that is
11420 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11421 appears as @samp{@{...@}}.
11423 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11424 with pointers and a memory allocation function. @xref{Expressions,
11427 @node Debugging C Plus Plus
11428 @subsubsection @value{GDBN} Features for C@t{++}
11430 @cindex commands for C@t{++}
11432 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11433 designed specifically for use with C@t{++}. Here is a summary:
11436 @cindex break in overloaded functions
11437 @item @r{breakpoint menus}
11438 When you want a breakpoint in a function whose name is overloaded,
11439 @value{GDBN} has the capability to display a menu of possible breakpoint
11440 locations to help you specify which function definition you want.
11441 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11443 @cindex overloading in C@t{++}
11444 @item rbreak @var{regex}
11445 Setting breakpoints using regular expressions is helpful for setting
11446 breakpoints on overloaded functions that are not members of any special
11448 @xref{Set Breaks, ,Setting Breakpoints}.
11450 @cindex C@t{++} exception handling
11453 Debug C@t{++} exception handling using these commands. @xref{Set
11454 Catchpoints, , Setting Catchpoints}.
11456 @cindex inheritance
11457 @item ptype @var{typename}
11458 Print inheritance relationships as well as other information for type
11460 @xref{Symbols, ,Examining the Symbol Table}.
11462 @cindex C@t{++} symbol display
11463 @item set print demangle
11464 @itemx show print demangle
11465 @itemx set print asm-demangle
11466 @itemx show print asm-demangle
11467 Control whether C@t{++} symbols display in their source form, both when
11468 displaying code as C@t{++} source and when displaying disassemblies.
11469 @xref{Print Settings, ,Print Settings}.
11471 @item set print object
11472 @itemx show print object
11473 Choose whether to print derived (actual) or declared types of objects.
11474 @xref{Print Settings, ,Print Settings}.
11476 @item set print vtbl
11477 @itemx show print vtbl
11478 Control the format for printing virtual function tables.
11479 @xref{Print Settings, ,Print Settings}.
11480 (The @code{vtbl} commands do not work on programs compiled with the HP
11481 ANSI C@t{++} compiler (@code{aCC}).)
11483 @kindex set overload-resolution
11484 @cindex overloaded functions, overload resolution
11485 @item set overload-resolution on
11486 Enable overload resolution for C@t{++} expression evaluation. The default
11487 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11488 and searches for a function whose signature matches the argument types,
11489 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11490 Expressions, ,C@t{++} Expressions}, for details).
11491 If it cannot find a match, it emits a message.
11493 @item set overload-resolution off
11494 Disable overload resolution for C@t{++} expression evaluation. For
11495 overloaded functions that are not class member functions, @value{GDBN}
11496 chooses the first function of the specified name that it finds in the
11497 symbol table, whether or not its arguments are of the correct type. For
11498 overloaded functions that are class member functions, @value{GDBN}
11499 searches for a function whose signature @emph{exactly} matches the
11502 @kindex show overload-resolution
11503 @item show overload-resolution
11504 Show the current setting of overload resolution.
11506 @item @r{Overloaded symbol names}
11507 You can specify a particular definition of an overloaded symbol, using
11508 the same notation that is used to declare such symbols in C@t{++}: type
11509 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11510 also use the @value{GDBN} command-line word completion facilities to list the
11511 available choices, or to finish the type list for you.
11512 @xref{Completion,, Command Completion}, for details on how to do this.
11515 @node Decimal Floating Point
11516 @subsubsection Decimal Floating Point format
11517 @cindex decimal floating point format
11519 @value{GDBN} can examine, set and perform computations with numbers in
11520 decimal floating point format, which in the C language correspond to the
11521 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11522 specified by the extension to support decimal floating-point arithmetic.
11524 There are two encodings in use, depending on the architecture: BID (Binary
11525 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11526 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11529 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11530 to manipulate decimal floating point numbers, it is not possible to convert
11531 (using a cast, for example) integers wider than 32-bit to decimal float.
11533 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11534 point computations, error checking in decimal float operations ignores
11535 underflow, overflow and divide by zero exceptions.
11537 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11538 to inspect @code{_Decimal128} values stored in floating point registers.
11539 See @ref{PowerPC,,PowerPC} for more details.
11542 @subsection Objective-C
11544 @cindex Objective-C
11545 This section provides information about some commands and command
11546 options that are useful for debugging Objective-C code. See also
11547 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11548 few more commands specific to Objective-C support.
11551 * Method Names in Commands::
11552 * The Print Command with Objective-C::
11555 @node Method Names in Commands
11556 @subsubsection Method Names in Commands
11558 The following commands have been extended to accept Objective-C method
11559 names as line specifications:
11561 @kindex clear@r{, and Objective-C}
11562 @kindex break@r{, and Objective-C}
11563 @kindex info line@r{, and Objective-C}
11564 @kindex jump@r{, and Objective-C}
11565 @kindex list@r{, and Objective-C}
11569 @item @code{info line}
11574 A fully qualified Objective-C method name is specified as
11577 -[@var{Class} @var{methodName}]
11580 where the minus sign is used to indicate an instance method and a
11581 plus sign (not shown) is used to indicate a class method. The class
11582 name @var{Class} and method name @var{methodName} are enclosed in
11583 brackets, similar to the way messages are specified in Objective-C
11584 source code. For example, to set a breakpoint at the @code{create}
11585 instance method of class @code{Fruit} in the program currently being
11589 break -[Fruit create]
11592 To list ten program lines around the @code{initialize} class method,
11596 list +[NSText initialize]
11599 In the current version of @value{GDBN}, the plus or minus sign is
11600 required. In future versions of @value{GDBN}, the plus or minus
11601 sign will be optional, but you can use it to narrow the search. It
11602 is also possible to specify just a method name:
11608 You must specify the complete method name, including any colons. If
11609 your program's source files contain more than one @code{create} method,
11610 you'll be presented with a numbered list of classes that implement that
11611 method. Indicate your choice by number, or type @samp{0} to exit if
11614 As another example, to clear a breakpoint established at the
11615 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11618 clear -[NSWindow makeKeyAndOrderFront:]
11621 @node The Print Command with Objective-C
11622 @subsubsection The Print Command With Objective-C
11623 @cindex Objective-C, print objects
11624 @kindex print-object
11625 @kindex po @r{(@code{print-object})}
11627 The print command has also been extended to accept methods. For example:
11630 print -[@var{object} hash]
11633 @cindex print an Objective-C object description
11634 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11636 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11637 and print the result. Also, an additional command has been added,
11638 @code{print-object} or @code{po} for short, which is meant to print
11639 the description of an object. However, this command may only work
11640 with certain Objective-C libraries that have a particular hook
11641 function, @code{_NSPrintForDebugger}, defined.
11644 @subsection Fortran
11645 @cindex Fortran-specific support in @value{GDBN}
11647 @value{GDBN} can be used to debug programs written in Fortran, but it
11648 currently supports only the features of Fortran 77 language.
11650 @cindex trailing underscore, in Fortran symbols
11651 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11652 among them) append an underscore to the names of variables and
11653 functions. When you debug programs compiled by those compilers, you
11654 will need to refer to variables and functions with a trailing
11658 * Fortran Operators:: Fortran operators and expressions
11659 * Fortran Defaults:: Default settings for Fortran
11660 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11663 @node Fortran Operators
11664 @subsubsection Fortran Operators and Expressions
11666 @cindex Fortran operators and expressions
11668 Operators must be defined on values of specific types. For instance,
11669 @code{+} is defined on numbers, but not on characters or other non-
11670 arithmetic types. Operators are often defined on groups of types.
11674 The exponentiation operator. It raises the first operand to the power
11678 The range operator. Normally used in the form of array(low:high) to
11679 represent a section of array.
11682 The access component operator. Normally used to access elements in derived
11683 types. Also suitable for unions. As unions aren't part of regular Fortran,
11684 this can only happen when accessing a register that uses a gdbarch-defined
11688 @node Fortran Defaults
11689 @subsubsection Fortran Defaults
11691 @cindex Fortran Defaults
11693 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11694 default uses case-insensitive matches for Fortran symbols. You can
11695 change that with the @samp{set case-insensitive} command, see
11696 @ref{Symbols}, for the details.
11698 @node Special Fortran Commands
11699 @subsubsection Special Fortran Commands
11701 @cindex Special Fortran commands
11703 @value{GDBN} has some commands to support Fortran-specific features,
11704 such as displaying common blocks.
11707 @cindex @code{COMMON} blocks, Fortran
11708 @kindex info common
11709 @item info common @r{[}@var{common-name}@r{]}
11710 This command prints the values contained in the Fortran @code{COMMON}
11711 block whose name is @var{common-name}. With no argument, the names of
11712 all @code{COMMON} blocks visible at the current program location are
11719 @cindex Pascal support in @value{GDBN}, limitations
11720 Debugging Pascal programs which use sets, subranges, file variables, or
11721 nested functions does not currently work. @value{GDBN} does not support
11722 entering expressions, printing values, or similar features using Pascal
11725 The Pascal-specific command @code{set print pascal_static-members}
11726 controls whether static members of Pascal objects are displayed.
11727 @xref{Print Settings, pascal_static-members}.
11730 @subsection Modula-2
11732 @cindex Modula-2, @value{GDBN} support
11734 The extensions made to @value{GDBN} to support Modula-2 only support
11735 output from the @sc{gnu} Modula-2 compiler (which is currently being
11736 developed). Other Modula-2 compilers are not currently supported, and
11737 attempting to debug executables produced by them is most likely
11738 to give an error as @value{GDBN} reads in the executable's symbol
11741 @cindex expressions in Modula-2
11743 * M2 Operators:: Built-in operators
11744 * Built-In Func/Proc:: Built-in functions and procedures
11745 * M2 Constants:: Modula-2 constants
11746 * M2 Types:: Modula-2 types
11747 * M2 Defaults:: Default settings for Modula-2
11748 * Deviations:: Deviations from standard Modula-2
11749 * M2 Checks:: Modula-2 type and range checks
11750 * M2 Scope:: The scope operators @code{::} and @code{.}
11751 * GDB/M2:: @value{GDBN} and Modula-2
11755 @subsubsection Operators
11756 @cindex Modula-2 operators
11758 Operators must be defined on values of specific types. For instance,
11759 @code{+} is defined on numbers, but not on structures. Operators are
11760 often defined on groups of types. For the purposes of Modula-2, the
11761 following definitions hold:
11766 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
11770 @emph{Character types} consist of @code{CHAR} and its subranges.
11773 @emph{Floating-point types} consist of @code{REAL}.
11776 @emph{Pointer types} consist of anything declared as @code{POINTER TO
11780 @emph{Scalar types} consist of all of the above.
11783 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
11786 @emph{Boolean types} consist of @code{BOOLEAN}.
11790 The following operators are supported, and appear in order of
11791 increasing precedence:
11795 Function argument or array index separator.
11798 Assignment. The value of @var{var} @code{:=} @var{value} is
11802 Less than, greater than on integral, floating-point, or enumerated
11806 Less than or equal to, greater than or equal to
11807 on integral, floating-point and enumerated types, or set inclusion on
11808 set types. Same precedence as @code{<}.
11810 @item =@r{, }<>@r{, }#
11811 Equality and two ways of expressing inequality, valid on scalar types.
11812 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
11813 available for inequality, since @code{#} conflicts with the script
11817 Set membership. Defined on set types and the types of their members.
11818 Same precedence as @code{<}.
11821 Boolean disjunction. Defined on boolean types.
11824 Boolean conjunction. Defined on boolean types.
11827 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11830 Addition and subtraction on integral and floating-point types, or union
11831 and difference on set types.
11834 Multiplication on integral and floating-point types, or set intersection
11838 Division on floating-point types, or symmetric set difference on set
11839 types. Same precedence as @code{*}.
11842 Integer division and remainder. Defined on integral types. Same
11843 precedence as @code{*}.
11846 Negative. Defined on @code{INTEGER} and @code{REAL} data.
11849 Pointer dereferencing. Defined on pointer types.
11852 Boolean negation. Defined on boolean types. Same precedence as
11856 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
11857 precedence as @code{^}.
11860 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
11863 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
11867 @value{GDBN} and Modula-2 scope operators.
11871 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
11872 treats the use of the operator @code{IN}, or the use of operators
11873 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
11874 @code{<=}, and @code{>=} on sets as an error.
11878 @node Built-In Func/Proc
11879 @subsubsection Built-in Functions and Procedures
11880 @cindex Modula-2 built-ins
11882 Modula-2 also makes available several built-in procedures and functions.
11883 In describing these, the following metavariables are used:
11888 represents an @code{ARRAY} variable.
11891 represents a @code{CHAR} constant or variable.
11894 represents a variable or constant of integral type.
11897 represents an identifier that belongs to a set. Generally used in the
11898 same function with the metavariable @var{s}. The type of @var{s} should
11899 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
11902 represents a variable or constant of integral or floating-point type.
11905 represents a variable or constant of floating-point type.
11911 represents a variable.
11914 represents a variable or constant of one of many types. See the
11915 explanation of the function for details.
11918 All Modula-2 built-in procedures also return a result, described below.
11922 Returns the absolute value of @var{n}.
11925 If @var{c} is a lower case letter, it returns its upper case
11926 equivalent, otherwise it returns its argument.
11929 Returns the character whose ordinal value is @var{i}.
11932 Decrements the value in the variable @var{v} by one. Returns the new value.
11934 @item DEC(@var{v},@var{i})
11935 Decrements the value in the variable @var{v} by @var{i}. Returns the
11938 @item EXCL(@var{m},@var{s})
11939 Removes the element @var{m} from the set @var{s}. Returns the new
11942 @item FLOAT(@var{i})
11943 Returns the floating point equivalent of the integer @var{i}.
11945 @item HIGH(@var{a})
11946 Returns the index of the last member of @var{a}.
11949 Increments the value in the variable @var{v} by one. Returns the new value.
11951 @item INC(@var{v},@var{i})
11952 Increments the value in the variable @var{v} by @var{i}. Returns the
11955 @item INCL(@var{m},@var{s})
11956 Adds the element @var{m} to the set @var{s} if it is not already
11957 there. Returns the new set.
11960 Returns the maximum value of the type @var{t}.
11963 Returns the minimum value of the type @var{t}.
11966 Returns boolean TRUE if @var{i} is an odd number.
11969 Returns the ordinal value of its argument. For example, the ordinal
11970 value of a character is its @sc{ascii} value (on machines supporting the
11971 @sc{ascii} character set). @var{x} must be of an ordered type, which include
11972 integral, character and enumerated types.
11974 @item SIZE(@var{x})
11975 Returns the size of its argument. @var{x} can be a variable or a type.
11977 @item TRUNC(@var{r})
11978 Returns the integral part of @var{r}.
11980 @item TSIZE(@var{x})
11981 Returns the size of its argument. @var{x} can be a variable or a type.
11983 @item VAL(@var{t},@var{i})
11984 Returns the member of the type @var{t} whose ordinal value is @var{i}.
11988 @emph{Warning:} Sets and their operations are not yet supported, so
11989 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
11993 @cindex Modula-2 constants
11995 @subsubsection Constants
11997 @value{GDBN} allows you to express the constants of Modula-2 in the following
12003 Integer constants are simply a sequence of digits. When used in an
12004 expression, a constant is interpreted to be type-compatible with the
12005 rest of the expression. Hexadecimal integers are specified by a
12006 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12009 Floating point constants appear as a sequence of digits, followed by a
12010 decimal point and another sequence of digits. An optional exponent can
12011 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12012 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12013 digits of the floating point constant must be valid decimal (base 10)
12017 Character constants consist of a single character enclosed by a pair of
12018 like quotes, either single (@code{'}) or double (@code{"}). They may
12019 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12020 followed by a @samp{C}.
12023 String constants consist of a sequence of characters enclosed by a
12024 pair of like quotes, either single (@code{'}) or double (@code{"}).
12025 Escape sequences in the style of C are also allowed. @xref{C
12026 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12030 Enumerated constants consist of an enumerated identifier.
12033 Boolean constants consist of the identifiers @code{TRUE} and
12037 Pointer constants consist of integral values only.
12040 Set constants are not yet supported.
12044 @subsubsection Modula-2 Types
12045 @cindex Modula-2 types
12047 Currently @value{GDBN} can print the following data types in Modula-2
12048 syntax: array types, record types, set types, pointer types, procedure
12049 types, enumerated types, subrange types and base types. You can also
12050 print the contents of variables declared using these type.
12051 This section gives a number of simple source code examples together with
12052 sample @value{GDBN} sessions.
12054 The first example contains the following section of code:
12063 and you can request @value{GDBN} to interrogate the type and value of
12064 @code{r} and @code{s}.
12067 (@value{GDBP}) print s
12069 (@value{GDBP}) ptype s
12071 (@value{GDBP}) print r
12073 (@value{GDBP}) ptype r
12078 Likewise if your source code declares @code{s} as:
12082 s: SET ['A'..'Z'] ;
12086 then you may query the type of @code{s} by:
12089 (@value{GDBP}) ptype s
12090 type = SET ['A'..'Z']
12094 Note that at present you cannot interactively manipulate set
12095 expressions using the debugger.
12097 The following example shows how you might declare an array in Modula-2
12098 and how you can interact with @value{GDBN} to print its type and contents:
12102 s: ARRAY [-10..10] OF CHAR ;
12106 (@value{GDBP}) ptype s
12107 ARRAY [-10..10] OF CHAR
12110 Note that the array handling is not yet complete and although the type
12111 is printed correctly, expression handling still assumes that all
12112 arrays have a lower bound of zero and not @code{-10} as in the example
12115 Here are some more type related Modula-2 examples:
12119 colour = (blue, red, yellow, green) ;
12120 t = [blue..yellow] ;
12128 The @value{GDBN} interaction shows how you can query the data type
12129 and value of a variable.
12132 (@value{GDBP}) print s
12134 (@value{GDBP}) ptype t
12135 type = [blue..yellow]
12139 In this example a Modula-2 array is declared and its contents
12140 displayed. Observe that the contents are written in the same way as
12141 their @code{C} counterparts.
12145 s: ARRAY [1..5] OF CARDINAL ;
12151 (@value{GDBP}) print s
12152 $1 = @{1, 0, 0, 0, 0@}
12153 (@value{GDBP}) ptype s
12154 type = ARRAY [1..5] OF CARDINAL
12157 The Modula-2 language interface to @value{GDBN} also understands
12158 pointer types as shown in this example:
12162 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12169 and you can request that @value{GDBN} describes the type of @code{s}.
12172 (@value{GDBP}) ptype s
12173 type = POINTER TO ARRAY [1..5] OF CARDINAL
12176 @value{GDBN} handles compound types as we can see in this example.
12177 Here we combine array types, record types, pointer types and subrange
12188 myarray = ARRAY myrange OF CARDINAL ;
12189 myrange = [-2..2] ;
12191 s: POINTER TO ARRAY myrange OF foo ;
12195 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12199 (@value{GDBP}) ptype s
12200 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12203 f3 : ARRAY [-2..2] OF CARDINAL;
12208 @subsubsection Modula-2 Defaults
12209 @cindex Modula-2 defaults
12211 If type and range checking are set automatically by @value{GDBN}, they
12212 both default to @code{on} whenever the working language changes to
12213 Modula-2. This happens regardless of whether you or @value{GDBN}
12214 selected the working language.
12216 If you allow @value{GDBN} to set the language automatically, then entering
12217 code compiled from a file whose name ends with @file{.mod} sets the
12218 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12219 Infer the Source Language}, for further details.
12222 @subsubsection Deviations from Standard Modula-2
12223 @cindex Modula-2, deviations from
12225 A few changes have been made to make Modula-2 programs easier to debug.
12226 This is done primarily via loosening its type strictness:
12230 Unlike in standard Modula-2, pointer constants can be formed by
12231 integers. This allows you to modify pointer variables during
12232 debugging. (In standard Modula-2, the actual address contained in a
12233 pointer variable is hidden from you; it can only be modified
12234 through direct assignment to another pointer variable or expression that
12235 returned a pointer.)
12238 C escape sequences can be used in strings and characters to represent
12239 non-printable characters. @value{GDBN} prints out strings with these
12240 escape sequences embedded. Single non-printable characters are
12241 printed using the @samp{CHR(@var{nnn})} format.
12244 The assignment operator (@code{:=}) returns the value of its right-hand
12248 All built-in procedures both modify @emph{and} return their argument.
12252 @subsubsection Modula-2 Type and Range Checks
12253 @cindex Modula-2 checks
12256 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12259 @c FIXME remove warning when type/range checks added
12261 @value{GDBN} considers two Modula-2 variables type equivalent if:
12265 They are of types that have been declared equivalent via a @code{TYPE
12266 @var{t1} = @var{t2}} statement
12269 They have been declared on the same line. (Note: This is true of the
12270 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12273 As long as type checking is enabled, any attempt to combine variables
12274 whose types are not equivalent is an error.
12276 Range checking is done on all mathematical operations, assignment, array
12277 index bounds, and all built-in functions and procedures.
12280 @subsubsection The Scope Operators @code{::} and @code{.}
12282 @cindex @code{.}, Modula-2 scope operator
12283 @cindex colon, doubled as scope operator
12285 @vindex colon-colon@r{, in Modula-2}
12286 @c Info cannot handle :: but TeX can.
12289 @vindex ::@r{, in Modula-2}
12292 There are a few subtle differences between the Modula-2 scope operator
12293 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12298 @var{module} . @var{id}
12299 @var{scope} :: @var{id}
12303 where @var{scope} is the name of a module or a procedure,
12304 @var{module} the name of a module, and @var{id} is any declared
12305 identifier within your program, except another module.
12307 Using the @code{::} operator makes @value{GDBN} search the scope
12308 specified by @var{scope} for the identifier @var{id}. If it is not
12309 found in the specified scope, then @value{GDBN} searches all scopes
12310 enclosing the one specified by @var{scope}.
12312 Using the @code{.} operator makes @value{GDBN} search the current scope for
12313 the identifier specified by @var{id} that was imported from the
12314 definition module specified by @var{module}. With this operator, it is
12315 an error if the identifier @var{id} was not imported from definition
12316 module @var{module}, or if @var{id} is not an identifier in
12320 @subsubsection @value{GDBN} and Modula-2
12322 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12323 Five subcommands of @code{set print} and @code{show print} apply
12324 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12325 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12326 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12327 analogue in Modula-2.
12329 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12330 with any language, is not useful with Modula-2. Its
12331 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12332 created in Modula-2 as they can in C or C@t{++}. However, because an
12333 address can be specified by an integral constant, the construct
12334 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12336 @cindex @code{#} in Modula-2
12337 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12338 interpreted as the beginning of a comment. Use @code{<>} instead.
12344 The extensions made to @value{GDBN} for Ada only support
12345 output from the @sc{gnu} Ada (GNAT) compiler.
12346 Other Ada compilers are not currently supported, and
12347 attempting to debug executables produced by them is most likely
12351 @cindex expressions in Ada
12353 * Ada Mode Intro:: General remarks on the Ada syntax
12354 and semantics supported by Ada mode
12356 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12357 * Additions to Ada:: Extensions of the Ada expression syntax.
12358 * Stopping Before Main Program:: Debugging the program during elaboration.
12359 * Ada Tasks:: Listing and setting breakpoints in tasks.
12360 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12361 * Ada Glitches:: Known peculiarities of Ada mode.
12364 @node Ada Mode Intro
12365 @subsubsection Introduction
12366 @cindex Ada mode, general
12368 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12369 syntax, with some extensions.
12370 The philosophy behind the design of this subset is
12374 That @value{GDBN} should provide basic literals and access to operations for
12375 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12376 leaving more sophisticated computations to subprograms written into the
12377 program (which therefore may be called from @value{GDBN}).
12380 That type safety and strict adherence to Ada language restrictions
12381 are not particularly important to the @value{GDBN} user.
12384 That brevity is important to the @value{GDBN} user.
12387 Thus, for brevity, the debugger acts as if all names declared in
12388 user-written packages are directly visible, even if they are not visible
12389 according to Ada rules, thus making it unnecessary to fully qualify most
12390 names with their packages, regardless of context. Where this causes
12391 ambiguity, @value{GDBN} asks the user's intent.
12393 The debugger will start in Ada mode if it detects an Ada main program.
12394 As for other languages, it will enter Ada mode when stopped in a program that
12395 was translated from an Ada source file.
12397 While in Ada mode, you may use `@t{--}' for comments. This is useful
12398 mostly for documenting command files. The standard @value{GDBN} comment
12399 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12400 middle (to allow based literals).
12402 The debugger supports limited overloading. Given a subprogram call in which
12403 the function symbol has multiple definitions, it will use the number of
12404 actual parameters and some information about their types to attempt to narrow
12405 the set of definitions. It also makes very limited use of context, preferring
12406 procedures to functions in the context of the @code{call} command, and
12407 functions to procedures elsewhere.
12409 @node Omissions from Ada
12410 @subsubsection Omissions from Ada
12411 @cindex Ada, omissions from
12413 Here are the notable omissions from the subset:
12417 Only a subset of the attributes are supported:
12421 @t{'First}, @t{'Last}, and @t{'Length}
12422 on array objects (not on types and subtypes).
12425 @t{'Min} and @t{'Max}.
12428 @t{'Pos} and @t{'Val}.
12434 @t{'Range} on array objects (not subtypes), but only as the right
12435 operand of the membership (@code{in}) operator.
12438 @t{'Access}, @t{'Unchecked_Access}, and
12439 @t{'Unrestricted_Access} (a GNAT extension).
12447 @code{Characters.Latin_1} are not available and
12448 concatenation is not implemented. Thus, escape characters in strings are
12449 not currently available.
12452 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12453 equality of representations. They will generally work correctly
12454 for strings and arrays whose elements have integer or enumeration types.
12455 They may not work correctly for arrays whose element
12456 types have user-defined equality, for arrays of real values
12457 (in particular, IEEE-conformant floating point, because of negative
12458 zeroes and NaNs), and for arrays whose elements contain unused bits with
12459 indeterminate values.
12462 The other component-by-component array operations (@code{and}, @code{or},
12463 @code{xor}, @code{not}, and relational tests other than equality)
12464 are not implemented.
12467 @cindex array aggregates (Ada)
12468 @cindex record aggregates (Ada)
12469 @cindex aggregates (Ada)
12470 There is limited support for array and record aggregates. They are
12471 permitted only on the right sides of assignments, as in these examples:
12474 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12475 (@value{GDBP}) set An_Array := (1, others => 0)
12476 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12477 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12478 (@value{GDBP}) set A_Record := (1, "Peter", True);
12479 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12483 discriminant's value by assigning an aggregate has an
12484 undefined effect if that discriminant is used within the record.
12485 However, you can first modify discriminants by directly assigning to
12486 them (which normally would not be allowed in Ada), and then performing an
12487 aggregate assignment. For example, given a variable @code{A_Rec}
12488 declared to have a type such as:
12491 type Rec (Len : Small_Integer := 0) is record
12493 Vals : IntArray (1 .. Len);
12497 you can assign a value with a different size of @code{Vals} with two
12501 (@value{GDBP}) set A_Rec.Len := 4
12502 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12505 As this example also illustrates, @value{GDBN} is very loose about the usual
12506 rules concerning aggregates. You may leave out some of the
12507 components of an array or record aggregate (such as the @code{Len}
12508 component in the assignment to @code{A_Rec} above); they will retain their
12509 original values upon assignment. You may freely use dynamic values as
12510 indices in component associations. You may even use overlapping or
12511 redundant component associations, although which component values are
12512 assigned in such cases is not defined.
12515 Calls to dispatching subprograms are not implemented.
12518 The overloading algorithm is much more limited (i.e., less selective)
12519 than that of real Ada. It makes only limited use of the context in
12520 which a subexpression appears to resolve its meaning, and it is much
12521 looser in its rules for allowing type matches. As a result, some
12522 function calls will be ambiguous, and the user will be asked to choose
12523 the proper resolution.
12526 The @code{new} operator is not implemented.
12529 Entry calls are not implemented.
12532 Aside from printing, arithmetic operations on the native VAX floating-point
12533 formats are not supported.
12536 It is not possible to slice a packed array.
12539 The names @code{True} and @code{False}, when not part of a qualified name,
12540 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12542 Should your program
12543 redefine these names in a package or procedure (at best a dubious practice),
12544 you will have to use fully qualified names to access their new definitions.
12547 @node Additions to Ada
12548 @subsubsection Additions to Ada
12549 @cindex Ada, deviations from
12551 As it does for other languages, @value{GDBN} makes certain generic
12552 extensions to Ada (@pxref{Expressions}):
12556 If the expression @var{E} is a variable residing in memory (typically
12557 a local variable or array element) and @var{N} is a positive integer,
12558 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12559 @var{N}-1 adjacent variables following it in memory as an array. In
12560 Ada, this operator is generally not necessary, since its prime use is
12561 in displaying parts of an array, and slicing will usually do this in
12562 Ada. However, there are occasional uses when debugging programs in
12563 which certain debugging information has been optimized away.
12566 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12567 appears in function or file @var{B}.'' When @var{B} is a file name,
12568 you must typically surround it in single quotes.
12571 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12572 @var{type} that appears at address @var{addr}.''
12575 A name starting with @samp{$} is a convenience variable
12576 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12579 In addition, @value{GDBN} provides a few other shortcuts and outright
12580 additions specific to Ada:
12584 The assignment statement is allowed as an expression, returning
12585 its right-hand operand as its value. Thus, you may enter
12588 (@value{GDBP}) set x := y + 3
12589 (@value{GDBP}) print A(tmp := y + 1)
12593 The semicolon is allowed as an ``operator,'' returning as its value
12594 the value of its right-hand operand.
12595 This allows, for example,
12596 complex conditional breaks:
12599 (@value{GDBP}) break f
12600 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12604 Rather than use catenation and symbolic character names to introduce special
12605 characters into strings, one may instead use a special bracket notation,
12606 which is also used to print strings. A sequence of characters of the form
12607 @samp{["@var{XX}"]} within a string or character literal denotes the
12608 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12609 sequence of characters @samp{["""]} also denotes a single quotation mark
12610 in strings. For example,
12612 "One line.["0a"]Next line.["0a"]"
12615 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12619 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12620 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12624 (@value{GDBP}) print 'max(x, y)
12628 When printing arrays, @value{GDBN} uses positional notation when the
12629 array has a lower bound of 1, and uses a modified named notation otherwise.
12630 For example, a one-dimensional array of three integers with a lower bound
12631 of 3 might print as
12638 That is, in contrast to valid Ada, only the first component has a @code{=>}
12642 You may abbreviate attributes in expressions with any unique,
12643 multi-character subsequence of
12644 their names (an exact match gets preference).
12645 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12646 in place of @t{a'length}.
12649 @cindex quoting Ada internal identifiers
12650 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12651 to lower case. The GNAT compiler uses upper-case characters for
12652 some of its internal identifiers, which are normally of no interest to users.
12653 For the rare occasions when you actually have to look at them,
12654 enclose them in angle brackets to avoid the lower-case mapping.
12657 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12661 Printing an object of class-wide type or dereferencing an
12662 access-to-class-wide value will display all the components of the object's
12663 specific type (as indicated by its run-time tag). Likewise, component
12664 selection on such a value will operate on the specific type of the
12669 @node Stopping Before Main Program
12670 @subsubsection Stopping at the Very Beginning
12672 @cindex breakpointing Ada elaboration code
12673 It is sometimes necessary to debug the program during elaboration, and
12674 before reaching the main procedure.
12675 As defined in the Ada Reference
12676 Manual, the elaboration code is invoked from a procedure called
12677 @code{adainit}. To run your program up to the beginning of
12678 elaboration, simply use the following two commands:
12679 @code{tbreak adainit} and @code{run}.
12682 @subsubsection Extensions for Ada Tasks
12683 @cindex Ada, tasking
12685 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12686 @value{GDBN} provides the following task-related commands:
12691 This command shows a list of current Ada tasks, as in the following example:
12698 (@value{GDBP}) info tasks
12699 ID TID P-ID Pri State Name
12700 1 8088000 0 15 Child Activation Wait main_task
12701 2 80a4000 1 15 Accept Statement b
12702 3 809a800 1 15 Child Activation Wait a
12703 * 4 80ae800 3 15 Runnable c
12708 In this listing, the asterisk before the last task indicates it to be the
12709 task currently being inspected.
12713 Represents @value{GDBN}'s internal task number.
12719 The parent's task ID (@value{GDBN}'s internal task number).
12722 The base priority of the task.
12725 Current state of the task.
12729 The task has been created but has not been activated. It cannot be
12733 The task is not blocked for any reason known to Ada. (It may be waiting
12734 for a mutex, though.) It is conceptually "executing" in normal mode.
12737 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12738 that were waiting on terminate alternatives have been awakened and have
12739 terminated themselves.
12741 @item Child Activation Wait
12742 The task is waiting for created tasks to complete activation.
12744 @item Accept Statement
12745 The task is waiting on an accept or selective wait statement.
12747 @item Waiting on entry call
12748 The task is waiting on an entry call.
12750 @item Async Select Wait
12751 The task is waiting to start the abortable part of an asynchronous
12755 The task is waiting on a select statement with only a delay
12758 @item Child Termination Wait
12759 The task is sleeping having completed a master within itself, and is
12760 waiting for the tasks dependent on that master to become terminated or
12761 waiting on a terminate Phase.
12763 @item Wait Child in Term Alt
12764 The task is sleeping waiting for tasks on terminate alternatives to
12765 finish terminating.
12767 @item Accepting RV with @var{taskno}
12768 The task is accepting a rendez-vous with the task @var{taskno}.
12772 Name of the task in the program.
12776 @kindex info task @var{taskno}
12777 @item info task @var{taskno}
12778 This command shows detailled informations on the specified task, as in
12779 the following example:
12784 (@value{GDBP}) info tasks
12785 ID TID P-ID Pri State Name
12786 1 8077880 0 15 Child Activation Wait main_task
12787 * 2 807c468 1 15 Runnable task_1
12788 (@value{GDBP}) info task 2
12789 Ada Task: 0x807c468
12792 Parent: 1 (main_task)
12798 @kindex task@r{ (Ada)}
12799 @cindex current Ada task ID
12800 This command prints the ID of the current task.
12806 (@value{GDBP}) info tasks
12807 ID TID P-ID Pri State Name
12808 1 8077870 0 15 Child Activation Wait main_task
12809 * 2 807c458 1 15 Runnable t
12810 (@value{GDBP}) task
12811 [Current task is 2]
12814 @item task @var{taskno}
12815 @cindex Ada task switching
12816 This command is like the @code{thread @var{threadno}}
12817 command (@pxref{Threads}). It switches the context of debugging
12818 from the current task to the given task.
12824 (@value{GDBP}) info tasks
12825 ID TID P-ID Pri State Name
12826 1 8077870 0 15 Child Activation Wait main_task
12827 * 2 807c458 1 15 Runnable t
12828 (@value{GDBP}) task 1
12829 [Switching to task 1]
12830 #0 0x8067726 in pthread_cond_wait ()
12832 #0 0x8067726 in pthread_cond_wait ()
12833 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
12834 #2 0x805cb63 in system.task_primitives.operations.sleep ()
12835 #3 0x806153e in system.tasking.stages.activate_tasks ()
12836 #4 0x804aacc in un () at un.adb:5
12839 @item break @var{linespec} task @var{taskno}
12840 @itemx break @var{linespec} task @var{taskno} if @dots{}
12841 @cindex breakpoints and tasks, in Ada
12842 @cindex task breakpoints, in Ada
12843 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
12844 These commands are like the @code{break @dots{} thread @dots{}}
12845 command (@pxref{Thread Stops}).
12846 @var{linespec} specifies source lines, as described
12847 in @ref{Specify Location}.
12849 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
12850 to specify that you only want @value{GDBN} to stop the program when a
12851 particular Ada task reaches this breakpoint. @var{taskno} is one of the
12852 numeric task identifiers assigned by @value{GDBN}, shown in the first
12853 column of the @samp{info tasks} display.
12855 If you do not specify @samp{task @var{taskno}} when you set a
12856 breakpoint, the breakpoint applies to @emph{all} tasks of your
12859 You can use the @code{task} qualifier on conditional breakpoints as
12860 well; in this case, place @samp{task @var{taskno}} before the
12861 breakpoint condition (before the @code{if}).
12869 (@value{GDBP}) info tasks
12870 ID TID P-ID Pri State Name
12871 1 140022020 0 15 Child Activation Wait main_task
12872 2 140045060 1 15 Accept/Select Wait t2
12873 3 140044840 1 15 Runnable t1
12874 * 4 140056040 1 15 Runnable t3
12875 (@value{GDBP}) b 15 task 2
12876 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
12877 (@value{GDBP}) cont
12882 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
12884 (@value{GDBP}) info tasks
12885 ID TID P-ID Pri State Name
12886 1 140022020 0 15 Child Activation Wait main_task
12887 * 2 140045060 1 15 Runnable t2
12888 3 140044840 1 15 Runnable t1
12889 4 140056040 1 15 Delay Sleep t3
12893 @node Ada Tasks and Core Files
12894 @subsubsection Tasking Support when Debugging Core Files
12895 @cindex Ada tasking and core file debugging
12897 When inspecting a core file, as opposed to debugging a live program,
12898 tasking support may be limited or even unavailable, depending on
12899 the platform being used.
12900 For instance, on x86-linux, the list of tasks is available, but task
12901 switching is not supported. On Tru64, however, task switching will work
12904 On certain platforms, including Tru64, the debugger needs to perform some
12905 memory writes in order to provide Ada tasking support. When inspecting
12906 a core file, this means that the core file must be opened with read-write
12907 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
12908 Under these circumstances, you should make a backup copy of the core
12909 file before inspecting it with @value{GDBN}.
12912 @subsubsection Known Peculiarities of Ada Mode
12913 @cindex Ada, problems
12915 Besides the omissions listed previously (@pxref{Omissions from Ada}),
12916 we know of several problems with and limitations of Ada mode in
12918 some of which will be fixed with planned future releases of the debugger
12919 and the GNU Ada compiler.
12923 Currently, the debugger
12924 has insufficient information to determine whether certain pointers represent
12925 pointers to objects or the objects themselves.
12926 Thus, the user may have to tack an extra @code{.all} after an expression
12927 to get it printed properly.
12930 Static constants that the compiler chooses not to materialize as objects in
12931 storage are invisible to the debugger.
12934 Named parameter associations in function argument lists are ignored (the
12935 argument lists are treated as positional).
12938 Many useful library packages are currently invisible to the debugger.
12941 Fixed-point arithmetic, conversions, input, and output is carried out using
12942 floating-point arithmetic, and may give results that only approximate those on
12946 The GNAT compiler never generates the prefix @code{Standard} for any of
12947 the standard symbols defined by the Ada language. @value{GDBN} knows about
12948 this: it will strip the prefix from names when you use it, and will never
12949 look for a name you have so qualified among local symbols, nor match against
12950 symbols in other packages or subprograms. If you have
12951 defined entities anywhere in your program other than parameters and
12952 local variables whose simple names match names in @code{Standard},
12953 GNAT's lack of qualification here can cause confusion. When this happens,
12954 you can usually resolve the confusion
12955 by qualifying the problematic names with package
12956 @code{Standard} explicitly.
12959 Older versions of the compiler sometimes generate erroneous debugging
12960 information, resulting in the debugger incorrectly printing the value
12961 of affected entities. In some cases, the debugger is able to work
12962 around an issue automatically. In other cases, the debugger is able
12963 to work around the issue, but the work-around has to be specifically
12966 @kindex set ada trust-PAD-over-XVS
12967 @kindex show ada trust-PAD-over-XVS
12970 @item set ada trust-PAD-over-XVS on
12971 Configure GDB to strictly follow the GNAT encoding when computing the
12972 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
12973 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
12974 a complete description of the encoding used by the GNAT compiler).
12975 This is the default.
12977 @item set ada trust-PAD-over-XVS off
12978 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
12979 sometimes prints the wrong value for certain entities, changing @code{ada
12980 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
12981 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
12982 @code{off}, but this incurs a slight performance penalty, so it is
12983 recommended to leave this setting to @code{on} unless necessary.
12987 @node Unsupported Languages
12988 @section Unsupported Languages
12990 @cindex unsupported languages
12991 @cindex minimal language
12992 In addition to the other fully-supported programming languages,
12993 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
12994 It does not represent a real programming language, but provides a set
12995 of capabilities close to what the C or assembly languages provide.
12996 This should allow most simple operations to be performed while debugging
12997 an application that uses a language currently not supported by @value{GDBN}.
12999 If the language is set to @code{auto}, @value{GDBN} will automatically
13000 select this language if the current frame corresponds to an unsupported
13004 @chapter Examining the Symbol Table
13006 The commands described in this chapter allow you to inquire about the
13007 symbols (names of variables, functions and types) defined in your
13008 program. This information is inherent in the text of your program and
13009 does not change as your program executes. @value{GDBN} finds it in your
13010 program's symbol table, in the file indicated when you started @value{GDBN}
13011 (@pxref{File Options, ,Choosing Files}), or by one of the
13012 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13014 @cindex symbol names
13015 @cindex names of symbols
13016 @cindex quoting names
13017 Occasionally, you may need to refer to symbols that contain unusual
13018 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13019 most frequent case is in referring to static variables in other
13020 source files (@pxref{Variables,,Program Variables}). File names
13021 are recorded in object files as debugging symbols, but @value{GDBN} would
13022 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13023 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13024 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13031 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13034 @cindex case-insensitive symbol names
13035 @cindex case sensitivity in symbol names
13036 @kindex set case-sensitive
13037 @item set case-sensitive on
13038 @itemx set case-sensitive off
13039 @itemx set case-sensitive auto
13040 Normally, when @value{GDBN} looks up symbols, it matches their names
13041 with case sensitivity determined by the current source language.
13042 Occasionally, you may wish to control that. The command @code{set
13043 case-sensitive} lets you do that by specifying @code{on} for
13044 case-sensitive matches or @code{off} for case-insensitive ones. If
13045 you specify @code{auto}, case sensitivity is reset to the default
13046 suitable for the source language. The default is case-sensitive
13047 matches for all languages except for Fortran, for which the default is
13048 case-insensitive matches.
13050 @kindex show case-sensitive
13051 @item show case-sensitive
13052 This command shows the current setting of case sensitivity for symbols
13055 @kindex info address
13056 @cindex address of a symbol
13057 @item info address @var{symbol}
13058 Describe where the data for @var{symbol} is stored. For a register
13059 variable, this says which register it is kept in. For a non-register
13060 local variable, this prints the stack-frame offset at which the variable
13063 Note the contrast with @samp{print &@var{symbol}}, which does not work
13064 at all for a register variable, and for a stack local variable prints
13065 the exact address of the current instantiation of the variable.
13067 @kindex info symbol
13068 @cindex symbol from address
13069 @cindex closest symbol and offset for an address
13070 @item info symbol @var{addr}
13071 Print the name of a symbol which is stored at the address @var{addr}.
13072 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13073 nearest symbol and an offset from it:
13076 (@value{GDBP}) info symbol 0x54320
13077 _initialize_vx + 396 in section .text
13081 This is the opposite of the @code{info address} command. You can use
13082 it to find out the name of a variable or a function given its address.
13084 For dynamically linked executables, the name of executable or shared
13085 library containing the symbol is also printed:
13088 (@value{GDBP}) info symbol 0x400225
13089 _start + 5 in section .text of /tmp/a.out
13090 (@value{GDBP}) info symbol 0x2aaaac2811cf
13091 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13095 @item whatis [@var{arg}]
13096 Print the data type of @var{arg}, which can be either an expression or
13097 a data type. With no argument, print the data type of @code{$}, the
13098 last value in the value history. If @var{arg} is an expression, it is
13099 not actually evaluated, and any side-effecting operations (such as
13100 assignments or function calls) inside it do not take place. If
13101 @var{arg} is a type name, it may be the name of a type or typedef, or
13102 for C code it may have the form @samp{class @var{class-name}},
13103 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13104 @samp{enum @var{enum-tag}}.
13105 @xref{Expressions, ,Expressions}.
13108 @item ptype [@var{arg}]
13109 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13110 detailed description of the type, instead of just the name of the type.
13111 @xref{Expressions, ,Expressions}.
13113 For example, for this variable declaration:
13116 struct complex @{double real; double imag;@} v;
13120 the two commands give this output:
13124 (@value{GDBP}) whatis v
13125 type = struct complex
13126 (@value{GDBP}) ptype v
13127 type = struct complex @{
13135 As with @code{whatis}, using @code{ptype} without an argument refers to
13136 the type of @code{$}, the last value in the value history.
13138 @cindex incomplete type
13139 Sometimes, programs use opaque data types or incomplete specifications
13140 of complex data structure. If the debug information included in the
13141 program does not allow @value{GDBN} to display a full declaration of
13142 the data type, it will say @samp{<incomplete type>}. For example,
13143 given these declarations:
13147 struct foo *fooptr;
13151 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13154 (@value{GDBP}) ptype foo
13155 $1 = <incomplete type>
13159 ``Incomplete type'' is C terminology for data types that are not
13160 completely specified.
13163 @item info types @var{regexp}
13165 Print a brief description of all types whose names match the regular
13166 expression @var{regexp} (or all types in your program, if you supply
13167 no argument). Each complete typename is matched as though it were a
13168 complete line; thus, @samp{i type value} gives information on all
13169 types in your program whose names include the string @code{value}, but
13170 @samp{i type ^value$} gives information only on types whose complete
13171 name is @code{value}.
13173 This command differs from @code{ptype} in two ways: first, like
13174 @code{whatis}, it does not print a detailed description; second, it
13175 lists all source files where a type is defined.
13178 @cindex local variables
13179 @item info scope @var{location}
13180 List all the variables local to a particular scope. This command
13181 accepts a @var{location} argument---a function name, a source line, or
13182 an address preceded by a @samp{*}, and prints all the variables local
13183 to the scope defined by that location. (@xref{Specify Location}, for
13184 details about supported forms of @var{location}.) For example:
13187 (@value{GDBP}) @b{info scope command_line_handler}
13188 Scope for command_line_handler:
13189 Symbol rl is an argument at stack/frame offset 8, length 4.
13190 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13191 Symbol linelength is in static storage at address 0x150a1c, length 4.
13192 Symbol p is a local variable in register $esi, length 4.
13193 Symbol p1 is a local variable in register $ebx, length 4.
13194 Symbol nline is a local variable in register $edx, length 4.
13195 Symbol repeat is a local variable at frame offset -8, length 4.
13199 This command is especially useful for determining what data to collect
13200 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13203 @kindex info source
13205 Show information about the current source file---that is, the source file for
13206 the function containing the current point of execution:
13209 the name of the source file, and the directory containing it,
13211 the directory it was compiled in,
13213 its length, in lines,
13215 which programming language it is written in,
13217 whether the executable includes debugging information for that file, and
13218 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13220 whether the debugging information includes information about
13221 preprocessor macros.
13225 @kindex info sources
13227 Print the names of all source files in your program for which there is
13228 debugging information, organized into two lists: files whose symbols
13229 have already been read, and files whose symbols will be read when needed.
13231 @kindex info functions
13232 @item info functions
13233 Print the names and data types of all defined functions.
13235 @item info functions @var{regexp}
13236 Print the names and data types of all defined functions
13237 whose names contain a match for regular expression @var{regexp}.
13238 Thus, @samp{info fun step} finds all functions whose names
13239 include @code{step}; @samp{info fun ^step} finds those whose names
13240 start with @code{step}. If a function name contains characters
13241 that conflict with the regular expression language (e.g.@:
13242 @samp{operator*()}), they may be quoted with a backslash.
13244 @kindex info variables
13245 @item info variables
13246 Print the names and data types of all variables that are defined
13247 outside of functions (i.e.@: excluding local variables).
13249 @item info variables @var{regexp}
13250 Print the names and data types of all variables (except for local
13251 variables) whose names contain a match for regular expression
13254 @kindex info classes
13255 @cindex Objective-C, classes and selectors
13257 @itemx info classes @var{regexp}
13258 Display all Objective-C classes in your program, or
13259 (with the @var{regexp} argument) all those matching a particular regular
13262 @kindex info selectors
13263 @item info selectors
13264 @itemx info selectors @var{regexp}
13265 Display all Objective-C selectors in your program, or
13266 (with the @var{regexp} argument) all those matching a particular regular
13270 This was never implemented.
13271 @kindex info methods
13273 @itemx info methods @var{regexp}
13274 The @code{info methods} command permits the user to examine all defined
13275 methods within C@t{++} program, or (with the @var{regexp} argument) a
13276 specific set of methods found in the various C@t{++} classes. Many
13277 C@t{++} classes provide a large number of methods. Thus, the output
13278 from the @code{ptype} command can be overwhelming and hard to use. The
13279 @code{info-methods} command filters the methods, printing only those
13280 which match the regular-expression @var{regexp}.
13283 @cindex reloading symbols
13284 Some systems allow individual object files that make up your program to
13285 be replaced without stopping and restarting your program. For example,
13286 in VxWorks you can simply recompile a defective object file and keep on
13287 running. If you are running on one of these systems, you can allow
13288 @value{GDBN} to reload the symbols for automatically relinked modules:
13291 @kindex set symbol-reloading
13292 @item set symbol-reloading on
13293 Replace symbol definitions for the corresponding source file when an
13294 object file with a particular name is seen again.
13296 @item set symbol-reloading off
13297 Do not replace symbol definitions when encountering object files of the
13298 same name more than once. This is the default state; if you are not
13299 running on a system that permits automatic relinking of modules, you
13300 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13301 may discard symbols when linking large programs, that may contain
13302 several modules (from different directories or libraries) with the same
13305 @kindex show symbol-reloading
13306 @item show symbol-reloading
13307 Show the current @code{on} or @code{off} setting.
13310 @cindex opaque data types
13311 @kindex set opaque-type-resolution
13312 @item set opaque-type-resolution on
13313 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13314 declared as a pointer to a @code{struct}, @code{class}, or
13315 @code{union}---for example, @code{struct MyType *}---that is used in one
13316 source file although the full declaration of @code{struct MyType} is in
13317 another source file. The default is on.
13319 A change in the setting of this subcommand will not take effect until
13320 the next time symbols for a file are loaded.
13322 @item set opaque-type-resolution off
13323 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13324 is printed as follows:
13326 @{<no data fields>@}
13329 @kindex show opaque-type-resolution
13330 @item show opaque-type-resolution
13331 Show whether opaque types are resolved or not.
13333 @kindex maint print symbols
13334 @cindex symbol dump
13335 @kindex maint print psymbols
13336 @cindex partial symbol dump
13337 @item maint print symbols @var{filename}
13338 @itemx maint print psymbols @var{filename}
13339 @itemx maint print msymbols @var{filename}
13340 Write a dump of debugging symbol data into the file @var{filename}.
13341 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13342 symbols with debugging data are included. If you use @samp{maint print
13343 symbols}, @value{GDBN} includes all the symbols for which it has already
13344 collected full details: that is, @var{filename} reflects symbols for
13345 only those files whose symbols @value{GDBN} has read. You can use the
13346 command @code{info sources} to find out which files these are. If you
13347 use @samp{maint print psymbols} instead, the dump shows information about
13348 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13349 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13350 @samp{maint print msymbols} dumps just the minimal symbol information
13351 required for each object file from which @value{GDBN} has read some symbols.
13352 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13353 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13355 @kindex maint info symtabs
13356 @kindex maint info psymtabs
13357 @cindex listing @value{GDBN}'s internal symbol tables
13358 @cindex symbol tables, listing @value{GDBN}'s internal
13359 @cindex full symbol tables, listing @value{GDBN}'s internal
13360 @cindex partial symbol tables, listing @value{GDBN}'s internal
13361 @item maint info symtabs @r{[} @var{regexp} @r{]}
13362 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13364 List the @code{struct symtab} or @code{struct partial_symtab}
13365 structures whose names match @var{regexp}. If @var{regexp} is not
13366 given, list them all. The output includes expressions which you can
13367 copy into a @value{GDBN} debugging this one to examine a particular
13368 structure in more detail. For example:
13371 (@value{GDBP}) maint info psymtabs dwarf2read
13372 @{ objfile /home/gnu/build/gdb/gdb
13373 ((struct objfile *) 0x82e69d0)
13374 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13375 ((struct partial_symtab *) 0x8474b10)
13378 text addresses 0x814d3c8 -- 0x8158074
13379 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13380 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13381 dependencies (none)
13384 (@value{GDBP}) maint info symtabs
13388 We see that there is one partial symbol table whose filename contains
13389 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13390 and we see that @value{GDBN} has not read in any symtabs yet at all.
13391 If we set a breakpoint on a function, that will cause @value{GDBN} to
13392 read the symtab for the compilation unit containing that function:
13395 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13396 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13398 (@value{GDBP}) maint info symtabs
13399 @{ objfile /home/gnu/build/gdb/gdb
13400 ((struct objfile *) 0x82e69d0)
13401 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13402 ((struct symtab *) 0x86c1f38)
13405 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13406 linetable ((struct linetable *) 0x8370fa0)
13407 debugformat DWARF 2
13416 @chapter Altering Execution
13418 Once you think you have found an error in your program, you might want to
13419 find out for certain whether correcting the apparent error would lead to
13420 correct results in the rest of the run. You can find the answer by
13421 experiment, using the @value{GDBN} features for altering execution of the
13424 For example, you can store new values into variables or memory
13425 locations, give your program a signal, restart it at a different
13426 address, or even return prematurely from a function.
13429 * Assignment:: Assignment to variables
13430 * Jumping:: Continuing at a different address
13431 * Signaling:: Giving your program a signal
13432 * Returning:: Returning from a function
13433 * Calling:: Calling your program's functions
13434 * Patching:: Patching your program
13438 @section Assignment to Variables
13441 @cindex setting variables
13442 To alter the value of a variable, evaluate an assignment expression.
13443 @xref{Expressions, ,Expressions}. For example,
13450 stores the value 4 into the variable @code{x}, and then prints the
13451 value of the assignment expression (which is 4).
13452 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13453 information on operators in supported languages.
13455 @kindex set variable
13456 @cindex variables, setting
13457 If you are not interested in seeing the value of the assignment, use the
13458 @code{set} command instead of the @code{print} command. @code{set} is
13459 really the same as @code{print} except that the expression's value is
13460 not printed and is not put in the value history (@pxref{Value History,
13461 ,Value History}). The expression is evaluated only for its effects.
13463 If the beginning of the argument string of the @code{set} command
13464 appears identical to a @code{set} subcommand, use the @code{set
13465 variable} command instead of just @code{set}. This command is identical
13466 to @code{set} except for its lack of subcommands. For example, if your
13467 program has a variable @code{width}, you get an error if you try to set
13468 a new value with just @samp{set width=13}, because @value{GDBN} has the
13469 command @code{set width}:
13472 (@value{GDBP}) whatis width
13474 (@value{GDBP}) p width
13476 (@value{GDBP}) set width=47
13477 Invalid syntax in expression.
13481 The invalid expression, of course, is @samp{=47}. In
13482 order to actually set the program's variable @code{width}, use
13485 (@value{GDBP}) set var width=47
13488 Because the @code{set} command has many subcommands that can conflict
13489 with the names of program variables, it is a good idea to use the
13490 @code{set variable} command instead of just @code{set}. For example, if
13491 your program has a variable @code{g}, you run into problems if you try
13492 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13493 the command @code{set gnutarget}, abbreviated @code{set g}:
13497 (@value{GDBP}) whatis g
13501 (@value{GDBP}) set g=4
13505 The program being debugged has been started already.
13506 Start it from the beginning? (y or n) y
13507 Starting program: /home/smith/cc_progs/a.out
13508 "/home/smith/cc_progs/a.out": can't open to read symbols:
13509 Invalid bfd target.
13510 (@value{GDBP}) show g
13511 The current BFD target is "=4".
13516 The program variable @code{g} did not change, and you silently set the
13517 @code{gnutarget} to an invalid value. In order to set the variable
13521 (@value{GDBP}) set var g=4
13524 @value{GDBN} allows more implicit conversions in assignments than C; you can
13525 freely store an integer value into a pointer variable or vice versa,
13526 and you can convert any structure to any other structure that is the
13527 same length or shorter.
13528 @comment FIXME: how do structs align/pad in these conversions?
13529 @comment /doc@cygnus.com 18dec1990
13531 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13532 construct to generate a value of specified type at a specified address
13533 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13534 to memory location @code{0x83040} as an integer (which implies a certain size
13535 and representation in memory), and
13538 set @{int@}0x83040 = 4
13542 stores the value 4 into that memory location.
13545 @section Continuing at a Different Address
13547 Ordinarily, when you continue your program, you do so at the place where
13548 it stopped, with the @code{continue} command. You can instead continue at
13549 an address of your own choosing, with the following commands:
13553 @item jump @var{linespec}
13554 @itemx jump @var{location}
13555 Resume execution at line @var{linespec} or at address given by
13556 @var{location}. Execution stops again immediately if there is a
13557 breakpoint there. @xref{Specify Location}, for a description of the
13558 different forms of @var{linespec} and @var{location}. It is common
13559 practice to use the @code{tbreak} command in conjunction with
13560 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13562 The @code{jump} command does not change the current stack frame, or
13563 the stack pointer, or the contents of any memory location or any
13564 register other than the program counter. If line @var{linespec} is in
13565 a different function from the one currently executing, the results may
13566 be bizarre if the two functions expect different patterns of arguments or
13567 of local variables. For this reason, the @code{jump} command requests
13568 confirmation if the specified line is not in the function currently
13569 executing. However, even bizarre results are predictable if you are
13570 well acquainted with the machine-language code of your program.
13573 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13574 On many systems, you can get much the same effect as the @code{jump}
13575 command by storing a new value into the register @code{$pc}. The
13576 difference is that this does not start your program running; it only
13577 changes the address of where it @emph{will} run when you continue. For
13585 makes the next @code{continue} command or stepping command execute at
13586 address @code{0x485}, rather than at the address where your program stopped.
13587 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13589 The most common occasion to use the @code{jump} command is to back
13590 up---perhaps with more breakpoints set---over a portion of a program
13591 that has already executed, in order to examine its execution in more
13596 @section Giving your Program a Signal
13597 @cindex deliver a signal to a program
13601 @item signal @var{signal}
13602 Resume execution where your program stopped, but immediately give it the
13603 signal @var{signal}. @var{signal} can be the name or the number of a
13604 signal. For example, on many systems @code{signal 2} and @code{signal
13605 SIGINT} are both ways of sending an interrupt signal.
13607 Alternatively, if @var{signal} is zero, continue execution without
13608 giving a signal. This is useful when your program stopped on account of
13609 a signal and would ordinary see the signal when resumed with the
13610 @code{continue} command; @samp{signal 0} causes it to resume without a
13613 @code{signal} does not repeat when you press @key{RET} a second time
13614 after executing the command.
13618 Invoking the @code{signal} command is not the same as invoking the
13619 @code{kill} utility from the shell. Sending a signal with @code{kill}
13620 causes @value{GDBN} to decide what to do with the signal depending on
13621 the signal handling tables (@pxref{Signals}). The @code{signal} command
13622 passes the signal directly to your program.
13626 @section Returning from a Function
13629 @cindex returning from a function
13632 @itemx return @var{expression}
13633 You can cancel execution of a function call with the @code{return}
13634 command. If you give an
13635 @var{expression} argument, its value is used as the function's return
13639 When you use @code{return}, @value{GDBN} discards the selected stack frame
13640 (and all frames within it). You can think of this as making the
13641 discarded frame return prematurely. If you wish to specify a value to
13642 be returned, give that value as the argument to @code{return}.
13644 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13645 Frame}), and any other frames inside of it, leaving its caller as the
13646 innermost remaining frame. That frame becomes selected. The
13647 specified value is stored in the registers used for returning values
13650 The @code{return} command does not resume execution; it leaves the
13651 program stopped in the state that would exist if the function had just
13652 returned. In contrast, the @code{finish} command (@pxref{Continuing
13653 and Stepping, ,Continuing and Stepping}) resumes execution until the
13654 selected stack frame returns naturally.
13656 @value{GDBN} needs to know how the @var{expression} argument should be set for
13657 the inferior. The concrete registers assignment depends on the OS ABI and the
13658 type being returned by the selected stack frame. For example it is common for
13659 OS ABI to return floating point values in FPU registers while integer values in
13660 CPU registers. Still some ABIs return even floating point values in CPU
13661 registers. Larger integer widths (such as @code{long long int}) also have
13662 specific placement rules. @value{GDBN} already knows the OS ABI from its
13663 current target so it needs to find out also the type being returned to make the
13664 assignment into the right register(s).
13666 Normally, the selected stack frame has debug info. @value{GDBN} will always
13667 use the debug info instead of the implicit type of @var{expression} when the
13668 debug info is available. For example, if you type @kbd{return -1}, and the
13669 function in the current stack frame is declared to return a @code{long long
13670 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13671 into a @code{long long int}:
13674 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13676 (@value{GDBP}) return -1
13677 Make func return now? (y or n) y
13678 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13679 43 printf ("result=%lld\n", func ());
13683 However, if the selected stack frame does not have a debug info, e.g., if the
13684 function was compiled without debug info, @value{GDBN} has to find out the type
13685 to return from user. Specifying a different type by mistake may set the value
13686 in different inferior registers than the caller code expects. For example,
13687 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13688 of a @code{long long int} result for a debug info less function (on 32-bit
13689 architectures). Therefore the user is required to specify the return type by
13690 an appropriate cast explicitly:
13693 Breakpoint 2, 0x0040050b in func ()
13694 (@value{GDBP}) return -1
13695 Return value type not available for selected stack frame.
13696 Please use an explicit cast of the value to return.
13697 (@value{GDBP}) return (long long int) -1
13698 Make selected stack frame return now? (y or n) y
13699 #0 0x00400526 in main ()
13704 @section Calling Program Functions
13707 @cindex calling functions
13708 @cindex inferior functions, calling
13709 @item print @var{expr}
13710 Evaluate the expression @var{expr} and display the resulting value.
13711 @var{expr} may include calls to functions in the program being
13715 @item call @var{expr}
13716 Evaluate the expression @var{expr} without displaying @code{void}
13719 You can use this variant of the @code{print} command if you want to
13720 execute a function from your program that does not return anything
13721 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13722 with @code{void} returned values that @value{GDBN} will otherwise
13723 print. If the result is not void, it is printed and saved in the
13727 It is possible for the function you call via the @code{print} or
13728 @code{call} command to generate a signal (e.g., if there's a bug in
13729 the function, or if you passed it incorrect arguments). What happens
13730 in that case is controlled by the @code{set unwindonsignal} command.
13732 Similarly, with a C@t{++} program it is possible for the function you
13733 call via the @code{print} or @code{call} command to generate an
13734 exception that is not handled due to the constraints of the dummy
13735 frame. In this case, any exception that is raised in the frame, but has
13736 an out-of-frame exception handler will not be found. GDB builds a
13737 dummy-frame for the inferior function call, and the unwinder cannot
13738 seek for exception handlers outside of this dummy-frame. What happens
13739 in that case is controlled by the
13740 @code{set unwind-on-terminating-exception} command.
13743 @item set unwindonsignal
13744 @kindex set unwindonsignal
13745 @cindex unwind stack in called functions
13746 @cindex call dummy stack unwinding
13747 Set unwinding of the stack if a signal is received while in a function
13748 that @value{GDBN} called in the program being debugged. If set to on,
13749 @value{GDBN} unwinds the stack it created for the call and restores
13750 the context to what it was before the call. If set to off (the
13751 default), @value{GDBN} stops in the frame where the signal was
13754 @item show unwindonsignal
13755 @kindex show unwindonsignal
13756 Show the current setting of stack unwinding in the functions called by
13759 @item set unwind-on-terminating-exception
13760 @kindex set unwind-on-terminating-exception
13761 @cindex unwind stack in called functions with unhandled exceptions
13762 @cindex call dummy stack unwinding on unhandled exception.
13763 Set unwinding of the stack if a C@t{++} exception is raised, but left
13764 unhandled while in a function that @value{GDBN} called in the program being
13765 debugged. If set to on (the default), @value{GDBN} unwinds the stack
13766 it created for the call and restores the context to what it was before
13767 the call. If set to off, @value{GDBN} the exception is delivered to
13768 the default C@t{++} exception handler and the inferior terminated.
13770 @item show unwind-on-terminating-exception
13771 @kindex show unwind-on-terminating-exception
13772 Show the current setting of stack unwinding in the functions called by
13777 @cindex weak alias functions
13778 Sometimes, a function you wish to call is actually a @dfn{weak alias}
13779 for another function. In such case, @value{GDBN} might not pick up
13780 the type information, including the types of the function arguments,
13781 which causes @value{GDBN} to call the inferior function incorrectly.
13782 As a result, the called function will function erroneously and may
13783 even crash. A solution to that is to use the name of the aliased
13787 @section Patching Programs
13789 @cindex patching binaries
13790 @cindex writing into executables
13791 @cindex writing into corefiles
13793 By default, @value{GDBN} opens the file containing your program's
13794 executable code (or the corefile) read-only. This prevents accidental
13795 alterations to machine code; but it also prevents you from intentionally
13796 patching your program's binary.
13798 If you'd like to be able to patch the binary, you can specify that
13799 explicitly with the @code{set write} command. For example, you might
13800 want to turn on internal debugging flags, or even to make emergency
13806 @itemx set write off
13807 If you specify @samp{set write on}, @value{GDBN} opens executable and
13808 core files for both reading and writing; if you specify @kbd{set write
13809 off} (the default), @value{GDBN} opens them read-only.
13811 If you have already loaded a file, you must load it again (using the
13812 @code{exec-file} or @code{core-file} command) after changing @code{set
13813 write}, for your new setting to take effect.
13817 Display whether executable files and core files are opened for writing
13818 as well as reading.
13822 @chapter @value{GDBN} Files
13824 @value{GDBN} needs to know the file name of the program to be debugged,
13825 both in order to read its symbol table and in order to start your
13826 program. To debug a core dump of a previous run, you must also tell
13827 @value{GDBN} the name of the core dump file.
13830 * Files:: Commands to specify files
13831 * Separate Debug Files:: Debugging information in separate files
13832 * Symbol Errors:: Errors reading symbol files
13833 * Data Files:: GDB data files
13837 @section Commands to Specify Files
13839 @cindex symbol table
13840 @cindex core dump file
13842 You may want to specify executable and core dump file names. The usual
13843 way to do this is at start-up time, using the arguments to
13844 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
13845 Out of @value{GDBN}}).
13847 Occasionally it is necessary to change to a different file during a
13848 @value{GDBN} session. Or you may run @value{GDBN} and forget to
13849 specify a file you want to use. Or you are debugging a remote target
13850 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
13851 Program}). In these situations the @value{GDBN} commands to specify
13852 new files are useful.
13855 @cindex executable file
13857 @item file @var{filename}
13858 Use @var{filename} as the program to be debugged. It is read for its
13859 symbols and for the contents of pure memory. It is also the program
13860 executed when you use the @code{run} command. If you do not specify a
13861 directory and the file is not found in the @value{GDBN} working directory,
13862 @value{GDBN} uses the environment variable @code{PATH} as a list of
13863 directories to search, just as the shell does when looking for a program
13864 to run. You can change the value of this variable, for both @value{GDBN}
13865 and your program, using the @code{path} command.
13867 @cindex unlinked object files
13868 @cindex patching object files
13869 You can load unlinked object @file{.o} files into @value{GDBN} using
13870 the @code{file} command. You will not be able to ``run'' an object
13871 file, but you can disassemble functions and inspect variables. Also,
13872 if the underlying BFD functionality supports it, you could use
13873 @kbd{gdb -write} to patch object files using this technique. Note
13874 that @value{GDBN} can neither interpret nor modify relocations in this
13875 case, so branches and some initialized variables will appear to go to
13876 the wrong place. But this feature is still handy from time to time.
13879 @code{file} with no argument makes @value{GDBN} discard any information it
13880 has on both executable file and the symbol table.
13883 @item exec-file @r{[} @var{filename} @r{]}
13884 Specify that the program to be run (but not the symbol table) is found
13885 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
13886 if necessary to locate your program. Omitting @var{filename} means to
13887 discard information on the executable file.
13889 @kindex symbol-file
13890 @item symbol-file @r{[} @var{filename} @r{]}
13891 Read symbol table information from file @var{filename}. @code{PATH} is
13892 searched when necessary. Use the @code{file} command to get both symbol
13893 table and program to run from the same file.
13895 @code{symbol-file} with no argument clears out @value{GDBN} information on your
13896 program's symbol table.
13898 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
13899 some breakpoints and auto-display expressions. This is because they may
13900 contain pointers to the internal data recording symbols and data types,
13901 which are part of the old symbol table data being discarded inside
13904 @code{symbol-file} does not repeat if you press @key{RET} again after
13907 When @value{GDBN} is configured for a particular environment, it
13908 understands debugging information in whatever format is the standard
13909 generated for that environment; you may use either a @sc{gnu} compiler, or
13910 other compilers that adhere to the local conventions.
13911 Best results are usually obtained from @sc{gnu} compilers; for example,
13912 using @code{@value{NGCC}} you can generate debugging information for
13915 For most kinds of object files, with the exception of old SVR3 systems
13916 using COFF, the @code{symbol-file} command does not normally read the
13917 symbol table in full right away. Instead, it scans the symbol table
13918 quickly to find which source files and which symbols are present. The
13919 details are read later, one source file at a time, as they are needed.
13921 The purpose of this two-stage reading strategy is to make @value{GDBN}
13922 start up faster. For the most part, it is invisible except for
13923 occasional pauses while the symbol table details for a particular source
13924 file are being read. (The @code{set verbose} command can turn these
13925 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
13926 Warnings and Messages}.)
13928 We have not implemented the two-stage strategy for COFF yet. When the
13929 symbol table is stored in COFF format, @code{symbol-file} reads the
13930 symbol table data in full right away. Note that ``stabs-in-COFF''
13931 still does the two-stage strategy, since the debug info is actually
13935 @cindex reading symbols immediately
13936 @cindex symbols, reading immediately
13937 @item symbol-file @r{[} -readnow @r{]} @var{filename}
13938 @itemx file @r{[} -readnow @r{]} @var{filename}
13939 You can override the @value{GDBN} two-stage strategy for reading symbol
13940 tables by using the @samp{-readnow} option with any of the commands that
13941 load symbol table information, if you want to be sure @value{GDBN} has the
13942 entire symbol table available.
13944 @c FIXME: for now no mention of directories, since this seems to be in
13945 @c flux. 13mar1992 status is that in theory GDB would look either in
13946 @c current dir or in same dir as myprog; but issues like competing
13947 @c GDB's, or clutter in system dirs, mean that in practice right now
13948 @c only current dir is used. FFish says maybe a special GDB hierarchy
13949 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
13953 @item core-file @r{[}@var{filename}@r{]}
13955 Specify the whereabouts of a core dump file to be used as the ``contents
13956 of memory''. Traditionally, core files contain only some parts of the
13957 address space of the process that generated them; @value{GDBN} can access the
13958 executable file itself for other parts.
13960 @code{core-file} with no argument specifies that no core file is
13963 Note that the core file is ignored when your program is actually running
13964 under @value{GDBN}. So, if you have been running your program and you
13965 wish to debug a core file instead, you must kill the subprocess in which
13966 the program is running. To do this, use the @code{kill} command
13967 (@pxref{Kill Process, ,Killing the Child Process}).
13969 @kindex add-symbol-file
13970 @cindex dynamic linking
13971 @item add-symbol-file @var{filename} @var{address}
13972 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
13973 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
13974 The @code{add-symbol-file} command reads additional symbol table
13975 information from the file @var{filename}. You would use this command
13976 when @var{filename} has been dynamically loaded (by some other means)
13977 into the program that is running. @var{address} should be the memory
13978 address at which the file has been loaded; @value{GDBN} cannot figure
13979 this out for itself. You can additionally specify an arbitrary number
13980 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
13981 section name and base address for that section. You can specify any
13982 @var{address} as an expression.
13984 The symbol table of the file @var{filename} is added to the symbol table
13985 originally read with the @code{symbol-file} command. You can use the
13986 @code{add-symbol-file} command any number of times; the new symbol data
13987 thus read keeps adding to the old. To discard all old symbol data
13988 instead, use the @code{symbol-file} command without any arguments.
13990 @cindex relocatable object files, reading symbols from
13991 @cindex object files, relocatable, reading symbols from
13992 @cindex reading symbols from relocatable object files
13993 @cindex symbols, reading from relocatable object files
13994 @cindex @file{.o} files, reading symbols from
13995 Although @var{filename} is typically a shared library file, an
13996 executable file, or some other object file which has been fully
13997 relocated for loading into a process, you can also load symbolic
13998 information from relocatable @file{.o} files, as long as:
14002 the file's symbolic information refers only to linker symbols defined in
14003 that file, not to symbols defined by other object files,
14005 every section the file's symbolic information refers to has actually
14006 been loaded into the inferior, as it appears in the file, and
14008 you can determine the address at which every section was loaded, and
14009 provide these to the @code{add-symbol-file} command.
14013 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14014 relocatable files into an already running program; such systems
14015 typically make the requirements above easy to meet. However, it's
14016 important to recognize that many native systems use complex link
14017 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14018 assembly, for example) that make the requirements difficult to meet. In
14019 general, one cannot assume that using @code{add-symbol-file} to read a
14020 relocatable object file's symbolic information will have the same effect
14021 as linking the relocatable object file into the program in the normal
14024 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14026 @kindex add-symbol-file-from-memory
14027 @cindex @code{syscall DSO}
14028 @cindex load symbols from memory
14029 @item add-symbol-file-from-memory @var{address}
14030 Load symbols from the given @var{address} in a dynamically loaded
14031 object file whose image is mapped directly into the inferior's memory.
14032 For example, the Linux kernel maps a @code{syscall DSO} into each
14033 process's address space; this DSO provides kernel-specific code for
14034 some system calls. The argument can be any expression whose
14035 evaluation yields the address of the file's shared object file header.
14036 For this command to work, you must have used @code{symbol-file} or
14037 @code{exec-file} commands in advance.
14039 @kindex add-shared-symbol-files
14041 @item add-shared-symbol-files @var{library-file}
14042 @itemx assf @var{library-file}
14043 The @code{add-shared-symbol-files} command can currently be used only
14044 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14045 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14046 @value{GDBN} automatically looks for shared libraries, however if
14047 @value{GDBN} does not find yours, you can invoke
14048 @code{add-shared-symbol-files}. It takes one argument: the shared
14049 library's file name. @code{assf} is a shorthand alias for
14050 @code{add-shared-symbol-files}.
14053 @item section @var{section} @var{addr}
14054 The @code{section} command changes the base address of the named
14055 @var{section} of the exec file to @var{addr}. This can be used if the
14056 exec file does not contain section addresses, (such as in the
14057 @code{a.out} format), or when the addresses specified in the file
14058 itself are wrong. Each section must be changed separately. The
14059 @code{info files} command, described below, lists all the sections and
14063 @kindex info target
14066 @code{info files} and @code{info target} are synonymous; both print the
14067 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14068 including the names of the executable and core dump files currently in
14069 use by @value{GDBN}, and the files from which symbols were loaded. The
14070 command @code{help target} lists all possible targets rather than
14073 @kindex maint info sections
14074 @item maint info sections
14075 Another command that can give you extra information about program sections
14076 is @code{maint info sections}. In addition to the section information
14077 displayed by @code{info files}, this command displays the flags and file
14078 offset of each section in the executable and core dump files. In addition,
14079 @code{maint info sections} provides the following command options (which
14080 may be arbitrarily combined):
14084 Display sections for all loaded object files, including shared libraries.
14085 @item @var{sections}
14086 Display info only for named @var{sections}.
14087 @item @var{section-flags}
14088 Display info only for sections for which @var{section-flags} are true.
14089 The section flags that @value{GDBN} currently knows about are:
14092 Section will have space allocated in the process when loaded.
14093 Set for all sections except those containing debug information.
14095 Section will be loaded from the file into the child process memory.
14096 Set for pre-initialized code and data, clear for @code{.bss} sections.
14098 Section needs to be relocated before loading.
14100 Section cannot be modified by the child process.
14102 Section contains executable code only.
14104 Section contains data only (no executable code).
14106 Section will reside in ROM.
14108 Section contains data for constructor/destructor lists.
14110 Section is not empty.
14112 An instruction to the linker to not output the section.
14113 @item COFF_SHARED_LIBRARY
14114 A notification to the linker that the section contains
14115 COFF shared library information.
14117 Section contains common symbols.
14120 @kindex set trust-readonly-sections
14121 @cindex read-only sections
14122 @item set trust-readonly-sections on
14123 Tell @value{GDBN} that readonly sections in your object file
14124 really are read-only (i.e.@: that their contents will not change).
14125 In that case, @value{GDBN} can fetch values from these sections
14126 out of the object file, rather than from the target program.
14127 For some targets (notably embedded ones), this can be a significant
14128 enhancement to debugging performance.
14130 The default is off.
14132 @item set trust-readonly-sections off
14133 Tell @value{GDBN} not to trust readonly sections. This means that
14134 the contents of the section might change while the program is running,
14135 and must therefore be fetched from the target when needed.
14137 @item show trust-readonly-sections
14138 Show the current setting of trusting readonly sections.
14141 All file-specifying commands allow both absolute and relative file names
14142 as arguments. @value{GDBN} always converts the file name to an absolute file
14143 name and remembers it that way.
14145 @cindex shared libraries
14146 @anchor{Shared Libraries}
14147 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14148 and IBM RS/6000 AIX shared libraries.
14150 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14151 shared libraries. @xref{Expat}.
14153 @value{GDBN} automatically loads symbol definitions from shared libraries
14154 when you use the @code{run} command, or when you examine a core file.
14155 (Before you issue the @code{run} command, @value{GDBN} does not understand
14156 references to a function in a shared library, however---unless you are
14157 debugging a core file).
14159 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14160 automatically loads the symbols at the time of the @code{shl_load} call.
14162 @c FIXME: some @value{GDBN} release may permit some refs to undef
14163 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14164 @c FIXME...lib; check this from time to time when updating manual
14166 There are times, however, when you may wish to not automatically load
14167 symbol definitions from shared libraries, such as when they are
14168 particularly large or there are many of them.
14170 To control the automatic loading of shared library symbols, use the
14174 @kindex set auto-solib-add
14175 @item set auto-solib-add @var{mode}
14176 If @var{mode} is @code{on}, symbols from all shared object libraries
14177 will be loaded automatically when the inferior begins execution, you
14178 attach to an independently started inferior, or when the dynamic linker
14179 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14180 is @code{off}, symbols must be loaded manually, using the
14181 @code{sharedlibrary} command. The default value is @code{on}.
14183 @cindex memory used for symbol tables
14184 If your program uses lots of shared libraries with debug info that
14185 takes large amounts of memory, you can decrease the @value{GDBN}
14186 memory footprint by preventing it from automatically loading the
14187 symbols from shared libraries. To that end, type @kbd{set
14188 auto-solib-add off} before running the inferior, then load each
14189 library whose debug symbols you do need with @kbd{sharedlibrary
14190 @var{regexp}}, where @var{regexp} is a regular expression that matches
14191 the libraries whose symbols you want to be loaded.
14193 @kindex show auto-solib-add
14194 @item show auto-solib-add
14195 Display the current autoloading mode.
14198 @cindex load shared library
14199 To explicitly load shared library symbols, use the @code{sharedlibrary}
14203 @kindex info sharedlibrary
14205 @item info share @var{regex}
14206 @itemx info sharedlibrary @var{regex}
14207 Print the names of the shared libraries which are currently loaded
14208 that match @var{regex}. If @var{regex} is omitted then print
14209 all shared libraries that are loaded.
14211 @kindex sharedlibrary
14213 @item sharedlibrary @var{regex}
14214 @itemx share @var{regex}
14215 Load shared object library symbols for files matching a
14216 Unix regular expression.
14217 As with files loaded automatically, it only loads shared libraries
14218 required by your program for a core file or after typing @code{run}. If
14219 @var{regex} is omitted all shared libraries required by your program are
14222 @item nosharedlibrary
14223 @kindex nosharedlibrary
14224 @cindex unload symbols from shared libraries
14225 Unload all shared object library symbols. This discards all symbols
14226 that have been loaded from all shared libraries. Symbols from shared
14227 libraries that were loaded by explicit user requests are not
14231 Sometimes you may wish that @value{GDBN} stops and gives you control
14232 when any of shared library events happen. Use the @code{set
14233 stop-on-solib-events} command for this:
14236 @item set stop-on-solib-events
14237 @kindex set stop-on-solib-events
14238 This command controls whether @value{GDBN} should give you control
14239 when the dynamic linker notifies it about some shared library event.
14240 The most common event of interest is loading or unloading of a new
14243 @item show stop-on-solib-events
14244 @kindex show stop-on-solib-events
14245 Show whether @value{GDBN} stops and gives you control when shared
14246 library events happen.
14249 Shared libraries are also supported in many cross or remote debugging
14250 configurations. @value{GDBN} needs to have access to the target's libraries;
14251 this can be accomplished either by providing copies of the libraries
14252 on the host system, or by asking @value{GDBN} to automatically retrieve the
14253 libraries from the target. If copies of the target libraries are
14254 provided, they need to be the same as the target libraries, although the
14255 copies on the target can be stripped as long as the copies on the host are
14258 @cindex where to look for shared libraries
14259 For remote debugging, you need to tell @value{GDBN} where the target
14260 libraries are, so that it can load the correct copies---otherwise, it
14261 may try to load the host's libraries. @value{GDBN} has two variables
14262 to specify the search directories for target libraries.
14265 @cindex prefix for shared library file names
14266 @cindex system root, alternate
14267 @kindex set solib-absolute-prefix
14268 @kindex set sysroot
14269 @item set sysroot @var{path}
14270 Use @var{path} as the system root for the program being debugged. Any
14271 absolute shared library paths will be prefixed with @var{path}; many
14272 runtime loaders store the absolute paths to the shared library in the
14273 target program's memory. If you use @code{set sysroot} to find shared
14274 libraries, they need to be laid out in the same way that they are on
14275 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14278 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14279 retrieve the target libraries from the remote system. This is only
14280 supported when using a remote target that supports the @code{remote get}
14281 command (@pxref{File Transfer,,Sending files to a remote system}).
14282 The part of @var{path} following the initial @file{remote:}
14283 (if present) is used as system root prefix on the remote file system.
14284 @footnote{If you want to specify a local system root using a directory
14285 that happens to be named @file{remote:}, you need to use some equivalent
14286 variant of the name like @file{./remote:}.}
14288 The @code{set solib-absolute-prefix} command is an alias for @code{set
14291 @cindex default system root
14292 @cindex @samp{--with-sysroot}
14293 You can set the default system root by using the configure-time
14294 @samp{--with-sysroot} option. If the system root is inside
14295 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14296 @samp{--exec-prefix}), then the default system root will be updated
14297 automatically if the installed @value{GDBN} is moved to a new
14300 @kindex show sysroot
14302 Display the current shared library prefix.
14304 @kindex set solib-search-path
14305 @item set solib-search-path @var{path}
14306 If this variable is set, @var{path} is a colon-separated list of
14307 directories to search for shared libraries. @samp{solib-search-path}
14308 is used after @samp{sysroot} fails to locate the library, or if the
14309 path to the library is relative instead of absolute. If you want to
14310 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14311 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14312 finding your host's libraries. @samp{sysroot} is preferred; setting
14313 it to a nonexistent directory may interfere with automatic loading
14314 of shared library symbols.
14316 @kindex show solib-search-path
14317 @item show solib-search-path
14318 Display the current shared library search path.
14322 @node Separate Debug Files
14323 @section Debugging Information in Separate Files
14324 @cindex separate debugging information files
14325 @cindex debugging information in separate files
14326 @cindex @file{.debug} subdirectories
14327 @cindex debugging information directory, global
14328 @cindex global debugging information directory
14329 @cindex build ID, and separate debugging files
14330 @cindex @file{.build-id} directory
14332 @value{GDBN} allows you to put a program's debugging information in a
14333 file separate from the executable itself, in a way that allows
14334 @value{GDBN} to find and load the debugging information automatically.
14335 Since debugging information can be very large---sometimes larger
14336 than the executable code itself---some systems distribute debugging
14337 information for their executables in separate files, which users can
14338 install only when they need to debug a problem.
14340 @value{GDBN} supports two ways of specifying the separate debug info
14345 The executable contains a @dfn{debug link} that specifies the name of
14346 the separate debug info file. The separate debug file's name is
14347 usually @file{@var{executable}.debug}, where @var{executable} is the
14348 name of the corresponding executable file without leading directories
14349 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14350 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14351 checksum for the debug file, which @value{GDBN} uses to validate that
14352 the executable and the debug file came from the same build.
14355 The executable contains a @dfn{build ID}, a unique bit string that is
14356 also present in the corresponding debug info file. (This is supported
14357 only on some operating systems, notably those which use the ELF format
14358 for binary files and the @sc{gnu} Binutils.) For more details about
14359 this feature, see the description of the @option{--build-id}
14360 command-line option in @ref{Options, , Command Line Options, ld.info,
14361 The GNU Linker}. The debug info file's name is not specified
14362 explicitly by the build ID, but can be computed from the build ID, see
14366 Depending on the way the debug info file is specified, @value{GDBN}
14367 uses two different methods of looking for the debug file:
14371 For the ``debug link'' method, @value{GDBN} looks up the named file in
14372 the directory of the executable file, then in a subdirectory of that
14373 directory named @file{.debug}, and finally under the global debug
14374 directory, in a subdirectory whose name is identical to the leading
14375 directories of the executable's absolute file name.
14378 For the ``build ID'' method, @value{GDBN} looks in the
14379 @file{.build-id} subdirectory of the global debug directory for a file
14380 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14381 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14382 are the rest of the bit string. (Real build ID strings are 32 or more
14383 hex characters, not 10.)
14386 So, for example, suppose you ask @value{GDBN} to debug
14387 @file{/usr/bin/ls}, which has a debug link that specifies the
14388 file @file{ls.debug}, and a build ID whose value in hex is
14389 @code{abcdef1234}. If the global debug directory is
14390 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14391 debug information files, in the indicated order:
14395 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14397 @file{/usr/bin/ls.debug}
14399 @file{/usr/bin/.debug/ls.debug}
14401 @file{/usr/lib/debug/usr/bin/ls.debug}.
14404 You can set the global debugging info directory's name, and view the
14405 name @value{GDBN} is currently using.
14409 @kindex set debug-file-directory
14410 @item set debug-file-directory @var{directories}
14411 Set the directories which @value{GDBN} searches for separate debugging
14412 information files to @var{directory}. Multiple directory components can be set
14413 concatenating them by a directory separator.
14415 @kindex show debug-file-directory
14416 @item show debug-file-directory
14417 Show the directories @value{GDBN} searches for separate debugging
14422 @cindex @code{.gnu_debuglink} sections
14423 @cindex debug link sections
14424 A debug link is a special section of the executable file named
14425 @code{.gnu_debuglink}. The section must contain:
14429 A filename, with any leading directory components removed, followed by
14432 zero to three bytes of padding, as needed to reach the next four-byte
14433 boundary within the section, and
14435 a four-byte CRC checksum, stored in the same endianness used for the
14436 executable file itself. The checksum is computed on the debugging
14437 information file's full contents by the function given below, passing
14438 zero as the @var{crc} argument.
14441 Any executable file format can carry a debug link, as long as it can
14442 contain a section named @code{.gnu_debuglink} with the contents
14445 @cindex @code{.note.gnu.build-id} sections
14446 @cindex build ID sections
14447 The build ID is a special section in the executable file (and in other
14448 ELF binary files that @value{GDBN} may consider). This section is
14449 often named @code{.note.gnu.build-id}, but that name is not mandatory.
14450 It contains unique identification for the built files---the ID remains
14451 the same across multiple builds of the same build tree. The default
14452 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
14453 content for the build ID string. The same section with an identical
14454 value is present in the original built binary with symbols, in its
14455 stripped variant, and in the separate debugging information file.
14457 The debugging information file itself should be an ordinary
14458 executable, containing a full set of linker symbols, sections, and
14459 debugging information. The sections of the debugging information file
14460 should have the same names, addresses, and sizes as the original file,
14461 but they need not contain any data---much like a @code{.bss} section
14462 in an ordinary executable.
14464 The @sc{gnu} binary utilities (Binutils) package includes the
14465 @samp{objcopy} utility that can produce
14466 the separated executable / debugging information file pairs using the
14467 following commands:
14470 @kbd{objcopy --only-keep-debug foo foo.debug}
14475 These commands remove the debugging
14476 information from the executable file @file{foo} and place it in the file
14477 @file{foo.debug}. You can use the first, second or both methods to link the
14482 The debug link method needs the following additional command to also leave
14483 behind a debug link in @file{foo}:
14486 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
14489 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
14490 a version of the @code{strip} command such that the command @kbd{strip foo -f
14491 foo.debug} has the same functionality as the two @code{objcopy} commands and
14492 the @code{ln -s} command above, together.
14495 Build ID gets embedded into the main executable using @code{ld --build-id} or
14496 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
14497 compatibility fixes for debug files separation are present in @sc{gnu} binary
14498 utilities (Binutils) package since version 2.18.
14503 @cindex CRC algorithm definition
14504 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
14505 IEEE 802.3 using the polynomial:
14507 @c TexInfo requires naked braces for multi-digit exponents for Tex
14508 @c output, but this causes HTML output to barf. HTML has to be set using
14509 @c raw commands. So we end up having to specify this equation in 2
14514 <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>
14515 + <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
14521 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
14522 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
14526 The function is computed byte at a time, taking the least
14527 significant bit of each byte first. The initial pattern
14528 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
14529 the final result is inverted to ensure trailing zeros also affect the
14532 @emph{Note:} This is the same CRC polynomial as used in handling the
14533 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
14534 , @value{GDBN} Remote Serial Protocol}). However in the
14535 case of the Remote Serial Protocol, the CRC is computed @emph{most}
14536 significant bit first, and the result is not inverted, so trailing
14537 zeros have no effect on the CRC value.
14539 To complete the description, we show below the code of the function
14540 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14541 initially supplied @code{crc} argument means that an initial call to
14542 this function passing in zero will start computing the CRC using
14545 @kindex gnu_debuglink_crc32
14548 gnu_debuglink_crc32 (unsigned long crc,
14549 unsigned char *buf, size_t len)
14551 static const unsigned long crc32_table[256] =
14553 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14554 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14555 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14556 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14557 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14558 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14559 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14560 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14561 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14562 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14563 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14564 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14565 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14566 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14567 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14568 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14569 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14570 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14571 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14572 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14573 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14574 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14575 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14576 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14577 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14578 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14579 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14580 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14581 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14582 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14583 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14584 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14585 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14586 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14587 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14588 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14589 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14590 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14591 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14592 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14593 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14594 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14595 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14596 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14597 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14598 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14599 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14600 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14601 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14602 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14603 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14606 unsigned char *end;
14608 crc = ~crc & 0xffffffff;
14609 for (end = buf + len; buf < end; ++buf)
14610 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14611 return ~crc & 0xffffffff;
14616 This computation does not apply to the ``build ID'' method.
14619 @node Symbol Errors
14620 @section Errors Reading Symbol Files
14622 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14623 such as symbol types it does not recognize, or known bugs in compiler
14624 output. By default, @value{GDBN} does not notify you of such problems, since
14625 they are relatively common and primarily of interest to people
14626 debugging compilers. If you are interested in seeing information
14627 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14628 only one message about each such type of problem, no matter how many
14629 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14630 to see how many times the problems occur, with the @code{set
14631 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14634 The messages currently printed, and their meanings, include:
14637 @item inner block not inside outer block in @var{symbol}
14639 The symbol information shows where symbol scopes begin and end
14640 (such as at the start of a function or a block of statements). This
14641 error indicates that an inner scope block is not fully contained
14642 in its outer scope blocks.
14644 @value{GDBN} circumvents the problem by treating the inner block as if it had
14645 the same scope as the outer block. In the error message, @var{symbol}
14646 may be shown as ``@code{(don't know)}'' if the outer block is not a
14649 @item block at @var{address} out of order
14651 The symbol information for symbol scope blocks should occur in
14652 order of increasing addresses. This error indicates that it does not
14655 @value{GDBN} does not circumvent this problem, and has trouble
14656 locating symbols in the source file whose symbols it is reading. (You
14657 can often determine what source file is affected by specifying
14658 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
14661 @item bad block start address patched
14663 The symbol information for a symbol scope block has a start address
14664 smaller than the address of the preceding source line. This is known
14665 to occur in the SunOS 4.1.1 (and earlier) C compiler.
14667 @value{GDBN} circumvents the problem by treating the symbol scope block as
14668 starting on the previous source line.
14670 @item bad string table offset in symbol @var{n}
14673 Symbol number @var{n} contains a pointer into the string table which is
14674 larger than the size of the string table.
14676 @value{GDBN} circumvents the problem by considering the symbol to have the
14677 name @code{foo}, which may cause other problems if many symbols end up
14680 @item unknown symbol type @code{0x@var{nn}}
14682 The symbol information contains new data types that @value{GDBN} does
14683 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
14684 uncomprehended information, in hexadecimal.
14686 @value{GDBN} circumvents the error by ignoring this symbol information.
14687 This usually allows you to debug your program, though certain symbols
14688 are not accessible. If you encounter such a problem and feel like
14689 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
14690 on @code{complain}, then go up to the function @code{read_dbx_symtab}
14691 and examine @code{*bufp} to see the symbol.
14693 @item stub type has NULL name
14695 @value{GDBN} could not find the full definition for a struct or class.
14697 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
14698 The symbol information for a C@t{++} member function is missing some
14699 information that recent versions of the compiler should have output for
14702 @item info mismatch between compiler and debugger
14704 @value{GDBN} could not parse a type specification output by the compiler.
14709 @section GDB Data Files
14711 @cindex prefix for data files
14712 @value{GDBN} will sometimes read an auxiliary data file. These files
14713 are kept in a directory known as the @dfn{data directory}.
14715 You can set the data directory's name, and view the name @value{GDBN}
14716 is currently using.
14719 @kindex set data-directory
14720 @item set data-directory @var{directory}
14721 Set the directory which @value{GDBN} searches for auxiliary data files
14722 to @var{directory}.
14724 @kindex show data-directory
14725 @item show data-directory
14726 Show the directory @value{GDBN} searches for auxiliary data files.
14729 @cindex default data directory
14730 @cindex @samp{--with-gdb-datadir}
14731 You can set the default data directory by using the configure-time
14732 @samp{--with-gdb-datadir} option. If the data directory is inside
14733 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14734 @samp{--exec-prefix}), then the default data directory will be updated
14735 automatically if the installed @value{GDBN} is moved to a new
14739 @chapter Specifying a Debugging Target
14741 @cindex debugging target
14742 A @dfn{target} is the execution environment occupied by your program.
14744 Often, @value{GDBN} runs in the same host environment as your program;
14745 in that case, the debugging target is specified as a side effect when
14746 you use the @code{file} or @code{core} commands. When you need more
14747 flexibility---for example, running @value{GDBN} on a physically separate
14748 host, or controlling a standalone system over a serial port or a
14749 realtime system over a TCP/IP connection---you can use the @code{target}
14750 command to specify one of the target types configured for @value{GDBN}
14751 (@pxref{Target Commands, ,Commands for Managing Targets}).
14753 @cindex target architecture
14754 It is possible to build @value{GDBN} for several different @dfn{target
14755 architectures}. When @value{GDBN} is built like that, you can choose
14756 one of the available architectures with the @kbd{set architecture}
14760 @kindex set architecture
14761 @kindex show architecture
14762 @item set architecture @var{arch}
14763 This command sets the current target architecture to @var{arch}. The
14764 value of @var{arch} can be @code{"auto"}, in addition to one of the
14765 supported architectures.
14767 @item show architecture
14768 Show the current target architecture.
14770 @item set processor
14772 @kindex set processor
14773 @kindex show processor
14774 These are alias commands for, respectively, @code{set architecture}
14775 and @code{show architecture}.
14779 * Active Targets:: Active targets
14780 * Target Commands:: Commands for managing targets
14781 * Byte Order:: Choosing target byte order
14784 @node Active Targets
14785 @section Active Targets
14787 @cindex stacking targets
14788 @cindex active targets
14789 @cindex multiple targets
14791 There are three classes of targets: processes, core files, and
14792 executable files. @value{GDBN} can work concurrently on up to three
14793 active targets, one in each class. This allows you to (for example)
14794 start a process and inspect its activity without abandoning your work on
14797 For example, if you execute @samp{gdb a.out}, then the executable file
14798 @code{a.out} is the only active target. If you designate a core file as
14799 well---presumably from a prior run that crashed and coredumped---then
14800 @value{GDBN} has two active targets and uses them in tandem, looking
14801 first in the corefile target, then in the executable file, to satisfy
14802 requests for memory addresses. (Typically, these two classes of target
14803 are complementary, since core files contain only a program's
14804 read-write memory---variables and so on---plus machine status, while
14805 executable files contain only the program text and initialized data.)
14807 When you type @code{run}, your executable file becomes an active process
14808 target as well. When a process target is active, all @value{GDBN}
14809 commands requesting memory addresses refer to that target; addresses in
14810 an active core file or executable file target are obscured while the
14811 process target is active.
14813 Use the @code{core-file} and @code{exec-file} commands to select a new
14814 core file or executable target (@pxref{Files, ,Commands to Specify
14815 Files}). To specify as a target a process that is already running, use
14816 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
14819 @node Target Commands
14820 @section Commands for Managing Targets
14823 @item target @var{type} @var{parameters}
14824 Connects the @value{GDBN} host environment to a target machine or
14825 process. A target is typically a protocol for talking to debugging
14826 facilities. You use the argument @var{type} to specify the type or
14827 protocol of the target machine.
14829 Further @var{parameters} are interpreted by the target protocol, but
14830 typically include things like device names or host names to connect
14831 with, process numbers, and baud rates.
14833 The @code{target} command does not repeat if you press @key{RET} again
14834 after executing the command.
14836 @kindex help target
14838 Displays the names of all targets available. To display targets
14839 currently selected, use either @code{info target} or @code{info files}
14840 (@pxref{Files, ,Commands to Specify Files}).
14842 @item help target @var{name}
14843 Describe a particular target, including any parameters necessary to
14846 @kindex set gnutarget
14847 @item set gnutarget @var{args}
14848 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
14849 knows whether it is reading an @dfn{executable},
14850 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
14851 with the @code{set gnutarget} command. Unlike most @code{target} commands,
14852 with @code{gnutarget} the @code{target} refers to a program, not a machine.
14855 @emph{Warning:} To specify a file format with @code{set gnutarget},
14856 you must know the actual BFD name.
14860 @xref{Files, , Commands to Specify Files}.
14862 @kindex show gnutarget
14863 @item show gnutarget
14864 Use the @code{show gnutarget} command to display what file format
14865 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
14866 @value{GDBN} will determine the file format for each file automatically,
14867 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
14870 @cindex common targets
14871 Here are some common targets (available, or not, depending on the GDB
14876 @item target exec @var{program}
14877 @cindex executable file target
14878 An executable file. @samp{target exec @var{program}} is the same as
14879 @samp{exec-file @var{program}}.
14881 @item target core @var{filename}
14882 @cindex core dump file target
14883 A core dump file. @samp{target core @var{filename}} is the same as
14884 @samp{core-file @var{filename}}.
14886 @item target remote @var{medium}
14887 @cindex remote target
14888 A remote system connected to @value{GDBN} via a serial line or network
14889 connection. This command tells @value{GDBN} to use its own remote
14890 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
14892 For example, if you have a board connected to @file{/dev/ttya} on the
14893 machine running @value{GDBN}, you could say:
14896 target remote /dev/ttya
14899 @code{target remote} supports the @code{load} command. This is only
14900 useful if you have some other way of getting the stub to the target
14901 system, and you can put it somewhere in memory where it won't get
14902 clobbered by the download.
14904 @item target sim @r{[}@var{simargs}@r{]} @dots{}
14905 @cindex built-in simulator target
14906 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
14914 works; however, you cannot assume that a specific memory map, device
14915 drivers, or even basic I/O is available, although some simulators do
14916 provide these. For info about any processor-specific simulator details,
14917 see the appropriate section in @ref{Embedded Processors, ,Embedded
14922 Some configurations may include these targets as well:
14926 @item target nrom @var{dev}
14927 @cindex NetROM ROM emulator target
14928 NetROM ROM emulator. This target only supports downloading.
14932 Different targets are available on different configurations of @value{GDBN};
14933 your configuration may have more or fewer targets.
14935 Many remote targets require you to download the executable's code once
14936 you've successfully established a connection. You may wish to control
14937 various aspects of this process.
14942 @kindex set hash@r{, for remote monitors}
14943 @cindex hash mark while downloading
14944 This command controls whether a hash mark @samp{#} is displayed while
14945 downloading a file to the remote monitor. If on, a hash mark is
14946 displayed after each S-record is successfully downloaded to the
14950 @kindex show hash@r{, for remote monitors}
14951 Show the current status of displaying the hash mark.
14953 @item set debug monitor
14954 @kindex set debug monitor
14955 @cindex display remote monitor communications
14956 Enable or disable display of communications messages between
14957 @value{GDBN} and the remote monitor.
14959 @item show debug monitor
14960 @kindex show debug monitor
14961 Show the current status of displaying communications between
14962 @value{GDBN} and the remote monitor.
14967 @kindex load @var{filename}
14968 @item load @var{filename}
14970 Depending on what remote debugging facilities are configured into
14971 @value{GDBN}, the @code{load} command may be available. Where it exists, it
14972 is meant to make @var{filename} (an executable) available for debugging
14973 on the remote system---by downloading, or dynamic linking, for example.
14974 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
14975 the @code{add-symbol-file} command.
14977 If your @value{GDBN} does not have a @code{load} command, attempting to
14978 execute it gets the error message ``@code{You can't do that when your
14979 target is @dots{}}''
14981 The file is loaded at whatever address is specified in the executable.
14982 For some object file formats, you can specify the load address when you
14983 link the program; for other formats, like a.out, the object file format
14984 specifies a fixed address.
14985 @c FIXME! This would be a good place for an xref to the GNU linker doc.
14987 Depending on the remote side capabilities, @value{GDBN} may be able to
14988 load programs into flash memory.
14990 @code{load} does not repeat if you press @key{RET} again after using it.
14994 @section Choosing Target Byte Order
14996 @cindex choosing target byte order
14997 @cindex target byte order
14999 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15000 offer the ability to run either big-endian or little-endian byte
15001 orders. Usually the executable or symbol will include a bit to
15002 designate the endian-ness, and you will not need to worry about
15003 which to use. However, you may still find it useful to adjust
15004 @value{GDBN}'s idea of processor endian-ness manually.
15008 @item set endian big
15009 Instruct @value{GDBN} to assume the target is big-endian.
15011 @item set endian little
15012 Instruct @value{GDBN} to assume the target is little-endian.
15014 @item set endian auto
15015 Instruct @value{GDBN} to use the byte order associated with the
15019 Display @value{GDBN}'s current idea of the target byte order.
15023 Note that these commands merely adjust interpretation of symbolic
15024 data on the host, and that they have absolutely no effect on the
15028 @node Remote Debugging
15029 @chapter Debugging Remote Programs
15030 @cindex remote debugging
15032 If you are trying to debug a program running on a machine that cannot run
15033 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15034 For example, you might use remote debugging on an operating system kernel,
15035 or on a small system which does not have a general purpose operating system
15036 powerful enough to run a full-featured debugger.
15038 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15039 to make this work with particular debugging targets. In addition,
15040 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15041 but not specific to any particular target system) which you can use if you
15042 write the remote stubs---the code that runs on the remote system to
15043 communicate with @value{GDBN}.
15045 Other remote targets may be available in your
15046 configuration of @value{GDBN}; use @code{help target} to list them.
15049 * Connecting:: Connecting to a remote target
15050 * File Transfer:: Sending files to a remote system
15051 * Server:: Using the gdbserver program
15052 * Remote Configuration:: Remote configuration
15053 * Remote Stub:: Implementing a remote stub
15057 @section Connecting to a Remote Target
15059 On the @value{GDBN} host machine, you will need an unstripped copy of
15060 your program, since @value{GDBN} needs symbol and debugging information.
15061 Start up @value{GDBN} as usual, using the name of the local copy of your
15062 program as the first argument.
15064 @cindex @code{target remote}
15065 @value{GDBN} can communicate with the target over a serial line, or
15066 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15067 each case, @value{GDBN} uses the same protocol for debugging your
15068 program; only the medium carrying the debugging packets varies. The
15069 @code{target remote} command establishes a connection to the target.
15070 Its arguments indicate which medium to use:
15074 @item target remote @var{serial-device}
15075 @cindex serial line, @code{target remote}
15076 Use @var{serial-device} to communicate with the target. For example,
15077 to use a serial line connected to the device named @file{/dev/ttyb}:
15080 target remote /dev/ttyb
15083 If you're using a serial line, you may want to give @value{GDBN} the
15084 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15085 (@pxref{Remote Configuration, set remotebaud}) before the
15086 @code{target} command.
15088 @item target remote @code{@var{host}:@var{port}}
15089 @itemx target remote @code{tcp:@var{host}:@var{port}}
15090 @cindex @acronym{TCP} port, @code{target remote}
15091 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15092 The @var{host} may be either a host name or a numeric @acronym{IP}
15093 address; @var{port} must be a decimal number. The @var{host} could be
15094 the target machine itself, if it is directly connected to the net, or
15095 it might be a terminal server which in turn has a serial line to the
15098 For example, to connect to port 2828 on a terminal server named
15102 target remote manyfarms:2828
15105 If your remote target is actually running on the same machine as your
15106 debugger session (e.g.@: a simulator for your target running on the
15107 same host), you can omit the hostname. For example, to connect to
15108 port 1234 on your local machine:
15111 target remote :1234
15115 Note that the colon is still required here.
15117 @item target remote @code{udp:@var{host}:@var{port}}
15118 @cindex @acronym{UDP} port, @code{target remote}
15119 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15120 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15123 target remote udp:manyfarms:2828
15126 When using a @acronym{UDP} connection for remote debugging, you should
15127 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15128 can silently drop packets on busy or unreliable networks, which will
15129 cause havoc with your debugging session.
15131 @item target remote | @var{command}
15132 @cindex pipe, @code{target remote} to
15133 Run @var{command} in the background and communicate with it using a
15134 pipe. The @var{command} is a shell command, to be parsed and expanded
15135 by the system's command shell, @code{/bin/sh}; it should expect remote
15136 protocol packets on its standard input, and send replies on its
15137 standard output. You could use this to run a stand-alone simulator
15138 that speaks the remote debugging protocol, to make net connections
15139 using programs like @code{ssh}, or for other similar tricks.
15141 If @var{command} closes its standard output (perhaps by exiting),
15142 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15143 program has already exited, this will have no effect.)
15147 Once the connection has been established, you can use all the usual
15148 commands to examine and change data. The remote program is already
15149 running; you can use @kbd{step} and @kbd{continue}, and you do not
15150 need to use @kbd{run}.
15152 @cindex interrupting remote programs
15153 @cindex remote programs, interrupting
15154 Whenever @value{GDBN} is waiting for the remote program, if you type the
15155 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15156 program. This may or may not succeed, depending in part on the hardware
15157 and the serial drivers the remote system uses. If you type the
15158 interrupt character once again, @value{GDBN} displays this prompt:
15161 Interrupted while waiting for the program.
15162 Give up (and stop debugging it)? (y or n)
15165 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15166 (If you decide you want to try again later, you can use @samp{target
15167 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15168 goes back to waiting.
15171 @kindex detach (remote)
15173 When you have finished debugging the remote program, you can use the
15174 @code{detach} command to release it from @value{GDBN} control.
15175 Detaching from the target normally resumes its execution, but the results
15176 will depend on your particular remote stub. After the @code{detach}
15177 command, @value{GDBN} is free to connect to another target.
15181 The @code{disconnect} command behaves like @code{detach}, except that
15182 the target is generally not resumed. It will wait for @value{GDBN}
15183 (this instance or another one) to connect and continue debugging. After
15184 the @code{disconnect} command, @value{GDBN} is again free to connect to
15187 @cindex send command to remote monitor
15188 @cindex extend @value{GDBN} for remote targets
15189 @cindex add new commands for external monitor
15191 @item monitor @var{cmd}
15192 This command allows you to send arbitrary commands directly to the
15193 remote monitor. Since @value{GDBN} doesn't care about the commands it
15194 sends like this, this command is the way to extend @value{GDBN}---you
15195 can add new commands that only the external monitor will understand
15199 @node File Transfer
15200 @section Sending files to a remote system
15201 @cindex remote target, file transfer
15202 @cindex file transfer
15203 @cindex sending files to remote systems
15205 Some remote targets offer the ability to transfer files over the same
15206 connection used to communicate with @value{GDBN}. This is convenient
15207 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15208 running @code{gdbserver} over a network interface. For other targets,
15209 e.g.@: embedded devices with only a single serial port, this may be
15210 the only way to upload or download files.
15212 Not all remote targets support these commands.
15216 @item remote put @var{hostfile} @var{targetfile}
15217 Copy file @var{hostfile} from the host system (the machine running
15218 @value{GDBN}) to @var{targetfile} on the target system.
15221 @item remote get @var{targetfile} @var{hostfile}
15222 Copy file @var{targetfile} from the target system to @var{hostfile}
15223 on the host system.
15225 @kindex remote delete
15226 @item remote delete @var{targetfile}
15227 Delete @var{targetfile} from the target system.
15232 @section Using the @code{gdbserver} Program
15235 @cindex remote connection without stubs
15236 @code{gdbserver} is a control program for Unix-like systems, which
15237 allows you to connect your program with a remote @value{GDBN} via
15238 @code{target remote}---but without linking in the usual debugging stub.
15240 @code{gdbserver} is not a complete replacement for the debugging stubs,
15241 because it requires essentially the same operating-system facilities
15242 that @value{GDBN} itself does. In fact, a system that can run
15243 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15244 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15245 because it is a much smaller program than @value{GDBN} itself. It is
15246 also easier to port than all of @value{GDBN}, so you may be able to get
15247 started more quickly on a new system by using @code{gdbserver}.
15248 Finally, if you develop code for real-time systems, you may find that
15249 the tradeoffs involved in real-time operation make it more convenient to
15250 do as much development work as possible on another system, for example
15251 by cross-compiling. You can use @code{gdbserver} to make a similar
15252 choice for debugging.
15254 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15255 or a TCP connection, using the standard @value{GDBN} remote serial
15259 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15260 Do not run @code{gdbserver} connected to any public network; a
15261 @value{GDBN} connection to @code{gdbserver} provides access to the
15262 target system with the same privileges as the user running
15266 @subsection Running @code{gdbserver}
15267 @cindex arguments, to @code{gdbserver}
15269 Run @code{gdbserver} on the target system. You need a copy of the
15270 program you want to debug, including any libraries it requires.
15271 @code{gdbserver} does not need your program's symbol table, so you can
15272 strip the program if necessary to save space. @value{GDBN} on the host
15273 system does all the symbol handling.
15275 To use the server, you must tell it how to communicate with @value{GDBN};
15276 the name of your program; and the arguments for your program. The usual
15280 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15283 @var{comm} is either a device name (to use a serial line) or a TCP
15284 hostname and portnumber. For example, to debug Emacs with the argument
15285 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15289 target> gdbserver /dev/com1 emacs foo.txt
15292 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15295 To use a TCP connection instead of a serial line:
15298 target> gdbserver host:2345 emacs foo.txt
15301 The only difference from the previous example is the first argument,
15302 specifying that you are communicating with the host @value{GDBN} via
15303 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15304 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15305 (Currently, the @samp{host} part is ignored.) You can choose any number
15306 you want for the port number as long as it does not conflict with any
15307 TCP ports already in use on the target system (for example, @code{23} is
15308 reserved for @code{telnet}).@footnote{If you choose a port number that
15309 conflicts with another service, @code{gdbserver} prints an error message
15310 and exits.} You must use the same port number with the host @value{GDBN}
15311 @code{target remote} command.
15313 @subsubsection Attaching to a Running Program
15315 On some targets, @code{gdbserver} can also attach to running programs.
15316 This is accomplished via the @code{--attach} argument. The syntax is:
15319 target> gdbserver --attach @var{comm} @var{pid}
15322 @var{pid} is the process ID of a currently running process. It isn't necessary
15323 to point @code{gdbserver} at a binary for the running process.
15326 @cindex attach to a program by name
15327 You can debug processes by name instead of process ID if your target has the
15328 @code{pidof} utility:
15331 target> gdbserver --attach @var{comm} `pidof @var{program}`
15334 In case more than one copy of @var{program} is running, or @var{program}
15335 has multiple threads, most versions of @code{pidof} support the
15336 @code{-s} option to only return the first process ID.
15338 @subsubsection Multi-Process Mode for @code{gdbserver}
15339 @cindex gdbserver, multiple processes
15340 @cindex multiple processes with gdbserver
15342 When you connect to @code{gdbserver} using @code{target remote},
15343 @code{gdbserver} debugs the specified program only once. When the
15344 program exits, or you detach from it, @value{GDBN} closes the connection
15345 and @code{gdbserver} exits.
15347 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15348 enters multi-process mode. When the debugged program exits, or you
15349 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15350 though no program is running. The @code{run} and @code{attach}
15351 commands instruct @code{gdbserver} to run or attach to a new program.
15352 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15353 remote exec-file}) to select the program to run. Command line
15354 arguments are supported, except for wildcard expansion and I/O
15355 redirection (@pxref{Arguments}).
15357 To start @code{gdbserver} without supplying an initial command to run
15358 or process ID to attach, use the @option{--multi} command line option.
15359 Then you can connect using @kbd{target extended-remote} and start
15360 the program you want to debug.
15362 @code{gdbserver} does not automatically exit in multi-process mode.
15363 You can terminate it by using @code{monitor exit}
15364 (@pxref{Monitor Commands for gdbserver}).
15366 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15368 The @option{--debug} option tells @code{gdbserver} to display extra
15369 status information about the debugging process. The
15370 @option{--remote-debug} option tells @code{gdbserver} to display
15371 remote protocol debug output. These options are intended for
15372 @code{gdbserver} development and for bug reports to the developers.
15374 The @option{--wrapper} option specifies a wrapper to launch programs
15375 for debugging. The option should be followed by the name of the
15376 wrapper, then any command-line arguments to pass to the wrapper, then
15377 @kbd{--} indicating the end of the wrapper arguments.
15379 @code{gdbserver} runs the specified wrapper program with a combined
15380 command line including the wrapper arguments, then the name of the
15381 program to debug, then any arguments to the program. The wrapper
15382 runs until it executes your program, and then @value{GDBN} gains control.
15384 You can use any program that eventually calls @code{execve} with
15385 its arguments as a wrapper. Several standard Unix utilities do
15386 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15387 with @code{exec "$@@"} will also work.
15389 For example, you can use @code{env} to pass an environment variable to
15390 the debugged program, without setting the variable in @code{gdbserver}'s
15394 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15397 @subsection Connecting to @code{gdbserver}
15399 Run @value{GDBN} on the host system.
15401 First make sure you have the necessary symbol files. Load symbols for
15402 your application using the @code{file} command before you connect. Use
15403 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15404 was compiled with the correct sysroot using @code{--with-sysroot}).
15406 The symbol file and target libraries must exactly match the executable
15407 and libraries on the target, with one exception: the files on the host
15408 system should not be stripped, even if the files on the target system
15409 are. Mismatched or missing files will lead to confusing results
15410 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15411 files may also prevent @code{gdbserver} from debugging multi-threaded
15414 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15415 For TCP connections, you must start up @code{gdbserver} prior to using
15416 the @code{target remote} command. Otherwise you may get an error whose
15417 text depends on the host system, but which usually looks something like
15418 @samp{Connection refused}. Don't use the @code{load}
15419 command in @value{GDBN} when using @code{gdbserver}, since the program is
15420 already on the target.
15422 @subsection Monitor Commands for @code{gdbserver}
15423 @cindex monitor commands, for @code{gdbserver}
15424 @anchor{Monitor Commands for gdbserver}
15426 During a @value{GDBN} session using @code{gdbserver}, you can use the
15427 @code{monitor} command to send special requests to @code{gdbserver}.
15428 Here are the available commands.
15432 List the available monitor commands.
15434 @item monitor set debug 0
15435 @itemx monitor set debug 1
15436 Disable or enable general debugging messages.
15438 @item monitor set remote-debug 0
15439 @itemx monitor set remote-debug 1
15440 Disable or enable specific debugging messages associated with the remote
15441 protocol (@pxref{Remote Protocol}).
15443 @item monitor set libthread-db-search-path [PATH]
15444 @cindex gdbserver, search path for @code{libthread_db}
15445 When this command is issued, @var{path} is a colon-separated list of
15446 directories to search for @code{libthread_db} (@pxref{Threads,,set
15447 libthread-db-search-path}). If you omit @var{path},
15448 @samp{libthread-db-search-path} will be reset to an empty list.
15451 Tell gdbserver to exit immediately. This command should be followed by
15452 @code{disconnect} to close the debugging session. @code{gdbserver} will
15453 detach from any attached processes and kill any processes it created.
15454 Use @code{monitor exit} to terminate @code{gdbserver} at the end
15455 of a multi-process mode debug session.
15459 @node Remote Configuration
15460 @section Remote Configuration
15463 @kindex show remote
15464 This section documents the configuration options available when
15465 debugging remote programs. For the options related to the File I/O
15466 extensions of the remote protocol, see @ref{system,
15467 system-call-allowed}.
15470 @item set remoteaddresssize @var{bits}
15471 @cindex address size for remote targets
15472 @cindex bits in remote address
15473 Set the maximum size of address in a memory packet to the specified
15474 number of bits. @value{GDBN} will mask off the address bits above
15475 that number, when it passes addresses to the remote target. The
15476 default value is the number of bits in the target's address.
15478 @item show remoteaddresssize
15479 Show the current value of remote address size in bits.
15481 @item set remotebaud @var{n}
15482 @cindex baud rate for remote targets
15483 Set the baud rate for the remote serial I/O to @var{n} baud. The
15484 value is used to set the speed of the serial port used for debugging
15487 @item show remotebaud
15488 Show the current speed of the remote connection.
15490 @item set remotebreak
15491 @cindex interrupt remote programs
15492 @cindex BREAK signal instead of Ctrl-C
15493 @anchor{set remotebreak}
15494 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
15495 when you type @kbd{Ctrl-c} to interrupt the program running
15496 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
15497 character instead. The default is off, since most remote systems
15498 expect to see @samp{Ctrl-C} as the interrupt signal.
15500 @item show remotebreak
15501 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
15502 interrupt the remote program.
15504 @item set remoteflow on
15505 @itemx set remoteflow off
15506 @kindex set remoteflow
15507 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
15508 on the serial port used to communicate to the remote target.
15510 @item show remoteflow
15511 @kindex show remoteflow
15512 Show the current setting of hardware flow control.
15514 @item set remotelogbase @var{base}
15515 Set the base (a.k.a.@: radix) of logging serial protocol
15516 communications to @var{base}. Supported values of @var{base} are:
15517 @code{ascii}, @code{octal}, and @code{hex}. The default is
15520 @item show remotelogbase
15521 Show the current setting of the radix for logging remote serial
15524 @item set remotelogfile @var{file}
15525 @cindex record serial communications on file
15526 Record remote serial communications on the named @var{file}. The
15527 default is not to record at all.
15529 @item show remotelogfile.
15530 Show the current setting of the file name on which to record the
15531 serial communications.
15533 @item set remotetimeout @var{num}
15534 @cindex timeout for serial communications
15535 @cindex remote timeout
15536 Set the timeout limit to wait for the remote target to respond to
15537 @var{num} seconds. The default is 2 seconds.
15539 @item show remotetimeout
15540 Show the current number of seconds to wait for the remote target
15543 @cindex limit hardware breakpoints and watchpoints
15544 @cindex remote target, limit break- and watchpoints
15545 @anchor{set remote hardware-watchpoint-limit}
15546 @anchor{set remote hardware-breakpoint-limit}
15547 @item set remote hardware-watchpoint-limit @var{limit}
15548 @itemx set remote hardware-breakpoint-limit @var{limit}
15549 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15550 watchpoints. A limit of -1, the default, is treated as unlimited.
15552 @item set remote exec-file @var{filename}
15553 @itemx show remote exec-file
15554 @anchor{set remote exec-file}
15555 @cindex executable file, for remote target
15556 Select the file used for @code{run} with @code{target
15557 extended-remote}. This should be set to a filename valid on the
15558 target system. If it is not set, the target will use a default
15559 filename (e.g.@: the last program run).
15561 @item set remote interrupt-sequence
15562 @cindex interrupt remote programs
15563 @cindex select Ctrl-C, BREAK or BREAK-g
15564 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
15565 @samp{BREAK-g} as the
15566 sequence to the remote target in order to interrupt the execution.
15567 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
15568 is high level of serial line for some certain time.
15569 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
15570 It is @code{BREAK} signal followed by character @code{g}.
15572 @item show interrupt-sequence
15573 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
15574 is sent by @value{GDBN} to interrupt the remote program.
15575 @code{BREAK-g} is BREAK signal followed by @code{g} and
15576 also known as Magic SysRq g.
15578 @item set remote interrupt-on-connect
15579 @cindex send interrupt-sequence on start
15580 Specify whether interrupt-sequence is sent to remote target when
15581 @value{GDBN} connects to it. This is mostly needed when you debug
15582 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
15583 which is known as Magic SysRq g in order to connect @value{GDBN}.
15585 @item show interrupt-on-connect
15586 Show whether interrupt-sequence is sent
15587 to remote target when @value{GDBN} connects to it.
15591 @item set tcp auto-retry on
15592 @cindex auto-retry, for remote TCP target
15593 Enable auto-retry for remote TCP connections. This is useful if the remote
15594 debugging agent is launched in parallel with @value{GDBN}; there is a race
15595 condition because the agent may not become ready to accept the connection
15596 before @value{GDBN} attempts to connect. When auto-retry is
15597 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
15598 to establish the connection using the timeout specified by
15599 @code{set tcp connect-timeout}.
15601 @item set tcp auto-retry off
15602 Do not auto-retry failed TCP connections.
15604 @item show tcp auto-retry
15605 Show the current auto-retry setting.
15607 @item set tcp connect-timeout @var{seconds}
15608 @cindex connection timeout, for remote TCP target
15609 @cindex timeout, for remote target connection
15610 Set the timeout for establishing a TCP connection to the remote target to
15611 @var{seconds}. The timeout affects both polling to retry failed connections
15612 (enabled by @code{set tcp auto-retry on}) and waiting for connections
15613 that are merely slow to complete, and represents an approximate cumulative
15616 @item show tcp connect-timeout
15617 Show the current connection timeout setting.
15620 @cindex remote packets, enabling and disabling
15621 The @value{GDBN} remote protocol autodetects the packets supported by
15622 your debugging stub. If you need to override the autodetection, you
15623 can use these commands to enable or disable individual packets. Each
15624 packet can be set to @samp{on} (the remote target supports this
15625 packet), @samp{off} (the remote target does not support this packet),
15626 or @samp{auto} (detect remote target support for this packet). They
15627 all default to @samp{auto}. For more information about each packet,
15628 see @ref{Remote Protocol}.
15630 During normal use, you should not have to use any of these commands.
15631 If you do, that may be a bug in your remote debugging stub, or a bug
15632 in @value{GDBN}. You may want to report the problem to the
15633 @value{GDBN} developers.
15635 For each packet @var{name}, the command to enable or disable the
15636 packet is @code{set remote @var{name}-packet}. The available settings
15639 @multitable @columnfractions 0.28 0.32 0.25
15642 @tab Related Features
15644 @item @code{fetch-register}
15646 @tab @code{info registers}
15648 @item @code{set-register}
15652 @item @code{binary-download}
15654 @tab @code{load}, @code{set}
15656 @item @code{read-aux-vector}
15657 @tab @code{qXfer:auxv:read}
15658 @tab @code{info auxv}
15660 @item @code{symbol-lookup}
15661 @tab @code{qSymbol}
15662 @tab Detecting multiple threads
15664 @item @code{attach}
15665 @tab @code{vAttach}
15668 @item @code{verbose-resume}
15670 @tab Stepping or resuming multiple threads
15676 @item @code{software-breakpoint}
15680 @item @code{hardware-breakpoint}
15684 @item @code{write-watchpoint}
15688 @item @code{read-watchpoint}
15692 @item @code{access-watchpoint}
15696 @item @code{target-features}
15697 @tab @code{qXfer:features:read}
15698 @tab @code{set architecture}
15700 @item @code{library-info}
15701 @tab @code{qXfer:libraries:read}
15702 @tab @code{info sharedlibrary}
15704 @item @code{memory-map}
15705 @tab @code{qXfer:memory-map:read}
15706 @tab @code{info mem}
15708 @item @code{read-spu-object}
15709 @tab @code{qXfer:spu:read}
15710 @tab @code{info spu}
15712 @item @code{write-spu-object}
15713 @tab @code{qXfer:spu:write}
15714 @tab @code{info spu}
15716 @item @code{read-siginfo-object}
15717 @tab @code{qXfer:siginfo:read}
15718 @tab @code{print $_siginfo}
15720 @item @code{write-siginfo-object}
15721 @tab @code{qXfer:siginfo:write}
15722 @tab @code{set $_siginfo}
15724 @item @code{threads}
15725 @tab @code{qXfer:threads:read}
15726 @tab @code{info threads}
15728 @item @code{get-thread-local-@*storage-address}
15729 @tab @code{qGetTLSAddr}
15730 @tab Displaying @code{__thread} variables
15732 @item @code{search-memory}
15733 @tab @code{qSearch:memory}
15736 @item @code{supported-packets}
15737 @tab @code{qSupported}
15738 @tab Remote communications parameters
15740 @item @code{pass-signals}
15741 @tab @code{QPassSignals}
15742 @tab @code{handle @var{signal}}
15744 @item @code{hostio-close-packet}
15745 @tab @code{vFile:close}
15746 @tab @code{remote get}, @code{remote put}
15748 @item @code{hostio-open-packet}
15749 @tab @code{vFile:open}
15750 @tab @code{remote get}, @code{remote put}
15752 @item @code{hostio-pread-packet}
15753 @tab @code{vFile:pread}
15754 @tab @code{remote get}, @code{remote put}
15756 @item @code{hostio-pwrite-packet}
15757 @tab @code{vFile:pwrite}
15758 @tab @code{remote get}, @code{remote put}
15760 @item @code{hostio-unlink-packet}
15761 @tab @code{vFile:unlink}
15762 @tab @code{remote delete}
15764 @item @code{noack-packet}
15765 @tab @code{QStartNoAckMode}
15766 @tab Packet acknowledgment
15768 @item @code{osdata}
15769 @tab @code{qXfer:osdata:read}
15770 @tab @code{info os}
15772 @item @code{query-attached}
15773 @tab @code{qAttached}
15774 @tab Querying remote process attach state.
15778 @section Implementing a Remote Stub
15780 @cindex debugging stub, example
15781 @cindex remote stub, example
15782 @cindex stub example, remote debugging
15783 The stub files provided with @value{GDBN} implement the target side of the
15784 communication protocol, and the @value{GDBN} side is implemented in the
15785 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
15786 these subroutines to communicate, and ignore the details. (If you're
15787 implementing your own stub file, you can still ignore the details: start
15788 with one of the existing stub files. @file{sparc-stub.c} is the best
15789 organized, and therefore the easiest to read.)
15791 @cindex remote serial debugging, overview
15792 To debug a program running on another machine (the debugging
15793 @dfn{target} machine), you must first arrange for all the usual
15794 prerequisites for the program to run by itself. For example, for a C
15799 A startup routine to set up the C runtime environment; these usually
15800 have a name like @file{crt0}. The startup routine may be supplied by
15801 your hardware supplier, or you may have to write your own.
15804 A C subroutine library to support your program's
15805 subroutine calls, notably managing input and output.
15808 A way of getting your program to the other machine---for example, a
15809 download program. These are often supplied by the hardware
15810 manufacturer, but you may have to write your own from hardware
15814 The next step is to arrange for your program to use a serial port to
15815 communicate with the machine where @value{GDBN} is running (the @dfn{host}
15816 machine). In general terms, the scheme looks like this:
15820 @value{GDBN} already understands how to use this protocol; when everything
15821 else is set up, you can simply use the @samp{target remote} command
15822 (@pxref{Targets,,Specifying a Debugging Target}).
15824 @item On the target,
15825 you must link with your program a few special-purpose subroutines that
15826 implement the @value{GDBN} remote serial protocol. The file containing these
15827 subroutines is called a @dfn{debugging stub}.
15829 On certain remote targets, you can use an auxiliary program
15830 @code{gdbserver} instead of linking a stub into your program.
15831 @xref{Server,,Using the @code{gdbserver} Program}, for details.
15834 The debugging stub is specific to the architecture of the remote
15835 machine; for example, use @file{sparc-stub.c} to debug programs on
15838 @cindex remote serial stub list
15839 These working remote stubs are distributed with @value{GDBN}:
15844 @cindex @file{i386-stub.c}
15847 For Intel 386 and compatible architectures.
15850 @cindex @file{m68k-stub.c}
15851 @cindex Motorola 680x0
15853 For Motorola 680x0 architectures.
15856 @cindex @file{sh-stub.c}
15859 For Renesas SH architectures.
15862 @cindex @file{sparc-stub.c}
15864 For @sc{sparc} architectures.
15866 @item sparcl-stub.c
15867 @cindex @file{sparcl-stub.c}
15870 For Fujitsu @sc{sparclite} architectures.
15874 The @file{README} file in the @value{GDBN} distribution may list other
15875 recently added stubs.
15878 * Stub Contents:: What the stub can do for you
15879 * Bootstrapping:: What you must do for the stub
15880 * Debug Session:: Putting it all together
15883 @node Stub Contents
15884 @subsection What the Stub Can Do for You
15886 @cindex remote serial stub
15887 The debugging stub for your architecture supplies these three
15891 @item set_debug_traps
15892 @findex set_debug_traps
15893 @cindex remote serial stub, initialization
15894 This routine arranges for @code{handle_exception} to run when your
15895 program stops. You must call this subroutine explicitly near the
15896 beginning of your program.
15898 @item handle_exception
15899 @findex handle_exception
15900 @cindex remote serial stub, main routine
15901 This is the central workhorse, but your program never calls it
15902 explicitly---the setup code arranges for @code{handle_exception} to
15903 run when a trap is triggered.
15905 @code{handle_exception} takes control when your program stops during
15906 execution (for example, on a breakpoint), and mediates communications
15907 with @value{GDBN} on the host machine. This is where the communications
15908 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
15909 representative on the target machine. It begins by sending summary
15910 information on the state of your program, then continues to execute,
15911 retrieving and transmitting any information @value{GDBN} needs, until you
15912 execute a @value{GDBN} command that makes your program resume; at that point,
15913 @code{handle_exception} returns control to your own code on the target
15917 @cindex @code{breakpoint} subroutine, remote
15918 Use this auxiliary subroutine to make your program contain a
15919 breakpoint. Depending on the particular situation, this may be the only
15920 way for @value{GDBN} to get control. For instance, if your target
15921 machine has some sort of interrupt button, you won't need to call this;
15922 pressing the interrupt button transfers control to
15923 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
15924 simply receiving characters on the serial port may also trigger a trap;
15925 again, in that situation, you don't need to call @code{breakpoint} from
15926 your own program---simply running @samp{target remote} from the host
15927 @value{GDBN} session gets control.
15929 Call @code{breakpoint} if none of these is true, or if you simply want
15930 to make certain your program stops at a predetermined point for the
15931 start of your debugging session.
15934 @node Bootstrapping
15935 @subsection What You Must Do for the Stub
15937 @cindex remote stub, support routines
15938 The debugging stubs that come with @value{GDBN} are set up for a particular
15939 chip architecture, but they have no information about the rest of your
15940 debugging target machine.
15942 First of all you need to tell the stub how to communicate with the
15946 @item int getDebugChar()
15947 @findex getDebugChar
15948 Write this subroutine to read a single character from the serial port.
15949 It may be identical to @code{getchar} for your target system; a
15950 different name is used to allow you to distinguish the two if you wish.
15952 @item void putDebugChar(int)
15953 @findex putDebugChar
15954 Write this subroutine to write a single character to the serial port.
15955 It may be identical to @code{putchar} for your target system; a
15956 different name is used to allow you to distinguish the two if you wish.
15959 @cindex control C, and remote debugging
15960 @cindex interrupting remote targets
15961 If you want @value{GDBN} to be able to stop your program while it is
15962 running, you need to use an interrupt-driven serial driver, and arrange
15963 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
15964 character). That is the character which @value{GDBN} uses to tell the
15965 remote system to stop.
15967 Getting the debugging target to return the proper status to @value{GDBN}
15968 probably requires changes to the standard stub; one quick and dirty way
15969 is to just execute a breakpoint instruction (the ``dirty'' part is that
15970 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
15972 Other routines you need to supply are:
15975 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
15976 @findex exceptionHandler
15977 Write this function to install @var{exception_address} in the exception
15978 handling tables. You need to do this because the stub does not have any
15979 way of knowing what the exception handling tables on your target system
15980 are like (for example, the processor's table might be in @sc{rom},
15981 containing entries which point to a table in @sc{ram}).
15982 @var{exception_number} is the exception number which should be changed;
15983 its meaning is architecture-dependent (for example, different numbers
15984 might represent divide by zero, misaligned access, etc). When this
15985 exception occurs, control should be transferred directly to
15986 @var{exception_address}, and the processor state (stack, registers,
15987 and so on) should be just as it is when a processor exception occurs. So if
15988 you want to use a jump instruction to reach @var{exception_address}, it
15989 should be a simple jump, not a jump to subroutine.
15991 For the 386, @var{exception_address} should be installed as an interrupt
15992 gate so that interrupts are masked while the handler runs. The gate
15993 should be at privilege level 0 (the most privileged level). The
15994 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
15995 help from @code{exceptionHandler}.
15997 @item void flush_i_cache()
15998 @findex flush_i_cache
15999 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16000 instruction cache, if any, on your target machine. If there is no
16001 instruction cache, this subroutine may be a no-op.
16003 On target machines that have instruction caches, @value{GDBN} requires this
16004 function to make certain that the state of your program is stable.
16008 You must also make sure this library routine is available:
16011 @item void *memset(void *, int, int)
16013 This is the standard library function @code{memset} that sets an area of
16014 memory to a known value. If you have one of the free versions of
16015 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16016 either obtain it from your hardware manufacturer, or write your own.
16019 If you do not use the GNU C compiler, you may need other standard
16020 library subroutines as well; this varies from one stub to another,
16021 but in general the stubs are likely to use any of the common library
16022 subroutines which @code{@value{NGCC}} generates as inline code.
16025 @node Debug Session
16026 @subsection Putting it All Together
16028 @cindex remote serial debugging summary
16029 In summary, when your program is ready to debug, you must follow these
16034 Make sure you have defined the supporting low-level routines
16035 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16037 @code{getDebugChar}, @code{putDebugChar},
16038 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16042 Insert these lines near the top of your program:
16050 For the 680x0 stub only, you need to provide a variable called
16051 @code{exceptionHook}. Normally you just use:
16054 void (*exceptionHook)() = 0;
16058 but if before calling @code{set_debug_traps}, you set it to point to a
16059 function in your program, that function is called when
16060 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16061 error). The function indicated by @code{exceptionHook} is called with
16062 one parameter: an @code{int} which is the exception number.
16065 Compile and link together: your program, the @value{GDBN} debugging stub for
16066 your target architecture, and the supporting subroutines.
16069 Make sure you have a serial connection between your target machine and
16070 the @value{GDBN} host, and identify the serial port on the host.
16073 @c The "remote" target now provides a `load' command, so we should
16074 @c document that. FIXME.
16075 Download your program to your target machine (or get it there by
16076 whatever means the manufacturer provides), and start it.
16079 Start @value{GDBN} on the host, and connect to the target
16080 (@pxref{Connecting,,Connecting to a Remote Target}).
16084 @node Configurations
16085 @chapter Configuration-Specific Information
16087 While nearly all @value{GDBN} commands are available for all native and
16088 cross versions of the debugger, there are some exceptions. This chapter
16089 describes things that are only available in certain configurations.
16091 There are three major categories of configurations: native
16092 configurations, where the host and target are the same, embedded
16093 operating system configurations, which are usually the same for several
16094 different processor architectures, and bare embedded processors, which
16095 are quite different from each other.
16100 * Embedded Processors::
16107 This section describes details specific to particular native
16112 * BSD libkvm Interface:: Debugging BSD kernel memory images
16113 * SVR4 Process Information:: SVR4 process information
16114 * DJGPP Native:: Features specific to the DJGPP port
16115 * Cygwin Native:: Features specific to the Cygwin port
16116 * Hurd Native:: Features specific to @sc{gnu} Hurd
16117 * Neutrino:: Features specific to QNX Neutrino
16118 * Darwin:: Features specific to Darwin
16124 On HP-UX systems, if you refer to a function or variable name that
16125 begins with a dollar sign, @value{GDBN} searches for a user or system
16126 name first, before it searches for a convenience variable.
16129 @node BSD libkvm Interface
16130 @subsection BSD libkvm Interface
16133 @cindex kernel memory image
16134 @cindex kernel crash dump
16136 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16137 interface that provides a uniform interface for accessing kernel virtual
16138 memory images, including live systems and crash dumps. @value{GDBN}
16139 uses this interface to allow you to debug live kernels and kernel crash
16140 dumps on many native BSD configurations. This is implemented as a
16141 special @code{kvm} debugging target. For debugging a live system, load
16142 the currently running kernel into @value{GDBN} and connect to the
16146 (@value{GDBP}) @b{target kvm}
16149 For debugging crash dumps, provide the file name of the crash dump as an
16153 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16156 Once connected to the @code{kvm} target, the following commands are
16162 Set current context from the @dfn{Process Control Block} (PCB) address.
16165 Set current context from proc address. This command isn't available on
16166 modern FreeBSD systems.
16169 @node SVR4 Process Information
16170 @subsection SVR4 Process Information
16172 @cindex examine process image
16173 @cindex process info via @file{/proc}
16175 Many versions of SVR4 and compatible systems provide a facility called
16176 @samp{/proc} that can be used to examine the image of a running
16177 process using file-system subroutines. If @value{GDBN} is configured
16178 for an operating system with this facility, the command @code{info
16179 proc} is available to report information about the process running
16180 your program, or about any process running on your system. @code{info
16181 proc} works only on SVR4 systems that include the @code{procfs} code.
16182 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16183 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16189 @itemx info proc @var{process-id}
16190 Summarize available information about any running process. If a
16191 process ID is specified by @var{process-id}, display information about
16192 that process; otherwise display information about the program being
16193 debugged. The summary includes the debugged process ID, the command
16194 line used to invoke it, its current working directory, and its
16195 executable file's absolute file name.
16197 On some systems, @var{process-id} can be of the form
16198 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16199 within a process. If the optional @var{pid} part is missing, it means
16200 a thread from the process being debugged (the leading @samp{/} still
16201 needs to be present, or else @value{GDBN} will interpret the number as
16202 a process ID rather than a thread ID).
16204 @item info proc mappings
16205 @cindex memory address space mappings
16206 Report the memory address space ranges accessible in the program, with
16207 information on whether the process has read, write, or execute access
16208 rights to each range. On @sc{gnu}/Linux systems, each memory range
16209 includes the object file which is mapped to that range, instead of the
16210 memory access rights to that range.
16212 @item info proc stat
16213 @itemx info proc status
16214 @cindex process detailed status information
16215 These subcommands are specific to @sc{gnu}/Linux systems. They show
16216 the process-related information, including the user ID and group ID;
16217 how many threads are there in the process; its virtual memory usage;
16218 the signals that are pending, blocked, and ignored; its TTY; its
16219 consumption of system and user time; its stack size; its @samp{nice}
16220 value; etc. For more information, see the @samp{proc} man page
16221 (type @kbd{man 5 proc} from your shell prompt).
16223 @item info proc all
16224 Show all the information about the process described under all of the
16225 above @code{info proc} subcommands.
16228 @comment These sub-options of 'info proc' were not included when
16229 @comment procfs.c was re-written. Keep their descriptions around
16230 @comment against the day when someone finds the time to put them back in.
16231 @kindex info proc times
16232 @item info proc times
16233 Starting time, user CPU time, and system CPU time for your program and
16236 @kindex info proc id
16238 Report on the process IDs related to your program: its own process ID,
16239 the ID of its parent, the process group ID, and the session ID.
16242 @item set procfs-trace
16243 @kindex set procfs-trace
16244 @cindex @code{procfs} API calls
16245 This command enables and disables tracing of @code{procfs} API calls.
16247 @item show procfs-trace
16248 @kindex show procfs-trace
16249 Show the current state of @code{procfs} API call tracing.
16251 @item set procfs-file @var{file}
16252 @kindex set procfs-file
16253 Tell @value{GDBN} to write @code{procfs} API trace to the named
16254 @var{file}. @value{GDBN} appends the trace info to the previous
16255 contents of the file. The default is to display the trace on the
16258 @item show procfs-file
16259 @kindex show procfs-file
16260 Show the file to which @code{procfs} API trace is written.
16262 @item proc-trace-entry
16263 @itemx proc-trace-exit
16264 @itemx proc-untrace-entry
16265 @itemx proc-untrace-exit
16266 @kindex proc-trace-entry
16267 @kindex proc-trace-exit
16268 @kindex proc-untrace-entry
16269 @kindex proc-untrace-exit
16270 These commands enable and disable tracing of entries into and exits
16271 from the @code{syscall} interface.
16274 @kindex info pidlist
16275 @cindex process list, QNX Neutrino
16276 For QNX Neutrino only, this command displays the list of all the
16277 processes and all the threads within each process.
16280 @kindex info meminfo
16281 @cindex mapinfo list, QNX Neutrino
16282 For QNX Neutrino only, this command displays the list of all mapinfos.
16286 @subsection Features for Debugging @sc{djgpp} Programs
16287 @cindex @sc{djgpp} debugging
16288 @cindex native @sc{djgpp} debugging
16289 @cindex MS-DOS-specific commands
16292 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16293 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16294 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
16295 top of real-mode DOS systems and their emulations.
16297 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
16298 defines a few commands specific to the @sc{djgpp} port. This
16299 subsection describes those commands.
16304 This is a prefix of @sc{djgpp}-specific commands which print
16305 information about the target system and important OS structures.
16308 @cindex MS-DOS system info
16309 @cindex free memory information (MS-DOS)
16310 @item info dos sysinfo
16311 This command displays assorted information about the underlying
16312 platform: the CPU type and features, the OS version and flavor, the
16313 DPMI version, and the available conventional and DPMI memory.
16318 @cindex segment descriptor tables
16319 @cindex descriptor tables display
16321 @itemx info dos ldt
16322 @itemx info dos idt
16323 These 3 commands display entries from, respectively, Global, Local,
16324 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
16325 tables are data structures which store a descriptor for each segment
16326 that is currently in use. The segment's selector is an index into a
16327 descriptor table; the table entry for that index holds the
16328 descriptor's base address and limit, and its attributes and access
16331 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
16332 segment (used for both data and the stack), and a DOS segment (which
16333 allows access to DOS/BIOS data structures and absolute addresses in
16334 conventional memory). However, the DPMI host will usually define
16335 additional segments in order to support the DPMI environment.
16337 @cindex garbled pointers
16338 These commands allow to display entries from the descriptor tables.
16339 Without an argument, all entries from the specified table are
16340 displayed. An argument, which should be an integer expression, means
16341 display a single entry whose index is given by the argument. For
16342 example, here's a convenient way to display information about the
16343 debugged program's data segment:
16346 @exdent @code{(@value{GDBP}) info dos ldt $ds}
16347 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
16351 This comes in handy when you want to see whether a pointer is outside
16352 the data segment's limit (i.e.@: @dfn{garbled}).
16354 @cindex page tables display (MS-DOS)
16356 @itemx info dos pte
16357 These two commands display entries from, respectively, the Page
16358 Directory and the Page Tables. Page Directories and Page Tables are
16359 data structures which control how virtual memory addresses are mapped
16360 into physical addresses. A Page Table includes an entry for every
16361 page of memory that is mapped into the program's address space; there
16362 may be several Page Tables, each one holding up to 4096 entries. A
16363 Page Directory has up to 4096 entries, one each for every Page Table
16364 that is currently in use.
16366 Without an argument, @kbd{info dos pde} displays the entire Page
16367 Directory, and @kbd{info dos pte} displays all the entries in all of
16368 the Page Tables. An argument, an integer expression, given to the
16369 @kbd{info dos pde} command means display only that entry from the Page
16370 Directory table. An argument given to the @kbd{info dos pte} command
16371 means display entries from a single Page Table, the one pointed to by
16372 the specified entry in the Page Directory.
16374 @cindex direct memory access (DMA) on MS-DOS
16375 These commands are useful when your program uses @dfn{DMA} (Direct
16376 Memory Access), which needs physical addresses to program the DMA
16379 These commands are supported only with some DPMI servers.
16381 @cindex physical address from linear address
16382 @item info dos address-pte @var{addr}
16383 This command displays the Page Table entry for a specified linear
16384 address. The argument @var{addr} is a linear address which should
16385 already have the appropriate segment's base address added to it,
16386 because this command accepts addresses which may belong to @emph{any}
16387 segment. For example, here's how to display the Page Table entry for
16388 the page where a variable @code{i} is stored:
16391 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
16392 @exdent @code{Page Table entry for address 0x11a00d30:}
16393 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
16397 This says that @code{i} is stored at offset @code{0xd30} from the page
16398 whose physical base address is @code{0x02698000}, and shows all the
16399 attributes of that page.
16401 Note that you must cast the addresses of variables to a @code{char *},
16402 since otherwise the value of @code{__djgpp_base_address}, the base
16403 address of all variables and functions in a @sc{djgpp} program, will
16404 be added using the rules of C pointer arithmetics: if @code{i} is
16405 declared an @code{int}, @value{GDBN} will add 4 times the value of
16406 @code{__djgpp_base_address} to the address of @code{i}.
16408 Here's another example, it displays the Page Table entry for the
16412 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
16413 @exdent @code{Page Table entry for address 0x29110:}
16414 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
16418 (The @code{+ 3} offset is because the transfer buffer's address is the
16419 3rd member of the @code{_go32_info_block} structure.) The output
16420 clearly shows that this DPMI server maps the addresses in conventional
16421 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
16422 linear (@code{0x29110}) addresses are identical.
16424 This command is supported only with some DPMI servers.
16427 @cindex DOS serial data link, remote debugging
16428 In addition to native debugging, the DJGPP port supports remote
16429 debugging via a serial data link. The following commands are specific
16430 to remote serial debugging in the DJGPP port of @value{GDBN}.
16433 @kindex set com1base
16434 @kindex set com1irq
16435 @kindex set com2base
16436 @kindex set com2irq
16437 @kindex set com3base
16438 @kindex set com3irq
16439 @kindex set com4base
16440 @kindex set com4irq
16441 @item set com1base @var{addr}
16442 This command sets the base I/O port address of the @file{COM1} serial
16445 @item set com1irq @var{irq}
16446 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
16447 for the @file{COM1} serial port.
16449 There are similar commands @samp{set com2base}, @samp{set com3irq},
16450 etc.@: for setting the port address and the @code{IRQ} lines for the
16453 @kindex show com1base
16454 @kindex show com1irq
16455 @kindex show com2base
16456 @kindex show com2irq
16457 @kindex show com3base
16458 @kindex show com3irq
16459 @kindex show com4base
16460 @kindex show com4irq
16461 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
16462 display the current settings of the base address and the @code{IRQ}
16463 lines used by the COM ports.
16466 @kindex info serial
16467 @cindex DOS serial port status
16468 This command prints the status of the 4 DOS serial ports. For each
16469 port, it prints whether it's active or not, its I/O base address and
16470 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
16471 counts of various errors encountered so far.
16475 @node Cygwin Native
16476 @subsection Features for Debugging MS Windows PE Executables
16477 @cindex MS Windows debugging
16478 @cindex native Cygwin debugging
16479 @cindex Cygwin-specific commands
16481 @value{GDBN} supports native debugging of MS Windows programs, including
16482 DLLs with and without symbolic debugging information.
16484 @cindex Ctrl-BREAK, MS-Windows
16485 @cindex interrupt debuggee on MS-Windows
16486 MS-Windows programs that call @code{SetConsoleMode} to switch off the
16487 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
16488 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
16489 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
16490 sequence, which can be used to interrupt the debuggee even if it
16493 There are various additional Cygwin-specific commands, described in
16494 this section. Working with DLLs that have no debugging symbols is
16495 described in @ref{Non-debug DLL Symbols}.
16500 This is a prefix of MS Windows-specific commands which print
16501 information about the target system and important OS structures.
16503 @item info w32 selector
16504 This command displays information returned by
16505 the Win32 API @code{GetThreadSelectorEntry} function.
16506 It takes an optional argument that is evaluated to
16507 a long value to give the information about this given selector.
16508 Without argument, this command displays information
16509 about the six segment registers.
16513 This is a Cygwin-specific alias of @code{info shared}.
16515 @kindex dll-symbols
16517 This command loads symbols from a dll similarly to
16518 add-sym command but without the need to specify a base address.
16520 @kindex set cygwin-exceptions
16521 @cindex debugging the Cygwin DLL
16522 @cindex Cygwin DLL, debugging
16523 @item set cygwin-exceptions @var{mode}
16524 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
16525 happen inside the Cygwin DLL. If @var{mode} is @code{off},
16526 @value{GDBN} will delay recognition of exceptions, and may ignore some
16527 exceptions which seem to be caused by internal Cygwin DLL
16528 ``bookkeeping''. This option is meant primarily for debugging the
16529 Cygwin DLL itself; the default value is @code{off} to avoid annoying
16530 @value{GDBN} users with false @code{SIGSEGV} signals.
16532 @kindex show cygwin-exceptions
16533 @item show cygwin-exceptions
16534 Displays whether @value{GDBN} will break on exceptions that happen
16535 inside the Cygwin DLL itself.
16537 @kindex set new-console
16538 @item set new-console @var{mode}
16539 If @var{mode} is @code{on} the debuggee will
16540 be started in a new console on next start.
16541 If @var{mode} is @code{off}, the debuggee will
16542 be started in the same console as the debugger.
16544 @kindex show new-console
16545 @item show new-console
16546 Displays whether a new console is used
16547 when the debuggee is started.
16549 @kindex set new-group
16550 @item set new-group @var{mode}
16551 This boolean value controls whether the debuggee should
16552 start a new group or stay in the same group as the debugger.
16553 This affects the way the Windows OS handles
16556 @kindex show new-group
16557 @item show new-group
16558 Displays current value of new-group boolean.
16560 @kindex set debugevents
16561 @item set debugevents
16562 This boolean value adds debug output concerning kernel events related
16563 to the debuggee seen by the debugger. This includes events that
16564 signal thread and process creation and exit, DLL loading and
16565 unloading, console interrupts, and debugging messages produced by the
16566 Windows @code{OutputDebugString} API call.
16568 @kindex set debugexec
16569 @item set debugexec
16570 This boolean value adds debug output concerning execute events
16571 (such as resume thread) seen by the debugger.
16573 @kindex set debugexceptions
16574 @item set debugexceptions
16575 This boolean value adds debug output concerning exceptions in the
16576 debuggee seen by the debugger.
16578 @kindex set debugmemory
16579 @item set debugmemory
16580 This boolean value adds debug output concerning debuggee memory reads
16581 and writes by the debugger.
16585 This boolean values specifies whether the debuggee is called
16586 via a shell or directly (default value is on).
16590 Displays if the debuggee will be started with a shell.
16595 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
16598 @node Non-debug DLL Symbols
16599 @subsubsection Support for DLLs without Debugging Symbols
16600 @cindex DLLs with no debugging symbols
16601 @cindex Minimal symbols and DLLs
16603 Very often on windows, some of the DLLs that your program relies on do
16604 not include symbolic debugging information (for example,
16605 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
16606 symbols in a DLL, it relies on the minimal amount of symbolic
16607 information contained in the DLL's export table. This section
16608 describes working with such symbols, known internally to @value{GDBN} as
16609 ``minimal symbols''.
16611 Note that before the debugged program has started execution, no DLLs
16612 will have been loaded. The easiest way around this problem is simply to
16613 start the program --- either by setting a breakpoint or letting the
16614 program run once to completion. It is also possible to force
16615 @value{GDBN} to load a particular DLL before starting the executable ---
16616 see the shared library information in @ref{Files}, or the
16617 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
16618 explicitly loading symbols from a DLL with no debugging information will
16619 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
16620 which may adversely affect symbol lookup performance.
16622 @subsubsection DLL Name Prefixes
16624 In keeping with the naming conventions used by the Microsoft debugging
16625 tools, DLL export symbols are made available with a prefix based on the
16626 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
16627 also entered into the symbol table, so @code{CreateFileA} is often
16628 sufficient. In some cases there will be name clashes within a program
16629 (particularly if the executable itself includes full debugging symbols)
16630 necessitating the use of the fully qualified name when referring to the
16631 contents of the DLL. Use single-quotes around the name to avoid the
16632 exclamation mark (``!'') being interpreted as a language operator.
16634 Note that the internal name of the DLL may be all upper-case, even
16635 though the file name of the DLL is lower-case, or vice-versa. Since
16636 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
16637 some confusion. If in doubt, try the @code{info functions} and
16638 @code{info variables} commands or even @code{maint print msymbols}
16639 (@pxref{Symbols}). Here's an example:
16642 (@value{GDBP}) info function CreateFileA
16643 All functions matching regular expression "CreateFileA":
16645 Non-debugging symbols:
16646 0x77e885f4 CreateFileA
16647 0x77e885f4 KERNEL32!CreateFileA
16651 (@value{GDBP}) info function !
16652 All functions matching regular expression "!":
16654 Non-debugging symbols:
16655 0x6100114c cygwin1!__assert
16656 0x61004034 cygwin1!_dll_crt0@@0
16657 0x61004240 cygwin1!dll_crt0(per_process *)
16661 @subsubsection Working with Minimal Symbols
16663 Symbols extracted from a DLL's export table do not contain very much
16664 type information. All that @value{GDBN} can do is guess whether a symbol
16665 refers to a function or variable depending on the linker section that
16666 contains the symbol. Also note that the actual contents of the memory
16667 contained in a DLL are not available unless the program is running. This
16668 means that you cannot examine the contents of a variable or disassemble
16669 a function within a DLL without a running program.
16671 Variables are generally treated as pointers and dereferenced
16672 automatically. For this reason, it is often necessary to prefix a
16673 variable name with the address-of operator (``&'') and provide explicit
16674 type information in the command. Here's an example of the type of
16678 (@value{GDBP}) print 'cygwin1!__argv'
16683 (@value{GDBP}) x 'cygwin1!__argv'
16684 0x10021610: "\230y\""
16687 And two possible solutions:
16690 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
16691 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
16695 (@value{GDBP}) x/2x &'cygwin1!__argv'
16696 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
16697 (@value{GDBP}) x/x 0x10021608
16698 0x10021608: 0x0022fd98
16699 (@value{GDBP}) x/s 0x0022fd98
16700 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
16703 Setting a break point within a DLL is possible even before the program
16704 starts execution. However, under these circumstances, @value{GDBN} can't
16705 examine the initial instructions of the function in order to skip the
16706 function's frame set-up code. You can work around this by using ``*&''
16707 to set the breakpoint at a raw memory address:
16710 (@value{GDBP}) break *&'python22!PyOS_Readline'
16711 Breakpoint 1 at 0x1e04eff0
16714 The author of these extensions is not entirely convinced that setting a
16715 break point within a shared DLL like @file{kernel32.dll} is completely
16719 @subsection Commands Specific to @sc{gnu} Hurd Systems
16720 @cindex @sc{gnu} Hurd debugging
16722 This subsection describes @value{GDBN} commands specific to the
16723 @sc{gnu} Hurd native debugging.
16728 @kindex set signals@r{, Hurd command}
16729 @kindex set sigs@r{, Hurd command}
16730 This command toggles the state of inferior signal interception by
16731 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
16732 affected by this command. @code{sigs} is a shorthand alias for
16737 @kindex show signals@r{, Hurd command}
16738 @kindex show sigs@r{, Hurd command}
16739 Show the current state of intercepting inferior's signals.
16741 @item set signal-thread
16742 @itemx set sigthread
16743 @kindex set signal-thread
16744 @kindex set sigthread
16745 This command tells @value{GDBN} which thread is the @code{libc} signal
16746 thread. That thread is run when a signal is delivered to a running
16747 process. @code{set sigthread} is the shorthand alias of @code{set
16750 @item show signal-thread
16751 @itemx show sigthread
16752 @kindex show signal-thread
16753 @kindex show sigthread
16754 These two commands show which thread will run when the inferior is
16755 delivered a signal.
16758 @kindex set stopped@r{, Hurd command}
16759 This commands tells @value{GDBN} that the inferior process is stopped,
16760 as with the @code{SIGSTOP} signal. The stopped process can be
16761 continued by delivering a signal to it.
16764 @kindex show stopped@r{, Hurd command}
16765 This command shows whether @value{GDBN} thinks the debuggee is
16768 @item set exceptions
16769 @kindex set exceptions@r{, Hurd command}
16770 Use this command to turn off trapping of exceptions in the inferior.
16771 When exception trapping is off, neither breakpoints nor
16772 single-stepping will work. To restore the default, set exception
16775 @item show exceptions
16776 @kindex show exceptions@r{, Hurd command}
16777 Show the current state of trapping exceptions in the inferior.
16779 @item set task pause
16780 @kindex set task@r{, Hurd commands}
16781 @cindex task attributes (@sc{gnu} Hurd)
16782 @cindex pause current task (@sc{gnu} Hurd)
16783 This command toggles task suspension when @value{GDBN} has control.
16784 Setting it to on takes effect immediately, and the task is suspended
16785 whenever @value{GDBN} gets control. Setting it to off will take
16786 effect the next time the inferior is continued. If this option is set
16787 to off, you can use @code{set thread default pause on} or @code{set
16788 thread pause on} (see below) to pause individual threads.
16790 @item show task pause
16791 @kindex show task@r{, Hurd commands}
16792 Show the current state of task suspension.
16794 @item set task detach-suspend-count
16795 @cindex task suspend count
16796 @cindex detach from task, @sc{gnu} Hurd
16797 This command sets the suspend count the task will be left with when
16798 @value{GDBN} detaches from it.
16800 @item show task detach-suspend-count
16801 Show the suspend count the task will be left with when detaching.
16803 @item set task exception-port
16804 @itemx set task excp
16805 @cindex task exception port, @sc{gnu} Hurd
16806 This command sets the task exception port to which @value{GDBN} will
16807 forward exceptions. The argument should be the value of the @dfn{send
16808 rights} of the task. @code{set task excp} is a shorthand alias.
16810 @item set noninvasive
16811 @cindex noninvasive task options
16812 This command switches @value{GDBN} to a mode that is the least
16813 invasive as far as interfering with the inferior is concerned. This
16814 is the same as using @code{set task pause}, @code{set exceptions}, and
16815 @code{set signals} to values opposite to the defaults.
16817 @item info send-rights
16818 @itemx info receive-rights
16819 @itemx info port-rights
16820 @itemx info port-sets
16821 @itemx info dead-names
16824 @cindex send rights, @sc{gnu} Hurd
16825 @cindex receive rights, @sc{gnu} Hurd
16826 @cindex port rights, @sc{gnu} Hurd
16827 @cindex port sets, @sc{gnu} Hurd
16828 @cindex dead names, @sc{gnu} Hurd
16829 These commands display information about, respectively, send rights,
16830 receive rights, port rights, port sets, and dead names of a task.
16831 There are also shorthand aliases: @code{info ports} for @code{info
16832 port-rights} and @code{info psets} for @code{info port-sets}.
16834 @item set thread pause
16835 @kindex set thread@r{, Hurd command}
16836 @cindex thread properties, @sc{gnu} Hurd
16837 @cindex pause current thread (@sc{gnu} Hurd)
16838 This command toggles current thread suspension when @value{GDBN} has
16839 control. Setting it to on takes effect immediately, and the current
16840 thread is suspended whenever @value{GDBN} gets control. Setting it to
16841 off will take effect the next time the inferior is continued.
16842 Normally, this command has no effect, since when @value{GDBN} has
16843 control, the whole task is suspended. However, if you used @code{set
16844 task pause off} (see above), this command comes in handy to suspend
16845 only the current thread.
16847 @item show thread pause
16848 @kindex show thread@r{, Hurd command}
16849 This command shows the state of current thread suspension.
16851 @item set thread run
16852 This command sets whether the current thread is allowed to run.
16854 @item show thread run
16855 Show whether the current thread is allowed to run.
16857 @item set thread detach-suspend-count
16858 @cindex thread suspend count, @sc{gnu} Hurd
16859 @cindex detach from thread, @sc{gnu} Hurd
16860 This command sets the suspend count @value{GDBN} will leave on a
16861 thread when detaching. This number is relative to the suspend count
16862 found by @value{GDBN} when it notices the thread; use @code{set thread
16863 takeover-suspend-count} to force it to an absolute value.
16865 @item show thread detach-suspend-count
16866 Show the suspend count @value{GDBN} will leave on the thread when
16869 @item set thread exception-port
16870 @itemx set thread excp
16871 Set the thread exception port to which to forward exceptions. This
16872 overrides the port set by @code{set task exception-port} (see above).
16873 @code{set thread excp} is the shorthand alias.
16875 @item set thread takeover-suspend-count
16876 Normally, @value{GDBN}'s thread suspend counts are relative to the
16877 value @value{GDBN} finds when it notices each thread. This command
16878 changes the suspend counts to be absolute instead.
16880 @item set thread default
16881 @itemx show thread default
16882 @cindex thread default settings, @sc{gnu} Hurd
16883 Each of the above @code{set thread} commands has a @code{set thread
16884 default} counterpart (e.g., @code{set thread default pause}, @code{set
16885 thread default exception-port}, etc.). The @code{thread default}
16886 variety of commands sets the default thread properties for all
16887 threads; you can then change the properties of individual threads with
16888 the non-default commands.
16893 @subsection QNX Neutrino
16894 @cindex QNX Neutrino
16896 @value{GDBN} provides the following commands specific to the QNX
16900 @item set debug nto-debug
16901 @kindex set debug nto-debug
16902 When set to on, enables debugging messages specific to the QNX
16905 @item show debug nto-debug
16906 @kindex show debug nto-debug
16907 Show the current state of QNX Neutrino messages.
16914 @value{GDBN} provides the following commands specific to the Darwin target:
16917 @item set debug darwin @var{num}
16918 @kindex set debug darwin
16919 When set to a non zero value, enables debugging messages specific to
16920 the Darwin support. Higher values produce more verbose output.
16922 @item show debug darwin
16923 @kindex show debug darwin
16924 Show the current state of Darwin messages.
16926 @item set debug mach-o @var{num}
16927 @kindex set debug mach-o
16928 When set to a non zero value, enables debugging messages while
16929 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
16930 file format used on Darwin for object and executable files.) Higher
16931 values produce more verbose output. This is a command to diagnose
16932 problems internal to @value{GDBN} and should not be needed in normal
16935 @item show debug mach-o
16936 @kindex show debug mach-o
16937 Show the current state of Mach-O file messages.
16939 @item set mach-exceptions on
16940 @itemx set mach-exceptions off
16941 @kindex set mach-exceptions
16942 On Darwin, faults are first reported as a Mach exception and are then
16943 mapped to a Posix signal. Use this command to turn on trapping of
16944 Mach exceptions in the inferior. This might be sometimes useful to
16945 better understand the cause of a fault. The default is off.
16947 @item show mach-exceptions
16948 @kindex show mach-exceptions
16949 Show the current state of exceptions trapping.
16954 @section Embedded Operating Systems
16956 This section describes configurations involving the debugging of
16957 embedded operating systems that are available for several different
16961 * VxWorks:: Using @value{GDBN} with VxWorks
16964 @value{GDBN} includes the ability to debug programs running on
16965 various real-time operating systems.
16968 @subsection Using @value{GDBN} with VxWorks
16974 @kindex target vxworks
16975 @item target vxworks @var{machinename}
16976 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
16977 is the target system's machine name or IP address.
16981 On VxWorks, @code{load} links @var{filename} dynamically on the
16982 current target system as well as adding its symbols in @value{GDBN}.
16984 @value{GDBN} enables developers to spawn and debug tasks running on networked
16985 VxWorks targets from a Unix host. Already-running tasks spawned from
16986 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
16987 both the Unix host and on the VxWorks target. The program
16988 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
16989 installed with the name @code{vxgdb}, to distinguish it from a
16990 @value{GDBN} for debugging programs on the host itself.)
16993 @item VxWorks-timeout @var{args}
16994 @kindex vxworks-timeout
16995 All VxWorks-based targets now support the option @code{vxworks-timeout}.
16996 This option is set by the user, and @var{args} represents the number of
16997 seconds @value{GDBN} waits for responses to rpc's. You might use this if
16998 your VxWorks target is a slow software simulator or is on the far side
16999 of a thin network line.
17002 The following information on connecting to VxWorks was current when
17003 this manual was produced; newer releases of VxWorks may use revised
17006 @findex INCLUDE_RDB
17007 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17008 to include the remote debugging interface routines in the VxWorks
17009 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17010 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17011 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17012 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17013 information on configuring and remaking VxWorks, see the manufacturer's
17015 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17017 Once you have included @file{rdb.a} in your VxWorks system image and set
17018 your Unix execution search path to find @value{GDBN}, you are ready to
17019 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17020 @code{vxgdb}, depending on your installation).
17022 @value{GDBN} comes up showing the prompt:
17029 * VxWorks Connection:: Connecting to VxWorks
17030 * VxWorks Download:: VxWorks download
17031 * VxWorks Attach:: Running tasks
17034 @node VxWorks Connection
17035 @subsubsection Connecting to VxWorks
17037 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17038 network. To connect to a target whose host name is ``@code{tt}'', type:
17041 (vxgdb) target vxworks tt
17045 @value{GDBN} displays messages like these:
17048 Attaching remote machine across net...
17053 @value{GDBN} then attempts to read the symbol tables of any object modules
17054 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17055 these files by searching the directories listed in the command search
17056 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17057 to find an object file, it displays a message such as:
17060 prog.o: No such file or directory.
17063 When this happens, add the appropriate directory to the search path with
17064 the @value{GDBN} command @code{path}, and execute the @code{target}
17067 @node VxWorks Download
17068 @subsubsection VxWorks Download
17070 @cindex download to VxWorks
17071 If you have connected to the VxWorks target and you want to debug an
17072 object that has not yet been loaded, you can use the @value{GDBN}
17073 @code{load} command to download a file from Unix to VxWorks
17074 incrementally. The object file given as an argument to the @code{load}
17075 command is actually opened twice: first by the VxWorks target in order
17076 to download the code, then by @value{GDBN} in order to read the symbol
17077 table. This can lead to problems if the current working directories on
17078 the two systems differ. If both systems have NFS mounted the same
17079 filesystems, you can avoid these problems by using absolute paths.
17080 Otherwise, it is simplest to set the working directory on both systems
17081 to the directory in which the object file resides, and then to reference
17082 the file by its name, without any path. For instance, a program
17083 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17084 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17085 program, type this on VxWorks:
17088 -> cd "@var{vxpath}/vw/demo/rdb"
17092 Then, in @value{GDBN}, type:
17095 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17096 (vxgdb) load prog.o
17099 @value{GDBN} displays a response similar to this:
17102 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17105 You can also use the @code{load} command to reload an object module
17106 after editing and recompiling the corresponding source file. Note that
17107 this makes @value{GDBN} delete all currently-defined breakpoints,
17108 auto-displays, and convenience variables, and to clear the value
17109 history. (This is necessary in order to preserve the integrity of
17110 debugger's data structures that reference the target system's symbol
17113 @node VxWorks Attach
17114 @subsubsection Running Tasks
17116 @cindex running VxWorks tasks
17117 You can also attach to an existing task using the @code{attach} command as
17121 (vxgdb) attach @var{task}
17125 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17126 or suspended when you attach to it. Running tasks are suspended at
17127 the time of attachment.
17129 @node Embedded Processors
17130 @section Embedded Processors
17132 This section goes into details specific to particular embedded
17135 @cindex send command to simulator
17136 Whenever a specific embedded processor has a simulator, @value{GDBN}
17137 allows to send an arbitrary command to the simulator.
17140 @item sim @var{command}
17141 @kindex sim@r{, a command}
17142 Send an arbitrary @var{command} string to the simulator. Consult the
17143 documentation for the specific simulator in use for information about
17144 acceptable commands.
17150 * M32R/D:: Renesas M32R/D
17151 * M68K:: Motorola M68K
17152 * MicroBlaze:: Xilinx MicroBlaze
17153 * MIPS Embedded:: MIPS Embedded
17154 * OpenRISC 1000:: OpenRisc 1000
17155 * PA:: HP PA Embedded
17156 * PowerPC Embedded:: PowerPC Embedded
17157 * Sparclet:: Tsqware Sparclet
17158 * Sparclite:: Fujitsu Sparclite
17159 * Z8000:: Zilog Z8000
17162 * Super-H:: Renesas Super-H
17171 @item target rdi @var{dev}
17172 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17173 use this target to communicate with both boards running the Angel
17174 monitor, or with the EmbeddedICE JTAG debug device.
17177 @item target rdp @var{dev}
17182 @value{GDBN} provides the following ARM-specific commands:
17185 @item set arm disassembler
17187 This commands selects from a list of disassembly styles. The
17188 @code{"std"} style is the standard style.
17190 @item show arm disassembler
17192 Show the current disassembly style.
17194 @item set arm apcs32
17195 @cindex ARM 32-bit mode
17196 This command toggles ARM operation mode between 32-bit and 26-bit.
17198 @item show arm apcs32
17199 Display the current usage of the ARM 32-bit mode.
17201 @item set arm fpu @var{fputype}
17202 This command sets the ARM floating-point unit (FPU) type. The
17203 argument @var{fputype} can be one of these:
17207 Determine the FPU type by querying the OS ABI.
17209 Software FPU, with mixed-endian doubles on little-endian ARM
17212 GCC-compiled FPA co-processor.
17214 Software FPU with pure-endian doubles.
17220 Show the current type of the FPU.
17223 This command forces @value{GDBN} to use the specified ABI.
17226 Show the currently used ABI.
17228 @item set arm fallback-mode (arm|thumb|auto)
17229 @value{GDBN} uses the symbol table, when available, to determine
17230 whether instructions are ARM or Thumb. This command controls
17231 @value{GDBN}'s default behavior when the symbol table is not
17232 available. The default is @samp{auto}, which causes @value{GDBN} to
17233 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17236 @item show arm fallback-mode
17237 Show the current fallback instruction mode.
17239 @item set arm force-mode (arm|thumb|auto)
17240 This command overrides use of the symbol table to determine whether
17241 instructions are ARM or Thumb. The default is @samp{auto}, which
17242 causes @value{GDBN} to use the symbol table and then the setting
17243 of @samp{set arm fallback-mode}.
17245 @item show arm force-mode
17246 Show the current forced instruction mode.
17248 @item set debug arm
17249 Toggle whether to display ARM-specific debugging messages from the ARM
17250 target support subsystem.
17252 @item show debug arm
17253 Show whether ARM-specific debugging messages are enabled.
17256 The following commands are available when an ARM target is debugged
17257 using the RDI interface:
17260 @item rdilogfile @r{[}@var{file}@r{]}
17262 @cindex ADP (Angel Debugger Protocol) logging
17263 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17264 With an argument, sets the log file to the specified @var{file}. With
17265 no argument, show the current log file name. The default log file is
17268 @item rdilogenable @r{[}@var{arg}@r{]}
17269 @kindex rdilogenable
17270 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17271 enables logging, with an argument 0 or @code{"no"} disables it. With
17272 no arguments displays the current setting. When logging is enabled,
17273 ADP packets exchanged between @value{GDBN} and the RDI target device
17274 are logged to a file.
17276 @item set rdiromatzero
17277 @kindex set rdiromatzero
17278 @cindex ROM at zero address, RDI
17279 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17280 vector catching is disabled, so that zero address can be used. If off
17281 (the default), vector catching is enabled. For this command to take
17282 effect, it needs to be invoked prior to the @code{target rdi} command.
17284 @item show rdiromatzero
17285 @kindex show rdiromatzero
17286 Show the current setting of ROM at zero address.
17288 @item set rdiheartbeat
17289 @kindex set rdiheartbeat
17290 @cindex RDI heartbeat
17291 Enable or disable RDI heartbeat packets. It is not recommended to
17292 turn on this option, since it confuses ARM and EPI JTAG interface, as
17293 well as the Angel monitor.
17295 @item show rdiheartbeat
17296 @kindex show rdiheartbeat
17297 Show the setting of RDI heartbeat packets.
17301 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17302 The @value{GDBN} ARM simulator accepts the following optional arguments.
17305 @item --swi-support=@var{type}
17306 Tell the simulator which SWI interfaces to support.
17307 @var{type} may be a comma separated list of the following values.
17308 The default value is @code{all}.
17321 @subsection Renesas M32R/D and M32R/SDI
17324 @kindex target m32r
17325 @item target m32r @var{dev}
17326 Renesas M32R/D ROM monitor.
17328 @kindex target m32rsdi
17329 @item target m32rsdi @var{dev}
17330 Renesas M32R SDI server, connected via parallel port to the board.
17333 The following @value{GDBN} commands are specific to the M32R monitor:
17336 @item set download-path @var{path}
17337 @kindex set download-path
17338 @cindex find downloadable @sc{srec} files (M32R)
17339 Set the default path for finding downloadable @sc{srec} files.
17341 @item show download-path
17342 @kindex show download-path
17343 Show the default path for downloadable @sc{srec} files.
17345 @item set board-address @var{addr}
17346 @kindex set board-address
17347 @cindex M32-EVA target board address
17348 Set the IP address for the M32R-EVA target board.
17350 @item show board-address
17351 @kindex show board-address
17352 Show the current IP address of the target board.
17354 @item set server-address @var{addr}
17355 @kindex set server-address
17356 @cindex download server address (M32R)
17357 Set the IP address for the download server, which is the @value{GDBN}'s
17360 @item show server-address
17361 @kindex show server-address
17362 Display the IP address of the download server.
17364 @item upload @r{[}@var{file}@r{]}
17365 @kindex upload@r{, M32R}
17366 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
17367 upload capability. If no @var{file} argument is given, the current
17368 executable file is uploaded.
17370 @item tload @r{[}@var{file}@r{]}
17371 @kindex tload@r{, M32R}
17372 Test the @code{upload} command.
17375 The following commands are available for M32R/SDI:
17380 @cindex reset SDI connection, M32R
17381 This command resets the SDI connection.
17385 This command shows the SDI connection status.
17388 @kindex debug_chaos
17389 @cindex M32R/Chaos debugging
17390 Instructs the remote that M32R/Chaos debugging is to be used.
17392 @item use_debug_dma
17393 @kindex use_debug_dma
17394 Instructs the remote to use the DEBUG_DMA method of accessing memory.
17397 @kindex use_mon_code
17398 Instructs the remote to use the MON_CODE method of accessing memory.
17401 @kindex use_ib_break
17402 Instructs the remote to set breakpoints by IB break.
17404 @item use_dbt_break
17405 @kindex use_dbt_break
17406 Instructs the remote to set breakpoints by DBT.
17412 The Motorola m68k configuration includes ColdFire support, and a
17413 target command for the following ROM monitor.
17417 @kindex target dbug
17418 @item target dbug @var{dev}
17419 dBUG ROM monitor for Motorola ColdFire.
17424 @subsection MicroBlaze
17425 @cindex Xilinx MicroBlaze
17426 @cindex XMD, Xilinx Microprocessor Debugger
17428 The MicroBlaze is a soft-core processor supported on various Xilinx
17429 FPGAs, such as Spartan or Virtex series. Boards with these processors
17430 usually have JTAG ports which connect to a host system running the Xilinx
17431 Embedded Development Kit (EDK) or Software Development Kit (SDK).
17432 This host system is used to download the configuration bitstream to
17433 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
17434 communicates with the target board using the JTAG interface and
17435 presents a @code{gdbserver} interface to the board. By default
17436 @code{xmd} uses port @code{1234}. (While it is possible to change
17437 this default port, it requires the use of undocumented @code{xmd}
17438 commands. Contact Xilinx support if you need to do this.)
17440 Use these GDB commands to connect to the MicroBlaze target processor.
17443 @item target remote :1234
17444 Use this command to connect to the target if you are running @value{GDBN}
17445 on the same system as @code{xmd}.
17447 @item target remote @var{xmd-host}:1234
17448 Use this command to connect to the target if it is connected to @code{xmd}
17449 running on a different system named @var{xmd-host}.
17452 Use this command to download a program to the MicroBlaze target.
17454 @item set debug microblaze @var{n}
17455 Enable MicroBlaze-specific debugging messages if non-zero.
17457 @item show debug microblaze @var{n}
17458 Show MicroBlaze-specific debugging level.
17461 @node MIPS Embedded
17462 @subsection MIPS Embedded
17464 @cindex MIPS boards
17465 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
17466 MIPS board attached to a serial line. This is available when
17467 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
17470 Use these @value{GDBN} commands to specify the connection to your target board:
17473 @item target mips @var{port}
17474 @kindex target mips @var{port}
17475 To run a program on the board, start up @code{@value{GDBP}} with the
17476 name of your program as the argument. To connect to the board, use the
17477 command @samp{target mips @var{port}}, where @var{port} is the name of
17478 the serial port connected to the board. If the program has not already
17479 been downloaded to the board, you may use the @code{load} command to
17480 download it. You can then use all the usual @value{GDBN} commands.
17482 For example, this sequence connects to the target board through a serial
17483 port, and loads and runs a program called @var{prog} through the
17487 host$ @value{GDBP} @var{prog}
17488 @value{GDBN} is free software and @dots{}
17489 (@value{GDBP}) target mips /dev/ttyb
17490 (@value{GDBP}) load @var{prog}
17494 @item target mips @var{hostname}:@var{portnumber}
17495 On some @value{GDBN} host configurations, you can specify a TCP
17496 connection (for instance, to a serial line managed by a terminal
17497 concentrator) instead of a serial port, using the syntax
17498 @samp{@var{hostname}:@var{portnumber}}.
17500 @item target pmon @var{port}
17501 @kindex target pmon @var{port}
17504 @item target ddb @var{port}
17505 @kindex target ddb @var{port}
17506 NEC's DDB variant of PMON for Vr4300.
17508 @item target lsi @var{port}
17509 @kindex target lsi @var{port}
17510 LSI variant of PMON.
17512 @kindex target r3900
17513 @item target r3900 @var{dev}
17514 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
17516 @kindex target array
17517 @item target array @var{dev}
17518 Array Tech LSI33K RAID controller board.
17524 @value{GDBN} also supports these special commands for MIPS targets:
17527 @item set mipsfpu double
17528 @itemx set mipsfpu single
17529 @itemx set mipsfpu none
17530 @itemx set mipsfpu auto
17531 @itemx show mipsfpu
17532 @kindex set mipsfpu
17533 @kindex show mipsfpu
17534 @cindex MIPS remote floating point
17535 @cindex floating point, MIPS remote
17536 If your target board does not support the MIPS floating point
17537 coprocessor, you should use the command @samp{set mipsfpu none} (if you
17538 need this, you may wish to put the command in your @value{GDBN} init
17539 file). This tells @value{GDBN} how to find the return value of
17540 functions which return floating point values. It also allows
17541 @value{GDBN} to avoid saving the floating point registers when calling
17542 functions on the board. If you are using a floating point coprocessor
17543 with only single precision floating point support, as on the @sc{r4650}
17544 processor, use the command @samp{set mipsfpu single}. The default
17545 double precision floating point coprocessor may be selected using
17546 @samp{set mipsfpu double}.
17548 In previous versions the only choices were double precision or no
17549 floating point, so @samp{set mipsfpu on} will select double precision
17550 and @samp{set mipsfpu off} will select no floating point.
17552 As usual, you can inquire about the @code{mipsfpu} variable with
17553 @samp{show mipsfpu}.
17555 @item set timeout @var{seconds}
17556 @itemx set retransmit-timeout @var{seconds}
17557 @itemx show timeout
17558 @itemx show retransmit-timeout
17559 @cindex @code{timeout}, MIPS protocol
17560 @cindex @code{retransmit-timeout}, MIPS protocol
17561 @kindex set timeout
17562 @kindex show timeout
17563 @kindex set retransmit-timeout
17564 @kindex show retransmit-timeout
17565 You can control the timeout used while waiting for a packet, in the MIPS
17566 remote protocol, with the @code{set timeout @var{seconds}} command. The
17567 default is 5 seconds. Similarly, you can control the timeout used while
17568 waiting for an acknowledgment of a packet with the @code{set
17569 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
17570 You can inspect both values with @code{show timeout} and @code{show
17571 retransmit-timeout}. (These commands are @emph{only} available when
17572 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
17574 The timeout set by @code{set timeout} does not apply when @value{GDBN}
17575 is waiting for your program to stop. In that case, @value{GDBN} waits
17576 forever because it has no way of knowing how long the program is going
17577 to run before stopping.
17579 @item set syn-garbage-limit @var{num}
17580 @kindex set syn-garbage-limit@r{, MIPS remote}
17581 @cindex synchronize with remote MIPS target
17582 Limit the maximum number of characters @value{GDBN} should ignore when
17583 it tries to synchronize with the remote target. The default is 10
17584 characters. Setting the limit to -1 means there's no limit.
17586 @item show syn-garbage-limit
17587 @kindex show syn-garbage-limit@r{, MIPS remote}
17588 Show the current limit on the number of characters to ignore when
17589 trying to synchronize with the remote system.
17591 @item set monitor-prompt @var{prompt}
17592 @kindex set monitor-prompt@r{, MIPS remote}
17593 @cindex remote monitor prompt
17594 Tell @value{GDBN} to expect the specified @var{prompt} string from the
17595 remote monitor. The default depends on the target:
17605 @item show monitor-prompt
17606 @kindex show monitor-prompt@r{, MIPS remote}
17607 Show the current strings @value{GDBN} expects as the prompt from the
17610 @item set monitor-warnings
17611 @kindex set monitor-warnings@r{, MIPS remote}
17612 Enable or disable monitor warnings about hardware breakpoints. This
17613 has effect only for the @code{lsi} target. When on, @value{GDBN} will
17614 display warning messages whose codes are returned by the @code{lsi}
17615 PMON monitor for breakpoint commands.
17617 @item show monitor-warnings
17618 @kindex show monitor-warnings@r{, MIPS remote}
17619 Show the current setting of printing monitor warnings.
17621 @item pmon @var{command}
17622 @kindex pmon@r{, MIPS remote}
17623 @cindex send PMON command
17624 This command allows sending an arbitrary @var{command} string to the
17625 monitor. The monitor must be in debug mode for this to work.
17628 @node OpenRISC 1000
17629 @subsection OpenRISC 1000
17630 @cindex OpenRISC 1000
17632 @cindex or1k boards
17633 See OR1k Architecture document (@uref{www.opencores.org}) for more information
17634 about platform and commands.
17638 @kindex target jtag
17639 @item target jtag jtag://@var{host}:@var{port}
17641 Connects to remote JTAG server.
17642 JTAG remote server can be either an or1ksim or JTAG server,
17643 connected via parallel port to the board.
17645 Example: @code{target jtag jtag://localhost:9999}
17648 @item or1ksim @var{command}
17649 If connected to @code{or1ksim} OpenRISC 1000 Architectural
17650 Simulator, proprietary commands can be executed.
17652 @kindex info or1k spr
17653 @item info or1k spr
17654 Displays spr groups.
17656 @item info or1k spr @var{group}
17657 @itemx info or1k spr @var{groupno}
17658 Displays register names in selected group.
17660 @item info or1k spr @var{group} @var{register}
17661 @itemx info or1k spr @var{register}
17662 @itemx info or1k spr @var{groupno} @var{registerno}
17663 @itemx info or1k spr @var{registerno}
17664 Shows information about specified spr register.
17667 @item spr @var{group} @var{register} @var{value}
17668 @itemx spr @var{register @var{value}}
17669 @itemx spr @var{groupno} @var{registerno @var{value}}
17670 @itemx spr @var{registerno @var{value}}
17671 Writes @var{value} to specified spr register.
17674 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
17675 It is very similar to @value{GDBN} trace, except it does not interfere with normal
17676 program execution and is thus much faster. Hardware breakpoints/watchpoint
17677 triggers can be set using:
17680 Load effective address/data
17682 Store effective address/data
17684 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
17689 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
17690 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
17692 @code{htrace} commands:
17693 @cindex OpenRISC 1000 htrace
17696 @item hwatch @var{conditional}
17697 Set hardware watchpoint on combination of Load/Store Effective Address(es)
17698 or Data. For example:
17700 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17702 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17706 Display information about current HW trace configuration.
17708 @item htrace trigger @var{conditional}
17709 Set starting criteria for HW trace.
17711 @item htrace qualifier @var{conditional}
17712 Set acquisition qualifier for HW trace.
17714 @item htrace stop @var{conditional}
17715 Set HW trace stopping criteria.
17717 @item htrace record [@var{data}]*
17718 Selects the data to be recorded, when qualifier is met and HW trace was
17721 @item htrace enable
17722 @itemx htrace disable
17723 Enables/disables the HW trace.
17725 @item htrace rewind [@var{filename}]
17726 Clears currently recorded trace data.
17728 If filename is specified, new trace file is made and any newly collected data
17729 will be written there.
17731 @item htrace print [@var{start} [@var{len}]]
17732 Prints trace buffer, using current record configuration.
17734 @item htrace mode continuous
17735 Set continuous trace mode.
17737 @item htrace mode suspend
17738 Set suspend trace mode.
17742 @node PowerPC Embedded
17743 @subsection PowerPC Embedded
17745 @value{GDBN} provides the following PowerPC-specific commands:
17748 @kindex set powerpc
17749 @item set powerpc soft-float
17750 @itemx show powerpc soft-float
17751 Force @value{GDBN} to use (or not use) a software floating point calling
17752 convention. By default, @value{GDBN} selects the calling convention based
17753 on the selected architecture and the provided executable file.
17755 @item set powerpc vector-abi
17756 @itemx show powerpc vector-abi
17757 Force @value{GDBN} to use the specified calling convention for vector
17758 arguments and return values. The valid options are @samp{auto};
17759 @samp{generic}, to avoid vector registers even if they are present;
17760 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
17761 registers. By default, @value{GDBN} selects the calling convention
17762 based on the selected architecture and the provided executable file.
17764 @kindex target dink32
17765 @item target dink32 @var{dev}
17766 DINK32 ROM monitor.
17768 @kindex target ppcbug
17769 @item target ppcbug @var{dev}
17770 @kindex target ppcbug1
17771 @item target ppcbug1 @var{dev}
17772 PPCBUG ROM monitor for PowerPC.
17775 @item target sds @var{dev}
17776 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
17779 @cindex SDS protocol
17780 The following commands specific to the SDS protocol are supported
17784 @item set sdstimeout @var{nsec}
17785 @kindex set sdstimeout
17786 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
17787 default is 2 seconds.
17789 @item show sdstimeout
17790 @kindex show sdstimeout
17791 Show the current value of the SDS timeout.
17793 @item sds @var{command}
17794 @kindex sds@r{, a command}
17795 Send the specified @var{command} string to the SDS monitor.
17800 @subsection HP PA Embedded
17804 @kindex target op50n
17805 @item target op50n @var{dev}
17806 OP50N monitor, running on an OKI HPPA board.
17808 @kindex target w89k
17809 @item target w89k @var{dev}
17810 W89K monitor, running on a Winbond HPPA board.
17815 @subsection Tsqware Sparclet
17819 @value{GDBN} enables developers to debug tasks running on
17820 Sparclet targets from a Unix host.
17821 @value{GDBN} uses code that runs on
17822 both the Unix host and on the Sparclet target. The program
17823 @code{@value{GDBP}} is installed and executed on the Unix host.
17826 @item remotetimeout @var{args}
17827 @kindex remotetimeout
17828 @value{GDBN} supports the option @code{remotetimeout}.
17829 This option is set by the user, and @var{args} represents the number of
17830 seconds @value{GDBN} waits for responses.
17833 @cindex compiling, on Sparclet
17834 When compiling for debugging, include the options @samp{-g} to get debug
17835 information and @samp{-Ttext} to relocate the program to where you wish to
17836 load it on the target. You may also want to add the options @samp{-n} or
17837 @samp{-N} in order to reduce the size of the sections. Example:
17840 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
17843 You can use @code{objdump} to verify that the addresses are what you intended:
17846 sparclet-aout-objdump --headers --syms prog
17849 @cindex running, on Sparclet
17851 your Unix execution search path to find @value{GDBN}, you are ready to
17852 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
17853 (or @code{sparclet-aout-gdb}, depending on your installation).
17855 @value{GDBN} comes up showing the prompt:
17862 * Sparclet File:: Setting the file to debug
17863 * Sparclet Connection:: Connecting to Sparclet
17864 * Sparclet Download:: Sparclet download
17865 * Sparclet Execution:: Running and debugging
17868 @node Sparclet File
17869 @subsubsection Setting File to Debug
17871 The @value{GDBN} command @code{file} lets you choose with program to debug.
17874 (gdbslet) file prog
17878 @value{GDBN} then attempts to read the symbol table of @file{prog}.
17879 @value{GDBN} locates
17880 the file by searching the directories listed in the command search
17882 If the file was compiled with debug information (option @samp{-g}), source
17883 files will be searched as well.
17884 @value{GDBN} locates
17885 the source files by searching the directories listed in the directory search
17886 path (@pxref{Environment, ,Your Program's Environment}).
17888 to find a file, it displays a message such as:
17891 prog: No such file or directory.
17894 When this happens, add the appropriate directories to the search paths with
17895 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
17896 @code{target} command again.
17898 @node Sparclet Connection
17899 @subsubsection Connecting to Sparclet
17901 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
17902 To connect to a target on serial port ``@code{ttya}'', type:
17905 (gdbslet) target sparclet /dev/ttya
17906 Remote target sparclet connected to /dev/ttya
17907 main () at ../prog.c:3
17911 @value{GDBN} displays messages like these:
17917 @node Sparclet Download
17918 @subsubsection Sparclet Download
17920 @cindex download to Sparclet
17921 Once connected to the Sparclet target,
17922 you can use the @value{GDBN}
17923 @code{load} command to download the file from the host to the target.
17924 The file name and load offset should be given as arguments to the @code{load}
17926 Since the file format is aout, the program must be loaded to the starting
17927 address. You can use @code{objdump} to find out what this value is. The load
17928 offset is an offset which is added to the VMA (virtual memory address)
17929 of each of the file's sections.
17930 For instance, if the program
17931 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
17932 and bss at 0x12010170, in @value{GDBN}, type:
17935 (gdbslet) load prog 0x12010000
17936 Loading section .text, size 0xdb0 vma 0x12010000
17939 If the code is loaded at a different address then what the program was linked
17940 to, you may need to use the @code{section} and @code{add-symbol-file} commands
17941 to tell @value{GDBN} where to map the symbol table.
17943 @node Sparclet Execution
17944 @subsubsection Running and Debugging
17946 @cindex running and debugging Sparclet programs
17947 You can now begin debugging the task using @value{GDBN}'s execution control
17948 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
17949 manual for the list of commands.
17953 Breakpoint 1 at 0x12010000: file prog.c, line 3.
17955 Starting program: prog
17956 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
17957 3 char *symarg = 0;
17959 4 char *execarg = "hello!";
17964 @subsection Fujitsu Sparclite
17968 @kindex target sparclite
17969 @item target sparclite @var{dev}
17970 Fujitsu sparclite boards, used only for the purpose of loading.
17971 You must use an additional command to debug the program.
17972 For example: target remote @var{dev} using @value{GDBN} standard
17978 @subsection Zilog Z8000
17981 @cindex simulator, Z8000
17982 @cindex Zilog Z8000 simulator
17984 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
17987 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
17988 unsegmented variant of the Z8000 architecture) or the Z8001 (the
17989 segmented variant). The simulator recognizes which architecture is
17990 appropriate by inspecting the object code.
17993 @item target sim @var{args}
17995 @kindex target sim@r{, with Z8000}
17996 Debug programs on a simulated CPU. If the simulator supports setup
17997 options, specify them via @var{args}.
18001 After specifying this target, you can debug programs for the simulated
18002 CPU in the same style as programs for your host computer; use the
18003 @code{file} command to load a new program image, the @code{run} command
18004 to run your program, and so on.
18006 As well as making available all the usual machine registers
18007 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18008 additional items of information as specially named registers:
18013 Counts clock-ticks in the simulator.
18016 Counts instructions run in the simulator.
18019 Execution time in 60ths of a second.
18023 You can refer to these values in @value{GDBN} expressions with the usual
18024 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18025 conditional breakpoint that suspends only after at least 5000
18026 simulated clock ticks.
18029 @subsection Atmel AVR
18032 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18033 following AVR-specific commands:
18036 @item info io_registers
18037 @kindex info io_registers@r{, AVR}
18038 @cindex I/O registers (Atmel AVR)
18039 This command displays information about the AVR I/O registers. For
18040 each register, @value{GDBN} prints its number and value.
18047 When configured for debugging CRIS, @value{GDBN} provides the
18048 following CRIS-specific commands:
18051 @item set cris-version @var{ver}
18052 @cindex CRIS version
18053 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18054 The CRIS version affects register names and sizes. This command is useful in
18055 case autodetection of the CRIS version fails.
18057 @item show cris-version
18058 Show the current CRIS version.
18060 @item set cris-dwarf2-cfi
18061 @cindex DWARF-2 CFI and CRIS
18062 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18063 Change to @samp{off} when using @code{gcc-cris} whose version is below
18066 @item show cris-dwarf2-cfi
18067 Show the current state of using DWARF-2 CFI.
18069 @item set cris-mode @var{mode}
18071 Set the current CRIS mode to @var{mode}. It should only be changed when
18072 debugging in guru mode, in which case it should be set to
18073 @samp{guru} (the default is @samp{normal}).
18075 @item show cris-mode
18076 Show the current CRIS mode.
18080 @subsection Renesas Super-H
18083 For the Renesas Super-H processor, @value{GDBN} provides these
18088 @kindex regs@r{, Super-H}
18089 Show the values of all Super-H registers.
18091 @item set sh calling-convention @var{convention}
18092 @kindex set sh calling-convention
18093 Set the calling-convention used when calling functions from @value{GDBN}.
18094 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18095 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18096 convention. If the DWARF-2 information of the called function specifies
18097 that the function follows the Renesas calling convention, the function
18098 is called using the Renesas calling convention. If the calling convention
18099 is set to @samp{renesas}, the Renesas calling convention is always used,
18100 regardless of the DWARF-2 information. This can be used to override the
18101 default of @samp{gcc} if debug information is missing, or the compiler
18102 does not emit the DWARF-2 calling convention entry for a function.
18104 @item show sh calling-convention
18105 @kindex show sh calling-convention
18106 Show the current calling convention setting.
18111 @node Architectures
18112 @section Architectures
18114 This section describes characteristics of architectures that affect
18115 all uses of @value{GDBN} with the architecture, both native and cross.
18122 * HPPA:: HP PA architecture
18123 * SPU:: Cell Broadband Engine SPU architecture
18128 @subsection x86 Architecture-specific Issues
18131 @item set struct-convention @var{mode}
18132 @kindex set struct-convention
18133 @cindex struct return convention
18134 @cindex struct/union returned in registers
18135 Set the convention used by the inferior to return @code{struct}s and
18136 @code{union}s from functions to @var{mode}. Possible values of
18137 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18138 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18139 are returned on the stack, while @code{"reg"} means that a
18140 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18141 be returned in a register.
18143 @item show struct-convention
18144 @kindex show struct-convention
18145 Show the current setting of the convention to return @code{struct}s
18154 @kindex set rstack_high_address
18155 @cindex AMD 29K register stack
18156 @cindex register stack, AMD29K
18157 @item set rstack_high_address @var{address}
18158 On AMD 29000 family processors, registers are saved in a separate
18159 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18160 extent of this stack. Normally, @value{GDBN} just assumes that the
18161 stack is ``large enough''. This may result in @value{GDBN} referencing
18162 memory locations that do not exist. If necessary, you can get around
18163 this problem by specifying the ending address of the register stack with
18164 the @code{set rstack_high_address} command. The argument should be an
18165 address, which you probably want to precede with @samp{0x} to specify in
18168 @kindex show rstack_high_address
18169 @item show rstack_high_address
18170 Display the current limit of the register stack, on AMD 29000 family
18178 See the following section.
18183 @cindex stack on Alpha
18184 @cindex stack on MIPS
18185 @cindex Alpha stack
18187 Alpha- and MIPS-based computers use an unusual stack frame, which
18188 sometimes requires @value{GDBN} to search backward in the object code to
18189 find the beginning of a function.
18191 @cindex response time, MIPS debugging
18192 To improve response time (especially for embedded applications, where
18193 @value{GDBN} may be restricted to a slow serial line for this search)
18194 you may want to limit the size of this search, using one of these
18198 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18199 @item set heuristic-fence-post @var{limit}
18200 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18201 search for the beginning of a function. A value of @var{0} (the
18202 default) means there is no limit. However, except for @var{0}, the
18203 larger the limit the more bytes @code{heuristic-fence-post} must search
18204 and therefore the longer it takes to run. You should only need to use
18205 this command when debugging a stripped executable.
18207 @item show heuristic-fence-post
18208 Display the current limit.
18212 These commands are available @emph{only} when @value{GDBN} is configured
18213 for debugging programs on Alpha or MIPS processors.
18215 Several MIPS-specific commands are available when debugging MIPS
18219 @item set mips abi @var{arg}
18220 @kindex set mips abi
18221 @cindex set ABI for MIPS
18222 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18223 values of @var{arg} are:
18227 The default ABI associated with the current binary (this is the
18238 @item show mips abi
18239 @kindex show mips abi
18240 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18243 @itemx show mipsfpu
18244 @xref{MIPS Embedded, set mipsfpu}.
18246 @item set mips mask-address @var{arg}
18247 @kindex set mips mask-address
18248 @cindex MIPS addresses, masking
18249 This command determines whether the most-significant 32 bits of 64-bit
18250 MIPS addresses are masked off. The argument @var{arg} can be
18251 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18252 setting, which lets @value{GDBN} determine the correct value.
18254 @item show mips mask-address
18255 @kindex show mips mask-address
18256 Show whether the upper 32 bits of MIPS addresses are masked off or
18259 @item set remote-mips64-transfers-32bit-regs
18260 @kindex set remote-mips64-transfers-32bit-regs
18261 This command controls compatibility with 64-bit MIPS targets that
18262 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18263 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18264 and 64 bits for other registers, set this option to @samp{on}.
18266 @item show remote-mips64-transfers-32bit-regs
18267 @kindex show remote-mips64-transfers-32bit-regs
18268 Show the current setting of compatibility with older MIPS 64 targets.
18270 @item set debug mips
18271 @kindex set debug mips
18272 This command turns on and off debugging messages for the MIPS-specific
18273 target code in @value{GDBN}.
18275 @item show debug mips
18276 @kindex show debug mips
18277 Show the current setting of MIPS debugging messages.
18283 @cindex HPPA support
18285 When @value{GDBN} is debugging the HP PA architecture, it provides the
18286 following special commands:
18289 @item set debug hppa
18290 @kindex set debug hppa
18291 This command determines whether HPPA architecture-specific debugging
18292 messages are to be displayed.
18294 @item show debug hppa
18295 Show whether HPPA debugging messages are displayed.
18297 @item maint print unwind @var{address}
18298 @kindex maint print unwind@r{, HPPA}
18299 This command displays the contents of the unwind table entry at the
18300 given @var{address}.
18306 @subsection Cell Broadband Engine SPU architecture
18307 @cindex Cell Broadband Engine
18310 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
18311 it provides the following special commands:
18314 @item info spu event
18316 Display SPU event facility status. Shows current event mask
18317 and pending event status.
18319 @item info spu signal
18320 Display SPU signal notification facility status. Shows pending
18321 signal-control word and signal notification mode of both signal
18322 notification channels.
18324 @item info spu mailbox
18325 Display SPU mailbox facility status. Shows all pending entries,
18326 in order of processing, in each of the SPU Write Outbound,
18327 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
18330 Display MFC DMA status. Shows all pending commands in the MFC
18331 DMA queue. For each entry, opcode, tag, class IDs, effective
18332 and local store addresses and transfer size are shown.
18334 @item info spu proxydma
18335 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
18336 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
18337 and local store addresses and transfer size are shown.
18341 When @value{GDBN} is debugging a combined PowerPC/SPU application
18342 on the Cell Broadband Engine, it provides in addition the following
18346 @item set spu stop-on-load @var{arg}
18348 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
18349 will give control to the user when a new SPE thread enters its @code{main}
18350 function. The default is @code{off}.
18352 @item show spu stop-on-load
18354 Show whether to stop for new SPE threads.
18356 @item set spu auto-flush-cache @var{arg}
18357 Set whether to automatically flush the software-managed cache. When set to
18358 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
18359 cache to be flushed whenever SPE execution stops. This provides a consistent
18360 view of PowerPC memory that is accessed via the cache. If an application
18361 does not use the software-managed cache, this option has no effect.
18363 @item show spu auto-flush-cache
18364 Show whether to automatically flush the software-managed cache.
18369 @subsection PowerPC
18370 @cindex PowerPC architecture
18372 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
18373 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
18374 numbers stored in the floating point registers. These values must be stored
18375 in two consecutive registers, always starting at an even register like
18376 @code{f0} or @code{f2}.
18378 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
18379 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
18380 @code{f2} and @code{f3} for @code{$dl1} and so on.
18382 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
18383 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
18386 @node Controlling GDB
18387 @chapter Controlling @value{GDBN}
18389 You can alter the way @value{GDBN} interacts with you by using the
18390 @code{set} command. For commands controlling how @value{GDBN} displays
18391 data, see @ref{Print Settings, ,Print Settings}. Other settings are
18396 * Editing:: Command editing
18397 * Command History:: Command history
18398 * Screen Size:: Screen size
18399 * Numbers:: Numbers
18400 * ABI:: Configuring the current ABI
18401 * Messages/Warnings:: Optional warnings and messages
18402 * Debugging Output:: Optional messages about internal happenings
18403 * Other Misc Settings:: Other Miscellaneous Settings
18411 @value{GDBN} indicates its readiness to read a command by printing a string
18412 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
18413 can change the prompt string with the @code{set prompt} command. For
18414 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
18415 the prompt in one of the @value{GDBN} sessions so that you can always tell
18416 which one you are talking to.
18418 @emph{Note:} @code{set prompt} does not add a space for you after the
18419 prompt you set. This allows you to set a prompt which ends in a space
18420 or a prompt that does not.
18424 @item set prompt @var{newprompt}
18425 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
18427 @kindex show prompt
18429 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
18433 @section Command Editing
18435 @cindex command line editing
18437 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
18438 @sc{gnu} library provides consistent behavior for programs which provide a
18439 command line interface to the user. Advantages are @sc{gnu} Emacs-style
18440 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
18441 substitution, and a storage and recall of command history across
18442 debugging sessions.
18444 You may control the behavior of command line editing in @value{GDBN} with the
18445 command @code{set}.
18448 @kindex set editing
18451 @itemx set editing on
18452 Enable command line editing (enabled by default).
18454 @item set editing off
18455 Disable command line editing.
18457 @kindex show editing
18459 Show whether command line editing is enabled.
18462 @xref{Command Line Editing}, for more details about the Readline
18463 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
18464 encouraged to read that chapter.
18466 @node Command History
18467 @section Command History
18468 @cindex command history
18470 @value{GDBN} can keep track of the commands you type during your
18471 debugging sessions, so that you can be certain of precisely what
18472 happened. Use these commands to manage the @value{GDBN} command
18475 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
18476 package, to provide the history facility. @xref{Using History
18477 Interactively}, for the detailed description of the History library.
18479 To issue a command to @value{GDBN} without affecting certain aspects of
18480 the state which is seen by users, prefix it with @samp{server }
18481 (@pxref{Server Prefix}). This
18482 means that this command will not affect the command history, nor will it
18483 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18484 pressed on a line by itself.
18486 @cindex @code{server}, command prefix
18487 The server prefix does not affect the recording of values into the value
18488 history; to print a value without recording it into the value history,
18489 use the @code{output} command instead of the @code{print} command.
18491 Here is the description of @value{GDBN} commands related to command
18495 @cindex history substitution
18496 @cindex history file
18497 @kindex set history filename
18498 @cindex @env{GDBHISTFILE}, environment variable
18499 @item set history filename @var{fname}
18500 Set the name of the @value{GDBN} command history file to @var{fname}.
18501 This is the file where @value{GDBN} reads an initial command history
18502 list, and where it writes the command history from this session when it
18503 exits. You can access this list through history expansion or through
18504 the history command editing characters listed below. This file defaults
18505 to the value of the environment variable @code{GDBHISTFILE}, or to
18506 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
18509 @cindex save command history
18510 @kindex set history save
18511 @item set history save
18512 @itemx set history save on
18513 Record command history in a file, whose name may be specified with the
18514 @code{set history filename} command. By default, this option is disabled.
18516 @item set history save off
18517 Stop recording command history in a file.
18519 @cindex history size
18520 @kindex set history size
18521 @cindex @env{HISTSIZE}, environment variable
18522 @item set history size @var{size}
18523 Set the number of commands which @value{GDBN} keeps in its history list.
18524 This defaults to the value of the environment variable
18525 @code{HISTSIZE}, or to 256 if this variable is not set.
18528 History expansion assigns special meaning to the character @kbd{!}.
18529 @xref{Event Designators}, for more details.
18531 @cindex history expansion, turn on/off
18532 Since @kbd{!} is also the logical not operator in C, history expansion
18533 is off by default. If you decide to enable history expansion with the
18534 @code{set history expansion on} command, you may sometimes need to
18535 follow @kbd{!} (when it is used as logical not, in an expression) with
18536 a space or a tab to prevent it from being expanded. The readline
18537 history facilities do not attempt substitution on the strings
18538 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
18540 The commands to control history expansion are:
18543 @item set history expansion on
18544 @itemx set history expansion
18545 @kindex set history expansion
18546 Enable history expansion. History expansion is off by default.
18548 @item set history expansion off
18549 Disable history expansion.
18552 @kindex show history
18554 @itemx show history filename
18555 @itemx show history save
18556 @itemx show history size
18557 @itemx show history expansion
18558 These commands display the state of the @value{GDBN} history parameters.
18559 @code{show history} by itself displays all four states.
18564 @kindex show commands
18565 @cindex show last commands
18566 @cindex display command history
18567 @item show commands
18568 Display the last ten commands in the command history.
18570 @item show commands @var{n}
18571 Print ten commands centered on command number @var{n}.
18573 @item show commands +
18574 Print ten commands just after the commands last printed.
18578 @section Screen Size
18579 @cindex size of screen
18580 @cindex pauses in output
18582 Certain commands to @value{GDBN} may produce large amounts of
18583 information output to the screen. To help you read all of it,
18584 @value{GDBN} pauses and asks you for input at the end of each page of
18585 output. Type @key{RET} when you want to continue the output, or @kbd{q}
18586 to discard the remaining output. Also, the screen width setting
18587 determines when to wrap lines of output. Depending on what is being
18588 printed, @value{GDBN} tries to break the line at a readable place,
18589 rather than simply letting it overflow onto the following line.
18591 Normally @value{GDBN} knows the size of the screen from the terminal
18592 driver software. For example, on Unix @value{GDBN} uses the termcap data base
18593 together with the value of the @code{TERM} environment variable and the
18594 @code{stty rows} and @code{stty cols} settings. If this is not correct,
18595 you can override it with the @code{set height} and @code{set
18602 @kindex show height
18603 @item set height @var{lpp}
18605 @itemx set width @var{cpl}
18607 These @code{set} commands specify a screen height of @var{lpp} lines and
18608 a screen width of @var{cpl} characters. The associated @code{show}
18609 commands display the current settings.
18611 If you specify a height of zero lines, @value{GDBN} does not pause during
18612 output no matter how long the output is. This is useful if output is to a
18613 file or to an editor buffer.
18615 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
18616 from wrapping its output.
18618 @item set pagination on
18619 @itemx set pagination off
18620 @kindex set pagination
18621 Turn the output pagination on or off; the default is on. Turning
18622 pagination off is the alternative to @code{set height 0}. Note that
18623 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
18624 Options, -batch}) also automatically disables pagination.
18626 @item show pagination
18627 @kindex show pagination
18628 Show the current pagination mode.
18633 @cindex number representation
18634 @cindex entering numbers
18636 You can always enter numbers in octal, decimal, or hexadecimal in
18637 @value{GDBN} by the usual conventions: octal numbers begin with
18638 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
18639 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
18640 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
18641 10; likewise, the default display for numbers---when no particular
18642 format is specified---is base 10. You can change the default base for
18643 both input and output with the commands described below.
18646 @kindex set input-radix
18647 @item set input-radix @var{base}
18648 Set the default base for numeric input. Supported choices
18649 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18650 specified either unambiguously or using the current input radix; for
18654 set input-radix 012
18655 set input-radix 10.
18656 set input-radix 0xa
18660 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
18661 leaves the input radix unchanged, no matter what it was, since
18662 @samp{10}, being without any leading or trailing signs of its base, is
18663 interpreted in the current radix. Thus, if the current radix is 16,
18664 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
18667 @kindex set output-radix
18668 @item set output-radix @var{base}
18669 Set the default base for numeric display. Supported choices
18670 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18671 specified either unambiguously or using the current input radix.
18673 @kindex show input-radix
18674 @item show input-radix
18675 Display the current default base for numeric input.
18677 @kindex show output-radix
18678 @item show output-radix
18679 Display the current default base for numeric display.
18681 @item set radix @r{[}@var{base}@r{]}
18685 These commands set and show the default base for both input and output
18686 of numbers. @code{set radix} sets the radix of input and output to
18687 the same base; without an argument, it resets the radix back to its
18688 default value of 10.
18693 @section Configuring the Current ABI
18695 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
18696 application automatically. However, sometimes you need to override its
18697 conclusions. Use these commands to manage @value{GDBN}'s view of the
18704 One @value{GDBN} configuration can debug binaries for multiple operating
18705 system targets, either via remote debugging or native emulation.
18706 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
18707 but you can override its conclusion using the @code{set osabi} command.
18708 One example where this is useful is in debugging of binaries which use
18709 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
18710 not have the same identifying marks that the standard C library for your
18715 Show the OS ABI currently in use.
18718 With no argument, show the list of registered available OS ABI's.
18720 @item set osabi @var{abi}
18721 Set the current OS ABI to @var{abi}.
18724 @cindex float promotion
18726 Generally, the way that an argument of type @code{float} is passed to a
18727 function depends on whether the function is prototyped. For a prototyped
18728 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
18729 according to the architecture's convention for @code{float}. For unprototyped
18730 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
18731 @code{double} and then passed.
18733 Unfortunately, some forms of debug information do not reliably indicate whether
18734 a function is prototyped. If @value{GDBN} calls a function that is not marked
18735 as prototyped, it consults @kbd{set coerce-float-to-double}.
18738 @kindex set coerce-float-to-double
18739 @item set coerce-float-to-double
18740 @itemx set coerce-float-to-double on
18741 Arguments of type @code{float} will be promoted to @code{double} when passed
18742 to an unprototyped function. This is the default setting.
18744 @item set coerce-float-to-double off
18745 Arguments of type @code{float} will be passed directly to unprototyped
18748 @kindex show coerce-float-to-double
18749 @item show coerce-float-to-double
18750 Show the current setting of promoting @code{float} to @code{double}.
18754 @kindex show cp-abi
18755 @value{GDBN} needs to know the ABI used for your program's C@t{++}
18756 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
18757 used to build your application. @value{GDBN} only fully supports
18758 programs with a single C@t{++} ABI; if your program contains code using
18759 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
18760 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
18761 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
18762 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
18763 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
18764 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
18769 Show the C@t{++} ABI currently in use.
18772 With no argument, show the list of supported C@t{++} ABI's.
18774 @item set cp-abi @var{abi}
18775 @itemx set cp-abi auto
18776 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
18779 @node Messages/Warnings
18780 @section Optional Warnings and Messages
18782 @cindex verbose operation
18783 @cindex optional warnings
18784 By default, @value{GDBN} is silent about its inner workings. If you are
18785 running on a slow machine, you may want to use the @code{set verbose}
18786 command. This makes @value{GDBN} tell you when it does a lengthy
18787 internal operation, so you will not think it has crashed.
18789 Currently, the messages controlled by @code{set verbose} are those
18790 which announce that the symbol table for a source file is being read;
18791 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
18794 @kindex set verbose
18795 @item set verbose on
18796 Enables @value{GDBN} output of certain informational messages.
18798 @item set verbose off
18799 Disables @value{GDBN} output of certain informational messages.
18801 @kindex show verbose
18803 Displays whether @code{set verbose} is on or off.
18806 By default, if @value{GDBN} encounters bugs in the symbol table of an
18807 object file, it is silent; but if you are debugging a compiler, you may
18808 find this information useful (@pxref{Symbol Errors, ,Errors Reading
18813 @kindex set complaints
18814 @item set complaints @var{limit}
18815 Permits @value{GDBN} to output @var{limit} complaints about each type of
18816 unusual symbols before becoming silent about the problem. Set
18817 @var{limit} to zero to suppress all complaints; set it to a large number
18818 to prevent complaints from being suppressed.
18820 @kindex show complaints
18821 @item show complaints
18822 Displays how many symbol complaints @value{GDBN} is permitted to produce.
18826 @anchor{confirmation requests}
18827 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
18828 lot of stupid questions to confirm certain commands. For example, if
18829 you try to run a program which is already running:
18833 The program being debugged has been started already.
18834 Start it from the beginning? (y or n)
18837 If you are willing to unflinchingly face the consequences of your own
18838 commands, you can disable this ``feature'':
18842 @kindex set confirm
18844 @cindex confirmation
18845 @cindex stupid questions
18846 @item set confirm off
18847 Disables confirmation requests. Note that running @value{GDBN} with
18848 the @option{--batch} option (@pxref{Mode Options, -batch}) also
18849 automatically disables confirmation requests.
18851 @item set confirm on
18852 Enables confirmation requests (the default).
18854 @kindex show confirm
18856 Displays state of confirmation requests.
18860 @cindex command tracing
18861 If you need to debug user-defined commands or sourced files you may find it
18862 useful to enable @dfn{command tracing}. In this mode each command will be
18863 printed as it is executed, prefixed with one or more @samp{+} symbols, the
18864 quantity denoting the call depth of each command.
18867 @kindex set trace-commands
18868 @cindex command scripts, debugging
18869 @item set trace-commands on
18870 Enable command tracing.
18871 @item set trace-commands off
18872 Disable command tracing.
18873 @item show trace-commands
18874 Display the current state of command tracing.
18877 @node Debugging Output
18878 @section Optional Messages about Internal Happenings
18879 @cindex optional debugging messages
18881 @value{GDBN} has commands that enable optional debugging messages from
18882 various @value{GDBN} subsystems; normally these commands are of
18883 interest to @value{GDBN} maintainers, or when reporting a bug. This
18884 section documents those commands.
18887 @kindex set exec-done-display
18888 @item set exec-done-display
18889 Turns on or off the notification of asynchronous commands'
18890 completion. When on, @value{GDBN} will print a message when an
18891 asynchronous command finishes its execution. The default is off.
18892 @kindex show exec-done-display
18893 @item show exec-done-display
18894 Displays the current setting of asynchronous command completion
18897 @cindex gdbarch debugging info
18898 @cindex architecture debugging info
18899 @item set debug arch
18900 Turns on or off display of gdbarch debugging info. The default is off
18902 @item show debug arch
18903 Displays the current state of displaying gdbarch debugging info.
18904 @item set debug aix-thread
18905 @cindex AIX threads
18906 Display debugging messages about inner workings of the AIX thread
18908 @item show debug aix-thread
18909 Show the current state of AIX thread debugging info display.
18910 @item set debug dwarf2-die
18911 @cindex DWARF2 DIEs
18912 Dump DWARF2 DIEs after they are read in.
18913 The value is the number of nesting levels to print.
18914 A value of zero turns off the display.
18915 @item show debug dwarf2-die
18916 Show the current state of DWARF2 DIE debugging.
18917 @item set debug displaced
18918 @cindex displaced stepping debugging info
18919 Turns on or off display of @value{GDBN} debugging info for the
18920 displaced stepping support. The default is off.
18921 @item show debug displaced
18922 Displays the current state of displaying @value{GDBN} debugging info
18923 related to displaced stepping.
18924 @item set debug event
18925 @cindex event debugging info
18926 Turns on or off display of @value{GDBN} event debugging info. The
18928 @item show debug event
18929 Displays the current state of displaying @value{GDBN} event debugging
18931 @item set debug expression
18932 @cindex expression debugging info
18933 Turns on or off display of debugging info about @value{GDBN}
18934 expression parsing. The default is off.
18935 @item show debug expression
18936 Displays the current state of displaying debugging info about
18937 @value{GDBN} expression parsing.
18938 @item set debug frame
18939 @cindex frame debugging info
18940 Turns on or off display of @value{GDBN} frame debugging info. The
18942 @item show debug frame
18943 Displays the current state of displaying @value{GDBN} frame debugging
18945 @item set debug gnu-nat
18946 @cindex @sc{gnu}/Hurd debug messages
18947 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
18948 @item show debug gnu-nat
18949 Show the current state of @sc{gnu}/Hurd debugging messages.
18950 @item set debug infrun
18951 @cindex inferior debugging info
18952 Turns on or off display of @value{GDBN} debugging info for running the inferior.
18953 The default is off. @file{infrun.c} contains GDB's runtime state machine used
18954 for implementing operations such as single-stepping the inferior.
18955 @item show debug infrun
18956 Displays the current state of @value{GDBN} inferior debugging.
18957 @item set debug lin-lwp
18958 @cindex @sc{gnu}/Linux LWP debug messages
18959 @cindex Linux lightweight processes
18960 Turns on or off debugging messages from the Linux LWP debug support.
18961 @item show debug lin-lwp
18962 Show the current state of Linux LWP debugging messages.
18963 @item set debug lin-lwp-async
18964 @cindex @sc{gnu}/Linux LWP async debug messages
18965 @cindex Linux lightweight processes
18966 Turns on or off debugging messages from the Linux LWP async debug support.
18967 @item show debug lin-lwp-async
18968 Show the current state of Linux LWP async debugging messages.
18969 @item set debug observer
18970 @cindex observer debugging info
18971 Turns on or off display of @value{GDBN} observer debugging. This
18972 includes info such as the notification of observable events.
18973 @item show debug observer
18974 Displays the current state of observer debugging.
18975 @item set debug overload
18976 @cindex C@t{++} overload debugging info
18977 Turns on or off display of @value{GDBN} C@t{++} overload debugging
18978 info. This includes info such as ranking of functions, etc. The default
18980 @item show debug overload
18981 Displays the current state of displaying @value{GDBN} C@t{++} overload
18983 @cindex expression parser, debugging info
18984 @cindex debug expression parser
18985 @item set debug parser
18986 Turns on or off the display of expression parser debugging output.
18987 Internally, this sets the @code{yydebug} variable in the expression
18988 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
18989 details. The default is off.
18990 @item show debug parser
18991 Show the current state of expression parser debugging.
18992 @cindex packets, reporting on stdout
18993 @cindex serial connections, debugging
18994 @cindex debug remote protocol
18995 @cindex remote protocol debugging
18996 @cindex display remote packets
18997 @item set debug remote
18998 Turns on or off display of reports on all packets sent back and forth across
18999 the serial line to the remote machine. The info is printed on the
19000 @value{GDBN} standard output stream. The default is off.
19001 @item show debug remote
19002 Displays the state of display of remote packets.
19003 @item set debug serial
19004 Turns on or off display of @value{GDBN} serial debugging info. The
19006 @item show debug serial
19007 Displays the current state of displaying @value{GDBN} serial debugging
19009 @item set debug solib-frv
19010 @cindex FR-V shared-library debugging
19011 Turns on or off debugging messages for FR-V shared-library code.
19012 @item show debug solib-frv
19013 Display the current state of FR-V shared-library code debugging
19015 @item set debug target
19016 @cindex target debugging info
19017 Turns on or off display of @value{GDBN} target debugging info. This info
19018 includes what is going on at the target level of GDB, as it happens. The
19019 default is 0. Set it to 1 to track events, and to 2 to also track the
19020 value of large memory transfers. Changes to this flag do not take effect
19021 until the next time you connect to a target or use the @code{run} command.
19022 @item show debug target
19023 Displays the current state of displaying @value{GDBN} target debugging
19025 @item set debug timestamp
19026 @cindex timestampping debugging info
19027 Turns on or off display of timestamps with @value{GDBN} debugging info.
19028 When enabled, seconds and microseconds are displayed before each debugging
19030 @item show debug timestamp
19031 Displays the current state of displaying timestamps with @value{GDBN}
19033 @item set debugvarobj
19034 @cindex variable object debugging info
19035 Turns on or off display of @value{GDBN} variable object debugging
19036 info. The default is off.
19037 @item show debugvarobj
19038 Displays the current state of displaying @value{GDBN} variable object
19040 @item set debug xml
19041 @cindex XML parser debugging
19042 Turns on or off debugging messages for built-in XML parsers.
19043 @item show debug xml
19044 Displays the current state of XML debugging messages.
19047 @node Other Misc Settings
19048 @section Other Miscellaneous Settings
19049 @cindex miscellaneous settings
19052 @kindex set interactive-mode
19053 @item set interactive-mode
19054 If @code{on}, forces @value{GDBN} to operate interactively.
19055 If @code{off}, forces @value{GDBN} to operate non-interactively,
19056 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19057 based on whether the debugger was started in a terminal or not.
19059 In the vast majority of cases, the debugger should be able to guess
19060 correctly which mode should be used. But this setting can be useful
19061 in certain specific cases, such as running a MinGW @value{GDBN}
19062 inside a cygwin window.
19064 @kindex show interactive-mode
19065 @item show interactive-mode
19066 Displays whether the debugger is operating in interactive mode or not.
19069 @node Extending GDB
19070 @chapter Extending @value{GDBN}
19071 @cindex extending GDB
19073 @value{GDBN} provides two mechanisms for extension. The first is based
19074 on composition of @value{GDBN} commands, and the second is based on the
19075 Python scripting language.
19077 To facilitate the use of these extensions, @value{GDBN} is capable
19078 of evaluating the contents of a file. When doing so, @value{GDBN}
19079 can recognize which scripting language is being used by looking at
19080 the filename extension. Files with an unrecognized filename extension
19081 are always treated as a @value{GDBN} Command Files.
19082 @xref{Command Files,, Command files}.
19084 You can control how @value{GDBN} evaluates these files with the following
19088 @kindex set script-extension
19089 @kindex show script-extension
19090 @item set script-extension off
19091 All scripts are always evaluated as @value{GDBN} Command Files.
19093 @item set script-extension soft
19094 The debugger determines the scripting language based on filename
19095 extension. If this scripting language is supported, @value{GDBN}
19096 evaluates the script using that language. Otherwise, it evaluates
19097 the file as a @value{GDBN} Command File.
19099 @item set script-extension strict
19100 The debugger determines the scripting language based on filename
19101 extension, and evaluates the script using that language. If the
19102 language is not supported, then the evaluation fails.
19104 @item show script-extension
19105 Display the current value of the @code{script-extension} option.
19110 * Sequences:: Canned Sequences of Commands
19111 * Python:: Scripting @value{GDBN} using Python
19115 @section Canned Sequences of Commands
19117 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19118 Command Lists}), @value{GDBN} provides two ways to store sequences of
19119 commands for execution as a unit: user-defined commands and command
19123 * Define:: How to define your own commands
19124 * Hooks:: Hooks for user-defined commands
19125 * Command Files:: How to write scripts of commands to be stored in a file
19126 * Output:: Commands for controlled output
19130 @subsection User-defined Commands
19132 @cindex user-defined command
19133 @cindex arguments, to user-defined commands
19134 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19135 which you assign a new name as a command. This is done with the
19136 @code{define} command. User commands may accept up to 10 arguments
19137 separated by whitespace. Arguments are accessed within the user command
19138 via @code{$arg0@dots{}$arg9}. A trivial example:
19142 print $arg0 + $arg1 + $arg2
19147 To execute the command use:
19154 This defines the command @code{adder}, which prints the sum of
19155 its three arguments. Note the arguments are text substitutions, so they may
19156 reference variables, use complex expressions, or even perform inferior
19159 @cindex argument count in user-defined commands
19160 @cindex how many arguments (user-defined commands)
19161 In addition, @code{$argc} may be used to find out how many arguments have
19162 been passed. This expands to a number in the range 0@dots{}10.
19167 print $arg0 + $arg1
19170 print $arg0 + $arg1 + $arg2
19178 @item define @var{commandname}
19179 Define a command named @var{commandname}. If there is already a command
19180 by that name, you are asked to confirm that you want to redefine it.
19181 @var{commandname} may be a bare command name consisting of letters,
19182 numbers, dashes, and underscores. It may also start with any predefined
19183 prefix command. For example, @samp{define target my-target} creates
19184 a user-defined @samp{target my-target} command.
19186 The definition of the command is made up of other @value{GDBN} command lines,
19187 which are given following the @code{define} command. The end of these
19188 commands is marked by a line containing @code{end}.
19191 @kindex end@r{ (user-defined commands)}
19192 @item document @var{commandname}
19193 Document the user-defined command @var{commandname}, so that it can be
19194 accessed by @code{help}. The command @var{commandname} must already be
19195 defined. This command reads lines of documentation just as @code{define}
19196 reads the lines of the command definition, ending with @code{end}.
19197 After the @code{document} command is finished, @code{help} on command
19198 @var{commandname} displays the documentation you have written.
19200 You may use the @code{document} command again to change the
19201 documentation of a command. Redefining the command with @code{define}
19202 does not change the documentation.
19204 @kindex dont-repeat
19205 @cindex don't repeat command
19207 Used inside a user-defined command, this tells @value{GDBN} that this
19208 command should not be repeated when the user hits @key{RET}
19209 (@pxref{Command Syntax, repeat last command}).
19211 @kindex help user-defined
19212 @item help user-defined
19213 List all user-defined commands, with the first line of the documentation
19218 @itemx show user @var{commandname}
19219 Display the @value{GDBN} commands used to define @var{commandname} (but
19220 not its documentation). If no @var{commandname} is given, display the
19221 definitions for all user-defined commands.
19223 @cindex infinite recursion in user-defined commands
19224 @kindex show max-user-call-depth
19225 @kindex set max-user-call-depth
19226 @item show max-user-call-depth
19227 @itemx set max-user-call-depth
19228 The value of @code{max-user-call-depth} controls how many recursion
19229 levels are allowed in user-defined commands before @value{GDBN} suspects an
19230 infinite recursion and aborts the command.
19233 In addition to the above commands, user-defined commands frequently
19234 use control flow commands, described in @ref{Command Files}.
19236 When user-defined commands are executed, the
19237 commands of the definition are not printed. An error in any command
19238 stops execution of the user-defined command.
19240 If used interactively, commands that would ask for confirmation proceed
19241 without asking when used inside a user-defined command. Many @value{GDBN}
19242 commands that normally print messages to say what they are doing omit the
19243 messages when used in a user-defined command.
19246 @subsection User-defined Command Hooks
19247 @cindex command hooks
19248 @cindex hooks, for commands
19249 @cindex hooks, pre-command
19252 You may define @dfn{hooks}, which are a special kind of user-defined
19253 command. Whenever you run the command @samp{foo}, if the user-defined
19254 command @samp{hook-foo} exists, it is executed (with no arguments)
19255 before that command.
19257 @cindex hooks, post-command
19259 A hook may also be defined which is run after the command you executed.
19260 Whenever you run the command @samp{foo}, if the user-defined command
19261 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19262 that command. Post-execution hooks may exist simultaneously with
19263 pre-execution hooks, for the same command.
19265 It is valid for a hook to call the command which it hooks. If this
19266 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19268 @c It would be nice if hookpost could be passed a parameter indicating
19269 @c if the command it hooks executed properly or not. FIXME!
19271 @kindex stop@r{, a pseudo-command}
19272 In addition, a pseudo-command, @samp{stop} exists. Defining
19273 (@samp{hook-stop}) makes the associated commands execute every time
19274 execution stops in your program: before breakpoint commands are run,
19275 displays are printed, or the stack frame is printed.
19277 For example, to ignore @code{SIGALRM} signals while
19278 single-stepping, but treat them normally during normal execution,
19283 handle SIGALRM nopass
19287 handle SIGALRM pass
19290 define hook-continue
19291 handle SIGALRM pass
19295 As a further example, to hook at the beginning and end of the @code{echo}
19296 command, and to add extra text to the beginning and end of the message,
19304 define hookpost-echo
19308 (@value{GDBP}) echo Hello World
19309 <<<---Hello World--->>>
19314 You can define a hook for any single-word command in @value{GDBN}, but
19315 not for command aliases; you should define a hook for the basic command
19316 name, e.g.@: @code{backtrace} rather than @code{bt}.
19317 @c FIXME! So how does Joe User discover whether a command is an alias
19319 You can hook a multi-word command by adding @code{hook-} or
19320 @code{hookpost-} to the last word of the command, e.g.@:
19321 @samp{define target hook-remote} to add a hook to @samp{target remote}.
19323 If an error occurs during the execution of your hook, execution of
19324 @value{GDBN} commands stops and @value{GDBN} issues a prompt
19325 (before the command that you actually typed had a chance to run).
19327 If you try to define a hook which does not match any known command, you
19328 get a warning from the @code{define} command.
19330 @node Command Files
19331 @subsection Command Files
19333 @cindex command files
19334 @cindex scripting commands
19335 A command file for @value{GDBN} is a text file made of lines that are
19336 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
19337 also be included. An empty line in a command file does nothing; it
19338 does not mean to repeat the last command, as it would from the
19341 You can request the execution of a command file with the @code{source}
19342 command. Note that the @code{source} command is also used to evaluate
19343 scripts that are not Command Files. The exact behavior can be configured
19344 using the @code{script-extension} setting.
19345 @xref{Extending GDB,, Extending GDB}.
19349 @cindex execute commands from a file
19350 @item source [@code{-v}] @var{filename}
19351 Execute the command file @var{filename}.
19354 The lines in a command file are generally executed sequentially,
19355 unless the order of execution is changed by one of the
19356 @emph{flow-control commands} described below. The commands are not
19357 printed as they are executed. An error in any command terminates
19358 execution of the command file and control is returned to the console.
19360 @value{GDBN} searches for @var{filename} in the current directory and then
19361 on the search path (specified with the @samp{directory} command).
19363 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
19364 each command as it is executed. The option must be given before
19365 @var{filename}, and is interpreted as part of the filename anywhere else.
19367 Commands that would ask for confirmation if used interactively proceed
19368 without asking when used in a command file. Many @value{GDBN} commands that
19369 normally print messages to say what they are doing omit the messages
19370 when called from command files.
19372 @value{GDBN} also accepts command input from standard input. In this
19373 mode, normal output goes to standard output and error output goes to
19374 standard error. Errors in a command file supplied on standard input do
19375 not terminate execution of the command file---execution continues with
19379 gdb < cmds > log 2>&1
19382 (The syntax above will vary depending on the shell used.) This example
19383 will execute commands from the file @file{cmds}. All output and errors
19384 would be directed to @file{log}.
19386 Since commands stored on command files tend to be more general than
19387 commands typed interactively, they frequently need to deal with
19388 complicated situations, such as different or unexpected values of
19389 variables and symbols, changes in how the program being debugged is
19390 built, etc. @value{GDBN} provides a set of flow-control commands to
19391 deal with these complexities. Using these commands, you can write
19392 complex scripts that loop over data structures, execute commands
19393 conditionally, etc.
19400 This command allows to include in your script conditionally executed
19401 commands. The @code{if} command takes a single argument, which is an
19402 expression to evaluate. It is followed by a series of commands that
19403 are executed only if the expression is true (its value is nonzero).
19404 There can then optionally be an @code{else} line, followed by a series
19405 of commands that are only executed if the expression was false. The
19406 end of the list is marked by a line containing @code{end}.
19410 This command allows to write loops. Its syntax is similar to
19411 @code{if}: the command takes a single argument, which is an expression
19412 to evaluate, and must be followed by the commands to execute, one per
19413 line, terminated by an @code{end}. These commands are called the
19414 @dfn{body} of the loop. The commands in the body of @code{while} are
19415 executed repeatedly as long as the expression evaluates to true.
19419 This command exits the @code{while} loop in whose body it is included.
19420 Execution of the script continues after that @code{while}s @code{end}
19423 @kindex loop_continue
19424 @item loop_continue
19425 This command skips the execution of the rest of the body of commands
19426 in the @code{while} loop in whose body it is included. Execution
19427 branches to the beginning of the @code{while} loop, where it evaluates
19428 the controlling expression.
19430 @kindex end@r{ (if/else/while commands)}
19432 Terminate the block of commands that are the body of @code{if},
19433 @code{else}, or @code{while} flow-control commands.
19438 @subsection Commands for Controlled Output
19440 During the execution of a command file or a user-defined command, normal
19441 @value{GDBN} output is suppressed; the only output that appears is what is
19442 explicitly printed by the commands in the definition. This section
19443 describes three commands useful for generating exactly the output you
19448 @item echo @var{text}
19449 @c I do not consider backslash-space a standard C escape sequence
19450 @c because it is not in ANSI.
19451 Print @var{text}. Nonprinting characters can be included in
19452 @var{text} using C escape sequences, such as @samp{\n} to print a
19453 newline. @strong{No newline is printed unless you specify one.}
19454 In addition to the standard C escape sequences, a backslash followed
19455 by a space stands for a space. This is useful for displaying a
19456 string with spaces at the beginning or the end, since leading and
19457 trailing spaces are otherwise trimmed from all arguments.
19458 To print @samp{@w{ }and foo =@w{ }}, use the command
19459 @samp{echo \@w{ }and foo = \@w{ }}.
19461 A backslash at the end of @var{text} can be used, as in C, to continue
19462 the command onto subsequent lines. For example,
19465 echo This is some text\n\
19466 which is continued\n\
19467 onto several lines.\n
19470 produces the same output as
19473 echo This is some text\n
19474 echo which is continued\n
19475 echo onto several lines.\n
19479 @item output @var{expression}
19480 Print the value of @var{expression} and nothing but that value: no
19481 newlines, no @samp{$@var{nn} = }. The value is not entered in the
19482 value history either. @xref{Expressions, ,Expressions}, for more information
19485 @item output/@var{fmt} @var{expression}
19486 Print the value of @var{expression} in format @var{fmt}. You can use
19487 the same formats as for @code{print}. @xref{Output Formats,,Output
19488 Formats}, for more information.
19491 @item printf @var{template}, @var{expressions}@dots{}
19492 Print the values of one or more @var{expressions} under the control of
19493 the string @var{template}. To print several values, make
19494 @var{expressions} be a comma-separated list of individual expressions,
19495 which may be either numbers or pointers. Their values are printed as
19496 specified by @var{template}, exactly as a C program would do by
19497 executing the code below:
19500 printf (@var{template}, @var{expressions}@dots{});
19503 As in @code{C} @code{printf}, ordinary characters in @var{template}
19504 are printed verbatim, while @dfn{conversion specification} introduced
19505 by the @samp{%} character cause subsequent @var{expressions} to be
19506 evaluated, their values converted and formatted according to type and
19507 style information encoded in the conversion specifications, and then
19510 For example, you can print two values in hex like this:
19513 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
19516 @code{printf} supports all the standard @code{C} conversion
19517 specifications, including the flags and modifiers between the @samp{%}
19518 character and the conversion letter, with the following exceptions:
19522 The argument-ordering modifiers, such as @samp{2$}, are not supported.
19525 The modifier @samp{*} is not supported for specifying precision or
19529 The @samp{'} flag (for separation of digits into groups according to
19530 @code{LC_NUMERIC'}) is not supported.
19533 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
19537 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
19540 The conversion letters @samp{a} and @samp{A} are not supported.
19544 Note that the @samp{ll} type modifier is supported only if the
19545 underlying @code{C} implementation used to build @value{GDBN} supports
19546 the @code{long long int} type, and the @samp{L} type modifier is
19547 supported only if @code{long double} type is available.
19549 As in @code{C}, @code{printf} supports simple backslash-escape
19550 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
19551 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
19552 single character. Octal and hexadecimal escape sequences are not
19555 Additionally, @code{printf} supports conversion specifications for DFP
19556 (@dfn{Decimal Floating Point}) types using the following length modifiers
19557 together with a floating point specifier.
19562 @samp{H} for printing @code{Decimal32} types.
19565 @samp{D} for printing @code{Decimal64} types.
19568 @samp{DD} for printing @code{Decimal128} types.
19571 If the underlying @code{C} implementation used to build @value{GDBN} has
19572 support for the three length modifiers for DFP types, other modifiers
19573 such as width and precision will also be available for @value{GDBN} to use.
19575 In case there is no such @code{C} support, no additional modifiers will be
19576 available and the value will be printed in the standard way.
19578 Here's an example of printing DFP types using the above conversion letters:
19580 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
19586 @section Scripting @value{GDBN} using Python
19587 @cindex python scripting
19588 @cindex scripting with python
19590 You can script @value{GDBN} using the @uref{http://www.python.org/,
19591 Python programming language}. This feature is available only if
19592 @value{GDBN} was configured using @option{--with-python}.
19595 * Python Commands:: Accessing Python from @value{GDBN}.
19596 * Python API:: Accessing @value{GDBN} from Python.
19599 @node Python Commands
19600 @subsection Python Commands
19601 @cindex python commands
19602 @cindex commands to access python
19604 @value{GDBN} provides one command for accessing the Python interpreter,
19605 and one related setting:
19609 @item python @r{[}@var{code}@r{]}
19610 The @code{python} command can be used to evaluate Python code.
19612 If given an argument, the @code{python} command will evaluate the
19613 argument as a Python command. For example:
19616 (@value{GDBP}) python print 23
19620 If you do not provide an argument to @code{python}, it will act as a
19621 multi-line command, like @code{define}. In this case, the Python
19622 script is made up of subsequent command lines, given after the
19623 @code{python} command. This command list is terminated using a line
19624 containing @code{end}. For example:
19627 (@value{GDBP}) python
19629 End with a line saying just "end".
19635 @kindex maint set python print-stack
19636 @item maint set python print-stack
19637 By default, @value{GDBN} will print a stack trace when an error occurs
19638 in a Python script. This can be controlled using @code{maint set
19639 python print-stack}: if @code{on}, the default, then Python stack
19640 printing is enabled; if @code{off}, then Python stack printing is
19644 It is also possible to execute a Python script from the @value{GDBN}
19648 @item source @file{script-name}
19649 The script name must end with @samp{.py} and @value{GDBN} must be configured
19650 to recognize the script language based on filename extension using
19651 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
19653 @item python execfile ("script-name")
19654 This method is based on the @code{execfile} Python built-in function,
19655 and thus is always available.
19659 @subsection Python API
19661 @cindex programming in python
19663 @cindex python stdout
19664 @cindex python pagination
19665 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
19666 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
19667 A Python program which outputs to one of these streams may have its
19668 output interrupted by the user (@pxref{Screen Size}). In this
19669 situation, a Python @code{KeyboardInterrupt} exception is thrown.
19672 * Basic Python:: Basic Python Functions.
19673 * Exception Handling::
19674 * Auto-loading:: Automatically loading Python code.
19675 * Values From Inferior::
19676 * Types In Python:: Python representation of types.
19677 * Pretty Printing:: Pretty-printing values.
19678 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
19679 * Commands In Python:: Implementing new commands in Python.
19680 * Functions In Python:: Writing new convenience functions.
19681 * Objfiles In Python:: Object files.
19682 * Frames In Python:: Accessing inferior stack frames from Python.
19683 * Blocks In Python:: Accessing frame blocks from Python.
19684 * Symbols In Python:: Python representation of symbols.
19685 * Symbol Tables In Python:: Python representation of symbol tables.
19686 * Lazy Strings In Python:: Python representation of lazy strings.
19690 @subsubsection Basic Python
19692 @cindex python functions
19693 @cindex python module
19695 @value{GDBN} introduces a new Python module, named @code{gdb}. All
19696 methods and classes added by @value{GDBN} are placed in this module.
19697 @value{GDBN} automatically @code{import}s the @code{gdb} module for
19698 use in all scripts evaluated by the @code{python} command.
19700 @findex gdb.execute
19701 @defun execute command [from_tty]
19702 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
19703 If a GDB exception happens while @var{command} runs, it is
19704 translated as described in @ref{Exception Handling,,Exception Handling}.
19705 If no exceptions occur, this function returns @code{None}.
19707 @var{from_tty} specifies whether @value{GDBN} ought to consider this
19708 command as having originated from the user invoking it interactively.
19709 It must be a boolean value. If omitted, it defaults to @code{False}.
19712 @findex gdb.parameter
19713 @defun parameter parameter
19714 Return the value of a @value{GDBN} parameter. @var{parameter} is a
19715 string naming the parameter to look up; @var{parameter} may contain
19716 spaces if the parameter has a multi-part name. For example,
19717 @samp{print object} is a valid parameter name.
19719 If the named parameter does not exist, this function throws a
19720 @code{RuntimeError}. Otherwise, the parameter's value is converted to
19721 a Python value of the appropriate type, and returned.
19724 @findex gdb.history
19725 @defun history number
19726 Return a value from @value{GDBN}'s value history (@pxref{Value
19727 History}). @var{number} indicates which history element to return.
19728 If @var{number} is negative, then @value{GDBN} will take its absolute value
19729 and count backward from the last element (i.e., the most recent element) to
19730 find the value to return. If @var{number} is zero, then @value{GDBN} will
19731 return the most recent element. If the element specified by @var{number}
19732 doesn't exist in the value history, a @code{RuntimeError} exception will be
19735 If no exception is raised, the return value is always an instance of
19736 @code{gdb.Value} (@pxref{Values From Inferior}).
19739 @findex gdb.parse_and_eval
19740 @defun parse_and_eval expression
19741 Parse @var{expression} as an expression in the current language,
19742 evaluate it, and return the result as a @code{gdb.Value}.
19743 @var{expression} must be a string.
19745 This function can be useful when implementing a new command
19746 (@pxref{Commands In Python}), as it provides a way to parse the
19747 command's argument as an expression. It is also useful simply to
19748 compute values, for example, it is the only way to get the value of a
19749 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
19753 @defun write string
19754 Print a string to @value{GDBN}'s paginated standard output stream.
19755 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
19756 call this function.
19761 Flush @value{GDBN}'s paginated standard output stream. Flushing
19762 @code{sys.stdout} or @code{sys.stderr} will automatically call this
19766 @findex gdb.target_charset
19767 @defun target_charset
19768 Return the name of the current target character set (@pxref{Character
19769 Sets}). This differs from @code{gdb.parameter('target-charset')} in
19770 that @samp{auto} is never returned.
19773 @findex gdb.target_wide_charset
19774 @defun target_wide_charset
19775 Return the name of the current target wide character set
19776 (@pxref{Character Sets}). This differs from
19777 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
19781 @node Exception Handling
19782 @subsubsection Exception Handling
19783 @cindex python exceptions
19784 @cindex exceptions, python
19786 When executing the @code{python} command, Python exceptions
19787 uncaught within the Python code are translated to calls to
19788 @value{GDBN} error-reporting mechanism. If the command that called
19789 @code{python} does not handle the error, @value{GDBN} will
19790 terminate it and print an error message containing the Python
19791 exception name, the associated value, and the Python call stack
19792 backtrace at the point where the exception was raised. Example:
19795 (@value{GDBP}) python print foo
19796 Traceback (most recent call last):
19797 File "<string>", line 1, in <module>
19798 NameError: name 'foo' is not defined
19801 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
19802 code are converted to Python @code{RuntimeError} exceptions. User
19803 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
19804 prompt) is translated to a Python @code{KeyboardInterrupt}
19805 exception. If you catch these exceptions in your Python code, your
19806 exception handler will see @code{RuntimeError} or
19807 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
19808 message as its value, and the Python call stack backtrace at the
19809 Python statement closest to where the @value{GDBN} error occured as the
19813 @subsubsection Auto-loading
19814 @cindex auto-loading, Python
19816 When a new object file is read (for example, due to the @code{file}
19817 command, or because the inferior has loaded a shared library),
19818 @value{GDBN} will look for a file named @file{@var{objfile}-gdb.py},
19819 where @var{objfile} is the object file's real name, formed by ensuring
19820 that the file name is absolute, following all symlinks, and resolving
19821 @code{.} and @code{..} components. If this file exists and is
19822 readable, @value{GDBN} will evaluate it as a Python script.
19824 If this file does not exist, and if the parameter
19825 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
19826 then @value{GDBN} will use for its each separated directory component
19827 @code{component} the file named @file{@code{component}/@var{real-name}}, where
19828 @var{real-name} is the object file's real name, as described above.
19830 Finally, if this file does not exist, then @value{GDBN} will look for
19831 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
19832 @var{data-directory} is @value{GDBN}'s data directory (available via
19833 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
19834 is the object file's real name, as described above.
19836 When reading an auto-loaded file, @value{GDBN} sets the ``current
19837 objfile''. This is available via the @code{gdb.current_objfile}
19838 function (@pxref{Objfiles In Python}). This can be useful for
19839 registering objfile-specific pretty-printers.
19841 The auto-loading feature is useful for supplying application-specific
19842 debugging commands and scripts. You can enable or disable this
19843 feature, and view its current state.
19846 @kindex maint set python auto-load
19847 @item maint set python auto-load [yes|no]
19848 Enable or disable the Python auto-loading feature.
19850 @kindex show python auto-load
19851 @item show python auto-load
19852 Show whether Python auto-loading is enabled or disabled.
19855 @value{GDBN} does not track which files it has already auto-loaded.
19856 So, your @samp{-gdb.py} file should take care to ensure that it may be
19857 evaluated multiple times without error.
19859 @node Values From Inferior
19860 @subsubsection Values From Inferior
19861 @cindex values from inferior, with Python
19862 @cindex python, working with values from inferior
19864 @cindex @code{gdb.Value}
19865 @value{GDBN} provides values it obtains from the inferior program in
19866 an object of type @code{gdb.Value}. @value{GDBN} uses this object
19867 for its internal bookkeeping of the inferior's values, and for
19868 fetching values when necessary.
19870 Inferior values that are simple scalars can be used directly in
19871 Python expressions that are valid for the value's data type. Here's
19872 an example for an integer or floating-point value @code{some_val}:
19879 As result of this, @code{bar} will also be a @code{gdb.Value} object
19880 whose values are of the same type as those of @code{some_val}.
19882 Inferior values that are structures or instances of some class can
19883 be accessed using the Python @dfn{dictionary syntax}. For example, if
19884 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
19885 can access its @code{foo} element with:
19888 bar = some_val['foo']
19891 Again, @code{bar} will also be a @code{gdb.Value} object.
19893 The following attributes are provided:
19896 @defivar Value address
19897 If this object is addressable, this read-only attribute holds a
19898 @code{gdb.Value} object representing the address. Otherwise,
19899 this attribute holds @code{None}.
19902 @cindex optimized out value in Python
19903 @defivar Value is_optimized_out
19904 This read-only boolean attribute is true if the compiler optimized out
19905 this value, thus it is not available for fetching from the inferior.
19908 @defivar Value type
19909 The type of this @code{gdb.Value}. The value of this attribute is a
19910 @code{gdb.Type} object.
19914 The following methods are provided:
19917 @defmethod Value cast type
19918 Return a new instance of @code{gdb.Value} that is the result of
19919 casting this instance to the type described by @var{type}, which must
19920 be a @code{gdb.Type} object. If the cast cannot be performed for some
19921 reason, this method throws an exception.
19924 @defmethod Value dereference
19925 For pointer data types, this method returns a new @code{gdb.Value} object
19926 whose contents is the object pointed to by the pointer. For example, if
19927 @code{foo} is a C pointer to an @code{int}, declared in your C program as
19934 then you can use the corresponding @code{gdb.Value} to access what
19935 @code{foo} points to like this:
19938 bar = foo.dereference ()
19941 The result @code{bar} will be a @code{gdb.Value} object holding the
19942 value pointed to by @code{foo}.
19945 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
19946 If this @code{gdb.Value} represents a string, then this method
19947 converts the contents to a Python string. Otherwise, this method will
19948 throw an exception.
19950 Strings are recognized in a language-specific way; whether a given
19951 @code{gdb.Value} represents a string is determined by the current
19954 For C-like languages, a value is a string if it is a pointer to or an
19955 array of characters or ints. The string is assumed to be terminated
19956 by a zero of the appropriate width. However if the optional length
19957 argument is given, the string will be converted to that given length,
19958 ignoring any embedded zeros that the string may contain.
19960 If the optional @var{encoding} argument is given, it must be a string
19961 naming the encoding of the string in the @code{gdb.Value}, such as
19962 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
19963 the same encodings as the corresponding argument to Python's
19964 @code{string.decode} method, and the Python codec machinery will be used
19965 to convert the string. If @var{encoding} is not given, or if
19966 @var{encoding} is the empty string, then either the @code{target-charset}
19967 (@pxref{Character Sets}) will be used, or a language-specific encoding
19968 will be used, if the current language is able to supply one.
19970 The optional @var{errors} argument is the same as the corresponding
19971 argument to Python's @code{string.decode} method.
19973 If the optional @var{length} argument is given, the string will be
19974 fetched and converted to the given length.
19977 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
19978 If this @code{gdb.Value} represents a string, then this method
19979 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
19980 In Python}). Otherwise, this method will throw an exception.
19982 If the optional @var{encoding} argument is given, it must be a string
19983 naming the encoding of the @code{gdb.LazyString}. Some examples are:
19984 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
19985 @var{encoding} argument is an encoding that @value{GDBN} does
19986 recognize, @value{GDBN} will raise an error.
19988 When a lazy string is printed, the @value{GDBN} encoding machinery is
19989 used to convert the string during printing. If the optional
19990 @var{encoding} argument is not provided, or is an empty string,
19991 @value{GDBN} will automatically select the encoding most suitable for
19992 the string type. For further information on encoding in @value{GDBN}
19993 please see @ref{Character Sets}.
19995 If the optional @var{length} argument is given, the string will be
19996 fetched and encoded to the length of characters specified. If
19997 the @var{length} argument is not provided, the string will be fetched
19998 and encoded until a null of appropriate width is found.
20002 @node Types In Python
20003 @subsubsection Types In Python
20004 @cindex types in Python
20005 @cindex Python, working with types
20008 @value{GDBN} represents types from the inferior using the class
20011 The following type-related functions are available in the @code{gdb}
20014 @findex gdb.lookup_type
20015 @defun lookup_type name [block]
20016 This function looks up a type by name. @var{name} is the name of the
20017 type to look up. It must be a string.
20019 If @var{block} is given, then @var{name} is looked up in that scope.
20020 Otherwise, it is searched for globally.
20022 Ordinarily, this function will return an instance of @code{gdb.Type}.
20023 If the named type cannot be found, it will throw an exception.
20026 An instance of @code{Type} has the following attributes:
20030 The type code for this type. The type code will be one of the
20031 @code{TYPE_CODE_} constants defined below.
20034 @defivar Type sizeof
20035 The size of this type, in target @code{char} units. Usually, a
20036 target's @code{char} type will be an 8-bit byte. However, on some
20037 unusual platforms, this type may have a different size.
20041 The tag name for this type. The tag name is the name after
20042 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20043 languages have this concept. If this type has no tag name, then
20044 @code{None} is returned.
20048 The following methods are provided:
20051 @defmethod Type fields
20052 For structure and union types, this method returns the fields. Range
20053 types have two fields, the minimum and maximum values. Enum types
20054 have one field per enum constant. Function and method types have one
20055 field per parameter. The base types of C@t{++} classes are also
20056 represented as fields. If the type has no fields, or does not fit
20057 into one of these categories, an empty sequence will be returned.
20059 Each field is an object, with some pre-defined attributes:
20062 This attribute is not available for @code{static} fields (as in
20063 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20064 position of the field.
20067 The name of the field, or @code{None} for anonymous fields.
20070 This is @code{True} if the field is artificial, usually meaning that
20071 it was provided by the compiler and not the user. This attribute is
20072 always provided, and is @code{False} if the field is not artificial.
20074 @item is_base_class
20075 This is @code{True} if the field represents a base class of a C@t{++}
20076 structure. This attribute is always provided, and is @code{False}
20077 if the field is not a base class of the type that is the argument of
20078 @code{fields}, or if that type was not a C@t{++} class.
20081 If the field is packed, or is a bitfield, then this will have a
20082 non-zero value, which is the size of the field in bits. Otherwise,
20083 this will be zero; in this case the field's size is given by its type.
20086 The type of the field. This is usually an instance of @code{Type},
20087 but it can be @code{None} in some situations.
20091 @defmethod Type const
20092 Return a new @code{gdb.Type} object which represents a
20093 @code{const}-qualified variant of this type.
20096 @defmethod Type volatile
20097 Return a new @code{gdb.Type} object which represents a
20098 @code{volatile}-qualified variant of this type.
20101 @defmethod Type unqualified
20102 Return a new @code{gdb.Type} object which represents an unqualified
20103 variant of this type. That is, the result is neither @code{const} nor
20107 @defmethod Type range
20108 Return a Python @code{Tuple} object that contains two elements: the
20109 low bound of the argument type and the high bound of that type. If
20110 the type does not have a range, @value{GDBN} will raise a
20111 @code{RuntimeError} exception.
20114 @defmethod Type reference
20115 Return a new @code{gdb.Type} object which represents a reference to this
20119 @defmethod Type pointer
20120 Return a new @code{gdb.Type} object which represents a pointer to this
20124 @defmethod Type strip_typedefs
20125 Return a new @code{gdb.Type} that represents the real type,
20126 after removing all layers of typedefs.
20129 @defmethod Type target
20130 Return a new @code{gdb.Type} object which represents the target type
20133 For a pointer type, the target type is the type of the pointed-to
20134 object. For an array type (meaning C-like arrays), the target type is
20135 the type of the elements of the array. For a function or method type,
20136 the target type is the type of the return value. For a complex type,
20137 the target type is the type of the elements. For a typedef, the
20138 target type is the aliased type.
20140 If the type does not have a target, this method will throw an
20144 @defmethod Type template_argument n [block]
20145 If this @code{gdb.Type} is an instantiation of a template, this will
20146 return a new @code{gdb.Type} which represents the type of the
20147 @var{n}th template argument.
20149 If this @code{gdb.Type} is not a template type, this will throw an
20150 exception. Ordinarily, only C@t{++} code will have template types.
20152 If @var{block} is given, then @var{name} is looked up in that scope.
20153 Otherwise, it is searched for globally.
20158 Each type has a code, which indicates what category this type falls
20159 into. The available type categories are represented by constants
20160 defined in the @code{gdb} module:
20163 @findex TYPE_CODE_PTR
20164 @findex gdb.TYPE_CODE_PTR
20165 @item TYPE_CODE_PTR
20166 The type is a pointer.
20168 @findex TYPE_CODE_ARRAY
20169 @findex gdb.TYPE_CODE_ARRAY
20170 @item TYPE_CODE_ARRAY
20171 The type is an array.
20173 @findex TYPE_CODE_STRUCT
20174 @findex gdb.TYPE_CODE_STRUCT
20175 @item TYPE_CODE_STRUCT
20176 The type is a structure.
20178 @findex TYPE_CODE_UNION
20179 @findex gdb.TYPE_CODE_UNION
20180 @item TYPE_CODE_UNION
20181 The type is a union.
20183 @findex TYPE_CODE_ENUM
20184 @findex gdb.TYPE_CODE_ENUM
20185 @item TYPE_CODE_ENUM
20186 The type is an enum.
20188 @findex TYPE_CODE_FLAGS
20189 @findex gdb.TYPE_CODE_FLAGS
20190 @item TYPE_CODE_FLAGS
20191 A bit flags type, used for things such as status registers.
20193 @findex TYPE_CODE_FUNC
20194 @findex gdb.TYPE_CODE_FUNC
20195 @item TYPE_CODE_FUNC
20196 The type is a function.
20198 @findex TYPE_CODE_INT
20199 @findex gdb.TYPE_CODE_INT
20200 @item TYPE_CODE_INT
20201 The type is an integer type.
20203 @findex TYPE_CODE_FLT
20204 @findex gdb.TYPE_CODE_FLT
20205 @item TYPE_CODE_FLT
20206 A floating point type.
20208 @findex TYPE_CODE_VOID
20209 @findex gdb.TYPE_CODE_VOID
20210 @item TYPE_CODE_VOID
20211 The special type @code{void}.
20213 @findex TYPE_CODE_SET
20214 @findex gdb.TYPE_CODE_SET
20215 @item TYPE_CODE_SET
20218 @findex TYPE_CODE_RANGE
20219 @findex gdb.TYPE_CODE_RANGE
20220 @item TYPE_CODE_RANGE
20221 A range type, that is, an integer type with bounds.
20223 @findex TYPE_CODE_STRING
20224 @findex gdb.TYPE_CODE_STRING
20225 @item TYPE_CODE_STRING
20226 A string type. Note that this is only used for certain languages with
20227 language-defined string types; C strings are not represented this way.
20229 @findex TYPE_CODE_BITSTRING
20230 @findex gdb.TYPE_CODE_BITSTRING
20231 @item TYPE_CODE_BITSTRING
20234 @findex TYPE_CODE_ERROR
20235 @findex gdb.TYPE_CODE_ERROR
20236 @item TYPE_CODE_ERROR
20237 An unknown or erroneous type.
20239 @findex TYPE_CODE_METHOD
20240 @findex gdb.TYPE_CODE_METHOD
20241 @item TYPE_CODE_METHOD
20242 A method type, as found in C@t{++} or Java.
20244 @findex TYPE_CODE_METHODPTR
20245 @findex gdb.TYPE_CODE_METHODPTR
20246 @item TYPE_CODE_METHODPTR
20247 A pointer-to-member-function.
20249 @findex TYPE_CODE_MEMBERPTR
20250 @findex gdb.TYPE_CODE_MEMBERPTR
20251 @item TYPE_CODE_MEMBERPTR
20252 A pointer-to-member.
20254 @findex TYPE_CODE_REF
20255 @findex gdb.TYPE_CODE_REF
20256 @item TYPE_CODE_REF
20259 @findex TYPE_CODE_CHAR
20260 @findex gdb.TYPE_CODE_CHAR
20261 @item TYPE_CODE_CHAR
20264 @findex TYPE_CODE_BOOL
20265 @findex gdb.TYPE_CODE_BOOL
20266 @item TYPE_CODE_BOOL
20269 @findex TYPE_CODE_COMPLEX
20270 @findex gdb.TYPE_CODE_COMPLEX
20271 @item TYPE_CODE_COMPLEX
20272 A complex float type.
20274 @findex TYPE_CODE_TYPEDEF
20275 @findex gdb.TYPE_CODE_TYPEDEF
20276 @item TYPE_CODE_TYPEDEF
20277 A typedef to some other type.
20279 @findex TYPE_CODE_NAMESPACE
20280 @findex gdb.TYPE_CODE_NAMESPACE
20281 @item TYPE_CODE_NAMESPACE
20282 A C@t{++} namespace.
20284 @findex TYPE_CODE_DECFLOAT
20285 @findex gdb.TYPE_CODE_DECFLOAT
20286 @item TYPE_CODE_DECFLOAT
20287 A decimal floating point type.
20289 @findex TYPE_CODE_INTERNAL_FUNCTION
20290 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
20291 @item TYPE_CODE_INTERNAL_FUNCTION
20292 A function internal to @value{GDBN}. This is the type used to represent
20293 convenience functions.
20296 @node Pretty Printing
20297 @subsubsection Pretty Printing
20299 @value{GDBN} provides a mechanism to allow pretty-printing of values
20300 using Python code. The pretty-printer API allows application-specific
20301 code to greatly simplify the display of complex objects. This
20302 mechanism works for both MI and the CLI.
20304 For example, here is how a C@t{++} @code{std::string} looks without a
20308 (@value{GDBP}) print s
20310 static npos = 4294967295,
20312 <std::allocator<char>> = @{
20313 <__gnu_cxx::new_allocator<char>> = @{<No data fields>@}, <No data fields>@},
20314 members of std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider:
20315 _M_p = 0x804a014 "abcd"
20320 After a pretty-printer for @code{std::string} has been installed, only
20321 the contents are printed:
20324 (@value{GDBP}) print s
20328 A pretty-printer is just an object that holds a value and implements a
20329 specific interface, defined here.
20331 @defop Operation {pretty printer} children (self)
20332 @value{GDBN} will call this method on a pretty-printer to compute the
20333 children of the pretty-printer's value.
20335 This method must return an object conforming to the Python iterator
20336 protocol. Each item returned by the iterator must be a tuple holding
20337 two elements. The first element is the ``name'' of the child; the
20338 second element is the child's value. The value can be any Python
20339 object which is convertible to a @value{GDBN} value.
20341 This method is optional. If it does not exist, @value{GDBN} will act
20342 as though the value has no children.
20345 @defop Operation {pretty printer} display_hint (self)
20346 The CLI may call this method and use its result to change the
20347 formatting of a value. The result will also be supplied to an MI
20348 consumer as a @samp{displayhint} attribute of the variable being
20351 This method is optional. If it does exist, this method must return a
20354 Some display hints are predefined by @value{GDBN}:
20358 Indicate that the object being printed is ``array-like''. The CLI
20359 uses this to respect parameters such as @code{set print elements} and
20360 @code{set print array}.
20363 Indicate that the object being printed is ``map-like'', and that the
20364 children of this value can be assumed to alternate between keys and
20368 Indicate that the object being printed is ``string-like''. If the
20369 printer's @code{to_string} method returns a Python string of some
20370 kind, then @value{GDBN} will call its internal language-specific
20371 string-printing function to format the string. For the CLI this means
20372 adding quotation marks, possibly escaping some characters, respecting
20373 @code{set print elements}, and the like.
20377 @defop Operation {pretty printer} to_string (self)
20378 @value{GDBN} will call this method to display the string
20379 representation of the value passed to the object's constructor.
20381 When printing from the CLI, if the @code{to_string} method exists,
20382 then @value{GDBN} will prepend its result to the values returned by
20383 @code{children}. Exactly how this formatting is done is dependent on
20384 the display hint, and may change as more hints are added. Also,
20385 depending on the print settings (@pxref{Print Settings}), the CLI may
20386 print just the result of @code{to_string} in a stack trace, omitting
20387 the result of @code{children}.
20389 If this method returns a string, it is printed verbatim.
20391 Otherwise, if this method returns an instance of @code{gdb.Value},
20392 then @value{GDBN} prints this value. This may result in a call to
20393 another pretty-printer.
20395 If instead the method returns a Python value which is convertible to a
20396 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
20397 the resulting value. Again, this may result in a call to another
20398 pretty-printer. Python scalars (integers, floats, and booleans) and
20399 strings are convertible to @code{gdb.Value}; other types are not.
20401 If the result is not one of these types, an exception is raised.
20404 @node Selecting Pretty-Printers
20405 @subsubsection Selecting Pretty-Printers
20407 The Python list @code{gdb.pretty_printers} contains an array of
20408 functions that have been registered via addition as a pretty-printer.
20409 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
20412 A function on one of these lists is passed a single @code{gdb.Value}
20413 argument and should return a pretty-printer object conforming to the
20414 interface definition above (@pxref{Pretty Printing}). If a function
20415 cannot create a pretty-printer for the value, it should return
20418 @value{GDBN} first checks the @code{pretty_printers} attribute of each
20419 @code{gdb.Objfile} and iteratively calls each function in the list for
20420 that @code{gdb.Objfile} until it receives a pretty-printer object.
20421 After these lists have been exhausted, it tries the global
20422 @code{gdb.pretty-printers} list, again calling each function until an
20423 object is returned.
20425 The order in which the objfiles are searched is not specified. For a
20426 given list, functions are always invoked from the head of the list,
20427 and iterated over sequentially until the end of the list, or a printer
20428 object is returned.
20430 Here is an example showing how a @code{std::string} printer might be
20434 class StdStringPrinter:
20435 "Print a std::string"
20437 def __init__ (self, val):
20440 def to_string (self):
20441 return self.val['_M_dataplus']['_M_p']
20443 def display_hint (self):
20447 And here is an example showing how a lookup function for the printer
20448 example above might be written.
20451 def str_lookup_function (val):
20453 lookup_tag = val.type.tag
20454 regex = re.compile ("^std::basic_string<char,.*>$")
20455 if lookup_tag == None:
20457 if regex.match (lookup_tag):
20458 return StdStringPrinter (val)
20463 The example lookup function extracts the value's type, and attempts to
20464 match it to a type that it can pretty-print. If it is a type the
20465 printer can pretty-print, it will return a printer object. If not, it
20466 returns @code{None}.
20468 We recommend that you put your core pretty-printers into a Python
20469 package. If your pretty-printers are for use with a library, we
20470 further recommend embedding a version number into the package name.
20471 This practice will enable @value{GDBN} to load multiple versions of
20472 your pretty-printers at the same time, because they will have
20475 You should write auto-loaded code (@pxref{Auto-loading}) such that it
20476 can be evaluated multiple times without changing its meaning. An
20477 ideal auto-load file will consist solely of @code{import}s of your
20478 printer modules, followed by a call to a register pretty-printers with
20479 the current objfile.
20481 Taken as a whole, this approach will scale nicely to multiple
20482 inferiors, each potentially using a different library version.
20483 Embedding a version number in the Python package name will ensure that
20484 @value{GDBN} is able to load both sets of printers simultaneously.
20485 Then, because the search for pretty-printers is done by objfile, and
20486 because your auto-loaded code took care to register your library's
20487 printers with a specific objfile, @value{GDBN} will find the correct
20488 printers for the specific version of the library used by each
20491 To continue the @code{std::string} example (@pxref{Pretty Printing}),
20492 this code might appear in @code{gdb.libstdcxx.v6}:
20495 def register_printers (objfile):
20496 objfile.pretty_printers.add (str_lookup_function)
20500 And then the corresponding contents of the auto-load file would be:
20503 import gdb.libstdcxx.v6
20504 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
20507 @node Commands In Python
20508 @subsubsection Commands In Python
20510 @cindex commands in python
20511 @cindex python commands
20512 You can implement new @value{GDBN} CLI commands in Python. A CLI
20513 command is implemented using an instance of the @code{gdb.Command}
20514 class, most commonly using a subclass.
20516 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
20517 The object initializer for @code{Command} registers the new command
20518 with @value{GDBN}. This initializer is normally invoked from the
20519 subclass' own @code{__init__} method.
20521 @var{name} is the name of the command. If @var{name} consists of
20522 multiple words, then the initial words are looked for as prefix
20523 commands. In this case, if one of the prefix commands does not exist,
20524 an exception is raised.
20526 There is no support for multi-line commands.
20528 @var{command_class} should be one of the @samp{COMMAND_} constants
20529 defined below. This argument tells @value{GDBN} how to categorize the
20530 new command in the help system.
20532 @var{completer_class} is an optional argument. If given, it should be
20533 one of the @samp{COMPLETE_} constants defined below. This argument
20534 tells @value{GDBN} how to perform completion for this command. If not
20535 given, @value{GDBN} will attempt to complete using the object's
20536 @code{complete} method (see below); if no such method is found, an
20537 error will occur when completion is attempted.
20539 @var{prefix} is an optional argument. If @code{True}, then the new
20540 command is a prefix command; sub-commands of this command may be
20543 The help text for the new command is taken from the Python
20544 documentation string for the command's class, if there is one. If no
20545 documentation string is provided, the default value ``This command is
20546 not documented.'' is used.
20549 @cindex don't repeat Python command
20550 @defmethod Command dont_repeat
20551 By default, a @value{GDBN} command is repeated when the user enters a
20552 blank line at the command prompt. A command can suppress this
20553 behavior by invoking the @code{dont_repeat} method. This is similar
20554 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
20557 @defmethod Command invoke argument from_tty
20558 This method is called by @value{GDBN} when this command is invoked.
20560 @var{argument} is a string. It is the argument to the command, after
20561 leading and trailing whitespace has been stripped.
20563 @var{from_tty} is a boolean argument. When true, this means that the
20564 command was entered by the user at the terminal; when false it means
20565 that the command came from elsewhere.
20567 If this method throws an exception, it is turned into a @value{GDBN}
20568 @code{error} call. Otherwise, the return value is ignored.
20571 @cindex completion of Python commands
20572 @defmethod Command complete text word
20573 This method is called by @value{GDBN} when the user attempts
20574 completion on this command. All forms of completion are handled by
20575 this method, that is, the @key{TAB} and @key{M-?} key bindings
20576 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
20579 The arguments @var{text} and @var{word} are both strings. @var{text}
20580 holds the complete command line up to the cursor's location.
20581 @var{word} holds the last word of the command line; this is computed
20582 using a word-breaking heuristic.
20584 The @code{complete} method can return several values:
20587 If the return value is a sequence, the contents of the sequence are
20588 used as the completions. It is up to @code{complete} to ensure that the
20589 contents actually do complete the word. A zero-length sequence is
20590 allowed, it means that there were no completions available. Only
20591 string elements of the sequence are used; other elements in the
20592 sequence are ignored.
20595 If the return value is one of the @samp{COMPLETE_} constants defined
20596 below, then the corresponding @value{GDBN}-internal completion
20597 function is invoked, and its result is used.
20600 All other results are treated as though there were no available
20605 When a new command is registered, it must be declared as a member of
20606 some general class of commands. This is used to classify top-level
20607 commands in the on-line help system; note that prefix commands are not
20608 listed under their own category but rather that of their top-level
20609 command. The available classifications are represented by constants
20610 defined in the @code{gdb} module:
20613 @findex COMMAND_NONE
20614 @findex gdb.COMMAND_NONE
20616 The command does not belong to any particular class. A command in
20617 this category will not be displayed in any of the help categories.
20619 @findex COMMAND_RUNNING
20620 @findex gdb.COMMAND_RUNNING
20621 @item COMMAND_RUNNING
20622 The command is related to running the inferior. For example,
20623 @code{start}, @code{step}, and @code{continue} are in this category.
20624 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
20625 commands in this category.
20627 @findex COMMAND_DATA
20628 @findex gdb.COMMAND_DATA
20630 The command is related to data or variables. For example,
20631 @code{call}, @code{find}, and @code{print} are in this category. Type
20632 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
20635 @findex COMMAND_STACK
20636 @findex gdb.COMMAND_STACK
20637 @item COMMAND_STACK
20638 The command has to do with manipulation of the stack. For example,
20639 @code{backtrace}, @code{frame}, and @code{return} are in this
20640 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
20641 list of commands in this category.
20643 @findex COMMAND_FILES
20644 @findex gdb.COMMAND_FILES
20645 @item COMMAND_FILES
20646 This class is used for file-related commands. For example,
20647 @code{file}, @code{list} and @code{section} are in this category.
20648 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
20649 commands in this category.
20651 @findex COMMAND_SUPPORT
20652 @findex gdb.COMMAND_SUPPORT
20653 @item COMMAND_SUPPORT
20654 This should be used for ``support facilities'', generally meaning
20655 things that are useful to the user when interacting with @value{GDBN},
20656 but not related to the state of the inferior. For example,
20657 @code{help}, @code{make}, and @code{shell} are in this category. Type
20658 @kbd{help support} at the @value{GDBN} prompt to see a list of
20659 commands in this category.
20661 @findex COMMAND_STATUS
20662 @findex gdb.COMMAND_STATUS
20663 @item COMMAND_STATUS
20664 The command is an @samp{info}-related command, that is, related to the
20665 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
20666 and @code{show} are in this category. Type @kbd{help status} at the
20667 @value{GDBN} prompt to see a list of commands in this category.
20669 @findex COMMAND_BREAKPOINTS
20670 @findex gdb.COMMAND_BREAKPOINTS
20671 @item COMMAND_BREAKPOINTS
20672 The command has to do with breakpoints. For example, @code{break},
20673 @code{clear}, and @code{delete} are in this category. Type @kbd{help
20674 breakpoints} at the @value{GDBN} prompt to see a list of commands in
20677 @findex COMMAND_TRACEPOINTS
20678 @findex gdb.COMMAND_TRACEPOINTS
20679 @item COMMAND_TRACEPOINTS
20680 The command has to do with tracepoints. For example, @code{trace},
20681 @code{actions}, and @code{tfind} are in this category. Type
20682 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
20683 commands in this category.
20685 @findex COMMAND_OBSCURE
20686 @findex gdb.COMMAND_OBSCURE
20687 @item COMMAND_OBSCURE
20688 The command is only used in unusual circumstances, or is not of
20689 general interest to users. For example, @code{checkpoint},
20690 @code{fork}, and @code{stop} are in this category. Type @kbd{help
20691 obscure} at the @value{GDBN} prompt to see a list of commands in this
20694 @findex COMMAND_MAINTENANCE
20695 @findex gdb.COMMAND_MAINTENANCE
20696 @item COMMAND_MAINTENANCE
20697 The command is only useful to @value{GDBN} maintainers. The
20698 @code{maintenance} and @code{flushregs} commands are in this category.
20699 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
20700 commands in this category.
20703 A new command can use a predefined completion function, either by
20704 specifying it via an argument at initialization, or by returning it
20705 from the @code{complete} method. These predefined completion
20706 constants are all defined in the @code{gdb} module:
20709 @findex COMPLETE_NONE
20710 @findex gdb.COMPLETE_NONE
20711 @item COMPLETE_NONE
20712 This constant means that no completion should be done.
20714 @findex COMPLETE_FILENAME
20715 @findex gdb.COMPLETE_FILENAME
20716 @item COMPLETE_FILENAME
20717 This constant means that filename completion should be performed.
20719 @findex COMPLETE_LOCATION
20720 @findex gdb.COMPLETE_LOCATION
20721 @item COMPLETE_LOCATION
20722 This constant means that location completion should be done.
20723 @xref{Specify Location}.
20725 @findex COMPLETE_COMMAND
20726 @findex gdb.COMPLETE_COMMAND
20727 @item COMPLETE_COMMAND
20728 This constant means that completion should examine @value{GDBN}
20731 @findex COMPLETE_SYMBOL
20732 @findex gdb.COMPLETE_SYMBOL
20733 @item COMPLETE_SYMBOL
20734 This constant means that completion should be done using symbol names
20738 The following code snippet shows how a trivial CLI command can be
20739 implemented in Python:
20742 class HelloWorld (gdb.Command):
20743 """Greet the whole world."""
20745 def __init__ (self):
20746 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20748 def invoke (self, arg, from_tty):
20749 print "Hello, World!"
20754 The last line instantiates the class, and is necessary to trigger the
20755 registration of the command with @value{GDBN}. Depending on how the
20756 Python code is read into @value{GDBN}, you may need to import the
20757 @code{gdb} module explicitly.
20759 @node Functions In Python
20760 @subsubsection Writing new convenience functions
20762 @cindex writing convenience functions
20763 @cindex convenience functions in python
20764 @cindex python convenience functions
20765 @tindex gdb.Function
20767 You can implement new convenience functions (@pxref{Convenience Vars})
20768 in Python. A convenience function is an instance of a subclass of the
20769 class @code{gdb.Function}.
20771 @defmethod Function __init__ name
20772 The initializer for @code{Function} registers the new function with
20773 @value{GDBN}. The argument @var{name} is the name of the function,
20774 a string. The function will be visible to the user as a convenience
20775 variable of type @code{internal function}, whose name is the same as
20776 the given @var{name}.
20778 The documentation for the new function is taken from the documentation
20779 string for the new class.
20782 @defmethod Function invoke @var{*args}
20783 When a convenience function is evaluated, its arguments are converted
20784 to instances of @code{gdb.Value}, and then the function's
20785 @code{invoke} method is called. Note that @value{GDBN} does not
20786 predetermine the arity of convenience functions. Instead, all
20787 available arguments are passed to @code{invoke}, following the
20788 standard Python calling convention. In particular, a convenience
20789 function can have default values for parameters without ill effect.
20791 The return value of this method is used as its value in the enclosing
20792 expression. If an ordinary Python value is returned, it is converted
20793 to a @code{gdb.Value} following the usual rules.
20796 The following code snippet shows how a trivial convenience function can
20797 be implemented in Python:
20800 class Greet (gdb.Function):
20801 """Return string to greet someone.
20802 Takes a name as argument."""
20804 def __init__ (self):
20805 super (Greet, self).__init__ ("greet")
20807 def invoke (self, name):
20808 return "Hello, %s!" % name.string ()
20813 The last line instantiates the class, and is necessary to trigger the
20814 registration of the function with @value{GDBN}. Depending on how the
20815 Python code is read into @value{GDBN}, you may need to import the
20816 @code{gdb} module explicitly.
20818 @node Objfiles In Python
20819 @subsubsection Objfiles In Python
20821 @cindex objfiles in python
20822 @tindex gdb.Objfile
20824 @value{GDBN} loads symbols for an inferior from various
20825 symbol-containing files (@pxref{Files}). These include the primary
20826 executable file, any shared libraries used by the inferior, and any
20827 separate debug info files (@pxref{Separate Debug Files}).
20828 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
20830 The following objfile-related functions are available in the
20833 @findex gdb.current_objfile
20834 @defun current_objfile
20835 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
20836 sets the ``current objfile'' to the corresponding objfile. This
20837 function returns the current objfile. If there is no current objfile,
20838 this function returns @code{None}.
20841 @findex gdb.objfiles
20843 Return a sequence of all the objfiles current known to @value{GDBN}.
20844 @xref{Objfiles In Python}.
20847 Each objfile is represented by an instance of the @code{gdb.Objfile}
20850 @defivar Objfile filename
20851 The file name of the objfile as a string.
20854 @defivar Objfile pretty_printers
20855 The @code{pretty_printers} attribute is a list of functions. It is
20856 used to look up pretty-printers. A @code{Value} is passed to each
20857 function in order; if the function returns @code{None}, then the
20858 search continues. Otherwise, the return value should be an object
20859 which is used to format the value. @xref{Pretty Printing}, for more
20863 @node Frames In Python
20864 @subsubsection Accessing inferior stack frames from Python.
20866 @cindex frames in python
20867 When the debugged program stops, @value{GDBN} is able to analyze its call
20868 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
20869 represents a frame in the stack. A @code{gdb.Frame} object is only valid
20870 while its corresponding frame exists in the inferior's stack. If you try
20871 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
20874 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
20878 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
20882 The following frame-related functions are available in the @code{gdb} module:
20884 @findex gdb.selected_frame
20885 @defun selected_frame
20886 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
20889 @defun frame_stop_reason_string reason
20890 Return a string explaining the reason why @value{GDBN} stopped unwinding
20891 frames, as expressed by the given @var{reason} code (an integer, see the
20892 @code{unwind_stop_reason} method further down in this section).
20895 A @code{gdb.Frame} object has the following methods:
20898 @defmethod Frame is_valid
20899 Returns true if the @code{gdb.Frame} object is valid, false if not.
20900 A frame object can become invalid if the frame it refers to doesn't
20901 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
20902 an exception if it is invalid at the time the method is called.
20905 @defmethod Frame name
20906 Returns the function name of the frame, or @code{None} if it can't be
20910 @defmethod Frame type
20911 Returns the type of the frame. The value can be one of
20912 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
20913 or @code{gdb.SENTINEL_FRAME}.
20916 @defmethod Frame unwind_stop_reason
20917 Return an integer representing the reason why it's not possible to find
20918 more frames toward the outermost frame. Use
20919 @code{gdb.frame_stop_reason_string} to convert the value returned by this
20920 function to a string.
20923 @defmethod Frame pc
20924 Returns the frame's resume address.
20927 @defmethod Frame block
20928 Return the frame's code block. @xref{Blocks In Python}.
20931 @defmethod Frame function
20932 Return the symbol for the function corresponding to this frame.
20933 @xref{Symbols In Python}.
20936 @defmethod Frame older
20937 Return the frame that called this frame.
20940 @defmethod Frame newer
20941 Return the frame called by this frame.
20944 @defmethod Frame find_sal
20945 Return the frame's symtab and line object.
20946 @xref{Symbol Tables In Python}.
20949 @defmethod Frame read_var variable @r{[}block@r{]}
20950 Return the value of @var{variable} in this frame. If the optional
20951 argument @var{block} is provided, search for the variable from that
20952 block; otherwise start at the frame's current block (which is
20953 determined by the frame's current program counter). @var{variable}
20954 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
20955 @code{gdb.Block} object.
20958 @defmethod Frame select
20959 Set this frame to be the selected frame. @xref{Stack, ,Examining the
20964 @node Blocks In Python
20965 @subsubsection Accessing frame blocks from Python.
20967 @cindex blocks in python
20970 Within each frame, @value{GDBN} maintains information on each block
20971 stored in that frame. These blocks are organized hierarchically, and
20972 are represented individually in Python as a @code{gdb.Block}.
20973 Please see @ref{Frames In Python}, for a more in-depth discussion on
20974 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
20975 detailed technical information on @value{GDBN}'s book-keeping of the
20978 The following block-related functions are available in the @code{gdb}
20981 @findex gdb.block_for_pc
20982 @defun block_for_pc pc
20983 Return the @code{gdb.Block} containing the given @var{pc} value. If the
20984 block cannot be found for the @var{pc} value specified, the function
20985 will return @code{None}.
20988 A @code{gdb.Block} object has the following attributes:
20991 @defivar Block start
20992 The start address of the block. This attribute is not writable.
20996 The end address of the block. This attribute is not writable.
20999 @defivar Block function
21000 The name of the block represented as a @code{gdb.Symbol}. If the
21001 block is not named, then this attribute holds @code{None}. This
21002 attribute is not writable.
21005 @defivar Block superblock
21006 The block containing this block. If this parent block does not exist,
21007 this attribute holds @code{None}. This attribute is not writable.
21011 @node Symbols In Python
21012 @subsubsection Python representation of Symbols.
21014 @cindex symbols in python
21017 @value{GDBN} represents every variable, function and type as an
21018 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
21019 Similarly, Python represents these symbols in @value{GDBN} with the
21020 @code{gdb.Symbol} object.
21022 The following symbol-related functions are available in the @code{gdb}
21025 @findex gdb.lookup_symbol
21026 @defun lookup_symbol name [block] [domain]
21027 This function searches for a symbol by name. The search scope can be
21028 restricted to the parameters defined in the optional domain and block
21031 @var{name} is the name of the symbol. It must be a string. The
21032 optional @var{block} argument restricts the search to symbols visible
21033 in that @var{block}. The @var{block} argument must be a
21034 @code{gdb.Block} object. The optional @var{domain} argument restricts
21035 the search to the domain type. The @var{domain} argument must be a
21036 domain constant defined in the @code{gdb} module and described later
21040 A @code{gdb.Symbol} object has the following attributes:
21043 @defivar Symbol symtab
21044 The symbol table in which the symbol appears. This attribute is
21045 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
21046 Python}. This attribute is not writable.
21049 @defivar Symbol name
21050 The name of the symbol as a string. This attribute is not writable.
21053 @defivar Symbol linkage_name
21054 The name of the symbol, as used by the linker (i.e., may be mangled).
21055 This attribute is not writable.
21058 @defivar Symbol print_name
21059 The name of the symbol in a form suitable for output. This is either
21060 @code{name} or @code{linkage_name}, depending on whether the user
21061 asked @value{GDBN} to display demangled or mangled names.
21064 @defivar Symbol addr_class
21065 The address class of the symbol. This classifies how to find the value
21066 of a symbol. Each address class is a constant defined in the
21067 @code{gdb} module and described later in this chapter.
21070 @defivar Symbol is_argument
21071 @code{True} if the symbol is an argument of a function.
21074 @defivar Symbol is_constant
21075 @code{True} if the symbol is a constant.
21078 @defivar Symbol is_function
21079 @code{True} if the symbol is a function or a method.
21082 @defivar Symbol is_variable
21083 @code{True} if the symbol is a variable.
21087 The available domain categories in @code{gdb.Symbol} are represented
21088 as constants in the @code{gdb} module:
21091 @findex SYMBOL_UNDEF_DOMAIN
21092 @findex gdb.SYMBOL_UNDEF_DOMAIN
21093 @item SYMBOL_UNDEF_DOMAIN
21094 This is used when a domain has not been discovered or none of the
21095 following domains apply. This usually indicates an error either
21096 in the symbol information or in @value{GDBN}'s handling of symbols.
21097 @findex SYMBOL_VAR_DOMAIN
21098 @findex gdb.SYMBOL_VAR_DOMAIN
21099 @item SYMBOL_VAR_DOMAIN
21100 This domain contains variables, function names, typedef names and enum
21102 @findex SYMBOL_STRUCT_DOMAIN
21103 @findex gdb.SYMBOL_STRUCT_DOMAIN
21104 @item SYMBOL_STRUCT_DOMAIN
21105 This domain holds struct, union and enum type names.
21106 @findex SYMBOL_LABEL_DOMAIN
21107 @findex gdb.SYMBOL_LABEL_DOMAIN
21108 @item SYMBOL_LABEL_DOMAIN
21109 This domain contains names of labels (for gotos).
21110 @findex SYMBOL_VARIABLES_DOMAIN
21111 @findex gdb.SYMBOL_VARIABLES_DOMAIN
21112 @item SYMBOL_VARIABLES_DOMAIN
21113 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
21114 contains everything minus functions and types.
21115 @findex SYMBOL_FUNCTIONS_DOMAIN
21116 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
21117 @item SYMBOL_FUNCTION_DOMAIN
21118 This domain contains all functions.
21119 @findex SYMBOL_TYPES_DOMAIN
21120 @findex gdb.SYMBOL_TYPES_DOMAIN
21121 @item SYMBOL_TYPES_DOMAIN
21122 This domain contains all types.
21125 The available address class categories in @code{gdb.Symbol} are represented
21126 as constants in the @code{gdb} module:
21129 @findex SYMBOL_LOC_UNDEF
21130 @findex gdb.SYMBOL_LOC_UNDEF
21131 @item SYMBOL_LOC_UNDEF
21132 If this is returned by address class, it indicates an error either in
21133 the symbol information or in @value{GDBN}'s handling of symbols.
21134 @findex SYMBOL_LOC_CONST
21135 @findex gdb.SYMBOL_LOC_CONST
21136 @item SYMBOL_LOC_CONST
21137 Value is constant int.
21138 @findex SYMBOL_LOC_STATIC
21139 @findex gdb.SYMBOL_LOC_STATIC
21140 @item SYMBOL_LOC_STATIC
21141 Value is at a fixed address.
21142 @findex SYMBOL_LOC_REGISTER
21143 @findex gdb.SYMBOL_LOC_REGISTER
21144 @item SYMBOL_LOC_REGISTER
21145 Value is in a register.
21146 @findex SYMBOL_LOC_ARG
21147 @findex gdb.SYMBOL_LOC_ARG
21148 @item SYMBOL_LOC_ARG
21149 Value is an argument. This value is at the offset stored within the
21150 symbol inside the frame's argument list.
21151 @findex SYMBOL_LOC_REF_ARG
21152 @findex gdb.SYMBOL_LOC_REF_ARG
21153 @item SYMBOL_LOC_REF_ARG
21154 Value address is stored in the frame's argument list. Just like
21155 @code{LOC_ARG} except that the value's address is stored at the
21156 offset, not the value itself.
21157 @findex SYMBOL_LOC_REGPARM_ADDR
21158 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
21159 @item SYMBOL_LOC_REGPARM_ADDR
21160 Value is a specified register. Just like @code{LOC_REGISTER} except
21161 the register holds the address of the argument instead of the argument
21163 @findex SYMBOL_LOC_LOCAL
21164 @findex gdb.SYMBOL_LOC_LOCAL
21165 @item SYMBOL_LOC_LOCAL
21166 Value is a local variable.
21167 @findex SYMBOL_LOC_TYPEDEF
21168 @findex gdb.SYMBOL_LOC_TYPEDEF
21169 @item SYMBOL_LOC_TYPEDEF
21170 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
21172 @findex SYMBOL_LOC_BLOCK
21173 @findex gdb.SYMBOL_LOC_BLOCK
21174 @item SYMBOL_LOC_BLOCK
21176 @findex SYMBOL_LOC_CONST_BYTES
21177 @findex gdb.SYMBOL_LOC_CONST_BYTES
21178 @item SYMBOL_LOC_CONST_BYTES
21179 Value is a byte-sequence.
21180 @findex SYMBOL_LOC_UNRESOLVED
21181 @findex gdb.SYMBOL_LOC_UNRESOLVED
21182 @item SYMBOL_LOC_UNRESOLVED
21183 Value is at a fixed address, but the address of the variable has to be
21184 determined from the minimal symbol table whenever the variable is
21186 @findex SYMBOL_LOC_OPTIMIZED_OUT
21187 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
21188 @item SYMBOL_LOC_OPTIMIZED_OUT
21189 The value does not actually exist in the program.
21190 @findex SYMBOL_LOC_COMPUTED
21191 @findex gdb.SYMBOL_LOC_COMPUTED
21192 @item SYMBOL_LOC_COMPUTED
21193 The value's address is a computed location.
21196 @node Symbol Tables In Python
21197 @subsubsection Symbol table representation in Python.
21199 @cindex symbol tables in python
21201 @tindex gdb.Symtab_and_line
21203 Access to symbol table data maintained by @value{GDBN} on the inferior
21204 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
21205 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
21206 from the @code{find_sal} method in @code{gdb.Frame} object.
21207 @xref{Frames In Python}.
21209 For more information on @value{GDBN}'s symbol table management, see
21210 @ref{Symbols, ,Examining the Symbol Table}, for more information.
21212 A @code{gdb.Symtab_and_line} object has the following attributes:
21215 @defivar Symtab_and_line symtab
21216 The symbol table object (@code{gdb.Symtab}) for this frame.
21217 This attribute is not writable.
21220 @defivar Symtab_and_line pc
21221 Indicates the current program counter address. This attribute is not
21225 @defivar Symtab_and_line line
21226 Indicates the current line number for this object. This
21227 attribute is not writable.
21231 A @code{gdb.Symtab} object has the following attributes:
21234 @defivar Symtab filename
21235 The symbol table's source filename. This attribute is not writable.
21238 @defivar Symtab objfile
21239 The symbol table's backing object file. @xref{Objfiles In Python}.
21240 This attribute is not writable.
21244 The following methods are provided:
21247 @defmethod Symtab fullname
21248 Return the symbol table's source absolute file name.
21252 @node Lazy Strings In Python
21253 @subsubsection Python representation of lazy strings.
21255 @cindex lazy strings in python
21256 @tindex gdb.LazyString
21258 A @dfn{lazy string} is a string whose contents is not retrieved or
21259 encoded until it is needed.
21261 A @code{gdb.LazyString} is represented in @value{GDBN} as an
21262 @code{address} that points to a region of memory, an @code{encoding}
21263 that will be used to encode that region of memory, and a @code{length}
21264 to delimit the region of memory that represents the string. The
21265 difference between a @code{gdb.LazyString} and a string wrapped within
21266 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
21267 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
21268 retrieved and encoded during printing, while a @code{gdb.Value}
21269 wrapping a string is immediately retrieved and encoded on creation.
21271 A @code{gdb.LazyString} object has the following functions:
21273 @defmethod LazyString value
21274 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
21275 will point to the string in memory, but will lose all the delayed
21276 retrieval, encoding and handling that @value{GDBN} applies to a
21277 @code{gdb.LazyString}.
21280 @defivar LazyString address
21281 This attribute holds the address of the string. This attribute is not
21285 @defivar LazyString length
21286 This attribute holds the length of the string in characters. If the
21287 length is -1, then the string will be fetched and encoded up to the
21288 first null of appropriate width. This attribute is not writable.
21291 @defivar LazyString encoding
21292 This attribute holds the encoding that will be applied to the string
21293 when the string is printed by @value{GDBN}. If the encoding is not
21294 set, or contains an empty string, then @value{GDBN} will select the
21295 most appropriate encoding when the string is printed. This attribute
21299 @defivar LazyString type
21300 This attribute holds the type that is represented by the lazy string's
21301 type. For a lazy string this will always be a pointer type. To
21302 resolve this to the lazy string's character type, use the type's
21303 @code{target} method. @xref{Types In Python}. This attribute is not
21308 @chapter Command Interpreters
21309 @cindex command interpreters
21311 @value{GDBN} supports multiple command interpreters, and some command
21312 infrastructure to allow users or user interface writers to switch
21313 between interpreters or run commands in other interpreters.
21315 @value{GDBN} currently supports two command interpreters, the console
21316 interpreter (sometimes called the command-line interpreter or @sc{cli})
21317 and the machine interface interpreter (or @sc{gdb/mi}). This manual
21318 describes both of these interfaces in great detail.
21320 By default, @value{GDBN} will start with the console interpreter.
21321 However, the user may choose to start @value{GDBN} with another
21322 interpreter by specifying the @option{-i} or @option{--interpreter}
21323 startup options. Defined interpreters include:
21327 @cindex console interpreter
21328 The traditional console or command-line interpreter. This is the most often
21329 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
21330 @value{GDBN} will use this interpreter.
21333 @cindex mi interpreter
21334 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
21335 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
21336 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
21340 @cindex mi2 interpreter
21341 The current @sc{gdb/mi} interface.
21344 @cindex mi1 interpreter
21345 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
21349 @cindex invoke another interpreter
21350 The interpreter being used by @value{GDBN} may not be dynamically
21351 switched at runtime. Although possible, this could lead to a very
21352 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
21353 enters the command "interpreter-set console" in a console view,
21354 @value{GDBN} would switch to using the console interpreter, rendering
21355 the IDE inoperable!
21357 @kindex interpreter-exec
21358 Although you may only choose a single interpreter at startup, you may execute
21359 commands in any interpreter from the current interpreter using the appropriate
21360 command. If you are running the console interpreter, simply use the
21361 @code{interpreter-exec} command:
21364 interpreter-exec mi "-data-list-register-names"
21367 @sc{gdb/mi} has a similar command, although it is only available in versions of
21368 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
21371 @chapter @value{GDBN} Text User Interface
21373 @cindex Text User Interface
21376 * TUI Overview:: TUI overview
21377 * TUI Keys:: TUI key bindings
21378 * TUI Single Key Mode:: TUI single key mode
21379 * TUI Commands:: TUI-specific commands
21380 * TUI Configuration:: TUI configuration variables
21383 The @value{GDBN} Text User Interface (TUI) is a terminal
21384 interface which uses the @code{curses} library to show the source
21385 file, the assembly output, the program registers and @value{GDBN}
21386 commands in separate text windows. The TUI mode is supported only
21387 on platforms where a suitable version of the @code{curses} library
21390 @pindex @value{GDBTUI}
21391 The TUI mode is enabled by default when you invoke @value{GDBN} as
21392 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
21393 You can also switch in and out of TUI mode while @value{GDBN} runs by
21394 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
21395 @xref{TUI Keys, ,TUI Key Bindings}.
21398 @section TUI Overview
21400 In TUI mode, @value{GDBN} can display several text windows:
21404 This window is the @value{GDBN} command window with the @value{GDBN}
21405 prompt and the @value{GDBN} output. The @value{GDBN} input is still
21406 managed using readline.
21409 The source window shows the source file of the program. The current
21410 line and active breakpoints are displayed in this window.
21413 The assembly window shows the disassembly output of the program.
21416 This window shows the processor registers. Registers are highlighted
21417 when their values change.
21420 The source and assembly windows show the current program position
21421 by highlighting the current line and marking it with a @samp{>} marker.
21422 Breakpoints are indicated with two markers. The first marker
21423 indicates the breakpoint type:
21427 Breakpoint which was hit at least once.
21430 Breakpoint which was never hit.
21433 Hardware breakpoint which was hit at least once.
21436 Hardware breakpoint which was never hit.
21439 The second marker indicates whether the breakpoint is enabled or not:
21443 Breakpoint is enabled.
21446 Breakpoint is disabled.
21449 The source, assembly and register windows are updated when the current
21450 thread changes, when the frame changes, or when the program counter
21453 These windows are not all visible at the same time. The command
21454 window is always visible. The others can be arranged in several
21465 source and assembly,
21468 source and registers, or
21471 assembly and registers.
21474 A status line above the command window shows the following information:
21478 Indicates the current @value{GDBN} target.
21479 (@pxref{Targets, ,Specifying a Debugging Target}).
21482 Gives the current process or thread number.
21483 When no process is being debugged, this field is set to @code{No process}.
21486 Gives the current function name for the selected frame.
21487 The name is demangled if demangling is turned on (@pxref{Print Settings}).
21488 When there is no symbol corresponding to the current program counter,
21489 the string @code{??} is displayed.
21492 Indicates the current line number for the selected frame.
21493 When the current line number is not known, the string @code{??} is displayed.
21496 Indicates the current program counter address.
21500 @section TUI Key Bindings
21501 @cindex TUI key bindings
21503 The TUI installs several key bindings in the readline keymaps
21504 (@pxref{Command Line Editing}). The following key bindings
21505 are installed for both TUI mode and the @value{GDBN} standard mode.
21514 Enter or leave the TUI mode. When leaving the TUI mode,
21515 the curses window management stops and @value{GDBN} operates using
21516 its standard mode, writing on the terminal directly. When reentering
21517 the TUI mode, control is given back to the curses windows.
21518 The screen is then refreshed.
21522 Use a TUI layout with only one window. The layout will
21523 either be @samp{source} or @samp{assembly}. When the TUI mode
21524 is not active, it will switch to the TUI mode.
21526 Think of this key binding as the Emacs @kbd{C-x 1} binding.
21530 Use a TUI layout with at least two windows. When the current
21531 layout already has two windows, the next layout with two windows is used.
21532 When a new layout is chosen, one window will always be common to the
21533 previous layout and the new one.
21535 Think of it as the Emacs @kbd{C-x 2} binding.
21539 Change the active window. The TUI associates several key bindings
21540 (like scrolling and arrow keys) with the active window. This command
21541 gives the focus to the next TUI window.
21543 Think of it as the Emacs @kbd{C-x o} binding.
21547 Switch in and out of the TUI SingleKey mode that binds single
21548 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
21551 The following key bindings only work in the TUI mode:
21556 Scroll the active window one page up.
21560 Scroll the active window one page down.
21564 Scroll the active window one line up.
21568 Scroll the active window one line down.
21572 Scroll the active window one column left.
21576 Scroll the active window one column right.
21580 Refresh the screen.
21583 Because the arrow keys scroll the active window in the TUI mode, they
21584 are not available for their normal use by readline unless the command
21585 window has the focus. When another window is active, you must use
21586 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
21587 and @kbd{C-f} to control the command window.
21589 @node TUI Single Key Mode
21590 @section TUI Single Key Mode
21591 @cindex TUI single key mode
21593 The TUI also provides a @dfn{SingleKey} mode, which binds several
21594 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
21595 switch into this mode, where the following key bindings are used:
21598 @kindex c @r{(SingleKey TUI key)}
21602 @kindex d @r{(SingleKey TUI key)}
21606 @kindex f @r{(SingleKey TUI key)}
21610 @kindex n @r{(SingleKey TUI key)}
21614 @kindex q @r{(SingleKey TUI key)}
21616 exit the SingleKey mode.
21618 @kindex r @r{(SingleKey TUI key)}
21622 @kindex s @r{(SingleKey TUI key)}
21626 @kindex u @r{(SingleKey TUI key)}
21630 @kindex v @r{(SingleKey TUI key)}
21634 @kindex w @r{(SingleKey TUI key)}
21639 Other keys temporarily switch to the @value{GDBN} command prompt.
21640 The key that was pressed is inserted in the editing buffer so that
21641 it is possible to type most @value{GDBN} commands without interaction
21642 with the TUI SingleKey mode. Once the command is entered the TUI
21643 SingleKey mode is restored. The only way to permanently leave
21644 this mode is by typing @kbd{q} or @kbd{C-x s}.
21648 @section TUI-specific Commands
21649 @cindex TUI commands
21651 The TUI has specific commands to control the text windows.
21652 These commands are always available, even when @value{GDBN} is not in
21653 the TUI mode. When @value{GDBN} is in the standard mode, most
21654 of these commands will automatically switch to the TUI mode.
21656 Note that if @value{GDBN}'s @code{stdout} is not connected to a
21657 terminal, or @value{GDBN} has been started with the machine interface
21658 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
21659 these commands will fail with an error, because it would not be
21660 possible or desirable to enable curses window management.
21665 List and give the size of all displayed windows.
21669 Display the next layout.
21672 Display the previous layout.
21675 Display the source window only.
21678 Display the assembly window only.
21681 Display the source and assembly window.
21684 Display the register window together with the source or assembly window.
21688 Make the next window active for scrolling.
21691 Make the previous window active for scrolling.
21694 Make the source window active for scrolling.
21697 Make the assembly window active for scrolling.
21700 Make the register window active for scrolling.
21703 Make the command window active for scrolling.
21707 Refresh the screen. This is similar to typing @kbd{C-L}.
21709 @item tui reg float
21711 Show the floating point registers in the register window.
21713 @item tui reg general
21714 Show the general registers in the register window.
21717 Show the next register group. The list of register groups as well as
21718 their order is target specific. The predefined register groups are the
21719 following: @code{general}, @code{float}, @code{system}, @code{vector},
21720 @code{all}, @code{save}, @code{restore}.
21722 @item tui reg system
21723 Show the system registers in the register window.
21727 Update the source window and the current execution point.
21729 @item winheight @var{name} +@var{count}
21730 @itemx winheight @var{name} -@var{count}
21732 Change the height of the window @var{name} by @var{count}
21733 lines. Positive counts increase the height, while negative counts
21736 @item tabset @var{nchars}
21738 Set the width of tab stops to be @var{nchars} characters.
21741 @node TUI Configuration
21742 @section TUI Configuration Variables
21743 @cindex TUI configuration variables
21745 Several configuration variables control the appearance of TUI windows.
21748 @item set tui border-kind @var{kind}
21749 @kindex set tui border-kind
21750 Select the border appearance for the source, assembly and register windows.
21751 The possible values are the following:
21754 Use a space character to draw the border.
21757 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
21760 Use the Alternate Character Set to draw the border. The border is
21761 drawn using character line graphics if the terminal supports them.
21764 @item set tui border-mode @var{mode}
21765 @kindex set tui border-mode
21766 @itemx set tui active-border-mode @var{mode}
21767 @kindex set tui active-border-mode
21768 Select the display attributes for the borders of the inactive windows
21769 or the active window. The @var{mode} can be one of the following:
21772 Use normal attributes to display the border.
21778 Use reverse video mode.
21781 Use half bright mode.
21783 @item half-standout
21784 Use half bright and standout mode.
21787 Use extra bright or bold mode.
21789 @item bold-standout
21790 Use extra bright or bold and standout mode.
21795 @chapter Using @value{GDBN} under @sc{gnu} Emacs
21798 @cindex @sc{gnu} Emacs
21799 A special interface allows you to use @sc{gnu} Emacs to view (and
21800 edit) the source files for the program you are debugging with
21803 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
21804 executable file you want to debug as an argument. This command starts
21805 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
21806 created Emacs buffer.
21807 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
21809 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
21814 All ``terminal'' input and output goes through an Emacs buffer, called
21817 This applies both to @value{GDBN} commands and their output, and to the input
21818 and output done by the program you are debugging.
21820 This is useful because it means that you can copy the text of previous
21821 commands and input them again; you can even use parts of the output
21824 All the facilities of Emacs' Shell mode are available for interacting
21825 with your program. In particular, you can send signals the usual
21826 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
21830 @value{GDBN} displays source code through Emacs.
21832 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
21833 source file for that frame and puts an arrow (@samp{=>}) at the
21834 left margin of the current line. Emacs uses a separate buffer for
21835 source display, and splits the screen to show both your @value{GDBN} session
21838 Explicit @value{GDBN} @code{list} or search commands still produce output as
21839 usual, but you probably have no reason to use them from Emacs.
21842 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
21843 a graphical mode, enabled by default, which provides further buffers
21844 that can control the execution and describe the state of your program.
21845 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
21847 If you specify an absolute file name when prompted for the @kbd{M-x
21848 gdb} argument, then Emacs sets your current working directory to where
21849 your program resides. If you only specify the file name, then Emacs
21850 sets your current working directory to to the directory associated
21851 with the previous buffer. In this case, @value{GDBN} may find your
21852 program by searching your environment's @code{PATH} variable, but on
21853 some operating systems it might not find the source. So, although the
21854 @value{GDBN} input and output session proceeds normally, the auxiliary
21855 buffer does not display the current source and line of execution.
21857 The initial working directory of @value{GDBN} is printed on the top
21858 line of the GUD buffer and this serves as a default for the commands
21859 that specify files for @value{GDBN} to operate on. @xref{Files,
21860 ,Commands to Specify Files}.
21862 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
21863 need to call @value{GDBN} by a different name (for example, if you
21864 keep several configurations around, with different names) you can
21865 customize the Emacs variable @code{gud-gdb-command-name} to run the
21868 In the GUD buffer, you can use these special Emacs commands in
21869 addition to the standard Shell mode commands:
21873 Describe the features of Emacs' GUD Mode.
21876 Execute to another source line, like the @value{GDBN} @code{step} command; also
21877 update the display window to show the current file and location.
21880 Execute to next source line in this function, skipping all function
21881 calls, like the @value{GDBN} @code{next} command. Then update the display window
21882 to show the current file and location.
21885 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
21886 display window accordingly.
21889 Execute until exit from the selected stack frame, like the @value{GDBN}
21890 @code{finish} command.
21893 Continue execution of your program, like the @value{GDBN} @code{continue}
21897 Go up the number of frames indicated by the numeric argument
21898 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
21899 like the @value{GDBN} @code{up} command.
21902 Go down the number of frames indicated by the numeric argument, like the
21903 @value{GDBN} @code{down} command.
21906 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
21907 tells @value{GDBN} to set a breakpoint on the source line point is on.
21909 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
21910 separate frame which shows a backtrace when the GUD buffer is current.
21911 Move point to any frame in the stack and type @key{RET} to make it
21912 become the current frame and display the associated source in the
21913 source buffer. Alternatively, click @kbd{Mouse-2} to make the
21914 selected frame become the current one. In graphical mode, the
21915 speedbar displays watch expressions.
21917 If you accidentally delete the source-display buffer, an easy way to get
21918 it back is to type the command @code{f} in the @value{GDBN} buffer, to
21919 request a frame display; when you run under Emacs, this recreates
21920 the source buffer if necessary to show you the context of the current
21923 The source files displayed in Emacs are in ordinary Emacs buffers
21924 which are visiting the source files in the usual way. You can edit
21925 the files with these buffers if you wish; but keep in mind that @value{GDBN}
21926 communicates with Emacs in terms of line numbers. If you add or
21927 delete lines from the text, the line numbers that @value{GDBN} knows cease
21928 to correspond properly with the code.
21930 A more detailed description of Emacs' interaction with @value{GDBN} is
21931 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
21934 @c The following dropped because Epoch is nonstandard. Reactivate
21935 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
21937 @kindex Emacs Epoch environment
21941 Version 18 of @sc{gnu} Emacs has a built-in window system
21942 called the @code{epoch}
21943 environment. Users of this environment can use a new command,
21944 @code{inspect} which performs identically to @code{print} except that
21945 each value is printed in its own window.
21950 @chapter The @sc{gdb/mi} Interface
21952 @unnumberedsec Function and Purpose
21954 @cindex @sc{gdb/mi}, its purpose
21955 @sc{gdb/mi} is a line based machine oriented text interface to
21956 @value{GDBN} and is activated by specifying using the
21957 @option{--interpreter} command line option (@pxref{Mode Options}). It
21958 is specifically intended to support the development of systems which
21959 use the debugger as just one small component of a larger system.
21961 This chapter is a specification of the @sc{gdb/mi} interface. It is written
21962 in the form of a reference manual.
21964 Note that @sc{gdb/mi} is still under construction, so some of the
21965 features described below are incomplete and subject to change
21966 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
21968 @unnumberedsec Notation and Terminology
21970 @cindex notational conventions, for @sc{gdb/mi}
21971 This chapter uses the following notation:
21975 @code{|} separates two alternatives.
21978 @code{[ @var{something} ]} indicates that @var{something} is optional:
21979 it may or may not be given.
21982 @code{( @var{group} )*} means that @var{group} inside the parentheses
21983 may repeat zero or more times.
21986 @code{( @var{group} )+} means that @var{group} inside the parentheses
21987 may repeat one or more times.
21990 @code{"@var{string}"} means a literal @var{string}.
21994 @heading Dependencies
21998 * GDB/MI General Design::
21999 * GDB/MI Command Syntax::
22000 * GDB/MI Compatibility with CLI::
22001 * GDB/MI Development and Front Ends::
22002 * GDB/MI Output Records::
22003 * GDB/MI Simple Examples::
22004 * GDB/MI Command Description Format::
22005 * GDB/MI Breakpoint Commands::
22006 * GDB/MI Program Context::
22007 * GDB/MI Thread Commands::
22008 * GDB/MI Program Execution::
22009 * GDB/MI Stack Manipulation::
22010 * GDB/MI Variable Objects::
22011 * GDB/MI Data Manipulation::
22012 * GDB/MI Tracepoint Commands::
22013 * GDB/MI Symbol Query::
22014 * GDB/MI File Commands::
22016 * GDB/MI Kod Commands::
22017 * GDB/MI Memory Overlay Commands::
22018 * GDB/MI Signal Handling Commands::
22020 * GDB/MI Target Manipulation::
22021 * GDB/MI File Transfer Commands::
22022 * GDB/MI Miscellaneous Commands::
22025 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22026 @node GDB/MI General Design
22027 @section @sc{gdb/mi} General Design
22028 @cindex GDB/MI General Design
22030 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
22031 parts---commands sent to @value{GDBN}, responses to those commands
22032 and notifications. Each command results in exactly one response,
22033 indicating either successful completion of the command, or an error.
22034 For the commands that do not resume the target, the response contains the
22035 requested information. For the commands that resume the target, the
22036 response only indicates whether the target was successfully resumed.
22037 Notifications is the mechanism for reporting changes in the state of the
22038 target, or in @value{GDBN} state, that cannot conveniently be associated with
22039 a command and reported as part of that command response.
22041 The important examples of notifications are:
22045 Exec notifications. These are used to report changes in
22046 target state---when a target is resumed, or stopped. It would not
22047 be feasible to include this information in response of resuming
22048 commands, because one resume commands can result in multiple events in
22049 different threads. Also, quite some time may pass before any event
22050 happens in the target, while a frontend needs to know whether the resuming
22051 command itself was successfully executed.
22054 Console output, and status notifications. Console output
22055 notifications are used to report output of CLI commands, as well as
22056 diagnostics for other commands. Status notifications are used to
22057 report the progress of a long-running operation. Naturally, including
22058 this information in command response would mean no output is produced
22059 until the command is finished, which is undesirable.
22062 General notifications. Commands may have various side effects on
22063 the @value{GDBN} or target state beyond their official purpose. For example,
22064 a command may change the selected thread. Although such changes can
22065 be included in command response, using notification allows for more
22066 orthogonal frontend design.
22070 There's no guarantee that whenever an MI command reports an error,
22071 @value{GDBN} or the target are in any specific state, and especially,
22072 the state is not reverted to the state before the MI command was
22073 processed. Therefore, whenever an MI command results in an error,
22074 we recommend that the frontend refreshes all the information shown in
22075 the user interface.
22079 * Context management::
22080 * Asynchronous and non-stop modes::
22084 @node Context management
22085 @subsection Context management
22087 In most cases when @value{GDBN} accesses the target, this access is
22088 done in context of a specific thread and frame (@pxref{Frames}).
22089 Often, even when accessing global data, the target requires that a thread
22090 be specified. The CLI interface maintains the selected thread and frame,
22091 and supplies them to target on each command. This is convenient,
22092 because a command line user would not want to specify that information
22093 explicitly on each command, and because user interacts with
22094 @value{GDBN} via a single terminal, so no confusion is possible as
22095 to what thread and frame are the current ones.
22097 In the case of MI, the concept of selected thread and frame is less
22098 useful. First, a frontend can easily remember this information
22099 itself. Second, a graphical frontend can have more than one window,
22100 each one used for debugging a different thread, and the frontend might
22101 want to access additional threads for internal purposes. This
22102 increases the risk that by relying on implicitly selected thread, the
22103 frontend may be operating on a wrong one. Therefore, each MI command
22104 should explicitly specify which thread and frame to operate on. To
22105 make it possible, each MI command accepts the @samp{--thread} and
22106 @samp{--frame} options, the value to each is @value{GDBN} identifier
22107 for thread and frame to operate on.
22109 Usually, each top-level window in a frontend allows the user to select
22110 a thread and a frame, and remembers the user selection for further
22111 operations. However, in some cases @value{GDBN} may suggest that the
22112 current thread be changed. For example, when stopping on a breakpoint
22113 it is reasonable to switch to the thread where breakpoint is hit. For
22114 another example, if the user issues the CLI @samp{thread} command via
22115 the frontend, it is desirable to change the frontend's selected thread to the
22116 one specified by user. @value{GDBN} communicates the suggestion to
22117 change current thread using the @samp{=thread-selected} notification.
22118 No such notification is available for the selected frame at the moment.
22120 Note that historically, MI shares the selected thread with CLI, so
22121 frontends used the @code{-thread-select} to execute commands in the
22122 right context. However, getting this to work right is cumbersome. The
22123 simplest way is for frontend to emit @code{-thread-select} command
22124 before every command. This doubles the number of commands that need
22125 to be sent. The alternative approach is to suppress @code{-thread-select}
22126 if the selected thread in @value{GDBN} is supposed to be identical to the
22127 thread the frontend wants to operate on. However, getting this
22128 optimization right can be tricky. In particular, if the frontend
22129 sends several commands to @value{GDBN}, and one of the commands changes the
22130 selected thread, then the behaviour of subsequent commands will
22131 change. So, a frontend should either wait for response from such
22132 problematic commands, or explicitly add @code{-thread-select} for
22133 all subsequent commands. No frontend is known to do this exactly
22134 right, so it is suggested to just always pass the @samp{--thread} and
22135 @samp{--frame} options.
22137 @node Asynchronous and non-stop modes
22138 @subsection Asynchronous command execution and non-stop mode
22140 On some targets, @value{GDBN} is capable of processing MI commands
22141 even while the target is running. This is called @dfn{asynchronous
22142 command execution} (@pxref{Background Execution}). The frontend may
22143 specify a preferrence for asynchronous execution using the
22144 @code{-gdb-set target-async 1} command, which should be emitted before
22145 either running the executable or attaching to the target. After the
22146 frontend has started the executable or attached to the target, it can
22147 find if asynchronous execution is enabled using the
22148 @code{-list-target-features} command.
22150 Even if @value{GDBN} can accept a command while target is running,
22151 many commands that access the target do not work when the target is
22152 running. Therefore, asynchronous command execution is most useful
22153 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
22154 it is possible to examine the state of one thread, while other threads
22157 When a given thread is running, MI commands that try to access the
22158 target in the context of that thread may not work, or may work only on
22159 some targets. In particular, commands that try to operate on thread's
22160 stack will not work, on any target. Commands that read memory, or
22161 modify breakpoints, may work or not work, depending on the target. Note
22162 that even commands that operate on global state, such as @code{print},
22163 @code{set}, and breakpoint commands, still access the target in the
22164 context of a specific thread, so frontend should try to find a
22165 stopped thread and perform the operation on that thread (using the
22166 @samp{--thread} option).
22168 Which commands will work in the context of a running thread is
22169 highly target dependent. However, the two commands
22170 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
22171 to find the state of a thread, will always work.
22173 @node Thread groups
22174 @subsection Thread groups
22175 @value{GDBN} may be used to debug several processes at the same time.
22176 On some platfroms, @value{GDBN} may support debugging of several
22177 hardware systems, each one having several cores with several different
22178 processes running on each core. This section describes the MI
22179 mechanism to support such debugging scenarios.
22181 The key observation is that regardless of the structure of the
22182 target, MI can have a global list of threads, because most commands that
22183 accept the @samp{--thread} option do not need to know what process that
22184 thread belongs to. Therefore, it is not necessary to introduce
22185 neither additional @samp{--process} option, nor an notion of the
22186 current process in the MI interface. The only strictly new feature
22187 that is required is the ability to find how the threads are grouped
22190 To allow the user to discover such grouping, and to support arbitrary
22191 hierarchy of machines/cores/processes, MI introduces the concept of a
22192 @dfn{thread group}. Thread group is a collection of threads and other
22193 thread groups. A thread group always has a string identifier, a type,
22194 and may have additional attributes specific to the type. A new
22195 command, @code{-list-thread-groups}, returns the list of top-level
22196 thread groups, which correspond to processes that @value{GDBN} is
22197 debugging at the moment. By passing an identifier of a thread group
22198 to the @code{-list-thread-groups} command, it is possible to obtain
22199 the members of specific thread group.
22201 To allow the user to easily discover processes, and other objects, he
22202 wishes to debug, a concept of @dfn{available thread group} is
22203 introduced. Available thread group is an thread group that
22204 @value{GDBN} is not debugging, but that can be attached to, using the
22205 @code{-target-attach} command. The list of available top-level thread
22206 groups can be obtained using @samp{-list-thread-groups --available}.
22207 In general, the content of a thread group may be only retrieved only
22208 after attaching to that thread group.
22210 Thread groups are related to inferiors (@pxref{Inferiors and
22211 Programs}). Each inferior corresponds to a thread group of a special
22212 type @samp{process}, and some additional operations are permitted on
22213 such thread groups.
22215 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22216 @node GDB/MI Command Syntax
22217 @section @sc{gdb/mi} Command Syntax
22220 * GDB/MI Input Syntax::
22221 * GDB/MI Output Syntax::
22224 @node GDB/MI Input Syntax
22225 @subsection @sc{gdb/mi} Input Syntax
22227 @cindex input syntax for @sc{gdb/mi}
22228 @cindex @sc{gdb/mi}, input syntax
22230 @item @var{command} @expansion{}
22231 @code{@var{cli-command} | @var{mi-command}}
22233 @item @var{cli-command} @expansion{}
22234 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
22235 @var{cli-command} is any existing @value{GDBN} CLI command.
22237 @item @var{mi-command} @expansion{}
22238 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
22239 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
22241 @item @var{token} @expansion{}
22242 "any sequence of digits"
22244 @item @var{option} @expansion{}
22245 @code{"-" @var{parameter} [ " " @var{parameter} ]}
22247 @item @var{parameter} @expansion{}
22248 @code{@var{non-blank-sequence} | @var{c-string}}
22250 @item @var{operation} @expansion{}
22251 @emph{any of the operations described in this chapter}
22253 @item @var{non-blank-sequence} @expansion{}
22254 @emph{anything, provided it doesn't contain special characters such as
22255 "-", @var{nl}, """ and of course " "}
22257 @item @var{c-string} @expansion{}
22258 @code{""" @var{seven-bit-iso-c-string-content} """}
22260 @item @var{nl} @expansion{}
22269 The CLI commands are still handled by the @sc{mi} interpreter; their
22270 output is described below.
22273 The @code{@var{token}}, when present, is passed back when the command
22277 Some @sc{mi} commands accept optional arguments as part of the parameter
22278 list. Each option is identified by a leading @samp{-} (dash) and may be
22279 followed by an optional argument parameter. Options occur first in the
22280 parameter list and can be delimited from normal parameters using
22281 @samp{--} (this is useful when some parameters begin with a dash).
22288 We want easy access to the existing CLI syntax (for debugging).
22291 We want it to be easy to spot a @sc{mi} operation.
22294 @node GDB/MI Output Syntax
22295 @subsection @sc{gdb/mi} Output Syntax
22297 @cindex output syntax of @sc{gdb/mi}
22298 @cindex @sc{gdb/mi}, output syntax
22299 The output from @sc{gdb/mi} consists of zero or more out-of-band records
22300 followed, optionally, by a single result record. This result record
22301 is for the most recent command. The sequence of output records is
22302 terminated by @samp{(gdb)}.
22304 If an input command was prefixed with a @code{@var{token}} then the
22305 corresponding output for that command will also be prefixed by that same
22309 @item @var{output} @expansion{}
22310 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
22312 @item @var{result-record} @expansion{}
22313 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
22315 @item @var{out-of-band-record} @expansion{}
22316 @code{@var{async-record} | @var{stream-record}}
22318 @item @var{async-record} @expansion{}
22319 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
22321 @item @var{exec-async-output} @expansion{}
22322 @code{[ @var{token} ] "*" @var{async-output}}
22324 @item @var{status-async-output} @expansion{}
22325 @code{[ @var{token} ] "+" @var{async-output}}
22327 @item @var{notify-async-output} @expansion{}
22328 @code{[ @var{token} ] "=" @var{async-output}}
22330 @item @var{async-output} @expansion{}
22331 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
22333 @item @var{result-class} @expansion{}
22334 @code{"done" | "running" | "connected" | "error" | "exit"}
22336 @item @var{async-class} @expansion{}
22337 @code{"stopped" | @var{others}} (where @var{others} will be added
22338 depending on the needs---this is still in development).
22340 @item @var{result} @expansion{}
22341 @code{ @var{variable} "=" @var{value}}
22343 @item @var{variable} @expansion{}
22344 @code{ @var{string} }
22346 @item @var{value} @expansion{}
22347 @code{ @var{const} | @var{tuple} | @var{list} }
22349 @item @var{const} @expansion{}
22350 @code{@var{c-string}}
22352 @item @var{tuple} @expansion{}
22353 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
22355 @item @var{list} @expansion{}
22356 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
22357 @var{result} ( "," @var{result} )* "]" }
22359 @item @var{stream-record} @expansion{}
22360 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
22362 @item @var{console-stream-output} @expansion{}
22363 @code{"~" @var{c-string}}
22365 @item @var{target-stream-output} @expansion{}
22366 @code{"@@" @var{c-string}}
22368 @item @var{log-stream-output} @expansion{}
22369 @code{"&" @var{c-string}}
22371 @item @var{nl} @expansion{}
22374 @item @var{token} @expansion{}
22375 @emph{any sequence of digits}.
22383 All output sequences end in a single line containing a period.
22386 The @code{@var{token}} is from the corresponding request. Note that
22387 for all async output, while the token is allowed by the grammar and
22388 may be output by future versions of @value{GDBN} for select async
22389 output messages, it is generally omitted. Frontends should treat
22390 all async output as reporting general changes in the state of the
22391 target and there should be no need to associate async output to any
22395 @cindex status output in @sc{gdb/mi}
22396 @var{status-async-output} contains on-going status information about the
22397 progress of a slow operation. It can be discarded. All status output is
22398 prefixed by @samp{+}.
22401 @cindex async output in @sc{gdb/mi}
22402 @var{exec-async-output} contains asynchronous state change on the target
22403 (stopped, started, disappeared). All async output is prefixed by
22407 @cindex notify output in @sc{gdb/mi}
22408 @var{notify-async-output} contains supplementary information that the
22409 client should handle (e.g., a new breakpoint information). All notify
22410 output is prefixed by @samp{=}.
22413 @cindex console output in @sc{gdb/mi}
22414 @var{console-stream-output} is output that should be displayed as is in the
22415 console. It is the textual response to a CLI command. All the console
22416 output is prefixed by @samp{~}.
22419 @cindex target output in @sc{gdb/mi}
22420 @var{target-stream-output} is the output produced by the target program.
22421 All the target output is prefixed by @samp{@@}.
22424 @cindex log output in @sc{gdb/mi}
22425 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
22426 instance messages that should be displayed as part of an error log. All
22427 the log output is prefixed by @samp{&}.
22430 @cindex list output in @sc{gdb/mi}
22431 New @sc{gdb/mi} commands should only output @var{lists} containing
22437 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
22438 details about the various output records.
22440 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22441 @node GDB/MI Compatibility with CLI
22442 @section @sc{gdb/mi} Compatibility with CLI
22444 @cindex compatibility, @sc{gdb/mi} and CLI
22445 @cindex @sc{gdb/mi}, compatibility with CLI
22447 For the developers convenience CLI commands can be entered directly,
22448 but there may be some unexpected behaviour. For example, commands
22449 that query the user will behave as if the user replied yes, breakpoint
22450 command lists are not executed and some CLI commands, such as
22451 @code{if}, @code{when} and @code{define}, prompt for further input with
22452 @samp{>}, which is not valid MI output.
22454 This feature may be removed at some stage in the future and it is
22455 recommended that front ends use the @code{-interpreter-exec} command
22456 (@pxref{-interpreter-exec}).
22458 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22459 @node GDB/MI Development and Front Ends
22460 @section @sc{gdb/mi} Development and Front Ends
22461 @cindex @sc{gdb/mi} development
22463 The application which takes the MI output and presents the state of the
22464 program being debugged to the user is called a @dfn{front end}.
22466 Although @sc{gdb/mi} is still incomplete, it is currently being used
22467 by a variety of front ends to @value{GDBN}. This makes it difficult
22468 to introduce new functionality without breaking existing usage. This
22469 section tries to minimize the problems by describing how the protocol
22472 Some changes in MI need not break a carefully designed front end, and
22473 for these the MI version will remain unchanged. The following is a
22474 list of changes that may occur within one level, so front ends should
22475 parse MI output in a way that can handle them:
22479 New MI commands may be added.
22482 New fields may be added to the output of any MI command.
22485 The range of values for fields with specified values, e.g.,
22486 @code{in_scope} (@pxref{-var-update}) may be extended.
22488 @c The format of field's content e.g type prefix, may change so parse it
22489 @c at your own risk. Yes, in general?
22491 @c The order of fields may change? Shouldn't really matter but it might
22492 @c resolve inconsistencies.
22495 If the changes are likely to break front ends, the MI version level
22496 will be increased by one. This will allow the front end to parse the
22497 output according to the MI version. Apart from mi0, new versions of
22498 @value{GDBN} will not support old versions of MI and it will be the
22499 responsibility of the front end to work with the new one.
22501 @c Starting with mi3, add a new command -mi-version that prints the MI
22504 The best way to avoid unexpected changes in MI that might break your front
22505 end is to make your project known to @value{GDBN} developers and
22506 follow development on @email{gdb@@sourceware.org} and
22507 @email{gdb-patches@@sourceware.org}.
22508 @cindex mailing lists
22510 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22511 @node GDB/MI Output Records
22512 @section @sc{gdb/mi} Output Records
22515 * GDB/MI Result Records::
22516 * GDB/MI Stream Records::
22517 * GDB/MI Async Records::
22518 * GDB/MI Frame Information::
22519 * GDB/MI Thread Information::
22522 @node GDB/MI Result Records
22523 @subsection @sc{gdb/mi} Result Records
22525 @cindex result records in @sc{gdb/mi}
22526 @cindex @sc{gdb/mi}, result records
22527 In addition to a number of out-of-band notifications, the response to a
22528 @sc{gdb/mi} command includes one of the following result indications:
22532 @item "^done" [ "," @var{results} ]
22533 The synchronous operation was successful, @code{@var{results}} are the return
22538 This result record is equivalent to @samp{^done}. Historically, it
22539 was output instead of @samp{^done} if the command has resumed the
22540 target. This behaviour is maintained for backward compatibility, but
22541 all frontends should treat @samp{^done} and @samp{^running}
22542 identically and rely on the @samp{*running} output record to determine
22543 which threads are resumed.
22547 @value{GDBN} has connected to a remote target.
22549 @item "^error" "," @var{c-string}
22551 The operation failed. The @code{@var{c-string}} contains the corresponding
22556 @value{GDBN} has terminated.
22560 @node GDB/MI Stream Records
22561 @subsection @sc{gdb/mi} Stream Records
22563 @cindex @sc{gdb/mi}, stream records
22564 @cindex stream records in @sc{gdb/mi}
22565 @value{GDBN} internally maintains a number of output streams: the console, the
22566 target, and the log. The output intended for each of these streams is
22567 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
22569 Each stream record begins with a unique @dfn{prefix character} which
22570 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
22571 Syntax}). In addition to the prefix, each stream record contains a
22572 @code{@var{string-output}}. This is either raw text (with an implicit new
22573 line) or a quoted C string (which does not contain an implicit newline).
22576 @item "~" @var{string-output}
22577 The console output stream contains text that should be displayed in the
22578 CLI console window. It contains the textual responses to CLI commands.
22580 @item "@@" @var{string-output}
22581 The target output stream contains any textual output from the running
22582 target. This is only present when GDB's event loop is truly
22583 asynchronous, which is currently only the case for remote targets.
22585 @item "&" @var{string-output}
22586 The log stream contains debugging messages being produced by @value{GDBN}'s
22590 @node GDB/MI Async Records
22591 @subsection @sc{gdb/mi} Async Records
22593 @cindex async records in @sc{gdb/mi}
22594 @cindex @sc{gdb/mi}, async records
22595 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
22596 additional changes that have occurred. Those changes can either be a
22597 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
22598 target activity (e.g., target stopped).
22600 The following is the list of possible async records:
22604 @item *running,thread-id="@var{thread}"
22605 The target is now running. The @var{thread} field tells which
22606 specific thread is now running, and can be @samp{all} if all threads
22607 are running. The frontend should assume that no interaction with a
22608 running thread is possible after this notification is produced.
22609 The frontend should not assume that this notification is output
22610 only once for any command. @value{GDBN} may emit this notification
22611 several times, either for different threads, because it cannot resume
22612 all threads together, or even for a single thread, if the thread must
22613 be stepped though some code before letting it run freely.
22615 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
22616 The target has stopped. The @var{reason} field can have one of the
22620 @item breakpoint-hit
22621 A breakpoint was reached.
22622 @item watchpoint-trigger
22623 A watchpoint was triggered.
22624 @item read-watchpoint-trigger
22625 A read watchpoint was triggered.
22626 @item access-watchpoint-trigger
22627 An access watchpoint was triggered.
22628 @item function-finished
22629 An -exec-finish or similar CLI command was accomplished.
22630 @item location-reached
22631 An -exec-until or similar CLI command was accomplished.
22632 @item watchpoint-scope
22633 A watchpoint has gone out of scope.
22634 @item end-stepping-range
22635 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
22636 similar CLI command was accomplished.
22637 @item exited-signalled
22638 The inferior exited because of a signal.
22640 The inferior exited.
22641 @item exited-normally
22642 The inferior exited normally.
22643 @item signal-received
22644 A signal was received by the inferior.
22647 The @var{id} field identifies the thread that directly caused the stop
22648 -- for example by hitting a breakpoint. Depending on whether all-stop
22649 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
22650 stop all threads, or only the thread that directly triggered the stop.
22651 If all threads are stopped, the @var{stopped} field will have the
22652 value of @code{"all"}. Otherwise, the value of the @var{stopped}
22653 field will be a list of thread identifiers. Presently, this list will
22654 always include a single thread, but frontend should be prepared to see
22655 several threads in the list. The @var{core} field reports the
22656 processor core on which the stop event has happened. This field may be absent
22657 if such information is not available.
22659 @item =thread-group-added,id="@var{id}"
22660 @itemx =thread-group-removed,id="@var{id}"
22661 A thread group was either added or removed. The @var{id} field
22662 contains the @value{GDBN} identifier of the thread group. When a thread
22663 group is added, it generally might not be associated with a running
22664 process. When a thread group is removed, its id becomes invalid and
22665 cannot be used in any way.
22667 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
22668 A thread group became associated with a running program,
22669 either because the program was just started or the thread group
22670 was attached to a program. The @var{id} field contains the
22671 @value{GDBN} identifier of the thread group. The @var{pid} field
22672 contains process identifier, specific to the operating system.
22674 @itemx =thread-group-exited,id="@var{id}"
22675 A thread group is no longer associated with a running program,
22676 either because the program has exited, or because it was detached
22677 from. The @var{id} field contains the @value{GDBN} identifier of the
22680 @item =thread-created,id="@var{id}",group-id="@var{gid}"
22681 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
22682 A thread either was created, or has exited. The @var{id} field
22683 contains the @value{GDBN} identifier of the thread. The @var{gid}
22684 field identifies the thread group this thread belongs to.
22686 @item =thread-selected,id="@var{id}"
22687 Informs that the selected thread was changed as result of the last
22688 command. This notification is not emitted as result of @code{-thread-select}
22689 command but is emitted whenever an MI command that is not documented
22690 to change the selected thread actually changes it. In particular,
22691 invoking, directly or indirectly (via user-defined command), the CLI
22692 @code{thread} command, will generate this notification.
22694 We suggest that in response to this notification, front ends
22695 highlight the selected thread and cause subsequent commands to apply to
22698 @item =library-loaded,...
22699 Reports that a new library file was loaded by the program. This
22700 notification has 4 fields---@var{id}, @var{target-name},
22701 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
22702 opaque identifier of the library. For remote debugging case,
22703 @var{target-name} and @var{host-name} fields give the name of the
22704 library file on the target, and on the host respectively. For native
22705 debugging, both those fields have the same value. The
22706 @var{symbols-loaded} field reports if the debug symbols for this
22707 library are loaded. The @var{thread-group} field, if present,
22708 specifies the id of the thread group in whose context the library was loaded.
22709 If the field is absent, it means the library was loaded in the context
22710 of all present thread groups.
22712 @item =library-unloaded,...
22713 Reports that a library was unloaded by the program. This notification
22714 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
22715 the same meaning as for the @code{=library-loaded} notification.
22716 The @var{thread-group} field, if present, specifies the id of the
22717 thread group in whose context the library was unloaded. If the field is
22718 absent, it means the library was unloaded in the context of all present
22723 @node GDB/MI Frame Information
22724 @subsection @sc{gdb/mi} Frame Information
22726 Response from many MI commands includes an information about stack
22727 frame. This information is a tuple that may have the following
22732 The level of the stack frame. The innermost frame has the level of
22733 zero. This field is always present.
22736 The name of the function corresponding to the frame. This field may
22737 be absent if @value{GDBN} is unable to determine the function name.
22740 The code address for the frame. This field is always present.
22743 The name of the source files that correspond to the frame's code
22744 address. This field may be absent.
22747 The source line corresponding to the frames' code address. This field
22751 The name of the binary file (either executable or shared library) the
22752 corresponds to the frame's code address. This field may be absent.
22756 @node GDB/MI Thread Information
22757 @subsection @sc{gdb/mi} Thread Information
22759 Whenever @value{GDBN} has to report an information about a thread, it
22760 uses a tuple with the following fields:
22764 The numeric id assigned to the thread by @value{GDBN}. This field is
22768 Target-specific string identifying the thread. This field is always present.
22771 Additional information about the thread provided by the target.
22772 It is supposed to be human-readable and not interpreted by the
22773 frontend. This field is optional.
22776 Either @samp{stopped} or @samp{running}, depending on whether the
22777 thread is presently running. This field is always present.
22780 The value of this field is an integer number of the processor core the
22781 thread was last seen on. This field is optional.
22785 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22786 @node GDB/MI Simple Examples
22787 @section Simple Examples of @sc{gdb/mi} Interaction
22788 @cindex @sc{gdb/mi}, simple examples
22790 This subsection presents several simple examples of interaction using
22791 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
22792 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
22793 the output received from @sc{gdb/mi}.
22795 Note the line breaks shown in the examples are here only for
22796 readability, they don't appear in the real output.
22798 @subheading Setting a Breakpoint
22800 Setting a breakpoint generates synchronous output which contains detailed
22801 information of the breakpoint.
22804 -> -break-insert main
22805 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22806 enabled="y",addr="0x08048564",func="main",file="myprog.c",
22807 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
22811 @subheading Program Execution
22813 Program execution generates asynchronous records and MI gives the
22814 reason that execution stopped.
22820 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22821 frame=@{addr="0x08048564",func="main",
22822 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
22823 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
22828 <- *stopped,reason="exited-normally"
22832 @subheading Quitting @value{GDBN}
22834 Quitting @value{GDBN} just prints the result class @samp{^exit}.
22842 Please note that @samp{^exit} is printed immediately, but it might
22843 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
22844 performs necessary cleanups, including killing programs being debugged
22845 or disconnecting from debug hardware, so the frontend should wait till
22846 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
22847 fails to exit in reasonable time.
22849 @subheading A Bad Command
22851 Here's what happens if you pass a non-existent command:
22855 <- ^error,msg="Undefined MI command: rubbish"
22860 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22861 @node GDB/MI Command Description Format
22862 @section @sc{gdb/mi} Command Description Format
22864 The remaining sections describe blocks of commands. Each block of
22865 commands is laid out in a fashion similar to this section.
22867 @subheading Motivation
22869 The motivation for this collection of commands.
22871 @subheading Introduction
22873 A brief introduction to this collection of commands as a whole.
22875 @subheading Commands
22877 For each command in the block, the following is described:
22879 @subsubheading Synopsis
22882 -command @var{args}@dots{}
22885 @subsubheading Result
22887 @subsubheading @value{GDBN} Command
22889 The corresponding @value{GDBN} CLI command(s), if any.
22891 @subsubheading Example
22893 Example(s) formatted for readability. Some of the described commands have
22894 not been implemented yet and these are labeled N.A.@: (not available).
22897 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22898 @node GDB/MI Breakpoint Commands
22899 @section @sc{gdb/mi} Breakpoint Commands
22901 @cindex breakpoint commands for @sc{gdb/mi}
22902 @cindex @sc{gdb/mi}, breakpoint commands
22903 This section documents @sc{gdb/mi} commands for manipulating
22906 @subheading The @code{-break-after} Command
22907 @findex -break-after
22909 @subsubheading Synopsis
22912 -break-after @var{number} @var{count}
22915 The breakpoint number @var{number} is not in effect until it has been
22916 hit @var{count} times. To see how this is reflected in the output of
22917 the @samp{-break-list} command, see the description of the
22918 @samp{-break-list} command below.
22920 @subsubheading @value{GDBN} Command
22922 The corresponding @value{GDBN} command is @samp{ignore}.
22924 @subsubheading Example
22929 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22930 enabled="y",addr="0x000100d0",func="main",file="hello.c",
22931 fullname="/home/foo/hello.c",line="5",times="0"@}
22938 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22939 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22940 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22941 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22942 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22943 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22944 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22945 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22946 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
22947 line="5",times="0",ignore="3"@}]@}
22952 @subheading The @code{-break-catch} Command
22953 @findex -break-catch
22956 @subheading The @code{-break-commands} Command
22957 @findex -break-commands
22959 @subsubheading Synopsis
22962 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
22965 Specifies the CLI commands that should be executed when breakpoint
22966 @var{number} is hit. The parameters @var{command1} to @var{commandN}
22967 are the commands. If no command is specified, any previously-set
22968 commands are cleared. @xref{Break Commands}. Typical use of this
22969 functionality is tracing a program, that is, printing of values of
22970 some variables whenever breakpoint is hit and then continuing.
22972 @subsubheading @value{GDBN} Command
22974 The corresponding @value{GDBN} command is @samp{commands}.
22976 @subsubheading Example
22981 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22982 enabled="y",addr="0x000100d0",func="main",file="hello.c",
22983 fullname="/home/foo/hello.c",line="5",times="0"@}
22985 -break-commands 1 "print v" "continue"
22990 @subheading The @code{-break-condition} Command
22991 @findex -break-condition
22993 @subsubheading Synopsis
22996 -break-condition @var{number} @var{expr}
22999 Breakpoint @var{number} will stop the program only if the condition in
23000 @var{expr} is true. The condition becomes part of the
23001 @samp{-break-list} output (see the description of the @samp{-break-list}
23004 @subsubheading @value{GDBN} Command
23006 The corresponding @value{GDBN} command is @samp{condition}.
23008 @subsubheading Example
23012 -break-condition 1 1
23016 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23017 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23018 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23019 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23020 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23021 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23022 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23023 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23024 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23025 line="5",cond="1",times="0",ignore="3"@}]@}
23029 @subheading The @code{-break-delete} Command
23030 @findex -break-delete
23032 @subsubheading Synopsis
23035 -break-delete ( @var{breakpoint} )+
23038 Delete the breakpoint(s) whose number(s) are specified in the argument
23039 list. This is obviously reflected in the breakpoint list.
23041 @subsubheading @value{GDBN} Command
23043 The corresponding @value{GDBN} command is @samp{delete}.
23045 @subsubheading Example
23053 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23054 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23055 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23056 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23057 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23058 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23059 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23064 @subheading The @code{-break-disable} Command
23065 @findex -break-disable
23067 @subsubheading Synopsis
23070 -break-disable ( @var{breakpoint} )+
23073 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
23074 break list is now set to @samp{n} for the named @var{breakpoint}(s).
23076 @subsubheading @value{GDBN} Command
23078 The corresponding @value{GDBN} command is @samp{disable}.
23080 @subsubheading Example
23088 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23089 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23090 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23091 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23092 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23093 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23094 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23095 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
23096 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23097 line="5",times="0"@}]@}
23101 @subheading The @code{-break-enable} Command
23102 @findex -break-enable
23104 @subsubheading Synopsis
23107 -break-enable ( @var{breakpoint} )+
23110 Enable (previously disabled) @var{breakpoint}(s).
23112 @subsubheading @value{GDBN} Command
23114 The corresponding @value{GDBN} command is @samp{enable}.
23116 @subsubheading Example
23124 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23125 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23126 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23127 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23128 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23129 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23130 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23131 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23132 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23133 line="5",times="0"@}]@}
23137 @subheading The @code{-break-info} Command
23138 @findex -break-info
23140 @subsubheading Synopsis
23143 -break-info @var{breakpoint}
23147 Get information about a single breakpoint.
23149 @subsubheading @value{GDBN} Command
23151 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
23153 @subsubheading Example
23156 @subheading The @code{-break-insert} Command
23157 @findex -break-insert
23159 @subsubheading Synopsis
23162 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
23163 [ -c @var{condition} ] [ -i @var{ignore-count} ]
23164 [ -p @var{thread} ] [ @var{location} ]
23168 If specified, @var{location}, can be one of:
23175 @item filename:linenum
23176 @item filename:function
23180 The possible optional parameters of this command are:
23184 Insert a temporary breakpoint.
23186 Insert a hardware breakpoint.
23187 @item -c @var{condition}
23188 Make the breakpoint conditional on @var{condition}.
23189 @item -i @var{ignore-count}
23190 Initialize the @var{ignore-count}.
23192 If @var{location} cannot be parsed (for example if it
23193 refers to unknown files or functions), create a pending
23194 breakpoint. Without this flag, @value{GDBN} will report
23195 an error, and won't create a breakpoint, if @var{location}
23198 Create a disabled breakpoint.
23200 Create a tracepoint. @xref{Tracepoints}. When this parameter
23201 is used together with @samp{-h}, a fast tracepoint is created.
23204 @subsubheading Result
23206 The result is in the form:
23209 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
23210 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
23211 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
23212 times="@var{times}"@}
23216 where @var{number} is the @value{GDBN} number for this breakpoint,
23217 @var{funcname} is the name of the function where the breakpoint was
23218 inserted, @var{filename} is the name of the source file which contains
23219 this function, @var{lineno} is the source line number within that file
23220 and @var{times} the number of times that the breakpoint has been hit
23221 (always 0 for -break-insert but may be greater for -break-info or -break-list
23222 which use the same output).
23224 Note: this format is open to change.
23225 @c An out-of-band breakpoint instead of part of the result?
23227 @subsubheading @value{GDBN} Command
23229 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
23230 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
23232 @subsubheading Example
23237 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
23238 fullname="/home/foo/recursive2.c,line="4",times="0"@}
23240 -break-insert -t foo
23241 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
23242 fullname="/home/foo/recursive2.c,line="11",times="0"@}
23245 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23246 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23247 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23248 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23249 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23250 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23251 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23252 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23253 addr="0x0001072c", func="main",file="recursive2.c",
23254 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
23255 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
23256 addr="0x00010774",func="foo",file="recursive2.c",
23257 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
23259 -break-insert -r foo.*
23260 ~int foo(int, int);
23261 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
23262 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
23266 @subheading The @code{-break-list} Command
23267 @findex -break-list
23269 @subsubheading Synopsis
23275 Displays the list of inserted breakpoints, showing the following fields:
23279 number of the breakpoint
23281 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
23283 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
23286 is the breakpoint enabled or no: @samp{y} or @samp{n}
23288 memory location at which the breakpoint is set
23290 logical location of the breakpoint, expressed by function name, file
23293 number of times the breakpoint has been hit
23296 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
23297 @code{body} field is an empty list.
23299 @subsubheading @value{GDBN} Command
23301 The corresponding @value{GDBN} command is @samp{info break}.
23303 @subsubheading Example
23308 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23309 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23310 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23311 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23312 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23313 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23314 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23315 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23316 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
23317 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23318 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
23319 line="13",times="0"@}]@}
23323 Here's an example of the result when there are no breakpoints:
23328 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23329 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23330 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23331 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23332 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23333 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23334 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23339 @subheading The @code{-break-passcount} Command
23340 @findex -break-passcount
23342 @subsubheading Synopsis
23345 -break-passcount @var{tracepoint-number} @var{passcount}
23348 Set the passcount for tracepoint @var{tracepoint-number} to
23349 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
23350 is not a tracepoint, error is emitted. This corresponds to CLI
23351 command @samp{passcount}.
23353 @subheading The @code{-break-watch} Command
23354 @findex -break-watch
23356 @subsubheading Synopsis
23359 -break-watch [ -a | -r ]
23362 Create a watchpoint. With the @samp{-a} option it will create an
23363 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
23364 read from or on a write to the memory location. With the @samp{-r}
23365 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
23366 trigger only when the memory location is accessed for reading. Without
23367 either of the options, the watchpoint created is a regular watchpoint,
23368 i.e., it will trigger when the memory location is accessed for writing.
23369 @xref{Set Watchpoints, , Setting Watchpoints}.
23371 Note that @samp{-break-list} will report a single list of watchpoints and
23372 breakpoints inserted.
23374 @subsubheading @value{GDBN} Command
23376 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
23379 @subsubheading Example
23381 Setting a watchpoint on a variable in the @code{main} function:
23386 ^done,wpt=@{number="2",exp="x"@}
23391 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
23392 value=@{old="-268439212",new="55"@},
23393 frame=@{func="main",args=[],file="recursive2.c",
23394 fullname="/home/foo/bar/recursive2.c",line="5"@}
23398 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
23399 the program execution twice: first for the variable changing value, then
23400 for the watchpoint going out of scope.
23405 ^done,wpt=@{number="5",exp="C"@}
23410 *stopped,reason="watchpoint-trigger",
23411 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
23412 frame=@{func="callee4",args=[],
23413 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23414 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
23419 *stopped,reason="watchpoint-scope",wpnum="5",
23420 frame=@{func="callee3",args=[@{name="strarg",
23421 value="0x11940 \"A string argument.\""@}],
23422 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23423 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23427 Listing breakpoints and watchpoints, at different points in the program
23428 execution. Note that once the watchpoint goes out of scope, it is
23434 ^done,wpt=@{number="2",exp="C"@}
23437 ^done,BreakpointTable=@{nr_rows="2",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="1",type="breakpoint",disp="keep",enabled="y",
23445 addr="0x00010734",func="callee4",
23446 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23447 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
23448 bkpt=@{number="2",type="watchpoint",disp="keep",
23449 enabled="y",addr="",what="C",times="0"@}]@}
23454 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
23455 value=@{old="-276895068",new="3"@},
23456 frame=@{func="callee4",args=[],
23457 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23458 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
23461 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23462 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23463 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23464 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23465 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23466 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23467 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23468 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23469 addr="0x00010734",func="callee4",
23470 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23471 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
23472 bkpt=@{number="2",type="watchpoint",disp="keep",
23473 enabled="y",addr="",what="C",times="-5"@}]@}
23477 ^done,reason="watchpoint-scope",wpnum="2",
23478 frame=@{func="callee3",args=[@{name="strarg",
23479 value="0x11940 \"A string argument.\""@}],
23480 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23481 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23484 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23485 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23486 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23487 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23488 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23489 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23490 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23491 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23492 addr="0x00010734",func="callee4",
23493 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23494 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
23499 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23500 @node GDB/MI Program Context
23501 @section @sc{gdb/mi} Program Context
23503 @subheading The @code{-exec-arguments} Command
23504 @findex -exec-arguments
23507 @subsubheading Synopsis
23510 -exec-arguments @var{args}
23513 Set the inferior program arguments, to be used in the next
23516 @subsubheading @value{GDBN} Command
23518 The corresponding @value{GDBN} command is @samp{set args}.
23520 @subsubheading Example
23524 -exec-arguments -v word
23531 @subheading The @code{-exec-show-arguments} Command
23532 @findex -exec-show-arguments
23534 @subsubheading Synopsis
23537 -exec-show-arguments
23540 Print the arguments of the program.
23542 @subsubheading @value{GDBN} Command
23544 The corresponding @value{GDBN} command is @samp{show args}.
23546 @subsubheading Example
23551 @subheading The @code{-environment-cd} Command
23552 @findex -environment-cd
23554 @subsubheading Synopsis
23557 -environment-cd @var{pathdir}
23560 Set @value{GDBN}'s working directory.
23562 @subsubheading @value{GDBN} Command
23564 The corresponding @value{GDBN} command is @samp{cd}.
23566 @subsubheading Example
23570 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
23576 @subheading The @code{-environment-directory} Command
23577 @findex -environment-directory
23579 @subsubheading Synopsis
23582 -environment-directory [ -r ] [ @var{pathdir} ]+
23585 Add directories @var{pathdir} to beginning of search path for source files.
23586 If the @samp{-r} option is used, the search path is reset to the default
23587 search path. If directories @var{pathdir} are supplied in addition to the
23588 @samp{-r} option, the search path is first reset and then addition
23590 Multiple directories may be specified, separated by blanks. Specifying
23591 multiple directories in a single command
23592 results in the directories added to the beginning of the
23593 search path in the same order they were presented in the command.
23594 If blanks are needed as
23595 part of a directory name, double-quotes should be used around
23596 the name. In the command output, the path will show up separated
23597 by the system directory-separator character. The directory-separator
23598 character must not be used
23599 in any directory name.
23600 If no directories are specified, the current search path is displayed.
23602 @subsubheading @value{GDBN} Command
23604 The corresponding @value{GDBN} command is @samp{dir}.
23606 @subsubheading Example
23610 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
23611 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
23613 -environment-directory ""
23614 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
23616 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
23617 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
23619 -environment-directory -r
23620 ^done,source-path="$cdir:$cwd"
23625 @subheading The @code{-environment-path} Command
23626 @findex -environment-path
23628 @subsubheading Synopsis
23631 -environment-path [ -r ] [ @var{pathdir} ]+
23634 Add directories @var{pathdir} to beginning of search path for object files.
23635 If the @samp{-r} option is used, the search path is reset to the original
23636 search path that existed at gdb start-up. If directories @var{pathdir} are
23637 supplied in addition to the
23638 @samp{-r} option, the search path is first reset and then addition
23640 Multiple directories may be specified, separated by blanks. Specifying
23641 multiple directories in a single command
23642 results in the directories added to the beginning of the
23643 search path in the same order they were presented in the command.
23644 If blanks are needed as
23645 part of a directory name, double-quotes should be used around
23646 the name. In the command output, the path will show up separated
23647 by the system directory-separator character. The directory-separator
23648 character must not be used
23649 in any directory name.
23650 If no directories are specified, the current path is displayed.
23653 @subsubheading @value{GDBN} Command
23655 The corresponding @value{GDBN} command is @samp{path}.
23657 @subsubheading Example
23662 ^done,path="/usr/bin"
23664 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
23665 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
23667 -environment-path -r /usr/local/bin
23668 ^done,path="/usr/local/bin:/usr/bin"
23673 @subheading The @code{-environment-pwd} Command
23674 @findex -environment-pwd
23676 @subsubheading Synopsis
23682 Show the current working directory.
23684 @subsubheading @value{GDBN} Command
23686 The corresponding @value{GDBN} command is @samp{pwd}.
23688 @subsubheading Example
23693 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
23697 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23698 @node GDB/MI Thread Commands
23699 @section @sc{gdb/mi} Thread Commands
23702 @subheading The @code{-thread-info} Command
23703 @findex -thread-info
23705 @subsubheading Synopsis
23708 -thread-info [ @var{thread-id} ]
23711 Reports information about either a specific thread, if
23712 the @var{thread-id} parameter is present, or about all
23713 threads. When printing information about all threads,
23714 also reports the current thread.
23716 @subsubheading @value{GDBN} Command
23718 The @samp{info thread} command prints the same information
23721 @subsubheading Example
23726 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
23727 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
23728 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
23729 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
23730 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
23731 current-thread-id="1"
23735 The @samp{state} field may have the following values:
23739 The thread is stopped. Frame information is available for stopped
23743 The thread is running. There's no frame information for running
23748 @subheading The @code{-thread-list-ids} Command
23749 @findex -thread-list-ids
23751 @subsubheading Synopsis
23757 Produces a list of the currently known @value{GDBN} thread ids. At the
23758 end of the list it also prints the total number of such threads.
23760 This command is retained for historical reasons, the
23761 @code{-thread-info} command should be used instead.
23763 @subsubheading @value{GDBN} Command
23765 Part of @samp{info threads} supplies the same information.
23767 @subsubheading Example
23772 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
23773 current-thread-id="1",number-of-threads="3"
23778 @subheading The @code{-thread-select} Command
23779 @findex -thread-select
23781 @subsubheading Synopsis
23784 -thread-select @var{threadnum}
23787 Make @var{threadnum} the current thread. It prints the number of the new
23788 current thread, and the topmost frame for that thread.
23790 This command is deprecated in favor of explicitly using the
23791 @samp{--thread} option to each command.
23793 @subsubheading @value{GDBN} Command
23795 The corresponding @value{GDBN} command is @samp{thread}.
23797 @subsubheading Example
23804 *stopped,reason="end-stepping-range",thread-id="2",line="187",
23805 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
23809 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
23810 number-of-threads="3"
23813 ^done,new-thread-id="3",
23814 frame=@{level="0",func="vprintf",
23815 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
23816 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
23820 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23821 @node GDB/MI Program Execution
23822 @section @sc{gdb/mi} Program Execution
23824 These are the asynchronous commands which generate the out-of-band
23825 record @samp{*stopped}. Currently @value{GDBN} only really executes
23826 asynchronously with remote targets and this interaction is mimicked in
23829 @subheading The @code{-exec-continue} Command
23830 @findex -exec-continue
23832 @subsubheading Synopsis
23835 -exec-continue [--reverse] [--all|--thread-group N]
23838 Resumes the execution of the inferior program, which will continue
23839 to execute until it reaches a debugger stop event. If the
23840 @samp{--reverse} option is specified, execution resumes in reverse until
23841 it reaches a stop event. Stop events may include
23844 breakpoints or watchpoints
23846 signals or exceptions
23848 the end of the process (or its beginning under @samp{--reverse})
23850 the end or beginning of a replay log if one is being used.
23852 In all-stop mode (@pxref{All-Stop
23853 Mode}), may resume only one thread, or all threads, depending on the
23854 value of the @samp{scheduler-locking} variable. If @samp{--all} is
23855 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
23856 ignored in all-stop mode. If the @samp{--thread-group} options is
23857 specified, then all threads in that thread group are resumed.
23859 @subsubheading @value{GDBN} Command
23861 The corresponding @value{GDBN} corresponding is @samp{continue}.
23863 @subsubheading Example
23870 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
23871 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
23877 @subheading The @code{-exec-finish} Command
23878 @findex -exec-finish
23880 @subsubheading Synopsis
23883 -exec-finish [--reverse]
23886 Resumes the execution of the inferior program until the current
23887 function is exited. Displays the results returned by the function.
23888 If the @samp{--reverse} option is specified, resumes the reverse
23889 execution of the inferior program until the point where current
23890 function was called.
23892 @subsubheading @value{GDBN} Command
23894 The corresponding @value{GDBN} command is @samp{finish}.
23896 @subsubheading Example
23898 Function returning @code{void}.
23905 *stopped,reason="function-finished",frame=@{func="main",args=[],
23906 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
23910 Function returning other than @code{void}. The name of the internal
23911 @value{GDBN} variable storing the result is printed, together with the
23918 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
23919 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
23920 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23921 gdb-result-var="$1",return-value="0"
23926 @subheading The @code{-exec-interrupt} Command
23927 @findex -exec-interrupt
23929 @subsubheading Synopsis
23932 -exec-interrupt [--all|--thread-group N]
23935 Interrupts the background execution of the target. Note how the token
23936 associated with the stop message is the one for the execution command
23937 that has been interrupted. The token for the interrupt itself only
23938 appears in the @samp{^done} output. If the user is trying to
23939 interrupt a non-running program, an error message will be printed.
23941 Note that when asynchronous execution is enabled, this command is
23942 asynchronous just like other execution commands. That is, first the
23943 @samp{^done} response will be printed, and the target stop will be
23944 reported after that using the @samp{*stopped} notification.
23946 In non-stop mode, only the context thread is interrupted by default.
23947 All threads (in all inferiors) will be interrupted if the
23948 @samp{--all} option is specified. If the @samp{--thread-group}
23949 option is specified, all threads in that group will be interrupted.
23951 @subsubheading @value{GDBN} Command
23953 The corresponding @value{GDBN} command is @samp{interrupt}.
23955 @subsubheading Example
23966 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
23967 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
23968 fullname="/home/foo/bar/try.c",line="13"@}
23973 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
23977 @subheading The @code{-exec-jump} Command
23980 @subsubheading Synopsis
23983 -exec-jump @var{location}
23986 Resumes execution of the inferior program at the location specified by
23987 parameter. @xref{Specify Location}, for a description of the
23988 different forms of @var{location}.
23990 @subsubheading @value{GDBN} Command
23992 The corresponding @value{GDBN} command is @samp{jump}.
23994 @subsubheading Example
23997 -exec-jump foo.c:10
23998 *running,thread-id="all"
24003 @subheading The @code{-exec-next} Command
24006 @subsubheading Synopsis
24009 -exec-next [--reverse]
24012 Resumes execution of the inferior program, stopping when the beginning
24013 of the next source line is reached.
24015 If the @samp{--reverse} option is specified, resumes reverse execution
24016 of the inferior program, stopping at the beginning of the previous
24017 source line. If you issue this command on the first line of a
24018 function, it will take you back to the caller of that function, to the
24019 source line where the function was called.
24022 @subsubheading @value{GDBN} Command
24024 The corresponding @value{GDBN} command is @samp{next}.
24026 @subsubheading Example
24032 *stopped,reason="end-stepping-range",line="8",file="hello.c"
24037 @subheading The @code{-exec-next-instruction} Command
24038 @findex -exec-next-instruction
24040 @subsubheading Synopsis
24043 -exec-next-instruction [--reverse]
24046 Executes one machine instruction. If the instruction is a function
24047 call, continues until the function returns. If the program stops at an
24048 instruction in the middle of a source line, the address will be
24051 If the @samp{--reverse} option is specified, resumes reverse execution
24052 of the inferior program, stopping at the previous instruction. If the
24053 previously executed instruction was a return from another function,
24054 it will continue to execute in reverse until the call to that function
24055 (from the current stack frame) is reached.
24057 @subsubheading @value{GDBN} Command
24059 The corresponding @value{GDBN} command is @samp{nexti}.
24061 @subsubheading Example
24065 -exec-next-instruction
24069 *stopped,reason="end-stepping-range",
24070 addr="0x000100d4",line="5",file="hello.c"
24075 @subheading The @code{-exec-return} Command
24076 @findex -exec-return
24078 @subsubheading Synopsis
24084 Makes current function return immediately. Doesn't execute the inferior.
24085 Displays the new current frame.
24087 @subsubheading @value{GDBN} Command
24089 The corresponding @value{GDBN} command is @samp{return}.
24091 @subsubheading Example
24095 200-break-insert callee4
24096 200^done,bkpt=@{number="1",addr="0x00010734",
24097 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24102 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24103 frame=@{func="callee4",args=[],
24104 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24105 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24111 111^done,frame=@{level="0",func="callee3",
24112 args=[@{name="strarg",
24113 value="0x11940 \"A string argument.\""@}],
24114 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24115 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24120 @subheading The @code{-exec-run} Command
24123 @subsubheading Synopsis
24126 -exec-run [--all | --thread-group N]
24129 Starts execution of the inferior from the beginning. The inferior
24130 executes until either a breakpoint is encountered or the program
24131 exits. In the latter case the output will include an exit code, if
24132 the program has exited exceptionally.
24134 When no option is specified, the current inferior is started. If the
24135 @samp{--thread-group} option is specified, it should refer to a thread
24136 group of type @samp{process}, and that thread group will be started.
24137 If the @samp{--all} option is specified, then all inferiors will be started.
24139 @subsubheading @value{GDBN} Command
24141 The corresponding @value{GDBN} command is @samp{run}.
24143 @subsubheading Examples
24148 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
24153 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24154 frame=@{func="main",args=[],file="recursive2.c",
24155 fullname="/home/foo/bar/recursive2.c",line="4"@}
24160 Program exited normally:
24168 *stopped,reason="exited-normally"
24173 Program exited exceptionally:
24181 *stopped,reason="exited",exit-code="01"
24185 Another way the program can terminate is if it receives a signal such as
24186 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
24190 *stopped,reason="exited-signalled",signal-name="SIGINT",
24191 signal-meaning="Interrupt"
24195 @c @subheading -exec-signal
24198 @subheading The @code{-exec-step} Command
24201 @subsubheading Synopsis
24204 -exec-step [--reverse]
24207 Resumes execution of the inferior program, stopping when the beginning
24208 of the next source line is reached, if the next source line is not a
24209 function call. If it is, stop at the first instruction of the called
24210 function. If the @samp{--reverse} option is specified, resumes reverse
24211 execution of the inferior program, stopping at the beginning of the
24212 previously executed source line.
24214 @subsubheading @value{GDBN} Command
24216 The corresponding @value{GDBN} command is @samp{step}.
24218 @subsubheading Example
24220 Stepping into a function:
24226 *stopped,reason="end-stepping-range",
24227 frame=@{func="foo",args=[@{name="a",value="10"@},
24228 @{name="b",value="0"@}],file="recursive2.c",
24229 fullname="/home/foo/bar/recursive2.c",line="11"@}
24239 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
24244 @subheading The @code{-exec-step-instruction} Command
24245 @findex -exec-step-instruction
24247 @subsubheading Synopsis
24250 -exec-step-instruction [--reverse]
24253 Resumes the inferior which executes one machine instruction. If the
24254 @samp{--reverse} option is specified, resumes reverse execution of the
24255 inferior program, stopping at the previously executed instruction.
24256 The output, once @value{GDBN} has stopped, will vary depending on
24257 whether we have stopped in the middle of a source line or not. In the
24258 former case, the address at which the program stopped will be printed
24261 @subsubheading @value{GDBN} Command
24263 The corresponding @value{GDBN} command is @samp{stepi}.
24265 @subsubheading Example
24269 -exec-step-instruction
24273 *stopped,reason="end-stepping-range",
24274 frame=@{func="foo",args=[],file="try.c",
24275 fullname="/home/foo/bar/try.c",line="10"@}
24277 -exec-step-instruction
24281 *stopped,reason="end-stepping-range",
24282 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
24283 fullname="/home/foo/bar/try.c",line="10"@}
24288 @subheading The @code{-exec-until} Command
24289 @findex -exec-until
24291 @subsubheading Synopsis
24294 -exec-until [ @var{location} ]
24297 Executes the inferior until the @var{location} specified in the
24298 argument is reached. If there is no argument, the inferior executes
24299 until a source line greater than the current one is reached. The
24300 reason for stopping in this case will be @samp{location-reached}.
24302 @subsubheading @value{GDBN} Command
24304 The corresponding @value{GDBN} command is @samp{until}.
24306 @subsubheading Example
24310 -exec-until recursive2.c:6
24314 *stopped,reason="location-reached",frame=@{func="main",args=[],
24315 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
24320 @subheading -file-clear
24321 Is this going away????
24324 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24325 @node GDB/MI Stack Manipulation
24326 @section @sc{gdb/mi} Stack Manipulation Commands
24329 @subheading The @code{-stack-info-frame} Command
24330 @findex -stack-info-frame
24332 @subsubheading Synopsis
24338 Get info on the selected frame.
24340 @subsubheading @value{GDBN} Command
24342 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
24343 (without arguments).
24345 @subsubheading Example
24350 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
24351 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24352 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
24356 @subheading The @code{-stack-info-depth} Command
24357 @findex -stack-info-depth
24359 @subsubheading Synopsis
24362 -stack-info-depth [ @var{max-depth} ]
24365 Return the depth of the stack. If the integer argument @var{max-depth}
24366 is specified, do not count beyond @var{max-depth} frames.
24368 @subsubheading @value{GDBN} Command
24370 There's no equivalent @value{GDBN} command.
24372 @subsubheading Example
24374 For a stack with frame levels 0 through 11:
24381 -stack-info-depth 4
24384 -stack-info-depth 12
24387 -stack-info-depth 11
24390 -stack-info-depth 13
24395 @subheading The @code{-stack-list-arguments} Command
24396 @findex -stack-list-arguments
24398 @subsubheading Synopsis
24401 -stack-list-arguments @var{print-values}
24402 [ @var{low-frame} @var{high-frame} ]
24405 Display a list of the arguments for the frames between @var{low-frame}
24406 and @var{high-frame} (inclusive). If @var{low-frame} and
24407 @var{high-frame} are not provided, list the arguments for the whole
24408 call stack. If the two arguments are equal, show the single frame
24409 at the corresponding level. It is an error if @var{low-frame} is
24410 larger than the actual number of frames. On the other hand,
24411 @var{high-frame} may be larger than the actual number of frames, in
24412 which case only existing frames will be returned.
24414 If @var{print-values} is 0 or @code{--no-values}, print only the names of
24415 the variables; if it is 1 or @code{--all-values}, print also their
24416 values; and if it is 2 or @code{--simple-values}, print the name,
24417 type and value for simple data types, and the name and type for arrays,
24418 structures and unions.
24420 Use of this command to obtain arguments in a single frame is
24421 deprecated in favor of the @samp{-stack-list-variables} command.
24423 @subsubheading @value{GDBN} Command
24425 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
24426 @samp{gdb_get_args} command which partially overlaps with the
24427 functionality of @samp{-stack-list-arguments}.
24429 @subsubheading Example
24436 frame=@{level="0",addr="0x00010734",func="callee4",
24437 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24438 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
24439 frame=@{level="1",addr="0x0001076c",func="callee3",
24440 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24441 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
24442 frame=@{level="2",addr="0x0001078c",func="callee2",
24443 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24444 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
24445 frame=@{level="3",addr="0x000107b4",func="callee1",
24446 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24447 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
24448 frame=@{level="4",addr="0x000107e0",func="main",
24449 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24450 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
24452 -stack-list-arguments 0
24455 frame=@{level="0",args=[]@},
24456 frame=@{level="1",args=[name="strarg"]@},
24457 frame=@{level="2",args=[name="intarg",name="strarg"]@},
24458 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
24459 frame=@{level="4",args=[]@}]
24461 -stack-list-arguments 1
24464 frame=@{level="0",args=[]@},
24466 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
24467 frame=@{level="2",args=[
24468 @{name="intarg",value="2"@},
24469 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
24470 @{frame=@{level="3",args=[
24471 @{name="intarg",value="2"@},
24472 @{name="strarg",value="0x11940 \"A string argument.\""@},
24473 @{name="fltarg",value="3.5"@}]@},
24474 frame=@{level="4",args=[]@}]
24476 -stack-list-arguments 0 2 2
24477 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
24479 -stack-list-arguments 1 2 2
24480 ^done,stack-args=[frame=@{level="2",
24481 args=[@{name="intarg",value="2"@},
24482 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
24486 @c @subheading -stack-list-exception-handlers
24489 @subheading The @code{-stack-list-frames} Command
24490 @findex -stack-list-frames
24492 @subsubheading Synopsis
24495 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
24498 List the frames currently on the stack. For each frame it displays the
24503 The frame number, 0 being the topmost frame, i.e., the innermost function.
24505 The @code{$pc} value for that frame.
24509 File name of the source file where the function lives.
24511 Line number corresponding to the @code{$pc}.
24514 If invoked without arguments, this command prints a backtrace for the
24515 whole stack. If given two integer arguments, it shows the frames whose
24516 levels are between the two arguments (inclusive). If the two arguments
24517 are equal, it shows the single frame at the corresponding level. It is
24518 an error if @var{low-frame} is larger than the actual number of
24519 frames. On the other hand, @var{high-frame} may be larger than the
24520 actual number of frames, in which case only existing frames will be returned.
24522 @subsubheading @value{GDBN} Command
24524 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
24526 @subsubheading Example
24528 Full stack backtrace:
24534 [frame=@{level="0",addr="0x0001076c",func="foo",
24535 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
24536 frame=@{level="1",addr="0x000107a4",func="foo",
24537 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24538 frame=@{level="2",addr="0x000107a4",func="foo",
24539 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24540 frame=@{level="3",addr="0x000107a4",func="foo",
24541 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24542 frame=@{level="4",addr="0x000107a4",func="foo",
24543 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24544 frame=@{level="5",addr="0x000107a4",func="foo",
24545 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24546 frame=@{level="6",addr="0x000107a4",func="foo",
24547 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24548 frame=@{level="7",addr="0x000107a4",func="foo",
24549 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24550 frame=@{level="8",addr="0x000107a4",func="foo",
24551 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24552 frame=@{level="9",addr="0x000107a4",func="foo",
24553 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24554 frame=@{level="10",addr="0x000107a4",func="foo",
24555 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24556 frame=@{level="11",addr="0x00010738",func="main",
24557 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
24561 Show frames between @var{low_frame} and @var{high_frame}:
24565 -stack-list-frames 3 5
24567 [frame=@{level="3",addr="0x000107a4",func="foo",
24568 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24569 frame=@{level="4",addr="0x000107a4",func="foo",
24570 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24571 frame=@{level="5",addr="0x000107a4",func="foo",
24572 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
24576 Show a single frame:
24580 -stack-list-frames 3 3
24582 [frame=@{level="3",addr="0x000107a4",func="foo",
24583 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
24588 @subheading The @code{-stack-list-locals} Command
24589 @findex -stack-list-locals
24591 @subsubheading Synopsis
24594 -stack-list-locals @var{print-values}
24597 Display the local variable names for the selected frame. If
24598 @var{print-values} is 0 or @code{--no-values}, print only the names of
24599 the variables; if it is 1 or @code{--all-values}, print also their
24600 values; and if it is 2 or @code{--simple-values}, print the name,
24601 type and value for simple data types, and the name and type for arrays,
24602 structures and unions. In this last case, a frontend can immediately
24603 display the value of simple data types and create variable objects for
24604 other data types when the user wishes to explore their values in
24607 This command is deprecated in favor of the
24608 @samp{-stack-list-variables} command.
24610 @subsubheading @value{GDBN} Command
24612 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
24614 @subsubheading Example
24618 -stack-list-locals 0
24619 ^done,locals=[name="A",name="B",name="C"]
24621 -stack-list-locals --all-values
24622 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
24623 @{name="C",value="@{1, 2, 3@}"@}]
24624 -stack-list-locals --simple-values
24625 ^done,locals=[@{name="A",type="int",value="1"@},
24626 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
24630 @subheading The @code{-stack-list-variables} Command
24631 @findex -stack-list-variables
24633 @subsubheading Synopsis
24636 -stack-list-variables @var{print-values}
24639 Display the names of local variables and function arguments for the selected frame. If
24640 @var{print-values} is 0 or @code{--no-values}, print only the names of
24641 the variables; if it is 1 or @code{--all-values}, print also their
24642 values; and if it is 2 or @code{--simple-values}, print the name,
24643 type and value for simple data types, and the name and type for arrays,
24644 structures and unions.
24646 @subsubheading Example
24650 -stack-list-variables --thread 1 --frame 0 --all-values
24651 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
24656 @subheading The @code{-stack-select-frame} Command
24657 @findex -stack-select-frame
24659 @subsubheading Synopsis
24662 -stack-select-frame @var{framenum}
24665 Change the selected frame. Select a different frame @var{framenum} on
24668 This command in deprecated in favor of passing the @samp{--frame}
24669 option to every command.
24671 @subsubheading @value{GDBN} Command
24673 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
24674 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
24676 @subsubheading Example
24680 -stack-select-frame 2
24685 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24686 @node GDB/MI Variable Objects
24687 @section @sc{gdb/mi} Variable Objects
24691 @subheading Motivation for Variable Objects in @sc{gdb/mi}
24693 For the implementation of a variable debugger window (locals, watched
24694 expressions, etc.), we are proposing the adaptation of the existing code
24695 used by @code{Insight}.
24697 The two main reasons for that are:
24701 It has been proven in practice (it is already on its second generation).
24704 It will shorten development time (needless to say how important it is
24708 The original interface was designed to be used by Tcl code, so it was
24709 slightly changed so it could be used through @sc{gdb/mi}. This section
24710 describes the @sc{gdb/mi} operations that will be available and gives some
24711 hints about their use.
24713 @emph{Note}: In addition to the set of operations described here, we
24714 expect the @sc{gui} implementation of a variable window to require, at
24715 least, the following operations:
24718 @item @code{-gdb-show} @code{output-radix}
24719 @item @code{-stack-list-arguments}
24720 @item @code{-stack-list-locals}
24721 @item @code{-stack-select-frame}
24726 @subheading Introduction to Variable Objects
24728 @cindex variable objects in @sc{gdb/mi}
24730 Variable objects are "object-oriented" MI interface for examining and
24731 changing values of expressions. Unlike some other MI interfaces that
24732 work with expressions, variable objects are specifically designed for
24733 simple and efficient presentation in the frontend. A variable object
24734 is identified by string name. When a variable object is created, the
24735 frontend specifies the expression for that variable object. The
24736 expression can be a simple variable, or it can be an arbitrary complex
24737 expression, and can even involve CPU registers. After creating a
24738 variable object, the frontend can invoke other variable object
24739 operations---for example to obtain or change the value of a variable
24740 object, or to change display format.
24742 Variable objects have hierarchical tree structure. Any variable object
24743 that corresponds to a composite type, such as structure in C, has
24744 a number of child variable objects, for example corresponding to each
24745 element of a structure. A child variable object can itself have
24746 children, recursively. Recursion ends when we reach
24747 leaf variable objects, which always have built-in types. Child variable
24748 objects are created only by explicit request, so if a frontend
24749 is not interested in the children of a particular variable object, no
24750 child will be created.
24752 For a leaf variable object it is possible to obtain its value as a
24753 string, or set the value from a string. String value can be also
24754 obtained for a non-leaf variable object, but it's generally a string
24755 that only indicates the type of the object, and does not list its
24756 contents. Assignment to a non-leaf variable object is not allowed.
24758 A frontend does not need to read the values of all variable objects each time
24759 the program stops. Instead, MI provides an update command that lists all
24760 variable objects whose values has changed since the last update
24761 operation. This considerably reduces the amount of data that must
24762 be transferred to the frontend. As noted above, children variable
24763 objects are created on demand, and only leaf variable objects have a
24764 real value. As result, gdb will read target memory only for leaf
24765 variables that frontend has created.
24767 The automatic update is not always desirable. For example, a frontend
24768 might want to keep a value of some expression for future reference,
24769 and never update it. For another example, fetching memory is
24770 relatively slow for embedded targets, so a frontend might want
24771 to disable automatic update for the variables that are either not
24772 visible on the screen, or ``closed''. This is possible using so
24773 called ``frozen variable objects''. Such variable objects are never
24774 implicitly updated.
24776 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
24777 fixed variable object, the expression is parsed when the variable
24778 object is created, including associating identifiers to specific
24779 variables. The meaning of expression never changes. For a floating
24780 variable object the values of variables whose names appear in the
24781 expressions are re-evaluated every time in the context of the current
24782 frame. Consider this example:
24787 struct work_state state;
24794 If a fixed variable object for the @code{state} variable is created in
24795 this function, and we enter the recursive call, the the variable
24796 object will report the value of @code{state} in the top-level
24797 @code{do_work} invocation. On the other hand, a floating variable
24798 object will report the value of @code{state} in the current frame.
24800 If an expression specified when creating a fixed variable object
24801 refers to a local variable, the variable object becomes bound to the
24802 thread and frame in which the variable object is created. When such
24803 variable object is updated, @value{GDBN} makes sure that the
24804 thread/frame combination the variable object is bound to still exists,
24805 and re-evaluates the variable object in context of that thread/frame.
24807 The following is the complete set of @sc{gdb/mi} operations defined to
24808 access this functionality:
24810 @multitable @columnfractions .4 .6
24811 @item @strong{Operation}
24812 @tab @strong{Description}
24814 @item @code{-enable-pretty-printing}
24815 @tab enable Python-based pretty-printing
24816 @item @code{-var-create}
24817 @tab create a variable object
24818 @item @code{-var-delete}
24819 @tab delete the variable object and/or its children
24820 @item @code{-var-set-format}
24821 @tab set the display format of this variable
24822 @item @code{-var-show-format}
24823 @tab show the display format of this variable
24824 @item @code{-var-info-num-children}
24825 @tab tells how many children this object has
24826 @item @code{-var-list-children}
24827 @tab return a list of the object's children
24828 @item @code{-var-info-type}
24829 @tab show the type of this variable object
24830 @item @code{-var-info-expression}
24831 @tab print parent-relative expression that this variable object represents
24832 @item @code{-var-info-path-expression}
24833 @tab print full expression that this variable object represents
24834 @item @code{-var-show-attributes}
24835 @tab is this variable editable? does it exist here?
24836 @item @code{-var-evaluate-expression}
24837 @tab get the value of this variable
24838 @item @code{-var-assign}
24839 @tab set the value of this variable
24840 @item @code{-var-update}
24841 @tab update the variable and its children
24842 @item @code{-var-set-frozen}
24843 @tab set frozeness attribute
24844 @item @code{-var-set-update-range}
24845 @tab set range of children to display on update
24848 In the next subsection we describe each operation in detail and suggest
24849 how it can be used.
24851 @subheading Description And Use of Operations on Variable Objects
24853 @subheading The @code{-enable-pretty-printing} Command
24854 @findex -enable-pretty-printing
24857 -enable-pretty-printing
24860 @value{GDBN} allows Python-based visualizers to affect the output of the
24861 MI variable object commands. However, because there was no way to
24862 implement this in a fully backward-compatible way, a front end must
24863 request that this functionality be enabled.
24865 Once enabled, this feature cannot be disabled.
24867 Note that if Python support has not been compiled into @value{GDBN},
24868 this command will still succeed (and do nothing).
24870 This feature is currently (as of @value{GDBN} 7.0) experimental, and
24871 may work differently in future versions of @value{GDBN}.
24873 @subheading The @code{-var-create} Command
24874 @findex -var-create
24876 @subsubheading Synopsis
24879 -var-create @{@var{name} | "-"@}
24880 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
24883 This operation creates a variable object, which allows the monitoring of
24884 a variable, the result of an expression, a memory cell or a CPU
24887 The @var{name} parameter is the string by which the object can be
24888 referenced. It must be unique. If @samp{-} is specified, the varobj
24889 system will generate a string ``varNNNNNN'' automatically. It will be
24890 unique provided that one does not specify @var{name} of that format.
24891 The command fails if a duplicate name is found.
24893 The frame under which the expression should be evaluated can be
24894 specified by @var{frame-addr}. A @samp{*} indicates that the current
24895 frame should be used. A @samp{@@} indicates that a floating variable
24896 object must be created.
24898 @var{expression} is any expression valid on the current language set (must not
24899 begin with a @samp{*}), or one of the following:
24903 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
24906 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
24909 @samp{$@var{regname}} --- a CPU register name
24912 @cindex dynamic varobj
24913 A varobj's contents may be provided by a Python-based pretty-printer. In this
24914 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
24915 have slightly different semantics in some cases. If the
24916 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
24917 will never create a dynamic varobj. This ensures backward
24918 compatibility for existing clients.
24920 @subsubheading Result
24922 This operation returns attributes of the newly-created varobj. These
24927 The name of the varobj.
24930 The number of children of the varobj. This number is not necessarily
24931 reliable for a dynamic varobj. Instead, you must examine the
24932 @samp{has_more} attribute.
24935 The varobj's scalar value. For a varobj whose type is some sort of
24936 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
24937 will not be interesting.
24940 The varobj's type. This is a string representation of the type, as
24941 would be printed by the @value{GDBN} CLI.
24944 If a variable object is bound to a specific thread, then this is the
24945 thread's identifier.
24948 For a dynamic varobj, this indicates whether there appear to be any
24949 children available. For a non-dynamic varobj, this will be 0.
24952 This attribute will be present and have the value @samp{1} if the
24953 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
24954 then this attribute will not be present.
24957 A dynamic varobj can supply a display hint to the front end. The
24958 value comes directly from the Python pretty-printer object's
24959 @code{display_hint} method. @xref{Pretty Printing}.
24962 Typical output will look like this:
24965 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
24966 has_more="@var{has_more}"
24970 @subheading The @code{-var-delete} Command
24971 @findex -var-delete
24973 @subsubheading Synopsis
24976 -var-delete [ -c ] @var{name}
24979 Deletes a previously created variable object and all of its children.
24980 With the @samp{-c} option, just deletes the children.
24982 Returns an error if the object @var{name} is not found.
24985 @subheading The @code{-var-set-format} Command
24986 @findex -var-set-format
24988 @subsubheading Synopsis
24991 -var-set-format @var{name} @var{format-spec}
24994 Sets the output format for the value of the object @var{name} to be
24997 @anchor{-var-set-format}
24998 The syntax for the @var{format-spec} is as follows:
25001 @var{format-spec} @expansion{}
25002 @{binary | decimal | hexadecimal | octal | natural@}
25005 The natural format is the default format choosen automatically
25006 based on the variable type (like decimal for an @code{int}, hex
25007 for pointers, etc.).
25009 For a variable with children, the format is set only on the
25010 variable itself, and the children are not affected.
25012 @subheading The @code{-var-show-format} Command
25013 @findex -var-show-format
25015 @subsubheading Synopsis
25018 -var-show-format @var{name}
25021 Returns the format used to display the value of the object @var{name}.
25024 @var{format} @expansion{}
25029 @subheading The @code{-var-info-num-children} Command
25030 @findex -var-info-num-children
25032 @subsubheading Synopsis
25035 -var-info-num-children @var{name}
25038 Returns the number of children of a variable object @var{name}:
25044 Note that this number is not completely reliable for a dynamic varobj.
25045 It will return the current number of children, but more children may
25049 @subheading The @code{-var-list-children} Command
25050 @findex -var-list-children
25052 @subsubheading Synopsis
25055 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
25057 @anchor{-var-list-children}
25059 Return a list of the children of the specified variable object and
25060 create variable objects for them, if they do not already exist. With
25061 a single argument or if @var{print-values} has a value for of 0 or
25062 @code{--no-values}, print only the names of the variables; if
25063 @var{print-values} is 1 or @code{--all-values}, also print their
25064 values; and if it is 2 or @code{--simple-values} print the name and
25065 value for simple data types and just the name for arrays, structures
25068 @var{from} and @var{to}, if specified, indicate the range of children
25069 to report. If @var{from} or @var{to} is less than zero, the range is
25070 reset and all children will be reported. Otherwise, children starting
25071 at @var{from} (zero-based) and up to and excluding @var{to} will be
25074 If a child range is requested, it will only affect the current call to
25075 @code{-var-list-children}, but not future calls to @code{-var-update}.
25076 For this, you must instead use @code{-var-set-update-range}. The
25077 intent of this approach is to enable a front end to implement any
25078 update approach it likes; for example, scrolling a view may cause the
25079 front end to request more children with @code{-var-list-children}, and
25080 then the front end could call @code{-var-set-update-range} with a
25081 different range to ensure that future updates are restricted to just
25084 For each child the following results are returned:
25089 Name of the variable object created for this child.
25092 The expression to be shown to the user by the front end to designate this child.
25093 For example this may be the name of a structure member.
25095 For a dynamic varobj, this value cannot be used to form an
25096 expression. There is no way to do this at all with a dynamic varobj.
25098 For C/C@t{++} structures there are several pseudo children returned to
25099 designate access qualifiers. For these pseudo children @var{exp} is
25100 @samp{public}, @samp{private}, or @samp{protected}. In this case the
25101 type and value are not present.
25103 A dynamic varobj will not report the access qualifying
25104 pseudo-children, regardless of the language. This information is not
25105 available at all with a dynamic varobj.
25108 Number of children this child has. For a dynamic varobj, this will be
25112 The type of the child.
25115 If values were requested, this is the value.
25118 If this variable object is associated with a thread, this is the thread id.
25119 Otherwise this result is not present.
25122 If the variable object is frozen, this variable will be present with a value of 1.
25125 The result may have its own attributes:
25129 A dynamic varobj can supply a display hint to the front end. The
25130 value comes directly from the Python pretty-printer object's
25131 @code{display_hint} method. @xref{Pretty Printing}.
25134 This is an integer attribute which is nonzero if there are children
25135 remaining after the end of the selected range.
25138 @subsubheading Example
25142 -var-list-children n
25143 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25144 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
25146 -var-list-children --all-values n
25147 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25148 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
25152 @subheading The @code{-var-info-type} Command
25153 @findex -var-info-type
25155 @subsubheading Synopsis
25158 -var-info-type @var{name}
25161 Returns the type of the specified variable @var{name}. The type is
25162 returned as a string in the same format as it is output by the
25166 type=@var{typename}
25170 @subheading The @code{-var-info-expression} Command
25171 @findex -var-info-expression
25173 @subsubheading Synopsis
25176 -var-info-expression @var{name}
25179 Returns a string that is suitable for presenting this
25180 variable object in user interface. The string is generally
25181 not valid expression in the current language, and cannot be evaluated.
25183 For example, if @code{a} is an array, and variable object
25184 @code{A} was created for @code{a}, then we'll get this output:
25187 (gdb) -var-info-expression A.1
25188 ^done,lang="C",exp="1"
25192 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
25194 Note that the output of the @code{-var-list-children} command also
25195 includes those expressions, so the @code{-var-info-expression} command
25198 @subheading The @code{-var-info-path-expression} Command
25199 @findex -var-info-path-expression
25201 @subsubheading Synopsis
25204 -var-info-path-expression @var{name}
25207 Returns an expression that can be evaluated in the current
25208 context and will yield the same value that a variable object has.
25209 Compare this with the @code{-var-info-expression} command, which
25210 result can be used only for UI presentation. Typical use of
25211 the @code{-var-info-path-expression} command is creating a
25212 watchpoint from a variable object.
25214 This command is currently not valid for children of a dynamic varobj,
25215 and will give an error when invoked on one.
25217 For example, suppose @code{C} is a C@t{++} class, derived from class
25218 @code{Base}, and that the @code{Base} class has a member called
25219 @code{m_size}. Assume a variable @code{c} is has the type of
25220 @code{C} and a variable object @code{C} was created for variable
25221 @code{c}. Then, we'll get this output:
25223 (gdb) -var-info-path-expression C.Base.public.m_size
25224 ^done,path_expr=((Base)c).m_size)
25227 @subheading The @code{-var-show-attributes} Command
25228 @findex -var-show-attributes
25230 @subsubheading Synopsis
25233 -var-show-attributes @var{name}
25236 List attributes of the specified variable object @var{name}:
25239 status=@var{attr} [ ( ,@var{attr} )* ]
25243 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
25245 @subheading The @code{-var-evaluate-expression} Command
25246 @findex -var-evaluate-expression
25248 @subsubheading Synopsis
25251 -var-evaluate-expression [-f @var{format-spec}] @var{name}
25254 Evaluates the expression that is represented by the specified variable
25255 object and returns its value as a string. The format of the string
25256 can be specified with the @samp{-f} option. The possible values of
25257 this option are the same as for @code{-var-set-format}
25258 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
25259 the current display format will be used. The current display format
25260 can be changed using the @code{-var-set-format} command.
25266 Note that one must invoke @code{-var-list-children} for a variable
25267 before the value of a child variable can be evaluated.
25269 @subheading The @code{-var-assign} Command
25270 @findex -var-assign
25272 @subsubheading Synopsis
25275 -var-assign @var{name} @var{expression}
25278 Assigns the value of @var{expression} to the variable object specified
25279 by @var{name}. The object must be @samp{editable}. If the variable's
25280 value is altered by the assign, the variable will show up in any
25281 subsequent @code{-var-update} list.
25283 @subsubheading Example
25291 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
25295 @subheading The @code{-var-update} Command
25296 @findex -var-update
25298 @subsubheading Synopsis
25301 -var-update [@var{print-values}] @{@var{name} | "*"@}
25304 Reevaluate the expressions corresponding to the variable object
25305 @var{name} and all its direct and indirect children, and return the
25306 list of variable objects whose values have changed; @var{name} must
25307 be a root variable object. Here, ``changed'' means that the result of
25308 @code{-var-evaluate-expression} before and after the
25309 @code{-var-update} is different. If @samp{*} is used as the variable
25310 object names, all existing variable objects are updated, except
25311 for frozen ones (@pxref{-var-set-frozen}). The option
25312 @var{print-values} determines whether both names and values, or just
25313 names are printed. The possible values of this option are the same
25314 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
25315 recommended to use the @samp{--all-values} option, to reduce the
25316 number of MI commands needed on each program stop.
25318 With the @samp{*} parameter, if a variable object is bound to a
25319 currently running thread, it will not be updated, without any
25322 If @code{-var-set-update-range} was previously used on a varobj, then
25323 only the selected range of children will be reported.
25325 @code{-var-update} reports all the changed varobjs in a tuple named
25328 Each item in the change list is itself a tuple holding:
25332 The name of the varobj.
25335 If values were requested for this update, then this field will be
25336 present and will hold the value of the varobj.
25339 @anchor{-var-update}
25340 This field is a string which may take one of three values:
25344 The variable object's current value is valid.
25347 The variable object does not currently hold a valid value but it may
25348 hold one in the future if its associated expression comes back into
25352 The variable object no longer holds a valid value.
25353 This can occur when the executable file being debugged has changed,
25354 either through recompilation or by using the @value{GDBN} @code{file}
25355 command. The front end should normally choose to delete these variable
25359 In the future new values may be added to this list so the front should
25360 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
25363 This is only present if the varobj is still valid. If the type
25364 changed, then this will be the string @samp{true}; otherwise it will
25368 If the varobj's type changed, then this field will be present and will
25371 @item new_num_children
25372 For a dynamic varobj, if the number of children changed, or if the
25373 type changed, this will be the new number of children.
25375 The @samp{numchild} field in other varobj responses is generally not
25376 valid for a dynamic varobj -- it will show the number of children that
25377 @value{GDBN} knows about, but because dynamic varobjs lazily
25378 instantiate their children, this will not reflect the number of
25379 children which may be available.
25381 The @samp{new_num_children} attribute only reports changes to the
25382 number of children known by @value{GDBN}. This is the only way to
25383 detect whether an update has removed children (which necessarily can
25384 only happen at the end of the update range).
25387 The display hint, if any.
25390 This is an integer value, which will be 1 if there are more children
25391 available outside the varobj's update range.
25394 This attribute will be present and have the value @samp{1} if the
25395 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
25396 then this attribute will not be present.
25399 If new children were added to a dynamic varobj within the selected
25400 update range (as set by @code{-var-set-update-range}), then they will
25401 be listed in this attribute.
25404 @subsubheading Example
25411 -var-update --all-values var1
25412 ^done,changelist=[@{name="var1",value="3",in_scope="true",
25413 type_changed="false"@}]
25417 @subheading The @code{-var-set-frozen} Command
25418 @findex -var-set-frozen
25419 @anchor{-var-set-frozen}
25421 @subsubheading Synopsis
25424 -var-set-frozen @var{name} @var{flag}
25427 Set the frozenness flag on the variable object @var{name}. The
25428 @var{flag} parameter should be either @samp{1} to make the variable
25429 frozen or @samp{0} to make it unfrozen. If a variable object is
25430 frozen, then neither itself, nor any of its children, are
25431 implicitly updated by @code{-var-update} of
25432 a parent variable or by @code{-var-update *}. Only
25433 @code{-var-update} of the variable itself will update its value and
25434 values of its children. After a variable object is unfrozen, it is
25435 implicitly updated by all subsequent @code{-var-update} operations.
25436 Unfreezing a variable does not update it, only subsequent
25437 @code{-var-update} does.
25439 @subsubheading Example
25443 -var-set-frozen V 1
25448 @subheading The @code{-var-set-update-range} command
25449 @findex -var-set-update-range
25450 @anchor{-var-set-update-range}
25452 @subsubheading Synopsis
25455 -var-set-update-range @var{name} @var{from} @var{to}
25458 Set the range of children to be returned by future invocations of
25459 @code{-var-update}.
25461 @var{from} and @var{to} indicate the range of children to report. If
25462 @var{from} or @var{to} is less than zero, the range is reset and all
25463 children will be reported. Otherwise, children starting at @var{from}
25464 (zero-based) and up to and excluding @var{to} will be reported.
25466 @subsubheading Example
25470 -var-set-update-range V 1 2
25474 @subheading The @code{-var-set-visualizer} command
25475 @findex -var-set-visualizer
25476 @anchor{-var-set-visualizer}
25478 @subsubheading Synopsis
25481 -var-set-visualizer @var{name} @var{visualizer}
25484 Set a visualizer for the variable object @var{name}.
25486 @var{visualizer} is the visualizer to use. The special value
25487 @samp{None} means to disable any visualizer in use.
25489 If not @samp{None}, @var{visualizer} must be a Python expression.
25490 This expression must evaluate to a callable object which accepts a
25491 single argument. @value{GDBN} will call this object with the value of
25492 the varobj @var{name} as an argument (this is done so that the same
25493 Python pretty-printing code can be used for both the CLI and MI).
25494 When called, this object must return an object which conforms to the
25495 pretty-printing interface (@pxref{Pretty Printing}).
25497 The pre-defined function @code{gdb.default_visualizer} may be used to
25498 select a visualizer by following the built-in process
25499 (@pxref{Selecting Pretty-Printers}). This is done automatically when
25500 a varobj is created, and so ordinarily is not needed.
25502 This feature is only available if Python support is enabled. The MI
25503 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
25504 can be used to check this.
25506 @subsubheading Example
25508 Resetting the visualizer:
25512 -var-set-visualizer V None
25516 Reselecting the default (type-based) visualizer:
25520 -var-set-visualizer V gdb.default_visualizer
25524 Suppose @code{SomeClass} is a visualizer class. A lambda expression
25525 can be used to instantiate this class for a varobj:
25529 -var-set-visualizer V "lambda val: SomeClass()"
25533 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25534 @node GDB/MI Data Manipulation
25535 @section @sc{gdb/mi} Data Manipulation
25537 @cindex data manipulation, in @sc{gdb/mi}
25538 @cindex @sc{gdb/mi}, data manipulation
25539 This section describes the @sc{gdb/mi} commands that manipulate data:
25540 examine memory and registers, evaluate expressions, etc.
25542 @c REMOVED FROM THE INTERFACE.
25543 @c @subheading -data-assign
25544 @c Change the value of a program variable. Plenty of side effects.
25545 @c @subsubheading GDB Command
25547 @c @subsubheading Example
25550 @subheading The @code{-data-disassemble} Command
25551 @findex -data-disassemble
25553 @subsubheading Synopsis
25557 [ -s @var{start-addr} -e @var{end-addr} ]
25558 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
25566 @item @var{start-addr}
25567 is the beginning address (or @code{$pc})
25568 @item @var{end-addr}
25570 @item @var{filename}
25571 is the name of the file to disassemble
25572 @item @var{linenum}
25573 is the line number to disassemble around
25575 is the number of disassembly lines to be produced. If it is -1,
25576 the whole function will be disassembled, in case no @var{end-addr} is
25577 specified. If @var{end-addr} is specified as a non-zero value, and
25578 @var{lines} is lower than the number of disassembly lines between
25579 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
25580 displayed; if @var{lines} is higher than the number of lines between
25581 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
25584 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
25588 @subsubheading Result
25590 The output for each instruction is composed of four fields:
25599 Note that whatever included in the instruction field, is not manipulated
25600 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
25602 @subsubheading @value{GDBN} Command
25604 There's no direct mapping from this command to the CLI.
25606 @subsubheading Example
25608 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
25612 -data-disassemble -s $pc -e "$pc + 20" -- 0
25615 @{address="0x000107c0",func-name="main",offset="4",
25616 inst="mov 2, %o0"@},
25617 @{address="0x000107c4",func-name="main",offset="8",
25618 inst="sethi %hi(0x11800), %o2"@},
25619 @{address="0x000107c8",func-name="main",offset="12",
25620 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
25621 @{address="0x000107cc",func-name="main",offset="16",
25622 inst="sethi %hi(0x11800), %o2"@},
25623 @{address="0x000107d0",func-name="main",offset="20",
25624 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
25628 Disassemble the whole @code{main} function. Line 32 is part of
25632 -data-disassemble -f basics.c -l 32 -- 0
25634 @{address="0x000107bc",func-name="main",offset="0",
25635 inst="save %sp, -112, %sp"@},
25636 @{address="0x000107c0",func-name="main",offset="4",
25637 inst="mov 2, %o0"@},
25638 @{address="0x000107c4",func-name="main",offset="8",
25639 inst="sethi %hi(0x11800), %o2"@},
25641 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
25642 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
25646 Disassemble 3 instructions from the start of @code{main}:
25650 -data-disassemble -f basics.c -l 32 -n 3 -- 0
25652 @{address="0x000107bc",func-name="main",offset="0",
25653 inst="save %sp, -112, %sp"@},
25654 @{address="0x000107c0",func-name="main",offset="4",
25655 inst="mov 2, %o0"@},
25656 @{address="0x000107c4",func-name="main",offset="8",
25657 inst="sethi %hi(0x11800), %o2"@}]
25661 Disassemble 3 instructions from the start of @code{main} in mixed mode:
25665 -data-disassemble -f basics.c -l 32 -n 3 -- 1
25667 src_and_asm_line=@{line="31",
25668 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
25669 testsuite/gdb.mi/basics.c",line_asm_insn=[
25670 @{address="0x000107bc",func-name="main",offset="0",
25671 inst="save %sp, -112, %sp"@}]@},
25672 src_and_asm_line=@{line="32",
25673 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
25674 testsuite/gdb.mi/basics.c",line_asm_insn=[
25675 @{address="0x000107c0",func-name="main",offset="4",
25676 inst="mov 2, %o0"@},
25677 @{address="0x000107c4",func-name="main",offset="8",
25678 inst="sethi %hi(0x11800), %o2"@}]@}]
25683 @subheading The @code{-data-evaluate-expression} Command
25684 @findex -data-evaluate-expression
25686 @subsubheading Synopsis
25689 -data-evaluate-expression @var{expr}
25692 Evaluate @var{expr} as an expression. The expression could contain an
25693 inferior function call. The function call will execute synchronously.
25694 If the expression contains spaces, it must be enclosed in double quotes.
25696 @subsubheading @value{GDBN} Command
25698 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
25699 @samp{call}. In @code{gdbtk} only, there's a corresponding
25700 @samp{gdb_eval} command.
25702 @subsubheading Example
25704 In the following example, the numbers that precede the commands are the
25705 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
25706 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
25710 211-data-evaluate-expression A
25713 311-data-evaluate-expression &A
25714 311^done,value="0xefffeb7c"
25716 411-data-evaluate-expression A+3
25719 511-data-evaluate-expression "A + 3"
25725 @subheading The @code{-data-list-changed-registers} Command
25726 @findex -data-list-changed-registers
25728 @subsubheading Synopsis
25731 -data-list-changed-registers
25734 Display a list of the registers that have changed.
25736 @subsubheading @value{GDBN} Command
25738 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
25739 has the corresponding command @samp{gdb_changed_register_list}.
25741 @subsubheading Example
25743 On a PPC MBX board:
25751 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
25752 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
25755 -data-list-changed-registers
25756 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
25757 "10","11","13","14","15","16","17","18","19","20","21","22","23",
25758 "24","25","26","27","28","30","31","64","65","66","67","69"]
25763 @subheading The @code{-data-list-register-names} Command
25764 @findex -data-list-register-names
25766 @subsubheading Synopsis
25769 -data-list-register-names [ ( @var{regno} )+ ]
25772 Show a list of register names for the current target. If no arguments
25773 are given, it shows a list of the names of all the registers. If
25774 integer numbers are given as arguments, it will print a list of the
25775 names of the registers corresponding to the arguments. To ensure
25776 consistency between a register name and its number, the output list may
25777 include empty register names.
25779 @subsubheading @value{GDBN} Command
25781 @value{GDBN} does not have a command which corresponds to
25782 @samp{-data-list-register-names}. In @code{gdbtk} there is a
25783 corresponding command @samp{gdb_regnames}.
25785 @subsubheading Example
25787 For the PPC MBX board:
25790 -data-list-register-names
25791 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
25792 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
25793 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
25794 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
25795 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
25796 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
25797 "", "pc","ps","cr","lr","ctr","xer"]
25799 -data-list-register-names 1 2 3
25800 ^done,register-names=["r1","r2","r3"]
25804 @subheading The @code{-data-list-register-values} Command
25805 @findex -data-list-register-values
25807 @subsubheading Synopsis
25810 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
25813 Display the registers' contents. @var{fmt} is the format according to
25814 which the registers' contents are to be returned, followed by an optional
25815 list of numbers specifying the registers to display. A missing list of
25816 numbers indicates that the contents of all the registers must be returned.
25818 Allowed formats for @var{fmt} are:
25835 @subsubheading @value{GDBN} Command
25837 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
25838 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
25840 @subsubheading Example
25842 For a PPC MBX board (note: line breaks are for readability only, they
25843 don't appear in the actual output):
25847 -data-list-register-values r 64 65
25848 ^done,register-values=[@{number="64",value="0xfe00a300"@},
25849 @{number="65",value="0x00029002"@}]
25851 -data-list-register-values x
25852 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
25853 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
25854 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
25855 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
25856 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
25857 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
25858 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
25859 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
25860 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
25861 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
25862 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
25863 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
25864 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
25865 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
25866 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
25867 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
25868 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
25869 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
25870 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
25871 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
25872 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
25873 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
25874 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
25875 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
25876 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
25877 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
25878 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
25879 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
25880 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
25881 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
25882 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
25883 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
25884 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
25885 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
25886 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
25887 @{number="69",value="0x20002b03"@}]
25892 @subheading The @code{-data-read-memory} Command
25893 @findex -data-read-memory
25895 @subsubheading Synopsis
25898 -data-read-memory [ -o @var{byte-offset} ]
25899 @var{address} @var{word-format} @var{word-size}
25900 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
25907 @item @var{address}
25908 An expression specifying the address of the first memory word to be
25909 read. Complex expressions containing embedded white space should be
25910 quoted using the C convention.
25912 @item @var{word-format}
25913 The format to be used to print the memory words. The notation is the
25914 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
25917 @item @var{word-size}
25918 The size of each memory word in bytes.
25920 @item @var{nr-rows}
25921 The number of rows in the output table.
25923 @item @var{nr-cols}
25924 The number of columns in the output table.
25927 If present, indicates that each row should include an @sc{ascii} dump. The
25928 value of @var{aschar} is used as a padding character when a byte is not a
25929 member of the printable @sc{ascii} character set (printable @sc{ascii}
25930 characters are those whose code is between 32 and 126, inclusively).
25932 @item @var{byte-offset}
25933 An offset to add to the @var{address} before fetching memory.
25936 This command displays memory contents as a table of @var{nr-rows} by
25937 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
25938 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
25939 (returned as @samp{total-bytes}). Should less than the requested number
25940 of bytes be returned by the target, the missing words are identified
25941 using @samp{N/A}. The number of bytes read from the target is returned
25942 in @samp{nr-bytes} and the starting address used to read memory in
25945 The address of the next/previous row or page is available in
25946 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
25949 @subsubheading @value{GDBN} Command
25951 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
25952 @samp{gdb_get_mem} memory read command.
25954 @subsubheading Example
25956 Read six bytes of memory starting at @code{bytes+6} but then offset by
25957 @code{-6} bytes. Format as three rows of two columns. One byte per
25958 word. Display each word in hex.
25962 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
25963 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
25964 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
25965 prev-page="0x0000138a",memory=[
25966 @{addr="0x00001390",data=["0x00","0x01"]@},
25967 @{addr="0x00001392",data=["0x02","0x03"]@},
25968 @{addr="0x00001394",data=["0x04","0x05"]@}]
25972 Read two bytes of memory starting at address @code{shorts + 64} and
25973 display as a single word formatted in decimal.
25977 5-data-read-memory shorts+64 d 2 1 1
25978 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
25979 next-row="0x00001512",prev-row="0x0000150e",
25980 next-page="0x00001512",prev-page="0x0000150e",memory=[
25981 @{addr="0x00001510",data=["128"]@}]
25985 Read thirty two bytes of memory starting at @code{bytes+16} and format
25986 as eight rows of four columns. Include a string encoding with @samp{x}
25987 used as the non-printable character.
25991 4-data-read-memory bytes+16 x 1 8 4 x
25992 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
25993 next-row="0x000013c0",prev-row="0x0000139c",
25994 next-page="0x000013c0",prev-page="0x00001380",memory=[
25995 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
25996 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
25997 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
25998 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
25999 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
26000 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
26001 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
26002 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
26006 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26007 @node GDB/MI Tracepoint Commands
26008 @section @sc{gdb/mi} Tracepoint Commands
26010 The commands defined in this section implement MI support for
26011 tracepoints. For detailed introduction, see @ref{Tracepoints}.
26013 @subheading The @code{-trace-find} Command
26014 @findex -trace-find
26016 @subsubheading Synopsis
26019 -trace-find @var{mode} [@var{parameters}@dots{}]
26022 Find a trace frame using criteria defined by @var{mode} and
26023 @var{parameters}. The following table lists permissible
26024 modes and their parameters. For details of operation, see @ref{tfind}.
26029 No parameters are required. Stops examining trace frames.
26032 An integer is required as parameter. Selects tracepoint frame with
26035 @item tracepoint-number
26036 An integer is required as parameter. Finds next
26037 trace frame that corresponds to tracepoint with the specified number.
26040 An address is required as parameter. Finds
26041 next trace frame that corresponds to any tracepoint at the specified
26044 @item pc-inside-range
26045 Two addresses are required as parameters. Finds next trace
26046 frame that corresponds to a tracepoint at an address inside the
26047 specified range. Both bounds are considered to be inside the range.
26049 @item pc-outside-range
26050 Two addresses are required as parameters. Finds
26051 next trace frame that corresponds to a tracepoint at an address outside
26052 the specified range. Both bounds are considered to be inside the range.
26055 Line specification is required as parameter. @xref{Specify Location}.
26056 Finds next trace frame that corresponds to a tracepoint at
26057 the specified location.
26061 If @samp{none} was passed as @var{mode}, the response does not
26062 have fields. Otherwise, the response may have the following fields:
26066 This field has either @samp{0} or @samp{1} as the value, depending
26067 on whether a matching tracepoint was found.
26070 The index of the found traceframe. This field is present iff
26071 the @samp{found} field has value of @samp{1}.
26074 The index of the found tracepoint. This field is present iff
26075 the @samp{found} field has value of @samp{1}.
26078 The information about the frame corresponding to the found trace
26079 frame. This field is present only if a trace frame was found.
26080 @xref{GDB/MI Frame Information}, for description of this field.
26084 @subsubheading @value{GDBN} Command
26086 The corresponding @value{GDBN} command is @samp{tfind}.
26088 @subheading -trace-define-variable
26089 @findex -trace-define-variable
26091 @subsubheading Synopsis
26094 -trace-define-variable @var{name} [ @var{value} ]
26097 Create trace variable @var{name} if it does not exist. If
26098 @var{value} is specified, sets the initial value of the specified
26099 trace variable to that value. Note that the @var{name} should start
26100 with the @samp{$} character.
26102 @subsubheading @value{GDBN} Command
26104 The corresponding @value{GDBN} command is @samp{tvariable}.
26106 @subheading -trace-list-variables
26107 @findex -trace-list-variables
26109 @subsubheading Synopsis
26112 -trace-list-variables
26115 Return a table of all defined trace variables. Each element of the
26116 table has the following fields:
26120 The name of the trace variable. This field is always present.
26123 The initial value. This is a 64-bit signed integer. This
26124 field is always present.
26127 The value the trace variable has at the moment. This is a 64-bit
26128 signed integer. This field is absent iff current value is
26129 not defined, for example if the trace was never run, or is
26134 @subsubheading @value{GDBN} Command
26136 The corresponding @value{GDBN} command is @samp{tvariables}.
26138 @subsubheading Example
26142 -trace-list-variables
26143 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
26144 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
26145 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
26146 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
26147 body=[variable=@{name="$trace_timestamp",initial="0"@}
26148 variable=@{name="$foo",initial="10",current="15"@}]@}
26152 @subheading -trace-save
26153 @findex -trace-save
26155 @subsubheading Synopsis
26158 -trace-save [-r ] @var{filename}
26161 Saves the collected trace data to @var{filename}. Without the
26162 @samp{-r} option, the data is downloaded from the target and saved
26163 in a local file. With the @samp{-r} option the target is asked
26164 to perform the save.
26166 @subsubheading @value{GDBN} Command
26168 The corresponding @value{GDBN} command is @samp{tsave}.
26171 @subheading -trace-start
26172 @findex -trace-start
26174 @subsubheading Synopsis
26180 Starts a tracing experiments. The result of this command does not
26183 @subsubheading @value{GDBN} Command
26185 The corresponding @value{GDBN} command is @samp{tstart}.
26187 @subheading -trace-status
26188 @findex -trace-status
26190 @subsubheading Synopsis
26196 Obtains the status of a tracing experiement. The result may include
26197 the following fields:
26202 May have a value of either @samp{0}, when no tracing operations are
26203 supported, @samp{1}, when all tracing operations are supported, or
26204 @samp{file} when examining trace file. In the latter case, examining
26205 of trace frame is possible but new tracing experiement cannot be
26206 started. This field is always present.
26209 May have a value of either @samp{0} or @samp{1} depending on whether
26210 tracing experiement is in progress on target. This field is present
26211 if @samp{supported} field is not @samp{0}.
26214 Report the reason why the tracing was stopped last time. This field
26215 may be absent iff tracing was never stopped on target yet. The
26216 value of @samp{request} means the tracing was stopped as result of
26217 the @code{-trace-stop} command. The value of @samp{overflow} means
26218 the tracing buffer is full. The value of @samp{disconnection} means
26219 tracing was automatically stopped when @value{GDBN} has disconnected.
26220 The value of @samp{passcount} means tracing was stopped when a
26221 tracepoint was passed a maximal number of times for that tracepoint.
26222 This field is present if @samp{supported} field is not @samp{0}.
26224 @item stopping-tracepoint
26225 The number of tracepoint whose passcount as exceeded. This field is
26226 present iff the @samp{stop-reason} field has the value of
26230 This field is an integer number of currently collected frames. This
26235 These fields tell the current size of the tracing buffer and the
26236 remaining space. These field is optional.
26240 @subsubheading @value{GDBN} Command
26242 The corresponding @value{GDBN} command is @samp{tstatus}.
26244 @subheading -trace-stop
26245 @findex -trace-stop
26247 @subsubheading Synopsis
26253 Stops a tracing experiment. The result of this command has the same
26254 fields as @code{-trace-status}, except that the @samp{supported} and
26255 @samp{running} fields are not output.
26257 @subsubheading @value{GDBN} Command
26259 The corresponding @value{GDBN} command is @samp{tstop}.
26262 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26263 @node GDB/MI Symbol Query
26264 @section @sc{gdb/mi} Symbol Query Commands
26268 @subheading The @code{-symbol-info-address} Command
26269 @findex -symbol-info-address
26271 @subsubheading Synopsis
26274 -symbol-info-address @var{symbol}
26277 Describe where @var{symbol} is stored.
26279 @subsubheading @value{GDBN} Command
26281 The corresponding @value{GDBN} command is @samp{info address}.
26283 @subsubheading Example
26287 @subheading The @code{-symbol-info-file} Command
26288 @findex -symbol-info-file
26290 @subsubheading Synopsis
26296 Show the file for the symbol.
26298 @subsubheading @value{GDBN} Command
26300 There's no equivalent @value{GDBN} command. @code{gdbtk} has
26301 @samp{gdb_find_file}.
26303 @subsubheading Example
26307 @subheading The @code{-symbol-info-function} Command
26308 @findex -symbol-info-function
26310 @subsubheading Synopsis
26313 -symbol-info-function
26316 Show which function the symbol lives in.
26318 @subsubheading @value{GDBN} Command
26320 @samp{gdb_get_function} in @code{gdbtk}.
26322 @subsubheading Example
26326 @subheading The @code{-symbol-info-line} Command
26327 @findex -symbol-info-line
26329 @subsubheading Synopsis
26335 Show the core addresses of the code for a source line.
26337 @subsubheading @value{GDBN} Command
26339 The corresponding @value{GDBN} command is @samp{info line}.
26340 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
26342 @subsubheading Example
26346 @subheading The @code{-symbol-info-symbol} Command
26347 @findex -symbol-info-symbol
26349 @subsubheading Synopsis
26352 -symbol-info-symbol @var{addr}
26355 Describe what symbol is at location @var{addr}.
26357 @subsubheading @value{GDBN} Command
26359 The corresponding @value{GDBN} command is @samp{info symbol}.
26361 @subsubheading Example
26365 @subheading The @code{-symbol-list-functions} Command
26366 @findex -symbol-list-functions
26368 @subsubheading Synopsis
26371 -symbol-list-functions
26374 List the functions in the executable.
26376 @subsubheading @value{GDBN} Command
26378 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
26379 @samp{gdb_search} in @code{gdbtk}.
26381 @subsubheading Example
26386 @subheading The @code{-symbol-list-lines} Command
26387 @findex -symbol-list-lines
26389 @subsubheading Synopsis
26392 -symbol-list-lines @var{filename}
26395 Print the list of lines that contain code and their associated program
26396 addresses for the given source filename. The entries are sorted in
26397 ascending PC order.
26399 @subsubheading @value{GDBN} Command
26401 There is no corresponding @value{GDBN} command.
26403 @subsubheading Example
26406 -symbol-list-lines basics.c
26407 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
26413 @subheading The @code{-symbol-list-types} Command
26414 @findex -symbol-list-types
26416 @subsubheading Synopsis
26422 List all the type names.
26424 @subsubheading @value{GDBN} Command
26426 The corresponding commands are @samp{info types} in @value{GDBN},
26427 @samp{gdb_search} in @code{gdbtk}.
26429 @subsubheading Example
26433 @subheading The @code{-symbol-list-variables} Command
26434 @findex -symbol-list-variables
26436 @subsubheading Synopsis
26439 -symbol-list-variables
26442 List all the global and static variable names.
26444 @subsubheading @value{GDBN} Command
26446 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
26448 @subsubheading Example
26452 @subheading The @code{-symbol-locate} Command
26453 @findex -symbol-locate
26455 @subsubheading Synopsis
26461 @subsubheading @value{GDBN} Command
26463 @samp{gdb_loc} in @code{gdbtk}.
26465 @subsubheading Example
26469 @subheading The @code{-symbol-type} Command
26470 @findex -symbol-type
26472 @subsubheading Synopsis
26475 -symbol-type @var{variable}
26478 Show type of @var{variable}.
26480 @subsubheading @value{GDBN} Command
26482 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
26483 @samp{gdb_obj_variable}.
26485 @subsubheading Example
26490 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26491 @node GDB/MI File Commands
26492 @section @sc{gdb/mi} File Commands
26494 This section describes the GDB/MI commands to specify executable file names
26495 and to read in and obtain symbol table information.
26497 @subheading The @code{-file-exec-and-symbols} Command
26498 @findex -file-exec-and-symbols
26500 @subsubheading Synopsis
26503 -file-exec-and-symbols @var{file}
26506 Specify the executable file to be debugged. This file is the one from
26507 which the symbol table is also read. If no file is specified, the
26508 command clears the executable and symbol information. If breakpoints
26509 are set when using this command with no arguments, @value{GDBN} will produce
26510 error messages. Otherwise, no output is produced, except a completion
26513 @subsubheading @value{GDBN} Command
26515 The corresponding @value{GDBN} command is @samp{file}.
26517 @subsubheading Example
26521 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26527 @subheading The @code{-file-exec-file} Command
26528 @findex -file-exec-file
26530 @subsubheading Synopsis
26533 -file-exec-file @var{file}
26536 Specify the executable file to be debugged. Unlike
26537 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
26538 from this file. If used without argument, @value{GDBN} clears the information
26539 about the executable file. No output is produced, except a completion
26542 @subsubheading @value{GDBN} Command
26544 The corresponding @value{GDBN} command is @samp{exec-file}.
26546 @subsubheading Example
26550 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26557 @subheading The @code{-file-list-exec-sections} Command
26558 @findex -file-list-exec-sections
26560 @subsubheading Synopsis
26563 -file-list-exec-sections
26566 List the sections of the current executable file.
26568 @subsubheading @value{GDBN} Command
26570 The @value{GDBN} command @samp{info file} shows, among the rest, the same
26571 information as this command. @code{gdbtk} has a corresponding command
26572 @samp{gdb_load_info}.
26574 @subsubheading Example
26579 @subheading The @code{-file-list-exec-source-file} Command
26580 @findex -file-list-exec-source-file
26582 @subsubheading Synopsis
26585 -file-list-exec-source-file
26588 List the line number, the current source file, and the absolute path
26589 to the current source file for the current executable. The macro
26590 information field has a value of @samp{1} or @samp{0} depending on
26591 whether or not the file includes preprocessor macro information.
26593 @subsubheading @value{GDBN} Command
26595 The @value{GDBN} equivalent is @samp{info source}
26597 @subsubheading Example
26601 123-file-list-exec-source-file
26602 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
26607 @subheading The @code{-file-list-exec-source-files} Command
26608 @findex -file-list-exec-source-files
26610 @subsubheading Synopsis
26613 -file-list-exec-source-files
26616 List the source files for the current executable.
26618 It will always output the filename, but only when @value{GDBN} can find
26619 the absolute file name of a source file, will it output the fullname.
26621 @subsubheading @value{GDBN} Command
26623 The @value{GDBN} equivalent is @samp{info sources}.
26624 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
26626 @subsubheading Example
26629 -file-list-exec-source-files
26631 @{file=foo.c,fullname=/home/foo.c@},
26632 @{file=/home/bar.c,fullname=/home/bar.c@},
26633 @{file=gdb_could_not_find_fullpath.c@}]
26638 @subheading The @code{-file-list-shared-libraries} Command
26639 @findex -file-list-shared-libraries
26641 @subsubheading Synopsis
26644 -file-list-shared-libraries
26647 List the shared libraries in the program.
26649 @subsubheading @value{GDBN} Command
26651 The corresponding @value{GDBN} command is @samp{info shared}.
26653 @subsubheading Example
26657 @subheading The @code{-file-list-symbol-files} Command
26658 @findex -file-list-symbol-files
26660 @subsubheading Synopsis
26663 -file-list-symbol-files
26668 @subsubheading @value{GDBN} Command
26670 The corresponding @value{GDBN} command is @samp{info file} (part of it).
26672 @subsubheading Example
26677 @subheading The @code{-file-symbol-file} Command
26678 @findex -file-symbol-file
26680 @subsubheading Synopsis
26683 -file-symbol-file @var{file}
26686 Read symbol table info from the specified @var{file} argument. When
26687 used without arguments, clears @value{GDBN}'s symbol table info. No output is
26688 produced, except for a completion notification.
26690 @subsubheading @value{GDBN} Command
26692 The corresponding @value{GDBN} command is @samp{symbol-file}.
26694 @subsubheading Example
26698 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26704 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26705 @node GDB/MI Memory Overlay Commands
26706 @section @sc{gdb/mi} Memory Overlay Commands
26708 The memory overlay commands are not implemented.
26710 @c @subheading -overlay-auto
26712 @c @subheading -overlay-list-mapping-state
26714 @c @subheading -overlay-list-overlays
26716 @c @subheading -overlay-map
26718 @c @subheading -overlay-off
26720 @c @subheading -overlay-on
26722 @c @subheading -overlay-unmap
26724 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26725 @node GDB/MI Signal Handling Commands
26726 @section @sc{gdb/mi} Signal Handling Commands
26728 Signal handling commands are not implemented.
26730 @c @subheading -signal-handle
26732 @c @subheading -signal-list-handle-actions
26734 @c @subheading -signal-list-signal-types
26738 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26739 @node GDB/MI Target Manipulation
26740 @section @sc{gdb/mi} Target Manipulation Commands
26743 @subheading The @code{-target-attach} Command
26744 @findex -target-attach
26746 @subsubheading Synopsis
26749 -target-attach @var{pid} | @var{gid} | @var{file}
26752 Attach to a process @var{pid} or a file @var{file} outside of
26753 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
26754 group, the id previously returned by
26755 @samp{-list-thread-groups --available} must be used.
26757 @subsubheading @value{GDBN} Command
26759 The corresponding @value{GDBN} command is @samp{attach}.
26761 @subsubheading Example
26765 =thread-created,id="1"
26766 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
26772 @subheading The @code{-target-compare-sections} Command
26773 @findex -target-compare-sections
26775 @subsubheading Synopsis
26778 -target-compare-sections [ @var{section} ]
26781 Compare data of section @var{section} on target to the exec file.
26782 Without the argument, all sections are compared.
26784 @subsubheading @value{GDBN} Command
26786 The @value{GDBN} equivalent is @samp{compare-sections}.
26788 @subsubheading Example
26793 @subheading The @code{-target-detach} Command
26794 @findex -target-detach
26796 @subsubheading Synopsis
26799 -target-detach [ @var{pid} | @var{gid} ]
26802 Detach from the remote target which normally resumes its execution.
26803 If either @var{pid} or @var{gid} is specified, detaches from either
26804 the specified process, or specified thread group. There's no output.
26806 @subsubheading @value{GDBN} Command
26808 The corresponding @value{GDBN} command is @samp{detach}.
26810 @subsubheading Example
26820 @subheading The @code{-target-disconnect} Command
26821 @findex -target-disconnect
26823 @subsubheading Synopsis
26829 Disconnect from the remote target. There's no output and the target is
26830 generally not resumed.
26832 @subsubheading @value{GDBN} Command
26834 The corresponding @value{GDBN} command is @samp{disconnect}.
26836 @subsubheading Example
26846 @subheading The @code{-target-download} Command
26847 @findex -target-download
26849 @subsubheading Synopsis
26855 Loads the executable onto the remote target.
26856 It prints out an update message every half second, which includes the fields:
26860 The name of the section.
26862 The size of what has been sent so far for that section.
26864 The size of the section.
26866 The total size of what was sent so far (the current and the previous sections).
26868 The size of the overall executable to download.
26872 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
26873 @sc{gdb/mi} Output Syntax}).
26875 In addition, it prints the name and size of the sections, as they are
26876 downloaded. These messages include the following fields:
26880 The name of the section.
26882 The size of the section.
26884 The size of the overall executable to download.
26888 At the end, a summary is printed.
26890 @subsubheading @value{GDBN} Command
26892 The corresponding @value{GDBN} command is @samp{load}.
26894 @subsubheading Example
26896 Note: each status message appears on a single line. Here the messages
26897 have been broken down so that they can fit onto a page.
26902 +download,@{section=".text",section-size="6668",total-size="9880"@}
26903 +download,@{section=".text",section-sent="512",section-size="6668",
26904 total-sent="512",total-size="9880"@}
26905 +download,@{section=".text",section-sent="1024",section-size="6668",
26906 total-sent="1024",total-size="9880"@}
26907 +download,@{section=".text",section-sent="1536",section-size="6668",
26908 total-sent="1536",total-size="9880"@}
26909 +download,@{section=".text",section-sent="2048",section-size="6668",
26910 total-sent="2048",total-size="9880"@}
26911 +download,@{section=".text",section-sent="2560",section-size="6668",
26912 total-sent="2560",total-size="9880"@}
26913 +download,@{section=".text",section-sent="3072",section-size="6668",
26914 total-sent="3072",total-size="9880"@}
26915 +download,@{section=".text",section-sent="3584",section-size="6668",
26916 total-sent="3584",total-size="9880"@}
26917 +download,@{section=".text",section-sent="4096",section-size="6668",
26918 total-sent="4096",total-size="9880"@}
26919 +download,@{section=".text",section-sent="4608",section-size="6668",
26920 total-sent="4608",total-size="9880"@}
26921 +download,@{section=".text",section-sent="5120",section-size="6668",
26922 total-sent="5120",total-size="9880"@}
26923 +download,@{section=".text",section-sent="5632",section-size="6668",
26924 total-sent="5632",total-size="9880"@}
26925 +download,@{section=".text",section-sent="6144",section-size="6668",
26926 total-sent="6144",total-size="9880"@}
26927 +download,@{section=".text",section-sent="6656",section-size="6668",
26928 total-sent="6656",total-size="9880"@}
26929 +download,@{section=".init",section-size="28",total-size="9880"@}
26930 +download,@{section=".fini",section-size="28",total-size="9880"@}
26931 +download,@{section=".data",section-size="3156",total-size="9880"@}
26932 +download,@{section=".data",section-sent="512",section-size="3156",
26933 total-sent="7236",total-size="9880"@}
26934 +download,@{section=".data",section-sent="1024",section-size="3156",
26935 total-sent="7748",total-size="9880"@}
26936 +download,@{section=".data",section-sent="1536",section-size="3156",
26937 total-sent="8260",total-size="9880"@}
26938 +download,@{section=".data",section-sent="2048",section-size="3156",
26939 total-sent="8772",total-size="9880"@}
26940 +download,@{section=".data",section-sent="2560",section-size="3156",
26941 total-sent="9284",total-size="9880"@}
26942 +download,@{section=".data",section-sent="3072",section-size="3156",
26943 total-sent="9796",total-size="9880"@}
26944 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
26951 @subheading The @code{-target-exec-status} Command
26952 @findex -target-exec-status
26954 @subsubheading Synopsis
26957 -target-exec-status
26960 Provide information on the state of the target (whether it is running or
26961 not, for instance).
26963 @subsubheading @value{GDBN} Command
26965 There's no equivalent @value{GDBN} command.
26967 @subsubheading Example
26971 @subheading The @code{-target-list-available-targets} Command
26972 @findex -target-list-available-targets
26974 @subsubheading Synopsis
26977 -target-list-available-targets
26980 List the possible targets to connect to.
26982 @subsubheading @value{GDBN} Command
26984 The corresponding @value{GDBN} command is @samp{help target}.
26986 @subsubheading Example
26990 @subheading The @code{-target-list-current-targets} Command
26991 @findex -target-list-current-targets
26993 @subsubheading Synopsis
26996 -target-list-current-targets
26999 Describe the current target.
27001 @subsubheading @value{GDBN} Command
27003 The corresponding information is printed by @samp{info file} (among
27006 @subsubheading Example
27010 @subheading The @code{-target-list-parameters} Command
27011 @findex -target-list-parameters
27013 @subsubheading Synopsis
27016 -target-list-parameters
27022 @subsubheading @value{GDBN} Command
27026 @subsubheading Example
27030 @subheading The @code{-target-select} Command
27031 @findex -target-select
27033 @subsubheading Synopsis
27036 -target-select @var{type} @var{parameters @dots{}}
27039 Connect @value{GDBN} to the remote target. This command takes two args:
27043 The type of target, for instance @samp{remote}, etc.
27044 @item @var{parameters}
27045 Device names, host names and the like. @xref{Target Commands, ,
27046 Commands for Managing Targets}, for more details.
27049 The output is a connection notification, followed by the address at
27050 which the target program is, in the following form:
27053 ^connected,addr="@var{address}",func="@var{function name}",
27054 args=[@var{arg list}]
27057 @subsubheading @value{GDBN} Command
27059 The corresponding @value{GDBN} command is @samp{target}.
27061 @subsubheading Example
27065 -target-select remote /dev/ttya
27066 ^connected,addr="0xfe00a300",func="??",args=[]
27070 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27071 @node GDB/MI File Transfer Commands
27072 @section @sc{gdb/mi} File Transfer Commands
27075 @subheading The @code{-target-file-put} Command
27076 @findex -target-file-put
27078 @subsubheading Synopsis
27081 -target-file-put @var{hostfile} @var{targetfile}
27084 Copy file @var{hostfile} from the host system (the machine running
27085 @value{GDBN}) to @var{targetfile} on the target system.
27087 @subsubheading @value{GDBN} Command
27089 The corresponding @value{GDBN} command is @samp{remote put}.
27091 @subsubheading Example
27095 -target-file-put localfile remotefile
27101 @subheading The @code{-target-file-get} Command
27102 @findex -target-file-get
27104 @subsubheading Synopsis
27107 -target-file-get @var{targetfile} @var{hostfile}
27110 Copy file @var{targetfile} from the target system to @var{hostfile}
27111 on the host system.
27113 @subsubheading @value{GDBN} Command
27115 The corresponding @value{GDBN} command is @samp{remote get}.
27117 @subsubheading Example
27121 -target-file-get remotefile localfile
27127 @subheading The @code{-target-file-delete} Command
27128 @findex -target-file-delete
27130 @subsubheading Synopsis
27133 -target-file-delete @var{targetfile}
27136 Delete @var{targetfile} from the target system.
27138 @subsubheading @value{GDBN} Command
27140 The corresponding @value{GDBN} command is @samp{remote delete}.
27142 @subsubheading Example
27146 -target-file-delete remotefile
27152 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27153 @node GDB/MI Miscellaneous Commands
27154 @section Miscellaneous @sc{gdb/mi} Commands
27156 @c @subheading -gdb-complete
27158 @subheading The @code{-gdb-exit} Command
27161 @subsubheading Synopsis
27167 Exit @value{GDBN} immediately.
27169 @subsubheading @value{GDBN} Command
27171 Approximately corresponds to @samp{quit}.
27173 @subsubheading Example
27183 @subheading The @code{-exec-abort} Command
27184 @findex -exec-abort
27186 @subsubheading Synopsis
27192 Kill the inferior running program.
27194 @subsubheading @value{GDBN} Command
27196 The corresponding @value{GDBN} command is @samp{kill}.
27198 @subsubheading Example
27203 @subheading The @code{-gdb-set} Command
27206 @subsubheading Synopsis
27212 Set an internal @value{GDBN} variable.
27213 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
27215 @subsubheading @value{GDBN} Command
27217 The corresponding @value{GDBN} command is @samp{set}.
27219 @subsubheading Example
27229 @subheading The @code{-gdb-show} Command
27232 @subsubheading Synopsis
27238 Show the current value of a @value{GDBN} variable.
27240 @subsubheading @value{GDBN} Command
27242 The corresponding @value{GDBN} command is @samp{show}.
27244 @subsubheading Example
27253 @c @subheading -gdb-source
27256 @subheading The @code{-gdb-version} Command
27257 @findex -gdb-version
27259 @subsubheading Synopsis
27265 Show version information for @value{GDBN}. Used mostly in testing.
27267 @subsubheading @value{GDBN} Command
27269 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
27270 default shows this information when you start an interactive session.
27272 @subsubheading Example
27274 @c This example modifies the actual output from GDB to avoid overfull
27280 ~Copyright 2000 Free Software Foundation, Inc.
27281 ~GDB is free software, covered by the GNU General Public License, and
27282 ~you are welcome to change it and/or distribute copies of it under
27283 ~ certain conditions.
27284 ~Type "show copying" to see the conditions.
27285 ~There is absolutely no warranty for GDB. Type "show warranty" for
27287 ~This GDB was configured as
27288 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
27293 @subheading The @code{-list-features} Command
27294 @findex -list-features
27296 Returns a list of particular features of the MI protocol that
27297 this version of gdb implements. A feature can be a command,
27298 or a new field in an output of some command, or even an
27299 important bugfix. While a frontend can sometimes detect presence
27300 of a feature at runtime, it is easier to perform detection at debugger
27303 The command returns a list of strings, with each string naming an
27304 available feature. Each returned string is just a name, it does not
27305 have any internal structure. The list of possible feature names
27311 (gdb) -list-features
27312 ^done,result=["feature1","feature2"]
27315 The current list of features is:
27318 @item frozen-varobjs
27319 Indicates presence of the @code{-var-set-frozen} command, as well
27320 as possible presense of the @code{frozen} field in the output
27321 of @code{-varobj-create}.
27322 @item pending-breakpoints
27323 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
27325 Indicates presence of Python scripting support, Python-based
27326 pretty-printing commands, and possible presence of the
27327 @samp{display_hint} field in the output of @code{-var-list-children}
27329 Indicates presence of the @code{-thread-info} command.
27333 @subheading The @code{-list-target-features} Command
27334 @findex -list-target-features
27336 Returns a list of particular features that are supported by the
27337 target. Those features affect the permitted MI commands, but
27338 unlike the features reported by the @code{-list-features} command, the
27339 features depend on which target GDB is using at the moment. Whenever
27340 a target can change, due to commands such as @code{-target-select},
27341 @code{-target-attach} or @code{-exec-run}, the list of target features
27342 may change, and the frontend should obtain it again.
27346 (gdb) -list-features
27347 ^done,result=["async"]
27350 The current list of features is:
27354 Indicates that the target is capable of asynchronous command
27355 execution, which means that @value{GDBN} will accept further commands
27356 while the target is running.
27360 @subheading The @code{-list-thread-groups} Command
27361 @findex -list-thread-groups
27363 @subheading Synopsis
27366 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
27369 Lists thread groups (@pxref{Thread groups}). When a single thread
27370 group is passed as the argument, lists the children of that group.
27371 When several thread group are passed, lists information about those
27372 thread groups. Without any parameters, lists information about all
27373 top-level thread groups.
27375 Normally, thread groups that are being debugged are reported.
27376 With the @samp{--available} option, @value{GDBN} reports thread groups
27377 available on the target.
27379 The output of this command may have either a @samp{threads} result or
27380 a @samp{groups} result. The @samp{thread} result has a list of tuples
27381 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
27382 Information}). The @samp{groups} result has a list of tuples as value,
27383 each tuple describing a thread group. If top-level groups are
27384 requested (that is, no parameter is passed), or when several groups
27385 are passed, the output always has a @samp{groups} result. The format
27386 of the @samp{group} result is described below.
27388 To reduce the number of roundtrips it's possible to list thread groups
27389 together with their children, by passing the @samp{--recurse} option
27390 and the recursion depth. Presently, only recursion depth of 1 is
27391 permitted. If this option is present, then every reported thread group
27392 will also include its children, either as @samp{group} or
27393 @samp{threads} field.
27395 In general, any combination of option and parameters is permitted, with
27396 the following caveats:
27400 When a single thread group is passed, the output will typically
27401 be the @samp{threads} result. Because threads may not contain
27402 anything, the @samp{recurse} option will be ignored.
27405 When the @samp{--available} option is passed, limited information may
27406 be available. In particular, the list of threads of a process might
27407 be inaccessible. Further, specifying specific thread groups might
27408 not give any performance advantage over listing all thread groups.
27409 The frontend should assume that @samp{-list-thread-groups --available}
27410 is always an expensive operation and cache the results.
27414 The @samp{groups} result is a list of tuples, where each tuple may
27415 have the following fields:
27419 Identifier of the thread group. This field is always present.
27420 The identifier is an opaque string; frontends should not try to
27421 convert it to an integer, even though it might look like one.
27424 The type of the thread group. At present, only @samp{process} is a
27428 The target-specific process identifier. This field is only present
27429 for thread groups of type @samp{process} and only if the process exists.
27432 The number of children this thread group has. This field may be
27433 absent for an available thread group.
27436 This field has a list of tuples as value, each tuple describing a
27437 thread. It may be present if the @samp{--recurse} option is
27438 specified, and it's actually possible to obtain the threads.
27441 This field is a list of integers, each identifying a core that one
27442 thread of the group is running on. This field may be absent if
27443 such information is not available.
27446 The name of the executable file that corresponds to this thread group.
27447 The field is only present for thread groups of type @samp{process},
27448 and only if there is a corresponding executable file.
27452 @subheading Example
27456 -list-thread-groups
27457 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
27458 -list-thread-groups 17
27459 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27460 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
27461 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27462 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
27463 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
27464 -list-thread-groups --available
27465 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
27466 -list-thread-groups --available --recurse 1
27467 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
27468 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
27469 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
27470 -list-thread-groups --available --recurse 1 17 18
27471 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
27472 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
27473 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
27477 @subheading The @code{-add-inferior} Command
27478 @findex -add-inferior
27480 @subheading Synopsis
27486 Creates a new inferior (@pxref{Inferiors and Programs}). The created
27487 inferior is not associated with any executable. Such association may
27488 be established with the @samp{-file-exec-and-symbols} command
27489 (@pxref{GDB/MI File Commands}). The command response has a single
27490 field, @samp{thread-group}, whose value is the identifier of the
27491 thread group corresponding to the new inferior.
27493 @subheading Example
27498 ^done,thread-group="i3"
27501 @subheading The @code{-interpreter-exec} Command
27502 @findex -interpreter-exec
27504 @subheading Synopsis
27507 -interpreter-exec @var{interpreter} @var{command}
27509 @anchor{-interpreter-exec}
27511 Execute the specified @var{command} in the given @var{interpreter}.
27513 @subheading @value{GDBN} Command
27515 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
27517 @subheading Example
27521 -interpreter-exec console "break main"
27522 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
27523 &"During symbol reading, bad structure-type format.\n"
27524 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
27529 @subheading The @code{-inferior-tty-set} Command
27530 @findex -inferior-tty-set
27532 @subheading Synopsis
27535 -inferior-tty-set /dev/pts/1
27538 Set terminal for future runs of the program being debugged.
27540 @subheading @value{GDBN} Command
27542 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
27544 @subheading Example
27548 -inferior-tty-set /dev/pts/1
27553 @subheading The @code{-inferior-tty-show} Command
27554 @findex -inferior-tty-show
27556 @subheading Synopsis
27562 Show terminal for future runs of program being debugged.
27564 @subheading @value{GDBN} Command
27566 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
27568 @subheading Example
27572 -inferior-tty-set /dev/pts/1
27576 ^done,inferior_tty_terminal="/dev/pts/1"
27580 @subheading The @code{-enable-timings} Command
27581 @findex -enable-timings
27583 @subheading Synopsis
27586 -enable-timings [yes | no]
27589 Toggle the printing of the wallclock, user and system times for an MI
27590 command as a field in its output. This command is to help frontend
27591 developers optimize the performance of their code. No argument is
27592 equivalent to @samp{yes}.
27594 @subheading @value{GDBN} Command
27598 @subheading Example
27606 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27607 addr="0x080484ed",func="main",file="myprog.c",
27608 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
27609 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
27617 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27618 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
27619 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
27620 fullname="/home/nickrob/myprog.c",line="73"@}
27625 @chapter @value{GDBN} Annotations
27627 This chapter describes annotations in @value{GDBN}. Annotations were
27628 designed to interface @value{GDBN} to graphical user interfaces or other
27629 similar programs which want to interact with @value{GDBN} at a
27630 relatively high level.
27632 The annotation mechanism has largely been superseded by @sc{gdb/mi}
27636 This is Edition @value{EDITION}, @value{DATE}.
27640 * Annotations Overview:: What annotations are; the general syntax.
27641 * Server Prefix:: Issuing a command without affecting user state.
27642 * Prompting:: Annotations marking @value{GDBN}'s need for input.
27643 * Errors:: Annotations for error messages.
27644 * Invalidation:: Some annotations describe things now invalid.
27645 * Annotations for Running::
27646 Whether the program is running, how it stopped, etc.
27647 * Source Annotations:: Annotations describing source code.
27650 @node Annotations Overview
27651 @section What is an Annotation?
27652 @cindex annotations
27654 Annotations start with a newline character, two @samp{control-z}
27655 characters, and the name of the annotation. If there is no additional
27656 information associated with this annotation, the name of the annotation
27657 is followed immediately by a newline. If there is additional
27658 information, the name of the annotation is followed by a space, the
27659 additional information, and a newline. The additional information
27660 cannot contain newline characters.
27662 Any output not beginning with a newline and two @samp{control-z}
27663 characters denotes literal output from @value{GDBN}. Currently there is
27664 no need for @value{GDBN} to output a newline followed by two
27665 @samp{control-z} characters, but if there was such a need, the
27666 annotations could be extended with an @samp{escape} annotation which
27667 means those three characters as output.
27669 The annotation @var{level}, which is specified using the
27670 @option{--annotate} command line option (@pxref{Mode Options}), controls
27671 how much information @value{GDBN} prints together with its prompt,
27672 values of expressions, source lines, and other types of output. Level 0
27673 is for no annotations, level 1 is for use when @value{GDBN} is run as a
27674 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
27675 for programs that control @value{GDBN}, and level 2 annotations have
27676 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
27677 Interface, annotate, GDB's Obsolete Annotations}).
27680 @kindex set annotate
27681 @item set annotate @var{level}
27682 The @value{GDBN} command @code{set annotate} sets the level of
27683 annotations to the specified @var{level}.
27685 @item show annotate
27686 @kindex show annotate
27687 Show the current annotation level.
27690 This chapter describes level 3 annotations.
27692 A simple example of starting up @value{GDBN} with annotations is:
27695 $ @kbd{gdb --annotate=3}
27697 Copyright 2003 Free Software Foundation, Inc.
27698 GDB is free software, covered by the GNU General Public License,
27699 and you are welcome to change it and/or distribute copies of it
27700 under certain conditions.
27701 Type "show copying" to see the conditions.
27702 There is absolutely no warranty for GDB. Type "show warranty"
27704 This GDB was configured as "i386-pc-linux-gnu"
27715 Here @samp{quit} is input to @value{GDBN}; the rest is output from
27716 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
27717 denotes a @samp{control-z} character) are annotations; the rest is
27718 output from @value{GDBN}.
27720 @node Server Prefix
27721 @section The Server Prefix
27722 @cindex server prefix
27724 If you prefix a command with @samp{server } then it will not affect
27725 the command history, nor will it affect @value{GDBN}'s notion of which
27726 command to repeat if @key{RET} is pressed on a line by itself. This
27727 means that commands can be run behind a user's back by a front-end in
27728 a transparent manner.
27730 The @code{server } prefix does not affect the recording of values into
27731 the value history; to print a value without recording it into the
27732 value history, use the @code{output} command instead of the
27733 @code{print} command.
27735 Using this prefix also disables confirmation requests
27736 (@pxref{confirmation requests}).
27739 @section Annotation for @value{GDBN} Input
27741 @cindex annotations for prompts
27742 When @value{GDBN} prompts for input, it annotates this fact so it is possible
27743 to know when to send output, when the output from a given command is
27746 Different kinds of input each have a different @dfn{input type}. Each
27747 input type has three annotations: a @code{pre-} annotation, which
27748 denotes the beginning of any prompt which is being output, a plain
27749 annotation, which denotes the end of the prompt, and then a @code{post-}
27750 annotation which denotes the end of any echo which may (or may not) be
27751 associated with the input. For example, the @code{prompt} input type
27752 features the following annotations:
27760 The input types are
27763 @findex pre-prompt annotation
27764 @findex prompt annotation
27765 @findex post-prompt annotation
27767 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
27769 @findex pre-commands annotation
27770 @findex commands annotation
27771 @findex post-commands annotation
27773 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
27774 command. The annotations are repeated for each command which is input.
27776 @findex pre-overload-choice annotation
27777 @findex overload-choice annotation
27778 @findex post-overload-choice annotation
27779 @item overload-choice
27780 When @value{GDBN} wants the user to select between various overloaded functions.
27782 @findex pre-query annotation
27783 @findex query annotation
27784 @findex post-query annotation
27786 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
27788 @findex pre-prompt-for-continue annotation
27789 @findex prompt-for-continue annotation
27790 @findex post-prompt-for-continue annotation
27791 @item prompt-for-continue
27792 When @value{GDBN} is asking the user to press return to continue. Note: Don't
27793 expect this to work well; instead use @code{set height 0} to disable
27794 prompting. This is because the counting of lines is buggy in the
27795 presence of annotations.
27800 @cindex annotations for errors, warnings and interrupts
27802 @findex quit annotation
27807 This annotation occurs right before @value{GDBN} responds to an interrupt.
27809 @findex error annotation
27814 This annotation occurs right before @value{GDBN} responds to an error.
27816 Quit and error annotations indicate that any annotations which @value{GDBN} was
27817 in the middle of may end abruptly. For example, if a
27818 @code{value-history-begin} annotation is followed by a @code{error}, one
27819 cannot expect to receive the matching @code{value-history-end}. One
27820 cannot expect not to receive it either, however; an error annotation
27821 does not necessarily mean that @value{GDBN} is immediately returning all the way
27824 @findex error-begin annotation
27825 A quit or error annotation may be preceded by
27831 Any output between that and the quit or error annotation is the error
27834 Warning messages are not yet annotated.
27835 @c If we want to change that, need to fix warning(), type_error(),
27836 @c range_error(), and possibly other places.
27839 @section Invalidation Notices
27841 @cindex annotations for invalidation messages
27842 The following annotations say that certain pieces of state may have
27846 @findex frames-invalid annotation
27847 @item ^Z^Zframes-invalid
27849 The frames (for example, output from the @code{backtrace} command) may
27852 @findex breakpoints-invalid annotation
27853 @item ^Z^Zbreakpoints-invalid
27855 The breakpoints may have changed. For example, the user just added or
27856 deleted a breakpoint.
27859 @node Annotations for Running
27860 @section Running the Program
27861 @cindex annotations for running programs
27863 @findex starting annotation
27864 @findex stopping annotation
27865 When the program starts executing due to a @value{GDBN} command such as
27866 @code{step} or @code{continue},
27872 is output. When the program stops,
27878 is output. Before the @code{stopped} annotation, a variety of
27879 annotations describe how the program stopped.
27882 @findex exited annotation
27883 @item ^Z^Zexited @var{exit-status}
27884 The program exited, and @var{exit-status} is the exit status (zero for
27885 successful exit, otherwise nonzero).
27887 @findex signalled annotation
27888 @findex signal-name annotation
27889 @findex signal-name-end annotation
27890 @findex signal-string annotation
27891 @findex signal-string-end annotation
27892 @item ^Z^Zsignalled
27893 The program exited with a signal. After the @code{^Z^Zsignalled}, the
27894 annotation continues:
27900 ^Z^Zsignal-name-end
27904 ^Z^Zsignal-string-end
27909 where @var{name} is the name of the signal, such as @code{SIGILL} or
27910 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
27911 as @code{Illegal Instruction} or @code{Segmentation fault}.
27912 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
27913 user's benefit and have no particular format.
27915 @findex signal annotation
27917 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
27918 just saying that the program received the signal, not that it was
27919 terminated with it.
27921 @findex breakpoint annotation
27922 @item ^Z^Zbreakpoint @var{number}
27923 The program hit breakpoint number @var{number}.
27925 @findex watchpoint annotation
27926 @item ^Z^Zwatchpoint @var{number}
27927 The program hit watchpoint number @var{number}.
27930 @node Source Annotations
27931 @section Displaying Source
27932 @cindex annotations for source display
27934 @findex source annotation
27935 The following annotation is used instead of displaying source code:
27938 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
27941 where @var{filename} is an absolute file name indicating which source
27942 file, @var{line} is the line number within that file (where 1 is the
27943 first line in the file), @var{character} is the character position
27944 within the file (where 0 is the first character in the file) (for most
27945 debug formats this will necessarily point to the beginning of a line),
27946 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
27947 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
27948 @var{addr} is the address in the target program associated with the
27949 source which is being displayed. @var{addr} is in the form @samp{0x}
27950 followed by one or more lowercase hex digits (note that this does not
27951 depend on the language).
27953 @node JIT Interface
27954 @chapter JIT Compilation Interface
27955 @cindex just-in-time compilation
27956 @cindex JIT compilation interface
27958 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
27959 interface. A JIT compiler is a program or library that generates native
27960 executable code at runtime and executes it, usually in order to achieve good
27961 performance while maintaining platform independence.
27963 Programs that use JIT compilation are normally difficult to debug because
27964 portions of their code are generated at runtime, instead of being loaded from
27965 object files, which is where @value{GDBN} normally finds the program's symbols
27966 and debug information. In order to debug programs that use JIT compilation,
27967 @value{GDBN} has an interface that allows the program to register in-memory
27968 symbol files with @value{GDBN} at runtime.
27970 If you are using @value{GDBN} to debug a program that uses this interface, then
27971 it should work transparently so long as you have not stripped the binary. If
27972 you are developing a JIT compiler, then the interface is documented in the rest
27973 of this chapter. At this time, the only known client of this interface is the
27976 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
27977 JIT compiler communicates with @value{GDBN} by writing data into a global
27978 variable and calling a fuction at a well-known symbol. When @value{GDBN}
27979 attaches, it reads a linked list of symbol files from the global variable to
27980 find existing code, and puts a breakpoint in the function so that it can find
27981 out about additional code.
27984 * Declarations:: Relevant C struct declarations
27985 * Registering Code:: Steps to register code
27986 * Unregistering Code:: Steps to unregister code
27990 @section JIT Declarations
27992 These are the relevant struct declarations that a C program should include to
27993 implement the interface:
28003 struct jit_code_entry
28005 struct jit_code_entry *next_entry;
28006 struct jit_code_entry *prev_entry;
28007 const char *symfile_addr;
28008 uint64_t symfile_size;
28011 struct jit_descriptor
28014 /* This type should be jit_actions_t, but we use uint32_t
28015 to be explicit about the bitwidth. */
28016 uint32_t action_flag;
28017 struct jit_code_entry *relevant_entry;
28018 struct jit_code_entry *first_entry;
28021 /* GDB puts a breakpoint in this function. */
28022 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
28024 /* Make sure to specify the version statically, because the
28025 debugger may check the version before we can set it. */
28026 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
28029 If the JIT is multi-threaded, then it is important that the JIT synchronize any
28030 modifications to this global data properly, which can easily be done by putting
28031 a global mutex around modifications to these structures.
28033 @node Registering Code
28034 @section Registering Code
28036 To register code with @value{GDBN}, the JIT should follow this protocol:
28040 Generate an object file in memory with symbols and other desired debug
28041 information. The file must include the virtual addresses of the sections.
28044 Create a code entry for the file, which gives the start and size of the symbol
28048 Add it to the linked list in the JIT descriptor.
28051 Point the relevant_entry field of the descriptor at the entry.
28054 Set @code{action_flag} to @code{JIT_REGISTER} and call
28055 @code{__jit_debug_register_code}.
28058 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
28059 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
28060 new code. However, the linked list must still be maintained in order to allow
28061 @value{GDBN} to attach to a running process and still find the symbol files.
28063 @node Unregistering Code
28064 @section Unregistering Code
28066 If code is freed, then the JIT should use the following protocol:
28070 Remove the code entry corresponding to the code from the linked list.
28073 Point the @code{relevant_entry} field of the descriptor at the code entry.
28076 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
28077 @code{__jit_debug_register_code}.
28080 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
28081 and the JIT will leak the memory used for the associated symbol files.
28084 @chapter Reporting Bugs in @value{GDBN}
28085 @cindex bugs in @value{GDBN}
28086 @cindex reporting bugs in @value{GDBN}
28088 Your bug reports play an essential role in making @value{GDBN} reliable.
28090 Reporting a bug may help you by bringing a solution to your problem, or it
28091 may not. But in any case the principal function of a bug report is to help
28092 the entire community by making the next version of @value{GDBN} work better. Bug
28093 reports are your contribution to the maintenance of @value{GDBN}.
28095 In order for a bug report to serve its purpose, you must include the
28096 information that enables us to fix the bug.
28099 * Bug Criteria:: Have you found a bug?
28100 * Bug Reporting:: How to report bugs
28104 @section Have You Found a Bug?
28105 @cindex bug criteria
28107 If you are not sure whether you have found a bug, here are some guidelines:
28110 @cindex fatal signal
28111 @cindex debugger crash
28112 @cindex crash of debugger
28114 If the debugger gets a fatal signal, for any input whatever, that is a
28115 @value{GDBN} bug. Reliable debuggers never crash.
28117 @cindex error on valid input
28119 If @value{GDBN} produces an error message for valid input, that is a
28120 bug. (Note that if you're cross debugging, the problem may also be
28121 somewhere in the connection to the target.)
28123 @cindex invalid input
28125 If @value{GDBN} does not produce an error message for invalid input,
28126 that is a bug. However, you should note that your idea of
28127 ``invalid input'' might be our idea of ``an extension'' or ``support
28128 for traditional practice''.
28131 If you are an experienced user of debugging tools, your suggestions
28132 for improvement of @value{GDBN} are welcome in any case.
28135 @node Bug Reporting
28136 @section How to Report Bugs
28137 @cindex bug reports
28138 @cindex @value{GDBN} bugs, reporting
28140 A number of companies and individuals offer support for @sc{gnu} products.
28141 If you obtained @value{GDBN} from a support organization, we recommend you
28142 contact that organization first.
28144 You can find contact information for many support companies and
28145 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
28147 @c should add a web page ref...
28150 @ifset BUGURL_DEFAULT
28151 In any event, we also recommend that you submit bug reports for
28152 @value{GDBN}. The preferred method is to submit them directly using
28153 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
28154 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
28157 @strong{Do not send bug reports to @samp{info-gdb}, or to
28158 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
28159 not want to receive bug reports. Those that do have arranged to receive
28162 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
28163 serves as a repeater. The mailing list and the newsgroup carry exactly
28164 the same messages. Often people think of posting bug reports to the
28165 newsgroup instead of mailing them. This appears to work, but it has one
28166 problem which can be crucial: a newsgroup posting often lacks a mail
28167 path back to the sender. Thus, if we need to ask for more information,
28168 we may be unable to reach you. For this reason, it is better to send
28169 bug reports to the mailing list.
28171 @ifclear BUGURL_DEFAULT
28172 In any event, we also recommend that you submit bug reports for
28173 @value{GDBN} to @value{BUGURL}.
28177 The fundamental principle of reporting bugs usefully is this:
28178 @strong{report all the facts}. If you are not sure whether to state a
28179 fact or leave it out, state it!
28181 Often people omit facts because they think they know what causes the
28182 problem and assume that some details do not matter. Thus, you might
28183 assume that the name of the variable you use in an example does not matter.
28184 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
28185 stray memory reference which happens to fetch from the location where that
28186 name is stored in memory; perhaps, if the name were different, the contents
28187 of that location would fool the debugger into doing the right thing despite
28188 the bug. Play it safe and give a specific, complete example. That is the
28189 easiest thing for you to do, and the most helpful.
28191 Keep in mind that the purpose of a bug report is to enable us to fix the
28192 bug. It may be that the bug has been reported previously, but neither
28193 you nor we can know that unless your bug report is complete and
28196 Sometimes people give a few sketchy facts and ask, ``Does this ring a
28197 bell?'' Those bug reports are useless, and we urge everyone to
28198 @emph{refuse to respond to them} except to chide the sender to report
28201 To enable us to fix the bug, you should include all these things:
28205 The version of @value{GDBN}. @value{GDBN} announces it if you start
28206 with no arguments; you can also print it at any time using @code{show
28209 Without this, we will not know whether there is any point in looking for
28210 the bug in the current version of @value{GDBN}.
28213 The type of machine you are using, and the operating system name and
28217 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
28218 ``@value{GCC}--2.8.1''.
28221 What compiler (and its version) was used to compile the program you are
28222 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
28223 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
28224 to get this information; for other compilers, see the documentation for
28228 The command arguments you gave the compiler to compile your example and
28229 observe the bug. For example, did you use @samp{-O}? To guarantee
28230 you will not omit something important, list them all. A copy of the
28231 Makefile (or the output from make) is sufficient.
28233 If we were to try to guess the arguments, we would probably guess wrong
28234 and then we might not encounter the bug.
28237 A complete input script, and all necessary source files, that will
28241 A description of what behavior you observe that you believe is
28242 incorrect. For example, ``It gets a fatal signal.''
28244 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
28245 will certainly notice it. But if the bug is incorrect output, we might
28246 not notice unless it is glaringly wrong. You might as well not give us
28247 a chance to make a mistake.
28249 Even if the problem you experience is a fatal signal, you should still
28250 say so explicitly. Suppose something strange is going on, such as, your
28251 copy of @value{GDBN} is out of synch, or you have encountered a bug in
28252 the C library on your system. (This has happened!) Your copy might
28253 crash and ours would not. If you told us to expect a crash, then when
28254 ours fails to crash, we would know that the bug was not happening for
28255 us. If you had not told us to expect a crash, then we would not be able
28256 to draw any conclusion from our observations.
28259 @cindex recording a session script
28260 To collect all this information, you can use a session recording program
28261 such as @command{script}, which is available on many Unix systems.
28262 Just run your @value{GDBN} session inside @command{script} and then
28263 include the @file{typescript} file with your bug report.
28265 Another way to record a @value{GDBN} session is to run @value{GDBN}
28266 inside Emacs and then save the entire buffer to a file.
28269 If you wish to suggest changes to the @value{GDBN} source, send us context
28270 diffs. If you even discuss something in the @value{GDBN} source, refer to
28271 it by context, not by line number.
28273 The line numbers in our development sources will not match those in your
28274 sources. Your line numbers would convey no useful information to us.
28278 Here are some things that are not necessary:
28282 A description of the envelope of the bug.
28284 Often people who encounter a bug spend a lot of time investigating
28285 which changes to the input file will make the bug go away and which
28286 changes will not affect it.
28288 This is often time consuming and not very useful, because the way we
28289 will find the bug is by running a single example under the debugger
28290 with breakpoints, not by pure deduction from a series of examples.
28291 We recommend that you save your time for something else.
28293 Of course, if you can find a simpler example to report @emph{instead}
28294 of the original one, that is a convenience for us. Errors in the
28295 output will be easier to spot, running under the debugger will take
28296 less time, and so on.
28298 However, simplification is not vital; if you do not want to do this,
28299 report the bug anyway and send us the entire test case you used.
28302 A patch for the bug.
28304 A patch for the bug does help us if it is a good one. But do not omit
28305 the necessary information, such as the test case, on the assumption that
28306 a patch is all we need. We might see problems with your patch and decide
28307 to fix the problem another way, or we might not understand it at all.
28309 Sometimes with a program as complicated as @value{GDBN} it is very hard to
28310 construct an example that will make the program follow a certain path
28311 through the code. If you do not send us the example, we will not be able
28312 to construct one, so we will not be able to verify that the bug is fixed.
28314 And if we cannot understand what bug you are trying to fix, or why your
28315 patch should be an improvement, we will not install it. A test case will
28316 help us to understand.
28319 A guess about what the bug is or what it depends on.
28321 Such guesses are usually wrong. Even we cannot guess right about such
28322 things without first using the debugger to find the facts.
28325 @c The readline documentation is distributed with the readline code
28326 @c and consists of the two following files:
28328 @c inc-hist.texinfo
28329 @c Use -I with makeinfo to point to the appropriate directory,
28330 @c environment var TEXINPUTS with TeX.
28331 @include rluser.texi
28332 @include inc-hist.texinfo
28335 @node Formatting Documentation
28336 @appendix Formatting Documentation
28338 @cindex @value{GDBN} reference card
28339 @cindex reference card
28340 The @value{GDBN} 4 release includes an already-formatted reference card, ready
28341 for printing with PostScript or Ghostscript, in the @file{gdb}
28342 subdirectory of the main source directory@footnote{In
28343 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
28344 release.}. If you can use PostScript or Ghostscript with your printer,
28345 you can print the reference card immediately with @file{refcard.ps}.
28347 The release also includes the source for the reference card. You
28348 can format it, using @TeX{}, by typing:
28354 The @value{GDBN} reference card is designed to print in @dfn{landscape}
28355 mode on US ``letter'' size paper;
28356 that is, on a sheet 11 inches wide by 8.5 inches
28357 high. You will need to specify this form of printing as an option to
28358 your @sc{dvi} output program.
28360 @cindex documentation
28362 All the documentation for @value{GDBN} comes as part of the machine-readable
28363 distribution. The documentation is written in Texinfo format, which is
28364 a documentation system that uses a single source file to produce both
28365 on-line information and a printed manual. You can use one of the Info
28366 formatting commands to create the on-line version of the documentation
28367 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
28369 @value{GDBN} includes an already formatted copy of the on-line Info
28370 version of this manual in the @file{gdb} subdirectory. The main Info
28371 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
28372 subordinate files matching @samp{gdb.info*} in the same directory. If
28373 necessary, you can print out these files, or read them with any editor;
28374 but they are easier to read using the @code{info} subsystem in @sc{gnu}
28375 Emacs or the standalone @code{info} program, available as part of the
28376 @sc{gnu} Texinfo distribution.
28378 If you want to format these Info files yourself, you need one of the
28379 Info formatting programs, such as @code{texinfo-format-buffer} or
28382 If you have @code{makeinfo} installed, and are in the top level
28383 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
28384 version @value{GDBVN}), you can make the Info file by typing:
28391 If you want to typeset and print copies of this manual, you need @TeX{},
28392 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
28393 Texinfo definitions file.
28395 @TeX{} is a typesetting program; it does not print files directly, but
28396 produces output files called @sc{dvi} files. To print a typeset
28397 document, you need a program to print @sc{dvi} files. If your system
28398 has @TeX{} installed, chances are it has such a program. The precise
28399 command to use depends on your system; @kbd{lpr -d} is common; another
28400 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
28401 require a file name without any extension or a @samp{.dvi} extension.
28403 @TeX{} also requires a macro definitions file called
28404 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
28405 written in Texinfo format. On its own, @TeX{} cannot either read or
28406 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
28407 and is located in the @file{gdb-@var{version-number}/texinfo}
28410 If you have @TeX{} and a @sc{dvi} printer program installed, you can
28411 typeset and print this manual. First switch to the @file{gdb}
28412 subdirectory of the main source directory (for example, to
28413 @file{gdb-@value{GDBVN}/gdb}) and type:
28419 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
28421 @node Installing GDB
28422 @appendix Installing @value{GDBN}
28423 @cindex installation
28426 * Requirements:: Requirements for building @value{GDBN}
28427 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
28428 * Separate Objdir:: Compiling @value{GDBN} in another directory
28429 * Config Names:: Specifying names for hosts and targets
28430 * Configure Options:: Summary of options for configure
28431 * System-wide configuration:: Having a system-wide init file
28435 @section Requirements for Building @value{GDBN}
28436 @cindex building @value{GDBN}, requirements for
28438 Building @value{GDBN} requires various tools and packages to be available.
28439 Other packages will be used only if they are found.
28441 @heading Tools/Packages Necessary for Building @value{GDBN}
28443 @item ISO C90 compiler
28444 @value{GDBN} is written in ISO C90. It should be buildable with any
28445 working C90 compiler, e.g.@: GCC.
28449 @heading Tools/Packages Optional for Building @value{GDBN}
28453 @value{GDBN} can use the Expat XML parsing library. This library may be
28454 included with your operating system distribution; if it is not, you
28455 can get the latest version from @url{http://expat.sourceforge.net}.
28456 The @file{configure} script will search for this library in several
28457 standard locations; if it is installed in an unusual path, you can
28458 use the @option{--with-libexpat-prefix} option to specify its location.
28464 Remote protocol memory maps (@pxref{Memory Map Format})
28466 Target descriptions (@pxref{Target Descriptions})
28468 Remote shared library lists (@pxref{Library List Format})
28470 MS-Windows shared libraries (@pxref{Shared Libraries})
28474 @cindex compressed debug sections
28475 @value{GDBN} will use the @samp{zlib} library, if available, to read
28476 compressed debug sections. Some linkers, such as GNU gold, are capable
28477 of producing binaries with compressed debug sections. If @value{GDBN}
28478 is compiled with @samp{zlib}, it will be able to read the debug
28479 information in such binaries.
28481 The @samp{zlib} library is likely included with your operating system
28482 distribution; if it is not, you can get the latest version from
28483 @url{http://zlib.net}.
28486 @value{GDBN}'s features related to character sets (@pxref{Character
28487 Sets}) require a functioning @code{iconv} implementation. If you are
28488 on a GNU system, then this is provided by the GNU C Library. Some
28489 other systems also provide a working @code{iconv}.
28491 On systems with @code{iconv}, you can install GNU Libiconv. If you
28492 have previously installed Libiconv, you can use the
28493 @option{--with-libiconv-prefix} option to configure.
28495 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
28496 arrange to build Libiconv if a directory named @file{libiconv} appears
28497 in the top-most source directory. If Libiconv is built this way, and
28498 if the operating system does not provide a suitable @code{iconv}
28499 implementation, then the just-built library will automatically be used
28500 by @value{GDBN}. One easy way to set this up is to download GNU
28501 Libiconv, unpack it, and then rename the directory holding the
28502 Libiconv source code to @samp{libiconv}.
28505 @node Running Configure
28506 @section Invoking the @value{GDBN} @file{configure} Script
28507 @cindex configuring @value{GDBN}
28508 @value{GDBN} comes with a @file{configure} script that automates the process
28509 of preparing @value{GDBN} for installation; you can then use @code{make} to
28510 build the @code{gdb} program.
28512 @c irrelevant in info file; it's as current as the code it lives with.
28513 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
28514 look at the @file{README} file in the sources; we may have improved the
28515 installation procedures since publishing this manual.}
28518 The @value{GDBN} distribution includes all the source code you need for
28519 @value{GDBN} in a single directory, whose name is usually composed by
28520 appending the version number to @samp{gdb}.
28522 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
28523 @file{gdb-@value{GDBVN}} directory. That directory contains:
28526 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
28527 script for configuring @value{GDBN} and all its supporting libraries
28529 @item gdb-@value{GDBVN}/gdb
28530 the source specific to @value{GDBN} itself
28532 @item gdb-@value{GDBVN}/bfd
28533 source for the Binary File Descriptor library
28535 @item gdb-@value{GDBVN}/include
28536 @sc{gnu} include files
28538 @item gdb-@value{GDBVN}/libiberty
28539 source for the @samp{-liberty} free software library
28541 @item gdb-@value{GDBVN}/opcodes
28542 source for the library of opcode tables and disassemblers
28544 @item gdb-@value{GDBVN}/readline
28545 source for the @sc{gnu} command-line interface
28547 @item gdb-@value{GDBVN}/glob
28548 source for the @sc{gnu} filename pattern-matching subroutine
28550 @item gdb-@value{GDBVN}/mmalloc
28551 source for the @sc{gnu} memory-mapped malloc package
28554 The simplest way to configure and build @value{GDBN} is to run @file{configure}
28555 from the @file{gdb-@var{version-number}} source directory, which in
28556 this example is the @file{gdb-@value{GDBVN}} directory.
28558 First switch to the @file{gdb-@var{version-number}} source directory
28559 if you are not already in it; then run @file{configure}. Pass the
28560 identifier for the platform on which @value{GDBN} will run as an
28566 cd gdb-@value{GDBVN}
28567 ./configure @var{host}
28572 where @var{host} is an identifier such as @samp{sun4} or
28573 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
28574 (You can often leave off @var{host}; @file{configure} tries to guess the
28575 correct value by examining your system.)
28577 Running @samp{configure @var{host}} and then running @code{make} builds the
28578 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
28579 libraries, then @code{gdb} itself. The configured source files, and the
28580 binaries, are left in the corresponding source directories.
28583 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
28584 system does not recognize this automatically when you run a different
28585 shell, you may need to run @code{sh} on it explicitly:
28588 sh configure @var{host}
28591 If you run @file{configure} from a directory that contains source
28592 directories for multiple libraries or programs, such as the
28593 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
28595 creates configuration files for every directory level underneath (unless
28596 you tell it not to, with the @samp{--norecursion} option).
28598 You should run the @file{configure} script from the top directory in the
28599 source tree, the @file{gdb-@var{version-number}} directory. If you run
28600 @file{configure} from one of the subdirectories, you will configure only
28601 that subdirectory. That is usually not what you want. In particular,
28602 if you run the first @file{configure} from the @file{gdb} subdirectory
28603 of the @file{gdb-@var{version-number}} directory, you will omit the
28604 configuration of @file{bfd}, @file{readline}, and other sibling
28605 directories of the @file{gdb} subdirectory. This leads to build errors
28606 about missing include files such as @file{bfd/bfd.h}.
28608 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
28609 However, you should make sure that the shell on your path (named by
28610 the @samp{SHELL} environment variable) is publicly readable. Remember
28611 that @value{GDBN} uses the shell to start your program---some systems refuse to
28612 let @value{GDBN} debug child processes whose programs are not readable.
28614 @node Separate Objdir
28615 @section Compiling @value{GDBN} in Another Directory
28617 If you want to run @value{GDBN} versions for several host or target machines,
28618 you need a different @code{gdb} compiled for each combination of
28619 host and target. @file{configure} is designed to make this easy by
28620 allowing you to generate each configuration in a separate subdirectory,
28621 rather than in the source directory. If your @code{make} program
28622 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
28623 @code{make} in each of these directories builds the @code{gdb}
28624 program specified there.
28626 To build @code{gdb} in a separate directory, run @file{configure}
28627 with the @samp{--srcdir} option to specify where to find the source.
28628 (You also need to specify a path to find @file{configure}
28629 itself from your working directory. If the path to @file{configure}
28630 would be the same as the argument to @samp{--srcdir}, you can leave out
28631 the @samp{--srcdir} option; it is assumed.)
28633 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
28634 separate directory for a Sun 4 like this:
28638 cd gdb-@value{GDBVN}
28641 ../gdb-@value{GDBVN}/configure sun4
28646 When @file{configure} builds a configuration using a remote source
28647 directory, it creates a tree for the binaries with the same structure
28648 (and using the same names) as the tree under the source directory. In
28649 the example, you'd find the Sun 4 library @file{libiberty.a} in the
28650 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
28651 @file{gdb-sun4/gdb}.
28653 Make sure that your path to the @file{configure} script has just one
28654 instance of @file{gdb} in it. If your path to @file{configure} looks
28655 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
28656 one subdirectory of @value{GDBN}, not the whole package. This leads to
28657 build errors about missing include files such as @file{bfd/bfd.h}.
28659 One popular reason to build several @value{GDBN} configurations in separate
28660 directories is to configure @value{GDBN} for cross-compiling (where
28661 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
28662 programs that run on another machine---the @dfn{target}).
28663 You specify a cross-debugging target by
28664 giving the @samp{--target=@var{target}} option to @file{configure}.
28666 When you run @code{make} to build a program or library, you must run
28667 it in a configured directory---whatever directory you were in when you
28668 called @file{configure} (or one of its subdirectories).
28670 The @code{Makefile} that @file{configure} generates in each source
28671 directory also runs recursively. If you type @code{make} in a source
28672 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
28673 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
28674 will build all the required libraries, and then build GDB.
28676 When you have multiple hosts or targets configured in separate
28677 directories, you can run @code{make} on them in parallel (for example,
28678 if they are NFS-mounted on each of the hosts); they will not interfere
28682 @section Specifying Names for Hosts and Targets
28684 The specifications used for hosts and targets in the @file{configure}
28685 script are based on a three-part naming scheme, but some short predefined
28686 aliases are also supported. The full naming scheme encodes three pieces
28687 of information in the following pattern:
28690 @var{architecture}-@var{vendor}-@var{os}
28693 For example, you can use the alias @code{sun4} as a @var{host} argument,
28694 or as the value for @var{target} in a @code{--target=@var{target}}
28695 option. The equivalent full name is @samp{sparc-sun-sunos4}.
28697 The @file{configure} script accompanying @value{GDBN} does not provide
28698 any query facility to list all supported host and target names or
28699 aliases. @file{configure} calls the Bourne shell script
28700 @code{config.sub} to map abbreviations to full names; you can read the
28701 script, if you wish, or you can use it to test your guesses on
28702 abbreviations---for example:
28705 % sh config.sub i386-linux
28707 % sh config.sub alpha-linux
28708 alpha-unknown-linux-gnu
28709 % sh config.sub hp9k700
28711 % sh config.sub sun4
28712 sparc-sun-sunos4.1.1
28713 % sh config.sub sun3
28714 m68k-sun-sunos4.1.1
28715 % sh config.sub i986v
28716 Invalid configuration `i986v': machine `i986v' not recognized
28720 @code{config.sub} is also distributed in the @value{GDBN} source
28721 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
28723 @node Configure Options
28724 @section @file{configure} Options
28726 Here is a summary of the @file{configure} options and arguments that
28727 are most often useful for building @value{GDBN}. @file{configure} also has
28728 several other options not listed here. @inforef{What Configure
28729 Does,,configure.info}, for a full explanation of @file{configure}.
28732 configure @r{[}--help@r{]}
28733 @r{[}--prefix=@var{dir}@r{]}
28734 @r{[}--exec-prefix=@var{dir}@r{]}
28735 @r{[}--srcdir=@var{dirname}@r{]}
28736 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
28737 @r{[}--target=@var{target}@r{]}
28742 You may introduce options with a single @samp{-} rather than
28743 @samp{--} if you prefer; but you may abbreviate option names if you use
28748 Display a quick summary of how to invoke @file{configure}.
28750 @item --prefix=@var{dir}
28751 Configure the source to install programs and files under directory
28754 @item --exec-prefix=@var{dir}
28755 Configure the source to install programs under directory
28758 @c avoid splitting the warning from the explanation:
28760 @item --srcdir=@var{dirname}
28761 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
28762 @code{make} that implements the @code{VPATH} feature.}@*
28763 Use this option to make configurations in directories separate from the
28764 @value{GDBN} source directories. Among other things, you can use this to
28765 build (or maintain) several configurations simultaneously, in separate
28766 directories. @file{configure} writes configuration-specific files in
28767 the current directory, but arranges for them to use the source in the
28768 directory @var{dirname}. @file{configure} creates directories under
28769 the working directory in parallel to the source directories below
28772 @item --norecursion
28773 Configure only the directory level where @file{configure} is executed; do not
28774 propagate configuration to subdirectories.
28776 @item --target=@var{target}
28777 Configure @value{GDBN} for cross-debugging programs running on the specified
28778 @var{target}. Without this option, @value{GDBN} is configured to debug
28779 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
28781 There is no convenient way to generate a list of all available targets.
28783 @item @var{host} @dots{}
28784 Configure @value{GDBN} to run on the specified @var{host}.
28786 There is no convenient way to generate a list of all available hosts.
28789 There are many other options available as well, but they are generally
28790 needed for special purposes only.
28792 @node System-wide configuration
28793 @section System-wide configuration and settings
28794 @cindex system-wide init file
28796 @value{GDBN} can be configured to have a system-wide init file;
28797 this file will be read and executed at startup (@pxref{Startup, , What
28798 @value{GDBN} does during startup}).
28800 Here is the corresponding configure option:
28803 @item --with-system-gdbinit=@var{file}
28804 Specify that the default location of the system-wide init file is
28808 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
28809 it may be subject to relocation. Two possible cases:
28813 If the default location of this init file contains @file{$prefix},
28814 it will be subject to relocation. Suppose that the configure options
28815 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
28816 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
28817 init file is looked for as @file{$install/etc/gdbinit} instead of
28818 @file{$prefix/etc/gdbinit}.
28821 By contrast, if the default location does not contain the prefix,
28822 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
28823 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
28824 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
28825 wherever @value{GDBN} is installed.
28828 @node Maintenance Commands
28829 @appendix Maintenance Commands
28830 @cindex maintenance commands
28831 @cindex internal commands
28833 In addition to commands intended for @value{GDBN} users, @value{GDBN}
28834 includes a number of commands intended for @value{GDBN} developers,
28835 that are not documented elsewhere in this manual. These commands are
28836 provided here for reference. (For commands that turn on debugging
28837 messages, see @ref{Debugging Output}.)
28840 @kindex maint agent
28841 @kindex maint agent-eval
28842 @item maint agent @var{expression}
28843 @itemx maint agent-eval @var{expression}
28844 Translate the given @var{expression} into remote agent bytecodes.
28845 This command is useful for debugging the Agent Expression mechanism
28846 (@pxref{Agent Expressions}). The @samp{agent} version produces an
28847 expression useful for data collection, such as by tracepoints, while
28848 @samp{maint agent-eval} produces an expression that evaluates directly
28849 to a result. For instance, a collection expression for @code{globa +
28850 globb} will include bytecodes to record four bytes of memory at each
28851 of the addresses of @code{globa} and @code{globb}, while discarding
28852 the result of the addition, while an evaluation expression will do the
28853 addition and return the sum.
28855 @kindex maint info breakpoints
28856 @item @anchor{maint info breakpoints}maint info breakpoints
28857 Using the same format as @samp{info breakpoints}, display both the
28858 breakpoints you've set explicitly, and those @value{GDBN} is using for
28859 internal purposes. Internal breakpoints are shown with negative
28860 breakpoint numbers. The type column identifies what kind of breakpoint
28865 Normal, explicitly set breakpoint.
28868 Normal, explicitly set watchpoint.
28871 Internal breakpoint, used to handle correctly stepping through
28872 @code{longjmp} calls.
28874 @item longjmp resume
28875 Internal breakpoint at the target of a @code{longjmp}.
28878 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
28881 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
28884 Shared library events.
28888 @kindex set displaced-stepping
28889 @kindex show displaced-stepping
28890 @cindex displaced stepping support
28891 @cindex out-of-line single-stepping
28892 @item set displaced-stepping
28893 @itemx show displaced-stepping
28894 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
28895 if the target supports it. Displaced stepping is a way to single-step
28896 over breakpoints without removing them from the inferior, by executing
28897 an out-of-line copy of the instruction that was originally at the
28898 breakpoint location. It is also known as out-of-line single-stepping.
28901 @item set displaced-stepping on
28902 If the target architecture supports it, @value{GDBN} will use
28903 displaced stepping to step over breakpoints.
28905 @item set displaced-stepping off
28906 @value{GDBN} will not use displaced stepping to step over breakpoints,
28907 even if such is supported by the target architecture.
28909 @cindex non-stop mode, and @samp{set displaced-stepping}
28910 @item set displaced-stepping auto
28911 This is the default mode. @value{GDBN} will use displaced stepping
28912 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
28913 architecture supports displaced stepping.
28916 @kindex maint check-symtabs
28917 @item maint check-symtabs
28918 Check the consistency of psymtabs and symtabs.
28920 @kindex maint cplus first_component
28921 @item maint cplus first_component @var{name}
28922 Print the first C@t{++} class/namespace component of @var{name}.
28924 @kindex maint cplus namespace
28925 @item maint cplus namespace
28926 Print the list of possible C@t{++} namespaces.
28928 @kindex maint demangle
28929 @item maint demangle @var{name}
28930 Demangle a C@t{++} or Objective-C mangled @var{name}.
28932 @kindex maint deprecate
28933 @kindex maint undeprecate
28934 @cindex deprecated commands
28935 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
28936 @itemx maint undeprecate @var{command}
28937 Deprecate or undeprecate the named @var{command}. Deprecated commands
28938 cause @value{GDBN} to issue a warning when you use them. The optional
28939 argument @var{replacement} says which newer command should be used in
28940 favor of the deprecated one; if it is given, @value{GDBN} will mention
28941 the replacement as part of the warning.
28943 @kindex maint dump-me
28944 @item maint dump-me
28945 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
28946 Cause a fatal signal in the debugger and force it to dump its core.
28947 This is supported only on systems which support aborting a program
28948 with the @code{SIGQUIT} signal.
28950 @kindex maint internal-error
28951 @kindex maint internal-warning
28952 @item maint internal-error @r{[}@var{message-text}@r{]}
28953 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
28954 Cause @value{GDBN} to call the internal function @code{internal_error}
28955 or @code{internal_warning} and hence behave as though an internal error
28956 or internal warning has been detected. In addition to reporting the
28957 internal problem, these functions give the user the opportunity to
28958 either quit @value{GDBN} or create a core file of the current
28959 @value{GDBN} session.
28961 These commands take an optional parameter @var{message-text} that is
28962 used as the text of the error or warning message.
28964 Here's an example of using @code{internal-error}:
28967 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
28968 @dots{}/maint.c:121: internal-error: testing, 1, 2
28969 A problem internal to GDB has been detected. Further
28970 debugging may prove unreliable.
28971 Quit this debugging session? (y or n) @kbd{n}
28972 Create a core file? (y or n) @kbd{n}
28976 @cindex @value{GDBN} internal error
28977 @cindex internal errors, control of @value{GDBN} behavior
28979 @kindex maint set internal-error
28980 @kindex maint show internal-error
28981 @kindex maint set internal-warning
28982 @kindex maint show internal-warning
28983 @item maint set internal-error @var{action} [ask|yes|no]
28984 @itemx maint show internal-error @var{action}
28985 @itemx maint set internal-warning @var{action} [ask|yes|no]
28986 @itemx maint show internal-warning @var{action}
28987 When @value{GDBN} reports an internal problem (error or warning) it
28988 gives the user the opportunity to both quit @value{GDBN} and create a
28989 core file of the current @value{GDBN} session. These commands let you
28990 override the default behaviour for each particular @var{action},
28991 described in the table below.
28995 You can specify that @value{GDBN} should always (yes) or never (no)
28996 quit. The default is to ask the user what to do.
28999 You can specify that @value{GDBN} should always (yes) or never (no)
29000 create a core file. The default is to ask the user what to do.
29003 @kindex maint packet
29004 @item maint packet @var{text}
29005 If @value{GDBN} is talking to an inferior via the serial protocol,
29006 then this command sends the string @var{text} to the inferior, and
29007 displays the response packet. @value{GDBN} supplies the initial
29008 @samp{$} character, the terminating @samp{#} character, and the
29011 @kindex maint print architecture
29012 @item maint print architecture @r{[}@var{file}@r{]}
29013 Print the entire architecture configuration. The optional argument
29014 @var{file} names the file where the output goes.
29016 @kindex maint print c-tdesc
29017 @item maint print c-tdesc
29018 Print the current target description (@pxref{Target Descriptions}) as
29019 a C source file. The created source file can be used in @value{GDBN}
29020 when an XML parser is not available to parse the description.
29022 @kindex maint print dummy-frames
29023 @item maint print dummy-frames
29024 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
29027 (@value{GDBP}) @kbd{b add}
29029 (@value{GDBP}) @kbd{print add(2,3)}
29030 Breakpoint 2, add (a=2, b=3) at @dots{}
29032 The program being debugged stopped while in a function called from GDB.
29034 (@value{GDBP}) @kbd{maint print dummy-frames}
29035 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
29036 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
29037 call_lo=0x01014000 call_hi=0x01014001
29041 Takes an optional file parameter.
29043 @kindex maint print registers
29044 @kindex maint print raw-registers
29045 @kindex maint print cooked-registers
29046 @kindex maint print register-groups
29047 @item maint print registers @r{[}@var{file}@r{]}
29048 @itemx maint print raw-registers @r{[}@var{file}@r{]}
29049 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
29050 @itemx maint print register-groups @r{[}@var{file}@r{]}
29051 Print @value{GDBN}'s internal register data structures.
29053 The command @code{maint print raw-registers} includes the contents of
29054 the raw register cache; the command @code{maint print cooked-registers}
29055 includes the (cooked) value of all registers; and the command
29056 @code{maint print register-groups} includes the groups that each
29057 register is a member of. @xref{Registers,, Registers, gdbint,
29058 @value{GDBN} Internals}.
29060 These commands take an optional parameter, a file name to which to
29061 write the information.
29063 @kindex maint print reggroups
29064 @item maint print reggroups @r{[}@var{file}@r{]}
29065 Print @value{GDBN}'s internal register group data structures. The
29066 optional argument @var{file} tells to what file to write the
29069 The register groups info looks like this:
29072 (@value{GDBP}) @kbd{maint print reggroups}
29085 This command forces @value{GDBN} to flush its internal register cache.
29087 @kindex maint print objfiles
29088 @cindex info for known object files
29089 @item maint print objfiles
29090 Print a dump of all known object files. For each object file, this
29091 command prints its name, address in memory, and all of its psymtabs
29094 @kindex maint print statistics
29095 @cindex bcache statistics
29096 @item maint print statistics
29097 This command prints, for each object file in the program, various data
29098 about that object file followed by the byte cache (@dfn{bcache})
29099 statistics for the object file. The objfile data includes the number
29100 of minimal, partial, full, and stabs symbols, the number of types
29101 defined by the objfile, the number of as yet unexpanded psym tables,
29102 the number of line tables and string tables, and the amount of memory
29103 used by the various tables. The bcache statistics include the counts,
29104 sizes, and counts of duplicates of all and unique objects, max,
29105 average, and median entry size, total memory used and its overhead and
29106 savings, and various measures of the hash table size and chain
29109 @kindex maint print target-stack
29110 @cindex target stack description
29111 @item maint print target-stack
29112 A @dfn{target} is an interface between the debugger and a particular
29113 kind of file or process. Targets can be stacked in @dfn{strata},
29114 so that more than one target can potentially respond to a request.
29115 In particular, memory accesses will walk down the stack of targets
29116 until they find a target that is interested in handling that particular
29119 This command prints a short description of each layer that was pushed on
29120 the @dfn{target stack}, starting from the top layer down to the bottom one.
29122 @kindex maint print type
29123 @cindex type chain of a data type
29124 @item maint print type @var{expr}
29125 Print the type chain for a type specified by @var{expr}. The argument
29126 can be either a type name or a symbol. If it is a symbol, the type of
29127 that symbol is described. The type chain produced by this command is
29128 a recursive definition of the data type as stored in @value{GDBN}'s
29129 data structures, including its flags and contained types.
29131 @kindex maint set dwarf2 max-cache-age
29132 @kindex maint show dwarf2 max-cache-age
29133 @item maint set dwarf2 max-cache-age
29134 @itemx maint show dwarf2 max-cache-age
29135 Control the DWARF 2 compilation unit cache.
29137 @cindex DWARF 2 compilation units cache
29138 In object files with inter-compilation-unit references, such as those
29139 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
29140 reader needs to frequently refer to previously read compilation units.
29141 This setting controls how long a compilation unit will remain in the
29142 cache if it is not referenced. A higher limit means that cached
29143 compilation units will be stored in memory longer, and more total
29144 memory will be used. Setting it to zero disables caching, which will
29145 slow down @value{GDBN} startup, but reduce memory consumption.
29147 @kindex maint set profile
29148 @kindex maint show profile
29149 @cindex profiling GDB
29150 @item maint set profile
29151 @itemx maint show profile
29152 Control profiling of @value{GDBN}.
29154 Profiling will be disabled until you use the @samp{maint set profile}
29155 command to enable it. When you enable profiling, the system will begin
29156 collecting timing and execution count data; when you disable profiling or
29157 exit @value{GDBN}, the results will be written to a log file. Remember that
29158 if you use profiling, @value{GDBN} will overwrite the profiling log file
29159 (often called @file{gmon.out}). If you have a record of important profiling
29160 data in a @file{gmon.out} file, be sure to move it to a safe location.
29162 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
29163 compiled with the @samp{-pg} compiler option.
29165 @kindex maint set show-debug-regs
29166 @kindex maint show show-debug-regs
29167 @cindex hardware debug registers
29168 @item maint set show-debug-regs
29169 @itemx maint show show-debug-regs
29170 Control whether to show variables that mirror the hardware debug
29171 registers. Use @code{ON} to enable, @code{OFF} to disable. If
29172 enabled, the debug registers values are shown when @value{GDBN} inserts or
29173 removes a hardware breakpoint or watchpoint, and when the inferior
29174 triggers a hardware-assisted breakpoint or watchpoint.
29176 @kindex maint space
29177 @cindex memory used by commands
29179 Control whether to display memory usage for each command. If set to a
29180 nonzero value, @value{GDBN} will display how much memory each command
29181 took, following the command's own output. This can also be requested
29182 by invoking @value{GDBN} with the @option{--statistics} command-line
29183 switch (@pxref{Mode Options}).
29186 @cindex time of command execution
29188 Control whether to display the execution time for each command. If
29189 set to a nonzero value, @value{GDBN} will display how much time it
29190 took to execute each command, following the command's own output.
29191 The time is not printed for the commands that run the target, since
29192 there's no mechanism currently to compute how much time was spend
29193 by @value{GDBN} and how much time was spend by the program been debugged.
29194 it's not possibly currently
29195 This can also be requested by invoking @value{GDBN} with the
29196 @option{--statistics} command-line switch (@pxref{Mode Options}).
29198 @kindex maint translate-address
29199 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
29200 Find the symbol stored at the location specified by the address
29201 @var{addr} and an optional section name @var{section}. If found,
29202 @value{GDBN} prints the name of the closest symbol and an offset from
29203 the symbol's location to the specified address. This is similar to
29204 the @code{info address} command (@pxref{Symbols}), except that this
29205 command also allows to find symbols in other sections.
29207 If section was not specified, the section in which the symbol was found
29208 is also printed. For dynamically linked executables, the name of
29209 executable or shared library containing the symbol is printed as well.
29213 The following command is useful for non-interactive invocations of
29214 @value{GDBN}, such as in the test suite.
29217 @item set watchdog @var{nsec}
29218 @kindex set watchdog
29219 @cindex watchdog timer
29220 @cindex timeout for commands
29221 Set the maximum number of seconds @value{GDBN} will wait for the
29222 target operation to finish. If this time expires, @value{GDBN}
29223 reports and error and the command is aborted.
29225 @item show watchdog
29226 Show the current setting of the target wait timeout.
29229 @node Remote Protocol
29230 @appendix @value{GDBN} Remote Serial Protocol
29235 * Stop Reply Packets::
29236 * General Query Packets::
29237 * Architecture-Specific Protocol Details::
29238 * Tracepoint Packets::
29239 * Host I/O Packets::
29241 * Notification Packets::
29242 * Remote Non-Stop::
29243 * Packet Acknowledgment::
29245 * File-I/O Remote Protocol Extension::
29246 * Library List Format::
29247 * Memory Map Format::
29248 * Thread List Format::
29254 There may be occasions when you need to know something about the
29255 protocol---for example, if there is only one serial port to your target
29256 machine, you might want your program to do something special if it
29257 recognizes a packet meant for @value{GDBN}.
29259 In the examples below, @samp{->} and @samp{<-} are used to indicate
29260 transmitted and received data, respectively.
29262 @cindex protocol, @value{GDBN} remote serial
29263 @cindex serial protocol, @value{GDBN} remote
29264 @cindex remote serial protocol
29265 All @value{GDBN} commands and responses (other than acknowledgments
29266 and notifications, see @ref{Notification Packets}) are sent as a
29267 @var{packet}. A @var{packet} is introduced with the character
29268 @samp{$}, the actual @var{packet-data}, and the terminating character
29269 @samp{#} followed by a two-digit @var{checksum}:
29272 @code{$}@var{packet-data}@code{#}@var{checksum}
29276 @cindex checksum, for @value{GDBN} remote
29278 The two-digit @var{checksum} is computed as the modulo 256 sum of all
29279 characters between the leading @samp{$} and the trailing @samp{#} (an
29280 eight bit unsigned checksum).
29282 Implementors should note that prior to @value{GDBN} 5.0 the protocol
29283 specification also included an optional two-digit @var{sequence-id}:
29286 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
29289 @cindex sequence-id, for @value{GDBN} remote
29291 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
29292 has never output @var{sequence-id}s. Stubs that handle packets added
29293 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
29295 When either the host or the target machine receives a packet, the first
29296 response expected is an acknowledgment: either @samp{+} (to indicate
29297 the package was received correctly) or @samp{-} (to request
29301 -> @code{$}@var{packet-data}@code{#}@var{checksum}
29306 The @samp{+}/@samp{-} acknowledgments can be disabled
29307 once a connection is established.
29308 @xref{Packet Acknowledgment}, for details.
29310 The host (@value{GDBN}) sends @var{command}s, and the target (the
29311 debugging stub incorporated in your program) sends a @var{response}. In
29312 the case of step and continue @var{command}s, the response is only sent
29313 when the operation has completed, and the target has again stopped all
29314 threads in all attached processes. This is the default all-stop mode
29315 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
29316 execution mode; see @ref{Remote Non-Stop}, for details.
29318 @var{packet-data} consists of a sequence of characters with the
29319 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
29322 @cindex remote protocol, field separator
29323 Fields within the packet should be separated using @samp{,} @samp{;} or
29324 @samp{:}. Except where otherwise noted all numbers are represented in
29325 @sc{hex} with leading zeros suppressed.
29327 Implementors should note that prior to @value{GDBN} 5.0, the character
29328 @samp{:} could not appear as the third character in a packet (as it
29329 would potentially conflict with the @var{sequence-id}).
29331 @cindex remote protocol, binary data
29332 @anchor{Binary Data}
29333 Binary data in most packets is encoded either as two hexadecimal
29334 digits per byte of binary data. This allowed the traditional remote
29335 protocol to work over connections which were only seven-bit clean.
29336 Some packets designed more recently assume an eight-bit clean
29337 connection, and use a more efficient encoding to send and receive
29340 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
29341 as an escape character. Any escaped byte is transmitted as the escape
29342 character followed by the original character XORed with @code{0x20}.
29343 For example, the byte @code{0x7d} would be transmitted as the two
29344 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
29345 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
29346 @samp{@}}) must always be escaped. Responses sent by the stub
29347 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
29348 is not interpreted as the start of a run-length encoded sequence
29351 Response @var{data} can be run-length encoded to save space.
29352 Run-length encoding replaces runs of identical characters with one
29353 instance of the repeated character, followed by a @samp{*} and a
29354 repeat count. The repeat count is itself sent encoded, to avoid
29355 binary characters in @var{data}: a value of @var{n} is sent as
29356 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
29357 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
29358 code 32) for a repeat count of 3. (This is because run-length
29359 encoding starts to win for counts 3 or more.) Thus, for example,
29360 @samp{0* } is a run-length encoding of ``0000'': the space character
29361 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
29364 The printable characters @samp{#} and @samp{$} or with a numeric value
29365 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
29366 seven repeats (@samp{$}) can be expanded using a repeat count of only
29367 five (@samp{"}). For example, @samp{00000000} can be encoded as
29370 The error response returned for some packets includes a two character
29371 error number. That number is not well defined.
29373 @cindex empty response, for unsupported packets
29374 For any @var{command} not supported by the stub, an empty response
29375 (@samp{$#00}) should be returned. That way it is possible to extend the
29376 protocol. A newer @value{GDBN} can tell if a packet is supported based
29379 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
29380 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
29386 The following table provides a complete list of all currently defined
29387 @var{command}s and their corresponding response @var{data}.
29388 @xref{File-I/O Remote Protocol Extension}, for details about the File
29389 I/O extension of the remote protocol.
29391 Each packet's description has a template showing the packet's overall
29392 syntax, followed by an explanation of the packet's meaning. We
29393 include spaces in some of the templates for clarity; these are not
29394 part of the packet's syntax. No @value{GDBN} packet uses spaces to
29395 separate its components. For example, a template like @samp{foo
29396 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
29397 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
29398 @var{baz}. @value{GDBN} does not transmit a space character between the
29399 @samp{foo} and the @var{bar}, or between the @var{bar} and the
29402 @cindex @var{thread-id}, in remote protocol
29403 @anchor{thread-id syntax}
29404 Several packets and replies include a @var{thread-id} field to identify
29405 a thread. Normally these are positive numbers with a target-specific
29406 interpretation, formatted as big-endian hex strings. A @var{thread-id}
29407 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
29410 In addition, the remote protocol supports a multiprocess feature in
29411 which the @var{thread-id} syntax is extended to optionally include both
29412 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
29413 The @var{pid} (process) and @var{tid} (thread) components each have the
29414 format described above: a positive number with target-specific
29415 interpretation formatted as a big-endian hex string, literal @samp{-1}
29416 to indicate all processes or threads (respectively), or @samp{0} to
29417 indicate an arbitrary process or thread. Specifying just a process, as
29418 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
29419 error to specify all processes but a specific thread, such as
29420 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
29421 for those packets and replies explicitly documented to include a process
29422 ID, rather than a @var{thread-id}.
29424 The multiprocess @var{thread-id} syntax extensions are only used if both
29425 @value{GDBN} and the stub report support for the @samp{multiprocess}
29426 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
29429 Note that all packet forms beginning with an upper- or lower-case
29430 letter, other than those described here, are reserved for future use.
29432 Here are the packet descriptions.
29437 @cindex @samp{!} packet
29438 @anchor{extended mode}
29439 Enable extended mode. In extended mode, the remote server is made
29440 persistent. The @samp{R} packet is used to restart the program being
29446 The remote target both supports and has enabled extended mode.
29450 @cindex @samp{?} packet
29451 Indicate the reason the target halted. The reply is the same as for
29452 step and continue. This packet has a special interpretation when the
29453 target is in non-stop mode; see @ref{Remote Non-Stop}.
29456 @xref{Stop Reply Packets}, for the reply specifications.
29458 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
29459 @cindex @samp{A} packet
29460 Initialized @code{argv[]} array passed into program. @var{arglen}
29461 specifies the number of bytes in the hex encoded byte stream
29462 @var{arg}. See @code{gdbserver} for more details.
29467 The arguments were set.
29473 @cindex @samp{b} packet
29474 (Don't use this packet; its behavior is not well-defined.)
29475 Change the serial line speed to @var{baud}.
29477 JTC: @emph{When does the transport layer state change? When it's
29478 received, or after the ACK is transmitted. In either case, there are
29479 problems if the command or the acknowledgment packet is dropped.}
29481 Stan: @emph{If people really wanted to add something like this, and get
29482 it working for the first time, they ought to modify ser-unix.c to send
29483 some kind of out-of-band message to a specially-setup stub and have the
29484 switch happen "in between" packets, so that from remote protocol's point
29485 of view, nothing actually happened.}
29487 @item B @var{addr},@var{mode}
29488 @cindex @samp{B} packet
29489 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
29490 breakpoint at @var{addr}.
29492 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
29493 (@pxref{insert breakpoint or watchpoint packet}).
29495 @cindex @samp{bc} packet
29498 Backward continue. Execute the target system in reverse. No parameter.
29499 @xref{Reverse Execution}, for more information.
29502 @xref{Stop Reply Packets}, for the reply specifications.
29504 @cindex @samp{bs} packet
29507 Backward single step. Execute one instruction in reverse. No parameter.
29508 @xref{Reverse Execution}, for more information.
29511 @xref{Stop Reply Packets}, for the reply specifications.
29513 @item c @r{[}@var{addr}@r{]}
29514 @cindex @samp{c} packet
29515 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
29516 resume at current address.
29519 @xref{Stop Reply Packets}, for the reply specifications.
29521 @item C @var{sig}@r{[};@var{addr}@r{]}
29522 @cindex @samp{C} packet
29523 Continue with signal @var{sig} (hex signal number). If
29524 @samp{;@var{addr}} is omitted, resume at same address.
29527 @xref{Stop Reply Packets}, for the reply specifications.
29530 @cindex @samp{d} packet
29533 Don't use this packet; instead, define a general set packet
29534 (@pxref{General Query Packets}).
29538 @cindex @samp{D} packet
29539 The first form of the packet is used to detach @value{GDBN} from the
29540 remote system. It is sent to the remote target
29541 before @value{GDBN} disconnects via the @code{detach} command.
29543 The second form, including a process ID, is used when multiprocess
29544 protocol extensions are enabled (@pxref{multiprocess extensions}), to
29545 detach only a specific process. The @var{pid} is specified as a
29546 big-endian hex string.
29556 @item F @var{RC},@var{EE},@var{CF};@var{XX}
29557 @cindex @samp{F} packet
29558 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
29559 This is part of the File-I/O protocol extension. @xref{File-I/O
29560 Remote Protocol Extension}, for the specification.
29563 @anchor{read registers packet}
29564 @cindex @samp{g} packet
29565 Read general registers.
29569 @item @var{XX@dots{}}
29570 Each byte of register data is described by two hex digits. The bytes
29571 with the register are transmitted in target byte order. The size of
29572 each register and their position within the @samp{g} packet are
29573 determined by the @value{GDBN} internal gdbarch functions
29574 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
29575 specification of several standard @samp{g} packets is specified below.
29580 @item G @var{XX@dots{}}
29581 @cindex @samp{G} packet
29582 Write general registers. @xref{read registers packet}, for a
29583 description of the @var{XX@dots{}} data.
29593 @item H @var{c} @var{thread-id}
29594 @cindex @samp{H} packet
29595 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
29596 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
29597 should be @samp{c} for step and continue operations, @samp{g} for other
29598 operations. The thread designator @var{thread-id} has the format and
29599 interpretation described in @ref{thread-id syntax}.
29610 @c 'H': How restrictive (or permissive) is the thread model. If a
29611 @c thread is selected and stopped, are other threads allowed
29612 @c to continue to execute? As I mentioned above, I think the
29613 @c semantics of each command when a thread is selected must be
29614 @c described. For example:
29616 @c 'g': If the stub supports threads and a specific thread is
29617 @c selected, returns the register block from that thread;
29618 @c otherwise returns current registers.
29620 @c 'G' If the stub supports threads and a specific thread is
29621 @c selected, sets the registers of the register block of
29622 @c that thread; otherwise sets current registers.
29624 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
29625 @anchor{cycle step packet}
29626 @cindex @samp{i} packet
29627 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
29628 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
29629 step starting at that address.
29632 @cindex @samp{I} packet
29633 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
29637 @cindex @samp{k} packet
29640 FIXME: @emph{There is no description of how to operate when a specific
29641 thread context has been selected (i.e.@: does 'k' kill only that
29644 @item m @var{addr},@var{length}
29645 @cindex @samp{m} packet
29646 Read @var{length} bytes of memory starting at address @var{addr}.
29647 Note that @var{addr} may not be aligned to any particular boundary.
29649 The stub need not use any particular size or alignment when gathering
29650 data from memory for the response; even if @var{addr} is word-aligned
29651 and @var{length} is a multiple of the word size, the stub is free to
29652 use byte accesses, or not. For this reason, this packet may not be
29653 suitable for accessing memory-mapped I/O devices.
29654 @cindex alignment of remote memory accesses
29655 @cindex size of remote memory accesses
29656 @cindex memory, alignment and size of remote accesses
29660 @item @var{XX@dots{}}
29661 Memory contents; each byte is transmitted as a two-digit hexadecimal
29662 number. The reply may contain fewer bytes than requested if the
29663 server was able to read only part of the region of memory.
29668 @item M @var{addr},@var{length}:@var{XX@dots{}}
29669 @cindex @samp{M} packet
29670 Write @var{length} bytes of memory starting at address @var{addr}.
29671 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
29672 hexadecimal number.
29679 for an error (this includes the case where only part of the data was
29684 @cindex @samp{p} packet
29685 Read the value of register @var{n}; @var{n} is in hex.
29686 @xref{read registers packet}, for a description of how the returned
29687 register value is encoded.
29691 @item @var{XX@dots{}}
29692 the register's value
29696 Indicating an unrecognized @var{query}.
29699 @item P @var{n@dots{}}=@var{r@dots{}}
29700 @anchor{write register packet}
29701 @cindex @samp{P} packet
29702 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
29703 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
29704 digits for each byte in the register (target byte order).
29714 @item q @var{name} @var{params}@dots{}
29715 @itemx Q @var{name} @var{params}@dots{}
29716 @cindex @samp{q} packet
29717 @cindex @samp{Q} packet
29718 General query (@samp{q}) and set (@samp{Q}). These packets are
29719 described fully in @ref{General Query Packets}.
29722 @cindex @samp{r} packet
29723 Reset the entire system.
29725 Don't use this packet; use the @samp{R} packet instead.
29728 @cindex @samp{R} packet
29729 Restart the program being debugged. @var{XX}, while needed, is ignored.
29730 This packet is only available in extended mode (@pxref{extended mode}).
29732 The @samp{R} packet has no reply.
29734 @item s @r{[}@var{addr}@r{]}
29735 @cindex @samp{s} packet
29736 Single step. @var{addr} is the address at which to resume. If
29737 @var{addr} is omitted, resume at same address.
29740 @xref{Stop Reply Packets}, for the reply specifications.
29742 @item S @var{sig}@r{[};@var{addr}@r{]}
29743 @anchor{step with signal packet}
29744 @cindex @samp{S} packet
29745 Step with signal. This is analogous to the @samp{C} packet, but
29746 requests a single-step, rather than a normal resumption of execution.
29749 @xref{Stop Reply Packets}, for the reply specifications.
29751 @item t @var{addr}:@var{PP},@var{MM}
29752 @cindex @samp{t} packet
29753 Search backwards starting at address @var{addr} for a match with pattern
29754 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
29755 @var{addr} must be at least 3 digits.
29757 @item T @var{thread-id}
29758 @cindex @samp{T} packet
29759 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
29764 thread is still alive
29770 Packets starting with @samp{v} are identified by a multi-letter name,
29771 up to the first @samp{;} or @samp{?} (or the end of the packet).
29773 @item vAttach;@var{pid}
29774 @cindex @samp{vAttach} packet
29775 Attach to a new process with the specified process ID @var{pid}.
29776 The process ID is a
29777 hexadecimal integer identifying the process. In all-stop mode, all
29778 threads in the attached process are stopped; in non-stop mode, it may be
29779 attached without being stopped if that is supported by the target.
29781 @c In non-stop mode, on a successful vAttach, the stub should set the
29782 @c current thread to a thread of the newly-attached process. After
29783 @c attaching, GDB queries for the attached process's thread ID with qC.
29784 @c Also note that, from a user perspective, whether or not the
29785 @c target is stopped on attach in non-stop mode depends on whether you
29786 @c use the foreground or background version of the attach command, not
29787 @c on what vAttach does; GDB does the right thing with respect to either
29788 @c stopping or restarting threads.
29790 This packet is only available in extended mode (@pxref{extended mode}).
29796 @item @r{Any stop packet}
29797 for success in all-stop mode (@pxref{Stop Reply Packets})
29799 for success in non-stop mode (@pxref{Remote Non-Stop})
29802 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
29803 @cindex @samp{vCont} packet
29804 Resume the inferior, specifying different actions for each thread.
29805 If an action is specified with no @var{thread-id}, then it is applied to any
29806 threads that don't have a specific action specified; if no default action is
29807 specified then other threads should remain stopped in all-stop mode and
29808 in their current state in non-stop mode.
29809 Specifying multiple
29810 default actions is an error; specifying no actions is also an error.
29811 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
29813 Currently supported actions are:
29819 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
29823 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
29828 The optional argument @var{addr} normally associated with the
29829 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
29830 not supported in @samp{vCont}.
29832 The @samp{t} action is only relevant in non-stop mode
29833 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
29834 A stop reply should be generated for any affected thread not already stopped.
29835 When a thread is stopped by means of a @samp{t} action,
29836 the corresponding stop reply should indicate that the thread has stopped with
29837 signal @samp{0}, regardless of whether the target uses some other signal
29838 as an implementation detail.
29841 @xref{Stop Reply Packets}, for the reply specifications.
29844 @cindex @samp{vCont?} packet
29845 Request a list of actions supported by the @samp{vCont} packet.
29849 @item vCont@r{[};@var{action}@dots{}@r{]}
29850 The @samp{vCont} packet is supported. Each @var{action} is a supported
29851 command in the @samp{vCont} packet.
29853 The @samp{vCont} packet is not supported.
29856 @item vFile:@var{operation}:@var{parameter}@dots{}
29857 @cindex @samp{vFile} packet
29858 Perform a file operation on the target system. For details,
29859 see @ref{Host I/O Packets}.
29861 @item vFlashErase:@var{addr},@var{length}
29862 @cindex @samp{vFlashErase} packet
29863 Direct the stub to erase @var{length} bytes of flash starting at
29864 @var{addr}. The region may enclose any number of flash blocks, but
29865 its start and end must fall on block boundaries, as indicated by the
29866 flash block size appearing in the memory map (@pxref{Memory Map
29867 Format}). @value{GDBN} groups flash memory programming operations
29868 together, and sends a @samp{vFlashDone} request after each group; the
29869 stub is allowed to delay erase operation until the @samp{vFlashDone}
29870 packet is received.
29872 The stub must support @samp{vCont} if it reports support for
29873 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
29874 this case @samp{vCont} actions can be specified to apply to all threads
29875 in a process by using the @samp{p@var{pid}.-1} form of the
29886 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
29887 @cindex @samp{vFlashWrite} packet
29888 Direct the stub to write data to flash address @var{addr}. The data
29889 is passed in binary form using the same encoding as for the @samp{X}
29890 packet (@pxref{Binary Data}). The memory ranges specified by
29891 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
29892 not overlap, and must appear in order of increasing addresses
29893 (although @samp{vFlashErase} packets for higher addresses may already
29894 have been received; the ordering is guaranteed only between
29895 @samp{vFlashWrite} packets). If a packet writes to an address that was
29896 neither erased by a preceding @samp{vFlashErase} packet nor by some other
29897 target-specific method, the results are unpredictable.
29905 for vFlashWrite addressing non-flash memory
29911 @cindex @samp{vFlashDone} packet
29912 Indicate to the stub that flash programming operation is finished.
29913 The stub is permitted to delay or batch the effects of a group of
29914 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
29915 @samp{vFlashDone} packet is received. The contents of the affected
29916 regions of flash memory are unpredictable until the @samp{vFlashDone}
29917 request is completed.
29919 @item vKill;@var{pid}
29920 @cindex @samp{vKill} packet
29921 Kill the process with the specified process ID. @var{pid} is a
29922 hexadecimal integer identifying the process. This packet is used in
29923 preference to @samp{k} when multiprocess protocol extensions are
29924 supported; see @ref{multiprocess extensions}.
29934 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
29935 @cindex @samp{vRun} packet
29936 Run the program @var{filename}, passing it each @var{argument} on its
29937 command line. The file and arguments are hex-encoded strings. If
29938 @var{filename} is an empty string, the stub may use a default program
29939 (e.g.@: the last program run). The program is created in the stopped
29942 @c FIXME: What about non-stop mode?
29944 This packet is only available in extended mode (@pxref{extended mode}).
29950 @item @r{Any stop packet}
29951 for success (@pxref{Stop Reply Packets})
29955 @anchor{vStopped packet}
29956 @cindex @samp{vStopped} packet
29958 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
29959 reply and prompt for the stub to report another one.
29963 @item @r{Any stop packet}
29964 if there is another unreported stop event (@pxref{Stop Reply Packets})
29966 if there are no unreported stop events
29969 @item X @var{addr},@var{length}:@var{XX@dots{}}
29971 @cindex @samp{X} packet
29972 Write data to memory, where the data is transmitted in binary.
29973 @var{addr} is address, @var{length} is number of bytes,
29974 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
29984 @item z @var{type},@var{addr},@var{kind}
29985 @itemx Z @var{type},@var{addr},@var{kind}
29986 @anchor{insert breakpoint or watchpoint packet}
29987 @cindex @samp{z} packet
29988 @cindex @samp{Z} packets
29989 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
29990 watchpoint starting at address @var{address} of kind @var{kind}.
29992 Each breakpoint and watchpoint packet @var{type} is documented
29995 @emph{Implementation notes: A remote target shall return an empty string
29996 for an unrecognized breakpoint or watchpoint packet @var{type}. A
29997 remote target shall support either both or neither of a given
29998 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
29999 avoid potential problems with duplicate packets, the operations should
30000 be implemented in an idempotent way.}
30002 @item z0,@var{addr},@var{kind}
30003 @itemx Z0,@var{addr},@var{kind}
30004 @cindex @samp{z0} packet
30005 @cindex @samp{Z0} packet
30006 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
30007 @var{addr} of type @var{kind}.
30009 A memory breakpoint is implemented by replacing the instruction at
30010 @var{addr} with a software breakpoint or trap instruction. The
30011 @var{kind} is target-specific and typically indicates the size of
30012 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
30013 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
30014 architectures have additional meanings for @var{kind};
30015 see @ref{Architecture-Specific Protocol Details}.
30017 @emph{Implementation note: It is possible for a target to copy or move
30018 code that contains memory breakpoints (e.g., when implementing
30019 overlays). The behavior of this packet, in the presence of such a
30020 target, is not defined.}
30032 @item z1,@var{addr},@var{kind}
30033 @itemx Z1,@var{addr},@var{kind}
30034 @cindex @samp{z1} packet
30035 @cindex @samp{Z1} packet
30036 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
30037 address @var{addr}.
30039 A hardware breakpoint is implemented using a mechanism that is not
30040 dependant on being able to modify the target's memory. @var{kind}
30041 has the same meaning as in @samp{Z0} packets.
30043 @emph{Implementation note: A hardware breakpoint is not affected by code
30056 @item z2,@var{addr},@var{kind}
30057 @itemx Z2,@var{addr},@var{kind}
30058 @cindex @samp{z2} packet
30059 @cindex @samp{Z2} packet
30060 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
30061 @var{kind} is interpreted as the number of bytes to watch.
30073 @item z3,@var{addr},@var{kind}
30074 @itemx Z3,@var{addr},@var{kind}
30075 @cindex @samp{z3} packet
30076 @cindex @samp{Z3} packet
30077 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
30078 @var{kind} is interpreted as the number of bytes to watch.
30090 @item z4,@var{addr},@var{kind}
30091 @itemx Z4,@var{addr},@var{kind}
30092 @cindex @samp{z4} packet
30093 @cindex @samp{Z4} packet
30094 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
30095 @var{kind} is interpreted as the number of bytes to watch.
30109 @node Stop Reply Packets
30110 @section Stop Reply Packets
30111 @cindex stop reply packets
30113 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
30114 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
30115 receive any of the below as a reply. Except for @samp{?}
30116 and @samp{vStopped}, that reply is only returned
30117 when the target halts. In the below the exact meaning of @dfn{signal
30118 number} is defined by the header @file{include/gdb/signals.h} in the
30119 @value{GDBN} source code.
30121 As in the description of request packets, we include spaces in the
30122 reply templates for clarity; these are not part of the reply packet's
30123 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
30129 The program received signal number @var{AA} (a two-digit hexadecimal
30130 number). This is equivalent to a @samp{T} response with no
30131 @var{n}:@var{r} pairs.
30133 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
30134 @cindex @samp{T} packet reply
30135 The program received signal number @var{AA} (a two-digit hexadecimal
30136 number). This is equivalent to an @samp{S} response, except that the
30137 @samp{@var{n}:@var{r}} pairs can carry values of important registers
30138 and other information directly in the stop reply packet, reducing
30139 round-trip latency. Single-step and breakpoint traps are reported
30140 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
30144 If @var{n} is a hexadecimal number, it is a register number, and the
30145 corresponding @var{r} gives that register's value. @var{r} is a
30146 series of bytes in target byte order, with each byte given by a
30147 two-digit hex number.
30150 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
30151 the stopped thread, as specified in @ref{thread-id syntax}.
30154 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
30155 the core on which the stop event was detected.
30158 If @var{n} is a recognized @dfn{stop reason}, it describes a more
30159 specific event that stopped the target. The currently defined stop
30160 reasons are listed below. @var{aa} should be @samp{05}, the trap
30161 signal. At most one stop reason should be present.
30164 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
30165 and go on to the next; this allows us to extend the protocol in the
30169 The currently defined stop reasons are:
30175 The packet indicates a watchpoint hit, and @var{r} is the data address, in
30178 @cindex shared library events, remote reply
30180 The packet indicates that the loaded libraries have changed.
30181 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
30182 list of loaded libraries. @var{r} is ignored.
30184 @cindex replay log events, remote reply
30186 The packet indicates that the target cannot continue replaying
30187 logged execution events, because it has reached the end (or the
30188 beginning when executing backward) of the log. The value of @var{r}
30189 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
30190 for more information.
30194 @itemx W @var{AA} ; process:@var{pid}
30195 The process exited, and @var{AA} is the exit status. This is only
30196 applicable to certain targets.
30198 The second form of the response, including the process ID of the exited
30199 process, can be used only when @value{GDBN} has reported support for
30200 multiprocess protocol extensions; see @ref{multiprocess extensions}.
30201 The @var{pid} is formatted as a big-endian hex string.
30204 @itemx X @var{AA} ; process:@var{pid}
30205 The process terminated with signal @var{AA}.
30207 The second form of the response, including the process ID of the
30208 terminated process, can be used only when @value{GDBN} has reported
30209 support for multiprocess protocol extensions; see @ref{multiprocess
30210 extensions}. The @var{pid} is formatted as a big-endian hex string.
30212 @item O @var{XX}@dots{}
30213 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
30214 written as the program's console output. This can happen at any time
30215 while the program is running and the debugger should continue to wait
30216 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
30218 @item F @var{call-id},@var{parameter}@dots{}
30219 @var{call-id} is the identifier which says which host system call should
30220 be called. This is just the name of the function. Translation into the
30221 correct system call is only applicable as it's defined in @value{GDBN}.
30222 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
30225 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
30226 this very system call.
30228 The target replies with this packet when it expects @value{GDBN} to
30229 call a host system call on behalf of the target. @value{GDBN} replies
30230 with an appropriate @samp{F} packet and keeps up waiting for the next
30231 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
30232 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
30233 Protocol Extension}, for more details.
30237 @node General Query Packets
30238 @section General Query Packets
30239 @cindex remote query requests
30241 Packets starting with @samp{q} are @dfn{general query packets};
30242 packets starting with @samp{Q} are @dfn{general set packets}. General
30243 query and set packets are a semi-unified form for retrieving and
30244 sending information to and from the stub.
30246 The initial letter of a query or set packet is followed by a name
30247 indicating what sort of thing the packet applies to. For example,
30248 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
30249 definitions with the stub. These packet names follow some
30254 The name must not contain commas, colons or semicolons.
30256 Most @value{GDBN} query and set packets have a leading upper case
30259 The names of custom vendor packets should use a company prefix, in
30260 lower case, followed by a period. For example, packets designed at
30261 the Acme Corporation might begin with @samp{qacme.foo} (for querying
30262 foos) or @samp{Qacme.bar} (for setting bars).
30265 The name of a query or set packet should be separated from any
30266 parameters by a @samp{:}; the parameters themselves should be
30267 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
30268 full packet name, and check for a separator or the end of the packet,
30269 in case two packet names share a common prefix. New packets should not begin
30270 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
30271 packets predate these conventions, and have arguments without any terminator
30272 for the packet name; we suspect they are in widespread use in places that
30273 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
30274 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
30277 Like the descriptions of the other packets, each description here
30278 has a template showing the packet's overall syntax, followed by an
30279 explanation of the packet's meaning. We include spaces in some of the
30280 templates for clarity; these are not part of the packet's syntax. No
30281 @value{GDBN} packet uses spaces to separate its components.
30283 Here are the currently defined query and set packets:
30288 @cindex current thread, remote request
30289 @cindex @samp{qC} packet
30290 Return the current thread ID.
30294 @item QC @var{thread-id}
30295 Where @var{thread-id} is a thread ID as documented in
30296 @ref{thread-id syntax}.
30297 @item @r{(anything else)}
30298 Any other reply implies the old thread ID.
30301 @item qCRC:@var{addr},@var{length}
30302 @cindex CRC of memory block, remote request
30303 @cindex @samp{qCRC} packet
30304 Compute the CRC checksum of a block of memory using CRC-32 defined in
30305 IEEE 802.3. The CRC is computed byte at a time, taking the most
30306 significant bit of each byte first. The initial pattern code
30307 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
30309 @emph{Note:} This is the same CRC used in validating separate debug
30310 files (@pxref{Separate Debug Files, , Debugging Information in Separate
30311 Files}). However the algorithm is slightly different. When validating
30312 separate debug files, the CRC is computed taking the @emph{least}
30313 significant bit of each byte first, and the final result is inverted to
30314 detect trailing zeros.
30319 An error (such as memory fault)
30320 @item C @var{crc32}
30321 The specified memory region's checksum is @var{crc32}.
30325 @itemx qsThreadInfo
30326 @cindex list active threads, remote request
30327 @cindex @samp{qfThreadInfo} packet
30328 @cindex @samp{qsThreadInfo} packet
30329 Obtain a list of all active thread IDs from the target (OS). Since there
30330 may be too many active threads to fit into one reply packet, this query
30331 works iteratively: it may require more than one query/reply sequence to
30332 obtain the entire list of threads. The first query of the sequence will
30333 be the @samp{qfThreadInfo} query; subsequent queries in the
30334 sequence will be the @samp{qsThreadInfo} query.
30336 NOTE: This packet replaces the @samp{qL} query (see below).
30340 @item m @var{thread-id}
30342 @item m @var{thread-id},@var{thread-id}@dots{}
30343 a comma-separated list of thread IDs
30345 (lower case letter @samp{L}) denotes end of list.
30348 In response to each query, the target will reply with a list of one or
30349 more thread IDs, separated by commas.
30350 @value{GDBN} will respond to each reply with a request for more thread
30351 ids (using the @samp{qs} form of the query), until the target responds
30352 with @samp{l} (lower-case el, for @dfn{last}).
30353 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
30356 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
30357 @cindex get thread-local storage address, remote request
30358 @cindex @samp{qGetTLSAddr} packet
30359 Fetch the address associated with thread local storage specified
30360 by @var{thread-id}, @var{offset}, and @var{lm}.
30362 @var{thread-id} is the thread ID associated with the
30363 thread for which to fetch the TLS address. @xref{thread-id syntax}.
30365 @var{offset} is the (big endian, hex encoded) offset associated with the
30366 thread local variable. (This offset is obtained from the debug
30367 information associated with the variable.)
30369 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
30370 the load module associated with the thread local storage. For example,
30371 a @sc{gnu}/Linux system will pass the link map address of the shared
30372 object associated with the thread local storage under consideration.
30373 Other operating environments may choose to represent the load module
30374 differently, so the precise meaning of this parameter will vary.
30378 @item @var{XX}@dots{}
30379 Hex encoded (big endian) bytes representing the address of the thread
30380 local storage requested.
30383 An error occurred. @var{nn} are hex digits.
30386 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
30389 @item qL @var{startflag} @var{threadcount} @var{nextthread}
30390 Obtain thread information from RTOS. Where: @var{startflag} (one hex
30391 digit) is one to indicate the first query and zero to indicate a
30392 subsequent query; @var{threadcount} (two hex digits) is the maximum
30393 number of threads the response packet can contain; and @var{nextthread}
30394 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
30395 returned in the response as @var{argthread}.
30397 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
30401 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
30402 Where: @var{count} (two hex digits) is the number of threads being
30403 returned; @var{done} (one hex digit) is zero to indicate more threads
30404 and one indicates no further threads; @var{argthreadid} (eight hex
30405 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
30406 is a sequence of thread IDs from the target. @var{threadid} (eight hex
30407 digits). See @code{remote.c:parse_threadlist_response()}.
30411 @cindex section offsets, remote request
30412 @cindex @samp{qOffsets} packet
30413 Get section offsets that the target used when relocating the downloaded
30418 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
30419 Relocate the @code{Text} section by @var{xxx} from its original address.
30420 Relocate the @code{Data} section by @var{yyy} from its original address.
30421 If the object file format provides segment information (e.g.@: @sc{elf}
30422 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
30423 segments by the supplied offsets.
30425 @emph{Note: while a @code{Bss} offset may be included in the response,
30426 @value{GDBN} ignores this and instead applies the @code{Data} offset
30427 to the @code{Bss} section.}
30429 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
30430 Relocate the first segment of the object file, which conventionally
30431 contains program code, to a starting address of @var{xxx}. If
30432 @samp{DataSeg} is specified, relocate the second segment, which
30433 conventionally contains modifiable data, to a starting address of
30434 @var{yyy}. @value{GDBN} will report an error if the object file
30435 does not contain segment information, or does not contain at least
30436 as many segments as mentioned in the reply. Extra segments are
30437 kept at fixed offsets relative to the last relocated segment.
30440 @item qP @var{mode} @var{thread-id}
30441 @cindex thread information, remote request
30442 @cindex @samp{qP} packet
30443 Returns information on @var{thread-id}. Where: @var{mode} is a hex
30444 encoded 32 bit mode; @var{thread-id} is a thread ID
30445 (@pxref{thread-id syntax}).
30447 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
30450 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
30454 @cindex non-stop mode, remote request
30455 @cindex @samp{QNonStop} packet
30457 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
30458 @xref{Remote Non-Stop}, for more information.
30463 The request succeeded.
30466 An error occurred. @var{nn} are hex digits.
30469 An empty reply indicates that @samp{QNonStop} is not supported by
30473 This packet is not probed by default; the remote stub must request it,
30474 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30475 Use of this packet is controlled by the @code{set non-stop} command;
30476 @pxref{Non-Stop Mode}.
30478 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
30479 @cindex pass signals to inferior, remote request
30480 @cindex @samp{QPassSignals} packet
30481 @anchor{QPassSignals}
30482 Each listed @var{signal} should be passed directly to the inferior process.
30483 Signals are numbered identically to continue packets and stop replies
30484 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
30485 strictly greater than the previous item. These signals do not need to stop
30486 the inferior, or be reported to @value{GDBN}. All other signals should be
30487 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
30488 combine; any earlier @samp{QPassSignals} list is completely replaced by the
30489 new list. This packet improves performance when using @samp{handle
30490 @var{signal} nostop noprint pass}.
30495 The request succeeded.
30498 An error occurred. @var{nn} are hex digits.
30501 An empty reply indicates that @samp{QPassSignals} is not supported by
30505 Use of this packet is controlled by the @code{set remote pass-signals}
30506 command (@pxref{Remote Configuration, set remote pass-signals}).
30507 This packet is not probed by default; the remote stub must request it,
30508 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30510 @item qRcmd,@var{command}
30511 @cindex execute remote command, remote request
30512 @cindex @samp{qRcmd} packet
30513 @var{command} (hex encoded) is passed to the local interpreter for
30514 execution. Invalid commands should be reported using the output
30515 string. Before the final result packet, the target may also respond
30516 with a number of intermediate @samp{O@var{output}} console output
30517 packets. @emph{Implementors should note that providing access to a
30518 stubs's interpreter may have security implications}.
30523 A command response with no output.
30525 A command response with the hex encoded output string @var{OUTPUT}.
30527 Indicate a badly formed request.
30529 An empty reply indicates that @samp{qRcmd} is not recognized.
30532 (Note that the @code{qRcmd} packet's name is separated from the
30533 command by a @samp{,}, not a @samp{:}, contrary to the naming
30534 conventions above. Please don't use this packet as a model for new
30537 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
30538 @cindex searching memory, in remote debugging
30539 @cindex @samp{qSearch:memory} packet
30540 @anchor{qSearch memory}
30541 Search @var{length} bytes at @var{address} for @var{search-pattern}.
30542 @var{address} and @var{length} are encoded in hex.
30543 @var{search-pattern} is a sequence of bytes, hex encoded.
30548 The pattern was not found.
30550 The pattern was found at @var{address}.
30552 A badly formed request or an error was encountered while searching memory.
30554 An empty reply indicates that @samp{qSearch:memory} is not recognized.
30557 @item QStartNoAckMode
30558 @cindex @samp{QStartNoAckMode} packet
30559 @anchor{QStartNoAckMode}
30560 Request that the remote stub disable the normal @samp{+}/@samp{-}
30561 protocol acknowledgments (@pxref{Packet Acknowledgment}).
30566 The stub has switched to no-acknowledgment mode.
30567 @value{GDBN} acknowledges this reponse,
30568 but neither the stub nor @value{GDBN} shall send or expect further
30569 @samp{+}/@samp{-} acknowledgments in the current connection.
30571 An empty reply indicates that the stub does not support no-acknowledgment mode.
30574 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
30575 @cindex supported packets, remote query
30576 @cindex features of the remote protocol
30577 @cindex @samp{qSupported} packet
30578 @anchor{qSupported}
30579 Tell the remote stub about features supported by @value{GDBN}, and
30580 query the stub for features it supports. This packet allows
30581 @value{GDBN} and the remote stub to take advantage of each others'
30582 features. @samp{qSupported} also consolidates multiple feature probes
30583 at startup, to improve @value{GDBN} performance---a single larger
30584 packet performs better than multiple smaller probe packets on
30585 high-latency links. Some features may enable behavior which must not
30586 be on by default, e.g.@: because it would confuse older clients or
30587 stubs. Other features may describe packets which could be
30588 automatically probed for, but are not. These features must be
30589 reported before @value{GDBN} will use them. This ``default
30590 unsupported'' behavior is not appropriate for all packets, but it
30591 helps to keep the initial connection time under control with new
30592 versions of @value{GDBN} which support increasing numbers of packets.
30596 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
30597 The stub supports or does not support each returned @var{stubfeature},
30598 depending on the form of each @var{stubfeature} (see below for the
30601 An empty reply indicates that @samp{qSupported} is not recognized,
30602 or that no features needed to be reported to @value{GDBN}.
30605 The allowed forms for each feature (either a @var{gdbfeature} in the
30606 @samp{qSupported} packet, or a @var{stubfeature} in the response)
30610 @item @var{name}=@var{value}
30611 The remote protocol feature @var{name} is supported, and associated
30612 with the specified @var{value}. The format of @var{value} depends
30613 on the feature, but it must not include a semicolon.
30615 The remote protocol feature @var{name} is supported, and does not
30616 need an associated value.
30618 The remote protocol feature @var{name} is not supported.
30620 The remote protocol feature @var{name} may be supported, and
30621 @value{GDBN} should auto-detect support in some other way when it is
30622 needed. This form will not be used for @var{gdbfeature} notifications,
30623 but may be used for @var{stubfeature} responses.
30626 Whenever the stub receives a @samp{qSupported} request, the
30627 supplied set of @value{GDBN} features should override any previous
30628 request. This allows @value{GDBN} to put the stub in a known
30629 state, even if the stub had previously been communicating with
30630 a different version of @value{GDBN}.
30632 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
30637 This feature indicates whether @value{GDBN} supports multiprocess
30638 extensions to the remote protocol. @value{GDBN} does not use such
30639 extensions unless the stub also reports that it supports them by
30640 including @samp{multiprocess+} in its @samp{qSupported} reply.
30641 @xref{multiprocess extensions}, for details.
30644 This feature indicates that @value{GDBN} supports the XML target
30645 description. If the stub sees @samp{xmlRegisters=} with target
30646 specific strings separated by a comma, it will report register
30650 Stubs should ignore any unknown values for
30651 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
30652 packet supports receiving packets of unlimited length (earlier
30653 versions of @value{GDBN} may reject overly long responses). Additional values
30654 for @var{gdbfeature} may be defined in the future to let the stub take
30655 advantage of new features in @value{GDBN}, e.g.@: incompatible
30656 improvements in the remote protocol---the @samp{multiprocess} feature is
30657 an example of such a feature. The stub's reply should be independent
30658 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
30659 describes all the features it supports, and then the stub replies with
30660 all the features it supports.
30662 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
30663 responses, as long as each response uses one of the standard forms.
30665 Some features are flags. A stub which supports a flag feature
30666 should respond with a @samp{+} form response. Other features
30667 require values, and the stub should respond with an @samp{=}
30670 Each feature has a default value, which @value{GDBN} will use if
30671 @samp{qSupported} is not available or if the feature is not mentioned
30672 in the @samp{qSupported} response. The default values are fixed; a
30673 stub is free to omit any feature responses that match the defaults.
30675 Not all features can be probed, but for those which can, the probing
30676 mechanism is useful: in some cases, a stub's internal
30677 architecture may not allow the protocol layer to know some information
30678 about the underlying target in advance. This is especially common in
30679 stubs which may be configured for multiple targets.
30681 These are the currently defined stub features and their properties:
30683 @multitable @columnfractions 0.35 0.2 0.12 0.2
30684 @c NOTE: The first row should be @headitem, but we do not yet require
30685 @c a new enough version of Texinfo (4.7) to use @headitem.
30687 @tab Value Required
30691 @item @samp{PacketSize}
30696 @item @samp{qXfer:auxv:read}
30701 @item @samp{qXfer:features:read}
30706 @item @samp{qXfer:libraries:read}
30711 @item @samp{qXfer:memory-map:read}
30716 @item @samp{qXfer:spu:read}
30721 @item @samp{qXfer:spu:write}
30726 @item @samp{qXfer:siginfo:read}
30731 @item @samp{qXfer:siginfo:write}
30736 @item @samp{qXfer:threads:read}
30742 @item @samp{QNonStop}
30747 @item @samp{QPassSignals}
30752 @item @samp{QStartNoAckMode}
30757 @item @samp{multiprocess}
30762 @item @samp{ConditionalTracepoints}
30767 @item @samp{ReverseContinue}
30772 @item @samp{ReverseStep}
30777 @item @samp{TracepointSource}
30784 These are the currently defined stub features, in more detail:
30787 @cindex packet size, remote protocol
30788 @item PacketSize=@var{bytes}
30789 The remote stub can accept packets up to at least @var{bytes} in
30790 length. @value{GDBN} will send packets up to this size for bulk
30791 transfers, and will never send larger packets. This is a limit on the
30792 data characters in the packet, including the frame and checksum.
30793 There is no trailing NUL byte in a remote protocol packet; if the stub
30794 stores packets in a NUL-terminated format, it should allow an extra
30795 byte in its buffer for the NUL. If this stub feature is not supported,
30796 @value{GDBN} guesses based on the size of the @samp{g} packet response.
30798 @item qXfer:auxv:read
30799 The remote stub understands the @samp{qXfer:auxv:read} packet
30800 (@pxref{qXfer auxiliary vector read}).
30802 @item qXfer:features:read
30803 The remote stub understands the @samp{qXfer:features:read} packet
30804 (@pxref{qXfer target description read}).
30806 @item qXfer:libraries:read
30807 The remote stub understands the @samp{qXfer:libraries:read} packet
30808 (@pxref{qXfer library list read}).
30810 @item qXfer:memory-map:read
30811 The remote stub understands the @samp{qXfer:memory-map:read} packet
30812 (@pxref{qXfer memory map read}).
30814 @item qXfer:spu:read
30815 The remote stub understands the @samp{qXfer:spu:read} packet
30816 (@pxref{qXfer spu read}).
30818 @item qXfer:spu:write
30819 The remote stub understands the @samp{qXfer:spu:write} packet
30820 (@pxref{qXfer spu write}).
30822 @item qXfer:siginfo:read
30823 The remote stub understands the @samp{qXfer:siginfo:read} packet
30824 (@pxref{qXfer siginfo read}).
30826 @item qXfer:siginfo:write
30827 The remote stub understands the @samp{qXfer:siginfo:write} packet
30828 (@pxref{qXfer siginfo write}).
30830 @item qXfer:threads:read
30831 The remote stub understands the @samp{qXfer:threads:read} packet
30832 (@pxref{qXfer threads read}).
30835 The remote stub understands the @samp{QNonStop} packet
30836 (@pxref{QNonStop}).
30839 The remote stub understands the @samp{QPassSignals} packet
30840 (@pxref{QPassSignals}).
30842 @item QStartNoAckMode
30843 The remote stub understands the @samp{QStartNoAckMode} packet and
30844 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
30847 @anchor{multiprocess extensions}
30848 @cindex multiprocess extensions, in remote protocol
30849 The remote stub understands the multiprocess extensions to the remote
30850 protocol syntax. The multiprocess extensions affect the syntax of
30851 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
30852 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
30853 replies. Note that reporting this feature indicates support for the
30854 syntactic extensions only, not that the stub necessarily supports
30855 debugging of more than one process at a time. The stub must not use
30856 multiprocess extensions in packet replies unless @value{GDBN} has also
30857 indicated it supports them in its @samp{qSupported} request.
30859 @item qXfer:osdata:read
30860 The remote stub understands the @samp{qXfer:osdata:read} packet
30861 ((@pxref{qXfer osdata read}).
30863 @item ConditionalTracepoints
30864 The remote stub accepts and implements conditional expressions defined
30865 for tracepoints (@pxref{Tracepoint Conditions}).
30867 @item ReverseContinue
30868 The remote stub accepts and implements the reverse continue packet
30872 The remote stub accepts and implements the reverse step packet
30875 @item TracepointSource
30876 The remote stub understands the @samp{QTDPsrc} packet that supplies
30877 the source form of tracepoint definitions.
30882 @cindex symbol lookup, remote request
30883 @cindex @samp{qSymbol} packet
30884 Notify the target that @value{GDBN} is prepared to serve symbol lookup
30885 requests. Accept requests from the target for the values of symbols.
30890 The target does not need to look up any (more) symbols.
30891 @item qSymbol:@var{sym_name}
30892 The target requests the value of symbol @var{sym_name} (hex encoded).
30893 @value{GDBN} may provide the value by using the
30894 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
30898 @item qSymbol:@var{sym_value}:@var{sym_name}
30899 Set the value of @var{sym_name} to @var{sym_value}.
30901 @var{sym_name} (hex encoded) is the name of a symbol whose value the
30902 target has previously requested.
30904 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
30905 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
30911 The target does not need to look up any (more) symbols.
30912 @item qSymbol:@var{sym_name}
30913 The target requests the value of a new symbol @var{sym_name} (hex
30914 encoded). @value{GDBN} will continue to supply the values of symbols
30915 (if available), until the target ceases to request them.
30920 @item QTDisconnected
30927 @xref{Tracepoint Packets}.
30929 @item qThreadExtraInfo,@var{thread-id}
30930 @cindex thread attributes info, remote request
30931 @cindex @samp{qThreadExtraInfo} packet
30932 Obtain a printable string description of a thread's attributes from
30933 the target OS. @var{thread-id} is a thread ID;
30934 see @ref{thread-id syntax}. This
30935 string may contain anything that the target OS thinks is interesting
30936 for @value{GDBN} to tell the user about the thread. The string is
30937 displayed in @value{GDBN}'s @code{info threads} display. Some
30938 examples of possible thread extra info strings are @samp{Runnable}, or
30939 @samp{Blocked on Mutex}.
30943 @item @var{XX}@dots{}
30944 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
30945 comprising the printable string containing the extra information about
30946 the thread's attributes.
30949 (Note that the @code{qThreadExtraInfo} packet's name is separated from
30950 the command by a @samp{,}, not a @samp{:}, contrary to the naming
30951 conventions above. Please don't use this packet as a model for new
30963 @xref{Tracepoint Packets}.
30965 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
30966 @cindex read special object, remote request
30967 @cindex @samp{qXfer} packet
30968 @anchor{qXfer read}
30969 Read uninterpreted bytes from the target's special data area
30970 identified by the keyword @var{object}. Request @var{length} bytes
30971 starting at @var{offset} bytes into the data. The content and
30972 encoding of @var{annex} is specific to @var{object}; it can supply
30973 additional details about what data to access.
30975 Here are the specific requests of this form defined so far. All
30976 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
30977 formats, listed below.
30980 @item qXfer:auxv:read::@var{offset},@var{length}
30981 @anchor{qXfer auxiliary vector read}
30982 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
30983 auxiliary vector}. Note @var{annex} must be empty.
30985 This packet is not probed by default; the remote stub must request it,
30986 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30988 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
30989 @anchor{qXfer target description read}
30990 Access the @dfn{target description}. @xref{Target Descriptions}. The
30991 annex specifies which XML document to access. The main description is
30992 always loaded from the @samp{target.xml} annex.
30994 This packet is not probed by default; the remote stub must request it,
30995 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30997 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
30998 @anchor{qXfer library list read}
30999 Access the target's list of loaded libraries. @xref{Library List Format}.
31000 The annex part of the generic @samp{qXfer} packet must be empty
31001 (@pxref{qXfer read}).
31003 Targets which maintain a list of libraries in the program's memory do
31004 not need to implement this packet; it is designed for platforms where
31005 the operating system manages the list of loaded libraries.
31007 This packet is not probed by default; the remote stub must request it,
31008 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31010 @item qXfer:memory-map:read::@var{offset},@var{length}
31011 @anchor{qXfer memory map read}
31012 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
31013 annex part of the generic @samp{qXfer} packet must be empty
31014 (@pxref{qXfer read}).
31016 This packet is not probed by default; the remote stub must request it,
31017 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31019 @item qXfer:siginfo:read::@var{offset},@var{length}
31020 @anchor{qXfer siginfo read}
31021 Read contents of the extra signal information on the target
31022 system. The annex part of the generic @samp{qXfer} packet must be
31023 empty (@pxref{qXfer read}).
31025 This packet is not probed by default; the remote stub must request it,
31026 by supplying an appropriate @samp{qSupported} response
31027 (@pxref{qSupported}).
31029 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
31030 @anchor{qXfer spu read}
31031 Read contents of an @code{spufs} file on the target system. The
31032 annex specifies which file to read; it must be of the form
31033 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31034 in the target process, and @var{name} identifes the @code{spufs} file
31035 in that context to be accessed.
31037 This packet is not probed by default; the remote stub must request it,
31038 by supplying an appropriate @samp{qSupported} response
31039 (@pxref{qSupported}).
31041 @item qXfer:threads:read::@var{offset},@var{length}
31042 @anchor{qXfer threads read}
31043 Access the list of threads on target. @xref{Thread List Format}. The
31044 annex part of the generic @samp{qXfer} packet must be empty
31045 (@pxref{qXfer read}).
31047 This packet is not probed by default; the remote stub must request it,
31048 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31050 @item qXfer:osdata:read::@var{offset},@var{length}
31051 @anchor{qXfer osdata read}
31052 Access the target's @dfn{operating system information}.
31053 @xref{Operating System Information}.
31060 Data @var{data} (@pxref{Binary Data}) has been read from the
31061 target. There may be more data at a higher address (although
31062 it is permitted to return @samp{m} even for the last valid
31063 block of data, as long as at least one byte of data was read).
31064 @var{data} may have fewer bytes than the @var{length} in the
31068 Data @var{data} (@pxref{Binary Data}) has been read from the target.
31069 There is no more data to be read. @var{data} may have fewer bytes
31070 than the @var{length} in the request.
31073 The @var{offset} in the request is at the end of the data.
31074 There is no more data to be read.
31077 The request was malformed, or @var{annex} was invalid.
31080 The offset was invalid, or there was an error encountered reading the data.
31081 @var{nn} is a hex-encoded @code{errno} value.
31084 An empty reply indicates the @var{object} string was not recognized by
31085 the stub, or that the object does not support reading.
31088 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
31089 @cindex write data into object, remote request
31090 @anchor{qXfer write}
31091 Write uninterpreted bytes into the target's special data area
31092 identified by the keyword @var{object}, starting at @var{offset} bytes
31093 into the data. @var{data}@dots{} is the binary-encoded data
31094 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
31095 is specific to @var{object}; it can supply additional details about what data
31098 Here are the specific requests of this form defined so far. All
31099 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
31100 formats, listed below.
31103 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
31104 @anchor{qXfer siginfo write}
31105 Write @var{data} to the extra signal information on the target system.
31106 The annex part of the generic @samp{qXfer} packet must be
31107 empty (@pxref{qXfer write}).
31109 This packet is not probed by default; the remote stub must request it,
31110 by supplying an appropriate @samp{qSupported} response
31111 (@pxref{qSupported}).
31113 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
31114 @anchor{qXfer spu write}
31115 Write @var{data} to an @code{spufs} file on the target system. The
31116 annex specifies which file to write; it must be of the form
31117 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31118 in the target process, and @var{name} identifes the @code{spufs} file
31119 in that context to be accessed.
31121 This packet is not probed by default; the remote stub must request it,
31122 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31128 @var{nn} (hex encoded) is the number of bytes written.
31129 This may be fewer bytes than supplied in the request.
31132 The request was malformed, or @var{annex} was invalid.
31135 The offset was invalid, or there was an error encountered writing the data.
31136 @var{nn} is a hex-encoded @code{errno} value.
31139 An empty reply indicates the @var{object} string was not
31140 recognized by the stub, or that the object does not support writing.
31143 @item qXfer:@var{object}:@var{operation}:@dots{}
31144 Requests of this form may be added in the future. When a stub does
31145 not recognize the @var{object} keyword, or its support for
31146 @var{object} does not recognize the @var{operation} keyword, the stub
31147 must respond with an empty packet.
31149 @item qAttached:@var{pid}
31150 @cindex query attached, remote request
31151 @cindex @samp{qAttached} packet
31152 Return an indication of whether the remote server attached to an
31153 existing process or created a new process. When the multiprocess
31154 protocol extensions are supported (@pxref{multiprocess extensions}),
31155 @var{pid} is an integer in hexadecimal format identifying the target
31156 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
31157 the query packet will be simplified as @samp{qAttached}.
31159 This query is used, for example, to know whether the remote process
31160 should be detached or killed when a @value{GDBN} session is ended with
31161 the @code{quit} command.
31166 The remote server attached to an existing process.
31168 The remote server created a new process.
31170 A badly formed request or an error was encountered.
31175 @node Architecture-Specific Protocol Details
31176 @section Architecture-Specific Protocol Details
31178 This section describes how the remote protocol is applied to specific
31179 target architectures. Also see @ref{Standard Target Features}, for
31180 details of XML target descriptions for each architecture.
31184 @subsubsection Breakpoint Kinds
31186 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
31191 16-bit Thumb mode breakpoint.
31194 32-bit Thumb mode (Thumb-2) breakpoint.
31197 32-bit ARM mode breakpoint.
31203 @subsubsection Register Packet Format
31205 The following @code{g}/@code{G} packets have previously been defined.
31206 In the below, some thirty-two bit registers are transferred as
31207 sixty-four bits. Those registers should be zero/sign extended (which?)
31208 to fill the space allocated. Register bytes are transferred in target
31209 byte order. The two nibbles within a register byte are transferred
31210 most-significant - least-significant.
31216 All registers are transferred as thirty-two bit quantities in the order:
31217 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
31218 registers; fsr; fir; fp.
31222 All registers are transferred as sixty-four bit quantities (including
31223 thirty-two bit registers such as @code{sr}). The ordering is the same
31228 @node Tracepoint Packets
31229 @section Tracepoint Packets
31230 @cindex tracepoint packets
31231 @cindex packets, tracepoint
31233 Here we describe the packets @value{GDBN} uses to implement
31234 tracepoints (@pxref{Tracepoints}).
31238 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
31239 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
31240 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
31241 the tracepoint is disabled. @var{step} is the tracepoint's step
31242 count, and @var{pass} is its pass count. If an @samp{F} is present,
31243 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
31244 the number of bytes that the target should copy elsewhere to make room
31245 for the tracepoint. If an @samp{X} is present, it introduces a
31246 tracepoint condition, which consists of a hexadecimal length, followed
31247 by a comma and hex-encoded bytes, in a manner similar to action
31248 encodings as described below. If the trailing @samp{-} is present,
31249 further @samp{QTDP} packets will follow to specify this tracepoint's
31255 The packet was understood and carried out.
31257 The packet was not recognized.
31260 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
31261 Define actions to be taken when a tracepoint is hit. @var{n} and
31262 @var{addr} must be the same as in the initial @samp{QTDP} packet for
31263 this tracepoint. This packet may only be sent immediately after
31264 another @samp{QTDP} packet that ended with a @samp{-}. If the
31265 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
31266 specifying more actions for this tracepoint.
31268 In the series of action packets for a given tracepoint, at most one
31269 can have an @samp{S} before its first @var{action}. If such a packet
31270 is sent, it and the following packets define ``while-stepping''
31271 actions. Any prior packets define ordinary actions --- that is, those
31272 taken when the tracepoint is first hit. If no action packet has an
31273 @samp{S}, then all the packets in the series specify ordinary
31274 tracepoint actions.
31276 The @samp{@var{action}@dots{}} portion of the packet is a series of
31277 actions, concatenated without separators. Each action has one of the
31283 Collect the registers whose bits are set in @var{mask}. @var{mask} is
31284 a hexadecimal number whose @var{i}'th bit is set if register number
31285 @var{i} should be collected. (The least significant bit is numbered
31286 zero.) Note that @var{mask} may be any number of digits long; it may
31287 not fit in a 32-bit word.
31289 @item M @var{basereg},@var{offset},@var{len}
31290 Collect @var{len} bytes of memory starting at the address in register
31291 number @var{basereg}, plus @var{offset}. If @var{basereg} is
31292 @samp{-1}, then the range has a fixed address: @var{offset} is the
31293 address of the lowest byte to collect. The @var{basereg},
31294 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
31295 values (the @samp{-1} value for @var{basereg} is a special case).
31297 @item X @var{len},@var{expr}
31298 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
31299 it directs. @var{expr} is an agent expression, as described in
31300 @ref{Agent Expressions}. Each byte of the expression is encoded as a
31301 two-digit hex number in the packet; @var{len} is the number of bytes
31302 in the expression (and thus one-half the number of hex digits in the
31307 Any number of actions may be packed together in a single @samp{QTDP}
31308 packet, as long as the packet does not exceed the maximum packet
31309 length (400 bytes, for many stubs). There may be only one @samp{R}
31310 action per tracepoint, and it must precede any @samp{M} or @samp{X}
31311 actions. Any registers referred to by @samp{M} and @samp{X} actions
31312 must be collected by a preceding @samp{R} action. (The
31313 ``while-stepping'' actions are treated as if they were attached to a
31314 separate tracepoint, as far as these restrictions are concerned.)
31319 The packet was understood and carried out.
31321 The packet was not recognized.
31324 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
31325 @cindex @samp{QTDPsrc} packet
31326 Specify a source string of tracepoint @var{n} at address @var{addr}.
31327 This is useful to get accurate reproduction of the tracepoints
31328 originally downloaded at the beginning of the trace run. @var{type}
31329 is the name of the tracepoint part, such as @samp{cond} for the
31330 tracepoint's conditional expression (see below for a list of types), while
31331 @var{bytes} is the string, encoded in hexadecimal.
31333 @var{start} is the offset of the @var{bytes} within the overall source
31334 string, while @var{slen} is the total length of the source string.
31335 This is intended for handling source strings that are longer than will
31336 fit in a single packet.
31337 @c Add detailed example when this info is moved into a dedicated
31338 @c tracepoint descriptions section.
31340 The available string types are @samp{at} for the location,
31341 @samp{cond} for the conditional, and @samp{cmd} for an action command.
31342 @value{GDBN} sends a separate packet for each command in the action
31343 list, in the same order in which the commands are stored in the list.
31345 The target does not need to do anything with source strings except
31346 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
31349 Although this packet is optional, and @value{GDBN} will only send it
31350 if the target replies with @samp{TracepointSource} @xref{General
31351 Query Packets}, it makes both disconnected tracing and trace files
31352 much easier to use. Otherwise the user must be careful that the
31353 tracepoints in effect while looking at trace frames are identical to
31354 the ones in effect during the trace run; even a small discrepancy
31355 could cause @samp{tdump} not to work, or a particular trace frame not
31358 @item QTDV:@var{n}:@var{value}
31359 @cindex define trace state variable, remote request
31360 @cindex @samp{QTDV} packet
31361 Create a new trace state variable, number @var{n}, with an initial
31362 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
31363 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
31364 the option of not using this packet for initial values of zero; the
31365 target should simply create the trace state variables as they are
31366 mentioned in expressions.
31368 @item QTFrame:@var{n}
31369 Select the @var{n}'th tracepoint frame from the buffer, and use the
31370 register and memory contents recorded there to answer subsequent
31371 request packets from @value{GDBN}.
31373 A successful reply from the stub indicates that the stub has found the
31374 requested frame. The response is a series of parts, concatenated
31375 without separators, describing the frame we selected. Each part has
31376 one of the following forms:
31380 The selected frame is number @var{n} in the trace frame buffer;
31381 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
31382 was no frame matching the criteria in the request packet.
31385 The selected trace frame records a hit of tracepoint number @var{t};
31386 @var{t} is a hexadecimal number.
31390 @item QTFrame:pc:@var{addr}
31391 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31392 currently selected frame whose PC is @var{addr};
31393 @var{addr} is a hexadecimal number.
31395 @item QTFrame:tdp:@var{t}
31396 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31397 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
31398 is a hexadecimal number.
31400 @item QTFrame:range:@var{start}:@var{end}
31401 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31402 currently selected frame whose PC is between @var{start} (inclusive)
31403 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
31406 @item QTFrame:outside:@var{start}:@var{end}
31407 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
31408 frame @emph{outside} the given range of addresses (exclusive).
31411 Begin the tracepoint experiment. Begin collecting data from tracepoint
31412 hits in the trace frame buffer.
31415 End the tracepoint experiment. Stop collecting trace frames.
31418 Clear the table of tracepoints, and empty the trace frame buffer.
31420 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
31421 Establish the given ranges of memory as ``transparent''. The stub
31422 will answer requests for these ranges from memory's current contents,
31423 if they were not collected as part of the tracepoint hit.
31425 @value{GDBN} uses this to mark read-only regions of memory, like those
31426 containing program code. Since these areas never change, they should
31427 still have the same contents they did when the tracepoint was hit, so
31428 there's no reason for the stub to refuse to provide their contents.
31430 @item QTDisconnected:@var{value}
31431 Set the choice to what to do with the tracing run when @value{GDBN}
31432 disconnects from the target. A @var{value} of 1 directs the target to
31433 continue the tracing run, while 0 tells the target to stop tracing if
31434 @value{GDBN} is no longer in the picture.
31437 Ask the stub if there is a trace experiment running right now.
31439 The reply has the form:
31443 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
31444 @var{running} is a single digit @code{1} if the trace is presently
31445 running, or @code{0} if not. It is followed by semicolon-separated
31446 optional fields that an agent may use to report additional status.
31450 If the trace is not running, the agent may report any of several
31451 explanations as one of the optional fields:
31456 No trace has been run yet.
31459 The trace was stopped by a user-originated stop command.
31462 The trace stopped because the trace buffer filled up.
31464 @item tdisconnected:0
31465 The trace stopped because @value{GDBN} disconnected from the target.
31467 @item tpasscount:@var{tpnum}
31468 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
31470 @item terror:@var{text}:@var{tpnum}
31471 The trace stopped because tracepoint @var{tpnum} had an error. The
31472 string @var{text} is available to describe the nature of the error
31473 (for instance, a divide by zero in the condition expression).
31474 @var{text} is hex encoded.
31477 The trace stopped for some other reason.
31481 Additional optional fields supply statistical information. Although
31482 not required, they are extremely useful for users monitoring the
31483 progress of a trace run. If a trace has stopped, and these numbers
31484 are reported, they must reflect the state of the just-stopped trace.
31488 @item tframes:@var{n}
31489 The number of trace frames in the buffer.
31491 @item tcreated:@var{n}
31492 The total number of trace frames created during the run. This may
31493 be larger than the trace frame count, if the buffer is circular.
31495 @item tsize:@var{n}
31496 The total size of the trace buffer, in bytes.
31498 @item tfree:@var{n}
31499 The number of bytes still unused in the buffer.
31503 @item qTV:@var{var}
31504 @cindex trace state variable value, remote request
31505 @cindex @samp{qTV} packet
31506 Ask the stub for the value of the trace state variable number @var{var}.
31511 The value of the variable is @var{value}. This will be the current
31512 value of the variable if the user is examining a running target, or a
31513 saved value if the variable was collected in the trace frame that the
31514 user is looking at. Note that multiple requests may result in
31515 different reply values, such as when requesting values while the
31516 program is running.
31519 The value of the variable is unknown. This would occur, for example,
31520 if the user is examining a trace frame in which the requested variable
31526 These packets request data about tracepoints that are being used by
31527 the target. @value{GDBN} sends @code{qTfP} to get the first piece
31528 of data, and multiple @code{qTsP} to get additional pieces. Replies
31529 to these packets generally take the form of the @code{QTDP} packets
31530 that define tracepoints. (FIXME add detailed syntax)
31534 These packets request data about trace state variables that are on the
31535 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
31536 and multiple @code{qTsV} to get additional variables. Replies to
31537 these packets follow the syntax of the @code{QTDV} packets that define
31538 trace state variables.
31540 @item QTSave:@var{filename}
31541 This packet directs the target to save trace data to the file name
31542 @var{filename} in the target's filesystem. @var{filename} is encoded
31543 as a hex string; the interpretation of the file name (relative vs
31544 absolute, wild cards, etc) is up to the target.
31546 @item qTBuffer:@var{offset},@var{len}
31547 Return up to @var{len} bytes of the current contents of trace buffer,
31548 starting at @var{offset}. The trace buffer is treated as if it were
31549 a contiguous collection of traceframes, as per the trace file format.
31550 The reply consists as many hex-encoded bytes as the target can deliver
31551 in a packet; it is not an error to return fewer than were asked for.
31552 A reply consisting of just @code{l} indicates that no bytes are
31555 @item QTBuffer:circular:@var{value}
31556 This packet directs the target to use a circular trace buffer if
31557 @var{value} is 1, or a linear buffer if the value is 0.
31561 @node Host I/O Packets
31562 @section Host I/O Packets
31563 @cindex Host I/O, remote protocol
31564 @cindex file transfer, remote protocol
31566 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
31567 operations on the far side of a remote link. For example, Host I/O is
31568 used to upload and download files to a remote target with its own
31569 filesystem. Host I/O uses the same constant values and data structure
31570 layout as the target-initiated File-I/O protocol. However, the
31571 Host I/O packets are structured differently. The target-initiated
31572 protocol relies on target memory to store parameters and buffers.
31573 Host I/O requests are initiated by @value{GDBN}, and the
31574 target's memory is not involved. @xref{File-I/O Remote Protocol
31575 Extension}, for more details on the target-initiated protocol.
31577 The Host I/O request packets all encode a single operation along with
31578 its arguments. They have this format:
31582 @item vFile:@var{operation}: @var{parameter}@dots{}
31583 @var{operation} is the name of the particular request; the target
31584 should compare the entire packet name up to the second colon when checking
31585 for a supported operation. The format of @var{parameter} depends on
31586 the operation. Numbers are always passed in hexadecimal. Negative
31587 numbers have an explicit minus sign (i.e.@: two's complement is not
31588 used). Strings (e.g.@: filenames) are encoded as a series of
31589 hexadecimal bytes. The last argument to a system call may be a
31590 buffer of escaped binary data (@pxref{Binary Data}).
31594 The valid responses to Host I/O packets are:
31598 @item F @var{result} [, @var{errno}] [; @var{attachment}]
31599 @var{result} is the integer value returned by this operation, usually
31600 non-negative for success and -1 for errors. If an error has occured,
31601 @var{errno} will be included in the result. @var{errno} will have a
31602 value defined by the File-I/O protocol (@pxref{Errno Values}). For
31603 operations which return data, @var{attachment} supplies the data as a
31604 binary buffer. Binary buffers in response packets are escaped in the
31605 normal way (@pxref{Binary Data}). See the individual packet
31606 documentation for the interpretation of @var{result} and
31610 An empty response indicates that this operation is not recognized.
31614 These are the supported Host I/O operations:
31617 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
31618 Open a file at @var{pathname} and return a file descriptor for it, or
31619 return -1 if an error occurs. @var{pathname} is a string,
31620 @var{flags} is an integer indicating a mask of open flags
31621 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
31622 of mode bits to use if the file is created (@pxref{mode_t Values}).
31623 @xref{open}, for details of the open flags and mode values.
31625 @item vFile:close: @var{fd}
31626 Close the open file corresponding to @var{fd} and return 0, or
31627 -1 if an error occurs.
31629 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
31630 Read data from the open file corresponding to @var{fd}. Up to
31631 @var{count} bytes will be read from the file, starting at @var{offset}
31632 relative to the start of the file. The target may read fewer bytes;
31633 common reasons include packet size limits and an end-of-file
31634 condition. The number of bytes read is returned. Zero should only be
31635 returned for a successful read at the end of the file, or if
31636 @var{count} was zero.
31638 The data read should be returned as a binary attachment on success.
31639 If zero bytes were read, the response should include an empty binary
31640 attachment (i.e.@: a trailing semicolon). The return value is the
31641 number of target bytes read; the binary attachment may be longer if
31642 some characters were escaped.
31644 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
31645 Write @var{data} (a binary buffer) to the open file corresponding
31646 to @var{fd}. Start the write at @var{offset} from the start of the
31647 file. Unlike many @code{write} system calls, there is no
31648 separate @var{count} argument; the length of @var{data} in the
31649 packet is used. @samp{vFile:write} returns the number of bytes written,
31650 which may be shorter than the length of @var{data}, or -1 if an
31653 @item vFile:unlink: @var{pathname}
31654 Delete the file at @var{pathname} on the target. Return 0,
31655 or -1 if an error occurs. @var{pathname} is a string.
31660 @section Interrupts
31661 @cindex interrupts (remote protocol)
31663 When a program on the remote target is running, @value{GDBN} may
31664 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
31665 a @code{BREAK} followed by @code{g},
31666 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
31668 The precise meaning of @code{BREAK} is defined by the transport
31669 mechanism and may, in fact, be undefined. @value{GDBN} does not
31670 currently define a @code{BREAK} mechanism for any of the network
31671 interfaces except for TCP, in which case @value{GDBN} sends the
31672 @code{telnet} BREAK sequence.
31674 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
31675 transport mechanisms. It is represented by sending the single byte
31676 @code{0x03} without any of the usual packet overhead described in
31677 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
31678 transmitted as part of a packet, it is considered to be packet data
31679 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
31680 (@pxref{X packet}), used for binary downloads, may include an unescaped
31681 @code{0x03} as part of its packet.
31683 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
31684 When Linux kernel receives this sequence from serial port,
31685 it stops execution and connects to gdb.
31687 Stubs are not required to recognize these interrupt mechanisms and the
31688 precise meaning associated with receipt of the interrupt is
31689 implementation defined. If the target supports debugging of multiple
31690 threads and/or processes, it should attempt to interrupt all
31691 currently-executing threads and processes.
31692 If the stub is successful at interrupting the
31693 running program, it should send one of the stop
31694 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
31695 of successfully stopping the program in all-stop mode, and a stop reply
31696 for each stopped thread in non-stop mode.
31697 Interrupts received while the
31698 program is stopped are discarded.
31700 @node Notification Packets
31701 @section Notification Packets
31702 @cindex notification packets
31703 @cindex packets, notification
31705 The @value{GDBN} remote serial protocol includes @dfn{notifications},
31706 packets that require no acknowledgment. Both the GDB and the stub
31707 may send notifications (although the only notifications defined at
31708 present are sent by the stub). Notifications carry information
31709 without incurring the round-trip latency of an acknowledgment, and so
31710 are useful for low-impact communications where occasional packet loss
31713 A notification packet has the form @samp{% @var{data} #
31714 @var{checksum}}, where @var{data} is the content of the notification,
31715 and @var{checksum} is a checksum of @var{data}, computed and formatted
31716 as for ordinary @value{GDBN} packets. A notification's @var{data}
31717 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
31718 receiving a notification, the recipient sends no @samp{+} or @samp{-}
31719 to acknowledge the notification's receipt or to report its corruption.
31721 Every notification's @var{data} begins with a name, which contains no
31722 colon characters, followed by a colon character.
31724 Recipients should silently ignore corrupted notifications and
31725 notifications they do not understand. Recipients should restart
31726 timeout periods on receipt of a well-formed notification, whether or
31727 not they understand it.
31729 Senders should only send the notifications described here when this
31730 protocol description specifies that they are permitted. In the
31731 future, we may extend the protocol to permit existing notifications in
31732 new contexts; this rule helps older senders avoid confusing newer
31735 (Older versions of @value{GDBN} ignore bytes received until they see
31736 the @samp{$} byte that begins an ordinary packet, so new stubs may
31737 transmit notifications without fear of confusing older clients. There
31738 are no notifications defined for @value{GDBN} to send at the moment, but we
31739 assume that most older stubs would ignore them, as well.)
31741 The following notification packets from the stub to @value{GDBN} are
31745 @item Stop: @var{reply}
31746 Report an asynchronous stop event in non-stop mode.
31747 The @var{reply} has the form of a stop reply, as
31748 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
31749 for information on how these notifications are acknowledged by
31753 @node Remote Non-Stop
31754 @section Remote Protocol Support for Non-Stop Mode
31756 @value{GDBN}'s remote protocol supports non-stop debugging of
31757 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
31758 supports non-stop mode, it should report that to @value{GDBN} by including
31759 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
31761 @value{GDBN} typically sends a @samp{QNonStop} packet only when
31762 establishing a new connection with the stub. Entering non-stop mode
31763 does not alter the state of any currently-running threads, but targets
31764 must stop all threads in any already-attached processes when entering
31765 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
31766 probe the target state after a mode change.
31768 In non-stop mode, when an attached process encounters an event that
31769 would otherwise be reported with a stop reply, it uses the
31770 asynchronous notification mechanism (@pxref{Notification Packets}) to
31771 inform @value{GDBN}. In contrast to all-stop mode, where all threads
31772 in all processes are stopped when a stop reply is sent, in non-stop
31773 mode only the thread reporting the stop event is stopped. That is,
31774 when reporting a @samp{S} or @samp{T} response to indicate completion
31775 of a step operation, hitting a breakpoint, or a fault, only the
31776 affected thread is stopped; any other still-running threads continue
31777 to run. When reporting a @samp{W} or @samp{X} response, all running
31778 threads belonging to other attached processes continue to run.
31780 Only one stop reply notification at a time may be pending; if
31781 additional stop events occur before @value{GDBN} has acknowledged the
31782 previous notification, they must be queued by the stub for later
31783 synchronous transmission in response to @samp{vStopped} packets from
31784 @value{GDBN}. Because the notification mechanism is unreliable,
31785 the stub is permitted to resend a stop reply notification
31786 if it believes @value{GDBN} may not have received it. @value{GDBN}
31787 ignores additional stop reply notifications received before it has
31788 finished processing a previous notification and the stub has completed
31789 sending any queued stop events.
31791 Otherwise, @value{GDBN} must be prepared to receive a stop reply
31792 notification at any time. Specifically, they may appear when
31793 @value{GDBN} is not otherwise reading input from the stub, or when
31794 @value{GDBN} is expecting to read a normal synchronous response or a
31795 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
31796 Notification packets are distinct from any other communication from
31797 the stub so there is no ambiguity.
31799 After receiving a stop reply notification, @value{GDBN} shall
31800 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
31801 as a regular, synchronous request to the stub. Such acknowledgment
31802 is not required to happen immediately, as @value{GDBN} is permitted to
31803 send other, unrelated packets to the stub first, which the stub should
31806 Upon receiving a @samp{vStopped} packet, if the stub has other queued
31807 stop events to report to @value{GDBN}, it shall respond by sending a
31808 normal stop reply response. @value{GDBN} shall then send another
31809 @samp{vStopped} packet to solicit further responses; again, it is
31810 permitted to send other, unrelated packets as well which the stub
31811 should process normally.
31813 If the stub receives a @samp{vStopped} packet and there are no
31814 additional stop events to report, the stub shall return an @samp{OK}
31815 response. At this point, if further stop events occur, the stub shall
31816 send a new stop reply notification, @value{GDBN} shall accept the
31817 notification, and the process shall be repeated.
31819 In non-stop mode, the target shall respond to the @samp{?} packet as
31820 follows. First, any incomplete stop reply notification/@samp{vStopped}
31821 sequence in progress is abandoned. The target must begin a new
31822 sequence reporting stop events for all stopped threads, whether or not
31823 it has previously reported those events to @value{GDBN}. The first
31824 stop reply is sent as a synchronous reply to the @samp{?} packet, and
31825 subsequent stop replies are sent as responses to @samp{vStopped} packets
31826 using the mechanism described above. The target must not send
31827 asynchronous stop reply notifications until the sequence is complete.
31828 If all threads are running when the target receives the @samp{?} packet,
31829 or if the target is not attached to any process, it shall respond
31832 @node Packet Acknowledgment
31833 @section Packet Acknowledgment
31835 @cindex acknowledgment, for @value{GDBN} remote
31836 @cindex packet acknowledgment, for @value{GDBN} remote
31837 By default, when either the host or the target machine receives a packet,
31838 the first response expected is an acknowledgment: either @samp{+} (to indicate
31839 the package was received correctly) or @samp{-} (to request retransmission).
31840 This mechanism allows the @value{GDBN} remote protocol to operate over
31841 unreliable transport mechanisms, such as a serial line.
31843 In cases where the transport mechanism is itself reliable (such as a pipe or
31844 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
31845 It may be desirable to disable them in that case to reduce communication
31846 overhead, or for other reasons. This can be accomplished by means of the
31847 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
31849 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
31850 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
31851 and response format still includes the normal checksum, as described in
31852 @ref{Overview}, but the checksum may be ignored by the receiver.
31854 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
31855 no-acknowledgment mode, it should report that to @value{GDBN}
31856 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
31857 @pxref{qSupported}.
31858 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
31859 disabled via the @code{set remote noack-packet off} command
31860 (@pxref{Remote Configuration}),
31861 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
31862 Only then may the stub actually turn off packet acknowledgments.
31863 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
31864 response, which can be safely ignored by the stub.
31866 Note that @code{set remote noack-packet} command only affects negotiation
31867 between @value{GDBN} and the stub when subsequent connections are made;
31868 it does not affect the protocol acknowledgment state for any current
31870 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
31871 new connection is established,
31872 there is also no protocol request to re-enable the acknowledgments
31873 for the current connection, once disabled.
31878 Example sequence of a target being re-started. Notice how the restart
31879 does not get any direct output:
31884 @emph{target restarts}
31887 <- @code{T001:1234123412341234}
31891 Example sequence of a target being stepped by a single instruction:
31894 -> @code{G1445@dots{}}
31899 <- @code{T001:1234123412341234}
31903 <- @code{1455@dots{}}
31907 @node File-I/O Remote Protocol Extension
31908 @section File-I/O Remote Protocol Extension
31909 @cindex File-I/O remote protocol extension
31912 * File-I/O Overview::
31913 * Protocol Basics::
31914 * The F Request Packet::
31915 * The F Reply Packet::
31916 * The Ctrl-C Message::
31918 * List of Supported Calls::
31919 * Protocol-specific Representation of Datatypes::
31921 * File-I/O Examples::
31924 @node File-I/O Overview
31925 @subsection File-I/O Overview
31926 @cindex file-i/o overview
31928 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
31929 target to use the host's file system and console I/O to perform various
31930 system calls. System calls on the target system are translated into a
31931 remote protocol packet to the host system, which then performs the needed
31932 actions and returns a response packet to the target system.
31933 This simulates file system operations even on targets that lack file systems.
31935 The protocol is defined to be independent of both the host and target systems.
31936 It uses its own internal representation of datatypes and values. Both
31937 @value{GDBN} and the target's @value{GDBN} stub are responsible for
31938 translating the system-dependent value representations into the internal
31939 protocol representations when data is transmitted.
31941 The communication is synchronous. A system call is possible only when
31942 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
31943 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
31944 the target is stopped to allow deterministic access to the target's
31945 memory. Therefore File-I/O is not interruptible by target signals. On
31946 the other hand, it is possible to interrupt File-I/O by a user interrupt
31947 (@samp{Ctrl-C}) within @value{GDBN}.
31949 The target's request to perform a host system call does not finish
31950 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
31951 after finishing the system call, the target returns to continuing the
31952 previous activity (continue, step). No additional continue or step
31953 request from @value{GDBN} is required.
31956 (@value{GDBP}) continue
31957 <- target requests 'system call X'
31958 target is stopped, @value{GDBN} executes system call
31959 -> @value{GDBN} returns result
31960 ... target continues, @value{GDBN} returns to wait for the target
31961 <- target hits breakpoint and sends a Txx packet
31964 The protocol only supports I/O on the console and to regular files on
31965 the host file system. Character or block special devices, pipes,
31966 named pipes, sockets or any other communication method on the host
31967 system are not supported by this protocol.
31969 File I/O is not supported in non-stop mode.
31971 @node Protocol Basics
31972 @subsection Protocol Basics
31973 @cindex protocol basics, file-i/o
31975 The File-I/O protocol uses the @code{F} packet as the request as well
31976 as reply packet. Since a File-I/O system call can only occur when
31977 @value{GDBN} is waiting for a response from the continuing or stepping target,
31978 the File-I/O request is a reply that @value{GDBN} has to expect as a result
31979 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
31980 This @code{F} packet contains all information needed to allow @value{GDBN}
31981 to call the appropriate host system call:
31985 A unique identifier for the requested system call.
31988 All parameters to the system call. Pointers are given as addresses
31989 in the target memory address space. Pointers to strings are given as
31990 pointer/length pair. Numerical values are given as they are.
31991 Numerical control flags are given in a protocol-specific representation.
31995 At this point, @value{GDBN} has to perform the following actions.
31999 If the parameters include pointer values to data needed as input to a
32000 system call, @value{GDBN} requests this data from the target with a
32001 standard @code{m} packet request. This additional communication has to be
32002 expected by the target implementation and is handled as any other @code{m}
32006 @value{GDBN} translates all value from protocol representation to host
32007 representation as needed. Datatypes are coerced into the host types.
32010 @value{GDBN} calls the system call.
32013 It then coerces datatypes back to protocol representation.
32016 If the system call is expected to return data in buffer space specified
32017 by pointer parameters to the call, the data is transmitted to the
32018 target using a @code{M} or @code{X} packet. This packet has to be expected
32019 by the target implementation and is handled as any other @code{M} or @code{X}
32024 Eventually @value{GDBN} replies with another @code{F} packet which contains all
32025 necessary information for the target to continue. This at least contains
32032 @code{errno}, if has been changed by the system call.
32039 After having done the needed type and value coercion, the target continues
32040 the latest continue or step action.
32042 @node The F Request Packet
32043 @subsection The @code{F} Request Packet
32044 @cindex file-i/o request packet
32045 @cindex @code{F} request packet
32047 The @code{F} request packet has the following format:
32050 @item F@var{call-id},@var{parameter@dots{}}
32052 @var{call-id} is the identifier to indicate the host system call to be called.
32053 This is just the name of the function.
32055 @var{parameter@dots{}} are the parameters to the system call.
32056 Parameters are hexadecimal integer values, either the actual values in case
32057 of scalar datatypes, pointers to target buffer space in case of compound
32058 datatypes and unspecified memory areas, or pointer/length pairs in case
32059 of string parameters. These are appended to the @var{call-id} as a
32060 comma-delimited list. All values are transmitted in ASCII
32061 string representation, pointer/length pairs separated by a slash.
32067 @node The F Reply Packet
32068 @subsection The @code{F} Reply Packet
32069 @cindex file-i/o reply packet
32070 @cindex @code{F} reply packet
32072 The @code{F} reply packet has the following format:
32076 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
32078 @var{retcode} is the return code of the system call as hexadecimal value.
32080 @var{errno} is the @code{errno} set by the call, in protocol-specific
32082 This parameter can be omitted if the call was successful.
32084 @var{Ctrl-C flag} is only sent if the user requested a break. In this
32085 case, @var{errno} must be sent as well, even if the call was successful.
32086 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
32093 or, if the call was interrupted before the host call has been performed:
32100 assuming 4 is the protocol-specific representation of @code{EINTR}.
32105 @node The Ctrl-C Message
32106 @subsection The @samp{Ctrl-C} Message
32107 @cindex ctrl-c message, in file-i/o protocol
32109 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
32110 reply packet (@pxref{The F Reply Packet}),
32111 the target should behave as if it had
32112 gotten a break message. The meaning for the target is ``system call
32113 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
32114 (as with a break message) and return to @value{GDBN} with a @code{T02}
32117 It's important for the target to know in which
32118 state the system call was interrupted. There are two possible cases:
32122 The system call hasn't been performed on the host yet.
32125 The system call on the host has been finished.
32129 These two states can be distinguished by the target by the value of the
32130 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
32131 call hasn't been performed. This is equivalent to the @code{EINTR} handling
32132 on POSIX systems. In any other case, the target may presume that the
32133 system call has been finished --- successfully or not --- and should behave
32134 as if the break message arrived right after the system call.
32136 @value{GDBN} must behave reliably. If the system call has not been called
32137 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
32138 @code{errno} in the packet. If the system call on the host has been finished
32139 before the user requests a break, the full action must be finished by
32140 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
32141 The @code{F} packet may only be sent when either nothing has happened
32142 or the full action has been completed.
32145 @subsection Console I/O
32146 @cindex console i/o as part of file-i/o
32148 By default and if not explicitly closed by the target system, the file
32149 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
32150 on the @value{GDBN} console is handled as any other file output operation
32151 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
32152 by @value{GDBN} so that after the target read request from file descriptor
32153 0 all following typing is buffered until either one of the following
32158 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
32160 system call is treated as finished.
32163 The user presses @key{RET}. This is treated as end of input with a trailing
32167 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
32168 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
32172 If the user has typed more characters than fit in the buffer given to
32173 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
32174 either another @code{read(0, @dots{})} is requested by the target, or debugging
32175 is stopped at the user's request.
32178 @node List of Supported Calls
32179 @subsection List of Supported Calls
32180 @cindex list of supported file-i/o calls
32197 @unnumberedsubsubsec open
32198 @cindex open, file-i/o system call
32203 int open(const char *pathname, int flags);
32204 int open(const char *pathname, int flags, mode_t mode);
32208 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
32211 @var{flags} is the bitwise @code{OR} of the following values:
32215 If the file does not exist it will be created. The host
32216 rules apply as far as file ownership and time stamps
32220 When used with @code{O_CREAT}, if the file already exists it is
32221 an error and open() fails.
32224 If the file already exists and the open mode allows
32225 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
32226 truncated to zero length.
32229 The file is opened in append mode.
32232 The file is opened for reading only.
32235 The file is opened for writing only.
32238 The file is opened for reading and writing.
32242 Other bits are silently ignored.
32246 @var{mode} is the bitwise @code{OR} of the following values:
32250 User has read permission.
32253 User has write permission.
32256 Group has read permission.
32259 Group has write permission.
32262 Others have read permission.
32265 Others have write permission.
32269 Other bits are silently ignored.
32272 @item Return value:
32273 @code{open} returns the new file descriptor or -1 if an error
32280 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
32283 @var{pathname} refers to a directory.
32286 The requested access is not allowed.
32289 @var{pathname} was too long.
32292 A directory component in @var{pathname} does not exist.
32295 @var{pathname} refers to a device, pipe, named pipe or socket.
32298 @var{pathname} refers to a file on a read-only filesystem and
32299 write access was requested.
32302 @var{pathname} is an invalid pointer value.
32305 No space on device to create the file.
32308 The process already has the maximum number of files open.
32311 The limit on the total number of files open on the system
32315 The call was interrupted by the user.
32321 @unnumberedsubsubsec close
32322 @cindex close, file-i/o system call
32331 @samp{Fclose,@var{fd}}
32333 @item Return value:
32334 @code{close} returns zero on success, or -1 if an error occurred.
32340 @var{fd} isn't a valid open file descriptor.
32343 The call was interrupted by the user.
32349 @unnumberedsubsubsec read
32350 @cindex read, file-i/o system call
32355 int read(int fd, void *buf, unsigned int count);
32359 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
32361 @item Return value:
32362 On success, the number of bytes read is returned.
32363 Zero indicates end of file. If count is zero, read
32364 returns zero as well. On error, -1 is returned.
32370 @var{fd} is not a valid file descriptor or is not open for
32374 @var{bufptr} is an invalid pointer value.
32377 The call was interrupted by the user.
32383 @unnumberedsubsubsec write
32384 @cindex write, file-i/o system call
32389 int write(int fd, const void *buf, unsigned int count);
32393 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
32395 @item Return value:
32396 On success, the number of bytes written are returned.
32397 Zero indicates nothing was written. On error, -1
32404 @var{fd} is not a valid file descriptor or is not open for
32408 @var{bufptr} is an invalid pointer value.
32411 An attempt was made to write a file that exceeds the
32412 host-specific maximum file size allowed.
32415 No space on device to write the data.
32418 The call was interrupted by the user.
32424 @unnumberedsubsubsec lseek
32425 @cindex lseek, file-i/o system call
32430 long lseek (int fd, long offset, int flag);
32434 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
32436 @var{flag} is one of:
32440 The offset is set to @var{offset} bytes.
32443 The offset is set to its current location plus @var{offset}
32447 The offset is set to the size of the file plus @var{offset}
32451 @item Return value:
32452 On success, the resulting unsigned offset in bytes from
32453 the beginning of the file is returned. Otherwise, a
32454 value of -1 is returned.
32460 @var{fd} is not a valid open file descriptor.
32463 @var{fd} is associated with the @value{GDBN} console.
32466 @var{flag} is not a proper value.
32469 The call was interrupted by the user.
32475 @unnumberedsubsubsec rename
32476 @cindex rename, file-i/o system call
32481 int rename(const char *oldpath, const char *newpath);
32485 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
32487 @item Return value:
32488 On success, zero is returned. On error, -1 is returned.
32494 @var{newpath} is an existing directory, but @var{oldpath} is not a
32498 @var{newpath} is a non-empty directory.
32501 @var{oldpath} or @var{newpath} is a directory that is in use by some
32505 An attempt was made to make a directory a subdirectory
32509 A component used as a directory in @var{oldpath} or new
32510 path is not a directory. Or @var{oldpath} is a directory
32511 and @var{newpath} exists but is not a directory.
32514 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
32517 No access to the file or the path of the file.
32521 @var{oldpath} or @var{newpath} was too long.
32524 A directory component in @var{oldpath} or @var{newpath} does not exist.
32527 The file is on a read-only filesystem.
32530 The device containing the file has no room for the new
32534 The call was interrupted by the user.
32540 @unnumberedsubsubsec unlink
32541 @cindex unlink, file-i/o system call
32546 int unlink(const char *pathname);
32550 @samp{Funlink,@var{pathnameptr}/@var{len}}
32552 @item Return value:
32553 On success, zero is returned. On error, -1 is returned.
32559 No access to the file or the path of the file.
32562 The system does not allow unlinking of directories.
32565 The file @var{pathname} cannot be unlinked because it's
32566 being used by another process.
32569 @var{pathnameptr} is an invalid pointer value.
32572 @var{pathname} was too long.
32575 A directory component in @var{pathname} does not exist.
32578 A component of the path is not a directory.
32581 The file is on a read-only filesystem.
32584 The call was interrupted by the user.
32590 @unnumberedsubsubsec stat/fstat
32591 @cindex fstat, file-i/o system call
32592 @cindex stat, file-i/o system call
32597 int stat(const char *pathname, struct stat *buf);
32598 int fstat(int fd, struct stat *buf);
32602 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
32603 @samp{Ffstat,@var{fd},@var{bufptr}}
32605 @item Return value:
32606 On success, zero is returned. On error, -1 is returned.
32612 @var{fd} is not a valid open file.
32615 A directory component in @var{pathname} does not exist or the
32616 path is an empty string.
32619 A component of the path is not a directory.
32622 @var{pathnameptr} is an invalid pointer value.
32625 No access to the file or the path of the file.
32628 @var{pathname} was too long.
32631 The call was interrupted by the user.
32637 @unnumberedsubsubsec gettimeofday
32638 @cindex gettimeofday, file-i/o system call
32643 int gettimeofday(struct timeval *tv, void *tz);
32647 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
32649 @item Return value:
32650 On success, 0 is returned, -1 otherwise.
32656 @var{tz} is a non-NULL pointer.
32659 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
32665 @unnumberedsubsubsec isatty
32666 @cindex isatty, file-i/o system call
32671 int isatty(int fd);
32675 @samp{Fisatty,@var{fd}}
32677 @item Return value:
32678 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
32684 The call was interrupted by the user.
32689 Note that the @code{isatty} call is treated as a special case: it returns
32690 1 to the target if the file descriptor is attached
32691 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
32692 would require implementing @code{ioctl} and would be more complex than
32697 @unnumberedsubsubsec system
32698 @cindex system, file-i/o system call
32703 int system(const char *command);
32707 @samp{Fsystem,@var{commandptr}/@var{len}}
32709 @item Return value:
32710 If @var{len} is zero, the return value indicates whether a shell is
32711 available. A zero return value indicates a shell is not available.
32712 For non-zero @var{len}, the value returned is -1 on error and the
32713 return status of the command otherwise. Only the exit status of the
32714 command is returned, which is extracted from the host's @code{system}
32715 return value by calling @code{WEXITSTATUS(retval)}. In case
32716 @file{/bin/sh} could not be executed, 127 is returned.
32722 The call was interrupted by the user.
32727 @value{GDBN} takes over the full task of calling the necessary host calls
32728 to perform the @code{system} call. The return value of @code{system} on
32729 the host is simplified before it's returned
32730 to the target. Any termination signal information from the child process
32731 is discarded, and the return value consists
32732 entirely of the exit status of the called command.
32734 Due to security concerns, the @code{system} call is by default refused
32735 by @value{GDBN}. The user has to allow this call explicitly with the
32736 @code{set remote system-call-allowed 1} command.
32739 @item set remote system-call-allowed
32740 @kindex set remote system-call-allowed
32741 Control whether to allow the @code{system} calls in the File I/O
32742 protocol for the remote target. The default is zero (disabled).
32744 @item show remote system-call-allowed
32745 @kindex show remote system-call-allowed
32746 Show whether the @code{system} calls are allowed in the File I/O
32750 @node Protocol-specific Representation of Datatypes
32751 @subsection Protocol-specific Representation of Datatypes
32752 @cindex protocol-specific representation of datatypes, in file-i/o protocol
32755 * Integral Datatypes::
32757 * Memory Transfer::
32762 @node Integral Datatypes
32763 @unnumberedsubsubsec Integral Datatypes
32764 @cindex integral datatypes, in file-i/o protocol
32766 The integral datatypes used in the system calls are @code{int},
32767 @code{unsigned int}, @code{long}, @code{unsigned long},
32768 @code{mode_t}, and @code{time_t}.
32770 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
32771 implemented as 32 bit values in this protocol.
32773 @code{long} and @code{unsigned long} are implemented as 64 bit types.
32775 @xref{Limits}, for corresponding MIN and MAX values (similar to those
32776 in @file{limits.h}) to allow range checking on host and target.
32778 @code{time_t} datatypes are defined as seconds since the Epoch.
32780 All integral datatypes transferred as part of a memory read or write of a
32781 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
32784 @node Pointer Values
32785 @unnumberedsubsubsec Pointer Values
32786 @cindex pointer values, in file-i/o protocol
32788 Pointers to target data are transmitted as they are. An exception
32789 is made for pointers to buffers for which the length isn't
32790 transmitted as part of the function call, namely strings. Strings
32791 are transmitted as a pointer/length pair, both as hex values, e.g.@:
32798 which is a pointer to data of length 18 bytes at position 0x1aaf.
32799 The length is defined as the full string length in bytes, including
32800 the trailing null byte. For example, the string @code{"hello world"}
32801 at address 0x123456 is transmitted as
32807 @node Memory Transfer
32808 @unnumberedsubsubsec Memory Transfer
32809 @cindex memory transfer, in file-i/o protocol
32811 Structured data which is transferred using a memory read or write (for
32812 example, a @code{struct stat}) is expected to be in a protocol-specific format
32813 with all scalar multibyte datatypes being big endian. Translation to
32814 this representation needs to be done both by the target before the @code{F}
32815 packet is sent, and by @value{GDBN} before
32816 it transfers memory to the target. Transferred pointers to structured
32817 data should point to the already-coerced data at any time.
32821 @unnumberedsubsubsec struct stat
32822 @cindex struct stat, in file-i/o protocol
32824 The buffer of type @code{struct stat} used by the target and @value{GDBN}
32825 is defined as follows:
32829 unsigned int st_dev; /* device */
32830 unsigned int st_ino; /* inode */
32831 mode_t st_mode; /* protection */
32832 unsigned int st_nlink; /* number of hard links */
32833 unsigned int st_uid; /* user ID of owner */
32834 unsigned int st_gid; /* group ID of owner */
32835 unsigned int st_rdev; /* device type (if inode device) */
32836 unsigned long st_size; /* total size, in bytes */
32837 unsigned long st_blksize; /* blocksize for filesystem I/O */
32838 unsigned long st_blocks; /* number of blocks allocated */
32839 time_t st_atime; /* time of last access */
32840 time_t st_mtime; /* time of last modification */
32841 time_t st_ctime; /* time of last change */
32845 The integral datatypes conform to the definitions given in the
32846 appropriate section (see @ref{Integral Datatypes}, for details) so this
32847 structure is of size 64 bytes.
32849 The values of several fields have a restricted meaning and/or
32855 A value of 0 represents a file, 1 the console.
32858 No valid meaning for the target. Transmitted unchanged.
32861 Valid mode bits are described in @ref{Constants}. Any other
32862 bits have currently no meaning for the target.
32867 No valid meaning for the target. Transmitted unchanged.
32872 These values have a host and file system dependent
32873 accuracy. Especially on Windows hosts, the file system may not
32874 support exact timing values.
32877 The target gets a @code{struct stat} of the above representation and is
32878 responsible for coercing it to the target representation before
32881 Note that due to size differences between the host, target, and protocol
32882 representations of @code{struct stat} members, these members could eventually
32883 get truncated on the target.
32885 @node struct timeval
32886 @unnumberedsubsubsec struct timeval
32887 @cindex struct timeval, in file-i/o protocol
32889 The buffer of type @code{struct timeval} used by the File-I/O protocol
32890 is defined as follows:
32894 time_t tv_sec; /* second */
32895 long tv_usec; /* microsecond */
32899 The integral datatypes conform to the definitions given in the
32900 appropriate section (see @ref{Integral Datatypes}, for details) so this
32901 structure is of size 8 bytes.
32904 @subsection Constants
32905 @cindex constants, in file-i/o protocol
32907 The following values are used for the constants inside of the
32908 protocol. @value{GDBN} and target are responsible for translating these
32909 values before and after the call as needed.
32920 @unnumberedsubsubsec Open Flags
32921 @cindex open flags, in file-i/o protocol
32923 All values are given in hexadecimal representation.
32935 @node mode_t Values
32936 @unnumberedsubsubsec mode_t Values
32937 @cindex mode_t values, in file-i/o protocol
32939 All values are given in octal representation.
32956 @unnumberedsubsubsec Errno Values
32957 @cindex errno values, in file-i/o protocol
32959 All values are given in decimal representation.
32984 @code{EUNKNOWN} is used as a fallback error value if a host system returns
32985 any error value not in the list of supported error numbers.
32988 @unnumberedsubsubsec Lseek Flags
32989 @cindex lseek flags, in file-i/o protocol
32998 @unnumberedsubsubsec Limits
32999 @cindex limits, in file-i/o protocol
33001 All values are given in decimal representation.
33004 INT_MIN -2147483648
33006 UINT_MAX 4294967295
33007 LONG_MIN -9223372036854775808
33008 LONG_MAX 9223372036854775807
33009 ULONG_MAX 18446744073709551615
33012 @node File-I/O Examples
33013 @subsection File-I/O Examples
33014 @cindex file-i/o examples
33016 Example sequence of a write call, file descriptor 3, buffer is at target
33017 address 0x1234, 6 bytes should be written:
33020 <- @code{Fwrite,3,1234,6}
33021 @emph{request memory read from target}
33024 @emph{return "6 bytes written"}
33028 Example sequence of a read call, file descriptor 3, buffer is at target
33029 address 0x1234, 6 bytes should be read:
33032 <- @code{Fread,3,1234,6}
33033 @emph{request memory write to target}
33034 -> @code{X1234,6:XXXXXX}
33035 @emph{return "6 bytes read"}
33039 Example sequence of a read call, call fails on the host due to invalid
33040 file descriptor (@code{EBADF}):
33043 <- @code{Fread,3,1234,6}
33047 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
33051 <- @code{Fread,3,1234,6}
33056 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
33060 <- @code{Fread,3,1234,6}
33061 -> @code{X1234,6:XXXXXX}
33065 @node Library List Format
33066 @section Library List Format
33067 @cindex library list format, remote protocol
33069 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
33070 same process as your application to manage libraries. In this case,
33071 @value{GDBN} can use the loader's symbol table and normal memory
33072 operations to maintain a list of shared libraries. On other
33073 platforms, the operating system manages loaded libraries.
33074 @value{GDBN} can not retrieve the list of currently loaded libraries
33075 through memory operations, so it uses the @samp{qXfer:libraries:read}
33076 packet (@pxref{qXfer library list read}) instead. The remote stub
33077 queries the target's operating system and reports which libraries
33080 The @samp{qXfer:libraries:read} packet returns an XML document which
33081 lists loaded libraries and their offsets. Each library has an
33082 associated name and one or more segment or section base addresses,
33083 which report where the library was loaded in memory.
33085 For the common case of libraries that are fully linked binaries, the
33086 library should have a list of segments. If the target supports
33087 dynamic linking of a relocatable object file, its library XML element
33088 should instead include a list of allocated sections. The segment or
33089 section bases are start addresses, not relocation offsets; they do not
33090 depend on the library's link-time base addresses.
33092 @value{GDBN} must be linked with the Expat library to support XML
33093 library lists. @xref{Expat}.
33095 A simple memory map, with one loaded library relocated by a single
33096 offset, looks like this:
33100 <library name="/lib/libc.so.6">
33101 <segment address="0x10000000"/>
33106 Another simple memory map, with one loaded library with three
33107 allocated sections (.text, .data, .bss), looks like this:
33111 <library name="sharedlib.o">
33112 <section address="0x10000000"/>
33113 <section address="0x20000000"/>
33114 <section address="0x30000000"/>
33119 The format of a library list is described by this DTD:
33122 <!-- library-list: Root element with versioning -->
33123 <!ELEMENT library-list (library)*>
33124 <!ATTLIST library-list version CDATA #FIXED "1.0">
33125 <!ELEMENT library (segment*, section*)>
33126 <!ATTLIST library name CDATA #REQUIRED>
33127 <!ELEMENT segment EMPTY>
33128 <!ATTLIST segment address CDATA #REQUIRED>
33129 <!ELEMENT section EMPTY>
33130 <!ATTLIST section address CDATA #REQUIRED>
33133 In addition, segments and section descriptors cannot be mixed within a
33134 single library element, and you must supply at least one segment or
33135 section for each library.
33137 @node Memory Map Format
33138 @section Memory Map Format
33139 @cindex memory map format
33141 To be able to write into flash memory, @value{GDBN} needs to obtain a
33142 memory map from the target. This section describes the format of the
33145 The memory map is obtained using the @samp{qXfer:memory-map:read}
33146 (@pxref{qXfer memory map read}) packet and is an XML document that
33147 lists memory regions.
33149 @value{GDBN} must be linked with the Expat library to support XML
33150 memory maps. @xref{Expat}.
33152 The top-level structure of the document is shown below:
33155 <?xml version="1.0"?>
33156 <!DOCTYPE memory-map
33157 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
33158 "http://sourceware.org/gdb/gdb-memory-map.dtd">
33164 Each region can be either:
33169 A region of RAM starting at @var{addr} and extending for @var{length}
33173 <memory type="ram" start="@var{addr}" length="@var{length}"/>
33178 A region of read-only memory:
33181 <memory type="rom" start="@var{addr}" length="@var{length}"/>
33186 A region of flash memory, with erasure blocks @var{blocksize}
33190 <memory type="flash" start="@var{addr}" length="@var{length}">
33191 <property name="blocksize">@var{blocksize}</property>
33197 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
33198 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
33199 packets to write to addresses in such ranges.
33201 The formal DTD for memory map format is given below:
33204 <!-- ................................................... -->
33205 <!-- Memory Map XML DTD ................................ -->
33206 <!-- File: memory-map.dtd .............................. -->
33207 <!-- .................................... .............. -->
33208 <!-- memory-map.dtd -->
33209 <!-- memory-map: Root element with versioning -->
33210 <!ELEMENT memory-map (memory | property)>
33211 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
33212 <!ELEMENT memory (property)>
33213 <!-- memory: Specifies a memory region,
33214 and its type, or device. -->
33215 <!ATTLIST memory type CDATA #REQUIRED
33216 start CDATA #REQUIRED
33217 length CDATA #REQUIRED
33218 device CDATA #IMPLIED>
33219 <!-- property: Generic attribute tag -->
33220 <!ELEMENT property (#PCDATA | property)*>
33221 <!ATTLIST property name CDATA #REQUIRED>
33224 @node Thread List Format
33225 @section Thread List Format
33226 @cindex thread list format
33228 To efficiently update the list of threads and their attributes,
33229 @value{GDBN} issues the @samp{qXfer:threads:read} packet
33230 (@pxref{qXfer threads read}) and obtains the XML document with
33231 the following structure:
33234 <?xml version="1.0"?>
33236 <thread id="id" core="0">
33237 ... description ...
33242 Each @samp{thread} element must have the @samp{id} attribute that
33243 identifies the thread (@pxref{thread-id syntax}). The
33244 @samp{core} attribute, if present, specifies which processor core
33245 the thread was last executing on. The content of the of @samp{thread}
33246 element is interpreted as human-readable auxilliary information.
33248 @include agentexpr.texi
33250 @node Trace File Format
33251 @appendix Trace File Format
33252 @cindex trace file format
33254 The trace file comes in three parts: a header, a textual description
33255 section, and a trace frame section with binary data.
33257 The header has the form @code{\x7fTRACE0\n}. The first byte is
33258 @code{0x7f} so as to indicate that the file contains binary data,
33259 while the @code{0} is a version number that may have different values
33262 The description section consists of multiple lines of @sc{ascii} text
33263 separated by newline characters (@code{0xa}). The lines may include a
33264 variety of optional descriptive or context-setting information, such
33265 as tracepoint definitions or register set size. @value{GDBN} will
33266 ignore any line that it does not recognize. An empty line marks the end
33269 @c FIXME add some specific types of data
33271 The trace frame section consists of a number of consecutive frames.
33272 Each frame begins with a two-byte tracepoint number, followed by a
33273 four-byte size giving the amount of data in the frame. The data in
33274 the frame consists of a number of blocks, each introduced by a
33275 character indicating its type (at least register, memory, and trace
33276 state variable). The data in this section is raw binary, not a
33277 hexadecimal or other encoding; its endianness matches the target's
33280 @c FIXME bi-arch may require endianness/arch info in description section
33283 @item R @var{bytes}
33284 Register block. The number and ordering of bytes matches that of a
33285 @code{g} packet in the remote protocol. Note that these are the
33286 actual bytes, in target order and @value{GDBN} register order, not a
33287 hexadecimal encoding.
33289 @item M @var{address} @var{length} @var{bytes}...
33290 Memory block. This is a contiguous block of memory, at the 8-byte
33291 address @var{address}, with a 2-byte length @var{length}, followed by
33292 @var{length} bytes.
33294 @item V @var{number} @var{value}
33295 Trace state variable block. This records the 8-byte signed value
33296 @var{value} of trace state variable numbered @var{number}.
33300 Future enhancements of the trace file format may include additional types
33303 @node Target Descriptions
33304 @appendix Target Descriptions
33305 @cindex target descriptions
33307 @strong{Warning:} target descriptions are still under active development,
33308 and the contents and format may change between @value{GDBN} releases.
33309 The format is expected to stabilize in the future.
33311 One of the challenges of using @value{GDBN} to debug embedded systems
33312 is that there are so many minor variants of each processor
33313 architecture in use. It is common practice for vendors to start with
33314 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
33315 and then make changes to adapt it to a particular market niche. Some
33316 architectures have hundreds of variants, available from dozens of
33317 vendors. This leads to a number of problems:
33321 With so many different customized processors, it is difficult for
33322 the @value{GDBN} maintainers to keep up with the changes.
33324 Since individual variants may have short lifetimes or limited
33325 audiences, it may not be worthwhile to carry information about every
33326 variant in the @value{GDBN} source tree.
33328 When @value{GDBN} does support the architecture of the embedded system
33329 at hand, the task of finding the correct architecture name to give the
33330 @command{set architecture} command can be error-prone.
33333 To address these problems, the @value{GDBN} remote protocol allows a
33334 target system to not only identify itself to @value{GDBN}, but to
33335 actually describe its own features. This lets @value{GDBN} support
33336 processor variants it has never seen before --- to the extent that the
33337 descriptions are accurate, and that @value{GDBN} understands them.
33339 @value{GDBN} must be linked with the Expat library to support XML
33340 target descriptions. @xref{Expat}.
33343 * Retrieving Descriptions:: How descriptions are fetched from a target.
33344 * Target Description Format:: The contents of a target description.
33345 * Predefined Target Types:: Standard types available for target
33347 * Standard Target Features:: Features @value{GDBN} knows about.
33350 @node Retrieving Descriptions
33351 @section Retrieving Descriptions
33353 Target descriptions can be read from the target automatically, or
33354 specified by the user manually. The default behavior is to read the
33355 description from the target. @value{GDBN} retrieves it via the remote
33356 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
33357 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
33358 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
33359 XML document, of the form described in @ref{Target Description
33362 Alternatively, you can specify a file to read for the target description.
33363 If a file is set, the target will not be queried. The commands to
33364 specify a file are:
33367 @cindex set tdesc filename
33368 @item set tdesc filename @var{path}
33369 Read the target description from @var{path}.
33371 @cindex unset tdesc filename
33372 @item unset tdesc filename
33373 Do not read the XML target description from a file. @value{GDBN}
33374 will use the description supplied by the current target.
33376 @cindex show tdesc filename
33377 @item show tdesc filename
33378 Show the filename to read for a target description, if any.
33382 @node Target Description Format
33383 @section Target Description Format
33384 @cindex target descriptions, XML format
33386 A target description annex is an @uref{http://www.w3.org/XML/, XML}
33387 document which complies with the Document Type Definition provided in
33388 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
33389 means you can use generally available tools like @command{xmllint} to
33390 check that your feature descriptions are well-formed and valid.
33391 However, to help people unfamiliar with XML write descriptions for
33392 their targets, we also describe the grammar here.
33394 Target descriptions can identify the architecture of the remote target
33395 and (for some architectures) provide information about custom register
33396 sets. They can also identify the OS ABI of the remote target.
33397 @value{GDBN} can use this information to autoconfigure for your
33398 target, or to warn you if you connect to an unsupported target.
33400 Here is a simple target description:
33403 <target version="1.0">
33404 <architecture>i386:x86-64</architecture>
33409 This minimal description only says that the target uses
33410 the x86-64 architecture.
33412 A target description has the following overall form, with [ ] marking
33413 optional elements and @dots{} marking repeatable elements. The elements
33414 are explained further below.
33417 <?xml version="1.0"?>
33418 <!DOCTYPE target SYSTEM "gdb-target.dtd">
33419 <target version="1.0">
33420 @r{[}@var{architecture}@r{]}
33421 @r{[}@var{osabi}@r{]}
33422 @r{[}@var{compatible}@r{]}
33423 @r{[}@var{feature}@dots{}@r{]}
33428 The description is generally insensitive to whitespace and line
33429 breaks, under the usual common-sense rules. The XML version
33430 declaration and document type declaration can generally be omitted
33431 (@value{GDBN} does not require them), but specifying them may be
33432 useful for XML validation tools. The @samp{version} attribute for
33433 @samp{<target>} may also be omitted, but we recommend
33434 including it; if future versions of @value{GDBN} use an incompatible
33435 revision of @file{gdb-target.dtd}, they will detect and report
33436 the version mismatch.
33438 @subsection Inclusion
33439 @cindex target descriptions, inclusion
33442 @cindex <xi:include>
33445 It can sometimes be valuable to split a target description up into
33446 several different annexes, either for organizational purposes, or to
33447 share files between different possible target descriptions. You can
33448 divide a description into multiple files by replacing any element of
33449 the target description with an inclusion directive of the form:
33452 <xi:include href="@var{document}"/>
33456 When @value{GDBN} encounters an element of this form, it will retrieve
33457 the named XML @var{document}, and replace the inclusion directive with
33458 the contents of that document. If the current description was read
33459 using @samp{qXfer}, then so will be the included document;
33460 @var{document} will be interpreted as the name of an annex. If the
33461 current description was read from a file, @value{GDBN} will look for
33462 @var{document} as a file in the same directory where it found the
33463 original description.
33465 @subsection Architecture
33466 @cindex <architecture>
33468 An @samp{<architecture>} element has this form:
33471 <architecture>@var{arch}</architecture>
33474 @var{arch} is one of the architectures from the set accepted by
33475 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
33478 @cindex @code{<osabi>}
33480 This optional field was introduced in @value{GDBN} version 7.0.
33481 Previous versions of @value{GDBN} ignore it.
33483 An @samp{<osabi>} element has this form:
33486 <osabi>@var{abi-name}</osabi>
33489 @var{abi-name} is an OS ABI name from the same selection accepted by
33490 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
33492 @subsection Compatible Architecture
33493 @cindex @code{<compatible>}
33495 This optional field was introduced in @value{GDBN} version 7.0.
33496 Previous versions of @value{GDBN} ignore it.
33498 A @samp{<compatible>} element has this form:
33501 <compatible>@var{arch}</compatible>
33504 @var{arch} is one of the architectures from the set accepted by
33505 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
33507 A @samp{<compatible>} element is used to specify that the target
33508 is able to run binaries in some other than the main target architecture
33509 given by the @samp{<architecture>} element. For example, on the
33510 Cell Broadband Engine, the main architecture is @code{powerpc:common}
33511 or @code{powerpc:common64}, but the system is able to run binaries
33512 in the @code{spu} architecture as well. The way to describe this
33513 capability with @samp{<compatible>} is as follows:
33516 <architecture>powerpc:common</architecture>
33517 <compatible>spu</compatible>
33520 @subsection Features
33523 Each @samp{<feature>} describes some logical portion of the target
33524 system. Features are currently used to describe available CPU
33525 registers and the types of their contents. A @samp{<feature>} element
33529 <feature name="@var{name}">
33530 @r{[}@var{type}@dots{}@r{]}
33536 Each feature's name should be unique within the description. The name
33537 of a feature does not matter unless @value{GDBN} has some special
33538 knowledge of the contents of that feature; if it does, the feature
33539 should have its standard name. @xref{Standard Target Features}.
33543 Any register's value is a collection of bits which @value{GDBN} must
33544 interpret. The default interpretation is a two's complement integer,
33545 but other types can be requested by name in the register description.
33546 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
33547 Target Types}), and the description can define additional composite types.
33549 Each type element must have an @samp{id} attribute, which gives
33550 a unique (within the containing @samp{<feature>}) name to the type.
33551 Types must be defined before they are used.
33554 Some targets offer vector registers, which can be treated as arrays
33555 of scalar elements. These types are written as @samp{<vector>} elements,
33556 specifying the array element type, @var{type}, and the number of elements,
33560 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
33564 If a register's value is usefully viewed in multiple ways, define it
33565 with a union type containing the useful representations. The
33566 @samp{<union>} element contains one or more @samp{<field>} elements,
33567 each of which has a @var{name} and a @var{type}:
33570 <union id="@var{id}">
33571 <field name="@var{name}" type="@var{type}"/>
33577 If a register's value is composed from several separate values, define
33578 it with a structure type. There are two forms of the @samp{<struct>}
33579 element; a @samp{<struct>} element must either contain only bitfields
33580 or contain no bitfields. If the structure contains only bitfields,
33581 its total size in bytes must be specified, each bitfield must have an
33582 explicit start and end, and bitfields are automatically assigned an
33583 integer type. The field's @var{start} should be less than or
33584 equal to its @var{end}, and zero represents the least significant bit.
33587 <struct id="@var{id}" size="@var{size}">
33588 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
33593 If the structure contains no bitfields, then each field has an
33594 explicit type, and no implicit padding is added.
33597 <struct id="@var{id}">
33598 <field name="@var{name}" type="@var{type}"/>
33604 If a register's value is a series of single-bit flags, define it with
33605 a flags type. The @samp{<flags>} element has an explicit @var{size}
33606 and contains one or more @samp{<field>} elements. Each field has a
33607 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
33611 <flags id="@var{id}" size="@var{size}">
33612 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
33617 @subsection Registers
33620 Each register is represented as an element with this form:
33623 <reg name="@var{name}"
33624 bitsize="@var{size}"
33625 @r{[}regnum="@var{num}"@r{]}
33626 @r{[}save-restore="@var{save-restore}"@r{]}
33627 @r{[}type="@var{type}"@r{]}
33628 @r{[}group="@var{group}"@r{]}/>
33632 The components are as follows:
33637 The register's name; it must be unique within the target description.
33640 The register's size, in bits.
33643 The register's number. If omitted, a register's number is one greater
33644 than that of the previous register (either in the current feature or in
33645 a preceeding feature); the first register in the target description
33646 defaults to zero. This register number is used to read or write
33647 the register; e.g.@: it is used in the remote @code{p} and @code{P}
33648 packets, and registers appear in the @code{g} and @code{G} packets
33649 in order of increasing register number.
33652 Whether the register should be preserved across inferior function
33653 calls; this must be either @code{yes} or @code{no}. The default is
33654 @code{yes}, which is appropriate for most registers except for
33655 some system control registers; this is not related to the target's
33659 The type of the register. @var{type} may be a predefined type, a type
33660 defined in the current feature, or one of the special types @code{int}
33661 and @code{float}. @code{int} is an integer type of the correct size
33662 for @var{bitsize}, and @code{float} is a floating point type (in the
33663 architecture's normal floating point format) of the correct size for
33664 @var{bitsize}. The default is @code{int}.
33667 The register group to which this register belongs. @var{group} must
33668 be either @code{general}, @code{float}, or @code{vector}. If no
33669 @var{group} is specified, @value{GDBN} will not display the register
33670 in @code{info registers}.
33674 @node Predefined Target Types
33675 @section Predefined Target Types
33676 @cindex target descriptions, predefined types
33678 Type definitions in the self-description can build up composite types
33679 from basic building blocks, but can not define fundamental types. Instead,
33680 standard identifiers are provided by @value{GDBN} for the fundamental
33681 types. The currently supported types are:
33690 Signed integer types holding the specified number of bits.
33697 Unsigned integer types holding the specified number of bits.
33701 Pointers to unspecified code and data. The program counter and
33702 any dedicated return address register may be marked as code
33703 pointers; printing a code pointer converts it into a symbolic
33704 address. The stack pointer and any dedicated address registers
33705 may be marked as data pointers.
33708 Single precision IEEE floating point.
33711 Double precision IEEE floating point.
33714 The 12-byte extended precision format used by ARM FPA registers.
33717 The 10-byte extended precision format used by x87 registers.
33720 32bit @sc{eflags} register used by x86.
33723 32bit @sc{mxcsr} register used by x86.
33727 @node Standard Target Features
33728 @section Standard Target Features
33729 @cindex target descriptions, standard features
33731 A target description must contain either no registers or all the
33732 target's registers. If the description contains no registers, then
33733 @value{GDBN} will assume a default register layout, selected based on
33734 the architecture. If the description contains any registers, the
33735 default layout will not be used; the standard registers must be
33736 described in the target description, in such a way that @value{GDBN}
33737 can recognize them.
33739 This is accomplished by giving specific names to feature elements
33740 which contain standard registers. @value{GDBN} will look for features
33741 with those names and verify that they contain the expected registers;
33742 if any known feature is missing required registers, or if any required
33743 feature is missing, @value{GDBN} will reject the target
33744 description. You can add additional registers to any of the
33745 standard features --- @value{GDBN} will display them just as if
33746 they were added to an unrecognized feature.
33748 This section lists the known features and their expected contents.
33749 Sample XML documents for these features are included in the
33750 @value{GDBN} source tree, in the directory @file{gdb/features}.
33752 Names recognized by @value{GDBN} should include the name of the
33753 company or organization which selected the name, and the overall
33754 architecture to which the feature applies; so e.g.@: the feature
33755 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
33757 The names of registers are not case sensitive for the purpose
33758 of recognizing standard features, but @value{GDBN} will only display
33759 registers using the capitalization used in the description.
33766 * PowerPC Features::
33771 @subsection ARM Features
33772 @cindex target descriptions, ARM features
33774 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
33775 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
33776 @samp{lr}, @samp{pc}, and @samp{cpsr}.
33778 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
33779 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
33781 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
33782 it should contain at least registers @samp{wR0} through @samp{wR15} and
33783 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
33784 @samp{wCSSF}, and @samp{wCASF} registers are optional.
33786 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
33787 should contain at least registers @samp{d0} through @samp{d15}. If
33788 they are present, @samp{d16} through @samp{d31} should also be included.
33789 @value{GDBN} will synthesize the single-precision registers from
33790 halves of the double-precision registers.
33792 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
33793 need to contain registers; it instructs @value{GDBN} to display the
33794 VFP double-precision registers as vectors and to synthesize the
33795 quad-precision registers from pairs of double-precision registers.
33796 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
33797 be present and include 32 double-precision registers.
33799 @node i386 Features
33800 @subsection i386 Features
33801 @cindex target descriptions, i386 features
33803 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
33804 targets. It should describe the following registers:
33808 @samp{eax} through @samp{edi} plus @samp{eip} for i386
33810 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
33812 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
33813 @samp{fs}, @samp{gs}
33815 @samp{st0} through @samp{st7}
33817 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
33818 @samp{foseg}, @samp{fooff} and @samp{fop}
33821 The register sets may be different, depending on the target.
33823 The @samp{org.gnu.gdb.i386.sse} feature is required. It should
33824 describe registers:
33828 @samp{xmm0} through @samp{xmm7} for i386
33830 @samp{xmm0} through @samp{xmm15} for amd64
33835 The @samp{org.gnu.gdb.i386.avx} feature is optional. It should
33836 describe the upper 128 bits of @sc{ymm} registers:
33840 @samp{ymm0h} through @samp{ymm7h} for i386
33842 @samp{ymm0h} through @samp{ymm15h} for amd64
33846 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
33847 describe a single register, @samp{orig_eax}.
33849 @node MIPS Features
33850 @subsection MIPS Features
33851 @cindex target descriptions, MIPS features
33853 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
33854 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
33855 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
33858 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
33859 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
33860 registers. They may be 32-bit or 64-bit depending on the target.
33862 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
33863 it may be optional in a future version of @value{GDBN}. It should
33864 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
33865 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
33867 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
33868 contain a single register, @samp{restart}, which is used by the
33869 Linux kernel to control restartable syscalls.
33871 @node M68K Features
33872 @subsection M68K Features
33873 @cindex target descriptions, M68K features
33876 @item @samp{org.gnu.gdb.m68k.core}
33877 @itemx @samp{org.gnu.gdb.coldfire.core}
33878 @itemx @samp{org.gnu.gdb.fido.core}
33879 One of those features must be always present.
33880 The feature that is present determines which flavor of m68k is
33881 used. The feature that is present should contain registers
33882 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
33883 @samp{sp}, @samp{ps} and @samp{pc}.
33885 @item @samp{org.gnu.gdb.coldfire.fp}
33886 This feature is optional. If present, it should contain registers
33887 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
33891 @node PowerPC Features
33892 @subsection PowerPC Features
33893 @cindex target descriptions, PowerPC features
33895 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
33896 targets. It should contain registers @samp{r0} through @samp{r31},
33897 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
33898 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
33900 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
33901 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
33903 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
33904 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
33907 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
33908 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
33909 will combine these registers with the floating point registers
33910 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
33911 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
33912 through @samp{vs63}, the set of vector registers for POWER7.
33914 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
33915 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
33916 @samp{spefscr}. SPE targets should provide 32-bit registers in
33917 @samp{org.gnu.gdb.power.core} and provide the upper halves in
33918 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
33919 these to present registers @samp{ev0} through @samp{ev31} to the
33922 @node Operating System Information
33923 @appendix Operating System Information
33924 @cindex operating system information
33930 Users of @value{GDBN} often wish to obtain information about the state of
33931 the operating system running on the target---for example the list of
33932 processes, or the list of open files. This section describes the
33933 mechanism that makes it possible. This mechanism is similar to the
33934 target features mechanism (@pxref{Target Descriptions}), but focuses
33935 on a different aspect of target.
33937 Operating system information is retrived from the target via the
33938 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
33939 read}). The object name in the request should be @samp{osdata}, and
33940 the @var{annex} identifies the data to be fetched.
33943 @appendixsection Process list
33944 @cindex operating system information, process list
33946 When requesting the process list, the @var{annex} field in the
33947 @samp{qXfer} request should be @samp{processes}. The returned data is
33948 an XML document. The formal syntax of this document is defined in
33949 @file{gdb/features/osdata.dtd}.
33951 An example document is:
33954 <?xml version="1.0"?>
33955 <!DOCTYPE target SYSTEM "osdata.dtd">
33956 <osdata type="processes">
33958 <column name="pid">1</column>
33959 <column name="user">root</column>
33960 <column name="command">/sbin/init</column>
33961 <column name="cores">1,2,3</column>
33966 Each item should include a column whose name is @samp{pid}. The value
33967 of that column should identify the process on the target. The
33968 @samp{user} and @samp{command} columns are optional, and will be
33969 displayed by @value{GDBN}. The @samp{cores} column, if present,
33970 should contain a comma-separated list of cores that this process
33971 is running on. Target may provide additional columns,
33972 which @value{GDBN} currently ignores.
33986 % I think something like @colophon should be in texinfo. In the
33988 \long\def\colophon{\hbox to0pt{}\vfill
33989 \centerline{The body of this manual is set in}
33990 \centerline{\fontname\tenrm,}
33991 \centerline{with headings in {\bf\fontname\tenbf}}
33992 \centerline{and examples in {\tt\fontname\tentt}.}
33993 \centerline{{\it\fontname\tenit\/},}
33994 \centerline{{\bf\fontname\tenbf}, and}
33995 \centerline{{\sl\fontname\tensl\/}}
33996 \centerline{are used for emphasis.}\vfill}
33998 % Blame: doc@cygnus.com, 1991.